JP2010288017A - Satellite communication system, ground station and satellite communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a satellite communication system capable of attaining reduction in circuit scale and in the power consumption of a satellite station. <P>SOLUTION: In the satellite communication system including a ground station, terminals, and a satellite station that uses a plurality of beams and relaying communication between a terminal in a cell constituted by beams and the ground station, cells are divided into groups, on the basis of locations, and group frequency regions for use in transmission from the ground station to the satellite station are determined per group, and the ground station includes a ground station switch matrix part 12, which obtains a group in which a destination terminal is located as a destination group with respect to each transmission data and arranges the transmission data on a frequency axis so that the transmission data are transmitted within the group frequency region of the destination group; and the satellite station includes per group, satellite station switch matrix parts which arrange reception data transmitted from the ground station, on the frequency axis per destination cell. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a satellite communication system and a satellite communication method including a satellite station that relays communication between a ground station and a mobile terminal.

  In a mobile satellite communication system composed of one or more ground stations, one or more satellite stations, and a plurality of terminals, the satellite stations receive signals from ground stations connected to an existing communication network. Then, a transmission signal is generated from the received signal, and the transmission signal is transmitted to a terminal on the ground. Alternatively, the terminal transmits a signal to the satellite station, and similarly, the satellite station generates a transmission signal from the received signal and transmits the transmission signal to the ground station.

  As a conventional mobile satellite communication system, for example, there is a system described in Non-Patent Document 1 below. In the mobile satellite communication system described in Patent Document 1, the antenna of the satellite station receives a transmission signal transmitted from the ground station, and the frequency converter converts the received radio frequency signal into a baseband signal. To do. An A / D (Analog / Digital) converter of the satellite station converts the received signal from analog to digital, and a demultiplexer demultiplexes the digitally received signal. The switch matrix unit of the satellite station rearranges the demultiplexed signals according to the communication partner, and the multiplexing unit combines the rearranged signals in units of transmission beams to be transmitted to the ground. To do. Then, the satellite station converts the transmission signal from digital to analog, further converts from the baseband band to the radio frequency transmission signal, and transmits it to the ground with a beam transmitted from the antenna. Receive.

  On the other hand, in Non-Patent Document 2 below, in a satellite communication system between a ground station and a terminal via a satellite station, the satellite station is equipped with a large antenna, and the service area Japan and the vicinity of Japan are composed of about 100 cells. A technique for performing such cell design and covering each of those cells with a multi-beam is disclosed.

  In the system described in Non-Patent Document 1 below, a ground station-satellite station (hereinafter, this line is referred to as a feeder link) and a satellite station-each terminal (hereinafter, this line is referred to as a user link) are upstream (transmission). ) Lines and downlink (reception) lines use different frequency bands. The feeder link uses 450 MHz in the Ka band and the user link uses 30 MHz in the S band on the upstream and downstream lines, respectively.

  In the system described in Non-Patent Document 1 below, from the viewpoint of frequency utilization efficiency, 7 cells are defined as 1 unit (hereinafter, this 1 unit is referred to as a cluster), and the same frequency is used in cluster units. A cell repetition method is used. The seven cells constituting the cluster use different frequencies, and the cells at the same position in the cluster use the same frequency between the clusters.

Yukio Hashimoto, “Voice exchange for voice communication”, Communications Research Laboratory quarterly report, Vol. 49, Nos. 3/4, 2003 Minoru Minowa, “Earth / Satellite Integrated Mobile Communication System for Safety and Security”, IEICE Transactions B, Vol. J91-B No. 12, pp. 1629-1640, 2008

  However, according to the technique described in Non-Patent Document 1, in order to realize a mobile communication system, a system is used in which each transmission signal is rearranged for each beam irradiated to a communication partner using a switch matrix. ing. For this reason, an increase in the service providing area or an increase in the frequency band used, or an increase in the number of beams used for operating the system for frequency utilization efficiency, or 100 as described in Non-Patent Document 2. In consideration of the beam system, the number of signals rearranged in the switch matrix portion becomes enormous. Therefore, there is a problem that the circuit scale of the switch matrix of the satellite station is increased and the power consumption is increased.

  The present invention has been made in view of the above, and is a satellite communication system and satellite that can simplify the processing performed by the switch matrix of the satellite station and can achieve a reduction in circuit scale and power consumption of the satellite station. The purpose is to obtain a communication method.

