Static and adaptive location management in mobile wireless networks

Location management is one of the most important issues in mobile computing. Location management consists of location updates, searches and search-updates. An update occurs when a mobile host changes location. A search occurs when a host wants to communicate with a mobile host whose location is unknown to the requesting host. A search-update occurs after a successful search, when the location information corresponding to the searched host is updated at some hosts. Various strategies can be designed for search, update and search-update. Static location management uses one fixed combination of search, update and search-update strategies. Simulations were carried out to evaluate the performance of different static location management strategies for various call-mobility patterns. It was noticed that performing search-updates significantly reduced the search costs without significantly increasing the cost of updates (upon moves and searches). To obtain good performance using static location management, the system designer should a priori have a fair idea of the call-mobility pattern of the users. Having this information, the system designer can select the combination which performs best for the given call-mobility pattern. The host behavior (call frequency, mobility) is not always available to the system designer. Thus, there is a need for adaptive location management. In this paper we present a scheme for adaptive location management. The basic assumption behind adaptive location management is that the past history of the system will reflect the behavior in the future. The adaptive scheme dynamically estimates the future host behavior with the help of the past call-mobility patterns. Results indicate that the adaptive scheme performs better than the static scheme for a wide range of call-mobility patterns.