JP2738878B2 - ATM exchange method - Google Patents

Description

Detailed Description of the Invention [Table of Contents] Overview Industrial application field Conventional technology (FIG. 7) Problems to be solved by the invention (FIGS. 8 to 10) Means for solving the problems (FIG. 1) Operation (FIG. 1) Embodiment (FIGS. 2 to 6) Effect of the Invention [Overview] An ATM switching system that accommodates a plurality of terminals and has a switching network controlled by a network control unit, such as when refreshing If the number of cells suddenly increases, the purpose of the network control is to enable the ATM switching network to control the cell transmission timing from the terminal so that cell discarding and deterioration of transmission efficiency do not occur. Unit is configured to transmit a cell number increase permission signal individually to each terminal at a required timing, and each terminal is configured to increase and output the number of cells after receiving the cell number increase permission signal from the network control unit. Or allow the network controller to increase the number of cells. In order to simultaneously transmit signals to each terminal, and to increase the number of cells in order so that each terminal does not overlap the cell transmission after each terminal receives the cell number increase permission signal from the network control unit, and to output the signals. Configure.

The present invention relates to an ATM switching system having an ATM (Asynchronous Transfer Mode) switching network that accommodates a plurality of terminals and is controlled by a network control unit.

In recent years, ATM switching technology using ATM, which combines the bandwidth flexibility of packet switching and the time transparency of
The agreement was reached at T, and research is being actively conducted at each institution.

[Prior Art] Conventionally, as shown in FIG.
An ATM switching system having an ATM switching network 2 that accommodates [i = 1, 2,..., N (n is a natural number)] and is controlled by a network control unit has been proposed.

In such an ATM switching system, a call setup is performed prior to transmission of a cell string from each incoming line. The call applies to the call control unit for various parameters representing the characteristics of the cell string. Then, based on this parameter, the call control unit determines whether or not to make a call connection. After the call is set in this way, a cell row is input from the incoming line. After that, a plurality of cells are multiplexed and exchanged within the network 2 by the statistical multiplexing technique.

[Problems to be Solved by the Invention] By the way, the cell row of each input to the network 2 involves a change in the number of cells per unit time. Normally, call control is performed at the time of call setup so that cell discard does not occur as shown in FIG. 8, but when bursts overlap as shown in FIG. 9, unexpected large input cell fluctuations cause Then, there is a possibility that the cell is discarded.

For example, consider a case where a high-compression video coding device is used as an input. The high-compression video coding apparatus uses ADPCM as a coding technique. Here, ADPCM refers to a method of encoding a difference between data estimated from past data and actual present data. At this time, both the transmitting side and the receiving side hold the same past data. Must be. If an error occurs in the differential data due to a transmission error or the like, the past data on the transmitting side and the past data on the receiving side do not match from the next data. Therefore, all subsequent data will be erroneous, and the image will be greatly disturbed. As an example of a method for preventing such a phenomenon, a high-compression moving image coding apparatus performs refresh.

Here, the term “refresh” refers to sending the same data, that is, PCM data, from the transmission side to the reception side when an error occurs in the difference data or periodically. Therefore, at the time of refresh, the data to be transmitted increases. In circuit switching, since the transmission rate is constant, the screen is fixed at the time of refreshing, or data that is not refreshed is compressed to send refresh data, but in ATM switching, variable rate transmission is possible. Therefore, it is sufficient to transmit the increased data as it is at the time of refresh (see FIG. 10).

However, in the ATM switching network, since the statistical multiplexing technique is used, it may not be possible to cope with a sudden increase in the number of cells. For example, if a plurality of inputs perform refresh at the same time, the number of network input cells increases rapidly, and cell discarding occurs in the ATM switching network. Such a phenomenon cannot be efficiently handled by good control.

Therefore, measures such as increasing the capacity (throughput) of the ATM switching network or rejecting another call after accepting a certain call are conceivable. However, in any case, the transmission efficiency is deteriorated. There is a problem.

