JP2509307B2 - Transmission control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Table of Contents] Outline Industrial field of use Conventional technology Problems to be solved by the invention Means for solving the problem Action Example I. Correspondence between Example and FIG. 1 II First Embodiment III. Second Embodiment IV. Third Embodiment V. Summary of Embodiment VI. Modification of Invention Effect of Invention [Summary] The signal of the own node is multiplexed and transmitted in an empty cell on the transmission path. For the purpose of improving the reliability and downsizing of the equipment, the transmission control method is to accommodate a plurality of nodes connected to the transmission line by a network terminating device, and to send the signals from each node to an empty cell on this transmission line. In the transmission control method for multiplexing, the network terminating device has a polling table that stores information regarding the communication capacity of each node, and the network terminating device performs polling based on the polling table.
It is configured by performing control to specify an empty cell for returning data from each node.

[Industrial applications]

The present invention relates to a transmission control method, and more particularly to a transmission control method for multiplexing and transmitting a signal of its own node in an empty cell on a transmission path.

In the wideband ISDN system that multiplexes and transmits not only data but also voice signals and image signals, ATM (Asynchronou
s Transfer Mode) method has been proposed. This ATM system is, for example, multiplexed transmission using cells having a fixed length such as an integral multiple of octets, and an image signal or the like is transmitted using a plurality of cells in one frame. When an optical signal is used, each node connected by an optical transmission line detects whether or not it is addressed to itself and performs reception processing, and also performs empty cell detection and transmission processing. It is a thing. In this case, it is necessary to reliably insert the optical signal to be transmitted into the detected empty cell.

[Conventional technology]

FIG. 4 is an explanatory diagram of a conventional optical active multiplexing system.

In the figure, a multiplexer 500 includes an optical-electrical conversion circuit (O / E circuit) 511 for converting an optical signal supplied via an optical transmission line 591 into an electric signal, and a first-in first-out (FIFO) memory. Two buffer memories consisting of 251,53
A selector 541 that selects one of 1 and 2 inputs, and an electro-optical conversion circuit (E / O circuit) 551 that converts an electric signal into an optical signal and sends the optical signal to the optical transmission path 593 are provided.

The optical signal transmitted by the optical transmission line 591 is transmitted to the O / E circuit 511.
Is converted to an electric signal and supplied to the buffer memory 521, and when there is no transmission data, the content of the buffer memory 521 is supplied as it is to the E / O circuit 551 through the selector 541 and converted to an optical signal for optical transmission. It is sent to path 593.

Further, when the transmission data is accumulated in the buffer memory 531, an empty cell is detected, and the selector 541 is controlled so that the transmission data from the buffer memory 531 is inserted into the empty cell. The transmission data in which the transmission data from 500 is inserted is supplied to the E / O circuit 551, converted into an optical signal, and sent out to the optical transmission line 593.

FIG. 5 is an explanatory diagram of a conventional optical passive multiplexing system.

In the figure, the multiplexer 600 is an optical coupler 651 that branches an optical signal supplied via an optical transmission path 691, an optical coupler 653 that combines the optical signals and sends the optical signals to the optical transmission path 691, and an optical signal. To an electric signal, an E / O circuit 641 for converting an electric signal to an optical signal, a buffer memory 631 formed of a FIFO memory, and a cell monitoring unit 6 for monitoring an empty cell.
It has 21 and.

The optical signal transmitted through the optical transmission line 691 is transmitted by the optical coupler 65.
It is transmitted to the next node via 1,653. Further, the optical signal branched by the optical coupler 651 is converted into an electric signal by the O / E circuit 611, and a cell monitoring unit for detecting an empty cell is detected.
Supplied to the 621.

When the transmission data exists, the cell monitoring unit 621 detects an empty cell, and the transmission data is read from the buffer memory 631 to the E / O circuit 641 so that the transmission data is inserted into the detected empty cell. The transmission data supplied and converted into an optical signal by the E / O circuit 641 is inserted into an empty cell,
The time-division multiplexed optical signal is transmitted through the optical transmission line 691.

[Problems to be Solved by the Invention]

By the way, in the above-mentioned conventional optical active multiplexing system, since it is converted into an electrical signal and then multiplexed, if a failure occurs in the multiplexing device 500, the optical transmission line 5
It has a drawback that reliability is lowered because the space between 91 and 593 is cut off.

