Random Access in Uplink Massive MIMO Systems: How to exploit asynchronicity and excess antennas

TL;DR

This paper introduces a novel random access method for uplink massive MIMO systems that leverages asynchronicity and excess antennas to resolve user collisions and estimate timing and channels effectively.

Contribution

It proposes a collision resolution and parameter estimation technique that exploits massive MIMO's large antenna arrays and inherent timing misalignments, improving access reliability.

Findings

Detects all collisions with over 90% probability

Provides reliable timing and channel estimates

Robust performance in overloaded scenarios

Abstract

Massive MIMO systems, where the base stations are equipped with hundreds of antennas, are an attractive way to handle the rapid growth of data traffic. As the number of users increases, the initial access and handover in contemporary networks will be flooded by user collisions. In this work, we propose a random access procedure that resolves collisions and also performs timing, channel, and power estimation by simply utilizing the large number of antennas envisioned in massive MIMO systems and the inherent timing misalignments of uplink signals during network access and handover. Numerical results are used to validate the performance of the proposed solution under different settings. It turns out that the proposed solution can detect all collisions with a probability higher than 90%, at the same time providing reliable timing and channel estimates. Moreover, numerical results demonstrate that it is robust to overloaded situations.