SIST ETS 300 575 E4:2003
(Main)Digital cellular telecommunications system (Phase 2) (GSM); Channel coding (GSM 05.03 version 4.5.1)
Digital cellular telecommunications system (Phase 2) (GSM); Channel coding (GSM 05.03 version 4.5.1)
Strategic CRs A012 to GSM 05.03 v.4.4.0
Digitalni celični telekomunikacijski sistem (faza 2) – Kodiranje kanalov (GSM 05.03, različica 4.5.1)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST ETS 300 575 E4:2003
01-december-2003
'LJLWDOQLFHOLþQLWHOHNRPXQLNDFLMVNLVLVWHP ID]D ±.RGLUDQMHNDQDORY *60
UD]OLþLFD
Digital cellular telecommunications system (Phase 2) (GSM); Channel coding (GSM
05.03 version 4.5.1)
Ta slovenski standard je istoveten z: ETS 300 575 Edition 4
ICS:
33.070.50 Globalni sistem za mobilno Global System for Mobile
telekomunikacijo (GSM) Communication (GSM)
35.040 Nabori znakov in kodiranje Character sets and
informacij information coding
SIST ETS 300 575 E4:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST ETS 300 575 E4:2003
---------------------- Page: 2 ----------------------
SIST ETS 300 575 E4:2003
EUROPEAN ETS 300 575
TELECOMMUNICATION December 1997
STANDARD Fourth Edition
Source: SMG Reference: RE/SMG-020503PR4
ICS: 33.020
Key words: Digital cellular telecommunications system, Global System for Mobile communications (GSM)
R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
Digital cellular telecommunications system (Phase 2);
Channel coding
(GSM 05.03 version 4.5.1)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
X.400: c=fr, a=atlas, p=etsi, s=secretariat - Internet: secretariat@etsi.fr
Tel.: +33 4 92 94 42 00 - Fax: +33 4 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1997. All rights reserved.
---------------------- Page: 3 ----------------------
SIST ETS 300 575 E4:2003
Page 2
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.
---------------------- Page: 4 ----------------------
SIST ETS 300 575 E4:2003
Page 3
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
Contents
Foreword.5
1 Scope .7
1.2 Normative references.7
1.3 Definitions and abbreviations .8
2 General.8
2.1 General Organization.8
2.2 Naming Convention .10
3 Traffic Channels (TCH) .10
3.1 Speech channel at full rate (TCH/FS and TCH/EFS) .10
3.1.1 Preliminary channel coding for EFR only .11
3.1.1.1 CRC calculation.11
3.1.1.2 Repetition bits .11
3.1.1.3 Correspondence between input and output of preliminary
channel coding.11
3.1.2 Channel coding for FR and EFR .12
3.1.2.1 Parity and tailing for a speech frame .12
3.1.2.2 Convolutional encoder .12
3.1.3 Interleaving.13
3.1.4 Mapping on a Burst .13
3.2 Speech channel at half rate (TCH/HS) .13
3.2.1 Parity and tailing for a speech frame.13
3.2.2 Convolutional encoder.14
3.2.3 Interleaving.15
3.2.4 Mapping on a burst.15
3.3 Data channel at full rate, 12,0 kbit/s radio interface rate (9,6 kbit/s services
(TCH/F9.6)).15
3.3.1 Interface with user unit .15
3.3.2 Block code.15
3.3.3 Convolutional encoder.16
3.3.4 Interleaving.16
3.3.5 Mapping on a Burst .16
3.4 Data channel at full rate, 6.0 kbit/s radio interface rate (4.8 kbit/s services (TCH/F4.8)) .16
3.4.1 Interface with user unit .16
3.4.2 Block code.17
3.4.3 Convolutional encoder.17
3.4.4 Interleaving.17
3.4.5 Mapping on a Burst .17
3.5 Data channel at half rate, 6.0 kbit/s radio interface rate (4.8 kbit/s services (TCH/H4.8)).17
3.5.1 Interface with user unit .17
3.5.2 Block code.17
3.5.3 Convolutional encoder.17
3.5.4 Interleaving.17
3.5.5 Mapping on a Burst .18
3.6 Data channel at full rate, 3,6 kbit/s radio interface rate (2,4 kbit/s and less services
(TCH/F2.4)).18
3.6.1 Interface with user unit .18
3.6.2 Block code.18
3.6.3 Convolutional encoder.18
