Folding Viterbi detector with reduced complexity for EPRML system applications

A folding Viterbi detector (FVD) is proposed, which has the usual state transition diagram folded with inverted states. Since most trellis-coded signals have symmetrical transition diagrams, if folded appropriately, branch metrics will appear when an add or subtract operation is carried out. In this scheme, one adder/subtractor replaces two adders. Compared with the EPR4 GVA detector, which requires eight adders, the proposed FVD requires only five adder/subtractors and the total gate count is reduced by 38% without BER performance degradation.