Claims
- 1. A method for correcting a received sequence of coded character symbols having one erasure, said method comprising the steps of:
- setting initial character value of position j, CV(j), equal to 0, where j denotes the position of the erasure;
- forming sum, F.sub.o, of preassigned character values associated with said character symbols, said sum being carried out for all sequence positions having an odd position number, said sum being carried out modulo N where N is odd and is also the number of code symbols;
- forming sum, F.sub.e, of preassigned character values associated with said character symbols, said sum being carried out for all sequence positions having an even position number, said sum being carried out modulo N;
- forming check sum F as F.sub.o +2 F.sub.e modulo N;
- computing character value of the erasure position, CV(j), as -F modulo N if j is odd and as [(N-1)/2].multidot.F modulo N if j is even; and
- associating a corrected erasure position character symbol with character value CV(j) in accordance with said preassigned character value association.
- 2. The method of claim 1 in which N is 35.
- 3. A method for decoding a received sequence of character symbols and erasure, said method comprising the steps of:
- determining how many erasures occurred;
- providing an indication of an uncorrectable error if the number of erasures exceeds one;
- determining if there is exactly one erasure and applying the correction procedure of claim 1 in this even;
- determining if there are no erasures and applying said forming steps to compute check sum F; and
- providing an indication of an uncorrectable error in the event that F is not equal to 0 (modulo N), otherwise accepting the received sequence as correct.
Parent Case Info
This is a continuation of copending application Ser. No. 07/370,935, filed on Jun. 23, 1989, now U.S. Pat. No. 5,070,504.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
3815495 |
Strackbein |
Jun 1974 |
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4742521 |
Nishida |
May 1988 |
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Continuations (1)
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Number |
Date |
Country |
Parent |
370935 |
Jun 1989 |
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