Patent Description:
<CIT>describes a flight vehicle which forms a multi-cell on a ground by irradiating beam towards the ground to provide a wireless communication service to a user terminal in the multi-cell. <CIT> describes a method of transmitting data by a terminal device operating in a wireless communications system comprising a non-terrestrial network access node and the terminal device, comprises the terminal device receiving an indication of an initial value of a set of one or more communications parameters for transmitting radio signals carrying the data, and modelling a state of a communications channel from the terminal device to a non-terrestrial network access node, in which a link adaptation procedure is used to select a revised value of the set of the one or more communications parameters with respect to the initial value of the set of the one or more communications parameters for the modelled channel state, and the method includes adapting the value of the set of the one or more communications parameters according to the revised value. The method then includes transmitting radio signals representing the data using the set of the one or more communications parameters. The method may also include determining whether the revised communications parameters have changed with respect to the initial parameters, and so only revising the communications parameters if these have changed with respect to the initial value. Accordingly, link adaptation can be performed without a requirement for feedback of a channel state of the communications channel at the receiver, which may the non-terrestrial network access node located on a satellite to which uplink data is transmitted.

According to an aspect of the present invention, there is provided a base station device. The base station device is mounted to a high-altitude platform system (HAPS) and forms a multi-cell including a plurality of cells on a ground to provide a wireless communication service to a user terminal in the multi-cell. The base station device includes a location information acquisition unit which is configured to acquire location information of a user terminal present in the multi-cell. The base station device includes a flight vehicle associated information acquisition unit which is configured to acquire flight vehicle associated information including location information and attitude information of the flight vehicle, the attitude information including the attitude of the HAPS during flight. The base station device includes an interference estimation unit which is configured to estimate, based on location information of a plurality of the user terminals and the flight vehicle associated information, an interfered user terminal having a chance of experiencing an interference from a cell other than a cell in which the user terminal is present among the plurality of user terminals and an interference amount. The base station device includes an MCS decision unit which is configured to decide an MCS of an uplink to be assigned to the interfered user terminal based on the interference amount. The base station device includes an MCS notification unit which is configured to notify the interfered user terminal of the MCS decided by the MCS decision unit.

The base station device may include a report acquisition unit which is configured to acquire report information received from the user terminal present in the multi-cell and related to a reception radio wave by the user terminal, and the interference estimation unit may be configured to estimate the interfered user terminal and the interference amount further based on the report information. The report acquisition unit may be configured to acquire an A3 event report received from the user terminal present in the multi-cell. The base station device may include a storage unit which is configured to store association data in which the location information acquired by the location information acquisition unit, the flight vehicle associated information acquired by the flight vehicle associated information acquisition unit, and the interference amount experienced by the user terminal which is received from the user terminal are associated with each other, and the interference estimation unit may be configured to use a plurality of pieces of association data stored in the storage unit as training data to generate an estimation model which estimates an interference amount to be experienced by the plurality of user terminals from the location information of the plurality of user terminals present in the multi-cell and the flight vehicle associated information, and to estimate the interfered user terminal having a chance of experiencing an interference from a cell other than the cell in which the user terminal is present and the interference amount by using the estimation model. The interference estimation unit may be configured to estimate, at timing at which a DMRS is received from the interfered user terminal, the interference amount at timing of PUSCH of the interfered user terminal based on the DMRS, location information of the interfered user terminal, and the flight vehicle associated information. The interference estimation unit may be configured to estimate, at the timing at which the DMRS is received from the interfered user terminal, an interference amount that has been experienced by the interfered user terminal at the timing at which the DMRS is received, and a variation of the interference amount at the timing of the PUSCH of the interfered user terminal while the interference amount is set as a reference. The MCS decision unit may be configured to decide MCSs to be assigned to a plurality of the user terminals present in the multi-cell. The MCS decision unit may be configured to decide an MCS based on the DMRS received from the user terminal with regard to the user terminal determined to have no chance of experiencing an interference from a cell other than the cell in which the user terminal is present. When an interference amount that has been experienced by the interfered user terminal at the timing at which the DMRS is received and a variation of the interference amount at the timing of the PUSCH of the interfered user terminal while the interference amount is set as the reference are estimated by the interference estimation unit, the MCS decision unit may be configured to decide the MCS to be assigned to the interfered user terminal based on these. When the interference amount at the timing of the PUSCH of the interfered user terminal is more than that at the timing at which the DMRS is received, the MCS decision unit may be configured to decide an MCS with an index value less than that of the MCS decided based on the DMRS. As the variation of the interference amount is further increased, the MCS decision unit may be configured to decide an MCS with a still smaller number than that of the MCS decided based on the DMRS. When the interference amount at the timing of the PUSCH of the interfered user terminal is less than that at the timing at which the DMRS is received, the MCS decision unit may be configured to decide an MCS with an index value more than that of the MCS decided based on the DMRS. As the variation of the interference amount is further increased, the MCS decision unit may be configured to decide an MCS with a still larger number than that of the MCS decided based on the DMRS.

