JP2972544B2 - Line switching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line switching method, and more particularly to a line switching control method at the time of failure / recovery of a working line.

[0002]

2. Description of the Related Art A transmitting end station and a receiving end station are installed at a transmitting end and a receiving end of a communication line composed of a plurality of working lines and one or a plurality of protection lines, respectively, and the operation status of the communication line is monitored. When the occurrence of a failure in the communication line is detected, the failed working line is switched to the protection line to secure the communication line, and when the failure line is restored, the protection line is switched back to the restored working line to disconnect the communication line. The line switching operation of the conventional line switching control device to be secured will be described.

FIG. 4 is a block diagram of a conventional line switching controller, and FIG. 5 is a timing chart showing the switching operation. As shown in FIG. 4, the line switching control device 20 of the receiving terminal station and the line switching control device 10 of the transmitting terminal station include a plurality of working lines 30-1 to 30-n, a protection line 40, and a control line 50.
And are connected by

[0004] The line switching control device 10 of the receiving end station includes a failure detection circuit 11-1 to 11-n for individually monitoring a failure of each of the working lines 30-1 to 30-n, and a failure transmitted by the failure detection circuit. A switching control circuit 12 that receives the occurrence information and the failure recovery information and controls switching from the working line to the protection line and switching back from the protection line to the working line, and switching between the working and protection lines according to an instruction from the switching control circuit 12 The receiving end switch 13 to be executed, and the transmitting end switch 2 of the line switching control device 20 of the transmitting end station in accordance with an instruction from the switching control circuit 12.
And a transmission / reception circuit 14 for transmitting and receiving a control signal for controlling the control signal 3.

[0005] The line switching control device 20 of the transmitting end station receives the transmission end switch control signal and the transmission end switching completion signal of the transmission end switching switch sent from the line switching control device 10 of the receiving end station. It comprises a transmission / reception circuit 24 for returning to the switching control device 10 and a transmission end switch 23 for switching between the working and protection lines according to an instruction from the line switching control device 10 of the receiving end station.

First, the line switching control operation at the time of detecting a failure in the line switching control device 10 of the receiving end station will be described with reference to FIG. 4 and FIG.

In the receiving end station, for example, a fault detection circuit 1
When 1-1 detects the failure of the working line 11-1 by a predetermined method, the switching control circuit 12 receives the failure information f shown in FIG.
(Logic 1) is sent. The switching control circuit 12 outputs the fault information f
And sends a transmission end switch control signal a (logic 1) shown in FIG. 5 to the line switching control device 20 of the transmission end station via the transmission / reception circuit 14 to the control line 50, and the transmission end switch 23 It waits for the sending end switching completion signal b to be returned.

[0008] The switching control circuit 12 receives the transmission end switching completion signal b (logic 1) shown in FIG. And the receiving end switch control signal d shown in FIG.
(Logic 1) is sent.

The receiving end switch 13 is provided with a switching control circuit 2
The working line 11-1, which is activated by the receiving end changeover switch control signal d received from 1, is disconnected and switched to the protection line 40. When the switching ends normally, the receiving end switch 13 switches the receiving end switching completion signal e shown in FIG.
(Logic 1) is sent to the switching control circuit 12, and the switching control circuit 12 identifies that the receiving end switching completion signal is logic 1, and confirms that the switching processing of the failed line has been completed normally. .

Next, the switching back operation at the time of failure recovery will be described with reference to FIGS. Line switching control device 1
When the failure detection circuit 11-1 of 0 detects the recovery of the working line 11-1 by a predetermined method, it sends failure recovery information f (logic 0) shown in FIG. Upon receiving the failure recovery information f, the switching control circuit 12 sends the receiving end switch control signal d (logic 0) shown in FIG.
The protection line 40 is activated by the receiving end changeover switch control signal d.
Is returned to the working line 11-1 and the receiving end switching completion signal e (logic 0) shown in FIG.

