JP2616473B2 - Standby switching system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection system switching system in a digital radio system having a working system and a protection system transceiver. The present invention relates to a standby system switching system that performs system switching by detecting the system.

[0002]

2. Description of the Related Art In a digital radio system for transmitting a digital signal through a radio line, only one wave is used as a transmission radio frequency (Radio Frequency) in order to effectively use the frequency. For this reason, in order to avoid a loss of communication when a failure occurs in a transmitter or a receiver, it is common to provide two working transceivers and a working transceiver for the same frequency. is there. In order to perform the switching in a short time, a so-called hot standby configuration is adopted, in which the switching is always performed through the same signal.

[0003] A digital radio system having a long transmission distance is composed of a transmitting end station disposed at a transmitting end, a receiving end station disposed at a receiving end, and a plurality of relay stations disposed therebetween. . A fault occurring in the transmitter of each station is detected by monitoring its output power. Further, the failure of the receiver is detected by checking whether the baseband signal of the signal transmitted after being modulated is normal or by checking the frame error of the data which has been framed and transmitted.

[0004] For example, when a failure of a working transmitter is detected at a transmitting end station, an output signal of a transmitting device is switched to an output of a standby transmitter which is always operating. In a relay station, when an abnormality is detected in a working receiver or transmitter, these are switched to a standby system. The same applies to the receiving end station. However,
A so-called silent failure, which is a failure that cannot be detected even by monitoring the output power of the transmitter, may occur. For example, an encoding circuit that frames data,
When an abnormality occurs in the oscillation frequency of the oscillator used in the modulator, no abnormality appears in the output power of the transmitter. These abnormalities are detected by the receiver of the opposite station, but by simply detecting the presence or absence of a failure, the receiving side determines whether the cause of the abnormality is in the own station's receiver or in the opposite transmitting station. Can not do it.

To solve this problem, Japanese Patent Laid-Open Publication No. Sho 63-28323 discloses a standby system switching system improved so that it is possible to determine whether the cause of a fault detected on the receiving side is caused by an opposite transmitting station.
No. 6 discloses this. In this device, when an abnormality is detected in both the standby system and the working system receiver, it is determined that an abnormality has occurred in the opposite transmitting station, and the occurrence of a failure is notified to the transmitting station through a reverse line, and the transmitter is notified. Is issued.

Japanese Patent Application Laid-Open No. 3-110941 discloses that
There is disclosed a standby system switching system in which a frame in which an error has occurred is reconfigured and transmitted to a receiving terminal station to detect a silent feria, and a switching instruction of a transmitter is performed from the receiving terminal station. When an error is detected in both the active and standby receivers, the frame is reconfigured to return the sub-signal line to the receiving terminal to normal, and an error occurs using the sub-signal line that has returned to normal. The information for specifying the specified station is transmitted to the receiving end station. Then, the receiving end station analyzes the error occurrence information transmitted through the sub-signal line, and sends an instruction to switch to the standby system to the transmitting station in which silent failure occurs through the reverse line.

[0007] In addition, a standby system switching system which detects occurrence of a silent failure by checking whether a parity error occurs in received digital data in a fixed manner or checking for abnormalities in certain digital pattern data is particularly characteristic. It is disclosed in JP-A-63-309033. The station that has detected the silent feria sends an instruction for forcibly switching the transmitter to the opposite station via the reverse line.

Even if the opposite station detects a silent failure and issues an instruction to switch the transmitter, if the switch itself is out of order and the occurrence of the fault is not warned, it takes a long time to recover from the fault. I will. JP-A-1-19452
In order to avoid this, Japanese Patent Laid-Open Publication No. 2 (1995) discloses a standby system switching system which detects a fault occurring in a switching device. In this apparatus, a silent feria generated in a switch for switching between a working transmitter and a backup transmitter is detected by using a reflected wave from the switch.

[0009]

It is necessary for the receiving station to detect a silent failure generated on the transmission side and to recover the fault from the detection of the silent failure. During this time, the data transmitted in an abnormal state one after another arrives at the following stations, and these stations erroneously detect that the opposite station has a silent failure. For this reason, the entire area from the station where the silent failure has actually occurred to the receiving end station is switched to the standby system. Since an error occurs in the line at the time of switching, there is a problem in that line errors increase due to unnecessary system switching.

