 Public User Identity. Support for additional access signaling security and UE authentication mechanisms. Support for provisioning, activation, configuration, and management of UEs. 11.9.1.2.2.3 IMS in Fixed Network Domain For fixed operators, IMS enables both VoIP and access to other multimedia services. IMS enables the support of PSTN/ISDN Emulation subsystem (PES) as stated in [21]. It addresses the interconnect market by enabling the support of IP peering with user specific services for transit calls. The PES supports the emulation of PSTN/ISDN services for legacy terminals connected to the next generation network, through residential gateways or access gateways. ISDN (Integrated Services Digital Network) is a circuit-switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires. In the last few years DSL (Digital Subscriber Line) has replaced majority of ISDN networks because of higher data rates and better performance. The following are the key enhancements to support IMS in fixed networks: Support for Network Address and Port Translation. Support for xDSL specific information. Optional support for SIP compression, media authorization, and SO on. Additional signaling for location management. 9 Data Over Cable Service Interface Specifications (DOCSIS) developed by CableLabs is an international standard that defines the communications and operation support interface requirements for a data over cable system. It permits the addition of high-speed data transfer to an existing Cable TV system. Next Generation Mobile Communications Ecosystem Mobile Phone Network Base Station ((o)) ADSL/FTTx line IP Network Femtocell Femtocell Indoor Network Access Point Controller Figure 11.18 Femtocell concept 11.9.1.3 Femtocells Femtocells are low cost in-building coverage solutions for CDMA and UMTS networks as shown in Figure 11.18. They not only increase existing voice and high speed data services but also provide a basis for next generation converged service