JPH04185121A - 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 a 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 a base band. CONSTITUTION:While a line exchange system MODEM device 4a is in standby synchronously with a common line channel for common use of a network and till a data terminal equipment(DTE) 3 makes a call and an individual line channel is assigned from a satellite line controller 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 a base band. Thus, a delay in the satellite in the transmission reception of the control signal 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 method for transmitting and receiving control signals on a common line channel between the common line modem and the circuit switched modem in a satellite communication system equipped with a centralized control station including a common line modem and a line switched modem. By doing this directly without going through a satellite, the access time for making and receiving calls 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. 5 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 50 and a plurality of VSAT stations (microsatellite communication ground stations) 60, and the central control station 50 is connected to a satellite line control device 51 and the satellite line control device 51 to modulate and demodulate common line signals. The vSAT station 60 includes a common line modem 52, a line switching modem 54 that is connected to a data terminal equipment (hereinafter referred to as DTE) 53 and modulates and demodulates individual line signals, and a combiner/distributor 55. A switched indoor device 61, a circuit switched outdoor device 62, and a DTE
63.

The operation of this satellite communication system is based on the connection method SCP C.
(Single Channel per Carri
Since it is a demand assignment method based on er), both the circuit switching modem 54 installed in the central control station 50 and the circuit switching indoor device 62 of the VSAT station 60 are synchronized to the common line channel 71 shared by the network during standby. When a call occurs, a channel allocation request is sent to the common channel modulation/demodulation device 52 of the central control station 50, and the satellite channel control device 5
1 is pooled in advance for the circuit-switched modem (or circuit-switched indoor device) of the station where the call occurred and the circuit-switched modem (or circuit-switched indoor device) of the communicating party. One set of individual line channels 42 is allocated. Then, the calling station and the communication partner station perform transmission and reception using the assigned individual line channel 72. When the call ends, both the calling station and the communicating party stand by in synchronization with the common line channel 71 that is shared by the network.

FIG. 4 is a block diagram showing an example of the centralized control station 50 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 modulation/demodulation device 2 which inputs a signal and outputs a modulated signal 103, and which demodulates a received signal 104 from a distributor 6 and outputs a common line signal 102;
06, and a line-switched modem 4 that inputs the individual line signal 105 and outputs the modulated signal 107, and demodulates the received signal 108 from the distributor 6 and outputs the individual line signal 106. , modulated signal 103 and modulated signal 1
07, combines both signals and outputs the modulated signal 113 to the antenna, and a distributor 6 that divides the received signal 114 from the antenna into a received signal 104 and a received signal 108 and outputs the signals. Contains.

As is clear from FIG. 4, when a call is made from the DTE 3 connected to the circuit switched modem 4, a control signal is sent between the common channel modem 2 connected to the satellite line control device 1 and the circuit switched modem 4. After transmission and reception are performed 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. Control signals are exchanged on the common line channel between VSAT stations via the satellite, even though they are located within the same central control station, so the access time until the line is connected is the same as when a call is made or 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 provides a satellite line control device, a common line modulation/demodulation device that is connected to the satellite line control device and modulates and demodulates a common line signal, a data terminal device, and a line exchange that is connected to the data terminal device and modulates and demodulates individual line signals. a system modulator/demodulator; a combiner that combines and transmits a modulated signal from the common line modulator/demodulator and a modulated signal from the circuit switched modulator/demodulator;
In a satellite communication system comprising a centralized control station including a distributor that distributes a received signal to the common channel modem and the circuit switched modem, the centralized control station is capable of transmitting signals when the current channel is a common channel. The present invention is characterized in that it includes control signal direct transmitting/receiving means for directly transmitting and receiving a control signal of a common channel between the common channel modulator and demodulator and the circuit switched modem and demodulator without going through a satellite.

Further, in the present invention, the control signal direct transmitting/receiving means comprises a first control signal transmitting/receiving circuit provided in the common line modem and transmitting/receiving the control signal of the common line channel to/from the line switched modem. , a second control signal transmitting/receiving circuit that is provided in the line-switched modem and transmits and receives a common line channel control signal to and from the common line modem when the current channel is a common line channel; I can do it.

