Location Tracking in PCS Networks Using Enhanced Caching

In personal communication service (PCS) networks, the user location tracking strategy plays a critical role in ensuring successful mobile communication in any place at any time. The IS-41 scheme in North America and the MAP of the GSM system in Europe are two current standard location tracking schemes. To reduce communication cost for the two basic schemes, several location tracking strategies, either caching or pointer forwarding strategies, have been proposed. Caching strategies aim to reduce the cost occurring upon call delivery; pointer forwarding strategies intend to reduce the cost due to registration. This paper presents a new caching strategy which uses forwarding pointers, instead of updating users' location information, to locate users who make frequent moves while using PCS. Enhanced by forwarding pointers, the new caching strategy is able to reduce the cost resulting from registration, cache hit but invalid and cache miss. On call delivery, we update the cache records based on the fact that users tend to revisit previous RAs and to visit previously called RAs, and thus result in higher cache hit and valid ratios. A thorough performance analysis on different location tracking strategies is conducted to prove the favorable performance and reduced cost of the proposed caching strategy.