(E)GPRS Radio Networks - Planning Theory RG10(S14)

7/27/2019 (E)GPRS Radio Networks - Planning Theory RG10(S14)

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(E)GPRS Radio NetworksPlanning TheoryVersion 4.0



2/169 Managed Services, NPOCapability Management

02/06/2009 Copyright 2007 Nokia Siemens Networks.All rights reserved.

DOCUMENT DESCRIPTION

Title and version (E)GPRS Radio Networks - Planning Theory v4.0ReferenceTarget Group Radio, Tranmission, E2ETechnology andSW release

GERAN - S14 (RG10)

Related ServiceItemsService ItemnumberAuthor Pal SzabadszallasiDateApprover Villa Salomaa

CHANGE RECORD

This section provides a history of changes made to this document

VERSION DATE EDITED BY SECTION/S COMMENTS

1.0 17.06.2005 Pal Szabadszallasi2.0 18.12.2006 Pal Szabadszallasi

3.0 16.12.2008 Pal Szabadszallasi4.0 02.06.2009 Pal Szabadszallasi

Copyright © Nokia Siemens Networks. This material, including documentation and any relatedcomputer programs, is protected by copyright controlled by Nokia Siemens Networks. All rights arereserved. Copying, including reproducing, storing, adapting or translating, any or all of this materialrequires the prior written consent of Nokia Siemens Networks. This material also containsconfidential information which may not be disclosed to others without the prior written consent ofNokia Siemens Networks.





Table of contents

1. Introduction....................................................................................... 7

1.1 (E)GPRS Dimensioning, Planning and Optimization Structure........................................8 1.2 Data hardware and site solutions....................................................................................8 1.2.1 BSC and PCU variants ...................................................................................................8 1.2.1.1 PCU2 Plug-in Unit Variants and Hardware Architecture..................................................9 1.2.1.2 PCU2 Software Architecture.........................................................................................10 1.2.1.3 PCU1 and PCU2 Software Differences on Air Interface................................................11 1.2.1.4 PCU2-E........................................................................................................................12 1.2.1.5 Mixed PCU configuration and asymmetrical PCU setup ............................................... 12 1.2.2 BTS variants.................................................................................................................13 1.3 Data features................................................................................................................13 1.3.1 S10 / S10.5ED..............................................................................................................13

1.3.2 S11 / S11.5...................................................................................................................14 1.3.3 S12...............................................................................................................................14 1.3.4 S13...............................................................................................................................15 1.3.5 S14...............................................................................................................................15

2. (E)GPRS Modulation ...................................................................... 16

2.1 GMSK and 8-PSK Modulation ......................................................................................16 2.2 Modulation Block Diagrams..........................................................................................17 2.3 Back-off in EGPRS.......................................................................................................18 2.4 Burst Structure .............................................................................................................20

3. Coding Schemes ............................................................................ 22 3.1 Protocol Architecture ....................................................................................................22 3.1.1 Physical Layer ..............................................................................................................23 3.1.2 RLC/MAC Layer ...........................................................................................................23 3.1.2.1 Radio Link Control........................................................................................................23 3.1.2.2 Medium Access Control................................................................................................23 3.1.2.3 RLC/MAC Header Formats...........................................................................................23 3.1.3 Logical Link Control ......................................................................................................28 3.1.4 SNDCP Layer...............................................................................................................29 3.1.5 IP, TCP/UDP and Application Layer .............................................................................29 3.2 RLC/MAC Coding Schemes .........................................................................................31 3.2.1 GPRS Coding Schemes (CSs) .....................................................................................31 3.2.2 EGPRS Modulation and Coding Schemes (MCSs).......................................................34

4. (E)GPRS Procedures...................................................................... 37

4.1 TBF Establishment .......................................................................................................37 4.1.1 Channel Request and Packet Immediate Assignment ..................................................37 4.1.2 DL TBF Assignment .....................................................................................................38 4.1.3 UL TBF Assignment .....................................................................................................40 4.1.3.1 Channel Request - Packet Access Procedure (CCCH / PCCH)....................................40 4.1.3.2 EGPRS Packet Channel Request.................................................................................41 4.1.3.3 Dynamic and Extended Dynamic Allocation on UL with and without USF4...................42 4.1.3.4 UL TBF ASSIGNMENT, MS on CCCH, 2 phase access...............................................43 4.1.3.5 UL TBF ASSIGNMENT, MS on CCCH, 1 phase access...............................................44 4.1.3.6 EGPRS UL TBF ASSIGNMENT, MS on PCCCH with 2 phase access.........................46 4.1.3.7 EGPRS UL TBF ASSIGNMENT, MS on PCCCH with 1 phase access.........................46





4.1.3.8 Establishment of EGPRS UL TBF when DL TBF is ongoing.........................................47 4.2 (E)GPRS Data Transfer................................................................................................48 4.2.1 (E)GPRS Data Transfer DL ..........................................................................................48 4.2.2 (E)GPRS Data Transfer UL ..........................................................................................48

4.3 Mobility with Cell-reselection ........................................................................................50 4.3.1 Intra PCU Cell-Reselection...........................................................................................50 4.3.2 Inter PCU Cell-reselection (Intra BSC)..........................................................................51 4.3.3 RA/LA Update (intra PAPU)..........................................................................................52 4.3.4 RA/LA Update (Inter PAPU or inter SGSN)...................................................................53 4.4 TBF Release ................................................................................................................54 4.4.1 Packet TBF Release Content .......................................................................................55 4.4.2 Abnormal Releases ......................................................................................................55 4.4.3 TBF Release in PCU2 ..................................................................................................56

5. (E)GPRS Accessibility .................................................................... 57

5.1 Air Interface Signaling Load..........................................................................................57 5.1.1 Common Control Channels ..........................................................................................58 5.1.1.1 Paging Channel............................................................................................................58 5.1.1.2 Access Grand Channel.................................................................................................58 5.1.1.3 Random Access Channel .............................................................................................59 5.1.2 SDCCH ........................................................................................................................59 5.2 TRXSIG Load...............................................................................................................60 5.2.1 TRXSIG Load Theory ...................................................................................................60 5.2.1.1 Abis Protocols ..............................................................................................................60 5.2.1.2 TRXSIG Load Components, Measurement and Analysis..............................................62 5.3 BCSU Load ..................................................................................................................65 5.3.1 BSC RAW Measurement Results .................................................................................65

5.3.2 Reporting Suit 184 Report ............................................................................................65 5.4 Signaling Load with DTM Usage...................................................................................66

6. Resource Allocation in BSS ............................................................ 67

6.1 Cell Reselection............................................................................................................68 6.1.1 C1 and C2 ....................................................................................................................68 6.1.2 C31/C32.......................................................................................................................69 6.1.3 Network Controlled Cell Reselection.............................................................................72 6.1.3.1 NCCR Benefits .............................................................................................................73 6.1.3.2 NCCR Functionality......................................................................................................73 6.1.3.3 Target cell selection......................................................................................................74

6.1.3.4 Signaling Flow..............................................................................................................75 6.1.3.5 BLER Limits are Needed for the Quality Control Function in PCU2 ..............................76 6.2 BTS Selection...............................................................................................................77 6.2.1 Initial BTS Selection .....................................................................................................77 6.2.2 BTS Selection for Reallocating TBF..............................................................................80 6.2.2.1 Uplink Rx Lev Reallocation...........................................................................................82 6.2.2.2 Downlink Rx Lev Reallocation ......................................................................................83 6.2.2.3 Downlink RX Lev Received First Time Reallocation .....................................................83 6.2.2.4 BTS Selection in PCU2.................................................................................................83 6.2.2.5 Territory Upgrade Request in PCU2.............................................................................84 6.3 Channel Scheduling .....................................................................................................85 6.3.1 Priority based Quality of Service...................................................................................85 6.3.2 Channel Allocation........................................................................................................86 6.3.3 TBF Scheduling............................................................................................................87 6.3.4 QoS Information Delivery..............................................................................................88





6.3.5 Nokia HLR QoS Settings ..............................................................................................89 6.4 DL Dual Carrier ............................................................................................................92 6.5 Flow Control on Gb.......................................................................................................92 6.6 Gb interface capacity for PCU2-D and PCU2-E............................................................93

6.6.1 PCU2-D........................................................................................................................93 6.6.2 PCU2-E........................................................................................................................94 6.6.3 Applicable for both PCU2-E / PCU2-D..........................................................................94 6.7 Gb over IP ....................................................................................................................94 6.8 (E)GPRS in DFCA........................................................................................................94

7. (E)GPRS Timeslot Data Rate ......................................................... 96

7.1 GSM Network Performance..........................................................................................96 7.1.1 Impact of Coverage Level.............................................................................................96 7.1.1.1 Signal Strength Requirements......................................................................................97 7.1.1.2 Receiving End ..............................................................................................................98

7.1.1.3 Measurement Results...................................................................................................99 7.1.2 Impact of Interference Level .......................................................................................101 7.1.2.1 Simulation Results......................................................................................................101 7.1.2.2 Spectrum Efficiency and Frequency Reuse ................................................................ 106 7.1.2.3 Measurement Results.................................................................................................107 7.1.3 Mixture of Signal Level and Interference.....................................................................107 7.2 TSL Utilization Improvement.......................................................................................109 7.2.1 Acknowledge Request Parameters.............................................................................109 7.2.1.1 GPRS DL/UL Penalty and Threshold..........................................................................109 7.2.1.2 (E)GPRS DL/UL Penalty and Threshold.....................................................................109 7.2.2 PRE_EMPTIVE_TRANSMISSIO................................................................................110 7.3 TBF Release Delay Parameters (S10.5 ED)...............................................................110

7.3.1 DL_TBF_RELEASE_DELAY......................................................................................110 7.3.2 DL_TBF_RELEASE_DELAY in PCU2........................................................................111 7.3.3 UL_TBF_RELEASE_DELAY......................................................................................111 7.3.4 Release of downlink Temporary Block Flow ............................................................... 112 7.3.5 Release of uplink Temporary Block Flow....................................................................112 7.4 TBF Release Delay Extended (S11 onwards).............................................................113 7.4.1 TBF is Continued based on EUTM .............................................................................113 7.4.2 TBF is Not Continued based on EUTM.......................................................................114 7.4.3 EUTM in PCU2...........................................................................................................115 7.5 BS_CV_MAX..............................................................................................................115 7.6 GPRS and EGPRS Link Adaptation............................................................................118 7.6.1 GPRS Link Adaptation (S11) ......................................................................................118 7.6.2 GPRS Link Adaptation with CS1-4 (PCU2).................................................................119 7.6.2.1 Link Adaptation Algorithm Used in Uplink Direction .................................................... 121 7.6.3 EGPRS Link Adaptation with Incremental Redundancy..............................................124 7.6.3.1 Link Adaptation Introduction .......................................................................................124 7.6.3.2 MCS Selection............................................................................................................126 7.6.3.3 Bit Error Probability.....................................................................................................128 7.6.3.4 Link Adaptation Procedure .........................................................................................134 7.6.3.5 Incremental Redundancy in EGPRS...........................................................................141 7.6.3.6 MCS Selection Based on BLER Limits .......................................................................145 7.6.3.7 EGPRS LA in PCU2...................................................................................................146 7.7 Multiplexing ................................................................................................................147

7.7.1 Synchronization..........................................................................................................147 7.7.2 Dynamic Allocation on UL...........................................................................................147 7.7.2.1 GPRS and EGPRS Dynamic Allocation......................................................................147





7.7.2.2 GPRS and EGPRS Dynamic Allocation without USF4............................................... 148 7.7.2.3 GPRS and EGPRS Dynamic Allocation with USF4.....................................................148 7.7.2.4 GPRS and EGPRS Extended Dynamic Allocation with/without USF4.........................149

8. (E)GPRS Territory Settings........................................................... 150

8.1 Timeslot Allocation between Circuit Switched and (E)GPRS Services........................150 8.1.1 PSW Territory.............................................................................................................150 8.1.1.1 Dedicated (E)GPRS Capacity.....................................................................................150 8.1.1.2 Default GPRS Capacity ..............................................................................................151 8.1.1.3 Additional (E)GPRS Capacity .....................................................................................151 8.1.2 CSW Territory.............................................................................................................151 8.1.2.1 Free Timeslots............................................................................................................152 8.1.3 Territory Upgrade/Downgrade – Dynamic Variation of Timeslots................................154 8.1.3.1 Downgrade.................................................................................................................154 8.1.3.2 Upgrade .....................................................................................................................155

8.1.3.3 Territory Upgrade and Downgrade S10 Changes....................................................... 155 8.1.3.4 Multislot TSL Allocation for Using max Capability of Mobile........................................156 8.2 Multislot Usage...........................................................................................................156 8.2.1 Average Window Size ................................................................................................158 8.3 High Multislot Class (HMC).........................................................................................158 8.4 DLDC .........................................................................................................................159

9. Mobility ......................................................................................... 160

9.1 Intra/Inter PCU Cell Re-selection................................................................................160 9.1.1 BSS and Data Outage ................................................................................................160 9.1.1.1 BSS Cell-reselection outage.......................................................................................161

9.1.1.2 Data outage................................................................................................................161 9.1.2 Benchmark Results ....................................................................................................163 9.2 LA /RA Cell-reselection...............................................................................................164 9.2.1 Data Outage...............................................................................................................164 9.2.1.1 Location Area Update.................................................................................................164 9.2.1.2 Routing Area Update ..................................................................................................164 9.2.1.3 Data outage (LA/RA Update)......................................................................................164 9.2.2 Benchmark Results ....................................................................................................166 9.3 Cell-reselect Hysteresis..............................................................................................167 9.4 Network Assisted Cell Change ...................................................................................168





1. Introduction

The (E)GPRS Radio Networks – Planning Theory document was prepared to providethe basic theoretical knowledge for (E)GPRS Radio Network dimensioning, planning

and optimization. The (E)GPRS Radio Networks planning document set structurelisted below:

• (E)GPRS Radio Networks – Planning Theory

• (E)GPRS Radio Networks – Dimensioning and Planning Guidelines

• (E)GPRS Radio Networks – Optimization Guidelines

The Planning Theory gives the theoretical knowledge while “Dimensioning andPlanning Guidelines” and “Optimization Guidelines” contain all the practicalinformation for daily planning and optimization activities.

The materials listed above are based on S10.5 ED, S11, S11.5, S12, S13 and S14BSS software releases; moreover both PCU1 and PCU2 with PCU2-E are taken intoaccount.

The detailed Abis, EDAP, PCU and Gb planning theory are not included in thisdocument. For more information pls. see the latest guidelines on the links below:

GSM Access:

https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/358201395

MW Radio Transmission (and Mobile Backhaul)


GERAN Radio


The 3GPP specifications can be found at the following intranet location:

http://www.3gpp.org/specification-numbering





1.1 (E)GPRS Dimensioning, Planning and OptimizationStructure

The general way of (E)GPRS radio dimensioning, planning and optimizationprocedure is listed below:

(E)GPRS Dimensioning and Planning

• Operators’ business plan investigation

• Operators’ BSS network structure audit (with core network)

• Deployment plan preparation

• Capacity calculations based on deployment plan

• Parameter setting

(E)GPRS Optimization

• Configuration and feature audit

• BSS and E2E Performance measurements

• GSM network optimization

• (E)GPRS network optimization

All the points above are described in (E)GPRS Radio Networks - Dimensioning andPlanning Guidelines and (E)GPRS Radio Networks - Optimization Guidelines.

(E)GPRS Radio Networks - Dimensioning and Planning Guidelines:


(E)GPRS Radio Networks - Optimization Guidelines:


1.2 Data hardware and site solutions

The following sessions describe the PS related hardware elements in the BSS chain.

1.2.1 BSC and PCU variants

Nokia Packet Control Unit (PCU) is a Plug-in unit in a Base Station Controller (BSC).PCU hardware is embedded in BSCs in every BCSU (BSC Signaling unit).

The Nokia PCU product family consists of following products:





PCU variant BSC Type Release BSS11

BSS11.5

ownwards

BTS 64 64

TRX 128 128

Radio TSLs 256 128

Abis 16 kbps channels 256 256

Gb 64 kbps channels 31 31

BTS 64 64

TRX 128 128

Radio TSLs 256 128



BTS 64 64

TRX 128 128

Radio TSLs 256 256



BTS N/A 128

TRX N/A 256Radio TSLs N/A 256

Abis 16 kbps channels N/A 256

Gb 64 kbps channels N/A 31

BTS 2 x 64 2 x 64

TRX 2 x 128 2 x 128

Radio TSLs 2 x 256 2 x 256

Abis 16 kbps channels 2 x 256 2 x 256

Gb 64 kbps channels 2 x 31 2 x 31

BTS N/A 2 x 128

TRX N/A 2 x 256

Radio TSLs N/A 2 x 256

Abis 16 kbps channels N/A 2 x 256

Gb 64 kbps channels N/A 2 x 31

PCU2-D BSC3i

PCU2-U

PCU-T BSCE, BSC2,

BSCi, BSC2i

BSCE, BSC2,

BSCi, BSC2i

PCU-B BSC3i

PCU BSCE, BSC2,

BSCi, BSC2i

PCU-S BSCE, BSC2,

BSCi, BSC2i

Table 1 PCU product family

The PCU-S is the first and PCU-T the second evolution of PCU variant having morememory and higher CPU clock rate.

1.2.1.1 PCU2 Plug-in Unit Variants and Hardware ArchitectureIn the PCU2 solution, there are two PCU2 plug-in unit variants which implement thenew hardware architecture. PCU2-D is used for BSC3i, which includes two logicalPCU2 units, and PCU2-U is used for the older BSC versions. For more information onthe PCU2 plug-in unit variants, see the PCU2 hardware plug-in unit descriptions inBSC/TCSM documentation.

PCU2 introduces more processing capacity for both PowerQuicc II (PQII) and digitalsignal processors (DSP) with external memory and hardware architectureenhancements to create a basis for new packet data related functionalities.

The functionalities include enhancements in following areas:

• Enhanced processing capabilities for PQII and DSPs with external memoryand a higher DSP-level Abis channel connectivity to fully support thesoftware architecture enhancements

• Actual traffic and O&M information separated on different paths between

PQII and DSPs





Figure 1 Main hardware blocks in the PCU1 and PCU2 variants

1.2.1.2 PCU2 Software ArchitectureThe new software architecture, with its modular decomposition and restructured taskmanagement, uses the hardware architecture changes to provide a basis for thenew packet data related functionalities.

With PCU2, the DSPs take care of more tasks than in PCU1. The tasks includeradio link control (RLC), scheduling, quality control, as well as Abis L1 processing.With PCU1, the DSPs only take care of the Abis L1 processing.

Figure 2 Restructured task management in PCU2

The PCU2’s new software architecture introduces enhancements in the followingareas:

• The RLC, Scheduler, and Quality control functionalities implemented on theDSPs improve the RTT and balances load between PQII and DSPs.





• The asynchronous data transfer of LLC PDUs, which is used instead of thesynchronous transfer of RLC/MAC blocks between PQII and DSP, reduces theload in the PQII – DSP interface and provides faster PQII – DSP transactions.

• Increased BTS and TRX resources: with PCU2, the BTS resources areincreased from 64 to 128, and the TRX resources extended from 128 to 256,consequently providing more flexibility to the segment concept used with Multi-BCF Control and Common BCCH.

• The new GPRS link adaptation algorithm enables the support for the GPRScoding schemes 3 and 4 (CS3&CS4). It also gives the possibility to reach ahigher throughput per subscriber when the GPRS coding schemes 3 and 4 areused.

• The use of uplink state flag (USF) granularity 4 improves the use of the radiointerface resources in a situation where the GPRS and EGPRS mobiles are in

the same radio time-slot (RTSL).

• Dynamic Abis improvements, which enable a more efficient use of EDAPs.The recommended number of EDAP’s in PCU1 is 1, 2, 4 or 8. Recommendednumber of EDAP’s is in PCU2 is 1-8.

• Improved end user service perception: The PCU2 software architectureimplements RLC on DSPs and, depending on the radio conditions, givesbenefit to application level delays i.e. active and idle RTTs. The active RTTmeasures delay from the data transfer point of view has an impact for exampleon the duration of file downloads experienced by the end users as well as onservices with fast interaction requirements. The idle RTT measures delay from

the access point of view, that is, the impact to TCP startup, improves on itspart the end user experience for example in downloading web pages.

• BTS selection improvements in case of Common BCCH / Multi BCF cell

• Dynamic Abis improvements

PCU2 doesn’t provide support for following functionalities available with PCU1:

• PBCCH/PCCCH

• GPRS support for InSite BTS

1.2.1.3 PCU1 and PCU2 Software Differences on Air InterfaceDue to different feature set and software architecture between PCU generations,there are multiple differences concerning to Air interface. These differences haveinfluences to radio resource allocation and scheduling, round-trip time, throughputand cell change times.

The most important differences are:

• New GPRS link adaptation algorithm in the PCU2 that can use CS-3 and CS-4, too

• Utilization of USF granularity 4 in the PCU2

• BTS selection differences





• Inter DSP TBF reallocation and cell change in the PCU2

The detailed description of the most important differences can be found in therelevant chapters below in this document.

1.2.1.4 PCU2-E

PCU2-E overcomes limitations of PCU2-D in terms of capacity and cost:

• increase in the number of channels served by a single logical PCU by factor of4: from 256 to 1024

• usage of the newest components made it possible to reduce cost per unit (andto increase its capacity significantly at the same time!)

o further CPU clock frequency and memory increase are required toachieve the desire capacity

o PCU2-E CPU/memory: 1.33GHz / 1GB

Usage of PCU2-E is mandatory in order to reach target Flexi BSC capacity figures interms of PS data traffic

• Max Flexi BSC configuration with 5 PCU2-E per BCSU and 6 active BCSU perBSC allows to control 30 720 Abis channels = 1024 Abis channels / PCU x 5PCU/BCSU x 6 BCSU/BSC

• 30 720 Abis channels corresponds to controllable Abis bandwidth of 491 Mbps

PCU2-E can be also freely used in the remaining BSC3i types (660/1000/2000)

• cost reduction is a prime reason to install PCU2-E in previous BSC3i types

o mixture of PCU2-E and PCU2-D is possible within BSC3i (see nextslides for details)

• due to connectivity limitation PCU2-E can not reach its max possible capacityin previous types of BSC3i

o PCU2-E can handle up to 512 Abis channels in BSC3i 660/1000/2000

• Flexi BSC can be equipped with either PCU2-E (recommended) or PCU2-D orboth (in mixed configuration)

1.2.1.5 Mixed PCU configuration and asymmetrical PCU setupDifferent amount of PCUs can be installed in different BCSUs of the same BSC or

different PCU HW variants can be installed in the same slots of different BCSUs.





Mixed PCU configuration in such context is a new functionality that leads to“asymmetrical” PCU configuration.

• PCU can be installed and activated according to actual

traffic needs with granularity 1 in every BCSU separately• each active BCSU can have different number of PCU

(depending on actual traffic requirements), i.e. it may happenthat some BCSU have no PCU units while the other oneshave some PCU installed

• different PCU types can be mixed in the same BSC/BCSU(restrictions concerning the same BCSU track exist -> seeprevious slide)

• BCSU which is marked as primary spare one mustbe equipped with the number of PCU sufficient to replaceany of the active BCSU

1.2.2 BTS variants

TALK InSite** PrimeSite MetroSite UltraSite FlexiEDGE

GSM Ok Ok Ok Ok Ok Ok

GPRS CS1 – 2 CS1 – 2 CS1 - 2 CS1 – 2* CS1-2* CS1-2*

EGPRS No No No MCS1-9 MCS1-9 MCS1-9

*CS1-4 with PCU2**Insite is not supported by PCU2

1.3 Data features

The next sessions describe the most important PS features on S release basis.

1.3.1 S10 / S10.5ED

The following features are implemented with S10/S10.5ED releases:

BSS 10091 Enhanced Data Rates for Global Evolution, EDGE

Detailed description of GPRS and EGPRS dimensioning and planning is available in

(E)GPRS Radio Networks - Dimensioning and Planning Guidelines:

https://sharenet-ims.inside.nokiasiemensnetworks.com/Download/362642110

Detailed description of GPRS and EGPRS optimization is available in (E)GPRS RadioNetworks - Optimization Guidelines


BSS 10045 Dynamic Abis Allocation


BSS 10074 Support of PCCCH/PBCCH





Support for PBCCH/PCCCH is no longer supported from S13 onwards.

BSS 10084 Priority Class Based Quality of Service

With Priority Based Scheduling, an operator can give users different priorities. Higherpriority users will get better service than lower priority users. There will be no extrablocking to any user, only the experienced service quality changes.

The concept of ‘Priority Class’ is based on a combination of the GPRS Delay class andGPRS Precedence class values. Packets will be evenly scattered within the (E)GPRSterritory between different time slots. After that packets with a higher priority are sentbefore packets that have a lower priority.

The description of priority based QoS is available in (E)GPRS Radio Networks -Optimization Guidelines


1.3.2 S11 / S11.5

The following features are implemented with S11/S11.5 releases:

BSS 11112 Network Controlled Cell Reselection (NCCR)

BSS 11506 Network Assisted Cell Change (NACC)

BSS 115171 Dynamic Abis Enhancements

BSS 11088 GPRS Coding Schemes CS3 and CS4

BSS 30065 GPRS Resume

BSS 11151 Extended Uplink TBF

BSS 11156 EGPRS: Channel Request on CCCH

The detailed description of below listed features are (E)GPRS Radio Networks -Dimensioning and Planning Guidelines:


(E)GPRS Radio Networks - Optimization Guidelines:


1.3.3 S12

The following features are implemented with S12 release:

BSS 20088 Dual Transfer Mode (DTM)

Dual Transfer Mode (DTM) provides mobile users with simultaneous circuit-switched(CS) voice and packet-switched (PS) data services. This means that users can, forexample, send and receive e-mail during an ongoing phone call.





The Planning Theory of DTM can be downloaded from the following link:


Information about DTM planning is available in DTM – Planning guidelines:


BSS 20084 High Multislot Classes (HMC)

More information about HMC is available in the (E)GPRS Radio Networks -Optimization Guidelines:


BSS 20089 Extended Dynamic Allocation (EDA)

More information about EDA is available in Chapter 7.7.2.

1.3.4 S13

The following feature is implemented with S13 releases:

BSS20094 Extended Cell for GPRS/EDGE

More information is available in extended cell range and Long Reach timeslot planningguidelines:


1.3.5 S14

The following features are implemented with S14:

BSS21161 SDCCH and PS Data Channels on DFCA TRX

BSS21228 Downlink Dual Carrier

Additionally PCU2-E is available if S14 is implemented.





2. (E)GPRS Modulation

(E)GPRS uses not only GMSK but 8PSK (8 Phase Shift Keying) modulation as well,producing a 3bit word for every change in carrier phase. This effectively triples the

data rate offered by GPRS.

The differences between GMSK and 8-PSK, the block diagram of modulators, and theburst structure with back-off are described below in this chapter.

2.1 GMSK and 8-PSK Modulation

GSM system is using GMSK (Gaussian Minimum Shift Keying), a constant-envelopemodulation scheme. The advantage of the constant envelope modulation is that itallows the transmitter power amplifiers to be operated in a non-linear (saturated)mode, offering high power efficiency. The saturation means that even if the inputsignal level is increased, no increasement will be seen in the output power, as shownon upper part of Figure 3.

8-PSK, in the form used in EDGE, has a varying envelope, see the lower part ofFigure 3. It means that the amplifier must be operated in the linear region in case of 8-PSK since distortion is to be avoided. (There is an additional 22.5 deg rotation toavoid zero crossing.)

GMSK

8PSK

(0,0,1)

(1,0,1)

(0,0,0)(0,1,0)

(0,1,1)

(1,1,1)

(1,1,0)

(1,0,0)

Time

Envelope (amplitude)

Time


GMSK

8PSK

(0,0,1)

(1,0,1)

(0,0,0)(0,1,0)

(0,1,1)

(1,1,1)

(1,1,0)

(1,0,0)

Time


Time


Time


TimeTime


Time


TimeTime


Figure 3 Modulation scheme for GMSK and 8-PSK





2.2 Modulation Block Diagrams

The Figure 4 and Figure 5 show that GMSK and 8-PSK modulation arrangements arecompletely different.

Figure 4 GSM - GMSK modulation

Figure 5 EDGE - 8-PSK modulation

differential

encoding

-1, +1

Gaussian

prefiltering

for frequency

pulses

frequency

modulator

local oscillator

rotation byk3pi/8

Linearized

Gaussian

Filterfor Dirac

pulses

Gray mapping

to 8PSK

constellation

3 bits per

symbol

I & Q





2.3 Back-off in EGPRS

This varying envelope generates peak-mean power difference that is 2-6 dB for 8-PSK, thus the mean output power in amplifier must be at least this amount down on

the saturated output power to achieve linearity.

Figure 6 Phase state vector diagram in 8-PSK

So the position of the information is there on the yellow dots of the dark blue circleabove in Figure 6 (yellow dots: where the phase and amplitude of the signal iscontaining the information). The area between the dark blue circle and red circle is theroom for overshooting.

This “overshoot” is required to ensure smooth and continuous transition betweenphase-states (as shown by the yellow trace above).

It means that the mean output power has to be app. 2-6 dB less (back-off) to avoidsaturation in amplifier. This ‘back-off’ is shown in Figure 7.





GMSK

8PSK

Time


Time


=> Peak to Average of ≅≅≅≅ 2-4 dB

Pin

Pout

Back Off= 2 dB

Compression point

Figure 7 Back-off in power amplifier

In practice, BTS equipment is less likely to be in saturation than MS equipment.Therefore the back-off for the two sets of equipment may be different, and in the linkbudget presented a 2dB back-off is assumed for BTS and the full 4dB for MS. Theamount of MS back-off also depends on the used system frequency (different outputpower, different PA characteristics, etc. – 900 MHz: 6dB; 1800 MHz: 4dB).

The UltraSite 2 dB APD and mobiles’ 4-6 dB applies only when the transmitter is setto maximum output power.

If the entire TRX is set to second highest output power, there is no difference betweenthe average power of 8-PSK and GMSK signals.





2.4 Burst Structure

3GPP TS 05.05, Annex B identifies the following GMSK/8-PSK burst structures fortransmitted power level versus time. The first figure below (Figure 8) shows the time

mask for normal duration bursts at GMSK modulation. The second figure (Figure 9)shows the time mask for normal duration bursts at 8-PSK modulations. The blue“envelope” shows a conceptual example of the appearance of a normal burst.

dB

t

- 6

- 30

+ 4

8 µs 10 µs 10 µs 8 µs

(147 bits)

7056/13 (542.8) µs 10 µs

(*)

10 µs

- 1+ 1

(***)

(**)

dB

t

- 6

- 30

+ 4

8 µs 10 µs 10 µs 8 µs

(147 bits)

7056/13 (542.8) µs 10 µs

(*)

10 µs

- 1+ 1

(***)

(**)

Figure 8 GMSK Burst

10 8 10 10 8 10 t (µs)

dB

-30

(*)

-6

+2,4

+4

-20

-2

(***)

(**)

2 2 22

7056/13 (542,8)µs

(147 symbols)

0

10 8 10 10 8 10 t (µs)

dB

-30

(*)

-6

+2,4

+4

-20

-2

(***)

(**)

2 2 22

7056/13 (542,8)µs

(147 symbols)

0

Figure 9 8-PSK Burst

The following figure (Figure 10) shows an example of GSM/EDGE BCCH TRX with a3TSL EDGE mobile active on the downlink 5 normal bursts in GMSK (Average Power

Decrease (APD)=0 dB) and 3 normal bursts in 8-PSK (APD=2 dB).





TSL1 TCH

GMSK

TSL2 TCH

GMSK

TSL3 TCH

GMSK

TSL4 TCH

GMSK

TSL5 PD T CH 8 - PSK / GMSK



TSL0 BCCH GMSK

P(dB)

t (us)

Figure 10 5 normal bursts in GMSK (APD=0 dB) for voice and 3 normal bursts in 8-PSK (APD=2 dB) for data

Note that the average power decreased by 2 dB during the last three bursts due toAPD of 2 dB.

This has the following key impacts on EDGE service:

1) “Slightly” lower throughput near cell edge or in poor C/I environment,

2) 2 dB lower signal level to neighboring cells or GSM phones evaluating neighbors.

If the operator decides to allow 8-PSK modulation on the BCCH carrier in certaincells, the cell selection, cell reselection and handover procedures involving these

cells will be somewhat sub-optimal. This is due to the fact that the signal levelmeasured by the MS at some instances in time will be affected by the possiblylower mean power level of the 8-PSK modulation and by the power fluctuationresulting from the 8-PSK modulation characteristics.

The extent of the performance degradation is dependent upon the measurementschedule in each particular MS as well as upon the used average power decrease(APD) and the current 8-PSK load. By limiting the maximum number of 8-PSKslots simultaneously allowed on the BCCH carrier, and/or carefully selecting thevalues of involved network parameters, the impact on the above-mentionedprocedures may be minimized. Additionally, in areas with very low cell overlap,some coverage loss effects may have to be taken into account by the operator

when selecting network parameters (the measurement of the cell for neighbordecision is based on the average value of TSLs’ signal level, so the reducedoutput power due to 8-PSK can modify this measurement results).

The power budget margins for handover are around 4/6 dB. This means the signalstrength in the neighbor EGPRS cell has to be 4/6 dB larger than the serving cellin order to perform the handover. Moreover, the mobiles have a certain inaccuracywhen performing neighbor measurements so the impact of average powerdifferences in GMSK and 8PSK will be probably minor.

Note that the average power remains constant since both GMSK and 8-PSK are

operating in the linear range of the PA.





3. Coding Schemes

The following subsections describe the protocol architecture used by (E)GPRS andthe coding schemes for GPRS, GPRS with CS1-4 and EGPRS.

3.1 Protocol Architecture

The following figure shows the different protocols between the different networkelements of a (E)GPRS networks. As it can be seen from Figure 11, the BSS networkrelated protocols are the physical (L1/RF) and RLC/MAC layers. The RLC/MAC, LLCand SNDCP layers are (E)GPRS specific layers, but the higher layers are applicationdependent.

LLC

SNDCP

LLC

SNDCP

L1/RF L1/RF

UmMS BTS

FR

NS

BSSGP

FR

NS

BSSGP

GbSGSN

GTP

UDP

IP

L1

L2

GTP

UDP

IP

L1

L2

GnGGSN

RLC/MAC RLC/MAC

DAbis DAbis

AbisBSC / PCU

IP

L1

L2

WWW/FTP

Server

Gi

TCP

HTTP

orFTP

L1

L2

IP

TCP

HTTP

orFTP

Figure 11 (E)GPRS Protocol Stack

The protocols are communicating via Service Access Points (SAP). The Figure 12shows the data block segmentation from IP to GSM RF.

LLC

SNDCP

IP

RLC

MAC

GSM RF

N-PDU

SN-DATA PDUs

LLC Frames

RLC Blocks

RLC/MAC Blocks

TDMA Bursts

Figure 12 Data Blocks segmentation between protocols





3.1.1 Physical Layer

The physical layer of the (E)GPRS networks is the standard GSM TDMA interface(with new modulation method for higher MCSs of EGPRS). Therefore the appropriate

functionality of the GSM network is basic requirement to provide good (E)GPRSservice.

The main tasks of the physical layer are listed below:

• Modulation/demodulation (GMSK and 8-PSK)

• TDMA frame formatting

• Bit inter-leaving

• Cell selection/reselection

• Tx power control

• Discontinuous reception (DRx)

The basic element of air interface in (E)GPRS planning is the timeslot. It lasts 0,577milliseconds (=15/26) which corresponds to 156,25 bits. Four TDMA TSLs areneeded to convey one RLC/MAC block as it can be seen in the Figure 12 above.

3.1.2 RLC/MAC Layer

This subsection briefly describes the Radio Resource layer (RLC/MAC) since thislayer is responsible for most of the important BSS related functionalities.

3.1.2.1 Radio Link ControlThe main tasks of Radio Link Control (RLC) are:

• Reliable transmission of data across air interface

• Segmentation/de-segmentation of data from/to LLC layer

The RLC layer can be operated in both acknowledged and unacknowledged modes,and this is defined by the Quality of Service (QoS) profile within the PDP context(reliability class).

3.1.2.2 Medium Access ControlThe following list shows the main tasks of Medium Access Control (MAC):

• Control of MS access to common air-interface medium

• Flagging of PDTCH/PACCH occupancy

This layer controls MS access to the common air interface and provides queuing andscheduling of the associated signaling.

3.1.2.3 RLC/MAC Header FormatsAll the header formats are described below.





The following figure shows the downlink GPRS RLC block with MAC header.