The switching control circuit 12, which has received the receiving end switching completion signal e, comprises a transmitting / receiving circuit 14, a control line 50, and a transmitting circuit 2.
4, the transmission end switch control signal a shown in FIG.
(Logic 0) is sent to the sending end switch 23.

The sending end switch 23 receives the sending end switch control signal a, switches back from the protection line 40 to the working line 11-1 from which the failure has been restored, and sends a sending end switch completion signal b (logic 0) shown in FIG. ) Is returned to the switching control circuit 12 of the receiving end station via the transmission / reception circuit 24, the control line 50, and the transmission / reception circuit 14. The line switching circuit 12 sets the transmission end switching completion signal b to logic 0.
It was confirmed that the return processing of the failed line was completed normally.

[0013]

In the conventional line switching method of the line switching control device, if the switching processing time is shortened, the influence of the transmission delay of the control / response signal between the transmitting and receiving end stations cannot be ignored.

That is, the sending end switch control signal a and the sending end switching completion signal b transmitted and received between the sending end station and the receiving end station via the control line 50 are controlled by the control line as shown in FIG. Times t1 and t2 are delayed. Therefore, if the line switching time is shortened and the communication line repeats the occurrence / recovery of the failure, the current transmission is completed before the transmission end switching completion signal b becomes logical 0 in the switching immediately after the failback due to the previous failure recovery. The end switching process ends and the receiving end switching operation starts. At this time, since the sending end switching completion signal is logic 1, the receiving end switch is switched. During this time, a logic 0 of the sending end switch control signal a is transmitted to the sending end station, the sending end switch is turned off, and there is a problem that a momentary interruption occurs in the failed communication line.

Therefore, a sequence number is assigned to the control signal and the response signal each time the sending end switch and the receiving end switch are switched, and the sequence number assigned to the switching control signal is assigned when the sending end and the receiving end are switched and switched back. There is another method of avoiding the above-mentioned instantaneous interruption by performing the switching operation only when the numbers are the same, but the switching control process is complicated in this case. There is.

An object of the present invention is to provide a line switching method for preventing a line switching malfunction due to a reduction in line switching processing time and facilitating a high-speed line switching operation.

[0017]

SUMMARY OF THE INVENTION A line switching method according to the present invention
Has established respectively at the receiving end the transmission terminal station and the reception terminal station and transmitting end of communication line, to monitor the operational status of the communication line, when detecting the occurrence of a line fault, the spare channel the working line the switching, also when the line fault is restored, the plurality between said Te line switching method smell of the communication line for failback to the working line that recover the protection line, a pre-Symbol transmission terminal station the reception terminal station , One or more protection lines, and a pair of control lines, and the transmitting end station exchanges line switching control information at the time of failure and recovery with the receiving end station via the control line. Transmitting and receiving circuit, accommodates the plurality of working lines and one or more protection lines, operates according to the line switching control information, switches from the failed working line to the protection line at the time of the fault, and When the fault is recovered, A transmitting end switch for switching back to the working line having recovered from the failure, wherein the receiving end station individually monitors the plurality of working lines and detects a failure; and A transmitting and receiving circuit for transmitting and receiving the line switching control information to and from the transmitting end station, and in the case of the failure, switching from the working line in which the failure has occurred to the protection line,
Further, at the time of restoration of the failure, a receiving end switch for switching back from the protection line to the working line where the failure has been restored, and failure information sent by the failure detection circuit at the time of failure detection and failure recovery, and A switching control circuit for controlling switching and switching back of the sending end switch and the receiving end switch of the receiving end station; and The pseudo-completion signal generating circuit for transmitting, and the switch control circuit, when receiving the fault information for detecting and transmitting a fault of any of the working lines corresponding to any of the fault detecting circuits, Based on the sending-end switching completion signal returned from the sending-end changeover switch, the sending-end changeover switch is identified as being in the operation completed state. A signal is sent to instruct the switching from the faulty line to the protection line. When a sending end switching completion signal returned from the sending end switch is received in response to the switching instruction, the receiving end switch is Sends a receiving end changeover switch control signal to instruct the switching from the faulty line to the protection line, and sets the receiving end changeover switch based on the receiving end changeover completion signal returned from the receiving end changeover switch. Recognizing that the operation is in the completed state, recognizing the normality of the switching process from the working line to the protection line, and receiving fault recovery information from the fault detection circuit that has detected recovery of the working line in which the fault has occurred. Then, the receiving end switch is sent to the receiving end switch control signal to instruct switching back from the protection line to the faulty line, from the receiving end switch. Identifying that the receiving end switch is in the operation completed state based on the received receiving end switch completion signal, and determining that the transmitting end switch is in the operation completed state based on the sending end switching completion signal. Upon identification, the pseudo-completion signal generation circuit is activated, and the pseudo-completion signal generation circuit calculates the logical sum of the pseudo-transmission-end switching completion signal and the transmission-end switching completion signal output for a predetermined period, and this calculation result Is a logical 1, when the sending end switch control signal is transmitted, and when the operation completion state of the sending end switch is identified based on the sending end switch completion signal returned from the sending end switch, It is characterized in that the normality of the switching process from the protection line to the working line where the failure has been recovered is recognized.