According to an aspect of the present invention, there is provided a system including the base station device and the flight vehicle.

According to an aspect of the present invention, there is provided a control method executed by a base station device which is mounted to a HAPS and forms a multi-cell including a plurality of cells on a ground to provide a wireless communication service to a user terminal in the multi-cell. The control method includes acquiring location information of a user terminal present in the multi-cell. The control method includes acquiring flight vehicle associated information including location information and attitude information of the HAPS, the attitude information including the attitude of the HAPS during flight. The control method includes estimating an interference by estimating, based on location information of a plurality of the user terminals and the flight vehicle associated information, an interfered user terminal having a chance of experiencing an interference from a cell other than a cell in which the user terminal is present among the plurality of user terminals and an interference amount. The control method includes deciding an MCS of an uplink to be assigned to the interfered user terminal based on the interference amount. The control method includes notifying the interfered user terminal of the MCS decided in the deciding the MCS.

According to an aspect of the present invention, there is provided a computer program comprising instructions which, when executed by a computer, cause the computer to carry out the steps of this method.

Note that the above-described summary clause does not necessarily describe all necessary features of the embodiments of the present invention. The invention may also include a sub-combination of the features described above.

In a case of a flight vehicle which forms a multi-cell on a ground while flying in a sky, a radio environment of a multi-cell configuration is likely to vary depending on a flight state (circling, and ascending and descending), and there is a tendency that an interference state to a user terminal (which may be referred to as UE (User Equipment)) is also likely to vary. Therefore, a case may occur where an appropriate MCS (Modulation and Coding Scheme) is not assigned depending on timing at which an MCS of a UL (UpLink) to the UE is decided, which leads to a fall of UE throughput. A base station device mounted to the flight vehicle according to the present embodiment regularly acquires, for example, flight vehicle associated information (such as a latitude and a longitude, an altitude, and a gradient), and assigns an appropriate MCS by inter-cell coordinated control of each cell of the multi-cell further based on DMRS (Demodulation Reference Signal) information of a plurality of UEs to aim for an improvement of the UE throughput.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to claims. In addition, not all of the combinations of features described in the embodiments are essential to solution of the invention.

<FIG> schematically illustrates an example of a HAPS <NUM>. The HAPS <NUM> may be an example of a flight vehicle. The HAPS <NUM> may function as a stratospheric platform. The HAPS <NUM> forms a feeder link <NUM> with a gateway <NUM> on the ground while flying in a stratosphere, for example, and also forms a multi-cell <NUM> by irradiating beam <NUM> towards the ground. The HAPS <NUM> provides a wireless communication service to a user terminal <NUM> in the multi-cell <NUM>.

The HAPS <NUM> includes a main body section <NUM>, a wing section <NUM>, and a solar panel <NUM>. Electric power generated by the solar panel <NUM> is stored in one or more batteries arranged in at least any of the main body section <NUM> or the wing section <NUM>. The electric power stored in the battery is used by each component included in the HAPS <NUM>.

A flight control device <NUM> and a base station device <NUM> are arranged in the main body section <NUM>. The flight control device <NUM> controls flight of the HAPS <NUM>. The base station device <NUM> controls communication of the HAPS <NUM>. The HAPS <NUM> and the base station device <NUM> may constitute a system.