  In order to solve the above-described problems and achieve the object, the present invention relays communication between a ground station, a terminal, and the terminal and the ground station in a cell formed by the beam using a plurality of beams. A satellite communication system comprising: a satellite communication system, wherein the cells are grouped into a plurality of groups based on the position of the cells, and the frequency used for transmission from the ground station to the satellite station for each group A group frequency region, which is a region, is determined in advance, and the ground station holds the location of the terminal as location information, and also holds the correspondence between the location of the cell and the group to which the cell belongs as cell information. For each transmission data, the location of the terminal that is the destination is obtained based on the transmission data and the location information, and a group corresponding to the obtained location is assigned to the destination group based on the cell information. A ground station switch matrix means for arranging the transmission data on the frequency axis so that the transmission data is transmitted at a frequency within the group frequency region corresponding to the obtained destination group. For each group, the satellite station uses the received data transmitted from the ground station at a frequency within the group frequency domain of the group for each cell to which the received data is destined for transmission to the terminal in the cell. Satellite station switch matrix means arranged on the frequency axis is provided so that the received data is transmitted to the terminal at a frequency within a cell frequency domain which is a frequency domain.

  According to the present invention, the ground station switch matrix means of the ground station transmits the transmission signal after performing the rearrangement of the cluster unit in advance on the transmission signal based on the position of the communication partner, and the satellite station switch matrix of the satellite station Since the rearrangement corresponding to the cells in the ground station cluster is performed on the transmission signals received by the means, the circuit scale and power consumption of the satellite station can be reduced.

FIG. 1 is a diagram illustrating a configuration example of the satellite communication system according to the first embodiment. FIG. 2 is a diagram illustrating a cell arrangement example according to the first embodiment. FIG. 3 is a diagram illustrating a configuration example of a ground station. FIG. 4 is a diagram showing an image of the rearrangement process performed by the ground station switch matrix unit. FIG. 5A is a diagram illustrating an example of a frequency image of a feeder link signal generated by a conventional ground station modulation unit. FIG. 5B is a diagram illustrating an example of a frequency image of the feeder link signal generated by the ground station modulation unit according to the present embodiment. FIG. 6 is a diagram illustrating a functional configuration example of the satellite station according to the first embodiment. FIG. 7 is a diagram illustrating an example of a transmission signal image for each destination cell in the cluster. FIG. 8 is a diagram illustrating a configuration example of the satellite communication system according to the second embodiment. FIG. 9 is a diagram illustrating an example of a frequency allocation image performed by the communication control unit. FIG. 10A is a diagram illustrating an example of transmission frequency allocation to clusters. FIG. 10B is a diagram of an example of assigning transmission frequencies to clusters. FIG. 11 is a diagram illustrating an example of an image of transmission frequency assignment that is not in cell number order. FIG. 12 is a diagram illustrating a functional configuration example of the ground station demodulation unit of the ground station.

  Embodiments of a satellite communication system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a first embodiment of a satellite communication system according to the present invention. As shown in FIG. 1, the satellite communication system according to the present embodiment includes a ground station 1, a satellite station 2, and various terminals 3-1 to 3-3. The ground station 1 is connected to a ground network 4, and a general telephone 5, a mobile base station 6, an IP network 7, an exchange switch 8, and the like are connected to the ground network 4. In addition, although the ground station 1 and the satellite station 2 have illustrated one each in this Embodiment, it is not restricted to this, A plurality may be sufficient as each. The various terminals 3-1 to 3-3 are, for example, terminals that can be carried and carried, shipboard wireless devices, and terminals that perform fixed point installation, and are often specified as long as they have equipment that can communicate with the satellite station 2. It is not limited to the type.

  In the present embodiment, a case will be described in which a signal is transmitted from the ground station 1 of FIG. 1 and communication with various terminals 3 is performed via the satellite station 2. In the satellite communication system of the present embodiment, the feeder link and the user link use different frequencies. Specifically, the feeder link uses a 450 MHz wide band in the Ka band frequency on the uplink / downlink, and the user link uses a 30 MHz wide band in the S band frequency on the uplink / downlink. . The service providing area is composed of 100 cells, and a 7-cell repetition method is used in which 7 cells are defined as 1 cluster and the same frequency is used in each cluster.

