Control device, user terminal, control method, and program

Abstract

This control device for a base station is characterized by comprising a control unit that executes: a mode selection step for adopting, in response to a beam change request transmitted by a user terminal, any of a plurality of modes including at least a first mode in which resources are allocated for each request and a second mode in which resources are periodically allocated in advance; a mode notification step for notifying the user terminal of the selected mode; and a beam change step for changing a beam used for communication with the user terminal in response to the beam change request from the user terminal.

Description

Control device, user terminal, control method, and program

[0001] This disclosure relates to beam management in wireless communications.

[0002] Beamforming is used in wireless communication such as 5th Generation Mobile Communication Systems (5G), especially in wireless communication using high-frequency radio waves. By narrowing the range of the radio waves and concentrating power in a smaller area, it is possible to extend the communication range.

[0003] Non-patent document 1 describes a beam management procedure. In the beam management procedure, the beam to be used for communication between the base station and the mobile station is determined. While communication is being conducted using the determined beam, the mobile station measures the received intensity of the beam and reports the measurement results to the base station. The measured value is typically the Reference Signal Received Power (RSRP) of the CSI-RS (Channel State Information Reference Signal) signal.

[0004] In recent years, a method called UE-initiated beam management (UEIBM) has been investigated, in which a mobile station reports beam measurement results to a base station when it determines that a beam change is necessary (Patent Document 1). With UE-initiated beam management, the mobile station does not need to periodically report measurement results to the base station, thus reducing the consumption of communication resources.

[0005] U.S. Patent No. 10582503

[0006] 3GPP TR 38.802 V14.2.0 (2017-09)

[0007] There is insufficient consideration of the specific procedures for beam renewal when implementing UE-led beam management.

[0008] One aspect of this disclosure aims to provide a novel and useful method for performing beam updates under the guidance of a mobile station.

[0009] One aspect of the present disclosure is a control device for a base station, comprising: a mode selection step that adopts one of a plurality of modes, including at least a first mode that allocates resources each time a beam change request is made in response to a beam change request transmitted by a user terminal, and a second mode that allocates resources periodically in advance; a mode notification step that notifies the user terminal of the selected mode; and a beam change step that changes the beam used for communication with the user terminal in response to a beam change request from the user terminal, wherein when the first mode is adopted, the beam change step includes: receiving a resource allocation request from the user terminal for transmitting a beam change request; allocating resources for transmitting a beam change request and notifying the user terminal; receiving a beam change request from the user terminal via the allocated resources; changing the beam used for communication; and notifying the user terminal of the changed beam. In the case where the second mode described above is adopted, the control device for a base station is characterized in that the beam change step includes the step of receiving a beam change request from the user terminal via the pre-allocated communication resources, the step of changing the beam used for communication, and the step of notifying the user terminal of the changed beam.

[0010] Another aspect of the present disclosure is a user terminal comprising: a control unit that performs: a mode notification step of receiving notification from a base station of which of a plurality of modes to adopt in response to a beam change request, which includes at least a first mode of allocating resources each time a request is made and a second mode of allocating resources periodically in advance; and a change request step of transmitting a beam change request to the base station according to the beam measurement result, wherein when the first mode is adopted, the change request step includes a step of transmitting a resource allocation request to the base station for transmitting a beam change request, a step of receiving notification of resource allocation for transmitting a beam change request, a step of transmitting a beam change request to the base station via the allocated resources, and a step of receiving notification of the changed beam from the base station, wherein when the second mode is adopted, the change request step includes a step of transmitting a beam change request to the base station via the pre-allocated communication resources, and a step of receiving notification of the changed beam from the base station.

[0011] According to this disclosure, UE-led beam renewal can be properly implemented.

[0012] Figure 1 is a diagram showing an example of the configuration of a communication system according to one embodiment. Figure 2 is a diagram showing an example of the hardware configuration of a control device according to one embodiment. Figure 3 is a diagram showing an example of the functional configuration of a control device according to one embodiment. Figure 4 is a diagram showing an example of the functional configuration of a base station according to one embodiment. Figures 5(A) and 5(B) are flowcharts showing two modes (mode A and mode B) in beam reporting according to one embodiment, respectively. Figure 6 is a flowchart showing an example of the beam reporting mode selection process. Figure 7 is a diagram illustrating the method for calculating the delay time when mode A is adopted according to one embodiment. Figure 8 is a flowchart showing another example of the beam reporting mode selection process.

