Region-aware querying strategies in infrastructure-less networks: Design, analysis, and evaluation



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As wireless and mobile devices are increasingly popular and become resource-rich, users (later nodes) can freely query any point-of-interest (POI) in anywhere and fully enjoy location-based service (LBS) deployed in diverse infrastructure-based wireless networks. Due to the limited coverage of 4G/5G networks, however, nodes may not be connected with the infrastructure but be remained uncovered for a certain period in such a blackspot, urban, or remotely isolated area. In particular, the current infrastructure could even be collapsed and unavailable in a disaster environment, e.g., recent hurricanes and earthquakes. Emergency communications and queries among rescue people involved in a mission-critical network should still be conducted through single- and multi-hop relays without the help of infrastructure. Designing an efficient query processing scheme is admittedly challenging in MANETs because of the lack of centralized coordination, limited computing and communication capabilities, and more importantly time-varying network topologies. Unlike traditional stationary POIs, it also becomes challenging to consider mobile POIs that can easily invalidate the prior queried result. To address these challenges, we investigate novel query processing strategies based on a validity region to efficiently query POIs in a MANET environment. The validity region is an area where a query result remains the same as long as a query issuing node is located within the area. In this research, we investigate three major issues. First, we develop basic rectangle and convex-hull based validity regions and their corresponding query processing operations for static POIs, and extend them by combining both techniques and considering an opportunistic overhearing. Second, we develop techniques in forming validity region for mobile POIs by either reducing the size of validity region on purpose, or assigning a set of re-query probabilities %to each cell located within the validity region. These techniques are designed to pro-actively reduce the effect of the mobility of nodes and POIs, resulting in an obsoleted validity region. Third, we develop an elastic validity region and its corresponding query operations by judiciously monitoring adjacent mobile POIs and interacting with the query replying nodes. This approach is primarily designed to adaptively update the initially built validity region as well as reduce the query traffic in the network. We conduct extensive simulation-based experiments for multi-dimensional performance comparisons and analyses by developing a customized and discrete event driven simulator based on the OMNeT++, and the simulation results show that our proposed querying strategies can be a viable approach in MANETs. In addition, we further identify and discuss two promising research issues in order to see the full potential of the proposed approaches: evacuation querying and privacy preserving.



Infrastructure-less networks, Mobile point-of interests, Query processing, Validity region