# Construction of One-Bit Transmit-Signal Vectors for Downlink MU-MISO Systems with PSK Signaling

## TL;DR

This paper proposes a low-complexity two-stage algorithm for constructing one-bit transmit-signal vectors in downlink MU-MISO systems with PSK signaling, improving performance and robustness while reducing computational complexity.

## Contribution

It introduces a novel two-stage algorithm combining iterative-hard-thresholding and bit-flipping to optimize one-bit precoding with antenna selection, addressing the combinatorial challenge.

## Key findings

- The proposed method achieves better performance-complexity tradeoff.
- Antenna selection improves SER performance by reducing error floors.
- Simulation results validate the effectiveness of the algorithm.

## Abstract

We study a downlink multi-user multiple-input single-output (MU-MISO) system in which the base station (BS) has a large number of antennas with cost-effective one-bit digital-to-analog converters (DACs). In this system, we first identify that antenna-selection can yield a non-trivial symbol-error-rate (SER) performance gain by alleviating an error-floor problem. Likewise the previous works on one-bit precoding, finding an optimal transmit-signal vector (encompassing precoding and antenna-selection) requires exhaustive-search due to its combinatorial nature. Motivated by this, we propose a low-complexity two-stage algorithm to directly obtain such transmit-signal vector. In the first stage, we obtain a feasible transmit-signal vector via iterative-hard-thresholding algorithm where the resulting vector ensures that each user's noiseless observation is belong to a desired decision region. In the second stage, a bit-flipping algorithm is employed to refine the feasible vector so that each user's received signal is more robust to additive Gaussian noises. Via simulation results, we demonstrate that the proposed method can yield a more elegant performance-complexity tradeoff than the existing one-bit precoding methods.