1). SRVCC Overview:
§ As SRVCC (as Voice call continuit) between IMS over PS access and CS access for calls, the IMS multimedia telephony sessions needs to be anchored in IMS when the UE is capable of transmitting/receiving on only one of those access networks at a given time.
§ Single Radio Voice Call Continuity (SRVCC) is used for Circuit Switched (CS) calls that are anchored in the IMS
§ from E‑UTRAN to CDMA2000 1xCS
§ from E‑UTRAN to UTRAN/GERAN
§ from HSPA to UTRAN/GERAN
§ SRVCC from E‑UTRAN/UTRAN (HSPA) access to 3GPP UTRAN/GERAN CS accesses for voice calls that are anchored in the IMS
§ Handling of SRVCC from 3GPP UTRAN/GERAN CS accesses to E‑UTRAN/UTRAN (HSPA) direction is not specified in this release (R8)
§ A 3GPP SRVCC UE is a UE enhanced for IMS Service Continuity with the additional UE capabilities described in this specification for SRVCC between two access networks as above.
2.1). SRVCC: from E-UTRAN to 3GPP UTRAN/GERAN
§ STN-SR = Session Transfer Number for SR-VCC
§ MME first receives the handover request from E‑UTRAN with the indication that this is for SRVCC handling,
§ Then MME triggers the SRVCC procedure with the MSC Server enhanced with SRVCC via the Sv interface if MME has SRVCC STN-SR information for this UE.
§ MSC Server enhanced for SRVCC then initiates the session transfer procedure to IMS and coordinates it with the CS handover procedure to the target UTRAN/GERAN cell.
§ MSC Server enhanced for SRVCC then sends PS-CS handover Response to MME, which includes the necessary CS HO command information for the UE to access the UTRAN/GERAN
§ Handling of any non‑voice PS bearer is done by the PS bearer splitting function in the MME.
§ MME starts the handover of non‑voice PS bearer during SRVCC procedure based on the information received from E‑UTRAN.
§ The MME is responsible to coordinate the Forward Relocation Response from SRVCC and PS‑PS handover procedure
2.2). SRVCC Architecture for E-UTRAN to 3GPP UTRAN/GERAN
§ http://docs.google.com/View?id=ddh56dhg_303g937w8gp
2.3). SRVCC architecture for E-UTRAN to 3GPP2 1xCS (N/A Here)
3.1). Emergency Call for SRVCC Overview:
§ E-STN-SR = Emergency Session Transfer Number for SRVCC
§
§ Emergency Session Transfer Number for SRVCC (E-STN-SR): A number used in the session transfer procedure for emergency calls for SRVCC, pointing toward the serving (visited if roaming) IMS E-SCC AS which handles the IMS emergency session transfer from PS to CS access
§ IP Multimedia Subsystem (IMS) Emergency Sessions is supported via E-CSCF
§ The Emergency solution should be able to provide continuity of location support the SR VCC of emergency calls by providing the PSAP with an accurate initial and updated location estimate
3.2). Emergency SRVCC Architecture for E-UTRAN to 3GPP UTRAN/GERAN
§ http://docs.google.com/View?id=ddh56dhg_305fx65xmhp
3.3). Emergency SRVCC for E-UTRAN to 3GPP UTRAN/GERAN
§ allow SR VCC for IMS emergency session from E-UTRAN to 2/
§ It uses E-STN-SR for session transfer procedure where the E-STN-SR is an Emergency Session Transfer Number for SR VCC.
§ MSC Server is enhanced for SR VCC (aka SR VCC MSC).
§ SR VCC MSC initiates the session transfer with E‑STN‑SR, using the same procedure as defined for regular SR VCC with STN-SR.
§ E-STN-SR points toward the serving (visited if roaming) IMS network which handles the IMS emergency session.
§ The E-SCC AS performs the session continuity when the INVITE (E-STN-SR) is received.
Note: The MME or SGSN has to be aware that the UE is having an emergency session.
3.4). Limited Service Mode (UICC-less) using equipment identifier
§ In order to support SRVCC emergency session domain transfer for UEs in Limited Service Mode (e.g. UICC-less) using equipment identifier, the MME shall support Limited Service Mode UE emergency attach using unauthenticated IMSI or equipment identifier.
§ When EUTRAN (UTRAN) determines that SR VCC is needed, MME/SGSN invokes SR VCC via Sv interface to MSC enhanced for SR VCC including in any case the UE's equipment identifier.
§ The equipment identifier is passed to MSC server via the MME.
§ The MSC enhanced for SR VCC will setup the call leg towards the E-SCC AS with the UE's equipment identifier.
§ If the MSC enhanced for SR VCC has a SIP interface, it shall carry equipment identifier as a SIP URI to the E-SCC AS.
§ If the MSC enhanced for SRVCC does not have a SIP interface, it may convey the equipment identifier by using the IAM message to the MGCF. The MGCF then sends this with an INVITE to
§ The E-SCC AS can then correlate the call legs according to the equipment identifier.
§ The equipment identifier is then communicated to the E-SCC AS to allow the E-SCC AS to correlate the session when updating the new leg.
