Process for starting up a modem containing a variable-phase echo canceller and modem in which such a process is implemented
US5572545A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 8, 1994 |
| Grant date | Nov 5, 1996 |
| Priority date | — |
| Expiry date | Sep 8, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B3/238
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A start-up method for a data modem having an echo cancelling loop between the send port and receive port, the loop including a transversal filter having adjustable coefficients, adjustable phase-shifter and a subtractor for subtracting send port data symbols which have been filtered and phase shifted from data symbols received at the receive port. During start-up, in response to a series of data symbols supplied at the send port, a microprocessor iteratively adjusts the filter coefficients and the phase shift to cancel any echo at the output of the subtractor. In order to reduce the convergence time, the start-up method includes estimating the power of the echo over a time period corresponding to a predetermined number of data symbols at the send port, quantizing the estimated power, and adjusting the filter coefficients and the phase shift on the basis of the quantized echo power level.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.