JP2020161927A - Satellite communication system and communication control method - Google Patents

Abstract

To prevent a communication line from being pressured by a control line.SOLUTION: A satellite communication system includes a master station terminal device, a slave station terminal device, and association means. The master station terminal device and the slave station terminal device communicate using a control line via a satellite. The association means associates information contained in a control packet defined by a control protocol used between the master station terminal device and the slave station terminal device with a bit at a predetermined position in a frame format of the control line.SELECTED DRAWING: Figure 8

Description

Embodiments of the present invention relate to satellite communication systems and communication control methods.

The satellite communication system realizes communication between a plurality of stations on the ground via artificial satellites (geostationary satellites) in geostationary orbit. In this type of system, for example, a device called VSAT (Very Small Aperture Terminal) is known. In recent years, a system for receiving a moving camera image at an earth station from a satellite communication station (called a vehicle station) mounted on a moving body such as a vehicle has begun to be studied. The vehicle station is positioned as a slave station when the earth station is the master station.

JP-A-2017-188746 Republished WO 2016/203553

Communication resources in a satellite communication system are roughly classified into a control line and a communication line. The control line is used, for example, for channel allocation between the vehicle station and the earth station, on / off control of each equipment, and the like. SNMP (Simple Network Management Protocol) has become the de facto standard as a protocol suitable for such applications.

A communication line is a resource for transmitting data such as video and audio. A system that uses a TDMA (Time Division Multiple Access) system for the control line and an SCPC (Single Channnel Per Carrier) system for the communication line, which is one of the frequency division multiplexing systems, is generally known.

By the way, the frequency band that can be used by a satellite repeater (transponder) is fixedly determined by a contract with a satellite operator. Therefore, if a large number of resources are occupied by the control line, the resources that can be used by the communication line are squeezed accordingly. This becomes more noticeable as the number of vehicle stations (slave stations) increases, and the bandwidth in which video and audio can be communicated becomes narrower, so countermeasures are required.
Therefore, an object of the present invention is to provide a satellite communication system and a communication control method that prevent the communication line from being compressed.

According to the embodiment, the satellite communication system includes a master station terminal device, a slave station terminal device, and an associating means. The master station terminal device and the slave station terminal device communicate using a control line via an artificial satellite. The associating means associates the information contained in the control packet defined by the control protocol used between the master station terminal device and the slave station terminal device with the bit at the default position in the frame format of the control line.

The figure which shows an example of the satellite communication system which concerns on embodiment. The figure for demonstrating an example of resource allocation in a satellite communication line. The figure for demonstrating an example of resource allocation in a satellite communication line. The functional block diagram which shows an example of the earth station 100. The functional block diagram which shows an example of a master station terminal apparatus 11. The functional block diagram which shows an example of the vehicle station 200. The functional block diagram which shows an example of a slave station terminal apparatus 29. The sequence diagram which shows an example of the processing procedure in an embodiment. The figure which shows an example of the GUI window displayed on the display part 110 of a master station terminal apparatus 11. The figure which shows an example of correspondence of the SNMP control packet and the satellite frame format in embodiment.

Hereinafter, embodiments of the present invention will be described.
A satellite communication system includes a plurality of stations, which communicate with each other via artificial satellites (satellite) in geostationary orbit. This kind of system is applied to the disaster prevention system of a wide area municipality such as a prefecture. For example, a live image of a disaster site can be transmitted from a vehicle station (slave station) dispatched to the site to an earth station (master station) such as the location of a prefectural office via a satellite line. This makes it possible to know the disaster situation quickly and accurately. It is also possible to make VoIP (Voice over IP) calls and video conferences using a communication line via satellite, and it can also be used for information sharing and disaster response discussions between related departments.

FIG. 1 is a diagram showing an example of a satellite communication system according to an embodiment. In FIG. 1, the earth station 100 is installed at, for example, the location of the prefectural office. The vehicle station 200 is mounted on a moving body 300 such as a vehicle. The moving body 300 can be dispatched to, for example, a disaster site, and can transmit a camera image taken while traveling to the earth station 100.

The earth station 100 and the vehicle station 200 can communicate with each other via the communication satellite 400 in geostationary orbit, and both are one form of the VSAT device. As an example of the line allocation method for the VSAT device, it is called DAMA (Demand Assignment Multiple Access). Control stations located at several points on the ground are responsible for controlling DAMA.

