1. COMBINING CIRCUIT AND PACKET BASED SERVICES IN CONVERGING NETWORKS Sauli Österman sauli.osterman@teliasonera.com

2. About Written at TeliaSonera Finland, in the Mobile System Planning department. Supervised by Prof. Raimo Kantola Instructed by M.Sc. Ville Helenius

3. Outline Background & Objective 3GPP release 6 network IP Multimedia subsystem Circuit Switched IMS Combinational Services Conferencing service utilising CSICS Conclusion

4. When using GERAN as access network, the experienced delay is too much for real-time IMS services Using GERAN as access network is appealing, because of the large coverage area The problem may be solved with utilising mobile network CS services for real-time media and PS services for other types of media For this purpose the 3rd Generation Partnership Project has standardised Circuit Switched IMS Combinational Services (CSICS) The objective is: –To study in which stage the standardization process at the moment –What features are included in the standardised first phase solution –To study how conferecing with this type of service might be implemented The study was performed as a literature study Background & outline

5. 3GPP release 6 network Different domains for CS and PS services IMS is connected to both PS domain and CS domain GERAN UTRAN CS domain PS domain IP networks IMS PSTN/PLMN

6. IP multimedia subsystem 3GPP specified access network independent service creation environment Two main signalling protocols: –SIP for call control –Diameter for database queries The signalling is always routed trough the controlling nodes, but the user data is routed via shortest path

7. CSICS phase 1 AS IMS 2 CS domaín AS UE1 PS domaín IMS 1 CS domaín Signalling traffic (SS7) User data (CS voice) Signalling traffic (SIP) User data (RTP/MSRP) PLMN1PLMN2 UE2 UTRANGERAN Standardization unfinished at the moment (included in the 3GPP release 7) Phase 1 CSICS is a service between two users Does not specify used medias Main challenge is with establishing the connection Problems with supplementary and CAMEL based services

8. Conferencing service utilising CSICS IMS CS domain Terminal 1 Terminal 2 Terminal 3 IMS CS domain Terminal 1 Terminal 2 Terminal 3 IMS Terminal 1 Terminal 2 Terminal 3 CS domain approach 3 approach 1 approach 4 CS voice call IMS session Conference service IMS CS domain Terminal 1 Terminal 2 Terminal 3 approach 2 Recognised 4 approaches with how to implement this type of service These were studied from the connection establishing point of view

9. Service offers support for real-time services, even when GERAN is only available access network The best approaches for implementing the CSICS conferencing service were concluded to be approaches 3 or 4 CSICS requires a lot from terminal. The success depends heavily on the amount of the capable terminals Synchronization of two separate media streams may cause problems to some applications Subjects fo further study: –Final CSICS phase 1 functionality (when standardization is finished) –CSICS phase 2 (when more information is published) –Other types of services with which the mobile operator may differ from the service providers in the internet Conclusion