JPH11103268A - No hit change over system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a no hit change over system allowed to be applied to a protection method by which no signal is branched and transmitted from a transmission side to a stand-by transmission line in a steady state. SOLUTION: Each of transmitting terminals (e.g. transmission line terminal parts 5, 6) transmits a multiframe pattern, receives a loop back signal from each of receiving terminals (transmission line terminal parts 7, 8) and respectively individually measures the absolute delay values of current and stand-by transmission lines by using transmitting/receiving multiframe patterns independently of the branch/non-branch of a signal to the stand-by transmission line. A relative delay value between both current and stand-by transmission lines is calculated from the absolute delay values and delay values to be applied to the receiving side delay buffers 9, 10 on the current and stand-by transmission lines are previously set up at the time of mutually switching these transmission lines. In a steady state such as 1:N redundant system constitution in which switching operation is not generated, the no hit change over system can be applied to the protection system by which no signal is branched and transmitted from the transmission side to the stand-by transmission line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line switching system of a digital transmission device facing a plurality of bidirectional digital transmission lines constituting a redundant system.

In particular, when there is a delay difference between signals passing through both transmission lines due to a distance difference between a working transmission line and a backup transmission line, instantaneous interruption for switching transmission lines without causing data loss or duplication. It relates to a switching method.

[0003]

2. Description of the Related Art In the conventional hitless switching system, two transmission paths are provided from a transmitting apparatus to a receiving apparatus, and the transmitting apparatus branches a transmission signal to both transmission paths and transmits the same signal. In addition, a transmission line switching system having a redundant configuration is used in which a receiving device selects one of signals received from both transmission lines.

FIG. 6 is a block diagram showing such a conventional non-stop switching method. In the figure, two transmission paths from the transmission side apparatus to the reception side apparatus include a transmission path terminating unit 104 which branches the transmission side signal and supplies the same signal.
Transmission line terminating unit 10 for receiving the same signal on the receiving side as 105
6, 107.

As the non-stop switching means, the transmitting side is provided with a multi-frame pattern inserting section 101 and a multi-frame generating section 100 in front of a branching section 103 for transmitting the same signal to both transmission systems. The pattern insertion unit 101 is configured to insert a multi-frame pattern generated from the multi-frame generation unit 100 into an empty time slot of a transmission signal. Also, the receiving side
Providing delay buffers 110 and 111 for delaying signals received from both transmission paths, multi-frame synchronization circuits 108 and 109 for synchronizing multi-frames, and a controller 112, the multi-frame synchronization circuits 108 and 109 Synchronize the multi-frame of the system, and
2 compares the phases of the multi-frames of the received signals of both systems, determines the relative delay difference at the receiving end, controls the amount of delay given to the delay buffers 110 and 111 based on the relative delay difference, and The phases of the latter two signals are matched.

As a result, the delay difference between the two transmission lines can be eliminated, so that when the signals of both systems are switched by the selection unit 113 on the receiving side, data loss or duplication does not occur, and instantaneous interruption switching is performed. Is realized.

Although FIG. 6 shows only a configuration in which attention is paid only to a signal in a one-way transmission line as a non-interruptible switching system, in a normal bidirectional transmission line, even in a transmission direction in the opposite direction. A similar configuration can be adopted, and instantaneous interruption switching in bidirectional communication with two bidirectional transmission line configurations is performed.

Further, there is provided a non-interruptible switching system having two bidirectional transmission paths, wherein one of the opposing transmission / reception apparatuses has a function of transmitting a periodic signal for measuring a delay time of the transmission path. Japanese Unexamined Patent Publication No. Hei 8-65282 discloses a non-instantaneous interruption switching system having a loopback function for the periodic signal.

In this non-interruptible switching system, one transmitting / receiving device transmits a periodic signal to a bidirectional transmission line, and compares the transmitted periodic signal with the periodic signal loop-backed and received by the other transmitting / receiving device. By doing, 2
By measuring three delay times due to a loopback in two bidirectional transmission lines and a loopback spanning between two bidirectional transmission lines, and calculating the measurement results of the three delay times, it is possible to calculate the three delay times. This is a non-stop switching method in a two-way communication system in which the amount of delay of a received signal is adjusted to reduce the number of components of one transmitting / receiving device and simplify management.

