Classifier for high speed voiceband digital data modem signals
US4979211A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 5, 1990 |
| Grant date | Dec 18, 1990 |
| Priority date | — |
| Expiry date | Jun 5, 2010 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/0012
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
An unknown voiceband digital data modem signal is classified as being generated by one of a plurality of possible digital data modem signal sources, e.g., CCITT V.29, CCITT V.32, CCITT V.33 or the like digital data modems. Classification is achieved by employing a blind, i.e., self-recovering, adaptive equalizer to remove effects of linear channel impairments and to generate a sequence of magnitude estimates at the symbol rate of the unknown voiceband digital data modem signal. The sequence of magnitude estimates is compared to predetermined representations of known possible voiceband digital data modem signals and the results of the comparison are used to identify the digital data modem signal source of the signal. In one example, the predetermined representations are templates of conditional density functions of magnitude estimates obtained from known voiceband digital data modem signals generated by corresponding digital data modem signal sources. The symbol rate detector detects bit rate and type of modulation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.