Open AccessSystematic Luby transform codes with modified grey‐mapped QAM constellation
Author(s) -
Xu Shengkai,
Xu Dazhuan
Publication year - 2018
Publication title -
electronics letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.375
H-Index - 146
eISSN - 1350-911X
pISSN - 0013-5194
DOI - 10.1049/el.2018.0482
Subject(s) - additive white gaussian noise , phase shift keying , quadrature amplitude modulation , algorithm , qam , decoding methods , mathematics , computer science , modulation (music) , electronic engineering , bit error rate , telecommunications , channel (broadcasting) , engineering , physics , acoustics
Systematic Luby transform (LT) codes with grey‐mapped QAM constellations over additive white Gaussian noise (AWGN) channels are investigated. For high‐order modulations, it can be learnt that the traditional Gaussian approximation method developed for binary PSK (BPSK) is not accurate any more. To improve BER performance of systematic LT codes with grey‐mapped QAM, therefore, presents a novel coded modulation scheme, which only extracts Gaussian alike log‐likelihood ratios for decoding, based on the modified QAM constellation. More importantly, the proposed scheme allows to optimise degree distributions for QAM‐modulated systematic LT codes as easily as for BPSK. Simulation results show that the degree distribution related to the proposed coded modulation scheme can provide outstanding BER performance for systematic LT codes over the AWGN channel.