Patent US5477535A successfully refreshed from Google Patents.
US5477535A
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Method of preventing a divergence of an adaptive echo canceller in a noisy signal environment
Assignee: Nokia Solutions and Networks Oy
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Filing: 1995-02-13
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Granted: 1995-12-19
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Expires: 2015-02-13
Abstract
Abstract A method of preventing an adaptive echo canceler from diverging in a noisy environment, including determining an average noise level (-45 dBmO) in the echo path, determining an attenuation (A e ) of the echo path and preventing an adaptation of the echo canceller, if the level of the signal (x(i)) to be transmitted to the echo path and causing echo (r(i)) is lower than a predetermined threshold level, which is to the extent of a preset margin and the echo path attenuation above the average noise level.
Inventors
- 👤 Heimo Lahdemaki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 21:51
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
137 words
A method of preventing an adaptive echo canceller from diverging in a noisy environment, comprising the steps of: converging a model of an echo path impulse response in an adaptive digital filter of said echo canceller which is operatively associated with said echo path to which a signal is to be transmitted, determining an average noise level in said echo path, determining an attenuation of the echo path, and preventing a divergence of said echo path impulse response in said noisy environment by disabling the adaptation of said adaptive digital filter, if the level of the signal to be transmitted to the echo path and causing echo is lower than a predetermined threshold level, which is to the extent of a predetermined margin and the echo path attenuation above the average noise level in said echo path.
Claim 2
Independent Claim
137 words
A method of preventing an adaptive echo canceller from diverging in a noisy environment, comprising the steps of: converging a model of an echo path impulse response in an adaptive digital filter of said echo canceller which is operatively associated with said echo path to which a signal is to be transmitted, determining an average noise level in said echo path, determining an attenuation of the echo path, and preventing a divergence of said echo path impulse response in said noisy environment by disabling the adaptation of said adaptive digital filter, if the level of the signal to be transmitted to the echo path and causing echo is lower than a predetermined threshold level, which is to the extent of a predetermined margin and the echo path attenuation above the average noise level in said echo path.
Claim 3
Dependent Claim
15 words
A method according to claim 1, wherein: said margin is about 1 to 5 dB.
Claim 4
Dependent Claim
45 words
A method according to claim 1, further including: calculating said average noise level of the echo path on the basis of the noise level received from the echo path, when no one is speaking at either end of a speech connection involving said echo path.
Claim 5
Dependent Claim
37 words
A method according to claim 1, further including: calculating said echo path attenuation on the basis of the difference between the signal level transmitted to the echo path and the signal level received from the echo path.
Claim 6
Dependent Claim
133 words
An adaptive echo canceller, comprising: means for converging a model of an echo path impulse response in an adaptive digital filter of said echo canceller which is operatively associated with said echo path to which a signal is to be transmitted, means for determining an average noise level in said echo path, means for determining an attenuation of the echo path, and means for preventing a divergence of said echo path impulse response in a noisy environment by disabling the adaptation of said adaptive digital filter, if the level of the signal to be transmitted to the echo path and causing echo is lower than a predetermined threshold level, which is to be the extent of a predetermined margin and the echo path attenuation above the average noise level in said echo path.
Claim 7
Dependent Claim
133 words
An adaptive echo canceller, comprising: means for converging a model of an echo path impulse response in an adaptive digital filter of said echo canceller which is operatively associated with said echo path to which a signal is to be transmitted, means for determining an average noise level in said echo path, means for determining an attenuation of the echo path, and means for preventing a divergence of said echo path impulse response in a noisy environment by disabling the adaptation of said adaptive digital filter, if the level of the signal to be transmitted to the echo path and causing echo is lower than a predetermined threshold level, which is to be the extent of a predetermined margin and the echo path attenuation above the average noise level in said echo path.
Claim 8
Dependent Claim
16 words
The adaptive echo canceller of claim 5, wherein: said margin is about 1 to 5 db.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-12-18 | 1999-06-19 | 1999-12-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-12-18 | 2003-06-19 | 2003-12-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-12-18 | 2007-06-19 | 2007-12-19 | $7700.00 | Window Closed / Lapsed |