Reduced complexity MLSD equalizers based on bidirectional DFEs

We propose a reduced complexity maximum likelihood sequence detection (MLSD) equalizer for large size constellation signals such as 8-VSB using bidirectional decision feedback equalizers (DFEs). We apply reduced-length two-level Viterbi algorithm to select one of two non-identical symbol estimates produced by a bidirectional DFE. Therefore, the computationally expensive MLSD algorithm is applied sparingly for two-level signals with the effective channel length shorter than the original channel, regardless of the original constellation size of the symbols. Simulations results show that the proposed algorithm outperforms existing combination schemes based on bidirectional DFEs, especially for large size constellation.