JPH1056416A - Satellite communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a satellite communication system in which communication using two channels of a satellite channel and a ground channel is attained by having only to provide one Internet protocol(IP) address to each terminal equipment. SOLUTION: A satellite channel connection module is made up of a satellite channel termination section 80, a ground channel termination section 82, an IP interface section 86, and an IP packet routing section 84 to execute real processing of a data link layer. The satellite channel termination section 80 executes real processing of the data link layer of the satellite channel, and a ground channel termination section 82 executes real processing of the data link layer of the ground channel. An IP interface section 86 conducts transmission reception of an IP packet with respect to an IP layer. The IP packet routing section 84 makes routing to the IP packet in this module. The satellite channel connection module sends the IP packet as one data link layer processing module to the IP layer of a host layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication system in which a server device storing information and a terminal requesting the information are connected via a terrestrial network and a satellite line.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a configuration example of a conventional satellite communication system. In this figure,
2 is a server device that stores information, 1 is a terminal for extracting information of the server device 2, 3 is a connection server that receives a connection from the terminal 1 via a terrestrial network, and gives an IP address for two-way communication by PPP, 4 A modem for connecting the terrestrial network to the terminal 1; 15 is mounted on the terminal 1; a satellite link data link layer module (satellite link DLM) for performing actual processing of a satellite link data link layer; 16 is mounted on the terminal 1; A terrestrial line data link layer module (terrestrial line D) that executes actual processing of the terrestrial line data link layer
LM), 5 is a router, 6 is a satellite line receiving device, 7 is a satellite line transmitting device, and 8 is a communication satellite.

In the satellite communication system shown in FIG. 1, a server device 2 and a plurality of terminals 1 are connected via a terrestrial network and a satellite line, and are both broadcast using UDP and both using TCP. Bidirectional communication is performed. In the above two-way communication, packets from the terminal 1 to the server device 2 pass through a ground network, and packets from the server device 2 to the terminal 1 pass through a satellite line. On the other hand, in the broadcast communication, only communication from the server device 2 to the terminal 1 is performed, and the packet passes through a satellite line. The terminal 1 and the server device 2 perform communication using UDP or TCP in the transport layer and use IP in the network layer.

[0004] In the satellite communication system, information transmitted from the server device 2 is transmitted to the terminal 1 using a broadband satellite channel. Therefore, when the information amount is large, the information is transmitted through a narrow-band terrestrial network. It is characterized in that the information transfer time can be reduced as compared with the case where the information is transmitted. In addition, since the satellite line has broadcast characteristics, when transmitting the same information to a plurality of terminals 1 using UDP, there is a feature that only one transmission is required.

FIG. 5 is an explanatory diagram showing an example of a protocol stack using IP in a conventional satellite communication system. As shown in the figure, a satellite link data link layer 10 and a terrestrial link data link layer 11 exist below the IP layer 12. In the satellite link data link layer 10, the satellite link data link layer module 15 (see FIG. 4) executes actual processing of the satellite link data link layer. In the terrestrial line data link layer 11, the terrestrial line data link layer module 16 (see FIG. 4) executes actual processing of the terrestrial line data link layer.

[0006] As described above, the data link layer (interface) for transmitting and receiving IP packets is the IP layer 12.
When there are a plurality of layers in the lower layer, when transmitting an IP packet, it is necessary for the user to specify a data link layer for performing the transmission for each destination IP address. For this reason,
In order to identify each data link layer, it is necessary to assign a different IP address to each data link layer.

FIG. 6 is a flowchart showing an example of an IP packet transmission process when two data link layers exist below the IP layer 12 in a conventional satellite communication system. Here, of the two data link layers, one IP address is IP1,
The other IP address is IP2. It is also assumed that the data link layer whose IP address is IP1 is designated as a default transmission route in a routing table (not shown) held in the terminal 1.

When the packet transmission process starts, the IP layer 12 first checks whether the network address of the IP address indicating the destination (ie, the destination IP address) is the same as the network address of IP1. (Step S91). If they are the same, the source IP address is set to IP1 (step S9).
2) The packet is transmitted to the data link layer of IP1 (step S93).

If the network address of the destination IP address is different from the network address of IP1,
It is confirmed whether or not it is the same as the network address of P2 (step S94). If they are the same, the source IP address is set to IP2 (step S95), and I
The packet is transmitted to the data link layer of P2 (step S96).

