ETSI TS 126 193 V17.0.0 (2022-05)

Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); LTE; 5G; Speech codec speech processing functions; Adaptive Multi-Rate - Wideband (AMR-WB) speech codec; Source controlled rate operation (3GPP TS 26.193 version 17.0.0 Release 17)

RTS/TSGS-0426193vh00

General Information

• Status: Not Published
• Technical Committee: 3GPP SA 4 - Codec
• Current Stage: 12 - Completion
• Completion Date: 04-May-2022

Standards Content (Sample)

TECHNICAL SPECIFICATION
Digital cellular telecommunications system (Phase 2+) (GSM);
Universal Mobile Telecommunications System (UMTS);
LTE;
5G;
Speech codec speech processing functions;
Adaptive Multi-Rate - Wideband (AMR-WB) speech codec;
Source controlled rate operation
(3GPP TS 26.193 version 17.0.0 Release 17)

3GPP TS 26.193 version 17.0.0 Release 17 1 ETSI TS 126 193 V17.0.0 (2022-05)

Reference
RTS/TSGS-0426193vh00
Keywords
5G,GSM,LTE,UMTS
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ETSI
3GPP TS 26.193 version 17.0.0 Release 17 2 ETSI TS 126 193 V17.0.0 (2022-05)
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ETSI
3GPP TS 26.193 version 17.0.0 Release 17 3 ETSI TS 126 193 V17.0.0 (2022-05)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 4
1 Scope . 5
2 Normative references . 5
3 Definitions, symbols and abbreviations . 5
3.1 Definitions . 5
3.2 Symbols . 6
3.3 Abbreviations . 6
4 General . 6
4.1 General organisation. 6
5 AMR-WB SCR operation . 7
5.1 Transmit (TX) side . 7
5.1.1 General operation . 7
5.1.2 Functions of the TX SCR handler . 8
5.1.2.1 AMR-WB SCR Timing procedures . 8
5.1.3 The TX part of the AN . 9
5.2 Receive (RX) side . 10
5.2.1 General operation . 10
5.2.3 Demands on the RX SCR handler . 11
5.3 AMR-WB SID Information format . 11
Annex A (normative): AMR-WB DTX handler for the GSM system . 12
A.1 Scope . 12
A.2 References . 12
A.3 Definitions, symbols and abbreviations . 13
A.3.1 Definitions . 13
A.3.2 Symbols . 13
A.3.3 Abbreviations . 13
A.4 General . 14
A.4.1 General organisation. 14
A.5 Transmit (TX) side . 14
A.5.1 General operation . 15
A.5.1.1 Functions of the TX DTX handler . 16
A.5.1.2 Functions of the TX Radio Subsystem . 17
A.5.1.2.1 Functions of the TX Radio Subsystem for TCH/WFS . 17
A.5.1.2.2 Functions of the Downlink TX Radio Subsystem for TFO . 17
A.5.1.2.4 Functions of the TX Radio Subsystem for RATSCCH . 18
A.6 Receive (RX) side . 18
A.6.1 General operation . 18
A.6.1.1 Functions of the RX radio subsystem . 19
A.6.1.2 Functions of the RX DTX handler . 19
Annex B: (informative) Change history . 21
History . 22