  FIG. 2 is a diagram illustrating a cell arrangement example according to the present embodiment. In the cell 9, the number of each cell is shown (# 1, # 2,..., # 7), and the seven cells # 1 to # 7 constitute clusters 10-1 to 10-4. In FIG. 2, cells corresponding to the clusters 10-1 to 10-4 are shown as a part of the 100 cells, but as a whole, 15 clusters of the cluster 10-1 to the cluster 10-15 are included. Exists. Within the cluster, the 30 MHz band is divided and assigned to each cell.

  The ground station 1 holds the position information of each of the various terminals 3-1 to 3-3 by a communication sequence via the satellite station 2. For example, the various terminals 3 receive a signal periodically emitted from the satellite station 2 and transmit a corresponding signal to the ground station 1 via the satellite station 2. You can know the location information. As means for knowing the position information of the various terminals 3, acquisition using GPS (Global Positioning System) information or means such as via equipment different from the ground station 1 on the ground may be used.

  FIG. 3 is a diagram illustrating a configuration example of the ground station 1. As shown in FIG. 3, the ground station 1 of the present embodiment includes a ground station modulation unit 100. Although the ground station 1 has functions other than the ground station modulation unit 100, the description thereof is omitted here because it is not used for the operation of the present embodiment. The ground station modulation unit 100 includes a communication control unit 11, a ground station switch matrix unit 12, modulation units 13-1 to 13-15, multiplexing units 14-1 to 14-15, and a frequency conversion unit 15-1. -15-15, the addition part 16, and the antenna part 17.

  When the ground station 1 receives various types of transmission data from the ground network 4, first, the communication control unit 11 of the ground station modulation unit 100 associates the transmission data with the position information of the various terminals 3 that are communication destinations. Done. The ground station switch matrix unit 12 rearranges the transmission data for each cluster where the communication partner is located.

  FIG. 4 is a diagram showing an image of the rearrangement process performed by the ground station switch matrix unit 12. As shown in FIG. 4, it is assumed that three transmission data D1 to D3 are input to the ground station switch matrix unit. The transmission data D1 to D3 are different from each other in communication partner, and the rectangular numbers indicating the transmission data D1 to D3 in the figure are numerical values indicating the cell where the communication partner of the transmission data is located. This number “# t-n” means that the communication partner exists in the cell #n (corresponding to the numbers in the cells in FIG. 2, # 1 to # 7) in the cluster 10-t. . As shown in FIG. 4, the ground station switch matrix unit 12 has the modulation unit 13-1 as a path corresponding to the cluster 10-1 with the transmission data D1 and the modulation unit as a path corresponding to the cluster 10-3 with the transmission data D2. In 13-3, rearrangement is performed so that the transmission data D3 is output to the modulation unit 13-10 as a path corresponding to the cluster 10-10.

  As described above, since the bandwidth of the feeder link is 450 MHz and the number of clusters is 15, here, for example, 450 MHz is divided into 15 bands, and for each divided band, the modulation unit 13- The processing from 1 to 13-15 is executed.

  After that, the modulation units 13-1 to 13-15 perform predetermined modulation processing on the transmission data rearranged for each input cluster to obtain modulated signals, and the multiplexing units 14-1 to 14-15. However, the modulation signal is multiplexed. Then, the frequency conversion unit 15 performs frequency conversion to the Ka band on the combined signal, and the addition unit 16 adds the frequency converted signal output from the frequency conversion unit 15 to the antenna unit. 17 sends the added signal to the satellite station 2 as a feeder link signal. In consideration of the current capability of each component, each cluster includes modulators 13-1 to 13-15, multiplexers 14-1 to 14-15, and frequency converters 15-1 to 15-15. However, the present invention is not limited to this. For example, one modulation unit, multiplexing unit, and frequency conversion unit may perform processing corresponding to all clusters.

  5A and 5B are diagrams illustrating examples of frequency images of feeder link signals generated by the ground station modulation unit 100. 5A and 5B, the horizontal axis represents the frequency. FIG. 5-1 shows an example of a frequency image of a feeder link signal generated by a conventional ground station, and FIG. 5-2 shows a frequency of the feeder link signal generated by the ground station modulation unit 100 of the present embodiment. An example of an image is shown. 5A and 5B, as in FIG. 4, information on the communication partner cluster and cell corresponding to each signal data is shown in a format “# t-n”. As shown in FIG. 5A, in the conventional ground station, the signals are arranged from places where the frequencies are vacant regardless of the communication partner. On the other hand, as shown in FIG. 5B, in the ground station modulation unit 100 according to the present embodiment, the ground station switch matrix unit 12 rearranges transmission signals for each cluster of communication partners.

