Patent Publication Number: US-2022232397-A1

Title: Control apparatus, computer readable storage medium, control method, and flying object

Description:
The contents of the following Japanese patent application(s) are incorporated herein by reference: 
     NO. 2019-202493 filed in JP on Nov. 7, 2019 
     NO. PCT/JP2020/031353 filed in WO on Aug. 19, 2020 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a control apparatus, a computer readable storage medium, a control method, and a flying object. 
     2. Related Art 
     A flying object having an antenna which flies through the stratosphere in order to provide a stratospheric platform has been proposed (see Patent document 1, for example). 
     RELATED ART LITERATURE 
     Patent Documents 
     
         
         Patent document 1: Japanese Patent Application Publication No. 2002-211496 
       
    
     Problem to be Solved 
     It is desirable to provide a technology with which flying object replacement can be appropriately executed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates one example of a HAPS  100 . 
         FIG. 2  schematically illustrates one example of a flow of replacement control processing by a control apparatus  300 . 
         FIG. 3  schematically illustrates one example of the flow of the replacement control processing by the control apparatus  300 . 
         FIG. 4  schematically illustrates one example of the flow of the replacement control processing by the control apparatus  300 . 
         FIG. 5  schematically illustrates one example of the flow of the replacement control processing by the control apparatus  300 . 
         FIG. 6  schematically illustrates another example of the flow of the replacement control processing by the control apparatus  300 . 
         FIG. 7  schematically illustrates another example of the flow of the replacement control processing by the control apparatus  300 . 
         FIG. 8  schematically illustrates another example of the flow of the replacement control processing by the control apparatus  300 . 
         FIG. 9  schematically illustrates another example of the flow of the replacement control processing by the control apparatus  300 . 
         FIG. 10  schematically illustrates one example of a functional configuration of the control apparatus  300 . 
         FIG. 11  schematically illustrates one example of a functional configuration of a control apparatus  130  included in the HAPS  100 . 
         FIG. 12  schematically illustrates one example of a hardware configuration of a computer  1200  configured to function as the control apparatus  130  or the control apparatus  300 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all combinations of the features described in the embodiments necessarily have to be essential to solving means of the invention. 
       FIG. 1  schematically illustrates one example of a high altitude platform station (HAPS)  100 . The HAPS  100  may be one example of a flying object having an antenna arranged to form a cell  120  on a ground and provide wireless communication service to a user terminal  30  in the cell  120 . 
     The HAPS  100  includes an object body  102 , a central part  104 , a propeller  106 , a pod  108 , and a solar panel  110 . A control apparatus  130  which is not illustrated in  FIG. 1  is arranged inside the central part  104 . 
     Electric power generated by the solar panel  110  is stored in one or more batteries arranged in at least any of the object body  102 , the central part  104 , and the pod  108 . The electric power stored in the battery is utilized by each of components included in the HAPS  100 . 
     The control apparatus  130  is configured to control flight of the HAPS  100 . The control apparatus  130  controls the flight of the HAPS  100  by, for example, controlling rotation of the propeller  106 . In addition, the control apparatus  130  may control the flight of the HAPS  100  by changing an angle of a flap or an elevator which are not illustrated in the drawing. The control apparatus  130  may include various types of sensors including positioning sensors such as a GPS sensor, a gyro sensor, and an acceleration sensor, and manage a location, a moving direction, and a moving speed of the HAPS  100 . 
     In addition, the control apparatus  130  is configured to control communication of the HAPS  100 . The control apparatus  130  provides the wireless communication service to the user terminal  30  on the ground by using a feeder link (FL) antenna  112  and a service link (SL) antenna  114 . The HAPS  100  may provide the wireless communication service to the user terminal  30  on the ground while flying in the stratosphere. 
     The FL antenna  112  is an antenna for feeder link. The control apparatus  130  forms a feeder link with a gateway  22  on the ground by the FL antenna  112 . The control apparatus  130  may access a network  20  via the gateway  22 . 
     The SL antenna  114  is an antenna for a service link. The SL antenna  114  may be an antenna having a lower directivity than the FL antenna  112 . The control apparatus  130  forms the cell  120  on the ground by the SL antenna  114 . The SL antenna  114  may be a multi beam antenna. The cell  120  may be multiple cells. 
     The user terminal  30  may be any terminal as long as it is a communication terminal capable of communicating with the HAPS  100 . For example, the user terminal  30  is a mobile phone such as a smartphone. The user terminal  30  may be a tablet terminal, a personal computer (PC), and the like. The user terminal  30  may be a so called Internet of Thing (IoT) device. The user terminal  30  may include any entities corresponding to a so called Internet of Everything (IoE). 
     The HAPS  100  is configured to provide the wireless communication service to the user terminal  30  by relaying, for example, communication between the user terminal  30  and the network  20 . The network  20  includes a mobile communication network. The mobile communication network may be in conformity to any of communication standards such as a  3 rd generation (3G) communication standard, a Long Term Evolution (LTE) communication standard, a 5th generation (5G) communication standard, and 6th generation (6G) and subsequent communication standards. The network  20  may include the Internet. 
     The HAPS  100  transmits data received from the user terminal  30  in the cell  120  to the network  20 , for example. In addition, when the HAPS  100  receives data addressed to the user terminal  30  in the cell  120  via the network  20 , for example, the HAPS  100  transmits the data to the user terminal  30 . 
     The HAPS  100  may access the network  20  via a communication satellite not illustrated in the drawing. In this case, the HAPS  100  has an antenna arranged to communicate with the communication satellite. 
     The HAPS  100  may be controlled by a control apparatus  300 . The HAPS  100  operates according to an instruction transmitted via the network  20  and the gateway  22  by the control apparatus  300 , for example. In addition, the HAPS  100  operates according to an instruction transmitted via the communication satellite by the control apparatus  300 , for example. 
