A location aware three-step vertical handoff scheme for 4G/B3G networks

Support of ubiquitous roaming in fourth generation or beyond third generation (4G/B3G) networks (M.R. Kibria et al., 2005) will require accurate vertical handoff prediction in order to reserve resources in neighboring cells and to keep the handoff call dropping probability within an acceptable level. However with random terminal mobility and different cell structures (e.g. microcells, macrocells), it becomes extremely difficult to accurately predict the time to initiate such a vertical handoff. In this paper we propose a mobile terminal (MT) controlled three-step handoff prediction algorithm that utilizes geographical location information to predict handoff. The location aware (step-I) MT initiates a handoff when a better access network becomes available at its current location (step-II). A suitable network selection process, adhering to user preferences, is therefore proposed to optimize system performance and resource usage. Following step-II, the terminal proceeds with predicting handoff to neighboring networks through a hysteresis based triggering mechanism as it approaches the handoff threshold near the current cell boundary (step-III). Simulation results demonstrate the accuracy of our algorithm in both microcells and macrocells