Further, in the above-described conventional optical passive multiplexing method, even if a failure occurs in the multiplexing device 600, the optical signal is transmitted through the optical couplers 651 and 653, so that the optical transmission path is blocked. However, during high-speed transmission, the time required for detecting an empty cell in the cell monitoring unit 621 cannot be ignored, and there is a drawback in that transmission data overlaps. To solve this drawback, the present applicant has already proposed Japanese Patent Application No. 63-44555 "optical signal transmission control system". In this optical signal transmission control method, by providing an optical delay unit for delaying at least the time required for empty cell detection between the optical coupler 651 and the optical coupler 653,
Although it controls the timing of multiplexing, the novel optical delay unit formed by an optical transmission line such as an optical fiber has a major drawback.

The present invention was created in view of the above point, and an object thereof is to provide a transmission control method that improves reliability and reduces the size of the device.

[Means for solving the problem]

FIG. 1 is a block diagram showing the principle of the transmission control method of the present invention.

In the figure, a network termination in a transmission control method in which a plurality of nodes 111 connected to a transmission path are accommodated by a network terminating device 121, and a signal from each of the nodes 111 is sent to an empty cell on this transmission path to perform multiplexing. The device 121 performs control by designating a free cell in which data is returned from each node 111 by polling based on the polling table 131.

[Work]

The network terminator 121 and the plurality of nodes 111 are connected via a transmission line. The network terminating device 121 has a polling table 131 that stores information about the communication capacity of each node 111, and polls each node 11 based on this polling table 131. Network terminator 121
Performs a control for designating an empty cell for returning data from each node 111 by polling based on the polling table 131.

In the present invention, since the signals transmitted from the respective nodes 111 are multiplexed in response to polling from the network terminating device 121, it is possible to prevent overlapping of transmission data and improve reliability. At the same time, a circuit for performing timing control associated with cell monitoring is not required,
The device scale can be reduced.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

2 and 3 show the configuration of a single embodiment to which the transmission control method of the present invention is applied.

I. Correspondence between Embodiment and FIG. 1 Here, the correspondence between the embodiment of the present invention and FIG. 1 will be described.

 The node 111 corresponds to the terminal devices (TE) 211 and TE311.

The network terminator 121 corresponds to the network terminators (NT) 221, NT321.

The polling table 131 is a dual-port (2-port) RAM231, 2-port RAM331, 2-port RAM333, 2-port RAM3.
Corresponds to the information about polling stored in each of the 35.

An embodiment of the present invention will be described below on the basis of the above correspondence.

II. First Embodiment FIG. 2 shows the configuration of a first embodiment to which the transmission control method of the present invention is applied.

In the figure, NT221 is a down bus 291 and an up bus 293.
It accommodates a plurality of TEs 211 via a line and is further connected to an ISDN exchange (not shown) via a line. Each TE211
Is connected to the downstream bus 291 via the optical coupler 213, receives the optical signal transmitted from the NT 231, and is connected to the upstream bus 293 via the optical coupler 215.
Sends an optical signal to 1.

Further, the NT221 converts the electrical signal into an optical signal and sends it to the down bus 291 and the bus transmission unit 241, and converts the optical signal supplied via the up bus 293 into an electrical signal, and converts the converted electrical signal. Bus receiver 24 that performs amplification, gain control, etc.
3 and the line receiver 2 that receives the signal supplied from the line side
51, and a line transmission unit 253 that sends a signal to the line side,
Call establishment unit 261 that sets up a call with the corresponding TE211
And a two-port RAM 231 for storing information (polling table) regarding the communication capacity of each TE 211, and a counter 271 for counting the read address of the information from the two-port RAM 231.

If there is a call setup instruction to TE211 via the line, N
The call setting unit 261 of T221 sets a call for the corresponding TE211 via the bus transmission unit 241 and the downlink bus 291. At this time, the corresponding TE211 is received via the upstream bus 293 and the bus reception unit 243.
Is notified of the communication capacity, and the embedded setting unit 261 stores this communication capacity in the polling table in the 2-port RAM 231.

Table 1 shows an example of the polling table in the 2-port RAM 231.

In the table, “counter” corresponds to the count value of the counter 271 and “TEI” indicates the identification number of TE211. For example, in the call setting process described above,
If the communication capacity notified from TE211 is "2" (the number of cells allocated to this TE211 is two), the identification number of this TE211 (for example, "TE1") is stored in two empty areas of the polling table. It

When the count value of the counter 271 is the address itself of the 2-port RAM 231, the above-mentioned "counter" column is unnecessary.

