Revisiting Censoring in Energy Harvesting Wireless Sensor Networks

Abstract

Censoring improves the lifetime of conventional wireless sensor networks (WSNs) by reducing the number of sensor node transmissions. However, this comes at the expense of performance since measurements from fewer nodes are available. We show that in energy harvesting (EH) WSNs, in which the sensor nodes harvest energy from the environment, this trade-off is fundamentally different. For a general model in which the nodes experience independent and non-identical fading and the EH process at a node is stationary and ergodic, we derive a lower bound on the mean squared error (MSE). It leads to an insightful and explicit characterization of the optimum censoring threshold for each node. We show that it is the point at which the probability that an EH node has sufficient energy to transmit becomes 1. We also analyze the MSE outage probability, which is an alternate and widely used performance measure, which characterizes the impact of channel fading.