JPH11112388A - Method for switching redundant system in communication system having no redundant transmission path - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To standardize an SDH device in accordance with the provisions of international standards, and to reliably detect a failure requiring switching, thereby improving the reliability of the system. SOLUTION: A first device (51, 54) and a second device (53, 56) constituting each terminal device 50A, 50B have a working / spare redundant configuration, and one terminal device 50A has The generated line fault is detected by the other terminal device 50B, and additional data including a line fault occurrence alarm is multiplexed on the working and standby main signals transmitted from the other terminal device to the one terminal device, or A fault occurrence alarm is inserted as an overhead byte, and one of the terminal devices detects an alarm included in the additional data or the overhead byte and switches the line.

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 method for a communication system having no redundant transmission line,
The present invention relates to a redundant system switching method for a communication system in which terminal apparatuses having a redundant configuration are connected by two uplink / downlink transmission lines having no redundant configuration.

[0002]

2. Description of the Related Art In an optical transmission system, an active (WOR)
K), 1 + 1 line switching point-to-point system is constructed by adding a switch controller to a 1 + 1 configuration having one line of protection (PROTECT) or a 1: N configuration of working N lines and one protection line By adding a switch controller to the network, a 1: N line switching point-to-point system is constructed, and when a failure occurs in the working line, the system can switch to the protection line and continue communication.

The transmission and reception of information regarding the switching of the optical signal line is performed using a new synchronous system (SDH: Synchronous Digital Hierarach).
y), which is stipulated by the international standard (SONET), and is performed using K1 / K2 bytes of the overhead bytes OHB. FIG. 10A is an explanatory diagram of a frame format of SONET STS-3 (OC-3), which is composed of 9 × 270 bytes per frame, and the first 9 × 9 bytes are section overhead.
SOH (Section Overhead), the rest is path overhead POH (P
ath Overhead) and the payload PL (payload). The section overhead SOH includes information indicating the beginning of the frame (frame synchronization signal), information specific to the transmission path (information for checking an error during transmission, information for maintaining the network, etc.), and a pointer indicating the position of the path overhead POH. And so on. Also, path overhead
The POH is a part for transmitting end-to-end monitoring information in the network, and the payload PL is a part for transmitting 150 Mbps information.

The section overhead SOH is composed of a 3 × 9 byte relay section overhead, a 1 × 9 byte pointer, and a 5 × 9 byte multiplex section overhead. The relay section overhead is shown in FIG.
As shown in (b), A1 to A2, C1, B1, E1,
It has F1, D1 to D3 bytes. The multiplex section overhead is B2, K1 to K2, D4 to D1.
2, Z1 and Z2 bytes. The relay section overhead and the multi-section overhead have a large number of undefined bytes, and their use is left to the carrier.

[0005] Among the overhead bytes, the K1 byte is mainly used for a switching request, and specifies the level of the switching request and the switching line. The K2 byte is mainly used for responding to the K1 byte, and further includes a system architecture, a switching mode, and an AIS (Alarm).
Indication Signal) / FERF (Far End Receive Fail)
ure). The switching request includes a switching request by a lockout, a forced switch, and a manual switch in addition to a switching request at the time of a signal failure. 11 and 12 show K1 / K defined by SONET.
Here is a list of 2-byte sequences and their meanings.

K1 byte The first four bits b1 to b4 of the K1 byte indicate a switching request.
The last four bits b5 to b8 represent a switching line, and can designate up to 14 transmission lines. Lockout ofProtecti
on is a switching request that prohibits switching to the backup transmission path,
The Forced Switch is an artificial request for switching the designated transmission path, and if the switching is performed, the switching is not performed even if another failure occurs. SF (Signal Failure) is a switching request when a signal on the transmission line is lost.
There are two priorities of Law. SD (Signal Degrade)
Is a switching request due to signal deterioration in the transmission line, and High and
There are two priorities of Law. Note that the SF switching request has a higher priority than the SD switching request. Manual Switch
Is an artificial switch request, which is given priority when another failure occurs.Wait-to-Restore switches after a predetermined time has passed even if a switchback request is issued after the failed line is restored. Exerciser is a request to return, and Exerciser is a request for actually switching whether the switching operation is performed normally and performing self-diagnosis, and No Request is a request to be sent when the switching operation is normal or when the bridge is released.

K2 byte The bits b1 to b4 of the K2 byte specify the transmission path number. If b5 to b8 of the received K1 byte are null, a null (000
0), and in other cases, the switched transmission line number. b5 bit indicates network configuration, "1" is 1
+1 system, "0" indicates 1: N system. b6-b
8 bytes indicate the switching mode, the content of the failure, and the like. The switching mode is a uni-directional mode in which only one-way signal is switched, and a bi-directional mode (Bi-directio
nal mode).

Switching sequence using K1 and K2 bytes In the case of the uni-directional mode, as shown in FIG.
st) to station A. Station A receives the K1 byte (Switch
request) to the line specified by the bridge (Bri
dge) Perform control. Bridge control is control for transmitting the same signal to both the working line and the protection line. Station A is Br
After performing the idge control, a K2 byte (Switch response) corresponding to the received K1 byte is transmitted to the opposite station (station B). The B station that has received the K2 byte performs Switch control. Switch control is control for switching a line signal in a designated reception direction to a protection line.

In the case of the Bi-directional mode, as shown in FIG. 13 (b), when the station B detects the SF, the K1 byte (Switt)
ch request) to station A. Station A sends a Bri to the line specified by the received K1 byte (Switch request).
Performs dge control, returns K2 bytes (Switch response) as in Uni-directional mode, and
Send K1 byte specifying quest (RR). Station B is RR
Is received, switch control and bridge control are performed on the line specified by the K1 byte transmitted by the own station,
The K2 byte (Switch response) is transmitted to the opposite station (station A). A that received this K2 byte (Switch response)
The station performs Switch control.

FIG. 14 is a detailed explanatory diagram of a switching system based on line protection using K1 and K2 bytes, where 1 is a terminal device (station A), and 2 is a terminal device (station B) which is an opposite station of station A. ), 3 is a working transmission line, 3a is a working uplink, 3b is a working downlink, 4 is a protection transmission line, 4a is a protection uplink, and 4b is a protection downlink. Terminal equipment (A
In the station 1, 1a is a demultiplexing section, 1b and 1c are working and protection transmitting sections (TX-W, TX-P) that transmit exactly the same signal, and 1d and 1e are working and protection receiving sections (TX-W and TX-P). RX-W, RX-P)
Receive exactly the same signal. Terminal equipment (B
In the station 2, 2a is a demultiplexing section, 2b and 2c are working and protection transmitting sections (TX-W, TX-P) that transmit exactly the same signal, and 2d and 2e are working and protection receiving sections (TX and W-TX). RX-W, RX-P)
Receive exactly the same signal. The working transmitter 1b of the terminal device 1 is connected to the terminal device 2 via the working uplink 3a.
, And the backup transmission unit 1c of the terminal device 1 is connected to the backup reception unit 2e of the terminal device 2 via the backup uplink line 4a. Similarly, the working transmitting unit 2b of the terminal device 2 is connected to the working receiving unit 1d of the terminal device 1 via the working downlink 3b,
“c” is connected to the standby receiving unit 1e of the terminal device 1 via the standby downlink 4b.

That is, in the transmission system of FIG. 14, the terminal device and the transmission line are both duplicated, and when a failure occurs in the working uplink 3a, it is switched to the protection uplink 4a. Further, when a failure occurs in the working downlink 3b, it is switched to the backup downlink 4b. For example, a failure occurs in the cross section of the uplink 3a, and signal loss (Signal Failure) or signal degradation (Si
gnal Degrade) occurs, the terminal device (station B) 2
F and SD are detected and the K1 byte (S
witch request) to the terminal device (station A) 1. The A station performs bridge control based on the received K1 byte, transmits the same signal to both the working line 3a and the protection line 4a, and transmits a K2 byte (Switch response) corresponding to the received K1 byte. Transmit to the opposite station (station B).
The station B receiving this K2 byte switches from the working line 3a to the protection line 4a by switch control. As described above, when an alarm is detected on any of the working and protection lines, switching from the failed line to the normal line is performed.

By the way, if a line redundant system is adopted in a communication system that is long-distance and has a high transmission path cost (for example, a submarine system that requires international communication), the number of lines and the number of repeaters increase. Costs are high and unrealistic. For this reason, there is a communication system in which only the devices have a redundant configuration and the lines do not have a redundant configuration.
FIG. 15 shows an example of a communication system without such a line redundancy configuration, and the same parts as those in FIG. 14 are denoted by the same reference numerals. In the figure, 5 is an additional device on the A station side, 6 is an additional device on the B station side, 7 is an upstream transmission line, 8 is a downstream transmission line, and the transmission lines 7 and 8 do not have a redundant configuration. In the additional device 5, 5a is a switch for selecting one of the signals input from the working and protection transmitting units 1b and 1c and sending out the signal to the uplink transmission line 7, and 5b is for switching the signal input from the downlink transmission line 8. Hybrid units 5c distributed to the working and standby receiving units 1d and 1e are control units and instruct a signal to be selected by the switch 5a. In the addition device 6, a switch 6a selects one of the signals input from the working and protection transmission units 2b and 2c and sends it to the downstream transmission line 8, and 6b switches a signal input from the upstream transmission line 7. A hybrid unit 6c for distributing the signals to the working and standby receiving units 2d and 2e is a control unit for instructing a signal to be selected by the switch 6a.

