alcatel amr

SFD : ADAPTIVE MULTI-RATE SPEECH CODEC (AMR)ED 02 RELEASED

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mAlcatel. Site

VELIZY MOBILE COMMUNICATION DIVISION

Originator(s)E. DESORBAY

SFD : ADAPTIVE MULTI-RATE SPEECH CODEC (AMR)

Domain : Alcatel 900/BSSDivision : Product DefinitionRubric : SYS-TLAType : System Feature DescriptionDistribution Codes Internal : External :

PREDISTRIBUTION:

MCD/TD:SYT: J. ACHARD E. DESORBAY

E. BRIGANT L. CORRE F. DELLA MEAA. FREULON R. MAUGERJ. BINGHAM O. VISBECQ A. WASNIEWSKI

BDC: G. VAN DIJCK S. BELLENS N. DE BODEN. WILLE

BTS-CC: R. SABELLEK M. DOBROSIELSKI G. HOENA. NAMASSE

O&M-CC: G. DAEL P. CREANGE JP. DELPIERREL. NADJAR F. FISCHER JY. DEBAILLON

CSI: C. SPIERSINT: O. BIGAYQAF: A. GOUILLY-FROSSARDPCO: M. TUCHENDLER J. GUINANDMCD/PCS: P. PELOUAS F. COLIN F. JARREAUSSD Velizy: M. JACOB T. HUYNH-QUANG

J. RZEZNIK Y. MARTY P. LOHATSSD Stuttgart: P. HUPPERICH

PREDISTRIBUTION: DOC. CENTRESMCD VELIZY MCD KONTICH MCD STUTTGART

B. Marliac L. Van Eyck I. Lentzsch

ABSTRACTThis SFD describes the "SFD : ADAPTIVE MULTI-RATE SPEECH CODEC (AMR)" feature.

ApprovalsName

App.

JP. GruauPM

M. TuchendlerPL

D. BerthoumieuxTSM

Name

App.


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mAlcatel. REVIEW

Ed. 01 proposal 03 23/04/99 MCD/TD/SYT/pfo/0220.99 (mail review)HISTORYEd. 01 proposal 01 2/03/99 Updated after TLAb7#0.3 according to minutes in

MCD/TD/SYT/ede/0086.99.Ed. 01 Proposal 02 1/04/99 Updated after TLAb7#2 according to minutes in MCD/TD/SYT/

ede/ 0134.99 and according to review report MCD/TD/SYT/pfo/0161.99.New template SFD instead of TFD.Removed channel mode adaptation for non-AMR calls.Moved some counters to the SFD PM counter improvements.Add BTS-CC and BSC-CC contributions.

Ed.01 Proposal 03 20/04/99 Updated after TLAb7#7 according to minutes inMCD/TD/SYT/ede/0190.99 and according to review reportMCD/TD/SYT/pfo/0212.99.

Ed.01 Released 23/04/99 Document released after mail review, see review reportMCD/TD /SYT/pfo/0220.99

Ed.02 Released 03/04/00 Alignment on step2 specifications. No review report.

INTERNAL REFERENCED DOCUMENTS

Not applicable

FOR INTERNAL USE ONLY

By derogation to the QS recommendation (see document 8BL 14106 0000 ASZZA - TDdocumentation layout) more than 3 levels used in the table of contents with agreement of the PQE.

END OF DOCUMENT


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mAlcatel. SYSTEM FEATURE DESCRIPTION

TABLE OF CONTENTS

1. INTRODUCTION ...................................................................................................................... 41.1 SCOPE ................................................................................................................................... 41.2 DOCUMENT STRUCTURE........................................................................................................... 41.3 DEFINITIONS AND PRE-REQUISITE .............................................................................................. 42. FEATURE DESCRIPTION........................................................................................................ 52.1 FUNCTIONAL REQUIREMENTS.................................................................................................... 52.2 COMPLIANCE TO THE MARKETING REQUIREMENTS....................................................................... 72.3 WORKING ASSUMPTIONS.......................................................................................................... 72.4 DEPENDENCIES ....................................................................................................................... 72.5 HW COVERAGE ...................................................................................................................... 82.6 RATIONALE ............................................................................................................................. 83. SYSTEM IMPACTS .................................................................................................................103.1 TELECOM...............................................................................................................................10

3.1.1 Functional architecture..................................................................................................103.1.2 Specification impacts....................................................................................................11

3.1.2.1 BTS layer 1....................................................................................................................... 113.1.2.2 AMR Codec adaptation ..................................................................................................... 133.1.2.3 TC / BTS interface ............................................................................................................ 163.1.2.4 Speech aspects ................................................................................................................ 173.1.2.5 Downlink DTX................................................................................................................... 183.1.2.6 Uplink DTX ....................................................................................................................... 223.1.2.7 Classmark handling .......................................................................................................... 233.1.2.8 Normal assignment........................................................................................................... 233.1.2.9 Radio measurements........................................................................................................ 233.1.2.10 Radio measurements data processing & Handover preparation......................................... 243.1.2.11 Resource allocation and management .............................................................................. 263.1.2.12 Handover Management..................................................................................................... 273.1.2.13 Internal channel change.................................................................................................... 273.1.2.14 External channel change................................................................................................... 273.1.2.15 Channel modification ........................................................................................................ 29

3.1.3 Interfaces......................................................................................................................303.1.3.1 Radio interface, physical layer (05.xx series) ..................................................................... 303.1.3.2 Radio interface - Layer 2 (04.06)....................................................................................... 303.1.3.3 Radio interface - Layer 3 (04.08)....................................................................................... 303.1.3.4 Abis interface (08.58)........................................................................................................ 303.1.3.5 A interface (08.08) ............................................................................................................ 31

3.2 OPERATION AND MAINTENANCE ................................................................................................323.2.1 Parameters...................................................................................................................323.2.2 PM counters .................................................................................................................343.2.3 Fault Management........................................................................................................35

4. SUBSYSTEM IMPACTS..........................................................................................................364.1 BTS......................................................................................................................................364.2 BSC .....................................................................................................................................37

4.2.1 Short description BSC impact .......................................................................................374.3 TRANSCODER.........................................................................................................................374.4 MFS .....................................................................................................................................384.5 OMC_R................................................................................................................................385. PERFORMANCE & SYSTEM DIMENSIONING .......................................................................385.1 TRAFFIC MODEL......................................................................................................................385.2 PERFORMANCE.......................................................................................................................385.3 LOAD CONSTRAINTS ................................................................................................................38


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mAlcatel. 6. OPEN POINTS ........................................................................................................................39

7. IMPACTS SUMMARY..............................................................................................................408. GLOSSARY.............................................................................................................................418.1 ABBREVIATIONS......................................................................................................................418.2 TERMINOLOGY........................................................................................................................42

02 03/04/00 RCD/TD & MCD/MP&S RCD/TD/SYT01 23/04/99 MCD/TD & MCD/MP&S MCD/TD/SYTED DATE CHANGE NOTE APPRAISAL AUTHORITY ORIGINATOR


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mAlcatel. HISTORY

Ed. 02 03/04/00 Alignment on step2 specifications.

REFERENCED DOCUMENTSAlcatel references

[1] 3DC 25199 0001 DRZZA MFD: Adaptive Multi-Rate Codec

GSM references

[2] GSM TS 05.03 Channel coding[3] GSM TS 05.05 Radio transmission and reception[4] GSM TS 05.09 Link adaptation[5] GSM TS 06.71 AMR Speech codec: General description[6] GSM TS 06.73 ANSI C code for the GSM Adaptive Multi Rate (AMR) speech codec[7] GSM TS 06.90 AMR speech transcoding[8] GSM TS 06.91 Substitution and muting of lost frames for AMR speech traffic channels[9] GSM TS 06.92 Comfort noise aspects for AMR speech traffic channels[10] GSM TS 06.93 DTX for AMR speech traffic channels[11] GSM TS 06.94 Voice Activity Detector for AMR speech traffic channels[12] GSM TS 08.60 Inband Control of Remote Transcoders and Rate Adaptors for EFR/FR[13] GSM TS 08.61 Inband Control of Remote Transcoder and Rate Adaptors;(Half Rate)[14] Tdoc 99-292 AMR channel coding compromise[15] Tdoc SMG11 99-056 Proposal for modification of the Requirements of the Wideband AMR[16] GSM TR 06.75 Performance Characterization of the GSM

Adaptive Multi-Rate (AMR) speech codec

RELATED DOCUMENTSAlcatel documents

[17] 3BK 10204 0478 DTZZA SFD Tandem Free Operation (TFO)[18] 3BK 10204 0470 DTZZA PM counters improvements B7GSM CRsNone.

