Throughput Maximization for the Full-Duplex Two-Way Relay System with Energy Harvesting

The full-duplex technique can improve the transmission capacity of the communication systems, and energy harvesting (EH) is a promising operation to prolong the lifespan of a wireless node by utilizing the radio-frequency signals. In this paper, the throughput performance of a full-duplex two-way energy EH capable relay system is investigated. In particular, a practical EH protocol, named the time-switching-based relaying (TSR) protocol, is used for EH and the decode-and-forward (DF) policy for information transmission. The outage probability is successfully obtained, and the corresponding system throughput for TSR protocol can be derived by it. The derived throughput is a function of different system parameters, including the time-switching (TS) ratio, power allocation ratio, and the length of the communication time slot. Meanwhile, the throughput is used to characterize a joint time and power allocation scheme for the system, and we aim to find the optimal time and power allocation to achieve the optimal throughput. Due to the existence of three variables and the integral form of throughput expression, an optimization for the throughput is difficult. However, a modified simulated annealing-based search (SABS) algorithm can be used to optimize the throughput. The modified SABS algorithm overcomes being highly impacted by the initial point, and derives the optimal solution fast. Simulation results show that the analytical throughput expression is related with the TS ratio, power allocation ratio, and the length of the communication time slot. The analytical curve of the throughput matches with the simulated one well, which shows that the obtained analytical system throughput for the TSR protocol is valid. Meanwhile, the proposed modified SABS algorithm could be used to derive accurate throughput when SNR is higher than 10 dB.