Method and arrangement of echo elimination in digital telecommunications system
First Claim
1. An arrangement for eliminating a network echo in a telecommunication system, said arrangement including a speech codec for encoding a first signal to be transmitted and for decoding a second signal received from a telecommunications network, said arrangement comprising:
- first means for variably delaying said first signal and for producing a delayed first signal;
second means for canceling said network echo, said second means being arranged to receive said delayed first signal and an output of said speech codec;
third means for controlling attenuation of said output of said speech codec, said third means being arranged in parallel with said second means;
fourth means for detecting a delay time of said network echo, said fourth means being coupled to said second means and controlling said first means using the detected delay time; and
fifth means for selecting one of the outputs of said second and third means, said fifth means selecting the output of said third means when said fourth means detects that the delay of said network echo exceeds an adaptive filtering capacity of said second means.
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Accused Products
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.
74 Citations
2 Claims
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1. An arrangement for eliminating a network echo in a telecommunication system, said arrangement including a speech codec for encoding a first signal to be transmitted and for decoding a second signal received from a telecommunications network, said arrangement comprising:
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first means for variably delaying said first signal and for producing a delayed first signal; second means for canceling said network echo, said second means being arranged to receive said delayed first signal and an output of said speech codec; third means for controlling attenuation of said output of said speech codec, said third means being arranged in parallel with said second means; fourth means for detecting a delay time of said network echo, said fourth means being coupled to said second means and controlling said first means using the detected delay time; and fifth means for selecting one of the outputs of said second and third means, said fifth means selecting the output of said third means when said fourth means detects that the delay of said network echo exceeds an adaptive filtering capacity of said second means. - View Dependent Claims (2)
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Specification