  FIG. 6 is a diagram illustrating a functional configuration example of the satellite station 2 according to the present embodiment. As shown in FIG. 6, the satellite station 2 includes a feeder link antenna 20, frequency conversion units 21-1 to 21-15, demultiplexing units 22-1 to 22-15, and a satellite station switch matrix unit 23-. 1 to 23-15, multiplexers 24-11 to 24-17, 24-21 to 24-27,..., 24-151 to 24-157, and frequency converters 25-11 to 25-17, 25- , 25-151 to 25-157, and user link antennas 26-11 to 26-17, 26-21 to 26-27, ..., 26-151 to 26-157. .

  The satellite station 2 receives the feeder link signal transmitted from the ground station 1 using the feeder link antenna 20. The frequency conversion units 21-1 to 21-15 of the satellite station 2 convert the received feeder link signal into a baseband signal. In the present embodiment, in consideration of the current hardware feasibility, the frequency conversion units 21-1 to 21-15 perform frequency conversion in units of 30 MHz each having the same bandwidth as one cluster. Yes. Therefore, in order to frequency-convert the received 450 MHz feeder link signal, a total of 15 frequency conversion units 21-1 to 21-15 are provided. However, this is not limited depending on the future hardware performance improvement, and 450 MHz bandwidth may be collectively converted.

  By the way, a plurality of signals having different signal bandwidths are included in the 30 MHz bandwidth signals frequency-converted by the frequency converters 21-1 to 21-15, respectively. This is because the required frequency band differs depending on the service used, such as whether the service used is a voice call or data communication, depending on the user. The demultiplexing unit 22-i (i = 1, 2,..., 15) demultiplexes the 30-MHz bandwidth signal frequency-converted by the frequency conversion unit 21-i, and extracts the signals in the respective use frequency bands. To do.

  The demultiplexed signals are sent from user link antennas 26-11 to 26-17, 26-21 to 26-27,..., 26-151 to 26-157 corresponding to the cell where the communication partner exists. Although it is transmitted to various terminals 3-1 to 3-3, it is necessary to synthesize transmission signals corresponding to the communication partner cell. The satellite station switch matrix units 23-1 to 23-15 rearrange the signals demultiplexed based on instructions from the control unit 27 in accordance with the communication partner cell. In addition, the presence position information of the various terminals 3-1 to 3-3 is held and updated by the communication control unit 11 of the ground station 1 as described above, and the ground station 1 is based on the position information. Information for controlling the satellite station switch matrix units 23-1 to 23-15, frequency arrangement of each signal, and cell area information to be transmitted are generated as control information, and are transmitted to the control unit 27 using another communication line. In response, the control information is transmitted. Based on the control information, the control unit 27 instructs the satellite station switch matrix units 23-1 to 23-15 to perform rearrangement.

  Since the feeder link signals transmitted from the ground station 1 are rearranged in units of clusters in the ground station switch matrix unit 12 of the ground station 1, the satellite station switch matrix units 23-1 to 23-15 have 1 What is necessary is just to rearrange the range in a cluster, ie, 7 cells.

  For example, assuming a voice service and assuming that the minimum signal bandwidth is 10 kHz, the demultiplexing units 22-1 to 22-15 demultiplex a 30 MHz wide-band transmission signal into a signal having a maximum of 3000 waves at 10 kHz. In this embodiment, since 15 demultiplexing units are provided, if the ground station switch matrix unit 12 does not rearrange transmission signals, the satellite station switch matrix unit of the satellite station 2 has a maximum of 45000. It is necessary to rearrange signals of waves (3000 waves × 15). On the other hand, in this embodiment, since the ground station switch matrix unit 12 rearranges the signals in units of clusters, the satellite station switch matrix units 23-1 to 23-15 transmit a maximum of 3000 transmission signals. In contrast, the signals may be rearranged.

  The satellite station switch matrix section needs to be provided in the same way as the frequency conversion section and the demultiplexing section, but it is sufficient that rearrangement processing of transmission signals of a maximum of 3000 waves is possible. The circuit scale can be reduced as compared with the case of rearranging signals of up to 45,000 waves.

