HO Preparation

ED 04 RELEASED HANDOVER PREPARATION

EVOLIUM 0400_04.doc 28/11/2005 3BK 11202 0400 DSZZA 1/110

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VELIZY

EVOLIUM™ SAS

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SYT

HANDOVER PREPARATION

RELEASE B9

System : ALCATEL 900/BSS Sub-system : SYS-TLA Document Category : PRODUCT DEFINITION

ABSTRACT

This document specifies the algorithms to be implemented in Release B9 of the Alcatel BSS for: − Handover preparation, − Directed retry preparation.

Approvals Name App.

C.LEJEUNE SYT DPM

R.MAUGER SYT CCM

ZHANG Y. BSC DPM

Name App.

U. TISCH BTS DPM



REVIEW

Edition 01 Proposal 02 14/04/2004 MRD/TD/SYT/rma/0188.2004

HISTORY

Version Date Changes

Edition 01 Proposal 01

9-03-2004 First working version for Release B9 based on the “B8 Handover Preparation” document (3BK 11202 0353 DSZZA Edition 03). The impacts of the following SFD have been included: − SFD: Autonomous Packet Resource Allocation


31-03-2004 Update based on review comments, according to review report MRD/TD/SYT/rma/0.162.2004 Takes into account B8 CR 20/138465.

Edition 01 Released

14/04/2004 Updated according to review report MRD/TD/SYT/rma/0188.2004.


15/05/2004 Updated to take into account the impacts of the SFD “Enhanced E-GSM band handling” (Ref. 3BK 10204 0612 DTZZA).


30/08/2004 Updated to take into account the impacts of the SFD “Dual Transfer Mode” (Ref. 3BK 10204 0604 DTZZA).

Edition 02 Released

29/09/2004 Updated according to review report MRD/TD/SYT/pmo/0468.2004.


08/04/2005 Removal of DTM impacts

Edition 03 Released

15/04/2005 Editorial update

Edition 04 Released

25/11/2005 Take into account: - CR 20/165276 (2G to 3G Handover) - Editorial updates



TABLE OF CONTENTS

1 SCOPE .............................................................................................................................................. 7

2 FUNCTIONAL DESCRIPTION.......................................................................................................... 7 2.1 Overview .................................................................................................................. 7 2.2 Cell configuration ................................................................................................... 7

2.2.1 Cell Environments............................................................................................................ 7 2.2.1.1 Conventional cell environment ............................................................................................................... 8 2.2.1.2 Hierarchical cell environment ............................................................................................................... 10 2.2.1.3 Multiband cell environment................................................................................................................... 11 2.2.1.4 3G cell environment. ............................................................................................................................ 12

2.2.2 Cell profiles .................................................................................................................... 12 2.2.3 3G cells.......................................................................................................................... 17

2.3 Handover preparation........................................................................................... 17 2.3.1 Functional entities of handover preparation................................................................... 17 2.3.2 Specific cases of application ......................................................................................... 18 2.3.3 Handover detection........................................................................................................ 18

2.3.3.1 Emergency intercell handovers ............................................................................................................ 20 2.3.3.1.1 Quality and Level causes (Causes 2, 3, 4, and 5) ................................................................... 20 2.3.3.1.2 Too long MS-BS distance cause (Cause 6) ............................................................................ 20 2.3.3.1.3 Too short MS-BS distance cause (Cause 22) ......................................................................... 21 2.3.3.1.4 Handovers specific to micro cells (Causes 7, 17, and 18)....................................................... 21

2.3.3.2 Better conditions intercell handovers.................................................................................................... 21 2.3.3.2.1 Power budget cause (Cause 12)............................................................................................. 21 2.3.3.2.2 Inter-layer handovers based on MS speed discrimination (Causes 12 and 14) ....................... 22 2.3.3.2.3 Preferred band cause (Cause 21) ........................................................................................... 23 2.3.3.2.4 Traffic handover (Cause 23) ................................................................................................... 24 2.3.3.2.5 General capture handover (Cause 24) .................................................................................... 24 2.3.3.2.6 Fast traffic handover (Cause 28)............................................................................................. 24

2.3.3.3 Emergency intracell handovers ............................................................................................................ 24 2.3.3.3.1 Interference or low level intracell handovers (Causes 10, 11, 15, and 16)............................... 24

2.3.3.4 Better conditions intracell handovers.................................................................................................... 25 2.3.3.4.1 Better conditions interzone handovers (Cause 13).................................................................. 25

2.3.3.5 Channel adaptation handovers............................................................................................................. 25 2.3.3.5.1 HR-to-FR channel adaptation (Cause 26) ............................................................................... 25 2.3.3.5.2 FR-to-HR channel adaptation (Cause 27) ............................................................................... 26

2.3.3.6 Resource management handovers ...................................................................................................... 26 2.3.3.7 2G-3G Handover.................................................................................................................................. 26

2.3.4 Handover candidate cell evaluation............................................................................... 27 2.3.4.1 Cell ordering according to target layer and target band ........................................................................ 27 2.3.4.2 Filtering process................................................................................................................................... 27 2.3.4.3 Candidate cell ranking.......................................................................................................................... 27 2.3.4.4 3G cell ranking ..................................................................................................................................... 28

2.3.5 Inhibition of handover .................................................................................................... 28 2.3.6 Functional diagram of Handover preparation ................................................................ 30

2.4 Directed retry preparation.................................................................................... 34 2.4.1 System aspects ............................................................................................................. 34 2.4.2 Functional description.................................................................................................... 34 2.4.3 Directed retry on handover alarms ................................................................................ 35 2.4.4 Forced directed retry...................................................................................................... 35 2.4.5 Inhibition of directed retry .............................................................................................. 35

3 DYNAMIC BEHAVIOUR ................................................................................................................. 37 3.1 Functions linked to handover preparation......................................................... 37

3.1.1 Biband mobile stations................................................................................................... 37 3.1.2 Concentric cell and multiband cell ................................................................................. 37

3.1.2.1 Allocation in the inner zone in case of Normal Assignment .................................................................. 37 3.1.2.2 Allocation in the inner zone in case of incoming handover ................................................................... 38 3.1.2.3 Handover in a concentric or multiband cell ........................................................................................... 39

3.1.3 MS speed discrimination ............................................................................................... 39 3.1.3.1 Basic principle...................................................................................................................................... 39 3.1.3.2 Required parameters and variables...................................................................................................... 40 3.1.3.3 Parameter initialisation and modification .............................................................................................. 41

3.1.4 Load management in hierarchical environment............................................................. 43 3.2 Handover preparation........................................................................................... 45

3.2.1 General .......................................................................................................................... 45 3.2.1.1 HO preparation configuration ............................................................................................................... 45



3.2.1.2 HO preparation enabling and disabling................................................................................................. 45 3.2.1.3 HO preparation function ....................................................................................................................... 45

3.2.2 Handover detection........................................................................................................ 46 3.2.2.1 Handover causes ................................................................................................................................. 47

3.2.2.1.1 Intercell handover causes ....................................................................................................... 48 3.2.2.1.2 Intracell handover causes ....................................................................................................... 58 3.2.2.1.3 2G-3G handover causes ......................................................................................................... 65

3.2.2.2 Handover causes priority...................................................................................................................... 66 3.2.2.3 Indication of raw cell list and preferred layer......................................................................................... 66

3.2.3 HO Candidate Cell Evaluation ....................................................................................... 69 3.2.3.1 Ordering process.................................................................................................................................. 69 3.2.3.2 Ordering process for 2G-3G handover ................................................................................................. 73 3.2.3.3 Filtering process................................................................................................................................... 73 3.2.3.4 ORDER cell evaluation process ........................................................................................................... 73 3.2.3.5 GRADE cell evaluation process ........................................................................................................... 74

3.2.4 Handover alarm management ....................................................................................... 76 3.2.4.1 Alarm filtering process based on the timer T_Filter .............................................................................. 76

3.2.4.1.1 General case .......................................................................................................................... 76 3.2.4.1.2 Specific case of resource management handovers (Cause 29 and 30)................................... 77 3.2.4.1.3 Specific case of fast traffic handovers (Cause 28) .................................................................. 77

3.2.4.2 Alarm filtering process based on the timer T_INHIBIT_CPT................................................................. 78 3.3 Directed retry preparation.................................................................................... 80

3.3.1 General .......................................................................................................................... 80 3.3.1.1 Directed retry preparation enabling and disabling................................................................................. 80 3.3.1.2 Directed retry preparation function ....................................................................................................... 80

3.3.2 Alarm Detection ............................................................................................................. 80 3.3.3 Candidate cell evaluation............................................................................................... 81

4 INTERFACES DESCRIPTION ........................................................................................................ 83 4.1 3GPP interfaces/Physical interfaces................................................................... 83 4.2 Internal interfaces ................................................................................................. 83 4.3 Timers list .............................................................................................................. 84 4.4 Parameters and variables list .............................................................................. 85

4.4.1 Handover ....................................................................................................................... 85 4.4.2 Directed retry ................................................................................................................. 96 4.4.3 Relationships between parameters ............................................................................... 98

5 GLOSSARY................................................................................................................................... 102 5.1 Abbreviations ...................................................................................................... 102 5.2 Definitions ........................................................................................................... 103

6 ANNEXES...................................................................................................................................... 105 6.1 Annex A................................................................................................................ 105 6.2 Annex B................................................................................................................ 106 6.3 Annex C................................................................................................................ 110



INTERNAL REFERENCED DOCUMENTS

[ 1] 3BK 10204 0327 DTZZA SFD: General handover improvements [ 2] 3BK 10204 0326 DTZZA SFD: Traffic management in handover algorithms [ 3] 3BK 10204 0363 DTZZA SFD: Improvements in radio channel selection [ 4] 3BK 10204 0364 DTZZA SFD: Controlled handover in multilayer/multivendor environment [ 5] 3BK 10204 0165 DRZZA SFD: External directed retry [ 6] 3BK 10204 0481 DRZZA SFD: Indoor layer support [ 7] 3BK 10204 0475 DRZZA SFD: Instantaneous peaks management [ 8] 3BK 10204 0479 DTZZA SFD: Adaptive multirate speech codec [ 9] 3BK 10204 0477 DTZZA SFD: Anti ping-pong improvements [ 10] 3BK 10204 0484 DTZZA SFD: Multiband cell improvements [ 11] 3BK 10204 0469 DTZZA SFD: Telecom improvement [ 12] 3BK 10204 0478 DTZZA SFD: Tandem free operation [ 13] 3BK 10204 0519 DTZZA SFD: E-GSM support [ 14] 3BK 10204 0547 DTZZA SFD: Support of the GSM 850 MHz band [ 15] 3BK 10204 0535 DTZZA SFD: CS Telecom Improvements [ 16] 3BK 10204 0540 DTZZA SFD: Location Services [ 17] 3BK 10204 0609 DTZZA SFD: Autonomous Packet Resource Allocation [ 18] 3BK 10204 615 DTZZA SFD: 2G-3G Handover Preparation

REFERENCED DOCUMENTS Alcatel references

[ 19] 3BK 11202 0194 DSZZA Application document 05.xx [ 20] 3BK 11202 0413 DSZZA Radio & link establishment [ 21] 3BK 11202 0412 DSZZA Normal Assignment [ 22] 3BK 11202 0403 DSZZA Radio measurements [ 23] 3BK 11202 0399 DSZZA Internal channel change [ 24] 3BK 11202 0386 DSZZA External channel change [ 25] 3BK 11202 0398 DSZZA Call release [ 26] 3BK 11202 0396 DSZZA BSS initialisation of the telecom part [ 27] 3BK 11203 0103 DSZZA BSS Telecom parameters [ 28] 3BK 11202 0388 DSZZA Handover management [ 29] 3BK 11202 0096 DSZZA Alcatel BSS Application document to 3GPP - General Overview [ 30] 3BK 11202 0387 DSZZA Resource allocation and management [ 31] 3BK 11202 0185 DSZZA Extended Cell [ 32] 3BK 11202 0295 DSZZA Power Control & Radio link supervision [ 33] 3BK 11202 0389 DSZZA System Information management [ 34] 3BK 11202 0294 DSZZA Radio Measurements Data Processing [ 35] 3BK 11202 0409 DSZZA Classmark Handling [ 36] 3BK 11202 0337 DSZZA LCS functional specification

3GPP references

[ 37] 3GPP TS 44.018 Mobile radio interface layer 3 specification [ 38] 3GPP TS 45.008 Radio subsystem link control [ 39] 3GPP TS 48.058 BSC-BTS layer 3 specification

Version numbers of the 3GPP Technical Specifications are given in [ 29].



RELATED DOCUMENTS [ 40] CCITT Z100. Structured Definition Language. [ 41] GEODE user manual. VERILOG. [ 42] ART/DST/PFK/20 - ALCATEL_BSS phase 1 description of radio link control algorithms and

guidelines for setting parameters values. ART/DST/PFK/20 Note : Most of the SDL diagrams have been produced with the software tool GEODE which is a trademark of VERILOG [ 41]. The SDL standard is defined in [ 42].

PREFACE Not applicable

OPEN POINTS / RESTRICTIONS Not applicable



1 SCOPE This document specifies the algorithms to be implemented in this release of the ALCATEL BSS for : − handover preparation, − directed retry preparation. Handover preparation consists of two functions which are considered separately in this document : − detection of the need to handover a radio connection, − candidate cell list evaluation. Directed retry preparation is specified along with handover preparation.

2 FUNCTIONAL DESCRIPTION

2.1 Overview The main objective of the handover preparation, in connection with power control (See [ 32]), is to allow a maximum number of MS to operate in the network while maintaining a minimum interference level. The algorithms shall ensure that any mobile is connected with the cell in which the output powers from the MS and the BS are as low as possible (to reduce MS power consumption and interference in the network) while keeping a satisfactory link quality. When on a sufficient duration the propagation conditions keep worsening, then action must be taken. The first action is to increase the output power levels at the MS or the BS (for further details, see [ 32]). When the maximum allowed value has been reached, a handover may become necessary. To reflect this philosophy in macrocells (not in microcellular environment), the algorithm allows for handover on quality and strength reasons only when the last step of power control has been reached. Great care must be taken in choosing the relative values of the thresholds for power control and handover as well as the averaging window sizes (smaller window size and higher threshold for power control than for handover). It must be remembered that, although it is desired that the MS transmits with the lowest possible power, it is more important not to lose a call. Thus early triggering for the power control is possible, by choosing small values for the averaging window sizes and higher comparison thresholds.

2.2 Cell configuration

2.2.1 Cell Environments Five types of cell environments are supported : conventional cell environment, hierarchical cell environment and multiband cell environment and cells with 3G neighboring. In the conventional cell environment, the cell planning is made so as to obtain a continuous geographical coverage . The hierarchical cell environment corresponds to a layout of three cell layers with different cell sizes. The larger outdoor cells layer is called "upper layer", the smaller outdoor cells layer "lower layer", and the indoor cell layer “indoor layer”. This environment is meant to be used in advanced networks. The interest of the indoor cell layer is to:

- ensure a better radio coverage inside large buildings such as hotels, shopping malls, and corporate centers,

- unload the outdoor cells which are accessible from these buildings. The interest of the lower cell layer is twofold:

- densify the traffic by providing a smaller frequency reuse distance in the lower layer - compensate traffic density unbalance by using small cells located at traffic "hot spots"



The interest of the upper cell layer is to : - provide continuous geographical coverage - handle fast moving mobiles in order to avoid high handover rate - provide overflow and rescue channels for the lower and indoor cell layers

Reflecting this representation, the upper layer cells are often called "umbrella cells". In a multiband network environment, the above three layers available for one frequency band can be duplicated for the other frequency band so as to form a multiband network composed of six layers:

− DCS upper layer and GSM upper layer, − DCS lower layer and GSM lower layer, − DCS indoor layer and GSM indoor layer,

where GSM stands for GSM900 or GSM850 bands and DCS stands for DCS1800 or DCS1900 bands.The interest of the multiband network is to increase the capacity or the coverage of the network. In a 3G cells environment, 2G cells can have 3G cells as neighbour cells. The 3G cells are described with their UTRAN-FDD frequency in the UMTS band and their scrambling codes.

2.2.1.1 Conventional cell environment Four different layouts are provided for conventional cell environment , in order to adapt to the traffic density :

- single cell Figure 1 represents the possible geographical layouts with single cells. - concentric cell : a macrocell with two frequency groups covering two concentric zones. This allows to use a smaller reuse distance for the inner zone frequencies and hence to densify an existing network by introducing a small number of frequencies at the needed places. Figure 2 shows the smaller reuse factor (here 3) for the inner zone frequencies in a traditional 9 cell cluster. - multiband cell : a concentric cell is made of

− an outer zone : This zoneincludes the BCCH, the SDCCH and several TCH channels and usesfrequencies from the classical band.

− an inner zone: This zone includes only TCH and usesfrequencies from the preferred band. A monoband MS has only access to the outer zone, whereas a biband MS (or a biband and E-GSM MS in the case of a EGSM-DCS1800 multiband cell), which supports both the frequency band of the outer zone and of the inner zone, has access to both the inner and the outer zones. - extended cell where two cells with collocated antennas provide coverage up to 70 km. The application fields are both the low density areas and the off-shore coverage for coastal radio communications. Figure 3 and Figure 4 illustrate the layout of two associated cells making an extended cell. For reference information on that feature, see [ 31].



sectorized cell for site reductionomnidirectional macrocell

Figure 1: Normal cell environment with one cell layer.

f1

f1

f3

f2

f2

f3

f3 f1

f2

Inner zone

Outer zone

One concentric cell

Figure 2: Concentric cell frequency planning.

outer cell

inner cell

Highw ay

70km

35 km



Figure 3: Extended cell with directional antennas.

inner cell

outer cell

50 km radius

outer limit

inner limitouter limit

Figure 4: Extended cell with omnidirectional antennas.

2.2.1.2 Hierarchical cell environment In much denser traffic areas, depending on the required traffic capacity, the operator may wish to have a hierarchical network, where continuous coverage is provided by a standard macrocell, and traffic hot spots are covered with dedicated cells of limited range. The solution for medium density areas is to have small macrocells (called mini cells), to handle pedestrian traffic, overlapped with one big umbrella macrocell, to handle fast moving mobiles. The solution for higher traffic densities will be to install microcells in all the streets where very dense traffic occurs, and to deploy indoor cells inside high traffic buildings. Umbrella macrocells will be providing the continuous coverage and the traffic channels for saturated microcells and "emergency" handovers. - mini cells with umbrella macrocells This configuration will be of main interest for dense urban areas where some hot-spots are covered by very small macrocells (less than 500 m radius) and continuous coverage is provided by a big macrocell (5 to 10 km radius). Figure 5 presents a possible application of the two-layer hierarchical network with macrocells for both layers, in a middle size town.

Super umbrella cellR~10 km

mini cells0.5<R<1 km

pedestrian area Figure 5: Cell layout with mini cells below one umbrella cell

- microcells with umbrella cells

One layout is provided for microcellular applications, that should apply to very highly dense traffic areas or when the available spectrum is very reduced. Figure 6 presents the cell layout for



microcells covered by an umbrella cell to provide continuous coverage and decreased blocking rate. The densification strategy for microcellular enables to use the already existing macrocell layer for the umbrella cells. Therefore, it may be possible for the operator to use already installed single (or concentric or multiband) cells as umbrella cells for a microcellular network.

existing cells1<R<2 km

microcellsR < 300 m

Figure 6: Typical microcellular layout

- indoor cells with lower layer cells and umbrella cells

In high traffic buildings, it is of main interest to install indoor cells. The addition of the indoor cells allows to unload the existing micro and umbrella outdoor cells and to ensure a better radio coverage inside buildings. Figure 7 shows an example of a cellular network including the indoor layer cells.

Figure 7: Typical cellular network using three cell layers and two frequency bands.

2.2.1.3 Multiband cell environment An operator with licenses in the different frequency bands (GSM900 and DCS1800) can mix in its network cells which use GSM frequency band with cells using DCS frequency band. This case is referred to as multiband cell environment. In the Alcatel BSS, the following multiband cells are not supported: - Multiband cells using GSM850 and DCS1900 bands, and, - Multiband cells using GSM900 and DCS1900 bands Multiband cell environment is supposed to be made out of a main part with cells of same frequency band. This band is the oldest one acquired by the operator and it is the most used in its network : it is called the classical band.



With the other new frequency band, the operator will add new cells to its network. These cells will be deployed either to extend the coverage of the existing network or to increase the traffic capacity of the network rather than to improve the coverage. When the operator cell deployment strategy is to increase the capacity of its network, the biband mobiles (mobiles with capability in both frequency bands) are preferentially directed towards the new cells which use the frequency band different from the classical one. That is why this band is called the preferred band. Multiband cell environment can be applied to conventional cell environment as well as hierarchical cell environment. In this last case, the multilayer structure will interact with the multiband concept.

2.2.1.4 3G cell environment. The 3G cells can be adjacent to any type of 2G cells environment: single, concentric, multiband, extended.

2.2.2 Cell profiles The optimisation of the use of the frequency resources is a main concern for network operators. The Alcatel BSS provides a span of cell environments that allows to cover the whole range of traffic density requirements : from very dense urban centres with microcells up to very low traffic areas (desert or off shore) with extended cell sites. These different types of cell environment must be controlled and administered in a flexible way by the operator. For this purpose, the Alcatel BSS provides a set of cell profiles, which enable the operator to make a starting point configuration by just applying the default values of the profile. Each profile provides all the configuration data associated to one given cell as default settable values. This includes handover parameters, but also power control settings, timers. Nine main monoband profiles are defined : single cell, micro cell, mini cell, umbrella cell, extended inner cell, extended outer cell, concentric cell, concentric umbrella cell, and indoor micro cell. These profiles are duplicated by the internal parameter cell_band_type which can have two different values for each profile. In order to give the operator the possibility to have its personal usage of the ALCATEL parameters, the profiles are user-editable. This means that all default values associated to one given profile can be modified to reflect the standard usage of the operator. These cell profiles correspond to one unique combination of the five parameters : - Cell dimension type : this parameter identifies the cell size in a finite set of cell dimensions(macro or

micro). - Cell layer type : this parameter defines the layer type of a cell in connection with other cells and with

itself. In single layer cell environment, all cells have the same layer type (single). In a hierarchical cell environment, three cell layer types distinguish the upper layer cells, the lower layer cells, and the indoor layer cells.

- Cell_partition type : this parameter defines the type of frequency partitioning that is used in the cell. - Cell range : this parameter identifies the cell as a normal cell or a part of an extended cell - Cell_band_type : this parameter defines the type of frequency band used in the cell The first three parameters are settable on a per cell basis and changeable on-line by O&M. The cell_range parameter is set at BTS initialisation time and only changeable off-line. Cell_band_type is an internal parameter derived from the BCCH frequency of the serving cell (BCCH_FREQUENCY) or from the BCCH frequency of the neighbour cells n (BCCH_FREQUENCY(n)), reported by the mobile. Cell dimension type Two values are possible : ### Macrocell.

### Microcell. Cell layer type



Four values are possible (See Figure 8): ### Single : this applies to all cells in normal environment (1 cell layer)

### Upper : this indicates the upper layer cells in a hierarchical cell environment with two or three layers. These cells are also called "umbrella cells" and they will have at least one associated lower or indoor layer cell, otherwise they are single cells.

### Lower : this indicates the lower layer cells in a hierarchical cell environment with two or three layers. Each lower layer cell will have one associated umbrella cell, otherwise it is deemed "single".

### Indoor : this indicates the indoor layer cells in a hierarchical cell environment with two or three layers. Each indoor layer cell will have one associated umbrella cell, otherwise it is deemed "single".

A single cell has no cells included within its coverage area. Cell partition type Two values are possible : ### Normal partition.

### Concentric partition. The concentric partition corresponds to the concentric or multiband cell case. In this case, the frequency carriers are assigned to one or the other of the two concentric zones : inner and outer. Cell range Three values are possible : ### Normal

### Extended inner ### Extended outer

Cell band type Two values are possible : ### GSM ### DCS Cell_band_type is an internal parameter whose value depends on the BCCH frequency of the serving

cell (BCCH_FREQUENCY) or on the BCCH frequency given by the mobile for every reported neighbour cell (BCCH_FREQUENCY(n), refer to [ 34]).

For the serving cell : Cell_band_type = GSM if BCCH_FREQUENCY is in the E-GSM or GSM850 frequency band. Cell_band_type = DCS if BCCH_FREQUENCY is in the DCS1800 or DCS1900 frequency band. For neighbour cell n : Cell_band_type(n) = GSM if BCCH_FREQUENCY(n) is in the E-GSM or GSM850 frequency band. Cell_band_type(n) = DCS if BCCH_FREQUENCY(n) is in the DCS1800 or DCS1900 frequency

band. Note : the correspondence between the neighbour cell index and the frequency band of the neighbour

cell n is performed through the neighbour cell list (for further details see [ 22]).



Figure 8: Allowed one, two and three layers configurations.

Cell configuration In the following "Cell configuration" will refer to the combination of the five parameters : − Cell dimension type, − Cell layer type, − Cell partition type, − Cell range, − Cell band type. The frequency range supported by the cell is indicated by the parameter FREQUENCY_RANGE. The allowed ranges are PGSM, EGSM, DCS1800, DCS1900, and GSM850 for monoband cells, and PGSM-DCS1800 or EGSM-DCS1800 for multiband cells. The term “E-GSM” is used for the whole GSM-900 frequency band, i.e. the primary band (890-915 MHz / 935-960 MHz) plus the extension band G1 (880-890 MHz / 925-935 MHz). The term “G1” is used for the extension band, whereas the term “P-GSM” is used for the primary band. In the following, a cell supporting only the E-GSM band, i.e. the P-GSM and G1 bands, is never referred to as a multiband cell. In this release of the ALCATEL BSS, all the possible monoband cell configurations are given in Table 1. In the first column “Cell Profile” of Table 1, the term GSM stands for the GSM900 or GSM850 band and the term DCS for the DCS1800 or DCS1900 band depending on the PLMN_FREQUENCY_BANDS parameter. All the other monoband cell configurations are forbidden as they are not relevant for operation. The O&M functions shall ensure that the cell configurations managed by the handover preparation are authorised. The selection of one given cell profile for applying default values will force the value of the cell configuration. In monoband cells, the frequency range parameter FREQUENCY_RANGE can be set to PGSM, EGSM, DCS1800, DCS1900, or GSM850. If the parameter FREQUENCY_RANGE equals to PGSM EGSM, or GSM850 the cell band type is GSM. If the parameter FREQUENCY_RANGE equals to DCS1800 or DCS1900, the cell band type is DCS.

Cell Profile Cell dimension

type

Cell layer type

Cell partition

type

Cell range Cell band type

Frequency range

GSM single cell Macro Single Normal Normal GSM PGSM, EGSM, or GSM850

DCS single cell Macro Single Normal Normal DCS DCS1800 or DCS1900

GSM micro cell Micro Lower Normal Normal GSM PGSM, EGSM, or GSM850

DCS micro cell Micro Lower Normal Normal DCS DCS1800 or DCS1900



GSM mini cell Macro Lower Normal Normal GSM PGSM, EGSM, or GSM850

DCS mini cell Macro Lower Normal Normal DCS DCS1800 or DCS1900

GSM umbrella cell Macro Upper Normal Normal GSM PGSM, EGSM, or GSM850

DCS umbrella cell Macro Upper Normal Normal DCS DCS1800 or DCS1900

GSM extended inner cell Macro Single Normal Extended-inner GSM PGSM, EGSM, or GSM850

DCS extended inner cell Macro Single Normal Extended-inner DCS DCS1800 or DCS1900

GSM extended outer cell Macro Single Normal Extended-outer GSM PGSM, EGSM, or GSM850

DCS extended outer cell Macro Single Normal Extended-outer DCS DCS1800 or DCS1900

GSM concentric cell Macro Single Concentric Normal GSM PGSM, EGSM, or GSM850

DCS concentric cell Macro Single Concentric Normal DCS DCS1800 or DCS1900

GSM concentric umbrella Macro Upper Concentric Normal GSM PGSM, EGSM, or GSM850

DCS concentric umbrella Macro Upper Concentric Normal DCS DCS1800 or DCS1900

GSM indoor micro cell Micro Indoor Normal Normal GSM PGSM, EGSM, or GSM850

DCS indoor micro cell Micro Indoor Normal Normal DCS DCS1800 or DCS1900

Table 1: Allowed monoband cell configurations.

Cell Profile Cell

dimension type

Cell layer type

Cell partition

type

Cell range

Cell band type

Frequency range

GSM900 multiband single cell Macro Single Concentric Normal GSM PGSM-DCS1800 or EGSM-DCS1800

DCS1800 multiband single cell Macro Single Concentric Normal DCS PGSM-DCS1800 or EGSM-DCS1800

GSM900 multiband micro cell Micro Lower Concentric Normal GSM PGSM-DCS1800 or EGSM-DCS1800

DCS1800 multiband micro cell Micro Lower Concentric Normal DCS PGSM-DCS1800 or EGSM-DCS1800

GSM900 multiband mini cell Macro Lower Concentric Normal GSM PGSM-DCS1800 or EGSM-DCS1800

DCS1800 multiband mini cell Macro Lower Concentric Normal DCS PGSM-DCS1800 or EGSM-DCS1800

GSM900 multiband umbrella cell Macro Upper Concentric Normal GSM PGSM-DCS1800 or EGSM-DCS1800

DCS1800 multiband umbrella cell Macro Upper Concentric Normal DCS PGSM-DCS1800 or EGSM-DCS1800

GSM900 multiband indoor micro cell

Micro Indoor Concentric Normal GSM PGSM-DCS1800 or EGSM-DCS1800



DCS1800 multiband indoor micro cell

Micro Indoor Concentric Normal DCS PGSM-DCS1800 or EGSM-DCS1800

Table 2: Allowed multiband cell configurations.

