JP3338193B2 - Failure detection method for loop transmission line - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a failure in a loop transmission line, and more particularly to a method for quickly and accurately detecting a failure in a system in which a master station and a slave station are connected by a parallel loop transmission line. About the method.

[0002]

2. Description of the Related Art In accordance with the diversification of information media, information of various media is transmitted at high speed and high reliability by the same transmission means. In the communication system 1 of FIG. 1A, a loop-type transmission line is provided between a master station 2 and a plurality of slave stations 3, and a first line 4 and a second line 5 are arranged in parallel on the loop. The reliability is enhanced with the current working and the other as a spare. Terminals T such as a telephone, a facsimile machine, and a personal computer are connected to the master station 2 and the slave station 3, respectively. Signals of various media such as a telephone voice signal, a facsimile signal, a personal computer digital data signal, and an image signal are transmitted. Transmitted.

In order to efficiently transmit signals of these different media, for example, JT-G7 of the Telegraph and Telephone Technical Committee (TTC)
The synchronization frame (FR) of FIG. 2 according to the 04 standard is used. This synchronous frame (FR) consists of an 8-bit time slot TS.
The digital information in each time slot TS is independent of each other and is a signal of an arbitrary medium, and is a time-division channel between the terminals T connected by the transmission lines 4 and 5. Is transmitted via Each synchronization frame (FR)
It has a synchronization bit F consisting of 5 bits for indicating the beginning of the frame and synchronizing between the frames, and an ST bit consisting of 16 bits for control. The ST bit monitors the status of each slave station, instructs each slave station, controls connection for allocating a channel between terminals to the time slot TS, and the like.

The synchronization bit F is replaced with the parity check bit C.
In order to use them as 1 to C5 or the game alarm bit S, it is also possible to use four synchronous frames (FR) consecutively and use them as four multiframes QM. Also, in order to use the control bits ST for control by blocking the time slots TS, eight synchronous frames (FR) are made continuous to form eight multiframes OM, and the control bits ST are set as shown in FIG. It is also possible to assign and use. In case of 8 multi-frame OM, JT
-The G704 standard specifies the control bit ST of the last synchronization frame (FR).
Is not limited to a specific use.

[0005]

A conventional communication system 1
In the case where a failure occurs in one of the transmission lines 4 or 5, information on the occurrence of the failure is sent to the master station 2 via the other sound transmission line 5 or 4, and transmission is continued by rapid line switching. The reliability is high. However, in the case of a double fault in which a fault occurs in one of the lines before the fault in the other line is recovered, there is no means for immediately transmitting the fault occurrence position and other fault information to the master station 2. For example, FIG.
A fault FL1 occurs in the clockwise first transmission line 4 (which may be referred to as a 0-system) in FIG.
After switching to the (system 1), if a failure FL2 occurs between the child stations 3c and 3d of the system 1 before the recovery of the failure FL1, if a failure FL2 occurs between the master station 2 and the slave station 3 in this case, Slave 3 equivalent to 75%
Transmission to a, 3b, 3c is interrupted. Even if the master station 2 attempts to perform loopback transmission in a sound part, it is not possible to immediately determine a slave station to be looped back because there is no means for transmitting fault location information. In some cases, each of the slave stations 3a, 3b, 3c, and 3d must sequentially determine a failure to detect the position of the failure FL2. Therefore, about 1
It takes seconds and the start of loopback transmission is delayed.

Accordingly, the present invention has been made to solve this problem, and an object of the present invention is to provide a method for detecting a failure in a loop transmission line in which a failure can be quickly detected in a master station.

[0007]

Means for Solving the Problems The present inventors have proposed JT-G704.
When the standard synchronization frame (FR) is used as the 8 multi-frame OM, the control bit (ST) of the last synchronization frame (FR) in the 8 multi-frame OM is not used. Using the bits, the master station was able to detect faults quickly.

