Appts. and method for non-linear processing in communication system

A non-linear processing and communication system technology, applied in the field of echo cancellation, can solve the problem of reducing the rate to determine the performance of the algorithm

Inactive Publication Date: 2008-01-09
GOOGLE TECH HLDG LLC
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Problems solved by technology

Thus, switching the synthesized comfort noise on and off can significantly degrade the performance of the rate determination algorithm

Method used

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  • Appts. and method for non-linear processing in communication system
  • Appts. and method for non-linear processing in communication system
  • Appts. and method for non-linear processing in communication system

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Embodiment Construction

[0023] In general, a modified nonlinear processor eliminates the source of comfort noise and replaces it with a direct input of a control signal to the noise suppression system. When the control signal is active, the noise suppression system uses the control signal to disable iterative revision of the background noise estimate, which prevents any residual echo from deviating from the noise estimate provided by the noise suppression system. Additionally, this control signal is used by a gain calculator in the noise suppression system to attenuate each frequency band to the maximum allowable amount plus the signal-to-noise ratio (SNR) of the current residual channel. According to this implementation, the noise suppression system can simulate the background noise of PSTN users or mobile station users.

[0024] More precisely, an apparatus for nonlinear processing in a communication system according to the present invention comprises, a means for analyzing an echo canceller refere...

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Abstract

An improved non-linear processor used in echo cancellation eliminates a comfort noise source (214) and instead inputs a control signal (224) directly into a noise suppression system (403). The noise suppression system (403) uses the control signal (224) to inhibit the iterative update of the background noise estimate when the control signal (224) is active, which prevents any residual echo from biasing the noise estimate provided by the noise suppression system (403). Additionally, the control signal (224) is used by a gain calculator (533) within the noise suppression system (403) to attenuate each frequency band to the maximum allowable amount plus the current residual channel signal-to-noise ratio (SNR). Depending on the implementation, the noise suppression system (403) models the background noise of either a user of the PSTN or a user of a mobile station.

Description

Technical field: [0001] The present invention relates generally to echo cancellation, and more particularly to improved nonlinear processing in communication systems. Background technique: [0002] The latest voice compression standards for digital cellular systems have considered noise suppression as an integral part of the signal preprocessing function. Although noise suppression is still optional in these standards, it is almost impossible to pass subjective conformance tests without noise suppression. While these standards address the need for noise suppression, they fail to address the impact of cascading noise suppression with other necessary preprocessing functions such as echo cancellation. Cascading an echo canceller with a noise suppressor can pose some problems. [0003] It is well known that when canceling electrical and acoustic echoes in communication systems, certain nonlinearities in the echo path (such as quantization noise, acoustic deviation, etc.) preve...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04M9/00H04M11/00H04B3/20H04M1/60H04B3/23H04M9/08
CPCH04M9/082H04B3/23
Inventor 詹姆斯·P·阿什利李·M·普罗克特
Owner GOOGLE TECH HLDG LLC
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