Patent Publication Number: US-2022231755-A1

Title: System, control apparatus, computer readable storage medium, and control method

Description:
The contents of the following Japanese patent application(s) are incorporated herein by reference: 
     NO. 2019-205783 filed in JP on Nov. 13, 2019 
     NO. PCT/JP2020/031474 filed in WO on Aug. 20, 2020 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a system, a control apparatus, a computer readable storage medium, and a control method. 
     2. Related Art 
     HAPS (High Altitude Platform Station) has been known for providing a terminal with wireless communication service by establishing a feeder link with a gateway on the ground, establishing a service link with a terminal on the ground, and relaying communication between the gateway and the terminal (for example, refer to Patent Document 1). 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: Japanese Patent Application Publication No. 2019-135823 
     Technical Problem 
     It is desirable that the service can be provided without installing a gateway on the ground for each HAPS. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically shows one example of a HAPS  100 . 
         FIG. 2  schematically shows one example of a system  10 . 
         FIG. 3  schematically shows one example of a coverage area  300  formed by a plurality of HAPSs  100  of the system  10 . 
         FIG. 4  schematically shows one example of a coverage area  300 , a coverage area  302 , and a coverage area  304 . 
         FIG. 5  schematically shows one example of a communication situation in the system  10 . 
         FIG. 6  schematically shows one example of a connection processing flow performed by the HAPS  100 . 
         FIG. 7  schematically shows one example of a connection performed by the HAPS  100 . 
         FIG. 8  schematically shows one example of a connection performed by the HAPS  100 . 
         FIG. 9  schematically shows one example of a connection performed by the HAPS  100 . 
         FIG. 10  schematically shows one example of replacement processing for the HAPS  100  in the system  10 . 
         FIG. 11  schematically shows one example of a functional configuration of a control apparatus  200 . 
         FIG. 12  shows an allocation example  250  of a beacon signal. 
         FIG. 13  schematically shows one example of a hardware configuration of a computer  1200  that functions as the control apparatus  200 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, (some) embodiment(s) of the present invention will be described. The embodiment(s) do(es) not limit the invention according to the claims. Moreover, some combinations of features described in the embodiments may be unnecessary for a solution of the invention. 
       FIG. 1  schematically shows one example of a HAPS  100 . The HAPS  100  may be one example of a flying object having a relaying function for relaying communication between a gateway  40  on the ground, and a user terminal  30  within a cell  101  formed by wirelessly connecting with the gateway  40  and irradiating a beam toward the ground. 
     The HAPS  100  includes a fuselage  110 , a central part  120 , a propeller  130 , a pod  140 , and a solar panel  150 . A control apparatus  200 , which is not shown in the diagram, is arranged within the central part  120 . 
     The solar panel  150  generates power which is then stored in one or more batteries arranged in at least any of the fuselage  110 , the central part  120 , and the pod  140 . The power stored in the battery is used by each configuration in the HAPS  100 . 
     The control apparatus  200  controls a flight and communication of the HAPS  100 . The control apparatus  200  controls the flight of the HAPS  100  by controlling rotation of the propeller  130 , for example. Also, the control apparatus  200  may control the flight of the HAPS  100  by changing an angle of a flap or an elevator, which are not shown in the diagram. The control apparatus  200  may include various types of sensors including a position measuring sensor such as a GPS sensor, a gyro sensor, and an acceleration sensor etc., and manage a position, a moving direction, and a moving speed of the HAPS  100 . 
     The control apparatus  200  forms a feeder link with a gateway  40  on the ground by using a FL (Feeder Link) antenna  121 . The control apparatus  200  may access a network  20  via the gateway  40 . 
     The control apparatus  200  forms the cell  101  on the ground by using a SL antenna  122 . The control apparatus  200  forms a service link with a user terminal  30  on the ground by using the SL antenna  122 . The SL antenna  122  may be an antenna having a directivity lower than that of the FL antenna  121 . The SL antenna  122  may be a multi-beam antenna. The cell  101  may be a multi-cell. 
     The user terminal  30  may be any type of communication terminal that is communicable with the HAPS  100 . For example, the user terminal  30  is a cellular phone such as a smartphone. The user terminal  30  may also be a tablet terminal, a PC (Personal Computer), and the like. The user terminal  30  may also be, so-called an IoT (Internet of Thing) device. The user terminal  30  can include anything that belongs to, so-called IoE (Internet of Everything). 
     The HAPS  100  relays communication between the gateway  40  and the user terminal  30  via the feeder link and the service link, for example. The HAPS  100  may provide the user terminal  30  with a wireless communication service by relaying the communication between the user terminal  30  and the network  20 . The network  20  includes a mobile communication network. The mobile communication network may comply with any of 3G (3rd Generation) communication standard, LTE (Long Term Evolution) communication standard, 5G (5th Generation) communication standard, and a communication standard for 6G (6th Generation) or later. The network  20  may include the Internet. 