Referring to FIG. 1, a method for detecting a failure in a loop transmission line according to the present invention comprises a parallel first transmission line 4 and a second transmission line 5 for connecting a master station 2 and a slave station 3 in a loop.
The synchronization bit (F) and the status bit (S) which can be the game alarm bit (S) due to the signaling multi-frame configuration
P) In a communication system 1 in which a synchronization frame (FR) including a control bit (ST) included in a column is circulated in the opposite direction, a predetermined number (N) of signaling multiframes corresponding to the number (n) of child stations A state form (SF) is constituted by the middle status bit (SP) sequence, a predetermined number (N) is made sufficiently large, a monitoring request (DM) is written in the first status bit (SP) sequence, and each of the slave stations is written. Monitors multiple status bits (SP) and responds (R
S), and the master station alternately sends the status form (SF) to the first and second transmission lines.

[0009] Here, the "signaling multi-frame structure" refers to eight multi-frames described in section 4.1.3.2 (2) signaling multi-frame structure of the JT-G704 standard (conforming to CCITT recommendation 1988 version G.704). .

[0010] A slave station in which reception is interrupted in one of the transmission lines is transmitted to the other transmission line with a synchronization frame (FR) in which a game alarm is written in the game alarm bit (S) and transmitted to the other transmission line. Status form (S) in response to receiving a line monitoring request (DM)
In F), a predetermined reception alarm (RG) is written in the monitoring response (RS) status bit (SP) assigned to the slave station and transmitted to both transmission lines. A neighbor station receiving the game alert is made to turn off the game alert, and is assigned to the neighbor station in the status form (SF) in response to receiving a monitoring request (DM) for any transmission line. Then, a predetermined transmission alarm (SG) is written in the status bit (SP) for the monitoring response (RS) and transmitted to the other transmission line.

In the master station, a fault (FL) is detected based on the reception alarm (RG) and the transmission alarm (SG) from the slave station.

[0012]

Referring to FIGS. 1, 2 and 5, the master station 2
As shown in FIG. 1 (B), an OM sequence including a state form (SF) having a monitoring request (DM) in the first 8 multi-frames OM is alternately transmitted to the 0 system and the 1 system as shown in FIG. I do. FIG.
In the example of (B), the number (N) of OMs required for the formation of the state form (SF) is 12, which corresponds to the slave station 3 in the communication system 1.
Assuming that the number (n) of the bits is 20, the status bit (S) for writing the start and monitoring request (DM) is included in the status form (SF).
P) and independent monitoring response (RS) for each of the 20 slave stations 3
This is necessary to secure the write status bit (SP) and the end write status bit (SP) at the end of the status form (SF). When the number (n) of slave stations 3 in the communication system 1 is four as shown in FIG. 1A, the number (N) of eight multi-frame OMs required for the state form (SF) is four.

FIG. 3 shows an example of the bit configuration of the monitor response (RS). The monitoring response (RS) of each slave station 3 is composed of 8 bits b0 to b7, and the monitoring response (RS) of the two slave stations is shown in FIG.
The assignment can be made as shown in FIG. Monitor response (R
S) includes device alarm (bit b0) and transmission alarm (bit b
1, b2), information on received alarms (bits b3, b4), and operation status (bits b5, b6). Information other than device alarms is shown separately for system 0 and system 1. Normal is 0 level and alarm is generated. Medium or non-operational is indicated at one level.

According to the sequence of FIG. 5, in response to the reception of the monitoring request (DM) from the master station 2, the slave station 3 sets the status form (S
FIG. 3 shows the status bits (SP) assigned to the own station in FIG.
And sends it to the master station 2. If it is healthy, the monitoring response (RS) does not include the alarm,
The master station determines that there is no obstacle.

