Performance Analysis of Massive MIMO Networks with Random Unitary Pilot Matrices

TL;DR

This paper analyzes the uplink performance of massive MIMO networks using different orthogonal pilot schemes, deriving SINR expressions and showing that the DOP scheme with random unitary matrices outperforms the traditional FPR scheme.

Contribution

It introduces a novel analysis of DOP schemes with Haar-distributed random unitary matrices, providing simple SINR expressions and demonstrating improved user capacity over FPR.

Findings

Asymptotic SINR closely matches finite system results.

DOP scheme with random unitary pilots yields higher user capacity.

Derived simple, computable SINR expressions for large systems.

Abstract

A common approach to obtain channel state information for massive MIMO networks is to use the same orthogonal training sequences in each cell. We call this the full-pilot reuse (FPR) scheme. In this paper, we study an alternative approach where each cell uses different sets of orthogonal pilot (DOP) sequences. Considering uplink communications with matched filter (MF) receivers, we first derive the SINR in the large system regime where the number of antennas at the base station, the number of users in each cell, and training duration grow large with fixed ratios. For tractability in the analysis, the orthogonal pilots are drawn from Haar distributed random unitary matrices. The resulting expression is simple and easy to compute. As shown by the numerical simulations, the asymptotic SINR approximates the finite-size systems accurately. Secondly, we derive the user capacity of the DOP scheme under a simple power control and show that it is generally better than that of the FPR scheme.