JP2008048213A - Transmission device, transmission method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission device, along with a transmission method and a program, for uninterrupted switching while suppressing delay with a shorter initial delay. <P>SOLUTION: The transmission device selects a signal of one transmission path among the signals from a plurality of transmission paths that are received from the transmission device on a transmission side, and transmits it to the device on the receiving side. It comprises a delay adding means in which the signal inputted from a specified transmission path is accumulated in a memory means, and then it is read and added with a specified delay; and a selecting means which selects the signal added with a specified delay by the delay adding means from among a plurality of signals inputted from the plurality of transmission paths, and transmits it to the device on the receiving side. It also comprises a control means which reads the signals stored in the memory means at the time point of interruption of input of normal signals from the specified transmission path while gradually increasing a delay. After all the signals stored in the memory means are read, the selecting means is instructed by the control means to select the signal of other transmission path instead of the signal of the specified transmission path. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmission apparatus that performs switching between transmission paths without interruption.

  2. Description of the Related Art Conventionally, there is an uninterruptible switching method in which a transmission system includes a transmission apparatus on the transmission side and a transmission apparatus on the reception side, and these are connected by a plurality of transmission paths, and the transmission paths are switched without interruption. A conventional non-instantaneous switching method will be described with reference to FIG.

  FIG. 1 shows a transmission system in which a transmission apparatus 1 on a transmission side and a transmission apparatus 2 on a reception side are connected by a plurality of transmission paths 3. In this transmission system, the transmission-side transmission device 1 attaches a mark (identifier) such as a sequence number to a signal to be transmitted, generates a copy of the signal for the number of transmission paths, and sends them to each transmission path. The signal transmitted here is, for example, a virtual container on an SDH frame, an Ethernet (registered trademark) frame, an ATM cell, an IP packet, or the like.

  The reception-side transmission device 2 includes a plurality of memories 4 corresponding to each transmission path and a selection unit 5 that selects one of the same signals received from the plurality of transmission paths. The receiving side transmission device 2 receives signals from each transmission path, determines the identity of the signals with reference to the marks of the respective signals, and grasps the delay difference between the same signals. Then, the receiving side transmission device 2 stores each signal in a corresponding memory, and inserts a delay in each system so that the phase of each signal is aligned in the system with the largest delay (referred to as the most delay system). Read signal from memory. Then, the selection unit 5 selects one system signal from the plurality of system signals read from the memory, and transmits the selected system signal to the reception-side apparatus.

  Here, when a failure occurs in the transmission path of the selected system, the selection unit 5 switches the system by selecting another system. At this time, since the phases of the signals of the respective systems received by the selection unit 5 are aligned, the systems can be switched without instantaneous interruption.

In addition, there exists a technique described in patent document 1 as an example of the prior art relevant to uninterruptible switching. Further, in the present specification, “non-instantaneous interruption” means that there is no missing signal and there is no phase jump to the extent that the user application is affected by switching.
JP-A-9-135228

  In the conventional non-instantaneous switching method, there is a problem that the absolute delay of the signal becomes large because the phase of all the system signals is always matched with the phase of the most delay system signal in preparation for a transmission line failure. For example, when a signal is transmitted from the user 1 to the user 2 shown in FIG. 2, if the above-described conventional technique is used, the transmission delay time is A + B + C, and the delay is much larger than the transmission delay time a + b + c in the shortest path. End up. For this reason, when the above-described conventional technology is applied to a real-time application sensitive to absolute delay such as voice, video, and net game, the application may be affected.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a technique for realizing non-instantaneous switching while suppressing delay.

  The above-described problem is a transmission apparatus that receives a plurality of signals from a transmission apparatus on the transmission side via a plurality of transmission paths, selects a signal on one transmission path, and transmits the selected signal to the reception-side apparatus. From the plurality of signals inputted from the plurality of transmission lines, the delay addition means for adding a predetermined delay to the signal by reading the signal inputted from the transmission line after being stored in the storage means, When an event occurs in which a selection unit that selects a signal to which a predetermined delay is added by a delay addition unit and transmits the signal to a receiving device and an event in which normal signal input from the predetermined transmission line is interrupted occur. When each signal stored in the storage means is read while gradually increasing the delay, all the signals stored in the storage means are read out, and then replaced with the signal of the predetermined transmission path. Other transmission lines Is solved by the transmission device, characterized in that it comprises a control means for instructing switching to the selection means to select the item.

  The magnitude of the predetermined delay added by the delay adding means is smaller than the delay difference between the signal on the predetermined transmission path and the signal on the other transmission path, and is stored in the storage means. The increase rate of the delay when reading the signal can be a predetermined rate that does not affect the operation of the application in the device that receives the signal transmitted from the transmission device.

