The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 29, 1999
Filed:
Jan. 08, 1997
David B Ribner, Andover, MA (US);
David H Robertson, Roxford, MA (US);
Analog Devices, Inc., Norwood, MA (US);
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 decimated samples of the oversampled up-stream signal and the decimated samples of the filter are fed to the subtractor at the predetermined rate.