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Digit-Online LDPC Decoding Open Access


Other title
Iterative Decoder Architecture
Message-Passing Decoding
Low-Density Parity Check (LDPC) Codes
Digit-Serial Arithmetic
Forward Error Correction (FEC)
Type of item
Degree grantor
University of Alberta
Author or creator
Marshall, Philip A.
Supervisor and department
Gaudet, Vincent (Electrical and Computer Engineering)
Elliott, Duncan (Electrical and Computer Engineering)
Examining committee member and department
Doucette, John (Mechanical Engineering)
Cockburn, Bruce (Electrical and Computer Engineering)
Thornton, Mitchell (Southern Methodist University, Dallas, Texas, USA)
Department of Electrical and Computer Engineering
Computer, Microelectronic Devices, Circuits and Systems
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Highly parallel VLSI implementations of low-density parity-check (LDPC) block code decoders have a large number of interconnections, which can result in designs with low logic density. Bit-serial architectures have been developed that reduce the number of wires needed. However, they do not fully realize the potential for deeply pipelined serial data processing. Digit-online arithmetic allows operations to be performed in a serial, digit-by-digit manner, making it ideal for use in implementing a digit-serial LDPC decoder. Digit-online circuits for the primitive operations required for an offset min-sum LDPC decoder are simple, and allow deep pipelining at the digit level. A new hardware architecture for LDPC decoding is demonstrated, using redundant notation to allow for most-significant-digit-first processing of log-likelihood-ration (LLR) messages at all nodes. We examine the effect of changing the precision of LLRs on the throughput, area and energy efficiency of bit-parallel and digit-online decoders for the irregular WiMAX rate 3/4A length-1056 code. Both single-frame and frame-interlaced decoding are considered. To examine post-layout and code size effects, 9-bit bit-parallel and digit-online decoders for the irregular WiMAX rate 3/4A and rate 5/6 codes are compared for code lengths varying from 576 to 2304. Post-layout decoder results are presented for the (2048,1723) 10GBASE-T LDPC code in a general-purpose 65-nm CMOS technology. The decoder requires a core area of 10.89 mm^2 and operates at a clock frequency of 980 MHz. Decoding can be done with a message precision of 4 or 10 bits. With 4-bit precision, the decoder achieves a coded throughput of 82.8 Gbit/s, 73% higher than the state-of-the-art published decoder. We extend the message precision of previously published 10GBASE-T decoders from 4-5 bits to 10 bits. In this 10-bit mode we achieve a throughput of 41.8 Gbit/s, only 12% less than the state-of-the-art 4-bit decoder.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Marshall, P., Gaudet, V. and Elliott, D. (2012) “Effects of Varying Message Precision in Digit-online LDPC Decoders”. IEEE Workshop on Signal Processing Systems (SiPS) 2012, 6 pages accepted for publicationMarshall, P., Gaudet, V. and Elliott, D. (2011) “Deeply Pipelined Digit-Serial LDPC Decoding”. IEEE Trans. on Circuits and Systems I: Regular Papers, 11 pages in print. DOI: 10.1109/TCSI.2012.2206461

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