Figure 13 DL RLC/MAC format

Detailed field description:

Uplink State Flag (USF) field is sent in all downlink RLC/MAC blocks and indicatesthe owner or use of the next uplink Radio block on the same timeslot. The USF field isthree bits in length and eight different USF values can be assigned, except on

PCCCH, where the value '111' (USF=FREE) indicates that the corresponding uplinkRadio block contains PRACH.

Supplementary/polling (S/P) bit is used to indicate whether the RRBP field is valid ornot.

bit 4 S/P

0 RRBP field is not valid1 RRBP field is valid

Table 2 S/P bit

Relative Reserved Block Period (RRBP) field specifies a single uplink block in

which mobile station shall transmit either a Packet Control Acknowledgementmessage or a PACCH block to the network. The mobile station shall only react onRLC/MAC block containing a valid RRBP field.





Final Block Indicator (FBI) bit indicates that the downlink RLC data block is the lastRLC data block of the DL TBF.

bit 1 Final block indicator

0 Current block is not last RLC data block in TBF1 Current block is last RLC data block in TBF

Table 3 FBI bit

Power reduction (PR) fields indicate the power level reduction of the current RLCblock. The coding of PR field depends on downlink power control mode – mode A andB definedin BTS_PWR_CTRL_MODE bit sent in assignment messages.

Payload Type field shall indicate the type of data contained in remainder of

RLC/MAC block. The encoding of the payload type field is shown below. The payloadType field is present in both downlink and uplink MAC header.

bit8 7

Payload Type

0 0 RLC/MAC block contains an RLC data block0 1 RLC/MAC block contains an RLC/MAC control block

that does not include the optional octets of theRLC/MAC control header

10 In the downlink direction, the RLC/MAC block containsan RLC/MAC control block that includes the optionalfirst octet of the RLC/MAC control header.In the uplink direction, this value is reserved.

1 1 Reserved. In this version of the protocol, the mobile

station shall ignore all fields of the RLC/MAC blockexcept for the USF field

Table 4 Payload Type field

Temporary Flow Identity (TFI) field in RLC data blocks identifies the TemporaryBlock Flow (TBF) to which the RLC data belongs. For the downlink and uplink TFI thefield is 5 bits in length and are encoded as a binary number with range 0 to 31.

Block Sequence Number (BSN) field carries the sequence absolute BlockSequence Number (BSN’) modulo 128 of each RLC data block within the TBF. TheBSN is 7 bits in length and is encoded as a binary number with range 0 to 127.

The following figure shows the uplink RLC block with MAC header.





Figure 14 UL RLC/MAC format

Detailed field description:

Retry (R) bit shall indicate whether the MS transmitted CHANNEL REQUESTmessage or PACKET CHANNEL REQUEST message one time or more than onetime during its most recent channel access. The mobile station shall send the samevalue for the R bit each uplink RLC/MAC block of the TBF.

bit 1 Retry (R) bit

0 MS sent channel request message once

1 MS sent channel request message twice or more

Table 5 Retry bit

The Stall indicator (SI) bit indicates whether the mobile's RLC transmit window canadvance (i.e. is not stalled) or cannot advance (i.e., is stalled). The mobile stationshall set the SI bit in all uplink RLC data blocks.

bit 2 Stall indicator

0 MS RLC transmit window is not stalled

1 MS RLC transmit window is stalled

Table 6 SI bit

The Countdown Value (CV) field is sent by the mobile station to allow the network tocalculate the number of RLC data blocks remaining for the current uplink TBF. TheCV field is 4 bits in length and is encoded as a binary number with range 0 to 15.

The TLLI Indicator (TI) bit indicates the presence of an optional TLLI field within the

RLC data block.





bit 1 TLLI indicator (TI) bit

0 TLLI field is not present1 TLLI field is present

Table 7 TLLI indicator bit

For EDGE the DL RLC/MAC header will change depends on the MCS used. TheMCS7, 8 and 9 have 5 octets header (header type 1) as shown on Table 8.

Bit8 7 6 5 4 3 2 1 Octet

TFI RRBP ES/P USF 1

BSN1 PR TFI 2BSN1 3

BSN2 BSN1 4CPS BSN2 5

Table 8 DL RLC/MAC header for EDGE MCS 7-9

Bit8 7 6 5 4 3 2 1 Octet

TFI RRBP ES/P USF 1BSN1 PR TFI 2

BSN1 3

CPS BSN1 4

Table 9 DL RLC/MAC header for EDGE MCS 5 and 6 (header type 2)

Bit8 7 6 5 4 3 2 1 Octet

TFI RRBP ES/P USF 1

BSN1 PR TFI 2BSN1 3

SPB CPS BSN1 4

Table 10 DL RLC/MAC header for EDGE MCS 1 to 4 (header type 3)

There are three header formats, because the header code rates are different forMCS1-4 and MCS5-9, and MCS5-6 have one RLC/MAC block while MCS7-9 havetwo RLC/MAC blocks (see Table 13).

The Downlink RLC/MAC control block together with its MAC header is formatted asshown in Table 11.

Bit8 7 6 5 4 3 2 1

Payload Type RRBP S/P USF MAC headerRBSN RTI FS AC Octet 1 (optional)

PR TFI D Octet 2 (optional)Octet M

Control Message Contents...Octet 21

Octet 22

Table 11 Downlink RLC/MAC control block together with its MAC header





The Uplink RLC/MAC control block together with its MAC header is formatted asshown in Table 12.

Bit8 7 6 5 4 3 2 1

Payload Type spare R MAC headerOctet 1Octet 2Octet 3

Control Message Contents...Octet 21

Octet 22

Table 12 Uplink RLC/MAC control block together with its MAC header

The detailed description of the different header formats can be found in 3GPP 04.60.

3.1.3 Logical Link Control

Logical Link Control (LLC) layer provides a reliable ciphered link between the SGSNand the MS. This protocol is independent of the underlying radio interface protocols.

LLC is considered to be a sub layer of layer 2 in the ISO 7-layer model. The purposeof LLC is to convey information between layer-3 entities in the MS and SGSN.Specifically, LLC shall support:

• multiple MSs at the Um interface;• multiple layer-3 entities within an MS.

LLC includes functions for:

• the provision of one or more logical link connections discriminated between bymeans of a DLCI;

• sequence control, to maintain the sequential order of frames across a logicallink connection;

• detection of transmission, format and operational errors on a logical link

connection;• recovery from detected transmission, format, and operational errors;• notification of unrecoverable errors;• flow control• ciphering

LLC layer functions provide the means for information transfer via peer-to-peer logicallink connections between an MS and SGSN pair.

This layer can be operated in both acknowledged and unacknowledged modes, andthis is defined by the Quality of Service (QoS) profile within the PDP context (reliabilityclass).





3.1.4 SNDCP Layer

Maps the network level Packet Data Units (N-PDU) on to the underlying Logical LinkControl (LLC) layer. The basic functionality of SNDCP layer is listed below:

• Multiplexer/demultiplexer for different network layer entities onto LLC layer

• Compression of protocol control information (e.g. TCP/IP header)

• Compression of data content (if used)

• Segmentation/de-segmentation of data to/from LLC layer

In details the SNDCP shall perform the following functions:

• Mapping of SN-DATA primitives onto LL-DATA primitives.

• Mapping of SN-UNITDATA primitives onto LL-UNITDATA primitives.• Multiplexing of N-PDUs from one or several network layer entities onto the

appropriate LLC connection.

• Establishment, re-establishment and release of acknowledged peer-to-peerLLC operation.

• Supplementing the LLC layer in maintaining data integrity for acknowledgedpeer-to-peer LLC operation by buffering and retransmission of N-PDUs.

• Management of delivery sequence for each NSAPI, independently.• Compression of redundant protocol control information (e.g., TCP/IP header)

at the transmitting entity and decompression at the receiving entity. Thecompression method is specific to the particular network layer or transportlayer protocols in use.

• Compression of redundant user data at the transmitting entity anddecompression at the receiving entity. Data compression is performedindependently for each SAPI, and may be performed independently for eachPDP context. Compression parameters are negotiated between the MS andthe SGSN.

• Segmentation and reassembly. The output of the compressor functions issegmented to the maximum length of LL-PDU. These procedures areindependent of the particular network layer protocol in use.

• Negotiation of the XID parameters between peer SNDCP entities using XIDexchange.

3.1.5 IP, TCP/UDP and Application Layer

The IP (Internet Protocol), TCP/UDP (Transmission Control Protocol/ User DatagramProtocol) and application layer’s functionality is described in EDGE_TCP_TWEAK_1_2document in QP.

The Internet Protocol (IP) is a network-layer (Layer 3) protocol that containsaddressing information and some control information that enables packets to be routed.IP is documented in RFC 791 and is the primary network-layer protocol in the Internetprotocol suite. Along with the Transmission Control Protocol (TCP), IP represents theheart of the Internet protocols. IP has two primary responsibilities: providingconnectionless, best-effort delivery of datagrams through an internetwork; and providingfragmentation and reassembly of datagrams to support data links with differentmaximum-transmission unit (MTU) sizes.





Transmission Control Protocol (TCP) provides reliable transmission of data in an IPenvironment. TCP corresponds to the transport layer (Layer 4) of the OSI referencemodel. Among the services TCP provides are stream data transfer, reliability, efficientflow control, full-duplex operation, and multiplexing.

With stream data transfer, TCP delivers an unstructured stream of bytes identified bysequence numbers. This service benefits applications because they do not have tochop data into blocks before handing it off to TCP. Instead, TCP groups bytes intosegments and passes them to IP for delivery.

TCP offers reliability by providing connection-oriented, end-to-end reliable packetdelivery through an internetwork. It does this by sequencing bytes with a forwardingacknowledgment number that indicates to the destination the next byte the sourceexpects to receive. Bytes not acknowledged within a specified time period areretransmitted. The reliability mechanism of TCP allows devices to deal with lost,delayed, duplicate, or misread packets. A time-out mechanism allows devices to detectlost packets and request retransmission.

TCP offers efficient flow control, which means that, when sending acknowledgmentsback to the source, the receiving TCP process indicates the highest sequence numberit can receive without overflowing its internal buffers.

Full-duplex operation means that TCP processes can both send and receive at thesame time.

User Datagram Protocol (UDP) is a connectionless transport-layer protocol (Layer 4)that belongs to the Internet protocol family. UDP is basically an interface between IP

and upper-layer processes. UDP protocol ports distinguish multiple applications runningon a single device from one another.

Unlike the TCP, UDP adds no reliability, flow-control, or error-recovery functions to IP.Because of UDP's simplicity, UDP headers contain fewer bytes and consume lessnetwork overhead than TCP.

UDP is useful in situations where the reliability mechanisms of TCP are not necessary,such as in cases where a higher-layer protocol might provide error and flow control.

UDP is the transport protocol for several well-known application-layer protocols,

including Network File System (NFS), Simple Network Management Protocol (SNMP),Domain Name System (DNS), and Trivial File Transfer Protocol (TFTP).

The UDP packet format contains four fields; these include source and destination ports,length, and checksum fields.

Application-layer protocols are one piece of a network application. For example theWeb's application layer protocol is HTTP, and defines format and sequence ofmessages, application layer protocols for Push to Talk over Cellular (PoC) are RTP andSIP.

Application-layer protocol defines:

• The types of messages exchanged, for example, request messages and responsemessages





• The syntax of the various message types, such as the fields in the message andhow the fields are delineated

• The semantics of the fields, that is, the meaning of the information in the fields• Rules for determining when and how a process sends messages and responds to

messages

3.2 RLC/MAC Coding Schemes

While the symbol rate is the same for GMSK and 8-PSK modulation the bit rate isdifferent since one GMSK symbol contains only 1 bit but one 8-PSK symbol contains3 bits altogether.

So the differentiations of RLC/MAC data rate of the different coding schemes arebased on convolutional coding and puncturing.

The CS1 and CS2 Coding Schemes (CS) are used for GPRS with PCU (PCU, PCU-S, PCU-T, PCU-B). If PCU2 (PCU2-U, PCU2-D) is implemented the CS3 and CS4 willbe used as well.

Modulation and Coding Schemes (MCS) are used for EGPRS both in GMSK and 8-PSK modulations.

3.2.1 GPRS Coding Schemes (CSs)

For error protection each RLC data block is encoded using one of the availablechannel coding schemes. ETSI has specified four coding schemes of which Nokiasupports coding scheme CS-1 and CS-2 only with PCU1, while PCU2 supports all the

four CSs (see the figure below).

CodingScheme

Payload (bits)per RLC block

Data Rate(kbit/s)

CS1 181 9.05

CS2 268 13.4

CS3 312 15.6

CS4 428 21.4

More Data=

Less ErrorCorrection

S11.5 with PCU2

D a t a

E r r o r

C o r r e c t i o n

PCU1

CodingScheme

Payload (bits)per RLC block

Data Rate(kbit/s)

CS1 181 9.05

CS2 268 13.4

CS3 312 15.6

CS4 428 21.4

More Data=

Less ErrorCorrection

S11.5 with PCU2

D a t a

E r r o r

C o r r e c t i o n

D a t a

E r r o r

C o r r e c t i o n

PCU1

Figure 15 Coding Schemes in GPRS

Each of the coding schemes has been developed based on a compromise betweenerror protection and the amount of user data carried. Coding scheme CS-1 has thelowest user data rate, but the highest error protection. CS-4 has the highest data ratebut no error protection on the user data.





The following figure shows the segmentation of an RLC block with MAC header incase of different CSs to/from the GSM TDMA frames.

CS-1

CS-2

CS-3

57 57 57 57 57 57 57 57

456 bits

MAC

USF BCS +4

puncturing

rate a/b convolutional coding

CS-1 CS-2 CS-3

RLC/MAC Block Size: 181 268 312

Block Check Sequence: 40 16 16

Precoded USF: 3 6 6

1/2 ~2/3 ~3/4

length: 456 588 676

0 132 220

Data rate (kbit/s): 9.05 13.4 15.6

interleaving

MAC

USF BCS

RLC/MAC Block Size: 428

BCS Size: 16

Precoded USF: 12

Data rate (kbit/s): 21.4

CS-4

20 ms

CS-1

CS-2

CS-3

57 57 57 57 57 57 57 57

456 bits

MAC

USF BCS +4

puncturing


CS-1 CS-2 CS-3



Precoded USF: 3 6 6

1/2 ~2/3 ~3/4

length: 456 588 676

0 132 220

Data rate (kbit/s): 9.05 13.4 15.6

interleaving

CS-1

CS-2

CS-3

57 57 57 57 57 57 57 57

456 bits

57 57 57 57 57 57 57 5757 575757 5757 57 575757 5757 57 575757 5757 57 575757 5757

456 bits

MAC

USF BCS +4

puncturing


CS-1 CS-2 CS-3



Precoded USF: 3 6 6

1/2 ~2/3 ~3/4

length: 456 588 676

0 132 220

Data rate (kbit/s): 9.05 13.4 15.6

interleaving

MAC

USF BCS


BCS Size: 16

Precoded USF: 12


CS-4

20 ms

MAC

USF BCS

MAC

USF BCS


BCS Size: 16

Precoded USF: 12


CS-4

20 ms 20 ms

Figure 16 Coding Scheme segmentation in GPRS

The detailed segmentation procedure for CS1 and CS2 can be seen in the followingfigures.

USF Header & Data BCS

1/2 rate convolutional

coding + 4 tail bits

3 181 40 224 bits

6 456 bits

181bits/20ms = 9.05kbit/s



coding + 4 tail bits

3 181 40 224 bits

6 456 bits

181bits/20ms = 9.05kbit/s

Figure 17 RLC/MAC segmentation for CS1






1/2 rate convolutionalcoding

6 268 16294 bits

12588 bits

Puncturing (132 bits)

456 bits12

268 bits/20ms = 13.4kbit/s


1/2 rate convolutionalcoding

6 268 16294 bits

12588 bits


456 bits12



When CS1-4 option is on, Dynamic Abis pool and (E)GPRS territories are createdand when a TBF is allocated to a TRX which supports EDAP then all GPRS codingschemes (CS1 – CS4) are available for data transfer according to the parameterspcu_cs_hopping and pcu_cs_non_hop. If these parameters indicate Link Adaptation,the LA algorithm determines for each TBF separately which coding scheme (CS1 –

CS4) is used.

The detailed segmentation procedure for CS3 and CS4 can be seen in the followingfigures.



coding

6 312 16338 bits

12676 bits


456 bits12




coding

6 312 16338 bits

12676 bits


456 bits12








12 428 16

428bits/20ms = 21.4 kbit/s


12 428 16

428bits/20ms = 21.4 kbit/s


CS3 and CS4 is using modified LA algorithm (more details are available in Section7.6.2.

Coding schemes CS3 and CS4 are supported only by PCU2. It is application softwarefeature requiring a separate license.

To ensure successful BCSU switch-over it is not possible to enable CS3 & CS4 ifthere are PCU1 units on the same slot as PCU2 in any of the BCSUs.

3.2.2 EGPRS Modulation and Coding Schemes (MCSs)

The EGPRS standard defines nine coding schemes MCS1 to MCS9, providingdifferent throughputs depending on the amount of redundancy implemented in eachcoding scheme.

In EGPRS MCSs the user data from higher layers and the RLC/MAC header arehaving different code rates. The header code rate is more robust for having the

header even in very bad radio conditions. That is why there are “bad header, baddata” and “valid header, bad data” counters.

The different data rates per timeslot are presented below:

Scheme Code rate HeaderCode rate

Modulation RLC blocksper Radio

Block(20ms)

Raw Datawithin one

Radio Block

Family BCS Tailpayload

HCS Data ratekb/s

MCS-9 1.0 0.36 2 2x592 A 59.2

MCS-8 0.92 0.36 2 2x544 A 54.4

MCS-7 0.76 0.36 2 2x448 B

2x12 2x6

44.8

MCS-6 0.49 1/3 1 592544+48 A 29.627.2

MCS-5 0.37 1/3

8PSK

1 448 B 22.4

MCS-4 1.0 0.53 1 352 C 17.6

MCS-3 0.80 0.53 1 296272+24

A 14.813.6

MCS-2 0.66 0.53 1 224 B 11.2

MCS-1 0.53 0.53

GMSK

1 176 C

12 6

8

8.8

NOTE: the italic captions indicate the padding.

Table 13 Coding scheme performance versus Eb/No.

The MCSs are divided into different families A, B and C. Each family has a differentbasic unit of payload: 37 (and 34), 28 and 22 octets respectively. Different code rates





within a family are achieved by transmitting a different number of payload units withinone Radio Block.

The family concept is used for retransmission only, so the retransmitted RLC/MAC

block’s MCS can be the initial MCS or an MCS inside the family.

For families A and B, 1 or 2 or 4 payload units are transmitted, for family C, only 1 or2 payload units are transmitted (see Figure 21 below).

37 octets 37 octets 37 octets37 octets

MCS-3

MCS-6

Family A

MCS-9


MCS-2

MCS-5

MCS-7

Family B

22 octets22 octets

MCS-1

MCS-4

Family C

34+3 octets34+3 octets

MCS-3

MCS-6Family Apadding

MCS-8



MCS-3

MCS-6

Family A

MCS-9


MCS-2

MCS-5

MCS-7

Family B

22 octets22 octets

MCS-1

MCS-4

Family C

34+3 octets34+3 octets

MCS-3

MCS-6Family Apadding

MCS-8


Figure 21 MCS Families

The following figure shows the RLC/MAC segmentation (convolutional coding andpuncturing) to 4 normal GSM bursts.





P2 P3P1 P2

puncturingpuncturing

1836 bits

USF RLC/MAC

Hdr.

36 bits

Rate 1/3 convolutional coding

135 bits

612 bits

612 bits124 bits36 bitsSB = 8

1392 bits

45 bits

Data = 592 bits BCS TB

612 bits

612 bits 612 bits

1836 bits

Rate 1/3 convolutional coding

EFBIData = 592 bits BCS TBEFBI

612 bits 612 bits 612 bits

P3 P1

3 bits

HCS

puncturing

Figure 22 MCS9 Coding and puncturing





4. (E)GPRS Procedures

The knowledge of (E)GPRS procedures can help to analyze the signaling traffic. Sobefore the analysis of signaling situation in Chapter 5 the procedure of

• TBF establishment

• Data transfer

• TBF release

should be studied in details.

After GPRS Attach and PDP Context Activation the next procedure is the TBFestablishment with Packet Immediate Assignment (attach and PDP context activationalso require TBF establishment, but that is not discussed here in this section).

4.1 TBF Establishment

The TBF establishment is triggered by Channel Request (UL), Paging (DL) andImmediate Assignment (DL).

4.1.1 Channel Request and Packet Immediate Assignment

On receipt of a CHANNEL REQUEST message indicating a packet access, thenetwork may allocate a temporary flow identity and assign a packet uplink resourcecomprising one PDCH for an uplink temporary block flow in GPRS TBF mode.

On receipt of an EGPRS PACKET CHANNEL REQUEST message, the network mayallocate a temporary flow identity and assign a packet uplink resource comprising onePDCH for an uplink temporary block flow in EGPRS TBF mode or GPRS TBF mode.(3GPP 04.18-8.0)

Channel Request Message: If the establishment cause in the CHANNEL REQUESTmessage indicates a request for a single block packet access, the network shall grantonly the single block period on the assigned packet uplink resource if the networkallocates resource for the mobile station.

EGPRS Packet Channel Request Message: If the establishment cause in the EGPRSPACKET CHANNEL REQUEST (EPCR) message indicates a request for a two phase

access, the network shall grant one or two radio blocks for the mobile station (within aMulti Block allocation) to send a PACKET RESOURCE REQUEST and possibly anADDITIONAL MS RADIO ACCESS CAPABILITIES messages on the assigned packetuplink resource if the network allocates resource for the mobile station.

Immediate Assignment Message: The packet uplink resource is assigned to themobile station in an IMMEDIATE ASSIGNMENT message sent in unacknowledgedmode on the same CCCH timeslot on which the network has received the CHANNELREQUEST or the EGPRS PACKET CHANNEL REQUEST message. There is nofurther restriction on what part of the downlink CCCH timeslot the IMMEDIATEASSIGNMENT message can be sent. Timer T3141 is started on the network side.





4.1.2 DL TBF Assignment

Reason for paging is DL user data or signaling while MS is on STANDBY state. Theterminal has to be paged by the network in the STANDBY state since its position is

known only on the Routing Area level.

5. Any LLC Frame

4. Any LLC Frame

3. GPRS Paging Request

2. Paging Request

1. PDP PDU

MS BSS SGSN

Figure 23 Paging flow chart

DL TBF Assignment, MS on CCCH

The DL TBF assignment is based on the following procedure (Figure 24).

TBF per priority 90000(S10)

/c72084(S9)packet_immed_ass_msg

/c72085(S9)packet_immed_ass_ack_msg

MS BTS BSC SGSN

P-Immediate Assignment

Immediate Assignment (CCCH)P-Immediate Assignment Ack

Packet Polling Request

Packet Polling Request (PACCH)

Packet Control AckPacket Control Ack (PACCH)

MS on ready state

Sent on the PDTCH to findout the MS Timing Advance.In Nokia implementation,always sent when DL TBFAssignment is from CCCH.Not sent when DL TBF isassigned on PACCH

Packet Power Control/Timing Advance

Alternatively, Packet DownlinkAssignmnet may be sent if moretimeslots are required


DL TBFEstabl.72005(S9)

DL RLC MAC /c72077(S9)

Max sim. DL TBF .72007(S9)


EGPRS DL TBF UNACK 72091(S10)

EGPRS DL TBF 72089(S10) PossiblyPossibly

Req 1 tsl DL72039(S9)

Alloc1 tslDL72049(S9)

Only 1 TCH isallocated first.

If requested andavailable


/c72084(S9)packet_immed_ass_msg

/c72085(S9)packet_immed_ass_ack_msg

MS BTS BSC SGSNMS BTS BSC SGSN

P-Immediate Assignment

Immediate Assignment (CCCH)P-Immediate Assignment Ack

Packet Polling Request

Packet Polling Request (PACCH)

Packet Control AckPacket Control Ack (PACCH)

MS on ready state

Sent on the PDTCH to findout the MS Timing Advance.In Nokia implementation,always sent when DL TBFAssignment is from CCCH.Not sent when DL TBF isassigned on PACCH


Alternatively, Packet DownlinkAssignmnet may be sent if moretimeslots are required







EGPRS DL TBF 72089(S10) PossiblyPossibly

Req 1 tsl DL72039(S9)

Alloc1 tslDL72049(S9)

Only 1 TCH isallocated first.

If requested andavailable

Figure 24 DL TBF Assignment, MS on CCCH





DL TBF Assignment when UL TBF is ongoing

If there is an UL TBF ongoing, the channel request and immediate assignment is notneeded. The DL TBF is allocated by sending Packet Downlink Assignment on

PACCH.

MS BTS BSC SGSN

Packet Downlink Assignment (PACCH)

DL TBF DUR. UL/c72075(S9)


DL RLC Data Block

LLC PDU


Req x tsl D L72039(S9)

Alloc x tsl DL72049(S9)


DL RLC ACK MSC1…9 /c79000(S10)

orDL RLC UNACK

MSC1…9 /c79001(S10)



EGPRS DL TBF 72089(S10)

New TBF is establishedin the same mode(GPRS, EGPRS) thanthe ongoing TBF.

If UL TBF isEGPRS



DL TBF DUR. UL/c72075(S9)


DL RLC Data Block

LLC PDU


Req x tsl D L72039(S9)

Alloc x tsl DL72049(S9)


DL RLC ACK MSC1…9 /c79000(S10)

orDL RLC UNACK

MSC1…9 /c79001(S10)



EGPRS DL TBF 72089(S10)


If UL TBF isEGPRS

Figure 25 DL TBF Assignment when UL TBF is ongoing





4.1.3 UL TBF Assignment

Depending on the network configuration different establishments procedures are usedduring the data connection. One phase access may reduce the TBF establishment

time when accessing the cell and allows the system to allocate more than 1 RTSL forthe UL TBF.

When CCCH is in use, the Uplink Establishment offers:

• GPRS: one-phase access is possible, but only 1 TSL can be allocated to theTBF. Timeslot reconfiguration would be needed for multi slot allocation

• EGPRS: two-phase access is mandatory (in case of EPCR (S11, SX 4.0)implemented on CCCH the one phase access is possible as well)

When PCCCH is in use, the Uplink Establishment offers:

• GPRS: one-phase access is possible. Network can allocate more than oneTSL to the UL TBF.

The gain is obtained from the transmission side due to timeslot allocation. InCCCH case only one TSL is assigned, while in PBCCH case there can bemore then one. This explains the increasing importance of the gain as theping packet size becomes bigger.

• EGPRS: one-phase access is possible only if “EGPRS Packet ChannelRequest” (EPCR) is supported by the network (see Chapter 4.1.3.2). (If EPCRis not supported, then EGPRS is forced to use two-phase access even if

working in the PCCCH.)

4.1.3.1 Channel Request - Packet Access Procedure (CCCH / PCCH)The following tables show the packet access procedure on CCCH (3GPP 04.18) andPCCH (3GPP 04.60).

The table describes the differences of the Channel Request (S10.5ED)and EGPRSPacket Channel Request (S11) functionality. All the access modes are described inunacknowledged and acknowledged mode (8>= bit or 8< bit).





Purpose of the packetaccess procedure

EGPRS PACKET CHANNEL REQUESTsupported in the cell

EGPRS PACKET CHANNEL REQUESTnot supported in the cell

User data transfer – requested RLC mode =unacknowledged

EGPRS PACKET CHANNEL REQUESTwith access type = 'Two-phase access'

CHANNEL REQUEST with establishmentcause = 'Single block packet access' forinitiation of a two-phase access

User data transfer –

requested RLC mode =acknowledged and numberof RLC data blocks ? 8(note 1)

EGPRS PACKET CHANNEL REQUEST

with access type = 'Short Access' or'One-phase access' or 'Two-phaseaccess'

CHANNEL REQUEST with establishment

cause = 'Single block packet access' forinitiation of a two-phase access

User data transfer – requested RLC mode =acknowledged and numberof RLC data blocks > 8(note 1)

EGPRS PACKET CHANNEL REQUESTwith access type = 'One-phase access' or'Two-phase access'

CHANNEL REQUEST with establishmentcause = 'Single block packet access' forinitiation of a two-phase access

Upper layer signallingtransfer (e.g. pageresponse, cell update, MMsignalling, etc)

EGPRS PACKET CHANNEL REQUESTwith access type = 'signalling' orCHANNEL REQUEST with establishmentcause 'one-phase access'

CHANNEL REQUEST with establishmentcause = 'Single block packet access' forinitiation of a two-phase access orCHANNEL REQUEST with establishmentcause value 'one-phase access'

Sending of a measurementreport or of a PACKETCELL CHANGE FAILURE

CHANNEL REQUEST with establishment cause = 'Single block packet access'

Sending of a PACKETPAUSE message

CHANNEL REQUEST with establishment cause = 'Single block packet access'(note 2)

NOTE 1: The number of blocks shall be calculated assuming channel coding scheme MCS-1.NOTE 2: Upon sending the first CHANNEL REQUESTmessage the mobile station shall start timer T3204. If timer

T3204 expires before an IMMEDIATE ASSIGNMENT message granting a single block period on anassigned packet uplink resource is received, the packet access procedure is aborted. If the mobile stationreceives an IMMEDIATE ASSIGNMENT message during the packet access procedure indicating apacket downlink assignment procedure, the mobile station shall ignore the message.

Table 14 Packet Access Procedure (CCCH)

Purpose of the packetaccess procedure

EGPRS PACKET CHANNEL REQUESTsupported in the cell

EGPRS PACKET CHANNEL REQUESTnot supported in the cell

User data transfer –

requested RLC mode =unacknowledged

EGPRS PACKET CHANNEL REQUEST

with access type = 'Two-phase access'

PACKET CHANNEL REQUEST with

access type = 'Two-phase access'(NOTE 2)

User data transfer – requested RLC mode =acknowledged and numberof RLC data blocks ? 8(NOTE 1)

EGPRS PACKET CHANNEL REQUESTwith access type = 'Short Access' or'One-phase access' or 'Two-phaseaccess'

PACKET CHANNEL REQUEST withaccess type = 'Two-phase access'(NOTE 2)

User data transfer – requested RLC mode =acknowledged and numberof RLC data blocks > 8(NOTE1)

EGPRS PACKET CHANNEL REQUESTwith access type = 'One-phase access' or'Two-phase access'

PACKET CHANNEL REQUEST withaccess type = 'Two-phase access'(NOTE 2)

Upper layer signallingtransfer (e.g. pageresponse, cell update, MMsignalling, etc)

EGPRS PACKET CHANNEL REQUESTwith access type = 'signalling' or PACKETCHANNEL REQUEST withcorresponding access type (NOTE 2)

PACKET CHANNEL REQUEST withaccess type = 'Two-phase access' orPACKET CHANNEL REQUEST withcorresponding access type (NOTE 2)

Sending of a measurement

report or of a PACKETCELL CHANGE FAILURE

PACKET CHANNEL REQUEST with access type = 'Single block without TBFestablishment' (NOTE 2)

Sending of a PACKETPAUSE message

PACKET CHANNEL REQUEST with access type = 'Single block without TBFestablishment' (NOTE 2) (NOTE 3)

NOTE 1: The number of blocks shall be calculated assuming channel coding scheme MCS-1.NOTE 2: The format to be used for the PACKET CHANNEL REQUEST message is defined by the parameter

ACC_BURST_TYPE.NOTE 3: Upon the first attempt to send a PACKET CHANNEL REQUEST message the mobile station shall start

timer T3204. If the mobile station receives a PACKET DOWNLINK ASSIGNMENT message before expiryof timer T3204, the mobile station shall ignore the message.

Table 15 Packet Access Procedure (PCCCH)

4.1.3.2 EGPRS Packet Channel RequestSI13 contains the EPCR information. PCU always includes Access TechnologyRequest into EDGE UL assignment. Therefore MS sends Packet Resource Request





(PRR) message in first allocated USF, and optionally the Additional Radio AccessCapability (ARAC) message in second one.

GPRS & EGPRS short access is basically same scenario as GPRS one phase

access; Access Technology Request is never included in UL assignment message.

MS requests one-phase access, PCU makes final decision whether used or not. (E.g.Common BCCH (multiband) and EGPRS territory in non-BCCH band => forced 2-phase access).

The following figure shows the flow chart of One phase access on EGPRS.

One Phase/Short Access

MS BSC / PCU

UL Data Block + TLLI

Immediate Assignment (UL assignment)

EGPRS Packet Channel Request - onephase access or short access

Packet UL ACK/NACK + TLLI

Packet Control ACK or

UL Data Block w/o TLLI

…

SI13 (EPCR Support)

Decision –one-phase vs.

two-phase

UL TBF ready

(Additional Radio Access capability)

(Packet Resource Request)

One Phase Access:If NW has requested RAC

info from MS inImmediate Assignment,

MS responds withPacket Resource

RequestOne PhaseAccess:

If not all RAC infofits in PRR, MS

sends thisadditionalmessage

One Phase/Short Access

MS BSC / PCU

UL Data Block + TLLI

Immediate Assignment (UL assignment)

EGPRS Packet Channel Request - onephase access or short access

Packet UL ACK/NACK + TLLI

Packet Control ACK or

UL Data Block w/o TLLI

…

SI13 (EPCR Support)

Decision –one-phase vs.

two-phase

UL TBF ready

(Additional Radio Access capability)

(Packet Resource Request)

One Phase Access:If NW has requested RAC

info from MS inImmediate Assignment,

MS responds withPacket Resource

RequestOne PhaseAccess:

If not all RAC infofits in PRR, MS

sends thisadditionalmessage

Figure 26 EGPRS one phase access on CCCH

4.1.3.3 Dynamic and Extended Dynamic Allocation on UL with and without USF4The number of RLC/MAC blocks to transmit is controlled by the USF_GRANULARITYparameter characterizing the uplink TBF. USF Granularity 1 means that the mobilestation shall transmit one RLC/MAC block. USF Granularity 4 means that the mobilestation shall transmit four consecutive RLC/MAC blocks.

PCU2 uses USF Granularity 4 for GPRS MSs in EGPRS territory.

USF granularity 4 is useful when there is GPRS UL TBF multiplexed in the sametimeslot with EGPRS DL TBF. In this case only every fourth DL data block need to be





GSMK coded, and the other three blocks can be 8-PSK coded. PCU1 uses alwaysUSF granularity 1, meaning that EGPRS DL TBF does not utilize 8-PSK codingschemes while a GPRS UL TBF is transferring data on the same timeslot.

The detailed description of Dynamic Allocation with and without USF4 and ExtebdedDynamic Allocation with/without USF4 can be found in Section 7.7.2.

4.1.3.4 UL TBF ASSIGNMENT, MS on CCCH, 2 phase accessAfter Channel Request and Immediate Assignment the network sendsPACKET_UL_ASSIGNMENT message including Single Block Allocation or MultiBlock Allocation , indicating 2-phase access.

MultiBlock Allocation may be used only if MS is EGPRS capable (e.g. networkreceives an EGPRS_PACKET_CHANNEL_REQ).

In PACKET_UL_ASSIGNMENT, network reserves limited resources on 1 PDCH for

the MS, and MS may transmit PACKET_RESOURCE_REQUEST and optionallyADDITIONAL MS RADIO ACCESSS CAPABILITIES.

In PBCCH, 2-phase access can be initiated by:

• Network: When sending a PACKET_UL_ASSIGNMENT it includes Single orMultiBLock Allocation, which forces the MS to send aPACKET_RESOURCE_REQ (-> 2-phase access).

• MS: By requiring a 2-phase access in the PACKET_CHANNEL_REQ orEGPRS_PACKET_CHANNEL_REQ. If access is granted, the Network shallorder the MS to send PACKET_RESOURCE_REQ in the

PACKET_UL_ASSIGNMENT.MS BTS BSC SGSN

Channel Request (RACH)

Immediate Assignment (CCCH)

P_Channel Required

P-Immediate Assignment Cmd

UL TBF ASSIGNMENT, MS ON CCCH. 2 phase access.

Packet Resource Request (PACCH)Packet Resource Request

Packet Uplink AssignmentPacket Uplink Assignment (PACCH)

RLC Data block

Packet Uplink Ack/Nack

RLC Data Block

Packet Uplink Ack/Nack (specs)

Single blockNOTE: BTS does not send Imm Ass Ackfor Single block Immediate Assignment

The Contention resolutionwas already done above.The PCU does not immediatelysend Packet UplinkAck/Nack (as it does in one phaseaccess for contentionresolution) but only after acertain amount of blocks orafter Final UL Data Block.

