Patent Description:
Flying bodies have been known that have antennas and fly in the stratosphere for providing stratospheric platforms (see, e.g., <CIT>). <CIT> describes that a first radio signal is received via a first satellite reception path, for example, an antenna or spot beam, which serves a satellite cell. The received first radio signal includes a desired satellite uplink signal transmitted from a first source using a frequency assigned to the satellite cell and an interfering signal transmitted from at least one second source using the frequency assigned to the satellite cell. A second radio signal is received via a second satellite reception path, for example, via another antenna or spot beam of the system and/or via a satellite antenna beam of another system. The second radio signal includes a measure of the interfering signal. The first and second radio signals are processed to recover the desired satellite uplink signal.

When providing a wireless communication service to a plurality of user terminal on the ground by a flying body. it is desirable to provide a technique which is capable of suppressing reduction of communication quality.

While the present invention will be described below by means of the embodiments of the invention, these embodiments below are not intended to limit the invention defined by the claims. All combinations of features set forth in the embodiments are not necessarily essential to the solutions of the present invention.

<FIG> shows schematically an example of a flying body <NUM>. The flying body <NUM> has a body unit <NUM>, a main wing unit <NUM>, propellers <NUM>, skids <NUM>, wheels <NUM>, and solar cell panels <NUM>.

The body unit <NUM> comprises a wireless communication device <NUM>, as well as a battery and a flight control apparatus that are not shown. The battery accumulates power generated by the solar cell panels <NUM>. The flight control apparatus controls flights of the flying body <NUM>. The flight control apparatus, for example, rotates the propellers <NUM> using the power accumulated in the battery to fly the flying body <NUM>. The wireless communication device <NUM> radiates a plurality of beams toward the ground, thereby forming a multi-cell <NUM> composed of a plurality of cells <NUM> to provide wireless communication services to a user terminal <NUM> in the multi-cell <NUM>. The wireless communication device <NUM> and the flight control apparatus may be integral with each other.

The flying body <NUM>, for example, flies in the stratosphere to provide the wireless communication services to the user terminal <NUM> on the ground. The flying body <NUM> may function as a stratosphere platform.

The user terminal <NUM> may be any terminal as long as it is a communication terminal communicable with the flying body <NUM>. For example, the user terminal <NUM> is a mobile phone such as a smart phone. The user terminal <NUM> may be such as a tablet terminal and a PC (Personal Computer). The user terminal <NUM> may be a so-called IoT (Internet of Thing) device. The user terminal <NUM> may include any device applicable to a so-called IoE (Internet of Everything).

The flying body <NUM>, for example, covers the ground area by the multi-cell <NUM> while circulating above the ground area targeted for coverage. The flying body <NUM> circling around above the ground area may be described as a fixed point flight. In addition, the flying body <NUM> covers the whole ground area by moving above the ground area while covering a portion of the ground area targeted for coverage by the multi-cell <NUM>.

The flying body <NUM>, for example, relays communication between the user terminal <NUM> and a network <NUM> on the ground to provide wireless communication services to the user terminal <NUM>. The network <NUM> may include a core network provided by a telecommunication carrier. The core network may comply with any mobile communication system, and for example, complies with a <NUM> (3rd Generation) communication system, an LTE (Long Term Evolution) communication system, a <NUM> (4th Generation) communication system, and a <NUM> (5th Generation) communication system and subsequent mobile communication systems. The network <NUM> may include the Internet.

The flying body <NUM>, for example, communicates with the network <NUM> on the ground via a gateway <NUM> in the multi-cell <NUM> among the gateways <NUM> arranged on various locations on the ground. In addition, for example, the flying body <NUM> communicates with the network <NUM> via a communication satellite <NUM>. In this case, the flying body <NUM> has an antenna for communicating with the communication satellite <NUM>.

The flying body <NUM>, for example, transmits data received from the user terminal <NUM> in the multi-cell <NUM> to the network <NUM>. In addition, for example, when data directed to the user terminal <NUM> in the multi-cell <NUM> is received via the network <NUM>, the flying body <NUM> transmits such data to the user terminal <NUM>.

The flying body <NUM> may be controlled by a management apparatus <NUM> on the ground. The flying body <NUM>, for example, flies or forms the multi-cell <NUM> in accordance with an instruction transmitted by the management apparatus <NUM> via the network <NUM> and the gateway <NUM>. The management apparatus <NUM> may transmit instructions to the flying body <NUM> via the communication satellite <NUM>.

