Millimeter Wave Analog Beamforming with Low Resolution Phase Shifters for Multiuser Uplink

We consider millimeter wave multiuser uplink system with low resolution phase shifters, where users transmit simultaneously to base station. Transmit and receive beamforming through large antenna arrays is used to compensate severe path loss of millimeter waves. We first propose a joint precoder and detector design based on the low-complexity local search algorithm that iteratively finds the preferred transmit and receive beamforming vectors, which maximizes the sum-rate of the multiuser uplink system. Although the joint design achieves similar sum-rate to a fully digital system, the computation complexity to determine good beamforming vectors is high. To reduce complexity, we then propose nonjoint designs of precoder and detector. For the precoder design, the transmit beamforming vectors are chosen to maximize either the signal to noise ratio or the signal to interference plus noise ratio of each user. For the detector design, the receiver beamforming vectors are selected using either an approximate ML detector or a successive cancellation detector. Through simulations, we show that our designs with low resolution phase shifters outperform the traditional methods using steering vectors as beamforming vectors with high resolution phase shifters.