JP2007228282A - Transmitting device, transmitting method, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform switching without short break of planned system switching while minimizing delay. <P>SOLUTION: This transmitting device for selecting one signal among the same signals received through a plurality of transmission paths and transmitting the signal to a downstream device gradually adds delay to a signal of a selected transmission path until the delay of the signal of the selected transmission path becomes equal to the delay of a signal of a transmission path of a switching destination from a prescribed time ahead of a switching preparation completion time to the switching preparation completion time and performs switching after the delays of the signals of the both systems become equal in receiving planned switching information about the selected transmission path. <P>COPYRIGHT: (C)2007,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 transmitting-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. The reception-side transmission device 2 stores each signal in a corresponding memory, and inserts a delay into each system so that the phase of each signal is aligned with the system with the largest delay (called the most delayed system). Read signal from. 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 a downstream apparatus.

  Here, when a failure occurs in the transmission path of the selected system or when it is necessary to manually switch the 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 no signal is lost and there is no phase jump associated with switching.
JP-A-9-135228

  In the prior art, 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 case of a transmission line failure. For example, when the conventional technique is used when a signal is transmitted from the user 1 to the user 2 shown in FIG. 2, 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. . For this reason, there are many cases where the above-described conventional technology cannot be applied to an application sensitive to an absolute delay such as a voice call.

  Now, on long-distance transmission lines, the frequency of disconnection of routes (optical fibers, etc.) caused by planned roads, bridge construction, etc. is higher than the frequency of disconnection due to failures in lines and relay devices. There are many cases. In such a case, there is an idea that it is sufficient to realize non-instantaneous switching only in the case of frequent planned construction. In addition, there is a need for an uninterruptible switching transmission system with low delay that can be applied to applications sensitive to absolute delay such as voice calls.

  Therefore, during normal operation without planned construction, the delay is not inserted in order to match the maximum delay system as described above, and instantaneous switching that is very unlikely to occur is allowed. It is possible to apply only uninterrupted switching.

In this case, in order to prepare for the planned construction, it is necessary to switch to a mode in which the above delay is inserted from a normal operation state (referred to as an uninterruptible switching mode). However, if the delay insertion is suddenly performed at this time, an instantaneous interruption occurs. That is, when changing from the normal state shown in FIG. 3A in which a system with little delay is selected without inserting a delay to the uninterruptible switching mode shown in FIG. In order to match the phase of the system to the 1 system, a delay of 2 signals is suddenly inserted into the 0 system. Therefore, in the 0 system, signals are interrupted by two signals, and there is a possibility that a momentary interruption may occur for the user. Further, there is a possibility that instantaneous interruption may occur when the delay is deleted when returning from the non-instantaneous interruption switching mode to the normal state.
In this case, there is a risk of instantaneous interruption occurring twice in the planned construction, ie, delay insertion and delay deletion, and such a method cannot be adopted.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a transmission apparatus that can perform uninterrupted switching for planned system switching.

  The above problem is that a plurality of signals with identifiers for determining the identity of signals are received from a transmission device on the transmission side via a plurality of transmission paths, and a signal on one transmission path is selected. A transmission device for transmitting to a downstream device, determining the identity of a signal using an identifier attached to each received signal, and determining a delay difference determination unit for determining a delay difference between a plurality of identical signals; From the delay difference adjustment means capable of adjusting the delay difference between the plurality of the same signal, the plan switching information received from the outside of the transmission device and the information on the delay difference between the signals acquired by the delay difference determination means, A switching preparation completion time that is a time at which preparation for switching should be completed when receiving the plan switching information for the selected transmission path. Ready for switching from a predetermined time before Over time, the delay is gradually added to or deleted from the signal of the selected transmission line until the delay of the signal of the selected transmission path becomes equal to the delay of the signal of the transmission destination transmission path. Control the delay difference adjusting means, and instruct the switch to the switching destination transmission line after the delay of the signal of the selected transmission path and the delay of the signal of the switching destination transmission path are equal in the delay difference adjusting means This can be solved by a transmission device characterized by the above.

  In the state before the plan switching, the transmission path with the smallest delay is determined based on the information on the delay difference between the signals acquired by the delay difference judging means, and the signal of the transmission line with the smallest delay is selected. Good.

  In the transmission apparatus, by adding a delay to the signal of the transmission path before switching, the delay of the signal of the transmission path of the switching destination is aligned with the delay of the signal of the transmission path before switching. After switching back from the transmission path to the transmission path before switching, the control means deletes the delay added to the signal of the transmission path before switching gradually over a predetermined time. The delay difference adjusting means may be controlled.