FIG. 1 shows a monitoring response (RS) when a failure FL occurs.
A description will be given of a case where reception is interrupted in the 0 system of the slave station 3b due to the line fault FL1 in FIG. The slave station 3b sends out the synchronization frame (FR) in which the game alarm is written in the game alarm bit (S) (at level 1) to the system 1 upon detection of the system 0 disconnection to the system 1 and the system 1 monitoring request ( When the DM is received, the own station status bit (SP) of the state form (SF) is added to the own station monitoring response (RS) bit b4.
= 1 is written and sent to the 0-system and 1-system. The adjacent station 3a that receives the station alarm (S = 1) receives the monitoring request (DM) of the 0-system or the 1-system, and sets the own-station monitoring response (RS) to the own-station status bit (SP) of the status form (SF). Bit b1 =
Write 1 transmission alarm (SG) and send it to the 1st system.

The master station 2 can detect the failure of the 0-system reception interruption of the slave station 3b by receiving the reception alarm (RG) and the transmission alarm (SG). In the failure detection in the master station 2, the slave station 3
Even if there is a station, the state form (SF) length is 12ms
Therefore, even if the following double matching is performed, it can be quickly performed in about one tenth of a second.

Before the line failure FL1 of the system 0 recovers, consider a case in which the reception failure of the slave station 3c due to the line failure FL2 of the system 1 occurs, resulting in a double failure. The slave station 3c sends the synchronization frame (FR) in which the game alarm is written in the game alarm bit (S) to the system 0 when the system 1 reception is detected to be interrupted. (DM) not received and receive alarm (RG)
Does not send Adjacent station 3d receiving the game alarm (S = 1)
Is the status form (SF) when the monitoring request (DM) of the first system is received
Of the local station monitoring response (RS) to the local station status bit (SP) of
Write the transmission alert (SG) of b2 = 1 and send it to the 0 system. The master station 2 can detect a failure in the reception interruption of the first system of the slave station 3c by receiving the transmission alarm (SG). The time required for the double fault detection in the master station 2 is substantially the same as the time required for detecting a single fault, so that even in the case of double verification, it can be performed in about one tenth of a second.

Accordingly, an object of the present invention is to provide a method for detecting a failure in a loop transmission line which can quickly detect a failure in a master station.
Is achieved.

[0019]

In the sequence shown in FIG. 5, the monitoring request (DM) and the monitoring response (RS) are sequentially transmitted and received in each of the 0-system and 1-system, and the same monitoring is alternately repeated in each system. The failure is detected when the same failure is found in two consecutive monitoring responses. This is the detection of so-called double matching. According to the present invention, it is possible to quickly detect a failure in a transmission line even if the accuracy of detection is increased by a double check.

FIG. 6 shows the status bit (SP) in the master station 2.
It is a block diagram which shows the handling of. An interface unit 11 for the first transmission line 4 and an interface unit 12 for the second transmission line 5 are connected to a line setting unit 13. control·
The monitoring unit 14 and the clock supply unit 15 are connected to the interface units 11 and 12 via the alarm line 16 and the status line 17. In the communication system 1 in which the present invention is used, a plurality of terminals T1 to T96, which are entities of communication means, are connected to the line setting unit 13 via the terminal interface 18 of the master station 2 and the demultiplexing unit 19. . The line setting unit 13 selects one of the first transmission line 4 and the second transmission line 5 by the line switch 20, and the demultiplexing unit 19 controls the plurality of terminals T1 to T96.
And a time slot (TS) of a synchronous frame (FR) are connected by a multiplexing method.

The control / monitoring unit 14 receives the incoming synchronization frame (F) based on the timing of the clock signal from the clock supply unit 15.
R) performs a required control operation in response to a command such as a monitoring request (DM), etc., and, via the interface units 11 and 12 based on the internal logical judgment, the above-described game alarm (S = 1),
Alarms such as a reception alarm (RG) and a transmission alarm (SG) are given to the status bit (SP) as appropriate. The control / monitoring unit 14 further operates via the status line 17 the operation status of the slave station 3 (bits b5 and b
A status signal such as 6) is also appropriately given to the status bit.

