JP2946744B2 - Satellite communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used for a satellite communication system to which a demand assignment system is applied.

The present invention is used particularly for the system configuration of the central control station.

〔Overview〕

The present invention relates to a satellite communication system provided with a centralized control station including a common line modem and a circuit-switched modem, wherein a control signal of a common channel is transmitted and received between the common line modem and the circuit-switched modem. Is performed directly by transmitting and receiving a modulated signal without passing through a satellite, thereby shortening the access time at the time of calling and receiving a call.

[Conventional technology]

First, an outline of a satellite communication system to which the demand assignment method is applied will be described below.

FIG. 4 is a block diagram showing a main part of a conventional satellite communication system using a demand assignment system.

The central control station 20 is composed of a central control station 20 and a plurality of VSAT stations (micro satellite communication ground stations) 30. The central control station 20 is connected to the satellite line control device 21 and modulates and demodulates a common line signal. The VSAT station 30 includes a common line modulation / demodulation device 22, a line switching modulation / demodulation device 24 connected to a data terminal device (hereinafter referred to as DTE) 23 for modulating and demodulating an individual line signal, and a coupler distributor 25. It includes a switching indoor unit 31, a circuit switching outdoor unit 32, and a DTE 33.

In the operation of this satellite communication system, the connection method is SCPC (Si
Since the demand assignment method is based on the channel assignment, the circuit switching modem 24 installed in the centralized control station 20 and the circuit switching indoor unit 32 of the VSAT station 30 are both on standby while the network is shared. When a call is generated, a channel assignment request is issued to the common line modem 22 of the central control station 20 and the satellite line controller 21
Were pooled in advance for the circuit-switching modem (or circuit-switching indoor unit) of the station where the call originated and the circuit-switching modem (or circuit-switching indoor unit) of the communication partner station. One set of dedicated channel 42 is assigned. Then, the calling station and the communication partner station perform transmission / reception using the assigned individual channel 42. When the call is over, both the calling station and the communicating station wait again in synchronization with the common channel 41 shared by the network.

FIG. 3 is a block diagram showing an example of the centralized control station 20 in FIG. A satellite channel control device 1 for inputting / outputting common line signals 101 and 102; a common line signal 101 being input and a modulation signal 103 being output;
A common line modem 2 that demodulates 04 and outputs a common line signal 102, and a DTE 3 that inputs and outputs individual line signals 105 and 106
While receiving the individual line signal 105 and outputting the modulated signal 107, while demodulating the received signal 108 from the distributor 8 to obtain the individual line signal 1
A circuit switching modulator / demodulator 4 that outputs 06 and a modulated signal 103
And the modulation signal 107, and combine the two signals to obtain the modulation signal 1
13 includes a combiner 7 for outputting to the antenna and a distributor 8 for distributing the received signal 114 from the antenna into the received signal 104 and the received signal 108 and outputting the received signal.

As is clear from FIG.
When a call is made from DTE3 that leads to
After a control signal has been exchanged between the common line modem 2 and the line switching modem 4 several times via a satellite, the call is transmitted to the line between the line switching modem 4 and the communication partner station. An individual line channel is assigned to the switching indoor unit, and the calling station and the communication partner station transmit and receive using the assigned individual line channel.

[Problems to be solved by the invention]

The above-mentioned conventional satellite communication system includes a circuit-switching modem and a common-line modem when calling from a circuit-switching modem installed in a central control station or receiving a call to the circuit-switching modem. Transmission and reception of control signals on the common line channel between the VSAT stations are performed via satellites even though they are in the same centralized control station. There was a drawback that it took a long time, almost irrespective of the access time.

The object of the present invention is to eliminate the disadvantages mentioned above,
It is an object of the present invention to provide a satellite communication system capable of shortening an access time when a call is generated by a circuit switching modulation / demodulation device installed in a central control station or when a call is received by the modulation / demodulation device.

[Means for solving the problem]

The present invention relates to a satellite channel controller, a common channel modulator / demodulator connected to the satellite channel controller for modulating and demodulating a common channel signal, a data terminal device, and a modem connected to the data terminal device for modulating and demodulating an individual channel signal. A switching circuit for outputting a switching signal of a different level depending on whether the channel is a common line channel or an individual line channel, a modulation signal from the common line modulation and demodulation device and a modulation signal from the circuit switching system In a satellite communication system including a centralized control station including a first combiner for combining and transmitting, and a first distributor for distributing a received signal to the common line modem and the line conversion system modem, The central control station, when the current channel is a common channel, sets a common channel between the common channel modem and the circuit switching modem. The modulated signal of control signal comprises a control signal directly transmitting and receiving means for transmitting and receiving directly without going through the satellite,
The circuit-switching modulation / demodulation device includes means for outputting a switching signal of a different level depending on whether a current channel is a common channel or an individual channel.

