JP2946745B2 - 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. The access time is reduced when calling and receiving calls by making the calls directly without passing through a satellite.

[Conventional technology]

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

FIG. 5 is a block diagram showing a main part of a satellite communication system according to a conventional demand assignment system.

The central control station 50 includes a central control station 50 and a plurality of VSAT stations (micro satellite communication ground stations) 60. The central control station 50 is connected to the satellite channel control device 51 and modulates and demodulates a common line signal. The VSAT station 60 includes a common line modem 52, a circuit switching modem 54 connected to a data terminal device (hereinafter referred to as DTE) 53 for modulating and demodulating individual line signals, and a coupler distributor 55. It includes a switching indoor unit 61, a circuit switching outdoor unit 62, and a DTE 63.

In the operation of this satellite communication system, the connection method is SCPC (Si
Since it is a demand assignment system based on the Ngle Channel per Carrier, the circuit switching modem 54 installed in the centralized control station 50 and the circuit switching indoor device 62 of the VSAT station 60 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 52 of the central control station 50, and the satellite line controller 51
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 dedicated channel 72. When the call is over, both the calling station and the communication partner station wait again in synchronization with the common channel 71 shared by the network.

FIG. 4 is a block diagram showing an example of the central control station 50 in FIG. A satellite channel control device 1 for inputting / outputting common line signals 101 and 102, and receiving a common signal 101 and outputting a modulated signal 103 while receiving a received signal 1
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, and demodulating the received signal 108 from the distributor 6 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 6 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. The 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 is a disadvantage that it takes 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 and modulating / demodulating a common channel signal, a data terminal device, and a channel switching device connected to the data terminal device and modulating / demodulating an individual channel signal. System modulator / demodulator, a combiner for combining and transmitting a modulation signal from the common line modem and a modulation signal from the circuit switching system, and a reception signal for the common line modem and the line conversion system In a satellite communication system including a central control station including a distributor that distributes the central control station, the central control station includes:
When the current channel is a common channel, control signal direct transmission / reception means for directly transmitting / receiving a control signal of a common channel between the common channel modem and the circuit switching system modem without passing through a satellite. It is characterized by including.

Further, in the present invention, the control signal direct transmission / reception means includes a first control signal transmission / reception circuit provided in the common line modem and for transmitting / receiving a control signal of a common channel to / from the circuit switching system. A second control signal transmission / reception circuit provided in the circuit switching type modem and for transmitting / receiving a control signal of a common channel to / from the common channel modem when the current channel is a common channel. Can be.

In the present invention, the communication system is preferably a demand assignment system.

[Action]

The control signal direct transmission / reception means establishes a satellite between the common line modem and the circuit-switched modem when a call is generated by the circuit-switched modem or a call arrives at the modem. The control signal of the common channel is directly transmitted and received without passing through.

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 providing the first and second control signal transmission / reception circuits in the common line modem and the circuit switching system modem, respectively.

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 for performing channel control for allocating one set of line channels; a satellite signal controller 1 connected to the satellite channel controller 1 for modulating a control signal 101 from the device to output a modulated signal 103; 101 is output as it is as a control signal 109, and at the same time, a received signal 104 which is input is demodulated to output a control signal 102 to the satellite channel controller 1, and a control signal 110 is input and the control signal 1 is input as it is.
02, a common line modem 2a that outputs to the satellite line controller 1, a DTE3 such as a telephone or a computer, and an individual line signal 105 that is connected to the DTE3 and input from the DTE3 to output a modulated signal 107 , Demodulates an input received signal 108 and outputs an individual line signal 106 to DTE3, and at the same time, if the current channel is a common line channel,
2a, receives a control signal 109, and outputs a control signal 110 to the common line modem 2a.
4a, a combiner 5 that receives the modulation signal 103 from the common line modem 2a and the modulation signal 107 from the circuit switching modem 4a, combines the two signals, and outputs a modulation signal 111 to the satellite line; It includes a distributor 6 which receives a received signal 112 from a satellite line, distributes the received signal 112 to a received signal 104 and a received signal 108, and outputs the received signal to a common line modem 2a and a circuit switching modem 4a, respectively.

FIG. 2 is a block diagram showing an example of the common channel modem 2a of FIG.

The common line modem 2a includes a driver receiver circuit 21 for transmitting and receiving signals to and from the satellite line controller 1, a driver receiver circuit 22 for transmitting and receiving signals to and from the line switching modem 4a, a CPU 25, a CPU 25, and a driver. Receiver circuit 21
And serial control units 23 and 24 connected between the CPU 25 and the modulation and demodulation board 27, respectively, and a buffer circuit 26 connected between the CPU 25 and the modulation and demodulation board 27.

FIG. 3 is a block diagram showing an example of the circuit-switching modem 4a shown in FIG.

The line switching modem 4a includes a satellite line control panel 31 for controlling a satellite line, a driver receiver circuit 32 for transmitting and receiving signals to and from the DTE3, and a driver receiver circuit for transmitting and receiving signals to and from the satellite line control panel 31. And a driver receiver circuit 34 for transmitting and receiving signals to and from the common line modem 2a.
And the CPU 37, the CPU 37 and the driver receiver circuits 33 and 34
Between the serial control units 35 and 36, a modem 41, a MUXDMUX circuit 40 for transmitting and receiving signals to and from the modem 41, and a MUXDMUX circuit 40.
And buffer circuits 38 and 39 connected between the driver receiver circuit 32 and the CPU 37, respectively.