  Then, the satellite station switch matrix unit 23-i rearranges the demultiplexed signal for each cell of the communication partner of the signal based on the instruction from the control unit 27, and matches the signal corresponding to the cell of the communication partner of the signal. Output to the wave sections 24-ij to 24-ij (j = 1, 2,..., 7). Note that the multiplexing units 24-ij to 24-ij perform processing corresponding to the cell #j. The multiplexing units 24-i1 to 24-i7 perform multiplexing processing in units of beams for transmitting signals input from the satellite station switch matrix unit 23-i to each cell.

  The frequency conversion units 25-i1 to 25-i7 perform frequency conversion on the combined signals to the S band, and send the frequency-converted signals to the corresponding user link antennas 26-i1 to 26-i7, respectively. Output. The user link antennas 26-i1 to 26-i7 transmit signals input toward the transmission destination cell. In this way, the signal transmitted from the satellite station 2 is irradiated to the ground with multi-beams directed to each cell, and the various terminals 3-1 to 3-3 receive signals transmitted from the satellite station 2. Is received and demodulated.

  FIG. 7 is a diagram illustrating an example of a transmission signal image for each destination cell in the cluster 10-1. In FIG. 7, the horizontal axis represents the frequency. The signal rearrangement performed by the satellite station switch matrix units 23-1 to 23-15 is performed, for example, as shown in (a) on the left side of FIG. 7, in which the frequency arrangement in the cell is changed to the cluster 10-1 in the feeder link signal. You may rearrange so that it may become the same order as the order of a corresponding frequency position, and may rearrange a frequency position in order of a cell number like (b) on the right side.

  In the present embodiment, the cell design for the service area is repeated for 7 cells, but the cell design may not be repeated for 7 cells. For example, the operation of the present embodiment can also be applied to a case of repeating three cells in which one cluster is composed of three cells, in which cell design is performed by dividing 30 MHz into three frequencies.

  In the present embodiment, the ground station switch matrix unit 12 rearranges the transmission signals in units of clusters in units of 7 cells. However, the present invention is not limited to this. The constituent cells are grouped into a plurality of groups based on the cell positions, and the ground station switch matrix unit 12 rearranges the transmission signals in units of groups, and the satellite station 2 rearranges the cells in the group. May be performed.

  As described above, in the present embodiment, the ground station switch matrix unit 12 of the ground station 1 transmits the transmission signal after performing the rearrangement of the cluster unit in advance based on the position of the communication partner with respect to the transmission signal, The satellite station switch matrix units 23-1 to 23-15 of the satellite station 2 perform the rearrangement corresponding to the cells in the ground station cluster on the received transmission signals. Therefore, the signal rearrangement process according to the signal transmission destination on the satellite station 2 side is simplified, and the circuit scale of the satellite station switch matrix units 23-1 to 23-15 of the satellite station 2 can be reduced.

Embodiment 2. FIG.
FIG. 8 is a diagram showing a configuration example of the second embodiment of the satellite communication system according to the present invention. The configuration of the satellite communication system of the present embodiment is the same as that of the satellite communication system of the first embodiment. Components having the same functions as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the first embodiment, the case where signals are transmitted from the ground station 1 to the various terminals 3-1 to 3-3 via the satellite station 2 has been described. However, in the present embodiment, the various terminals 3-1 to 3-3 are transmitted. A case where a signal is transmitted from -3 to the ground station 1 via the satellite station 2 will be described. The satellite station 2 of the present embodiment is similar to the satellite station 2 of the first embodiment, but further includes the components shown in FIG. For various antennas (feeder link antenna 20, user link antennas 26-11 to 26-17, 26-21 to 26-27,..., 26-151 to 26-157), both transmission and reception functions are provided. It has the same reference numerals as the embodiment in FIG. 6 and has both the function described in the first embodiment and the function described in the present embodiment. Different antennas may be used.

  Also, the satellite station switch matrix units 23-1 to 23-15 have both the functions described in the first embodiment and the functions described in the present embodiment, but will be described in the present embodiment. In addition to the satellite station switch matrix units 23-1 to 23-15 of the first embodiment, 15 satellite station switch matrix units having functions may be provided.

