O2RD 04 021 Compressed Mode Strategy 1

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O2 'Do Once' Radio Design Document Reference : O2RD/04/021 Compressed Mode Scenarios and Strategy Page : 1 of 52

Version : Issue 1 Date: 22/04/04

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Compressed Mode Scenarios and Strategy Document Type: Report

Summary:

Inter-system and inter-frequency handovers typically require a set of compressed mode neighbour cell measurements. Handover may be triggered for reasons of coverage, load or traffic. This report focuses upon coverage reason handover. Handover scenarios have been categorised using four dimensions – rate of change of propagation conditions, service, triggering mechanism and measurement purpose. These dimensions have been used as a basis for balancing trade-offs and generating recommended compressed mode configurations. The 3GPP compressed mode parameter set has been identified and compared with the Nokia compressed mode parameter set. The O2 preferred compressed mode configuration has been identified based upon a set of primarily theoretical arguments. Field experience has been presented and used to a limited extent. The impact of using the Nokia default configuration rather than the O2 preferred configuration has been evaluated. Recommendations have been made in terms of adjusting configurable RNC parameters and requesting changes to non-configurable RNC parameters.

Author(s): Chris Johnson Author(s) Operating Business:

Nokia UK

Date: 22nd April 2004 Version: Issue 1 Reference: O2RD/04/021

Approved by: Name: Oscar Clop

Role / Authority: Signature:

Date:

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DISTRIBUTION LIST

O2 Nokia Ian Miller Aleksi Toikkanen Brendan O'Reilly Mike Lawrence Tony Conlan George Grayland Nick Outram Chris Johnson Oscar Clop Colm Jones Jude Saldanha Filippo Belloni Lara Pazienza

CHANGE HISTORY

Tool used Microsoft Word 2000 File location Create, save & print dates 08/02/2002 00:00 22/04/2004 18:04:00 27/04/2011 09:59:00

Version Date Changed by Changes Draft A 08/02/04 Chris Johnson Document created Issue 1 22/04/04 Chris Johnson Raised to Issue 1 status

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EXECUTIVE SUMMARY: Compressed mode forms an essential part of inter-system and inter-frequency handover for the majority of dual mode UE. It may be avoided in some cases if UE are equipped with a dual receiver. Inter-system handover will be more important than inter-frequency handover until O2 starts to deploy dual carrier Node B. Inter-system handover will be required at coverage boundaries between the WCDMA and GSM systems. These boundaries may or may not be planned. It is desirable to maximise the coverage of the WCDMA system and minimise the quantity of inter-system handovers. The extent of WCDMA connected mode coverage is defined by the set of thresholds which are used to trigger inter-system handover. The extent of WCDMA idle mode coverage is defined by the equivalent set of thresholds for cell re-selection. Compressed mode scenarios can be categorised using four dimensions. These dimensions are the measurement purpose (GSM RSSI, BSIC identification, FDD measurement); the service being used (AMR speech, RT data, NRT data); the triggering mechanism (uplink transmit power, downlink transmit power, CPICH Ec/Io, CPICH RSCP, uplink quality); and the rate of change of propagation conditions (high, low). A compressed mode strategy may be developed for each combination of the variables associated with these four dimensions. Compressed mode functionality and signalling has been standardised by 3GPP. The standardisation of compressed mode allows both inter-operability and flexibility. The flexibility means that the implementation of compressed mode involves making a set of design decisions. Nokia has implemented compressed mode according to the 3GPP specifications using a combination of configurable and non-configurable RNC parameters. These parameters provide some but not complete flexibility. Some aspects of compressed mode have been implemented without parameterisation. This report has identified the trade-offs associated with each compressed mode parameter. The Nokia default configuration and the O2 preferred configuration have been identified. The impact of applying the Nokia default configuration rather than the O2 preferred configuration has been evaluated. This evaluation has been based primarily upon theoretical expectations and arguments. A relatively limited quantity of field trial experience has been made available for this report. The quantity of experience will increase throughout 2004 as O2’s WCDMA network performance is evaluated and refined. A number of configurable parameter changes have been proposed within the recommendations section of this report. These parameter changes can be made by O2 but should be tested during a localised parameter trial prior to deploying across a large area. The majority of arguments for these proposed parameter changes are theoretical rather than being based upon field trial experience. A number of non-configurable parameter changes have been proposed within the recommendations section of this report. These parameter changes cannot be made by O2 and require requests to be made to Nokia product line for future implementation. Requests for these parameter changes should be prioritised with other outstanding requests to Nokia product line. The majority of arguments for these proposed parameter changes are theoretical rather than being based upon field trial experience.

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TABLE OF CONTENTS

1. Scope and Objectives ............................................................................................................ 6

2. Introduction .......................................................................................................................... 7

3. Scenarios ............................................................................................................................... 9

3.1. Coverage Reason ................................................................................................................................. 9 3.2. Load Reason ...................................................................................................................................... 11 3.3. Traffic Reason .................................................................................................................................... 12

4. Compressed Mode Methods and Patterns ......................................................................... 13

4.1. Method ............................................................................................................................................... 14 4.2. Timing ................................................................................................................................................ 18 4.3. Direction ............................................................................................................................................ 21 4.4. Power Control .................................................................................................................................... 21 4.5. Scrambling Code ................................................................................................................................ 23 4.6. Downlink Frame Type ....................................................................................................................... 24 4.7. Measurement Reporting ..................................................................................................................... 24 4.8. Other Configuration Parameters ........................................................................................................ 25

5. Preferred Compressed Mode Methods and Patterns ........................................................ 26


6. Impact of using the Nokia Default Parameter Set............................................................. 40


7. Field Experience ................................................................................................................. 44

7.1. Spreading Factor Division by 2 ......................................................................................................... 44 7.2. Higher Layer Scheduling ................................................................................................................... 45 7.3. Puncturing .......................................................................................................................................... 45

8. Recommendations .............................................................................................................. 46

9. Conclusions ......................................................................................................................... 49

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10. References ........................................................................................................................... 50

11. Abbreviations ..................................................................................................................... 51

Appendix A. Example UE capability message ...................................................................... 52

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1. Scope and Objectives The scope of this report is based upon the timescales of Nokia RNC software release RAN1.5.2.ED2 and the contents of the 3GPP R99 specifications. These timescales limit the use of compressed mode to coverage reason handovers. Load and traffic reason handover scenarios are referenced although they are not addressed in detail. Compressed mode is treated as one part of the inter-frequency and inter-system handover procedures. Thresholds defining the initial triggering of these handover procedures are outside the scope of this report although the triggering mechanisms themselves are accounted for when defining the compressed mode strategies. The handover and associated service break subsequent to the use of compressed mode are also outside the scope of this report. Although the scope includes both inter-frequency and inter-system handovers, the focus has been directed towards inter-system handovers. This is aligned with the expectation that a second 3G carrier is unlikely to be deployed within the timescales of RAN1.5.2.ED2. The report is primarily theoretical although one section is included to present indicative compressed mode performance observed during Nokia field trials. The objectives of this report are to provide:

• a description of scenarios where the use of compressed mode will be required • a strategy defining how compressed mode should be customised for each scenario • a specification of the compressed mode parameter sets used by 3GPP and Nokia • recommendations for how the 3GPP compressed mode parameter set can be customised for each

measurement purpose and for each service type • An evaluation of the impact of using Nokia’s compressed mode implementation with Nokia’s

recommended compressed mode parameter set • Recommendations for refining Nokia’s compressed mode parameter set and if appropriate, for

requesting changes to Nokia’s compressed mode implementation

The report has been generated with the intention of making it applicable to O2 business operations in the UK, Ireland and Germany.

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2. Introduction Compressed mode forms an essential part of inter-system and inter-frequency handover for the majority of dual mode UE. It may be avoided in some cases if UE are equipped with a dual receiver. Inter-system handover will be more important than inter-frequency handover until O2 starts to deploy dual carrier Node B. Inter-system handover will be required at coverage boundaries between the WCDMA and GSM systems. These boundaries may or may not be planned. It is desirable to maximise the coverage of the WCDMA system and minimise the quantity of inter-system handovers. The extent of WCDMA connected mode coverage is defined by the set of thresholds which are used to trigger inter-system handover. The extent of WCDMA idle mode coverage is defined by the equivalent set of thresholds for cell re-selection. There is a delay associated with completing the compressed mode measurements procedure. This means that the thresholds used to trigger inter-system handover must incorporate a back-off that allows sufficient time for the compressed mode procedure and for the handover to occur prior to the WCDMA radio links failing. The back-off should be minimised to avoid a significant reduction in WCDMA coverage. Large back-offs will also result in more frequent inter-system handovers. It is possible to define a strategy that tunes the back-off factor on a per scenario basis. For example, low mobility scenarios may have a smaller back-off as a result of UE having more time to complete the compressed mode measurements. Alternatively, the same back-off could be applied to all scenarios and greater time could be allowed for compressed mode measurements in low mobility scenarios. This strategy would have the effect of making compressed mode measurements more reliable in low mobility scenarios. The delay associated with compressed mode measurements depends to a large extent upon the service and whether the associated handover is inter-system or inter-frequency. Inter-system handover of real time services have a relatively large delay associated with them due to the requirement to complete GSM RSSI measurements and GSM BSIC identification. BSIC identification is not required for the inter-system handover of non-real time services. Figure 1 illustrates these measurement purposes.

Inter-System Handover

Inter-Frequency Handover

Real Time Services

Non-Real Time Services

• GSM RSSI Measurement• BSIC Identification

• GSM RSSI Measurement

• FDD Measurement

• FDD Measurement

Inter-System Handover

Inter-Frequency Handover

Real Time Services

Non-Real Time Services

• GSM RSSI Measurement• BSIC Identification

• GSM RSSI Measurement

• FDD Measurement

• FDD Measurement

Figure 1 – Compressed mode measurement purposes as a function of service and handover type

The compressed mode delay also depends upon the configuration of compressed mode in terms of its transmission gaps and transmission gap patterns. Smaller transmission gaps and longer transmission gap patterns tend to reduce the impact of compressed mode but also increase the compressed mode delay. The current strategy is to complete compressed mode with a short delay such that handover can occur rapidly and the back-offs associated with the inter-system handover triggering mechanisms can be reduced. Compressed mode should not however be completed so rapidly that its reliability becomes poor. Transmission gaps may be generated using a set of standardised compressed mode methods. These methods include puncturing, spreading factor reduction, and higher layer scheduling. Puncturing is only applicable to the downlink. The R99 3GPP specifications limit the use of puncturing and higher layer scheduling according to whether the transport channel starting position is fixed or flexible. For example, higher layer scheduling is only applicable to transport channels using flexible starting positions. The AMR speech service uses fixed starting positions in the downlink direction to allow UE to complete blind AMR bit rate detection.

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This means that higher layer scheduling can not be applied to the AMR speech service in the downlink. It can however be applied to the AMR speech service in the uplink. Each compressed mode method has a different impact upon system performance. Puncturing is applied on a per TTI basis and requires an increased SIR target to achieve the Eb/No. Increasing the SIR target has an impact upon both the coverage and capacity of the system. Spreading factor reduction is applied on a per frame basis and also requires an increased SIR target. Higher layer scheduling is applied on a per TTI basis and results in a reduced service throughput. In this case the MAC layer is responsible for selecting a lower transport format combination. All compressed mode methods have a similar impact upon the performance of inner loop power control, i.e. transmit power control commands are stopped during the transmission gaps and the average transmit power tends to increase. There is a requirement to select and customise each compressed mode method on a per scenario basis. Compressed mode functionality and signalling has been standardised by 3GPP. The relevant specifications are listed as references [1], [2], [3], [4], [5], [6], [7], [8]. The standardisation of compressed mode allows both inter-operability and flexibility. The flexibility means that the implementation of compressed mode involves making a set of design decisions. Nokia has implemented compressed mode according to the 3GPP specifications using a combination of configurable and non-configurable RNC parameters. These parameters provide some but not complete flexibility. Some aspects of compressed mode have been implemented without parameterisation. The contents of this report are equally applicable to Omni-Transmit Sector Receive (OTSR) and Sector Transmit Sector Receive (STSR) Node B. Separate OTSR and STSR compressed mode strategies are not required. It is more likely that separate OTSR and STSR strategies are required for inter-system and inter-frequency handovers. For example, the CPICH RSCP inter-system handover triggering threshold is likely to be different for OTSR and STSR Node B. The term OTSR is equivalent to Nokia’s term Roll-Out Configuration (ROC) whereas the term STSR is equivalent to Nokia’s term Capacity Enhanced Configuration (CEC).

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3. Scenarios Dual mode UE may be required to handover from the WCDMA system to the GSM system as a result of moving into an area of relatively poor WCDMA coverage. Handover may also be required if the WCDMA system becomes heavily loaded or if the UE requests a service which is provided by the GSM system. These reasons for inter-system handover provide the basis for defining a set of compressed mode scenarios:

� coverage reason compressed mode � load reason compressed mode

� traffic reason compressed mode

These inter-system handover reasons may also be applied to inter-frequency handovers. Inter-system handovers require compressed mode transmission gaps for RSSI measurements and BSIC identification. Inter-frequency handovers require compressed mode transmission gaps for FDD measurements.

3.1. Coverage Reason Coverage reason compressed mode may be used for either inter-frequency or inter-system handover. Inter-frequency handover will be required at a coverage boundary between a group of Node B which have two carriers assigned and a group of Node B which have only a single carrier assigned. UE using the second carrier belonging to a dual carrier Node B will be required to handover onto the first carrier as they move toward a single carrier Node B. Inter-frequency handover is less likely to be required for coverage reasons when a UE is located within an area of contiguous dual carrier Node B coverage. The coverage footprint of the two carriers will be approximately equal and there will be little or no coverage gain when moving from one carrier to the other. Inter-system handovers will be required at coverage boundaries between the WCDMA and GSM systems. Coverage boundaries may be either planned or a result of a gap in planned coverage. Coverage reason compressed mode scenarios in terms of their location are illustrated in Figure 2.

Edge of Planned WCDMA Coverage

Gap within Planned WCDMA Coverage

Coverage Based

• Coverage boundary at the edge of an urban/suburban area

• Coverage boundary within an urban/suburban area

• Coverage boundary on an open stretch of road

• Coverage boundary on an open stretch of rail

• Coverage boundary when leaving a railway station

• Coverage boundary when leaving an airport

• Coverage boundary when leaving a motorway service station

• Coverage boundary when leaving a special events venue

• Coverage boundary when entering a building

• Coverage hole within an urban/suburban area

• Coverage hole within a building

• Coverage hole on an open stretch of road

• Coverage hole on an open stretch of rail



Coverage Based














Figure 2 – Coverage reason compressed mode scenarios (location)

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It is equally important for compressed mode and inter-system handover to be successful in all of these location based scenarios. In all cases there is a requirement to maximise the reliability of the compressed mode and inter-system handover procedures. Some scenarios also have a requirement to complete the compressed mode and inter-system handover procedures more rapidly than other scenarios. This requirement is generated by the rate of change of propagation conditions associated with each scenario. If coverage is changing relatively slowly for a scenario then more time can be spent completing inter-frequency and inter-system measurements to help ensure that the subsequent handover is reliable. Figure 2 can be expanded by considering that dual mode UE may encounter any of these scenarios while using any of the supported services. Figure 3 expands Figure 2 to include a service dependence.