Also, in the present invention, the control signal direct transmission / reception means includes a second combiner, a second distributor, a first switch, and a second switch, wherein the second distributor is connected to the common line. The modulation signal from the modem is distributed to the first combiner and the second switch, and the first switch converts the modulation signal from the circuit-switched modem into and out of the first switch according to the switch signal. Switching between outputting to the combiner or outputting to the second combiner, the second combiner converts the received signal from the first distributor and the modulation signal from the first switcher. Combined and output to the common line modem, the second switch switches between the received signal from the first distributor and the modulated signal from the second distributor according to the switching signal. The output may be configured to output to the circuit-switching modem.

In the present invention, it is preferable that the communication system is a demand assignment system.

[Action]

The control signal direct transmission / reception means uses a switching signal output from the circuit-switched modulation / demodulation device when a call is generated by the circuit-switched modulation / demodulation device or when a call is received to the same modulation / demodulation device. The control signal is directly transmitted and received between the common line modem and the circuit switching modem without passing through the satellite.

Therefore, it is possible to shorten the access time when the dedicated channel is allocated.

Further, the control signal direct transmission / reception means can be easily realized by, for example, one combiner and distributor for performing distribution, synthesis, and switching of the modulation signal, and two switchers.

Further, the present invention is applied to a demand assignment type satellite communication system.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a main part of an embodiment of the present invention, showing a central control station.

The present embodiment monitors the operation state of a circuit-switching modem and a circuit-switching indoor unit of a VSAT station that is waiting in synchronization with a common channel, and individually pools in advance when a call occurs. A satellite channel controller 1 that performs channel control for allocating one set of channel channels, and a satellite channel controller 1 that is connected to the satellite channel controller 1 and modulates a control signal 101 from the device to output a modulated signal 103; Received signal 1
A common line modulator / demodulator 2 that demodulates the 04 and outputs a control signal 102 to the satellite line controller 1, a DTE3 such as a telephone or a computer, and modulates an individual line signal 105 connected to the DTE3 and outputs a modulated signal 107 On the other hand, a circuit switching modulation / demodulation device that demodulates an input received signal 108 and outputs an individual line signal 106 to DTE3 and simultaneously changes the level of a switching signal 117 depending on whether the current channel is a common line channel or an individual line channel. 4a
, A modulator 5 which receives the modulated signal 103 from the common line modem 2, distributes the modulated signal 103 and the modulated signal 110, and outputs the modulated signal 103 and the modulated signal 110;
A switch 6 for switching between outputting a modulation signal 112 or outputting a modulation signal 111 in response to a switching signal 117 from the same device, a modulation signal 109 from the distributor 5 and a modulation signal 111 from the switch 6. And a combiner 7 that combines the two signals to output a modulated signal 113 to the satellite link, and a received signal 114 from the satellite link, and distributes and outputs the received signal 115 and the received signal 116. The distributor 8 and the modulation signal 112 from the switch 6
And a receiving signal 115 from the distributor 8, combine the two signals, and output the received signal 104 to the common line modem 2. A switching signal 117 from the circuit switching modem 4a
And a distributor 10 for selecting either the modulated signal 110 from the distributor 5 or the received signal 116 from the distributor 8 and outputting it as a received signal 108 to the circuit-switching modem 4a. .

A feature of the present invention is that, in FIG. 1, when a dedicated channel is allocated, a control for directly transmitting and receiving a modulation signal of a control signal of a common channel between the common channel modem 2 and the circuit switching modem 4a is performed. The circuit switching modem 4a includes a second combiner 9, a second distributor 5, a first switch 6, and a second switch 10 as signal transmission / reception means. This is to include means (not shown) that outputs a switching signal 117 of a different level depending on whether the channel is an individual channel or an individual channel.

Next, the operation of this embodiment will be described with reference to the operation signal path diagram shown in FIG.

Since the line connection of the satellite communication system of the present embodiment is a demand assignment system, unless the DTE 3 connected to the line switching modem 4a originates a call, the line switching modem 4a
Are waiting in synchronization with the common channel shared by the network. As described above, when the channel of the line switching modem 4a is a common channel, the switching signal
The switch 6 is controlled by the switch 117 so as to output the modulation signal 107 from the circuit switching modem 4a to the synthesizer 9 as a modulation signal 112. Similarly, the switch 10 controls the modulation signal from the distributor 5 It is controlled so that 110 is selected and output as a received signal 108 to the circuit switching modem 4a.

