JPH09307523A - Sdh relay system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent out of synchronism by insertion prescribed overhead data on the occurrence of a channel fault in the SDH relay system consisting of connection of a plurality of SDH relay stations each having active and standby repeaters. SOLUTION: An active (standby) repeater 15(16) has an MS-AIS detection circuit 5 at a next-stage of its RSOH extract circuit 6. The MS-AIS indicates it that a concerned channel is abnormal, and when bits (b6-b8) of the K2 byte included in an MSOH of the signal are all '1', the MS-AIS detection circuit 5 detects it and informs the MS-AIS to a control circuit 8. ON the occurrence of a line abnormality in a pre-stage relay station, since signals other than the RSOH are all fixed to '1' in the relay stations of post-stages, the MS-AIR is detected. In this case, the control circuit 8 provides output of RSOH extract data and a data clock outputted from the RSOH extract circuit 6 of the standby repeater 16 to external equipment via changeover devices 10, 11.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an SDH (Synchronous
ous Digital Hierarchy) relay station, and more particularly to an SDH relay system for RSOH (Radio Section Over Head) transmission in an SDH relay station.

[0002]

2. Description of the Related Art FIG. 3 shows a block diagram of a conventional SDH relay station which relays two working / standby lines.
Referring to FIG. 3, this relay station includes a working line relay device 17, a protection line relay device 18, a control circuit 14, and switching devices 9, 10, and 11.

In the relay device 17, the disconnection detection circuit 2, the frame synchronization circuit 4, the RSOH extraction circuit 6, the ALL1 (all-or-nichi) insertion circuit 3 and the RSOH insertion circuit 7 are sequentially connected, and the ALL1 insertion circuit 3 oscillates. The circuit 12 is connected. The spare relay device 18 has the same configuration as the active relay device 17.

First, the operation of the active relay device 17 will be described. The disconnection detection circuit 2 detects the presence / absence of an input received signal, and if the received signal is disconnected, the disconnection detection circuit 2 sends an LO signal to the control circuit 14.
Notify S (Loss Of Signal) alarm. The frame synchronization circuit 4 refers to the A1 and A2 bytes (frame synchronization byte) in the received signal to establish frame synchronization. When the frame synchronization is not established, the control circuit 14 receives the LOF (Loss
s Of Frame) Notify the alarm.

The RSOH extraction circuit 6 receives an E1 byte for an order wire, an F1 byte for a user channel, a data
Communication channel (Data Communication C
The RSOH data including D1 to D3 bytes for a channel) and the clock are extracted, and the RSOH extraction data is output to the switch 10 and the RSOH extraction clock is output to the switch 9.

Under the control of the control circuit 14, the ALL1 insertion circuit 3 can send the data fixed to the logic 1 level to the subsequent stage by the clock output from the oscillator 12. The RSOH insertion circuit 7 sends the RSOH insertion clock to the switch 11, and inserts RSOH insertion data (E1 byte, F1 byte, D1-D3 byte, etc.) input from the outside into the main signal. The relay device 18 also operates simultaneously,
That is, they are operated in parallel.

The control circuit 14 includes a relay device 17 for the working line.
And the alarm notified from the relay device 18 of the protection line, and when both are normal, the working side is selected,
When the above-mentioned LOS or LOF alarm is notified from the working side, the standby side is selected, and when both the working and standby alarms are notified, the working side is selected.
The switch 9 controls the switch 10 and the switch 11. Also,
The ALL insertion circuit 3 on the side notified of the alarm is controlled to send the data fixed to [1] to the subsequent stage by the clock of the oscillator 12.

The switch 9 and the switch 10 are the RSOH extraction clock and RSOH extracted from the working line and the protection line.
The extracted data is switched and output under the control of the control circuit 14. The switch 11 switches and outputs an RSOH insertion clock for inserting RSOH in the working line and the protection line under the control of the control circuit 14. RSOH insertion data input from the outside is input to both the RSOH insertion circuit 7 of the relay device 17 of the working line and the RSOH insertion circuit 7 of the relay device 18 of the protection line. In this way, the relay station performs the switching operation so that the data is always transmitted correctly.

FIG. 4 shows a system configuration in the case where a failure occurs in the working line in the transmission path including the above-mentioned relay stations in two or more stages. Referring to FIG. 4, a failure 19 occurs in the working line in front of the relay station 40 in the preceding stage,
The case where the line is disconnected is shown. The relay stations 40 and 50 at the front stage and the rear stage are common to the relay station 3 in FIG. 3, but are shown in a simplified manner.

