Handover Control

Handover Control

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# Nokia Siemens Networks 1 (247)

RNC3267Nokia WCDMA RAN, Rel. RAS06, SystemLibrary, v. 3

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2 (247) # Nokia Siemens Networks DN03471612Issue 8-2 en13/12/2007

Handover Control

Contents

Contents 3

List of tables 7

List of figures 8

Summary of changes 11

1 Handover control 13

2 Types of handovers 192.1 Introduction to soft handover 192.2 Introduction to intra-frequency hard handover 202.3 Introduction to inter-frequency handover 202.4 Introduction to inter-system handover 212.5 Introduction to IMSI-based handover 232.5.1 Purpose of IMSI-based handover 242.5.2 Functional restrictions on IMSI-based handover 272.6 Introduction to load- and service-based IF/IS handover 28

3 Compressed mode 333.1 Halving the spreading factor 353.2 Higher layer scheduling 373.3 Restrictions because of cell capacity 40

4 Macro diversity combining 43

5 WCDMA frequency bands 51

6 Directed RRC connection setup 57

7 Directed RRC connection set-up for HSDPA layer 63

8 HSPA layering for UEs in common channels 738.1 Decision of layer change 758.2 HSDPA load balancing 76

9 Functionality of intra-frequency handover 779.1 Functionality of soft handover 779.1.1 Reporting event 1A for adding cells to the active set 789.1.2 Reporting event 1B for deleting cells from the active set 809.1.3 Reporting event 1C for replacing cells in the active set 819.1.4 Event-triggered periodic intra-frequency measurement reporting 849.1.5 Time-to-trigger mechanism for modifying measurement reporting

behaviour 859.1.6 Cell individual offsets for modifying measurement reporting behaviour 869.1.7 Mechanism for forbidding a cell to affect the reporting range 879.1.8 Reporting events 6F and 6G for deleting cells from the active set 88

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9.1.9 Function in abnormal conditions 899.2 Functionality of intra-frequency hard handover 919.2.1 Time interval between hard handover attempts 93

10 Functionality of inter-frequency handover 9510.1 Coverage reason inter-frequency handover 9610.1.1 Inter-frequency handover because of uplink DCH quality 9610.1.2 Inter-frequency handover because of UE transmission power 9710.1.3 Inter-frequency handover because of CPICH RSCP 9910.1.4 Handover decision procedure 10010.2 Quality reason inter-frequency handover 10110.2.1 Inter-frequency handover because of Downlink DPCH power 10210.2.2 Inter-frequency handover because of CPICH Ec/ No 10510.2.3 Handover decision procedure 10610.3 Interactions between handover causes 10710.4 Interaction with handover to GSM 10810.5 Measurement procedure 10910.6 Function in abnormal conditions 111

11 Functionality of inter-system handover 11311.1 Coverage reason inter-system handover 11511.1.1 Inter-system handover because of uplink DCH quality 11611.1.2 Inter-system handover because of UE transmission power 11711.1.3 Inter-system handover because of CPICH RSCP 11911.1.4 Inter-system handover because of downlink DPCH power 12011.1.5 Inter-system handover because of CPICH Ec/No 12311.1.6 Handover decision procedure 12411.2 Interactions between handover causes 12511.3 Interaction with inter-frequency handover 12611.4 Measurement procedure 12711.5 Function in abnormal conditions 129

12 Functionality of IMSI-based handover 13112.1 Configuration of IMSI-based handover 13112.2 IMSI-based intra-frequency handover 13312.3 IMSI-based inter-frequency handover 13412.4 IMSI-based inter-system handover 134

13 Functionality of immediate IMSI-based handover 13713.1 Immediate IMSI-based inter-frequency handover 13713.2 Immediate IMSI-based inter-system handover 138

14 Functionality of load-based and service-based IF/IS handover 14114.1 Load-based handover 14114.1.1 Total interference load of the cell exceeds a predefined threshold 14114.1.2 Rejection rate of PS NRT traffic capacity requests exceeds a predefined

threshold 14414.1.3 Downlink spreading codes are lacking in the cell 14414.1.4 HW or logical resources are limited in the cell 14514.1.5 Processing of measurement results indicating load 14614.1.6 Number of UEs simultaneously in the load-based handover

procedure 150


Handover Control

14.1.7 Selection of RRC connections for the load-based handoverprocedure 150

14.2 Service-based handover 15214.2.1 Number of RRC connections simultaneously in the service-based

handover procedure 15214.2.2 Selecting RRC connections for the service-based handover

procedure 15314.2.3 Defining the target for the service-based handover 15414.3 Service priority 15414.3.1 Iu interface service priority 15414.3.2 RNC-based service priority handover profile table 15514.3.3 Combined service priority list 15614.3.4 Multi services in case of service-based and load-based handovers 15914.3.5 Availability of the target WCDMA layers and GSM system 16114.4 Load of the target cells 16114.4.1 Common load measurement over Iur 16114.4.2 Load of the target WCDMA cell 16214.4.3 Load of the target GSM/GPRS cell 16314.4.4 Congested target WCDMA or GSM cell 16314.5 Inter-frequency and inter-RAT measurement procedures 16414.5.1 Selecting the service and load-based inter-frequency handover

method 16414.5.2 Selecting the service and load-based inter-RAT handover method 16514.5.3 Measurement parameters 16514.5.4 Inter-frequency and inter-RAT neighbour cell lists 16614.5.5 Number of UEs in compressed mode 16714.6 Handover decision procedure 16814.6.1 Load- and service-based inter-frequency handover 16814.6.2 Load- and service-based inter-RAT handover 16914.7 Handover signalling 17014.7.1 Load- and service-based inter-frequency handover 17014.7.2 Load- and service-based inter-RAT handover and cell change 17114.7.3 Service downgrading and upgrading because of inter-RAT handover 17114.7.4 Restriction on repetitive load- and service-based handover attempts 171

15 SRNS relocation overview 173

16 Soft handover signalling 175

17 Intra-frequency hard handover signalling 181

18 Serving RNC relocation signalling 185

19 Compressed mode preparation signalling 187

20 Inter-frequency handover signalling 189

21 Inter-system handover signalling 197

22 Handover control statistics 205

23 Handover control restrictions 209

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24 Management parameters for handover control 21124.1 RNC parameters 21124.2 WCDMA BTS parameters (WBTS) 21724.3 WCDMA cell parameters (WCEL) 21824.4 Intra-frequency measurement control parameters (FMCS) 22524.5 Inter-frequency measurement control parameters (FMCI) 22824.6 Inter-system (GSM) measurement control parameters (FMCG) 23124.7 Intra-frequency neighbour cell parameters (ADJS) 23424.8 Inter-frequency neighbour cell parameters (ADJI) 23524.9 Inter-system (GSM) neighbour cell parameters (ADJG) 23624.10 Intra-frequency handover path parameters (HOPS) 23724.11 Inter-frequency handover path parameters (HOPI) 23824.12 Inter-system (GSM) handover path parameters (HOPG) 24024.13 WCDMA authorised network parameters (WANE) 24124.14 WCDMA subscriber group parameters (WSG) 242

Related Topics 243


Handover Control

List of tables

Table 1. Handover types 13

Table 2. Handover types according to shifts between the BTSs and RNCs 14

Table 3. Use of load- and service-based handovers according to the servicetype 31

Table 4. UTRA absolute radio frequency channel numbers defined by 3GPP 53

Table 5. Allowed channel numbers of US WCDMA 1900 in band II 53

Table 6. UARFCN definition (general) 54

Table 7. UARFCN definition (additional channels) 55

Table 8. Variables for measurement report on event 1A 79

Table 9. Variables for measurement report on event 1B 80

Table 10. Variables for measurement report on event 1C 82

Table 11. Criteria for enabling the RRC connection release 90

Table 12. Measurement result criteria for intra-frequency hard handover 92

Table 13. Variables for inter-system handover 102

Table 14. Variables for inter-system handover 121

Table 15. RNC-based service priority handover profile table 156

Table 16. Combination of service priority information 157

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List of tables

List of figures

Figure 1. IMSI definition 23

Figure 2. IMSI-based handover in geographical sharing concept 25

Figure 3. IMSI-based handover in common shared RAN concept 26

Figure 4. IMSI-based handover in mobile virtual network operator concept 27

Figure 5. Load of the source cell 28

Figure 6. Example of transmission gaps created with compressed mode 34

Figure 7. Halving the spreading factor (single frame method) 36

Figure 8. Higher layer scheduling (double frame method) 38

Figure 9. Selection of the higher layer scheduling mode 39

Figure 10. Macro diversity combining 46

Figure 11. Handover scenario: branch addition rejected 48

Figure 12. Definition of uplink DCH own-cell load threshold LDRRC 58

Figure 13. Principle of directed RRC connection setup 62

Figure 14. Principles of directed RRC connection setup for HSDPA layer 63

Figure 15. Signalling of directed RRC connection setup for HSDPA layer 64

Figure 16. Calculation of HSDPA power per user 67

Figure 17. Calculation of HSDPA power per user without HSDPA power 68

Figure 18. Example of layer selection in RRC connection setup phase in non-HSDPAlayer 69

Figure 19. Example of layer selection in RRC connection setup phase in HSDPAlayer 70

Figure 20. Signalling of HSPA layering for UEs in common channels 74

Figure 21. Formula for calculating the UE measurement report on event 1A 79

Figure 22. Formula for calculating the UE measurement report on event 1B 80

Figure 23. Formula for calculating the UE measurement report on event 1C 82

Figure 24. A cell that is not in the active set becomes better than a cell in a full activeset 83

Figure 25. Formula for calculating the UE measurement report on event 1C 83

Figure 26. Periodic reporting triggered by event 1A 84


Handover Control

Figure 27. Time-to-trigger limits the number of measurement reports 86

Figure 28. A positive offset is applied to cell 3 before event evaluation in the UE 87

Figure 29. Cell 3 is forbidden to affect the reporting range 88

Figure 30. Measuring procedure 110

Figure 31. Measuring procedure 128

Figure 32. An example of selecting the authorised network list 132

Figure 33. Definition of uplink DCH own cell load threshold LLHO 142

Figure 34. Measurement procedure for all four load triggers 147

Figure 35. Branch addition 176

Figure 36. Branch deletion 178

Figure 37. Branch replacement 180

Figure 38. Intra-frequency hard handover 183

Figure 39. SRNC relocation 186

Figure 40. Compressed mode preparation 187

Figure 41. Intra-RNC inter-frequency handover because of UE transmission power(continued in the next picture) 190

Figure 42. Intra-RNC inter-frequency handover because of UE transmission power(continued from the previous picture) 191

Figure 43. MSC controlled inter-RNC inter-frequency handover because of CPICHEcNo (quality reason), source RNC (continued in the next picture) 192

Figure 44. MSC controlled inter-RNC inter-frequency handover because of CPICHEcNo (quality reason), source RNC (continued from the previouspicture) 193

Figure 45. SGSN controlled inter-RNC inter-frequency handover because of UEtransmission power (coverage reason), source RNC (continued in thenext picture) 194

Figure 46. SGSN controlled inter-RNC inter-frequency handover because of UEtransmission power (coverage reason), source RNC (continued fromthe previous picture) 195

Figure 47. Inter-system handover from WCDMA to GSM (continued in the nextpicture) 198

Figure 48. Inter-system handover from WCDMA to GSM (continued from the previouspicture) 199

Figure 49. Inter-system cell change from WCDMA to GSM/GPRS (continued in thenext picture) 201

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Figure 50. Inter-system cell change from WCDMA to GSM/GPRS (continued from theprevious picture) 202

Figure 51. Inter-system handover from WCDMA to GSM with CS and PS multiservices 203

Figure 52. Inter-system hard handover from GSM to WCDMA 204


Handover Control

Summary of changes

Changes between document issues are cumulative. Therefore, the latestdocument issue contains all changes made to previous issues.

Changes between issues 8-1 and 8-2

Sections HSPA layering for UEs in common channels and Directed RRCconnection setup for HSDPA layer:

Information on layer changes has been added.

Sections Functionality of inter-frequency handover and Functionality ofinter-system handover:

Information on Nokia proprietary NBAP interface has been removed sinceit is not supported any longer.


Section Functionality of Load- and Service-based IF/IS handover:

In Section Downlink spreading codes are lacking in the cell, information onReservedSC has been added.


Section Compressed mode:

. Information on restrictions because of cell capacity is extended.

Section Macro diversity combining:

. Changes are made in Figure Macro diversity combining.

Section Directed RRC connection setup:

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. Information on directed RRC connection setup is extended.

Section Directed RRC connection setup for HSDPA layer:

. Information on Directed RRC connection setup for HSDPA layer isextended.

. Sections Basic functionality and Enhanced functionality are added.

Section HSPA layering for Ues in common channels:

. new modul

Section Functionality of Load- & Service-based IF/IS handover:

. Information on Total interference load of the cell exceeds apredefined threshold is extended

Section Functionality of directed retry of WPS call:

. REMOVED

Section Inter-system handover signalling:

. Figures Inter-system handover from WCDMA to GSM and Inter-system cell change from WCDMA toGSM/GPRS are updated.

Section Directed retry of WPS call signalling:

. REMOVED

Section Handover control statistics:

. Information on Intra- and Inter-System Handover measurements isadded.

Section Management parameters for handover control:

. RNC are WCDMA cell parameters are extended.


Handover Control

1 Handover control

The purpose of handover control is to manage the mobility aspect of aRadio Resource Control(RRC) connection. This means keeping track ofthe user equipment (UE) as it moves around in the network, and ensuringthat its connections are uninterrupted and meet the negotiated Quality ofService (QoS) requirements.

Besides supporting the mobility of the UE, handovers play a key role inmaintaining high capacity in the network. Since the capacity of aWideband Code Division Multiple Access (WCDMA) network is directlyproportional to the level of interference in the network, it is crucial toregulate the transmission power of all transmitting elements in the network.Each transmission adds to the interference in the network. The requiredtransmission power, in turn, depends on the bit rate, the interference andthe distance between the UE and the WCDMA Base Station (BTS).

In order to keep the power of its signal constant, the UE must raise itstransmission power as it moves further away from the WCDMA BTS. Tominimise transmission powers, and consequently interference, the UEshould at all times be connected to the strongest cell. In this way, handovercontrol is directly related to power control, which is the algorithm thatkeeps transmission powers in check. Handover control and power control,in turn, are both part of radio resource management.

Handover types

The table below summarises the different handover types.

Table 1. Handover types

Handover type Soft Hard Evaluated by

Compressedmodeneeded

Generalfeature

Intra-frequency Yes Yes Mobile No Yes

Inter-frequency No Yes Network Yes Yes

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Table 1. Handover types (cont.)

Handover type Soft Hard Evaluated by

Compressedmodeneeded

Generalfeature

Inter-system No Yes Network Yes No

Radio access network (RAN) supports intra-frequency, inter-frequencyand inter-system handover procedures. In an intra-frequency handover theUE shifts between cells using the same carrier frequency. Inter-frequencyhandovers differ from this in that the cells use different carrier frequencies.Inter-system handover means that the cells use different radio accesstechnologies (RAT), and consequently different frequencies, too. Ahandover between a GSM cell and a WCDMA cell is, for example, a typicalinter-system handover.

Intra-frequency soft and hard handovers and inter-frequency handoversare general features in the RAN, whereas inter-system handover is anoptional feature.

There is a fundamental difference between the intra-frequency handoversand the other handover types; the intra-frequency handovers areindispensable as they allow the UE to move around, whereas the othertypes of handover provide added coverage.

Handovers are divided into soft and hard handovers. In soft handovers, theUE is simultaneously connected to more than one WCDMA BTS, which alluse the same carrier frequency. In soft handover, the UE is notdisconnected at all - instead it simply drops one out of two or more radiolinks, which remain active. The inter-frequency and inter-systemhandovers are always hard handovers. Hard handovers cause a veryshort disconnection of real-time bearers (for example speech connectionsfall into this category), as the UE switches to another frequency orbetween GSM and WCDMA cells.

The table below illustrates the relationships between intra- and inter-BTSand RNC handovers in different handover types.

Table 2. Handover types according to shifts between the BTSs and RNCs

Handover type Intra-BTS Inter-BTS Intra-RNC Inter-RNC

Softer handover x

Soft handover x x x


Handover Control

Table 2. Handover types according to shifts between the BTSs and RNCs(cont.)

Handover type Intra-BTS Inter-BTS Intra-RNC Inter-RNC

Hard handovers

. Intra-frequencyhandover

x

. Inter-frequencyhandover

x x x x

Neighbour cell definitions

When the UE is in connected mode, the RNC follows it on cell level. Onceit knows in which cell the UE is located, the RNC checks information aboutall the neighbouring cells and transmits the data back to the UE. The RNCupdates continuously the neighbour cell lists in order to reflect thechanging neighbourhood of a moving mobile station in connected mode.

The neighbouring cells are defined on a cell-by-cell basis, that is, each cellcan have its own set of neighbouring cells. A neighbour cell definitionincludes, for example, information about the radio access technology,carrier frequency, and scrambling codes of the neighbour cell.Neighbouring cell definitions are stored in the RNW configurationdatabase.

By relaying information about neighbour cells to the UE, the RNC iseffectively telling it what to look for, and the RNC knows what the availableoptions are, if the load in the serving cell increases too much. Neighbourcell definitions also speed up cell re-selection procedures, as the UE doesnot have to decode the scrambling codes of other cells.

Neighbour cell parameters are defined on a neighbouring cell-by-cell basisfor each handover type (intra-, inter-frequency and inter-system)separately by attaching a specified parameter set to a specified neighbourcell. The parameter set defines the handover path from the serving cell tothe neighbour cell in question.

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Neighbour cell list generation during soft handover

The RNC generates a new intra-frequency neighbour cell list after everyactive set update procedure. The RNC transmits the new intra-frequencyneighbour cell list to the mobile station if the new list differs from the intra-frequency neighbour cell list that is currently used by the mobile station.The RNC does not modify inter-frequency or GSM neighbour cell lists afterthe active set update procedure because of the limited running time ofthese periodic measurements.

If the neighbour cell lists of two or more active set cells, which areparticipating in soft handover, are different, the RNC combines the lists intoone common neighbour cell list which is transmitted to the mobile station.The combination of intra-frequency neighbour cell lists is carried out in thefollowing steps 1, 2, 3 and 4. The combination procedure for the inter-frequency and GSM neighbour cell lists consists of the steps 2, 3 and 4below.

1. Active set cells

First the RNC selects the active set cells into the neighbour cell list.

2. Neighbour cells which are common to three active set cells

During the second step of neighbour cell list combination the RNCselects those neighbour cells which are common to all three activeset cells. If the total number of relevant neighbour cells exceeds themaximum number of 32 after the second step, the RNC removes inrandom order those surplus cells from the combined neighbour celllist which are selected during the second step.

3. Neighbour cells which are common to two active set cells

During the third step of neighbour cell list combination the RNCselects those neighbour cells which are common to two active setcells. If the total number of relevant neighbour cells exceeds themaximum number of 32 after the third step, the RNC removes inrandom order those surplus cells from the combined neighbour celllist which are selected during the third step.

4. Neighbour cells which are defined for only one active set cell

During the fourth step of neighbour cell list combination the RNCselects those neighbour cells which are defined for only one activeset cell. If the total number of relevant neighbour cells exceeds themaximum number of 32 after the fourth step, the RNC removesthose surplus neighbours from the combined neighbour cell listwhich are selected during the fourth step, starting from theneighbours of the weakest (CPICH Ec/No) active set cell.


Handover Control

Hierarchical cell structure

From the network operator's point of view, it does not make sense to offerthe same amount of capacity everywhere. Instead, the capacity should beconcentrated to those places where users commonly require it. Nokiaoffers solutions that allow operators to tune the capacity to the local needsby creating hierarchical cell structures (HCSs). By creating microcellsinside macrocells - and even picocells inside microcells - operators canoffer both great coverage and high capacity where it is most needed.

Different layers use different frequencies, but it is also possible to usedifferent frequencies on the same layer, in order to boost the capacity. Theend result can be a very complex hierarchy involving several layers andfrequencies.

In addition, GSM cells, which offer additional capacity, also have to betaken into account. This setup, with multiple frequencies and radio accesstechnologies, complicates things for handover control. Regarding radionetwork optimisation, all radio resources should be at the disposal of radioresource management; consequently, handover control must allow the UEto move between all types of cells.

HSDPA (High Speed Downlink Packet Access)

HSDPA-specific mobility control includes the features Serving HS-DSCHCell Change and SHO of the Associated DCH. HSPA inter-RNC mobility isprovided by the HSPA inter-RNC cell change feature.

HS-PDSCH allocation for a given UE belongs to only one of the radio linksassigned to the UE: the serving HS-DSCH radio link. The cell associatedwith the serving HS-DSCH radio link is defined as the serving HS-DSCHcell. A serving HS-DSCH cell change facilitates the transfer of the servingHS-DSCH radio link’s role from one radio link belonging to the source HS-DSCH cell to a radio link belonging to the target HS-DSCH cell.

The serving HS-DSCH cell change is based on the intra-frequencyCPICHEc/No measurements reported periodically by the UE and dedicatedUL SIRerror measurements reported periodically by the BTS.

For more information on HSDPA-related mobility control, see SectionHSDPA mobility handling in Radio Resource Management of HSDPA.

For more information on directed RRC connection setup for the HSDPAlayer, see Section Directed RRC connection setup for HSDPA layer.

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Handover Control

2 Types of handovers

2.1 Introduction to soft handover

Soft handover means that the UE is connected to more than one WCDMABTS at the same time (this is why it is also called a "macro diversityhandover"). When in connected mode, the UE continuously measuresserving and neighbouring WCDMA BTSs (cells indicated by the RNC) onthe current carrier frequency. The UE compares the measurement resultswith handover thresholds, which have been provided by the RadioNetwork Controller (RNC). When a measurement yields a value thatexceeds a given threshold, the UE sends a measurement report to theRNC. Soft handover is a Mobile Evaluated Handover (MEHO).

The main decision algorithm of soft handover is located in the RNC. Basedon the measurement report received from the UE, the RNC orders the UEto add or remove cells from its active set, that is, the set of cellsparticipating in the soft handover.

The types of intra-frequency handover for both real-time (RT) and non-real-time (NRT) radio access bearers (RABs) are:

. softer handover between cells (having different coverage areas)within one WCDMA BTS

. soft handover between WCDMA BTSs within one RNC (intra-RNCsoft handover)

. soft handover between WCDMA BTSs controlled by different RNCs(inter-RNC soft handover).

In the WCDMA system, the vast majority of handovers are intra-frequencyhandovers. Different types of intra-frequency handovers can take placesimultaneously. For example, the RAN is able to perform soft (intra-RNCas well as inter-RNC) and softer handovers at the same time. The benefitsof soft and softer handover are the following:

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. a seamless handover without a disconnection of the RAB

. fast closed-loop power control optimisation (the UE is always linkedwith the strongest cell)

. a sufficient reception level for maintaining communications bycombining reception signals (macrodiversity) from multiple cellswhen the UE moves to cell boundary areas and cannot obtain asufficient reception from a single cell

. the macrodiversity gain achieved by combining the reception signalin the WCDMA BTS (softer handover) and in the RNC (softhandover), improves the uplink signal quality and decreases therequired transmission power of the UE

Soft and softer handover consume radio access capacity because the UEis occupying more than one radio link connection in the Uu interface.However, the added capacity gained from interference reduction is biggerand hence the system capacity is actually increased when soft and softerhandovers are used.

2.2 Introduction to intra-frequency hard handover

Intra-frequency hard handover is a general feature in the RAN. Intra-frequency hard handover causes only a short disconnection of a real-timeradio access bearer. As for non-real-time bearers, there is nodisconnection at all as packet scheduling momentarily halts thetransmission of data. Intra-frequency hard handover is required, forexample, to ensure handover path between WCDMA BTSs controlled bydifferent RNCs when inter-RNC soft handover is not available (due tocongestion at the Iur interface, for example).

Intra-frequency hard handover decisions made by the RNC are based onthe intra-frequency measurement results which are usually applied to thesoft handover procedure. Thus the intra-frequency hard handover is amobile evaluated handover (MEHO).

2.3 Introduction to inter-frequency handover

Inter-frequency handover is a general feature in the RAN. Inter-frequencyhandovers are needed to support mobility between carrier frequencies inthe network. Inter-frequency handovers are always hard handovers, thatis, they cause a short disconnection of RT RABs.


Handover Control

Handover control in RAN supports the following types of inter-frequencyhandover:

. intra-BTS hard handover

. intra-RNC hard handover

. inter-RNC (-MSC) hard handover.

Inter-frequency handover is a network-evaluated handover (NEHO). Thedecision algorithm of inter-frequency handover is located in the RNC. TheRNC makes the handover decision on the basis of periodical inter-frequency measurement reports received from the UE and relevant controlparameters. The RNC orders the UE to start the periodical reporting ofinter-frequency measurement results only when an inter-frequencyhandover is needed. The measurement object information (cells andfrequencies) for the inter-frequency measurement is determined by theRNC. Because the UE is not expected to receive from the two differentfrequencies at the same time, compressed mode must be used at the L1 ofthe radio interface while the UE makes the required inter-frequencymeasurements.

After the hard handover decision, the RNC allocates radio resources fromthe target cell, establishes a new radio link for the connection between theUE and the target cell, and orders the UE to make an inter-frequencyhandover to the target cell.

2.4 Introduction to inter-system handover

This feature is a part of application software.

Handover control of the RAN supports inter-system handovers, fromWCDMA to GSM and from GSM to WCDMA. Inter-system handover isrequired so that the coverage areas of GSM and WCDMA cancomplement each other. When the coverage areas of WCDMA and GSMare overlapping each other, an inter-system handover can be used tocontrol the load and/or services between the systems. Inter-systemhandover is a hard handover, which means that an inter-system handovercauses a short disconnection of an RT RAB.

Inter-system handover is a network-evaluated handover (NEHO). Thedecision algorithm of the inter-system handover and network initiated cellreselection is located in the RNC. The RNC makes the decision on thebasis of periodical inter-system measurement reports received from theUE and relevant control parameters. The RNC orders the UE to start the

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Types of handovers

periodical reporting of inter-system measurement results only when aninter-system handover or cell reselection is needed. The measurementobject information for the inter-system measurement is determined by theRNC.

When an RAB is handed over from one system to another, both the corenetwork and the target RNC (or BSC) are responsible for adapting theQuality of Service(QoS) parameters of the RAB according to the target(GSM or WCDMA) system.

For inter-system handovers to be possible, the UE has to supportcompressed mode . The UE must also support both WCDMA and GSMRATs before an inter-system handover is possible.

WCDMA to GSM

The decision algorithm of the inter-system handover from WCDMA toGSM is located in the RNC. The RNC recognizes the possibility of inter-system handover based on the configuration of the radio network(neighbour cell definitions and relevant control parameters).

If an inter-system handover from WCDMA to GSM is required, the RNCinitiates an inter-system relocation procedure in order to allocate radioresources from the GSM system. If the resource allocation is successful inthe GSM system, the RNC orders the mobile station to make an inter-system handover to the GSM system.

If an inter-system handover (network-initiated cell reselection) fromWCDMA to general packet radio service (GPRS) is required, the RNCsends a cell change command to the UE, and the UE is responsible forcontinuing the already existing PS connection via GPRS RAN.

GSM to WCDMA

The decision algorithm of the inter-system handover from GSM toWCDMA is located in the GSM base station controller (BSC). Thus theGSM Base Station Subsystem (BSS) must support the inter-systemhandover before the handover from GSM to WCDMA is possible.

After the handover decision, the BSC initiates an inter-system relocationprocedure in order to allocate radio resources from the target RNC. If theresource allocation is successful in the target RNC, the BSC orders themobile station to make an inter-system handover to the WCDMA system.


Handover Control

2.5 Introduction to IMSI-based handover


The purpose of the IMSI-based handover feature is to enable a mobilesubscriber visiting another network to hand over only to cells which belongto specified (home or authorised) PLMNs. The input for the selectivehandover control is the PLMN identifier that is included in the IMSI of thesubscriber.

The PLMN identifier, which consists of Mobile Country Code (MCC) andMobile Network Code (MNC) is included in the IMSI of the subscriber asshown in the figure below.

Figure 1. IMSI definition

The IMSI-based handover feature can be enabled separately for intra-frequency, inter-frequency and inter-system handovers. When the featureis enabled, the RNC makes the neighbour cell lists for the inter-frequencyand inter-system (GSM) measurements on a subscriber-by-subscriberbasis according to the PLMN identifier that is included in the IMSI of thesubscriber, and performs the corresponding handover selectively to theneighbouring cell which either belongs to the home PLMN of thesubscriber or to a PLMN which is defined in the authorised network list.

When the feature is enabled for intra-frequency handovers, the RNC addsa new cell to the active set only if the PLMN identifier of the cell (that hastriggered reporting event 1A or 1C) is included in the list of authorisednetworks, it has the same PLMN identifier as the subscriber or it has thesame PLMN identifier as an existing active set cell.

IMSI = MCC + MNC + MSIN

PLMN id

IMSIMCCMNCMSINPLMN

International Mobile Subscriber IndetityMobile Country CodeMobile Network CodeMobile Subscriber Identification NumberPublic Land Mobile Network

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A list of authorised networks contains a maximum of six PLMN identifiers(MCC + MNC) that are considered equal to the home PLMN of asubscriber. The radio network database contains ten separate authorisednetwork lists. The RNC is able to link up to 128 specified home PLMNidentifiers with the specified authorised network lists.

2.5.1 Purpose of IMSI-based handover

IMSI-based handover benefits from roaming-based network provisioningand some RAN-sharing concepts by enabling directed handover from theshared WCDMA network to the home network of the subscriber or to theauthorised WCDMA or GSM network, when coverage becomes available.The IMSI-based handover can be used in different cases:

. geographical sharing

. common shared RAN with gateway core

. Mobile Virtual Network Operator (MVNO)

IMSI-based handover and geographical sharing

Figure IMSI-based handover in geographical sharing concept belowshows the function of IMSI-based handover in the geographical sharingconcept. In geographical sharing, operators cover separate areas andshare networks via national roaming. However, there are areas where bothoperators provide coverage (for example big city areas). The IMSI-basedhandover feature directs the subscriber to the subscriber’s home WCDMAnetwork when coverage becomes available. When the WCDMA coverageends, the subscriber is handed over to the subscriber’s home GSMnetwork.


Handover Control

Figure 2. IMSI-based handover in geographical sharing concept

IMSI-based handover and common shared RAN

Figure IMSI-based handover in common shared RAN concept belowshows the function of IMSI-based handover in the common shared RAN(with gateway core) concept, where operators build common radio accessand core networks in the shared area. When a subscriber moves from theshared area to the area where both operators have their own coverageavailable, the subscriber is handed over to the subscribers home WCDMAnetwork. When the WCDMA coverage ends, the subscribers are handedover to their home GSM networks.

GSM GSM GSM GSM GSM GSM GSM

WCDMA WCDMA WCDMA WCDMA

WCDMA WCDMAWCDMA WCDMA

GSM GSM GSM GSM GSM GSM GSM

Based on IMSI,operator B user ishanded over to its

own WCDMA networkwhen coverage

becomes available

Based on IMSI,operator A user ishanded over to its


becomes available

Based on IMSI,users are handed

over to their own GSMnetworks when

WCDMA coverage ends

Based on IMSI, loadand service-based inter-system HOs to their own

GSM network inshared area

Operator A GSM cell

Operator A own WCDMA cell

Operator A controlled sharedWCDMA cell

Operator A user path

Operator B GSM cell

Operator B own WCDMA cell

Operator B controlled sharedWCDMA cell

Operator B user path

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Figure 3. IMSI-based handover in common shared RAN concept

IMSI-based handover and mobile virtual network operator

Figure IMSI-based handover in mobile virtual network operator conceptbelow shows the function of IMSI-based handover in the mobile virtualnetwork operator concept, where operators have their own GSM networksand one operator is operating as a virtual operator in other operator’sWCDMA network. The IMSI-based handover feature enables load andservice-based inter-system handovers to the subscriber’s home GSMnetwork from the virtual mobile network. When the WCDMA coverageends, subscribers are handed over to their home GSM networks.

GSM GSM GSM GSM GSM

GSM GSM GSM GSM GSM

Based on IMSI,operator B user ishanded over to its


becomes available

Based on IMSI,operator A user ishanded over to its


becomes available



WCDMA coverage ends



Operator A GSM cell

Operator A own WCDMA cell


Common shared WCDMA cell

Operator B GSM cell

Operator B own WCDMA cell


WCDMA

WCDMA

WCDMA WCDMA WCDMA


Handover Control

Figure 4. IMSI-based handover in mobile virtual network operator concept

2.5.2 Functional restrictions on IMSI-based handover

When the IMSI based handover feature is used in the geographicalsharing concept or in the common shared RAN (with gateway core)concept, the shared area must have a PLMN identifier of its own.Otherwise it may be impossible to control a subscriber’s mobility.

The RNC identifier (RncId) uniquely identifies an RNC within the UTRAN.The RNC identifier together with the PLMN identifier is used to globallyidentify the RNC. When the IMSI-based handover feature is enabled in theRNC, it is possible to define (in addition to the primary PLMN identifier that

GSM GSM GSM

GSM GSM GSM



WCDMA coverage ends



Operator A GSM cell


Operator A controlled WCDMA cell

Operator B GSM cell


WCDMA WCDMA

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is a part of the CN domain identifier) secondary PLMN identifiers under theRNC. The secondary PLMN identifiers are assigned to shared networkareas where the subscribers of the partner operator can have access. TheRNC identifier must be unique within the primary and secondary PLMNs.

2.6 Introduction to load- and service-based IF/IShandover

Load- and Service-based IF/IS Handover is an optional feature.

Load- and service-based handovers take care of load sharing and servicedifferentiation inside the WCDMA system as well as between the WCDMAand GSM/GPRS systems. Both load and service are taken into accountsimultaneously, but the measured load defines the way of operation.

Figure Load of the source cell below clarifies the dependency.

The load indicators that can be measured are UL/DL interference, NRTtraffic delay, DL spreading code availability, and HW/logical resourceusage.

Figure 5. Load of the source cell

Load of the source cell (WCDMA)

Load based handoversaccording to service priorities

only service handovers

Percentagecomparedtothetargetedload

100%

80%

0%

Operator only needsto set this load threshold


Handover Control

This feature also enables the operator to set different handover profiles forthe service classes. The service classes are split according to the trafficclasses specified for the RABs, separating the speech and data servicesfrom the CS and PS domains. The RNC-based handover profile definesthe preferred system or WCDMA hierarchical cell layer (GSM, WCDMAmacro, WCDMA micro, none). By default, only the RTservices are handedover, because the NRT dedicated traffic channel (DCH) allocations areexpected to be too short for these kinds of handover procedures. However,the operator may enable handovers also for the NRT services in case oflonger DCH allocations.

The list below shows an example of service priority definitions. For eachservice, the operator sets a preferred system/layer.

. conversational CS speech -> GSM

. conversational CS transparent data -> WCDMA, macro

. conversational PS speech -> WCDMA, macro

. conversational PS RT data -> WCDMA, micro

. streaming CS non-transparent data -> WCDMA, macro

. streaming PS RT data -> WCDMA, micro

. interactive PS NRT data -> WCDMA, micro

The handover profile is followed in both load-based and service-basedhandover decisions unless the core network provides a Service Priorityinformation element (IE) on RAB setup. This, for example, overrides thehandover profile if the handover decision for the UE in question is madebetween the WCDMA and GSM systems.

