QAM detector which compensates for received symbol distortion induced by a cellular base station
US5640417A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 24, 1995 |
| Grant date | Jun 17, 1997 |
| Priority date | — |
| Expiry date | Jul 24, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04W88/08
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A cellular subscriber modem for receiving CCITT-type quadrature amplitude modulated (QAM) signals. The cellular modem includes a novel symbol detector that converts received symbol information to polar notation. The detector's constellation thresholds include a circular threshold having a radius greater than the magnitude of the innermost symbols, but less than the magnitude of the outermost symbols, and radially spaced thresholds, which further discriminate between the outermost symbols. As a result, special cellular-compatible modem equipment need not be connected between the public-access switched telephone network and the computer equipment at the other end, which means that a CCITT-compatible cellular subscriber modem can then be treated as any other type of CCITT-modem. The detector may be implemented in the software of a standard modem processor, or as several analog comparator circuits.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.