PREFACEThis document is the input paper for the feature Adaptive Multi-Rate Speech Codec (AMR) insideTD. It will further on be used as reference for the development of that feature in each subsystem.


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mAlcatel.

1. INTRODUCTION

1.1 ScopeThe present document aims to be the basis for decision of a proposed change to be made on theBSS system. Then it provides all necessary information related to functional description, gains,description of the system impacts and subsystem impacts.

1.2 Document StructureThe section 2 of this document presents the functional requirements, the HW coverage and therationale of the feature addressed by the present SFD.

The section 3 identifies the system impacts : it gives the principles and presents the functional splitof the feature between subsystems. Impact on Step2 specifications is also given in this section.

The section 4 contains the description of impacts for each subsystem.

The section 5 addresses the performance and system dimensioning concerns.

The section 6 identifies and describes the open points.

The section 7 is a sum up of the system impacts.

The section 8 contains the glossary of the present document.

1.3 Definitions and Pre-requisite

The text in italics is informative. It typically consists of:- background information eg standardisation information.- references to future BSS enhancements to guide design choices (eg for future AMR + TFO).- references to NSS functionalities.


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mAlcatel.

2. FEATURE DESCRIPTIONThis feature is described in the MFD ref.[1].The main speech codec currently used in GSM networks, speech Full Rate, is quite old. It has beenspecified more than 10 years ago.Around 1992, to increase network capacity, GSM has specified a half rate speech codec. But thiscodec showed strong limitations in terms of speech quality, especially for mobile to mobile calls(double transcoding degrades very much the speech quality of the half rate codec) and under poorradio conditions.

A few years later, when GSM started to be introduced in North America, American operators askedfor an improved speech codec for full rate channels. Indeed speech quality was a major argument forcustomers used to have a good speech quality with analogue systems. For that issue, EFR wasspecified for GSM.

Recently, studies on AMR where launched to provide a solution for: Increasing speech quality in full rate and half rate, Increasing network capacity by offering a good half rate solution, Using a long-term solution, avoiding to add more and more codecs handled independently

from the others. Taking into account Tandem Free Operation (TFO), especially between MS on half rate on

one side and on full rate on the other side.

2.1 Functional Requirements

The AMR principle is to have a set of codecs and, for any radio conditions, to use the one with thebest speech quality.

Under good radio conditions, a codec with a high bit-rate is used. Speech is encoded with moreinformation so the quality is better. In the channel coding, only little place is left for redundancy.

Under poor radio conditions, a codec with a low bit-rate is chosen. Speech is encoded with lessinformation, but this information can be well protected due to redundancy in the channel coding.

The BSS adapts dynamically the codec in uplink direction and in downlink direction, taking intoaccount the C/I measured by the BTS (for uplink adaptation) and by the MS (for downlinkadaptation).The codec used in uplink and used in downlink can be different: the adaptation is independent ineach direction.

This permits to use an optimal codec for each C/I value of each direction, as indicated in the figurebelow.


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C/I [dB]

SpeechQuality[dBQ]or

[MOS]High bit rate (for example 12.2 kbit/s: EFR)Medium bit rate (for example 7.95 kbit/s)Low bit rate (for example 5.90 kbit/s)

AMR-FR with codec subset (12.2, 7.95, 5.90)

Figure 1: AMR principle

Codec subset:List of AMR codecs:

Codec bit-rate Full Rate Half Rate12.2 kbit/s (EFR) X10.2 kbit/s X7.95 kbit/s X X (*)7.40 kbit/s (IS-641) X X (EFR codec for D-AMPS standard)6.70 kbit/s X X5.90 kbit/s X X5.15 kbit/s X X4.75 kbit/s X X

(*) : Not supported by the Alcatel BSS.During a call, a subset of 1 to 4 codecs is used, configured by O&M on a per BSS basis.A different number of codecs and different subsets may be defined for FR (1 to 4 codecs out of the 8codecs available) and for HR (1 to 4 codecs out of the 6 codecs available).The codec subset is the same in uplink and downlink.

To change from one codec to another codec, a list of thresholds and hysteresis are configured byO&M. These thresholds are identical in uplink and downlink.

The Alcatel default codec subset is derived from the optimal codec subset defined in the ETSI AMRcharacterization report, see ref. [16], taking into account that the HR 7.95 codec is not supported.Note: in the context of TFO with AMR (not supported by Alcatel), an operator shall be able to defineits own codec subset (limited to the supported codec modes), especially for TFO operation betweenBSSs from different manufacturers. Indeed some BSSs may not be able to support all the AMR

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Edited by Foxit ReaderCopyright(C) by Foxit Software Company,2005-2007For Evaluation Only.


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mAlcatel. codec modes, especially because of implementability problems with channel coding. In that case the

operator will define a codec subset limited to the common codec modes supported by all the BSSs ofits network.

Codec mode adaptation:The codec mode adaptation is the dynamic change from one codec to another codec, using thesame channel (FR or HR). This adaptation is performed by the layer 1 of the BTS. It is transparentfor the BSC and the layer 3 of the BTS.

The metric used for codec mode adaptation is the evaluation of the ratio: signal over interference.This ratio is noted C/I in the current document.

Channel mode adaptation:The channel mode adaptation is the change from one FR channel to an HR channel and vice-versa.This adaptation is handled by the layer 3, independently from the codec mode currently used.

The metric used for channel mode adaptation is RX_QUAL in uplink & downlink..

2.2 Compliance to the Marketing Requirements

Feature Item Compliance CommentsAMR / FR 12.2 YAMR / FR 10.2 YAMR / FR 7.95 YAMR / FR 7.40 YAMR / FR 6.70 YAMR / FR 5.90 YAMR / FR 5.15 YAMR / FR 4.75 YAMR / HR 7.95 N 16 kbit/s TRAU frames are needed,

see note.AMR / HR 7.40 YAMR / HR 6.70 YAMR / HR 5.90 YAMR / HR 5.15 YAMR / HR 4.75 YChannel mode adaptation for AMR calls YTFO with AMR N Standard not availableAMR TRXs for concentric application (tighterreuse pattern on AMR frequencies)

N Technical concept not validated.

Note: in addition, performance characterization has shown virtually no difference between HR/7.95and HR/7.4, see ref [16].

2.3 Working Assumptions

2.4 Dependencies

The feature AMR requires the following features:

Feature DependencyHalf Rate speech AMR is supported only on BSS equipments supporting HR.AMR mobiles AMR can only be used with AMR mobiles.


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mAlcatel. NSS AMR can only be used if the NSS implements it.

The feature AMR is enhanced by the following features:

Feature EnhancementTandem Free Operation (TFO) Improved speech quality for MS to MS calls.

TFO is not supported for AMR, but TFO can force AMR calls tofallback to another speech version allowing TFO operation, seeSFD TFO.

The feature AMR is incompatible with the following features:

Feature IncompatibilityNone. None.

The feature AMR will be enhanced by the following future evolutions:

Feature Future enhancementWideband AMR One new codec may be standardised to increase the speech

quality under good radio conditions, using the full bandwidth ofa full rate radio channel. With the current radio interface, themaximum usable bitrate is around 14.5 kbit/s.Operators proposed that this wideband codec should have aquality equivalent to the wideband codec ITU-T G.722 at 48kbit/s (7kHz): see Tdoc SMG11 99-056, ref.[15].

2.5 HW CoverageBSC HW support:- BSC EVOLIUMTM (BSC G2)BTS HW support:All BTS HW in B7 except FUMO support AMR:- BTS G1 with DRFU- BTS G2 with DRFU- Micro-BTS M1M- Micro-BTS M2M- Micro-BTS A910 (M4M-S)- BTS EVOLIUMTM

TC HW support:- DT16- MT120

2.6 Rationale

AMR is a new end-user service, providing:- For the mobile phone users : a real audible improvement.- For operators : an increase of their network capacity by :

- using HR channels with good speech quality- densifying their network by authorising an increase of the interference level with low impacton speech quality.

Competition:Alcatel BSS supports all the standardised codec modes except 7.95 kbit/s in Half Rate mode.Especially, codec modes using high protection (polynomials with constraint length = 7) are supported


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mAlcatel. whereas several other manufacturers seem to not support these codec modes. These manufacturers

(Nokia, Motorola) are consequently unable to propose an optimised codec subset.


