Dual-mode analog/digital adaptive echo cancellation in communication systems with asymmetric spectrum
First Claim
1. In a full-duplex communication system having a transmit path and a receive path, a system for echo cancellation comprising:
- a digital echo estimator unit for generating a digital echo estimate signal based on the transmit path;
a switch communicatively coupled to the digital echo estimator unit, the switch configured to select between an analog echo cancellation path and a digital echo cancellation path;
a digital to analog converter (DAC) communicatively coupled to the analog echo cancellation path of the switch for converting the digital echo estimate signal to an analog echo estimate signal;
an analog subtractor communicatively coupled to the DAC for receiving the analog echo estimate signal and communicatively coupled to the receive path of the communication system for receiving a received signal superimposed with a local echo signal, wherein the analog subtractor creates an error signal by differencing the analog echo estimate signal and the received signal; and
a digital subtractor communicatively coupled to the digital echo cancellation path of the switch for receiving the digital echo estimate signal and communicatively coupled to the receive path of the communication system for receiving a received signal superimposed with a local echo signal, wherein the digital subtractor creates an error signal by differencing the digital echo estimate signal and the received signal.
5 Assignments
0 Petitions
Accused Products
Abstract
An echo cancellation (EC) system for use in a full-duplex communication system having asymmetric signal sampling rates, in particular an ADSL system, is described. The system performs the cancellation of local echo signal in digital or analog domain depending on the loop condition using a switching logic. The EC system further includes an EC unit that generates a digital echo estimate signal at the lower sampling rate of the transmitted signal and then interpolates the digital signal to higher sampling rate to cancel echo signal thereby reducing computation complexity. The digital interpolated echo estimate signal is converted to analog form for use in analog echo cancellation. The subtracted signal resulting from the analog echo cancellation is converted into digital domain and used as feedback for the EC unit to adaptively improve the accuracy of the echo estimate.
28 Citations
18 Claims
-
1. In a full-duplex communication system having a transmit path and a receive path, a system for echo cancellation comprising:
-
a digital echo estimator unit for generating a digital echo estimate signal based on the transmit path; a switch communicatively coupled to the digital echo estimator unit, the switch configured to select between an analog echo cancellation path and a digital echo cancellation path; a digital to analog converter (DAC) communicatively coupled to the analog echo cancellation path of the switch for converting the digital echo estimate signal to an analog echo estimate signal; an analog subtractor communicatively coupled to the DAC for receiving the analog echo estimate signal and communicatively coupled to the receive path of the communication system for receiving a received signal superimposed with a local echo signal, wherein the analog subtractor creates an error signal by differencing the analog echo estimate signal and the received signal; and a digital subtractor communicatively coupled to the digital echo cancellation path of the switch for receiving the digital echo estimate signal and communicatively coupled to the receive path of the communication system for receiving a received signal superimposed with a local echo signal, wherein the digital subtractor creates an error signal by differencing the digital echo estimate signal and the received signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A method for training an echo cancellation system in a full-duplex communication system, the method comprising:
-
generating a digital echo estimate signal based upon a transmitted signal; selecting between analog echo cancellation and digital echo cancellation; responsive to selecting analog echo cancellation; converting the digital echo estimate signal to an analog echo estimate signal; differencing the analog echo estimate signal and a received signal superimposed with a local echo signals resulting in an analog error signal; and converting the analog error signal to a digital error signal; and
responsive to selecting digital echo cancellation;differencing the digital echo estimate signal and a received signal superimposed with a local echo signal, resulting in a digital error signal. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
-
Specification