Method and apparatus for network echo cancellation using a proportionate normalized least mean squares algorithm
AssigneeAgere Systems Inc.
InventorsJacob Benesty, Steven Leslie Gay
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Abstract
The invention is a method and apparatus for performing adaptive filtering, and particularly echo cancellation, utilizing an efficient and effective adaptive algorithm. The invention is particularly useful in connection with network echo cancellation but is more broadly applicable to any situation where an adaptive estimate of a signal must be generated in real-time. The invention includes an improved proportionate normalized least mean squares algorithm for generating an impulse response estimate that is useful for generating an echo cancellation signal to be subtracted from the echo containing signal.
Claims24
A method of generating an estimate signal of an impulse response of a communications system to an original signal, said estimate signal comprising a plurality of discrete time values, each of said discrete time values comprising a plurality of coefficients, said method comprising the steps of:
- (1) receiving said original signal;
- and
- (2) generating each of said discrete time values by updating each one of said coefficients corresponding to said discrete time value independently of the others of said coefficients corresponding to said discrete time value by adjusting an adaptation step size in proportion to said coefficient corresponding to a preceding discrete time using the sum of the average of the absolute values of all of said coefficients and the absolute value of said one of said coefficients to take into account the structure of said impulse response.
A method of generating an estimate signal that is an estimate of an impulse response of a communications system to an original signal, said method comprising the steps of:
- (1) receiving said original signal;
- and
- (2) generating an estimate of an impulse response to said original signal by means of a proportionate normalized least mean squares algorithm using:
- 12 h ^ ( n ) = h ^ ( n - 1 ) + μ x T ( n ) O 1 ( n - 1 ) x ( n ) + δ IPNLMS O 1 ( n - 1 ) x ( n ) e ( n ) .
A method of generating an estimate signal ĥ(n), where n denotes one of a plurality of consecutive discrete times, of an echo of an original signal x(n) received at a transceiver via a communications system, said original signal x(n) being coupled into a signal y(n) that is transmitted from said transceiver via said communications system, said estimate signal ĥ(n) comprising a plurality of coefficients h0, h1, h2, . . . h1, . . . hL-1, said method comprising the steps of:
- (1) receiving said original signal x(n);
- and
- (2) generating said estimate signal ĥ(n) by updating each one of said coefficients h1(n) independently of the others of said coefficients by adjusting an adaptation step size μ in proportion to said coefficient for time n−1, h1(n−1) using the sum of the average of the absolute values of all of said coefficients and the absolute value of said one of said coefficients to take into account the structure of said impulse response.
A method of generating a signal that is an estimate of an echo of an original signal received at a transceiver via a communications system, said original signal being coupled into a signal that is transmitted from said transceiver via said communications system, said method comprising the steps of:
- (1) receiving said original signal;
- and
- (2) generating an estimate of an impulse response to said original signal by means of a proportionate normalized least mean squares algorithm using:
- 17 h ^ ( n ) = h ^ ( n - 1 ) + μ x T ( n ) O 1 ( n - 1 ) x ( n ) + δ IPNLMS O 1 ( n - 1 ) x ( n ) e ( n ) .
The method of claim 95 wherein:
- O1(n−1)=diag{o1,0(n−1), . . . ,o1,L−1(n−1)},
- 18 O 1 ( n - 1 ) = diag { o 1 , 0 ( n - 1 ) , … , o 1 , L - 1 ( n - 1 ) } , = 1 || o ( n - 1 ) || 1 diag { o 0 ( n - 1 ) … , o L - 1 ( n - 1 ) } .
A method of performing echo cancellation in a communications system, said method comprising the steps of:
- (1) receiving a signal that is a potential source of echo;
- (2) generating an estimate signal of an impulse response corresponding to echo of said original signal, said estimate signal comprising a plurality of discrete time values, each of said discrete time values comprising a plurality of coefficients, by means of a proportionate normalized least mean squares algorithm by generating each of said discrete time values by updating each one of said coefficients corresponding to said discrete time value independently of the others of said coefficients corresponding to said discrete time value by adjusting an adaptation step size in proportion to said coefficient corresponding to a preceding discrete time using the sum of the average of the absolute values of all of said coefficients and the absolute value of said one of said coefficients to take into account the structure of said impulse response;
- and
- (3) subtracting said estimate signal from a transmitted signal in order to cancel said echo from said transmitted signal.
An apparatus for performing echo cancellation in a transceiver, said apparatus comprising:
- (1) a transmit electrical path upon which transmit signals are imposed by said transceiver;
- (2) a receive electrical path upon which are received signals that are a potential source of echo that may be coupled onto said transmit path are received at said transceiver;
- (3) a circuit for generating an estimate signal of an impulse response corresponding to echo of said original signal that may be coupled onto said transmit path, said estimate signal comprising a plurality of discrete time values, each of said discrete time values comprising a plurality of coefficients, said signal being generated by means of a proportionate normalized least mean squares algorithm in which each of said discrete time values is generated by updating each one of said coefficients corresponding to said discrete time value independently of the others of said coefficients coefficients corresponding to said discrete time value by adjusting an adaptation step size in proportion to said coefficient for a preceding time value using the sum of the average of the absolute values of all of said coefficients and the absolute value of said one of said coefficients to take into account the structure of said impulse response;
- and
- (4) a subtracter coupled to receive said estimate signal at a first input thereto and coupled to receive said transmitted signal at a second input thereto and generate at an output thereof a signal that is the difference between said first and second inputs in order to cancel said echo from said transmitted signal.
An apparatus for performing echo cancellation in a transceiver, said apparatus comprising:
- (1) a transmit electrical path upon which transmit signals are imposed by said transceiver;
- (2) a receive electrical path upon which are received signals that are a potential source of echo that may be coupled onto said transmit path are received at said transceiver;
- (3) a circuit for generating a signal that is an estimate of an impulse response corresponding to echo of said received signals that may be coupled onto said transmit path, said circuit generating said estimate signal by means of a proportionate normalized least mean squares algorithm using:
- 27 h ^ ( n ) = h ^ ( n - 1 ) + μ x T ( n ) O 1 ( n - 1 ) x ( n ) + δ IPNLMS O 1 ( n - 1 ) x ( n ) e ( n ) ;
- and
- (4) a subtracter coupled to receive said estimate signal at a first input thereto and coupled to receive said transmitted signal at a second input thereto and generate at an output thereof a signal that is the difference between said first and second inputs in order to cancel said echo from said transmitted signal.
Dependencies are inferred from the claim text.