JP2821401B2 - Cell fluctuation absorbing method and method for ATM echo canceller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an echo canceling method and an echo canceling method for canceling an echo from an audio signal, and more particularly to a method for absorbing cell fluctuation of an ATM echo canceller of an ATM (Asynchronous Transfer Mode) cellized audio signal and its method. About the method.

[0002]

2. Description of the Related Art Conventional STM (Synchronous Transfer M)
ode) In the network, an STM-based echo canceller technique is used.

[0003]

SUMMARY OF THE INVENTION An audio signal from a telephone or the like is transmitted by A
When transmission is performed using the TM network, the delay time is longer than that of the conventional STM network due to cell / decell delay and queuing delay in the network. Therefore, in the ATM network, S
The need for an echo canceller is higher than that of a TM network. However, when operating an echo canceller in an ATM network, cell delay fluctuations occur depending on the state of the network.
It is necessary to absorb this delay fluctuation.

SUMMARY OF THE INVENTION An object of the present invention is to apply a conventional STM-based echo canceller method to absorb a cell delay fluctuation occurring in an ATM network by utilizing an ATM-STM and STM-ATM conversion technique, thereby achieving a simple configuration. ATM
An object of the present invention is to provide a cell fluctuation absorbing method and its method for an echo canceller.

[0005]

SUMMARY OF THE INVENTION A cell fluctuation absorbing method of an ATM echo canceller according to the present invention, in order to achieve the above object, converts a voice signal into an ATM cell and transmits / receives the ATM signal. Inputting an ATM cell from a far-end line, absorbing fluctuations in the far-end line, converting it into an STM signal, and outputting the signal; and inputting the STM signal as a first input; Generating and outputting a pseudo echo from an input and other second and third inputs; receiving the pseudo echo signal as input, converting the pseudo echo signal into cells to absorb fluctuations in cell arrival from a near-end line And outputting a signal obtained by subtracting the output of absorbing the cell arrival fluctuation from the near-end line from the ATM cell signal from the near-end line, The subtraction output signal is input, the fluctuation in the near-end line is absorbed, converted into an STM signal and used as the second input, and the ATM cell signal from the near-end line is input and the fluctuation in the near-end line is input. And converting it into an STM signal to be the third input.

Further, the cell fluctuation absorbing system of the ATM echo canceller of the present invention is a cell fluctuation absorbing system of the ATM echo canceller in a cell transmission / reception control for converting a voice signal into an ATM cell and transmitting / receiving the ATM signal.
M cell input, absorbs fluctuations at the far end line,
A first buffer for converting the signal into an M signal and outputting the converted signal;
And a pseudo-echo generator for generating and outputting a pseudo-echo by the first input and the other second and third inputs, and a signal from the pseudo-echo generator. A pseudo-echo signal is input, the pseudo-echo signal is converted into cells, and a second buffer for absorbing the fluctuation of arrival of cells from the near-end line, and an ATM cell signal from the near-end line, from the second buffer, A subtractor that outputs a signal obtained by subtracting an output, and an output signal from the subtractor as an input, absorbs fluctuations in a near-end line, converts the signal into an STM signal, and converts the signal into an STM signal as the second input. A from near end line
A third buffer is provided which receives a TM cell signal as input, absorbs fluctuations in the near-end line, converts the signal into an STM signal, and serves as the third input.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The cell fluctuation absorbing system of the ATM echo canceller according to the present invention has a simple structure without adding a delay to an ATM network, and a pseudo echo generating circuit, a subtractor and an ATM using a conventional STM-based echo canceller. −ST
The buffer to which the M and STM-ATM conversion technology is applied absorbs the cell delay fluctuation generated in the ATM network.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a buffer that absorbs network delay fluctuation on the far end line side and performs STM conversion, 2 denotes a buffer that absorbs network delay fluctuation on the near end line side, and 3 denotes a network delay fluctuation on the near end line side. Is a buffer for absorbing STM and performing STM conversion, 4 is an STM-based pseudo echo generator, and 5 is a subtractor.

FIG. 2 is a time chart showing the operation principle of the buffer 1 shown in FIG. The generated voice cell arrives at the echo canceller buffer 1 with a time d delay through the far-end line. The maximum value of the delay d generated in the far-end line, that is, the maximum fluctuation width of the cell is m ₀ . The cell input to the buffer 1 is subjected to a header check, and if the channel of the voice cell is to be echo canceled, the payload in the cell is copied and stored in the buffer 1. In the buffer 1, and STM converted after absorbing the fluctuation of the cell of the far end lines by placing a weight of maximum fluctuation width m ₀ of the far-end line cells, the converted STM signal a first input of echo replica generator Output as

The pseudo echo generator 4 is an STM-based pseudo echo generator, and converts an STM signal from the buffer 1, an STM signal containing a residual echo from the buffer 3, and an STM signal before echo canceling. Internal processing is performed as an input, and an echo generated by a 2-wire 4-wire converter on the near-end line side is pseudo-generated. The pseudo echo generated and output by the pseudo echo generator 4 is input to the buffer 2.