Coverage Based














Service 1

Service 2

Service 3

Service 1

Service 2

Service 3



Coverage Based














Service 1

Service 2

Service 3

Service 1

Service 2

Service 3

Figure 3 – Coverage reason inter-system handover scenarios (location and service)

The set of services supported by the WCDMA system can be categorised according to how sensitive they are to the effects of compressed mode. The selection of the various compressed mode methods and parameter sets should account for the service requirements. Real time data services should be configured such that compressed mode does not cause a throughput reduction. The AMR speech service is able to incur a reduction in throughput if a lower AMR bit rate is available. Table 1 presents a set of example services which shall be considered when defining compressed mode strategies on a per service basis.

Application CN Domain Traffic Class AMR Speech CS Conversational Video Call CS Conversational Video Streaming CS Streaming Audio Streaming CS Streaming Internet Browsing PS Interactive WAP Browsing PS Interactive Interactive Gaming PS Interactive File Transfer PS Background Email PS Background

Table 1 – Example set of WCDMA services

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Conversational and streaming services are treated as real time service and assumed to be throughput sensitive (with the exception of the speech AMR service which has the ability to operate at a reduced throughput). Interactive and background services are treated as non-real time services and assumed to be less throughput sensitive. Figure 3 can be expanded by considering that a range of coverage related mechanisms may be used to trigger compressed mode measurements and the subsequent handover. Figure 4 expands Figure 3 to include a set of coverage related triggering mechanisms.



Coverage Based














Service 1

Service 2

Service 3

Service 1

Service 2

Service 3

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Triggering Mechanisms



Coverage Based














Service 1

Service 2

Service 3

Service 1

Service 2

Service 3

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Triggering Mechanisms

Figure 4 – Coverage reason inter-system handover scenarios (location, service and triggering mechanism)

Five triggering mechanisms have been specified. These are aligned with the capability of Nokia’s RAN1.5.2.ED2 RNC software. They are not necessarily aligned with the capability of specific UE. For example, a specific model of UE may not support measurement reports triggered by uplink transmit power. It is important to consider these triggering mechanisms when defining a compressed mode strategy because they provide an indication of whether or not a particular compressed mode configuration is likely to be feasible. One technique used to generate compressed mode transmission gaps is to reduce the spreading factor. This increases the air-interface bit rate and allows the same amount of data to be transmitted in less time. It also requires a transient increase in transmit power. If compressed mode has been triggered by either the uplink or downlink transmit power mechanism then it may not be possible to increase the transmit power to support a reduction in spreading factor.

3.2. Load Reason Load reason compressed mode may be used for either inter-frequency or inter-system handover. Inter-frequency handover may be applicable if a Node B is configured with multiple carriers and there is an unequal distribution of load between those carriers. Directed RRC establishment can be used to help achieve a relatively even load between carriers. Unequal loads are likely to occur at coverage boundaries between

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dual carrier Node B and single carrier Node B. All UE which use soft handover to move from a single carrier Node B to a dual carrier Node B will remain on the first carrier unless instructed to complete a inter-frequency handover. Load reason compressed mode for inter-system handover is applicable to any Node B which is incurring high quantities of traffic. Nokia’s RAN1.5.2.ED2 and RAN04 RNC software releases do not support load reason inter-frequency nor inter-system handover. The required functionality is planned for the RAN05 RNC software release. These timescales mean that this report places little focus upon load reason inter-frequency and inter-system handover.

3.3. Traffic Reason

Traffic reason compressed mode may be used for either inter-frequency or inter-system handover. Inter-frequency handover may be applicable if a strategy has been defined to link specific services with specific carriers. When a UE initiates a capacity request for a specific service then it may be desirable to move the UE to a different carrier. Inter-system handover may be applicable if a strategy has been defined to link specific services with specific systems. Similar to the inter-frequency scenario, when a UE initiates a capacity request for a specific service then it may be desirable to move the UE to the GSM system. Nokia’s RAN1.5.2.ED2 and RAN04 RNC software releases do not support traffic reason inter-frequency nor inter-system handover. The required functionality is planned for the RAN05 RNC software release. These timescales mean that this report places little focus upon traffic reason inter-frequency and inter-system handover.

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4. Compressed Mode Methods and Patterns Compressed mode methods and the associated compressed mode patterns are controlled by the RNC. The Node B is informed of the configuration using the dedicated NBAP: RADIO LINK RECONFIGURATION PREPARE and the dedicated NBAP: COMPRESSED MODE COMMAND messages. The UE is informed of the configuration using either the RRC: PHYSICAL CHANNEL RECONFIGURATION and RRC MEASUREMENT CONTROL messages, or the RRC: TRANSPORT CHANNEL RECONFIGURATION and RRC: MEASUREMENT CONTROL messages. Selection between the RRC: PHYSICAL CHANNEL RECONFIGURATION message and the RRC: TRANSPORT CHANNEL RECONFIGURATION message depends upon the specific parameters affected by compressed mode. Figure 5 illustrates an example of the NBAP and RRC signalling for an inter-system handover of a CS service.

UE Node B RNC

RRC: Measurement Report

RRC: Measurement Control

NBAP: Radio Link Reconfiguration Prepare

NBAP: Radio Link Reconfiguration Ready

NBAP: Radio Link Reconfiguration Commit

RRC: Physical Channel Reconfiguration

RRC: Physical Channel Reconfiguration Complete

NBAP: Compressed Mode Command






RRC: Handover from UTRAN Command

GSM BSIC Identification

GSM RSSI Measurement

ISHO triggering

Initial Compressed Mode Configuration

UE Node B RNC



NBAP: Radio Link Reconfiguration Prepare

NBAP: Radio Link Reconfiguration Ready

NBAP: Radio Link Reconfiguration Commit

RRC: Physical Channel Reconfiguration

RRC: Physical Channel Reconfiguration Complete







RRC: Handover from UTRAN Command

GSM BSIC Identification

GSM RSSI Measurement

ISHO triggering

Initial Compressed Mode Configuration

Figure 5 – Example NBAP and RRC signalling used to configure and activate compressed mode

The signalling flow for a PS service inter-system handover makes use of the RRC: CELL CHANGE ORDER FROM UTRAN message rather than the RRC: HANDOVER FROM UTRAN COMMAND message. In addition, a PS service inter-system handover does not require GSM BSIC identification. The signalling flow for an inter-frequency handover makes use of FDD carrier measurement rather than GSM RSSI measurement and GSM BSIC identification. The remainder of this section provides a description of 3GPP specified and Nokia implemented compressed mode methods and patterns. This section is intended to be a statement of implementation rather than an evaluation of the associated trade-offs. Section 5 evaluates the trade-offs associated with specific compressed mode configurations. Nokia’s RAN1.5.2.ED2 implementation makes use of two separate compressed mode strategies – an advanced strategy and a normal strategy. The normal strategy includes fewer combinations of compressed mode configurations. The non-configurable RNC databuild parameter CompressedModeStrategy is used to define which strategy is used. This parameter is currently configured such that the RNC uses the normal compressed mode strategy. This section describes both the normal and advanced strategies. Inclusion of the advanced strategy is for information only.

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4.1. Method The RNC is able to configure the method used to generate the compressed mode transmission gaps. This is done independently for the uplink and downlink.

4.1.1. Uplink

3GPP TS25.331 and TS25.433 specify that uplink compressed mode transmission gaps may be achieved using either spreading factor division by 2 (SF/2) or higher layer scheduling (HLS). These methods are presented in Table 2.

3GPP Name Description 3GPP Range

Uplink Compressed Mode Method

Defines the uplink compressed mode method SF/2, HLS

Table 2 – 3GPP uplink compressed mode method parameter

This information is provided to the Node B within the Dedicated NBAP: RADIO LINK RECONFIGURATION PREPARE message and to the UE within the RRC: PHYSICAL/TRANSPORT CHANNEL RECONFIGURATION message. Nokia’s normal compressed mode strategy configures the compressed mode method based upon service type. No account is taken of the mechanism that has triggered compressed mode. Table 3 presents the compressed mode methods used by the normal strategy.

AMR Speech RT Data NRT Data Uplink Compressed Mode

Method SF/2 SF/2 HLS

Table 3 – Nokia uplink compressed mode methods (normal strategy)

Nokia’s advanced compressed mode strategy configures the compressed mode method based upon service type and triggering mechanism. Nokia’s RAN1.5.2.ED2 supports five coverage reason compressed mode triggering mechanisms – high uplink transmit power, high downlink transmit power, low CPICH Ec/Io, low CPICH RSCP and low uplink quality. In the case of the AMR speech service, the SF/2 method is used independent of the compressed mode triggering mechanism. Selection of the SF/2 method is presented in Table 4.

Triggered by 1st Choice for CM Method 2nd choice for CM Method 3rd Choice for CM Method UL Tx Power SF/2 and adding of lower TF - - DL Tx Power SF/2 and adding of lower TF - - CPICH Ec/Io SF/2 and adding of lower TF - - CPICH RSCP SF/2 and adding of lower TF - - Uplink Quality SF/2 and adding of lower TF - -

Table 4 – Nokia AMR speech service uplink compressed mode methods (advanced strategy)

The addition of a lower AMR speech transport format corresponds to a lower AMR bit rate. This helps the UE maintain its connection in case it starts to approach its maximum transmit power capability. The lower AMR speech transport format is limited by the RNC databuild parameter LowerULAMRmodeCM. This parameter is presented in Table 5.

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3GPP Name Nokia Name Scope Configurable Nokia Range Nokia Default

Not applicable LowerULAMRmodeCM RNC No 1 (12.2 kbps), 2 (10.2 kbps), 3 (7.95 kbps), 4 (7.4 kbps), 5 (6.7 kbps), 6 (5.9 kbps), 7 (5.15 kbps), 8 (4.75 kbps)

1

Table 5 – AMR speech service uplink compressed mode lower transport format bit rate

The LowerULAMRmodeCM parameter is currently configured with a value of 1, i.e. an AMR bit rate of 12.2 kbps. This means that a lower bit rate transport format is not added. In the case of CS data services, the SF/2 method is used independent of the compressed mode triggering mechanism. Selection of the SF/2 method is presented in Table 6.

Triggered by 1st Choice for CM Method 2nd choice for CM Method 3rd Choice for CM Method UL Tx Power SF/2 - - DL RL Power SF/2 - - CPICH Ec/Io SF/2 - - CPICH RSCP SF/2 - - Uplink Quality SF/2 - -

Table 6 – Nokia CS data service uplink compressed mode methods (advanced strategy)

Unlike the AMR speech service, CS data services are assumed to be sensitive to throughput and a lower transport format is not added. In the case of PS data services, the SF/2 and HLS methods are used. These methods are presented in Table 7.

Triggered by 1st Choice for CM Method 2nd choic e for CM Method 3rd Choice for CM Method UL Tx Power SF/2 and adding of lower TF ½ rate HLS ¾ rate HLS DL RL Power SF/2 and adding of lower TF ½ rate HLS ¾ rate HLS CPICH Ec/Io SF/2 ½ rate HLS ¾ rate HLS CPICH RSCP SF/2 ½ rate HLS ¾ rate HLS Uplink Quality SF/2 ½ rate HLS ¾ rate HLS

Table 7 – Nokia PS data service uplink compressed mode methods (advanced strategy)

The preferred method is SF/2. If the triggering mechanism is uplink or downlink transmit power then a lower transport format may also be added to help reduce the transmit power requirement. If the spreading factor being used prior to entering compressed mode is equal to 4 then the SF/2 method is not possible and HLS must be used. ½ rate HLS corresponds to transmitting 8 slots out of the 15 slots (single frame method when using a transmission gap length of 7 slots) and ¾ rate HLS corresponds to transmitting 11 slots out of the 15 (double frame method when using a transmission gap length of 7 slots). Nokia’s RAN1.5.2.ED2 implementation includes the RNC databuild parameter HLSModeSelection, to define whether or not ½ data rate HLS can be used. The HLSModeSelection parameter is presented in Table 8.

3GPP Name Nokia Name Scope Configurable Nokia Rang e Nokia Default

Not applicable HLSModeSelection RNC Yes 0 (1/2 HLS allowed), 1 (1/2 HLS not allowed)

0

Table 8 – Use of ½ data rate higher layer scheduling

If the HLSModeSelection parameter specifies that ½ data rate HLS is not permitted then ¾ rate HLS must be used.

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4.1.2. Downlink 3GPP TS25.331 and TS25.433 specify that downlink compressed mode transmission gaps may be achieved using either puncturing, spreading factor division by 2 (SF/2) or higher layer scheduling (HLS). These options are presented in Table 9.


Downlink Compressed Mode Method

Defines the Downlink compressed mode method Puncturing, SF/2, HLS

Table 9 – 3GPP downlink compressed mode method parameter

This information is provided to the Node B within the Dedicated NBAP: RADIO LINK RECONFIGURATION PREPARE message and to the UE within the RRC: PHYSICAL/TRANSPORT CHANNEL RECONFIGURATION message. Nokia’s normal compressed mode strategy configures the compressed mode method based upon service type. No account is taken of the mechanism that has triggered compressed mode. Table 10 presents the compressed mode methods used by the normal strategy.

AMR Speech RT Data NRT Data Downlink Compressed

Mode Method SF/2 SF/2 HLS

Table 10 – Nokia downlink compressed mode methods (normal strategy)

Nokia’s advanced compressed mode strategy configures the compressed mode method based upon service and triggering mechanism. Nokia’s RAN1.5.2.ED2 supports five coverage reason compressed mode triggering mechanisms – high uplink transmit power, high downlink transmit power, low CPICH Ec/Io, low CPICH RSCP and low uplink quality. In the case of the AMR speech service, the preferred compressed mode method is SF/2 for all triggering mechanisms except the downlink transmit power mechanism. In the case of the downlink transmit power mechanism, the preferred compressed mode method is puncturing. Puncturing has been selected to help avoid the increased downlink transmit power requirement associated with a reduction in spreading factor. Table 11 presents the compressed mode methods for the AMR speech service.

Triggered by 1st Choice for CM Method 2nd choice for CM Method 3rd Choice for CM Method UL Tx Power SF/2 SF/2 with alternative SC - DL Tx Power Puncturing for lower AMR mode SF/2 SF/2 with alternative SC CPICH Ec/Io SF/2 SF/2 with alternative SC - CPICH RSCP SF/2 SF/2 with alternative SC - Uplink Quality SF/2 SF/2 with alternative SC -

Table 11 – Nokia AMR speech service downlink compressed mode methods (advanced strategy)

If puncturing is used then sufficient bits must be removed to allow the use of a lower AMR mode. The lower AMR mode is limited by the RNC databuild parameter presented in Table 12.


Not applicable MinDLAMRmodeCM RNC No 1(12.2 kbps), 2(10.2 kbps), 4(7.95 kbps), 8(7.4 kbps), 16(6.7 kbps), 32(5.9 kbps), 64(5.15 kbps), 128(4.75 kbps)

1

Table 12 – AMR speech service downlink compressed mode lower transport format bit rate

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The LowerDLAMRmodeCM parameter is currently configured with a value of 1, i.e. an AMR bit rate of 12.2 kbps. This means that a lower AMR mode is not used and the second preferred compressed mode method is considered. If puncturing is used as a downlink compressed mode method then the RNC databuild parameter DlpuncturingLimit is used to limit the number of bits that can be removed. This parameter is presented in Table 13.