Benefits

Load- and service-based handovers are powerful enhancements for theRAN handover functionality: load balancing provides more capacity,hardware investments are used better, and there is less blocking in thenetwork. It allows effective traffic sharing between the GSM and WCDMAnetworks and their layers. It is also possible to do service-prioritisedhandovers to support different services on cell level. When CS calls arehanded over to an existing GSM network, it is possible to prioritisecoverage deployment to urban areas first (where the market demand ishigh), and use the existing GSM layer in rural areas.

With this feature, the operator can shift investments to the future, or withGSM, even prevent the need for capacity enhancement investments.

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Load-based handover

Load-based inter-frequency and inter-RAT handovers are used to balancethe load between different WCDMA carriers/cells and between WCDMAand GSM/GPRS systems and by that way fully use the trunking gain. Thebigger the channel pool, the better the efficiency of the channel usage. Theadvantages of a bigger channel pool come up especially if high bit ratechannels are used. If load-based handovers are not possible for somereason, normal load control actions take place.

If the load of a specified WCDMA cell exceeds a predefined threshold(s),the RNC starts to hand over certain UEs to other WCDMA cells working inanother frequency or to the GSM system. First, the RNC selects the UEsto be handed over. The preferred target RATor hierarchical WCDMA layerfor each selected UE is determined by combining the Iu interface servicepriority information and the RNC-based service priority information. Next,the RNC starts the inter-frequency and inter-RAT measurements for theselected UEs with normal or modified neighbour cell lists. Finally, theselected UEs are handed over – if possible, according to the measurementresults – to the WCDMA cells and/or to the GSM/GPRS cells which aremost suitable.

Iu interface service priority information provides guidelines for the targetsystem. However, the final decision is made by UTRAN.

Note that load-based handover is partly also a service-based handover,because the service that the UE is using and both RAB-based and RNC-based service priorities are inputs for the procedure.

Load-based inter-frequency and inter-RAT HO/NCCR can be performedalso for the UEs using a packet-scheduled non-real time service.

Service-based handover

Service-based handovers are used to move UEs using certain services tothe GSM/GPRS system or to another WCDMA hierarchical cell layer. TheRNC performs periodical checks in the cell (irrespectively of the load levelof the cell) to see if there are any UEs in connected mode whose servicepriority information received from the Iu interface indicates that “Handoverto GSM should be performed”, or whose RNC-based service priorityhandover profile table indicates that the given UE using a certain serviceprefers the GSM/GPRS system or another WCDMA hierarchical cell layer.Those UEs are candidates for the service-based handover procedure, andan attempt is made to hand them over one by one to the GSM/GPRSsystem or to another WCDMA hierarchical cell layer.


Handover Control

Control of load- and service-based handovers

The use of load- and/or service-based handovers can be defined withRNC configuration parameters (RNC) separately for different servicetypes.

See an example in the following table:

Table 3. Use of load- and service-based handovers according to the servicetype

Service type used by the UE Handover type used

Conversational, Circuit-switched speech For example, Load & Service HO

Conversational, Circuit-switchedtransparent data

For example, Load & Service HO

Conversational, Packet-switched speech For example, Load HO

Conversational, Packet-switched real timedata

For example, Load HO

Streaming, Circuit-switched non-transparent data

For example, Service HO

Streaming, Packet-switched real-time data For example, Service HO

Interactive, Packet-switched non-real timedata

For example, None

Background, Packet-switched non-realtime data

For example, None

The used service type is predefined, and for each of the eight servicetypes, one of the following alternatives can be defined:

. Load & Service HO

. Load HO

. Service HO

. None (neither Service HO nor Load HO is used)

Note

In case of a multiservice, all services must support service-based orload-based handover before they are possible.

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Handover Control

3 Compressed mode

Compressed mode is a radio path feature that enables the UserEquipment (UE) to maintain the current connection on a certain frequencywhile performing measurements on another frequency. This allows the UEto monitor neighbouring cells on another frequency (FDD) or RAT, typicallyGSM. Compressed mode means that transmission and reception arehalted for a short time - a few milliseconds - to perform a measurement onanother frequency or RAT. The required reception/transmission gap isproduced without any loss of DCH user data by compressing the datatransmission in the time domain.

The following methods are used to compress the data transmission:

. Halving the spreading factor

This temporarily doubles the physical channel data rate in the radiochannel. The same amount of data can be sent in half the time itwould normally take. Halving the spreading factor does not affect theDCH user data rate.

. Higher layer scheduling

Higher layer scheduling temporarily reduces the DCH user data ratein the radio channel by restricting the high bit rate transport formatcombinations (TFCs).

The reception/transmission gap always has seven slots. A gap can beplaced within one frame or within two consecutive frames depending onthe compressed mode method. The figure below shows an example oftransmission gaps created with the compressed mode:

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Compressed mode

Figure 6. Example of transmission gaps created with compressed mode

The UE informs the RNC whether or not it requires compressed mode toperform inter-frequency or inter-RAT (GSM) measurements. Compressedmode is activated separately for the uplink and downlink directionsaccording to the measurement capabilities of the UE. The type of receiverthat the UE is equipped with determines the need for downlinkcompressed mode. A UE equipped with a single receiver requiresdownlink compressed mode to perform inter-frequency and GSMmeasurements, whereas a UE equipped with a dual receiver can performthe measurements in question without downlink compressed mode. Theneed for uplink compressed mode depends on whether transmission onthe currently used uplink radio frequency can interfere with downlinkmeasurements on the monitored frequency.

For compressed mode to be possible, it has to be enabled in the RNC; thisis indicated by the RNP parameter Compressed mode master switch(CMmasterSwitch). Furthermore, the capabilities of the UE as well as thefrequency to be monitored also play a role.

When the feature is enabled, the RNC can activate compressed mode forthe purpose of inter-frequency or GSM measurements. Note that, for mostUEs, inter-frequency and inter-RAT (GSM) handovers are only possible ifcompressed mode is used.

UE

WCDMA BTS

Single framegap

Double framegap

Normal frame Normal frame

4 slots 7 slots

11 slots

CM frame

4 slots 7 slots

12 slots7 slots

CM frame CM frame

Normal frame(15 slots)

Normal frame

4 slots 4 slots

CM frame


Handover Control

The method that is employed to compress the data depends on the serviceas follows:

. Halving the spreading factor is used for circuit-switched services,conversational packet-switched data services, streaming packet-switched data services and multi services related to them.

. Higher layer scheduling is used for interactive and backgroundpacket-switched data services and multi services where all theconnections are interactive or background packet-switched dataservices.

. These rules have the following exception: higher layer scheduling isused in case of uplink circuit-switched conversational + interactive/background 256 kbps DCH multi service. In this case SF=4 is usedand it does not allow halving the spreading factor.

The same compressed mode method is used for uplink and downlink radiochannels according to the measurement capabilities of the UE. Thecompressed mode pattern sequence is the same for all measurementpurposes (be it FDD, GSM carrier RSSI or GSM initial BSIC identification).

3.1 Halving the spreading factor

Halving the spreading factor is used for circuit-switched services,conversational packet-switched data services, streaming packet-switcheddata services and multiservices. Halving the spreading factor does notaffect the DCH user data rate, but it does increase the transmission powerof the compressed frames by 3 dB. The transmission power of thecompressed frames is increased to keep the quality (BER /BLER )constant despite the reduced processing gain.

A single frame method is used to halve the spreading factor. Thetransmission gap is seven slots long. As the name of the method implies,the spreading factor (SF) used for the compressed frames is only half ofthat used for normal frames. For example, if the connection would normallyuse SF 128, then SF 64 will be used for compressed frames. The originalspreading code is used for the normal frames between the compressedframes. The following figure shows an example of transmission gapscreated by halving the spreading factor.

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Figure 7. Halving the spreading factor (single frame method)

The Gap position single frame (GapPositionSingleFrame) RNP parametercontrols the position of the transmission gap within the compressed frame.The parameter determines the starting slot of the transmission gap withinthe compressed frame.

Using the single frame method, a transmission gap pattern contains onecompressed frame and at least one normal frame. The total number offrames within the transmission gap pattern is controlled with the RNPparameters listed below. In case of multiservice, the RNC selects theshortest transmission gap pattern length from the applicable parameters.

. Transmission gap pattern length in case of single frame: AMRservice and IF measurement (TGPLsingleframeAMRinterFreg)defines the length of the transmission gap pattern for inter-frequencymeasurements in case of compressed mode with single frame gapand UE using AMR service.

. Transmission gap pattern length in case of single frame: CS serviceand IF measurement (TGPLsingleframeCSinterFreq) defines thelength of the transmission gap pattern for inter-frequencymeasurements in case of compressed mode with single frame gapand UE using circuit-switched data service.

. Transmission gap pattern length in case of single frame: RT PSservice and IF measurement (TGPLsingleframeRTPSinterFreq)defines the length of the transmission gap pattern for inter-frequencymeasurements in case of compressed mode with single frame gapand UE using real-time packet-switched data service.

. Transmission gap pattern length in case of single frame: AMRservice and GSM measurement (TGPLsingleframeAMRgsm)defines the length of the transmission gap pattern for GSMmeasurements in case of compressed mode with single frame gapand UE using AMR service.

Gaps

CM on

SF/2Original SF

CM off


Handover Control

. Transmission gap pattern length in case of single frame: CS serviceand GSM measurement (TGPLsingleframeCSgsm) defines thelength of the transmission gap pattern for GSM measurement incase of compressed mode with single frame gap and UE usingcircuit-switched data service.

. Transmission gap pattern length in case of single frame: RT PSservice and GSM measurement (TGPLsingleframeRTPSgsm)defines the length of the transmission gap pattern for GSMmeasurement in case of compressed mode with single frame gapand UE using real-time packet-switched data service.

If the downlink spreading code to be used for the compressed frames isunavailable (already allocated), an alternative scrambling code can beused. The use of alternative scrambling code makes it possible to allocatethe required spreading code from another, free spreading code tree. Thedisadvantage of using this approach is that the downlink orthogonalitysuffers from the use of an alternative scrambling code and this mayincrease the downlink transmission power level on the carrier in question.The Compressed Mode: Alternative scrambling code(AltScramblingCodeCM) RNP parameter determines whether the use ofan alternative scrambling code is allowed. If the use of an alternativescrambling code is not allowed and the spreading code to be used for thecompressed frame is not available, the RNC is not able to start the inter-frequency or GSM measurements.

3.2 Higher layer scheduling

Higher layer scheduling is used for interactive and background packet-switched data services. It produces the required transmission gaps forinter-frequency and GSM measurements by reducing the DCH user datarate in the radio channel. Higher layer scheduling reduces the DCH userdata rate by restricting high bit rate transport format combinations (TFC).Because the maximum number of bits delivered to the physical layerduring compressed radio frames is known, a transmission gap can begenerated. Higher layer scheduling does not modify the maximum user bitrate of individual DCHs. The following figure shows an example oftransmission gaps created with higher layer scheduling:

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Figure 8. Higher layer scheduling (double frame method)

Higher layer scheduling can use both single and double frame method; thetransmission gap is seven slots long in both cases. The Higher LayerScheduling mode selection (HLSModeSelection) RNP parameterdetermines which of these two compressed mode methods is used.

Note that even if the use of the single frame method is allowed, it may notbe possible to construct a suitable transport format combination set(TFCS) ; in such a case the RNC can use the double frame method. Thefollowing figure describes the selection procedure when the single framemethod is allowed:

Gaps

CM on Certain TFCs are not allowed to use CM off

10 ms

P

t


Handover Control

Figure 9. Selection of the higher layer scheduling mode

Current TFS(s)allows *) doubleframe method?

Possibleto add non-zero

TF(s) to TFS(s) so thatsingle frame method

is possible *)

Possible toadd non-zero TF(s)

to TFS(s) so that double framemethod ispossible *)

Single frame ispossible if non-zeroTF(s) in TFS(s)are not allowed

to use

Double frame method

HLS mode selection

Single frame method

Double frame method

Single frame method

TrCH reconfigurationand single frame method

TrCH reconfigurationand double frame method

Current TFS(s)allows *)

single framemethod?

No

No

No

No

No

Yes

Yes

Yes

Yes

Yes

*) Gap is possible to obtain without restricting

highest allowed TF to zero

Note: RNP parameter HLSModeSelection defineswhether HLS 1/2 is allowed to be used

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One transmission gap pattern consists of one compressed frame and atleast one normal frame when the single frame method is used. When thedouble frame method is used, one transmission gap pattern consists oftwo compressed frames and at least one normal frame. The total numberof frames within the transmission gap pattern is controlled with thefollowing RNP parameters:

. Transmission gap pattern length in case of single frame: NRT PSservice and IF measurement (TGPLsingleframeNRTPSinterFreq)defines the length of the transmission gap pattern for WCDMA inter-frequency measurements in case of compressed mode with singleframe gap and UE using non-real-time packet-switched data service.

. Transmission gap pattern length in case of double frame: NRT PSservice and IF measurement (TGPLdoubleframeNRTPSinterFreq)defines the length of the transmission gap pattern for WCDMA inter-frequency measurements in case of compressed mode with doubleframe gap and UE using non-real-time packet-switched data service.

. Transmission gap pattern length in case of single frame: NRT PSservice and GSM measurement (TGPLsingleframeNRTPSgsm)defines the length of the transmission gap pattern for GSM inter-RATmeasurements in case of compressed mode with single frame gapand UE using non-real-time packet-switched data service.

. Transmission gap pattern length in case of double frame: NRT PSservice and GSM measurement (TGPLdoubleframeNRTPSgsm)defines the length of the transmission gap pattern for GSM inter-RATmeasurements in case of compressed mode with double frame gapand UE using non-real-time packet-switced data service.

When the single frame method is used, the position of the transmissiongap within the compressed frame is controlled with the Gap position singleframe (GapPositionSingleFrame)RNP parameter. The parameterdetermines the starting slot of the transmission gap within the compressedframe. When the double frame method is used, the number of thetransmission gap-starting slot is always eleven.

3.3 Restrictions because of cell capacity

Compressed mode has an effect on the cell capacity, coverage and qualitybecause both the UE and the BTS tend to increase their transmissionpower for compressed frames. To keep this this problem in check, it ispossible to limit the number of UEs in compressed mode on a cell-by-cell


Handover Control

basis. The Compressed Mode: Maximum number of UEs(MaxNumbUECMcoverHO) RNP parameter determines the maximumnumber of UEs that can be in compressed mode at the same time withinthe cell.

If the number of UEs in compressed mode has already reached theallowed maximum, the RNC does not activate compressed mode even if itis needed. As concerns soft handover, the number of UEs in compressedmode must be below the maximum limit in all cells participating in softhandover before the RNC can activate compressed mode. Oncecompressed mode has been activated, to secure the mobility of the UEs, itis possible to add a new cell (soft handover branch) into the active seteven though the number of UEs in compressed mode in the cell inquestion should exceed the maximum.

The RNC also verifies the total received interference power or the totaltransmitted power (depending on the measurement capabilities of the UE)in all active set cells before it activates compressed mode:

. If either the total received interference power or the total transmittedpower exceeds the first overload threshold (PrxTarget +PrxOffset,PtxTarget + PtxOffset), the RNC does not activate compressedmode even if the number of UEs in compressed mode is below themaximum limit. Uplink condition is not considered if the currentuplink DCH own cell load factor LDCH,CELL does not exceed theminimum uplink DCH load threshold value LminDCH,CELL.

. If the total received interference power and the total transmittedpower are below the first overload thresholds but one or the other (orboth) exceed the target level (PrxTarget, PtxTarget) in the cell, theRNC can activate compressed mode only for one UE during theradio resource indication (RRI) interval. Uplink condition is notconsidered if the current uplink DCH own cell-load factor LDCH,CELLdoes not exceed the minimum uplink DCH load threshold valueLminDCH,CELL.

. If the total received interference power and the total transmittedpower in the cell are below the target levels (PrxTarget, PtxTarget),the RNC can activate compressed mode as long as the number ofUEs in compressed mode does not exceed the maximum limit in thecell.

The RNC maintains in each cell the Uplink DCH own cell load factor LDCH,CELL of the DCH users. For more information on how to produce the valueof the LDCH,CELL see Section Estimations for the received throughputand interference in Admission Control.

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LminDCH is the planned minimum uplink DCH own cell load factor; its valueis defined with Interference margin for the minimum UL DCH load(PrxLoadMarginDCH) management parameter. For more information, seeSection Estimations for the received throughput and interference inAdmission Control. The CRNC is allowed to allocate the uplink DCHresources up to this throughput limit without considering the receivedwideband interference.

Note that in the case of HSDPA Dynamic Resource Allocation, if there is atleast one HS-DSCH MAC-d flow allocated in the cell, non-HSPAtransmitted power (Transmitted carrier power of all codes not used for HS-PDSCH, HS-SCCH, E-AGCH, E-RGCH or E-HICH transmission) is usedinstead of total transmitted power. Dynamic target threshold for packetscheduling (PtxTargetPS), which is internally adjusted by the RNC, is usedinstead of PtxTarget. In the case of HSDPA Static Resource AllocationPtxTargetHSDPA and PtxOffsetHSDPA target levels are used instead ofPtxTarget and PtxOffset.

In the case of the dynamic sharing of the received interference betweenthe HSPA and DCH users, if there is at least one E-DCH MAC-d flowestablished in the cell, the PrxNonEDCH measurement and dynamicallyadjusted target threshold PrxTargetPS of the uplink NRT DCH packetscheduling are used instead of PrxTotal and PrxTarget. For moreinformation, see Section Sharing interference between HSPA and NRTDCH users in Radio Resource Management of HSUPA.

When the UE does not need compressed mode in a particular direction(uplink or downlink), the RNC does not verify the load in that directionbecause the measurement does not affect the power budget in question.


Handover Control

4 Macro diversity combining

Keeping the UE connected to more than one BTS at one and the sametime is a waste of system capacity since one connection is in principleenough. However, through a process called Macro Diversity Combining(MDC), the Radio Network Controller (RNC) is able to combine the signalsthat it receives from the UE through different BTSs. Inversely, the RNC canreplicate the downlink signal and send it to the UE over more than oneBTS.

Because the system has the ability to combine a number of uplink datastreams in the RNC, the UE can use less transmission power, whichreduces interference and, consequently, increases capacity. Thisreduction of interference outweighs the capacity wasted by maintainingseveral radio links for the UE. MDC is the best way to enhance thesubjective quality of a call in Wideband Code Division Multiple Access(WCDMA), as the UE is not allowed to simply increase its transmissionpower.

Unless a piece of transmitting equipment is equipped with a smart antennasystem or some functional equivalent, the signals from it propagateomnidirectionally. Typically the radio signal has bounced off variousobstacles in the radio path a number of times before it reaches thereceiver. As a result the receiver is bombarded, over a very short timespan, with a number of components of the same signal, called multipathcomponents. These multipath components were all transmitted at thesame instant, but travelled along different paths (of varying length) beforereaching the receiver.

Multipath propagation may be beneficial or harmful, as the multipathcomponents interfere with each other; sometimes the result is astrengthened signal, sometimes an attenuated one. Graphically, theresultant, received signal contains a number of noticeable spikes. Due tothe high frequencies and consequent short wavelengths used in WCDMARadio Access Network (RAN), even the slightest displacement of the UEhas a great effect on how the multipath components interfere with eachother. Because of this, the signal often experiences so-called fast fading,that is, it is rapidly attenuated only to bounce back an instant later.

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Macro diversity combining

To be able to process the signal under these circumstances, the networkhas to be capable of tracking the fast fading profile of the signal andadjusting the transmission power to compensate. Also, it is a greatadvantage if the same signal can be picked up by a number of receivers,as this increases the likelihood of a continuous, even quality. In WCDMARAN, this is exactly what is done with a process known as macro diversitycombining.

At face value, multipath propagation, and the consequent unreliable signalstrength, would seem to be a big problem. However, with the help ofadvanced digital signal processing WCDMA RAN takes what logicallyseems like a major obstacle and turns it into an advantage. Because itknows the scrambling code, the WCDMA receiver can separate themultipath components over a brief period of time, and compare thecomponents to each other. The only requirement is that the componentsare offset by at least one chip when received.

Since the chip rate is fixed at 3.84Mchips/second in WCDMA RAN, thelength of one chip is always 78 meters (speed of light / chip rate). So,provided that the radio path of one multipath component - or branch - is 78m or more longer than that of another multipath component, the receivercan distinguish the two components as separate signals.

Before the UE transmits any data it has to be split into transport blocks(TB), each of which receives cyclic redundancy check (CRC) error coding.The transport blocks, in turn, become part of a frame, the size of whichdepends on the interleaving length used. Each frame is tagged with aconnection frame number (CFN). In Figure Macro diversity combining,three BTSs receive the signal sent by the UE. Each of these BTSsseparately estimates the quality of the signal that it has received; theWCDMA checks the CRC for each transport block and determineswhether the data in the transport block is reliable or not. Next it makes aquality estimate (QE) for the whole frame, based on the BER of thetransport channel.

If more than one transport block passes the CRC check, the onebelonging to the frame with the highest quality estimate is selected. If twotransport blocks prove to be equally good one of them is selectedrandomly. If none of the transport blocks is OK, the one with the lowestBER is selected. Thus, it is possible, on a transport block-by-transportblock basis, to select the best signal.

In the macro diversity point in the following figure, for example, the signalfrom the UE is collected from three base stations and two RNCs. Thus, theServing Radio Network Controller (SRNC) receives Iub and Iur DedicatedTraffic Channel (DCH) data streams coming from different BTSs and


Handover Control

combines them. After the SRNC there is only one uplink DCH data stream.Similarly, the DCH data stream is split towards the BTSs in the downlink;the signal is transmitted to the UE from three base stations. The UEperforms macro diversity combining on the downlink DCH data streams.

Because of the high frequency used, WCDMA signals vary constantly. Ifthe UE was allowed to connect only to one BTS at a time the quality of thesignal would fluctuate constantly. Because the UE can be, and typically is,connected to two or more BTSs, there is a much greater chance that atleast one of the BTS receives a signal of adequate quality at any one time.Likewise, in the downlink direction, the UE can choose the best of anumber of signals. In the uplink and downlink direction alike the choicetypically varies many times per second.

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Figure 10. Macro diversity combining

Thanks to macro diversity combining, less transmission power can beused, both in the uplink and the downlink. This is directly related to theinherent fluctuating signal strength, which makes the signal equally likelyto be strong or weak. Since the signal is received by two or more BTSs,the same signal travels along different paths yielding completely differentsignal strengths from one BTS to the next.

CFN=3QE=5

TB CRC = NOK

TB CRC = OK

TB CRC = NOK

TB CRC = OK

BTS1

CFN=3QE=4

TB CRC = NOK

TB CRC = OK

TB CRC = NOK

TB CRC = NOK

BTS2

CFN=3QE=4

TB CRC = NOK

TB CRC = NOK

TB CRC = OK

TB CRC = NOK

BTS3

ActiveSet

BTS1

BTS2

BTS3

RNC

RNC

Macro DiversityPoint

CoreNetwork


Handover Control

Consider the scenario exemplified by Figure Handover scenario: branchaddition rejected: At time T1 the UE is connected to BTS10, BTS11 andBTS14. The UE proceeds to a new location and at T2 finds itself withinrange of BTS5, BTS2 and BTS1, of which BTS5 is temporarily overloaded.The strength of the pilot signals from BTS5, BTS2 and BTS1, as measuredby the UE, indicates that BTS5 provides the best signal. The UE relays themeasurement results to the RNC which initiates a branch addition request(for BTS5). Because of the heavy load in the cell admission control rejectsthe request and the RRC connection of the UE is dropped.

The reason for this is that, if the UE had been allowed to connect to BTS5,it could have decreased its transmission power and consequently theamount of interference produced by it. Likewise, if the UE were allowed toconnect to the second-best candidates, BTS1 and BTS2 in this case,BTS1 and BTS2 would have to transmit with unnecessarily high powerlevels. Lastly, the abnormally high transmission powers used in such asituation would further deteriorate the situation in cell BTS5. For thisreason the UE possibly never be connected to the second-best BTS.

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Figure 11. Handover scenario: branch addition rejected

Dropping an RRC connection due to momentary overload is a drasticsolution and is, because of the design of radio resource management, arare event in WCDMA RAN. An RRC connection is dropped only once allother possibilities have been exhausted. The number of possibilities at thenetwork's disposal depends largely on the quality requirements of theservice in question and on the network configuration at the particular placewhere the UE is located. One solution is to hand the connection over toanother carrier frequency or radio access technology (for example GSM).

Optimum cell selection, together with fast closed loop power control,guarantees that the network elements use the lowest possibletransmission power at all times, thus reducing the amount of interferencein the network. This in turn impacts on the quality, capacity and coveragethat the network can offer.

BTS1 BTS2

BTS5 BTS6 BTS7

BTS9 BTS10 BTS11

BTS13 BTS14

Active set:BTS1, 2 - branch to BTS5 rejected

Active set:BTS10, 11 and 14


Handover Control

For a more technical description of the macro diversity combining, seeSection Signal processing in RNC in Signal Processing.

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Handover Control

5 WCDMA frequency bands

The supported FDD frequency bands are WCDMA 2100 (RF band I),WCDMA 1900 (RF band II), WCDMA 1800 (RF band III), WCDMA 1700/2100 (RF band IV), WCDMA 850 (RF band V), WCDMA 900 (RF bandVIII), and WCDMA 1700 (RF band IX). All seven frequency bands supportthe same features, with only one exception: directed emergency call inter-system handover (EMISHO) is supported only in the WCDMA 1900,WCDMA 1700/2100, and WCDMA 850 bands.

The RF band I for WCDMA 2100 is the following:

. Uplink: 1920 MHz – 1980 MHz, UARFCN 9612 – 9888.

. Downlink: 2110 MHz – 2170 MHz, UARFCN 10562 – 10838.

. Duplex distance 190 MHz.

The RF band II for WCDMA 1900 is the following:

. Uplink: 1850 MHz – 1910 MHz, UARFCN 9262 – 9538 andadditional channels 12, 37, 62, 87, 112, 137, 162, 187, 212, 237,262, 287.

. Downlink: 1930 MHz – 1990 MHz, UARFCN 9662 – 9938 andadditional channels 412, 437, 462, 487, 512, 537, 562, 587, 612,637, 662, 687.


The RF band III for WCDMA 1800 is the following:

. Uplink: 1710 MHz – 1785 MHz, UARFCN 937 – 1288

. Downlink: 1805 MHz – 1880 MHz, UARFCN 1162 – 1513

. Duplex distance 95 MHz

The RF band IV for WCDMA 1700/2100 is the following:

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WCDMA frequency bands

. Uplink: 1710 MHz – 1755 MHz, UARFCN 1312 – 1513 andadditional channels 1662, 1687, 1712, 1737, 1762, 1787, 1812,1837, 1862

. Downlink: 2110 MHz – 2155 MHz, UARFCN 1537 – 1738 andadditional channels 1887, 1912, 1937, 1962, 1987, 2012, 2037,2062, 2087


The RF band V for WCDMA 850 is the following:

. Uplink: 824 MHz - 849 MHz, UARFCN 4132 - 4233 and additionalchannels 782, 787, 807, 812, 837, 862.

. Downlink: 869 MHz - 894 MHz, UARFCN 4357 - 4458 and additionalchannels 1007, 1012, 1032, 1037, 1062, 1087.


The RF band VIII for WCDMA 900 is the following:

. Uplink: 880 MHz – 915 MHz, UARFCN 2712 – 2863

. Downlink: 925 MHz – 960 MHz, UARFCN 2937 – 3088


The RF band IX for WCDMA 1700 is the following:

. Uplink: 1749.9 MHz – 1784.9 MHz, UARFCN 8762 – 8912

. Downlink: 1844.9 MHz – 1879.9 MHz, UARFCN 9237 – 9387


The normal channel raster is 200 kHz, which means that in bands I, III,VIII, and IX the center frequency must be an integer multiple of 200 kHz. Inbands II, IV, and V, the normal channel raster can be used, but alsoadditional centre frequencies are specified and the centre frequencies forthese channels are shifted 100 kHz in relation to the normal raster. TableUTRA absolute radio frequency channel numbers defined by 3GPP belowintroduces the channel numbering space according to the centrefrequency of the carriers in bands I, II, III, IV, V, VIII, and IX. These channelnumbers are defined by 3GPP. The allowed channel numbers in USWCDMA 1900, band II, are a subset of these (see UARFCNparameterdescription in WCDMA RAN Parameter Dictionary).


Handover Control

NED?action=retrieve&library=ran_rnc_rel_06_3_0_v3_2008_01_27&identifier=dn00211177&edition=213&language=en&coverage=global&encoding=pdf_online_a4&component=data&item=data

Table 4. UTRA absolute radio frequency channel numbers defined by 3GPP

Frequency band Uplink UE transmit,BTS receive

Downlink UE receive,BTS transmit

RF band I 9612 to 9888 10562 to 10838

RF band II 9262 to 9538 andadditional channels 12, 37,62, 87, 112, 137, 162, 187,212, 237, 262, 287

9662 to 9938 andadditional channels 412,437, 462, 487, 512, 537,562, 587, 612, 637, 662,687

RF band III 937 to 1288 1162 to 1513

RF band IV 1312 to 1513 andadditional channels 1662,1687, 1712, 1737, 1762,1787, 1812, 1837, 1862

1537 to 1738 andadditional channels 1887,1912, 1937, 1962, 1987,2012, 2037, 2062, 2087

RF band V 4132 to 4233 andadditional channels782,787, 807, 812, 837, 862

4357 to 4458 andadditional channels1007,1012, 1032, 1037, 1062,1087

RF band VIII 2712 to 2863 2937 to 3088

RF band IX 8762 to 8912 9237 to 9387

Table Allowed channel numbers of US WCDMA 1900 in band II belowintroduces the allowed channel numbers in each frequency block of USWCDMA 1900 in frequency band II.

Table 5. Allowed channel numbers of US WCDMA 1900 in band II

Uplink Downlink

Block Frequency Allowed channelnumbers

Frequency Allowed channelnumbers

A 1850 - 1865 9263 - 9312, 12, 37, 62 1930 - 1945 9663 - 9712, 412, 437,462

B 1870 - 1885 9363 - 9412, 112, 137,162

1950 - 1965 9763 - 9812, 512, 537,562

C 1895 - 1910 9488 - 9537, 237, 262,287

1975 - 1990 9888 - 9937, 637, 662,687

D 1865 - 1870 87 1945 - 1950 487

E 1885 - 1890 187 1965 - 1970 587

F 1890 - 1895 212 1970 - 1975 612

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The UARFCN RNP parameter defines the downlink channel number andthe carrier frequency of the serving cell, and the AdjiUARFCN RNPparameter defines the downlink channel number and the carrier frequencyof the inter-frequency neighbour cell.

The relation between the UARFCN and the corresponding carrierfrequency [MHz] in the RF bands I, II, III, IV, V, VIII, and IX is defined in thefollowing way:

Uplink: NU = 5 * (FUL – FUL_Offset), for the carrier frequencyrange FUL_low ≤ FUL ≤ FUL_high

Downlink: ND = 5 * (FDL – FDL_Offset), for the carrier frequencyrange FDL_low ≤ FDL ≤ FDL_high

For each operating band, FUL_Offset, FUL_low, FUL_high, FDL_Offset, FDL_low,and FDL_high are defined in Table UARFCN definition (general) below forthe normal 200 kHz channel raster. For the additional UARFCN, FUL_Offset,FDL_Offset and the specific FUL and FDL are defined in Table UARFCNdefinition (additional channels).

Table 6. UARFCN definition (general)

Band UPLINK (UL)

UE transmit, Node B receive

DOWNLINK (DL)

UE receive, Node B transmit

UARFCNformulaoffsetFUL_Offset[MHz]

Carrier frequency (FUL)range [MHz]

UARFCNformulaoffsetFDL_Offset[MHz]

Carrier frequency (FDL)range [MHz]

FUL_low FUL_high FDL_low FDL_high

I 0 1922.4 1977.6 0 2112.4 2167.6

II 0 1852.4 1907.6 0 1932.4 1987.6

III 1525 1712.4 1782.6 1575 1807.4 1877.6

IV 1450 1712.4 1752.6 1805 2112.4 2152.6

V 0 826.4 846.6 0 871.4 891.6

VIII 340 882.4 912.6 340 927.4 957.6

IX 0 1752.4 1782.4 0 1847.4 1877.4


Handover Control

Table 7. UARFCN definition (additional channels)

Band UPLINK (UL)

UE transmit, Node B receive

DOWNLINK (DL)

UE receive, Node B transmit

UARFCNformulaoffsetFUL_Offset[MHz]

Carrier frequency [MHz](FUL)

UARFCNformulaoffsetFDL_Offset[MHz]

Carrier frequency [MHz](FDL)

II 1850.1 1852.5, 1857.5, 1862.5,1867.5, 1872.5, 1877.5,1882.5, 1887.5, 1892.5,1897.5, 1902.5, 1907.5

1850.1 1932.5, 1937.5, 1942.5,1947.5, 1952.5, 1957.5,1962.5, 1967.5, 1972.5,1977.5, 1982.5, 1987.5

IV 1380.1 1712.5, 1717.5, 1722.5,1727.5, 1732.5, 1737.5 1742.5,1747.5, 1752.5

1735.1 2112.5, 2117.5, 2122.5,2127.5, 2132.5, 2137.5,2142.5, 2147.5, 2152.5

V 670.1 826.5, 827.5, 831.5, 832.5,837.5, 842.5

670.1 871.5, 872.5, 876.5, 877.5,882.5, 887.5

The RNC derives the uplink carrier frequency from the downlink carrierfrequency and the duplex distance. The duplex distance is 190 MHz infrequency band I, 80 MHz in frequency band II, 95 MHz in frequency bandIII, 400 MHz in frequency band IV, 45 MHz in frequency band V, 45 MHz infrequency band VIII, and 95 MHz in frequency band IX.

The RNC supports inter-frequency handovers between the WCDMA 900,WCDMA 1800, and WCDMA 2100 frequency bands, between theWCDMA 1700 and WCDMA 2100 frequency bands, and between theWCDMA 850, WCDMA 1700/2100, and WCDMA 1900 frequency bands.The inter-system handovers from the WCDMA 2100, WCDMA 900, andWCDMA 1800 frequency bands to the GSM/EDGE 900 and GSM/EDGE1800 frequency bands and vice versa are supported. The inter-systemhandovers from the WCDMA 850, WCDMA 1700/2100, and WCDMA1900 frequency bands to the GSM/EDGE 850 and GSM/EDGE 1900frequency bands and vice versa are supported as well.

The RNC requests information from the UE about the WCDMA FDDfrequency bands and the GSM frequency bands which the UE supports.

The RNC checks that the UE supports the FDD frequency band, which isused in an inter-frequency neighbour cell before it can select the cell intothe neighbour cell list which is transmitted to the UE for inter-frequencymeasurements. Similarly, the RNC checks that the UE supports the GSMfrequency band, which is used in a GSM neighbour cell before it can selectthe cell into the neighbour cell list which is transmitted to the UE for inter-system measurements.

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Handover Control

6 Directed RRC connection setup

Directed RRC connection setup is a general feature in the RAN. DirectedRRC connection setup provides an efficient way to balance load betweentwo (or more) carrier frequencies within one base station. The RNCbalances the load by establishing the RRC connection on the carrierfrequency (cell) which has less load.

The prerequisite for the directed RRC connection setup procedure is thatthe cells involved belong to the same sector of the base station. TheSector Identifier (SectorID) parameter uniquely identifies the sector of thebase station a cell belongs to. Two (or more) cells can belong to the samesector if they have equal coverage areas. The coverage areas can beconsidered as equal if the cells have identical values for the followingparameters (the RNC is not able to check whether the antenna beams ofthe cells are directed equally):

. Transmission power of the primary CPICH channel(PtxPrimaryCPICH )

. Offset of the P-CPICH and reference service powers(CPICHtoRefRABoffset)

. PLMN code (MCC + MNC)

For a description of the parameters, see WCDMA RAN ParameterDictionary.

