Robust Beamforming and Power Splitting for Secrecy Wireless Information and Power Transfer in Cognitive Relay Networks

In this letter, we study the problem of secrecy wireless information and power transfer in a cognitive relay network (CRN), where a secondary transmitter (ST) aids the signal transmission from a primary transmitter to a primary receiver (PR), while it also transmits its own signal to a second receiver (SR). Both the PR and SR decode information and harvest energy from the received signals based on a power splitting strategy. Due to the open architecture of a CRN, the information for SR is prone to be eavesdropped by PR. This letter aims to minimize the transmit power at ST while guaranteeing minimum information rates and the amounts of harvested energy at PR and SR, and constraining the potential eavesdropping rate at PR. Considering imperfect channel state information at ST, we propose a joint robust beamforming and transformation matrix at ST and power splitting at the PR and SR schemes, which can minimize the transmit power in the worst case. Finally, simulation results validate the effectiveness of the proposed scheme.