[0010]

In the conventional hitless switching system, the phases of the received signals are matched at the stage prior to the receiving-side selection unit, so that the transmitting side uses the same transmission system in which a multi-frame pattern is embedded in two transmission systems. Send the signal, and on the receiving side,
This is a method in which the relative phase difference between the multi-frame patterns received from both systems is compared, and a signal whose phase is relatively advanced is delayed so as to match the phases of the two systems.

Although this system is suitable for a protection system in which a signal is always branched to both systems at a transmitting end and a reception signal of both systems can be constantly monitored at a receiving end, such as a 1 + 1 redundant system, In a system in which the signal of each working channel cannot be branched and transmitted to the protection transmission line in a steady state where the switching operation is not performed as in the 1: N redundant system configuration, the reception side receives the signals from the working and protection transmission lines. However, there is a problem that the phases of the signals to be adjusted cannot be compared with each other, and the control of the phase adjustment cannot be constantly performed.

In the instantaneous interruption switching method in the two-way communication system, since it is necessary to measure a delay amount due to a loop-back across two bidirectional transmission lines among the delay amount measurements, 1: N In the case of a system in which signals of a plurality of working channels cannot be branched and transmitted to a spare transmission line in a steady state as in a redundant system configuration, signals of a plurality of working channels are also spared in a steady state where switching operation is not performed. Since the signal cannot be branched and transmitted to the transmission path, the phases of the signals received from the working and protection transmission paths cannot be compared, and the phase adjustment control cannot be performed constantly. Furthermore, in this method, it is necessary to perform three loop-back controls and measurements for measuring the amount of delay, which complicates transmission / reception control of periodic signals and arithmetic processing, and necessitates synchronization of the active system and the standby system. Therefore, there is a problem that the device configuration is complicated.

In order to solve such a problem, regardless of whether the working channel signal is transmitted to the transmission paths of both systems, the multi-frame information is transmitted using the overhead bytes transmitted and received unconditionally. In this method, it is necessary to synchronize multiframes inserted in both interface units at the transmission ends of both transmission lines, and a mechanism for this is required.

(Object of the Invention) An object of the present invention is to provide a protection system which cannot be applied by the conventional hitless switching system, ie, a switching operation, like a 1: N redundant system configuration. It is an object of the present invention to provide a hitless switching method applicable to a protection method in which a transmitting side does not branch and transmit a signal to a protection transmission line in an unsteady state.

[0015]

The instantaneous interruption switching system of the present invention comprises a means (16, 15 in FIG. 2) for independently generating and transmitting a multi-frame for the active system and the standby system, and a multi-frame for the received signal. Means for transmitting a multi-frame in the same phase as the received multi-frame phase by looping back the received multi-frame pattern to the transmission side signal of the same interface (17, 18, and 15 in FIG. 2)
Means for monitoring the multi-frame pattern looped back and comparing the multi-frame pattern with the phase of the multi-frame generated by its own device, and calculating the absolute delay amount of the round trip between the active system and the standby system as the comparison result (19 in FIG. 2). , 20).

Further, the relative delay amount between the transmission paths is obtained by comparing the absolute delay amounts of the working system and the standby system (13 or 14 in FIG. 1), and the delay amount with respect to the received signal is determined according to the obtained relative delay amount. Is set (5, 6 or 7, 8 in FIG. 1).

(Operation) Regardless of whether or not the signal is branched to the protection transmission line at the transmitting end, the absolute delay amount of each transmission line is independently measured, and the two absolute delay amounts are used to determine the absolute delay amount between the two transmission lines. Is calculated by a predetermined calculation formula, and a delay amount to be given to the delay buffer on the receiving side of each transmission path when switching between the working and protection transmission paths is set in advance.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a transmission line redundant configuration to which a hitless switching method according to the present embodiment is applied.
FIG. 2 is a block diagram showing the configuration of the transmission line terminating units 5, 6, 7, and 8 in FIG.

First, the basic configuration and operation of the transmission line redundant system and switching of the present embodiment shown in FIG. 1 will be described.

The configuration of the transmission line redundant system includes a working transmission line and a protection transmission line in both directions, transmission line terminating units 5, 7 and 6, 8 connected to their respective ends, and the transmission line terminating unit. Working channels and extra traffic channels connected to 5, 7 and 6, 8 and delay buffers 9, 11, 1 connected to the reception signal lines of each channel.
0, 12, transmission end switches 1 and 3 connected to the transmission lines of the respective channels, and reception end switches 2 and 4 connected to the reception lines of the respective channels.