The wireless communication device <NUM> comprises a BBU (Base Band Unit) and a plurality of RRHs (Remote Radio Heads). The BBU causes each of the plurality of RRHs to form the cell <NUM>, thereby forming the multi-cell <NUM>. The BBU may be an example of a control unit. The RRH may be an example of a radio unit.

The wireless communication device <NUM> mounted to the flying body <NUM> will be subject to size constraints, so that the plurality of RRHs will be closely arranged. As the number of the cells <NUM> composing the multi-cell <NUM> increases, the distance between the plurality of RRHs decreases. Thus, unlike ground radio base stations which are installed in locations geographically remote from each other, the uplink interference may possibly become significant, so that uplink interference countermeasures constitute the critical challenge. The wireless communication device <NUM> according to the present embodiment provides the technique to reduce the uplink interference.

In addition, when functioning as the stratosphere platform, the wireless communication device <NUM> is considered to change dynamically the number of beams, the number of cells, the position of a footprint, the size of the footprint, and the shape of the footprint or the like, depending on such as the position for the flying body <NUM> to fly and the condition of the ground to be covered. Along with such changes, the relationship between each of the plurality of cells <NUM> composing the multi-cell <NUM> and the neighboring cell can be changed dynamically. Thereby, the uplink interference countermeasures depending on such changes in the conditions can also constitute the critical challenge. The wireless communication device <NUM> according to the present embodiment can provide the technique that handles such changes in the conditions.

<FIG> illustrate contents of processing by the wireless communication device <NUM>. In <FIG>, while only two cells <NUM> and <NUM> are shown among the plurality of cells <NUM> included in the multi-cell <NUM> produced by the wireless communication device <NUM>, the illustration of other cells is omitted. In addition, as examples of the user terminal <NUM> located in the area of the cell <NUM> and the user terminal <NUM> located in the area of the cell <NUM>, the user terminal <NUM> and the user terminal <NUM> are illustrated.

That the user terminal <NUM> is located in the area of the cell <NUM> may mean that the user terminal <NUM> is placed in the cell <NUM> and has established the wireless communication connection with the wireless communication device <NUM>. In the example shown in <FIG>, the user terminal <NUM> is located in the area of the cell <NUM> formed by a first RRH among the plurality of RRHs. In addition, the user terminal <NUM> is located in the area of the cell <NUM> formed by a second RRH among the plurality of RRHs.

In the example shown in <FIG>, the user terminal <NUM> outputs a transmission radio wave containing a transmission signal <NUM>, and the user terminal <NUM> outputs a transmission radio wave containing a transmission signal <NUM>, wherein a component of the transmission radio wave output by the user terminal <NUM> is contained as an interference wave in the transmission radio wave containing the transmission signal <NUM>. In this manner, a signal interfering with the transmission signal <NUM> is illustrated as an interference signal <NUM>. In the wireless communication device <NUM> mounted to the flying body <NUM>, the plurality of RRHs are closely arranged, possibly generating such uplink interference.

<FIG> illustrates a reception radio wave band <NUM> that indicates the band of the reception radio wave received by the first RRH forming the cell <NUM>, the reception radio wave being the transmission radio wave containing the transmission signal <NUM> transmitted by the user terminal <NUM>, and a reception radio wave band <NUM> that indicates the band of the reception radio wave received by the second RRH forming the cell <NUM>, the reception radio wave being the transmission radio wave containing the transmission signal <NUM> transmitted by the user terminal <NUM>. As shown in <FIG>, the reception radio wave band <NUM> contains a signal <NUM> corresponding to the transmission signal <NUM>. The reception radio wave band <NUM> contains a signal <NUM> corresponding to the transmission signal <NUM> interfered with the interference signal <NUM>.

For example, the LTE communication system utilizes an identical frequency band for the plurality of cells <NUM>. Since the allocation control of radio resources is performed in one cell <NUM>, the uplink interference is not generated in the one cell <NUM>. However, since the allocation control of radio resources is performed in each of the plurality of cells <NUM>, the identical frequency band can be allocated to the user terminals <NUM> located in areas of different cells <NUM>. In addition, for the wireless communication device <NUM> mounted to the flying body <NUM>, the plurality of RRHs are closely arranged, possibly generating the interference as described above.

