# Branch-and-Bound Precoding for Multiuser MIMO Systems with 1-Bit Quantization

## TL;DR

This paper introduces a branch-and-bound precoding method for multiuser MIMO systems with 1-bit DACs, improving error rates and sum-rate while maintaining low complexity and near-infinite resolution performance.

## Contribution

It presents a novel branch-and-bound precoding algorithm for 1-bit DAC MIMO systems, offering exact solutions with polynomial complexity and outperforming existing methods.

## Key findings

- Outperforms existing 1-bit precoding methods in error rate and sum-rate
- Achieves near-infinite DAC resolution performance with low complexity
- Provides an exact discrete optimization solution for 1-bit precoding

## Abstract

Multiple-antenna systems is a key technique to serve multiple users in future wireless systems. For low energy consumption and hardware complexity we first consider transmit symbols with constant magnitude and then 1-bit digital-to-analog converters. We propose precoding designs which maximize the minimum distance to the decision threshold at the receiver. The precoding design with 1-bit DAC corresponds to a discrete optimization problem, which we solve exactly with a branch-and-bound strategy. We alternatively present an approximation based on relaxation. Our results show that the proposed branch-and-bound approach has polynomial complexity. The proposed methods outperform existing precoding methods with 1-bit DAC in terms of uncoded bit error rate and sum-rate. The performance loss in comparison to infinite DAC resolution is small.