In such a communication system, it is assumed that the working unit signal is selected by the switch unit 5a and the working unit signal is distributed to the working and standby receiving units 2d and 2e by the hybrid unit 6b. In such a case, if a failure occurs with the mark “x”, the terminal device (station B) 2 sets the working and protection lines 3
signal loss SF or signal degradation S at a ', 4a'
D is detected at the same time. S on the working and protection lines simultaneously
When F and SD are detected, the line is not switched because it does not make sense to switch according to the provisions of the international standard. But,
In the configuration of FIG. 15, when the line is switched from the working line to the standby line, communication can be continued. For this reason, in a communication system having no line redundancy configuration, S
Even when F and SD are detected, it is necessary to perform line switching so that communication can be continued.

In recent years, ultra-high bit rate communication technology, communication technology using a relay span extension means (optical amplification, code correction, etc.), and optical wavelength multiplexing communication technology have advanced, and various devices have been developed based on these technologies. Is being developed. These developed devices are installed between an SDH device and a transmission line, and are used to reduce communication costs as much as possible. However, these devices may not be able to detect alarms on all transmission paths, and in such a case, it is necessary to detect and respond to the SDH device.

In order to satisfy the above demand, a communication system shown in FIG. 16 has been proposed. This communication system
Two 2.5 Gbps SDH devices (SDH MUX A, SDH MUX
C) An upper device (SLTE-A) 13 of 11, 12 and 5 Gbps, and two 2.5 Gbps SDH devices (SDH MUX B, SDH M
MUX D) 14 and 15 and a 5 Gbps higher-level device (SLTE-B) 16.
7 and 18 are connected. The host device 13 multiplexes 2.5 Gbps signals from the respective SDH devices (SDH MUX) 11 and 12 and multiplexes the signals.
A 5 Gbps signal is transmitted to the transmission path 17, and the 5 Gbps multiplexed signal from the transmission path 18 is split into two working / standby systems, each of which is separated into 2.5 Gbps signals, and each SDH device (SDH MUX) is separated. ) Input to 11 and 12. The host device 16
The 2.5 Gbps signals from the SDH devices (SDHMUX) 14 and 15 are multiplexed and transmitted to the transmission line 18 as a 5 Gbps signal, and the 5 Gbps multiplexed signal from the transmission line 17 is transmitted to two working / standby systems. The signal is branched, and each signal is separated into 2.5 Gbps signals and input to each SDH device (SDH MUX) 14, 15.

The SDH devices 11 to 12 and 14 to 15 have the same configuration, and each has the following units. That is, each SDH device (SDH MUX) includes a working transmitting unit (WTX) 21, a working receiving unit (WRX) 22, a spare transmitting unit (PTX) 23, a spare receiving unit (PRX) 24, and incoming lines # 1 to # 1. A multiplexing unit (MUX) 25 that multiplexes a signal input from #n and distributes the multiplexed signal to working / spare transmitting units 21 and 23, and separates one multiplexed signal input from working / spare receiving units 22 and 24. (DMUX) to send out to outgoing lines # 1 to #n
26. Counterpart device alarm detector (DET) that detects counterpart device alarms sent from the counterpart device and outputs a line switching request
27. A failure detection unit (AL) that detects signal loss SF or signal deterioration SD in a line and instructs to transmit an opposing device alarm.
M) 28, a control unit (CONT) for sending out an opposing device alarm in response to an opposing device alarm transmission trigger. Each SDH device 1
1 to 12 and 14 to 15 do not show all of the above units, but show only those units necessary for explanation.

The host devices (SDH MUX) 13 and 16 have the same configuration and the following units. For example, the host device (SDH MUX) 13 multiplexes the 2.5 Gbps signal from each of the active transmission units 21 of the SDH devices (SDH MUX) 11 and 12 into a 5 Gbps signal and sends it to the transmission path 17 via the switch unit. At the same time, the 5 Gbps multiplexed signal input from the transmission line 18 via the hybrid unit is separated into 2.5 Gbps signals and the SDH devices (SDH MUX) 11, 1
2 multiplexes 2.5 Gbps signals from the working multiplexing / demultiplexing unit (WMLDM) 31 and the spare transmitting units 23 of the SDH devices (SDH MUX) 11 and 12 to be input to each of the working receiving units 22 to obtain a 5 Gbps signal. And transmits the multiplexed signal of 5 Gbps input from the transmission line 18 through the hybrid unit to the transmission line 17 through the switch.
Separated into 2.5Gbps signals and SDH devices (SDH MUX) 11, 12
Multiplexing / demultiplexing unit for separating and inputting to each of the auxiliary receiving units 24
(PMLDM) 32, working system demultiplexer (WMLDM) 31, and protection system demultiplexer (PM
A switch unit (SW) 33 for selecting one of the multiplexed signals input from the LDM) 32 and transmitting the selected multiplexed signal to the transmission line 17; A hybrid unit (HYB) 34 for distributing the signals to 31, 32, a switch for controlling a switch unit 33 in response to a line switching request instructed from an opposite device alarm detection unit (DET) 27 to send a working or protection signal to the transmission line 17 And a controller (SW CONT) 35. It should be noted that not all units described above are shown in each higher-level device 16, but only units necessary for the description.

The active system signal is transmitted upward through the switch unit 33 along the route indicated by the dotted line, and similarly, the active system signal is transmitted downward via the switch unit 33 along the route indicated by the alternate long and short dash line. In the following, a line switching procedure in the case where a line failure occurs at the mark marked “x” will be described. In this case, (a) the switching is performed by the higher-level device (SLTE MUX
A) 13, (b) The SDH device (SDHMUX B) 14, which detects the transmission line alarm and transmits the opposing device alarm, (c) Detects the alarm from the opposing device (opposite device alarm) and requests a line switch. Is output from the SDH device (SDH MUX A) 11.

When a failure occurs at a location indicated by a cross,
The signal on the line indicated by the dotted line is lost (SF) or the signal is degraded (SD). As a result, the active and standby receivers 22 and 24 of the SDH device (SDH MUX B) 14 simultaneously transmit the transmission path alarm (S
F, SD) are detected. The failure detection unit (ALM) 28 generates a trigger for transmitting an alarm from the opposite device when an alarm (signal loss SF or signal deterioration SD) is simultaneously detected in both the working and standby systems. If an alarm is detected in only one of the systems, no alarm is transmitted from the other device. For example, host device 1
6 demultiplexing unit 31 and the active system receiving unit 22 of the SDH device 14
If a failure occurs at point b, the failure detection unit (ALM)
Reference numeral 28 indicates an alarm (signal loss SF or signal deterioration SD) only in the active system. In such a case, the failure detection unit (ALM) 28
Notifies the control unit 29 of that fact. Thereby, the control unit 29 controls a demultiplexing unit (DMUX) (not shown), and the demultiplexing unit separates the signal from the standby receiving unit 24 in place of the signal from the active receiving unit 22 and separates the signals from the predetermined lines # 1 to # 4. Control to send to #n.

When the control unit (CONT) 29 receives the trigger for transmitting the opposing device alarm, the control unit (CONT) 29 transmits the opposing device alarm to the SDH device 11 by using the K2 byte of the overhead OHB along the dashed line route. The active and standby receiving units 22 and 24 of the SDH device 11 detect the opposite device alarm sent from the SDH device 14 and notify the opposite device alarm detection unit (DET) 27. The opposing device alarm detector (DET) 27 issues a switching request to the host device 13 when an opposing device alarm is detected in either the working or standby system. Upon receiving the switching request, the host device 13 instructs the switch unit 33 to switch the line. In response to the switching instruction, the switch unit 33 replaces the signal from the working multiplex / demultiplex unit 31 and thereafter selects the signal from the backup multiplex / demultiplex unit 32 and sends it to the transmission line 17. Thus, communication is continued. As described above, when the transmission path is restored in the standby system,
The switching control is released in this order.

[0021]

As described above, FIG.
According to the configuration described above, in a communication system having no line redundancy configuration, line switching control can be performed even when alarms (signal loss SF, signal deterioration SD) are detected in both the working and standby systems simultaneously. However, prior art SDH devices
Contrary to the provisions of the international standard, when an alarm is detected simultaneously in both the active and standby systems, the line is switched, which is a problem. Further, in the related art, when there is a switching request, switching is performed in a toggle format, and it cannot be determined whether the switching request is from the working side to the protection side or from the protection side to the working side. For this reason, if switching occurs frequently, there is a problem in the prior art that confusion occurs and switching cannot be performed correctly.

In order to solve such a problem, after the switching operation is completed, the counterpart device cancels the alarm insertion, and a guard time is provided until the released signal returns to its own device to complete the switching. Confirmation is performed, but there is a problem that communication is interrupted during such switching confirmation. Further, when a failure occurs in the transmission lines 17 and 18, the line switching is meaningless and unnecessary. However, in the related art, there is a problem that unnecessary line switching is performed even in such a case.

As described above, an object of the present invention is to configure an SDH device (MUX device as a subordinate device) in accordance with international standard rules,
Another object of the present invention is to make it possible to standardize and reliably detect a failure that requires switching to improve the reliability of the system. It is an object of the present invention to be able to determine whether a switching request is from the working side to the protection side or from the protection side to the working side. An object of the present invention is to prevent unnecessary line switching when a transmission line failure occurs.

