An iterative FFT-based antenna subset modulation for secure millimeter wave communications

Antenna subset modulation has been proposed as a physical layer security technique for millimeter-wave (mmWave) wireless communications. In antenna subset modulation, the transmitter selects a subset of antennas at the symbol rate to differ the sidelobes of the nonuniform arrays in undesired directions and orients the mainlobe in the target direction by steer beamforming. In this paper, we propose an optimized antenna subset selection based on an iterative fast Fourier transform (FFT) algorithm for large-scale arrays. The analysis shows that the computational complexity of our proposed algorithm is significantly reduced compared with existing algorithms. Apart from the low computational complexity, simulation results show that the proposed algorithm has smaller sidelobes than other existing algorithms. Even if an eavesdropper is sufficiently sensitive, it is impossible to recover information when the sidelobes is small. Therefore, our proposed algorithm can provide more security with low computational complexity.