Dynamic Coverage and Related Problems in Ad-hoc Sensor Networks

Ad-hoc networks of sensor nodes are in general semi-permanently deployed. However, the topology of such networks continuously changes over time, due to the power of some sensors wearing out, to new sensors being inserted into the network, or even due to designers moving sensors around during a network re-design phase (for example, in response to a change in the requirements of the network). In this paper, we address the problem of how to dynamically maintain two important measures on the quality of the coverage of a sensor network: We maintain a (1 + ǫ)-approximation on the best-case coverage distance and a ( √ 2 + ǫ)-approximation on the worst-case coverage distance of the network, for any fixed ǫ > 0. We assume that the ratio between upper and lower transmission power of sensors is bounded by a polynomial of n, where n is the number of sensors. Our algorithms have amortized or worst-case poly-logarithmic update costs when the motion of mobile sensors can be described as a low-degree polynomial function of time. We are able to efficiently maintain the connectivity of the regions on the plane with respect to the sensor network, by extending the concatenable queue data structure to also serve as a priority queue. In addition, we present an algorithm that finds the shortest maximum support path in time O(n log n), improving on the O(n logn) running time of centralized implementation of the previously best known algorithm by Li, Wan, and Frieder. ∗Department of Computer Science and Engineering, Arizona State University, Tempe, AZ 85287-5406, USA. This work was supported in part by NSF CAREER Award CCR–9985284. Tel: 1-480-965-7555 Fax: 1-480-965-2751 Email: {hai, aricha}@asu.edu †Communication Systems Engineering Department, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel. Tel: 972-8-6477234 Fax: 972-8-6472883 Email: [email protected]