3gpp-ics-gene3GPP IMS Centralized Services (ICS) Overviewral-overview

1

3GPP IMS Centralized Services (ICS) Overview

James Ni

12/11/2009

2

IMS ICS Overview

3

IMS Centralized Services (ICS) Highlights

� Emphasizing the IMS core network

• Ultimate goal: all network elements are IMS capable

• All network services are provided via IMS

– Existing basic call and supplementary services

– New multi-media services (MMTel, Video etc.)

• Allows legacy UE access

– Best effort service delivery – up to the UE capability

– Access adaptation – allows non-IMS UE to gain access to IMS network

� Leading to future

• Achieve the fix mobile convergence (FMC) goal

• Unified core network and services, diversified access methods

– IMS core and IMS centered multi-media services

– IMS access via wireless or wire-line accesses

– Non-IMS legacy accesses

� Challenges

• Service continuity

– Across different networks

– Deal with different UEs, especially non-IMS capable ones

• Service consistency

– IMS services shall be consistently provided using different network accesses

4

IMS Centralized Services (ICS) Architecture

IMS

PSTNPSTN WLAN

(IP-CAN)

WLAN

(IP-CAN)

GSMGSMCable DSL

(IP-CAN)

Cable DSL

(IP-CAN)

Access Networks

Circuit

Switch

Network

Circuit

Switch

Network

Core Network

User Equipments

5

IMS Centralized Services (ICS): Provided Services

6

IMS Centralized Services (ICS) Requirements

� Services

• Service control always performed by home IMS network

• Service providers can be– Home IMS network

– Visited IMS network

– 3rd party provider

• Service coverage– IMS supplementary services (3GPP TS 24.173)

– Other provider specific IMS services

• Service delivery– Best effort: deliver the service up to UE and access network capabilities

� Support for legacy devices

• No absolute need to upgrade to IMS UEs to receive ICS

• Service offerings to legacy UEs will be limited

� Support for roaming

• ICS need to support the following roaming cases– Roaming within the home network

– Roaming between home and visited networks (subject to roaming agreement)

– Roaming between different access networks (GSM/UMTS, WLAN, Wireline Broadband etc.)

• In case of ICS is not or only partially supported by roaming partners– Only the subset of ICS services are provided or

– Only basic call services are supported or

– Roaming to these networks is barred

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IMS Centralized Services (ICS) Requirements

� Service Continuity

• Service continuity shall be sustained as much as possible across different access networks

• User device and access network capabilities may have constraints on service continuity

� Service Consistency

• Services hosted in IMS shall be available via any access networks– A reduced set of ICS may be offered subject to constrains of the access network

– Call independent services (e.g. Cal Forwarding) shall be supported

– Emergency calls shall be supported

– Priority services for ICS users are desired.

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IMS Centralized Services (ICS) Key Network Elements

� UE

• ICS UE

• Non-ICS UE

� MSC Server

• Enhanced for ICS

• Not enhanced for ICS

� IM CN Entities

• x-CSCF

• Other element (?)

ICS UE A MSC Server IM CN Entities SCC AS UE B

� SCC AS• Service Centralization & Continuity Application

Server

• An ICS AS

• Roles:

– ICS User Agent (IUA)

– CS Access Adaptation (CAA)

– Terminating Access Domain Selection (T-ADS)

– I1 Service Control Signalling Termination

• Functionalities

– Registration

– Call / SS control / convergence

– Service continuity support

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IMS ICS Service Centralization & Continuity

Application Server

(SCC AS)

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IMS Centralized Services (ICS) SCC AS

� SCC AS is a Home network element

• provides functionality required to enable IMS Centralized Services.

• in the session path using originating and terminating Initial filter criteria (iFC)

– the first AS in the originating iFC chain

– the last AS in the terminating iFC chain

• May be invoked through the use of PSI termination procedures when using CS access.

� SCC AS main roles

• ICS User Agent (IUA): provides SIP UA behaviour on behalf of the UE

• CS Access Adaptation (CAA): provides interworking functions for CS UE access to IMS network elements

• Terminating Access Domain Selection (T-ADS):

– Directs an incoming session to an ICS User

– For one or more UEs of an ICS User:

» Influences the selection of one or more contacts amongst the registered contacts

» Influences the selection of an access network for delivery of the incoming session to the

selected contact

» Performs breakout to the CS Domain by fetching the CSRN.

