Ultra-Flash CSFB(SRVCC based CSFB)



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SA WG2 Meeting #100 S2-134315 11 - 15 November 2013, San Francisco, USA Ultra-Flash CSFB(SRVCC based CSFB) Source Company: Huawei, HiSilicon, Bharti, China Unicom, Deutsche Telekom Content Ultra-Flash CSFB introduction Ultra-Flash CSFB Discussion - PowerPoint PPT Presentation
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SA WG2 Meeting #100 S2-134315 11 - 15 November 2013, San Francisco, USA Ultra-Flash CSFB(SRVCC based CSFB) Source Company: Huawei, HiSilicon, Bharti, China Unicom, Deutsche Telekom Content Ultra-Flash CSFB introduction Ultra-Flash CSFB Discussion Summary What is Ultra-Flash CSFB? MME LTE SRVCC Inter RAT Handover SRVCC Inter RAT Handover VoLTE w/ SRVCC MME MME CSFB LTE LTE SRVCC Session Transfer Redirection Redirection SGs SGs SGSN Sv Sv G/U SGSN SGSN MSC G/U G/U MSC MSC IMS Ultra-Flash CSFB, SRVCC Session Transfer is not needed as it is a CS call setup procedure rather than VoLTE to 2/3G hand over Ultra-Flash CSFB requires UE to support standard SRVCC feature SRVCC IRAT HO SRVCC IRAT HO Ultra-Flash CSFB Ultra-Flash CSFB is a solution used SRVCC IRAT handover to accelerate CSFB Ultra Flash CSFB with SRVCC capable UE Per UE’s SRVCC capability and without a QCI=1 bearer, eNB triggers SRVCC HO during CSFB MME does not delete a QCI=1 bearer as the SRVCC procedure is due to CSFB and there is no QCI=1 bearer (1) The MSC does not initiate the Session Transfer procedure and only triggers a normal CS Handover preparation (2) the MSC sends Disconnect to clear the dummy call instance due to SRVCC procedure Ultra Flash CSFB with SRVCC capable UE- MO Huawei Analysis As shown in green lines, the UE start CS call and CC sublayer allocate (TI=0,TI Flag=0) CS voice session The MM sublayer find out the UE in E-UTRAN side and indicate EMM sublayer to initiate ESR procedure The LTE AS layer forward HO CMD to GERAN/UTRAN AS layer GERAN/UTRAN AS layer access the GERAN/UTRAN and SRVCC handling is triggered MM sublayer gives an indication to the CC sublayer to establish CS call(TI=0,TI Flag=1)due to SRVCC per step b6 And derives GERAN/GERAN security contexts for the CS domain from the current EPS security context Upon receiving step b6, CC sublayer allocates(TI=0, TI Flag=1) for SRVCC and proceed with (TI=0,TI Flag=0) call setup procedure by sending CM Service Request and Setup with TI=0 MSC send disconnect(TI=0,TI Flag=1) to clear the dummy call object (TI=0, TI Flag = 1) in UE side Ultra Flash CSFB with L->U SRVCC - MT Per UE’s SRVCC capability and without a QCI=1 bearer, eNB triggers SRVCC HO during CSFB MME does not delete a QCI=1 bearer as the SRVCC procedure is due to CSFB and there is no QCI=1 bearer (1) The MSC does not initiate the Session Transfer procedure and only triggers a normal CS Handover preparation (2) the MSC sends Disconnect to clear the dummy call instance due to SRVCC procedure (3)SRVCCMSC send setup(TI=1) to the UE Ultra Flash CSFB with SRVCC capable UE- MT Huawei Analysis As shown in green lines, the UE(LTE part) receive CSFB paging call and trigger the CSFB procedure accordingly The LTE AS layer forward HO CMD to GERAN/UTRAN AS layer GERAN/UTRAN AS layer access the GERAN/UTRAN and SRVCC handling is triggered MM sublayer gives an indication to the CC sublayer to establish CS call with TI =0 due to SRVCC per step b6 And derives GERAN/GERAN security contexts for the CS domain from the current EPS security context CC sublayer allocate TI=0 CS session per