The UE initiates the RRC connection setup procedure in the cell on whichit camped in idle mode (that is, source cell). The RNC can direct the RRCconnection setup request to another (target) cell within the same sector ifthe target cell has less load than the source cell. The decision procedure iscontrolled with the following parameters:

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Directed RRC connection setup



. Prx Offset for DRRC (DRRCprxOffset) determines the thresholdlevel which the total received wideband interference power (uplinkload) in the source cell must exceed before the RNC may direct theRRC connection setup to another cell within the sector.

. Ptx Offset for DRRC (DRRCptxOffset) determines the thresholdlevel which the total transmitted power (downlink load) in the sourcecell must exceed before the RNC can direct the RRC connectionsetup to another cell within the sector.

. Prx Margin for DRRC (DRRCprxMargin) determines the margin bywhich the uplink load of the source cell must exceed the uplink loadof the target cell before the RNC can direct the RRC connectionsetup to the target cell.

. Ptx Margin for DRRC (DRRCptxMargin) determines the margin bywhich the downlink load of the source cell must exceed the downlinkload of the target cell before the RNC can direct the RRC connectionsetup to the target cell.

In addition to the received wideband interference, the uplink load is alsomeasured in the DCH throughput domain. RNC maintains in each cell theUplink DCH own cell load factor LDCH,CELL of the DCH users; how toproduce the value of the LDCH,CELL see Section Estimations for thereceived throughput and interference in Admission Control. The value ofthe load factor in the target cell(n) is denoted with LDCH,CELL (n).

A particular uplink DCH own- cell load threshold LDRRC is defined in thethroughput domain for the needs of the DRRC with the equation

Figure 12. Definition of uplink DCH own-cell load threshold LDRRC

Quantity Ptarget+DRRC is the linear value of the sum of the dB-values of thePrxTarget and DRRCprxOffset management parameters. Uplink own cellDCH threshold LDRCC(n) is defined with the similar equation in the targetcell(n).

LminDCH is the planned minimum uplink DCH own cell load factor; its valueis defined with Section Interference margin for the minimum UL DCH load(PrxLoadMarginDCH) management parameter. For more information, seethe Estimations for the received throughput and interference in Admission

LDRRC = MAX 0, MIN 1-1

Ptarget + DRRC

, LminDCH


Handover Control

Control. The CRNC is allowed to allocate the uplink DCH resources up tothis throughput limit without considering the received widebandinterference. LminDCH(n) denotes the value of the threshold in the target cell(n).

The RNC uses also a planned maximum uplink DCH own cell load factorLmaxDCH in its uplink DCH resource allocation. The value of the load factorLDCH,CELL does not exceed the value of LmaxDCH. Interference margin forthe maximum UL DCH load (PrxLoadMarginMaxDCH) managementparameter defines the value of defines the value of LmaxDCH. For moreinformation, see Section Estimations for the received throughput andinterference in Admission Control. The value of the threshold in the targetcell(n) is denoted with LmaxDCH(n)

When either the uplink load or the downlink load in the source cell exceedsthe relevant threshold level, as defined by the following equations, theRNC examines the difference in loading between the source cell and thetarget cell (or cells):

(50) SourceCellPrxTotal > PrxTarget + DRRCprxOffset AND LDCH,CELL >LDRRC

(51) SourceCellPtxTotal > PtxTarget + DRRCptxOffset

(52) LDCH,CELL > LmaxDCH · lin(DRRCprxOffset)

Quantity lin(DRRCprxOffset) is the value of the DRRCprxOffset parameterin the linear notation.

The RNC examines the differences in loading between the source cell andthe target cell(n) by means of the following conditions:

(53) [SourceCellPrxTotal - PrxTarget > TargetCellPrxTotal(n) - PrxTarget(n)- DRRCprxMargin(n)] OR [LDCH,CELL(n) < LDRRC(n)]

(54) SourceCellPtxTotal - PtxTarget > TargetCellPtxTotal(n) - PtxTarget(n)- DRRCptxMargin(n)

(55) LDCH,CELL/LmaxDCH > LDCH,CELL(n) / LmaxDCH(n)·lin(DRRCptxMargin(n))

(56) [(TargetCellPrxTotal(n) < PrxTarget(n) + DRRCprxOffset(n)) OR(LDCH,CELL (n) ≤ LDRRC(n))] AND [LDCH,CELL(n) < LmaxDCH(n)·lin(DRRCptxMargin(n))]

(57) TargetCellPtxTotal(n) < PtxTarget(n) + DRRCptxOffset(n)

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The measurement results in the equations are defined as follows:

. SourceCellPrxTotal is the total received wideband interferencepower in the source cell.

. SourceCellPtxTotal is the total transmitted power in the source cell.

. TargetCellPrxTotal(n) is the total received wideband interferencepower in the target cell(n).

. TargetCellPtxTotal(n) is the total transmitted power in the target cell(n).

Quantity lin(DRRCptxMargin) is the value of the DRRCptxMarginparameter in the linear notation.

Cell(n), which belongs to the same sector as the source cell, can be takenas the target cell of the DRRC attempt, if the equations (53), (54), (55), (56)and (57) are satisfied as described in the table below. Column CHECK INTARGET CELL(n) of the table shows what must be checked. Checkingsare done depending on the triggers conditions (50) , (51) and (52). Targetcell check aims at preventing the source cell become the new target cell ofthe target cell(n) in DRRC.

Table 8 Triggers of DRRC and checkings in the target cell

THRESHOLD EXCEEDED INCURRENT CELL

CHECK IN TARGET CEL(n)

>ULthreshold(50)

>DLthreshold(51)

> loadfactoroverloadthreshold(52)

>ULmargin(53)

>DLmargin(54)

>loadfactormargin(55)

<ULthreshold(56)

<DLthreshold(57)

TRUE FALSE FALSE TRUE - - - TRUE

FALSE FALSE TRUE - - TRUE TRUE TRUE

FALSE TRUE FALSE - TRUE - TRUE -

TRUE TRUE TRUE/FALSE

TRUE TRUE - - -

FALSE TRUE TRUE - TRUE TRUE TRUE -

TRUE FALSE TRUE TRUE - TRUE - TRUE

TRUE means that the condition is true, FALSE means that the condition isnot true, '-' means that the condition is not applicable.


Handover Control

If the target cell(n) passes the checkings, the RRC connection isestablished in the target cell(n) if the admission decision is successful in it.If none of the cells which belong to the same sector as the current cellsatisfy the needed equations (53), (54), (55), (56) and (57) or theadmission decision does not succeed in the target cell, RNC does theadmission decision in the source cell.

When the HSUPA configuration has been set up in a cell as specified inthe HSUPA.01 of [25], average PrxNonEDPCH value and PrxTargetPSMax,which is the maximum allowed value for dynamically adjustedPrx_target_PS threshold, is used instead of PrxTotal and PrxTarget in theload-based HO (HC.120) and Directed RRC connection setup algorithms(HC.171). Production of PrxNonEDPCH and maximum thresholdPrxTargetPSMax are defined in HSUPA.130 and HSUPA.131 [25].

Note that in the case of the dynamic sharing of the received interferencebetween the HSPA and DCH users, if there is at least one E-DCH MAC-dflow established in the cell at issue, the non-E-DCH interference powerPrxNonEDCH value is used in the cell instead of total receivedinterference power PrxTotaI in the interference based decisions.Furthermore, the maximum value of the dynamic target threshold for uplinkDCH packet scheduling, defined by the operator adjustablePrxTargetPSMax management parameter, is used as the interferencethreshold instead of the PrxTarget. For more information, see RadioResource Management of HSUPA.

Note that in the case of HSDPA Dynamic Resource Allocation, if there is atleast one HS-DSCH MAC-d flow allocated in the cell, non-HSPAtransmitted power (Transmitted carrier power of all codes not used for HS-PDSCH, HS-SCCH, E-AGCH, E-RGCH or E-HICH transmission) is usedinstead of total transmitted power. The maximum value of the dynamictarget threshold for the downlink DCH packet scheduling, defined by theoperator adjustable PtxTargetPSMax management parameter, is usedinstead of PtxTarget. In the case of HSDPA Static Resource AllocationPtxTargetHSDPA and PtxOffsetHSDPA target levels are used instead ofPtxTarget and PtxOffset.

If loading in the source cell do not exceed the relevant thresholds, or thedifference in loading between the source cell and the target cell (or cells) isnot sufficient, the RNC continues the RRC connection setup procedure inthe source cell.

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Figure 13. Principle of directed RRC connection setup

For more information, see Section Call setup and release in Call setup andrelease and Section Radio resource management functions in PacketScheduler.

UTRANUE

Cell1_load > Cell2_load + load_threshold===> Directed RRC connection setup

Frequency 1

Frequency 2

RRC CONNECTION REQUEST

RRC CONNECTION SETUP

RRC CONNECTION SETUP COMPLETE


Handover Control

7 Directed RRC connection set-up forHSDPA layer

Directed RRC connection setup for HSDPA layer feature is meant formultilayer networks where High Speed Downlink Packet Access (HSDPA)is supported in some layer(s) (carrier frequency). The primary target of thisfeature is to direct HSDPA capable UEs to the cell that supports HSDPA.On the other hand, non-HSDPA UE is removed from HSDPA layer(s). Ifseveral HSDPA capable layers exist, the HSDPA load balancing betweenthese layers is used.

Figure 14. Principles of directed RRC connection setup for HSDPA layer

The signalling flow is identical to the Directed RRC connection setupfeature and it is presented in Figure Signalling of directed RRC connectionsetup for HSDPA layerbelow. Likewise, the prerequisite for the directedRRC connection setup for HSDPA layer is that the cells involved belong tothe same sector of the base station. The Sector Identifier (SectorID)parameter uniquely identifies the sector of the base station a cell belongsto. Two cells can belong to the same sector if they have equal coverageareas. The coverage areas can be considered as equal if the cells haveidentical values for the following parameters (The RNC is not able to checkwhether the antenna beams of the cells are directed equally.):

f2, HSDPA + Rel’99

f1, Rel’99

Rel’99 and Rel-4 UEand Rel-6 or newer

non-HSDPA capable UE

Rel-5 UEand Rel-6 or newerHSDPA capable UE

abc def

mnojklghi

pqrs tuv wxyz

+

abc def

mnojklghi

pqrs tuv wxyz

+

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Directed RRC connection set-up for HSDPA layer




Figure 15. Signalling of directed RRC connection setup for HSDPA layer

The UE initiates the RRC connection setup procedure in the cell on whichit camped in idle mode (that is, source cell). When UE initiates the RRCconnection setup it indicates 3GPP release (that is, Rel-4, Rel-5, Rel-6,...)it supports (access stratum release indicator IE ) and Rel-6 UE indicates ifit supports HSDPA and HSUPA (UE capability indication IE). According tothat information RNC directs the UE to the other (layer) cell within thesame sector if needed. If the UE is already on the right layer, the RRCconnection is established in the current cell.

The usage of the Directed RRC connection setup for HSDPA layer featureis controlled with the DirectedRRCForHSDPAEnabled managementparameter.

UTRANUE

Directed RRC connection setup forHSDPA layer

Frequency 1

Frequency 2

RRC CONNECTION REQUEST

RRC CONNECTION SETUP

RRC CONNECTION SETUP COMPLETE


Handover Control

7.1 Basic functionality

DirectedRRCForHSDPALayerEnhanc parameter defines if improvementsdone with HSDPA layering for UEs in common channels feature areactivated or not. If the parameter is disabled, the Directed RRC connectionsetup for HSDPA layer works as described in this section.

3GPP release 5 or newer UE is directed from non-HSDPA supporting cellto the cell, which supports HSDPA (controlled by the managementparameter HSDPA enabled). 3GPP release 99 or release 4 UE is directedfrom HSDPA supporting cell to the cell, which does not support HSDPA.Load of target cell is not taken into account.

The Directed RRC connection setup for HSDPA layer cannot be usedsimultaneously in the cell with the Directed RRC connection setup feature.The Directed RRC connection setup would move also potential HSDPAusers away from HSDPA supporting cell.

When the Directed RRC connection setup for HSDPA layer is used, themaximum number of cells (layers) in one sector of the base station thatcan be configured, is two. If three-layer network is used one of the DCHlayers (not supporting HSDPA) has to have different Sector Identifier inbase station than in layers (DCH layer and HSDPA layer) where theDirected RRC connection setup for HSDPA layer is supported.

7.2 Enhanced functionality

DirectedRRCForHSDPALayerEnhanc parameter defines if improvementsdone with HSDPA layering for UEs in common channels feature areactivated or not. If the DirectedRRCForHSDPALayerEnhanc parameter isenabled, the Directed RRC connection setup for HSDPA layer works asdescribed in this section.

7.2.1 Decision of layer change

If the RNC decides, it needs a layer change, it is based on the followinginformation:

. 3GPP release that UE supports (Rel-4, Rel-5, Rel-6,…) (accessstratum release indicator IE )

. HSDPA and HSUPA capability of the UE (UE capability indicationIE). Only Rel-6 and newer UEs indicate this.

. The service UE is going to use based on the establishment cause(Establishment cause IE).

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. The services are defined with the DRRCForHSDPALayerServicesparameter. (These are directed to HSDPA layer.)

. HSDPA and HSUPA capability of the source cell and the cells in thesame sector under same BTS.

Note that layer changes are not done for emergency calls.

Non HSDPA UE

The UE is interpreted as non-HSDPA capable if it is Release 99 capable(no release indicated in access stratum release indicator IE) or Release 4capable. In the case of release 6 or newer UE, it is interpreted to be non-HSDPA capable if it does not indicate HSDPA capability.

These non-HSDPA capable UEs are directed away from the HSDPAcapable cell if DirectedRRCForHSDPAEnabled is enabled in the cell, thethe non-HSDPA capable cell is in the same sector and the load of thetarget cell is not too big; target cell load shall satisfy the conditions (56) and(57) introduced in Section Directed RRC connection setup. The idea is notto direct the UE to the layer in which the load is so big that it can trigger theDirected RRC connection setup to the source cell.

HSDPA capable UE

The UE is interpreted as HSDPA capable if it is Release 6 capable ornewer and it indicates HSDPA capability. Also UE indicating Release 5capability is interpreted to be HSDPA capable.

These HSDPA capable UEs are directed from the non-HSDPA capablecell to the HSDPA capable cell if DirectedRRCForHSDPAEnabled isenabled in the source cell, establishment cause indicated by the UE isactivated with DRRCForHSDPALayerServices parameter, the HSDPAcapable cell is in the same sector and the HSDPA load of the target cell isnot too big (the maximum number of HS-DSCH users reached). If severalcandidates exist the HSDPA load balancing is applied as described in thenext section.

These HSDPA capable UEs can be directed from HSDPA capable cell toother HSDPA capable cell for load balancing reasons ifDirectedRRCForHSDPAEnabled is enabled in source cell, establishmentcause indicated by the UE is activated withDRRCForHSDPALayerServices parameter, HSDPA capable cell is insame sector and the HSDPA load of the target cell is suitable (see nextchapter). HSDPA load balancing is described in next section.


Handover Control

HSUPA capable UE

UE is interpreted as HSUPA capable if it is Release 6 capable or newerand it indicates HSDPA and HSUPA capability.

HSUPA capable UE is also HSDPA capable and the decision goes as forHSDPA capable UE with the following exception. HSUPA capable UE isdirected to the HSUPA capable cell if it is possible. The HSUPA capableUE is not directed away from the HSUPA capable cell.

HSDPA load balancing

HSDPA load balancing is used when there are two or more layers thatsupport the HSDPA. The idea is to ensure efficient usage of the HSDPAresources. When there are only a few users, it is more efficient to havethem in the same layer. That is why there is a threshold parameter calledHSDPALayerLoadShareThreshold. This defines the number of UEs afterwhich the load balancing starts. Below this threshold the UEs are directedto the same layer. Above this threshold the UEs are directed so that theavailable HSDPA power per user is as equal as possible between differentlayers.

There is also the operator parameter calledCellWeightForHSDPALayering, which is used to direct more HSDPA UEsto some layer. Relatively bigger value in one cell compared to other cells inthe same sector directs more HSDPA UEs to that cell. This can be used if,for example, cell1 in frequency f1 has 5 HSDPA codes available and cell2in frequency f2 has 15 HSDPA codes available (both are in the samesector). If we now give bigger weight value for cell2 than for cell1, we getmore HSDPA users to cell2 and use HSDPA codes more efficiently.

When the number of UEs in every cell in the sector is under the thresholdHSDPALayerLoadShareThreshold, the cell whichCellWeightForHSDPALayering has biggest value is chosen. If those areequal, the cell which has most of the UEs is selected.

When the number of UEs in every cell in the sector is above the thresholdHSDPALayerLoadShareThreshold,the cell which gives the best HSDPApower per user is selected. HSDPA power per user is calculated using thefollowing equation.

Figure 16. Calculation of HSDPA power per user

HSDPApowerPerUser =(PMax-PtxNonHSPA) x CellWeightForHSDPALayering

NumberOfHSDPAusers + 1

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PMax [W] is the maximum transmission power in the BTS. PtxNonHSPA[W] is the transmitted carrier power of all codes not used for HS-PDSCH,HS-SCCH, E-AGCH, E-RGCH or E-HICH transmission. It is averaged.CellWeightForHSDPALayering is the weight value for the cell as describedabove. NumberOfHSDPAusers is number of HS-DSCH allocations in thecell currently.

HSDPApowerPerUser (watts/user) is calculated to every candidate cell.The cell which has the highest value (the users get potentially the highestthroughput in this cell) is selected.

If we do not want to use available HSDPA power in the selection, but wewant to distribute the users between the cells in some ratio, theDisablePowerInHSDPALayeringDecision parameter can be used. If theusage of power is disabled with this parameter, the following equation isused in decision making.

Figure 17. Calculation of HSDPA power per user without HSDPA power

HSDPAcellWeightPerUser is calculated to every candidate cell and thecell which has the highest value is selected.

Note also that, if the maximum number of HSPDA users is reached in acell, that cell is not selected.

Layer selection examples

The following examples illustrate layer selection.

Example 1: UE establishing RRC connection in non-HSDPA capablelayer.

HSDPAcellWeightPerUser =CellWeightForHSDPALayering

NumberOfHSDPAusers + 1


Handover Control

Figure 18. Example of layer selection in RRC connection setup phase in non-HSDPA layer

The layer selection algorithm goes in the following steps. When the layercan be selected in any of the steps 1 – 4, the other steps are ignored.

1. According to UE HSDPA capability against cells HSDPA capability(f1). UE A -> current layer (f1) is selected. UEs B and C -> check f2 and f3 2

2. According to service against parameterization. UEs B and C if

Establishment cause IE ≠ DRRCForHSDPALayerServices(parameter) -> current layer (f1) is selected

. UEs B and C if

Establishment cause IE = DRRCForHSDPALayerServices(parameter) -> check f2 & f3

UE reporting Rel-6HSDPA & HSUPA capability

UE reporting Rel5 orRel-6 & HSDPA capability

Any other UE

C

B

A

f3, HSDPA&HSUPA

f2, HSDPA

f1, R’99

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3. According to UE HSPA capability against cells HSPA capability (f2and f3). UE B -> check f2 and f3. UE C -> f3 is selected

4. Better available HSDPA throughput. UE B: f2 or f3 is selected

Example 2: UE establishing RRC connection in HSDPA capable layer.

Figure 19. Example of layer selection in RRC connection setup phase inHSDPA layer

The layer selection algorithm goes in the following steps. When the layercan be selected in any of the steps 1 – 4, the other steps are ignored.

1. According to UE HSDPA capability against cells HSDPA capability(f2/f3). UE A -> f1 is selected. UEs B and C -> check f2 and f3

UE reporting Rel-6HSDPA & HSUPA capability

UE reporting Rel5 orRel-6 & HSDPA capability

Any other UE

C

B

A

f3, HSDPA&HSUPA

f2, HSDPA

f1, R’99


Handover Control

2. According to service against parameterisation. UEs B and C if

Establishment cause IE ≠ DRRCForHSDPALayerServices(parameter) -> current layer (f2/f3) is selected

. UEs B and C if

Establishment cause IE = DRRCForHSDPALayerServices(parameter) -> check f2 & f3

3. According to UE HSPA capability against cells HSPA capability (f2and f3). UE B -> check f2 and f3. UE C -> f3 is selected

4. Better available HSDPA throughput. UE B: f2 or f3 is selected

7.2.4 Interaction with directed RRC connection setup

When the Directed RRC connection setup is enabled (handle withDirectedRRCEnabled parameter) simultaneously with Directed RRCconnection setup for the HSDPA layer feature (handle withDirectedRRCForHSDPAEnabled parameter), the decision making goes inthe following order.

. First the decision of Directed RRC connection setup for the HSDPAlayer is done. If the layer is decided to change, the UE is directed tonew layer. If the layer is decided not to change, the decision makingfor the Directed RRC connection setup can be done.

. If the UE is interpreted as HSDPA capable in the HSDPA capablecell and it requests interactive or background service, the DirectedRRC connection setup feature does not move the UE to the non-HSDPA capable cell.

. If the UE is interpreted as HSDPA capable in the non-HSDPAcapable cell and the load in source cell is big enough to trigger theDirected RRC connection setup feature, the HSDPA capable targetcell is selected if possible.

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Handover Control

8 HSPA layering for UEs in commonchannels

HSPA layering for UEs in common channels feature is meant for multilayer networks where high speed downlink packet access (HSDPA) issupported in some layer(s) (carrier frequency). The primary target of thisfeature is to direct the HSDPA UE to the cell that supports HSDPA. On theother hand non-HSDPA UE is removed from HSDPA layer(s). If severalHSDPA capable layers exist, the HSDPA load balancing between theselayers is used used. This feature is intended to be used together with theDirected RRC connection setup for the HSDPA feature as theycomplement each others.

The layer change in HSPA layering for UEs in common channels is doneinside the sector belonging to the same base station just like for theDirected RRC connection setup for the HSDPA layer. From this follows thesame prerequisite that the cells involved must have same sector identifier(defined with the SectorID parameter). Two cells can belong to the samesector if they have equal coverage areas. The coverage areas can beconsidered as equal if the cells have identical values for the followingparameters (The RNC is not able to check whether or not the antennabeams of the cells are directed equally.):


. Offset of the P-CPICH and reference service powers(CPICHtoRefRABoffset)


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HSPA layering for UEs in common channels

Figure 20. Signalling of HSPA layering for UEs in common channels

HSPA layering for UEs in common channel feature directs the UE toanother layer in state transition from Cell_FACH to Cell_DCH, if it isneeded. The HSDPA capable UE is directed to the HSDPA layer and thenon-HSDPA capable UE is directed away from the HSDPA layer. If UE isdirected to another layer the new frequency is indicated in Frequency infoIE in the Radio Bearer Reconfiguration message to it.

UE RNCBTS

UE is in CELL_FACH or CELL_PCH state

UE is in CELL_DCH state

RRC:Measurement Report

RRC:Radio Bearer Reconfiguration

(Frequency Info)

RRC: Radio BearerReconfiguration Complete

UL capacity need isdetected by MAC

(AND/OR)

Frequency layer / cell selectionand capacity allocation

DL capacity need is detectedby MAC or RAB Assignment

Request from CS core

UE moves to CELL_DCH stateand to new frequency

RLC parameters needto be changed

NBAP Radio Link Setup procedure


Handover Control

The usage of HSPA layering for UEs in common channels feature iscontrolled with the HSDPALayeringCommonChEnabled managementparameter.

8.1 Decision of layer change

The RNC decides if layer change is needed based on the followinginformation:

. HSDPA and HSUPA capability of the UE.

. RAB type which is going to be established (CS/PS).

. The services (CS/PS) defined with ServicesToHSDPALayerparameter.(These are directed to HSDPA layer.)

. HSDPA and HSUPA capability of the source cell and the cells in thesame sector under the same BTS.

Note that layer changes are not done for emergency calls.

The Non HSDPA UE

The Non-HSDPA capable UEs are directed away from the HSDPAcapable cell if HSDPALayeringCommonChEnabled is enabled in the cell,the non-HSDPA capable cell is in the same sector and the load of thetarget cell is not too big. The idea is not to direct the UE to a layer in whichthe load is so big that it can trigger the Directed RRC connection setup tothe source cell.

The HSDPA capable UE

The HSDPA capable UEs are directed from the non-HSDPA capable cellto the HSDPA capable cell if HSDPALayeringCommonChEnabled isenabled in the source cell, operation is allowed for RAB type (CS/PS)defined with ServicesToHSDPALayer parameter, the HSDPA capable cellis in the same sector and the HSDPA load of the target cell is not too big(the maximum number of HS-DSCH users is reached). If severalcandidates exists the HSDPA load balancing is applied as described in thefollowing section.

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HSPA layering for UEs in common channels

The HSDPA capable UEs can be directed from the HSDPA capable cell toanother HSDPA capable cell for load balancing reasons ifHSDPALayeringCommonChEnabled is enabled in the source cell, the UEis requesting interactive or background service, the HSDPA capable cell isin the same sector and the HSDPA load of the target cell is suitable (seethe next section). For more information on HSDPA load balancing, seeSection HSDPA load balancing.

The HSUPA capable UE

The HSUPA capable UE is also HSDPA capable and the decision goes asfor the HSDPA capable UE with the following exception. The HSUPAcapable UE is directed to the HSUPA capable cell if it is possible. TheHSUPA capable UE is not directed away from the HSUPA capable cell.

8.2 HSDPA load balancing

HSDPA load balancing is identical for HSPA layering for UEs in commonchannels and the Directed RRC connection setup for HSDPA layerfeatures. For more information see description under the Directed RRCconnection setup for HSDPA layer.


Handover Control

9 Functionality of intra-frequencyhandover

Intra-frequency handovers can be soft or hard handovers. The vastmajority of intra-frequency handovers in the Wideband Code DivisionMultiple Access (WCDMA) radio access network are soft handovers. Thefollowing sections describe the algorithms involved in intra-frequency softand hard handover. For the signalling procedures involved, see SectionsSoft handover signalling and Intra-frequency hard handover signalling.

9.1 Functionality of soft handover

The handover decision algorithm of the Radio Network Controller (RNC)for intra-frequency handover is based on the event-triggered measurementreports. When in active mode, the 3G User Equipment (UE) continuouslymeasures the Common Pilot Channel (CPICH) of the serving andneighbouring cells (indicated by the RNC) on the current carrier frequency.The measurement quantity is CPICH Ec/No (received energy per chipdivided by the power density in the band, that is, CPICH RSCP/UTRACarrier RSSI). The UE compares the measurement results with handoverthresholds, which have been provided by the RNC, and sends ameasurement report to the RNC when the handover thresholds arefulfilled.

Based on the measurement report, the RNC orders the UE to add, replaceor remove cells from its active set, that is, the set of cells participating insoft handover. The RNC limits the number of cells participating in softhandover. The maximum size of the active set is three cells. The handoverdecision algorithm of the RNC is fairly straightforward for soft (and softer)handover: the algorithm accepts practically everything the UE suggestsaccording to the measurement reporting events.

The handover control of the RNC contains the following measurementreporting events and mechanisms for modifying measurement reportingbehaviour:

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Functionality of intra-frequency handover

. reporting event 1A for adding cells to the active set

. reporting event 1B for deleting cells from the active set

. reporting event 1C for replacing cells in the active set

. event-triggered periodic intra-frequency measurement reporting

. time-to-trigger mechanism for modifying measurement reportingbehaviour

. cell individual offsets for modifying measurement reportingbehaviour

. mechanism for forbidding a cell to affect the reporting range

. reporting events 6F and 6G for deleting cells from the active set

Note

The admission control of the RNC may overrule the handover algorithmdecision due to capacity reasons. For more information, see SectionsRadio resource management functions and Function in abnormalconditions.

9.1.1 Reporting event 1A for adding cells to the active set

Reporting event 1A is controlled with the following parameters:

. Active Set Weighting Coefficient (ActiveSetWeightingCoefficient)

. Addition Time (AdditionTime)

. Addition Window (AdditionWindow).

. CPICH Ec/No Offset (AdjsEcNoOffset)

. Maximum Active Set Size (MaxActiveSetSize)


Reporting event 1A is used for adding cells in the active set. The UE sendsthe event 1A-triggered measurement report when a cell enters thereporting range as defined by the following formula:


Handover Control



Figure 21. Formula for calculating the UE measurement report on event 1A

The variables in the formula are defined as follows:

Table 8. Variables for measurement report on event 1A

Variable Description

MNew Measurement result of the cell enteringthe reporting range

Mi Measurement result of a cell in the activeset, not forbidden to affect the reportingrange

NA Number of cells not forbidden to affect thereporting range in the current active set

MBest Measurement result of the strongest cellin the active set, not forbidden to affectthe reporting range and not taking intoaccount any cell individual offset

W Active Set Weighting Coefficient(ActiveSetWeightingCoefficient) parametersent from the RNC to the UE

R Addition Window (AdditionWindow)parameter sent from the RNC to the UE

H1a Hysteresis, which is zero for event 1A

CIOnew CPICH Ec/No Offset (AdjsEcNoOffset)parameter of the neighbour cell enteringthe reporting range

A time-to-trigger mechanism can be used to modify the measurementreporting behaviour of event 1A. If the time-to-trigger mechanism is used,the cell must continuously stay within the reporting range for a given periodof time before the UE can send the event 1A-triggered measurementreport to the RNC. The length of this period is controlled by the RNPparameter Addition Time (AdditionTime).

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9.1.2 Reporting event 1B for deleting cells from the active set

Reporting event 1B is controlled with the following parameters:

. Active Set Weighting Coefficient (ActiveSetWeightingCoefficient)

. Drop Time (DropTime)

. Drop Window (DropWindow)



Reporting event 1B is used for deleting cells in the active set. The UEsends the event 1B-triggered measurement report when a cell leaves thereporting range as defined by the following formula:

Figure 22. Formula for calculating the UE measurement report on event 1B

The variables in the formula are defined as follows:

Table 9. Variables for measurement report on event 1B


MOld Measurement result of the cell leaving thereporting range

Mi Measurement result of a cell in the activeset, not forbidden to affect the reportingrange

NA Number of cells not forbidden to affect thereporting range in the current active set

MBest Measurement result of the strongest cellin the active set, not forbidden to affectthe reporting range and not taking intoaccount any cell individual offset.


Handover Control



Table 9. Variables for measurement report on event 1B (cont.)


W Active Set Weighting Coefficient(ActiveSetWeightingCoefficient) parametersent from RNC to UE

R Drop Window (DropWindow) parametersent from RNC to UE

H1b Hysteresis, which is zero for the event 1B

CIOnew CPICH Ec/No Offset (AdjsEcNoOffset)parameterof the neighbour cell enteringthe reporting range

A time-to-trigger mechanism can be used to modify the measurementreporting behaviour of event 1B. If the time-to-trigger mechanism is used,the cell must continuously stay outside the reporting range for a givenperiod of time before the UE can send the event 1B-triggeredmeasurement report to the RNC. The length of this period is controlled bytheDrop Time (DropTime) RNP parameter.

Note

The RNC does not remove a cell from the active set if it is the only cellin the active set which has uplink physical layer synchronisation.

9.1.3 Reporting event 1C for replacing cells in the active set

Reporting event 1C is controlled with the following parameters:

. Maximum Active Set Size (MaxActiveSetSize)

. Replacement Time (ReplacementTime)

. Replacement Window (ReplacementWindow).



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Reporting event 1C is used for replacing cells in the active set. The UEsends the event 1C-triggered measurement report when the number ofcells in the active set is equal to the Maximum Active Set Size(MaxActiveSetSize) parameter and a cell that is not included in the activeset becomes better than a cell in the active set as defined by the followingformula:

Figure 23. Formula for calculating the UE measurement report on event 1C

Table 10. Variables for measurement report on event 1C


MNew Measurement result of the cell notincluded in the active set

MInAS Measurement result of a cell in the activeset which has the lowest measurementresult in the active set

H1c Replacement window parameter sent fromthe RNC to the UE

CIONew CPICH Ec/No Offset (AdjsEcNoOffset)parameter of the cell not included in theactive set

CIOinAS CPICH Ec/No Offset (AdjsEcNoOffset)parameter of the cell in the active set

In the following figure, cells 1, 2 and 3 are in the active set, but cell 4 is not(yet) in the active set.


Handover Control

Figure 24. A cell that is not in the active set becomes better than a cell in a fullactive set

A time-to-trigger mechanism can be used to modify the measurementreporting behaviour of event 1C. If the time-to-trigger mechanism is used,the cell must continuously stay within the triggering condition for a givenperiod of time before the UE can send the event 1C-triggeredmeasurement report to the RNC. The length of this period is controlled bythe Replacement Time (ReplacementTime)RNP parameter.

The cell (not included in the active set) leaves the triggering condition if itagain becomes worse than the cells in the active set as defined by thefollowing formula:

Figure 25. Formula for calculating the UE measurement report on event 1C

Note

The RNC does not replace a cell in the active set if it is the only cell inthe active set which has uplink physical layer synchronisation.

MeasurementquantityCPICH Ec/No CELL 1

CELL 2

CELL 3

CELL 4

Replacement Window

Reportingevent 1C

Time

10 LogMNew + CIONew < 10 LogMInAS + CIOInAs - Hlc / 2,x x

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9.1.4 Event-triggered periodic intra-frequency measurement reporting

The reporting period is controlled with the following parameters:

. Addition Reporting Interval (AdditionReportingInterval)

. Replacement Reporting Interval (ReplacementReportingInterval)


When a cell enters the reporting range and triggers event 1A or 1C, the UEtransmits a measurement report message to the RNC to update the activeset.

The RNC can be unable to add the cell to the active set due to capacityshortage, for example. If the reported cell is not added to the active set, theUE continues reporting by changing to periodical measurement reporting.This is illustrated in Figure Periodic reporting triggered by event 1Abelow.

During periodical reporting, the UE transmits measurement reportmessages to the RAN at pre-defined intervals. The reports includeinformation on the active and monitored cells in the reporting range.

Figure 26. Periodic reporting triggered by event 1A

Time

MeasurementquantityCPICH Ec/No

AdditionWindow

CELL 1

CELL 2

CELL 3

Reportingterminated

Event-triggeredreport

Periodicreport

Periodic

report


Handover Control



Event-triggered periodic measurement reporting is terminated either whenthere are no more monitored cell(s) within the reporting range or when theRNC has updated the active set so that it includes the optimal cells.

9.1.5 Time-to-trigger mechanism for modifying measurement reportingbehaviour

The value of the time-to-trigger is controlled separately for each event withthe following parameters:

. Addition Time (AdditionTime)

. Drop Time (DropTime)

. Replacement Time (ReplacementTime)

For a description of the parameters, see WCDMA RAN ParameterDictionary .

A time-to-trigger parameter can be connected with reporting events 1A, 1Band 1C.

When the time-to-trigger mechanism is applied, the report is triggered onlyafter the conditions for the event have existed for the specified time. In thefollowing example, cell 3 enters the reporting range (event 1A), but it is notreported until it has been within the range for the time indicated by theAddition Time (AdditionTime) parameter.

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Figure 27. Time-to-trigger limits the number of measurement reports

9.1.6 Cell individual offsets for modifying measurement reportingbehaviour

Individual offsets can be controlled with the CPICH Ec/No Offset(IntraFreqNcellEcNoOffset) parameter.

For a description of the parameter, see WCDMA RAN ParameterDictionary.

The individual offset mechanism can be used to change the reporting of anindividual cell, and as a result, to move the cell border. For each cell that ismonitored, an offset value can be defined which the UE adds to themeasurement result (CPICH Ec/No) of the neighbour cell before itcompares the Ec/No value with the reporting criteria. The offset can beeither positive or negative.

