JPH0356025B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synchronous switching system, and more particularly to a synchronous switching system for a digital signal transmission line consisting of a plurality of working systems and one backup system.

Generally, in a synchronous switching method for a digital signal transmission line consisting of N working systems and 1 standby system, these working systems are distributed and accommodated in groups of several systems on multiple racks.
A configuration is adopted in which a standby system and the remaining active systems are housed in a mixed manner on a specific rack.

For example, in the case of 11 active systems and 1 backup system, the first rack has 3 active systems and 1 backup system.
system, and the racks of the second and third machines can accommodate four systems in use (therefore, the second and third machines have the same configuration).

When adopting such a configuration, for example, on the transmitting side, all switching signals that should be synchronously switched and transmitted to the backup system in the event of an emergency from each active system are guided to the switch of the backup system, and depending on the selection of this switch It must be configured so that any switching signals of the active system can be transmitted through the protection system.

The number of interframe or intraframe wiring cables required to distribute this switching signal varies depending on the modulation method of the signal to be transmitted, but for example, the signal is transmitted using the 16-value QAM modulation method. In the case of a system, the number of cables required per system is 4 for data, and 1 for clock, for a total of 5 cables.As mentioned above, in the case of 11 active systems and 1 standby system, as mentioned above, It is necessary to lead 5 x 12 = 60 cables to the switch and connect them so that one of them can be selected.

Interfacing such a large number of cables directly to the standby system switch also has disadvantages in terms of timing coordination for synchronous switching, which made overhead wiring extremely difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a synchronous switching method that eliminates the above-mentioned conventional drawbacks.

Next, the present invention will be explained in detail with reference to the drawings.

First, the synchronous switching method will be explained based on a conventional example.

FIG. 1 is a block diagram for explaining the synchronous switching method.

This example consists of one backup system 100 and n active systems 101 to 10n.
Each working system receives a bipolar digital signal from the upper multiplexer from the input SYS IN, and outputs a hybrid 1 signal for the working protection line branch.
The bipolar-unipolar conversion circuit 3, which is the interface with the multiplexer,
The bipolar signal is converted into a unipolar signal used for code processing within the device itself. Thereafter, this unipolar signal undergoes code speed conversion, a multiplex conversion circuit 4 inserts radio line monitoring bits, frame synchronization bits, etc., is modulated by a PCM transmitter 5, and is transmitted as radio waves to the other station.

In addition, the multiplex conversion circuit 4 of each active system outputs a signal (hereinafter defined as a switching signal) to be transmitted via the standby system 100 with the same output as the output supplied to the PCM transmitter 5 of its own system.
is output and supplied to an IC switching circuit 11 provided in the standby system 100.

This IC switching circuit 11 is connected to the backup system 100.
The output of the multiplex conversion circuit 4 of the active system and the above-mentioned switching signal outputs of the multiplex conversion circuit 4 of each active system are input, and one of them is selected under the control of the control signal CONT-T to switch the output of the backup system 100. It is supplied to the PCM transmitter 5.

In this way, on the transmitting side, e.g.
When the active first system is selected by CONT-T, the transmission signal of the active first system is not only transmitted through the active first system 101, but also transmitted through the backup system 100, and the sending ends of both systems are parallel. The transmission that was taken will be performed.

On the receiving side, the signal received and demodulated by the PCM receiver 6 is subjected to frame synchronization in the radio section by the frame synchronization circuit 7, and the inserted radio channel monitoring bit, frame synchronization bit, etc. are extracted. The transmitted data signal is also supplied to the speed inversion and IC switching circuit 8 together with the clock.

The circuit 8 is equipped with a buffer memory for speed inversion and an IC switch for switching the contents of the memory.

For example, when the control signal CONT-R selects the current system side in the first active system 101, the data signal supplied from the circuit 7 is immediately read into the buffer memory for speed inversion, and this is speed inverted. The data read out by the read clock undergoes rate inversion conversion, and the data signal returned to the original pulse train is further converted into a bipolar signal by the unipolar-bipolar conversion circuit 9 and passed to the lower multiplexing device.

On the other hand, in the backup system 100, the data and clock (hereinafter defined as a distribution signal) output from the frame synchronization circuit 7 are sent to the circuit 8 of each active system 101 to 10n via the distribution circuit 12 provided in the backup system 100. distributed. For this reason, for example, in the current first system 101, the control signal
When CONT-R selects the backup system side, the signal data received by the PCM receiver 6 of the backup system 100 is transferred to the active first system 101.
It will be passed to the lower multiplexing device as an output.

