JP2590100B2 - Satellite communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to an improvement of a satellite communication system to which a demand assignment system is applied.

(Prior Art) In recent years, the transmission of voice and data is often performed using a satellite communication system. In the satellite communication system, a pre-assignment method in which a fixed communication line is previously allocated between each earth station. And a demand assignment method. In the demand assignment method, a fixed number of satellite communication lines are pooled in common for each earth station, and each time a terminal device connected to the earth station issues a line allocation request, the satellite communication line is selected from the above satellite communication lines. A vacant line is selected and this line is allocated to the terminal device, and a limited satellite communication line can be efficiently used by dynamic line allocation. The demand assignment method includes a centralized control method and a distributed control method. Among them, the centralized control system first provides a centralized control station as an upper station of each earth station to which the terminal device is connected, and the centralized control station supervises selection of a free line, assignment of a line to each earth station, and the like. It is what you do. On the other hand, in the distributed control method, the central control station is not provided, and each of the earth stations to which the terminal device is connected selects an available line, and is approved by requesting another earth station to use the line. For example, the above line is allocated to a terminal device.

By the way, in a satellite communication system to which the demand assignment system is applied, it is necessary to transmit and receive control information between each earth station when performing a line allocation control, regardless of whether the system is a centralized control system or a distributed control system. In general, transmission and reception of this control information is performed by using a common signal line (CSC).
Channel) for control. For this reason, the call concentration, that is, the throughput amount increases, and when the processing amount of the control unit in the earth station increases, the information transmission delay on the common signal line increases. FIG. 5 shows a change in the transmission delay time with respect to the throughput amount when the slotted random access method is applied to the common signal line. In this case, when the throughput amount approaches 0.4, the delay time becomes infinitely large. . That is, in a system to which the demand assignment method is applied,
When requests such as calling and disconnection from the terminal device are concentrated in a short period of time, the control unit of the earth station is busy with these processes and exchanges control information with other earth stations using a common signal line. There is no room to do so, and as a result, the system cannot assign a line to the terminal device even though there are vacant lines. This state is referred to as a congestion state. When the terminal apparatus falls into the congestion state, the terminal device operator generally abandons the call once and frequently re-calls immediately. In this case, the system cannot easily recover from the congestion state, and becomes in a state equivalent to the actual system down.

(Problems to be Solved by the Invention) As described above, in the conventional system, when requests such as calling and disconnection are concentrated in a short period of time and this causes a congestion state, the communication between the earth stations by the common signal line is performed. The present invention focuses on this point, and the common signal line is congested. It is an object of the present invention to prevent this from happening and to prevent the occurrence of a system down, thereby providing a satellite communication system having high reliability and excellent serviceability.

[Structure of the Invention] (Means for Solving the Problems) According to the present invention, as shown in FIG. 1, an earth station includes a concentration monitoring means A and a call restriction means B, and the concentration monitoring means A monitors the degree of concentration of various requests generated from the terminal device, and the degree of concentration of the various requests exceeds a predetermined value based on the throughput characteristics of the satellite common signal line by the degree of concentration monitoring means A. When it is determined that the terminal device has been called, the call restriction means B restricts the call to the terminal device.

(Operation) As a result, requests such as calling and disconnection are generated from each terminal device in a concentrated manner, and when the concentration exceeds a prescribed value set in advance based on the throughput characteristic of the satellite common signal line, the calling is performed. Since call control is performed on each terminal by the call control means B and subsequent call requests are not accepted, the increase in the processing amount of the earth station is suppressed, and the satellite common signal line may be saturated. The system can be prevented from becoming in a congested state without any problem. Therefore, the occurrence of a system down is reliably prevented, thereby improving reliability and serviceability.

Embodiment FIG. 2 is a schematic configuration diagram of a satellite communication system according to an embodiment of the present invention. This system adopts a distributed control system, and a plurality of earth stations 10, 10 each having a plurality of terminal devices 20 connected thereto, and a communication for connecting these earth stations 10, 10 via a satellite communication line 40. And a satellite (hereinafter referred to as a space station) 30. The earth stations 10 and 10 include an exchange 11 for switching and connecting the terminal device 20 and a line control device 12.
And a modem (M / D) 13 for modulating and demodulating voice or data output from the terminal device 20 and a transmitting / receiving unit 14 for transmitting / receiving data via the antenna 15.

The line controller 12 includes an input / output controller for controlling the input / output of signals to / from the exchange 11 and the modem 13 as shown in FIG.
21 and call processing when an incoming call occurs, capture of the communication line,
A main control unit 22 that performs various controls associated with selection of a free line or acquisition of a line when a line allocation request is issued by the terminal device 20, and information between the input / output control unit 21 and the main control unit 22. And a buffer unit 23 for transmitting the
A monitoring control unit 24 is provided as a control unit. This monitoring control unit 24 constantly monitors the amount of various processing queues in the buffer unit 23, for example, the amount of the failure processing queue, the maintenance processing queue, and the exchange processing queue, and the amount of these queues is reduced in advance. When the value exceeds a prescribed value, the exchange 11 is caused to perform a process of restricting the calling of the terminal device 20 via the input / output control unit 21. The specified value is set to a value that does not cause the system to enter a congestion state, for example, a value corresponding to the throughput amount 0.3 in the case of FIG.