The flight control device <NUM> controls the flight of the HAPS <NUM> by controlling, for example, a rotation of a propeller, an angle of a flap or an elevator, or the like. The flight control device <NUM> may manage various types of sensors included in the HAPS <NUM>. Examples of the sensors include a positioning sensor such as a GPS (Global Positioning System) sensor, a gyro sensor, an acceleration sensor, a wind sensor, and the like. The flight control device <NUM> may manage a location, an attitude, a movement direction, a movement speed, and the like of the HAPS <NUM> by outputs of the various types of sensors.

The base station device <NUM> may form the feeder link <NUM> with the gateway <NUM> by using an FL (Feeder Link) antenna. The base station device <NUM> may access a network <NUM> via the gateway <NUM>.

The base station device <NUM> may form the multi-cell <NUM> by irradiating the beam <NUM> towards the ground by using an SL (Service Link) antenna. The multi-cell <NUM> is configured by a plurality of cells <NUM>. In <FIG>, a case has been exemplified where the number of cells <NUM> is seven but the number of cells <NUM> is not limited to this. The base station device <NUM> may establish a service link with the user terminal <NUM> in the multi-cell <NUM>.

The base station device <NUM> relays communication between the network <NUM> and the user terminal <NUM> via the feeder link <NUM> and the service link, for example. The base station device <NUM> may provide the wireless communication service to the user terminal <NUM> by relaying the communication between the user terminal <NUM> and the network <NUM>.

The network <NUM> may include a core network managed by a telecommunications carrier. The core network may be compliant to an LTE (Long Term Evolution) communication system. That is, the core network may be an EPC (Evolved Packet Core). The core network may be compliant to a <NUM> (5th Generation) communication system. That is, the core network may be a 5GC (5th Generation Core network). The core network may be compliant to a <NUM> (3rd Generation) communication system, or may be compliant to a <NUM> (6th Generation) communication system and subsequent communication systems. The network <NUM> may include the Internet.

The user terminal <NUM> may be any communication terminal as long as the user terminal <NUM> is able to communicate with the HAPS <NUM>. For example, the user terminal <NUM> is a cellular phone such as a smartphone. The user terminal <NUM> may also be a tablet terminal, a PC (Personal Computer), and the like. The user terminal <NUM> may also be a so-called IoT (Internet of Thing) device. The user terminal <NUM> may include anything that belongs to so-called IoE (Internet of Everything).

The HAPS <NUM> may circle in a sky above a target area in order to cover the target area on the ground by the multi-cell <NUM>. For example, while carrying out patrol flight in the sky above the target area in a predetermined flight path such as a circular, D-shaped, or <NUM>-shaped flight path, the HAPS <NUM> maintains the feeder link <NUM> with the gateway <NUM> by adjusting an orientation direction of the FL antenna, and maintains the coverage of the target area by the multi-cell <NUM> by adjusting an orientation direction of the SL antenna. In this manner, patrolling in a fixed flight path in the sky above the target area may be referred to as a fixed point flight.

A location and an attitude of the HAPS <NUM> regularly varies because of the flight. In addition, the attitude of the HAPS <NUM> may minutely vary or largely vary depending on an influence of wind or the like. Therefore, a radio environment of the multi-cell <NUM> is likely to vary depending on a flight state of the HAPS <NUM>. The HAPS <NUM> forms the multi-cell <NUM> by a plurality of beams, and all the cells <NUM> may uniformly move, or each of the plurality of cells <NUM> may separately move.

<FIG> is an explanatory diagram for describing an interference caused by a location variation of the HAPS <NUM> or the like. Herein, while focus is on only a cell <NUM> and a cell <NUM> which are two cells out of the multi-cell <NUM>, a case where a location of the cell <NUM> is shifted will be used as an example in the description. In the present example, a user terminal <NUM> and a user terminal <NUM> are present in the cell <NUM>, and a user terminal <NUM> and a user terminal <NUM> are present in the cell <NUM>.

Before the location of the cell <NUM> is shifted, the user terminal <NUM> is located in the cell <NUM>, and the user terminal <NUM> is located in the cell <NUM>, but after the location of the cell <NUM> is shifted, the user terminal <NUM> is located in both the cell <NUM> and the cell <NUM>. In such a case, when a resource block with a same frequency band and also a same time slot as those of a resource block for the user terminal <NUM> in the cell <NUM> is assigned to the user terminal <NUM> located in proximity to the user terminal <NUM>, communication of the user terminal <NUM> interferes with the user terminal <NUM>, and the throughput falls.

