Nonlinear viterbi complexity reduction

A method of computing a plurality of branch metrics for use in identifying information in a signal, comprising:

• receiving the signal;
• comparing the received signal to a set of signal values that correspond to a plurality of branches in a state-based diagram;
• selecting a subset of the signal values based on the comparison, wherein selecting a subset of the signal values comprises choosing the signal values closest to the received signal;
• computing a first set of branch metrics for branches that correspond to the selected subset of the signal values;
• and
• computing a second set of branch metrics based on the first set of branch metrics.

An apparatus for computing a plurality of branch metrics for use in identifying information in a signal, comprising:

• means for selecting a first set of branches associated with signal values closest to the signal;
• means for computing a first set of branch metrics for the first set of branches using a first process;
• and
• means for computing a second set of branch metrics for a second set of branches using a second process, wherein the first set of branches and the second set of branches are distinct, and wherein the means for computing the second set of branch metrics uses fewer resources for each branch metric computation than the means for computing the first set.

An apparatus for computing a plurality of branch metrics for use by a detector, comprising:

• means for receiving a signal;
• means for comparing the received signal to a set of signal values that correspond to a plurality of branches in a state-based diagram;
• means for selecting a subset of the signal values based on the comparison, wherein the means for selecting a subset of the signal values comprises means for choosing the signal values closest to the received signal;
• means for computing a first set of branch metrics for branches that correspond to the selected subset of the signal values;
• and
• means for computing a second set of branch metrics based on the first set of branch metrics.

A system for computing a plurality of branch metrics for use by a detector, comprising:

• a receiver for receiving a signal;
• a comparator for comparing the received signal to a set of signal values that correspond to a plurality of branches in a state-based diagram;
• a screening unit for selecting a subset of the signal values based on the comparison, wherein the screening unit chooses the signal values closest to the received signal;
• a selective branch metric computation unit for computing a first set of branch metrics for branches that correspond to the selected subset of the signal values;
• and
• a branch metric propagation unit for computing a second set of branch metrics based on the first set of branch metrics.