     The control apparatus  300  is configured to control the HAPS  100  by transmitting an instruction. The control apparatus  300  may cause the HAPS  100  to circle in the sky above a target area  40  in order to cover the target area  40  on the ground by the cell  120 . In order for the HAPS  100  to cover the target area  40 , circling in the sky above the target area  40  may be described as fixed point flight. While flying in the sky above the target area  40  in a circular orbit, for example, the HAPS  100  adjusts an orientation direction of the FL antenna  112  to maintain the feeder link with the gateway  22 , and adjusts an orientation direction of the SL antenna  114  to maintain the cover of the target area  40  by the cell  120 . The control apparatus  300  may cause the HAPS  100  to carry out the fixed point flight for each of a plurality of target areas to cover each of the plurality of target areas. 
     Communication performed by the user terminal  30  via the HAPS  100  may be managed by a communication management apparatus  400 . The communication management apparatus  400  is arranged in a core network of a communication carrier, for example. The communication management apparatus  400  may provide communication information related to the communication performed by the user terminal  30  via the HAPS  100  to the outside. The communication information includes a reception radio wave situation by the user terminal  30 . The communication management apparatus  400  may acquire a transmission source of radio waves received by the user terminal  30  and a reception radio wave intensity by referring to, for example, a measurement report (may be referred to as MR) transmitted by the user terminal  30  to the HAPS  100 . The communication management apparatus  400  may refer to the MR, for example, by receiving from the HAPS  100  the MR received by the HAPS  100  from the user terminal  30 . In a case where the communication management apparatus  400  is arranged in a radio access network (RAN) and is a repeater type, the communication management apparatus  400  may directly refer to the MR. In addition, the communication information includes, for example, communication traffic of the communication executed by the user terminal  30  via the HAPS  100 . The communication management apparatus  400  may transmit the communication information to the control apparatus  300  via the network  20 . It should be noted that the control apparatus  300  and the communication management apparatus  400  may be integrated with each other. That is, the control apparatus  300  may function as the communication management apparatus  400 . 
     The control apparatus  300  according to the present embodiment executes replacement control processing of replacing the HAPS  100  covering the target area  40  with another HAPS  100 . For example, when maintenance of the HAPS  100  covering the target area  40  is to be carried out, the control apparatus  300  replaces the HAPS  100  with the other HAPS  100 . In addition, the control apparatus  300  replaces the HAPS  100  covering the target area  40  with the other HAPS  100  according to an instruction of an operator at any timing. 
     In wireless communication service in related art, radio base stations are installed on a steel tower, a rooftop of a building, and the like, and the service can be provided to a certain area on a semipermanent basis with stable power supply as long as a failure or the like does not occur, but in the case of the HAPS  100 , since the battery and the object body have a limited life or the like, it is necessary to periodically perform replacement with the other HAPS  100 . Upon replacement, it is necessary to perform cell switching without causing adverse effect to the user terminal  30  on the ground. For example, after radio waves of the HAPS  100  of a replacement target are stopped, when emission of radio waves of the new HAPS  100  is to be started, the user terminal  30  on the ground cannot temporarily utilize the service due to radio wave interruption, and also, since communication concurrently occurs at the start of the radio wave emission, congestion or the like may occur due to excessive load on the network. 
     For example, when a first HAPS  100  covering the target area  40  by the first cell  120  is to be replaced with a second HAPS  100 , the control apparatus  300  according to the present embodiment controls the second HAPS  100  in a manner that the second HAPS  100  forms the second cell  120  in a part of the target area  40  and continuously expands the second cell  120  while approaching a location corresponding the first HAPS  100  to continuously broaden a coverage of the target area  40  by the second cell  120 . The control apparatus  300  may control the first HAPS  100  and the second HAPS  100  in a manner that while a state where the first cell  120  is partially overlapped with the second cell  120  is maintained, the first HAPS  100  continuously reduces the first cell  120 , and the second HAPS  100  continuously expands the second cell  120 . 
       FIG. 2  to  FIG. 5  schematically illustrate one example of a flow of replacement control processing by the control apparatus  300 . Herein, for distinguishment, a HAPS to be replaced is set as a HAPS  100 , a replacing HAPS is set as a HAPS  200 , a cell formed by the HAPS  100  is set as a cell  120 , and a cell formed by the HAPS  200  is set as a cell  220 . 
     The control apparatus  300  controls the HAPS  100  and the HAPS  200  in a manner that the HAPS  100  is to be replaced with the HAPS  200  by appropriately transmitting instructions to the HAPS  100  and the HAPS  200 , for example. The control apparatus  300  may transmit a necessary instruction to each of the HAPS  100  and the HAPS  200  at necessary timing. In addition, the control apparatus  300  may transmit a series of instructions used for replacement control to the HAPS  100  and the HAPS  200  in advance. In this case, the HAPS  100  and the HAPS  200  operate according to a series of received instructions. Here, descriptions will be provided by mainly exemplifying a case where the control apparatus  300  appropriately transmits the instructions. 
     The control apparatus  300  understands locations of the HAPS  100  and the HAPS  200  by periodically receiving location information from each of the HAPS  100  and the HAPS  200 . First, the control apparatus  300  causes the HAPS  100  to set the cell  220  of the HAPS  200  as a neighboring cell for a cell setting of the HAPS  100 . 
     In addition, the control apparatus  300  causes the HAPS  200  to set the cell  120  of the HAPS  100  as a neighboring cell for a cell setting of the HAPS  200 . It should be noted that the cell setting of the HAPS  200  may be set by an operator on the ground or the like before the HAPS  200  takes off. 
     In this manner, by causing each of the HAPS  100  and the HAPS  200  to set the mutual cells as the neighboring cells, smooth cell reselection and handover from the cell  120  to the cell  220  can be performed. 
