Secure MIMO Communication Relying on Movable Antennas

This paper considers a movable antenna (MA)-aided secure multiple-inputmultiple-output (MIMO) communication system consisting of a base station (BS),a legitimate information receiver (IR) and an eavesdropper (Eve), where the BSis equipped with MAs to enhance the system's physical layer security (PLS).Specifically, we aim to maximize the secrecy rate (SR) by jointly optimizingthe transmit precoding (TPC) matrix, the artificial noise (AN) covariancematrix and the MAs' positions under the constraints of the maximum transmitpower and the minimum distance between MAs. To solve this non-convex problemwith highly coupled optimization variables, the block coordinate descent (BCD)method is applied to alternately update the variables. Specifically, we firstreformulate the SR into a tractable form by utilizing the minimum mean squareerror (MMSE) method, and derive the optimal TPC matrix and the AN covariancematrix with fixed MAs' positions by applying the Lagrangian multiplier methodin semi-closed forms. Then, the majorization-minimization (MM) algorithm isemployed to iteratively optimize each MA's position while keeping others fixed.Finally, simulation results are provided to demonstrate the effectiveness ofthe proposed algorithms and the significant advantages of the MA-aided systemover conventional fixed position antenna (FPA)-based system in enhancingsystem's security.