Not applicable DLpuncturingLimit RNC Yes 0 (0.4), 1 (0.44), 2 (0.48), 3 (0.52), 4 (0.56), 5 (0.6), 6 (0.64), 7 (0.68. default), 8 (0.72), 9 (0.76), 10 (0.8), 11 (0.84), 12 (0.88), 13 (0.92), 14 (0.96), 15 (1)

7

Table 13 – Downlink puncturing limit

If the puncturing method is not used for the downlink transmit power triggering mechanism then the SF/2 method is applied for all triggering mechanisms. If possible, the same scrambling code is used to ensure that downlink orthogonality is maintained. If the required channelisation code is not available then an alternative scrambling code may be used. Downlink orthogonality is lost for the compressed radio link if an alternative scrambling code is used. The RNC databuild parameter AltScramblingCodeCM defines whether or not an alternative scrambling code can be used. This parameter is presented in Table 14.


Not applicable AltScramblingCodeCM WCEL Yes 0 (allowed), 1 (not allowed)

0

Table 14 – Use of an alternative scrambling code for downlink compressed mode

In the case of CS data services, the puncturing method is preferred for the uplink and downlink transmit power triggering mechanisms. The SF/2 method is preferred for the CPICH and uplink quality triggering mechanisms. It is assumed that CS data services are throughput sensitive and are unable to incur the throughput reduction associated with HLS. Table 15 presents the compressed mode methods for CS data services.

Triggered by 1st Choice for CM Method 2nd choice for CM Method 3rd Choice for CM Method UL Tx Power Puncturing SF/2 SF/2 with alternative SC DL RL Power Puncturing SF/2 SF/2 with alternative SC CPICH Ec/Io SF/2 SF/2 with alternative SC - CPICH RSCP SF/2 SF/2 with alternative SC - Uplink Quality SF/2 SF/2 with alternative SC -

Table 15 – CS data service downlink compressed mode methods (advanced strategy)

If puncturing is applied, the RNC databuild parameter, DlpuncturingLimit is used to limit the number of bits that can be removed. This parameter is presented in Table 13. If SF/2 is applied, the use of an alternative scrambling code is controlled using the RNC databuild parameter, AltScramblingCodeCM. This parameter is presented in Table 14. In the case of PS data services, the puncturing method is preferred for the uplink transmit power triggering mechanism. ½ rate HLS is preferred for the downlink transmit power triggering mechanism. SF/2 is preferred for the remaining triggering mechanisms. Table 16 presents the compressed mode methods for PS data services.

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Triggered by 1st Choice for CM Method

2nd choice for CM Method

3rd Choice for CM Method

4th Choice for CM Method

5th Choice for CM Method

UL Tx Power Puncturing SF/2 SF/2 with alternative SC

½ HLS ¾ HLS

DL RL Power ½ HLS ¾ HLS - - - CPICH Ec/Io SF/2 SF/2 with

alternative SC ½ HLS ¾ HLS -

CPICH RSCP SF/2 SF/2 with alternative SC

½ HLS ¾ HLS -

Uplink Quality SF/2 SF/2 with alternative SC

½ HLS ¾ HLS -

Table 16 – PS data service downlink compressed mode methods (advanced strategy)

If SF/2 is applied, the use of an alternative scrambling code is controlled using the RNC databuild parameter, AltScramblingCodeCM. This parameter is presented in Table 14. When the preference is to use SF/2 and there are other options available, the RNC databuild parameter PowerMarginCMcodeHalving, is used to determine whether or not SF/2 is used. This parameter is presented in Table 17.


Not applicable PowerMarginCMcodeHalving RNC Yes 0..10 dB, step 0.25 dB 3 dB

Table 17 – Downlink transmit power margin required to half the spreading factor

Based upon the default value of this parameter, if the downlink transmit power is within 3 dB of the maximum, HLS is used. Nokia’s RAN1.5.2.ED2 implementation includes the HLSModeSelection RNC databuild parameter to define whether or not ½ data rate HLS can be used. This parameter is presented in Table 8.

4.2. Timing 3GPP TS25.331 and TS25.433 specify that the RNC is able to configure a maximum of 6 compressed mode transmission gap pattern sequences. These pattern sequences are identified by their Transmission Gap Pattern Sequence Identifier (TGPSI). A different pattern sequence can be defined for each Transmission Gap Measurement Purpose (TGMP). Nokia’s RAN1.5.2.ED2 implementation makes use of three compressed mode pattern sequences to support three measurement purposes. TGPSI 1 is used for FDD inter-frequency measurements, TGPSI 2 is used for GSM RSSI measurements and TGPSI 3 is used for GSM BSIC identification. Nokia’s RAN1.5.2.ED2 does not support GSM BSIC re-confirmation. 3GPP TS25.215 specifies that each transmission gap pattern sequence includes two transmission gap patterns. Each transmission gap pattern includes one or two transmission gaps. The transmission gap patterns are repeated according to the value of the Transmission Gap Pattern Repetition Count (TGPRC). Figure 6 illustrates the transmission gap patterns within a transmission gap pattern sequence.

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TG Pattern 1 TG Pattern 2 TG Pattern 1 TG Pattern 2

TGSN TGL1

TGD

TGPL1

TGL2 TGSN TGL1

TGD

TGPL2

TGL2

#1 #2 #3 #4

TG Pattern 1 TG Pattern 2 TG Pattern 1 TG Pattern 2

TGSN TGL1

TGD

TGPL1

TGL2 TGSN TGL1

TGD

TGPL2

TGL2

#1 #2 #3 #4

Figure 6 – 3GPP Transmission gap patterns within a transmission gap pattern sequence

The 3GPP specified parameters which define the timing of the transmission gap patterns and the transmission gap pattern sequences are presented in Table 18.

3GPP Acronym


TGSN Transmission Gap Starting Slot Number

Slot number of the first transmission gap slot within the first radio frame of the transmission gap pattern

Integer (0 to 14)

TGL1 Transmission Gap Length 1 Duration of the first transmission gap expressed in terms of the number of slots.

Integer (1 to 14)

TGL2 Transmission Gap Length 2 Duration of the second transmission gap expressed in terms of the number of slots. If not configured by higher layers then assumed to equal TGL1.

Integer (1 to 14)

TGD Transmission Gap start Distance

Duration between starting slots of two consecutive transmission gaps within a transmission gap pattern expressed in terms of the number of slots. A value of 0 indicates only 1 transmission gap in the transmission gap pattern

Integer (0, 15 to

269) TGPL1 Transmission Gap Pattern

Length 1 Duration of transmission gap pattern 1 expressed in terms of the number of frames.

Integer (1 to 144,…)

TGPL2 Transmission Gap Pattern Length 2

Duration of transmission gap pattern 2 expressed in terms of the number of frames. If not configured by higher layers then TGPL2 = TGPL1.

Integer (1 to 144,…)

TGPRC Transmission Gap Pattern Repetition Count

Number of transmission gap patterns within the transmission gap sequence. A value of 0 corresponds to an infinite number until requested to stop.

Integer (0 to 511)

TGCFN Transmission Gap Connection Frame Number

CFN of the first radio frame of the first pattern 1 within the transmission gap pattern sequence.

Integer (0 to 255)

Table 18 – 3GPP transmission gap pattern and transmission gap pattern sequence timing parameters

The TGSN, TGL1, TGL2, TGD, TGPL1 and TGPL2 are provided to the Node B within the Dedicated NBAP: RADIO LINK RECONFIGURATION PREPARE message. The TGPRC and TGCFN are provided to the Node B within the Dedicated NBAP: COMPRESSED MODE COMMAND message. The TGSN, TGL1, TGL2, TGD, TGPL1, TGPL2 and TGPRC are provided to the UE within the RRC: PHYSICAL/TRANSPORT CHANNEL RECONFIGURATION message. The TGCFN is provided to the UE within the RRC: MEASUREMENT CONTROL message. The transmission gaps may be located such that they do or do not span two consecutive radio frames. The former is known as the double frame approach whereas the latter is known as the single frame approach. In each case the transmission gap must be defined such that at least 8 slots are transmitted in each radio frame. Nokia’s RAN1.5.2.ED2 implementation of these timing parameters includes a set of RNC databuild parameters which are configurable and a set which are non-configurable. These RNC databuild parameters are presented in Table 19.

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TGSN (for single frame method)

GapPositionSingleFrame RNC Yes 0..8 , step 1 slot 4

TGSN (for double frame method)

No parameter name. RNC No - slot 11

TGL1 (for single & double frame method)

No parameter name. RNC No - 7 slots

TGL2 (for single & double frame method)

Not applicable because TGD defined as 0.

- - - -

TGD (for single & double frame method)

No parameter name. RNC No - 0 slots

TGPL1 (for single frame method)

TGPLsingleframeAMRgsm TGPLsingleframeAMRinterFreq TGPLsingleframeNRTPSgsm TGPLsingleframeNRTPSinterFreq TGPLsingleframeCSgsm TGPLsingleframeCSinterFreq TGPLsingleframeRTPSgsm TGPLsingleframeRTPSinterFreq

RNC RNC RNC RNC RNC RNC RNC RNC

Yes Yes Yes Yes Yes Yes Yes Yes

2..144 , step 1 2..18 , step 1

2..144 , step 1 2..18 , step 1

2..144 , step 1 2..18 , step 1

2..144 , step 1 2..18 , step 1

4 frames 4 frames 4 frames 4 frames 4 frames 4 frames 4 frames 4 frames

TGPL1 (for double frame method)

TGPLdoubleframeAMRgsm TGPLdoubleframeAMRinterFreq TGPLdoubleframeNRTPSgsm TGPLdoubleframeNRTPSinterFreq

RNC RNC RNC RNC

Yes Yes Yes Yes

3..144 , step 1 3..18 , step 1

3..144 , step 1 3..18 , step 1

4 frames 4 frames 4 frames 4 frames

TGPL2 (for single frame method)

Not configured and so TGPL2 = TGPL1

- - - -

TGPL2 (for double frame method)

Not configured and so TGPL2 = TGPL1

- - - -

TGPRC (for single & double frame method)

No parameter name. RNC No - 0 (infinite)

Table 19 – Nokia transmission gap pattern and transmission gap pattern sequence timing parameters

Nokia’s use of the single and double frame transmission gap approaches is a function of the compressed mode method. Compressed mode methods are described in Section 4.1. If spreading factor division by 2 or ½ data rate higher layer scheduling is used then the single frame approach is adopted. If puncturing or ¾ data rate higher layer scheduling is used then the double frame approach is adopted. Figure 7 illustrates the timing of the single and double frame methods based upon the default Nokia parameter set.

TGL1= 7 slots

TGL1= 7 slots

TGPL1 = 4 frames

Single frame

method

Double frame

method

TGL1= 7 slots

TGL1= 7 slots

TGPL1 = 4 frames

Single frame

method

Double frame

method

Figure 7 – Nokia default transmission gap patterns within a transmission gap pattern sequence

3GPP TS25.331 specifies that when the transmission gap pattern sequence has been configured for GSM BSIC identification, a limit is placed upon the maximum number of pattern repetitions that the UE is allowed to decode the unknown BSIC. 3GPP TS25.331 also specifies that when the transmission gap has been configured for GSM BSIC re-confirmation, a limit is placed upon the maximum time that the UE is allowed to re-confirm the BSIC. These limits are defined by the parameters presented in Table 20.

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N Identify abort

Indicates the maximum number of repeats of patterns that the UE shall use to attempt to decode the unknown BSIC of the GSM cell in the initial BSIC identification procedure.

Integer (1 to 128)

T Reconfirm abort

Indicates the maximum time allowed for the re-confirmation of the BSIC of one GSM cell in the BSIC re-confirmation procedure. The time is given in steps of 0.5 seconds.

Real (0.5 to 10.0,

step 0.5)

Table 20 – 3GPP parameters used to limit BSIC identification and BSIC re-confirmation

This information is provided to the UE within the RRC: PHYSICAL/TRANSPORT CHANNEL RECONFIGURATION message. Nokia’s RAN1.5.2.ED2 implementation supports the BSIC identification measurement purpose but not the BSIC re-confirmation measurement purpose. The Nokia implementation of the associated parameters is presented in Table 21.


N Identify abort

No parameter name. RNC No - 128 patterns

T Reconfirm abort

Not applicable because BSIC re-confirmation is not supported.

- - - -

Table 21 – Nokia parameters used to limit BSIC identification and BSIC re-confirmation times

The UE is permitted a maximum of 128 pattern repetitions to decode an unknown BSIC. Based upon a 4 frame TGPL, this corresponds to 5.12 s.

4.3. Direction 3GPP TS25.331 and TS25.433 specify that the RNC is able to configure compressed mode such that it is activated in the uplink alone, in the downlink alone or in both the uplink and downlink. The parameter used to define the compressed mode direction is defined in Table 22.

3GPP Name Description 3GPP Range UL/DL mode Defines whether only DL, only UL, or combined UL/DL compressed mode is

used. Enumerated(Code change, No code

change)

Table 22 – 3GPP direction of compressed mode parameter

This information is provided to the Node B within the Dedicated NBAP: RADIO LINK RECONFIGURATION PREPARE message and to the UE within the RRC: PHYSICAL/TRANSPORT CHANNEL RECONFIGURATION message. Nokia’s RAN1.5.2.ED2 implementation configures uplink and downlink compressed mode according to the UE capability information. This information is provided to the RNC as part of the RRC: RRC CONNECTION SETUP COMPLETE message.

4.4. Power Control TS25.331, TS25.433 and TS25.214 specify that the RNC is able to configure increases in the uplink and downlink SIR targets during compressed mode. Table 23 presents the 3GPP parameters which specify the increase in uplink SIR target.

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DeltaSIR1 SIR target increase to be set in the Node B during the frame containing the start of the first transmission gap in the transmission gap pattern (without including the effect of the bit-rate increase)

Integer (0 to 3 dB, step 0.1)

DeltaSIRafter1 SIR target increase to be set in the Node B one frame after the frame containing the start of the first transmission gap in the transmission gap pattern.


DeltaSIR2 SIR target increase to be set in the Node B during the frame containing the start of the second transmission gap in the transmission gap pattern (without including the effect of the bit-rate increase) When omitted, DeltaSIR2 = DeltaSIR1.


DeltaSIRafter2 SIR target increase to be set in the Node B one frame after the frame containing the start of the second transmission gap in the transmission gap pattern. When omitted, DeltaSIRafter2 = DeltaSIRafter1.


Table 23 – 3GPP increase in uplink SIR target parameters

This information is provided to the Node B within the Dedicated NBAP: RADIO LINK RECONFIGURATION PREPARE message. Nokia’s RAN1.5.2.ED2 implementation makes use of only a single transmission gap within each transmission gap pattern and so the DeltaSIR2 and DeltaSIRafter2 parameters are not applicable. The relevant Nokia RNC databuild parameters are presented in Table 24.

3GPP Name Nokia Name Scope Configurable Nokia Range Nokia Default DeltaSIR1 ULdeltaSIR1 RNC No 0..3 dB, step 0.1 dB 1.5 dB

DeltaSIRafter1 ULdeltaSIRafter1 RNC No 0..3 dB, step 0.1 dB 0.7 dB for 0 slot gap, 1.5 dB for 3

slots gap

Table 24 – Nokia increase in uplink SIR target parameters

Table 25 presents the 3GPP parameters which specify the increase in downlink SIR target.


