QoS-Constrained Optimization of Intelligent Reflecting Surface Aided Secure Energy-Efficient Transmission

We propose an intelligent reflecting surface (IRS)-aided secure energy-efficient transmission that minimizes transmit power under constraints on the signal-to-noise ratios at the legitimate user and the eavesdroppers. This is achieved by jointly optimizing the beamforming weights at the transmitter and the phase shift coefficients at the IRS. To overcome the non-convexity of the problem, an alternating optimization algorithm is proposed. More specifically, by iteratively calculating the beamforming weights of a transmitter and the phase-shift coefficients at an IRS, the original optimization problem is separately approximated by a second-order cone programming problem. The results of the proposed algorithm are guaranteed to be the same as the solution of the original problem.