JP3597130B2 - Echo canceller control system and method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an echo canceller that cancels echo contained in a telephone network connected to an ATM (Asynchronous Transfer Mode) network that performs high-speed, large-capacity transmission. In particular, the present invention relates to an echo canceller control system and method for controlling operation stop and recovery of an echo canceller according to different types of telephone networks.
[0002]
[Prior art]
In connection with a recent connection between a telephone network and an ATM or conversion of a telephone network to an ATM, a form in which telephone communication is performed from an existing two-line analog subscriber line via an ATM network has been considered.
In such a case, an echo canceller for canceling the echo generated by the two-wire / four-wire conversion circuit (H) is essential.
Contrary to the above case, depending on the form of the network, the installation position of the echo canceller, etc., a subordinate connection of the echo canceller may occur.
[0003]
Furthermore, a terminal that does not originally generate an echo and does not require an echo canceller, such as an ISDN (Integrated Service Digital Network) terminal that employs a ping-pong transmission method, may be connected to the echo canceller.
In the case of the above-described subordinate connection of the echo canceller, in the case of a terminal that does not require an echo canceller, there is a problem of deterioration of speech quality.Therefore, in the subordinate connection, the latter-stage echo canceller is stopped. It is necessary to stop the echo canceller.
[0004]
Hereinafter, an example of the echo canceller to be stopped will be specifically described.
FIG. 10 is a diagram showing a schematic configuration for explaining the stop of the echo canceller related to the cascade connection of the echo canceller. This figure shows a configuration example in the case where communication of the existing telephone networks 123 and 124 is performed via the ATM network 125.
It is assumed that the telephones 121 and 122 accommodated in the existing telephone networks 123 and 124 respectively make telephone calls via the ATM 125.
[0005]
In the case of passing through the ATM 125, the delay increases due to the delay caused by the conversion of the ATM cells into the ATM cells in the nodes 126 and 127, so that the echo cancellers 128 and 129 are required.
In the case of FIG. 10, echo cancelers 128 and 129 may be installed at nodes 126 and 127 which are connection points between the existing telephone networks 123 and 124 and the ATM network 125, respectively.
[0006]
The echo canceller 128 cancels the echo generated in the two-wire / four-wire conversion circuit (H: hybrid circuit) 130 in which the telephone 121 is accommodated. Similarly, the echo canceller 129 is a two-wire / four-wire conversion circuit in which the telephone 121 is accommodated. (H) The echo generated at 130 is deleted.
That is, in the communication between the telephones 121 and 122, two echo cancellers 128 and 129 are installed, one on each side.
[0007]
In this case, for example, instead of the telephone 121, a user of a company or the like uses a PBX (Private Branch Exchange) 133 in which the echo canceller 135 is installed, and the two-wire / four-wire conversion circuit (H) 134 and the echo canceller 135 under the PBX 133. The analog telephone 132 may be connected to the ATM network 125 through the network.
In this case, a plurality of echo cancellers 128 and 135 are cascaded where one echo canceller should respond to the two-wire / four-wire conversion circuit (H) 134 where an echo occurs.
[0008]
In such a cascade connection of the echo cancelers 128 and 135, there is a first problem that the communication quality of the second-stage echo canceller 128 is lower than that of the first-stage echo canceller 135 until the operation is stabilized. .
For this reason, when the echo cancelers 128 and 135 are subordinate, it is necessary to stop the operation of the second-stage echo canceller.
[0009]
FIG. 11 is a diagram for explaining the stop of the echo canceller related to the two-wire digital extension system (ping-pong transmission system) of the digital multifunction telephone.
As shown in the figure, when a digital multi-function telephone 201 such as an ISDN terminal is used as a terminal, the digital multi-function telephone 201 and the digital multi-function telephone 201 are physically accommodated in the digital PBX extension circuit 202 with two wires 208. Since ping-pong transmission is performed so that signals do not overlap with the PBX 202, no echo is generated in the two-wire / four-wire conversion circuits (H) 206 and 207.
[0010]
FIG. 12 is a diagram for explaining the stop of echo cancellation for the 4-wire digital extension system of the digital multifunction telephone.
