JPH03231522A - Satellite communication system - Google Patents

Abstract

PURPOSE:To enhance the utilizing efficiency of a transponder by installing lots of fixed stations and utilizing an idle transponder from the fixed stations to transmit a TV signal when the requirement of the transmission of a television signal (TV) from an on-vehicle station (SNG station) is received. CONSTITUTION:A master station line controller 18 seeks an idle transponder in a communication satellite 1 based on the transmission requirement signal of the TV signal and applies each identification number of a relevant SNG station 20 and a fixed station 30 with respect to the SNG station 20 on request if an idle transponder is present there on, a transmission permission signal of the TV signal, a frequency band for TV signal transmission corresponding to the transponder and a reception frequency band to the fixed station 30 receiving the TV signal to an order wire(OW) modulator 5a as digital signals. The digital signal is modulated by the OW modulator 5a, amplified by a large power amplifier 11 and sent to the communication satellite 1 through an antenna 14.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a satellite communication system for transmitting television (hereinafter referred to as TV) signals using communication satellites, and in particular, the present invention relates to a satellite communication system that transmits television (hereinafter referred to as TV) signals using communication satellites, and in particular, TV signals are transmitted from a plurality of vehicle-mounted stations to a fixed station. This invention relates to a satellite communication method for transmitting data via communication satellites.

[Conventional technology]

Conventionally, this type of communication satellite was used to transmit TV signals to multiple in-vehicle stations (Satellite NewsGatheri).
ng) (hereinafter referred to as SNG stations) to multiple fixed stations. Only certain transponders are used in a fixed manner.

Furthermore, since TV signals require a wide frequency band of at least about 20 MHz, it is necessary to occupy one transponder as described above in order to transmit one channel of TV signals.

That is, the number of fixed stations is limited by the number of transponders mounted on a communication satellite, and even if there are vacant transponders, only transponders that are predetermined cannot be used.

[Problem to be solved by the invention]

In the conventional satellite communication system described above, each measuring station can only use predetermined transponders, and the SN
Opportunities for transmitting TV signals using G stations are, for example, when reporting on entertainment events or unexpected incidents, and it is difficult to use the transponders installed on communication satellites due to their infrequent use. It was difficult to raise the price.

Furthermore, it was difficult to install more fixed stations than the number of transponders.

The present invention makes it possible to install a large number of fixed stations without being limited by the number of transponders mounted on a communication satellite, and the SN
When there is a request to transmit a TV signal from a G station, these fixed stations can use vacant transponders to transmit the above-mentioned TV signal, and the satellite can efficiently utilize these transponders. The goal is to provide a communication method.

[Means to solve the problem]

The satellite communication system of the present invention includes multiple SNGs that transmit TV signals.
a plurality of fixed stations that receive the signals via a plurality of transponders mounted on a communication satellite; and the plurality of SNGs.
TV using a control station that controls the station and the plurality of fixed stations.
In a satellite communication system for transmitting signals, the plurality of S
A first terminal common to the plurality of SNG stations is used to request the transmission of a TV signal from the NG station to the control station via the communication satellite.
One control line is used to permit and prohibit transmission from the control station to the plurality of SNG stations, specify the transmission frequency band in the case of permission to transmit, and specify the reception frequency to the plurality of fixed stations. A second common control line is used for specifying the frequency band, and these first and second control lines and voice meeting lines between the plurality of SNG stations and the plurality of fixed stations are connected to the plurality of above-mentioned fixed stations. One of the transponders is shared, the remaining transponders are each used to transmit one TV signal, and the control station reports the usage status of the remaining transponders via the first and second control lines. Monitor the plurality of S
Specifying and controlling the operating frequency band of the TV signal transmission transponder used by the plurality of SNG stations and the plurality of fixed stations using the second control line in response to a TV signal transmission request from an NG station. It is characterized by

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a network diagram showing an embodiment of the present invention, and FIGS. 2(a) and 2(b) are diagrams showing the frequency arrangement of each transponder mounted on the communication satellite in FIG. 1.

