Communication device and communication method

Abstract

To share an encryption key between a sender and a receiver to prevent interception by spoofing without using any other communication system.SOLUTION: A communication device includes a first extratropospheric communication unit 33A that communicates encrypted user data over a first extratropospheric communication line 6 relayed to a first extratropospheric mobile object 4 moving at a first altitude included outside the troposphere that is higher than the troposphere, and a second extratropospheric communication unit 33B that communicates, with a communication partner 12, communication control data including at least one of an encryption key used by an encryption device 15 through a second extratropospheric communication line 8 relayed to a second extratropospheric mobile object 5 moving at a second altitude before the first extratropospheric communication unit 33A communicates the encrypted user data, and a decryption key used when the communication partner 12 decrypts encrypted user data and communicates, with the communication partner 12, communication control data containing at least one of the encryption key used by the communication partner 12 and the decryption key used when the decryption device 15 decrypts the encrypted user data.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This disclosure relates to communication equipment and communication methods for communicating over a communication line relayed by an artificial satellite or a mobile object moving in the stratosphere. [Background technology]

[0002] In mobile communications, technologies for expanding communication areas to include locations other than land are attracting attention. To this end, systems integrating geostationary satellites (GEO), low-Earth orbit satellites (LEO), and high-altitude platform stations (HAPS) with ground-based mobile communication networks are being considered. Because geostationary, low-Earth orbit, and high-altitude platform stations (HAPS) are at different altitudes, their transmission speeds and latency differ due to differences in communication path length. Currently, communication systems are being developed that leverage the advantages of each type of satellite. However, communication services using geostationary, low-Earth orbit, and high-altitude platform stations are currently provided by different providers and operate as separate communication networks.

[0003] Satellite communications offer excellent broadcasting capabilities due to their wide coverage area provided by a single satellite. However, because satellite communications cover such a vast area, there is a risk of interception by spoofed devices.

[0004] To prevent unauthorized authentication requesters from tracking signals, a method has been proposed that uses a guard spot beam for authentication (see Patent Document 1). In satellite communications, which are characterized by wide coverage and broadcasting capabilities, it is difficult to prevent third parties from intercepting radio waves, and signal scrambling and encryption are common countermeasures. For example, an encryption method has been proposed that, although not primarily intended for satellite communications, is aimed at protecting terminal identification information (see Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5976774 [Patent Document 2] Special Publication 2020-532235 [Overview of the project] [Problems that the invention aims to solve]

[0006] In satellite communications using artificial satellites and high-altitude pseudo-satellites, when encryption is implemented to prevent interception by spoofed terminals, there is a challenge in how to share the encryption key between the sender and receiver. Possible methods for sharing the encryption key include sending the key via a terrestrial line and having the user input the key. However, since use is expected in remote areas, on islands, and on mobile devices where connection to terrestrial lines (including mobile phone networks and terrestrial wireless relay networks) is difficult, sharing the encryption key using other communication systems may be difficult, posing a challenge in the method of sharing the encryption key.

[0007] This disclosure was made to solve the problems described above, and aims to provide a communication device and communication method that enables the sharing of encryption keys between the sender and receiver without using other communication systems, and that enables the communication of encrypted user data. [Means for solving the problem]

[0008] The communication device relating to this disclosure is an out-of-tropic communication line which is a communication line relayed to an out-of-tropic relay station which is a relay station mounted on an out-of-tropic mobile body which is a mobile body that moves outside the troposphere at an altitude higher than the troposphere, and is an out-of-tropic communication line which is an out-of-tropic communication line relayed to an out-of-tropic relay station which is mounted on a first out-of-tropic mobile body which is a mobile body that moves at a first altitude included in the out-of-troposphere, and comprises a first out-of-tropic communication unit which communicates encrypted user data, which is data to be communicated, with a communication partner, an encryption device which generates encrypted user data by encrypting the user data to be transmitted with an encryption key, a decryption device which generates user data by decrypting the received encrypted user data with a decryption key, and the encrypted user data to the first out-of-tropic communication line The system comprises a second out-of-tropic communication unit which, before the communication unit communicates, is relayed to a second out-of-tropic relay station, which is mounted on a second out-of-tropic relay station, which is mounted on a second out-of-tropic mobile body, which is an out-of-tropic mobile body, moving at a second altitude, which is included in the out-of-tropic zone and is different from the first altitude, and which communicates communication control data, which is data communicated in order to communicate encrypted user data with the communication partner, and which includes at least one of the encryption key used by the encryption device and the decryption key used by the communication partner when decrypting encrypted user data generated by the encryption device, and communicates communication control data, which includes at least one of the encryption key used by the communication partner and the decryption key used by the decryption device when decrypting encrypted user data generated by the communication partner, with the communication partner.

[0009] The communication method relating to this disclosure is an out-of-tropic communication line, which is a communication line relayed to an out-of-tropic relay station, which is a relay station mounted on an out-of-tropic mobile body, which is a mobile body that moves outside the troposphere at an altitude higher than the troposphere, and is an out-of-tropic communication line, which is an out-of-tropic communication line relayed to an out-of-tropic relay station, which is mounted on a first out-of-tropic mobile body, which is an out-of-tropic communication line, which is an out-of-tropic communication line, which is an out-of-tropic communication line, which is a first out-of-tropic communication line, which is a first out-of-tropic communication unit that communicates encrypted user data, which is the data to be communicated, with the communication partner, and encrypts the user data to be transmitted using an encryption key and encrypts it A communication device comprising: an encryption device that generates user data; a decryption device that decrypts received encrypted user data using a decryption key to generate user data; and a second out-of-tropic communication unit that communicates with a communication partner via a second out-of-tropic communication line, which is relayed to a second out-of-tropic relay station mounted on a second out-of-tropic mobile body, which is an out-of-tropic mobile body that moves at a second altitude included in the out-of-troposphere, different from the first altitude; and a communication method for communicating between a requesting communication terminal, which is a communication terminal connected to one of the communication partners; and a requesting communication terminal, which is a communication terminal connected to the other of the communication device and the communication partner. The communication method includes the following steps: a procedure in which one of the communication devices and the communication partner receives a request to initiate communication from the requesting communication terminal to the requesting communication terminal; a procedure in which the second out-of-the-range communication unit communicates with the communication partner at least one of the encryption keys used by the encryption device when it encrypts user data to generate encrypted user data and the decryption key used by the communication partner when it decrypts the encrypted user data encrypted with the encryption device; a procedure in which the second out-of-the-range communication unit communicates with the communication partner at least one of the encryption keys used by the communication partner when it encrypts user data to generate encrypted user data and the decryption key used by the decryption device when it decrypts the encrypted user data encrypted with the decryption key; a procedure in which the encryption device encrypts user data from the requesting communication terminal with its encryption key, or the communication partner encrypts it with the partner encryption key, to generate encrypted user data; and a procedure in which the first out-of-the-range communication unit communicates with the first out-of-the-range communication unit the encrypted user data from the requesting communication terminal. The system comprises the following steps: a procedure for communicating with a communication partner over a transmission line; a procedure for the communication partner to decrypt encrypted user data received by the communication partner using their decryption key, or for the encryption device to decrypt encrypted user data received by the communication device using its own decryption key, thereby generating user data from the requesting communication terminal; a procedure for the communication partner or communication device to send the decrypted user data from the requesting communication terminal to the requesting communication terminal; a procedure for the communication partner to encrypt user data from the requesting communication terminal using their own encryption key, or for the encryption device to encrypt it using its own encryption key, thereby generating encrypted user data; a procedure for communicating the encrypted encrypted user data from the requesting communication terminal to the communication partner over a first out-of-convection communication line; a procedure for the decryption device to decrypt encrypted user data received by the first out-of-convection communication unit using its own decryption key, or for the communication partner to decrypt it using their own decryption key, thereby generating user data from the requesting communication terminal; and a procedure for the communication device or communication partner to send the decrypted user data from the requesting communication terminal to the requesting communication terminal. [Effects of the Invention]

[0010] According to the communication device and communication method described herein, it is possible to share encryption keys between the sender and receiver without using other communication systems, and to communicate encrypted user data. [Brief explanation of the drawing]

[0011] [Figure 1] This diagram shows a schematic configuration of a satellite communication system including a communication device according to Embodiment 1. [Figure 2] This is a diagram showing the configuration of the communication device according to Embodiment 1. [Figure 3] This is a flowchart of a communication method in which a communication terminal connected to a communication device according to Embodiment 1 initiates communication with a communication terminal connected to a communication partner. [Figure 4] This is a continuation of the flowchart for a communication method in which a communication terminal connected to a communication device according to Embodiment 1 initiates communication with a communication terminal connected to a communication partner. [Figure 5] This is a flowchart illustrating the process of determining the encryption key and decryption key used when a communication terminal connected to a communication device according to Embodiment 1 communicates with a communication terminal connected to a communication partner. [Figure 6] This is a continuation of the flowchart illustrating the process of determining the encryption and decryption keys used when a communication terminal connected to the communication device according to Embodiment 1 communicates with a communication terminal connected to a communication partner. [Figure 7] This is a flowchart illustrating the process by which the communication device according to Embodiment 1 encrypts user data and transmits it to a low Earth orbit satellite. [Figure 8] This is a flowchart illustrating the process by which the communication partner of the communication device according to Embodiment 1 decrypts encrypted user data received by the communication device and transmits it to the communication terminal. [Figure 9] This is a flowchart illustrating the process by which the communication partner of the communication device according to Embodiment 1 encrypts user data and transmits it to a low Earth orbit satellite. [Figure 10] This is a flowchart illustrating the process by which a communication device according to Embodiment 1 decrypts encrypted user data received and transmits it to a communication terminal. [Figure 11]This is a flowchart of the process by which the communication device according to Embodiment 1 transmits communication control data to a geostationary satellite. [Figure 12] This is a flowchart illustrating the process by which the communication partner of the communication device according to Embodiment 1 receives communication control data. [Figure 13] This is a flowchart illustrating the process by which the communication partner of the communication device according to Embodiment 1 transmits communication control data to a geostationary satellite. [Figure 14] This is a flowchart of the process by which the communication device according to Embodiment 1 receives communication control data. [Figure 15] This diagram shows a schematic configuration of a satellite communication system including a communication device according to Embodiment 2. [Figure 16] This is a diagram showing the configuration of the communication device according to Embodiment 2. [Figure 17] This is a flowchart showing the process when a communication terminal connected to a communication device according to Embodiment 2 initiates communication with a communication terminal connected to a communication partner. [Figure 18] This is a continuation of the flowchart showing the process when a communication terminal connected to a communication device according to Embodiment 2 initiates communication with a communication terminal connected to a communication partner. [Figure 19] This is a flowchart illustrating the process of determining the encryption key and decryption key used when a communication terminal connected to a communication device according to Embodiment 2 communicates with a communication terminal connected to a communication partner. [Figure 20] This is a continuation of the flowchart illustrating the process of determining the encryption and decryption keys used when a communication terminal connected to a communication device according to Embodiment 2 communicates with a communication terminal connected to a communication partner. [Figure 21] This is a flowchart illustrating the process by which the communication device according to Embodiment 2 encrypts user data and transmits it to a high-altitude pseudo-satellite. [Figure 22] This is a flowchart illustrating the process by which the communication partner of the communication device according to Embodiment 2 decrypts encrypted user data received by the communication device and transmits it to the communication terminal. [Figure 23] This is a flowchart illustrating the process by which the communication partner of the communication device according to Embodiment 2 encrypts user data and transmits it to a high-altitude pseudo-satellite. [Figure 24] This is a flowchart illustrating the process by which a communication device according to Embodiment 2 decrypts encrypted user data received and transmits it to a communication terminal. [Figure 25] This is a flowchart illustrating the process by which the communication device according to Embodiment 2 transmits communication control data to a low Earth orbit satellite. [Figure 26] This is a flowchart illustrating the process by which the communication partner of the communication device according to Embodiment 2 transmits communication control data to a low Earth orbit satellite. [Figure 27] This is a diagram showing the configuration of the communication device according to Embodiment 3. [Figure 28] This is a flowchart showing the process when a communication terminal connected to a communication device according to Embodiment 3 initiates communication with a communication terminal connected to a communication partner. [Figure 29] This is a continuation of the flowchart showing the process when a communication terminal connected to a communication device according to Embodiment 3 initiates communication with a communication terminal connected to a communication partner. [Figure 30] This is a diagram showing the configuration of the communication device according to Embodiment 4. [Figure 31] This diagram shows a schematic configuration of a satellite communication system including a communication device according to Embodiment 5. [Figure 32] This is a diagram showing the configuration of the communication device according to Embodiment 5. [Figure 33] This is a flowchart of a communication method in which a communication terminal connected to a communication device according to Embodiment 5 initiates communication with a communication terminal connected to a communication partner that is communicating with the same high-altitude pseudo-satellite. [Figure 34] This is a continuation of the flowchart for a communication method in which a communication terminal connected to a communication device according to Embodiment 5 initiates communication with a communication terminal connected to a communication partner that is communicating with the same high-altitude pseudo-satellite. [Figure 35] This is a flowchart of a communication method in which a communication terminal connected to a communication device according to Embodiment 5 initiates communication with a communication terminal connected to a communication partner that communicates with a different high-altitude pseudo-satellite. [Figure 36]This is a continuation of the flowchart for a communication method in which a communication terminal connected to a communication device according to Embodiment 5 initiates communication with a communication terminal connected to a communication partner that communicates with a different high-altitude pseudo-satellite. [Figure 37] This flowchart illustrates the procedure from when a communication terminal connected to a communication device according to Embodiment 5 communicates with a communication terminal connected to a communication partner that communicates with a different high-altitude pseudo-satellite, up to when the high-altitude pseudo-satellite receives radio waves and when the other high-altitude pseudo-satellite emits radio waves. [Figure 38] This flowchart illustrates the procedure from when a communication terminal connected to a communication device according to Embodiment 5 communicates with a communication partner that communicates with a different high-altitude pseudo-satellite, up to when the different high-altitude pseudo-satellite receives radio waves and when the high-altitude pseudo-satellite emits radio waves. [Figure 39] This is a flowchart of a communication method in which a communication terminal connected to a communication device according to Embodiment 5 initiates communication with a communication terminal connected to a communication partner connected to a terrestrial communication network. [Figure 40] This is a continuation of the flowchart for a communication method in which a communication terminal connected to a communication device according to Embodiment 5 initiates communication with a communication terminal connected to a communication partner connected to a terrestrial communication network. [Figure 41] This flowchart illustrates the procedure from when a communication terminal connected to a communication device according to Embodiment 5 communicates with a communication terminal connected to a communication partner connected to a terrestrial communication network, to when a high-altitude pseudo-satellite receives radio waves and when encrypted user data is transmitted over the terrestrial communication network. [Figure 42] This flowchart illustrates the procedure from the time encrypted user data is transmitted over the terrestrial communication network until the high-altitude pseudo-satellite emits radio waves when a communication terminal connected to a communication device according to Embodiment 5 communicates with a communication terminal connected to a communication partner connected to a terrestrial communication network. [Modes for carrying out the invention]

[0012] Embodiment 1. Figure 1 shows a schematic configuration of the satellite communication system according to Embodiment 1. The satellite communication system 100 includes earth stations 11 and 12, networks 21 and 22, communication terminals 31 and 32, low-Earth orbit satellites 41 and 42, and a geostationary satellite 5. Communication terminal 31 is connected to earth station 11 via network 21. Communication terminal 32 is connected to earth station 12 via network 22. Earth stations 11 and 12 have the same configuration. All earth stations, or earth stations that are not specifically designated, are referred to as earth station 1. The same applies to network 2, communication terminal 3, low-Earth orbit satellite 4, etc. Earth station 1 may be fixed to the Earth's surface, or it may move on the ground, water surface, underground, underwater, or in the air.

[0013] In the satellite communication system 100, communication terminals 31 and 32 communicate using satellite communication links relayed by low-Earth orbit satellites 41 and 42 and satellite communication links relayed by geostationary satellite 5. Network 21 may be a LAN (Local Area Network) or a WAN (Wide Area Network). Network 21 may be a dedicated network or a public network. The same applies to network 22. There are multiple communication terminals 31 connected to earth station 11. There are also multiple communication terminals 32 connected to earth station 12. Here, we will explain the case where a communication terminal 31 connected to earth station 11 initiates communication with a communication terminal 32 connected to earth station 12.

[0014] Earth station 11 and Earth station 12 can communicate via low-Earth orbit satellite communication links 61 and 62 and low-Earth orbit satellite communication link 7, which are relayed by low-Earth orbit satellites 41 and 42. Low-Earth orbit satellite communication link 61 is a satellite communication link used for communication between Earth station 11 and low-Earth orbit satellite 41. Low-Earth orbit satellite communication link 62 is a satellite communication link used for communication between Earth station 12 and low-Earth orbit satellite 42. Low-Earth orbit satellite communication link 7 is an inter-satellite communication link connecting low-Earth orbit satellite 41 and low-Earth orbit satellite 42. NIf an intermediary is present, there will be multiple low-Earth orbit satellite communication links 7. If low-Earth orbit satellite 41 and low-Earth orbit satellite 42 are the same, earth station 11 and earth station 12 will communicate without going through the low-Earth orbit satellite communication link 7.

[0015] Earth station 11 and Earth station 12 can communicate using geostationary satellite communication links 81 and 82, which are relayed by geostationary satellite 5. Geostationary satellite communication link 81 is a satellite communication link used for communication between Earth station 11 and geostationary satellite 5. Geostationary satellite communication link 82 is a satellite communication link used for communication between Earth station 12 and geostationary satellite 5. The communication partner is the communication device of the device with which Earth station 1, which is a communication device, communicates. Earth station 11's communication partner is Earth station 12. Earth station 12's communication partner is Earth station 11.

[0016] Encrypted data (user data) is transmitted over the low Earth orbit satellite communication links 61 and 62 and the low Earth orbit satellite communication link 7. Geostationary satellite communication links 81 and 82 transmit information necessary to use the data transmitted over the low Earth orbit satellite communication links 61 and 62 and the low Earth orbit satellite communication link 7, such as decryption keys for decrypting encrypted user data. In the satellite communication system related to this disclosure, the use of two types of satellite communication links prevents third parties from intercepting communications between communication terminals 31 and 32. User data, which is the subject of communication, is not transmitted over the geostationary satellite communication links 81 and 82. User data transmitted over the low Earth orbit satellite communication links 61 and 62 and the low Earth orbit satellite communication link 7 is encrypted. Even if either the geostationary satellite communication links 81 and 82 or the low Earth orbit satellite communication links 61 and 62 is intercepted, it is not possible to decrypt and obtain the user data transmitted by communication terminal 31 or communication terminal 32. In Embodiment 1, the encryption method is a symmetric-key encryption scheme in which the encryption key used to encrypt the data and the decryption key used to decrypt the encrypted data are the same.

[0017] Referring to Figure 2, the configuration of Earth Station 1 will be explained. Earth Station 1 is an antenna device 11 A , 11 B , frequency converter 12 A , 12 B, Demodulator 13 A , 13 B , has a data processing device 14, an encryption device 15, and a network interface unit 16 (abbreviated as network IF unit). The data processing device 14 has a satellite communication interface unit 50 (abbreviated as satellite communication IF unit), a line control unit 51, a tracking control unit 52, a satellite position management unit 53, a sequence control unit 54, an encryption key decryption key management unit 55, an encryption device control unit 56, a communication control data processing unit 57, and a data storage unit 58. Antenna device 11 A , 11 B For matters common to, they are described with the symbol of the antenna device 11. The same applies to the frequency converter 12 and the like. Note that the earth station 1 as a communication device may be considered not to include the antenna device 11 A , 11 B either.

[0018] The antenna device 11 is an antenna whose pointing direction is mechanically changed. The antenna device 11 also includes an amplifier that amplifies the transmission signal, an amplifier that amplifies the reception signal, and a mechanism unit that changes the pointing direction of the antenna. Antenna device 11 A transmits and receives radio waves to and from, for example, the low-earth orbit satellite 4. Antenna device 11 B transmits and receives radio waves to and from, for example, the geostationary satellite 5. The antenna device 11 may be a phased array antenna that electrically changes the pointing direction. The antenna device 11 may be a phased array antenna supported by a mechanism that mechanically changes the pointing direction. There are also phased array antennas in which the receiving antenna device and the transmitting antenna device are separate devices.

[0019] Frequency converter 12 A converts the transmission signal transmitted by the antenna device 11 A to the frequency of the radio wave, and converts the frequency of the reception signal received by the antenna device 11 A to the intermediate frequency or the frequency of the baseband signal. Frequency converter 12 B converts the transmission signal transmitted by the antenna device 11 B to the frequency of the radio wave, and the antenna device 11 BThe frequency of the received signal is converted to the frequency of the intermediate frequency or baseband signal. (Modulator 13) A The modulated transmission signal is transmitted via the frequency converter 12 A Output to frequency converter 12 A Demodulates the received signal input from the modulator / demodulator 13. B The modulated transmission signal is transmitted via the frequency converter 12 B Output to frequency converter 12 B The received signal input from the antenna device 11 is demodulated. A , frequency converter 12 A and modulator / demodulator 13 A The A-series satellite communications unit 33 A It is called [this]. Antenna device 11 B , frequency converter 12 B and modulator / demodulator 13 B The B-series satellite communications unit 33 B It is called that. Earth station 1 as a communication device is antenna device 11 A , 11 B If not included, frequency converter 12 A and modulator / demodulator 13 A However, Satellite Communications Department 33 A This is the frequency converter 12. B and modulator / demodulator 13 B However, Satellite Communications Department 33 B That is the case.

[0020] Frequency converter 12 A , 12 B and modulator / demodulator 13 A , 13 B A switch is provided between the frequency converter 12 A and modulator / demodulator 13 B The and are connected, and frequency converter 12 B and modulator / demodulator 13 A It may be possible to make it possible for the two to be connected. If the device can process multiple channels simultaneously, then the frequency converter 12 A , 12 B This can be done with a single frequency converter. (Modulator 13) A , 13 B This can be combined into a single modulator / demodulator.

[0021] The data processing device 14 is a modulator / demodulator 13 A or modulator / demodulator 13 B The encrypted user data input from either of the two sources is decrypted by the encryption device 15. The data processing device 14 outputs the decrypted user data or unencrypted data to the network IF unit 16. The data processing device 14 encrypts the transmission data input from the network IF unit 16 using the encryption device 15 if encryption is required. The data processing device 14 processes the encrypted or unencrypted transmission data from the encryption device 15 into the modulator / demodulator 13 according to the data type. A or modulator / demodulator 13 B Output is sent to [location]. Encryption device 15 is an encryption device that encrypts the user data to be transmitted using an encryption key to generate encrypted user data. Encryption device 15 is also a decryption device that decrypts the received encrypted user data using a decryption key to generate user data.

[0022] The data processing device 14 is provided with two terminals, and the two terminals and the modulator / demodulator 13 A , 13 B A switch may be provided to switch between the two connections. The two terminals are called the A-series terminal and the B-series terminal. The switch connects the A-series terminal to the modulator / demodulator 13 A It is connected to the transformer / demodulator 13, and the terminals of the B series are connected to the transformer / demodulator 13 B The state in which it is connected, and the terminals of the A series are connected to the transformer / demodulator 13 B It is connected to the transformer / demodulator 13, and the terminals of the B series are connected to the transformer / demodulator 13 A It can be in one of two states: connected or otherwise. The switch state can be toggled.

[0023] The network interface unit 16 outputs user data transmitted by the communication terminal 3, which is input from network 2, to the data processing unit 14. The network interface unit 16 also outputs user data that the communication terminal 3 should receive, which is output by the data processing unit 14, to the communication terminal 3 via network 2. The network interface unit 16 is a terminal connection unit that exchanges user data with the communication terminal.

[0024] The satellite communication IF unit 50 is connected to the satellite communication unit 33 A ,33 B It exchanges packets with the other party. The satellite communication IF unit 50 also exchanges data with the encryption device control unit 56, the communication control data processing unit 57, and the network IF unit 16.