[0010] The time required for detecting and recovering from a failure may vary from station to station. Therefore, after the switching to the standby system is completed at the transmitting end station, the system switching may be performed at the relay station. As a result, a new line error occurs due to the switching operation of the relay station that occurs after the transmitting end station is normally restored. Due to the occurrence of this error, the subsequent station will again send a system switching instruction. For this reason, the switching between the active system and the standby system causes flapping. In order to avoid this, the time for detecting an abnormality in the received signal is gradually increased from the transmitting terminal station to the receiving terminal station. However, the work of setting the time for detecting an abnormality to be different for each station is complicated, and if the setting of the detection time is erroneous, a failure may occur and there is a problem that system maintenance is difficult. Furthermore, there is a problem that the detection time becomes longer as approaching the receiving end station, and it takes more time to recover from the failure as the number of relay stations increases.

In the standby system switching system disclosed in Japanese Patent Application Laid-Open No. H3-110941, such a problem does not occur because the receiving end station sends a switching instruction collectively. In addition, there is a problem that the configuration of the apparatus becomes complicated, for example, information for identifying the station where the failure has occurred must be carried. Also, if the reconstructed frame is broken again due to a subsequent relay station failure,
Only the abnormality of the station where the failure occurred on the most downstream side can be grasped. For this reason, when a failure occurs in a plurality of stations, the recovery is performed sequentially from the downstream station, and there is a problem that it takes a long time to recover from the failure. Further, in the standby system switching system disclosed in Japanese Patent Application Laid-Open No. 63-283236, all the stations downstream of the failed station are switched to the standby system. In the case where faulty stations in the standby system are mixed, the line cannot be restored only by the switching operation of the transmitter, and there is a problem that it may not be possible to cope when a fault occurs in a plurality of stations.

SUMMARY OF THE INVENTION An object of the present invention is to provide a standby system switching system having a simple structure in which only a station in which a silent failure has occurred switches a transmitter.

[0013]

According to the first aspect of the present invention, there is provided a receiving means for receiving a signal transmitted from a predetermined station, and a method for detecting a failure in a predetermined station based on the received signal. Fault detecting means for detecting, a plurality of transmitting means prepared for transmitting a received signal to a predetermined relay destination station, and selecting one of these transmitting means to the relay destination station Means for performing transmission of a signal, and detection of a failure transmitted from the relay station when the relay station determines that the transmission means selected by the selection means has a failure based on the transmitted signal. Failure notification receiving means for receiving a failure notification indicating the above, and transmission means changing means for switching the transmission means selected by the selection means to a transmission means different from the one selected at this time when the failure notification is received from the relay destination station And the fault detection means And it is provided with a switching inhibiting means for inhibiting the switching of the transmission unit by the transmitting means changing means to the standby system switching system when a failure of the constant station side is detected.

In other words, according to the first aspect of the present invention, when the fault detecting means detects that the source of the received signal has a fault, the fault notification is sent from the relay destination station. Even if it comes, it does not switch its own transmission means. When a failure is detected in the received signal, the failure is also detected in the station to which the signal is relayed, so that a failure notification is sent from the relay destination station to the own station. But,
When a failure is detected in the signal received by the failure detection means of the own station, it is possible to determine that the cause of the failure detected at the relay destination station is not in the own station. In this case, switching of the transmission means is performed. I try not to do it.

According to the second aspect of the present invention, there are provided a receiving means for receiving a signal transmitted from a predetermined station, and a failure detecting means for detecting that a failure has occurred in a predetermined station based on the received signal. A fault notification transmitting means for transmitting a fault notification indicating a fault to the predetermined station when the fault is detected by the fault detecting means; and a fault notification transmitting means for transmitting the received signal to a predetermined relay destination station. A plurality of transmission means,
A selection means for selecting one of these transmission means to transmit to the relay destination station; and a relay destination station having a failure in the transmission means selected by the selection means based on the transmitted signal. Fault notification receiving means for receiving a fault notification indicating detection of a fault sent from this station when it is determined that there is a fault notification;
When a failure notification is received from the relay destination station, the transmission means selected by the selection means is switched to a transmission means different from the one selected at this time, and a failure on a predetermined station side is detected by the failure detection means. When the setting is made, the switching means for inhibiting the switching of the transmitting means by the transmitting means changing means is provided in the standby system switching system.