  The time from the start of reading of the signal stored in the storage means after the occurrence of the event until the end of reading is the signal of the predetermined transmission path and the signal of the other transmission path And when the delay is increased at the predetermined speed over the delay difference time, the magnitude of the delay inserted into the signal of the predetermined transmission path is the delay difference Thus, the predetermined delay amount added by the delay adding means can be determined.

In the transmission apparatus, the signal is a virtual container signal included in a basic frame used in a digital synchronous network, and the transmission apparatus transmits a virtual container signal from each of the basic frames received via a plurality of transmission paths. It is also possible to further comprise signal extraction means for extracting the stuff and stuff control means for performing positive / negative stuff control with a pointer in accordance with the delay of the virtual container signal output from the selection means.
Further, the present invention is a transmission apparatus that receives a plurality of signals from a transmission apparatus on the transmission side via a plurality of transmission paths, selects a signal on one transmission path, and transmits the selected signal to the reception apparatus. A selection means for selecting a signal input from a predetermined transmission path from a plurality of signals input from the plurality of transmission paths and transmitting the selected signal to a receiving apparatus, and a normal signal from the predetermined transmission path When an event that is a precursor of an event that interrupts the input of the signal occurs, the delay of the signal input from the predetermined transmission path starts to increase gradually when the event that becomes the precursor is generated. Control means for instructing the selection means to switch so as to select the signal of the other predetermined transmission path instead of the signal of the predetermined transmission path after being equal to the delay of the signal of the predetermined transmission path A transmission device characterized by comprising Rukoto can also.

  Furthermore, the present invention provides a transmission method executed by a transmission apparatus that receives a plurality of signals from a transmission apparatus on the transmission side via a plurality of transmission paths, selects a signal on one transmission path, and transmits the selected signal to the reception apparatus. A delay adding step of adding a predetermined delay to the signal by reading out the signal input from the predetermined transmission path after accumulating in the storage means, and a plurality of signals input from the plurality of transmission paths A selection step of selecting a signal to which a predetermined delay is added in the delay addition step and transmitting the selected signal to a receiving-side device, and an event in which normal signal input from the predetermined transmission line is interrupted In this case, each signal stored in the storage unit at the time when the event occurs is read while gradually increasing the delay, and after all the signals stored in the storage unit are read, the predetermined transmission is performed. Instead of the signal of the road may be configured as a transmission method characterized by a control step for instructing switching to the selection means to select a signal of the other transmission path.

  The present invention also relates to a transmission method in a transmission apparatus that receives a plurality of signals from a transmission apparatus on a transmission side via a plurality of transmission lines, selects a signal on one transmission path, and transmits the selected signal to the reception side apparatus. A selection step of selecting a signal input from a predetermined transmission path from a plurality of signals input from the plurality of transmission paths and transmitting the selected signal to a receiving-side apparatus; When an event that is a precursor of an event in which normal signal input is interrupted occurs, the delay of the signal input from the predetermined transmission path is gradually increased when the event that becomes the precursor occurs, and the delay After the same delay as the signal of the other predetermined transmission path, the selection unit is instructed to switch to select the signal of the other predetermined transmission path instead of the signal of the predetermined transmission path. And having a control step It may be configured as a transmission method for.

  The present invention can also be configured as a program that causes a transmission apparatus to execute each step in the transmission method.

  According to the present invention, when an event occurs in which an initial delay is given to a signal of a predetermined transmission path and a normal signal input from the predetermined transmission path is interrupted, the storage means is generated when the event occurs. It is possible to switch without interruption while reducing the initial delay and suppressing the delay. Become.

  In addition, when an event that is a precursor of an event in which normal signal input from a predetermined transmission line is interrupted occurs, the delay of the signal input from the predetermined transmission line when the event that becomes the precursor occurs By starting to gradually increase and switching after the delay becomes equal to the delay of the signal on the switching destination transmission line, there is no need to insert an initial delay, and the delay can be further reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 3 shows the configuration of the transmission apparatus 10 according to the first embodiment of the present invention. The transmission apparatus 10 shown in FIG. 3 can be used as each transmission apparatus in the transmission system shown in FIG. 2, but the transmission apparatus according to the present embodiment is characterized in the configuration for signal reception. 3 shows a configuration for signal reception. As a configuration for signal transmission, for example, the configuration of the transmission device on the transmission side in FIG. 1 can be provided. The transmission apparatus also includes a switch for selecting a signal route, but these are not shown.

  Hereinafter, the case where the transmission apparatus illustrated in FIG. 3 is used as the reception-side transmission apparatus in section 2 in the transmission system of FIG. 2 will be described. The signal to be transmitted is assumed to be a packet such as an ATM cell, an Ethernet (registered trademark) frame, or an IP packet. Further, as an example of a redundant configuration, two transmission paths are used, the transmission path of path 1 is longer than the transmission path of path 2, the signal transmission delay in the transmission path of path 1 is B, and the transmission of path 2 It is assumed that B> b holds when the signal transmission delay on the road is b. Hereinafter, a system corresponding to the path 1 is referred to as a system 1 or a long distance system, and a system corresponding to the path 2 is referred to as a system 2 or a short distance system.