As shown in the figure, when the telephone is accommodated by four wires, the driver 224 of the digital multifunction telephone 221 and the receiver 227 of the digital PBX extension circuit 222, and the receiver 225 of the digital multifunction telephone 221 and the digital PBX extension circuit Since the driver 228 of the 222 is connected to the four lines 226 independently of each other in the upward and downward directions, naturally, no echo is generated.
[0011]
If the echo canceller is applied to a place where no echo occurs, there is a second problem that the operation is not guaranteed.
Therefore, it is necessary to stop the operation of the echo canceller even when no echo occurs.
Further, the first problem will be described in detail.
[0012]
As a method for stopping the operation of the echo canceller, for example, as disclosed in Japanese Patent Application Laid-Open No. H11-289280, the residual echo attenuates to a predetermined value and converges to a steady state. The time until the value becomes less than or equal to the predetermined value is measured, and the operation of the echo canceller is stopped when the measured time exceeds a predetermined value, that is, when the convergence time is longer than usual.
[0013]
A conventional echo canceller disclosed in Japanese Patent Application Laid-Open No. 11-289280 will be described below.
FIG. 13 is a diagram illustrating the configuration of a conventional echo canceller. As shown in the figure, the echo canceller 101 includes a far-end signal 102, a pseudo echo generation circuit 103, a two-wire / four-wire conversion circuit (H) 104, a near-end signal 105, an echo cancellation circuit 106, and a residual echo measurement circuit. 107, a judgment circuit 108, operation / stop control circuits 109 and 110, and an input pattern detection circuit 111.
[0014]
Next, the operation will be described in detail. A pseudo echo is generated by the pseudo echo generation circuit 103 based on the far-end signal 102.
In practice, a part of the far-end signal 102 wraps around as an echo in the two-wire / four-wire conversion circuit 104 and is superimposed on the near-end signal 105 and input to the echo canceller 101.
The echo canceling circuit 106 takes in the far-end signal 102 and calculates the near-end signal 105 on which the pseudo-echo generated by the pseudo-echo generation circuit 103 and the echo generated by the two-wire / four-wire conversion circuit 104 are superimposed. , Realizing echo cancellation.
[0015]
However, since the pseudo echo generation circuit 103 cannot immediately generate a pseudo echo with high accuracy, the residual echo measurement circuit 107 measures the output residual echo of the echo cancellation circuit 106 and feeds back the pseudo echo generation circuit 103. .
The residual echo measuring circuit 107 measures the magnitude of the residual echo and measures the time during which the state where the magnitude is equal to or greater than a predetermined value continues.
[0016]
The determination circuit 108 generates an echo canceller stop signal when the duration measured by the residual echo measurement circuit 107 becomes equal to or longer than a predetermined value.
The echo canceler operation stop control circuits 109 and 110 operate or stop the echo canceller based on the reset or echo canceler stop signal from the determination circuit 108.
[0017]
When the echo canceller is in a stopped state, when the input signal of the echo canceller changes from a predetermined pattern to a normal input, for example, when all data is changed from “0” to some data, It has been proposed to reset the echo canceller to put the echo canceller into operation.
FIG. 14 is a diagram illustrating the amount of echo with respect to the elapsed time at the first-stage and second-stage echo canceller Sout terminals.
[0018]
A detailed description will be given of the operation of the cascade connection, in this case, the two-stage connection, with reference to FIG.
As shown in the figure, the time from T0 to T1 until the echo amount reaches the predetermined value x is measured, and if the residual echo amount at the time when the measurement time has elapsed is equal to or larger than the predetermined value x, the echo canceller stop signal Is generated and the echo canceller is stopped.
[0019]
That is, since the second-stage echo canceller learns based on the output of the first stage, it becomes unstable during the learning, and converges to the specified value x of the second stage that is cascaded from the first stage. It has a characteristic that the time T2 becomes longer.
The resetting of the echo canceller from the stop state to the operating state is an operation normally performed as an echo canceller when the echo path changes, such as when a new call is set, and is normally performed by a call signal.
[0020]
When a new call is set up, the decision circuit 108 in FIG. 13 starts a decision operation. On the other hand, when a new call is set, it is time to shift from a non-communication state to a state in which a signal is transmitted and received, as viewed from the input signal of the echo canceller.
In a state of no call, a predetermined pattern such as a silent pattern is input, and the level does not normally change.
[0021]
On the other hand, in a call state, a signal accompanied by some level change due to a background sound or the like is input even if there is no sound.
