We study the important problem of tracking moving targets in wireless sensor networks. We try to overcome the limitations of standard state of the art tracking methods based on continuous location tracking, i.e. the high energy dissipation and communication overhead imposed by the active participation of sensors in the tracking process and the low scalability, especially in sparse networks. Instead, our approach uses sensors in a passive way: they just record and judiciously spread information about observed target presence in their vicinity; this information is then used by the (powerful) tracking agent to locate the target by just following the traces left at sensors. Our protocol is greedy, local, distributed, energy efficient and very successful, in the sense that (as shown by extensive simulations) the tracking agent manages to quickly locate and follow the target; also, we achieve good trade-offs between the energy dissipation and latency.
A standard centralized approach to tracking ( @cite_4 ), is sensor specific'', in the sense that it uses some smart powerful sensors that have high processing abilities. In particular, this algorithm assumes that each node is aware of its absolute location (e.g. via a GPS) or of a relative location. The sensors must be capable of estimating the distance of the target from the sensor readings. The process of tracking a target has three distinct steps: detecting the presence of the target, determining the direction of motion of the target and alerting appropriate nodes in the network. Thus, in their approach a very large part of the network is actively involved in the tracking process, a fact that may lead to increased energy dissipation. Also, in contrast to our method that can simultaneously handle multiple targets, their protocol can only track one target in the network at any time. Overall, their method has several strengths (reasonable estimation error, precise location of the tracked source, real time target tracking, but there are weaknesses as well (intensive computations, intensive radio transmissions).
@cite_4
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Networks of small, densely distributed wireless sensor nodes are capable of solving a variety of collaborative problems such as monitoring and surveillance. We develop a simple algorithm that detects and tracks a moving target, and alerts sensor nodes along the projected path of the target. The algorithm involves only simple computation and localizes communication only to the nodes in the vicinity of the target and its projected course. The algorithm is evaluated on a small-scale testbed of Berkeley motes using a light source as the moving target. The performance results are presented emphasizing the accuracy of the technique, along with a discussion about our experience in using such a platform for target tracking experiments.