     The HAPS  100  transmits data received from the user terminal  30  within the cell  101  to the network  20 , for example. Also, the HAPS  100  transmits this data to the user terminal  30  when data for the user terminal  30  within the cell  101  has been received via the network  20 , for example. 
     The HAPS  100  may be managed by a management system  50 . The HAPS  100  operates according to an instruction transmitted by the management system  50  via the network  20  and the gateway  40 , for example. 
     The management system  50  controls a flying object  100  by transmitting the instruction. The management system  50  may cause the HAPS  100  to circulate in the sky over a target area so that the target area on the ground is covered by the cell  101 . In some cases, a fixed-point flight refers to the HAPS  100  circulating in the sky in the target area in order to cover the target area. For example, while the HAPS  100  flies in a circular orbit in the sky above the target area, the HAPS  100  maintains a feeder link with the gateway  40  by adjusting a pointing direction of the FL antenna  121 , and maintains covering the target area by the cell  101  by adjusting a pointing direction of the SL antenna  122 . 
     Installing one gateway  40  for one HAPS  100  requires creating the same number of gateways  40  as HAPSs  100  in accordance with enlargement of an area, in which case, developing the area consumes time, money, and labor-power. Also, it is difficult to install a gateway  40  in an area such as an island region, therefore, a method for enlarging an area with an extended number of HAPSs  100  while having as few gateways  40  as possible is needed. 
     The HAPS  100  according to the present embodiment has a function of sharing the gateway  40  with another HAPS  100  by wirelessly communicating with the other HAPS  100  directly. For example, two HAPSs  100  can provide a wireless communication service through one gateway  40  by causing a first HAPS  100  being wirelessly connected with the gateway  40 , and another second HAPS  100  to wirelessly connect with each other, and causing the first HAPS  100  to relay communication between the second HAPS  100  and the gateway  40 . 
       FIG. 2  schematically shows one example of a system  10 . The system  10  according to the present embodiment includes a plurality of HAPSs  100  being wirelessly communicable with each other. In  FIG. 2 , the plurality of HAPSs  100  is illustrated as a HAPS  102  being wirelessly connected with the gateway  40 , a HAPS  104  being wirelessly connected with the HAPS  102 , and a HAPS  106  being wirelessly connected with the HAPS  104 . 
     In some cases, a rank of the HAPS  102  being wirelessly connected with the gateway  40  is referred to as “Master”, a rank of the HAPS  104  being wirelessly connected with the HAPS  102  is referred to as “Slave  1 ”, and a rank of the HAPS  106  being wirelessly connected with the HAPS  104  is referred to as “Slave  2 ”. “Master” may be one example of a first rank. “Slave  1 ” may be one example of a second rank. “Slave  2 ” may be one example of a third rank. 
     The plurality of HAPSs  100  may be connected to each other in planer star network topology. For example, among a plurality of HAPSs  100 , a HAPS  100  that is wirelessly connected with the gateway  40  becomes a master node, from which the HAPSs  100  are radially connected to each other in a star network topology. 
     The HAPS  104  being “Slave  1 ” may communicate with the HAPS  102  being “Master” via the gateway  40 . The HAPS  106  being “Slave  2 ” may communicate with the gateway  40  via the HAPS  104  being “Slave  1 ” and the HAPS  102  being “Master”. In this way, the HAPS  104  and the HAPS  106  can access the network  20  without arranging on the ground a gateway  40  corresponding to the HAPS  104  and a gateway  40  corresponding to the HAPS  106 . 
       FIG. 3  schematically shows one example of a coverage area  300  formed by the plurality of HAPSs  100  in the system  10 .  FIG. 3  illustrates the coverage area  300  formed with a cell  103  formed by the HAPS  102  being “Master”, a cell  105  formed by a plurality of HAPSs  104  being “Slave  1 ”, and a cell  107  formed by a plurality of HAPSs  106  being “Slave  2 ”. 
     In the example shown in  FIG. 3 , the plurality of HAPSs  104  are flying in each of a plurality of second flight areas arranged so as to surround a first flight area for the HAPS  102 , and a plurality of HAPSs  106  are flying in each of a plurality of third flight areas arranged outside the plurality of second flight areas so as to surround the first flight area. Each of the plurality of HAPSs  104  forms each of a plurality of cells  105  arranged so as to surround the cell  103 , and each of the plurality of HAPSs  106  forms each of a plurality of cells  107  arranged outside the plurality of cells  105  so as to surround the cell  103 . According to the example shown in  FIG. 3 , one gateway  40  can be shared between 19 HAPSs  100 . 