3.6.4 Interleaving.18
3.6.5 Mapping on a Burst .18
3.7 Data channel at half rate, 3.6 kbit/s radio interface rate (2.4 kbit/s and less services
(TCH/H2.4)) .18
---------------------- Page: 5 ----------------------
SIST ETS 300 575 E4:2003
Page 4
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
3.7.1 Interface with user unit. 18
3.7.2 Block code . 19
3.7.3 Convolutional encoder . 19
3.7.4 Interleaving . 19
3.7.5 Mapping on a Burst. 19
4 Control Channels . 19
4.1 Slow associated control channel (SACCH). 19
4.1.1 Block constitution. 19
4.1.2 Block code . 19
4.1.3 Convolutional encoder . 20
4.1.4 Interleaving . 20
4.1.5 Mapping on a Burst. 20
4.2 Fast associated control channel at full rate (FACCH/F). 20
4.2.1 Block constitution. 20
4.2.2 Block code . 20
4.2.3 Convolutional encoder . 20
4.2.4 Interleaving . 20
4.2.5 Mapping on a Burst. 21
4.3 Fast associated control channel at half rate (FACCH/H) . 21
4.3.1 Block constitution. 21
4.3.2 Block code . 21
4.3.3 Convolutional encoder . 21
4.3.4 Interleaving . 21
4.3.5 Mapping on a Burst. 22
4.4 Broadcast, Paging, Access grant and Cell broadcast channels (BCCH, PCH, AGCH,
CBCH). 22
4.5 Stand-alone dedicated control channel (SDCCH). 22
4.6 Random access channel (RACH) . 23
4.7 Synchronization channel (SCH) . 23
4.8 Handover Access Burst. 24
Annex A (informative): Summary of Channel Types . 36
Annex B (informative): Summary of Polynomials used for Convolutional Codes. 37
History. 38
---------------------- Page: 6 ----------------------
SIST ETS 300 575 E4:2003
Page 5
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
Foreword
This fourth edition European Telecommunication Standard (ETS) has been produced by the Special
Mobile Group (SMG) of the European Telecommunications Standards Institute (ETSI).
This ETS specifies the channel coding of used within the digital cellular telecommunications system
(Phase 2).
The specification from which this ETS has been derived was originally based on CEPT documentation,
hence the presentation of this ETS may not be entirely in accordance with the ETSI/PNE Rules.
Transposition dates
Date of adoption of this ETS: 5 December 1997
Date of latest announcement of this ETS (doa): 31 March 1998
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 30 September 1998
Date of withdrawal of any conflicting National Standard (dow): 30 September 1998
---------------------- Page: 7 ----------------------
SIST ETS 300 575 E4:2003
Page 6
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
Blank page
---------------------- Page: 8 ----------------------
SIST ETS 300 575 E4:2003
Page 7
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
1 Scope
A reference configuration of the transmission chain is shown in GSM 05.01. According to this reference
configuration, this European Telecommunication Standard (ETS) specifies the data blocks given to the
encryption unit.
It includes the specification of encoding, reordering, interleaving and the stealing flag. It does not specify
the channel decoding method.
The definition is given for each kind of logical channel, starting from the data provided to the channel
encoder by the speech coder, the data terminal equipment, or the controller of the MS or BS. The
definitions of the logical channel types used in this technical specification are given in GSM 05.02, a
summary is in annex 1.
1.2 Normative references
This ETS incorporates by dated and undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references, the
latest edition of the publication referred to applies.
[1] GSM 01.04 (ETR 100): "Digital cellular telecommunications system (Phase 2);
Abbreviations and acronyms".