In the following example, an offset is added to the measurement result ofcell 3, and the dotted curve is used in evaluating if an event occurs.Measurement reports from the UE to the RNC are therefore triggeredwhen the cell including the corresponding offset (the dotted curve) leavesand enters the reporting range.


CELL 1

CELL 2

CELL 3

Reportingrange

Reportingevent 1A

Time

Time-to-trigger


Handover Control



When positive offset is used, as in the following example, the UE sendsmeasurement reports as if the cell (CPICH) is offset x dB better than whatit really is. Therefore, cell 3 is included in the active set earlier than shouldhave been the case without the positive offset. The cell in question canreside in an area where it often becomes good very quickly (due to streetcorners, for instance).

Figure 28. A positive offset is applied to cell 3 before event evaluation in the UE

9.1.7 Mechanism for forbidding a cell to affect the reporting range

The mechanism for forbidding cells to affect the reporting range iscontrolled with the following parameter:

. Disable Effect on Reporting Range (AdjsDERR) indicates whether ornot the neighbour cell is forbidden to affect the reporting range(addition/drop window) calculation, if it belongs to the active set.

For a description of the parameter, see WCDMA RAN ParameterDictionary.

The Addition Window (AdditionWindow) and Drop Window (DropWindow)parameters affect reporting events 1A and 1B. The reporting ranges ofevents 1A and 1B are relative to the measurement results of those cells inthe active set which are not forbidden to affect the reporting range.

In the following figure, cell 3 is forbidden to affect the reporting range, forexample, because it is very unstable in a specific area.

MeasurementquantityCPICH Ec/No CELL 1

CELL 2

CELL 3

Reportingrange

Offset forCELL 3

Reportingevent 1B

Reportingevent 1A

Time

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Figure 29. Cell 3 is forbidden to affect the reporting range

Note

The UE ignores the mechanism if all cells in the active set are forbiddento affect the reporting range.

9.1.8 Reporting events 6F and 6G for deleting cells from the active set

UE Rx-Tx time difference measurement is controlled with the followingparameters:

. Upper Rx-Tx Time Difference Threshold (UpperRxTxTimeDiff)determines the upper threshold which is used by the UE to triggerthe reporting event 6F due to UE Rx-Tx time difference.

. Lower Rx-Tx Time Difference Threshold (LowerRxTxTimeDiff)determines the lower threshold which is used by the UE to trigger thereporting event 6G due to UE Rx-Tx time difference.



CELL 1

CELL 2

CELL 3

Reportingrange Reporting

range

Time


Handover Control



When the UE Rx-Tx time difference for a cell included in the active setbecomes larger than the threshold defined by the parameter Upper Rx-TxTime Difference Threshold (UpperRxTxTimeDiff), the UE sends an event6F-triggered measurement report message to the RNC and the RNCdeletes the cell from the active set. Similarly, the RNC deletes the cell fromthe active set if the UE sends an event 6G-triggered measurement reportmessage to the RNC when the UE Rx-Tx time difference for the cell hasbecome smaller than the threshold defined by the Lower Rx-Tx TimeDifference Threshold (LowerRxTxTimeDiff)parameter.

9.1.9 Function in abnormal conditions

This section describes the functioning of the RNC in case of anunsuccessful soft handover and radio link failure. In abnormal conditions,the RNC can release the RRC connection to avoid excessive uplinkinterference. If the conditions for the RRC connection release and theintra-frequency hard handover are met simultaneously, the hard handoverhas the higher priority.

RRC connection release due to unsuccessful soft handover

The parameters related to handling of RRC connection release because ofan unsuccessful soft handover are:

. CPICH Ec/No Averaging Window (EcNoAveragingWindow)determines the number of event triggered periodic intra-frequencymeasurement reports from which the RNC calculates the averagedCPICH Ec/No values.

. Enable RRC Connection Release (EnableRRCRelease) determineswhether RRC connection release (excluding emergency calls) isallowed in situations when soft handover branch addition (orreplacement) fails.

. Release Margin for Average Ec/No (ReleaseMarginAverageEcNo)determines the maximum allowed difference between the averagedCPICH Ec/No of the neighbour cell and the averaged CPICH Ec/Noof the best cell in the active set in situations when the RNC is notable to perform a soft handover between these cells.

. Release Margin for Peak Ec/No (ReleaseMarginPeakEcNo)determines the maximum allowed difference between the CPICHEc/No of the neighbour cell and the CPICH Ec/No of the best cell inthe active set in situations when the RNC is not able to perform a softhandover between these cells.


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When an intra-frequency neighbour cell enters the reporting range andtriggers either event 1A (cell addition) or event 1C (cell replacement), theUE transmits a measurement report to the RNC to add the neighbour cellto the active set. If the RNC is not able to add the neighbour cell to theactive set and the requested neighbour cell should be the strongest cell,the Enable RRC Connection Release (EnableRRCRelease) parameterdetermines whether or not an RRC connection release (excludingemergency calls) is allowed to avoid excessive uplink interference due tonon-optimum fast closed loop power control (that is, the UE is not linkedwith the strongest cell anymore).

The UE proceeds to the periodic measurement reporting if the RNC cannotadd the requested cell into the active set. If the RRC connection release isallowed, the RNC makes the decision on the release on the basis of theCPICH Ec/No of the best cell in the active set, the CPICH Ec/No of therequested neighbour cell and the Release Margin for Average Ec/No andRelease Margin for Peak Ec/Nocontrol parameters.

The RRC connection release is required when the measurement results ofthe requested neighbour cell satisfies one of the following equations:

AveEcNoDownlink + ReleaseMarginforAveEc/No (n) < AveEcNoNcell (n)

or

EcNoDownlink + ReleaseMarginforPeakEc/No (n) < EcNoNcell (n)


Table 11. Criteria for enabling the RRC connection release


AveEcNoDownlink averaged CPICH Ec/No of the best cell inthe active set

AveEcNoNcell(n) averaged CPICH Ec/No of theneighbouring cell

EcNoDownlink CPICH Ec/No of the best cell in the activeset

EcNoNcell(n) CPICH Ec/No of the neighbouring cell

The RNC calculates the averaged values from a specified number ofperiodic intra-frequency measurement reports. Averaging is controlled withthe CPICH Ec/No Averaging Window (EcNoAveragingWindow) parameter.


Handover Control

Radio link failure

When a radio link in the active set loses uplink physical layersynchronisation, the RNC deletes the radio link (cell) from the active set ifthe uplink physical layer remains out of synchronisation for a period of timewhich is specified by an internal constant. After the radio link deletionprocedure, the UE can start sending reporting event 1A to the RNC toreturn the cell back to the active set.

If all radio links in the active set lose uplink synchronisation, the RNCinitiates either an RRC Connection Re-establishment or an RRCConnection Release procedure. For more information, see Packet DataTransfer States.

9.2 Functionality of intra-frequency hard handover

Intra-frequency hard handover is required to ensure handover betweencells controlled by different RNCs in situations when an inter-RNC softhandover is not possible, for example, because of Iur congestion.Furthermore, the Enable Inter-RNC Soft Handover (EnableInterRNCsho)RNP parameter determines whether the inter-RNC handover from theserving cell to a specified neighbour cell is performed as a soft handover oras a hard handover.

The intra-frequency hard handover is controlled with the following RNPparameters:

. Enable Inter-RNC Soft Handover (EnableInterRNCsho) determineswhether or not the neighbour cell can participate in a soft handover ifit is controlled by an RNC other than the local RNC.

. CPICH Ec/No Averaging Window (EcNoAveragingWindow)determines the number of event-triggered periodic intra-frequencymeasurement reports from which the RNC calculates the averagedCPICH Ec/No values.

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. HHO Margin for Average Ec/No (HHOMarginAverageEcNo)determines the maximum allowed difference between the averagedCPICH Ec/No of the neighbouring cell and the averaged CPICH Ec/No of the best active cell in situations when an inter-RNC softhandover is not possible between these cells.

. HHO Margin for Peak Ec/No (HHOMarginPeakEcNo) determinesthe maximum allowed difference between the CPICH Ec/No of theneighbour cell and the CPICH Ec/No of the best active cell insituations when an inter-RNC soft handover is not possible betweenthese cells.


The RNC makes the intra-frequency hard handover decision on the basisof event-triggered periodic intra-frequency measurement reports, whichare usually applied to soft handover, and the above-mentioned controlparameters. The UE proceeds to the periodic measurement reporting if theRNC cannot add the requested cell into the active set.

The handover decision is based on the downlink Ec/No of the best cell inthe active set, downlink Ec/No of the neighbour cell and handover marginswhich are used as a threshold to prevent repetitive hard handoversbetween cells. The measurement results of the neighbour cell must satisfyone of the following two equations before the intra-frequency hardhandover is possible:

AveEcNoDownlink + HHOMarginForAverageEcNo (n) < AveEcNoNcell (n)

or

EcNoDownlink + HHOMarginForPeakEcNo (n) < EcNoNcell (n)


Table 12. Measurement result criteria for intra-frequency hard handover


AveEcNoDownlink Averaged downlink Ec/No of the best cellin the active set

AveEcNoNcell(n) Averaged downlink Ec/No of theneighbour cell (n)

EcNoDownlink Downlink Ec/No of the best cell in theactive set


Handover Control



Table 12. Measurement result criteria for intra-frequency hard handover (cont.)


EcNoNcell(n) Downlink Ec/No of the neighbour cell

The RNC calculates the averaged Ec/No values from a specified numberof periodical intra-frequency measurement reports. Averaging is controlledwith the CPICH Ec/No Averaging Window (EcNoAveragingWindow). Themaximum allowed difference between the averaged or peak CPICH powerlevel of the neighbouring cell (n) and that of the best active set cell isdefined with a parameter in situations when the RNC cannot perform aninter-RNC soft handover between these cells. If the difference in theaveraged or peak Ec/No values exceeds the value of the relevantparameter, the RNC performs an intra-frequency hard handover to avoidexcessive uplink interference because of fast closed loop power controlthat is no longer optimal.

9.2.1 Time interval between hard handover attempts

The RNC does not set any limit for the minimum interval between the inter-RNC intra-frequency hard handovers. However, to prevent repetitiveunsuccessful inter-RNC intra-frequency hard handover attempts to thesame target cell, the RNC determines a time interval during which an intra-frequency hard handover to the cell in question is not allowed. The lengthof the interval is fixed 2 seconds for emergency calls. Otherwise the lengthof the interval depends on the number of unsuccessful hard handoverattempts related to the same target cell during the same RRC connection.This interval increases 2 seconds per unsuccessful hard handover attempt(to the same target cell during the same RRC connection), up to themaximum of 10 seconds. The RNC determines the interval in the followingway:

TIME_INTERVAL = min (10 seconds, NUMBER_OF HHO_FAILS * 2seconds)

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Handover Control

10 Functionality of inter-frequencyhandover

The RNC makes the decision on the need for Inter-Frequency Handover(IFHO). When an inter-frequency handover is needed, the radio networkcontroller (RNC) orders the user equipment (UE) to start the periodicreporting of inter-frequency measurement results. The RNC recognisesthe following inter-frequency handover causes:

. inter-frequency handover because of Uplink Dedicated TrafficChannel (DCH) quality

. inter-frequency handover because of UE transmission power

. inter-frequency handover because of Downlink dedicated physicalchannel (DPCH) power

. inter-frequency handover because of Common Pilot Channel(CPICH) RSCP

. inter-frequency handover because of CPICH Ec/No

. immediate IMSI-based handover (for more information, see SectionFunctionality of immediate IMSI-based handover)

. load-based handover (for more information, see SectionFunctionality of Load- and Service-based IF/IS handover)

. service-based handover (for more information, see SectionFunctionality of Load- and Service-based IF/IS handover)

The RNC does not start inter-frequency measurements or handover whenonly a Signalling Radio Bearer (SRB) is allocated for the RRC connection.

The RNC makes the handover decision on the basis of periodic inter-frequency measurement reports received from the UE and relevant controlparameters. The measurement reporting criteria and the object information(cells and frequencies) for the inter-frequency measurement aredetermined by the RNC.

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Functionality of inter-frequency handover

Unless the UE is equipped with dual receivers it can only be tuned to onefrequency at a time. Therefore, compressed mode must be used at thephysical layer of the radio interface to allow the UE to make the requiredinter-frequency measurements while maintaining its existing connection.

Once the RNC has decided to attempt an inter-frequency handover, theRNC allocates radio resources from the target cell, establishes a new radiolink for the connection between the UE and the target cell, and orders theUE to make an inter-frequency handover to the target cell.

Note

The admission control of the RNC can overrule the handover algorithmdecision because of capacity reasons. For more information, seeSection Radio resource management functions.

10.1 Coverage reason inter-frequency handover

The RNC supports the following inter-frequency handovers because ofcoverage reasons(and cell reselections) ot GSM for both real time (RT)and non-real time (NRT) radio bearers:

. inter-system handover because of Uplink DCH quality

. inter-system handover because of UE transmission power

. inter-system handover because of CPICH RSCP

. inter-system handover because of CPICH Ec/No

. Immediate IMSI-based handover (for more information, see SectionFunctionality of immediate IMSI-based handover).

10.1.1 Inter-frequency handover because of uplink DCH quality

The quality deterioration report from the uplink outer loop power controlcan be used to trigger off inter-frequency handover to GSM if the servingcell (or cells participating in soft handover) has GSM neighbour cells. Theuplink outer loop power control sends the quality deterioration report to thehandover control if the uplink quality stays constantly worse than the BER/BLER target although the uplink SIR target has reached the maximumvalue (the UE has reached either its maximum Tx power capability or themaximum allowed transmission power level on the DPCH).


Handover Control

The reporting criteria of the quality deterioration report is controlled withthe following RNP parameters (for a description of the parameters, seeWCDMA RAN Parameter Dictionary):

. Quality deterioration report from UL OLPC controller(EnableULQualDetRep) indicates whether or not the uplink outerloop PC can send a quality deterioration report to the handovercontrol in situations when the quality stays worse than the BER/BLER target despite of the maximum uplink SIR target.

. UL quality deterioration reporting threshold(ULQualDetRepThreshold) determines the period during which thequality must constantly stay worse than the BER/BLER target(despite of the maximum uplink SIR target) before the uplink outerloop PC can send a quality deterioration report.

The uplink OLPC repeats the quality deterioration reports to the handovercontrol periodically until the uplink SIR target decreases below themaximum value.

The IFHO caused by UL DCH Quality (IFHOcauseUplinkQuality) RNPparameter indicates whether or not an inter-frequency handover causedby Uplink DCH quality is enabled. In case of RT data connection (CS orPS), also the maximum allocated user bitrate on the uplink DPCH must belower than or equal to the bitrate threshold which is controlled with theMaximum Allowed UL User Bitrate in HHO (HHoMaxAllowedBitrateUL)RNP parameter, before the RNC can start the inter-frequencymeasurement because of Uplink DCH quality. This limitation in uplinkbitrate is not applied for NRTservices. When the inter-frequency handover/measurement is enabled, the RNC starts the inter-frequencymeasurement. For more information, see Section Measurementprocedure.

The RNC makes the handover decision on the basis of periodic inter-frequency measurement reports received from the UE and relevant controlparameters. For more information, see Section Handover decisionprocedure.

10.1.2 Inter-frequency handover because of UE transmission power

If the serving cell (or cells participating in soft handover) has GSMneighbour cells, an event-triggered UE transmission power measurementreport can be used to trigger off handover to GSM when the transmissionpower of the UE approaches either its maximum RF output powercapability or the maximum transmission power level the UE can use on theDPCH.

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The IFHO caused by UE TX Power (GSMcauseTxPwrUL) RNP parameterindicates whether an inter-system handover to GSM caused by UEtransmission power is enabled or not. In addition, the maximum allocateduser bitrate on the uplink DPCH must be lower than or equal to the bitratethreshold which is controlled with theMaximum Allowed UL User Bitrate inHHO (HHoMaxAllowedBitrateUL)RNP parameter, before the RNC canstart the inter-system (GSM) measurement because of UE transmissionpower. When the inter-system handover/measurement is enabled, theRNC starts a UE-internal measurement to monitor the UE transmissionpower level. The measurement reporting criteria for the UE transmissionpower measurement is controlled with the following RNP parameters:

. UE TX Power Filter Coefficient (InterFreqUETxPwrFilterCoeff)controls the higher layer filtering (averaging) of the physical layertransmission power measurements in the UE. The physical layermeasurement period for the UE transmission power is one slot.

. UE TX Power Threshold for AMR (InterFreqUETxPwrThrAMR)determines the UE transmission power threshold for a circuit-switched voice connection.

. UE TX Power Threshold for CS (InterFreqUETxPwrThrCS)determines the UE transmission power threshold for a circuit-switched data connection.

. UE TX Power Threshold for NRT PS (InterFreqUETxPwrThrNrtPS)determines the UE transmission power threshold for a non-real timepacket-switched data connection.

. UE TX Power Threshold for RT PS (InterFreqUETxPwrThrRtPS)determines the UE transmission power threshold for a real-timepacket-switched data connection.

. UE TX Power Time Hysteresis (InterFreqUETxPwrTimeHyst)determines the time period during which the UE transmission powermust stay below the transmission power threshold before the UEcalls off the handover cause (event 6B).

Note that the UE transmission power is not used as a handover cause for aservice type if the value of the corresponding UE transmission powerthreshold parameter is ‘not used’. The power thresholds are relative to themaximum transmission power level a UE can use on the DPCH in the cell(or the maximum RF output power capability of the UE in WCDMA,whichever is lower). In case of multi service, the RNC selects theparameters in the following order: 1st priority AMR, 2nd priority CS data, 3rd

priority RT PS data and 4th priority NRT PS. For the description of theparameters, see WCDMA RAN Parameter Dictionary.


Handover Control


If the UE transmission power becomes greater than the reporting threshold(event6), the UE sends the measurement report (event 6A) to the RNC,and the RNC starts the inter-system (GSM) measurement as described inSection Measurement procedure.

The RNC makes the handover decision on the basis of periodical inter-system measurement reports received from the UE and relevant controlparameters, as described in Section Handover decision procedure.

Note

The RNC does not break off ongoing inter-system (GSM) measurementeven if the transmission power of the UE decreases below the reportingthreshold (event 6B) during the measurement and the UE sends thecorresponding measurement report (event 6B) to the RNC.

10.1.3 Inter-frequency handover because of CPICH RSCP

Received Signal Code Power (RSCP) measurement result on the PrimaryCPICH can be used to trigger off inter-system handover to GSM if theserving cell (or cells participating in soft handover) has GSM neighbourcells.

The IFHO caused by CPICH RSCP (GSMcauseCPICHrscp) RNPparameter indicates whether an inter-system handover to GSM caused bylow measured absolute CPICH RSCP is enabled or not. When the inter-system handover is enabled, the RNC sets up an intra-frequencymeasurement to monitor the absolute CPICH RSCP value. Themeasurement reporting criteria for the intra-frequency CPICH RSCPmeasurement is controlled with the following RNP parameters:

. CPICH RSCP HHO Threshold (HHoRscpThreshold) determines theabsolute CPICH RSCP threshold which is used by the UE to triggerthe reporting event 1F.

. CPICH RSCP HHO Time Hysteresis (HHoRscpTimeHysteresis)determines the time period during which the CPICH RSCP of theactive set cell must stay worse than the thresholdHHoRscpThreshold before the UE can trigger the reporting event 1F.

. CPICH RSCP HHO Cancellation (HHoRscpCancel) determines theabsolute CPICH RSCP threshold which is used by the UE to triggerthe reporting event 1E.

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. CPICH RSCP HHO Cancellation Time (HHoRscpCancelTime)determines the time period during which the CPICH RSCP of theactive set cell must stay better than the threshold HHoRscpCancelbefore the UE can trigger the reporting event 1E.

. CPICH RSCP HHO Filter Coefficient (HHoRscpFilterCoefficient)controls the higher layer filtering (averaging) of physical layer CPICHRSCP measurements before the event evaluation andmeasurement reporting is performed by the UE. The UE physicallayer measurement period for intra-frequency CPICH RSCPmeasurement is 200 ms.

If the CPICH RSCP measurement result of an active set cell becomesworse than or equal to the absolute threshold/parameterHHoRscpThreshold, the UE sends an event 1F-triggered measurementreport to the RNC. The UE cancels event 1F by sending an event 1E-triggered measurement report to the RNC if the CPICH RSCPmeasurement result of the active set cell increases again and becomesbetter than or equal to the threshold HHoRscpCancel. If the CPICH RSCPmeasurement result of all active set cells has become worse than thereporting threshold HHoRscpThreshold (event 1F is valid for all active setcells simultaneously), the RNC starts the inter-system (GSM)measurement as described in Section Measurement procedure.

The RNC makes the handover decision on the basis of periodic inter-frequency measurement reports received from the UE and relevant controlparameters, as described in Section Handover decision procedure.

Note

The RNC does not break off ongoing inter-system (GSM) measurementeven if the measured CPICH RSCP of one or more active set cellsincreases again above the reporting threshold HHoRscpCancel and theUE sends the corresponding event 1E triggered intra-frequencymeasurement report to the RNC.

10.1.4 Handover decision procedure

An inter-frequency handover because of coverage reasons is possiblewhen the signal of the best neighbour cell meets the conditions in thefollowing equations:

AVE_EcNo_NCELL (n) > AdjiMinEcNo (n) CPICH_POWER -AVE_CPICH RSCP > CPICH_POWER_NCELL (n) -AVE_RSCP_NCELL(n) + AdjiPlossMargin (n)


Handover Control

In the above equations, AVE_RSCP_NCELL(n) and AVE_EcNo_NCELL(n) are the averaged CPICH Ec/No and RSCP values of the best(according to CPICH Ec/No) neighbour cell (n). AVE_CPICH_RSCP is theaveraged CPICH RSCP of the best (according to pathloss) active set cell.

The Minimum CPICH Ec/No for IFHO (AdjiMinEcNo) RNP parameterdetermines the minimum required CPICH Ec/No (dB) level in the bestneighbour cell (n). The RNP parameter Pathloss Margin for IFHO(AdjiPlossMargin) determines the margin (dB) by which the propagationloss of the best active set cell must exceed the propagation loss of the bestneighbour cell (n) before the inter-frequency handover is possible.

CPICH_POWER indicates the transmission power of the Primary CPICHof the best active set cell. CPICH_POWER_NCELL (n) indicates thedownlink transmission power of the Primary CPICH of the best neighbourcell (n).

The Neighbour Cell Search Period (InterFreqNcellSearchPeriod) RNPparameter determines the period starting from inter-frequencymeasurement setup during which an inter-frequency handover is notpossible. After the period has expired, the RNC evaluates the radio linkproperties of the best neighbour cell after every inter-frequencymeasurement report. The RNC performs the inter-frequency handover to abest neighbour (target) cell as soon as the best neighbour cell meets therequired radio link properties.

Regarding averaging values, the RNC calculates them directly from themeasured dB and dBm values, linear averaging is not used in this case.The sliding averaging window is controlled with the MeasurementAveraging Window (InterFreqMeasAveWindow) RNP parameter. TheRNC starts averaging already from the first measurement sample, that is,the RNC calculates the averaged values from those measurementsamples which are available until the number of samples is adequate tocalculate averaged values over the whole averaging window.

10.2 Quality reason inter-frequency handover

The RNC supports the following quality reason inter-frequency handoversfor both real time (RT) and non-real time (NRT) radio bearers:

. inter-frequency handover because of Downlink DPCH power

. inter-frequency handover because of CPICH Ec/No

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10.2.1 Inter-frequency handover because of Downlink DPCH power

The BTS measures and averages the downlink code power of each radiolink separately and reports the averaged measurement results to thecontrolling RNC at regular intervals with a 3GPP NBAP: DEDICATEDMEASUREMENT REPORT. The BTS measures the downlink code powerfrom the pilot bits of the dedicated physical control channel (DPCCH). Incase of an inter-RNC soft handover, the drifting RNC forwards themeasurement results to the serving RNC in the RNSAP: DEDICATEDMEASUREMENT REPORT message.

In 3GPP NBAP the Reporting Period is controlled with the DedicatedMeasurement Reporting Period (Dedicated MeasReportPeriod),Dedicated Measurement Reporting Period CS data(DediMeasRepPeriodCSdata), Dedicated Measurement Reporting PeriodPS data (DediMeasRepPeriodPSdata)RNP parameters. All of thesemeasurement reports can trigger off inter-system handover to GSMwhenthe downlink transmission power of the radio link approaches its maximumallowed power level.

The IFHO caused by DL DPCH TX Power (GSMcauseTxPwrDL) RNPparameter determines whether an inter-system handover to GSM causedby high downlink DPCH power level is enabled or not. In addition, themaximum allocated user bit rate on the downlink DPCH must be lowerthan or equal to the bitrate threshold defined by the Maximum Allowed DLUser Bitrate in HHO (HhoMaxAllowedBitrateDL)RNP parameter, beforethe RNC can start the inter-system measurement and handover becauseof Downlink DPCH power.

When the handover to GSM is enabled, the RNC starts the inter-systemmeasurement procedure (as described in Section Measurementprocedure) if the measured downlink code power of a single radio linkmeets the condition in the following equation:

DL_CODE_PWR - PowerOffsetDLdpcchPilot >= CPICH_POWER +MAX_DL_DPCH_TXPWR + DL_DPCH_TXPWR_THRESHOLD

The variables in the formula are defined in the following table.

Table 13. Variables for inter-system handover


DL_CODE_PWR indicates the measured downlink codepower


Handover Control

Table 13. Variables for inter-system handover (cont.)


PowerOffsetDLdpcchPilot a constant that defines the power offsetfor the pilot fields of the DPCCH,expressed as a relative value with respectto the DPDCH power

CPICH_POWER indicates the transmission power of theprimary CPICH of an active set cell

MAX_DL_DPCH_TXPWR indicates the maximum transmissionpower level of the DPDCH symbols abase station can use on the DPCH,expressed as a relative value (dB) withrespect to the primary CPICH power(dBm).

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DL_DPCH_TXPWR_THRESHOLD Is controlled with the following inter-frequency measurement controlparameters, depending on the servicetype:. DL DPCH TX Power Threshold for RT

PS (InterFreqDLTxPwrThrRtPS)determines the downlink DPCHtransmission power threshold for a real-time packet-switched data connection.

. DL DPCH TX Power Threshold for NRTPS (InterFreqDLTxPwrThrNrtPS)determines the downlink DPCHtransmission power threshold for a non-real time packet-switched dataconnection.

. DL DPCH TX Power Threshold for CS(InterFreqDLTxPwrThrCS) determinesthe downlink DPCH transmission powerthreshold for a circuit-switched dataconnection.

. DL DPCH TX Power Threshold forAMR (InterFreqDLTxPwrThrAMR)determines the downlink DPCHtransmission power threshold for acircuit-switched voice connection.

The downlink DPCH transmission powerthresholds are relative (dB) to theallocated maximum transmission power ofthe DPCH.

In case of a multiservice, the RNC selectsthe lowest threshold value for thecalculation (for example, when thealternative threshold values are -1dB and-3dB, the RNC selects the -3dB thresholdvalue). Downlink transmission power shallnot be used as a handover cause for aservice type if the value of thecorresponding threshold parameter is 'notused'.

The RNC makes the handover decision on the basis of periodic inter-system measurement reports received from the UE and relevant controlparameters, as described in Section Handover decision procedure.


Handover Control

10.2.2 Inter-frequency handover because of CPICH Ec/ No

The IFHO caused by CPICH Ec/No (GSMcauseCPICHEcNo) RNPparameter indicates whether an inter-system handover to GSM caused bylow measured absolute CPICH Ec/No is enabled or not. When the inter-frequency handover is enabled, the RNC sets up an intra-frequencymeasurement to monitor the absolute CPICH Ec/No value. Themeasurement reporting criteria for the intra-frequency CPICH Ec/Nomeasurement is controlled by the following parameters:

. CPICH Ec/No HHO Threshold (HHoEcNoThreshold) determines theabsolute CPICH Ec/No threshold which is used by the UE to triggerthe reporting event 1F

. CPICH Ec/No HHO Time Hysteresis (HHoEcNoTimeHysteresis)determines the time period during which the CPICH Ec/No of theactive set cell must stay worse than the thresholdHHoEcNoThreshold before the UE can trigger the reporting event1F.

. CPICH Ec/No HHO Cancellation (HHoEcNoCancel) determines theabsolute CPICH Ec/No threshold which is used by the UE to triggerthe reporting event 1E.

. CPICH Ec/No HHO Cancellation Time (HHoEcNoCancelTime)determines the time period during which the CPICH Ec/No of theactive set cell must stay better than the threshold HHoEcNoCancelbefore the UE can trigger the reporting event 1E

. CPICH Ec/No Filter Coefficient (EcNoFilterCoefficient) controls thehigher layer filtering (averaging) of physical layer CPICH Ec/Nomeasurements before the event evaluation and measurementreporting is performed by the UE. The UE physical layermeasurement period for intra-frequency CPICH Ec/Nomeasurements is 200 ms.

If the CPICH Ec/No measurement result of an active set cell becomesworse than or equal to the HhoEcNoThreshold absolute threshold/parameter, the UE sends the event 1F-triggered measurement report tothe RNC. The UE cancels event 1F by sending an event 1E-triggeredmeasurement report to the RNC if the CPICH Ec/No measurement resultof the active set cell increases again and becomes better than or equal tothe threshold HHoEcNoThreshold(event 1F is valid for all active set cellssimultaneously), the RNC starts the inter-system (GSM) measurement asdescribed in Section Measurement procedure.

The RNC makes the handover decision on the basis of periodic inter-system measurement reports received from the UE and relevant controlparameters, as described in Section Handover decision procedure.

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Note

The RNC does not break off ongoing inter-system measurement even ifthe measured CPICH Ec/No of one or more active set cells increasesagain above the reporting threshold HHoEcNoCancel and the UEsends the corresponding event 1E triggered intra-frequencymeasurement report to the RNC.


The measurement results of the GSM neighbouring cell must satisfy thefollowing equation before the inter-system handover or cell change toGSM/GPRS is possible:

AVE_RSCP_NCELL (n) > AdjiMinRSCP (n) + max( 0, AdjiTxPwrDPCH (n)- P_MAX )

AVE_EcNo_NCELL (n) > AVE_CPICH EcNo + AdjiEcNoMargin(n)

In the equations above, AVE_RSCP_NCELL(n) and AVE_EcNo_NCELLare the averaged CPICH Ec/No RSCP values of the best (according toCPICH Ec/No) neighbouring cell (n).

AVE_CPICH_EcNo is the averaged CPICH Ec/No of the best active setcell.

The Minimum CPICH RSCP for IFHO (AdjiMinRSCP)(n) parameterdetermines the minimum required CPICH RSCP (dBm) level in the bestneighbouring cell (n).

The CPICH Ec/No Margin for IFHO (AdjiEcNoMargin) (n) parameterdetermines the margin (dB) by which the CPICH Ec/No of the bestneighbouring cell (n) must exceed the CPICH Ec/No of the best active setcell before the inter-frequency handover is possible. The neighbour cellparameter AdjiTxPwrDPCH(n) indicates the maximum transmission powerlevel (dBm) a UE can use on the DPCH. P_MAX indicates the maximumRF output power capability of the UE (dBm).

The Neighbour Cell Search Period (InterFreqNcellSearchPeriod)parameter determines the period starting from inter-frequencymeasurement setup during which an inter-frequency handover is notpossible. After the period has expired, the RNC evaluates the radio link


Handover Control

properties of the best neighbour cell after every inter-frequencymeasurement report. The RNC performs the inter-frequency handover to abest neighbouring (target) cell as soon as the best neighbouring cell meetsthe required radio link properties.

Regarding averaging values, the RNC calculates them directly from themeasured dB and dBm values, linear averaging is not used in this case.The sliding averaging window is controlled with the MeasurementAveraging Window (interFreqMeasAveWindow)parameter. The RNCstarts averaging already from the first measurement sample, that is, theRNC calculates the averaged values from those measurement sampleswhich are available until the number of samples is adequate to calculateaveraged values over the whole averaging window.

10.3 Interactions between handover causes

The handover cause, which has triggered first has the highest priority. Thatis, the RNC does not stop or modify ongoing inter-frequency (GSM)measurement and handover decision procedures if another handovercause is triggered during the handover procedures. If two or more inter-frequency (GSM) handover causes are triggered simultaneously, the RNCselects the cause, which has the highest priority. The priority order is thefollowing:

1. Immediate IMSI-based inter-frequency handover has higher prioritythan the other inter-frequency handover causes (for moreinformation, see Section Functionality of immediate IMSI-basedhandover).

2. Quality and coverage reason inter-frequency handovers. The RNCsupports the following quality and coverage reason inter-frequencyhandovers to GSM (the handover causes are not presented in anyparticular order):. inter-frequency handover to GSM/GPRS because of Uplink

DCH quality. inter-frequency handover to GSM/GPRS because of UE Tx

power. inter-frequency handover to GSM/GPRS because of Downlink

DPCH power. inter-frequency handover to GSM/GPRS because of CPICH

RSCP. inter-frequency handover to GSM/GPRS because of CPICH

Ec/No

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3. Load-based inter-frequency handover (for more information, seeSection Functionality of Load- and Service-based IF/IS handover)

4. Service-based inter-frequency handover (for more information, seeSection Functionality of Load- and Service-based IF/IS handover)

10.4 Interaction with handover to GSM

If the serving cell (or cells participating in soft handover) has neighbourcells both on another carrier frequency and on another RAT (GSM), theRNC determines the priorities between inter-frequency and inter-systemhandovers on the basis of Service Handover IE value. The RNC receivesthe Service Handover IE from the core network in the RAB ASSIGNMENTREQUEST or RELOCATION REQUEST (RANAP) message. If the RNCdoes not receive the Service Handover IE from the core network, inter-frequency handover has priority over inter-system handover to GSM as adefault value.

. Should be handed over to GSM:

Inter-system handover takes precedence over inter-frequencyhandover. In this case the RNC does not start inter-frequencymeasurements until the inter-system measurements have beencompleted, that is, when no neighbour GSM cell is good enough forthe quality and/or coverage reason handover.

. Should not be handed over to GSM:

Inter-frequency handover takes precedence over inter-systemhandover. In this case the RNC does not start the inter-systemmeasurements until the inter-frequency measurements have beencompleted, that is, when no neighbouring cell is good enough for thequality and/or coverage reason inter-frequency handover.

. Shall not be handed over to GSM:

In this case, the RNC does not start inter-system measurements orhandover to GSM even if no neighbour cell is good enough for thequality and/or coverage reason inter-frequency handover. Thismeans that the RNC does not initiate handover to GSM for the UEunless the RABs with this indication have first been released with thenormal release procedures.


Handover Control

10.5 Measurement procedure

The measurement procedure, the scenario of which is presented in FigureMeasuring procedure below, is controlled by a number of parameters setduring the radio network planning. These parameters are:

1. Measurement Reporting Interval (InterFreqMeasRepInterval)

This parameter determines the measurement reporting interval forperiodical inter-system (GSM) measurements.

2. Neighbour Cell Search Period (InterFreqNcellSearchPeriod)

This parameter determines the number of periodic inter-frequencymeasurement reports, starting from the first report after themeasurement setup, during which an inter-frequency handover isnot allowed. This period allows the UE to find and report all potentialneighbouring cells before the handover decision.

3. Maximum Measurement Period (GsmMaxMeasPeriod)

This parameter determines the maximum number of periodicmeasurement reports during an inter-frequency measurement (thatis, the maximum allowed duration of the inter-frequencymeasurement). If the RNC is not able to execute the inter-frequencyhandover, it stops the inter-frequency measurement after the UE hassent a predefined number of measurement reports to the RNC.