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 transmits the satellite signal between the common line modem and the circuit switched modem when a call occurs at the line switched modem or a call arrives at the line switched modem. Transmission and reception of control signals on the common line channel is performed directly without going through the communication line.

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

Further, the direct control signal transmitting/receiving means can be easily realized by providing first and second control signal transmitting/receiving circuits in the common line modem and the line switching modem, respectively.

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.

FIG. 1 is a block diagram showing the main parts 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 a 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. 10
1 as is as a control signal 109, and at the same time demodulates the manually input received signal 104 and outputs the control signal 102 to the satellite line control device 1. Furthermore, the control signal 110 is inputted as it is and as the control signal 102 to the satellite line control device 1. common line modulation/demodulation device 2a that outputs to
A modulated signal 1 is obtained by modulating the individual line signal 105 manually input from
07, while demodulating the input received signal 108 and outputting the individual line signal 106 to the DTE 3. At the same time, if the current channel is a common channel channel, it receives a control signal 109 from the common channel modulation/demodulation device 2a, Furthermore, the circuit switching modem 4a outputs the control signal 110 to the common line modem 2a, the modulation signal 103 from the common line modem 2a and the modulation signal 107 from the line switching modem 4a are input, and both A synthesizer 5 that combines signals and outputs a modulated signal 111 to the satellite line, and a synthesizer 5 that inputs the received signal 112 from the satellite line and outputs the received signal 104 and the received signal 10.
8 and a distributor 6 for outputting to the common line modem 2a and the line switching modem 4a, respectively.

FIG. 2 is a block diagram showing an example of the common channel modulation/demodulation device 2a of FIG. 1.

The common line modem 2a includes a driver receiver circuit 21 that sends and receives signals to and from the satellite line control device 1, a driver receiver circuit 22 that sends and receives signals to and from the line switching modem 4a, and a CPU 25c! , serial control units 23 and 2 connected between the CPU 25 and the driver receiver circuits 21 and 22, respectively.
4, a modulation/demodulation board 27, and a buffer circuit 26 connected between the CPU 25 and the modulation/demodulation board 27.

FIG. 3 is a block diagram showing an example of the line-switched modem 4a of FIG. 1.

The line switching system modem 4a includes a satellite line control panel 31 that controls the satellite line, a driver receiver circuit 32 that sends and receives signals to and from the DTE3, and a driver receiver circuit that sends and receives signals to and from the satellite line control panel 31. 33, a driver receiver circuit 34 that transmits and receives signals with the common line modem 2a, a CPU 37, serial control units 35 and 36 connected between the CPU 37 and the driver receiver circuits 33 and 34, respectively, and a modulator/demodulator 2a. board 41, a MUXDMUX circuit 40 that sends and receives signals to and from the modulation/demodulation board 41, the MUXDMUX circuit 40, the driver receiver circuit 32, and the CPU 37.
buffer circuits 38 and 3 respectively connected between
9.

In FIGS. 2 and 3, the parts surrounded by broken lines are newly added parts in this embodiment.

The feature of the present invention is that in FIGS. 1, 2, and 3, when the current channel is a common line channel, the common line modem 2a and the circuit switched modem 4a communicate the common line channel. As a control signal direct transmitting/receiving means for directly transmitting and receiving control signals without going through the satellite, a control signal direct transmitting/receiving means is provided in the common channel modem 2a and transmits/receives control signals of the common channel to/from the circuit switched modem 4a. A driver receiver circuit 22 and a serial control unit 24 as one control signal transmitting/receiving circuit are provided in the line switching modem 4a, and when the current channel is a common line channel, the common line modem transmits the control signal of the common line channel to the common line modem. A driver L/'y-c circuit 34o and a serial control unit 36 are provided as a second control signal transmitting/receiving circuit for transmitting and receiving signals to and from the CP 2a, respectively.
The reason is that it can be controlled by U25 and CPU U37.

Next, the operation of this embodiment will be explained.