FIG. 7 shows a signal line for the slave station 3 in FIG.
Is a block diagram similar to the above, and the same elements are indicated by the same symbols or numbers. The loop-back changeover switch 21 is for making a signal of one transmission line make a U-turn in the slave station 3 and returning the signal to the other transmission line during operation in a loop-back mode described below.

When the active system is, for example, system 1, and a system 1 failure such as FL2 in FIG. 1A is detected by the double-checking of the sequence of FIG. In order to continue the operation by the system 0, a 1-0 system switching command (SWCD) is written to, for example, the first state bit string (SP) of the state form (SF) and sent to all the slave stations 3 in the communication system 1, In each slave station 3, the line-side interface 12 of the system 1 is switched to the line-side interface 11 of the system 0 by the line changeover switch 20 of FIG. 7 to switch the operation line from the second line 5 to the first line 4.
The master station 2 further switches the first line 4 from the second line 5 by switching the line interface 12 of the system 1 to the line interface 11 of the system 0 with its own line switch 20.
After switching the operation line from the working system (system 1) to the protection system (system 0), each slave station 2 transmits the control response of FIG.
By sending b5 to the 0 level and bit b6 to the 1 level, the master station 2 is sent to the master station 2. The master station 2 confirms the completion of the required switching by the control response, and continues the operation in the 0 system. If the recovery from the system 1 failure FL2 is confirmed by any means, the 0-1 system switching command of FIG. 5 is transmitted from the master station 2 and the procedure according to the already described 1-0 system switching command is performed. The system returns from the spare 0 system to the current 1 system.

If, for example, the fault FL1 shown in FIG. 1A occurs in the system 0 before the recovery from the fault 1 of the system 1 and the double fault occurs, the master station 2 quickly detects this as described above. After that, the slave station 3 transmits a loopback command (LBCD), and accordingly, the slave station separates the faulty section and continues the loopback operation only in the healthy section. FIG. 4 shows an operation state in which the system 0 fault FL1 is isolated in the slave station 3a and the system 1 fault FL2 is isolated in the slave station 3d.

[0025]

As described above in detail, the method for detecting a failure in a loop transmission line according to the present invention is applied to a loop communication system in which a synchronous frame is circulated on a working and protection parallel line between a master station and a slave station. Since the failure information is reported to the master station using the bits reserved when the synchronization frame is multiframed, the following remarkable effects are achieved.

(A) A double fault in the working and protection parallel lines can be quickly detected. (B) Line faults can be detected and reported separately for the working system and the protection system, and switching between the two systems can be performed quickly. (C) Switching to the loopback operation can be quickly performed when a double fault is detected between the active system and the standby system.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention.

FIG. 2 is an explanatory diagram of a synchronization frame.

FIG. 3 is an explanatory diagram of a monitoring response bit.

FIG. 4 is an explanatory diagram of a loopback operation.

FIG. 5 is a diagram showing a monitoring signal transmission / reception sequence.

FIG. 6 is a block diagram of a master station.

FIG. 7 is a block diagram of a slave station.

[Description of Signs] 1 Communication system 2 Master station 3 Slave station 4 First line 5 Second line 11, 12 Line side interface unit 13 Line setting unit 14 Control / monitoring unit 15 Clock supply unit 16 Alarm line 17 Status line 18 Terminal Interface unit 19 Demultiplexing unit 20 Line switching switch 21 Loopback switching switch F Synchronization bit n Number of slave stations N Predetermined number S Station alarm bit T Terminal DM Monitoring request FL Fault FR Synchronization frame 0M 8 multiframe QM 4 multiframe RG Received alert RS monitor response SF status form SG Transmitted alert SP status bit ST control bit TS time slot SMF signaling multi-frame SWCD switch command LBCD loopback command.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Takashi Sugino 1 in Higashi-ku, Higashi-ku, Nagoya-shi, Aichi Chubu Electric Power Company (56) References JP-A-60-29082 (JP, A) JP-A-61-77447 (JP, A) JP-A-61-214638 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/437

