JPH0691516B2 - Instantaneous disconnection line switch - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hitless line switch in a hitless line switching system for digital wireless communication, and particularly when the transmission delay difference between a working line and a protection line is large. The present invention also relates to a non-interruptive line switching device that can perform non-interruptive switching, and also reduces and improves the amount of phase fluctuation of communication signals during line switching.

(Prior Art) Conventionally, a digital radio communication system has one spare circuit for one or a plurality of working lines, and when a line failure occurs in the working line, the working line in which the line failure occurs The communication signal transmitted by the line is also transmitted by the protection line, that is, the same communication signal is transmitted in parallel by both the working line and the protection line, and the receiving end side switches from the working line to the protection line without interruption. (Hitless Switch)
To repair the faulty line.

The operation for switching the circuit without interruption will be described below with reference to the drawings.

FIG. 3 is a block diagram of a non-instantaneous line switching system, showing an example in which the working line is N lines and the backup line is 1 line (N
Is a natural number). 1 is a transmission line switching controller that controls the line switching so that the communication signal of the faulty line is also transmitted on the protection line when a fault occurs on the working line, and 2-1, ..., 2-N are communications transmitted on the working line. A transmitter switch that connects the signal to the protection line, 3 is a pilot signal generator that generates a pilot signal to be transmitted on the protection line, 4-0 is a protection line multiplexer, 4-
1, ..., 4-N is a multiplexer for the working line, 5 is a receiving end line switching controller that controls switching between the working line and the protection line for the faulty line, 6-1, ..., 6-N is An uninterruptible line switch that connects the working line and the protection line without interruption, 7 is a pilot signal detector that detects the pilot signal transmitted on the protection line, 8-
0 is a line monitor that monitors the line status of the standby line, 8-1, ...,
8-N is a line monitor for monitoring the line status of the working line, 9-0 is a spare line demultiplexer, and 9-1, ..., 9-N is a working line demultiplexer. In FIG. 3, the line switching operation will be described by taking as an example the case where a line failure occurs in the working line (No. 1) and the line is switched to the protection line.

The line monitor 8-1 monitors the line status of the working line (No. 1), and the line monitor signal 100-1 indicating the monitoring result is input to the receiving end line switching controller 5. When the line supervisory signal 100-1 indicates a line fault occurrence state, the receiving end line switching controller 5 receives the line supervisory signal 100 from the line supervisor 8-0 of the protection line.
-0 is used to check if there is any failure in the protection line.
If there is no failure on the protection line, the pilot signal detection signal 101 from the pilot signal detector 7 is used to confirm the usage status of the protection line. When there is no failure in the working line and the protection line is not used for communication signal transmission, the pilot signal 102 output from the pilot signal generator 3 is output.
Is being transmitted on the protection line. Therefore, the unused state of the protection line can be known by detecting the pilot signal with the pilot signal detector 7 of the protection line.

When the protection line is not used, the receiving end line switching controller 5 sends the sending end line switching instruction signal 103 to the sending end line switching controller 1. Next, the sending end line switching controller 1 outputs the sending end switching control signal 104-1 to the sending end switching device 2-1 of the working line (No. 1) in which the failure has occurred. The sending end switch 2-1 connects the input communication signal 105 to the protection line so that the input communication signal 105 transmitted on the working line (No. 1) is also transmitted on the protection line. That is, the sending end switch 2-1 is the working line (1
No.) and the protection line are connected so that the input communication signal 105 is transmitted. Next, on the receiving end side, the communication signal 106 received on the working line (No. 1) in which a failure has occurred and the communication signal 107 received on the protection line are input to the non-interruptive line switch 6-1. The receiving end line switching controller 5
The receiving line switching control signal 109-1 from the working line (1
No.) communication signal 106 is switched to the protection line communication signal 107, and the output communication signal 108 is output to complete the repair of the faulty line.

In the non-interruptible line switching system described above, in order to switch the line from the faulty working line to the protection line to non-interruptible line switching, conventionally, the non-interruptible line switching device described below is used. Has been.

FIG. 2 is a block diagram of a conventional non-interruptible line switching device, 10 is a buffer memory circuit for temporarily storing and outputting the communication signal of the working line and the communication signal of the protection line, 11 is a buffer memory circuit 10 A clock signal generation circuit that generates a clock signal whose phase is controlled based on the phase control signal, and 12 is a switching circuit that switches the working line communication signal and the standby line communication signal output from the buffer memory circuit 10 to output the communication signal. is there. The communication signal 106 transmitted on the working line and the communication signal 107 transmitted on the protection line are stored in the buffer memory circuit 10.
Has been entered in.

Further, the clock signal 110, the clock signal 111, and the clock signal 112 are input to the buffer memory circuit 10. The clock signal 110 is a regenerated clock signal of the working line system, and the clock signal 111 is a regenerated clock signal of the protection line system. The clock signal 112 is a clock signal generated by the clock signal generation circuit 11.
The communication signal 106 is written in the storage element of the buffer memory circuit 10 based on the clock signal 110 and stored.
106 is read from the storage element based on the clock signal 112, and the working line communication signal 113 is output from the buffer memory circuit 10. The communication signal 107 is written to the storage element based on the clock signal 111, the stored communication signal 107 is read from the storage element based on the clock signal 112,
The protection line communication signal 114 is output from the buffer memory circuit 10. Further, the buffer memory circuit 10 switches and selects the clock signal 110 and the clock signal 111 based on the receiving end switching control signal 109, compares the phases of the selected clock signal and the clock signal 112, and outputs the phase control signal 115. Is output.

