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Jamming attacks can severely affect the performance of Wireless Sensor Networks (WSNs) due to their broadcast nature. The most reliable solution to reduce the impact of such attacks is to detect and localize the source of the attack. In this paper, we investigate the feasibility of localizing an omni-antenna jammer. We propose Catch the Jammer (CJ), an efficient jammer localization scheme whereby victim nodes at the border of the jammed region share their location information with their one-hop neighbor nodes which further collaborate to find the position of the jammer. This new localization technique first computes a convex hull for the set of victim nodes and further extracts the corresponding minimum covering circle. Simulation results show that CJ outperforms most of the existing localization algorithms depending on the variation of the jammer's transmission range and the position of the jammer.

– Frequent location updates from mobile clients make the server a bottleneck for severe communication and processing overhead in large scale location-based information sharing system. From our observation, implanted information is not distributed uniformly in geography, which leads to some blank zones. In existing systems, the client needs to update its location on the server periodically no matter whether any information needs to be shared, which brings extra communication overhead. We present an information indexing scheme, providing on-demand information request for mobile clients. In this scheme, an information matrix is built on the server and synchronized to clients, in which each element indicates whether the information is implanted in the associated zone. Clients decide when to request for downloading related information as distributed mode instead of server central mode. Experimental results show that the scheme can greatly eliminate communication overhead and work well especially for applications with unevenly distributed information.Abstract – Frequent location updates from mobile clients make the server a bottleneck for severe communication and processing overhead in large scale location-based information sharing system. From our observation, implanted information is not distributed uniformly in geography, which leads to some blank zones. In existing systems, the client needs to update its location on the server periodically no matter whether any information needs to be shared, which brings extra communication overhead. We present an information indexing scheme, providing on-demand information request for mobile clients. In this scheme, an information matrix is built on the server and synchronized to clients, in which each element indicates whether the information is implanted in the associated zone. Clients decide when to request for downloading related information as distributed mode instead of server central mode. Experimental results show that the scheme can greatly eliminate communication overhead and work well especially for applications with unevenly distributed information.