Online Resource Management for the Uplink of Wideband Hybrid Beamforming System

TL;DR

The paper tackles uplink radio resource management for a single-cell mmWave system employing codebook-based hybrid beamforming with $K$ RF chains and $U$ UEs where $U>K$. It develops four online sequential heuristics that vary the order and coupling of beam selection (BSel), user selection (USel), and power allocation (PA), and introduces techniques such as PBS$^+$, load-aware beam selection (WSRB), and interference-down dropping (IDD). Results on a mmWave OFDMA system show that the final approach, S2, which combines load-aware BSel with interference-aware USel and IDD, can achieve up to $6\times$ gains over the benchmark, with substantial improvements over earlier variants (roughly $70\%$ from $S_0$ to $S_2$ in some regimes) while adding only modest complexity; a final water-filling PA step provides no further benefit in the tested scenarios. The study highlights the critical role of inter-beam interference and the coupling among BSel, USel, and PA for practical uplink RRM in constrained-RF mmWave systems, offering a path toward real-time, PF-driven RRM implementations.

Abstract

This paper studies the radio resource management (RRM) for the uplink (UL) of a cellular system with codebook-based hybrid beamforming. We consider the often neglected but highly practical multi-channel case with fewer radio frequency chains in the base station than user equipment (UEs) in the cell, assuming one RF chain per UE. As for any UL RRM, a per-time slot solution is needed as the allocation of power to subchannels by a UE can only be done once it knows which subchannels it has been allocated. The RRM in this system comprises beam selection, user selection and power allocation, three steps that are intricately coupled and we will show that the order in which they are performed does impact performance and so does the amount of coupling that we take into account. Specifically, we propose 4 online sequential solutions with different orders in which the steps are called and of different complexities, i.e., different levels of coupling between the steps. Our extensive numerical campaign for a mmWave system shows how a well-designed heuristic that takes some level of couplings between the steps can make the performance exceedingly better than a benchmark.

Figures (3)

• Figure 1: Our RRM solutions: RR: round robin, IU: interference unaware, IA: interference aware LA: load aware, LU: load unaware, EPA: equal power allocation, PBS: per beam selection, WSRB: weighted sum rate beam selection.
• Figure 2: $\overline{GM}$ vs. $K$ with fixed $U$, $N_b=128$, $N_u=16$, $B_b=32$, $B_u=4$.
• Figure 3: $\overline{GM}$ vs $U$ with fixed $K$, $N_b=128$, $N_u=16$, $B_b=32$, $B_u=4$.