(Configuration of transmission apparatus 10)
The transmission apparatus 10 shown in FIG. 3 includes an interface unit 11 (IF_a), an interface unit 12 (IF_b), a failure detection unit 13, a delay difference determination unit 14, a delay difference adjustment unit 15 including a memory 151 and a memory 152, and system selection. A unit 16, a control unit 17, a transmission management unit 18, and an interface unit 19 (IF_c).

  The interface unit 11 (IF_a) is an interface that receives a signal from the transmission path of the path 1. The interface unit 12 (IF_b) is an interface that receives a signal from the transmission path of the path 2. The transmission apparatus on the transmission side performs the same operation as that described in the background art, and the interface unit 11 (IF_a) and the interface unit 12 (IF_b) receive the marked signals.

  The failure detection unit 13 is a functional unit that detects a system failure. For example, when a signal from a transmission line of a certain system does not arrive for a certain time, it is determined that the system is in failure. Each of the interface unit 11 (IF_a) and the interface unit 12 (IF_b) includes a light break detection function unit. When the light break detection function unit detects light break, the light break detection function unit May be notified to the failure detection unit 13, and the failure detection unit 13 may detect the failure by receiving the notification. Further, the light break detection function unit may directly notify the control unit 17 of the failure. The “failure” detected by the failure detection unit 13 or the light break detection function unit is not only a general failure that occurs unexpectedly, but also an event in which the transmission line is cut off due to planned transmission line construction, and the like. Is included. This is the same in other embodiments.

  The delay difference determination unit 14 determines the identity of the signals using the marks attached to the respective signals received from the failure detection unit 13 and determines the delay difference between the same signals. The delay difference information is provided to the control unit 17.

  The memory 151 and the memory 152 in the delay difference adjustment unit 15 are associated with the transmission path signal of the path 1 and the transmission path signal of the path 2, respectively. The delay difference adjustment unit 15 has a function of temporarily storing the signal received from the delay difference determination unit 14 in a corresponding memory, reading the stored signal, and supplying the signal to the system selection unit 16. Further, the delay difference adjusting unit 15 receives a delay amount control instruction from the control unit 17 and delays the timing for reading the signal from the memory in accordance with the instruction, thereby adding a delay to the signal or by accelerating the reading timing. It has a function to delete the delay.

  The system selection unit 16 selects one of the signals corresponding to the two systems received from the delay difference adjustment unit 15 in accordance with an instruction from the control unit 17 and transmits the selected signal to the transmission management unit 18. It has. The transmission management unit 18 has a function of controlling signal transmission so that there is no duplication of signals transmitted to the subsequent stage by checking the mark attached to the signal.

  The interface unit 19 (IF_c) has a function of transmitting a signal received from the transmission management unit 18 to a receiving device.

  The control unit 17 controls the system selection unit 16 so as to select the short-distance system in a state where there is no failure (this will be referred to as a normal state). Further, in the normal state, the control unit 17 inserts a predetermined delay amount X (also referred to as initial delay) smaller than the delay difference (B−b) between the long distance system and the short distance system into the memory 152 corresponding to the short distance system. The delay difference adjusting unit 15 is controlled to do so.

  In addition, when the short-distance fault detection information is received from the fault detection unit 13, the control unit 17 delays the delay difference adjustment unit 15 so that the reading speed of the signal stored in the memory 152 is slower than that in the normal state. Instruct. When the memory 152 becomes empty, the control unit 17 sends a system switching instruction from the short-distance system to the long-distance system to the system selection unit 16. The switching operation when a failure occurs will be described in detail later.

  The transmission device 10 described above can be realized, for example, by mounting a device having an interface with a transmission path and a program for executing the operation of each functional unit on a computer having a CPU or the like. It is. Further, it is possible to configure the configuration other than the control unit 17 mainly by hardware and to realize the operation of the control unit 17 by a program.

<Operation of transmission device>
Hereinafter, the operation of the transmission apparatus 10 will be described along the processing procedure shown in the flowchart of FIG. FIG. 5 is a diagram showing the amount of delay inserted into the short-range system in time series, and will be referred to as appropriate in the description.

(Switching action)
In a normal state in which there is no failure in either system (step 1), the delay difference determination unit 14 determines the identity of the signal based on the signal received from each of the transmission path of the path 1 and the transmission path of the path 2. The delay difference between the same signals is determined, and this is notified to the control unit 17.

  The control unit 17 determines the system with the smaller delay, and instructs the delay difference adjusting unit 15 to insert a certain delay amount X (where X <B−b) into the memory corresponding to the system with the smaller delay. In this embodiment, since the delay is smaller in the path 2, the delay X is inserted by delaying the signal reading from the memory 152 corresponding to the system 2. Further, the control unit 17 instructs the system selection unit 16 to select a system with a smaller delay. In the present embodiment, the system selection unit 16 operates to select a signal read from the memory 152. This state corresponds to the state before failure detection in FIG.