A BBU <NUM> according to the present embodiment performs, based on the first reception radio wave in which the first transmission radio wave containing the transmission signal <NUM> transmitted by the user terminal <NUM> is received by the first RRH, and the second reception radio wave in which the second transmission radio wave containing the transmission signal <NUM> transmitted by the user terminal <NUM> is received by the second RRH, removal processing to remove a component of the first transmission radio wave contained as an interference wave in the second reception radio wave. The BBU <NUM> may acquire the signal <NUM> from the second reception radio wave by performing such removal processing.

The BBU <NUM>, for example, performs the removal processing to remove a component of the first transmission radio wave contained as the interference wave in the second reception radio wave by utilizing the UL-CoMP technique. The BBU <NUM>, for example, acquires a second signal from the second reception radio wave by synthesizing the signal <NUM> acquired from the first reception radio wave and the signal <NUM> acquired from the second reception radio wave to remove the signal contained as an interference signal in the second reception radio wave.

<FIG> shows conceptually a content of the removal processing. The BBU <NUM> can remove an interference wave signal by assuming that: as shown as a reception signal <NUM>, the first RRH receives the transmission signal <NUM> (which may be described as S1) through four antennas out of eight antennas; as shown in a reception signal <NUM>, the second RRH receives a signal (which may be described as S2+S1') composed of the transmission signal <NUM> (which may be described as S2) containing the interference signal <NUM> (which may be described as S1') through four antennas out of the eight antennas; and as shown in a reception signal <NUM>, the cell of the eight antennas is subject to the interference wave.

The BBU <NUM>, for example, passes the signal S1 received at the cell <NUM> to the cell <NUM> side through a backplane. The BBU <NUM>, for example, passes the signal S1 received at the cell <NUM> to the cell <NUM> side via the SRIO (Serial Rapid IO) Switching. Then, the BBU <NUM> synthesizes S1 and S2+S1' as shown in the reception signal <NUM>. Since the phase of the signal S1 received at the cell <NUM> can be identified, the BBU <NUM> can identify the interference signal S1' contained in S2+S1' and can remove S1' from S2+S1'.

<FIG> shows schematically an example of a functional configuration of the wireless communication device <NUM>. Herein, the case where the wireless communication device <NUM> comprises one BBU <NUM> and seven RRHs <NUM> is shown. The BBU <NUM> can cause each of the seven RRHs <NUM> to form a cell, thereby forming a multi-cell consisting of seven cells. The number of the RRHs <NUM> included in the wireless communication device <NUM> may not be limited thereto, and the wireless communication device <NUM> may comprise any number of RRHs.

The BBU <NUM> has a target identifying unit <NUM>, a removal processing performing unit <NUM>, a status information acquisition unit <NUM>, an offset determination unit <NUM>, and an offset transmission unit <NUM>. The BBU <NUM> does not necessarily have all of these configurations.

The target identifying unit <NUM> identifies, from the plurality of RRHs <NUM>, the RRH <NUM> forming the cell <NUM> acting as an interference source and the RRH <NUM> forming the cell <NUM> targeted for reducing the interference. The target identifying unit <NUM>, for example, based on a measurement report which is transmitted by the user terminal <NUM> located in an area of any of the plurality of cells <NUM> and reporting the condition of the radio wave received by the user terminal <NUM>, identifies the cell <NUM> acting as the interference source and the cell <NUM> targeted for reducing the interference. Such a measurement report may be a so-called MR (Measurement Report).

The target identifying unit <NUM>, for example, upon receiving the MR transmitted by the user terminal <NUM> according to a transmission trigger of an A3 event in an event-type trigger, identifies the cell <NUM> acting as the interference source and the cell <NUM> targeted for reducing the interference. The target identifying unit <NUM> may, by referring to the MR, when such MR is received which is transmitted by the user terminal <NUM> located in an area of a certain cell <NUM> if the reception quality of a radio wave from a neighboring cell is higher than the reception quality of a radio wave from the own cell by a predetermined or larger amount of offset, determine the neighboring cell in the MR as the cell <NUM> targeted for reducing the interference and determine the own cell in the MR as the cell <NUM> acting as the interference source.