     In some cases, an area covered by the cell  103  is referred to as “zone  0 ”, an area covered by the plurality of cells  105  is referred to as “zone  1 ”, and an area covered by the plurality of cells  107  is referred to as “zone  2 ”. “Zone  1 ” is a group of coverage areas closest from “zone  0 ” in each and every direction. “Zone  2 ” is a group of coverage areas having “zone  1 ” on a straight line between “zone  2 ” and “zone  0 ”. 
       FIG. 4  schematically shows one example of the coverage area  300 , a coverage area  302 , and a coverage area  304  which are formed by the plurality of HAPSs  100  in the system  10 .  FIG. 4  illustrates a case in which three gateways  40  are used. According to the example shown in  FIG. 4 , the three gateways  40  can be shared between 57 HAPSs  100 . Likewise, according to the system  10  of the present embodiment, a large area can be covered by a relatively small number of gateways  40 . 
       FIG. 5  schematically shows one example of a communication situation in the system  10 . In order to schematically show the communication situation, illustrated here are a central part  120  of a “Master” HAPS  100  (may be referred to as a “Master” object), a central part  120  of a “Slave  1 ” HAPS  100  (may be referred to as a “Slave  1 ” object), and a central part  120  of a “Slave  2 ” HAPS  100  (may be referred to as a “Slave  2 ” object). 
     There are a FL antenna  121 , a SL antenna  122 , a flying object communication antenna  123 , and a flying object communication antenna  124  installed on the central part  120 . The FL antenna  121  may be one example of a first antenna. The SL antenna  122  may be one example of a second antenna. The flying object communication antenna  123  may be one example of a third antenna for communicating with another HAPS  100 . The flying object communication antenna  124  may be one example of a fourth antenna for communicating with another HAPS  100 . 
     The flying object communication antenna  123  may be an omni-directional antenna (may also be referred to as an omni antenna, an omnidirectional antenna, or the like). The flying object communication antenna  124  may be an omni directional trackable antenna capable of tracking all directions by moving a directional antenna. 
     The “Master” object periodically broadcasts its own position information, and a beacon signal including rank information representing that the flying object is “Master”, by means of the flying object communication antenna  123 . The beacon signal may be broadcasted at irregular timing. 
     The “Slave  1 ” object receives the beacon signal transmitted by the “Master” object by means of the flying object communication antenna  124 , tracks the “Master” object with the use of the position information included in the beacon signal by means of the flying object communication antenna  124 , and communicates with the “Master” object. The “Slave  1 ” object periodically broadcasts its own position information, and a beacon signal including rank information representing that the flying object is “Slave  1 ”, by means of the flying object communication antenna  123 . The beacon signal may be broadcasted at irregular timing. 
     The “Slave  2 ” object receives the beacon signal transmitted by the “Slave  1 ” object by means of the flying object communication antenna  124 , tracks the “Slave  1 ” object with the use of the position information included in the beacon signal by means of the flying object communication antenna  124 , and communicates with the “Slave  1 ” object. The “Slave  2 ” object periodically broadcasts its own position information, and a beacon signal including rank information representing that the flying object is “Slave  2 ”, by means of the flying object communication antenna  123 . The beacon signal may be broadcasted at irregular timing. 
     In the system  10 , a communication frequency used between the “Master” object and the “Slave  1 ” object may be different from a communication frequency used between the “Slave  1 ” object and the “Slave  2 ” object. In this way, interference can be avoided between communication between the “Master” object and the “Slave  1 ” object, and communication between the “Slave  1 ” object and the “Slave  2 ” object. 
       FIG. 6  schematically shows one example of the flying object communication antenna  124 . The flying object communication antenna  124  has a base  125 , a shaft  126 , a supporting portion  127 , and a directional antenna  128 . 
     The base  125  is installed on the central part  120 , and rotatably supports the shaft  126 . The shaft  126  may be able to rotate 360 degrees around a central axis thereof. The supporting portion  127  is arranged on the shaft  126 , and supports the directional antenna  128 . The supporting portion  127  supports the directional antenna  128  in a way that the directional antenna  128  can tilt in a vertical direction. A tilt range of the directional antenna  128  may be 180 degrees. 
     Since the base  125  supports the shaft  126  in a way that the shaft  126  can rotate 360 degrees, and the supporting portion  127  supports the directional antenna  128  in the way that the directional antenna  128  can tilt 180 degrees in the vertical direction, radio waves from all directions can be received by the directional antenna  128 , and radio waves can be transmitted in all directions. The control apparatus  200  can track radio waves in all directions by controlling the rotation of the shaft  126  by virtue of the base  125 , and the tilting of the directional antenna  128  by virtue of the supporting portion  127 . 
       FIG. 7  schematically shows one example of a connection processing flow performed by the HAPS  100 . In order to have a flexibility in an operation place, and a cellular phone to be connected with, it is desirable for the HAPS  100  to be able to determine a connection target based on a rank, without recognizing a zone. In that case, there is an issue in determining which HAPS  100  to connect with, when beacon signals are received from a plurality of HAPSs  100 . 
