IP-based Multimedia Services (IMS) is a part of the UMTS specification (as of Release 5) that provides IP transport in the core network and the radio access network (UTRAN). IMS enables the convergence of data, speech, and mobile network technology over an IP–based infrastructure.
IMS was designed to fill the gap between the existing traditional telecommunications technology and Internet technology. This will allow operators to offer end-to-end IP services. This increases the potential for new inoovative services and service integration with other networks such as the Internet.
IMS enriches the way people communicate with each other by combining voice, image, and video into a single session. IMS uses SIP and session description protocol (SDP) underneath architecture to communicate between various IMS components. The architecture of IMS specifically helps enable and enhance real-time multimedia mobile services such as rich voice services, video telephony, messaging, conferencing, and push services.
IMS enables these user-to-user communication services via a number of key mechanisms such as session negotiation and management, quality of service (QoS) and mobility management. However, IMS enables much more than just real-time user-to-user services.