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Multiple error trapping

  • US 4,843,607 A
  • Filed: 12/17/1987
  • Issued: 06/27/1989
  • Est. Priority Date: 12/17/1987
  • Status: Expired due to Fees
First Claim
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1. An error trapping decoder adapted to decode a received codeword having r redundant check symbols in r predetermined check locations in said received codeword, said error trapping decoder comprising:

  • means responsive to specification of a given set of r virtual check locations different from said r check locations, for computing r virtual check symbols corresponding to said given set of r virtual check locations;

    permuting means for specifying to said computing means successive sets of r virtual check locations so that said computing means computes successive sets of r virtual check symbols; and

    means, responsive whenever said permuting means specifies a particular set of r virtual check locations for which the corresponding r virtual check symbols are all zero except for no more than predetermined number, for adding the non-zero ones of said particular set of r virtual check symbols to symbols occupying the corresponding virtual check locations in said received codeword, whereby to generate a corrected codeword.

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