     In the system  10  according to the present embodiment, for example, the HAPS  100  functioning as “Master” first moves to a flight area instructed by the management system  50 , and wirelessly connects with the gateway  40 . Next, the HAPS  100  that has moved into the flight area instructed by the management system  50  determines by itself a HAPS  100  to connect with by executing the processing shown in  FIG. 7 , and wirelessly connects with the HAPS  100 . 
     In step (a step may be referred to as S in short)  102 , the HAPS  100  measures strength of a radio wave received from another HAPS  100 . The HAPS  100  may measure strength of a received radio wave of a beacon signal periodically broadcasted by another HAPS  100 . 
     In S 104 , the HAPS  100  identifies a HAPS  100  from which the strength of the radio wave received and measured in S 102  is a predetermined threshold or more. If there is one HAPS  100  being at the highest rank, (YES at S 106 ), the processing proceeds to S 108 . Among the HAPSs  100  identified in S 104 , if there are HAPSs  100  being at different ranks and a plurality of HAPSs  100  are at the highest rank, or if the HAPSs  100  identified in S 104  are at the same rank (NO at S 106 ), the processing proceeds to S 110 . 
     In S 108 , the HAPS  100  determines a HAPS  100  being at the highest rank as a connection target. In S 110 , among the plurality of HAPSs  100  being at the highest rank, the HAPS  100  determines to connect with a HAPS  100  from which the strength of the radio wave received is the strongest. In S 112 , the HAPS  100  wirelessly connects with the HAPS  100  determined to be connected with. Then, the connection processing ends. 
       FIG. 8  schematically shows one example of connection processing performed by the HAPS  100 . Here, a case is described in which a new HAPS  100  has reached “zone  1 ”. The HAPS  100  may move to a flight area designated by the management system  50  without recognizing a zone. 
     The HAPS  100  that has reached the designated flight area then measures strength of a radio wave received from another HAPS  100 . Then, the HAPS  100  identifies another HAPS  100  from which the strength of the radio wave received is stronger than the predetermined threshold. In the example shown in  FIG. 8 , one HAPS  102  and two HAPSs  104  included in a group  82  are identified. 
     In the group  82 , since there is one HAPS  102  being at the highest rank, the HAPS  100  determines to connect with the HAPS  102 . Then, the HAPS  100  wirelessly connects with the HAPS  102  and functions as “Slave  1 ” itself. 
       FIG. 9  schematically shows one example of connection processing performed by the HAPS  100 . Here, a case is described in which a new HAPS  100  has reached “zone  2 ”. The HAPS  100  may move to a flight area designated by the management system  50  without recognizing a zone. 
     The HAPS  100  that has reached the designated flight area then measures strength of a radio wave received from another HAPS  100 . Then, the HAPS  100  identifies another HAPS  100  from which the strength of the radio wave received is stronger than the predetermined threshold. In the example shown in  FIG. 9 , for example, three HAPSs  104  included in a group  84  are identified. Depending on the threshold, only one HAPS  104  being closest to the HAPS  100  is identified. 
     In the group  84 , since all the HAPSs  104  are at the same rank, among the three HAPSs  104 , the HAPS  100  determines a HAPS  104  from which the strength of the radio wave received is the strongest to connect with. When only one HAPS  104  being closest to the HAPS  100  is identified, the HAPS  100  determines to connect with this HAPS  104 . 
     For example, if a connection target is determined merely based on the strength of the received radio wave, in the example shown in  FIG. 8 , the HAPS  104  may be determined to be connected with. In that case, the HAPS  100  would communicate with the gateway  40  via the HAPS  104  and the HAPS  102 , which would cause a communication delay and unnecessary use of relay resource. 
     Also, for example, if a connection target is determined merely based on the rank, in the example shown in  FIG. 9 , the HAPS  102  may be determined to be connect with. In that case, because the HAPS  100  and the HAPS  102  to be wirelessly connected together have a long distance between them, usually communication quality decreases, which then causes a problem in performance. 
     On the other hand, by determining a connection target according to the processing algorism shown in  FIG. 7 , it is possible to prevent the HAPS  104  from being selected as the connection target in the example shown in  FIG. 8 , and to select the HAPS  102  as the connection target. This enables the communication delay and the unnecessary use of relay resource to be prevented. In addition, it is possible to exclude the HAPS  102  from being a candidate for the connection target in the example shown in  FIG. 9 . This enables the decrease in communication quality to be prevented. 
       FIG. 10  schematically shows one example of replacement processing for the HAPS  100  in the system  10 . In the system  10 , when any HAPS  100  among a plurality of HAPSs  100  breaks down or stops forming a cell  101  in order to move down to the ground for maintenance, a HAPS  100  which is at a rank lower than this HAPS  100 , and which had been wirelessly connected with this HAPS  100  replaces this HAPS  100 . 