[0025] The line control unit 51 is connected to the satellite communication unit 33 A ,33 B For each of these, the relay satellite, transmission frequency, reception frequency, modulation / demodulation method, and error correction method are managed. The satellite communication unit 33 uses the same modulation / demodulation method and the same error correction method for both transmission and reception. Possible methods for the modulation / demodulation method and error correction method include those specified in public standards for digital television broadcasting or mobile communication systems. The tracking control unit 52 controls the antenna device 11 A , 11 B The antenna device 11 is positioned to face the direction of the satellite from which the signal is relayed. A , 11 B The tracking control unit 52 controls the following. As the low-Earth orbit satellite 4 moves relative to the Earth's surface, the low-Earth orbit satellite 4 that can communicate with Earth Station 1 changes over time. The tracking control unit 52 also controls the handover of the low-Earth orbit satellite 4. When the low-Earth orbit satellite 4 is handed over, the line control unit 51 also operates, and the satellite communication unit 33 A ,33 B In any of the series communicating with the low-Earth orbit satellite 4, the relay satellite, transmission frequency, reception frequency, modulation / demodulation method, and error correction method are changed. The satellite position management unit 53 obtains orbital data of the low-Earth orbit satellite 4 and the geostationary satellite 5 from an external source. The satellite position management unit 53 uses the orbital data to control the antenna device 11 at predetermined intervals. A , 11 B This determines the position of the satellite being tracked.

[0026] The series control unit 54 sends terminal management data (C-plane) and user data (U-plane) to the satellite communication unit 33 for each communication terminal 3 connected via the network 2. A ,33 BThis controls which plane to use for communication. Separating the C-plane and U-plane is a key aspect of the fifth-generation mobile communication system (5G:5 th This is similar to (Generation mobile communication systems). In the communication device relating to this disclosure, the satellite communication link for communicating C-planes and the satellite communication link for communicating U-planes are separate.

[0027] Terminal management data includes communication control data. Communication control data is data that is communicated by the communication device to communicate encrypted user data with the communication partner. The series control unit 54 is a communication control unit that controls the communication of encrypted user data by the satellite communication unit 33 on the U-plane side and the communication control data by the satellite communication unit 33 on the C-plane side.

[0028] A communication terminal 3 connected to an earth station 1, which is a communication device, is called a local communication terminal. A communication terminal 3 that any of the local communication terminals 3 communicate with is called a partner communication terminal. A partner communication terminal connects to another earth station 1 (communication partner). The encryption key / decryption key management unit 55 manages the encryption key used for each local communication terminal and for each series. The encryption key is the encryption key used when encrypting user data transmitted by the local communication terminal. The encryption key / decryption key management unit 55 manages the decryption key used for each partner communication terminal and for each series. The decryption key is the decryption key used when decrypting encrypted user data transmitted by the partner communication terminal.

[0029] The encryption key / decryption key management unit 55 determines and manages an encryption key for each communication terminal 3. Since it is a symmetric-key encryption scheme, the encryption key is also the decryption key. The encryption device control unit 56 provides the encryption device 15 with the encryption key and the data to be encrypted, and instructs it to encrypt. The encryption device control unit 56 provides the encryption device 15 with the decryption key and the data to be decrypted, and instructs it to decrypt. The communication control data processing unit 57 interprets the communication control data and causes other control units to perform the actions instructed by the communication control data. The communication control data processing unit 57 also creates communication control data to be sent to the communication partner.

[0030] The data storage unit 58 stores the data necessary for the operation of the earth station 1. The data storage unit 58 stores the communication satellite 80 A 、80 B 、the reception frequency 81 A 、81 B 、the transmission frequency 82 A 、82 B 、the modulation / demodulation method 83 A 、83 B 、the error correction method 84 A 、84 B 、the own station position 85, the satellite position 86 A 、86 B 、the satellite existence direction 87 A 、87 B 、the used series 88, the encryption key 89 and the decryption key 90.

[0031] The communication satellite 80 A is data that stores the satellite through which the communication line used by the satellite communication unit 33 A is relayed. The communication satellite 80 B is data that stores the satellite through which the communication line used by the satellite communication unit 33 B is relayed. The reception frequency 81 A is the frequency of the radio wave received by the antenna device 11 A . The reception frequency 81 B is the frequency of the radio wave received by the antenna device 11 B . The transmission frequency 82 A is the frequency of the radio wave transmitted by the antenna device 11 A . The transmission frequency 82 B is the frequency of the radio wave transmitted by the antenna device 11 B . The frequency converter 12 A converts the frequency referring to the reception frequency 81 A and the transmission frequency 82 A . The frequency converter 12 B converts the frequency referring to the reception frequency 81 B and the transmission frequency 82 B . The communication satellite 80 A 、80 B 、the reception frequency 81 A 、81 B and the transmission frequency 82A , 82 B This is set by the line control unit 51.

[0032] Modulation / Demodulation Method 83 A , is the modulator / demodulator 13 A This is data that stores the modulation / demodulation method to be used. Modulation / Demodulation Method 83 B , is the modulator / demodulator 13 B This is data that stores the modulation / demodulation method to be used. Error correction method 84 A , is the modulator / demodulator 13 A This is data that stores the error correction scheme to be used. Error correction scheme 84 B , is the modulator / demodulator 13 B This is data that stores the error correction method used.

[0033] The local position 85 is the location of Earth Station 1. If Earth Station 1 does not move, the local position 85 will remain unchanged. If Earth Station 1 moves, the local position 85 will be the position of the mobile device on which Earth Station 1 is mounted. The position of the mobile device is input from outside Earth Station 1. Satellite position 86 A This refers to the current situation and future communication points within a defined range of satellite 80 A This is the location where it exists. Satellite position 86 B This refers to the current situation and future communication points within a defined range of satellite 80 B This is the location where it exists. Satellite position 86 A , 86 B This is set by the satellite position management unit 53. The satellite position management unit 53 operates at predetermined intervals and sets the satellite position 86 from the time of operation to a predetermined future point in time. A , 86 B Set the satellite location direction to 87. A From local position 85 to satellite position 86 A This is the direction towards the satellite. Satellite location direction 87 B From local position 85 to satellite position 86 B This is the direction toward. The tracking control unit 52 controls the antenna device 11 A The direction of orientation is the direction of the satellite's presence 87 A Antenna device 11 to match AThe tracking control unit 52 controls the antenna device 11. B The direction of orientation is the direction of the satellite's presence 87 B Antenna device 11 to match B Control.

[0034] The operating series 88 has a C-plane and a U-plane, respectively, connected to the satellite communication unit 33 for each communication terminal 3. A ,33 B This data indicates which communication method will be used. The maximum number of communication terminals 3 that can connect to Earth Station 1 is represented by the variable N. max It is represented as follows. The number of sequences used is 2*N for sequence 88. max This is a data set containing 2*N data points. The encryption key 89 is data that stores the encryption key used for encryption for each communication terminal 3 and for each series. The number of encryption keys 89 is 2*N. max This is a data set. The decryption key 90 is data that stores the decryption key used to decrypt encrypted user data sent by the other communication terminal, for each communication terminal and for each series. The maximum number of communication terminals 3 that one communication terminal 3 communicates with simultaneously is assumed to be variable K. MAX This is represented as follows. The number of decryption keys 90 is 2*K. max *N max This is a single data point. Since it uses a symmetric-key encryption scheme, the decryption key used to decrypt data encrypted with the encryption key is the same as the encryption key. The usage sequence involves all communication terminals 3 connecting to the U-Plane and C-Plane respectively via the satellite communication unit 33. A ,33 B This data can also be used to switch between two communication methods.

[0035] The data storage unit 58 is an encryption key storage unit that stores the encryption key used by the encryption device 15 for each communication terminal, which is a communication terminal connected to the terminal connection unit. The encryption key used by the encryption device 15 is stored in the data storage unit 58 as encryption key 89. The data storage unit 58 is also a corresponding decryption key storage unit that stores the corresponding decryption key, which is the decryption key used by the encryption device 15 to decrypt the data encrypted with the encryption key, for each communication terminal. Since a symmetric key encryption scheme is used, the corresponding decryption key, which is the decryption key used to decrypt the data encrypted with the encryption key, is the same as the encryption key. Therefore, the corresponding decryption key is stored in the data storage unit 58 as encryption key 89. The data storage unit 58 is also a used decryption key storage unit that stores the used decryption key, which is the decryption key used by the encryption device 15 when decrypting received encrypted user data, for each communication terminal that is the source of the encrypted user data. The used decryption key is stored in the data storage unit 58 as decryption key 90.

[0036] In the data processing unit 14, C-plane packets from the network IF unit 16 are forwarded to the communication control data processing unit 57. When the satellite communication IF unit 50 receives a C-plane packet from the communication control data processing unit 57, it forwards the modulator / demodulator 13(13) of the sequence set on the C-plane side in the communication terminal 3 usage sequence 88 corresponding to the source address written in the packet header. A or 13 B The packet is output to the following: The communication terminal 3 corresponding to the source address listed in the packet header is called the source communication terminal. The communication terminal 3 corresponding to the destination address listed in the packet header is called the destination communication terminal.

[0037] When the satellite communication IF unit 50 receives a U-plane packet from the network IF unit 16, the modulator / demodulator 13 (13) of the sequence set on the U-plane side in the source communication terminal's usage sequence 88 B or 13 AThe packet is output to the ). Note that the U-plane user data (packet) needs to be encrypted, so the encryption device control unit 56 has the encryption device 15 encrypt the user data using the encryption key 89 stored on the U-plane side of the source communication terminal and generates encrypted user data. The satellite communication IF unit 50 outputs the encrypted user data to the modulator / demodulator 13 (13) of the sequence set on the U-plane side in the source communication terminal's usage sequence 88. B or 13 A Output to ).

[0038] The satellite communication IF unit 50 controls the modulator / demodulator 13 (13) of the sequence set on the C-plane side in the sequence 88 used by the source communication terminal. A or 13 B When a packet is received from ), it is forwarded to the communication control data processing unit 57. The communication control data processing unit 57 interprets the C-plane packet (communication control data) and either performs the processing instructed by the communication control data itself or has another processing unit perform the processing.

[0039] The satellite communication IF unit 50 controls the modulator / demodulator 13 (13) of the sequence set on the U-plane side in the transmission source communication terminal's usage sequence 88. B or 13 A When a packet (encrypted user data) is received from the source communication terminal, it is forwarded to the encryption device control unit 56. The encryption device control unit 56 obtains the decryption key stored on the U-plane side in the source communication terminal's usage sequence 88 from the decryption key 90, and uses the obtained decryption key to have the encryption device 15 decrypt the data and generate user data. The user data is sent to the source communication terminal via the network IF unit 16.

[0040] When explaining the functions of the encryption key / decryption key management unit 55 and the communication control data processing unit 57, the communication terminal that sent the communication start request is referred to as the requesting communication terminal, and the communication terminal specified as the communication partner in the communication start request is referred to as the requesting communication terminal.

[0041] The encryption key / decryption key management unit 55 determines an encryption key when it receives a communication start request from the requesting communication terminal or earth station 1, and stores it in the encryption key 89.

[0042] When the encryption key / decryption key management unit 55 receives a communication start request from the requesting communication terminal, it checks whether the encryption key of the requesting communication terminal on the U-Plane side is stored in the encryption key 89 in the usage sequence 88. If it is not stored, the encryption key / decryption key management unit 55 determines an encryption key. The encryption key / decryption key management unit 55 stores the determined encryption key in the encryption key 89 as the encryption key of the requesting communication terminal on the U-Plane side in the usage sequence 88. The encryption key of a terminal is the encryption key used when encrypting user data transmitted by that terminal.

[0043] When the encryption key / decryption key management unit 55 receives communication control data for a communication start request sent from another earth station 1 (communication partner), it stores the decryption key of the requesting communication terminal included in the communication control data for the communication start request in the decryption key 90 as the decryption key of the requesting communication terminal on the U-Plane side in the usage sequence 88. The decryption key of a terminal is the decryption key used to decrypt encrypted user data that the user data transmitted by that terminal has been encrypted. The encryption key / decryption key management unit 55 then checks whether the encryption key of the requesting communication terminal specified in the communication start request is stored on the U-Plane side in the usage sequence 88 in the encryption key 89. If it is not stored, the encryption key / decryption key management unit 55 determines an encryption key. The encryption key / decryption key management unit 55 then stores the determined encryption key in the usage sequence 88 as the encryption key of the requesting communication terminal on the U-Plane side in the encryption key 89.

[0044] When the encryption key / decryption key management unit 55 receives communication control data for accepting the commencement of communication transmitted from another earth station 1 (communication partner), it stores the corresponding decryption key of the requesting communication terminal included in the communication control data for accepting the commencement of communication in the decryption key 90 as the decryption key of the requesting communication terminal on the U-Plane side in the usage sequence 88.

[0045] If the encryption key of the requesting communication terminal is not stored in the encryption key storage unit, the encryption key and corresponding decryption key management unit 55 determines the encryption key and corresponding decryption key, stores the determined encryption key in the encryption key storage unit as the encryption key of the requesting communication terminal, and stores the determined corresponding decryption key in the corresponding decryption key storage unit as the corresponding decryption key of the requesting communication terminal.

[0046] When the encryption key / decryption key management unit 55 receives communication control data for a communication start request, it stores the corresponding decryption key of the requesting communication terminal included in the received communication control data as the decryption key used by the requesting communication terminal in the used decryption key storage unit. If the encryption key of the requesting communication terminal is not stored in the encryption key storage unit, it determines the encryption key and corresponding decryption key, stores the determined encryption key as the encryption key of the requesting communication terminal in the encryption key storage unit, and stores the determined corresponding decryption key as the corresponding decryption key of the requesting communication terminal in the corresponding decryption key storage unit.

[0047] When the encryption key / decryption key management unit 55 receives communication control data accepting the commencement of communication, it stores the corresponding decryption key of the requesting communication terminal included in the received communication control data as the decryption key to be used by the requesting communication terminal in the use-decryption key storage unit.

[0048] When the communication control data processing unit 57 receives communication control data for a communication start request from the requesting communication terminal, it creates communication control data for the communication start request that includes the requesting communication terminal, the requesting communication terminal, and the encryption key of the requesting communication terminal determined by the encryption key / decryption key management unit 55, and outputs it to the satellite communication IF unit 50. The satellite communication IF unit 50 outputs the communication control data to the modulator / demodulator 13 on the C-Plane side in the usage sequence 88. Here, the encryption key of a certain terminal is the encryption key used when encrypting user data transmitted by that terminal. The satellite communication unit 33, including the modulator / demodulator 13 on the C-Plane side in the usage sequence 88, communicates the communication control data for the communication start request with the communication partner.

[0049] When the communication control data processing unit 57 receives communication control data for a communication start request transmitted from the communication partner, it creates communication control data for accepting the start of communication, including the requesting communication terminal, the requesting communication terminal, and the encryption key of the requesting communication terminal, and outputs it to the satellite communication IF unit 50. The satellite communication IF unit 50 outputs the communication control data to the modulator / demodulator 13 on the C-Plane side in the usage sequence 88. The satellite communication unit 33, including the modulator / demodulator 13 on the C-Plane side in the usage sequence 88, communicates the communication control data for accepting the start of communication with the communication partner.

[0050] The communication control data processing unit 57 is a communication control data generation unit that, upon receiving a communication start request from its own communication terminal, the requesting communication terminal, to the requesting communication terminal, which is a communication terminal connected to the communication partner via the network, generates communication control data for the communication start request, including the requesting communication terminal, the requesting communication terminal, and the corresponding encryption key for the requesting communication terminal. It also generates communication control data for accepting the communication start request, including the corresponding encryption key for the requesting communication terminal, upon receiving communication control data for the communication start request from the communication partner.

[0051] The operation will now be explained. Figures 3 and 4 are flowcharts illustrating the general procedure of a communication method in which a communication terminal 31 connected to earth station 11 communicates with a communication terminal 32 connected to earth station 12. Figure 3 illustrates the process up to step S08, and Figure 4 illustrates the process from step S09 onwards. Assume that in earth stations 11 and 12, series A is a U-Plane and series B is a C-Plane. In step S01, communication terminal 31 sends a communication start request to earth station 11 to communicate with communication terminal 32, and the network IF unit 16 of earth station 11 receives it. In step S02, earth stations 11 and 12 determine the encryption key and decryption key to be used for communication between communication terminal 31 and communication terminal 32 and store them in the data storage unit 58. The process in S02 will be explained using the flowcharts shown in Figures 5 and 6. Here, earth station 11 is assumed to be the communication device and earth station 12 is the communication partner. Earth station 12 may be a communication device, and earth station 11 may be the communication partner.

[0052] S01 is the procedure for the earth station 11 to receive a communication start request from the requesting communication terminal to the requesting communication terminal. S02 includes the procedure for determining the local encryption key CK1, which is the encryption key used by the encryption device 15 of the communication device (earth station 11) when it encrypts user data and generates encrypted user data, and the remote decryption key CK1, which is the decryption key used by the communication partner (earth station 12) when it decrypts the encrypted user data encrypted with the local encryption key, and the procedure for determining the remote encryption key CK2, which is the encryption key used by the communication partner when it encrypts user data and generates encrypted user data, and the local decryption key CK2, which is the decryption key used by the decryption device when it decrypts the encrypted user data encrypted with the remote encryption key.

[0053] Steps S03 onwards are the processes for communicating user data and communication control data between communication terminal 31 and communication terminal 32. Steps S03 to S05 are the procedure for sending user data UD1 from communication terminal 31 to communication terminal 32. Steps S06 to S08 are the procedure for sending user data UD2 from communication terminal 32 to communication terminal 31. Steps S09 to S11 are the procedure for sending communication control data CC1 from communication terminal 31 or earth station 11 to earth station 12. Steps S12 to S14 are the procedure for sending communication control data CC2 from communication terminal 32 or earth station 12 to earth station 11. The processes S03 to S05, S06 to S08, S09 to S11, and S12 to S14 are executed in parallel.

[0054] In step S03, the earth station 11 converts the user data UD1 that communication terminal 31 transmits to communication terminal 32 into encrypted user data CD1 and radiates it as radio wave RU1 towards low orbit satellite 41. In step S04, the low orbit satellite 41 receives radio wave RU1, frequency-converts and amplifies it, and radiates it as radio wave RC1. The low orbit satellite 42 receives radio wave RC1, frequency-converts and amplifies it, and radiates it as radio wave RD2. In step S05, the earth station 12 receives radio wave RD2, demodulates and decodes it to generate user data UD1. The earth station 12 transmits user data UD1 to communication terminal 32. The process in S03 is explained in the flowchart shown in Figure 7. The process in S05 is explained in the flowchart shown in Figure 8.

[0055] In step S06, the earth station 12 converts the user data UD2 that communication terminal 32 transmits to communication terminal 31 into encrypted user data CD2 and radiates it as radio wave RU2 towards low orbit satellite 42. In step S07, low orbit satellite 42 receives radio wave RU2, frequency-converts and amplifies it, and radiates it as radio wave RC2. Low orbit satellite 41 receives radio wave RC2, frequency-converts and amplifies it, and radiates it as radio wave RD1. In step S08, earth station 11 receives radio wave RD1, demodulates and decodes it to generate user data UD2. Earth station 11 transmits user data UD2 to communication terminal 31. The process in S06 is explained in the flowchart shown in Figure 9. The process in S08 is explained in the flowchart shown in Figure 10.

[0056] In step S09, Earth station 11 transmits the communication control data CC1 to Earth station 12 via radio waves RU directed towards geostationary satellite 5. C1 It emits as radio waves. In step S10, geostationary satellite 5 emits radio waves RU C1 Receiving radio waves, C1 The signal is frequency converted and amplified to produce radio waves (RD). C2 It emits as radio waves RD. In step S11, earth station 12 emits radio waves RD. C2 Receiving radio waves, RD C2The signal is demodulated to generate communication control data CC1. Earth station 12 processes the communication control data CC1 to control communication between communication terminal 31 and communication terminal 32. The process in S09 is explained in the flowchart shown in Figure 11. The process in S11 is explained in the flowchart shown in Figure 12.

[0057] In step S12, Earth station 12 transmits the communication control data CC2 to Earth station 11 via radio waves RU directed towards geostationary satellite 5. C2 It emits as radio waves. In step S13, geostationary satellite 5 emits radio waves RU C2 Receiving radio waves, C2 The signal is frequency converted and amplified to produce radio waves (RD). C1 It emits as radio waves RD. In step S14, earth station 11 emits radio waves RD. C1 Receiving radio waves, RD C1 The signal is demodulated to generate communication control data CC2. Earth station 11 processes the communication control data CC2 to control communication between communication terminal 31 and communication terminal 32. The process in S12 is explained in the flowchart shown in Figure 13. The process in S14 is explained in the flowchart shown in Figure 14.

[0058] Referring to Figures 5 and 6, the procedure for determining and storing the encryption and decryption keys used for communication between communication terminals 31 and 32 in the data storage unit 58 in step S02 will be explained. In step S21, the data processing unit 14 of earth station 11 receives a communication start request from communication terminal 31 and transfers it to the communication control data processing unit 57. In step S22, the encryption key / decryption key management unit 55 activated in the communication control data processing unit 57 checks whether the encryption key 89 is set for the U-Plane side (series A) of communication terminal 31. If the encryption key is not set (NO in S22), in step S23, the encryption key / decryption key management unit 55 determines the encryption key CK1 for the U-Plane side (series A) of communication terminal 31. The encryption key / decryption key management unit 55 stores the determined encryption key CK1 in the encryption key 89. If, after the execution of S23, the encryption key for the U-Plane side (series A) of the communication terminal 31 is set with encryption key 89 (YES in S22), proceed to step S24. Encryption key CK1 is the self-encryption key used by earth station 11. Encryption key CK1 is also the other party decryption key used by earth station 12.

[0059] In step S24, the communication control data processing unit 57 of the earth station 11 generates communication control data CC1, a communication start request including communication terminals 31 and 32, and the encryption key CK1 (which is also the decryption key) of communication terminal 31, and transmits it to the satellite communication IF unit 50. The encryption key CK1 is obtained from the encryption key 89. In step S25, the satellite communication IF unit 50 transmits the communication control data CC1 to the satellite communication unit 33, which is the C-Plane side (series B) of communication terminal 31. B It transmits to the satellite communications unit 33 of Earth station 11 in step S26. B It transmits communication control data CC1 as radio wave RU1 towards geostationary satellite 5. Specifically, the satellite communications unit 33 of earth station 11 B The modulator / demodulator 13 B The transmission signal SS1 is generated by modulating it with the communication control data CC1. Frequency converter 12 B The antenna device 11 converts the frequency of the transmitted signal SS1. B It transmits the frequency-converted transmission signal SS1 as radio wave RU1 towards geostationary satellite 5.

[0060] In step S27, geostationary satellite 5 receives radio wave RU1, converts its frequency, amplifies it, and transmits radio wave RD1. In step S28, the satellite communications unit 33 of earth station 12 B The satellite receives radio wave RD1 and generates communication control data CC1. The satellite communication IF unit 50, having received the communication control data CC1, forwards the communication control data CC1 to the communication control data processing unit 57. In step S29, the communication control data processing unit 57 extracts the requesting communication terminal 31 and the decryption key CK1 from the communication control data CC1 and activates the encryption key / decryption key management unit 55.

[0061] In step S30, the encryption key / decryption key management unit 55 stores the decryption key CK1 extracted from the communication control data CC1 in the decryption key 90 as the decryption key used on the U-Plane side (series A) of the communication terminal 31. In step S31, the encryption key / decryption key management unit 55 checks whether the encryption key on the U-Plane side (series A) of the requesting communication terminal 32 is set to encryption key 89. If no encryption key is set (NO in S31), in step S32, the encryption key / decryption key management unit 55 determines the encryption key CK2 for the U-Plane side (series A) of the communication terminal 32. The encryption key / decryption key management unit 55 stores the determined encryption key CK2 in encryption key 89. After the execution of S32, if the encryption key for the U-Plane side (series A) of the communication terminal 32 is set to encryption key 89 (YES in S31), the process proceeds to step S33. The encryption key CK2 is the remote encryption key used by Earth Station 12. The encryption key CK2 is also the self-decryption key used by Earth Station 11.