As shown in FIG. 2, two resources, a control line and a communication line, are set in the satellite communication line between the earth station 100 and the vehicle station 200 (mobile body 300 (301, 302)). The TDMA method is adopted for the control line, and the SCPC method is adopted for the communication line. When SNMP is used for monitoring control from the earth station 100 to the vehicle station 200 in this type of system, the bandwidth of the control line increases according to the number of SNMP agents. As long as the number of mobile bodies 300 is small as shown in FIG. 2, there is a margin in the communication band.

As shown in FIG. 3, on the other hand, as the number of mobile bodies 300 (301 to 30n) increases, the uplink (uplink) and downlink (downlink) time slots of the control line are occupied. Communication line resources are overwhelmed. That is, there are events such as (1) to (3).

(1) Since there are a plurality of SNMP agents (encoders, communication modems, NW devices, etc.) in each vehicle station 200, it is necessary to increase the speed of the control line in consideration of the congestion of the control line due to the SNMP packets.
(2) The control line (uplink) needs to carry packets by TDMA in a time lot divided into, for example, tens of tenths according to the number of mobile bodies 300. Therefore, it is necessary to increase the speed per time slot.
(3) From the viewpoint of preventing radio wave interference, it is necessary to set the power density of the moving communication to be lower than that of the fixed state. In return, if the modulation method is changed to a noise-resistant method, the frequency band used will be widened.
In any case, the bandwidth of the communication line is compressed, and the bandwidth for sending important information (video) is narrowed. The techniques that can prevent such a situation will be described below.

[Constitution]
FIG. 4 is a functional block diagram showing an example of the earth station 100. The earth station 100 includes a communication modem 13 and a line control modem 14 provided according to the number of vehicle stations 200 as cores. Of these, the control signal transmitted by TDMA from the line control modem 14 is combined with the transmission signal from the communication modem 13 by the synthesis distributor 15, and the obtained multiplex signal is a solid state power amplifier (SSPA). Sent to 16. The SSPA 16 amplifies the multiplex signal to the transmission level and transmits it from the antenna 18 to the communication satellite 400.

The signal arriving from the vehicle station 200 via the communication satellite 400 is received by the antenna 18, amplified and frequency-converted by the LNB (low-noise block downconverter) 17, and sent to the synthesis distributor 15. The composite distributor 15 distributes and inputs the received signal to the communication modem 13 and the line control modem 14. The communication modem 13 and the line control modem 14 are connected to the network (NW) device 12.

A decoder 10 and a master terminal device 11 are also connected to the NW device 12. The decoder 10 decodes the video and audio received from the vehicle station 200, which is the other party, and sends the video and audio to the master station terminal device 11 and the playback device (not shown) via the NW device 12. The master station terminal device 11 includes a display unit 110, and displays a GUI (Graphical User Interface) window on the display unit 110. The user can arbitrarily select the vehicle station 200 and give an instruction by using this GUI window. That is, the master station terminal device 11 has a function as a user interface for remotely controlling the vehicle station 200.

FIG. 5 is a functional block diagram showing an example of the master station terminal device 11. The master station terminal device 11 is a computer including a processor 34 such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit), a ROM (Read Only Memory) 31 and a RAM (Random Access Memory) 32. The master station terminal device 11 further includes a storage unit 33 such as a hard disk drive (HDD), a media drive 35, a display unit 110 such as an LCD (Liquid Crystal Display) panel, and an interface unit (I / F). 36 is provided.

The ROM 31 stores basic programs such as BIOS (Basic Input Output System) and UEFI (Unified Extensible Firmware Interface), and various setting data. The RAM 32 stores the programs and data loaded from the storage unit 33, and the conversion table 32a.

The conversion table 32a is a conversion table for associating the command message included in the SNMP packet with the bit at the default position of the satellite frame format on the control line. A similar conversion table is also stored in the vehicle station 200 and is operated as a common rule.

The media drive 35 reads digital data recorded on a recording medium such as a CD-ROM 37. Various programs executed by the master station terminal device 11 are recorded and distributed on, for example, a CD-ROM 37. The program stored in the CD-ROM 37 is read by the media drive 35 and installed in the storage unit 33.

The interface unit 36 includes a connection interface with the NW device 12, and controls communication with each unit shown in FIG.
The storage unit 33 stores the program 33a executed by the processor 34. The program 33a can be downloaded from the server via, for example, the interface unit 36 and installed in the storage unit 33.

The processor 34 executes an OS (Operating System) and various programs. Further, the processor 34 includes a conversion unit 34a, a reproduction unit 34b, and a control unit 34c as processing functions according to the embodiment. These functional blocks can be understood as a process generated by loading the program 33a stored in the storage unit 33 into the RAM 32 and executing the calculation process by the processor 34 as the program progresses. That is, the program 33a is a program for operating the master station terminal device 11, and operates the master station terminal device 11 which is a computer as a conversion unit 34a, a reproduction unit 34b, and a control unit 34c.