The clock signal generation circuit 11 generates a clock signal 112 whose phase is controlled based on the phase control signal 115. That is, the clock signal 112 is in phase synchronization with the clock signal (clock signal 110 or clock signal 111) selected based on the receiving end switching control signal 109. The working line communication signal 113 and the backup line communication signal 114 output from the buffer memory circuit 10 are input to the switching circuit 12. Switching circuit 12
Switches between the working line communication signal 113 and the protection line communication signal 114 based on the receiving end switching control signal 109, and outputs the output communication signal 108. By the above operation, non-instantaneous switching is performed.

If there is a transmission delay difference between the working and protection lines, there is a phase difference between the communication signal 106 of the working line and the communication signal 107 of the protection line, and due to this phase difference,
The output communication signal 108 has a phase fluctuation (phase jitter:
Phase Jitter). Therefore, in order to suppress this phase fluctuation amount to a predetermined value or less, the noise bandwidth of the PLL (Phase Locked Loop) circuit in the clock signal generation circuit 11 is extremely narrowed to perform clock phase synchronization. .

(Problems to be solved by the invention) However, in the above-mentioned conventional non-interruptible line switching device, in order to suppress the amount of phase fluctuation at the time of line switching to a predetermined value or less, the noise bandwidth of the PLL of the clock signal generation circuit is reduced. Is extremely narrow, the phase difference that occurs when the line is switched becomes large when the transmission delay difference between the working and protection lines is large, and the clock phase synchronizing operation of the clock signal generation circuit against this large phase difference. There is a problem that it is not possible to follow up and becomes out of synchronization, making it impossible to switch without interruption.

An object of the present invention is to provide a clock signal including a PLL circuit having a noise bandwidth that enables clock phase synchronization even for a large phase difference in order to solve the problems of the conventional hitless line switching device. By including the generation circuit and the phase fluctuation suppression circuit after the switching circuit to suppress the phase fluctuation, even when the transmission delay difference between the working and protection lines is large, it is possible to switch without interruption and the phase fluctuation amount. Is to provide a non-instantaneous line switching device that outputs a communication signal suppressed to a predetermined value or less.

(Means for Solving the Problem) In order to achieve the above object, the present invention has the following means configuration.

That is, the hitless line switching device of the present invention is a line switching system for a working line and a protection line in a hitless line switching system for digital wireless communication having one protection line for one or a plurality of working lines. Clock signal generating means for generating a clock signal phase-synchronized with the clock signal of the working line system or the clock signal of the protection line system which is switched and selected based on the receiving end switching control signal for control; communication signal received on the working line And the communication signal received by the protection line as an input, the communication signal of the working line is stored based on the clock signal of the working line system, and the stored communication signal is output based on the clock signal of the clock signal generating means. In addition, the communication signal of the protection line is stored based on the clock signal of the protection line system, and the stored communication signal is output from the clock signal. Storage means for outputting with a clock signal output from the means; inputting the communication signal of the working line and the communication signal of the protection line output from the storage means, and inputting the communication signal of the working line or the protection line based on the receiving end switching control signal Switching means for selectively selecting and outputting a communication signal; and phase fluctuation suppressing means for receiving a communication signal output from the switching means and suppressing a phase fluctuation amount of the communication signal to a predetermined value or less. It is what

(Operation) Next, the operation of the present invention configured as described above will be described.

The communication signal of the working line and the communication signal of the protection line input to the non-instantaneous line switching unit are input to the storage means. The communication signal of the working line is stored based on the clock signal of the working line system, and the communication signal of the protection line is stored based on the clock signal of the protection line system. The stored communication signal of the working line and the stored communication signal of the protection line are output based on the clock signal output from the clock signal generating means. The clock signal output from the clock signal generating means is in phase synchronization with the clock signal of the working line system or the clock signal of the protection line system. That is, the clock signal generating means selects either the working line system clock signal or the standby line system clock signal which is switch-selected based on the receiving end switching control signal for controlling the line switching between the working line and the protection line. A clock signal that is phase-synchronized with the clock signal is generated. The communication signal of the working line and the communication signal of the protection line output from the storage unit are input to the switching unit. Based on the receiving end switching control signal, the switching means selectively selects and outputs the input communication signal of the working line or the communication signal of the protection line. The communication signal output from the switching means is input to the phase fluctuation suppressing means. The phase fluctuation suppressing unit suppresses the phase fluctuation of the input communication signal and outputs the communication signal having the phase fluctuation amount suppressed to a predetermined value or less.