The present invention has been made in view of such problems,
When the number of cells suddenly increases as in the case of refreshing, the ATM switching network side can control the cell transmission timing from the terminal so that the ATM switching network does not cause cell discarding and deterioration of transmission efficiency. It aims to provide a scheme.

[Means for Solving the Problems] FIG. 1 is a principle block diagram of the present invention according to claims 1 and 2.

In FIG. 1, 1-i (i = 1, 2,..., N) are terminals, and these terminals 1-4i are all accommodated in the ATM switching network 2.

The ATM switching network 2 includes an ATM switching switch unit 21 and a network control unit 22.

Here, the ATM switching unit 21 exchanges cells input from the incoming line and outputs the cells to the required outgoing line.

The network control unit 22 controls the switching and the like of the ATM exchange switch unit 21. In addition, the network control unit 22 transmits a cell number increase permission signal that permits a rapid increase in the cell number to each terminal 1-i on the incoming line side. It is configured to individually transmit at the required timing. In this case, each terminal 1-i is configured to increase and output the number of cells after receiving the cell number increase permission signal from the network control unit 22 (the above is a configuration requirement of claim 1). .

Further, the network control unit 22 can be configured to simultaneously transmit a cell number increase permission signal that permits a rapid increase in the cell number to each terminal 1-i. In this case, each terminal 1-i After receiving the cell number increase permission signal from the network control unit 22, each terminal 1-i is configured to sequentially increase and output the number of cells so that the cell transmissions do not overlap. ).

[Operation] In the ATM switching system according to the first aspect of the present invention, the network control unit 22 sends a cell number increase permission signal for permitting a rapid increase in the cell number to each terminal 1-i on the incoming line side. At the required timing, in this case, each terminal 1-i receives a cell number increase permission signal from the network control unit 22,
The number of cells can be increased and output.

In the ATM switching system according to the second aspect of the present invention, the network control unit 22 simultaneously transmits a cell number increase permission signal for permitting a rapid increase in the cell number to each terminal 1-i.
In this case, after receiving the cell number increase permission signal from the network control unit 22, each terminal 1-i can sequentially increase and output the number of cells so that cell transmission does not overlap at each terminal 1-i. .

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention. In FIG. 2, 1-i (in this embodiment, i = 1 to 1)
9) is a terminal for videoconference, and each terminal 1-i has a transmission system portion including a TV camera 11A, an encoding unit 12A, a cell assembling unit 13A, a buffer unit 14, and a signal multiplexing unit 15A as shown in FIG. , Monitor 11B,
It is composed of a receiving system part including a decoding unit 12B, a cell decomposing unit 13B, and a signal separating unit 15B, and a control system unit including a signal control unit 16 and a terminal control unit 17.

Here, the TV camera 11A is provided in a conference room or the like and shoots a person having a meeting, and the encoding unit 12A is a TV camera 1A.
The signal from 1A is converted to digital data and subjected to encoding such as ADPCM.The cell assembling unit 13A assembles cells to convert encoded data into cells, and the buffer unit 14 temporarily stores cells. The signal multiplexing unit 15A multiplexes the signal from the buffer unit 14 and the signal from the signal control unit 16.

In addition, the monitor 11B is provided in a conference room or the like to project a party having a meeting, the decoding unit 12B performs decoding such as inverse ADPCM, and the cell decomposition unit 13B performs cell decomposition. The signal separation unit 15B separates a signal to the signal control unit 16.

The signal control unit 16 transmits and receives signals exchanged between the terminal 1-i and the ATM switching network 2 via the signal multiplexing unit 15A and the signal demultiplexing unit 15B. , A refresh transmission permission signal (described later) or a refresh transmission synchronization signal (described later) as a cell number increase permission signal transmitted from the network control unit 22 of the ATM switching network 2.