If the network address of the destination IP address is different from the network address of IP1,
If it is different from the network address of P2, a default transmission route is searched by referring to the routing table (step S97). Here, as an example,
Since the IP address of the data link layer specified as the default transmission route is IP1, the IP 1 is set as the source IP address (step S98), and the packet is transmitted to the data link layer (step S99).

In the above conventional method, when two data link layers (satellite link data link layer 10 and terrestrial link data link layer 11) exist below the IP layer 12, it is necessary to identify each data link layer. ,
A different IP address must be assigned to each data link layer, and two IP addresses are required for one terminal. Furthermore, in this case, the I-link is also used for the satellite link data link layer that only receives IP packets.
There is a disadvantage that the P address must be assigned, and the limited resource of the IP address is inefficiently used.

Further, since the IP layer 12 operates only after an IP address is assigned to the data link layer, it cannot receive a packet without assigning an IP address. Therefore, in order to receive a broadcast packet via a satellite line, an IP address is fixedly assigned to each terminal, or PPP or DHCP (Dynamic Host Configuration Protocol) or the like is used before starting communication. It must be used to give an IP address from another device.

FIG. 7 is a flowchart showing an example of communication processing in a terminal when a fixed IP address is assigned in a conventional satellite communication system. When a fixed IP address is assigned to a terminal, the IP address (hereinafter referred to as “fixed I
The packet is transmitted / received using the “P address”.

In the case of two-way communication, when communication is started, if a received packet exists, the IP address of the received packet is compared with the fixed IP address (step S2).
1) If both match, a packet is received (step S22). When sending packets, use a fixed IP
The address is transmitted as the source address (step S
23).

In the case of broadcast communication as well, when communication is started, if a received packet exists, the IP address of the received packet is compared with the fixed IP address (step S2).
4) If both match, the packet is received (step S25).

FIG. 8 is a flowchart showing an example of communication processing in a terminal in a case where an IP address is assigned using PPP before starting communication in a conventional satellite communication system. In the case of two-way communication, when communication is started, first, connection is made to the connection server 3 (step S31), and an IP address is assigned (step S32). After the IP address is assigned, the packet is transmitted and received. If a received packet exists, the IP address of the received packet is compared with the assigned IP address (hereinafter, referred to as “assigned IP address”) (step S33). Yes (Step S3
4). When transmitting a packet, the packet is transmitted with the assigned IP address as a source address (step S35). To end the communication, the assigned IP address is released (step S36), and the communication is disconnected.

In the case of broadcast communication, first, the connection is made to the connection server 3 (step S38), and an IP address is assigned (step S39). After the IP address is assigned, the packet is transmitted and received. If there is a received packet, the IP address of the received packet is compared with the assigned IP address (step S40), and if they match, the packet is received (step S41). To end the communication, release the assigned IP address (step S
42), cut.

In the communication method (method of fixedly assigning an IP address) shown in FIG. 7, even when a broadcast packet is received from a server device without performing bidirectional communication by TCP, the communication method is fixed to each terminal. Has to be assigned an IP address, and when the number of accommodated terminals increases, the IP address is depleted.

In the communication method shown in FIG. 8 (method of assigning an IP address before communication starts), even when a broadcast packet is received from a satellite line, a terrestrial network is assigned to assign an IP address. Need to connect. for that reason,
When a public network is used as the terrestrial network, it is necessary to connect the public network in order to receive a broadcast packet, and there is a disadvantage that the connection fee increases accordingly.

[0020]

The problems of the prior art described above are summarized as follows. When a plurality of data link layers exist below the IP layer, a different IP address must be assigned to each data link layer, and a limited resource such as an IP address is inefficiently used. When a fixed IP address is assigned, even when a broadcast packet is received, it is necessary to assign an IP address to each terminal, and when the number of accommodated terminals increases, the IP address is depleted. When an IP address is assigned before the start of communication, it is necessary to connect to a terrestrial network to assign the IP address, and the connection fee increases accordingly.

[0021] The present invention has been made to solve the above-described problem, and only assigns one IP address to one terminal without assigning an IP address to each data link layer. Accordingly, it is an object of the present invention to provide a satellite communication system capable of performing communication using two lines, a satellite line and a terrestrial line.

Further, the present invention relates to a UD from a satellite line.
It is an object of the present invention to provide a satellite communication system capable of receiving a P / IP packet without giving an IP address to each terminal fixedly and without connecting to a terrestrial network even when receiving a P / IP packet. Aim.

