Distributed Pilot Assignment for Distributed Massive-MIMO Networks

TL;DR

This work tackles pilot contamination in distributed massive MIMO by proposing a fully distributed pilot assignment framework that jointly handles PA and AP-UE association. The method introduces a controller-AP selection, a contamination-aware distributed PA, and AP-UE clustering to ensure at most one UE per pilot per AP, while prioritizing UEs most susceptible to contamination. The authors provide a complexity and overhead analysis and demonstrate, through extensive simulations, that the scheme yields notable improvements in 90%-likely downlink and uplink SE over centralized and distributed baselines, with robustness that scales with the number of UEs. The proposed distributed approach offers reduced signaling, faster convergence, and enhanced fault-tolerance, making it a strong candidate for scalable deployments in distributed mMIMO networks where pilot resources are scarce. Overall, the paper advances practical distributed resource allocation for interference-limited dense networks and highlights the value of joint PA and AP-UE association in mitigating pilot contamination.

Abstract

Pilot contamination is a critical issue in distributed massive MIMO networks, where the reuse of pilot sequences due to limited availability of orthogonal pilots for channel estimation leads to performance degradation. In this work, we propose a novel distributed pilot assignment scheme to effectively mitigate the impact of pilot contamination. Our proposed scheme not only reduces signaling overhead, but it also enhances fault-tolerance. Extensive numerical simulations are conducted to evaluate the performance of the proposed scheme. Our results establish that the proposed scheme outperforms existing centralized and distributed schemes in terms of mitigating pilot contamination and significantly enhancing network throughput.

Figures (6)

• Figure 1: 90%-likely downlink SE vs $T$.
• Figure 2: Average downlink SE vs $T$.
• Figure 3: CDF of downlink SE, when $\frac{T}{L_p}=3$.
• Figure 4: 90%-likely uplink SE vs $T$.
• Figure 5: Average uplink SE vs $T$.