The conversion unit 34a sends a command message included in the SNMP packet sent and received between the master station terminal device 11 and the slave station terminal device 29 provided in the vehicle station 200 in a predetermined satellite frame format on the control line. Convert to the bit at the default position. The conversion table 32a of the RAM 32 is referred to in the conversion process. The satellite frame format signal including this bit is transmitted to the vehicle station 200 via the communication satellite 400.

The reproduction unit 34b reproduces the SNMP response message from the bit at the predetermined position of the satellite frame format signal arriving from the vehicle station 200 via the communication satellite 400. The conversion table 32a of the RAM 32 is referred to during the reproduction process.

Based on the reproduced response message, the control unit 34c controls the control target in the vehicle station 200 of the transmission source, and updates the contents of the GUI window of the display unit 110.

FIG. 6 is a functional block diagram showing an example of the vehicle station 200. The signal arriving from the earth station 100 via the communication satellite 400 is received by, for example, the satellite antenna 20 mounted on the vehicle roof, frequency-converted by the LNC (low-noise converter) 22, and sent to the synthesis distributor 23. The composite distributor 23 distributes the received signal into a communication signal and a control signal, and inputs the received signal to the communication modem 24 and the line control modem 25, respectively.

The communication modem 24 and the line control modem 25 are connected to the NW device 26, and are subject to control by the earth station 100 together with the encoder 27 which is also connected to the NW device 26. A camera 28 that acquires live audio and live video is connected to the encoder 27, and this camera 28 can also be controlled by the earth station 100.

For example, the video signal from the camera 28 is encoded by the encoder 27 into a signal of a default compression method and sent to the communication modem 24 via the NW device 26. The communication signal from the communication modem 24 and the control signal from the line control modem 25 are multiplexed by the synthesis distributor 23, and the multiplexed signal is sent to the BUC (Block Up Converter) 21. The BUC 21 frequency-converts the multiplex signal and transmits the transmission level multiplex signal from the satellite antenna 20 to the communication satellite 400. In the ground-satellite section, for example, a signal obtained by QPSK (Quadrature Phase Shift Keying) modulation of a Ku band carrier wave is used.

Further, the slave station terminal device 29 is connected to the NW device 26. The slave station terminal device 29 is realized as, for example, a personal computer in which a dedicated application is installed, and performs communication with the earth station 100 and control based on SNMP for each control target. In particular, as the slave station terminal device 29, it is desirable to use a device known as a tough computer that can withstand a harsh environment.

FIG. 7 is a functional block diagram showing an example of the slave station terminal device 29. The slave station terminal device 29 includes a processor 44, a ROM 41, a RAM 42, a storage unit 43, a media drive 45, a display unit 48, and an interface unit (I / F) 46.

The ROM 41 stores basic programs such as BIOS and UEFI, and various setting data. The RAM 42 stores the programs and data loaded from the storage unit 43, and the conversion table 42a.

The conversion table 42a is a conversion table for associating the command message included in the SNMP packet with the bit at the default position of the satellite frame format on the control line. A similar conversion table is also stored in the earth station 100 and is operated as a common rule.

The media drive 45 reads digital data recorded on a recording medium such as a CD-ROM 47. Various programs executed by the slave station terminal device 29 are recorded and distributed on, for example, a CD-ROM 47. The program stored in the CD-ROM 47 is read by the media drive 45 and installed in the storage unit 43.

The interface unit 46 includes a connection interface with the NW device 26, and controls communication with each unit shown in FIG.
The storage unit 43 stores the program 43a executed by the processor 44. The program 43a may be downloaded via the satellite communication line, for example, via the interface unit 46, and installed in the storage unit 43.

The processor 44 executes the OS and various programs. Further, the processor 44 includes a reproduction unit 44a, a control unit 44b, and a conversion unit 44c as processing functions according to the embodiment. These functional blocks can be understood as a process generated by loading the program 43a stored in the storage unit 43 into the RAM 42 and executing the calculation process by the processor 44 as the program progresses. That is, the program 43a is a program for operating the slave station terminal device 29, and operates the slave station terminal device 29, which is a computer, as the reproduction unit 44a, the control unit 44b, and the conversion unit 44c.

The reproduction unit 44a decodes the bit string in the satellite frame format signal received from the earth station 100 via the communication satellite 400, and reproduces the SNMP command message from the on / off state of each bit at the predetermined position. The conversion table 42a of the RAM 42 is referred to during the reproduction process.