In other words, according to the second aspect of the present invention, when a failure occurring on the side of the source station is detected based on the received signal, a failure notification indicating the failure is sent back to the source station. As a result, the source station can be notified of the occurrence of the abnormality. Further, when a failure is detected from the received signal, the switching of the transmission means based on the failure notification sent from the relay destination station is not performed.
For example, when a plurality of relay stations are arranged, a faulty signal is transmitted to subsequent stations one after another, so that a fault is detected in all of these stations. As a result, each station sends a fault notification to the station in front of it, but the stations that have detected that the source of the received signal has a fault do not switch their own transmission means. Even if the relay station is arranged, the switching of the transmission means is performed only for the station where the failure actually occurs.

According to a third aspect of the present invention, there is provided a receiving means for receiving a signal transmitted from a predetermined station, and a fault detecting means for detecting that a fault has occurred in a predetermined station based on the received signal. A fault notification transmitting means for transmitting a fault notification indicating the fault to the predetermined station when the fault is detected by the fault detecting means; and a fault notification transmitting means for transmitting the received signal to a predetermined relay destination station. A plurality of transmission means,
A selection means for selecting one of these transmission means to transmit to the relay destination station; and a relay destination station having a failure in the transmission means selected by the selection means based on the transmitted signal. Fault notification receiving means for receiving a fault notification indicating detection of a fault sent from this station when it is determined that there is a fault notification;
When a failure notification is received from the relay destination station, the transmission means selected by the selection means is switched to a transmission means different from the one selected at this time, and a failure on a predetermined station side is detected by the failure detection means. The standby system switching system is provided with switching inhibiting means for inhibiting the switching of the transmitting means by the transmitting means changing means until a predetermined period of time elapses after the detection is stopped and from when this is detected. .

That is, according to the third aspect of the present invention, the relay destination is maintained until a predetermined time elapses even after the failure occurring in the source station of the received signal is no longer detected. Switching of transmission means based on the failure notification sent from the other station is prohibited. Since a failure is detected at the relay destination station after a certain period of time has passed since the local station detected the failure at the source station, the failure at the source station is restored and the failure at the local station occurs. A failure notification may be sent from the relay destination station after the detection is stopped. Switching the transmission means of the own station by mistake due to the failure notification arriving at such a delay means that a failure from the relay destination station will continue until a certain time elapses after the failure is no longer detected by the own station. This is prevented by prohibiting switching based on the notification.

According to the fourth aspect of the present invention, the fixed time for prohibiting the switching of the transmission means is longer than the time required from when the failure detection means no longer detects the failure until the failure notification reaches the relay destination station. You have set.

In other words, in the invention according to claim 4, a certain period of time for extending the period for prohibiting switching is required from the point in time when the failure detection unit of the own station no longer detects the failure until the failure notification arrives from the relay destination station. It is set longer than the time. As a result, it is possible to reliably prevent the transmission unit from being erroneously switched by the failure notification from the relay destination station when the own station is not the cause of the failure. Further, since the fixed time only needs to be considered in relation to the relay destination station, the setting is easy.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows an arrangement of each station of a digital radio system using a standby system switching system according to an embodiment of the present invention. First and second relay stations 13 and 14 are provided between main signal switching terminal stations 11 and 12 as terminal stations.
Is arranged. There are an up-link 15 and a down-link 16 as radio lines. In the up-link, the main signal switching terminal 11 is a transmitting terminal and the main signal switching terminal 12 is a receiving terminal. The reverse relationship is established in the downlink 12. The main signal switching terminals 11, 12 are connected to transmitters 17 ₁ , 1
7 ₂ and a receiver 18 ₁ 18 ₂ . In addition, the first and second relay stations 13 and 14 are provided with the transceiver 1 for uplink.
9 ₁ and 19 ₂ and transceivers 19 ₃ and 19 ₄ for downlink.

