Secure wireless energy harvesting-enabled AF-relaying SWIPT networks

Simultaneous wireless information and power transfer (SWIPT) has recently drawn much attention for its dual use of radio signals. A new type of relays, wireless energy harvesting (WEH)-enabled relays, are thus motivated to support cooperation. In this paper, we consider the use of power splitter (PS) at such relays for a distributed WEH-enabled amplify-and-forward (AF) relaying network, where a multi-antenna transmitter communicates with a single-antenna receiver with the aid of several single-antenna WEH-enabled AF relays, in the presence of a single-antenna eavesdropper. Assuming global channel state information (CSI) at the transmitter but local CSI from/to legitimate parties at the relays, the secrecy rate maximization problem is studied to optimize the beamforming vector at the transmitter as well as the PS ratios and the AF coefficients at the relays. We devise an efficient secure relay beamforming (SRB) algorithm to first obtain the PS ratios in a distributed manner and then iteratively adapt the transmit beam and the AF coefficients. The efficiency of the proposed algorithm is evaluated against other heuristic schemes by simulations.