Claims
- 1. An echo cancellation method using a model of an echo path for forming a residual signal, comprising the steps of:determining a residual power estimate of said residual signal; determining a non-linear error power estimate of said residual signal; determining a dynamic threshold that depends on said non-linear error power estimate; comparing said residual power estimate to said dynamic threshold; and attenuating said residual signal if said residual power estimate falls below said dynamic threshold.
- 2. The method of claim 1, further comprising:determining a linear error power estimate of said residual signal; and determining a dynamic threshold that depends on both said linear error power estimate and said non-linear error power estimate.
- 3. The method of claim 1 wherein the attenuation is increased each time said residual power estimate falls below said dynamic threshold until said residual signal is substantially suppressed.
- 4. The method of claim 3, wherein said residual signal is attenuated as a non-linear function of the amplitude of said residual signal each time said residual power estimate falls below said dynamic threshold and as a linear function of the amplitude of said residual signal each time said residual power estimate does not fall below said dynamic threshold.
- 5. The method of claim 4, wherein said non-linear function is a linear function for amplitudes of said residual signal that are below an estimated noise level and a constant function for amplitudes that exceed said noise level.
- 6. The method of claim 5, wherein said dynamic threshold is formed by the sum of said linear and non-linear error power estimates.
- 7. The method of claim 6, wherein said dynamic threshold is formed in accordance with the formulaγ{α(n)·Rx(n)+β(n)·Re(n)}whereRx(n) is a power estimate of an input signal to said echo path, Re(n) is a power estimate of an output signal from said echo path, α(n) and β(n) are continuously updated scale factors, and γ is a constant scale factor.
- 8. An echo canceller using a model of an echo path for forming a residual signal, comprising:means for determining a residual power estimate of said residual signal; means for determining a non-linear error power estimate of said residual signal; means for determining a dynamic threshold that depends on said non-linear error power estimate; means for comparing said residual power estimate to said dynamic threshold; and means for attenuating said residual signal if said residual power estimate falls below said dynamic threshold.
- 9. The apparatus of claim 8, comprising:means for determining a linear error power estimate of said residual signal; and means for determining a dynamic threshold that depends on both linear error power estimate and said non-linear error power estimate.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9504520 |
Dec 1995 |
SE |
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Parent Case Info
This application is a continuation of International Application No. PCT/SE96/01610, filed Dec. 6, 1996, which designated the United States, and which is expressly incorporated here by reference.
US Referenced Citations (8)
Foreign Referenced Citations (2)
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Date |
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0 604 948 |
Jul 1994 |
EP |
9519085 |
Jul 1995 |
WO |
Non-Patent Literature Citations (2)
Entry |
Slock, Dirk, “On the Convergence Behavior of the LMS and the Normalized LMS Algorithms”, Jour. of Lightwave Technology, IEEE, v41, n9, p2811-2845, Sep. 1993. |
Ljung, Lennart et al., “Theory and Practice of Recursive Indentification”, MIT Press, p 12-16, 88-96, 1983. |
Continuations (1)
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Number |
Date |
Country |
Parent |
PCT/SE96/01610 |
Dec 1996 |
US |
Child |
09/098506 |
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US |