Sum Rates, Rate Allocation, and User Scheduling for Multi-User MIMO Vector Perturbation Precoding

TL;DR

This paper analyzes sum rates in multi-user MIMO broadcast channels with vector perturbation precoding, deriving bounds, proposing rate allocation modifications, and introducing a low-complexity user selection algorithm that improves sum rate performance.

Contribution

It derives a tight high-SNR sum rate upper bound, introduces a rate allocation modification for vector perturbation, and proposes an effective low-complexity user selection algorithm.

Findings

High-SNR sum rate upper bound is tight and useful.

Rate allocation can be simplified to user selection.

Proposed user selection algorithm outperforms similar methods.

Abstract

This paper considers the multiuser multiple-input multiple-output (MIMO) broadcast channel. We consider the case where the multiple transmit antennas are used to deliver independent data streams to multiple users via vector perturbation. We derive expressions for the sum rate in terms of the average energy of the precoded vector, and use this to derive a high signal-to-noise ratio (SNR) closed-form upper bound, which we show to be tight via simulation. We also propose a modification to vector perturbation where different rates can be allocated to different users. We conclude that for vector perturbation precoding most of the sum rate gains can be achieved by reducing the rate allocation problem to the user selection problem. We then propose a low-complexity user selection algorithm that attempts to maximize the high-SNR sum rate upper bound. Simulations show that the algorithm outperforms other user selection algorithms of similar complexity.