 sessions, true mobility in hardware devices, and new cross-network services for operators and wireless service providers. Enhancements to the Mobile IP technique are being developed to improve mobile communications in certain circumstances by making the processes more secure and more efficient. These enhancements include Mobile IPv6 and Hierarchi- cal Mobile IPv6 (HMIPv6). Chapter 16 Emerging Wireless Applications The IP Multimedia Subsystem The IP Multimedia Subsystem (IMS) is the most recent refinement of an enhanced services architecture. It is an architectural framework for introducing a wide vari- ety of IP-based services to the wireless realm, and it is designed to ease conver- gence via its various specifications. Whereas 3G wireless technology addresses the issue of growing bandwidth requirements, the purpose of IMS is to address the crit- ical signaling and session controls issues associated with multimedia services. Advanced radio technology alone is not sufficient to provide true multimedia ser- vices. Other enabling technologies are crucial components of IMS, such as session management protocols, confidentiality and integrity protection schemes, end-to- end quality of service (QoS), traffic management, service control platforms, and billing. IMS, which establishes IP connections between various client devices, was developed with two main goals: to support access convergence with 2G, 3G, 4G, Wi-Fi, and WiMax networks and to support multimedia convergence of voice, video, messaging, and data. IMS was created by 3GPP, which, as discussed in Chapter 14, develops techni- cal specifications for IMT-2000, the ITU framework for 3G standards. The group represents a global effort, involving six of the world's major standards bodies from China, Europe, Japan, Korea, and the United States. As a note of historical refer- ence, enhanced services have traditionally been deployed as a collection of single solutions, delivered using a vertically integrated approach. The 3GPP architects recognized that this traditiona