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3. SYSTEM IMPACTS

3.1 Telecom

3.1.1 Functional architecture

In-band signalling functional architecture:

MS

BTS

Radiolinkadaptation

Channelcoding &decoding

TC

- Codec Mode Command- Codec Mode Indication

- Codec Mode Request- Codec Mode Indication - Codec Mode Request

- Codec Mode Indication

- Codec Mode Request (1)- Codec Mode Indication

Figure 2: Speech and in-band signalling

(1) When TFO is not active, Codec Mode Request from the TC to the BTS contains no validinformation and is ignored by the BTS.

Codec Mode Indication (uplink and downlink) : indicates the codec of the codec subset that has beenused to encode the current speech frame and the next speech frame.

Codec Mode Command (downlink) : after analysis of the uplink radio link, the BTS commands themore optimal codec of the codec subset. The MS shall apply this command for the next uplinkspeech frame containing Codec Mode Indication.

Codec Mode Request (uplink) : after having analysed the downlink quality of the radio link, the MSrequests the more optimal codec of the codec subset. The BTS may apply this request for the nextdownlink speech frame containing Codec Mode Indication.

Layer 3 signalling functional architecture:

MS

BTS

Radiolinkadaptation

MSC

BSC

Channelmode

adaptation

Figure 3: Layer 3 signalling

The complete architecture of the AMR codec adaptation function is shown in the figure below, seeref.[5]:

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mAlcatel. MSBTSTRAU

UL codec mode (received)

UL-Mode Ctrl

UL-Meas.

SPE

SPE

CHE CHD

SPD CHD CHE

SPD

DL-Meas.

DL-Mode Ctrl

DL codec modeUL Mode Command

UL Quality Indicator

UL Mode Command(received)

DL Mode Request(received)

speech data

speech data

DL codec mode (received)

networkcontrol

DL-Req.Gen

DL Quality Indicator

DL Mode Request

Figure 4: Block diagram of the AMR system.

3.1.2 Specification impacts

3.1.2.1 BTS layer 1

Channel types:- all TCH/AFS and TCH/AHS are supported except TCH/AHS 7.95.- The RATSCCH channel is not supported.Note: CMI/CMR phase alignment is performed on the Abis interface, which is more efficient thanradio interface alignment which is subject to error cases.

Channel coding:The channel coding for AMR speech frames is described in ref.[2].SPEECH frames:Speech frames are coded in the following steps:

- step 1: In-band data codingCodec Mode Request and Codec Mode Indication are information on two bits. This informationneeds to be sent on the radio interface in-band.These two bits are coded and protected into 8 in-band bits (FR) or 4 in-band bits (HR). Thesecoded bits are the first bits of the radio frame.

- step 2: Speech bit orderingThe speech bits are ordered according to their subjective importance. Three classes aredefined: class 1a, class 1b and class 2 (only used in HR).The most important bits, class 1a, are protected by CRC and convolutional code.Class 1b bits are protected by convolutional code.The less important bits, class 2, are sent without any protection. They are only used in HR.

- step 3: Parity and tailingThe 6-bit CRC is calculated over class 1a bits, and these 6 parity bits are merged with class 1aand class 1b bits.


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mAlcatel. - step 4: Convolutional encoder

The bits resulting from step 3 are encoded using a recursive convolutional coding (RSC)depending on the codec mode. This RSC is more efficient than the classical convolutionalcodes.

The following polynomials are used for the convolutional encoding:

Source Rate(Codec mode) Rate

Constraintlength

Used polynomials

FR 12.2 R=1/2 K=5 G0/G0, G1/G0FR 10.2 R=1/3 K=5 G1/G3, G2/G3, G3/G3FR 7.95 R=1/3 K=7 G4/G4, G5/G4, G6/G4FR 7.4 R=1/3 K=5 G1/G3, G2/G3, G3/G3FR 6.7 R=1/4 K=5 G1/G3, G2/G3, G3/G3, G3/G3FR 5.9 R=1/4 K=7 G4/G6, G5/G6, G6/G6, G6/G6FR 5.15 R=1/4 K=5 G1/G3, G1/G1, G2/G3, G3/G3, G3/G3FR 4.75 R=1/5 K=7 G4/G6, G4/G6, G5/G6, G6/G6, G6/G6HR 7.4 R=1/2 K=5 G0/G0, G1/G0HR 6.7 R=1/2 K=5 G0/G0, G1/G0HR 5.9 R=1/2 K=5 G0/G0, G1/G0HR 5.15 R=1/3 K=5 G1/G3, G2/G3, G3/G3HR 4.75 R=1/3 K=7 G4/G4, G5/G4, G6/G4

With:G0 = 1 + D3 + D4G1 = 1 + D + D3 + D4G2 = 1 + D2 + D4G3 = 1 + D + D2 + D3 + D4G4 = 1 + D2 + D3 + D5 + D6G5 = 1 + D + D4 + D6G6 = 1 + D + D2 + D3 + D4 + D6

G0, G1, G2 and G3 are already used for FR channel coding, speech or data.G4, G5 and G6 are already used for HR speech channel coding.

The coded bits are appended to the in-band signalling bits.In HR, the class 2 bits are appended at the end of the frame.

- step 5: interleaving and mapping on burstThe existing procedures for TCH/FS and TCH/HS are used.

CMI/CMR8 bits

Protected class 1 bits448 bits

CMI/CMR4 bits 224 bits

Protected class 1 bits class 2 bits

AMR FR SPEECH radio frame:

AMR HR SPEECH radio frame:456 bits

The ratio of class 1 (protected) bits versusclass 2 bits depend on the codec mode

228 bits

Figure 5: Speech radio frames

SID_UPDATE frames:The SID_UPDATE frames contain comfort noise description.


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mAlcatel. Refer to ref.[2] for the detailed description of these frames.

CMI + CMR32 bits

212 bits for identification marker, merged with212 protected bits for Comfort noise

CMI + CMR16 bits

AMR FR SID_UPDATE radio frame:

AMR HR SID_UPDATE radio frame:456 bits

Identification marker212 bits

CMI + CMR16 bits

Protected comfort noise212 bits

456 bits

Figure 6: SID_UPDATE radio frames

Other framesThe other radio frames carry only in-band signalling information.

In FR: SID_FIRST and ONSET frames.In HR: SID_UPDATE_INH, SID_FIRST_P1, SID_FIRST_P2, SID_FIRST_INH and ONSET frames.

Refer to ref.[2] for the detailed description of these signalling frames.

3.1.2.2 AMR Codec adaptation

A new step2 specification is introduced to detail the codec adaptation.

3.1.2.2.1 Link quality estimationThe quality of the radio link is estimated by evaluating the carrier on interference ratio C/I. Thenormalised value of the metric is called C/Inorm.

C/Inorm is derived from an estimate of the current carrier to interferer ratio (C/Iest), using the filteringprocess described in annex A (informative) of GSM TS 05.09 ref.[4].When uplink DTX is active,- the C/Inorm computation is stopped,- it resumes upon reception of a valid frame, by filling in the missing samples with the C/Iest of thereceived frame.

With uplink DTX active, the MS sends:- for FR, one SID_UPDATE every 8th frame,- for HR, one SID_UPDATE every 8th frame.This allows the BTS to update the C/Iest regularly.3.1.2.2.2 Threshold comparisonFor each pair of adjacent codecs, a threshold and an hysteresis is given by O&M.The figure below shows the case where four codecs are included in the subset.


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mAlcatel.

AMR_THR_3 + AMR_HYST

High

Low

CODEC_MODE_4(less robust)

C/Inorm

AMR_FR_THR_3CODEC_MODE_3

CODEC_MODE_2

CODEC_MODE_1(most robust)

AMR_THR_2 + AMR_HYSTAMR_FR_THR_2

AMR_THR_1 + AMR_HYSTAMR_FR_THR_1

Figure 7: Thresholds for codec modification, example for FR

If only three codecs are present in the subset, then CODEC_MODE_4 is not used andAMR_(FR/HR)_THR_3 is not defined.If only two codecs are present, then CODEC_MODE_3 is also not used and AMR_(FR/HR)_THR_2is also not defined.If only one codec is present in the subset, then no threshold is defined because no adaptation ispossible. The codec remains fixed.3.1.2.2.3 Inband signalling on the radio interfaceOn the radio interface, the codec mode adaptation is performed using in-band signalling, with smallplace left. The different Codec Modes to send are:- Codec Mode Request (CMR) and Codec Mode Indication (CMI) in uplink,- Codec Mode Command (CMC) and Codec Mode Indication (CMI) in downlink.These Codec Modes are coded using their relative position in the codec subset. As the number ofcodec modes is limited to 4 per subset, only two bits are necessary:

00 CODEC_MODE_1 Lowest codec mode (lowest bit-rate).01 CODEC_MODE_2 Second lowest mode, if the subset contains more than 1 mode.10 CODEC_MODE_3 Third lowest mode, if the subset contains more than 2 modes.11 CODEC_MODE_4 Highest mode, if the subset contains 4 modes.