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3GPP TS 26.193 version 17.0.0 Release 17 4 ETSI TS 126 193 V17.0.0 (2022-05)
Foreword
This Technical Specification has been produced by the 3GPP.
The present document describes the operation of the Adaptive Multi Rate Wideband speech codec during Source
Controlled Rate (SCR) operation within the 3GPP system.
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 this TS, it will be re-released by the TSG with an identifying
change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the specification;
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3GPP TS 26.193 version 17.0.0 Release 17 5 ETSI TS 126 193 V17.0.0 (2022-05)
1 Scope
This document describes the Source Controlled Rate (SCR) operation of the Adaptive Multi-Rate Wideband speech
Codec. The implementation of this SCR operation is mandatory in all UMTS equipment implementing the Adaptive
Multi-Rate Wideband speech Codec.
The description is structured according to the block diagram in Figure 1. This structure of distributing the various
functions between system entities is not mandatory for implementation, as long as the operation on the speech decoder
output remains the same.
Annex A describes the Discontinuous Transmission (DTX) operation of the Adaptive Multi-Rate Wideband speech
Codec in Codec Type FR_AMR-WB for the GSM system.
2 Normative references
This document 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 document only when incorporated in
it by amendment or revision. For undated references, the latest edition of the publication referred to applies.
[1] 3GPP TS 26.171 : "AMR Wideband Speech Codec; General description".
[2] 3GPP TS 26.173 : "AMR Wideband Speech Codec; ANSI-C code".
[3] 3GPP TS 26.174 : "AMR Wideband Speech Codec; Test sequences".
[4] 3GPP TS 26.190 : "AMR Wideband Speech Codec; Transcoding functions".
[5] 3GPP TS 26.191 : "AMR Wideband Speech Codec; Error concealment of lost frames".
[6] 3GPP TS 26.192 : "AMR Wideband Speech Codec; Comfort noise aspects".
[7] 3GPP TS 26.194 : "AMR Wideband Speech Codec; Voice Activity Detector (VAD)".
[8] 3GPP TS 26.201 : "AMR Wideband Speech Codec; Frame structure".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purpose of this document, the following definitions apply.
frame: Time interval of 20 ms, corresponding to the time segmentation of the Adaptive Multi-Rate Wideband speech
Codec, also used as a short term for a traffic frame.
traffic frame: Block of 132.477 information bits transmitted on the speech traffic channels.
SID frame: Frame that conveys information about the acoustic background noise.
speech frame: Traffic frame that has been classified as SPEECH_GOOD, SPEECH_BAD or SPEECH_LOST frame.
VAD flag: Boolean flag, generated by the VAD algorithm indicating the presence ("1") or the absence ("0") of a speech
frame.
RX_TYPE: classifies the received frame.
TX_TYPE: classifies the frame to be transmitted.
hangover period: A period of frames added at the end of a speech burst in which VAD flag ="0" and TX_TYPE is
="SPEECH_GOOD", this period provides the encoder with an extra window to derive the Comfort Noise parameters .
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3.2 Symbols
For the purpose of this document, the following symbols apply.
N Number of elapsed frames since the last updated SID frame.
elapsed
3.3 Abbreviations
For the purpose of this document , the following abbreviations apply.
AN Access Network
SCR Source Controlled Rate operation
TS Telecommunication Standard, Technical Specification
GSM Global System for Mobile Telecommunication
UE User Equipment
RAN Radio Access Network
RX Receive
SID Silence Descriptor
TX Transmit
VAD Voice Activity Detector
4 General
Source Controlled Rate operation (SCR) is a mechanism for the AMR Wideband Speech Codec, which allows to
encode the input signal at a lower average rate by taking speech inactivity into account. The SCR scheme may be used
for the following purposes:
-to save power in the User Equipment;
-to reduce the overall interference and load in the networks.
SCR in the transmitting path (uplink) shall be in operation in UEs, if commanded so by the network. The UE shall
handle SCR in the receiving path (downlink) at any time, regardless, whether SCR in the transmitting path is
commanded or not.
4.1 General organisation
The default SCR mechanism described in this 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 transmission
is switched off.
The Voice Activity Detector (VAD) is defined in [7] and the comfort noise functions in [6]. Both are based partly on
the speech Codec and its internal variables, defined in [4].
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. These functions are defined in [5].
An overall description of the speech processing parts can be found in [1]. An overview of one link SCR operation is
shown in Figure 1.
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TX SCR handler “Network” RX SCR handler
Speech Speech
Information bits
Encoder Information bits Decoder
Information
packeting,
Voice Mode Indication
Mode Indication
Error
transport and
Activity
Concealment
classification
Detector
RX_TYPE
TX_TYPE
Comfort Noise
Comfort
Parameter
Noise
Computation
Generation
Figure 1: Block diagram of one link SCR operation
5 AMR-WB SCR operation
5.1 Transmit (TX) side
A block diagram of the transmit side SCR functions is shown in Figure 2.
TX SCR handler TX Access Network
Framing
T
Speech
S
Encoder Information bits
Information bits
Voice
Mode Indication
Frame Type
TX of
.
Activity
information
Detector
TX_TYPE
FQI
Comfort Noise
Parameter
Computation
Figure 2: Block diagram of SCR functions at the TX side
5.1.1 General operation
The TX SCR handler passes traffic frames, individually marked by TX_TYPE, to the Framing unit. Each frame consists
of bit fields containing the information bits, the codec mode indication, and the TX_TYPE. TX_TYPE shall be 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.
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Table 1: SCR TX_TYPE identifiers for UMTS_AMR-WB and FR_AMR-WB
TX_TYPE Information Bits Mode Indication
SPEECH_GOOD Speech frame, size 132.477 bits, Current codec mode
depending on codec mode
SPEECH_BAD Corrupt speech frame (bad CRC), Current codec mode
size 132.477 bits, depending on
codec mode
SPEECH_LOST No useful information. No useful information
(Note: If implementation does not
support the SPEECH_LOST,
SPEECH_BAD shall be used
instead)
SID_FIRST Marker for the end of talkspurt, no The codec mode that would have
further information, all 35 comfort been used if TX_TYPE had been