<FIG> schematically illustrates an example of an interference variation <NUM> of the user terminal <NUM>. When the user terminal <NUM> is covered by a radio base station on the ground, the interference experienced by the user terminal <NUM> does not vary too much. However, when the user terminal <NUM> is covered by the HAPS <NUM>, since the multi-cell <NUM> circles, the multi-cell <NUM> moves, or a locational relationship between each of the plurality of cells <NUM> changes according to the flight state of the HAPS <NUM>, as exemplified in <FIG>, the interference experienced by the user terminal <NUM> largely varies.

In a conventional radio base station, a DMRS received from the user terminal <NUM> covered by the radio base station has been analyzed to determine a CQI (Channel Quality Indicator) to decide an MCS, and the MCS has been assigned to the user terminal <NUM> by UL Grant (PDCCH (Physical Downlink Control Channel)). The user terminal <NUM> has performed PUSCH (Physical Uplink Shared CHannel) transmission by using the assigned MCS. In a case of the radio base station on the ground, there has been no large difference in the interference experienced by the user terminal <NUM> at timing at which the radio base station receives the DMRS and timing at which the user terminal <NUM> performs the PUSCH transmission.

However, in a case of the HAPS <NUM>, as exemplified in <FIG>, a chance in which a difference occurs in the interference experienced by the user terminal <NUM> at the timing at which the DMRS is received (timing at which the MCS is decided) and the timing at which the user terminal <NUM> performs the PUSCH transmission becomes higher as compared with that of the radio base station on the ground. For example, when the interference at the time of the MCS decision is higher than the interference at the time of the PUSCH transmission, an MCS that is too small is assigned as a result, and the throughput of the user terminal <NUM> falls. In addition, for example, when the interference at the time of the MCS decision is lower than the interference at the time of the PUSCH transmission, numerous CRC (Cyclic Redundancy Check) errors are generated, and the throughput of the user terminal <NUM> falls.

<FIG> schematically illustrates an example of a flow of processing which is executed by the base station device <NUM>. Herein, a state where a plurality of user terminals <NUM> are present in the multi-cell <NUM> is used as a start state in the description.

In step (step may be abbreviated and denoted as S) <NUM>, location information of the user terminal <NUM> in each cell <NUM> is acquired. In S104, flight vehicle associated information (such as a latitude and a longitude, an altitude, an orientation, and a gradient) is acquired.

In S106, a variation of the interference state in each cell <NUM> is acquired by report information transmitted by the user terminals <NUM> present in the multi-cell <NUM>. The base station device <NUM> acquires the variation of the interference state in each cell <NUM>, for example, by an A3 event report or the like which is transmitted when a reception intensity from a neighboring cell becomes higher than a reception intensity from a primary cell by an offset or more and location information of the user terminal <NUM> which has transmitted the report.

In S108, the user terminal <NUM> having a chance of experiencing an interference and an interference amount are estimated with regard to each of the plurality of cells <NUM> based on the information acquired in S102, S104, and S106. The base station device <NUM> estimates the interference amount at the timing of the PUSCH transmission by the user terminal <NUM> based on these pieces of information, for example, at the timing at which the DMRS is received from the user terminal <NUM>. For example, when it is predicted that an adjacent cell <NUM> approaches the user terminal <NUM> due to the flight state of the HAPS <NUM>, the base station device <NUM> estimates an increase amount of the interference from a locational relationship between the user terminal <NUM> and the adjacent cell <NUM> and the presence of another user terminal <NUM> which is present in the adjacent cell <NUM> and located in proximity to the user terminal <NUM>.

In S110, MCSs are decided which are to be assigned to the plurality of user terminals <NUM> present in the multi-cell <NUM>. The base station device <NUM> decides an MCS based on the DMRS received from the user terminal <NUM> with regard to the user terminal <NUM> having no chance of experiencing an interference, and decides an MCS by taking into account the interference amount estimated in S108 with regard to the user terminal <NUM> having a chance of experiencing an interference. For example, when the interference increases more at the timing at which the user terminal <NUM> performs the PUSCH transmission than that at the timing at which the DMRS is received, the base station device <NUM> decides an MCS with an index value less than that of the MCS decided based on the DMRS as the MCS to be assigned to the user terminal <NUM>. In S112, the user terminals <NUM> are notified of the MCSs decided in S110.