Including TLLI for contention resolution

Including TLLI for contention resolution UL TBF Establ.72000(S9)

UL RLC CS1/c72062(S9)

UL RLC CS2 /c72064(S9)or

/c72084(S9)

packet_immed_ass_msg

/c72082(S9)

packet_ch_req

UL RLC MAC /c72076(S9)


Max.sim.UL TBF 72002(S9)

ReqX tslUL72034(S9)

Alloc X tsl UL72044(S9)


Establ.cause '2-ph.access'

More than 1 TCHcan be allocated.


UL TBF UNACK 72010(S9)Possibly

Max.sim.UL TBF UNACK 72012(S9) Possibly




P_Channel Required





RLC Data block


RLC Data Block


Single blockNOTE: BTS does not send Imm Ass Ackfor Single block Immediate Assignment

The Contention resolutionwas already done above.The PCU does not immediatelysend Packet UplinkAck/Nack (as it does in one phaseaccess for contentionresolution) but only after acertain amount of blocks orafter Final UL Data Block.


Including TLLI for contention resolution UL TBF Establ.72000(S9)

UL RLC CS1/c72062(S9)

UL RLC CS2 /c72064(S9)or

/c72084(S9)


/c72082(S9)

packet_ch_req




ReqX tslUL72034(S9)

Alloc X tsl UL72044(S9)







Figure 27 UL TBF ASSIGNMENT, MS on CCCH, 2 phase access





4.1.3.5 UL TBF ASSIGNMENT, MS on CCCH, 1 phase accessContention Resolution

Before establishing an UL TBF, the network must assign a TFI to the TLLI, which

identifies uniquely the MS (3GPP 04.60):

• Until contention resolution the TLLI must be included in every RLC block, andif MCS9-7 is used, in both RLC blocks

• TLLI shall be included in PACKET_RESOURCE_REQUEST andADDITIONAL_MS_RADIO_ACCESS_CAPABILITIES

• It applies for retransmission of RLC blocks as well

• NW responds with TLLI in PACKET_UL_ACK/NACK

• For an EGPRS TBF the network may respond withPACKET_UL_ASSIGNMENT if resources allocated to the TBF need to bereallocated

• On network side, Contention Resolution is completed when the networkreceives RLC block with TLLI and TFI associated to the TBF

• On MS side, Contention Resolution is completed when MS receivesPACKET_UL_ACK/NACK with TLLI and TFI. MS shall then stop T3166 andN3104

MS sends a PACKET_CONTROL_ACK containing the TA index if a valid RRBP is

received.

CCCH p- imm.ass./c72084(S9)


MS BTS BSC SGSN



P-Channel Required

P-Immediate Assignment Cmd(CCCH)

P-Immediate Assignment Ack

UL TBF ASSIGNMENT,MS ON CCCH.1 phase access.

Sent 6 TDMA frames beforethe Imm Ass goes to air.Includes the air-if TDMA framenumber of the Imm Assmessage

RACH p-ch.req./c72082(S9)

packet_ch_req

CCCH p- imm.ass. ack/c72085(S9)packet_immed_ass_ack_msg

UL TBF Establ.72000(S9)


Req 1 tsl UL72034(S9)

Alloc 1 tsl UL72044(S9)


Only 1 TCH canbe allocated.

CCCH p- imm.ass./c72084(S9)





P-Channel Required

P-Immediate Assignment Cmd(CCCH)

P-Immediate Assignment Ack

UL TBF ASSIGNMENT,MS ON CCCH.1 phase access.

Sent 6 TDMA frames beforethe Imm Ass goes to air.Includes the air-if TDMA framenumber of the Imm Assmessage

RACH p-ch.req./c72082(S9)

packet_ch_req

CCCH p- imm.ass. ack/c72085(S9)packet_immed_ass_ack_msg



Req 1 tsl UL72034(S9)

Alloc 1 tsl UL72044(S9)


Only 1 TCH canbe allocated.

Figure 28 UL TBF ASSIGNMENT, MS on CCCH, 1 phase access

The PACKET_UL_ASSIGNMENT construction contains the following information(3GPP 04.18-8.0):





• Temporary flow identity, TFI;

• USF value, if the medium access method is dynamic allocation; orthe fixed allocation bitmap, if the medium access method is fixed allocation;

• Channel coding scheme for RLC data blocks;

• Power control parameters;

• Polling bit;

• Optionally, the timing advance index (see 3GPP TS 05.10);

• Optionally, the TBF starting time (note: TBF starting time is mandatory ifmedium access method is fixed allocation).

In addition, the EGPRS packet uplink assignment construction also contains:

• EGPRS modulation and coding scheme;

• Information whether retransmitted uplink data blocks shall be resegmented ornot;

• EGPRS window size to be used within the transmission;

• Optionally a request for the mobile station to send its radio access capabilityinformation.





4.1.3.6 EGPRS UL TBF ASSIGNMENT, MS on PCCCH with 2 phase access


MS BTS BSC SGSN

Packet Resource Request (PACCH)

Packet Resource Request


RLC Data block


RLC Data Block


The Contention resolutionwas already done above.The PCU does not immediatelysend Packet Uplink

Ack/Nack (as it does in one phaseaccess for contention

resolution) but only after acertain amount of blocks orafter Final UL Data Block.




UL RLC ACK MSC1…9 /c79002(S10)

or




ReqX ts lUL72034(S9)

AllocX tsl UL72044(S9)




EGPRS Packet Channel Request (PRACH)EGPRS Packet Channel Request

PRACH p-ch req./c91002 (S10)nbr_of_packet_channel_reqs

Packet UL Assignment (PCCCH)

Packet UL Assignment

/c91021(10)

p_ul_ass_msgs_on_pccch

EGPRS UL TBF UNACK 72090(S10)

EGPRS UL TBF 72088(S10)

UL RLC UNACK MSC1…9 /c79003(S10)




PossiblyEGPRS TBF ifthere are resouces

Possibly



Packet Resource Request (PACCH)

Packet Resource Request


RLC Data block


RLC Data Block


The Contention resolutionwas already done above.The PCU does not immediatelysend Packet Uplink

Ack/Nack (as it does in one phaseaccess for contention

resolution) but only after acertain amount of blocks orafter Final UL Data Block.




UL RLC ACK MSC1…9 /c79002(S10)

or




ReqX ts lUL72034(S9)

AllocX tsl UL72044(S9)




EGPRS Packet Channel Request (PRACH)EGPRS Packet Channel Request

PRACH p-ch req./c91002 (S10)nbr_of_packet_channel_reqs



/c91021(10)

p_ul_ass_msgs_on_pccch



UL RLC UNACK MSC1…9 /c79003(S10)




PossiblyEGPRS TBF ifthere are resouces

Possibly

Figure 29 EGPRS UL TBF ASSIGNMENT, MS on PCCCH with 2 phase access

4.1.3.7 EGPRS UL TBF ASSIGNMENT, MS on PCCCH with 1 phase access

MS BTS BSC SGSN

EGPRS Packet Channel Request (PRACH)


EGPRS Packet Channel Request


UL TBF ASSIGNMENT,MS ON PCCCH.1 phase access.

/c91021(10)p_ul_ass_msgs_on_pccch


More than 1 TCH can be requested

QoSinformation.

PRACH p-ch req./c91002 (S10)

nbr_of_packet_channel_reqs


UL TBF establ.72000(S9)


Req x tsl UL72034..38(S9)

Alloc x tsl UL72044..48(S9)

EGPRS UL TBF 72088(S10) Possibly

EGPRS TBF ifthere are resouces


EGPRS Packet Channel Request (PRACH)


EGPRS Packet Channel Request


UL TBF ASSIGNMENT,MS ON PCCCH.1 phase access.

/c91021(10)p_ul_ass_msgs_on_pccch


More than 1 TCH can be requested

QoSinformation.

PRACH p-ch req./c91002 (S10)

nbr_of_packet_channel_reqs


UL TBF establ.72000(S9)


Req x tsl UL72034..38(S9)

Alloc x tsl UL72044..48(S9)

EGPRS UL TBF 72088(S10) Possibly

EGPRS TBF ifthere are resouces

Figure 30 EGPRS UL TBF ASSIGNMENT, MS on PCCCH with 1 phase access





4.1.3.8 Establishment of EGPRS UL TBF when DL TBF is ongoing

MS BTS BSC SGSN

Packet Uplink Assignment (PACCH)

EGPRS Packet_DL_Ack/Nack(Channel Request Description)


UL RLC Data Block

The MS may request UL TBF by including a Channel Request Description IE in a Packet Downlink Ack/Nack message

UL RLC ACK

MSC1…9 /c79002(S10)

orUL RLC UNACK MSC1…9 /c79003(S10)



UL RLC MAC

/c72076(S9)

UL TBF DUR. DL/c72074(S9)

Req X tsl U L

72034(S9)

Alloc X tsl UL

72044(S9)


UL TBFEstabl.72000(S9)




Possibly



Packet Uplink Assignment (PACCH)

EGPRS Packet_DL_Ack/Nack(Channel Request Description)


UL RLC Data Block

The MS may request UL TBF by including a Channel Request Description IE in a Packet Downlink Ack/Nack message

UL RLC ACK

MSC1…9 /c79002(S10)

orUL RLC UNACK MSC1…9 /c79003(S10)



UL RLC MAC

/c72076(S9)

UL TBF DUR. DL/c72074(S9)

Req X tsl U L

72034(S9)

Alloc X tsl UL

72044(S9)


UL TBFEstabl.72000(S9)




Possibly


Figure 31 Establishment of EGPRS UL TBF when DL TBF is ongoing





4.2 (E)GPRS Data Transfer

After TBF establishment the data transfer signaling is conveyed on PACCH.

4.2.1 (E)GPRS Data Transfer DLMS BTS BSC SGSN

DL TBFASSIGNMENT

DL Data Packets The SGSNencrypt s each DLpacket accordingto parametersnegortiated inPDP cont extactivation

Downlink Data Packets

Downlink Data Packets (PDTCH)

Gtp_packets_sent_in_dl /c3001

Gtp_data_in_bytes_sent_in_dl /c3003

bytes_in_of_vjhc_in_sndcp /c3008

bytes_out_of_vjhc_in_sndcp /c3009

Header com

bytes_in_of_v42bis_in_sndcp /c3010

bytes_out_of_v42bis_in_sndcp /c3011

Data com

NSCV_passed_data_in_bytes /c3017

Packet Downlink Ack/Nack (PACCH)Packet Downlink Ack/Nack

If NACK received andack mode usedDownlink Data Packets


DL RLC retransmCS1/c72068(S9)

or DL RLC retransmCS2 /c72069(S9)


After TBF released

Flowrate per priority /c90005/90006(S10) 1sec sampling

(retransm.not incl.)

DL TBF releasecounter group

DL RLC blockcounter

PCU controls how oftenthe ack should come

(polling in DL data block).It is about every 18blocks but gets adaptedto radio conditions.


DL TBFASSIGNMENT

DL Data Packets The SGSNencrypt s each DLpacket accordingto parametersnegortiated inPDP cont extactivation



Gtp_packets_sent_in_dl /c3001

Gtp_data_in_bytes_sent_in_dl /c3003



Header com



Data com

NSCV_passed_data_in_bytes /c3017


If NACK received andack mode usedDownlink Data Packets


DL RLC retransmCS1/c72068(S9)

or DL RLC retransmCS2 /c72069(S9)


After TBF released

Flowrate per priority /c90005/90006(S10) 1sec sampling

(retransm.not incl.)


DL RLC blockcounter

PCU controls how oftenthe ack should come

(polling in DL data block).It is about every 18blocks but gets adaptedto radio conditions.

Figure 32 (E)GPRS Data Transfer DL

4.2.2 (E)GPRS Data Transfer UL





MS BTS BSC SGSN

UL TBFASSIGNMENT

Packet Uplink Ack/Nack (PACCH)Packet Uplink Ack/Nack (FAI=1 when last)

Packet control ack (PACCH)Packet control ack

"First data blocks" (PDTCH) "First data blocks" (PDTCH)

LLC frames The LLCframeis already ciphered

LLC ack (window 1-16)

Gtp_packets_sent_in_ul /c3000

Gtp_data_in_bytes_sent_in_ul /c3002



Header compr.



Data compr.



There is a dummy DL MACblock before each UL data block


DL dummy control block

RLC blocks per priority 90001(S10)

Also if priority changed

Flowrate per priority /c90005/90006(S10)

1sec sampling

UL TBF releasecounter group

UL RLC blockcounter

PCU controls after howmany blocks the ack is

sent. It is about every 20blocks but can beadapted to radioconditions.


UL TBFASSIGNMENT

Packet Uplink Ack/Nack (PACCH)Packet Uplink Ack/Nack (FAI=1 when last)


"First data blocks" (PDTCH) "First data blocks" (PDTCH)

LLC frames The LLCframeis already ciphered

LLC ack (window 1-16)

Gtp_packets_sent_in_ul /c3000

Gtp_data_in_bytes_sent_in_ul /c3002



Header compr.



Data compr.



There is a dummy DL MACblock before each UL data block


DL dummy control block

RLC blocks per priority 90001(S10)

Also if priority changed

Flowrate per priority /c90005/90006(S10)

1sec sampling

UL TBF releasecounter group

UL RLC blockcounter

PCU controls after howmany blocks the ack is

sent. It is about every 20blocks but can beadapted to radioconditions.

Figure 33 (E)GPRS Data Transfer UL





4.3 Mobility with Cell-reselection

The following mobility related signaling flowcharts are show in this chapter:

• Intra PCU cell-reselection

• Inter PCU cell-reselection (intra BSC)

• RA/LA Update (intra PAPU)

• RA/LA Update (Inter PAPU or inter SGSN)

4.3.1 Intra PCU Cell-Reselection

08.18:

Queued BSSGP signalling, e.g. pages,shall not be affected by Flush. Thesewill thus go wasted if Cell Changehappens.

MS BTS1 BSC SGSN

DLTBFASSIGNMENT, MSON CCCH, via BTS1

DL Data Packets

The SGSNencrypts each DLpacket accordingto parametersnegortiated inPDPcontextactivation

BTS2

DL Data PacketsDL Data Packets (PDTCH)

The MS notices a need for a cell change (measurement strategy in 05.08).The MS stops receiving the DL Data Packets and tunes to the new frequency.While doing the neighboring measurement, the MS also checks for a possible RAchange; if the cell change results in RA change, a RA update is performedinstead of a cell update.

03.60:: "LLC frame of any type, including MS identity"

03.60:: "LLC frame of any type", BSS adds CGI

PCU buffers LLCpdu's in RLCACK-mode until all RLC blocks ofthe LLC pdu are acknowledged.

(reliabili ty class 1-3)

In RLC UNACK-mode PCU buffersuntil all RLC blocks of LLCpdu aresent.

DLTBFASSIGNMENT, via BTS2


Flush-LL PDU( Old BVCI+MS TLLI)

If new BVCI is given in Flush-LL, and thenew BVCI is served by the same NSE,the queued data packets are forwarded tothe new BVCI. In the Intra-PCU case theNSE is the same, since In the Nokiaimplementation each PCU represents one andonly one Network Service Entity (NSE).

In Flush-LLAck the PCU tellswhether the queued data packetswere deleted or forwarded tonew BVCI

The SGSN does notwait for Flush-LLackbefore it forwardsnew DL Data Packetstowards newBVCI

If MS is in UL datatransfer it starts UL TBFin the new cell to transferdata. Cell Update isperformed, too.

UL flush /c72058(S9)

DL flush /c72059(S9)

DL Data Packets

Flush-LL Ack

UL TBFASSIGNMENT, MS ON CCCH, via BTS2

08.18:

Queued BSSGP signalling, e.g. pages,shall not be affected by Flush. Thesewill thus go wasted if Cell Changehappens.

MS BTS1 BSC SGSN

DLTBFASSIGNMENT, MSON CCCH, via BTS1

DL Data Packets

The SGSNencrypts each DLpacket accordingto parametersnegortiated inPDPcontextactivation

BTS2


The MS notices a need for a cell change (measurement strategy in 05.08).The MS stops receiving the DL Data Packets and tunes to the new frequency.While doing the neighboring measurement, the MS also checks for a possible RAchange; if the cell change results in RA change, a RA update is performedinstead of a cell update.



PCU buffers LLCpdu's in RLCACK-mode until all RLC blocks ofthe LLC pdu are acknowledged.

(reliabili ty class 1-3)

In RLC UNACK-mode PCU buffersuntil all RLC blocks of LLCpdu aresent.

DLTBFASSIGNMENT, via BTS2



If new BVCI is given in Flush-LL, and thenew BVCI is served by the same NSE,the queued data packets are forwarded tothe new BVCI. In the Intra-PCU case theNSE is the same, since In the Nokiaimplementation each PCU represents one andonly one Network Service Entity (NSE).

In Flush-LLAck the PCU tellswhether the queued data packetswere deleted or forwarded tonew BVCI

The SGSN does notwait for Flush-LLackbefore it forwardsnew DL Data Packetstowards newBVCI

If MS is in UL datatransfer it starts UL TBFin the new cell to transferdata. Cell Update isperformed, too.


DL flush /c72059(S9)

DL Data Packets

Flush-LL Ack


Figure 34 Intra PCU Cell-reselection





4.3.2 Inter PCU Cell-reselection (Intra BSC)

MS Cell1 BSC SGSN

DL TBFASSIGNMENT, MS ON CCCH, via BTS1

DL Data Packets

The SGSNencrypt s each DLpacket accordingto parametersnegortiatedinPDPcontextactivation

Cell2


The MS notices a need for a cell change (measurement strategy in 05.08).The MS stops receiving the DL Data Packets and tunes to the new frequency.While doing the neighbouring measurement, the MS also checks for a possible RAchange; if the cell change results in RA change, a RA update is performedinstead of a cell update.




PCU buffers unti l RLC/MACack (relaibili ty class 1-3)

DL TBFASSIGNMENT, via BTS2

DL Data Packets



In Nokia implementation, the inter-PCU cellchange is also a inter-NSE cell change, thusthe PCU destroys queued data packets aftera Flush that follows inter-PCU cell change.

Thus if PCU is sending DL data when MSmakes an inter PCU cell change,data is probably lost and retransmiss ionsrely on the LLC layer acknowlegements

Flush-LL Ack

In Flush-LLAckthe PCU tellswhether the queued data packetswere deleted or forwarded tonew BVCI


DL flush /c72059(S9)Related

to cell1

MS Cell1 BSC SGSN

DL TBFASSIGNMENT, MS ON CCCH, via BTS1

DL Data Packets

The SGSNencrypt s each DLpacket accordingto parametersnegortiatedinPDPcontextactivation

Cell2


The MS notices a need for a cell change (measurement strategy in 05.08).The MS stops receiving the DL Data Packets and tunes to the new frequency.While doing the neighbouring measurement, the MS also checks for a possible RAchange; if the cell change results in RA change, a RA update is performedinstead of a cell update.




PCU buffers unti l RLC/MACack (relaibili ty class 1-3)

DL TBFASSIGNMENT, via BTS2

DL Data Packets



In Nokia implementation, the inter-PCU cellchange is also a inter-NSE cell change, thusthe PCU destroys queued data packets aftera Flush that follows inter-PCU cell change.

Thus if PCU is sending DL data when MSmakes an inter PCU cell change,data is probably lost and retransmiss ionsrely on the LLC layer acknowlegements

Flush-LL Ack

In Flush-LLAckthe PCU tellswhether the queued data packetswere deleted or forwarded tonew BVCI


DL flush /c72059(S9)Related

to cell1

Figure 35 Inter PCU Cell-reselection (Intra BSC)





4.3.3 RA/LA Update (intra PAPU)

1. Routeing Area Update Request

3. Routeing Area Update Accept

2. Security Functions

MS BSS SGSN

4. Routeing Area Update Complete

Figure 36 RA/LA Update (intra PAPU)

MS BTS BSC New SGSN

DL TBFASSIGNMENT

Routeing Area Update Accept

Routing Area Update Accept (PDCCH)Routing Area Update Accept

Location update request (SDDCH)

Routing Area Update complete (PDCH)Routing Area Update complete

First System information message [1].

Location update request

Location Update AcceptLocation Update Accept



P_Channel Required


Caneel Release (SDCCH)

SECURITYFUNCTIONS ASSETBY THEOPERATOR

Routing Area Update RequestRouting Area Update Request (PDTCH) Rout ing Area Update Request

Location area Update [2].

Routing area Update [3]. C e l l r e s e l e c t i o n

d a t a O u t a g e

First System information message(BCCH)

MS BTS BSC New SGSNMS BTS BSC New SGSN

DL TBFASSIGNMENT










P_Channel Required



SECURITYFUNCTIONS ASSETBY THEOPERATOR




d a t a O u t a g e


Figure 37 RA/LA Update (intra PAPU) in BSS network





4.3.4 RA/LA Update (Inter PAPU or inter SGSN)

MS BSS new SGSN HLRGGSNold SGSN

2. SGSN Context Response

3. Security Functions

1. Routeing Area Update Request2. SGSN Context Request

6. Update PDP Context Request

6. Update PDP Context Response

7. Update Location

10. Update Location Ack

11. Routeing Area Update Accept

8. Cancel Location

8. Cancel Location Ack

9. Insert Subscriber Data Ack

9. Insert Subscriber Data

12. Routeing Area Update Complete

5. Forward Packets

4. SGSN Context Acknowledge

Figure 38 RA/LA Update (Inter PAPU or inter SGSN)

In case of inter-PAPU RA replace SGSN with PAPU.

The flow chart for RA/LA Update from the radio part point of view is included below:





MS BTS BSC New SGSN

Routeing Area Update Request (PDTCH) Routeing Area Update Request

Packet Uplink Ack/Nack (PACCH)




Including TLLI for contention resolutionIncluding TLLI for contention resolution

Routeing Area Update Request

DLTBFASSIGNMENT


Routeing Area Update AcceptRouteing Area Update Accept


SECURITYFUNCTIONS ASSETBYTHEOPERATOR





UL TBFreleasecounter group


UL RLC blockcounter

DL RLC blockcounter

Start T3330, 15s(max.5 t ries)


New SGSN sends context req to oldSGSN. Old SGSN sends response andstarts tunneling data to new SGSN . NewSGSN sends ‘Update PDP contextrequest’ to GGSN. New SGSN informsHLR about SGSN change by sending‘Upate location’. HLR sends ‘Cancellocation’ to old SGSN.

UL TBFASSIGNMENT, MSON CCCH1-ph.access


Routeing Area Update Request (PDTCH) Routeing Area Update Request






Routeing Area Update Request

DLTBFASSIGNMENT


Routeing Area Update AcceptRouteing Area Update Accept


SECURITYFUNCTIONS ASSETBYTHEOPERATOR







UL RLC blockcounter

DL RLC blockcounter



New SGSN sends context req to oldSGSN. Old SGSN sends response andstarts tunneling data to new SGSN . NewSGSN sends ‘Update PDP contextrequest’ to GGSN. New SGSN informsHLR about SGSN change by sending‘Upate location’. HLR sends ‘Cancellocation’ to old SGSN.

UL TBFASSIGNMENT, MSON CCCH1-ph.access

Figure 39 RA/LA Update (Inter PAPU or inter SGSN) in BSS network 1/2

MS BTS BSC New SGSN

UL TBFASSIGNMENT

Routeing Area Update Complete (PDTCH) Routeing Area Update Complete






Routeing Area Update Complete

Succ_inter_sgsn_ra_updat /c1019DL RLC MAC

/c72077(S9)


UL RLC blockcounter


UL TBFASSIGNMENT

Routeing Area Update Complete (PDTCH) Routeing Area Update Complete






Routeing Area Update Complete

Succ_inter_sgsn_ra_updat /c1019DL RLC MAC

/c72077(S9)


UL RLC blockcounter

Figure 40 RA/LA Update (Inter PAPU or inter SGSN) in BSS network 2/2

4.4 TBF Release

PACKET TBF RELEASE message is sent on the PACCH by the network to themobile station to initiate release of an uplink or downlink TBF.





The delayed TBF functionality is described in section 7.3 and section 7.4.

4.4.1 Packet TBF Release Content

The PACKET TBF RELEASE information element contains the following informationamong others (3GPP 04.60):

Global TFI IE

This information element contains the TFI of the mobile station's which uplink and/ordownlink TBF to be released.

Uplink_Release (1 bit field) Downlink_Release (1 bit field) These fields indicate which TBF shall be release, uplink or downlink. Both directionscan be released at the same time.

0 TBF shall not be released1 TBF shall be released

TBF_RELEASE_CAUSE (8 bit field)This field indicates the reason for the release of the TBF. This field is encodedaccording to the following table:

bit 4 3 2 1 0 0 0 0 Normal release 0 0 1 0 Abnormal releaseAll other values are reserved, the same behavior in reception as if 'Abnormal release'.

The network may initiate immediate abnormal release of a downlink TBF bytransmitting a PACKET TBF RELEASE message to the mobile station on the PACCH.

The mobile station shall immediately stop monitoring its assigned downlink PDCHs. Ifa valid RRBP field is received as part of the PACKET TBF RELEASE message, themobile station shall transmit a PACKET CONTROL ACKNOWLEDGMENT messagein the uplink radio block specified.

If there is no on-going uplink TBF, the mobile station in packet transfer mode shallenter packet idle mode.

4.4.2 Abnormal Releases

In Nokia implementation the following abnormal releases can be listed:

• TBF Releases due to CSW traffic will occur when during a data session theCS call or SMS is received.

• TBF Releases due to Flush will occur during a cell change.

• TBF Release due to no response from MS will occur when the mobile willloose the connection e.g. due to lack of coverage – TBF drop.

• The TBF release due to suspend.





4.4.3 TBF Release in PCU2

Network may send PACKET TBF RELEASE message on the PACCH to the mobilestation to initiate release of an uplink or downlink TBF. /44.060/

PCU1 never uses PACKET TBF RELEASE.

PCU2 uses PACKET TBF RELEASE message with following scenarios:

• Abnormal release because of N3101/N3103/N3105 counters reachingmaximum value for the TBF.

• Abnormal release because of T3193 timer expiry.

• TBF release because of territory downgrade or cell delete or Abis sync loss.

• When Channel Request Description IE and FAI=1 is received in PACKETDOWNLINK ACK/NACK from the MS, PCU2 sends PACKET TIMESLOTRECONFIGURE and establish both the UL and DL TBFs. If the MS hasstarted using new resources and there is no DL PDU at PCU, then PCU2releases the DL TBF by sending PACKET TBF RELEASE.

• If Uplink/Downlink TBF establishment fails, then in some cases PCU2 sendsPacket TBF release message to the MS to make sure that the MS move toCCCH.

• Reallocation Failure from non-hopping to hopping band. After initial allocationon non-hopping/BCCH band, if BTS reallocation to Hopping BTS fails then

PACKET TBF RELEASE message is sent to mobile. See Note1.

Note 1. If EGPRS is configured to hopping non-BCCH BTS, EGPRS DLTBF may be initially established on non-EGPRS BCCH band, but theTBF is immediately reallocated to EGPRS band. If there is congestionin EGPRS territory, the PCU releases the EGPRS TBF and establishnew GPRS TBF for the MS. Because the PCU2 can send PACKET TBFRELEASE message to the MS then PCU2 can initiate GPRS DL TBF tothe MS immediately. In the same situation the PCU1 does wait 5seconds until it can initiate GPRS DL TBF to the MS

PACKET PDCH RELEASE message is sent on PACCH by the network to notify allmobile stations listening to that PDCH that one or more PDCHs will be immediatelyreleased and become unavailable for packet data traffic. /44.060/

PCU2 sends PACKET PDCH RELEASE message on all timeslots of the territory.PCU1 does not send PACKET PDCH RELEASE message on the timeslots that werenot allocated to any MS.





5. (E)GPRS Accessibility

The fast access to the network is very important in (E)GPRS functionality. If the TBFestablishment is delayed due to congestion on signaling channels, the (E)GPRS

performance will be degraded.

The aim of signaling load analysis and planning is to avoid service degradation on(E)GPRS due to overload situation on signaling channels.

The signaling traffic analysis is important from CSW point of view as well, becausethe (E)GPRS attach/detach, PDP Context Activation, TBF establishment and(E)GPRS mobility using the signaling channels and generate additional BSS signalingtraffic on top of the CSW signaling load (except for PBCCH usage).

The signaling load analysis in BSS network is based on the following items:

• Air interface signaling

• TRXSIG on Abis interface

• BCSU in BSC

In the following subsections the above-mentioned items are described from analysisand planning point of view.

5.1 Air Interface Signaling Load

The logical channels are split into traffic channels (TCH), Common Channels (CCH)

and Dedicated Channels (DCH).

The CCH is further divided to Broadcast Channels (BCH) and Common ControlChannels (CCCH).

The BCH is downlink channel and contains three logical channels: FrequencyCorrection Channel (FCCH), Synchronization Channel (SCH) and Broadcast ControlChannel (BCCH).

The DCH contains the Stand Alone Dedicated Control Channel (SDCCH), SlowAssociated Control Channel (SACCH) and Fast Associated Control Channel(FACCH).

The BCH channels do not need any planning consideration, but the CCCH channelsand SDCCH can limit the (E)GPRS performance.

The implementation of PBCCH brings additional capacity and features, too. Thefollowing figures show the logical channels for GSM and channels with PBCCH.





COMMONCHANNELSCOMMON

CHANNELS

BROADCASTCHANNELS

BROADCASTCHANNELS

COMMONCONTROL

CHANNELS

COMMONCONTROL

CHANNELS

DEDICATEDCONTROL

CHANNELS

DEDICATEDCONTROL

CHANNELS

TRAFFICCHANNELSTRAFFIC

CHANNELS

FCCHFCCH SCHSCH BCCHBCCH SDCCHSDCCH SACCHSACCH FACCHFACCH

PCHPCH RACHRACH AGCHAGCH TCH/FTCH/F TCH/HTCH/H TCH/EFRTCH/EFR

DEDICATEDCHANNELSDEDICATED

CHANNELS

LOGICAL

CHANNELSLOGICAL

CHANNELS

Figure 41 Logical Channels

5.1.1 Common Control Channels

The Common Control Channel contains the following channels:

• RACH, Random Access Channel;

• AGCH, Access Grant Channel;

• PCH, Paging channel;

• CBCH, Cell Broadcast Channel;

Common control channels are multiplexed in a 51 slots multiframe with the broadcastchannel BCCH, different configurations are possible, they are explained below.

5.1.1.1 Paging ChannelWhen the system initiates a communication towards a mobile station (for a call, anauthentication, a short message service), the identity is broadcast in a group of cells(location area). The information is sending on the Paging Channel. It includes thesubscriber's identity, either its TMSI or IMSI. The IMSI is anyway sent by the MSC to

compute the paging group (see below).

PAGING REQUEST comes in 3 types:

Type 1 carries 2 identities (IMSI or TMSI)

Type 2 carries 3 identities (2 TMSI + 1 TMSI/IMSI)

Type 3 carries 4 identities (TMSI).

PCH is a downlink non-dedicated logical channel.

5.1.1.2 Access Grand Channel

When the request has reached the system, a dedicated signaling resource has to beallocated to the original mobile to continue the process (identification, authentication,





set-up, etc.). This allocation is done on a set of downlink slots, which constitute theAGCH. It is a downlink non-dedicated logical channel.

The allocation message contains information about the carrier to use: channel

number, slot number, frequency hopping description if used and an estimated timingadvance. The message is called IMMEDIATE ASSIGNMENT. If BSC is not able toallocate a resource, it will warn the mobile station and forbid it to retry within a timeindication, this message is called IMMEDIATE ASSIGNMENT REJECT. If, forcongestion reason, BTS is not able to send an IMMEDIATE ASSIGNMENT messageon the air-interface, it will send a DELETE INDICATION to the BSC, indicating theoverload.

Each AGCH can carry:

• 1 Immediate Assignment

• 2 Immediate Assignment Extended

• Up to 4 Immediate Assignments Reject

5.1.1.3 Random Access ChannelWhen a mobile station has to execute any kind of operation with the system (locationupdate, call establishment, emergency call, etc.), it has to establish a contact. A shortrequest (coded on one burst, called Access Burst) is sent on a particular slot using asynchronized ALOHA (see GSM recommendation) access type; the set of these slotsis called RACH.

RACH is an uplink non-dedicated logical channel, shared between mobile stations

served by a specific cell.

5.1.2 SDCCH

The SDCCH is a dedicated signaling channel utilized on the air interface betweenmobile station and base station. The SDCCH channel is allocated between the MSand BTS following successful MS RACH and access grant by the BSC.

SDCCH usage is required for the 5 cases listed below:

• Call set-up (includes MOC, SMS, SS activation’s)

• Answer to paging

• Emergency call

• Call re-establishment

• Other reasons (which includes most commonly, location updates)

The random access by the mobile can be due to call set up, location update requestor to answer a paging message from the Network. The RACH message is very datacontent limited with the initial RACH not controlled by the network. Accordingly, theaccess grant procedure is reasonably complex culminating in the initial channelassignment of a dedicated signaling channel.





This dedicated signaling channel is then utilized by the network to control thesubsequent network access by the mobile. Thus the SDCCH channel is key inachieving successful & efficient RA/LA update in (E)GPRS cell-reselection.

5.2 TRXSIG LoadOne TRX signaling channel (also called LAPD channel or D-channel) is defined foreach TRX in Nokia BTS. The capacity of a LAPD channel is 16 kbps, 32 kbps or 64kbps.

Many of the customer’s end-user service is generating new TRX load to existingnetwork. Also the load profile has been changed due to the changes of the end userbehavior compared to the days the network was dimensioned. The signaling loadmight also have been increased in a given signaling link due to a recent BSS featureactivation in the BSS network.

To ensure that the A-bis signaling links are able to carry the increased signaling trafficit is recommended to offer the A-bis signaling optimization service, whenever eitherthe radio network is optimized or an upper level end-user service is optimized. Non-optimized A-bis signaling could easily be the bottleneck in achieving the targetperformance level.

In addition to A-bis signaling link optimization service the physical layer transmissionquality audits could be considered as an offered service module as the physical layeris the foundation for the whole A-bis respectively. [1]

The signaling is generated on TRXSIG and data TSLs as PACCH. In case of PBCCHthe TRXSIG is not loaded by (E)GPRS signaling anymore.

5.2.1 TRXSIG Load Theory

The Abis protocols and TRXSIG load components are described below:

5.2.1.1 Abis ProtocolsThe protocol layers of Abis can be seen in the Figure 42 below:





Figure 42 Abis protocol layer

TRXSIG Load on DL

Overload could occur in downlink direction because of high amount of paging,immediate assignment, location update, etc. The buffer of the LAPD links handling theAbis signaling may overflow especially with the 16 kbit/s Abis links.

In heavy downlink situation normally paging and immediate assignment rejectmessages are being discarded on the LAPD signaling link to ensure the uninterruptedflow of call signaling traffic which always has the highest priority. If the situation getsworse and the congestion level of the transmit buffers still very high, all the signalingmessages on the channels causing the congestion may be discarded.

In order to ensure paging does not overload the TRXSIG link in downlink, aprecaution is needed, and traffic margin is given. In theory, the length of the paging

message including Layer 2 header is about 21 octets (vary depends on TMSI or IMSIbeing used).

According to the system documentation of BSC nominal load and call mix, if thesystem is running on 50% of entire TRXSIG link capacity is consider running on thelimit and it is referring to maximum system capacity.

About 60% of maximum system capacity is allocated for paging messages. Thus theaverage paging message for 16kbit/s link is calculated as 0.6 * 1000 octets / 21 octets= 29 pages per second, which roughly equals to 100 000 pages per hour.

As a result of the case studies conducted, the downlink messages putting the highestload on the Abis link in BCCH TRXSIG is paging message.





TRXSIG Load on UL

Most of the messages received by the BCSU are radio measurements coming fromthe MS and access requests. These messages come from the LAPD link, and those

are distributed to the RCSPRB (Radio Connection Supervision Program Block) in theBSC that processes them further. Before the distribution, the load state of the BCSUis checked. If the load exceeds a certain predefined limit, the messages arediscarded.

If the load does not exceed the limit, messages are distributed and handled normally.The loss of the radio measurement result does not affect the service qualitysignificantly; some reports are lost anyway due to the load on the LAPD link. Themethod of discarding messages is random as well, so the loss of messages for oneparticular connection stays within reasonable limits.

However, if the uplink traffic load is heavy enough and the LAPD buffer is full, the

BTS starts to delete messages. When the LAPDm receives a message from theRadio Resources (RR management), buffer availability is checked and the messageis deleted if there is no free space available. L3 messages (including RACHmessages) are deleted if there are over 35 messages in the buffer, and measurementresults are deleted if there are over six messages in the LAPD buffer.

In Nokia’s BSS implementation, a heavy traffic load usually first comes to attention viamissing measurement results. If the traffic load gets heavier, other messages will alsobe deleted.

In order to reduce the uplink signaling traffic, measurement results can be averagedout from the BTS before sending to the network with the help of the BMA parameter.

The value of the BMA can vary from 1 to 4.

