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TECHNICAL SPECIFICATION
Digital cellular telecommunications system (Phase 2+) (GSM);
GSM/EDGE Link adaptation
(3GPP TS 45.009 version 15.0.0 Release 15)
R
GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
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3GPP TS 45.009 version 15.0.0 Release 15 1 ETSI TS 145 009 V15.0.0 (2018-07)
Reference
RTS/TSGR-0645009vf00
Keywords
GSM
ETSI
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3GPP TS 45.009 version 15.0.0 Release 15 2 ETSI TS 145 009 V15.0.0 (2018-07)
Intellectual Property Rights
Essential patents
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pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
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Foreword
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
.
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
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3GPP TS 45.009 version 15.0.0 Release 15 3 ETSI TS 145 009 V15.0.0 (2018-07)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 4
1 Scope . 5
1.1 References . 5
1.2 Abbreviations . 5
2 General . 5
3 Adaptive Multi-Rate inband control and link adaptation . 6
3.1 General operation . 6
3.1.1 Operation without Tandem Free Operation . 6
3.1.2 Operation with ongoing Tandem Free Operation . 7
3.1.3 Operation at handover with ongoing Tandem Free Operation . 7
3.2 Inband Signalling . 7
3.2.1 Frequent inband signalling for AMR codec mode adaptation . 7
3.2.1.1 General aspects . 7
3.2.1.2 Operation with DTX enabled . 7
3.2.1.3 Transmitter/Receiver Synchronisation . 8
3.2.2 Robust inband signalling for AMR configuration modification . 9
3.2.2.1 General aspects . 9
3.2.2.2 RATSCCH protocol . 9
3.2.2.3 RATSCCH messages . 10
3.2.2.3.1 ACK_OK message . 11
3.2.2.3.2 ACK_ERR message . 11
3.2.2.3.3 ACK_UNKNOWN message . 11
3.2.2.3.4 CMI_PHASE_REQ message . 11
3.2.2.3.5 AMR_CONFIG_REQ message . 12
3.2.2.3.6 THRESH_REQ message . 13
3.3 Codec mode adaptation . 13
3.3.1 Channel quality measure . 13
3.3.2 Generation of Codec Mode Commands and Requests . 13
3.3.3 Performance requirements . 14
3.3.3.1 MS response to the Codec Mode Command . 14
3.3.3.2 BTS response to the Codec Mode Request . 14
3.3.3.3 Performance of the Codec Mode Request Generation . 14
3.4 Setup procedures . 15
3.4.1 Definition of the AMR Active Codec Set . 15
3.4.2 Definition of Codec Mode Command/Request decision thresholds . 15
3.4.3 Initial Codec Mode Selection at Call Setup and Handover . 16
Annex A (informative): Example Solution for Link quality estimation . 17
Annex B (informative): Example Definition of Mode Command/Request decision thresholds . 18
Annex C (informative): Principles for AMR codec mode adaptation with TFO . 20
C.1 Downgrading . 20
C.1.1 Uplink downgrading . 20
C.1.2 Downlink downgrading . 21
C.2 Upgrading . 21
C.2.1 Downlink upgrading . 21
C.2.2 Uplink upgrading . 22
Annex D (informative): Change history . 24
History . 26
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Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version 8.x.y
where:
8 indicates release 1999.
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.
ETSI
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3GPP TS 45.009 version 15.0.0 Release 15 5 ETSI TS 145 009 V15.0.0 (2018-07)
1 Scope
The requirements described in the present document are mandatory for implementation in all GSM MSs and BSSs
capable of supporting the Adaptive Multi-Rate speech traffic channel, unless otherwise stated.
Unless otherwise specified, references to GSM include GSM at any frequency band.
1.1 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. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 44.018: "Mobile radio interface layer 3 specification, Radio Resource Control Protocol".
[3] 3GPP TS 45.002: "Multiplexing and multiple access on the radio path".
[4] 3GPP TS 45.003: "Channel Coding".
[5] 3GPP TS 45.005: "Radio transmission and reception".
[6] 3GPP TS 48.008: "Mobile-services Switching Centre - Base Station System (MSC - BSS)
interface, Layer 3 specification".
[7] 3GPP TS 28.062: "Inband Tandem Free Operation (TFO) of Speech Codecs".
1.2 Abbreviations
For the purposes of the present document, the following abbreviations apply. Further GSM related abbreviations are
listed in 3GPP TR 21.905.
AMR Adaptive Multi-Rate
AMR-WB Adaptive Multi-Rate Wideband
ACS Active Codec Set
CMC Codec Mode Command
CMI Codec Mode Indication
CMR Codec Mode Request
ICM Initial Codec Mode
RATSCCH Robust AMR Traffic Synchronized Control Channel
2 General
The present document gives the detailed requirements for the correct operation of in call service specific link adaptation
and control for GSM services implemented in GSM Mobile Stations (MS)s and Base Station Systems (BSS)s.