     First, the control apparatus  300  transmits an instruction to the HAPS  200  so as to move to a location corresponding to the HAPS  100 . The location corresponding to the HAPS  100  may be optionally determined. For example, a location above the HAPS  100  is determined as the location corresponding to the HAPS  100 . The HAPS  200  starts to move to the location corresponding to the HAPS  100  according to the received instruction. 
     The control apparatus  300  causes the HAPS  200  to form the cell  220  in a part of the target area  40  in response to a state where a distance between the HAPS  200  and the location corresponding to the HAPS  100  is equal to or shorter than a predetermined distance. The control apparatus  300  may cause the HAPS  200  to form the cell  220  in a part on an outer edge side of the target area  40 . For example, the control apparatus  300  instructs a location where the cell  220  is to be formed and a size of the cell  220  to the HAPS  200 . The HAPS  200  operates so as to form the cell  220  with the instructed size at the instructed location. It should be noted that the control apparatus  300  may transmit a parameter necessary to form the cell  220  to the HAPS  200 . For example, the control apparatus  300  instructs an emission direction of beam and a width of the beam to the HAPS  200 . The HAPS  200  adjusts the beam of the SL antenna  114  according to the received parameter. 
     The control apparatus  300  controls the HAPS  100  and the HAPS  200  in a manner that a reception radio wave intensity from the cell  220  by the user terminal  30  is higher than a reception radio wave intensity from the cell  120  by the user terminal  30  in a section where the cell  120  is overlapped with the cell  220 . For example, the control apparatus  300  causes the HAPS  200  to increase a radio wave output intensity or causes the HAPS  100  to decrease a radio wave output intensity. 
     The control apparatus  300  controls the HAPS  100  and the HAPS  200  in a manner that, for example, the HAPS  100  and the HAPS  200  output radio waves at a precalculated intensity to set the reception radio wave intensity from the cell  220  to be higher than the reception radio wave intensity from the cell  120 . In addition, for example, the control apparatus  300  acquires a reception radio wave situation by the user terminal  30  from the communication management apparatus  400  in the section where the cell  120  is overlapped with the cell  220 , and when the reception radio wave intensity from the cell  120  is higher than the reception radio wave intensity from the cell  220 , performs an adjustment or the like to cause the HAPS  200  to increase the radio wave output intensity such that the reception radio wave intensity from the cell  220  is to be higher than the reception radio wave intensity from the cell  120 . 
     When the control is performed to set the reception radio wave intensity from the cell  220  to be higher than the reception radio wave intensity from the cell  120  by the user terminal  30  in the overlapped section where the cell  120  is overlapped with the cell  220 , the cell reselection and handover of the user terminal  30  in the section can be realized, and connection of the user terminal  30  can be switched from the cell  120  to the cell  220 . 
     As illustrated in  FIG. 3  and  FIG. 4 , the control apparatus  300  controls the HAPS  100  and the HAPS  200  in a manner that while a state where the cell  120  is partially overlapped with the cell  220  is maintained, the HAPS  200  continuously expands the cell  220  to continuously broaden a coverage of the target area  40  by the cell  220 , and the HAPS  100  continuously reduces the cell  120  to continuously narrow a coverage of the target area  40  by the cell  120 . The control apparatus  300  may control the HAPS  200  in a manner that the cell  220  is continuously expanded from a first section on an outer edge side of the target area  40  where the cell  220  is formed towards a second section facing the first section on the outer edge side of the target area  40 , and may control the HAPS  100  in a manner that the cell  120  is continuously reduced from the first section towards the second section. 
     The control apparatus  300  may cause the HAPS  100  to reduce the cell  120  while confirming that the user terminal  30  located in the overlapped section where the cell  120  is overlapped with the cell  220  switches the connection destination from the cell  120  to the cell  220 . For example, the control apparatus  300  causes the HAPS  100  to reduce the cell  120  in a manner that after all the user terminals  30  present in the cell  120  in the overlapped section where the cell  120  is overlapped with the cell  220  in the target area  40  switch the connection destination to the cell  220  by the cell reselection or handover, the cell  120  is to depart from the overlapped section. 
     As illustrated in  FIG. 5 , after an entirety of the target area  40  is covered by the cell  220 , the control apparatus  300  may control the HAPS  100  to stop formation of the cell  120 . After the entirety of the target area  40  is covered by the cell  220 , the control apparatus  300  may control the HAPS  100  in a manner that after it is confirmed that the connection destination of all the user terminals  30  in the target area  40  is switched from the cell  120  to the cell  220 , the formation of the cell  120  is to be stopped. 
     The control apparatus  300  then controls the HAPS  100  so as to move to a predetermined location on the ground. The predetermined location may be optionally determined, and for example, a location in the vicinity of a facility for carrying out maintenance of the HAPS  100 , a storage for storing the HAPS  100 , or the like may be set. 
     When the above described replacement processing is executed, it is possible to cause the HAPS  100  to stop the formation of the cell  120  after the user terminal  30  present in the cell  120  switches the connection destination from the cell  120  to the cell  220 , and the user terminal  30  can receive the service by the HAPS  200  in succession to the service by the HAPS  100 . That is, in accordance with the control apparatus  300  according to the present embodiment, temporary service interruption or temporary service quality degradation occurring in the user terminal  30  can be suppressed. 
     The example in which the cell  220  is expanded from a part on the outer edge side of the target area  40  has been described with reference to  FIG. 2  to  FIG. 5 , but is not limited to this. The control apparatus  300  may cause the HAPS  200  to expand the cell  220  from a part inside the target area  40 . 
