JPH098723A - Satellite communication system - Google Patents

Abstract

PURPOSE: To monitor the conditions of abnormal end caused by slave station input power supply reduction at a master station concerning a satellite communication system to use a DAMA system. CONSTITUTION: When the drop of an impressed voltage is detected by an input impressed voltage monitor part 101 of a slave station 60, this drop signal is sent to a common control part 102. The common control part 102 detects a non-used line out of plural voice lines prepared for the slave station and reports a voltage drop through a control line to a master station 3. The master station 3, which receives the report, waits for the time enough for this slave station 60 to reach an operational defect caused by the voltage drop, cancels a pair of transmission/reception frequencies allocated to this slave station 60 and returns the line to a pool.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a plurality of slave stations, a master station and a satellite, and any slave station communicates via the satellite with a pair of transmission / reception frequencies allocated by the ratio request multiple access system. In particular, the present invention relates to a satellite communication system having a means for a master station to recognize an abnormal termination of a slave station.

[0002]

2. Description of the Related Art Conventionally, in a satellite communication system, an SCPC (Single Channel P) that allocates one carrier to one voice channel.
erCarrier) communication system is used, and for the purpose of effective use of frequencies, a ratio request multiple access (Demand Assignment Multip) is used.
le Access, hereinafter referred to as DAMA. ) Method has been used.

In the DAMA system, a master station that manages the frequency of a large number of SCPC radio channels pools a fixed number of channels in common to each earth station (slave station), and a common pool is generated each time a call occurs. It is a line system that allocates a pair of frequencies for transmission and reception in an empty channel among them, receives the call termination notice from the slave station, releases the allocation, and returns to the empty channel. In the normally used DAMA method, the master station only controls the line and does not monitor the usage status of the assigned line. Hereinafter, description will be given with reference to the block diagram of the satellite communication system using the conventional DAMA method shown in FIG.

In FIG. 2, DAMA processing units 1 and 2 of arbitrary two opposing stations among a plurality of slave stations 6 having the same configuration are subscriber terminals 10 and 2 such as telephones and facsimiles, respectively.
0, and is connected via a satellite 4 to a master station 3 that performs line allocation control by the DAMA method. The satellite line comprises a call line 50 and a control line (CSC channel) 51. For example, the connection of the communication path between the DAMA processing units 1 and 2 is performed by the following procedure. In the configuration of the DAMA processing units 1 and 2 in FIG. 2, only the portion related to the DAMA function is described, and the high frequency circuit, the audio signal transmission path, etc. are omitted.

In the DAMA processing unit 1, when the call detection circuit 14 detects an off-hook of the terminal 10, the control unit 17 sets the frequency of the tuning circuit 18 to the frequency of the control line 51, and the modulator / demodulator 19 sends the DAMA signal. A connection request containing the connection with the processing unit 2 is sent to the control line 51.

In the master station 3, the tuning circuit 35 uses the control line 5
Since the frequency is set to 1, the connection request sent from the DAMA processing unit 1 to the control line 51 is demodulated by the modulator / demodulator 33 and transmitted to the control unit 31. Control unit 31
Determines the line (call line 50 shown in the figure) used by the DAMA processing unit 1 and the DAMA processing unit 2.

After that, a master station control signal 60 is formed which allocates a pair of transmission / reception frequencies to be used in the communication line 50 and shifts the DAMA processing units 1 and 2 to transmission / reception in the communication line 50. Then, it is sent from the modulator / demodulator 33 to the control line 51.

In the DAMA processing units 1 and 2, the master station control signal 60 transmitted to the control line 51 is demodulated by the modulators / demodulators 19 and 29 and input to the control units 17 and 27. The control units 17 and 27 set the frequency of the tuning circuits 18 and 28 to a predetermined transmission / reception frequency according to the content of the master station control signal 60. As a result, call connection is established and communication between both slave stations is started.

As a result, when a call is started between the slave stations,
The master station 3 is disconnected from the communication line 50 used by the DAMA processing units 1 and 2. Therefore, the master station 3 uses DAMA
It is not possible to directly monitor whether the communication line 50 used by the processing units 1 and 2 is still in use or normal.

Therefore, in each slave station, the presence / absence of a call is monitored by the call detection circuits 16 and 26, and when the call ends, the control units 17 and 27 control the frequencies of the tuning circuits 18 and 28 of the control line 15. The frequency is set, and a slave station control signal 61 having a normal end is sent to the master station 3. As a result, the master station 3 cancels the assigned pair of transmission and reception frequencies and returns the line to the pool.