Now, synchronous switching of lines is performed as follows.

For example, when synchronously switching the active first system 101 to the backup system 100, the active first system is selected by the control signal CONT-T to the IC switching circuit 11, and the active first system is switched as described above.
The system 101 and the backup system 100 are connected in parallel at the sending end.

As a result, the switching signal of the active first system 101 is transmitted through the backup system 100, and the frame synchronization circuit 7 of the backup system 100 establishes frame synchronization with this transmitted signal.

After frame synchronization is established, the control signal CONT-R for the circuit 8 of the first system 101 is used to switch the output from the circuit 7 on the active system 101 side to the distribution signal from the backup system 100 side, thereby changing the output data to the transmission data. Synchronous switching is performed without momentary interruptions.

Instead of the above, the sending end side changeover switch 2 on the input side of the system takes the sending end parallel, and the receiving end side changeover switch 10 on the output side of the system makes the switch to perform synchronous switching without momentary interruption in the transmitted data. This is extremely difficult because the wireless sections are generally not synchronized with each other, and therefore the difference in transmission time between the working and standby systems cannot be eliminated.

As described above, in order to perform synchronous switching, each active system 101 to 1 must be
It is necessary to lead all the outputs of the switching signals from the 0n multiplex conversion circuit 4 to the IC switching circuit 11 provided in the standby system 100. In addition, on the receiving side, the distribution signal from the frame synchronization circuit 7 of the backup system 100 is converted into the speed of each system and
It is necessary to distribute it to the IC switching circuit 8.

However, the number of cables required to guide this switching signal is, for example, 16, as mentioned above.
When using the QAM modulation method, five cables are required for each system, and in an example of 11 active systems + 1 backup system, the number of cables connected to the IC switching circuit 11 is 60 in total. Realization will be extremely difficult.

Similar difficulties occur in the receiving distribution circuit 12 on the receiving side.

FIGS. 2A and 2B briefly illustrate the conventional transmission synchronization switching circuit (IC switching circuit 11 in FIG. 1) and reception distribution circuit (distribution circuit 12 in FIG. 1) of the conventional example described above.

As is clear from FIG. 2A, the transmission synchronization switching circuit concentrates here the signal SP of the standby system and the switching signals W1 to Wn of each working system, selects one of them, and transmits it to the outside. Although it has the function of outputting data, the number of active systems that need to be rescued by one backup system increases, and the number of 16-value
As mentioned above, it is extremely difficult to properly implement systems that employ complex modulation methods such as QAM. The situation is exactly the same in the reception distribution circuit shown in FIG. 2B.

An object of the present invention is to avoid such difficulties and easily realize an appropriate synchronous switching method.

Next, the synchronous switching method of the present invention will be explained in detail.

FIGS. 3A and 3B are block diagrams for explaining one embodiment of the synchronous switching system of the present invention.

In this embodiment, as an example, there is a configuration in which there is one backup system for 11 active systems.

It is assumed that these 12 systems in total are divided into three equal parts on the sending side and receiving side, and are mounted on separate racks, three on the sending side and three on the receiving side.

In other words, as shown in Figure 4A, the backup system and the transmitters from the first working system to the third working system are installed on the transmitting side of the first unit, and the transmission from the fourth working system to the seventh working system is implemented. It is assumed that the transmitting side is installed on the transmitting side of the second machine, and the transmitting sides of the current 8th system to the 11th system are installed on the transmitting side of the third machine. Also,
As shown in FIG. 4B, the receiving side of each system is also assumed to be installed on the receiving side of each corresponding machine in the same manner as above.

Now, the transmitting side of each unit includes all the equipment necessary for the transmitting side shown in Figure 1 of each of the above systems implemented by each machine (excluding the IC switching circuit 11 shown in Figure 1). ). In addition, one transmission synchronization switching circuit is installed on each transmission side of each machine.

This transmission synchronization switching circuit corresponds to the IC switching circuit 11 of the conventional example shown in FIG. They are distributed for each machine.