The removal processing performing unit <NUM> performs the removal processing for the cell <NUM> targeted for reducing the interference which is identified by the target identifying unit <NUM>. The removal processing performing unit <NUM> performs the removal processing to remove a component of the first transmission radio wave contained as the interference wave in the second reception radio wave, for example, based on the first reception radio wave in which the first RRH <NUM> forming the cell <NUM> received the first transmission radio wave which includes a first signal transmitted by the user terminal <NUM> which is located in the area of the cell <NUM> acting as the interference source and has transmitted the MR, and the second reception radio wave in which the second RRH <NUM> forming the cell <NUM> received the second transmission radio wave which includes the second signal transmitted by the user terminal <NUM> located in the area of the cell <NUM> which is targeted for reducing the interference,. The removal processing performing unit <NUM> acquires the second signal from the second reception radio wave by performing the removal processing.

The removal processing performing unit <NUM>, for example, performs the removal processing to remove a component of the first transmission radio wave contained as the interference wave in the second reception radio wave by utilizing the UL-CoMP technique. The removal processing performing unit <NUM> may acquire the second signal from the second reception radio wave by synthesizing a signal acquired from the first reception radio wave and a signal acquired from the second reception radio wave to remove the first signal contained as the interference signal in the second reception radio wave. The removal processing performing unit <NUM> may assume, based on the first reception radio wave received by the first RRH <NUM> through a first plurality of antennas and the second reception radio wave received by the second RRH <NUM> through a second plurality of antennas, that a cell composed of the first plurality of antennas and the second plurality of antennas has received the first reception radio wave and the second reception radio wave, thereby removing a component of the first transmission radio signal contained as the interference wave in the second reception radio wave.

The removal processing performing unit <NUM> may remove a component of the first transmission radio wave from the second reception radio wave by identifying the component of the first transmission radio wave contained as the interference wave in the second reception radio wave by means of a phase derived from the first reception radio wave. Thereby, the second signal can be acquired by removing the component of the first signal contained as the interference signal in the signal contained in the second reception radio wave.

The status information acquisition unit <NUM> acquires status information that indicates a status of the flying body <NUM> having the wireless communication device <NUM> mounted thereto. The status information acquisition unit <NUM> may receive the status information from the flight control apparatus mounted to the flying body <NUM>. The flight control apparatus, for example, transmits the status information that indicates changes in position information from a GPS or changes in attitudes of the flying body <NUM> from a gyro sensor to the wireless communication device <NUM>.

The offset determination unit <NUM> determines, based on the status information acquired by the status information acquisition unit <NUM>, an offset value at the A3 event transmitted to the user terminal <NUM> located in the area of the wireless communication device <NUM>. The offset transmission unit <NUM> transmits the offset value determined by the offset determination unit <NUM> to the user terminal <NUM> located in the area of the wireless communication device <NUM>.

The offset transmission unit <NUM>, for example, first transmits a default offset value to the user terminal <NUM> located in the area of the wireless communication device <NUM>. Note that the user terminal <NUM> may store the default offset value before being located in the area of the wireless communication device <NUM>. The offset determination unit <NUM> determines the offset value if the status of the flying body <NUM> indicated by the status information acquired by the status information acquisition unit <NUM> satisfies a predetermined condition, and the offset transmission unit <NUM> transmits the offset value determined by the offset determination unit <NUM> to the user terminal <NUM> located in the area of the wireless communication device <NUM>.

For example, the offset determination unit <NUM> determines an offset value smaller than the default offset value when a magnitude of flight vibration of the flying body <NUM> is greater than a predetermined magnitude. The flight vibration of the flying body <NUM> is the vertical vibration of the flying body <NUM>, for example.

In addition, the flight vibration of the flying body <NUM> may be the pitch vibration of the flying body <NUM>. That is, the flight vibration of the flying body <NUM> may be the rotational vibration about the lateral axis of the flying body <NUM>.

Moreover, the flight vibration of the flying body <NUM> may be the roll vibration of the flying body <NUM>. That is, the flight vibration of the flying body <NUM> may be the rotational vibration about the longitudinal axis of the flying body <NUM>.

Furthermore, the flight vibration of the flying body <NUM> may be the yaw vibration of the flying body <NUM>. That is, the flight vibration of the flying body <NUM> may be the rotational vibration about the vertical axis of the flying body <NUM>.