[0018] Further, a plurality of working lines, one or a plurality of protection lines, and a pair of control lines are provided between the transmitting terminal station and the receiving terminal station, and the transmitting terminal station is provided with the control line. A transmission / reception circuit for transmitting and receiving line switching control information at the time of failure and recovery with the receiving end station, and accommodating the plurality of working lines and one or more protection lines, operating according to the line switching control information, A switching unit that switches from the working line in which the failure has occurred to the protection line in the case of the failure, and switches back to the working line in which the failure has been restored from the protection line when the failure is recovered; and A failure detection circuit that individually monitors the plurality of working lines to detect a failure, a transmission / reception circuit that transmits and receives the line switching control information to and from the transmitting end station via the control line, and the failure occurs when the failure occurs. Said working times From the protection line to the protection line, and to switch back to the working line from the protection line when the failure is recovered, and to receive the failure information sent by the failure detection circuit when the failure is detected and when the failure is recovered. A switching control circuit for controlling switching and switching back of the transmitting end switch of the transmitting end station and the receiving end switch of the receiving end station; and A pseudo-completion signal generating circuit for transmitting an end switching completion signal for a predetermined period, wherein the switching control circuit detects and transmits a failure of any of the working lines corresponding to any of the failure detection circuits. When the transmission-end switching switch is in an operation completed state based on the transmission-end switching completion signal returned from the transmission-end switching switch, the transmission-end switching switch is identified. A transmission end switch control signal is sent to the switch to instruct switching from the faulty line to the protection line, and a transmission end switch completion signal returned from the transmission end switch is received in response to the switching instruction. Then, a receiving end switch control signal is sent to the receiving end switch to instruct switching from the faulty line to the protection line, and a receiving end switch completion signal returned from the receiving end switch is returned. The receiving end switch recognizes that the operation is completed, recognizes the normality of the switching process from the working line to the protection line, and detects the recovery of the working line in which the failure has occurred. When receiving the failure recovery information from the failure detection circuit, the receiving end switch sends the receiving end switch control signal to the receiving end switch to instruct switching back from the protection line to the failure line. And identifying that the receiving end switch is in an operation completed state based on the receiving end switch completion signal returned from the receiving end switch, and based on the transmitting end switch completion signal. When the pseudo completion signal generation circuit is activated, the pseudo completion signal generation circuit is activated, and the logic of the pseudo transmission end switching completion signal and the transmission end switching completion signal output by the pseudo completion signal generation circuit for a predetermined period of time. A sum is calculated, and when the result of the calculation is logic 1, the sending end switch control signal is transmitted, and the operation of the sending end switch is performed based on the sending end switching completion signal returned from the sending end switch. When the completion state is identified, the normality of the switching process from the protection line to the working line having the failure recovered is recognized.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a line switching control device according to an embodiment of the present invention. FIG. 2 is a block diagram showing a basic configuration of a communication line switching system using the line switching control device of the present invention. FIG. 3 is a timing chart showing the line switching operation of the present invention.