  The satellite station 2 of the present embodiment includes a feeder link antenna 20, user link antennas 26-11 to 26-17, 26-21 to 26-27, ..., 26-151 to 26-157, and frequency conversion. 28-11 to 28-17, 28-21 to 28-27, ..., 28-151 to 28-157, and demultiplexers 29-11 to 29-17, 29-21 to 29-27, ..., 29 -151 to 29-157, satellite station switch matrix units 23-1 to 23-15, multiplexing units 30-1 to 30-15, frequency converting units 31-1 to 31-15, and adding unit 32 It is equipped with.

  Next, the operation of the present embodiment will be described. The various terminals 3-1 to 3-3 perform transmission using the transmission frequency managed by the communication control unit 11 of the ground station 1 notified from the ground station 1 via the satellite station 2. The communication control unit 11 of the ground station 1 holds the position information of the various terminals 3-1 to 3-3, and when the various terminals 3-1 to 3-3 make a call based on the position information. Assign the transmission frequency to be used.

  FIG. 9 is a diagram illustrating an example of a frequency allocation image performed by the communication control unit 11. In the present embodiment, as described with reference to FIG. 2 of the first embodiment, the service providing area is composed of 100 cells, and 7 cells constitute one cluster. As shown in FIG. 9, the communication control unit 11 assigns and manages transmission frequencies for each cell so that the used frequencies of the cells in the cluster do not overlap. In addition, the communication control unit 11 notifies the use frequency via the satellite station 2 to the various terminals 3-1 to 3-3 that are about to start communication. Note that the transmission frequency within one cluster may be equally allocated to each cell, or may be dynamically changed according to the frequency usage situation.

  10A and 10B are diagrams illustrating an example of transmission frequency allocation to the cluster 10-1. FIG. 10A illustrates an example in which the use frequency band is equally divided and allocated to the cell # 1 to the cell # 7 of the cluster 10-1. When the total frequency band of the cluster 10-1 is 30 MHz, 30/7 MHz is allocated to each cell. On the other hand, FIG. 10-2 illustrates an example in which the communication control unit 11 performs allocation to each cell in consideration of the frequency usage status. In this example, it is assumed that there are many various terminals that transmit transmission signals in cell # 2 and cell # 3 of cluster 10-1, and that cell # 6 and cell # 7 have relatively few various terminals. The communication control unit 11 detects this situation based on the communication situation, and determines that the cell # 2 and the cell # 3 require a large number of transmission frequencies, and the cell # 6 and the cell # 7 do not need so much. However, a larger number of transmission frequencies used in cell # 2 and cell # 3 are allocated, and the allocated amounts of cell # 6 and cell # 7 are reduced accordingly.

  Also, transmission frequency assignments may not be in the order of cell numbers. FIG. 11 is a diagram illustrating an example of an image of transmission frequency assignment that is not in cell number order. FIG. 11 shows a state of transmission frequency allocation of a certain cluster. In the transmission frequency allocation shown in FIG. 11, when there is a request for transmission from various terminals existing in each cell, not in the order of cell numbers as shown in FIGS. The transmission frequency to be used is assigned to a cell in which various terminals exist.

  The satellite station 2 uses the signals transmitted from the various terminals 3-1 to 3-3 as user link antennas 26-11 to 26-17, 26-21 to 26-27,..., 26-151 to 26-157. Receive at. Frequency converters 28-11 to 28-17, 28-21 to 28-27,..., 28-151 to 28-157 convert received signals from a radio frequency band to a baseband band. The demultiplexing units 29-11 to 29-17, 29-21 to 29-27,..., 29-151 to 29-157 are included in the received signals converted into basebands. 3 performs demultiplexing processing of various signals received from 3.

  The satellite station switch matrix unit 23-i (i = 1, 2,..., 15) is demultiplexed from one cluster (= 7 cells) output from the demultiplexing unit 29-i1 to the demultiplexing unit 29-i7. The processed received signal is divided into a signal to be transmitted to the ground station 1 and a signal to be transmitted to the various terminals 3-1 to 3-3, and the signals are rearranged. As shown in FIGS. 10-1 and 10-2, the signals transmitted to the ground station 1 have predetermined transmission frequency bands used by the terminals 3-1 to 3-3. The matrix units 23-1 to 23-15 collect the signals of the various terminals 3-1 to 3-3 in the same cluster and collect the signals to the multiplexing units 30-1 to 30-15. 3, the frequency indicating the frequency arrangement of the feeder link is transferred to the multiplexing unit 30-i together with the position information. Note that the frequency allocation information is determined and held by the control unit 27. In addition, the frequency allocation of the feeder link at this time is assumed to be a frequency allocation for each cluster, for example, as in FIG. 5-2 described in the first embodiment.

