JP6273943B2 - Communication system and communication satellite - Google Patents

Description

  The present invention relates to a mobile station that communicates with a multi-beam communication satellite having a plurality of beams, and a communication satellite.

  A communication satellite that communicates with a mobile station mounted on a mobile body such as a vehicle, train, ship, or aircraft, or a handheld mobile station that is brought into or out of the mobile body, uses multiple beams with a single satellite. A multi-beam satellite is also used. A multi-beam satellite generally has a narrow service area covered by one beam as the number of beams increases. Therefore, the number of times of beam switching generated by the movement of the mobile station increases as the number of beams increases when the trajectory of the mobile station is the same.

  In the conventional switching method, a mobile station requests beam switching to a base station via a satellite, and the base station performs line allocation associated with beam switching based on a beam switching request from the mobile station ( For example, see Patent Document 1).

  Most of the conventional communication satellites have a bent pipe (non-regenerative relay) method, and data received from a mobile station or a base station is transmitted to the base station and the mobile station without being decoded within the satellite. Therefore, a bent pipe type satellite cannot extract data transmitted from a mobile station or a base station.

Patent No. 4037302

  In the conventional beam switching, it is necessary to exchange information between the mobile station and the base station for at least one and a half times for beam switching, which takes time for beam switching and cannot communicate for beam switching. There is a problem that becomes longer. If a mobile station is provided with a plurality of antenna devices and can communicate with a plurality of communication lines simultaneously, the time during which the mobile station cannot communicate at the time of beam switching can be eliminated. However, if a mobile station is provided with a plurality of antennas, the apparatus becomes larger and the weight increases, so that there is a problem that applicable mobile bodies are limited.

  An object of the present invention is to reduce the time required for beam switching in a mobile station that communicates via a satellite as compared with a conventional method.

Communication system according to the present invention, in the communication system is relayed to the communication satellite and the earth station and the mobile station communicates, moves Dokyoku a plurality of beams emitted respectively having a plurality of communication lines in the respective communication areas A plurality of transmission / reception antennas for receiving radio waves from the communication area, a line management unit for managing the communication line, a beam setting information storage unit for storing the communication area of each beam, and a plurality of the transmission / reception antennas. Communicates with a communication satellite having an earth station communication unit that communicates with the earth station, and a relay unit that relays communication between the earth stations using the plurality of transmission / reception antennas, and is relayed to the communication satellite. A satellite communication unit that communicates with the earth station and a local station position measurement unit that measures the position of the local station. In a state where the own station position is in both the communication area of the used beam that is the beam to which the used line belongs and the communication area of the switched beam that is the beam different from the used beam The satellite communication unit uses the post-switching line, which is the communication line belonging to the post-switching beam, assigned by the line management unit.

  The communication satellite according to the present invention radiates a plurality of beams having a plurality of communication lines in each communication area and receives a radio wave from the communication area, respectively, and the communication of each beam A beam setting information storage unit for storing an area, an earth station communication unit for communicating with an earth station using a plurality of the transmission / reception antennas, and a communication between the earth stations using a plurality of the transmission / reception antennas The communication area of the in-use beam, which is the beam to which the in-use line, which is the communication line in use by a mobile station, manages the communication line, and the in-use beam, The communication line belonging to the switched beam in a state where the position of the mobile station is in both the communication area of the switched beam that is a different beam. It is obtained by a line management unit for assigning a rear line exchange to the mobile station.

  According to the present invention, the time required for beam switching can be shortened as compared with the conventional method.

