Design and Comparison of Advanced Modulation Formats Based on Generalized Mutual Information

Generalized mutual information (GMI) has been comprehensively studied in multidimensional constellation and probabilistic-shaped (PS) constellation together with different forward error correction (FEC) coding schemes. The simulation results confirm that GMI is an efficient and accurate tool to comp...

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Bibliographic Details
Published in:Journal of lightwave technology 2018-01, Vol.36 (2), p.416-423
Main Authors: Zhang, Shaoliang, Yaman, Fatih
Format: Article
Language:English
Subjects:
Coding
Computer simulation
Design optimization
Encoding
Entropy
Error correction
Forward error correction
Generalized mutual information
geometric shaping
Modulation
Mutual information
Noise levels
optimized constellation
pairwise optimization
Parity check codes
probabilistic shaping
Signal to noise ratio
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Summary:Generalized mutual information (GMI) has been comprehensively studied in multidimensional constellation and probabilistic-shaped (PS) constellation together with different forward error correction (FEC) coding schemes. The simulation results confirm that GMI is an efficient and accurate tool to compare their post-FEC performance. In particular for uniformly geometric-shaped constellation, the pre-FEC Q-factor is highly correlated with GMI though the correlation is reduced at lower FEC coding rate. Furthermore, GMI can be used to design optimized constellation together with generalized pairwise optimization algorithm to mitigate the GMI loss in non-Gray-mapped constellation. The GMI-optimized 32QAM (opt32) shows \sim 0.5 dB signal-to-noise ratio improvement between 3 and 4 b/s GMI in both simulated and experimental results. Optimized two-dimensional 8 QAM is also designed to show the consistent GMI improvement over multi-dimensional 8 QAM-equivalent formats. In simulations, PS-64 QAM outperforms opt32 when a long sequence block is used in the distribution matcher.
ISSN:0733-8724
1558-2213
DOI:10.1109/JLT.2017.2779753