JPS62231539A - Switching system for transmission signal - Google Patents

Abstract

PURPOSE:To eliminate the disconnection of a signal and to stably switch a circuit at a high speed by opening a gate provided for a transmission route so as to pass through a signal and operating a transmission signal switch after a preset time passes when the digital signal of an alternative radio circuit is switched to the signal of a current radio circuit. CONSTITUTION:If the current radio circuit TP1 develops fading and a switch control signal is transmitted from a reception terminal station, a switch control part 40 transmits a control signal '1' to open a gate to the control terminal (b) of a gate circuit 21 in the current radio circuit TP1. After t1mus passes, said part 40 transmits the control signal '1' to the control terminal (d) of a switch 31 in a transmission signal switch 30, and gives instructions that a signal line 300 is switched to a signal line 301. After t0mus passes, the part 40 switches the control signal '1' transmitted to the gate circuit 20 of the alternative radio circuit SP to a control signal '2'. Thus the cutting of a signal input never occurs at the time of switching. Therefore an abnormal increase in bit errors and the instantaneous disconnection, both of which are caused by the delay of a circuit switching time due to step out, never occur when fading arises.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a transmission signal switching method, and in particular, to a transmitting end station of a digital wireless communication line that employs a synchronous switching method as a countermeasure against fading, it is possible to transmit a digital This invention relates to a transmission signal switching method that switches signals at high speed.

[Conventional technology]

In digital wireless communication lines, in order to prevent an increase in bit errors when processing occurs, a synchronous switching method is used in which the transmission signal of the working wireless line where fading has occurred is switched at high speed to the backup wireless line. In this synchronous switching method, when fading occurs and bit errors in the working radio line begin to increase and reach a certain value, the receiving terminal detects this and sends a switching control signal to the transmitting terminal.

The transmitting terminal station that receives this sends the digital signal being transmitted on this working wireless line to the backup wireless line in parallel,
After the receiving end station adjusts the timing of both, synchronized switching without pitting errors is performed.

This switching needs to be completed within about IQms, taking into account the speed at which the reception level decreases due to fading.

For this reason, switching of the modulation input signal of the backup radio line, which is performed at the transmitting terminal station for parallel transmission, is performed at high speed by a transmission signal switcher consisting of an electronic circuit installed at the modulation input of the backup radio line. be exposed. In general, the amount of attenuation for the cutoff signal of a switch made of electronic circuits is not very large, and this transmit signal switch alone cannot provide sufficient attenuation, so it is necessary to use a transmit signal processing board that processes and branches digital signals. A gate circuit is provided, and the gate circuit is closed to cut off digital signals that are not to be transmitted on the backup wireless line, and the gate circuit is opened to send only the digital signals that are to be transmitted on the backup wireless line to the transmission signal switch. has been done. When the switching control unit of the transmitting terminal station that directly controls these receives the switching control signal sent from the receiving terminal station, it simultaneously sends out a control/IR signal to each gate circuit to be controlled and the transmitting signal switch. It is composed of

[Problems that the invention attempts to resolve]

With the conventional transmission signal switching system described above, there is no problem if the transmission signal processing board for each wireless line and the transmission signal switching device are installed close together and the difference in signal transmission delay time is small. In many cases, the installation location of the transmission signal processing board for the working wireless line is far from the installation location of the transmission signal processing board for the transmission signal switcher and the backup wireless 1 line, and the signal transmission delay time increases. If a large difference occurs, the transmission signal switcher operates and disconnects the digital signal (first signal) for monitoring the backup wireless line that is being transmitted, and then disconnects the digital signal (first signal) of the working wireless line that is transmitted in parallel. There may be a slight gap in time before the signal (2) is actually input, and during this time the signal input to the backup wireless line may be cut off. It is fine if the signal input interruption time is short, but if it becomes long, some receiving devices that perform regenerative relay at each relay station on the backup wireless line may
Loss of bit synchronization information may cause out-of-synchronization. For this reason, after the digital signal is re-inputted, the synchronization acquisition operation from bit synchronization must be performed again, and it takes several tens of milliseconds for the receiving end station to complete the timing adjustment and be able to switch synchronization. lQms mentioned above
Since it is impossible to switch the line within 10 seconds, there is a problem that a significant increase in bit errors or a momentary interruption of communication may occur.

An object of the present invention is to provide a transmission signal switching method that does not cause the above-mentioned signal interruption when switching digital signals on a standby radio line and enables stable and high-speed line switching regardless of equipment installation conditions. .

