JPH0483429A - Residual echo suppressing system - Google Patents

Abstract

PURPOSE:To reduce the level of a residual echo at the time of starting a call by selecting either one of a signal outputted from a pseudo echo circuit and an incoming sound signal in accordance with a signaling signal and subtracting the echo component of an outgoing voice signal from the selected signal. CONSTITUTION:The pseudo echo circuit 11 imparts a delay time and an attenuation value corresponding to an echo route and a switching means 13 selects either one of a signal outputted from the circuit 11 and an incoming voice signal in accordance with a signaling signal applied from an digital exchange and a satellite relay circuit correspondingly to a speaking/non-speaking state and outputs the selected signal. An echo canceller 15 subtracts the echo component of the outgoing signal from the signal applied by the means 13 and sends the obtained signal to the satellite relay circuit. Even when speaking is started before restoring the echo canceller 15 to a steady state, a noise signal can be reduced and the quality of speaking at the time of its starting can be improved.

Description

[Detailed Description of the Invention] [Summary] A residual echo suppression method that converges the level of residual echo output as a noise signal from an echo canceller in a short time in response to instantaneous interruptions and disturbances that occur in a satellite relay line when there is no call. With regard to the upstream voice signal and In an audio device that interfaces with downlink audio signals provided from a satellite relay line, there is a pseudo-echo circuit that provides the downlink audio signal with a delay time and attenuation equivalent to the echo path formed within the digital exchange, and a call/no-call state. a switching means for selecting and outputting either the signal output from the doubtful echo circuit or the upstream audio signal in accordance with the signaling signal given from the digital exchange and the satellite relay line in response to the above;
and an echo canceller that subtracts the echo component of the downlink audio signal from the signal given by the switching means and sends the obtained signal to the satellite relay line.

[Industrial Application Field] The present invention provides a residual echo suppression method that converges the level of residual echo output as a noise signal from an echo canceller in a short time in response to instantaneous interruptions or disturbances that occur in a satellite relay line when there is no call. Regarding.

[Conventional technology]

The scope of application of satellite communication systems is now expanding to include not only international communications (domestic communications, mobile communications, etc.), but also communication networks connected via satellite relay lines Digitalization is underway to meet the demands of transformation.

FIG. 3 is a diagram showing an example of the configuration of an interface between a digital exchange and a satellite relay line.

In the figure, a subscriber terminal 31 is connected to a digital exchange 32 via a two-wire subscriber line. digital exchange 3
In 2, this subscriber line includes an OD! - 2-wire/4-wire conversion is performed by rank 34, and a time switch 35 that configures the communication path, and a DTK that takes a predetermined interface for each line)) Takes a predetermined interface to connect to the satellite relay line via rank 36 It is connected to the satellite relay line interface section 37.

The satellite relay line interface section 37 is connected to the audio device 38. The audio bag W38 includes an echo canceller 39 that subtracts echo components from the upstream audio signal provided from the digital exchange 32. The audio device 3 is also connected to the satellite relay line via the multiplexing/demultiplexing unit 40, and provides an interface between the digital exchange 32 and the satellite relay line regarding upstream audio signals and downstream audio signals provided from the satellite relay line. Take. The multiplexing/demultiplexing unit 40 performs multiplexing/demultiplexing according to the line configuration of the wireless section connecting the earth station and the communication satellite.
Perform separation.

In an interface system with such a configuration, the satellite relay line and the digital exchange 32 are connected via a 4-wire interface corresponding to the above-mentioned wireless section, and the connection between the digital exchange and the subscriber terminal 31 is a 2-wire interface. connected via a formal subscriber line.

Therefore, a part of the downlink audio signal (hereinafter referred to as "echo component") that is input to the digital exchange 32 via the audio device 38 during a call is transmitted to the hybrid circuit 33, time switch 35, DTK trunk 36, and satellite relay line. The sound is returned to the audio bag W38 via the echo path formed by the interface section 37. Note that such a reverberation path is formed by impedance imbalance between the hybrid circuit 33 and its peripheral circuits. Audio device 38
Then, the echo canceller 39 subtracts an echo component corresponding to the downlink audio signal from the uplink audio signal, and the signal thus obtained is sent to the multiplexing/demultiplexing section 40. Note that if the echo canceller 39 cannot sufficiently remove the echo component, the echo component remaining in the upstream audio signal will be transmitted to the caller of the terminal device connected via the satellite relay line as an echo of the own voice. It appears as if.

[Problem to be solved by the invention]

By the way, in such a conventional interface system, since the communication path within the digital exchange 32 is not formed when there is no call, the above-mentioned echo path is also not formed. Therefore, in the audio device 38, since there is no correlation between the upstream audio signal and the downstream audio signal applied to the echo canceller 39, the echo canceller 39 responds to noise and other input signals, but quickly returns to a steady state. cannot return to.

That is, when the echo canceller 39 is given a noise signal due to a momentary interruption or disturbance that occurs in the satellite relay line when there is no call, the echo canceller 39 outputs the noise signal as a residual echo obtained as a result of calculation according to this noise signal. It takes a long time for the noise signal to disappear and return to the no-signal state.

Furthermore, if a call starts on this line before the echo canceller 39 returns to a steady state, this noise signal (residual echo) is sent to the subscriber terminal via the satellite relay line.

SUMMARY OF THE INVENTION An object of the present invention is to provide a residual echo suppression method capable of reducing the level of residual echo transmitted to a subscriber terminal via a communication path at the start of a call.

[Means to solve the problem] FIG. 1 is a block diagram of the principle of the present invention.