[0062] In step S33, the communication control data processing unit 57 of the earth station 12 generates communication control data CC2 for accepting the start of communication, which includes communication terminal 31, communication terminal 32, and the encryption key CK2 (which is also the decryption key) of communication terminal 32 obtained from the encryption key 89, and transmits it to the satellite communication IF unit 50. In step S34, the satellite communication IF unit 50 transmits the communication control data CC2 to the satellite communication unit 33, which is the C-Plane side (series B) of communication terminal 31. B It transmits to the satellite communications unit 33 of the earth station 12 in step S35. BIt transmits communication control data CC2 as radio waves RU2 towards geostationary satellite 5. Specifically, the satellite communications unit 33 of earth station 12 B The modulator / demodulator 13 B The transmission signal SS2 is generated by modulating it with communication control data CC2. Frequency converter 12 B The antenna device 11 converts the frequency of the transmitted signal SS2. B It transmits the frequency-converted transmission signal SS2 as radio wave RU2 towards geostationary satellite 5.

[0063] In step S36, geostationary satellite 5 receives radio wave RU2, converts its frequency, amplifies it, and transmits radio wave RD2. In step S37, the satellite communications unit 33 of earth station 11 B The satellite receives radio wave RD2 and generates communication control data CC2. The satellite communication IF unit 50, having received the communication control data CC2, forwards it to the communication control data processing unit 57.

[0064] In step S38, the communication control data processing unit 57 extracts the communication terminal 32, which is the requesting communication terminal, and the decryption key CK2 from the communication control data CC2, and activates the encryption key / decryption key management unit 55. In step S39, the encryption key / decryption key management unit 55 stores the decryption key CK2 in the decryption key 90 as the decryption key for the U-Plane side (series A) of the communication terminal 32.

[0065] Referring to FIG. 7, the procedure of the process in which the user data UD1 transmitted from the communication terminal 31 of S03 to the communication terminal 32 is converted by the earth station 11 into encrypted user data CD1 and radiated as radio wave RU1 toward the low-earth orbit satellite 41 will be described. In step S41, the communication terminal 31 transmits the user data UD1 to be transmitted to the communication terminal 32 to the earth station 11, and the network IF unit 16 of the earth station 11 receives it. In step S42, the network IF unit 16 of the earth station 11 outputs the user data UD1 to the data processing device 14. In step S43, the encryption device control unit 56 refers to the encryption key 89 and acquires the encryption key CK1 of the communication terminal 31. In step S44, the encryption device control unit 56 instructs the encryption device 15 to encrypt the user data UD1 with the encryption key CK1, and the encryption device 15 generates the encrypted user data CD1. S44 is the procedure in which the encryption device encrypts the user data from the requesting communication terminal with its own encryption key CK1 to generate the encrypted user data.

[0066] In step S45, the encryption device control unit 56 inputs the encrypted user data CD1 on the U-Plane side of the communication terminal 31, i.e., to the satellite communication unit 33 A In step S46, the satellite communication unit 33 of the earth station 11 A radiates the encrypted user data CD1 as radio wave RU1 toward the low-earth orbit satellite 41. Specifically, the satellite communication unit 33 of the earth station 11 A uses the modulator / demodulator 13 A it has to modulate the encrypted user data CD1 to generate the transmission signal SS1. The frequency converter 12 A frequency-converts the transmission signal SS1. The antenna device 11 A radiates the frequency-converted transmission signal SS1 as radio wave RU1 toward the low-earth orbit satellite 41.

[0067] Referring to FIG. 8, in S05, the procedure of the process in which the earth station 12 receives the radio wave RD2, demodulates and decrypts the radio wave RD2, and transmits the generated user data UD1 to the communication terminal 32 will be described. In step S51, the satellite communication unit 33 of the earth station 12 A receives the radio wave RD2 and generates the encrypted user data CD1. Specifically, the satellite communication unit 33 of the earth station 12 AThe antenna device 11 it has A receives the radio wave RD2 and generates the received signal RS2. The frequency converter 12 A frequency-converts the received signal RS2. The demodulator 13 A demodulates the frequency-converted received signal RS2 and generates the encrypted user data CD1.

[0068] In step S52, the satellite communication unit 33 A outputs the generated encrypted user data CD1 to the satellite communication IF unit 50. In step S53, the encryption device control unit 56 of the earth station 12 obtains the decryption key CK1 of the communication terminal 31 by referring to the decryption key 90. In step S54, the encryption device control unit 56 instructs the encryption device 15 to decrypt the encrypted user data CD1 with the decryption key CK1, and the encryption device 15 generates the user data UD1. In step S55, the data processing device 14 transmits the user data UD1 to the communication terminal 32 via the network IF unit 16 and the network 22, and the communication terminal 32 receives it.

[0069] S54 is a procedure in which the communication partner decrypts the received encrypted user data with the partner's decryption key to generate user data. S55 is a procedure in which the communication partner sends the user data decrypted with the partner's decryption key to the destination communication terminal.

[0070] Referring to Figure 9, the procedure for the process in which, in S06, the earth station 12 converts the user data UD2 that the communication terminal 32 transmits to the communication terminal 31 into encrypted user data CD2 and radiates it as radio waves RU2 toward the low Earth orbit satellite 42 will be explained. Figure 9 is the same as Figure 7. In step S61, the communication terminal 32 transmits the user data UD2 to the earth station 12, which is received by the network IF unit 16 of the earth station 12. In step S62, the network IF unit 16 of the earth station 12 outputs the user data UD2 to the data processing device 14. In step S63, the encryption device control unit 56 refers to the encryption key 89 and obtains the encryption key CK2 of the communication terminal 32. In step S64, the encryption device control unit 56 instructs the encryption device 15 to encrypt the user data UD2 with the encryption key CK2, and the encryption device 15 generates encrypted user data CD2. S63 is the procedure in which the communication partner encrypts the user data from the requesting communication terminal with the other party's encryption key to generate encrypted user data.

[0071] In step S65, the satellite communication IF unit 50 sends encrypted user data CD2 to the satellite communication unit 33 on the U-Plane side. A Enter the information into the satellite communication unit 33. In step S66, A The encrypted user data CD2 is transmitted as radio wave RU2 towards the low-Earth orbit satellite 42. Specifically, the satellite communications unit 33 of Earth Station 12 A The modulator / demodulator 13 A However, the transmitted signal SS2 is generated by modulating it with encrypted user data CD2. Frequency converter 12 A However, the transmitted signal SS2 is frequency-converted. Antenna device 11 A However, the frequency-converted transmission signal SS2 is radiated as radio wave RU2 towards the low-Earth orbit satellite 42.

[0072] Referring to Figure 10, the procedure for the process in which, in S08, the earth station 11 receives the radio wave RD1, demodulates and decodes the radio wave RD1 to generate user data UD2 and transmits it to the communication terminal 31 will be explained. Figure 10 is the same as Figure 8. In step S71, the satellite communication unit 33 of the earth station 11 AThe satellite communications unit 33 of Earth Station 11 receives the radio wave RD1 and generates encrypted user data CD2. Specifically, Earth Station 11 A Antenna device 11 A The frequency converter 12 receives the radio wave RD1 and generates the received signal RS1. A The received signal RS1 is frequency-converted. (Modulator 13) A The frequency-converted received signal RS1 is demodulated to generate encrypted user data CD2.

[0073] In step S72, satellite communications unit 33 A The generated encrypted user data CD2 is output to the satellite communication IF unit 50. In step S73, the encryption device control unit 56 of the earth station 11 refers to the decryption key 90 and obtains the decryption key CK2 of the communication terminal 32. In step S74, the encryption device control unit 56 instructs the encryption device 15 to decrypt the encrypted user data CD2 with the decryption key CK2, and the encryption device 15 generates user data UD2. In step S75, the data processing device 14 transmits the user data UD2 to the communication terminal 31 via the network IF unit 16 and the network 21, and the communication terminal 31 receives it.

[0074] S74 is the procedure in which the decryption device decrypts the encrypted user data received by the first out-of-convection communication unit using its own decryption key to generate user data. S75 is the procedure in which the user data decrypted with the own decryption key is sent to the requesting communication terminal.

[0075] Referring to Figure 11, in S09, Earth station 11 transmits the communication control data CC1 to Earth station 12 via radio waves RU directed towards geostationary satellite 5. C1The procedure for the radiating process is described below. In step S80, the communication terminal 31 sends a communication control request regarding communication with the communication terminal 32 to the earth station 11, which is received by the network IF unit 16 of the earth station 11. In step S81, the network IF unit 16 outputs the communication control request to the data processing unit 14. In step S82, the data processing unit 14 inputs the communication control request to the communication control data processing unit 57. In step S83, the communication control data processing unit 57 generates communication control data CC1 based on the communication control request. Note that the communication control data processing unit 57 may generate communication control data CC1 that is not based on a communication control request from the communication terminal 31. In that case, processing starts from S83.

[0076] In step S84, the communication control data processing unit 57 of the earth station 11 outputs the communication control data CC1 to the satellite communication IF unit 50. In step S85, the satellite communication IF unit 50 outputs the satellite communication unit 33, which is the C-Plane side of the communication terminal 31. B Communication control data CC1 is output. In step S86, the satellite communication unit 33 of the earth station 11 B The communication control data CC1 is transmitted via radio waves RU C1 It will be radiated towards geostationary satellite 5. Specifically, the satellite communications unit 33 of earth station 11 B The modulator / demodulator 13 B The transmission signal SS1 is generated by modulating it with the communication control data CC1. Frequency converter 12 B The antenna device 11 converts the frequency of the transmitted signal SS1. B However, the frequency-converted transmission signal SS1 is directed towards the geostationary satellite 5 and radio waves RU are sent. C1 It emits radiation as such.

[0077] Referring to Figure 12, in S11, Earth station 12 receives radio waves RD C2 Receiving radio waves, RD C2 The procedure for controlling communication between communication terminal 32 and communication terminal 31 by processing the communication control data CC2 generated by demodulating the data is described. In step S87, the satellite communication unit 33 of earth station 12 B Radio wave RD C2 It receives the signal and generates communication control data CC1. Specifically, the satellite communications unit 33 of Earth station 12B Antenna device 11 B However, radio wave RD C2 The frequency converter 12 receives the signal and generates the received signal RS2. B However, the received signal RS2 is frequency-converted. (Modulator 13) B However, the frequency-converted received signal RS2 is demodulated to generate communication control data CC1. In step S88, the satellite communication IF unit 50, which has received the communication control data CC1, forwards it to the communication control data processing unit 57. In step S89, the communication control data processing unit 57 of the earth station 12 controls the communication between communication terminal 31 and communication terminal 32 based on the communication control data CC1.

[0078] Referring to Figure 13, in S12, Earth station 12 transmits the communication control data CC2 to Earth station 11 via radio waves RU directed towards geostationary satellite 5. C2 The procedure for the radiating process is described below. Figure 13 is the same as Figure 11. In step S90, the communication terminal 32 sends a communication control request regarding communication with the communication terminal 31 to the earth station 12, which is received by the network IF unit 16 of the earth station 12. In step S91, the network IF unit 16 outputs the communication control request to the data processing unit 14. In step S92, the data processing unit 14 inputs the communication control request to the communication control data processing unit 57. In step S93, the communication control data processing unit 57 generates communication control data CC2 based on the communication control request. Note that the communication control data processing unit 57 may generate communication control data CC2 that is not based on a communication control request from the communication terminal 32. In that case, processing starts from S93.

[0079] In step S94, the communication control data processing unit 57 of the earth station 12 outputs the communication control data CC2 to the satellite communication IF unit 50. In step S95, the satellite communication IF unit 50 outputs the satellite communication unit 33, which is the C-Plane side of the communication terminal 32. B Communication control data CC2 is output. In step S96, the satellite communications unit 33 of the earth station 12 B The communication control data CC2 is transmitted via radio waves RU C2 It will be radiated towards geostationary satellite 5. Specifically, the satellite communications unit 33 of earth station 12 BThe modulator / demodulator 13 B The transmission signal SS2 is generated by modulating it with communication control data CC2. Frequency converter 12 B The antenna device 11 converts the frequency of the transmitted signal SS2. B However, the frequency-converted transmission signal SS2 is directed towards the geostationary satellite 5 via radio waves RU C2 It emits radiation as such.

[0080] Referring to Figure 14, in S14, Earth station 11 receives radio waves RD C1 Receiving radio waves, RD C1 The procedure for controlling communication between communication terminal 31 and communication terminal 32 by processing the communication control data CC2 generated by demodulating the data is described. In step S97, the satellite communication unit 33 of earth station 11 B Radio wave RD C1 It receives the signal and generates communication control data CC2. Specifically, the satellite communications unit 33 of Earth Station 11 B Antenna device 11 B However, radio wave RD C1 The frequency converter 12 receives the signal and generates the received signal RS1. B However, the received signal RS1 is frequency-converted. (Modulator 13) B However, the frequency-converted received signal RS1 is demodulated to generate communication control data CC2. In step S98, the satellite communication IF unit 50, which has received the communication control data CC2, forwards it to the communication control data processing unit 57. In step S99, the communication control data processing unit 57 of the earth station 11 controls the communication between communication terminal 31 and communication terminal 32 based on the communication control data CC2.

[0081] Earth station 1 encrypts user data and communicates it via low Earth orbit satellite communication link 6. Earth station 1 communicates the encryption key and decryption key for encrypting the user data via geostationary satellite communication link 8. Therefore, even if user data communicated via low Earth orbit satellite communication link 6 is intercepted, the content of the user data cannot be known because it is encrypted. Since the encryption key and decryption key are communicated via geostationary satellite communication link 8, even if the low Earth orbit satellite communication link 6 through which user data is transmitted is intercepted, the encryption key and decryption key will not be leaked. User data is not communicated via geostationary satellite communication link 8, so even if the geostationary satellite communication link 8 is intercepted, the content of the user data cannot be known. In this embodiment 1, a symmetric-key encryption scheme is used, so the encryption key and decryption key are the same. The encryption scheme may also be a public-key encryption scheme or a hybrid encryption scheme.

[0082] Incidentally, satellite communication systems are characterized by their wide coverage, broadcasting capabilities, and disaster resistance. Due to these characteristics, some satellite communication operators keep information regarding wireless communications, such as frequency, modulation / demodulation methods, error correction methods, transmission speed, and coding rate, confidential. Even if information regarding wireless communications is kept confidential, signal interception by third parties can be carried out over a wide area within the communication range of the satellite. To prevent interception through impersonation, measures such as data scrambling and encryption are necessary.

[0083] There are generally two methods for encrypting data: public-key cryptography and symmetric-key cryptography. In public-key cryptography, the encryption key used for encryption and the decryption key used for decryption are different. In public-key cryptography, data encrypted with the encryption key (public key) is decrypted with the decryption key (private key). In public-key cryptography, there is no need to share the decryption key, and even if the public key is leaked, the data cannot be decrypted. Public-key cryptography requires a large amount of computation for decryption and takes a long time to process. On the other hand, in symmetric-key cryptography, the encryption key used for encryption and the decryption key used for decryption are the same. Compared to public-key cryptography, symmetric-key cryptography requires less computing resources and has a shorter processing time. There is a possibility that the symmetric key (encryption key) may be leaked when it is shared between the sender and receiver.

[0084] Satellite communications are also intended for use in remote areas, isolated islands, and mobile devices where terrestrial connections (including mobile phone networks and terrestrial wireless relay networks) are difficult. Therefore, in satellite communications, sharing the symmetric key used in symmetric-key cryptography schemes based on terrestrial communication systems can be challenging, posing a challenge in how to share these keys. Similarly, communication systems using relay lines operated by mobile devices moving in the stratosphere also face challenges in sharing symmetric keys.

[0085] Earth station 1, which is a communication device according to this disclosure, does not require ground infrastructure (ground communication system). Earth station 1 can easily expand the communication area in a mobile communication system. Earth station 1 does not require the use of a guard spot beam as described in Patent Document 1.

[0086] Earth station 1 can share encryption keys (including decryption keys) with the sender and receiver without using other communication systems. Earth station 1 can communicate encrypted user data.

[0087] Since the encryption key and the decryption key are determined for each requesting communication terminal, even if some of the encryption key and the decryption key are known (leaked) externally, not all communications will be intercepted. Since the encryption key and the decryption key are determined each time communication is started, even if the encryption key and the decryption key used at a certain time by a certain communication terminal are leaked, when communicating next, another encryption key and decryption key will be used. Therefore, the encrypted user data to be communicated cannot be decrypted with the leaked decryption key, and the content of the data to be communicated will not be known externally.

[0088] Although the low-earth orbit satellite communication line 6 and the geostationary satellite communication line 8 are used, a high-altitude pseudo satellite communication line relayed by a high-altitude pseudo satellite moving in the stratosphere may also be used. The high-altitude pseudo satellite is a stratosphere mobile body that is a moving body moving in the stratosphere. As the stratosphere mobile body, something different from the high-altitude pseudo satellite may be used. Two or more different types of satellite communication lines relayed by communication satellites moving at two or more different altitudes lower than the geostationary satellite may also be used. Two types of extra-atmospheric communication lines may be selected from at least three types of extra-atmospheric communication lines and used as the first extra-atmospheric communication line and the second extra-atmospheric communication line.

[0089] Terms such as extra-atmospheric communication lines will be explained. The extra-atmosphere is an altitude higher than the troposphere from the Earth's surface. The extra-atmosphere includes, in order from the closest to the Earth's surface, the stratosphere, the mesosphere, the thermosphere, the exosphere, and outer space. A moving body moving at an altitude included in the extra-atmosphere is an extra-atmospheric moving body. An extra-atmospheric moving body moving at a first altitude included in the extra-atmosphere is a first extra-atmospheric moving body. An extra-atmospheric moving body moving at a second altitude different from the first altitude included in the extra-atmosphere is a second extra-atmospheric moving body. A relay station mounted on an extra-atmospheric moving body is an extra-atmospheric relay station. An extra-atmospheric relay station mounted on a first extra-atmospheric moving body is a first extra-atmospheric relay station. An extra-atmospheric relay station mounted on a second extra-atmospheric moving body is a second extra-atmospheric relay station. A communication line relayed by an extra-atmospheric relay station is an extra-atmospheric communication line. An extra-atmospheric communication line relayed by a first extra-atmospheric relay station is a first extra-atmospheric communication line. An extra-atmospheric communication line relayed by a second extra-atmospheric relay station is a second extra-atmospheric communication line.

[0090] For each altitude at which an out-of-troposphere mobile device travels, there is one type of out-of-troposphere communication link. The at least three types of out-of-troposphere communication links are out-of-troposphere communication links relayed by out-of-troposphere relay stations mounted on at least three out-of-troposphere mobile devices traveling at different altitudes within the out-of-troposphere zone. Of the two types of out-of-troposphere communication links used, the first out-of-troposphere communication link is used to transmit encrypted user data. The second out-of-troposphere communication link is used to communicate the encryption key used to encrypt the user data and the decryption key used to decrypt the encrypted user data with the communication partner before communication on the first out-of-troposphere communication link.

[0091] Selecting an out-of-tropic communication link means selecting an out-of-tropic mobile device equipped with a relay station that relays the out-of-tropic communication link. The first and second out-of-tropic mobile devices may each be an out-of-tropic mobile device selected from at least three different types of out-of-tropic mobile devices located outside the troposphere, each moving at a different altitude.

[0092] Each of the first and second extratropical mobile bodies may be an extratropical mobile body selected from an extratropical mobile body set that includes a stratospheric mobile body which is a mobile body that moves in the stratosphere, a geostationary satellite, and artificial satellites which move at altitudes lower than the geostationary satellite and at least two different altitudes.

[0093] At Earth Station 1, the low-Earth orbit satellite communication link 6 and the low-Earth orbit inter-satellite communication link 7 constitute the first out-of-troposphere communication link. The geostationary satellite communication link 8 constitutes the second out-of-troposphere communication link. Satellite Communication Unit 33 A However, the first out-of-the-zone communication unit communicates encrypted user data, which is the encrypted user data, with the communication partner in the first out-of-the-zone communication round. Satellite communication unit 33 BHowever, it is a second out-of-the-range communication unit that communicates communication control data with the communication partner, which includes at least one of the encryption key used by the encryption device (self-encryption key) and the decryption key used by the communication partner when decrypting encrypted user data generated by the encryption device (recipient decryption key), and also communicates communication control data with the communication partner, which includes at least one of the encryption key used by the communication partner (recipient-encryption key) and the decryption key used by the decryption device when decrypting encrypted user data generated by the communication partner (self-decryption key).

[0094] The first out-of-troposphere communication link may be a geostationary satellite communication link 8, and the second out-of-troposphere communication link may be a low-Earth orbit satellite communication link 6 and a low-Earth orbit inter-satellite communication link 7.

[0095] When communicating via an out-of-troposphere communication line, the data storage unit 58 stores the satellite 80 being communicated. A The Satellite Communications Department 33 A The memory is stored for the out-of-troposphere mobile device equipped with a relay station that relays the out-of-troposphere communication line used by [the device]. B The Satellite Communications Department 33 B The system stores information about out-of-tropic mobile devices equipped with relay stations that relay the out-of-tropic communication lines used by [the system].

[0096] In terms of the communication method, steps S26 to S28 shown in Figure 5 are the procedure for the second out-of-convection communication unit to communicate with the communication partner using at least one of the local encryption key and the other party's decryption key. Steps S35 to S37 shown in Figure 6 are the procedure for the second out-of-convection communication unit to communicate with the communication partner using at least one of the other party's encryption key and the local decryption key. Step S46 shown in Figure 7 is the procedure for the first out-of-convection communication unit to transmit encrypted user data encrypted with the local encryption key to the communication partner via the first out-of-convection communication line. Step S51 shown in Figure 8 is the procedure for the communication partner to receive the encrypted user data transmitted via the first out-of-convection communication line. Step S66 shown in Figure 9 is the procedure for the communication partner to transmit encrypted user data encrypted with the other party's encryption key via the first out-of-convection communication line. Step S71 shown in Figure 10 is the procedure for the first out-of-convection communication unit to receive the encrypted user data transmitted by the communication partner via the first out-of-convection communication line.

[0097] Antenna device 11A , 11 B The communication device, which is Earth Station 1 and does not include two modulators / demodulators 13 A , 13 B and two frequency converters 12 A , 12 B The system comprises the following: The sequence control unit 54 is a sequence allocation unit that allocates one frequency converter 12 and one modulator / demodulator 13 to be used as a first out-of-convection communication unit, and allocates the other frequency converter 12 and the other modulator / demodulator 13 to be used as a second out-of-convection communication unit.

[0098] The sequence control unit 54 modulates and demodulates encrypted user data in one modulator / demodulator 13 and causes one frequency converter 12 to perform frequency conversion between the frequency used in the first out-of-convection communication line and the frequency of the signal processed by the modulator / demodulator 12. The sequence control unit 54 modulates and demodulates communication control data in the other modulator / demodulator 13 and causes the other frequency converter 12 to perform frequency conversion between the frequency used in the second out-of-convection communication line and the frequency of the signal processed by the modulator / demodulator 13.

[0099] The tracking control unit 52 controls one antenna device 11 connected to one frequency converter 12 to track the first out-of-troposphere mobile object, and controls the other antenna device 11 connected to the other frequency converter 12 to track the second out-of-troposphere mobile object.

[0100] If Earth Station 1 uses a symmetric-key cryptography scheme, the second out-of-tropic-space communication unit communicates communication control data containing the decryption key used by the communication partner when decrypting encrypted user data generated by the cryptographic device, and also communicates communication control data containing the decryption key used by the decryption device when decrypting encrypted user data generated by the communication partner. If a secret-key cryptography scheme is used, the second out-of-tropic-space communication unit communicates communication control data containing the encryption key used by the cryptographic device, and also communicates communication control data containing the encryption key used by the communication partner.

[0101] The second out-of-the-zone communication unit only needs to communicate communication control data with the communication partner, which includes at least one encryption key used by the encryption device and at least one decryption key used by the communication partner when decrypting encrypted user data generated by the encryption device, and communicate communication control data with the communication partner via the second out-of-the-zone communication line, which includes at least one encryption key used by the communication partner and at least one decryption key used by the decryption device when decrypting encrypted user data generated by the communication partner.

[0102] In the wireless communication system 100, the encryption key and decryption key are determined at Earth Station 1 for each source communication terminal. Alternatively, the encryption key and decryption key may be determined for each pair of source and destination communication terminals. Alternatively, the same encryption key and decryption key may be used regardless of the terminal, and the encryption key and decryption key may be changed depending on the time of day. If permissible from a security standpoint, the encryption key and decryption key to be used may be determined for each Earth Station. The unit for determining the encryption method, encryption key, and decryption key, as well as the cycle for changing them, may be determined in any way as long as the necessary security level is ensured.