[0013] (Embodiment 1) Hereinafter, embodiments of the present disclosure will be described based on the drawings. The following embodiments are merely illustrative for illustrative purposes, and the present disclosure is not limited to the configuration of these embodiments. For example, the following describes an example using mobile communication, particularly 5G standard cellular communication (mobile communication), but the technology of the present disclosure may also be applied to cellular communication other than the 5G standard, or to wireless communication other than cellular communication.

[0014] [System Overview] Figure 1 is a diagram showing an example of the system configuration of the communication system 100 according to the first embodiment. The communication system 100 is a distributed MIMO system including a mobile station 3, a control device 1, and a plurality of distributed base stations. The distributed base stations, together with other distributed base stations in the same communication area, provide radio access to the mobile station 3 located within that communication area. The two distributed base stations shown in Figure 1 are assumed to be located within the same communication area. Each distributed base station is connected to the control device 1.

[0015] A distributed base station is equipped with multiple antennas. These multiple antennas are, for example, adaptive array antennas. An adaptive array antenna is an array antenna in which multiple antenna elements are arranged. The adaptive array antenna can electrically change its directivity by adaptively controlling the weighting of each antenna element according to the propagation environment. The beam pattern can also be described as the directivity of the adaptive array antenna. The beam pattern of a distributed base station is controlled by control device 1.

[0016] Mobile station 3 is, for example, a smartphone, tablet device, wearable device, or vehicle-mounted data communication device. However, it is not limited to these, and mobile station 3 may also be a stationary terminal device. Mobile station 3 is also referred to as a terminal station or user terminal.

[0017] In the example shown in Figure 1, there are two transmitting points: distributed base stations RU#1 and RU#2. Distributed base station RU#1 transmits three beams, b0, b1, and b2. Distributed base station RU#2 transmits two beams, b3 and b4. In the example shown in the figure, mobile station 3 is communicating using beam b1. Due to the movement of mobile station 3 or other changes in the radio wave environment, the communication quality of beam b1 may deteriorate, in which case the control device 1 changes the beam used for communication with mobile station 3.

[0018] Mobile station 3 receives designation from control device 1 for multiple beams, including a communication beam and a measurement beam. Mobile station 3 measures the received signal strength of the reference signal for these multiple beams at predetermined intervals and reports the measurement results to control device 1 when it determines that a beam refresh is necessary. Since mobile station 3 reports the measurement results when a beam refresh is necessary, the reporting of the measurement results can be interpreted as a request for a beam refresh. The specific procedure for performing a beam refresh will be described later.

[0019] [Configuration] Figure 2 is a diagram illustrating the hardware configuration of the control device 1. The control device 1 includes a CPU 101, a main memory 102, an auxiliary memory 103, an input device 104, an output device 105, and a communication device 106. The CPU 101 is also called a processor or arithmetic unit. The CPU 101 is not limited to a single processor and may be a multi-processor configuration. In addition to the CPU 101, a Graphics Processing Unit (GPU), a Digital Signal Processor (DSP), etc. may also be provided. Furthermore, the CPU 101 may be linked with hardware circuits such as a Field Programmable Gate Array (FPGA).

[0020] The CPU 101 executes a computer program that has been loaded into the main memory 102 in an executable format, and provides processing for the control device 1. The main memory 102 stores the computer program executed by the CPU 101, data processed by the CPU 101, etc. The main memory 102 is a Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), Read Only Memory (ROM), etc. Furthermore, the auxiliary storage device 103 is used as a storage area that assists the main memory 102, and stores the computer program executed by the CPU 101, data processed by the CPU 101, etc. The auxiliary storage device 103 is a hard disk drive, a Solid State Drive (SSD), etc. Furthermore, a drive device for a removable storage medium may be connected to the control device 1. Removable storage mediums are, for example, Blu-ray discs, Digital Versatile Discs (DVDs), Compact Discs (CDs), flash memory cards, etc. The CPU 101 is an example of a "control unit" of a "control device".