The relay device 41 and the relay device 51 correspond to the active-side relay device 17 in FIG. The relay device 42 and the relay device 52 correspond to the relay device 18 on the standby side in FIG. The control circuit 43 and the control circuit 53 correspond to the control circuit 14 of FIG. The switch 44 and the switch 54 correspond to a combination of the switch 9 and the switch 10 in FIG. The switch 45 and the switch 55 correspond to the switch 11 of FIG. Therefore, the output lines 46 and 47 and the output lines 56 and 57 correspond to the data lines and clock lines of the internal RSOH extraction data. The input lines 49 and 59 are external RSOH insertion data lines,
Output lines 48 and 58 are clock lines for inserting external RSOH data.

Next, the operation of the relay station 40 will be described. The relay device 41 on the working line side detects the LOS alarm and notifies the control circuit 43 of it. The control circuit 43 controls the ALL1 insertion circuit in the relay device 41 by the LOS alarm from the relay device 41, and fixes all signals to [1]. Further, the control circuit 43 controls the switch 44 to select the RSOH extraction data and the RSOH extraction clock extracted from the relay device 42 on the protection line side where no alarm is generated, and output the output lines 47 and 46 to the output lines 47 and 46, respectively. Output. Similarly,
The control circuit 43 controls the switch 45 to output the RSOH insertion clock output from the relay device 42 on the protection line side where the alarm is not generated, to the output line 48. RSO
RSOH insertion data synchronized with the H insertion clock is input from the input line 49, distributed to the relay device 41 and the relay device 42, and inserted into the main signal.

At this time, in the relay device 41, A
A fixed value such as 1, A2 bytes or the like, or RSOH data for inserting a calculation result like B1 bytes is generated by a clock (synchronized with an oscillator in the relay device 41) extracted from a signal on the working line. . Therefore, the main signal and these RSOH data are synchronized, and the RSOH data is normally inserted in the main signal.

However, externally input E1, F1,
RSOH insertion data 49 such as D1-D3 bytes is RS of the output line 48 output from the relay device 42 on the protection line side.
Since the signal is input in synchronization with the OH insertion clock (which is synchronized with the signal on the protection line), the signal on the working line and the RSOH data are asynchronous. Therefore, slippage occurs due to the frequency difference, and RSOH data is not normally inserted in the main signal in the relay device 41. (In the relay device 42, since the main signal and the RSOH insertion data are synchronized, the RSO
The H data is normally inserted. )

Next, the operation of the relay station 50 will be described. In the repeater 51 on the working line side, detection of disconnection of the input signal and A1,
A failure is detected by frame synchronization with A2 bytes (frame synchronization byte). The signals on the working line are A1 and A2.
Since the byte is inserted normally, the LOF alarm is not detected and the working line side is judged to be normal. In this case, the control circuit 53 determines that both the working line and the protection line are normal, controls the switch 54, and extracts the RSOH extraction data and RSOH extraction clock extracted from the working line side. To output to the outside.
However, on the working line side, the RSOH byte is not normally inserted in the relay station 40, so that the RSOH byte is not normally transmitted. As described above, there is a problem that the signal in which the RSOH byte is not normally inserted is transmitted to the relay station 50 at the next stage.

FIG. 5 for explaining the "digital radio transmission system" disclosed in Japanese Patent Laid-Open No. 22271/1990.
Referring to (a), as shown in (a), when the relay station relays the received signal, SDH is performed without speed conversion.
It is a frame synchronization method that can access the overhead signal of the network. The transmitting station receives the input SDH signal from 1 to 9
The error-correction coding block indicated by the arithmetic numeral is divided, and a ROH (overhead for radio section) signal is added to each block consisting of 2160 bits, which is error-correction-coded to multiplex redundant bits (FEC). To form a radio frame, and the error correction coded block is
Number of information bits excluding ROH bits included in it (2
It is formed by using the error correction code length and the number of ROH bits such that an integer multiple (27 times) of 880 bits and an integer multiple (4 times) of the number of bits of one SDH frame (19440 bits) match. Therefore, the wireless frame is as shown in (b) of FIG.
Frame synchronization is established for each double SDH frame.