[0103] When determining encryption and decryption keys for each pair of source and destination communication terminals, the earth station 1 to which the source communication terminal is connected may determine the encryption key used by the communication partner when encrypting user data from the destination communication terminal. In this case, the communication control data of the communication start request that earth station 1 communicates with the communication partner earth station 1 includes the decryption key used by the communication partner when decrypting encrypted user data generated by the encryption device, and the encryption key used by the communication partner. This communication control data of the communication start request is communication control data that includes at least one of the encryption key used by the encryption device and the decryption key used by the communication partner when decrypting encrypted user data generated by the encryption device, and also communication control data that includes at least one of the encryption key used by the communication partner and the decryption key used by the decryption device when decrypting encrypted user data generated by the communication partner.

[0104] Earth station 1 transmits encrypted user data through the first out-of-troposphere communication unit, and transmits communication control data through the second out-of-troposphere communication unit. Communication control data may also be transmitted encrypted. Encrypted user data and encrypted communication control data may be allocated and transmitted to the first and second out-of-troposphere communication units by some method.

[0105] The communication partner does not have to be a communication device related to this disclosure. The communication partner may be, for example, a communication device connected to a terrestrial communication network.

[0106] The communication device relating to this disclosure only needs to communicate encrypted user data over a first out-of-convection communication line and communication control data over a second out-of-convection communication line. The communication path for communicating encrypted user data may include a portion that is not the first out-of-convection communication line. The communication path for communicating communication control data may also include a portion that is not the second out-of-convection communication line.

[0107] The earth station may not have a network IF unit 16, and the earth station may communicate user data with the earth station of the communication partner.

[0108] The requesting communication terminal is a communication terminal connected to either the communication device or the communication partner. The requesting communication terminal is a communication terminal connected to the other of the communication device and the communication partner. The communication device includes an encryption device (which is also a decryption device), a first out-of-convection communication unit, and a second out-of-convection communication unit. The communication method relating to this disclosure only needs to have the following procedure. (a) A procedure for one of the communication devices and the other party to receive a request from the requesting communication terminal to initiate communication with the requesting communication terminal. (i) A procedure for communicating with the communication partner in the second out-of-convection communication unit at least one of the following: the local encryption key, which is the encryption key used by the encryption device when it encrypts user data and generates encrypted user data, and the partner decryption key, which is the decryption key used by the communication partner when they decrypt the encrypted user data encrypted with the local encryption key. (c) A procedure for communicating with the communication partner in the second out-of-convection communication unit at least one of the following: the partner encryption key, which is the encryption key used by the communication partner when encrypting user data and generating encrypted user data, and the local decryption key, which is the decryption key used by the decryption device when decrypting encrypted user data encrypted with the partner encryption key. (e) A procedure for generating encrypted user data by having the encryption device encrypt user data from the requesting communication terminal using its own encryption key, or by having the communication partner encrypt it using the other party's encryption key. (e) A procedure for the first out-of-convection communication unit to communicate encrypted user data from the requesting communication terminal to the communication partner via the first out-of-convection communication line. (c) A procedure in which the communication partner decrypts the encrypted user data received by the communication partner using the other party's decryption key, or the encryption device decrypts the encrypted user data received by the communication device using its own decryption key, thereby generating user data from the requesting communication terminal. (k) Procedure for the communication partner or communication device to send the decrypted user data from the requesting communication terminal to the requesting communication terminal. (k) A procedure for generating encrypted user data by having the communication partner encrypt user data from the requesting communication terminal using their encryption key, or by having the encryption device encrypt it using its own encryption key. (k) A procedure for communicating encrypted user data from an encrypted requesting communication terminal to a communication partner via the first out-of-convection communication line. (c) A procedure for generating user data from the requesting communication terminal by having the decryption device decrypt encrypted user data received by the first convection zone communication unit using its own decryption key, or by having the communication partner decrypt it using the other party's decryption key. (c) Procedure for the communication device or communication partner to send the decrypted user data from the requesting communication terminal to the requesting communication terminal. The above also applies to other embodiments.

[0109] Embodiment 2. Embodiment 2 is an embodiment based on Embodiment 1, in which a communication line is used that is relayed by two mobile bodies at different altitudes selected from three or more mobile bodies moving at different altitudes that are located outside the troposphere, and the method for managing encryption and decryption keys is changed to a public-key cryptography scheme.

[0110] Figure 15 shows the schematic configuration of the satellite communication system according to Embodiment 2. The differences between Figure 15 and Figure 1 in Embodiment 1 will be explained below. Satellite communication system 100C has modified earth stations 1C1 and 1C2 and has high-altitude pseudo-satellites 91 and 92. High-altitude pseudo-satellites 91 and 92 are also called HAPS (High Altitude Platform Station). The high-altitude pseudo-satellites 9 fly at an altitude of about 20 km and can communicate with earth stations located within a diameter range of about 100 km on the Earth's surface. The high-altitude pseudo-satellites 9 can communicate with each other. By having several dozen high-altitude pseudo-satellites 9 form a communication network in the stratosphere, communication becomes possible throughout Japan via communication lines relayed by the high-altitude pseudo-satellites 9. Artificial satellites or high-altitude pseudo-satellites 9 are extratropical mobile bodies that move outside the troposphere, which is an altitude higher than the Earth's troposphere.

[0111] Earth station 1C1 and Earth station 1C2 can communicate via high-altitude pseudo-satellite communication links 211 and 212 and high-altitude pseudo-satellite inter-communication link 22, which are relayed by high-altitude pseudo-satellites 91 and 92. High-altitude pseudo-satellite communication link 211 is a communication link used for communication between Earth station 1C1 and high-altitude pseudo-satellite 91. High-altitude pseudo-satellite communication link 212 is a communication link used for communication between Earth station 1C2 and high-altitude pseudo-satellite 92. High-altitude pseudo-satellite inter-communication link 22 is a communication link connecting high-altitude pseudo-satellite 91 and high-altitude pseudo-satellite 92. Note that there is another high-altitude pseudo-satellite 9 between high-altitude pseudo-satellite 91 and high-altitude pseudo-satellite 92. NIf an intermediary is present, there will be multiple high-altitude pseudo-satellite communication links 22. If high-altitude pseudo-satellite 91 and high-altitude pseudo-satellite 92 are the same, earth station 1C1 and earth station 1C2 will communicate without going through the high-altitude pseudo-satellite communication link 22. The high-altitude pseudo-satellite communication links 21 and 22 are out-of-troposphere communication links that are relayed by an out-of-troposphere mobile station, which is a relay station mounted on an out-of-troposphere mobile vehicle.

[0112] The configuration of Earth Station 1C will be explained with reference to Figure 16. Figure 16 is a diagram showing the configuration of the communication device (Earth Station 1C) according to Embodiment 2. The differences between Figure 16 and Figure 2 in Embodiment 1 will be explained. Earth Station 1C has a satellite selection input unit 59 and has modified line control unit 51C, encryption device 15C, tracking control unit 52C, satellite position management unit 53C, encryption key / decryption key management unit 55C, communication control data processing unit 57C, and data storage unit 58C.

[0113] The cryptographic device 15C differs from the cryptographic device 15, which uses a symmetric-key cryptography scheme, in that it encrypts and decrypts using a public-key cryptography scheme.

[0114] Earth Station 1C has Satellite Communications Unit 33 A ,33 B The user selects and inputs the type of extratropospheric mobile object to be used for communication in each of these. The satellite selection input unit 59 accepts the type of extratropospheric mobile object input by the user. The data storage unit 58C accepts the mobile object type 92 A , 92 B It also has. Mobile type 92 A The Satellite Communications Department 33 A It stores the type of extratropical mobile object it communicates with. Mobile object type 92 B The Satellite Communications Department 33 B The system stores the type of extratropospheric mobile object it communicates with. Extratropospheric mobile objects can be geostationary satellites, low Earth orbit satellites, or high-altitude pseudo-satellites. If medium Earth orbit satellites or multiple low Earth orbit satellites at different altitudes are also available, the system determines the mobile object type for all available types of extratropospheric mobile objects to distinguish between them.

[0115] The line control unit 51C controls the satellite communication unit 33 A ,33 B For each of these, mobile type 92 A , 92 B The tracking control unit 52C manages the relayed out-of-troposphere mobile object, transmission frequency, and reception frequency by referring to the antenna device 11 A , 11 B The antenna device 11 is positioned so as to face the direction in which the extratroposphere mobile object from which the signal is relayed is located. A , 11 B The tracking control unit 52C controls the following. The tracking control unit 52C can also track the high-altitude pseudo-satellite 9. The high-altitude pseudo-satellite 9 flies above a predetermined point on the Earth's surface. If Earth station 1C does not move, the high-altitude pseudo-satellite 9 that can communicate with Earth station 1C is predetermined.

[0116] The satellite position management unit 53C obtains orbital data from an external source for an extratropospheric mobile that can be used as the first extratropospheric mobile and the second extratropospheric mobile. The satellite position management unit 53C is a mobile type 92 A , 92 B For the type of extratroposphere mobile object specified, the communication satellite 80 A , 80 B The satellite position management unit 53C operates at a predetermined cycle and communicates with satellite 80. A , 80 B Based on orbital data, the position is determined from the time of operation to a predetermined future point in time, and the determined position is recorded as satellite position 94. A , 94 B Set to this.

[0117] The data storage unit 58C stores the decryption key 89C, the encryption key used 90C, and the corresponding encryption key 91C. The decryption key 89C is data that stores the decryption key to be used for each communication terminal 3 and for each series. The decryption key is also called the secret key. The number of decryption keys 89C is 2*N. maxThis is a data set containing 2*N elements. The encryption key used to encrypt encrypted data that can be decrypted with a decryption key is called the corresponding encryption key that corresponds to the decryption key. The corresponding encryption key is also called the public key. The corresponding encryption key 91C is data that stores the corresponding encryption key for each decryption key stored in the decryption key 89C. The number of corresponding encryption keys 91C is 2*N. max This is a data set containing 2*K entries. The encryption key used, 90C, is data that stores the encryption key used for each communication terminal and each series. The encryption key used by the communication terminal is the corresponding encryption key for the communication terminal at Earth Station 1C to which the communication terminal is connected. The number of encryption keys used, 90C, is 2*K. max *N max This is a single data point.

[0118] The data storage unit 58C is a decryption key storage unit that stores a decryption key for each local communication terminal, which is a communication terminal connected to the terminal connection unit, for decrypting the received encrypted user data. The decryption key used by the encryption device 15C is stored in the data storage unit 58C as decryption key 89C. The data storage unit 58C is a corresponding encryption key storage unit that stores a corresponding encryption key for each local communication terminal, which is the encryption key used to encrypt the data that the encryption device 15C decrypts with the decryption key. The corresponding encryption key is stored in the data storage unit 58C as corresponding encryption key 91C. The data storage unit 58C is a used encryption key storage unit that stores a used encryption key for each destination communication terminal, which is the encryption key used by the encryption device 15C. The encryption key used by the encryption device 15C is stored in the data storage unit 58C as used encryption key 90C.

[0119] The encryption key / decryption key management unit 55C determines and manages a decryption key and a corresponding encryption key for each communication terminal 3. When the encryption key / decryption key management unit 55C receives a communication start request from a requesting communication terminal, it determines a decryption key and a corresponding encryption key for each sending communication terminal. The encryption key / decryption key management unit 55C stores the determined decryption key and corresponding encryption key in the decryption key 89C and the corresponding encryption key 91C. When the encryption key / decryption key management unit 55C receives a communication start request from a communication partner (earth station 1C), it stores the encryption key included in the communication start request in the encryption key used 90C as the encryption key used for each requesting communication terminal.

[0120] When the encryption key / decryption key management unit 55C receives a communication start request from the requesting communication terminal, it checks in the decryption key 89C whether the decryption key for the requesting communication terminal on the U-Plane side is stored in the usage sequence 88. If it is not stored, the encryption key / decryption key management unit 55C determines the decryption key and the corresponding encryption key. The encryption key / decryption key management unit 55C stores the determined decryption key in the decryption key 89C as the decryption key for the requesting communication terminal on the U-Plane side in the usage sequence 88. The encryption key / decryption key management unit 55C stores the determined corresponding encryption key in the corresponding encryption key 91C in the usage sequence 88 as the corresponding encryption key for the requesting communication terminal on the U-Plane side.

[0121] When the encryption key / decryption key management unit 55C receives communication control data for a communication start request sent from another earth station 1C (communication partner), it stores the corresponding encryption key of the requesting communication terminal included in the communication control data of the communication start request in the usage sequence 88 as the encryption key used by the requesting communication terminal on the U-Plane side in the usage encryption key 90C. The encryption key / decryption key management unit 55C then checks whether the decryption key of the requesting communication terminal specified in the communication start request is stored on the U-Plane side in the usage sequence 88 in the decryption key 89C. If it is not stored, the encryption key / decryption key management unit 55C determines the decryption key and the corresponding encryption key. The encryption key / decryption key management unit 55C stores the determined decryption key in the usage sequence 88 as the decryption key of the requesting communication terminal on the U-Plane side in the decryption key 89C. The encryption key / decryption key management unit 55C stores the determined corresponding encryption key in the usage sequence 88 as the corresponding encryption key of the requesting communication terminal on the U-Plane side in the corresponding encryption key 90C.

[0122] When the encryption key / decryption key management unit 55C receives communication control data for accepting the commencement of communication transmitted from another earth station 1C (communication partner), it stores the corresponding encryption key of the requesting communication terminal included in the communication control data for accepting the commencement of communication in the usage sequence 88 as the encryption key used by the requesting communication terminal on the U-Plane side in the usage encryption key 90C.

[0123] If the decryption key of the requesting communication terminal is not stored in the decryption key storage unit, the encryption key and corresponding encryption key management unit 55C determines the encryption key and corresponding encryption key, stores the determined decryption key in the decryption key storage unit as the decryption key of the requesting communication terminal, and stores the determined corresponding encryption key in the corresponding encryption key storage unit as the corresponding encryption key of the requesting communication terminal. When the encryption key / decryption key management unit 55C receives communication control data for a communication start request, it stores the corresponding encryption key of the requesting communication terminal included in the received communication control data as the encryption key used by the requesting communication terminal in the encryption key storage unit. If the decryption key of the requesting communication terminal is not stored in the decryption key storage unit, it determines the decryption key and the corresponding encryption key, stores the determined decryption key as the decryption key of the requesting communication terminal in the decryption key storage unit, and stores the determined corresponding encryption key as the corresponding encryption key of the requesting communication terminal in the corresponding encryption key storage unit. When the encryption key / decryption key management unit 55C receives communication control data for accepting the commencement of communication, it stores the corresponding encryption key of the requesting communication terminal included in the received communication control data as the encryption key used by the requesting communication terminal in the encryption key storage unit.

[0124] When the communication control data processing unit 57C receives communication control data for a communication start request from the requesting communication terminal, it creates communication control data for a communication start request that includes the requesting communication terminal, the requesting communication terminal, and the corresponding encryption key of the requesting communication terminal determined by the encryption key / decryption key management unit 55C, and outputs it to the satellite communication IF unit 50. The satellite communication IF unit 50 outputs the communication control data to the modulator / demodulator 13 on the C-Plane side using the operating sequence 88.

[0125] When the communication control data processing unit 57C receives communication control data for a communication start request transmitted from the communication partner, it creates communication control data for accepting the start of communication, including the requesting communication terminal, the requesting communication terminal, and the corresponding encryption key for the requesting communication terminal, and outputs it to the satellite communication IF unit 50. The satellite communication IF unit 50 outputs the communication control data to the modulator / demodulator 13 on the C-Plane side in the usage sequence 88.

[0126] The communication control data processing unit 57C is a communication control data generation unit that, upon receiving a communication start request from its own communication terminal, the requesting communication terminal, to the requesting communication terminal, which is a communication terminal connected to the communication partner via the network, generates communication control data for the communication start request, including the requesting communication terminal, the requesting communication terminal, and the corresponding encryption key for the requesting communication terminal. It also generates communication control data for accepting the communication start request, including the corresponding encryption key for the requesting communication terminal, upon receiving communication control data for the communication start request from the communication partner.

[0127] The operation will be explained. Figures 17 and 18 are flowcharts illustrating the general procedure when a communication terminal 31 connected to earth station 1C1 communicates with a communication terminal 32 connected to earth station 1C2. Figure 17 illustrates the process up to step S08C, and Figure 18 illustrates the process from step S09C onwards. At earth station 1C1 and earth station 1C2, the satellite communication unit 33 of series A A The communication is relayed via a communication line on a high-altitude pseudo-satellite 9, and the satellite communication unit 33 of series B B They communicate via a communication link relayed by low-Earth orbit satellite 4. At earth stations 1C1 and 1C2, sequence A is the U-Plane and sequence B is the C-Plane. At each earth station 1C, for each communication terminal, the U-Plane should be either sequence A or sequence B, and the C-Plane the other.

[0128] In wireless communication system 100C, the high-altitude pseudo-satellite 9 is the first out-of-troposphere mobile object. The low-Earth orbit satellite 4 is the second out-of-troposphere mobile object. The high-altitude pseudo-satellite communication link 21 and the high-altitude pseudo-satellite inter-communication link 22 constitute the first out-of-troposphere communication link. The low-Earth orbit satellite communication link 6 and the low-Earth orbit inter-satellite communication link constitute the second out-of-troposphere communication link. Satellite communication unit 33 A However, this is the 1st Out-of-Tropospheric Communications Department. Satellite Communications Department 33 B This is the second out-of-troposphere communication unit. The first and second out-of-troposphere communication links are selected from at least three types of out-of-troposphere communication links that are relayed by out-of-troposphere relay stations mounted on at least three out-of-troposphere mobile bodies that are moving at different altitudes and are located outside the troposphere.

[0129] In step S01, communication terminal 31 sends a communication start request to earth station 1C1 to communicate with communication terminal 32, which is received by the network IF unit 16 of earth station 1C1. In step S02C, earth stations 1C1 and 1C2 determine the encryption key and decryption key to be used for communication between communication terminal 31 and communication terminal 32 and store them in the data storage unit 58C. The process of S02C is explained by the flowcharts shown in Figures 19 and 20. The process of S02C differs from the process of S02 in that it is relayed by the low-Earth orbit satellite 4 instead of the geostationary satellite 5. The process of S02C also differs in that it determines the encryption key and decryption key for a public-key cryptography scheme.

[0130] Steps S03C onward are the process of communicating user data and communication control data between communication terminal 31 and communication terminal 32. Steps S03C to S05C are the procedure for sending user data UD1 from communication terminal 31 to communication terminal 32. Steps S06C to S08C are the procedure for sending user data UD2 from communication terminal 32 to communication terminal 31. Steps S09C to S11 are the procedure for sending communication control data CC1 from communication terminal 31 or earth station 1C1 to earth station 1C2. S11 is the same process as in the case of earth station 11. Steps S12C to S14 are the procedure for sending communication control data CC2 from communication terminal 32 or earth station 1C2 to earth station 1C1. S14 is the same process as in the case of earth station 11. The processes S03C to S05C, S06C to S08C, S09C to S11, and S12C to S14 are executed in parallel.

[0131] The processing from S03C to S05C is the same as that from S03 to S05, except that it is relayed by the high-altitude pseudo-satellite 9. The processing from S06C to S08C is the same as that from S06 to S08, except that it is relayed by the high-altitude pseudo-satellite 9. The processing from S09C to S11 is the same as that from S09 to S11, except that it is relayed by the low-Earth orbit satellite 4. The processing from S12C to S14 is the same as that from S12 to S14, except that it is relayed by the low-Earth orbit satellite 4.

[0132] In step S03C, the earth station 1C1 converts the user data UD1 that communication terminal 31 transmits to communication terminal 32 into encrypted user data CD1 and radiates it as radio wave RU1 towards the high-altitude pseudo-satellite 91. In step S04C, the high-altitude pseudo-satellite 91 receives radio wave RU1, frequency-converts and amplifies it, and radiates it as radio wave RC1. The high-altitude pseudo-satellite 92 receives radio wave RC1, frequency-converts and amplifies it, and radiates it as radio wave RD2. In step S05C, the earth station 1C2 receives radio wave RD2, demodulates and decodes radio wave RD2 to generate user data UD1. The earth station 1C2 transmits the user data UD1 to communication terminal 32. The process of S03C is explained in the flowchart shown in Figure 21. The process of S05C is explained in the flowchart shown in Figure 22.

[0133] In step S06C, the earth station 1C2 converts the user data UD2 that communication terminal 32 transmits to communication terminal 31 into encrypted user data CD2 and radiates it as radio wave RU2 towards high-altitude pseudo-satellite 91. In step S07C, high-altitude pseudo-satellite 92 receives radio wave RU2, frequency-converts and amplifies it, and radiates it as radio wave RC2. High-altitude pseudo-satellite 91 receives radio wave RC2, frequency-converts and amplifies it, and radiates it as radio wave RD1. In step S08C, earth station 1C1 receives radio wave RD1, demodulates and decodes it to generate user data UD2. Earth station 1C1 transmits user data UD2 to communication terminal 31. The process of S06C is explained in the flowchart shown in Figure 23. The process of S08C is explained in the flowchart shown in Figure 24.

[0134] In step S09C, Earth station 1C1 transmits the communication control data CC1 to Earth station 1C2 via radio RU directed towards low orbit satellite 41. C1 It emits as such. In step S10C, low orbit satellite 41 emits radio waves RU C1 Receiving radio waves, C1 The signal is frequency converted and amplified to produce radio waves (RD). C1 It emits as radio waves. Low Earth orbit satellite 42 emits radio waves RD C1 Receives radio waves, RDC1 The signal is frequency converted and amplified to produce radio waves (RD). C2 It is emitted as follows. In S11, Earth station 1C2 emits radio waves RD. C2 Receiving radio waves, RD C2 The signal is demodulated to generate communication control data CC1. Earth station 1C2 processes the communication control data CC1 to control communication between communication terminal 31 and communication terminal 32. The processing of S09C is explained in the flowchart shown in Figure 25.

[0135] In step S12C, Earth station 1C2 transmits the communication control data CC2 to Earth station 1C1 via radio RU directed towards low orbit satellite 42. C2 It emits as such. In step S13C, low orbit satellite 42 emits radio waves RU C2 Receiving radio waves, C2 The signal is frequency converted and amplified to produce radio waves (RD). C2 It emits as radio waves. Low Earth orbit satellite 41 uses radio waves (RD). C2 Receives radio waves, RD C2 The signal is frequency converted and amplified to produce radio waves (RD). C1 It emits as radio waves RD. In step S14, earth station 1C1 emits radio waves RD. C1 Receiving radio waves, RD C1 The signal is demodulated to generate communication control data CC2. Earth station 1C1 processes the communication control data CC2 to control communication between communication terminal 31 and communication terminal 32. The processing of S12C is explained in the flowchart shown in Figure 26.

[0136] Referring to Figures 19 and 20, the procedure for determining the decryption key and encryption key used for communication between communication terminal 31 and communication terminal 32 and storing them in the data storage unit 58C in S02C will be explained. Regarding Figures 19 and 20, the differences from Figures 5 and 6 in the case of satellite communication system 100 will be explained. Since communication control data for communication start request and communication start acceptance are communicated over the low-Earth orbit satellite communication line 6 and the inter-low-Earth orbit satellite communication line 7, which are relayed by the low-Earth orbit satellite 4, rather than the geostationary satellite communication line 8 which is relayed by the geostationary satellite 5, steps S26C, S27C, S28C and steps S35C, S36C, S37C have been modified. The encryption key / decryption key management unit 55C of Earth Station 1C manages decryption keys, not encryption keys, for each source communication terminal, so steps S22C, S23C, S24C, S29C, S30C, S31C, S32C, S33C, S38C, and S39C are modified.

[0137] In step S21, the data processing unit 14 of the earth station 1C1 forwards the communication start request from the communication terminal 31 to the communication control data processing unit 57C. In step S22C, the encryption key / decryption key management unit 55C activated by the communication control data processing unit 57C checks whether the decryption key for the U-Plane side (series A) of the communication terminal 31 is set with the decryption key 89C. If the decryption key is not set (NO in S22C), in step S23C, the encryption key / decryption key management unit 55C determines the decryption key DK1 and the corresponding encryption key CK1 for the U-Plane side (series A) of the communication terminal 31. The encryption key / decryption key management unit 55C stores the determined decryption key DK1 in the decryption key 89C and stores the corresponding encryption key CK1 in the corresponding encryption key 91C. If, after the execution of S23C, the decryption key for the U-Plane side (series A) of the communication terminal 31 is set with decryption key 89C (YES in S22C), proceed to step S24C.