In S114, it is determined whether provision of the wireless communication service is to be ended. When it is determined that the provision is not to be ended, the flow returns to S102, and when it is determined that the provision is to be ended, the processing is ended.

<FIG> schematically illustrates an example of a functional configuration of the base station device <NUM>. The base station device <NUM> includes a storage unit <NUM>, a flight vehicle associated information reception unit <NUM>, a core communication unit <NUM>, a terminal communication unit <NUM>, and a communication control unit <NUM>.

The flight vehicle associated information reception unit <NUM> receives flight vehicle associated information from the flight control device. The flight vehicle associated information reception unit <NUM> receives, for example, location information of the HAPS <NUM>. The flight vehicle associated information reception unit <NUM> receives, for example, attitude information of the HAPS <NUM>. The flight vehicle associated information reception unit <NUM> receives, for example, pitch, roll, and yaw information of the HAPS <NUM>. In addition, the flight vehicle associated information reception unit <NUM> receives wind power information output by a wind sensor. The flight vehicle associated information reception unit <NUM> stores the received information in the storage unit <NUM>.

The core communication unit <NUM> communicates with a core network. The core communication unit <NUM> may establish the feeder link <NUM> with the gateway <NUM> by the FL antenna for communication with the gateway <NUM> on the ground. The core communication unit <NUM> may communicate with the core network on the ground via the feeder link <NUM>.

The terminal communication unit <NUM> communicates with the user terminal <NUM>. The terminal communication unit <NUM> may form the multi-cell <NUM> by irradiating the beam <NUM> towards the ground by using the SL antenna. The terminal communication unit <NUM> may establish a service link with the user terminal <NUM> in the multi-cell <NUM>.

The communication control unit <NUM> controls communication of the user terminal <NUM>. The communication control unit <NUM> performs establishment of wireless communication connection with the user terminal <NUM> or the like to assign a radio resource to the user terminal <NUM> and control the communication of the user terminal <NUM>.

The communication control unit <NUM> includes a location information acquisition unit <NUM>, a flight vehicle associated information acquisition unit <NUM>, a report acquisition unit <NUM>, an interference estimation unit <NUM>, an MCS decision unit <NUM>, and an MCS notification unit <NUM>.

The location information acquisition unit <NUM> acquires location information of the user terminal <NUM> present in the multi-cell <NUM>. The location information acquisition unit <NUM> may acquire the location information of the user terminal <NUM> which has been received by the terminal communication unit <NUM> from the user terminal <NUM>. The user terminal <NUM> may measure its own location information by at least any of, for example, GPS positioning, base station positioning, or Wi-Fi (registered trademark) positioning.

The flight vehicle associated information acquisition unit <NUM> acquires flight vehicle associated information. The flight vehicle associated information acquisition unit <NUM> may acquire flight vehicle associated information stored in the storage unit <NUM>.

The report acquisition unit <NUM> acquires the report information related to a reception radio wave by the user terminal <NUM> which has been received from the user terminal <NUM> present in the multi-cell <NUM>. The report acquisition unit <NUM> may indicate a reception intensity of the radio wave received by the user terminal <NUM>. In addition, the report acquisition unit <NUM> may indicate an interference amount of the interference experienced by the user terminal <NUM>. The report acquisition unit <NUM> acquires, for example, an A3 event report.

The interference estimation unit <NUM> estimates an interfered user terminal having a chance of experiencing an interference from a cell <NUM> other than a cell <NUM> in which the user terminal <NUM> is present among a plurality of user terminals <NUM> present in the multi-cell <NUM>, and an interference amount. The interference estimation unit <NUM> may use location information of each of the plurality of user terminals <NUM> which has been acquired by the location information acquisition unit <NUM> for the estimation. The interference estimation unit <NUM> may use the flight vehicle associated information acquired by the flight vehicle associated information acquisition unit <NUM> for the estimation. The interference estimation unit <NUM> may use the report information acquired by the report acquisition unit <NUM> for the estimation.

