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Echo detection method and device

A detection method and echo technology, applied in the direction of line transmission monitoring/testing, line transmission components, wired transmission systems, etc.

Inactive Publication Date: 2013-01-23
TELEFON AB LM ERICSSON (PUBL)
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0012]The common disadvantage of the two methods described above is that neither of them can be directly applied to encoded speech without first decoding the speech signal.

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  • Echo detection method and device

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Embodiment Construction

[0026] In the following description, elements performing the same or similar functions are given the same reference names.

[0027] In order to detect echoes (echoes are reflections of a signal), a similarity measurement between the downlink and uplink signals is required. The echo path of an echo generated by a mobile handset is nonlinear and not stationary, making traditional similarity measurements using waveforms applied directly to the signal difficult.

[0028] In the following description, the GSM AMR (Adaptive Multi-Rate) speech codec will be used as an example, but many other speech codecs can be used for similar discussions, especially those based on CELP (Code Excited Linear Prediction) codec. The AMR codec works on a 20ms (160 samples) frame divided into four 5ms (40 samples) subframes. The parameters available in the AMR-decoded bitstream are the LSP (line spectral pair) vector, the fractional pitch lag (pitch period), the innovation code vector, and the pitch a...

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Abstract

An echo detector includes means (34) for forming a set of distance measures between pitch estimates of a first signal and pitch estimates of a second signal at predetermined delays with respect to the first signal. A selector (36) selects a distance measure from the set corresponding to the highest similarity between the first and second signals. A classifier (32) classifies the second signal as including an echo if the selected distance measure has a predetermined relation to a similarity threshold (TH).

Description

technical field [0001] The present invention relates generally to detection of signal similarity, and more particularly to echo detection in telecommunication systems. Background technique [0002] In some applications it is necessary to detect the presence of a possible modified version of a known speech signal in a received signal which may consist of several speech and noise components and to estimate the relative delay of the component of interest. Examples of such applications are echo control, network statistics collection, and multi-party conference bridges. [0003] Figure 1 illustrates a potential problem. The known speech signal is delayed in a delay block 10 and subjected to an unknown transition 12 on the way to the summing point. The known speech signal may or may not reach the summing point (switch 16 may be open or closed). At the summing point, the signal is mixed with other speech signals and noise. On the way back to the point where the signal was orig...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B3/46
CPCH04B3/468G10L21/02H04B3/493G10L21/0216H04B3/20
Inventor T·特鲁姆普A·埃里克森
Owner TELEFON AB LM ERICSSON (PUBL)