It can be estimated that, when the flight vibration of the flying body <NUM> is large, variation in the footprint of the multi-cell <NUM> will also be large. Since the positional relationship between the user terminal <NUM> during communication and the neighboring cell varies as the footprint of the multi-cell <NUM> varies, the uplink interference as described above becomes more likely to be generated. In response thereto, lowering the offset value in the A3 event stored in the user terminal <NUM> can cause the user terminal <NUM> more likely to transmit the MR and the removal processing performing unit <NUM> to activate readily a removal processing function, possibly resulting in the uplink interference to be reduced suitably.

<FIG> shows schematically an example of a processing flow by the target identifying unit <NUM>. Here, a status where the wireless communication device <NUM> provides the wireless communication service to the user terminal <NUM> while the flying body <NUM> is flying is explained as an initial status.

At Step (the step may be described by the abbreviation "S") <NUM>, it is decided whether the target identifying unit <NUM> has identified the RRH <NUM> that forms the cell acting as the interference source (which may be described as the interference source RRH) and the RRH <NUM> that forms the cell targeted for reducing the interference (which may be described as the reduction target RRH). The target identifying unit <NUM>, for example, identifies the interference source RRH and the reduction target RRH upon receiving the MR of the A3 event from the user terminal <NUM> located in the area of the wireless communication device <NUM>. The target identifying unit <NUM> may identify a plurality of interference source RRHs and a plurality of reduction target RRHs when there are a plurality of combinations of the interference source RRH and the reduction target RRH. If decided that the target identifying unit <NUM> has identified, the process proceeds to S104.

At S104, the removal processing performing unit <NUM> activates the removal processing function. At S106, the removal processing performing unit <NUM> performs the removal processing. The removal processing performing unit <NUM> removes a component of the first transmission radio wave contained as the interference wave in the second reception radio wave, based on the first reception radio wave in which the interference source RRH received the first transmission radio wave which includes the first signal transmitted by the user terminal <NUM> which is located in the area of the cell acting as the interference source and has transmitted the MR, and the second reception radio wave in which the reduction target RRH received the second transmission radio wave which includes the second signal transmitted by the user terminal <NUM> which is located in the area of the cell targeted for reducing the interference source. The removal processing performing unit <NUM> may perform the removal processing for a plurality of user terminals <NUM> located in the area of the cell targeted for reducing the interference.

The removal processing performing unit <NUM> performs the removal processing until it is decided that the removal processing is to be terminated. The removal processing performing unit <NUM> may decide that the removal processing is to be terminated according to any condition. For example, the removal processing performing unit <NUM> decides that the removal processing is to be terminated when a predetermined period is expired from the activation of the removal processing function at S104. In addition, for example, the removal processing performing unit <NUM> decides that the removal processing is to be terminated when the interference does not occur such as when the MR of the A3 event is not transmitted from any user terminal <NUM>.

<FIG> shows schematically an example of a processing flow by the BBU <NUM>. Here, a flow of processing is shown schematically where the user terminal <NUM> located in the area of the wireless communication device <NUM> stores the default offset of the A3 event and changes the offset depending on the condition.

At S202, the status information acquisition unit <NUM> acquires the status information that indicates the status of the flying body <NUM> having the wireless communication device <NUM> mounted thereto. At S204, the status information acquisition unit <NUM> decides whether the status of the flying body <NUM> indicated by the status information acquired at S202 satisfies a predetermined condition. If decided that it is satisfied, the process proceeds to S206.

At S206, the offset determination unit <NUM> determines the offset at the A3 event based on the condition satisfied at S204. The offset determination unit <NUM>, for example, determines an offset smaller than the offset stored in the user terminal <NUM> when a magnitude of the flight vibration of the flying body <NUM> is greater than the predetermined magnitude. The offset determination unit <NUM> may determine a reduction amount of the offset of the A3 event when the magnitude of the flight vibration of the flying body <NUM> is greater than the predetermined magnitude.

At S208, the offset transmission unit <NUM> transmits the offset determined at S206 to the user terminal <NUM> located in the area of the wireless communication device <NUM>. The offset transmission unit <NUM> may transmit, when the reduction amount of the offset of the A3 event is determined at S206, the reduction amount to the user terminal <NUM> located in the area of the wireless communication device <NUM>.

