Analysis of Broad Beam Beamforming for Collocated and Distributed MIMO

Broad beam beamforming (BF) design in multiple-input multiple-output (MIMO) can be convenient for initial access, synchronization, and sensing capabilities in cellular networks by avoiding overheads of sweeping methods while making efficient use of resources. Phase-only BF is key for maximizing power efficiency across antennas. A successful method to produce broad beams is the phase-only dual-polarization BF (DPBF). However, its efficiency has not been proved in non-line-of-sight (NLoS). Therefore, this paper contributes by evaluating DPBF in collocated and distributed MIMO configurations under both line-of-sight (LoS) and NLoS channel conditions. We model the reflection coefficients for different materials in NLoS conditions and propose the use of orthogonal space-time block code to improve the coverage compared to the DPBF in collocated MIMO (C-MIMO). We further propose a DPBF method for distributed MIMO and show that it achieves better coverage than C-MIMO with DPBF.