In FIG. 2, the line switching control device 10 at the receiving end station and the line switching control device 20 at the transmitting end station include a communication line 30 comprising a plurality of working lines 30-1 to 30-n and a protection line 40 And a control line 50.

In FIG. 1, a line switching control device 10 of a receiving station includes a failure detection circuit 11-1 to 11-n for individually monitoring a failure of each of the working lines 30-1 to 30-n, and a failure detection circuit. And a switching control circuit 12 for controlling switching from the working line to the protection line and switching back from the protection line to the working line, and switching between the working and protection lines according to an instruction from the switching control circuit. A sending-end switch 12 and a receiving-end switch 13, and a sending-end switch control signal for controlling the sending-end switch 23 of the line-switching control device 20 of the sending station according to an instruction from the switching control circuit, and switching of the sending-end switch. A transmission / reception circuit 14 for transmitting and receiving a completion signal via the control line 50, and a pseudo-transmission-end switching completion signal for preventing a switching malfunction due to a transmission delay of the communication line for a predetermined period. It consists pseudo completion signal generating circuit 15 for.

Further, the line switching control device 20 of the transmitting end station receives the transmission end switch control signal and the switching completion signal of the transmitting end switch transmitted from the line switching control device 10 of the receiving end station. The transmission / reception circuit 24 which returns to the control device 10 and the transmission end switch control signal transmitted from the line switching control device 10 of the receiving end station are operated. And a sending end switch 23 for sending to the control device 10.

First, the line switching operation for detecting a failure in the line switching control device 10 of the receiving end station will be described with reference to FIGS.
This will be described with reference to FIG.

At the receiving end station, for example, the fault detection circuit 11
When -1 detects a failure of the working line 30-1 in the same manner as in the prior art, it sends failure information f (logic 1) shown in FIG. When the switching control circuit 12 receives the failure information f, the switching control circuit 12 of the transmitting end station receives the failure information f from the line switching control device 20 of the transmitting end station by the transmission end switching completion signal b received via the control line 50 to the transmitting / receiving circuit 14. Understand the operation status of the device.

That is, if the sending end switch completion signal b is logic 1, it is determined that the sending end switch 23 is performing the switching operation, and the sending of the sending end switch control signal a is interrupted. The sending end switch 23 determines that the switch is in the reverting state, and sends the sending end switch control signal a (logic 1) to the line switching control device 20 of the sending end station via the transmission / reception circuit 14 to the control line 50. Then, it waits for the sending end switching completion signal b returned from the sending end switch 23.

The sending end switch 23 of the sending end station operates according to the sending end switch control signal a (logic 1) received from the receiving end station, and switches the working line 30-1 in which a failure has occurred to the protection line 40. When the switching operation is completed, the transmitting end switching completion signal b (logic 1) is returned to the receiving end station via the transmitting / receiving circuit 24 to the control line 50. The switching control circuit 12 of the receiving end station
It identifies that the sending end switching completion signal b received from the sending end station is logic 1, and sends a receiving end switch control signal d (logic 1) to the receiving end switch 13.

The receiving end switch 13 is a switch control circuit 1
2 control signal d (logic 1) received from
To switch the working line 30-1 in which the failure has occurred to the protection line 40. The receiving end switch 13 returns the receiving end switching completion signal e (logic 1) to the switching control circuit 12 when the switching is completed normally, and the switching control circuit 12 determines that the receiving end switching completion signal e is logic 1 The switching process is completed by identifying that there is.

Next, a description will be given of the line switching operation at the time of recovery from a failure. As described above, after the failure of the working line 30-1 has occurred and the failure of the working line 30-1 has been restored after switching to the protection line 40, the failure detection circuit 11 detects the failure recovery, and the switching control circuit 12 Recovery information f (logic 0) for
Is sent.

