JPH04185122A - Satellite communication system - Google Patents

Abstract

PURPOSE:To reduce the access time at the assignment of an individual line channel by implementing transmission reception of a control signal in at common line channel between a line exchange system MODEM device and a common line MODEM device installed in a central control station not via a satellite at an intermediate frequency level. CONSTITUTION:So long as a data terminal equipment(DTE) 3 connecting to a line exchange system MODEM device 4a does not make a call, the line exchange system MODEM device 4a is in standby while being synchronously with the common line channel in common use for the network. During the standby state and till the DTE 3 makes a call and the individual channel is assigned from a satellite line control circuit 1, the transmission reception of a control signal in a common line channel between the line exchange system MODEM device 4a and a common line MODEM device 2a installed in a central control station is implemented not via a satellite at an intermediate frequency level. Thus, a delay in the satellite in the transmission reception of the control signals 101, 102 is eliminated. Thus, after a call takes place in the DTE 3 connecting to the line exchange system MODEM device 4a till the communication is started in the individual line channel, the access time is reduced.

Description

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

The present invention is particularly applied to the system configuration of the central control station.

〔overview〕

The present invention provides a satellite communication system equipped with a centralized control station including a common line modem and a circuit-switched modem, in which a common line channel control signal is transmitted and received between the common line modem and the line-switched modem. By transmitting and receiving modulated signals directly without going through a satellite, access time during call origination and call reception is shortened.

[Conventional technology]

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

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

It is composed of a central control station 20 and a plurality of VSAT stations (microsatellite communication ground stations) 30, and the central control station 20 is connected to a satellite line control device 21 and the satellite line control device 21, and modulates and demodulates a common line signal. The VSAT station 30 includes a common line modem 22, a line switching modem 24 that is connected to a data terminal equipment (hereinafter referred to as DTE) 23 and modulates and demodulates individual line signals, and a combiner/distributor 25. A switching indoor device 31, a circuit switching outdoor device 32, and a DTE
Contains 33.

The operation of this satellite communication system is based on the connection method SCP C.
(Single Channel per Carri
Since the demand assignment method is based on
Also, the VSAT station 300 circuit-switched indoor device 32 is synchronized with the network network common channel 41 while on standby, and when a call occurs, it sends a channel allocation request to the common channel modem 22 of the central control station 20. , the satellite line control device 21 transmits the following information to the line-switched modem (or line-switched indoor device) of the station where the call occurred and the line-switched modem (or line-switched indoor device) of the communication partner station. One set of individual line channels 42 pooled in advance is allocated. Then, the calling station and the communication partner station perform transmission and reception using the assigned individual line channel 42.

When the call ends, both the calling station and the communicating party stand by in synchronization with the common line channel 41 that is shared by the network.

FIG. 3 is a block diagram showing an example of the centralized control station 20 in FIG. Common line signals 101 and 102
a satellite line control device 1 that outputs a signal, and a common line signal 101
a common line modulator/demodulator 2 which manually outputs a modulated signal 103 while demodulating a received signal 104 from a distributor 8 and outputs a common line signal 102; and a DTE 3 which inputs and outputs individual line signals 105 and 106. , a circuit-switched modulation/demodulation device 4 which manually inputs the individual line signal 105 and outputs a modulated signal 107, demodulates the received signal 108 from the distributor 8 and outputs the individual line signal 106, and modulates the modulated signal 103. signal 1
07, combines both signals and outputs the modulated signal 113 to the antenna, and a distributor 8 divides the received signal 114 from the antenna into the received signal 104 and the received signal 108 and outputs the signals. Contains.

As is clear from FIG. 3, when a call is made from the DTE 3 connected to the line-switched modem 4, a control signal is sent between the common line modem 2 connected to the satellite line controller 1 and the line-switched modem 4. After transmission and reception are carried out several times via the satellite, a separate line channel is assigned to the circuit-switched modem 4 that made the call and the circuit-switched indoor device of the communication partner station, and the calling station and the communication partner station are assigned Transmission and reception are performed using the dedicated dedicated line channel.

[Problem to be solved by the invention]

In the conventional satellite communication system described above, when a call is made from a circuit-switched modem installed in a central control station or a call is received at a circuit-switched modem, the circuit-switched modem and the common line modem are connected to each other. Even though control signals are sent and received on the common line channel between VSAT stations within the same central control station, the access time until the line is connected is the same as when calls are made and received between VSAT stations. It has the disadvantage that it takes a long time, almost the same as the access time when accessing.

An object of the present invention is to reduce the access time when a call occurs at a circuit-switched modem installed in a central control station or when a call arrives at the same modem by eliminating the above-mentioned drawbacks. The purpose is to provide a satellite communication system that can shorten the time required.