[2] GSM 04.08 (ETS 300 557): "Digital cellular telecommunications system
(Phase 2); Mobile radio interface layer 3 specification".
[3] GSM 04.21 (ETS 300 562): "Digital cellular telecommunications system
(Phase 2); Rate adaption on the Mobile Station - Base Station System (MS -
BSS) Interface ".
[4] GSM 05.01 (ETS 300 573): "Digital cellular telecommunications system
(Phase 2); Physical layer on the radio path; General description".
[5] GSM 05.02 (ETS 300 574): "Digital cellular telecommunications system
(Phase 2); Multiplexing and multiple access on the radio path".
[6] GSM 05.05: (ETS 300 577): "Digital cellular telecommunications system
(Phase 2); Radio transmission and reception".
[7] GSM 06.10 (ETS 300 580-2): "Digital cellular telecommunications system
(Phase 2); Full rate speech transcoding".
[8] GSM 06.20 (ETS 300 581-2): "Digital cellular telecommunications system; Half
rate speech Part 2: Half rate speech transcoding".
[9] GSM 06.60 (prEN 301 245): "Digital cellular telecommunications system
(Phase 2); Enhanced Full Rate (EFR) speech transcoding".
---------------------- Page: 9 ----------------------
SIST ETS 300 575 E4:2003
Page 8
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
1.3 Definitions and abbreviations
Abbreviations used in this ETS are listed in GSM 01.04.
2 General
2.1 General Organization
Each channel has its own coding and interleaving scheme. However, the channel coding and interleaving
is organized in such a way as to allow, as much as possible, a unified decoder structure.
Each channel uses the following sequence and order of operations:
- The information bits are coded with a systematic block code, building words of information + parity
bits.
- These information + parity bits are encoded with a convolutional code, building the coded bits.
- Reordering and interleaving the coded bits, and adding a stealing flag, gives the interleaved bits.
All these operations are made block by block, the size of which depends on the channel. However, most
of the channels use a block of 456 coded bits which is interleaved and mapped onto bursts in a very
similar way for all of them. Figure 1 gives a diagram showing the general structure of the channel coding.
This block of 456 coded bits is the basic structure of the channel coding scheme. In the case of full rate
speech TCH, this block carries the information of one speech frame. In case of control channels, it carries
one message.
In the case of half rate speech TCH, the information of one speech frame is carried in a block of
228 coded bits.
In the case of the Enhanced full rate speech the information bits coming out of the source codec first go
though a preliminary channel coding. Then the channel coding as described above takes place.
In the case of FACCH, a coded message block of 456 bits is divided into eight sub-blocks. The first four
sub-blocks are sent by stealing the even numbered bits of four timeslots in consecutive frames used for
the TCH. The other four sub-blocks are sent by stealing the odd numbered bits of the relevant timeslot in
four consecutive used frames delayed 2 or 4 frames relative to the first frame. Along with each block of
456 coded bits there is, in addition, a stealing flag (8 bits), indicating whether the block belongs to the TCH
or to the FACCH. In the case of SACCH, BCCH or CCCH, this stealing flag is dummy.
Some cases do not fit in the general organization, and use short blocks of coded bits which are sent
completely in one timeslot. They are the random access messages of the RACH on uplink and the
synchronization information broadcast of the SCH on downlink.
