JPH02244826A - Satellite communication system - Google Patents

Abstract

PURPOSE:To automatically, quickly, and surely restore an abnormal state where unfinished sequence is repeated at the common signal line system of a slave station to a normal state even when it occurs by providing a monitoring means to monitor the operating state of the common signal line system of the slave station and a compulsory restoring signal sending means on a reference station, and providing an initializing means on the slave station. CONSTITUTION:The monitoring means 15 which monitors the operating state of the common signal line system of the slave station B20 and the compulsory recovery signal sending means 16 which sends a compulsory recovery signal to the slave station B20 via an idle line when the occurrence of abnormality is detected in the common signal line system of the slave station B20 by the monitoring means 15 are provided on the reference station A20. And the initializing means 25 which initializes the operating state of the common signal line system of its own station when the compulsory recovery signal is sent is provided. Therefore, even when the slave station B20 falls in the state where the unfinished sequence is repeated during using the common signal line system, the abnormal state is detected by the reference station A20, and the compulsory recovery signal is sent, and the common signal line system of the slave station B20 is automatically initialized compulsorily. In such a manner, the abnormal state of the slave station can be restored in the short time.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention provides control signals that are transmitted between a reference station and a slave station among a plurality of earth stations via a common signal line by a line request allocation method. This invention relates to an i-star communication system that allocates and releases satellite communication lines by sending and receiving information.

(Prior Art) In a satellite communication system, as a method for allocating satellite lines when multiple connection is made between a plurality of earth stations, for example, fixed allocation (pre-assignment) in which a line is fixedly allocated to each earth station is used. Assfgns+ent Mul
tiple＾ccess) method and line request assignment (Demand Assignment) method.
nt Multiple Access) method is known. Among these, the line request allocation method involves pooling a certain number of satellite communication lines in common at each earth station, and each time a call occurs, a pair of transmitting and receiving lines in the common pool is allocated between the earth stations. When the process is completed, the allocation is canceled and the line is returned to the pool. If this allocation method is adopted, a limited number of lines can be used blindly by a large number of earth stations.

FIG. 4 shows an example of the configuration of a satellite communication system to which the above-mentioned line request allocation method is applied.
, Bl, C1 are a plurality of subscriber lines A5. B5. A circuit exchange containing C5, A2°B2. C2 is the circuit exchange A above.
1. A plurality of trunk lines A4. B4. Each earth station connected via C4 is shown. Note that in the figure, only one of the plurality of trunk lines is shown for convenience of explanation.

Earth station A2. B2. C2 is a terminal device A21.C2 equipped with a multiplexing section, a modem section, etc. B21. C21, a transmitting/receiving device (T/R) A that includes a frequency conversion section, an amplification section, an antenna, etc.
22. B22. C22, and line controller KA23. B23
．． C23. Among these, line control equipment can be roughly divided into network control equipment (NCP: Net
work Cor+trolProcessor) and station control device (SCP: 5tationCont)
rolProcessor). N.C.
P: ■Satellite communication line management, allocation and release functions;
■SCP management function, ■Maintenance operation function, ■Common signal line (CS C)
annel ) control functions, while SCP
has line allocation request, configuration and release functions.

In such a configuration, suppose that the line control device 1 of the earth station C has the NCP function, and in this state, for example, the terminal A3 connected to the line exchange A1 is connected to the terminal B3 connected to the line exchange B1. Assume that a call is made to . Then, first, the line exchange A1 determines whether the trunk line A4 connecting between the line exchange A1 and the earth station A2 is vacant or not, and if there is a vacant trunk line, a call request is made via this trunk line. is the line control device A23 of earth station A2.
sent to. Incidentally, if there is no vacant space on the trunk line, a busy tone is sent back from the circuit exchange A1 to the calling terminal A3.

When the above call request arrives, the line controller (SCP) A2
3 receives the other party's station identification number and called subscriber number from 3 to the calling terminal, and accordingly sends a line allocation request to the terminal equipment EA.
21 and the transmitting/receiving device A22, the common signal 1t[cs
c to the line control device C23 of the earth station C2, which has the NCP function. When the above-mentioned line allocation request arrives, the line controller (NCP) C23 first determines whether there is an empty line among all the satellite communication lines using its own management table, and if there is an empty line, the called party After confirming that trunk line B4 of earth station B2 is free, the vacant satellite communication line is connected to the line controller (SCP) A23 of calling earth station A2 and the called earth via common signal line C8C. The line controller (SCP) 823 of station B2 is notified.