     For example, when a HAPS  104  withdraws, a HAPS  106  which had been wirelessly connected to this HAPS  104  replaces this HAPS  104 . After the replacement, this HAPS  106  functions as “Slave  1 ”, and puts rank information representing that this HAPS  106  is “Slave  1 ” in a beacon signal. 
       FIG. 11  schematically shows one example of a functional configuration of a control apparatus  200 . The control apparatus  200  includes a flight control unit  210 , a communication control unit  220 , a flying object identification unit  230 , and a connection target determination unit  240 . 
     The flight control unit  210  controls a flight of a HAPS  100  (may be referred to as its own flying object) on which the control apparatus  200  is mounted. The flight control unit  210  may control flight of its own flying object by controlling rotation of the propeller  130 , changing an angle of the flap or the elevator, and so forth. The flight control unit  210  may include various types of sensors including a position measuring sensor such as a GPS sensor, a gyro sensor, and an acceleration sensor etc., and manage a locate, a moving direction, and a moving speed of its own flying object. 
     The flight control unit  210  may control flight of its own flying object according to an instruction received from the management system  50 . For example, the flight control unit  210  controls flight of its own flying object such that its own flying object moves to a flight area designated by the management system  50 . Also, the flight control unit  210  controls flight of its own flying object in order to perform a fixed-point flight in the flight area designated by the management system  50 . 
     Note that, the control apparatus  200  may not include the flight control unit  210 . In that case, a flight controller for controlling flight of its own flying object is arranged within the central part  120  so as to be communicable with the control apparatus  200 . 
     The communication control unit  220  has a FL communication unit  222 , a SL communication unit  224 , and a flying object communication unit  226 , and a flying object communication unit  228 . The FL communication unit  222  wirelessly connects with the gateway  40  by means of the FL antenna  121 , and establishes a feeder link with the gateway  40 . The SL communication unit  224  forms the cell  101  on the ground by means of the SL antenna  122 . The SL communication unit  224  wirelessly connects with a user terminal  30  within the cell  101 , and establishes a service link with the user terminal  30 . 
     The flying object communication unit  226  wirelessly communicates with another HAPS  100  by means of the flying object communication antenna  123 . The flying object communication unit  226  may be one example of a first flying object communication unit. The flying object communication unit  228  wirelessly communicates with another HAPS  100  by means of the flying object communication antenna  124 . The flying object communication unit  228  may be one example of a second flying object communication unit. 
     The flying object communication unit  226  periodically or irregularly broadcasts, when its own flying object is wirelessly connected with the gateway  40  by means of the FL antenna  121 , i.e., when its own flying object is functioning as “Master”, a beacon signal including rank information representing that its own flying object is “Master”, and position information for its own flying object, by means of the flying object communication antenna  123 . The flying object communication unit  226  may be one example of a beacon signal transmission unit. 
     The flying object communication unit  226  periodically or irregularly transmits, when its own flying object is wirelessly connected with a “Master” object by means of the flying object communication antenna  124 , i.e., when its own flying object is functioning as “Slave  1 ”, a beacon signal including rank information representing that its own flying object is “Slave  1 ”, and position information for its own flying object, by means of the flying object communication antenna  123 . 
     The flying object communication unit  226  periodically or irregularly transmits, when its own flying object is wirelessly connected with the “Slave  1 ” object by means of the flying object communication antenna  124 , i.e., when its own flying object is functioning as “Slave  2 ”, a beacon signal including rank information representing that its own flying object is “Slave  2 ”, and position information for its own flying object by means of the flying object communication antenna  123 . 
     When the flying object communication unit  226  is wirelessly connected with the gateway  40 , i.e., when functioning as “Master”, the flying object communication unit  226  may use a frequency different from when it is wirelessly connected with a “Master” object, i.e., when functioning as “Slave  1 ”. 
     The flying object communication unit  226  may put in a beacon signal, when the flying object communication unit  226  is functioning as “Slave  1 ” or “Slave  2 ”, information that enables its own flying object to be identified from other HAPSs  100 . The flying object communication unit  226  puts in the beacon signal, an identification number for a cell formed by the SL antenna  122 , for example. The ECGI (E-UTRAN Cell Global ID) consists of eNB (eNodeB) or the like can be adopted as the identification number for the cell. 
     The flying object communication unit  228  communicates with a “Master” object by means of the flying object communication antenna  124 , when the flying object communication unit  228  is wirelessly connected with the “Master” object by means of the flying object communication antenna  124 , i.e., when its own flying object is functioning as “Slave  1 ”. The flying object communication unit  228  tracks the “Master” object by moving the directional antenna  128 , by controlling the base  125  and the supporting portion  127 . The flying object communication unit  228  may track the “Master” object by moving the directional antenna  128  by using position information for the “Master” object, which is included in a beacon signal transmitted by the “Master” object. The flying object communication unit  228  may be one example of a flying object tracking unit. 