Further, between the slave stations, the control units 17 and 27 control the out-of-band transmitters 15 and 25 to generate out-of-band signals 63 and 64 at predetermined time intervals during the call period.
This is a burst signal of a predetermined cycle, and is sent to the partner slave station via the line 50 in communication. At each slave station, this burst signal is sent to the out-of-voice signal receivers 16 and 2 respectively.
In step 6, the reception processing is performed and the result is sent to the control units 17 and 27, and it is confirmed whether or not the burst signal is normally received.

That is, both slave stations send and receive burst signals during the call period and monitor the state of the line. Then, when an abnormality occurs in transmission / reception of the burst signal, the control units 17 and 27 in both slave stations recognize the line connection failure, and the tuning circuit 18 and
The frequency of 28 is set to the frequency of the control line 51, and the slave station control signal 61 having the content of abnormal termination is sent to the master station 3. As a result, the master station 3 cancels the assigned pair of transmission and reception frequencies and returns the line to the pool.

As described above, the master station 3 cannot directly monitor the line status of the allocated slave station, but can only indirectly monitor it. Regarding this conventional DAMA operation, for example, Japanese Patent Publication No. 53-144208 and Japanese Patent Laid-Open No.
Details are described in JP-A-0-33746.

[0014]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The satellite communication method using the method has the following problems.

That is, in this method, when the slave station operates on battery power and both battery power are exhausted during a call and normal transmission / reception operations cannot be performed, the slave station notifies the master station of abnormal termination. I don't have the means to do Therefore, the master station has a problem that it cannot recognize the abnormal termination of call connection between slave stations and cannot return the allocated line to the common pool. Furthermore, the line charge is charged for the call. In some cases, there is a problem of causing overcharge.

An object of the present invention is to provide a satellite communication system using DAMA, which can surely notify a master station of an abnormal end before an abnormal transmission / reception operation occurs due to a power drop of a slave station. To provide.

[0017]

A satellite communication system of the present invention is a demand-assigned (DAMA) system, which is a satellite line composed of a pair of transmitting and receiving frequencies allocated from a plurality of wireless lines prestored in a master station. In the satellite communication system in which the slave stations communicate with each other, the slave station independently controls the communication signal between the master station and the DAMA control signal for each of a plurality of terminals or the partner slave station with which the communication is performed. And a plurality of DAMA processing means for transmitting the signal, and the plurality of D's when the power supply voltage input to the slave station becomes a predetermined voltage or less.
Common control means for selecting a DAMA processing means not used for communication among the AMA processing means, and the selected DA
Notification means for notifying the master station of abnormal voltage information of the slave station by using MA processing means, and the master station notifies the slave station at a predetermined time after receiving the notification means by the control line. And a control means for returning the assigned pair of transmitted and received frequencies to the plurality of prestored wireless lines.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a satellite communication system equipped with a small earth station according to an embodiment of the present invention.

The same components as those in the conventional satellite communication system shown in FIG. 2 are designated by the same reference numerals.

In FIG. 1, a plurality of slave stations 60 having the same structure are provided.
It is composed of the DAMA processing units 100 and 200 of two arbitrary stations, a master station 3 and a satellite 4. Although the power source is not shown, the slave station 60 in this figure is a portable small earth station that can be operated by a battery power source. Here, the configuration of the DAMA processing unit 100 has a plurality (N) of DAMA processing units 1 shown in FIG. 2 and can transmit and receive a plurality of channels.
Further, the common unit includes an input applied voltage monitoring unit 101, an alarm sound oscillation unit 104, an alarm lamp 103, and a common control unit 102.

Further, the common control unit 102 includes the control units 17-1 to 17-N in the DAMA processing units 1-1 to 1-N.
(However, it is omitted in FIG. 1), and control signals are transmitted and received. Similarly, DA
As for the MA processing unit 200, DAMA processing units 2-1 to 2-1
2-N is provided to enable transmission and reception of a plurality of wireless signals,
Further, as a common part, the input applied voltage monitoring part 201, the alarm sound oscillating part 204, the alarm lamp 203, the common control part 202
have.

Input applied voltage monitoring units 101 and 20 of both slave stations
1 monitors the level of the voltage supplied from the battery power source,
When the voltage drops below the specified voltage, the voltage level drop signals are sent to the common control units 102 and 202, respectively. The common control units 102 and 202 include input applied voltage monitoring units 101 and 201.
When the voltage level lowering signal is further received, the alarm sound oscillating units 104 and 204 are caused to output alarm sounds and the alarm lamps 103 and 203 are turned on. As a result, the operator of the small earth station can know the decrease in the power supply voltage.