       FIG. 6  and  FIG. 7  schematically illustrate another example of the flow of the replacement control processing by the control apparatus  300 . Here, a different aspect from  FIG. 2  to  FIG. 5  will be mainly described. In  FIG. 6  and  FIG. 7 , an example will be illustrated in which after the HAPS  200  moves to a location above the HAPS  100 , the HAPS  200  forms the cell  220  inside the target area  40  and expands the cell  220 . 
     In a state where the HAPS  100  covers the entirety of the target area  40  by the cell  120 , the control apparatus  300  causes the HAPS  200  to form the cell  220  in a part inside the target area  40 . Then, in a state where the HAPS  100  covers the entirety of the target area  40  by the cell  120 , the control apparatus  300  causes the HAPS  200  to continuously expand the cell  220 . The control apparatus  300  controls the HAPS  100  and the HAPS  200  in a manner that the reception radio wave intensity from the cell  220  is higher than the reception radio wave intensity from the cell  120  by the user terminal  30  located in the overlapped section where the cell  120  is overlapped with the cell  220  in the target area  40 . 
     The control apparatus  300  controls the HAPS  100  and the HAPS  200  in a manner that, for example, the radio waves are output at a precalculated intensity to set the reception radio wave intensity from the cell  220  to be higher than the reception radio wave intensity from the cell  120  by the user terminal  30 . In addition, for example, the control apparatus  300  acquires the reception radio wave situation by the user terminal  30  in the section where the cell  120  is overlapped with the cell  220  from the communication management apparatus  400 , and when the reception radio wave intensity from the cell  120  is higher than the reception radio wave intensity from the cell  220 , performs an adjustment or the like to cause the HAPS  200  to increase the radio wave output intensity such that the reception radio wave intensity from the cell  220  is to be higher than the reception radio wave intensity from the cell  120  by the user terminal  30 . 
     After the entirety of the target area  40  is covered by the cell  220 , the control apparatus  300  may control the HAPS  100  to stop the formation of the cell  120 . After the entirety of the target area  40  is covered by the cell  220 , the control apparatus  300  may control the HAPS  100  in a manner that after it is confirmed that the connection destination of all the user terminals  30  in the target area  40  is switched from the cell  120  to the cell  220 , the formation of the cell  120  is to be stopped. The control apparatus  300  then controls the HAPS  100  so as to move to the predetermined location on the ground. 
       FIG. 8  schematically illustrates another example of the flow of the replacement control processing by the control apparatus  300 . In  FIG. 8 , the flow of the replacement control processing will be described in a case where the HAPS  100  forms the cell  120  configured by a plurality of sub cells  121 , and the HAPS  200  is caused to form the cell  220  configured by a plurality of sub cells  221 . Here, a part different from the example illustrated in  FIG. 2  to  FIG. 5  will be mainly described. 
     First, the control apparatus  300  controls the HAPS  200  in a manner that each of the plurality of sub cells  221  is formed in a part on an outer edge side of an area covered by each of the plurality of sub cells  121 . The control apparatus  300  then control the HAPS  100  and the HAPS  200  in a manner that while a state where each of the plurality of sub cells  121  is partially overlapped with each of the plurality of sub cells  221  is maintained, the HAPS  100  continuously reduces each of the plurality of sub cells  121 , and the HAPS  200  expands each of the plurality of sub cells  221 . 
       FIG. 9  schematically illustrates another example of the flow of the replacement control processing by the control apparatus  300 . In  FIG. 9 , the flow of the replacement control processing will be described in a case where the HAPS  100  forms the cell  120  configured by the plurality of sub cells  121 , and the HAPS  200  is caused to form the cell  220  configured by the plurality of sub cells  221 . Here, a part different from the example illustrated in  FIG. 6  and  FIG. 7  will be mainly described. 
     The control apparatus  300  controls the HAPS  200  in a manner that in a state where the HAPS  100  covers the entirety of the target area  40  by the plurality of sub cells  121 , each of the plurality of sub cells  221  is formed in a part inside the area covered by each of the plurality of sub cells  121 . The control apparatus  300  then controls the HAPS  200  so as to continuously expand each of the plurality of sub cells  221 . 
       FIG. 10  schematically illustrates one example of a functional configuration of the control apparatus  300 . The control apparatus  300  includes an instruction acceptance unit  312 , a communication information acquisition unit  314 , a flying object communication unit  320 , and an control unit  330 . 
     The instruction acceptance unit  312  is configured to accept various types of instructions. The instruction acceptance unit  312  accepts an instruction for designating the target area  40 , for example. In addition, for example, the instruction acceptance unit  312  accepts an instruct for designating a trajectory for the HAPS  100  to perform the fixed point flight. In addition, for example, the instruction acceptance unit  312  accepts an instruction for designating a location where the cell  120  is to be formed. 
     The instruction acceptance unit  312  may accept an instruction input via an operation unit included in the control apparatus  300 . In addition, the instruction acceptance unit  312  may accept an instruction received via the network  20 , via a communication unit included in the control apparatus  300 . 
     The communication information acquisition unit  314  is configured to acquire communication information related to communication in the wireless communication service provided by the cell  120  formed by the HAPS  100  to the user terminal  30 . The communication information acquisition unit  314  acquires, for example, a reception radio wave situation by the user terminal  30 . In addition, the communication information acquisition unit  314  acquires, for example, information related to the communication traffic. The communication information acquisition unit  314  may receive the communication information from the communication management apparatus  400 . 
     The flying object communication unit  320  is configured to communicate with the HAPS  100 . The flying object communication unit  320  may communicate with the HAPS  100  via the network  20  and the gateway  22 . The flying object communication unit  320  may communicate with the HAPS  100  via a communication satellite. 
     The flying object communication unit  320  transmits, for example, the instruction accepted by the instruction acceptance unit  312  to the HAPS  100 . In addition, the flying object communication unit  320  receives, for example, various types of information from the HAPS  100 . The flying object communication unit  320  receives, for example, location information of the HAPS  100  from the HAPS  100 . 
