Method and apparatus for pre-compensation of an XDSL modem
US6963603B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 6, 2001 |
| Grant date | Nov 8, 2005 |
| Priority date | — |
| Expiry date | May 29, 2023 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2025/03802
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
An apparatus and method is provided for minimizing frequency distortion in the transmit path of an XDSL modem implementing digital multi-tone (DMT) line code. The current invention provides a means for both determining and correcting for distortion in the frequency domain. The apparatus may be incorporated in an existing X-DSL architecture without additional circuitry. In an embodiment of the invention the apparatus may include a calibration phase which may be implemented using the existing analog-to-digital (ADC) conversion and demodulation capabilities on the receive path of the modem. This calibration phase takes place before the training phase associated with establishing communications with a remote site. During the calibration phase a calibration sequence with known spectral characteristics in the frequency domain is injected digitally at the beginning of the transmit path into each of the tone bins of the inverse Fourier Transform engine (IFFT). The receive path is configured to receive feedback of a resultant analog output signal from the transmit path. A frequency analyzer is used to determine the spectral properties of the feedback from the analog output signal and a norm…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.