Low Complexity Hybrid Beamforming Methods for Single-User Millimeter Wave Mimo Systems

Abstract

Millimeter wave communication is an attractive new research area due to specilization for high symbol rate wireless system and increasingly serious spectrum congestion. The benefits of mmWave communication system include realizing high speed, low latency data transmission, offering higher bandwidth communication channels and so on. However, the signal processing is so different compared with low-frequency propagation, such as larger penetration losses, limited transmission range and lower diffraction in front of obstacles. To solve these problems mentioned, beamforming has been proposed. In this paper, multiple precoding implementations are introduced including full-digital as well as the hybrid one under the single-user condition. First, a digital system is constructed while the signal is processed using zero-forcing-Serial Interference Cancellation criterion (ZF-SIC) and Minimum Mean Square Error (MMSE)-Serial Interference Cancellation criterion (MMSE-SIC) respectively. Then, two hybrid beamforming (HBF) algorithms based on different criteria are introduced. We utilize the spatial structure of the millimeter wave channel to formulate the precoding/combining problem as a sparse re-construction problem and this hybrid precoding algorithm is applied to approach optimal unconstrained precoders and combiners. Subsequently, an energy efficient HBF method with sub-connected architecture is investigated, which is able to reduce the energy consumption and computation complexity.' The results of all the algorithms are compared and the performance of different precoding methods is presented in terms of spectral efficiency and Signal to Noise Ratio (SNR).