DeltaSIR1 SIR target increase to be set in the Node B during the frame containing the start of the first transmission gap in the transmission gap pattern (without including the effect of the bit-rate increase)


DeltaSIRafter1 SIR target increase to be set in the Node B one frame after the frame containing the start of the first transmission gap in the transmission gap pattern.


DeltaSIR2 SIR target increase to be set in the Node B during the frame containing the start of the second transmission gap in the transmission gap pattern (without including the effect of the bit-rate increase) When omitted, DeltaSIR2 = DeltaSIR1.


DeltaSIRafter2 SIR target increase to be set in the Node B one frame after the frame containing the start of the second transmission gap in the transmission gap pattern. When omitted, DeltaSIRafter2 = DeltaSIRafter1.


Table 25 – 3GPP increase in downlink SIR target parameters

This information is provided to the UE within the RRC: PHYSICAL/TRANSPORT CHANNEL RECONFIGURATION message. Nokia’s RAN1.5.2.ED2 implementation makes use of only a single transmission gap within each transmission gap pattern and so the DeltaSIR2 and DeltaSIRafter2 parameters are not applicable. The relevant Nokia RNC databuild parameters are presented in Table 26.

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3GPP Name Nokia Name Scope Configurable Nokia Range Nokia Default DeltaSIR1 DLdeltaSIR1 RNC No 0..3 dB, step 0.1 dB 1.5 dB

DeltaSIRafter1 DLdeltaSIRafter1 RNC No 0..3 dB, step 0.1 dB 0.7 dB for 0 slots gap, 1.5 dB for 3

slots gap

Table 26 – Nokia increase in downlink SIR target change parameters

TS25.331 and TS25.214 specify that a UE should increase its transmit power at the start of the first slot after an uplink or downlink transmission gap. The Initial Transmit Power (ITP) mode has an impact upon this increase. TS25.331 and TS25.214 also specify that a UE should use a modified power control algorithm during the transmission gap recovery period. The modified power control algorithm is known as the Recovery Period Power (RPP) control algorithm. The 3GPP ITP and RPP parameters are presented in Table 27.

3GPP Acronym

3GPP Name Description Range

ITP Initial Transmit Power Initial Transmit Power is the uplink power control method to be used to compute the initial transmit power after the compressed mode gap.

Enumerated (0, 1)

RPP Recovery Period Power Recovery Period Power control mode during the frame after the transmission gap within the compressed frame. Indicates whether normal PC mode or compressed PC mode is applied

Enumerated (0, 1)

Table 27 – 3GPP ITP and RPP power control parameters

This information is provided to the UE within the RRC: PHYSICAL/TRANSPORT CHANNEL RECONFIGURATION message. Table 28 presents the equivalent Nokia RNC databuild parameters.


ITP UpLinkInitialTransmitPowerMode RNC Yes 0, 1 0 RPP UpLinkRecoveryPeriodPowerMode RNC Yes 0, 1 0

Table 28 – Nokia ITP and RPP power control parameters

4.5. Scrambling Code 3GPP TS25.213 specifies that when the spreading factor division by 2 method is used for downlink compressed mode then it is possible for the RNC to configure the use of an alternative scrambling code. The parameter used to do this is presented in Table 29.

3GPP Name Description 3GPP Range Scrambling Code Change Indicates whether or not an alternative scrambling code is used for

compressed mode method 'SF/2'. Enumerated

(code change, no code change)

Table 29 – 3GPP alternative scrambling code parameter

This information is provided to the Node B within the Dedicated NBAP: RADIO LINK RECONFIGURATION PREPARE message and to the UE within the RRC: PHYSICAL/TRANSPORT CHANNEL RECONFIGURATION message. Nokia’s RAN1.5.2.ED2 implementation includes the RNC databuild parameter, AltScramblingCodeCM to control whether or not an alternative scrambling code may be used. This parameter is presented in Table 14.

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4.6. Downlink Frame Type The RNC is able to configure whether downlink frame type ‘A’ or ‘B’ shall be used for downlink compressed mode. Frame type ‘A’ is intended to maximise the transmission gap length. Frame type ‘B’ is optimised for power control. Frame types ‘A’ and ‘B’ are illustrated in Figure 8.

Figure 8 – Downlink frame types ‘A’ and ‘B’

The 3GPP frame type configuration parameter is presented in Table 30.

3GPP Name Description 3GPP Range Downlink Frame Type Defines the downlink frame structure type A, B

Table 30 – 3GPP downlink frame type parameter

This information is provided to the Node B within the Dedicated NBAP: RADIO LINK RECONFIGURATION PREPARE message and to the UE within the RRC: PHYSICAL/TRANSPORT CHANNEL RECONFIGURATION message. Table 31 presents the equivalent Nokia RNC databuild parameter.


Downlink Frame Type No parameter name RNC No - A

Table 31 – Nokia downlink frame type parameter

The downlink frame type is configured independently of the downlink slot format. Downlink slot structure ‘A’ is used for HLS and puncturing whereas downlink slot structure ‘B’ is used for SF/2. In the uplink direction, DPDCH slot structures are not defined specifically for compressed mode. Uplink DPCCH slot structures are defined specifically for compressed mode. The choice of uplink DPCCH slot structure depends upon the number of slots transmitted and whether or not TFCI bits are transmitted.

4.7. Measurement Reporting 3GPP TS25.331 specifies the parameter to define the interval between periodic measurement reports. This parameter is presented in Table 32.

3GPP Name Description 3GPP Range Periodic Reporting Interval Defines the interval between periodic measurement

reports 250, 500, 1000, 2000, 3000, 4000, 6000, 8000, 12000, 16000, 20000, 24000, 28000, 32000, 64000

Table 32 – 3GPP periodic measurement reporting interval

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This information is provided to the UE within the RRC: MEASUREMENT CONTROL message. Nokia’s RAN1.5.2.ED2 implementation includes RNC databuild parameters that can be defined independently for inter-frequency and inter-system measurements. In addition to the periodic reporting interval there are also parameters that define, the minimum number of measurement reports that must be received by the RNC prior to making a handover decision and the maximum number of measurement reports than can be received prior to the RNC cancelling the measurement procedure. These parameters are presented in Table 33.


Periodic Reporting Interval

InterFreqMeasRepInterval FMCI Yes 2 (0.5 s), 3 (1 s), 4 (2 s), 5 (3 s), 6 (4 s)

2

Not applicable InterFreqNcellSearchPeriod FMCI Yes 0..20 MeasReport, step 1 MeasReport

0

Not applicable InterFreqMaxMeasPeriod FMCI Yes 1..120 MeasReport, step 1 MeasReport

20

Periodic Reporting Interval

GsmMeasRepInterval FMCG Yes 2 (0.5 s), 3 (1 s), 4 (2 s), 5 (3 s), 6 (4 s)

2

Not applicable GsmNcellSearchPeriod FMCG Yes 0..20 MeasReport, step 1 MeasReport

0

Not applicable GsmMaxMeasPeriod FMCG Yes 1..120 MeasReport, step 1 MeasReport

20

Table 33 – Nokia periodic measurement reporting parameters

The default value for the minimum number of reports required prior to making a handover decision is 0. This means that the RNC can proceed immediately after receiving the first measurement report. The default value for the maximum number of periodic measurement reports is 20. The RNC will cancel the measurement procedure if handover hasn’t been completed after receiving 20 measurement reports.

4.8. Other Configuration Parameters Nokia’s RAN1.5.2.ED2 implementation includes a number of additional RNC databuild parameters which are applicable to compressed mode. These are presented in Table 34.


Not applicable CMmasterSwitch RNC Yes 0 (false), 1 (true) 1 Not applicable MaxNumbUECMcoverHO WCEL Yes 0..255 , step 1 16 Not applicable PrxTarget WCEL Yes 0..30 dB step 0.1 4 dB Not applicable PrxOffset WCEL Yes 0..6 dB step 0.1 1 dB Not applicable PtxTarget WCEL Yes -10..50 dBm step 0.1 40 dBm Not applicable PtxOffset WCEL Yes 0..6 dB step 0.1 1 dB

Table 34 – Additional Nokia RNC databuild parameters applicable to compressed mode

The CMmasterSwitch parameter defines whether or not compressed mode is used within any cell connected to the RNC. The MaxNumbUECMcoverHO parameter defines the maximum number of UE which are permitted to simultaneously use compressed mode within a single cell. If a UE is in soft handover then this limit applies to all cells to which the UE is connected. If a Node B uplink RSSI measurement exceeds PrxTarget while MaxNumbUECMcoverHO has not been reached, then one more UE can have compressed mode activated within that radio resource indication period. If ]a Node B uplink RSSI measurement exceeds PrxTarget + PrxOffset then no more UE can have compressed mode activated within that radio resource indication period. Similar rules are applied in the downlink direction using PtxTarget and PtxOffset.

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5. Preferred Compressed Mode Methods and Patterns This section identifies the trade-offs associated with adopting various strategies in terms of compressed mode methods and compressed mode patterns. The scenarios identified in section 3 are used as a basis for balancing each trade-off and generating a set of preferred compressed mode configurations. These scenarios have four dimensions, i.e.

� rate of change of propagation conditions: high or low � service: AMR speech, RT data or NRT data � triggering mechanism: uplink transmit power, downlink transmit power, CPICH Ec/Io, CPICH

RSCP or uplink quality � measurement purpose: GSM RSSI measurement, GSM BSIC identification or FDD measurement

Recommendations are made specifically for each of these four dimensions. The discussion is primarily theoretical and is not limited by Nokia’s implementation. The field experience presented in section 7 is used to a limited extent.

5.1. Method Section 4.1 introduced the three methods that may be used to generate compressed mode transmission gaps, i.e. puncturing, spreading factor division by 2 (SF/2) and higher layer scheduling (HLS). The choice of which method to adopt is one of the most important compressed mode design decisions. The choice cannot be made in isolation but requires consideration of other compressed mode design decisions. For example, selecting puncturing as a compressed mode method has implications upon the maximum transmission gap length and whether the transmission gaps need to span single or multiple radio frames. The choice of compressed mode method must also account for limitations imposed by other areas of system design. For example, the AMR speech service must use fixed downlink transport channel starting positions if the UE is required to apply blind detection of the AMR bit rate. The R99 3GPP specifications do not support HLS with fixed transport channel starting positions and so this method must be discounted from the selection process.

5.1.1. Uplink

Uplink compressed mode methods are limited to spreading factor division by 2 (SF/2) and high layer scheduling (HLS). SF/2 compressed mode does not necessitate the use of a lower transport format combination. The physical layer is reconfigured to convey the same quantity of data within a shorter period of time. The reduction in spreading factor is applied on a per radio frame basis rather than on a per transmission time interval (TTI) basis. For example, if the 20 ms TTI AMR speech service were to use SF/2 compressed mode configured using the single frame approach, a single 7 slot transmission gap and a 4 frame transmission gap pattern length, then every 60 slots, 8 slots would be transmitted with a halved spreading factor, 7 slots would not be transmitted and 45 slots would be transmitted using the non-compressed mode format. The 8 slots transmitted with a halved spreading factor would require approximately 3 dB greater transmit power than the slots transmitted using the non-compressed mode format. This short term increase in UE transmit power means that SF/2 is not suitable for scenarios in which the UE is transmitting close to its maximum transmit power capability. It may be possible to combine SF/2 with a reduction in transport format combination to decrease the UE transmit power requirement. The transport format combination can be reduced for services which are not sensitive to changes in throughput, i.e. AMR speech and NRT data services. SF/2 compressed

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mode is applicable to all services except those that use a spreading factor of 4. The field experience presented in Section 7 illustrates that the average UE transmit power increases by 1.3 dB when SF/2 is used with the single frame approach and a 7 slot transmission gap. This increase in average transmit power is generated by the compressed mode inner loop power control behaviour rather than the short term increase caused by the spreading factor reduction. SF/2 compressed mode may use either the single or double frame approach although it is usually associated with the single frame approach to limit the number of slots which are transmitted with a reduced spreading factor. Relatively large transmission gaps can be generated if the double frame approach is used. HLS necessitates the use of a lower transport format combination while the physical layer remains unchanged, i.e. less data is transmitted within a shorter period of time. The MAC layer within the UE is responsible for selecting an appropriate lower transport format combination. Layer 3 of the RNC is not required to remove any higher transport format combinations. The result of using a lower transport format combination is a reduction in service throughput. The R99 3GPP specifications do not support HLS for transport channels using fixed starting positions. The AMR speech, RT data and NRT data services all use flexible transport channel starting positions in the uplink direction. HLS is not appropriate for RT data services because of their sensitivity to variations in throughput. HLS can be applied to the AMR speech service if a lower AMR bit rate can be used. The cost of using a lower AMR bit rate is a reduction in speech quality. HLS can be applied to NRT data services because of their ability to incur variations in throughput. The field experience presented in Section 7 illustrates that the average UE transmit power increases by approximately 1.6 dB when HLS is used with the single frame approach and a 7 slot transmission gap. This increase in average transmit power is generated by the compressed mode inner loop power control behaviour. HLS can use either the single or double frame approach. Relatively large transmission gaps can be generated if the double frame approach is used. Table 35 presents a summary of the uplink compressed mode methods which may be used for each service.

Compressed Mode Method Service HLS SF/2

AMR Speech Available* Available RT Data Not Available Available

NRT Data Available Available * only available if it is possible to use a lower AMR bit rate

Table 35 – Summary of uplink compressed mode methods

Table 36 presents the preferred methods for generating uplink compressed mode transmission gaps These are independent of the compressed mode measurement purpose and the rate of change of propagation conditions.

Compressed Mode Triggering Mechanism Service UL Transmit

Power DL Transmit

Power CPICH Ec/Io CPICH RSCP UL Quality

AMR Speech HLS* HLS* HLS* HLS* HLS* RT Data SF/2 SF/2 SF/2 SF/2 SF/2

NRT Data HLS HLS HLS HLS HLS * only if it is possible to use a lower AMR bit rate. Otherwise SF/2 should be used.

Table 36 – Preferred uplink compressed mode methods

SF/2 is the only compressed mode method that is available for RT data services. HLS has been chosen for the AMR speech service on the basis that it is acceptable to incur a temporary speech quality reduction. If AMR bit rates below 12.2 kbps are not supported by either the network or the UE then SF/2 must be used by the AMR speech service. HLS has been chosen for NRT data services on the basis that it is acceptable to incur a temporary reduction in throughput.