[Failure to solve the problem]

The transmission signal switching method of the present invention is implemented at a transmitting end station of a digital wireless communication line consisting of a working and a standby wireless line.
A transmission signal switch consisting of an electronic circuit that is connected to the modulation power of the backup radio line and selectively connects one of the plurality of input signals to the output signal, and a transmission path for each digital signal input to the transmission signal switch. In the transmission signal switching method, the digital signal transmitted to the backup radio line is switched at high speed by controlling a gate circuit provided in the backup radio line, and the digital signal transmitted to the backup radio line is switched between the digital signals transmitted on the backup radio line during normal operation. When switching from the first signal transmitted by the wireless channel to the second signal transmitted by the working wireless line during normal
After opening the second gate circuit provided in the transmission path of the signal and allowing the second signal to pass through, the transmission signal switch is operated after a predetermined time has elapsed, and the input signal is By switching the connection of the line and closing the gate circuit of the cabinet 1 provided on the transmission path of the first signal,
is configured to block the signal.

〔Example〕

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

FIG. 1 is a block diagram of an embodiment of the present invention, showing the configuration of a transmission signal switching system of a transmitting terminal station of a digital wireless communication line having 6 working wireless lines ξ for one backup wireless line. There is. In FIG. 1, a bipolar test signal 100 for monitoring the backup wireless line system generated by a test signal generator (not shown) is converted into a unipolar signal by a transmission signal processing unit (TXDPU) 10 of the backup wireless line SP. After the conversion, the digital signal 200 undergoes signal processing such as insertion of additional bits and scrambling, and is sent to the transmission signal switch 30 via the gate circuit 20 and signal line 300. Two switching devices 31.3
2 and is sent from terminal 400 to a modulation section of a transmitting device (not shown) of the backup radio line.

On the other hand, input signals 101 to 106 from the carrier terminal equipment (not shown) of the working radio lines Tr1 to '1' P6 are subjected to similar signal processing in transmission signal processing boards 11 to 16, and then converted into digital signals, respectively. 201 to 206, terminal 4
01 to 406 to the transmitting device (not shown) of each working wireless line, and are branched to the gate circuit 2.
1 to 26. Among the outputs of each gate circuit, the branch signals of the working wireless lines TPI and TP2 are connected to the signal line 301.
．． 302 to the transmission signal switch 30, the working wireless line T
The branch signals P3 to TP5 are connected to the switch 33 via signal lines 303 to 306, and the output of the switch 33 is the signal &13.
07 to the transmission signal switch 30. The switching control unit 40 receives the switching control signal from the receiving terminal station and sends a control signal of "1'" or 0 to the control terminals ak of each switch and gate circuit, but no fading occurs. During normal operation, the gate circuit 20 of the backup wireless line SP
"1" is added only to the 0 control terminal a, and "0" is added to all the inputs of the other control terminals. At this time, the digital signal 200 passes through the switching devices 31 and 32 to the terminal 400.
is transmitted to the backup wireless line from the working wireless line TPl to T
Each of the digital signals 201 to 206 of P5 is blocked by both the gate circuit and the switch to ensure necessary attenuation. Note that each circuit above the dash-dot line AA'' is implemented in one device and is installed near the modulation input of the standby radio circuit, but each circuit below the dash-dot line 1ilAA' It is assumed that the two are installed in a device and are installed separately.

When aging occurs in the working radio line TPI and a switching control signal is sent from the receiving terminal station, the switching control unit 40 first sends a control signal "1" to open the gate to the control terminal of the gate circuit 21 of the working radio line TPI. ”, and after t and ps have elapsed, a control signal “1” is sent to the control terminal d of the switch 31 in the transmission signal switch 30 to instruct switching from signal line 300 to 301, and after L μs, the The control signal sent to the gate circuit 20 of the wireless MASF is changed from "1" to "O".
”.Here, if tI and to are selected to be larger than the delay time difference that may occur due to the cable length and the operation delay time of the logic circuit, the switch 31 will actually operate and the input signal &! 301, the digital signal 20 is always input to the switch 31.
0 and 201 exist, and switching will not result in a signal input disconnection state.

The same applies when fading occurs in the working radio line TP2, and the control signal at the control terminal e of the switching device 31 is set to "1".
By doing so, the signal line 300 is switched to 302.

When fading occurs in the working wireless line TP3, the switching control unit 40 first sends a control signal "1" to the gate circuit 23 and the switching device 33 at the same time to switch the signal lines 303 and 307.
The digital signal 203 is transmitted by connecting t! μ
After s, the control signal "1" is sent to the switch 32 of the transmission signal switch 30.
” to instruct the selection of the signal line 307, and then
After s, the control signal of the gate circuit 20 is changed from "1" to "0" to close the gate and cut off the gain signal 200.