     The flying object communication unit  228  communicates with a “Slave  1 ” object by means of the flying object communication antenna  124 , when the flying object communication unit  228  is wirelessly connected with the “Slave  1 ” object by means of the flying object communication antenna  124 , i.e., when its own flying object is functioning as “Slave  2 ”. The flying object communication unit  228  tracks the “Slave  1 ” object by moving the directional antenna  128 , by controlling the base  125  and the supporting portion  127 . The flying object communication unit  228  may track the “Slave  1 ” object by moving the directional antenna  128  based on position information for the “Slave  1 ” object, which is included in a beacon signal transmitted by the “Slave  1 ” object. 
     The flying object communication unit  228  measures strength of a radio wave received from another HAPS  100  by means of the flying object communication antenna  124 . The flying object communication unit  228  measures the strength of the received radio wave by using a beacon signal broadcasted by the other HAPS  100 , for example. The flying object communication unit  228  may be one example of a radio wave strength measurement unit. 
     The flying object identification unit  230  identifies a plurality of HAPSs  100  to be candidates for a connection target, for example when wirelessly connecting with another HAPS  100  after moving into a flight area designated by the management system  50 , based on strength of a radio wave received from each of a plurality of other HAPSs  100  measured by the flying object communication unit  228 . The flying object identification unit  230  may identify as candidates for a connection target, HAPSs  100  from which the strength of the radio wave received is more than a predetermined threshold. This threshold can be set at any value, and can be changed. 
     The connection target determination unit  240  determines a HAPS  100  to be connected, among the HAPSs  100  identified by the flying object identification unit  230 . When there is one HAPS  100  identified by the flying object identification unit  230 , the connection target determination unit  240  may identify this HAPS  100  as the connection target. 
     When a plurality of HAPSs  100  is identified by the flying object identification unit  230 , the connection target determination unit  240  may determine a connection target based on strength of a radio wave received from each of the plurality of HAPSs  100 , and the ranks of the plurality of HAPSs  100 . 
     The connection target determination unit  240  determines as a connection target, for example, when there is one HAPS  100  having the highest rank among the plurality of HAPSs  100  identified by the flying object identification unit  230 , the flying object having this highest rank. For example, when one “Master” object and one or more “Slave  1 ” objects are identified by the flying object identification unit  230 , the connection target determination unit  240  determines the “Master” object as a connection target. For another example, when one “Slave  1 ” object and one or more “Slave  2 ” objects are identified by the flying object identification unit  230 , the connection target determination unit  240  determines the “Slave  1 ” object as a connection target. 
     The connection target determination unit  240  determines as a connection target, for example, when there is more than one HAPSs  100  having the highest rank among the plurality of HAPSs  100  identified by the flying object identification unit  230 , a HAPS  100  from which the strength of the received radio wave measured by the flying object communication unit  228  is the highest among the plurality of HAPSs  100  having this highest rank. For example, when there is a plurality of “Slave  1 ” objects and one or more “Slave  2 ” objects identified by the flying object identification unit  230 , the connection target determination unit  240  determines as a connection target a “Slave  1 ” object from which the strength of the received radio wave measured by the flying object communication unit  228  is the highest among the plurality of “Slave  1 ” object. 
     The connection target determination unit  240  determines as a connection target, for example, when a plurality of HAPSs  100  identified by the flying object identification unit  230  has the same rank, a HAPS  100  from which the strength of the received radio wave measured by the flying object communication unit  228  is the highest among this plurality of HAPSs  100 . For example, when there is a plurality of “Slave  1 ” objects identified by the flying object identification unit  230 , the connection target determination unit  240  determines as a connection target a “Slave  1 ” object from which the strength of the received radio wave measured by the flying object communication unit  228  is the highest among the plurality of “Slave  1 ” objects. For another example, when there is a plurality of “Slave  2 ” objects identified by the flying object identification unit  230 , the connection target determination unit  240  determines as a connection target a “Slave  2 ” object from which the strength of the received radio wave measured by the flying object communication unit  228  is the highest among the plurality of “Slave  2 ” objects. 
       FIG. 12  shows an allocation example  250  of a beacon signal. The flying object communication unit  226  may put a beacon signal in each frame, as shown in  FIG. 12 . In  FIG. 12 , an example is illustrated in which the beacon signal is allocated at the beginning of the frame, whereas allocation of the beacon signal is not limited to this example. The beacon signal can be allocated at any position in the frame. In addition, the flying object communication unit  226  may put a beacon signal in every arbitrary frame such as every two frames, instead of in every frame. 
