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TR 26.916SA4
Media Handling and Quality aspects of SRVCC

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V14.2.0 (PDF)  2016/09  64 p.

Rapporteur:  Mr. Gabin, Frederic

Enhanced Single Radio - Voice Call Continuity (eSRVCC) is an existing standard specifying the handover of a Voice or Video call from LTE access to CS-radio access, either to GERAN (2G) or to UTRAN (3G) or other CS networks. The present document considers only enhanced SRVCC for voice calls between 3GPP accesses. This study assumes that the Codecs defined in TS 26.114 are used on the LTE access and the Codecs defined in TS 26.103 on the CS accesses.
In the IMS Core Network, the voice call is typically anchored in the ATCF/ATGW (Access Transfer Control Function/ Access Transfer GateWay). The eSRVCC procedure, as specified, may cause additional transcoding between the target radio leg and the ATGW, even though in theory it would be possible to avoid it. As a result, the eSRVCC procedures may add one or more unnecessary transcoding point(s) for the call and thereby degrade the quality of the ongoing call unnecessarily.
The main objectives of this study are to analyse example call scenarios and find potential solutions to minimize the number of transcoding cases. Another objective is to optimize the interworking and the transition between EVS and AMR-WB during eSRVCC. The study should also show the reasons and potential solutions for too long speech path interruptions during eSRVCC.

full Table of Contents for  TR 26.916  Word version:   14.2.0

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1  ScopeWord-p. 7
2  ReferencesWord-p. 8
3  Definitions, symbols and abbreviations
4  eSRVCC Reference Architecture
5  eSRVCC Reference ProcedureWord-p. 12
6  Selected example scenarios for eSRVCC
7  Identified Problems with current eSRVCCWord-p. 25
8  Speech Quality and Media Handling AspectsWord-p. 30
9  Codec Mode Control before, during and after SRVCCWord-p. 34
10  SDP Offer-Answer between MSC and ATCF
11  Codec Compatibility
12  Enhancements for media and quality aspects
13  Proposals for Stage 2 and Stage 3Word-p. 61
A  Change historyWord-p. 62

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