By performing such an operation, the transmission delay in section 2 is b + X in a normal state without failure (excluding the transmission delay of each functional unit in the apparatus). A method for determining the delay X will be described later.
Next, it is assumed that the failure detection unit 13 detects a failure by detecting that the signal does not arrive for a certain time (step 2 in FIG. 4). The failure detection unit 13 notifies the control unit 17 of failure information including information on a system that has detected a failure.

  Since the system selection unit 16 selects the system 2 which is a short-distance system, if the failure is a failure in the transmission path of the system 1 which is a long-distance system (No in step 3), the control unit 17 Does not perform operations such as switching. The operation when a failure occurs in the short-haul transmission line (Yes in step 3) will be described next.

  When the controller 17 detects from the failure information received from the failure detector 13 that a failure has occurred in the short-distance transmission path, the speed at which the signal stored in the memory 152 corresponding to the short-distance system is read is reduced. By doing so, the delay difference adjusting unit 15 is instructed to insert the delays. Based on this instruction, the speed at which the signal stored in the memory 152 is read out becomes slow, and a delay is inserted step by step (step 4). This state continues for a period of TS seconds in FIG.

  Since a new signal is not accumulated in the memory 152 after a short-distance transmission line failure occurs, the memory 152 is empty when all the signals accumulated in the memory 152 at the time of the failure are read out. become. At that time, the delay difference adjustment unit 15 notifies the control unit 17 that the memory 152 is empty. Upon receiving the notification, the control unit 17 detects that the memory 152 is empty (Yes in step 5), and instructs the system selection unit 16 to switch the system. Upon receiving this instruction, the system selection unit 17 performs system switching from the short-distance system to the long-distance system (step 6 in FIG. 4 and the point of delay insertion in FIG. 5).

  Thereafter, a long-distance signal is sent from the system selection unit 16. Since the long-distance system has a larger delay than the short-distance system, the same signal as the short-distance system signal already sent by the system selection unit 16 is sent over the long distance. There is a possibility of sending from the system. Therefore, the transmission management unit 18 confirms the mark of the signal and checks not to transmit the already transmitted signal again.

(Effect of switching operation of this embodiment)
By performing the switching operation as described above, it is possible to reduce the influence on the application due to the interruption of the signal at the time of system switching while making the delay at the normal time smaller than that of the conventional technology. Hereinafter, this effect will be described with reference to FIGS.

  6A shows signals of the long-distance system and the short-distance system in the latter part (a) of the interface units 11 and 12 in FIG. 3, and FIG. 6B shows the system in FIG. FIG. 6C shows the signals of the long-distance system and the short-distance system in the former part (b) of the selection unit 16, and FIG. 6C shows the signal of the latter part (c) of the system selection unit 16 in FIG. Show. The upper part of (c) of FIG. 6 shows a case where the reading speed from the memory 152 is assumed to be the same as that before the failure, and the lower part of (c) is the case of the present embodiment, that is, from the memory 152. This shows a case where the reading speed is made slower than the reading speed before the failure.

  In each figure, the horizontal axis indicates a time axis, and the time goes to the past as it goes to the right. In each figure, the wider the signal interval, the slower the signal speed. Note that the mark attached to the signal “9” is attached to make it easy to understand the difference in delay.

  As shown in FIG. 6A, it is assumed that a short-distance transmission line failure has occurred at time T1 after the signal “12” is input from the short-distance transmission line. In this case, the signal input from the short distance transmission line after T1 is interrupted.

  As shown in FIG. 6B, in the short-distance system, a signal of “9” is read from the memory 152 by T1, and three signals “10” to “12” are read from the memory 152 at time T1. Have been accumulated. Here, even if a failure occurs, if the signal reading speed from the memory 152 is the same as the signal reading speed before the failure occurrence, as shown in the upper part of FIG. Is output from the system selection unit 16 until a signal “13”, which is a long-distance signal after switching, is output from the system selection unit 16, and there is a large interval, which affects the application. growing.

  On the other hand, as shown in the lower part of (c), the interval between signals can be narrowed by making the signal read rate from the memory 152 after the failure occurs slower than the signal read rate before the failure occurs. Thereby, the influence on the application at the time of switching can be reduced. Further, if the amount of signal accumulated in the memory 152 (that is, the delay amount X) is determined so that the interval between the signals does not affect the application, the influence on the application can be eliminated at the time of switching. .

  In FIG. 6, the case where the system is switched immediately after the memory 152 becomes empty is indicated by a dotted upward arrow. In addition, a solid line upward arrow indicates a case where switching is performed immediately before the signal of the long distance system next to the last signal among the signals stored in the memory 152 reaches the system selection unit 16. The switching may be performed at any timing, but by performing the switching at the timing of the solid upward arrow, the signals output from the system selection unit 16 do not overlap, so the transmission management unit 18 is not necessary. .

