Robust Secure Beamforming for Multiantenna Relay Networks with Multiple Eavesdroppers

Physical layer security has recently emerged as a promising approach to achieve security and communication integration. The built-in security mechanism based on the characteristics of the wireless channel provides a feasible idea for the realization of “one secret at a time.†It has significant potential applications in high-rate data transmission encryption, authentication, integrity protection of service data, and Internet of Things lightweight encryption. This paper investigates the robust secure transmit design problem for amplify-and-forward multiantenna relay networks in the presence of multiple single-antenna eavesdroppers. A robust artificial noise (AN) aided secure beamforming design is proposed by taking into account the imperfect channel state information (CSI) of the eavesdroppers. The goal is to jointly design the beamforming matrix and the AN covariance matrix at the relay based on the imperfect CSI of eavesdroppers, such that the worst-case secrecy rate is maximized subject to the total power and the per-antenna power constraints. Aiming at the nonconvex optimization problem, a two-level optimization algorithm based on semidefinite relaxation (SDR) and S-procedure is proposed. It is proven that there is a rank-one optimal solution for the SDR problem. Simulation results show that the proposed scheme is robust and superior to existing schemes.