4. Minimum Measurement Interval (GsmMinMeasInterval)

This parameter determines the minimum interval between anunsuccessful inter-frequency measurement or handover procedureand the beginning of the following inter-frequency measurementprocedure related to the same RRC connection. Repetitive inter-frequency measurements are disabled when the value is zero.

5. Minimum Interval Between HOs (InterFreqMinHoInterval)

This parameter determines the minimum interval between asuccessful inter-frequency handover and the following inter-frequency handover attempt related to the same RRC connection.Repetitive inter-frequency handovers are disabled when the value ofthe parameter is zero.

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Figure 30. Measuring procedure

The RNC measures one frequency at a time. If there are more than onefrequency to be measured, the RNC selects a subset of inter-frequencyneighbour cells (having the same UTRA RF channel number) which aremeasured first. The measurement order is controlled with the followingRNP parameters defined for each neighbour cell:

. Ncell Priority for Quality IFHO (AdjiPriorityQuality) determines themeasurement order in case of a quality reason inter-frequencyhandover.

. Ncell Priority for Coverage IFHO (AdjiPriorityCoverage) determinesthe measurement order in case of a coverage reason inter-frequency handover.

If the measurement results of the first measured frequency indicate that aninter-frequency handover can be done, the RNC starts the handoverattempt immediately (the RNC does not measure remaining frequenciesand corresponding cells any more). If none of the neighbouring cells wasgood enough according to the first inter-frequency measurement, the RNCcan directly repeat the measurement and decision procedures for theremaining subsets of inter-frequency neighbouring cells until allfrequencies and neighbouring cells are measured, or a target cell for theinter-frequency handover is found. The maximum measurement periodwhich is allowed for each carrier frequency is controlled by theInterFreqMaxMeasPeriod RNP parameter.

Frequency 3

Frequency 2

Frequency 1

HO

3

4

Time2

14

4

5


Handover Control

10.6 Function in abnormal conditions

If an attempted handover to a target frequency fails, the RNC successivelyextends the interval during which another attempt to hand the same RRCconnection over to the same target frequency is disallowed. The durationof the interval depends on the number of previous handover failures. TheRNC determines the interval in the following way:

TIME_INTERVAL = ( 1 + NUMBER_OF IFHO_FAILS ) *InterFreqMinMeasInterval

The Minimum Measurement Interval (InterFreqMinMeasInterval)parameter determines the minimum interval between an unsuccessfulinter-frequency measurement (or handover attempt) procedure and thefollowing inter-frequency measurement procedure related to the sameRRC connection.

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Handover Control

11 Functionality of inter-system handover


Inter-System Handovers (ISHOs) allow WCDMA and GSM networks tocomplement each other in terms of quality, capacity and coverage. TheUser Equipment (UE) must support both WCDMA and GSM radio accesstechnologies before an inter-system handover is possible. The RNCsupports inter-system handovers for circuit-switched voice services bothfrom WCDMA to GSM and from GSM to WCDMA.

Inter-system handover of packet-switched services between WCDMA andGSM/GPRS is based on the cell reselection procedure. The RNC supportsnetwork-initiated cell reselection from WCDMA to GSM/GPRS inCELL_DCH state of connected mode. In CELL_PCH and URA_PCHstates of connected mode, the cell reselection is initiated by the UE. TheRNC does not support cell reselection from WCDMA to GSM/GPRS inCELL_FACH state of connected mode (however, a UE equipped with adual receiver can perform the cell reselection also in CELL_FACH state).The RNC sees the cell reselection from GSM/GPRS to WCDMA as anRadio Resource Control (RRC) connection establishment, and the UE-initiated cell reselection from WCDMA to GSM/GPRS as an Iu connectionrelease.

The RNC does not start inter-system handover or cell reselection to GSMwhen only a signalling radio bearer (SRB) is allocated for the RRCconnection.

Inter-system handover and cell reselection are enabled separately foreach service type by means of the following parameters. For thedescription of the parameters, see WCDMA RAN Parameter Dictionary:

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Functionality of inter-system handover


. Handover of AMR Service to GSM (GsmHandoverAMR) determineswhether an inter-system handover to GSM is allowed for circuit-switched voice services.

. Handover of RT PS Service to GSM (GsmHandoverRtPS)determines whether an inter-system handover (cell change) to GSM/GPRS is allowed for real-time packet-switched data services inCELL_DCH state of connected mode.

. Handover of NRT PS Service to GSM (GsmHandoverNrtPS)determines whether an inter-system handover (cell change) to GSM/GPRS is allowed for non-real time packet switched data services inCELL_DCH state of connected mode.

The RNC makes the decision on the need for inter-system handover.When an inter-system handover (or cell reselection) to GSM is needed, theRNC orders the UE to start the periodic reporting of inter-systemmeasurement results. The RNC recognises the following inter-systemhandover causes:

. inter-system handover because of uplink Dedicated Traffic Channel(DCH) quality


. inter-system handover because of downlink Dedicated PhysicalChannel (DPCH) power

. inter-system handover because of Common Pilot Channel (CPICH)RSCP


. immediate IMSI-based handover (for more information, see SectionFunctionality of immediate IMSI-based handover)

. load-based handover (for more information, see SectionFunctionality of Load- and Service-based IF/IS handover)

. service-based handover (for more information, see SectionFunctionality of Load- and Service-based IF/IS handover)

The RNC makes the handover decision on the basis of periodic inter-system measurement reports received from the UE and relevant controlparameters. The measurement reporting criteria and the object information(cells and frequencies) for the inter-system measurement are determinedby the RNC.


Handover Control

Unless the UE is equipped with dual receivers, it can only be tuned to onefrequency at a time. Therefore, compressed mode must be used at thephysical layer of the radio interface to allow the UE to make the requiredinter-system (GSM) measurements while maintaining its existingconnection.

Once the RNC has decided to attempt an inter-system handover fromWCDMA to GSM, it initiates an inter-system relocation procedure in orderto allocate radio resources from the target GSM BSS. If the resourceallocation is successful, the RNC orders the mobile station to make aninter-system handover from UMTS Terrestrial Radio Access Network(UTRAN) to GSM.

In the case of a network-initiated cell reselection from WCDMA to GSM/GPRS, the RNC sends a cell change command to the UE, which then isresponsible for actually transferring the existing packet-switchedconnection to the target GSM/GPRS network.

The decision algorithm of the inter-system handover from GSM toWCDMA is located in the GSM Base Station Controller (BSC). After thehandover decision, the BSC initiates an inter-system relocation procedurein order to allocate radio resources from the target RNC. If the resourceallocation is successful in the target RNC, the BSC orders the UE to makean inter-system handover to the WCDMA radio access network. When aradio access bearer is handed over from one radio access technology toanother, the core network is responsible for adapting the Quality of Service(QoS) parameters of the radio access bearer according to the new (GSM/GPRS or WCDMA) radio access network.

11.1 Coverage reason inter-system handover

The RNC supports the following coverage reason inter-system handovers(and cell reselections) to GSM for both real-time (RT) and Non-Real Time(NRT) radio bearers:

. inter-system handover because of uplink DCH quality


. inter-system handover because of CPICH RSCP

. inter-system handover because of downlink DPCH power


. Immediate IMSI-based handover (for more information, see SectionFunctionality of immediate IMSI-based handover)

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Note

In the inter-system handover context, the last two handovers on theabove list (inter-system handover because of downlink DPCH powerand inter-system handover because of CPICH Ec/No) are regarded ascoverage reason handovers.

11.1.1 Inter-system handover because of uplink DCH quality

The quality deterioration report from the uplink outer loop power controlcan be used to trigger off inter-system handover to GSM if the serving cell(or cells participating in soft handover) has GSM neighbour cells. Theuplink outer loop power control sends the quality deterioration report to thehandover control, if the uplink quality stays constantly worse than the BitError Ratio (BER)/Block Error Ratio (BLER) target although the uplinkSignal-to-Interference Ratio (SIR) target has reached the maximum value(the UE has reached either its maximum Tx power capability or themaximum allowed transmission power level on the DPCH).

The reporting criteria of the quality deterioration report is controlled withthe following Radio Network Planning (RNP) parameters:

. Quality deterioration report from UL OLPC controller(EnableULQualDetRep) indicates whether the uplink outer loop PCcan send a quality deterioration report to the handover control insituations when the quality stays worse than the BER/BLER targetdespite of the maximum uplink SIR target.

. UL quality deterioration reporting threshold(ULQualDetRepThreshold ) determines the period during which thequality must constantly stay worse than the BER/BLER target(despite of the maximum uplink SIR target) before the uplink outerloop PC may send a quality deterioration report.

For a description of the parameters, see WCDMA RAN ParameterDictionary which can be found in the Reference category of thisdocumentation library.

The uplink outer loop PC repeats the quality deterioration reports to thehandover control periodically until the uplink SIR target decreases belowthe maximum value.

Handover control does not interrupt an ongoing inter-system (GSM)measurement procedure even if the uplink outer loop PC stops sendingthe quality deterioration reports.


Handover Control



The GSM HO caused by UL DCH Quality (GSMcauseUplinkQuality)parameter indicates whether an inter-system handover to GSM caused byUplink DCH quality is enabled. In case of RT data connection (CircuitSwitched (CS) or Packet Switched (PS)), also the maximum allocated userbitrate on the uplink DPCH must be lower than or equal to the bitratethreshold which is controlled with the parameter Maximum Allowed ULUser Bitrate in HHO (HHoMaxAllowedBitrateUL), before the RNC maystart the measurement because of uplink DCH quality. This limitation inuplink bitrate is not applied for NRT services. When the inter-systemhandover/measurement is enabled, the RNC starts the inter-system(GSM) measurement as described in Section Measurement procedure.

The RNC makes the handover decision on the basis of the periodical inter-system measurement reports received from the UE and relevant controlparameter as described in Section Handover decision procedure.

11.1.2 Inter-system handover because of UE transmission power

If the serving cell (or cells participating in soft handover) has GSMneighbour cells, event triggered UE transmission power measurementreport can be used to trigger off handover to GSM when the transmissionpower of the UE approaches either its maximum RF output powercapability or the maximum transmission power level the UE can use on theDPCH.

The GSM HO caused by UE TX Power (GSMcauseTxPwrUL) RNPparameter indicates whether an inter-system handover to GSM caused bythe UE transmission power is enabled. In addition, the maximum allocateduser bitrate on the uplink DPCH must be lower than or equal to the bitratethreshold which is controlled with the RNP parameter Maximum AllowedUL User Bitrate in HHO (HHoMaxAllowedBitrateUL), before the RNC maystart the inter-system (GSM) measurement because of UE transmissionpower. When the inter-system handover/measurement is enabled, theRNC starts the UE internal measurement in order to monitor the UEtransmission power level. The measurement reporting criteria for the UEtransmission power measurement is controlled with the following RNPparameters:

. UE TX Power Filter Coefficient (GsmUETxPwrFilterCoeff) controlsthe higher layer filtering (averaging) of the physical layertransmission power measurements in the UE. The physical layermeasurement period for the UE transmission power is one slot.

. UE TX Power Threshold for AMR (GsmUETxPwrThrAMR)determines the UE transmission power threshold for a circuit-switched voice connection.

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. UE TX Power Threshold for CS (GsmUETxPwrThrCS) determinesthe UE transmission power threshold for a circuit-switched dataconnection.

. UE TX Power Threshold for NRT PS (GsmUETxPwrThrNrtPS)determines the UE transmission power threshold for a non-real timepacket-switched data connection.

. UE TX Power Threshold for RT PS (GsmUETxPwrThrRtPS)determines the UE transmission power threshold for a real-timepacket-switched data connection.

. UE TX Power Time Hysteresis (GsmUETxPwrTimeHyst) determinesthe time period during which the UE transmission power must staybelow the transmission power threshold before the UE calls off thehandover cause (event 6B).

Note that the UE transmission power is not used as a handover cause for aservice type if the value of the corresponding UE transmission powerthreshold parameter is 'not used'. The power thresholds are relative to themaximum transmission power level a UE can use on the DPCH in the cell(or the maximum RF output power capability of the UE in WCDMA,whichever is lower). In case of multiservice, the RNC selects theparameters in the following order: 1st priority AMR, 2nd priority CS data, 3rd

priority RT PS data and 4th priority NRT PS. For the description of theparameters, see WCDMA RAN Parameter Dictionary.

If the UE transmission power becomes greater than the reporting threshold(event 6A), the UE sends the measurement report (event 6A) to the RNC,and the RNC starts the inter-system (GSM) measurement as described inSection Measurement procedure.

The RNC makes the handover decision on the basis of the periodical inter-system measurement reports received from the UE and relevant controlparameters as described in Section Handover decision procedure.

Note

The RNC does not break off ongoing inter-system (GSM) measurementeven if the transmission power of the UE decreases below the reportingthreshold (event 6B) during the measurement and the UE sends thecorresponding measurement report (event 6B) to the RNC.


Handover Control

11.1.3 Inter-system handover because of CPICH RSCP

Received Signal Code Power (RSCP) measurement result on the PrimaryCPICH can be used to trigger off inter-system handover to GSM if theserving cell (or cells participating in soft handover) has GSM neighbourcells.

The GSM HO caused by CPICH RSCP (GSMcauseCPICHrscp) RNPparameter indicates whether an inter-system handover to GSM caused bylow measured absolute CPICH RSCP is enabled. When the inter-systemhandover is enabled, the RNC sets up an intra-frequency measurement inorder to monitor the absolute CPICH RSCP value. The measurementreporting criteria for the intra-frequency CPICH RSCP measurement iscontrolled with the following RNP parameters:

. CPICH RSCP HHO Threshold (HHoRscpThreshold) determines theabsolute CPICH RSCP threshold which is used by the UE to triggerreporting event 1F.

. CPICH RSCP HHO Time Hysteresis (HHoRscpTimeHysteresis)determines the time period during which the CPICH RSCP of theactive set cell must stay worse than the thresholdHHoRscpThreshold before the UE can trigger reporting event 1F.

. CPICH RSCP HHO Cancellation (HHoRscpCancel) determines theabsolute CPICH RSCP threshold which is used by the UE to triggerreporting event 1E.

. CPICH RSCP HHO Cancellation Time (HHoRscpCancelTime)determines the time period during which the CPICH RSCP of theactive set cell must stay better than the threshold HHoRscpCancelbefore the UE can trigger the reporting event 1E.

. CPICH RSCP HHO Filter Coefficient (HHoRscpFilterCoefficient)controls the higher layer filtering (averaging) of physical layer CPICHRSCP measurements before the event evaluation andmeasurement reporting is performed by the UE. The UE physicallayer measurement period for intra-frequency CPICH RSCPmeasurement is 200 ms.

If the CPICH RSCP measurement result of an active set cell becomesworse than or equal to the absolute threshold/parameterHHoRscpThreshold, the UE sends an event 1F-triggered measurementreport to the RNC. The UE cancels event 1F by sending an event 1E-triggered measurement report to the RNC if the CPICH RSCPmeasurement result of the active set cell increases again and becomesbetter than or equal to the threshold HHoRscpCancel. If the CPICH RSCP

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measurement result of all active set cells has become worse than thereporting threshold HHoRscpThreshold (event 1F is valid for all active setcells simultaneously), the RNC starts the inter-system (GSM)measurement as described in Section Measurement procedure.

The RNC makes the handover decision on the basis of the periodical inter-system measurement reports received from the UE and relevant controlparameters , see Section Handover decision procedure.

Note

The RNC does not break off ongoing inter-system (GSM) measurementeven if the measured CPICH RSCP of one or more active set cellsincreases again above the reporting threshold HHoRscpCancel and theUE sends the corresponding event 1E-triggered intra-frequencymeasurement report to the RNC.

11.1.4 Inter-system handover because of downlink DPCH power

The Base Station (BTS) measures and averages the downlink code powerof each radio link separately and reports the averaged measurementresults to the controlling RNC at regular intervals with a 3GPP NBAP:DEDICATED MEASUREMENT REPORT. The base station measures thedownlink code power from the pilot bits of the dedicated physical controlchannel (DPCCH). In case of an inter-RNC soft handover, the drifting RNCforwards the measurement results to the serving RNC in the RNSAP:DEDICATED MEASUREMENT REPORT message. In 3GPP NBAP, theReporting Period is controlled with the Dedicated Measurement ReportingPeriod (Dedicated MeasReportPeriod), Dedicated MeasurementReporting Period CS data (DediMeasRepPeriodCSdata), DedicatedMeasurement Reporting Period PS data (DediMeasRepPeriodPSdata)RNP parameters. All of these measurement reports can trigger off inter-system handover to GSM when the downlink transmission power of theradio link approaches its maximum allowed power level.

The GSM HO caused by DL DPCH TX Power (GSMcauseTxPwrDL) RNPparameter determines whether an inter-system handover to GSM causedby high downlink DPCH power level is enabled. In addition, the maximumallocated user bitrate on the downlink DPCH must be lower than or equalto the bitrate threshold defined by the Maximum Allowed DL User Bitrate inHHO (HhoMaxAllowedBitrateDL) RNP parameter, before the RNC maystart the inter-system measurement and handover because of downlinkDPCH power.


Handover Control

When the handover to GSM is enabled, the RNC starts the inter-systemmeasurement procedure (see Section Measurement procedure) if themeasured downlink code power of a single radio link satisfies the followingequation:

DL_CODE_PWR - PowerOffsetDLdpcchPilot >= CPICH_POWER +MAX_DL_DPCH_TXPWR + DL_DPCH_TXPWR_THRESHOLD

The variables in the formula are defined in the following table.

Table 14. Variables for inter-system handover


DL_CODE_PWR indicates the measured downlink codepower

PowerOffsetDLdpcchPilot is a constant that defines the power offsetfor the pilot fields of the DPCCH,expressed as a relative value with respectto the DPDCH power

CPICH_POWER indicates the transmission power of theprimary CPICH of an active set cell

MAX_DL_DPCH_TXPWR indicates the maximum transmissionpower level of the DPDCH symbols abase station can use on the DPCH,expressed as a relative value (dB) withrespect to the primary CPICH power(dBm)

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DL_DPCH_TXPWR_THRESHOLD is controlled with the following inter-system measurement control parameters,depending on the service type:. DL DPCH TX Power Threshold for RT

PS (GsmDLTxPwrThrRtPS )determines the downlink DPCHtransmission power threshold for a realtime packet-switched data connection

. DL DPCH TX Power Threshold for NRTPS (GsmDLTxPwrThrNrtPS)determines the downlink DPCHtransmission power threshold for a non-real time packet switched dataconnection

. DL DPCH TX Power Threshold for CS(GsmDLTxPwrThrCS) determines thedownlink DPCH transmission powerthreshold for a circuit-switched dataconnection

. DL DPCH TX Power Threshold forAMR (GsmDLTxPwrThrAMR)determines the downlink DPCHtransmission power threshold for acircuit-switched voice connection

The downlink DPCH transmission powerthresholds are relative (dB) to theallocated maximum transmission power ofthe DPCH.

In case of a multiservice, the RNC selectsthe lowest threshold value for thecalculation (e.g. when the alternativethreshold values are -1dB and -3dB, theRNC selects the -3dB threshold value).Downlink transmission power shall not beused as a handover cause for a servicetype if the value of the correspondingthreshold parameter is 'not used'.

The RNC makes the handover decision on the basis of periodic inter-system measurement reports received from the UE and relevant controlparameters, see Section Handover decision procedure.


Handover Control

11.1.5 Inter-system handover because of CPICH Ec/No

CPICH Ec/No measurement result (received energy per chip divided bythe power density in the band, that is, CPICH RSCP/UTRA Carrier RSSI)can be used to trigger off inter-system handover to GSM if the serving cell(or cells participating in soft handover) has GSM neighbour cells.

The GSM HO caused by CPICH Ec/No (GSMcauseCPICHEcNo) RNPparameter indicates whether an inter-system handover to GSM caused bylow measured absolute CPICH Ec/No is enabled. When the inter-systemhandover is enabled, the RNC sets up an intra-frequency measurement inorder to monitor the absolute CPICH Ec/No value. The measurementreporting criteria for the intra-frequency CPICH Ec/No measurement iscontrolled with the following RNP parameters:

. CPICH Ec/No HHO Threshold (HHoEcNoThreshold) determines theabsolute CPICH Ec/No threshold which is used by the UE to triggerreporting event 1F

. CPICH Ec/No HHO Time Hysteresis (HHoEcNoTimeHysteresis)determines the time period during which the CPICH Ec/No of theactive set cell must stay worse than the thresholdHHoEcNoThreshold before the UE can trigger reporting event 1F

. CPICH Ec/No HHO Cancellation (HHoEcNoCancel) determines theabsolute CPICH Ec/No threshold which is used by the UE to triggerreporting event 1E

. CPICH Ec/No HHO Cancellation Time (HHoEcNoCancelTime)determines the time period during which the CPICH Ec/No of theactive set cell must stay better than the threshold HHoEcNoCancelbefore the UE can trigger reporting event 1E

. CPICH Ec/No Filter Coefficient (EcNoFilterCoefficient) controls thehigher layer filtering (averaging) of physical layer CPICH Ec/Nomeasurements before the event evaluation and measurementreporting is performed by the UE. The UE physical layermeasurement period for intra-frequency CPICH Ec/Nomeasurements is 200 ms.

If the CPICH Ec/No measurement result of an active set cell becomesworse than or equal to the absolute threshold/parameterHHoEcNoThreshold, the UE sends an event 1F-triggered measurementreport to the RNC. The UE cancels event 1F by sending an event 1E-triggered measurement report to the RNC if the CPICH Ec/Nomeasurement result of the active set cell increases again and becomesbetter than or equal to the threshold HHoEcNoCancel. If the CPICH Ec/No

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measurement result of all active set cells has become worse than thereporting threshold HHoEcNoThreshold (event 1F is valid for all active setcells simultaneously), the RNC starts the inter-system (GSM)measurement, see Section Measurement procedure.

The RNC makes the handover decision on the basis of periodic inter-system measurement reports received from the UE and relevant controlparameters, see Section Handover decision procedure.

Note

The RNC does not break off ongoing inter-system measurement even ifthe measured CPICH Ec/No of one or more active set cells increasesagain above the reporting threshold HHoEcNoCancel and the UEsends the corresponding event 1E triggered intra-frequencymeasurement report to the RNC.


The measurement results of the GSM neighbour cell must satisfy thefollowing equation before the inter-system handover or cell change toGSM/GPRS is possible:

AVE_RXLEV_NCELL(n) > AdjgRxLevMinHO (n) + max( 0,AdjgTxPwrMaxTCH (n) - P_MAX )

In the equation above, AVE_RXLEV_NCELL(n) is the averaged GSMcarrier RSSI value of the GSM neighbour cell (n). The RNC calculates theaveraged value directly from the measured dBm values, linear averagingis not used in this case. The sliding averaging window is controlled with theMeasurement Averaging Window (GsmMeasAveWindow) parameter. TheRNC starts averaging already from the first measurement sample, that is,the RNC calculates the averaged values from those measurementsamples, which are available until the number of samples is adequate tocalculate averaged values over the whole averaging window.

The Minimum RX Level for Coverage (AdjgRxLevMinHO) RNP parameterdetermines the minimum required RSSI (dBm) level which the averagedRSSI value of the GSM neighbour cell (n) must exceed before the inter-RAT handover is possible. The neighbour cell parameter Maximum MS TXPower on TCH (AdjgTxPwrMaxTCH) indicates the maximum transmissionpower (dBm) a UE may use in the GSM neighbour cell (n). P_MAXindicates the maximum RF output power capability of the UE (dBm) inGSM.


Handover Control

The GSM Neighbour Cell Search Period (GsmNcellSearchPeriod) RNPparameter determines the period, starting from the measurement setup,during which a handover to GSM is not possible. This period allows the UEto find and report all potential GSM cells before the handover decision.After the search period has expired, the RNC evaluates the radio linkproperties of the best GSM neighbour cells after every measurementreport. The RNC initiates a handover attempt to the best GSM neighbour(target) cell as soon as the best GSM neighbour cell satisfies the requiredradio link properties.

If there are several GSM cells which satisfy the required radio linkproperties at the same time, the RNC ranks the potential GSM cellsaccording to the priority levels and selects the highest ranked GSM cell tobe the target cell. The priority order is controlled with the Ncell Priority forCoverage HO (AdjgPriorityCoverage) RNP parameter which is defined foreach GSM neighbour cell. The crucial principle is that high-priority cells areconsidered better than low-priority cells, that is, a cell is ranked higher thananother cell if it has a higher priority level even though its signal strengthcondition is worse; signal strength conditions have effect only betweencells which have the same priority level.

11.2 Interactions between handover causes

The handover cause, which has triggered first has the highest priority. Thatis, the RNC does not stop or modify ongoing inter-system (GSM)measurement and handover decision procedures if another handovercause is triggered during the handover procedures.

If two or more inter-system (GSM) handover causes are triggeredsimultaneously, the RNC selects the cause, which has the highest priority.The priority order is the following:

1. Immediate IMSI-based inter-system handover has higher prioritythan the other inter-system handover causes (for more information,see Section Functionality of immediate IMSI-based handover).

2. Quality and coverage reason inter-system handovers. The RNCsupports the following quality and coverage reason inter-systemhandovers to GSM (the handover causes are not presented in anyparticular order):. inter-system handover to GSM/GPRS because of uplink DCH

quality. inter-system handover to GSM/GPRS because of UE Tx

power

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. inter-system handover to GSM/GPRS because of downlinkDPCH power

. inter-system handover to GSM/GPRS because of CPICHRSCP

. inter-system handover to GSM/GPRS because of CPICH Ec/No

3. Load-based inter-frequency handover (for more information, seeSection Functionality of Load- and Service-based IF/IS handover)

4. Service-based inter-frequency handover (for more information, seeSection Functionality of Load- and Service-based IF/IS handover)

11.3 Interaction with inter-frequency handover

If the serving cell (or cells participating in soft handover) has neighbourcells both on another carrier frequency and on another radio accesstechnology (GSM), the RNC determines the priorities between inter-frequency and -system handovers on the basis of Service Handover IEvalue. The RNC receives the Service Handover IE from the core networkin the RAB ASSIGNMENT REQUEST or RELOCATION REQUEST(RANAP) message. If the RNC does not receive the Service Handover IEfrom the core network, inter-frequency handover has priority over inter-system handover to GSM as a default value.

. Should be handed over to GSM:

Handover to GSM has priority over the inter-frequency handover. Inthis case the RNC shall not start inter-frequency measurements untilthe inter- system (GSM) measurements are completed, that is, whenno neighbouring GSM cell is good enough for the quality and/orcoverage reason handover.

. Should not be handed over to GSM:

Inter-frequency handover has priority over the handover to GSM. Inthis case the RNC shall not start the GSM measurements until theinter- frequency measurements are completed, that is, when noneighbouring cell is good enough for the quality and/or coveragereason inter-frequency handover.

. Shall not be handed over to GSM:


Handover Control

Inter-frequency handover has priority over the handover to GSM. Inthis case the RNC shall not start GSM measurements or handover toGSM even if no neighbouring cell is good enough for the quality and/or coverage reason inter-frequency handover. This means that theRNC does not initiate handover to GSM for the UE unless the RABswith this indication have first been released with the normal releaseprocedures.

11.4 Measurement procedure

The measurement procedure, the scenario of which is presented in FigureMeasuring procedure, is controlled by a number of parameters set duringradio network planning. These parameters are:

1. Measurement Reporting Interval (GsmMeasRepInterval) determinesthe measurement reporting interval for periodical inter-system(GSM) measurements.

2. GSM Neighbour Cell Search Period (GsmNcellSearchPeriod)determines the number of periodical inter-system (GSM)measurement reports, starting from the first report after themeasurement setup, during which a handover to GSM is notpossible. This period allows the UE to find and report all potentialGSM neighbour cells before the handover decision.

3. Maximum Measurement Period (GsmMaxMeasPeriod) defines themaximum allowed duration of the measurement by means of themaximum number of periodical inter-system (GSM) measurementreports during the measurement. If the RNC is not able to executethe handover to GSM, it shall stop the GSM measurement after theUE has sent the predefined number of measurement reports to theRNC.

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4. Minimum Measurement Interval (GsmMinMeasInterval) determinesthe minimum interval between an unsuccessful inter-system (GSM)measurement or handover procedure and the following GSMmeasurement procedure related to the same RRC connection.Repetitive GSM measurements are disabled when the value of theparameter is zero.

Figure 31. Measuring procedure

5. Minimum Interval Between HOs (GsmMinHoInterval) determines theminimum interval between a successful inter-system handover fromGSM to UTRAN and the following inter-system handover attemptback to GSM related to the same RRC connection. A returnhandover back to GSM is disabled when the value of the parameteris zero.

When an inter-system (GSM) measurement is initially started, themeasurement quantity is GSM Carrier RSSI. The RNC selects the highestranked GSM neighbour cell which meets the required radio link properties,to be the target cell. After the target cell selection, the RNC can repeat theinter-system measurement for the target GSM carrier and request theBSIC identification before the execution of inter-system handover to GSM.

In the case of CS data/voice services, the RNC always requests the BSICidentification of the target cell before the execution of the inter-systemhandover so that the mobile station can synchronise to the GSM cellbefore the handover execution, and also to verify the identification if two ormore neighbouring GSM cells have the same BCCH Frequency. In thecase of PS data (RTor NRT) services, the RNC does not verify the BSIC ofthe target cell before the execution of the inter-system cell change to GSM/GPRS unless two or more neighbouring GSM cells have the same BCCHFrequency.

GSM frequency

Frequency 1

HO

3

4 4

Time2

1

554


Handover Control

11.5 Function in abnormal conditions

If an attempted inter-system handover to GSM fails, the RNC determinesan extra time interval during which an inter-system handover to the targetcell of the unsuccessful hard handover attempt is not allowed. Theduration of the time interval depends on the number of inter-system hardhandover failures related to the same GSM cell during the same RRCconnection. The RNC determines the time interval in the following way:

TIME_INTERVAL = ( 1 + NUMBER_OF ISHO_FAILS ) *GsmMinMeasInterval

The Minimum Measurement Interval (GsmMinMeasInterval) RNPparameter determines the minimum interval between an unsuccessfulinter-system measurement (or handover attempt) procedure and thefollowing inter-system (GSM) measurement procedure related to the sameRRC connection.

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Handover Control

12 Functionality of IMSI-based handover

12.1 Configuration of IMSI-based handover

WCDMA subscriber group (WSG)

WCDMA subscriber group (WSG) refers to all subscribers of one operator,which are identified with the same PLMN identifier that is included in theIMSI of the subscribers. Up to 128 different WCDMA subscriber groupscan be defined.

The WCDMA subscriber group links the home PLMN of the subscriberwith specified authorised networks (PLMNs). The RNC is able to associatethe maximum of 128 specified home PLMNs with specified authorisednetworks. The WSG parameters are composed of the followingparameters:

. Subscriber Group Identifier (SubscriberGroupId) identifies asubscriber group uniquely within the RNC.

. Subscriber Home PLMN (HomePLMN) contains the identifier of thehome PLMN of a subscriber.

. Identifier of the Authorised Network (WSGAuthorisedNetworkId)identifies a group of authorised PLMNs which are considered equalto the home PLMN of a subscriber.


An example of selecting the authorised network identifier is illustrated inFigure An example of selecting the authorised network list below. ThePLMN identifier of the subscriber is 123 45.

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Functionality of IMSI-based handover



Figure 32. An example of selecting the authorised network list

All PLMNs are authorised for a subscriber when the value of the Identifierof the Authorised Network (WSGAuthorisedNetworkId) parameter is zero.If the home PLMN of a subscriber does not belong to a subscriber group,the RNC uses a default authorised network. The identifier of the defaultauthorised network is determined by the parameter Identifier of the DefaultAuthorised Network (DefaultAuthorisedNetworkId).

WCDMA authorised networks (WANE)

WCDMA Authorised Networks (WANE) refers to a group of PLMNs thatare considered equal to the home PLMN of a subscriber. This means thata subscriber has the same access rights to all PLMNs which belong to theWANE. One WANE list contains a maximum of six PLMN identifiers. Up to10 different WANE lists can be defined. The WANE parameters arecomposed of the following parameters:

. Authorised Network Identifier (AuthorisedNetworkId) identifies agroup of PLMNs that are considered equal to the home PLMN of asubscriber.

. List of authorised Networks (AuthorisedNetworkList) determines thePLMN identifiers which are considered equal to the home PLMN ofthe subscriber.

. Authorised Network PLMN (AuthorisedNetworkPLMN) determines aPLMN identifier which is considered equal to the home PLMN of thesubscriber.

. Technology Used in Authorised Network (Technology) determinesthe radio network technology (WCDMA, GSM, or both) which isrelated to the PLMN of an authorised network.

WSGId

HomePLMN WSGAuthorisedNetwork

1

2

3

126

127

128

123 12

123 34

123 45

1

0

2

PLMN 123 45Authorisednetwork Id 2


Handover Control

Note that when the Technology parameter has the value 'GSM', thesubscriber is only allowed to make handovers to GSM cells includingthe corresponding PLMN identifier. If the parameter value is'WCDMA', handovers can only be made to WCDMA cells includingthe corresponding PLMN identifier. If the parameter value is 'GSMand WCDMA', the subscriber is allowed to make handovers to allcells (both GSM and WCDMA) containing the corresponding PLMNidentifier.

Inter-PLMN handover within RNC

When the IMSI-based handover feature is enabled in the RNC, the RNC isable to perform intra-RNC handovers between cells which belong todifferent PLMNs.

When the IMSI-based handover feature is enabled in the RNC, it ispossible to define (in addition to the primary PLMN identifier that is a partof the CN domain identifier) secondary PLMN identifiers under the RNC.The secondary PLMN identifiers are assigned to shared network areaswhere the subscribers of the partner operator can have access. Themaximum number of secondary PLMN identifiers is three. Thus the PLMNa cell belongs to, can be selected from four alternative (1 primary and 3secondary) PLMNs if the IMSI-based handover feature is enabled in theRNC.

The List of shared area PLMNs (SharedAreaPLMNlist) parameterdetermines the PLMN identifiers of the shared network to which thesubscribers of the partner operator can have access.

12.2 IMSI-based intra-frequency handover

The IMSI Based SHO (IMSIbasedSHO) measurement control parameterindicates whether the IMSI-based intra-frequency handover is enabled inthe cell.

The IMSI-based handover feature does not affect the intra-frequencymeasurement procedure. That is, the RNC makes the neighbour cell listsfor the intra-frequency measurement regardless of the PLMN identifiers ofthe neighbouring cells.

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When the IMSI-based intra-frequency handover is enabled in an active setcell, the RNC adds a new cell to the active set only if the PLMN identifier ofthe cell, which has triggered reporting event 1A or 1C, is included in therelevant WANE list, or it must have the same PLMN identifier as thesubscriber or an active set cell. For more information, see SectionConfiguration of IMSI-based handover.

Similarly, in case of an inter-RNC intra-frequency hard handover, thePLMN identifier of the target cell must be included in the relevant WANElist, or it must have the same PLMN identifier as the subscriber or an activeset cell before the RNC can perform the intra-frequency hard handover tothe target cell.

If the neighbour cell does not fulfil any of the preceding PLMNrequirements and the neighbour cell is clearly the strongest intra-frequency cell, the RNC can release the RRC connection to avoidexcessive uplink interference because of non-optimum fast closed looppower control (that is, the UE is not linked with the strongest cell anymore).For more information, see Section Functionality of intra-frequencyhandover.

12.3 IMSI-based inter-frequency handover

The IMSI Based IFHO (IMSIbasedIFHO) measurement control parameterindicates whether the IMSI-based inter-frequency handover is enabled inthe cell.

