Beam Allocation based on Spatial Compatibility for Hybrid Beamforming C-RAN Networks

In this work, we consider a beam allocation problem in hybrid beamforming (HBF) cloud radio access networks (C-RANs) to maximize the sum rate. The problem considers a codebook-based analog beamforming performed at the remote radio head (RRH) and digital beamforming at the baseband unit (BBU). Differently from previous works, we assume that a given user equipment (UE) can be served by multiple beams, without being specifically associated to a given RRH. Due to the relation between the analog beam allocation and the digital beamforming, we consider a new metric based on channel correlation and channel attenuation for the analog beamforming solution. The metric measures the spatial compatibility in order to improve the spectral efficiency before the digital beamforming solution. In order to evaluate the proposed metric we present a low-complexity greedy algorithm, which is shown to provide a reasonable performance/complexity trade-off.