It is a figure explaining the structure of the mobile satellite communication system which this invention makes object. It is a figure explaining the beam switching performed by the communication area and mobile station of each beam of a communication satellite having a plurality of beams by way of example. It is a functional block diagram which shows the structure of the mobile station which concerns on Embodiment 1 of this invention. It is a functional block diagram which shows the structure of the communication satellite which concerns on Embodiment 1 of this invention. It is a processing flowchart in the case of implementing beam switching in the mobile station and communication satellite which concern on Embodiment 1 of this invention. It is a functional block diagram which shows the structure of the mobile station which concerns on Embodiment 2 of this invention. It is a functional block diagram which shows the structure of the communication satellite which concerns on Embodiment 2 of this invention. It is a processing flowchart in the case of implementing beam switching in the mobile station and communication satellite which concern on Embodiment 2 of this invention. It is a functional block diagram which shows the structure of the mobile station which concerns on Embodiment 3 of this invention. It is a functional block diagram which shows the structure of the communication satellite which concerns on Embodiment 3 of this invention. It is a processing flowchart in the case of implementing beam switching in the mobile station and communication satellite which concern on Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining the configuration of a mobile satellite communication system targeted by the present invention. The mobile satellite communication system includes a communication satellite 1, a mobile station 2, and a ground station 3. The mobile station 2 that moves together with the mobile object is relayed to the communication satellite 1 to communicate with the ground station 3 or another mobile station 2. The ground station 3 is relayed to the communication satellite 1 to communicate with the mobile station 2 and enables the mobile station 2 to connect to the ground network 60. The ground station 3 is a communication station fixed on the ground. A ground station having a function of managing a mobile satellite communication system among the ground stations is also called a base station. Mobile stations and ground stations are collectively referred to as earth stations.

  FIG. 2 is a diagram illustrating an example of beam switching performed by a mobile station and a communication area of each beam of a communication satellite having a plurality of beams. A broken circle in FIG. 2 is a communication area 4 that is a geographical range in which communication can be performed by each of a plurality of (three in FIG. 2) beams of the communication satellite 1. The communication area 4 is determined so that adjacent communication areas 4 overlap each other. Each beam has a plurality of communication lines. The locus 5 of the mobile station 2 is shown by a one-dot chain line. In the figure, the circle with H in it is the beam switching 6 performed by the mobile station 2. The mobile station 2 passes through the three beam communication areas 4 and performs the beam switching 6 twice. Beam switching is also called beam handover.

  FIG. 3 is a functional block diagram showing the configuration of the mobile station according to Embodiment 1 of the present invention. The mobile station 2 includes a transmission / reception antenna 11, an antenna driving device 12 that drives the transmission / reception antenna 11, a GPS reception device 13 that is a local station position measurement unit that measures the position of the mobile station 1 itself, and transmission / reception. An amplifying device 14 that amplifies the signal received by the antenna 11, an amplifying device 15 that amplifies the signal transmitted to the transmitting / receiving antenna 11, a frequency converting device 16 that converts the frequency of the received signal, and a frequency of the signal to be transmitted is converted. A frequency converter 17, a demodulator 18 that demodulates a received signal, a modulator 19 that modulates a transmission signal, a controller 20 that controls the antenna driver 12, etc., and a beam that is used to communicate with a communication satellite A beam switching control unit 21 that controls switching of the beam and a communication area storage unit 22 that stores the communication area of each beam of the communication satellite 1. That.

  The satellite communication unit 23 that communicates with the communication satellite 1 and is relayed to the communication satellite 1 and communicates with the earth station includes a transmission / reception antenna 11, an antenna driving device 12, an amplification device 14, an amplification device 15, a frequency conversion device 16, and a frequency conversion device 17. , A demodulator 18 and a modulator 19.

  In FIG. 3, a solid arrow means a signal flow. Dashed arrows mean control. Although not shown, the control device 20 includes an antenna driving device 12, a GPS receiving device 13, an amplifying device 14, an amplifying device 15, a frequency converting device 16, a frequency converting device 17, a demodulating device 18, a modulator 19, and a beam switching control unit 21. And the communication area storage unit 22 is controlled.

  The beam switching control unit 21 determines the necessity of beam switching based on the local station position, which is the position of the mobile station 2 measured by the GPS receiver 13, and the communication area of each beam stored in the communication area storage unit 22. When the beam switching necessity determination unit 24 and the beam switching necessity determination unit 24 determine that beam switching is necessary, a switching request generation unit 25 that generates a beam switching request for requesting beam switching to the communication satellite 1, a beam switching request A switching unit 26 that makes the satellite communication unit 23 use the switched line assigned by the communication satellite 1 for the switch, and a switch that generates a beam switching completion notification that notifies the communication satellite 1 that the switched line has been switched to A completion notification creation unit 27 is included.

