A Secret Multiuser Transmission Scheme With Dual-Phase-Shifter Structure for mmWave Wireless Communication

Phased array antenna or analog beamformer is widely used in millimeter-wave (mmWave) communication system for its simple structures and low costs. In this letter, we propose a new analog secret mmWave communication system with a structure of dual phase shifters, to enable directional modulation (DM) based secret multiuser communication by overcoming the constant-modulus limitation of the radio frequency (RF) branch with a single phase shifter. By adjusting the values of the two phase shifters, both the phase and the magnitude of each RF branch can vary. We propose an arbitrary polygon construction based approach to establish a linear constrained optimization problem. With different polygon constructions, a lot of different qualified transmitting weight vectors for multiuser communication can be obtained. By varying such obtained weight vectors at the symbol rate, the DM based secret multiuser communication can be achieved. Finally, simulations are presented to demonstrate the effectiveness of the proposed scheme.