In addition, after notification of this satellite communication line to be used, the line control device (NC
P) C23 rewrites the contents of its own management table.

When the satellite communication line used above is notified, the calling earth station A
2 and each line control device (SCP) of called earth station B2.
A23. After B23 sets up the satellite communication line and conducts a continuity test, it sends the called subscriber number from the calling earth station A2 to the called earth station B2. When this called subscriber number is sent, the line controller (SCP) of the called earth station B2
B23 sends an incoming call request to line exchange B1 via trunk line B4. Then, line exchange B1 captures the corresponding subscriber line B5, sends a calling signal to terminal B3 via this subscriber line B5, and if the called terminal B3 responds to this, connects subscriber line B5 and trunk line B4. . In this way, the calling terminal A3 and the called terminal B3 are connected via the satellite line, and communication between the two terminals becomes possible from then on. This communication state is maintained until one terminal performs call termination processing, thereby releasing the satellite line.

Incidentally, FIG. 3 shows an example of the frame structure of the common signal line C8C, and one frame includes time division multiplexed signals (TD
M signal) and a slotted random access signal are arranged with an appropriate guard time between them. The TDM signal is used to send a line control signal from the NCP of the reference station to the SCP of each slave station, and the slotted random access signal is used by the SCP of the slave station to send a line control signal to the NCP of the reference station when necessary. used.

(Problem to be Solved by the Invention) By the way, in this type of conventional satellite communication system, the SCP of the slave station uses C8C while using the common signal line CSC.
If C5C becomes unreceivable due to a failure in the receiving system, or if the CPU of the SCP goes out of control due to a software error, this SCP will transmit the common signal line C to the NCP of the reference station.
The state is such that the SC signal is constantly sent. In other words, the system ends up repeatedly executing a never-ending sequence. When such a situation occurs, other slave stations cannot access the common signal line C8C even if a call request or release request occurs, since conventional satellite communication systems usually have only one system of common signal line CSC. First, as a result, there is a problem in that a series of controls related to line allocation and release cannot be performed.

The present invention focuses on this point, and even if the common signal line system of the slave station falls into a state in which an unfinished sequence repeats, this abnormal state can be automatically recovered quickly and reliably with a simple configuration. It is an object of the present invention to provide a satellite communication system that can improve the reliability of the system by eliminating the problem that a common signal line becomes unusable for a long time.

[Structure of the Invention] (Means for Solving the Problems) The present invention transmits and receives control signals between a reference station and a slave station among a plurality of earth stations via a common signal line using a line request allocation method. In a satellite communication system that allocates and releases satellite communication lines by means of When it is detected that an abnormality has occurred in the common signal line system, the forced recovery signal sending means sends a forced recovery signal to the corresponding slave station via a predetermined free line other than the common signal line, and The slave station is provided with an initialization means, and when a forced restoration signal is sent from the reference station, the initialization means initializes the operating state of the common signal line system of the own station.

(Function) As a result, even if any slave station were to repeat a sequence that never ends while using the common signal line, the base station would detect this abnormal condition and send a forced recovery signal from the base station to the slave station. As a result, the common signal line system of the slave station is automatically and forcedly initialized. Therefore, the abnormal state of the slave station is recovered in a short time, and as a result, the problem of the common signal line becoming unusable for a long period of time is resolved. Therefore, the operational reliability of the system is increased.

(Embodiment) FIG. 1 shows the configuration of a satellite communication system in an embodiment of the present invention. In addition, in the figure, only one of the plurality of slave stations is shown for convenience of explanation.

First, the terminal device A24 of the reference station A20 includes a communication signal modulation/demodulation circuit (DTMOD) 11 that modulates and demodulates communication signals transmitted and received via a satellite communication line for communication, and a common signal line C8.
In addition to the common signal line modulation/demodulation circuit (CSCMOD) 12 that modulates and demodulates control signals transmitted and received via C, a forced recovery signal modulation circuit (R
STMOD) 13. In addition, 14 is the above DT
MOD11, CS CMOD 12 and R8TMOD
This is a separation/combination circuit 14 that combines and separates each of the 13 transmission signals.