The interference estimation unit <NUM> may store, in the storage unit <NUM>, association data in which the flight vehicle associated information of the HAPS <NUM> which patrols in a predetermined flight path which has been acquired by the flight vehicle associated information acquisition unit <NUM>, the location information of the user terminal <NUM> which has been acquired by the location information acquisition unit <NUM>, and the interference amount to be experienced by the user terminal <NUM> which has been received by the user terminal <NUM> are associated with each other. Then, the interference estimation unit <NUM> may use past association data stored in the storage unit <NUM> as training data, and generate and store an estimation model which estimates an interference amount to be experienced by the plurality of the user terminals <NUM> from the location information of the plurality of user terminals <NUM> present in the multi-cell <NUM> and the flight vehicle associated information in the storage unit <NUM>. The interference estimation unit <NUM> may estimate an interference amount of each of the plurality of user terminals <NUM> by using the estimation model.

The interference estimation unit <NUM> may identify a locational relationship between the plurality of mutual cells <NUM> constituting the multi-cell <NUM> based on the report information acquired by the report acquisition unit <NUM>. The interference estimation unit <NUM> may store, in the storage unit <NUM>, association data in which the flight vehicle associated information, the locational relationship of the plurality of mutual cells <NUM>, the location information of the user terminal <NUM>, and the interference amount to be experienced by the user terminal <NUM> are associated with each other. Then, the interference estimation unit <NUM> may use past association data stored in the storage unit <NUM> as training data, and generate and store an estimation model which estimates the interference amount to be experienced by the plurality of the user terminals <NUM> from the locational relationship of the plurality of mutual cells <NUM>, the location information of the plurality of user terminals <NUM> present in the multi-cell <NUM>, and the flight vehicle associated information in the storage unit <NUM>. The interference estimation unit <NUM> may estimate the interference amount of each of the plurality of user terminals <NUM> by using the estimation model.

The interference estimation unit <NUM> may estimate, at timing at which the DMRS is received from the interfered user terminal, the interference amount at timing of the PUSCH of the interfered user terminal based on the DMRS, location information of the interfered user terminal, and the flight vehicle associated information. The interference estimation unit <NUM> may estimate, at the timing at which the DMRS is received from the interfered user terminal, an interference amount that has been experienced by the interfered user terminal at the timing at which the DMRS is received, and a variation of the interference amount at the timing of the PUSCH of the interfered user terminal while the interference amount is set as a reference.

The MCS decision unit <NUM> decides MCSs to be assigned to the plurality of user terminals <NUM> present in the multi-cell <NUM>. The MCS decision unit <NUM> may decide an MCS based on the DMRS received from the user terminal <NUM> with regard to the user terminal <NUM> determined to have no chance of experiencing an interference from a cell other than the cell in which the user terminal <NUM> is present.

The MCS decision unit <NUM> decides an MCS to be assigned to the interfered user terminal based on the interference amount estimated by the interference estimation unit <NUM> with regard to the user terminal <NUM> determined to have a chance of experiencing an interference from a cell other than the cell in which the user terminal <NUM> is present. When an interference amount at the timing of the PUSCH of the interfered user terminal is estimated by the interference estimation unit <NUM>, the MCS decision unit <NUM> may decide the MCS based on the interference amount.

When an interference amount that has been experienced by the interfered user terminal at the timing at which the DMRS is received and a variation of the interference amount at the timing of the PUSCH of the interfered user terminal while the interference amount is set as the reference are estimated by the interference estimation unit <NUM>, the MCS decision unit <NUM> may decide the MCS to be assigned to the interfered user terminal based on these. For example, the MCS decision unit <NUM> provisionally decides an MCS based on the DMRS by using a conventional technique, and decides the MCS to be assigned to the interfered user terminal by adjusting the provisionally decided MCS based on the variation of the interference amount.

For example, when the interference amount at the timing of the PUSCH of the interfered user terminal is more than that at the timing at which the DMRS is received, the MCS decision unit <NUM> decides an MCS with an index value less than that of the MCS decided based on the DMRS. As the variation of the interference amount is further increased, the MCS decision unit <NUM> may decide an MCS with a still smaller number than that of the MCS decided based on the DMRS. Thus, as compared with a case where the MCS decided based on the DMRS is assigned, the generation of the CRC errors can be suppressed, and it is possible to contribute to an improvement of the throughput of the user terminal <NUM>.

