A framework for battery-aware sensor management

A distributed sensor network (DSN) designed to cover a given region R, is said to be alive if there is at least one subset of sensors that can collectively cover (sense) the region R. When no such subset exists, the network is said to be dead. A key challenge in the design of a DSN is to maximize the operational life of the network. Since sensors are typically powered by batteries, this requires maximizing the battery lifetime. One way to achieve this is to determine the optimal schedule for transitioning sets of sensors between active and inactive states while satisfying user specified performance constraints. This requires identification of feasible subsets (covers) of sensors and a scheme for switching between such subsets. We present an algorithmic solution to compute all the sensor covers in an implicit manner by formulating the problem as unate covering problem (UCP). The representation of all possible sensor sets is extremely efficient and can accommodate very large number of sensor covers. The representation and formulation makes it possible to consider the residual battery charge when switching between covers. We develop algorithms for switching between sensor covers aimed at maximizing the lifetime of the network. The algorithms take into account the transmission/reception costs of sensors, a user specified quality constraint and also utilize a novel battery model that accounts for the rate-dependent capacity effect and charge recovery during idle periods. Our simulation results show that lifetime improvement can be achieved by exploiting the charge recovery process. The work presented here constitutes a framework for battery aware sensor management in which various types of constraints can be incorporated and a range of other communication protocols can be examined.