Digit-Online LDPC Decoding

  • Author / Creator
    Marshall, Philip A.
  • 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.

  • Subjects / Keywords
  • Graduation date
    Spring 2013
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.