  The signal may be a virtual container signal included in a basic frame used in a digital synchronous network. In this case, the transmission apparatus transmits a virtual container from each of the basic frames received via a plurality of transmission paths. Signal extraction means for extracting a signal, and stuff control means for performing positive / negative stuff control with a pointer in accordance with a delay of the virtual container signal output from the system selection means are further provided.

  In addition, the present invention receives a plurality of signals with identifiers for determining the identity of a signal from a transmission apparatus on the transmission side via a plurality of transmission paths, and selects a signal of one transmission path. The transmission method in the transmission device that transmits to the downstream device, and when the planned switching information for the selected transmission path is received from the outside, the switching preparation completion time that is the time at which the preparation for switching should be completed From the predetermined time before the switching preparation completion time, gradually delay the signal of the selected transmission path until the delay of the signal of the selected transmission path becomes equal to the delay of the signal of the transmission path of the switching destination As a transmission method characterized by adding or deleting a signal, and switching to the switching destination transmission path after the delay of the signal of the selected transmission path is equal to the delay of the signal of the switching destination transmission path. You can configure .

  In addition, the present invention receives a plurality of signals with identifiers for determining the identity of a signal from a transmission apparatus on the transmission side via a plurality of transmission paths, and selects a signal of one transmission path. A transmission apparatus for transmitting to a downstream apparatus, determining the identity of the signal using an identifier attached to each received signal, and determining a delay difference between a plurality of identical signals; The transmission apparatus comprising the delay difference adjusting means capable of adjusting the delay difference between the plurality of the same signals, when the plan switching information about the selected transmission path is received from the outside, the preparation for switching is completed. The selection is made until the delay of the signal of the selected transmission path becomes equal to the delay of the signal of the transmission path of the switching destination from the predetermined time before the switching preparation completion time which is a power time to the switching preparation completion time. Gradually against the signal on the transmission line Means for controlling the delay difference adjusting means to add or delete a delay, and switching after the delay of the signal of the selected transmission path and the delay of the signal of the switching destination transmission path are equal in the delay difference adjusting means It can also be configured as a program for functioning as means for instructing switching to the previous transmission path.

  According to the present invention, the switching is performed after the phase of the selection system signal and the switching destination system signal are aligned by gradually inserting or deleting the delay with respect to the planned switching. In addition, it is possible to reduce the influence on the downstream apparatus during delay insertion. In addition, when there is no plan switching, a signal with a minimum delay is selected, so that the delay can be kept to a minimum.

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

[First Embodiment]
FIG. 4 shows the configuration of the transmission apparatus according to the first embodiment of the present invention. The transmission apparatus shown in FIG. 4 can be used as each transmission apparatus in the transmission system shown in FIG. 2, but the transmission apparatus of this embodiment is characterized by the configuration for signal reception. The structure for signal reception is shown. 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 path, but is not illustrated.

  Hereinafter, the case where the transmission apparatus shown in FIG. 4 is used as the reception-side transmission apparatus in section 2 in the transmission system of FIG. 2 will be described. Further, it is assumed that a signal to be transmitted is 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, and a system corresponding to the path 2 is referred to as a system 2.

(About configuration of transmission equipment)
4 includes an interface unit 11 (IF_a), an interface unit 12 (IF_b), a delay difference determination unit 13, a delay difference adjustment unit 14 including a memory 141 and a memory 142, a system selection unit 15, and a control unit. 16 and an interface unit 17 (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 delay difference determination unit 13 determines the identity of the signal received by the interface unit 11 (IF_a) and the signal received by the interface unit 12 (IF_b) by using a mark attached to the signal. It has a function of determining a delay difference between signals and notifying the controller 16 of information on the delay difference.

  The memory 141 and the memory 142 in the delay difference adjusting unit 14 are associated with the transmission path signal of path 1 and the transmission path signal of path 2, respectively. The delay difference adjustment unit 14 has a function of temporarily storing the signal received from the delay difference determination unit 13 in a corresponding memory, reading the stored signal, and supplying the signal to the system selection unit 15. Also, the delay difference adjusting unit 14 receives a delay amount control instruction from the control unit 16 and delays the timing for reading a signal from the memory in accordance with the instruction, thereby adding a delay to the signal or by advancing the reading timing. It has a function to delete the delay.

