Successive Null-Space Precoder Design for Downlink MU-MIMO with Rate Splitting and Single-Stage SIC

TL;DR

This paper introduces a novel successive null-space precoding scheme for downlink MU-MIMO systems with rate splitting and single-stage SIC, improving interference management and system throughput.

Contribution

It proposes a new SNS precoding method that leverages null-space basis vectors and solves a non-convex optimization problem for enhanced performance.

Findings

SNS precoders outperform block diagonalization methods

Proposed scheme approaches the sum rate of dirty paper coding

Simulation results demonstrate significant performance gains

Abstract

In this paper, we consider the precoder design for an under-loaded or critically loaded downlink multi-user multiple-input multiple-output (MU-MIMO) communication system. We propose novel precoding and decoding schemes which enhance system performance based on rate splitting at the transmitter and single-stage successive interference cancellation at the receivers. The proposed successive null-space (SNS) precoding scheme utilizes linear combinations of the null-space basis vectors of the successively augmented MIMO channel matrices of the users as precoding vectors to adjust the inter-user-interference experienced by the receivers. We formulate a non-convex weighted sum rate (WSR) optimization problem, and solve it via successive convex approximation to obtain a suboptimal solution for the precoding vectors and the associated power allocation. Our simulation results reveal that the proposed SNS precoders outperform block diagonalization based linear and rate splitting designs, and in many cases, have a relatively small gap to the maximum sum rate achieved by dirty paper coding.