Downlink MIMO-RSMA With Successive Null-Space Precoding

In this paper, we consider the precoder design for an underloaded or critically loaded downlink multi-user multiple-input multiple-output (MIMO) communication system. We propose novel precoding and decoding schemes which enhance system performance based on rate splitting at the transmitter and singl...

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Bibliographic Details
Published inIEEE transactions on wireless communications Vol. 21; no. 11; pp. 9170 - 9185
Main Authors Krishnamoorthy, Aravindh, Schober, Robert
Format Journal Article
LanguageEnglish
Published New York IEEE 01.11.2022
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects
Communication systems
Communications systems
Downlink
Downlinking
Interference
linear algebra
Mathematical analysis
MIMO communication
multiple access
Multiple-input multiple-output (MIMO) communication
Optimization
Performance enhancement
Precoding
Receivers
Robustness
Sensitivity analysis
Splitting
Symbols
Vectors (mathematics)
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Summary:In this paper, we consider the precoder design for an underloaded or critically loaded downlink multi-user multiple-input multiple-output (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 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 optimization problem for the precoding vectors and the associated power allocation for the proposed SNS-based MIMO-rate-splitting multiple access (RSMA) scheme. We obtain a suboptimal solution for this problem via successive convex approximation. Moreover, we study the robustness of the proposed precoding scheme to imperfect channel state information (CSI) at the base station via derivative-based sensitivity analysis. Our analysis and simulation results reveal the enhanced performance and robustness of the proposed SNS-based MIMO-RSMA scheme over several baseline multi-user MIMO schemes, especially for imperfect CSI.
ISSN:1536-1276
1558-2248
DOI:10.1109/TWC.2022.3173463