The input pattern detection circuit 111 shown in FIG. 13 monitors the input signal while the operation is stopped, detects a point in time when a signal accompanied by a level change is input from a predetermined pattern in a no-communication state, and resets the echo canceller accordingly. Then, the determination circuit 108 can start the determination operation.
[0022]
The first problem is that, in the above-described prior art, the echo canceller cannot be stopped until after the convergence time, so that the speech quality deteriorates due to instability in the convergence process until the echo canceller stops. That is the problem.
[0023]
[Problems to be solved by the invention]
Accordingly, the present invention has been made in view of the above-described problems, and has made it possible to prevent the quality deterioration caused by the instability of the convergence process until the echo canceller is stopped for the second and subsequent echo cancellers in the cascade connection. It is another object of the present invention to provide an echo canceller control system and method for guaranteeing operation of an echo canceller to which an echo canceler unnecessary terminal that does not originally generate an echo is connected.
[0024]
[Means for Solving the Problems]
The present invention solves the above problems, in an echo canceller control system for canceling an echo generated in a telephone network connected to a high-speed, large-capacity transmission network, measuring an input echo amount, An echo measuring unit for calculating an input echo increase / decrease amount from the input echo amount, and an operation for canceling and stopping the operation of the echo based on the input echo amount measured by the echo measuring unit and the calculated input echo increase / decrease amount. -To provide an echo canceller control system including an operation stop unit.
[0025]
By this means, it is possible to prevent the call quality from being deteriorated due to the instability of the convergence process until the echo canceller stops in the second and subsequent stages in the cascade connection, and originally no echo is generated. The operation is guaranteed for the echo canceller to which an echo canceler unnecessary terminal is connected.
Preferably, the echo measurement unit is provided with a double talk detection circuit, wherein the double talk detection circuit detects double talk in which a signal from the network side and a signal from the telephone network side are simultaneously input, and detects the double talk. Sometimes, the measurement of the input echo amount and the calculation of the input echo increase / decrease amount are stopped, and the operation / operation stop unit stops the operation of canceling the echo.
[0026]
By this means, when the double talk occurs, the echo amount cannot be measured correctly, so that the measurement of the input echo amount and the calculation of the input echo increase / decrease amount are not performed, and further, the operation of canceling the echo can be stopped.
Preferably, the echo measuring unit is provided with a timer, the timer generates a timing of a cycle shorter than the convergence time of the echo attenuated, to measure the input echo amount, to calculate the input echo increase / decrease amount Let me use it.
[0027]
By this means, it is possible to quickly stop and restore the operation of the echo canceller according to different types of telephone networks.
Preferably, the operation / operation stop unit includes:If the calculated input echo increase / decrease is equal to or greater than the first predetermined value, the operation of echo cancellation is stopped, and the calculated input echo increase / decrease is equal to or greater than the first predetermined value. If it is the echo increase amount, the operation of echo cancellation is performed.
[0028]
Furthermore, preferably, the operation / operation stop unit includes:When the calculated input echo increase / decrease amount is less than a first predetermined value, and the measured input echo amount is less than a second predetermined value, the operation of echo cancellation is stopped, and the calculated When the input echo increase / decrease amount is less than the first predetermined value and the measured input echo amount is equal to or more than the second predetermined value, an echo canceling operation is performed.
By these means, it is possible to recognize and determine whether the echo canceller is the first stage or the second stage in the cascade connection, so that the operation of canceling the echo can be stopped.
[0029]
Further, since it is possible to recognize and determine whether or not the first stage of the echo canceller has an echo, it is possible to perform the operation of canceling the echo.
In addition, regardless of whether or not there is an echo canceller at the connection destination, the device can be freely designed, the products can be easily shared, and the cost can be reduced.
Preferably, the high-speed, large-capacity transmission network is an ATM network, and the telephone network includes a telephone network without echo cancellation, a telephone network with echo cancellation, and a digital telephone network without echo generation.
[0030]
By this means, it becomes possible to apply the ATM network as a high-speed, large-capacity transmission network.
Further, the present invention provides an echo canceller control method for canceling an echo generated in a telephone network connected to a high-speed, large-capacity transmission network, wherein the input echo amount is measured, and the input echo is increased or decreased from the measured input echo amount. An echo canceling operation based on the measured input echo amount and the calculated input echo increase / decrease amount. .