[Means to solve the problem]

The present invention includes a satellite line control device, a common line modulation/demodulation device connected to the satellite line control device that modulates and demodulates a common line signal, a data terminal device, and a common line modulation/demodulation device that is connected to the data terminal device and modulates and demodulates individual line signals. a circuit-switched modulation/demodulator that outputs switching signals of different levels depending on whether the channel is a common line channel or an individual line channel; In a satellite communication system equipped with a centralized control station including a first combiner that combines and transmits, and a first distributor that distributes received signals to the common line modem and the line switched modem, When the current channel is a common line channel, the centralized control station transmits a modulated signal of a control signal of the common line channel directly between the common line modem and the circuit switched modem without going through a satellite. The line-switched modulation/demodulator includes means for directly transmitting and receiving control signals for transmitting and receiving control signals to and from the network, and the line-switched modem apparatus includes means for outputting switching signals of different levels depending on whether the current channel is a common line channel or an individual line channel. .

Further, in the present invention, the control signal direct transmitting/receiving means includes a second combiner, a second distributor, a first switch, and a second switch, and the second distributor is connected to the common line. The modulated signal from the modem is distributed to the first combiner and the second switch, and the first switch distributes the modulated signal from the circuit switched modem to the first combiner in accordance with the switching signal. or the second combiner, and the second combiner outputs the received signal from the first distributor and the modulated signal from the first switch. The synthesized signal is combined and output to the common line modulation/demodulation device, and 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 signal may be configured to be output to the line-switched modulation/demodulation device.

Further, in the present invention, it is preferable that the communication method is a demand assignment method.

[Effect]

The control signal direct transmitting/receiving means uses a switching signal output from the circuit-switched modem when a call occurs at the circuit-switched modem or when a call arrives at the circuit-switched modem. The modulated signal is transmitted and received directly between the common line modem and the line-switched modem without going through the satellite.

Therefore, it is possible to shorten the access time when allocating individual line channels.

Further, the control signal direct transmitting/receiving means can be easily realized by, for example, one combiner and distributor and two switchers that distribute, combine, and switch modulated signals.

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

〔Example〕

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

1st TI! J is a block diagram showing a main part of an embodiment of the present invention, and shows a centralized control station.

This embodiment monitors the operating status of the circuit-switched modem and the circuit-switched indoor equipment of the VSAT station, which are on standby in synchronization with the common line channel, and also monitors the operating status of the circuit-switched indoor equipment of the VSAT station. A satellite line control device 1 is connected to the satellite line control device 1 that performs line control to allocate one set of line channels, and is connected to the satellite line control device 1, and modulates a control signal 101 from the device and outputs a modulated signal 103. A common line modulator/demodulator 2 demodulates a received signal 104 and outputs a control signal 102 to the satellite line controller 1; a DTE 3 such as a telephone or computer; While outputting 107,
Demodulates the input received signal 108 and converts it into an individual line signal 106
At the same time as outputting the signal to the DTE 3, the circuit switching modem 4a changes the level of the switching signal 117 depending on whether the current channel is a common line channel or an individual line channel, and the modulation signal 103 from the common line modem 2 is manually input. A distributor 5 that divides and outputs the modulated signal 109 and the modulated signal 110, and a circuit switching system converter (the modulated signal 10 from the JJ modulator 4)
7 to modulated signal 1 in response to switching signal 117 from the same device.
The modulated signal 109 from the distributor 5 and the modulated signal 111 from the switch 6 are input to a switch 6 that switches whether to output the signal 12 or the modulated signal 111, and the two signals are combined and sent to the satellite line. a synthesizer 7 that outputs a modulated signal 113;
The received signal 114 from the satellite line is manually processed and the received signal 11
5 and the received signal 116 and output the divided signals;
A synthesizer 9 that manually combines the modulated signal 112 from the switch 6 and the received signal 115 from the distributor 8, and outputs the received signal 104 to the common line modulation/demodulation device 2, and the circuit switching system modulation/demodulation device 4a. The modulated signal 110 from the distributor 5 or the received signal 1 from the distributor 8 in response to the switching signal 117 from the
16 and outputs the selected signal as a received signal 108 to the line-switched modulation/demodulation device 4a.

A feature of the present invention is that, in FIG. 1, when individual line channels are allocated, the common line modem 2 and the line switched modem 4a directly transmit and receive modulated signals of the control signal of the common line channel. A second combiner 9, a second distributor 5, and a first switch 6 as signal transmitting/receiving means
, and a second switching device 10, and the circuit switching modem 4a includes means (not shown) for outputting switching signals 117 of different levels depending on whether the current channel is a common line channel or an individual line channel. It is in.

