Joint Optimization of Power Splitting and Beamforming in Energy Harvesting Cooperative Networks

A new joint best relay and jammer selection (JBRJS) scheme is conceived for enhancing the physical layer security (PLS) of cooperative networks relying on multiple energy harvesting (EH) aided intermediate nodes, which accumulate energy based on the power splitting (PS) protocol. Specifically, we select the best intermediate node as the relay, whilst exploiting all the remaining nodes as friendly jammers. Furthermore, we investigate the joint optimization of the PS ratio and the relay-aided beamforming for maximizing the system's secrecy rate and present a full channel state information (CSI) based joint PS and beamforming (fJPSB) scheme as the optimal solution by converting the optimization problem formulated into a singlevariable optimization problem. We also propose a partial-CSI based JPSB (pJPSB) method for the scenario where only the main link's CSI is available. Our numerical results show that the proposed JBRJS scheme beneficially enhances the PLS compared to the joint random relay and jammer selection (JRRJS) and to the pure best relay selection (PBRS) schemes. Moreover, the secrecy rate of the proposed fJPSB and pJPSB schemes is obviously higher than that of the fixed PS and beamforming (FPSB) method, and it further increases with the number of the relay's transmit antennas.