In other words, as shown in FIG. 2, the common path between the line switching modem 4a and the common line modem 2 is on standby and before the DTE 3 calls and the satellite channel controller 1 allocates an individual channel. The transmission and reception of the control signal in the line channel is performed at the intermediate frequency level without passing through the satellite.

Therefore, the conventional satellite delay in the transmission and reception of the control signals 101 and 102 is eliminated, and the access time from when a call is generated in the DTE 3 connected to the circuit switching modem 4a to when communication is started on the individual line channel is reduced. Becomes possible.

On the other hand, from the satellite link controller 1 to the circuit switching modem
After the individual line channel is allocated to 4a, the switch 6 converts the modulated signal 107 from the circuit switching modem 4a to the combiner 7a.
To be output to the
Is switched so that the received signal 116 from the distributor 8 is selected and output as the received signal 108 to the circuit-switching modem 4a.

That is, after the individual channel is allocated, the configuration becomes the same as that of the conventional satellite communication system of FIG. 3, and the circuit switching modem 4a communicates with the circuit switching indoor unit of the communication partner station via the satellite. Do.

〔The invention's effect〕

As described above, according to the present invention, the transmission and reception of a control signal on a common channel between a circuit switching modem and a common line modem installed in a centralized control station are performed at intermediate frequency levels without passing through a satellite. This has the effect of shortening the access time when a call is generated by the circuit-switching modem installed in the central control station or when a call is received to the modem.

Further, since there is no influence of rain attenuation and thermal noise on the transmission line, reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of one embodiment of the present invention. FIG. 2 is an explanatory diagram showing the operation signal path. FIG. 3 is a block diagram showing a main part of a conventional example. FIG. 4 is a block diagram showing an example of a conventional satellite communication system using a demand assignment system. 1, 21 ... satellite line control device, 2, 22 ... common line modem, 3, 23, 33 ... data terminal device (DTE), 4, 4
a, 24 ... circuit switching modem, 5, 8 ... distributor,
6, 10 switcher, 7, 9 synthesizer, 20 central control station, 25 coupler distributor, 30 VSAT station, 31 circuit-switching outdoor equipment, 32 line Switching indoor unit, 41: common line channel, 42: individual line channel, 101, 102: control signal, 105, 106 ... individual line signal: 103, 107, 109, 110-
113: Modulated signal, 104, 108, 114 to 116: Received signal, 1
17 ... Switch signal.

Claims (3)

(57) [Claims] 1. A satellite channel controller, a common channel modulator / demodulator connected to the satellite channel controller and modulating / demodulating a common line signal, a data terminal device, and a modem connected / disconnected to the data terminal device for modulating and demodulating an individual line signal. A circuit-switched modulation / demodulation device that outputs a switching signal of a different level depending on whether the current channel is a common line channel or an individual line channel, a modulation signal from the common line modulation / demodulation device, and a modulation signal from the circuit-switched modulation / demodulation device. In a satellite communication system provided with a centralized control station including a first combiner that combines and transmits a received signal, and a first distributor that distributes a received signal to the common line modem and the line conversion system modem. The central control station, when the current channel is a common channel, sets a common channel between the common channel modem and the circuit-switched modem. A control signal direct transmission / reception means for directly transmitting / receiving a modulation signal of the control signal without passing through a satellite, wherein the circuit-switching type modulator / demodulator has different levels depending on whether a current channel is a common channel or an individual channel. A satellite communication system, comprising: means for outputting a switching signal. 2. The control signal direct transmission / reception means includes a second combiner, a second distributor, a first switch, and a second switch, wherein the second distributor is the common line modem. A modulation signal from the device is distributed to the first combiner and the second switch, and the first switch converts the modulation signal from the circuit switching modulator / demodulator into the first signal according to the switch signal. Switching between outputting to a combiner or outputting to the second combiner, the second combiner combines the received signal from the first distributor and the modulated signal from the first switcher And output to the common line modem, the second switch switches between the received signal from the first distributor and the modulation signal from the second distributor according to the switching signal, 2. The satellite communication system according to claim 1, wherein the satellite communication system is configured to output the signal to a circuit switching system modem. . 3. The satellite communication system according to claim 1, wherein the communication system is a demand assignment system.