FIG. 2 shows an outline of a circuit configuration in the main signal switching terminal shown in FIG. The circuit configurations of the main signal switching terminal stations 11 and 12 are the same. Here, the main signal switching terminal station 11 is shown, and the description of the main signal switching terminal station 12 is omitted. First, the circuit configuration of the transmitting device in the terminal station will be described. A main signal 21 as a data signal to be transmitted on the uplink 15 is input to a distributor 22 that splits the signal into two. One output of the distributor 22 is input to a working transmission device 23 indicated by a dotted line, and the other output is input to a protection transmission device 24. The active transmission device 23 and the standby transmission device 24 have the same configuration, and a description of the standby transmission device 24 will be omitted.

The output of divider 22 is input data to be transmitted to the transmission code processor 25 ₁ and outputting the frame configuration of. Transmission code processor 25 _1, the sub-signal such as a control signal, is adapted to the frame constituted by the main signal and the multiplex. The output of the transmission code processor 25 ₁ is the modulator 2
Is input to the 6 _1, modulated signal is inputted to the transmitter 27 _1. The output of the transmitter 27 ₁ is transmitted from the antenna 31 to the opposite station via the switch 28 and the transmission duplexer 29. The switch 28 selectively switches the outputs of the transmitters 27 ₁ and 27 ₂ of the active transmitter 23 and the standby transmitter 24 according to the control signal output from the switch controller 32 and sends the output to the duplexer 29. It has become.

The detector 33 ₁ is a circuit portion for monitoring the output power of the transmitter 27 _1, when the output power falls below a predetermined value, and outputs an abnormality detection signal 34 _1. The switching controller 32 supplies the abnormality detection signals 34 ₁ , 34
₂ and a silent feria detection signal 36 output from the control signal separator 35 are input. The switching controller 32 outputs a control signal for switching the transmitter when any of these signals becomes active. For example, when the switching unit 28 selects the primary system transmission device 23, when the output power of the transmitter 27 ₁ of the primary system by the detector 43 ₁ is detected to have fallen below the prescribed value, the backup system Can be switched. Also, when the silent feria detection signal 36 is input, the system is switched similarly. The control signal separator 35 and the silent Feria detection signal 36 will be described later. The active transmission device 23 and the standby transmission device 24
The hot standby configuration is such that the same signal distributed by the distributor 22 operates in parallel, and when a failure occurs in one system, the system is immediately switched to the other system.

Next, the circuit configuration of the receiving device in the terminal station will be described.

The radio wave received by the antenna 31 is
The signal is input to the distributor 37 via the duplexer 29.
One of the signals branched by the distributor 37 is used for the current system.
To the receiving device 38 and the other to the standby receiving device 39
And these are in a hot standby configuration.
I have. The working system and the protection system have the same configuration for the receiver.
Therefore, the description of the standby system is omitted. Distributor
One of the signals after being distributed at 37 is₁Through
Demodulator 42₁Has been entered. Demodulator 42 ₁Is
Digital signal that is framed by demodulating the transmitted signal
This is a circuit that outputs a signal. Demodulator 42₁Output to
The digital signal is received by the reception code processor 43.₁Has been entered.
Receive code processor 43₁Is the main frame
This is a circuit that separates and extracts a signal and a sub-signal.
Further, the occurrence of a frame error and the demodulator 42₁By
To detect abnormalities in the baseband signal of the demodulated signal.
Error detection signal 44₁Is output.

