[[alternative]]Movement-Based Location Update in Wireless Networks with Sparse Microcell Overlays

[[abstract]]This research focuses on developing cost-effective location update schemes for tracking mobile users in wireless networks underlaid sparsely with microcells. The proposed schemes are able to take advantage of lower location update cost through microcells by using movement-based strategies with a novel mechanism of reporting. The effects are achieved essentially through the use of two movement thresholds for decision on which tier to report to. Each mobile platform (MP) has a counter to record the number of macrocell transitions from the last reported cell. If the number is greater or equal to the lower threshold, called the s-threshold, the MP updates its location through the control channel of a microcell being visited. If the number reaches the higher threshold, called the h-threshold, the MP updates location immediately through the control channel of the macrocell it currently visits. This work examines the performance of total update cost per call arrival for the proposed scheme in several scenarios of network topology. In addition, adaptive schemes that adjust s-threshold according to local estimate of microcell density are proposed to further exploit potential cost gain from spatial variation of microcell density. Furthermore, the effects of using one more cell-ID buffer in MPs to reduce unnecessary location update are presented.