For a long time, IP Multimedia Subsystem (IMS) was nothing more than just a revolutionary idea to move all existing teleservices, including telephony to the PS domain of the mobile network and to create a vast variety of brand new teleservices totally based on end-to-end IP connectivity. Today, thanks to Rich Communication Suite-enhanced (RCS-e) initiative, there is a clear path and agreement on how to turn IMS into practice. RCS-e ensures that the same initial subset of IMS services will be introduced by all operators, infrastructure and terminal vendors and will work smoothly also in inter-operator scenarios. The course explains RCS-e services, underpaying IMS architecture and basic procedures and their impact on existing operator infrastructure.

1. 7-1
Multi-device environment
(optional)

2. 7-2
Multi-device environment
Mobile Operator
B’s MSISDN
Primary RCS client
(regulatory and telephony functions)
Secondary RCS client

3. 7-3
Incoming voice call
Mobile Operator Primary RCS client
(regulatory and telephony functions)
Secondary RCS client
CC SETUP
SIP INVITE
”SIP forking” like behaviour

4. 7-4
Multi-device environment and service discovery
200 OK200 OK
A’ R2 A’’ R2
OPTIONS
200 OK
B
S-CSCF A
OPTIONS
OPTIONS
200 OK
OPTIONS
OPTIONS
200 OK
A’’ service capabilities unknown to B (service discovery via SIP OPTIONS)
Since SMS is not an RCS capability, in case the primary mobile client A’ is not registered
the other users are not informed that an instant SMS towards A is unavailable.

5. 7-5
Multi-device environment and Presence Service
NOTIFY (GRUU A’’)
NOTIFY (GRUU A’’)
200 OK
SUBSCRIBE (A, GRUU A’)
NOTIFY (GRUU A’)
200 OK
SUBSCRIBE (A, GRUU A”)
S-CSCF RLS ASA’ A’’
SUBSCRIBE (A, GRUU A’)
200 OK200 OK
NOTIFY (GRUU A’)
200 OK
SUBSCRIBE (A, GRUU A”)
200 OK
200 OK
NOTIFY (GRUU A’’)
200 OK
presence event
NOTIFY (GRUU A’) NOTIFY (GRUU A’)
NOTIFY (GRUU A’’)
200 OK 200 OK

6. 7-6
Multi-device environment and Presence Service
PUBLISH (presence info update)
PS AS RLS ASA’ A’’
NOTIFY (presence info update)
NOTIFY (presence info update)
NOTIFY (presence info update)
A’ and A’’ service capabilities are combined by a PS AS
when presented towards other subscribers.
A’ and A’’ terminals social presence information is
synchronised via PS AS.

7. 7-7
Multi-device environment and IS&VS
200 OK 200 OK
A’ R2 A’’ R2
Voice call
B
S-CSCF A
INVITEINVITE
INVITE
100 TRYING and/or 180 RINGING
CANCEL
200 OK
487 Cancelled
Image / Video Sharing
ACK ACK
IS or VS session can be accepted by any user’s A registered terminal
(not only the one involved in a voice call)

8. 7-8
Multi-device environment and IM/Chat & FT
200 OK 200 OK
A’ R2 A’’ R2 B
S-CSCF A
INVITE (subject message)INVITE
INVITE
100 TRYING and/or 180 RINGING
CANCEL
200 OK
487 Canceled
IM/Chat or File Transfer
ACK ACK
The first message (subject message) delivered to all user’s A registered
terminals. The IM/Chat or FT can be accepted only from one terminal.