SIST EN 301 707 V7.3.1:2003

SLOVENSKI STANDARD
01-december-2003
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Digital cellular telecommunications system (Phase 2+) (GSM); Discontinuous
Transmission (DTX) for Adaptive Multi-Rate (AMR) speech traffic channels (GSM 06.93
version 7.3.1 Release 1998)
Ta slovenski standard je istoveten z: EN 301 707 Version 7.3.1
ICS:
33.070.50 Globalni sistem za mobilno Global System for Mobile
telekomunikacijo (GSM) Communication (GSM)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

European Standard (Telecommunications series)
Digital cellular telecommunications system (Phase 2+);
Discontinuous Transmission (DTX) for Adaptive Multi-Rate
(AMR) speech traffic channels
(GSM 06.93 version 7.3.1 Release 1998)
R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
2 ETSI EN 301 707 V7.3.1 (2001-03)
(GSM 06.93 version 7.3.1 Release 1998)
Reference
REN/SMG-110693Q7R2
Keywords
Digital cellular telecommunications system,
Global System for Mobile communications
(GSM), AMR
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© European Telecommunications Standards Institute 2001.
All rights reserved.
ETSI
3 ETSI EN 301 707 V7.3.1 (2001-03)
(GSM 06.93 version 7.3.1 Release 1998)
Content
Intellectual Property Rights .4
Foreword.4
1 Scope.5
2 References.5
3 Definitions, symbols and abbreviations .6
3.1 Definitions . 6
3.2 Symbols . 6
3.3 Abbreviations. 7
4 General.7
4.1 General organisation. 7
5 Transmit (TX) side .8
5.1 General operation. 8
5.1.1 Functions of the TX DTX handler . 9
5.1.2 Functions of the TX Radio Subsystem. 10
5.1.2.1 Functions of the TX Radio Subsystem for TCH/AFS. 10
5.1.2.2 Functions of the TX Radio Subsystem for TCH/AHS . 10
5.1.2.3 Functions of the Downlink TX Radio Subsystem for TFO. 11
5.1.2.4 Functions of the TX Radio Subsystem for RATSCCH. 11
6 Receive (RX) side.12
6.1 General operation. 12
6.1.1 Functions of the RX radio subsystem. 12
6.1.2 Functions of the RX DTX handler . 13
Annex A (informative): Document change history .14
History .15
ETSI
4 ETSI EN 301 707 V7.3.1 (2001-03)
(GSM 06.93 version 7.3.1 Release 1998)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://www.etsi.org/ipr).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This European Standard (Telecommunications series) has been produced by ETSI Technical Committee Special Mobile
Group (SMG).
The present document describes the general baseband operation of Adaptive Multi-Rate speech traffic channels in the
transmitter and in the receiver of GSM Mobile Stations and Base Station Systems during Discontinuous Transmission
(DTX) within the digital cellular telecommunications system.
The present document corresponds to GSM technical specification, GSM 06.93 AMR, version X.X.X
The contents of the present document is subject to continuing work within SMG and may change following formal
SMG approval. Should SMG modify the contents of the present document it will be re-released with an identifying
change of release date and an increase in version number as follows:
Version 7.x.y
where:
7 indicates Release 1998 of GSM Phase 2+
x the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
y the third digit is incremented when editorial only changes have been incorporated in the specification.
National transposition dates
Date of adoption of this EN: 9 March 2001
Date of latest announcement of this EN (doa): 30 June 2001
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 31 December 2001
Date of withdrawal of any conflicting National Standard (dow): 31 December 2001
ETSI
5 ETSI EN 301 707 V7.3.1 (2001-03)
(GSM 06.93 version 7.3.1 Release 1998)
1 Scope
The present document gives a description of the general baseband operation of Adaptive Multi-Rate speech traffic
channels in the transmitter and in the receiver of GSM Mobile Stations (MS)s and Base Station Systems (BSS)s during
Discontinuous Transmission (DTX).
For clarity, the description is structured according to the block diagrams in figures 1 and 3. Except in the case described
next, this structure of distributing the various functions between system entities is not mandatory for implementation, as
long as the operation on the air interface and on the speech decoder output remains the same.