On the radio interface, the CMI and the CMR/CMC are sent alternately on speech frames. Tosynchronise, the following rule is used:

When no DTX is active:FR: Codec Mode indication is sent on the speech frame starting on TDMA frame number 0[modulo 26] and then alternately with CMR/CMC.HR: Codec Mode indication is sent on the speech frame starting on TDMA frame 0 or 1[modulo 26], depending on sub-channel, and then alternately with CMR/CMC.

When DTX is active:The same rule is used for speech frames and SID_FIRST frames.For SID_UPDATE frames, both CMI and CMR/CMC are sent in each frame.For ONSET frames, CMI of the next speech frame is always sent.

BSS MAY 6Highlight



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mAlcatel. The following figure shows the uplink TDMA frame with a full rate channel and with a half rate

channel, with DTX not active.

TCH/FS (Full rate)

TCH/HS (Half rate)

Sub-channel 0

Sub-channel 1

CMI0 1 2 3

S

TDMA frame(modulo 26)

CMI : Speech frame carrying Codec Mode IndicationCMR : Speech frame carrying Codec Mode RequestS : SACCHI : Idle

(1) : SACCH frame or idle frame, see GSM TS 05.02

TDMA frame(modulo 26) . . .4 5 6 7 8 9 10 11 12 13 14 15 16

I17 18 19 20 21 22 23 24 25 0 1 2 3

One FR speech frame (20 ms),interleaved over 8 TDMA frames

0 1 2 3 4 5 6 7 8 9 10 11 12CMI

CMR

CMICMR

CMRCMI CMI

CMR CMRCMI

(1)

(1)13 14 15 16 17 18 19 20 21 22 23 24 25

CMICMR

CMICMR

(1)

(1). . .

CMICMR

0 1 2 3CMI

CMICMICMR

One HR speech frame (20 ms), interleavedover 4 TDMA frames of one sub-channel

Figure 8: Multiplexing of CMI and CMR on the radio interface

Interaction with TFO:When TFO is active, the radio interfaces of both sides may not be synchronised. In that case, one TCdecides to invert the sequence of CMI and CMR/CMC on the radio interface.3.1.2.2.4 Uplink codec mode adaptation:The BTS evaluates the C/Inorm and compares it to the thresholds sent by the BSS in the layer 3message CHANNEL ACTIVATION.If the BTS evaluates that the uplink codec shall be changed, then the BTS sends a Codec ModeCommand to the MS in the in-band signalling.

The TC receives a frame with the new codec indicated in Codec Mode Indication field and is able todecode the speech.

Codec Mode Command(new codec mode)

MS BTS TC

C/I evaluation &thresholds comparison

Codec Mode Indication(new codec mode) Codec Mode Indication

(new codec mode)

Figure 9: Uplink codec mode adaptation

3.1.2.2.5 Downlink codec mode adaptation:The MS evaluates C/Inorm and compares it to the thresholds sent by the BSS in the layer 3 message(ASSIGNMENT COMMAND or HANDOVER COMMAND).


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mAlcatel. If the MS evaluates that the downlink codec shall be changed, then the MS sends a Codec Mode

Request to the BTS in the in-band signalling.

If the BTS agrees to change the downlink codec (see section on error handling, below), then the BTSforwards immediately the Codec Mode Request to the TC. The TC then changes its downlink codecin the TRAU frame containing a Codec Mode Indication.

Codec Mode Request(new codec mode)

MS BTS TC

C/I evaluation &thresholds comparison

Codec Mode Request(new codec mode)

Codec Mode Indication(new codec mode)

Codec Mode Indication(new codec mode)

Figure 10: Downlink codec mode adaptation

Error handling:The BTS refuses the Codec Mode Request from the MS and keeps the current downlink codec modein the following situations:- The Codec Mode Request contains a Codec Mode that is not adjacent to the currently used CodecMode. However if repeated, a non adjacent Codec Mode will be accepted.- The Codec Mode Request contains a Codec Mode that is not part of the codec subset (when thecodec subset contains less than 4 codecs).

3.1.2.3 TC / BTS interface

Downlink CMI / CMR synchronisation between TRAU frames and radio frames:When the speech path is established after an assignment or a handover, the TC and the BTS are notsynchronised. An existing mechanism is performed to synchronise the TRAU frames with the radioframes (time alignment mechanism, see GSM TS 08.60 ref.[12] and GSM TS 08.61 ref.[13]).At the same time, the BTS checks if the Request or Indication Flag (RIF) given in the TRAU frame iscoherent with the type of Codec Mode (Indication or Command) that should be sent on the radiointerface.

If the BTS detects a desynchronisation, then it sends an Align_CMI_CMR command to the TC inthe next uplink frame.The TC inverts the Request or Indication Flag (RIF) to align the CMI / CMR.

Note 1: During the whole synchronisation phase, the Codec Mode Indication and the Codec ModeCommand sent by the BTS on the radio interface are equal to the startup value.


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mAlcatel.

TRAU (CMR)

MS BTS TC

Speech (CMI) delayTRAU (time alignment command)

TRAU (CMI)Speech (CMC) delay

TRAU (time alignment command)TRAU (CMR)Speech (CMI)

no delay

Codec modeadaptation is frozen

TRAU ("Align_CMI_CMR")TRAU (CMI)Speech (CMC)

TRAUTRAU (CMI)Speech (CMI)

Codec modeadaptation is started

Figure 11: Example of TRAU frames synchronisationOnce the BTS detects that downlink CMI / CMR is synchronised between the TRAU frames and theradio interface, it starts codec mode adaptation.

Note 2: The BTS always ignores the Codec Mode Request from the TC.The BTS monitors only the Codec Mode Indication.

TRAU frame format:For FR, the existing principles for the speech frames are used, with the existing synchronisationmechanism. The static time alignment procedure remains unchanged, by skipping T-bits in oneframe.For HR, T-bits are skipped when available; for higher througputs, one data bit can be skipped whenno T-bits are defined.

The description of the frames, codec per codec, is given in GSM TS 08.60, ref.[12].

3.1.2.4 Speech aspects

For all the items described below, the corresponding C-code is given in GSM TS 06.73, ref.[6].Speech transcodingThe AMR speech transcoding is described in GSM TS 06.90, ref.[7].The speech received by the TC from the fixed network is made of input blocks of 160 speechsamples in 8-bit PCM format, either a-law or -law. Sampling rate is 8000 samples/s.For each input block, the TC provides to the BTS a TRAU frame containing an output block in theformat corresponding to the current downlink codec type and the frame format (8/16Kb).The TC performs also the reverse action, from the BTS to the fixed network.

The speech coding uses the Algebraic Code Excited Linear Prediction Coder (ACELP), see ref.[7].Muting and substitutionWhen speech frames or SID frames are lost due to frame stealing or bad radio conditions,substitution and muting is triggered. It is described in GSM TS 06.91, ref.[8].

BSS MAY 6Highlight

BSS MAY 6Highlight

BSS MAY 6Highlight

BSS MAY 6Highlight

BSS MAY 6Highlight



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mAlcatel. Substitution is used for isolated frames lost. In this case the TC substitutes the lost frame by a frame

based on the previous speech or SID frame.

Muting is used when several consecutive frames are not received. This warns the user that thecommunication has been lost.

Ref.[8] provides two solutions for substitution and muting: ECU/BFH Solution 1 and ECU/BFHSolution 2.The Alcatel TC supports the ECU/BFH Solution 1, as it is the most complete solution.

DTX aspectsTo trigger DTX, the voice activity detection evaluates if speech is present or not in the input signal.This detection is described in GSM TS 06.94, ref.[11].When DTX is active, the comfort noise aspects are described in GSM TS 06.92, ref.[9].

3.1.2.5 Downlink DTX

The downlink DTX is controlled specifically for AMR, see parameter section..The downlink DTX indicator set on a per call basis by the MSC is ignored,for all AMR and non AMR calls.

Speech aspects of DTX for AMR is described in GSM TS 06.93, ref. [10].During a call, the TC sends the speech frames to the BTS with the following information:- TX_TYPE,- Mode_indication,- Information bits.

