1. Introduction 4
1.1 References 5
1.2 Terminology 6
2. Overview of the AMR System 7
3. Speech Coding (Adaptive Multi-Rate) 9
3.1 DTX 9
4. Noise Suppression 11
5. Link Adaptation 12
5.1 Setup Procedure 12
5.1.1 Definition of the AMR Active Codec Set 13
5.1.2 Default AMR Configuration 14
5.1.3 AMR Configuration Order Link Information Element 14
5.1.4 Initial Codec Mode Selection at Call Setup and Handover 15
5.1.5 Definition of Codec Mode Command/Request Decision Thresholds 15
5.2 Inband Signaling 17
5.3 Out-of-Band Signaling 18
5.3.1 Inband Signaling During DTX 18
5.3.2 AMR Configuration Using FACCH 18
5.4 Codec Mode Adaptation 18
5.4.1 Channel Quality Measure 18
5.4.2 Generation of Codec Mode Commands and Requests 19
5.4.3 Reference C/(I+N) Performance 19
5.4.4 Performance Requirements 20
5.5 Transmitter/Receiver Inband Channel Synchronization 21
6. Optimization for Tandem Free Operation 22
6.1 Operation with Ongoing TFO 22
6.2 DTX with Ongoing TFO 22
6.3 Comfort Noise in DL with TFO 22
6.4 Operation during Handoff with Ongoing TFO 23
7. Channel Coding 24
7.1 Definitions of Terms, Nomenclature and Assumptions 25
7.2 Overview 25
7.3 Interleaving Options 26
7.4 Subjective Ordering 27
7.5 Channel Coding – Mobile Station 27
7.5.1 Speech Data Classes 28
7.5.2 Cyclic Redundancy Check (CRC) 29
7.5.3 Convolutional Encoding 30
Active Codec Set (ACS) Bit Map 13
Codec Mode Information Encoding 14
Link Information Element 14
Definition of Threshold and Hysteresis 16
Encoding of Thresholds 17
Encoding of Hysteresis 17
Reference C/(I+N) Performance for Full-Rate 19
Reference C/(I+N) Performance for Half-Rate 20
Interleaving Formats for Full-rate 26
Interleaving Format for Half-rate 26
Speech Encoder Frame Size for Each Mode 27
Bit Classification for Full-rate Uplink 29
Bit Classification for Half-rate Uplink 29
High Level AMR Block Diagram 8
Definition of Threshold and Hysteresis for Codec Mode Adaptation 16
Overview of the Full-rate Uplink Channel Encoding 28
Overview of the Half-rate Uplink Channel Encoding 28
This document provides a description of the AMR speech service, including speech coding, channel coding and link adaptation.
GSM references in this specification are specific, in the sense that they refer to release and version numbers. If there are future changes that require changes to the channel coding or other parts, this specification will have to be revisited. See Section 3 for specific references.
Section 2 provides an overview of the AMR system.
Section 3 describes the speech coding.
Section 4 describes the optional noise suppression.
Section 5 describes the link adaptation and inband signaling that control the mode adaptation.
Section 6 describes support for tandem free operation (TFO).
Section 7 provides a detailed description of the channel encoder. The channel decoder is not considered a part of this standard, and may be performed with any method capable of decoding Recursive Systematic Convolutional (RSC) codecs and block codes.
The implementations of the speech codec in the MS shall be bit-exact. Bit-exact implementation shall conform to the fixed point C-code, see GSM 06.73,, and is subject to the test vectors defined in the ETSI specification for AMR, see GSM 06.74, . The implementation of the speech codec in the BS is not required to be bit-exact; however, non bit-exact implementation is subject to the minimum performance requirements for the AMR codec, contained in TIA/EIA-136-240.
References and Definitions
GSM 06.71, v7.0.2 Digital cellular telecommunications system (Phase 2+); Adaptive Multi-Rate (AMR); Speech processing functions; General description
GSM 06.73, v7.4.0 Digital cellular telecommunications system (Phase 2+); Adaptive Multi Rate (AMR) speech; ANSI-C code for the AMR speech codec
GSM 06.74, v7.0.1 Digital cellular telecommunication system (Phase 2+); Test sequences for the Adaptive Multi-Rate (AMR) speech codec
GSM 06.90, v7.2.0 Digital cellular telecommunications system (Phase 2+); Adaptive Multi-Rate (AMR) speech transcoding
GSM 06.91, v7.1.0 Digital cellular telecommunications system (Phase 2+); Substitution and muting of lost frames for Adaptive Multi Rate (AMR) speech traffic channels
GSM 06.92, v7.1.1 Digital cellular telecommunication system (Phase 2+); Comfort noise aspects for Adaptive Multi-Rate (AMR) speech traffic channels
GSM 06.93, v7.3.0 Digital cellular telecommunication system (Phase 2+); Discontinuous Transmission (DTX) for Adaptive Multi-Rate (AMR) speech traffic channels
GSM 06.94, v7.1.1 Digital cellular telecommunications system (Phase 2+); Voice Activity Detector (VAD) for Adaptive Multi-Rate (AMR) speech traffic channels; General description
GSM 05.09, v7.3.0 Digital cellular telecommunications system (Phase 2+); Link Adaptation
GSM 05.03, v7.1.1 Digital cellular telecommunications system (Phase 2+); Channel coding
GSM 06.77, v8.0.0 Minimum Performance Requirements for Noise Suppresser Aplication to the AMR Speech Encoder.
IS-853, Noise Suppression Minimum Performance for AMR