---------------------- Page: 10 ----------------------
SIST ETS 300 575 E4:2003
Page 9
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
TCH/EFS
(Enhanced full
rate speech TCH)
speech fram e
244 bits
3.I
cyclic code
+ repetition
in: 244
out: 260
3.I.I
interface
0
TC H/FS
TCH/HS SACCH, FACCH,
(full rate
(half rate RACH,
BCCH, CBCH, PCH
speech TCH)
speech TCH) data TCH s SCH
AGCH, SDCCH
speech frame speech frame
data fram e
message message
112 bits 260 bits
N0 bits
184 bits P0 bits
3.2 3.1 3.n.1
4.6, 4.7
4.1.1
interface
1
cyclic code cyclic code cyclic code
Fire code
+tail
+ tail + tail
+ tail
+tail
in: N0 bits
in: 112 bits in: 260 bits in: P0 bits
in: 184 bits
out: N 1 bits
out: 121 bits out: 267 bits out: P1 bits
out: 228 bits
3.n.2
3.2.1 4.6, 4.7
3.1.2.1 4.1.2
interface
2
convolutional convolutional
convolutional convolutional convolutional
code code
code code code
k=7, 2 classes k=5, 2 classes
k=5, rate 1/2 k=5, rate r k=5, rate 1/2
in: 121 bits in: 267 bits
in: 228 bits in: N1 bits in: P1 bits
out: 228 bits out: 456 bits
out: 456 bits out: 456 bits out: 2*P1 bits
3.2.2
3.1.2.2 4.1.3 3.n.3 4.6, 4.7
interface
3
TCH/F2.4 others
reordering and partitioning reordering and partitioning
+stealing flag
+stealing flag
in: 456 bits
in: 228 bits
diagonal interleaving
out: 4 blocks out: 8 blocks
+ stealing flags
3.2.3 3.1.3, 4.1.4, 4.3.4
in: 456 bits
out: 4 blocks
TCH/FS , FACCH others
diagonally interleaved
TCH/F2.4 TCH/EFS
to depth 19, starting
on consecutive bursts
block diagonal block diagonal
block rectangular
3.n.4
interleaving
interleaving
in te rlea v in g
in: 4 blocks in: 8 blocks
in: 8 blocks
out: pairs of out: pairs of
out: pairs of
blocks blocks
blocks
3.2.3 3.1.3, 4.3.4
4.1.4
interface
4
encryption unit
Figure 1: Channel Coding and Interleaving Organization
In each box, the last line indicates the chapter defining the function. In the case of RACH, P0=8 and
P1=18; in the case of SCH, P0=25 and P1=39. In the case of data TCHs, N0, N1 and n depend on
the type of data TCH.
Interfaces:
1) information bits (d);
2) information + parity + tail bits (u);
3) coded bits (c);
4) interleaved bits (e).
---------------------- Page: 11 ----------------------
SIST ETS 300 575 E4:2003
Page 10
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
2.2 Naming Convention
For ease of understanding a naming convention for bits is given for use throughout the technical
specification:
- General naming
"k" and "j" for numbering of bits in data blocks and bursts;
"K " gives the amount of bits in one block, where "x" refers to the data type;
x
"n" is used for numbering of delivered data blocks where;
"N" marks a certain data block;
"B" is used for numbering of bursts or blocks where;
"B " marks the first burst or block carrying bits from the data block with n = 0 (first data block in the
0
transmission).
- Data delivered to the preliminary channel encoding unit (for EFR only):
s(k) for k = 1., K
s
- Data delivered by the preliminary channel encoding unit (for EFR only) before bits rearrangement
w(k) for k = 1., K
w
- Data delivered to the encoding unit (interface 1 in figure 1):
d(k) for k = 0,1,.,K - 1
d
- Data after the first encoding step (block code, cyclic code; interface 2 in figure 1):
u(k) for k = 0,1,.,K - 1
u
- Data after the second encoding step (convolutional code; interface 3 in figure 1):
c(n,k) or c(k) for k = 0,1,.,K - 1
c
n = 0,1,.,N,N + 1,.
- Interleaved data:
i(B,k) for k = 0,1,.,K - 1
i
B = B , B +1,.
0 0
- Bits in one burst (interface 4 in figure 1):
e(B,k) for k = 0,1,.,114,115
B = B , B + 1,.
0 0
3 Traffic Channels (TCH)
Two kinds of traffic channel are considered: speech and data. Both of them use the same general
structure (see figure 1), and in both cases, a piece of information can be stolen by the FACCH.
3.1 Speech channel at full rate (TCH/FS and TCH/EFS)
The speech coder (whether Full rate or Enhanced full rate) delivers to the channel encoder a sequence of
blocks of data. In case of a full rate and enhanced full rate speech TCH, one block of data corresponds to
one speech frame.