The terminal control unit 17 exchanges signals with the signal control unit 16 to control the state of cell transmission from the buffer unit 14. For example, although this point will be described later,
When the terminal 1-i receives the refresh transmission permission signal or the refresh transmission synchronization signal from the ATM switching network 2, the terminal control unit 17 can increase the number of cells stored in the buffer unit 14 and output the cells at a required timing. Control.

Further, the ATM switching network 2 shown in FIG. 2 includes an ATM switching switch unit 21 and a network control unit 22. To be more specific, the ATM switching network 2 has a self-routing communication path. Is used. That is, in this example, the 3 × 3 unit self-routing switch (hereinafter, the unit self-routing switch is sometimes referred to as a unit switch) is connected to the incoming line (see S ₁₁ , S ₁₂ , and S ₁₃ ) and the middle (S
₂₁ , S ₂₂ , S ₂₃ ), 3 on the outgoing line side (see S ₃₁ , S ₃₂ , S ₃₃ )
Number Yes, primary link L _11, L _12, L ₁₃ is connected to each first input end of the intermediate switches S ₂₁ to S ₂₃ the three output terminals of the incoming line side switch S _11, the primary link L ₂₁ ~L _23, L ₃₁ ~L ₃₃ is also equivalent thereto. Secondary link M ₁₁ ~M ₁₃ connects the three output terminals of the intermediate switches S ₂₁ to the first input terminal of the three switches S ₃₁ to S ₃₃ of the outgoing line side, secondary link M ₂₁ ~ M _23, M ₃₁ ~M ₃₃ is also equivalent thereto.

In this self-routing channel, switch S
_11, S ₂₁ ~S _23, idea to install the S _31, the switch S ₁₂ and S _32,
Installation of S ₁₃ and S ₃₃ without changing any of the existing parts can be simply performed by simply connecting as shown links _{L 21 ~L 23, L 31 ~L} 33.

Also, for example, the path leading the incoming line I9 to the outgoing line O3 is a switch S
₁₃ and S ₂₁ and the switches S _31, S ₁₃ and switches S ₂₂ and S _31, the switch S ₁₃ and there are 3 paths of the switch S ₂₃ and the switch S _31, the switch S ₁₃ and traffic switches S ₂₁ between switch S ₃₁
Can be distributed to the to S _23, further optionally have traffic is concentrated on the switch S ₂₁ as delay out is allowed better, thereby the delay by changing the path through the switch S ₂₂ or switch S ₂₃ It can be reduced as much as possible.

On the incoming line side, a signal separating device 23 for separating the incoming line signal is provided, and on the outgoing line side, a signal multiplexing device 24 for multiplexing the signal to the outgoing line is provided.

The self-routing communication path, the signal separation device 23, and the signal multiplexing device 24 constitute the ATM switching unit 21 in this manner.

Further, the ATM switching network 2 is provided with a call control unit 25, a signal control unit 26, and a switch control unit 27 that constitute the network control unit 22.

Here, the call control unit 25, the signal control unit 26, the switch control unit 27
Are connected to each other via a bus line,
The control unit 25 performs control for call connection based on various parameters, and transmission and reception of signals for the control by the call control unit 25 are performed via the signal control unit 26 and the switch control unit 27.

Further, the call control unit 25 can individually transmit a refresh transmission permission signal as a cell number increase permission signal for permitting a rapid increase in the number of cells to each terminal 1-i on the incoming line side at a required timing. And the fourth
It has a cell increase timing table 261 as shown in the figure. By the way, this cell increase timing table 26
1 is used as follows. First, at the time of call setting, the table 261 is accessed to determine at what timing the cell increase of the setting request call should be performed. Then, when the call setting is accepted, the accepted terminal number (in this example, the number of the terminal 1-i is written as i) is written at the corresponding timing. At the end of the call, the corresponding terminal number is deleted. The table 261 is always accessed periodically, so that a refresh transmission permission signal is transmitted to the corresponding terminal at the corresponding timing.

