2 research outputs found
Polar Decomposition of Mutual Information over Complex-Valued Channels
A polar decomposition of mutual information between a complex-valued
channel's input and output is proposed for a input whose amplitude and phase
are independent of each other. The mutual information is symmetrically
decomposed into three terms: an amplitude term, a phase term, and a cross term,
whereby the cross term is negligible at high signal-to-noise ratio. Theoretical
bounds of the amplitude and phase terms are derived for additive white Gaussian
noise channels with Gaussian inputs. This decomposition is then applied to the
recently proposed amplitude phase shift keying with product constellation
(product-APSK) inputs. It shows from an information theoretical perspective
that coded modulation schemes using product-APSK are able to outperform those
using conventional quadrature amplitude modulation (QAM), meanwhile maintain a
low complexity
High-Rate Regular APSK Constellations
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