Beam Selection Methods for Massive MIMO Systems with Hybrid Radio Frequency and Baseband Precoding

With massive MIMO and/or millimeter wave technologies, the system has large numbers of antennas and/or frequency bands to increase the capacity and the number of the accessed users. In this case, conventional precoding method performed at the baseband becomes impractical, since the processing complexity is large and the cost of the hardware is high. Therefore, hybrid radio frequency (RF) and baseband (BB) precoding is an alternative to achieve the tradeoff between complexity and performance. In this paper, beam selection methods based on the thought of spatial correlation, variable beamwidth and beam combination are proposed for RF beamforming used in single-user and multiple- user scenarios, respectively. Simulation results show that the proposed beam selection methods perform well with much lower complexity than brute- force search.