Presentation
Ultra-Flash CSFB(SRVCC based CSFB)
Source Company: Huawei, HiSilicon, Bharti, China Unicom, Deutsche Telekom
SA WG2 Meeting #100 S2-134315
11 - 15 November 2013, San Francisco, USA
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HUAWEI TECHNOLOGIES CO., LTD.
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Content
Ultra-Flash CSFB introduction
Ultra-Flash CSFB Discussion
Summary
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LTE
G/U
SGs
MSC
SGSN
MME
Redirection
What is Ultra-Flash CSFB?
MSC
SGSN
MME
IMS
SRVCC Session Transfer
LTE
G/U
Sv
SRVCC Inter
RAT Handover
SRVCC IRAT HO
Sv
SRVCC Inter
RAT Handover
SRVCC IRAT HO
CSFB
VoLTE
w/ SRVCC
Ultra-Flash CSFB is a solution used SRVCC IRAT handover to accelerate CSFB
LTE
G/U
SGs
MSC
SGSN
MME
Redirection
Ultra-Flash CSFB
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.
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3
Ultra Flash CSFB with SRVCC capable UE
Per UEs 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
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Ultra Flash CSFB with SRVCC capable UE - MO
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2013/11/11
5
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.
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Ultra Flash CSFB with L->U SRVCC - MT
Per UEs 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)SRVCC MSC send setup(TI=1) to the UE
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Ultra Flash CSFB with SRVCC capable UE - MT
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2013/11/11
8
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
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Ultra-Flash CSFB VS NW-Initiated CS Services while UE is in IMS VoIP session in 8.4.2.2
8.4.2.2NW-Initiated CS Services while UE is in IMS VoIP session0
Ultra Flash CSFB
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NW-Initiated CS Services while UE is in IMS VoIP session in 8.4.2.2 Vs Ultra-Flash CSFB
NW-Initiated CS Services while UE is in IMS VoIP sessionUltra-Flash CSFB1MME Need to delete QCI=1 bearer during SRVCC Do not delete QCI=1 bearer during SRVCC as there is no QCI=1 bearer.2MSCInitiates Session Transfer to move VoLTE to 2/.3G CS (1)MSC does not Initiates Session Transfer during SRVCC procedure.(2) Send Disconnect to clear due to SRVCC HO procedure.(3) MSC sends Setup message to UE with TI value of the voice call to "001" and TI flag value as in mobile terminated call since UE.3eNBBased on UE measurement reports and UEs SRVCC capability and QCI = bearer, decides to trigger an SRVCC handover to UTRAN/GERAN.Based on UE measurement reports and CS Fallback Indicator and UEs SRVCC capability , decides to trigger an SRVCC handover to UTRAN/GERAN.4BSC/RNCNo impact No impact5UEStandard VoLTE/SRVCC UEStandard CSFB/SRVCC UE
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Content
Ultra-Flash CSFB introduction
Ultra-Flash CSFB Discussion
Summary
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Call Setup Time Comparison(Fall back to GSM)
SRVCC
IRAT HO
Ultra-Flash CSFB to GSM
R8
R9(Flash)
Ultra-Flash call Ultra-Flash
GSM C