After that, the count value of the counter 271 is “0” or “2”.
At the time of, TE21 specified by identification number "TE1" from NT221
The polling signal for 1 is sent, and the TE 211 receiving this polling signal sends a response to the empty cell on the upstream bus 293.

The optical signal transmitted from the NT 221 to the downstream bus 291 includes the above-mentioned polling signal (Po) and the cell transmitted from the NT 221 to the TE 211.

Also, as the optical signal sent from each TE211 to the NT221,
It includes a guard time (Tg) for preventing overlapping of transmission data due to the state of the upstream bus 293, a preamble signal (Pa) for extracting a clock signal, and data to be transmitted. The "cell" that is the unit of signal transmission is
This preamble signal and data are included.

III. Second Embodiment FIG. 3 shows the configuration of a second embodiment to which the transmission control method of the present invention is applied.

In the figure, TE311 is a down bus 391 and an up bus 393.
A plurality of TE311s are accommodated via the, and are further connected to an ISDN exchange via a line.

The TE 311 also includes a bus transmission unit 341, a bus reception unit 343, a line reception unit 351, a line transmission unit 353, a call setting unit 361, and three 2-port RAMs 331, 333, 335 that store information regarding polling.
A counter 371 that performs a counting operation, two selectors 373 and 375 that select one of the two inputs, a FIFO 383 for holding data, a write control unit 381 that performs write control on the FIFO 383, and an input value. Subtractor 3 that subtracts 1
37 and.

When setting a call from the NT321 to the TE311, the communication capacity of the corresponding TE311 is notified via the upstream bus 393 and the bus receiving unit 343, and the call setting unit 361 causes the call setting unit 361 to identify the corresponding identification number "TEI". Is stored in the 2-port RAM 331 and the communication capacity is stored in the corresponding area of the 2-port RAM 333.

Table 2 shows an example of the polling table in the 2-port RAM 331, and the third table shows an example of the polling capacity table in the 2-port RAM 333.

In the table, “cell number” indicates the number of cells assigned to the corresponding TE311.

First, according to the count value of the counter 371, the corresponding TE311
Is read out and supplied to the bus transmission unit 341 via the selector 373. The NT 321 polls the corresponding TE 311 according to the identification number supplied to the bus transmission unit 341.

TE311 which received the polling signal, as a response,
A cell consisting of a preamble signal, data, and a data flag (Df) is returned. When the transmission of data is not completed by one response (when there is more data than the capacity of one cell), this TE 311 returns a response with the data flag set.

In the NT 321, when the data flag included in the returned response is set and the communication capacity is within the communication capacity assigned to the TE 311, the TE 311 is polled again.

TE311 polls when call setup is done
Communication capacity is read from the 2-port RAM333 and the selector
It is stored in the 2-port RAM 335 via the 375 and the subtractor 337.
For example, in the case of TE311 specified by "TE1", the number of cells "5" is read from the 2-port RAM 333, and "1" is read from this value.
The number of cells “4” obtained by subtracting is stored in the 2-port RAM 335.
The value stored in the 2-port RAM 335 indicates the number of remaining cells in the assigned communication capacity, and the write control unit 381 determines that the number of cells stored in the 2-port RAM 335 is other than “0”. The corresponding TE311 identification number "TE1"
Store in FIFO383. After that, the NT 321 polls according to this FIFO 383.

Since the number of cells stored in the 2-port RAM 335 is subtracted by the subtractor 337 each time polling is performed, even if the number is the largest, polling will be performed according to the communication capacity.

IV. Third Embodiment Next, a third embodiment to which the transmission control method of the present invention is applied will be described.

Table 4 shows an example of the polling table stored in the 2-port RAM 331 in the third embodiment. The configuration of the network terminator of the third embodiment is assumed to be the same as that of NT321 shown in FIG. 3, and the third embodiment will be described using NT321.

In the table, the "setting flag" is a flag that is set to indicate the empty state of the cell, and is set when the corresponding cell is in use (stores "1").

The NT321 sends a polling signal to the corresponding TE311, and when the data flag in the response corresponding to this polling signal is set, the "setting flag" and 2 ports of the polling table shown in Table 4 are used. Depending on the number of remaining cells of the communication capacity stored in RAM335, the same TE
Poll 311.

