Two stage detector having viterbi detector matched to a channel and post processor matched to a channel code

A two-stage detector for a partial response channel having a known channel transfer function and including a channel code encoder for encoding information sequences into blocks of code words in accordance with a predetermined channel code enabling detection of any single occurrence within a code word of an error-event of a list of error-events known likely to occur on the partial response channel and comprising impermissible code words, the channel further including a channel sampler, the two-stage detector comprising:

• a first-stage detector connected to receive samples from the channel sampler, the first-stage detector being matched to characteristics of the known channel transfer function and not to the channel code imposed by the encoding process of the encoder, for putting out unchecked bit estimates comprising code words, and
• a second stage post-processor tailored to characteristics of the channel code, connected to receive the samples and the unchecked bit estimates, for deriving detector decision metrics information from the samples, the unchecked bit estimates and the channel transfer function;
• for checking and correcting multiple error-events within a single code word in accordance with the predetermined channel code and the decision metrics information;
• and, for putting out post-processed code words to a channel code decoder.

A method for detecting and correcting-events within a modulation code block passing through a partial response channel having a channel transfer function including the steps of:

• determining checking information for the modulation code block in accordance with a predetermined channel code,
• appending the checking information to the modulation code block to form a channel code encoded block,
• passing the channel code encoded block through the partial response channel,
• sampling the passed channel code encoded block to provide samples,
• passing the samples through a first stage detector matched to a transfer function of the channel imposed by a channel encoding process, in order to provide unchecked bit estimates,
• passing the samples and the unchecked bit estimates through a second stage post-processor, tailored to characteristics of the channel code, for checking the unchecked bit estimates in accordance with the appended checking information, for deriving first stage detector decision metrics information from the samples, the unchecked bit estimates and the channel transfer function;
• for correcting a channel code encoded block determined to include at least two error-events within the channel code block based upon the decision metrics information, the appended checking information and the channel code.

A two-stage detector for a partial response channel having a known channel transfer function;

• the channel having a channel code encoder for encoding information sequences into code words in accordance with a predetermined channel code enabling detection of any single occurrence within a code word of an error-event of a list of error-events known likely to occur on the partial response channel, the list of error-events being characterized in that adding any error-event from the list to any code word of the channel code will not produce another code word;
• the channel code including modulation codes concatenated with systematic parity codes, the channel code not including matched-spectral-null codes and not including linear block codes with Hamming distance greater than a number of bit errors in each of the error-events on the list;
• the two-stage detector including:
• a channel sampler for providing samples of the partial response channel equalized in accordance with a time domain response characteristic of the partial response channel;
• a first-stage detector connected to receive the samples from the channel sampler, the first-stage detector being matched to characteristics of the partial response channel and not to the channel code imposed by the encoding process of the encoder, for putting out unchecked bit estimates;
• and,
• a second-stage post-processor connected to receive the unchecked bit estimates and the samples;
• the post-processor including:
• (i) a parity checker for checking parity of the unchecked bit estimates, (ii) a sequence checker for detecting error-events in the unchecked code words and (iii) a sequence corrector for correcting the most-likely combination of error-events based on channel metric information generated from the samples, the unchecked bit estimates, the known channel transfer function, and the channel code, and for putting out checked bit estimates, wherein if the parity is correct, the sequence corrector does not take corrective action.

A two-stage detector for a partial response channel having a known channel transfer function and including a channel code encoder for encoding information sequences into blocks of code words in accordance with a predetermined channel code enabling detection of any single occurrence within a code word of an error-event of a list of error-events known likely to occur on the partial response channel and comprising impermissible code words, the channel further including a channel sampler, the two-stage detector comprising:

• a first-stage detector connected to receive samples from the channel sampler, the first-stage detector being matched to characteristics of the known channel transfer function and not to the channel code imposed by the encoding process of the encoder, for putting out unchecked bit estimates comprising code words, and
• a second stage post-processor being connected to receive the samples and the unchecked bit estimates, for checking parity of the unchecked bit estimates;
• for deriving detector decision metrics information from the samples, the unchecked bit estimates and the channel transfer function;
• for checking and correcting multiple error-events within a single code word in accordance with the predetermined channel code and the decision metrics information;
• and, for putting out post-processed code words to a channel code decoder, wherein if the parity is correct, the second-stage post-processor does not take corrective action.

A method for detecting and correcting error-events within a modulation code block passing through a partial response channel having a channel transfer function including the steps of:

• determining checking information for the modulation code block in accordance with a predetermined channel code,
• appending the checking information to the modulation code block to form a channel code encoded block,
• passing the channel code encoded block through the partial response channel,
• sampling the passed channel code encoded block to provide samples,
• passing the samples through a first stage detector matched to a transfer function of the channel and not to the channel code imposed by a channel encoding process, in order to provide unchecked bit estimates,
• passing the samples and the unchecked bit estimates through a second stage post-processor for checking the unchecked bit estimates in accordance with the appended checking information, for deriving first stage detector decision metrics information from the samples, the unchecked bit estimates and the channel transfer function;
• correcting a channel code encoded block determined to include at least two error-events within the channel code block based upon the decision metrics information, the appended checking information and the channel code, wherein if the unchecked bit estimates check in accordance with the appended checking information, the second-stage post-processor does not take corrective action.