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5.1.2. Downlink Downlink compressed mode methods are puncturing, spreading factor division by 2 (SF/2) and high layer scheduling (HLS). The R99 3GPP specifications do not support puncturing for transport channels using flexible starting positions. The RT data and NRT data services use flexible transport channel starting positions in the downlink. The AMR speech service uses fixed transport channel starting positions in the downlink. Puncturing removes layer 1 bits after channel coding and causes an increase in the downlink SIR target. Puncturing is applied on a per TTI basis. This means that the double and single frame approaches have similar impacts if the double frame approach transmission gap spans two frames belonging to the same TTI. If the double frame approach is synchronised with the TTI such that the transmission gap spans two frames belonging to different TTI then the puncturing ratio is reduced. However, in this case two TTI rather than one are affected. The precise extent to which coded transport blocks can be punctured for compressed mode depends upon the non-compressed mode rate matching attributes and the maximum acceptable increase in SIR target. If the non-compressed mode rate matching attributes indicate repetition rather than puncturing then there is increased scope for puncturing for compressed mode. Typically, the maximum total puncturing applied to a transport channel is such that approximately 70 % of the coded bits remain after puncturing. Puncturing for the AMR speech service may necessitate the use of a lower AMR bit rate. Similar to the uplink, downlink SF/2 compressed mode requires the physical layer to be reconfigured to convey the same quantity of data within a shorter period of time. The reduction in spreading factor is applied on a per radio frame basis rather than on a per transmission time interval (TTI) basis. For example, if the AMR speech service were to use SF/2 compressed mode configured using the single frame approach, a single 7 slot transmission gap and a 4 frame transmission gap pattern length, then every 60 slots, 8 slots would be transmitted with a halved spreading factor, 7 slots would not be transmitted and 45 slots would be transmitted using the non-compressed mode format. The 8 slots transmitted with a halved spreading factor would require approximately 3 dB greater transmit power than the slots transmitted using the non-compressed mode format. This short term increase in downlink transmit power means that SF/2 is not suitable for scenarios in which the cell is transmitting close to its maximum radio link transmit power. It may be possible to combine SF/2 with a reduction in transport format combination to decrease the cell transmit power requirement. The transport format combination can be reduced for services which are not sensitive to changes in throughput, i.e. AMR speech and NRT data services. SF/2 compressed mode is applicable to all services except those that use a spreading factor of 4. The increase in average transmit power during SF/2 compressed mode is generated by the inner loop power control behaviour rather than the short term increase caused by the spreading factor reduction. SF/2 compressed mode may use either the single or double frame approaches although it is usually associated with the single frame format to limit the number of slots which are transmitted with a reduced spreading factor. SF/2 in the downlink direction may require the use of an alternative scrambling code. There is a one-to-one relationship between the original channelisation code and the channelisation code with half the spreading factor. If the channelisation code with half the spreading factor is blocked by another connection then it must be applied with an alternative scrambling code. The use of an alternative scrambling code means that downlink orthogonality is lost for that radio link and downlink transmit powers for all radio links will increase. Similar to the uplink, downlink HLS necessitates the use of a lower transport format combination while the physical layer remains unchanged, i.e. less data is transmitted within a shorter period of time. The MAC layer within the RNC is responsible for selecting an appropriate lower transport format combination. Layer 3 of the RNC is not required to remove the higher transport format combinations. The result of using a lower transport format combination is a reduction in service throughput. The R99 3GPP specifications do not support HLS for transport channels using fixed transport channel starting positions. The RT data and NRT

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data services make use of flexible transport channel starting positions in the downlink. The AMR speech services makes use of fixed transport channel starting positions in the downlink. Fixed transport channel positions are used to allow blind detection of the AMR bit rate at the UE. HLS is not appropriate for RT data services because of their sensitivity to variations in throughput. HLS can be applied to NRT data services because of their ability to incur variations in throughput. The field experience presented in Section 7 illustrates that the average cell transmit power increases by approximately 6.5 dB when HLS is used with the single frame approach and a 7 slot transmission gap. This increase is considerably greater than expected and warrants further investigation. The increase in average transmit power is generated by the compressed mode inner loop power control behaviour. HLS can use either the single or double frame approach. Relatively large transmission gaps can be generated if the double frame approach is used Table 37 presents a summary of the compressed mode methods which may be used with each service type.

Compressed Mode Method Service Puncturing HLS SF/2

AMR Speech Available Not Available Available RT Data Not Available Not Available Available

NRT Data Not Available Available Available

Table 37 – Summary of downlink compressed mode methods

Table 38 presents the preferred methods for generating downlink compressed mode transmission gaps These are independent of the compressed mode measurement purpose and the rate of change of propagation conditions.

Compressed Mode Triggering Mechanism Service UL Transmit

Power DL Transmit

Power CPICH Ec/Io CPICH RSCP UL Quality

AMR Speech Puncturing Puncturing Puncturing Puncturing Puncturing RT Data SF/2 SF/2 SF/2 SF/2 SF/2

NRT Data HLS HLS HLS HLS HLS

Table 38 – Preferred downlink compressed mode methods

SF/2 is the only compressed mode method that is available for RT data services. Puncturing has been chosen for the AMR speech service because it avoids the transient increase in downlink transmit power requirement associated with SF/2. HLS has been chosen for NRT data services on the basis that it is acceptable to incur a temporary reduction in throughput.

5.2. Timing Section 4.2 introduced the parameter set associated with the timing of compressed mode patterns. This parameter set is summarised below:

� TGSN � TGL1 � TGL2 � TGD � TGPL1 � TGPL2 � TGPRC � TGCFN � N Identify Abort � T Reconfirm Abort

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The most important of these are the TGL, TGPL and TGSN. Selecting an appropriate TGL involves balancing the efficiency with which measurements can be made with the impact upon layer 1 and layer 2 performance. Large TGL are more efficient in terms of the number of measurements that can be completed per unit time but have a greater impact upon layer 1 and layer 2. Layer 1 performance is affected in terms of inner loop power control independent of the compressed mode method. Larger TGL result in less correlation between the propagation conditions before and after the transmission gap. This makes it more difficult for the inner loop power control to recover. In the case of compressed mode by puncturing, larger TGL require larger quantities of puncturing and result in larger SIR target increases. In the case of compressed mode by HLS, larger TGL require the use of lower transport format combinations and result in lower layer 2 throughput. In the case of compressed mode by SF/2, larger TGL require the use of the double frame approach meaning that two radio frames rather than a single radio frame have their spreading factor reduced. The fundamental requirement for a specific TGL originates from the compressed mode measurement purpose. Table 39 presents the relationship between the TGL and the minimum requirement for the UE’s ability to sample GSM RSSI. These figures have been extracted from 3GPP TS25.133. The third column represents the efficiency with which measurements are made. Also included in the table is the equivalent time required to complete 16 and 32 GSM RSSI measurements based upon 3 samples per measurement and a TGPL of 4 radio frames.

TGPL = 4 Frames Transmission Gap Length

(slots)

Number of GSM carrier RSSI samples in each

gap

Number of GSM carrier RSSI samples in each

gap per slot

Time to complete 16 GSM RSSI meas. (3

samples / meas.)

Time to complete 32 GSM RSSI meas. (3

samples / meas.) 3 1 0.33 1920 ms 3840 ms 4 2 0.50 960 ms 1920 ms 5 3 0.60 640 ms 1280 ms 7 6 0.86 320 ms 640 ms 10 10 1.00 200 ms 400 ms 14 15 1.07 160 ms 280 ms

Table 39 – TGL impact upon GSM RSSI measurement

GSM RSSI measurements are made without acquiring GSM synchronisation and do not require the compressed mode transmission gap to coincide with a particular section of the GSM radio frame. The measurement efficiency becomes relatively poor for transmission gap lengths of less than 7 slots. Quantifying the impact upon inner loop power control requires either link level simulations or field measurements. The field measurements presented in Section 7 indicate that a TGL of 7 slots with a TGPL of 4 frames degrades inner loop power control to the extent that the average uplink transmit power increases by between 1.3 to 1.6 dB. Table 40 presents the preferred GSM RSSI TGL as a function of the service and compressed mode method. These are independent of the compressed mode triggering mechanism and the rate of change of propagation conditions.

Uplink Downlink Service HLS SF/2 Puncturing HLS SF/2

AMR Speech 7 7 7 Not applicable 7 RT Data Not applicable 7 Not applicable Not applicable 7

NRT Data 10 10 Not applicable 10 10

Table 40 – Preferred TGL for GSM RSSI measurements

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A TGL of 7 slots has been selected for the AMR speech and RT data services. This value has been selected on the basis of balancing the efficiency with which measurements can be made with the impact upon inner loop power control. A TGL of 7 slots can be generated relatively comfortably by each compressed mode method and may use either the single or double frame approach. A TGL of 10 slots has been selected for NRT services. This value has been selected on the basis that NRT services are less sensitive to L1 and L2 performance. NRT services can make use of layer 2 re-transmissions if the performance of inner loop power becomes poor. NRT services are also able to incur a decreased layer 2 throughput if in the case of HLS, a 10 slot transmission gap requires a lower transport format combination than a 7 slot transmission gap. In the case of the BSIC identification compressed mode measurement purpose, the frame structure and timing of the GSM system has a more significant impact upon the required transmission gap length. The GSM system is based upon an 8 slot radio frame structure with a duration of 4.615 ms. The first slot of each frame is dedicated to the BCCH. The BSIC is broadcast periodically within the SCH of the BCCH. There are 51 GSM frames within a GSM multi-frame and the SCH is transmitted 5 times within each multi-frame. Assuming that frame numbering starts at 0 then the frames occupied by the SCH are numbers 1, 11, 21, 31 and 41. The UE has no knowledge of the timing of the GSM system and must capture 9 slot’s worth of GSM data to be sure of capturing the BCCH. A compressed mode TGL of 7 slots is equivalent to 4.667 ms and provides a high probability of capturing the BCCH. Shorter transmission gap lengths could be used but doing so would reduce the probability of capturing the BCCH. The fact that the BSIC is broadcast 5 times per 51 frames means that multiple transmission gaps are likely to be required. Table 41 presents the relationship between the TGL and the BSIC identification time that guarantees the UE at least two attempts at decoding the BSIC. These figures have been extracted from 3GPP TS25.133.

TGL (slots)

Guaranteed attempts at decoding the BSIC

TGPL (frames)

Number of transmission gap patterns

Equivalent time

7 2 3 51 1.5 s 7 2 8 65 5.2 s 10 2 12 23 2.7 s 14 2 8 22 1.8 s 14 2 24 21 5.0 s

Table 41 – TGL impact upon GSM BSIC identification

In practise the BSIC identification times may be less than those presented in Table 41. It is possible that the UE manages to identify the BSIC within the first transmission gap. Longer TGL and shorter TGPL result in more rapid BSIC identification times. The drawback of using long TGL and short TGPL is the associated impact upon layer 1 and layer 2 performance. Table 42 presents the preferred BSIC identification TGL as a function of the service and compressed mode method. These are independent of the compressed mode triggering mechanism and the rate of change of propagation conditions.


AMR Speech 7 7 7 Not applicable 7 RT Data Not applicable 7 Not applicable Not applicable 7

NRT Data 10 10 Not applicable 10 10

Table 42 – Preferred TGL for GSM BSIC identification

A TGL of 7 slots has been selected for the AMR speech and RT data services. This value has been selected on the basis of balancing the efficiency with which BSIC can be identified with the impact upon inner loop power control. A TGL of 7 slots can be generated relatively comfortably by each compressed mode method and may use either the single or double frame approach. A TGL of 10 slots has been selected for NRT

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services. This value has been selected on the basis that NRT services are less sensitive to L1 and L2 performance. NRT services can make use of layer 2 re-transmissions if the performance of inner loop power becomes poor. NRT services are also able to incur a decreased layer 2 throughput if in the case of HLS, a 10 slot transmission gap requires a lower transport format combination than a 7 slot transmission gap. In the case of the FDD inter-frequency compressed mode measurement purpose, 3GPP TS25.133 specifies that the UE must be capable of completing 6 inter-frequency CPICH measurements within Tmeasurement_inter ms.

msNT

msms,msMAXT Freq

erinterint_tmeasuremen

××= 48050480

Where,

TInter = the minimum time available for inter-frequency measurements within a 480 ms period. NFreq = the number of FDD carriers to be measured.

Consider the example of the AMR service which has been configured with fixed transport channel starting positions to allow blind detection of the AMR bit rate. If blind detection is used then TFCI bits are not required and downlink slot format 8B can be used during SF/2 compressed mode. This slot format has a spreading factor of 64. Downlink slot format 8B includes 8 pilot bits. If the compressed mode transmission gap includes 7 slots then actual gap is equal to (7 * 0.667) – (8 * 0.008) = 4.605 ms. 3GPP TS25.133 specifies that a 0.5 ms implementation margin should be introduced at each end of the transmission gap. This reduces the gap duration to 3.605 ms. 3GPP TS25.133 also specifies that subsequent to the inclusion of the implementation margin only full slots should be included in the calculation. This reduces the duration to 5 slots (1 slot discounted from the start of the transmission gap and 1 slot discounted from the end of the transmission gap). If a TGPL of 4 frames is assumed then there are 12 gaps within the 480 ms period. The time permitted to complete 6 inter-frequency CPICH measurements then becomes:

ms.

msms,msMAXT erint_tmeasuremen 6001

333312

48050480 =

×

××=

Table 43 presents the results of the same calculation for a range of TGL and TGPL

TGL (slots)

TGPL (frames)

Time to measure 6 inter -frequency neighbours

7 4 600 ms 10 4 480 ms 14 4 480 ms 7 8 1200 ms 10 8 750 ms 14 8 500 ms

Table 43 – TGL impact upon FDD inter-frequency measurement (AMR speech service)

Longer TGL and shorter TGPL result in more rapid inter-frequency measurement times. The drawback of using long TGL and short TGPL is the associated impact upon layer 1 and layer 2 performance. Table 44 presents the preferred GSM BSIC identification TGL as a function of the service and compressed mode method. These are independent of the compressed mode triggering mechanism and the rate of change of propagation conditions.


AMR Speech 7 7 7 Not applicable 7

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RT Data Not applicable 7 Not applicable Not applicable 7 NRT Data 10 10 Not applicable 10 10

Table 44 – Preferred TGL for FDD inter-frequency measurements

A TGL of 7 slots has been selected for the AMR speech and RT data services. This value has been selected on the basis of balancing the efficiency with which inter-frequency measurements can be completed with the impact upon inner loop power control. A TGL of 7 slots can be generated relatively comfortably by each compressed mode method and may use either the single or double frame approach. A TGL of 10 slots has been selected for NRT services. This value has been selected on the basis that NRT services are less sensitive to L1 and L2 performance. NRT services can make use of layer 2 re-transmissions if the performance of inner loop power becomes poor. NRT services are also able to incur a decreased layer 2 throughput if in the case of HLS, a 10 slot transmission gap requires a lower transport format combination than a 7 slot transmission gap. 3GPP TS25.331 and TS25.433 allow the configuration of TGL1 and TGL2, i.e. having two transmission gaps per transmission gap pattern separated by TGD. This increases the flexibility with which transmission gap patterns can be designed. This additional flexibility is not required at this point in time and it is recommended that the design includes a single transmission gap per transmission gap pattern. This means that the TGD should be configured as 0 slots and that TGL1 = TGL and TGL2 does not require configuration. The TGPL provides a trade-off between the time spent in compressed mode and the potential impact upon layer 1 and layer 2 performance. Long TGPL increase the time spent in compressed mode. This means that compressed mode must be triggered relatively early to prevent radio link failure occurring prior to completing a successful handover. Triggering compressed mode relatively early means that compressed mode will also be triggered more frequently. The TGPL should be defined such that compressed mode can be triggered relatively late and less frequently. The benefit of using a long TGPL is that inner loop power control has more time to recover between transmission gaps. Throughput reductions caused by higher layer scheduling and L2 re-transmissions will also be less frequent and thus will have lower average impact. The TGPL should also account for the service specific transmission time interval (TTI). In general, the TGPL should not be defined such that multiple transmission gaps occur within the same TTI. The maximum TTI specified by 3GPP within TS25.331 is 80 ms. The maximum TTI used by Nokia’s RAN1.5.2.ED2 implementation is 40 ms. As long as the TGPL is greater than 4 radio frames then multiple transmission gaps will never occur within the same TTI (based upon the assumption of a single transmission gap per transmission gap pattern). Table 45 presents the preferred TGPL as a function of the service, compressed mode measurement purpose and rate of change of propagation conditions. These are independent of the compressed mode triggering mechanism.