• I1 Service Control Signalling Termination :

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� SCC AS major Functionalities

• Provide service consistency support

– Registration

– Call convergence

– Supplementary services convergence

• Provide service continuity support

– Single Radio Voice Call Continuity (SRVCC) support

� handoff

– IMS Service Continuity support

� PS – CS service continuity

� PS – PS service continuity

� Inter UEs transfer

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YesYesYes, only if I1 is

supported

As driven by

operator

policy and

VPLMN

support.

As driven by

operator

policy and

VPLMN

support.

YesNoRequired

T-ADSIUACAAGmI1

SCC ASTransparent control channelICS UEMSC Server with ICS

enhancements

ICS function support needs in different deployment scenarios

• An operator who only supports UEs that have ICS functionality for their ICS Users

• An operator who only supports non ICS UEs for their ICS Users

YesConditional*NoNoNoNoYesRequired

T-ADSIUACAAGmI1


enhancements

• An operator who supports UE’s for their ICS Users that do / do not have ICS functionality

YesYesYes, if I1 is

supported

As driven by operator

policy and

VPLMN support.

As driven by operator

policy and

VPLMN support.

YesYesRequired

T-ADSIUACAAGmI1


enhancements

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� SCC AS Interfaces

• I1: ICS UE access to SCC AS via CS (for service control signalling)

– I1 reference point is optional and implemented using USSD transport via CS

network elements.

• Gm: ICS UE access to SCC AS via PS (through CSCF/ISC)

• I2: Non-ICS UE access to SCC via CS (through MSC Server enhanced for ICS

and CSCF/ISC)

IMS Service Centralization and Continuity Reference Architecture

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� ICS UE �� SCC AS Signaling paths

• Service control signaling path:

– Used to transport service control signalling between ICS UE and SCC AS

– For enabling IMS services via CS or PS access

– Used when needed

• CS bearer control signaling path:

– Used to transport media bearer control signaling

– For managing service required bearer media resources.

� What SCC AS does in controlling services

• Acting as a B2BUA

• Combines the service control signalling and CS Bearer Control Signalling to

form the Access Leg

• Using IMS signaling to interact with CSCF on behalf of UE as the remote Leg

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� SCC AS Accessing Option 1: Sessions established using Gm

• Using Gm over PS network for Service Control Signalling Path

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� SCC AS Accessing Option 2: Sessions established using I1

• Using I1 via CS network for Service Control Signalling Path

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� SCC AS Accessing Option 3: Sessions established using CS call control and

MSC Server

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ICS SCC AS Functionalities

Service Consistency Support

Registration

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IMS ICS SCC AS Control Flows : Registration

UE IMS registration when using an MSC Server enhanced for ICS

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Call Control Convergence

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IMS ICS SCC AS Control Flows: Basic MO Call

ICS UE origination with CS media using Gm when using an MSC Server enhanced for ICS

22


ICS UE origination with CS media using Gm when using an MSC Server NOT enhanced for ICS

23


CS UE origination when using an MSC Server enhanced for ICS — multiple codecs used

24


CS UE origination when using an MSC Server enhanced for ICS – one codec used

25


CS UE origination when using an MSC Server not enhanced for ICSU E V M S C M G C F

I n t e r m e d i a t e I M

C N s u b s y s t e m

e n t i t i e s

S C C A S

2 . S E T U P

3 . O r i g i n a t i o n

t r i g g e r s

5 . I S U P / B I C C I A M

7 . S I P I N V I T E

9 . R e t r i e v e

o r i g i n a l c a l l i n g

a n d c a l l e d p a r t y

i n f o r m a t i o n

8 . S I P 1 0 0

( T r y i n g )

1 0 . S I P I N V I T E

1 2 . S I P I N V I T E

1 3 . S I P 1 0 0

( T r y i n g )

1 1 . S I P 1 0 0

( T r y i n g )

1 5 . S I P 2 0 0 ( O K )

1 6 . S I P 2 0 0 ( O K )

