Conditionally Input Saturated Viterbi Detector

A method for data decoding using conditional input saturation, the method comprising:

• providing a branch metric calculator, wherein the branch metric calculator is operable to calculate a branch metric associated with a branch with an expected branch input;
• receiving an actual input at the branch metric calculator;
• comparing the actual input with an expected range, wherein a comparison result is created;
• creating a saturated input;
• and
• calculating the branch metric, wherein depending upon a combination of the expected branch input and the comparison result, one of the actual input and the saturated input is used to calculate the branch metric.

A Viterbi detector, wherein the Viterbi decoder comprises:

• a branch metric calculator, wherein the branch metric calculator is operable to:
• receive an actual input,
• compare the actual input with an expected range, wherein a comparison result is created indicating that the actual input is greater than the expected range;
• create a saturated input, wherein the saturated input is equal to the upper boundary of the expected range;
• calculate a first branch metric associated with a first branch, wherein the first branch has an expected value equal to an upper boundary of the expected range, and wherein calculating the first branch metric is done using the saturated input;
• and
• calculate a second branch metric associated with a second branch, wherein the second branch has an expected value different from the upper boundary of the expected range, and wherein calculating the second branch metric is done using the actual input;
• and
• a path metric calculator, wherein the path metric calculator is operable to:
• calculate a first path metric, wherein the first path metric uses the first branch metric;
• calculate a second path metric, wherein the second path metric uses the second branch metric;
• and
• determine which of the first path metric and the second path metric is associated with a most likely codeword.