[0138] In step S24C, the communication control data processing unit 57C of earth station 1C1 generates communication control data CC1 of a communication start request, which includes the corresponding encryption key CK1 of communication terminal 31 obtained from communication terminal 31, communication terminal 32, and corresponding encryption key 91C, and transmits it to the satellite communication IF unit 50. In step S25, the satellite communication IF unit 50 transmits the communication control data CC1 to the satellite communication unit 33, which is the C-Plane side (series A) of communication terminal 31. A Send to: In step S26C, satellite communications unit 33 of earth station 1C1 A It transmits communication control data CC1 as radio wave RU1 towards the low-Earth orbit satellite 41. Specifically, the satellite communications unit 33 of Earth station 1C1 A The modulator / demodulator 13 A The transmission signal SS1 is generated by modulating it with the communication control data CC1. Frequency converter 12 A The antenna device 11 converts the frequency of the transmitted signal SS1. A However, the frequency-converted transmission signal SS1 is radiated as radio wave RU1 towards the low-Earth orbit satellite 41.

[0139] In step S27C, the low-Earth orbit satellite 41 receives radio wave RU1, converts its frequency, amplifies it, and transmits radio wave RD1. The low-Earth orbit satellite 42 receives radio wave RD1, converts its frequency, amplifies it, and transmits it as radio wave RD2. In step S28C, the satellite communications unit 33 of Earth station 1C2 A The satellite receives radio wave RD2 and generates communication control data CC1. The satellite communication IF unit 50 receives the communication control data CC1 and forwards it to the communication control data processing unit 57C. In step S29C, the communication control data processing unit 57C extracts the requesting communication terminal 31 and the encryption key CK1 from the communication control data CC1 and activates the encryption key / decryption key management unit 55C.

[0140] In step S30C, the encryption key / decryption key management unit 55C stores the encryption key CK1 extracted from the communication control data CC1 as the encryption key used on the U-Plane side (series A) of the communication terminal 31 in the encryption key 90C. In step S31C, the encryption key / decryption key management unit 55C checks whether the decryption key on the U-Plane side (series A) of the communication terminal 32, which is the requesting communication terminal, is set to the decryption key 89C. If no decryption key is set (NO in S31C), in step S32C, the encryption key / decryption key management unit 55C determines the decryption key DK2 and the corresponding encryption key CK2 for the U-Plane side (series A) of the communication terminal 32. The encryption key / decryption key management unit 55C stores the determined decryption key DK2 in the decryption key 89C and stores the corresponding encryption key CK2 in the corresponding encryption key 91C. If, after the execution of S32C, the decryption key for the U-Plane side (series A) of the communication terminal 32 is set with the decryption key 89C (YES in S31C), proceed to step S33C.

[0141] In step S33C, the communication control data processing unit 57C of earth station 1C2 generates communication control data CC2 for accepting the start of communication, which includes communication terminal 31, communication terminal 32, and the corresponding encryption key CK2 of communication terminal 32 obtained from the corresponding encryption key 91C, and transmits it to the satellite communication IF unit 50. In step S34, the satellite communication IF unit 50 transmits the communication control data CC2 to the satellite communication unit 33, which is the C-Plane side (series A) of communication terminal 31. A Send to: In step S35C, the satellite communications unit 33 of earth station 1C2 A It transmits communication control data CC2 as radio waves RU2 towards low-Earth orbit satellite 42. Specifically, the satellite communications unit 33 of Earth station 1C2 A The modulator / demodulator 13 A The transmission signal SS2 is generated by modulating it with communication control data CC2. Frequency converter 12 A The antenna device 11 converts the frequency of the transmitted signal SS2. A However, the frequency-converted transmission signal SS2 is radiated as radio wave RU2 towards the low-Earth orbit satellite 42.

[0142] In step S36C, low Earth orbit satellite 42 receives radio wave RU2, converts its frequency, amplifies it, and transmits radio wave RD2. Low Earth orbit satellite 41 receives radio wave RD2, converts its frequency, amplifies it, and transmits radio wave RD1. In step S37C, the satellite communications unit 33 of earth station 1C1 A The satellite receives radio wave RD1 and generates communication control data CC2. The satellite communication IF unit 50 receives the communication control data CC2 and forwards it to the communication control data processing unit 57C. In step S38C, the communication control data processing unit 57C extracts the communication terminal 32, which is the requesting communication terminal, and the encryption key CK2 from the communication control data CC2 and activates the encryption key / decryption key management unit 55C. In step S39, the encryption key / decryption key management unit 55C stores the encryption key CK2 in the encryption key 90C used as the encryption key for the U-Plane side (series A) of the communication terminal 32.

[0143] Referring to Figure 21, the procedure for the process in which the earth station 1C1 converts user data UD1, transmitted from the S03C's communication terminal 31 to the communication terminal 32, into encrypted user data CD1 and radiates it as radio waves RU1 toward the high-altitude pseudo-satellite 91 will be explained. Regarding Figure 21, the differences from Figure 7, which is for the earth station 11, will be explained.

[0144] Earth station 1C determines and manages an encryption key for each source communication terminal. Earth station 1C determines and manages a decryption key for each source communication terminal. In step S43C, the encryption device control unit 56C refers to the encryption key 90C to obtain the encryption key CK2 for communication terminal 32. In step S44C, the encryption device control unit 56C instructs the encryption device 15C to encrypt the user data UD1 with the encryption key CK2, and the encryption device 15C generates the encrypted user data CD1.

[0145] Step S46C, Earth station 1C1 satellite communications unit 33 A The encrypted user data CD1 is transmitted as radio wave RU1 towards the high-altitude pseudo-satellite 91. Specifically, the satellite communications unit 33 of earth station 1C1 A The modulator / demodulator 13 A However, the transmitted signal SS1 is generated by modulating it with encrypted user data CD1. Frequency converter 12 AHowever, the transmitted signal SS1 is frequency-converted. Antenna device 11 A However, the frequency-converted transmission signal SS1 is radiated as radio wave RU1 towards the high-altitude pseudo-satellite 91.

[0146] Referring to Figure 22, the procedure for the process in S05C in which earth station 1C2 receives radio wave RD2, demodulates and decodes radio wave RD2 to generate user data UD1, and transmits it to communication terminal 32 will be explained. Regarding Figure 22, the differences from Figure 8 for earth station 11 will be explained.

[0147] In step S53C, the cryptographic device control unit 56C of the earth station 1C2 refers to the decryption key 89C and obtains the decryption key DK2 of the communication terminal 32. In step S54C, the cryptographic device control unit 56C instructs the cryptographic device 15C to decrypt the encrypted user data CD1 with the decryption key DK2, and the cryptographic device 15C generates the user data UD1.

[0148] Referring to Figure 23, the procedure for the process in S06C in which the earth station 1C2 converts the user data UD2 transmitted from the communication terminal 32 to the communication terminal 31 into encrypted user data CD2 and radiates it as radio waves RU2 toward the high-altitude pseudo-satellite 92 will be explained. Figure 23 is the same as Figure 21. The differences between Figure 23 and Figure 9 for the case of earth station 11 will be explained.

[0149] In step S63C, the encryption device control unit 56C refers to the encryption key 90C to obtain the encryption key CK1 of the communication terminal 31. In step S64C, the encryption device control unit 56C instructs the encryption device 15C to encrypt the user data UD2 with the encryption key CK1, and the encryption device 15C generates the encrypted user data CD2.

[0150] In step S66C, satellite communications unit 33 A The encrypted user data CD2 is transmitted as radio wave RU2 towards the high-altitude pseudo-satellite 92. Specifically, the satellite communications unit 33 of earth station 1C2 A The modulator / demodulator 13 A However, the transmitted signal SS2 is generated by modulating it with encrypted user data CD2. Frequency converter 12 AHowever, the transmitted signal SS2 is frequency-converted. Antenna device 11 A However, the frequency-converted transmission signal SS2 is radiated as radio wave RU2 towards the high-altitude pseudo-satellite 92.

[0151] Referring to Figure 24, the procedure for the process in S08C in which earth station 1C1 receives radio wave RD1, demodulates and decodes radio wave RD1 to generate user data UD2 and transmits it to communication terminal 31 will be explained. Figure 24 is the same as Figure 22. The differences between Figure 24 and Figure 10 for the case of earth station 11 will be explained.

[0152] In step S73C, the cryptographic device control unit 56C of the earth station 1C1 refers to the decryption key 89C and obtains the decryption key DK1 of the communication terminal 31. In step S74C, the cryptographic device control unit 56C instructs the cryptographic device 15C to decrypt the encrypted user data CD2 with the decryption key DK1, and the cryptographic device 15C generates the user data UD2.

[0153] Referring to Figure 25, in S09C, Earth station 1C1 transmits the communication control data CC1 to Earth station 1C2 via radio RU directed towards low Earth orbit satellite 41. C1 The procedure for the radiation process will be explained. Regarding Figure 25, the differences from Figure 11 in the case of Earth Station 11 will be explained.

[0154] Step S86C, Earth station 1C1 satellite communications unit 33 A The communication control data CC1 is transmitted via radio waves RU C1 It will then be radiated towards low-Earth orbit satellite 41. Specifically, from the satellite communications unit 33 of Earth station 1C1. A The modulator / demodulator 13 A The transmission signal SS1 is generated by modulating it with the communication control data CC1. Frequency converter 12 A The antenna device 11 converts the frequency of the transmitted signal SS1. A However, the frequency-converted transmission signal SS1 was directed towards the low-Earth orbit satellite 41 via radio waves RU C1 It emits radiation as such.

[0155] Referring to Figure 26, in S12C, Earth station 1C2 transmits the communication control data CC2 to Earth station 1C1 via radio RU to low Earth orbit satellite 42. C2 The procedure for the process of radiating as follows will be explained. Figure 26 is the same as Figure 25. Regarding Figure 26, the differences from Figure 13 in the case of Earth Station 11 will be explained.

[0156] Step S96C, Earth station 1C2 satellite communications unit 33 A The communication control data CC2 is transmitted via radio waves RU C2 It will then be radiated towards low Earth orbit satellite 42. Specifically, from the satellite communications unit 33 of Earth station 1C2. A The modulator / demodulator 13 A The transmission signal SS2 is generated by modulating it with communication control data CC2. Frequency converter 12 A The antenna device 11 converts the frequency of the transmitted signal SS2. A However, the frequency-converted transmission signal SS2 was directed towards the low-Earth orbit satellite 42 via radio waves RU C2 It emits radiation as such.

[0157] Earth station 1C encrypts user data and transmits it via the high-altitude pseudo-satellite communication link 21. Earth station 1C transmits the encryption key and decryption key for encrypting the user data via the low-Earth orbit satellite communication link 6. Therefore, even if user data transmitted via the high-altitude pseudo-satellite communication link 21 is intercepted, the content of the user data will not be known because it is encrypted. Since the encryption key and decryption key are transmitted via the low-Earth orbit satellite communication link 6, even if the high-altitude pseudo-satellite communication link 21 through which user data is transmitted is intercepted, the encryption key and decryption key will not be leaked. User data is not transmitted via the low-Earth orbit satellite communication link 6, so even if the low-Earth orbit satellite communication link 6 is intercepted, the content of the user data will not be known.

[0158] Earth Station 1C does not require ground infrastructure. Earth Station 1C can easily expand the communication area in mobile communication systems.

[0159] Earth station 1C can share encryption keys (including decryption keys) between the sender and receiver without using other communication systems. Earth station 1C can communicate encrypted user data.

[0160] Earth station 1C uses public-key cryptography and does not communicate the decryption key (private key). Earth station 1C can manage the decryption key more securely than Earth station 1, which uses symmetric-key cryptography.

[0161] Earth station 1C can select a first and second out-of-tropic communication link from at least three types of out-of-tropic communication links relayed by relay stations mounted on at least three out-of-tropic mobile bodies moving at altitudes included in the out-of-troposphere. Therefore, if there is a problem with the first or second out-of-tropic communication link, communication can be performed using the other out-of-tropic communication links.

[0162] Embodiment 3. Embodiment 3 is an embodiment that modifies Embodiment 2 to use a single set of phased array antenna devices and satellite communication units in time division. In the satellite communication system 100D, the earth station 1D is modified. The configuration of the earth station 1D will be described with reference to Figure 27. Figure 27 is a diagram showing the configuration of the communication device (earth station 1D) according to Embodiment 3. The differences between Figure 27 and Figure 16 in the case of Embodiment 2 will be explained. Embodiment 1 or other embodiments may be modified to use a single set of phased array antenna devices and satellite communication units in time division.

[0163] Earth station 1D is antenna device 11 A , 11 B Instead, it has a receiving antenna device 17 and a transmitting antenna device 18. The receiving antenna device 17 and the transmitting antenna device 18 are phased array antennas. Phased array antennas can electrically change their directional direction at high speed. The receiving antenna device 17 and the transmitting antenna device 18 communicate with satellite 80 A The period during which the extratropospheric mobile object (extratropospheric mobile object A) stored in the satellite 80 is tracked, and the period during which satellite 80 is in communication BThe system alternates between tracking an out-of-tropospheric mobile object (out-of-tropospheric mobile object B) stored in the system. During the period when tracking out-of-tropospheric mobile object A, Earth station 1D communicates via out-of-tropospheric communication link A, which is relayed by a relay station onboard out-of-tropospheric mobile object A. During the period when tracking out-of-tropospheric mobile object B, Earth station 1D communicates via out-of-tropospheric communication link B, which is relayed by a relay station onboard out-of-tropospheric mobile object B. At Earth station 1D1, out-of-tropospheric mobile object A is a high-altitude pseudo-satellite 91, and out-of-tropospheric mobile object B is a low-Earth orbit satellite 41. At Earth station 1D2, out-of-tropospheric mobile object A is a high-altitude pseudo-satellite 92, and out-of-tropospheric mobile object B is a low-Earth orbit satellite 42. Out-of-tropospheric mobile object A and out-of-tropospheric mobile object B only need to select two types of out-of-tropospheric mobile objects from at least two types of out-of-tropospheric mobile objects. The tropospheric mobile bodies A and B may be swapped.

[0164] Earth station 1D is equipped with a time-division control unit 60 and a transmit buffer 34 to enable time-division operation. A , 34 B The following have been added, and the frequency converter 12D, modulator / demodulator 13D, satellite communication IF unit 50D, tracking control unit 52D, and data storage unit 58D have been modified. The receiving antenna device 17, transmitting antenna device 18, frequency converter 12D, and modulator / demodulator 13D constitute one set of satellite communication units 33D. The satellite communication units 33D are time-division multiplexed. A Or Satellite Communications Department 33 B It operates as such.

[0165] Satellite communications unit 33D is Satellite communications unit 33 A During the period in which it operates as such, the satellite communication unit 33D operates to communicate via the high-altitude pseudo-satellite communication link 211 at earth station 1D1, and the satellite communication unit 33D operates to communicate via the high-altitude pseudo-satellite communication link 212 at earth station 1D2.

[0166] Satellite communications unit 33D is Satellite communications unit 33 BDuring the period in which it operates as such, the satellite communication unit 33D operates to communicate via the low-Earth orbit satellite communication link 61 at Earth station 1D1, and the satellite communication unit 33D operates to communicate via the low-Earth orbit satellite communication link 62 at Earth station 1D2. The satellite communication unit 33D may be considered as not including the receiving antenna device 17 and the transmitting antenna device 18.

[0167] The time-division control unit 60 controls the receiving antenna device 17, transmitting antenna device 18, frequency converter 12D, and modulator / demodulator 13D to operate in a time-division manner. The tracking control unit 52D controls the receiving antenna device 17 and transmitting antenna device 18 to track the out-of-troposphere mobile object A during the period when communication is being conducted on the out-of-troposphere communication line A. The tracking control unit 52D controls the receiving antenna device 17 and transmitting antenna device 18 to track the out-of-troposphere mobile object B during the period when communication is being conducted on the out-of-troposphere communication line B.

[0168] The data processing unit 14D operates in the same manner as the data processing unit 14. Since the modulator / demodulator 13D operates in time division, a transmit buffer 34 is placed between the output from the data processing unit 14D and the modulator / demodulator 13D. A , 34 B To establish.

[0169] The receiving antenna device 17 includes a receiving antenna unit 62 having a plurality of element receiving antennas 61, and an element receiving signal processing unit 63 that processes element receiving signals received by the element receiving antennas 61. The transmitting antenna device 18 includes a transmitting antenna unit 65 having a plurality of element transmitting antennas 64, and an element transmitting signal generation unit 66 that generates element transmitting signals to be transmitted by the element transmitting antennas 64.

[0170] The element receiving signal processing unit 63 has an output terminal 67, a combining circuit 68, and a receiving module 69 provided for each element receiving antenna 61. The output terminal 67 is connected to the frequency converter 12D. That is, the receiving antenna device 17 is connected to the frequency converter 12D. The element receiving signal generated by the element receiving antenna 61 when it receives radio waves is input to the receiving module 69. The signals output by multiple receiving modules 69 are combined by the combining circuit 68 and output from the output terminal 67.

[0171] The element transmission signal generation unit 66 has an input terminal 70, a distribution circuit 71, and a transmission module 72 provided for each element transmission antenna 64. The input terminal 70 is connected to the frequency converter 12D. That is, the transmission antenna device 18 is connected to the frequency converter 12D. The transmission signal input to the input terminal 70 is distributed by the distribution circuit 71 and input to the multiple transmission modules 72. The element transmission signals output by the transmission modules 72 are input to the element transmission antenna 64. The element transmission antenna 64 radiates the input element transmission signals into space as radio waves.

[0172] The element receiving signal processing unit 63 combines the element receiving signals output by each element receiving antenna 61 by changing the phase for each element receiving antenna 61. The amount of phase change is determined according to the direction of direction, the position of that element receiving antenna 61 within the entire receiving antenna unit 62, and the receiving frequency. By changing the phase of multiple element receiving signals and combining them, the receiving antenna unit 62 gains directionality and can receive radio waves from the direction of direction (receiving direction). The receiving antenna unit 62 can change its direction of direction while remaining stationary. Changing the direction of direction while the antenna remains stationary is called electronically changing the direction of direction. To electronically change the direction of direction, the receiving module 69 has a phase shifter 73 and an amplifier 74. The amount of phase change (phase shift amount) that the phase shifter 73 changes is input from the tracking control unit 52D.

[0173] By controlling the phase of the radio waves radiated by each of the multiple element transmitting antennas 63, the transmitting antenna unit 65 can radiate radio waves in a predetermined directional direction (transmission direction). The phase of the element transmission signal input to each element transmitting antenna 3 is determined according to the position of that element transmitting antenna 64 within the entire transmitting antenna unit 65 and the transmission frequency. The element transmission signal generation unit 66 generates an element transmission signal that can radiate radio waves of the transmission frequency in a predetermined directional direction. The generated element transmission signal is radiated into space as a radio wave by the corresponding element transmitting antenna 3. The transmitting module 72 has a phase shifter 75 and an amplifier 76. The phase shift amount of the phase shifter 75 is input from the tracking control unit 52D.

[0174] Transmit buffer 34 A , 34 B This is a buffer that temporarily stores the transmitted data so that the modulator / demodulator 13D can operate in time division. Transmit buffer 34 A This buffers the transmitted data on the out-of-troposphere communication line relayed by the out-of-troposphere mobile device A. Transmit Buffer 34 B It buffers the transmitted data on the out-of-troposphere communication line, which is relayed by the out-of-troposphere mobile device B.

[0175] The satellite communication IF unit 50D transmits user data encrypted by the encryption device 15C or unencrypted communication control data to the transmission buffer 34 according to the data type. A or transmit buffer 34 B Output to the satellite communication IF unit 50D transmits encrypted user data to the transmission buffer 34. A The output is sent to the satellite communication IF unit 50D. The communication control data is sent to the transmission buffer 34. B Output to: Satellite communication unit 33D, Satellite communication unit 33 A The period during which it operates as is the transmit buffer 34 A It receives transmitted data from the satellite communication unit 33D. B The period during which it operates as is the transmit buffer 34 BThe transmitted data is received from the transmitter. The data decoded by the modulator / demodulator 13D is input to the satellite communication IF unit 50D. The satellite communication IF unit 50D determines whether the data stored in the data packet is encrypted user data or communication control data based on the packet type.

[0176] The data storage unit 58D also contains time-division control data 93. The time-division control data 93 is data that represents the period during which the satellite communication unit 33D and the tracking control unit 52D operate in time division. The time-division control unit 60 and the tracking control unit 52D refer to the time-division control data 93 to control the receiving antenna device 17, the transmitting antenna device 18, the frequency converter 12D, and the modulator / demodulator 13D to operate in time division.

[0177] The time-division control unit 60 controls the frequency converter 12D and the modulator / demodulator 13D to communicate in time division over the high-altitude pseudo-satellite communication link 21 and the low-Earth orbit satellite communication link 6. During the period of communication over the high-altitude pseudo-satellite communication link 21, which is the first out-of-troposphere communication link (first communication period), the time-division control unit 60 controls the frequency converter 12D to perform frequency conversion between the frequency used in the high-altitude pseudo-satellite communication link 21 and the frequency of the signal processed by the modulator / demodulator 13D. The signal demodulated by the modulator / demodulator 13D is input to the satellite communication IF unit 50D without buffering. During the first communication period, the time-division control unit 60 transmits the data modulated by the modulator / demodulator 13D to the transmission buffer 34 A Control to acquire from. The first communication period is the period during which the modulator / demodulator 13D and frequency converter 12D are used as the first out-of-tropic communication unit. Also, during the first communication period, the receiving antenna device 17, transmitting antenna device 18, frequency converter 12D and modulator / demodulator 13D are controlled to acquire from the satellite communication unit 33. A It can be considered as constituting [something].

[0178] During the period of communication on the second out-of-troposphere communication link, the low-Earth orbit satellite communication link 7 (second communication period), the time-division control unit 60 controls the frequency converter 12D to perform frequency conversion between the frequency used on the low-Earth orbit satellite communication link 7 and the frequency of the signal processed by the modulator / demodulator 13D. During the second communication period, the time-division control unit 60 transmits the data modulated by the modulator / demodulator 13D to the transmission buffer 34 B Control to acquire from. The second communication period is the period during which the modulator / demodulator 13D and frequency converter 12D are used as the second out-of-tropic communication unit. Also, during the second communication period, the receiving antenna device 17, transmitting antenna device 18, frequency converter 12D and modulator / demodulator 13D are controlled to the satellite communication unit 33. B It can be considered as constituting [something].

[0179] The tracking control unit 52D controls the receiving antenna device 17 and the transmitting antenna device 18 to track the high-altitude pseudo-satellite 9, which is the first out-of-troposphere mobile object, during the first communication period, and controls the receiving antenna device 17 and the transmitting antenna device 18 to track the second out-of-troposphere mobile object, which is the first out-of-troposphere mobile object, during the second communication period.

[0180] During the first communication period, the tracking control unit 52D determines the satellite's position 87 A Receiving frequency 81 A And based on the arrangement of each element receiving antenna 61 within the entire receiving antenna section 62, a receiving module 69 processes the element receiving signals received by that element receiving antenna 61. A The phase shifter 73 A The phase shift amount is calculated, and each receiving module 69 changes the phase by the calculated phase shift amount. A Controls the satellite's orientation 87. A The direction in which the high-altitude pseudo-satellite 9 is located is stored. Receiving frequency 81 A and transmission frequency 82 A This contains the receiving and transmitting frequencies used in the high-altitude pseudo-satellite communication link 21.

[0181] During the first communication period, the tracking control unit 52D determines the satellite's position 87 A, transmission frequency 82 A And based on the arrangement of each element transmitting antenna 63 within the entire transmitting antenna section 64, a transmitting module 72 outputs an element transmitting signal that is input to that element transmitting antenna 63. A The phase shift amount of the phase shifter 75 is calculated, and each transmitting module 72 changes the phase by the calculated phase shift amount. A Control.