  The system selection unit 15 selects one of the signals corresponding to the two systems received from the delay difference adjustment unit 14 in accordance with an instruction from the control unit 16 and sends the selected signal to the interface unit 17 (IF_c). It has. The interface unit 17 (IF_c) has a function of transmitting a signal received from the system selection unit 15 to a downstream device.

  The control unit 16 can receive plan switching information from a monitoring control device (OpS) outside the transmission device 10 and has a function of reserving system switching according to the information. In this case, a switching instruction is given to the system selection unit 15 at the reserved time. It is also possible to receive a switching instruction from the monitoring control device and to perform a switching instruction to the system selection unit 15 according to the instruction. In addition, the control unit 16 has a function of switching the mode from the normal switching mode to the uninterruptible switching mode based on the plan switching information received from the monitoring control device, and performing a control for returning the mode. Details of the normal switching mode and the non-instantaneous switching mode will be described later.

  The above transmission device can be realized, for example, by mounting a device that is 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 also possible to configure the components other than the control unit mainly by hardware, and realize the operation of the control unit by a program.

(About operation of transmission equipment)
Hereinafter, the operation of the transmission apparatus 10 will be described along the processing procedure shown in the flowchart of FIG.

  First, it is assumed that the transmission apparatus 10 is in a normal switching mode, which is a normal state in which no planned work or the like is planned (step 1). At this time, the delay difference determination unit 13 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, determines the delay difference between the same signals, Notify the control unit 16.

  The control unit 16 determines the system with the smaller delay, and instructs the system selection unit 15 to select the system with the smaller delay. In the present embodiment, since the delay is smaller in the path 2, the system selection unit 15 operates to select the signal read from the memory 142 corresponding to the transmission path of the path 2.

  By performing such an operation, the transmission delay in section 2 is b in the normal switching mode (excluding the transmission delay of each functional unit in the apparatus). Since the delay difference adjusting unit 14 does not align the delay between the same signals, a failure may occur in the transmission path of the route 2 in this state, and an instantaneous interruption may occur when the system is switched. Is small.

  Subsequently, the control unit 15 receives the plan switching information from the monitoring control device (step 2 in FIG. 5). This plan switching information includes information on a system that is disconnected for construction work (construction execution system) and a time at which the transmission apparatus 10 performs switching (hereinafter referred to as a plan switching time). The plan switching time may be either absolute time or relative time. The control unit 15 determines the construction execution system from the plan switching information, and enters the preparation for switching if the construction execution system is the system 2 which is the currently selected system (steps 3 and 4 in FIG. 5).

  In the switching preparation stage, first, based on the planned switching time, a switching preparation completion time that is a time at which switching preparation should be completed is determined. If the switching is performed as soon as the switching preparation is completed, the planned switching time and the switching preparation completion time are the same time. In addition, if switching is performed after confirmation of switching preparation completion by the monitoring control device, the switching preparation completion time is set a predetermined time before the planned switching time.

  Thereafter, a delay is gradually inserted into the system 2, which is the system with the smaller delay, from the predetermined time (TS) before the switching preparation completion time until the phases of the same signals of the systems 1 and 2 match. Specifically, the delay is inserted as follows.

  Normally, signals (packets) written in each memory of the delay difference adjusting unit 14 are immediately read out at the same speed as the writing speed. When a delay is inserted, the time from when a signal is written to the memory until it is read out is delayed. That is, since the signal of system 1 is delayed by B−b with respect to the signal of system 2, if the signal written in the memory 142 is read after the time of B−b, the signal of system 1 and the signal of system 2 The signal phase is aligned. Here, in this embodiment, in order to prevent an instantaneous interruption by suddenly inserting a delay of B−b, the delay is gradually inserted until B−b is reached.

  That is, as shown in FIG. 6A, when delays are inserted all at once, there is a possibility that there will be an interval between packets, which may affect applications and the like. On the other hand, as shown in FIG. 6B, if delays are gradually inserted, the interval between packets does not increase compared to the case where the delays are inserted all at once, and the influence on the application or the like can be reduced.

  More specifically, as shown in FIG. 7, a delay is gradually inserted before a predetermined time (TS) before the time when the phases of both systems are aligned (switching preparation completion time) so that the target delay is reached at the switching preparation completion time. To. In FIG. 7, the delay amount inserted per unit time is fixed and the delay is increased so as to be directly proportional to the time. However, any method can be used as long as the delay is not suddenly inserted. May be. For example, the TS may be divided into several stages, and an amount of delay that does not affect the user may be inserted for each stage.