The signal control unit 26 is a control interface for inputting the signal separated by the signal separation device 23 to the call control unit 25 and multiplexing the signal from the call control unit 25 to the signal multiplexing device 24. For example, there is a refresh transmission permission signal described above.

Switch control unit 27 controls the switches S ₁₁ to S ₃₃ based on the control signal from the call control unit 25.

With the above-described configuration, the ATM switching network 2 performs multiplexing and switching of a plurality of cells using a statistical multiplexing technique with respect to an input cell sequence, but the network control unit 22 in the ATM switching network 2
Input terminal 1 to perform a refresh operation at the time of call setup
-Access the cell increase timing table 261 for i to determine at what timing the cell increase of the setting request call should be performed. And when the call setup is accepted,
The received terminal number i is written at the corresponding timing. Then, at the corresponding timing, a refresh transmission permission signal is transmitted to the corresponding terminal 1-i.

In this manner, the refresh transmission permission signal is transmitted from the ATM switching network 2 to the corresponding terminal 1-i, and the corresponding terminal 1-i having received the signal operates as follows. That is, the terminal 1-i has the buffer unit 14 as described above, but normally transmits the cell string from the encoding device 12A as it is. By the way, when the number of cells increases due to the refresh, the number of output cells is suppressed to about the usual number of cells by the buffer unit 14. When the refresh transmission permission signal is received from the ATM switching network 2 after that,
The number of output cells is increased, and the refresh data stored in the buffer unit 14 is transmitted.

FIGS. 5A to 5F show the state at this time for the three terminals 1-1 to 1-3. That is, from FIGS. 5 (a) to 5 (f), the refresh transmission permission signal is output at different timings for each terminal. When each terminal receives the refresh transmission permission signal, the number of cells increases. You can see that it is sending. Since the refresh transmission permission signal is output at a different timing for each terminal, it can be seen that the timing at which the number of transmission cells increases also differs.

As a result, the number of cells input to the network can be made uniform while minimizing the cell transmission limit of the input terminal, and as a result, the efficiency of the network can be increased and cell discarding can be reduced. is there.

Note that the terminal has a right to increase the number of output cells for the terminal 1-i because the terminal 1-i receives the refresh transmission permission signal from the ATM switching network 2. Therefore, when there is no refresh operation, the terminal 1-i receives the refresh transmission permission signal. Needless to say, the usual number of cells is transmitted.

By the way, a refresh transmission synchronization signal is used as a cell number increase permission signal for permitting a sharp increase in the cell number.
i, the network control unit 22 of the ATM switching network 2
(Especially the call control unit 25). Then, in this case, after receiving the refresh transmission synchronizing signal from the network control unit 22, each terminal 1-i sequentially increases the number of cells so that each terminal 1-i does not overlap the cell transmission and outputs it. Be composed.

 The operation in such a case is as follows.

First, the network control unit 22 of the ATM switching network 2 notifies each input terminal of the timing of sending refresh data at the time of call setup. Then, a refresh transmission synchronization signal is periodically transmitted from the network simultaneously to all the input terminals 1-i.
Then, each terminal 1-i receiving this operates as follows. That is, the terminal 1-i is connected to the buffer
14, but usually transmits the cell string from the encoding device 12A as it is. By the way, even if the number of cells increases due to refreshing, the number of output cells is stored in the buffer section.
The number of output cells is reduced to about the usual number of cells by the number of output cells. Sends the refresh data stored in the.

FIGS. 6A to 6F show the state at this time for the three terminals 1-1 to 1-3. That is, from FIGS. 6 (a) to 6 (f), a refresh transmission synchronizing signal is output to each of the terminals 1-1 to 1-3 at the same timing. When the timing time notified at the time of call setup elapses (when the time t1 elapses in the terminal 1-1, the terminal 1-2
At time t2, and at terminal t3 at time t3)
It can be seen that the transmission is performed with the number of cells increased. Since the timing at which the number of cells to be transmitted increases in each terminal is different in this manner, in this case as well, the number of cells input to the network can be made uniform while minimizing the cell transmission restriction of the input terminal. As a result, network efficiency can be increased and cell loss can be reduced.

