US4977591A
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Dual mode LMS nonlinear data echo canceller
Assignee: Verizon Patent and Licensing Inc
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Filing: 1989-11-17
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Granted: 1990-12-11
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Expires: 2009-11-17
Abstract
Abstract An adaptive nonlinear data driven echo canceller is disclosed. Unlike other approaches to nonlinear echo cancellation, the inventive echo canceller treats the nonlinearity of the echo path as nonlinear noise associated with transmitting data symbols through a linear echo path. In comparison to a conventional LMS data driven linear echo canceller, the inventive echo canceller utilizes only an additional small random access memory for storing a nonlinear function for estimating the effect of the nonlinear echo path on transmitted data symbols. The same LMS algorithm is used to estimate the linear echo path and the nonlinear function. The signal processing power of a conventional linear data driven LMS echo canceller is sufficient to implement the inventive nonlinear echo canceller and the convergence speed of the nonlinear echo canceller can be less than three times that of the conventional linear LMS echo canceller.
Inventors
- 👤 Walter Y. Chen
- 👤 Richard A. Haddad
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 17:13
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H04B3/231; H04B3/238
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
99 words
An echo canceller for cancelling an echo signal comprising means operative during a training period and using a least mean square algorithm to estimate a finite impulse response of a linear component of an echo path, and means operative during a subsequent dual mode phase and using a least mean square algorithm for estimating both a nonlinear function representative of a nonlinear component of said echo path and said finite impulse response of said linear component of said echo path, wherein said means operative during said dual mode phase alternately estimates said nonlinear function and said finite impulse response.
Claim 2
Dependent Claim
99 words
An echo canceller for cancelling an echo signal comprising means operative during a training period and using a least mean square algorithm to estimate a finite impulse response of a linear component of an echo path, and means operative during a subsequent dual mode phase and using a least mean square algorithm for estimating both a nonlinear function representative of a nonlinear component of said echo path and said finite impulse response of said linear component of said echo path, wherein said means operative during said dual mode phase alternately estimates said nonlinear function and said finite impulse response.
Claim 3
Dependent Claim
27 words
The echo canceller of claim 1 wherein said means operative during said dual mode phase includes a random access memory for storing values of said nonlinear function.
Claim 4
Dependent Claim
142 words
An echo canceller for generating an estimated echo signal e(k) to cancel an echo signal e(k) generated by a transmission channel from a data signal X(k), where k is a time index, said echo canceller comprising memory means for storing a vector f(X k ) k where f(.) is a nonlinear function representative of a nonlinear component of an echo transmission path of said echo signal and X k is a vector formed from the values of the signal X(k) for the last n values of the time index k where n is an integer, means for obtaining a vector H k corresponding to an estimated finite impulse response of a linear component of said echo transmission path, and means for obtaining the product of (X k +f(X k ) k ) and H k to form said estimated echo signal e(k).
Claim 5
Dependent Claim
142 words
An echo canceller for generating an estimated echo signal e(k) to cancel an echo signal e(k) generated by a transmission channel from a data signal X(k), where k is a time index, said echo canceller comprising memory means for storing a vector f(X k ) k where f(.) is a nonlinear function representative of a nonlinear component of an echo transmission path of said echo signal and X k is a vector formed from the values of the signal X(k) for the last n values of the time index k where n is an integer, means for obtaining a vector H k corresponding to an estimated finite impulse response of a linear component of said echo transmission path, and means for obtaining the product of (X k +f(X k ) k ) and H k to form said estimated echo signal e(k).
Claim 6
Dependent Claim
29 words
The echo canceller of claim 3 wherein said echo canceller includes means for iteratively estimating said vector f(X k ) k and for iteratively estimating said finite impulse response.
Claim 7
Dependent Claim
30 words
The echo canceller of claim 4 wherein said estimating means utilize a least means square algorithm to estimate both said vector f(X k ) k and said finite impulse response.
Claim 8
Independent Claim
122 words
A method for cancelling an echo in a telecommunications channel used to transmit a digital data signal, said method comprising the steps of during a training period, using a least mean square algorithm to estimate the finite impulse response of a linear component of an echo path, and during a subsequent dual mode phase, using a least mean square algorithm to both estimate a nonlinear function representative of a nonlinear component of said echo path and said finite impulse response of said linear component of said echo path, wherein during said dual mode phase, alternately, said nonlinear function is estimated and said finite impulse response is held constant and said finite impulse response is estimated and said nonlinear function is held constant.