High rate of change of propagation conditions

Low rate of change of propagation conditions

Service GSM RSSI GSM BSIC Inter -Freq. GSM RSSI GSM BSIC Inter -Freq. AMR Speech 4 4 4 6 6 6

RT Data 4 4 4 6 6 6 NRT Data 4 4 4 6 6 6

Table 45 – Preferred TGPL

A relatively short TGPL has been selected on the basis of minimising the time spent in compressed mode and thus allowing compressed mode to be triggered relatively late and less frequently. A TGPL of 4 has been selected for scenarios associated with a high rate of change of propagation conditions. A TGPL of 6 has been selected for scenarios associated with a low rate of changed of propagation conditions. The low rate of change of propagation conditions means that more time is available to complete the compressed mode

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measurements (assuming that the same inter-system and inter-frequency handover triggering threshold is used for both high and low rate of change of propagation conditions). 3GPP TS25.331 and TS25.433 allow the configuration of TGPL1 and TGPL2. This increases the flexibility with which transmission gap patterns can be designed. This additional flexibility is not required at this point in time and it is recommended that TGPL1 = TGPL2 = TGPL. Configuring TGPL1 and TGPL2 in this way simplifies the design and any subsequent field trial measurement analysis. The TGSN is dictated to some extent by the TGL. 3GPP TS25.212 specifies that at least 8 slots must be transmitted within each 15 slot radio frame. This means that if the TGL is greater than 7 then the TGSN must be configured to ensure that the transmission gap spans two radio frames. When the transmission gap spans two radio frames then it is preferable that the gap is equally distributed between those frames. This means that the DPCCH and DPDCH belonging to each of the two frames has an equal allocation of bits. Table 46 presents the preference in terms of adopting the single or double frame approach. The preference is defined as a function of the TGL and compressed mode method. The preference is independent of the service, compressed mode triggering mechanism and the rate of change of propagation conditions.

Uplink Downlink TGL HLS SF/2 Puncturing HLS SF/2

7 Double Frame Single Frame Double Frame Double Frame Single Frame 10 Double frame Double frame Double frame Double frame Double frame 14 Double frame Double frame Double frame Double frame Double frame

Table 46 – Preferred single or double frame approach

The double frame approach is required for any TGL greater than 7 slots. The double frame approach is preferred for a TGL of 7 slots when the HLS or puncturing compressed mode methods are used. These compressed mode methods are completed on a per TTI basis and it is preferable for the transmission gap to span two frames belonging to separate TTI. The single frame approach is preferred for a TGL of 7 slots when the SF/2 compressed mode method is used. This is because the SF/2 method is applied on a per frame basis and adopting the single frame approach limits the spreading factor reduction to a single frame. Table 47 presents the preference for TGSN based upon the single and double frame approach preferences specified in Table 46.

TGL TGSN (single frame approach)

TGSN (double frame approach)

7 4 11 10 Not applicable 10 14 Not applicable 8

Table 47 – Preferred TGSN

The TGSN has been selected such that the transmission gap is positioned at the center of the radio frame when the single frame approach is adopted. This provides a small improvement in layer 1 interleaving performance. The TGSN has been selected such that the transmission gap is equally distributed between two frames when the double frame approach is adopted. The TGPRC should be sufficiently large to allow the UE to complete its measurements. If it is known that a UE can complete its measurements within a specific period of time then the TGPRC can be used to limit the time spent in compressed mode. Otherwise the TGPRC can be disabled to allow the UE to remain in compressed mode until instructed otherwise by the network. At this point in time there is insufficient field experience to configure a refined value of the TGPRC. The current preference is to disable the TGPRC.

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The importance of the TGCFN depends upon whether the single or double frame approach has been adopted. If the single frame approach has been adopted the TGCFN has little impact upon performance. In this case the transmission gap is always limited to a single frame and a single TTI. If the double frame approach has been adopted then it is preferable to synchronise the transmission gap with the TTI such that the transmission gap spans two frames belonging to different TTI rather than two frames belonging to the same TTI. In the case of HLS this may allow a higher transport format combination to be selected by the MAC layer. In the case of puncturing this makes it less likely that the maximum permissible level of puncturing is exceeded. Synchronising the transmission gap with the TTI for the SF/2 compressed mode method has little impact because the spreading factor reduction is applied on a per frame basis rather than a per TTI basis. The value of ‘N Identify Abort’ should be sufficiently large to allow the UE to successfully decode an unknown BSIC. If it is known that a UE can complete BSIC identification within a specific period of time then ‘N Identify Abort’ can be used to limit the time spent in compressed mode. Otherwise ‘N Identify Abort’ should be configured with a relatively large value. At this point in time there is insufficient field experience to configure a refined value of the ‘N Identify Abort’. The current preference is to configure ‘N Identify Abort’ with its maximum allowed value of 128 transmission gap patterns. At this point in time, the value of ‘T Reconfirm Abort’ is not important because the Nokia RNC1.5.2.ED2 implementation does not support BSIC re-confirmation. Once BSIC re-confirmation is supported then ‘T Reconfirm Abort’ should be sufficiently large to allow the UE to successfully re-confirm a BSIC. If it is known that a UE can complete re-confirmation within a specific period of time then ‘T Reconfirm Abort’ can be used to limit the time spent in compressed mode. Otherwise ‘T Reconfirm Abort’ should be configured with a relatively large value. At this point in time there is insufficient field experience to configure a refined value of the ‘T Reconfirm Abort’. The current preference is to configure ‘T Reconfirm Abort’ with its maximum allowed value of 10 s.

5.3. Direction The requirement for uplink and downlink compressed mode depends upon the UE receiver implementation. The RNC is informed of the relevant aspects of the UE receiver implementation in the UE capability information included within the RRC: RRC CONNECTION SETUP COMPLETE message. An example of this message is presented in Appendix A. The RNC should configure compressed mode according to the information included within this message. If a UE has a single receiver with a fixed duplex spacing then it will require both uplink and downlink compressed mode for inter-frequency measurements. If a UE has a dual receiver then downlink compressed mode is not required and the requirement for uplink compressed mode depends upon the frequency separation of the carrier to be measured and the carrier of the existing uplink transmission. The existing uplink transmission is likely to interfere with any measurements if the frequency separation is not sufficiently large. The compressed mode design decision regarding direction, is that the RNC should configure compressed mode in the directions indicated by the UE within its capability information. This design decision is independent of the scenarios identified in Section 3.

5.4. Power Control Section 4.4 introduced the parameter set associated with inner loop power control behaviour during compressed mode. This parameter set is summarised below:

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� Uplink DeltaSIR1 � Uplink DeltaSIRafter1 � Uplink DeltaSIR2 � Uplink DeltaSIRafter2 � Downlink DeltaSIR1

� Downlink DeltaSIRafter1 � Downlink DeltaSIR2 � Downlink DeltaSIRafter2 � ITP � RPP

The design decision to configure a single transmission gap per transmission gap pattern means that the deltaSIR2 nor deltaSIRafter2 parameters are not applicable. Configuring the deltaSIR1 parameters with relatively high values leads to increased transmit powers but also increases the ability of inner loop power control to recover subsequent to a transmission gap. Outer loop power control is able to reduce the SIR target back to its normal operating point subsequent to a transmission gap increase. Field experience evaluating the impact of these SIR target increases has not been identified. It may be beneficial to use a larger SIR target increase for scenarios associated with a high rate of change of propagation conditions. In these cases there will be less correlation between the propagation conditions before and after a transmission gap. The compressed mode design decision regarding the SIR target increases, is that the Nokia default configuration should be used, i.e. 1.5 dB for uplink and downlink deltaSIR1; 0.7 dB for deltaSIRafter1 if the transmission gap is not included in the frame; 1.5 dB for deltaSIRafter1 if the transmission gap is included in the frame. This design decision is independent of the scenarios identified in Section 3. Once the quantity of field experience has increased there may be a requirement to refine these values. The ITP parameter provides a means to control the UE transmit power immediately after a transmission gap. TS25.214 specifies that a UE should apply a change in the transmit power of its DPCCH at the start of the first slot after an uplink or downlink transmission gap. The size of this change is given by:

PilotsumeReDPCCH ∆+∆=∆ Where,

gapTPCsumeRe cmd_TPC×∆=∆ if ITP = 0

lastsumeRe δ=∆ if ITP = 1 )N/N(LOG Curr_PilotevPr_PilotPilot ×=∆ 10

sciTPCiilast kcmd_TPC.. ××∆×−×== − 96875093750 1δδδ In the case of an uplink transmission gap, TPC_cmdgap is the value of the TPC_cmd derived in the first slot of the uplink transmission gap, if a downlink TPC command is transmitted in that slot. Otherwise TPC_cmdgap is equal to zero. ∆TPC is the power control step size. Npilot_Prev is the number of pilot bits in the most recently transmitted slot and Npilot_Curr is the number of pilot bits in the current slot. TPC_cmdi is the power control command derived from the current downlink slot. ksc is equal to zero if power scaling has been applied in the current and previous slot as a result of the UE reaching its maximum power. Otherwise ksc is equal to 1. Field experience evaluating the impact of the ITP parameter has not been identified. The compressed mode design decision regarding ITP, is that it should be configured with a value of 0. This design decision is independent of the scenarios identified in Section 3. Using a value of 0 is a simpler approach and will simplify the interpretation of field measurement results. Once the quantity of field experience has increased there may be a requirement to change the value of ITP to 1. The RPP parameter provides a means to control the behaviour of inner loop power control during the recovery period. The recovery period is defined as the minimum of the TGL and 7 slots. The recovery period

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starts after a transmission gap once there is simultaneous uplink and downlink transmission. Configuring RPP as 0 means that inner loop power control behaves as normal during the recovery period. Configuring RPP as 1 means that uplink power control algorithm 1 is used during the recovery period with a modified power control step size. If uplink power control algorithm 1 is being used, the modified step size is given by the minimum of 3 dB and twice the normal step size. If uplink power control algorithm 2 is being used then the modified step size is 1 dB. Field experience evaluating the impact of the RPP parameter has not been identified. The compressed mode design decision regarding RPP, is that it should be configured with a value of 0. This design decision is independent of the scenarios identified in Section 3. Using a value of 0 is a simpler approach and will simplify the interpretation of field measurement results. Once the quantity of field experience has increased there may be a requirement to change the value of RPP to 1.

5.5. Scrambling Code SF/2 in the downlink direction may require the use of an alternative scrambling code. There is a one-to-one relationship between the original channelisation code and the channelisation code with half the spreading factor. If the channelisation code with half the spreading factor is blocked by another connection then it must be applied with an alternative scrambling code. The use of an alternative scrambling code means that downlink orthogonality is lost for that radio link and downlink transmit powers for all radio links will increase. The trade-off associated with the use of an alternative scrambling code is thus to allow the use of an alternative scrambling code and incur short term increases in downlink transmit power or to forbid the use of an alternative scrambling code and deny compressed mode requests when the required SF/2 channelisation code is not available. The probability of the required SF/2 channelisation code not being available is dependent upon the traffic loading the cell, the existing spreading factor and the effectiveness of the routines used to de-fragment the channelisation code tree. As the level of traffic increases there will be more frequent instances of the required SF/2 channelisation code not being available. This is especially true for high data rate services which require channelisation codes that block large parts of the code tree. The compressed mode design decision regarding scrambling code is that the RNC should allow the use of an alternative scrambling code when the required SF/2 channelisation code is not available from the primary scrambling code. This design decision is independent of the scenarios identified in Section 3.

5.6. Downlink Frame Type The RNC is able to select between downlink frame type ‘A’ and downlink frame type ‘B’. These frame types are illustrated in Figure 8. Frame type ‘A’ maximises the duration of the transmission gap. The transmission gap duration for frame type ‘A’ is equal to the duration of the number of transmission gap slots minus the duration of the DPCCH pilot field. As an example consider a 7 slot transmission gap applied to the AMR speech service using downlink slot format 8. The duration of 7 slots is 4.67 ms. The duration of the 4 pilot bits associated with downlink slot format 8 is 0.07 ms. The resulting transmission gap is thus 4.60 ms. Frame type ‘B’ reduces the duration of the transmission gap in return for an additional uplink power control command. The reduction in transmission gap length is defined by the duration of the DPDCH data1 field plus the duration of the DPCCH TPC field. In the case of the AMR speech service using downlink slot format 8, the transmission gap is reduced from 4.60 ms to 4.47 ms. The benefit of the additional uplink power control command depends upon the transmission gap length. As the transmission gap length increases

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the relative benefit of the additional command decreases. The benefit decreases because there is less correlation between the propagation conditions before and after the transmission gap. The relative reduction in transmission gap length also decreases as transmission gap length increases. Based upon the assumption that transmission gaps will always have a duration of at least 7 slots, the additional TPC command provided by frame type ‘B’ is not expected to provide a significant benefit. The compressed mode design decision regarding downlink frame type is that the RNC should configure the use of frame type ‘A’. This design decision is independent of the scenarios identified in Section 3.

5.7. Measurement Reporting The RNC is able to configure the interval between periodic compressed mode measurement reports. A short interval increases the responsiveness of the system but also increases the quantity of signalling traffic. While the level of network traffic is relatively low, this trade-off can be balanced in the direction of making the system more responsive. The minimum value permitted by 3GPP is 250 ms. The compressed mode design decision regarding the reporting interval is that an interval of 250 ms should be used. This design decision is independent of the scenarios identified in Section 3. The RNC is able to configure the minimum number of measurement reports that are required prior to being able to make a handover decision. Increasing the number of measurement reports increases the probability of the UE identifying the best cell but also increases the handover delay. The current compressed mode strategy is to minimise the handover delay. The design decision regarding the minimum number of measurement reports is that the RNC should be able to make a handover decision as soon as it receives the first measurement report. This design decision is independent of the scenarios identified in Section 3. The RNC is also able to configure the maximum number of measurement reports after which the UE is instructed to stop measurements. Decreasing the maximum number of measurement reports limits the probability of the UE identifying the best cell. The design decision regarding the maximum number of measurement reports is that the RNC should be allow up to 20 measurement reports. This design decision is independent of the scenarios identified in Section 3.

