Selective Avoidance of Cycles in Irregular LDPC Code Construction

2004/08/01 by Ting Tian, T. Tian, Chris Jones +5 · 8 citations
Computer Science · Engineering · #Advanced Wireless Communication Techniques #Cooperative Communication and Network Coding #Error Correcting Code Techniques

paper · doi:10.1109/tcomm.2004.833048

openalex publication_date 2004/08/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

This letter explains the effect of graph connectivity on error-floor performance of low-density parity-check (LDPC) codes under message-passing decoding. A new metric, called extrinsic message degree (EMD), measures cycle connectivity in bipartite graphs of LDPC codes. Using an easily computed estimate of EMD, we propose a Viterbi-like algorithm that selectively avoids small cycle clusters that are isolated from the rest of the graph. This algorithm is different from conventional girth conditioning by emphasizing the connectivity as well as the length of cycles. The algorithm yields codes with error floors that are orders of magnitude below those of random codes with very small degradation in capacity-approaching capability.

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