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Content for  TS 26.454  Word version:  16.0.0

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1  ScopeWord‑p. 6

The Enhanced Voice Services (EVS) Codec is specified in Technical Specifications TS 26.441, TS 26.442, TS 26.443, TS 26.444, TS 26.445, TS 26.446, TS 26.447, TS 26.448, TS 26.449, TS 26.450, TS 26.451 and TS 26.452. The generic frame format for 3G CS networks is specified in TS 26.453. The allowed EVS Configurations of the UMTS_EVS Codec Type are specified in TS 26.103.
The present document specifies the mapping of the EVS generic frame format (TS 26.453) to the Iu Interface (TS 25.415) and the Uu Interface, including handling of the EVS-CMR by the UE and the Iu-terminating MGW.
The present document specifies also the mapping to the Nb Interface in a BICC-based circuit switched core network. (TS 29.415) and the Nb-Interface in a SIP-I-based circuit switched core network (TS 23.231).
The present document specifies also the interworking of different EVS Configurations on the terminations of the MGW and the interworking between EVS and AMR-WB on the terminations of the MGW.
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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. 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]
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]
TR 41.001: "GSM Specification set".
→ to date, withdrawn by 3GPP
[3]
TS 23.231: "SIP-I based circuit-switched core network; Stage 2".
[4]
TS 25.415: "Iu Interface CN-UTRAN User plane Protocols".
[5]
TS 29.163: "Interworking between the IP Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networks"
[6]
TS 29.414: "Core network Nb data transport and transport signalling".
[7]
TS 29.415: "Core Network Nb Interface User Plane Protocols".
[8]
RFC 3550  (2003): "RTP: A Transport Protocol for Real-Time Applications", H. Schulzrinne, S. Casner, R. Frederick and V. Jacobson.
[9]
RFC 4733  (2006): "RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals", H. Schulzrinne and T. Taylor.
[10]
TS 25.133: "Requirements for support of radio resource management (FDD)".
[11]
TS 26.441: "Codec for Enhanced Voice Services (EVS); General overview".
[12]
TS 26.445: "Codec for Enhanced Voice Services (EVS); Detailed algorithmic description".
[13]
TS 26.446: "Codec for Enhanced Voice Services (EVS); Adaptive Multi-Rate - Wideband (AMR-WB) backward compatible functions".
[14]
TS 26.447: "Codec for Enhanced Voice Services (EVS); Error concealment of lost packets".
[15]
TS 26.448: "Codec for Enhanced Voice Services (EVS); Jitter buffer management".
[16]
TS 26.449: "Codec for Enhanced Voice Services (EVS); Comfort Noise Generation (CNG) aspects".
[17]
TS 26.450: "Codec for Enhanced Voice Services (EVS); Discontinuous Transmission (DTX)".
[18]
TS 26.451: "Codec for Enhanced Voice Services (EVS); Voice Activity Detection (VAD)".
[19]
TS 26.453: "Codec for Enhanced Voice Services (EVS); Speech codec frame structure".
[20]
TS 26.103: "Speech codec list for GSM and UMTS".
[21]
TS 26.114: "IP Multimedia Subsystem (IMS); Multimedia Telephony; Media handling and interaction".
[22]
TS 26.442: "Codec for Enhanced Voice Services (EVS); ANSI C code (fixed-point)".
[23]
TS 26.443: "Codec for Enhanced Voice Services (EVS); ANSI C code (floating-point)".
[24]
TS 26.444: "Codec for Enhanced Voice Services (EVS); Test Sequences".
[25]
TS 26.452: "Codec for Enhanced Voice Services (EVS); ANSI C code; Alternative fixed-point using updated basic operators".
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3  Definitions and abbreviationsWord‑p. 7

3.1  Definitions

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.
Active EVS-CMR:
EVS-CMR containing the requested (maximum) bit rate, (maximum) audio bandwidth and the major operation mode.
DL EVS-CMR:
the most recent successfully in downlink (DL) received codec mode request, relevant for encoding at the local UE.
EVS Configuration for Iu:
The MSC selects the EVS configuration for Iu and informs the MGW and the RNC in RAB Assignment.
EVS Configuration for Uu:
The RNC selects the EVS configuration for Uu.
EVS Configuration for UE:
The UE deducts the EVS configuration for UE from the Radio Bearer Configuration, i.e. the Set of TFCs.
EVS Configuration for Nb:
The MSC selects the EVS configuration for Nb and informs the MGW.
major operation mode:
This is either an EVS Primary mode of operation or an EVS AMR-WB IO mode of operation.
Set of available rates:
Rates of the EVS Configuration for UE, constrained further by RNC allowed TFCs and further constrained by the UE autonomous rate.
UE autonomous rate:
Maximum bit rate set by UE transport layer to optimize uplink performance (frame loss rate) if the TX power limit is reached.
UL EVS-CMR:
EVS-CMR sent by the UE in uplink (UL); relevant for encoding at the remote media-sender (e.g. remote UE or remote CN Transcoder), requesting the (maximum) codec mode to be used on the local DL to the UE.
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3.2  AbbreviationsWord‑p. 8