1 7 . S I P 2 0 0 ( O K )

1 9 . I S U P / B I C C

A N M

2 4 . S I P A C K

2 5 . S I P A C K

2 6 . S I P A C K

2 0 . C O N N E C T

2 1 . C O N N A C K

1 . D e t e r m i n a t i o n o f

c a l l e s t a b l i s h m e n t

d o m a i n

C S b e a r e r I M S b e a r e r

M G W

6 . S I P I N V I T E

1 4 . 1 8 0 ( R i n g i n g ) , I S U P / B I C C A C M a n d A L E R T I N G

1 8 . S I P 2 0 0 ( O K )

2 2 . S I P A C K

2 3 . H . 2 4 8 i n t e r a c t i o n w i t h

t h e M G W

4 . R e d i r e c t i o n t o

I M C N s u b s y s t e m

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ICS UE origination when using I1 interface

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IMS ICS SCC AS Control Flows: Basic MT Call

Termination to a CS UE registered in IMS using an MSC Server enhanced for ICS – multiple codecs used

28


Termination to a CS UE not registered in IMS

29


Termination to an ICS UE with CS media using Gm reference point when using an MSC server enhanced for ICS

30


Termination to an ICS UE with CS media using Gm when using an MSC Server not enhanced for ICS

31

ICC SCC AS Functionalities


Supplementary Services

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IMS ICS SCC AS Control Flows: Supplementary Services

Communication Hold/Resume with Announcement

33


Explicit Communication Transfer using Gm reference point, ICS UE as transfer recipient

34


Communication Waiting

35


Communication Waiting via the MSC Server enhanced for ICS

36


Conferencing via Gm

37


Communication Forwarding on Busy User flow over the I1

38


Communication Forwarding No Reply flow over the I1

39


Communication Forwarding Not Reachable flow over the I1

S-CSCFTASSCC ASMSC ServerICS UE B UE A

4. INVITE

1. INVITE

2. INVITE

3. INVITE

5. User not reachable

7. SIP response (user unreachable)

6. SIP response (user unreachable)

8. CFNRc Logic

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Communication Deflection flow over the I1

S-CSCFTASSCC ASMSC ServerICS UE B UE A

9. SIP Response (C-party)

4. INVITE

1. INVITE

7. I1: Call Deflection Request (C-party)

8. SIP Response (C-party)

2. INVITE

3. INVITE

5. I1: Incoming Call

6. User Deflects Call

10. CD Logic

41


Service Continuity Support

Single Radio Voice Call Continuity

(SRVCC)

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� Main focus

• SRVCC between E-UTRAN access and 3GPP2's 1xCS

• SRVCC between E-UTRAN access and UTRAN/GERAN accesses

• SRVCC between UTRAN (HSPA) access and UTRAN/GERAN accesses

� All for Circuit Switched (CS) calls that are anchored in the IMS

� SCC AS serves the IMS Service Continuity control functions

IMS ICS SCC AS Service Continuity: SRVCC

43


SRVCC from E-UTRAN to 3GPP2 1xCS

U E M M E1 x C SIW S

1 x R T TM S C

1 x R T T

C S a c c e s sE -U T R A N

1 a . I M S E m e r g e n c y S e s s i o n o n g o i n g o v e r E -U T R A N a c c e s s

1 b . M M E i n d i c a t e s to E -U T R A N t h a t C N a n d U E a r e S R V C C

c a p a b l e

2 . M e a s u r e m e n t

R e p o r t s

3 . S R V C C H a n d o v e r t o C D M A 2 0 0 1 x

i s r e q u i r e d a s d e f i n e d i n T S 2 3 . 2 1 6

4 . I n i t i a t e s I n t e r -T e c h n o l o g y E m e r g e n c y S R V C C H a n d o v e r

6 . E m e r g e n c y v o i c e o n g o i n g c a l l o v e r th e C S l e g e s t a b l i s h e d o v e r 1 x R T T a c c e s s