A multiband cell is declared by setting the FREQUENCY_RANGE to either PGSM-DCS1800 or EGSM-DCS1800. The CELL_PARTITION_TYPE of the cell is then forced to CONCENTRIC. The allowed cell profiles for multiband cells are given together within Table 2. Note : - The duplication of the main profiles according to the values of the cell band type is performed

for every main profile. It gives a few cell profiles not really relevant (such as DCS extended outer cell profile) but it prevents from dealing with exceptions.

Figure 9 depicts the outdoor monoband configurations of Table 1 for cell_range = normal and with different values of cell band type. In Figure 9, GSM stands for GSM900/GSM850 and DCS for DCS1800/DCS1900.

Cell_dimension type : macroCell_layer_type : upperCell_partition_type : concentricCell_band_type : GSM

Cell_dimension type : macroCell_layer_type : upperCell_partition_type : normalCell_band_type : GSM

Cell_dimension type : macroCell_layer_type : singleCell_partition_type : concentricCell_band_type : DCS

Cell_dimension type : macroCell_layer_type : lowerCell_partition_type : normalCell_band_type : GSM

Cell_dimension_type : macroCell_layer_type : singleCell_partition_type : normalCell_band_type : DCS

Cell_dimension type : microCell_layer_type : lowerCell_partition_type : normalCell_band_type : DCS

Figure 9: Allowed outdoor monoband cell configurations for cell_range = normal and different values of cell band type. The indoor micro cells are not represented here.

EGSM radio resource allocation strategy The EGSM radio resource allocation strategy is defined by the O&M parameter EGSM_RR_ALLOC_STRATEGY. Two strategies are possible :

− Different behaviour for E-GSM capable MS: The BSS handles differently E-GSM capable MS from P-GSM only capable MS in E-GSM cells. When this value is used, only E-GSM capable MSs are allowed to use to the E-GSM TRXs. Non EGSM capable MSs are served on P-GSM TRXs.

− Same behaviour for E-GSM capable MS: The BSS handles in the same way only P-GSM capable MS as E-GSM capable MS in E-GSM cells, i.e. the BSS assumes that all GSM900 MS are E-GSM capable.



2.2.3 3G cells The 3G cells are described by means of specifics cells attributes:

- Local Cell Identity. It identifies uniquely a 3G cell locally in the 2G BSS.

- Mobile Country Code of a neighbor 3G cell of the own or of a foreign PLMN.

- Mobile Network Code of a neighbor 3G cell of the own PLMN or of a foreign PLMN.

- Scrambling_code_3g: a list of the primary scrambling codes of the 3G cell.

- UMTS Absolute Radio Frequency Channel Number of the 3G cell frequency.

2.3 Handover preparation This function can also be named "handover algorithms" as the algorithms described in section 3 are the "heart" of this function. In the following the word "handover preparation" will be preferred to "handover algorithms". The ALCATEL handover preparation is derived from the basic algorithm found in Annex A of the 3GPP Technical Specification 05.08 [ 38]. The main differences between both algorithms are described in [ 19].

2.3.1 Functional entities of handover preparation The handover preparation is in charge of detecting a need for handover and proposing a list of target cells. Therefore it can be divided into two processes : handover detection and handover candidate cell evaluation. The handover detection process analyses the radio measurements reported by the BTS and the possible alarms sent by RAM. Then, the candidate cell evaluation process is started each time a handover cause (emergency or better conditions type) is fulfilled. The handover candidate cell evaluation works out a list of possible candidate cells for the handover. This list is sorted according to the evaluation of each cell as well as the layer they belong to (in a hierarchical network) and the frequency band they use (in a multiband network). Once the handover preparation is completed, the handover decision and execution (handover management entity refer to [ 28) is performed under the MSC or BSC control. The directed retry preparation (see definition in section 2.4) is performed by the handover preparation function. Once the directed retry preparation is completed, the directed retry is performed either under the BSC control (internal directed retry) or under the MSC control (external directed retry). These procedures use signalling protocols described respectively in [ 23] and [ 24]. An example of implementation of these functions except for directed retry is given in the 3GPP Technical Specification 45.008 [ 38]. The handover preparation requires indirectly (see below) input parameters provided by the function in charge of the radio link measurements. This function is described in [ 22]. Most of the input data required by the handover functions are provided by a function called : Active channel pre-processing. This function is described in [ 34]. It processes raw data given by the radio link measurements (quality, level and distance) through the A-bis interface in compression mode or non compression mode. The compression mode uses two functions: Radio measurements data compression in the BTS and Radio measurements data decompression in the BSC. They are described in [ 34].



The functions handover detection and handover candidate cell evaluation are specified in this document. Figure 10 depicts in a general way : - the interconnections between these functions, - the implementation of these functions in the ALCATEL BSS. The functions which are specified in this document are represented in bold type.

Figure 10: Assignment of HO functions in the ALCATEL BSS.

2.3.2 Specific cases of application The handover preparation applies both for TCH and SDCCH , i.e. it uses the same messages and parameters. Whenever a different handling is necessary, it is indicated in the text. These few cases are : - counting of free channels and load of cells (See [ 30]), - number of frames in reporting period (102 for SDCCH, 104 for TCH), - weighting in case of DTX on TCH/FS. DTX is not allowed on SDCCH (refer to [ 34]). - inhibition of SDCCH handover when SDCCH_COUNTER is running (see section 3.2.1.2). - inhibition of better conditions intercell handovers from SDCCH to SDCCH except for the cause power budget (see section 3.2.2.1.1.3). In case of directed retry from SDCCH to TCH on handover alarms the better conditions intercell handover causes are not inhibited (except Cause 28).

2.3.3 Handover detection The handover detection process is achieved in the BSC. Its role is to detect the need for handovers. Five families of handovers are defined in order to ease the presentation of the handover detection process: − Emergency handover family: The emergency handovers are triggered in a situation of emergency.

The triggering is based on the radio measurements made by the MS and the BTS. − Better conditions handover family: When better radio conditions are detected, a better conditions

handover is triggered. The triggering is based on the radio measurements made by the MS and the BTS.

− Channel adaptation handover family: The channel adaptation handovers are triggered to adapt the channel rate to the voice quality of the communication. The triggering is based on the radio measurements made by the MS and the BTS.

− Resource management family: The resource management handovers are triggered when a handover request is sent by RAM to HOP [ 30].



− 2G-3G handover: This handover is based on the radio measurements. Each time there is at least one UTRAN neighbour cell for which the filtered (averaged) Ec/No is sufficient, a need for handover is detected and the target cell evaluation process is triggered.

For the handovers based on the radio measurements, each time a set of preprocessed (averaged) measurements is available, the HO detection process checks whether a handover is needed or not. If the need for a handover is detected, the target cell evaluation process is triggered. The need for handovers often comes to compare a predefined threshold with a radio measurement. That is why this process is sometimes called ‘HO threshold comparison’. In case of an intercell handover alarm, the handover detection process gives to the cell evaluation process : − the preferred target cell layer : indoor, lower, upper or none − the raw candidate cell list, which can be either all neighbours, or the subset which verify the

handover causes (plus other specific cells in particular cases). With each cell is given one of the handover causes which have been verified.

Depending of the context of application, the emergency and better conditions HOs can be either intercell or intracell HO. Six HO categories are then defined as shown in Table 3.



Context of application →

↓ Handover family

Intracell HO Intercell HO

Emergency HO Emergency intracell HO

Emergency intercell HO

Better conditions HO Better conditions intracell HO

Better conditions intercell HO

Channel adaptation HO Channel adaptation HO

N/A

Resource management HO Resource management HO

N/A

2G-3G Handover N/A 2G-3G external HO Table 3: Main categories of handover

The detection of a need for handover is performed through handover causes which are going to be detailed. In what follows, each cause is thus identified with a number. The following sections detail the different categories of handover according to the context of application (intercell or intracell) and the handover cause.

2.3.3.1 Emergency intercell handovers These handovers are triggered when the call conditions deteriorate significantly in order to rescue the call. The handover causes concerned are listed in Table 4.

Handover Cause Cause Number Too low quality on the uplink Cause 2 Too low level on the uplink Cause 3 Too low quality on the downlink Cause 4 Too low level on the downlink Cause 5 Too long MS-BS distance Cause 6 Too short MS-BS distance Cause 22 Consecutive bad SACCH frames received in a microcell Cause 7 Too low level on the uplink in a microcell compared to a high threshold Cause 17 Too low level on the downlink in a microcell compared to a high threshold Cause 18

Table 4: Emergency intercell handover causes.

2.3.3.1.1 Quality and Level causes (Causes 2, 3, 4, and 5) The aim of these causes is to keep the call going when the radio link is degrading otherwise the radio link failure might be detected and the call released. These causes wait generally for the power control process to increase the BS and MS power to their maximum values. Handover on "too low level" is used to avoid situations where the interference level is low, while the attenuation is quite high. These conditions may appear for example in big city streets which enable a line of sight propagation from the BTS antenna. There is in this case a risk of abrupt quality degradation, if the MS moves away from the line of sight street. In case of simultaneous low-level low-quality signals, an intercell handover is requested.

2.3.3.1.2 Too long MS-BS distance cause (Cause 6) This cause is used when a dominant cell provides a lot of scattered coverages inside other cells, due to propagation conditions of operational network. These spurious coverages have the consequence of producing a high level of co-channel interference probability [ 42]). This cause is different from the others as it is more preventive. It does not make use of the propagation conditions of a call. It just does not allow a MS to talk to a BS if it is too far away.



It may happen for example that some peculiar propagation conditions exist at one point in time that provide exceptional quality and level although the serving BS is far and another is closer and should be the one the mobile should be connected with if the conditions were normal. It may then happen that these exceptional conditions suddenly drop and the link is lost which would not have happened if the mobile had been connected to the closest cell. For these reasons also, this cause does not wait for the power control to react.

2.3.3.1.3 Too short MS-BS distance cause (Cause 22) The too short MS-BS distance handovers are introduced to detect when a MS that is located in an extended outer cell reaches the inner/outer extended cell limit and requires to be handed over towards the extended inner cell. Therefore, it is only valid when the MS is in an extended outer cell. The case the MS is in the extended inner cell and requires to be handed over the extended outer cell can be performed by using the handover Cause 6.

2.3.3.1.4 Handovers specific to micro cells (Causes 7, 17, and 18) In a microcellular network, the radio propagation conditions vary so fast that the handover requires to be triggered without waiting for the action of the power control process. An example of this phenomena is the street corner effect. The handovers Cause 7 come to check if the last consecutive SACCH frames have been correctly received. The handovers Causes 17 and 18 are triggered when the level of the received signal is below a certain threshold. These latter causes are sometimes called “level dropping under high threshold”.

2.3.3.2 Better conditions intercell handovers Better conditions intercell handovers are triggered to improve the overall system traffic capacity. This spans : interference reduction, signalling load reduction, traffic unbalance smoothing. The basic assumption for these handovers is that they should respect the cell planning decided by the operator. The better conditions intercell handover causes are listed in Table 5.

Handover Cause Cause Number Power budget Cause 12 High level in neighbour lower or indoor cell for slow mobile Cause 14 High level in neighbour cell in the preferred band Cause 21 Traffic handover Cause 23 General capture handover Cause 24 Fast traffic handover Cause 28

Table 5: Better conditions intercell handover causes.

The main drawback of this handover category is the risk of "ping-pong" effect, which is an oscillating back and forth handover between two (or three) cells. As the "better conditions intercell" handover are meant to find the "best cell", the variation of the radio conditions will trigger a big amount of better conditions intercell handovers, if the algorithms have a too sensitive reaction. Hence, some mechanisms are forecast, in order to prevent these oscillations from occurring repeatedly at given places. In order to avoid the cancellation of an on-going location service procedure, HOP inhibits the better conditions intercell handovers for TCH to TCH or from SDCCH to SDCCH when a location procedure is on-going (whatever the positioning method that the SMLC has selected).

2.3.3.2.1 Power budget cause (Cause 12) In this case, there is another cell with a better power budget i.e. the link quality can be improved or maintained with a reduced transmission power of both the MS and the BTS. The radio link is not degraded but there is the opportunity to decrease the overall interference level by changing the serving cell of the given MS. In conjunction with power control it presents the advantage to keep the interference as low as possible, since it minimises the path loss between the BTS and MS.



This cause is especially designed to cope with the requirement that the mobile should be connected with the cell with which the lowest possible output powers are used. To assess which of the cells is this "best cell", the algorithm performs every measurement reporting period the comparison of the path loss in the current and in the neighbour cell. This is a feature special to the 3GPP standard which is made possible because the mobile measures the adjacent cell signal levels and reports the six best ones. The power budget calculation is described in details in Section 6.1. This power budget gives the difference in path loss between the current cell and the adjacent cells reported by the mobile. When PBGT(n) is greater than 0, then the path loss from cell n is less than the path loss from the serving cell and thus the radiated power in the downlink direction, and therefore in the uplink direction as well, will be lower in cell n than in the current cell. However it would not be advisable to hand over the MS to another cell as soon as PBGT is greater than 0, because the MS would probably oscillate between the two adjacent cells as the propagation conditions vary. A hysteresis mechanism is implemented to avoid this undesirable effect. The MS may be handed over from the serving cell indexed 0 to a neighbour cell indexed n only if the power budget exceeds the handover Margin(0,n). The handover Margin(0,n) can be modified according to the traffic situation in the serving cell and the neighbour cell n. In this way, power budget handover can be delayed towards a loaded cell and traffic load handover can be triggered from a loaded cell (see section 2.3.3.2.4.). Once the MS is handed over, the same algorithm is applied in the new cell, and a new PBGT is computed (which will be close to the opposite value of PBGT in the old cell) and compared to a new HOMargin. (Thus, the global hysteresis (from cell 0 to cell n and back to cell 0) is the sum of the two HOMargins). However, It is still possible that a ping-pong mechanism is created by different handover causes, for instance a handover may be triggered towards a neighbour cell for bad quality, but in the neighbour cell, a handover back may be triggered for power budget reasons. In order to avoid this, an additional anti-ping-pong mechanism is implemented in the power budget calculation. It enables to penalise for a certain time the cell on which the call has precedently been (See Section 6.1). In case of handover from SDCCH to SDCCH, this cause does not take the traffic situation into account. In multiband cell environment, the mobile can operate in a different band than the frequency band of the BCCHs. This can lead to circular ping-pong handovers from the inner zone if the new band is DCS 1800 or to the impossibility to trigger PBGT handovers from the inner zone if the preferred band is GSM 900. To avoid this problem, when the MS is in the inner zone of a multiband cell, it may be handed over from the serving cell indexed 0 to a neighbour multiband cell indexed n only if the power budget exceeds the handover Margin(0,n) plus the offset handover margin which allows to handicap or favour the PBGT (In the inner zone, the cause “power budget” is only checked between multiband cells, in a way to maintain the MS in the preferred band). The offset handover margin can possibly be used in concentric cells. In some specific network, the operator may have two different frequency band areas in its network, the first one using the classical frequency band cell (e.g. GSM900 or GSM850), and the second one using the new frequency band (e.g. DCS1800 or DCS1900). At the border of these two areas, handovers based on a power budget comparison are required so as to approach the behaviour of power budget handovers between cells having the same frequency band. These handovers are allowed by setting the specific flag EN_MULTIBAND_PBGT_HO defined on a per cell basis at the OMC. Only biband MS can perform these multiband power budget handovers.

2.3.3.2.2 Inter-layer handovers based on MS speed discrimination (Causes 12 and 14) In a hierarchical cell environment, the following types of inter-layer handovers based on the MS speed discrimination can be triggered (See Figure 11):

− Handovers from an indoor layer cell to an upper layer cell, − Handovers from a lower layer cell to an upper layer cell,



− Handovers from an upper layer cell to an lower layer cell, − Handovers from an upper layer cell to an indoor layer cell, − Handovers from a lower layer cell to an indoor layer cell.

Figure 11: Interlayer handovers based on the MS speed discrimination.

The MS speed is estimated from the measure of the residence time of the MS in the indoor and lower layer cells. If this residence time is shorter than a certain threshold, the MS is deemed to move fast. On the other hand, if the residence time is higher that another threshold, the MS is deemed to move slowly. A MS which moves fast in a lower or indoor layer cell is preferentially handed over to an upper layer cell, i.e. an umbrella cell, so as to limit the repetition of intra-layer handovers that would have occurred if the MS were stayed in the same layer cells. This has also the advantage of reducing the signalling generated by the repetitive intra-layer handovers. In such a situation, the power budget cause (Cause 12) associated with the MS speed measure is employed to trigger a handover from a lower or indoor layer to an upper layer. The frequencies on the upper layer can not be reused within a small range and will therefore be a critical resource in hierarchical cell structures. Therefore, the load of the umbrella cell may be a critical problem and a mechanism is required to stop handovers into the upper layer when it becomes overloaded. That is why the estimation of the MS speed and the calculation of the power budget PBGT(n) depend on the load of the upper layer cells. Another advantage of the hierarchical cell structure is that the umbrella cell can offer a number of overflow channels, for calls which are queued in the lower or indoor layers (see directed retry Section 2.4). This allows a much better usage of the traffic capacity of the lower or indoor layers cells, especially when they have only 1 or 2 TRX. This is a second reason why the upper layer cells should not be overloaded. In order to unload the umbrella cells, the MS that moves slowly in an upper layer cell must be handed over the lower or indoor layers cells. Without such an handover, the GSM Phase 1 slow moving MS can connect to the upper layer cell, and can stay in this layer even if the MS do not move at all. The handovers (Cause 14) from an upper layer cell to an indoor or lower layer cell allow to capture the slow mobile. When a MS moves slowly in a lower layer cell and receives a good signal from a neighbour indoor layer cell, the MS will be captured by the indoor layer cell with Cause 14. This type of capture allows to unload the lower layer cell. Cause 14 is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.3 Preferred band cause (Cause 21) If two frequency bands (either GSM900 and DCS1800 bands, or GSM850 and DCS1800 bands, or GSM850 and DCS1900 bands) coexist in the same network, an operator can define a preferred band (PREFERRED_BAND parameter adjustable on a per BSS basis) where the biband mobiles (mobiles with the both frequency bands capability) should be transferred in case of too much traffic load in the classical band (the opposite of the preferred band) and no high load in the preferred band.



This is achieved by monitoring the traffic load of the cells which use the classical band and the preferred band. If a biband mobile is connected to a cell in the classical band where a specific condition on the traffic load is verified, and if this mobile receives good signal level from one neighbour cell which uses the preferred band and where the traffic load is considered as not high, the preferred band cause will be verified for this mobile. Then, an intercell multiband handover will be performed towards the neighbour cell. The only requirement for this handover is that the serving cell uses the classical band and the target cell, the preferred band. This cause is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.4 Traffic handover (Cause 23) The principle of this handover is to reduce the size of the serving cell when it is high loaded relatively to a low loaded cell. When the mobile moves away from the BTS, the power budget will increase and a better cell handover will be triggered earlier. It is recommended to inhibit Traffic handover towards 1 TRX cells. These cells do not have enough resources to receive incoming handovers due to congestion of neighbour cells. Moreover because of the great variation of traffic in the 1 TRX cells, traffic load is never considered as low. This cause is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.5 General capture handover (Cause 24) In hierarchical network where cells use different frequency bands, a general capture handover is required to manage, on a per cell adjacency basis, the possibility for the mobiles to be captured. This is needed in order to synchronise the capture from a macrocell to a microcell (as described in 2.3.3.2.2) or from the same macrocell to another cell of preferred band (as described in 2.3.3.2.3). This general capture handover takes into account the load in the serving and in the target cell. This cause is inhibited for handover from SDCCH to SDCCH.

2.3.3.2.6 Fast traffic handover (Cause 28) A fast traffic handover is initiated by the RAM request “Fast traffic handover request” when the serving cell is congested. Like directed retry, a fast traffic handover is triggered when a call request is queued in RAM. However, instead of pushing the queued request into a neighbour cell, the fast traffic handover pushes an established call out in a neighbour cell in order for the queued request to be served in the serving cell. With the fast traffic handover alarms, HOP detects the MS that could perform such an handover. Cause 28 only applies to handovers from TCH to TCH.

2.3.3.3 Emergency intracell handovers The causes specific to emergency intracell handovers are listed in Table 6.

Handover Cause Cause Number Too low level on the uplink, inner zone Cause 10 Too low level on the downlink, inner zone Cause 11 Too high interference level on the uplink Cause 15 Too high interference level on the downlink Cause 16

Table 6: Emergency intracell handover causes.

2.3.3.3.1 Interference or low level intracell handovers (Causes 10, 11, 15, and 16) Emergency handovers Causes 15 and 16 are triggered for intracell application when the radio link is deemed to suffer a high level of interference. In this case, the channel assigned to the call is changed for another channel in the same cell, on which the measured interference level is the smallest possible. Since AMR calls can be performed over worse carrier-to-interference ratios than non AMR calls, the parameter setting for Causes 15 and 16 is different for non AMR and AMR calls. In the case of concentric cell or multiband cell environment, emergency intracell handovers Causes 10 and 11 concern handovers from the inner to the outer zone of the same cell (they are called interzone



handovers) as well as handovers performed within one zone (they are called intrazone handovers). The possible interzone handovers in a concentric or multiband cell are shown in Figure 12.

Figure 12: Possible interzone handovers in a concentric or multiband cell.

2.3.3.4 Better conditions intracell handovers The only better conditions intracell handovers is shown in Table 7.

Handover Cause Cause Number Too high level on the uplink and downlink, outer zone Cause 13

Table 7: Better conditions intracell handover causes.

In order to avoid the cancellation of an on-going location service procedure, HOP inhibits the better conditions intracell handovers (always from TCH to TCH) when a location procedure is on-going (whatever the positioning method that the SMLC has selected).

2.3.3.4.1 Better conditions interzone handovers (Cause 13) For concentric cells, the "outer zone uplink and downlink level too high" cause forces an intracell handover from an outer zone TCH to an inner zone TCH. This handover is considered as interzone handover (See Figure 12). Then the MS can operate on frequency channels with lower BS and MS maximum powers. If the inner zone is congested, the MS will stay on the outer zone. The flag EN_LOAD_BALANCE can be enabled at the OMC to balance the load between the inner and outer zones. In case the load balance is allowed, the handovers Cause 13 are inhibited as long as the inner zone is more loaded than the outer zone. For multiband cells, this same cause forces an intracell handover from an outer zone TCH in the classical band to an inner zone TCH in the preferred band. The handover detection is made on signal levels coming from the serving cell and possibly from the neighbour cells.

2.3.3.5 Channel adaptation handovers The causes specific to the channel adaptation handovers are listed in Table 8.

Handover Cause Cause Number HR-to-FR channel adaptation due to bad radio quality Cause 26 FR-to-HR channel adaptation due to good radio quality Cause 27

Table 8: Channel adaptation handover causes.

2.3.3.5.1 HR-to-FR channel adaptation (Cause 26) The HR-to-FR channel adaptation handovers aim to increase the channel rate of the ongoing call when a bad radio quality is detected. The channel adaptation consists in changing the current half rate TCH to a full rate TCH. The handover only applies to adaptive multirate (AMR) calls. When a Cause 26 is



triggered, a HR-to-FR channel adaptation together with an intracell handover due to bad quality is performed. The related handover cause is called “HR-to-FR channel adaptation due to bad radio quality”. There are two ways to trigger Cause 26. The first way consists of triggering Cause 26 only if a previous intracell handover Cause 15 or 16 have been previously detected in the serving cell for the current MS. This way is intended to non-hopping channels for which an intracell handover Cause 15 or 16 is sometimes not sufficient to improve the quality of the call. If the quality is not sufficient due to a too high interference level, instead of continuing triggering intracell handover Cause 15 or 16, a HR-to-FR channel adaptation is triggered thanks to Cause 26. The second way applies when the intracell handover Causes 15 and 16 are both disable for AMR calls. If a too high level of interference is detected in the serving cell for the current MS, Cause 26 is then triggered. This second way intends to improve the quality of hopping channels which quality is generally not much improved after an intracell handover Cause 15 or 16.

2.3.3.5.2 FR-to-HR channel adaptation (Cause 27) The FR-to-HR channel adaptation handovers aim to reduce the number of busy TCH when the radio quality is very good and the serving cell becomes high loaded. The channel adaptation consists to change the current full rate TCH to a half rate TCH. The handover only applies to adaptive multirate calls. The related cause is called “FR-to-HR channel adaptation due to good radio quality”. In order to avoid the cancellation of an on-going location service procedure, HOP inhibits the FR-to-HR channel adaptation handovers when a location procedure is on-going (whatever the positioning method that the SMLC has selected).

2.3.3.6 Resource management handovers The resource management handovers are listed in Table 9. In the opposite of the others handover causes which are based on the radio measurements given by the active channel processing function (See Section 2.3.1), the need for Causes 29 and 30 are detected in RAM. When detected, the related handover alarms are sent to HOP in the message “Start HO”, which contains the HO cause number, and the reference of the call concerned by the handover.

Handover Cause Cause Number TFO handover Cause 29 Move from PS to CS zone Cause 30

Table 9: Resource management handovers cause.

In case of codec mismatch between two MS in communication, an handover Cause 29 is performed in order to match their speech codec. For further details on Cause 29, refer to [ 30]. In HOP, Cause 29 consists in checking whether the current call is the one concerned by the call reference. Then, when Cause 29 is triggered, HOP sends the alarm to HOM with the serving cell as only candidate cell. The new codec type is also forwarded to HOM. From resource allocation point of view, in case of a CS ongoing call is located in PS preference zone, not only non pre-emptable PS zone, but also MAX_SPDCH_LIMIT zone, at this situation, an intra-cell handover should be triggered to move the CS call to CS preference zone. NOTE: MAX_SPDCH_LIMIT is the number of SPDCHs that the BSC will allocate to the MFS, see ref[ 30].

2.3.3.7 2G-3G Handover The 2G-3G handover aims to favour the handover towards a 3G cell when in the list of cells, reported by the MS, there is at least one UTRAN neighbour cell for which the Ec/No averaged by the BSS is sufficient. The Ec/No is the only criteria taken into account for 3G cells.



Handover Cause Cause Number

2G-3G Handover Ec/No Cause 31 Table 10: 2G-3G Handover handovers cause.

2.3.4 Handover candidate cell evaluation The handover candidate cell evaluation process is performed in the BSC and only applies to intercell handovers, i.e. emergency and better conditions HO and 2G-3G handovers. Once a need for handover is detected, this process looks for possible target cells (except if it is an intracell handover) and provides HOM entity with the list of candidate cells, the HO Cause (per cell in the list), and the MS zone indication (per concentric cell in the list).

2.3.4.1 Cell ordering according to target layer and target band In hierarchical or multiband environment, cells are characterised by the layer they belong to or/and the frequency band they use. The candidate cell evaluation process takes into account these characteristics in the candidate cell ordering. In hierarchical environment, the HO detection process can indicate a preferred layer where the handover must be directed to. If this indication is used, the candidate cell evaluation puts in the first places of the list, the candidate cells belonging to the preferred layer. They are followed by the cells of the other layer, providing they are also correct candidates. After this possible distinction, in each part of the list, the candidate cell evaluation sorts the candidate cells according to the parameter PRIORITY(0,n) (parameter on line changeable from the OMC-R). The cells having the highest priority are put in the first place of the list. They are followed by the cells having lowest priorities. The PRIORITY(0,n) is only used when the flag EN_PRIORTY_ORDERING is set to enable. In case of emergency handover, for each category (preferred layer and other layer) and between cells having the same priority, the candidate cell evaluation sorts the candidate cells according to the frequency band they use : the cells which use the same frequency band as the serving cell are put first and they are followed by the cells which use the other frequency band. The cell evaluation function (see section 3.2.3.) is then applied to the different candidate cell lists defined from the preferred layer indication, the PRIORITY(0,n) parameter and the frequency band of the serving cell (only in case of emergency handover).

2.3.4.2 Filtering process The filtering process allows filtering out cells from the target list before sending them to the ORDER or GRADE evaluation process. It can be enabled/disabled on-line on a per cell basis from the OMC-R with the flag EN_PBGT_FILTERING. The candidate cells are filtered on their power budget in relation to a handover margin threshold based on the handover cause.

2.3.4.3 Candidate cell ranking Two types of cell evaluation algorithms can be used : ORDER and GRADE. ORDER and GRADE are two different methods of cell ranking. They both consist in giving a mark or ’figure of merit’ to each candidate cell. The basic differences between ORDER and GRADE are that : with ORDER

- The candidate cell evaluation process interacts with the handover detection by use of cause dependent handover margins.

