1. A method of determining a trellis for a Viterbi detector based on estimated channel energy comprising the steps of: receiving a sequence of n symbols; defining partitioned sets according to a decision tree structure; determining a size of each set partitioning according to tap energy of the channel; determining a reduced set of connection paths between the current layer and a destination layer in the trellis by: determining a value of a most likely oldest partitioned set in a current layer; and calculating branch metrics only for the current layers in the trellis in which the oldest partitioned set matches the determined value.