Block-Level Interference Exploitation Precoding without Symbol-by-Symbol Optimization

TL;DR

This paper introduces a block-level precoding scheme that exploits constructive interference in multi-user MISO systems, achieving similar benefits to symbol-level precoding but with reduced computational complexity by optimizing over entire blocks.

Contribution

It proposes a novel CI-based block-level precoding method that simplifies optimization to a single quadratic programming problem per block, improving efficiency over traditional symbol-level approaches.

Findings

Superior performance over traditional BLP and SLP methods

Reduced computational cost due to single optimization per block

Effective exploitation of constructive interference across symbol blocks

Abstract

Symbol-level precoding (SLP) based on the concept of constructive interference (CI) is shown to be superior to traditional block-level precoding (BLP), however at the cost of a symbol-by-symbol optimization during the precoding design. In this paper, we propose a CI-based block-level precoding (CI-BLP) scheme for the downlink transmission of a multi-user multiple-input single-output (MU-MISO) communication system, where we design a constant precoding matrix to a block of symbol slots to exploit CI for each symbol slot simultaneously. A single optimization problem is formulated to maximize the minimum CI effect over the entire block, thus reducing the computational cost of traditional SLP as the optimization problem only needs to be solved once per block. By leveraging the Karush-Kuhn-Tucker (KKT) conditions and the dual problem formulation, the original optimization problem is finally shown to be equivalent to a quadratic programming (QP) over a simplex. Numerical results validate our derivations and exhibit superior performance for the proposed CI-BLP scheme over traditional BLP and SLP methods, thanks to the relaxed block-level power constraint.