5.2.1.2 TRXSIG Load Components, Measurement and AnalysisThe overload of TRXSIG can degrade the (E)GPRS performance, because e.g. theTBF establishment needs resources from TRXSIG. Therefore the first step inaccessibility analysis and planning is the TRXSIG load analysis.

TRXSIG is a signaling link located on Abis interface. It conveys signaling messages(including SMS) between TRX and BSC using LAPD protocols.

When the signaling link gets congested, the buffer of conveyed messages becomesfull on both side of the Abis interface then the signaling messages will be discarded.

This can lead to failure of any function that is using the signaling connection.

From RF signaling planning point of view, the TRXSIG link is used to transmit thosemessages that are sent between MS and BSC on the following channels (dependingon the channel configuration of the concrete TRX):

BCCH

TRXSIG is used to download SYS INFO messages to BTS; BTS then sendsthem continuously on the BCCH.

CCCH subchannels (RACH, AGCH, PCH and CBCH)

SDCCH and its assigned SACCH

FACCH and SACCH assigned to a TCH





The TRXSIG conveys the e.g. Radio Link Layer management and TRX managementmessages as well, but these massages are not related to RF signaling.

In (E)GPRS the signaling information can be transmitted on TRXSIG channel but also

on PACCH traffic channel (16 kbit/s PCU frames, a derivative of TRAU frames). Sothe signaling on PACCH is not transmitted over TRXSIG.

(E)GPRS mobile may or may not (this is controlled by the network) send anymeasurement report. These messages are sent using PCU frames, since the PCUcontrols the MS power. This MS power control information is signaled to the mobilevia transparent RLC/MAC signaling messages, which are sent using PCU frames.Therefore, all of these messages (measurements and MS power control information)are not sent through the TRXSIG link.

The load measurement are generated in BSC and based on the following activities:

1. Data Collection

As the Abis signaling link service is flexible and can be anything between a24h snap shot to continuous trend monitoring the actual tasks need to beplanned carefully.

The LAPD-channel potential overload is taking place during the busy hour ofthe LAPD-channel. Different cells have the busy hour in different moment. Inorder to detect the potential overload situations it is essential to collect thedata so that the busy hour of each LAPD-channel is covered. If the individualLAPD-channel busy hour is not known it is recommended to use at least twoweeks continuous data collection period.

At least the following issues need to be planned and agreed before startingthe data collection.

• The duration of the measurement period(s)• The start time of the measurement(s)• The BSCs included in each measurement• Agreement who (having necessary operating rights) is responsible for

the required file-transfer activities and running the Unix scripts.• Awareness of the other planned work for the same BSS areas

2. Data Processing

Data processing is done off-line and it is not causing load to the BSSnetwork. The log files are transferred from the NMS to the Windows PC. Firstthe files are prepared by the Excel macro tool and then they are furtherprocessed by the MS Access tool.

3. Data Analysis

The agreed service delivery may contain one or more of the followinganalysis.

• Unavailability analysis

• Load Analysis• Quality Analysis• Delay Analysis





• Configuration Analysis

The data collection period is also agreed and may be a series of consecutive30 min periods (e.g. 48 periods each 30 min for 24h) or samples of limited

consecutive period in given intervals (e.g. 15:00 to 23:00 every Friday). Forcomprehensive error analysis it is recommended to have consecutive datacollection periods covering sufficient time period.

The detailed description of TRXSIG load measurement and analysis can be found inthe link below:


LAPD KPIs

The evaluation of KPI can be implemented via MML using the command ZDMF,

which gives the Total amount of Traffic Transmitted and Received in number ofOctets in 30-minute windows.

To come in line with the KPI, the amount of data in each direction should not exceed30% capacity of the existing link capacity otherwise an upgrade is necessary. Forexample TRANSMITTED TOTAL OCTET COUNT and RECEIVED TOTAL OCTETCOUNT should not exceed 1080 000 octets for 30-minutes in case of a 16kbps TRXsignaling link applied.

The OCTET COUNT figures in ZDMF report do not include the FCS- and Flag fieldsof the LAPD frame.

To compliment the KPI, MML’s command ZDMI is used to interrogate the workingcondition of the LAPD link. (The transmission quality of the abis links cannot bemeasured, except by sending people out to measure).

LAPD load and quality KPIs in S13

Abi_6a indicates the LAPD link (D-channel) load. It reports maximum of DL and ULload in a given D-channel.

Abi_4a gives DL D-channel load and abi_5a UL D-channel load.

Abi_1a to abi_3a are used to monitor LADP link and thus the whole Abis lineconnection quality._

These KPIs are available in LAPD Statistics for Abis Interface report.





5.3 BCSU Load

The BCSU handles the LAPD (TRXSIG and OMUSIG) and SS7.

The BSC elements’ load measurements register information on the peak and theaverage load rate of the computer units inside the BSC.

5.3.1 BSC RAW Measurement Results

An example of load results can be seen below (Table 16):

Table 16 BSC Unit Load Measurement Results from raw BSC measurement file converted withPCBSCS105 program

5.3.2 Reporting Suit 184 Report





The RS 184 report contains the BSC Unit load per hour for each BSC. For processorunits the average load of 70% is critical and the average of 60% should not beexceeded. For MB the average load should not exceed 50%. An example can beseen in Table 17.

Unit name and index Average load

(%)

Min peak load

(%)

Max peak load

(%)

Peak hour

(YYYYMMDDHH)

BCSU-0 0 1 1 2004120200

BCSU-1 6.7 15 15 2004120215

BCSU-2 7.01 17 17 2004120219

BCSU-3 7.15 17 17 2004120218

BCSU-4 7.15 17 17 2004120215

BCSU-5 6.02 15 15 2004120219

BCSU-6 5.26 14 14 2004120219

BCSU-7 7.52 18 18 2004120215

BCSU-8 8.07 20 20 2004120219

MB-0 2.28 19 19 2004120214

MCMU-0 8.95 79 79 2004120214

MCMU-1 5.71 27 27 2004120214

OMU-0 1.18 32 32 2004120215

Table 17 SD 184 report example

5.4 Signaling Load with DTM Usage

The signaling load generated by the DTM co-ordination is dependent on thepenetration of DTM mobiles.

• When the large majority of the mobiles are DTM capable, then the DTM co-ordination will generate a considerable signaling load at the PCUSIG interface

• In the overload situation the BSC is perhaps not able to handle all the DTMco-ordination messages generated and the message might be discarded. Thefollowing can happen

• The PCU may not receive an indication that a DTM MS has entered dedicatedmode.

• If the PCU receives a data PDU for the MS in this case, the DL TBFestablishment fails and the MS is considered as unreachable.

• The PCU may not receive an indication that a DTM MS has left dedicatedmode. The PCU is not able to remove the MS from the IMSI record resulting ina ‘hanging’ record that consumes memory of the PCU.





6. Resource Allocation in BSS

In the previous chapter the accessibility has been investigated from signaling capacityand signaling limitation point of view in the whole BSS chain.

If the required signaling capacity is provided, the next step will be to find the mostappropriate source for maximizing the user data rate (based on maximized RLC/MACdata rate).

The network resources are usually limited (capacity, coverage and interferencelimited); therefore the proper allocation of users among the resources is veryimportant.

The (E)GPRS traffic is allocated among:

• Cells (Segments)

In some of the cases the resource allocations are based on simple andindependent measurements (C1, C2) while others are using many planningparameters like C31/C32.

From S11.5 Network Controlled Cell Reselection (NCCR) can be used as wellbased on planning parameters.

• BTSs inside segments

The resource allocation inside segment is based on some parameters likeGENA, EGENA and PCU allocation algorithm as well.

• TSLs inside BTS

The resource allocation among TSLs is based mainly on PCU algorithm (loadcalculations), as well as in case of QoS or EQoS scheduling.

In BSS network further bottlenecks can limit the access to the resources, like EDAPand PCU limitations.

So the resource allocation is based on the following items below:

• Cell-Reselection

• BTS selection and TSL allocation

• Scheduling

The terminal is firstly allocated to a cell, secondly to a BTS inside segment (ifMultiBCF / CBCCH is used) and at the end the allocation is finally based onscheduling.





6.1 Cell Reselection

First step in resource allocation procedure is the cell selection (and reselection inmobility). The cell selection and reselection is based on C1, C2, C31/C32, NCCR and

NACC.

ETSI define three network control order parameters, which determine themeasurement reporting and network control on the MS.

• NC0: MS controlled cell reselection, no measurement reporting;

• NC1: MS controlled cell reselection, MS sends measurement reports;

• NC2: Network controlled cell reselection, MS sends measurement.

6.1.1 C1 and C2

The Nokia BSS supports network control order NC0, and therefore there are nonetwork controlled handovers in GPRS, the cell is selected autonomously by themobile using the existing path loss criteria C1 and cell reselection parameter C2.

The network broadcasts on the BCCH the Modified system info 3 and System info 13parameters related to mobility management, which the (E)GPRS mobiles utilize toensure that they are camped on the cell offering best service in each area (thePBCCH functionality will be described later on in this document). The process for thispurpose is called Cell Selection and is based on C1 and C2 comparison.

The MS calculates the value of C1 and C2 for the serving cell and will re-calculate C1

and C2 values for the neighbouring cells every 5 seconds. The MS will then checkwhether:

• The path loss criterion (C1) for current serving cell falls below zero for a periodof 5 seconds. This indicates that the path loss to the cell has become too high.

• The calculated value of C2 for a non-serving suitable cell exceeds the value ofC2 for the serving cell for a period of 5 seconds.

If, however, in the case of the new cell being in a different location area or, for aGPRS MS, in a different routing area or always for a GPRS MS in ready state, the C2value for the new cell shall exceed the C2 value of the serving cell by at least

CELL_RESELECT_HYSTERESIS dB.

The idea is that the MS compares field strength levels of different cells defined in theidle mode BA list and selects the most appropriate using the C1 criteria:

C1 =(a-Max(B,0))

A= received level Average – p1

B= p2-maximum RF Power of the Mobile Station

p1= Rxlevel access min (gprsRxLevAccessMin)

p2= MS TXPower MAX CCH (gprsMsTxpwrMaxCCH)

All values are expressed in dBm. POWER_OFFSET is not used.





The C2 parameter can be utilized together with the C1 parameter to provide theoperator with greater traffic management capability. The C2 parameter wasintroduced in GSM phase two and designed for use in layered-architecture networks(micro/macro cell/Dual Band).

The C2 feature brings associated parameters that are related to microcellularplanning.

• penaltyTime (20 ... 640 s) describes the time delay before the finalcomparison is made between two cells.

• temporaryOffset (0 ... 70 dB) describes how much field strength could havebeen dropped during this penalty time,

• cellReselectOffset (0 ... 126 dB) describes an offset to cell reselection. C2

cell reselection is calculated by equation

C2 = C1 + cellReselectOffset - temporaryOffset x H(penaltyTime-T) whenpenaltyTime < 640

or

C2 = C1 - cellReselectOffset when penaltyTime=640

6.1.2 C31/C32

The C31/C32 parameters will give the possibility to optimize the cell reselection for(E)GPRS without affecting the circuit switched cell reselection behavior. This willallow more flexible use of cell resources, allowing, for example, some cells to bepacket free if this is the intention.

The C31/32 functionality will only be applicable if the PBCCH is allocated, otherwisethe circuit switch signaling channels will be used and consequently C1 and C2.

In a multi-vendor environment one requirement is that all the vendors should supportbroadcasting of the C31/C32 parameters.

C31 parameter

Signal strength threshold criterion (C31) for hierarchical cell structures (HCS) is usedto decide whether the cell is qualified for prioritized hierarchical cell selection.

C31(s) = RLA(s) - hcsThreshold (s)(serving cell)

C31(n) = RLA(n) – hcsThreshold (n) - TO (n) * L(n) (neighbor cell)

Where

HCS_THR = signal threshold for applying HCS reselection

TO(n) = gprsTemporaryOffset (n) * H(gprsPenaltyTime (n) – T(n))

L(n) = 0, if hcsPriorityClass (n) = PRIORITY_CLASS(s)





1, if hcsPriorityClass (n) ‡ hcsPriorityClass (s)

H(x) = 0, if x < 0

1, if x >= 0

gprsTemporaryOffset applies a negative offset to C31/C32 for the duration ofgprsPenaltyTime after the timer T has started for that cell.

T is a timer implemented for each cell in the list of strongest carriers. T shall bestarted from zero at the time the cell is placed by the MS on the list of strongestcarriers, except when the previous serving cell is placed on the list of strongestcarriers at cell reselection. In this case, T shall be set to the value of PENALTY_TIME(i.e. expired).

C32 parameter

The cell ranking criterion (C32) is used to select cells among those with the samepriority

C32(s) = C1(s) (serving cell)

C32(n) = C1(n) + gprsReselectOffset (n) – TO (n) * (1 – L(n))(neighbour cell)

Where

gprsReselectOffset applies an offset and hysteresis value to each cell.

TO and L as in C31.

gprsReselectOffset applies an offset and hysteresis value to each cell.

The MS must select the cell having the highest C32 value among those that have thehighest priority class among those that fulfill the criterion C31 >= 0. The priorityclasses may correspond to different HCS layers. If no cells fulfill the C31>=0 criterion,the MS must select the cell having the highest C32 value.

If PBCCH is not allocated to the cell, criterions C1 and C2 are used as they are usedin current CSW services.





Q3 parametername

Range MMLdefault

gprsRxLevAccessMin -110…-47 dBm

-105

gprsMsTxpwrMaxCCH 5 .. 43 dBm with 2

dBm step for GSM

850 and 900

0 .. 36 dBm with 2

dBm step for GSM

1800

0 .. 32 dBm with 2

dBm step and 33dBm for GSM 1900

33 dBm for GSM

850 and 900.

30 dBm for GSM

1800 and 1900.

hcsThreshold -110, -108, …,,-48 dBwith 2dB step

N (notused)

gprsTemporaryOffset 0 .. 70 dB with a

step size of 10 dB

0

gprsPenaltyTime 10 .. 320 (s) with a

step size of 10 s

10

hcsPriorityClass 0 to 7 7

gprsReselectOffset -52, -48,..., -12, -

10,..., 12, 16, ...,48

(dB)

0

gprsCellReselHysteresis 0, 2, 4, 6, 8, 10, 12,

14 dB

4

c31Hysteresis Y/N N

c32Qual Y/N N

raReselectHysteresis 0, 2, 4, 6, 8, 10, 12,

14 dB

4

Table 18 GPRS parameters





MS cell reselection algorithm

MS makes cell reselection if path loss criterion (C1) for the serving cell falls belowzero.

MS can make cell reselection also when it founds a non-serving suitable cell betterthan the serving cell. The best cell is the cell with the highest value of C32 among thecells with the highest PRIORITY_CLASS and fulfill the criterion C31 >= 0 or all cells ifthere no cell fulfilling the C31 >= 0 criterion.

If c32Qual parameter is set, positive gprsReselectOffset values shall only beapplied to the neighbour cell with the highest RLA_P value of those cells for whichC32 is compared above.

When the MS is in ready state, time defined by gprsCellReselHysteresis value issubtracted from C32 value for neighbour cells. If parameter c31Hysteresis is set the

GPRS_CELL_RESELECT_HYSTERESIS is subtracted also from C31 neighbourcells. When the new cell is from different routing area raReselectHysteresis parameter value is subtracted from C32 for neighbour cells. In case of a cellreselection occurred within the previous 15 seconds, 5 dBs are subtracted from C32for neighbour cells.

Abnormal Cell reselection

Whenever the MS receives PACKET UL ACK/NACK (Packet Ack/Nack is PAN) thatallows the advancement of data transmit, the mobile station shall increment N3102 bythe broadcast value PAN_INC , however N3102 shall never exceed the valuePAN_MAX . Each time T3182 expires the mobile station shall decrement N3102 by

the broadcast value PAN_DEC . When N3102 <= 0 is reached, the mobile stationshall perform an abnormal release with cell reselection.

BSC parameters:

• An other reason for abnormal cell reselection is MS not being able to readPSI1 in 60 sec. (both in packet idle or in packet transfer mode)

• Abnormal cell reselection will happen if randomAccessRetry = 1

• Going back to the original cell is prohibited by parameter tResel sec if anothersuitable cell is available.

More information about cell reselection parameters and its optimization can be foundin (E)GPRS Radio Networks – Optimization Guidelines.

6.1.3 Network Controlled Cell Reselection

Target cell to which the cell reselection is done, can be selected by the MS itself or bythe network.

In earlier releases Nokia implemented only MS controlled cell reselection withoutmeasurement reports, which is basically commanded by Network Control Order 0(NC0). In NC0, cell reselection is controlled by MS alone in both MM Ready and MMStandby states whether MS is in Packet Idle Mode or Packet Transfer Mode. When

there is NCCR in the network cell reselection for MSs in MM Ready state arecontrolled by the network. When MSs go back to MM Stand By state, cell reselection





is done by MS as in NC0. NCCR support is indicated by setting the Network ControlOrder to NC2.

PBCCH is not needed for NCCR.

NCCR can be enabled for Release97 mobiles onward.Handover procedure, where cell resources are reserved in the target cell beforeordering MS cell change is not provided for packet switched services in 3GPP release4.

6.1.3.1 NCCR Benefits

Benefits that S11.5 Network Controlled Cell Reselection introduces:

o Efficient allocation of EGPRS resources. Some operators introduce EGPRSTRXs gradually in GSM networks. Some cells have EGPRS TRXs and somewill not. EGPRS resources will be scarce and will need to be allocatedefficiently. PCU will push EGPRS capable MSs to EGPRS cells and GPRS

capable MSs to non-EGPRS capable cells by power budget NCCR criterion.Cell attractiveness can be defined neighbour cell specifically also taking intoaccount each neighbour cell’s capacities (e.g. CS-3/CS-4 or EQoS support).

o Quality criterion allows NCCR when the serving cell quality drops even if thesignal level is good.

o Quality Control may trigger NCCR. It means that EQoS can trigger NCCR tomake cell selection.

o Service based NCCR is possible (SGSN UTRAN CCO BSSGP procedure)

o Possibility to select WCDMA network as soon as it is available or when GSMcoverage ends, depending on operator choice.

NCCR is an optional feature. Operator can set the feature on/off on BSC level, anddecide whether NCCR to WCDMA FDD cells is allowed.

NCCR is a standard feature for MS and SGSN. However, there may be MSs, whichdo not support NCCR and the PCU has to be prepared for that. PCU will monitor onlyMSs, which send neighbour cell measurement reports. Further there is a possibility toswitch the NCCR off on 3GPP release basis (Release 97, 99, 04).

6.1.3.2 NCCR FunctionalityThe operator has to set cell adjacencies, NCCR algorithm parameters, NetworkControl Order (NCO) mode and MS reporting period parameters.

Cell adjacencies and NCO mode are broadcast to MS. Depending on the operatorparameter the MS may be commanded to send neighbour cell measurements bybroadcasting the command to all MSs or by commanding individual MSs during TBF.

Once commanded to report neighbour cell measurements MS will send neighbour cellmeasurements to PCU in a frequency defined by the reporting period parameters. MSsends neighbour cell measurements in MM ready state, i.e. RR packet transfer andpacket idle modes.

PCU sets MS NCCR context for each MS, which has been commanded, to NCOwhen first TBF is set for such MS or when first measurement report from such MS is

received. PCU performs averaging for the measurements and applies NCCRalgorithm to averaged measurements. The NCCR algorithm is based on operator setthreshold values, so when certain threshold triggers NCCR is started.





S11.5 includes following NCCR criteria:

• Power budget NCCR

(NCCR EGPRS PBGT margin, NCCR GPRS PBGT margin, NCCR streamingTBF offset, NCCR other PCU cell offset)

• Quality Controlled NCCR

• Coverage reason ISNCCR

The later BSS releases will introduce the following NCCR types:

• EQoS Quality Control

When serving cell cannot provide the guaranteed throughput or thetransmission quality is below operator set threshold, NCCR may be tried tooffer better service.

The Quality Control (QC) NCCR triggering is described in EQoS planningmaterials. The radio link quality based NCCR is required even irrespective ofS11.5 EQoS feature implementation. Target cell selection is performed whenthe QC NCCR trigger comes and always when new PACKET (ENHANCED)MEASUREMENT REPORT message is received until:

• MS NCCR context is deleted

• TBF is released, or

• QC cancels the NCCR trigger.

• Service based ISNCCR

6.1.3.3 Target cell selectionThe target cell evaluation is based on an RXLEV threshold algorithm, depicted inFigure 43. In this figure it is shown the algorithm that the BSC would apply for anEGPRS MS. For GPRS MSs the algorithm is the same except for the Rx level margincomparison, which is:

AV_RXLEV_NCELL(N) > AV_RXLEV_SERV + CellReselMarginQualforGPRSMS(n)

for GPRS MS.

Due to separate thresholds for EGPRS capable and non-capable MSs, this criterioncannot be used before the MS EGPRS capability is known.





Measurement report processing

Is reported BLER over

BLER_THRESHOLD?

Search for the neighbouring cell with

highest AV_RXLEV_NCELL(n)

NO

YES

NO

YES

AV_RXLEV_NCELL(n) >

AV_RXLEV_SERV +

CellReselMarginQualforEGPRSMS(n)

NOYESTrigger NCCR to cell (n)

NCCR successful

NO

YES

AV_RXLEV_NCELL(n) >

RxLevMinCell(n) + Max(0, Pa)

Erase the cell where the failure

occurred from target candidate cell

list until timer

T_NCELL_PENALTY expires

Figure 43 Target cell selection

6.1.3.4 Signaling FlowThe signaling flow of NCCR can be seen below:





Uplink Packet Data transfer

PACCH

Packet (Enhanced)Measurement Report

MS Serving cell

PACCHPacket Cell Change Order

Measurement andNCCR information

regarding target cell

T3174 startsTarget cell

PBCCH

Current TBF on serving cell is aborted!

PBCCH

PBCCH of target cell is received

Waits until PSI1 ocurrence in B0

PBCCHPSI messages

• data transmission is resumedin target cell after all therelevant PSI messageshavebeen received

• The service outage is2-5 sec

Packet Channel Request

Packet Uplink Assignment

PRACH

PAGCH

T3174 stops

Uplink Packet Data transfer

PACCH

Packet (Enhanced)Measurement Report

MS Serving cell

PACCHPacket Cell Change Order

Measurement andNCCR information


T3174 startsTarget cell

PBCCH

Current TBF on serving cell is aborted!

PBCCH

PBCCH of target cell is received

Waits until PSI1 ocurrence in B0

PBCCHPSI messages

• data transmission is resumedin target cell after all therelevant PSI messageshavebeen received

• The service outage is2-5 sec

Packet Channel Request

Packet Uplink Assignment

PRACH

PAGCH

T3174 stops

Figure 44 NCCR signaling flow

6.1.3.5 BLER Limits are Needed for the Quality Control Function in PCU2The maximum block error rate (BLER) limit is set with different parameters in PCU1and PCU2.

For PCU1:

• MAXIMUM BLER IN ACKNOWLEDGED MODE (BLA)

• MAXIMUM BLER IN UNACKNOWLEDGED MODE (BLU)

For PCU2:

• PFC ACK BLER LIMIT FOR TRANSFER DELAY 1 (ABL1)

• PFC UNACK BLER LIMIT FOR SDU ERROR RATIO 1 (UBL1)

The EQoS specific packet flow context (PFC) feature is not applicable with BSC SWrelease S11.5 and PCU2 Only the ABL1 and UBL1 parameters are used, although allABL1-5 and UBL 1-6 parameters are visible. All BLER limit parameters are visibleregardless of the EQoS feature’s state.

In Quality Control function the above corresponding parameters are used similarly inboth PCU1 and PCU2.The BLER parameter values are not directly comparablethough, so they are not converted in the upgrade.





6.2 BTS Selection

The Common BCCH/Multi BCF features are bringing the new Segment (SEG)concept into planning. The affect on GPRS is that there may be more than one BTS

under one segment, which supports GPRS. Therefore at the TBF establishment andalso later for reallocations of the TBF (if necessary) a BTS selection procedure will beutilized.

For example there is one Talk family BTS, which supports GPRS, and EGPRScapable BTS, which can also support GPRS, under the same segment. Also theoperating frequency of the BTSs under one segment can be different for example theBTS which carries BCCH/PBCCH operates in 900 MHz and the other BTS(s)operates in 1800 MHz.

The main principle of BTS selection is primarily to allocate GPRS TBF to a GPRSBTS and EGPRS TBF to an EGPRS BTS.

Multi BCF feature can be used in single band environment and this feature will allowalso having only one BCCH in the segment. For dual band solution common BCCHhas to be applied. Common BCCH is an optional feature while multi BCF is standard.

6.2.1 Initial BTS Selection

Initial BTS from SEG is selected in CHM (Channel Management) when new TBF iscreated.

The main steps of initial BTS selection is listed below:

• BTSs supporting the frequency bands, which are indicated in Radio AccessCapability (RAC) of the (E) GPRS MS, are selected.

RAC may not be known at the time of TBF initiation (RAC information isdelivered to the SGSN during the GPRS attach). Therefore for a DL TBF theSGSN most probably has the RAC of the (E)GPRS MS. It is more likely thatfor the UL TBF, the RAC is not known at the establishment. (For more on RACrefer to 3GPP 04.60). If the RAC is not known then BTSs supporting the samefrequency band as BCCH BTS are selected. Therefore there must be GPRSterritory in the BCCH band.

• The signal level must be good enough on the selected BTS:

- If RX_level (C-value) is known then the BTS selected for allocation hasto satisfy the following: RX_Lev - BTS's non_bcch_layer_offset >BTS's GPRS_non_BCCH_layer_rxlev_upper_limit.

- If RX_level is not known then Direct access BTS is selected.Direct_GPRS_access_threshold parameter is used to compare BTSobjects relative preference: when the value ofDirect_GPRS_access_threshold parameter is higher than the value ofthe parameter non BCCH layer offset then the BTS is valid forallocation.

At the TBF establishment phase there may not be any Rx-lev measurementresults yet because of that RX-Lev criteria cannot be used. TBF is initially





allocated to a BTS where DirectGPRSAccessBTS is set on (in practice itmeans that DirectGPRSaccessBTS > nonBCCHlayerOffset)*.

• An EGPRS capable BTS will be selected for a GPRS TBF only if:

- The segment doesn’t have GPRS capable BTS, or

- TBF/TSL > MaxTBFinTSL in every TSL in every GPRS capable BTS(i.e. the GPRS territory is totally full) AND average TBF/TSL <MaxTBFinTSL in every EGPRS capable BTS.

• If there are several possible BTSs then the BTS in segment with minimumdownlink TBF/TSL QoS load is selected.

• If there is no possible BTS then BTS is not selected and TBF is not created.

*DirectGPRSaccessBTS concept has basically been developed for selecting theappropriate BTS at the initial BTS selection. It is possible to indicate the preferredBTSs for allocation if the Rx_lev is not known at the TBF establishment. PreferredGPRS BTS has nonBCCHlayerOffset parameter set so that it is smaller than DirectGPRSaccessBTS . This parameter (nonBCCHlayerOffset) indicates coveragearea of a BTS in the segment compared to the BCCH BTS. The smaller the value is,the closer the coverage of the BTS is to the BCCH BTS. DirectGPRSaccessBTS indicates the risk that can be allowed when allocating a non BCCH BTS in case of noRx_Lev measurement.

So if the DirectGPRSaccessBTS = 2 in this segment this means that BTSs with 2dB less coverage than the BCCH BTS to be allocated as an initial BTS for a TBF. Andif compare the nonBCCHlayerOffset with this parameter it is checked whether theBTS fulfils this requirement. Then list the BTSs that are appropriate for initial BTSselection, of course BCCH BTS is also included. Operator may want to direct all theGPRS traffic to the non BCCH BTS(s). In order to do that the GPRSenabledTRX parameter on all the TRXs in the BCCH BTS must be set to OFF. However it ispossible that the RAC of the MS is unknown during initial TBF selection. In that casethe non-BCCH BTS must be from the same band as BCCH band.

Rx-Lev Measurements are used as BTS selection criteria, when available;

The DL Rx_Lev measurements (C_value) are sent to the PCU in the DLACK/NACK messages. The receiving frequency of these measurements depends onthe polling frequency of the TBF. Actually the Rx-lev reported is averaged by the MSduring the polling period.

The UL Rx- Lev measurement is included to each PCU frame by the BTS. Thereceiving frequency of these measurements depends on how often the uplink TBFgets a transmission turn. These measurements are averaged in PCU and the averageis used by the allocation algorithm.

For more information on measurements done by MS please check 3GPP 05.08.

The following figure shows the block diagram of initial BTS selection.





START

MS RAC ?MS is EGPRS capable

Is there anyEGPRS BTS in theBTS_LIST_2 ?

Is there anyGPRS BTS in theBTS_LIST_2 ?

RemoveEGPRS BTSsfrom BTS_LIST_2

Yes

RemoveGPRS BTSs fromBTS_LIST_2

Yes No

TBF type ? concurrent

UL and DL

READY

Select the BTS that

is already servingthe MS

MS is only GPRS capable

Select BTSs whose frequency band is included inthe MS RAC band information and save them inBTS_LIST_1 Note1, Note2, Note3, Note4

BTS_LIST_2empty ?

Yes

No

No

Select from BTS_LIST_1 the BTSs

whose non_bcch_layer_offset is lessthan direct_gprs_access_ thresholdand save them in BTS_LIST_2

Select the BTS who has thelowest QoS load among theBTSs in the BTS_LIST_2

READY

RX-level ?

RX-level isknown

RX-level is notknown

Select from BTS_LIST_1 the BTSs for

whom(RX-level - non_bcch_layer_offset) isbigger than GPRS_non_BCCH_ layer_rxlev_upper_limitand save them in BTS_LIST_2

Select fromBTS_LIST_1 the BTSwhosenon_bcch_layer_offsetis lowest

READY

Figure 45 Initial BTS selection

Note1: If MS RAC band is not known then BCCH band BTSs are selected

Note2: BTSs that don’t have PSW territory or channels for PSW are not selected.

Note3: UL: BTSs whose average TBF/TSL is not less thanMaximumNumberOfULTBF are not selectedNote4: DL: BTSs whose average TBF/TSL is not less thanMaximumNumberOfDLTBF are not selected





6.2.2 BTS Selection for Reallocating TBF

TBF reallocation processing can take place if better quality data transfer is expected(related to Rx_level) or BTS packet traffic load is unevenly spread in a segment or

between supported frequency bands in a segment.

Procedures used to check TBF reallocation activation need in Channel Management(CHM) are in order below. Reallocation request to MAC shall be activated in any ofthe procedures at once (1-4).

1. BTS Load reallocation

2. Uplink Rx level reallocation

3. Downlink Rx level reallocation

4. Downlink RX level received first time reallocation

Periodical checks are done every time TBF_LOAD_GUARD_THRSHLD amount ofblock periods are used by the TBF after the last reallocation.

Periodic reallocation check in PCU2 is tied to the amount of transmitted data, not totime as in PCU1.

PCU2 does periodic reallocation check for all non-streaming TBFs to check andreallocate if there are better resources that could be allocated to an MS. Reallocationcheck is triggered on transmission of TBF_LOAD_GUARD_THRSHLD RLC datablocks to the MS.

PCU1 triggers periodic reallocation check after TBF_LOAD_GUARD_THRSHLD RLCblock periods. With TBF_LOAD_GUARD_THRSHLD parameter’s default value,PCU1 does periodic reallocation check for an MS once in second.

For example, if there are heavy traffic and an MS get transmission turns not so often,time between periodic reallocation checks for the MS in PCU2 is longer. A certainamount of data blocks are transmitted before PCU2 triggers periodic reallocationcheck.

If the result of checking is that reallocation is needed then the CHM requests for areallocation from MAC. It can happen that there are several simultaneous reasons forreallocation. The CHM should take care that when it has requested a reallocation for

a TBF, it will not anymore request reallocations for the same TBF.

Selection algorithm for BTS reallocation is quite similar to the case of BTS initialselection but more information is available: Rx-level measurement data is normallyavailable as well as MS RAC information. The same algorithm is used for both uplinkand downlink reallocation.

The mode of the TBF is not changed during reallocation. It means that EGPRS TBFcannot be reallocated to GPRS BTS.

GPRS TBF is reallocated primarily to GPRS BTS. If there is not suitable GPRS BTSthen EGPRS BTS can be used. When better acceptable BTS is not found, the TBF is

not reallocated.





Concurrent TBF means that the MS has uplink TBF and downlink TBF. Both TBFs areof same mode, either EGPRS or GPRS.

The following figure shows the block diagram of TBF reallocation process:

Reason forreallocation?

other

Select from BTS_LIST_1 the BTSs forwhom(RX-level - non_bcch_layer_offset) isbigger than GPRS_non_BCCH_ layer_rxlev_upper_limitand save them in BTS_LIST_2

RX-level ?

RX-level isknown RX-level is notknown

Select fromBTS_LIST_1 the BTSswhosenon_bcch_layer_offsetis less than or equal tothe value of current BTSand save them inBTS_LIST_2

UL signal level is too low

Select from BTS_LIST_1the BTSs whosenon_bcch_layer_offset islower than the value ofcurrent BTSand save them inBTS_LIST_2

START

Select BTSs whose frequency band is included in theMS RAC band information and save them inBTS_LIST_1 Note1, Note2, Note3 for UL andconcurrent TBF, Note4 for DL and concurrent TBF

Note1: If MS RAC band is not known thenBCCH band BTSs are selected Note2: BTSs that don’t have PSW territoryor channels for PSW are not selected.Note3: BTSs whose average TBF/TSL is notless than MaximumNumberOfULTBF are notselected (special case: current BTS)Note4: BTSs whose average TBF/TSL is notless than MaximumNumberOfDLTBF are notselected (special case: current BTS)

BTS_LIST_2empty ?

Yes

No

Select the BTS that isalready serving the TBF

READY

Select the BTS who has thelowest QoS load among theBTSs in the BTS_LIST_2

READY

TBF mode ?EGPRS TBF

Is there anyGPRS BTS in theBTS_LIST_2?

No

Yes

GPRS TBF

RemoveEGPRS BTSsfrom BTS_LIST_2

RemoveGPRS BTSsfrom BTS_LIST_2

Is there anyEGPRS BTS in theBTS_LIST_2 ?

Yes

No

(UL or concurrent TBF)

Figure 46 TBF reallocation process

BTS Load Reallocation

The load checking is based on QoS load. The BTS, TSL and TBF QoS load is

described below:

• BTS_QoS_load: Average QoS load in the BTS.





PSforallocatedtimeslotssBTS'of number

timeslotallsBTS'of adTSL_QoS_lo∑

• TSL_QoS_load: Sum of TBF_QoS_load of TSL’s all TBF

• TBF_QoS_load: Calculated value for load that TBF creates on a TSL. Thecalculated value is weighted with QoS class of the TBF.

There are three load checks:

1. BTS QoS load is too high when compared to other BTS

The target is to balance BTS_QoS_load between BTSs.

For GPRS TBF: if there is a GPRS BTS with 30% lower QoS load and withsuitable MS RAC band and with proper signal levels then CHM requests for areallocation from MAC (or a concurrent reallocation if a concurrent TBF exist).

For EGPRS TBF: if there is an EGPRS BTS with 30% lower QoS load andwith suitable MS RAC band and with proper signal levels then CHM requestsfor a reallocation from MAC (or a concurrent reallocation if a concurrent RATexist).

2. GPRS TBF in EGPRS territory

This check is done for GPRS TBF in EGPRS BTS. The target is to reallocate a

GPRS TBF away from EGPRS territory.

If there is GPRS BTS with proper UL/DL signal levels and the averageTBF/TSL of the GPRS BTS is less than maximum_number_of_UL_TBF / maximum_number_of_DL_TBF then CHM requests for a reallocation fromMAC (or a concurrent reallocation if a concurrent TBF exist).

3. BTS timeslot load too high when compared to BTS load

The target is to balance TSL_QoS_load inside the BTS.

If BTS_QoS_load / (average QoS load of timeslots where the TBF is

allocated) is less than 0.7, then the CHM requests reallocation from the MAC.

6.2.2.1 Uplink Rx Lev ReallocationThe TBF uplink Rx-lev Reallocation check is triggered always when uplink block withsignal level value is received. This is done for uplink TBFs and concurrent TBFs. If theaverage uplink value gets too low:

Uplink_Lev < BTS's GPRS_non_BCCH_layer_rxlev_lower_limit

and the segment has ms_supported bands (as indicated in RAC) with lowernon_bcch_layer_offset values than the BTS of the current allocation, then CHMrequests for a reallocation from MAC (or a concurrent reallocation if a concurrent TBFexist).

Target is to reallocate TBF to BTS with lower non_bcch_layer_offset value.