With the above operation, even if the transmission delay difference between the working line and the protection line is large, it is possible to switch without interruption, and a communication signal whose phase fluctuation amount at the time of switching is not more than a predetermined value can be obtained.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an uninterruptible line switch according to an embodiment of the present invention, in which 11 'is a clock signal generating circuit and 13 is a phase fluctuation suppressing circuit. The components to which other numbers are assigned are the same as the components to which the same numbers are assigned in the configuration diagram of the conventional hitless line switching device of FIG. The difference between the embodiment of the present invention in FIG. 1 and the conventional example in FIG. 2 is that the noise bandwidth of the PLL circuit in the clock signal generating circuit 11 'and the noise bandwidth of the PLL circuit in the clock signal generating circuit 11 are different. The width is different, and the phase fluctuation suppressing circuit 13 is added to the embodiment of the present invention. Therefore, in the following, the operations of the clock signal generation circuit 11 'and the phase fluctuation suppression circuit 13 will be described, and description of the other components similar to those of the conventional example will be omitted.

The clock signal generation circuit 11 'of the embodiment of the present invention includes a PLL circuit, and its noise bandwidth is wider than that of the conventional example. That is, even if the transmission delay difference between the working and protection lines is large and the phase difference generated at the time of line switching is large, the clock phase synchronization operation can follow based on the phase control signal 115, and the phase-locked clock signal 112 can be generated. You can Therefore, even if the transmission delay difference between the working and protection lines is large, it is possible to switch without interruption.

Further, the output communication signal 108 output from the switching circuit 12 at this time may have a phase fluctuation amount of a predetermined value or more, however, the output communication signal 108 is input to the phase fluctuation suppressing circuit 13 and is equal to or less than a predetermined value. Output communication signal suppressed by the amount of phase fluctuation of
108 'is output from the phase fluctuation suppressing circuit 13. The phase fluctuation suppressing circuit 13 has a PLL circuit, and its noise bandwidth is set so that the phase fluctuation amount can be suppressed to a predetermined value or less. When the transmission delay difference between the working line and the protection line is large, the phase difference between the communication signal 106 of the working line and the communication signal 107 of the protection line input to the buffer memory circuit 10 is large, but the clock signal generation circuit 11 ′ Output clock signal
Since the output communication signal 108 switched and selected by the switching circuit 12 and output from the buffer memory circuit 10 based on 112 has the phase fluctuation reduced, the phase fluctuation suppressing circuit 13 causes out of synchronization. It is possible to suppress the amount of phase fluctuation to a predetermined value or less without having to do so.

(Effects of the Invention) As described above, according to the present invention, by adding the phase fluctuation suppressing means to the conventional hitless line switching device, even when the transmission delay difference between the working line and the protection line is large, there is no interruption. There is an effect that switching can be performed and a communication signal in which the amount of phase fluctuation at the time of switching the line is suppressed to a predetermined value or less can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a hitless line switching device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional hitless line switching device, and FIG. 3 is a block diagram of a hitless line switching system. . 1 ... Sending end line switching controller, 2-1 to 2-N ... Sending end switching device,
3 ... Pilot signal generator, 4-0,4-1 to 4-N ... Multiplexer, 5 ... Reception line switching controller, 6-1 to 6-N ... No-interruption line switching device , 7 ... Pilot signal detector, 8-0,8-1 to 8-N
...... Line monitor, 9-0,9-1 to 9-N …… Separator, 10 …… Buffer memory circuit, 11,11 ′ …… Clock signal generator, 1
2 …… Switching circuit, 13 …… Phase fluctuation suppression circuit, 100-0,100-1
~ 100-N ...... Line supervisory signal, 101 ...... Pilot signal detection signal, 102 ...... Pilot signal, 103 ...... Sending end line switching instruction signal, 104-1 to 104-N ...... Sending end switching control signal, 105 ......
Input communication signal, 106 ... Working line reception communication signal, 107 ...
Backup line reception communication signal, 108, 108 '... Output communication signal, 1
09,109-1 to 109-N …… Reception end switching control signal, 110 …… Working line system clock signal, 111 …… Standby line system clock signal, 1
12 ... Clock signal, 113 ... Working line communication signal, 114 ...
... standby line communication signal, 115 ... phase control signal.

Claims (1)

[Claims] 1. A receiver switching control signal for controlling line switching between a working line and a protection line in a non-interruption line switching system for digital radio communication having one protection line for one or a plurality of working lines. Clock signal generating means for generating a clock signal phase-synchronized with the clock signal of the working line system or the clock signal of the protection line system, which is switched and selected based on the above ;; a communication signal received by the working line and a communication signal received by the protection line Is input, the communication signal of the working line is stored based on the clock signal of the working line system, the stored communication signal is output based on the clock signal of the output of the clock signal generating means, and the communication of the protection line is performed. Stores a signal based on the clock signal of the protection line system,
Storage means for outputting the stored communication signal as a clock signal output from the clock signal generating means; inputting a communication signal on the working line and a communication signal on the protection line output from the storage means, based on the receiving end switching control signal Switching means for selectively selecting and outputting the communication signal of the working line or the communication signal of the protection line; and a phase fluctuation for suppressing the phase fluctuation amount of the communication signal to a predetermined value or less by inputting the communication signal output from the switching means. A non-instantaneous line switching device comprising: a suppressing unit.