[0031]
By this means, similarly to the above invention, it is possible to prevent the speech quality deterioration caused by the instability of the convergence process until the echo canceller stops in the second and subsequent stages in the cascade connection, The operation is guaranteed for an echo canceller connected to a terminal that does not generate an echo and that does not require an echo canceller.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of an echo canceller control system according to the present invention.
As shown in the figure, the echo canceller 301 is provided with a Rin terminal 313, a Rout terminal 314, a Sin terminal 315, and a Sout terminal 316.
[0033]
A Rout terminal 314 outputs a reception signal to a two-wire / four-wire conversion circuit (H: hybrid circuit) 304, and a Sin terminal 315 receives a near-end signal 303 as a transmission signal from the two-wire / four-wire conversion circuit (H) 304. I do.
In the near-end signal 303, a part of the far-end signal 302 generated due to impedance mismatch of the two-wire / four-wire conversion circuit (H) 304 is superimposed on the transmission signal.
[0034]
The Rout terminal 314 receives the far-end signal 302, which is a received signal, from the network side, and the Sout terminal 316 outputs a transmission signal from which the echo of the received signal has been eliminated to the network side.
The echo canceller 301 includes an echo measuring unit 320 and an operation / operation stopping unit 330.
The operation / stop unit 330 of the echo canceller 301 is provided with a pseudo echo generation circuit 305, and the pseudo echo generation circuit 305 generates a pseudo echo based on the far-end signal 302.
[0035]
An echo canceling circuit 310 is connected to the pseudo echo generating circuit 305. The echo canceling circuit 310 cancels the echo by subtracting the pseudo echo generated by the pseudo echo generating circuit 305 from the near-end signal 303.
Note that the pseudo echo generation circuit 305 is connected to the output of the echo cancellation circuit 310, obtains a residual echo, and uses this as feedback.
[0036]
Pass / bypass circuits 311 and 312 are provided before and after the echo canceling circuit 310, and the passing / bypassing circuits 311 and 312 enable the near-end signal 303 to pass through or bypass the echo canceling circuit 310.
Further, an echo measuring circuit 308 is provided in the echo measuring unit 320 of the echo canceller 301, and the echo measuring circuit 308 inputs the far-end signal 302 and the near-end signal 303, and calculates the input echo amount of the near-end signal 303. Measure and calculate input echo increase / decrease.
[0037]
A timer 306 is connected to the echo measurement circuit 308, and the timer 306 generates a period that is extremely shorter than the convergence time of the echo cancellation. The timer 306 measures the input echo amount and calculates the input echo increase / decrease amount at predetermined intervals. Let it do. The generation of such an extremely short period enables measurement of the input echo amount and calculation of the input echo increase / decrease amount at an extremely short timing, and promptly switches the operation of the echo canceller and the stop of the operation according to different types of telephone networks. It is possible to do.
[0038]
Further, a double talk detection circuit 307 is connected to the echo measurement circuit 308. The double talk detection circuit 307 receives the far-end signal 302 and the near-end signal 303, detects double talk, and outputs double talk detection information. Output to the echo measurement circuit 308.
The switching determination circuit 309 of the operation / operation stopping unit 330 is connected to the echo measurement circuit 308 and the timer 306, and the switching determination circuit 309 determines the pseudo echo generation circuit 305 and the pass / fail based on the outputs of the echo measurement circuit 308 and the timer 306. The detour circuits 311 and 312 are controlled.
[0039]
That is, the switching determination circuit 309 determines the input echo attenuationPlaceTo determine the convergence of the input echo amount when it exceeds the fixed valuePlaceIf the value is less than the predetermined value, the pseudo echo generation circuit 305 is controlled to stop the generation of the pseudo echo, and the pass / bypass circuits 311 and 312 are controlled to the echo cancellation circuit 310 for the near-end signal 303. Enable detours.
[0040]
Further, the switching determination circuit 309 determines the input echo increase amount.PlaceTo determine the convergence of the input echo amount when it exceeds the fixed valuePlaceIf the value is equal to or more than the predetermined value, the pseudo echo generation circuit 305 is controlled to enable restoration of the generation stop of the pseudo echo, and the pass / bypass circuits 311 and 312 are controlled to the echo cancellation circuit 310 for the near-end signal 303. Allow the passage of
[0041]
FIG. 2 is a diagram illustrating the double talk detection circuit 307 in FIG. As shown in the figure, the far-end signal 302 is input to the Rin terminal 313 from the network side, and the near-end signal 303 is input to the Sin terminal 303 from the two-wire / four-wire conversion circuit (H) 304.
