GSM Coding Scheme

Copyright 2003, ZTE CORPORATION Copyright 2003, ZTE CORPORATION

GSM Coding SchemeGSM Coding Scheme

MOBILE DIVISIONMOBILE DIVISION

ZTE CORPORATIONZTE CORPORATION

Oct, 2004Oct, 2004

Copyright 2003, ZTE CORPORATION

GSM Voice ServiceGSM Voice Service

GSM Packet ServiceGSM Packet Service

AgendaAgenda


Voice service of GSMVoice service of GSM

FRFR

Full Rate Full Rate speech/channelspeech/channel

EFREFR

Enhanced Enhanced Full RateFull Rate

HRHR

Half Rate Half Rate speech/channelspeech/channel

AMRAMR

Adaptive Muti-Rate Adaptive Muti-Rate speechspeech


Voice service flow of GSMVoice service flow of GSM

MSCBTS BSCMS

Um 22.8kbps/11.4kbps

A interface A-law 64kbps

Abis interface 16kbps/8

kVoice Code(TC)

Channel Code(CCU)


Voice ServiceVoice Service

Sampling frequency

8KHz(0 ～ 3400Hz voice)

Speech frame: 20ms

8KHz×20ms=160


Compare with PSTN and PHSCompare with PSTN and PHS

PSTN

PCM: 64kbps (A-law or µ-law), MOS ＝ 4.3

PHS （ PCS ）

ADPCM: 32kbps, MOS ＝ 4.3

GSM

<16kbps. MOS<4.1

Specific codec algorithm shall be adopted.


FR(Full Rate)FR(Full Rate)

Algorithm: RPE-LTP-LPC

Data rate after encoding: 13kbps

Quality of data after encoding: MOS ＝ 3.8

LPC LTP RPE13kbps64kbps

FR encoding

encoding

decoding


EFR(Enhanced Full Rate)EFR(Enhanced Full Rate)

Algorithm: ACELP

Data rate after encoding: 12.2kbps


LPC LTP ACE12.2kbps64kbps

EFR encoding

encoding

decoding


HR(Half Rate)HR(Half Rate)

LPC LTP VSE5.6kbps64kbps

HR encoding

encoding

decoding

Algorithm: VSELP

Data rate after encoding: 5.6kbps



AMR(Adaptive Multi-Rate)AMR(Adaptive Multi-Rate)

LPC LTP MR-ACEAMR64kbps

HR encoding

encoding

decoding

Algorithm: MR-ACELP

Data rate after encoding: 4.75 kbps - 12.2kbps



0 4.75 kbps 1 5.15 kbps 2 5.90 kbps 3 6.70 kbps4 7.40 kbps5 7.95 kbps 6 10.2 kbps 7 12.2 kbps (GSM EFR)

AMR(Adaptive Multi-Rate)AMR(Adaptive Multi-Rate)

1. Select proper encoding rate adaptively according to

state report of different channel.

2. Be prepared for transition from 2G to 3G.

3. Changeable data data rate is suitable for packet

transmission such as IP transmission.


Voice decode modelVoice decode model

A(z)1 s(n)^

+

v(n)

c(n)

u(n)

g c

fixedcodebook

adaptive codebook g p

LP synthesis

post-filterings'(n)^


Comparison of GSM voice code schemesComparison of GSM voice code schemes

encodingscheme

rate (kbps) Quality(MOS) complexitycost

/channeltransit to

3GFR 13 normal(3.8) lowest lowest No

EFR 12.2 high(4.1) high high No

HR 5.6lower(3.7), declining very

rapidly as environmentgoes bad

higher highest No

AMR 4.75~12.2

Aim at 3G. The bestquality for both networkand subscriber. MOS isbetween HR and EFR.

highest highest Yes


Protection of voice channel encoding

Um:

FR: 22.8kbps

HR: 11.4kbps

Protect bit:

FR ： 13 ＋ 9.8 ＝ 22.8 (kbps)

