Symbol-Level Precoding Design for Max-Min SINR in Multiuser MISO Broadcast Channels

TL;DR

This paper proposes a convex reformulation of symbol-level precoding for multiuser MISO channels to maximize the minimum SINR, enabling efficient optimization and demonstrating its effectiveness through simulations.

Contribution

It introduces a novel convex reformulation of the max-min SINR problem in symbol-level precoding, leveraging properties of constructive interference regions.

Findings

The reformulation is convex, simplifying the original non-convex problem.

The power of received signals on unbounded DPCIRs increases with certain parameters.

Simulation results validate the effectiveness of the proposed approach.

Abstract

In this paper, we address the symbol level precoding (SLP) design problem under max-min SINR criterion in the downlink of multiuser multiple-input single-output (MISO) channels. First, we show that the distance preserving constructive interference regions (DPCIR) are always polyhedral angles (shifted pointed cones) for any given constellation point with unbounded decision region. Then we prove that any signal in a given unbounded DPCIR has a norm larger than the norm of the corresponding vertex if and only if the convex hull of the constellation contains the origin. Using these properties, we show that the power of the noiseless received signal lying on an unbounded DPCIR is an strictly increasing function of two parameters. This allows us to reformulate the originally non-convex SLP max-min SINR as a convex optimization problem. We discuss the loss due to our proposed convex reformulation and provide some simulation results.