[0024]

SUMMARY OF THE INVENTION According to the present invention, there is provided a first apparatus for transmitting a working / spare main signal to an opposite station and receiving a working / spare main signal from the opposite station.
And one of the working / spare main signals output from the first device to the opposing station and transmitting it to the opposing station, and branching the main signal transmitted from the opposing station. Two terminal devices each including a second device for inputting to the first device as a working / spare main signal, and an uplink having no redundant configuration between the second devices of each terminal device. Means for making the first and second devices constituting the two terminal devices of the downlink / downstream into a working / standby redundant configuration, and detecting a line failure occurring at one terminal device by the other terminal device. Means for multiplexing additional data including a line failure occurrence alarm in a main signal transmitted from the other terminal device to one terminal device, and detecting an alarm included in the additional data in one terminal device. System switching of a communication system having means for switching lines by switching It is achieved by law.

[0025] Further, the above object is to provide a means for making the first and second devices constituting the terminal equipment a working / spare redundant structure.
On the other hand, the first terminal station device multiplexes the active system identification pattern as additional data on the active main signal, multiplexes the standby system identification pattern on the standby main signal as additional data, and outputs the active / standby system signal. Means for selecting one of the main signals and transmitting the selected signal to the other second terminal device via the upstream transmission path, wherein the second terminal device comprises a pattern multiplexed with the signal transmitted from the first terminal device. Means for detecting the line failure of the first terminal device by monitoring the signal deterioration or loss of the transmitted signal, and detecting the line failure of the second terminal device when the line failure is detected. Means for multiplexing additional data including a failure generating system determined by a pattern into a main signal and transmitting the multiplexed data to a first terminal device via a downlink transmission line; Line disconnection based on system It is achieved by the redundant system switchover method of a communication system comprising means for performing e.

Further, the above object is to provide means for making the first and second devices constituting the terminal device a working / spare redundant structure,
On the other hand, the first terminal device inserts the fixed pattern into the working system and the protection system main signal using the overhead byte, and
Means for selecting one of the working system and the protection system main signal and transmitting the selected signal to the other second terminal device via the upstream transmission line. The second terminal device transmits the main signal transmitted from the first terminal device. Means for restoring the pattern inserted into the fixed pattern by referring to the overhead byte, means for comparing the restored pattern with the fixed pattern, and when the restored pattern does not match the fixed pattern, the second terminal station transmits a line fault to the main signal. Means for multiplexing the additional data including the generated alarm and transmitting the multiplexed data to the first terminal device via the downlink transmission line, wherein the first terminal device identifies the alarm included in the additional data and switches the line This is achieved by a redundant system switching method for a communication system including:

[0027] Further, the above object is to provide a means for making the first and second devices constituting the terminal device a working / spare redundant structure;
On the other hand, the first terminal station device inserts the active system identification pattern into the active system main signal using the overhead byte, inserts the standby system identification pattern into the standby system main signal, and outputs the active system and standby system main signal. Means for selecting one of the two and transmitting it to the other second terminal device via the first transmission path. The second terminal device is inserted in the main signal transmitted from the first terminal device. Means for restoring the pattern with reference to the overhead byte, means for comparing the restored pattern with the identification pattern of the working system or the protection system, and when the restoration pattern does not match the identification pattern, the second terminal device outputs a line failure occurrence alarm Means for multiplexing additional data including a fault occurrence system into a main signal and transmitting the multiplexed data to a first terminal device via a downlink transmission path;
The terminal device is achieved by a redundant system switching method for a communication system including means for switching a line based on an alarm and identification data included in the additional data.

Further, the above object is to provide a means for making the first and second devices constituting the terminal device a working / spare redundant structure.
On the other hand, the first terminal device inserts the fixed pattern into the working system and the protection system main signal using the overhead byte, and
Means for selecting one of the working system and the protection system main signal and transmitting the selected signal to the other second terminal device via the upstream transmission line. The second terminal device transmits the main signal transmitted from the first terminal device. Means for restoring the pattern inserted into the fixed pattern with reference to the overhead byte, means for comparing the restored pattern with the fixed pattern, if the restored pattern does not match the fixed pattern, the second terminal device uses the overhead byte A line fault occurrence alarm is inserted into the main signal and the first
The means for transmitting to the terminal equipment, the first terminal equipment includes means for checking whether or not a line failure occurrence alarm has been notified by referring to the overhead byte, and for switching the line if the alarm has been notified. And a redundant system switching method for a communication system.

Further, the above object is to provide a means for making the first and second devices constituting the terminal device redundant in working / spare.
On the other hand, the first terminal station device inserts the active system identification pattern into the active system main signal using the overhead byte, inserts the standby system identification pattern into the standby system main signal, and outputs the active system and standby system main signal. Means for selecting one of the two and transmitting it to the other second terminal device via the upstream transmission line. The second terminal device converts the pattern inserted in the main signal transmitted from the first terminal device. Means for restoring by referring to the overhead byte; means for comparing the restored pattern with the identification pattern of the working system or the standby system; if the restoration pattern does not match the identification pattern, the second terminal equipment uses the overhead byte Means for inserting a fault occurrence alarm and a fault occurrence system into a main signal and transmitting the signal to the first terminal device via a downlink transmission line, wherein the first terminal device refers to the overhead byte to detect a line fault occurrence And it is accomplished by redundancy system switching method of a communication system comprising means for switching the line to identify the failure type.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION

(A) Communication system to which the line switching method of the present invention can be applied (a) Configuration FIG. 1 is a configuration diagram of a communication system to which the line switching method of the present invention can be applied, 50A is a terminal device on the A station side, 50B Is a terminal device on the B station side. In the terminal device 50A on the A station side, 51 and 52 are 2.5 Gbps SDH devices (SDH MUX A, SDH
MUX C), 53 is a 5 Gbps higher-level device (SLTE-
A). In the terminal device 50B on the B station side, 54,5
5 is a 2.5 Gbps SDH device (SDH MUX B, SDH MUX D), 56 is a 5 Gbps upper device (SLTE-B) that performs demultiplexing, and 57 is a higher device of the terminal device 50B to a higher device of the terminal device 50B. An upstream transmission line for transmitting a signal to the device 56;
6 is a downlink transmission path for transmitting a signal from the host device 6 to the host device 53.

The host device 53 includes an SDH device (SDH MUX) 5
The 2.5 Gbps signals from 1, 52 are multiplexed into 5 Gbps signals and transmitted to the transmission line 57, and the 5G
Splits bps multiplexed signal and splits each split signal to 2.5Gbps
And input to each SDH device (SDH MUX) 51, 52. The higher-level device 56 includes SDH devices (SDH MUX) 54 and 5
The 2.5 Gbps signal from 5 is multiplexed and converted into a 5 Gbps signal and transmitted to the transmission line 58, and the 5 Gbps multiplexed signal from the transmission line 57 is branched, and each branched signal is separated into a 2.5 Gbps signal. Input to each SDH device (SDH MUX) 54, 55. The SDH devices 51 to 52 and 54 to 55 have the same configuration, and respectively have a working transmitter (WTX) 61, a working receiver (WRX) 62, a spare transmitter (PTX) 63, and a spare receiver ( PRX) 64.

The host device (SDH MUX) 53 has the following units. That is, the higher-level device (SDH MUX) 53 multiplexes the 2.5 Gbps signal from each of the active transmission units 61 of the SDH devices (SDH MUX) 51 and 52 into a 5 Gbps signal to the transmission path 57 via the switch unit. At the same time, the multiplexed signal of 5 Gbps input from the transmission line 58 via the hybrid unit is separated into 2.5 Gbps signals to be separated into SDH devices (SDH MUX) 51,5.
2, a 2.5 Gbps signal from each of the working transmission / reception units 62 and 2.5 Gbps signals from each of the spare transmission units 63 of the SDH devices (SDH MUX) 51 and 52 to be input to a 5 Gbps signal. And transmits the signal to the transmission line 57 via the switch unit, and separates the 5 Gbps multiplexed signal input from the transmission line 58 via the hybrid unit into a 2.5 Gbps signal to generate SDH MUXs 51 and 5.
2, a standby multiplexing / demultiplexing unit (PMLDM) 72, a working multiplexing / demultiplexing unit (WMLDM) 71, and a standby multiplexing / demultiplexing unit (PM
A switch unit (SW) 73 that selects one of the 5 Gbps multiplexed signals input from the LDM) 72 and sends it out to the transmission path 57, and converts the 5 Gbps multiplexed signal input from the transmission path 58 into a working and protection demultiplexing unit. A hybrid unit (HYB) 74 for branching and inputting to the 71 and 72 is provided. Host device (SDH MUX) 5
6 has the same configuration as that of the host device 53, although the arrangement of the units is reversed.

(B) Signal transmission Signal transmission from the station A to the station B is performed as follows. The working system signals input from the outside to the SDH devices 51 and 52 of the A station are input to the working system demultiplexing unit 71 of the host device 53 via the working transmission unit 61 of the SDH devices 51 and 52, respectively. The signals are time-division multiplexed and input to the switch unit 73. In parallel with the above, SDH devices 51 and 52 of station A
Of the standby system input to the SDH devices 51 and 5 respectively.
The signal is input to the standby multiplexing / demultiplexing unit 72 of the higher-level device 53 via the second standby transmitting unit 63, where it is time division multiplexed and input to the switch unit 73. The switch unit 73 selects, for example, a signal from the active system and sends it out to the transmission path 57.

