JPH0484523A - Satellite communication system - Google Patents

Abstract

PURPOSE:To attain stable data transmission by discriminating a caller ground station and a receiver ground station from a signal communicated between data terminal means, setting a master clock or a slave clock automatically from the result of discrimination and setting master and slave operation of each ground station based on the clock. CONSTITUTION:Each ground station 1 has a discrimination means discriminating a caller side and a receiver side based on a signal communicated between respective data terminal equipments 11 and is provided with an interface conversion section 12 selecting a master clock or a slave clock by a clock selection means in response to the result of discrimination by the discrimination means and giving the clock to the data terminal equipment 11 of the ground station of the caller and the receiver as a timing signal. Thus, the master operation and the slave operation of each ground station are optionally set and stable data transmission is stably implemented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a satellite communication system that employs a demand assignment method.

(Prior art) Conventionally, as a satellite communication system adopting the demand assignment method, multiple ground stations ASBSC are used as shown in Fig. 4.
, D, data transmission between each station is performed via a communication satellite S. In this case, in data transmission using the demand assignment method, the destination is not fixed, and the destination to which data is to be transmitted is selected and connected each time.
A partner selection connection will be performed.

By the way, in such a satellite communication system, the ground station A
CCITT Recommendation In this case, CCITT Recommendation X, 21
The interface is designed to drive both transmit data and receive data with one timing signal, and operates in synchronization with an externally supplied clock.

For this reason, devices using such a CCITT Recommendation X, 2] interface cannot basically operate as a master by themselves. However, in a dual demand assignment satellite communication system, the network side may not be the master.
CITT Recommendation X, 2] enables ground stations using the interface to perform master operations.

However, if you do this, ground stations A and B.

For C and D, depending on the presence or absence of a clock generation source, the master operation and slave operation are fixedly set in advance, so for example, stations A and C are set as masks, and stations B and D are set as slaves. If this is the case, data transmission between stations A and B or D, and between stations C and B or D, which are in a master-slave relationship, can be carried out without any problems, but the data transmission between the master and the master Stations A and C have a relationship of
In data transmission between stations or between stations B and D in a slave-slave relationship, a problem arises in the timing of data transmission, resulting in unstable data transmission.

(Problem to be Solved by the Invention) In this way, the data terminal equipment of the ground station is
CITT Recommendation There was a problem in that stable data transmission was not possible.

The present invention has been made in view of the above circumstances, and provides a communication satellite system that can set the master operation and slave operation at each ground station as desired, and can always achieve stable data transmission (3% Let that be [1 point].

[Structure of the Invention] (Means for Solving the Problem) A plurality of communication satellite systems of the present invention include a ground station and a communication satellite forming a data transmission path between these ground stations;
Data transmission between each ground station is carried out via a data terminal means having an interface that drives both transmission data and reception data using a single timing signal. , has a determining means for determining the transmitting side and the receiving side from the signals exchanged between the respective data terminal means, and selects a master clock or a slave clock from the clock selecting means according to the determination result of the determining means, An interface conversion means is provided to provide this clock as a timing signal to the pig terminal equipment of the ground station on the transmitting side and the receiving side.

(Function) As a result, according to the present invention, it is determined from the signals exchanged between the respective data terminal means whether the ground station is the transmitting side or the receiving side, and the master clock or slave clock is automatically set based on the result of this determination. Since this clock is used to perform the master and slave operations of each ground station, even if the network side cannot perform the mask operation, a clock corresponding to the master and slave operations of each ground station can be secured. , This allows stable data transmission to be performed.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration of the same embodiment. In the figure, 1 is the ground station, and this ground station] is #1, #2,
.

In this case, the data terminal device 1 in the local station 1 is equipped with a CCITT Recommendation .

Further, the ground station satellite unit 13 complies with CCrTT Recommendation V, 35 or CCITT Recommendation V, 28/V.

It has 24 interfaces.

Here, prior to data transmission, each ground station 1 transmits a control signal C at the rHJ level from the originating side to the destination ground station 1, as shown in FIG. While the signal I' is set to rHJ level, this display signal 1
', the control signal C' is set to the rHJ level, and further,
By transmitting this control signal C- to the originating ground station 1 and setting the display signal I of this originating ground station to the rHJ level, subsequent data transmission is enabled.

FIG. 2 shows the circuit configuration of the interface conversion section 12.