[0021] The input device 104 is a device for the operator to input information to the control device 1, and is, for example, a keyboard, mouse, or a touch panel with a touch sensor superimposed on a display. The output device 105 is a device for outputting information to the outside, in particular to the operator, and is, for example, a display device such as a liquid crystal display or an electroluminescent panel. The output device 105 may also include speakers or other devices that output sound. The communication device 106 communicates with other devices via wireless or wired communication through a communication interface. The control device 1 is configured to communicate with the base station 2 and the core network 4 via the communication device 106.

[0022] Figure 3 shows an example of the functional configuration of the control device 1. The control device 1 includes a control unit 10, and the control unit 10 includes a mode selection unit 11, a mode notification unit 12, a resource allocation unit 13, and a beam update unit 14 as its sub-function units. The mode selection unit 11 determines whether UE-led beam management will be performed in mode A or mode B. The mode notification unit 12 notifies the mobile station 3 of the determined mode. The resource allocation unit 13 allocates communication resources to be used in the beam management procedure. The beam update unit 14 updates (changes) the beam used for communication with the mobile station 3. The functions of the control unit 10 and its sub-function units are realized by the CPU 101 executing a program loaded into the main memory 102, but some or all of these functions may be realized by dedicated hardware circuits.

[0023] Figure 4 shows an example of the functional configuration of base station 2. Base station 2 includes a Radio Unit (RU) 21, a Distributed Unit (DU) 22, and a Centralized Unit (CU) 23. The RU 21 is a functional unit that controls the antenna array to transmit and receive radio waves with the mobile station 3, and also controls MIMO and beamforming. The antenna array of the RU 21 is also called the Transmission Reception Point (TRP). The antenna array of the RU 21 can also be called the transmission point or the reception point. In this disclosure, the location of base station 2 means the location of the antenna array (i.e., the transmission point, transmission point, or reception point). The DU 22 is a functional unit that performs signal modulation / demodulation and MAC layer communication control. The CU 23 is a functional unit that controls the DU 22 and RU 21, and performs PDCP protocol processing such as connection with the core network (CN) 4 and packet encryption, and RRC protocol processing such as radio resource management. Multiple RU21 units may be connected to one DU22 unit, and multiple DU22 units may be connected to one CU23 unit. The functional units of RU21, DU22, and CU23 may be located in geographically separate locations, or they may be located in the same location or within the same device. RU21, DU22, and CU23 are communicated with the control device 1 and perform control based on commands from the control device. The control device 1 may be located in geographically separate locations from RU21, DU22, and CU23, or it may be located in the same location or within the same device.

[0024] Mobile station 3 comprises a CPU, main memory, auxiliary memory, output device, operating device, wireless communication device, and antenna. Mobile station 3 connects to a wireless access network via the antenna using a mobile wireless communication method such as 5G, and performs wireless communication via a base station. The wireless communication device also performs functions such as measuring the base station beam, reporting the measurement results to the base station, and executing communication using the beam notified by the base station.

[0025] [Reporting Mode] Figures 5(A) and 5(B) illustrate two modes (referred to as Mode A and Mode B) in UE-led beam management.

[0026] Mode A is a mode in which the mobile station 3 requests the allocation of reporting communication resources from the base station 2 each time it reports measurement results. Mode B is a mode in which the base station 2 periodically allocates reporting communication resources in advance, and the mobile station 3 that makes the report uses the pre-allocated communication resources to make the report. Details of each mode will be further explained with reference to the diagrams.

[0027] In Mode A, as shown in Figure 5(A), the base station 2 notifies the mobile station 3 of the set of beams to be used for communication with the mobile station 3 and the set of beams to be measured by the mobile station 3, and initiates communication (S11). The mobile station 3 communicates using the designated beams, measures the communication beam and the measurement beam, and determines whether or not it is necessary to report the measurement results (S12). If reporting is necessary (S13-YES), the mobile station 3 creates request data to request the allocation of communication resources to be used for measurement reporting (S14) and transmits the request data to the base station 2 via PUCCH (Physical Uplink Control Channel) (S15). Upon receiving the request data, the base station 2 allocates a reporting communication resource (S16) and notifies the mobile station 3 of the allocated resource (S17). Here, it is assumed that resource 40 has been allocated. Upon receiving notification of the reporting resource, the mobile station 3 creates report data (S18) and reports the measurement results using the notified communication resource 40 (S19). Mode A corresponds to the first mode in this disclosure.