With such a configuration, each earth station is normally
The line control devices 10 and 10 are connected to the main control unit 22 in response to a request for an outgoing or incoming call from the terminal device 20 or another earth station.
Performs various controls. At the same time, as shown in FIG. 4, the monitoring control unit 24 inputs the queue amounts of various processes from the buffer unit 23 in step 4a.
At 4b, the amount of this queue is determined.

In this state, if, for example, calls and incoming calls are concentrated in a short time due to the occurrence of a disaster, and the queue size of the processing in the buffer unit 23 increases and exceeds a specified value, the monitoring of the line controller 12 As shown in FIG. 4, the controller 24 detects in step 4b that the specified value has been exceeded, and then proceeds to step 4c to output a transfer restriction signal. Then, the call restriction signal is transmitted to the exchange via the input / output control unit 21.
The switching device 11 controls the calling of the terminal device 20 as a result. For example, the SR line of the trunk corresponding to each terminal device 20 is forcibly set to the ground state, thereby setting each trunk to a state equivalent to the state in which an incoming call occurs and not accepting a call from the terminal device 20 State. Therefore, the terminal device 20
Cannot make a call, whereby the processing queue in the buffer unit 23 of the line controller 12 gradually decreases without further increasing. Therefore, the throughput amount does not increase any more, thereby avoiding the occurrence of the congestion state.
When the amount of processing queue in the buffer unit 23 decreases, and becomes, for example, an arbitrary value smaller than the specified value, the monitoring control unit 24 outputs a call restriction release signal in step 4d, thereby The SR line of each of the 11 trunks is returned to the “H” level. Thus, the calling restriction on the terminal device 20 is released, and thereafter the terminal device 20 can make a call.

As described above, according to the present embodiment, even when processing related to outgoing calls and incoming calls is concentrated in a short period of time, and the throughput amount increases, the switching device 11 can stop the processing when the amount of the processing queue exceeds the specified value. Since the call control for the terminal device is performed, there is no concern that the system will be in a congested state without saturation of the satellite common signal line, thereby avoiding the occurrence of the system down, and improving the reliability and serviceability of the system. Can be increased.

The present invention is not limited to the above embodiment.
For example, in the above embodiment, the case of the distributed control method has been described as an example, but the present invention may be applied to the case of the centralized control method.
In this case, the frequency of processing requests from other earth stations is monitored by the earth station serving as the central control station, and when the frequency of occurrence exceeds a specified value, a call control signal is sent to the other earth stations. May be output to regulate the call request. In addition, the configuration of the concentration monitoring unit and the call restricting unit, the configuration of the system itself, and the like can be variously modified without departing from the gist of the present invention.

[Effects of the Invention] As described above in detail, according to the present invention, the earth station is provided with the concentration monitoring means and the call control means, and the concentration monitoring means concentrates various requests generated from the terminal device. If the concentration monitoring unit determines that the concentration of the various requests exceeds a predetermined value based on the throughput characteristic of the satellite common signal line, the call restriction unit By restricting outgoing calls to the terminal equipment, it is possible to prevent the satellite common signal line from becoming congested and prevent the system from going down, thereby providing high reliability and serviceability. And an excellent satellite communication system can be provided.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of a satellite communication system of the present invention, FIG. 2 is a schematic configuration diagram of a satellite communication system in one embodiment of the present invention, and FIG. FIG. 4 is a flowchart showing a control procedure and control contents of a supervisory control unit of the same line control device, and FIG. 5 is a diagram showing an example of a change of an information transmission delay amount of a common signal line with respect to a throughput amount. is there. A: Concentration monitoring means, B: Call control means, 10: Earth station, 11: Switch, 12: Circuit control device, 13: Modem, 14: Transmitter / receiver unit, 15: Antenna, 20 terminal device, 21 input / output control unit, 22 main control unit, 23 buffer unit, 24 monitoring control unit, 30 space station, 40 satellite communication line.

Claims (1)

(57) [Claims] A plurality of earth stations and a communication satellite for connecting these earth stations via a satellite communication line. Each time a terminal device connected to the earth station issues a line allocation request. In a satellite communication system to which a demand assignment system for transmitting and receiving control information between each earth station via a satellite common signal line and allocating an empty line to a terminal device is applied, the earth station receives various requests generated from the terminal device. A concentration monitoring means for monitoring the degree of concentration, and when the concentration degree of the various requests is determined by the concentration degree monitoring means to exceed a predetermined value based on the throughput characteristic of the satellite common signal line. A satellite communication system comprising: a call restricting means for restricting a call to the terminal device.