Throughput analysis of cognitive wireless acoustic sensor networks with energy harvesting

Abstract

We consider a wireless acoustic sensor network, where an energy-constrained acoustic node as relay initially harvests energy through the received radio frequency signal from the primary transmitter, and then, it forwards the primary acoustic signal together with its own message by using the harvested energy. Considering that a preset fixed transmission power is used for relaying, a continuous time energy harvesting scheme is adopted. We further consider two wireless information and energy transmission protocols, namely, time-switching relaying (TSR) protocol and power-splitting relaying (PSR) protocol in this system. For both protocols, we derive exact expressions of the throughput efficiency for both primary and secondary systems. Moreover, we address optimal power allocation strategy for both protocols under the performance criteria, and prove that the optimization problem with TSR can be solved by analyzing the monotonicity of optimization function and non-convex optimization problem with PSR can be converted into a convex problem. Two corresponding optimal algorithms are proposed to solve optimization problems. Numerical results reveal that the proposed protocols not only facilitate both the primary and secondary signals transmission but also outperform the existing fixed time duration energy harvesting scheme in terms of achievable rate. Furthermore, the PSR protocol can achieve higher secondary transmission rate than the TSR protocol in lower relaying transmission power.