Study of Robust Resource Allocation in Cell-Free Multiple-Antenna Networks

TL;DR

This work addresses robust downlink resource allocation in user-centric cell-free mMIMO under imperfect CSI. It introduces a sequential framework that combines robust scheduling (RC-ESG) with two robust power allocation schemes (RGDPA and WRGDPA), supported by convexity analysis and computational-cost considerations. The approach yields substantial SR gains in simulations (up to about 30% under CSI uncertainty) and shows performance approaching that of perfect CSI systems, demonstrating practical robustness for dense, distributed CF-mMIMO deployments. The results highlight the importance of incorporating worst-case CSI considerations and MSE-based power loading to achieve reliable, high-rate downlink performance in realistic wireless networks.

Abstract

Cell-free networks outperform cellular networks in many aspects, yet their efficiency is affected by imperfect channel state information (CSI). In order to address this issue, this work presents a robust resource allocation framework designed for the downlink of user-centric cell-free massive multi-input multi-output (CF-mMIMO) networks. This framework employs a sequential resource allocation strategy with a robust user scheduling algorithm designed to maximize the sum-rate of the network and two robust power allocation algorithms aimed at minimizing the mean square error, which are developed to mitigate the effects of imperfect CSI. An analysis of the proposed robust resource allocation problems is developed along with a study of their computational cost. Simulation results demonstrate the effectiveness of the proposed robust resource allocation algorithms, showing a performance improvement of up to 30\% compared to existing techniques.

Figures (6)

• Figure 1: Illustration of a user-centric cell-free network and the clustered APs
• Figure 2: Block diagram of the proposed robust resource allocation.
• Figure 5: Comparison of the C-ESG multiuser scheduling in perfect CSI and imperfect CSI UCCF networks and the RC-ESG for MMSE precoder and EPL power loading, when $\alpha=0.15$ for imperfect CSI case, $L=16$, $N=4$, $K=32$ and $n=16$.
• Figure 6: Comparison of the RGDPA power allocation, GDPA with ICSI and GDPA with PSCI, when $\alpha=0.15$ for imperfect CSI case, $L=16$, $N=4$, $K=32$, $n=16$ and MMSE precoder.
• Figure 7: Comparison of WRGDPA and RGDPA power allocation, GDPA with ICSI and GDPA with PSCI, when $\alpha=0.15$ for imperfect CSI case, $L=16$, $N=4$, $K=32$, $n=16$ and ZF precoder.