Also in this case, the terminal has a right to increase the number of output cells for the terminal with the refresh transmission synchronization signal from the ATM switching network 2. Therefore, the terminal receives the refresh transmission synchronization signal and a predetermined time elapses. However, if there is no refresh operation, it goes without saying that the usual number of cells is transmitted.

Note that, in the above embodiment, the case where the present invention is applied at the time of refresh is shown, but the present invention can also be applied to still image search. That is, the traffic of the still image search is usually small, and the traffic increases when the searched still image data is transmitted. Therefore, by controlling this timing for each terminal, it is possible to prevent traffic collision.

Further, the present invention is not necessarily limited to only control of a terminal whose traffic increases periodically.

[Effects of the Invention] As described in detail above, according to the ATM switching system of the present invention, a network control unit is configured to send a cell number increase permission signal individually to each terminal at a required timing, and each terminal Is configured to increase and output the number of cells after receiving the cell number increase permission signal from the network control unit (claim 1), or the network control unit is configured to send the cell number increase permission signal to all terminals simultaneously. In addition, each terminal is configured to sequentially increase and output the number of cells after receiving the cell number increase permission signal from the network control unit so that cell transmission does not overlap at each terminal (claim 2). In addition, it is possible to equalize the number of cells input to the network while minimizing the cell transmission limit of the input terminal, thereby increasing the efficiency of the network and reducing cell discarding.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a block diagram showing a terminal configuration, FIG. 5 (a) to 5 (f) are diagrams for explaining the relationship between the refresh transmission permission signal and the number of cells transmitted per unit, and FIGS. 6 (a) to 6 (f) are the refresh transmission synchronization signal and transmission per unit. FIG. 7 is a diagram for explaining the relationship with the number of cells, FIG. 7 is a block diagram for explaining the ATM switching system, FIGS. 8 and 9 are diagrams for explaining the operation in the ATM switching system, and FIG. FIG. 4 is a diagram illustrating a case where refresh data is transmitted in the ATM switching system. In the figure, 1-i is a terminal, 2 is an ATM switching network, 11A is a TV camera, 11B is a monitor, 12A is an encoding unit, 12B is a decoding unit, 13A is a cell assembly unit, 13B is a cell disassembly unit, and 14 is Buffer unit, 15A is a signal multiplexing unit, 15B is a signal demultiplexing unit, 16 is a signal control unit, 17 is a terminal control unit, 21 is an ATM switch unit, 22 is a network control unit, 23 is a signal demultiplexer, and 24 is a signal multiplexing unit. device, 25 is a call control unit, 26 signal control unit, 27 a switch control unit, 261 cells increased timing _{table, L 11 ~L 33, M 11} ~M 33 links, S ₁₁ to S ₃₃ in the unit switch is there.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-42543 (JP, A) JP-A-3-272242 (JP, A) JP-A-63-50227 (JP, A) JP-A-3- 268542 (JP, A)

Claims (2)

(57) [Claims] An ATM having an ATM switching network (2) that accommodates a plurality of terminals (1-i) and is controlled by a network controller (22).
In the switching system, the network control unit (22) is configured to individually transmit a cell number increase permission signal permitting a rapid increase in the cell number to each terminal (1-i) at a required timing. The ATM switching system, wherein each terminal (1-i) is configured to increase and output the number of cells after receiving the cell number increase permission signal from the network control unit (22). 2. An ATM having an ATM switching network (2) accommodating a plurality of terminals (1-i) and controlled by a network control unit (22).
In the switching system, the network control unit (22) is configured to simultaneously transmit a cell number increase permission signal permitting a rapid increase in the cell number to each terminal (1-i). -I) is configured so that after receiving the cell number increase permission signal from the network control unit (22), each terminal (1-i) sequentially increases the number of cells and outputs the cells so that cell transmission does not overlap. The ATM exchange method, which has been done.