Here, the transmission end switches 1 and 3 selectively transmit, as transmission signals, a working channel signal to be transmitted to the working transmission path and an extra traffic signal to be transmitted to the protection transmission path via the protection transmission path. And the receiving end switches 2, 4
Is configured to be switchable so that a working channel signal received from a working transmission line and a working channel signal or an extra traffic signal received from a protection transmission line as a reception signal can be selectively received via the protection transmission line. ing.

In the steady state, the transmitting end switches 1 and 3 transmit the working channel signal to the working transmission line from both directions, and similarly transmit the extra traffic channel signal to the protection transmission line from both directions. The contacts of the receiving end switches 2 and 4 are set at the positions shown in FIG.

When a failure occurs in the working transmission line or when a switching control command is received from the operator, first,
The transmitting end switch 1 or 3 in the transmission direction specified by the fault or the command selects the working channel signal and transmits the working channel signal also to the protection transmission line. That is, the working transmission path,
It is assumed that the same signal is branched and transmitted to both of the protection transmission lines. Next, the corresponding receiving end switch 4 or 2 switches to receive the working channel signal from the protection transmission line, thereby completing the transmission line switching operation.

Next, a more detailed configuration and operation of the instantaneous interruption switching system according to the present embodiment will be described.

In the instantaneous interruption switching method according to the present embodiment, FIG.
As shown in the figure, delay buffers 9, 10, 11, 10
And the delay buffer is controlled by delay control units 13 and 14 which receive a signal from a transmission line termination unit.

FIG. 2 is a block diagram showing the configuration of the transmission path terminating units 5, 6, 7, and 8. In the figure, a transmission line termination unit establishes multiframe synchronization for a received signal from a transmission line and extracts a multiframe pattern, a multiframe generation unit 16 that generates a multiframe, A multi-frame pattern insertion unit 15 for inserting a multi-frame pattern into a transmission signal; a multi-frame synchronization unit 17; and a selection unit 18 for selecting an output of the multi-frame generation unit 16 or the multi-frame synchronization unit 17
And a delay measuring unit 19 for comparing the multi-frame phases output from the multi-frame generating unit 16 and the multi-frame synchronizing unit 17 to calculate the absolute delay amount of the round trip of the transmission path, and the delay of the delay buffers 9, 10, 11, and 12. Control unit 2 for controlling the delay control units 13 and 14 for setting the amounts by the absolute delay amount
0.

In FIG. 2, a multi-frame generation unit 16
Generates a multi-frame pattern in which the ID of the own device is inserted, and outputs the multi-frame pattern to the selection unit 18 and the delay measurement unit 19. Further, when receiving the loopback instruction signal from the control unit 20, the multiframe generating unit 16 turns on the loopback information in the generated multiframe.

The multi-frame synchronizing unit 17 synchronizes the received signal with the multi-frame, extracts a multi-frame synchronizing pattern, and outputs it to the selecting unit 18 and the delay measuring unit 19.

When a multi-frame pattern in which the loop-back information is turned on is received, the multi-frame pattern is looped back and the multi-frame pattern insertion unit 15 is returned.
The selector 18 is controlled so that the signal is multiplexed with the signal and transmitted.

The selecting section 18 normally selects the multi-frame pattern generated by the multi-frame generating section 16 and outputs the selected multi-frame pattern to the multi-frame pattern inserting section 15. If received, the multi-frame pattern is output to the multi-frame pattern insertion unit 15.

The delay measuring section 19 compares the phase of the multi-frame generated by the multi-frame generating section 16 with the phase of the multi-frame received by the multi-frame synchronizing section 17 to calculate the phase difference α. .

The control unit 20 inserts loopback information of a multi-frame into the multi-frame generation unit 16 continuously or periodically or when a fault condition of a transmission line or a switching control command is received from an operator. Of the phase difference α calculated by the delay measurement unit 19 and the delay control unit 1
Output to 3 and 14.

Next, the operation of each part in FIGS. 1 and 2 will be described with reference to FIGS.

The multi-frame used in the present embodiment is an n-multi-frame as shown in FIG. 3, and the n-multi-frame is multiplexed by multiplexing a multi-frame pattern using an empty time slot of an overhead byte in the frame. Send and receive. The multi-frame pattern is
A loopback control bit LP for giving a loopback instruction,
It is composed of a device ID and a multi-frame synchronization pattern.