At S210, it is decided whether the change in the offset of the A3 event depending on the condition is to be terminated. If decided that it is not to be terminated, the process returns to S202. At S202, the status information of the flying body <NUM> is acquired, and at S204, it is decided whether the status of the flying body <NUM> satisfies the predetermined condition. Here, for example, if the magnitude of the flight vibration of the flying body <NUM> is reduced lower than the predetermined magnitude, the default value for an A3 offset may be determined as an A3 offset at S206. Thus, the BBU <NUM> may reduce the offset value of the A3 event lower than the default value only while the magnitude of the flight vibration of the flying body <NUM> is greater than the predetermined magnitude.

<FIG> shows schematically an example of a hardware configuration of a computer <NUM> functioning as the wireless communication device <NUM>. A program installed in the computer <NUM> can cause the computer <NUM> to function as one or more "units" of an apparatus according to the present embodiment, or cause the computer <NUM> to perform operations associated with the apparatus or perform one or more "units" thereof according to the present embodiment, and/or cause the computer <NUM> to perform the process according to the present embodiment or perform the steps of the process. Such a program may be executed by a CPU <NUM> to cause the computer <NUM> to perform specific operations associated with some or all of the blocks in the flow charts and block diagrams described in the specification.

The computer <NUM> according to the present embodiment includes a CPU <NUM>, a RAM <NUM>, and a graphics controller <NUM>, which are connected to each other via a host controller <NUM>. The computer <NUM> also includes a communication interface <NUM>, a storage device <NUM>, and an I/O unit such as an IC card drive, which are connected to the host controller <NUM> via an I/O controller <NUM>. The storage device <NUM> may be such as a hard disk drive and a solid state drive. The computer <NUM> also includes a legacy I/O unit such as a ROM <NUM> and a keyboard, which are connected to the I/O controller <NUM> via an I/O chip <NUM>.

The CPU <NUM> operates in accordance with a program stored in the ROM <NUM> and the RAM <NUM>, thereby controlling each unit. The graphics controller <NUM> acquires image data generated by the CPU <NUM> in a frame buffer provided in the RAM <NUM> or in the RAM <NUM> itself, so that the image data is displayed on a display device <NUM>.

The communication interface <NUM> communicates with other electronic devices via a network. The storage device <NUM> stores a program and data used by the CPU <NUM> in the computer <NUM>. The IC card drive reads out the program or data from an IC card, and/or write the program or data in the IC card.

The ROM <NUM> stores a boot program or the like executed by the computer <NUM> upon activation, and/or a program dependent on hardware of the computer <NUM>. The I/O chip <NUM> may also connect various I/O units to the I/O controller <NUM> via a USB port, a parallel port, a serial port, a keyboard port, a mouse port, or the like.

The program is provided to a computer-readable storage medium such as the IC card. The program is read out from the computer-readable storage medium, installed in the storage device <NUM>, the RAM <NUM>, or the ROM <NUM> serving also as an example of the computer-readable storage medium, and executed by the CPU <NUM>. Such a program describes information processing, which is read out by the computer <NUM> to link the program with the various types of hardware resources as mentioned above. The apparatus or method may be configured by implementing information operation or processing using the computer <NUM>.

For example, upon performing the communication between the computer <NUM> and an external device, the CPU <NUM> may execute a communication program loaded in the RAM <NUM> and, based on the processing described in the communication program, instruct the communication interface <NUM> to perform communication processing. The communication interface <NUM>, under control of the CPU <NUM>, reads out transmission data stored in a transmission buffer processing area provided in a recording medium such as the RAM <NUM>, the storage device <NUM>, or the IC card, and transmits the read-out transmission data to the network, or otherwise writes the received data received from the network in a reception buffer processing area or the like provided on the recording medium.

In addition, the CPU <NUM> may allow the RAM <NUM> to read out all or necessary parts of a file or database stored in an external recording medium, such as the storage device <NUM> and the IC card, to perform various types of processing for the data stored on the RAM <NUM>. The CPU <NUM> then writes back the processed data in 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 for information processing. On the data read out from the RAM <NUM>, the CPU <NUM> may perform various types of processing including various types of operations, information processing, condition determination, conditional branching, unconditional branching, and information retrieval/conversion, which are described anywhere in the present disclosure and specified by an instruction sequence of a program, and write back the result in the RAM <NUM>. The CPU <NUM> may also retrieve information in a file or database in the recording medium. For example, when the recording medium stores a plurality of entries each having a first attribute value associated with a second attribute value, the CPU <NUM> may retrieve an entry from the plurality of entries that meets a condition where the first attribute value is specified, read out the second attribute value stored in the entry, thereby acquiring the second attribute value associated with the first attribute value that satisfies a predetermined condition.