The control unit 44b inputs the reproduced SNMP command message to the control target under its control. The subordinate control targets are, for example, an encoder 27, a camera 28, an NW device 26, a communication modem 24, a line control modem 25, a synthesis distributor 23, a BUC21, an LNC22, and the like, which are shown in FIG. It is the actual situation that is positioned as an agent in. The Earth Station 100 is positioned as a manager for this agent.

The conversion unit 44c converts a response message based on the result of inputting an SNMP command message to the SNMP agent into bits at a predetermined position in a predefined satellite frame format on the control line. The conversion table 42a of the RAM 42 is referred to in the conversion process. A signal in satellite frame format including this bit is transmitted to the earth station 100 via the communication satellite 400.

The conversion unit 34a of the master station terminal device 11 and the reproduction unit 44a of the slave station terminal device 29 function as associating means in the control route in the direction from the earth station 100 to the vehicle station 200. Further, the conversion unit 44c of the slave station terminal device 29 and the reproduction unit 34b of the master station terminal device 11 function as associating means in the control route in the direction from the vehicle station 200 to the earth station 100. Next, the operation in the above configuration will be described.

[Action]
FIG. 8 is a sequence diagram showing an example of the processing procedure in the embodiment. In the earth station 100, a GUI window as shown in FIG. 9, for example, is displayed on the display unit 110 of the master station terminal device 11. The operator specifies the vehicle station (vehicle 1, vehicle 2, ...) To be connected in [Line setting] of FIG. 9, and selects (connect) or (disconnect) in [line connection]. In [Video receiving station switching], the control line (control wave) can be turned on / off for each central station (earth station 100) and branch station 1 (if there are multiple stations, they may be distinguished by number). There is.

Steering such a screen, the operator requests the designated vehicle station 200 to transmit the video (step S1). Based on this request, the master station terminal device 11 generates an SNMP control packet for operating the controlled object of the destination vehicle station 200 (step S2). Here, it is assumed that a message (set request) as shown in FIG. 10 is generated. Next, the master station terminal device 11 converts the SNMP control packet into the satellite frame format, and associates the contents of the SNMP control packet with the on / off of the bits at each position in the satellite frame format (step S3).

FIG. 10 is a diagram showing an example of correspondence between the SNMP control packet and the satellite frame format. The packet structure of SNMP has a complicated structure including a header part and a payload part. As an SNMP command, for example, the control packet length for instructing Value 1 for the OID 1.3.6.1.4.1.186.29.5.1.0 of the destination 192.168.24.225 requires 94 bytes.

In the embodiment, this information is arranged in, for example, 1-byte units of b0 to b7 over four columns ([0], [1], [2], [3]) in a bit state at a default position of a frame format. Corresponds to (0/1). For example, the area shown in FIG. 10 may be allocated to the communication modems 13 and 24. In FIG. 10, the information of the control packet is associated with the bit (b5) in the [3] column. As a result, 94 bytes of information can be compressed to 1 bit. This association is ruled in the conversion tables 32a and 42a.

In FIG. 10, in addition to this, areas such as TxF1, RxF2, modQPSK, and TxON are defined, and the slave terminal device 29 associates these bits with 1 (ON) and 0 (OFF) and associates them with the SNMP control packet. Information corresponding to the contents of is transmitted to the communication modem 24.

The explanation will be continued by returning to FIG. The satellite frame format signal is transmitted from the earth station 100 via the control line of the satellite communication line (step S4), and is received by the destination vehicle station 200 (step S5).

The slave station terminal device 29 in the destination vehicle station 200 interprets the state of each bit of the received satellite frame format and reproduces the SNMP control packet (step S6). The reproduced message is input to the control target (communication modem 24, encoder 27, etc.) as a (set request) command (step S7).

The communication modem 24 and the encoder 27 that have received this command control and set each of them according to the content of the command (step S8), and generate an SNMP message (get response) for returning the result (step S9). The SNMP control packet including the generated SNMP message is converted into the satellite frame format in the slave station terminal device 29 (step S11), and is transmitted from the vehicle station 200 to the earth station 100 via the control line via the communication satellite 400 (step S11). Step S12).

The earth station 100 that has received the signal of the control line passes the received signal to the master station terminal device 11 (step S13). The master station terminal device 11 reproduces the SNMP control packet from the acquired satellite frame format (step S14). The obtained (get response) message is reflected in the GUI of the display unit 110 (step S15), and thereafter, video transmission between the earth station 100 and the vehicle station 200 is established. As a result, the real-time image taken by the vehicle station 200 can be viewed by the earth station 100.

