Abstract-In wireless sensor networks (WSNs), jamming attacks have become a great concern recently. Finding the location of a jamming device is important so as to take security actions against the jammer and restore the network communication. In this paper, we take a comprehensive study on the jammer localization problem, and propose a simple while effective algorithm called Double Circle Localization (DCL). DCL is based on minimum bounding circle (MBC) and maximum inscribed circle (MIC). We implement and evaluate DCL under different conditions, including different node densities, jammer's transmission powers and antenna orientations, and compare it with three existing jammer localization algorithms through both simulation and experiments. Our evaluation results have demonstrated that, compared with all other approaches, DCL achieves the best accuracy in jammer localization.

Jamming is one of the most severe attacks in wireless sensor networks (WSNs). While existing countermeasures mainly focus on designing new communication mechanisms to survive under jamming, a proactive solution is to first localize the jammer(s) and then take necessary actions. Unlike the existing work that focuses on localizing a single jammer in WSNs, this work solves a multi-jammer localization problem, where multiple jammers launch collaborative attacks. We develop two multijammer localization algorithms: a multi-cluster localization (M-cluster) algorithm and an X-rayed jammed-area localization (Xray) algorithm. Our extensive simulation results demonstrate that with one run of the algorithms, both M-cluster and X-ray are efficient in localizing multiple jammers in a wireless sensor network with small errors.

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Abstract-Mobile agents are autonomous programs that may be dispatched through computer networks. Using a mobile agent is a potentially efficient method to perform transactions and retrieve information in networks. Unknown congestion in a network causes uncertainty in the routing times of mobile agents so the routing of mobile agents cannot rely solely on the average travel time. In this paper we deal with a given stochastic network in which the mobile agent routing time is a random variable. Given pre-specified values R and PR, the objective is to find the path with the minimum expected time under the constraint that the probability that the path time is less than R is at least PR. We show that this problem is NP-hard, and construct an exact pseudo-polynomial algorithm and an ε-approximation algorithm (FPTAS) for the problem.Index Terms-Agent-based architecture, fast routing algorithm, FPTAS, stochastic routing.