Patent EP0518383A2 successfully refreshed from Google Patents.
EP0518383A2
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EP
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Method and arrangement of echo elimination in digital telecommunications system
Assignee: NEC Corp
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Filing: 1992-06-15
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Granted: —
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Expires: 2012-06-15
Abstract
Abstract In order to reduce the complexity of an adaptive digital filter used to cancel delayed network echoes, a delay circuit is arranged in series therewith and arranged to compensate for the delay inherent with a speech codec. In the case of a variable delay circuit, the degree by which the echo is delayed is detected in the adaptive digital filter and used to modify the delay time. A gain control arrangement can be provided and used to reduce the gain of the received signal when the near-end party is talking and the adaptive capacity of the adaptive digital filter is exceeded.
Inventors
- 👤 Hideo C/O Nec Corporation Sano
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 09:07
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
91 words
In a digital telecommunication system wherein a speech codec is arranged to encode a first signal to be transmitted and decode a second signal received, a method comprising the steps of: delaying said first signal by a first amount; supplying the delayed first signal to an adaptive digital filter; and producing a fourth signal by subtracting the output of said adaptive digital filter from a third signal which is produced by decoding the second signal at said speech codec and which exhibits a delay due to passage through said speech codec.
Claim 2
Dependent Claim
55 words
A method as claimed in claim 1, further comprising the steps of: monitoring the fourth signal and determining the amount by which an echo contained therein, is delayed; and varying said first amount by which said first signal is delayed in accordance with the amount by which the echo in said fourth signal is delayed.
Claim 3
Dependent Claim
104 words
A method as claimed in claim 2, further comprising the steps of: monitoring the level of the delayed first signal; monitoring the level of said third signal; monitoring the load on the adaptive digital filter; comparing the levels of the delayed first signal and said third signal; attenuating the third signal to produce a fifth signal in the event that the level of the delayed first signal is greater than the level of said third signal; and selecting said fifth signal in place of said fourth signal in the event that the load on the adaptive digital filter is above a predetermined load level.
Claim 4
Dependent Claim
107 words
A method as claimed in claim 2, further comprising the steps of: monitoring the level of the delayed first signal; monitoring the level of said third signal; monitoring the load on the adaptive digital filter; comparing the levels of the delayed first signal and said third signal; giving no attenuation to the third signal and producing a fifth signal in the event that the level of the delayed first signal is less than the level of said third signal; and selecting said fifth signal in place of said fourth signal in the event that the load on the adaptive digital filter is above a predetermined load level.
Claim 5
Dependent Claim
136 words
A method as claimed in claim 2, further comprising the steps of: monitoring the level of the delayed first signal; monitoring the level of said third signal; monitoring the load on the adaptive digital filter; comparing the levels of the delayed first signal and said third signal; attenuating the third signal to produce a fifth signal in the event that the level of the delayed first signal is greater than the level of said third signal; giving no attenuation to the third signal and producing a fifth signal in the event that the level of the delayed first signal is less than the level of said third signal; and selecting said fifth signal in place of said fourth signal in the event that the load on said adaptive digital filter is above a predetermined load level.
Claim 6
Dependent Claim
101 words
An arrangement for use in a digital telecommunication system, said arrangement including a speech codec for encoding a first signal to be transmitted and decoding a second signal received, said arrangement comprising: first means for delaying said first signal by a first amount; second means for supplying the delayed first signal to an adaptive digital filter; and third means for producing a fourth signal by subtracting the output of said adaptive digital filter from a third signal which is produced by decoding the second signal at said speech codec and which exhibits a delay due to passage through said speech codec.
Claim 7
Dependent Claim
56 words
An arrangement as claimed in claim 6, further comprising: means for monitoring the fourth signal and determining the amount by which an echo contained therein, is delayed; and means for varying said first amount by which said first signal is delayed in accordance with the amount by which the echo in said fourth signal is delayed.
Claim 8
Dependent Claim
142 words
An arrangement as claimed in claim 6, further comprising: means for monitoring the levels of the delayed first signal and said third signal; means for monitoring the load on the adaptive digital filter; means for comparing the levels of the delayed first signal and said third signal; means for attenuating the third signal to produce a fifth signal in the event that the level of the delayed first signal is greater than the level of said third signal and for giving no attenuation to the third signal and producing a fifth signal in the event that the level of the delayed first signal is less than the level of said third signal; and means for selecting said fifth signal in place of said fourth signal in the event that the load on said adaptive digital filter is above a predetermined load level.
References Cited (Backward Citations)
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