Here, 13 is set longer than tl in consideration of the transmission delay time of the control signal from the switching control m40 to the gate circuit 23 and the transmission delay time of the digital signal from the gate circuit 23 to the switch 32. There is no possibility that the signal input will be cut off during switching. In addition, flI of the switch 32
The control signal "l" is applied to the enable control terminal g of the switch 31 at the same time as the IJ control terminal f, so that the switch 31 does not malfunction. In addition, the working wireless line T
P4 to TP5 are also the same as TP3 above.

7 When aging recovers, parallel transmission to the backup radio line is stopped and the normal standby state is restored. At this time, the modulation input signal of the backup radio line SP is switched for all working radio ports iM'l'P1 to TP6. The switching is performed at the same intervals as the switching during parallel transmission of TP1 described above. That is,
First, the gate circuit 20 of the backup wireless line SP is opened to allow the digital signal 200 to pass through, and after tIps, the switch 31 or 32 is activated to switch the signal line, and then the signal line is switched.
- After μs, the gate circuits of the working radio ports JljTPl to TP6 are closed to cut off the digital signals 201 to 206.

As a result, the normal standby state can be quickly restored without any signal input interruption at the time of switching, and it is possible to cope with the occurrence of the next seven aging events.

According to the method described above, the time it takes for the transmission signal switch 30 to actually switch the transmission signal is shorter than in the conventional method in which the switching control section 40 sends out each control signal at the same time without any time difference. , t+μS or 1,μ3, but this delay is small compared to the entire line switching time (several milliseconds), as the value of t is usually sufficient within 10-odd μs. It's not a problem. On the other hand, the signal input interruption during switching, which was a problem in the past, does not occur at all, so it is possible to prevent an abnormal increase in bit errors or instantaneous interruptions when fading occurs due to a delay in line switching time due to loss of synchronization. The effect of prevention is significant.

In the above embodiment, even when fading is recovered and the digital signal (second signal) being transmitted in parallel on the backup wireless line is switched to the monitoring digital signal (first signal),
Although the configuration is such that no signal input disconnection occurs, compared to the case where fading occurs and the monitoring signal is switched to a parallel transmission signal, synchronization will occur due to signal input disconnection, and the impact will be much smaller. Since the number of control signals is small, when switching back to a monitoring signal, even if each control signal is sent out at the same time as in the past, the effect will not be significantly reduced. In addition, in the above embodiment, the working radio port 1151TPl, in which the transmission No. 18 processing board with the gate circuit is mounted in the same device as the transmission signal switch and the switching control section,
TP2 is also configured to send control signals with a time difference so that there is no interruption of signal input at the time of switching, but the current wireless port IN+ITP3~T, which is mounted on a different device,
Control is provided with a time difference only for P6, and 'rp1. T
Even if P2 is configured to send control signals at the same time, the effect remains almost the same. In addition, as an alternative to providing a certain time difference between the sending of control signals, a signal detector is installed at the input end of the input signal line of the transmission signal switcher, and after receiving this detection signal, the control signal is sent to the transmission signal switcher. A method of transmitting data is also considered, but it has the disadvantage of complicating the configuration and increasing delay time.

〔Effect of the invention〕

As explained in detail above, according to the transmission signal switching method of the present invention, unless fading occurs and the digital signals of the working wireless line are transmitted in parallel, large signal input interruptions occur regardless of the installation location of the equipment. This has the advantage that high-speed line switching is always possible and there is no risk of degrading the return quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a signal switching system according to an embodiment of the present invention, in which reference numbers 10 to 16 are transmission signal processing boards, 20 to 26 are gate circuits, and 30 is a transmission signal switching device. 31 to 33 are switching devices, and 40 is a switching control section.

Claims (1)

[Claims] A transmitting terminal station of a digital wireless communication line consisting of working and backup radio lines, consisting of an electronic circuit that is connected to the modulation input of the backup wireless line and selectively connects one of the multiple input signal lines to the output signal line. A transmission signal switching device that controls a signal switching device and a gate circuit provided in a transmission path of each digital signal input to the transmission signal switching device, and switches digital signals transmitted on the backup wireless line at high speed. In the method, when switching the digital signal to be sent to the backup wireless line from a first signal transmitted on the backup wireless line to a second signal transmitted on the working wireless line, the transmission path of the second signal is switched. after opening a second gate circuit provided in the gate to allow the second signal to pass through, and after a predetermined time has elapsed, actuating the transmission signal switch to switch the connection of the input signal line. . A transmission signal switching method, characterized in that the first gate circuit provided in the transmission path of the first signal is closed to cut off the first signal.