Active receiving device 38, standby receiving device 39
Main signal separated by the reception code processor 43 _1, 43 ₂ is input to the main signal switching device 45. The main signal switch 45 selects one of the working system and the standby system and outputs the separated main signal to the outside. Similarly, the sub-signals separated by the reception code processors 43 ₁ and 43 ₂ are:
The sub signal is input to the sub signal switch 46, and one of the selected sub signals is input to the control signal separator 35. Error detection signal 44 output from reception code processors 43 ₁ and 43 _2
1, 44 ₂ is inputted to the reception signal monitor unit 47. This circuit, when both of the error detection signal 44 ₁ and 44 ₂ is input, and determined that the silent Feria occurs in transmission station opposing, switching instruction for switching the transmitter of the opposite station to the other system A signal 48 is output. If only one of the error signals is input, it is determined that an abnormality has occurred in the receiver currently selected by the own station, and the main signal switch 45 and the sub signal switch 46 are connected to the other system. Is switched over.

The switching instruction signal 48 output from the reception signal monitor 47 is input to the control signal multiplexer 49, where the switching instruction is multiplexed with the sub signal. The multiplexed sub-signals of the switching instruction are input to the transmission code processors 25 ₁ and 25 ₂ of the working transmission device 23 and the protection transmission device 24, respectively. Thus, when the receiving apparatus detects a silent failure generated in the opposite station, a switching instruction of the transmitter is transmitted to the opposite station via the reverse line.

The control signal separator 35 is a circuit for separating the control signal from the sub-signal and determining whether or not the control signal includes a switching instruction from the opposite station. When the switching instruction is included, a silent feria detection signal 36 is output to notify the switching controller 32 that the silent feria has been detected at the opposite station.

FIG. 3 shows an outline of a circuit configuration of the first relay station shown in FIG. The circuit configuration of the second relay station 14 is the same as that of the first relay station 13, and thus the description thereof is omitted. Also, the same circuit portions as those of the terminal station shown in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.
The first relay station transceiver 1 downlink an uplink transceiver 19 ₁
It is equipped with a 9 _3. These configurations are the same, the circuit configuration of the uplink transceiver 19 ₁ in the figure, the downlink transceiver 19 ₃
Of shows only a circuit portion connected to the upstream transceiver 19 ₁ are omitted in the other parts.

The antenna 31₁The radio waves received by
Transmitter / receiver 29₁Transmission / reception device 19 via₁Minute
It is input to the distributor 37. After branching at distributor 37
One signal of the receiver 41₁, Demodulator 42₁Sent via
Receive code processor 51₁Has been entered. In the distributor 37
The other signal distributed to the receiver 41_Two, Demodulator 42_TwoTo
Transmission / reception code processor 51_TwoHas been entered. Sending and receiving
Signal processor 51₁, 51_TwoAre both the received signal
When the frame is decomposed and separated into main and sub signals,
To detect frame errors and abnormal baseband signals.
Error detection signal 44₁, 44_TwoOutput
It has become. Also, the transmission / reception code processor 51 ₁, 51
_TwoIs a sub-signal input from the control signal multiplexer 49, and
The main signal separated from the transmitted frame
And output it.

The signals newly framed by the transmission / reception code processors 51 ₁ and 512 ₂ correspond to the corresponding modulator 2 respectively.
The signals are input to transmitters 27 ₁ and 27 ₂ via 6 ₁ and 26 _2, and one output of the transmitters 27 ₁ and 27 ₂ is selected by the switch 28 and transmitted to the opposite station. Further, the error detection signal 44 _1, 44 ₂ to the output of the transmitting and receiving encoded processor 51 _1, 51 ₂ is inputted both to the received signal monitoring unit 47. Error detection signals 44 ₁ , 44
Since ₂ both when active believed silent Feria occurs in the opposite station, the received signal monitoring unit 47 ₁
Outputs the switching instruction signal 48 at this time. Switching instruction signal 48 includes a delay circuit 52, it is inputted to the control signal multiplexer 49 _{and second} downlink transceiver 19 _3. Thus, the silent Feria is detected in the uplink transceiver 19 _1, it is sent to the opposite station through a downlink.

The error detection signal 44 _1, 44 ₂ is a signal that is continuously output until the error is not detected, so that the switching instruction signal 48 is output for a period corresponding to this . The delay circuit 52 starts outputting the mask signal 53 when the switching instruction signal 48 is input, and stops outputting the mask signal 53 after a predetermined time has elapsed since the switching instruction signal 48 is no longer input. Circuit. Mask signal 5 output from delay circuit 52
3 is inputted to the AND circuit 54 _1.

