Abstract: This letter proposes a low-complexity ‘harvest-and-forward’ relay strategy in simultaneous wireless information and power transfer (SWIPT) relay channels. In the first phase of relay transmission, the relay’s antennas are divided into two subsets. The signals received by the antennas in one subset are converted to energy, and the signals received by the antennas in the other subset are combined. In the second phase, the relay forwards the combined signal using all antennas with the harvested energy. A low complexity antenna selection (AS) algorithm is given to maximize the achievable rate over fading channels. The simulation results show that the achievable rate of this strategy is close to that of the two-stage strategy where a two-state procedure is proposed to determine the optimal ratio of received signal power split for energy harvesting, and the optimized antenna set engaged in information forwarding. The proposed strategy has better performance than the two-stage strategy when the relay is equipped with medium-scale antennas, and the performance gap between two strategies grows with the increase of the number of the relay’s antennas. The computational complexity of the proposed strategy is O(N2) (N is the number of relay antennas), which is obviously lower than that of the two-stage strategy (O(3N3)).

Key words: AS, SWIPT, energy harvesting (EH), relay