Alerting SRVCCAlerting SRVCC

Ram Chockalingam

aSRVCC

What – able to continue the call in CS when handover triggered during alerting.

T-Mobile US intends to provide to launch alerting SRVCC to enrich the customer experience during call alerting

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during alerting. When - eNodeB will trigger SRVCC Handover when the signal

threshold reaches -120 dBm during call alerting stage. Why - is required due to limitations with SRVCC during ringing

Customer Experience will improve. Drop call Rate and VoLTE KPI’s will improve.

Network Architecture

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aSRVCC Originating Call Flow

MT is sending 180 ringing to MO

1. INVITE(AT) from MSC to ATCF

2. Reserve Media Resources

3. INVITE(AT) to TAS(SCC-AS)

4. SIP INFO from SCCAS to MSC to inform call in alerting state

5. MSC – will change status to call alerting state

I/S CSCFI/S CSCFATGWATGW

IMS Core

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MSC-SMSC-S

6. MT answers and send 200 OK, MSC will change status to active state.

7. MO call connected in CS

8. Clear up resource of PS leg of UE-A

6

5

UE-AUE-AUE-BUE-B

67

8

SCCASSCCASATCFATCF

12

3

4

in CSin CS

aSRVCC Terminating Call Flow

MO is sending INVITE to MT and received180 ringing response

1. INVITE(AT) from MSC to ATCF

2. Reserve Media Resources

3. INVITE(AT) to TAS(SCC-AS)

4. SIP INFO from SCCAS to MSC to inform call in alerting state

5. UE–B on CS answers the call, MSC moves to call received state.

I/S CSCFI/S CSCFATGWATGW

IMS Core

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6. SIP INFO from MSC to SCCAS to inform Call accepted

7. 200 OK for INVITE from SCCAS to UE-A

8. Clear up resource of PS leg of UE-B leg

MSC-SMSC-S

5

UE-BUE-BUE-AUE-A

7

8

SCCASSCCASATCFATCF

12

3

46

in CSin CS

Questions ?

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THANK YOU