Performance analysis of power beacon-assisted energy harvesting NOMA multi-user relaying system over Nakagami-m fading channels

Abstract

In this paper, we propose and analyze a multi-user non-orthogonal multiple access (NOMA) relaying system under the effect of Nakagami-m fading. In this system, both source and the relay harvest the energy from a multiple-antenna power beacon (PB) in the first time duration by using the time switching protocol and then use the harvested energy to transmit and receive the signals in the remaining time duration. We derive the exact closed-form expressions of the outage probability in two cases of successive interference cancellation (SIC), i.e., perfect SIC and imperfect SIC. Moreover, we determine the optimal time switching ratio that maximizes the system throughput. We also compare the achievable sum rate of the proposed NOMA relaying system with that of the orthogonal multiple access (OMA) relaying system. The correctness of all derived mathematical expressions results in this paper is verified by Monte-Carlo simulations. Numerical results show that: (1) the fading severity of wireless channels has a significant impact on the outage probability and the diversity; (2) increasing the number of antennas of PB helps to lower the outage probability, decrease the energy harvesting time, and increase the throughput; (3) the sum rate of the proposed NOMA relaying system is proportional to the SIC quality and is higher than that of the OMA relaying system in the low and moderate signal-to-noise ratio (SNR) regimes.