Artificial-noise-aided secure beamforming in full-duplex wireless-powered relaying system

Abstract

This paper studies a wireless powered relaying (WPR) system in which a source transmits an information signal to a destination with the help of an energy constrained relay in the presence of an eavesdropper. This work considers a scenario in the full-duplex WPR system where the information transmission/reception and the energy harvesting are performed simultaneously at the relay. For the case in which global channel state information is available, we formulate a joint optimization problem of artificial-noise-aided secure beamforming to maximize the achievable secrecy rate. Then, an efficient semi-definite relaxation (SDR) based algorithm is proposed to obtain the optimal beamforming. Furthermore, we also propose two suboptimal beamforming but low computational complexity schemes. Comparisons are carried out among the performances of the proposed optimal and suboptimal schemes. For the case in which only statistical information on the eavesdropper channel is available, the secrecy outage probability and its upper bound are obtained when beamforming vectors are designed in a heuristic manner. Then, the power allocation between the information signal and artificial noise is studied to minimize the secrecy outage probability.