     The control unit  330  is configured to execute various types of controls. The control unit  330  performs various types of settings for the HAPS  100  via the flying object communication unit  320 , for example. When, for example, replacement of the first HAPS  100  with the second HAPS  100  is to be performed, the control unit  330  transmits cell identification information of the cell  120  of the second HAPS  100  to the first HAPS  100  to cause the first HAPS  100  to set the second cell  120  as a neighboring cell. In addition, the control unit  330  transmits cell identification information of the cell  120  of the first HAPS  100  to the second HAPS  100  to cause the second HAPS  100  to set the first cell  120  as a neighboring cell. The control unit  330  may be one example of a setting control unit. 
     The control unit  330  may execute replacement control processing of the HAPS  100 . The control unit  330  may be one example of the replacement control unit. The control unit  330  may control the HAPS  100  by transmitting various types of instructions to the HAPS  100  via the flying object communication unit  320 . The control unit  330  may transmit a plurality of instructions to the HAPS  100  in accordance with each timing, and may also transmit a plurality of instructions to the HAPS  100  at once. 
     The control unit  330  may control the replacement of the first HAPS  100  covering the target area  40  on the ground by the first cell  120  with the second HAPS  100 . For example, the control unit  330  controls the second HAPS  100  in a manner that after the second HAPS  100  moving towards a location corresponding to a location of the first HAPS  100  is caused to form the second cell  120  in a part of the target area  40 , the second cell  120  is continuously expanded to continuously broaden the coverage of the target area  40  by the second cell  120 . 
     The control unit  330  may control the second HAPS  100  in a manner that after the second cell  120  is formed in a part of the target area  40 , the second HAPS  100  continuously expands the second cell  120  while moving towards the location corresponding to the location of the first HAPS  100  to continuously broaden the coverage of the target area  40  by the second cell  120 . The control unit  330  may control the first HAPS  100  and the second HAPS  100  in a manner that while a state where the first cell  120  is partially overlapped with the second cell  120  is maintained, the first HAPS  100  continuously reduces the first cell  120 , and the second HAPS  100  continuously expands the second cell  120 . 
     The control unit  330  may control the first HAPS  100  in a manner that the first HAPS  100  continuously expands the first cell  120  by beamforming. For example, for the first HAPS  100 , the control unit  330  transmits an instruction for continuously expanding the first cell  120  by beamforming to the first HAPS  100 . In addition, for example, the control unit  330  may transmit a control parameter of beamforming for continuously expanding the first cell  120  to the first HAPS  100 . For example, the control unit  330  determines a direction and a width of beam from a location of the target area  40  and a location and a flight direction of the first HAPS  100 , and generates and transmits a control parameter of beamforming for realizing the direction and the width of the beam to the first HAPS  100 . 
     The control unit  330  may control the second HAPS  100  in a manner that the second HAPS  100  continuously reduces the second cell  120  by beamforming. For example, for the second HAPS  100 , the control unit  330  transmits an instruction for continuously reducing the second cell  120  by beamforming to the second HAPS  100 . In addition, for example, the control unit  330  may transmit a control parameter of beamforming for continuously reducing the second cell  120  to the second HAPS  100 . The control unit  330  determines a direction and a width of beam from, for example, a location of the target area  40  and a location and a flight direction of the second HAPS  100 , and generates and transmits a control parameter of beamforming for realizing the direction and the width of the beam to the second HAPS  100 . 
     The control unit  330  may control the second HAPS  100  in a manner that the second HAPS  100  forms the second cell  120  in a first section on the outer edge side of the target area  40 , and continuously expands the second cell  120  from the first section towards a second section facing the first section on the outer edge side of the target area  40 . In addition, the control unit  330  may control the first HAPS  100  in a manner that the first HAPS  100  continuously reduces the first cell  120  from the first section towards the second section. After the user terminal  30  present in the first cell  120  in the overlapped section where the first cell  120  is overlapped with the second cell  220  in the target area  40  switches the connection destination to the second cell  120 , the control unit  330  may cause the first HAPS  100  to reduce the first cell  120  such that the first cell  120  is to depart from the overlapped section. 
     The control unit  330  may control the first HAPS  100  and the second HAPS  100  in a manner that at a speed at which fluctuation per unit time of a number of at least one user terminal  30  that switches the connection destination from the first cell  120  to the second cell  120  is within a predetermined range, the first HAPS  100  reduces the first cell  120 , and the second HAPS  100  expands the second cell  120 . The control unit  330  acquires a switching situation of the connection destination from the first cell  120  to the second cell  120  from the communication management apparatus  400  via the communication information acquisition unit  314  while, for example, executing the reduction of the first cell  120  and the expansion of the second cell  120 . The control unit  330  then continually identifies the number per unit time of the user terminals  30  that switch the connection destination from the first cell  120  to the second cell  120 . In a case where the number per unit time which is continually identified is about to exceed a predetermined upper limit number, the control unit  330  may decrease at least any of a reduction speed of the first cell  120  and an expansion speed of the second cell  120 . In addition, in a case where the number per unit time which is continually identified is about to fall below a predetermined lower limit number, the control unit  330  may increase at least any of the reduction speed of the first cell  120  and the expansion speed of the second cell  120 . With this configuration, it is possible to avoid excessive increase or decrease in the number of user terminals  30  that switch the connection destination from the first cell  120  to the second cell  120  in a same time period, and disturbance in a communication environment can be suppressed. 
