Simultaneous wireless information and power transfer for cognitive two-path successive relaying networks

Wireless powered relay (WPR) is an emerging application scenario for simultaneous wireless information and power transfer (SWIPT), which has drawn significant attentions. In this paper, we propose a cognitive two-path relay (TPR) network with the capability of power splitting (PS)-SWIPT. With the aid of PS, the successive source and relay transmissions can overcome spectral efficiency loss compared with half-duplex (HD) relay-assisted PS-SWIPT networks. An optimization problem is formulated, with jointly optimizing the PS factors of two relays to maximize the minimum signal-to-interference-plus-noise ratio (SINR) at the destination during two successive time slots. Through ratiocination and proving, the optimal solutions can be obtained by iterative methods. In consideration of inter-relay interference (IRI) cancellation, we also investigate the optimal PS factors under the condition of sufficiently small IRI channel gains. The simulation results demonstrate that, in the proposed scheme, the optimal PS factors with IRI cancellation are almost identical with the solutions with IRI when the IRI channel gains lower than a certain threshold, which can be set as the initial values of the iteration to reduce the iteration times in practical networks.