Coding for odd error multiplication in digital systems with differential coding
US4530094A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 28, 1982 |
| Grant date | Jul 16, 1985 |
| Priority date | — |
| Expiry date | Sep 28, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L25/497
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
Differential encoding is commonly used in data transmission systems because it allows correct recovery of the data even though the polarity may have changed during transmission. However, single errors which are introduced result in double errors, i.e., error of an even number following the differential decoding process. Because many error detection schemes rely upon parity checks, which look for an odd number to determine if an error has occurred, the conversion of the single error to a double error means that single errors normally would not be detected. A precoder is used to introduce correlation by modulo two addition of the precoded present digit with a selected combination of past digits. The differential decoder will still provide double errors but a subsequent decoder, which reverses the precoding process, at least partially changes double errors into errors of an odd number.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.