  Next, an example of a TS determination method will be described with reference to FIG. In FIG. 8, TY is the time from when the plan switching information is received until the switching preparation completion time. S is a delay amount to be inserted per unit time so as not to affect the application. This delay amount is predetermined, and a large amount is desirable as long as it does not affect the application. TD is a delay amount to be inserted, and is a value measured by the delay difference determination unit 13.

  (1) When TY ≧ TD / S, that is, when there is sufficient time from the reception of the plan switching information to the switching preparation completion time, TS = TD / S.

  (2) On the other hand, when TY <TD / S, that is, when there is no sufficient time from the reception of the plan switching information to the switching preparation completion time, TS = TY.

  In the case of (2), since the delay amount to be inserted per unit time is TD / TY> S, there is a possibility that the user's application may be momentarily interrupted. small.

  After the preparation for switching is completed, plan switching is executed as shown in FIG. 9 (step 5 in FIG. 5). That is, switching is performed so that the system selection unit 15 selects the system 1 signal instead of selecting the system 2 signal. Since the Bb delay is added to the signal read from the memory 142 due to the plan switching preparation, the phase of the signal read from the memory 142 and the signal read from the memory 141 are the same, and no instantaneous interruption occurs during system switching.

  The monitoring control device may detect that the preparation for switching has been completed, and the monitoring control device may perform switching by instructing switching accordingly, or the control unit 16 may be autonomous when the switching preparation is completed. Alternatively, a switching instruction may be given. Subsequently, the transmission path construction for path 2 is performed. At this time, the system selection unit 15 has selected the system 1, so there is no influence by the transmission path construction of the path 2.

  After the construction is completed, when the control unit 16 receives information indicating the completion of the planned construction from the monitoring control device (step 6 in FIG. 5), the transmission device 10 performs a switch-back process for returning the uninterruptible switching mode to the normal switching mode. enter.

  Here, if the delay relationship between system 1 and system 2 is the same as before construction, it will switch back from system 1 to system 2, but the distance of the constructed transmission line will change due to the influence of the construction of the transmission line. Therefore, at the time when the transmission line construction is completed, the magnitude relationship between the delays of the system 1 and the system 2 is unknown. Therefore, first, the delay difference determination unit 13 determines the delay of both systems (step 7 in FIG. 5), and notifies the control unit 16 of the information. Here, if the system 1, which is the currently selected system, has a shorter delay than the system 2, this state is set as the normal switching mode and the operation is continued.

  If the delay of system 2 is shorter than that of system 1 as before switching, a process of switching back from system 1 which is the currently selected system to system 2 is performed (step 8 in FIG. 5). In this case, first, the delay amount of the system 2 is adjusted by adjusting the signal read timing from the memory 142 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 15 switches the system from the system 1 back to the system 2. This switching back may be performed by an instruction from the monitoring control device, or may be performed autonomously when the control unit 15 detects that the phases are aligned.

  Since the phase is aligned in the system 1 with a large delay at the time when the switch back is completed, the delay of the system 2 is gradually reduced so as to be a short delay of the system 2 (step 9 in FIG. 5). In other words, as shown in FIG. 10A, if the delay is deleted at once, the packet may be burst output or the packet may be discarded, which may affect the application. By gradually deleting the delay as described above, it is possible to prevent occurrence of bursts and discard of packets, and to reduce the influence on the application.

  More specifically, as shown in FIG. 11, the delay that has been inserted when reading a signal from the memory 142 over a predetermined time TE is gradually reduced. FIG. 11 shows a case where the delay difference is B−b even after the construction. Next, a TE determination method will be described with reference to FIG.

  The sizes of TD and S shown in FIG. 12 are the same as those in FIG. When the delay is gradually deleted, there is no time limit and sufficient time can be secured, so TE = TD / S.

  In the above embodiment, the delay insertion amount is set to 0 in the normal switching mode. Thus, communication with the shortest delay amount can be provided in the normal switching mode. However, when Bb, which is the difference between the delay amounts of the system 1 and the system 2, is very large, the delay amount to be inserted to switch from the normal switching mode to the uninterruptible switching mode and the delay to be deleted to switch back Since the amount increases, even if the delay amount is gradually inserted / deleted, there is a possibility that it may have an undesirable effect depending on the application.