In FIG. 1, a communication satellite 1 is equipped with a plurality of transponders used for relaying TV signals, and an SNG station 20 is equipped with a plurality of transponders.
moves on the ground as necessary, and transmits TV signals to the communication satellite 1 from, for example, the site where a specific incident has occurred.

The fixed station 30 receives the TV signal sent from the SNG station 20 via the communication satellite 1.

The control station 40 controls the transmission frequency of the SNG station 20, the reception frequency of the fixed station 30, and the start and end of transmission of the TV signal from the SN0 station 20.

There are N transponders onboard the communication satellite 1. For example, transponder 1 has a receiving frequency band T and a transmitting frequency band tl as shown in FIG. 2(a), and transponder 2 has
has a receiving frequency band T2 and a transmitting frequency band t2, and similarly, the transponder N has a receiving frequency band TN and a transmitting frequency band t.
Let us have N.

For example, when the signal is transmitted from the SN0 station 20 to the communication satellite 1 using the frequency band t1, the transponder 1 receives it, amplifies it, converts it to the frequency T1, and sends it to the fixed station 30.

Among these N transponders 1 to N, transponder N is used for relaying a voice meeting line between the SN0 station 20 and the fixed station 30.

This transponder N also receives a request for sending a TV signal from the SN0 station 20 to the control station 40, and the above-mentioned control station 40
It is also used to relay the order wire line for permission of transmission from the SN0 station 20 to the SN0 station 20 and allocation of frequencies to be used for the fixed station 30 that receives signals from the SN0 station 20 and this SNG station.

This order wire line is used not only for normal voice discussions between stations, but also as a control line for controlling the frequencies used by the above-mentioned SN0 station 20 and fixed station 30.

The remaining transponders l to N-1 are used for relaying TV signals.

The required frequency bandwidth of the above-mentioned voice meeting line C and the line for controlling the SN0 station 20 and the fixed station 30 is approximately 1 smaller than the frequency required bandwidth for TV signal transmission described above.
/100 or less, the transponder N can simultaneously transmit and receive all the above-mentioned order wire lines.

All of these order wire lines communicate using the 5 cpc (single channel bar carrier) system, and the carrier frequencies are arranged as shown in FIG. 2(b).

That is, on the receiving side of the transponder N, the frequency band T
The line using the carrier frequency FTC in N is commonly used by all SN0 stations 2o, and is used when requesting permission from the control station 4o to send out a TV signal.

Transponder N receives carrier frequency F from SN0 station 2o.
When a signal with Tc is received, after amplifying this signal,
It is converted into a signal having a carrier frequency fTC in the transmission frequency band tN of this transponder and sent to the control station 4o.

The FRC in Figure 2 is for all SN0 stations 2 from control station 4o.
Permission and prohibition of sending TV signals for 0, T to be sent
This is the carrier frequency of the transmission signal of the control station 4o, which is used to designate the frequency band to be used for the V signal and to designate the receiving frequency band for all fixed stations 3o.

When the transponder N receives the line signal having the carrier frequency FFLC, it converts it into a signal having the carrier frequency fRC and sends it to the SN0 station 2o and the fixed station 3°.

These carrier frequencies FRC and fRC correspond to the reception frequency band TN and transmission frequency band t of the transponder N, respectively.
Contained within N.

The m carrier frequencies F1 to F in the reception frequency band TN of the transponder N and the carrier frequencies f1 to f in the transmission frequency band tN are for a voice meeting line between the SN0 station 20 and the fixed station 3o. Each carrier frequency is shown.

In order to request the transmission of a TV signal from one of the SN0 stations 20, a series of transmission requests, the identification number of the own station, and the destination of the TV signal must be sent each time according to a predetermined format. The identification number of the fixed station may be converted into a digital signal having a carrier frequency FTC and sent to the transponder N mounted on the communication satellite 1.

The timing of this digital signal is determined by constantly modulating the clock signal at the carrier frequency FλC from the control station 4o, sending it toward the communication satellite 1, and transmitting it to the transponder N on this communication satellite.
After a predetermined time interval from the rise of each clock pulse of this reference clock signal, the signal received by the SNG station 20 is received and demodulated by the SNG station 20, and the signal is received by the SNG station 20, converted to a carrier frequency fRC, and sent out. T mentioned above
It is sufficient to send out a digital signal requesting to send a V signal.