7 . H a n d o v e r

e x e c u t i o n

5 . 1 x t r a f f i c a s s i g n m e n t & 3 G P P 2 e m e r g e n c y

V C C p r o c e d u r e

8 . R e c o n f i g u r e L o c a t i o n S u p p o r t

44


SRVCC from E-UTRAN to UTRAN/GERAN

45


SRVCC from UTRAN (HSPA) to UTRAN/GERAN

46

IMS ICS SCC AS Service Continuity: SRVCC Flow

SRVCC from E-UTRAN to GERAN without DTM support

U E S o u rc e E -U T R A N

S o u r c e M M E

M S C S e r v e r / M G W

T a rg e t M S C

1 4 . H a n d o v e r C o m m a n d

T a r g e t B S S

1 . M e a s u r e m e n t re p o r ts

3 . H a n d o v e r R e q u ir e d

S G W

2 . D e c is io n fo r H O

5 .P S to C S R e q

6 .P r e p H O R e q

7 . H O R e q u e s t /A c k

8 .P r e p H O R e s p

9 . E s ta b l is h c i rc u it

1 9 . H O C o m p le te

2 0 .S E S (H O C o m p le te )

2 1 . A N S W E R

1 3 .P S t o C S R e s p

1 5 . H O f r o m E U T R A N c o m m a n d

H S S /

H L R

2 3 .U p d a te L o c

1 0 . In i t ia t io n o f S e s s io n T r a n s fe r ( IS U P / S T N -S R o r E -S T N -S R )

1 1 . S e s s io n t r a n s fe r a n d U p d a te re m o te e n d

IM S (S C C A S )

1 2 . R e le a s e o f IM S a c c e s s le g

2 2 . P S t o C S C o m p le te /A c k

T a r g e t S G S N

1 6 . U E tu n e s to G E R A N

1 7 . H O D e te c t io n

1 8 . S u s p e n d ( s e e T S 2 3 .0 6 0 )

1 8 . S u s p e n d 1 8 . S u s p e n d R e q u e s t / R e s p o n s e

1 8 . U p d a te B e a r e r

4 . B e a r e r S p li t t in g

G M L C 2 4 . S u b s c r ib e r L o c a t io n R e p o r t

47

IMS ICS SCC AS Services Continuity: SRVCC

SRVCC from E-UTRAN to UTRAN or GERAN with DTM HO support

1 3 . H a n d o v e r C o m m a n d

1 . M e a s u r e m e n t r e p o r t s

3 . H a n d o v e r R e q u i r e d

2 . D e c i s io n fo r H O

5 a . P S t o C S R e q

1 7 a . R e lo c /H O C o m p le t e

1 7 b . S E S ( H O C o m p le t e )

1 7 c . A N S W E R

1 2 . P S t o C S R e s p

1 8 a . R e lo c /H O C o m p le t e

1 8 c . U p d a te b e a r e r

H S S /

H L R 1 7 e . U p d a t e L o c

5 b . P r e p H O R e q

8 b . P r e p H O R e s p

8 c . E s t a b l is h c i r c u i t

6 a . F o r w a r d R e lo c R e q 6 b . R e lo c / H O R e q

5 c . R e lo c /H O R e q

8 a . R e lo c /H O R e q A c k

7 b . F o r w a r d R e lo c R e s p

7 a . R e lo c / H O R e q A c k

1 1 . R e le a s e o f IM S a c c e s s l e g

1 0 . S e s s io n t r a n s f e r a n d u p d a te r e m o t e l e g

9 . I n i t ia t i o n o f S e s s io n T r a n s f e r ( I S U P : S T N - S R o r E - S T N - S R )

U E S o u r c e E - U T R A N

S o u r c e M M E


T a r g e t M S C

T a r g e t R N S /B S S

S G W IM S ( S C C A S )

T a r g e tS G S N

1 4 . H O f r o m E U T R A N c o m m a n d

1 7 d . P S t o C S C o m p le t e /A c k

1 8 b . F o r w a r d R e lo c C o m p le te /A c k

1 6 . H O D e t e c t i o n

4 . B e a r e r S p l i t t i n g

1 5 . U E t u n e s t o U T R A N /G E R A N

G M L C 1 9 . S u b s c r i b e r L o c a t io n R e p o r t

48

IMS ICS SCC AS Control Flows: Services Continuity

SRVCC from UTRAN (HSPA) to GERAN without DTM support

U E S o u r c e

U T R A N ( H S P A )