For example, when the interference amount at the timing of the PUSCH of the interfered user terminal is less than that at the timing at which the DMRS is received, the MCS decision unit <NUM> decides an MCS with an index value more than that of the MCS decided based on the DMRS. As the variation of the interference amount is further increased, the MCS decision unit <NUM> may decide an MCS with a still larger number than that of the MCS decided based on the DMRS. Thus, as compared with a case where the MCS decided based on the DMRS is assigned, a frequency resource can be effectively utilized, and it is possible to contribute to an improvement of the throughput of the user terminal <NUM>.

The MCS notification unit <NUM> notifies the user terminal <NUM> of the MCS decided by the MCS decision unit <NUM>. The MCS notification unit <NUM> assigns the MCS to the user terminal <NUM> by the UL Grant (PDCCH).

<FIG> schematically illustrates an example of a hardware configuration of a computer <NUM> which functions as the base station device <NUM>. Programs installed in the computer <NUM> can cause the computer <NUM> to function as one or more "units" of the device according to the present embodiment or can cause the computer <NUM> to execute operations associated with the devices according to the present embodiment or the one or more "units", and/or can cause the computer <NUM> to execute a process according to the present embodiment or 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 flowcharts 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>. In addition, the computer <NUM> includes input/output units such as a communication interface <NUM>, a storage device <NUM>, and a DVD drive and an IC card drive, which are connected to the host controller <NUM> through an input/output controller <NUM>. The storage device <NUM> may be a hard disk drive, a solid-state drive, and the like. The computer <NUM> also includes a ROM <NUM> and a legacy input/output unit such as a keyboard, which are connected to the input/output controller <NUM> via an input/output chip <NUM>.

The CPU <NUM> operates according to the programs stored in the ROM <NUM> and the RAM <NUM>, thereby controlling each unit. The graphics controller <NUM> obtains image data which is generated by the CPU <NUM>, in a frame buffer or the like provided in the RAM <NUM> or in itself so as to cause the image data to be 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 the program and data from an IC card, and/or writes the program and data to the IC card.

The ROM <NUM> stores therein a boot program or the like executed by the computer <NUM> at the time of activation, and/or a program depending on the hardware of the computer <NUM>. The input/output chip <NUM> may also connect various input/output units via a USB port, a parallel port, a serial port, a keyboard port, a mouse port, or the like to the input/output controller <NUM>.

A program is provided by a computer readable storage medium such as the DVD-ROM or the IC card. The program is read from the computer readable storage medium, installed into the storage device <NUM>, RAM <NUM>, or ROM <NUM>, which are also examples of a computer readable storage medium, and executed by the CPU <NUM>. Information processing written in these programs is read by the computer <NUM>, and provides cooperation between the programs and the various types of hardware resources described above. A device or method may be constituted by realizing the operation or processing of information in accordance with the usage of the computer <NUM>.

For example, in a case where a communication is performed between the computer <NUM> and an external device, the CPU <NUM> may execute a communication program loaded in the RAM <NUM> and instruct the communication interface <NUM> to perform communication processing based on a process written in the communication program. The communication interface <NUM>, under control of the CPU <NUM>, reads transmission data stored on a transmission buffer region provided in a recording medium such as the RAM <NUM>, the storage device <NUM>, 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 <NUM> may cause all or a necessary portion of a file or a database to be read into the RAM <NUM>, the file or the database having been stored in an external recording medium such as the storage device <NUM>, the DVD drive (DVD-ROM), the IC card, etc., and perform various types of processing on the data on the RAM <NUM>. Then, the CPU <NUM> may write the processed data back 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 to undergo information processing. The CPU <NUM> may execute, on the data read from the RAM <NUM>, various types of processing including various types of operations, information processing, conditional judgement, conditional branching, unconditional branching, information retrieval/replacement, or the like described throughout the present disclosure and specified by instruction sequences of the programs, to write the results back to the RAM <NUM>. In addition, the CPU <NUM> may retrieve information in a file, a database, or the like in the recording medium. For example, when a plurality of entries, each having an attribute value of a first attribute associated with an attribute value of a second attribute, are stored in the recording medium, the CPU <NUM> may search for an entry whose attribute value of the first attribute matches a designated condition, from among 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 a predetermined condition.