  The multiplexing unit 30-i combines a signal for transmitting the signal output from the satellite station switch matrix unit 23-i to the ground station 1 based on the frequency arrangement information obtained from the satellite station switch matrix unit 23-i. To process. Then, the frequency conversion unit 31-i performs frequency conversion of the signal combined by the combining unit 30-i from the baseband band to the Ka band, and outputs the frequency-converted signal to the addition unit 32. The adder 32 adds the signals output from the frequency converters 31-1 to 31-15 to obtain a feeder link signal having a total bandwidth of 450 MHz, and the feeder link antenna 20 transmits the feeder link signal to the ground station 1. Is done.

  FIG. 12 is a diagram illustrating a functional configuration example of the ground station demodulation unit 101 of the ground station 1. The ground station 1 includes the ground station modulation unit 100 as described in the first embodiment, but the components shared with the ground station modulation unit 100 are denoted by the same reference numerals as those in the first embodiment. As illustrated in FIG. 12, the ground station demodulation unit 101 of the ground station 1 includes a feeder link antenna 41, frequency conversion units 42-1 to 42-15, demultiplexing units 43-1 to 43-15, and demodulation. Units 44-1 to 44-15, a ground station switch matrix unit 12, and a communication control unit 11.

  The feeder link antenna 41 receives a feeder link signal having a bandwidth of 450 MHz transmitted from the satellite station 2. The ground station demodulation unit 101 of the ground station 1 includes 15 frequency conversion units and 15 demultiplexing units. Each frequency conversion unit converts each received signal 30 MHz divided in units of clusters from the Ka band to the baseband, and the demultiplexing unit extracts signals from each cell included in the divided 30 MHz. Perform demultiplexing.

  The demodulating units 44-1 to 44-15 perform demodulation processing on the signals demultiplexed in cluster units, and are configured by a plurality of demodulators so that signals having different bit rates can be demodulated. The reception signals demodulated by the demodulating units 44-1 to 44-15 become bit data and are input to the ground station switch matrix unit 12. The ground station switch matrix unit 12 rearranges the bit data in cluster units in the reverse flow to that in the first embodiment, and outputs the rearranged bit data to the communication control unit 11. The communication control unit 11 performs control related to the rearrangement process of the ground station switch matrix unit 12. Finally, the communication control unit 11 transmits bit data to the terrestrial network 4.

  Thus, in the present embodiment, the communication control unit 11 of the ground station 1 uses the frequencies used by the various terminals 3-1 to 3-3 for transmission at the positions (cells) where the various terminals 3-1 to 3-3 exist. ). Therefore, it is not necessary for the satellite station switch matrix units 23-1 to 23-15 of the satellite station 2 to rearrange the signals, and the circuit scale of the satellite station 2 can be reduced.

  As described above, the satellite communication system and the satellite communication method according to the present invention are useful for a satellite communication system including a satellite station that relays communication between a ground station and a mobile terminal, and are configured with a large number of cells. Suitable for satellite communication systems using multi-beams.

DESCRIPTION OF SYMBOLS 1 Ground station 2 Satellite station 3-1 to 3-3 Various terminals 4 Ground network 5 General telephone 6 Mobile base station 7 IP network 8 Exchange switch 9 Cell 10-1 to 10-4 Cluster 11 Communication control part 12 Ground station switch Matrix section 13-1 to 13-15 Modulating section 14-1 to 14-15 Multiplexing section 15-1 to 15-15, 21-1 to 21-15, 25-11 to 25-17, 25-21 to 25 -27, ..., 25-151 to 25-157, 28-11 to 28-17, 28-21 to 28-27, ..., 28-151 to 28-157, 31-1 to 31-15, 42-1 ~ 42-15 Frequency conversion part 16 Addition part 17 Antenna part 20, 41 Feeder link antennas 22-1 to 22-15, 29-11 to 29-17, 29-21 to 29-27, ..., 29-1 1-29-157, 43-1 to 43-15 Demultiplexing unit 23-1 to 23-15 Satellite station switch matrix unit 24-11 to 24-17, 24-21 to 24-27, ..., 24-151 24-157, 30-1 to 30-15 multiplexer 26-11 to 26-17, 26-21 to 26-27,..., 26-151 to 26-157 User link antenna 27 Control unit 32 Adder 44 -1 to 44-15 Demodulator 100 Ground station modulator 101 Ground station demodulator D1, D2, D3 Transmission data