In this specification the term AMR refers to both narrow-band and wide-band AMR codecs if not otherwise stated.
For the Adaptive Multi-Rate (AMR) speech service, the detailed description and requirements for the associated inband
signaling, AMR codec mode adaptation, and AMR codec configuration are given.
An inband signalling channel is defined for AMR which enables the MS and the BTS to exchange messages on applied
or requested speech and channel codec modes. Codec mode adaptation for AMR is based on received channel quality
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estimation in both MS and BTS, followed by a decision on the most appropriate speech and channel codec mode to
apply at a given time.
The overall operation of AMR, in terms of used codec modes as well as general adaptation behaviour is controlled by
the network.
3 Adaptive Multi-Rate inband control and link
adaptation
3.1 General operation
3.1.1 Operation without Tandem Free Operation
A high-level block diagram of the complete AMR system is depicted in figure 1. The system consists of the major
components TRAU and BTS on the network side and the MS. On the network side, speech encoder (SPE) and channel
encoder (CHE) as well as channel decoder (CHD) and speech decoder (SPD) are connected via the serial A-bis
interface. For each link, quality information is derived by estimating the current channel state. Based on the channel
state, and also taking into consideration possible constraints from network control, the codec mode control, which is
located on the network side, selects the codec modes to be applied.
The channel mode to use (TCH/AFS, TCH/AHS, O-TCH/AHS, TCH/WFS, O-TCH/WFS or O-TCH/WHS) is
controlled by the network. Uplink and downlink always apply the same channel mode.
For codec mode adaptation the receiving side performs link quality measurements of the incoming link. The
measurements are processed yielding a Quality Indicator. For uplink adaptation, the Quality Indicator is directly fed
into the UL mode control unit. This unit compares the Quality Indicator with certain thresholds and generates, also
considering possible constraints from network control, a Codec Mode Command indicating the codec mode to be used
on the uplink. The Codec Mode Command is then transmitted inband to the mobile side where the incoming speech
signal is encoded in the corresponding codec mode. For downlink adaptation, the DL Mode Request Generator within
the mobile compares the DL Quality indicator with certain thresholds and generates a Codec Mode Request indicating
the preferred codec mode for the downlink. The Codec Mode Request is transmitted inband to the network side where it
is fed into the DL Mode Control unit. This unit generally grants the requested mode. However, considering possible
constraints from network control, it may also override the request. The resulting codec mode is then applied for
encoding of the incoming speech signal in downlink direction. Both for uplink and downlink, the presently applied
codec mode is transmitted inband as Codec Mode Indication together with the coded speech data. At the decoder, the
Codec Mode Indication is decoded and applied for decoding of the received speech data.
TRAU BTS MS
speech data
SPE CHE CHD SPD
DL codec mode DL codec mode (received)
UL Mode Command
DL- UL- UL Mode Command
DL-
(received)
Mode Ctrl Mode Ctrl
Meas.
DL Quality Indicator
network UL Quality Indicator
control
UL- DL-
Req.Gen
DL Mode Request
Meas.
r(eceived)
DL Mode Request
UL codec mode (received)
SPD CHD CHE SPE
speech data
Figure 1: High level AMR block diagram
Codec mode selection is done from a set of codec modes (ACS, Active Codec Set), which may include 1 to 4 AMR
codec modes. Associated with this set is a list of 1 to 3 switching thresholds and hysteresis used by the DL Mode
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Request Generator and the UL mode control unit to generate the Codec Mode Requests and Codec Mode Commands.
These configuration parameters (ACS, thresholds, hysteresis) are defined at call set-up and can be modified at handover
or during a call.
3.1.2 Operation with ongoing Tandem Free Operation
If tandem free operation is ongoing (see 3GPP TS 28.062) then the speech signal has to be transmitted over two radio
links, first uplink (MS1 to BTS1) and then downlink (BTS2 to MS2), respectively symmetrically in the reverse
direction. The optimal Codec Mode in direction MS1 to MS2 shall be derived from the Codec Mode Command for the
first uplink (CMC1, within BTS1) and the Codec Mode Request derived for the second downlink (CMR2 within MS2)
in the following way: MS2 shall send the CMR2 back to BTS2 in the usual way. BTS2 shall either accept this CMR2
(default) or may modify it according to network control needs: CMR2´. Then BTS2 shall send the CMR2´ further
uplink to its TRAU2, to TRAU1 and downlink to BTS1 (see 3GPP TS 28.062 on how this transmission shall be handled
on Abis and A interfaces). BTS1 combines the received CMR2´ with its own derived CMC1 by taking the minimum of
both values. If needed, BTS1 may modify this minimum value according to own network control (--> CMC1´´) and
shall send it finally downlink to MS1 as CMC. The identical procedure shall be performed in the reverse direction.