  For reference, FIG. 7 shows signals in the prior art. The upper part of FIG. 7C shows a signal in the part of FIG. 3C when the system is switched from the short distance system to the long distance system without storing the signal in the memory 152. As shown in the figure, the time interval of the delay difference between both systems is vacated with switching. The lower part of FIG. 7C shows a signal in conventional uninterruptible switching in which a delay is inserted into the short-distance system so that the short-distance system and the long-distance system have the same delay. As shown in the figure, an increase in signal interval or the like does not occur with switching. However, as described above, in this case, even in the short-distance system, the delay is always the same as that in the long-distance system, and the application can be affected even in the normal state. On the other hand, as shown in the lower part of FIG. 6C, by using the method of the present embodiment, it is possible to eliminate the influence on the application at the time of switching while suppressing the delay in the normal state.

(Method for determining the delay amount X)
Next, a method for determining the delay amount X to be inserted into the memory 152 will be described with reference to FIG. In FIG. 5, TS is the time required to insert a delay. In the present embodiment, it is necessary to complete the delay insertion before the long-distance signal next to the last signal accumulated in the short-distance memory 152 arrives at the preceding stage of the system selection unit 16. Accordingly, the required time TS is less than or equal to the delay difference (Bb) between both paths. If the required time TS is made smaller than the delay difference (Bb) between the two paths, the last signal accumulated in the memory 152 is read out, and then the next long-distance signal arrives at the preceding stage of the system selector 16. In this embodiment, the required time is set to TS = Bb.

  The slope S in FIG. 5 is a predetermined maximum delay amount that can be inserted per unit time without affecting the application. If S is set to 1 or more, a delay amount larger than the delay difference between both systems is inserted into the short-distance system when TS (= Bb) has elapsed from the start of delay insertion. <1.

  Since S is the maximum delay amount that can be inserted per unit time, (B−b−X) / (B−b) ≦ S must be satisfied. Therefore, X ≧ (1-S) (B−b) holds. If X is (1−S) (Bb) or higher, switching can be performed without affecting the application, but the smaller the initial delay, the better, so X = (1−S) (Bb) is determined. To do.

(Switch back operation)
Next, the switch-back operation after failure recovery will be described. After the failure is recovered, when the control unit 17 receives a system switchback instruction from the monitoring controller that monitors the transmission apparatus 10 (step 7 in FIG. 4), the transmission apparatus 10 enters a system switchback process. Instead of performing the switch-back process after receiving an instruction from the supervisory control device, the transmission device 10 starts the switch-back operation autonomously when the failure detection unit 13 detects the failure recovery. Also good.

  Here, if the magnitude relationship between the delays of the system 1 and the system 2 is the same as before the failure, the system 1 is switched back to the system 2. However, the distance of the recovered transmission line changes due to the influence of the transmission line failure. Therefore, the magnitude relationship between the delays of the system 1 and the system 2 is unknown at the time when the failure is recovered. Therefore, first, the delay difference determination unit 14 determines the delay of both systems (step 8 in FIG. 4), and notifies the control unit 17 of the information. Here, if the system 1 which is the currently selected system has a shorter delay than the system 2, the operation is continued in this state.

  If the delay of system 2 is shorter than that of system 1 as before the failure, a process of switching back from system 1 which is the currently selected system to system 2 is performed (step 9 in FIG. 4). In this case, first, the delay amount of the system 2 is adjusted by adjusting the signal read timing from the memory 152 so that the delay amount in the system 1 and the delay amount in the system 2 are equal. Then, when the phases of the system 2 and the system 1 are aligned, the system selection unit 16 switches the system from the system 1 back to the system 2. This switch back may be performed by an instruction from the monitoring control device, or may be performed autonomously when the control unit 17 detects that the phases are aligned.

  Since the phase is aligned with the system 1 having a large delay at the time when the switch back is completed, the delay of the system 2 is gradually reduced so as to become the short delay (b + X) of the system 2 (step 10 in FIG. 4). ). If the delay is deleted at once, the packet may be output in bursts or the packet may be discarded, which may affect the application. By gradually deleting the delay, bursts or packet Disposal can be prevented and the impact on the application can be reduced.

  More specifically, as shown in FIG. 5, the delay inserted when reading the signal from the memory 152 is gradually reduced over a predetermined time TE. In the example shown in the figure, TE = (B−b−X) / S so that the delay amount to be deleted per unit time is S. In addition, when deleting a delay, since there is time, it is good also as deleting a delay taking time longer than said TE. FIG. 5 shows a case where the delay difference is B−b even after failure recovery.

