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Error correction on burst channels by sequential decoding

  • US 4,291,406 A
  • Filed: 08/06/1979
  • Issued: 09/22/1981
  • Est. Priority Date: 08/06/1979
  • Status: Expired due to Term
First Claim
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1. A sequential decoder and system for determining error patterns for making error correction on burst and random noise channels using convolutionally encoded data comprising:

  • de-interleaver means for time-demultiplexing the convolutionally encoded data from a data channel into a predetermined transformed order;

    a decoded data buffer for storing received data which has been decoded by said de-interleaver;

    a syndrome bit generator connected to the output of said de-interleaver means for calculating a syndrome bit from a combination of the presently received subblock together with a given number of previous sub-blocks received from said de-interleaver means and stored in said decoded data buffer, said syndrome bit indicating if the current assumption of the path through a convolutional tree is correct;

    burst tracking means, connected to the output of said de-interleaver means, for tracking burst errors and deriving burst indicator bits which indicate the presence of burst errors in a channel, said burst tracking means also being connected to said decoded data buffer which stores previously decoded received data;

    memory means for storing tables of error likelihood and error pattern values derived from known error statistics about the data channel, statistics of probability of random errors and burst errors, error severity within a burst, and average burst duration, said memory means being connected to and addressed by a calculating means for providing error likelihood and error pattern values to said decoded data buffer; and

    said calculating means connected to both said syndrome bit generator and said burst tracking means for using said syndrome bits and said burst indicator bits to calculate a table address in said tables of error likelihood and error pattern values, said table address providing a likelihood value and an error pattern which are used to update a total likelihood value and determine an error pattern which are used to change received subblock data.

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