In FIGS. 2 and 3, a portion surrounded by a broken line is a portion newly added in this embodiment.

A feature of the present invention is that, in FIG. 1, FIG. 2 and FIG. 3, when the current channel is a common channel channel, the common channel channel is switched between the common channel modem 2a and the line switching modem 4a. As a control signal direct transmission / reception means for directly transmitting / receiving a control signal without passing through a satellite, the control signal is provided in the common line modem 2a, and transmits / receives a control signal of a common channel to / from the line switching modem 4a. A driver receiver circuit 22 and a serial control unit 24 as one control signal transmission / reception circuit;
When the current channel is a common channel, a driver receiver circuit 34 and a serial control unit 36 as a second control signal transmitting / receiving circuit for transmitting / receiving a control signal of the common channel to / from the common channel modem 2a are provided. And control by the CPU 25 and the CPU 37 respectively.

 Next, the operation of the present embodiment will be described.

As is clear from FIG. 2, the common channel modem 2a transmits the control signal 101 from the satellite channel controller 1 to the driver receiver circuit 21 and the serial control unit.
The data is once captured by the CPU 25 via the interface 23, and is again input to and output from the circuit switching modem 4a via the serial control unit 24 and the driver receiver circuit 22.

On the other hand, in the circuit switching modem 4a of FIG.
U37 receives information on whether the current channel is a common line channel or an individual line channel from the satellite line control panel 31 in the device via the driver receiver circuit 33 and the serial control unit 35, and the current channel is In the case of a line channel, while receiving the control signal 109 of the common line modem 2a via the driver receiver circuit 34 and the serial control unit 36, the control signal 110 is output to the common line modem 2a.

That is, the circuit-switched modem 4a is synchronized with the common channel shared by the network and waits while waiting.
Until E3 is called and the individual line channel is allocated from the satellite line controller 1, the transmission / reception of the control signal on the common line channel between the line switching modulator / demodulator 4a and the common line modulator / demodulator 2a is performed by the satellite. It will be done in baseband without going through.

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

On the other hand, after the individual channel is allocated, the configuration becomes the same as that of the conventional satellite communication system shown in FIG. 4, and the circuit-switching modem 4a communicates with the circuit-switching indoor unit of the communication partner station via the satellite. I do.

〔The invention's effect〕

As described above, according to the present invention, transmission and reception of control signals on a common channel between a circuit switching modem and a common line modem installed in a central control station are performed in baseband without passing through a satellite. By doing so, there is an effect that the access time when a call is generated by the circuit-switching modulation / demodulation device installed in the central control station or when a call is received to the modulation / demodulation device can be shortened.

Further, according to the present invention, the control signal for line setting is not affected by rain attenuation or thermal noise on the transmission line at all, so that it is possible to provide a satellite communication system with improved reliability. Since the baseband interface between the common line modem and the circuit switching modem can be connected in the form of a bus, no additional hardware is required when adding a circuit switching modem in the central control station. An economic satellite communication system can be provided, and the effect is great.

[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 a block diagram showing an example of the common line modem. FIG. 3 is a block diagram showing an example of the circuit switching type modem. FIG. 4 is a block diagram showing a main part of a conventional example. FIG. 5 is a block diagram showing an example of a conventional satellite communication system using a demand assignment system. 1, 51 ... satellite line control device, 2, 2a, 52 ... common line modem device, 3, 53, 63 ... data terminal device (DTE),
4, 4a, 54 circuit switching system modulator / demodulator, 5, 7 synthesizer, 6 distributor, 21, 22, 32 to 34 driver receiver circuit, 23, 24, 35, 36 serial Control unit, 25, 37 ... CPU, 26, 38, 39 ... buffer circuit, 2
7, 41: Modem panel, 40: MUXDMUX circuit, 50: Central control station, 55: Coupler distributor, 60: VSAT station, 61: Circuit switching outdoor equipment, 62: Circuit switching system Indoor equipment, 71: Common line channel, 72: Individual line channel, 101, 102, 10
9, 110 ... control signal, 103, 107, 111 ... modulation signal, 10
4, 108, 112: Received signal, 105, 106: Individual line signal.

Claims (3)

(57) [Claims] 1. A satellite line controller, a common line modulator / demodulator connected to the satellite line controller and modulating / demodulating a common line signal, a data terminal device, and a line connected to the data terminal device and modulating / demodulating an individual line signal. A switching system modem, a combiner for combining and transmitting a modulation signal from the common line modem and a modulation signal from the circuit switching system, and a received signal to the common line modem and the line conversion system. A satellite communication system including a centralized control station including a distributor for distributing the common channel to a device, wherein the centralized control station is configured such that, when a current channel is a common channel, the common channel modem and the circuit switching modem And a control signal direct transmission / reception means for directly transmitting / receiving a control signal of a common channel without passing through a satellite to / from the satellite communication system. 2. The control signal direct transmission / reception means includes: a first control signal transmission / reception circuit provided in the common line modulation / demodulation device for transmitting / receiving a control signal of a common channel to / from the line switching type modulation / demodulation device; A second control signal transmission / reception circuit provided in the circuit switching type modem and for transmitting / receiving a control signal of a common channel to / from the common channel modem when the current channel is a common channel. Item 2. A satellite communication system according to item 1. 3. The satellite communication system according to claim 1, wherein the communication system is a demand assignment system.