The hybrid unit 74 of the host device 56 of the station B
Branches the multiplexed signal transmitted from the station A via the transmission line 57 to the working / standby multiplexing / demultiplexing units 71 and 72. The working system demultiplexing unit 71 separates the input multiplexed signal, and inputs the separated signals to the working system receiving unit 62 of the SDH devices 54 and 55, respectively. To send to. Also, the standby multiplex separation unit 72
Separates the input multiplexed signal, inputs the separated signals to the standby receiving unit 64 of the SDH devices 54 and 55, and the standby receiving unit 64 sends the signal to the outside as a standby signal. If, for example, a failure occurs at point a of the working line during such signal transmission, the switch unit 73 is controlled by the line switching configuration of the present invention to be described later to replace the working multiplex signal with the protection multiplex signal and transmit the protection multiplex signal to the transmission line 57. To continue the communication. The above is the case where the signal is transmitted from the station A to the station B. The same applies to the case where the signal is transmitted from the station B to the station A.

(C) Configuration of Demultiplexing Unit Some of the demultiplexing units 71 and 72 have a function of transmitting signals other than the main signal simultaneously with the main signal, and others have no function. (c-1) When there is no simultaneous transmission function When the demultiplexing units 71 and 72 do not have the function of transmitting signals other than the main signal simultaneously with the main signal, the demultiplexing unit 7
At the time of multiplexing, the main signals 1 and 72 time-division multiplex the main signals input from the SDH devices 51 and 52 simply at a bit rate twice as high as the main signals and transmit them to the switch unit 73. Also, at the time of separation, the multiplexed signal branched and input from the hybrid unit 74 is separated, and the separated signal is sent to the SDH devices 51 and 52 at a bit rate of ビ ッ ト the bit rate of the multiplexed signal.

(C-2) Case of Simultaneous Transmission Function When the demultiplexing units 71 and 72 have a function of transmitting signals other than the main signal at the same time as the main signal, the demultiplexing unit converts the main signal into Time-division multiplexing is performed at a speed higher than twice the bit rate to create a blank time slot, and the additional data ADDT is added to the time slot and transmitted. FIG. 2A is an explanatory view of such a multiplexing principle, wherein the SDH device 5
The data DATA A and DATA C input from 1, 52 are
An empty time slot is generated by multiplexing at a speed higher than the double bit rate, and the additional data ADDT generated from the additional data generator 75 is multiplexed into the time slot and transmitted to the switch unit 73.

FIG. 2B is a configuration diagram of a multiplexing unit in the demultiplexing unit. Data DATA A and DATA C transmitted from the SDH devices 51 and 52 are stored in the first and second memories 76a and 76b in synchronization with the low-speed clock LCLK, respectively. The PLL 76c uses the low-speed clock LCLK to generate a clock HCLK that is faster than twice the low-speed clock and inputs the clock HCLK to the multiplexing control unit 76d. Each time the high-speed clock HCLK is generated, the multiplex control unit 76d adds the additional data ADDT → DATA A → DATA
These data are read from the memory in the order of C. That is, the multiplexing control unit 76d first transmits the additional data ADDT in synchronization with the high-speed clock HCLK, then transmits one frame of data DATA A, and then transmits one frame of data DATA A.
DATA C is transmitted, and thereafter, the additional data ADDT, data DATAA, and DATA C are multiplexed and transmitted in the above order.

At the time of demultiplexing, the demultiplexing units 71 and 72 synchronize the multiplexed signal DATA input from the hybrid unit 74 with the high-speed clock HCLK as shown in FIG. ′ And data DATA C ′, and these are separated into additional data analyzer 75 ′ SDH device 51,
Send to 52. FIG. 3B is a configuration diagram of a demultiplexing unit in the demultiplexing unit. The multiplexed data DATA input from the hybrid unit 74 is subjected to additional data ADDT ', data DTTA A',
The data is separated into DATA C '. Additional data ADDT 'is ADDT
Input to the analysis unit 75 ', data DTTA A', data DATA
C 'is also written in the first and second memories 77b and 77c. Each of the PLLs 77d and 77e generates a low-speed clock LCLK from the high-speed clock, and the memories 77b and 77c store data DTTA A 'and data DATA C' in synchronization with the low-speed clock.
It is sent to SDH devices 51 and 52.

(B) Embodiment An embodiment of line switching when a line failure occurs in the communication system shown in FIG. 1 will be described below. However, the SDH devices 52 and 55 are omitted in the configuration diagrams of the embodiments. In addition, the working system demultiplexing unit 71 and the standby system demultiplexing unit 72 in FIG. 1 are respectively divided into a multiplexing unit and a demultiplexing unit, and the respective multiplexing units are integrally shown as a multiplexing unit (MUX) 81. And is shown as a separation unit (DMUX) 82.

(A) First Embodiment (a-1) Configuration FIG. 4 is a diagram showing a line switching configuration according to a first embodiment of the present invention, and the same parts as those in FIG. 1 are denoted by the same reference numerals. The multiplexing unit 81 has a function of multiplexing the main data with the additional data ADDT and transmitting the multiplexed signal. The separating unit 82 has a function of separating the multiplexed signal into the main signal and the additional data ADDT and outputting the same. In the first embodiment of FIG. 4, reference numeral 83 denotes an AND circuit provided in the higher-level device 56 on the B station side, and calculates the logical product of the active and standby alarm detection signals ALM1 and ALM2, and the operation result is obtained. "
When the value is 1 ", the opposing device alarm is input to the multiplexing unit 81 as additional data ADDT. Reference numeral 84 denotes an OR circuit provided in the higher-level device 53 on the A station side. A logical OR operation is performed to determine whether one of the additional data ADDT of the system multiplexed signal includes an opposite device alarm, and when the operation result is "1", the switch unit 73 is controlled to execute line switching.

(A-2) Line switching control The working system signal inputted from the outside to the SDH device 51 of the station A is transmitted via the working system transmitting section 61 to the working system multiplex 8 of the upper apparatus 53.
1a, where it is time-division multiplexed with the working signal from the SDH device 52 (not shown) and input to the switch unit 73. The signal of the standby system input to the SDH device 51 of the station A is transmitted via the standby transmission unit 63 of the SDH device 51 to the host device 5.
3 is input to the standby multiplexing unit 81b, where the SDH device 52
The signal is time-division multiplexed with a standby signal from a not shown (not shown) and input to the switch unit 73. The switch unit 73 selects, for example, a signal from the active system and sends it out to the transmission path 57.

Hybrid section 74 of host apparatus 56 of station B
Inputs the multiplexed signal transmitted from the station A via the transmission line 57 to each of the working / standby demultiplexers 82a and 82b. The working system separation unit 82a separates the input multiplexed signal, and inputs the separated signals to the working system receiving unit 62 of the SDH device 54 and the SDH device 55 (not shown), respectively. Is sent to the outside as a working signal. Also, the separation unit 82b of the standby system separates the input multiplex signal, and separates the separated signals into SDH devices 54 and 55 (not shown).
, And sends the signal to the outside as a standby signal. The above is the case where the signal is transmitted from the station A to the station B. The same applies to the case where the signal is transmitted from the station B to the station A.

At the time of such normal transmission, the current use of the SDH device 54 /
The spare receiving units 62 and 64 output an alarm detection signal ALM of "0" indicating that there is no alarm (no line failure has occurred).
1 and ALM2 are notified to the host device 56. Host device 56
Since the logical operation result is "0", the AND circuit 83 inputs no alarm to the multiplexing units 81a and 81b.
a and 81b transmit the additional data ADDT to be multiplexed to the main signal to the A station side with no alarm included. The separation unit 82 of the higher-level device 53 of the station A monitors whether the additional data ADDT sent from the station A includes an alarm signal, and compares the monitoring result with the OR circuit 8.
Enter 4 If not included, the OR circuit 84
Is "0", the communication is continued without switching the line. In this state, a
When a failure occurs at the point, the working and backup receiving units 62 and 64 of the SDH device 54 of the station B detect a signal loss SF or a signal deterioration SD, and therefore, a high level alarm detection signal ALM.
1, Output ALM2 respectively.

As a result, the AND operation result of the AND circuit 83 becomes “1”, and the AND circuit 83
As the DT, the active and standby multiplexing units 81a,
Input to 81b. Working and backup multiplexing units 81a, 81
b adds the opposite device alarm to the main signal and sends it to the A station side. The working and protection demultiplexing units 82a and 82b of the higher-level device 53 of the A station check whether the working and protection multiplexed signal includes an opposite device warning, and when the multiplexed signal includes the opposite device warning, a detection signal of a high-level opposite device warning. D1 and D2 are output.
The OR circuit 84 is the additional data of the active and standby multiplex signals.
A signal D indicating that the ADDT includes a remote device alarm
The logical sum of D1 and D2 is calculated, and when the calculation result is "1", that is, when either one of them receives the opposing device alarm, the switch unit 73 is instructed to switch the line. This allows
The switch unit 73 selects the spare multiplexed signal output from the standby multiplexing unit 81b in place of the working multiplexed signal from the working multiplexing unit 81, sends it out to the transmission line 58, and continues the communication. As described above, according to the first embodiment, the line switching can be realized by causing the higher-level devices 53 and 56 to transmit and detect the counterpart device alarm, which has been conventionally performed by the SDH device. As a result, the SDH device performs the counterpart device alarm procedure. Standardization can be performed while complying with international standards.