- The candidate cell evaluation process takes into account the number of free TCH in the candidate cells.



with GRADE, :

- The candidate cell evaluation process does not interact with the handover detection. - The candidate cell evaluation process takes into account the relative load of traffic channels in the

candidate cells. The type of cell evaluation is chosen by the operator on a (serving) cell basis and is provided to the BSC with the parameter CELL_EV. Each algorithm uses the following parameters to compare candidate cells:

ORDER GRADE Power budget X X Number of free TCH/FS X(1) Cell load (%) X(1) Handover type X Table 11: Comparison of candidate cell evaluation algorithms

(1) The number of free TCH in the calculation of ORDER and the cell load in the calculation of

GRADE will only be used in case of an internal candidate cell and when the flag EN_LOAD_ORDER is set to ENABLE. Otherwise, there is no offset due to load information in the candidate cell evaluation.

2.3.4.4 3G cell ranking When in the serving cell, there is one UTRAN neighbour cell for which the Ec/No, averaged by the BSS (AV_ECNO), is higher or equal to a predefined threshold (THR_ECNO), the reported UTRAN cells are ranked according to this averaged Ec/No:

- for each UTRAN Cell(n), meeting the criteria AV_ECNO(n) ≥ THR_ECNO, the Cell n shall be added in the list of candidate cells, the cause 31 is added together with the 3G cell identity in the list.

- the 3G candidate cells shall be ranked according to AV_ECNO(n) in increasing order, the cell with the highest AV_ECNO placed on the top of the list. The 3G candidate cells are on top of the list preceding the 2G candidate cells that are also evaluated.

Note: The BSC maintains a filtered list with both 2G and 3G cells with associated handover causes, because in the case where all the 3G cells are rejected, it shall be possible to handover to a 2G cell.

2.3.5 Inhibition of handover The operator has the possibility to inhibit selectively the different handover causes via O&M commands on a cell basis. Inhibition and control of handover management The following flags are set per cell and are on-line changeable. These flags are used by the handover management entity (see [ 28]). They are not used by the handover preparation function, except for HO_INTERCELL_ALLOWED and EN_INTRACELL_REPEATED. They are mentioned only for information with respect to the flags described in the next paragraph. The following flags can be used to inhibit and control the execution of a handover in the BSC : - HO_INTERCELL_ALLOWED : enable/disable intercell handover, - HO_INTRACELL_ALLOWED : inhibition of all intracell (BSC internal) handovers (TCH and SDCCH).

This flag does not control the inhibition of interzone handover (see below). - EN_IC_HO : inhibition of all incoming handovers - EN_INTRACELL_REPEATED : inhibition of repetition of intracell handover , by triggering an intercell

handover with cause "Quality too low".



Inhibition of the handover preparation The following flags can be used to inhibit the detection of a handover cause. - HO_INTERCELL_ALLOWED : enable/disable intercell handover causes, - EN_INTRACELL_REPEATED : enable/disable repetition of intracell handover causes, - EN_RXQUAL_UL : enable/disable too low quality uplink cause, - EN_RXQUAL_DL : enable/disable too low quality downlink cause, - EN_RXLEV_UL : enable/disable too low level uplink cause, - EN_RXLEV_DL : enable/disable too low level downlink cause, - EN_PBGT_HO : enable/disable power budget cause, - EN_MULTIBAND_PBGT_HO : enable/disable the power budget handovers Cause 12 and the

traffic handovers Cause 23 between cells belonging to different frequency bands - EN_DIST_HO : enable/disable too long MS-BS distance cause, - EN_INTRA_UL : enable/disable too high interference uplink cause for non AMR calls, - EN_INTRA_UL_AMR : enable/disable too high interference uplink cause for AMR calls, - EN_INTRA_DL : enable/disable too high interference downlink cause for non AMR calls, - EN_INTRA_DL_AMR : enable/disable too high interference downlink cause for AMR calls, - EN_MCHO_H_UL : enable/disable level uplink, high threshold, microcell cause, - EN_MCHO_H_DL : enable/disable level downlink, high threshold, microcell cause, - EN_MCHO_RESCUE : enable/disable microcell to macrocell handover on missing MS measurement

reports, - EN_MCHO_NCELL : enable/disable upper to lower layer handover cause. - EN_PREFERRED_BAND_HO : enable/disable multiband handover cause. - EN_BETTER_ZONE_HO : enable/disable too high level on the uplink and the downlink, outer zone cause. - EN_TRAFFIC_HO(0,n) : enable/disable traffic HO cause from the serving cell to the cell n. - EN_GENERAL_CAPTURE_HO : enable/disable general capture handover cause. - EN_AMR_CA : enable/disable intracell HO for AMR channel adaptation (Causes 26 and 27) When these flags are set to DISABLE, the corresponding handover alarms are not checked by the handover detection function. - EN_3G_HO: enable/disable Inter-system Handover. For the flags controlling handover cause : - If the flag is set to "ENABLE", the checking of the handover cause is enabled. - If the flag is set to "DISABLE" the checking is disabled. Note 1: For the multiband handover cause, the enabling of the flag EN_PREFERRED_BAND_HO

does not imply automatically the execution of multiband handovers. It depends also on the flag EN_INTERBAND_NEIGH used on a per BSS basis (see [ 33]).

Note 2: The flag to enable or disable Cause 29 and 30 arecontrolled by RAM (cause 29 and 30) and the transcoder (cause 29 only) (See [ 30]).

The flags are per cell and on-line changeable, this means that for each cell the operator can enable or disable some handover causes without releasing active calls in the cell. Consistency checks are performed by the OMC-R, in order to maintain the overall coherence of all flags with the type of the cell. Providing the conditions defined in Section 3.2.4 are fulfilled, the timer T_INHIBIT_CPT inhibits the capture handover causes for a while so as to avoid the ping pong effects in a multilayer/multiband environment. The parameter SDCCH_COUNTER allows to inhibit SDCCH handovers after completion of the Immediate Assignment procedure during SDCCH_COUNTER successive SACCH frames (See Section 3.3). Particular cases for concentric or multiband cells



In the case of concentric or multiband cells, a handover cause due to high interference level (causes 15 or 16, see 3.2.2) triggers an intrazone or an interzone handover. Those are particular cases of intracell handovers. A handover cause due to too low level in the inner zone (causes 10 or 11) or the better zone cause (cause 13) triggers an interzone handover (see section 3.2.2.1.2). An interzone handover is a particular case of intracell handover. The two HO causes (10, 11) cannot be enabled or disabled individually. These causes are enabled and disabled when the parameter CELL_PARTITION_TYPE = CONCENTRIC and = NORMAL respectively (see sections 2.2 and 3.2.2). Moreover the HO cause 13 must not be disabled in case of allocation in the inner zone during Normal Assignment (the flag EN_BETTER_ZONE_HO should not be looked at when deciding whether the MS should go to the inner zone or outer zone). Therefore, HO_INTRACELL_ALLOWED flag does not control the enabling/disabling of the interzone handover, but only of the intrazone handover (or interzone handover causes 15 or 16). Finally , the flag EN_INTRACELL_REPEATED does not control the repetition of the interzone handover.

2.3.6 Functional diagram of Handover preparation Figure 13 is the SADT diagram of the handover functions in the BSC. This diagram is just a functional description. It does not constrain the implementation. The BSC receives raw measurement data from the BTS in the message MEASUREMENT RESULT if EN_MEAS_COMPRESSION=DISABLE or compressed measurement data in the message PREPROCESSED MEASUREMENT RESULT every SACCH multiframe period (see radio link measurements, ref. [ 22] and Radio measurements data processing, ref. [ 34]). The BSC pre-processes that data to detect HO threshold conditions for emergency, better conditions, and channel adaptation handovers. The preprocessed measurement reports are therefore generated internally by the BSC which uses them also for candidate cell evaluation. The Active Channel Preprocessing function is not specified in this document (refer to [ 34]). That is why it is not represented in bold type.

Active channelpreprocessing

Handoverdetectionaveraged measurements

for handover detection

P

MS & BSparameters

HO candidatecell evaluation

“TCH usage information”

CELL_EV

candidate cell evaluation parameters

T_FILTER

“Alarm”

HO and DRenabling flags

HO detection parameters

HO cause,raw cell list,

"Start DR algos" EN_LOAD_ORDER

MS speed discrimination parameters

PREF_LAYERNew codec type

cellconfigurationparameters

T_HCP

"Start T_HCP" EN_CAUSE_28

“MS Zone Indication Request”

"Fast traffic HO Request"

“MS Zone Indication ACK (ZONE)”

“Fast traffic HO ACK”

T_INHIBIT_CPT

"Start T_INHIBIT_CPT"

"Start HO"

Figure 13: SADT diagram of handover functions in the BSC



Flows description The description is done at BSC level (see Figure 13). Input flows - “TCH usage information”

* FREEfactor(n), LOADfactor(n), AV_LOAD, t(n): respectively correction factor of ORDER depending on free level of cell n, correction factor of GRADE depending on load of cell n, averaged traffic load and absolute number of free TCH in the cell n (refer to [ 30]). In concentric cells, if the flag EN_LOAD_OUTER is set to enable, the load is evaluated considering the TCH resource in the outer zone instead of in the whole cell. If E-GSM TRXs are defined in the cell, and the flag EN_LOAD_EGSM is set to enable, and the EGSM_ALLOC_STRATEGY is set to Different behaviour for E-GSM capable MS, the load is evaluated including the EGSM TCH resource of the cell (See [ 30] for more details in the specific case of concentric cells). These flows are BSC internal. * Traffic_load(n): situation of the traffic in the cell n (refer to [ 30]). * LOAD_SV3(n): indicates whether or not the cell n is loaded [ 30]. * EN_CAUSE_13: flag that indicates in concentric or multiband cells whether or not the inner zone is more loaded than the outer zone.

- Averaged measurements for handover detection :

* AV_RXQUAL_UL_HO, AV_RXQUAL_DL_HO, AV_RXLEV_UL_MCHO, * AV_RXLEV_UL_HO, AV_RXLEV_DL_HO, AV_RXLEV_DL_MCHO, * BS_TXPWR, MS_TXPWR, AV_RANGE_HO, AV_RXLEV_PBGT_DR, * AV_BS_TXPWR_HO, AV_BS_TXPWR_DR, * AV_RXLEV_PBGT_HO, AV_RXLEV_NCELL(n), AV_RXLEV_NCELL_BIS(n). * AV_RXLEV_NCELL_DR(n), n=1..BTSnum. * BFI_SACCH * AV_RXQUAL_DL_CA_HR_FR, AV_RXQUAL_UL_CA_HR_FR, * AV_RXQUAL_DL_CA_FR_HR, AV_RXQUAL_UL_CA_FR_HR, * AV_ECNO(n)

Control flows - Cell configuration parameters : CELL_DIMENSION_TYPE, CELL_LAYER_TYPE, CELL_PARTITION_TYPE, CELL_BAND_TYPE, ZONE_TYPE, CELL_RANGE, FREQUENCY_RANGE. - MS and BS parameters :

Maximum and minimum MS/BS powers allowed in the cell : MS_TXPWR_MAX, BS_TXPWR_MAX, MS_TXPWR_MIN, BS_TXPWR_MIN, Maximum MS power in the inner zone of a concentric or multiband cell : MS_TXPWR_MAX_INNER, Maximum BS power in the inner zone of a concentric or multiband cell : BS_TXPWR_MAX_INNER.

- T_FILTER : Time after which a “no alarm” message (an alarm message with no candidate cell, see

section 3.2.4) is sent to the handover management entity, if no new alarm has been detected whilst running.

- T_HCP : time during which penalty PING_PONG_HCP is applied to the preceding cell (cause 12);

time during which penalty is applied to the preceding inner zone (cause 13). - T_INHIBIT_CPT: Time during which the capture handover Causes 14, 21, and 24 are inhibited.



- P : MS classmark (maximum MS power) for the concerned frequency band(s) (GSM900, GSM850, DCS1800, DCS1900). In case of biband mobiles, depending on the setting of the PLMN_FREQUENCY_BANDS parameter, the following MS classmark are considered:

- both MS classmark for GSM900 band and MS classmark for DCS1800 band, or, - both MS classmark for GSM850 band and MS classmark for DCS1800 band, or,

- both MS classmark for GSM850 band and MS classmark for DCS1900 band, or, - both MS classmark for GSM900 band and MS classmark for DCS1900 band.

- Candidate cell evaluation parameters :

* MS_TXPWR_MAX(n) : n=1..NBR_ADJ, * HO_MARGIN(0,n) : n=1..NBR_ADJ, * HO_MARGIN_LEV(0,n) : n=1..NBR_ADJ, * HO_MARGIN_QUAL(0,n) : n=1..NBR_ADJ, * HO_MARGIN_DIST(0,n) : n=1..NBR_ADJ, * PRIORITY(0,n) : n=1..NBR_ADJ, * EN_PRIORITY_ORDERING, * OFFSET_HO_MARGIN_INNER, * RXLEV_MIN(n) : n=1..NBR_ADJ, * LINKFACTOR(0,n) : n=1..NBR_ADJ, * NBR_ADJ : number of adjacent cells. * identity (BSIC + BCCH ARFN) of the preceding cell if internal to the BSC * EN_SPEED_DISC : flag enabling the sending of fast MS to the umbrellas * EN_PBGT_FILTERING : flag enabling/disabling the filtering process * L_LOAD_OBJ : maximum load on the umbrella to hand over a fast moving mobile * PING_PONG_HCP : handicap applied to the preceding cell for power budget calculation or handicap applied to the preceding inner zone in the cause 13. See definition of these parameters in section 3.2.2. * AV_ECNO(n) : n=1..NBR_ADJ_3G

- CELL_EV : indicator of GRADE/ORDER handover (cell evaluation indicator). - "Start DR algos " : indication to the handover preparation to start the preparation for directed retry.

This message is sent by the HOM entity. - "Start HO" : indication to the handover preparation to start the handover for Causes 28 , 29 and 30.

This message is sent by the RAM entity. - "Fast traffic HO request" : Request from the RAM entity for checking if the current call can

perform a fast traffic handover. - “Move from PS to CS zone HO” : Request from RAM entity to make an intra-cell handover ,

to optimise packet radio resource allocation. - “MS zone Indication Request”: Request from the RAM entity (refer to [ 30]) for determining the

zone location of the mobile in a concentric or multiband cell (see section 3.1.1) in case of allocation during Normal assignment in the concentric or multiband cell.

- HO and DR enabling flags : HO_INTERCELL_ALLOWED, EN_INTRACELL_REPEATED, EN_FORCED_DR, EN_RXQUAL_UL, EN_RXLEV_UL, EN_RXQUAL_DL, EN_RXLEV_DL, EN_DIST_HO, EN_PBGT_HO, EN_MULTIBAND_PBGT_HO EN_INTRA_UL, EN_INTRA_UL_AMR, EN_INTRA_DL, EN_INTRA_DL_AMR, EN_MCHO_H_UL, EN_MCHO_H_DL, EN_MCHO_RESCUE, EN_MCHO_NCELL, EN_PREFERRED_BAND_HO, EN_GENERAL_CAPTURE_HO, EN_TRAFFIC_HO(0,n), EN_BETTER_ZONE_HO, EN_AMR_CA.



- EN_LOAD_ORDER : flag controlling the use of the FREEFACTOR and LOADFACTOR in the

calculation of candidate cell list (ORDER and GRADE modes). - HO detection parameters : * RXLEV_UL_ZONE, RXLEV_DL_ZONE, ZONE_HO_HYST_UL, ZONE_HO_HYST_DL, * L_RXQUAL_UL_H, L_RXQUAL_UL_H_AMR, L_RXLEV_UL_H, RXLEV_UL_IH, * L_RXQUAL_DL_H, L_RXQUAL_DL_H_AMR, L_RXLEV_DL_H, RXLEV_DL_IH, * U_TIME_ADVANCE, L_TIME_ADVANCE, * N_BAD_SACCH, * L_RXLEV_CPT_HO(0,n), n=1..NBR_ADJ, * U_RXLEV_UL_MCHO, U_RXLEV_DL_MCHO, * L_RXLEV_NCELL_DR(n), n = 1..NBR_ADJ, * EN_BI-BAND_MS(n), * OUTDOOR_UMB_LEV(0,n), n ### { neighbour umbrella cells}

* PREFERRED_BAND : Frequency band type preferably used by biband mobiles. * MULTIBAND_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a multiband handover. * CAPTURE_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a general capture handover. * NEIGHBOUR_RXLEV(0,n), * RXLEV_LIMIT_PBGT_HO, * DELTA_INC_HO_margin, DELTA_DEC_HO_margin, * THR_RXQUAL_CA_HIGH, THR_RXQUAL_CA_NORMAL, * OFFSET_CA_HIGH, OFFSET_CA_NORMAL.

* EN_LOAD_BALANCE : Flag that enables or disables the load balance between the inner and outer zones in concentric cells,

* EN_AMR_HR, EN_AMR_FR, * THR_ECNO

- Speed discrimination parameters and variables * MS_SPEED * PREC_LAYER_TYPE * C_DWELL * L_LOAD_OBJ, H_LOAD_OBJ * MIN_DWELL_TIME, MIN_CONNECT_TIME * L_MIN_DWELL_TIME, H_MIN_DWELL_TIME, DWELL_TIME_STEP Internal flows - Candidate cell evaluation input

* HO cause * raw cell list of potential candidate cells with the MS zone indication in concentric cells * PREF_LAYER : preferred target cell layer * New codec type for Cause 29

- "Start T_HCP" : This timer is started in the target cell after an incoming internal handover. This timer is also started after an intracell handover in a concentric cell when the preceding zone is the inner zone.

- “Start T_INHIBIT_CPT”: This timer is started under the conditions specified in Section 3.2.4. While

running, it inhibits the capture handover Causes 14, 21, and 24. - EN_CAUSE_28: This flag enables or disables the triggering of Cause 28 in HOP. The enabling of

Cause 28 is controlled via RAM messages. Output flows



- “Alarm”: message that is sent to HOM when an alarm has been detected. This message contains the Candidate cells list (with the MS Zone Indication for each concentric cell of the candidate cells list), the HO cause, and the new codec type (for Cause 29). - “Fast handover alarm ACK”: message that is sent to RAM when a fast traffic handover has been

detected. This message contains the reference of the queued request, and the call reference. - “MS Zone Indication ACK(ZONE)”: message that is sent to RAM (refer [ 30]). This message

contains the zone in the concentric or multiband cell where the mobile is situated.

2.4 Directed retry preparation

2.4.1 System aspects The directed retry consists in an SDCCH to TCH intercell handover during the call set-up process. The directed retry is triggered when given radio conditions are met and the serving cell is congested. The handover to TCH in another cell reduces the call set-up time (queuing phase) and allows the sharing of resources from one cell with another, thus overcoming traffic load unbalance. In this release of the ALCATEL BSS, the directed retry can be internal or external to the BSS (see [ 23] and [ 24]). The start and stop of the directed retry preparation are described in Section 3.3.1.1. The directed retry may be performed : - either on handover alarms : If a handover alarm is detected during queuing, and the candidate cell

evaluation process indicates at least an internal or external cell, then the BSS will perform a directed retry .

- or on alarm of forced directed retry : If during queuing, an internal or external neighbour cell is

reported with a sufficient level and has free TCH, then the BSS will perform a directed retry . The expression "Forced directed retry" refers to this case, because the radio conditions in the serving cell do not represent a need for handover. The cause which leads to forced directed retry is assimilated to a "better conditions cause" in the handover preparation.

2.4.2 Functional description The directed retry preparation is supported : - by the same processes as the handover preparation for directed retry on handover alarms, - by a specific condition in the alarm detection process (new cause pertaining to forced directed retry) and a specific candidate cell list evaluation process for forced directed retry. The detection process for directed retry consists in the checking of the handover alarms and of the forced directed retry alarm. If an alarm for forced directed retry is raised, then the target cell evaluation is performed by the candidate cell evaluation process for forced directed retry. For all other alarms, the target cell evaluation is performed by the candidate cell evaluation process for handover (see section 3.2.3.). For further details about this process and the alarm priority order, refer to section 3.2.2.2.



2.4.3 Directed retry on handover alarms The preparation of directed retry on handover alarms is performed by the handover preparation function. All the processes of this function operate in the same way as for preparation of SDCCH or TCH handover at the exception of the candidate cell evaluation process. The candidate cell evaluation process (see section 3.2.3.) looks for target cells so as to do an SDCCH to TCH handover. TCH load (i.e. Freelevels and Loadlevels related to TCH) in neighbour cells may be used for target cell evaluation and ranking (the TCH load is not known in case of external cells). Note : in case of handover preparation, the candidate cell evaluation process looks for target cells so as to do a SDCCH handover. The SDCCH load is not taken into account (see section 3.2.3).

2.4.4 Forced directed retry The preparation of forced directed retry is composed of two processes : - forced directed retry detection, - candidate cell evaluation. The forced directed retry detection requires specific preprocessed measurements (refer to [ 34]). The detection is performed every SACCH measurement reporting period when preprocessed measurements are available. The averaged received levels of all neighbour cells are compared to a threshold. If one or several cells are found with a received level higher than the threshold, an alarm of forced directed retry is raised : high level in a neighbour cell for forced directed retry. This cause is included in the "better conditions causes" of the handover preparation. When detected, this alarm is sent , with the list of internal and external cells fulfilling the condition, to the candidate cell evaluation process for forced directed retry if there is no handover alarm raised at the same time. A handover alarm raised at the same time is prior and is sent to the candidate cell evaluation process (see section 3.2.3.). Then, the candidate cell evaluation process looks for cells : a. where the MS can communicate, b. where the received level at MS is higher than a given threshold, c. and which have a minimum number of TCH channels free (in case of internal cell). The condition b. allows the control of the interference level in the network. The condition c. is a means to forbid "retry traffic" from a congested cell to a neighbour cell if the neighbour cell has less than a minimum number of channels free. This condition controls the amount of "retry traffic" and therefore the additional interference generated by this type of traffic.

2.4.5 Inhibition of directed retry Outgoing directed retry The directed retry from a serving cell is inhibited by the O&M flag EN_DR. This flag is defined in [ 13]. When EN_DR = ENABLE, the type of directed retry is determined by the combination of all inhibition flags for handover (see section 2.3.5) and forced directed retry detection : The forced directed retry is enabled/disabled on a per cell basis with the O&M flag EN_FORCED_DR. EN_FORCED_DR : DISABLE = forced directed retry disabled. ENABLE = forced directed retry enabled. The flag EN_FORCED_DR is only relevant when EN_DR = ENABLE as the detection of forced directed retry may operate only when the directed retry function is enabled. On the opposite, the handover alarm detection operates whatever the value of EN_DR flag as this detection is used not only for directed retry but also for SDCCH handover. The flag HO_INTERCELL_ALLOWED applies to the cause of forced directed retry as for the other handover causes (see section 2.3.5).



Incoming directed retry ### Forced directed retry : the incoming retry traffic in a cell n can be forbidden by setting the

parameter FREElevel_DR(n) to its maximum value i.e. 255 (see section 3.3.3). ### Directed retry on handover alarms : the incoming retry traffic in a cell can be forbidden by setting

the parameters FREEfactors_i and LOADfactors_i to their minimum values.



3 DYNAMIC BEHAVIOUR

3.1 Functions linked to handover preparation

3.1.1 Biband mobile stations In this document, an MS is defined as biband if it supports the two frequency bands given by the parameter PLMN_FREQUENCY_BANDS. In other terms, a biband MS supports [20bis]:

− the PGSM and DCS1800 bands if PLMN_FREQUENCY_BANDS = “GSM900 and DCS1800 bands”,

− the GSM850 and DCS1800 bands if PLMN_FREQUENCY_BANDS = “GSM850 and DCS1800 bands”,

− the GSM850 and DCS1900 bands if PLMN_FREQUENCY_BANDS = “GSM850 and DCS1900 bands”.

− the GSM900 and DCS1900 bands if PLMN_FREQUENCY_BANDS = “GSM900 and DCS1900 bands”.

3.1.2 Concentric cell and multiband cell A concentric cell is identified in the BSS by setting its attached flag CELL_PARTITION_TYPE to CONCENTRIC. A multiband cell is identified in the BSS by setting its FREQUENCY_RANGE to PGSM-DCS1800 or EGSM DCS1800 (CELL_PARTITION_TYPE is forced to concentric). It can be noted that in a EGSM-DCS1800 multiband cell defined in a network where the EGSM_ALLOC_STRATEGY is set to Different behaviour for E-GSM capable MS, the configuration where only EGSM TRXs are defined in the inner zone, and DCS1800 TRXs are defined in the outer zone is supported. Each frequency carrier of the cell is allocated to either the inner zone or the outer zone. This allocation is indicated by the flag ZONE_TYPE (OUTER ZONE or INNER ZONE) on a per frequency carrier basis. Any SDCCH connection is always allocated to the outer zone (ZONE_TYPE = OUTER ZONE).

3.1.2.1 Allocation in the inner zone in case of Normal Assignment In order to assign from the start a TCH in the zone corresponding to the MS location, the information on the measured level gathered by the handover detection function is used. The RAM entity (refer to [ 30]) during Normal Assignment in a concentric cell or in a multiband cell will request to the handover detection function (with the indication “MS Zone Indication Request”, see section 2.3.6) the zone where the MS is deemed to be : inner or outer zone. The HOP entity first checks whether or not the MS supports the frequency band of the inner zone: − If the MS is in a PGSM-DCS1800 or a EGSM-DCS1800 multiband cell and the MS is not biband ,

then the indication is set to OUTER. − If the MS is in a EGSM-DCS1800 multiband cell, the EGSM_ALLOC_STRATEGY is set to

Different behaviour for E-GSM capable MS, there is only EGSM TRXs in the inner zone, and the MS is biband but does not support the E-GSM band, then the indication is set to OUTER.

To this avail, the handover detection function will check all the relations in the cause "outer zone too high” (cause 13) except the condition EN_BETTER_ZONE_HO=ENABLE in (HO-17) using

− the AV_RXLEV_UL/DL_HO averages, if A_LEV_HO measurements have been received, − the average of the RXLEV_UL/DL measurements already received.

The checking of Cause 13 will indicate in which zone the MS is deemed to be on a radio criterion.



The load balance between the inner and outer zones is managed by the RAM. The MS is allocated to the inner zone if the MS is deemed to be in the inner zone on a radio criterion, and the inner zone is less loaded than the outer zone. The MS zone indication is sent to RAM in the message “MS zone indication ACK” (See Sections 2.4.2 and 4.2). In (HO-17), the average of the RXLEV_NCELL(n) measurements is computed for each neighbour cell with a same window whose size is determined by the number of MEASUREMENT RESULT messages which have already been received since the first received MEASUREMENT RESULT message with a Layer 3 info present. As long as this number is lower than A_PBGT_HO, it is used as window to calculate these averages. When this number becomes higher than A_PBGT_HO, then A_PBGT_HO is used as window to calculate these averages.

3.1.2.2 Allocation in the inner zone in case of incoming handover Two cases must be distinguished according that the incoming handover is based on a SDCCH channel or on a TCH channel. Case of an incoming handover on SDCCH In case of an incoming intercell handover on SDCCH a channel of the outer zone of the concentric or multiband cell is always assigned to the mobile station. Case of an incoming handover on TCH In case of an incoming intercell handover on TCH, the MS will be handed over in the zone corresponding to its location if the flag EN_BETTER_ZONE_HO is set to enable (if EN_BETTER_ZONE_HO is set to disable the MS is handed over in the OUTER ZONE). For that the information on the downlink measured level of the target cell RXLEV_NCELL is used. Each time, a candidate cells list is provided to the HOM entity, it must indicate for each concentric or multiband cell, the zone where the MS is deemed to be in the target cell: inner or outer zone. If the MS is in a PGSM-DCS1800 or a EGSM-DCS1800 multiband cell and the MS is not biband, the indication is always OUTER zone. Furthermore, if the MS is in a EGSM-DCS1800 multiband cell, the EGSM_ALLOC_STRATEGY is set to Different behaviour for E-GSM capable MS, there is only EGSM TRXs in the inner zone, and the MS is biband but does not support the E-GSM band, then the indication is always OUTER. So each time a concentric or multiband cell is in the candidate cells list, the handover detection function checks the equation (HO-0) in a way to determine the MS zone location in this concentric or multiband cell. As mentioned in Section 3.1.2.1, the load balance between the inner and outer zones is managed by RAM.

MS zone location If { AV_RXLEV_NCELL(n) > RXLEV_DL_ZONE + ZONE_HO_HYST_DL (HO-0) + BS_TXPWR_MAX – BS_TXPWR_MAX_INNER, and EN_BETTER_ZONE_HO } Then The MS is in the inner zone Else The MS is in the outer zone.

The equation is checked using: - the AV_RXLEV_NCELL(n) average, if A_LEV_HO measurements have been received from this target cell n.



- the average of the RXLEV_NCELL(n) measurements already received from the neighbour cell target cell n (if between two measurements, in which the neighbour cell is reported, a measurement comes in, in which the neighbour cell is not reported, a 0 will be used to calculate the average). RXLEV_DL_ZONE, ZONE_HO_HYST_DL, BS_TXPWR and BS_TXPWR_MAX_INNER are the parameters of the target concentric or multiband cell. They are available only if the intercell handover is performed in the same BSC.