The TX_TYPE is described in the table below:

TX_TYPE Legend Information Bits Mode IndicationSPEECH_GOOD speech frame, size 95..244 bits

depending on codec modecurrent code mode

SID_FIRST no useful information the codec mode that would have beenused if TX_TYPE had beenSPEECH_GOOD

SID_UPDATE comfort noise, 35 bits the codec mode that would have beenused if TX_TYPE had beenSPEECH_GOOD

NO_DATA no useful information no useful information

After a reset of the system, the first frames are considered as speech frames even if no speech ispresent in the input signal.

Then the TC monitors on a per frame basis, in the input signal, if speech is present or absent. Whena transition from speech to silence occurs, a hangover period of 8 speech frames is respected toevaluate the background noise and build a corresponding SID frame. During the hangover period,the TC goes on sending speech frames to the BTS.The first frame sent by the TC to the BTS after this hangover period is a SID_FIRST frame, followedby two NO_DATA frames and one SID_UPDATE frame.

During the silence period, the TC sends to the BTS:- for FR, one SID_UPDATE every 8th 20 ms frame,- for HR, one SID_UPDATE every 8th 20 ms frame.These frames allow the MS to evaluate the C/I of the downlink link and allow the BTS to send theCodec Mode Commands to the MS.


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mAlcatel. The frames sent in-between are NO_DATA frames.

The transmission of frames on the radio interface is controlled by the TC. The BTS acts as a slave,following the TX_TYPE value:- all speech frames, SID_FIRST and SID_UPDATE frames are transmitted by the BTS on the radiointerface,- the NO_DATA frames are not transmitted on the radio interface (see details below).The BTS adapts the channel coding and the interleaving to the TX_TYPE and the channel mode (FRor HR), as described in ref. [10].FR channels:With FR channels, in case of a transition from NO_DATA or SID_UPDATE to SPEECH_GOOD, thenthe BTS sends an ONSET frame followed by the first SPEECH_GOOD frame. The aim of theONSET frame is to indicate to the MS the codec mode used by the speech frame that follows.

SPEECH

MS BTS TC Enduser

SpeechSPEECH SPEECHSPEECH

Silence

Hangoverperiod(8 speech frames)

SPEECHSPEECHSPEECHSPEECH

SID_FIRSTSID_FIRSTNO_DATANo emissionNO_DATANo emission

SID_UPDATESID_UPDATENO_DATANo emission

. . .

. . .

NO_DATANo emissionSID_UPDATESID_UPDATENO_DATANo emission

. . .

. . .

NO_DATANo emissionSPEECHONSET

SPEECHSPEECH SpeechSPEECH

Figure 12: Downlink DTX with FR channel

Note: in the figure, SPEECH stands for TX_TYPE = SPEECH_GOOD.

At the end of the figure above, it appears that two frames are sent on the radio interface (ONSETand SPEECH_GOOD) when only one frame is received from the TC (SPEECH_GOOD). This ispossible because the ONSET frame is 228 bits long (half of a speech frame) and is interleaved over4 radio blocks. These radio blocks are also used by the speech frame that triggered the ONSETframe. The ONSET frame uses the odd numbered bits, the speech frame uses the even numberedbits. The second part of the speech frame is sent on the 4 next radio blocks, using the odd numberedbits, as shown on the figure below. See also ref. [2].


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mAlcatel.

ONSET(odd bits)

Speech frame 1

s1 ons1 on . . .

Radio block 1

s1 ons1 on . . .

Radio block 4

. . . s2 s1s2 s1 . . .

Radio block 5

. . . s2 s1s2 s1 . . .

Radio block 8

Speech frame 2

20 ms

456 bits 456 bits

228 bits

Figure 13: Restart of speech transmission: frames interleaving (FR)

HR channels:In case of HR channels, transitions are handled as follows:- From NO_DATA to SPEECH_GOOD: an ONSET frame followed by a SPEECH_GOOD frame issent (same as FR).- From SID_FIRST to SPEECH_GOOD: a SID_FIRST_INH frame followed by a SPEECH_GOODframe is sent.- From SID_UPDATE to SPEECH_GOOD: a SID_UPDATE_INH frame followed by aSPEECH_GOOD frame is sent.- From SID_FIRST to NO_DATA: a SID_FIRST_P1 followed by a SID_FIRST_P2 is sent.

The figure below shows the case where the speech restarts just after the sending of a SID_UPDATEframe.


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mAlcatel.

SPEECH

MS BTS TC Enduser

SpeechSPEECH SPEECHSPEECH

Silence

Hangoverperiod

(8 frames)

SPEECHSPEECHSPEECHSPEECH

SID_FIRSTSID_FIRST_P1NO_DATANO_DATANo emission

SID_UPDATESID_UPDATENO_DATANo emission

. . .

. . .

NO_DATANo emissionSID_UPDATESID_UPDATENO_DATANo emission

. . .

. . .

SID_UPDATESPEECHSID_UPDATE_INH

SPEECHSPEECH Speech

SID_FIRST_P2

SID_UPDATE

SPEECH

Figure 14: Downlink DTX with HR channel

Note: in the figure, SPEECH stands for TX_TYPE = SPEECH_GOOD.

SID_UPDATE_INH, SID_FIRST_INH and ONSET frames are interleaved with the first half of thecorresponding speech frame, as in the FR case with the ONSET frame. See also ref. [2].In this example, only half of the SID_UPDATE frame (2 radio blocks out of 4) has been transmittedto the MS when speech restarts. As the first speech frames occupies only the half of each radioblocks, the second half of each radio block is filled by a SID_UPDATE_INH frame until the beginningof the second speech frame, see figure below.


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mAlcatel.

SID_UPDATE_INH(odd bits)

SID UPDATE

su susu su . . .

Radio block 1

su susu su . . .

Radio block 2

s1 inhs1 inh . . .

Radio block 3

s1 inhs1 inh . . .

Radio block 4

Speech frame 1

20 ms

456 bits, using allbits of 4 radio blocks

228 bits,even bits of 2 first radio blocks,odd bits of 2 second radio blocks

114 bits

s2 s1s2 s1 . . .

Radio block 5

Speech frame 2

The transmission of theSID_UPDATE is interrupted by thespeech frame

228 bits

Figure 15: Restart of speech transmission: frames interleaving (HR)

3.1.2.6 Uplink DTX

The uplink DTX is controlled using the generic radio interface signalling:The uplink DTX information is indicated to the MS- through System information sent on BCCH (system information 3)- and SACCH (system information 6), in cell options IE.Uplink DTX is mandatory (shall), forbidden (shall not) or optional (may).On SACCH, DTX can be independently configured for AMR, see the parameter section.

Speech aspects of DTX for AMR is described in GSM TS 06.93, ref. [10].During a call, the BTS sends the uplink speech frames to the TC with the following information:- RX_TYPE,- Mode_indication,- Information bits.

The RX_TYPE is described in the table below:

RX_TYPE Legend DescriptionSPEECH_GOOD Speech frame with CRC OK, Channel Decoder

soft values also OKSPEECH__DEGRADED Speech frame with CRC OK, but 1B bits and

class2 bits may be corrupted

SPEECH_BAD (likely) speech frame, bad CRC (or very badChannel Decoder measures)

SID_FIRST first SID marks the beginning of a comfort noiseperiod

SID_UPDATE SID update frame (with correct CRC)SID_BAD Corrupt SID update frame (bad CRC; applicable

only for SID_UPDATE frames)ONSET Precedes the first speech frame of a speech

burst.NO_DATA Nothing usable was received


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mAlcatel. The BTS first checks if the radio frame is a SID_UPDATE or a SID_FIRST frame.

When receiving uplink frames, the TC shall:- For SPEECH_GOOD frames, transmit them to the speech decoder,- For SPEECH_BAD or SID_BAD, trigger substitution and muting,- For SID_FIRST, generate comfort noise using the parameters from the last speech frames.- For SID_UPDATE, generate comfort noise using the comfort noise parameters included in theframe.

Note: After a handover, the first frame sent by an AMR MS is a SID_UPDATE frame. This avoidsthe muting of comfort noise when the TC changes (i.e. external channel change).

3.1.2.7 Classmark handling

No impact.

The fact that an MS is AMR-compatible or not is indicated in the MS bearer capabilities. Thisinformation is transparent for the BSS.