(B) Second Embodiment (b-1) Configuration FIG. 5 is a diagram of a line switching configuration according to a second embodiment of the present invention, and the same parts as those in FIG. The multiplexing unit 81 has a function of multiplexing the main data with the additional data ADDT and transmitting the multiplexed signal. The separating unit 82 converts the multiplexed signal into the main signal and the additional data ADDT.
It has a function to output separately. The working system multiplexing section 81a provided in the host device 53 of the station A multiplexes the working system identification pattern (W system pattern) on the main signal and sends it out. The protection system multiplexing section 81b adds the protection system identification pattern (P Multiplexed and transmitted. The active system separation unit 82a provided in the upper apparatus 56 of the station B extracts the system identification pattern multiplexed on the active system main signal and inputs the extracted system identification pattern to the additional data creation unit 86 described later. The system identification pattern multiplexed on the system main signal is extracted and input to the additional data creation unit 86.

An alarm discriminating unit (ALM DET) 85 is provided in the host device 56 on the B station side, and outputs an alarm signal ALM when the alarm detection signals ALM1 and ALM2 of the active system and the standby system simultaneously become high level. . When the alarm signal ALM is output from the alarm identification unit (ALM DET) 85, the additional data creation unit (MIX) 86 outputs the additional data AD composed of the system identification pattern input from the opposing device alarm and separation units 82a and 82b.
A DT is created and input to the active and standby multiplexing units 81a and 81b. The opposing device alarm detector (DET / CONT) 87 is provided in the higher-level device 53 on the station A side and multiplexes the additional data multiplexed with the working signal and the protection signal sent from the station B.
The ADDT identifies the alarm of the opposing device and the system in which a failure has occurred (working system / standby system), and instructs the switch unit 73 to switch the line based on the identification result.

(B-2) Line switching control The working system signal inputted from the outside to the SDH device 51 of the station A is transmitted to the working system multiplex 8
1a, where it is time-division multiplexed with the working signal and the W pattern from the SDH device 52 (not shown) and input to the switch unit 73. Further, the standby signal input to the SDH device 51 of the station A is input to the standby multiplexing unit 81b of the host device 53 via the standby transmission unit 63 of the SDH device 51, where the SDH device 52 (shown in FIG. ) And the standby signal from P
The signal is time-division multiplexed with the system pattern and input to the switch unit 73. The switch unit 73 selects, for example, a signal from the active system (W system pattern is multiplexed) and sends it to the transmission path 57. The hybrid unit 74 of the higher-level device 56 of the station B inputs the multiplexed signal transmitted from the station A via the transmission line 57 to each of the working / standby demultiplexers 82a and 82b. The active system separation unit 82a separates the input multiplex signal, and
The system pattern is input to the additional data creation unit (MIX) 86, and the separated main signals are input to the active system receiving unit 62 of the SDH device 54 and the SDH device 55 (not shown), respectively.
2 sends the signal to the outside as a working signal.

The standby separation unit 82b separates the input multiplexed signal and outputs the separated main signals to the SDH device 5 respectively.
4, input to the standby receiving unit 64 of the SDH device 55 (not shown), and the standby receiving unit 64 sends the signal to the outside as a standby signal. The above is the case where the signal is transmitted from the station A to the station B. The same applies to the case where the signal is transmitted from the station B to the station A. During such normal transmission, the SDH device 5
The working / spare receiving units 62 and 64 of No. 4 notify the alarm detecting unit 85 of the host device 56 that there is no alarm. As a result, the alarm detector 85 indicates that there is no alarm in the additional data generator (MIX) 8.
Enter 6 The additional data creating unit (MIX) 86 creates additional data ADDT that includes a W-system pattern and does not include the counterpart device alarm, and inputs it to the multiplexing units 81a and 81b. Multiplexing section 81
a and 81b multiplex the additional data ADDT on the main signal and transmit it to the A station side.

The separating section 82 of the host apparatus 53 of the station A extracts the additional data ADDT sent from the station B and inputs the same to the alarm identification section 87 of the opposing apparatus. The opposite device alarm identification section 87 does not switch the line because the additional data ADDT does not include the opposite device alarm. In this state, if a failure occurs at point a of the working line, the working and protection receiving units 62 and 64 of the SDH device 54 of the station B detect the signal loss SF or the signal deterioration SD. Therefore, it outputs the high-level alarm detection signals ALM1 and ALM2, respectively. As a result, the alarm signal detector 85 inputs the high-level alarm signal ALM to the additional data generator (MIX) 86.

By the way, even if a fault occurs at the point a, the working system multiplexing section 81 of the host apparatus 53 multiplexes the W system pattern on the working / spare main signal and sends it out. For this reason, the active system separation unit 82a of the host apparatus 56 of the station B extracts the W system pattern and inputs it to the additional data creation unit (MIX) 86. When the alarm signal ALM goes to a high level, the additional data generator 86 outputs the additional data AD including the counterpart device alarm and the W-related pattern.
A DT is created and input to the active and standby multiplexing units 81a and 81b. The active and standby multiplexing units 81a and 81b multiplex the additional data ADDT on the main signal and transmit it to the A station. The opposing device alarm detection unit (DET / CONT) 87 is provided with the additional data AD extracted by the active and standby separation units 82a and 82b.
Based on the DT, an alarm of the opposing device and a failure generating system (active system) are identified, and the switching unit 73 is instructed to switch the line based on the identification result.

When the line switching operation is completed, the system identification pattern is automatically changed from the W system pattern to the P system pattern, and the P system pattern is returned to the A station host device 53 via the B station host device 56. Will be. At this time, by confirming the presence or absence of the alarm, it can be confirmed whether the switching has been performed and the alarm has been released. The above is a case where a failure occurs at the point a of the working line, but a failure may occur at the point b of the transmission line 57. When a failure occurs in the transmission path 57, line switching is meaningless and is unnecessary. By the way, the system identification pattern is not input to the additional data for failure generator 86 in the transmission path 57. Therefore, it is determined that the generation of the alarm for which the system identification pattern is not input is a failure of the transmission path 57, and the additional data creating unit 86 does not include the opposite device alarm in the additional data ADDT.
Avoid switching the line. As described above, according to the second embodiment, the same effect as that of the first embodiment can be achieved, and the fault system can be identified. Further, according to the second embodiment, it is possible to prevent unnecessary line switching when a failure occurs in the transmission path.

(C) Third Embodiment (c-1) Configuration FIG. 6 is a diagram showing a line switching configuration according to a third embodiment of the present invention, and the same parts as those in FIG. Reference numeral 87 denotes an opposite device alarm detection unit (DET / CONT), which is provided in the higher-level device 53 on the A station side and is based on the additional data ADDT multiplexed on the working signal and the protection signal sent from the B station. The switch unit 7 is identified based on the identification result based on the identification result of the opposing device.
3 instructs line switching. Reference numeral 91 denotes a pattern generator provided in the host device 53 of the A station,
A predetermined pattern is generated, and the pattern is input to the active and standby transmission units 61 and 63 of the SDH device 51. The transmitting units 61 and 63 transmit the overhead byte O of the main signal.
Undefined bytes D1 to D12, F1, E1 to E in HB
The above pattern is sent to the B station by using 2.

Reference numeral 92 denotes a pattern identification unit provided in the host device 56 of the station B. The working system and standby system receiving units 62 and 64 of the station B identify the patterns transmitted in predetermined undefined bytes D1 to D12 and F1 and E1 to E2 among the overhead bytes OHB of the main signal, and a pattern identifying unit 92.
To enter. The pattern identification unit 92 compares the patterns input from the active system and standby system receiving units 62 and 64 with the known patterns and checks whether they match, and if none of them match, a line fault has occurred. Is determined, and the additional data ADDT including the alarm of the opposing device is created and input to the working and backup multiplexing units 81a and 81b.

(C-2) Line switching control The active and standby transmission units 61 of the SDH device 51 of the station A,
63 inserts the pattern input from the pattern generator 91 into the working and protection main signals using the undefined bytes of the overhead byte OHB, and inputs the patterns to the working and protection system multiplexing units 81a and 81b of the host device 53. . The working system multiplexing unit 81a time-division multiplexes the working system signals from the SDH devices 51 and 52 (not shown) and switches the switching unit 73.
To enter. The standby multiplexing unit 81b is connected to the SDH device 51, S
The standby signal from the DH device 52 (not shown) is time-division multiplexed and input to the switch unit 73. The switch unit 73 selects, for example, a signal from the active system and sends it out to the transmission path 57.

Hybrid section 74 of host apparatus 56 of station B
Inputs the multiplexed signal transmitted from the station A via the transmission line 57 to each of the working / standby demultiplexers 82a and 82b. The working system separation unit 82a separates the input multiplexed signal and inputs the separated main signals to the working system receiving unit 62 of the SDH device 54 and the SDH device 55 (not shown), respectively. Active receiver 6
2 sends the signal to the outside as a working signal,
A pattern is extracted from the undefined byte of the overhead byte OHB of the main signal and input to the pattern identification unit 92.
The standby separation unit 82b separates the input multiplexed signal and separates the separated main signals into the SDH device 54 and the SDH device 5 respectively.
5 (not shown). The standby system receiving unit 64 sends the signal to the outside as a standby system signal, extracts a pattern from an undefined byte of the overhead byte OHB of the main signal, and inputs the extracted pattern to the pattern identifying unit 92.

