JP3950741B2 - Non-instantaneous switching method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention detects a transmission delay of an operation system and a standby system in a point-to-point transmission apparatus having a 1 + 1 redundancy configuration in an SDH transmission apparatus or a ring configuration transmission apparatus, and switches without interruption when a trouble is transferred. The present invention relates to an uninterruptible switching method.
[0002]
[Prior art]
A 1 + 1 redundant SDH transmission system in which the receiving and sending stations are connected by two transmission lines, the active and standby, normally transmits signals using either transmission line as the main transmission line. However, the same signal is always transmitted to the other transmission line at the same time. By adopting such a configuration, when any failure occurs in the main transmission line, the other transmission line can be switched as the main transmission line and the transmission can be continued.
[0003]
Such a 1 + 1 redundant configuration is robust against a transmission path failure, and is a general configuration of an SDH transmission system that requires high reliability. However, in the SDH transmission system having the 1 + 1 redundancy configuration, when a signal is simultaneously transmitted from the transmitting terminal station to the active system and the standby system transmission path, the transmission path of both systems is changed due to a difference in path length between the transmission paths of both systems. There is a difference (delay time difference) in the time when the transmitted signal arrives at the receiving station. For this reason, a phase difference occurs between the signals of both systems received at the receiving terminal station, and when the transmission path is switched during reception, a part of the signal transmitted from the transmitting terminal station is lost. , Phenomenon such as interruption.
[0004]
[Problems to be solved by the invention]
Conventionally, in order to realize non-instantaneous switching between operation backups, phase adjustment is performed with H / W as shown in FIG. However, only the phase difference determination using 64 frames of J1 has a problem that the phase difference for 32 frames becomes the upper limit of the phase matching range. This is based on the condition that the difference between the transmission delays is within 32 frames when the memory is synchronized with 64 frames, because all of them are detected by H / W, so that it is not possible to determine whether it is late or early. This is because the judgment is made early or late. In addition, when a redundant signal is input with a phase difference of 32 frames or more, there is a possibility that the early / late determination is erroneous.
[0005]
As a means for solving the above problem, there is a method of inserting a maximum delay amount that can be stuffed into the memory in advance, but in this case, there is a problem that the data delay amount becomes the maximum and an excessive transmission delay occurs.
[0006]
[Means for Solving the Problems]
According to the uninterruptible switching system of the present invention, the active system and the standby system in an SDH transmission system having a 1 + 1 redundancy configuration in which a receiving terminal station and a transmitting terminal station are connected by two transmission paths of an active system and a standby system. A non-instantaneous switching method for predicting a delay difference between the active standby transmission lines, and absorbing the predicted delay difference in an internal memory as an optimal delay amount. In the non-instantaneous switching method that eliminates the delay difference, the optimum delay amount is replaced with the actual delay amount when the difference between the actual delay amount and the predicted delay amount is a certain value or more .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The operation of the embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the delay difference detection unit 1 detects an actual delay amount difference between the active system and the standby system and notifies the operation 2. The write / read counter memories 3 and 4 not only insert a useless delay amount by setting an optimum value for the read phase from the operation side based on the setting from the operation in units of frames. It is possible to perform switching between operation backups without instantaneous interruption without performing phase alignment again for path changes involving any delay amount change.
[0008]
In particular, in the case of a transmission apparatus having a 1 + 1 redundant configuration with a ring configuration, the transmission path may be as shown in FIG . In this, the operation determines what route the active and standby routes take, and leaves up to the user setting up to what uninterruptible function needs to be satisfied. The user determines from the priority of the line and the importance of high-speed transmission, determines which route can be switched without interruption, and then performs settings through the operation.
[0009]