In this case, the control signal C sent from the data terminal device 11 to the communication satellite 2 side is given to the delay circuit [2],
The signal is sent to the communication satellite 2 after a predetermined time delay. In other words, the control signal C changes its rHJ level output to
The signal is transmitted to the communication satellite 2 after a predetermined time delay required for the entire system to stabilize.

Further, this control signal C is given to the latch circuit 122, and is also applied to the AND circuit 12 via the inverter 123.
4 is applied to one of the input terminals.

On the other hand, the display signal I given from the communication satellite 2 to the data terminal device 11 is transmitted to the latch circuit 1 via the inverter 125.
22 and the other input terminal of the AND circuit 124.

The latch circuit 122 outputs the rHJ level when the control signal C is at the rHJ level and the display signal I is at the rLJ level,
When the control signal C is at rLJ level and the display signal I is at rHJ level, "L" level is output.

Then, the output of this latch circuit 122 is transmitted to the selection circuit 12.
Sent to 6. This selection circuit 126 selects either the master clock MC or the slave clock SC.
When a level output is given, the master clock MC is selected, and when an "L" level output is given from the latch circuit 22, the slave clock SC is selected.

In this case, the master clock MC consists of a clock with a predetermined timing necessary for the mask operation, and is connected to the CCITT Recommendation X, 21 interface and CCITT Recommendation V, 35 or CCITT Recommendation
, 28/V.

The signal is sent as a timing signal TM to the ground station 1 on the receiving side, which operates as a slave, via the ground station satellite section 13 having an X.24 interface. Further, the slave clock SC is the master clock MC of the originating ground station 1 which is operated as a master via the communication satellite 2 side.

The output of AND circuit 124 is sent to monopulse generator 127. This single pulse generator 127 is connected to the AND circuit 12
When the "H" level is output from 4, the rH level remains for a predetermined period of time.
J level is output, and the output of the latch circuit 122 is made to be at the rLJ level in the initial state.

Next, the operation of the embodiment configured as above will be explained.

Now, a case where data transmission is performed from #1 ground station 1 to #2 ground station], #1 ground station 1 operates as master, and #2 ground station 1 operates as slave will be described.

In this case, in the standby state, neither the #1 ground station 1 nor the #2 ground station 1 outputs the control signal C and the display signal I.

From this state, in order to transmit data from #1 ground station 1 to #2 ground station 1, first, prior to data transmission,
As shown in FIG. 3(a), the #1 ground station 1 on the transmitting side outputs a control signal C at the rHJ level, and this control signal C is sent to the communication satellite 2 via the delay circuit 121.
It is transmitted to #2 ground station 1 on the receiving side.

When the #2 ground station on the receiving side receives the control signal C from the #1 ground station 1, the display signal I' becomes rHJ level as shown in (d) of the same figure, and the display signal I- is In response, the control signal C' is rHJ as shown in the same figure (C).
level, and this control signal C' is returned to the #1 ground station 1 on the transmitting side via the communication satellite 2.

Then, at the #] ground station 1 on the originating side, the display signal becomes the level ■ or rHJ, as shown in FIG. 3(b), and data transmission becomes possible.

In this case, in the exchange of these signals, the interface converter 12 of the #1 ground station 1 on the originating side
In the first part until data transmission starts as shown in FIGS. (a) and (b), the control signal C at the rHJ level and the display signal I at the rLJ level are given to the latch circuit 122. An output of the rHJ level is generated, and the output is sent to the selection circuit 126.

As a result, the selection circuit 126 selects the master clock MC.
This master clock MC is given as a timing signal TM to the CCITT Recommendation X, 21 interface of the data terminal equipment 11, and at the same time
Recommendation V, Recommended Floor or CCITT Recommendation V, Recommended Floor V, 24
It is also sent as a timing signal TM to the #2 ground station 1 on the receiving side via the communication system N2 having an interface.

On the other hand, in the interface converter 12 of #2 ground station 1 on the receiving side, the control signal
Since the display signal I at the rHJ level is given to the latch circuit 122, an output at the rLJ level is generated from the latch circuit 122, and this output causes the selection circuit 126 to select the master clock MC from the originating side #] ground station 1. is selected as the slave clock SC, and this slave clock SC is sent to the own data terminal device ]1 as a timing signal TM.

