Chapter 6

IMS Centralized Services

IMS Centralized Services (ICS) architecture as specified by 3GPP (3GPP TS 23.292) aims to provide telephony services by using IP multimedia subsystem (IMS)-based service enablers regardless of the used access technology of the end user. IMS-based service enablers relevant to the scope of this book are mainly multimedia telephony services offered by a telephony application server (TAS). However other service enablers that can be offered by IMS architecture can be such as presence services provided by an open mobile alliance (OMA) presence server, various service configuration-related services provided by a XML document management server (XDMS) as well as instant messaging services provided by an OMA instant messaging server to name a few enablers. These service enablers belong within the scope of a rich communication suite (RCS) that is an individual initiative within the global system for mobile communications association (GSMA) to enrich the end user experience.

Additionally all future 3GPP standardisation related to IMS is expected to be based on the existence of ICS-based IMS architecture including features such as multimedia session continuity as defined by 3GPP (3GPP TS 23.237) enabling more flexible control of individual multimedia streams by user equipment (UE) and network as well as single radio voice call continuity (SR-VCC) from UMTS terrestrial radio access network (UTRAN)/GSM/EDGE radio access network (GERAN) to evolved UMTS terrestrial ...

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