In other words, as shown in FIG. 3A, the transmission synchronization switching circuit 11-1T installed in the first machine is a channel selector that selects one output from five inputs, and each input has multiple conversions from the backup system. Output SP of circuit 4, signal output W for switching of multiplex conversion circuit 4 from the first system in use to the third system
1 to W3 and the transmission synchronization switching circuit 11-2 implemented in the lower ranked machine (No. 2 machine)
T's selection output SA is connected. The selection output SO of this switching circuit 11-1T is for the backup system.
The signal is supplied to the PCM transmitter 5. Control signal determines which of the 5 inputs is connected to the selected output.
CONT-1T is specified, but normally the output SP of the multiplex conversion circuit 4 of the backup system is selected, and any one of the active systems 1 to 3 is selected.
When one system is to be rescued, the switching signal outputs W1 to W3 of the multiplex conversion circuit 4 of the corresponding system
Select. When restoring other current systems, the output SA of the switching circuit 11-2T installed in the lower ranked machine is selected.

Similarly, the transmission synchronization switching circuit 11-2T installed in the second machine has five inputs with a similar configuration, and four of these inputs include the multiplex conversion circuit 4 from the fourth system currently in use to the seventh system currently in use. Signal output W for switching
4 to W7 are connected, and the selection output SB of the transmission synchronization switching circuit 11-3T mounted on the transmission side of the lower ranked machine (third machine) is connected to the fifth input.

Further, the output SA of this switching circuit 11-2T is connected to the fifth input of the switching circuit 11-1T mounted on the transmitting side of the higher ranked machine (first machine) as described above.

The control signal determines which input among the 5 inputs of circuit 11-2T is selected and connected to the output SA.
CONT-2T, but the current
If any one of the systems up to the 7th system in use is to be rescued, the corresponding switching signal W4~
When any one of W7 is selected and the currently used eighth system and subsequent systems are to be rescued, the selection output SB of the circuit 11-3T is selected.

In exactly the same way, the transmission synchronization switching circuit 11-3T installed on the transmission side of the third machine has the same configuration as above, and its connection is controlled by the control signal CONT-3T, but the circuit 11-3T is mounted on the transmission side of the third machine. The connection of each input/output of the 3T and its control will be clear from FIG. 3A and the above description.

The switching circuit 11-3T installed on the transmitting side of the No. 3 machine may have only 4 inputs, or it may have the same configuration as the other No. 3 machines with 5 inputs, with the 5th input being used for future transfers. You may leave it as a dummy connection as a preparation.

It will be clear that the above-described configuration enables parallel connection of the transmitting ends, which is necessary for performing the above-described synchronous switching, between any active system and standby system in this embodiment as well.

Moreover, in this embodiment, the problem of all switching signal cables being concentrated in the IC switching circuit 10 of a specific standby system 100, which causes configuration difficulties, as seen in the conventional example, can be avoided.
Each rack can have almost the same configuration. Furthermore, each transmission synchronization switching circuit 11- mounted on each rack
The signal led to the input side of 1T to 11-3T is 1
Except for the input, everything else is led from the circuit in the same rack (same machine number), so the length of the connecting cable can be shortened.
It becomes possible to fix the length, which makes it easier to compensate for the delay time between each system.

Furthermore, the interframe connection is only for this one input, thus greatly simplifying the interframe connection compared to the conventional example, and making preparations for future expansion easier.

Next, the present embodiment will be explained on the receiving side.

In the same way as explained for the transmitting side, the receiving side of each unit includes all the equipment necessary for the receiving side shown in Figure 1 of each of the above-mentioned systems implemented by each machine (however, Distribution circuit 12 shown in
is not included and can be replaced by the reception distribution circuit described below). In addition, one reception distribution circuit is installed on each reception side of each machine.

This reception distribution circuit corresponds to the distribution circuit 12 of the conventional example shown in FIG. The transmission side synchronization switching circuits 11-1T to 11-3T are distributed and provided for each machine. That is, as shown in FIG. 3B, the reception distribution circuit 12 installed in each machine
-1R to 12-3R are distribution circuits that distribute one input to five outputs. For example, the reception distribution circuit 12-1R installed on the reception side of the first machine receives its input as the output of the frame synchronization circuit 7 of the backup system. One output is supplied to the input SS of the speed conversion circuit 8 of the backup system 100, and the following three are connected to the speed conversion and distribution signal input of the IC switching circuit 12 from the first working system to the third working system. Side R1~R
Connect to 3. The remaining one output is connected to the input side DA of the reception distribution circuit 12-2R installed on the receiving side of the lower ranked machine (second machine).

Reception distribution circuit 12- installed in the second machine
2R and the input/output connections of the reception distribution circuit 12-3R installed in the third machine will also be clear from the above explanation and FIG. 3B.

In addition, the circuit 12-3 installed in the No. 3 machine
R may have 4 outputs, or may have 5 outputs, with 1 output FC remaining for future expansion.

