Multitree decoding and multitree-aided LDPC decoding

New decoding algorithms for linear codes are proposed. The first part of the paper considers decoding general binary linear codes by searching multiple trees, which is shown to achieve near maximum-likelihood performance for short block lengths. The second part of the paper considers decoding low-density parity check (ldpc) codes by means of repeated decoding attempts by standard sum-product message passing. Each decoding attempt starts from modified channel output, where some of the bits are clamped to a fixed value. The values of the fixed bits are obtained from multitree search.