---------------------- Page: 12 ----------------------
SIST ETS 300 575 E4:2003
Page 11
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
For the full rate coder each block contains 260 information bits, including 182 bits of class 1 (protected
bits), and 78 bits of class 2 (no protection), (see table 2).
The bits delivered by the speech coder are received in the order indicated in GSM 06.10 and have to be
rearranged according to table 2 before channel coding as defined in subclauses 3.1.1 to 3.1.4. The
rearranged bits are labelled {d(0),d(1),.,d(259)}, defined in the order of decreasing importance.
For the EFR coder each block contains 244 information bits. The block of 244 information bits, labelled
s(1)., s(244), passes through a preliminary stage, applied only to EFR (see figure 1) which produces
260 bits corresponding to the 244 input bits and 16 redundancy bits. Those 16 redundancy bits
correspond to 8 CRC bits and 8 repetition bits, as described in subclause 3.1.1. The 260 bits, labelled
w(1).w(260), have to be rearranged according to table 7 before they are delivered to the channel
encoding unit which is identical to that of the TCH/FS. The 260 bits block includes 182 bits of class
1(protected bits) and 78 bits of class 2 (no protection). The class 1 bits are further divided into the class 1a
and class 1b, class 1a bits being protected by a cyclic code and the convolutional code whereas the class
1b are protected by the convolutional code only.
3.1.1 Preliminary channel coding for EFR only
3.1.1.1 CRC calculation
An 8-bit CRC is used for error-detection. These 8 parity bits (bits w253-w260) are generated by the cyclic
8 4 3 2
generator polynomial: g(D) = D + D + D + D + 1 from the 65 most important bits (50 bits of class 1a
and 15 bits of class 1b). These 65 bits (b(1)-b(65)) are taken from the table 5 in the following order (read
row by row, left to right):
s39 s40 s41 s42 s43 s44 s48 s87 s45 s2
s3 s8 s10 s18 s19 s24 s46 s47 s142 s143
s144 s145 s146 s147 s92 s93 s195 s196 s98 s137
s148 s94 s197 s149 s150 s95 s198 s4 s5 s11
s12 s16 s9 s6 s7 s13 s17 s20 s96 s199
s1 s14 s15 s21 s25 s26 s28 s151 s201 s190
s240 s88 s138 s191 s241
The encoding is performed in a systematic form, which means that, in GF(2), the polynomial:
72 71 8 7 6 1
b(1)D + b(2)D +.+b(65)D + p(1)D + p(2)D +.+ p(7)D + p(8)
p(1) - p(8): the parity bits (w253-w260)
b(1) - b(65) = the data bits from the table above
when divided by g(D), yields a remainder equal to 0.
3.1.1.2 Repetition bits
The repeated bits are s70, s120, s173 and s223. They correspond to one of the bits in each of the
PULSE_5, the most significant one not protected by the channel coding stage.
