Securing Near-Field MIMO Communications via Dynamic Metasurface Antennas

Secure transmission is challenging for wireless systems because the open nature of wireless channels leads to vulnerability to malicious attacks by eavesdroppers. Dynamic metasurface antennas (DMAs) are promising technologies that have great potential to significantly improve secure communication performance. Therefore, this paper introduce DMA to a multiple-input multiple-output (MIMO) communications system with an eavesdropper. Due to the high carrier frequency and large antenna aperture, both the receiver and eavesdropper are located in the near-field region. The formulated nonconvex optimization problem is to jointly design the digital precoding vector and the DMA weight matrix via alternating optimization (AO) algorithm for maximizing the secrecy capacity. In the proposed scheme, a closed-form expression of the optimal digital precoding vector is derived, and the DMA weight matrix is optimized by using successive convex approximation and the Majorization-Minimization (MM) algorithm. Numerical results validate the superiority of the proposed scheme.