step b6 MM sublayer sends paging response to MSC and MSC sends setup(TI=1) to the UE as TI=0 is already in CC sublayer MSC further sends Disconnect(TI=0) to the UE in order to release the TI=0 CS session Ultra-Flash CSFB VS NW-Initiated CS Services while UE is in IMS VoIP session in 8422 8422NW-Initiated CS Services while UE is in IMS VoIP session0 Ultra Flash CSFB NW-Initiated CS Services while UE is in IMS VoIP session in 8422 Vs Ultra-Flash CSFB Content Ultra-Flash CSFB introduction Ultra-Flash CSFB Discussion Summary Call Setup Time Comparison(Fall back to GSM) Ultra-Flash CSFB to GSM SRVCC/PS HO Authentication/encryption/UE Capacity identify 2G call 2G CS RAB establishment Ultra-Flash CSFB Read SI SRVCC IRAT HO UE access to 2G cell Basic call procedure R8 R9(Flash) Ultra-Flash call Ultra-Flash GSM Call LTE call LTE, both MO/MT fall back Based on Huawei Lab testing Call Setup Time Comparison(Fall back to UMTS) Ultra-Flash CSFB to UMTS SRVCC/PS HO PS HO Ultra-Flash CSFB Authentication/encryption/UE Capacity identify 3G call 3G CS RAB establishment SRVCC IRAT HO Read SI UE access to 3G cell Basic call procedure R8 PSHO Ultra-Flash call Ultra-Flash UMTS Call LTE call LTE, both MO/MT fall back Based on Huawei Lab Test Why Ultra-Flash CSFB Achieve the Shortest Call Setup ? Sv 3 SGs Both Sv and SGs interfaces supported, SRVCC IRAT HO was used to accelerate CSFB 2 SRVCC MSC 4 1 MME Ultra-Flash CSFB Reduce Call Setup Time in Following 4 Steps eNB BSC/RNC How Ultra-Flash CSFB Reduce Impact to Current Network IMS Core Proxy solution, reduce the impact to CS network SRVCC MSC Sv SGs EPC Naturally support VoLTE/SRVCC,without MME/MSC upgrade again VMSC MME BSC/RNC eNodeB Could update some (one at the minimum) MSC Servers rather than all the MSC Servers How Rel-8 CSFB and Ultra-Flash CSFB co-exist Add software patch on SRVCC feature and no impact on Rel-8 CSFB SRVCC MSC SGs Sv SGs MME MSC eNB BSC/RNC Per 23272-b50, during combined Attach/TAU procedure If UE supports SRVCC, MME selects a MSC/VLR which is both SRVCC and CSFB capable If UE does not support SRVCC, MME selects a MSC/VLR which is CSFB capable During the CSFB procedure, based on UE capability If UE support SRVCC capability, eNB is to perform Ultra-Flash CSFB ie executing SRVCC HO If UE does not support SRVCC capability, eNB is to perform Rel-8 CSFB IMS Core Content Ultra-Flash CSFB introduction Ultra-Flash CSFB Discussion Summary Ultra-Flash CSFB Value and Principle Easy Deployment Principle Call Setup Time 4 2 SRVCC HO SRVCC UE MSC MME MSC eNB MME 1 3 2 Ultra-Flash R8 CSFB Avoid to update RNC/BSC Fall back GSM and UMTS Supported SRVCC HO LTE G/U In parallel UE fallback and call in MSC L->U 6 ~ 9 s L->G 10-12 s 3 ~ 5 s Shorter than the Traditional CS Call Delay Reuse SRVCC handover to accelerate CSFB and smooth evolution to VoLTE/SRVCC Avoid to update 2G/3G Radio Proposed to add deployment option in Rel-12 that enables faster and more reliable CSFB for UEs and networks supporting SRVCC VoLTE configured UE support Ultra-Flash CSFB Directly If IMS has been deployed,MMEindicateUE IMS Voice over PS session supported If IMS has not been deployed,MMEindicate IMS Voice over PS session NOT supported MME VoLTE PGW SGW Ultra-Flash CSFB IMS PS voice priority, CS Voice secondary is configured in UE MSC Value: If IMS has not been deployed, VoLTE/SRVCC UE can use Ultra-Flash CSFB After IMS has been deployed, UE can use VoLTE directly without reconfiguration UE decide to use VoLTE or Ultra-Flash CSFB according to MME indication