  Therefore, when B−b is larger than a value that adversely affects the application (a predetermined value), the amount of delay to be inserted in order to switch from the normal switching mode to the uninterruptible switching mode is determined by the application. A delay is inserted in the short delay system even in the normal switching mode so as not to have an influence. In other words, for example, if the delay insertion amount is smaller than B-b by F, the delay is inserted by F if it does not affect the application. Note that F is a value larger than 0 and smaller than B−b.

  FIG. 13 shows a change in the delay insertion amount in the memory 142 in this case. As shown in FIG. 13, F is added as an initial delay amount. After receiving the plan switching information, a delay of (B−b) −F is inserted between the switching preparation start time and the switching preparation completion time, and after the completion of the switching, (B−b) −F The delay is removed. In this case, it is assumed that the delay difference between system 1 and system 2 is the same before and after construction.

[Second Embodiment]
FIG. 14 shows a 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 a digital embodiment such as SDH (Synchronous Digital Hierarchy). This is an embodiment when applied to a synchronous network.

  In the second embodiment, the inter-signal phase is adjusted in VC-4 units (virtual container units) on the STM-1 (155.52 Mbps) (basic frame) shown in FIG. is doing. 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 according to the second embodiment illustrated in FIG. 14 is the same as that of the transmission apparatus 10 according to the first embodiment, except that the SOH termination units 18, 19, and 20 are included. The SOH termination units 18 and 19 have a function of extracting a VC-4 signal from the STM-1 frame and inserting it into the delay difference determination unit 13. In addition, the SOH termination unit 20 has a function of performing stuff control using an AU pointer according to the delay amount of the VC-4 signal output from the system selection unit 15. The functions of the delay difference determination unit 13, the delay difference adjustment unit 14, the system selection unit 15, and the control unit 16 of the second embodiment are the same as those of the first embodiment. 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 apparatus 30 according to the second embodiment will be described focusing on differences from the operation of the transmission apparatus 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 18 and 19. Each SOH termination unit extracts a VC-4 signal from the STM-1 frame and passes it to the delay difference determination unit 13. The delay difference determination unit 13 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 of information on the delay difference. The information of the VC-4 signal of each system is accumulated in the memory and read out, and the VC-4 signal of the system selected by the system selection unit 15 is sent to the SOH control unit 20, where stuff control is performed, and STM- The STM-1 frame is sent from the interface unit 17 (IF_c) to the next device.

  When shifting from the normal switching mode to the non-instantaneous switching mode, a delay is gradually inserted when reading from the memory, as in the first embodiment. At this time, as shown in FIG. 16B, the interval of the VC-4 signal is widened. However, when the SOH terminal unit 20 places the STM-1 frame, the stuffing control is performed with the AU pointer.

  When switching back to the mode, the delay is gradually deleted at the time of reading from the memory as in the first embodiment. At this time, as shown in FIG. 16C, 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. However, since the stuff insertion amount has an upper limit (3 bytes of H3 bytes) in the SDH specification, the speed of delayed insertion / deletion There are also restrictions. For example, in the STM-1 frame, the delay insertion / deletion rate is a maximum of ± 8000 × 3 bytes time (± about 1.23 ms / second) per second. For this reason, it cannot be applied when the delay insertion / deletion speed is higher than the above maximum value, such as when there is no delay insertion time, but switching is planned with sufficient margin in most cases for planned construction. This method can be applied to most cases by combining, as necessary, the method of putting the initial delay F described at the end of the first embodiment in advance. is there.

  As described above, by using the transmission apparatus described in the present embodiment, it is possible to perform uninterruptible switching at the time of planned switching while normally realizing low delay. The delay is inserted / deleted at the time of switching / switching back, but since the delay is gradually inserted / deleted, the phase jump can be sufficiently reduced, and the possibility of affecting the user is reduced. Even at the time of switching, it is only necessary to increase the amount of delay in the section to be switched, and the delay can be made smaller than in the case where a delay is inserted in each section as in the prior art. In the present embodiment, two transmission paths, system 1 and system 2, are shown. However, the present invention can be applied even when there are three or more transmission lines. For example, when three systems of transmission lines are used and planned construction occurs in the minimum delay system, the system with the second smallest delay can be switched as the switching destination system. In addition, when planned construction occurs on two transmission lines including the minimum delay system, the remaining system may be set as the switching destination. The present invention can also be applied to an optical path network.