The operation of simulating the apparatus configuration on the operation side and predicting the transmission delay amount in the case of the route a and the route b for the terminal points A and B will be described. In the case of the route a, there is a device-specific value (several micros) from the branch point (0 point) after insertion of J1 to the point a1, which is a device-specific value. The delay amount between a1 and a2 depends on the fiber length, and is uniquely determined in a situation where the ring is configured (delay amount n). Further, since the delay amount between a2 and a3 is the in-device delay to be dropped, similarly to the time between 0 and a1, the value is unique to the device. On the other hand, in the path b, similarly to 0-a1, the delay amount q, b3 during the device-specific through-throw between the device-specific value (delay amount m) and the delay amount b2-b3 depending on the fiber length between b1-b2 Fiber delay (r) between b4 and b4, Through delay between b4 and b5 (q), Delay between b5 and b6 (s), Delay between b6 and b7 (o) and delay in the device are determined As a result, prediction becomes possible. Assuming that the device-specific delay amounts of Add and Drop are the same between paths a and b, the delay difference between the paths is “delay difference = total difference of fiber × unit delay in fiber + difference in number passing through X It can be predicted by the delay amount P ″.
[0010]
The predicted delay difference is set for the write / read counter memories 3 and 4 at the end point B after the calculation. If it is determined that the transmission delay in path b is greater in path a and path b than in path b, the read phase at point B is determined with a margin that takes into account the delay amount variation in the write value of b. . When a and b are within the prediction error range and the delay amount is the same, the read phase may be determined from either write value.
[0011]
When the line is actually operated, it is confirmed that there is no difference between the actual delay amount and the predicted delay amount. If there is a difference, the predicted value is replaced with an actual measurement value, and this is replaced with a new delay amount. Predicted value. When constructing a protection line on this line, the predicted value is already optimal, and the standby system extracts the read timing of the operation system, so there is no reset of the delay amount in the operation system, and the operation system There is no instantaneous interruption of the main signal.
[0012]
Furthermore, in the case of a ring configuration as shown in FIG. 2, it is unnecessary by calculating in advance the transmission delay difference between the complicated operation reserves at the time of the ring configuration, and optimally setting the added delay amount. Can be switched without instantaneous rephasing.
[0013]
In addition, the present invention is an endpoint A. Although a means for absorbing the delay amount between B is described, this method can be realized throughout the network beyond the frame of the apparatus. In this case, the J1 byte for multi-frame synchronization is inserted at the end point A ′ of the entire network, the delay amount for each device to which this line is allocated is managed by the device operation, and then passed to the upstream operation for managing the entire network. By managing the delay amount of the entire network, it is also possible to realize non-instantaneous switching at the time of failure transfer at the end point B ′.
[0014]
【The invention's effect】
As described above, according to the present invention, the amount of delay for phase difference absorption can be minimized by placing the amount of delay under the management of operations and the like. Further, by minimizing the delay amount, the absorbable delay amount can be doubled compared to the conventional case, and the memory can be halved compared to the conventional case. In addition, a transmission delay difference that can be switched without instantaneous interruption of 32 frames can be changed to 64 frames. In addition, by setting a delay amount that takes into account the transmission phase amount due to route change etc. in advance on the operation side, even if a route change etc. occurs, an uninterruptible function of trouble transfer is realized without performing rephase alignment. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a diagram in which the present invention is applied to a complex network.
FIG. 3 is a block diagram showing a conventional technique.
[Explanation of symbols]
1 Delay Difference Detection Unit 2 Operation 3, 4 Write / Read Counter Memory

Claims (1)

In the 1 + 1 redundant SDH transmission system in which the receiving end station and the transmitting end station are connected by two transmission lines of the active system and the standby system, there is no instantaneous disconnection between the active system and the standby system. In a switching method that predicts a delay difference between the active standby transmission lines and absorbs the predicted delay difference in an internal memory as an optimum delay amount to eliminate the delay difference between redundancy . A non-instantaneous switching method, wherein the optimum delay amount is replaced with the actual delay amount when the difference between the actual delay amount and the predicted delay amount is equal to or greater than a predetermined value .

Images