Claim 9
Independent Claim
122 words
A method for cancelling an echo in a telecommunications channel used to transmit a digital data signal, said method comprising the steps of during a training period, using a least mean square algorithm to estimate the finite impulse response of a linear component of an echo path, and during a subsequent dual mode phase, using a least mean square algorithm to both estimate a nonlinear function representative of a nonlinear component of said echo path and said finite impulse response of said linear component of said echo path, wherein during said dual mode phase, alternately, said nonlinear function is estimated and said finite impulse response is held constant and said finite impulse response is estimated and said nonlinear function is held constant.
Claim 10
Dependent Claim
37 words
The method of claim 6 wherein during said dual mode phase, said finite impulse response is estimated during every m th iteration of said least mean square algorithm, where M is a number between 2 and 5.
Claim 11
Independent Claim
107 words
A method for cancelling an echo in a telecommunications channel used to transmit a digital data signal, said method comprising the steps of during a training period, using a least mean square algorithm to estimate the finite impulse response of a linear component of an echo path, and during a subsequent dual mode phase, using a least mean square algorithm to both estimate a nonlinear function representative of a nonlinear component of said echo path and said finite impulse response of said linear component of said echo path, wherein said method further comprises the step of storing values of said nonlinear function in a random access memory.
Claim 12
Independent Claim
107 words
A method for cancelling an echo in a telecommunications channel used to transmit a digital data signal, said method comprising the steps of during a training period, using a least mean square algorithm to estimate the finite impulse response of a linear component of an echo path, and during a subsequent dual mode phase, using a least mean square algorithm to both estimate a nonlinear function representative of a nonlinear component of said echo path and said finite impulse response of said linear component of said echo path, wherein said method further comprises the step of storing values of said nonlinear function in a random access memory.
Claim 13
Dependent Claim
21 words
The method of claim 10 wherein said nonlinear function representative of said nonlinear component of said echo path includes no delay.
Claim 14
Independent Claim
130 words
A method for generating an estimated echo signal e(k) for use in an echo canceller to cancel an echo signal e(k) where k is a time index comprising the steps of storing a nonlinear data vector Y k =ψ(X k ), where X k is a data vector formed from the values of said signal X(k) being transmitted for the last n values of the index k where n is an integer and where ψ is a nonlinear function representing the effect of a nonlinear component of a transmission path of said echo signal e(k), and forming the product of Y k H k where H k is an estimate of a finite impulse response of a linear component of said echo path to obtain said estimated echo signal e(k).
Claim 15
Independent Claim
130 words
A method for generating an estimated echo signal e(k) for use in an echo canceller to cancel an echo signal e(k) where k is a time index comprising the steps of storing a nonlinear data vector Y k =ψ(X k ), where X k is a data vector formed from the values of said signal X(k) being transmitted for the last n values of the index k where n is an integer and where ψ is a nonlinear function representing the effect of a nonlinear component of a transmission path of said echo signal e(k), and forming the product of Y k H k where H k is an estimate of a finite impulse response of a linear component of said echo path to obtain said estimated echo signal e(k).
Claim 16
Dependent Claim
28 words
The method of claim 10 wherein said nonlinear data vector Y k and said finite impulse response H k are estimated iteratively using a least mean square algorithm.
Claim 17
Dependent Claim
40 words
The method of claim 11 wherein alternatively, said finite impulse response is held constant and said nonlinear vector Y k is estimated and said nonlinear vector Y k is held constant and said finite impulse response H k is estimated.
Claim 18
Dependent Claim
66 words
An echo canceller comprising means for storing values of a nonlinear function representative of a nonlinear component of an echo path, means for storing values representative of a finite impulse response of a linear component of said echo path, and means for executing a least mean square algorithm for alternately estimating said values of said nonlinear function and said values representative of said finite impulse response.
Claim 19
Dependent Claim
66 words
An echo canceller comprising means for storing values of a nonlinear function representative of a nonlinear component of an echo path, means for storing values representative of a finite impulse response of a linear component of said echo path, and means for executing a least mean square algorithm for alternately estimating said values of said nonlinear function and said values representative of said finite impulse response.
Claim 20
Independent Claim
67 words
A method for cancelling an echo in a communications channel comprising storing values of a nonlinear function representative of a nonlinear component of an echo path, storing values representative of a finite impulse response of a linear component of an echo path, and executing a least mean square algorithm for alternately estimating said values of said nonlinear function and said values representative of said finite impulse response.
Claim 21
Independent Claim
67 words
A method for cancelling an echo in a communications channel comprising storing values of a nonlinear function representative of a nonlinear component of an echo path, storing values representative of a finite impulse response of a linear component of an echo path, and executing a least mean square algorithm for alternately estimating said values of said nonlinear function and said values representative of said finite impulse response.
References Cited (Backward Citations)
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Cited
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