Low Complexity Hybrid Precoding Using Beam Steering for mmWave MIMO Systems

Abstract

Millimeter wave MIMO systems provide orders of magnitude in data rates due to larger bandwidth than conventional MIMO systems. On the other hand, they experience severe free-space pathloss as carrier frequency ten-fold increases. The resulting small wavelength helps to overcome pathloss with beamforming gain using massive antennas, known as precoding. In mmWave MIMO system, hybrid beamforming combines analog beamforming with digital precoding to reduce the energy consumption and complexity. Hybrid beamforming uses a smaller number of RF chains, which have large power consumption, than the number of antennas. In order to design analog and digital precoder, a large number of calculations such as the SVD of channel is required. In this paper, we propose low complexity hybrid precoding algorithm using beam steering, which utilizes array response vectors of the channel. We first propose the method of selection the analog beamforming matrix without any SVD or inversion of matrices. Then, we find the digital precoding matrix which performs a maximum of the total sum rate with fixed analog beamforming matrix. Since our proposed algorithm applies a set of array response vectors that are used to form the channel, there is no need for complicated operations as SVD like traditional precoding algorithms. Simulation results show that proposed algorithm can reduce the computational complexity while achieving about 93% the same performance in achievable rate compared to typical hybrid precoding in mmWave MIMO systems.