Annex C gives an informative description.
3.1.3 Operation at handover with ongoing Tandem Free Operation
Before and during an handover at one or both sides of the MS-to-MS connection, it may be needed to freeze the codec
mode adaptation for a short while, e.g. to optimise the common Active Codec Set, or to allow fast (re-)synchronisation
between BTS and TRAU or to optimise the CMI Phase in downlink. Both BTSs may therefore enable or disable the
codec mode adaptation (see 3GPP TS 28.062). As long as the codec mode adaptation is frozen to a specific codec mode,
then this codec mode shall be used in both directions as long as tandem free operation is ongoing, or tandem free
operation shall be discontinued. The Codec Mode Requests from the MSs may be taken into account to decide whether
to continue TFO or not, but not for codec mode adaptation.
3.2 Inband Signalling
The AMR inband signalling consists of two parts:
- Frequent signalling, used for Codec Mode Indication and Codec Mode Command/Request.
- Robust, less frequent signalling, based on frame stealing, used for changing the AMR configuration
(RATSCCH).
3.2.1 Frequent inband signalling for AMR codec mode adaptation
3.2.1.1 General aspects
The codec mode information, which has to be transmitted on each link, consists of Codec Mode Indications and Codec
Mode Commands in the downlink, respectively Codec Mode Indications and Codec Mode Requests in the uplink.
Codec Mode Indications inform the receiver about the currently applied codec mode. Codec Mode Commands inform
the other end about the codec mode to be applied on the other link. Codec Mode Requests inform the other end about
the preferred codec mode on the other link.
Codec mode information is transmitted inband in the speech traffic channel, using a part of its transmission capacity.
The coding of codec modes in the inband signalling is given in subclause 3.4.1. Channel coding of codec mode
information is specified in 3GPP TS 45.003 [4] for all frame types.
Codec modes are constrained to change only every second speech frame. Codec Mode Commands/Requests and Codec
Mode Indications are sub-sampled such that they occur only every second frame. Codec Mode Indications and Codec
Mode Commands/Requests shall be transmitted alternating within consecutive speech frames.
Both, Codec Mode Indication and Codec Mode Command/Request, shall be transmitted together within every
RATSCCH frame.
3.2.1.2 Operation with DTX enabled
For SID_FIRST frames, the Codec Mode Indication or Codec Mode Command/Request in phase with the alternating
transmission shall be transmitted (same phase as in speech frames).
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Both, Codec Mode Indication and Codec Mode Command/Request, shall be transmitted together in every
SID_UPDATE frame (as in RATSCCH frames).
For ONSET frames the Codec Mode Indication for the subsequent speech frame shall be transmitted, regardless of the
phase of the inband signalling. The general phase of the inband signalling shall not be changed by that.
3.2.1.3 Transmitter/Receiver Synchronisation
The alternating transmission of the codec mode information requires synchronisation of transmitting and receiving ends,
such that Codec Mode Indications and Codec Mode Commands/Requests are decoded in correct order. To ensure
proper synchronisation, the codec mode information shall be transmitted aligned to the 26-multiframe structure of the
GSM system.
The default transmission phase for TCH/AFS, TCH/WFS, and O-TCH/WFS shall be such that Codec Mode Indications
are sent with speech frames having their first burst sent on TDMA frames according to table 3.2.1.3-1.
Table 3.2.1.3-1. TDMA frames for Codec Mode Indication for TCH/AFS, TCH/WFS and O-TCH/WFS.
Downlink Uplink
4, 13, 21 (modulo 26) 0, 8, 17 (modulo 26)
NOTE: TDMA frame numbering defined in 3GPP TS 45.002 [3]
The default transmission phase for TCH/AHS, O-TCH/AHS, and O-TCH/WHS shall be such that Codec Mode
Indications are sent with speech frames having their first burst sent on TDMA frames according to table 3.2.1.3-2.
Table 3.2.1.3-2. TDMA frames for Codec Mode Indication for TCH/AHS, O-TCH/AHS and O-TCH/WHS.
(1) (1)
Downlink Uplink
4, 13, 21 (modulo 26), or, 0, 8, 17 (modulo 26), or,
5, 14, 22 (modulo 26) 1, 9, 18 (modulo 26)
NOTE 1: The mapping is dependent on the subchannel as defined in 3GPP TS 45.002 [3].
