Asymmetric digital subscriber loop modem and method
US5917809A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 8, 1997 |
| Grant date | Jun 29, 1999 |
| Priority date | — |
| Expiry date | Jan 8, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B3/23
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for operating an asymmetric digital subscriber loop modem system. A modem at a central office transmits information to a modem at a remote terminal on a down-stream signal having a predetermined bandwidth and the modem at the remote terminal transmits information to the modem at the central office on an up-stream signal having a bandwidth lower than the predetermined bandwidth of the down-stream signal. Digital samples of the up-stream signal in the central office modem are produced. Digital samples representative of an estimated echo signal in the central office modem are also produced. The digital samples of the up-stream signal and the digital samples representative of an estimated echo signal are both fed to a subtractor at the same rate. In a preferred embodiment, the up-stream signal is oversampled (i.e., is sampled at a rate greater than the Nyquist sampling rate) in producing the digital samples thereof. Samples of the down-stream signal are fed to an echo cancellation filter. The filter output is decimated to a predetermined rate. The samples of the oversampled up-stream signal are decimated producing samples at the predetermined rate. Both the decim…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.