[0023]

According to the first aspect of the present invention,
UDP (User Datagram Protocol) / IP
(Internet Protocol), a computer communication performed using TCP (Transmission Control Protocol) / IP technology, wherein a server device storing information and a terminal requesting the information are transmitted via a terrestrial network and a satellite line. It is connected and performs broadcast communication using UDP and bidirectional communication using TCP. In bidirectional communication, a packet from a terminal to a server device passes through a terrestrial network, and a packet from the server device to the terminal is a satellite line. In the broadcast communication, only the communication from the server device to the terminal is performed, and the packet is a module that executes processing of a data link layer lower than the IP layer in a communication system via a satellite line, A function to execute the actual processing of the satellite link data link layer protocol, and a terrestrial link data link The function of executing the actual processing of the ear protocol, the function of transmitting the IP packet from the terminal to the interface of the terrestrial line, the function of transmitting the IP packet via the satellite line and the IP packet via the terrestrial line to the upper layer IP layer Transmitting an IP packet to an upper-layer IP layer, and having a satellite line connection module for transmitting the IP packet as one data link layer processing module for the IP layer. Features. According to a second aspect of the present invention, in the communication system according to the first aspect, a PPP (point-to-point protocol) is used as a data link protocol of a terrestrial line, and an IP address assigned to each terminal every time communication is started. , A multicast communication is performed using a virtual IP address that is fixedly assigned to each terminal in advance and that is not used for the two-way communication.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a satellite line connection module used in a satellite communication system according to an embodiment of the present invention. In addition,
This figure corresponds to claim 1. The satellite line connection module 88 shown in this figure is used instead of the satellite line data link layer module 15 and the terrestrial line data link layer module 16 shown in FIG. Therefore,
As shown in FIG. 1, the satellite link connection module 88 executes actual processing of the data link layer in the data link layer.

In this figure, a satellite line connection module 88 includes a satellite line terminating unit 80 for terminating a satellite line data link layer protocol, a terrestrial line terminating unit 82 for terminating a terrestrial line data link layer protocol,
It comprises an IP packet routing unit 84 for routing P packets in the satellite line connection module 88, and an IP interface unit 86 for transmitting and receiving IP packets to and from the IP layer.

The satellite line terminating unit 80 receives the data via the satellite line, executes the actual processing of the data link layer of the satellite line, and transmits the IP packet to the IP packet routing unit 84. The terrestrial line termination unit 82 receives the IP packet from the IP packet routing unit 84, executes the actual processing of the terrestrial line data link layer, and transmits it to the terrestrial line using the terrestrial line data link protocol.

The IP interface unit 86 transmits and receives IP packets to and from the IP layer, transmits the IP packets (via the satellite line and the terrestrial line) received from the IP packet routing unit 84 to the IP layer,
The IP packet received from the P layer is transmitted to the IP packet routing unit 84.

The IP packet routing unit 84
When transmitting a packet to the terrestrial network, it receives an IP packet from the IP interface unit 86 and transmits the IP packet to the terrestrial line termination unit 82. When receiving the IP packet from the satellite line, the IP packet routing unit 84 receives the IP packet from the satellite line terminating unit 80 and transmits the IP packet to the IP interface unit 86.

The satellite line connection module shown in FIG.
It has a P interface unit 86 and an IP packet routing unit 84, and transmits an IP packet as one data link layer processing module to the upper IP layer.

FIG. 2 is a flowchart showing an example of IP packet transmission processing in satellite line connection module 88 shown in FIG. Here, the IP address assigned to the satellite line connection module 88 is IP1.
When the packet transmission process starts, the IP layer sets the source IP address to IP1 (step S100),
The packet is transmitted to the data link layer of IP1 (step S102).

In the satellite line connection module 88 shown in FIG. 1, the only interface between the IP layer and the satellite line connection module 88 is the IP interface unit 86. The IP layer has two types of interfaces (satellite line and terrestrial interface). There is no need to be aware that the interface exists. Therefore, even when communication is performed using a satellite line and a terrestrial line, it is not necessary to set a data link layer (interface) for transmitting an IP packet for each destination IP address. In addition, since an interface conventionally divided into the satellite link data link module 15 and the terrestrial link data link module 16 (see FIG. 4) can be changed to an interface using the satellite link connection module 88 shown in FIG. Only one IP address needs to be assigned to the interface.

