Enhanced D-Tree - An Index Structure For Window Queries In Location Based Services

Location based services is considered as a killer application in the wireless data market that provide information based on locations specified in the queries. We consider wireless data broadcasting as a way of disseminating information to a massive number of users. To address the issues of responsiveness, energy consumption and bandwidth contention in wireless communications, an index has to minimize the search time and maintain a small storage overhead. A linear index structure based on the D-tree is used to support location dependent queries, which is reduced to planar point queries. In this paper, we propose a modified D-tree index structure for processing location dependent information focusing on window queries via wireless data broadcast in a mobile environment. Hilbert curve is used to reduce the data regions that have to be searched from the whole space. Filtering mechanisms are used to find the real answer set. To improve the query processing two techniques namely, fixed grid assignment by which the given space is partitioned into several disjoint sub-grids and caching mechanism that improves access latency were used.