Claims (6)

(57) [Claims] 1. A synchronization bit (F) and a state that can become a station alarm bit (S) by a signaling multi-frame configuration to a parallel first transmission line and a second transmission line connecting a master station and a slave station in a loop. In a communication system in which a synchronization frame (FR) including a control bit (ST) as a bit (SP) sequence is circulated in the opposite direction, a predetermined number (N) of signaling multiplexes corresponding to the number (n) of slave stations is provided. A state form (SF) is constituted by a sequence of status bits (SP) in a frame; the predetermined number (N) is made sufficiently large to write a monitoring request (DM) in the first status bit (SP) sequence, and the slave station is written. A plurality of status bits (SP) for each of the supervisory responses (RS);
F) is alternately transmitted to both transmission lines; a slave station whose reception is interrupted on one transmission line is used as a slave station, and a synchronization frame (FR) in which a game alarm is written in the game alarm bit (S) is transmitted to the other transmission line. In response to receiving a monitoring request (DM) of the other transmission line, a predetermined reception alarm is added to a monitoring response (RS) status bit (SP) assigned to the slave station in the status form (SF) in response to receiving a monitoring request (DM) of the other transmission line. (RG) is written and transmitted to both transmission lines; the adjacent station receiving the game alarm is made to erase the game alarm, and the state is set in response to the reception of a monitoring request (DM) of any transmission line. A predetermined transmission alert (SG) is added to the status bit (SP) for the supervisory response (RS) assigned to the adjacent slave station in the form (SF).
And sending it to the other transmission line; a failure detection method for a loop transmission line, wherein the failure (FL) is detected by the master station using the reception alarm (RG) and the transmission alarm (SG). 2. The fault detection method according to claim 1, wherein said master station receives two consecutive reception alerts (RG) or two reception alerts (RG) in response to two consecutive transmissions of said monitoring request (DM). RG) and transmission alarm (SG), and receiving (FL)
A method for detecting a failure in a loop transmission line by detecting a failure. 3. The fault detecting method according to claim 1, wherein
When the fault (FL) is detected, the fault (F
A switch command (SWCD) from the transmission line in which L) is detected to the other transmission line is written in the first state bit (SP) column of the state form (SF) and transmitted, and each slave station performs In response to the reception of the switching command (SWCD), the other transmission line is connected to the slave station, and the connected transmission line is written in the monitoring response (RS) status bit (SP) assigned to the slave station. A method for detecting a fault in a loop transmission line transmitted to the other transmission line. 4. The fault detecting method according to claim 3, wherein when the fault (FL) on the other transmission line after the switching is detected before the recovery from the fault (FL) before the switching, the specific slave station is transmitted to the master station. In response to receiving the loopback switching command (LBCD), the specific slave station writes the loopback switching command (LBCD) to the first status bit (SP) column of the status form (SF) and sends it out. A fault detection method for a loop-type transmission line, which switches to a loopback connection and writes the connection status after the switching to a status bit (SP) for a monitor response (RS) assigned to the slave station and sends it to the master station. . 5. The fault detecting method according to claim 1, wherein the number of bits of said synchronous frame (FR) is 789, 5 bits at one end thereof are synchronous bits (F), and ) Is a control bit (ST), and the synchronization bit (F) is composed of 8 multi-frames.
At least one bit of the control signal (S) and the 16 control bits (S) of the last synchronization frame (FR).
A method for detecting a failure in a loop transmission line using T) as a sequence of status bits (SP). 6. The fault detecting method according to claim 5, wherein the number (n) of the slave stations is 20, and the status form (SF) is constituted by a sequence of 12 status bits (SP). ) Is assigned to the command and start bits, the twelfth status bit (SP) is assigned to the end bit, and the remaining status bits (SP) are used for the monitoring response (RS) of each slave station. A method of detecting a failure in a loop transmission line assigned to each of the following.