Also, the line control bag flf (NCP) A25 of the reference station A20
In addition to line allocation control means associated with incoming and outgoing calls, line release control means associated with call termination operations, etc., it is equipped with slave station monitoring means 15 and forced recovery signal sending control means 16. The monitoring means 15 monitors the S of the other slave station while exchanging control signals with any slave station via the common signal line C8C.
This detects whether or not the CP is in a state where it repeats an endless sequence. Forced recovery signal sending control means 1
6 generates a forced recovery signal when the monitoring means 15 detects that the SCP of the other slave station is in a state of repeating a sequence that does not terminate, and responds to this signal via an idle line among the satellite communication lines. The signal is sent to the slave station.

On the other hand, the terminal device tB24 of the slave station B20 is connected to the reference station A2.
Similarly to 0, a communication signal modulation/demodulation circuit (DTMoo) 21,
In addition to the common signal line modulation/demodulation circuit (ccscMOD) 22 and the separation/combination circuit 24, it is further provided with a forced recovery signal demodulation circuit (R3TMOD) 23 for demodulating the forced recovery signal sent from the reference station A20.

Further, the line control device (SCP) B25 of the slave station B20 is equipped with an initialization means 25 in addition to a line allocation control means associated with outgoing/incoming calls, a line release control means associated with a call termination operation, and the like. This initialization means 25 operates a reset circuit provided in the SCP to self-reset the CPU when a forced recovery signal is received by the R8TMOD 23, thereby restoring the SCP to its initial state. be.

Next, the operation of the system configured as above will be explained. Assume that during the allocation or release control of the satellite communication line, an abnormality occurs in the receiving system of the common signal line in the slave station B20 on the calling side, and as a result, it is no longer possible to receive the response signal from the reference station A20. Then, slave B20
The line control device (SCP) B25 of the reference station A20 assumes that the request signal has not reached the line control device (NCP) A25 of the reference station A20, and performs retransmission processing. In normal line control procedures, retransmission processing is repeated infinitely. Therefore, the line control device (SCP) B25 of the slave station B20 falls into a state where it repeatedly executes an endless sequence.

By the way, at this time, the line control device (NC
P) A25 monitors the operation abnormality of the other slave station based on the transmission state of the control signal of the other slave station.

For example, slave B counts the number of times its own response signal is sent and waits until slave B transmits the response signal a preset number of times.
It is detected whether a predetermined signal arrives from 20 or not. In this state, even if the response signal is sent a predetermined number of times, the slave station B20
Suppose that a predetermined signal is not sent from. Then,
The line controller (NCP) A25 of the X sub-station A20 determines that the sub-station B20 has fallen into a state of repeating an endless sequence, and generates a forced recovery signal. Then, a free line among the satellite communication lines is selected, and the forced recovery signal is supplied to the terminal device A24 in order to send the forced recovery signal to the slave station B20 via this free line.

Then, this forced recovery signal is transmitted to R5 of the terminal device A24.
After being modulated by TMOD13, it is supplied to the transmitting/receiving device tA22 via the separation/combining circuit 14, and this transmitting/receiving device fA2
2 to slave station B20. Fig. ff12 shows an example of a signal format used for transmitting the forced recovery signal, in which the station function code of the subordinate station is inserted into the unique word UW, and the forced recovery signal is inserted into the information field.

On the other hand, slave station B20 monitors the arrival of the forced recovery signal during line allocation or release control. In this state, when the arrival of the forced recovery signal is detected by the R5TMOD23 of the terminal device B24, the line control device (S
The initialization means 25 of the CPU) B25 operates and the reset circuit forcibly resets the CPU. As a result, the line control device B25 was in a state of repeating a never-ending sequence.
is initialized, and as a result, the common signal line C5C is released from the unnecessary exclusive use state by the slave station B20 and restored to its normal state.

