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Four-Dimensional Coded Modulation with Bit-Wise Decoders for Future Optical Communications

Alex Alvarado ; Erik Agrell (Institutionen för signaler och system, Kommunikationssystem)
Journal of Lightwave Technology (0733-8724). Vol. 33 (2015), 10, p. 1993-2003.
[Artikel, refereegranskad vetenskaplig]

Coded modulation (CM) is the combination of forward error correction (FEC) and multilevel constellations. Coherent optical communication systems result in a four-dimensional (4D) signal space, which naturally leads to 4D-CM transceivers. A practically attractive design paradigm is to use a bit-wise decoder, where the detection process is (suboptimally) separated into two steps: soft-decision demapping followed by binary decoding. In this paper, bit-wise decoders are studied from an information-theoretic viewpoint. 4D constellations with up to 4096 constellation points are considered. Metrics to predict the post-FEC bit-error rate (BER) of bit-wise decoders are analyzed. The mutual information is shown to fail at predicting the post-FEC BER of bit-wise decoders and the so-called generalized mutual information is shown to be a much more robust metric. For the suboptimal scheme under consideration, it is also shown that constellations that transmit and receive information in each polarization and quadrature independently (e.g., PM-QPSK, PM-16QAM, and PM-64QAM) outperform the best 4D constellations designed for uncoded transmission. Theoretical gains are as high as 4 dB, which are then validated via numerical simulations of low-density parity check codes.

Nyckelord: Bit-interleaved coded modulation (BICM), bit-wise (BW) decoders, channel capacity, coded

Denna post skapades 2015-07-29. Senast ändrad 2016-04-28.
CPL Pubid: 220044


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Institutioner (Chalmers)

Institutionen för signaler och system, Kommunikationssystem



Chalmers infrastruktur