When the IMSI-based inter-frequency handover is enabled in an active setcell, the RNC selects only those neighbouring cells into the inter-frequencyneighbour cell list whose PLMN identifier is either included in the relevantWANE list or which have the same PLMN identifier as the subscriber. Theprocedure is the same for all inter-frequency handover causes. For moreinformation, see Section Configuration of IMSI-based handover.

12.4 IMSI-based inter-system handover

The IMSI Based GSM HO (IMSIbasedGsmHo)measurement controlparameter indicates whether the IMSI based inter-system handover toGSM is enabled in the cell or not.


Handover Control

When the IMSI based inter-system handover is enabled in an active setcell, the RNC selects only those GSM neighbour cells into the inter-systemneighbour cell list whose PLMN identifier is either included in the relevantWANE list or which have the same PLMN identifier as the subscriber. Theprocedure is the same for all inter-system handover causes. For moreinformation, see Section Configuration of IMSI-based handover.

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Handover Control

13 Functionality of immediate IMSI-basedhandover

13.1 Immediate IMSI-based inter-frequency handover

Immediate IMSI based inter-frequency handover is controlled with thefollowing parameters (for a description of the parameters, see WCDMARAN Parameter Dictionary):

. IMSI Based SHO (IMSIbasedSHO) indicates whether the IMSI-based intra-frequency handover is enabled in the cell or not.

. IMSI Based IFHO (IMSIbasedIFHO) indicates whether theimmediate IMSI-based inter-frequency handover is enabled in thecell or not.

. Minimum CPICH Ec/No for IFHO (AdjiMinEcNo) determines theminimum required CPICH Ec/No (dB) level in the best inter-frequency neighbour cell.

. Minimum CPICH RSCP for IFHO (AdjiMinRscp) determines theminimum required CPICH RSCP (dBm) level in the best inter-frequency neighbour cell (n).

. Maximum UE TX Power on DPCH (AdjiTxPwrDPCH) indicates themaximum transmission power level (dBm) an UE can use on theDPCH in the neighbouring cell.

When both the IMSI-based intra-frequency handover and the immediateIMSI-based inter-frequency handover are enabled in an active set cell, theRNC initiates an immediate IMSI-based handover procedure if the RNCcannot add a cell into the active set because the PLMN identifier of the celldoes not fulfil the requirement of home/authorised/active set PLMNs. Formore information, see IMSI-based intra-frequency handover inFunctionality of IMSI-based handover.

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The RNC selects only those neighbouring cells into the inter-frequencyneighbour cell list whose PLMN identifier is either included in the relevantWANE list or which have the same PLMN identifier as the subscriber. TheRNC performs the inter-frequency measurement as described inMeasurement procedure in Functionality of inter-frequency handover.

The measurement results of the best inter-frequency neighbour cell mustsatisfy the following equations before the immediate IMSI-based inter-frequency handover is possible:

AVE_EcNo_NCELL (n) > AdjiMinEcNo (n)

AVE_RSCP_NCELL (n) > AdjiMinRscp (n) + max( 0, AdjiTxPwrDPCH (n)– P_MAX )

In the equations above, AVE_EcNo_NCELL (n) and AVE_RSCP_NCELL(n) are the averaged CPICH Ec/No and RSCP values of the best(according to CPICH Ec/No) inter-frequency neighbour cell (n). P_MAXindicates the maximum RF output power capability of the UE (dBm) inWCDMA.

The Neighbour Cell Search Period (InterFreqNcellSearchPeriod)parameter determines the period starting from inter-frequencymeasurement setup during which an inter-frequency handover is notpossible. After the period has expired, the RNC evaluates the radio linkproperties of the best neighbour cell after every inter-frequencymeasurement report. The RNC performs the immediate IMSI-based inter-frequency handover to a best neighbour (target) cell as soon as the bestneighbour cell meets the required radio link properties.

Regarding averaging values, the RNC calculates them directly from themeasured dB and dBm values, linear averaging is not used in this case.The sliding averaging window is controlled with the parameterMeasurement Averaging Window (InterFreqMeasAveWindow). The RNCstarts averaging already from the first measurement sample, that is, theRNC calculates the averaged values from those measurement sampleswhich are available until the number of samples is adequate to calculateaveraged values over the whole averaging window.

13.2 Immediate IMSI-based inter-system handover

Immediate IMSI-based inter-system handover is controlled with thefollowing parameters (for a description of the parameters, see WCDMARAN Parameter Dictionary):


Handover Control



. IMSI Based SHO (IMSIbasedSHO) indicates whether the IMSIbased intra-frequency handover is enabled in the cell or not.

. IMSI Based GSM HO (IMSIbasedGsmHo) indicates whether theimmediate IMSI based inter-system handover to GSM is enabled inthe cell or not.

When both the IMSI-based intra-frequency handover and the immediateIMSI-based inter-system handover are enabled in an active set cell, theRNC initiates an immediate IMSI-based handover procedure if the RNCcannot add a cell into the active set because the PLMN identifier of the celldoes not fulfil the requirement of home/authorised/active set PLMNs. Formore information, see section IMSI-based intra-frequency handover inFunctionality of IMSI-based handover.

The RNC selects only those GSM cells into the neighbour cell list whosePLMN identifier is either included in the relevant WANE list or which havethe same PLMN identifier as the subscriber. The RNC performs the inter-system (GSM) measurement as described in Measurement procedure inFunctionality of inter-system handover.

The RNC makes the handover decision on the basis of periodic inter-system measurement reports received from the UE and relevant controlparameters, as described in Handover decision procedure in Functionalityof inter-system handover.

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Handover Control

14 Functionality of load-based and service-based IF/IS handover

14.1 Load-based handover

The RNC checks load-based handover triggers periodically in each cell.Checking is performed every time when new interference information isreceived from the BTS or a cell.

The following reasons can trigger a load-based handover procedure in acell:

. The total interference load of the cell exceeds a predefinedthreshold.

. PS NRT traffic capacity request rejection rate exceeds a predefinedthreshold.

. Downlink spreading codes are lacking in the cell.

. HW or logical resources are limited in the cell.

If one of the preceding reasons is fulfilled, the cell is in a load-basedhandover state. Note that a load-based handover state in the cell does notstop service-based handovers.

14.1.1 Total interference load of the cell exceeds a predefined threshold

Thresholds for the interference load are defined with the following RNP(WCEL) parameters:

. LHOPwrOffsetUL

. LHOPwrOffsetDL

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Functionality of load-based and service-based IF/IS handover

These parameters define power offset in dB compared to PrxTarget (UL)and PtxTarget (DL).

The CRNC observes the interference load of the cell in the following way.Target for the interference load of the cell is defined with the PtxTargetRNP parameter. Target of the total received interference power is definedwith the PrxTarget RNP parameter.

In addition to the received wide band interference, the uplink load is alsomeasured in the DCH throughput domain. The RNC maintains in each cellthe Uplink DCH own cell load factor LDCH,CELL of the DCH users; theAdmission Control describes in detail how the value of the LDCH,CELL isproduced. A particular uplink DCH own cell load threshold LLHO is definedin the throughput domain for the needs of the load-based handover withthe equation

Figure 33. Definition of uplink DCH own cell load threshold LLHO

Quantity Ptarget+LHO is the linear value of the sum of the dB-values of thePrxTarget and LHOPwrOffsetUL management parameters.

LminDCH is the planned minimum uplink DCH own cell load factor; its valueis defined with the Interference margin for the minimum UL DCH load(PrxLoadMarginDCH) management parameter. For more information, seeSection Estimations for the received throughput and interference inAdmission Control. The CRNC is allowed to allocate the uplink DCHresources up to this throughput limit without considering the receivedwideband interference.

The RNC also uses a planned maximum uplink DCH own cell load factorLmaxDCH in its uplink DCH resource allocation. The value of the load factorLDCH,CELL does not exceed the value of LmaxDCH. The value of LmaxDCH isdefined with the Interference margin for the maximum UL DCH load(PrxLoadMarginMaxDCH) management parameter. For more information,see Section Estimations for the received throughput and interference inAdmission Control.

If one of the two following conditions is true, the load-based handover statebegins in the cell.

LLHO = MAX 0, MIN 1-1

Ptarget + LHO

, LminDCH


Handover Control

(31) (PrxTotal > PrxTarget + LHOPwrOffsetUL) AND (LDCH,CELL > LLHO)

OR LDCH,CELL > LmaxDCH ·lin(LHOPwrOffsetUL)

(32) PtxTotal > PtxTarget + LHOPwrOffsetDL

Quantity lin(LHOPwrOffsetUL) is the value of the LHOPwrOffsetULparameter in the linear notation.

Condition (31) enables the uplink load-based handover decision in thethroughput domain and the decision remains interference based, when theuplink DCH allocations are done as interference based. The load-basedpart of it states that the cell have enough uplink DCH traffic, in anothercase, the load-based handover state is not set though the adjacent cellinterference or interference spikes were experienced in the cell. When theminimum uplink throughput threshold has been exceeded, the traffic istransferred from the spiking cell. Load-based handover state is alsoentered if the noise level was overestimated.and the uplink DCH load isobserved to approach the throughput- based overload threshold.

Note that if the PrxTotal of the cell is higher than PrxTarget + PrxOffset andLDCH,CELL is bigger than LminDCH or PtxTotal of the cell is higher thanPtxTarget ,the activation of the compressed mode is denied, which meansthat the handover measurements with CM are not possible.

Note that in the case of the dynamic sharing of the received interferencebetween the HSPA and DCH users, if there is at least one E-DCH MAC-dflow established in the cell at issue, the non-E-DCH interference powerPrxNonEDCH value is used in the cell instead of the total receivedinterference power PrxTotaI in the interference based decisions.Furthermore, the maximum value of the dynamic target threshold for uplinkDCH packet scheduling, defined by the operatoradjustablePrxTargetPSMax management parameter, is used as theinterference threshold instead of the PrxTarget. For more information, seeRadio Resource Management of HSUPA.

Note that when using the HSDPA Dynamic Resource Allocation, if there isat least one HS-DSCH MAC-d flow allocated in the cell, the non-HSPAtransmitted power (transmitted carrier power of all codes not used for HS-PDSCH, HS-SCCH, E-AGCH, E-RGCH or E-HICH transmission) is usedinstead of the total transmitted power (PtxTotal). The maximum value ofthe dynamic target threshold for packet scheduling, defined by theoperator adjustable PtxTargetPSMax management parameter, is usedinstead of PtxTarget. When using the HSDPA Static Resource AllocationPtxTargetHSDPA and PtxOffsetHSDPA target levels are also used insteadof PtxTarget and PtxOffset.

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14.1.2 Rejection rate of PS NRT traffic capacity requests exceeds apredefined threshold

If the rejection rate of PS NRT traffic capacity request in a cell exceeds apredefined threshold, in either downlink or uplink direction, load-basedhandover actions take place in the cell.

The of PS NRT traffic capacity request rejection rate is defined in thefollowing way:

(33) CapaReqRejRateUL = RejectedRequestsCellUL /(AllCapacityRequestsCellUL + LHONRTTrafficBaseLoad)

(34) CapaReqRejRateDL = RejectedRequestsCellDL /(AllCapacityRequestsCellDL + LHONRTTrafficBaseLoad)

Those PS NRT traffic capacity requests that cannot be satisfied aredivided by the sum of all PS NRT traffic capacity requests and NRT trafficbase load in this cell in both uplink and downlink directions.

The NRT traffic base load is defined with the LHONRTTrafficBaseLoad(WCEL) RNP parameter. It is used to prevent the measurement from beingtoo sensitive when there is minor actual NRT traffic with low success ratioin the cell.

The following RNP (WCEL) parameters define threshold points in uplinkand downlink directions:

. LHOCapaReqRejRateUL

. LHOCapaReqRejRateDL

The following equations are used to evaluate the situation:

(35) CapaReqRejRateUL > LHOCapaReqRejRateUL

(36) CapaReqRejRateDL > LHOCapaReqRejRateDL

If one of the previous equations is true, load-based handover actions takeplace in this cell.

14.1.3 Downlink spreading codes are lacking in the cell

Sometimes the interference load of the cell is not the limiting factor, butrather the lack of downlink spreading codes. The following equationdefines the measurement for the lack of downlink spreading codes:


Handover Control

(37) ReservationRateSC(SF=128) = ReservedSC / NumbAvailableSC *100

The equation defines the percentage of reserved spreading codes dividedby all possible spreading codes in the spreading code tree in the level SF =128.

ReservedSC contains only the minimum number of HS-PDSCH codesdefined by the lowest value in the HSPDSCHCodeSet managementparameter. If the number of allocated HS-PDSCH codes is greater than theminimum value, those HS-PDSCH codes exceeding the minimum valueare not considered as reserved ones in terms of spreading code load.

The following RNP (WCEL) parameter defines the threshold for thereservation situation of the downlink spreading codes. The range is from 0% to 100 %.

. LHOResRateSC

The following equation is used to evaluate the situation:

(38) ReservationRateSC > LHOResRateSC

If the inequality is true, load-based handover actions take place in this cell.

14.1.4 HW or logical resources are limited in the cell

There are no exact meters for investigating the HW or logical resourcereservation rate of the cell. The HW or logical resource reservation ratecan be detected only when congestion is faced.

A load-based handover state is triggeredbecause of HW or logicalresource congestion in the cell when a quotient of the number of samplesindicating cell-specific hard blocking and all samples added with the baseload during the measurement period exceeds the threshold. This thresholdis defined with the LHOHardBlockingRatioRNP parameter. Hard-blockingbase load is defined with the LHOHardBlockingBaseLoadRNP parameter.Hard blocking occurs when a DCH setup attempt faces congestion of theBTS or Iub AAL2 transmission capacity. ‘All samples’ is defined to be thenumber of successful and unsuccessful BTS or Iub AAL2 transmissioncapacity hunts in the DCH setup attempts.

The following equation is used to evaluate the situation:

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(39) NumberOfSamplesHardBlocking /(AllSamplesHWhuntDuringMeasPeriod + LHOHardBlockingBaseLoad) *100 % > LHOHardBlockingRatio

14.1.5 Processing of measurement results indicating load

A load situation in the WCDMA cell can vary a lot even during a shortperiod of time. That is why both the starting and stopping of the load-basedhandover state in the cell is based on averaged measurement results. It ispractical to have the averaging period of starting (LHOWinSizeON*) longerthan the averaging period of stopping (LHOWinSizeOFF*).

When the value of the LHOWinSizeON* parameter is higher than the valueof the LHOWinSizeOFF* parameter, load-based handover procedures arestarted if the averaged load in both starting and stopping window risesabove the load threshold and stays there for the requested hysteresis time.Load-based handover procedures are stopped if the averaged load withinthe stopping window goes below the load threshold.

When the value of the LHOWinSizeON* parameter is lower than the valueof the LHOWinSizeOFF* parameter, load-based handover procedures arestarted if the averaged load in the starting window rises above the loadthreshold and stays there for the requested hysteresis time. Load-basedhandover procedures are stopped if the averaged load in both starting andstopping window goes below the load threshold.

One load reason is enough to trigger the load-based handover state in thecell. All the load reasons must be OFF until the load-based handover stateis stopped.

In all cases, the averaging window has to be full until the calculation iscompleted. If the averaging window for starting load-based handovers isdefined as 0, the corresponding load trigger is not used in the cell.

The following figure illustrates the principles of the measurementprocedure and the triggering of the load-based handover. The sameprocedure is used with all four load triggers.


Handover Control

Figure 34. Measurement procedure for all four load triggers

Interference load of the cell

Arithmetical averaging is used. The same period is used for both uplinkand downlink directions.

Measurement periods are defined with the following RNP (WCEL)parameters:

. LHOWinSizeONInterference [seconds]

. LHOWinSizeOFFInterference [seconds]

Load-based handovers are started if the averaged load rises above therequested threshold and stays there for the requested hysteresis time.Hysteresis time for the interference load measurement is defined with thefollowing RNP (WCEL) parameter:

. LHOHystTimeInterference [seconds]

Load based HOs arestarted if load risesabove the thresholdand stays there forthe hysteresis time

Load basedHO state

triggers ONLoad based HO state

"ON" indication shall bebroadcasted in this point

1. Sliding window toaverage measurementsamples when startingload based HO state

2. Hysteresistime

3. Sliding window toaverage measurementsamples when stoppingload based HO state

Load HOs

Activation of new loadbased HOs stopped

Load based HO state"OFF" indication shall bebroadcasted in this point

Load basedHO state

triggers OFF

4. Timer which delaysbroadcasting of loadbased HO state "OFF"

indication

1. 2.3.1.

3.3.

1.

4.t

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The delay in the removal of the load-based handover state from the cell iscontrolled with the following RNP (WCEL) parameter:

. LHODelayOFFInterference [seconds]

The measurement window is moved every time new interferenceinformation is received from the BTS (RRI period).

PS NRT traffic capacity request rejection rate in the cell

Arithmetical averaging is used. The same period is used for both uplinkand downlink directions.


. LHOWinSizeONCapaReqRejRate [seconds]

. LHOWinSizeOFFCapaReqRejRate [seconds]

Load-based handovers are started if the averaged load rises above therequested threshold and stays there for the requested hysteresis time.

Hysteresis time for the NRT load measurement is defined with thefollowing RNP (WCEL) parameter:

. LHOHystTimeCapaReqRejRate [seconds]

The delay in the remove of the load-based handover state from the overcell is controlled with the following RNP (WCEL) parameter:

. LHODelayOFFCapaReqRejRate [seconds]

The number of capacity requests counter is updated during themeasurement window when a resource is allocated for the capacityrequest or when the capacity request is rejected because of any reason.The measurement window is moved once a second.

Lack of downlink spreading codes in the cell

The RNC checks the load situation in the cell every time when a spreadingcode reservation rate is calculated.

The following RNP parameters (WCEL) define the period over which theDL SC reservation rates are averaged arithmetically:


Handover Control

. LHOWinSizeONResRateSC [seconds]

. LHOWinSizeOFFResRateSC [seconds]


Hysteresis time for the DL SC reservation rate measurement is definedwith the following RNP (WCEL) parameter:

. LHOHystTimeResRateSC [seconds]


. LHODelayOFFResRateSC [seconds]

The measurement window is moved every time new interferenceinformation is received from the BTS (RRI period).

Lack of HW or logical resources in the cell


. LHOWinSizeONHardBlocking [seconds]

. LHOWinSizeOFFHardBlocking [seconds]


Hysteresis time for the hard-blocking measurement is defined with thefollowing RNP (WCEL) parameter:

. LHOHystTimeHardBlocking [seconds]


. LHODelayOFFHardBlocking [seconds]

Both counters number of all attempts and number of unsuccessfulattempts are updated when the corresponding hunting attempt issuccessfully or unsuccessfully terminated. The measurement window ismoved once a second.

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14.1.6 Number of UEs simultaneously in the load-based handoverprocedure

The following RNP (WCEL) parameters define the maximum number ofUEs that are simultaneously in a load-based handover procedure in thecell:

. LHONumbUEInterFreq

. LHONumbUEInterRAT

The load-based handover feature is not in use in the cell if the parameter isdefined as zero.

The aim is that when the load-based handover state is on in the cell, theRNC selects as many UEs as possible to the procedure until the load-based handover state is over. That is, when the load-based handoverprocedure of one UE ends, a new UE is selected to the procedure.

14.1.7 Selection of RRC connections for the load-based handoverprocedure

The following criteria are used to select UEs for the load-based handoverprocedure. The criteria are presented in order of priority.

Note that if the predefined number of UEs can be selected during the firstfive steps of the following procedure, the last steps (6…8) are not checked.

At the beginning, all the RRC connections in the cell which can perform aload-based handover according to the service type are candidates for theload-based handover procedure.

1. RRC connections whose SRNC is the RNC where the load-basedhandover was triggered.

Those RRC connections are not selected whose SRNC is other thanthe RNC where the load-based handover has triggered. That isbecause RRC signalling terminates in the SRNC and there is no wayto transmit load-based handover commands from the DRNC toSRNC through the Iur interface.

2. RRC connections which are not performing inter-frequency or inter-RAT handover measurements.

If an RRC connection is already performing inter-frequency or inter-RAT handover measurements, it means that the handoverprocedure is ongoing because of some other handover reason.


Handover Control

3. RRC connections whose repetitive handover or network-controlledcell reselection procedures are not restricted.

4. RRC connection using a pure NRT service is accepted only if itsDCH allocation has lasted over a certain period of time.

The period is defined with the LHOMinNrtDchAllocTime (RNC) RNCconfiguration parameter. Note that DCH allocation can take a longtime.

5. RRC connections which are not in the preferred RAT or hierarchicalWCDMA layer and RRC connections which are in preferredhierarchical WCDMA layer but at least one equal target is available.

The RNC investigates which RRC connections are not in thepreferred RAT or hierarchical WCDMA layer, checks if the selectedtarget is available, and selects those as candidates for the load-based handover procedure. Also RRC connections which are inpreferred hierarchical WCDMA layer but at least one equal target isavailable are selected as candidates for the load-based handoverprocedure.

In the first phase, only first priority cases are selected as candidatesfor the load-based handover procedure. If there are not enough RRCconnections available for the procedure in the first phase, thesecond phase takes place and second priority cases are selected ascandidates for the load-based handover procedure. Finally, if thereare not enough RRC connections that can be selected in the firstand second phases, the third phase takes place.

If no RRC connection can be selected even after the third phase, nohandover procedures are performed and, finally, overload control ofthe RNC performs its actions if needed.

6. RRC connections which cause the highest load in the cell.

The selection of RRC connections depends on the load trigger whichhas triggered:. If DL interference load has triggered, RRC connections with

the highest downlink power are selected.. If UL interference load has triggered, RRC connections with

the smallest minimum UL spreading factor are selected.. If DL NRT capacity request rejection rate has triggered, RRC

connections with the highest downlink power are selected.. If UL NRT capacity request rejection rate has triggered, RRC

connections with the smallest minimum UL spreading factorare selected.

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. If DL spreading code capacity has triggered, RRC connectionswith the smallest minimum DL spreading factor are selected.

. If HW or logical resource capacity of the cell has triggered, theRRC connections with the smallest minimum UL and DLspreading factor are selected.

7. RRC connections which do not require a compressed mode toperform inter-frequency or inter-RAT measurements (the relevantmeasurement type depends on the type of the load-basedhandover).

8. Finally, the RNC selects the required number of RRC connections infree order from the group of RRC connections which are selectedduring the previous steps.

14.2 Service-based handover

14.2.1 Number of RRC connections simultaneously in the service-basedhandover procedure

Service-based handover actions are started in a certain cell periodically.The following RNP parameters (WCEL) define the duration of the period:

. ServHOPeriodInterFreq

. ServHOPeriodInterRAT

The service-based handover feature is not in use in the cell if theparameter is defined as zero.

Each time a service-based handover is started in the cell, a certain numberof RRC connections is selected in the procedure, if possible. The numberof selected RRC connections is defined with the following RNPparameters (WCEL):

. ServHONumbUEInterFreq

. ServHONumbUEInterRAT


Handover Control

14.2.2 Selecting RRC connections for the service-based handoverprocedure

The following criteria are used to select RRC connections for the service-based handover procedure. The criteria are listed in order of priority. Notethat if the predefined number of RRC connections can be selected duringthe first five steps of the following procedure, the last steps (6-7) are notchecked.

At the beginning, all the RRC connections in the cell which can perform aservice-based handover according to the service type are candidates forthe service-based handover procedure.

1. RRC connections whose SRNC is the RNC where the service-basedhandover has triggered.

Those RRC connections are not selected whose SRNC is other thanthe RNC where the cell-based service handover has triggered. Thatis because RRC signalling terminates in the SRNC and there is noway to transmit service-based handover commands from the DRNCto the SRNC through the Iur interface.

2. RRC connections which do not perform inter-frequency or inter-RAThandover measurements.

If the RRC connection already performs inter-frequency or inter-RAThandover measurements, it means that the handover procedure isongoing because of some other handover reason.

3. RRC connections whose repetitive handover or network-controlledcell re-selection procedures are not restricted.

4. RRC connections that are in the CELL_DCH state.

Service-based handovers are performed only for those RRCconnections that are in the CELL_DCH state.

5. RRC connections that are not in the preferred RAT or hierarchicalWCDMA layer according to the combined service priority list (seeTable Combination of service priority information in SectionCombined service priority list).

The RNC investigates which RRC connections are not in thepreferred RAT or hierarchical WCDMA layer, checks if the selectedtarget is available, and selects those as candidates for the service-based handover procedure.

Only those RRC connections which are in category 1 of this list canbe included in the service-based handover procedure.

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6. RRC connections which do not require the compressed mode toperform inter-frequency or inter-RAT measurements (the relevantmeasurement type depends on the type of the service-basedhandover).

7. Finally, the RNC selects the predefined number of RRC connectionsin free order from the group of RRC connections that have beenselected as described in steps 1-6.

If no RRC connection can be selected, service-based handovers are notperformed and the next connection is selected after the timer expires.

14.2.3 Defining the target for the service-based handover

The preferred RAT or preferred hierarchical WCDMA layer of each RRCconnection in the service-based handover is determined according tocombined service priority information (see Table Combination of servicepriority information in Section Combined service priority list).

If the UE is not in the preferred RAT or hierarchical WCDMA layer and thepreferred RAT or hierarchical WCDMA layer is available, the UE isselected into the set of possible candidates for the service-basedhandover procedure. Only those RRC connections that are in category 1of the above list are included in the service-based handover procedure.

14.3 Service priority

14.3.1 Iu interface service priority

Iu interface service priority information defines the target system forservice- and load-based handovers.

The Service Handover IE received from the Iu interface through RANAPsignalling provides the following alternatives:

1. Handover to GSM should be performed.

2. Handover to GSM should not be performed.

3. Handover to GSM shall not be performed.

The Iu interface service priority information is used to produce a combinedservice priority list.


Handover Control

Note

The Iu interface service priority information is RAB-based and optional.An RNC-based service priority handover profile table is used tocomplement it if needed, or instead of it, if it is not available.

14.3.2 RNC-based service priority handover profile table

For each of the eight service types the UE uses, the following alternativescan be defined by using RNC configuration parameters:

. GSM

. WCDMA

. WCDMA macro cell

. WCDMA micro cell

. Not defined (WCDMA or GSM)

Different WCDMA layers are handled according to the following rules:

. WCDMA macro cell means HCS priorities from 0 to 3.

. WCDMA micro cell means HCS priorities from 4 to 7.

. HCS priority 0 is the highest priority for a service type that prefersmacro cells.

. HCS priority 7 is the highest priority for a service type that prefersmicro cells.

. WCDMA macro cell or WCDMA micro cell definition defines thedirection in the hierarchical WCDMA layer structure which theservice type used by the UE prefers.

. The main principle is that an attempt is made to hand over a certainservice type to the cell/layer which has the highest available priorityfor it.

The HCS priority of the serving cell is determined by the HCS_PRIO(WCEL) RNP parameter, and the HCS priority of an inter-frequencyneighbour cell is determined by the AdjiHCSpriority (HOPI) parameter.

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Note

Iu interface service priority information has a higher priority than theRNC-based table below. If RAB-based Iu interface service priorityinformation is not available, only the information in this table is used. Inaddition, this table defines the preferred layer inside the WCDMAsystem, and that information is used to complement the Iu interfaceservice priority information.

Table 15. RNC-based service priority handover profile table

Service type used by the UE Preferred RAT or WCDMA layer

Conversational, Circuit-switched speech GSMConversational

Circuit-switched transparent data GSMConversational

Packet-switched speech WCDMA Conversational

Packet-switched real-time data WCDMA Streaming

Circuit-switched non-transparent data WCDMA macro layer Streaming

Packet-switched real-time data WCDMA macro layer Interactive

Packet-switched non-real time data WCDMA micro layer Background

Packet-switched non-real time data Not defined

14.3.3 Combined service priority list

The RNC produces a combined service priority list based on the Iuinterface service priority information and the RNC-based service priorityhandover profile table.

If the UE is not in the preferred RATor hierarchical WCDMA layer, and thepreferred RAT or hierarchical WCDMA layer is available, the UE isselected into the set of possible candidates for the service-basedhandover procedure.

If the UE is not in preferred RAT or hierarchical WCDMA layer andpreferred RAT or hierarchical WCDMA layer is available or if the UE is inpreferred hierarchical WCDMA layer but at least one other equal preferredhierarchical WCDMA layer is available, the UE is selected into the set ofpossible candidates for the load-based handover procedure.


Handover Control

The serving WCDMA layer is 'WCDMA micro' or 'WCDMA macro' if all setactive cells are such. Otherwise, the serving layer is 'WCDMA'.

Table Combination of service priority information below defines thecombined service priority list which is used in service and load-basedhandovers. The Service Handover IE and the service priority handoverprofile table are not used alone but rather as combined service priorityinformation. The combined service priority list defines the preferred targetRATor hierarchical WCDMA layer for each phase according to the servicethat the UE uses.

The following abbreviations are used in Table Combination of servicepriority information:

1. Indicates the target for RAB in both service-basedand load-based handover procedures in the firstphase.

2. Indicates the target for RAB in a load-basedhandover procedure if there are not enough UEs inthe cell in the first phase (second phase).

3. Indicates the target for RAB in a load-basedhandover procedure if there are not enough UEs inthe cell in the first and second phases (third phase).

WCDMA WCDMA alone means that the preferred WCDMAlayer is not defined and, because of load reasons, theRRC connection can be handed over to any WCDMAlayer.

Because of load reasons, an attempt is made to hand over one RRCconnection only to one target (GSM, WCDMA, WCDMA micro, or WCDMAmacro).

Definitions in the following table cannot be controlled with RNPparameters.

Table 16. Combination of service priority information

Iu interface service priorityinformation

RNC-based service priorityinformation

Combined service priority list

Handover to GSM should beperformed

GSM 1. GSM

2. GSM

3. WCDMA

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Table 16. Combination of service priority information (cont.)




WCDMA 1. GSM

2. GSM

3. WCDMA

WCDMA macro 1. GSM

2. WCDMA macro layer

3. WCDMA

WCDMA micro 1. GSM

2. WCDMA micro layer

3. WCDMA

Not defined 1. GSM

2. GSM

3. WCDMA

Handover to GSM should not beperformed

GSM 2. WCDMA

3. GSM

WCDMA 2. WCDMA

3. GSM

WCDMA macro 1. WCDMA macro layer

2. WCDMA

3. GSM

WCDMA micro 1. WCDMA micro layer

2. WCDMA

3. GSM

Not defined 2. WCDMA

3. GSM

Handover to GSM shall not beperformed

GSM 2. WCDMA

3. WCDMA

WCDMA 2. WCDMA

3. WCDMA


2. WCDMA

3. WCDMA


Handover Control

Table 16. Combination of service priority information (cont.)





2. WCDMA

3. WCDMA


3. WCDMA

Iu interface service priorityinformation not available

GSM 1. GSM

2. GSM

3. WCDMA

WCDMA 2. WCDMA

3. GSM


2. WCDMA

3. GSM


2. WCDMA

3. GSM


3. GSM

14.3.4 Multi services in case of service-based and load-based handovers

Service-based or load-based handovers are not performed for those multiservice connections where combined service priority lists between RABshave contradictions. Table Combination of service priority information inSection Combined service priority list defines RAB-based combinedservice priority lists.

A contradiction exists if all RABs of the multi service connection do nothave the same preferred RAT or hierarchical WCDMA layer. A pureWCDMA definition means that both WCDMA micro and WCDMA macrolayers are suitable. A contradiction exists also if the preferred RAT andhierarchical WCDMA layer inside the WCDMA system are not defined for acertain service in a certain phase (see Table Combination of servicepriority information). This can happen only in the first phase.

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In the first phase, it is easy to check if a contradiction exists. In the secondand third phases, it is possible that the preferred RAT and hierarchicalWCDMA layers of RABs are in a different priority order. In these cases, theWCDMA system is selected assuming that WCDMA is defined as thepreferred target for all RABs in that phase or earlier phase(s).

Example

In the third phase:

RAB1 has definitions 1. GSM, 2. GSM, 3. WCDMA, and

RAB2 has definitions 2. WCDMA, 3. GSM,

which means that the WCDMA system is selected if it is available.

Note that this same RRC connection cannot be selected in the first orsecond phase because a contradiction exists in those phases.

Example

In the third phase:

RAB1 has definitions 1. GSM, 2. GSM, 3. WCDMA, and

RAB2 has definitions 1. WCDMA micro layer, 2. WCDMA, 3. GSM,

which means that WCDMA micro layer is selected if it is available.

Note that this same RRC connection cannot be selected in the first orsecond phase because a contradiction exists in those phases.

NRT RAB can be a part of the multi service.

A pure PS multi service RRC connection is allowed to hand over to theGSM/GPRS system because of a service-based or load-based handoverreason. However, a CS/PS multi service RRC connection is not handedover to the GSM/GPRS system because of a service-based or load-basedhandover reason.


Handover Control

14.3.5 Availability of the target WCDMA layers and GSM system

The RNC investigates the availability of the target WCDMA layers andGSM system in the neighbour cell list of the UE, which is selected in theservice and load-based handover procedure. Note that the neighbour celllist consists of a combination of all neighbour cells of active set cells.

The RNC checks if the inter-frequency neighbour cell list has anydefinitions. If one or more of the other layer cells in the neighbour cell listare marked as blocked cells in the SLHO procedure, theAdjiHandlingBlockedCellSLHO (ADJI) RNP parameter defines whetherthat layer is used as a target layer or not. If any suitable target WCDMAlayer is found, the WCDMA system is available for the service-based andload-based inter-frequency procedure.

A WCDMA inter-frequency layer can be considered as a 'micro' layer if allthe cells according to the neighbour cell list defined in the layer are definedas 'micro' cells. Similarly, a WCDMA inter-frequency layer can beconsidered as a 'macro' layer if all the cells according to the neighbour celllist defined in the layer are defined as 'macro' cells. If so, a WCDMA 'micro'or 'macro' layer is available for the service/based and load-based inter-frequency procedure.

The RNC checks if the GSM inter-system neighbour cell list has anydefinitions which the penalty time (AdjgPenaltyTimeNCHO) is not running.If it does, the GSM system is available for the service and load-basedinter-RAT procedure.

If a selected WCDMA target layer or GSM system is not available for aspecific UE, the service-based or load-based handover procedure of thatUE is stopped.

14.4 Load of the target cells

14.4.1 Common load measurement over Iur

The SRNC initiates common load measurements over Iur to certainDRNC's cells for the service and load-based handover. The reason for themeasurement is to prevent service and load-based handover attempts tocells that are already loaded.

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The AdjiComLoadMeasDRNCCellNCHO (ADJI) RNP parameter controlsthe common load measurement of an inter-frequency neighbour cell that iscontrolled by the DRNC. The measurement is controlled over Iur by usingRNSAP signalling. If the common load measurement is activated, the RNCconfiguration parameters and rules listed below define the measurement.

The used measurement is event-based. The report characteristics usedare 'Event A' (load is over threshold) and 'Event B' (load is belowthreshold).

The following RNC configuration parameters (RNC) define common loadmeasurement over Iur for the service and load-based handover to indicatea high load in the target cell:

. Measurement threshold is common for both events. It is defined withthe NCHOThrComLoadMeasDRNCCell (RNC) RNC configurationparameter. The range of the parameter is from 0 to 100.

. Measurement hysteresis is common for both events. It is definedwith the NCHOHystComLoadMeasDRNCCell (RNC) RNCconfiguration parameter.

. Measurement filter coefficient is defined with theNCHOFiltercoeffComLoadMeasDRNCCell (RNC) RNCconfiguration parameter.