On the other hand, the transmission / reception code processor 51₁, 51_TwoTo
Accordingly, the separated sub-signals are supplied to the sub-signal switch 46.
, And one of the selected sub-signals is a control signal.
Separator 35₁Has been entered. Is the opposite station in the sub signal
When the switching instruction is included, the control signal separator 35
₁From the control signal 36₁Is output and this is the downlink transceiver
19_ThreeAND circuit 54_TwoHas been entered. Same as this
Downlink transceiver 19 _ThreeControl signal separator 35_TwoOut of
The input control signal is the uplink transceiver 19₁AND circuit 5
4₁Has been entered. AND circuit 54₁Is the upstream
The received signal monitor 47 detects the silent failure generated at the station.
₁Is detected from the opposite station downstream from the own station.
Will not accept switching instructions sent over the line
Playing a role. In other words,
No. monitor 47₁Is outputting the switching instruction signal 48
Is a silent failure detected by the opposite station downstream of the own station.
The cause of the rear is in the opposite station upstream from the own station,
The switching instruction is not accepted.

Further, the silent station is no longer detected at the downstream station after a certain period of time has passed since the error is no longer detected at the local station. Therefore,
The switching signal may be sent from the opposite station for a certain period after the error is no longer detected in the own station.
After the error is no longer detected, the delay circuit stops the output of the mask signal after a period longer than this time elapses, so that the error is no longer detected at the own station, and the signal is sent from the downstream opposite station. It does not respond to incoming switching signals. The output of the AND circuit 54 ₁ is input as a silent Feria detection signal 36 ₂ to the switching controller 32.

FIG. 4 shows that a silent feria is generated.
The signal waveforms at each part of the terminal and relay station circuits.
It is a representation. Here, the uplink 15 of the terminal station 11
Wave when silent feria occurs on the side
The shape is shown. Time T₁₁At terminal station 11
Shall be done. But the obstacle is Silent Feria
, The detector 33 of the terminal station 11₁Abnormal detection from
Outgoing signal (a in the figure) 34 ₁Is not output. When this obstacle
Time T₁₂Is detected by the first relay station 13 and the received signal is monitored.
Sight 47₁Switch instruction signal (c in the same figure) 48 is turned on.
Become. In response to this, the delay signal from the delay circuit 52
FIG. D) 53 is output. Switching instruction is through the down line
Transmitted to the terminal station 11 at the time T₁₃The terminal station switching controller 32
Control signal (b in the figure) for switching to the standby system
And the failure of the terminal station 11 is time T ₁₄To recover. Terminal 1
1 indicates that the failure recovery processing has been completed at time T_FifteenFirst
And the switching instruction signal is
Turns off. Time T_FifteenAfter time 61 has passed since
Time T₁₆Then, the mask signal 53 is turned off.

A fault that has occurred in the terminal station 11 at the time T ₁₁ is also detected in the second relay station 14 via the first relay station 13. As a result, the second relay station at the time T ₁₃ 1
The switching instruction signal (g in the figure) of the reception signal monitor 471 of _No. 4 is turned "on". The switching instruction is transmitted from the second relay station 14 to the first relay station.
At the time T
₁₇ the first control signal from the control signal separator 35 RS ₂ 13 (FIG e) is output to. However, the mask signal 53
Is turned on, the control signal is blocked and the first
Silent Feria detection signal which is the output of the AND circuit 54 ₁ of the relay station 13 in (FIG f) is not "on". Therefore, the switch does not switch to the standby system in the first relay station. The first is from the control signal separator 35 RS ₂ 13, the time T ₁₅ is also switching instruction signal subsequent to a failure at the end station ₁₁ has detected that it has recovered (FIG e) is output. However, the mask signal 53, the first relay station by switching instruction arriving from the second relay station 14 after recovery because it is output until time T ₁₆ is never switched to the standby system.