During normal operation, the working and protection receiving sections 62
The pattern extracted at 64 is a pattern generator 91
Matches the pattern generated from. Therefore, the pattern identification unit 92 adds the additional data ADDT not including the counterpart device alarm.
Is created and input to the multiplexing units 81a and 81b. Multiplexer 8
1a and 81b multiplex the additional data ADDT into the main signal and
Send to the station. The separation unit 82 of the higher-level device 53 of the station A
The additional data ADDT sent from the station is extracted and input to the opposing device alarm detector 87. Since the opposite device alarm detection unit 87 does not include the opposite device alarm in the additional data ADDT,
Does not switch lines.

In this state, if a failure occurs at point a of the working line, the working and protection receiving sections 62 and 64 cannot extract the pattern generated from the pattern generator 91, and the working and protection receiving sections 62 and 64 Will no longer match the known pattern. In this state, the pattern identification unit 92 determines that a line failure has occurred, creates additional data ADDT including the alarm of the opposite device, and inputs the additional data ADDT to the active and standby multiplexing units 81a and 81b. The working and standby multiplexing units 81a and 81b multiplex the additional data ADDT on the main signal and transmit it to the A station. The opposing device alarm detector (DET / CONT) 87 identifies the opposing device alarm from the additional data ADDT extracted by the active / standby separating units 82a and 82b, and switches the line to the switch unit 73 based on the identification result. Instruct.

When the line switching operation is completed, the above pattern is sent back to the host A 53 of the station A via the host 56 of the station B. At this time, by confirming the presence or absence of the alarm, it can be confirmed whether the switching has been performed and the alarm has been released. As described above, according to the third embodiment, the same effect as that of the first embodiment can be achieved, and even when the line failure cannot be clearly detected based on the signal loss SF or the signal deterioration SD, it is ensured by the pattern mismatch. In addition, line switching can be performed by quickly detecting a line failure.

(D) Fourth Embodiment (d-1) Configuration FIG. 7 is a diagram showing a line switching configuration according to a fourth embodiment of the present invention, and the same parts as those in FIG. Reference numeral 87 denotes an opposite device alarm detection unit (DET / CONT), which is provided in the higher-level device 53 on the A station side and is based on the additional data ADDT multiplexed on the working signal and the protection signal sent from the B station. The switch unit 7 is identified based on the identification result based on the identification result of the opposing device.
3 is instructed to switch the line. Reference numeral 93 denotes a pattern generator provided in the higher-level device 53 of the station A, which constantly generates a W-system pattern / P-system pattern, and transmits the W-system pattern / P-system pattern to the working system / standby system of the SDH device 51, respectively. Input to the sections 61 and 63. Active / standby transmission unit 6
Reference numerals 1 and 63 use the undefined bytes D1 to D12 and F1 and E1 to E2 of the overhead bytes OHB of the main signal to insert the W pattern / P pattern into the main signal and send it to the B station.

Reference numeral 94 denotes a pattern identification unit provided in the host device 56 of the station B. The working system and standby system receiving units 62 and 64 of the station B identify the patterns transmitted in predetermined undefined bytes D1 to D12 and F1 and E1 to E2 among the overhead bytes OHB of the main signal, and a pattern identifying unit 92.
To enter. The pattern identification unit 92 compares the patterns input from the active system and standby system receiving units 62 and 64 with a known pattern (W system or P system pattern) and checks whether they match. It is determined that a line failure has occurred, and additional data ADDT including an alarm of the opposite device is created, and the working and protection multiplexing sections 81a, 81a,
Input to 81b.

(C-2) Line switching control Active / standby transmission units 61 and 6 of SDH device 51 of station A
3 uses the undefined byte of the overhead byte OHB to insert the W-system pattern / P-system pattern input from the pattern generator 91 into the active / standby main signal, respectively, and to multiplex the active / standby system of the host device 53. Part 81a,
Input to 81b. The working system multiplexing unit 81a is the SDH device 5
1. A working signal from an SDH device 52 (not shown) is time-division multiplexed and input to a switch unit 73. Further, the standby multiplexing unit 81b time-division multiplexes the standby signals from the SDH devices 51 and 52 (not shown) and inputs the multiplexed signals to the switch unit 73. The switch unit 73 selects, for example, a signal (in which a W-system pattern is inserted) from the working system multiplexing unit 81a and sends it to the transmission path 57.

Hybrid section 74 of host apparatus 56 of station B
Inputs the working multiplex signal transmitted from the station A via the transmission line 57 to the working / spare demultiplexers 82a and 82b. The working system separation unit 82a separates the input working system multiplexed signal and inputs the separated main signals to the working system receiving unit 62 of the SDH device 54 and the SDH device 55 (not shown). The active system receiving unit 62 sends the signal as an active system signal to the outside, extracts a W system pattern from an undefined byte of the overhead byte OHB of the main signal, and extracts the W system pattern.
Enter 4 The standby separation unit 82b separates the input standby multiplex signal, and separates the separated main signals into SD signals.
Standby unit 6 of the H device 54 and the SDH device 55 (not shown)
Enter 4 The standby system receiving unit 64 sends the signal to the outside as a standby system signal, extracts a W system pattern from an undefined byte of the overhead byte OHB of the main signal, and inputs the extracted W system pattern to the pattern identification unit 94.

During normal operation, the working and protection receiving sections 62
The pattern extracted at 64 matches the W pattern.
Accordingly, the pattern identification unit 94 creates additional data ADDT that includes the W-system pattern and does not include the counterpart device alarm, and inputs it to the working and backup multiplexing units 81a and 81b. Each of the multiplexing sections 81a and 81b multiplexes the additional data ADDT into a main signal and transmits the multiplexed signal to the A station. The active / standby separating units 82a and 82b of the upper apparatus 53 of the station A extract the additional data ADDT sent from the station B and input the additional data ADDT to the opposing apparatus alarm detector 87. The opposite device alarm detection section 87 does not switch the line because the additional data ADDT does not include the opposite device alarm. In this state, if a failure occurs at point a of the working line, the working and protection receiving units 62 and 64 cannot extract the W pattern. In this state, the pattern identification unit 94 determines that a line failure has occurred, creates additional data ADDT including the W-system pattern and the opposite device alarm, and inputs the additional data ADDT to the working and standby system multiplexing units 81a and 81b.
The active and standby multiplexing units 81a and 81b store the additional data.
ADDT is multiplexed with the main signal and transmitted to the A station.

The opposing device alarm detection unit (DET / CONT) 87 identifies the opposing device alarm from the additional data ADDT extracted by the active and standby separation units 82a and 82b, and detects the fault system from the W system pattern. And instructs the switch unit 73 to switch the line from the active system to the standby system based on the identification result. When the line switching operation is completed, the system identification pattern becomes W
The system pattern is changed to the P system pattern, and the P system pattern is returned to the host device 53 of the station A via the host device 56 of the station B. At this time, by confirming the presence or absence of the alarm, it can be confirmed whether the switching has been performed and the alarm has been released. As described above, according to the fourth embodiment, the same effect as that of the first embodiment can be achieved, and the fault system can be identified.
Further, according to the fourth embodiment, even if the line failure cannot be clearly detected based on the signal loss SF or the signal deterioration SD, the line failure can be reliably and promptly detected due to the pattern mismatch and the line failure can be detected. Switching can be performed.

(E) Fifth Embodiment (e-1) Configuration FIG. 8 is a diagram showing a line switching configuration according to a fifth embodiment of the present invention, and the same parts as those in FIG. Reference numeral 88 denotes an opposite device alarm detection unit (ALM DET / CONT), which is provided in the higher-level device 53 on the A station side and uses the K1 byte of the working and backup main signal overhead byte OHB sent from the B station to detect the opposite device. It identifies whether an alarm has been sent, and instructs the switch unit 73 to switch the line based on the identification result. Reference numeral 90 denotes an alarm signal generation unit that notifies an alarm signal to the active and standby transmission units 61 and 63 of the SDH device 54 when a line failure is detected. The transmission units 61 and 63 to which the alarm signal is input notify the A station of the occurrence of the failure using the K1 byte of the working and backup main signal overhead bytes OHB.

Reference numeral 91 denotes a pattern generator provided in the higher-level device 53 of the A station, which generates a predetermined pattern and inputs the pattern to the active and standby transmitting units 61 and 63 of the SDH device 51. I do. The transmitting units 61 and 63 transmit the above-mentioned pattern to the B station using the undefined bytes D1 to D12 and F1 and E1 to E2 among the overhead bytes OHB of the main signal. Reference numeral 92 denotes a pattern identification unit provided in the host apparatus 56 of the station B. The active and standby receivers 62 and 64 of the station B are provided with an overhead byte OHB of the main signal.
Predetermined undefined bytes D1 to D12, F1, E1 to
The pattern transmitted in E2 is identified and input to the pattern identification unit 92. The pattern identifying unit 92 compares the patterns input from the active and standby receiving units 62 and 64 with known patterns to check whether they match,
If they do not match, it is determined that a line failure has occurred, and that fact is input to the alarm signal generator (ALM GEN) 90.

(E-2) Line switching control The transmitting unit 61 of the working system and the protection system of the SDH device 51 of the station A,
Reference numeral 63 denotes a high-level device 5 that inserts a fixed pattern input from the pattern generator 91 into the working and protection main signals using undefined bytes of the overhead byte OHB.
3 are input to the active and standby multiplexing units 81a and 81b. The working system multiplexing unit 81a includes the SDH device 51 and the SDH device 52.
A working signal from a not-shown signal is time-division multiplexed and input to the switch unit 73. Further, the standby multiplexing unit 81b time-division multiplexes the standby signals from the SDH devices 51 and 52 (not shown) and inputs the multiplexed signals to the switch unit 73. The switch unit 73 selects, for example, a signal from the active system and sends it out to the transmission path 57.