     The control unit  330  may control the first HAPS  100  and the second HAPS  100  in a manner that a reduction speed of the first cell  120  and an expansion speed of the second cell  120  in an area where communication by the user terminals  30  is more congested are slower than a reduction speed of the first cell  120  and an expansion speed of the second cell  120  in an area where communication by the user terminals  30  is less congested in the target area  40 . The control unit  330  acquires the communication traffic of the communication by the user terminals  30  from the communication management apparatus  400  via the communication information acquisition unit  314  in each section of the target area  40 , for example. The control unit  330  then controls the first HAPS  100  and the second HAPS  100  in a manner that a reduction speed of the first cell  120  and an expansion speed of the second cell  120  in an area where there is more communication traffic are slower than a reduction speed of the first cell  120  and an expansion speed of the second cell  120  in an area where there is less communication traffic. With this configuration, it is possible to suppress deterioration in user sensory quality due to adverse effect in the communication environment which is caused by frequent switching of the connection destination despite a state where the communication is congested, and the replacement of the HAPS  100  can be promptly realized at timing at which the communication environment is hardly affected. 
     The control unit  330  may control the first HAPS  100  in a manner that after the entirety of the target area  40  is covered by the second cell  120 , the first HAPS  100  stops the formation of the first cell  120 . 
     The control unit  330  may determine timing at which the replacement control processing of the first HAPS  100  with the second HAPS  100  is to be executed based on various types of situations. For example, the control unit  330  confirms a fluctuation situation of the communication traffic for one day in the target area  40  covered by the first HAPS  100  of the replacement target based on communication information acquired by the communication information acquisition unit  314  from the communication management apparatus  400 , and selects a time slot with less communication traffic as a time slot in which the replacement control processing is to be executed. 
     The control unit  330  may determine the timing at which the replacement control processing is to be executed according to a type of the target area  40  covered by the first HAPS  100  of the replacement target. For example, the control unit  330  determines the timing at which the replacement control processing is to be executed at night in a case where the target area  40  is a metropolitan important area, and determines the timing at which the replacement control processing is to be executed without temporal restrictions in a case where the target area  40  is not an important area. 
     When the first cell  120  is configured by a plurality of sub cells  121 , the control unit  330  may control the first HAPS  100  and the second HAPS  100  in a manner that while a state where each of the plurality of sub cells  121  configuring the first cell  120  is partially overlapped with each of a plurality of sub cells  121  configuring the second cell  120  is maintained, the first HAPS  100  continuously reduces each of the plurality of sub cells  121  of the first cell  120 , and the second HAPS  100  continuously expands each of the plurality of sub cells  121  of the second cell  120 . 
     The control unit  330  may control the first HAPS  100  and the second HAPS  100  in a manner that in a state where the first HAPS  100  covers the entirety of the target area  40  by the first cell  120 , the second HAPS  100  continuously expands the second cell  120 . 
     The control unit  330  may control the second HAPS  100  in a manner that the second HAPS  100  forms the second cell  120  in a first section inside the target area  40 , and continuously expands the second cell  120  from the first section towards the outward direction of the target area. The control unit  330  may control the first HAPS  100  and the second HAPS  100  in a manner that the reception radio wave intensity from the second cell  120  is higher than the reception radio wave intensity from the first cell  120  by the user terminal  30  located in the overlapped section where the first cell  120  is overlapped with the second cell  120  in the target area  40 . 
     When the first cell  120  is configured by the plurality of sub cells  121 , the control unit  330  may control the first HAPS  100  and the second HAPS  100  in a manner that in a state where the first HAPS  100  covers the entirety of the target area  40  by the plurality of sub cells  121  configuring the first cell  120 , the second HAPS  100  forms the second cell  120  configured by a plurality of sub cells  121  each of which is included in each of the plurality of sub cells  121  of the first cell  120 , and continuously expands the plurality of sub cells  121  of the second cell  120 . 
       FIG. 11  schematically illustrates one example of a functional configuration of the control apparatus  130  included in the HAPS  100 . The control apparatus  130  includes a wireless communication unit  132  and a control unit  140 . 
     The wireless communication unit  132  is configured to execute various types of communications. The wireless communication unit  132  may form a feeder link with the gateway  22  on the ground by using the FL antenna  112 . The wireless communication unit  132  may access the network  20  via the gateway  22 . The wireless communication unit  132  communicates with the control apparatus  300  and the communication management apparatus  400  via, for example, the gateway  22  and the network  20 . 
     The wireless communication unit  132  may form the cell  120  on the ground by using the SL antenna  114 . The wireless communication unit  132  may communicate with the user terminal  30  by forming a service link with the user terminal  30 . The wireless communication unit  132  may execute communication with a communication satellite. 
     The control unit  140  is configured to control flight of the HAPS  100 . In addition, the control unit  140  is configured to control communication by the wireless communication unit  132 . The control unit  140  may control the flight and communication of the HAPS  100  according to an instruction from the control apparatus  300 . 
     The control unit  140  has a communication information acquisition unit  142  and a replacement control unit  144 . The communication information acquisition unit  142  is configured to acquire communication information related to communication in the wireless communication service provided by the cell  120  formed by the HAPS  100  to the user terminal  30 . The communication information acquisition unit  142  acquires, for example, a reception radio wave situation by the user terminal  30 . In addition, the communication information acquisition unit  142  acquires, for example, information related to communication traffic. The communication information acquisition unit  142  may acquire communication information from the communication management apparatus  400  via the wireless communication unit  132 . 
     The replacement control unit  144  is configured to control replacement with another HAPS  100 . When, for example, its own flying object (the HAPS  100  to which the replacement control unit  144  is mounted may be referred to as its own flying object) covers the target area  40  by the first cell  120  formed by the wireless communication unit  132  while performing fixed point flight in the sky above the target area  40  on the ground, the replacement control unit  144  executes replacement control processing of replacing its own flying object with the other HAPS  100  to cover the target area  40 . 