Each of the transmission line terminators of each bidirectional transmission line has the configuration shown in FIG.
Numeral 8 selects the multi-frame pattern generated by the multi-frame generation unit 16, which is multiplexed with a signal in the multi-frame pattern insertion unit 15 and transmitted to the transmission path.

When the control unit 20 outputs a loopback instruction signal for instructing the multiframe generation unit 16 to insert loopback information into the multiframe, the multiframe generation unit 16 outputs the loopback information in the generated multiframe. Turn ON. By doing so, the multi-frame pattern with the loop-back control information turned ON is transmitted to the opposing device.

On the other hand, the loopback information of the opposing device is ON.
When the multi-frame pattern is received, the selecting unit 1
8 selects a multi-frame pattern received from the multi-frame synchronization unit 17 and
Then, the multi-frame pattern received from the transmission path is transmitted after being looped back.

The transmitted multi-frame pattern is returned from the opposite device, and the multi-frame synchronizer 17 receives the multi-frame pattern, extracts the multi-frame pattern, and outputs the extracted multi-frame pattern to the delay measuring unit 19. The delay measurement unit 19 calculates the phase difference α by comparing the phase of the multi-frame generated by the multi-frame generation unit 16 with the phase of the multi-frame received by the multi-frame synchronization unit 17.

FIG. 4 is a diagram showing a relationship between a transmission signal and a reception signal. As shown in the figure, the phase of the multi-frame transmitted to the transmission line and the phase of the multi-frame returned by the opposite device can be detected as the phase difference α based on the delay time of the transmission line. Is equivalent to the distance of

The above-described calculation of the phase difference α is also performed in other bidirectional transmission lines, and the position output from the control unit of the two transmission line terminating units 5, 6 or 7, 8 of each bidirectional transmission line. The phase difference α is output to the delay control unit 13 or.

The delay controllers 13 and 14 acquire the phase difference α from the transmission line terminating units 5 and 6 or 7 and 8 of both systems, respectively, and based on the difference between the phase differences α / 2 in one direction, Calculate the delay difference of the transmission path for the direction. Then, control is performed so that the delay of the delay difference is added to the delay buffer 9, 10, 11, or 12 with respect to the signal on the transmission line whose phase is further advanced.

As a result, the delay buffers 9, 10
Alternatively, the phases of the signals of both systems can be matched at the input points output from the switches 11 and 12 to the receiving end switches 3 and 4.

The switching of the receiving end switch 2 or 4 shown in FIG. 1 is executed in a state where the phases of the signals of both systems match.

[0044]

Next, an embodiment of the present invention will be described with reference to FIG.

The working spare transmission line and the channel configuration of this embodiment, the operation of each block in the transmission line terminating units 5, 6, 7 and 8, and the operation of the delay control units 13 and 14 are shown in FIGS. This operation is the same as that of ITU-T Recommendation G. The present invention relates to a redundant system configuration for performing switching without instantaneous interruption in a transmission method defined in 707, in which a high-order group path signal to which a POH (pathoverhead) is added is used as a transmission signal.

The redundant system is a 1: N redundant system (for simplicity, an example of N = 1 is shown) in the above-described embodiment, and a high-order group path of extra traffic is usually provided on a spare transmission line. It is assumed that the high-order group bus of the working channel is branched and transmitted to the spare transmission line only when the transmission is being performed and the switching is executed.

The transmission path terminating units 5, 6, 7, and 8 of the working transmission path and the protection transmission path use S
An OH (section overhead) is added and transmitted to the transmission path. The SDH frame received from the transmission path is terminated at the SOH and passed to the delay buffers 9, 10, 11, and 12.

The structure of the multi-frame is, for example, 64 multi-frames, and the undefined bytes of the section overhead are allocated for multi-frame pattern transmission. In the case of 64 multiframes, 125 μsec × 64 in time conversion
= 8 milliseconds, which is a multi-frame configuration capable of absorbing the delay difference of 8 milliseconds.

FIG. 5 is a diagram showing a 64 multi-frame pattern applied to the present embodiment. A total of 64 bytes is used to use one overhead byte per frame.
It is a byte configuration. One byte is an area for inserting loopback information, and two bytes are an area for inserting a device ID.
ASCII is used as a multi-frame synchronization pattern for bytes.
Character code CR / LF (carriage return /
Line feed).

