A New LLR Approximation for BICM Systems with HARQ

Jin Whan KANG; Sang-Hyo KIM; Seokho YOON; Tae Hee HAN; Hyoung Kee CHOI

doi:10.1587/transcom.E93.B.1628

IEICE Transactions on Communications

Online ISSN : 1745-1345
Print ISSN : 0916-8516

Regular Section

A New LLR Approximation for BICM Systems with HARQ

Jin Whan KANG, Sang-Hyo KIM, Seokho YOON, Tae Hee HAN, Hyoung Kee CHOI

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Keywords: log-likelihood ratio, BICM, HARQ, QAM, demapper

JOURNAL RESTRICTED ACCESS

2010 Volume E93.B Issue 6 Pages 1628-1632

DOI https://doi.org/10.1587/transcom.E93.B.1628

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Abstract

In this letter, a new approximation of log-likelihood ratio (LLR) for soft input channel decoding is proposed. Conventional simplified LLR using log-sum approximation can degrade the performance of bit interleaved coded modulation (BICM) systems employing hybrid automatic repeat request (HARQ) at low SNR. The proposed LLR performs as well as the exact LLR, and at the same time, requires only a small number of elementary operations.

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