The hybrid section 74 of the host apparatus 56 of the station B
Inputs the multiplexed signal transmitted from the station A via the transmission line 57 to the working system separation unit 82a and the protection system separation unit 82b. The working system separation unit 82a separates the input multiplexed signal, and separates the separated main signals into the SDH device 54 and the SDH device 5 respectively.
5 (not shown). The working system receiving section 62 sends the signal to the outside as a working system signal, extracts a pattern from the undefined byte of the overhead byte OHB of the main signal, and inputs the pattern to the pattern identifying section 92. The standby separation unit 82b separates the input multiplexed signal and separates the separated main signals into the SDH devices 54 and SDH, respectively.
The signal is input to the standby receiving unit 64 of the device 55 (not shown). The standby system receiving unit 64 sends the signal to the outside as a standby system signal, extracts a pattern from an undefined byte of the overhead byte OHB of the main signal, and inputs the extracted pattern to the pattern identifying unit 92.

During normal operation, the working and protection receiving sections 62
The pattern extracted at 64 is a pattern generator 91
Matches the pattern generated from. Therefore, the pattern identification section 92 inputs the pattern matching signal to the alarm generation section 90, and the alarm generation section 90 recognizes that no line failure has occurred. As a result, the line failure is not notified by the overhead byte OHB, so that the counterpart device alarm detector 88 does not switch the line. In this state, if a failure occurs at point a of the working line, the patterns output from the working and protection receiving units 62 and 64 do not match the known patterns due to signal loss / deterioration. As a result, the pattern identification section 92 inputs a pattern mismatch signal to the alarm generation section 90. The alarm generation unit 90 receives the mismatch signal,
The active / standby transmission unit 6 of the SDH device 54
Notify 1,63. Working and backup transmission units 61 and 63
Is the overhead byte OHB due to the notification of the line failure occurrence
(K1 byte) transmits an opposing device alarm.

The SDH devices 62 and 64 of the A station extract the overhead byte OHB (K1 byte) and input it to the opposite device alarm detector 88. The opposite device alarm detector 88 detects the line failure due to the overhead byte OHB (K1 byte). Is notified, and the switch unit 73 is instructed to switch the line. As described above, according to the fifth embodiment, the same effect as that of the first embodiment can be achieved, and even if the terminal device does not have a function of multiplexing the additional data ADDT to the main signal and transmitting the same, the pattern and the pattern can be controlled by the overhead byte OMB. The line switching can be performed by transmitting the opposite device alarm to the opposite terminal device.

(F) Sixth Embodiment (f-1) Configuration FIG. 9 is a diagram showing a line switching configuration according to a sixth embodiment of the present invention, and the same parts as those in FIG. 1 are denoted by the same reference numerals. Reference numeral 88 denotes an opposite device alarm detection unit (ALM DET / CONT), which is provided in the higher-level device 53 on the A station side and uses the K1 byte of the working and backup main signal overhead byte OHB sent from the B station to detect the opposite device. It identifies whether an alarm has been sent, and instructs the switch unit 73 to switch the line based on the identification result. Reference numeral 90 denotes an active / standby transmission unit 61, 63 of the SDH device 54 when a line failure is detected.
Is an alarm signal generating unit for notifying the user. The transmission units 61 and 63 that have received the notification of the occurrence of the line fault notify the station A of the fault occurrence (opposite device alarm) using the K1 byte of the working and backup main signal overhead bytes OHB.

Reference numeral 93 denotes a pattern generator provided in the higher-level device 53 of the station A, which constantly generates a W-system pattern / P-system pattern and converts the W-system pattern / P-system pattern into the active system / standby system of the SDH device 51, respectively. Transmission units 61 and 63 of the system
To enter. The active / standby transmission units 61 and 63 transmit the undefined byte D1 of the overhead byte OHB of the main signal.
ＤD12, F1, E1ＥE2, the W-system pattern / P-system pattern is inserted into the working / spare main signal, respectively, and transmitted to the B station. Reference numeral 94 denotes a pattern identification unit provided in the host device 56 of the station B. The active and standby receivers 62 and 64 of the station B are provided with an overhead byte OHB of the main signal.
Predetermined undefined bytes D1 to D12, F1, E1 to
The pattern transmitted in E2 is identified and input to the pattern identification unit 94. The pattern identification unit 94 compares the patterns respectively input from the active system and standby system receiving units 62 and 64 with a known pattern (W system or P system pattern) and checks whether they match, and when none of them match, The mismatch signal is input to the alarm generator 90.

(C-2) Line switching control Active / standby transmission units 61, 6 of SDH device 51 of station A
3 uses the undefined byte of the overhead byte OHB to insert the W-system pattern / P-system pattern input from the pattern generator 91 into the working / spare main signal, respectively, to multiplex the working / standby system of the host device 53. Part 81a,
Input to 81b. The working system multiplexing unit 81a is the SDH device 5
1. A working signal from an SDH device 52 (not shown) is time-division multiplexed and input to a switch unit 73. Further, the standby multiplexing unit 81b time-division multiplexes the standby signals from the SDH devices 51 and 52 (not shown) and inputs the multiplexed signals to the switch unit 73. The switch unit 73 selects, for example, a signal (in which a W-system pattern is inserted) input from the working-system multiplexing unit 81a and sends it to the transmission path 57.

The hybrid unit 74 of the host device 56 of the station B
Inputs the working multiplex signal transmitted from the station A via the transmission line 57 to the working / spare demultiplexers 82a and 82b. The working system separation unit 82a separates the input working system multiplexed signal and inputs the separated main signals to the working system receiving unit 62 of the SDH device 54 and the SDH device 55 (not shown). The active system receiving unit 62 sends the signal as an active system signal to the outside, extracts a W system pattern from an undefined byte of the overhead byte OHB of the main signal, and extracts the W system pattern.
Enter 4 The standby separation unit 82b separates the input standby multiplex signal, and separates the separated main signals into SD signals.
Standby unit 6 of the H device 54 and the SDH device 55 (not shown)
Enter 4 The standby system receiving unit 64 sends the signal to the outside as a standby system signal, extracts a W system pattern from an undefined byte of the overhead byte OHB of the main signal, and inputs the extracted W system pattern to the pattern identification unit 94.

During normal operation, the working and protection receiving sections 62
The pattern extracted at 64 matches the W pattern.
Therefore, the pattern identification section 94 inputs the pattern matching signal to the alarm generation section 90, and the alarm generation section 90 recognizes that no line failure has occurred. As a result, since the line failure is not notified by the overhead byte OHB (K1 byte), the opposite device alarm detection unit 88 does not perform the line switching.
In this state, if a failure occurs at point a of the working line, the patterns output from the working and protection receiving units 62 and 64 do not match the known W-system patterns due to signal loss / deterioration. As a result, the pattern identification unit 94 inputs a pattern mismatch signal to the alarm generation unit 90. The alarm generator 90 detects the occurrence of a line failure by inputting a mismatch signal.
The current and backup transmission units 61 and 63 of the SDH device 54 are notified. The active and standby transmission units 61 and 63 transmit the opposing device alarm using the overhead byte OHB in response to the notification of the occurrence of the line failure.

The SDH devices 62 and 64 of the station A extract the overhead byte OHB (K1 byte) and input it to the opposite device alarm detector 88. The opposite device alarm detector 88 is notified of the line failure by the overhead byte OHB. Therefore, the switching unit 73 is instructed to switch the line. The station B sends the pattern identified by the overhead byte OHB (the pattern to be received by the station B) to the station A in a normal state, and sends the pattern to be received to the station A with the overhead byte OHB in the overhead byte OHB at the time of notification of the occurrence of a line failure. I will send it.
By doing so, the station A can identify the faulty system at the time of receiving the counterpart device alarm, and can instruct the switch unit 73 to switch the line from the faulty system to the normal system based on the identification result. When the line switching is completed, the system identification pattern is switched, and the pattern is changed to A by the higher-level device 56 of the station B.
Since it is returned to the host apparatus 53 of the station, it is possible to confirm that the line has been switched and the alarm has been canceled by confirming the presence or absence of the alarm at this time.

As described above, according to the sixth embodiment, the same effect as that of the first embodiment can be achieved, and the faulty system can be identified. Further, according to the sixth embodiment, even if the terminal device does not have a function of multiplexing the additional data ADDT on the main signal and transmitting the same, the pattern or the alarm of the opposite device is transmitted to the partner terminal device by the overhead byte OHB. Line switching can be performed. As described above, the present invention has been described with reference to the embodiments. However, the present invention can be variously modified in accordance with the gist of the present invention described in the claims, and the present invention does not exclude these.

[0078]

As described above, according to the present invention, the line switching can be realized by causing the higher-level device to transmit and detect the alarm of the opposite device, which has been conventionally performed by the SDH device. Can be standardized while complying with international standards. Further, according to the present invention, by transmitting the working system / standby system pattern together with the main signal, a faulty system can be identified and line switching can be performed correctly. It is possible to prevent unnecessary line switching when a failure occurs.