     The replacement control unit  144  controls its own flying object in a manner that the first cell  120  is continuously reduced in accordance with a state where the other HAPS  100  forms the second cell  120  in a part of the target area  40  and continuously expands the second cell  120  while moving towards a location corresponding to a location of its own flying object. The replacement control unit  144  may control the SL antenna  114  so as to continuously reduce the first cell  120  by beamforming. 
     The replacement control unit  144  may control its own flying object in a manner that in accordance with a state where the other HAPS  100  forms the second cell  120  in a first section on the outer edge side of the target area  40  and continuously expands the second cell  120  from the first section towards a second section facing the first section on the outer edge side of the target area  40 , the first cell  120  is continuously reduced from the first section towards the second section. 
     The replacement control unit  144  may control its own flying object in a manner that while a state where the first cell  120  is partially overlapped with the second cell  120  is maintained, the first cell  120  is continuously reduced. The replacement control unit  144  may control its own flying object in a manner that after the user terminal  30  present in the first cell  120  in the overlapped section where the first cell  120  is overlapped with the second cell  120  in the target area  40  switches the connection destination to the second cell  120 , the first cell  120  is reduced to cause the first cell  120  to depart from the overlapped section. 
     The replacement control unit  144  may control its own flying object so as to reduce the first cell  120  at a speed at which fluctuation per unit time of a number of at least one user terminal  30  that switches the connection destination from the first cell  120  to the second cell  120  is within a predetermined range. The replacement control unit  144  may also control its own flying object in a manner that a reduction speed of the first cell  120  in an area where communication by the user terminals  30  is more congested is slower than a reduction speed of the first cell  120  in an area where communication by the user terminals  30  is less congested in the target area  40 . The replacement control unit  144  may control its own flying object in a manner that after the second cell  120  covers the entirety of the target area  40 , the formation of the first cell  120  is to be stopped. 
     The replacement control unit  144  may execute various types of controls according to an instruct of the control apparatus  300 , for example. In addition, the replacement control unit  144  may execute various types of controls while communicating with the other HAPS  100 . Its own flying object may communicate with the other HAPS  100  via the gateway  22  and the network  20 , via a communication satellite, or via the control apparatus  300 . 
     The replacement control unit  144  may also execute replacement processing of replacing the other HAPS  100  covering the target area  40  on the ground by the first cell  120  with its own flying object to cover the target area  40 . The replacement control unit  144  may control its own flying object in a manner that, for example, after the second cell  120  is formed in a part of the target area  40 , the second cell  120  is continuously expanded to continuously broaden a coverage of the target area  40  by the second cell  120 . 
     The replacement control unit  144  may control its own flying object in a manner that after the second cell  120  is formed, its own flying object continuously expands the second cell  120  while moving towards a location corresponding to a location of the other HAPS  100  to continuously broaden the coverage of the target area  40  by the second cell  120 . The replacement control unit  144  may control the SL antenna  114  so as to continuously expand the second cell  120  by beamforming. 
     The replacement control unit  144  may control its own flying object in a manner that while a state where the first cell  120  is partially overlapped with the second cell  120  is maintained, the second cell  120  is continuously expanded. The replacement control unit  144  may control its own flying object in a manner that the second cell  120  is formed in a first section on the outer edge side of the target area  40 , and the second cell  120  is continuously expanded from the first section towards a second section facing the first section on the outer edge side of the target area  40 . 
     The replacement control unit  144  may control its own flying object so as to continuously expand the second cell  120  at a speed at which fluctuation per unit time of a number of at least one user terminal  30  that switches the connection destination from the first cell  120  to the second cell  120  is within a predetermined range. The replacement control unit  144  may also control its own flying object in a manner that an expansion speed of the second cell  120  in an area where communication by the user terminals  30  is more congested is set to be slower than an expansion speed of the second cell  120  in an area where communication by the user terminals  30  is less congested in the target area  40 . 
     The replacement control unit  144  may also control its own flying object so as to continuously expand the second cell  120  in a state where the other HAPS  100  covers the entirety of the target area  40  by the first cell  120 . The replacement control unit  144  may control its own flying object in a manner that the second cell  120  is formed in a first section inside the target area  40 , and the second cell  120  is continuously expanded from the first section towards an outward direction of the target area  40 . The replacement control unit  144  may control its own flying object in a manner that the reception radio wave intensity from the second cell  120  is higher than the reception radio wave intensity from the first cell  120  by the user terminal  30  in a location in the overlapped section where the first cell  120  is overlapped with the second cell  120  in the target area  40 . 
       FIG. 12  schematically illustrates one example of a hardware configuration of a computer  1200  which functions as the control apparatus  130  or the control apparatus  300 . A program that is installed in the computer  1200  can cause the computer  1200  to function as one or more units in an apparatus of the present embodiment, or cause the computer  1200  to execute operations associated with the apparatus of the present embodiment or the one or more units thereof, and/or cause the computer  1200  to execute processes of the present embodiment or steps thereof. Such program may be executed by a CPU  1212  so as to cause the computer  1200  to execute certain operations associated with some or all of the blocks of flowcharts and block diagrams described herein. 
     The computer  1200  in accordance with the present embodiment includes a CPU  1212 , a RAM  1214 , and a graphics controller  1216 , which are mutually connected by a host controller  1210 . The computer  1200  also includes input and output units such as a communication interface  1222 , a storage apparatus  1224 , a DVD drive and an IC card drive, which are connected to the host controller  1210  via an input and output controller  1220 . The storage apparatus  1224  may be a hard disk drive, a solid state drive, and the like. The computer  1200  also includes legacy input and output units such as a ROM  1230  and a keyboard, which are connected to the input and output controller  1220  via an input and output chip  1240 . 
     The CPU  1212  is configured to operate according to programs stored in the ROM  1230  and the RAM  1214 , thereby controlling each unit. The graphics controller  1216  is configured to acquire image data generated by the CPU  1212  on a frame buffer or the like provided in the RAM  1214  or in itself, and to cause the image data to be displayed on a display device  1218 . 
