Log-Likelihood Ratio Calculation Using 3-Bit Soft-Decision for Error Correction in Visible Light Communication Systems

Dinh-Dung LE
Duc-Phuc NGUYEN
Thi-Hong TRAN
Yasuhiko NAKASHIMA

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E101-A    No.12    pp.2210-2212
Publication Date: 2018/12/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E101.A.2210
Type of Manuscript: Special Section LETTER (Special Section on Information Theory and Its Applications)
Category: Communication Theory and Signals
Keyword: 
visible light communication,  VLC,  soft-decision decoding,  Polar code,  

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Summary: 
Forward Error Correction (FEC) schemes have played an important role in intensity-modulation direct-detection (IM/DD) Visible Light Communication (VLC) systems. While hard-decision FEC schemes are inferior to soft-decision FEC codes in terms of decoding performance, they are widely used in these VLC systems because receivers are only capable of recognizing logical values 0 and 1. In this letter, we propose a method to calculate the log-likelihood ratios (LLR) values which are used as input of soft-decision FEC decoders. Simulation results show that Polar decoder using proposed method performs better than that of using the hard-decision technique.