Downtilts adjustment and power allocation algorithm based on PSO for 3D MIMO systems

Since the 3-dimension (3D) beamforming technology and the Active Antenna System (AAS) have been extensively employed in Long Term Evolution-Advanced (LTE-A) systems, a cell can be divided into several sectors both horizontally and vertically to improve the performances of the systems. An issue of joint downtilts adjustment and power allocation of two vertical beams is addressed in this paper. The system model is built and a particle swarm optimization (PSO) based beams optimization algorithm is proposed to maximize the cell spectral efficiency, in which the downtilts and powers of the two vertical beams are mapped onto particles and the cell spectral efficiency is defined as the fitness function. By updating the positions and velocities of the particles according to some principles dealing with all constraints, the optimum or suboptimum solution can be obtained. Simulation results show that a high cell spectral efficiency can be achieved with a low complexity by the proposed algorithm.