When the switching control circuit 12 receives the failure recovery information f, it sends out a receiving end switch control signal d (logic 0) to the receiving end switch 13. The receiving end changeover switch 13 is activated by the receiving end changeover control signal d, switches back the protection line 40 to the working line 30-1 in which the failure has been recovered, and outputs the receiving end changeover completion signal e (logic 0) to the switching control circuit 12.
Return to

The switching control circuit 12 includes a receiving end switching switch 13.
After identifying that the receiving end switching completion signal e received from the terminal is logical 0, the transmitting end switch control signal a (logical 0) is transmitted to the line switching control of the transmitting end station via the transmitting / receiving circuit 14 to the control line 50. Send to device 20.

The transmission end switch 23 of the line switching control device 20 is activated by the received transmission end switch control signal a (logic 0) and restores the protection line 40 to the active line 3 which has recovered from the failure.
After switching back to 0-1, the transmitting end switching completion signal b (logic 0) is returned to the receiving end station via the transmitting / receiving circuit 24 to the control line 50. The switching control circuit 12 of the receiving end station monitors the sending end switching completion signal b and identifies whether the sending end switching completion signal b immediately after the sending end switching control signal a becomes logic 0 is logic 1 or logic 0. I do. When it is determined to be logic 0, a start signal h is sent to the pseudo completion signal generation circuit 15.

That is, when the sending end switching completion signal b immediately after the sending end switching control signal a becomes the logic 0 and the sending end switching completion signal b is the logic 1, the switching control circuit 12 sets the sending end switch to the switching operation. When the logic is 0, it is determined that the switching back of the switching operation due to the previous failure has been completed, and the switching back of the switching operation due to the current failure has not been completed. If it is set to 0, the pseudo completion signal generation circuit 15 is activated to transmit the pseudo sending end switching completion signal c for a certain period of time.

The switching control circuit 12 includes a transmission end switching completion signal b received from the transmission / reception circuit 14 and the pseudo completion signal generation circuit 1
5 and the pseudo-transmission-end switching completion signal c received from
R), the logical sum output is used for the switching process as a normal sending end switching completion signal.

Therefore, the pseudo sending end switching completion signal c or
Sending end switch completion signal b received from sending end switch 23
If either of them is logic 1, the activation of the next switching operation is suppressed. When the sending end switching completion signal b becomes logic 1, the pseudo completion signal generation circuit 15 stops generating the pseudo sending end switching completion signal c.

As described above, the conventional line switching is
At the timing A in FIG. 5, the switching control circuit 12 starts the switching operation because the transmission end switching completion signal b is logic 0, but at this time, the transmission end switch 23 is performing the switching operation. This is the sending end switch 23 at the time of the last failure.
Is returned by the transmission end switching completion signal b, which arrives at the receiving end station with a delay due to the transmission delay of the communication line, whereby the receiving end changeover switch 13 is switched as shown by the timing B in FIG. While the sending end switch 23 is turned back during the operation and the instantaneous line disconnection occurs, according to the present invention, at the timing A in FIG. 3, the switching control circuit 12
Since the logical sum of the transmission end switching completion signal b and the pseudo transmission end switching completion signal c is logic 1, the line switching operation is suppressed, and no instantaneous interruption at the time of line switching occurs at the timing B in FIG.

[0036]

As described above, according to the present invention, by using the pseudo transmission end switching completion signal generated by the pseudo completion signal generation circuit, the malfunction of line switching due to the arrival delay of the transmission end switching completion signal can be detected by the sequence number or the like. Can be prevented without performing complicated sequence management using, and instantaneous interruption at the time of line switching at the time of line failure can be avoided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a line switching control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a basic configuration of a communication line monitoring system according to the present invention.

FIG. 3 is a timing chart showing a line switching operation of the communication line switching device of the present invention.

FIG. 4 is a block diagram showing a basic configuration of a conventional communication line monitoring system.