3.1.2.3 Handover in a concentric or multiband cell For concentric cell environment, the cause "power budget" is applied in the inner zone as well as in the outer zone. For multiband cell environment, the cause "power budget" is applied in the inner zone as well as in the outer zone. In the inner zone, if the flag EN_MULTIBAND_PBGT_HO is set to disable, the cause “power budget” is only checked between multiband cells, in a way to maintain the MS in the preferred band. In order to avoid unnecessary handover alarms on SDCCH for all mobiles geographically located in the inner zone, the handover alarms cause 13 on SDCCH (from outer zone towards inner zone) must be filtered by the handover preparation function. For initiation of an intercell handover between a concentric or multiband cell (inner and outer zone) and the defined adjacent cell, the same handover criteria and handover strategies hold true as for non-concentric cells. The criteria for handover between the inner and outer zones is based either on the received signal level or on the interference level (see section 3.2.2.1.2). This kind of handover is called "interzone handover". A handover due to interference (cause = 15 or 16) will change, when it is possible, the frequency of the radio channel in case of non-hopping channels. As the inner zone contains only a few frequencies, this will give the opportunity to make an interzone handover from the inner to the outer zone in case of interference problems in the inner zone. In case of interference problems in the outer zone, the MS will always make an intrazone handover (it will stay connected to the outer zone). In case of hopping channels an interzone handover may occur from the inner to outer zone but never in the reverse direction (as with non-hopping channels). Both intrazone and interzone handovers are intracell handovers.

3.1.3 MS speed discrimination

3.1.3.1 Basic principle The speed discrimination procedure can only be activated in a hierarchical cell environment, i.e. when the serving CELL_LAYER_TYPE = upper or lower or indoor . It is based on the dwell time in the lower or indoor layer cells, either as serving or neighbour cells. The knowledge of the speed of a MS is indicated with a flag MS_SPEED that has the values "fast", "slow" and "indefinite". The value of this flag is kept for the whole call duration, once it has been set to "fast". This choice relates to the assumption that a prediction is possible on the MS speed. Whenever the MS moves into another cell and was not recognised "fast" at this occasion, or at a precedent occasion, the MS_SPEED is reset to "indefinite". The time experienced in a serving lower or indoor layer cell is kept in a counter C_DWELL (in SACCH multiframes).



When a handover cause "power budget" is triggered, and the preceding cell was already a lower layer cell (Respectively an indoor layer cell), this time is compared to a threshold MIN_CONNECT_TIME. If it is found smaller than the threshold, this indicates that the MS has crossed the serving lower layer cell (Respectively the serving indoor layer cell), in less than MIN_CONNECT_TIME seconds. In this case , the MS is considered to be moving fast and the handover is directed towards the upper layer preferentially. If it is found bigger than the threshold, this indicates that the MS has not yet been recognised as fast and the handover is directed towards the neighbour lower layer cell (Respectively the neighbour indoor layer cell). The handover cause power budget is used because it is assumed that in any cell environment this cause will indicate that the MS is leaving the "better cell" zone of the serving cell, and not because of interference, shadowing, or street corner effect. The MS speed discrimination can only happen when the preceding cell is already a lower layer cell (Respectively indoor layer cell) this ensures that the MS has entered the cell at its edge and not at an arbitrary position inside the cell. This would be the case after call setup, or after a handover from an umbrella cell. Because the measured dwell time in the serving lower or indoor layer cell is taken between two points located at the edge of the cell, the time interval can be related to the MS speed, assuming that the main road on which fast moving mobiles are, is known beforehand. The MIN_CONNECT_TIME shall be set to the value necessary for a fast moving car (mean speed v about 40 km/h) necessary to travel along the cell on the main road. If there is no information available about a privileged direction of fast MS, then the

MIN_CONNECT_TIME shall be set to the value 2xCell_ Diameter

v∏ × where v represents the average

speed of fast moving mobiles. The speed discrimination function can be enabled/disabled on a per cell basis, using a flag : EN_SPEED_DISC. If EN_SPEED_DISC is set to DISABLE, then the dwell time in a serving lower or indoor layer cell is not used to determine if an MS is fast. Nevertheless, when the MS is on the upper layer, the dwell time in the neighbour lower and indoor layer cells is used to decide a handover to the lower layer or to the indoor layer cell, after a fixed period of time. The same behaviour applies if the MS is on the lower layer: the dwell time in the serving lower layer cell is used to decide a handover to the indoor layer after a fixed period of time. Table 12 shows which cells is used for the estimation of the MS speed as a function of the serving cell layer.

Layer of the serving cells

Cells used for the estimation of MS_SPEED

Upper layer The neighbour lower cells and

The neighbour indoor cells Lower layer The serving lower layer cell Indoor layer The serving indoor layer cell

Table 12: Cells used for the estimation of the MS speed as a function of the layer of the serving cell.

3.1.3.2 Required parameters and variables For each call a variable PREC_LAYER_TYPE is used to store the cell layer type of the preceding cell. It has five values : single, upper, lower, indoor, or indefinite. For each call, a variable MS_SPEED is used to store the already determined mobile speed, if any. It has three values : "fast", "slow" and "indefinite". The initialisation of the parameters will occur at call set-up and after external handover. After internal handover, the variables MS_SPEED and PREC_LAYER_TYPE will be transferred to the new call context, after possible modification. For each call on the upper layer,



for each neighbour cell n belonging to the lower or indoor layer a counter C_DWELL(n) measures the number of SACCH periods of monitoring the neighbour cell n over a threshold L_RXLEV_CPT_HO(0,n) (see 3.1.2.3)

each time the cell n is monitored, C_DWELL(n) is compared to threshold 2*MIN_DWELL_TIME(n) For each call on the lower or indoor layer

a counter C_DWELL measures the number of SACCH periods of connection to the serving cell (see 3.1.2.3). a threshold MIN_CONNECT_TIME is used at PBGT handover to decide on the MS speed

3.1.3.3 Parameter initialisation and modification In what follows, the counters C_DWELL and C_DWELL(n) are expressed in SACCH periods, and the thresholds MIN_CONNECT_TIME and MIN_DWELL_TIME are expressed in second. Hence, an approximation of the SACCH period to 0.5 s is made. This will have no impact on the behaviour of the speed discrimination process. The initialisation and modification of the MS speed parameters depend on the layer of the serving cell. ### Case the serving cell is an indoor layer cell (CELL_LAYER_TYPE = indoor) After call set-up or inter-cell handover C_DWELL = 0. After an intra-cell handover, C_DWELL is kept unchanged. After call set-up or external handover PREC_LAYER_TYPE = indefinite MS_SPEED = indefinite After an internal handover : MS_SPEED is kept to the preceding value. PREC_LAYER_TYPE is set to the preceding CELL_LAYER_TYPE (upper, lower, single, or indoor). Both values are transmitted to the new call context. Each time a MEASUREMENT RESULT is received for a call in an indoor layer cell

C_DWELL is incremented by 1. When it reaches the maximum value of 255, it is no more incremented.

When a handover cause "power budget" is triggered in an indoor layer cell and PREC_LAYER_TYPE = indoor and the parameter EN_SPEED_DISC = enable for the serving cell and C_DWELL < 2*MIN_CONNECT_TIME , then MS_SPEED is set to "fast". Note 1: By default, the flag EN_SPEED_DISC is set to disable for indoor layer cells. ### Case the serving cell is a lower layer cell (CELL_LAYER_TYPE = lower) After call set-up or inter-cell handover C_DWELL = 0. After an intra-cell handover, C_DWELL is kept unchanged. After call set-up or external handover PREC_LAYER_TYPE = indefinite MS_SPEED = indefinite



After an internal handover : MS_SPEED is kept to the preceding value. PREC_LAYER_TYPE is set to the preceding CELL_LAYER_TYPE (upper, lower, single, or indoor). Both values are transmitted to the new call context. Each time a MEASUREMENT RESULT is received for a call in a lower layer cell

C_DWELL is incremented by 1. When it reaches the maximum value of 255, it is no more incremented.

When a handover cause "power budget" is triggered in a lower layer cell and PREC_LAYER_TYPE is lower and the parameter EN_SPEED_DISC = ENABLE for the serving cell and C_DWELL < 2*MIN_CONNECT_TIME , then MS_SPEED is set to "fast". ### Case the serving cell is an upper layer cell (CELL_LAYER_TYPE = upper) After call set-up, intra-cell or inter-cell handover

for every neighbour cell n belonging to the lower or indoor layer : if EN_SPEED_DISC = ENABLE

Phase 1 MS : C_DWELL(n) = (MIN_DWELL_TIME - L_MIN_DWELL_TIME)*2 Phase 2 MS : C_DWELL(n) = 0

else if EN_SPEED_DISC = DISABLE C_DWELL(n) = (MIN_DWELL_TIME - L_MIN_DWELL_TIME) * 2

After call set-up and external handover PREC_LAYER_TYPE = indefinite MS_SPEED = indefinite After internal handover MS_SPEED is turned to "indefinite" if it was not precedently "fast", otherwise it is kept to "fast". PREC_LAYER_TYPE is set to the preceding CELL_LAYER_TYPE (upper, lower, single, or indoor) and transmitted to the new call context. Each time a MEASUREMENT RESULT is received for a call on the upper layer :

- Each time a measurement is received for the neighbour lower layer cell n or for the neighbour indoor layer cell n (in MEASUREMENT REPORT), with a value RXLEV_NCELL(n) strictly above the threshold L_RXLEV_CPT_HO(0,n), C_DWELL(n) is incremented by 1. When it reaches the maximum value of 255, it is no more incremented. - Each time no measurement is received or the reported level is smaller or equal to the threshold L_RXLEV_CPT_HO(0,n), C_DWELL(n) is decremented by 1. When it reaches the minimum value of 0, it is no more decremented. If for one neighbour lower or indoor layer cell n, C_DWELL(n) ### 2*MIN_DWELL_TIME, and the MS_SPEED was "indefinite" then MS_SPEED is set to "slow".

Remarks : For phase 1 MS, or when EN_SPEED_DISC = DISABLE in the umbrella cell, the initialisation of C_DWELL(n) is done in such way that they will make a handover to the lower or indoor layer, after L_MIN_DWELL_TIME seconds, provided they are under the coverage area of a lower or indoor layer cell. This will give an efficient way to reduce the load of the umbrella cell, caused by a large proportion of Phase 1 MS, which will camp on this cell, because it has the best received level.



For phase 2 MS and when EN_SPEED_DISC = ENABLE in the umbrella cell, the mobiles will have to receive sufficient level from a lower or indoor layer cell during MIN_DWELL_TIME seconds before leaving the upper layer for the lower or indoor layer. The variable MIN_DWELL_TIME is modified according to the traffic load in the umbrella cell in order to enable the slow mobiles to leave more easily a loaded umbrella cell (see 3.1.3.). The "leaky bucket" mechanism on counter C_DWELL(n) allows to do with the statistical shadowing affecting raw level measurements : if exactly 50% of the measurements are strictly above the L_RXLEV_CPT_HO(0,n) threshold, the value of C_DWELL(n) grows, otherwise it stays at 0. The value for the threshold L_RXLEV_CPT_HO(0,n) should be equal to the measured or planned mean signal level at the border of the lower or indoor layer cells. The counters C_DWELL(n) only work for neighbour cells, which belong to the lower layer or to the indoor layer. The counter C_DWELL only work for the serving cell which belongs to the lower layer or to the indoor layer. In other words, C_DWELL is never used for a serving cell in the upper layer.

3.1.4 Load management in hierarchical environment In a hierarchical environment, it is very important to control the traffic load of the umbrella cells. The reason for this is that the umbrella cell may get saturated very easily, and hence unable to assume its two major functionalities : handle fast moving mobiles and provide overflow channels for the lower or indoor layers, in order to improve the total capacity at a constant grade of service. Therefore, a control mechanism is forecast, in order to have the averaged traffic load on the umbrella cell held between two limits L_LOAD_OBJ and H_LOAD_OBJ. This is done by two actions :

- not performing handover towards the umbrella cell for power budget cause with fast mobiles when the umbrella is loaded (see section 3.2.2.3). - reducing the MIN_DWELL_TIME variable, so as to enable slow MS to leave more quickly the umbrella cell (see section 3.1.2. and below).

Thus, the variable MIN_DWELL_TIME is modified according to the averaging of traffic load, called AV_LOAD (refer to [ 30]), on the umbrella cell (See Figure 14). Each time the averaged load on the umbrella is recalculated, AV_LOAD is compared with the values L_LOAD_OBJ and H_LOAD_OBJ. If AV_LOAD > H_LOAD_OBJ

MIN_DWELL_TIME := max(MIN_DWELL_TIME - DWELL_TIME_STEP, L_MIN_DWELL_TIME) If AV_LOAD < L_LOAD_OBJ

MIN_DWELL_TIME := min(MIN_DWELL_TIME + DWELL_TIME_STEP, H_MIN_DWELL_TIME)

The default value of MIN_DWELL_TIME will be H_MIN_DWELL_TIME.

The setting of the DWELL_TIME_STEP parameter will be made using experiences in pilot sites. It will be incorporated in the user-settable default cell profile for umbrella cells, taking advantage of the compromise value found between reactivity and oscillating behaviour. Note : The umbrella load control mechanism can be disabled by setting the L_LOAD_OBJ to 0% and H_LOAD_OBJ to 100%, in this way MIN_DWELL_TIME is blocked to its current value. For setting MIN_DWELL_TIME to H_MIN_DWELL_TIME, the operation (setting L_LOAD_OBJ to 0% and H_LOAD_OBJ to 100%) must be made off-line or with no load in the cell.



L_MIN_DWELL_TIMEH_MIN_DWELL_TIME

load in umbrella cell

100 %

H_LOAD_OBJ

L_LOAD_OBJ

start : low traffic

end : low traffic

regulation of traffic peak

DWELL_TIME_STEP

Figure 14: Traffic regulation with MIN_DWELL_TIME modified according to the traffic load



3.2 Handover preparation

3.2.1 General

3.2.1.1 HO preparation configuration At BSS initialisation, the parameters of handover preparation (see control flows of SADT diagrams in section 2.3.6) are contained in the BSC database (for further details on BSS initialisation, see [ 26]). Concerning the BSS reconfiguration, all the handover preparation parameters can be modified at OMC side and then provided to the concerned BSS. For both initialisation and reconfiguration, the algorithms are configured in the BTS by the BSC with the message PREPROCESS CONFIGURE (see message description [ 23]). This message is sent on the Abis radio signalling link (see [ 39]) on a TRX basis. Note : In case of TCU restart, the message is sent to the BTS (i.e. to the TRX(s) connected to the corresponding TCU).

3.2.1.2 HO preparation enabling and disabling Enabling The enabling may result from : - the establishment of a new connection, - an intracell handover, - an intercell handover, - an handover request from RAM. So, the specifications are the following ones : - the BSC enables the algorithms upon receipt of the ESTABLISH INDICATION message from the BTS. During an SDCCH connection, the BSC filters internally the handover alarms for a given number of MEASUREMENT RESULT messages (defined by the parameter SDCCH_COUNTER, for further details refer to [ 20]). For further details on the call establishment and handover protocol refer [ 21], [ 23], and [ 24]. Disabling - the BSC disables the algorithms whenever it initiates a channel release on the radio interface. For further details on the call release procedure, refer to [ 10].

3.2.1.3 HO preparation function The handover preparation function is completely handled by the BSC. The input parameters of this function are provided by the Active channel preprocessing function every SACCH multiframe (refer to [ 34]), and by the RAM entity (See [ 19]). The following sections describe the general behaviour of the handover preparation function with its two processes : - HO detection : see section 3.2.2, - HO candidate cells list evaluation : see section 3.2.3. Handover detection



An emergency, better conditions, and channel adaptation handover alarm can be detected every SACCH multiframe upon reception of the averaged measurements for handover detection. A resource management handover is detected as soon as the message “Start HO” is received from RAM, and concerns the current MS. Handover candidate cells list evaluation Once a handover alarm is detected, the HO detection process sends to the HO candidate cell evaluation process the list of the MS neighbouring cells with for each of them one of the handover causes which have been verified. It is an internal BSC action (implementation dependent). The handover candidate cells list evaluation builds a cells list which is, according to the case and the value of the timer T_FILTER, sent or not to HOM (see 3.2.4.). The specific management of Cause 28 is explained in Section 3.2.4.1.3. Within the list of candidate cell, the message sent to HOM also contains the HO cause, the zone indication for concentric cells, and the new codec type for Cause 29. In order to have an overview of the HOP entity, Figure 15 gives an SDL diagram of the HO preparation function. However, in case of discrepancy between this diagram and the text of the document, the text takes precedence over the diagram. Note : the event "HO parameters change" corresponds to a on-line reconfiguration (managed by the network operator) of the handover parameters used for HO detection and HO candidate cell evaluation.

Figure 15: SDL diagram - HO preparation/BSC.- partition 1/1. The specific alarm management for Causes 28 , 29 and 30 are not described in the figure.

3.2.2 Handover detection

Document produced by GEODE <VERILOG (C)>

Partition 1/1

1.5

DESCRIPTION: PCHO

PROCESS PCHO/Handover_preparation/Mode_B/BSC

Page: 1

03-Feb-1995

HO thresholdcomparison

HO candidatecell evaluation

idle channel

activate HOpreparation

’init T FILTER’

active channel

active channel

HOparameters

change

active channel

deactivateHO

preparation

idle channel

preproc measfor HO

HO thresholdcomparison

’conditionoccurs?’

(Yes)

HO candidatecell

evaluation

candidate cells ,HOcause TOHO execution

’triggerT FILTER’

Wait T FILTER

(No)

active channel

wait T FILTER

HOparameters

change

Wait T FILTER

T FILTERexpiry

active channel

deactivateHO

preparation

idle channel

for HO

comparison

’conditionoccurs?’

(Yes)

HO candidatecell

evaluation

candidate cells ,HOcause TOHO execution

’restartT FILTER’

Wait T FILTER

preproc meas

HO threshold

(No)

Wait T FILTER

‘Candidate celllist changes?'

(Yes)(No)

Wait T FILTER

'restartT FILTER'



When dealing with emergency, better conditions and channel adaptation handovers, the HO detection process is also called ’HO threshold comparison’. Threshold comparisons are performed for every new set of average values AV_xxx_HO (i.e. every SACCH multiframe period) to detect possible need for handover. The detection of a handover cause can be enabled/disabled by flags. For each possible handover cause a flag is foreseen except for Causes 10 and 11 (See Section 2.3.5). These two latter causes are automatically enabled in a concentric cell. For resource management handover Cause 29 and 30, the HO detection process consists in checking if a message “Start HO” concerning the current call is received from RAM. The flag that allows to enable or disable Cause 29 and 30 are controlled by RAM (causes 29 and 30) and the transcoder (cause 29 only). Accordingly, HO alarms are sent to initiate the candidate cell evaluation function when a threshold condition occurs or an appropriate message is received from RAM. After each intercell handover alarm, the raw list of candidate cells and the preferred target cell layer are indicated to the handover candidate evaluation process.

3.2.2.1 Handover causes Twenty six different causes can lead the ALCATEL handover algorithm to detect a need for handover. These causes are identified with a number that is used for performance measurement counters (See Table 13).



Handover causes Reference

Too low quality on the uplink 2

Too low level on the uplink 3

Too low quality on the downlink 4

Too low level on the downlink 5

Too long MS-BS distance 6

Several consecutive bad SACCH frames received (rescue microcell handover) 7

Too low level on the uplink, inner zone (inner to outer zone handover, concentric or multiband cell)

10

Too low level on the downlink, inner zone (inner to outer zone handover, concentric or multiband cell)

11

Power budget 12

Too high level on the uplink and the downlink, outer zone (out. to in. zone hand., concentric or multiband cell)

13

High level in neighbour lower layer cell for slow mobile 14

Too high interference level on the uplink 15

Too high interference level on the downlink 16

Too low level on the uplink in a microcell compared to a high threshold 17

Too low level on the downlink in a microcell compared to a high threshold 18

Forced Directed Retry 20

High level in neighbour cell in the preferred band 21

Too short MS-BTS distance 22

Traffic HO 23

General capture HO 24

HR-to-FR channel adaptation due to bad radio quality 26

FR-to-HR channel adaptation due to good radio quality 27

Fast traffic handover 28

TFO handover 29

Move from PS to CS zone 30

2G-3G Handover Ec/No 31 Table 13: Handover causes

These causes can be sorted into the five families : - emergency HO causes : 2,3,4,5,6,7,10,11,15,16,17,18,22 - better conditions HO causes : 12,13,14,20,21,23,24,28 - channel adaptation HO causes : 26, 27 - resource management : 29, 30 - 2G-3G HO causes: 31 Note : the relationships between the handover cause values used on the A interface and the handover cause values used by the ALCATEL BSS are given in reference [ 23]. In the following, the handover causes will be detailed according to the handover categories, as defined in 2.3.3. The recapitulation of the cell types allowed for the serving and the candidate cell for each handover cause can be found in Section 6.2.

3.2.2.1.1 Intercell handover causes



The equations (HO-1) to (HO-6) and (HO-18) to (HO-26) are checked only if HO_INTERCELL_ALLOWED = ENABLE.

3.2.2.1.1.1 Emergency intercell handover causes The following general remarks need to be taken into account when reading this section. The 3GPP coding of quality is contra-intuitive, since the value 0 codes for the best quality and 7 for the worst. Thus, the comparison between two quality values must be understood in the opposite way in terms of quality. In order to take into account the frequency hopping in the RXQUAL evaluation the variable OFFSET_RXQUAL_FH is introduced (for more information refer to [ 30]). If on the corresponding channel, Frequency hopping is applied then OFFSET_RXQUAL_FH = Offset_Hopping_HO otherwise OFFSET_RXQUAL_FH = 0 Offset_Hopping_HO is a parameter defined on a per cell basis. In case of concentric or multiband cell, if an MS uses a TCH which belongs to the inner zone, MS_TXPWR_MAX must be replaced by MS_TXPWR_MAX_INNER in (HO-1) and (HO-2) and BS_TXPWR_MAX must be replaced by BS_TXPWR_MAX_INNER in (HO-3) and (HO-4). The case where L_RXQUAL_XX_H_XXX + OFFSET_RXQUAL_FH > 7 corresponds in the equations to L_RXQUAL_XX_H_XXX + OFFSET_RXQUAL_FH = 7. Cause 2

CAUSE = 2 (too low quality on the uplink) AV_RXQUAL_UL_HO > L_RXQUAL_UL_H + OFFSET_RXQUAL_FH (HO-1) and AV_RXLEV_UL_HO <= RXLEV_UL_IH and MS_TXPWR = min(P, MS_TXPWR_MAX) and EN_RXQUAL_UL = ENABLE

Note : This handover cause can also be triggered in case of repetitive intracell handover, see section 3.2.2.1.1.2 Cause 3

CAUSE = 3 (too low level on the uplink) AV_RXQUAL_UL_HO <= L_RXQUAL_UL_H + OFFSET_RXQUAL_FH (HO-2) and AV_RXLEV_UL_HO < L_RXLEV_UL_H and MS_TXPWR = min(P, MS_TXPWR_MAX) and EN_RXLEV_UL = ENABLE

In (HO-1) and (HO-2), MS_TXPWR is the last MS_TXPWR_CONF value reported by the BTS in the message MEASUREMENT RESULT or PREPROCESSED MEASUREMENT RESULT (refer to [ 34]). Cause 4



CAUSE = 4 (too low quality on the downlink) AV_RXQUAL_DL_HO > L_RXQUAL_DL_H + OFFSET_RXQUAL_FH (HO-3) and AV_RXLEV_DL_HO <= RXLEV_DL_IH and BS_TXPWR = BS_TXPWR_MAX and EN_RXQUAL_DL = ENABLE

Note : This handover cause can also be triggered in case of repetitive intracell handover, see section 3.2.2.1.1.2 Cause 5

CAUSE = 5 (too low level on the downlink) AV_RXQUAL_DL_HO <= L_RXQUAL_DL_H + OFFSET_RXQUAL_FH (HO-4) and AV_RXLEV_DL_HO < L_RXLEV_DL_H and BS_TXPWR = BS_TXPWR_MAX and EN_RXLEV_DL = ENABLE

Unlike the previous causes, the five following handover causes do not take into account the increase of the MS or the BS power to its maximum. Cause 6

CAUSE = 6 (too long MS-BS distance) AV_RANGE_HO > U_TIME_ADVANCE (HO-5) and EN_DIST_HO = ENABLE

Cause 22 Cause 22 is only checked if the Cell range of the cell is set to extended_outer.

CAUSE = 22 (too short MS-BS distance) AV_RANGE_HO ≤ L_TIME_ADVANCE (HO-23)

- L_TIME_ADVANCE : Minimum distance for handover from the extended outer zone The three following equations are only used in microcells, i.e. the corresponding flags are set to ENABLE if the cell profile is microcell (or CELL_DIMENSION_TYPE = micro) and to DISABLE for all other cell profiles. Cause 7



CAUSE = 7 (consecutive bad SACCH frames received in a microcell)) last N_BAD_SACCH consecutive SACCH frames are not correctly received (HO-20) and EN_MCHO_RESCUE = ENABLE

The cause 7 is managed with an internal BSC variable which counts the number of bad SACCH frames consecutively received : - this counter is incremented every time a MEASUREMENT RESULT or PREPROCESSED MEASUREMENT RESULT message with BFI = 1(Bad Frame Indication) is received, - this counter is reset every time a MEASUREMENT RESULT or PREPROCESSED MEASUREMENT RESULT message with BFI = 0 is received. The format of these two messages is given in [ 34]. Cause 17

CAUSE = 17 (Too low level on the uplink in a microcell compared to a high threshold) AV_RXLEV_UL_MCHO(i) ### U_RXLEV_UL_MCHO (HO-18) and AV_RXLEV_UL_MCHO(i-1) > U_RXLEV_UL_MCHO and EN_MCHO_H_UL = ENABLE

In (HO-18) and (HO-19), ’i’ is the index of the last MS measurement report. Cause 18

CAUSE = 18 (Too low level on the downlink in a microcell compared to a high threshold) AV_RXLEV_DL_MCHO(i) ### U_RXLEV_DL_MCHO (HO-19) and AV_RXLEV_DL_MCHO(i-1) > U_RXLEV_DL_MCHO and EN_MCHO_H_DL = ENABLE

3.2.2.1.1.2 Forced intercell handover cause on quality If on the uplink or on the downlink : i. either the intracell handovers for AMR or non AMR calls are forbidden in the serving cell (i.e.

EN_INTRA_UL/DL = DISABLE or EN_INTRA_UL/DL_AMR = disable), ii. or the repetition of intracell handover is not allowed in the serving cell, the handover detection function will indicate an intercell handover with cause "UL/DL quality too low", so far as the conditions on power level MS/BS_TXPWR_MAX, and on the flags EN_RXQUAL_UL/DL and HO_INTERCELL_ALLOWED are fulfilled. If EN_INTRA_UL/DL = disable, the condition AV_RXLEV_UL/DL=<RXLEV_UL/DL_IH is not checked for non AMR calls as it is done for a non-forced quality handover (see equations (HO-1) and (HO-3)). If EN_INTRA_UL/DL_AMR = disable, the condition AV_RXLEV_UL/DL=<RXLEV_UL/DL_IH is not checked for AMR calls as it is done for a non-forced quality handover (see equations (HO-1) and (HO-3)). The priority order of UL/DL is UL (uplink) and then DL (downlink).



The repetition may be inhibited by setting the O&M flag EN_INTRACELL_REPEATED to DISABLE. Concerning the case ii, the condition ’no previous intracell handover for this connection failed’ is given by the function handling the call in the BSC. This condition is used to avoid repetitive intracell handovers. If an intracell handover for a given connection was not successful (handover failure, no free timeslot, etc...) it is not repeated when the next handover alarm occurs. If an intracell handover is still required for this connection, the handover is turned into an intercell handover as described above. Then for the same call in the new cell, intracell handover is allowed again.

3.2.2.1.1.3 Better conditions intercell handover causes Cause 12 Cause 12 is checked over all the neighbour cells belonging to the same layer . It means that it is checked between cells whose CELL_LAYER_TYPE is single or upper, between cells whose CELL_LAYER_TYPE is lower, and between cells whose CELL_LAYER_TYPE is indoor. In addition to the condition on the cell layer type, the cell frequency band condition for checking Cause 12 in Eq. (HO-6) is as follows whether or not the MS is in the inner zone of a multiband cell: Case the MS is not in the inner zone of a multiband cell

− If the flag EN_MULTIBAND_PBGT_HO is set to disable, Cause 12 must not be checked between cells which use different frequency band (i.e cells having different CELL_BAND_TYPE).