As is clear from FIG. 2, in the common line modulation/demodulation device 2a, the control signal 101 from the satellite line control device 1 is once received by the CPU 25 via the driver receiver circuit 21 and the serial control unit 23, and then serial control is performed again. The circuit-switched modem 4a is inputted and outputted via the unit 24 and the driver-receiver circuit 22.

On the other hand, in the line-switched modem 4a of FIG.
The P U 37 receives information from the satellite line control panel 31 in the device via the driver receiver circuit 33 and serial control unit 35 as to whether the current channel is a common line channel or an individual line channel. In the case of a common line channel, the control signal 109 of the common line modem 2a is received via the driver receiver circuit 34 and the serial control unit 36, while the control signal 110 is output to the common line modem 2a.

That is, while the line-switched modem 4a is on standby in synchronization with the common line channel shared by the network and
Until the TE3 makes a call and the individual line channel is assigned by the satellite line controller 1, the line-switched modem 4a
The transmission and reception of control signals on the common line channel between the common line modulator and demodulator 2a is performed in the baseband without going through the satellite.

Therefore, the conventional satellite delay in sending and receiving control signals is eliminated, and it is possible to shorten the access time from the time a call occurs at the DTE 3 connected to the circuit-switched modem 4a until the start of communication on the 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. I do.

〔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 switching modem and a common line modem installed in a central control station using base band without going through a satellite. By doing so, it is possible to shorten 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.

Further, according to the present invention, the control signal for line setting is not affected by rain attenuation or thermal noise on the transmission path, so it is possible to provide a satellite communication system with improved reliability. Since the baseband interface between the common line modem and the line-switched modem can be connected in the form of a bus, no additional hardware is required even if the line-switched modem is added to the central control station. It is possible to provide an economical satellite communication system without any problems, and its effects are great.

[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 a block diagram showing an example of the common channel modulation/demodulation device. FIG. 3 is a block configuration diagram showing an example of the line switching modem/demodulator. FIG. 4 is a block diagram showing the main parts of a conventional example. FIG. 5 is a block diagram showing an example of a conventional satellite communication system using the demand assignment method. 1.51...Satellite line control device, 2.2a, 52...
・Common line modulation/demodulation equipment, 3.53.63...Data terminal equipment (DTE), 4.4a, 54-...Line switching modem/demodulation equipment, 5.7...Synthesizer, 6...Distributor ,
21.22.32-34...driver receiver circuit,
23.24.35.36...Serial control unit, 25.37...CPU. 26.38.39...Buffer circuit, 27.41...
・Modulation/demodulation board, 40...M [JXDMTJX circuit, 50
...centralized control station, 55...combiner/distributor, 60...
・VSAT station, 61...Circuit switching outdoor equipment, 62・
...Circuit switching indoor equipment, 71...Common line channel node 72...Individual line channel, 101.102.109.
110... Control signal, 103.107.111...
Modulated signal, 104.108.112... Received signal, 1
05.106...Individual line 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 line-switched modem that modulates and demodulates; a combiner that combines and transmits a modulated signal from the common line modem and a modulated signal from the line-switched modem; and a combiner that combines and transmits a received signal between the common line modem and the line. In a satellite communication system equipped with a centralized control station including a switching system modem and a distributor for distributing between the common line modem and the line switching, when the current channel is a common line channel, the central control station connects the common line modem and the line switching. A satellite communication system comprising a control signal direct transmitting/receiving means for directly transmitting/receiving a common line channel control signal to and from a system modem/demodulator without going through a satellite. 2. The control signal direct transmitting/receiving means includes a first control signal transmitting/receiving circuit provided in the common line modem and transmitting/receiving the control signal of the common line channel to and from the line switched modem and the line switched modem. 2. A second control signal transmitting/receiving circuit provided in the system modem/demodulator and transmitting/receiving a control signal of the common line channel to/from the common line modem when the current channel is a common line channel. Satellite communication system described. 3. Claim 1, wherein the communication method is a demand assignment method.
Or the satellite communication system according to claim 2.