# High-Rate Regular APSK Constellations

## TL;DR

This paper introduces a new RAPSK-based coded modulation scheme with multilevel coding and decoding, offering improved phase noise protection and lower PAPR compared to traditional QAM, suitable for high-data-rate systems.

## Contribution

It proposes a novel RAPSK modulation scheme with multilevel coding and decoding, enhancing phase noise resilience and reducing PAPR in high-rate communication systems.

## Key findings

- Outperforms QAM in phase noise environments
- Reduces peak-to-average power ratio (PAPR)
- Enables low-complexity soft decoding

## Abstract

The majority of modern communication systems adopts quadrature amplitude modulation (QAM) constellations as transmission schemes. Due to their square structure, however, QAM do not provide satisfying protection to phase noise effects as the number of constellation points grows, increasing at the same time their peak to average power ratio (PAPR). This requires an expensive power amplifier and oscillator at the transmitter to guarantee low distortion, complicating the adoption of dense transmission schemes in practical high-data rate systems. In this paper, we construct a coded modulation scheme based on regular amplitude and phase shift keying (RAPSK) modulations. We propose a novel multilevel coding (MLC) labeling for the constellation points separating amplitude and phase domains. We provide a novel multistage decoding (MSD) scheme allowing for a low-complexity log-likelihood ratio (LLR) calculation for soft-input decoding of component codes, along with a suitable rate design. Finally, we compare the proposed scheme with state-of-the-art QAM constellations and optimized constellations in the presence of phase noise.