− If the flag EN_MULTIBAND_PBGT_HO is set to enable, Cause 12 will be checked over all

the neighbours cells without any cell frequency band restriction. Case the MS is in the inner zone of a multiband cell

− If the flag EN_MULTIBAND_PBGT_HO is set to disable, Cause 12 is checked over all the neighbour multiband cells (FREQUENCY_RANGE= PGSM-DCS1800 or EGSM-DCS1800) which belong to the same BSC as the serving cell.


the neighbours cells without any cell frequency band restriction. In addition, in order not to cancel an on-going location procedure, Cause 12 for handovers from TCH to TCH is not checked when a location procedure is on-going for the call. Cause 12 for handover from TCH to TCH and for directed retry on handover alarms from SDCCH to TCH is:

CAUSE = 12 (Power budget) If EN_TRAFFIC_HO(0,n)=ENABLE (HO-6) then PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER + max(0, DELTA_HO_MARGIN(0,n)) (n=1...BTSnum) else PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER and AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HO and EN_PBGT_HO = ENABLE with PBGT(n) = AV_RXLEV_NCELL(n) - AV_RXLEV_PBGT_HO (HO-7) - (BS_TXPWR_MAX - AV_BS_TXPWR_HO) - (MS_TXPWR_MAX(n) - MS_TXPWR_MAX)

- PING_PONG_MARGIN(n,call_ref)



Note 1: Since a monoband MS can only receive measurements from the target cells having the same

frequency band as the serving cell, the case the flag EN_MULTIBAND_PBGT_HO is set to enable and the MS is monoband is equivalent to check Cause 12 over all the target cells having the same frequency band as the serving cell.

Note 2: In case the flag EN_MULTIBAND_PBGT_HO is set to enable and the MS is in the inner zone

of a multiband cell, the offset OFFSET_HO_MARGIN_INNER is kept unchanged whatever the target cell frequency band is.

Note 3: In (HO-7), OFFSET_HO_MARGIN_INNER is only used in the inner zone of a concentric or

multiband cell. In addition to the same layer condition, the cell frequency band condition for checking Cause 12 in Eq. (HO-6bis) is:

− If the flag EN_MULTIBAND_PBGT_HO is set to disable, Cause 12 must not be checked between cells which use different frequency band (i.e. cells having different CELL_BAND_TYPE).


the neighbours cells without any cell frequency band restriction. In addition, in order not to cancel an on-going location procedure, Cause 12 for handovers from SDCCH to SDCCH is not checked when a location procedure is on-going for the call. Cause 12 for handover from SDCCH to SDCCH is:

CAUSE = 12 (Power budget) PBGT(n) > HO_MARGIN(0,n) (n=1...BTSnum) (HO-6bis) and AV_RXLEV_PBGT_HO ≤ RXLEV_LIMIT_PBGT_HO and EN_PBGT_HO = ENABLE

The equation of PBGT is explained in details in Section 6.1. - RXLEV_LIMIT_PBGT_HO : threshold above which it is not necessary to trigger a handover on power

budget. - AV_RXLEV_NCELL(n) : average of RXLEV_NCELL(n) over A_PBGT_HO measurements

(neighbour cell(n)). - AV_RXLEV_PBGT_HO : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUB over

A_PBGT_HO measurements (serving cell). - BS_TXPWR_MAX : max power of the BTS in the serving cell (fixed value for each BTS). - AV_BS_TXPWR_HO : Average of BS_POWER over A_PBGT_HO measurements. - MS_TXPWR_MAX(n) : max. power level the MS is allowed to use in its neighbour cell(n). - MS_TXPWR_MAX : max. power the MS is allowed to use in the serving cell. - OFFSET_HO_MARGIN_INNER: offset which allows to take account of the radio differences between

outer and inner zone (especially in case of multiband cell). - PING_PONG_MARGIN(n,call_ref) is a penalty put on the cell n if :

it is the immediately precedent cell on which the call has been, this cell belongs to the same BSC as the serving cell, the call has not performed a forced directed retry towards the serving cell, less than T_HCP seconds have elapsed since the last handover. In this case PING_PONG_MARGIN(n,call_ref) = PING_PONG_HCP. If the call was not precedently on cell n, or if the preceding cell was external to the serving BSS, or if the call has just performed a forced directed retry, or if the timer T_HCP has expired, then PING_PONG_MARGIN(n,call_ref) = 0



- DELTA_HO_MARGIN(0,n) is evaluated according to the traffic situation of the serving cell and the neighbour cell n (Traffic_load(n), refer to [ 30]) in the following way.

If Traffic_load(0)=high and Traffic_load(n)=low DELTA_HO_MARGIN(0,n)= -DELTA_DEC_HO_margin If Traffic_load(0)=low and Traffic_load(n)=high DELTA_HO_MARGIN(0,n)= DELTA_INC_HO_margin else DELTA_HO_MARGIN(0,n)=0 where DELTA_DEC_HO_margin allows the cause 23 (traffic handover) detection

when the traffic in the serving cell is high and is low in the cell n. DELTA_INC_HO_margin allows to penalise the cause 12 detection when the traffic

in the serving cell is low and is high in the cell n. Note 1: In the case of concentric or multiband cells, if the channel is in the inner zone (ZONE_TYPE

= INNER), BS_TXPWR_MAX and MS_TXPWR_MAX in equation (HO-7) must be replaced by BS_TXPWR_MAX_INNER and MS_TXPWR_MAX_INNER respectively.

If the channel is in the outer zone (ZONE_TYPE = OUTER), the formulation of equation (HO-7) is not changed.

Note 2: The value of PBGT(n) is calculated every SACCH period for each neighbour cell n whose

measures are kept in the book-keeping list. Note 3: If no traffic load evaluation is available in an external cell n, the Traffic_Load(n) parameter is

set to indefinite. The four following equations are only checked for handover from TCH to TCH and for directed retry on handover alarms from SDCCH to TCH. For handover from SDCCH to SDCCH, they are not checked. Cause 14 Cause 14 is checked if and only if CELL_LAYER_TYPE = upper or lower (this rule is applied at the OMC by disabling the flag EN_MCHO_NCELL when CELL_LAYER_TYPE is different from both upper and lower). The two following cases have to be considered depending on the cell layer of the serving cell. Case the serving cell is in the upper layer (CELL_LAYER_TYPE(0) = upper)

− If the MS is in the inner zone of a multiband cell, the cause 14 is checked over all the neighbour cells with CELL_LAYER_TYPE(n) = lower or indoor except the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n)=CELL_BAND_TYPE(0).

− If the MS is not in the inner zone of a multiband cell and the MS is in a cell with

CELL_BAND_TYPE(0)=PREFERRED_BAND, the cause 14 is checked over all the neighbour cells with CELL_LAYER_TYPE(n) = lower or indoor except the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n)<>PREFERRED_BAND.


CELL_BAND_TYPE(0)<>PREFERRED_BAND, the cause 14 is checked over all the neighbour cells with CELL_LAYER_TYPE(n) = lower or indoor.

Case the serving cell is in the lower layer (CELL_LAYER_TYPE(0) = lower)

− If the MS is in the inner zone of a multiband cell, the cause 14 is checked over all the neighbour cells with CELL_LAYER_TYPE(n) = indoor except the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n)=CELL_BAND_TYPE(0).


CELL_BAND_TYPE(0)=PREFERRED_BAND, the cause 14 is checked over all the



neighbour cells with CELL_LAYER_TYPE(n) = indoor except the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n)<>PREFERRED_BAND.


CELL_BAND_TYPE(0)<>PREFERRED_BAND, the cause 14 is checked over all the neighbour cells with CELL_LAYER_TYPE(n) = indoor.

In order to limit the ping-pong effect, Cause 14 is not checked while the timer T_INHIBIT_CPT is running (See section 3.2.4). In addition, in order not to cancel an on-going location procedure, Cause 14 for handover from TCH to TCH is not checked when a location procedure is on-going for the call.

CAUSE = 14 (high level in neighbour lower or indoor layer cell for slow mobile)

(HO-21) CELL_LAYER_TYPE(0) = upper and AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) n = (1...BTSnum) and MS_SPEED = slow and EN_MCHO_NCELL = ENABLE Or CELL_LAYER_TYPE(0) = lower and AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) n = (1...BTSnum) and MS_SPEED <> fast and EN_MCHO_NCELL = ENABLE

Note 1: In (HO-21), the condition on the MS_SPEED variable depends on the cell layer type. The

reason for this is that the MS_SPEED variable is by default set to indefinite. Then, the MS_SPEED can changed from indefinite to slow only when the MS is in a upper layer cell. To give an ease access to the MS in the indoor layer, it is therefore necessary to allow Cause 14 when MS_SPEED = indefinite in the lower layer.

Cause 21 Cause 21 is checked if and only if CELL_BAND_TYPE is different from the parameter PREFERRED_BAND (This checking is performed at the BSC). It is checked for all neighbour cells n in the preferred band (i.e. CELL_BAND_TYPE(n) = PREFERRED_BAND). If the parameter PREFERRED_BAND is set to ’none’, the equation is never checked. In order to limit the ping-pong effect, Cause 21 is not checked while the timer T_INHIBIT_CPT is running (See section 3.2.4). In addition, in order not to cancel an on-going location procedure, Cause 21 for handover from TCH to TCH is not checked when a location procedure is on-going for the call.

CAUSE = 21 (high level in neighbour cell in the preferred band) (HO -22) Traffic_load(0) = MULTIBAND_TRAFFIC_CONDITION and Traffic_load(n) <> high and AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max(0,[MS_TXPWR_MAX(n)-P]) and EN_PREFERRED_BAND_HO = ENABLE

- Traffic_load(0) : situation of the traffic in the serving cell. - MULTIBAND_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a multiband handover. This parameter can have three different values: ANY_LOAD: the condition on traffic load is always fulfilled.



NOT_LOW: the condition on traffic load is fulfilled only if Traffic_load(0)<>low. HIGH: the condition on traffic load is fulfilled only if Traffic_load(0)=high. Note : MS_TXPWR_MAX(n) and P are the powers in the preferred band. Cause 23 Cause 23 is checked over all the neighbour cells belonging to the same layer. It means that it is checked between cells whose CELL_LAYER_TYPE is single or upper, between cells whose CELL_LAYER_TYPE is lower, and between cells whose CELL_LAYER_TYPE is indoor. In addition to the condition on the cell layer type, the cell frequency band condition for checking Cause 23 is as follows whether or not the MS is in the inner zone of a multiband cell: a) Case the MS is not in the inner zone of a multiband cell

− If the flag EN_MULTIBAND_PBGT_HO is set to disable, Cause 23 must not be checked between cells which use different frequency band (i.e cells having different CELL_BAND_TYPE).


the neighbour cells without any cell frequency band restriction. b) Case the MS is in the inner zone of a multiband cell

− If the flag EN_MULTIBAND_PBGT_HO is set to disable, Cause 23 is checked over all the neighbour multiband cells (FREQUENCY_RANGE= PGSM-DCS1800 or EGSM-DCS1800) which belong to the same BSC as the serving cell.


the neighbour cells without any cell frequency band restriction. In addition, in order not to cancel an on-going location procedure, Cause 23 for handover from TCH to TCH is not checked when a location procedure is on-going for the call.

CAUSE = 23 (Traffic HO) (HO -24) DELTA_HO_MARGIN(0,n) < 0dB and PBGT(n) > HO_MARGIN(0,n) + OFFSET_HO_MARGIN_INNER + DELTA_HO_MARGIN(0,n) (n=1...BTSnum) and EN_TRAFFIC_HO(0,n) = ENABLE

DELTA_HO_MARGIN(0,n) is evaluated as for cause 12. Cause 24 If the MS is in the inner zone of a multiband cell, Cause 24 is checked over all the neighbour cells except the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n) = CELL_BAND_TYPE(0). If the MS is not in the inner zone of a multiband cell and the MS is in a cell with CELL_BAND_TYPE(0)=PREFERRED_BAND, the cause 24 is checked over all the neighbour cells except the ones with EN_BI-BAND_MS(n)=DISABLE and CELL_BAND_TYPE(n) <> PREFERRED_BAND. If the MS is not in the inner zone of a multiband cell and the MS is in a cell with CELL_BAND_TYPE(0)<>PREFERRED_BAND, the cause 24 is checked over all the neighbour cells.



In order to limit the ping-pong effect, Cause 24 is not checked while the timer T_INHIBIT_CPT is running (See section 3.2.4). In addition, in order not to cancel an on-going location procedure, Cause 24 for handover from TCH to TCH is not checked when a location procedure is on-going for the call.

CAUSE = 24 (General capture HO) (HO -25) Traffic_load(0) = CAPTURE_TRAFFIC_CONDITION And Traffic_load(n) <> high And AV_RXLEV_NCELL(n) > L_RXLEV_CPT_HO(0,n) + max(0,[MS_TXPWR_MAX(n)-P]) And EN_GENERAL_CAPTURE_HO = ENABLE

- Traffic_load(0) : situation of the traffic in the serving cell. - CAPTURE_TRAFFIC_CONDITION : Condition on traffic load in the serving cell for a general capture handover. This parameter can have three different values: ANY_LOAD: the condition on traffic load is always fulfilled. NOT_LOW: the condition on traffic load is fulfilled only if Traffic_load(0)<>low. HIGH: the condition on traffic load is fulfilled only if Traffic_load(0)=high. Cause 28 Cause 28 is only checked if the channel of the current MS can support the channel rate required by the queued request. If the channel rate of the queued request is HR, Cause 28 is only checked if the MS is using a HR or a FR channel on a dual rate TRX. If the channel rate of the queued request is FR, Cause 28 is only checked if the MS is using a FR channel whatever the TRX type is dual rate or not. In case the serving cell is a monoband cell, and CELL_BAND_TYPE = GSM, and PLMN_FREQUENCY_BANDS is set to “GSM900_and_DCS1800_bands” or to “GSM900 and DCS1900 bands”, Cause 28 is only checked if the current MS is allocated to a P-GSM TRX. In case the serving cell is a concentric cell or a multiband cell, Cause 28 is only checked if the current MS is located in the outer zone of the serving cell. Furthermore, if CELL_BAND_TYPE = GSM and PLMN_FREQUENCY_BANDS is set to “GSM900_and_DCS1800_bands” or to “GSM900 and DCS1900 bands”, Cause 28 is checked only if the current MS is allocated to a P-GSM TRX. In addition, in order not to cancel an on-going location procedure, Cause 28 is not checked when a location procedure is on-going for the call. This cause only applies to handovers from TCH to TCH.

CAUSE = 28 (Fast traffic HO) AV_RXLEV_NCELL(n) > L_RXLEV_NCELL_DR(n) + max(0,[MS_TXPWR_MAX(n)-P]) for n = 1,..., BTSnum (HO - 26)

and t(n) > FREElevel_DR(n) and EN_CAUSE_28 = enable where - FREElevel_DR(n) is the minimum threshold of free TCHs in the neighbour cell n for forced directed retry and fast traffic handover. - t(n) is the absolute number of free TCHs in the neighbour cell n. Note 1: The threshold L_RXLEV_NCELL_DR(n) is the observed level from the neighbour cell n at the

border of the area where fast traffic handovers are enabled. This threshold fixes the size of the overlapping area where fast traffic handovers can be performed. It should be greater than RXLEVmin(n).



Note 2: For external cells, t(n) is fixed to the arbitrary value t(n) = 255. Therefore, setting FREElevel_DR(n) to 255 for an external cell inhibits outgoing external fast traffic handover towards this cell. Setting FREElevel_DR(n) to any other value will allow outgoing external fast traffic handover towards this cell.

Note 3: If the BTS has dual rate capability, t(n) = absolute number of free Dual Rate TCH Note 4: The flag EN_CAUSE_28 is not an OMC flag but an HOP flag. Its enabling and disabling is

explained in Section 3.2.4.

3.2.2.1.2 Intracell handover causes The following general remarks need to be taken into account when reading this section. The 3GPP coding of quality is contra-intuitive, since the value 0 codes for the best quality and 7 for the worst. Thus, the comparison between two quality values must be understood in the opposite way in terms of quality. In order to take into account the frequency hopping in the RXQUAL evaluation the variable OFFSET_RXQUAL_FH is introduced (for more information refer to [ 30]). If on the corresponding channel, Frequency hopping is applied then OFFSET_RXQUAL_FH = Offset_Hopping_HO otherwise OFFSET_RXQUAL_FH = 0 Offset_Hopping_HO is a parameter defined on a per cell basis. The case where L_RXQUAL_XX_H_XXX + OFFSET_RXQUAL_FH > 7 corresponds in the equations to L_RXQUAL_XX_H_XXX + OFFSET_RXQUAL_FH = 7.

3.2.2.1.2.1 Emergency intracell handover causes Cause 15 Two set of parameters are defined to control Cause 15 whether the current call is AMR or not:

− If the current call is not an AMR call, EN_CAUSE_15 = EN_INTRA_UL, THR_RXQUAL_CAUSE_15 = L_RXQUAL_UL_H.

− If the current call is an AMR call, EN_CAUSE_15 = EN_INTRA_UL_AMR, THR_RXQUAL_CAUSE_15 = L_RXQUAL_UL_H_AMR.

CAUSE = 15 (too high interference level on the uplink) AV_RXQUAL_UL_HO > THR_RXQUAL_CAUSE_15 + OFFSET_RXQUAL_FH (HO-8) and AV_RXLEV_UL_HO > RXLEV_UL_IH and EN_CAUSE_15 = ENABLE and ( no previous intracell handover for this connection failed

or EN_INTRACELL_REPEATED = ENABLE ). Note 1: The variables EN_CAUSE_15 and THR_RXQUAL_CAUSE_15 are specific to HOP. Cause 16 Two sets of parameters are defined to control Cause 16 whether the current call is AMR or not:

− If the current call is not an AMR call, EN_CAUSE_16 = EN_INTRA_DL, THR_RXQUAL_CAUSE_16 = L_RXQUAL_DL_H.

− If the current call is an AMR call,



EN_CAUSE_16 = EN_INTRA_UL_AMR, THR_RXQUAL_CAUSE_16 = L_RXQUAL_DL_H_AMR.

CAUSE = 16 (too high interference level on the downlink) AV_RXQUAL_DL_HO > THR_RXQUAL_CAUSE_16 + OFFSET_RXQUAL_FH (HO-9) and AV_RXLEV_DL_HO > RXLEV_DL_IH and EN_CAUSE_16 = ENABLE and (no previous intracell handover for this connection failed

A or EN_INTRACELL_REPEATED = ENABLE ) Note 1: The variables EN_CAUSE_16 and THR_RXQUAL_CAUSE_16 are specific to HOP. The following handover Causes 10 and 11 are specific to concentric or multiband cell configurations. They are checked only if CELL_PARTITION_TYPE = CONCENTRIC and the active channel is a TCH. Furthermore, they are only valid for handover from the inner zone to the outer zone of the concentric or multiband cell. Thus, the following conditions are checked only if ZONE_TYPE = INNER_ZONE (it means that the channel is in the inner zone partition). Cause 10

CAUSE = 10 (too low level on the uplink, inner zone) AV_RXLEV_UL_HO < RXLEV_UL_ZONE (HO-15) and MS_TXPWR = min(P, MS_TXPWR_MAX_INNER)

Cause 11

CAUSE = 11 (too low level on the downlink, inner zone) AV_RXLEV_DL_HO < RXLEV_DL_ZONE (HO-16) and BS_TXPWR = BS_TXPWR_MAX_INNER

3.2.2.1.2.2 Better conditions intracell handover cause Cause 13 Cause 13 is specific to concentric or multiband cell configurations. It is checked only if CELL_PARTITION_TYPE = CONCENTRIC and the active channel is a TCH. Furthermore, it is only valid for handover from the outer zone to the inner zone of the concentric or multiband cell. Thus, the following condition is checked only if ZONE_TYPE = outer (it means that the channel is in the outer zone partition). If the FREQUENCY_RANGE = PGSM-DCS1800 or EGSM-DCS1800 (the MS is in a multiband cell), the cause is checked only if the MS is biband. Furthermore, if the MS is in a EGSM-DCS1800 multiband cell, the EGSM_ALLOC_STRATEGY is set to Different behaviour for E-GSM capable MS, there is only EGSM TRXs in the inner zone, and the MS is biband but does not support the E-GSM band, then the cause is not checked. The following cause must be checked for all the neighbour cells in the same layer and the same frequency band as the serving cell.



If the load balance between the inner and outer zones is allowed, i.e. EN_LOAD_BALANCE = enable, Cause 13 is only checked if the flag EN_CAUSE_13 is set to enable. This later flag is sent to HOP by RAM in the “TCH usage information” message. EN_CAUSE_13 is set to enable by RAM when the inner zone is less loaded than the outer zone. In addition, in order not to cancel an on-going location procedure, Cause 13 is not checked when a location procedure is on-going for the call.

CAUSE = 13 (Too high level on the uplink and the downlink, outer zone) AV_RXLEV_UL_HO > RXLEV_UL_ZONE + ZONE_HO_HYST_UL + (HO-17) (MS_TXPWR - MS_TXPWR_MAX_INNER) + PING_PONG_MARGIN(0, call_ref) and AV_RXLEV_DL_HO > RXLEV_DL_ZONE + ZONE_HO_HYST_DL + BS_TXPWR - BS_TXPWR_MAX_INNER + PING_PONG_MARGIN(0, call_ref) and AV_RXLEV_NCELL_BIS(n) ≤ NEIGHBOUR_RXLEV(0,n) and EN_CAUSE_13 = enable and EN_BETTER_ZONE_HO = ENABLE

ZONE_TYPE= OUTER ZONE

means that the channel is in the outer zone partition.

RXLEV_DL_ZONE expressed in dBm Threshold of downlink received level for interzone handover,

RXLEV_UL_ZONE expressed in dBm Threshold of uplink receive level for interzone handover,

ZONE_HO_HYST_UL expressed in dB Hysteresis uplink for interzone handover from the outer to the inner zone which also takes account of the propagation difference between GSM and DCS in the case of multiband cell,

ZONE_HO_HYST_DL expressed in dB Hysteresis downlink for interzone handover from the outer to the inner zone which also takes account of the propagation difference between GSM and DCS and of the difference of output power in the BTS in the two bands in the case of multiband cell,

MS_TXPWR_MAX_INNER

expressed in dBm Maximum permissible transmission power of the mobile station in the inner zone of the concentric or multiband cell,

BS_TXPWR_MAX_INNER :

expressed in dB Maximum permissible transmission power of the base station in the inner zone of the concentric or multiband cell,

AV_RXLEV_DL_HO expressed in dBm see previous sections

AV_RXLEV_UL_HO expressed in dBm see previous sections

MS_TXPWR expressed in dBm last BS_POWER reported by the BTS in the MEASUREMENT RESULT (see section 4.1).

BS_TXPWR expressed in dB last MS_TXPWR_CONF reported by the BTS in the MEASUREMENT RESULT (see section 4.1).

NEIGHBOUR_RXLEV(0,n) :

expressed in dBm Threshold of maximum downlink received level from the neighbour cells.

PING_PONG_MARGIN(0,call_ref)

expressed in dB It is a penalty put on the cause 13 if :



the immediately precedent zone on which the call has been is the inner zone of the serving cell, the last handover was not an external intracell handover (case which can occur in the DCS inner zone of a multiband cell in case of emergency handover see 3.2.2.3), less than T_HCP seconds have elapsed since the last handover. In this case PING_PONG_MARGIN(0,call_ref) = PING_PONG_HCP. If the call was not precedently on the serving cell’s inner zone (case of intercell or intrazone handover), or if the timer T_HCP has expired, then PING_PONG_MARGIN(0,call_ref) = 0

Note: 1) For the computation of AV_RXLEV_NCELL_BIS(n) refer to [ 34]. 2) The encoding of MS power levels depends on the frequency band. In multiband cells, the BSC shall then compute the difference (MS_TXPWR – MS_TXPWR_MAX_INNER) considering that MS_TXPWR is encoded with the encoding scheme of the outer zone, whereas MS_TXPWR_MAX_INNER is encoded with the encoding scheme of the inner zone.

3.2.2.1.2.3 Channel adaptation handover causes Cause 26 The triggering of Cause 26 depends on the set of parameters and the triggering of Causes 15 and 16 for AMR calls. When the intracell HO Causes 15 or 16 are allowed for an AMR call in the serving cell, i.e. EN_INTRA_UL_AMR = enable or EN_INTRA_DL_AMR = enable, Cause 26 shall be checked only if a previous intracell HO Cause 15 or 16 has already been triggered for this call in the serving cell. This condition allows to perform one intracell HO before triggering a HR-to-FR channel adaptation. The check of Cause 26 is always allowed when the intracell HO Causes 15 and 16 are both set to disable, i.e. EN_INTRA_UL_AMR = disable and EN_INTRA_DL_AMR = disable. Cause 26 is only checked if the current channel is half rate, and corresponds to an AMR call. Furthermore, the current channel has to be dual rate (DR) and changes allowed (CA) for checking Cause 26. According to the load of the serving cell, the variables THR_RXQUAL_CA and OFFSET_CA are set as follows: If LOAD_SV3(0) = false THR_RXQUAL_CA = THR_RXQUAL_CA_NORMAL OFFSET_CA = OFFSET_CA_NORMAL If LOAD_SV3(0) = true THR_RXQUAL_CA = THR_RXQUAL_CA_HIGH OFFSET_CA = OFFSET_CA_HIGH Cause 26 only applies to handovers from TCH to TCH.



CAUSE = 26 (HR-to-FR channel adaptation due to bad radio quality)

Current rate is Half Rate (HO-27) and The current channel is dual rate and changes allowed and EN_AMR_FR = enable and { { AV_RXQUAL_UL_CA_HR_FR > THR_RXQUAL_CA + OFFSET_CA + OFFSET_RXQUAL_FH and AV_RXLEV_UL_HO > RXLEV_UL_IH } or { AV_RXQUAL_DL_CA_HR_FR > THR_RXQUAL_CA + OFFSET_CA + OFFSET_RXQUAL_FH and AV_RXLEV_DL_HO > RXLEV_DL_IH } } and EN_AMR_CA = enable and { (a previous intracell HO Cause 15 or 16 has been raised for this call in the serving cell) or (EN_INTRA_UL_AMR = disable and EN_INTRA_DL_AMR = disable) } }

Note 1: The variables THR_RXQUAL_CA and OFFSET_CA are specific to Causes 26 and 27 in

HOP. The relevant parameters that have to be set at the OMC are THR_RXQUAL_CA_NORMAL, THR_RXQUAL_CA_HIGH, OFFSET_CA_NORMAL, and OFFSET_CA_HIGH.

Note 2: Only the speech channels are allowed for Cause 26. Cause 27 Cause 27 is only checked if the current channel is full rate and corresponds to an AMR call. Furthermore, the current channel has to be dual rate (DR) and changes allowed (CA) for checking Cause 27. In addition, in order not to cancel an on-going location procedure, Cause 27 is not checked when a location procedure is on-going for the call. According to the load of the serving cell, the variable THR_RXQUAL_CA is set as follows: If LOAD_SV3(0) = false THR_RXQUAL_CA = THR_RXQUAL_CA_NORMAL, If LOAD_SV3(0) = true THR_RXQUAL_CA = THR_RXQUAL_CA_HIGH Cause 27 only applies to handovers from TCH to TCH.



CAUSE = 27 (FR-to-HR channel adaptation due to good radio quality)

Current rate is Full Rate and The current channel is dual rate (DR) and changes allowed (CA) and EN_AMR_HR = enable and AV_RXQUAL_UL_CA_FR_HR ≤ THR_RXQUAL_CA + OFFSET_RXQUAL_FH and AV_RXQUAL_DL_CA_FR_HR ≤ THR_RXQUAL_CA + OFFSET_RXQUAL_FH (HO-28) and EN_AMR_CA = enable

Note 1: The variable THR_RXQUAL_CA is specific to Causes 26 and 27 in HOP. The relevant

parameters that have to be set at the OMC are THR_RXQUAL_CA_NORMAL, THR_RXQUAL_CA_HIGH.

Note 2: Only the speech channels are allowed for Cause 27. The way Cause 27 interacts with Cause 26 is illustrated in Figure 16.

Figure 16: Thresholds for channel adaptation. The frequency hopping offset is not shown in the figure.

3.2.2.1.2.4 Resource management handover cause Unlike the other handover causes, the resource management handover cause is triggered upon the reception of a message from RAM independently of the radio measurements available every SACCH frame. Cause 29 Cause 29 is checked upon the reception of the message “Start HO” from RAM. If Cause 29 is triggered, the new codec type is forwarded to HOM (See Section 3.2.4). This cause shall be triggered only once per received message checking the cause.



CAUSE = 29 (TFO handover)

(HO-29) The HO cause parameter in the message “Start HO” equals 29 and The call reference parameter in the message “Start HO” is the reference of the current call

Note 1: The enabling/disabling of Cause 29 is independent of the flag HO_INTRACELL_ALLOWED. Cause 30 Similar as cause 29, if the cause 30 is enabled in RAM, when the HO condition meets, RAM triggers this HO by sending message to HOP.

CAUSE = 30 (Move PS to CS zone)

(HO-30) The HO cause parameter in the message “Start HO” equals 30 and The call reference parameter in the message “Start HO” is the reference of the current call.

Note 2: The enabling/disabling of Cause 30 is independent of the flag HO_INTRACELL_ALLOWED. Figure 17 is the state diagram of the handover detection process (signal level - signal quality) in case of conventional cell environment. The HO causes for microcellular handover are not shown. The threshold values are only indicative.

Figure 17: State diagram for handover detection (signal level - signal quality)

RXLEV

RXQUAL

605040302010

0

0

1

2

3

4

5

6

7

L_RXQUAL_XX_H

L_RXLEV_XX_H L_RXLEV_XX_IH

(HO-8,HO-9)

Levelintercell HO

(HO-2,HO-4)

Quality intercell HO Intracell HO

(HO-1,HO-3)

Power Control



Figure 18 represents the triggering areas of PBGT and traffic handovers according to the traffic load in the serving cell and in the neighbour cell.

