Antenna array thinning for interference mitigation in multi-directional antenna subset modulation

Due to the increasing demand for wireless communications, millimeter-wave band has gained a great attention recently. Also, achieving secure wireless communications is of high importance. Antenna subset modulation is a low complexity single beam directional modulation technique suitable for millimeter-wave wireless communications, whereas multi-beam antenna subset modulation is a multi-directional, generalized form of antenna subset modulation. In this paper, interference mitigation for multi-beam antenna subset modulation via side lobe level reduction is introduced. A method for designing thinned arrays with minimum side lobe levels for antenna subset modulation is introduced and generalized for multi-beam antenna subset modulation. A new variable constraint is applied to the optimization problem to control the localization of optimum solution within the antenna array. Two solutions are introduced, convex optimization combined with local search and local search assisted genetic algorithm. Simulation results show the superiority of the proposed algorithms compared to simulated annealing algorithm and traditional genetic algorithm.