Secure Beamforming in DLA-Based CAP-MIMO

This work proposes a novel secure beamforming design for discrete lens array (DLA)-based continuous aperture phased (CAP) multiple-input multiple-output wiretap channels. The base station exploits a switching network to connect a subset of its analog beams or DLA feed antennas to the available radio frequency chains. The switching network and transmit beamformers are jointly designed to maximize the weighted secrecy sum-rate for this setting. The principal design problem reduces to an NP-hard mixed-integer non-linear programming. We invoke the fractional programming technique and the penalty dual decomposition method to develop a tractable iterative algorithm that effectively approximates the optimal design. Our numerical investigations validate the effectiveness of the proposed algorithm and its superior performance compared with the benchmark.