In the above embodiments and the like, an example of a 1: 1 redundant configuration has been described as a redundant system configuration. However, the present invention is generally applicable to a switching system applicable to a 1: N redundant configuration. As described above. Also, when applied in a 1: N redundant configuration, a fixed amount is added to the delay buffer of the longest transmission line among the 1 + N transmission lines based on the delay time calculated between the working system and the standby system in a steady state. By controlling the amount of delay given to the other N transmission lines based on the total delay time of the transmission line including the delay in the delay buffer, so that Match the phases of the signals of the system and the standby system.

[0051]

According to the present invention, in a bidirectional transmission system having a redundant configuration, only the delay difference between the two systems is independently measured in advance, and the amount of delay given by the delay buffer at the receiving end is adjusted. Since the phases of the signals of both systems can be matched at the preceding stage of the receiving end switch, the switching during operation of the bidirectional transmission path can be executed without an instantaneous interruption.

Further, since the absolute amount of propagation delay due to the transmission line can be measured independently of both systems irrespective of whether or not the transmission signal is branched to the spare transmission line, switching to a 1: N redundant system or the like is possible. It is possible to determine the amount of delay to be provided at the receiving end for a protection scheme in which a transmission signal is not split at the transmitting end in a steady state where no error occurs.

Further, the present invention is a method for independently measuring the delay time of both systems, and there is no need to synchronize both systems with respect to a multi-frame generated at the transmitting end. The device configuration can be realized relatively easily.

[0054]

[Brief description of the drawings]

FIG. 1 is an overall view showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a transmission line termination unit in FIG.

FIG. 3 is a diagram showing a multi-frame configuration used in the embodiment of the present invention.

FIG. 4 is a diagram showing a time chart that supplements the operation of the exemplary embodiment of the present invention.

FIG. 5 is a diagram showing a multi-frame format in an embodiment of the present invention.

FIG. 6 is a configuration diagram showing a conventional hitless switching method.

[Explanation of symbols]

 1, 2 transmitting end switch 3, 4 receiving end switch 5, 6, 7, 8 transmission line termination unit 9, 10, 11, 12 delay buffer 13, 14 delay control unit 15 multi-frame pattern insertion unit 16 multi-frame generation unit 17 Multi-frame synchronization unit 18 Selection unit 19 Delay measurement unit 20 Control unit 100 Multi-frame pattern generation unit 101 Multi-frame pattern insertion unit 103 Branch unit 104, 105, 106, 107 Transmission path termination unit 108, 109 Multi-frame synchronization circuit 110, 111 Delay buffer 112 control unit 113 selection unit

Claims (4)

[Claims] In a non-stop switching method in a bidirectional transmission line having a redundant configuration, an absolute delay amount of reciprocation for each bidirectional transmission line between opposing stations is measured, and transmission is performed based on the measured absolute delay amount. Calculating a relative delay amount between paths, adjusting a delay amount given to a received signal based on the obtained relative delay amount, and matching a phase at a stage preceding the active / standby switching selector; Switching method. 2. Each of the opposite stations includes a multi-frame pattern insertion unit, a multi-frame pattern loop-back unit of a reception signal, a multi-frame pattern inserted into a transmission signal, and a multi-frame pattern looped back to a reception signal. 2. The hitless non-interruptible switching system according to claim 1, further comprising: delay measuring means for measuring a round trip absolute delay amount for each of the bidirectional transmission paths. 3. The wireless communication system according to claim 1, wherein said two-way transmission line having a redundant configuration comprises a plurality of active-system two-way transmission lines and one standby-system two-way transmission line. Instantaneous interruption switching method. 4. A means for generating and transmitting a multi-frame including a source device number, loop-back instruction information, and a multi-frame synchronization pattern in a hitless switching method in a bidirectional transmission line having a redundant configuration, Means for looping back the same pattern to the transmitting side through the same bidirectional transmission line in phase with the received signal when loopback instruction information is detected from the opposite device, and generating the multiframe. Means for comparing the phases of the multiframe and the looped-back multiframe during transmission, obtaining the absolute delay amount of the round trip of the transmission line, and calculating the relative delay amount between the transmission lines from the absolute delay amount of each transmission line. And a delay buffer for setting a delay amount for the received signal in accordance with the obtained relative delay amount. Non-instantaneous interruption switching method characterized by matching the phases in stages.