JPH0563683A - Redundancy system switching device for digital transmission - Google Patents

Abstract

PURPOSE:To attain switching of a redundancy system at restoration of a fault or the like without causing momentary interruption of a main signal. CONSTITUTION:The switching device is provided with a signal branch section 2 branching an input signal into two systems (active system and standby system) of signal paths, two systems of buffer memories 11, 12 equipped with each output of the two systems of signal paths and having a delay of one frame of a main signal, and a CRC insert section 1 implementing CRC calculation of the main signal of the frame just before the input to the signal branch section 2 and inserting an arithmetic value to an overhead, and also with a selector 13, as required, selecting the active system or the standby system and connecting the selected system externally, the selector 13 is provided with CRC error check sections 9, 10 checking a CRC error of the main signal just before it is sent to each buffer memory, and the selector is provided with a switching function corresponding to an error switching one of the two systems of signal path into the other in response to an output of the CRC error check section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a redundant system switching device for digital transmission, and more particularly to a redundant system in a digital transmission system, whereby a redundant system is automatically or forcibly provided to a standby system in case of device failure and maintenance work. The present invention relates to a redundant system switching device for digital transmission that performs switching to suppress the influence on traffic.

[0002]

2. Description of the Related Art Heretofore, this type of redundant system switching device has switched from the active system to the standby system by using a device failure detected by internal monitoring as a switching trigger. As shown in FIG. 2, the input signal passes through the in-device monitoring information inserting section 14 to the signal branching section 2 and two in-apparatus signal paths (0-system signal path composing sections 3 to 5) consisting of an active system and a standby system are provided. , And 1-system signal path constituent units 6 to 8), and is connected to the selector 13 and to the 0-system device error detection unit 15 and the 1-system device error detection unit 16.

The in-device monitoring information insertion unit 14 inserts error monitoring information (eg, parity) of the main signal into the overhead and sends the main signal immediately before entering the selector through signal paths 3 to 8 of the 0 system / 1 system. It is also connected to the error detection unit 15/16 in the 0-system / 1-system device that performs error detection, and at the time of error detection, the signal path is selected to be switched to the backup system side.

[0004]

In the above-mentioned conventional redundant system switching method, even if the failure is recovered by the redundant system switching in the occurrence of a failure in the device or an erroneous operation in maintenance, the main error still occurs. Since the signal has already been sent to the rear,
There has been an inconvenience of adversely affecting the user who is using the troughwick.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the inconvenience of the conventional example, and more particularly, to a redundant system switching device for digital transmission which can carry out a redundant system switching at the time of restoration of a failure without accompanying a momentary interruption of the main signal. The purpose is to provide.

[0006]

A signal branching unit for branching an input signal into two signal paths of a working system and a standby system, and one frame of a main signal provided on each output side of the two system signal paths. It has a two-system buffer memory having a delay amount, and a CRC insertion section for performing CRC calculation of the main signal of the frame immediately before input on the signal input side of the signal branching section and inserting the calculated value in the overhead. A selector for switching between the active system and the standby system for external connection is provided as needed, and a CRC error detection unit for detecting a CRC error of the main signal immediately before being sent to each buffer memory is also provided for this selector. The selector has an error-corresponding switching function that operates in response to the output of the CRC error detector to switch the two signal paths from one to the other. This aims to achieve the above-mentioned object.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In the embodiment shown in FIG. 1, a signal branching unit 2 for branching an input signal into two signal paths, a working system and a standby system.
And a two-system buffer memory 1 equipped on each output side of these two-system signal paths and having a delay amount of one frame of the main signal
1 and 12 and a CRC insertion unit 1 that performs CRC calculation of the main signal of the frame immediately before input on the signal input side of the signal branching unit 2 and inserts the calculated value into the overhead. A selector 13 for switching between the active system and the standby system for external selection is provided as needed, and a CRC error for detecting a CRC error of the main signal immediately before being sent to each of the buffer memories 11 and 12 is provided in the selector 13. The detectors 9 and 10 are provided side by side. Also, the selector 13
Has an error-corresponding switching function that operates in accordance with the outputs of the CRC error detection units 9 and 10 to switch the signal paths of the two systems from one to the other. Here, the CRC configuration (Cyclic Redundancy Check) means a cyclic redundancy check.

That is, a signal branching unit 2 for branching an input signal into two internal signal paths consisting of an active system and a standby system,
Two-system buffer memory (hereinafter referred to as ES) 11, 12 having a delay amount of one frame in terms of the frame length of the main signal,
A CRC insertion unit 1 that performs a CRC operation on the main signal of the immediately preceding frame and inserts an operation value into the overhead before the separation unit of the two-system signal paths, and the ES units 11 and 12 through the two-system signal paths. It has a selector 13 for performing CRC error detection of the main signal immediately before entering and for selecting a signal path switching to the standby system side when an error is detected in the active system. Then, the input main signal is connected to the signal branching unit 2 through the CRC inserting unit 1, passes through the two system internal signal paths (0 system signal paths 3 to 5, 1 system signal paths 6 to 8), and It is connected to the selector 13 through the system ES unit 11 and the 1-system ES 12. On the other hand, the main signals immediately before the 0-system ES unit 11 and the 1-system ES 12 are the 0-system CRC error detection unit 9 and the 1-system CR, respectively.
It is connected to the C error detection unit 10.

Next, the operation will be described. Input signal is CR
After the CRC calculation of the main signal is performed by the C insertion unit 1 and the calculation value is inserted in the overhead, the signal branching unit 2
Branch to the signal path in the system. It is assumed that the 0 system side is operating in the 0 system / 1 system signal path. When a failure occurs in the signal path in operation and the 0-system error detection unit 9 detects a CRC error, the selector 13 is switched to the 1-system selection direction, and the data of the 1-system ES unit 12 is transferred to the selector 1
Send out through 3. Since the 0-system ES11 and the 1-system ES12 perform writing / reading synchronously, the main signal data of the 0-system ES11 containing an error is discarded and normal 1-system main signal data is adopted.

[0010]

As described above, according to the present invention,
In a digital transmission system with a redundant configuration, it can be executed without any interruption of the main signal between the occurrence of a failure and the completion of switching, and even if the signal path component in operation is accidentally removed during maintenance work. Similarly, it is possible to switch without affecting the main signal at all, and thereby it is possible to switch the redundant system without interrupting the main signal even at the time of restoration work in case of a failure etc. A redundant system switching device for transmission can be provided.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a conventional example.

[Explanation of symbols]

 1 CRC Insertion Unit 2 Signal Dividing Unit 3 to 5 0 System Signal Path Constructing Unit (30) 6 to 8 1 System Signal Path Constructing Unit (60) 9 0 System CRC Error Detection Unit 10 1 System CRC Error Detection Unit 11 0 System Buffer Memory (ES) 12 1-system buffer memory (ES) 13 Selector

Claims (1)

[Claims] 1. A signal branching unit for branching an input signal into two signal paths, a working signal line and a backup signal path, and a delay amount for one frame of a main signal, which is provided at each output side of the two signal paths. It has a two-system buffer memory and a CRC insertion unit for performing CRC calculation of the main signal of the frame immediately before input on the signal input side of the signal branching unit and inserting the calculated value in the overhead, and if necessary, to the active system. A selector for switching the standby system and making an external connection is provided, and a CRC error detection unit for detecting a CRC error of the main signal immediately before being sent to each buffer memory is also provided in the selector. A digital circuit having an error-corresponding switching function that operates according to the output of an error detection unit and switches the signal paths of the two systems from one to the other. Redundant system switching device for transmission.