6.2.2.2 Downlink Rx Lev ReallocationThe TBF Rx-lev Reallocation check is triggered always when Rx_lev value isreceived. This is done for downlink TBFs and concurrent TBFs. If RX_Lev(BCCH) istoo low:

RX_Lev(BCCH) - BTS's non_bcch_layer_offset < BTS'sGPRS_non_BCCH_layer_rxlev_lower_limit

and the segment has ms_supported bands with lower non_bcch_layer_offset valuesthan the BTS of the current allocation, then CHM requests for a reallocation fromMAC (or a concurrent reallocation if a concurrent TBF exist).

The target is to find BTS with:

RX_Lev(BCCH) - BTS's non_bcch_layer_offset > BTS'sGPRS_non_BCCH_layer_rxlev_upper_limit

The next figure can help to understand the functionality of Rx Lev dependent TBFreallocation.

BTS 1

BTS 2

-48

Time

Segment 1NBL (Offset). Can be used for between Bands

GRPSNonBCCHlayerRxlevUpperLimit = -48

GRPSNonBCCHlayerRxlevLowerLimit = -70



BTS 1

BTS 2

-48

Time

Segment 1NBL (Offset). Can be used for between Bands





Figure 47 Level based TBF reallocation

6.2.2.3 Downlink RX Lev Received First Time ReallocationWhen RX_Lev of a TBF had not been defined (its value is 0xFF) and a value isreceived for the first time, CHM checks if the TBF should be reallocated to BTS ofanother band.

If received RX_Lev allows reallocation into a different ms_supported band and thatBTS has 30% lower load than the BTS currently used by the mobile.

CHM requests reallocation from MAC. The purpose of this is to minimize the loss dueto not being able to allocate directly into e.g. 1800 band by doing a reallocation assoon as possible.

6.2.2.4 BTS Selection in PCU2In PCU1, BTS selection is made in a way that GPRS MSs are primarily allocated toGPRS BTS and EGPRS MSs to EGPRS BTSs.





PCU2 has solution which selects the BTS that provides best calculated capacity forthe MS. The calculation is done by using throughput-factor parameters, the amount ofchannels and the usage of the channels. There can be situation, where the selectedBTS is GPRS BTS (although the MS is EDGE capable). In that case TBF will be

GPRS TBF to the end of the TBF. So the TBF cannot be changed to EGPRS TBFbefore the TBF has ended.

PCU1 solution is done to avoid multiplexing, but in PCU2 multiplexing is notconsidered as such problem since USF Granularity 4.

6.2.2.5 Territory Upgrade Request in PCU2Moreover, if there are both GPRS and EGPRS TBFs multiplexed in same TSL in aterritory, PCU1 triggers territory upgrade request when 1TBF/TSL is exceeded.

PCU2 uses normal 1.5 TBF/TSL triggering. PCU2 has not lower territory upgradetrigger for multiplexing situation, because multiplexing is not considered as such

problem in PCU2 since USF Granularity 4.





6.3 Channel Scheduling

In the GPRS Rel1 the scheduling was done by giving equal amount of air time foreach TBF sharing the same TSL. This way the TBFs on the same TSL would share

the capacity of the channel equally. In the scheduling in GPRS Rel2 priority is takeninto account. Thus, higher priority TBFs will have a bigger share of the shared TSLscompared to lower priority TBFs.

6.3.1 Priority based Quality of Service

With the GPRS Rel1 all the users have the same priority. This means that theyexperience the same level of service. They use the same resources equally. This isthe result of the scheduling algorithm in the PCU. The PCU scheduling algorithm,Priority Based Scheduling, is used with S10.5. Priority Based Scheduling isintroduced as a first step towards QoS defined by 3GPP. With the Priority BasedScheduling in BSC the operator can assign different priorities to he users. The PCU

scheduling algorithm will make use of the priority information in the schedulingprocess. The service experienced (QoE) by high priority users and low priority usersare different from each other.

QoS is actually associated with the PDP context. Every subscriber has a QoS profilein the operator’s HLR. The subscriber promised or perceived quality is a combinationof the different attributes defined by the 3GPP. Below is the table showing the QoSattributes in GPRS Release 97/98 and the correspondence to GPRS Release 99. Inthis document we use the R99 attributes.

Figure 48 QoS mapping

An operator may support some combinations of those factors. During the PDP contextactivation the Network and the MS negotiate the QoS. The MS may request certainvalues for each attribute. Network checks the resource situation and the subscriber

QoS profile in the HLR. Eventually the Network sends the QoS to be used to the MS.Later on if the SGSN decides to change the QoS of an MS, a PDP Context





Modification message is sent to the MS, informing the new QoS. If the MS does notaccept the new QoS it can deactivate the PDP context.

The RLC/MAC layer supports four Radio Priority levels and an additional level for

signaling messages. Upon uplink access the MS can indicate one of the four prioritylevels, and whether the cause for the uplink access is user data or signaling messagetransmission. Depending on the QoS agreed with the SGSN the MS will requestcertain Radio Priority in accessing the network. Also the radio priority level to be usedfor user data transmission shall be determined by the SGSN based on the negotiatedQoS profile and shall be delivered to the MS during the PDP Context Activation andPDP Context Modification procedures.

In the UL the MS uses the Radio Priority information in accessing the network. This isa part of the 3GPP QoS description as mentioned above. The 4 Radio Priority will bemapped to 4 UL scheduling priorities in PCU: Gold, Silver, Bronze and Best Effort.The MS will indicate the network, which Radio Priority it requires and the PCU will

take it into account while scheduling on UL TSLs for that UL TBF.

In the DL the allocation/retention priority in the PDP context profile is used. They willbe mapped to 3 scheduling priorities: Gold, Silver and Best Effort. The PCU will takethis information into account while scheduling the DL data. The allocation/retentionpriority values high, normal, low priorities are mapped to Gold, Silver, Best EffortPriority classes respectively.

In both UL and DL higher priority users will be given better service because the PCUwill schedule their transmission more often thus they will be given chance to use theradio interface more often than lower priority subscribers. Lower priority subscriberswill not experience more blocking than before, meaning that no GPRS call will be

rejected due to QoS, but they will experience worse service. Therefore new prioritybased scheduling does not affect the number of subscribers served as compared tothe Nokia GPRS Rel1.

6.3.2 Channel Allocation

QoS is also taken into account during the channel allocation. Previously in S9, thechannel allocation used plainly chose the best combination of TSL for the datacapacity. The new algorithm tries to find channel combination, which will also providethe best QoS for the TBF. The algorithm, tries to distribute the high priority TBFsevenly equal to the available channels. The reason is that high priority users will bescheduled more often because they are given higher promise to use the radio

resources. If they are collected onto the same TSLs they limit each other.

Here comes a new concept called the QoS capacity of the channel. The QoS capacitywill be used instead of the actual capacity in the allocation decisions. QoS capacitywill be calculated, taking all the available channels into account. The QoS capacity ofall the possible combinations, which can be given to the TBF, will be calculated.Finally, configuration with the highest QoS capacity will be chosen.

The QoS capacity of a number (A) of channels is estimated as the sum of the QoScapacity estimates of all the single channels:

c(A)=∑ c(ch),, ch=1…A

The estimation of the QoS capacity of a channel is affected by the below factors:





The Scheduling Step Sizes (SSS) of the TBFs, which are on that channel. (More onthe SSS later)

Preference of channels (dedicated channels are preferred to default channels, default

channels are preferred to additional channels)

6.3.3 TBF Scheduling

The scheduling is channels independent. All the TBFs which are assigned to that TSLwait in a queue for that TLS. The current implementation of the scheduling algorithmgives every TBF a so-called latest service time, before which a TBF must be servedmeaning that it should get a turn to use the TSL. After each time a TBF uses thechannel it is given a new latest service time. This time is acquired by adding thepredefined Scheduling Step Size (SSS) to the current time. The current time is a TSLspecific virtual time .The connection with the smallest latest service time uses theradio resource at a time. Periodically the scheduling algorithm checks the queue to

find whose turn it is to use the TSL. In S9 the step sizes are the same value for everyTBF. This results in every user having the same priority because there is no way todifferentiate any TBF from the others. Every TBF equally uses the TSL.

The new algorithm in S10.5 makes use of the priorities. Different scheduling priorities(QoS classes) have different SSS values. That way different TBFs have differentlatest service times. A high priority TBF will be using a smaller SSS so it will haveearlier latest service time, every time after its service. It will wait less for its turn next.This way it will take more turns than a low priority TBF on that TSL.

SSS are operator definable. There are 4 SSS for UL and 3 SSS for DL.

For determining their turn in scheduling each TBF has the following parameters:

• SSS, by which the current time is increased each time the TBF is served.

• A TSL specific latest service time.

Also there is a virtual time in the TSL, which is showing the current time as in the S9algorithm.

Scheduling is done as follows:

• TBFs are in a queue in the TSL

• In each TSL the first TBF with the smallest latest service time is selected. Afteris it served the latest service time is increased with the SSS

• Virtual time is set equal to the smallest 'latest service time' that is found nextand scheduling continues.

• When a new TBF is added for scheduling, its latest service time is the virtualtime of the TSL.

• QoS does not affect the scheduling of the control messages; they are handledas they are handled in the S9 (there is not prioritization among user data andsignaling).

The following figure tries to visualize the functionality of Priority based QoS featurewith latest service time and SSS parameters.





1 ©NOKIA FILENAMs.PPT/ DATE/ NN

7

Queue

1 2 3 4 5 6 7 7 8 9 10 11 12

1 2 3 4 5 6 6 7 8 9 10 11

6 6 6 6 6 6 7 12 12 12 12 12

TBF1 with SSS=6

TBF2 with SSS=1

(virtual time)

52 TDMA frames= 240 ms= 12 blocks

i t it

The scheduling is done based on latest service time, one TBF at a time is served by the RTSL

...Latest service time

Latest Service Time = Current Time + Scheduling Step Size

Figure 49 Priority based scheduling based on SSS parameters

6.3.4 QoS Information Delivery

In the UL the Radio Priority Information is used to indicate the scheduling (user)priority. MS may start the UL TBF in different ways:

• If the access is one phase access on RACH, CHANNEL REQUEST is used.In the CHANNEL REQUEST message there is no space for Radio PriorityInformation thus QoS information is not available. MS cannot declare thepriority of the TBF. Therefore the priority of the TBF in this case is fixed, it isalways "best effort". Whenever there is one phase access on RACH what willhappen in the BSC is that the UL priority for that TBF will be set as best effortin the RLC/MAC layer. The scheduling will use the set SSS for that particularpriority class for the scheduling of that TBF. The priority information will bepassed to the SGSN too.

• If the access is single block access (two phase access) on RACH, moredetails about the access can be given to the network with the PACKETRESOURCE REQUEST on PACCH later. The PACKET RESOURCEREQUEST has the two bits for Radio Priority information, which is mappedinto the scheduling priority. What will happen in the BSC is that the UL priorityfor that TBF will be set in the RLC/MAC layer as indicated by the RadioPriority. RLC/MAC layer informs the scheduling of the priority of the UL TBF,so that it is taken into account during the scheduling. The scheduling will usethe set SSS for that particular priority class for the scheduling of that TBF. Thepriority information will also be forwarded to the SGSN.

• If the access is on PRACH, in case of One Phase Access and Short Access

Request, PACKET CHANNEL REQUEST is used. PACKET CHANNELREQUEST has two bits for Radio Priority information. In case of Two PhaseAccess the following PACKET RESOURCE REQUEST on PACCH again has





the Radio Priority information available. What will happen in the BSC is thatthe UL priority for that TBF will be set in the RLC/MAC layer as indicated bythe Radio Priority. RLC/MAC layers inform the scheduler of the priority of theUL TBF, so that it is taken into account during the scheduling. The scheduling

will use the set SSS for that particular priority class for the scheduling of thatTBF. The priority information will also be forwarded to the SGSN.

If the MS wants to change the priority of an existing TBF, PACKET RESOURCEREQUEST message is used. The RLC/MAC informs the new priority to the scheduler.And the scheduler starts to use the new priority.

On downlink direction every DL DataUnit from SGSN to BSC includes the QoS .Thepriority is delivered in the Allocation/Retention priority field in QoS Profile. TheAllocation/Retention priority values (high, normal, low) are mapped to threescheduling priorities (Gold, Silver, Best effort). Thus, PCU stores theAllocation/Retention priority of each LLC PDU. Priorities (QoS) are then forwarded to

the scheduler. The scheduler will schedule the blocks from this TBF according to thepriority values. The set SSS for that particular priority class will be used.

Also in the DL the PCU may receive LLC PDUs with different priority class than theone, which is currently used. The scheduler has to adjust its scheduling for that TBF.

QoS change in UL or DL affects the scheduling. Naturally it also affects the channelallocation of new TBFs. QoS change doesn’t trigger any reallocations evaluation.However, TSL load may cause reallocations when periodic reallocation occurs.

6.3.5 Nokia HLR QoS Settings

The Basic feature Quality of Services (QoS) allows different priority levels based onthe APNs configurations per user in HLR. The Interactive and Background traffic classmust be used when considering BSS10.5/SG3/PCU1. Streaming traffic class (withadmission control and guaranteed bit rates) will be available with PCU2 Release2 andEQoS combination.

Different application servers are connected to the dedicated APNs. In HLR there isdefined the QoS profile per APN and subscriber.

The QoS attributes are part of PDP context between the terminal and GGSN. Basedon the attribute values the data can be marked and directed into different queues inthe network elements and thus the packets are treated differently depending on their

QoS attributes.





Figure 50 QoS Priority Queues

Nokia HLR Parameters and Configuration:

Each user has several APNs configured in the HLR user profile. For each APN peruser, there are two main parameters related to QoS: ARP and THP.

• ARP (Allocation/Retention Priority). With this parameter, the priority of eachAPN is defined:

- ARP=1 means High Priority;

- ARP=2 means Normal Priority;

-ARP=3 means Low Priority.

The ARP information will be used by the BSS (PCU) to identify the trafficfrom priority APNs and the SSS parameters can be applied. Please referto the item “TBF Scheduling” for details.

• THP (Traffic Handling Priority).

For each APN configured for a user, there is also the indication of amapped QoS Profile. This QoS Profile contains the requirements foreach traffic class (Delivery Order, Delivery of erroneous SDUs, ResidualBER, SDU error rate etc). Another information contained in the QoSProfile is Traffic Handling Priority. To allow the usage of the QoSFeature, the THP information must have the same value of ARP. TheTHP information will be used by the SGSN and GGSN to route the trafficto one of the three priority queues. Please refer to the previous figure.





Follow examples of a Nokia user profile (left) configured in HLR and a QoS profile(right):

GPRS SUBSCRIBER DATA HANDLING COMMAND <MN_>

GPRS DATA PARAMETERS

IMSI ........................ XXXXXX103140304

SGSN ADDRESS ................ XXXXXX95035

MT-SMS VIA SGSN ............. N

CELL UPDATE INFORMATION ..... N

NETWORK ACCESS .............. BOTH

CHARGING CHARACTERISTIC .....

GPRS ROAMING PROFILE ........ N

PDP CONTEXT ID .............. 1

PDP TYPE .................... IPv4

PDP ADDRESS .................

VPLMN ALLOWED ............... Y

ALLOCATION CLASS ............ 2

QUALITY OF SERVICES PROFILE . 1

APN ......................... INTERNET.OPERATOR.COM

PDP CHARGING CHARACTERISTIC . NORM

PDP CONTEXT ID .............. 10

PDP TYPE .................... IPv4

PDP ADDRESS .................

VPLMN ALLOWED ............... N

ALLOCATION CLASS ............ 1

QUALITY OF SERVICES PROFILE . 6

APN .........................POC.OPERATOR.COM

PDP CHARGING CHARACTERISTIC . NORM

PROFILE HANDLING COMMAND <MY_>

QOS PROFILE INFORMATION:

INDEX..QOS PROFILE INDEX.................... 6

NAME...QOS PROFILE NAME.....................

POCxxx

CLASS..TRAFFIC CLASS........................ I

ORDER..DELIVERY ORDER....................... N

DELERR.DELIVERY OF ERRONEOUS SDU............ ND

SDUMAX.MAXIMUM SDU SIZE.....................

1500

DWNMAX.MAXIMUM BIT RATE FOR DOWNLINK.........16

UPMAX..MAXIMUM BIT RATE FOR UPLINK.......... 16

BER....RESIDUAL BER......................... 7

SDUERR.SDU ERROR RATIO...................... 7

DELAY..TRANSFER DELAY....................... 50

UPBR...GUARANTEED BIT RATE FOR UPLINK....... 16

DWNBR..GUARANTEED BIT RATE FOR DOWNLINK..... 16

PRIOR..TRAFFIC HANDLING PRIORITY............ 1

Figure 51 Nokia QoS HLR Settings Example

The most important HLR parameters are listed below:

Delivery order - indicates whether the UMTS bearer shall provide in-sequence SDUdelivery or not.

Residual BER - indicates the undetected BER in the delivered SDU.

SDU error rate – indicates the fraction of SDUs lost or detected as erroneous

Delivery of erroneous SDUs – whether or not error detection is needed and if the errormessages should be forwarded or not.





6.4 DL Dual Carrier

DL Dual Carrier (DLDC) allows to allocated max 10 RTSLs allocated to one TBF,therefore the maximum throughput is around 500 kbps on RLC/MAC layer in practice.

The channel allocation steps are listed below:

• BTS selectiono in single-BTS scenarios this step is omitted

• TRX selectiono TRX pair providing the best DLDC capacity is determinedo TRX providing the best Single Carrier capacity is selected

• Determination of the Rx/Tx-window sizeo the number of TSLs to be allocated to TBF(s)

• Determination of DLDC allocation candidates

o all configurations which could be assigned to MS considering currentresources availability• Selection of the highest-capacity DLDC allocation• Selection of the highest-capacity single carrier (SC) allocation• Final allocation selection

o the best one of the previously determined DLDC and SC allocations

The following flow chart shows the way how the resources are allocated for DLDCconnections:

readyready

TRX(sTRX(s)) selectionselection

Rx/Rx/TxTx windowwindowdeterminationdetermination

DLDC allocation selectionDLDC allocation selection(capacity calculation and(capacity calculation and

validity checks)validity checks)

Single Carrier allocation selectionSingle Carrier allocation selection(capacity criterion)(capacity criterion)

Final allocation selectionFinal allocation selection(SC and DC comparison)(SC and DC comparison)

startstart

BTS selectionBTS selection

needed?needed?

YesYes NoNo

BTSBTS selectionselection

(including TRX selection)(including TRX selection)

DLDC allocation candidatesDLDC allocation candidates

determinationdetermination

6.5 Flow Control on Gb





6.6.2 PCU2-E

The max Gb throughput per logical PCU (incl. both user traffic and overheads): 8Mbps (128 TSL x 64 kbps).

The number of FRBC per logical PCU is 16 FRL/NS-VC.

The capacity per FRBC: 1…31 TSL (1984 kbps).

6.6.3 Applicable for both PCU2-E / PCU2-D

The max Gb throughput can be reached with more than 1 FRBC.

Regardless of how many FRBC are created within a PCU their total rate can notexceed 32 x 64 kbps and 128 x 64 kbps for PCU2-D and PCU2-E, respectively.

Gb over FR: capacity of the transport links may limit the throughput.

Gb over IP: PCU processing capacity is the limiting factor

More information about Gb planning is available in Gb Detailed Planning Guidedocument in IMS.

6.7 Gb over IP

The increased demand for packet switched traffic transmission cost efficiency can bemet by deploying IP in the transmission network.

IP offers an alternative way to configure the subnetwork of the Gb interface:

• the subnetwork is IP-based and the physical layer is Ethernet

The introduction of IP makes it possible to build an efficient transport network for the IPbased multimedia services of the future. Both the IPv6 and IPv4 protocol versions aresupported.

IP transport can be used in parallel with FR under the same BSC and BCSU

• Within one BCSU, separate PCUs can use different transmission media

In the BSC, the capacity of the Gb interface remains the same, regardless of whether IPor FR is used as the transport technology.

6.8 (E)GPRS in DFCA

DFCA was introduced in BSS 11.5 and up to BSS 14 DFCA requires its own layer.

DFCA layer is dedicated for Circuit Switched services only, so speech is allocated toregular or BCCH layer, while (E)GPRS must be allocated to BCCH or regular layers andPS territory cannot be extended into the DFCA layer.





DFCA in S14 will support (E)GPRS on DFCA layer, so there is not any need for regularlayer anymore.





7. (E)GPRS Timeslot Data Rate

RLC/MAC timeslot data rate and the number of allocated TSLs to one user give theexact picture about (E)GPRS functionality in BSS network.

Therefore the BSS network capacity is planned by RLC/MAC data rate and territorysettings (see Chapter 8), moreover the network can be optimized by the same items,as well.

The (E)GPRS TSL data rate is depending on the following items:

• GSM network performance

• TSL Utilization

• TBF Release Delay

• BS_CV_MAX

• Link Adaptation Functionality

• Power Control (UL)

• Multiplexing

All the items above are further described in the subsections below.

7.1 GSM Network Performance

The (E)GPRS TSL data rate is characterized by signal level and C/I ratio of the GSMnetwork. The impact of both of these items is described in the following subsectionsbelow:

7.1.1 Impact of Coverage Level

The radio wave propagation formulas are the basis of coverage prediction. Thedesign provides the basis for Uplink and Downlink Budget calculations. However,unlike CS network planning, packet services can tolerate delay and throughput

variations and maximize the capacity thanks to advanced features like LA and IR.

The link budget calculation in excel format can be downloaded from the following link:


The physical layer of EGPRS is the existing GSM network. Therefore the EGPRScoverage area is depending on GSM service area. However the different codingschemes have different coverage area, as it can be seen in Figure 53.





EGPRS Coverage Relative to MCS-5 (noise limited)

0

0.5

1

1.5

2

2.5

M C S 1

M C S 2

M C S 3

M C S 4

M C S 5

M C S 6

M C S 7

M C S 8

M C S 9

R e l a t i v e r a n g

Figure 53 EGPRS Relative coverage to MCS5

The MCS-5 coverage is approx 50% of MCS-1, while MCS-8 coverage is approx 40%of MCS-5.

The normal GSM voice coverage value is somewhere between MCS1 and MCS2.

7.1.1.1 Signal Strength RequirementsSignal-to-noise levels in digitally modulated systems are commonly expressed interms of Eb/No, Es/No or C/N.

• Eb/No is the available bit energy (received power * bit duration) divided by thenoise spectral density (-174dBm/Hz).

• Es/No is the equivalent for the symbol case (1 bit = 1 symbol in GMSK, 3bits= 1 symbol in 8-PSK).

• C/N is received power divided by the total noise in the relevant RF bandwidth.

• C/N and Eb/No are linked by the spectral efficiency of the modulation scheme.For schemes with 1bit/s/Hz, Eb/No is equal to C/N. In GSM the spectralefficiency is 271kbit/s/200kHz =1.35 bit/s/Hz for GMSK modulation, assumingthe receiver noise bandwidth is matched to the channel bandwidth. Thisrepresents on offset of 1.3dB in log terms, with C/N being Eb/No + 1.3dB.

For 8-PSK, Es/No = 3*Eb/No which is 10*log(3) = 4.77 in log terms. The above canbe summarized in the Table 19.





GSMModulation

Es/No C/N

GMSK Es/No=Eb/No C/N = Eb/No +1.3dB

8-PSK Es/No = Eb/No +4.77dB

C/N = Es/No + 1.3dB = Eb/No +6.07dB

Table 19 Signal-to-noise measurement equivalence

The required Es/No is based on the required Eb/No (bit energy divided by noisespectral density) from simulation results. Typically link budgets may consider a certainmodulation and coding scheme at a certain block error rate, however it is alsopossible to calculate for a given data rate. This latter case will become more widelyused as functionality such as link adaptation and incremental redundancy will tend tomask, to some extent, the actual underlying channel performance.

7.1.1.2 Receiving EndThe receiving end contains the following items:

Sensitivity

Base station sensitivity should be checked from appropriate marketing personnelbefore each dimensioning (or other) exercise. UltraSite sensitivity is found to be a bitbetter than the previous generation's BTSs (Talk family).

Additional fast fading margin

For packet transmission, as no handover scheme is implemented, the link is based onretransmission and cell reselection. A 2 dB fast fading margin is assumed in the voicetraffic case.

Cable loss + connector and Rx antenna gain

The system sensitivity is depending on cable and connector loss, antenna gain, MHAgain if applicable, additional noise, etc.

At the BS, a 16.5 dB antenna gain is assumed. However, depending onconfigurations lower antenna gains are found (14 dB in the GSM 900 bands).Moreover, antenna gains may vary across a network.

At the MS, the PDA type of configuration is assumed to have a 3dB advantagecompared to MS near the head. Note that isotropic antenna will help in the Rxdiversity schemes as the number of scatterers is increased (increased diversity andless subject to higher signal variation as well).

Body loss

As the next generation of data terminals is assumed to be hand-held in a PDAfashion, no body loss is taken into account for (E)GPRS scenarios. This compareswith an assumed loss of 3dB for a handset held near the head.

MHA Gain

If the cable loss is that high that the signal level reaches or cross the noise floor at theinput, the SNR will not be enough to guarantee the quality of the reception. However,





the SNR without MHA will always be better if the noise floor is down enough. Thedifference between the SNR with MHA and without corresponds to the noise figure ofthe amplifier.

The usage of MHA is directly depending of the sensitivity and the noise floor at theinput of the receiver and the loss the cable or the feeder is causing.

Diversity Gain

The diversity gain is depending on the separation of receiver antennas. In case ofhorizontal separation 4 meters separation generate around 3 dB diversity gain.Transmitting End

Tx RF output peak power

• The BS Tx powers are listed below:

GSM 900 Talk family: 43dBm

GSM 1800 Talk Family: 41.5 dBm

Ultrasite: 44.5 dBm

UltraSite EDGE BTS Mini: 47 dBm

FlexiEDGE: 47 dBm

• The MS Tx powers are listed below:

GSM 850/900: 33 dBm (2W)

GSM 1800/1900: 30 dBm (1W)

Back-off for 8-PSK

Pls. Refer to chapter 2.3.

Isolator+combiner+filter

Particular attention should be given to the configurations (combiner by-passed, 2:1WBC, 4:1 WBC, RTC) as it impacts on the actual radiated power at the antenna.

Cable loss + connector and Tx antenna gain

It is same as in case of Receiving End.

UltraSite coverage for downlink MCS-5 very similar to Talk speech (within 0.5dB),while UltraSite coverage for uplink MCS-5 4dB worse than Talk speech.

7.1.1.3 Measurement ResultsThe following figure shows the impact of signal level on RLC/MAC data rate (withoutinterference):





RLC/MAC Data Rate (2 TSLs)

0

20

40

60

80

100

120

-74 -76 -78 -80 -82 -84 -86 -88 -90 -92 -94 -96 -98 -100 -102 -104

RxLev (dBm)

k b p s

RLC/MAC Data Rate (2M Download on 2 TSLs)

Figure 54 Signal level vs. RLC/MAC data rate





7.1.2 Impact of Interference Level

The C/I target values will determine the (E)GPRS coverage and it is likely thatfrequency planning will need reconsidering in order to meet the required values.

At high load levels, C/I can be degraded, however it is worth notice that if the existingGPRS traffic tends to convert to EGPRS, the higher data rates will lead to reducedTCH occupancy, and, in turn, an increase in C/I.

7.1.2.1 Simulation ResultsThe following figures show results of link-level simulations from RAS/Oulu. They dogive a good estimation of the data rates achievable with EDGE and the effect ofchannel environment and frequency hopping.

Figure 55 8-PSK TU3 non-hopping, impairments included

8-PSK modulation is sensitive to distortion in the RF hardware. So ther is tx/rximpairment because of phase noise and non-linearity. (Phase noise: in an oscillator,

rapid, short-term, random fluctuations in the phase of a wave, caused by time-domaininstabilities.)

C

kbit/s





Figure 56 8-PSK TU3 ideal frequency hopping, impairments NOT included

Observing the maximum available data rates it can be seen that MCS-9 withincremental redundancy offers the highest throughputs at all but the lowest C/Is. Aconsequence of this is that there is no hopping gain (in fact there is a small hopping‘loss’ of up to 1.5dB). This is because MCS-9 has no Forward Error Correction (FEC)on the user data and, on average; frequency hopping can actually increase BLER dueto the action of randomizing the error distribution. The same applies to MCS-7 andMCS-8, although for these the loss is closer to zero.

MCS-9 is also the MCS with the highest susceptibility to errors due to impairments, asthere is no FEC to correct any errors that may occur. As a consequence of this, it maybe more appropriate in some C/I intervals to select MCS-7 or MCS-8 which, althoughhaving slightly worse C/I in the ‘ideal’ case might perform better in the situation withimpairments.

Simulations have been performed that indicate typical data throughputs that might beachievable in practical networks.





Figure 57 Data rates – re-use 1/3 load =50%

The following simulation results show for static trials the throughput in a 3 sector sitewith 50% load and reuse 1/3. It is of interest to compare it with EDGE simulationwhere a 3/9 reuse pattern is implemented.

New C/I target values resulting coverage will be highly dependent on frequency reusefactors. On the other hand, higher reuse factors decrease the spectrum efficiency.Smaller reuse factor will limit those higher data rates on smaller coverage near theBase Station (BS) and will reduce to best effort during peak hours.





Figure 58 Data rates – re-use 3/9 load =50%

Expected real scenarios should demonstrate average data rates of nearly 3 times

GPRS data rates (roughly the increase due to higher modulation scheme).

Throughput [kbps/slot] vs reuse factor and range

0

10

2030

40

50

60

MCS8-IR

reuse 1/3

MCS8-FEC

reuse 1/3

MCS8-IR

reuse 3/9

MCS8-FEC

reuse 3/9

coding schemes combination

t h r o u

g h p u t

Whole cell

range< 2kmrange< 1km

Figure 59 Data performance v re-use and range

In case of FEC the IR is not used, while in case of IR bars the incrementalredundancy is under operation.





The following figures show the throughput from static simulations for MCS1 andMCS5. The closer to the BS, the highest is the probability to achieve the maximum

data rates. The system simulated is close to a 7/21 re-use.

Figure 60 MCS-1 performance





Figure 61 MCS-5 performance

Control channel performance is also of primary concern as it conditions the trafficchannels data rates. The following Figure shows the probability of error free receptionof control blocks, e.g., access grants. From the results, for RLC block to work properlyat BLER of 5%, indicates that reuse factors of at least 3/9 are needed. Depending onthe real layout of Base stations, higher frequency reuse might be required.

Control channel performance

0

0.2

0.4

0.6

0.8

1

1.2

Whole cell range< 2km range< 1km

Range

B L E R < 5 % 4/12

3/9

1/3

Figure 62 Control Channel performance vs. Range

In dense network environment the 1/3 reuse’s performance can be the samecompared to 3/9 and 4/12. If the cell range is bigger than 2 km, the 1/3 reuse has theworse performance compared to 3/9 and 4/12.

7.1.2.2 Spectrum Efficiency and Frequency ReuseAs it can be seen from the Figure 63 the 2/6 reuse brings the most effective spectralusage.

The figure below shows the impact of reuse on spectral efficiency.





Spectrum efficiency values with QoS criteria (IR + LA)

140

145

150

155

160

165

170

175

180

S p e c t r u m e f f i c i e n c y [ k b i t / s / k m

2 / M H z ]

Reuse 1/3 174

Reuse 2/6 177.5

Reuse 3/9 175.4

Reuse 4/12 146.3

Figure 63 Reuse vs. spectral efficiency

7.1.2.3 Measurement ResultsThe Figure 64 below shows the impact of interference on RLC/MAC data rate (thesignal level is high enough to measure the impact of C/I only).

C/I dependency (FTP Download on 2 TSLs)

0

20

40

60

80

100

120

36 34 32 30 28 26 24 22 20 18 16 15 14 13 12 11 10 9

C/I

k b p s

RLC/MAC Data Rate (2M Download 2TSLs)

Figure 64 C/I vs. RLC/MAC data rate

7.1.3 Mixture of Signal Level and Interference

The following figure shows the impact of signal level and interference:





RLC/MAC Data Rate (FTP Download on 2 TSLs)

0

20

40

60

80

100

120

-65 -70 -75 -80 -85 -90 -95 -100 -105

Signal level (dBm)

k b p s

No Interference

C/I 25 dB

C/I 20 dB

C/I 15 dB

Figure 65 Impact of signal level and interference on RLC/MAC data rate





7.2 TSL Utilization Improvement

The timeslot should be fully utilized. So the higher ratio of RLC/MAC data blockscompared to signaling on PACCH will lead to better user perception.

The TSL utilization can be optimized by

• Acknowledge Request

• Pre-emptive Transmission

7.2.1 Acknowledge Request Parameters

These parameters below are used by the RLC acknowledgement algorithm todetermine how frequently the PCU polls the mobile station having a DL / UL TBF inEGPRS mode. The PCU has a counter, which is incremented by one whenever an

RLC data block is transmitted for the first time or retransmitted pre-emptively. Thecounter is incremented by (1 + (E)GPRS_DOWNLINK_PENALTY((E)GPRS_UPLINK_PENALTY)) whenever a negatively acknowledged RLC datablock is retransmitted. The mobile station is polled when the counter exceeds thethreshold value of (E)GPRS_DOWNLINK_THRESHOLD((E)GPRS_UPLINK_PENALTY).

7.2.1.1 GPRS DL/UL Penalty and Threshold• GPRS Uplink Penalty is used in RLC to trigger an uplink acknowledge

message to the MS.

• GPRS Uplink Threshold is used in RLC to trigger an uplink acknowledge

message to the MS.

• GPRS Downlink Penalty is used in RLC to trigger a downlink acknowledge pollto the MS.

• GPRS Downlink Threshold is used in RLC to trigger a downlink acknowledgepoll to the MS.

7.2.1.2 (E)GPRS DL/UL Penalty and Threshold• EGPRS Uplink Penalty is used in RLC to trigger an uplink acknowledge

message to the MS.

• EGPRS Uplink Threshold is used in RLC to trigger an uplink acknowledgemessage to the MS.

• EGPRS Downlink Penalty is used in RLC to trigger a downlink acknowledgepoll to the MS.

• EGPRS Downlink Threshold is used in RLC to trigger a downlink acknowledgepoll to the MS.





7.2.2 PRE_EMPTIVE_TRANSMISSIO

If the pre-emptive transmission bit is set to '1' in the PACKET UPLINK ACK/NACKmessage and there are no further RLC data blocks available for transmission, the

sending side shall transmit the oldest RLC data block which is in PENDING_ACKstate.

The RLC selects RLC data blocks as specified in [04.60, 9.1.3.2 Acknowledge StateArray V(B) for EGPRS TBF Mode].

The following principle is used. See details from [04.60].

1) The oldest NACKED state block is selected (In BSN order)

2) If no NACKED state block exists then a new block is generated

3) If no NACKED state block exists and transmit window is stalled or there is notnew data then the oldest PENDING_ACK state block is selected

PRE_EMPTIVE_TRANSMISSION (1 bit field) bit informs the mobile station if it may ormay not transmit the oldest RLC data block whose corresponding element in V(B) hasthe value PENDING_ACK when the protocol is stalled or has no more RLC datablocks to transmit.

0 The mobile station shall not use pre-emptive transmission.

1 The mobile station shall use pre-emptive transmission.

7.3 TBF Release Delay Parameters (S10.5 ED)The TBF Release Delay parameters are used to avoid the unnecessary TBFestablishments and hereby provide faster data rate.

There are two modifiable parameters related to Delayed TBF feature among PRFILEparameters:

• DL_TBF_RELEASE_DELAY

• UL_TBF_RELEASE_DELAY

7.3.1 DL_TBF_RELEASE_DELAY

This parameter is used to adjust the delay in downlink TBF release (0,1-5sec, def 1s).An appropriate delay time increases the system performance, since the possiblyfollowing uplink TBF can be established faster or if the new data arrive to thePCU the transmission can be immediately resumed. When using delayed TBFfrequent releases and re-establishments of downlink TBF can be avoided.

When the MS wants to send data or upper layer signaling messages to the network, itrequests the establishment of an uplink TBF from the BSC. There are the followingmain alternatives for the TBF establishment:

• on PACCH; used when a concurrent DL TBF exists





The UL TBF establishment is faster if there is a concurrent DL TBF, thereforethe longer delay in DL TBF Release can help to have faster signaling andfinally faster data rate.

• on CCCH; used when there is no PCCCH in the cell and no concurrent DLTBF

• on PCCCH; used when a PCCCH exists in the cell and there is no concurrentDL TBF

During the delayed period the TBF is kept alive based on sending DL RLC/MACblocks (generated by dummy LLC frames) in DL TBF (Polling the mobile, at least onetime every 360 ms).

