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Design and Comparison of Advanced Modulation Formats Based on Generalized Mutual Information
Ist Teil von
Journal of lightwave technology, 2018-01, Vol.36 (2), p.416-423
Ort / Verlag
New York: IEEE
Erscheinungsjahr
2018
Quelle
IEEE Xplore
Beschreibungen/Notizen
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 <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula> 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.