On the Performance of MRC Receiver with Unknown Timing Mismatch-A Large Scale Analysis

TL;DR

This paper analyzes the impact of unknown timing mismatches on the performance of MRC receivers in large-scale MU-MIMO systems, proposing new algorithms to mitigate these effects and improve uplink rates.

Contribution

It introduces the MRC-ZF receiver design that handles timing asynchrony without requiring explicit delay synchronization, enhancing system robustness.

Findings

Timing mismatch significantly degrades MRC performance.

MRC-ZF outperforms traditional MRC under timing asynchrony.

Analytical and simulation results confirm the effectiveness of proposed algorithms.

Abstract

There has been extensive research on large scale multi-user multiple-input multiple-output (MU-MIMO) systems recently. Researchers have shown that there are great opportunities in this area, however, there are many obstacles in the way to achieve full potential of using large number of receive antennas. One of the main issues, which will be investigated thoroughly in this paper, is timing asynchrony among signals of different users. Most of the works in the literature, assume that received signals are perfectly aligned which is not practical. We show that, neglecting the asynchrony can significantly degrade the performance of existing designs, particularly maximum ratio combining (MRC). We quantify the uplink achievable rates obtained by MRC receiver with perfect channel state information (CSI) and imperfect CSI while the system is impaired by unknown time delays among received signals. We then use these results to design new algorithms in order to alleviate the effects of timing mismatch. We also analyze the performance of introduced receiver design, which is called MRC-ZF, with perfect and imperfect CSI. For performing MRC-ZF, the only required information is the distribution of timing mismatch which circumvents the necessity of time delay acquisition or synchronization. To verify our analytical results, we present extensive simulation results which thoroughly investigate the performance of the traditional MRC receiver and the introduced MRC-ZF receiver.