Fractional Pilot Reuse in Massive MIMO Systems

TL;DR

This paper introduces a fractional pilot reuse scheme in massive MIMO systems that reduces pilot contamination by reusing pilots among nearby cells, leading to significant spectral efficiency improvements.

Contribution

It proposes a novel pilot allocation method inspired by fractional frequency reuse, optimizing pilot reuse parameters and user scheduling for enhanced spectral efficiency.

Findings

Spectral efficiency is significantly improved over existing methods.

Optimal pilot reuse parameters are derived for different linear combining techniques.

Numerical results confirm the effectiveness of the proposed scheme.

Abstract

Pilot contamination is known to be one of the main impairments for massive MIMO multi-cell communications. Inspired by the concept of fractional frequency reuse and by recent contributions on pilot reutilization among non-adjacent cells, we propose a new pilot allocation scheme to mitigate this effect. The key idea is to allow users in neighboring cells that are closest to their base stations to reuse the same pilot sequences. Focusing on the uplink, we obtain expressions for the overall spectral efficiency per cell for different linear combining techniques at the base station and use them to obtain both the optimal pilot reuse parameters and the optimal number of scheduled users. Numerical results show a remarkable improvement in terms of spectral efficiency with respect to the existing techniques.