  The beam switching necessity determination unit 24 is configured to determine a beam for switching after switching, which is a beam different from the beam in use and the communication area of the beam in use, which is a beam to which the line in use that is a communication line used by the satellite communication unit 23 belongs. It is determined that switching to the post-switching beam is necessary when the determined condition is satisfied in the state where the local station position is in both the communication area. Here, the determined condition is, for example, the case where the local station position leaves the use area of the beam in use and enters the use area of the beam after switching with respect to the use area assigned to each beam without duplication. The necessity of beam switching and the post-switching beam may be determined using information that the mobile station plans to move.

  The switching request creation unit 25 creates a beam switching request for requesting switching to the post-switching beam when the beam switching necessity determining unit 24 determines that switching to the post-switching beam is necessary.

  The line switching unit 26 uses the antenna drive device 12 and the frequency conversion device 16 so as to match the frequency and polarization direction of the switched line so that the satellite communication unit 23 uses the switched line notified by the line switching notification. The frequency converter 17, the demodulator 18 and the modulator 19 are controlled or their settings are changed.

  FIG. 4 is a functional block diagram showing the configuration of the communication satellite according to the first embodiment. In order to form a multi-beam, a plurality of transmission / reception antennas 31 that radiate a beam to each communication area are required, and the communication satellite 1 has a number of transmission / reception antennas 31 equal to or greater than the number of beams. Each transmitting / receiving antenna 31 receives a radio wave from each communication area. Note that the transmission / reception antenna 31 of the communication satellite 1 may be mounted separately for transmission and reception. A case in which transmission and reception are different antennas is also included in the transmission / reception antenna. Furthermore, the low noise amplifier 32 that amplifies the signal received by the transmission / reception antenna 31, the reception frequency converter 33 that changes the frequency of the amplified signal, the correspondence between the frequency and polarization direction of the communication line used for reception and the beam. A reception side switch matrix 34 for storing and a demodulation / decoding device 35 for demodulating and decoding the received signal are provided.

  The signal output from the demodulation / decoding device 35 is a signal obtained by restoring the data transmitted from the mobile station 2 or the ground station 3. The signal output from the demodulation / decoding device 35 can be used in the communication satellite 1.

  Furthermore, a switching router 36 that sends a signal to the destination indicated in the signal, a modulation and coding device 37 that modulates and encodes, and a transmission that stores the correspondence between the frequency and polarization direction of the communication line used for transmission and the beam It includes a side switch matrix 38, a transmission frequency converter 39 that converts the frequency of the transmission signal, and an amplifier 40 that amplifies the frequency-converted transmission signal. A signal transmitted from the demodulation / decoding device 35 or a beam switching control device 43 to be described later passes through a switching router 36, a modulation / coding device 37, a transmission-side switch matrix 38, a transmission frequency conversion device 39, and an amplifier 40, and a communication line. It is sent to one of the transmission / reception antennas 31 that can transmit radio waves to the ground station 3 or the mobile station 2 that are determined as communication partners.

  When the communication satellite 1 relays communication between the earth stations that are the mobile station 2 or the ground station 3, devices in the range of the relay unit 41 indicated by the broken line in FIG. 4, that is, the low noise amplifier 32, the reception frequency It is only necessary to have the conversion device 33, the reception side switch matrix 34, the transmission side switch matrix 38, the transmission frequency conversion device 39, and the amplifier 40.

  In order for the communication between the earth station and the communication satellite 1, in addition to the devices in the range of the earth station communication unit 42 shown by the one-dot chain line in FIG. It is necessary to have a router 36 and a modulation encoding device 37.

  In order to control beam switching within the communication satellite 1, there are a beam switching control device 43 that controls beam switching and data related to each beam such as a communication area of each beam that is referred to by the beam switching control device 43 at the time of beam switching. The stored beam setting information storage unit 44 and a line management unit 45 that manages communication lines and allocates communication lines in response to requests. The beam switching control device 43 is connected to the switching router 36, and a signal created by the beam switching control device 43 is transmitted to the mobile station 2 or the ground station 3.

  The line management unit 45 uses a communication line that is not used in the communication line that belongs to the post-switching beam requested by the beam switching request transmitted from the mobile station 2 and that the mobile station 2 uses in the post-switching beam. Is assigned as a post-switching line.

  The beam switching control device 43 can communicate with the line switching instruction creating unit 46 that creates a line switching instruction for notifying the mobile station 2 of the switched line and the mobile station 2 transmitted to the earth station that communicates with the mobile station 2. Communication start notification generating unit 47 for generating a communication start notification for notifying communication, and communication disconnection for generating a communication disconnection notification for notifying the earth station that communication with the mobile station 2 cannot be performed because the mobile station 2 is switching the beam. And a notification creation unit 48.

  Next, the operation will be described. FIG. 5 is a process flow diagram when beam switching is performed in the mobile station and communication satellite according to Embodiment 1 of the present invention. However, when the mobile station 2 is artificially switched from the ground station 3 by remote operation, the processing flow is different from that in FIG.

  The first state is a state F1 in which communication between the mobile station 2 and the communication satellite 1 and between the communication satellite 1 and the ground station 3 is established. In the state F1, the mobile station 2 moves in the beam in use and enters the state F2. In the state F2, the beam switching necessity determination unit 24 is in a state in which the own station position is in both the communication area of the beam in use and the communication area of the beam after switching that is a beam different from the beam in use. Since the determined condition is satisfied, it is determined that switching to the beam after switching is necessary.

  The switching request creation unit 25 creates a beam switching request i1 for requesting switching to a beam after switching, and the beam switching request i1 is transmitted to the communication satellite 1 to enter the state F3. When the communication satellite 1 receives the beam switching request i1, the state is F4.

  In the state F4, the line management unit 45 assigns a communication line that is not used among the communication lines belonging to the switched beam requested by the beam switching request i1 as the switched line. After the allocation, the earth station communication unit 42 waits for communication from the mobile station 2 on the switched line. Then, the line switching instruction i 2 created by the line switching instruction creating unit 46 is transmitted to the mobile station 2. Thus, the state F5 is entered. Further, the mobile station 2 receives the line switching instruction i2, and enters the state F6.

  In the state F4 or the state F5, the communication disruption notification i3 created by the communication disruption notification creating unit 48 is transmitted to the ground station 3. The ground station 3 receives the communication interruption notification i3 in any state after the state F4, and the ground station 3 stops communication with the mobile station 2.

  In the state F6, the setting is changed to match the frequency and polarization direction of the switched line so that the satellite communication unit 23 uses the switched line notified by the line switching instruction i2. A beam switching completion notification i4 for notifying the communication satellite 1 of switching to the post-switching line created by the switching completion notification creating unit 27 is transmitted, and the state changes to F7. The communication satellite 1 receives the beam switching completion notification i4 and enters the state F8.

  In the state F8, the communication start notification i5 created by the communication start notification creation unit 47 is transmitted to the ground station 3, and the communication start notification i6 is transmitted to the mobile station 2 to enter the state F9. The ground station 3 receives the communication start notification i5, the mobile station 2 receives the communication start notification i6, and the communication between the mobile station 2, the ground station 3 and the communication satellite 1 is performed by the switched beam. F10.

  Compared to the case where line allocation is performed in the ground station 3, the transmission of a beam switching request from the communication satellite 1 to the ground station 3 and the transmission of a line switching instruction from the ground station 3 to the communication satellite 1 become unnecessary. The time required for switching can be shortened. Furthermore, there may be a case where the time during which communication cannot be performed by beam switching can be shortened.

  Since the communication interruption notification is transmitted to the earth station of the mobile station as a communication partner, it is possible to prevent communication failure from being transmitted from the earth station of the communication partner to the mobile station whose beam is being switched.

The local station position may be transmitted to the communication satellite, and the communication satellite may perform beam switching necessity determination. The communication satellite may have a line switching unit for using the switched line. Even when the beam switching is performed by a procedure different from that of the first embodiment, the beam switching is performed more than the case where the channel allocation is performed by the ground station as long as the channel allocation is performed according to the beam switching by the communication satellite. The time required can be shortened.
The above applies also to other embodiments.

Embodiment 2. FIG.
In the second embodiment, the mobile station transmits its own station position to the communication satellite, and the communication satellite determines whether beam switching is necessary. FIG. 6 is a functional block diagram showing the configuration of the mobile station according to Embodiment 2 of the present invention. FIG. 7 is a functional block diagram showing the configuration of the communication satellite according to Embodiment 2 of the present invention. Only differences from the first embodiment will be described.

  In FIG. 6, the mobile station 2 </ b> A does not have the communication area storage unit 22. The beam switching control unit 21A included in the mobile station 2A does not include the beam switching necessity determination unit 24 and the switching request creation unit 25. Therefore, the local station position periodically measured by the GPS receiver 13 is input to the modulator 19A. The modulation device 19A creates local station position information for transmitting the local station position to the communication satellite, and outputs the local station position information to the frequency converter 18 together with information to be originally communicated. If there is no information to be communicated, only the local station location information is output. Modulator 19A is also a local station position information creation unit that creates local station position information for transmitting the local station position to a communication satellite.

  In FIG. 7, the beam switching control device 43A included in the communication satellite 1A includes a beam switching necessity determination unit 49 that determines whether or not beam switching is required in the mobile station 2A based on the local position information transmitted from the mobile station 2A. Have A mobile station that transmits its own location information is called a target mobile station. The mobile station 2A transmits to both the used beam communication area to which the used line that is the communication line used by the target mobile station belongs and the switched beam communication area that is a beam different from the used beam. In the state where the position of the mobile station 2A based on the own station position information is included, it is determined that switching to the beam after switching is necessary when the determined condition is satisfied. The position of the mobile station 2A determined from the local station position information transmitted from the mobile station 2A is also referred to as a mobile station position.

  Next, the operation will be described. FIG. 8 is a process flow diagram in the case of performing beam switching in the mobile station and communication satellite according to Embodiment 2 of the present invention.

  The first is a state F1 in which communication between the mobile station 2A and the communication satellite 1A and between the communication satellite 1A and the ground station 3 is established. In the state F1 and the subsequent states, the local station position information i0 is periodically transmitted from the mobile station 2A to the communication satellite 1A. In the state F1, the mobile station 2 moves in the beam in use and enters the state F2A. In the state F2A, the beam switching necessity determination unit 49 is transmitted from the mobile station 2A to both the used beam communication area of the mobile station 2A and the switched beam communication area which is a beam different from the used beam. Since the determined condition is satisfied in a state where the position of the mobile station 2A based on the local station position information is included, it is determined that the mobile station 2A needs to switch to the beam after switching. Thus, the state F4 is entered. Since the communication satellite 1A determines whether or not beam switching is required, the state F3 in which the beam switching request is transmitted from the mobile station to the communication satellite does not exist in the second embodiment.

  In the state F4, the line management unit 45 assigns a communication line that is not used among the communication lines belonging to the switched beam determined by the beam switching necessity determination unit 49 as the switched line. After the allocation, the earth station communication unit 42 waits for communication from the mobile station 2A over the switched line. Then, the line switching instruction i 2 created by the line switching instruction creating unit 46 is transmitted to the mobile station 2. Thus, the state F5 is entered. Thus, the operation after state F4 is the same as that in the first embodiment.

  Compared to the case where line allocation is performed in the ground station 3, the transmission of a beam switching request from the communication satellite 1 to the ground station 3 and the transmission of a line switching instruction from the ground station 3 to the communication satellite 1 become unnecessary. The time during which communication cannot be performed by switching can be shortened. Since it is determined whether or not beam switching is required by the communication satellite, it is not necessary to transmit a beam switching request from the mobile station to the communication satellite, and the time during which communication cannot be performed by beam switching can be further shortened.

Embodiment 3 FIG.
In the third embodiment, when a mobile station uses a line having the same frequency and polarization direction regardless of a beam when the mobile station communicates with a communication satellite, the line setting in the mobile station is performed at the time of beam switching. This is a case where the line setting is changed by the communication satellite without changing. FIG. 9 is a functional block diagram showing the configuration of the mobile station according to Embodiment 3 of the present invention. FIG. 10 is a functional block diagram showing a configuration of a communication satellite according to Embodiment 3 of the present invention. Only differences from the first embodiment will be described.

  In FIG. 8, the beam switching control unit 21B included in the mobile station 2B does not include the line switching unit 26 and the switching completion notification creation unit 27.

  In FIG. 9, the beam switching control device 43B included in the communication satellite 1B is a line switching unit 50 that changes the settings of the reception side switch matrix 34 and the transmission side switch matrix 38 at the time of beam switching, and the time at which beam switching is performed. A switching time setting unit 51 that sets a beam switching time and a switching time notification creation unit 52 that creates a beam switching time notification that notifies the beam switching time are included.

The contents of processing performed by the line switching unit 50 will be described. Define the following variables:
f1: The frequency of the line that the mobile station 2B receives from the communication satellite 1B.
h1: Polarization direction of the line received by the mobile station 2B from the communication satellite 1B.
f2: frequency of the line transmitted from the mobile station 2B to the communication satellite 1B.
h2: Polarization direction of the line transmitted from the mobile station 2B to the communication satellite 1B.
BM1: Beam used for the mobile station 2B before beam switching.
BM2: Beam used for the mobile station 2B after beam switching.
RX (jb, jf: jh): A variable representing the state of the line used in each beam represented by the receiving side switch matrix 34. jb means a beam, jf: jh means a line with frequency jf and polarization direction jh. Used when RX (jb, jf: jh) = 1, not used when RX (jb, jf: jh) = 0.
SX (jb, jf: jh): A variable representing the state of the line used for each beam represented by the transmission side switch matrix 38. Used when SX (jb, jf: jh) = 1, not used when SX (jb, jf: jh) = 0.

The state is as follows before the beam switching.
RX (BM1, f1: h1) = 1, for jb ≠ BM1, RX (jb, f1: h1) = 0
SX (BM1, f2: h2) = 1, for jb ≠ BM1, SX (jb, f2: h2) = 0
After beam switching, the following state is obtained.
RX (BM2, f1: h1) = 1, for jb ≠ BM2, RX (jb, f1: h1) = 0
SX (BM2, f2: h2) = 1, for jb ≠ BM2, SX (jb, f2: h2) = 0
The line switching unit 50 changes the settings of the reception side switch matrix 34 and the transmission side switch matrix 38 as described above.

The switching time setting unit 51 sets the beam switching time. The beam switching time is set so that beam switching occurs during communication between the mobile station 2B and the ground station 3 and no data loss occurs due to beam switching. When the time when the beam switching request is received is t0, and Tc is a time set appropriately so that beam switching does not occur during communication, the beam switching time t1 is calculated by the following equation.
t1 = t0 + Tc
Here, Tc is a normally assumed maximum value of the time for one round trip of the signal between the communication satellite 1 and the mobile station 2B, and the normal time for one round trip of the signal between the communication satellite 1 and the ground station 3. It is set longer than the assumed maximum value. The switching time notification creation unit 52 creates a beam switching time notification from the beam switching time t1.

  Next, the operation will be described. FIG. 11 is a process flow diagram when beam switching is performed in the mobile station and communication satellite according to Embodiment 3 of the present invention.

  The first is a state F11 in which communication is established between the mobile station 2B and the communication satellite 1B and between the communication satellite 1B and the ground station 3. In the state F11, the mobile station 2 moves in the beam in use and enters the state F12. In the state F12, the beam switching necessity determination unit 24 is in a state where the own station position is in both the communication area of the beam in use and the communication area of the beam after switching that is a beam different from the beam in use. Since the determined condition is satisfied, it is determined that switching to the beam after switching is necessary.

  The switching request creation unit 25 creates a beam switching request i1 for requesting switching to the beam after switching, and the beam switching request i1 is transmitted to the communication satellite 1 to enter the state F13. When the communication satellite 1 receives the beam switching request i1, the state becomes the state F14.

  In the state F14, the line management unit 45 allocates the communication line dedicated to the mobile station 2B in the frequency and polarization direction among the communication lines belonging to the switched beam requested by the beam switching request i1 as the switched line. The switching time setting unit 51 sets the beam switching time t1, and the switching time notification creating unit 52 creates a beam switching time notification for notifying the mobile station 2B and the ground station 3 of the beam switching time t1. A beam switching time notification i7 is transmitted to the ground station 3, and a beam switching time notification i8 is transmitted to the mobile station 2B. Thus, the state F15 is obtained. Further, the ground station 3 receives the beam switching time notification i7, and the mobile station 2B receives the beam switching time notification i8, so that the state F16 is entered.

  In the state F16, the mobile station 2B and the ground station 3 stop communication. At the beam switching time t1, the line switching unit 50 changes the setting of the communication line accompanying the beam switching, and enters the state F17. Then, the mobile station 2B and the ground station 3 resume communication.

  Compared to the case where the ground setting is changed at the initiative of the ground station 3, the transmission of the beam switching request from the communication satellite 1 to the ground station 3 becomes unnecessary. In the case of the initiative of the ground station 3, the time Tc that is set so that beam switching does not occur during communication is greater than the normally assumed maximum value of the time that the signal makes one round trip between the mobile station and the ground station. Also need to be long. On the other hand, the normally assumed maximum value for the time for one round trip of the signal between the communication satellite 1 and the mobile station 2B, and the normal assumption for the time for one round trip of the signal between the communication satellite 1 and the ground station 3 Longer than the maximum value to be achieved, Tc is reduced to about half, and beam switching can be performed quickly.

  The same effect can be obtained when the communication satellite determines whether beam switching is necessary. If there are both mobile stations that use a line with the same frequency and polarization direction regardless of the beam and a mobile station to which a free line is assigned for each beam, Performs beam switching by the method of the first or second embodiment or another method.

DESCRIPTION OF SYMBOLS 1, 1A, 1B Communication satellite 2, 2A, 2B Mobile station 3 Ground station 4 Communication area 5 Mobile station locus 6 Beam switching 11 Transmission / reception antenna 12 Antenna drive device 13 GPS receiver (local station position measurement unit)
14 Amplifying device 15 Amplifying device 16 Frequency converting device 17 Frequency converting device 18 Demodulating device 19 Modulating device, 19A Modulating device (local station position information creation unit)
20 Control devices 21, 21A, 22B Beam switching control unit 22 Communication area storage unit 23 Satellite communication unit 24 Beam switching necessity determination unit 25 Switching request creation unit 26 Line switching unit 27 Switching completion notification creation unit 31 Transmission / reception antenna 32 Low noise Amplifying device 33 Reception frequency conversion device 34 Reception side switch matrix 35 Demodulation encoding device 36 Switching router 37 Modulation encoding device 38 Transmission side switch matrix 39 Transmission frequency conversion device 40 Amplifying device 41 Relay unit 42 Earth station communication units 43, 43A, 43B Beam switching control device 44 Beam setting information storage unit 45 Line management unit 46 Line switching instruction creation unit 47 Communication start notification creation unit 48 Communication interruption notification creation unit 49 Beam switching necessity judgment unit 50 Line switching unit 51 Switching time setting unit 52 Switching time notification creation unit 60 Terrestrial network

Claims (11)

In a communication system in which an earth station and a mobile station communicate via a communication satellite,
The mobile station respectively radiates a plurality of beams having a plurality of communication lines in each communication area, and receives a plurality of transmission / reception antennas respectively receiving radio waves from the communication area, a line management unit for managing the communication lines, A beam setting information storage unit that stores the communication area of the beam, an earth station communication unit that communicates with the earth station using the plurality of transmission / reception antennas, and earth stations that use the plurality of transmission / reception antennas a satellite communications unit for relaying communication in communication with the communication satellite having a relay unit communicates with the earth station is relayed to the communication satellite between,
With its own position measurement unit that measures its own position, which is its own position,
The communication area of the used beam that is the beam to which the used line that is the communication line that is used by the satellite communication unit, and the communication area of the post-switching beam that is the beam different from the used beam The satellite communication unit uses the switched line, which is the communication line belonging to the switched beam, assigned by the line management unit in a state where the own station position is in both Communication system. The mobile station is configured so that the satellite communication unit uses the post-switching line obtained by communication with the communication satellite; and
The communication system according to claim 1, further comprising: a switch completion notification creating unit configured to create a beam switch completion notification for notifying the switching to the post-switching line, which is transmitted to the communication satellite via the post-switching line . The communication system according to claim 1, wherein the communication satellite includes a line switching unit that allows the earth station communication unit to use the switched line . The mobile station includes a communication area storage unit that stores the communication area of each beam of the communication satellite;
The local station position is in both the communication area of the beam in use and the communication area of the post-switching beam, and switching to the post-switching beam is necessary when a predetermined condition is satisfied. A beam switching necessity determination unit to determine;
A beam switching request creating unit for creating a beam switching request for requesting the communication satellite to switch to the beam after switching when the beam switching necessity determining unit determines that switching to the beam after switching is necessary; In addition,
4. The communication satellite that has received the beam switching request assigns the switched line belonging to the switched beam requested by the beam switching request by the line management unit. The communication system according to any one of the above . The mobile station further includes a local station location information creation unit that creates local station location information for transmitting the local station location to the communication satellite,
The communication satellite includes the self-station of the target mobile station in both the communication area of the beam in use of the target mobile station that is the mobile station that has transmitted the position information of the local station and the communication area of the beam after switching. The own station position that is determined from the station position information is included, and has a beam switching necessity determination unit that determines that switching to the beam after switching is necessary when the determined condition is satisfied,
The communication satellite allocates the switched line belonging to the switched beam of the target mobile station by the channel management unit when the beam switching necessity determining unit determines that switching to the switched beam is necessary. The communication system according to any one of claims 1 to 3, characterized in that: A plurality of transmitting and receiving antennas that respectively radiate a plurality of beams having a plurality of communication lines in each communication area and receive radio waves from the communication area;
A beam setting information storage unit for storing the communication area of each beam;
An earth station communication unit that communicates with the earth station using a plurality of the transmitting and receiving antennas;
A relay unit that relays communication between earth stations using a plurality of the transmitting and receiving antennas;
The communication area is managed, and the communication area of the in-use beam that is the beam to which the in-use line to which the mobile station is in use belongs, and the beam that is different from the in-use beam after switching A communication satellite comprising: a line management unit for allocating a switched line, which is the communication line belonging to the switched beam, to the mobile station in a state where the position of the mobile station is in both the communication area of the beam . A line switching instruction creating unit for creating a line switching instruction for notifying the mobile station of the switched line;
After receiving the beam switching completion notification notified by the mobile station that it has been switched to the post-switching line notified by the line switching instruction, communication with the mobile station transmitted to the earth station communicating with the mobile station is performed. The communication satellite according to claim 6, further comprising: a communication start notification creating unit that creates a communication start notification for notifying that it can be performed.   When the earth station communication unit transmits the line switching instruction to the mobile station, communication for notifying that communication with the mobile station is not possible on the busy line transmitted to the earth station communicating with the mobile station The communication satellite according to claim 7, further comprising a communication disruption notification creation unit that creates a disruption notification.   The communication satellite according to claim 6, further comprising a line switching unit that causes the earth station communication unit to use the switched line.   In response to a beam switching request transmitted and received from the mobile station and requesting switching to the post-switching beam, the line management unit transmits the post-switching line belonging to the post-switching beam requested by the beam switching request. The communication satellite according to any one of claims 6 to 9, wherein the communication satellite is assigned. The mobile station position that is the position of the mobile station transmitted from the mobile station is in both the communication area of the beam in use and the communication area of the beam after switching, and the determined condition is A beam switching necessity judgment unit that judges that switching to the post-switching beam is necessary when established,
The line management unit allocates the post-switching line belonging to the post-switching beam of the mobile station when the beam switching necessity determining unit determines that switching to the post-switching beam is necessary. The communication satellite according to any one of claims 6 to 9.

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