DFT-based multi-directions directional modulation

In this letter, a physically secure multi-directions directional modulation scheme is proposed. The scheme provides an adaptive beam-width assignment, where each user is granted a different beam width based on its channel condition. The scheme can be efficiently implemented using a discrete Fourier transform (DFT)-based algorithm that divides the spatial dimension into orthogonal narrow sub-beams. Each user is assigned multiple sub-beams that satisfies its pre-set direction of transmission and beam-width requirements. The scheme preserves the secrecy properties of directional modulation algorithms, where each legitimate user is guaranteed a secure communication link to its trusted receiver. The proposed scheme is practically efficient since it can be directly implemented using a DFT-based signal processing core.