4). Functional Entity for SRVCC:
4.1). SRVCC for Functional Entity - Serving/PDN GW
§ No additional requirement on S-GW or P-GW due to SRVCC
4.2). SRVCC for Functional Entity - HSS
§ SRVCC STN-SR and MSISDN are downloaded to MME from HSS during E-UTRAN attach procedure
4.3). SRVCC for Functional Entity – UE with SRVCC
§ 3GPP SRVCC UE shall support UE assisted T-ADS functionality for selecting the CS domain for terminating voice calls, and 3GPP SRVCC UE indicates to the network that the UE is SRVCC capable when being configured for using IMS speech service supported by the home operator
§ 3GPP2 SRVCC UE is capable to perform SRVCC to the 3GPP2 1xCS system
And enhanced for Emergency SRVCC
§ The SRVCC UE has IMS emergency call capabilities
4.4). SRVCC for Functional Entity – MSC Server
MSC Server provides the following functions enhanced for SRVCC:
§ Handling the Relocation Preparation procedure requested for the voice component from MME via Sv reference point;
§ Invoking the session transfer procedure from IMS to CS
§ Coordinating the CS Handover and session transfer procedures;
§ Handling the MAP_Update_Location procedure without it being triggered from the UE
And enhanced for Emergency SRVCC
§ Support of location continuity
§ Support of Limited Service Mode.
4.5). SRVCC for Functional Entity – E-UTRAN
§ Between UE and E-UTRAN, no additional functionality is required for the E‑UTRAN.
§ When E‑UTRAN selects a target cell for SRVCC handover, it needs to send an indication to MME that this handover procedure requires SRVCC.
§ E-UTRAN may be capable of determining the neighbor cell list (3GPP2 1xCS or 3GPP UTRAN/GERAN) based on the
4.6). SRVCC for Functional Entity – MME
MME (operator) supports the interworking to 3GPP CS, and MME shall support the following additions and clarifications:
§ Performing the PS bearer splitting function by separating the voice PS bearer from the non-voice PS bearers.
§ Handling the non-voice PS bearers handover with the target cell as according to Inter RAT handover procedure
§ Initiating the SRVCC handover procedure for handover of the voice component to the target cell via the Sv interface.
§ Coordinating PS handover and SRVCC handover procedures when both procedures are performed,
And enhanced for Emergency SRVCC
§ Identifies the UE and indicates emergency call as part of handover request.
§ May send location information to support location continuity
§ Shall send equipment identifier to the MSC server during the handover procedure for the case of UEs operating in limited service mode.
4.7). SRVCC for Functional Entity – SGSN
SGSN (operator) supports the interworking to 3GPP CS, the SGSN shall follow the rules and procedures with the following additions and clarifications:
§ Performing the PS bearer splitting function by separating the voice PS bearer from the non-voice PS bearers.
§ Handling the non-voice PS bearers handover with the target cell as according to Inter/Intra RAT handover procedure
§ Initiating the SRVCC handover procedure for handover of the voice component to the target cell via the Sv interface.
§ Coordinating PS handover and SRVCC handover procedures when both procedures are performed.
And enhanced for Emergency SRVCC
§ Identifies the UE and indicates emergency call as part of handover request.
§ May send location information to support location continuity
§ Shall send equipment identifier to the MSC server during the handover procedure for the case of UEs operating in limited service mode.
4.8). SRVCC for Functional Entity – 1xCS IWS (N/A Here)
4.9). Emergency SRVCC for Functional Entity – E-CSCF
§ E‑CSCF shall provide the procedures for the insertion of the E‑SCC‑AS into the signalling path of an IMS emergency call.
4.10). Emergency SRVCC for Functional Entity – E-SCC AS
§ E‑SCC‑AS shall provide the procedures for IMS session anchoring and PS to CS session transfer.
§ The E‑SCC‑AS acts as a routing B2BUA which invokes third party call control (3pcc) for enablement of Session Transfers
5). Interface for SRVCC:
5.1). S102: MME – 3GPP2 1xCS IWS
§ The S102 provides a tunnel between MME and 3GPP2 1xCS IWS to relay 3GPP2 1xCS signalling messages.
5.2). Sv: MME/GGSN – MSC Server
§ The Sv provides SRVCC support between 3GPP E-UTRAN/UTRAN (HSPA) and 3GPP UTRAN/GERAN.
§ The Sv application defines a set of messages between the MME/SGSN and MSC Server to provide SRVCC
§ Sv interface is used to support Inter-RAT handover from VoIP/IMS over EPS to CS domain over 3GPP UTRAN/GERAN access or from UTRAN (HSPA) to 3GPP UTRAN/GERAN access
§ The Sv messages are based on GTP.
§ A SRVCC PS to CS Request message shall be sent across Sv interface from the MME/SGSN to the target MSC server as part of the MME/SGSN SRVCC procedure
5.3). S1-MME: E-UTRAN – MME
§ For 3GPP2 1xCS SRVCC, the S1‑MME provides S1 Information Transfer message between UE and MME to relay the 3GPP2 1xCS signalling messages.
§ For 3GPP SRVCC, the S1‑MME allows handover signalling between E‑UTRAN and MME.
5.4). Iu-ps: UTRAN (HSPA) – SGSN
§ For 3GPP HSPA SRVCC, the Iu-ps allows handover signalling between UTRAN and SGSN.
5.5). S
§ For 3GPP SRVCC, the s
6). Call Flow: (N/A Here)
沒有留言:
張貼留言