When the far-end signal 302 and the near-end signal 303 are simultaneously input to the double-talk detection circuit 307, double-talk is detected. When double talk occurs, the echo amount cannot be correctly measured. Therefore, the double talk detection circuit 307 outputs information of double talk detection to the echo measurement circuit 306, and inputs the echo to the echo measurement circuit 308 when double talk is detected. The measurement of the amount and the calculation of the input echo increase / decrease amount are not performed.
[0042]
When double talk is detected, the switching determination circuit 309 performs a bypass operation of the passing / bypass circuits 311 and 312 with respect to the echo cancellation circuit 310.
FIG. 3 is a diagram illustrating the measurement of the input echo amount by the echo measurement circuit 308 and the calculation of the input echo increase / decrease amount. As shown in the figure, in the echo measurement circuit 308, the horizontal axis represents time (t) and the vertical axis represents the echo amount (E). , Tn + 1, tn + 2,...
[0043]
Further, the echo measurement circuit 308 receives the far-end signal 302 from the Rin terminal 313 and the near-end signal 303 from the Sin terminal 315, and uses the above timings tn, tn + 1, tn + 2,. , En + 1, En + 2,...
Further, the echo measuring circuit 308 obtains the input echo increase / decrease amounts Δ..., ΔEn, ΔEn + 1,... Using the measured input echo amounts..., En, En + 1, En + 2,. Can be
ΔEn = ΔEn + 1−ΔEn
[0044]
FIG. 4 is a diagram illustrating the switching determination of the switching determination circuit 309. First, the switching determination circuit 309 forms a switching control signal of stop recovery / pass, stop / bypass based on the input echo increase / decrease amount by using the timings... Tn, tn + 1, tn + 2,.
That is, the input echo increase / decrease amounts..., ΔEn, ΔEn + 1, ΔEn + 2,... Input from the echo measurement circuit 308 are divided by ± ΔE0, and a switching control signal depending on the divided range is output.
[0045]
That is, in a range exceeding + ΔE0, the switching determination circuit 309 outputs an operation / pass switching control signal.
In a range below −ΔE0, the switching determination circuit 309 outputs an operation stop / bypass switching control signal.
.., En, En + 1, En + 2,... Input from the echo measurement circuit 308 are divided by ΔE0 in the range of ± ΔE0, and are switched in the range exceeding E0, as shown in FIG. The decision circuit 309 outputs an operation / pass switching control signal.
[0046]
When the input echo amount is in the range between 0 and E0, the switching determination circuit 309 outputs an operation stop / bypass switching control signal.
FIG. 5 illustrates an example in which the echo canceller 301 according to the present invention is used as a node in an ATM network. As shown in the figure, an echo canceller 301 is provided at one node 410 of an ATM network 420 that performs high-speed, large-capacity transmission.
A plurality of telephone networks 401 to 403, ..., 404 to 406, ..., 407 to 409, ... are connected to the node 410.
[0047]
It is assumed that a plurality of telephone networks 401 to 403 are provided with telephones 401A to 403A and two-wire / four-wire conversion circuits (H) 401B to 403B, respectively, and do not have an echo canceller.
The plurality of telephone networks 404 to 406 are PBXs (Private Branch Exchanges), which are provided with telephones 404A to 404A, 2-wire to 4-wire conversion circuits (H) 404B to 406B, and echo cancellers 404C to 406C, respectively.
[0048]
The plurality of telephone networks 407 to 409 are ISDN (Integrated Service Digital Network) digital PBX (Private Branch Exchange) networks employing a ping-pong transmission scheme, or 4-wire digital extension type digital PBX (Private Branch Exchange) networks. , Which are provided with digital multifunction telephones 407A to 409A, respectively.
[0049]
FIG. 6 shows a case where a plurality of telephone networks 404 to 406 are connected to the echo canceller 301 shown in FIG. It is a figure which shows a quantity.
