IEEE Transactions on Information Theory - Part 1
IEEE Transactions on Information Theory
Distance properties of expander codes
IEEE Transactions on Information Theory
Upper bounds on the rate of LDPC codes as a function of minimum distance
IEEE Transactions on Information Theory
Improved Nearly-MDS Expander Codes
IEEE Transactions on Information Theory
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The minimum distance of codes on bipartite graphs (BG codes) over GF(q) is studied. A new upper bound on the minimum distance of BG codes is derived. The bound is shown to lie below the Gilbert-Varshamov bound when q 驴 32. Since the codes based on bipartite expander graphs (BEG codes) are a special case of BG codes and the resulting bound is valid for any BG code, it is also valid for BEG codes. Thus, nonbinary (q 驴 32) BG codes are worse than the best known linear codes. This is the key result of the work. We also obtain a lower bound on the minimum distance of BG codes with a Reed-Solomon constituent code and a lower bound on the minimum distance of low-density parity-check (LDPC) codes with a Reed-Solomon constituent code. The bound for LDPC codes is very close to the Gilbert-Varshamov bound and lies above the upper bound for BG codes.