Tracking targets with quality in wireless sensor networks

Tracking of moving targets has attracted more and more attention due to its importance in utilizing sensor networks for surveillance. In this paper, we consider the issue of how to track mobile targets with certain level of quality of monitoring (QoM), while conserving power. We address the target tracking problem by taking into account of both the coverage and the QoM. In particular, QoM ensures that the probability of reporting inaccurate monitoring information (such as false alarm or target miss) should be as small as possible, even in the presence of noises and signal attenuation. We also analytically whether or not the detection/observation made by a single sensor suffices to tracking the target in a reasonably populated sensor network. Our finding gives a confirmative answer and challenges the long-held paradigm that high tracking quality (low tracking error) necessarily requires high power consumption. To rigorously analyze the impact of target movement on QoM, we derive both lower and upper bounds on the number of sensors (called duty sensors) required to keep track of a moving target. Based on the analysis, we have devised a cooperative, relay-area-based scheme that determines which sensor should become the next duty sensor when the target is moving. The simulation study indicates that the number of duty sensor required in the proposed scheme is, in the worst case, approximately 1.2 times larger than the lower bound. It also indicates that a trade-off exists among QoM, the number of duty sensors required, and the load balance