As shown in the figure, when the communication path to the echo canceller 301 is switched in the order of the telephone networks 404 to 406, the echo amount has not yet been eliminated at the Sin terminal of each first-stage echo canceller, so that the echo amount has been reduced. Although it is constant, the echo amount is reduced at the Sin terminal 315 of the second stage echo canceller 301 according to the present invention because the echo is canceled immediately after the switching of the communication path.
[0050]
Therefore, it is possible to recognize and determine whether the echo canceller 301 itself is the first stage or the second stage by using the difference between the echo amounts at the Sin terminal 315 of the echo canceller 301.
In such a case, in the echo canceller 301 of the present invention, the switching / decision circuit 309 controls the passing / bypass circuits 311 and 312 based on the attenuation amount of the input echo amount, and the near-end signal 303 is converted to the echo cancellation circuit 310. Will be bypassed.
[0051]
In this manner, in the cascade connection, the second-stage echo canceller 301 recognizes the existence of the first-stage echo canceller based on the attenuation amount of the input echo amount, and cancels the echo in the first-stage echo canceller. Therefore, the operation of the second-stage echo canceller 301 itself is stopped before the convergence of the echo. As a result, it is possible to prevent the deterioration of the communication quality caused by the instability of the convergence process occurring until the stop after the convergence as in the related art.
[0052]
FIG. 7 is a diagram illustrating an echo amount with respect to the elapsed time of the Sin terminal 315 when a plurality of telephone networks 401 to 403 or a plurality of telephone networks 407 to 409 are connected to the echo canceller 301 of FIG.
As shown in FIG. 3A, when the echo canceller 301 according to the present invention is connected to one of the telephone networks 401 to 403, the echo amount has not yet been canceled at the Sin terminal 305 of the echo canceller 301, so that the echo amount Is constant.
[0053]
In such a case, in the echo canceller 301 of the present invention, the change of the input echo increase / decrease amount is small and the input echo amount is constant, but the input echo amount is E.0Since the switching / detouring circuits 311 and 312 are controlled by the switching determination circuit 309 based on the input echo amount, the near-end side signal 303 passes through the echo canceling circuit 310.
In this way, it is possible to recognize the plurality of telephone networks 401 to 403 having no echo canceller, operate the echo canceller 301 for the plurality of telephone networks 401 to 403, and cancel the echo.
[0054]
As shown in FIG. 3B, when the echo canceller 301 according to the present invention is connected to one of the telephone networks 407 to 409, no echo is generated in the telephone networks 407 to 409, so that the Sin of the echo canceller 301 The terminal 305 shows a constant value with a small echo amount.
That is, when an echo source such as a two-wire / four-wire conversion circuit (H) is not visible from the echo canceller 301 (is not connected), the amount of echo at the Sin end 315 of the echo canceller 301 is small regardless of the passage of time. Indicates a constant value.
[0055]
By utilizing this characteristic, it is possible to recognize and determine that the echo source is not visible from the echo canceller 301.
In such a case, in the echo canceller 301 of the present invention, the change of the input echoSmallTherefore, the pass / bypass circuits 311 and 312 are controlled by the switching determination circuit 309, and the near-end signal 303 bypasses the echo cancellation circuit 310.
[0056]
In this way, the plurality of telephone networks 407 to 409 that do not generate an echo canceller are recognized, and the operation of the echo canceller 301 stops for the plurality of telephone networks 407 to 409.
As a result, it is possible to prevent the deterioration of the communication quality due to the operation of the echo canceller 301 for a plurality of telephone networks 407 to 409 that do not generate an echo as in the related art.
According to the above description, it is possible to freely design an apparatus regardless of whether or not an echo canceller is present at the connection destination, and it is easy to use common products and to reduce costs.
[0057]
FIG. 8 is a diagram showing the amount of echo with respect to the elapsed time of the Sin terminal 315 when a different telephone network is connected to the echo canceller 301 of FIG.
As shown in FIG. 7A, the connection of the path is switched from a state in which telephone networks 407 to 409 that do not generate an echo are connected to the echo canceller 301 to a telephone network 401 to 403 that does not have an echo canceller.
In such a case, in the echo canceller 301 of the present invention, the change in the input echo increase E ΔE of the input echo E becomes large (> + ΔE) at the time when the connection of the passage is switched.0)Therefore, the switching / judging circuit 309 switches the passing / bypass circuits 311 and 312 from the bypass control to the pass control.