Claims (7)

A satellite communication system comprising a ground station, a terminal, and a satellite station that relays communication between the terminal and the ground station in a cell formed by the beam using a plurality of beams,
The cells are grouped into a plurality of groups based on the location of the cells, and a group frequency region that is a frequency region used for transmission from the ground station to the satellite station is determined in advance for each group,
The ground station is
The location of the terminal is held as location information, and the correspondence between the location of the cell and a group to which the cell belongs is held as cell information. For each transmission data, a destination address is determined based on the transmission data and the location information. The position of the terminal is determined, a group corresponding to the determined position is determined as a destination group based on the cell information, and the transmission data is transmitted at a frequency in the group frequency region corresponding to the determined destination group. Ground station switch matrix means for arranging transmission data on the frequency axis,
With
The satellite station
For each group, the received data transmitted from the ground station at a frequency within the group frequency domain of the group, for each destination cell of the received data, the frequency used by the satellite station to transmit to the terminal in the cell Satellite station switch matrix means arranged on the frequency axis so that the received data is transmitted to the terminal at a frequency within the cell frequency domain,
A satellite communication system comprising: The ground station is
For each cell, a frequency region used when a terminal located in the cell transmits data to the satellite station is determined as a terminal frequency region, and based on the location of the terminal, a cell in which the terminal is located is obtained and obtained. Communication control means for notifying the terminal of the terminal frequency region corresponding to the cell;
Further comprising
The terminal transmits data to the satellite station using the notified terminal frequency region.
The satellite communication system according to claim 1.   The communication control means determines the terminal frequency region based on at least one of the number of terminals present in the cell for each cell and the number of terminals present in a neighboring cell of the cell. The satellite communication system according to claim 2. The group is a cluster composed of a plurality of the cells adjacent to each other.
The satellite communication system according to claim 1, 2, or 3. The ground station obtains the location of the terminal based on GPS information.
The satellite communication system according to claim 1, wherein the satellite communication system is a satellite communication system. A ground station in a satellite communication system comprising a ground station, a terminal, and a satellite station that relays communication between the terminal and the ground station in a cell formed by the beam using a plurality of beams,
The cells are grouped into a plurality of groups based on the location of the cells, and a group frequency region that is a frequency region used for transmission from the ground station to the satellite station is determined in advance for each group,
The location of the terminal is held as location information, and the correspondence between the location of the cell and a group to which the cell belongs is held as cell information. For each transmission data, a destination address is determined based on the transmission data and the location information. The position of the terminal is determined, a group corresponding to the determined position is determined as a destination group based on the cell information, and the transmission data is transmitted at a frequency in the group frequency region corresponding to the determined destination group. Ground station switch matrix means for arranging transmission data on the frequency axis,
A ground station comprising: A satellite communication method in a satellite communication system comprising a ground station, a terminal, and a satellite station that relays communication between the terminal and the ground station in a cell formed by the beam using a plurality of beams,
The cells are grouped into a plurality of groups based on the location of the cells, and a group frequency region that is a frequency region used for transmission from the ground station to the satellite station is determined in advance for each group,
The ground station holds the location of the terminal as location information, and also holds the correspondence between the location of the cell and the group to which the cell belongs as cell information. For each transmission data, the transmission data and the location information Based on the cell information, a group corresponding to the obtained position is obtained as a destination group, and the transmission data is transmitted at a frequency in the group frequency region corresponding to the obtained destination group. A ground station frequency placement step for placing the transmission data on the frequency axis so as to be transmitted;
For each group, the satellite station transmits received data transmitted from the ground station at a frequency within the group frequency domain of the group to each terminal cell of the received data. A satellite station frequency arrangement step for arranging on the frequency axis so that the received data is transmitted at a frequency in the cell frequency domain, which is a frequency domain used for transmission of
A satellite communication method comprising:

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