In the delayed period, a DL dummy block with S/P = 1 is sent in order to poll the MS.There can be lot of “TBF lost due to no response from MS”, because it seems that

some mobiles are not supporting the transmission of dummy blocks in the delayedperiod very well, in the sense that some MSs do not respond to the dummy block withS/P set to 1. Probably, this situation is even more critical when the C/I conditions arebad and the MS has some problems in decoding USF.

7.3.2 DL_TBF_RELEASE_DELAY in PCU2

Delayed downlink TBF polling rate is different for PCU1 and PCU2.

In PCU2, POLLING_INTERVAL_BG defines the time in block periods how often theMS is polled during delayed downlink TBF release.

In PCU1 the time is not adjustable by any parameter.

PCU1 PCU2How often the MS ispolled during delayeddownlink TBF release.

Defined by RLC RTT. Newpoll is sent as soon as the MShas responded to previouspoll.

Typical value is 220 ms(every 11 block periods).

Defined by PRFILEparameter:POLLING_INTERVAL_BG.

Default value is 80 ms(every 4 block periods).

Note: The first poll periodmay be longer (240 -280

ms) but after that the periodis defined byPOLLING_INTERVAL_BG.

7.3.3 UL_TBF_RELEASE_DELAY

This parameter is used to adjust the delay in uplink TBF release (0,1-3sec, def 0,5s).An appropriate delay time increases the system performance, since the possiblyfollowing downlink TBF can be established faster. If more data will arrive from theupper layer during the delayed period they can not be sent within existing TBF.

This parameter is Nokia specific and is not linked to the Extended UL TBF Rel 4feature.





The DL TBF establishment obviously takes time and done in one of the followingways:

• on PACCH; used when 1.) concurrent UL TBF exists or 2.) when the timer

T3192 is running in the MS

1.) The effect of UL TBF release delay is taken into account when there is noconcurrent DL TBF for the same MS. The purpose of the delay is to speed upthe possibly following DL TBF establishment. No USF turns are scheduledduring this delay. The establishment is done with aPACKET_DOWNLINK_ASSIGNMENT or PACKET_TIMESLOT_RECONFIGURE message.

2.) When the DL TBF is released, the MS starts the timer T3192 andcontinues monitoring the PACCH of the released TBF until T3192 expires.During the timer T3192 the PCU makes the establishment of a new DL TBF by

sending a PACKET_DOWNLINK_ASSIGNMENT on the PACCH of the 'old' DLTBF.

• on CCCH; used when there is no PCCCH in the cell, no concurrent UL TBF,and T3192 is not running

• on PCCCH; used when a PCCCH exists in the cell, and there is no concurrentUL TBF and T3192 is not running

The faster DL TBF establishment can be achieved by using PACCH.

But during the release phase, the TBF is kept alive based on sending PACKET UL

ACK/NACK in UL TBF.

According to test measurement results, HTTP likes it but PoC does not like TBFRelease Delay.

7.3.4 Release of downlink Temporary Block Flow

The network initiates the release of a downlink TBF by sending an RLC data blockwith the Final Block Indicator (FBI) set to the value '1' and with a valid RRBP field.The RLC data block sent must have the highest BSN' (Block Sequence Number) ofthe downlink TBF. The network shall start timer T3191. While timer T3191 is runningthe network may retransmit the RLC data block with the FBI bit set to the value '1'.

For each retransmission the timer T3191 is restarted.

7.3.5 Release of uplink Temporary Block Flow

The mobile station initiates release of the uplink TBF by beginning the countdownprocess. When the mobile station has sent the RLC data block with CV = 0 and thereare no elements in the V(B) array set to the value Nacked, it shall start timer T3182.The mobile station shall continue to send RLC data blocks on each assigned uplinkdata block, according to the algorithm defined in sub-clause 3GPP 04.60 9.1.3.

If the network has received all RLC data blocks when it detects the end of the TBF(when CV=0), it shall send the PACKET UPLINK ACK/NACK message with the FinalAck Indicator bit set to '1', include a valid RRBP field in the RLC/MAC control blockheader and clear counter N3103.





7.4 TBF Release Delay Extended (S11 onwards)

EUTM is Rel4 feature and both MS and NW-support are required (the network usesMS RAC to distinguish EUTM support).

MS Radio Access Capability (RAC) received from SGSN or MS with Packet ResourceRequest (PRR) message (one or two-phase access).

Extended UL TBF delay is used always when supported (with and without concurrentDL TBF)

EUTM might need MML-activation and BCSU restart (ZWOA:2,899,A;)

7.4.1 TBF is Continued based on EUTM

The following figure shows the flow chart when the TBF is continued based on EUTM.

U L

T B F

e x t e n d e d

s t a t e

MS BSC / PCU

Data block with CV = 0

EUTM delay timer starts

Schedule USF turn for MS

Data block with new BSN and CV


UL dummy control block

EUTM delay timer stopped,TBF continues

PACKET UL ACK/NACK (FAI=0, Polling=NO)

Data block

UL TBF Schedule Rate Ext

U L

T B F

e x t e n d e d

s t a t e

MS BSC / PCU




Data block with new BSN and CV



EUTM delay timer stopped,TBF continues


Data block


Figure 66 TBF is Continued based on EUTM

Countdown procedure is ongoing. EUTM supporting mobile is allowed to recalculateCountdown value (CV) during procedure, if it gets more data to send. PCU noticesthis by monitoring Block Sequence Number (BSN) and CV sent by MS.

After receiving CV=0 block PCU starts UL extended state. It sends Packet Uplink

Ack/Nack message to MS with no Final Ack Indicator (FAI) on, but acknowledging allreceived blocks.





During UL extended state PCU schedules USFs for MS according adjustablescheduling rate parameter. If MS has no new data to send it sends UL dummy controlblocks on its sending turn.

When UL extended state ends, according adjustable release delay parameter, PCUsends Packet Uplink Ack/Nack message to MS with FAI on.

7.4.2 TBF is Not Continued based on EUTM

The following figure shows the flow chart when the TBF is not continued based onEUTM.

MS BSC / PCU







EUTM delay timer expiresPACKET UL ACK/NACK (FAI=1, Polling=YES)


PACKET CONTROL ACKUL TBF terminated


U L

T B F

e x t e n d e d s

t a t e




MS BSC / PCU







EUTM delay timer expiresPACKET UL ACK/NACK (FAI=1, Polling=YES)


PACKET CONTROL ACKUL TBF terminated


U L

T B F

e x t e n d e d s

t a t e




Figure 67 TBF is not continued based on EUTM

Countdown procedure is ongoing. EUTM supporting mobile is allowed to recalculateCV during procedure, if it gets more data to send. PCU notices this by monitoringBlock Sequence Number (BSN) and Countdown value (CV) sent by MS.

After receiving CV=0 block PCU starts UL extended state. It sends Packet UplinkAck/Nack message to MS with no Final Ack Indicator (FAI) on, but acknowledging allreceived blocks.

During UL extended state PCU schedules USFs for MS according adjustablescheduling rate parameter. If MS has no new data to send it sends UL dummy control

blocks on its sending turn.





When UL extended state ends, according adjustable release delay parameter, PCUsends Packet Uplink Ack/Nack message to MS with Final Ack Indicator (FAI) on.

7.4.3 EUTM in PCU2

Extended Uplink TBF Scheduling rate parameters and usage of those parameters aredifferent for PCU1 and PCU2.

In PCU1, UL_TBF_SCHED_RATE_EXT defines the next block period when a TBF inextended mode is given a transmission turn. However, a TBF in extended modecannot have better residual capacity than it would in normal mode.

In PCU2, POLLING_INTERVAL_BG defines the time in block periods that TBF in

extended state cannot have transmission time. After POLLING_INTERVAL is elapsed, TBF

is returned to scheduling and is gets a transmission turn when scheduler decides so.

PCU1 PCU2How often a USF isscheduled for theMS during theinactivity period inExtended UL TBFMode.

Defined by PRFILEparameter: UL_TBF_SCHED_R

ATE_EXT

Default value is 80ms (every 4 blockperiods).

Defined by PRFILEparameter:POLLING_INTERVAL_BG.

Default value is80 ms (every 4block periods).

7.5 BS_CV_MAX

The most important functionalities of BS_CV_MAX parameter from network planningpoint of view:

1) If the number of RLC block periods between the end of the RLC block period usedfor the last transmission of the corresponding RLC data block and the beginningof the block period containing the PACKET UPLINK ACK/NACK message is lessthan (max(BS_CV_MAX,1) – 1) (i.e., the RLC data block was recentlyretransmitted and thus can not be validly negatively acknowledged in thisparticular PACKET UPLINK ACK/NACK message), then the MS is not expectingto receive a nack for the transmitted block.

The mobile assumes that it takes at least BS_CV_MAX block period to:

-Transmit the block to the network and

-Transmit an acknowledgement message to the mobile.

2) T3200

The mobile station shall start an instance of timer T3200 following the receipt of anRLC/MAC control block whose RTI (Radio Transaction Identifier) value does notcorrespond to the RTI value of a partially received RLC/MAC control message or if





the RLC/MAC control blocks were received on different PDCHs. In non-DRX modethe duration of timer T3200 shall be four BS_CV_MAX block periods. In DRX modethe duration of timer T3200 shall be four times the DRX period (see 3GPP TS 03.64).

• On receipt of an RLC/MAC control block containing a segment of anRLC/MAC control message such that the mobile station now has thecomplete RLC/MAC control message, the mobile station shall stop thecorresponding instance of timer T3200.

• If the mobile station discards a partially received RLC/MAC controlmessage while the corresponding instance of timer T3200 is running, themobile station shall stop the corresponding instance of timer T3200.

• On expiry of an instance of timer T3200, the mobile station shall discardand ignore all segments of the corresponding partially received RLC/MACcontrol message.

• Upon successful change of PDCH allocation, the mobile station shalldiscard all partially received RLC/MAC control messages and stop thecorresponding instances of timer T3200.

• The mobile station shall discard any control message segment thatcontains an unknown TFI.

3) N3104

When the mobile station sends the first RLC/MAC block the counter N3104 shall beinitialized to 1. For each new RLC/MAC block the mobile station sends it shallincrement N3104 by 1 until the first correct PACKET UPLINK ACK/NACK message isreceived. Then N3104 shall not be further incremented. If the N3104 counter is equalto N3104_MAX and no correct PACKET UPLINK ACK/NACK message has beenreceived, the contention resolution fails and the mobile station behaves as specified in04.60 sub-clause 7.1.2.3.

N3104_MAX shall have the value:

N3104_MAX = 3 * (BS_CV_MAX + 3) * number of uplink timeslotsassigned.

4) Countdown procedure

When the mobile station nears the end of the close-ended TBF, it shall begin thecount down procedure so that it sends the last RLC data block when CV = 0 (see04.60 sub-clause 9.3.1). The mobile station and network shall then follow theappropriate procedure for release of TBF defined in 04.60 sub-clause 9.3.2.3 or sub-clause 9.3.3.3. Upon receipt of a PACKET TBF RELEASE message during a closed-end TBF, the mobile station shall follow the procedure in 04.60 sub-clause 8.1.1.4. Ifthe number of RLC data blocks granted is not sufficient to empty the mobile station's

send buffer, the mobile station shall attempt to establish a new uplink TBF for thetransmission of the outstanding LLC frames following the end of the close-ended TBF.





After a modification to this parameter it takes about 5 minutes for processes to get thenew values. After 5 minutes disable and then re-enable GPRS in those cells whereGPRS is active for the change to take effect.

Recommended values: 9

Planning: If the BS_CV_MAX parameter has too high value (e.g. 15), then the mobilemay ignore some nacks that would require retransmissions. So in some cases a blockhas to be nacked twice before the mobile is willing to make the retransmission. Thismay reduce the performance slightly.

Basically the BS_CV_MAX parameter should define the RLC round-trip delay in blockperiods.

If the BS_CV_MAX parameter is lower than the actual round-trip delay or if the mobileis not able to do accurate time stamping for the UL RLC blocks, then the mobile may

transmit needless retransmissions after processing a Packet UL ACK/NACKmessage.

On the other hand, if the BS_CV_MAX parameter is too large or if the mobile is notable to do accurate time stamping for the UL RLC blocks, then the mobile may ignoresome negative acknowledgements that were received in the Packet UL ACK/NACKmessage. This may distort the ARQ procedure slightly.

The Figure 68 below shows the impact of BS_CV_MAX parameter (NTN results:RxLev –70 dBm, C/I 15 dB, 2 TSLs).

61.5

23.0

62.7

22.7

62.6

23.7

66.2

24.7

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

kbps

6 9 11 13

BS_CV_MAX

BS_CV_MAX

RLC/MAC Data Rate (2M Download x2) RLC/MAC Data Rate (500K Upload x2)

Figure 68 Impact of BS_CV_MAX on data rate

There is slightly improvement both on DL and UL when the BS_CV_MAX value isincreased.





7.6 GPRS and EGPRS Link Adaptation

The RLC/MAC TSL data rate is depending on the 3GPP specifications (modulation,MCSs, etc.) and also Nokia implementation.

The Link Adaptation (LA) and Incremental Redundancy (IR) are specified by 3GPPbut the implementation is Nokia dependant as well.

The following subsections describe the LA for GPRS and EGPRS.

7.6.1 GPRS Link Adaptation (S11)

Currently the coding schemes CS-1 and CS-2 are supported. The BSC levelparameters coding scheme no hop (COD) and coding scheme hop (CODH) define whether the fixed CS value (CS-1/CS-2) is used or if the coding scheme ischanged dynamically according to the Link Adaptation algorithm. In unacknowledged

RLC mode CS-1 is always used regardless of the parameter values. When the LinkAdaptation algorithm is deployed, then the initial value for the CS at the beginning of aTBF is CS-2.

For synchronization purposes, the network sends at least one radio block using CS-1in the downlink direction every 360 milliseconds on every timeslot that has eitheruplink or downlink TBFs.

The Link Adaptation (LA) algorithm is used to select the optimum channel codingscheme (CS-1 or CS-2) for a particular RLC connection and it is based on detectingthe occurred RLC block errors.

Essential for the LA algorithm is the crosspoint, where the two coding schemes givethe same bit rate. In terms of block error rate (BLER) the following equation holds atthe crosspoint: 8.0 kbps * (1 - BLER_CP_CS1) = 12 kbps * (1 - BLER_CP_CS2) where:

• 8.0 kbps is the theoretical maximum bit rate for CS-1

• 12.0 kbps is the theoretical maximum bit rate for CS-2

• BLER_CP_CS1 is the block error rate at the crosspoint when CS-1 is used

• BLER_CP_CS2 is the block error rate at the crosspoint when CS-2 is used

If CS-1 is used and if BLER is less than BLER_CP_CS1, then it would beadvantageous to change to CS-2. If CS-2 is used and if BLER is larger thanBLER_CP_CS2, then it would be advantageous to change to CS-1. Since CS-1 ismore robust than CS-2, BLER_CP_CS2 is larger than BLER_CP_CS1.

The crosspoint can be determined separately for UL and DL directions as well as forfrequency hopping (FH) and non-FH cases. For this purpose the following BSC-levelparameters are used by the LA algorithm:

• UL BLER crosspoint for CS selection hop (ULBH)

• DL BLER crosspoint for CS selection hop (DLBH)

• UL BLER crosspoint for CS selection no hop (ULB)





• DL BLER crosspoint for CS selection no hop (DLB)

The given parameters correspond to the BLER_CP_CS1 (see equation above).

During transmission, two counters are updated: N_Number gives the total number ofRLC data blocks and K_Number gives the number of corrupted RLC data blocks thathave been transmitted after the last link adaptation decision.

More information is available in NED.

7.6.2 GPRS Link Adaptation with CS1-4 (PCU2)

In PCU2 the coding schemes CS-1 - CS-4 are supported. The BTS level parametersDL coding scheme in acknowledged mode (DCSA), ULcoding scheme in acknowledged mode (UCSA), DL coding scheme in unacknowledged mode (DCSU)and UL coding scheme in unacknowledged mode (UCSU) define whether the fixed

CS value (CS-1 - CS-4) is used or if the coding scheme is changed dynamicallyaccording to the Link Adaptation algorithm.

The BTS level parameter adaptive LA algorithm (ALA) defines whether the Link

Adaptation algorithm is adaptive or not. The new Link Adaptation algorithm can beused both in RLC acknowledged and in unacknowledged modes both in uplink anddownlink direction.

When the Link Adaptation algorithm is deployed, the initial values for the CS at thebeginning of a TBF can also be defined with the parameters DL coding scheme in acknowledged mode (DCSA), UL coding scheme in acknowledged mode (UCSA), DLcoding scheme in unacknowledged mode (DCSU) and UL coding scheme in

unacknowledged mode (UCSU).

The new Link Adaptation algorithm replaces the current LA algorithm in GPRS andcovers the coding schemes:

• CS-1 and CS-2 if the CS-3 and CS-4 support is not enabled in the territory

• CS-1, CS-2, CS-3 and CS-4, if the CS3 and CS-4 support is enabled in theterritory

The Link Adaptation algorithm is applied to measure the signal quality for each TBF interms of RXQUAL, which refers to received signal quality. RXQUAL describes thechannel quality with the accuracy of eight levels. It is expressed with three bits.RXQUAL is measured for each received RLC radio block being thus a more accurateestimate than the BLER, which has two levels: 0 and 1.

The PCU determines internally the average BLER separately for each coding schemeand the reported RXQUAL value. This is done separately for each segment bycollecting continuously statistics from all the connections in the correspondingterritory. The PCU can estimate the BLER if CS-1, CS-2, CS-3 or CS-4 codingschemes were deployed for this particular TBF. Moreover, based on BLER estimatesthe PCU can determine which coding scheme will give the best performance.

Link Adaptation Algorithm Used in Downlink Direction

When a new territory is created for (E)GPRS, two 2-dimensional tables are created(ACKS and NACKS) for the territory (another set of ACKS and NACKS tables are





needed for UL direction). In these tables, the first index refers to the coding schemeand the second index refers to the RXQUAL value.

In territory creation the ACKS and NACKS tables are initialized with values obtained

from the simulations. This is because the operation of the LA algorithm is initiallybased on the simulation results, whereas in case of traditional LA algorithmspredefined threshold values are used.

Separate initialization is needed for hopping and non-hopping BTSs.

During the DL data transfer the mobile station measures the signal quality (RXQUAL)from the RLC radio blocks that are successfully decoded and addressed to the mobilestation. The RXQUAL is averaged over the received RLC blocks and the averagedRXQUAL estimate is sent to the network in the Packet DL Ack/Nack messages. Therecan be eight different values for the RXQUAL. When RLC receives a valid Packet DLAck/Nack message for the DL TBF that operates in an RLC acknowledged mode, the

received bitmap is analyzed and the corresponding RLC blocks are marked asACKED, if a positive acknowledgement is received, or as NACKED, if a negativeacknowledgement is received. In this procedure, the RLC updates the ACKS andNACKS tables as follows:

• Whenever an RLC block is positively acknowledged, ACKS [CS][RXQ] =ACKS [CS][RXQ] + 1, where CS indicates the coding scheme with which thisRLC block was transmitted and RXQ refers to the RXQUAL value received inthis particular Packet DL Ack/Nack message.

• Whenever an RLC block is negatively acknowledged, NACKS [CS] [RXQ] =NACKS [CS][RXQ] + 1, where CS indicates the coding scheme with which this

RLC block was originally transmitted and RXQ refers to the RXQUAL valuereceived in this particular Packet DL Ack/Nack message.

If the value of the parameter adaptive LA algorithm (ALA) is N (disabled), the RLCdoes not update ACKS and NACKS tables but only the initial values of those tableswill be used when the LA algorithm selects the optimal CS.

To avoid the BLER estimation disturbance caused by the pending ack transmissions,the PCU updates ACKS and NACKS tables based only on those RLC blocks thathave never been transmitted as pending_ack blocks.

With this mechanism the LA algorithm can collect statistics about the actual block

error rate. Based on this statistics it is possible to select a coding scheme that gives,on the average, the highest throughput with respect to the specific channel qualityestimate.

Note that ACKS and NACKS tables contain ever-increasing figures. In the long runthe figures would overflow resulting in erroneous behavior. To solve this, both figuresare divided by 2, when the sum (ACKS [CS][RXQ] + NACKS [CS] [RXQ]) for CS andRXQ exceeds the threshold value, for instance:

• ACKS [CS][RXQ] = ACKS [CS][RXQ] / 2

• NACKS [CS][RXQ] = NACKS [CS][RXQ] / 2

Downlink Direction in RLC Acknowledged Mode





After the bitmap is processed by RLC, the LA algorithm selects the optimal codingscheme for this particular link as follows:

1. The throughput of the link is estimated for each coding scheme separately as

follows: throughput [CS] = K * ACKS [CS][RXQ] / (ACKS [CS][RXQ] +NACKS [CS][RXQ]) * RATE[CS], where: CS = CS-1, CS-2, CS-3, CS- 4, ifCS-3 and CS-4 support is enabled in the territory, otherwise CS = CS- 1, CS-2.

• K is a correction factor that takes into account the throughput reductiondue to the RLC protocol stalling

• RXQ is the RXQUAL value that was received in the newly-processedPacket DL Ack/Nack message

• RATE[4] -table contains the theoretical maximum throughput values for

the available channel coding schemes

2. The coding scheme is selected based on the highest throughput with thecondition of BLER (CS) < QC_ACK_BLER_LIMIT_T, where BLER (CS) =NACKS [CS] [RXQ] / (ACKS[CS] [RXQ] + NACKS [CS] [RXQ]). If no CSfulfills this condition, the coding scheme CS-1 is selected.

The correction factor K depends on the BLER and on the number of RLC radio blocksscheduled to the TBF within the RLC acknowledgement delay. Its value has beendetermined by simulations.

If the MS does not answer to polling, the coding number will be decreased step-by-

step.

Downlink direction in RLC unacknowledged mode

In unacknowledged mode RLC does not have to update the ACKS and NACKS tablesbut it can use the same ACKS and NACKS tables updated by the TBFs inacknowledged mode.

The coding schemes that are in an unacknowledged mode are selected by choosingthe highest CS for which BLER (CS) < QC_UNACK_BLER_LIMIT_T, where BLER(CS) = NACKS [CS] [RXQ] / (ACKS[CS] [RXQ] + NACKS [CS] [RXQ]) and RXQ is theRXQUAL estimate that is received in the Packet DL Ack/Nack message. If these

conditions are not fulfilled the coding scheme CS-1 is selected.

7.6.2.1 Link Adaptation Algorithm Used in Uplink DirectionIn UL direction the channel quality estimate can be either RXQUAL or GMSK_BEPdepending on the Abis interface. The PCU data frame used in the non-EDGE Abisinterface reports the channel quality in terms of RXQUAL, which is expressed withthree bits. In this case the only possible coding schemes are CS-1 and CS-2.Whereas the PCU master data frame used in the EDGE Abis interface reports thechannel quality in terms of GMSK_BEP, which is expressed with four bits. Thepossible coding schemes are CS-1, CS-2, CS-3 and CS-4.

When a new territory is created for (E)GPRS, two 2-dimensional tables ACKS and

NACKS are created for the territory (another set of ACKS and NACKS tables isneeded for DL direction). In these tables, the first index refers to the coding schemeand the second index refers to the RXQUAL or GMSK BEP value. In territory creation





the ACKS and NACKS tables are initialized to the values obtained from thesimulations. There can be a separate initialization for hopping and non-hopping BTSs.

In case of RXQUAL, the RLC averages the RXQUAL estimates sent by the BTS for

the correctly received RLC radio blocks. This is done for each uplink TBF.

In case of GMSK_BEP, the RLC averages the GMSK_BEP estimates sent by theBTS for both correctly and erroneously received RLC radio blocks. This is done foreach UL TBF. The GMSK_BEP estimate should also be made from the bad framesbecause the GMSK_BEP estimate for successfully received CS-4 blocks aloneapproaches zero in all radio conditions (there is no error correction in CS- 4).

During the UL data transfer the RLC can estimate the number of successfully andunsuccessfully received RLC radio blocks for BLER estimation purposes as follows(this needs to be done only in RLC acknowledged mode):

Whenever RLC receives a new RLC block successfully, ACKS [CS][RXQ] = ACKS[CS][RXQ] + 1, where CS indicates the coding scheme with which this RLC block wastransmitted and RXQ refers to the RXQUAL value is the current RXQUAL or GMSKBEP estimate for this UL TBF. Whenever RLC receives a RLC block unsuccessfully,NACKS [CS][RXQ] = NACKS [CS][RXQ] + 1, where CS indicates the coding schemewith which this RLC block was transmitted and RXQ refers to the RXQUAL value isthe current RXQUAL or GMSK BEP estimate for this UL TBF.

When RLC constructs a Packet UL Ack/Nack message for an UL TBF that operates inRLC acknowledged mode, the RLC updates the ACKS and NACKS tables as follows:

• ACKS [CS][RXQ] = ACKS [CS][RXQ] + N_acks[CS], where CS runs through the

available coding schemes and RXQ is the current RXQUAL or GMSK BEPestimate for this UL TBF (RXQUAL is derived from the averaged BER estimateand GMSK BEP is derived from the averaged BEP estimate)

• NACKS [CS][RXQ] = NACKS [CS][RXQ] + N_nacks[CS], where CS runs throughthe available coding schemes and RXQ is the current RXQUAL or GMSK BEPestimate for this UL TBF (RXQUAL is derived from the averaged BER estimateand GMSK BEP is derived from the averaged BEP estimate).

• After the ACKS and NACKS tables have been updated the counters N_acks[CS]and N_nacks[CS] are reset to zero.

As in the DL case the figures in the ACKS and NACKS tables are restricted so thatwhen the sum (ACKS [CS][RXQ] + NACKS [CS][RXQ]) for certain CS and RXQexceeds a certain threshold value, both figures are divided by 2, for instance:

• ACKS [CS][RXQ] = ACKS [CS][RXQ] / 2

• NACKS [CS][RXQ] = NACKS [CS][RXQ] / 2.

After the bitmap for the Packet UL Ack/Nack message is constructed by the RLC, theLA algorithm selects the commanded coding scheme for the UL TBF as follows:

Uplink direction in RLC acknowledged mode

1. The throughput of the link is estimated for each coding scheme separately asfollows: throughput [CS] = K * ACKS [CS][RXQ] / (ACKS [CS][RXQ] + NACKS[CS][RXQ]) * RATE [CS], where: CS = CS-1, CS-2, CS-3, CS- 4, if CS-3 and





CS-4 support is enabled in the territory, otherwise CS = CS- 1, CS-2. K is acorrection factor that takes into account the throughput reduction due to theRLC protocol stalling, RXQ is the current RXQUAL or GMSK BEP estimate forthis UL TBF and RATE [4] -table contains the theoretical maximum throughput

values for the available channel coding schemes.

2. The coding scheme is selected based on the highest throughput with thecondition of BLER (CS) <QC_ACK_BLER_LIMIT_T, where BLER (CS) =NACKS [CS] [RXQ] / (ACKS [CS] [RXQ] + NACKS [CS] [RXQ]). If no CSfulfills this condition, the coding scheme CS-1 is selected. The samecorrection factor table K can be used as in the DL case.

Uplink direction in RLC unacknowledged mode

In unacknowledged mode the RLC message does not have to update the ACKS andNACKS tables but it can use the same ACKS and NACKS tables that are updated by

the TBFs in acknowledged mode. The coding schemes are selected inunacknowledged mode as follows:

The coding schemes that are in an unacknowledged mode are selected by choosingthe highest CS for which BLER (CS) < QC_UNACK_BLER_LIMIT_T, where BLER(CS) = NACKS [CS] [RXQ] / (ACKS [CS] [RXQ] + NACKS [CS] [RXQ]) and RXQ isthe current RXQUAL or GMSK BEP estimate for this UL TBF. If these conditions arenot fulfilled for any CS the coding scheme CS-1 is selected. When an (E)GPRSterritory is removed, the corresponding ACKS and NACKS tables can be removed aswell.

The LA algorithm in PCU1 operates only in the RLC acknowledged mode. In the

RLC unacknowledged mode, PCU1 uses always CS1. The LA algorithm in PCU2operates in both in the RLC acknowledged and RLC unacknowledged modes.

The LA algorithm in PCU2 can be operated in two different modes:

• In adaptive mode (ADAPTIVE LA ALGORITHM = TRUE), the look-up tablesthat are used for RXQUAL -> BLER mapping are updated automatically basedon the statistics gathered from the TBF connections.

• In non-adaptive mode (ADAPTIVE LA ALGORITHM = FALSE), the look-uptables have constant values that have been determined by means ofsimulations.

The LA algorithm in PCU1 uses the following parameters:

• DL ADAPTATION PROBABILITY THRESHOLD (DLA)

• DL BLER CROSSPOINT FOR CS SELECTION HOP (DLBH)

• DL BLER CROSSPOINT FOR CS SELECTION NO HOP (DLB)

• UL ADAPTATION PROBABILITY THRESHOLD (ULA)

• UL BLER CROSSPOINT FOR CS SELECTION HOP (ULBH)

• UL BLER CROSSPOINT FOR CS SELECTION NO HOP (ULB)

The LA algorithm in PCU2 uses the following parameters:

• DL CODING SCHEME IN ACKNOWLEDGED MODE (DCSA)

• DL CODING SCHEME IN ACKNOWLEDGED MODE (DCSA)





• UL CODING SCHEME IN ACKNOWLEDGED MODE (UCSA)

• DL CODING SCHEME IN UNACKNOWLEDGED MODE (DCSU)

• UL CODING SCHEME IN UNACKNOWLEDGED MODE (UCSU)

• ADAPTIVE LA ALGORITHM (ALA)

7.6.3 EGPRS Link Adaptation with Incremental Redundancy

Link Adaptation (LA) means that in order to adjust to channel conditions, a particularmodulation and coding scheme combination is selected.

The increased data rate in GMSK and 8PSK modulations implies an increasedsensitivity to noise in coverage-limited areas and to interference in interference limitedcells.

The task of the LA algorithm is to select the optimal MCS for each radio conditions to

maximize RLC/MAC data rate, so the LA algorithm is used to adapt to situationswhere signal strength and/or C/I level is low and changing within time.

Link Adaptation Algorithm with Incremental Redundancy

Normally, LA adapts to path loss and shadowing but not fast fading, while IncrementalRedundancy (IR) is better suited to compensate fast fading.

The retransmission process is using IR, so the LA must take into account if IRcombining is performed at the receiver and the effect of finite IR memory, too. Itmeans that the MCS selection is not the same in case of initial transmission andretransmission.

7.6.3.1 Link Adaptation IntroductionRLC control blocks are transmitted with GPRS CS-1 coding, so the LA is not used incase of control blocks.

LA is done independently for each UL TBF and DL TBF on RLC level, but the LAalgorithm is the same for uplink and downlink direction.

LA algorithm works differently for acknowledged mode and unacknowledged mode.The details are described below:

• Downlink

o Ack: Downlink EGPRS packet transfer is controlled by RLC by usingacknowledges and retransmission. Downlink acknowledges are polledfrom MS by RLC to keep up the status of the transmitted RLC datablocks (acked/nacked) and to monitor the quality of the radio link.

o Unack: The transfer of RLC data blocks in the RLC unacknowledgedmode does not include any retransmissions, except during the releaseof a downlink TBF where the last transmitted downlink RLC data blockmay be retransmitted (max four times).

The MS sends Packet Ack/Nack messages in order to convey the

necessary other control signaling (e.g. monitoring of channel quality fordownlink transfer).

• Uplink





o Ack: The RLC requests packet re-sending in uplink transfer from MSfor the packets not received correctly. The RLC sends uplinkacknowledgements within PACKET UPLINK ACK/NACK messages toMS. The PCU sends Packet Ack/Nack messages also in order to

update the necessary other control signaling (e.g. timing advancecorrection for uplink transfers).

The PRE_EMPTIVE_TRANSMISSIO PRFILE parameter defines if theMS is allowed to send unacknowledged ‘PENDING_ACK’ RLC datablocks. To allow MS to send unacknowledged ‘PENDING_ACK’ RLCdata blocks the PRE_EMPTIVE_TRANSMISSION shall be allowed, i.e.Value “0” shall be used in the Packet Uplink Ack/Nack field.

o Unack: The transfer of RLC data blocks in the RLC unacknowledgedmode does not include any retransmissions, except during the releaseof an uplink TBF where the last transmitted uplink RLC data block may

be retransmitted.

The PCU sends Packet Ack/Nack messages in order to update thenecessary other control signaling (e.g. timing advance correction foruplink transfers).

The following figure shows the block diagram of MCS selection procedure:

Uplink averaging

PCU receives EGPRSPacket DownlinkAck/Nack message.

The BEPs from themessage are delivered

to adaptation algorithm.

PCU receivesUplink radio block

UPLINKDOWNLINK

Link Adaptation algorithm

Downlink case outputs:- MCS for initial transmission- MCS for retransmission

PCU decides to sendPacket Uplink Ack/Nackmessage.

The BEPs fromaveraging are delivered


Uplink case output:- MCS that is sent to MS in Packet

Uplink Ack/Nack message

Averaged BEPs

Figure 69 Link Adaptation in PCU





7.6.3.2 MCS SelectionThe MCS selection process is described below on block diagram level.

In DL case the MCS selection is based on EGPRS Channel Quality Report received

in EGPRS PACKET DOWNLINK ACK/NACK message sent from the MS to networkusing PACCH to indicate the status of the downlink RLC data blocks received.

In DL the MCS selection is based on using the BEP measurement data from MS(which is available there in EGPRS PACKET DOWNLINK ACK/NACK message) andit is done by RLC.

RLC uses the Channel Management (CHM) and Dynamic Abis Management (DAM)in the decision as well.

RLC / Downlink TBF

LA

MCSs

MCSselection

Selected MCS fordownlink radio block

CHM

DAM

read

write

Init MCS

Figure 70 MCS selection on DL

Downlink MCS selection is done every time when the RLC sends a RLC data block tothe MS.

The CHM hasallocated the

TSLs of one TRXto DL TBFs

START

MCS limiting by CHM

Dynamic Abis allocation by DAM

Data block and MCS selection by RLC

READY

Data block and MCS prediction by RLC

Figure 71 MCS selection for TSLs of one TRX on DL





In UL case the MCS selection is based on the respective BEP values, which arereceived within the UL PCU frames.

CHM

DAM

RLC / Uplink TBF

LA

MCS

CommandedMCS selection

read

write

Commanded MCS foruplink is sent to MS

Init MCS

MS

MCSselection

Figure 72 MCS selection on UL

So the MCS selection is based on RLC estimation but for the final decision theChannel Management and Dynamic Abis Management have to give the permission

as well.

Channel Management: Generally the CHM accepts the MCS/CS from the RLC, butduring scheduling the CHM checks if lower coding scheme must be used than theRLC has selected. Reasons for lower coding scheme:

• GPRS TBF and EGPRS TBF multiplexing

• MS synchronization

Dynamic Abis Management: The DAM allocates Abis slave channels for the TRX’sTSLs based on the MCS that the RLC/CHM has selected. If there are not enough

slave channels available, as it is required by RLC and CHM, the DAM allocates fewerslaves and informs the RLC about next lower MCS that fits on the allocated Abiscapacity.

Generally the MCS decided for initial transmission by LA algorithm is used.

Exceptions:

• If MCS would be MCS-9 or MCS-8 but the RLC could generate only one datablock (Note1) then the RLC selects MCS-6

• If MCS would be MCS-7 but the RLC could generate only one data block

(Note1) then the RLC selects MCS-5

• The CHM or the DAM has required lower MCS. If the RLC asked 8PSK MCSbut the returned MCS is MCS-4 then the RLC decreases it to MCS-3





• Operator defined initial MCS is used at the beginning of TBF

• Operator defined initial MCS is used after TBF reallocation to other BTS in theSEG

Note1: The RLC can generate only one data block if there is no RLC data block to beused as the second block. This can happen if the next RLC data block to betransmitted has a status of NACKED or PENDING and cannot be retransmitted withthe MCS selected for the first block.

7.6.3.3 Bit Error ProbabilityThe LA algorithm is mainly based on Bit Error Probability (BEP), because the RLCselects MCS according to the BEP values. In GSM specification, there is a full supportfor BEP based LA algorithm.

The BEP is measured at the receiver (both for UL and DL) before the decoding. The

receiver has to convert each symbol into bit(s) and during this process it estimates thebit error probability, which is the BEP.

The BEP is a decision, which includes information about the reliability of the decision(i.e. how sure the receiver is that the received bit is decided correctly) - BEP can becalculated from that certainty information.

BEP is invariant of the used coding scheme, but it depends on the modulation though.Both in ack and unack mode the BEP is used to estimate the BLER for each MCS,but BEP does not take BLER into account (ACK/NACK information).