Figure 18: PBGT(n) according to the traffic load in the serving cell and the neighbour cell.

3.2.2.1.3 2G-3G handover causes Cause 31 The cause 31 is checked when there a 3G cell whose averaged Ec/No given by the radio measurement process is greater or equal to a predefined threshold.

CAUSE = 31 (2G-3G handover Ec/No)

AV_ECNO(n) ≥ THR_ECNO (HO-31)

Note 1: The enabling/disabling of Cause 31 is dependent of the flag EN_3G_HO.



3.2.2.2 Handover causes priority The handover causes are checked with the priority order defined in Table 14. The order 1 corresponds to the highest priority whereas the order 19 to the lowest. The resource management handovers 29 , 30 and 31 will have no priority since they are checked with a different trigger than the other handover causes. Order HO family HO cause HO cause

reference 1 Emergency HO Consecutive bad SACCH frames Cause = 7 2 Emergency HO Level uplink microcell - high threshold Cause = 17 3 Emergency HO Level downlink microcell - high threshold Cause = 18 4 Emergency HO Too low quality Uplink Cause = 2 5 Emergency HO Too low quality Downlink Cause = 4 6 Emergency HO Too low level Uplink Cause = 3 7 Emergency HO Too low level Downlink Cause = 5 8 Emergency HO Too long MS-BS distance Cause = 6 9 Emergency HO Too short MS-BS distance Cause = 22 10 Emergency HO Inner zone too low level Uplink Cause = 10 11 Emergency HO Inner zone too low level Downlink Cause = 11 12 Channel adapt. HO HR-to-FR channel adaptation due to bad quality Cause = 26 13 Emergency HO Too high interference intracell Uplink Cause = 15 14 Emergency HO Too high interference intracell Downlink Cause = 16 15 Better conditions HO High level in neighbour cell in the preferred band Cause = 21 Better conditions HO High level in neighbour lower layer cell for slow MS Cause = 14 Better conditions HO General capture handover Cause = 24 Better conditions HO Power budget Cause = 12 Better conditions HO Traffic handover Cause = 23 16 Better conditions HO Outer zone level Uplink & Downlink Cause = 13 17 Channel adaptation FR-to-HR channel adaptation due to good quality Cause = 27 18 Better conditions HO Forced Directed Retry Cause = 20 19 Better conditions HO Fast traffic handover Cause = 28

Table 14: Priority order of alarms for Handover.

The better condition causes 21, 14, 24, 12 and 23 have the same priority. For each cell in the list of possible candidate cell is associated a cause. If a cell is in the candidate cell list because of 2 different causes, only the one with the highest priority in the ordered list (cause 21, cause 14, cause 24, cause 12 and cause 23) in which cause 21 has the highest priority is kept.

3.2.2.3 Indication of raw cell list and preferred layer This section is skipped for intracell handovers. After an inter cell handover alarm has been detected, the candidate cell evaluation receives a raw cell list with for each cell one of the handover causes which have been verified and the indication of the preferred layer for the target cell. ### Case the serving CELL_LAYER_TYPE is single When the serving CELL_LAYER_TYPE is single, the following rules are applied : The raw cell list is :

− for Better conditions intercell handover (Causes 12, 14, 20, 21, 23, 24, and 28) : the neighbour cells which verify the cause,

− for Emergency handover : all neighbour cells; and if the MS is in the DCS1800 inner zone of a multiband cell, the serving cell must be added to the raw cell list with the MS zone indication OUTER.

However, in both cases, if the serving cell is an extended-inner cell, the extended-outer cell must be filtered from the raw cell list except in case of handover cause 6.



If the serving cell is an extended-outer cell, the extended-inner cell must be filtered from the raw cell list except in case of handover cause 22. The indication of the preferred layer is PREF_LAYER = upper+single ### Case the serving CELL_LAYER_TYPE is upper When the serving CELL_LAYER_TYPE is upper, the following rules are applied : The cell raw list is calculated as :

- for better conditions intercell handover causes (causes 12, 14, 20, 21, 23, 24, and 28) the subset of neighbour cells which verify the handover causes.

- for emergency handover causes:

the whole set of neighbour cells; and if the MS is in the DCS1800 inner zone of a multiband cell, the serving cell must be added to the raw cell list with the MS zone indication OUTER.

The indication of the preferred layer is calculated on basis of two rules

- Better conditions intercell handover causes (12, 14, 20, 21, 23, 24, and 28) will indicate :

PREF_LAYER = none

- the "Emergency" handover causes will indicate :

PREF_LAYER = upper+single

### Case the serving CELL_LAYER_TYPE is lower or indoor When the serving CELL_LAYER_TYPE is lower or indoor, the following rules are applied : The cell raw list is calculated as :

- for better conditions intercell handover causes (causes 12, 14, 20, 21, 23 , 24, and 28) the subset of neighbour cells which verify the handover causes. If there is a cell in the list because of Cause 12, and MS_SPEED = fast, the cell raw list must also contain the whole set of internal neighbour umbrella cells with information Traffic_load(n) = low and CELL_LAYER_TYPE(n) = upper (they do not need to verify the HO cause).

- for emergency handover causes

Select the whole set of neighbour cells except the umbrella cells n (CELL_LAYER_TYPE(n) = upper), which do not verify: AV_RXLEV_NCELL(n)>OUTDOOR_UMB_LEV(0,n) and if the MS is in the inner zone of a multiband cell, the serving cell must be added to the raw cell list with the MS zone indication OUTER.

The indication of the preferred layer is calculated on basis of two rules

-"Better conditions intercell" handover causes (12, 14, 20, 21, 23 , 24, and 28) will indicate :



If there is a cell in the list because of Cause 12 and MS_SPEED = fast then PREF_LAYER = upper, else PREF_LAYER = none.

- the "Emergency" handover causes will indicate :

if EN_RESCUE_UM = enable (used generally for microcells) then PREF_LAYER = upper + single if EN_RESCUE_UM = disable (used for other cell types ) then PREF_LAYER = lower + indoor if EN_RESCUE_UM = indefinite then PREF_LAYER = none

Table 15 and Table 16 resume the indications given to the candidate cell evaluation process when the serving CELL_LAYER_TYPE = lower or indoor.

Indication MS_SPEED = fast and there is a cell in the list because of cause 12

MS_SPEED <> fast or Handover cause <> 12

Raw cell list for Better cell HO

subset of cells verifying the HO causes plus all

neighbour umbrella cells with

Traffic_load(n)=low

subset of cells verifying the HO causes

PREF_LAYER for Better cell HO

upper none

Table 15: Indications to candidate evaluation for better conditions intercell handovers when the serving CELL_LAYER_TYPE = lower or indoor.

Indication EN_RESCUE_UM =

ENABLE EN_RESCUE_UM =

DISABLE EN_RESCUE_UM =

indefinite Raw cell list for Emergency HO

all neighbour cells (1) except the umbrella cells

which do not verify AV_RXLEV_NCELL(n)>OUTDOOR_UMB_LEV(0

,n).

all neighbour cells (1) except the umbrella cells

which do not verify AV_RXLEV_NCELL(n)>OUTDOOR_UMB_LEV(0

,n).

all neighbour cells (1) except the umbrella cells which do not

verify AV_RXLEV_NCELL(n)>OUTDOOR_UMB_L

EV(0,n). PREF_LAYER for Emergency HO

upper + single lower + indoor none

Table 16: indications to candidate evaluation for emergency handovers when the serving CELL_LAYER_TYPE = lower or indoor.

(1): if the MS is in the DCS inner zone of a multiband cell, the serving cell must be added to the raw cell list with the MS zone indication OUTER.



3.2.3 HO Candidate Cell Evaluation The HO candidate evaluation process is run after all intercell handover alarms as shown in Figure 19. In case of intra-cell handover alarm (HO causes 10, 11, 13, 15, 16, 26, 27,29 and 30), the candidate cell evaluation process is skipped since the target cell is also the serving cell. For intracell handovers in a concentric or multiband cell, the zone which the MS is currrently allocated to (either outer or inner zone) is forwarded to RAM via HOM together with the serving cell. In this case, the MS zone indication is not determined by the radio criterion presented in Cause 13 and Section 3.1.2.1. �

�

�

HO Detection

Handover causes 2, 3, 4, 5, 6, 7,17,

18, 22, 28

Handover cause 20�

Handover causes 12,14, 21, 23, 24�

Handover causes 10, 11, 13, 15, 16, 26,

27, 29, 30

HO Candidate Cell Evaluation

Filtering process�

Ordering process for emergency HO based on the ORDER/GRADE evaluation

Ordering process for emergency HO based on the forced directed retry evaluation

Ordering process for better conditions HO based on the ORDER/GRADE evaluation

Handover cause 31�

Ordering process for 2G-3G HO based on the 3G cell ranking criteria�

Figure 19: Functional diagram of the HO candidate cell evaluation function.

3.2.3.1 Ordering process The handover detection gives as indication the raw cell list and the preferred layer for the handover. In case of emergency handover alarms, Cause 20 alarm, or Cause 28 alarm, the cell evaluation will order the cells given in the raw list, putting in the first position the cells belonging to the preferred layer, having the highest priority (if EN_PRIORITY_ORDERING=ENABLE) and/or having the same frequency band type as the serving cell. In case of an intercell handover alarm, if the serving cell belongs to the raw cell list (emergency handover from the DCS inner zone of a multiband cell), this cell is put at the end of the candidate cell list with the MS zone indication OUTER. In case of better condition handover alarms (except Causes 20 and 28), the cell evaluation will order the cells given in the raw list, putting in the first position the cells belonging to the preferred layer and having the highest priority (if EN_PRIORITY_ORDERING=ENABLE). Input parameters The ordering process receives (refer to input flows described in section 2.3.6) :

- measurements of up to 32 neighbour cells (TCU internal indication) handled by the BSC cell book-keeping function. - the raw cell list of potential candidates to be ordered with for each of them one of the handover causes which have been verified.



- the preferred layer for the target cell indicated by the variable PREF_LAYER - the cell configuration parameters which contains the variable CELL_BAND_TYPE.

Ordering process for emergency HO alarm (plus Causes 20 and 28) In case of emergency handover alarm, cause 20 alarm, or Cause 28 alarm, the target cell list is built from the cell ordering according to target layer, target band (see Section 2.3.4.1) and the priority of each cells (if EN_PRIORITY_ORDERING=ENABLE) and from the cell evaluation function indicated by the flag CELL_EV associated to the serving cell (see Sections 3.2.3.4 and 3.2.3.5). Unlike the other causes, the cell evaluation of Cause 20 is directly based on the directed retry power budget PBGT_DR(n) without using the ORDER and GRADE cell evaluation processes. The specific case of Cause 20 is further detailed in Section 3.3.3. The priority of each cells is defined by the parameter PRIORITY(0,n). The cell priority introduced here shall not be confused with the cause priority of Section 3.2.2.2. The ordering of the target cell list (from the higher priority to the lower one) is performed according to the following scheme : {Candidate cells whose CELL_LAYER_TYPE = PREF_LAYER { Candidate cells which have the lowest PRIORITY(0,n) { Candidate cells whose CELL_BAND_TYPE = serving CELL_BAND_TYPE { cell ordering according to cell evaluation function } Candidate cells whose CELL_BAND_TYPE <> serving CELL_BAND_TYPE { cell ordering according to cell evaluation function } } Candidate cells which have the next lowest PRIORITY(0,n) { Candidate cells whose CELL_BAND_TYPE = serving CELL_BAND_TYPE { cell ordering according to cell evaluation function } Candidate cells whose CELL_BAND_TYPE <> serving CELL_BAND_TYPE { cell ordering according to cell evaluation function } }

.

.

. } Candidate cells whose CELL_LAYER_TYPE <> PREF_LAYER { Candidate cells which have the lowest PRIORITY(0,n) { Candidate cells whose CELL_BAND_TYPE = serving CELL_BAND_TYPE { cell ordering according to cell evaluation function } Candidate cells whose CELL_BAND_TYPE <> serving CELL_BAND_TYPE { cell ordering according to cell evaluation function }



} Candidate cells which have the next lowest PRIORITY(0,n) { Candidate cells whose CELL_BAND_TYPE = serving CELL_BAND_TYPE { cell ordering according to cell evaluation function } Candidate cells whose CELL_BAND_TYPE <> serving CELL_BAND_TYPE { cell ordering according to cell evaluation function } }

.

.

. } Serving cell (MS zone indication = OUTER) } Ordering process for better conditions HO alarm (except Causes 20 and 28) In case of better condition handover alarm except causes 20 and 28, the target cell list is built from the cell ordering according to target layer and the priority of each cells (if EN_PRIORITY_ORDERING=ENABLE) and from the cell evaluation function indicated by the flag CELL_EV associated to the serving cell (see Sections 3.2.3.4 and 3.2.3.5). The priority of each cells is defined by the parameter PRIORITY(0,n). The cell priority introduced here shall not be confused with the cause priority of Section 3.2.2.2. The ordering of the target cell list (from the higher priority to the lower one) is performed according to the following scheme : Candidate cells whose CELL_LAYER_TYPE = PREF_LAYER { Candidate cells which have the lowest PRIORITY(0,n) { cell ordering according to cell evaluation function } Candidate cells which have the next lowest PRIORITY(0,n) { cell ordering according to cell evaluation function }

.

.

. } Candidate cells whose CELL_LAYER_TYPE <> PREF_LAYER { Candidate cells which have the lowest PRIORITY(0,n) { cell ordering according to cell evaluation function } Candidate cells which have the next lowest PRIORITY(0,n) { cell ordering according to cell evaluation function }

.

.

. }



Note : - if PREF_LAYER = none, only the second part of the scheme (i.e. candidate cells whose

CELL_LAYER_TYPE <> PREF_LAYER) is considered. - if PREF_LAYER = upper+single, the condition for the first part of the scheme will be :

CELL_LAYER_TYPE = upper or CELL_LAYER_TYPE = single. The condition for the second part will be CELL_LAYER_TYPE <> upper and CELL_LAYER_TYPE <> single.

- if PREF_LAYER = lower+indoor, the condition for the first part of the scheme will be : CELL_LAYER_TYPE = lower or CELL_LAYER_TYPE = indoor. The condition for the second part will be CELL_LAYER_TYPE <> lower and CELL_LAYER_TYPE <> indoor.

- if EN_PRIORITY_ORDERING=DISABLE, the priority(0,n) is not taken into account. The flag CELL_EV is managed by the network operator on a per cell basis. It has two values, which correspond to the two cell evaluation functions ORDER and GRADE (see Sections 3.2.3.4 and 3.2.3.5) . A filtering process can be applied to the target list before the ORDER or GRADE evaluation process in case of emergency handovers. The filtering process, the ORDER or GRADE evaluation process are not applied to the serving cell when it is in the target cell list. The serving cell is always at the end of the target cell list. After the cell evaluation processing, the list of candidate target cells with their cause is provided to HOM. For Cause 28, the list of candidate cells is sent to the HOM only when the message “Start HO” concerning the current call and Cause 28 has been received from RAM. Output parameters The ordering process (after the filtering process) should provide to the handover alarm management described in Section 3.2.4 the list of candidate cells with their cause and with the serving cell at the end of the list in case of emergency handover from the DCS inner zone of a multiband cell. The HO causes together with the CELL_PARTITION_TYPE parameter shall be used by HOM (for further details, see [ 28] and [ 30]) as described in Table 17:

CELL_PARTITION_TYPE ### HO cause ###

Normal Concentric

15, 16

Intracell handover Select a channel in the same cell

Intrazone or interzone handover Select a channel in the same cell

26, 27 Intracell handover Change the speech channel rate and select a channel in the same cell

Intracell handover Change the speech channel rate and select a channel in the same cell

29 Intracell handover Select a new codec type

Intracell handover Select a new codec type

30 Intracell handover Move TCH from PS preference zone to CS preference zone.

Intracell handover Move TCH from PS preference zone to CS preference zone.

10, 11, 13

Not applicable

Interzone handover Select a channel in the other zone

Others

Intercell handover Channel allocation is described in [ 28] and [ 30].

Intercell handover Channel allocation is described in [ 28] and [ 30].

Table 17: Channel allocation strategy



3.2.3.2 Ordering process for 2G-3G handover The handover detection gives as indication the raw cell list. The cell evaluation will order the 3G cells given in the raw list, putting in the first position the 3G cell having the highest averaged Ec/No and ranking the remaining 3G cells in decreasing average Ec/No order. The ranked 3G cells are on top of the 2G candidate cells list if any. Input parameters The ordering process receives (refer to input flows described in section 2.3.6):

− average Ec/No measurements of 1 to NBR_ADJ_3G 3G neighbour cells handled by the BSC cell book-keeping function.

− the raw cell list of 3G potential candidates to be ordered with for each of them one of the handover causes which have been verified.

Output parameters The ordering process should provide to the handover alarm management described in Section 3.2.4 the list of 3G candidate cells with their cause on top of the list of the 2G candidate cells if any.

3.2.3.3 Filtering process The filtering process allows to filter out cells from the target list before the ORDER or GRADE evaluation process. This process can be enabled or disabled by the flag EN_PBGT_FILTERING. This filtering process is inhibited for better conditions intercell handovers (HO causes 12, 14, 20, 21, 23, or 24) except for Cause 28. It is not applied to the serving cell when it is in the target cell list. If EN_PBGT_FILTERING is set to enable, all the cells(n) which do not fulfil the following condition (HO-13) are rejected from the cell list sent to the ORDER or GRADE evaluation process.

PBGT(n) > HO_MARGIN_XX(0,n) + OFFSET_HO_MARGIN_INNER (HO-13)

OFFSET_HO_MARGIN_INNER is only applied when the MS is in the inner zone of a concentric or multiband cell. HO_MARGIN_XX(0,n) has the following values: HO_MARGIN_XX(0,n)=HO_MARGIN_QUAL(0,n) If cause =2, 4 or 7 HO_MARGIN_XX(0,n)=HO_MARGIN_LEV(0,n) If cause =3, 5, 17, 18, or 28 HO_MARGIN_XX(0,n)=HO_MARGIN_DIST(0,n) If cause =6 or 22 If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target cell list is empty and no further action is carried out. If the target list is not empty, it is sent to the ORDER or GRADE evaluation process according to CELL_EV.

3.2.3.4 ORDER cell evaluation process The ORDER cell evaluation process is used by the ordering process of Section 3.2.3.1. Note that the word "PATHLOSS" was in the past sometimes used instead of "ORDER". The value of ORDER(n) for each neighbour cell(n) is computed according to the following formula : if EN_LOAD_ORDER = ENABLE and cell n is internal to the BSC



ORDER(n) = PBGT(n) + LINKfactor(0,n)

(HO-10) + FREEfactor(n) - FREEfactor(0) - HO_MARGIN_XX(0,n) if EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

ORDER(n) = PBGT(n) + LINKfactor(0,n) - HO_MARGIN_XX(0,n)

(HO-10bis) For emergency handover causes (plus Cause 28), HO_MARGIN_XX(0,n) has the following values: HO_MARGIN_XX(0,n)=HO_MARGIN_QUAL(0,n) If cause =2, 4 or 7 HO_MARGIN_XX(0,n)=HO_MARGIN_LEV(0,n) If cause =3, 5, 17,18, or 28 HO_MARGIN_XX(0,n)=HO_MARGIN_DIST(0,n) If cause =6 or 22 For better cell handover causes, HO_MARGIN_XX(0,n)=HO_MARGIN(0,n) - The flag EN_LOAD_ORDER is settable by OMC command. - LINKfactor(0,n), HO_MARGIN_QUAL(0,n), HO_MARGIN_LEV(0,n), HO_MARGIN_DIST(0,n) and

HO_MARGIN(0,n) are parameters set by OMC command for each neighbour cell(n). - FREEfactor(n) : weighting factor that takes into account the number of free traffic channels in a cell. It

is received in the message “TCH usage information” from RAM. - For TCH, FREEfactor(n) is set to the value specified in [ 30], - for SDCCH : FREEfactor(n) = 0.

- PBGT(n) is the power budget between the serving cell(0) and cell(n). For the formula, see Section 6.1. All neighbour cells(n) which fulfil the following condition (HO-11) are sorted according to their ORDER(n) :

AV_RXLEV_NCELL(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (HO-11)

For multiband handover, P considered in (HO-11) corresponds to the classmark power in the frequency band used by the cell n. Equation (HO-11) ensures that the MS can communicate in the cell n. For any handover cause, the first cell in the list is taken as target cell, i.e. the cell with the highest value of ORDER(n). The cells do not need to fulfil any other condition. If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target cell list is empty and no further action is carried out.

3.2.3.5 GRADE cell evaluation process The GRADE cell evaluation process is used by the ordering process of Section 3.2.3.1. The value of GRADE(n) for each neighbour cell(n) is computed according to the following formula : if EN_LOAD_ORDER = ENABLE and cell n is internal to the BSC

GRADE(n) = PBGT(n) + LINKfactor(0,n) (HO-12) + LOADfactor(n)



if EN_LOAD_ORDER = DISABLE or cell n is external to the BSC

GRADE(n) = PBGT(n) + LINKfactor(0,n) (HO-12bis) - The flag EN_LOAD_ORDER is settable by OMC command. - LINKfactor(0,n) is a parameter set by OMC command for each cell(n).

LINKfactor (n1,n2) allows the operator to handicap or to favour the cell n1 with respect to its neighbour cell n2. In particular, it can be used to disadvantage an external cell when an internal cell is also a possible candidate.

- LOADfactor(n) : weighting factor that takes into account the relative load of traffic channels in a cell. It is received in the message “TCH usage information” from RAM.

For TCH: LOADfactor(n) is set to the value specified in [ 30], For SDCCH : LOADfactor(i) = 0.

The real time traffic load and corresponding FREEfactor and LOADfactor are only known for the cells that are controlled by the current BSC. For the cells controlled by another BSC the traffic load does not influence the candidate evaluation.

- PBGT(n) is the power budget between the serving cell(0) and the cell(n) (see Section 6.1 for

definition). The greater is GRADE(n), the most suitable is the neighbour cell n compared to the serving cell. All neighbour cells(n) which fulfil the following condition are sorted according to their GRADE(n). Equation (HO-11) ensures that the MS can communicate in the cell n.

AV_RXLEV_NCELL(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (HO-11)

For multiband handover, P considered in (HO-11) corresponds to the classmark power in the frequency band used by the cell n. For any handover cause the first cell in the list is taken as target cell, i.e. the cell with the highest value of GRADE(n). If no cell fulfils the condition and the serving cell does not belong to the target cell list, the target cell list is empty and no further action is carried out.



3.2.4 Handover alarm management The handover alarm management is a part of the handover candidate cell evaluation entity. Its main role is to prepare the message that should be sent to HOM when an handover alarm has been detected.

3.2.4.1 Alarm filtering process based on the timer T_Filter

3.2.4.1.1 General case The purpose of the alarm filtering process is (i) to avoid to send several times the same alarm to the HOM entity, and (ii) to send a specific message when the alarm disappears. This process is based on the timer T_FILTER. Each time a candidate cell list is provided by the handover candidate cell evaluation function or by the candidate cell evaluation function for forced directed retry and T_FILTER is not running, the message “Alarm” is sent to the HOM entity, and T_FILTER is started. This message contains: − The list of the candidate 2G, 3G cells as given by the handover candidate cell evaluation function, − The HO Cause (per cell in the list), which is the number of the handover cause, − The MS zone location (per concentric cell in the list), − The new codec type for Cause 29. Each time a candidate cell list is provided by the handover candidate cell evaluation function or by the candidate cell evaluation function for forced directed retry and T_FILTER is running, T_FILTER is restarted and the new list is compared to the previous candidate cell list (See Figure 20). If the list has changed (ie one or more cells have disappeared in relation to the previous list and/or

one or more cells are new in the list), a handover alarm containing the candidate list is sent to the HOM entity.

If the new list has not changed (ie the cells are the same, the number of cells is the same but the order in the list can be different see note1), no handover alarm is sent to the handover management entity.

Figure 20: Alarm filtering process based on the timer T_FILTER.



If the timer T_FILTER expires, a handover alarm message containing no candidate cell is sent to the handover management entity. This message means: “no more alarm”. The expiry of T_FILTER means that the handover alarm initially triggered is considered as no longer valid. Note 1: This behaviour also concerns the 3G cells.

3.2.4.1.2 Specific case of resource management handovers (Cause 29 and 30) Each time a HO Cause 29 and cause 30 are triggered by the handover detection process, T_FILTER is started or restarted, and an “Alarm” message is sent to HOM independently of the triggering of the other causes. In this case, only the serving cell is in the list of candidate cells.

3.2.4.1.3 Specific case of fast traffic handovers (Cause 28) The specific alarm management for Cause 28 is described in this section. Two steps are required in HOP to deal with Cause 28. The first step consist in checking whether the current MS is capable of performing a fast traffic handover when requested by RAM. In a second step, if RAM sends the “Start HO” message and it concerns the current call and Cause 28, HOP will send the HO alarm Cause 28 to HOM through the T_FILTER mechanism. Upon the reception of the message “Fast traffic HO request” from RAM, the check of Cause 28 is enabled by setting the HOP flag EN_CAUSE_28 to enable, and the reference and the channel rate of the queued request is stored. When a new candidate cell list is received from the HO candidate cell evaluation function because of Cause 28, the checking of Cause 28 is disabled by setting EN_CAUSE_28 to disable, and the message “Fast traffic HO ACK” is sent to RAM. This message contains (See also Section 4.2):

− The reference of the queued request, which is given in the message “Fast traffic HO request” sent by RAM,

− The call reference, which is the reference of the current call. At this step, even if Cause 28 is detected, the “Alarm” message is not send to HOM. This message handling is described in Figure 21. If two “Fast traffic HO request” arrive after each other, only the last one will be taken into account. This last one concerns the top request of the queue. So only for the last received queued request reference and channel rate, Cause 28 will be checked on reception of measurements. Every new received “Fast traffic HO request” will overwrite the queued request reference and channel rate to be taken into account when checking Cause 28.



Figure 21: Enabling and disabling of the HOP flag EN_CAUSE_28.

In the same way that the Causes 29 and 30 are managed, we introduced here the Cause 28bis. Cause 28bis is checked upon the reception of the message “Start HO” from RAM. This cause shall be triggered only once per received message checking the cause.

CAUSE = 28bis (Fast traffic handover bis)

(HO-31) The HO cause parameter in the message “Start HO” equals 28 and The call reference parameter in the message “Start HO” is the reference of the current call

When an HO alarm is detected because of Cause 28bis, the handover detection function is computed with the available radio measurements. All the relations for Cause 28 in (HO-26) are checked except the condition EN_CAUSE_28 = enable. The handover cell evaluation function is then performed including Cause 28 if triggered. If a candidate cell list is received from the candidate cell evaluation function because of Cause 28, the timer T_FILTER is started or restarted, and the message “Alarm” is sent to HOM containing the list of the candidate cells. The interaction of Cause 28 with the T_FILTER mechanism is described in Figure 20. Note 1: Since several MS can acknowledge the “Fast traffic HO request”, RAM needs to obtain the call

reference to distinguish the different MS acknowledgement.

3.2.4.2 Alarm filtering process based on the timer T_INHIBIT_CPT The role of the timer T_INHIBIT_CPT is to inhibit the capture handover Causes 14, 21, and 24 for a while so as to reduce the ping-pong effect. The immediately preceding cell on which the MS has been



is here denoted n-1. According to the layer of the serving cell the following conditions must be checked for starting the timer T_INHIBIT_CPT: − Case the serving cell is in the upper or single layer (CELL_LAYER_TYPE(n0) = upper or single)

Condition 1: The immediately preceding cell n-1 is in the indoor or lower layer, i.e.

CELL_LAYER_TYPE(n–1) = lower or indoor, or the frequency band of the immediately preceding cell n-1 is different from the frequency band of the serving cell n0, i.e. CELL_BAND_TYPE(n–1) <> CELL_BAND_TYPE(n0).

Condition 2: The call has previously performed i) an emergency internal handover on quality (Cause 2, 4, and 7) towards the serving cell or ii) an external handover with the A interface GSM cause “uplink quality or downlink quality” and there is a bi-directional adjacency link between the preceding external cell n-1and the serving cell n0.

If Conditions 1 and 2 are fulfilled the timer T_INHIBIT_CPT is started.

− Case the serving cell is in the lower layer (CELL_LAYER_TYPE(n0) = lower)

Condition 3: The immediately preceding cell is in the indoor layer, i.e. CELL_LAYER_TYPE(n–1) = indoor, or the frequency band of the immediately preceding cell n-1 is different from the frequency band of the serving cell n0, i.e. CELL_BAND_TYPE(n–1) <> CELL_BAND_TYPE(n0).

Condition 4: The call has previously performed i) an emergency internal handover on quality (Cause 2, 4, and 7) towards the serving cell or ii) an external handover with the A interface GSM cause “uplink quality or down link quality” and there is a bi-directional adjacency link between the precedent external cell n-1and the serving cell n0.

