Interference Exploitation Precoding for Multi-Level Modulations: Closed-Form Solutions

We study closed-form interference-exploitation precoding for multi-level modulations in the downlink of multi-user multiple-input single-output (MU-MISO) systems. We consider two distinct cases: first, when the number of served users is not larger than the number of transmit antennas at the base sta...

Full description

Saved in:
Bibliographic Details
Published in:IEEE transactions on communications Vol. 69; no. 1; pp. 291 - 308
Main Authors: Li, Ang, Masouros, Christos, Vucetic, Branka, Li, Yonghui, Swindlehurst, A. Lee
Format: Journal Article
Language:English
Published: New York IEEE 01.01.2021
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Antennas
Closed form solutions
constructive interference
Equivalence
Exact solutions
Exploitation
Interference
Iterative algorithms
Iterative methods
Kuhn-Tucker method
Lagrangian
Matrix methods
Measurement
MIMO
MISO (control systems)
multi-level modulations
Multiplexing
Optimization
Phase shift keying
Precoding
Quadratic programming
Transmitting antennas
Vectors (mathematics)
ISSN:0090-6778, 1558-0857
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We study closed-form interference-exploitation precoding for multi-level modulations in the downlink of multi-user multiple-input single-output (MU-MISO) systems. We consider two distinct cases: first, when the number of served users is not larger than the number of transmit antennas at the base station (BS), we mathematically derive the optimal precoding structure based on the Karush-Kuhn-Tucker (KKT) conditions. By formulating the dual problem, the precoding problem is transformed into a pre-scaling operation using quadratic programming (QP) optimization. We further consider the case where the number of served users is larger than the number of transmit antennas at the BS. By employing the pseudo inverse, we show that the optimal solution of the pre-scaling vector is equivalent to a linear combination of the right singular vectors corresponding to zero singular values, and derive the equivalent QP formulation. We also present the condition under which multiplexing more streams than the number of transmit antennas is achievable. For both considered scenarios, we propose a modified iterative algorithm to obtain the optimal precoding matrix, as well as a sub-optimal closed-form precoder. Numerical results validate our derivations on the optimal precoding structures for multi-level modulations, and demonstrate the superiority of interference-exploitation precoding for both scenarios.
Bibliography:ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 14
ISSN:0090-6778
1558-0857
DOI:10.1109/TCOMM.2020.3031616