     The communication interface  1222  is configured to communicate with other electronic devices via a network. The storage apparatus  1224  is configured to store programs and data used by the CPU  1212  within the computer  1200 . The DVD drive is configured to read the programs or the data from a DVD-ROM or the like, and to provide the storage apparatus  1224  with the programs or the data. The IC card drive is configured to read programs and data from an IC card, and/or to write programs and data into the IC card. 
     The ROM  1230  is configured to store therein a boot program or the like that is executed by the computer  1200  at the time of activation, and/or a program depending on the hardware of the computer  1200 . The input and output chip  1240  may also be configured to connect various input and output units to the input and output controller  1220  via a USB port, a parallel port, a serial port, a keyboard port, a mouse port and the like. 
     A program is provided by a computer readable storage medium such as a DVD-ROM or an IC card. The program is read from the computer readable storage medium, is installed into the storage apparatus  1224 , RAM  1214 , or ROM  1230 , which are also examples of computer readable storage medium, and is executed by the CPU  1212 . The information processing described in these programs is read into the computer  1200 , resulting in cooperation between a program and the above mentioned various types of hardware resources. An apparatus or method may be constituted by realizing the operation or processing of information in accordance with the usage of the computer  1200 . 
     For example, when communication is performed between the computer  1200  and an external device, the CPU  1212  may execute a communication program loaded onto the RAM  1214  to instruct communication processing to the communication interface  1222 , based on the processing described in the communication program. The communication interface  1222 , under control of the CPU  1212 , reads transmission data stored on a transmission buffer region provided in a recording medium such as the RAM  1214 , the storage apparatus  1224 , the DVD-ROM, or the IC card, and transmits the read transmission data to a network or writes reception data received from a network to a reception buffer region or the like provided on the recording medium. 
     In addition, the CPU  1212  may be configured to cause all or a necessary portion of a file or a database, which has been stored in an external recording medium such as the storage apparatus  1224 , the DVD drive (DVD-ROM), the IC card and the like, to be read into the RAM  1214 , thereby executing various types of processing on the data on the RAM  1214 . The CPU  1212  may be configured to then 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 the recording medium to undergo information processing. The CPU  1212  may also be configured to execute various types of processing on the data read from the RAM  1214 , which includes various types of operations, processing of information, condition judging, conditional branching, unconditional branching, search/replacement of information and the like described in the present disclosure and designated by an instruction sequence of programs, and to write the result back to the RAM  1214 . The CPU  1212  may also be configured to search for information in a file, a database, etc., 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, is stored in the recording medium, the CPU  1212  may search for an entry matching the condition whose attribute value of the first attribute is designated, from the plurality of entries, 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 satisfying the predetermined condition. 
     The above described program or software modules may be stored in the computer readable storage medium on or near the computer  1200 . In addition, a recording medium such as a hard disk or a RAM provided in a server system connected to a dedicated communication network or the Internet can be used as the computer readable storage medium, thereby providing the programs to the computer  1200  via the network. 
     In the present embodiment, blocks of the flowcharts and the block diagrams may represent steps of processes in which operations are executed or units of apparatuses responsible for performing operations. Certain steps and units may be implemented by dedicated circuitry, programmable circuitry supplied with computer readable instructions stored on computer readable storage media, and/or processors supplied with computer readable instructions stored on computer readable storage media. Dedicated circuitry may include digital and/or analog hardware circuits and may include integrated circuits (IC) and/or discrete circuits. Programmable circuitry may include, for example, reconfigurable hardware circuits comprising logical AND, OR, XOR, NAND, NOR, and other logical operations, flip-flops, registers, and memory elements, such as field-programmable gate arrays (FPGA), programmable logic arrays (PLA), etc. 
     Computer readable storage medium may include any tangible device that can store instructions for execution by a suitable device, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which can be performed to create means for performing operations specified in the flowcharts or block diagrams. Examples of a 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, etc. More specific examples of a computer readable storage medium may include a floppy (registered trademark) disk, 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. 
     Computer readable instructions may include any of assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk (registered trademark), JAVA (registered trademark), C++, etc., and conventional procedural programming languages, such as the “C” programming language or similar programming languages. 
     Computer readable instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, or to programmable circuitry, locally or via a local area network (LAN), wide area network (WAN) such as the Internet, etc., so that the processor of the general purpose computer, special purpose computer, or other programmable data processing apparatus, or the programmable circuitry performs the computer readable instructions to create means for performing operations specified in the flowcharts or block diagrams. Examples of processors include computer processors, processing units, microprocessors, digital signal processors, controllers, microcontrollers, etc. 
     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 or 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, and the like of each process performed by an apparatus, system, program, and method illustrated in the claims, embodiments, 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 process is not used in a later process. Even if the process flow is described using phrases such as “first” or “next” in the claims, embodiments, or diagrams, it does not necessarily mean that the process must be performed in this order. 
     EXPLANATION OF REFERENCES 
       20 : network,  22 : gateway,  30 : user terminal,  40 : target area,  100 : HAPS,  102 : object body,  104 : central part,  106 : propeller,  108 : pod,  110 : solar panel,  112 : FL antenna,  114 : SL antenna,  120 : cell,  121 : sub cell,  200 : HAPS,  220 : cell,  221 : sub cell,  300 : control apparatus,  312 : instruction acceptance unit,  314 : communication information acquisition unit,  320 : flying object communication unit,  330 : control unit,  400 : communication management apparatus,  1200 : computer,  1210 : host controller,  1212 : CPU,  1214 : RAM,  1216 : graphics controller,  1218 : display device,  1220 : input and output controller,  1222 : communication interface,  1224 : storage apparatus,  1230 : ROM,  1240 : input and output chip