Second concept for providing IPTV services over NGN architecture is described in TISPAN IMS based IPTV [36], [1]. Main difference as name said that IP Multimedia Subsystem is used to service and session control of IPTV services. Main advantage is reusing existing capabilities (IMS registration, authentification, session management, routing, service trigger, identity management, personalization, mobility, charging) of IMS and possibility to integrate service control layer to unified service control platform by utilization for IMS.
Disadvantage of IMS based IPTV is higher complexity and less backward compatibility with existing standards (beside that several part of concept reused existing standard and protocols).
IMS based IPTV functional entities (see Figure above):
The IMS based IPTV has number of advantages because IMS can act as unified service control subsystem for all NGN services instead of establishing an additional specialized subsystem (case of NGN dedicated IPTV subsystem). Additionally IMS can more naturally support mobility, interaction with NGN service enablers (like messaging or presence), service personalization or quadruple play services (voice, data, video, mobile).