In the figure, the audio device interfaces between the digital exchange and the satellite relay line for upstream voice signals provided from the digital exchange and downstream voice signals provided from the satellite relay line.

In the residual echo suppression method in the audio device, the pseudo-echo circuit 11 gives the downlink audio signal a delay time and an attenuation amount corresponding to the echo path formed within the digital exchange.

The switching means 13 selects either the signal output from the pseudo-echo circuit 11 or the upstream audio signal in response to the signaling signal given from the digital exchange and the satellite relay line in response to the call/no-call state. and output it.

The echo canceller 15 subtracts the echo component of the downstream audio signal from the signal provided by the switching means 13,
The obtained signal is sent to a satellite relay line.

[For production]

In the present invention, the switching means 13 recognizes whether the corresponding line is in a call state or a non-call state according to the signaling signal given from the digital exchange and the satellite relay line, and when the corresponding line is in a call state, an echo canceller is used. 15 is given an upstream voice signal from the exchange. The echo canceller 15 subtracts the echo component of the downstream audio signal from the applied upstream audio signal, and sends the obtained signal to the satellite relay line.

On the other hand, the pseudo-echo circuit 11 always outputs the downstream audio signal by giving it a delay time and an attenuation amount corresponding to the echo path formed in the digital exchange. The switching means 13 supplies the signal output from the pseudo-echo circuit 11 to the echo canceller 15 when there is no call.

In this way, the echo canceller 15 operates with the same echo path connected regardless of whether there is a call or no call.

Therefore, instantaneous interruption of the satellite relay line due to no call,
If a call starts on this line immediately after a noise signal is given as a downlink voice signal due to a disturbance, the echo canceller 15 quickly returns to a steady state, so the echo canceller 15 responds to the above-mentioned noise signal to the terminal. The noise signal (residual echo) sent to the device is reduced.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention.

In the figure, the same components and functions as those in FIG. 3 are denoted by the same reference numerals, and the explanation thereof will be omitted here.

The configuration that characterizes the present invention is that in this embodiment, the audio device 2
1 is S R (Sig
5S (S'r) signal provided from the satellite relay line interface section 37
Gnalling 5end > Signal C and below, these are -
These are collectively referred to as "signaling signals." ), a feedback circuit 23 that constitutes an echo path (pseudo-echo path) in place of the digital exchange 32, and an upstream audio signal provided from the satellite relay line interface section 37 and an upstream audio signal provided via the feedback circuit 23. The present invention includes a selector circuit 24 that selects one of the downstream audio signals according to the signal output from the OR gate 22 and supplies the selected signal to the echo canceller 39. The feedback circuit 23 is composed of a delay circuit 25 that gives a predetermined delay time to the applied downstream audio signal, and an attenuator 26 that has a predetermined amount of attenuation. have equivalent characteristics. Regarding the correspondence with the principle block diagram shown in FIG.
corresponds to the switching means 13.

In the audio device 21 having such a configuration, in a no-call state, the selector circuit 24 provides the echo canceller 39 with the signal output from the feedback circuit 23 instead of the upstream audio signal in response to the switching signal provided from the OR gate 22. . Therefore, the echo canceller 39 is provided with a noise signal generated in response to a momentary interruption or disturbance in the satellite relay line during a no-call state as a downlink audio signal, and the echo canceller 39 is configured to combine that noise signal with the noise signal provided via the feedback circuit 23. Since there is a certain correlation between the two, the steady state is quickly restored.

Additionally, if a call is started using this line before the echo canceller 39 returns to a steady state, the selector circuit 2
4 provides the upstream audio signal provided from the digital exchanger 32 to the echo canceller 39 in response to the switching signal provided from the OR gate 22. However, exchange 32
In this case, the communication path via the digital time switch 35 is formed prior to this, and the echo path via the hybrid circuit 33 is also formed at the same time. The correlation between the signal given to No. 39 and the downstream audio signal remains unchanged.

Therefore, the echo canceller 39 quickly returns to a steady state, and the noise signal sent to the subscriber terminal via the satellite relay line is reduced.

[Effects of the Invention] As described above, according to the present invention, it is possible to maintain a constant correlation between the upstream audio signal and the downstream audio signal input to the echo canceller in both the no-call state and the conversation state. can.

That is, the echo canceller is given a noise signal due to momentary interruption or disturbance of the satellite relay line when there is no call, but it quickly returns to a steady state.

Therefore, if a call is started using this line before the echo canceller returns to a steady state, the noise signal sent to the subscriber terminal via the satellite relay line is reduced, and the call quality at the start of the call is improved. improves.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing an example of the configuration of an interface between a digital exchange and a satellite relay line. In the figure, 1 is a pseudo echo circuit, 3 is a switching means, 5.39 is an echo canceller, 1.3 is an audio device, 2 is an OR gate, 3 is a feedback circuit, 4 is a selector circuit, 5 is a delay circuit, and 6 is a delay circuit. Attenuator, ■ is subscriber terminal, 2 is digital exchange, 3 is hybrid circuit, 4 is OD trunk, 5 is time switch, 6 is DTK) rank, 7 is satellite trunk line interface section, 0 is multiplexing/demultiplexing section be.

Claims (1)

[Claims] (1) In an audio device that interfaces between a digital exchange and a satellite relay line for upstream audio signals provided from the digital exchange and downstream audio signals provided from the satellite relay line, a pseudo echo circuit (11) that provides a delay time and an attenuation amount corresponding to the echo path formed in the echo path; a switching means (13) for selecting and outputting either the signal output from the pseudo-reverberation circuit (11) or the upstream audio signal; An echo canceller (15) that subtracts an echo component of the signal and sends the obtained signal to the satellite relay line.