Path Semantic Caching for Mobile Continuous Nearest Neighbor Query

Location Based Services (LBS) have received increasing attention in recent years. In a mobile environment, the client, server and object may change their location. Given the limitations in mobile database, it is strongly recommended to minimize the number of connections and volume of data transmission from the servers. Data caching technique will be a profitable solution for this problem. In this paper we propose a new caching strategy called Path Semantic Caching (PSC) for Continuous Nearest-Neighbor Query (CNNQ), in which the mobile user issues a query to retrieve the Nearest-Neighbor (NN) of every point on a path. A Voronoi-based index is used in the server to support a CNNQ, while PSC is proposed to reduce the need for connecting and transmitting data from server which is costly. A simulation is conducted to examine the performance of our proposed caching technique in comparison with the case where no cache is used. The result shows that the PSC provides a considerable improvement in response time, number of connections to the server, and cache hit ratio.