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GSM Traffic Channel Processing through physical layer

Introduction

This article on traffic channel processing through physical layer covers Speech channel at Full rate(TCH/FS),Speech channel at Half rate(TCH/HS), Speech channel at Half rate(TCH/EFR),Adaptive Multi rate speech channel at full rate(TCH/AFS), Adaptive Multi rate speech channel at full rate(TCH/AHS),Wideband Adaptive Multi Rate Speech Channel at full rate (TCH/WFS),Data Channel at full rate 12.0 Kbits/s radio interface rate (TCH/F9.6) as per 3GPP TS 45.003 standard. The idea of this article is to provide block schematic view of traffic channel processing(speech/data).

Speech channel at Full rate(TCH/FS)

speech channel full rate TCH/FS

Speech channel at Half rate(TCH/HS)

speech channel half rate TCH/HS

Speech channel at Half rate(TCH/EFR)

speech channel half rate TCH/EFR

Adaptive Multi rate speech channel at full rate(TCH/AFS)

This section of the page describes the coding for the different frame formats used for TCH/AFS.
SID_UPDATE Used to convey comfort noise parameters during DTX
SID_FIRST Marker to define end of speech, start of DTX
ONSET Used to signal the Codec mode for the first speech frame after DTX
SPEECH Speech frames
RATSCCH Frames used to convey RATSCCH messages

Codec Mode Rate No. of input bits to Conv.Encoder No. of output bits from Conv.Encoder No. of punctured bits
TCH/AFS12.2 1/2 250 508 60
TCH/AFS10.2 1/3 210 642 194
TCH/AFS7.95 1/3 165 513 65
TCH/AFS7.4 1/3 154 474 26
TCH/AFS6.7 1/4 140 576 128
TCH/AFS5.9 1/4 124 520 72
TCH/AFS5.15 1/5 109 565 117
TCH/AFS4.75 1/5 101 535 87


Adaptive Multi rate speech channel full rate AMR/TCH-AFS/SID UPDATE


Adaptive Multi rate speech channel full rate AMR/TCH-AFS/SID FIRST


Adaptive Multi rate speech channel full rate AMR/TCH-AFS/ONSET


gsm physical layer transmitter


gsm physical layer transmitter



Adaptive Multi rate speech channel at full rate(TCH/AHS)

This section of the page describes the coding for the different frame formats used for TCH/AHS.
SID_UPDATE Used to convey comfort noise parameters during DTX
SID_UPDATE_INH Used to inhibit the second part of a SID_UPDATE frame if there is a speech onset
SID_FIRST_P1 First part of marker to define end of speech, start of DTX
SID_FIRST_P2 Second part of marker to define end of speech, start of DTX
SID_FIRST_INH Used to inhibit the second part of a SID_FIRST_P1 frame if there is a speech onset
ONSET Used to signal the Codec mode for the first speech frame after DTX
SPEECH Speech frames
RATSCCH_MARKER Marker to identify RATSCCH frames
RATSCCH_DATA Frame that conveys the actual RATSCCH message

Codec Mode No. of input bits to Conv.Encoder Rate No. of output bits from Conv.Encoder No. of punctured bits
TCH/AHS7.4 129 1/2 266 78
TCH/AHS7.4 126 1/2 260 64
TCH/AHS6.7 116 1/2 240 40
TCH/AHS5.9 108 1/2 224 16
TCH/AHS5.15 97 1/3 303 91
TCH/AHS4.75 89 1/3 285 73

Wideband Adaptive Multi Rate Speech Channel at full rate (TCH/WFS)

This section of the page describes the coding for the different frame formats used for TCH/WFS.
SID_UPDATE Used to convey comfort noise parameters during DTX
SID_FIRST Marker to define end of speech, start of DTX
ONSET Used to signal the Codec mode for the first speech frame after DTX
SPEECH Speech frames
RATSCCH Frames used to convey RATSCCH messages

Codec Mode Rate No. of input bits to Conv.Encoder No. of output bits from Conv.Encoder No. of punctured bits
TCH/WFS12.65 1/2 259 526 78
TCH/WFS8.85 1/3 183 561 113
TCH/WFS6.60 1/4 140 576 128

Data Channel at full rate 12.0 Kbits/s radio interface rate (TCH/F9.6)

data channel full rate TCH/F9.6

Useful Links

GSM tutorial covering GSM basics,network architecture,network elements,system specifications,applications,GSM burst types,GSM frame structure or frame hierarchy, logical channels,physical channels, GSM physical layer or speech processing and GSM mobile network entry or call setup procedure, Read more.
GSM Protocol stack , covers layer 1,2 and 3 of GSM network elements MS,BTS,BSC and MSC.READ MORE.

GSM Standard References

3GPP TS 45.002 describes burst building and burst multiplexing
3GPP TS 45.003 describes coding and interleaving
3GPP TS 45.004 describes differential encoding and modulation
3GPP TS 45.005 describes transmitter,receiver and antenna part
3GPP TS 43.020 & 23.221 describes encryption/ciphering part

RELATED LINKS

GSM RF planning
GSM mobile originated call flow
GSM Mobile Terminated Call flow
GSM Tutorial
GSM protocol stack
GSM physical layer
GPRS protocol stack
GPRS tutorial

RF and Wireless Terminologies


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