Sequence detection device using maximum likelihood sequence detection with programmable branch metric computation reduction and associated sequence detection method

A sequence detection device comprising:

• a feed-forward filter, configured to process a received signal to generate a first equalized signal;
• a feedback filter, configured to process a symbol decision signal to generate a second equalized signal;
• a combining circuit, configured to combine the first equalized signal and the second equalized signal to generate a sample signal;
• a decision circuit, configured to perform hard decision upon the sample signal to generate the symbol decision signal;
• and
• a sequence detection circuit, configured to perform sequence detection upon the first equalized signal to generate and output a symbol sequence, wherein the sequence detection circuit comprises:
• a region estimation circuit, independent of the decision circuit and configured to categorize each of a plurality of samples included in the sample signal into one of a plurality of regions;
• and
• a trellis selection circuit, configured to select one of a plurality of trellis schemes for branch metric calculation according to region estimation results of two of the plurality of samples output from the region estimation circuit.