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FPGA-based LDPC-coded APSK for optical communication systems.

Ding Zou, Changyu Lin, Ivan B Djordjevic

|March 1, 2017

Summary

This summary is machine-generated.

Geometrically shaped Amplitude Phase Shift Keying (APSK) modulation, when combined with Low-Density Parity-Check (LDPC) coding and bit interleaving, approaches the Shannon limit more closely than Quadrature Amplitude Modulation (QAM). This advanced system demonstrates superior performance in hardware-efficient applications.

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Area of Science:

Digital Communications
Information Theory
Signal Processing

Background:

Quadrature Amplitude Modulation (QAM) is a widely used digital modulation scheme.
Achieving performance close to the Shannon limit is a key goal in digital communication system design.
Low-Density Parity-Check (LDPC) codes offer powerful error correction capabilities.

Purpose of the Study:

To evaluate the performance of geometrically shaped Amplitude Phase Shift Keying (APSK) modulation schemes.
To compare APSK with conventional Quadrature Amplitude Modulation (QAM) in terms of approaching the Shannon limit.
To investigate the impact of LDPC coding and interleaving strategies on APSK performance.

Main Methods:

Mutual information and Generalized Mutual Information (GMI) capacity analyses were employed.
Field Programmable Gate Array (FPGA) based emulation of LDPC-coded APSK systems was performed.
Comparisons were made between block interleaver-based and bit interleaver-based systems.

Main Results:

Geometrically shaped APSK, particularly 16-APSK and 64-APSK with Gray-mapping, approaches the Shannon limit more closely than QAM under specific Forward Error Correction (FEC) overheads.
LDPC-coded APSK systems show significant improvement in hardware-efficient bit interleaver-based configurations.
LDPC-coded 64-APSK outperformed 64-QAM by 0.1-0.3 dB at spectral efficiencies of 4.2-4.8 b/s/Hz.
LDPC-coded 64-APSK remained within 1.6-2.2 dB of the GMI capacity across tested spectral efficiencies.

Conclusions:

Geometrically shaped APSK offers a viable alternative to QAM for achieving near-Shannon limit performance.
Bit interleaver-based LDPC-coded APSK systems provide a hardware-efficient and high-performance solution for advanced digital communication.
Further research can explore optimal APSK constellations and coding schemes for various communication scenarios.