A Novel Heap-based Pilot Assignment for Full Duplex Cell-Free Massive MIMO with Zero-Forcing

TL;DR

This paper introduces a heap-based pilot assignment algorithm for full-duplex cell-free massive MIMO systems, improving spectral efficiency and reducing pilot contamination through joint power control and AP-UE association optimization.

Contribution

The paper proposes a novel heap-based pilot assignment method and a simple iterative algorithm for joint optimization in FD CF-mMIMO systems, enhancing performance and reducing complexity.

Findings

Significant improvement in spectral efficiency over existing methods.

Effective mitigation of pilot contamination.

Reduced computational complexity of the optimization process.

Abstract

This paper investigates the combined benefits of full-duplex (FD) and cell-free massive multiple-input multipleoutput (CF-mMIMO), where a large number of distributed access points (APs) having FD capability simultaneously serve numerous uplink and downlink user equipments (UEs) on the same time-frequency resources. To enable the incorporation of FD technology in CF-mMIMO systems, we propose a novel heapbased pilot assignment algorithm, which not only can mitigate the effects of pilot contamination but also reduce the involved computational complexity. Then, we formulate a robust design problem for spectral efficiency (SE) maximization in which the power control and AP-UE association are jointly optimized, resulting in a difficult mixed-integer nonconvex programming. To solve this problem, we derive a more tractable problem before developing a very simple iterative algorithm based on inner approximation method with polynomial computational complexity. Numerical results show that our proposed methods with realistic parameters significantly outperform the existing approaches in terms of the quality of channel estimate and SE.