FIG. 3 is a flowchart showing an example of communication processing in a terminal used in the satellite communication system according to one embodiment of the present invention. This figure corresponds to claim 2. In the processing shown in this figure, the same virtual IP address is assigned to each terminal in advance. here,
The virtual IP address is an IP address that is not used as a source address when transmitting a packet from a terminal. And when performing broadcast communication, that is,
When a plurality of terminals receive a broadcast packet via a satellite line, the packets addressed to the own terminal are identified using the virtual IP address. On the other hand, when performing two-way communication,
The same processing as the conventional technique shown in FIG. 8 is performed.

Hereinafter, the communication process will be described with reference to FIG. In the case of two-way communication, when communication is started, first, connection is made to the connection server 3 (step S61), and an IP address is given (step S62). After the IP address is assigned, the packet is transmitted and received. If the received packet exists, the IP address of the received packet is compared with the assigned IP address (step S6).
3) If both match, the packet is received (step S65). When transmitting the packet, the IP address is transmitted as the transmission source address (step S67). When ending the communication, the assigned IP
The address is released (step S68) and disconnected. The two-way communication processing described above is the same as the two-way communication processing shown in FIG.

In the case of broadcast communication, if a received packet exists, the IP address of the received packet and the virtual I
The packet is compared with the P address (step S71), and if they match, the packet is received (step S72).

According to the processing shown in FIG. 3, even when a broadcast packet is received from a satellite line, there is no need to connect to a terrestrial network. In addition, a virtual IP address that is not actually transmitted from a terminal to a network (a satellite line and a terrestrial line) is used, and the virtual IP address is used only when a broadcast packet is received. An address can be assigned, and even when the number of terminals increases, it is possible to prevent the IP address from being depleted.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and changes in design and the like can be made without departing from the gist of the present invention. Even if there is, it is included in the present invention.

[0037]

As described above, according to the present invention, a satellite communication system using a satellite line and a terrestrial line with one IP address without providing an IP address for each data link layer is provided. This makes it possible to prevent inefficient use of the IP address resource. Also, even when a broadcast packet from a satellite line is received without fixedly assigning an IP address to each terminal, reception is possible without connection to a terrestrial network. The effect of reducing the increase in the connection fee can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a satellite line connection module used in a satellite communication system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an example of an IP packet transmission process in the satellite line connection module 88 shown in FIG.

FIG. 3 is a flowchart showing an example of communication processing in a terminal used in the satellite communication system according to one embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration example of a satellite communication system according to a conventional technique.

FIG. 5 is a diagram illustrating a conventional satellite communication system;
FIG. 4 is an explanatory diagram showing an example of a protocol stack using the “.”

FIG. 6 illustrates a conventional satellite communication system,
11 is a flowchart illustrating an example of an IP packet transmission process when two data link layers exist below a layer 12.

FIG. 7 is a flowchart illustrating an example of communication processing in a terminal when an IP address is fixedly assigned in a satellite communication system of the related art.

FIG. 8 is a flowchart illustrating an example of communication processing in a terminal in a case where an IP address is assigned using PPP before starting communication in a satellite communication system of the related art.

[Explanation of symbols]

80: Satellite line termination unit 82: Terrestrial line termination unit
84: IP packet routing unit, 86: IP
Interface section

Claims (2)

[Claims] 1. UDP (User Datagram Protocol) / IP (Internet Protocol), TCP
(Transmission Control Protocol) /
A computer communication performed using IP technology.
A server device storing information and a terminal requesting the information are connected via a terrestrial network and a satellite line, and perform a broadcast communication using UDP and a bidirectional communication using TCP,
In two-way communication, packets from the terminal to the server pass through the ground network, packets from the server to the terminal pass through a satellite line, and in broadcast communication, only communication from the server to the terminal is performed. Is a module for executing processing of a data link layer lower than the IP layer in a communication system via a satellite line, a function of executing actual processing of a satellite line data link layer protocol, and a data link of a terrestrial line. The function to execute the actual processing of the layer protocol, the function to transmit the IP packet from the terminal to the terrestrial line interface, and the function to transmit the IP packet via the satellite line and the IP packet via the terrestrial line to the upper layer IP layer When transmitting an IP packet to an upper layer IP layer,
A satellite communication system comprising a satellite line connection module for transmitting an IP packet as one data link layer processing module for the IP layer. 2. The communication system according to claim 1, wherein a PPP (point-to-point protocol) is used as a data link protocol of the terrestrial line, and an IP address assigned to each terminal at each start of communication is used. A satellite communication system which performs two-way communication, performs fixed communication in advance to each terminal, and performs broadcast communication using a virtual IP address not used for two-way communication.