       FIG. 13  schematically shows one example of a hardware configuration of a computer  1200  that functions as the control apparatus  200 . A program installed on the computer  1200  can cause the computer  1200  to function as one or more “units” of the device according to the above embodiment, or cause the computer  1200  to execute an operation or one or more “units” associated with the device according to the above embodiment, and/or cause the computer  1200  to execute a process or steps of the process according to the above embodiment. Such a program may be executed by a CPU  1212  in order to cause the computer  1200  to execute certain operations associated with some or all of blocks of the flowcharts and the block diagrams described herein. 
     The computer  1200  according to the present embodiment includes the CPU  1212 , a RAM  1214 , and a graphics controller  1216 , which are interconnected by a host controller  1210 . In addition, the computer  1200  includes input/output units such as a communication interface  1222 , a storage device  1224 , and a DVD driver and an IC card drive, which are connected to the host controller  1210  through an input/output controller  1220 . The storage device  1224  may be a hard disk drive, a solid-state drive, or the like. The computer  1200  also includes a ROM  1230  and a legacy input/output unit such as a keyboard, which are connected to the input/output controller  1220  via an input/output chip  1240 . 
     The CPU  1212  operates according to the programs stored in the ROM  1230  and the RAM  1214 , thereby controlling each unit. The graphics controller  1216  obtains image data which is generated, by the CPU  1212 , in a frame buffer or the like provided in the RAM  1214  or in itself so as to cause the image data to be displayed on a display device  1218 . 
     The communication interface  1222  communicates with other electronic devices via a network. The storage device  1224  stores programs and data used by the CPU  1212  in the computer  1200 . The IC card drive reads the program and data from an IC card, and/or writes the program and data to the IC card. 
     The ROM  1230  stores, in itself, a boot program or the like that is executed by the computer  1200  during activation, and/or a program that depend on hardware of the computer  1200 . The input/output chip  1240  may also connect various input/output units to the input/output controller  1220  via a USB port, a parallel port, a serial port, a keyboard port, a mouse port, or the like. 
     A program is provided by a computer readable storage medium such as the DVD-ROM or the IC card. The program is read from the computer readable storage medium, installed in the storage device  1224 , the RAM  1214 , or the ROM  1230 , which is also an example of the computer readable storage medium, and executed by the CPU  1212 . Information processing written in these programs are read by the computer  1200 , and provides a link between the program and various types of hardware resources described above. A device or a method may be configured by implementing the operation or processing of the information according to the use of the computer  1200 . 
     For example, when a communication is executed between the computer  1200  and an external device, the CPU  1212  may execute a communication program loaded in the RAM  1214 , and instruct the communication interface  1222  to perform the communication processing based on the processing written in the communication program. The communication interface  1222 , under the control of the CPU  1212 , reads transmission data stored in a transmission buffer region provided in a recording medium such as the RAM  1214 , the storage device  1224 , the DVD-ROM, or the IC card, transmits the read transmission data to the network, or writes reception data received from the network into a receiving buffer region or the like provided on the recording medium. 
     In addition, the CPU  1212  may cause all or a necessary portion of a file or a database to be read into the RAM  1214 , the file or the database having been stored in an external recording medium such as the storage device  1224 , the DVD driver (DVD-ROM), the IC card, etc., and perform various types of processing on the data on the RAM  1214 . Then, the CPU  1212  may write back the processed data to the external recording medium. 
     Various types of information such as various types of programs, data, tables, and databases may be stored in recording media and subjected to the information processing. The CPU  1212  may execute various types of processing on the data read from the RAM  1214  to write back a result to the RAM  1214 , the processing being described throughout the present disclosure, specified by an instruction sequence of the program, and including various types of operations, information processing, condition determinations, conditional branching, unconditional branching, information retrievals/replacements, or the like. Further, the CPU  1212  may search for information in the file, the database, or the like in the recording medium. For example, when a plurality of entries each having an attribute value of a first attribute associated with an attribute value of a second attribute are stored in the recording medium, the CPU  1212  may search, from the plurality of entries, for an entry that matches a condition in which the attribute value of the first attribute is specified, and read the attribute value of the second attribute stored in the entry, thereby obtaining the attribute value of the second attribute associated with the first attribute that satisfies a predetermined condition. 
     The program or software module described above may be stored on the computer  1200  or in a computer readable storage medium near the computer  1200 . Further, a recording medium such a hard disk or a RAM provided in a server system connected to a dedicated communication network or the Internet can be used as a computer readable storage medium, thereby providing the program to the computer  1200  via the network. 
