The IP Multimedia Subsystem (IMS) dates from 3GPP release 5 almost a decade ago, but is now becoming a reality with the rollout of IMS-based LTE networks. Since the introduction of IMS has most significantly affected wireless network equipment and its deployment, much of the attention has been paid to the network itself. However, IMS and its imminent deployment with LTE will also have significant implications for mobile device designers.
This paper provides an overview of IMS, its architecture and applications from the perspective of LTE User Equipment (UE). It also provides a look at the evolution to a data-only LTE network and includes a discussion of the challenges and requirements to support delivery of voice services (including VoLTE) over an all-IP network.