Read channel data signal detection with reduced-state trellis

A method comprising the steps of:

• determining a first set of soft outputs, hard decisions and reliability indicators for a read channel data signal;
• determining a second set of soft outputs, hard decisions and reliability indicators based at least in part on the first set of soft outputs, hard decisions and reliability indicators;
• and
• performing an iterative decoding process to decode the read channel data signal based at least in part on the second set of soft outputs, hard decisions and reliability indicators;
• wherein the first set of soft outputs, hard decisions and reliability indicators are used to determine a reduced-state trellis for determining the second set of soft outputs, hard decisions and reliability indicators.

A storage device comprising:

• at least one storage medium;
• a read head configured to read data from the storage medium;
• and
• control circuitry coupled to the read head and configured to process data received from the read head;
• the control circuitry comprising:
• read channel circuitry;
• and
• signal processing circuitry associated with the read channel circuitry, the signal processing circuitry being configured to:
• determine a first set of soft outputs, hard decisions and reliability indicators for a read channel data signal;
• determine a second set of soft outputs, hard decisions and reliability indicators based at least in part on the first set of soft outputs, hard decisions and reliability indicators;
• and
• perform an iterative decoding process to decode the read channel data signal based at least in part on the second set of soft outputs, hard decisions and reliability indicators;
• wherein the first set of soft outputs, hard decisions and reliability indicators are used to determine a reduced-state trellis for determining the second set of soft outputs, hard decisions and reliability indicators.