If Conditions 3 and 4 are fulfilled the timer T_INHIBIT_CPT is started. If these conditions are not fulfilled, the timer T_INHIBIT_CPT is not started. The BSC detects that there is a bi-directional adjacency link between a given Cell Cext and a given Cell Cint as follows. When the BSC receives an handover request from Cell Cext to Cell Cint, the BSC checks whether or not there is an outgoing handover adjacency link defined from Cell Cint to Cell Cext. If this adjacency link exists, the BSC considers that there is a bi-directional adjacency link between Cells Cint and Cext. When performing this check, the BSC uses the Cell Global Identifier (CGI) of each cell (i.e. the CGI where CGI = MCC + MNC + LAC + CI).



3.3 Directed retry preparation

3.3.1 General

3.3.1.1 Directed retry preparation enabling and disabling Enabling The directed retry preparation is enabled upon reception of an indication from the handover management entity (BSC internal message, see [ 28]). This indication is called "Start DR algos " in the SADT diagram of section 2.3.6. The directed retry is supported by the same processes as the handover preparation except for forced directed retry (see section 2.4), consequently : - for directed retry on handover alarms, the enabling consists in changing the behaviour of the

candidate cell evaluation process (see section 3.2.3). This process looks for target cells for TCH channel instead of SDCCH channel.

- for forced directed retry : both the detection and candidate cell evaluation processes are enabled at this point in time.

Note : The handover preparation function is enabled when the SDCCH connection is established (reception of the ESTABLISH INDICATION from the corresponding BTS). Therefore the handover preparation is always enabled before the directed retry preparation. This allows the detection process for forced directed retry, after its enabling, to get immediately measurements from the neighbouring cell measurements book-keeping.

When the directed retry preparation is enabled, SDCCH_COUNTER is stopped and not restarted. Disabling The directed retry preparation is disabled whenever the BSC initiates a channel release on the radio interface.

3.3.1.2 Directed retry preparation function The directed retry preparation function is completely handled by the BSC. The input parameters of this function are provided by the active channel preprocessing function (refer [ 34]) which handles the neighbour cell list book-keeping. As the handover preparation function, the directed retry preparation function can be divided into two processes : Alarm detection and Candidate cell evaluation. Once the directed retry preparation enabled, a directed retry on handover alarms or forced directed retry alarm can be detected every SACCH multiframe upon reception of the averaged measurements for directed retry detection. Once a directed retry alarm is detected, the alarm detection process sends to the candidate cell evaluation process the list of MS neighbouring cells with for each of them one of the handover causes which have been verified. The candidate cell evaluation builds a cells list which is according to the case and the value of T_FILTER sent or not to the BSC function in charge of the handover management entity (see 3.2.4.).

3.3.2 Alarm Detection Directed retry on handover alarms



The detection process is the Handover detection process described in Section 3.2.2 except that intracell handover alarms and Cause 28 must be ignored. Only intercell handover alarms are taken into account i.e. all handover causes except causes mentioned above. Forced directed retry The following condition is checked every measurement reporting period and if at least one input preprocessed parameter AV_RXLEV_NCELL_DR(n) is available.

CAUSE = 20 (high level in neighbour cell for forced directed retry) AV_RXLEV_NCELL_DR(n) > L_RXLEV_NCELL_DR(n) ( n = 1 ... BTSnum ) (DR - 1) and EN_FORCED_DR = ENABLE

The threshold L_RXLEV_NCELL_DR(n) is the observed level from the neighbour cell n at the border of the area where forced directed retry is enabled (See Section 2.4.1). This threshold fixes the size of the overlapping area where forced directed retry can be performed. It should be greater than RXLEVmin(n). Alarms priority As explained in section 2.4, the handover alarms have priority over the forced directed retry alarm (HO cause 20). The priority order for handover alarms is indicated in Section 3.2.2.2.

3.3.3 Candidate cell evaluation Directed retry on handover alarms The candidate cell evaluation process is the one described in Section 3.2.3 for TCH channel. Forced directed retry The candidate cell evaluation is performed when an alarm for forced directed retry is raised (cause = 20). This candidate cell evaluation process is performed as specified in Section 3.2.3. except that the cell evaluation function is reduced to a specific power budget evaluation called PBGT_DR(n). All neighbour cells n which meet the following condition (DR-3) and (DR-4) are sorted according to the ordering process for emergency HO described in Section 3.2.3.1 . Instead of using the ORDER or GRADE cell evaluation processes, the cell evaluation is computed according to the PBGT_DR(n) : PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) - AV_RXLEV_PBGT_DR (DR-2) - (BS_TXPWR_MAX - AV_BS_TXPWR_DR) - (MS_TXPWR_MAX(n) - MS_TXPWR_MAX) For further details on the PBGT formula, see Section 3.2.2.1.1.3 and Section 6.1.

AV_RXLEV_NCELL_DR(n) > RXLEVmin(n) + max(0,[MS_TXPWR_MAX(n)-P]) (DR-3)

t(n) > FREElevel_DR(n) (DR-4)



with : − FREElevel_DR(n) : minimum threshold of free TCHs in the neighbour cell n for forced directed

retry. − t(n) : absolute number of free TCHs in the neighbour cell n. For external cells, t(n) is fixed to the arbitrary value t(n)=255. Therefore, setting FREElevel_DR(n) to 255 for an external cell inhibits outgoing external directed retry towards this cell. Setting FREElevel_DR(n) to any other value will allow outgoing external directed retry towards this cell. Note : if the BTS has dual rate capability, t(n) = absolute number of free Dual Rate TCH L_RXLEV_NCELL_DR(n) and FREElevel_DR(n) are parameters set by O&M for each neighbour cell n. If no cell fulfils the condition, the target cell list is empty and no further action is carried out.



4 INTERFACES DESCRIPTION

4.1 3GPP interfaces/Physical interfaces The messages used by the handover algorithms are carried on the Abis interface only. Note that for handover decision and execution, all the relevant messages transmitted on the Air, Abis, A interfaces are described in [ 23] and [ 24]. Note : In [ 34] is given the general structure of the Abis messages required by the handover algorithm. In particular, the fields for which it is stated in the 3GPP Technical Specification 05.08 [ 38] "the coding of this field requires further elaboration" are described. For the coding of the others information elements, refer to [ 39].

4.2 Internal interfaces The different BSC internal interfaces with HOP are detailed in this section (See Figure 22). The information exchanged between handover functions is also described in Sections 2 and 4.4. HOP : Handover preparation This entity is responsible of triggering handover alarms. To detect handover alarm, HOP checks continuously i) the radio environment of the mobile (radio level, radio quality, possible target cells, traffic load, multi-layer network, etc.) and ii) the requests for handovers sent by RAM. HOM : Handover management This entity is responsible of managing the channel changes depending on handover alarms sent by the HOP entity, the O&M configuration of the BSS, the events arriving from the protocol entities, etc. The HOM behaviour is described in [ 28]. ICC : Internal channel change This entity is responsible of running the internal channel change protocol when the HOM asks for it. The ICC behaviour is described in [ 23]. ECC : External channel change This entity is responsible of running the external channel change protocol, either for an outgoing external channel change when the HOM asks for it (serving BSC) or autonomously for an incoming channel change (target BSC). The ECC behaviour is described in [ 24]. RAM : Resource allocation and management This entity is responsible for managing the radio resources of the BSS. RAM can also trigger handover alarm messages that are sent to HOP. The RAM behaviour is described in [ 30].

Direction Message Parameters of information RAM --> HOP TCH usage information − Cell reference

− Total number of free TCH − LOADfactor and FREEfactor − AV_LOAD − Traffic_load − LOAD_SV3 − EN_CAUSE_13

MS zone indication request Fast traffic HO request − Reference of the queued request

− Channel rate of the queued request Start HO − HO cause

− Call reference − New codec type (for Cause 29)



Move PS to CS zone − Channel description HOP --> RAM MS zone indication ACK − Indication of the zone where the MS is located in

the serving cell: outer or inner Fast traffic HO ACK − Call reference

− Reference of the queued request HOM --> HOP Start DR algos HOP --> HOM Alarm − HO cause (per cell in the list)

− List of the candidate cells − MS zone indication (per concentric cell in the list) − New codec type (for Cause 29)

Table 18: Details of the BSC internal interfaces with HOP.

Figure 22: BSC internal interfaces with HOP.

4.3 Timers list NAME RANGE BIN.RANGE BITS

T_FILTER (0 to 31)x960 ms 0:31 8

Time after which a “no alarm” message (an alarm message with no candidate cell, see section 3.3.) is sent to the handover management entity, if no new alarm has been detected whilst running.

0=0 ms

31=31x960ms

T_HCP (0 to 240 ) sec 0:240 8



Time during which a handicap of PING_PONG_HCP is applied to the preceding cell power budget

0=0 s 240 = 240 s

T_INHIBIT_CPT (0 to 240 ) sec 0:240 8

Time during which the HO Causes 14, 21, and 24 are inhibited

0=0 s 240 = 240 s

LOAD_EV_PERIOD 1 to 30 1:30 8

Number of load samples (received every TCH_INFO_PERIOD) for load averaging

1=1 , 30 = 30

TCH_INFO_PERIOD 2 to 25.5 sec 20:255 8

periodicity of the sending of the message ’TCH usage information’ to the TCUs.

20=2 s, 255 = 25.5 s

4.4 Parameters and variables list This section provides a list of all the variables and parameters used in the algorithms and thus encountered in the text. For each entry will be found : − its name, − its meaning, − its physical range, − its binary range, − the number of bits into which it is encoded. The variables and parameters are ranked in the alphabetical order.

4.4.1 Handover NAME RANGE BIN. RANGE BITS AV_BS_TXPWR_DR max -30 to min 0 dB 0:30 5

Average Transmit Power at BS for PBGT_DR evaluation

step size 1 dB (relative value)

0 = 0 dB 30 = -30 dB

AV_BS_TXPWR_HO max -30 to min 0 dB 0:30 5

Average Transmit Power at BS for PBGT evaluation step size 1 dB (relative value)

0 = 0 dB 30 = -30 dB

AV_ECNO(n) -110 to –47 dBm 0:63 8

Average Ec/No of the 3G neighbour cell n step size 1 dBm 0=-110

63=-47 AV_LOAD(n) 0 to 100 % 0:100 8

Averaging load of the cell n step size 1%

with a period equal to LOAD_EV_PERIOD AV_RXLEV_DL_HO -110 to -47 dBm 0:63 8

Average Receive Downlink Level step size 1 dBm 0=-110

of serving cell (used for Handover) 63=-47



AV_RXLEV_DL_MCHO -110 to -47 dBm 0:63 8

Average Receive Downlink Level of serving step size 1 dBm 0=-110

cell (used for Microcellular Handover) 63=-47

AV_RXLEV_NCELL(n) -110 to -47 dBm 0:63 8

Average Receive Level step size 1 dBm 0=-110

neighbour cell n at MS 63=-47

AV_RXLEV_NCELL_BIS(n) -110 to -47 dBm 0:63 8

Average Receive Level step size 1 dBm 0=-110

neighbour cell n at MS used for cause 13 63=-47 AV_RXLEV_UL_HO -110 to -47 dBm 0:63 8

Average Receive Uplink Level step size 1 dBm 0=-110

of serving cell (used for Handover) 63=-47 AV_RXLEV_UL_MCHO -110 to -47 dBm 0:63 8

Average Receive Uplink Level of serving step size 1 dBm 0=-110

cell (used for Microcellular Handover) 63=-47 AV_RXLEV_PBGT_HO -110 to -47 dBm 0:63 8

Average Receive Downlink Level of step size 1 dBm 0=-110

serving cell (PBGT calculation) 63=-47 AV_RXQUAL_DL_CA_HR_FR 0 to 7 0:7 coded with a 8

Average receive downlink quality of stepsize 0.1 stepsize of 0.1

serving cell (HR-to-FR channel adaptation) AV_RXQUAL_UL_CA_HR_FR 0 to 7 0:7 coded with a 8

Average receive uplink quality of stepsize 0.1 stepsize of 0.1

serving cell (HR-to-FR channel adaptation) AV_RXQUAL_DL_CA_FR_HR 0 to 7 0:7 coded with a 8

Average receive downlink quality of stepsize 0.1 stepsize of 0.1

serving cell (FR-to-HR channel adaptation) AV_RXQUAL_UL_CA_FR_HR 0 to 7 0:7 coded with a 8

Average receive uplink quality of stepsize 0.1 stepsize of 0.1

serving cell (FR-to-HR channel adaptation) AV_RXQUAL_UL_HO 0 to 7 0:7 coded with a 8

Average Receive Uplink Quality of stepsize 0.1 step size of 0.1

serving cell (used for Handover) AV_RXQUAL_DL_HO 0 to 7 0:7 coded with a 8

Average Receive Downlink Quality of stepsize 0.1 step size of 0.1

serving cell (used for Handover) AV_RANGE_HO 0 to 63 x 3.69µs 0:63 8

Average Distance between MS and BS BCCH_FREQUENCY 0 to 1023 0:1023 16



BCCH frequency used in the serving cell. BCCH_FREQUENCY(n) 0 to 1023 0:1023 16

BCCH frequency used in the neighbour cell n. SACCH_BFI 0 or 1 0:1 1

Bad Frame Indicator 0 : good frame

of the SACCH frame 1 : bad frame BS_TXPWR max -30 to min 0 dB 0:15 5

Transmit Power at BS step size 2 dB (relative value)

0 = 0 dB 15 = -30 dB

BS_TXPWR_MAX max -30 to min 0 dB 0:15 8

Maximum Transmit Power at BS step size 2 dB 0 = 0 dB

(relative value) 15= -30 dB BS_TXPWR_MAX_INNER max - 30 to min 0 dB 0:15 8

Maximum BS Transmit Power permissible in the step size 2 dB 0 = 0 dB

inner zone of the concentric or multiband cell. (relative value) 15= -30 dB BS_TXPWR_MIN max - 30 to min 0 dB 0:15 8

Minimum Transmit Power at BS step size 2 dB 0 = 0 dB

(relative value) 15= -30 dB BSIC(n) 0 to 63 0:63 8

Base Station Identity Code of cell n BTSnum 0 to 32 0:32 8

Number of neighbouring cells for which measurements made by the MS are available

CAPTURE_TRAFFIC_CONDITION ANY_LOAD, NOT_LOW,

HIGH 0 : 2 8

Condition on traffic load in the serving cell for a general capture handover

0 : ANY_LOAD 1 : NOT_LOW 2 : HIGH

C_DWELL counter for time during which the MS has been inside the serving lower layer cell

0 : 255 SACCH frames stepsize 1

0 : 255 0

C_DWELL(n) counter for time during which the MS has been reporting the neighbour lower layer cell when on the upper layer with a minimum receive level of L_RXLEV_CPT_HO(0,n)

0 : 255 SACCH frames stepsize 1

0 : 255 0

CELL_BAND_TYPE GSM or DCS 1 : GSM 2

Indication of the BCCH frequency band 2 : DCS

CELL_DIMENSION_TYPE Macro or Micro 0 : Macro 2

Indicator of BTS dimension type 1 : Micro CELL_EV ORDER or GRADE 0 : ORDER 1

Indicator of which cell evaluation process is chosen 1 : GRADE



CELL_LAYER_TYPE Indicator of BTS layer type

Single, or Upper, Lower, indoor

0 : Single 1 :Upper

2

2 : Lower 3: indoor

CELL_PARTITION_TYPE Normal or Concentric 0 : Normal 2

Indicator of cell partition type (frequency use) 1 : Concentric CELL_RANGE Normal, Extended inner

or Extended outer 0 : Normal 1 : Extended outer

2

Indicator of extended cell feature 2 : Extended inner DELTA_DEC_HO_margin 0 to 24 dB 0:24 8

allows the cause 23 detection when the traffic in the serving cell is high and is low in the cell n

stepsize 1 dB

DELTA_HO_MARGIN(0,n) 0 0 8

-DELTA_DEC_HO_margin DELTA_INC_HO_margin

-DELTA_DEC_HO_margin DELTA_INC_HO_margin

DELTA_INC_HO_margin 0 to 24 dB 0:24 8

penalises the cause 12 detection when the traffic in the serving cell is low and is high in the cell n

stepsize 1 dB

DWELL_TIME_STEP 0 :30 s 0:0 8

increment or decrement value of MIN_DWELL_TIME stepsize 1s 30 : 30

for traffic load control in the umbrella cells

EN_AMR_CA enable or disable 0 : disable 1

Enable/disable intracell HO for AMR channel adaptation (Causes 26 and 27)

1 : enable

EN_AMR_FR enable or disable 0 : disable 1

Enable/disable AMR full rate 1 : enable

EN_AMR_HR enable or disable 0 : disable 1

Enable/disable AMR half rate 1 : enable

EN_BETTER_ZONE_HO enable or disable 0 : disable 1

Enable/disable flag for HO cause 13 1 : enable

EN_BI-BAND_MS(n) enable or disable 0 : disable 1

Enables/disables the incoming handovers of bi-band MSs from the preferred-band into a classical band cell

1 : enable

EN_CAUSE_13 enable or disable 0 : disable 1

Enable/disable flag for HO cause 13. The flag is set to enable when the inner zone is less loaded than the outer zone

1 : enable




Enable/disable variable for HO cause 15 1 : enable


Enable/disable variable for HO cause 16 1 : enable


HOP enable/disable variable for HO cause 28 1 : enable

EN_DIST_HO enable or disable 0 : disable 1


EN_GENERAL_CAPTURE_HO enable or disable 0 : disable 1


EN_INTRACELL_REPEATED enable or disable 0 : disable 1

Enable/disable flag for repetition of intracell HO 1 : enable

EN_INTRA_DL enable or disable 0 : disable 1

Enable/disable flag for HO cause 16 for non AMR calls

1 : enable

EN_INTRA_DL_AMR enable or disable 0 : disable 1

Enable/disable flag for HO cause 16 for AMR calls 1 : enable

EN_INTRA_UL enable or disable 0 : disable 1

Enable/disable flag for HO cause 15 for non AMR calls

1 : enable

EN_INTRA_UL_AMR enable or disable 0 : disable 1

Enable/disable flag for HO cause 15 for AMR calls 1 : enable EN_LOAD_BALANCE enable or disable 0 : disable 1

Enable/disable load balance between inner and outer zones

1 : enable

EN_LOAD_ORDER enable or disable 0 : disable 1

Enable/disable influence of traffic load in the candidate cell ranking process

1 : enable

EN_MCHO_NCELL enable or disable 0 : disable 1

Enable/disable flag for HO cause 14 1 : enable EN_MCHO_H_DL enable or disable 0 : disable 1


EN_MCHO_H_UL enable or disable 0 : disable 1

Enable/disable flag for HO cause 17 1 : enable EN_MCHO_RESCUE enable or disable 0 : disable 1


EN_PREFERRED_BAND_HO enable or disable 0 : disable 1




EN_PBGT_HO enable or disable 0 : disable 1


EN_MULTIBAND_PBGT_HO enable or disable 0 : disable 1

Enable/disable the power budget handovers Cause 12 and the traffic handovers Cause 23 between cells belonging to different frequency bands

1 : enable

EN_PBGT_FILTERING enable or disable 0 : disable 1

Enable/disable flag for filtering process 1 : enable

EN_PRIORITY_ORDERING enable or disable 0 : disable 1

Enables/disables the use of the parameter PRIORITY(0,n) in the candidate cell evaluation process

1 : enable

EN_RESCUE_UM enable, disable or

indefinite 0 : disable 2

Enable/disable to direct emergency handovers towards umbrellas preferentially

1 : enable 2 : indefinite

EN_RXLEV_DL enable or disable 0 : disable 1


EN_RXLEV_UL enable or disable 0 : disable 1


EN_RXQUAL_DL enable or disable 0 : disable 1


EN_RXQUAL_UL enable or disable 0 : disable 1

Enable/disable flag for HO cause 2 1 : enable EN_SPEED_DISC enable or disable 0 : disable 1

Enable/disable flag for speed discrimination on mobiles in the lower layer cells

1 : enable

EN_TRAFFIC_HO(0,n) enable or disable 0 : disable 1

Enable/disable flag for HO cause 23 from the serving cell and the cell n

1 : enable

EN_3G_HO enable or disable 0 : disable 1

Enable/disable the 2G-3G Handover 1 : enable FREEfactor_k -16 to 16 dB -16:16 8

5 correction factors of ORDER depending on free level of cell (n) expressed in number of free TCH (See [ 30]).

step size 1 dB

FREElevel_k 0 to 255 channels 0:255 8

4 boundaries for free TCH channel classification (See [ 30])

step size : 1 channel



FREQUENCY_RANGE Indicates in which frequency range the cell operates.

PGSM, DCS1800, EGSM, DCS1900, PGSM-DCS1800, EGSM-DCS1800, GSM850

0:6 0 : PGSM 1 : DCS18002 : EGSM 3 : DCS1900 4 : PGSM-DCS1800 5 : EGSM-DCS1800 6: GSM850

8

GRADE(n) -179 to 149 dB -179:+149 16

Grade Evaluation of cell n used for ranking

H_LOAD_OBJ 0 to 100% 0 : 10 8

Maximum desired load on umbrella cell step size 10 % 0 = 0 %

defined for each umbrella cell 10 = 100%

H_MIN_DWELL_TIME 0 to 120 s 0 : 0 s 1

maximum value for MIN_DWELL_TIME step size 1 s 120 : 120 s

HO Cause Handover Cause

2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 26, 27, 28, 29,30

0:29 0=0.. 29=29

8

HO_INTERCELL_ALLOWED enable or disable 0 : disable 1

Enable/disable flag for HO intercell 1 : enable HO_MARGIN(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover between cell n1 and n2 step size 1 dB HO_MARGIN_DIST(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover (distance causes) between cell n1 and n2

step size 1 dB

HO_MARGIN_LEV(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover (level causes) between cell n1 and n2

step size 1 dB

HO_MARGIN_QUAL(n1,n2) -127 to +127 dB -127 :+127 8

Basic Margin for Handover (quality causes) between cell n1 and n2

step size 1 dB

L_LOAD_OBJ 0 to 100% 0 : 10 8

Minimum desired load on umbrella cells step size 10 % 0 = 0 %

defined for each umbrella cell 10 = 100% L_MIN_DWELL_TIME 0 to 120 s 0 : 0 s 1

minimum value for MIN_DWELL_TIME step size 1 s 120 : 120s L_RXLEV_DL_H -110 to –47 dBm 0:63 8

Minimum Receive Level step size 1 dBm 0=-110 dBm

for Downlink Level Handover 63=-47 dBm



L_RXLEV_CPT_HO(0,n) -110 to –47 dBm 0:63 8

Minimum Receive Level on Downlink for handover step size 1 dBm 0=-110 dBm

from umbrella to neighbour lower layer cell n or from classical band cell to preferred band cell n

63=-47 dBm

L_RXLEV_UL_H -110 to –47 dBm 0:63 8


for Uplink (Handover) 63=-47 dBm L_RXQUAL_DL_H 0 to 7 0:7 coded with a 8

Minimum Receive Quality stepsize 0.1 stepsize of 0.1

on Downlink (Handover) for non AMR calls L_RXQUAL_DL_H_AMR 0 to 7 0:7 coded with a 8


on Downlink (Handover) for AMR calls

L_RXQUAL_UL_H 0 to 7 0:7 coded with a 8


on Uplink (Handover) for non AMR calls

L_RXQUAL_UL_H_AMR 0 to 7 0:7 coded with a 8


on Uplink (Handover) for AMR calls L_TIME_ADVANCE 0 to 63 x 3.69µs 0:63 8

Minimum Distance for Handover from the extended outer zone of a cell

LINKfactor(n1,n2) -24 to +24 dB -24:24 8

static handicap for handover evaluation between cell n1 and n2

step size 1 dB

LOAD_SV3(n) true or false 0 : false 1

Flag that indicates for AMR calls whether or not the cell n is loaded

1 : true

LOADfactor_k -16 to 0 dB -16:0 8 - correction factors of GRADE depending on

load of cell(n) expressed in percentage of TCH load (See [ 30]]

LOADlevel_k 0 to 100 (% of free TCH) 0:100 8 4 boundaries for TCH cell load classification (See [ 30]]

NBR_ADJ_3G 0 to 8 cells 0:8 8

Number of 3G cell handover adjacencies 0=0

for a 2G cell. 8=8 MIN_CONNECT_TIME 0 to 120 s 0 : 0 s 8

time in a lower layer cell to separate slow and fast MS step size 1 s 120 : 120 s MIN_DWELL_TIME 0 to 120 s 0 : 0 s 8



time reporting a neighbour lower layer cell in an umbrella cell to trigger a handover to the lower layer

step size 1 s 120 : 120 s

MS_SPEED Estimation for mobile speed discrimination process

indefinite, slow, fast

0 :2, 0 : indefinite 1 : slow 2 : fast

2

MS_TXPWR Transmit Power at MS

See [ 32] See [ 32] 5

MS_TXPWR_CONF See [ 32] See [ 32] 8

Confirmation of new Transmit Power to BS MS_TXPWR_MAX Maximum Transmit Power at MS

See [ 32] See [ 32] 8

MS_TXPWR_MAX(n) Maximum Transmit Power from MS allowed by cell n

See [ 32] See [ 32] 8

MS_TXPWR_MAX_INNER Maximum MS transmit power permissible in the inner zone of the concentric or multiband cell.

See [ 32] See [ 32] 8

MS_TXPWR_MIN Minimum Transmit Power at MS

See [ 32] See [ 32] 8

MULTIBAND_TRAFFIC_CONDITION ANY_LOAD, NOT_LOW,

HIGH 0 : 2 8

Condition on traffic load in the serving cell for a multiband handover

0 : ANY_LOAD 1 : NOT_LOW 2 : HIGH

N_BAD_SACCH 1 to 128 1:128 8

Threshold of consecutive bad SACCH frames 1=1 SACCH frames

128=128 SACCH frames

NBR_ADJ 0 to 64 cells 0:64 8

Number of adjacent 0=0

cells for this BTS 64=64 NEIGHBOUR_RXLEV(0,n) -110 to –47 dBm 0:63 8

Threshold of maximum downlink received level from step size 1 dBm 0=-110 dBm

the neighbour cells for cause 13. 63=-47 dBm OFFSET_CA 0 to 7 stepsize 0.1 0:70 8

Offset for channel adaptation hysteresis 0=0 70=7

OFFSET_CA_HIGH 0 to 7 stepsize 0.1 0:70 8

Offset for channel adaptation hysteresis under high load

0=0 70=7

OFFSET_CA_NORMAL 0 to 7 stepsize 0.1 0:70 8

Offset for channel adaptation hysteresis under normal load

0=0 70=7



OFFSET_RXQUAL_FH 0 to 7 stepsize 0.1 0:70 8

Offset added to quality thresholds 0=0 70=7

Offset_Hopping_HO 0 to 7 step size 0.1 0:70 8

Offset used in handover quality causes in case of frequency hopping

0=0 70=7

OFFSET_HO_MARGIN_INNER -127 to +127 dB -127 :+127 8

Offset which allows to take account of the radio differences between the inner and the outer zone (especially in multiband cells)

step size 1 dB

ORDER(n) -290 to 260 dB -290:+290 16

Order Evaluation of cell n used for ranking

OUTDOOR_UMB_LEV(0,n) 0 to 63 dBm 0:63 8

minimum receive level to trigger HO towards umbrella cell n for all emergency causes triggered in lower layer.

Step size 1 dBm 0=-110 dBm 63=-47 dBm

P Maximum Transmit Power for class of MS and for the corresponding frequency band (GSM900, GSM850, DCS1800, DCS1900)

See [ 32] See [ 32] 8

PBGT(n) -147 to +97 dB -147:+97 8

Power Budget evaluation of reception

of cell n related to current cell

PING_PONG_HCP Dynamic handicap applied to the precedent cell on which the call has been (see appx B). Defined on a cell basis.

0 to 20 dB stepsize 1 dB

0:20 8

PREC_LAYER_TYPE indefinite,upper, 0 : 4 8

indication of the CELL_LAYER_TYPE of the preceding cell

lower,single, indoor 0 : indefinite 1 : upper 2 : lower 3 : single 4 : indoor

PREF_LAYEindication of the preferred layer for the target cell

none, upper, lower + indoor, upper+single

0:3 ; 0 = none 1 = upper 2 = lower + indoor 3 = upper + single

2

PREFERRED_BAND none, GSM or DCS 0 = none 2

Frequency band type where the biband 1 = GSM

mobiles will be preferably directed 2 = DCS

PRIORITY(n1,n2) 0 to 5 step size 1 0:5 3

Priority of cell n2 when serving cell=n1 0: highest priority

5: lowest priority

RXLEV_DL_IH -110 to –47 dBm 0:63 8



Maximum Receive Level step size 1 dBm 0=-110 dBm

for Downlink (intracell and quality Handover) 63=-47 dBm RXLEV_UL_IH -110 to –47 dBm 0:63 8

Maximum Receive Level step size 1 dBm 0=-110 dBm

for Uplink (intracell and quality Handover) 63=-47 dBm RXLEV_DL_ZONE -110 to –47 dBm 0:63 8


for Downlink (Interzone Handover) 63=-47 dBm RXLEV_LIMIT_PBGT_HO -110 to –47 dBm 0:63 8

Minimum Level above which an handover on power step size 1 dBm 0=-110 dBm

budget is not triggered 63=-47 dBm RXLEV_UL_ZONE -110 to –47 dBm 0:63 8


for Uplink (Interzone Handover) 63=-47 dBm RXLEV_DL_FULL -110 to –47 dBm 0:63 6

Measurement of signal level assessed step size 1 dBm 0=-110

over the full set of TDMA frames 0=-47

within an SACCH block on the Downlink RXLEV_DL_SUB -110 to –47 dBm 0:63 6

Measurement of signal level assessed step size 1 dBm 0=-110

over a subset of 12 TDMA frames within 0=-47

an SACCH block on the Downlink RXLEV_NCELL(n) -110 to –47 dBm 0:63 6

Receive Level from step size 1 dBm 0=-110

neighbour cell n at MS 63=-47 RXLEV_UL -110 to –47 dBm 0:63 6

Measurement of Level on step size 1 dBm 0=-110

the Uplink 63=-47 RXLEVmin(n) -110 to –47 dBm 0:63 8

Minimum allowable received step size 1 dBm 0=-110

Level at the MS from cell n 63=-47 THR_ECNO -110 to –47dBm 0:63 coded with a 6

Ec/No threshold above which a 3G cell is selected and a handover to UTRAN. may be triggered.

