Physical-Layer Security for Multi-User Communications With Frequency Diverse Array-Based Directional Modulation

By resorting to the technology of frequency diverse array (FDA)-based directional modulation (DM), this paper designs the physical-layer security in system uplink and downlink. Specifically, the FDA-based single-beam DM is employed to deliver confidential messages from each legitimate user (LU) to the base station (BS) in the uplink. To eliminate mutual interference caused by the simultaneous arriving signals at BS, we propose the FDA-based multi-carrier allocation scheme together with the receiver structure. On the other side of the coin, the FDA-based multi-beam DM is employed to send secrecy information from BS to LUs in the downlink. Moreover, the maximum signal to leakage and noise ratio (MSLNR) and the maximum eavesdroppers to LUs interference and noise ratio (MELINR) are proposed to design the beamforming matrix and the protection matrix, respectively, to enhance downlink security. Simulation results show that the proposed method has better security performance than the zero-forcing (ZF) and singular value decomposition (SVD) methods in the downlink. Moreover, the proposed FDA method outperforms the conventional phased-array system in both uplink and downlink.