FIG. 5 shows signal waveforms in respective circuit portions of the first and second relay stations when a silent failure occurs in the first relay station. Shall silent Feria occurs in the first transmission system of the relay station at the time T _21. Since the end station 11 is silent Feria not occurred, switching instruction signal from a received signal monitoring unit 47 ₁ of the first relay station 13 (FIG. A) is not output. Therefore, the mask signal (b in the figure) 53 is not output from the delay circuit 52. Failures occurred in the first relay station 13 is detected at time T ₂₂ in the second relay station 14, this time the second switching instruction signal, the relay station 14 (FIG e) a mask signal (Fig f) Is turned on. Thus, the first switching instruction, the relay station 13 is outputted to the AND circuit 54 _1, a control signal for switching the time T ₂₃ from the switching controller 32 to the standby system (FIG c) is outputted. At this time, the mask signal 53 is output from the delay circuit 52 of the first relay station 13.
Since but not output, silent Feria detection signal output from the AND circuit 54 ₁ (FIG d) is "on". Therefore, switching to the standby system is performed in the first relay station. Due to fault in the first relay station 13, switching instruction is reached from the reception terminal station 12 at time T ₂₄ to the second relay station 14, the control signal from the control signal separator (FIG g) is Is output. However, this is prevented by the mask signal, and the silent-fear detection signal (h in the figure) is not output from the AND circuit 54 of the second relay station.

As described above, the station which has detected the silent failure generated in the opposite station is not adapted to receive the switching instruction sent from the downstream station through the reverse line, so that the cause of the failure is its own station. The system is switched only for stations that exist in. Further, since only the necessary stations are switched, the line error generated at the time of switching can be reduced. Further, since the delay circuit absorbs the difference in detection time between the station on the downstream side and the station on the downstream side, flapping does not occur during switching. In addition, the delay time set by the delay circuit only needs to consider the detection time difference between the adjacent stations, and it is not necessary to set the delay time to be gradually longer toward the downstream. Therefore, a setting error hardly occurs, the initial setting and maintenance of the system become easy, and the time required for recovery from the failure can be shortened. Further, since only the failed station is switched, even if a failure occurs in a plurality of stations, the system can be appropriately switched.

In the embodiment described above, a case where a failure has occurred in the uplink has been described as an example, but it goes without saying that the same operation is performed when a failure has occurred in the downlink. In addition, terminal devices may be used in combination in the relay station. In this case, the output of the reception signal monitor of the reception device is branched, one of the outputs is input to the AND circuit via the delay circuit, and the output of the control signal separator of the other terminal device to be combined is output to the AND circuit. What is necessary is just to connect to the other input. Then, the output of the AND circuit may be input to the switching controller as a silent Feria detection signal. Further, although the active system and the standby system are switched, it goes without saying that three or more transmitting devices may be prepared and switched.

[0042]

As described above, according to the first aspect of the present invention, when it is detected that the source station of a received signal has a cause of failure, a failure notification is sent from the relay destination station. Since the transmission means of the own station is not switched even if it is transmitted, the transmission means can be switched only when the own station actually has a cause of failure. As a result, unnecessary switching does not occur, and line errors that occur during switching can be reduced.

According to the second aspect of the present invention, when a failure occurring on the side of the source station is detected based on the received signal, a failure notification indicating this is sent back to the source station. As a result, the source station can be notified of the occurrence of the abnormality. Further, when a failure is detected from a received signal, the switching of the transmission means based on the failure notification sent from the relay destination station is not performed. The switching of the transmission means can be performed only for the station where the transmission has occurred. Further, since only the failed station is switched, the system can be appropriately switched even when a failure occurs in a plurality of stations.

Further, according to the third aspect of the present invention, the switching of the transmitting means is continued until a predetermined period of time has elapsed even after the failure of the source station of the received signal is no longer detected. Is not performed, the transmission means is not erroneously switched by a failure notification arriving late from the relay destination station. As a result, there is no flapping of switching caused by the difference in the time point of failure detection between the stations. Also, there is no need to gradually increase the fault detection time toward the downstream,
The time required for recovery from a failure can be reduced.