In such a configuration, the number of information bits is 28.
80x27 = 19440, which is the number of bits in one SDH frame
Since it becomes × 4, it is a so-called least common multiple frame synchronization forming method that establishes frame synchronization, and is not a configuration that normalizes the data itself in which an overhead pulse is erroneously inserted as in the prior art, and the clock is also used. It is not a configuration in which the pulse itself is improved. Further, there is a problem that the number of ROH bits is limited.

Further, referring to FIG. 6 for explaining the "SDH transmission device" disclosed in Japanese Patent Laid-Open No. 5-911119, only the case where a loop-shaped transmission line is constructed by the SDH system will be considered as a problem. It has been pointed out that the phenomenon in which the clock paths are disconnected, especially the mutual synchronization between the slave stations, causes the clock to be out of synchronization.
As shown in, the relay means 2 connects the input / output of the low-order group signals of both the multiplex transmission equipment 61, the signal switching means 63 switches and outputs the low-order group signals of the both multiplex transmission equipment 61, and the signal distribution means. At 64, the low-order group signals are distributed to both of the multiplex transmission devices 61, the low-order group signals to be relayed or dropped at each station are arbitrarily set, and the low-order group signals in different directions are switched by switching the signal switching means 63 at any station. Two routes are created by selecting and dropping signals.

Further, a clock in a fixed direction from the main station shown in (b) is used as an active system and a clock in the opposite direction is used as a standby system, and the clock switching means 67 changes the clock in accordance with a signal indicating an abnormality in the transmission path. Select and configure to connect to network synchronizer.

In such a configuration, the two routes are used to prevent the loss of synchronization of the clock, and the selection of either of the two clock systems is intended to prevent the loss of synchronization. Although the loop-shaped transmission path-specific relay means 62 and the like are provided, the clock synchronization in the transmission path between the relay stations of the one-to-one correspondence type in which the clock bus is not in the loop configuration and the countermeasures against it There is no disclosure.

Further, in the event of a failure, the time delay until switching to another route line becomes non-negligible, and if there are many relay stations intervening in the loop, there is the problem that transmission will not be possible for a while.

[0021]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to transmit a signal in which an overhead byte is not normally inserted to a conventional SDH relay station by merely adding a circuit to a part thereof. However, because of block synchronization, it is not necessary to set a limit on the number of bits of overhead data, and data can be transmitted normally even in a system that does not have a looped clock bus, and even if there are many relay stations. An object of the present invention is to provide an SDH relay system which can be controlled without causing a time delay.

[0022]

In order to achieve the above-mentioned object, an SDH relay system according to the present invention is an SDH relay station comprising a plurality of SDH relay stations each having an active relay device and a backup relay device. In the relay system, some S
When a line failure occurs in front of the DH relay station and a specific overhead data is fixed to a constant logical value, a control means for normally inserting the predetermined overhead data is provided.

Here, the control means has a function of externally outputting the overhead data and the overhead clock output from the backup relay device, and the specific overhead data is multiplexed.・
This is a predetermined byte of data included in the section overhead.

[0024]

FIG. 1 shows an embodiment of the present invention.
In this SDH relay station, the active relay station apparatus 15 and the backup relay apparatus 16 output MS-AIS (Mult) for output from the next stage of the RSOH extraction circuit 6 to the control circuit 8.
iplex Section-Alarm Indication Signal) Detection circuit 5
3 is different from the conventional example shown in FIG. 3 in that it has both the above and the function of processing the MS-AIS signal as the control function of the control circuit 8, and other functional blocks. 3 are common to those in FIG. 3, the common arithmetic numerals are used and the description of the overlapping operation is omitted.

MS-AIS indicates that the line concerned is abnormal, and MSOH (Multiplex Section Over
Head), the K2 byte [b6-b8] is logical
In the case of [1,1,1], it is detected by the MS-AIS detection circuit 5. In other words, the relay station in front detects a line abnormality,
MS-AIS is also detected when logic [1] is inserted in all signals other than RSOH.

As described above, M which is usually not detected by the relay station
The S-AIS is detected, and the MS is used as the switching condition of the extracted RSOH data / clock and the RSOH clock for insertion.
-By including AIS, the problems of the prior art can be solved.

The MS-AIS detection circuit 5 analyzes b6-b8 of the K2 byte in the received signal. When the MS-AIS is detected, the control circuit 8 is notified of the MS-AIS.