If 'Event A' is detected, the service and load-based handover attempts arenot performed to this cell, that is, the cell is blocked from the SLHOprocedure. 'Event B' cancels 'Event A'.

Whether or not the cell controlled by the DRNC, whose common loadmeasurement is not activated or whose activation has not beensuccessful, is blocked in the service and load-based handover procedure,is defined with the SLHOHandlingOfCellLoadMeasNotActRNCconfiguration parameter. Whether or not the loaded/blocked neighbour cellblocks the whole frequency layer from the set of possible service and load-based handover targets is defined with the AdjiHandlingBlockedCellSLHO(ADJI) RNP parameter.

14.4.2 Load of the target WCDMA cell

The RNC checks the load of the target WCDMA cell before a service-based or load-based inter-frequency handover. That is done in one of twoways:either by checking the load-based handover state status information,which is received from the target cell as a broadcast sent inside the RNC,or by checking the status of the event-triggered common loadmeasurement (if available) of the neighbour cells controlled by the DRNC.


Handover Control

The RNC also checks whether the SLHO penalty time of that cell isrunning or not. The AdjiPenaltyTimeNCHO RNP parameter defines thepenalty time.

The SLHOHandlingOfCellLoadMeasNotAct RNC configuration parameterdefines whether or not the cell (controlled by the SRNC or DRNC) thatdoes not have active load measurement is interpreted as a blocked cell inthe SLHO procedure. Service- and load-based handovers are notperformed to the cell that is blocked in the SLHO procedure.

Whether or not the cell that is blocked in the SLHO procedure blocks thewhole frequency layer from the set of possible service and load-basedhandover targets is defined with the AdjiHandlingBlockedCellSLHO (ADJI)RNP parameter.

The load on the target WCDMA cells is checked when the availability ofthe target WCDMA layer is investigated, the neighbour cell list is built up,and it is checked whether the cells blocked in the service and load-basedhandover procedure are outside the soft handover range of the selectedbest-target cell or not.

Note that the load-based handover state information of the cells controlledby the drifting RNCs is not available.

14.4.3 Load of the target GSM/GPRS cell

The exact load of the target GSM/GPRS cell is not checked by the sourceRNC in case of a service or load -based inter-RAT handover. The targetBSC checks its own load situation and rejects the handover if necessary.

The source RNC checks whether the SLHO penalty time(AdjgPenaltyTimeNCHO) of that cell is running or not. That is done whenthe availability of the target system is checked and the neighbour cell list isbuilt up.

14.4.4 Congested target WCDMA or GSM cell

If a handover of any type (quality, coverage, and so on) to the GSM systemis started and the target GSM cell is selected based on measurements, butthe relocation to the GSM system is unsuccessful and the 'RANAP:Relocation Preparation Failure' IE is received from the core network,service and load-based handovers and network-controlled cellreselections to this target cell are not performed during a certain period.The period is defined with the AdjgPenaltyTimeNCHO (HOPG) RNPparameter. When the timer expires, service- and load-based handovers

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and network-controlled cell reselections to the target cell are possibleagain. This penalty time is not set if an unsuccessful network-controlledcell reselection happens or if resources from the target cell are reservedsuccessfully but after that the radio phase fails.

The RNC sets a similar penalty time to WCDMA inter-frequency cells. Thepenalty is set if a handover of any type (quality, coverage, and so on) failsto reserve resources from the target cell. This penalty time is not set if anunsuccessful network-controlled cell reselection happens or if resourcesfrom the target cell are reserved successfully but after that the radio phasefails. The penalty time is defined with the AdjiPenaltyTimeNCHO (HOPI)RNP parameter.

14.5 Inter-frequency and inter-RAT measurementprocedures

Service- and load-based inter-frequency and inter-RAT handovermeasurements are similar to the ones used in coverage and quality-basedhandovers. For more information, see Sections Functionality of inter-frequency handover and Functionality of inter-system handover.

14.5.1 Selecting the service and load-based inter-frequency handovermethod

Service and load-based inter-frequency handovers are performed only forRRC connections that are in the CELL_DCH state.

In case of an RT connection or RT/NRT multi service connection, normalinter-frequency measurements are performed.

In case of a NRT connection, normal inter-frequency measurements areperformed by using the compressed mode or dual-receiver function, or ahandover procedure is not performed at all. Whether the inter-frequencymeasurements of the NRT connection using the compressed mode areallowed to be performed or not, is controlled with the RNP parameterSLHOCmAllowedNRT (RNC) RNP parameter. UE capability defineswhether inter-frequency measurements using the dual-receiver functionare possible or not.

In the inter-frequency handover (CS domain service, CS/PS domainservice, or PS domain service in the CELL_DCH state), resources from thetarget cell are always reserved before the handover command is sent tothe UE. An inter-frequency handover is performed in the CELL_DCH statebased on the measurements.


Handover Control

14.5.2 Selecting the service and load-based inter-RAT handover method

Service-based and load-based inter-system handovers and network-controlled cell reselections are performed only for RRC connections thatare in the CELL_DCH state.

In case of a RT connection or a RT/NRT multi service connection, normalinter-RAT measurements are performed.

In case of a NRT connection, normal inter-RAT measurements areperformed by using the compressed mode or dual-receiver function, or anetwork-controlled cell reselection procedure is not performed at all.Whether the inter-RAT measurements of the NRT connection using thecompressed mode are allowed to be performed or not, is controlled withthe SLHOCmAllowedNRT (RNC)RNP parameter. UE capability defineswhether the inter-RAT measurements using the dual-receiver function arepossible or not.

In the inter-RAT handover (CS or CS/PS domain service), resources fromthe target cell are always reserved before the handover command to theUE is sent. Inter-RAT handover is performed in the CELL_DCH statebased on the measurements.

Note

In the inter-RAT network-controlled cell reselection (PS domainservice), resources from the target are not reserved beforehand. Theinter-RAT network-controlled cell reselection is performed in theCELL_DCH state based on the measurements.

14.5.3 Measurement parameters

The measurement parameters of the service- and load-based handoverare similar to the ones used in coverage- and quality-based handovers.(See also Sections Measurement procedure for inter-frequency handoverand Measurement procedure for inter-system handover.) However, thefollowing is an exception.

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The InterFreqMinHoInterval and GsmMinHoInterval RNP parameters areused also in case of service- and load-based handovers. However, if theprevious handover reason is known to be service- or load-basedhandover, the InterFreqMinSLHOInterval (FMCI) andGsmMinSLHOInterval (FMCG) RNP parameters are used. This allows atimer to be set longer and prevents repetitive handovers between cellsduring one RRC connection.

InterFreqMinSLHOInterval defines the minimum interval between asuccessful service- or load-based inter-frequency handover and thefollowing service- or load-based inter-frequency handover attempt duringthe same RRC connection. Repetitive service- and load-based inter-frequency handovers are disabled when the value of the parameter iszero.

GsmMinSLHOInterval defines the minimum interval between a successfulservice- or load-based inter-RAT handover from GSM to UTRAN and thefollowing service-based or load-based inter-RAT handover attempt back toGSM during the same RRC connection. The return of the service- or load-based handover back to GSM is disabled when the value of the parameteris zero.

Note

If the RAB-based 'RANAP: Service Handover' IE is reconfigured after arelocation by the core network, the timer related to the RNP parameterGsmMinSLHOInterval is reset (if it is running).

14.5.4 Inter-frequency and inter-RAT neighbour cell lists

When the target of the service- or load-based handover is GSM/GPRS, theused inter-RAT neighbour cell list is the same as in a coverage- or quality-reason handover, but cells that are blocked in the SLHO procedure arereduced.

When the target of the service- or load-based handover is WCDMA macrocell, those layer(s) are selected from the normal inter-frequency neighbourcell list which are not blocked in the SLHO procedure and where all thecells have the definition 'HCS = 0 … 3'. The cells of the found layer(s) formthe neighbour cell list used in measurements.


Handover Control

When the target of the service- or load-based handover is WCDMA microcell, those layer(s) are selected from the normal inter-frequency neighbourcell list which are not blocked in the SLHO procedure and where all cellshave the definition 'HCS = 4 … 7'. The cells of the found layer(s) form theneighbour cell list used in measurements.

When the target of the service- and load-based handover is WCDMA, theinter-frequency neighbour cell list is the same as in a handover because ofcoverage or quality reasons, but the frequency layers that are blocked inthe SLHO procedure are reduced.

If there is more than one frequency to be measured, the RNC selects asubset of inter-frequency neighbour cells (with the same UTRA RFchannel number) which are measured first. The measurement order iscontrolled with the AdjiPrioritySLHO (HOPI) RNP parameter which isdefined for each inter-frequency neighbour cell. If the RNC cannot definethe measurement order by using the parameters, it measures the least-loaded frequencies first. The load is evaluated in each frequency bycalculating the quotient of the number of neighbour cells blocked in theSLHO procedure and all the neighbour cells. The frequency with thesmallest result is the least loaded one. If this is not possible to solve, theRNC measures frequencies in random order.

14.5.5 Number of UEs in compressed mode

The following RNP (WCEL) parameter defines how many UEs can besimultaneously in the compressed mode in one cell because of service orload -based handover procedures performing handover measurements:

. MaxNumberUECmSLHO

This amount is dedicated to service- or load-based handovermeasurement purposes. The compressed mode measurements becauseof a load reason have a higher priority than measurements because of aservice reason. Also, quality and coverage reason handovers can stealcapacity from this amount of UEs in CM if needed.

In case of a service and load reason, CM interference load of the cell ischecked similarly as in a quality and coverage reason CM. In a high-loadsituation, it is better to let the overload function operate than to cause moreinterference with new compressed modes.

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Note

The measurement capability IE of certain UEs can indicate that the CMis not needed, that is, the UEs have dual-receiver capability.

14.6 Handover decision procedure

14.6.1 Load- and service-based inter-frequency handover

The measurement results of the best neighbour cell must satisfy thefollowing equations before the service- and load-based inter-frequencyhandover is possible:

(40) AVE_RSCP_NCELL(n) > AdjiMinRscpNCHO(n) + max(0,AdjiTxPwrDPCH(n) – P_max)

(41) AVE_EcNo_NCELL(n) > AdjiMinEcNoNCHO(n)

where AVE_RSCP_NCELL(n) and AVE_EcNo_NCELL(n) are theaveraged CPICH RSCP and EcNo values of the best (according to CPICHEcNo) neighbour cell (n). The RNC calculates the average values directlyfrom the measured dB and dBm values, so linear averaging is not used inthis case. The sliding averaging window is controlled with theInterFreqMeasAveragingWindow RNP parameter. The RNC starts theaveraging already from the first measurement sample, that is, the RNCcalculates the averaged values from those measurement samples whichare available until the number of measurement samples is adequate tocalculate the averaged values over the whole averaging window.

The AdjiMinRscpNCHO(n) (HOPI) RNP parameter determines theminimum required CPICH RSCP value in dBm of the best neighbour cell.The AdjiMinEcNoNCHO(n) (HOPI) RNP parameter determines theminimum required CPICH EcNo value in dB of the best neighbour cell. TheAdjiTxPwrDPCH(n) neighbour cell parameter indicates the maximum Txpower in dBm an UE can use on the DPCH. P_max indicates themaximum RF output power capability of the UE in dBm in WCDMA.

The InterFreqCellSearchPeriod RNP parameter determines the periodstarting from inter-frequency measurement setup during which an inter-frequency handover is not possible. After the time period has expired, theRNC evaluates the radio link properties of the current best neighbour cellafter every inter-frequency measurement report. The RNC performs theinter-frequency handover to a best neighbour (target) cell as soon as the


Handover Control

best neighbour cell meets the required radio link properties (see theequations at the beginning of this section). However, the handoverdecision cannot be performed before the UE has reported the EcNo resultof all the cells which are blocked in the service- and load-based handoverprocedure.

The RNC checks if the cells which are blocked in the service- and load-based handover procedure are outside the soft handover range of theselected best target cell. The following equation has to be true until aservice- and load-based handover to the best neighbour cell is possible:

(42) AveEcNoNcell(target) – AdjiEcNoOffsetNCHO(target) >AveEcNoNcell(blocked)

AveEcNoNcell(target) and AveEcNoNcell(blocked) are the averagedEcNo values of the selected best target cell and a blocked cellcorrespondingly. The AdjiEcNoOffsetNCHO(target) (ADJI) RNP parameterdefines the offset for the procedure to ensure that the UE does not performan immediate soft handover to a blocked cell in the new frequency layer.

14.6.2 Load- and service-based inter-RAT handover

The measurement results of the GSM neighbour cell must satisfy thefollowing equation before the service- and load-based inter-RAT handoveror cell change from WCDMA to GSM/GPRS is possible:

(43) AVE_RXLEV_Ncell(n) > AdjgMinRxLevNCHO(n) + max(0,AdjgTxPwrMaxTCH(n) – P_Max)

where AVE_RXLEV_Ncell(n) is the averaged GSM carrier RSSI value ofthe GSM neighbour cell (n). The RNC calculates the averaged valuesdirectly from the measured dBm values, so linear averaging is not used inthis case. The sliding averaging window is controlled with theGSMMeasAveWindow parameter. The RNC starts the averaging alreadyfrom the first measurement sample, that is, the RNC calculates theaveraged values from those measurement samples which are availableuntil the number of measurement samples is adequate to calculate valuesover the whole averaging window.

The AdjgMinRxLevNCHO(n) (HOPG) parameter determines the minimumrequired GSM carrier RSSI level in dBm which the averaged RSSI value ofthe neighbour cell (n) must exceed before the service- and load-basedinter-system handover is possible. The AdjgTxPwrMaxTCH(n) neighbourcell parameter indicates the maximum Tx power level in dBm an UE canuse in the GSM neighbour cell (n). P_Max indicates the maximum RFoutput power capability in dBm of the UE in GSM.

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The GsmNcellSearchPeriod RNP parameter determines the periodstarting from inter-RAT measurement setup during which an inter-RAThandover to GSM is not possible. After the GSM neighbour cell searchperiod has expired, the RNC evaluates the radio link properties of the bestneighbour GSM cells after every inter-RAT measurement report. The RNCperforms the inter-RAT handover to the best GSM neighbour (target) cellas soon as the best GSM neighbour cell meets the required radio linkproperties (see the equation at the beginning of this section).

If there are several neighbour GSM cells which meet the required radio linkproperties at the same time, the RNC ranks the potential target cellsaccording to the priority levels and select the highest-ranked GSMneighbour cell to be the target cell. The priority order is controlled with theAdjgPrioritySLHO (HOPG) RNP parameter which is defined for each GSMneighbour cell. The crucial principle is that high-priority cells areconsidered better than low-priority cells, that is, a cell is ranked higher thananother cell if it has a higher priority level even though its signal strengthcondition was worse. Signal strength conditions have effect only betweencells which have the same priority level.

In the case of CS data and voice services, the RNC always verifies theBSIC of the target cell before the execution of the inter-RAT handover toGSM so that the mobile station can synchronise to the GSM cell before thehandover execution, and to verify the identification if two or moreneighbour GSM cells have the same BCCH Frequency. In the case of PSdata (RT or NRT) services, the RNC does not verify the BSIC of the targetcell before the execution of the inter-RAT cell change to GSM/GPRSunless two or more neighbour GSM cells have the same BCCHFrequency.

14.7 Handover signalling

14.7.1 Load- and service-based inter-frequency handover

The signalling procedure of an inter-frequency handover is described inSection Inter-frequency handover signalling.

When the relocation takes place, the source RNC sets the followingRANAP cause values to the RANAP: Relocation Required message:

. Resource Optimisation Relocation if the reason for the handover isservice-based

. Relocation desirable for radio reasons if the reason for the handoveris load-based


Handover Control

14.7.2 Load- and service-based inter-RAT handover and cell change

The signalling procedure of an inter-RAT (GSM) handover is described inSection Inter-system handover signalling.

When the relocation takes place, the source RNC sets the followingRANAP cause values to the RANAP: Relocation Required message:

. Resource Optimisation Relocation if the reason for the handoverreason is service-based

. Relocation desirable for radio reasons if the reason for the handoveris load-based

14.7.3 Service downgrading and upgrading because of inter-RAT handover

Non-transparent CS data connections can be downgraded in an inter-RAThandover from WCDMA to GSM and also upgraded back in an inter-RAThandover from GSM to WCDMA. These negotiations are done by the corenetwork, RAN and BSS via the Iu and A interfaces based on QoSparameters. Same procedures are used than in quality/service-basedinter-system handovers.

Note

Transparent CS data connections cannot be downgraded.

14.7.4 Restriction on repetitive load- and service-based handover attempts

Repetitive load-based or service-based handover (or network-controlledcell reselection) attempts of a RRC connection are restricted. If the load-based or service-based HO/NCCR attempt is unsuccessful, the next load-or service-based HO/NCCR attempt is possible after a certain period. Theperiod is hard-coded and defined to be 30 (after the first attempt), 60 (afterthe second attempt), 120, 120, 120, …seconds.

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Handover Control

15 SRNS relocation overview

The SRNS relocation is used for moving the SRNC functionality from oneRNC to another RNC closer to the UE if the UE moves during thecommunication. Both the radio access network (RAN) and the corenetwork are involved.

This section handles the SRNS relocation procedures while there arededicated channel resources, that is, radio link(s) allocated for the UE andthe handover control algorithm of the serving RNC control the mobilityprocedures of the RRC connection. Only SRNS relocation procedures inCELL_DCH state are handled here, that is, from a data forwarding point ofview. Mobility management during the other RRC states (Cell_FACH,Cell_PCH or URA_PCH) is based on cell reselections performed by theUE and Cell/URA Update procedures. When a Cell/URA Update isreceived through the Iur interface from the neighbouring RNC (DRNC), theRRC entity of the SRNC initiates a SRNS relocation procedure for packet-switched non-real time service (if SRNS relocation is supported by thepeer elements).

Note

URA_PCH is not supported in the current release.

HSPA inter-RNC cell change feature is described in the customerdocument Radio Resource Management of HSDPA.

Each RNC can control hundreds of BTSs. The vast majority of handoversin the WCDMA domain occurs inside one RNC area, that is, between cellscontrolled by one RNC, and thus causes no SRNS relocation. On the otherhand, in addition to normal intra-WCDMA SRNS relocations, inter-systemhandovers between WCDMA and GSM can occur.

For more information on different handover procedures, see SectionsFunctionality of intra-frequency handover, Functionality of inter-frequencyhandover and Functionality of inter-system handover.

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SRNS relocation overview

Handovers and SRNS relocation

The main purpose of handovers is to maintain the traffic connectionbetween the UE and the RNC when the UE is moving from the coveragearea (cell) of one BTS to that of another BTS. The reason for the handoveris that the signal of the new BTS becomes better. Besides pure mobilitymanagement concerns, handovers are performed for capacity reasons,that is, to minimise interference.

Regarding the UEs mobility it is really the handovers that count. TheSRNS relocation procedures can be seen as a subset for handoverprocedures: there are handovers without SRNS relocation but no SRNSrelocations without handovers.

Since an RNC can have hundreds of BTSs in its area, SRNS relocationsare much more infrequent than handovers. On the other hand, a handoveris always performed before or during an SRNS relocation. It should benoted, however, that unnecessary relocations can be avoided throughsmart radio network planning and optimisation.

Some evident benefits of SRNS relocation

. Radio resource optimisation is done in the RNC that has the bestinputs for the algorithms (for example handover decision).

. Transmission route is always optimised - every RNC does not haveto be configured as a neighbour RNC for other RNCs.

. Iur interface is not critical: congestion or failure situations do notaffect UE mobility since handovers can be done without Iur interface(hard handover) - Iur interface dimensioning is easier.

. Lost calls can be avoided.

. Excessive traffic load in hot spot RNCs (for example railway stations,airports and subway stations) can be avoided.


Handover Control

16 Soft handover signalling

Soft handovers can be intra-RNC or inter-RNC handovers. In other words,soft handovers occur between WCDMA BTSs controlled by one RNC ortwo RNCs. Softer handovers occur between cells within one WCDMABTS. All different types of soft and softer handover have procedures forbranch adding, deleting and replacement. In the following, the proceduresare described as they occur in inter-RNC soft handover. In other words, aradio link is set up or added through a WCDMA BTS controlled by anotherthan the serving RNC.

The UE sends the measurement report to the RNC only when it isnecessary to add, replace or remove cells from its active set (cellsparticipating in soft handover). The UE sends the measurement report tothe RNC in the measurement report message. If the RNC is not able toadd the requested cell into the active set, for example, because of capacityreasons, the UE must temporarily proceed to event-triggered periodicmeasurement reporting until the requested cell is either added into theactive set or branch addition is not required anymore.

Branch addition

The RNC starts a branch addition procedure if the intra-frequencymeasurement event 1A is triggered. Branch addition refers to theprocedure where the UE adds a new cell to its active set of cells. The UEinitiates the branch addition procedure by sending a measurement reportmessage to the RNC on the dedicated control channel (DCCH). Onebranch addition procedure can simultaneously start several radio linksetup and addition procedures, depending on the number of event resultsin the measurement report.

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Soft handover signalling

Figure 35. Branch addition

One radio link setup or addition procedure is required per each WCDMABTS. For example, if all candidate cells are controlled by different WCDMABTSs, the number of radio link setup or addition procedures equals thenumber of measurement event results. The number of radio link setup oraddition procedures is one if all candidate cells are controlled by the sameWCDMA BTS.

The alternative types of the radio link setup (or addition) procedures arethe following:

ServingRNC

UEDriftingRNC

BTS

RNSAP: RADIO LINK ADDITION REQUEST

BTS-SRNC Data Transport Bearer Sync.

Decision toset up new RL

NBAP: RADIO LINK SETUP REQUEST

NBAP: RADIO LINK SETUP RESPONSE

Start RX

Start TX

RRC: ACTIVE SET UPDATE

(Radio Link Addition)

RRC: ACTIVE SET UPDATE COMPLETE

AAL2 Setup

RNSAP: RADIO LINK ADDITION RESPONSE


Handover Control

. Intra-RNC radio link setup (the common NBAP procedure is usedwhen the UE does not have an existing communication context inthe target BTS)

. Intra-RNC radio link addition (the dedicated NBAP procedure is usedwhen the UE already has an existing communication context in thetarget BTS)

. Inter-RNC radio link setup (the RNSAP procedure is used when theUE does not have any existing diversity handover branches in thedrifting RNC)

. Inter-RNC radio link addition (the RNSAP procedure is used whenthe UE already has one or more existing diversity handoverbranches in the drifting RNC).

One radio link setup or addition procedure can simultaneously set severalradio links up. In case of an intra-RNC soft or softer handover, the numberof radio links equals the number of candidate cells in a particular WCDMABTS. In case of an inter-RNC soft handover, the number of radio linksequals the number of candidate cells in a particular drifting RNC.

The controlling RNC (CRNC) allocates the downlink power, decides on thedownlink admission, and allocates the downlink channelisation code (orcodes) for the new radio link (or links). It also allocates the identifier of theCRNC communication context. The CRNC communication contextcontains information on radio links that have been allocated from onespecified WCDMA BTS for one specified UE. The identifier of the CRNCcommunication context is unique within one WCDMA BTS.

The RNC sends an active set update message to the UE, whichacknowledges receiving the message to the RNC after the radio link orlinks have been set up.

Branch deletion

The RNC starts a branch deletion procedure if the intra-frequencymeasurement event 1B is triggered. Branch deletion refers to theprocedure where the UE deletes a cell from its active set of cells throughwhich it has an active radio connection. Like branch addition, branchdeletion is started by the UE by sending the measurement report messageto the RNC on the dedicated control channel (DCCH).

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Figure 36. Branch deletion

One branch deletion procedure can simultaneously delete several radiolinks, depending on the number of event results in the measurementreport. In case of an intra-RNC soft or softer handover, one radio linkdeletion procedure is required per each WCDMA BTS. If all radio links tobe deleted are controlled by separate base stations, the number of radiolink deletion procedures equals the number of measurement event results.The number of radio link deletion procedures is one if all radio links to bedeleted are controlled by the same WCDMA BTS.

The RNC sends an active set update message to the UE whichacknowledges receiving the message to the RNC. After that, the RNCdeletes the radio link or links.

ServingRNC

UEDriftingRNC

RRC: ACTIVE SET UPDATE

BTS

(Radio Link Deletion)


RNSAP: RADIO LINK DELETION REQUEST

NBAP: RADIO LINK DELETION REQUEST

NBAP: RADIO LINK DELETION RESPONSE

Decision to deleteold RL

Stop RX and TX

AAL2 Release

RNSAP: RADIO LINK DELETION RESPONSE


Handover Control

Branch replacement

The RNC starts a branch replacement procedure if the intra-frequencymeasurement event 1C indicates that a cell is better than an active cell in afull active set. One branch replacement procedure can simultaneouslystart several radio link setup, addition and deletion procedures, dependingon the number of event results in the measurement report. In case of anintra-RNC soft or softer handover, one radio link setup, addition or deletionprocedure is required per each WCDMA BTS. For the alternative radio linksetup or addition procedures, see the section Branch addition above.

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Figure 37. Branch replacement

ServingRNC

UEDriftingRNC

BTSServing RNC

BTSDrifting RNC

NBAP: RADIO LINK SETUP REQUEST


RNSAP: RADIO LINK ADDITION REQUEST

BTS-SRNC Data Transport Bearer Sync.

RRC: ACTIVE SET UPDATE COMMAND

(Radio Link Addition & Deletion)


NBAP: RADIO LINK DELETION

NBAP: RADIO LINK DELETION RESPONSE

Decision to set upnew RL andrelease old RL

RNSAP: RADIO LINK ADDITION RESPONSE

Start RX

Start TX

Stop RX and TX

AAL2 Setup

AAL2 Release


Handover Control

17 Intra-frequency hard handover signalling

Intra-frequency hard handover is required to ensure a handover betweencells controlled by different radio network controllers (RNCs) when aninter-RNC soft handover is not possible, for example, because of Iurcongestion. In addition, the Enable Inter-RNC Soft Handover(EnableInterRNCsho) parameter of the intra-frequency handover pathdefines whether intra-frequency handover from the serving cell to aspecified neighbour cell is performed as soft or hard. For more information,see section Functionality of intra-frequency hard handover.

Intra-frequency hard handover is non-synchronised hard handover. Non-synchronised intra-frequency hard handover means that the UE replacesall radio links (cells) in the active set with a new radio link (target cell) alongwith the change in the uplink transmission timing and the confusionmessage (CFN) according to the system frame number (SFN) of the targetcell.

The radio access network application part (RANAP) signalling procedureused is Serving RNC relocation. In this case, the 3G UE is involved in theServing RNC relocation procedure which makes the procedure a hardhandover from the point of view of the UE and the RAN.

The target RNC sets up a radio link on the target cell of the intra-frequencyhandover. If the radio link setup procedure is successful, the target RNCprepares a hard handover message ('Physical channel reconfiguration','Radio bearer establishment', 'Radio bearer reconfiguration', 'Radio bearerrelease' or 'Transport channel reconfiguration') and sends the content ofthe RRC message to the source RNC through the CN. The source RNCsends the appropriate RRC (for example, PHYSICAL CHANNELRECONFIGURATION) message to the UE, after which the UE stopstransmitting and receiving on the old radio links and starts on the new radiolink.

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Intra-frequency hard handover signalling

It is also possible that there is no RNSAP signalling interface between thesource RNC and the target RNC. In that case a RNSAP:RELOCATIONCOMMIT message is not sent from the source RNC to the target RNC, anda RANAP:RELOCATION DETECTION message is triggered when thetarget RNC receives a NBAP:SYNCHRONIZATION INDICATIONmessage.

Intra-frequency inter-RNC hard handovers can be controlled by the mobileservices switching centre (MSC), the serving GPRS support node (SGSN)or both CNs. The following figure illustrates the MSC-controlled intra-frequency hard handover.


Handover Control

Figure 38. Intra-frequency hard handover

CS CNUERNCTarget

RNCSource

BTSTarget

BTSSource

NBAP: RADIO LINK SETUP


RRC:MEASUREMENT REPORT

RANAP:RELOCATION REQUIRED

RANAP:RELOCATION REQUEST

AAL2 Setup

AAL2 Setup

RANAP:RELOCATION REQUEST ACKNOWLEDGED

RANAP:RELOCATION COMMAND

AAL2 Release

AAL2 Release

RRC:PHYSICAL CHANNEL RECONFIGURATION

RNSAP:RELOCATION COMMIT

RANAP:RELOCATION DETECTION

NBAP:SYNCHRONIZATION INDICATION

RRC:PHYSICAL CHANNEL RECONFIGURATION COMPLETE

RANAP:RELOCATION COMPLETE

RANAP:IU RELEASE COMMAND

RANAP:IU RELEASE COMPLETE

NBAP:RADIO LINK DELETION

NBAP:RADIO LINK DELETION RESPONSE

RNC switch

L1 synchronisation

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Handover Control

18 Serving RNC relocation signalling

As the UE is moving, it may need to take the drifting RNC as the newserving RNC, if there are no more connections needed through the servingRNC. The serving RNC relocation procedure is started after the last cellunder the SRNC has been deleted from the UE's active set. The servingRNC functionality of a specific RRC connection is relocated from one RNCto another without changing the radio resources or even withoutinterrupting the user data flow.

The following example illustrates the SGSN-controlled serving RNCrelocation.

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Serving RNC relocation signalling

Figure 39. SRNC relocation

GTP Tunnel Setup



HC makes relocationdecision

UE SRNC DRNC PS CN



RANAP:RELOCATION REQUEST ACKNOWLEDGED


RNSAP:SRNC RELOCATION COMMIT


RRC:UTRAN MOBILITY

RRC:UTRAN MOBILITY COMPLETE


Release of GTP tunnels


Handover Control

19 Compressed mode preparationsignalling

In practice signalling in compressed mode is a similar procedure in allhandover types.

The following figure illustrates the preparation of compressed mode.

Figure 40. Compressed mode preparation

RNCBTS 1BTS 2UE

Compressed mode preparation procedures

NBAP: RADIOLINK RECONFIGURATIONPREPARE

NBAP: RADIOLINK RECONFIGURATIONREADY

NBAP: RADIOLINK RECONFIGURATIONCOMMIT

RRC: TRANSPORT CHANNEL RECONFIGURATION COMPLETE

RRC: TRANSPORT CHANNEL RECONFIGURATION

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Compressed mode preparation signalling


Handover Control

20 Inter-frequency handover signalling

Inter-frequency handovers can be intra-RNC or inter-RNC handovers.Inter-RNC handovers can be controlled by the MSC, the SGSN or bothCNs.

Inter-frequency hard handover is non-synchronised hard handoverbecause the UE cannot measure the SFN timing of the target cell beforethe execution of the handover. The purpose of the non-synchronised inter-frequency hard handover procedure is to replace all radio links (cells) inthe active set with a new radio link (target cell) by changing the carrierfrequency, the uplink transmission timing and the CFN in the UE accordingto the SFN of the target cell.

Intra-RNC inter-frequency handover

In intra-RNC inter-frequency handover, the handover procedure isperformed alone by the serving RNC. The serving RNC sets up a radio linkon the target cell of the inter-frequency handover. If the radio link setup issuccessful, the serving RNC prepares a hard handover message('Physical channel reconfiguration', 'Radio bearer establishment', 'Radiobearer reconfiguration', 'Radio bearer release' or 'Transport channelreconfiguration') and sends the RRC message to the UE. The hardhandover message contains the information element Timing Indication.The value of the Timing Indication IE is set to 'Initialise' to initiate a non-synchronised hard handover.

The following example illustrates the intra-RNC inter-frequency handover.

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Inter-frequency handover signalling

Figure 41. Intra-RNC inter-frequency handover because of UE transmissionpower (continued in the next picture)

RNCBTS 1BTS 2UE

1. Activation of the feature.

An inter-frequencyhandover cause byUE Tx power is enabled.

RRC:MEASUREMENT CONTROL (Setup UE Tx power meas)

Reporting event6A is triggered

RRC:MEASUREMENT REPORT (UE Tx power, event 6A)

RRC:MEASUREMENT CONTROL (setup additional intra-freq meas)

NBAP:COMPRESSED MODE COMMAND(CFN, TGPSI)

RRC:MEASUREMENT CONTROL (setup inter-freq,CFN,TGPSI, include additional measurement results)

RRC:MEASUREMENT REPORT (inter-frequency + additional intra-frequency measurement results)

* * *RRC:MEASUREMENT REPORT (inter-frequency + additional intra-frequency measurement results)

2. Compressed mode preparation procedures.

3. Activation of compressed mode and inter-frequency measurement.

4. Periodical inter-frequency measurement reporting.

Inter-frequency handoverdecision due to coveragereason; UE Tx power.

5. Inter-frequency intra-RNC handover signalling

Decision to activate inter-frequency measurement.RNC determines CMpattern.


Handover Control

Figure 42. Intra-RNC inter-frequency handover because of UE transmissionpower (continued from the previous picture)

Inter-RNC inter-frequency handover

The target RNC sets up a radio link on the target cell of the inter-frequencyhandover. If the radio link setup procedure is successful, the target RNCprepares a hard handover message ('Physical channel reconfiguration','Radio bearer establishment', 'Radio bearer reconfiguration', 'Radio bearerrelease' or 'Transport channel reconfiguration') and sends the content ofthe RRC message to the source RNC through the CN. The hard handovermessage contains the Timing Indication information element. The value ofthe IE Timing Indication is ‘Initialise’ which indicates non-synchronisedhard handover.

The source RNC sends the appropriate RRC (for example, PHYSICALCHANNEL RECONFIGURATION) message to the UE, after which the UEstops transmitting and receiving on the old radio links and starts on thenew radio link.

The following example illustrates the MSC controlled inter-frequencyhandover.

RNCBTS 1BTS 2UE

NBAP:RADIOLINK SETUP

NBAP:RADIOLINK SETUP RESPONSE


6. Release of old resources.

L1 Sync

NBAP:SYNCRONIZATION INDICATION

RRC:PHYSICAL CHANNEL RECONF COMPLETE

NBAP:RADIO LINK DELETION REQUEST

NBAP:RADIOLINK DELETION RESPONSE

AAL2 release

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Figure 43. MSC controlled inter-RNC inter-frequency handover because ofCPICH EcNo (quality reason), source RNC (continued in the nextpicture)

MSCRNCBTS 1UE

1. Activation of the event 1E & 1F in the UE

RRC:MEASUREMENT CONTROL (setup CPICH EcNo events 1E and 1F)

RRC:MEASUREMENT REPORT (CPICH EcNo, event 1F, cell 1)

Decision to activate inter-frequency measurements.Determination of CM pattern.

An inter-frequency handovercause by CPICH EcNo isenabled.

RRC:MEASUREMENT CONTROL ( set additional intra-freq meas)

NBAP:COMPRESSED MODE COMMAND (CFN, TGPSI)

RRC:MEASUREMENT CONTROL (inter-freq, CFN, TGPSI, include additional measurement results)


Inter-frequency handoverdecision due to quality reason;CPICH EcNo

Reporting event 1F triggersfor active set cell 1.

Reporting event 1F triggersfor active set cell 2.

2. Compressed mode preparation procedures.

3. Activation of compressed more and starting of inter-frequency measurement.

4. Periodical inter-frequency measurement reporting and handover decision.

RRC:MEASUREMENT REPORT (CPICH EcNo, event 1F, cell 2)



Handover Control

Figure 44. MSC controlled inter-RNC inter-frequency handover because ofCPICH EcNo (quality reason), source RNC (continued from theprevious picture)

The following example illustrates the SGSN controlled inter-frequencyhandover.