The rules of BEP measurements and calculations are described in the following three

points:

• Decoding L1 data and converting in RLC

o The BEP values are based on the received signal quality and BTSreports the measurement data to the PCU in the Abis L1 frame(MEAN_BEP, VAR_BEP). The measurement element is one burst.

o Before the reported values can be used for averaging the RLCconverts MEAN_BEP to MEAN_BEP_gmsk, MEAN_BEP_8psk, VAR_BEP to CV_BEP for the RLC/MAC block. The measurementelement is one RLC block (four radio bursts). The tables below show

the conversions:

VAR_BEPreceived from BTS

CV_BEP

0 0.25

1 0.75

2 1.25

3 1.75

Table 20 An incoming VAR_BEP value is converted into CV_BEP





MEAN_BEPreceived from BTS

MEAN_BEP_gmsk(if GMSK MCS used)

MEAN_BEP_8psk(if 8-PSK MCS used)

0 0.0002 0.00025

1 0.0005 0.00075

2 0.0008 0.0015

3 0.0015 0.0035

4 0.0025 0.0075

5 0.0035 0.0155

6 0.0050 0.0325

7 0.0080 0.0565

8 0.0130 0.076

9 0.0205 0.0915

10 0.0325 0.11

11 0.0515 0.13

12 0.0815 0.155

13 0.1300 0.19

14 0.2050 0.23

15 0.2900 0.275

Table 21 An incoming MEAN_BEP value is converted for GMSK or 8-PSK depending on MCS used

• Averaging of the decoded L1 data

o The PCU averages the quality parameters of the block individually foreach MS per TSL and per modulation type (Mean_BEP_TNn,CV_BEP_TNn) (05.08, 10.2.3). The information element is theRLC/MAC blocks between two Ac/Nack messages.

The PCU averages the quality parameters of the block individually perTBF and per modulation type as follows [05.08]:

R is calculated for every block period. BEP values are calculated forblock periods carrying block for the TBF.

For block periods carrying block for the TBF the R and BEP values ofmodulation of received packet are calculated as follows:





eRe)(1R 1nn +⋅−=−

nblock,

n

1n

n

n MEAN_BEPR

eNMEAN_BEP_T)

R

e(1NMEAN_BEP_T ⋅+⋅−=

−

nblock,

n

1n

n

n CV_BEPR

eCV_BEP_TN)

R

e(1CV_BEP_TN ⋅+⋅−=

−

and for the other modulation the R value is calculated as follows:

1nn Re)(1R−

⋅−=

Where: n is the iteration index, incremented per each uplink radio block for TBF.

Value from DX 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

BEP_PERIOD Reserved 25 20 15 12 10 7 5 4 3 2 1e - 0.08 0.1 0.15 0.2 0.25 0.3 0.4 0.5 0.65 0.8 1

When an R-value reduces under a limit, BEP values are not used in Link

Adaptation algorithm for that modulation (instead conversion table isused, see table 8). Limit is based on BEP_PERIOD as follows:

Value from DX 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0BEP_PERIOD Reserved 25 20 15 12 10 7 5 4 3 2 1

- 4.343885e-1

3.486784e-1

1.968744e-1

1.073742e-1

5.631351e-2

2.824752e-2

6.046618e-3

9.765625e-04

2.75855e-5

1.024e-7

0

Table values are calculated from equation: n

n e)(1R −=

Where: n is set to 101

• BEP value is calculating from the averaged data

o If GMSK MCS was used then new GMSK_MEAN_BEP andGMSK_CV_BEP are defined from the averaged values using the tablein [05.08, 8.2.5]. These values are used in the BEP matrix tables (seechapter 0).

1 Note! Currently n value means number of block periods carrying data blocks after which BEP values are ignored inLA calculation.





Log10(MEAN_BEP_TN) GMSK_MEAN_BEP

-0.6 < log 0

-0.7 < log <= -0.6 1

-0.8 < log <= -0.7 2

-0.9 < log <= -0.8 3

-1.0 < log <= -0.9 4

-1.1 < log <= -1.0 5

-1.2 < log <= -1.1 6

-1.3 < log <= -1.2 7

-1.4 < log <= -1.3 8

-1.5 < log <= -1.4 9

-1.6 < log <= -1.5 10

-1.7 < log <= -1.6 11

-1.8 < log <= -1.7 12

-1.9 < log <= -1.8 13

-2.0 < log <= -1.9 14

-2.1 < log <= -2.0 15

-2.2 < log <= -2.1 16

-2.3 < log <= -2.2 17

-2.4 < log <= -2.3 18

-2.5 < log <= -2.4 19

-2.6 < log <= -2.5 20

-2.7 < log <= -2.6 21

-2.8 < log <= -2.7 22

-2.9 < log <= -2.8 23

-2.0 < log <= -2.9 24

-3.1 < log <= -3.0 25





-3.2 < log <= -3.1 26

-3.3 < log <= -3.2 27

-3.4 < log <= -3.3 28

-3.5 < log <= -3.4 29

-3.6 < log <= -3.5 30

log <= -3.6 31

Table 22 GMSK_MEAN_BEP [05.08]

o If 8-PSK MCS was used then new 8PSK _MEAN_BEP and 8PSK _CV_BEP are defined from the averaged values using the table in

[05.08, 8.2.5]

Log10(MEAN_BEP_TN) 8-PSK _MEAN_BEP

-0.6 < log 0

-0.64 < log <= -0.60 1

-0.68 < log <= -0.64 2

-0.72 < log <= -0.68 3

-0.76 < log <= -0.72 4

-0.80 < log <= -0.76 5

-0.84 < log <= -0.80 6

-0.88 < log <= -0.84 7

-0.92 < log <= -0.88 8

-0.96 < log <= -0.92 9

-1.00 < log <= -0.96 10

-1.04 < log <= -1.00 11

-1.08 < log <= -1.04 12

-1.12 < log <= -1.08 13

-1.16 < log <= -1.12 14

-1.20 < log <= -1.16 15

-1.36 < log <= -1.20 16





-1.52 < log <= -1.36 17

-1.68 < log <= -1.52 18

-1.84 < log <= -1.68 19

-2.00 < log <= -1.84 20

-2.16 < log <= -2.00 21

-2.32 < log <= -2.16 22

-2.48 < log <= -2.32 23

-2.64 < log <= -2.48 24

-2.80 < log <= -2.64 25

-2.96 < log <= -2.80 26

-3.12 < log <= -2.96 27

-3.28 < log <= -3.12 28

-3.44 < log <= -3.28 29

-3.6 < log <= -3.44 30

log <= -3.6 31

Table 23 8-PSK_MEANBEP [05.08]

CV_BEP_TN 8-PSK/GMSK CV_BEP

1.75 < cv <= 2.00 0

1.50 < cv <= 1.75 1

1.25 < cv <= 1.50 2

1.00 < cv <= 1.25 3

0.75 < cv <= 1.00 4

0.50 < cv <= 0.75 5

0.25 < cv <= 0.50 6

0.00 < cv <= 0.25 7

Table 24 CV_BEP [05.08]





Usage of BEP on DL

BEP measurements are initiated to MS in downlink using IMMEDIATEASSIGNMENT, PACKET_TIMESLOT_RECONFIGURE or PACKET DOWNLINK

ASSIGNMENT messages when TBF is created.

Operator setting for Initial MCS is used until first BEPs measured by MS are receivedin EGPRS Packet Downlink Ack/Nack message.

Input parameters for downlink link adaptation algorithm are the BEP values in theEGPRS Packet Downlink Ack/Nack message (GMSK_MEAN_BEP, 8-PSK_MEAN_BEP, GMSK_CV_BEP, 8-PSK_CV_BEP).

Downlink Link Adaptation algorithm produces two MCS values, a MCS for initialtransmission and a MCS for retransmission.

If no BEPs have arrived during the entire TBF, the MCS from parameter initial MCS isused.

Usage of BEP on UL

When uplink TBF is created PACKET UPLINK ASSIGNMENT orPACKET_TIMESLOT_RECONFIGURE is used to set TBF properties.

• EGPRS Channel Coding Command, operator setting for initial MCS is used

• RESEGMENT, always 0 = Retransmitted RLC data blocks shall not be re-segmented (IR)

Operator setting for Initial MCS is used until the first Packet Uplink Ack/Nack is sentafter the first uplink measurement has become available.

Input parameters for uplink link adaptation algorithm are the BEP values fromaveraging as follows: GMSK_MEAN_BEP, 8-PSK_MEAN_BEP, GMSK_CV_BEP, 8-PSK_CV_BEP.

The RLC activates Link adaptation for uplink TBF when the RLC decides to send ackto the MS (no polling on UL).

Uplink Link Adaptation algorithm produces one MCS value that is sent to MS in the

Packet Uplink Ack/Nack message.

7.6.3.4 Link Adaptation ProcedureIf the operator has disabled EGPRS link adaptation then the LA algorithm does notchange the output MCS values. LA is controlled with EGPRS Link adaptation enabled parameter that has three values:

0 = EGPRS link adaptation is disabled

1 = EGPRS link adaptation is enabled for RLC acknowledged mode

2 = EGPRS link adaptation is enabled for both RLC acknowledged andRLC unacknowledged modes





If the operator setting for Initial MCS is bigger than max_MCS then Initial MCS isreplaced with max_MCS (parameter in DX 200, BSC non directly modifiable).

In the Figure 73 below the LA algorithm flowchart in PCU is shown.

The BEPs from theEGPRS PacketDownlink Ack/Nackmessage are delivered


UPLINKDOWNLINK

Adaptation algorithm

RLCmode?Define MCS candidate Abasing on BLER limits *)

Define MCS candidate Busing optimal MCS method *)

Define MCS

basing onBLER limits *)

unackack

Select the smaller of the candidates A and B

Downlink case outputs:- MCS for initial transmission- MCS for retransmission

Uplink case output:- MCS for initial transmission

*) when defining uplink MCSthe output of these phases isa GMSK MCS if the MS is not8-PSK capable in uplink

Handle missing modulation data

Add user defined mean_bep_offsets

Downlink only:Define retransmission MCS

Downlink only:If MS IR memory full then restrict MCSs

READY

START

The BEPs from Uplinkaveraging are deliveredto adaptation algorithm.

For CX3.2 only:Change MCS8/9 to MCS7

Figure 73 Flowchart of link adaptation algorithm





MCS Selection with BEP Matrix Tables

MCS selection can be divided in four classes:

1. Initial MCS to be used when entering the packet transfer mode

2. Modulation selection

3. MCS selection for initial transmissions of each RLC block in ACK mode

4. MCS to be used for retransmissions

Remember that, the algorithm is activated on downlink whenever a measurementreport from MS is received. The algorithm is activated on uplink whenever the channelcoding command is to be transmitted from network to the MS.

The LA procedure is based on static MCS selection tables in the PCU.

1. Initial MCS to be used when entering the packet transfer mode.

The initial MCS selection is set by means of the following BTS level parameters:

InitMcsAckMode set by default to the highest value (=9 which correspond to MCS9)

InitMcsUnackMode set by default to value 6 (MCS=6)

In reliability class 3 (RLC/MAC acknowledged mode and LLC not acknowledged) wecan set the initial MCS via initMcsAckMode to be used on first transmission beforethe MS start measuring the air interface and reporting to the network via ACK/NACK

messages. Once the information is exchanged to the network then LA algorithm willselect the proper MCS using so called look-up tables whose values is hard-coded andwhose entries consist of mean BEP levels and CV BEP level.

2. Modulation selection

Even before the real coding scheme selection, the modulation needs to be selected.

Modulation selection is based on 8-PSK MEAN_BEP, 8-PSK CV_BEP andGMSK_MEAN BEP according to the table below (Table 25).

If MS does not support 8-PSK in the uplink, GMSK shall be chosen in the uplinkalgorithm.





8PSK CV_BEP-class

8PSKMEAN_BEP-class

1 2 3 4 5 6 7

0 4 4 4 4 4 4 41 6 6 6 6 6 5 52 9 9 9 9 9 7 63 – – – 21 12 11 84 – – – – 20 13 125 – – – – 24 21 21

6 – 31 – – – – – – –

Table 25 Modulation selection table (BEP limits for modulation selection)

The items in the table above are the 8PSK MEAN_BEP and CV_BEP values. Thetable is used as follows: the algorithm locates an entry in the table based onmeasured 8PSK MEAN_BEP and CV_BEP values. This entry is compared to themeasured GMSK MEAN_BEP value. If the measured value is larger modulationGMSK is chosen, otherwise 8PSK is chosen.

If BEP for only one modulation is reported, the other one missing, the Table 26 shallbe used to convert the MEAN_BEP value to the other modulation. The same CV_BEPvalue can be used for both modulations.

If both reports are missing, the previous ones shall be used. If no reports have arrivedduring the entire TBF, the MCS from parameter initial MCS shall be used.





Reported

GMSK

MEAN_BEP

Estimation for

8-PSK

MEAN_BEP

Reported

8-PSK

MEAN_BEP

Estimation for

GMSK

MEAN_BEP

0 – 7 0 0 3

8 – 9 1 1 8

10 – 11 2 2 10

12 – 13 3 3 12

14 – 15 4 4 14

16 – 18 5 5 17

19 – 20 6 6 19

21 – 23 7 7 22

24 – 25 8 8 24

26 – 28 9 9 27

29 – 30 10 10 29

31 20 11-31 31

Table 26 Conversion from GMSK to 8-PSK and vice versa

With parameter meanBepOffsetGMSK and meanBepOffset8PSK an offset isintroduced that will affect one of the two entries (mean bit error probability level range)of the look-up table in such a way to modify the commanded MCS to be used. In thisway the modification of the offset could lead to a MCS higher or lower than the onewhich should have been commanded according to the C/I status of the air interface.

Final values is the following:

GMSK_MEAN_BEP = GMSK_MEAN_BEP + MEAN_BEP_OFFSET_GMSK;

8-PSK_MEAN_BEP = 8-PSK_MEAN_BEP + MEAN_BEP_OFFSET_8-PSK;

3. MCS selection for transmissions of each RLC block in ACK mode

Following is the optimal MCS selection.

For EGPRS, the MS shall calculate the following values for each radio block (4 burstsmeaning Burst Period) addressed to it:

MEAN_BEPblock = mean(BEP) Mean Bit Error Probability (BEP) of a radio block

CV_BEPblock = std(BEP)/mean(BEP) Coefficient of variation of the Bit Error

Probability of a radio block (a normalizedstandard deviation)





Here, mean(BEP) and std(BEP) are the mean and the standard deviation respectivelyof the measured BEP values of the four bursts in the radio block, calculated in a linearscale. The appropriate table below is consulted for MCS selection for GMSK and 8-PSK (Table 27 and Table 28).

GMSK_CV_BEP

GMSK_MEAN_BEP

0 1 2 3 4 5 6 7

0 – 3 1 1 1 1 1 1 1 1

4 2 2 1 1 1 1 1 1

5 2 2 2 1 1 1 1 1

6 2 2 2 2 2 2 1 1

7 – 9 2 2 2 2 2 2 2 2

10 – 19 3 3 3 3 3 3 3 3

20 – 31 4 4 4 4 4 4 4 4

Table 27 MCS selection for GMSK

8-PSK_CV_BEP

8-PSK_MEAN_BEP

0 1 2 3 4 5 6 7

0 – 3 5 5 5 5 5 5 5 5

4 6 5 5 5 5 5 5 5

5 6 6 5 5 5 5 5 5

6 6 6 6 5 5 5 5 5

7 6 6 6 5 5 5 5 5

8 6 6 6 6 5 5 5 5

9 6 6 6 6 6 5 5 5

10 – 16 6 6 6 6 6 6 6 6

17 – 21 7 7 7 7 7 7 7 7

22 – 25 8 8 8 8 8 8 8 8

26 – 31 9 9 9 9 9 9 9 9





Table 28 MCS selection for 8-BSK

MCS limiting for CX3.2 BTS software

The CX3.2 software does not support MCS-8 and MCS-9.

The DX 200 SW informs the PCU about maximum MCS that the RLC is allowed touse in a cell. In the case of UltraSite CX3.2 the system sets maximum MCS to MCS-7, otherwise to MCS-9. The BSC internal parameter max_MCS is used for thispurpose. The system checks the UltraSite SW level from the BTS SW package, andmakes the decision based on that.

If the LA has given bigger MCS than the max_MCS (set in DX200 not operatordefinable) then the RLC replaces the MCS with max_MCS . The RLC does it for bothinitial transmission MCS and retransmission MCS .

If the operator setting for Initial MCS is bigger than max_MCS then Initial MCS isreplaced with max_MCS .

Max_MCS parameter is not used from CX3.3.

4. MCS selection downlink for retransmissions in ACK mode

If modulation selection has selected to GMSK, GMSK will also be used forretransmissions of 8-PSK blocks by splitting the block (TBC)

For 8-PSK modulation, the table below shows the maximum MCS used forretransmissions.

CV_BEP-class

MEAN_BEP-class

0 1 2 3 4 5 6 7

0 – 3 6 6 6 6 6 6 6 64 7 7 7 7 7 7 7 7

5 – 31 9 9 9 9 9 9 9 9

Table 29 Adaptation and retransmission with re-segment bit to 0

MCS reducing for downlink transmission if MS out of memory (IR), ack mode

The MCS selected in retransmission (as well as in transmission) can also be affectedby the memory size of the MS and the fact that such size can be running out notallowing the highest MCS.

There is a PRFILE parameter that controls this function. TheMEMORY_OUT_FLAG_SUM PRFILE parameter is used to activate the MS Out ofMemory exception procedure in RLC to reduce the number of MCSs used. Allowedvalues for MEMORY_OUT_FLAG_SUM are 0 - 7. Value 0 deactivates algorithm use.

During IR operation in downlink packet transfer, MS may report MS Out of Memorycondition in EGPRS PACKET DOWNLINK ACK/NACK Message. If there has beensuch report in MEMORY_OUT_FLAG_SUM or more consecutive EGPRS PACKET

DOWNLINK ACK/NACK Message the RLC reduces the MCSs given by linkadaptation. The RLC reduces MCSs using the tables below. The reduction is doneuntil MS reports it has enough memory.





MCS from LA algorithm Reduced MCS

1 1

2 1

3 2

4 3

5 5

6 5

7 6

8 7

9 7

Table 30 MCS for initial downlink transmission (MS Out of Memory)

MCS from LA algorithm Reduced MCS

6 6

7 6

9 7

Table 31 MCS for downlink retransmission (MS Out of Memory)

Nokia implementation will select MCS3 as preferential GMSK coding scheme to beselected when downgraded from 8-PSK to GMSK.

7.6.3.5 Incremental Redundancy in EGPRSIncremental Redundancy (IR) matches the code rate to the channel conditions. TheIR algorithm use a low rate convolutional code and puncture the code to get higherrate transmissions. If the first transmission of the radio block is unsuccessful, re-transmission is done with another puncturing storing the bits previously sent with adifferent puncturing to be used later for soft combination in order to recover the datablock.

In the IR mode (available when the selected reliability class in SGSN allows RLCacknowledged mode), redundancy is increased gradually (Type II Hybrid ARQ). If thefirst transmission of radio block fails, it is retransmitted with a different puncturingscheme (P1, P2, P3 depending on the starting MCS) and soft combined with the olddata. See Figure 74 below.





Data Block

P1 P2 P3

P1 P2 P3

P1

P2

P3

Protection Level 1

1st transmission 2nd retransmission upon reception failure

Stored

Stored

No datarecovered

No datarecovered

Combination : Protection Level x 2

Combination : Protection Level x 3

Stored

Transmitter

ReceiverP1

P1 P2

One MCS

1st retransmission upon reception failure

Figure 74 Incremental redundancy processes

It should be noted that IR combining functionality is mandatory in EDGE MSs (as

specified by ETSI, being the MS the receiving side). IR is not mandatory on the BSSside, but Nokia provides such functionality also from the BTS side.

Note then that for DL data retransmission the RLC selects MCS using the same oranother in the MCS family in such a way that Incremental Redundancy is possible inthe MS.

In UL data transfer the MS is either allowed or forbidden to use resegmentation forretransmissions, that is to say depending if the BSS side is set to store and combinethe data or not. The RLC sets resegmentation always to non-active in the MS,supporting Incremental Redundancy in the BTS. Actually the RLC setsresegmentation according to EGPRS_RE_SEGMENTATION PRFILE parameter but

the parameter value is always non-active by default.

This process is quite different to GPRS operation. For GPRS, if it is not be possible tocorrect for all introduces errors, then the block is discarded. In RLC acknowledgedmode a retransmission will be requested. Should the retransmission fail, and then thereceived block will again be discarded. There is therefore no attempt to store thoseportions of the block that have been received correctly.

IR can offer significant gains in system throughput, but there are implications for thememory storage requirements in the MS/BTS, since storage of several versions of anumber of RLC blocks may be required.

The IR performance (based on Nokia simulations) is shown in Figure 75. Note thatthe throughput is affected differently depending on the coding scheme - IR couldnearly double the throughput for the higher coding schemes (MCS7-9) (especially true





at lower Es/No value corresponding to lower C/I) as retransmission helps to correcterrors in the block, as opposed to situations where redundancy is of no help.

Gain of IR vs C/I (TU3 iFH)

0

0.5

1

1.5

2

2.5

3

3.5

0 5 10 15 20 25 30

C/I [dB]

G a i n [ d B ]

Figure 75 Incremental Redundancy gain

The implication of this is that the 8-PSK schemes actually become the optimalschemes to use over practically the entire range of C/I where IR is implemented,provided that MS memory capabilities are sufficient to allow the highest MCS. (See onthis regard more about MEMORY_OUT_FLAG_SUM PRFILE parameter and itsrelation with IR in Chapter 0).

Note that the gain introduced by IR is less at higher C/I values, in a normal network

the average C/I corresponds range between 10 and 15 dB where the IR gain isaround 2.5.

Overall, the IR process can be thought of as a means of increasing the redundancycontained within the data transmission where required. The below figure illustratesthis.

original data

1/3 coded data

1st xmission

2nd xmission

3rd xmission

1st decoding attempt

2nd decoding attempt

3rd decoding attempt

r = 1/3

r = 1/2

r = 1/1

r = 1/1

r = 1/1

r = 1/1

IR: Increasing redundancy

Figure 76 IR Procedures





The example in the figure assumes MCS-4 or MCS-9 where an initial code rate of 1/1is used. Upon reception of the second transmission the code rate is now, in effect, ½.After the third transmission the code rate is 1/3. Because the retransmissions onlyoccur where needed, IR is designed to optimize the code rate to the channel

conditions.

The standards allow for a change in MCS between transmissions of the same sourcedata, and this is based on the concept of MCS families. An MCS family is basically aset of possibilities of coding a block of source data into one or more RLC blocks fortransmission over the air interface. Therefore a block that is initially sent in MCS-6may be retransmitted with MCS-9. This leads to hybrid MCSs, such as MCS–6-9 orMCS-5-7. Typically the first transmission will be with the lowest MCS and thenretransmissions will use the higher MCS.

IR is independent of LA, and to be specific IR won’t take into consideration thecondition of the network as it happens with LA. In IR there is no measurements and

averaging, the only thinks that is checked is the re-segmentation bit based on which,if LA is selected, different rules are followed in retransmission.

The re-segment field is used to select acknowledge mode to ARQI or ARQII(incremental redundancy) for UL TBF direction. NOTE that in DL the ARQII ismandatory (for MS). ETSI 04.60.

The re-segment field is determined by the network and indicated by the re-segmentbit in messages PACKET UPLINK ACK/NACK, PACKET UPLINK ASSIGNMENT orPACKET TIMESLOT RECONFIGURE

Setting the retransmission to re-segment active "1" requires MS to use an MCS within

the initial MCS family and the payload may be split (and in such a way IR notpossible).

Setting the retransmission to re-segment non-active "0" requires the MS to use MCSwithin initial family without payload split (IR possible).

The uplink ARQ II mode (incremental redundancy) decoding is done in the BTS andRLC (BSC) receives full-encoded RLC data blocks together with information of MCSused in uplink for RLC header decoding purposes.

The downlink retransmissions are done by the BTS and RLC informs the BTS onlythe data block and MCS class and puncturing scheme PS to be used (IR combining is

done in the MS). Figure 77 show how the MCSs are selected for retransmissiondepending on the re-segmentation bit (valid for the UL TBF only).





Scheme used for

initial transmi

ssion

Scheme to use for retransmissions after switching to a different MCS

MCS-9 Comm anded

MCS-8 Comm anded

MCS-7 Comm anded

MCS- 6-9

Comm

anded

MCS-6 Comm anded

MCS- 5-7

Comm

anded

MCS-5 Comm anded

MCS-4 Comm anded

MCS-3 Comm anded

MCS-2 Comm anded

MCS-1 Comm anded

MCS-9 MCS-9 MCS-6 MCS-6 MCS-6 MCS-6 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-8 MCS-8 MCS-8 MCS-6

(pad) MCS-6 (pad)

MCS-6 (pad)

MCS-3 (pad)

MCS-3 (pad)

MCS-3 (pad)

MCS-3 (pad)

MCS-3 pad)

MCS-3 (pad)

MCS-7 MCS-7 MCS-7 MCS-7 MCS-5 MCS-5 MCS-5 MCS-5 MCS-2 MCS-2 MCS-2 MCS-2 MCS-6 MCS-9 MCS-6 MCS-6 MCS-9 MCS-6 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-5 MCS-7 MCS-7 MCS-7 MCS-5 MCS-5 MCS-7 MCS-5 MCS-2 MCS-2 MCS-2 MCS-2 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-1 MCS-1 MCS-1 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1

Scheme used for

Initial transmi

ssion

Scheme to use for retransmissions after switching to a different MCS

MCS-9 Comm anded

MCS-8 Comm anded

MCS-7 Comm anded

MCS- 6-9

Comm anded

MCS-6 Comm anded

MCS- 5-7

Comm anded

MCS-5 Comm anded

MCS-4 Comm anded

MCS-3 Comm anded

MCS-2 Comm anded

MCS-1 Comm anded

MCS-9 MCS-9 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-8 MCS-8 MCS-8 MCS-6

(pad) MCS-6 (pad)

MCS-6 (pad)

MCS-6 (pad)

MCS-6 (pad)

MCS-6 (pad)

MCS-6 (pad)

MCS-6 (pad)

MCS-6 (pad)

MCS-7 MCS-7 MCS-7 MCS-7 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5 MCS-6 MCS-9 MCS-6 MCS-6 MCS-9 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-5 MCS-7 MCS-7 MCS-7 MCS-5 MCS-5 MCS-7 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1

Re - segment bit to "1" - >re - segmentation active

Re - segment bit to "0" - >re - segmentation non active

ETSI 04.60, Tables 2 and 3

ARQ Type I (No Increm. Redundancy)

ARQ Type II (Incremental Redundancy)

Figure 77 Tables for IR and adaptation behavior with the families

A re-segment bit is included within each PACKET UPLINK ACK/NACK,

PACKET UPLINK ASSIGNMENT and PACKET TIMESLOT RECONFIGUREmessages.

These messages are sent in the DL. For initial transmissions of new RLC blocks thechannel coding commanded is applied. The resegment bit is used to set the ARQmode to type I or type II (incremental redundancy) for uplink TBFs (allowing softcombining on BTS side). For retransmissions, setting the resegment bit to ‘1’ (type IARQ) requires the mobile station to use an MCS within the same family as the initialtransmission and the payload may be split (refer to table 1). For retransmissions,setting the resegment bit to ‘0’ (type II ARQ) requires the mobile station shall use anMCS within the same family as the initial transmission without splitting the payloadeven if the network has commanded it to use MCS-1, MCS-2 or MCS-3 for

subsequent RLC blocks.

NOTE: This bit is particularly useful for networks with uplink IR capability (IR possiblein BTS side) since it allows combining on retransmissions.

It should be noted that in EGPRS it is possible to retransmit a given RLC block in adifferent MCS (but within the same MCS family). This is not the case for GPRS whereit is necessary to retransmit in the original CS in which the RLC block was sent.

7.6.3.6 MCS Selection Based on BLER LimitsAt the end of decision of the MCS also the BLER limits are checked by RLC withinPCU (ack/unack mode).

There is a table per MCS that maps the pair (MEAN_BEP, CV_BEP) to BLER. TheBLER values for each MCS are searched and compared to the operator parameters





"MaxBlerAckmode " or " MaxBlerunackmode ” on whether the mode is ACKed orUNACKed. The highest MCS that satisfies the BLER limit is chosen.

The GMSK _MEAN_BEP and GMSK _CV_BEP are used with GMSK BLER tables

and 8-PSK _MEAN_BEP and 8-PSK _CV_BEP are used with 8-PSK BLER tables.

For UNACKed mode, this is the selected MCS used for all transmissions.

For ACKed mode, the minimum of this value and the value from optimal MCSselection is the selected MCS for initial transmissions of each new RLC block.

7.6.3.7 EGPRS LA in PCU2The EGPRS LA algorithm is same in both PCUs. However, PCU2 provides about 20ms shorter RLC RTT time, that mean LA in PCU2 gets response from MS faster thanin PCU1. So, when compared to PCU1, the LA in PCU2 may react faster to radiocondition changes.

PCU2 chooses initial MCS differently for sequential same direction TBF in certainsituation. PCU1 uses always initial MCS value read from user parameter for newestablished TBF. PCU2 instead uses last used MCS of previous TBF as initial MCSfor new TBF in situation when opposite direction of TBF has been active from lastTBF release to new TBF establishment (so the MS context has stayed stored inPCU2 memory), and if no BTS re-selection was done for opposite direction of TBF.





7.7 Multiplexing

The TSL data rate can be decreased by multiplexing as well.

The multiplexing has the following effects:

• Synchronization (every 18th Radio Block)

• GPRS USF on DL EGPRS TBF

• TSL sharing – more than one TBF on a TSL

7.7.1 Synchronization

3GPP requires that for synchronization purpose, the network shall ensure that eachMS with an active TBF in uplink or downlink receives at least one block transmittedwith a coding scheme and a modulation that can be decoded by that MS every 360millisecond interval (78 TDMA frames) to be used for DL power control. This functionis implemented in the CHM. Timeslot scheduling algorithm in the CHM ensures thatthere is on each timeslot on downlink at least one Radio Block at least every 360 msusing MCS-1 (EGPRS TBF) or CS-1 (GPRS TBF) coding scheme.

S11.5 onwards:

For synchronization purposes, the network sends at least one radio block every 360milliseconds using a MCS or CS low enough that all mobiles can be expected to beable to decode the block. If there are only EGPRS TBFs in the timeslot, thesynchronization block is sent using CS-1 or a low enough MCS. If there are GPRSTBFs as well, the synchronization block is sent using CS-coding.

7.7.2 Dynamic Allocation on UL

In (E)GPRS the scheduling of UL and DL resources are independent. In the UL therecan be three different allocation modes (MAC modes): fixed allocation, dynamicallocation and extended dynamic allocation.

The current Nokia implementation uses dynamic allocation to allocate resources touplink TBFs. This means that in order for the MS to use a particular timeslot foruplink, it needs to listen to the downlink part of that timeslot to decode the USF (whichtells which MS is allowed to use the uplink part of the timeslot).

So using 3 timeslots for uplink would mean that the MS should listen to the same 3timeslots for downlink. This then means that a class 12 MS (max 5 UL/DL timeslots)cannot use more than 2 timeslots for uplink, as long as dynamic allocation is used bythe network.

7.7.2.1 GPRS and EGPRS Dynamic AllocationIn Nokia system GPRS and EGPRS TBFs can be multiplexed dynamically on thesame timeslot (fixed allocation is not implemented).

When USF is addressed to GPRS TBF the downlink RLC radio block carrying the

USF must use GMSK coding scheme, that is MCS-1 to MCS-4 if the DL RLC radioblock is addressed to EGPRS TBF or CS-1 to CS-2, if the DL RLC radio block isaddressed to GPRS TBF (without PCU2).





If there are uplink GPRS TBF and downlink EGPRS TBF multiplexed on the sametimeslot then the CHM restricts the EGPRS TBF to use MCS1-4 (MCS3 in Nokiaimplementation).

NOTE: The stealing bits in the EGPRS GMSK blocks to indicate CS-4. The codingand interleaving of the USF is done as defined for CS-4. That leads to:

1. A standard GPRS mobile station is able to detect the USF in EGPRS GMSKblocks. The risk that the rest of the block will be misinterpreted as validinformation is low.

2. An EGPRS mobile station cannot differentiate CS-4 blocks and EGPRSGMSK blocks by decoding the stealing bits. However, an EGPRS mobilestation in EGPRS TBF mode needs only to decode GMSK blocks assumingeither of MCS-1 to MCS-4, in order to determine if they were aimed for it.

If fixed allocation is used, uplink blocks of the PDCH are reserved for only one mobilestation at a time. Using fixed allocation, there is no particular restriction for themultiplexing of GPRS and EGPRS mobile stations on the same PDCH.

7.7.2.2 GPRS and EGPRS Dynamic Allocation without USF4

DL TSLs (originally 4 DL 8-PSK TSLs (TSL 4-7), but now TSL 7 is GMSK modulated,because of USF is pointed to GPRS MS (request for UL transmission on TSL 7))

0 1 2 3 4 5 6 7Round 1 USF*

Round 2 USFRound 3 USF... USF... USF... …

*USF with GMSK modulation for all the USF cases in these tables

DL TSLs (originally 4 DL 8-PSK TSLs (TSL 4-7), but now TSL6 and 7 are GMSKmodulates, because of USFs is pointed to GPRS MS (request for UL transmission onTSL 6 and 7))

0 1 2 3 4 5 6 7

Round 1 USF USFRound 2 USF USFRound 3 USF USF... USF USF... USF USF... … …

7.7.2.3 GPRS and EGPRS Dynamic Allocation with USF4The Dynamic Allocation on UL with USF4 is described below:





On DL 4 TSLs are used by 8-PSK modulation (TSL 4-7), but now TSL 7 is GMSKmodulated, because of USF is pointed to GPRS MS (request for UL transmission onTSL 7))

0 1 2 3 4 5 6 7Round 1 USFRound 2Round 3...... USF... …

On DL 4 TSLs are used by 8-PSK modulation (TSL 4-7), but now TSL 7 is GMSKmodulated, because of USF is pointed to GPRS MS (request for UL transmission onTSL 6 and 7))

0 1 2 3 4 5 6 7

Round 1 USF USFRound 2Round 3...... USF USF... … …

7.7.2.4 GPRS and EGPRS Extended Dynamic Allocation with/without USF4Extended Dynamic Allocation functionality on UL is shown below:

On DL 4 TSLs are used by 8-PSK modulation (TSL 4-7), but now TSL 7 is GMSKmodulated, because of USF is pointed to GPRS MS (request for UL transmission onTSL 7))

0 1 2 3 4 5 6 7

Round 1 USFRound 2 USFRound 3 USF... USF... USF... …

On DL 4 TSLs are used by 8-PSK modulation (TSL 4-7), but now TSL 7 is GMSKmodulated, because of USF is pointed to GPRS MS (request for UL transmissionon TSL 4, 5, 6 and 7), but EDA is used)

0 1 2 3 4 5 6 7

Round 1 USFRound 2 USFRound 3 USF... USF... USF... …

*If max 2 TSLs are needed on UL for GMSK MS, Dynamic Allocation (DA) will beused with USF4.





8. (E)GPRS Territory Settings

The following subchapters describe the territory definitions and allocations betweenCSW and PSW services.

Additionally to the territory settings the rate reduction due to territory occupancy isdescribed as well.

8.1 Timeslot Allocation between Circuit Switched and (E)GPRSServices

The primary technique for dividing resources between circuit-switched (CSW) andpacket ((E)GPRS) traffic in Nokia GSM is known as the Territory Method. In this,timeslots within a cell are dynamically divided into CSW and (E)GPRS territories. Thismeans that a certain number of consecutive traffic timeslots are reserved for CSW

GSM calls with the remainder being available for (E)GPRS traffic. Dynamic variationof the territory boundary (and hence number of timeslots in each territory) is controlledby territory parameters. This enables the system to adapt to different load levels, andtraffic proportions, thus offering optimized performance under a variety of loadconditions.

Figure 78 illustrates how traffic resource within a cell (2 TRX in this case) can bedivided into CSW and (E)GPRS territories.

TRX 1

TRX 2

CCCH TS TS TS TS TS TS TS

TS TS TS TS TS TS TSTS

CircuitSwitchedTerritory

PacketSwitchedTerritory

Territory border movesDynamically based on Circuit

Switched traffic load

Default(E)GPRSCapacity

Dedicated(E)GPRSCapacity

TS TS

Additional(E)GPRSCapacity

TS TS

Figure 78 Illustration of cell territories.

8.1.1 PSW Territory

The PSW territory divided to dedicated, default and additional territories.