As a result, the originating side #1 ground station 1 will be operated as a master, and the receiving side #2 ground station 1 will be operated as a slave, and data transmission between these ground stations #1 and #2 will be performed as a master. This will be executed via the communication satellite 2 in synchronization with the clock MC.

After that, data transmission from #1 ground station 1 to #2 ground station 1 is completed, and control signal C and display signal I are both r
When the LJ level is reached, the output of the AND circuit]24 becomes rHJ.
level and is sent to the monopulse generator 127. Then, this single pulse generator 127 generates r for a predetermined time.
Since an HJ level output is generated, the latch circuit 122
The output becomes the rLJ level of the initial state, and the initial state is restored.

Note that in the above case, in the case of data transmission from #1 ground station 1 to #2 ground station, #] ground station 1 operates as the master, and #2
Although the case where the ground station 1 is operated as a slave has been described, when data is transmitted from the #2 ground station 1 to the #1 ground station 1, the same operation as described above can be performed. In this case, the #2 ground station] operates as a master, and the #1 ground station 1 operates as a slave. Of course, the present invention can be similarly implemented using combinations other than these ground stations 1.

Therefore, if this is done, the control signal C is sent from the originating ground station 1 to the receiving ground station 1 before the data is transmitted between the ground stations, and the display signal I' of the receiving ground station 1 is transmitted. At the same time, the control signal C- is raised in response to the display signal ■', and this control signal C' is sent to the originating ground station 1, and the display signal I is raised and the data transmission is enabled. , detects the rising edge of display signal 1 after control signal C, selects master clock MC, sends this as a timing signal to data terminal device 1 of own station and destination ground station 1, and also detects the rise of display signal I. Later, when the rising edge of the control signal C is detected, the master clock from the originating ground station is selected as the slave clock SC, and this is sent as a timing signal to the data terminal equipment 11 of the own station, so that the master clock from the network side or the master Even when the terminal cannot operate, the master operation and slave operation of each terrestrial station can be set appropriately, and data transmission in this state can be performed stably.

Note that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications within the scope without changing the gist.

For example, in the above-described embodiment, the master black tsuta is output by mastering the three rounds of the land set on the calling side, but by mastering the three rounds of the land set on the receiving side, The present invention is also applicable to a configuration in which a master crotter is output.

[Effects of the Invention] The multiple communication satellite system of the present invention includes a ground station and a communication satellite forming a data transmission path between these ground stations,
Data transmission between each ground station is performed through data terminal means having an interface that drives both transmission data and reception data with one timing signal,
Prior to data transmission, each ground station uses a determining means to determine the originating side and receiving side based on the signals exchanged between the respective data terminal means, and also uses a clock selecting means to determine the master clock according to the determination result of this determining means. Since the system is equipped with an interface conversion means that selects a clock or a slave clock and supplies this clock as a timing signal to the data terminal equipment of the transmitting and receiving ground stations, each ground station The master clock or slave clock is automatically set to the data terminal equipment of the originating and receiving ground stations based on the results of the originating and receiving sides determined from the signals exchanged between the respective data terminal means. It is now possible to supply a timing signal (1), and even if the network side cannot operate as a master, it is possible to secure a clock that corresponds to the master operation and slave operation of each ground station, thereby ensuring stable data transmission. can be executed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the circuit configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing the circuit configuration of an interface converter used in the embodiment, and FIG. 3 is a block diagram showing the circuit configuration of an interface converter used in the embodiment. The flowchart for explaining the operation, FIG. 4, is as follows:
FIG. 1 is a configuration diagram for explaining a conventional communication satellite system. 1... Ground station, 11... Data terminal device, 12...
・Yelon Turf Ace Conversion Department, 13...Ground Station Satellite Department, ]2
1...Delay circuit, 122...Latch circuit, 124
...AND circuit, 126...Selection circuit, 127...
・Single pulse generator, 2...Communication satellite. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] It has a plurality of ground stations and a communication satellite that forms a data transmission path between these ground stations, and each ground station is connected to each ground station via a data terminal means that has an interface that drives both transmitted data and received data with one timing signal. In a satellite communication system in which data is transmitted between An interface having a clock selection means for selecting a master clock or a slave clock according to the determination result of the transmitting side and the receiving side by the means, and transmitting this clock as a timing signal to the data terminal equipment of the transmitting side and receiving side ground station. A satellite communication system characterized by comprising conversion means.