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
BICC
Bearer Independent Call Control
CN
Core Network
CMR
Codec Mode Request (for AMR and AMR-WB, often also used for EVS)
DL
Downlink
EVS
Enhanced Voice Services
EVS-CMR
Codec Mode Request for EVS (here explicitly used to differentiate)
EVS-SID
SID for EVS (here explicitly used to differentiate)
FQC
Frame Quality Classification (Iu and Nb Interfaces)
IM-MGW
IP Multimedia Media Gateway Function
Nb
Interconnection point between two MGWs of the CS Core Network
Nc
Interconnection point between two MSCs of the CS Core Network
NO_REQ
No Requirement (is present)
Mb
Interconnection point between the MGW of the CS Core Network and the IMS
NboIP
Nb-Interface user plane transport over RTP/UDP/IP when SIP-I is used on Nc
RC Ack
Rate Control Procedure Acknowledgement (on Iu)
RC Proc
Rate Control Procedure Request (on Iu)
RFC
RAB sub-flow Combination (on Iu and Nb)
RFCI
RFC Indicator
RFCS
RFC Set
SCR
Source Controlled Rate, synonym for DTX
SIP-I
SIP with encapsulated ISUP (variant of ISUP)
SMpSDU
Support Mode for Predefined SDU sizes
TC
Transcoder
TrFO
Transcoder Free Operation
UMTS_EVS
Name of the EVS Codec Type in CS Networks
Uu
The radio interface between UTRAN and the User Equipment
WB-CMR
CMR for AMR-WB
WB-SID
SID for AMR-WB (and EVS AMR-WB IO)
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4  General

The Iu-Interface is defined in two different variants for speech telephony in CS networks:
  1. for the ATM bearer with Iu-framing; and
  2. for the IP bearer with Iu-framing.
The Nb-Interface is defined in three different variants for speech telephony:
  1. for the ATM bearer with Nb-framing in a BICC-based Core Network,
  2. for the IP bearer with Nb-framing in a BICC-based Core Network, and
  3. for the IP bearer with RTP packing in a SIP-I-based Core Network.
The Mb-Interface is defined in one variant for speech telephony:
  1. for the IP bearer with RTP packing.
The mapping of the EVS generic frame format (TS 26.453) to the Iu interface specifies the speech data exchange between the RNC and the Iu-terminating MGW in PDU Type 0 (see TS 25.415). This mapping is independent of the radio interface in the sense that it has the same structure for both Frequency Division Duplex and Time Division Duplex modes of UTRAN.
The EVS-CMR is transported on the Iu and Uu interfaces appended to the speech payload, transparent to the RNC. The RNC Rate Control commands (UL RC Proc), sent uplink to the Iu-terminating MGW for downlink rate control, are contained in PDU Type 14 messages (see TS 25.415). The Iu-terminating MGW combines the UL EVS-CMR, received in uplink from the UE, with the UL RNC Rate Control commands, received in uplink from the RNC. The present document describes the interworking.
The mapping of the EVS Speech Codec parameters to the Nb interface in a BICC-based Core Network specifies the speech data exchange between two MGWs in PDU Type 0. This mapping is very similar to the mapping on the Iu interface. However, PDU Type 14 is not used for Rate Control on Nb. The present document specifies the User Plane interworking between Iu and Nb.
The mapping into PDU Type 0 on the Nb Interface in a BICC-based Core Network is identical to the one on the Iu Interface. In case of Transcoder Free Operation, the MGW is relaying the Speech Data Units unaltered between Iu and Nb Interfaces. The EVS-CMR, contained in Iu and Nb frames, may be modified by the MGW.
The mapping of the EVS Speech Codec parameters to the Nb interface in a SIP-I-based Core Network is as specified in TS 26.445, with some restrictions, as specified in the present document.
The mapping between the EVS Codec and the Radio Access Network within the UE is not an open interface and need not to be detailed. The present document specifies the interworking within the UE between EVS-CMR, Rate Control by the RNC and transmit-power-limitations.
For the 3GPP Codec Type UMTS_EVS the framing is 20 ms and also the packing time is 20 ms in all versions of the Iu and Nb-Interface. On the Mb interface, a different RTP packing may be applied.
The mapping of the EVS Speech Codec parameters to the Mb interface specifies the speech data exchange in RTP packets between the CS network and the IMS network. This mapping is specified in TS 26.445. TS 29.163 specifies the User Plane interworking between Nb and Mb; the present document specifies further details.
The present document specifies also the Interworking within the MGWs on User Plane and the interworking in case of the EVS Channel Aware Mode.
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