3.1.2.8 Normal assignment

The AMR is controlled on a per call basis by the MSC. In the ASSIGNMENT REQUEST, the MSCgives the Channel type IE, which indicates:- in octet 4 if FR or HR shall be used and if the BSS is allowed to change,- in octet 5 and followings, may indicate that AMR is allowed in HR or FR (GSM Speech full rateversion 3, referred also as AMR full rate speech version 1, or GSM Speech half rate version 3,referred also as AMR half rate speech version 1).The BSC activates the channel in the BTS by sending a CHANNEL ACTIVATION message,containing the IE Multirate configuration. It indicates the subset of codecs used for FR (or HR,respectively) link adaptation, the threshold and hysteresis sent to the MS for FR (or HR, respectively)link adaptation and, optionally, the start mode (i.e. the initial codec mode), see the parametersection.

If the initial codec mode is not given, the BTS chooses the default start mode depending on thenumber of codec modes contained in the subset:- 1 mode, then it is the default start mode.- 2 or 3 modes, then the most robust mode is chosen (lowest bit rate).- 4 modes, then second most robust is chosen (second lowest bit rate).Once the channel is activated within the BTS, the BSC sends all AMR relevant parameters to the MSin the ASSIGNMENT COMMAND message.

When the speech path is established and synchronisation performed between the TC and the BTS,the BTS checks if the Request or Indication Flag (RIF) given in the TRAU frame is coherent with thetype of Codec Mode (Indication or Command) that should be sent on the radio interface. Ifnecessary, a CMI_CMR alignment command is sent to the TC, see section TC / BTS interface.

Once the BTS detects that downlink CMI / CMR is synchronised between the TRAU frames and theradio interface, it starts codec mode adaptation.

3.1.2.9 Radio measurements

No impact.The metric for AMR codec adaptation is described in the new specification "AMR codec adaptation".


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mAlcatel. 3.1.2.10 Radio measurements data processing & Handover preparation

Channel adaptation principle:Two new handover causes are introduced for AMR channel mode adaptation (changing from FR toHR and vice-versa) of AMR calls.:- Cause 26: HR to FR channel adaptation due to low radio quality- Cause 27: FR to HR channel adaptation due to high radio qualityThese two causes are enabled by a single flag: EN_AMR_CA.These two causes of intracell handover belong to a new family called "Channel adaptation HO".As such,- they are checked after intercell emergency handover causes,- they must satisfy the intra-cell Level condition, whilst their trigger is based on quality criteria.

There are two ways to trigger Cause 26.The first way consists in triggering Cause 26 only if a previous intracell handover Cause 15 or 16have been previously detected in the serving cell for the current MS. This way is intended to non-hopping channels for which an intracell handover Cause 15 or 16 is sometimes not sufficient toimprove the quality of the call. If the quality is not sufficient due to a too high interference level,instead of continuing triggering intracell handover Cause 15 or 16, a HR-to-FR channel adaptation istriggered thanks to Cause 26.The second way applies when the intracell handover Causes 15 and 16 are both disable for AMRcalls. If a too high level of interference is detected in the serving cell for the current MS, Cause 26 isthen triggered. This second way intends to improve the quality of hopping channels which quality isgenerally not much improved after an intracell handover Cause 15 or 16.Since AMR is performing well in interference conditions, the thresholds for cause 15 & 16 areinstanciated for AMR, see parameter section.

The Cause 27 channel adaptation handover aims to reduce the number of busy TCH when the radioquality is very good and the serving cell becomes loaded. The channel adaptation consists inchanging the current full rate TCH to a half rate TCH.

Detailed trigger of channel adaptation cause 26 / 27:To evaluate the uplink & downlink quality of the radio link, the existing metric RXQUAL (0..7) is used.The downlink RXQUAL is measured by the MS and sent to the BTS in MEASUREMENT REPORTmessages.

A new threshold, THR_RXQUAL_CA (CA for Channel Adaptation), is introduced. It corresponds tothe limit, in terms of quality, between HR and FR usage: if the quality is below, FR channel shall beused, if the quality is better then a HR channel is sufficient.Its value depends on the load of the cell. In a cell heavily loaded, a HR channel is preferred evenwith a bad quality.

THR_RXQUAL_CA is an internal variable and is set to:- THR_RXQUAL_CA_NORMAL (O&M parameter) if LOAD_SV3 is set to FALSE,- THR_RXQUAL_CA_HIGH (O&M parameter) if LOAD_SV3 is set to TRUE.Recommended rule:THR_RXQUAL_CA_HIGH THR_RXQUAL_CA_NORMAL

A new variable OFFSET_CA is also introduced to have an hysteresis between FR and HR channels.Its value depends on the load of the cell.

OFFSET_CA is an internal variable and is set to:- OFFSET_CA_NORMAL (O&M parameter) if LOAD_SV3 is set to FALSE,- OFFSET_CA_HIGH (O&M parameter) if LOAD_SV3 is set to TRUE.

BSS MAY 6Highlight

BSS MAY 6Highlight



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mAlcatel. LOAD_SV3 is evaluated using existing mechanisms based on the ratio [free TCH / total TCH] and

comparison with an upper and a lower threshold set by O&M. See the Resource Allocation &Management section for details on the computation of LOAD_SV3.

AV_RXQUAL_UL_CA and AV_RXQUAL_DL_CA are the averaging of, respectively, the uplinkquality metric measured by the BTS and the quality measured by the MS, averaged overA_QUAL_CA_FR_HR or A_QUAL_CA_HR_FR measurements (respectively for adaptation FR to HRor HR to FR) with W_QUAL_CA as weighting parameter.To trigger channel mode adaptation, the following equations are checked during any AMR call.

Note: In the equations, the quality indicators are represented by their numeric value andconsequently are contra intuitive. RXQUAL(a) > RXQUAL(b) means that, for example,RXQUAL(a) = 7 and RXQUAL(b) = 0, i.e. RXQUAL(b) represents a better quality thanRXQUAL(a).The offset taking into account frequency hopping does not show in the equations to easereadibility.

If the following cause is true, then an intra-cell handover from HR to FR is triggered.Cause = 26 (HR to FR channel adaptation due to bad radio quality)

Current channel is Half Rate and EN_AMR_FR = enabledand Channel type is dual rate, changes allowedand AV_RXQUAL_UL_CA RXQUAL_CA + OFFSET_CA

or AV_RXQUAL_DL_CA RXQUAL_CA + OFFSET_CAand EN_AMR_CA = enabled

On A interface, this handover cause is mapped to "Uplink quality".

If the following cause is true, then an intra-cell handover from FR to HR is triggered.Cause = 27 (FR to HR channel adaptation due to good radio quality)

Current channel is Full Rate and EN_AMR_HR = enabledand Channel type is dual rate, changes allowedand AV_RXQUAL_UL_CA < RXQUAL_CAand AV_RXQUAL_DL_CA < THR_RXQUAL_CAand EN_AMR_CA = enabled

On A interface, this handover cause is mapped to "Better cell.

Interaction with intracell quality handover (cause 15 & 16):To control the interaction between cause 15/16 and channel adaptation (see channel adaptationprinciple), specific flags are introduced to activate separetely cause 15 and 16 for AMR calls, seeparameter section.To take into account AMR specific robustness to interference, specific thresholds are introduced forcause 15 & 16, see parameter section.

Interaction with inter-cell handover:The cause 26 is checked after cause 2 (too low quality on the uplink) and cause 4 (too low quality onthe downlink). That means that in case of bad quality and bad level, if an adjacent cell is availablethen an inter-cell handover will be triggered before any channel mode adaptation.


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mAlcatel.

THR_RXQUAL_CA_NORM

THR_RXQUAL_CA_HIGH

good quality: 0

bad quality: 7

THR_RXQUAL_CA_NORM +OFFSET_CA_NORM

THR_RXQUAL_CA_HIGH +OFFSET_CA_HIGH

Load = FALSE Load = TRUE

HO cause 26

HO cause 27

Full Rate

Half Rate

Quality

HO cause 26

HO cause 27

Full Rate

Half Rate

Figure 16: Thresholds for channel mode adaptation

Interaction with power control:The cause 26 is triggered even if the MS or the BTS does not transmit at maximum power. If thequality decreases, power control may be increasing the transmit power of the MS or the BTS justwhen the handover cause 26 (HR to FR) is triggered.The cause 26/27 are triggered independently from the power control algorithms.