[0058]
As shown in FIG. 6B, the connection of the path is switched from the state in which the telephone networks 401 to 403 without an echo canceller are connected to the echo canceller 301 to the telephone networks 407 to 409 which do not generate an echo.
In such a case, in the echo canceller 301 of the present invention, the change of the input echo attenuation E of the input echo E becomes large (<-ΔE) at the time of switching the connection of the passage.0)Therefore, the switching / judgment circuit 309 switches the passage / detour circuits 311 and 312 from pass control to detour control.
[0059]
FIG. 9 is a flowchart illustrating a series of operations of the echo canceller control system in FIG.
In step S101, a cycle that is extremely shorter than the convergence time of echo cancellation generated by the timer 306 is used as a trigger, and the flowchart from step S101 to step S110 is executed. First, double talk is detected by the double talk detection circuit 307. Is The process ends while double talk is being detected.
[0060]
If double talk is not detected in step S102, the echo measurement circuit 308 measures the amount of input echo.
In step S103, the input echo increase / decrease amount is calculated and obtained using the previous measurement value of the input echo amount.
In step S104, the switching judgment circuit 309 judges whether or not the input echo increase / decrease amount has an input echo attenuation amount equal to or more than a predetermined value. If there is no input echo attenuation equal to or more than the predetermined value, the process proceeds to step S107.
[0061]
If the input echo attenuation is equal to or more than the predetermined value in steps 105 and S106, the switching determination circuit 309 stops the operation of the pseudo echo generation circuit 305 and performs the detour operation of the echo cancellation circuit 310, and ends the processing. stand by.
If it is determined in step S107 that the input echo increase / decrease amount does not exceed the predetermined value by the switching determination circuit 309, the process proceeds to step S110.
[0062]
In steps S108 and S109, if there is an input echo increase amount equal to or larger than the predetermined value, the switching determination circuit 309 performs the operation restoration of the pseudo echo generation circuit 305 and the passing operation of the echo cancellation circuit 310, and waits for processing.
In step S110, it is determined whether or not convergence has been performed using the measured value of the input echo amount. If the measured value of the input echo amount is equal to or larger than the predetermined value, it is determined that the input echo amount has not converged, and the process proceeds to step S108.
[0063]
Further, when the measured value of the input echo amount is smaller than the predetermined value, it is determined that the input echo amount has converged, and the process proceeds to step S105.
As described above, the echo canceller 301 measures and calculates the input echo amount and the input echo increase / decrease amount of the Sin end 315 by the echo measuring circuit 308, and thereby the echo canceller 301 is the first stage or the second stage in the cascade connection. Can be recognized and determined.
[0064]
Further, it is possible to recognize and determine whether or not the first stage of the echo canceller 301 has no echo.
[0065]
【The invention's effect】
As described above, according to the present invention, the input echo amount is measured, the input echo increase / decrease amount is calculated from the measured input echo amount, and the measured input echo amount is calculated based on the calculated input echo increase / decrease amount. Since the operation of canceling the echo and stopping the operation are performed, the operation is guaranteed for the echo canceller connected to the terminal which does not originally generate the echo and which does not need the echo canceller, and the second and subsequent echoes in the subordinate connection are performed. It is possible to prevent the speech quality from being degraded due to the instability of the convergence process until the echo canceller is stopped.
[0066]
In other words, the presence or absence of an echo canceller can be determined based on the increase or decrease of the input echo amount, and the result can be reflected in the operation of the echo canceller. And the call quality is improved.
Echo amount,ThatBy measuring and calculating the increase / decrease amount and comparing it with a predetermined value, the presence / absence of the two-wire / four-wire conversion circuit (H) and the presence / absence of the echo canceller can be determined, and the result is reflected in the operation of the echo canceller. Regardless of whether or not there is an echo canceller, the device can be freely designed, the products can be easily shared, and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an echo canceller control system according to the present invention.
FIG. 2 is a diagram illustrating a double talk detection circuit 307 in FIG.
FIG. 3 is a diagram illustrating measurement of an input echo amount and calculation of an input echo increase / decrease amount by an echo measurement circuit 308.
FIG. 4 is a diagram illustrating switching determination by a switching determination circuit 309.
FIG. 5 illustrates an example in which the echo canceller 301 according to the present invention is used as a node in an ATM network.
FIG. 6 is a diagram showing an example in which a plurality of telephone networks 404 to 406 are connected to the echo canceller 301 shown in FIG. It is a figure showing a quantity.