Further, the common control units 102 and 202 detect the line which is not currently used among a plurality of voice lines prepared for this small earth station (slave station) in combination with the above operation. At this time, this unused line, for example, DAMA
The frequency of the line tuning circuit 18-1 handled by the DAMA processing unit 1-1 in the processing unit 100 is set to the control line 51. Therefore, the common controller 102 is the controller 1
Via 7-1, the control line 51 notifies the master station 3 that the input applied voltage of the slave station will drop and normal operation will soon stop.

Upon receiving the notification, the master station 3 has its controller 31
However, after the DAMA processing unit 100 detects the input applied voltage drop, it takes a sufficient time (T
1), monitor the operation status of the DAMA processing unit 100,
If the operation of the voice line is still recognized by the slave station even after T1, the DAMA processing unit 100 regards it as an abnormal termination, cancels the assigned pair of transmission and reception frequencies, and pools the line. Return to.

Here, when all the voice lines prepared in the slave station are in use, the common control units 102 and 202 are used.
However, for any one voice line among them, the control unit 17-
Calls are forcibly disconnected via 1 and 27-1, the tuning circuits 18-1 and 28-1 are set in the control line 51, and the master station 3 is notified of a decrease in the input applied voltage. The arbitrary one voice line is stored in the common control units 102 and 202 in advance depending on the operating status of the slave station.

[0027]

As described above, according to the satellite communication system of the present invention, even though the operator recognizes that the input voltage has dropped, the call continues and the abnormal operation state of the slave station is reached. Further, even if the slave station is not restarted by the spare battery power source, the master station 3 can surely cancel the frequency assigned to the main slave station after T1, and the effective use of the frequency can be realized. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of a satellite communication system including a small earth station according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a satellite communication system including a conventional small earth station.

[Explanation of symbols]

 Each component is shown below. 1 DAMA processing unit 2 DAMA processing unit 3 Parent station 4 Satellite 6 Slave station 10 Subscriber terminal 14, 24 Call detection circuit 15, 25 Voice out-of-band signal oscillator 16, 26 Voice-out-of-band signal receiver 17, 27 Control unit 18, 28 Tuning circuit 19, 29 Modulator / demodulator 31 Control part 32 Voice out-of-band signal oscillator 33 Modulator / demodulator 34 Voice out-of-band signal receiver 35 Tuning circuit 50 Call line 51 Control line 60 Slave station 100, 200 DAMA processing part 101, 201 Input Applied voltage monitoring unit 102,202 Common control unit 103,203 Alarm lamp 104,204 Alarm sound oscillation unit

Claims (5)

[Claims] 1. A satellite communication in which a slave station communicates by a demand-assigned (DAMA) system with a satellite line consisting of a pair of transmission / reception frequencies allocated among a plurality of wireless lines pre-stored in a master station. In the method, the slave station independently operates the master station and the DAM for each of a plurality of terminals.
A plurality of DAMA processing means for transmitting a control signal for A or a communication signal with a communication partner slave station, and the plurality of DAMA processing means when the power supply voltage input to the slave station becomes a predetermined voltage or less. There is provided common control means for selecting a DAMA processing means not used for communication among the processing means, and notifying means for notifying the master station of abnormal voltage information of the slave station by using the selected DAMA processing means. The master station, after receiving the notification means on the control line, has a control means for returning a pair of transmission / reception frequencies assigned to the slave station to the plurality of wireless lines stored in advance at a predetermined time. Satellite communication system characterized by the following. 2. The common control means receives the power supply voltage and compares the input voltage with a predetermined voltage, and an alarm sound generator that generates an alarm sound when the power supply voltage drops. An alarm lamp that lights up when the power supply voltage drops, and outputs the power supply drop information to the unused DAMA processing means that receives the output from the input applied voltage monitoring unit, and the input applied voltage 2. The satellite communication system according to claim 1, comprising a common control unit that controls a monitoring unit and the alarm sound generation unit. 3. The call detection circuit for detecting opening / closing of a subscriber line of a subscriber terminal connected to the outside, the DAMA processing means, and the master station and the control line receiving a detection signal of the call detection circuit. And a tuning circuit for controlling the frequency of the modulator / demodulator so as to enable transmission / reception and transmitting information necessary for the DAMA operation, and a tuning circuit for controlling the frequency of the modulator / demodulator by the frequency controlled by the controller. In the case of communication between stations, it is characterized by having an out-of-band signal oscillator for sending a predetermined burst signal out of the voice band, and an out-of-band signal receiver for receiving the predetermined burst signal. The satellite communication system according to claim 1. 4. The satellite communication system according to claim 2, wherein the common control unit forcibly stops the use and sends the power supply drop information when all the DAMA processing units are in use. . 5. The satellite communication system according to claim 1, wherein the slave station can operate by using a battery as an input power source.