Joint Pilot Sequence Design and Power Control for Max-Min Fairness in Uplink Massive MIMO

TL;DR

This paper proposes a joint optimization of pilot sequences and power control in Massive MIMO uplink systems to improve fairness and spectral efficiency, addressing pilot contamination with an efficient algorithm.

Contribution

It introduces a novel approach to directly optimize pilot sequences and powers, providing a tractable solution for max-min spectral efficiency in Massive MIMO.

Findings

The proposed algorithm achieves near-optimal spectral efficiency.

Significant performance gains over existing algorithms.

Efficient polynomial complexity optimization method.

Abstract

This paper optimizes the pilot assignment and pilot transmit powers to mitigate pilot contamination in Massive MIMO (multiple-input multiple-output) systems. While prior works have treated pilot assignment as a combinatorial problem, we achieve a more tractable problem formulation by directly optimizing the pilot sequences. To this end, we compute a lower bound on the uplink (UL) spectral efficiency (SE), for Rayleigh fading channels with maximum ratio (MR) detection and arbitrary pilot sequences. We optimize the max-min SE with respect to the pilot sequences and pilot powers, under power budget constraints. This becomes an NP-hard signomial problem, but we propose an efficient algorithm to obtain a local optimum with polynomial complexity. Numerical results manifest the near optimality of the proposed algorithm and show significant gains over existing suboptimal algorithms.