The rapid growth of Internet and increased demand for ubiquitous wireless access in recent years have led to intense research activities towards the design of all IP wireless networks. The convergence of the wireless evolutionary systems and the Internet aims to offer seamless IP multimedia services to mobile hosts across a variety of heterogeneous access technologies such as UMTS Terrestrial Radio Access Network, Wireless LANs and emerging 4G systems. This will meet the demands of both enterprise and public environments, anywhere and anytime. One of the research challenges for next-generation all-IP wireless systems is the design of the intelligent mobility management techniques that take advantage of IP-based technologies to achieve global roaming among heterogeneous networks. This thesis addresses mobility management issues in the evolving all-IP wireless networks, namely beyond 3G networks, with particular-emphasis on inter-system handover management and location management. The cross-layer solutions for vertical handover management are considered with special focus on seamless IP Multimedia service continuity. A novel cross-layer signalling design is proposed to enable the communication between Mobile IP and SIP, which enhances the mobility support for real time multimedia services in pure IP wireless networks. Having carefully investigated the seamless IP Multimedia service continuity support in UMTS-WLAN interworking scenarios, an improved cross-layer solution is proposed and analysed, which is designed for better coordination between the link layer, network layer and application layer. The location management strategies in UMTS and future networks are studied. An improved local anchor scheme is proposed for UMTS networks for reducing the signalling cost. An analytical model is developed to investigate the performance of the inactivity counter mechanism proposed in 3GPP, followed by the proposal of a novel scheme that can be used to reduce the overall location management cost for users in PMM-Idle state. In addition a novel cell-mapping mechanism is proposed as a location management solution in UMTS-WLAN interworking architecture.