Multi-accessfortheIMSnetwork.PDF

Multi-access for the IMS network Rogier Noldus, Ralf Keller and Bo Åström IMS multi-access (IMA) gives non-IMS-capable devices access to the IMS in operation. IMA is also architecturally core network and services. It thus enables operators to provide IMS to the aligned with IMS-based Voice Call Continu- billions of GSM and ISDN terminals that are already in operation. IMA plays ity (VCC, discussed below). a pivotal role in concentrating service control in the IMS network regard- less of access network and in providing consistent user experience to IMS IMS network architecture subscribers via multiple terminals. revisited IMS, introduced in 3GPP Rel-5, has been built around a collection of core components Premise of IMS: ferent environments. A prominent example with distinctive functionality (Figure 1). SIP, multi-access, single-core today is a dual-mode phone that supports which is the main traffic-control protocol in GSM and WLAN, where the WLAN side IMS, was developed by the Internet Engi- The IP Multimedia Subsystem (IMS) is transports SIP and RTP for access to the IMS neering Task Force (IETF) and adopted by positioned to serve as the core network for network. 3GPP for IMS. A quick look under the hood the foreseeable future. As such, it will fa- Despite the use of different terminals shows that IMS applies many prove