Adaptive Discrete-Time-Switching-Based Energy-Harvesting Relaying Systems

In this paper, to perform an energy-efficient and high-throughput time-switching (TS)-based energy-harvesting (EH) relaying in a practical block-by-block manner, an adaptive discrete TS-based EH relaying scheme is proposed. Specifically, focusing on both dual-hop amplify-and-forward (AF) and decode-and-forward (DF) systems, we make full use of the channel state information (CSI) at the relay to determine an adaptive relaying power as well as an adaptive TS factor based on the relay's current accumulated energy. For such, an effective analytical framework is proposed to characterize the throughput performance of the proposed scheme, which shows the superiority of the proposed scheme over the conventional one. In particular, the limiting throughput efficiency of the proposed scheme is shown to achieve the limiting/best throughput efficiency of 50% for half-duplex relaying regardless of channel fading types, while the limiting throughput efficiency of the conventional scheme is always less than 50%. Furthermore, simulation results are given to validate our theoretical analysis, showing that for AF mode, the proposed scheme can provide up to 7.4 dB threshold signal-to-noise ratio (SNR) gain over the conventional solution. In addition, a comprehensive comparison between the proposed scheme and other state-of-the-art protocols is also made via representative numerical examples.