FIG. 3 is a time chart showing the principle of operation of the buffer 2. The buffer 2 includes a pseudo echo generator 4
After the STM signal of the pseudo-echo input from is converted to a cell, the weight of the maximum fluctuation width M of the cell of the near-end line is given, and the pseudo-echo of the fluctuation width α of the first cell is added to the buffer capable of the fluctuation width M. Buffer the signal. The buffer 2 monitors the cell arriving from the near-end line side by a separate means (not shown), and if the channel is a voice cell corresponding to the generated pseudo echo, the buffer 2 is buffered in the buffer 2 in synchronization with the cell arriving. The extracted cell is taken out and output to the subtractor 5. As described above, the buffer 2 absorbs the fluctuation of the cell of the near-end line by placing the weight of the fluctuation width α of the first cell of the near-end line.

The subtractor 5 receives a cell containing an echo component from the near-end line side and a pseudo echo cell from the pseudo echo generator 4 and converts the payload of the former cell signal into the payload of the latter cell signal. Subtract. Thereby, the echo component generated in the two-wire / four-wire converter on the near-end line side is removed. The cell signal output from the subtractor 5 is transmitted to the far end line side. However, since the echo generated by the pseudo echo generator 4 does not completely match the echo generated on the near-end line side, the cell signal output from the subtractor 5 includes a residual echo.

The audio signal including the residual echo after the echo canceling and the audio signal before the echo canceling are fed back to the pseudo echo generator 4 so that the residual echo converges to zero. The signal is input to the pseudo echo generator 4 via

FIG. 4 is a time chart showing the operation principle of the buffer 3. The voice cell generated on the near-end line side includes an echo component generated by the two-line / four-wire converter on the near-end line side. The voice cell arriving at the subtractor 5 after a delay of time α through the near-end line is echo-canceled by the subtractor 5, but still includes a residual echo. The maximum value of the delay α occurring in the near-end line, that is, the maximum fluctuation width of the cell is M. The cell input to the buffer 3 is subjected to a header check, and if the channel is a voice cell corresponding to the generated pseudo echo, the payload in the cell is copied and stored in the buffer 3. The buffer 3 absorbs the fluctuation of the cell of the near-end line by placing a weight of the maximum fluctuation width M of the cell of the near-end line, and then performs STM conversion.
The signal is input to the pseudo echo generator 4, and a voice signal including a residual echo is fed back to the pseudo echo generator 4.

Thus, the buffer 1 and the buffer 3
Except for the difference between the cell weight values m ₀ and M, the operation is performed according to the same operation principle.

[0018]

As described above, the present invention provides an ATM-STM conversion and an S-to-STM conversion between an ATM network and a pseudo echo generator.
A buffer for TM-ATM conversion is provided, and by performing conversion inside the buffer, cell delay fluctuations occurring in the ATM network can be absorbed.
There is an effect that an M-based pseudo echo generator can be used.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a time chart showing the operation principle of the buffer 1 in FIG.

FIG. 3 is a time chart illustrating an operation principle of a buffer 2 in FIG. 1;

FIG. 4 is a time chart illustrating an operation principle of the buffer 3 in FIG. 1;

[Explanation of symbols]

 1 buffer 2 buffer 3 buffer 4 pseudo echo generator 5 subtractor

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Fujitani 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Kazuma Miura 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-4-177922 (JP, A) JP-A-4-352557 (JP, A) JP-A-4-111479 (JP, A) (58) Fields investigated (Int.Cl. ⁶ , DB name) H04L 12/28 H03H 17/00 601

Claims (2)

(57) [Claims] 1. A cell fluctuation absorbing method for an ATM echo canceller in a cell transmission / reception control for converting a voice signal into an ATM cell and transmitting / receiving the ATM signal, wherein an ATM cell from a far-end line is input and the fluctuation in the far-end line is absorbed. Converting the STM signal into a first input, generating a pseudo echo from the first input and the other second and third inputs, and outputting the pseudo echo. Receiving a pseudo-echo signal, converting the pseudo-echo signal into cells to absorb cell arrival fluctuations from a near-end line, and converting cell arrival fluctuations from the near-end line from an ATM cell signal from a near-end line. Outputting a signal after subtracting the absorbed output; receiving the subtracted output signal as an input, absorbing fluctuations in a near-end line, converting the signal into an STM signal, and converting the signal into an STM signal; And the near-end as an input the ATM cell signal from the line, to absorb fluctuations in the near-end line, ATM echo canceller cell fluctuation absorption method comprising the step of said third input is converted into STM signal. 2. A cell fluctuation absorbing system for an ATM echo canceller in a cell transmission / reception control for converting a voice signal into an ATM cell for transmission / reception, wherein an ATM cell from a far-end line is input and a fluctuation on a far-end line is absorbed. , A first buffer that converts the signal into an STM signal and outputs the signal, and a STM signal from the first buffer as a first input, and generates a pseudo echo by the first input and other second and third inputs. A pseudo-echo generator that generates and outputs a second buffer that receives the pseudo-echo signal from the pseudo-echo generator, converts the pseudo-echo signal into cells, and absorbs fluctuations in the arrival of cells from the near-end line; A subtractor that outputs a signal obtained by subtracting an output from the second buffer from an ATM cell signal from a near-end line, and an output signal from the subtractor as an input. Absorbs fluctuations and converts them into STM signals as the second input, inputs ATM cell signals from the near-end line, absorbs fluctuations in the near-end lines, converts them into STM signals and converts them into the third signals. A cell fluctuation absorption system of an ATM echo canceller having a third buffer as an input to the ATM echo canceller.