[0182] During the second communication period, the tracking control unit 52D determines the satellite's position 87 B Receiving frequency 81 B And based on the arrangement of each element receiving antenna 61 within the entire receiving antenna section 62, a receiving module 69 processes the element receiving signals received by that element receiving antenna 61. B The phase shifter 73 B The phase shift amount is calculated, and each receiving module 69 changes the phase by the calculated phase shift amount. B Controls the satellite's orientation 87. B The direction in which low-Earth orbit satellite 4 is located is stored. Receiving frequency 81 B and transmission frequency 82 B This contains the receiving and transmitting frequencies used in the low orbit communication line 6.

[0183] During the second communication period, the tracking control unit 52D determines the satellite's position 87 B , transmission frequency 82 B And based on the arrangement of each element transmitting antenna 63 within the entire transmitting antenna section 64, a transmitting module 72 outputs an element transmitting signal that is input to that element transmitting antenna 63. B The phase shifter 75 B The phase shift amount is calculated, and each transmitting module 72 changes the phase by the calculated phase shift amount. B Control.

[0184] The operation will now be explained. Figures 28 and 29 are flowcharts illustrating the general procedure when a communication terminal 31 connected to earth station 1D1 communicates with a communication terminal 32 connected to earth station 1D2. Figures 28 and 29 will be explained in terms of differences from Figures 17 and 18 in the case of wireless communication system 100C.

[0185] Because it operates in time-division multiplexing, during the first communication period, the processes from S03C to S05C and the processes from S06C to S08C are executed in parallel. During the second communication period, the processes from S09C to S11 and the processes from S12C to S14 are executed in parallel.

[0186] For communication from Earth Station 1D1 to Earth Station 1D2, a step S15 is added between S03C and S09C to check whether the first communication period has ended. If the first communication period has not ended (NO in S15), return to S03C. If the first communication period has ended (YES in S15), proceed to S09C. After S11, a step S16 is added to check whether the second communication period has ended. If the second communication period has not ended (NO in S16), return to S09C. If the first communication period has ended (YES in S16), return to S03C.

[0187] The operation of S03C is the same as the flowcharts in Figures 19 to 26 that describe the operation of Earth Station 1C. However, the satellite communication unit 33 A This should be read as Satellite Communications Unit 33D during the first communications period. Satellite Communications Unit 33 B This should be interpreted as the satellite communications section 33D during the first communications period.

[0188] For communication from Earth Station 1D2 to Earth Station 1D1, a step S17 is added between S06C and S12C to check whether the first communication period has ended. If the first communication period has not ended (NO in S17), return to S06C. If the first communication period has ended (YES in S17), proceed to S12C. After S14, a step S18 is added to check whether the second communication period has ended. If the second communication period has not ended (NO in S18), return to S12C. If the first communication period has ended (YES in S18), return to S06C.

[0189] Earth station 1D operates similarly to earth station 1C, except that it communicates using time-division multiplexing, and achieves the same effect. Earth station 1D can share encryption keys (including decryption keys) between the sender and receiver without using other communication systems. Earth station 1D can communicate encrypted user data. Because the second out-of-tropic communication link for communicating encryption keys and the first out-of-tropic communication link for communicating encrypted user data are separate, the content of the user data cannot be known even if only one of them is intercepted.

[0190] Since the receiving antenna device 17 and transmitting antenna device 18 are phased array antennas, the size of the earth station can be made more compact than when using two mechanically driven antenna devices.

[0191] Embodiment 4. Embodiment 4 is a modification of Embodiment 2, using a pair of phased array antennas that transmit and receive radio waves in two directions, which can be changed independently of each other. The encryption method has been changed to a symmetric key encryption method. In the satellite communication system 100E, the earth station 1E has been modified. The configuration of earth station 1E will be explained with reference to Figure 30. Figure 30 is a diagram showing the configuration of the communication device (earth station 1E) according to Embodiment 4. The differences between Figure 30 and Figure 16 in Embodiment 2 will be explained.

[0192] Earth station 1E has antenna equipment 11 A , 11B Instead, it has a receiving antenna device 17E and a transmitting antenna device 18E. The receiving antenna device 17E and the transmitting antenna device 18E are phased array antennas. The receiving antenna device 17E receives radio waves from two directions that can be changed independently of each other. The transmitting antenna device 18E transmits radio waves in two directions that can be changed independently of each other. The earth station 1E modifies the tracking control unit 52E of the data processing device 14E.

[0193] The receiving antenna device 17E includes a receiving antenna section 62 having a plurality of element receiving antennas 61, and an element receiving signal processing section 63E that processes element receiving signals received by the element receiving antennas 61.

[0194] The element receiving signal processing unit 63E has an output terminal 67 A , 67 B and the synthesis circuit 68 A , 68 B And, two receiving modules 69 are provided for each element receiving antenna 61. A ,69 B It has the following: Receiving module 69 A ,69 B Each of these receives an element reception signal generated by the element receiving antenna 61 when it receives radio waves. Multiple receiving modules 69 A The signal output by is from the combining circuit 68 A Combined and output terminal 67 A Output is produced from output terminal 67. A The frequency converter 12 A Connects to multiple receiving modules 69. B The signal output by is from the combining circuit 68 B Combined and output terminal 67 B Output is produced from output terminal 67. B The frequency converter 12 B Connect to: Receiver module 69 A is a phase shifter 73 A and amplifier 74 A It has a receiving module 69. B is a phase shifter 73 B and amplifier 74 BEach phase shifter 73 A , 73 B The amount of phase shift can be controlled. Each amplifier 74 A , 74 B The amplification factor can be controlled.

[0195] In the element receiving signal processing unit 63E, output terminal 67 A , synthesis circuit 68 A and receiving module 69 A This is called the element receiving signal processing unit 63E of series A. Output terminal 67 B , synthesis circuit 68 B and receiving module 69 B This is called the element receiving signal processing unit 63E of series B.

[0196] The receiving antenna device 17E has each phase shifter 73 A By controlling the phase shift amount, the device outputs a received signal of a first receiving frequency from a first receiving direction that can be electronically changed. The receiving antenna device 17E controls each phase shifter 73 B By controlling the phase shift amount, a received signal with a second receiving frequency different from the first receiving frequency is output from a second receiving direction, which can be electronically changed independently of the first receiving direction.

[0197] The receiving antenna device 17E receives radio waves of different frequencies from two different directions. The receiving antenna device 17E can be thought of as having two series of receiving antenna devices 17E. The receiving antenna device 17E of series A consists of a receiving antenna section 62 and an element receiving signal processing section 63E of series A. The receiving antenna device 17E of series B consists of a receiving antenna section 62 and an element receiving signal processing section 63E of series B.

[0198] The transmitting antenna device 18E includes a transmitting antenna section 65 having a plurality of element transmitting antennas 64, and an element transmitting signal generation section 66E that generates element transmitting signals to be transmitted by the element transmitting antennas 64.

[0199] The element transmission signal generation unit 66E has an input terminal 70 A , 70 B and distribution circuit 71A , 71 B And, two transmitting modules 72 are provided for each element transmitting antenna 64. A , 72 B It has the following: Input terminal 70 A The frequency converter 12 A Connect to input terminal 70. A The transmission signal input to the distribution circuit 71 A Distributed to multiple transmitting modules 72 A Input is sent to: Input terminal 70 B The frequency converter 12 B Connect to input terminal 70. B The transmission signal input to the distribution circuit 71 B Distributed to multiple transmitting modules 72 B It is input to the transmitting module 72. A , 72 B The element transmission signal output by is input to the element transmission antenna 64. The element transmission antenna 64 radiates the input element transmission signal into space as radio waves. Transmitting module 72 A is a phase shifter 75 A and amplifier 76 A It has. Transmitter module 72 B is a phase shifter 75 B and amplifier 76 B Each phase shifter 75 A , 75 B The amount of phase shift can be controlled. Each amplifier 76 A , 76 B The amplification factor can be controlled.

[0200] In the element transmission signal generation unit 66E, input terminal 70 A , distribution circuit 71 A and transmission module 72 A This is called the element transmission signal generation unit 66E of series A. Input terminal 70 B , distribution circuit 71 B and transmission module 72 B This is called the element transmission signal generation unit 66E of series B.

[0201] The transmitting antenna device 18E has each phase shifter 75 ABy controlling the phase shift amount, radio waves of the first transmission frequency can be radiated in the first transmission direction which can be electronically changed. The transmitting antenna device 18E has each phase shifter 75 B By controlling the phase shift amount, radio waves of a second transmission frequency can be radiated in a second transmission direction, which can be electronically changed independently of the first transmission direction.

[0202] The transmitting antenna device 18E transmits radio waves of different frequencies in two different directions. The transmitting antenna device 18E can be thought of as having two series of transmitting antenna devices 18E. The transmitting antenna device 18E of series A consists of a transmitting antenna section 64 and an element transmission signal generation section 66E of series A. The transmitting antenna device 18E of series B consists of a transmitting antenna section 64 and an element transmission signal generation section 66E of series B.

[0203] Receiving antenna device 17E and transmitting antenna device 18E of series A, frequency converter 12 A and modulator / demodulator 13 A This is a set of satellite communications unit 33E A It can be considered that this constitutes the following: the receiving antenna device 17E and transmitting antenna device 18E of series B, and the frequency converter 12 B and modulator / demodulator 13 B This is a set of satellite communications unit 33E B It can be considered as constituting [something].

[0204] Satellite direction 87 A ,87 BThe system stores the directions in which the out-of-tropospheric mobile objects A and B exist. Here, it is assumed that in Earth Station 1E1 and Earth Station 1E2, sequence A is a U-Plane and sequence B is a C-Plane. Since user data is communicated in the U-Plane, out-of-tropospheric mobile object A is the first out-of-tropospheric mobile object. Out-of-tropospheric mobile object B is the second out-of-tropospheric mobile object. Note that if sequence A is a C-Plane and sequence B is a U-Plane, then out-of-tropospheric mobile object A is the second out-of-tropospheric mobile object and out-of-tropospheric mobile object B is the first out-of-tropospheric mobile object. Out-of-tropospheric mobile objects A and B do not need to be of the same type. For example, out-of-tropospheric mobile object A may be geostationary satellite 5 and out-of-tropospheric mobile object B may be high-altitude pseudo-satellite 9.

[0205] Receiving frequency 81 A and transmission frequency 82 A The receiving and transmitting frequencies used for the first out-of-convection communication line are stored there. In other words, the receiving frequency 81 A The first receiving frequency is stored in the device, and the transmitting frequency is 82 A The first transmission frequency is stored there. Receiving frequency 81 B and transmission frequency 82 B The receiving and transmitting frequencies used for the first out-of-convection communication line are stored there. In other words, the receiving frequency 81 B The second receiving frequency is stored in the device, and the transmission frequency is 82 B The second transmission frequency is stored there.

[0206] In Earth Station 1E, the Line Control Unit 51C is a frequency setting unit that sets the reception frequency and transmission frequency of the first out-of-convection communication line as the first reception frequency and first transmission frequency, respectively, and sets the reception frequency and transmission frequency of the second out-of-convection communication line as the second reception frequency and second transmission frequency, respectively.

[0207] The tracking control unit 52E controls the receiving antenna device 17E and the transmitting antenna device 18E to track the out-of-troposphere mobile object A and the out-of-troposphere mobile object B. That is, the tracking control unit 52E controls the first receiving direction and the first transmitting direction to coincide with the direction in which out-of-troposphere mobile object A is located. The direction in which out-of-troposphere mobile object A is located is the satellite location direction 87 A It is stored in. The tracking control unit 52E controls the second receiving direction and the second transmitting direction so that they coincide with the direction in which the extratropospheric mobile object B is located. The direction in which the extratropospheric mobile object B is located is the satellite location direction 87 B It is remembered.

[0208] Specifically, the tracking control unit 52E controls as follows: (a) The tracking control unit 52E adjusts each receiving module 69 so that the direction in which the out-of-troposphere moving object A is located coincides with the first receiving direction. A The phase shifter 73 A The phase shift amount is calculated, and the calculated phase shift amount is used in the phase shifter 73 A Input to the following. The tracking control unit 52E controls each receiving module 69 A The phase shift amount is determined by the first receiving direction, the first receiving frequency, and each receiving module 69 A The calculation is based on the arrangement of the element receiving antenna 61, which outputs the element receiving signal processed by the system, within the entire receiving antenna section 62.

[0209] (b) The tracking control unit 52E adjusts each transmission module 72 so that the direction in which the out-of-troposphere moving object A is located coincides with the first transmission direction. A The phase shifter 75 A The phase shift amount is calculated, and the calculated phase shift amount is used with the phase shifter 75 A Input to the following: The tracking control unit 52E controls each transmission module 72 A The phase shift amount is determined by the first transmission direction, the first transmission frequency, and each transmission module 72 A The calculation is based on the arrangement of the element transmitting antenna 63, which outputs the element receiving signal processed by the system, within the entire transmitting antenna section 64.

[0210] (c) The tracking control unit 52E adjusts each receiving module 69 so that the direction in which the out-of-troposphere moving object B is located coincides with the second receiving direction. B The phase shifter 73 B The phase shift amount is calculated, and the calculated phase shift amount is used in the phase shifter 73 B Input to the following. The tracking control unit 52E controls each receiving module 69 B The phase shift amount is determined by the second receiving direction, the second receiving frequency, and each receiving module 69 B The calculation is based on the arrangement of the element receiving antenna 61, which outputs the element receiving signal processed by the system, within the entire receiving antenna section 62.

[0211] (d) The tracking control unit 52E adjusts each transmission module 72 so that the direction in which the out-of-troposphere moving object B is located coincides with the second transmission direction. B The phase shifter 75 B The phase shift amount is calculated, and the calculated phase shift amount is used with the phase shifter 75 B Input to the following: The tracking control unit 52E controls each transmission module 72 B The phase shift amount is determined by the second transmission direction, the second transmission frequency, and each transmission module 72 B The calculation is based on the arrangement of the element transmitting antenna 63, which outputs the element receiving signal processed by the system, within the entire transmitting antenna section 64.

[0212] Earth station 1E operates similarly to earth station 1C and achieves the same effect. However, earth station 1E differs from earth station 1C in that it uses a symmetric-key cryptographic scheme. Also, in the flowcharts from Figures 17 to 26 that explain the operation of earth station 1C, the satellite communication unit 33 A ,33 B Satellite Communications Unit 33E A , 33E B Reinterpret it as follows.

[0213] Earth station 1E can share encryption keys (including decryption keys) between the sender and receiver without using other communication systems. Earth station 1E can communicate encrypted user data. Because the second out-of-tropic communication circuit for communicating encryption keys and the first out-of-tropic communication circuit for communicating encrypted user data are separate, the content of the user data cannot be known even if only one of them is intercepted.

[0214] Since the receiving antenna unit 17E and transmitting antenna unit 18E are phased array antennas, the size of the earth station can be made more compact than when using two mechanically driven antenna units.

[0215] The receiving antenna device 17E can output received signals from two independently controllable directions. The transmitting antenna device 18E can transmit radio waves in two independently controllable directions. Therefore, time-division control is unnecessary for the receiving antenna device 17E and the transmitting antenna device 18E. Control of the receiving antenna device and the transmitting antenna device is simpler at earth station 1E than at earth station 1D. The receiving antenna device 17E and the transmitting antenna device 18E can always communicate user data and communication control data in parallel.

[0216] Embodiment 5. Embodiment 5 is a case where a high-altitude pseudo-satellite does not communicate with other high-altitude pseudo-satellites, and communication is performed using the communication device (earth station) according to Embodiment 2, which has been modified to use a symmetric-key cryptography scheme. Figure 31 is a diagram showing the schematic configuration of a satellite communication system including the communication device according to Embodiment 5. The differences between Figure 31 and Figure 15 in the case of Embodiment 2 will be explained below.

[0217] Satellite communication system 100F has modified earth stations 1F1, 1F2, and 1F3, and high-altitude pseudo-satellite 9 does not communicate with other high-altitude pseudo-satellites 9. Satellite communication system 100F has a ground core network 40, ground core network equipment 411, 412, ground networks 421, 422, geostationary satellite ground station 43, low-Earth orbit satellite ground station 44, high-altitude pseudo-satellite ground stations 451, 452, and earth station 46. Communication terminal 33 is connected to earth station 1F3 via network 23.

[0218] A communication terminal 34 is connected to Earth station 46 via network 24. Earth station 46 does not have an antenna device for communication on an out-of-troposphere communication line. Earth station 46 has an encryption device and can decrypt encrypted user data encrypted by Earth station 1F, and can generate encrypted user data that Earth station 1F can decrypt.

[0219] Earth station 1F1 can communicate with earth stations 1F2, 1F3, and earth station 46. Earth station 1F2 communicates with low-Earth orbit satellite 41 using low-Earth orbit satellite communication link 62. Earth station 1F2 communicates with high-altitude pseudo-satellite satellite 91 using high-altitude pseudo-satellite communication link 212. Earth station 1F3 communicates with geostationary satellite 5 using geostationary satellite communication link 83. Earth station 1F3 communicates with low-Earth orbit satellite 42 using low-Earth orbit satellite communication link 63. Earth station 1F3 communicates with high-altitude pseudo-satellite satellite 92 using high-altitude pseudo-satellite communication link 213.

[0220] The terrestrial core network 40 is a network of high-capacity communication lines laid on the ground. Terrestrial core network devices 411 and 412 connect the terrestrial core network 40 to the other terrestrial networks 421 and 422, respectively. Terrestrial network 421 is connected to geostationary satellite ground station 43, low orbit satellite ground station 44, and high-altitude pseudo-satellite ground station 451. Terrestrial network 422 is connected to high-altitude pseudo-satellite ground station 452 and earth station 46.

[0221] Geostationary satellite ground station 43 enables communication between geostationary satellite 5 and communication equipment (such as earth stations 46) connected to the ground network 42 (including those connected via the ground core network 40). Geostationary satellite ground station 43 communicates with geostationary satellite 5 using geostationary satellite communication link 84. Low Earth orbit satellite ground station 44 enables communication between low Earth orbit satellite 4 and communication equipment connected to the ground network 42. Low Earth orbit satellite ground station 44 enables communication with low Earth orbit satellite 41 using low Earth orbit satellite communication link 64. High-altitude pseudo-satellite ground station 451 enables communication between high-altitude pseudo-satellite satellite 91 and communication equipment connected to the ground network 42. High-altitude pseudo-satellite ground station 451 communicates with high-altitude pseudo-satellite satellite 91 using high-altitude pseudo-satellite communication link 214. High-altitude pseudo-satellite ground station 452 enables communication between high-altitude pseudo-satellite satellite 92 and communication equipment connected to the ground network 42. The high-altitude pseudo-satellite ground station 452 communicates with the high-altitude pseudo-satellite 92 using the high-altitude pseudo-satellite communication link 215.

[0222] Since low Earth orbit satellite ground station 44 exists, earth station 46 and earth station 1F can communicate encryption keys for encrypting user data and decryption keys for decrypting it using the low Earth orbit satellite communication link 6.

[0223] Earth station 1F is a modified version of Earth station 1C that uses public-key cryptography. The configuration of Earth station 1F will be explained with reference to Figure 32. Figure 32 is a diagram showing the configuration of the communication device (Earth station 1F) according to Embodiment 5. The differences between Figure 32 and Figure 16 in Embodiment 2 will be explained. Earth station 1F has modified encryption device 15, encryption key / decryption key management unit 55, communication control data processing unit 57, and data storage unit 58F. The encryption device 15, encryption key / decryption key management unit 55, and communication control data processing unit 57 are the same as those in Earth station 1.

[0224] The data storage unit 58F does not have a decryption key 89C, a used encryption key 90C, and a corresponding encryption key 91C, but it has an encryption key 89 and a decryption key 90. Compared to the data storage unit 58, the data storage unit 58F has a different mobile type 92. A , 92 B This has been added.

[0225] Let's explain the operation. First, we'll explain the case where communication terminal 31 connected to earth station 1F1 communicates with communication terminal 32 connected to earth station 1F2. Earth station 1F1 and earth station 1F2 communicate with the same high-altitude pseudo-satellite 91. Figures 33 and 34 are flowcharts illustrating the general procedure for communication between communication terminal 31 connected to earth station 1F1 and communication terminal 32 connected to earth station 1F2. Figure 33 shows the processing up to step S08F, and Figure 34 shows the processing from step S09C onwards. Note that the processing from S09C onwards shown in Figure 34 is the same as in Figure 18.

[0226] At Earth Station 1F1 and Earth Station 1F2, Satellite Communications Unit 33 of Network A A The communication is relayed via a communication line on a high-altitude pseudo-satellite 9, and the satellite communication unit 33 of series B B They communicate via a communication link relayed by low-Earth orbit satellite 4. At Earth Station 1F1 and Earth Station 1F2, sequence A is assumed to be U-Plane and sequence B is assumed to be C-Plane.

[0227] Figures 33 and 34 will be explained in terms of differences from Figures 17 and 18 in the case of Earth Station 1C. In step S02F, Earth Station 1F1 and Earth Station 1F2 determine the encryption key and decryption key to be used for communication between communication terminal 31 and communication terminal 32 and store them in the data storage unit 58. The processing of S02F differs from that of S02C only in that an encryption key using a symmetric key encryption scheme is determined. The processing of S02F is the same as that of S02, except that the low-Earth orbit satellite communication link 7 is used instead of the geostationary satellite communication link 8.

[0228] In step S03F, earth station 1F1 transmits encrypted user data CD1 from communication terminal 31, encrypted using a symmetric-key cryptography scheme, as radio wave RU1 towards high-altitude pseudo-satellite 91. In step S04F, high-altitude pseudo-satellite 91 receives radio wave RU1, frequency-converts and amplifies it, and transmits it as radio wave RD2. In step S05F, earth station 1F2 receives radio wave RD2, demodulates and decrypts it to generate user data UD1. Earth station 1F2 transmits user data UD1 to communication terminal 32. The process in S03F is almost the same as in S03C. S03F differs from S03C in that it uses a symmetric-key cryptography scheme. The process in S05F is almost the same as in S05C. S05F differs from S05C in that it uses a symmetric-key cryptography scheme.

[0229] In step S06F, earth station 1F2 transmits encrypted user data CD2 from communication terminal 32, encrypted using a symmetric-key cryptography scheme, as radio wave RU2 towards high-altitude pseudo-satellite 91. In step S07F, high-altitude pseudo-satellite 91 receives radio wave RU2, frequency-converts and amplifies it, and transmits it as radio wave RD1. In step S08F, earth station 1F1 receives radio wave RD1, demodulates and decrypts it to generate user data UD2. Earth station 1F1 transmits user data UD2 to communication terminal 31. The processing in S06F is almost the same as in S06C. S06F differs from S06C in that it uses a symmetric-key cryptography scheme and transmits radio wave RU2 towards high-altitude pseudo-satellite 91. The processing in S08F is almost the same as in S08C. S08F differs from S08C in that it uses a symmetric-key cryptography scheme.

[0230] The process by which earth stations 1F1 and 1F2 communicate communication control data is the same as the process by which earth stations 1C1 and 1C2 communicate communication control data. The difference is that earth stations 1F1 and 1F2 communicate only via low-Earth orbit satellite 41. In step S10F, low-Earth orbit satellite 41 transmits radio RU C1 Receiving radio waves, C1 The signal is frequency converted and amplified to produce radio waves (RD). C2It is emitted as follows. In step S11F, Earth station 1F2 receives radio waves RD emitted by low orbit satellite 41. C2 Receiving radio waves, RD C2 The signal is demodulated to generate communication control data CC1. Earth station 1F2 processes the communication control data CC1 to control communication between communication terminal 31 and communication terminal 32.

[0231] In step S12F, Earth station 1F2 transmits the communication control data CC2 to Earth station 1F1 via radio RU directed towards low orbit satellite 41. C2 It emits as such. In step S13F, low orbit satellite 42 emits radio waves RU C2 Receiving radio waves, C2 The signal is frequency converted and amplified to produce radio waves (RD). C1 It emits radiation as such.

[0232] Even if one high-altitude pseudo-satellite 9 does not communicate with other high-altitude pseudo-satellites 9, encrypted user data can be communicated between two earth stations 1F located within the communication area of ​​one high-altitude pseudo-satellite 9 using the high-altitude pseudo-satellite communication link 21.