S o u r c e S G S N


T a r g e t M S C

1 4 . R e lo c a t i o n C o m m a n d

T a r g e t B S S

1 . M e a s u r e m e n t r e p o r t s

3 . R e lo c a t io n R e q u i r e d

G G S N

2 . D e c i s io n f o r H O

5 . P S t o C S R e q

6 . P r e p H O R e q

7 . H O R e q u e s t /A c k

8 . P r e p H O R e s p

9 . E s ta b l i s h c i r c u i t

1 9 . H O C o m p le te

2 0 . S E S ( H O C o m p le te )

2 1 . A N S W E R

1 3 . P S t o C S R e s p

1 5 . H O f r o m U T R A N c o m m a n d

4 . B e a r e r S p l i t t in g

H S S /

H L R

2 3 . U p d a t e L o c

1 0 . I n i t i a t i o n o f S e s s io n T r a n s f e r ( I S U P : S T N - S R o r E - S T N - S R )

1 1 . S e s s io n t r a n s f e r a n d U p d a t e R e m o te e n d

IM S ( S C C A S )

1 2 . R e le a s e o f IM S a c c e s s l e g

2 2 . P S t o C S C o m p le te / A c k

T a r g e t S G S N

1 6 . U E t u n e s t o G E R A N

1 7 . H O D e t e c t io n

1 8 . S u s p e n d ( s e e T S 2 3 . 0 6 0 )

1 8 . S u s p e n d 1 8 . S u s p e n d R e q u e s t / R e s p o n s e

1 8 . U p d a t e B e a r e r

G M L C 2 4 . S u b s c r ib e r L o c a t io n R e p o r t

49

IMS ICS SCC AS Services Continuity: SRVCC

SRVCC from UTRAN (HSPA) to UTRAN or GERAN with DTM HO support

13. Relocation Command

1. Measurement reports

3. Relocation Required

2. Decision for HO

5a. PS to CS Req

17a. Reloc/HO Complete

17b. SES (HO Complete)

17c. ANSWER

12. PS to CS Resp

18a. Reloc/HO Complete

18c. Update bearer

HSS/

HLR 17e. UpdateLoc

5b. Prep HO Req

8b. Prep HO Resp

8c. Establish circuit

6a. Forward Reloc Req 6b. Reloc / HO Req

5c. Reloc /HO Req

8a. Reloc/HO Req Ack

7b. Forward Reloc Resp

7a. Reloc/HO Req Ack

11. Release of IMS access leg

10. Session transfer and Update Remote end

9. Initiation of Session Transfer (ISUP: STN-SR or E-STN-SR)

UE Source UTRAN (HSPA)

SourceSGSN

MSC Server/ MGW

Target MSC

Target RNS/BSS

GGSN IMS (SCC AS)

TargetSGSN

14. HO from UTRAN command

17d. PS to CS Complete/Ack

18b. Forward Reloc Complete/Ack

16. HO Detection

4. Bearer Splitting

15. UE tunes to UTRAN/GERAN

GMLC 19. Subscriber Location Report

50


Service Continuity Support

IMS Service Continuity

51

IMS ICS SCC AS Services Continuity: IMS SC

� Main focus

• Access Transfer – enabling service continuity between access networks

– PS-CS Access Transfer

– PS-PS Access Transfer

– PS-PS Access Transfer in conjunction with PS-CS Access Transfer

– Adding and/or removing media flows to support service

– MSC Server assisted mid-call feature

– SRVCC session transfer of IMS emergency session

• Inter-UE transfer

– Establishment and release of a Collaborative Session

– Transfer of media flows to a target UE whilst keeping Collaborative Session control

in the Controller UE

– Transfer of all media flows to a target UE without establishing a Collaborative

Session

• All transfer procedures are executed and controlled by SCC AS

� Solutions for service continuity using IMS procedures

� SCC AS serves as SIP-AS in the signaling path of all IMS sessions

52

IMS ICS SCC AS Services Continuity: IMS SC Flow

Signalling flows for multiple registrations

53


Signalling flow for PS-CS Access Transfer: CS to PS

54


Signalling flow for PS-CS access transfer: PS to CS

55


Signalling flow for access transfer PS to PS

56


Signalling flow for PS - PS in conjunction with PS - CS Access Transfer: PS to CS