3.1.1.3 Correspondence between input and output of preliminary channel coding
The preliminary coded bits w(k) for k = 1 to 260 are hence defined by:
w(k) = s(k) for k = 1 to 71
w(k) = s(k-2) for k = 74 to 123
w(k) = s(k-4) for k = 126 to 178
w(k) = s(k-6) for k = 181 to s230
w(k) = s(k-8) for k = 233 to s252
---------------------- Page: 13 ----------------------
SIST ETS 300 575 E4:2003
Page 12
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
Repetition bits:
w(k) = s(70) for k = 72 and 73
w(k) = s(120) for k = 124 and 125
w(k) = s(173) for k = 179 and 180
w(k) = s(223) for k = 231 and 232
Parity bits:
w(k = p(k-252) for k = 253 to 260
3.1.2 Channel coding for FR and EFR
3.1.2.1 Parity and tailing for a speech frame
a) Parity bits:
The first 50 bits of class 1 (known as class 1a for the EFR) are protected by three parity bits used
for error detection. These parity bits are added to the 50 bits, according to a degenerate (shortened)
cyclic code (53,50,2), using the generator polynomial:
3
g(D) = D + D + 1
The encoding of the cyclic code is performed in a systematic form, which means that, in GF(2), the
polynomial:
52 51 3 2
d(0)D + d(1)D +. + d(49)D + p(0)D + p(1)D + p(2)
where p(0), p(1), p(2) are the parity bits, when divided by g(D), yields a remainder equal to:
2
1 + D + D
b) Tailing bits and reordering:
The information and parity bits of class 1 are reordered, defining 189 information + parity + tail bits
of class 1, {u(0),u(1),.,u(188)} defined by:
u(k) = d(2k) and u(184-k) = d(2k+1) for k = 0,1,.,90
u(91+k) = p(k) for k = 0,1,2
u(k) = 0 for k = 185,186,187,188 (tail bits)
3.1.2.2 Convolutional encoder
The class 1 bits are encoded with the 1/2 rate convolutional code defined by the polynomials:
3 4
G0 = 1 + D + D
3 4
G1 = 1 + D + D + D
The coded bits {c(0), c(1),., c(455)} are then defined by:
- class 1: c(2k) = u(k) + u(k-3) + u(k-4)
c(2k+1) = u(k) + u(k-1) + u(k-3) + u(k-4) for k = 0,1,.,188
u(k) = 0 for k < 0
- class 2: c(378+k) = d(182+k) for k = 0,1,.,77
---------------------- Page: 14 ----------------------
SIST ETS 300 575 E4:2003
Page 13
ETS 300 575 (GSM 05.03 version 4.5.1): December 1997
3.1.3 Interleaving
The coded bits are reordered and interleaved according to the following rule:
i(B,j) = c(n,k), for k = 0,1,.,455
n = 0,1,.,N,N+1,.
B = B + 4n + (k mod 8)
0
j = 2((49k) mod 57) + ((k mod 8) div 4)
See table 1. The result of the interleaving is a distribution of the reordered 456 bits of a given data block,
n = N, over 8 blocks using the even numbered bits of the first 4 blocks (B = B + 4N + 0, 1, 2, 3) and odd
0
numbered bits of the last 4 blocks (B = B + 4N + 4, 5, 6, 7). The reordered bits of the following data
0
block, n = N + 1, use the even numbered bits of the blocks B = B + 4N + 4, 5, 6, 7 (B = B + 4(N+1) + 0,
0 0
1, 2, 3) and the odd numbered bits of the blocks B = B + 4(N+1) + 4, 5, 6, 7. Continuing with the next
0
data blocks shows that one block always carries 57 bits of data from one data block (n = N) and 57 bits of
data from the next block (n = N+1), where the bits from the data block with the higher number always are
the even numbered data bits, and those of the data block with the lower number are the odd numbered
bits.
The block of coded data is interleaved "block diagonal", where a new data block starts every 4th block and
is distributed over 8 blocks.
3.1.4 Mapping on a Burst
The mapping is given by the rule:
e(B,j) = i(B,j) and e(B,59+j) = i(B,57+j) for j = 0,1,.,56
and
e(B,57) = hl(B) and e(B,58) = hu(B)
The two bits, labelled hl(B) and hu(B) on burst number B are flags used for indication of control channel
signalling. For each TCH/FS block not stolen for signalling purposes:
hu(B )= 0 for the first 4 bursts (indicating status of even numbered bits)
hl(B) = 0 for the last 4 bursts (indicating status of odd numbered bits)
For the use of hl(B) and hu(B) when a speech frame is stolen for signalling purposes see subclause 4.2.5.
3.2 Speech channel at half rate (TCH/HS)
The speech coder delivers to the channel encoder a sequence of blocks of data. In case of a half rate
speech TCH, one block of data corresponds to one speech frame. Each block contains 112 bits, including
95 bits of class 1 (protected bits), and 17 bits of class 2 (no protection), see tables 3a and 3b.
The bits delivered by the speech coder are received in the order indicated in GSM 06.20 and have to be
arranged according to either table 3a or table 3b before channel encoding as defin
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.