FIG. 5 is a timing chart showing a line switching operation of a conventional communication line switching device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Communication line switching control device of receiving end station 11 Fault detection circuit 12 Switching control circuit 13 Receiving end switch 14 Transmission / reception circuit of receiving end station 15 Pseudo completion signal generation circuit 20 Communication line switching control device of sending end station 22 Sending end station 23 Sending end switch 30-30-n Working line 40 Protection line 50 Control line a Sending end switch control signal b Sending end switching completion signal c Pseudo sending end switching completion signal d Receiving end switching switch control signal e Receiving End switch completion signal f Fault information h Start signal

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04B 1/74 H04L 1/00 H04L 1/08-1/24 H04M 3/08-3/14 H04M 3/22-3 / 36 H04Q 1/20-1/26

Claims (1)

(57) [Claims] 1. A respectively transmit and receive ends of the communication line set up a transmission terminal station and the reception terminal station monitors the operational status of the communication line, when detecting the occurrence of a line fault, the working line switched to the protection line, also when the line fault is restored, the Te line switching method smell of the communication line for failback to the working line that recover the protection line, the receiving and the transmission terminal station
Multiple working lines and one or more backup
Line, and a pair of control lines, wherein the transmitting end station communicates with the receiving end station via the control line at the time of failure and recovery.
A transmitting and receiving circuit for transmitting and receiving line switching control information;
Accommodates the working line and one or more protection lines,
It operates according to the line switching control information.
Switch from the working line to the protection line
When the failure is recovered, the failure is recovered from the protection line.
A transmitting end switch for switching back to a working line, wherein the receiving end station individually monitors the plurality of working lines and detects a fault.
A detecting circuit, and the transmitting terminal station and the loop through the control line.
A transmission / reception circuit for transmitting and receiving line switching control information;
From the working line where the failure occurred to the protection line
At the time of switching and recovery from the fault,
A receiving end switch for switching back to the working line that has been restored,
The fault detection circuit sends a signal when a fault is detected and when a fault is recovered.
Receiving the fault information, the sending end switching switch of the sending end station.
Switch of the receiving end switch of the switch and the receiving end station
And a switching control circuit for controlling switching back and forth,
After confirming that the switch has been switched back, the pseudo sending end switch completion signal is
The pseudo-completion signal generating circuit for transmitting for a predetermined period, wherein the switching control circuit is connected to any of the working lines to which any of the fault detecting circuits corresponds.
When receiving the fault information to detect and send out the fault,
Sending end switch completion signal returned from the sending end switch
The sending end switch is in the operation completed state based on
Is identified, and the sending end changeover switch is
And sends a backup control signal from the faulty line to the standby circuit.
Command to switch to the line, and
Receiving the transmission end switching completion signal is sent back from the switching switch
When the receiving end changeover switch is
Sending a control signal from the faulty line to the protection line
Command to switch to the receiving end switch.
The receiving end switch is operated based on the receiving end switching completion signal
Operation is completed, and the
Recognizing the normality of the switching process to the backup line, and detecting the recovery of the working line in which the failure has occurred.
When failure recovery information is received from the failure detection circuit,
The receiving end changeover switch control signal is sent to the end changeover switch.
Send back from the protection line to the failed line
And the receiving end switch returned from the receiving end changeover switch
The receiving end switch is in the operation completed state based on the change completion signal.
And based on the sending end switching completion signal,
Identifies that the sending end switch is in the operation completed state
Then, the pseudo completion signal generation circuit is activated,
The pseudo sending end switching in which the completion signal generating circuit outputs for a predetermined period.
Compute the logical sum of the completion signal and the sending end switching completion signal,
When the result of this operation is logic 1, the sending end switch
Control signal is sent back from the sending end switch.
The operation of the transmission end switch is performed based on the transmission end switching completion signal.
When the operation complete state is identified, the
Recognize the normality of the restoration process to the restored working line
A line switching method, characterized in that: