JP2007013513A - Mobile satellite communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile satellite communications system, in which a mobile communication terminal used for mobile satellite communication is further reduced in size, weight, and power consumption, for assuring proper communication capacity, based on the demand for communication caused by regionality, and for flexibly coping with temporary increase in the demand for communication. <P>SOLUTION: A flying relay station A1 that flies above the communication area of a low-orbit communication satellite S2 relays communication between mobile communication terminals C1-C4 in the communication area and the low-orbit communication satellite S2, resulting in realizing mobile satellite communication. If the relay function of a flying relay station A2 that flies above the communication area of the low-orbit communication satellite S4 cannot conduct communication between mobile communication terminals C5-C10 in the communication area and the low-orbit communication satellite S4, a flying relay station A3 is added in the same communication area. Accordingly, the flying relay stations A2 and A3 share for relaying communication between the mobile communication terminals C5-C10 and the low orbit communication satellite S4, thus providing flexible response with respect to the increase in communication demand. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mobile satellite communication system that realizes communication of a portable communication terminal that can move on the ground or on water using a plurality of low orbit communication satellites arranged in a low orbit of several hundred kilometers to several thousand kilometers on the ground.

  As shown in FIG. 9, a mobile satellite communication system that covers or covers the entire earth, which is implemented or planned using a plurality of low-orbit communication satellites, has a plurality of low-orbit communication over several hundred to several thousand kilometers. A satellite (for example, S1 to S5) and a portable communication terminal (for example, C1 to C10) on the ground or on the water set up a direct line by radio waves so that communication with a remote portable communication terminal can be performed via a low orbit communication satellite (For example, refer to Patent Document 1).

US Pat. No. 5,500,168

  However, the conventional mobile satellite communication system as described in Patent Document 1 has a large antenna gain so that a mobile communication terminal on the ground or water can communicate with a low-orbit communication satellite located at a long distance. In addition, transmission power, a large-capacity power supply for power supply, and the like are required, and there is a limit to miniaturization, light weight, and power saving of portable communication terminals.

  If a relay station is placed between a mobile communication terminal on the ground or water and a low orbit communication satellite, the relay station can communicate with the low orbit communication satellite. Since it is only necessary to provide a function capable of communicating with a station, there is a possibility that the mobile communication terminal can be easily reduced in size, weight and power saving. For example, in the case of a satellite communication system that directly communicates with a fixed station on the ground and a communication satellite, the maximum communication capacity of the fixed land station is fixed. Therefore, the relay station has a communication function that can handle the maximum communication capacity. Therefore, it is easy to provide a relay station corresponding to a fixed land station.

  However, in mobile satellite communication systems, the required line capacity differs greatly between densely populated and depopulated areas, and the communication capacity temporarily increases due to seasonal events and sudden disasters. Therefore, the communication service may be hindered unless the relay station has sufficient communication capacity that allows for such communication demand. However, if the relay station has a communication function that can cope with the maximum communication demand, whether it occurs several times a year or not for several hours, it will have a considerable impact on the cost of the entire mobile satellite communication system. There is a problem in building a practical system.

  In view of the problems as described above, the present invention aims to further reduce the size, weight, and power of mobile communication terminals by disposing a flight relay station equipped with a communication line relay function over several tens of kilometers. It is another object of the present invention to provide a mobile satellite communication system that can flexibly cope with securing an appropriate communication capacity according to communication demands caused by regional characteristics and the like, and a temporary increase in temporary communication demand.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a communication by a mobile communication terminal on the ground or on the water via a plurality of low-orbit communication satellites arranged in a low orbit of several hundred kilometers to several thousand kilometers on the ground. In the mobile satellite communication system that performs the above, it flies over several kilometers to several tens of kilometers between the low orbit communication satellite and its communication area, and relays the communication between the low orbit communication satellite and the portable communication terminal. The flight relay station has a function of communicating with a portable communication terminal using radio waves and a function of communicating with a low-orbit communication satellite using a laser beam, from a plurality of portable communication terminals within the same communication area. If one flight relay station cannot cope with the increase in communication capacity, a plurality of flight relay stations can be arranged above the same communication area, so that the communication between the low-orbit communication satellite and the portable communication terminal is possible. Multiple communication Wherein the relaying shared by Sho relay station.