[0028] In Mode B, as shown in Figure 5(B), the base station 2 pre-allocates reporting resources periodically (S20) and notifies the mobile station 3 of the reporting resources (S21). Resources 40-1 to 40-4 represent the periodically allocated resources. The base station 2 notifies the mobile station 3 of the set of beams to be used for communication with the mobile station 3 and the set of beams that the mobile station 3 should measure, and then initiates communication (S22). The mobile station 3 communicates using the designated beams, measures the communication beam and the measurement beam, and determines whether or not it is necessary to report the measurement results (S23). If reporting is necessary (S24-YES), the mobile station 3 creates notification data indicating which of the pre-allocated periodic reporting resources to use for reporting (S25) and transmits the notification data to the base station 2 via PUCCH (S26). The mobile station 3 creates report data (S27) and reports the measurement results using the notified communication resource 40 (S28). In this example, the mobile station 3 uses resource 40-4 from the periodically allocated communication resources to make the report. Mode B corresponds to the second mode in this disclosure.

[0029] Comparing Mode A and Mode B, Mode A has a longer delay time between determining that a report is necessary and actually submitting the report, but it has less overhead in terms of communication resources. Mode A also has the advantage of allowing resource requests to be made according to the size of the report data. On the other hand, Mode B can shorten the delay time, but it has a larger overhead in terms of communication resources because allocated resources may not be used for reporting. Furthermore, the size of the report data is fixed in Mode B.

[0030] Thus, since Mode A and Mode B each have their own advantages and disadvantages, it is desirable to select the appropriate mode.

[0031] [Mode Selection Process] Figure 6 is a flowchart showing an example of the mode selection process performed by base station 2. The processing of base station 2 is carried out according to the control of control device 1, but control device 1 can be considered as the main operator of the processing. In the following explanation, base station 2 may also be described as the main operator.

[0032] In step S101, the mode selection unit 11 determines from the history data the elapsed time τ from beam notification to beam change request. ０ The elapsed time τ is calculated. The history data includes the time from when the beam notification was issued (for example, at step S11 in Figure 5(A) or step S22 in Figure 5(B)) to when the beam change request was issued (similarly, at step S19 or step S28) for mobile stations 3 that have previously communicated with base station 2. The history data is stored in the auxiliary storage device 103 of the control device 1 or in an external storage device. ０ This may be determined as the elapsed time relative to the beamset most recently assigned to the mobile station 3 (hereinafter also referred to as the target mobile station) to which the beamset is to be assigned. Alternatively, the elapsed time τ ０ This may be the average of the elapsed time (e.g., simple moving average) or weighted average (e.g., exponential moving average) of the most recent beamset allocations of the target mobile station. Alternatively, the elapsed time τ ０ This may be determined based on the elapsed time of other mobile stations that were previously located at the same location as the current location of the target mobile station, or the most recent elapsed time of one or more other mobile stations that previously followed a similar route to the target mobile station's travel path. The elapsed time τ thus obtained ０ This can also be interpreted as a predicted time or delay threshold for the beamset that base station 2 allocates to mobile station 3, until an update request occurs.

[0033] In step S102, when the mode selection unit 11 adopts mode A, it calculates the delay time τ required for beam change based on the slot configuration used for communication with the mobile station 3. FIG. 7 is a diagram for explaining the calculation method of the delay time τ based on the slot configuration. Here, as illustrated, it is assumed that one frame period is divided into an uplink period and a downlink period. However, the slot configuration is not limited to such a two-way division and can have various patterns, but the calculation method of the delay time τ can be applied to any of them. In the figure, T1 is the timing at which the control device 1 (base station 2) transmits a reference signal. Here, in order to obtain the worst value of the delay time, it is assumed that the reference signal is transmitted in the first slot of the downlink period 701D. When the mobile station 3 measures the reference signal and determines that a report is necessary, it transmits a request for allocation of reporting resources to the base station 2 at T2, which is any time in the next uplink period 702U. The base station 2 allocates the reporting resources to any slot in the next uplink period 703U and notifies it at T3, which is any time in the downlink period 702D. Then, the mobile station 3 reports to the base station using the allocated resources. The timing T4 for reporting is assumed to be the last slot of the uplink period 703U in order to obtain the worst value of the delay time. And the delay time τ is obtained as T4 - T1.