In this embodiment, the reference station A2 is controlled during line control.
0, the slave station B20 monitors the operation abnormality of the other slave station B20.
When it is detected that the line control unit (SCP) B25 has fallen into a state of repeating an unfinished sequence, it sends a forced recovery signal to the other slave station B20 via the idle line,
This forced recovery signal causes the line control device (S
CP) Since the operating state of B25 is initialized, even if the slave station B20 is connected to the common signal line C8C during line control.
Even if the station falls into a state where an endless sequence repeats due to a failure in the receiving system or the like, this state can be automatically and forcibly recovered from the reference station A20 side. Therefore, the unnecessary exclusive use state of the common signal line C8C can be quickly and reliably released, and thereby the system can be quickly normalized. Incidentally, in the past, when the line control device of a slave station was in a state of repeating an endless sequence, maintenance personnel determined the condition and manually reset the reset circuit of the slave station to recover. For this reason, it required a lot of time and effort to restore the system.

In addition, as another conventional solution, a common signal line C8C
It has also been considered to duplicate the transmitting and receiving equipment, but this has the problem of making the system large and expensive. However, in the system of this embodiment, the state of the line control device of the slave station is initialized by sending a forced recovery signal through the free line of the satellite communication line without increasing the number of common signal lines C8C. There is no need to worry about the system becoming large and expensive.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, an empty line of the satellite communication line is used as the line for transmitting the forced recovery signal, but it is also possible to provide one line for maintenance and use it. If the pilot reference signal has a spare line for the pilot reference signal, this line may be used for transmission. In addition, the signal structure of the forced recovery signal, the transmission means, the structure of the monitoring means, the structure and control contents of the forced recovery signal sending control means, etc. can be modified and implemented in various ways without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, the reference station is provided with a monitoring means for monitoring the operating state of the common signal line system of the slave stations, and a forced recovery signal sending means, and the monitoring means allows the slave stations to When it is detected that an abnormality has occurred in the common signal line system, the forced recovery signal sending means sends a forced recovery signal to the corresponding slave station via a predetermined free line other than the common signal line, and The slave station is equipped with an initialization means, and when a forced recovery signal is sent from the reference station, this initialization means initializes the operating state of the common signal line system of the slave station. Even if the signal line system is in a state where a sequence that does not terminate is repeated, this abnormal state can be automatically and quickly and reliably recovered with a simple configuration, thereby preventing the common signal line from being unusable for a long period of time. Therefore, it is possible to provide a satellite communication system that can improve the reliability of the system by eliminating the problems that occur.

[Brief explanation of drawings]

Fig. 1 is a circuit block diagram showing the main part configuration of a satellite communication system according to an embodiment of the present invention, Fig. 2 is a diagram showing a signal format for transmitting a forced recovery signal of the same system, and Fig. 3 is a common diagram. FIG. 4, which is a diagram showing an example of a signal format of a signal line, is a schematic configuration diagram of a satellite communication system to which the line request allocation method is applied. Al, Bl, C1... line exchange, A2. B2゜C2
...Earth station, A3. B3. C3...Terminal, A4゜B
4. C4... Relay line, A5. B5. C5... Joining line, A20... Base station, B20... Slave station, A21°B21. C21, A24. B24...One end station device, A2
2. B22. C22... Transmitting/receiving device, A23°B23
．． C23, A25. B25... line control device, 11.
21... Communication signal modulation/demodulation circuit (DTMOD), 1
2.22...Modulation/demodulation circuit for common signal line (C10MO
D), 13... Forced recovery signal modulation circuit (RSTM
OD), 23... Forced recovery signal demodulation circuit (RST)
MOD), 14.24...Separation and synthesis circuit, 15...
Monitoring means, 16... Forced recovery signal sending control means, 25
... Initialization means. Applicant's agent Patent attorney Takehiko Suzue A25 / Figure

Claims (1)

[Claims] In a satellite communication system in which a satellite communication line is allocated and released by transmitting and receiving control signals between a reference station and a slave station among a plurality of earth stations via a common signal line using a line request allocation method, the reference station , a monitoring means for monitoring the operating state of the common signal line system of the slave station, and when the monitoring means detects that an abnormality has occurred in the common signal line system of the slave station, a forced recovery signal is transmitted to a predetermined signal line other than the common signal line system of the slave station. a forced recovery signal sending means for sending to the corresponding slave station via the free line of the base station, and initializes the operating state of the common signal line system of the own station when the forced recovery signal is sent from the reference station to the slave station. A satellite communication system characterized by comprising initialization means.