  Hybrid beamforming (HBF) multi-user multiple-input multiple-output (MU-MIMO)
is a key technology for unlocking the directional millimeter-wave (mm-wave)
nature for spatial multiplexing beyond current codebook-based 5G-NR networks.
In order to suppress co-scheduled users' interference, HBF MU-MIMO is
predicated on having sufficient radio frequency chains and accurate channel
state information (CSI), which can otherwise lead to performance losses due to
imperfect interference cancellation. In this work, we propose IABA, a 5G-NR
standard-compliant beam pair link (BPL) allocation scheme for mitigating
spatial interference in practical HBF MU-MIMO networks. IABA solves the network
sum throughput optimization via either a distributed or a centralized BPL
allocation using dedicated CSI reference signals for candidate BPL monitoring.
We present a comprehensive study of practical multi-cell mm-wave networks and
demonstrate that HBF MU-MIMO without interference-aware BPL allocation
experiences strong residual interference which limits the achievable network
performance. Our results show that IABA offers significant performance gains
over the default interference-agnostic 5G-NR BPL allocation, and even allows
HBF MU-MIMO to outperform the fully digital MU-MIMO baseline, by facilitating
allocation of secondary BPLs other than the strongest BPL found during initial
access. We further demonstrate the scalability of IABA with increased gNB
antennas and densification for beyond-5G mm-wave networks.