5.8. Other Configuration Parameters Nokia’s RAN1.5.2.ED2 implementation allows the RNC to enable or disable compressed mode measurements on a per RNC basis. This is done using the RNC databuild parameter CMmasterSwitch. It is not possible to enable or disable compressed mode measurements on a per cell nor per Node B basis. Based upon the assumption that compressed mode measurements form an essential part of inter-system and inter-frequency handover, the design decision regarding the CMmasterSwitch parameter is that it should be configured to enable compressed mode. This design decision is independent of the scenarios identified in Section 3. Nokia’s RAN1.5.2.ED2 implementation allows the RNC to limit the number of simultaneous compressed mode UE. This is done using the RNC databuild parameter MaxNumbUECMcoverHO. At this point in time there is insufficient field experience to indicate the impact upon system performance when large number of UE are simultaneously in compressed mode. The design decision regarding the MaxNumbUECMcoverHO parameter is that it should be configured to allow a maximum of 16 UE to simultaneously use compressed mode. This figure represents approximately one third of the cell’s capacity when the cell is loaded by speech users, i.e. the maximum capacity of a cell is expected to be approximately 50 speech users. There may be a requirement to reduce this figure on a per cell basis once the quantity of field experience has increased. This design decision is independent of the scenarios identified in Section 3.

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Nokia’s RAN1.5.2.ED2 implementation makes use of the PrxTarget and PrxOffset RNC databuild parameters for uplink admission control. At this point in time there is little field experience indicating the effectiveness of uplink admission control. The design decision regarding the PrxTarget parameter is that it should be configured with its maximum value of 30 dB. This effectively disables uplink admission control and removes the requirement to configure PrxOffset with a refined value. There may be a requirement to reduce PrxTarget on a per cell basis once the quantity of field experience has increased. This design decision is independent of the scenarios identified in Section 3. Nokia’s RAN1.5.2.ED2 implementation makes use of the PtxTarget and PtxOffset RNC databuild parameters for downlink admission control purposes. The design decision regarding the PtxTarget and PtxOffset parameters is that they should be configured with their default values of 40 dBm and 1 dB respectively. There may be a requirement to increase PtxTarget once the quantity of field experience has increased. This design decision is independent of the scenarios identified in Section 3.

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6. Impact of using the Nokia Default Parameter Set This section evaluates the impact of using the Nokia default configuration presented in Section 4 rather than the O2 preferred configuration presented in Section 5.

6.1. Method Compressed mode methods are specified separately for the uplink and downlink.

6.1.1. Uplink

Table 3 presents the Nokia default configuration in terms of uplink compressed mode method. The SF/2 method is applied to the AMR speech and RT data services whereas the HLS method is applied to the NRT data service. Table 36 presents the O2 preferred configuration in terms of uplink compressed mode method. The SF/2 method is applied to the RT data service whereas the HLS method is applied to the AMR speech and NRT data services. These preferences are independent of the rate of change of propagation conditions, triggering mechanism and measurement purpose. The only difference between the two configurations is the compressed mode method applied to the AMR speech service. The O2 preferred configuration of HLS is only possible if a lower AMR bit rate is supported by both the UE and the network. If lower AMR bit rates are not supported, the SF/2 method must be applied. At this point in time, lower AMR bit rates are not widely supported and it is acceptable to apply SF/2 rather than HLS as a compressed mode method for the AMR speech service. Use of the SF/2 method means that the UE must be capable of supporting the short term 3 dB increase in transmit power associated with the halved spreading factor. The requirement for an increase in the UE transmit power increases the importance of the UE transmit power compressed mode triggering mechanism. Additional care is required when using UE that do not support this triggering mechanism. In this case, the threshold associated with the CPICH RSCP triggering mechanism may be adjusted to reflect the path loss associated with a specific UE transmit power.

6.1.2. Downlink Table 10 presents the Nokia default configuration in terms of downlink compressed mode method. The SF/2 method is applied to the AMR speech and RT data services whereas the HLS method is applied to the NRT data service. Table 38 presents the O2 preferred configuration in terms of downlink compressed mode method. The puncturing method is applied to the AMR speech service. The SF/2 method is applied to the RT data service whereas the HLS method is applied to the NRT data service. These preferences are independent of the rate of change of propagation conditions, triggering mechanism and measurement purpose. The only difference between the two configurations is the compressed mode method applied to the AMR speech service. The Nokia default configuration of using the SF/2 method means that the cell must be capable of supporting a 3 dB short term increase in transmit power. This requirement is most significant when the downlink transmit power is responsible for triggering compressed mode. The use of SF/2 also places a greater requirement upon the downlink channelisation code tree and the potential requirement for

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the use of an alternative scrambling code. The AMR speech service uses a relatively high downlink spreading factor of 128 meaning that the channelisation code tree requirement is less than that of a high bit rate service.

6.2. Timing Table 19 presents the Nokia default configuration in terms of TGL. The Nokia default configuration applies a TGL of 7 slots to all compressed mode measurement patterns. Table 40, Table 42 and Table 44 present the O2 preferred configurations in terms of TGL for GSM RSSI measurements, GSM BSIC identification and FDD inter-frequency measurements respectively. The O2 preferred configurations specify a TGL of 7 slots for the AMR speech and RT data services and TGL of 10 slots for the NRT data service. O2 prefer a larger transmission gap for NRT data services to increase the efficiency with which measurements can be made and to reduce the time spent in compressed mode. Reducing the time spent in compressed mode means that compressed mode can be triggered relatively late and less frequently. NRT services are able to incur the throughput reduction associated with a larger transmission gap. Applying the Nokia default configuration means that the compressed mode measurements for the NRT data service will have the same efficiency as for the AMR speech and RT data services. It also means that the time spent in compressed mode should be approximately the same for all services. It does not necessarily mean that the compressed mode triggering points should be the same for all services because BSIC confirmation is not required for the inter-system handover of NRT data services, i.e. less time is spent in compressed mode for the inter-system handover of NRT data services. The Nokia default and O2 preferred configurations are aligned in terms of configuring a single transmission gap per transmission gap pattern, i.e. TGD = 0 and TGL1 = TGL2 = TGL. Table 19 presents the Nokia default configuration in terms of TGPL. The Nokia default configuration applies a TGPL of 4 frames to all compressed mode measurement patterns. Table 45 presents the O2 preferred configuration in terms of TGPL for scenarios with high and low rates of change of propagation conditions. The O2 preferred configuration specifies a TGPL of 4 frames for scenarios with a high rate of change of propagation conditions and a TGPL of 6 frames for scenarios with a low rate of change of propagation conditions. A TGPL of 6 frames was chosen for low rate of change of propagation conditions on the basis that more time was available to complete the compressed mode measurements and that for these scenarios the average impact of compressed mode could be reduced by distributing the measurements over a longer period of time. The assumption that more time is available for measurements assumes that equal triggering thresholds are applied to both the high and low rate of change of propagation condition scenarios. The impact of applying a TGPL of 4 frames rather than 6 frames is that compressed mode measurements will be completed more rapidly but potentially less reliably and with greater average impact. The Nokia default and O2 preferred configurations are aligned in terms of configuring a single transmission gap pattern, i.e. TGPL1 = TGLP2 = TGPL. Table 19 presents the Nokia default configuration in terms of TGSN. The Nokia default configuration applies a TGSN of slot 4 for the single frame approach and a TGSN of slot 11 for the double frame approach. These figures are based upon a TGL of 7 slots. Table 47 presents the O2 preferred configuration in terms of TGSN for TGL of 7, 10 and 14 slots. The O2 preferred configuration is aligned with the Nokia default configuration when the TGL is 7 slots. Nokia does not have a default configuration for a TGL of 10 and 14 slots. However the basis of the O2 preferred figures is the same as that for the Nokia default figures, i.e. position the transmission gap at the center of a frame when the single frame approach is used and distribute the transmission gap equally between two frames when the double frame approach is used.

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Both the Nokia default configuration and the O2 preferred configuration define the TGPRC as 0 transmission gap patterns. This is interpreted as an indication that the TGPRC should be disabled and that compressed mode measurements should continue until instructed otherwise by the RNC. The Nokia default configuration defines the TGCFN independently of the timing of the transmission time interval (TTI), i.e. the two are not synchronised. This is aligned with the O2 preferred configuration when using the single frame approach and when using the double frame approach with SF/2. The O2 preferred configuration for the double frame approach when using puncturing or HLS is to synchronise the TGCFN with the TTI such that transmission gaps always span two frames belonging to different TTI. The impact of not synchronising the TGCFN with the TTI for these scenarios means that either more puncturing must be applied or a lower transport format combination must be selected. The requirement for greater puncturing will increase the associated SIR requirement and may make the puncturing method impractical. The requirement to select a lower transport format combination reduces service throughput. Both the Nokia default configuration and the O2 preferred configuration define ‘N Identify Abort’ as 128 transmission gap patterns. This represents the maximum allowed value. The Nokia default configuration does not include a value for ‘T Reconfirm Abort’ because the Nokia RNC1.5.2.ED2 implementation does not support BSIC re-confirmation. The O2 preferred configuration for ‘T Reconfirm Abort’ is 10 s. This represents the maximum allowed value and is likely to reflect the Nokia default configuration once BSIC re-confirmation is supported.

6.3. Direction Both the Nokia default and the O2 preferred use of uplink and downlink compressed mode is according to the capability information provided by the UE. This information is provided within the RRC: RRC CONNECTION SETUP COMPLETE message. Making use of this information ensures that the use of uplink and downlink compressed mode is adjusted according to the requirements of specific UE.

6.4. Power Control Table 24 and Table 26 present the Nokia defaults in terms of uplink and downlink SIR target increases. These defaults are, a 1.5 dB increase for uplink and downlink deltaSIR1; a 0.7 dB increase for deltaSIRafter1 if the transmission gap is not included in the frame; and a 1.5 dB increase for deltaSIRafter1 if the transmission gap is included in the frame. Section 5.4 presents the equivalent O2 preferred configuration. The O2 preferred configuration is aligned with the Nokia default configuration. Table 28 presents the Nokia defaults for the ITP and RPP parameters. The Nokia default value for ITP is 0 and the Nokia default value for RPP is 0. Section 5.4 presents the equivalent O2 preferred configuration. The O2 preferred configuration is aligned with the Nokia default configuration.

6.5. Scrambling Code Both the Nokia default and the O2 preferred compressed mode scrambling code strategy is to allow the use of an alternative scrambling code when required by the SF/2 method. The alternative scrambling code is non-orthogonal and increases downlink transmit powers but it also helps to prevent requests for compressed mode being denied when the appropriate channelisation code is not available.

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6.6. Downlink Frame Type Both the Nokia default and the O2 preferred downlink frame type is type ‘A’. This maximises the length of the transmission gap at the expense of a potentially slightly reduced uplink inner loop power control performance.

6.7. Measurement Reporting Table 33 presents the Nokia default configuration in terms of inter-system and inter-frequency periodic measurement reporting interval. The Nokia default configuration defines a 500 ms reporting interval for both inter-system and inter-frequency measurement reports. Section 5.7 presents the O2 preferred configuration in terms of periodic measurement reporting interval. The O2 preferred configuration specifies a reporting interval of 250 ms. Specifying a shorter reporting interval makes the system more responsive but increases the quantity of signalling traffic. Table 33 presents the Nokia default configuration in terms of the minimum number of measurement reports which are required prior to making a handover decision and the maximum number of measurement reports after which measurements are cancelled. The minimum number of measurement reports is configured as 0 and the maximum as 20. Section 5.7 presents the O2 preferred configuration in terms of these minimum and maximum number of measurement reports. The O2 preferred configuration is aligned with the Nokia default configuration.

6.8. Other Configuration Parameters Table 34 presents the Nokia default configuration for the RNC databuild parameters CMmasterSwitch and MaxNumbUECMcoverHO. The Nokia default configuration enables compressed mode on a per RNC basis and allows a maximum of 16 simultaneous compressed mode UE. Section 6.8 presents the O2 preferred configuration. The O2 preferred configuration is aligned with the Nokia default configuration. It acceptable for the CMmasterSwitch parameter to be defined on a per RNC basis rather than on a per cell or per Node B basis because other parameters can be used to effectively disable compressed mode on a per cell or per Node B basis, e.g. triggering thresholds may be configured such that compressed mode is never triggered. There may be a requirement to reduce the value of MaxNumbUECMcoverHO once a greater quantity of field experience has been obtained. Table 34 presents the Nokia default configuration for the RNC databuild parameters PrxTarget and PrxOffset. The Nokia default configuration defines PrxTarget as 4 dB and PrxOffset as 1 dB. Section 6.8 presents the O2 preferred configuration. The O2 preferred configuration defines PrxTarget as 30 dB and PrxOffset as 1 dB. Increasing the value of PrxTarget to 30 dB effectively disables uplink admission control. Disabling uplink admission control means that increases in the uplink interference floor could become relatively large and could compromise uplink coverage. At this point in time there is an uncertainty regarding the effectiveness of uplink admission control. This has led to the decision to disable uplink admission control. The value of PrxTarget may be reduced as the quantity of field experience increases. Table 34 presents the Nokia default configuration for the RNC databuild parameters PtxTarget and PtxOffset. The Nokia default configuration defines PtxTarget as 40 dBm and PtxOffset as 1 dB. Section 6.8 presents the O2 preferred configuration. The O2 preferred configuration is aligned with the Nokia default configuration.

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7. Field Experience The majority of this report is based upon theoretical arguments. This section has been included to help provide an indication of the performance which can be expected from the field. The measurements presented in this section have been recorded during the second half of 2003, i.e. before the release of RAN1.5.2.ED2. Compressed mode performance is not expected to be significantly different for RAN1.5.2.ED2. It should however be recognised that system performance may change as new UE, Node B and RNC software is introduced. The measurements in this section are organised in terms of the method used to generated the compressed mode transmission gaps.

7.1. Spreading Factor Division by 2 Spreading factor division by 2 (SF/2) compressed mode has been studied for an inter-system handover of the AMR speech service. The single frame approach was configured with a 7 slot transmission gap and a 4 frame transmission gap pattern length. Figure 9 presents the UE transmit power characteristic recorded while using this compressed mode configuration.

7 slot transmission gap every 60 slots

UE

tran

smit

pow

er

Time

Figure 9 – UE transmit power during SF/2 compressed mode (AMR speech service)

The transmission gaps are clearly visible whereas the increase in UE transmit power resulting from spreading factor reduction is less clearly visible. The average increase in UE transmit power caused by compressed mode was evaluated by driving the same route with and without compressed mode active. An average increase in UE transmit power of 1.3 dB was observed. This result is reasonable when considering that 8 slots out of every 60 slots have their UE transmit power approximately doubled while 7 slots out of every 60 slots have no UE transmit power. The increase in uplink transmit power results from a combination of the SIR target changes and the recovery period power control rather than directly from the spreading factor reduction. Changes in the downlink transmit power were not recorded during this set of measurements. An average compressed mode activation time of 1.0 s was observed. The activation time represents the delay between the RNC receiving a measurement report which triggers the requirement for compressed mode and the RNC sending the measurement control which instructs the UE to start compressed mode. The subsequent delay between the RNC instructing the UE to start compressed mode measurements and the UE providing all of its GSM RSSI measurements was observed to be 1.3 s. The delay associated with identifying the relevant GSM BSIC was 2.0 s. The UE was thus in compressed mode for an average of 3.3 s with an initial triggering delay of 1.0 s.

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7.2. Higher Layer Scheduling Higher layer scheduling (HLS) compressed mode has been studied for an inter-system handover of the PS data service. The single frame approach was configured with a 7 slot transmission gap and a 4 frame transmission gap pattern length. A downlink file transfer was completed during the compressed mode period. The measurements were repeated for downlink PS data rates of 64 kbps and 128 kbps and 384 kbps. Figure 9 presents the downlink throughput characteristic for the 128 kbps PS data service.

