Patent ID: 8345784

Claim:
A method in a wireless receiver for equalizing a received signal transmitted through a dispersive channel, the method comprising: forming a trellis comprising a plurality of stages, each stage corresponding to a symbol time and comprising a plurality of nodes, each node having a node state comprising a candidate received symbol value for the node and one or more predecessor candidate received symbol values; and identifying a sequence of most likely symbol values corresponding to the received signal by evaluating cumulative state metrics for the nodes according to maximum-likelihood sequence estimation or decision-feedback sequence estimation criteria; wherein forming the trellis comprises: selecting, for each node of the trellis, a set of fan-out branches for the node by identifying, of all possible state transition branches from the node to successor nodes in the succeeding stage, those state transition branches that have a spherical branch metric less than a pre-determined metric limit, wherein selecting the set of fan-out branches for a given node comprises performing a tree search among candidate state transition branches based on calculating partial sums of a spherical branch metric formulation and comparing the partial sums to the pre-determined metric limit; and determining the cumulative state metric for the node as a function of the cumulative state metrics for predecessor nodes in the preceding stage and the spherical branch metrics for fan-out branches connecting the predecessor nodes to the node.