Examples of configurations: An operator who wants to have:

- under normal load, only FR calls,- under high load, HR calls for qualities 0 to 3, with an hysteresis of 1,will set:THR_RXQUAL_CA_NORMAL = 0.0 THR_RXQUAL_CA_HIGH = 2.0OFFSET_CA_NORMAL = 0.0 OFFSET_CA_HIGH = 1.0

An operator who wants to have:- under normal load, HR calls for qualities 0 and 1, with an hysteresis of 1,- under high load, HR calls for qualities 0 to 4, with an hysteresis of 2,will set:THR_RXQUAL_CA_NORMAL = 0.0 THR_RXQUAL_CA_HIGH = 2.0OFFSET_CA_NORMAL = 1.0 OFFSET_CA_HIGH = 2.0

3.1.2.11 Resource allocation and management

Cell Load evaluation and HR / FR decision (normal assignment, inter-cell handover):The load evaluation strategy to decide on HR / FR allocation is modified to take benefit of AMR HRbetter quality compared to HR speech v1. The principle is to introduce specific load thresholds forAMR HR allocation, so that when load increases, AMR HR is allocated first and HR speech v1 is onlyallocated as a last resort. In other words, the cell can be declared "Loaded" sooner for AMR HRcapable mobiles. See the parameter section.

Note: this Load calculation is also used for Cause 26 / 27 evaluation.


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mAlcatel. Allocation for normal assignment:

No other impact.

Allocation for channel change:For AMR intra-cell handover, the channel mode is kept unchanged except for handover causes 26and 27 (see section 3.1.2.9 Handover Preparation). Resource Allocation and Management entityshall therefore be aware of the handover cause before allocating the target channel.

For AMR inter-cell channel change (internal or external, handover or directed retry), the existingmechanism is kept.

3.1.2.12 Handover Management

For internal handovers, HOM filters the candidate cells based on EN_AMR_HR/HR.

3.1.2.13 Internal channel change

When an AMR call has to perform an internal channel change, the BSC shall give to the target BTSall the AMR relevant parameters in the CHANNEL ACTIVATION message. Once the channel isactivated within the target BTS, the BSC sends all AMR relevant parameters to the MS in theASSIGNMENT COMMAND or HANDOVER COMMAND message only if these AMR parameters aredifferent than the ones used on the serving cell. If these AMR parameters remain identical, thennothing is added in the ASSIGNMENT COMMAND or HANDOVER COMMAND message and theMS switches to the target channel using the same AMR parameters as on the serving channel.

To establish the speech path on target channel, the MS and the BTS use the start mode (implicit orexplicit). The target BTS freezes the codec mode adaptation until the downlink synchronisationbetween CMI/CMR in TRAU frames and on the radio interface is assured, see section 3.1.2.3 TC /BTS interface.

3.1.2.14 External channel change

Serving BSS:In the HANDOVER REQUIRED message, the serving BSC uses the IE Old BSS to New BSSinformation to give to the target BSS the set of AMR codec used, the threshold and hysteresis sentto the MS for link adaptation and, optionally, the initial codec mode.

Target BSS:When a HANDOVER REQUEST is received concerning an incoming AMR call, the target BSC shallgive to the target BTS all the AMR parameters in the CHANNEL ACTIVATION message.

Once the channel is activated on the target BTS, the target BSC builds the HANDOVER COMMANDmessage, with all AMR relevant parameters only if these AMR parameters are different than theones used on the serving BSC. If these AMR parameters remain identical, then nothing is added inthe HANDOVER COMMAND message. To know the AMR parameters used by the serving BSC, thetarget BSC decodes the IE Old BSS to New BSS information contained in the HANDOVERREQUEST message.

When the MS receives the HANDOVER COMMAND message, if no AMR parameters are presentthen the MS switches to the target channel using the same AMR parameters as on the servingchannel.

To establish the speech path on target channel, the MS and the BTS use the start mode (implicit orexplicit). The target BTS freezes the codec mode adaptation until the downlink synchronisation


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mAlcatel. between CMI/CMR in TRAU frames and on the radio interface is assured, see section 3.1.2.3 TC /

BTS interface.

The figure below shows the case where the serving BSC and the target BSC use the same set ofAMR parameters, named set A.

HANDOVER REQUIRED(AMR param. A)

AMR on-going withparameters "A"

HANDOVER REQUEST(AMR param. A)

HANDOVER REQUEST ACK(HANDOVER COMMAND)

HANDOVER COMMAND(HANDOVER COMMAND)

HANDOVER COMMAND

CHANNEL ACTIVATION(AMR param. A)

CHANNEL ACTIVATION ACK

The MS establishes on target channel

TargetBTS

TargetBSC MSC

ServingBSC

ServingBTS


Figure 17: External handover with identical AMR parameters

The figure below shows the case where the AMR parameters are not identical in the two BSCs:

HANDOVER REQUIRED(AMR param. A)


HANDOVER REQUEST(AMR param. A)

HANDOVER REQUEST ACK(HANDOVER COMMAND,

AMR param. B)HANDOVER COMMAND(HANDOVER COMMAND,

AMR param. B)HANDOVER COMMAND

(AMR param. B)

CHANNEL ACTIVATION(AMR param. B)

CHANNEL ACTIVATION ACK

The MS establishes on target channel

TargetBTS

TargetBSC MSC

ServingBSC

ServingBTS

AMR on-going withparameters "B"

Figure 18: External handover with different AMR parameters


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mAlcatel. 3.1.2.15 Channel modification

When an in-call mode modification occurs from data to AMR speech, then the MODE MODIFYmessage sent to the BTS contains all the AMR parameters.

Once the new mode has been activated in the BTS, then the BSC sends a CHANNEL MODEMODIFY to the MS, with the AMR parameters.

To initiate the speech path, the MS and the BTS use the start mode (implicit or explicit). The BTSfreezes the codec mode adaptation until the downlink synchronisation between CMI/CMR in TRAUframes and on the radio interface is assured, see section 3.1.2.3 TC / BTS interface.

The mode modify procedure is never used to change AMR parameters following a logicalconfiguration change. On-line modification of AMR parameters is only taken into account for newcalls or after a handover.


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mAlcatel.

3.1.3 Interfaces

3.1.3.1 Radio interface, physical layer (05.xx series)

New AMR radio frames, with associated in-band signalling:

FR:- SPEECH frames with different codec modes- SID_UPDATE- SID_FIRST- ONSET

HR:- SPEECH frames with different codec modes- SID_UPDATE- SID_UPDATE_INH- SID_FIRST_P1- SID_FIRST_P2- SID_FIRST_INH- ONSET

3.1.3.2 Radio interface - Layer 2 (04.06)

No impact.

3.1.3.3 Radio interface - Layer 3 (04.08)

04.08 - CC part (for information)IE Bearer information, field speech version indication:- New codepoint for AMR full rate capability: GSM full rate speech version 3- New codepoint for AMR half rate capability: GSM half rate speech version 3

04.08 RR partASSIGNMENT COMMAND

IE Channel mode: new codepoint for AMR (Speech version 3)New IE MR configuration

HANDOVER COMMANDIE Channel mode: new codepoint for AMR (Speech version 3)New IE MR configuration

CHANNEL MODE MODIFYIE Channel mode: new codepoint for AMR (Speech version 3)New IE MR configuration

3.1.3.4 Abis interface (08.58)

CHANNEL ACTIVATIONIE Channel mode: new codepoint for AMR (Speech version 3)New IE MR configuration


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mAlcatel. MODE MODIFY

IE Channel mode: new codepoint for AMR (Speech version 3)New IE MR configuration

3.1.3.5 A interface (08.08)

HANDOVER REQUIREDField MR configuration information in the IE Old BSS to New BSS information.

HANDOVER REQUESTNew codes in Channel type IE.Field MR configuration information in the IE Old BSS to New BSS information.

ASSIGNMENT REQUESTNew codes in Channel type IE.

Note: new circuits pools have been added for the handling of AMR. The modified IE in GSM TS08.08 is IE 3.2.2.45 Circuit pool. This has no impact as circuit pools are not handled by the AlcatelBSS.

SFD:ADAPTIVE

MULTI

-RATESPEECH

CODEC

(AMR)

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All rights reserved. Passing on and copying of th isdocument, use and communication of its contents

not permitted without written authorisa tion from Alcate l.

3.2Operation

andmaintenance

3.2.1Param

eters


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Name Definition

A_QUAL_CA_FR_HR Quality averaging window size for FR-to-HR channel adaptation

A_QUAL_CA_HR_FR Quality averaging window size for HR-to-FR channel adaptation

AMR_FR_HYST Hysteresis for AMR FR codec mode adaptation

AMR_FR_SUBSET Bitmap (8 bits) defining the codec subset that shall be used forAMR FR calls (1 to 4 codecs).

AMR_FR_THR_1 Thresholds for AMR FR codec mode adaptation (I = 1, 2, 3)AMR_FR_THR_2 Thresholds for AMR FR codec mode adaptation (I = 1, 2, 3)AMR_FR_THR_3 Thresholds for AMR FR codec mode adaptation (I = 1, 2, 3)AMR_HR_HYST Hysteresis for AMR HR codec mode adaptation

AMR_HR_SUBSET Bitmap (6 bits) defining the codec subset that shall be used forAMR HR calls (1 to 4 codecs).