[0034] In step S103, the mode selection unit 11 calculates the ratio Γ ０ between the predicted value τ τ of the elapsed time and the delay time τ ０ = τ / τ τ and compares it with a predetermined threshold Γ0. If Γ ０ is smaller than the threshold Γ τ (S103 - NO), that is, when it is determined that the delay is small even if mode A is adopted, the process proceeds to step S104, and the mode selection unit 11 selects mode A. On the other hand, if Γ ０ is greater than or equal to Γ ０ (S103 - YES), that is, when the delay is too large if mode A is adopted, the process proceeds to step S104, and the mode selection unit 11 selects mode B. Threshold Γ ０is a value greater than 0 and less than or equal to 1. When mode B is selected, the mode selection unit 11 further determines, in step S106, the period of the reporting slot such that the delay time τ satisfies τ = C τ × τ ０ . The value C τ is a value greater than 0 and less than or equal to 1, and is determined by referring to the slot configuration in the same manner as in step S101.

[0035] Fig. 8 is a flowchart showing another example of the mode selection process performed by the base station 2. In step S11, the mode selection unit 11 obtains the allowable delay time τ ０ from the mobile station 3. For example, the mode selection unit 11 transmits a request for obtaining the allowable delay time to the mobile station 3, and the mobile station 3 obtains the allowable delay time from the upper layer and reports it to the control device 1. Thereby, the control device 1 can obtain the allowable delay time required by the application of the mobile station 3. The allowable delay time τ ０ can be regarded as a delay time threshold.

[0036] Since the processes of steps S202 to S206 are the same as the processes of steps S102 to S106 in Fig. 6, repeated description is omitted.

[0037] [Beam update process] The overall flow of the beam update process in each mode is as shown in Figs. 5(A) and 5(B). Here, the data included in the beam update request will be described in more detail.

[0038] In mode A, since resource allocation for reporting is requested each time a report is made, more data can be included in the report. Therefore, in the case of mode A, the mobile station 3 reports the signal strength for all beams that satisfy the reporting conditions notified by the control device 1 among the beam sets for which measurement has been instructed by the control device 1. The notification of the measurement beam and the measurement conditions is performed in step S11. Examples of the reporting conditions include, for example, a predetermined number of top beams whose reference signal received power (RSRP) exceeds a threshold value, all beams with higher intensity than the communication beam, and the like. The mobile station 3 includes the required data size in the resource allocation request data and requests allocation of communication resources sufficient to send this data size. In this case, the process of step S18 may be performed prior to step S14, and first, the report data may be created first, and then request data for requesting resource allocation sufficient to transmit this report data may be created.

[0039] Since a large amount of data is included in the measurement report, the control device 1 executes a complex beam update algorithm based on this data to perform beam update.

[0040] In mode B, the mobile station 3 transmits including less beam measurement data than in mode A. For example, when the beam with the maximum intensity changes, only the beam ID with the maximum intensity may be notified, or only the fact that the beam with the maximum intensity has changed may be notified. In other words, in mode B, the mobile station 3 transmits information indicating that the beam update condition is satisfied as a measurement result. By doing so, the amount of resources periodically allocated in mode B can be reduced.

[0041] (Other modifications) The above embodiments are merely examples, and the present disclosure can be appropriately modified and implemented without departing from the gist thereof.

[0042] The above example describes a scenario where there are two reporting modes, Mode A and Mode B. However, there may be three or more reporting modes, including modes other than these. Furthermore, Mode A and Mode B may be used in combination. Specifically, while Mode B is in use, Mode A may be requested to allocate communication resources for reporting according to the procedure.