[effect]
As described above, in the embodiment, the satellite frame format is constructed between the earth station 100 and the vehicle station 200 according to the bit allocation corresponding to the SNMP packet which is a common rule in advance. Then, in the air section (section via the communication satellite 400), communication is performed in the satellite frame format, and in the earth station 100 and the vehicle station 200, the SNMP packet is extracted from the satellite frame format. This makes it possible to send and receive monitoring control information at a low bit rate on the control line of the satellite communication line.

In the existing technology, when monitoring and controlling by SNMP from the earth station 100 to the vehicle station 200, the SNMP packet is sent as it is, so that the bandwidth of the control line is enlarged and the communication line is compressed by that amount. It was.

On the other hand, in the embodiment, by associating the content of the message transmitted by the SNMP packet with the bit string of the satellite frame format, the amount of information can be remarkably compressed without losing the content. Therefore, the occupied band of the control line can be reduced, and the frequency band that can be used in the communication line for video transmission can be increased. From these facts, according to the embodiment, it becomes possible to provide a satellite communication system and a communication control method in which a control line can be saved and a communication line can be secured to the maximum.

Although the embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. This novel embodiment can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

10 ... Decoder, 11 ... Master station terminal device, 12 ... Network equipment, 13 ... Communication modem, 14 ... Line control modem, 15 ... Synthetic distributor, 16 ... SSPA, 17 ... LNB, 18 ... Antenna, 20 ... Satellite antenna , 23 ... Synthetic distributor, 24 ... Communication modem, 25 ... Line control modem, 26 ... NW equipment, 27 ... Encoder, 28 ... Camera, 29 ... Slave terminal device, 31 ... ROM, 32 ... RAM, 32a ... Conversion Table, 33 ... storage unit, 33a ... program, 34 ... processor, 34a ... conversion unit, 34b ... playback unit, 34c ... control unit, 35 ... media drive, 36 ... interface unit, 41 ... ROM, 42 ... RAM, 42a ... Conversion table, 43 ... storage unit, 43a ... program, 44 ... processor, 44a ... playback unit, 44b ... control unit, 44c ... conversion unit, 45 ... media drive, 46 ... interface unit, 48 ... display unit, 100 ... earth station , 110 ... Display, 200 ... Vehicle station, 300 ... Mobile, 400 ... Communication satellite.

Claims (8)

In a satellite communication system including a master station terminal device and a slave station terminal device that communicates with the master station terminal device using a control line via an artificial satellite.
A means for associating information contained in a control packet defined by a control protocol used between the master station terminal device and the slave station terminal device with a bit at a predetermined position in a frame format of the control line is provided. Satellite communication system. The associating means
A conversion unit provided in the master station terminal device that converts a command message included in the control packet into bits at the predetermined position, and a conversion unit.
A reproduction unit provided in the slave terminal device and reproducing the command message from the bit at the predetermined position is included.
The satellite communication system according to claim 1, wherein the slave station terminal device includes a control unit that inputs the reproduced command message to a subordinate control target. The associating means
A conversion unit provided in the slave terminal device and converting a response message based on the result of inputting a command message included in the control packet into a control target under the control packet to a bit at the predetermined position.
A reproduction unit provided in the master station terminal device and reproducing the response message from the bit at the predetermined position is included.
The satellite communication system according to claim 1, wherein the master station terminal device includes a control unit that controls the control target based on the reproduced response message. The satellite communication system according to any one of claims 1 to 3, wherein the control protocol is SNMP (Simple Network Management Protocol). A communication control method applicable to a satellite communication system including a master station terminal device and a slave station terminal device that communicates with the master station terminal device using a control line via an artificial satellite.
The information contained in the control packet defined by the control protocol used between the master station terminal device and the slave station terminal device is used by the master station terminal device and the slave station terminal device to frame the control line. A communication control method that communicates by associating with the bit at the default position in the format. The master station terminal device converts the command message included in the control packet into the bit at the predetermined position, and then converts the command message into the bit at the predetermined position.
The slave station terminal device reproduces the command message from the bit at the predetermined position,
The communication control method according to claim 5, wherein the slave station terminal device inputs the reproduced command message to a control target under its control. The slave terminal device converts the response message based on the result of inputting the command message included in the control packet into the control target under the control packet into the bit at the predetermined position.
The master station terminal device reproduces the response message from the bit at the predetermined position,
The communication control method according to claim 5, wherein the master station terminal device controls the control target based on the reproduced response message. The communication control method according to any one of claims 5 to 7, wherein the control protocol is SNMP (Simple Network Management Protocol).