Tomlinson-Harashima Precoding for Multiuser MIMO Systems with Quantized CSI Feedback and User Scheduling

TL;DR

This paper analyzes the sum rate performance of a low complexity quantized CSI-based Tomlinson-Harashima precoding scheme with greedy user selection in multiuser MIMO systems, showing it achieves optimal sum rate scaling as the number of users grows large.

Contribution

It provides a theoretical analysis demonstrating that the proposed quantized CSI-based TH precoding scheme achieves optimal sum rate scaling and converges to the sum capacity in large user regimes.

Findings

Achieves optimal sum rate scaling with large user numbers.

Converges to the sum capacity of the MIMO broadcast channel.

Provides insights into multiuser interference effects from quantized CSI.

Abstract

This paper studies the sum rate performance of a low complexity quantized CSI-based Tomlinson-Harashima (TH) precoding scheme for downlink multiuser MIMO tansmission, employing greedy user selection. The asymptotic distribution of the output signal to interference plus noise ratio of each selected user and the asymptotic sum rate as the number of users K grows large are derived by using extreme value theory. For fixed finite signal to noise ratios and a finite number of transmit antennas $n_T$, we prove that as K grows large, the proposed approach can achieve the optimal sum rate scaling of the MIMO broadcast channel. We also prove that, if we ignore the precoding loss, the average sum rate of this approach converges to the average sum capacity of the MIMO broadcast channel. Our results provide insights into the effect of multiuser interference caused by quantized CSI on the multiuser diversity gain.