  The invention according to claim 2 is the mobile satellite communication system according to claim 1, wherein the low orbit communication satellite stores information received from another low orbit communication satellite or a flight relay station. A server function is provided.

  The invention according to claim 3 is the mobile satellite communication system according to claim 1 or 2, wherein the flight relay station stores information received from a low-orbit communication satellite or another flight relay station. A server function is provided.

  The invention according to claim 4 is the mobile satellite communication system according to any one of claims 1 to 3, wherein the low orbit communication satellite and a flight relay station that flies within the communication area are provided. Is characterized by having a communication function capable of mutually transmitting and receiving radio waves.

  According to a fifth aspect of the present invention, in the mobile satellite communication system according to any one of the first to fourth aspects, the low orbit communication satellite and a portable communication terminal located in the communication area Is characterized in that it has a communication function capable of mutually transmitting and receiving radio waves and can be switched to direct communication not via a flight relay station.

  The invention according to claim 6 is the mobile satellite communication system according to any one of claims 1 to 5, wherein the plurality of flight relay stations arranged in the same communication area are mobile communication. A communication relay function capable of relaying communication from terminals to each other is provided, and communication between portable communication terminals in the same communication area is relayed without using a low-orbit communication satellite.

  According to the first aspect of the present invention, by using the flight relay station that flies over several kilometers to several tens of kilometers between the low-orbit communication satellite and its communication area, the portable communication terminal can reach the flight relay station. Since it is sufficient to have a communication function using radio waves, the mobile communication terminal can be further reduced in size, weight, and power can be saved. In addition, communication between the low-orbit communication satellite and the flight relay station employs communication using laser light, which can easily increase the capacity, so that one flight relay station can respond by communication with a portable communication terminal using radio waves. Since communication capacity sufficiently larger than the upper limit of capacity can be secured for communication with low orbit communication satellites, communication between low orbit communication satellites and mobile communication terminals can be shared and relayed by multiple flight relay stations It becomes possible. Therefore, by appropriately setting the number of flight relay stations to be deployed, it is possible to secure an appropriate communication capacity according to the communication demand due to regional characteristics, etc. Can respond flexibly to the rapid increase in

  According to the second aspect of the invention, the low-orbit communication satellite has a server function for storing information received from other low-orbit communication satellites or flight relay stations. Since it is only necessary to refer to the information accumulated by the server function of the low orbit communication satellite, such as when a re-request is made from the communication terminal, there is no need to acquire information from the source via the satellite network line. It can respond quickly to requests and contribute to a reduction in traffic.

  According to the invention of claim 3, since the flight relay station has a server function for accumulating information received from the low orbit communication satellite or other flight relay stations, the mobile communication is performed for the same information already transmitted. Since it is only necessary to refer to the information accumulated by the server function of the flight relay station, such as when a re-request is made from the terminal, there is no need to acquire information from the source via the satellite network line. In addition to being able to respond quickly, it can also contribute to reducing the amount of communication.

  According to the invention of claim 4, since the low-orbit communication satellite and the flight relay station flying in the communication area have a communication function capable of mutually transmitting and receiving radio waves, the flight relay station and the low-orbit communication When the laser link with the satellite is broken and re-acquisition is difficult, it is possible to avoid complete communication interruption between the low-orbit communication satellite and the flight relay station by switching to radio communication.

  According to the fifth aspect of the present invention, the low-orbit communication satellite and the mobile communication terminal located in the communication area have a communication function capable of transmitting and receiving radio waves to and from each other, and are directly communicated without using a flight relay station. Therefore, it is possible to prevent the mobile satellite communication from being disabled in an emergency such as when a failure occurs in the flight relay station. In addition, for a communication area where communication demand is very low, an operation method that reduces costs without deploying a flight relay station can be employed.

  According to the invention of claim 6, a plurality of flight relay stations arranged in the same communication area have a communication relay function capable of relaying communication from the mobile communication terminal to each other via the low orbit communication satellite. Since the communication between the portable communication terminals in the same communication area is relayed, efficient communication can be expected.

  Next, several embodiments of the mobile satellite communication system according to the present invention will be described with reference to the accompanying drawings.

  The schematic configuration diagram of FIG. 1 shows a first embodiment of the mobile satellite communication system according to the present invention (when the communication capacity is appropriate), and the schematic configuration diagram of FIG. 2 shows the first embodiment of the mobile satellite communication system according to the present invention. The form (when the communication capacity is increased) is shown. The low orbit communication satellites S1 to S5 in both figures are geostationary satellites deployed in a low orbit at a distance L1 (for example, 3,000 kilometers) from the ground, and these low orbit communication satellites S1 to S5 are mutually laser beams (see FIG. (Indicated by a thick line). A flight relay station A is provided above the distance L2 (for example, 20 kilometers) from the ground of the communication area set for each of the low-orbit communication satellites S1 to S5, and this flight relay station A is mobile in the communication area. By communicating with the communication terminal C by radio waves (indicated by a thin line in the figure) and by communicating with the low-orbit communication satellite S by a laser beam (indicated by a thick line in the figure), the low-orbit satellite S and its The communication with the mobile communication terminal C existing in the communication area is relayed.

  Thus, by using the flight relay station A that flies over several kilometers to several tens of kilometers between the low orbit communication satellite S and its communication area, the mobile communication terminal C can communicate with the flight relay station A. Since it is sufficient if the communication function is provided, the mobile communication terminal C can be further reduced in size, weight and power saving. Further, at the altitude at which the flight relay station A flies, the influence of atmospheric fluctuations that make optical communication difficult is reduced, so that it is easy to increase the capacity as communication between the low-orbit communication satellite S and the flight relay station A. Communication with a low-orbit communication satellite S can be adopted, and a communication capacity sufficiently larger than the upper limit of communication capacity that one flight relay station A can handle by communication with a portable communication terminal C by radio waves can be adopted. It is possible to secure in advance for communication.

  The flight relay station A is a flying body having a communication function for relaying (a communication function with a portable communication terminal C by radio waves and a communication function with a low-orbit communication satellite S by laser light). Is always on standby over the communication area in charge of relaying. The flight method is not particularly limited, and it may be one that flies with propulsion by gas injection like a jet aircraft, one that flies with propulsion by rotary blades like a propeller aircraft, or a helicopter In addition, a buoyancy can be obtained by rotating blades, or a float can be floated by a light gas like an airship. In addition, if a solar cell, a fuel cell, a nuclear battery, or the like is used as an operating power source for the flight relay station A, the flight time can be prolonged.

  Here, as shown in FIG. 1, from the mobile communication terminal C1 relayed by the flight relay station A1 flying over the communication area of the low orbit communication satellite S2, to the mobile communication terminal C10 belonging to the communication area of the low orbit communication satellite S4. A case of realizing the communication will be described. The flight relay station A1 that has received radio wave communication from the portable communication terminal C1 sends this communication request to the low orbit communication satellite S2 by communication using laser light, and from this low orbit communication satellite S2 via the low orbit communication satellite S3. The data is transmitted to the low-orbit communication satellite S4 that knows that the mobile communication terminal C10 is in its own communication area.

  However, since the line capacity of the flight relay station A2 flying over the communication area of the low orbit communication satellite S4 is fully used, it is not possible to call the mobile communication terminal C10 to open the communication line. In this case, communication from the mobile communication terminal C1 to the mobile communication terminal C10 cannot be realized.

  Therefore, when it is assumed that the communication capacity that the flight relay station A2 is responsible for relaying approaches the upper limit and it is difficult to satisfy further communication demands, as shown in FIG. 2, the communication is over the communication area of the low orbit communication satellite S4. Additional flight relay station A3 is installed to enable communication between the low-orbit communication satellite S4 and the portable communication terminals C5 to C10 to be shared by the flight relay stations A2 and A3 to increase communication capacity. If prepared so that it can respond, when the low-orbit communication satellite S4 instructs the flight relay stations A2 and A3 to call the mobile communication terminal C10 in response to the communication request received from the mobile communication terminal C1, the flight relay station A3 , The mobile communication terminal C10 can be called, and communication between the mobile communication terminal C1 and the mobile communication terminal C10 can be realized.

  As described above, by adopting the laser beam communication as the communication between the low orbit communication satellite S4 and the flight relay station A, a large communication capacity (for example, one flight relay station A is connected to the mobile communication terminal C). A communication capacity between the low-orbit communication satellite S and the portable communication terminal C is shared and relayed by a plurality of flight relay stations A. It becomes possible. Therefore, by appropriately setting the number of flying relay stations A that fly over the communication area of the low-orbit communication satellite S, appropriate communication according to communication demand caused by regional characteristics such as densely populated areas or depopulated areas If the flight relay station A is additionally provided in preparation for an increase in demand due to seasonal events that can be predicted in advance, the capacity can be flexibly dealt with. Even if communication demand increases rapidly due to sudden circumstances such as the occurrence of a disaster, it is possible to ensure sufficient communication capacity without delay if the flight relay station A is additionally deployed promptly.

  In addition, when a plurality of flight relay stations A share the same communication area and relay communication with the mobile communication terminal C, the sharing method of the mobile communication terminal C in charge of each flight relay station A is not particularly limited. Alternatively, the flight relay stations A flying over the same communication area may communicate with each other so that both share the same communication capacity, or the main flight relay station A shares the communication capacity to the full. Then, the subordinate flight relay station A may assist the portion that cannot be covered. Further, the flight relay station A may operate by fully autonomous control, so that it can determine whether or not additional deployment is necessary, and a management center provided for each communication area of the low-orbit communication satellite S is in charge. It may be managed.

  A schematic configuration of the mobile communication terminal C used in the mobile satellite communication system described above is shown in FIG. The mobile communication terminal C includes a relay station communication radio antenna 11 that can transmit and receive radio waves at a predetermined frequency with the flight relay station A, a relay station communication transceiver 12 that demodulates received signals and modulates transmission signals, A buffer unit 13 that temporarily stores data, a controller unit 14 that performs overall control of each unit, a memory unit 15 that stores various control information and received data, an interface unit 16 that is operated by a user, and the like are provided.

  FIG. 4 shows a schematic configuration of the flight relay station A used in the mobile satellite communication system described above. The flight relay station A is a satellite communication optical antenna 21a capable of transmitting / receiving laser light to / from the low orbit communication satellite S, a satellite communication transmitting / receiving unit 22a for demodulating a reception signal and modulating a transmission signal, and temporarily transmitting / receiving data. A buffer unit 23a, a radio wave antenna 21b for inter-relay station communication that can transmit and receive radio waves of a predetermined frequency with other flight relay stations A flying over the same communication area, demodulation of received signals, and transmission signals Inter-relay station communication transmitter / receiver 22b for performing modulation of the received signal, buffer unit 23b for temporarily holding transmission / reception data, and mobile terminal communication capable of transmitting / receiving radio waves of a predetermined frequency to / from mobile communication terminal C located in the communication area Radio wave antenna 21c, mobile terminal communication transmitting / receiving unit 22c that demodulates received signals and modulates transmission signals, and buffer unit 23 that temporarily stores transmitted / received data , A memory unit 25 for storing the controller unit 24, various control information and receiving data or the like for each unit control overall.

  The memory unit 25 has a large storage capacity, and the controller unit 24 has a server function that can store information received from the low-orbit communication satellite S or other flight relay station A in the memory unit 25 at any time and retrieve it as needed. If the mobile communication terminal C makes a re-request for the same information that has already been transmitted, the information stored by the server function of the flight relay station A may be referred to. There is no need to acquire information from the caller via the network, so that a quick response to a re-request can be made, and it is possible to contribute to a reduction in traffic.

  FIG. 5 shows a schematic configuration of the low orbit communication satellite S used in the mobile satellite communication system described above. The low-orbit communication satellite S includes an inter-satellite communication optical antenna 31a capable of transmitting and receiving laser light to and from another low-orbit communication satellite A, an inter-satellite communication transmitting / receiving unit 32a that demodulates a reception signal and modulates a transmission signal, Buffer unit 33a for temporarily holding transmission / reception data, optical antenna 31b for relay station communication capable of transmitting / receiving laser light to / from the flying relay station A flying over the communication area, demodulation of the received signal and transmission signal A relay station communication transmitting / receiving unit 32b that performs modulation, a buffer unit 33b that temporarily stores transmission / reception data, a controller unit 34 that performs overall control of each unit, a memory unit 35 that stores various control information, received data, and the like. Prepare.

  The memory unit 35 has a large storage capacity, and the controller unit 34 has a server function that can store information received from other low-orbit communication satellites S or the flight relay station A in the memory unit 25 at any time and retrieve it as necessary. If the mobile communication terminal C makes a re-request for the same information that has already been transmitted, the information stored by the server function of the low-orbit communication satellite S can be referred to. There is no need to acquire information from the sender via the network, and it is possible to respond quickly to re-requests and to contribute to a reduction in the traffic.

  Further, in order to enable the low-orbit communication satellite S to perform optical communication with the plurality of flight relay stations A simultaneously in parallel, a plurality of relay station communication optical antennas 31b are provided in advance according to the number of flight relay stations A that can be handled. You may make it provide. As described above, when the low-orbit communication satellite S includes the plurality of relay station communication optical antennas 31b, for example, the capture tracking of the flight relay station A2 and the capture tracking of the flight relay station A3 can be performed independently. Therefore, even when the flight air space of the flight relay station A2 and the flight air space of the flight relay station A3 are separated, the flight relay station A2 and the flight relay station A3 and the laser link can be individually held.

  Next, a second embodiment of the mobile satellite communication system will be described with reference to FIG. In the present embodiment, the low orbit communication satellite S and the flight relay station A flying in the communication area are provided with a communication function capable of transmitting and receiving with radio waves. In this case, when the laser link between the flight relay station A3 and the low-orbit communication satellite S4 is cut off and re-acquisition is difficult, both are switched to radio communication (indicated by a thin line in FIG. 6). Thus, it is possible to avoid the communication interruption between the low orbit communication satellite S4 and the flight relay station A3.

  For example, if the cause of the laser link disconnection between the low-orbit communication satellite S and the flight relay station A is a communication environment factor such as weather conditions, there is a high possibility that optical communication will be restored soon. However, if the cause is that the optical communication function of the flight relay station A is damaged, it is necessary to replace the standby flight relay station A waiting at the ground management center with the low-orbit communication satellite S. The optical communication with the flight relay station A cannot be recovered. Until such a change of the flight relay station A is completed, as an emergency means, if the low-orbit communication satellite S and the flight relay station A are communicating by radio waves, the communication area that the low-orbit communication satellite S is responsible for It can be avoided that the communication service is completely down.

  Note that the configuration of the flight relay station A used in the mobile communication system of the present embodiment is a low orbit communication compared to FIG. 4 showing the block configuration of the flight relay station A used in the mobile communication system of the first embodiment described above. A satellite communication radio antenna that can transmit and receive radio waves to and from the satellite S, a satellite communication transmission / reception unit that demodulates reception signals and modulates transmission signals, and a buffer unit that temporarily stores transmission / reception data may be added. When the re-acquisition allowable time (predetermined predetermined time) is exceeded from the start of re-acquisition based on the laser link disconnection with the low-orbit communication satellite S, the change control from optical communication to radio wave communication is controlled by the controller unit 24 May be automatically performed, or a change from optical communication to radio wave communication may be performed by a command from a management center or the like.

  Further, the configuration of the low orbit communication satellite S used in the mobile communication system of the present embodiment is communication with respect to FIG. 5 showing the block configuration of the low orbit communication satellite S used in the mobile communication system of the first embodiment described above. Relay station communication radio antenna capable of transmitting / receiving radio waves to / from flying relay station A flying over the area, relay station communication transmitter / receiver for demodulating received signals and modulating transmitted signals, temporarily transmitting / receiving data For example, when the re-acquisition allowable time (predetermined predetermined time) is exceeded from the start of re-acquisition based on the disconnection of the laser link with the flight relay station A, the controller unit 34 The change control from the optical communication to the radio communication may be automatically performed by the control, or the change from the optical communication to the radio communication is performed by a command from the management center or the like. It may be.

  Next, a third embodiment of the mobile satellite communication system will be described with reference to FIG. In the present embodiment, the low orbit communication satellite S and the mobile communication terminal C located in the communication area have a communication function that allows mutual transmission and reception with radio waves. In this case, the mode can be switched to the mode in which the low-orbit communication satellite S and the mobile communication terminal C communicate directly without going through the flight relay station A. For example, over the communication area of the low-orbit communication satellite S2 In the event of an emergency such as a failure occurring in the flight relay station A1 that has been flying in the air and the normal relay operation becomes impossible (both the low-orbit communication satellite S2 and the mobile communication terminals C1 and C3 are in the flight relay station A1 Switch to a mode in which the low-orbit communication satellite S and the mobile communication terminal C perform direct communication using radio waves, and the communication service is completely within the communication area that the low-orbit communication satellite S is responsible for. Can be avoided.

  Also, for communication areas where communication demand is very low, the flight relay station A is not deployed from the beginning, and the mode in which the low-orbit communication satellite S and the mobile communication terminal C communicate directly is standard, and the flight relay station An operation method that reduces the input / maintenance cost of A can also be adopted.

  The configuration of the low orbit communication satellite S used in the mobile communication system of the present embodiment is the same as that of FIG. 5 showing the block configuration of the low orbit communication satellite S used in the mobile communication system of the first embodiment described above. A communication radio antenna that can directly transmit and receive radio waves to and from the mobile terminal C, a communication transmission / reception unit that demodulates reception signals and modulates transmission signals, and a buffer unit that temporarily holds transmission / reception data, For example, when the re-acquisition allowable time (predetermined predetermined time) is exceeded from the start of re-acquisition based on the laser link disconnection with the flight relay station A, direct communication (radio wave) with the mobile terminal C is controlled by the controller unit 34. To the direct communication with the portable terminal C according to a command from the management center or the like. There. Alternatively, as described in the above-described second embodiment, when the configuration is such that the radio relay communication with the flight relay station A can be changed, the radio relay communication with the flight relay station A is attempted and the flight relay station A When the change to the communication with the relay station A by the radio wave is impossible, the communication may be changed to the direct communication with the mobile terminal C.

  The mobile communication terminal C used in the mobile communication system of the present embodiment has a function of communicating with the flight relay station A in a predetermined frequency band and a function of communicating with the low-orbit communication satellite S in a predetermined frequency band. Hybrid antenna system (for example, a hybrid antenna that supports both the frequency for communication with the flight relay station A and the frequency for communication with the low-orbit communication satellite S, two transmission / reception units each corresponding to the two frequencies, and transmission / reception data temporarily For example, when the communication disconnection with the flight relay station A exceeds a predetermined time, the controller unit 14 controls the low-orbit communication satellite S. The change control to direct communication (communication by radio wave) may be automatically performed, or by the user himself / herself who recognizes a communication failure warning, etc. It may be to switch the mobile terminal C to the direct communication mode.

