Performance of multi-antenna wireless-powered communications with nonlinear energy harvester

In this paper, we investigate the average throughput of a multi-antenna wireless powered communication network where an energy-constrained user harvests energy from a hybrid access-point (AP) equipped with multiple antennas in the downlink, and then transmits information to the AP in the uplink using the harvested energy. Specifically, we consider a more practical scenario, i.e., nonlinear energy harvester, as compared with the traditional linear model. In order to evaluate the key parameters, such as the transmit power, antenna numbers, timesplitting, channel fading severity, on the performance of the considered system, we derive closed-form expressions of the average throughput for both delay tolerant and delay intolerant transmission modes in Nakagami-m fading channel. In addition, to further exploit the insights on the application of the considered system, the asymptotic analysis for the achievable throughput are also provided in two special cases, i.e., high transmit power regime and high saturation threshold regime. Finally, our results demonstrate that the considered system exhibits the throughput saturation phenomenon, and the parameters of channel fading severity produce a different impact on the average throughput in the two transmission modes.