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

Since the line connection of the satellite communication system of this embodiment is based on a demand assignment method, unless the DTE 3 connected to the line-switched modem 4a makes a call, the line-switched modem 4a connects to the common line channel shared by the network. Waiting in sync. In this way, the circuit switched modem 4a
When the channel is a common line channel, the switching device 6 is controlled by the switching signal 117 from the same device to output the modulated signal 107 from the line-switched modulation/demodulation device 4a to the combiner 9 as the modulated signal 112. Similarly, the switch 10 is controlled to select the modulated signal 110 from the distributor 5 and output it as the received signal 108 to the line-switched modem 4a.

That is, while on standby and until the DTE 3 makes a call and a dedicated line channel is assigned from the satellite line control device 1,
As shown in FIG. 2, control signals are exchanged on the common line channel between the line switching modem 4a and the common line modem 2 at an intermediate frequency level without going through a satellite.

Therefore, the conventional satellite delay in sending and receiving control signals 101 and 102 is eliminated, and the access time from when a call is generated at the DTE 3 connected to the circuit-switched modem 4a to when communication starts on the individual line channel is shortened. becomes possible.

On the other hand, from the satellite line control device 1 to the line switching modem 4
After the individual line channel is assigned to a, the switch 6 switches to send the modulated signal 107 from the line-switched modem 4a to the combiner 7, and similarly, the switch 10 switches to the divider. The received signal 116 from 8 is selected and outputted as the received signal 108 to the line-switched modulation/demodulation device 4a.

In other words, after the dedicated channel is allocated, the third
The configuration is the same as that of the conventional satellite communication system shown in the figure, and the line-switched modulation/demodulator 4a communicates with the line-switched indoor device of the communication partner station via the satellite.

〔Effect of the invention〕

As explained above, the present invention enables transmission and reception of control signals on a common line channel between a line-switched modem and a common line modem installed in a central control station at an intermediate frequency level without going through a satellite. This has the effect of shortening the access time when a call is generated at a circuit-switched modem installed in a central control station or when a call is received at the same modem.

Furthermore, since it is not affected by rain attenuation or thermal noise on the transmission path, it is possible to improve reliability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the operation signal path. FIG. 3 is a block diagram showing the main parts of a conventional example. FIG. 4 is a block diagram showing an example of a conventional satellite communication system using the demand assignment method. 1.21...Satellite line control device, 2.22...Common line modulation/demodulation device, 3.23.33...Data terminal equipment (DTE), 4.4a, 24...Line switching modem/demodulation device , 5.8...Distributor, 6.10...Switcher, 7.
9... Combiner, 20... Central control station, 25... Combiner/distributor, 30... VSAT station, 31... Circuit switching outdoor device, 32... Circuit switching indoor device , 41・
...Common line channel, 42...Individual line channel, 10
1.102 =・control n signal, 105.106−[! 11
Signal, 103.107.109.110-113...
Modulation signal, 104.108.114-116... Received signal, 117... Switching signal.

Claims (1)

[Claims] 1. A satellite line control device, a common line modulation/demodulation device connected to the satellite line control device for modulating and demodulating a common line signal, a data terminal device, and a common line modulation/demodulation device connected to the data terminal device for modulating and demodulating a common line signal. a circuit-switched modem that modulates and demodulates and outputs switching signals of different levels depending on whether the current channel is a common line channel or an individual line channel; A satellite equipped with a centralized control station including a first combiner that combines and transmits a modulated signal, and a first distributor that distributes a received signal to the common line modem and the line switched modem. In the communication system, when the current channel is a common line channel, the central control station transmits a modulated signal of a control signal of a common line channel between the common line modem and the circuit-switched modem via a satellite. the circuit-switched modem device includes means for outputting switching signals of different levels depending on whether the current channel is a common line channel or an individual line channel; A satellite communication system featuring: 2. The control signal direct transmission/reception means includes a second combiner, a second distributor, a first switch, and a second switch, and the second distributor receives signals from the common line modulation/demodulation device. The modulated signal is distributed to the first combiner and the second switch, and the first switch distributes the modulated signal from the circuit-switched modem to the first combiner according to the switching signal. The second combiner combines the received signal from the first distributor and the modulated signal from the first switch, and outputs the signal to the second combiner. and 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, and the second switch switches between the received signal from the first distributor and the modulated signal from the second distributor. The satellite communication system according to claim 1, wherein the satellite communication system is configured to output to a modulation/demodulation device. 3. The satellite communication system according to claim 1 or 2, wherein the communication method is a demand assignment method.