In the case of BSSs where the speech transcoder is located remote from the Base Transceiver Station (BTS), the
implementation of the interfaces between the DTX handlers and the Radio Sub System (RSS) as described in the
present document together with all their flags is mandatory, being part of the A-bis interface as described in GSM 08.60
and GSM 08.61.
The DTX functions described in this technical specification are mandatory for implementation in the GSM MSs. The
receiver requirements are mandatory for implementation in all GSM BSSs, the transmitter requirements only for those
where downlink DTX or Tandem Free Operation will be used.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies.
• A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the same
number.
• For this Release 1998 document, references to GSM documents are for Release 1998 versions (version 7.x.y).
[1] GSM 01.04: "Digital cellular telecommunication system (Phase 2+); Abbreviations and
acronyms".
[2] GSM 04.08: "Digital cellular telecommunication system (Phase 2+); Mobile radio interface layer 3
specification".
[3] GSM 05.03: "Digital cellular telecommunication system (Phase 2+); Channel coding".
[4] GSM 05.05: "Digital cellular telecommunication system (Phase 2+); Radio transmission and
reception".
[5] GSM 05.08: "Digital cellular telecommunication system (Phase 2+); Radio subsystem link
control".
[6] GSM 05.09: "Digital cellular telecommunication system (Phase 2+); Link adaptation".
[7] GSM 06.71: "Digital cellular telecommunications system (Phase 2+); Adaptive Multi-Rate (AMR)
speech processing functions; General description".
[8] GSM 06.73: "Digital cellular telecommunications system (Phase 2+); ANSI-C code for the GSM
Adaptive Multi-Rate speech codec".
[9] GSM 06.74: "Digital cellular telecommunications system (Phase 2); Test vectors for the GSM
Adaptive Multi-Rate speech codec".
ETSI
6 ETSI EN 301 707 V7.3.1 (2001-03)
(GSM 06.93 version 7.3.1 Release 1998)
[10] GSM 06.90: "Digital cellular telecommunications system (Phase 2+); Adaptive Multi-Rate speech
transcoding".
[11] GSM 06.91: "Digital cellular telecommunications system (Phase 2+); Substitution and muting of
lost frame for Adaptive Multi-Rate speech traffic channels".
[12] GSM 06.92: "Digital cellular telecommunications system (Phase 2+); Comfort noise aspects for
Adaptive Multi-Rate speech traffic channels".
[13] GSM 06.94: "Digital cellular telecommunications system (Phase 2+); Voice Activity Detector
(VAD) for Adaptive Multi-Rate speech traffic channels".
[14] GSM 08.60: "Digital cellular telecommunication system (Phase 2+); Inband control of remote
transcoders and rate adaptors for Full Rate traffic channels".
[15] GSM 08.61: "Digital cellular telecommunication system (Phase 2+); Inband Control of Remote
Transcoders and Rate Adaptors for Half Rate traffic channels".
[16] GSM 08.62: "Digital cellular telecommunications system; Inband Tandem Free Operation (TFO)
of Speech Codecs".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purpose of the present document, the following terms and definitions apply:
frame: time interval of 20 ms, corresponding to the time segmentation of the Adaptive Multi Rate speech transcoder
(GSM 06.90 [9]), also used as a short term for a traffic frame
traffic frame: block of 95.244 information bits transmitted on the TCH/AFS or TCH/AHS speech traffic channels
SID frame: frame characterised by the SID (Silence Descriptor) gross bit patterns. It may convey information on the
acoustic background noise
speech frame: traffic frame that has been classified as a SPEECH frame
VAD flag: boolean flag, generated by the VAD algorithm defined in GSM 06.94 indicating the presence ("1") or the
absence ("0") of a speech frame
RX_TYPE: flag with eight values, generated by the RX radio subsystem, indicating to the RX DTX handler the type of
data in the current frame (efer to table 2)
TX_TYPE: flag with eight values, generated by the TX DTX handler, indicating to the TX radio subsystem the type of
data in the current frame (refer to table 1)
hangover period: period of 7 frames added at the end of a speech burst in which VAD flag ="0" and TX_TYPE is
"SPEECH"
3.2 Symbols
For the purpose of the present document, the following symbol apply:
N Number of elapsed frames since the last updated SID frame
elapsed
ETSI
7 ETSI EN 301 707 V7.3.1 (2001-03)
(GSM 06.93 version 7.3.1 Release 1998)
3.3 Abbreviations
For the purpose of the present document, the following abbreviations apply:
BSC Base Station Controller
BSS Base Station System
BTS Base Transceiver Station
CHD Channel Decoder
CHE Channel Encoder
DTX Discontinuous Transmission
ETS European Telecommunication Standard
FACCH Fast Associated Control CHannel
GSM Global System for Mobile Telecommunications
MS Mobile Station
RATSCCH Robust Amr Traffic Synchronised Control CHannel
RSS Radio Sub System
RX Receive
SACCH Slow Associated Control CHannel
SID SIlence Descriptor
TX Transmit
VAD Voice Activity Detector
For abbreviations not given in this clause, see GSM 01.04.