Average = 121 kbps

HLS startsT

hrou

ghpu

t

Time

Average = 71 kbps

Figure 10 – Downlink throughput during ½ rate higher layer scheduling (128 kbps PS data service)

The downlink throughput reduction caused by higher layer scheduling is clearly visible. The average throughput drops from 121 kbps to 71 kbps. The variance of the throughput is significantly greater during the period of compressed mode. Larger reductions in throughput were observed for the 64 kbps and 384 kbps downlink data rates, i.e. a reduction from 55 kbps to 15 kbps for the 64 kbps data service and a reduction from 270 kbps to 30 kbps for the 384 kbps data service. It is not clear why the compressed mode throughput associated with the 384 kbps data service is less than the compressed mode throughput associated with the 128 kbps data service. The throughput associated with the 384 kbps data service is relatively low prior to entering compressed mode indicating that some other factors may be influencing the results for this service. The average increase in the uplink and downlink SIR targets caused by compressed mode was evaluated by driving the same route with and without compressed mode active. The uplink SIR target was observed to increase by 1.6 dB and the downlink SIR target by 6.5 dB. The uplink figure is similar to the average increase in UE transmit power observed for the AMR speech service when applying SF/2 compressed mode. The downlink figure is considerably greater than expected. An average compressed mode activation time of 1.4 s was observed. The activation time represents the delay between the RNC receiving a measurement report which triggers the requirement for compressed mode and the RNC sending the measurement control which instructs the UE to start compressed mode. The subsequent delay between the RNC instructing the UE to start compressed mode measurements and the UE providing all of its GSM RSSI measurements was observed to be 1.2 s. The UE was thus in compressed mode for an average of 1.2 s with an initial triggering delay of 1.4 s.

7.3. Puncturing Puncturing compressed mode measurement results were not available for presentation within this report.

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8. Recommendations The following recommendations have resulted from the work completed.

1. The preferred set of compressed mode parameters should be identified on a per scenario basis. Compressed mode scenarios should be categorised according to the measurement purpose (GSM RSSI, BSIC identification, FDD measurement); the service being used (AMR speech, RT data, NRT data); the triggering mechanism (uplink transmit power, downlink transmit power, CPICH Ec/Io, CPICH RSCP, uplink quality); and the rate of change of propagation conditions (high, low).

2. The focus should be directed towards coverage reason compressed mode for inter-system handover.

Compressed mode for inter-frequency handover should be introduced once there are plans for Node B to be configured with multiple carriers. Load and traffic reason compressed mode should be evaluated prior to RAN05.

3. Nokia’s current compressed mode implementation is relatively simplistic in terms of customising the

compressed mode method to suit the compressed mode scenario, i.e. SF/2 compressed mode is always used for AMR speech and RT data services whereas HLS is always used for NRT data services. Consideration should be given to requesting Nokia to implement a more sophisticated set of rules for associating specific compressed mode methods to specific compressed mode scenarios.

4. Consideration should be given to requesting Nokia to use HLS as a compressed mode method for the

uplink speech service once both the network and UE support lower AMR bit rates. It is acceptable to use the Nokia default compressed mode methods for other uplink services. The selection of a specific uplink compressed mode method is currently not configurable by O2.

5. Consideration should be given to requesting Nokia to use puncturing as a compressed mode method

for the downlink speech service once both the network and UE support lower AMR bit rates. It is acceptable to use the Nokia default compressed mode methods for other downlink services. The selection of a specific downlink compressed mode method is currently not configurable by O2.

6. Consideration should be given to requesting Nokia to use a transmission gap length (TGL) of 10

slots rather than 7 slots for NRT data services. It is acceptable to use the Nokia default of 7 slots for other services. The selection of a specific TGL is not currently configurable by O2.

7. It is acceptable to use the Nokia default strategy of configuring single transmission gap patterns with

a single transmission gaps. The additional flexibility provided by configuring a second transmission gap pattern and a second transmission gap is not viewed as necessary.

8. Consideration should be given to requesting Nokia to define the transmission gap pattern length

(TGPL) parameters on a per cell basis rather than on a per RNC basis. Consideration could then be given to configuring the use of a transmission gap pattern length (TGPL) of 6 frames rather than 4 frames for scenarios associated with a low rate of change of propagation conditions. It is acceptable to use the Nokia default of 4 frames for scenarios associated with a high rate of change of propagation conditions. The selection of a specific TGPL is configurable by O2 but only on a per RNC basis.

9. Consideration should be given to requesting Nokia to synchronise the transmission gap connection

frame number (TGCFN) with the transmission time interval (TTI) when the compressed mode

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method is puncturing or HLS and the double frame approach has been adopted. The TGCFN and TTI should be synchronised such that double frame transmission gaps span two frames belonging to different TTI.

10. It is acceptable to use the Nokia default strategy of configuring the transmission gap starting slot

number (TGSN) such that the transmission gap is positioned at the center of a frame when the single frame approach is used and to distribute the transmission gap equally between two frames when the double frame approach is used. O2 are able to configure the TGSN for the single frame approach but currently are not able to configure the TGSN for the double frame approach.

11. It is acceptable to use the Nokia default strategy in terms of allowing compressed mode

measurements to continue until instructed otherwise by the RNC, i.e. configuring the transmission gap pattern repetition count (TGPRC) with a value of 0. The value of TGPRC may be refined once a greater quantity of field experience has been gained. The selection of a specific TGPRC is not currently configurable by O2.

12. It is acceptable to use the Nokia default of configuring ‘N Identify Abort’ with its maximum value of

128 patterns. The value of ‘N Identify Abort’ may be refined once a greater quantity of field experience has been gained. The selection of a specific ‘N Identify Abort’ is not currently configurable by O2.

13. It is acceptable to use the Nokia default strategy of configuring uplink and downlink compressed

mode according to the capability information provided by the UE. The use of uplink and downlink compressed mode is currently not configurable by O2.

14. It is acceptable to use the Nokia default parameter values for the behaviour of inner loop power

control during compressed mode. The parameter values may be refined once a greater quantity of field experience has been gained. The selection of a specific SIR target increase is not currently configurable by O2. The selection of the initial transmit power increase mode and recovery period power control mode are configurable by O2.

15. It is acceptable to use the Nokia default of allowing the use of an alternative scrambling code when

the SF/2 compressed mode method is applied and the required channelisation code is not available from the primary scrambling code. The use of an alternative scrambling code is configurable by O2.

16. It is acceptable to use the Nokia default of configuring compressed mode to make use of downlink

frame type ‘A’. The selection of a specific frame type is not currently configurable by O2.

17. Consideration should be given to requesting Nokia to use a shorter compressed mode periodic measurement reporting interval, i.e. 250 ms rather than 500 ms. The periodic reporting interval can be configured by O2 but 500 ms is currently the lowest supported value.

18. It is acceptable to use the Nokia default values for the compressed mode measurement reporting

parameters which define the minimum required and maximum allowed number of measurement reports. These parameters are configurable by O2.

19. It is acceptable to use the Nokia default for the maximum number of simultaneous compressed mode

UE per cell, i.e. 16. This value may be refined once a greater quantity of field experience has been gained. The relevant parameter is configurable by O2.

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20. A field measurement campaign should be completed to evaluate the impact of compressed mode upon the performance of layers 1 and 2. The measurement campaign should focus upon the transmit power requirement, SIR target, RLC re-transmission rate and layer 2 throughput. The dominant compressed mode triggering mechanism should also be identified.

21. A field measurement campaign should be completed to evaluate the delay associated with

compressed mode measurements. The measurement campaign should focus upon a range of services, a range of transmission gap patterns and a range of compressed mode methods.

22. Results from the field measurement campaigns should be used to help define the thresholds that

trigger compressed mode measurements. If the delay is found to be short then the thresholds may be configured such that compressed mode is triggered relatively late and less frequently. If the delay is found to be long then the thresholds should be configured such that compressed mode is triggered relatively early and more frequently.

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9. Conclusions The following conclusions have resulted from the work completed:

1. Compressed mode scenarios can be categorised according to the measurement purpose (GSM RSSI, BSIC identification, FDD measurement); the service being used (AMR speech, RT data, NRT data); the triggering mechanism (uplink transmit power, downlink transmit power, CPICH Ec/Io, CPICH RSCP, uplink quality); and the rate of change of propagation conditions (high, low).

2. Compressed mode will initially be limited to coverage reason inter-system handover scenarios. Inter-

frequency handover scenarios will become applicable once O2 starts to configure Node B with multiple carriers. Load and traffic reason handovers will become applicable once RAN05 RNC software is available.

3. Compressed mode functionality and signalling is standardised by 3GPP. There are however a set of

design decisions required in terms of selecting a compressed mode method and configuring the associated transmission gap patterns. Nokia’s current implementation of compressed mode is compliant with the R99 version of 3GPP specifications. Nokia’s implementation makes use of a set of configurable RNC databuild parameters and a set on non-configurable RNC databuild parameters.

4. This report has identified the trade-offs associated with each compressed mode parameter. The

Nokia default configuration and the O2 preferred configuration have been identified. The impact of applying the Nokia default configuration rather than the O2 preferred configuration has been evaluated.

5. A number of configurable parameter changes have been proposed within the recommendations

section of this report. These parameter changes can be made by O2 but should be tested during a localised parameter trial prior to deploying across a large area. The majority of arguments for proposed parameter changes are theoretical rather than being based upon field trial experience.

6. A number of non-configurable parameter changes have been proposed within the recommendations

section of this report. These parameter changes cannot be made by O2 and require requests to be made to Nokia product line for future implementation. Requests for these parameter changes should be prioritised with other outstanding requests to Nokia product line. The majority of arguments for proposed parameter changes are theoretical rather than being based upon field trial experience.

7. A relatively limited quantity of field trial experience has been made available for this report. The

quantity of experience will increase throughout 2004 as O2’s WCDMA network performance is evaluated and refined.

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10. References

[1] 3GPP TS25.133 ‘Requirements for the support of radio resource management’

[2] 3GPP TS25.211 ‘Physical channels and mapping of transport channels onto physical channels’

[3] 3GPP TS25.212 ‘Multiplexing and channel coding’

[4] 3GPP TS25.213 ‘Spreading and modulation’

[5] 3GPP TS25.214 ‘Physical layer procedures’

[6] 3GPP TS25.215 ‘Physical layer measurements’

[7] 3GPP TS25.331 ‘Radio resource control protocol specification’

[8] 3GPP TS25.433 ‘UTRAN Iub interface NBAP signalling’

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11. Abbreviations AMR Adaptive Multi-Rate BCCH Broadcast Control Channel BSIC Base Station Identifier Code CEC Capacity Enhanced Configuration CM Compressed Mode CPICH Common Pilot Channel CS Circuit Switched DPCCH Dedicated Physical Control Channel DPCH Dedicated Physical Channel DPDCH Dedicated Physical Data Channel FDD Frequency Division Duplex FMCI Inter-Frequency Measurement Control FMCG Inter-System Measurement Control HLS Higher Layer Scheduling IFHO Inter-Frequency Handover ISHO Inter-System Handover ITP Initial Transmit Power method NBAP Node B Application Protocol NRT Non-Real Time OTOR Omni Transmit Omni Receive OTSR Omni Transmit Sector Receive PS Packet Switched RAN Radio Access Network RLC Radio Link Control RNC Radio Network Controller ROC Roll-Out Configuration RPP Recovery Period Power control mode RRC Radio Resource Control RSCP Received Signal Code Power RSSI Received Signal Strength Indicator RT Real Time SF Spreading Factor SIR Signal to Interference Ratio STSR Sector Transmit Sector Receive TGCFN Transmission Gap Connection Frame Number TGD Transmission Gap Distance TGL Transmission Gap Length TGMP Transmission Gap Measurement Purpose TGPL Transmission Gap Pattern Length TGPRC Transmission Gap Pattern Repetition Count TGPSI Transmission Gap Pattern Sequence Identifier TGSN Transmission Gap Starting slot Number TPC Transmit Power Control TTI Transmission Time Interval UE User Equipment UMTS Universal Mobile Telecommunications System UTRAN UMTS Terrestrial Radio Access Network

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In Confidence

Appendix A. Example UE capability message This appendix provides an example RRC: RRC CONNECTION SETUP COMPLETE message. This message includes the UE capability information which specifies the UE’s capability in terms of uplink and downlink compressed mode measurements. UL-DCCH-Message : { message rrcConnectionSetupComplete : { rrc-TransactionIdentifier 0, startList { { cn-DomainIdentity cs-domain, start-Value '00000000000000011000'B }, { cn-DomainIdentity ps-domain, start-Value '11111111111111111111'B } }, ue-RadioAccessCapability { accessStratumReleaseIndicator r99, pdcp-Capability { losslessSRNS-RelocationSupport FALSE, supportForRfc2507 notSupported : NULL }, rlc-Capability { totalRLC-AM-BufferSize kb50, maximumRLC-WindowSize mws2047, maximumAM-EntityNumber am6 }, transportChannelCapability { dl-TransChCapability { maxNoBitsReceived b5120, maxConvCodeBitsReceived b1280, turboDecodingSupport supported: b512 0, maxSimultaneousTransChs e8, maxSimultaneousCCTrCH-Count 1, maxReceivedTransportBlocks tb16, maxNumberOfTFC tfc96, maxNumberOfTF tf64 }, ul-TransChCapability { maxNoBitsTransmitted b3840, maxConvCodeBitsTransmitted b1280, turboEncodingSupport supported: b384 0, maxSimultaneousTransChs e8, modeSpecificInfo fdd : NULL, maxTransmittedBlocks tb8, maxNumberOfTFC tfc32, maxNumberOfTF tf32 } }, rf-Capability { fddRF-Capability { ue-PowerClass 4, txRxFrequencySeparation mhz190 } }, physicalChannelCapability { fddPhysChCapability {

downlinkPhysChCapability { maxNoDPCH-PDSCH-Codes 3, maxNoPhysChBitsReceived b9600, supportForSF-512 FALSE, supportOfPDSCH FALSE, simultaneousSCCPCH-DPCH-Reception notSupported : NULL }, uplinkPhysChCapability { maxNoDPDCH-BitsTransmitted b2400, supportOfPCPCH FALSE } } }, ue-MultiModeRAT-Capability { multiRAT-CapabilityList { supportOfGSM TRUE, supportOfMulticarrier FALSE }, multiModeCapability fdd }, securityCapability { cipheringAlgorithmCap { ciphuea0 }, integrityProtectionAlgorithmCap { integuia1 } }, ue-positioning-Capability { standaloneLocMethodsSupported FALSE, ue-BasedOTDOA-Supported FALSE, networkAssistedGPS-Supported noNetworkAssistedGP S, supportForUE-GPS-TimingOfCellFrames FALSE, supportForIPDL FALSE }, measurementCapability { downlinkCompressedMode { fdd-Measurements TRUE, gsm-Measurements { gsm900 TRUE, dcs1800 TRUE, gsm1900 FALSE }, multiCarrierMeasurements FALSE }, uplinkCompressedMode { fdd-Measurements TRUE, gsm-Measurements { gsm900 TRUE, dcs1800 TRUE, gsm1900 FALSE }, multiCarrierMeasurements FALSE } } } }

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O2RD 04 021 Compressed Mode Strategy 1

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