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Content for  TR 23.886  Word version:  10.0.0

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1 Scope  2 References  3 Definitions and abbreviations  4 Assumptions and requirements 
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1  Scope  p. 6

The objective of the feasibility study is to investigate a solution for supporting single radio the video call continuity from E-UTRAN/HSPA to UTRAN-CS based on the Rel-8/9 Single Radio Voice Call Continuity (SRVCC) architecture as specified in TS 23.216 and TS 23.237, and study the mechanisms to resolve the key issues. It is not expected that the SRVCC architecture will be modified unless any of the key issues cannot be resolved with the current architecture.
The study will be performed to the scenarios where IMS session using bidirectional voice and synchronised video such as defined in TS 22.173, originated in E-UTRAN/HSPA and the UE moves to UTRAN and continues the service over UTRAN in the CS domain.
The video call continuity from E-UTRAN/HSPA to GERAN is not supported.
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2  References  p. 6

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]
TS 23.216: "Single Radio Voice Call Continuity (SRVCC): Stage 2".
[3]
TS 23.237: "IP Multimedia Subsystem (IMS) Service Continuity; Stage 2".
[4]
TS 22.173: "IP Multimedia Core Network Subsystem (IMS) Multimedia Telephony Service and supplementary services; Stage 1".
[5]
TS 22.101: "Technical Specifications and Technical Reports for a UTRAN-based 3GPP system".
[6]
TS 22.278: "Service requirements for the Evolved Packet System (EPS)".
[7]
TS 26.114: "IP Multimedia Subsystem (IMS); Multimedia Telephony, Media handling and interaction".
[8]
TS 26.111: "Codec for circuit switched multimedia telephony service; Modifications to H.324".
[9]
ITU-T Recommendation H.324, Annex K: "Media oriented negotiation acceleration procedure" and associated changes to Annex J".
[10]
ITU-T Recommendation H.245: "Control protocol for multimedia communications".
[11]
TS 23.401: "GPRS Enhancements for E-UTRAN Access".
[12]
TS 23.172: "Technical realization of Circuit Switched (CS) multimedia service; UDI/RDI fallback and service modification; Stage 2".
[13]
TS 23.203: "Policy and charging control architecture".
[14]
TR 26.911: "Codec(s) for Circuit-Switched (CS) multimedia telephony service; Terminal implementer's guide".
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3  Definitions and abbreviations  p. 7

3.1  Definitions  p. 7

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.
Video Call:
For IMS over E-UTRAN/HSPA, it represents the session using bidirectional voice and synchronised real time video as specified in TS 22.173. For UTRAN-CS, it represents the Circuit Switched (CS) multimedia calls as specified in TS 22.101.
Single Radio Video Call Continuity:
Video call continuity from IMS over E-UTRAN/HSPA access to UTRAN access for calls that are anchored in IMS when the UE is capable of transmitting/receiving on only one of those access networks at a given time. The definition of SRVCC as specified in TS 23.216 could mean the process of continuing a voice (or video) call as a user moves from IMS over E-UTRAN/HSPA access to UTRAN access. However, the usage of the term SRVCC in 3GPP specifications will keep its original meaning, i.e. voice call continuity. In this technical report, the term vSRVCC is introduced for single radio video call continuity to differentiate it from single radio voice call continuity (SRVCC).
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3.2  Abbreviations  p. 7

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.
SRVCC
Single Radio Voice Call Continuity
vSRVCC
Single Radio Video Call Continuity

4  Assumptions and requirements  p. 7

4.1  Assumptions  p. 7

Followings are the assumptions of the vSRVCC from E-UTRAN/HSPA to UTRAN-CS handover:
  • The video call by IMS over E-UTRAN/HSPA is the MMTEL with video which uses separate EPS bearers for video and voice components, respectively.

4.2  Architectural requirements  p. 7

Followings are the requirements for the vSRVCC from E-UTRAN/HSPA to UTRAN-CS from an architectural perspective.
  • The solution shall not require UE with multiple RATs capability to simultaneously signal on two different RATs.
  • Impact on user service quality experience, e.g. QoS, call drop, interruption time, should be minimized.
  • Overall duration of the vSRVCC handover from E-UTRAN/HSPA to UTRAN-CS procedure shall be minimized.
  • It shall be possible to restrict RAT/domain selection change to access systems and subscribers depending on operator policies, and capabilities of the network and the UE, and these shall be network initiated and under network control.
  • In roaming cases, the VPLMN shall be able to control the RAT/domain selection change while taking into account any related HPLMN policies for MMTEL video call.
  • The signalling to the HPLMN for inter-domain continuity from E-UTRAN/HSPA to UTRAN-CS in the VPLMN should be minimized.
  • Rel-8/9 SRVCC architecture, as specified in TS 23.216, shall not be modified unless any of the key issues cannot be resolved.
  • For PS bearer(s) other than the ones for voice and video, PS continuity from E-UTRAN/HSPA to UTRAN-CS and from E-UTRAN to UTRAN/HSPA as specified in TS 23.401 shall not be impacted.
  • It shall be possible to fallback to Rel-8/9 SRVCC and maintain the voice component of MMTEL session if the Rel-10 vSRVCC cannot be completed due to, for instance, resource shortage in UTRAN-CS.
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4.3  Performance requirements  p. 8

  • In the RAT change procedure executed to enable vSRVCC, the audio component of the MMTEL session shall be subject to interruption times equivalent to Rel-8/9 SRVCC performance, i.e. target interruption time is not higher than 300 ms for voice as defined in TS 22.278.
  • In the RAT change procedure executed to enable vSRVCC, the time of the additional transfer of the video component(s) of the MMTEL session should be equivalent to the time it takes to complete the H.245 codec negotiation [10], as defined in TS 23.237, in order to minimize the perceivable video disruption for the user.
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