Static and Dynamic Location Management in Distributed MobileEnvironments

Location management is one of the most important issues in distributed 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 requesting host updates the location information corresponding to the mobile host. Various strategies can be designed for search, update and search-update. Static location management uses one combination of search, update and search-update strategies throughout the execution. Simulations were carried out to evaluate the performance of diierent static location management strategies for various communication and mobility patterns. It was noticed that performing search-updates signiicantly reduced the search costs with very little cost to pay for updates (upon moves and searches). In order to obtain good performance using static location management, the system designer should a priori have a fair idea of the communication and the mobility pattern of the users. Having this information, the system designer can select the combination which performs best for the given values of communication and mobility. The host behavior (communication frequency, mobility) is not always available to the system designer. Thus, there is a need for dynamic location management. In this paper we present a scheme for dynamic location management. The basic philosophy behind dynamic management is that the past history of the system will reeect the behavior in the future. Hence, by keeping track of the past history and modifying the management strategy accordingly, one expects to perform well for any call and mobility pattern. Simulation results show that the performance of dynamic location management is better than static location management.