That is, communication may be performed using a slotted random access method and a time division multiplexing method.

In addition, permission is given to the SN0 station 20 that has requested transmission of TV signals, designation of the transmission frequency band, and
The reception frequency band for the fixed station that is to receive the signal is specified by transmitting it from the control station 40 to the communication satellite 1 at a carrier frequency FRC modulated with a digital signal in a predetermined format synchronized with the aforementioned clock signal. Bye.

The SN0 station 20 allows transmission of the above-mentioned digital signals.
An identification number for identifying each fixed station 30 and an identification number for identifying each fixed station 30 are also included.

Signals having carrier frequencies F,, F2, . . . It is converted into a signal with f2...f and retransmitted.

That is, when a signal with a carrier frequency F1 is transmitted from the SN0 station 20, the fixed station 30 transmits a signal with a carrier frequency f,
can be received as a waiting signal.

Therefore, if you decide in advance the carrier frequency to be used for the order wire line for voice meetings for each fixed station,
The SN0 station 20 attempting to communicate with this fixed station 30 may select and use the carrier frequency used by the above-mentioned fixed station 30.

FIG. 3 is a block diagram showing an example of the configuration of the SN0 station 20 that can be used in the present invention.

As an OW (order wire) signal 15, a TV transmission request signal, the identification number of the desired destination fixed station among the plurality of fixed stations 30, and a TV signal transmission request are sent as digital signals according to a predetermined format. Adding the sudden modulator 5 for OW,
The line control device 6 which monitors this sudden modulator 5 signal for OW judges the above-mentioned signal as a request to send a TV signal, and changes the carrier frequency for OW so that the carrier frequency converted by the transmission frequency converter 8 becomes FTc. The carrier frequency of the baseband in the sudden modulator 5 is controlled.

The line control device 6 also controls the transmission switch 3 to cut off the output from the video modulator 2, and then issues a TV signal transmission request, its own station identification number, and the identification number of the fixed station to which transmission is desired. Each signal is sent as a digital signal according to a predetermined format to the above-mentioned OW modulator 5,
This OW modulator 5 modulates the signal and inputs it to the transmission frequency converter 8.

The transmission frequency converter 8 converts the frequency of this input signal so that the carrier frequency becomes the above-mentioned FTC, and inputs the signal to the high power amplifier 11 via the synthesizer 10.

This input signal is amplified to a desired power by a large power amplifier 11, and then passed through a transmitter/receiver splitter 13 to an antenna 1.
4 toward the communication satellite 1.

The signal having the carrier FTc described above is received and amplified by the transponder N mounted on the communication satellite 1, and converted into a signal having the carrier frequency fTc, which is sent to the control station 4.
Sent to 0.

In addition, the above-mentioned line control device 6 is designed so that when the carrier frequency of the received signal inputted to the receiving frequency converter 9 via the antenna 14, the transmitter/receiver splitter 13, and the low-noise amplifier 12 is fRC, it is correctly demodulated. Controls the OWW demodulator 7.

FIG. 4 shows one of the control stations 40 that can be used in the present invention.
This is a block diagram showing an example, in which a TV signal transmission request signal sent from the aforementioned SN0 station 20 at a carrier frequency ftc is transmitted from an antenna 14 through a transmission/reception duplexer 13, and then amplified by a low noise amplifier 12. After being converted to a baseband frequency by the receiving frequency converter 9, the OWW demodulator 7a
The signal is demodulated by the SNG station and applied to the master station line control device 18 as a TV signal transmission request signal from the SNG station.

This master station line control device 18 constantly records the usage status of all transponders for transmitting TV signals in the communication satellite, and based on the above-mentioned TV signal transmission request signal, the master station line control device 18 constantly records the usage status of all transponders for transmitting TV signals in the communication satellite. Search for a transponder and, if available, transmit the requested transmission frequency band to this TV.
The OW modulator 5a adds a reception frequency band to a fixed station that receives the signal as a digital signal in a predetermined format.

