NDLI: Finite-Precision Analysis of Demappers and Decoders for LDPC-Coded M-QAM Systems

Content Provider	IEEE Xplore Digital Library
Author	Baldi, M. Chiaraluce, F. Cancellieri, G.
Copyright Year	1963
Abstract	LDPC codes are state-of-art error correcting codes, included in several standards for broadcast transmissions. Iterative soft-decision decoding algorithms for LDPC codes reach excellent error correction capability; their performance, however, is strongly affected by finite-precision issues in the representation of inner variables. Great attention has been paid, in recent literature, to the topic of quantization for LDPC decoders, but mostly focusing on binary modulations and analysing finite precision effects in a disaggregrated manner, i.e., considering separately each block of the receiver. Modern telecommunication standards, instead, often adopt high order modulation schemes, e.g. M-QAM, with the aim to achieve large spectral efficiency. This puts additional quantization problems, that have been poorly debated in previous literature. This paper discusses the choice of suitable quantization characteristics for both the decoder messages and the received samples in LDPC-coded systems using M-QAM schemes. The analysis involves also the demapper block, that provides initial likelihood values for the decoder, by relating its quantization strategy with that of the decoder. A new demapper version, based on approximate expressions, is also presented, that introduces a slight deviation from the ideal case but yields a low complexity hardware implementation.
Sponsorship	IEEE Broadcast Technology Society
Starting Page	239
Ending Page	250
Page Count	12
File Size	1419678
File Format	PDF
ISSN	00189316
Volume Number	55
Issue Number	2
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2009-06-01
Publisher Place	U.S.A.
Access Restriction	One Nation One Subscription (ONOS)
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Digital video broadcasting Parity check codes Code standards Quantization Error correction codes Iterative decoding Satellite broadcasting Telecommunication standards TV broadcasting HDTV quantization Demodulation digital communication error correction codes fixed point arithmetic
Content Type	Text
Resource Type	Article
Subject	Electrical and Electronic Engineering Media Technology

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