[Second Embodiment]
FIG. 8 shows the configuration of a transmission apparatus 30 according to the second embodiment of the present invention. The first embodiment is an embodiment when the present invention is applied to a packet transmission apparatus such as an ATM transmission apparatus, but the second embodiment is an embodiment of the present invention such as SDH (Synchronous Digital Hierarchy). This is an embodiment when applied to a digital synchronous network.

  In the second embodiment, the phase between signals is adjusted in units of VC-4 (units of virtual containers) on the STM-1 (155.52 Mbps) (basic frame) shown in FIG. ing. The STM type and container type are not limited to this example, and any STM type and container type (including concatenation / virtual concatenation containers) may be used. For example, STM-1 and VC-3 × 3, STM-1 and VC-3-Xv (X = 1 to 3), STM-4 and VC-4-4c, STM-16 and VC-4-16c, etc. Can be used. The SONET (Synchronous Optical Network) standard can also be applied in the same manner as SDH.

  The basic configuration of the transmission apparatus 30 of the second embodiment shown in FIG. 8 is the same as that of the transmission apparatus 10 of the first embodiment, but is different in that it includes SOH termination units 20, 21, and 22. The SOH termination units 20 and 21 have a function of extracting a VC-4 signal from the STM-1 frame and inserting it into the failure detection unit 13. Further, the SOH termination unit 22 has a function of performing stuff control using an AU pointer according to the delay amount of the VC-4 signal output from the transmission management unit 18. The functions of the failure detection unit 13, the delay difference determination unit 14, the delay difference adjustment unit 15, the system selection unit 16, the control unit 17, and the transmission management unit 18 of the second embodiment are the same as those of the first embodiment. It is the same. However, in the second embodiment, a VC-4 signal is used as a signal whose phase is to be adjusted. In the second embodiment, in order to determine the identity between signals (between VC-4 signals), a mark is attached using an empty byte in the overhead of the VC-4 signal.

  Hereinafter, the operation of the transmission device 30 according to the second embodiment will be described focusing on differences from the operation of the transmission device 10 according to the first embodiment.

  The interface unit 11 (IF_a) and the interface unit 12 (IF_b) receive the STM-1 frame from the transmission paths of the system 1 and the system 2, respectively, and send them to the SOH termination units 20 and 21. Each SOH termination unit extracts a VC-4 signal from the STM-1 frame and passes it to the failure detection unit 13. The failure detection unit 13 performs failure detection by monitoring a predetermined byte of the path overhead. Further, similarly to the first embodiment, a failure can be detected based on a notification from the light break detection function unit provided in the interface units 11 and 12.

  The delay difference determination unit 14 identifies the same signal by a mark attached to the VC-4 signal, determines a delay difference between the same signals, and notifies the control unit 17 of information on the delay difference. The VC-4 signal of each system is stored in the memory and read out, and the VC-4 signal of the system selected by the system selection unit 16 is sent to the SOH control unit 22 via the transmission management unit 18, where staff control is performed. Is put on the STM-1 frame, and the STM-1 frame is sent from the interface unit 19 (IF_c) to the next device.

  In the normal state, the initial delay X is inserted into the short-distance system as in the first embodiment, and when the short-distance system fails, the delay is gradually inserted when signals are read from the memory 152 corresponding to the short-distance system. At this time, as shown in FIG. 10B, the interval of the VC-4 signal is widened. However, when the SOH terminal unit 22 puts it on the STM-1 frame, normal stuff control is performed with the AU pointer.

  When the system is switched back, the delay is gradually deleted when reading from the memory 152 as in the first embodiment. At this time, as shown in FIG. 10C, the interval of the VC-4 signal is narrowed, but negative stuff control is performed with the AU pointer when the SOH terminal unit 20 places the STM-1 frame.

  The VC-4 signal interval is adjusted by performing positive and negative stuff control as described above, but the stuff insertion amount has an upper limit (3 bytes of H3 bytes) in the SDH specification, so the speed of delayed insertion / deletion There are also restrictions. For example, in the STM-1 frame, the delay insertion / deletion speed is a maximum of ± 8000 × 3 bytes time (± about 1.23 ms / second) per second. Therefore, this method cannot be applied when the delay insertion / deletion speed exceeding the above-mentioned maximum value is required. However, if the initial delay X is adjusted, the delay insertion / deletion speed can be adjusted. It is applicable to.

[Third Embodiment]
Next, a third embodiment will be described. FIG. 11 shows the configuration of the transmission apparatus 40 in the third embodiment. The transmission device 40 includes an error correction function unit 34. Further, the function of the failure detection unit 33 is different from the function of the failure detection unit 13 of the first embodiment. The other configuration is basically the same as that of the transmission apparatus 10 of the first embodiment.

