Smart Phone and Next Generation Mobile Computing

Mobile Networking Challenges 275

scenario because it lacks support for SIP, a seemingly prevalent

multimedia session management protocol in all-IP networks. 3GPP

proposed an alternative solution called IP Multimedia Subsystem

(IMS). Unlike UMA, IMS supports SIP and largely utilizes the Inter-

net for call routing and presence services. Compared to UMA, IMS

is a more fully fledged all-IP solution for 3G systems. The IMS

architecture supports multiple application servers providing both

traditional telephony services and enhanced data services such as

instant messaging (IM), push-to-talk (PTT), audio and video stream-

ing, or multimedia messaging service (MMS). Readers interested in

reading more about IMS should refer to the following 3GPP techni-

cal specifications: ...