Optimal multi-slot spectrum sensing in energy harvesting cognitive radio systems

In this paper, we consider a cognitive radio (CR) system operating in slotted mode, where the secondary user (SU) has no wired power supplies and is powered exclusively through extracting energy from ambient environment. Due to hardware limitation, the SU can only perform either of energy harvesting, spectrum sensing or data transmission at the same time and we assume that a timeslot is partitioned into three non-overlapping fractions. Considering a generalized multi-slot spectrum sensing paradigm with data fusion rule, we focus on the "saving-sensing-throughput" tradeoff and joint optimization for save-ratio, sensing duration as well as sensing threshold to maximize the SU\´s expected achievable throughput while keeping primary users (PUs) sufficiently protected. By translating the original optimization problem into a convex one, we show that the optimal solutions for sample number, mini-slot number as well as sensing threshold are non-unique and single-slot spectrum sensing is more practically preferable. We also investigate the impact of system parameters to the optimal sensing strategy.