[0233] Next, we will explain the case where communication terminal 31 connected to earth station 1F1 communicates with communication terminal 33 connected to earth station 1F3, which communicates with a different high-altitude pseudo-satellite. Here, earth station 1F1 communicates with high-altitude pseudo-satellite 91. Earth station 1F3 communicates with high-altitude pseudo-satellite 92. High-altitude pseudo-satellite 91 and high-altitude pseudo-satellite 92 cannot communicate directly.

[0234] Figures 35 and 36 are flowcharts illustrating the general procedure for communication between a communication terminal 31 connected to earth station 1F1 and a communication terminal 33 connected to earth station 1F3, which communicates with a different high-altitude pseudo-satellite. Figure 35 illustrates the process up to step S08F, and Figure 36 illustrates the process from step S09C onwards. Note that the process from S09C onwards shown in Figure 36 is the same as in Figure 18. In Figure 36, earth station 1F3, rather than earth station 1C2, performs each step, which is a difference from Figure 18.

[0235] Figure 35 will be explained in terms of its differences from Figure 33. In step S04G, the encrypted user data CD1 reaches the high-altitude pseudo-satellite 92 via the high-altitude pseudo-satellite 91, high-altitude pseudo-satellite ground station 451, ground network 421, ground core network equipment 411, ground core network 40, ground core network equipment 412, ground network 422, and high-altitude pseudo-satellite ground station 452. The high-altitude pseudo-satellite 92 emits radio waves RD2 for communicating the encrypted user data CD1. The process of S04G will be explained in the flowchart shown in Figure 37.

[0236] In step S05G, earth station 1F3 receives radio wave RD2, demodulates and decodes it to generate user data UD1. Earth station 1F3 transmits user data UD1 to communication terminal 33. S05G is the same process as S05F. S05G differs from S05F only in that it is performed by earth station 1F3 and transmitted to communication terminal 33.

[0237] In step S06G, the earth station 1F3 converts the user data UD2 that communication terminal 33 transmits to communication terminal 31 into encrypted user data CD2 and radiates it as radio waves RU2 towards the high-altitude pseudo-satellite 92. S06G is the same process as S06F. S06G differs from S06F only in that it is performed by earth station 1F3 and the user data UD2 is transmitted by communication terminal 33.

[0238] In step S07G, the encrypted user data CD2 reaches the high-altitude pseudo-satellite 91 via the high-altitude pseudo-satellite 92, high-altitude pseudo-satellite ground station 452, ground network 422, ground core network equipment 412, ground core network 40, ground core network equipment 411, ground network 421, and high-altitude pseudo-satellite ground station 451. The high-altitude pseudo-satellite 91 emits radio waves RD1 for communicating the encrypted user data CD2. The process of S07G is explained in the flowchart shown in Figure 38.

[0239] Referring to Figure 37, the process from when the high-altitude pseudo-satellite 91 receives the radio wave RU1 to when the high-altitude pseudo-satellite 92 emits the radio wave RD2 in order to communicate the encrypted user data CD1 in S04G will be explained. In step S101, the high-altitude pseudo-satellite 91 receives the radio wave RU1, converts its frequency, amplifies it, and emits it as the radio wave RD1. In step S102, the high-altitude pseudo-satellite ground station 451 receives the radio wave RD1, demodulates the radio wave RD1, and generates the encrypted user data CD1.

[0240] In step S103, the high-altitude pseudo-satellite ground station 451 transmits a packet of encrypted user data CD1 to the communication terminal 32 to the ground network 421. In step S104, the packet of encrypted user data CD1 reaches the high-altitude pseudo-satellite ground station 452 via the ground network 421, ground core network equipment 411, ground core network 40, ground core network equipment 412, and ground network 422. It is known that in the ground communication network (ground communication network) of the communication system 100F, packets to the communication terminal 32 are communicated from the high-altitude pseudo-satellite ground station 452 using the high-altitude pseudo-satellite communication link 213. Also, the route from the high-altitude pseudo-satellite ground station 451 to the high-altitude pseudo-satellite ground station 452 is determined by some method.

[0241] In step S105, the high-altitude pseudo-satellite ground station 452 radiates a packet of encrypted user data CD1 as radio wave RU1 toward the high-altitude pseudo-satellite 92. In step S106, the high-altitude pseudo-satellite 92 receives radio wave RU1, converts its frequency, amplifies it, and radiates it as radio wave RD2.

[0242] Referring to Figure 38, the process from when the high-altitude pseudo-satellite 92 receives the radio wave RU2 to when the high-altitude pseudo-satellite 91 emits the radio wave RD1 in order to communicate the encrypted user data CD2 in S07G will be explained. In step S111, the high-altitude pseudo-satellite 92 receives the radio wave RU2, converts its frequency, amplifies it, and emits it as the radio wave RD2. In step S112, the high-altitude pseudo-satellite ground station 452 receives the radio wave RD2, demodulates the radio wave RD2, and generates the encrypted user data CD2.

[0243] In step S113, the high-altitude pseudo-satellite ground station 452 transmits a packet of encrypted user data CD2 to the communication terminal 31 to the ground network 422. In step S114, the packet of encrypted user data CD2 reaches the high-altitude pseudo-satellite ground station 451 via the ground network 422, ground core network equipment 412, ground core network 40, ground core network equipment 411, and ground network 421. In the ground communication network of the communication system 100F, it is known that packets to the communication terminal 31 are communicated from the high-altitude pseudo-satellite ground station 451 using the high-altitude pseudo-satellite communication link 211. Also, the route from the high-altitude pseudo-satellite ground station 452 to the high-altitude pseudo-satellite ground station 451 is determined by some method.

[0244] In step S115, the high-altitude pseudo-satellite ground station 451 radiates a packet of encrypted user data CD2 as radio wave RU1 towards the high-altitude pseudo-satellite 91. In step S116, the high-altitude pseudo-satellite 91 receives radio wave RU1, frequency-converts and amplifies radio wave RU1, and radiates it as radio wave RD1.

[0245] Even if one high-altitude pseudo-satellite 9 does not communicate with another high-altitude pseudo-satellite 9, encrypted user data can be communicated between two earth stations 1F located in the communication area of ​​different high-altitude pseudo-satellite 9 via a communication path that includes a high-altitude pseudo-satellite communication link 21 that passes through the two high-altitude pseudo-satellite 9 and the ground communication network.

[0246] Next, we will explain the case where communication terminal 31 connected to earth station 1F1 communicates with communication terminal 34 connected to earth station 46 connected to the ground communication network. Earth station 1F1 communicates with high-altitude pseudo-satellite 91. Earth station 46 communicates with high-altitude pseudo-satellite 91 via a communication path that goes through high-altitude pseudo-satellite ground station 452. Earth station 46 communicates with low-Earth orbit satellite 42 via a communication path that goes through low-Earth orbit satellite ground station 44.

[0247] Figures 39 and 40 are flowcharts illustrating the general procedure for communication between a communication terminal 31 connected to earth station 1F1 and a communication terminal 34 connected to earth station 46 connected to the terrestrial communication network. Figure 39 illustrates the process up to step S08F, and Figure 40 illustrates the process from step S09C onwards.

[0248] Figures 39 and 40 will be explained in terms of differences from Figures 33 and 40. In step S02H, earth station 1F1 and earth station 46 determine the encryption key and decryption key to be used for communication between communication terminal 31 and communication terminal 34 and store them in the data storage unit 58F. Earth station 1F1 and earth station 46 communicate the decryption key over the communication path, which includes the low-Earth orbit satellite communication link 6 and the ground communication network.

[0249] In step S04H, the encrypted user data CD1 reaches the earth station 46 via the high-altitude pseudo-satellite 91, high-altitude pseudo-satellite ground station 451, ground network 421, ground core network equipment 411, ground core network 40, ground core network equipment 412, and ground network 422. The process of S04H is explained by the flowchart shown in Figure 41.

[0250] In step S05H, the earth station 46 receives encrypted user data CD1, decrypts the encrypted user data CD1, and generates user data UD1. The earth station 46 transmits user data UD1 to the communication terminal 34.

[0251] In step S06H, the earth station 46 converts the user data UD2 that communication terminal 34 transmits to communication terminal 31 into encrypted user data CD2 and transmits it to the ground network 422.

[0252] In step S07H, the encrypted user data CD2 reaches the high-altitude pseudo-satellite 91 via the ground network 422, ground core network equipment 412, ground core network 40, ground core network equipment 411, ground network 421, and high-altitude pseudo-satellite ground station 451. The high-altitude pseudo-satellite 91 emits radio waves RD1 for communicating the encrypted user data CD2. The process of S07H is explained in the flowchart shown in Figure 42.

[0253] In step S10H, low Earth orbit satellite 41 radio RU C1 Receiving radio waves, C1 The signal is frequency converted and amplified to produce radio waves (RD). C1 It emits as radio waves. Low Earth orbit satellite 42 emits radio waves RD C1 Receives radio waves, RD C1 The signal is frequency converted and amplified to produce radio waves (RD). C2 It emits as radio waves. Low Earth orbit satellite ground station 44 uses radio waves RD C1 The satellite receives and demodulates the signal to generate communication control data CC1. The low Earth orbit satellite ground station 44 transmits the communication control data CC1 to the ground network 421. The communication control data CC1 reaches the earth station 46 via the ground network 421, ground core network equipment 411, ground core network 40, ground core network equipment 412, and ground network 422.

[0254] In step S11H, earth station 46 receives communication control data CC1 from the ground network 422. Earth station 46 processes the communication control data CC1 to control communication between communication terminal 31 and communication terminal 34.

[0255] In step S12H, Earth station 46 transmits communication control data CC2 to Earth station 11 to the ground network 422. In step S13H, the communication control data CC2 reaches the low orbit satellite ground station 44 via the ground network 422, ground core network equipment 412, ground core network 40, ground core network equipment 411, and ground network 421. The low orbit satellite ground station 44 transmits the communication control data CC2 to the low orbit satellite 41 via radio waves RU C2 It emits as radio waves. Low Earth orbit satellite 41 emits radio waves RU C2 Receiving radio waves, C2 The signal is frequency converted and amplified to produce radio waves (RD). C1 It emits radiation as such.

[0256] Referring to Figure 41, the process from when the high-altitude pseudo-satellite 91 receives the radio wave RU1 for the purpose of communicating encrypted user data CD1 in S04H, to when it is transmitted to the earth station 46 via the ground communication network, will be explained. The differences between Figure 41 and Figure 37 will be explained.

[0257] In step S104H, the encrypted user data CD1 packet is transmitted to Earth station 46 via terrestrial network 421, terrestrial core network equipment 411, terrestrial core network 40, terrestrial core network equipment 412, and terrestrial network 422.

[0258] Referring to Figure 42, the process from when Earth Station 46 transmits encrypted user data CD2 to the ground network 421 in order to communicate the encrypted user data CD2 in S07H, until when High Altitude Pseudo-Satellite 91 emits radio waves RD1, will be explained. Figure 42 will be explained in terms of the differences from Figure 38.

[0259] In Figure 42, steps S111 through S113 are omitted, and the process begins at S114. At S114, the encrypted user data CD2 packet transmitted by Earth Station 46 reaches High Altitude Pseudo-Satellite Ground Station 451 via Ground Network 422, Ground Core Network Equipment 412, Ground Core Network 40, Ground Core Network Equipment 411, and Ground Network 421. Steps S115 and S116 are the same as in Figure 38.

[0260] Thus, Earth station 1F can communicate encrypted user data via a communication path including the high-altitude pseudo-satellite communication link 21 to any of the following: Earth stations communicating with the same high-altitude pseudo-satellite 9, Earth stations communicating with different high-altitude pseudo-satellite 9, and Earth stations connected to a terrestrial communication network that cannot communicate with the high-altitude pseudo-satellite 9 by itself. Earth station 1F can communicate the encryption key for encryption and the decryption key for decryption to the communication partner via a communication path including the low-orbit satellite communication link 6. Therefore, even if user data transmitted via a communication path including the high-altitude pseudo-satellite communication link 21 is intercepted, the content of the user data will not be known because it is encrypted. Since the encryption key and decryption key are communicated via a communication path including the low-orbit satellite communication link 6, even if the high-altitude pseudo-satellite communication link 21 through which user data is transmitted is intercepted, the encryption key and decryption key will not be leaked. User data is not transmitted via the low-orbit satellite communication link 6, so even if the low-orbit satellite communication link 6 is intercepted, the content of the user data will not be known.

[0261] Earth Station 1F does not require ground infrastructure. Earth Station 1F can easily expand the communication area in mobile communication systems.

[0262] Earth Station 1F can share encryption keys (including decryption keys) between the sender and receiver without using other communication systems. Earth Station 1F can transmit encrypted user data.

[0263] A communication device (earth station) according to any of Embodiments 1 to 4 can communicate encrypted user data via a communication path including the high-altitude pseudo-satellite communication line 21 with any earth station communicating with the same high-altitude pseudo-satellite 9, an earth station communicating with a different high-altitude pseudo-satellite 9, or an earth station connected to a terrestrial communication network that cannot communicate with the high-altitude pseudo-satellite 9 by itself.

[0264] The first out-of-tropic communication link for transmitting encrypted user data may be a different out-of-tropic communication link from the high-altitude pseudo-satellite communication link 21. The second out-of-tropic communication link for transmitting encryption keys, etc., may be a different out-of-tropic communication link from the low-orbit satellite communication link 6. The first and second out-of-tropic communication links may be two different out-of-tropic communication links at different altitudes.

[0265] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0266] The various aspects of this disclosure are summarized below as an appendix.

[0267] (Note 1) An out-of-tropic communication line is a communication line relayed to an out-of-tropic relay station, which is a relay station mounted on an out-of-tropic mobile body, which is a mobile body that moves outside the troposphere at an altitude higher than the troposphere, and the first out-of-tropic communication line is a first out-of-tropic communication line relayed to an out-of-tropic relay station, which is mounted on a first out-of-tropic mobile body, which is an out-of-tropic mobile body that moves at a first altitude included in the out-of-tropic zone, and the first out-of-tropic communication line communicates encrypted user data, which is the data to be communicated, with the communication partner, An encryption device that encrypts the user data to be transmitted using an encryption key to generate the encrypted user data, A decryption device that decrypts the received encrypted user data using a decryption key to generate user data, A communication device comprising: a second out-of-tropic communication line, which is an out-of-tropic communication line, relayed to a second out-of-tropic relay station, which is mounted on a second out-of-tropic mobile body, which is an out-of-tropic mobile body, moving at a second altitude included in the out-of-tropic area, different from the first altitude, before the first out-of-tropic communication unit communicates the encrypted user data; the second out-of-tropic communication unit communicates the communication control data, which is data communicated in order to communicate the encrypted user data with the communication partner, and includes at least one of the encryption key used by the encryption device and the decryption key used by the communication partner when decrypting the encrypted user data generated by the encryption device; and communicates the communication control data, which includes at least one of the encryption key used by the communication partner and the decryption key used by the decryption device when decrypting the encrypted user data generated by the communication partner, with the communication partner. (Note 2) A communication terminal connected via a network and a terminal connection unit that exchanges user data, For each communication terminal which is the communication terminal connected to the terminal connection unit, there is an encryption key storage unit which stores the encryption key used by the encryption device, The encryption device includes a corresponding decryption key storage unit that stores a corresponding decryption key, which is the decryption key used to decrypt data encrypted with the encryption key, for each of the self-communication terminals, A decryption key storage unit stores a decryption key, which is the decryption key used by the encryption device when decrypting the received encrypted user data, for each communication terminal that is the source of the encrypted user data. A communication control data generation unit generates communication control data for a communication start request, including the corresponding decryption key of the requesting communication terminal, when it receives a communication start request from the requesting communication terminal, which is the local communication terminal, to the requesting communication terminal, which is the communication terminal connected to the communication partner via the network, and when it receives the communication control data for a communication start request from the communication partner, it generates communication control data for accepting the communication start request, including the corresponding decryption key of the requesting communication terminal. If the encryption key of the requesting communication terminal is not stored in the encryption key storage unit, the encryption key and the corresponding decryption key are determined, the determined encryption key is stored in the encryption key storage unit as the encryption key of the requesting communication terminal, and the determined corresponding decryption key is stored in the corresponding decryption key storage unit as the corresponding decryption key of the requesting communication terminal. When the communication control data of the communication start request is received, the corresponding decryption key of the requesting communication terminal included in the received communication control data is stored in the used decryption key storage unit as the used decryption key of the requesting communication terminal; if the encryption key of the requesting communication terminal is not stored in the encryption key storage unit, the encryption key and the corresponding decryption key are determined, the determined encryption key is stored in the encryption key storage unit as the encryption key of the requesting communication terminal, and the determined corresponding decryption key is stored in the corresponding decryption key storage unit as the corresponding decryption key of the requesting communication terminal. The system includes an encryption key decryption key management unit that, upon receiving the communication control data for accepting the commencement of communication, stores the corresponding decryption key of the requesting communication terminal included in the received communication control data as the decryption key used by the requesting communication terminal in the used decryption key storage unit, The second troposphere-extraterrestrial communication unit is a communication device as described in Appendix 1, which communicates the communication control data for the communication start request and the communication control data for the communication start acceptance to the communication partner. (Note 3) A communication terminal connected via a network and a terminal connection unit that exchanges user data, Each communication terminal, which is the communication terminal connected to the terminal connection unit, has a decryption key storage unit that stores the decryption key for decrypting the received encrypted user data, A corresponding encryption key storage unit stores a corresponding encryption key for each of the self-communication terminals, which is the encryption key used to encrypt the data that the decryption device decrypts with the decryption key. For each of the aforementioned communication terminals that are recipients of the transmission, there is a used encryption key storage unit that stores the used encryption key, which is the encryption key used by the encryption device, A communication control data generation unit, upon receiving a communication start request from the requesting communication terminal, which is the self-communicating terminal, to the requesting communication terminal, which is the communication terminal connected to the communication partner via the network, generates communication control data for the communication start request, including the requesting communication terminal, the requesting communication terminal, and the corresponding encryption key of the requesting communication terminal, and upon receiving the communication control data for the communication start request from the communication partner, generates communication control data for accepting the communication start, including the corresponding encryption key of the requesting communication terminal, If the decryption key of the requesting communication terminal is not stored in the decryption key storage unit, the decryption key and the corresponding encryption key are determined, the determined decryption key is stored in the decryption key storage unit as the decryption key of the requesting communication terminal, and the determined corresponding encryption key is stored in the corresponding encryption key storage unit as the corresponding encryption key of the requesting communication terminal. When the communication control data of the communication start request is received, the corresponding encryption key of the requesting communication terminal included in the received communication control data is stored in the encryption key storage unit as the encryption key used by the requesting communication terminal. If the decryption key of the requesting communication terminal is not stored in the decryption key storage unit, the decryption key and the corresponding encryption key are determined, the determined decryption key is stored in the decryption key storage unit as the decryption key of the requesting communication terminal, and the determined corresponding encryption key is stored in the corresponding encryption key storage unit as the corresponding key of the requesting communication terminal. The system includes an encryption key decryption key management unit that, upon receiving the communication control data for accepting the commencement of communication, stores the corresponding encryption key of the requesting communication terminal included in the received communication control data as the encryption key used by the requesting communication terminal in the used encryption key storage unit, The second troposphere-extraterrestrial communication unit is a communication device as described in Appendix 1, which communicates the communication control data for the communication start request and the communication control data for the communication start acceptance to the communication partner. (Note 4) A communication device according to any one of the appendices 1 to 3, comprising a communication control unit that controls the communication of the encrypted user data by the first out-of-tropic communication unit and the communication control data by the second out-of-tropic communication unit. (Note 5) The communication device according to any one of the appendices 1 to 4, wherein each of the first and second extratropical mobile bodies is an extratropical mobile body selected from at least three types of extratropical mobile bodies located in the extratroposphere and moving at different altitudes. (Note 6) The communication device according to any one of the appendices 1 to 4, wherein each of the first extratroposphere mobile body and the second extratroposphere mobile body is an extratroposphere mobile body selected from an extratroposphere mobile body set that includes a stratospheric mobile body which is a mobile body that moves in the stratosphere, a geostationary satellite, and artificial satellites which move at least two different altitudes that are included in the extratroposphere and are lower than the geostationary satellite. (Note 7) Two modulators and demodulators, Two frequency converters, The system comprises a sequence assignment unit that assigns one of the frequency converters and one of the modulators / demodulators to be used as the first out-of-convection communication unit, and assigns the other frequency converter and the other modulator / demodulator to be used as the second out-of-convection communication unit, The aforementioned series allocation unit is, One of the modulators / demodulators modulates and demodulates the encrypted user data. One of the frequency converters is made to perform frequency conversion between the frequency used in the first out-of-the-zone communication line and the frequency of the signal processed by the modulator / demodulator. The other modulator / demodulator modulates and demodulates the communication control data. The communication device according to any one of the appendices 1 to 6, wherein the other frequency converter performs frequency conversion between the frequency used in the second out-of-convection communication line and the frequency of the signal processed by the modulator / demodulator. (Note 8) Transformer / Demodulator, A frequency converter connected to the aforementioned modulator / demodulator, The system includes a time-division control unit that controls the modulator / demodulator and the frequency converter to be used as the first out-of-convection communication unit or the second out-of-convection communication unit in a time-division manner, The aforementioned time-division control unit, During the period in which it is used as the first out-of-the-zone communication unit, the modulator / demodulator modulates and demodulates the encrypted user data, and the frequency converter performs frequency conversion between the frequency used in the first out-of-the-zone communication line and the frequency of the signal processed by the modulator / demodulator. A communication device according to any one of the appendices 1 to 6, wherein, during the period in which it is used as the second out-of-the-zone communication unit, the modulator / demodulator modulates and demodulates the communication control data, and the frequency converter performs frequency conversion between the frequency used in the second out-of-the-zone communication line and the frequency of the signal processed by the modulator / demodulator. (Note 9) Two antenna devices, The communication device according to Appendix 7, comprising a tracking control unit that controls one of the antenna devices connected to one of the frequency converters to track the first out-of-troposphere moving object, and the other antenna device connected to the other frequency converter to track the second out-of-troposphere moving object. (Note 10) A receiving antenna device comprising: a receiving antenna section having multiple element receiving antennas that receive radio waves and output element receiving signals; and an element receiving signal processing section that processes the multiple element receiving signals and outputs a receiving signal of a first receiving frequency from a first receiving direction that can be electronically changed to one of the frequency converters, and a receiving signal of a second receiving frequency different from the first receiving frequency from a second receiving direction that can be electronically changed independently of the first receiving direction to the other frequency converter; A transmitting antenna device comprising: a transmitting antenna section having a plurality of element transmitting antennas to which element transmitting signals are each input and which transmit radio waves; and an element transmitting signal generation section that receives a transmission signal of a first transmission frequency output by one of the frequency converters and a transmission signal of a second transmission frequency different from the first transmission frequency output by the other frequency converter, and generates a plurality of element transmitting signals to which the plurality of element transmitting antennas are each input, such that the transmitting antenna section transmits radio waves of the first transmission frequency in a first transmission direction that can be electronically changed, and the transmitting antenna section transmits radio waves of the second transmission frequency in a second transmission direction that can be electronically changed independently of the first transmission direction; A frequency setting unit sets the reception frequency and transmission frequency of the first out-of-convection communication line to the first reception frequency and the first transmission frequency, respectively, and sets the reception frequency and transmission frequency of the second out-of-convection communication line to the second reception frequency and the second transmission frequency, respectively. The communication device according to Appendix 7, further comprising a tracking control unit that controls the first receiving direction and the first transmitting direction to track the first out-of-troposphere moving object, and controls the second receiving direction and the second transmitting direction to track the second out-of-troposphere moving object. (Note 11) A receiving antenna device which is a phased array antenna connected to the frequency converter, A transmitting antenna device which is a phased array antenna connected to the frequency converter, The communication device according to Appendix 8, comprising a tracking control unit that controls the receiving antenna device and the transmitting antenna device to track a first out-of-troposphere mobile object during the period when the modulator / demodulator and the frequency converter are used as the first out-of-troposphere communication unit, and controls the receiving antenna device and the transmitting antenna device to track a second out-of-troposphere mobile object during the period when the modulator / demodulator and the frequency converter are used as the second out-of-troposphere communication unit. (Note 12) An out-of-tropic communication line is a communication line relayed to an out-of-tropic relay station, which is a relay station mounted on an out-of-tropic mobile body, which is a mobile body that moves outside the troposphere at an altitude higher than the troposphere, and the out-of-tropic communication line is a first out-of-tropic communication line relayed to an out-of-tropic relay station, which is mounted on a first out-of-tropic mobile body, which is a first out-of-tropic communication line that moves at a first altitude included in the out-of-tropic zone, and the first out-of-tropic communication line is a first out-of-tropic communication unit that communicates encrypted user data, which is data to be communicated, with a communication partner, and an encryption key that encrypts the user data to be transmitted and generates the encrypted user data. A communication device comprising: a decryption device; a decryption device that decrypts the received encrypted user data using a decryption key to generate user data; and a second out-of-tropic communication unit that communicates with the communication partner over a second out-of-tropic communication line, which is relayed to a second out-of-tropic relay station mounted on a second out-of-tropic mobile body, which is an out-of-tropic mobile body that moves at a second altitude included in the out-of-tropic zone, different from the first altitude; a requesting communication terminal which is a communication terminal connected to one of the communication partners; and a communication method for communicating between the communication device and the other of the communication partners, A procedure for either the communication device or the communication partner to receive a request to initiate communication from the requesting communication terminal to the requesting communication terminal, A procedure for communicating with the communication partner at the second out-of-convection communication unit at least one of the local encryption key, which is the encryption key used by the encryption device when it encrypts the user data and generates the encrypted user data, and the partner decryption key, which is the decryption key used by the communication partner when the communication partner decrypts the encrypted user data encrypted with the local encryption key, A procedure for communicating with the communication partner in the second out-of-the-zone communication unit at least one of the following: the other party encryption key, which is the encryption key used by the communication partner when encrypting the user data to generate the encrypted user data, and the self-decryption key, which is the decryption key used by the decryption device when decrypting the encrypted user data encrypted with the other party encryption key; A procedure for generating encrypted user data by having the encryption device encrypt the user data from the requesting communication terminal with its own encryption key, or by having the communication partner encrypt it with the other party's encryption key, A procedure for the first out-of-convection communication unit to communicate the encrypted user data from the requesting communication terminal to the communication partner via the first out-of-convection communication line, A procedure for generating user data from the requesting communication terminal, wherein the communication partner decrypts the encrypted user data received by the communication partner using the partner decryption key, or the encryption device decrypts the encrypted user data received by the communication device using its own decryption key, A procedure for the decrypted user data from the requesting communication terminal to be sent by the communication partner or the communication device to the requesting communication terminal, A procedure for generating encrypted user data by having the communication partner encrypt the user data from the requesting communication terminal using the partner's encryption key, or by having the encryption device encrypt it using its own encryption key, A procedure for communicating the encrypted user data from the requesting communication terminal to the communication partner via the first out-of-convection communication line, A procedure for generating user data from the requesting communication terminal by having the decryption device decrypt the encrypted user data received by the first out-of-convection communication unit using its own decryption key, or by having the communication partner decrypt it using their own decryption key, A communication method comprising the steps for the communication device or the communication partner to send the decrypted user data from the requesting communication terminal to the requesting communication terminal. [Explanation of symbols]

