Optimal saving-sensing-transmitting structure in self-powered cognitive radio systems with wireless energy harvesting

In this paper, we consider a CR system operating in slotted mode, in which the SU has no fixed power supplies and extract energy only via wireless energy harvesting from ambient radio signal. It is assumed that the SU operates in a saving-sensing-transmitting (SST) fashion, which partitions a timeslot into non-overlapping fractions for the three operations. Considering the tradeoff between durations of saving, sensing and transmitting, we focus on the optimal structure for the three operations that maximizes the achievable throughput. By formulating the achievable throughput optimization as a mixed-integer non-linear programming (MINLP) problem, we derive the optimal SST structure via a modified differential evolution (DE) algorithm and perform in-depth numerical analysis. The simulation results demonstrate the performance gain of the optimal structure over non-optimal ones as well as affects of energy harvesting rate.