8.1.1.1 Dedicated (E)GPRS CapacityIt is possible to assign dedicated (E)GPRS capacity, where a number of timeslots areallocated on a permanent basis to (E)GPRS. These timeslots are always configured

for (E)GPRS and cannot be used by circuit-switched traffic. This ensures that(E)GPRS capacity is always available in a cell. The drawback with this approach isthat, for a given cell configuration, blocking levels for CSW traffic will increase sincethe number of available channels will be reduced. This change in blocking decreases





with increasing cell capacity (TRX count), and can be readily calculated using theErlang-B formula.

The decision on whether to assign dedicated (E)GPRS territory is a trade-off between

providing a minimum level of (E)GPRS service and increasing the blocking for CSWservices. This decision needs to take into account operator priorities, networkperformance and predicted (E)GPRS usage levels.

The dedicated capacity can be set anywhere between zero and the full cell capacity.

If there are lot of dedicated territory, default territory in the PCU, the DSP allocationmay not be efficiency, ending on performance decrease.

8.1.1.2 Default GPRS CapacityAnother type of (E)GPRS capacity that can be defined is default (E)GPRS capacity.The default (E)GPRS territory is an area that will always be included in the

instantaneous (E)GPRS territory provided that the current CSW traffic levels permit.With the exception of the dedicated (E)GPRS area, CSW services always take priorityover (E)GPRS services and so, if circuit switched traffic levels dictate, circuit switchedtraffic will occupy as much (E)GPRS default territory as is needed. If, havingpreviously occupied some of the (E)GPRS default territory, the CSW level decreases,these timeslots will automatically be re-allocated back to (E)GPRS irrespective of theactual (E)GPRS load.

Where circuit-switched traffic levels are falling, but outside the (E)GPRS defaultterritory, allocation to (E)GPRS will only occur if the (E)GPRS load reaches a pre-defined condition (see later).

The setting of the default (E)GPRS territory level is a trade-off between improving thelevel of service (data rate, delay) for (E)GPRS users and high use of resources.Setting a higher level of default (E)GPRS territory will tend to increase the level ofservice experienced by the (E)GPRS users. However, a higher level for the numberof default (E)GPRS territory timeslots may affect the overall (E)GPRS systemcapacity if a large number of (E)GPRS timeslots are taking up PCU connectionswithout actually carrying (E)GPRS traffic. Another issue with setting a high level fordefault (E)GPRS territory is that it will tend to increase the number of intra-cellhandovers for CSW users with the aim of keeping the (E)GPRS default territory freefor (E)GPRS. Initially, it is recommended that the default territory is set to a level justbelow the anticipated mean load level. This will probably be with a minimum of threeTCHs, however, to accommodate, where possible, 3-timeslot-capable mobiles at

maximum available data rate without having to negotiate resource allocation with theCSRRM.

8.1.1.3 Additional (E)GPRS CapacityWhere additional (E)GPRS capacity is assigned in response to load demand beyondthat given by the default capacity, this capacity is termed additional (E)GPRScapacity. The upgrade/downgrade sections describe when this capacity will be used.

8.1.2 CSW Territory

In addition to the circuit-switched traffic load, the system attempts to keep one ormore timeslots free in the CSW territory. The reason for this follows from the fact that

if the CSW territory becomes fully occupied and further CSW connections need to beaccommodated, then one or more timeslots from the (E)GPRS territory would be re-





allocated for CSW use. This re-allocation introduces a delay due to associatedsignaling requirements.

8.1.2.1 Free Timeslots

In order to avoid passing this delay onto the CSW user, the system attempts to keepa number of timeslots free (spare CSW timeslot) for such CSW allocations. Thenumber of timeslots kept free is dependent on cell size and whether a downgrade oran upgrade has last occurred. Table 32 shows the values implemented initially (S9).

The values used for ‘after downgrade’ in table 1 are based on a 95% probability that afurther downgrade would not be required while there is already a downgrade inprocess.

The values used for ‘after upgrade’ have been chosen with the aim of providing a95% probability that there will be no need for a subsequent (E)GPRS downgradewithin 4 seconds of an upgrade having occurred.

No. of TRXs Free TSLs (afterdowngrade)

Free TSLs (afterupgrade)

Mean free TSL inCSW

1 1 1 1

2 1 2 1.5

3 1 2 1.5

4 2 3 2.5

5 2 4 3

6 2 4 3

Table 32 Free timeslots retained in CSW territory (valid for GPRS rel.1)

The effect of the free timeslots is a decrease in overall cell capacity. It should benoted, however, that the free slots will be occupied when required by the circuitswitched traffic load.

Therefore, when considering overall cell (or TRX) capacity, this overhead must betaken into account.

With S10.5 ED the number of free TSLs after a downgrade or an upgrade becomeoperator modifiable parameters following the rules as explained below.

The margin of idle TCH/Fs that is required as a condition for starting a GPRS territoryupgrade is defined by the BSC parameter free TSL for CS upgrade

freeTSLsCsUpgrade . In fact, the parameter defines how many traffic channel radiotime slots have to be left free after the GPRS territory upgrade. When defining themargin, a two-dimensional table is used. In the two-dimensional table the columns arefor different amounts of available resources (TRXs) in the BTS. The rows indicate aselected time period (seconds) during which probability for an expected downgrade isno more than 5%. The operator can modify the period with the BSC parameterfreeTSLsCsUpgrade . Default value for the period length is 4 seconds.





TRXs 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

1 0 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3

2 1 1 2 2 2 3 3 3 3 4 4 4 4 5 5 5

3 1 1 2 3 3 3 4 4 4 5 5 6 6 6 6 6

4 1 2 2 3 4 4 4 5 5 6 6 6 7 7 7 7

5 1 2 3 3 4 5 5 5 6 6 7 7 7 8 8 8

6 1 2 3 4 4 5 5 6 6 7 7 8 8 8 9 9

7 1 2 3 4 5 5 6 7 7 7 8 8 9 9 9 9

8 1 3 4 4 5 6 6 7 7 7 8 9 9 9 9 9

9 1 3 4 5 5 6 7 7 8 8 9 9 9 9 9 9

10 2 3 4 5 6 7 7 8 8 8 9 9 9 9 9 9

The operator defines the margin of idle TCHs that the BSC tries to maintain free in a

BTS for the incoming circuit switched resource requests using parameter free TSLfor CS downgrade freeTSLsCsDowngrade . If the number of idle TCH resourcesin the circuit switched territory of the BTS decreases below the defined margin, aGPRS territory downgrade is started if possible. The definition of the margin involvesa two-dimensional table. One index of the table is the number of TRXs in the BTS.Another index of the table is the needed amount of idle TCHs. Actual table items arepercentage values indicating probability for TCH availability during a one-seconddowngrade operation with the selected resource criterion. Default probability 95% canbe changed through the free TSL for CS downgrade parameterfreeTSLsCsDowngrade .

TRXs 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

TCH0 94 84 76 69 63 58 54 50 48 45 43 41 40 38 37 35

1 99 98 96 93 91 87 85 82 79 77 74 72 70 68 66 64

2 100 99 99 99 98 97 96 94 93 92 90 89 87 86 84 83

3 100 99 99 99 98 98 97 97 96 95 94 94 93

4 100 99 99 99 99 99 98 98 98 97

5 100 100 99 99 99 99

6 100 100 100

7 100 100

8 100% 100% 100% 100%

9 100 100

That means that if we have 4TRXs/cell and at a certain moment we have a decreasednumber of TSLs for example the number of idle TSLs falls to 2 the associatedprobability of being free is 93%, less than the threshold (95%), that means that aGPRS downgrade will be started in such a way that the idle TSLs will be 3 where theprobability for them of being free will be higher than said threshold.

The values above are Nokia simulated values.

There’s another parameter to include when talking about territory and that’s ismaxGPRScapacity. With this parameter we limit the number of PSW channel perBTS which could be a problem especially when introducing the segment concept due

to the possibility to have a GPRS capable BTS and a EGPRS capable BTS with theirseparated territory parameters defined and that would lead to a capacity problem dueto PCU limitation.





The following figure shows the number of free TSLs in case of different parametersets.

TSL number after CS downgrade

TRX number 1 2 3 4 5

70 0 0 0 1 1

95 1 1 1 2 2

99 1 1 2 2 3

TSL number after CS upgrade

TRX number 1 2 3 4 5

1 0 1 1 1 2

4 1 2 2 3 4

7 1 2 3 4 5

10 2 3 4 5 6

free TSL for CS downgrade (%)

(CSD)

free TSL for CS upgrade (sec)

(CSU)

Figure 79 # of free TSLs with different setup

8.1.3 Territory Upgrade/Downgrade – Dynamic Variation of Timeslots

In order to facilitate dynamic variations in the CSW/(E)GPRS territories in response tochanging load conditions, mechanisms have been introduced to enableupgrades/downgrades of the (E)GPRS territory to occur.

The upgrade/downgrade procedures utilize three parameters - X1, X2 and X3. Theseparameters are not user-configurable but are set at pre-defined values that have beenidentified through detailed simulations aimed at establishing the optimum values formixed circuit-switched and (E)GPRS operation. For (E)GPRS deployment, the valuesfor these parameters are set to 1.5, 1.0 and 0.5, respectively (hard coded values in

PCU). It should be noted that some refinements might be made to functionality priorto the deployment of EGPRS services to optimize performance. The function of theabove parameters is described in the following sections.

8.1.3.1 DowngradeA (E)GPRS downgrade is requested/initiated if;

• A PSW territory timeslot is blocked or it loses synchronization.o RRM attempts to upgrade and rearrange a PSW territory to the

default configuration when timeslots in the original defaultterritory become blocked.

o If the timeslot that is carrying the synchronization master channel

is blocked, RRM removes all PSW territory timeslots of the TRX.• A TRX containing PSW territory timeslots is blocked.• More CSW resources are required and the PSW territory contains

additional or default timeslots.• CHM requests a PSW territory downgrade.

For RRM to initiate a PSW territory downgrade it is also required that the previousPSW territory operation in the BTS has been completed.

In radio cells with both GPRS and EGPRS BTSs, CHM provides RRM withinformation on whether an upcoming downgrade should preferably be carried out ona GPRS PSW territory or on an EGPRS PSW territory. CHM bases this preference

on the BTS channel loads in the radio cell; downgrade in the territory with lesschannel load is preferred.This territory balance information is sent to RRM if the following conditions are met:





• The ratio of aggregate GPRS and EGPRS BTS channel loads the lower

aggregate load divided by the higher in the radio cell is less thanTERRIT_BALANCE_THRSHLD.

• The preferred territory is not the same as that indicated in the previousterritory balance information message.

• At least TERRIT_UPD_GTIME_GPRS has elapsed since the previous territorybalance information message was sent.

RRM takes the territory balance information into account when it removes PSWtimeslots to accommodate new CSW connections.

8.1.3.2 Upgrade A (E)GPRS upgrade is requested/initiated if;

• A blocked or out-of-synch timeslot inside a default PSW territorybecomes serviceable again.

• CSW traffic situation and the operator parameter CMAX allow a PSWterritory extension, and either:

o CHM requests a PSW territory upgrade.o PSW territory has less timeslots than defined for the default

territory.

For RRM to initiate a PSW territory upgrade it is also required that the previousterritory operation in the BTS has been completed and idle GPRS capable resources

are available in the BTS.

RRM allows PSW territory upgrades if the existing CSW connections will not beunfavorably affected and a predefined amount of idle timeslots will remain in the CSWterritory as an instant reserve for new CSW connections. This margin of idle timeslotsis defined by operator parameters CSU (free TSL for CS upgrade) and CSD (free TSLfor CS downgrade). If the requirements for a PSW territory upgrade are met but aCSW connection occupies a timeslot, which is to be allocated to PSW, RRM initiatesan intra-cell handover to find a new channel allocation for the CSW connection.

Operator parameter GTUGT (GPRS territory update guard time) defines an intervalbetween successive territory upgrades. The purpose of this interval is to prevent

constant update request from channel management functions: while the timer isrunning, CHM does not send an upgrade request immediately after detecting an

upgrade need but waits until the next expiry of the timer and sends a request onlyif a territory update is still needed at that time. Also RRM observes this guard timewhen it initiates BTS territory configuration updates.

8.1.3.3 Territory Upgrade and Downgrade S10 ChangesIn S10 the segment concept has been added. Segment ID has been added toupgrade and downgrade messages. In CHM segment concept will be implementedeither by adding segment ID into BTS structure or a separate segment structure is tobe used.

In S10, the amount of channels in a territory is limited by maxGPRScapacity given inthe upgrade message. In CHM this is taken into account as follows:





• If the territory contains the maximum amount of channels, PCU will notrequest for more channels.

• When PCU requests for more channels, it will limit the number of requested

channels so that gprs_maximum_capa will not be exceeded.

If an upgrade would result in more channels than maxGPRScapacity , then PCU willreject the upgrade.

In territory upgrade in S9 implementation a response to DX 200 is sent only when theupgrade was successful. In S10 in case of a failure, psw_territory_downgrade_nack_s / psw_territory_downgrade_nack_s is sent.

In S10 a new field is added to:

psw_territory_downgrade_ack_s / psw_territory_upgrade_ack_s messages:

• Egprs / Gprs territory suggestion for next downgrade

When the CHM receives upgrade/downgrade request from the RRM the CHM countsTBF amount in GPRS territories in the segment and TBF amount in EGPRS territoriesin the segment. Then the CHM sends in ack message to RMM the territory type withsmaller TBF amount.

8.1.3.4 Multislot TSL Allocation for Using max Capability of MobilePCU1 does not take TSL amount into account in TSl allocation, if there are lesschannels available than preferred allocation requires. PCU2 does it.

For example, for multislot class 6 MSs, if 3+1 allocation is the preferred allocation andthere is only 2 TSLs available for allocation, in such situation PCU1 allocates 2+1allocation but PCU2 allocates 2+2 allocation to MS. Same analogy can be found frommultislot class 10 MSs. If 4+1 is the wanted allocation and only 3 TSLs are available,then PCU1 allocates 3+1 but PCU2 3+2.

8.2 Multislot Usage

An MS may be allocated several PDTCH/Us or PDTCH/Ds for one mobile originatedor one mobile terminated communication respectively. In this context allocation refersto the list of PDCH that may dynamically carry the PDTCHs for that specific MS. The

PACCH may be mapped onto any of the allocated PDCHs. If there are m timeslotsallocated for reception and n timeslots allocated for transmission, there shall beMin(m,n) reception and transmission timeslots with the same timeslot number.

For multislot class Type 1 MS (Type 1 MS are not required to transmit and receive atthe same time), the following table lists the number of slots that are possible toallocate (provided that it is supported by the MS according to its multislot class) fordifferent medium access modes (see 3GPP TS 05.02). It also indicates if Tra or Tta (see 3GPP TS 05.02 Annex B) shall be applied for measurements.





Medium access mode No of Slots Tra shall apply

Tta shall apply

Note

Downlink, any mode 1-6 Yes -7-8 No - 1,2

Uplink, Fixed 1-4 Yes -

5-6 - Yes 37-8 - No 1,2,3

Uplink, Dynamic 1-2 Yes -Uplink, Ext. Dynamic 1-3 Yes -

Down + up, Fixed d+u = 2-5 Yes -d+u = 6 No No 1,2

Down + up, Dynamic d+u = 2-5 Yes -Down + up, Ext. Dynamic d+u = 2-4 Yes -

d+u = 5, d > 1 Yes -

Note 1 Normal measurements are not possible (see 3GPP TS 05.08).Note 2 Normal BSIC decoding is not possible (see 3GPP TS 05.08).Note 3 Normal PACCH reception not possible (see 3GPP TS 04.60)

Table 33 Possible allocations in multislot usage

When an MS supports the use of multiple timeslots it shall belong to a multislot classas defined below:

Multislotclass

Maximum number of slots Minimum number of slots Type

Rx Tx Sum Tta Ttb Tra Trb

1 1 1 2 3 2 4 2 1

2 2 1 3 3 2 3 1 1

3 2 2 3 3 2 3 1 1

4 3 1 4 3 1 3 1 1

5 2 2 4 3 1 3 1 1

6 3 2 4 3 1 3 1 1

7 3 3 4 3 1 3 1 18 4 1 5 3 1 2 1 1

9 3 2 5 3 1 2 1 1

10 4 2 5 3 1 2 1 1

11 4 3 5 3 1 2 1 1

12 4 4 5 2 1 2 1 1

13 3 3 NA NA a) 3 a) 2

14 4 4 NA NA a) 3 a) 2

15 5 5 NA NA a) 3 a) 2

16 6 6 NA NA a) 2 a) 2

17 7 7 NA NA a) 1 0 2

18 8 8 NA NA 0 0 0 2

19 6 2 NA 3 b) 2 c) 1

20 6 3 NA 3 b) 2 c) 121 6 4 NA 3 b) 2 c) 1

22 6 4 NA 2 b) 2 c) 1

23 6 6 NA 2 b) 2 c) 1

24 8 2 NA 3 b) 2 c) 1

25 8 3 NA 3 b) 2 c) 1

26 8 4 NA 3 b) 2 c) 1

27 8 4 NA 2 b) 2 c) 1

28 8 6 NA 2 b) 2 c) 1

29 8 8 NA 2 b) 2 c) 1

Details can be found in 3GPP TS 05.02 Annex B.

In Nokia S11 and S11.5 max 4 tsl downlink, max 2 tsl uplink are supported.





8.2.1 Average Window Size

For EGPRS the window size (WS) shall be set by the network according to thenumber of timeslots allocated in the direction of the TBF (uplink or downlink). The

allowed window sizes are shown in Table 34. Preferably, the selected window sizeshould be the maximum.

Timeslots allocated (Multislot capability)Windowsize

Coding1 2 3 4 5 6 7 8

64 00000

96 00001

128 00010

160 00011

192 00100 Max

224 00101

256 00110 Max

288 00111320 01000

352 01001

384 01010 Max

416 01011

448 01100

480 01101512 01110 Max

544 01111

576 10000

608 10001

640 10010 Max

672 10011

704 10100

736 10101

768 10110 Max

800 10111

832 11000864 11001

896 11010 Max

928 11011

960 11100

992 11101

1024 11110 Max

Reserved 11111 x x x x x x x X

Table 34 Max Window Size vs. multislot usage

The window size may be set independently on uplink and downlink. MS shall supportthe maximum window size corresponding to its multislot capability. The selected WSshall be indicated within PACKET UL/DL ASSIGNMENT and PACKET TIMESLOTRECONFIGURE using the coding defined in the Table 34.

Once a window size is selected for a given MS, it may be changed to a larger size butnot to a smaller size, in order to prevent dropping data blocks from the window.

If the MS multislot class is not indicated during the packet data connectionestablishment (short access, access request for signaling message transfer), then adefault window size (corresponding to the minimum window size for 1 timeslot) shallbe selected.

8.3 High Multislot Class (HMC)

High Multislot Classes increases GPRS/EDGE peak downlink throughput to 296kbit/s.

3GPP release 4 or earlier MSs are limited to combined downlink and uplink timeslotsum of 5.

3GPP release 5 (TS 45.002) introduces new MS multislot classes which allow sum ofdownlink and uplink timeslots of 6





• New maximum allocation configurations

• Downlink + uplink: 5+1 and 4+2

•

With Extended Dynamic Allocation Application Software

• Downlink + uplink: 3+3 and 2+4

8.4 DLDC

DLDC needs two TRXs involved in PS territory. The CDEF recommendation for DLDCterritory is 11 RTSLs if one of the TRXs is BCCH TRX and 13, if both of the DLDCTRXs are nonBCCH TRXs.

The detailed information about DLDC planning will be described in DLDC planningguidelines, which will be published in the second half of 2009.





9. Mobility

The aim of mobility optimization is to reduce the cell-outage time during cell-reselection. The cell-outage time depends on the type of cell-reselection. It can be:

o intra-PCU / inter-PCU

o RAU cell-reselection

o Inter PAPU and Inter SGSN

This chapter below contains the description of cell-reselection types, Cell-reselectHysteresis and Network Assisted Cell Change (NACC) as well.

9.1 Intra/Inter PCU Cell Re-selectionThe intra and inter PCU cell-reselection events and measurements are describedbelow.

9.1.1 BSS and Data Outage

The cell-reselection events without LA/RA Update are listed below:

1. Mobile station (MS) is camped on Cell A and it notices a better Cell B

2. MS abnormally stops all the temporary block flow sessions (TBFs) from Cell A.

(The network has no idea what is happening.)3. MS camps on the new Cell B and reads system information (SI) messages

4. When MS has successfully read the SI messages, it asks for a channel andresources by sending CHANNEL REQUEST message for cell update andpacket resource request message (Note: 2phase access for EDGE phone onCCCH)

5. PCU responds with an immediate assignment message and packet uplinkassignment message respectively.

6. SGSN recognizes TLLI (in the packet resource request message) and

understands that a cell reselection occurred and it sends Flush LLC packetdata unit to the PCU. Note: The MS data stored in Cell A buffer is kept in thePCU buffer if Cell A and Cell B belong to the same PCU otherwise it is deletedand has to be retransmitted.

7. PCU sends an acknowledgement (FLUSH-LLC-ACK) to the SGSN.

8. SGSN sends an LLC PDU to the PCU.

9. PCU sends downlink assignment message for DL TBF establishment onPACCH.

10. Data transfer resumes

In the analysis we separated the BSS cell-reselection outage from data outage.





9.1.1.1 BSS Cell-reselection outageIt is the time it takes a mobile phone to synchronize to the target cell and establish anUL TBF in that target cell during cell reselection.

o In the measurements the first time stamp is taken for the first systeminformation message after the last RCL/MAC block

o The last time is the time stamp from the packet uplink assignment

9.1.1.2 Data outageThe cell reselection outage is the period after the last RLC/MAC block transmission inthe old cell and the first payload DL RLC block transmission at the target cell.

o First time stamp is taken from the first system information messageafter the last RCL/MAC block transmitted.

oThe last time is the time stamp from the packet downlink assignment.

The following figures show the cell-reselection process on signaling in case of FTPdownload.

MS BTS BSC SGSN



P_Channel Required


UL TBF ASSIGNMENT, MS ON CCCH. 2 phase access [2].





LLC PDUDL TBF Establishment when UL TBF is ongoing [3]


Packet Downlink Assignment




RLC Data blocks (PDTCH)RLC Data blocks

C e l l R e s e l e c t i o n B S S O

u t a g e

Packet downlink dummy control blocksPacket downlink dummy control blocks

C e l l r e s e l e c t i o n

d a t a O u t a g e





P_Channel Required







LLC PDUDL TBF Establishment when UL TBF is ongoing [3]


Packet Downlink Assignment




RLC Data blocks (PDTCH)RLC Data blocks

C e l l R e s e l e c t i o n B S S O

u t a g e

Packet downlink dummy control blocksPacket downlink dummy control blocks

C e l l r e s e l e c t i o n

d a t a O u t a g e


Figure 80 Cell-selection procedures for download





Event name Time Channel Message

RLC/MAC Uplink 20:42.0 PACCH "EGPRS_PACKET_DOWNLINK_ACK/NACK"

Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_1"



Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_4"… … … …


Cell Reselection 20:42.8 from CI 5032 to CI 5033



Layer 3 Uplink 20:43.1 RACH "CHANNEL_REQUEST"

Layer 3 Downlink 20:43.2 CCCH "IMMEDIATE_ASSIGNMENT"

Layer 3 Downlink 20:43.2 CCCH "PAGING_REQUEST_TYPE_1"





RLC/MAC Uplink 20:43.8 PACCH "PACKET_RESOURCE_REQUEST"

RLC/MAC Downlink 20:44.0 PACCH "PACKET_UPLINK_ASSIGNMENT"

RLC/MAC Downlink 20:44.0 PACCH "PACKET_DOWNLINK_DUMMY_CONTROL_BLOCK"

RLC/MAC Downlink 20:44.0 PACCH "PACKET_DOWNLINK_DUMMY_CONTROL_BLOCK"… … … …


RLC/MAC Downlink 20:44.2 PACCH "PACKET_DOWNLINK_ASSIGNMENT"


Table 35 Layer3 and RLC/MAC messages from Nemo TOM for download

The following figures show the cell-reselection process on signaling in case of FTPupload.

MS BTS BSC SGSN



P_Channel Required





RLC Data block (PDCH)


RLC Data Block


NOTE: BTS does not send Imm Ass Ackfor Single block Immediate Assignment





Uplink Data Packets

B S S / D a t a C e l l R e s e l e c

t i o n O u t a g e





P_Channel Required





RLC Data block (PDCH)


RLC Data Block


NOTE: BTS does not send Imm Ass Ackfor Single block Immediate Assignment





Uplink Data Packets

B S S / D a t a C e l l R e s e l e c

t i o n O u t a g e






Figure 81 Cell-selection procedures for upload

Event name Time Channel Message


Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_1"Layer 3 Downlink 20:42.0 BCCH "SYSTEM_INFORMATION_TYPE_2"




Cell Reselection 20:42.8 from CI 5032 to CI 5033



Layer 3 Uplink 20:43.1 RACH "CHANNEL_REQUEST"

Layer 3 Downlink 20:43.2 CCCH "IMMEDIATE_ASSIGNMENT"


Layer 3 Downlink 20:43.2 CCCH "PAGING_REQUEST_TYPE_1"Layer 3 Downlink 20:43.3 CCCH "PAGING_REQUEST_TYPE_1"



RLC/MAC Uplink 20:43.8 PACCH "PACKET_RESOURCE_REQUEST"

RLC/MAC Downlink 20:44.0 PACCH "PACKET_UPLINK_ASSIGNMENT"


Table 36 Layer3 and RLC/MAC messages from Nemo TOM for upload

9.1.2 Benchmark Results

The following table shows the BSS outage and Data Outage in case of intra and interPCU cell-reselection.

Diff. Between BSS and

till Packet Uplink Assign. (ms) till Packet Downlink Assign. (ms) full cell-outage (ms)

2.07 2.341 0.27

3.07 3.349 0.28

2.09 2.354 0.26

2.10 2.358 0.26

2.09 2.375 0.28

2.11 2.393 0.28

2.10 2.658 0.56

2.09 2.355 0.26

2.11 2.395 0.282.10 2.38 0.28

6.00 6.254 0.26

2.12 2.379 0.26

2.094 2.629 0.54

2.09 2.631 0.54

2.14 2.7 0.56

2.07 4.011 1.94

2.10 2.379 0.28

2.10 2.385 0.28

average 2.37 2.80 0.43

From EGPRS PACKET DOWNLINK ACK/NACK

Table 37 Cell-reselection measurement results from Nemo TOM





The results show that the BSS cell outage is almost same both in intra and inter PCUcells, but the data outage on downlink, where the Packet Downlink Assignment isneeded based on LLC PDU from the SGSN, is half a ms longer.

9.2 LA /RA Cell-reselectionThe RA cell-reselection events and measurements are described below.

9.2.1 Data Outage

The cell-reselection events without RA Update are listed below:

1. MS is camped on Cell A and it notices a better Cell B

2. MS abnormally stops all the temporary block flow sessions (TBFs) from Cell A.

3. MS camps on the new Cell B and reads system information (SI) messages

4. When it has successfully read the SI messages, MS sends CHANNELREQUEST message for location area update.

5. An SDCCH channel is created for this purpose.

6. MS then sends location area update

7. Security functions set by the operator take place.

8. When authentication is complete the SDCCH channel is released

9. Routing area update request is sent to the network

10. A channel and resources are requested for routing area update (Note: 2phaseaccess for EDGE phone on CCCH)

11. When granted network sends routing area update accept to MS

12. And the MS acknowledges receipt of this message by sending routing areaupdate complete

In the analysis we separated the Location Area Update, Routing Area Update andLA/RA Update BSS cell-reselection from each other.

9.2.1.1 Location Area UpdateThe LAU time is the period between Channel_Request and Channel_Release forLAU.

o First time stamp is taken from the Channel_Request for LAU

o The last time is the time stamp from Channel_Release afterLocation_Updating_Accept message.

9.2.1.2 Routing Area Updateo First time stamp is taken from the Routing_Area_Request

o The last time is the time stamp from Routing_Area_Update_Complete

9.2.1.3 Data outage (LA/RA Update)





o First time stamp is taken from the first system information messageafter the last RCL/MAC block transmitted.

o The last time is the time stamp from Routing_Area_Update_Complete

The following figures show the cell-reselection process with RAU on signaling.

MS BTS BSC New SGSN

DL TBFASSIGNMENT










P_Channel Required



SECURITYFUNCTIONSASSETBYTHEOPERATOR




d a t a O u t a g e



DL TBFASSIGNMENT










P_Channel Required



SECURITYFUNCTIONSASSETBYTHEOPERATOR




d a t a O u t a g e


Figure 82 LA / RA Cell-selection procedures





Event name Time Channel Message… … … …

Layer 3 Downlink 8:44:05.801 BCCH "SYSTEM_INFORMATION_TYPE_1"… … … …

Layer 3 Downlink 8:44:10.797 BCCH "SYSTEM_INFORMATION_TYPE_13"

Cell Reselection 8:44:10.906 from 5691 to 5753

Layer 3 Downlink 8:44:11.018 BCCH "SYSTEM_INFORMATION_TYPE_2"… … … …

Layer 3 Uplink 8:44:11.997 RACH "CHANNEL_REQUEST"

Layer 3 Downlink 8:44:12.101 CCCH "IMMEDIATE_ASSIGNMENT"

Layer 3 Uplink 8:44:12.313 SDCCH "LOCATION_UPDATING_REQUEST"

Layer 3 Downlink 8:44:12.353 SACCH "SYSTEM_INFORMATION_TYPE_6"

Layer 3 Uplink 8:44:12.388 SACCH "MEASUREMENT_REPORT"

Layer 3 Uplink 8:44:12.548 SDCCH "CLASSMARK_CHANGE"

Layer 3 Downlink 8:44:12.764 SDCCH "CIPHERING_MODE_COMMAND"

Layer 3 Uplink 8:44:12.784 SDCCH "GPRS_SUSPENSION_REQUEST"

Layer 3 Uplink 8:44:13.020 SDCCH "CIPHERING_MODE_COMPLETE"

Layer 3 Downlink 8:44:13.224 SDCCH "IDENTITY_REQUEST"

Layer 3 Uplink 8:44:13.350 SACCH "MEASUREMENT_REPORT"Layer 3 Uplink 8:44:13.490 SDCCH "IDENTITY_RESPONSE"

Layer 3 Downlink 8:44:13.697 SDCCH "LOCATION_UPDATING_ACCEPT"


Layer 3 Downlink 8:44:14.168 SDCCH "MM_INFORMATION"


Layer 3 Downlink 8:44:14.399 SDCCH "CHANNEL_RELEASE"… … … …

Layer 3 Uplink 8:44:16.258 PDTCH "ROUTING_AREA_UPDATE_REQUEST"… … … …

Layer 3 Uplink 8:44:16.752 RACH "CHANNEL_REQUEST"

Layer 3 Downlink 8:44:16.829 CCCH "IMMEDIATE_ASSIGNMENT"… … … …

Layer 3 Uplink 8:44:16.258 PDTCH "ROUTING_AREA_UPDATE_REQUEST"

RLC/MAC Uplink 8:44:17.401 PACCH "PACKET_RESOURCE_REQUEST"RLC/MAC Downlink 8:44:17.607 PACCH "PACKET_UPLINK_ASSIGNMENT"

… … … …

RLC/MAC Downlink 8:44:17.886 PACCH "PACKET_DOWNLINK_ASSIGNMENT"… … … …

Layer 3 Downlink 8:44:18.950 PDTCH "ROUTING_AREA_UPDATE_ACCEPT"

Layer 3 Uplink 8:44:18.964 PDTCH "ROUTING_AREA_UPDATE_COMPLETE"

RLC/MAC Uplink 8:44:19.119 PACCH "EGPRS_PACKET_DOWNLINK_ACK/NACK"… … … …

Table 38 Layer3 and RLC/MAC messages from Nemo TOM

9.2.2 Benchmark ResultsThe next table shows the RAU cell-reselection results.





Time to LAC [sec.] Time for RAC [sec.] Full LAU/RAU [sec.]

4.056 3.37 10.227

2.808 3.15 8.785

3.886 2.99 9.61

3.813 2.96 9.573

3.814 3.53 10.146

2.888 2.925 8.602

2.922 2.949 8.617

3.042 2.953 8.618

2.868 2.637 8.326

3.048 2.955 8.832

3.82 2.10 8.635

2.865 3.32 8.8

2.811 2.95 8.618

1.045 3.301 11.088

2.918 2.953 8.616

average 3.11 3.00 9.14

Table 39 LA / RA Cell-reselection measurement results from Nemo TOM

9.3 Cell-reselect Hysteresis

Path loss criteria and timings for cell reselection:

The MS is required to perform the following measurements (see 3GPP TS 03.22) toensure that the path loss criterion to the serving cell is acceptable.

At least every 5 s the MS shall calculate the value of C1 and C2 for the serving celland re-calculate C1 and C2 values for non-serving cells (if necessary). The MS shallthen check whether:

i) The path loss criterion (C1) for current serving cell falls below zero for a period of 5seconds. This indicates that the path loss to the cell has become too high.

ii) The calculated value of C2 for a non-serving suitable cell exceeds the value of C2for the serving cell for a period of 5 seconds, except;

a) in the case of the new cell being in a different location area or, for aGPRS MS, in a different routing area or always for a GPRS MS in readystate in which case the C2 value for the new cell shall exceed the C2value of the serving cell by at least

CELL_RESELECT_HYSTERESIS dB as defined by the BCCH

data from the current serving cell, for a period of 5 seconds; or

b) in case of a cell reselection occurring within the previous 15 secondsin which case the C2 value for the new cell shall exceed the C2 value ofthe serving cell by at least 5 dB for a period of 5 seconds.

This indicates that it is a better cell.

Cell reselection for any other reason (see 3GPP TS 03.22) shall take placeimmediately, but the cell that the MS was camped on shall not be returned to within 5seconds if another suitable cell can be found. If valid RLA_C values are not available,the MS shall wait until these values are available and then perform the cell reselection

if it is still required. The MS may accelerate the measurement procedure within therequirements in sub clause 6.6.1 to minimize the cell reselection delay.





If no suitable cell is found within 10 seconds, the cell selection algorithm of 3GPP TS03.22 shall be performed. Since information concerning a number of channels isalready known to the MS, it may assign high priority to measurements on thestrongest carriers from which it has not previously made attempts to obtain BCCH

information, and omit repeated measurements on the known ones.

A GPRS MS in Ready state applies the READY_STATE CELL RESELECTIONHYSTERESIS together with the path loss criterion when reselecting the cell within theregistration area. The GPRS MS in Ready state shall inform the network about cellreselection within the registration area by the cell update procedure.

So if the terminal is not in ready state, then the cell reselect hysteresis is used onlybetween RAUs. It can modify the results of this test.

9.4 Network Assisted Cell Change

3GPP specified Network Assisted Cell Change (NACC) procedure is enhancement toNCCR (NACC can work also without NCCR). NACC specifies procedures for networkto send target cell system information prior to actual cell change. This reduces thedata transmission break time during the cell change procedure.

NACC feature aims on reduce of service outage time for all QoS classes when aGPRS MS in packet transfer mode moves between GSM cells. NACC aims atreducing this packet data transfer outage time from seconds down to 300 msec – 1sec, depending on the other features used.

Assistance is given by sending the specific set of neighbour cell (target cell) systeminformation to certain MS during the cell change procedure while it’s still locating the

serving cell.

When NCCR has triggered and NACC has been applied, PCU commands MS totarget cell. The procedures in the MS and in the target PCU continue as if the cellreselection would have been triggered the MS.

The following figure shows the signaling flow of NACC:





Measurement andNCCRinformation


Networkdoes not order the cellchange until:

• PSI information regarding targetcell is provided in serving cell

•PSI STATUSis supported in thetarget cell

•Theservice outage isonly 300 - 700 ms

Uplink Packet Datatransfer

PACCH

Packet EnhancedMeasurement Report

MS Serving cell

PACCH

Packet Cell ChangeOrder

T3174starts

Target cell

Packet ChannelRequest

Packet UplinkAssignment

PRACH

PAGCH

Packet Neighbour CellData 1

Packet Neighbour CellData n

Current TBF on serving cellisaborted!

PACCH

PACCH

T3174stops

PACKET SI STATUS

Measurement andNCCRinformation


Networkdoes not order the cellchange until:

• PSI information regarding targetcell is provided in serving cell

•PSI STATUSis supported in thetarget cell

•Theservice outage isonly 300 - 700 ms


PACCH


MS Serving cell

PACCH


T3174starts

Target cell



PRACH

PAGCH




PACCH

PACCH

T3174stops


PACCH


MS Serving cell

PACCH


T3174starts

Target cell



PRACH

PAGCH




PACCH

PACCH

T3174stops

PACKET SI STATUS

(E)GPRS Radio Networks - Planning Theory RG10(S14)

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