  Next, a fourth embodiment of the mobile satellite communication system will be described with reference to FIG. In the present embodiment, a plurality of flight relay stations A arranged in the same communication area have a communication relay function (for example, a communication function using laser light) that can relay communication from the mobile communication terminal C to each other. . In this case, when the communication request from the mobile communication terminal C5 relayed by the flight relay station A2 is the mobile communication terminal 10 in charge of the relay by the flight relay station A3, the S4 low orbit communication satellite is used. Without any problem, the communication relay function between the flight relay station A2 and the flight relay station A3 can realize communication between the mobile communication terminal C5 and the mobile communication terminal C10 in the same communication area, so that efficient communication can be expected.

  The configuration of the flight relay station A used in the mobile communication system of the present embodiment is the same communication area as that of FIG. 4 showing the block configuration of the flight relay station A used in the mobile communication system of the first embodiment described above. Inter-relay station communication optical antenna capable of transmitting / receiving laser light to / from other flying relay stations A flying above, Inter-relay station communication transmitting / receiving section for demodulating received signals and modulating transmitted signals, transmitting / receiving A buffer unit for temporarily holding data may be added. However, the communication relay function between the flight relay stations A in the same area is not limited to the laser beam communication capable of securing a large communication capacity, and may be a radio wave communication.

It is a schematic block diagram which shows 1st Embodiment (when communication capacity is appropriate) of the mobile satellite communication system which concerns on this invention. It is a schematic block diagram which shows 1st Embodiment (at the time of communication capacity increase) of the mobile satellite communication system which concerns on this invention. It is a block block diagram of a portable communication terminal. It is a block block diagram of a flight relay station. It is a block block diagram of a low orbit communication satellite. It is a schematic block diagram which shows 2nd Embodiment of the mobile satellite communication system which concerns on this invention. It is a schematic block diagram which shows 3rd Embodiment of the mobile satellite communication system which concerns on this invention. It is a schematic block diagram which shows 4th Embodiment of the mobile satellite communication system which concerns on this invention. It is a schematic block diagram which shows the conventional mobile satellite communication system.

Explanation of symbols

S Low orbit communication satellite A Flight relay station C Mobile communication terminal L1 Distance from ground to low orbit communication satellite L2 Distance from ground to flight relay station

Claims (6)

In a mobile satellite communication system that performs communication with a mobile communication terminal on the ground or water via a plurality of low orbit communication satellites deployed in a low orbit of several hundred kilometers to several thousand kilometers above the ground,
A flight relay station that flies over several kilometers to several tens of kilometers between the low orbit communication satellite and its communication area, and relays communication between the low orbit communication satellite and the portable communication terminal,
The flight relay station has a communication function with a portable communication terminal using radio waves and a communication function with a low-orbit communication satellite using a laser beam,
If one flight relay station cannot cope with an increase in communication capacity from a plurality of mobile communication terminals in the same communication area, by arranging a plurality of flight relay stations above the same communication area, A mobile satellite communication system characterized in that communication between a low-orbit communication satellite and a portable communication terminal is relayed by a plurality of flight relay stations.   2. The mobile satellite communication system according to claim 1, wherein the low orbit communication satellite has a server function for storing information received from another low orbit communication satellite or a flight relay station.   The mobile satellite communication system according to claim 1 or 2, wherein the flight relay station includes a server function for storing information received from a low-orbit communication satellite or another flight relay station.   The said low orbit communication satellite and the flight relay station which flies within the communication area are equipped with the communication function which can mutually transmit / receive with an electromagnetic wave, The any one of Claims 1-3 characterized by the above-mentioned. Mobile satellite communication system.   The low orbit communication satellite and the mobile communication terminal located in the communication area have a communication function capable of transmitting and receiving with each other by radio waves, and can be switched to direct communication without using a flight relay station. The mobile satellite communication system according to any one of claims 1 to 4.   A plurality of flight relay stations arranged in the same communication area have a communication relay function capable of relaying communications from portable communication terminals to each other, and are not in a low orbit communication satellite and are in the same communication area. The mobile satellite communication system according to any one of claims 1 to 5, wherein communication between each other is relayed.

Images