AMR_HR_THR_1 Thresholds for AMR HR codec mode adaptation (I = 1, 2, 3)AMR_HR_THR_2 Thresholds for AMR HR codec mode adaptation (I = 1, 2, 3)AMR_HR_THR_3 Thresholds for AMR HR codec mode adaptation (I = 1, 2, 3)AMR_START_MODE_FR Indicates the codec used at the beginning of a FR AMR call,

until codec mode adaptation is started by the BTS.

AMR_START_MODE_HR Indicates the codec used at the beginning of a HR AMR call,until codec mode adaptation is started by the BTS.

Downlink_DTX_enable_AMR_FR Enables / disables the use of downlink DTX for AMR FR speechcalls.

Downlink_DTX_enable_AMR_HR Enables / disables the use of downlink DTX for AMR HRspeech calls.

DTX_INDICATOR_SACCH_AMR Controls uplink DTX usage for GSM phase 2 MS. Applies only toAMR FR and AMR HR.

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

EN_AMR_FR controls wether AMR full rate is allowed in the cell

EN_AMR_HR controls wether AMR half rate is allowed in the cell

EN_INTRA_DL_AMR Enables/disables the detection of intracell downlink handovercause (cause 16) for AMR calls

EN_INTRA_UL_AMR Enables/disables the detection of intracell uplink handover


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mAlcatel. cause (cause 15) for AMR calls

L_RXQUAL_DL_H_AMR Downlink quality threshold for handovers (cause 16) on AMRcalls

L_RXQUAL_UL_H_AMR Uplink quality threshold for handovers (cause 15) on AMR callsOFFSET_CA_HIGH Offset for channel adaptation hysteresis under high load

OFFSET_CA_NORMAL Offset for channel adaptation hysteresis under normal load

THR_FR_LOAD_L_SV3 Lower load threshold for allocation policy of AMR HR in a dualrate cell supporting AMR HR

THR_FR_LOAD_U_SV3 higher load threshold for allocation policy of AMR HR in a dualrate cell supporting AMR HR

THR_RXQUAL_CA_HIGH Threshold for channel adaptation under high load

THR_RXQUAL_CA_NORMAL Threshold for channel adaptation under normal load

W_QUAL_CA Averaging weight applicable for full quality (Channel adaptation)

3.2.2 PM counters

Name Definition

NB_TCH_HO_ATPT_27_GoodQualFR

Number of intracell handover -attempts, with the cause 27: "FRto HR channel adaptation due to good radio quality" on a TCHchannel.

NB_TCH_HO_ATPT_26_BadQualHR

Number of intracell handover -attempts, with the cause 26:"HR to FR channel adaptation due to bad radio quality" on aTCH channel.

NB_TCH_NOR_AMR_HR_ALLOC number of TCH normal assignment/mode modify in HR AMRusage - whose channel is allocated in the BSC

NB_TCH_NOR_AMR_FR_ALLOC number of TCH normal assignment/mode modify in FR AMRusage - whose channel is allocated in the BSC

NB_TCH_AMR_REQ Number of TCH normal assignment requests from AMRmobiles

NB_TCH_NOR_AMR_ALLOC = NB_TCH_NOR_AMR_FR_ALLOC+ NB_TCH_NOR_AMR_HR_ALLOC

NB_TCH_HO_ATPT_QUAL_AMR = NB_TCH_HO_ATPT_26_BadQualHR+ NB_TCH_HO_ATPT_27_GoodQualFR

SFD:ADAPTIVE

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3.2.3FaultM

anagem

ent

Nonew

requirement

.


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mAlcatel.

4. SUBSYSTEM IMPACTS

4.1 BTS

Layer 1

Encoder

Manages channel coding according to the Codec_Mode control bits received in the downlink TRAUframe and which indicate the codec used.

Manages DTX according to the TX_TYPE (SPEECH_GOOD, SID_FIRST, SID_UPDATE,NO_DATA) control bits received in the downlink TRAU frame.Manages the in-band signalling to insert the CMI/CMR commands. CMI is received from thetranscoder and CMR is received from the decoder. CMI/CMR shall be aligned with the TDMA frameaccording to the rules defined in GSM 05.02 (the rules are not the same depending on whether DTXis active or not).Decoder

Memorises the codec subset to be used for the call.

Manages channel decoding according to the CMI bits received with the uplink speech frame by in-band signalling (CMI is sent each two speech frames).Manages the codec mode adaptation algorithm in uplink. It evaluates if the MS shall change thecurrent codec. When the codec shall be changed it sends a message to the encoder with the CMRcommand containing the new codec to be used. Only change between two adjacent codecs can berequested.

Interface encoder-decoder

The IX_ROU message shall be modified to include information for alignment of CMI/CMR on Abisinterface with CMI/CMR on radio interface.

The IX_ROU message shall be used to include information to allow the decoder to start codec modeadaptation at the end of the synchronisation phase.

The IX_ROU message shall also be used to transfer the CMR command to be inserted in thedownlink speech frame. This message is sent by the decoder each time it wants to change the codecused in uplink by the MS.

TRAU Interface

For AMR full rate, TRAU frames based on the same synchronisation pattern as for FR/EFR and withframe type set to AMR shall be supported. The definition of control bits and data bits of the AMRTRAU frame is defined in GSM 08.60.

For AMR half rate, 8 Kb/s TRAU frames use a specific synchronisation pattern, see GSM 08.61.

Layer 3


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mAlcatel. The checking of the Channel Activation and Mode Modify messages shall include the checking of the

new IE MR configuration and of the speech version 3 (AMR) code point in the IE ChannelMode.

Interface layer 1/layer 3

The configuration message (ID_CHC) shall include: The sub-set of AMR codec used The thresholds and hysteresis used to change from one codec mode to another codec mode.

4.2 BSC

4.2.1 Short description BSC impact

The AMR impact on the BSC can be divided in two parts:

Impact due to codec mode adaptation:

After checking the MS and cell capability for AMR the same AMR-related information mustbe delivered towards the BTS and the MS to make the codec adaptation possible.

This information consists in: The subset of codecs for FR/HR configured by O&M on a BSS basis. The threshold values and the hysteresis values to allow codec mode changes

In case of external and internal handover the target BSC has to compare the AMRparameters it receives from the serving BSC (via MSC) with the available AMR parameters.If differentiating, the available parameters should be sent towards the MS and BTS.

Impact due to channel mode adaptation:

The Channel mode adaptation capability for AMR will be verified by checking a new AMRdependent flag.

For intra-cell handovers two new causes will be defined to check the possibility ofadapting FR to HR and reverse for AMR calls.

For inter-cell handovers AMR calls will be handled as normal calls: checking on rate/typepreferences and load conditions (no additional impact).

Impact due to new cell load evaluation for AMR calls

4.3 Transcoder

Supports all speech codecs for AMR full rate.

Supports all speech codecs for AMR half rate except 7.95.

Changes from one codec mode to another according to the DL_codec_mode received in the uplinkTRAU frame.


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mAlcatel. 4.4 MFS

None.

4.5 OMC_RGenerally for Telecom features, this is a simple reference to the Operations and Maintenancesection.However when needed the principles and guidelines for the presentation towards the operator shallbe given here.What needs to be presented/adjusted by the OMC-R operator ?What shall be autonomously determined by the OMC-R SW ?New parameters: see section 3.2.1.

5. PERFORMANCE & SYSTEM DIMENSIONING

5.1 Traffic model

The intra-cell handover rate is increased with AMR calls when channel adaptation is enabled.

5.2 Performance

Radio performances:The BTS respects the performance requirements given in GSM TS 05.05, ref.[3].

5.3 Load constraints

The rate of intra-cell handover for channel mode adaptation may increase the BSC processing loadand the Abis signalling load. These aspects have to be introduced in the tools for load simulation.

SFD:ADAPTIVE

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6.OPEN

POINTS

None.


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7. IMPACTS SUMMARYEquipments:

BTS BSC MFS TC OMC-RSW SW none SW SW

Interfaces:

TelecomRadio Abis A Ater BTS-TC MFS-BTS MFS-BSC GbX X X none X none none none

O&MAbis-O&M BSC-O&M TC-O&M MFS-O&M Q3none X none none X

List of Impacted Step2:

TelecomNormal AssignmentChannel modificationResource A

alcatel amr

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