This digital signal is modulated by an OW modulator 5a, converted to a signal with a carrier frequency FRC by a transmission frequency converter 8, amplified by a large power amplifier 11, passed through a transmitting/receiving duplexer 13, and then communicated by an antenna 14. It is sent towards Satellite 1.

This signal is converted into a signal having a carrier frequency fRC by the transponder N and sent to the SN0 station 20 and each fixed station 30.

When the SN0 station 20 in FIG. 3 receives a signal with the carrier frequency fRC from the control station 40 described above, this received signal is demultiplexed by the transmitter/receiver splitter 13, amplified by the low noise amplifier 12, and further converted to the reception frequency. The frequency is converted by the device 9, and O
It is added to the WW demodulator 7. Since the signal from the control station 40 is a digital signal in a predetermined format as described above, the signal demodulated by the OWW demodulator 7 is applied to the line control device 6.

This line control device 6 determines that the signal sent from the control station 40 described above is a signal destined for the own station if the identification number is equal to the identification number of the own station, and the signal sent from the control station 40 is The specified TV is sent to the SN0 station 20 included in the signal.
The output of the video modulator 2 is connected to the input side of the transmission frequency converter 4 by controlling the transmission frequency converter 4 and also controlling the transmission switch 3 so as to match the transmission frequency of the signal.

Next, the above-mentioned line control device 6 controls the OW sudden modulator 5OWW demodulator 7 so that it can transmit and receive signals according to the carrier frequency of the voice order wire line of the fixed station 30 that receives the TV signal. .

That is, if the transmission carrier frequency of the audio order wire line used by the fixed station 30 to which the TV signal is sent is F.
, the line control device 6 sets S so that the transmitting carrier frequency of the voice order wire line of this SNG station also becomes Fl, and the receiving carrier frequency becomes fl.
The OW abrupt modulator 5 and the OWW demodulator 7 of the N0 station 20 are controlled.

The aforementioned OWW demodulator 7 outputs as an OWW signal output 16 an output after demodulating signals using carriers 1 to f on a normal voice meeting line.

This OWW signal output 16 is used for reception from the fixed station 30 during an audio meeting with the fixed station 30.

In addition, the OWW signal 15 for voice meetings is input to the OW modulator 5, and is modulated by this OWW signal input.
The fixed station 3 to which the TV signal is transmitted is transmitted by the transmission frequency converter 8.
The signal is converted into a signal having a carrier frequency corresponding to 0, that is, one of F1 to F, and is input to the synthesizer 10.

The TV signal 17 is modulated by the video modulator 2, passed through the transmission switch 3, converted to the frequency band used by the transponder specified by the control station 40 by the transmission frequency converter 4, and then sent to the synthesizer 10 as well. The signals are combined into an OW multiplied signal for the above-mentioned voice meeting, amplified to the required power by a large power amplifier 11, passed through a transmitter/receiver splitter 13, and transmitted from an antenna 14 toward the communication satellite 1.

When transmitting and receiving the above-mentioned audio OW multiplied signal with the fixed station to which the TV signal is sent, the SNG station 2 intra-0 extension control device 6 controls the OW sudden modulator 5OWW demodulator 7 to set the predetermined carrier frequency. Configure settings to enable sending and receiving.

FIG. 5 shows one of the fixed stations 30 to which the present invention can be applied.
FIG. 2 is a block diagram illustrating an example.

The carrier frequency fRC is used as a control signal from the control station 40.
When a signal with 2 is received by the antenna 14, this signal passes through the transmitter/receiver splitter 13, is amplified by the low noise amplifier 12, is demultiplexed by the splitter 18, and is output to the reception frequency converter 9 side. , is converted into a baseband frequency by this frequency converter 9, and is input to the OWW demodulator 7b. This OWW
The signal demodulated by the demodulator 7b is applied to the line control device 6.

Only when this input signal specifies reception of the local station, the line control device 6 determines that the above-mentioned signal is a signal for the local station, and converts the reception frequency converter to match the TV signal reception frequency designated for reception. Control one.

