Device and method for linear listener echo cancellation
First Claim
1. A listener echo canceller (LECR) for reducing a listener echo interference in a digital communication system having a selected sampling interval, and having an input and an output, said input comprising a sum of a desired signal and a listener echo interference, and said output being free of listener echo interference, said listener echo canceller comprising:
- a bulk delay line means, operably coupled to receive and store at least one sample of one of;
the input and the output of said listener echo canceller, to provide a bulk delay line output;
an adaptive listener echo interference estimator means, operably coupled to receive the bulk delay line output for utilizing a listener echo bulk delay relative to the received data signal in place of a talker far echo bulk delay relative to the near echo to generate an estimate of the listener echo interference; and
an interference cancelling means, operably coupled to receive the input of the listener echo canceller and the estimate of the listener echo interference, for producing said output by subtracting said estimate of the listener echo interference from said input of the listener echo canceller,wherein said adaptive listener echo interference estimator means further includes compensating means, operably coupled to receive the input of the LECR and to receive a phase-corrected listener echo estimate, for compensating a frequency offset in the said estimate of the listener echo interference utilizing a talker far echo frequency offset as an estimate of far echo cancellation, andwherein the means for compensating the frequency offset includes;
a phase-error estimating means, operably coupled to receive the input of the LECR and to receive a phase-corrected listener echo estimate, for generating a phase error that is a phase difference between the estimate of the listener echo estimate and the said input of the LECR; and
a phase-locked loop, operably coupled to receive the said phase error, for generating a phase correction estimate; and
a phase-correction means, operably coupled to receive the phase correction estimate, for generating a phase-corrected listener echo estimate.
2 Assignments
0 Petitions
Accused Products
Abstract
A device and method utilize a linear feedback/feedforward configuration to estimate and cancel a listener echo wherein equalizer (202) and listener echo cancellation (204 and 208) units are jointly updated, allowing determination of an error signal once (204 and 208), in place of the former method of separate error signal determination for each of an equalizer and a listener echo canceller. An improved phase-correction scheme is utilized to compensate the frequency offset in the listener echo. The relationship between the listener echo and talker far echo is utilized to facilitate the listener echo cancellation.
-
Citations
48 Claims
-
1. A listener echo canceller (LECR) for reducing a listener echo interference in a digital communication system having a selected sampling interval, and having an input and an output, said input comprising a sum of a desired signal and a listener echo interference, and said output being free of listener echo interference, said listener echo canceller comprising:
-
a bulk delay line means, operably coupled to receive and store at least one sample of one of;
the input and the output of said listener echo canceller, to provide a bulk delay line output;an adaptive listener echo interference estimator means, operably coupled to receive the bulk delay line output for utilizing a listener echo bulk delay relative to the received data signal in place of a talker far echo bulk delay relative to the near echo to generate an estimate of the listener echo interference; and an interference cancelling means, operably coupled to receive the input of the listener echo canceller and the estimate of the listener echo interference, for producing said output by subtracting said estimate of the listener echo interference from said input of the listener echo canceller, wherein said adaptive listener echo interference estimator means further includes compensating means, operably coupled to receive the input of the LECR and to receive a phase-corrected listener echo estimate, for compensating a frequency offset in the said estimate of the listener echo interference utilizing a talker far echo frequency offset as an estimate of far echo cancellation, and wherein the means for compensating the frequency offset includes; a phase-error estimating means, operably coupled to receive the input of the LECR and to receive a phase-corrected listener echo estimate, for generating a phase error that is a phase difference between the estimate of the listener echo estimate and the said input of the LECR; and a phase-locked loop, operably coupled to receive the said phase error, for generating a phase correction estimate; and a phase-correction means, operably coupled to receive the phase correction estimate, for generating a phase-corrected listener echo estimate. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A device for minimizing a listener echo signal interference in a selectively demodulated communication signal received over a channel having simultaneous transmission and reception, the device comprising;
-
equalizing means, operably coupled to receive the selectively demodulated communication signal, for providing an equalized signal; a first correcting means, operably coupled to the equalizing means and to a second correcting means, and being configured for; receiving the equalized signal; determining a listener echo estimate; and combining the equalized signal with the listener echo estimate to provide a first corrected signal; wherein the second correcting means is operably coupled to the first correcting means and to the equalizing means, and is configured for; providing a phase correction to the first corrected signal to generate and output a second corrected signal that is an equalized listener echo corrected and phase-corrected communication signal; providing an error signal to the equalizing means for adjusting an equalization process of the equalizing means and to the first correcting means for adjusting the listener echo estimation; and providing a rotated reference signal in reference-directed training mode for facilitating an initial training of a listener echo estimation. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
-
-
19. A modem having a linear listener echo cancelling device, the modem being utilized for communicating information with a remote device in both directions over a channel, the modem comprising:
-
transmission means, operably coupled to receive the information to be communicated, for preparing an analog signal carrying that information for transmission; hybrid coupling means, operably coupled to the transmission means and to a receiving means, for transmitting the analog signal and for receiving another analog signal from a remote device; talker echo estimating means, operably coupled to the transmission means, for providing a talker echo estimate to the receiving means; and the receiving means, operably coupled to the talker echo estimating means and to the hybrid coupling means, for recovering information from the analog signal transmitted by the remote device, said receiving means including one of; a linear feedback listener echo canceller, and a linear feedforward listener echo canceller, for reducing a listener echo interference, encoding means, operably coupled to receive the information to be communicated, for providing an encoded data signal; modulation means operably coupled to the encoding means, for providing a modulated signal; and transmission filtering means, operably coupled to the modulation means, for providing a modulated filtered transmission data signal at a desired sampling rate; and digital-to-analog converting means, operably coupled to the transmission filtering means, for converting the modulated filtered transmission data signal to an analog signal. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
-
-
36. A method for minimizing a listener echo signal interference in a selectively demodulated, equalized communication signal received over a channel having simultaneous transmission and reception, said method comprising the steps of:
-
receiving said selectively demodulated communication signal, for providing an equalized signal; determining a listener echo estimate; and combining said equalized signal with said listener echo estimate to provide a first corrected signal; providing a phase correction to said first corrected signal to generate and output a second corrected signal that is an equalized, listener echo-corrected and phase-corrected communication signal; providing an error signal for adjusting said equalization signal and said listener echo estimate; providing a rotated reference signal in a reference-directed training mode for facilitating an initial training of said listener echo estimate. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
-
Specification