According to the present invention, even when a line failure cannot be clearly detected based on signal loss or signal deterioration, a line failure can be detected reliably and quickly due to the mismatch between the inserted pattern and the detected pattern. To switch the line. According to the present invention, additional data ADDT
Even if the terminal device does not have a function of multiplexing and transmitting the main signal to the main signal, the line can be switched by transmitting the pattern and the alarm of the opposing device to the opposing terminal device by the overhead byte OHB.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a communication system to which line switching according to the present invention is applied.

FIG. 2 is an explanatory diagram of a multiplexing unit of a demultiplexing unit.

FIG. 3 is an explanatory diagram of a demultiplexing unit of a demultiplexing unit.

FIG. 4 is a diagram illustrating a line switching configuration according to the first embodiment.

FIG. 5 is a diagram illustrating a line switching configuration according to a second embodiment.

FIG. 6 is a diagram illustrating a line switching configuration according to a third embodiment.

FIG. 7 is a diagram illustrating a line switching configuration according to a fourth embodiment;

FIG. 8 is a diagram illustrating a line switching configuration according to a fifth embodiment.

FIG. 9 is a line switching configuration diagram of a sixth embodiment.

FIG. 10 is an explanatory diagram of a SONET OC-3 frame format.

FIG. 11 is an explanatory diagram of a K1 byte.

FIG. 12 is an explanatory diagram of a K2 byte.

FIG. 13 is a transmission and reception sequence of K1 and K2 bytes.

FIG. 14 shows a switching method using line protection.

FIG. 15 is a communication system having no line redundancy configuration.

FIG. 16 is a configuration diagram of a conventional communication system that enables line switching even when a failure is simultaneously detected in both a working line and a protection line.

[Explanation of symbols]

Terminal device of station A 50A Terminal device of station B 50, SD terminal device of station 52, SDH device (SDH MUX A,
SDH MUX C), higher-level equipment (SLTE-A) provided at station 53 A, SDH equipment (SDH MUX B,
SDH MUX D) 56 ··· Upper device (SLTE-B) provided on B station side 57 ··· Uplink transmission line 58 ··· Downlink transmission line

Claims (7)

[Claims] 1. A first apparatus for transmitting a working / spare main signal to an opposite station side and receiving a working / spare main signal from the opposite station side, and from the first apparatus to the opposite station. One of the working / spare main signals to be output is selected and sent to the opposite station, and the main signal sent from the opposite station is branched and input to the first device as a working / spare main signal. Communication system provided with two terminal devices each including a second device and a second device connected to each other by two uplink / downlink transmission lines having no redundant configuration. In the redundant system switching method, the first and second devices constituting the terminal device are provided with a working / spare redundant configuration, and a line failure occurring on one terminal device is detected by the other terminal device. The main signal sent from the other terminal equipment to one terminal equipment is System for multiplexing additional data including a report and detecting a warning included in the additional data in one of the terminal devices and switching the line. . 2. The first terminal device of the other terminal device monitors signal deterioration or loss of both working and protection signals transmitted from one terminal device and monitors the signal of the one terminal device. In the second device of the other terminal device, additional data including a line failure occurrence alarm is multiplexed and transmitted to the main signal transmitted to the one terminal device, and 2. The redundant system switching method for a communication system without a redundant transmission line according to claim 1, wherein the second device detects an alarm included in the additional data and performs line switching. 3. A first device for transmitting a working / spare main signal to the opposite station side and receiving a working / spare main signal from the opposite station side, and from the first device to the opposite station. One of the working / spare main signals to be output is selected and sent to the opposite station, and the main signal sent from the opposite station is branched and input to the first device as a working / spare main signal. Communication system provided with two terminal devices each including a second device and a second device connected to each other by two uplink / downlink transmission lines having no redundant configuration. In the redundant system switching method, the first and second devices constituting the terminal device are provided with a working / spare redundant configuration, and the first terminal device adds a working identification pattern to a working main signal. Multiplexed as data, and added a standby system identification pattern to the standby main signal. Data is multiplexed, and one of the main signal of the working system and the protection system is selected and transmitted to the other second terminal device via the uplink transmission line, and the second terminal device is connected to the first terminal device. In addition to identifying a pattern multiplexed with the transmitted signal and monitoring signal deterioration or loss of the transmitted signal, the first signal is monitored.
Upon detecting a line failure, the second terminal device multiplexes additional data including a line failure occurrence alarm and a failure occurrence system determined from the pattern into a main signal upon detection of the line failure, via a downlink transmission line. Transmitting a signal to the first terminal device, wherein the first terminal device switches the line based on an alarm and a failure generation system included in the additional data. System switching method. 4. A first apparatus for transmitting a working / spare main signal to the opposite station side and receiving a working / spare main signal from the opposite station side, and from the first apparatus to the opposite station. One of the working / spare main signals to be output is selected and sent to the opposite station, and the main signal sent from the opposite station is branched and input to the first device as a working / spare main signal. Communication system provided with two terminal devices each including a second device and a second device connected to each other by two uplink / downlink transmission lines having no redundant configuration. In the redundant system switching method, the first and second devices constituting the terminal device are provided with a working / spare redundant configuration, and the first terminal device uses an overhead byte to change a fixed pattern between the working system and the working system. Inserted into the standby main signal, and
One of the working system and the protection system main signal is selected and transmitted to the other second terminal device via the uplink transmission line, and the second terminal device receives the main signal transmitted from the first terminal device. The inserted pattern is restored with reference to the overhead byte, and the restored pattern is compared with the fixed pattern. If the restored pattern does not match the fixed pattern, the second terminal station sends a line failure alarm to the main signal. The additional data including the additional data is multiplexed and transmitted to the first terminal device via the downlink transmission path, and the first terminal device switches the line by identifying an alarm included in the additional data. A redundant system switching method for a communication system having no redundant transmission path. 5. A first apparatus for transmitting a working / spare main signal to the opposite station side and receiving a working / spare main signal from the opposite station side, and from the first apparatus to the opposite station. One of the working / spare main signals to be output is selected and sent to the opposite station, and the main signal sent from the opposite station is branched and input to the first device as a working / spare main signal. Communication system provided with two terminal devices each including a second device and a second device connected to each other by two uplink / downlink transmission lines having no redundant configuration. In the redundant system switching method, the first and second devices constituting the terminal device are provided with a working / spare redundant structure, and the first terminal device uses the overhead byte as the working main signal. The system identification pattern is inserted, and the standby system identification signal is added to the standby system main signal. , And selects one of the main signal of the working system and the main signal of the protection system and transmits the selected signal to the other second terminal device via the first transmission line. The pattern inserted in the main signal transmitted from the station device is restored by referring to the overhead byte, and the restored pattern is compared with the identification pattern of the working system or the standby system. If the second
The terminal device multiplexes the additional data including the line fault occurrence alarm and the fault generation system into a main signal and transmits the multiplexed signal to the first terminal device via the downlink transmission path, and the first terminal device includes the additional data in the additional data. A redundant system switching method for a communication system having no redundant transmission line, wherein the system switches a line based on an alarm and identification data. 6. A first apparatus for transmitting a working / spare main signal to the opposite station side and receiving a working / spare main signal from the opposite station side, and from the first apparatus to the opposite station. One of the working / spare main signals to be output is selected and sent to the opposite station, and the main signal sent from the opposite station is branched and input to the first device as a working / spare main signal. Communication system provided with two terminal devices each including a second device and a second device connected to each other by two uplink / downlink transmission lines having no redundant configuration. In the redundant system switching method, the first and second devices constituting the terminal device are provided with a working / spare redundant configuration, and the first terminal device uses an overhead byte to change a fixed pattern between the working system and the working system. Inserted into the standby main signal, and
One of the working system and the protection system main signal is selected and transmitted to the other second terminal device via the uplink transmission line, and the second terminal device receives the main signal transmitted from the first terminal device. The inserted pattern is restored with reference to the overhead byte, and the restored pattern is compared with the fixed pattern. If the restored pattern does not match the fixed pattern, the second terminal station uses the overhead byte to generate a line failure. The alarm is inserted into the main signal and transmitted to the first terminal device via the downlink transmission path, and the first terminal device checks whether or not the line fault occurrence alarm has been notified by referring to the overhead byte, and A redundant system switching method for a communication system without a redundant transmission line, characterized in that a line is switched when notified. 7. A first apparatus for transmitting a working / spare main signal to the opposite station side and receiving a working / spare main signal from the opposite station side, and from the first apparatus to the opposite station. One of the working / spare main signals to be output is selected and sent to the opposite station, and the main signal sent from the opposite station is branched and input to the first device as a working / spare main signal. Communication system provided with two terminal devices each including a second device and a second device connected to each other by two uplink / downlink transmission lines having no redundant configuration. In the redundant system switching method, the first and second devices constituting the terminal device are provided with a working / spare redundant structure, and the first terminal device uses the overhead byte as the working main signal. The system identification pattern is inserted, and the standby system identification signal is added to the standby system main signal. , And selects one of the main signal of the working system and the main signal of the protection system and sends the selected signal to the other second terminal device via the upstream transmission line. Restores the pattern inserted in the main signal sent from the host device by referring to the overhead byte, compares the restored pattern with the identification pattern of the working system or the standby system, and when the restoration pattern does not match the identification pattern, Second
The terminal device inserts the line fault occurrence alarm and the fault generation system into the main signal using the overhead byte and transmits the signal to the first terminal device via the downlink transmission path, and the first terminal device transmits the overhead byte to the main terminal. A redundant system switching method for a communication system having no redundant transmission path, characterized in that a line failure occurrence alarm and a failure occurrence system are identified with reference to switching of a line.