noise bits set to "0" "SPEECH_GOOD"

SID_UPDATE 35 comfort noise bits The codec mode that would have
been used if TX_TYPE had been
"SPEECH_GOOD"
SID_BAD Corrupt SID update frame (bad The codec mode that would have
CRC) been used if TX_TYPE had been
"SPEECH_GOOD"
NO_DATA No useful information, nothing to No useful information
be transmitted
TX_TYPE = "SPEECH_LOST" indicates that the Information Bit and Codec Mode fields do not contain any useful
data (but still should be transmitted over AN). The purpose of this TX_TYPE is indicate that the frame was transmitted
but lost on some previous phase. This TX_TYPEs may occur only in TFO and TrFO situations. Note, that it is possible
to replace SPEECH_LOST with SPEECH_BAD but this may degrade the quality of the error concealment in the
receiving end because concealment may try to use part of the received parameters from the frame which do not contain
any useful information.
TX_TYPE = "NO_DATA" indicates that the Information Bit and Codec Mode fields do not contain any useful data
(and should not be transmitted over AN). The purpose of this TX_TYPE is to provide the option to save network
transmission between the transcoder and AN.
Note, the TX_TYPEs "SPEECH_BAD", "SPEECH_LOST" and "SID_BAD" may occur in TFO and TrFO situations.
The scheduling of the frames for transmission on the Access Network is controlled by the TX SCR handler by the use
of the TX_TYPE field.
5.1.2 Functions of the TX SCR handler
If TX SCR operation is disabled, the TX SCR handler continuously generates speech frames, i.e. frames marked with
TX_TYPE="SPEECH_GOOD".
If the TX SCR operation is enabled, the VAD flag controls the TX SCR handler operation as described in the following
paragraphs.
5.1.2.1 AMR-WB SCR Timing procedures
To allow an exact verification of the TX SCR handler functions, all frames before the reset of the system are treated as
if there were speech frames of an infinitely long time. Therefore, and in order to ensure the correct estimation of
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3GPP TS 26.193 version 17.0.0 Release 17 9 ETSI TS 126 193 V17.0.0 (2022-05)
comfort noise parameters at RX SCR side, the first 7 frames after the reset or after enabling the SCR operation shall
always be marked with TX_TYPE= "SPEECH_GOOD", even if VAD flag ="0" (hangover period, see figure 3).
The Voice Activity Detector (VAD) shall operate all the time in order to assess whether the input signal contains speech
or not. The output is a binary flag (VAD flag ="1" or VAD flag ="0", respectively) on a frame by frame basis (see [7]).
The VAD flag controls indirectly, via the TX SCR handler operations described below, the overall SCR operation on
the transmit side.
Whenever VAD flag ="1", the speech encoder output frame along with mode information shall be passed directly to the
AN, marked with TX_TYPE =" SPEECH_GOOD "
At the end of a speech burst (transition VAD flag ="1" to VAD flag ="0"), it takes eight consecutive frames to make a
new updated SID analysis available (see [6]). Normally, the first seven speech encoder output frames after the end of
the speech burst shall therefore be passed directly to the AN, marked with TX_TYPE =" SPEECH_GOOD "
("hangover period").
The end of the speech is then indicated by passing frame eight after the end of the speech burst to the AN, marked with
TX_TYPE = "SID_FIRST" (see figure 3). SID_FIRST frames do not contain data.