The programs or software module described above may be stored on the computer <NUM> or in a computer readable storage medium near the computer <NUM>. 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 program to the computer <NUM> via the network.

Blocks in flowcharts and block diagrams in the present embodiments may represent steps of processes in which operations are performed or "units" of devices responsible for performing operations. A specific step and "unit" may be implemented by dedicated circuitry, programmable circuitry supplied along with a computer readable instruction stored on a computer readable storage medium, and/or a processor supplied along with the computer readable instruction stored on the computer readable storage medium. The dedicated circuitry may include a digital and/or analog hardware circuit, or may include an integrated circuit (IC) and/or a discrete circuit. The programmable circuitry may include, for example, a reconfigurable hardware circuit including logical AND, logical OR, logical XOR, logical NAND, logical NOR, and other logical operations, and a flip-flop, a register, and a memory element, such as a field-programmable gate array (FPGA) and a programmable logic array (PLA).

The computer readable storage medium may include any tangible device capable of storing an instruction performed by an appropriate device, so that the computer readable storage medium having the instruction stored thereon constitutes a product including an instruction that may be performed in order to provide means for performing an operation specified by a flowchart or a block diagram. An example of the computer readable storage medium may include an electronic storage medium, a magnetic storage medium, an optical storage medium, an electromagnetic storage medium, or a semiconductor storage medium. More specific examples of computer readable storage media may include a floppy disc (registered trademark), a diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an electrically erasable programmable read-only memory (EEPROM), a static random access memory (SRAM), a compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a BLU-RAY (registered trademark) disc, a memory stick, an integrated circuit card, etc..

The computer readable instruction may include an assembler instruction, an instruction-set-architecture (ISA) instruction, a machine instruction, a machine dependent instruction, a microcode, a firmware instruction, state-setting data, or either of 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), and C++, and a conventional procedural programming language such as a "C" programming language or a similar programming language.

The computer readable instruction may be provided to a general purpose computer, a special purpose computer, or a processor or programmable circuitry of another programmable data processing device locally or via a local area network (LAN), a wide area network (WAN) such as the Internet or the like in order that the general purpose computer, the special purpose computer, or the processor or the programmable circuitry of the other programmable data processing device performs the computer readable instruction to provide means for performing operations specified by the flowchart or the block diagram. An example of the processor includes a computer processor, a processing unit, a microprocessor, a digital signal processor, a controller, a microcontroller, or the like.

According to the above described embodiment, the HAPS <NUM> has been used in the description as an example of the flight vehicle having the antenna which forms the wireless communication area by irradiating the beam towards the ground to provide the wireless communication service to the user terminal in the wireless communication area, but the flight vehicle is not limited to this. Examples of the flight vehicle include a balloon, an airship, an aircraft, and an unmanned flight vehicle such as a drone which can form the wireless communication area.

The operations, procedures, steps, stages, and the like of each process performed by an apparatus, system, program, and method shown 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.

Claim 1:
A base station device (<NUM>) which is mounted to a high-altitude platform system, HAPS, (<NUM>) and forms a multi-cell (<NUM>) including a plurality of cells (<NUM>) on a ground to provide a wireless communication service to a user terminal (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) in the multi-cell (<NUM>), the base station device (<NUM>) comprising:
a location information acquisition unit (<NUM>) which is configured to acquire location information of a user terminal (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) present in the multi-cell (<NUM>);
a flight vehicle associated information acquisition unit (<NUM>) which is configured to acquire flight vehicle associated information including location information and attitude information of the HAPS (<NUM>), the attitude information including the attitude of the HAPS (<NUM>) during flight;
an interference estimation unit (<NUM>) which is configured to estimate, based on location information of a plurality of the user terminals (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and the flight vehicle associated information, an interfered user terminal (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) having a chance of experiencing an interference from a cell (<NUM>) other than a cell (<NUM>) in which the user terminal (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is present among the plurality of user terminals (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and an interference amount;
an MCS decision unit (<NUM>) which is configured to decide an MCS of an uplink to be assigned to the interfered user terminal (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) based on the interference amount; and
an MCS notification unit (<NUM>) which is configured to notify the interfered user terminal (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) of the MCS decided by the MCS decision unit (<NUM>).