A complexity- and delay-efficient simplification of the sum-product algorithm (SPA) for decoding low-density parity-check (LDPC) codes is presented. The key feature of the new algorithm consists of a modification of the complexity-intensive and delay-causing update equations at the check nodes of the factor graph of the LDPC code. The modified update equations at a check node are based on ordering the reliability values of the incoming messages and on using a balanced tree topology to achieve optimum parallel processing. Furthermore, the complexity of the new algorithm can be adjusted: the least complex version of the algorithm corresponds to the so-called min-sum approximation, and the most complex version gives the full SPA.
By: Xiao-Yu Hu and Thomas Mittelholzer
Published in: RZ3451 in 2002
LIMITED DISTRIBUTION NOTICE:
This Research Report is available. This report has been submitted for publication outside of IBM and will probably be copyrighted if accepted for publication. It has been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be limited to peer communications and specific requests. After outside publication, requests should be filled only by reprints or legally obtained copies of the article (e.g., payment of royalties). I have read and understand this notice and am a member of the scientific community outside or inside of IBM seeking a single copy only.
Questions about this service can be mailed to reports@us.ibm.com .