Improved Algorithms for the Connected Sensor Cover Problem

Wireless sensor networks have recently posed many new system-building challenges. One of the main problems is energy conservation since most of the sensors are devices with limited battery life and it is infeasible to replenish energy via replacing batteries. An effective approach for energy conservation is scheduling sleep intervals for some sensors, while the remaining sensors stay active providing continuous service, i.e., maintain sensing coverage and network connectivity. In this paper we consider the problem of selecting a set of active sensors of minimum cardinality satisfying the above requirements. We develop constant-factor approximation algorithms for fixed and variable sensor locations. Our algorithms are based on different techniques, which allows to find the desired trade-off between the complexity and the quality of approximation. We also present an improved 6-approximation algorithm for the minimum connected dominating set problem in unit disk graphs. Finally, we propose algorithms for connecting a covering set.