  The failure detection unit 33 of the present embodiment has a function of detecting a sign of failure. As a function for detecting a sign of failure, for example, there is a signal error rate measurement function. In this case, a signal error rate that is a sign of failure is determined in advance, and the failure detection unit 33 determines that it is a sign of failure when the signal error rate is reached. Alternatively, each of the interface units 11 and 12 may be provided with an optical input power measurement function, and may be determined to be a sign of failure when the input optical power is equal to or lower than a predetermined optical input power. Hereinafter, the system switching operation in the transmission apparatus 40 of the present embodiment will be described with reference to the delay insertion time series diagram shown in FIG. 12 as appropriate. In the following example, it is assumed that a sign of failure is detected by signal error rate measurement.

  In the normal state, the short distance system is selected, but the initial delay X is not inserted. When the failure detection unit 33 detects that the error rate of the signal from the short-distance transmission line is equal to or higher than a predetermined error rate, the failure detection unit 33 notifies the control unit 17 of this as failure precursor information. Upon receiving the notification, the control unit 17 sends an instruction to the delay difference adjustment unit 15 to insert the delay into the memory 152. Upon receiving this instruction, as shown in FIG. 12, the delay difference adjustment unit 15 sets a delay amount of S (maximum delay amount that can be inserted per unit time that does not affect the application) per unit time, A delay is inserted into the short-range system until the delay difference Bb between the system and the short-range system is reached.

  When the delay is inserted until Bb is reached, the control unit 17 instructs the system selection unit 16 to switch the system, and the system selection unit 16 switches the system from the short distance system to the long distance system. Do. In order to avoid the accumulation of the erroneous signal input in the memory 152 from the time when the error rate is increased until the system switchover, the error correction function unit 34 detects the error of the erroneous signal. Make corrections.

  Here, it is necessary to finish the insertion of the delay after the occurrence of a failure sign until the transmission line is actually cut off (error correction is impossible). Therefore, in the present embodiment, the expected time TR from when a failure sign is generated until the transmission line is cut off is determined according to the type of the failure sign (optical power attenuation, error rate increase, etc.). Then, when a sign of failure occurs, the time (Bb) / S from the delay insertion start time to the delay insertion end time is compared with TR, and if (Bb) / S <TR, then FIG. As shown, a delay is inserted until Bb is reached, and switching is performed after the delay is inserted.

  When (Bb) / S ≧ TR, a delay is inserted with a slope S from the delay insertion start time to TR, and after the insertion, the signal stored in the memory 152 is read in the same manner as in the method of the first embodiment. Switch at a slower speed. Alternatively, switching is performed in the same manner as in the method of the first embodiment after a disconnection is actually detected.

In addition, when there is little variation in Bb and TR, the initial delay X is inserted in advance in the short-range system so that (BbX) / S <TR. It is also possible to insert a delay until the time is reached, and to switch after the delay has been inserted.
Also according to the present embodiment, as in the first embodiment, it is possible to perform non-instantaneous switching while suppressing delay.

  The present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the claims.

It is a figure for demonstrating the conventional non-instantaneous switching method. It is a figure which shows an example of a transmission system. It is a block diagram of the transmission apparatus of 1st Embodiment. It is a flowchart for demonstrating operation | movement of a transmission apparatus. It is the figure which showed the delay insertion operation in time series. It is a figure for demonstrating the effect of 1st Embodiment. It is a figure for demonstrating the effect of 1st Embodiment. It is a block diagram of the transmission apparatus of 2nd Embodiment. It is a figure which shows an example of the flame | frame structure of SDH. It is a figure for demonstrating staff control. It is a block diagram of the transmission apparatus of 3rd Embodiment. It is a figure for demonstrating the delay insertion operation | movement in 3rd Embodiment.

Explanation of symbols

10, 30, 40 Transmission device 11, 12, 17, 19 Interface unit 13, 33 Failure detection unit 14 Delay difference determination unit 15 Delay difference adjustment unit 16 System selection unit 17 Control unit 18 Transmission management unit 20, 21, 22 SOH termination Part 34 Error correction function part

Claims (11)

