User scheduling and beamformer design method, apparatus, and storage medium based on two-stage beamformer for massive MIMO downlink

Abstract

Disclosed herein are a user scheduling and beamformer design method, apparatus, and storage medium for multi-user MIMO downlink based on two-stage beamforming or single-stage beamforming. The user scheduling and beamformer design method includes 1) a two-step feedback approach, 2) the use of orthonormal reference beam vectors, 3) computation of the angle between the user's channel vector and each of the orthonormal reference beam vectors, 4) first-step feedback of the reference beam index to which the user's channel vector's angle is less than a certain threshold and feedback of the user's channel vector's norm, 5) selection of roughly orthogonal users with large channel norm based on the use of reference beam vectors and the channel norm feedback, 6) second-step feedback of the channel state information (CSI) from the scheduled users, 7) design of multi-user downlink beamformer for the scheduled users based on the second-step feedback of the CSI of the scheduled users. The main key point of this invention is that in the first step of user selection, we propose to use the channel norm or noise-plus-interference-divided channel norm as the feedback quantity and we propose to use only the angle between each of the reference beam vectors and the user's channel vector to identify the closest reference beam vector.