SERE: A Stabilized Element-Wise Method for Downlink Rate Estimation in Clustered Cell-Free Networks

2026-05-17

AI Summary

This work addresses the lack of efficient and accurate algorithms for estimating downlink ergodic achievable rates in clustered cell-free networks, particularly the challenge of jointly handling inter-cluster interference while accommodating both regularized zero-forcing (RZF) and zero-forcing (ZF) precoding. To this end, the paper proposes a stabilized per-element rate estimation method. By establishing pointwise convergence of the diagonal entries of the resolvent matrix, it derives deterministic equivalents for inter-cluster interference and downlink rates. A carefully designed variable transformation is introduced to mitigate numerical instability under small regularization parameters. This approach constitutes the first per-element convergence analysis of inter-cluster interference in clustered architectures and yields a unified, low-complexity estimation framework applicable to both RZF and ZF. The method achieves relative errors below 6% while significantly outperforming Monte Carlo simulations in computational efficiency.

Abstract

Clustered cell-free networks have emerged as a promising architecture for sixth generation ultra-dense wireless communication systems by enabling local cooperation among base stations while controlling system complexity. For resource allocation and performance optimization of such networks, accurate and efficient estimation of the ergodic achievable downlink rate is a fundamental prerequisite. Existing rate estimation approaches mainly rely on computationally prohibitive Monte Carlo simulations or adopt random matrix theory-based methods, which have been well-developed for conventional cellular and cell-free networks. However, existing RMT-based methods have not addressed the unique inter-subnetwork interference in clustered cell-free networks, and therefore lack an efficient solution for accurate downlink rate estimation under both regularized zero-forcing and zero-forcing precoding. In this paper, we propose a stabilized element-wise rate estimation method for downlink rate estimation in clustered cell-free networks. We establish the diagonal element-wise convergence of resolvent matrices, which enables the derivation of deterministic equivalents for inter-subnetwork interference and the downlink ergodic rate. We further introduce a stabilized variable transformation to address the numerical instability when the regularization parameter is very small, hereby enabling a unified formulation applicable to both regularized zero-forcing and zero-forcing precoding. Simulation results show that the proposed method achieves a relative error below 6% while significantly reducing computational complexity compared with the Monte Carlo simulation.

Problem

• clustered cell-free networks
• downlink rate estimation
• inter-subnetwork interference
• ergodic achievable rate
• precoding

Innovation

• clustered cell-free networks
• downlink rate estimation
• element-wise convergence
• regularized zero-forcing
• deterministic equivalents