Next, referring to FIG. 2 in order to explain the operation of the MS-AIS detection circuit, when a fault 19 occurs in the working line input to the relay station 20 at the preceding stage (when the line is disconnected). ) The operation of the relay station 30 in the latter stage is shown.

The relay stations 20 and 30 are simplifications of the relay station shown in FIG. The relay device 21 and the relay device 31 correspond to the active-side relay device 15 in FIG. 1. The relay device 22 and the relay device 32 correspond to the relay device 16 on the standby side in FIG. 1. The control circuit 23 and the control circuit 33 are
Although it corresponds to the control circuit 8 in FIG. 1, the function is different. The switch 24 and the switch 34 are the switch 9 and the switch 10 of FIG.
It corresponds to the one that is summarized. The switch 25 and the switch 35 correspond to the switch 11 of FIG.

Regarding the operation of the present embodiment, description of the parts common to the conventional example of FIG. 4 will be omitted, and only the different parts will be described.

In the repeater 22, the RSOH data is normally inserted because the main signal and the RSOH insertion data are synchronized, but E1, F1, D1 input from the outside are input.
RSOH insertion data (data of the input line 29) such as D3 bytes is input in synchronization with the RSOH insertion clock 28 (synchronized with the signal of the protection line) output from the relay device 22, and thus the relay device 21 Then, the main signal and RSOH
The data is asynchronous.

In the relay device 31 on the working line side, detection of disconnection of the input signal, frame synchronization by A1 and A2 bytes, and M
Fault detection is performed by detecting S-AIS.

Since the A1 and A2 bytes are normally inserted in the signal on the working line side, the LOF alarm is not detected. However, since all data other than RSOH is fixed to [1] in the relay station 20, the relay device 31 on the working side is used.
The MS-AIS detection circuit 5 detects the MS-AIS and notifies the control circuit 33 thereof. As a result, the control circuit 33 determines that the working line is abnormal, controls the switch 34, and outputs the RS output from the relay device 32 on the protection line side.
The OH extraction data and RSOH extraction clock (RSOH data clock extracted from the protection line) are output to the output lines 36 and 3.
Select to output to the outside via 7. Thus
Solved the problem that wrong data (data that was not normally inserted) in the relay device 31 was output to the outside.
SOH transmission is normally performed.

In the present embodiment, the MS-AIS signal has been described, but the present invention is not limited to this, and it is stable if the overhead is fixed when all the data is fixed to logic 1 and a line failure can be detected. RSOH bytes can be transmitted.

[0035]

As described above, according to the SDH relay system of the present invention, the RSOH byte can be transmitted normally in the SDH relay station composed of the working / standby. Is achieved in a hurry.

[Brief description of drawings]

FIG. 1 is a block diagram showing an SDH relay station of an embodiment of an SDH relay system according to the present invention.

FIG. 2 is a diagram for explaining the operation of the MS-AIS detection circuit according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional SDH relay station.

FIG. 4 is a block diagram showing a conventional SDH relay system.

FIG. 5 is a configuration diagram of a conventional SDH frame.

FIG. 6 is a block diagram showing a conventional multiplex transmission device of a loop transmission line.

[Explanation of symbols]

2 disconnection detection circuit 3 ALL1 insertion circuit 4 frame synchronization circuit 5 MS-AIS detection circuit 6 RSOH extraction circuit 7 RSOH insertion circuit 8, 14 control circuit 9, 10, 11, 12, 25, 34, 35, 44, 4
5,54,55 switching device 12 oscillator 15, 16.17.18, 21, 31, 32, 41, 4
2, 51, 52 Relay device 19 Failure 20, 30, 40, 50 Relay station 61 Multiplex transmission device 62 Relay means 63 Signal switching means 64 Signal distribution means 67 Clock switching means

Claims (3)

[Claims] 1. In an SDH relay system comprising a plurality of SDH relay stations each having an active relay device and a backup relay device connected to each other, a line failure occurs before a certain SDH relay station, and a specific overhead An SDH relay system comprising control means for normally inserting predetermined overhead data when the data is fixed to a constant logical value. 2. The SDH relay system according to claim 1, wherein the control means has a function of externally outputting the overhead data and the overhead clock output from the backup relay device. 3. The SDH relay system according to claim 1, wherein the specific overhead data is a predetermined byte of data included in the multiplex section overhead.