A framework for seamless roaming across heterogeneous next generation wireless networks

In the future, wireless and mobile users will have increased demands for seamless roaming across different types of wireless networks, quality of service guarantees and support of different types of services. This awareness has led to research activities directed towards inter-system and global roaming and can be noticed in the numerous products like multimode handsets, inter-working gateways and some ongoing standards and research work on signaling protocols for inter-system roaming. This article proposes a global mobility management framework. The framework is like an overlay network comprising of Inter-System Interface Control Units IICU to support inter-network communication and control for Location Management. The protocols and functions of this framework will be distributed and exist partly within the wireless networks and partly within the core-network. A hierarchy introduced among the IICUs will accommodate for the varying mobility coverage required by the mobile user. The IICU may be configured to perform various functions depending on its placement in the hierarchy of the framework. This approach aims to optimize across call set up delays, signaling traffic, database processing, handoff facilitation for seamless roaming and QoS mapping and negotiations as the user moves across different wireless networks. It avoids centralized database dependency with its associated single-point bottleneck and failures(1). We restrict our analysis of the framework to a 2-network and a 3-network roaming scenario. The presentation has been further restricted to cost and delay analysis of the location update and call delivery procedures. We have taken into account the signalling requirements when the mobile user roams across networks with and without an active call.