Optimal Throughput of the Full-duplex Two-way Relay System with Energy Harvesting

Full-duplex operation can enhance the transmission capacity of the communication systems, and energy harvest is a promising technique to prolong the lifetime of wireless nodes by utilizing the radio-frequency signals. In this paper, we investigate the throughput performance of a full-duplex two-way energy harvesting (EH) capable relay system. In particular, we focus on the time switching-based relaying (TSR) protocol for EH and amplify-and-forward for information transmission. The full-duplex system has two different ways of applying TSR protocol, named time switching-based full-duplex relaying I (TS-FDR-I) protocol and time switching-based full-duplex relaying II (TS-FDR-II) protocol. We consider both protocols and successfully obtain the outage probability and the system throughput for each protocol. The throughput of the system with TS-FDR-I protocol is a function of time-switching (TS) ratio, and we prove that the upper bound function of it is a log-concave function so that the close-to-optimal throughput and TS ratio could be computed efficiently. Meanwhile, the system with TS-FDR-II protocol has a fixed TS ratio, and its throughput is only related with signal-to-noise ratio (SNR). Simulation results show that the throughput function for TS-FDR-I protocol is log-concave and the performance of TS-FDR-I protocol is better than TS-FDR-II protocol when SNR is higher than 22dB.