  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 figure for demonstrating the problem in the case of performing delay insertion rapidly. 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 a figure for demonstrating the advantage in the case of inserting a delay gradually. It is a figure for demonstrating the method of inserting a delay gradually. It is a figure for demonstrating the method to determine TS. It is a figure which shows the transmission apparatus of the state which performs switching. It is a figure for demonstrating the advantage in the case of deleting a delay gradually. It is a figure for demonstrating the method of deleting a delay gradually. It is a figure for demonstrating the method to determine TE. It is a figure which shows the change of the amount of delay when inserting an initial delay into a short delay system. 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.

Explanation of symbols

10, 30 Transmission device 11, 12, 17 Interface unit 13 Delay difference determination unit 14 Delay difference adjustment unit 15 System selection unit 16 Control unit 18, 19, 20 SOH termination unit

Claims (6)

A plurality of signals with identifiers for determining the identity of signals are received from a transmission apparatus on the transmission side via a plurality of transmission paths, and a signal on one transmission path is selected and transmitted to a downstream apparatus. A transmission device for
A delay difference determination means for determining the identity of a signal using an identifier attached to each received signal, and determining a delay difference between a plurality of identical signals;
A delay difference adjusting means capable of adjusting a delay difference between the plurality of identical signals;
Control means for controlling the delay difference adjusting means from the plan switching information received from the outside of the transmission device and the information of the delay difference between the signals acquired by the delay difference judging means,
The control means includes
When the planned switching information for the selected transmission line is received, the switching transmission completion time from the predetermined time before the switching preparation completion time, which is the time at which preparation for switching should be completed, to the switching preparation completion time, is selected. Controlling the delay difference adjusting means to gradually add or delete the delay of the signal of the selected transmission path until the delay of the signal becomes equal to the delay of the signal of the transmission path of the switching destination,
The transmission apparatus characterized in that the delay difference adjusting means performs switching to the switching destination transmission path after the delay of the signal of the selected transmission path is equal to the delay of the signal of the switching destination transmission path. .   2. The transmission path with the smallest delay is determined based on the information on the delay difference between the signals acquired by the delay difference determination means in the state before the plan switching, and the signal of the transmission path with the smallest delay is selected. The transmission device described. By adding a delay to the signal of the transmission path before switching, the switching of the transmission path of the switching destination is performed in a state where the delay of the signal of the transmission path of the switching destination and the delay of the signal of the transmission path before switching are aligned. After switching back to the previous transmission line,
3. The delay difference adjusting unit according to claim 2, wherein the control unit controls the delay difference adjusting unit so that the delay added to the signal on the transmission path before the switching is gradually deleted over a predetermined time. Transmission equipment. 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 according to any one of claims 1 to 3, further comprising: stuff control means for performing positive / negative stuff control by a pointer in accordance with a delay of a virtual container signal output from the system selection means. apparatus. A plurality of signals with identifiers for determining the identity of signals are received from a transmission apparatus on the transmission side via a plurality of transmission paths, and a signal on one transmission path is selected and transmitted to a downstream apparatus. A transmission method in a transmission device,
When the planned switching information for the selected transmission line is received from the outside, the selected transmission is performed from the predetermined time before the switching preparation completion time, which is the time at which preparation for switching should be completed, to the switching preparation completion time. A delay is gradually added to or deleted from the signal of the selected transmission path until the delay of the signal of the path becomes equal to the delay of the signal of the transmission path of the switching destination, and the signal of the signal of the selected transmission path is A transmission method characterized in that switching to a switching destination transmission path is performed after the delay and the signal delay of the switching destination transmission path become equal. A plurality of signals with identifiers for determining the identity of signals are received from a transmission apparatus on the transmission side via a plurality of transmission paths, and a signal on one transmission path is selected and transmitted to a downstream apparatus. A delay difference determination means for determining the identity of a signal using an identifier attached to each received signal and determining a delay difference between a plurality of the same signals, and the plurality of the same signals A transmission apparatus comprising delay difference adjusting means capable of adjusting a delay difference between
When the planned switching information for the selected transmission line is received from the outside, the selected transmission is performed from the predetermined time before the switching preparation completion time, which is the time at which preparation for switching should be completed, to the switching preparation completion time. Means for controlling the delay difference adjusting means to gradually add or remove a delay from the signal of the selected transmission path until the delay of the signal of the path becomes equal to the delay of the signal of the transmission path of the switching destination;
Means for instructing switching to the transmission path of the switching destination after the delay of the signal of the selected transmission path is equal to the delay of the signal of the transmission path of the switching destination in the delay difference adjusting means;
Program to function as.

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