High-Rate Regular APSK Constellations

The majority of modern communication systems adopt 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. This requires an expensive power amplifier and an 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 modulations. We propose a novel multilevel coding labeling for the constellation points separating the amplitude and phase domains. We provide a novel multistage decoding scheme allowing for a low-complexity log-likelihood ratio calculation for soft-input decoding of component codes, along with a suitable rate design. Finally, we compare the proposed scheme with the state-of-the-art QAM constellations and optimize the constellations in the presence of phase noise.