7 is a diagram showing an echo amount with respect to an elapsed time of a Sin terminal 315 when a plurality of telephone networks 401 to 403 or a plurality of telephone networks 407 to 409 are connected to the echo canceller 301 of FIG.
8 is a diagram illustrating an echo amount with respect to an elapsed time of a Sin terminal when a different telephone network is connected to the echo canceller in FIG.
FIG. 9 is a flowchart illustrating a series of operations of the echo canceller control system in FIG. 1;
FIG. 10 is a diagram illustrating stoppage of the echo canceller related to the dependent connection of the echo canceller.
FIG. 11 is a diagram for explaining the stop of the echo canceller related to the two-wire digital extension system (ping-pong transmission system) of the digital multifunction telephone.
FIG. 12 is a diagram illustrating stoppage of an echo canceller in a digital multifunction telephone with respect to a 4-wire digital extension system.
FIG. 13 is a diagram illustrating a configuration of a conventional echo canceller.
FIG. 14 is a diagram illustrating an echo amount with respect to an elapsed time at a first-stage and second-stage echo canceller Sout terminal.
[Explanation of symbols]
301 ... Echo canceller
302: far end signal
303: Near-end signal
304: 2-wire 4-wire conversion circuit (H)
305 ... Pseudo echo generation circuit
306 ... Timer
307 ... double talk detection circuit 307
308 ... Echo measurement circuit
309 ... Switching judgment circuit
310 ... Echo cancellation circuit
311, 312 ... pass / bypass circuit
313 ... Rin terminal
314 ... Rout terminal
315 ... Sin terminal
316 ... Sout terminal
320 ... Echo measurement unit
330 ... operation / operation stop unit
401-409: telephone network
401A to 409A: Telephone
401B-406B ... 2-wire 4-wire conversion circuit (H)
404C-406C ... Echo canceller
410 ... node
420 ... ATM network

Claims (7)

In an echo canceller control system for canceling an echo included in a telephone network connected to a high-speed, large-capacity transmission network,
An echo measurement unit that measures an input echo amount and calculates an input echo increase / decrease amount from the measured input echo amount;
An echo canceller control system comprising: an echo canceling operation and an operation / operation stopping unit that stops an operation based on the input echo amount measured by the echo measuring unit and the calculated input echo increase / decrease amount. The echo measuring unit is provided with a double talk detection circuit, and the double talk detection circuit detects double talk in which a signal from the high-speed, large-capacity transmission network side and a signal from the telephone network side are simultaneously inputted, and 2. The echo according to claim 1, wherein the measurement of the input echo amount and the calculation of the input echo increase / decrease amount are stopped when a talk is detected, and the operation / operation stop unit stops the operation of canceling the echo. Canceller control system. The echo measuring unit is provided with a timer, the timer generates a timing of a cycle shorter than the convergence time of the echo decay, and is used for measuring the input echo amount and calculating the input echo increase / decrease amount. The echo canceller control system according to claim 1, wherein: The operation / operation stop unit stops the operation of echo cancellation when the calculated input echo increase / decrease amount is an input echo attenuation amount equal to or greater than a first predetermined value, and the calculated input echo increase / decrease amount is 2. The echo canceller control system according to claim 1, wherein an echo canceling operation is performed when the input echo increment is equal to or greater than a first predetermined value . The operation / operation stop unit is configured to perform an echo canceling operation when the calculated input echo increase / decrease amount is less than a first predetermined value and the measured input echo amount is less than a second predetermined value. Stopping, and performing an echo canceling operation when the calculated input echo increase / decrease amount is less than a first predetermined value and the measured input echo amount is equal to or more than a second predetermined value. The echo canceller control system according to claim 1, characterized in that: The high-speed, large-capacity transmission network is an ATM network, and the telephone network includes a telephone network without echo cancellation, a telephone network with echo cancellation, and a digital telephone network without echo generation. Item 2. An echo canceller control system according to item 1. In an echo canceller control method for canceling an echo included in a telephone network connected to a high-speed, large-capacity transmission network,
Measuring the input echo amount and calculating the input echo increase / decrease amount from the measured input echo amount;
Performing an echo canceling operation and stopping the operation based on the measured input echo amount and the calculated input echo increase / decrease amount.

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