With the configuration described above, the connection in this embodiment is essentially the same as the connection on the receiving side shown in FIG. 1, so it is clear that synchronous switching can be performed in the same manner as described above. It is.

Furthermore, the advantages of the various types described above regarding the transmitting side of this embodiment also apply to the receiving side. Incidentally, a specific example of a reception distribution circuit is shown in FIG. In this way, the control signal CONT is used so that the output distributed to each currently used system is supplied only to the necessary system using the AND gate.
- Control by 1R to 11R to remove unnecessary interference in speed inversion and IC switching circuit 8,
Necessary isolation between each system signal can be ensured, and malfunctions due to leakage can be prevented.

Furthermore, it is clear that in the case where the delay times between the systems are different, it is possible to easily match the delay times by inserting a delay compensation circuit for each system in this embodiment.

Note that the configurations of the transmitting side and receiving side of each system, the number of active systems, and the number of standby systems described above are merely examples, and the present invention is not limited to these.

Now, in the above embodiment, each machine is connected in series on both the transmitting side and the receiving side. This has the advantage that the cable between the frames is very simple, but conversely, for example, if an abnormality occurs in the second unit, the transmission synchronization switching circuit 11 of the second unit
- If the 2T stops working properly, the second
This has the disadvantage that not only is it impossible to switch from each active system installed in the No. 1 unit to the backup system, but also it is impossible to switch from each active system installed in the No. 3 unit to the backup system. There is.

In order to avoid this, a parallel connection configuration can be used as shown below.

That is, when adopting the configuration shown in FIGS. 4A and 4B described above, as shown in FIG.
is configured such that one input can be selected from at least six inputs, and for each input, the output SP of the multiplex conversion circuit 4 of the standby system, and the current The switching signal outputs W1 to W3 of all the multiplex conversion circuits 4 from the system to the third system, the selection output SA' of the transmission synchronization switching circuit 11'-2T installed in the second unit, and the transmission The selection output SB' of the synchronous switching circuit 11'-3T is directly connected to one input of this circuit 11'-1T without going through the second machine.

In addition, the transmission synchronization switching circuits 11'-2T and 11'-3 installed in the second and third machines
At T, the switching signal outputs W4 to W7 and W8 to W1 from the multiplex conversion circuits 4 of all the active systems mounted on the same rack are input.
1 is input to each circuit, one of them is selected in these switching circuits 11'-2T and 11'-3T, and this selection output SA' and
SB' is supplied in parallel to two different inputs of the switching circuit 11'-1T of the first machine.

With this configuration, each switching circuit 11'-
Each control signal CONT'- for 1T to 11'-3T
It is clear that if one appropriate input is selected for each switching circuit using 1T to 3T, the aforementioned sending-end parallel connection required for synchronous switching can be obtained between any working system and standby system. be.

In addition, on the receiving side, as shown in FIG. 6B, each rack has receiving distribution circuits 12'-1R and 12'-2.
R and 12'-3R are implemented, and the configuration corresponds to the above-mentioned transmitting side.

By doing this, the simplicity of the overhead cable is somewhat compromised, but the aforementioned drawbacks are eliminated and the reliability is increased accordingly.

The rack configuration shown above is an example; if there are many racks, all synchronous switching circuit outputs from each rack with only the active system installed can be directly transferred to the rack containing the standby system. It is sufficient to lead them in parallel to different inputs of the synchronous switching circuit.

Furthermore, as shown in FIG. 7, the above-described cascading connection and parallel connection can be used together if necessary.

As described above, by using the present invention, when multiple active systems and one backup system are distributed and accommodated in multiple racks in the synchronous switching method of digital signal transmission lines, the rack that accommodates the backup system can be used. This avoids the problem of cables for switching signals concentrating on each other and causing difficulties, and each rack can have almost the same configuration. Furthermore, the cable length required for intra-frame wiring for transmitting switching signals and distribution signals is shortened, and the number of cables required for inter-frame wiring is also reduced. This simplifies the connection between the bridges and makes it easier to compensate for the delay time between each system.
Further, it is possible to easily prepare for future system expansion.