In addition, when the OWW demodulator 7b receives a signal having a carrier used in a line for a voice meeting that has been assigned in advance to its own station, the OWW demodulator 7b converts the demodulated signal into an OWW signal.
The multiplied signal is output as 16.

The TV signal from the SN0 station 20 that requested transmission is transmitted from the antenna 14 to the low-noise amplifier 12, demultiplexed by the demultiplexer 18, inputted to the reception frequency converter 19, converted to the baseband frequency, and then demodulated for video. demodulated by the device 20,
It is output as a TV signal 21.

The OW sudden modulator 5b of this fixed station 30 is set so that an OWW signal input 15 for a voice meeting is transmitted toward the communication satellite 1 at a carrier frequency predetermined for this station. .

In such a situation, the TV signal transmission/reception is
This is possible between the NG station and the designated fixed station, and
A voice meeting line can also be used between these stations.

In addition, when ending the transmission of the TV signal by the SN0 station 20 mentioned above, a digital signal of a transmission end request is sent in a predetermined format as the OWW number 15 in FIG. 3.
When the sudden modulator 5 for W is added, this signal is identified by the line control device 6, and the sudden modulator 5 for OW is added as in the case of the TV signal transmission request.
The OWW demodulator 7 is controlled so that the carrier frequency can be transmitted using FTc and received using fRC.

Subsequently, when control station 40 shown in FIG. 1 to N-1 are updated, and the identification number and transmission prohibition signal of the SN0 station 20 that requested termination of transmission are sent as a digital signal in a predetermined format with a carrier frequency FRC. .

The aforementioned transponder N converts a signal having a carrier frequency FRC into a signal having a carrier frequency fRC, and transmits the signal to the SN0 station 20.

The signal with this carrier frequency fRC is SN0 in Fig. 3.
When the station 20 receives the signal, the line control device 6 detects this signal and determines that the signal is for the own station only when the received signal has the identification number of the own station, controls the transmission switch 3, and transmits the video. The output circuit from the transmitter modulator 2 to the transmission frequency converter 4 is cut off.

FIG. 6 shows that from the TV signal transmission request from SN0 station 20, T
FIG. 2 is an explanatory diagram showing a process from transmission of a V signal to the end of sending out a TV signal.

That is, the carrier frequency F commonly used by these SN0 stations 20 is transmitted from any one of the plurality of SN0 stations 20.
When a digital signal according to a predetermined format is sent to the communication satellite 1 using the TC, it is converted into a signal having a common carrier frequency fTC by a transponder mounted on the communication satellite and sent to the control station 40. received at

Based on this signal, the control station 40 searches for a vacant transponder, grants permission to transmit this TV signal, and transfers the frequency band of this vacant transponder to the aforementioned SN0 station 20.
, the plurality of SN0 stations 20 and the plurality of fixed stations 30 are attached with the identification number of the SNG station to be permitted and the identification number of the fixed station so as to be used as the transmission frequency band of the TV signal.
The control signal is transmitted to the communication satellite 1 as a control signal using the carrier frequency FRC that is commonly used by the satellites.

This signal with carrier frequency FRC is converted into a signal with carrier frequency fRC by the transponder, and the SN
0 station 20 and fixed station 30.

Transmission of the TV signal is performed between stations that are permitted to transmit and receive by the control station 40. When the transmission of the TV signal is finished, the same carrier frequency FTc as described above is used by the SN0 station 20 that is transmitting the TV signal. The signal sends out a TV signal transmission termination request, and in response to this, the control station 40 uses the same carrier frequency FRC as in the case described above to send out a signal regarding the TV signal transmission prohibition designation.

This process is performed from the start to the end of TV signal transmission.

In the embodiments so far, each of the plurality of fixed stations 30 has decided in advance a different carrier frequency to be used for a meeting line using voice.
The aforementioned control station 40 constantly monitors the usage status of the carrier frequency for the meeting line using multiple voices, and
The carrier frequency to be used for the meeting line may be specified by the control station 40 each time the station 20 requests transmission of a TV signal.

Such designation of the carrier frequency by the control station 40 may be performed using the carrier frequency FRC described above. That is, a demand assignment multiple access (DAMA) method may be used.