57


Signalling flow for PS - PS in conjunction with PS - CS Access Transfer: CS to PS

58


Remote End Initiation case – Removing media from split CS and PS sessions

59


Signaling flow for inter UE transfer without Collaborative Session establishment H P L M N o f t h e t e r m i n a t i n g U EH P L M N o f t h e o r i g i n a t i n g U E

S C C A S

M e d i a p a t h b e t w e e n U E - 1 a n d U E - 3


C N s u b s y t e m

e n t i t i t i e sU E - 2


C N s u b s y t e m

e n t i t i t i e sU E - 1 U E - 3

1 . U E - 1 i s o n a n a c t i v e m u l t i m e d i a s e s s i o n w i t h U E - 3 . C a l l i s a n c h o r e d i n S C C A S

2 . S I P R E F E R

3 . i F C E v a l u a t i o n

4 . S I P R E F E R

2 5 . S I P 2 0 0 I N V I T E

1 2 . S I P I N V I T E

1 5 . R e m o t e L e g U p d a t e

I M S S e r v i c e C o n t r o l

6 . S I P R E F E R

1 6 . S I P r e - I N V I T E

1 7 . S I P r e - I N V I T E

1 8 . S I P r e - I N V I T E

1 9 . S I P 2 0 0 r e - I N V I T E

2 0 . S I P 2 0 0 r e - I N V I T E

2 1 . S I P 2 0 0 r e - I N V I T E

2 3 . S I P A C K

2 7 . S I P A C K

2 9 b . M e d i a p a t h b e t w e e n U E - 2 a n d U E - 3

2 2 . S I P A C K

3 8 . S I P B Y E

3 9 . S I P B Y E

4 0 . S I P 2 0 0 B Y E

2 4 . S I P A C K

2 9 a . I M S S e r v i c e C o n t r o l

7 . S I P R E F E R

8 . S I P 2 0 2 R E F E R

9 . S I P 2 0 2 R E F E R

1 0 . S I P 2 0 2 R E F E R

1 1 . S I P 2 0 2 R E F E R

1 4 . S I P I N V I T E

2 6 . S I P 2 0 0 I N V I T E

2 8 . S I P A C K

3 2 . S I P N O T I F Y ( S I P

2 0 0 )

3 0 . S I P N O T I F Y ( S I P

2 0 0 ) 3 1 . S I P N O T I F Y ( S I P

2 0 0 )

3 3 . S I P N O T I F Y ( S I P 2 0 0 )

3 4 . S I P 2 0 0 N O T I F Y

3 5 . S I P 2 0 0 N O T I F Y

3 6 . S I P 2 0 0 N O T I F Y

3 7 . S I P 2 0 0 N O T I F Y

4 1 . S I P 2 0 0 B Y E

1 3 . i F C E v a l u a t i o n

5 . R E F E R r e q u e s t a u t h o r i z a t i o n

60


Release of Collaborative Session initiated by Controller UE

61


Signaling flow for PS-CS Transfer: CS to PS with MSC server assisted mid-call feature

62


Signaling flow for PS-CS Transfer: PS to CS with MSC server assisted mid-call feature

63

References

� 3GPP TS 23.292 V9.3.0 (2009-09) IP Multimedia Subsystem (IMS) centralized services Stage 2

� 3GPP TS 24.292 V9.1.0 (2009-09) Multimedia (IM) Core Network (CN) subsystem Centralized Services

(ICS) Stage 3

� 3GPP TS 23.216 V9.1.0 (2009-09) Single Radio Voice Call Continuity (SRVCC) Stage 2

� 3GPP TS 23.237 V9.2.0 (2009-09) IP Multimedia Subsystem (IMS) Service Continuity Stage 2

� 3GPP TS 24.237 V9.0.0 (2009-09) IP Multimedia Subsystem (IMS) Service Continuity Stage 3

3gpp-ics-gene3GPP IMS Centralized Services (ICS) Overviewral-overview

Documents

network services

roaming ics

subset of ics services

media services ims access

ics service offerings

ics users

case of ics

ims ues