[0268] 100, 100C, 100D, 100E, 100F satellite communication systems. 1, 11, 12, 1C, 1D, 1E, 1F Earth station (communication equipment), Networks 2, 21, 22, 23, and 24 3, 31, 32, 33, 34 communication terminals, 4, 41, 42 low orbit satellites, 5 Geostationary satellite 6, 61, 62, 63, 64 Low Earth orbit satellite communication links, 7. Low Earth orbit inter-satellite communication links, 8, 81, 82, 83, 84 Geostationary satellite communication links, 9, 91, 92 high altitude pseudosatellites, 11, 11 A , 11 B Antenna equipment, 12, 12 A , 12 B , 12D frequency converter, 13, 13 A , 13 B , 13D modulator / demodulator, 14, 14C, 14D, 14E, 14F Data Processing Units 15, 15C encryption device (decryption device), 16 Network Interface Section (Network IF Section, Terminal Connection Section), 17, 17E Receiving antenna equipment, 18, 18E transmitting antenna equipment, 21, 211, 212, 213, 214, 215 High-altitude pseudo-satellite communication links, 22 High-altitude pseudo-satellite communication links, 33, 33 A ,33 B , 33D Satellite Communications Department (1st Extratropical Communications Department, 2nd Extratropical Communications Department), 33E A , 33E B Satellite Communications Department (1st Extratropical Communications Department, 2nd Extratropical Communications Department), 34, 34 A , 34 B Send buffer, 40. Terrestrial core network, 41, 411, 412 Ground core network equipment, 42, 421, 422 terrestrial network, 43 Geostationary satellite ground station, 44 Low orbit satellite ground station, 45, 451, 452 high altitude pseudosatellite ground station, 46 earth station, 50, 50D Satellite Communication Interface Unit (Satellite Communication IF Unit), 51, 51C Line control unit (frequency setting unit), 52, 52C, 52D, 52E Tracking control unit, 53, 53C Satellite position management department, 54. Series Control Unit (Communication Control Unit, Series Assignment Unit), 55, 55C Cryptographic Key and Decryption Key Management Unit, 56, 56C Cryptographic device control unit, 57, 57C Communication control data processing unit (communication control data generation unit), 58, 58E, 58F Data storage unit (encryption key storage unit, corresponding decryption key storage unit, used decryption key storage unit), 58C, 58D Data storage unit (decryption key storage unit, corresponding encryption key storage unit, used encryption key storage unit), 59 Satellite selection input section, 60-hour time-division control unit, 61-element receiving antenna, 62 Receiving antenna section, 63, 63E Element receiving signal processing unit, 64-element transmitting antenna, 65 Transmitting antenna section, 66, 66E Element transmission signal generation unit, 67, 67 A , 67 B Output terminals, 68, 68 A , 68 B synthesis circuit, 69, 69 A ,69 B Receiving module, 70, 70 A , 70 B Input terminals, 71, 71 A , 71 B distribution circuit, 72, 72 A , 72 B Transmitter module, 73, 73 A , 73 B phase shifter, 74, 74 A , 74 B amplifier, 75, 75 A , 75B phase shifter, 76, 76 A , 76 B amplifier, 80 A , 80 B Satellites in communication, 81 A , 81 B Receiving frequency, 82 A , 82 B Transmission frequency, 83 A ,83 B Modulation / demodulation method, 84 A , 84 B Error correction method, 85. My own location, 86 A , 86 B satellite position, 87 A ,87 B Satellite direction, 88 Use series, 89 encryption keys, 89C decryption key, 90 decryption keys, 90C encryption key used, 91C compliant encryption key, 92 A , 92 B By type of mobile device, 93. Time-division control data.

Claims

1. An out-of-tropic communication line is a communication line relayed to an out-of-tropic relay station, which is a relay station mounted on an out-of-tropic mobile body, which is a mobile body that moves outside the troposphere at an altitude higher than the troposphere, and the first out-of-tropic communication line is a first out-of-tropic communication line relayed to an out-of-tropic relay station, which is mounted on a first out-of-tropic mobile body, which is an out-of-tropic mobile body that moves at a first altitude included in the out-of-troposphere, and the first out-of-tropic communication line is a first out-of-tropic communication unit that communicates encrypted user data, which is the data to be communicated, with the communication partner, An encryption device that encrypts the user data to be transmitted using an encryption key to generate the encrypted user data, A decryption device that decrypts the received encrypted user data using a decryption key to generate user data, A communication device comprising: a second out-of-tropic communication line, which is an out-of-tropic communication line, relayed to a second out-of-tropic relay station, which is mounted on a second out-of-tropic mobile body, which is an out-of-tropic mobile body, moving at a second altitude included in the out-of-tropic area, different from the first altitude, before the first out-of-tropic communication unit communicates the encrypted user data; the second out-of-tropic communication unit communicates the communication control data, which is data communicated in order to communicate the encrypted user data with the communication partner, and which includes at least one of the encryption key used by the encryption device and the decryption key used by the communication partner when decrypting the encrypted user data generated by the encryption device; and the second out-of-tropic communication unit communicates the communication control data, which includes at least one of the encryption key used by the communication partner and the decryption key used by the decryption device when decrypting the encrypted user data generated by the communication partner, with the communication partner.

2. A communication terminal connected via a network and a terminal connection unit that exchanges user data, For each communication terminal which is the communication terminal connected to the terminal connection unit, there is an encryption key storage unit which stores the encryption key used by the encryption device, The encryption device includes a corresponding decryption key storage unit that stores a corresponding decryption key, which is the decryption key used to decrypt data encrypted with the encryption key, for each of the self-communication terminals, A decryption key storage unit stores a decryption key, which is the decryption key used by the encryption device when decrypting the received encrypted user data, for each communication terminal that is the source of the encrypted user data. A communication control data generation unit generates communication control data for a communication start request, including the corresponding decryption key of the requesting communication terminal, when it receives a communication start request from the requesting communication terminal, which is the local communication terminal, to the requesting communication terminal, which is the communication terminal connected to the communication partner via the network, and when it receives the communication control data for a communication start request from the communication partner, it generates communication control data for accepting the communication start request, including the corresponding decryption key of the requesting communication terminal. If the encryption key of the requesting communication terminal is not stored in the encryption key storage unit, the encryption key and the corresponding decryption key are determined, the determined encryption key is stored in the encryption key storage unit as the encryption key of the requesting communication terminal, and the determined corresponding decryption key is stored in the corresponding decryption key storage unit as the corresponding decryption key of the requesting communication terminal. When the communication control data of the communication start request is received, the corresponding decryption key of the requesting communication terminal included in the received communication control data is stored in the used decryption key storage unit as the used decryption key of the requesting communication terminal; if the encryption key of the requesting communication terminal is not stored in the encryption key storage unit, the encryption key and the corresponding decryption key are determined, the determined encryption key is stored in the encryption key storage unit as the encryption key of the requesting communication terminal, and the determined corresponding decryption key is stored in the corresponding decryption key storage unit as the corresponding decryption key of the requesting communication terminal. The system includes an encryption key decryption key management unit that, upon receiving the communication control data for accepting the commencement of communication, stores the corresponding decryption key of the requesting communication terminal included in the received communication control data as the decryption key used by the requesting communication terminal in the used decryption key storage unit, The communication device according to claim 1, wherein the second out-of-tropic-range communication unit communicates the communication control data for the communication start request and the communication control data for the communication start acceptance with the communication partner.

3. A communication terminal connected via a network and a terminal connection unit that exchanges user data, Each communication terminal, which is the communication terminal connected to the terminal connection unit, has a decryption key storage unit that stores the decryption key for decrypting the received encrypted user data, A corresponding encryption key storage unit stores a corresponding encryption key for each of the self-communication terminals, which is the encryption key used to encrypt the data that the decryption device decrypts with the decryption key. For each of the aforementioned communication terminals that are recipients of the transmission, there is a used encryption key storage unit that stores the used encryption key, which is the encryption key used by the encryption device, A communication control data generation unit, upon receiving a communication start request from the requesting communication terminal, which is the self-communicating terminal, to the requesting communication terminal, which is the communication terminal connected to the communication partner via the network, generates communication control data for the communication start request, including the requesting communication terminal, the requesting communication terminal, and the corresponding encryption key of the requesting communication terminal, and upon receiving the communication control data for the communication start request from the communication partner, generates communication control data for accepting the communication start, including the corresponding encryption key of the requesting communication terminal, If the decryption key of the requesting communication terminal is not stored in the decryption key storage unit, the decryption key and the corresponding encryption key are determined, the determined decryption key is stored in the decryption key storage unit as the decryption key of the requesting communication terminal, and the determined corresponding encryption key is stored in the corresponding encryption key storage unit as the corresponding encryption key of the requesting communication terminal. When the communication control data of the communication start request is received, the corresponding encryption key of the requesting communication terminal included in the received communication control data is stored in the encryption key storage unit as the encryption key used by the requesting communication terminal. If the decryption key of the requesting communication terminal is not stored in the decryption key storage unit, the decryption key and the corresponding encryption key are determined, the determined decryption key is stored in the decryption key storage unit as the decryption key of the requesting communication terminal, and the determined corresponding encryption key is stored in the corresponding encryption key storage unit as the corresponding key of the requesting communication terminal. The system includes an encryption key decryption key management unit that, upon receiving the communication control data for accepting the commencement of communication, stores the corresponding encryption key of the requesting communication terminal included in the received communication control data as the encryption key used by the requesting communication terminal in the used encryption key storage unit, The communication device according to claim 1, wherein the second out-of-tropic-range communication unit communicates the communication control data for the communication start request and the communication control data for the communication start acceptance with the communication partner.

4. The communication device according to claim 1, further comprising a communication control unit that controls the communication of the encrypted user data by the first out-of-tropic communication unit and the communication control data by the second out-of-tropic communication unit.

5. The communication device according to any one of claims 1 to 4, wherein each of the first extratropical mobile body and the second extratropical mobile body is an extratropical mobile body selected from at least three types of extratropical mobile bodies that are located outside the troposphere and move at different altitudes.

6. The communication device according to any one of claims 1 to 4, wherein each of the first extratroposphere mobile body and the second extratroposphere mobile body is an extratroposphere mobile body selected from an extratroposphere mobile body set that includes a stratospheric mobile body which is a mobile body which moves in the stratosphere, a geostationary satellite, and artificial satellites which move at least two different altitudes that are included in the extratroposphere and are lower than the geostationary satellite.

7. Two modulators and demodulators, Two frequency converters, The system includes a sequence assignment unit that assigns one of the frequency converters and one of the modulators / demodulators to be used as the first out-of-convection communication unit, and controls the other frequency converter and the other modulator / demodulator to be used as the second out-of-convection communication unit, The aforementioned series allocation unit is, One of the modulators / demodulators modulates and demodulates the encrypted user data. One of the frequency converters is made to perform frequency conversion between the frequency used in the first out-of-bounds communication line and the frequency of the signal processed by the modulator / demodulator. The other modulator / demodulator modulates and demodulates the communication control data. The communication device according to any one of claims 1 to 4, wherein the other frequency converter performs frequency conversion between the frequency used in the second out-of-convection communication line and the frequency of the signal processed by the modulator / demodulator.

8. Two modulators and demodulators, Two frequency converters, The system includes a sequence assignment unit that assigns one of the frequency converters and one of the modulators / demodulators to be used as the first out-of-convection communication unit, and controls the other frequency converter and the other modulator / demodulator to be used as the second out-of-convection communication unit, The aforementioned series allocation unit is, One of the modulators / demodulators modulates and demodulates the encrypted user data. One of the frequency converters is made to perform frequency conversion between the frequency used in the first out-of-bounds communication line and the frequency of the signal processed by the modulator / demodulator. The other modulator / demodulator modulates and demodulates the communication control data. The communication device according to claim 5, wherein the other frequency converter performs frequency conversion between the frequency used in the second out-of-convection communication line and the frequency of the signal processed by the modulator / demodulator.

9. Transformer / Demodulator, A frequency converter connected to the aforementioned modulator / demodulator, The system includes a time-division control unit that controls the modulator / demodulator and the frequency converter to be used as the first out-of-convection communication unit or the second out-of-convection communication unit in a time-division manner, The aforementioned time-division control unit, During the period in which it is used as the first out-of-the-zone communication unit, the modulator / demodulator modulates and demodulates the encrypted user data, and the frequency converter performs frequency conversion between the frequency used in the first out-of-the-zone communication line and the frequency of the signal processed by the modulator / demodulator. The communication device according to any one of claims 1 to 4, wherein during the period in which it is used as the second out-of-the-zone communication unit, the modulator / demodulator modulates and demodulates the communication control data, and the frequency converter performs frequency conversion between the frequency used in the second out-of-the-zone communication line and the frequency of the signal processed by the modulator / demodulator.

10. Transformer / Demodulator, A frequency converter connected to the aforementioned modulator / demodulator, The system includes a time-division control unit that controls the modulator / demodulator and the frequency converter to be used as the first out-of-convection communication unit or the second out-of-convection communication unit in a time-division manner, The aforementioned time-division control unit, During the period in which it is used as the first out-of-the-zone communication unit, the modulator / demodulator modulates and demodulates the encrypted user data, and the frequency converter performs frequency conversion between the frequency used in the first out-of-the-zone communication line and the frequency of the signal processed by the modulator / demodulator. The communication device according to claim 5, wherein, during the period in which it is used as the second out-of-the-zone communication unit, the modulator / demodulator modulates and demodulates the communication control data, and the frequency converter performs frequency conversion between the frequency used in the second out-of-the-zone communication line and the frequency of the signal processed by the modulator / demodulator.

11. Two antenna devices, The communication device according to claim 7, further comprising a tracking control unit that controls one of the antenna devices connected to one of the frequency converters to track the first out-of-troposphere moving object, and the other antenna device connected to the other frequency converter to track the second out-of-troposphere moving object.

12. Two antenna devices, The communication device according to claim 8, further comprising a tracking control unit that controls one of the antenna devices connected to one of the frequency converters to track the first out-of-troposphere moving object, and controls the other antenna device connected to the other frequency converter to track the second out-of-troposphere moving object.

13. A receiving antenna device comprising: a receiving antenna section having multiple element receiving antennas that receive radio waves and output element receiving signals; and an element receiving signal processing section that processes the multiple element receiving signals and outputs a receiving signal of a first receiving frequency from a first receiving direction that can be electronically changed to one of the frequency converters, and a receiving signal of a second receiving frequency different from the first receiving frequency from a second receiving direction that can be electronically changed independently of the first receiving direction to the other frequency converter; A transmitting antenna device comprising: a transmitting antenna section having a plurality of element transmitting antennas to which element transmitting signals are each input and which transmit radio waves; and an element transmitting signal generation section that receives a transmission signal of a first transmission frequency output by one of the frequency converters and a transmission signal of a second transmission frequency different from the first transmission frequency output by the other frequency converter, and generates a plurality of element transmitting signals to which the plurality of element transmitting antennas are each input, such that the transmitting antenna section transmits radio waves of the first transmission frequency in a first transmission direction that can be electronically changed, and the transmitting antenna section transmits radio waves of the second transmission frequency in a second transmission direction that can be electronically changed independently of the first transmission direction; A frequency setting unit sets the reception frequency and transmission frequency of the first out-of-convection communication line to the first reception frequency and the first transmission frequency, respectively, and sets the reception frequency and transmission frequency of the second out-of-convection communication line to the second reception frequency and the second transmission frequency, respectively. The communication device according to claim 7, further comprising a tracking control unit that controls the first receiving direction and the first transmitting direction to track the first out-of-troposphere moving object, and controls the second receiving direction and the second transmitting direction to track the second out-of-troposphere moving object.

14. A receiving antenna device comprising: a receiving antenna section having multiple element receiving antennas that receive radio waves and output element receiving signals; and an element receiving signal processing section that processes the multiple element receiving signals and outputs a receiving signal of a first receiving frequency from a first receiving direction that can be electronically changed to one of the frequency converters, and a receiving signal of a second receiving frequency different from the first receiving frequency from a second receiving direction that can be electronically changed independently of the first receiving direction to the other frequency converter; A transmitting antenna device comprising: a transmitting antenna section having a plurality of element transmitting antennas to which element transmitting signals are each input and which transmit radio waves; and an element transmitting signal generation section that receives a transmission signal of a first transmission frequency output by one of the frequency converters and a transmission signal of a second transmission frequency different from the first transmission frequency output by the other frequency converter, and generates a plurality of element transmitting signals to which the plurality of element transmitting antennas are each input, such that the transmitting antenna section transmits radio waves of the first transmission frequency in a first transmission direction that can be electronically changed, and the transmitting antenna section transmits radio waves of the second transmission frequency in a second transmission direction that can be electronically changed independently of the first transmission direction; A frequency setting unit sets the reception frequency and transmission frequency of the first out-of-convection communication line to the first reception frequency and the first transmission frequency, respectively, and sets the reception frequency and transmission frequency of the second out-of-convection communication line to the second reception frequency and the second transmission frequency, respectively. The communication device according to claim 8, further comprising a tracking control unit that controls the first receiving direction and the first transmitting direction to track the first out-of-troposphere moving object, and controls the second receiving direction and the second transmitting direction to track the second out-of-troposphere moving object.

15. A receiving antenna device which is a phased array antenna connected to the frequency converter, A transmitting antenna device which is a phased array antenna connected to the frequency converter, The communication device according to claim 9, further comprising a tracking control unit that controls the receiving antenna device and the transmitting antenna device to track a first out-of-troposphere mobile object during the period when the modulator / demodulator and the frequency converter are used as the first out-of-troposphere communication unit, and controls the receiving antenna device and the transmitting antenna device to track a second out-of-troposphere mobile object during the period when the modulator / demodulator and the frequency converter are used as the second out-of-troposphere communication unit.

16. A receiving antenna device which is a phased array antenna connected to the frequency converter, A transmitting antenna device which is a phased array antenna connected to the frequency converter, The communication device according to claim 10, further comprising a tracking control unit that controls the receiving antenna device and the transmitting antenna device to track a first out-of-troposphere mobile object during the period when the modulator / demodulator and the frequency converter are used as the first out-of-troposphere communication unit, and controls the receiving antenna device and the transmitting antenna device to track a second out-of-troposphere mobile object during the period when the modulator / demodulator and the frequency converter are used as the second out-of-troposphere communication unit.

17. An out-of-tropic communication line is a communication line relayed to an out-of-tropic relay station, which is a relay station mounted on an out-of-tropic mobile body, which is a mobile body that moves outside the troposphere at an altitude higher than the troposphere, and the first out-of-tropic communication line is a communication line relayed to an out-of-tropic relay station, which is mounted on a first out-of-tropic mobile body, which is a first out-of-tropic communication line that moves at a first altitude included in the out-of-tropic zone, and the first out-of-tropic communication line is a communication line relayed to an out-of-tropic relay station, which is a first out-of-tropic communication line that communicates encrypted user data, which is data to be communicated, with a communication partner, and an encryption key is used to encrypt the user data to be transmitted and generate the encrypted user data. A communication device comprising: a decryption device; a decryption device that decrypts the received encrypted user data using a decryption key to generate user data; and a second out-of-tropic communication unit that communicates with the communication partner over a second out-of-tropic communication line, which is relayed to a second out-of-tropic relay station mounted on a second out-of-tropic mobile body, which is an out-of-tropic mobile body that moves at a second altitude included in the out-of-tropic zone, different from the first altitude; a requesting communication terminal which is a communication terminal connected to one of the communication partners; and a communication method for communicating between the communication device and the other of the communication partners, A procedure for either the communication device or the communication partner to receive a request to initiate communication from the requesting communication terminal to the requesting communication terminal, A procedure for communicating with the communication partner at the second out-of-convection communication unit at least one of the local encryption key, which is the encryption key used by the encryption device when it encrypts the user data and generates the encrypted user data, and the partner decryption key, which is the decryption key used by the communication partner when the communication partner decrypts the encrypted user data encrypted with the local encryption key, A procedure for communicating with the communication partner at the second out-of-the-range communication unit at least one of the following: the other party encryption key, which is the encryption key used by the communication partner when encrypting the user data to generate the encrypted user data, and the self-decryption key, which is the decryption key used by the decryption device when decrypting the encrypted user data encrypted with the other party encryption key; A procedure for generating encrypted user data by having the encryption device encrypt the user data from the requesting communication terminal with its own encryption key, or by having the communication partner encrypt it with the other party's encryption key, A procedure for the first out-of-convection communication unit to communicate the encrypted user data from the requesting communication terminal to the communication partner via the first out-of-convection communication line, A procedure for generating user data from the requesting communication terminal, wherein the communication partner decrypts the encrypted user data received by the communication partner using the partner decryption key, or the encryption device decrypts the encrypted user data received by the communication device using its own decryption key, A procedure for the decrypted user data from the requesting communication terminal to be sent by the communication partner or the communication device to the requesting communication terminal, A procedure for generating encrypted user data by having the communication partner encrypt the user data from the requesting communication terminal using the partner's encryption key, or by having the encryption device encrypt it using its own encryption key, A procedure for communicating the encrypted user data from the requesting communication terminal to the communication partner via the first out-of-convection communication line, A procedure for generating user data from the requesting communication terminal by having the decryption device decrypt the encrypted user data received by the first out-of-convection communication unit using its own decryption key, or by having the communication partner decrypt it using their decryption key, A communication method comprising the steps for the communication device or the communication partner to send the decrypted user data from the requesting communication terminal to the requesting communication terminal.

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