NOTE 2: TDMA frame numbering defined in 3GPP TS 45.002 [3]
For a mobile station indicating support for VAMOS, the default transmission phase for TCH/AFS and TCH/WFS shall
be such that Codec Mode Indications are sent with speech frames having their first burst sent on TDMA frames
according to table 3.2.1.3-3.
Table 3.2.1.3-3. TDMA frames for Codec Mode Indication for TCH/AFS, TCH/WFS for VAMOS.
(1)
VAMOS mobile Assigned TSC
Transmission phase
support level set
Downlink Uplink
VAMOS I Set 1, 2, 3 or 4
4, 13, 21 (modulo 26)
VAMOS II/III Set 1 or 3 0, 8, 17 (modulo 26)
VAMOS II/III Set 2 or 4 4, 12, 21 (modulo 26)
NOTE 1: TDMA frame numbering defined in 3GPP TS 45.002 [3]
NOTE 2: The use of TSC set 3 and TSC set 4 is only applicable for mobile stations
indicating support for Extended TSC sets, see 3GPP TS 24.008.
For a mobile station indicating support for VAMOS, the default transmission phase for TCH/AHS shall be such that
Codec Mode Indications are sent with speech frames having their first burst sent on TDMA frames according to table
3.2.1.3-4.
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Table 3.2.1.3-4. TDMA frames for Codec Mode Indication for TCH/AHS for VAMOS.
(1) (2)
VAMOS mobile Assigned TSC
Transmission phase
support level set
Downlink Uplink
VAMOS I Set 1, 2, 3 or 4
4, 13, 21 (modulo 26)
VAMOS II/III Set 1 or 3
or
0, 8, 17 (modulo 26)
5, 14, 22 (modulo 26)
or
VAMOS II/III Set 2 or 4 4, 12, 21 (modulo 26) 1, 9, 18 (modulo 26)
or
5, 14, 22 (modulo 26)
NOTE 1: TDMA frame numbering defined in 3GPP TS 45.002 [3]
NOTE 2: Depending on the half-rate subchannel as defined in 3GPP TS 45.002 [3]
NOTE 3: The use of TSC set 3 and TSC set 4 is only applicable for mobile stations
indicating support for Extended TSC sets, see 3GPP TS 24.008.
This default phase of the Codec Mode Indication in downlink direction is called "odd", the alternative phase, one speech
frame shifted, is called "even". The phase in uplink is always the same and is never changed.
At call set-up, after a channel mode modify with consistent MultiRate configuration IE and after each reallocation of the
circuit switched channel, the default phase (odd) shall be used in downlink direction. During a call, the phase of Codec
Mode Indication may be changed in downlink by using a RATSCCH message. In case of reallocation failure and fall
back to the channel before the reallocation attempt, the phase before the channel reallocation attempt shall be used again
(except if a RATSCCH procedure is pending, see section 3.2.2.2 bullet 6).
3.2.2 Robust inband signalling for AMR configuration modification
3.2.2.1 General aspects
The RATSCCH mechanism may be used in case of Tandem Free Operation to modify the AMR Configuration on the
radio interface without interruption of the speech transmission. Its application for TFO is described in 3GPP TS 28.062.
This recommendation defines the RATSCCH protocol and the RATSCCH messages. The channel coding is defined in
3GPP TS 45.003 and the receiver performance in 3GPP TS 45.005. RATSCCH handling is mandatory for MS and
optional for BTS.
RATSCCH is based on frame stealing. On TCH/AFS, TCH/WFS and O-TCH/WFS, one speech frame is stolen for each
RATSCCH message, and on TCH/AHS, O-TCH/AHS and O-TCH/WHS two speech frames are stolen. In TCH/AHS
and O-TCH/AHS RATSCCH is mapped onto two consecutive speech frames, the RATSCCH_MARKER and the
RATSCCH_DATA. Both shall be sent always as one pair.
FACCH frames have higher priority than RATSCCH frames. If FACCH and RATSCCH are scheduled for
transmission for the same speech frame, then the FACCH shall be sent first, followed by the RATSCCH. If the
RATSCCH is delayed due to FACCH, then the appropriate counters shall also be started as per section 3.2.2.2, based on
actual transmission of the RATSCCH on the radio interface. If in the case of TCH/AHS, O-TCH/AHS and O-
TCH/WHS, FACCH steals the second frame of one RATSCCH message (RATSCCH_DATA), the complete
RATSCCH message (RATSCCH_MARKER and RATSCCH_DATA) shall be sent following the FACCH frame.
3.2.2.2 RATSCCH protocol
The RATSCCH protocol elements consist of a number of REQuest Messages and three ACKnowledgement Messages.
One inform
...