EFR ： 12.2 ＋ 10.6 ＝ 22.8 (kbps)

HR ： 5.6 ＋ 5.8 ＝ 11.4(kbps)

AMR ：？？＋？？＝ 22.8 (kbps)

？？＋？？＝ 11.4 (kbps)


Voice Quality of HRVoice Quality of HR

Encodingscheme

Algorithmbit rate after

encoding (bps)bit rate onAbis (bps)

MOS

FR RPE-LTP-LPC 13k 16k 3.8EFR ACELP 12.2k 16k 4.1HR VSELP 5.6k 8k/16k 3.7


Abis interface unit and TRAU shall be upgraded to support HR

HRHR

BBTTSS

BBSSCC

TTCCUU

BBSSCC

RRMMMM

OMC-R server OMC-R Client

LAN

BBSSCC

SSCCMM

BBTTSS

BBSSCC

TTCCUU

BBSSCC

TTCCUU

BBSSCC

RRMMMM

BBSSCC

RRMMMM

OMC-R server OMC-R Client

LAN

BBSSCC

SSCCMM

BBSSCC

SSCCMM

Processing of HR frame

Processing of HR configuration, PM and service flow

Uplink: 8k to 16k conversionDownlink: 16k to 8k conversion

Uplink: HR frame decoded to 64k voice channelDownlink: 64k voice channel encoded to 16k HR channel

16k HR channel16k HR channel A interface 64k voice channel

Abis interface 8k HR channelSupport HR

handset service

Processing of HR configuration, PM and related OMM


1. Load of MP

a) Load of MP increase by about 1 ％ . The structure of database is more complicated and the quantity of PM counter increase.

2. RF parameters

a) Network congestion will be improved

b) No impact to the coverage

c) Quality of voice is lower

Effect of HR to the systemEffect of HR to the system


GSM Voice ServiceGSM Voice Service

GSM Packet ServiceGSM Packet Service

AgendaAgenda


GPRSGPRS

(General Packet Radio Services)(General Packet Radio Services)

Scheme Code

Rate

USF

bits

Pre-

coded

USF

bits

Radio

Block

(excl.

USF

and BCS)

BCS Tail

bits

Coded

bits

Punctured

bits

Data

Rate

(kbps)

CS-1 1/2 3 3 181 40 4 456 0 9.05

CS-2 ~2/3 3 6 268 16 4 588 132 13.4

CS-3 ~3/4 3 6 312 16 4 676 220 15.6

CS-4 1 3 12 428 16 0 456 0 21.4


Enhanced GSM Phase II+, higher bit rate.

The max bit rate of GSM data service is 14.4kbps, and the max bit rate of EDGE can reach up to 48kbps.

EDGE is a good alternative of UMTS 3G.

EDGEEDGE

((Enhanced Data rate for GSM EvolutionEnhanced Data rate for GSM Evolution ) )


EDGE EDGE channel encoding schemechannel encoding scheme

凿孔方案（ P1-P3 ）的设计要遵循一定的规则和流程，比如每个 MCS 可有多个凿孔方

Scheme ModulateMax bit rate

(kbps)code rate

rate ofhead code

Pics(20ms)

Sector

MCS-9 59. 2 1 0. 36 2 AMCS-8 59. 2 0. 92 0. 36 2 AMCS-7 44. 8 0. 76 0. 36 2 BMCS-6 29. 6 0. 49 1/3 1 AMCS-5 22. 4 0. 37 1/3 1 BMCS-4 17. 6 1 0. 51 1 CMCS-3 14. 8 0. 85 0. 51 1 AMCS-2 11. 2 0. 66 0. 51 1 BMCS-1 8. 8 0. 53 0. 51 1 C

GMSK

8PSK

Copyright 2003, ZTE CORPORATION Copyright 2003, ZTE CORPORATION

GSM Coding Scheme

Documents

rate speechchannel efr

ms 8khz20ms