Step size.1dBm 0=-110

63= -47 THR_RXQUAL_CA 0 to 7 0:7 coded with a 8

Threshold for channel adaptation stepsize 0.1 stepsize of 0.1 THR_RXQUAL_CA_HIGH 0 to 7 0:7 coded with a 8

Threshold for channel adaptation under high load stepsize 0.1 stepsize of 0.1 THR_RXQUAL_CA_NORMAL 0 to 7 0:7 coded with a 8

Threshold for channel adaptation under normal load stepsize 0.1 stepsize of 0.1



THR_RXQUAL_CAUSE_15 0 to 7 0:7 coded with a 8


on Downlink (Handover) used for Cause 15

Traffic_load(n) indefinite, low, high 0 : 2 8

Situation of the traffic in the cell n 0 : indefinite 1 : low 2 : high

U_RXLEV_DL_MCHO -110 to –47 dBm 0:63 8

High threshold of minimum Receive Level step size 1 dBm 0=-110 dBm

for Downlink (Level microcellular Handover) 63=-47 dBm

U_RXLEV_UL_MCHO -110 to –47 dBm 0:63 8

High threshold of minimum Receive Level step size 1 dBm 0=-110 dBm

for Uplink (Level microcellular Handover) 63=-47 dBm

U_TIME_ADVANCE 0 to 63 x 3.69µs 0:63 8

Maximum Distance for Handover

ZONE_HO_HYST_DL -40 to +40 dB 0 : 80 8

Hysteresis downlink for Interzone Handover from the outer

step size 1 dB

zone to the inner zone of a concentric cell or multiband cell

ZONE_HO_HYST_UL -40 to +40 dB 0 : 80 8

Hysteresis uplink for interzone Handover from the outer zone to the inner zone of a concentric cell or

step size 1 dB

multiband cell

ZONE_TYPE outer or inner 0 : Outer 1

Indicator of cell zone 1 : Inner

4.4.2 Directed retry The following parameters are used by the directed retry procedure only. NAME RANGE BIN. RANGE BITS AV_RXLEV_NCELL_DR(n) -110 to –47 dBm 0:63 8

Average receive level of neighbour step size 1 dBm 0=-110

cell n at MS for forced directed retry 63=-47 AV_RXLEV_PBGT_DR -110 to –47 dBm 0:63 8

Average receive level of serving cell step size 1 dBm 0=-110

at MS for forced directed retry (PBGT) 63=-47 EGSM_RR_ALLOC_STRATEGY 0 or 1

0: Different behaviour for E-

1



Defines the radio resource allocation strategy used in E-GSM cells

GSM capable MS.

1: Same behaviour for E-GSM capable MS:

EN_DR enable or disable 0 : disable 1

Enable/disable directed retry procedure 1 : enable EN_EXT_DR enable or disable 0 : disable 1

Enable/disable external directed retry procedure 1 : enable EN_FORCED_DR enable or disable 0 : disable 1

Enable/disable forced directed retry (cause 20) 1 : enable FREElevel_DR(n) 0 to 255 TCH channels 0:255 16

Min. threshold of free TCH channels in neighbour cell n for forced directed retry

step size : 1 channel

L_RXLEV_NCELL_DR(n) -110 to –47 dBm 0:63 8

Min. threshold of receive level at MS for step size 1 dBm 0=-110

forced directed retry to neighbour cell n 63=-47 RXLEV_NCELL(n) -110 to –47 dBm 0:63 6

Receive Level from step size 1 dBm 0=-110

neighbour cell n at MS 63=-47 SDCCH_COUNTER 0 to 31 0:31 5

Time during which SDCCH handovers are forbidden after completion of the Immediate Assignment procedure

step size : 1 SACCH frame

0=0 31=31



4.4.3 Relationships between parameters The document “BSS telecom parameters[ 27] specifies also the rules to be fulfilled by the handover parameters. The present specification is the reference document in case of discrepancy. The default values for parameters are indicated in the document [ 27]. Each relationship is either mandatory or recommended. The recommended relationships are not checked by an automatic procedure. Note : - for thresholds relative to quality measurements, the 3GPP coding is assumed, as already stated,

it is contra-intuitive. - The relationships between the parameters relative to HO preparation and the ones relative to Power

control are included. The parameters of power control are characterised by the suffix _P or _PC. For more information about them, refer to [ 32].

Mandatory relationships ### RXLEV_UL_IH > L_RXLEV_UL_H. ### U_RXLEV_UL_P > L_RXLEV_UL_H. ### RXLEV_DL_IH > L_RXLEV_DL_H. ### U_RXLEV_DL_P > L_RXLEV_DL_H. ### Relations between LOADlevel_i :

For i=1 to 3, LOADlevel_i < LOADlevel_i+1 ### Relations between LOADfactor_i :

For i=1 to 4, LOADfactor_i >= LOADfactor_i+1 ### Relations between FREElevel_i :

For i=1 to 3, FREElevel_i < FREElevel_i+1 ### Relations between FREEfactor_i :

For i=1 to 4, FREEfactor_i =< FREEfactor_i+1 ### L_LOAD_OBJ =< H_LOAD_OBJ Recommended relationships ### L_RXQUAL_UL_H >= L_RXQUAL_UL_P. ### L_RXQUAL_UL_H_AMR >= L_RXQUAL_UL_P. ### L_RXQUAL_DL_H >= L_RXQUAL_DL_P. ### L_RXQUAL_DL_H_AMR >= L_RXQUAL_DL_P. ### L_RXLEV_UL_H < L_RXLEV_UL_P. ### L_RXLEV_DL_H < L_RXLEV_DL_P. ### A_LEV_HO = 2 * A_LEV_PC. ### A_QUAL_HO = 2 * A_QUAL_PC.



### A_PBGT_HO = 2 * A_LEV_HO • T_FILTER > 0.5 seconds ### ZONE_HO_HYST >= BS_TXPWR_MAX – BS_TXPWR_MAX_INNER • L_RXLEV_NCELL_DR(n) >= RXLEVmin(n) ### FREElevel_DR(n) > N_TCH_HO(n). N_TCH_HO(n) is the number of TCH channel reserved in the best interference band (See [ 30] for

further details]. ### The parameters FREElevel_k shall be updated according to the cell load

evaluation. For instance, in a concentric cell, if EN_LOAD_OUTER = enable, only the TCH resources of the outer zone of the cell shall be considered for the determination of the parameters FREElevel_k. Regarding the EGSM TCH resources of the cell, these parameters shall also be updated according to the value of the parameters EN_LOAD_EGSM and EGSM_ALLOC_STRATEGY [ 30].

### For a microcell configuration, it is recommended : N_BAD_SACCH = RADIO_LINK_TIMEOUT_BS – N_BSTXPWR_M + 1 (for more information, see [ 32]]. Cause 7 shall be checked before the release of the channel by the autocleaning procedure.

Therefore, N_BAD_SACCH x 0.5 s < T_AUTOCLEANING_MEAS_REP + 30 s (See also [ 30]] ### It is recommended to inhibit Traffic handover towards 1 TRX cells. These cells do not have enough resources to receive incoming handovers due to congestion of neighbour cells. Moreover because of the great variation of traffic in the 1 TRX cells, their Traffic_load is always different from low. ### If PRIORITY(0,n) is used from cell of preferred band to cell of classical band, then it is recommended: EN_PREFERRED_BAND_HO = DISABLE in the classical band cell. ### If PRIORITY(0,n) is applied in order to manage inter-bands handover in a multiband network, then it is recommended: PREFERRED_BAND = none. ### If PRIORITY(0,n) is used from microcell to macrocell, then it is recommended: EN_RESCUE_UM = INDEFINITE in the microcell. • For transferring fast mobiles from a minicell n1 to an umbrella cell n2 through a power budget

handover, it is recommended : - if CELL_EV=GRADE HO_MARGIN(n1,n2)=-127dB LINKfactor(n1,n2)=24dB • THR_RXQUAL_CA_HIGH >=THR_RXQUAL_CA_NORMAL • OFFSET_CA_HIGH >= OFFSET_CA_NORMAL • A_QUAL_CA_FR_HR >= A_QUAL_CA_HR_FR



• When the channel adaptation handovers are enabled together with Causes 15 and 16 in the cell, it is recommanded to use the same window size for averaging the quality measurements of Cause 15, 16 and 26: A_QUAL_CA_HR_FR = A_QUAL_HO and W_QUAL_CA = W_QUAL_HO.

• SDCCH_COUNTER <= T_SDCCH_PC. The parameter T_SDCCH_PC is defined in [ 32]. • In multiband cells, setting both flags EN_LOAD_OUTER and EN_LOAD_BALANCE to enable

must be avoided. Setting the flag EN_LOAD_OUTER to enable is useful when the population of monoband MS is higher than biband ones, whereas setting the flag EN_LOAD_BALANCE to enable is useful when the population of biband MS is higher than monoband ones.

### Compatibility checking between cell configurations and handover inhibition flags. For the definition of the different cell profiles, see section 2.4 The following relationships are mandatory, whatever CELL_BAND_TYPE. - Single cell profile

EN_MCHO_NCELL = DISABLE. EN_MCHO_H_DL = DISABLE. EN_MCHO_H_UL = DISABLE. EN_MCHO_RESCUE = DISABLE EN_SPEED_DISC = DISABLE

- Micro cell profile

EN_MCHO_NCELL = DISABLE if there is no indoor layer

- Mini cell profile

EN_MCHO_NCELL = DISABLE if there is no indoor layer EN_MCHO_H_DL = DISABLE. EN_MCHO_H_UL = DISABLE. EN_MCHO_RESCUE = DISABLE

- Umbrella cell profile

EN_MCHO_H_DL = DISABLE. EN_MCHO_H_UL = DISABLE. EN_MCHO_RESCUE = DISABLE

- Extended inner and outer cell profile HO_SDCCH_INHIBIT = DISABLE (SDCCH handovers are disabled) FREElevel_DR = 255 for the serving inner and outer cell EN_MCHO_NCELL = DISABLE. EN_MCHO_H_DL = DISABLE. EN_MCHO_H_UL = DISABLE. EN_MCHO_RESCUE = DISABLE EN_SPEED_DISC = DISABLE



- Concentric cell profile

EN_MCHO_H_DL = DISABLE. EN_MCHO_H_UL = DISABLE. EN_MCHO_RESCUE = DISABLE EN_MCHO_NCELL = DISABLE EN_SPEED_DISC = DISABLE

- Concentric Umbrella cell profile EN_MCHO_H_DL = DISABLE. EN_MCHO_H_UL = DISABLE. EN_MCHO_RESCUE = DISABLE

- Indoor micro cell profile

EN_MCHO_NCELL = DISABLE.

### Cells in the preferred band.

If BCCH_FREQUENCY is in the P-GSM or GSM850 frequency band and if PREFERRED_BAND = GSM,

or if BCCH_FREQUENCY is in the DCS1800 or DCS1900 frequency band, and if PREFERRED_BAND = DCS,

then it is recommended to check that EN_PREFERRED_BAND_HO = DISABLE. ### Cells having different frequency bands Providing the conditions:

− the cells n1 and n2 are adjacent − the flag EN_MULTIBAND_PBGT_HO is set to disable in the cell n1 and in the cell n2 or

CELL_LAYER_TYPE(n1) <> CELL_LAYER_TYPE(n2) − the frequency band of the cell n1 is different from the one of cell n2. In other words,

If BCCH_FREQUENCY(n1) is in the P-GSM or GSM850 frequency band.

And BCCH_FREQUENCY(n2) is in the DCS1800 or DCS1900 frequency band or if BCCH_FREQUENCY(n1) is in the DCS1800 or DCS1900 frequency band and BCCH_FREQUENCY(n2) is in the P-GSM or GSM850 frequency band then it is recommended: HO_MARGIN_QUAL(n1,n2) = -127 dB HO_MARGIN_LEV(n1,n2) = -127 dB HO_MARGIN_DIST(n1,n2) = -127 dB



5 GLOSSARY

5.1 Abbreviations 3GPP 3rd Generation Partnership Project AMR Adaptive multi-rate ARFCN Absolute Radio Frequency Channel Number BA BCCH-allocation BFI Bad Frame Indication BS Base Station BSC Base Station Controller BSIC Base Station Identity Code BSS Base Station Subsystem BTS Base Transceiver Station CA Channel adaptation or Changes allowed dB deciBel DC Direct Current DR Directed Retry or dual rate DTX Discontinuous transmission DCS-1800 Digital Cellular system using the uplink frequency band [1710,...,1785] MHz and the

downlink frequency band [1805,...,1880] MHz DCS-1900 Digital Cellular system using the uplink frequency band [1850,...,1910] MHhz and the

downlink frequency band [1930,...,1990] Mhz E-GSM Extended-GSM Ec/No Energy per chip divided by the power density per band measured on the Primary

CPICH by the terminal. FH Frequency Hopping FR Full rate GSM850 Global System for Mobile communications using the uplink frequency band

[824,...,849] MHz and the downlink frequency band [869,...,894] MHz GSM-900 Global System for Mobile communications using the uplink frequency band

[880,...,915] MHz and the downlink frequency band [925,...,960] MHz (including the G1 band)

HO Handover HOP Handover preparation HOM Handover management HR Hall rate LCS Location Services LOS Line Of Sight MSC Mobile Switching Centre MS Mobile Station O&M Operation and Maintenance OMC Operation and Maintenance Centre P-GSM Primary-GSM PBGT Power Budget PC Power Control RAM Resource allocation and management SACCH Slow associated control channel SADT Structured Analysis and Design Technics SDCCH Slow dedicated control channel SDL Specification Description Language SMLC Serving Mobile Location Centre TFO Tandem free operation TCH Traffic channel TCH/FS Traffic channel Full Speech TCU Terminal Control Unit TOA Time Of Arrival TRX Transmitter Receiver



TS Technical Specification UTRAN Universal Terrestrial Radio Access Network Note : all the parameters and variables used in the algorithms are thoroughly described in the dedicated sections and in section 4.

5.2 Definitions - internal HO : the handover execution is controlled by the BSC (only intracell and intercell-intra-

BSC HO). - external HO : the handover execution is controlled by the MSC (necessary for all intercell-inter-

BSC HO, possible for intercell-intra-BSC HO). - intracell HO : handover between two channels of the same cell. - intercell HO : handover between two channels of adjacent cells. The old channel belongs to the

serving cell, the new channel to the target cell. - Inter-system HO: Here covers the 2G-3G handover between a serving 2G cell and a 3G cell

external to the BSC. The handover execution is controlled by the MSC. - intra-BSC HO : the serving cell and the target cell belong to the same BSC. - Interlayer HO: An interlayer HO is an intercell HO which is performed between two different

layers. This HO is encountered in a hierarchical environment. - Intralayer HO: An intralayer HO is an intercell HO which is performed between two cells pertaining

to the same layer. - interzone HO : intracell handover between the inner zone and the outer zone of a concentric or

multiband cell configuration. - intrazone HO : intracell handover within a zone (inner or outer) of a concentric or multiband cell

configuration. - directed retry : handover from SDCCH to TCH when the serving cell is congested at the starting

time of the assignment procedure. In this release of the ALCATEL BSS, the directed retry is internal or external to the BSS. - decibel unit : The “decibel” is a unit currently used in radio communications. It is the logarithmic expression of the ratio of two terms : N dB = 10 log10(P1/P2) with P1, P2 = signal power. M dB = 20log10(V1/V2) with V1, V2 = signal voltage. The “dB” is the usual unit for the gains of power or voltage. The dBm is a variant of the dB unit : Power expressed in dBm = 10 log10(P) with P expressed in mW. Ex : 1W corresponds to 30 dBm. 1pW (10-9 mW) corresponds to –90dBm.



The dBW is a variant of the dB unit : Power expressed in dBW = 10 log10(P) with P expressed in W. Ex : 10W corresponds to 10 dBW. The dBi is a variant of the dB unit which is currently used for the antenna gains. The index “i” means “isotropic” as an antenna gain is referred to the gain of an isotropic antenna (same gain in all directions). - log normal fading : The signal attenuation during propagation is the product of small independent

attenuations. Expressed in dB, this attenuation becomes a random variable which has a normal (or gaussian) pdf, (central limit theorem). The log normal fading is defined as a centred (mean value is 0) gaussian variable that must be added to the mean signal value resulting from propagation attenuation in order to have the reported value of the signal level (by MS or BS).

The log normal fading standard deviation ### normally ranges about 6-7 dB in urban macrocellular environment and about 5 dB for rural environment.



6 ANNEXES

6.1 Annex A Power budget equation The Power budget criterion PBGT is used to estimate the difference of path loss between two neighbouring cells.

PBGT(n) = AV_RXLEV_NCELL(n) – AV_RXLEV_PBGT_HO - (BS_TXPWR_MAX – AV_BS_TXPWR_HO) - (MS_TXPWR_MAX(n) – MS_TXPWR_MAX)

- PING_PONG_MARGIN(n,call_ref)

PBGT_DR(n) = AV_RXLEV_NCELL_DR(n) – AV_RXLEV_PBGT_DR - (BS_TXPWR_MAX – AV_BS_TXPWR_DR)

- (MS_TXPWR_MAX(n) – MS_TXPWR_MAX)

with : - AV_RXLEV_NCELL(n) : average of RXLEV_NCELL(n) over A_PBGT_HO or A_PBGT_DR

measurements (neighbour cell(n)). - AV_RXLEV_NCELL_DR(n) : average of RXLEV_NCELL(n) over A_PBGT_DR measurements

(neighbour cell(n)). - AV_RXLEV_PBGT_HO : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUB over

A_PBGT_HO measurements (serving cell). - AV_RXLEV_PBGT_DR : average of the received levels RXLEV_DL_FULL or RXLEV_DL_SUB over

A_PBGT_DR measurements (serving cell). - BS_TXPWR_MAX : max power of the BTS in the serving cell (fixed value for each BTS). - AV_BS_TXPWR_HO : average of the BS_POWER values over A_PBGT_HO measurements. - AV_BS_TXPWR_DR : average of the BS_POWER value over A_PBGT_DR measurements. - MS_TXPWR_MAX(n) : max power level the MS is allowed to use in its neighbour cell(n). - MS_TXPWR_MAX : max. power the MS is allowed to use in the serving cell. - PING_PONG_MARGIN(n,call_ref) is a penalty put on the cell n if :

it is the immediately precedent cell on which the call has been, this cell belongs to the same BSC as the serving cell, the call has not performed a forced directed retry towards the serving cell, less than T_HCP seconds have elapsed since the last handover. In this case PING_PONG_MARGIN(n,call_ref) = PING_PONG_HCP., If the call was not precedently on cell n, or if the preceding cell was external, or if the call has just performed a forced directed retry, or if the timer T_HCP has expired, then PING_PONG_MARGIN(n,call_ref) = 0

With abstraction of the PING_PONG_MARGIN, which is purely a handicap given to the preceding cell for a certain time, the PBGT can be described in two steps : ### ###BCCH = AV_RXLEV_NCELL(n) – (AV_RXLEV_PBGT_HO + C) with C = BS_TXPWR_MAX – AV_BS_TXPWR_HO.



###BCCH corresponds to the difference of received BCCH signal levels. A correction factor C is taken into account for the serving cell, because the received signal level (i.e. AV_RXLEV_PBGT_HO) may not be measured on BCCH, Then, another correction factor must be taken into account because the maximum BS powers of the serving and neighbouring cells may be different : ### ###TXPWR = MS_TXPWR_MAX(n) – MS_TXPWR_MAX. As the first step of calculation is based on the downlink parameters, this correction factor should be based on the maximum BS powers used in the serving and neighbouring cells. Two reasons (which are not completely decorrelated) for not using the BS powers can be envisaged : - for a given cell, the 3GPP standard does not specify formally the maximum BS power of the

neighbouring cells. Only BS_TXPWR_MAX is defined (it is sent on the air interface), - it is not easy for the evaluating BSC to know the maximum BS powers of the neighbouring cells. The use of the maximum MS powers requires that the difference of MS powers is equal to the difference of BS powers. This condition is met in most cases. If it is not the case, the difference can be corrected by the operator with the HO_MARGIN(0,n) parameter (HO hysteresis). PBGT >0 : the neighbour cell is more advantageous as the path loss is less than in the current cell. PBGT <0 : the serving cell is more advantageous as the current cell. The PBGT equation (without temporary handicap) can be interpreted in another way. PBGT = ###BCCH - ###TXPWR The PBGT is a balance or a trade-off between two opposite indicators. As a matter of fact : ### ###BCCH > 0 : the neighbouring cell n is more advantageous than the serving cell as the

reception of BCCH is better. ### ###BCCH < 0 : the neighbouring cell n is more disadvantageous than the serving cell. ### ###TXPWR > 0 : the neighbouring cell n is more disadvantageous than the serving cell as the

maximum permissible power of the MS is higher. ### ###TXPWR < 0 : the neighbouring cell n is more advantageous than the serving cell. The PBGT can be seen as a balance, at MS side, between a probability to have a better reception and the probability of requests of transmission at higher levels in the neighbouring cells.

6.2 Annex B Recapitulation of the cell types allowed for the serving and the candidate cell for each handover cause

Handover causes Serving cell / zone types Target cell / zone types Too low quality uplink (cause 2) All All cells except serving cell

(See note 1) Too low level uplink (cause 3) All All cells except serving cell

(See note 1) Too low quality downlink (cause 4) All All cells except serving cell

(See note 1) Too low level downlink (cause 5) All All cells except serving cell

(See note 1)



Too long distance (cause 6) All All cells except serving cell (See note 1)

Bad SACCH frames (cause 7) CELL_DIMENSION_TYPE = micro

All cells except serving cell (See note 1)

Too low level uplink, inner zone (cause 10)

CELL_PARTITION TYPE = concentric

ZONE_TYPE = inner

Same cell ZONE_TYPE = outer

Too low level downlink, inner zone (cause 11)

CELL_PARTITION TYPE = concentric

ZONE_TYPE = inner

Same cell ZONE_TYPE = outer

Power budget (cause 12)

(CELL_LAYER_TYPE = single or

CELL_LAYER_TYPE = upper)

CELL_LAYER_TYPE = single or

CELL_LAYER_TYPE = upper

Same CELL_BAND_TYPE (if EN_MULTIBAND_PBGT_HO =

disable) (See note 2) The MS is not in the inner zone of a multiband cell

CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = lower or upper (if MS_SPEED = fast)

Same CELL_BAND_TYPE (if

EN_MULTIBAND_PBGT_HO = disable) (See note 2)

CELL_LAYER_TYPE = indoor CELL_LAYER_TYPE = indoor or

upper (if MS_SPEED = fast)


disable) (See note 2) Power budget (cause 12) The MS is in the inner zone of a multiband cell


CELL_LAYER_TYPE = upper)


CELL_LAYER_TYPE = upper) and FREQUENCY_RANGE= PGSM-DCS1800 or EGSM-

DCS1800 (if EN_MULTIBAND_PBGT_HO =

disable) (See note 2) CELL_LAYER_TYPE = lower (CELL_LAYER_TYPE = lower

or upper (if MS_SPEED = fast)) and FREQUENCY_RANGE = PGSM-DCS1800 or EGSM-


disable) (See note 2) CELL_LAYER_TYPE = indoor (CELL_LAYER_TYPE = indoor

or upper (if MS_SPEED = fast)) and FREQUENCY_RANGE = PGSM-DCS1800 or EGSM-


disable) (See note 2) Too high level uplink or downlink outer zone (cause 13)

CELL_PARTITION_TYPE = concentric

ZONE_TYPE = outer

Same cell ZONE_TYPE = inner



High level in neighbour lower or indoor layer cell for slow mobile (cause 14) The MS is in the inner zone of a multiband cell


CELL_LAYER_TYPE = lower or indoor and

(EN_BI-BAND_MS(n)=ENABLE or CELL_BAND_TYPE(n) <>

CELL_BAND_TYPE(0))

CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = indoor

and (EN_BI-BAND_MS(n)=ENABLE

or CELL_BAND_TYPE(n) <> CELL_BAND_TYPE(0))

High level in neighbour lower or indoor layer cell for slow mobile (cause 14) The MS is not in the inner zone of a multiband cell


and CELL_BAND_TYPE = PREFERRED_BAND

CELL_LAYER_TYPE = lower or indoor and

(EN_BI-BAND_MS(n)=ENABLE or CELL_BAND_TYPE(n) =

PREFERRED_BAND)

CELL_LAYER_TYPE = upper and

CELL_BAND_TYPE <> PREFERRED_BAND

CELL_LAYER_TYPE = lower or indoor

CELL_LAYER_TYPE = lower

and CELL_BAND_TYPE = PREFERRED_BAND

CELL_LAYER_TYPE = indoor and

(EN_BI-BAND_MS(n)=ENABLE or CELL_BAND_TYPE(n) =

PREFERRED_BAND)

CELL_LAYER_TYPE = lower and


CELL_LAYER_TYPE = indoor

Too high interference level uplink (cause 15)

All Same cell

Too high interference level downlink (cause 16)

All Same cell

Too low level uplink compared to High Threshold (cause 17)

CELL_DIMENSION_TYPE = micro


Too low level downlink compared to High Threshold (cause 18)

CELL_DIMENSION_TYPE = micro


Forced directed retry (cause 20) All All cells except serving cell High level in neighbour cell in the preferred band (cause 21)


CELL_BAND_TYPE = PREFERRED_BAND

Too short distance (cause 22) CELL_RANGE = extended outer

All cells except serving cell

Traffic handover (cause 23) The MS is not in the inner zone of a multiband cell






disable) (See note 2)

CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = lower





CELL_LAYER_TYPE = indoor CELL_LAYER_TYPE = indoor


disable) (See note 2) Traffic handover (cause 23) The MS is in the inner zone of a multiband cell




CELL_LAYER_TYPE = upper) and

FREQUENCY_RANGE = PGSM-DCS1800 or EGSM-



CELL_LAYER_TYPE = lower CELL_LAYER_TYPE = lower and

FREQUENCY_RANGE = PGSM-DCS1800 or EGSM-


disable) (See note 2) CELL_LAYER_TYPE = indoor CELL_LAYER_TYPE = indoor

and FREQUENCY_RANGE =

PGSM-DCS1800 or EGSM-DCS1800 (if

EN_MULTIBAND_PBGT_HO = disable) (See note 2)

General capture handover (cause 24) The MS is in the inner zone of a multiband cell

All EN_BI-BAND_MS(n)=ENABLE or

CELL_BAND_TYPE(n) <> CELL_BAND_TYPE(0)

General capture handover (cause 24) The MS is not in the inner zone of a multiband cell

CELL_BAND_TYPE = PREFERRED_BAND

EN_BI-BAND_MS(n)=ENABLE or

CELL_BAND_TYPE(n) = PREFERRED_BAND



Fast traffic handover (Cause 28) (CELL_PARTITION_TYPE = concentric and ZONE_TYPE =

outer) or

CELL_PARTITION_TYPE = normal


TFO handover (Cause 29) All Same cell Move from PS to CS zone (cause 30)

All Same cell

2G-3G Handover Ec/No All 3G cell Note 1: The serving cell is a candidate cell if the MS is connected to the inner GSM 1800 zone of a multiband cell. Note 2: For handover causes 12 and 23, the conditions on the frequency band (“Same CELL_BAND_TYPE” and “FREQUENCY_RANGE = PGSM-DCS1800 or EGSM-DCS1800”) are only checked by the BSC if the EN_MULTIBAND_PBGT_HO flag is set to disable.



6.3 Annex C Compliancy with the 3GPP requirements Handover algorithm As stated in [ 38] : "the exact handover strategies will be determined by the network operator". Document [ 38] provides also a "detailed example of a basic overall algorithm" which is the basis of the one implemented in the ALCATEL BSS. The complete ALCATEL algorithm is described in section 3.2 of this document. For further details about the compliance of this function with the requirements of the 3GPP Technical Specification 05.08 (See [ 38] and [ 19]). Directed retry algorithm The 3GPP standard has not specified any requirement. The algorithm is implementation dependent.

END OF DOCUMENT

HO Preparation

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