E cient Location Management in Mobile Wireless Networks

The existing wireless cellular networks are likely to be upgraded for personal communication services (PCS). Studies indicate that the anticipated signalling load due to the location management functions for PCS will be signiicant using current techniques 4, 14]. This report proposes alternate techniques to reduce network load due to location management functions for PCS users. Location management is one of the most important issues in mobile wireless networks. It consists of location update and search protocols. The trade-oo in location management is between the cost of searches and the cost of updates. The goal of an \eecient" location management strategy is to reduce the search and update costs. In this report, we show that using forwarding pointers in addition to home location servers helps in providing eecient location management. It is also shown that using forwarding pointers reduces the network load during updates, but may increase the search cost due to long chain lengths. We present two heuristics, namely, movement-based and search-based, to limit the number of forwarding pointers traversed during a search. We analyze the performance of these heuristics and compare them with the IS-41 standard. The performance of the heuristics depends mainly on (i) call-mobility ratio of the user, and (ii) cost of forwarding. Our approach is shown to achieve signiicant performance improvement over the IS-41 scheme. It was also observed that for most of the call-mobility patterns, the search-based heuristic performed better than the movement-based heuristic. On the downside, forwarding pointers (i) are prone to failures, (ii) might require high maintenance costs, and also (iii) might incur a large memory overhead. Omission/corruption of a forwarding pointer could cause the mobile host to be intractable. To overcome this problem, we propose techniques for fault tolerance and automatic recovery of the network. We propose cost-eeective techniques for forwarding pointer maintenance. We show that the memory overhead required to implement the forwarding pointer scheme is insigniicant. A search-update occurs after a successful search, when the location information corresponding to the searched mobile host is updated at some hosts. This report proposes a strategy for search-updates. Performance analysis of the strategy shows that performing search-updates signiicantly reduces the search costs and the network load.