According to the fourth aspect of the present invention, a certain period of time for extending the period for prohibiting switching is set to the time required for the failure notification to arrive from the relay destination station after the failure is no longer detected in the own station. Since it is set to be longer than this, it is possible to reliably prevent switching to the standby system by mistake due to a failure notification arriving late from the relay destination station. In addition, since this fixed time only needs to be considered in relation to the relay destination station, its setting is easy.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an arrangement of each station of a digital wireless system using a standby system switching system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an outline of a circuit configuration in a main signal switching terminal shown in FIG.

FIG. 3 is a block diagram showing an outline of a circuit configuration of a first relay station shown in FIG.

FIG. 4 is various waveform diagrams showing signal waveforms at various parts of a terminal station and a relay station when a silent feria occurs.

FIGS. 5A and 5B are various waveform diagrams showing signal waveforms in respective circuit portions of the first and second relay stations when a silent feria occurs in the first relay station.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 transmitting end station 12 receiving end station 13, 14 relay station 22, 37 distributor 27 transmitter 28 switch 32 switching controller 35 control signal separator 36 silent Feria detection signal 41 receiver 47 reception signal monitor 49 control signal multiplexing Container 52 delay circuit 54 AND circuit

Claims (4)

(57) [Claims] 1. A receiving means for receiving a signal transmitted from a predetermined station, a failure detecting means for detecting that a failure has occurred on the predetermined station side based on the received signal, A plurality of transmitting means provided for transmitting to a predetermined relay destination station; selecting means for selecting one of these transmitting means to perform transmission to the relay destination station; A fault receiving a fault notification from the station indicating the detection of a fault when the relay destination station determines that the transmitting means selected by the selecting means has a fault based on the received signal. Notification receiving means, transmitting means changing means for switching the transmitting means selected by the selecting means to a transmitting means different from the one selected at this time when a fault notification is received from the relay destination station, and the fault detecting means The predetermined station A switching prohibition unit for prohibiting switching of the transmission unit by the transmission unit change unit when a failure on the side is detected. 2. A receiving means for receiving a signal transmitted from a predetermined station, a fault detecting means for detecting that a fault has occurred on the predetermined station side based on the received signal, and a fault detecting means. A failure notification transmitting means for transmitting a failure notification indicating the failure to the predetermined station when the failure is detected, and a plurality of transmission means provided for transmitting the received signal to a predetermined relay destination station. Means, selecting means for selecting one of these transmitting means and performing transmission to the relay destination station, and selecting the selecting means by the relay destination station based on the transmitted signal. Failure notification receiving means for receiving a failure notification indicating the detection of a failure sent from this station when it is determined that the transmitting means has a failure, and selecting the failure notification when receiving a failure notification from the relay destination station. Transmission means selected by means Transmitting means for switching to a transmitting means different from the one selected at this time, and when the fault detecting means detects a fault on the predetermined station side, switching of the transmitting means by the transmitting means changing means And a switching prohibiting means for prohibiting the switching. 3. A receiving means for receiving a signal transmitted from a predetermined station, a fault detecting means for detecting that a fault has occurred in the predetermined station based on the received signal, and a fault detecting means. A failure notification transmitting means for transmitting a failure notification indicating the failure to the predetermined station when a failure is detected, and a plurality of transmission means provided for transmitting the received signal to a predetermined relay destination station. Means, selecting means for selecting one of these transmitting means and performing transmission to the relay destination station, and selecting the selecting means by the relay destination station based on the transmitted signal. Failure notification receiving means for receiving a failure notification indicating the detection of a failure sent from this station when it is determined that the transmitting means has a failure, and selecting the failure notification when receiving a failure notification from the relay destination station. Transmission means selected by means A transmission means changing means for switching to a transmission means different from the one selected at this time, and a predetermined constant after the failure of the predetermined station side is detected by the failure detection means after the failure is no longer detected. A switching system for prohibiting switching of the transmitting unit by the transmitting unit changing unit until time elapses. 4. The apparatus according to claim 3, wherein the predetermined time is longer than a time required from when the failure detection unit no longer detects the failure to when a failure notification is received from the relay destination station. Standby switching system.