A degree-matched check node approximation for LDPC decoding

Sheryl L. Howard, Christian Schlegel, Vincent C. Gaudet

Research output: Contribution to journalConference articlepeer-review

20 Scopus citations


This paper examines ways to recoup the performance loss incurred when using the min-sum approximation instead of the exact sum-product algorithm for decoding low-density parity check codes (LDPCs). Approximations to the correction factor exactly expressing the difference between these two decoding algorithms exist for degree 3 check nodes, and can be applied to higher degree nodes by subdividing them into component degree 3 nodes. However, this results in replication of the approximation. An asymptotic expression for the correction factor at a check node of any degree is derived in this paper, and used to develop two simple approximations to the correction factor, matched to the check node degree. One has very low complexity, and both only need be applied once per check node extrinsic message. Simulation results are presented for each check node approximation when decoding a regular and an irregular LDPC. Both degree-matched check node approximations achieve sum-product decoding performance.

Original languageEnglish (US)
Article number1523516
JournalIEEE International Symposium on Information Theory - Proceedings
StatePublished - 2005
Event2005 IEEE International Symposium on Information Theory, ISIT 05 - Adelaide, Australia
Duration: Sep 4 2005Sep 9 2005

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Information Systems
  • Modeling and Simulation
  • Applied Mathematics


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