last speech frame
end of speech burst
first pause frame Frame
(20 ms)
Hangover
VAD flag
N e.g.     35   36   37   38   39   40   41    42    43   44   45    0    1
elapsed
S S S S S S S S S S F N N U N
Frames
to AN
TX Type
TX Types: “S” = SPEECH; “F” = SID_FIRST; “U” = “SID_UPDATE; “N” = NO DATA
N : No. of elapsed frames since last SID_UPDATE
elapsed
Figure 3: Normal hangover procedure for AMR-WB (N > 23)
elapsed
If, however, at the end of the speech burst, less than 24 frames have elapsed since the last SID_UPDATE frame was
computed, then this last analysed SID_UPDATE frame should be passed to the AN whenever a SID_UPDATE frame
is to be produced, until a new updated SID analysis is available (8 consecutive frames marked with VAD flag
="0").This reduces the load on the network in cases where short background noise spikes are taken for speech, by
avoiding the "hangover" waiting for the SID frame computation.
Once the SID_FIRST frame has been passed to the AN, the TX SCR handler shall at regular intervals compute and pass
updated SID_UPDATE (Comfort Noise) frames to the AN as long as VAD flag = "0". SID_UPDATE frames shall be
th
generated every 8 frame. The first SID_UPDATE shall be sent as the third frame after the SID_FIRST frame.
The speech encoder is operated in full speech modality if TX_TYPE = " SPEECH_GOOD " and otherwise in a
simplified mode, because not all encoder functions are required for the evaluation of comfort noise parameters and
because comfort noise parameters are only to be generated at certain times.
5.1.3 The TX part of the AN
The TX part of the AN has the following overall functionality. The transmission is cut after the transmission of a
SID_FIRST frame when the speaker stops talking. During speech pauses the transmission is resumed at regular
intervals for transmission of one SID_UPDATE frame, in order to update the generated comfort noise on the RX side.
The operation of
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the TX part of the AN is controlled by the TX SCR handler via the TX_TYPE.
All frames, marked with SPEECH_GOOD, SID_FIRST or SID_UPDATE shall be transmitted by the TX part of the
AN.
5.2 Receive (RX) side
A block diagram of the receive side SCR functions is shown in Figure 3 below.
RX SCR handler De-framing RX Access Network
T
Speech
S
AMR-WB
Decoder
Information bits
Information bits
Frame Type
Detection
Mode Indication .
Error Frame Type
Concealment 2
Error
RX_TYPE
FQI
Correction &
Comfort
Detection
Noise
Generation
Figure 4: Block diagram of the receive side SCR functions
5.2.1 General operation
The AN passes all the received traffic frames to the RX SCR handler, classified with RX_TYPE, as described in Table
2 (see TS 26.201). The RX SCR handles the frame accordingly.
Table 2: RX_TYPE identifiers for AMR-WB
RX_TYPE Information Bits
SPEECH_GOOD Speech frame without detected errors.
SPEECH_BAD (likely) speech frame with bad CRC (or estimated to
be very bad by the RX part of the AN )
SPEECH_LOST No frame received. Indicates that this frame was
transmitted, but never received.
SID_FIRST This SID-frame marks the beginning of a comfort
noise period.
Correct SID update frame
SID_UPDATE
SID_BAD Corrupt SID update frame (bad CRC; applicable only
for SID_UPDATE frames)
Nothing useable was received. The synthesis mode of
NO_DATA
the previous frame type is used.

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5.2.3 Demands on the RX
...