P05.Single Radio Voice Call Continuity (SRVCC) and CSFB Vs SRVCC.pdf

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1. VoLTE
SRVCC

Single Radio
Voice Call
Continuity

2. What is
(Single Radio Voice Call Continuity)

3GPP TS 23.216

3. Evolution of Voice Call

4G 4G
Network - Network —
CSFB call VoLTE +
2G Radio on 3G SRVCC

3G Radio 4G 4G
Network — Network —
VOLTE Call VoLTE +
on 4G SRVCC +
CSFB : Circuit Switched Fall Back eSRVCC +
VoLTE : Voice over LTE aSRVCC

SRVCC : Single Radio Voice Call Continuity
eSRVCC : Enhanced SRVCC

aSRVCC : Alerting SRVCC

4. Various Approach to
CSFB

Voice Call start
in underlying

2G , 3G Radio

Non-VoLTE N/W

Service Based
Handover

CSFB : Circuit Switched Fall Back

VoLTE + SRYCC

4G Coverage

K VoLTE N/W
_sowTiong

<Q
Coverage Based WM ”
Handover

5. Evolution of SRVCC

Basic a
SRVCC Rel 8 Call Continuity from E-UTRAN to UTRAN/GRAN
aSRVCC Rel 10 Packet switched to Circuit Switched call transfer
during Alerting Phase
Enhanced SRVCC (Support for MSC Server
BSRVES Rel za assisted Mid Call Feature)
vSRVCC Rel11 Video SRVCC
rSRVCC Rel 11 | SRVCC from UTRAN/GRAN to E-UTRAN

Improve User experience

„u
GSMA GSMA IR.64

Pr 3GPP TS 23.216

http://TelecomTutorial.info

6. 2G/3G

e Continuity, Networ

(ce)

A

Interface
3GPP TS 29.280

7. SRVCC Call flow

3GPP TS 23.216 Page 39

our MSC Server] aga] [eus Tage | [FONPEN WS
MME MG msc] Keen RNsiBs:
T

a pe _
cr | Handover Preparation
4, Bearer Spiting Flow

Ba PS CS gg

THO Req

by, Reloc/HO,Rea
La. Rotos HO Req Ack

| 6a. Forward Reloc Req

| Tb. Forward Reloc Resp

Ba. Relge HO Reg Ack
gb. Prep HO Resp |]
ppm 0 Rep
le Establish ce
|__ 9. Intation of Session Transfer (STH-SR or ESTNNSR)

(12. PS toCSResp ===>
E 10. Session transfer a
13. Handover Command update remote leg

14. HO ffgm EUTRAN command

15, UE tunes to
UTRANGERAN

16. HO Detection

http://TelecomTutorial.info

9. 2G/3G
Network

2G/3G
Network

10. Measurement

> Teports

e.)

2G/3G
Network

T9AOPUEeH

11. £
3
E
3
2
&

2G/3G
Measurement Network

2G/3G
Network

T9AOPUEeH

SGSN — TN nea

SGW / PGW

Relocation

12. Relocation

2G/3G

Network

Forward
< Relocation Reg
Ack >

sGW / PGW

2G/3G
Network

——

Relocation

Ack

13. 2G/3G
Network

2G/3G
Network

Relocation
Relocation

Forward
< Relocation Reg

Ack

sew/row ke Response

Release of IMS access leg

3GPP TS 23.237

14. 2G/3G
Network

2G/3G
Network

15. SRVCC Call flow

3GPP TS 23.216 Page 39

ETS
MSC

13. Hando
1: Handover |

14 HONG EUTRAN pat Handover Execution Flow

15. UE tunes to
UTRANIGERAN

16. HO Detection

17a. RelocHO Complete}
BIT mia

17». SES (HO Complete)

TS ANSWER

171. TMSI Reallocation,
hemos

182. Reloc/HO Complete
PL,
18b. Forward Reloc Complete/Ack
| fé. Update bearer
180. Release Resources | — 18d. Dalete Session AE
—— e

http://TelecomTutorial.info

16. 2G/3G
Network

2G/3G
Network

17. 2G/3G
Network

2G/3G
Network

Reloc/ HOYA

PS to CS Complete/Ack

18. Session transfer number for
SRVCC (STN-SR)

+ Used for Session Transfer of Call ¢ Used for correlation of sessions
to CS Domain at access transfer

+ E.164 Nomenclature ( Similar to + MSISDN of User in CS Network

MSRN ) + Helps to Identify Session to be
e Flow Transferred

¢ HSS -> MME (56, Attach Flow)
+ MME -> MSC (Sv, PS->CS Req)
© MSC -> IMS ( Voice Call )

http://TelecomTutorial.info

19. Network Changes required for Enabling SRVCC

ATCF ATGW MSS

E-UTRAN MME HSS

SR-VCC-
(WE: L SCC-AS

20. Enhanced SRVCC ( eSRVCC )

¢ Interruption Time Reduced + Anchoring Point Change
+ SRVCC : 800-1000 ms + SRVCC : Home SCC-AS ( Call
© eSRVCC : < 300 ms Must Go Back to Home
Network for Roamers )
¢ eSRVCC : Serving Network
ATCF/ATGW ( Call can be
Switched in Visited Network
Itself — This Saves Time )

http://TelecomTutorial.info

21. Further Study ..

GSMA, IR.92 IMS Profile for Voice and SMS

GSMA, IR.94 IMS Profile for Conversational Video Service

3GPP, TS.23.216 Single Radio Voice Call Continuity (SRVCC)

GSMA, IR.64 IMS Service Centralization and Continuity Guidelines V6.0

3GPP, TS22.278 Service Requirements for the Evolved Packet System (EPS)
3GPP, TS23.237 IP Multimedia Subsystem (IMS) Service Continuity Stage 2

http://TelecomTutorial.info

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