     The flowchart and the blocks in the block diagrams according to the present embodiment may represent a step of a process in which an operation is executed or a “part” of a device which has a role of executing an operation. A specific step and “part” may be implemented by a dedicated circuit, a programmable circuit supplied along with a computer readable instruction stored on a computer readable storage medium, and/or a processor supplied along with the computer readable instruction stored on the computer readable storage medium. The dedicated circuit may include a digital and/or analog hardware circuit, or may include an integrated circuit (IC) and/or a discrete circuit. The programmable circuit may include, for example, a reconfigurable hardware circuit including logical AND, logical OR, logical XOR, logical NAND, logical NOR, and other logical operations, and a flip-flop, a register, and a memory element, such as a field programmable gate array (FPGA) and a programmable logic array (PLA). 
     The computer readable storage medium may include any tangible device capable of storing an instruction executed by an appropriate device, so that the computer readable storage medium having the instruction stored thereon includes a product including an instruction that may be executed in order to provide means to execute an operation specified by a flowchart or a block diagram. Examples of the computer readable storage medium may include an electronic storage medium, a magnetic storage medium, an optical storage medium, an electromagnetic storage medium, a semiconductor storage medium, or the like. More specific examples of computer readable storage media may include a floppy disc (registered trademark), a diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an electrically erasable programmable read-only memory (EEPROM), a static random access memory (SRAM), a compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a BLU-RAY (registered trademark) disc, a memory stick, an integrated circuit card, etc. 
     The computer readable instruction may include either of source code or object code written in any combination of one or more programming languages including: an assembler instruction, an instruction-set-architecture (ISA) instruction, a machine instruction, a machine dependent instruction, a microcode, a firmware instruction, state-setting data; or an object oriented programming language such as Smalltalk (registered trademark), JAVA (registered trademark), C++, or the like; and a conventional procedural programming language such as a “C” programming language or a similar programming language. 
     The computer readable instruction may be provided to a general purpose computer, a special purpose computer, or a processor or a programmable circuit of another programmable data processing apparatus locally or via a local area network (LAN), a wide area network (WAN) such as the Internet or the like so that the general purpose computer, the special purpose computer, or the processor or the programmable circuit of another programmable data processing apparatus executes the computer readable instruction to provide means to execute operations specified by the flowchart or the block diagram. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers, and the like. 
     In the above embodiment, a case in which the flying object communication antenna  124  described as one example of the fourth antenna is the omni directional trackable antenna has been mainly described by way of example, whereas the flying object communication antenna  124  is not limited to be omni directional trackable antenna. The fourth antenna may be an omni-directional antenna. In that case, it is preferable for a plurality of HAPSs  100  being at the same rank to use a frequency different from each other for communication using the fourth antenna. That is, the plurality of HAPSs  100  being at the same rank may use the frequency different from each other for executing wireless communication using the fourth antenna. 
     While the embodiments of the present invention have been described, the technical scope of the present invention is not limited to the above described embodiments. It is apparent to persons skilled in the art that various alterations and improvements can be added to the above-described embodiments. It is also apparent from the scope of the claims that the embodiments added with such alterations or improvements can be included in the technical scope of the present invention. 
     The operations, procedures, steps, stages etc. of every processing performed by an apparatus, system, program, and method shown in the claims, specification, or diagrams can be performed in any order as long as the order is not indicated by “prior to,” “before,” or the like and as long as the output from a previous processing is not used in a later processing. Even if the operation flow is described with phrases such as “first” or “next” in the claims, specification, or diagrams, they do not necessarily mean that the flow must be performed in this order. 
     EXPLANATION OF REFERENCES 
       10 : system; 
       20 : network; 
       30 : user terminal; 
       40 : gateway; 
       50 : management system; 
       82 : group; 
       84 : group; 
       100 : HAPS; 
       101 : cell; 
       102 : HAPS; 
       103 : cell; 
       104 : HAPS; 
       105 : cell; 
       106 : HAPS; 
       107 : cell; 
       110 : fuselage; 
       120 : central part; 
       121 : FL antenna; 
       122 : SL antenna; 
       123 : flying object communication antenna; 
       124 : flying object communication antenna; 
       125 : base; 
       126 : shaft; 
       127 : supporting portion; 
       128 : directional antenna; 
       130 : propeller; 
       140 : pod; 
       150 : solar panel; 
       200 : control apparatus; 
       210 : flight control unit; 
       220 : communication control unit; 
       222 : FL communication unit; 
       224 : SL communication unit; 
       226 : flying object communication unit; 
       228 : flying object communication unit; 
       230 : flying object identification unit; 
       240 : connection target determination unit; 
       250 : allocation example; 
       300 ,  302 ,  304 : coverage area; 
       1200 : computer; 
       1210 : host controller; 
       1212 : CPU; 
       1214 : RAM; 
       1216 : graphics controller; 
       1218 : display device; 
       1220 : input/output controller; 
       1222 : communication interface; 
       1224 : storage device; 
       1230 : ROM; 
       1240 : input/output chip