[Brief explanation of drawings]

Fig. 1 is a block diagram for explaining the synchronous switching system, Fig. 2A is a block diagram showing a conventional transmitting synchronous switching circuit, Fig. 2B is a block diagram showing a conventional receiving distribution circuit, and Fig. 3A is a block diagram of the present invention. FIG. 3B is a block diagram for explaining the transmitting side of an embodiment of the invention, FIG. 3B is a block diagram for explaining the receiving side, and FIG. Figure 4B
5 is a diagram for explaining the rack configuration on the receiving side of this embodiment, and FIG. 5 is a diagram showing an example of a reception distribution circuit.
FIGS. 6A and 6B and FIG. 7 are diagrams for explaining another embodiment. In the figure, 1...Hybrid for branching working protection line, 2...Sending end side changeover switch, 3...Bipolar unipolar conversion circuit, 4...Multiple conversion circuit, 5...PCM transmitter, 6...PCM reception Machine, 7
...Frame synchronization circuit, 8...Speed inversion and
IC switching circuit, 9... Unipolar bipolar conversion circuit, 10... Receiving end side switching switch, 11...
IC switching circuit, 12...Distribution circuit, 11-1T~
11-3T, 11'-1T to 11'-3T...Transmission synchronization switching circuit, 12-1R to 12-3R, 12'
-1R to 12'-3R...reception distribution circuit.

Claims (1)

[Scope of Claims] 1. In a synchronous switching method of a digital signal transmission line consisting of a plurality of active systems and one standby system, when the system is composed of a plurality of racks each accommodating a plurality of systems, On the other hand, each rack is ranked so that the rack containing the backup system is at the highest rank, and a channel selector is provided for each rack on the sending side. Either one of the switching signal to be synchronously transmitted to the standby system according to the needs of each active system installed on the same rack, and the transfer switching signal to be transferred from a lower ranked rack is transmitted as described above. This can be selected with the channel selector and transmitted to the rack ranked higher as a transfer switching signal for that rack, and the rack ranked highest can also be used to transmit the signals required for each active system installed on this rack. Either one of the switching signal to be synchronously transmitted to the standby system according to the above, the transmission signal of the standby system, and the transfer switching signal transferred from the lower ranked rack is mounted on this rack. The synchronous switching system is characterized in that the channel selector selects the selected signal and transmits the selected signal through the transmission line of the standby system. 2. A distribution circuit is provided for each rack on the receiving side, and in the highest ranked rack that accommodates the receiving side of the backup system, the receiving side of each active system is distributed from the receiving side of the backup system necessary for synchronous switching. The distribution signal to be distributed to the side is input to the distribution circuit mounted on this rack, and each output of the distribution circuit is supplied as a distribution signal to the receiving side of each current system installed on this rack, and One output is supplied as a transfer distribution signal to a lower ranked rack, and for racks other than the highest ranked rack, the transfer distribution signal from the higher ranked rack is applied to the distribution installed on this rack. Supply each output of the circuit as an input signal to the circuit as a distribution signal to the receiving side of each active system mounted on this rack, and supply one output of the circuit as the transfer distribution signal to the rack ranked lower. A synchronous switching system according to claim 1, characterized in that the synchronous switching system is configured to: 3 In a synchronous switching method for a digital signal transmission line consisting of multiple active systems and one standby system, when the system is configured with multiple racks each accommodating multiple systems, a channel selector must be set for each rack on the sending side. and one of the switching signals to be synchronously transmitted to the backup system according to the needs of each active system mounted on the same rack other than the rack accommodating the backup system is sent to the channel selector. This can be selected and transferred as a transfer switching signal to the rack accommodating the backup system, and in the rack accommodating the backup system, the backup system is switched according to the needs of each active system installed on this rack. Any one of the switching signal to be synchronously transmitted, the transmission signal of the backup system, and the transfer switching signal transferred from a rack other than the rack accommodating the backup system is mounted on this rack. A synchronous switching system characterized in that the channel selector selects a signal and transmits the selected signal through a transmission path of the standby system. 4 A distribution circuit is provided for each rack on the receiving side, and in the rack that accommodates the receiving side of the standby system, the distribution that should be distributed from the receiving side of the standby system to the receiving side of each active system in order to perform synchronous switching is provided. The signal is input to the distribution circuit mounted on this rack, each output of the distribution circuit is supplied as a distribution signal to the receiving side of each currently used system mounted on this rack, and furthermore, the signal is transferred and distributed to racks other than this rack. In each rack on the receiving side other than the rack accommodating the receiving side of the backup system, the supplied transfer distribution signal is used as the input signal of the distribution circuit mounted on this rack, and each output of the circuit is 4. The synchronous switching system according to claim 3, wherein the synchronous switching system is supplied as a distribution signal to the receiving side of each currently used system mounted on the rack.