5. Inter-frequency inter-RNC handover signalling.









AAL2 release

MSCRNCBTS 1UE

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Figure 45. SGSN controlled inter-RNC inter-frequency handover because ofUE transmission power (coverage reason), source RNC (continuedin the next picture)

UE Target RNC SGSN


RRC:MEASUREMENT CONTROL (setup UE Tx Power measurement)



2. Compressed mode preparation procedures, TGPSI.

4. Periodical inter-frequency measurement reporting and handover decision.




RRC:TRANSPORT CHANNEL RECONFIGURATION

RNSAP:RELOCATION COMMIT

RRC:MEASUREMENT CONTROL ( setup additional measurement)

COMPRESSED MODE COMMAND (CFN, TGPSI)

RRC:MEASUREMENT CONTROL (inter-freq, CFN, TGPSI, include additional measurement results)

An inter-frequency handovercause by UE Tx power is enabled.

BTS RNC

Decision to activate inter-frequency measurement. RNCdetermines CM pattern.

3. Activation of compressed mode and inter-frequency measurement.

5. Handover signalling


Handover Control

Figure 46. SGSN controlled inter-RNC inter-frequency handover because ofUE transmission power (coverage reason), source RNC (continuedfrom the previous picture)

Downlink NRT data forwarding from source RNC totarget RNC via Forwarding GTP tunnel




NBAP:RADIOLINK DELETION RESPONSE

AAL2 release

UE Target RNC SGSNBTS RNC


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Handover Control

21 Inter-system handover signalling

The inter-system handovers can be performed either from WCDMA toGSM system or from GSM to WCDMA system.

The following example illustrates the inter-system handover from WCDMAto GSM.

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Inter-system handover signalling

Figure 47. Inter-system handover from WCDMA to GSM (continued in the nextpicture)


RRC:MEASUREMENT CONTROL (setup UE Tx power meas)


UE RNCBTS 1 MSC


An inter-system handover causeby UE Tx power is enabled.

Decision to activate inter-systemmeasurement. RNC determinesCM pattern.

2. Compressed mode preparation procedures (TPGSI).

3. Activation of compressed mode and inter-system measurement.

NBAP:COMPRESSED MODE COMMAND (CFN, TGPSI)

RRC:MEASUREMENT CONTROL (GSM RSSI, CFN, TGPSI)

RRC:MEASUREMENT REPORT (GSM RSSI, BCCH ARFCN)

RRC.MEASUREMENT REPORT (GSM RSSI, BCCH ARFCN)

Handover decision,BSIC verification required.

NBAP:COMPRESSED MODE COMMAND (CFN TGPSI)

RRC:MEASUREMENT CONTROL (BSIC,CFN,TGPSI)

RRC:MEASUREMENT REPORT (GSM RSSI, GSM cell index)

5. Inter-system handover signalling

4. Periodic inter-system measurement reporting, BSIC verification and handover decision.


Handover Control

Figure 48. Inter-system handover from WCDMA to GSM (continued from theprevious picture)

UE MSCRNCBTS 1

1. Activation of the feature

2. Compressed mode preparation procedures (TPGSI)

3. Activation of compressed mode and inter-system measurement

4. Periodic inter-system measurement reporting,BSIC verification and handover decision


RCC:MEASUREMENT CONTROL

(setup UE Tx Power)

RCC:MEASUREMENT REPORT(UE Tx power, event 6A)

RCC:MEASUREMENT CONTROL(GSM RSSI, CFN, TGPSI)

RCC:MEASUREMENT REPORT(GSM RSSI, BCCH ARFCN)

NBAP:COMPRESSED MODECOMMAND (CFN, TGPSI)


Decision to activate inter-systemmeasurement. RNC

determines CM pattern


Handover decision,BSIC verification required



(BSICI, CFN, TGPSI)


RCC:MEASUREMENT REPORT(GSM RSSI, GSM cell index)

Periodical GSM RSSImeasurement reporting

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The following example illustrates the cell change from WCDMA to GSM/GPRS.


Handover Control

Figure 49. Inter-system cell change from WCDMA to GSM/GPRS (continued inthe next picture)

UE SGSNRNCBTS 1

1. Activation of the feature

2. Compressed mode preparation procedures

3. Activation of compressed mode and inter-system measurement

4. Periodic inter-system measurement reporting and handover decision



(setup UE Tx Power)

RCC:MEASUREMENT REPORT(UE Tx power, event 6A)

RCC:MEASUREMENT CONTROL(GSM RSSI, CFN, TGPSI)




Decision to activate inter-systemmeasurement. RNC

determines OM pattern


Periodical GSMRSSI measurement

reporting

Handover decision,BSIC verification not needed.

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Figure 50. Inter-system cell change from WCDMA to GSM/GPRS (continuedfrom the previous picture)

The following example illustrates the inter-system handover from WCDMAto GSM with CS and PS multi services.

RRC:CELL CHANGE ORDER FROM UTRAN

RANAP:SRNC CONTEXT REQUEST

RANAP: SRNC CONTEXT RESPONSE

RANAP:SRNC DATA FORWARDING COMMAND

Downlink NRT data is returned from sourceRNC back to 2G/3G SGSN via ForwardingGTP tunnel






AAL2 release

SGSNRNCBTS 1UE


Handover Control

Figure 51. Inter-system handover from WCDMA to GSM with CS and PS multiservices

The following example illustrates the inter-system hard handover fromGSM to WCDMA.

SGSNRNCBTS 1UE MSC



RRC:HANDOVER FROM UTRAN COMMAND


RANAPIU RELEASE COMPLETE

RANAP:SRNC CONTEXT REQUEST

RANAP:SRNC CONTEXT RESPONSE

RANAP:SRNC DATA FORWARDING COMMAND

Downlink NRT data is returned from source RNCback to 2G/3G SGSN via Forwarding GTP tunnel





AAL2 release

5. Handover signalling, two CNs

Inter-system handover decision.BSIC verification required.


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Figure 52. Inter-system hard handover from GSM to WCDMA

MSCRNCBTS 1UE

1. Resource reservation.

NBAP:RADIO LINK SETUP REQUEST


NBAP:RADIO LINK SETUP RESPONSE

AAL2 setup

AAL2 setup

RANAP:RELOCATION REQUEST ACK

L1 Sync

NBAP:SYNCRONIZATION INDICATION


RRC:HANDOVER TO UTRAN COMPLETE


2. Handover signalling


Handover Control

22 Handover control statistics

Handover statistics in the radio access network (RAN) include thefollowing measurement types:

. Soft Handover measurement

. Intra-System Handover (intra- and inter-frequency hard handover)measurement

. Inter-System Handover measurement

For more information on the soft and hard handover measurement, seeRNC counters - RNW part.

Soft handover measurement

Soft handover measurement collects statistics on the cell level and on thenetwork level. Statistics are compiled in the following counters reserved foreach traffic type (RT and NRT) and for each cell:

. One...three cells in the active set

. Softer handover duration on the SRNC side

. Softer handover duration on the DRNC side

. Inter-RNC soft handover duration on the SRNC side

. Inter-RNC soft handover duration on the DRNC side

. Cell addition request

. Cell deletion request

. Cell replacement request

. Cell addition failure

. Cell replacement failure

. Successful active set updates

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Handover control statistics


. Unsuccessful active set updates

. High UE Rx-Tx time difference

. Low UE Rx-Tx time difference

Intra System Handover measurement

Hard handover measurement collects statistics on the intra- and inter-frequency hard handover procedure. Statistics are compiled in countersreserved for each traffic type (RT and NRT) and for each cell.

Common hard handover failure counters are:

. UTRAN cannot execute HHO

. UE cannot execute HHO

. Compressed mode is not possible.

Intra-frequency hard handover counters are:

. Cell addition failure because of SHO incapability

. Cell replacement failure because of SHO incapability

. HHO attempts caused by SHO incapability

. Immediate HHO attempts caused by SHO incapability

. Successful hard handovers caused by SHO incapability

. Unsuccessful hard handovers caused by SHO incapability

. RRC connection drops during HHO caused by SHO incapability.

Inter-frequency hard handover counters per each handover cause are:

. No inter-frequency neighbour cell is good enough for the handover

. Inter-frequency handover attempts

. Successful inter-frequency hard handovers

. Unsuccessful inter-frequency hard handovers

. RRC connection drops during inter-frequency hard handover

Intra System Handover measurement includes statistics also for:


Handover Control

. IMSI-based handover

. Load and Service based handover.

Inter-System Handover measurement

Inter-system (GSM) handover measurement collects statistics of theperformance of the handover from WCDMA to GSM. Statisctics arecompiled in the following counters reserved for each traffic type (RT andNRT) and for each cell:

Common inter-system handover failure counters:

. GSM BSS cannot execute the inter-system handover

. UE cannot execute the inter-system handover

. Compressed mode is not possible.

Inter-system handover counters per each handover cause:

. No GSM neighbour cell is good enough for the handover

. Inter-system (GSM) handover attempts

. Successful inter-system hard handovers

. Unsuccessful inter-system hard handovers

. RRC connection drops during inter-system hard handover.

Inter System Handover measurement includes statistics also for:

. IMSI-based handover

. Load and Service based handover

. Wireless Priority Service call

For the whole topic summary, see Section Handover control.

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Handover control statistics


Handover Control

23 Handover control restrictions

Handover control does not support inter-frequency or inter-systemhandovers during anchoring.

For the whole topic summary, see Section Handover control.

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Handover control restrictions


Handover Control

24 Management parameters for handovercontrol

24.1 RNC parameters

RNC parameters that are related to handover control:

Parameter name: Upper Rx-Tx TD Threshold

Abbreviated name: UpperRxTxTimeDiff

Parameter name: Lower Rx-Tx TD Threshold

Abbreviated name: LowerRxTxTimeDiff

Parameter name: Handover of AMR service to GSM

Abbreviated name: GsmHandoverAMR

Parameter name: Handover of CS service to GSM

Abbreviated name: GsmHandoverCS

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Management parameters for handover control

Parameter name: Handover of NRT PS service to GSM

Abbreviated name: GsmHandoverNrtPS

Parameter name: Handover of RT PS service to GSM

Abbreviated name: GsmHandoverRtPS

Parameter name: Enable UL Quality Deterioration report

Abbreviated name: EnableULQualDetRep

Parameter name: UL Quality Deterioration ReportingThreshold

Abbreviated name: ULQualDetRepThreshold

Parameter name: Identifier of Default Authorised Network

Abbreviated name: DefaultAuthorisedNetworkId

Parameter name: List of shared area PLMNs

Abbreviated name: SharedAreaPLMNlist

Parameter name: Shared area PLMN identity

Abbreviated name: SharedAreaPLMNid

Parameter name: Shared area Mobile Country Code


Handover Control

Abbreviated name: SharedAreaMCC

Parameter name: Shared area Mobile Network Code

Abbreviated name: SharedAreaMNC

Parameter name: Use of SLHO for CS speech

Abbreviated name: SLHOUseConvCSSpeech

Parameter name: Use of SLHO for Transparent CS data

Abbreviated name: SLHOUseConvCSTData

Parameter name: Use of SLHO for PS speech

Abbreviated name: SLHOUseConvPSSpeech

Parameter name: Use of SLHO for Conversational PS data

Abbreviated name: SLHOUseConvPSRTData

Parameter name: Use of SLHO for Non-transparent CSdata

Abbreviated name: SLHOUseStreamCSNTData

Parameter name: Use of SLHO for Streaming PS data

Abbreviated name: SLHOUseStreamPSRTData

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Parameter name: Use of SLHO for Interactive PS data

Abbreviated name: SLHOUseInteractivePSNRTData

Parameter name: Use of SLHO for Background PS data

Abbreviated name: SLHOUseBackgroundPSNRTData

Parameter name: LHO Minimum NRT DCH Allocation Time

Abbreviated name: LHOMinNrtDchAllocTime

Parameter name: Service Profile for CS speech in SLHO

Abbreviated name: SLHOProfileConvCSSpeech

Parameter name: Service Profile for Transparent CS data inSLHO

Abbreviated name: SLHOProfileConvCSTData

Parameter name: Service Profile for PS speech in SLHO

Abbreviated name: SLHOProfileConvPSSpeech

Parameter name: Service Profile for Conversational PS datain SLHO

Abbreviated name: SLHOProfileConvPSRTData


Handover Control

Parameter name: Service profile for Non-transparent CSdata in SLHO

Abbreviated name: SLHOProfileStreamCSNTData

Parameter name: Service profile for Streaming PS data inSLHO

Abbreviated name: SLHOProfileStreamPSRTData

Parameter name: Service profile for Interactive PS data inSLHO

Abbreviated name: SLHOProfileInteractivePSNRTData

Parameter name: Service profile for Background PS data inSLHO

Abbreviated name: SLHOProfileBackgroundPSNRTData

Parameter name: CM allowed for NRT connection in SLHO

Abbreviated name: SLHOCmAallowedNRT

Parameter name: NCHO threshold common loadmeasurement DRNC cell

Abbreviated name: NCHOThrComLoadMeasDRNCCell

Parameter name: NCHO hysteresis common loadmeasurement DRNC cell

Abbreviated name: NCHOHystComLoadMeasDRNCCell

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Parameter name: NCHO filter coefficient common loadmeas DRNC cell

Abbreviated name: NCHOFiltercoeffComLoadMeasDRNCCell

Parameter name: Non-active Load Measurement in SLHO

Abbreviated name: SLHOHandlingOfCellLoadMeasNotAct

Parameter name: Services for DRRC connection setup forHSDPA layer

Abbreviated name: DRRCForHSDPALayerServices

Parameter name: HSDPA layers load sharing threshold

Abbreviated name: HSDPALayerLoadShareThreshold

Parameter name: Disable power in decision making forHSDPA layering

Abbreviated name: DisablePowerInHSDPALayeringDecision

Parameter name: DRRC connection setup for HSDPA layerenhancements

Abbreviated name: DirectedRRCForHSDPALayerEnhanc

Parameter name: Services to HSDPA layer in statetransition


Handover Control

Abbreviated name: ServicesToHSDPALayer

24.2 WCDMA BTS parameters (WBTS)

WCDMA BTS parameters that are related to handover control:

Parameter name: RL Measurement Reporting Period

Abbreviated name: RLMeasRepPeriod

Parameter name: Dedicated Measurement Reporting Period

Abbreviated name: DedicatedMeasReportPeriod

Parameter name: Dedicated Measurement Reporting PeriodCS data

Abbreviated name: DediMeasRepPeriodCSdata

Parameter name: Dedicated Measurement Reporting PeriodPS data

Abbreviated name: DediMeasRepPeriodPSdata

Parameter name: Measurement Filter Coefficient

Abbreviated name: MeasFiltCoeff

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24.3 WCDMA cell parameters (WCEL)

WCDMA cell parameters that are related to handover control:

Parameter name: RT FMCS Identifier

Abbreviated name: RtFmcsIdentifier

Parameter name: NRT FMCS Identifier

Abbreviated name: NrtFmcsIdentifier

Parameter name: Maximum Allowed DL User Bitrate inHHO

Abbreviated name: HHoMaxAllowedBitrateDL

Parameter name: Maximum Allowed UL User Bitrate inHHO

Abbreviated name: HHoMaxAllowedBitrateUL

Parameter name: RT FMCI Identifier

Abbreviated name: RtFmciIdentifier

Parameter name: NRT FMCI Identifier

Abbreviated name: NrtFmciIdentifier


Handover Control

Parameter name: RT FMCG Identifier

Abbreviated name: RtFmcgIdentifier

Parameter name: NRT FMCG Identifier

Abbreviated name: NrtFmcgIdentifier

Parameter name: Sector Identifier

Abbreviated name: SectorID

Parameter name: Prx Offset for DRRC

Abbreviated name: DRRCprxOffset

Parameter name: Ptx Offset for DRRC

Abbreviated name: DRRCptxOffset

Parameter name: Prx Margin for DRRC

Abbreviated name: DRRCprxMargin

Parameter name: Ptx Margin for DRRC

Abbreviated name: DRRCptxMargin

Parameter name: Directed RRC connection setup enabled

Abbreviated name: DirectedRRCEnabled

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Parameter name: Load HO UL Power Offset

Abbreviated name: LHOPwrOffsetUL

Parameter name: Load HO DL Power Offset

Abbreviated name: LHOPwrOffsetDL

Parameter name: Load HO UL NRT Capacity requestRejection rate

Abbreviated name: LHOCapaReqRejRateUL

Parameter name: Load HO DL NRT Capacity requestRejection rate

Abbreviated name: LHOCapaReqRejRateDL

Parameter name: Load HO Reservation rate of DLSpreading codes

Abbreviated name: LHOResRateSC

Parameter name: Load HO Hard Blocking ratio

Abbreviated name: LHOHardBlockingRatio

Parameter name: Window size for InterferenceMeasurement to Start Load HOs


Handover Control

Abbreviated name: LHOWinSizeONInterference

Parameter name: Window size for InterferenceMeasurement to Stop Load HOs

Abbreviated name: LHOWinSizeOFFInterference

Parameter name: Hysteresis time for InterferenceMeasurement to Start Load HOs

Abbreviated name: LHOHystTimeInterference

Parameter name: Delay to Broadcast Interference basedLHO state over info

Abbreviated name: LHODelayOFFInterference

Parameter name: Window size for NRT Load Measurementto Start Load HOs

Abbreviated name: LHOWinSizeONCapaReqRejRate

Parameter name: Window size for NRT Load Measurementto Stop Load HOs

Abbreviated name: LHOWinSizeOFFCapaReqRejRate

Parameter name: Hysteresis time for NRT LoadMeasurement to Start Load HOs

Abbreviated name: LHOHystTimeCapaReqRejRate

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Parameter name: Delay to Broadcast NRT Load based HOState over

Abbreviated name: LHODelayOFFCapaReqRejRate

Parameter name: Load HO NRT traffic base load

Abbreviated name: LHONRTTrafficBaseLoad

Parameter name: Window size for DL SC Reservation rateMeasurement to Start LHOs

Abbreviated name: LHOWinSizeONResRateSC

Parameter name: Window size for DL SC Reservation rateMeasurement to Stop LHOs

Abbreviated name: LHOWinSizeOFFResRateSC

Parameter name: Hysteresis time for DL SC Reservationrate Measurement to Start LHOs

Abbreviated name: LHOHystTimeResRateSC

Parameter name: Delay to Broadcast DL SC Reservationbased LHO state over

Abbreviated name: LHODelayOFFResRateSC

Parameter name: Window size for Hard BlockingMeasurement to Start Load HOs

Abbreviated name: LHOWinSizeONHardBlocking


Handover Control

Parameter name: Window size for Hard BlockingMeasurement to Stop Load HOs

Abbreviated name: LHOWinSizeOFFHardBlocking

Parameter name: Hysteresis time for Hard BlockingMeasurement to Start LHOs

Abbreviated name: LHOHystTimeHardBlocking

Parameter name: Delay to Broadcast Hard Blocking basedLHO State over info

Abbreviated name: LHODelayOFFHardBlocking

Parameter name: Maximum Number of UEs in CM due toSLHO Measurement

Abbreviated name: MaxNumberUECmSLHO

Parameter name: Number of UEs in Inter-frequency LoadHO

Abbreviated name: LHONumbUEInterFreq

Parameter name: Number of UEs in Inter-RAT Load HO

Abbreviated name: LHONumbUEInterRAT

Parameter name: Period to Start Inter-frequency ServiceHOs

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Abbreviated name: ServHOPeriodInterFreq

Parameter name: Period to Start Inter-RAT Service HOs

Abbreviated name: ServHOPeriodInterRAT

Parameter name: Number of Inter-frequency Service HOs

Abbreviated name: ServHONumbUEInterFreq

Parameter name: Number of Inter-RAT Service HOs

Abbreviated name: ServHONumbUEInterRAT

Parameter name: Hard Blocking Base Load for LHO

Abbreviated name: LHOHardBlockingBaseLoad

Parameter name: Directed RRC connection setup forHSDPA layer enabled

Abbreviated name: DirectedRRCForHSDPALayerEnabled

Parameter name: HSDPA layering for UEs in commonchannels enabled

Abbreviated name: HSDPALayeringCommonChEnabled

Parameter name: Cell weight for HSDPA layering

Abbreviated name: CellWeightForHSDPALayering


Handover Control

24.4 Intra-frequency measurement control parameters(FMCS)

The radio network database can contain the maximum of 100 separatemeasurement control parameter sets for intra-frequency measurements.Measurement reporting criteria are defined on a cell-by-cell basis byattaching a specified measurement control parameter set to a specifiedcell.

Parameter name: Addition Window

Abbreviated name: AdditionWindow

Parameter name: Addition Time

Abbreviated name: AdditionTime

Parameter name: Addition Reporting Interval

Abbreviated name: AdditionReportingInterval

Parameter name: Drop Window

Abbreviated name: DropWindow

Parameter name: Drop Time

Abbreviated name: DropTime

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Parameter name: Replacement Window

Abbreviated name: ReplacementWindow

Parameter name: Replacement Time

Abbreviated name: ReplacementTime

Parameter name: Replacement Reporting Interval

Abbreviated name: ReplacementReportingInterval

Parameter name: Maximum Active Set Size

Abbreviated name: MaxActiveSetSize

Parameter name: CPICH Ec/No Filter Coefficient

Abbreviated name: EcNoFilterCoefficient

Parameter name: Active Set Weighting Coefficient

Abbreviated name: ActiveSetWeightingCoefficient

Parameter name: CPICH Ec/No HHO Cancellation

Abbreviated name: HHoEcNoCancel

Parameter name: CPICH Ec/No HHO Cancellation Time

Abbreviated name: HHoEcNoCancelTime


Handover Control

Parameter name: CPICH Ec/No HHO Threshold

Abbreviated name: HHoEcNoThreshold

Parameter name: CPICH Ec/No HHO Time Hysteresis

Abbreviated name: HHoEcNoTimeHysteresis

Parameter name: CPICH RSCP HHO Cancellation

Abbreviated name: HHoRscpCancel

Parameter name: CPICH RSCP HHO Cancellation Time

Abbreviated name: HHoRscpCancelTime

Parameter name: CPICH RSCP HHO Filter Coefficient

Abbreviated name: HHoRscpFilterCoefficient

Parameter name: CPICH RSCP HHO Threshold

Abbreviated name: HHoRscpThreshold

Parameter name: CPICH RSCP HHO Time Hysteresis

Abbreviated name: HHoRscpTimeHysteresis

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Parameter name: IMSI Based SHO

Abbreviated name: IMSIbasedSHO

24.5 Inter-frequency measurement control parameters(FMCI)

The radio network database can contain the maximum of 100 separatemeasurement control parameter sets for inter-frequency measurements.Measurement reporting criteria are defined on a cell-by-cell basis byattaching a specified measurement control parameter set to a specifiedcell.

Parameter name: IFHO caused by CPICH Ec/No

Abbreviated name: IFHOcauseCPICHEcNo

Parameter name: IFHO caused by CPICH RSCP

Abbreviated name: IFHOcauseCPICHrscp

Parameter name: IFHO caused by DL DPCH TX Power

Abbreviated name: IFHOcauseTxPwrDL

Parameter name: IFHO caused by UE TX Power

Abbreviated name: IFHOcauseTxPwrUL

Parameter name: IFHO caused by UL DCH Quality

Abbreviated name: IFHOcauseUplinkQuality


Handover Control

Parameter name: DL DPCH TX Power Threshold for AMR

Abbreviated name: InterFreqDLTxPwrThrAMR

Parameter name: DL DPCH TX Power Threshold for CS

Abbreviated name: InterFreqDLTxPwrThrCS

Parameter name: DL DPCH TX Power Threshold for NRTPS

Abbreviated name: InterFreqDLTxPwrThrNrtPS

Parameter name: DL DPCH TX Power Threshold for RT PS

Abbreviated name: InterFreqDLTxPwrThrRtPS

Parameter name: Maximum Measurement Period

Abbreviated name: InterFreqMaxMeasPeriod

Parameter name: Measurement Averaging Window

Abbreviated name: InterFreqMeasAveWindow

Parameter name: Measurement Reporting Interval

Abbreviated name: InterFreqMeasRepInterval

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Parameter name: Minimum Interval Between IFHOs

Abbreviated name: InterFreqMinHoInterval

Parameter name: Minimum Measurement Interval

Abbreviated name: InterFreqMinMeasInterval

Parameter name: Neighbour Cell Search Period

Abbreviated name: InterFreqNcellSearchPeriod

Parameter name: UE TX Power Filter Coefficient

Abbreviated name: InterFreqUETxPwrFilterCoeff

Parameter name: UE TX Power Threshold for AMR

Abbreviated name: InterFreqUETxPwrThrAMR

Parameter name: UE TX Power Threshold for CS

Abbreviated name: InterFreqUETxPwrThrCS

Parameter name: UE TX Power Threshold for NRT PS

Abbreviated name: InterFreqUETxPwrThrNrtPS

Parameter name: UE TX Power Threshold for RT PS

Abbreviated name: InterFreqUETxPwrThrRtPS


Handover Control

Parameter name: UE TX Power Time Hysteresis

Abbreviated name: InterFreqUETxPwrTimeHyst

Parameter name: IMSI Based IFHO

Abbreviated name: IMSIbasedIFHO

Parameter name: Minimum Interval between IF SLHOs

Abbreviated name: InterFreqMinSLHOInterval

24.6 Inter-system (GSM) measurement controlparameters (FMCG)

The radio network database can contain the maximum of 100 separatemeasurement control parameter sets for inter-system (GSM)measurements. Measurement reporting criteria are defined on a cell-by-cell basis by attaching a specified measurement control parameter set to aspecified cell.

Parameter name: GSM HO caused by CPICH Ec/No

Abbreviated name: GSMcauseCPICHEcNo

Parameter name: GSM HO caused by CPICH RSCP

Abbreviated name: GSMcauseCPICHrscp

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Parameter name: GSM HO caused by DL DPCH TX Power

Abbreviated name: GSMcauseTxPwrDL

Parameter name: GSM HO caused by UE TX Power

Abbreviated name: GSMcauseTxPwrUL

Parameter name: GSM HO caused by UL DCH Quality

Abbreviated name: GSMcauseUplinkQuality

Parameter name: DL DPCH TX Power Threshold for AMR

Abbreviated name: GsmDLTxPwrThrAMR

Parameter name: DL DPCH TX Power Threshold for CS

Abbreviated name: GsmDLTxPwrThrCS

Parameter name: DL DPCH TX Power Threshold for NRTPS

Abbreviated name: GsmDLTxPwrThrNrtPS

Parameter name: DL DPCH TX Power Threshold for RT PS

Abbreviated name: GsmDLTxPwrThrRtPS

Parameter name: Maximum Measurement Period


Handover Control

Abbreviated name: GsmMaxMeasPeriod

Parameter name: Measurement Averaging Window

Abbreviated name: GsmMeasAveWindow

Parameter name: Measurement Reporting Interval

Abbreviated name: GsmMeasRepInterval

Parameter name: Minimum Interval Between HOs

Abbreviated name: GsmMinHoInterval

Parameter name: Minimum Measurement Interval

Abbreviated name: GsmMinMeasInterval

Parameter name: GSM Neighbour Cell Search Period

Abbreviated name: GsmNcellSearchPeriod

Parameter name: UE TX Power Filter Coefficient

Abbreviated name: GsmUETxPwrFilterCoeff

Parameter name: UE TX Power Threshold for AMR

Abbreviated name: GsmUETxPwrThrAMR

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Parameter name: UE TX Power Threshold for CS

Abbreviated name: GsmUETxPwrThrCS

Parameter name: UE TX Power Threshold for NRT PS

Abbreviated name: GsmUETxPwrThrNrtPS

Parameter name: UE TX Power Threshold for RT PS

Abbreviated name: GsmUETxPwrThrRtPS

Parameter name: TX Power Time Hysteresis

Abbreviated name: GsmUETxPwrTimeHyst

Parameter name: IMSI Based GSM HO

Abbreviated name: IMSIbasedGsmHo

Parameter name: Minimum Interval Between IS SLHOs

Abbreviated name: GsmMinSLHOInterval

24.7 Intra-frequency neighbour cell parameters (ADJS)

A WCDMA cell can have the maximum of 31 intra-frequency neighbourcells. The following intra-frequency neighbour cell parameters (ADJS) arerelated to the handover control as such:


Handover Control

Parameter name: RT HOPS Identifier

Abbreviated name: RtHopsIdentifier

Parameter name: NRT HOPS Identifier

Abbreviated name: NrtHopsIdentifier

Parameter name: CPICH Ec/No Offset

Abbreviated name: AdjsEcNoOffset

Parameter name: Disable Effect on Reporting Range

Abbreviated name: AdjsDERR

24.8 Inter-frequency neighbour cell parameters (ADJI)

A WCDMA cell can have the maximum of 48 inter-frequency neighbourcells. The following inter-frequency neighbour cell parameters (ADJI) arerelated to the handover control as such:

Parameter name: RT HOPI Identifier

Abbreviated name: RtHopiIdentifier

Parameter name: NRT HOPI Identifier

Abbreviated name: NrtHopiIdentifier

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Parameter name: EcNo offset for non-critical HO

Abbreviated name: AdjiEcNoOffsetNCHO

Parameter name: Handling of blocked IF neighbour cell inSLHO procedure

Abbreviated name: AdjiHandlingBlockedCellSLHO

Parameter name: NCHO activity of common loadmeasurement DRNC cell

Abbreviated name: AdjiComLoadMeasDRNCCellNCHO

24.9 Inter-system (GSM) neighbour cell parameters(ADJG)

A WCDMA cell can have the maximum of 32 GSM neighbour cells. Thefollowing GSM neighbour cell parameters (ADJG) are related to thehandover control as such:

Parameter name: RT HOPG Identifier

Abbreviated name: RtHopgIdentifier

Parameter name: NRT HOPG Identifier

Abbreviated name: NrtHopgIdentifier


Handover Control

24.10 Intra-frequency handover path parameters (HOPS)

The radio network database can contain the maximum of 100 separateparameter sets (HOPS) for the intra-frequency handover path. The intra-frequency handover path is defined on a neighbour cell-by-cell basis byattaching a specified HOPS parameter set to a specified neighbour cell.The following HOPS parameters define the intra-frequency handover path:

Parameter name: HHO Margin for Average Ec/No

Abbreviated name: HHOMarginAverageEcNo

Parameter name: HHO Margin for Peak Ec/No

Abbreviated name: HHOMarginPeakEcNo

Parameter name: Release Margin for Average Ec/No

Abbreviated name: ReleaseMarginAverageEcNo

Parameter name: Release Margin for Peak Ec/No

Abbreviated name: ReleaseMarginPeakEcNo

Parameter name: CPICH Ec/No Averaging Window

Abbreviated name: EcNoAveragingWindow

Parameter name: Enable RRC Connection Release

Abbreviated name: EnableRRCRelease

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Parameter name: Enable Inter-RNC Soft Handover

Abbreviated name: EnableInterRNCsho

24.11 Inter-frequency handover path parameters (HOPI)

The radio network database can contain the maximum of 100 separateparameter sets (HOPI) for the inter-frequency handover path. The inter-frequency handover path is defined on a neighbour cell-by-cell basis byattaching a specified HOPI parameter set to a specified neighbour cell.The following HOPI parameters define the inter-frequency handover path:

Parameter name: CPICH Ec/No Margin for IFHO

Abbreviated name: AdjiEcNoMargin

Parameter name: Minimum CPICH Ec/No for IFHO

Abbreviated name: AdjiMinEcNo

Parameter name: Minimum CPICH RSCP for IFHO

Abbreviated name: AdjiMinRSCP

Parameter name: Pathloss Margin for IFHO

Abbreviated name: AdjiPlossMargin

Parameter name: Ncell Priority for Coverage IFHO


Handover Control

Abbreviated name: AdjiPriorityCoverage

Parameter name: Ncell Priority for Quality IFHO

Abbreviated name: AdjiPriorityQuality

Parameter name: Ncell Priority for Service and Load IFHO

Abbreviated name: AdjiPrioritySLHO

Parameter name: Minimum CPICH RSCP for non-criticalIFHO

Abbreviated name: AdjiMinRscpNCHO

Parameter name: Minimum CPICH Ec/No for non-criticalIFHO

Abbreviated name: AdjiMinEcNoNCHO

Parameter name: Penalty Time for WCDMA Cell in non-critical HO

Abbreviated name: AdjiPenaltyTimeNCHO

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24.12 Inter-system (GSM) handover path parameters(HOPG)

The radio network database can contain the maximum of 100 separateparameter sets (HOPG) for the inter-system handover path to GSM. Thehandover path to GSM is defined on a neighbour cell-by-cell basis byattaching a specified HOPG parameter set to a specified GSM neighbourcell. The following HOPG parameters define the handover path to GSM:

Parameter name: Ncell Priority for Coverage HO

Abbreviated name: AdjgPriorityCoverage

Parameter name: Minimum RX Level for Coverage HO

Abbreviated name: AdjgRxLevMinHO

Parameter name: Penalty Time for GSM cell in non-criticalHO

Abbreviated name: AdjgPenaltyTimeNCHO

Parameter name: Minimum RX Level for non-critical HO

Abbreviated name: AdjgMinRxLevNCHO

Parameter name: Ncell Priority for SLHO

Abbreviated name: AdjgPrioritySLHO


Handover Control

24.13 WCDMA authorised network parameters (WANE)

WCDMA authorised network parameters are related to the IMSI-basedhandover are listed below.

Parameter name: List of Authorised Networks

Abbreviated name: AuthorisedNetworkList

Parameter name: Authorised Network PLMN

Abbreviated name: AuthorisedNetworkPLMN

Parameter name: Authorised Network Mobile Country Code

Abbreviated name: AuthorisedNetworkMCC

Parameter name: Authorised Network Mobile Network Code

Abbreviated name: AuthorisedNetworkMNC

Parameter name: Authorised Network Identifier

Abbreviated name: AuthorisedNetworkId

Parameter name: Technology Used in Authorised Network

Abbreviated name: Technology

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24.14 WCDMA subscriber group parameters (WSG)

WCDMA subscriber group parameters are related to the IMSI-basedhandover are listed below.

Parameter name: Subscriber Group Identifier

Abbreviated name: SubscriberGroupId

Parameter name: Subscriber Home PLMN

Abbreviated name: HomePLMN

Parameter name: Home PLMN Mobile Country Code

Abbreviated name: HomePlmnMCC

Parameter name: Home PLMN Mobile Network Code

Abbreviated name: HomePlmnMNC

Parameter name: Identifier of Authorised Network

Abbreviated name: WSGAuthorisedNetworkId


Handover Control

Related Topics

Handover control

Descriptions

Types of handovers

Compressed mode



WCDMA radio resource management

Power control

Types of handovers

Descriptions






DN03471612Issue 8-2 en13/12/2007


Related Topics

Compressed mode

Descriptions

Handover control


Radio resource management functions


Descriptions

Handover control


Descriptions

Handover control

Types of handovers


Descriptions

Handover control



Handover Control


Descriptions

Handover control

Types of handovers


Descriptions

Handover control

Types of handover


Descriptions

Handover control

Types of handover


Relocation for circuit-switched services

Relocation for NRT PS services

Relocation for NRT PS services started by the Cell/Ura Update messagefrom target RNC (CELL_FACH state relocation)

Relocation for RT PS services

DN03471612Issue 8-2 en13/12/2007


Related Topics

RNC anchoring for RT (and NRT in Cell_DCH state) data services

Management parameters for SRNS relocation

Statistics for SRNS relocation


Descriptions

Handover control

Types of handovers



Descriptions

Handover control

Types of handovers


Serving RNC relocation signalling

Descriptions

Handover control

Types of handovers



Handover Control


Descriptions

Handover control

Compressed mode


Descriptions

Handover control

Types of handovers



Descriptions

Handover control

Types of handovers


DN03471612Issue 8-2 en13/12/2007


Related Topics

Handover Control

Documents

Transcript of Handover Control