At the end of the first poll, the corresponding TE31
The identification number of 1 is stored in the FIFO383 and the 2-port RA
The number of cells obtained by subtracting 1 from the communication capacity (the number of cells) read from M333 is stored in the 2-port RAM 335.

Next, when the data flag in the response in this first polling is set, the 2-port RAM 331 (polling table) corresponding to the next count value of the counter 371.
Read the setting flag of. At this time, if the setting flag is not set (the next cell is unused), FI
Poll the TE311 corresponding to the identification number stored in FO383.

After that, when the setting flag “0” in the polling table of Table 4 is continuous, the same TE 311 is polled according to the number of remaining cells stored in the 2-port RAM 335. When the setting flag “0” in the polling table is interrupted (when the setting flag is set), the FIFO 383 and the 2-port RAM 335 described above are once cleared and set in the polling table. The identification number corresponding to the setting flag is FIFO383
1 from the number of cells stored in the corresponding 2-port RAM333
The number of cells obtained by subtracting is stored in the 2-port RAM 335.

V. Summary of Embodiments As described above, the network terminating device (NT221, 321) polls each terminal device based on the polling table (or the polling table and the polling capacity table). When there is data to be sent to each terminal device, the cell is sent following the polling signal. The terminal device receiving this polling signal returns data as a response.

In the NT 221 of the first embodiment, polling is performed according to the polling order determined at the time of call setup, regardless of the amount of transmission data from the terminal device. Further, in the NT 321 of the second embodiment, when there is a large amount of transmission data from the terminal device, polling for the same terminal device is repeated within the range of the communication capacity determined at the time of call setup. Further, in the NT321 of the third embodiment, polling is performed according to the polling order determined at the time of call establishment. However, when continuous empty cells exist, polling for the same terminal device is repeated within the range of communication capacity. it can.

In this way, by issuing a data return instruction from the terminal device by polling, it is possible to specify an empty cell for data transmission, prevent overlapping of data, and improve reliability, and at the same time, each terminal device Since a circuit for controlling the timing of data transmission is unnecessary in the above, the device scale can be reduced.

VI. Modification of Invention In the above-described embodiment of the present invention, a case was considered in which a network terminating device and a plurality of terminal devices were bus-connected via an optical coupler, but a signal was transmitted via a transmission line. Other connection methods (ring connection or the like) may be used as long as they are multiplexed.

In addition, in “I. Correspondence between Example and FIG. 1”,
Although the correspondence between the present invention and the embodiments has been described, the present invention is not limited to this, and those skilled in the art can easily contemplate that the present invention has various modifications.

〔The invention's effect〕

As described above, according to the present invention, the signals transmitted from the respective nodes are multiplexed in response to the polling from the network terminator, so that the overlap of the transmission data is prevented and the reliability is improved. In addition, since a circuit for performing timing control associated with cell monitoring and the like is not required, the device scale can be reduced, which is extremely useful in practice.

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle of the transmission control method of the present invention, FIG. 2 is a block diagram of an embodiment to which the transmission control method of the present invention is applied, and FIG. 3 is an implementation of the transmission control method of the present invention. FIG. 4 is an explanatory diagram of an optical active multiplexing system of a conventional example, and FIG. 5 is an explanatory diagram of an optical passive multiplexing system of a conventional example. In the figure, 111 is a node, 121 is a network terminating device, 131 is a polling table, 211, 311 are terminal devices (TE), 213, 215, 313, 315 are optical couplers, 221, 321 is a network terminating device (NT), 231, 331, 333, 335 is 2-port RAM, 241, 341 is bus transmission. Part, 243,343 is a bus receiving part, 251,351 is a line receiving part, 253,353 is a line sending part, 261,361 is a call setting part, 291,391 is a down bus, 293,393 is an up bus, 337 is a subtractor, 371 is a counter, 373,375 is a selector, 381 Is a write controller, and 383 is a FIFO.

Claims (1)

(57) [Claims] 1. A transmission control method for accommodating a plurality of nodes connected to a transmission line by a network terminating device, and transmitting signals from each of the nodes to an empty cell on the transmission line for multiplexing. The network terminating device has a polling table containing information on the communication capacity of each of the nodes, and the network terminating device specifies an empty cell for returning data from each node by polling based on the polling table. A transmission control method characterized by performing control.