A transmission apparatus that receives a plurality of signals from a transmission apparatus on a transmission side via a plurality of transmission paths, selects a signal on one transmission path, and transmits the selected signal to a reception-side apparatus,
A delay adding means for adding a predetermined delay to the signal by reading out the signal input from the predetermined transmission path after accumulating in the storage means;
A selection unit that selects a signal to which a predetermined delay is added by the delay addition unit from among a plurality of signals input from the plurality of transmission paths, and transmits the selected signal to a reception-side apparatus;
When an event occurs in which normal signal input from the predetermined transmission line is interrupted, each signal stored in the storage unit at the time when the event occurs is read while gradually increasing the delay, Control means for instructing the selection means to switch so as to select a signal of another transmission path instead of the signal of the predetermined transmission path after reading all the signals stored in the storage means, Transmission equipment.   The transmission apparatus according to claim 1, wherein the predetermined transmission path is a transmission path with the smallest signal delay among the plurality of transmission paths.   The magnitude of the predetermined delay added by the delay adding means is smaller than a delay difference between the signal on the predetermined transmission path and the signal on the other transmission path. The transmission device described.   The rate of increase in delay when reading each signal stored in the storage means is a predetermined rate that does not affect the operation of the application in the device that receives the signal transmitted from the transmission device. The transmission apparatus according to claim 3, wherein the transmission apparatus is provided.   The time from the start of reading of the signal stored in the storage means after the occurrence of the event until the end of the read is between the signal of the predetermined transmission path and the signal of the other transmission path When the delay is increased at the predetermined speed over the delay difference, the delay difference inserted into the signal on the predetermined transmission path is the delay difference. The transmission apparatus according to claim 4, wherein the predetermined delay added by the delay adding means is determined. The signal is a virtual container signal included in a basic frame used in a digital synchronous network,
The transmission device includes a signal extraction unit that extracts a virtual container signal from each of basic frames received via a plurality of transmission paths;
The transmission apparatus according to claim 1, further comprising: stuff control means that performs positive / negative stuff control by a pointer according to a delay of the virtual container signal output from the selection means. . A transmission apparatus that receives a plurality of signals from a transmission apparatus on a transmission side via a plurality of transmission paths, selects a signal on one transmission path, and transmits the selected signal to a reception-side apparatus,
A selection means for selecting a signal input from a predetermined transmission path from a plurality of signals input from the plurality of transmission paths, and transmitting the selected signal to a receiving device;
When an event that is a precursor of an event in which normal signal input from the predetermined transmission line is interrupted occurs, the delay of the signal input from the predetermined transmission line is gradually increased when the event that becomes the precursor occurs. In order to select the signal of the other predetermined transmission path instead of the signal of the predetermined transmission path after the delay becomes the same as the delay of the signal of the other predetermined transmission path. And a control means for instructing the selection means to switch. A transmission method executed by a transmission apparatus that receives a plurality of signals from a transmission apparatus on a transmission side via a plurality of transmission paths, selects a signal on one transmission path, and transmits the signal to a reception-side apparatus,
A delay adding step of adding a predetermined delay to the signal by reading out the signal input from the predetermined transmission path after accumulating in the storage means;
A selection step of selecting a signal to which a predetermined delay is added by the delay addition step from a plurality of signals input from the plurality of transmission lines, and transmitting the selected signal to a reception-side device;
When an event occurs in which normal signal input from the predetermined transmission line is interrupted, each signal stored in the storage unit at the time when the event occurs is read while gradually increasing the delay, A control step of instructing the selection means to switch so as to select a signal of another transmission path instead of the signal of the predetermined transmission path after reading out all the signals stored in the storage means. Transmission method. A transmission method in a transmission apparatus that receives a plurality of signals from a transmission apparatus on a transmission side via a plurality of transmission paths, selects a signal on one transmission path, and transmits the selected signal to a reception-side apparatus,
A selection step of selecting a signal input from a predetermined transmission path from a plurality of signals input from the plurality of transmission paths, and transmitting the selected signal to a receiving device;
When an event that is a precursor of an event in which normal signal input from the predetermined transmission line is interrupted occurs, the delay of the signal input from the predetermined transmission line is gradually increased when the event that becomes the precursor occurs. In order to select the signal of the other predetermined transmission path instead of the signal of the predetermined transmission path after the delay becomes the same as the delay of the signal of the other predetermined transmission path. And a control step for instructing the selection means to perform switching. To a transmission device that receives a plurality of signals from a transmission device on the transmission side via a plurality of transmission channels, selects a signal on one transmission channel, and transmits the signal to the device on the reception side.
A delay addition procedure for adding a predetermined delay to the signal by reading out the signal input from the predetermined transmission path after accumulating in the storage means;
A selection procedure for selecting a signal to which a predetermined delay is added by the delay adding means from a plurality of signals input from the plurality of transmission paths, and transmitting the selected signal to a receiving device;
When an event occurs in which normal signal input from the predetermined transmission line is interrupted, each signal stored in the storage unit at the time when the event occurs is read while gradually increasing the delay, A program that, after reading all signals stored in the storage means, executes a procedure of selecting a signal of another transmission path instead of the signal of the predetermined transmission path. To a transmission device that receives a plurality of signals from a transmission device on the transmission side via a plurality of transmission channels, selects a signal on one transmission channel, and transmits the signal to the device on the reception side.
A procedure of selecting a signal input from a predetermined transmission path from a plurality of signals input from the plurality of transmission paths, and transmitting the selected signal to a receiving device;
When an event that is a precursor of an event in which normal signal input from the predetermined transmission line is interrupted occurs, the delay of the signal input from the predetermined transmission line is gradually increased when the event that becomes the precursor occurs. A step of selecting the signal of the other predetermined transmission path instead of the signal of the predetermined transmission path after the delay becomes equal to the delay of the signal of the other predetermined transmission path; A program that executes

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