4 General
Discontinuous Transmission (DTX) is a mechanism, which allows the radio transmitter to be switched off most of the
time during speech pauses for the following two purposes:
- to save power in the Mobile Station (MS);
- to reduce the overall interference level over the air interface.
DTX in uplink shall be in operation within the GSM MS, if commanded so by the network, see GSM 04.08. The MS
shall handle DTX in downlink at any time, regardless, whether DTX in uplink is commanded or not.
4.1 General organisation
The overall DTX mechanism described in the present document requires the following functions:
- a Voice Activity Detector (VAD) on the transmit (TX) side;
- evaluation of the background acoustic noise on the transmit (TX) side, in order to transmit characteristic
parameters to the receive (RX) side;
- generation on the receive (RX) side of a similar noise, called comfort noise, during periods where the radio
transmission is switched off.
The Voice Activity Detector (VAD) is defined in GSM 06.94 and the comfort noise functions in GSM 06.92. Both are
based partly on the speech transcoder and its internal variables, defined in GSM 06.90.
In addition to these functions, if the parameters arriving at the RX side are detected to be seriously corrupted by errors,
the speech or comfort noise must be generated from substituted data in order to avoid seriously annoying effects for the
listener. This function is defined in GSM 06.91.
An overall description of the speech processing parts can be found in GSM 06.71.
The description for Tandem Free Operation is given in GSM 08.62.
ETSI
8 ETSI EN 301 707 V7.3.1 (2001-03)
(GSM 06.93 version 7.3.1 Release 1998)
5 Transmit (TX) side
A block diagram of the transmit side DTX functions is shown in figure 1.
TX DTX handler TX Radio subsystem
Speech
encoder
Information bits
Channel
Encoder
Voice
Mode Indication
Activity
Detector
TX_TYPE
TX_TYPE
Monitoring
Comfort
Noise
NSYNC
Computation
Figure 1: Block diagram of the transmit side DTX functions
5.1 General operation
The TX DTX handler passes traffic frames, individually marked by TX_TYPE, to the Radio Subsystem (RSS). Each
frame passed to the RSS consists of bit fields containing the information bits, the codec mode indication, and the
TX_TYPE. TX_TYPE is used to specify the contents of the frame. The table below provides an overview of the
different TX_TYPEs used and explains the required contents in the information bit and the mode indication bit fields. In
case of ongoing Tandem Free Operation (see GSM 08.62) frames with errors may arrive in downlink in the BTS.
Table 1: TX TYPE identifiers
TX_TYPE Legend Information Bits Mode Indication
SPEECH_GOOD speech frame, size 95.244 bits depending current code mode
on codec mode;
no errors known.
SPEECH_DEGRADED Speech frame, size 95.244 bits, depending current codec mode
(only in downlink in on codec mode;
TFO) there might be errors in class 2 bits.
SPEECH_BAD Speech frame, size 95.244 bits, depending current codec mode
(only in downlink in on codec mode;
TFO) there are errors in class 1 bits.
SID
...