FIG. 7 is a block diagram showing an example of a fixed station 30 that can be used in the above-described demand assignment multiple access system. A signal having a carrier frequency fRC is received from the OWW demodulator 7c, and the signal demodulated by the OWW demodulator 7c is applied to the line control device 6. This signal is judged by the line control device 6, and the carrier frequency for the specified meeting line to be used is determined by the line control device 6. This line control device 6 is OW so that it can modulate and demodulate a signal with
It is sufficient to control the sudden modulator 5OWW demodulator 7c, respectively.

For the above-described demand assignment multiple access system, the SN0 station 20 having the configuration shown in FIG. 3 can be used. However, the line control device 6 is designed to enable transmission and reception on the carrier frequency for the meeting line using the voice specified by the control station 40.
It is sufficient to add a function to control the OW abrupt modulator 5OWW demodulator 7 in response to a signal transmitted from the control station at the carrier frequency fRC.

Control station 4 used in the demand assignment multiple access method described above
The configuration of SN0 station 2o may be the same as that shown in FIG. Each time a transmission request is issued, in addition to searching for an empty transponder used for transmitting the TV signal, we also search for an empty meeting line for the above-mentioned voice communication and set the carrier frequency F.
The designation of the meeting line using voice as described above may be sent by a signal with RC. [Effects of the Invention] As explained above, according to the present invention, multiple transponders can be commonly used for fixed stations that exceed the number of these transponders,
Furthermore, these transponders can be used more frequently and more effectively.

[Brief explanation of drawings]

Fig. 1 is a network diagram showing an embodiment of the present invention, Figs. 2 (a) and (b) are explanatory diagrams showing the frequency arrangement of transponders, and Fig. 3 is an example of the configuration of the SNG station in Fig. 1. FIG. 4 is a block diagram showing an example of the configuration of the control station in FIG. 1, FIG. 5 is a block diagram showing an example of the configuration of the fixed station in FIG. FIG. 7 is an explanatory diagram showing the process from the start to the end of communication according to the invention, and is a block diagram showing another example of the structure of the fixed station in FIG. DESCRIPTION OF SYMBOLS 1... Communication satellite, 2... Video modulator, 3... Transmission switch, 4... Transmission frequency converter, 5.5a. 5b... sudden modulator for OW 6... line control device, 7a
. 7b, 7c...OWW demodulator, 8...Transmission frequency converter, 9...Reception frequency converter, 10...Synthesizer, 18...Demultiplexer, 19...Reception frequency conversion vessel, 2
0... SNG station, 30... Fixed station, 40... Control station.

Claims (1)

[Claims] 1. A plurality of SNG stations that transmit TV signals, a plurality of fixed stations that receive these signals via a plurality of transponders mounted on a communication satellite, the plurality of SNG stations, and the plurality of fixed stations. In a satellite communication system in which a TV signal is transmitted using a control station that controls a plurality of SNG stations, the plurality of SNG stations transmit a TV signal transmission request from the plurality of SNG stations to the control station via the communication satellite. Permission and prohibition of transmission from the control station to the plurality of SNG stations, designation of a transmission frequency band in the case of permission of transmission, and the fixed number of the plurality of SNG stations, using a first control line common to all stations. A second common control line is used to designate a reception frequency band for the station, and these first and second control lines and the plurality of SNGs
A voice communication line between the station and the plurality of fixed stations is shared by one of the plurality of transponders, each of the remaining transponders is used for transmitting one of the TV signals, and the control station transmits the TV signal. The usage status of the remaining transponders is monitored by the first and second control lines, and the TV from the plurality of SNG stations is monitored.
The TV used by the plurality of SNG stations and the plurality of fixed stations by the second control line in response to a signal transmission request.
A satellite communication method characterized by specifying and controlling the frequency band used by a signal transmission transponder. 2. In the satellite communication system according to claim 1, the first and second
A satellite communication system characterized in that the control station uses the second common control line to perform monitoring in the same way as a TV signal, and in response to a request from an SNG station, the control station uses the second common control line to perform control. .