The programs or software modules described above may be stored on the computer <NUM> or a computer-readable storage medium in the vicinity of the computer <NUM>. A recording medium such as a hard disk or RAM provided in a server system connected to a dedicated communication network or the Internet is usable as the computer-readable storage medium, thereby providing the program to the computer <NUM> via the network.

In the flow charts and block diagrams in the present embodiment, the blocks may represent "units" of an apparatus having a role to perform steps of the process for performing operations or to perform the operations. A specific step or "unit" may be implemented by a dedicated circuit, a programmable circuit provided along with computer-readable instructions stored on a computer-readable storage medium, and/or a processor provided along with the computer-readable instructions 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 a reconfigurable hardware circuit, such as a field programmable gate array (FPGA) and a programmable logic array (PLA), for example, including AND, OR, XOR, NAND, NOR, as well as other logical operations, flip-flops, registers, and memory elements.

The computer-readable storage medium may include any tangible device that can store instructions to be executed by a suitable device, so that the computer-readable storage medium having instructions stored thereon comprises a product including instructions that can be executed to configure means for performing operations specified in the flow charts or block diagrams. Examples of the computer-readable storage medium may include an electronic storage medium, a magnetic storage medium, an optical storage medium, a magneto-electric storage medium, and a semiconductor storage medium, or the like. More specific examples of the computer-readable storage medium may include a floppy (registered trademark) disk, a diskette, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), electrically-erasable programmable read-only memory (EEPROM), static random access memory (SRAM), compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a Blu-ray (registered trademark) disk, a memory stick, and an integrated circuit card, or the like.

The computer-readable instructions may include assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcodes, firmware instructions, status setting data, or any of source codes or object codes described in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk (registered trademark),, JAVA (registered trademark), or C++, and conventional procedural programming languages, such as C programming languages or similar programming languages.

The computer-readable instructions may be provided to a processor of a general-purpose computer, a dedicated computer or other programmable data processing apparatuses, or a programmable circuit, locally or via the local area network (LAN) or the wide area network (WAN) such as the Internet, so that the processor of the general-purpose computer, the dedicated computer or other programmable data processing apparatuses, or the programmable circuit executes the computer-readable instructions to generate means for performing the operations specified in the flow charts or block diagrams. The processors include a computer processor, a processing unit, a microprocessor, a digital signal processor, a controller, and a microcontroller, or the like.

While the embodiments of the present invention have been described, the technical scope of the 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.

Claim 1:
A wireless communication device (<NUM>) mounted to a flying body (<NUM>) to radiate a plurality of beams toward the ground, thereby forming a multi-cell (<NUM>) to provide wireless communication services to a user terminal (<NUM>, <NUM>, <NUM>) in the multi-cell (<NUM>), the wireless communication device (<NUM>) comprising:
a plurality of radio units (<NUM>); and
a control unit (<NUM>) configured to control each of the plurality of radio units (<NUM>) to form a cell (<NUM>), thereby forming the multi-cell (<NUM>), wherein the control unit (<NUM>) comprises:
a target identifying unit (<NUM>) configured to identify a first radio unit that forms a cell (<NUM>) acting as an interference source and a second radio unit that forms a cell (<NUM>) targeted for reducing the interference among the plurality of radio units;
a removal processing performing unit (<NUM>) configured to, based on a first reception radio wave in which the identified first radio unit received a first transmission radio wave which includes a first signal transmitted by a first user terminal (<NUM>, <NUM>, <NUM>) located in an area of a first cell (<NUM>) formed by the identified first radio unit, and a second reception radio wave in which the identified second radio unit received a second transmission radio wave which includes a second signal transmitted by a second user terminal (<NUM>, <NUM>, <NUM>) located in an area of a second cell (<NUM>) formed by the identified second radio unit, perform removal processing to remove a component of the first transmission radio wave contained as an interference wave in the second reception radio wave.