Voice over IP/Standard Architectures for Next Generation Networks
IMS(IP Multimedia Subsystem) 
IMS is currently in development and testing phases, and was originally developed by 3GPP as an architecture for Mobile Networks.
IMS describes a full architecture that uses IP technologies to transport all traffic (both Voice and Data). It tries to re-use existing protocols defined by IETF and other standards bodies instead of re-inventing the wheel. Some of the protocols it reuses are SIP, MEGACO/H.248, SIGTRAN and DIAMETER.
TISPAN reuses as much as possible from the IMS architecture and complements it with the required elements to serve fixed/wireless networks.
The work developed by TISPAN is then feed back into IMS.