VRSense: Validity region sensitive query processing strategies for static and mobile point-of-interests in MANETs

摘要

Querying any point-of-interest (POI) in anywhere is a major part of location-based services (LBS) and has been applied to diverse wireless and/or mobile networks for realizing seamless services and mobile and ubiquitous computing. In particular, designing an efficient query processing scheme is admittedly challenging in mobile ad hoc networks (MANETs) because of the lack of centralized coordination, limited computing and communication capabilities, and time-varying network topologies. Unlike traditional stationary POIs, it also becomes challenging to consider mobile POIs that can invalidate prior query result. To address these challenges, we propose a set of query processing strategies based on a validity region to efficiently update the freshness of the queried POI and reduce the query traffic in MANETs. We first present and analyze time- and location-sensitive query types in the presence of static and mobile POIs and identify their corresponding query processing operations and implications. A time-sensitive query targets a POI containing a time-varying information while a location-sensitive query retrieves a location information. In this paper, we focus on location-sensitive query for both static and mobile POIs. Unlike a static POI, which is stationary and never changes its location, a mobile POI refers to a moving object and its location information is time varying. Then we propose basic rectangle and convex hull based validity regions and their corresponding query processing operations, and extend them by combining both techniques and considering an opportunistic overhearing. We also propose two more techniques in forming validity region for mobile POIs and their corresponding query processing operations to flexibly approximate the validity region. We conduct extensive simulation experiments using the OMNeT + + for performance evaluation and analysis, in which an infrastructure-based query processing approach is modified to work in MANETs for performance comparison. The simulation results indicate that the validity region based query processing strategies can reduce the number of queries and increase the time staying in the validity region.