[0043] Although the above embodiment shows an example of application to 5G standard cellular communication, it is applicable to other standards such as 3G, 4G, and 6G cellular communication, as well as wide-area wireless communication and narrow-area wireless communication other than cellular communication. Examples of wide-area wireless communication include wide-area wireless LAN (IEEE 802.11ah) and WiMax (IEEE 802.16). Examples of narrow-area wireless communication include wireless LAN (IEEE 802.11 / a / b / g / n / ac / ax), Bluetooth®, DSRC, and ZigBee®. Furthermore, although the above embodiment was explained using communication between a base station and a mobile station as an example, the method of this disclosure is applicable to communication between any wireless communication devices.

[0044] The present disclosure can also be realized by supplying a computer program implementing the functions described in the embodiments above to a computer, and having one or more processors in the computer read and execute the program. Such a computer program may be provided to the computer by a non-temporary computer-readable storage medium that can be connected to the computer's system bus, or it may be provided to the computer via a network. Non-temporary computer-readable storage mediums include, for example, any type of disk such as magnetic disks (floppy disks, hard disk drives (HDDs), etc.), optical disks (CD-ROMs, DVDs, Blu-ray discs, etc.), read-only memory (ROM), random access memory (RAM), EPROM, EEPROM, magnetic cards, flash memory, optical cards, and any type of medium suitable for storing electronic instructions.

[0045] 1: Control device 2: Base station 3: Mobile station 10: Control unit 11: Mode selection unit 12: Mode notification unit 13: Resource allocation unit 14: Beam update unit

Claims

1. A control device for a base station, comprising a control unit that performs: a mode selection step of adopting one of a plurality of modes, including at least a first mode in which resources are allocated each time a beam change request is made in response to a beam change request transmitted by a user terminal, and a second mode in which resources are allocated periodically in advance; a mode notification step of notifying the user terminal of the selected mode; and a beam change step of changing the beam used for communication with the user terminal in response to a beam change request from the user terminal, wherein when the first mode is adopted, the beam change step includes: receiving a resource allocation request from the user terminal for transmitting a beam change request; allocating resources for transmitting a beam change request and notifying the user terminal; receiving a beam change request from the user terminal via the allocated resources; changing the beam used for communication; and notifying the user terminal of the changed beam, wherein when the second mode is adopted, the beam change step includes: receiving a beam change request from the user terminal via the pre-allocated communication resources; changing the beam used for communication; and notifying the user terminal of the changed beam. A control device for a base station, characterized by the following features.

2. The control device according to claim 1, characterized in that, in the mode selection step, if the delay time required for beam change when the first mode is adopted is longer than the delay time threshold, the second mode is selected, and otherwise the first mode is selected.

3. The control device according to claim 2, wherein the mode selection step further includes the step of determining the delay time threshold based on the elapsed time in the history data from the notification of the beam to the occurrence of a beam change request.

4. The control device according to claim 3, characterized in that the delay time threshold is determined based on the history data of the user terminal.

5. The control device according to claim 3, characterized in that the delay time threshold is determined based on historical data of other user terminals that have followed a similar travel path to the user terminal.

6. The control device according to claim 3, characterized in that the delay time threshold is determined based on the allowable delay time notified from the user terminal.

7. The control device according to claim 3, characterized in that the delay time required for the beam change is determined based on the slot configuration used for communication with the user terminal.

8. The control device according to claim 3, characterized in that, when the second mode is selected, the period of the resources to be allocated in advance is determined such that the delay time required for beam change is less than or equal to the delay time threshold.

9. A user terminal comprising: a control unit that performs a mode notification step of receiving notification from a base station of which of a plurality of modes to adopt in response to a beam change request, which includes at least a first mode of allocating resources each time a request is made and a second mode of allocating resources periodically in advance; and a change request step of transmitting a beam change request to the base station according to the beam measurement result, wherein when the first mode is adopted, the change request step includes a step of transmitting a resource allocation request to the base station for transmitting a beam change request, a step of receiving notification of resource allocation for transmitting a beam change request, a step of transmitting a beam change request to the base station via the allocated resources, and a step of receiving notification of the changed beam from the base station, wherein when the second mode is adopted, the change request step includes a step of transmitting a beam change request to the base station via the pre-allocated communication resources, and a step of receiving notification of the changed beam from the base station.

10. The user terminal according to claim 9, characterized in that, in the change request step, beam measurement data is included in the beam change request and the amount of beam measurement data included in the beam change request is greater in the first mode than in the second mode.

11. The user terminal according to claim 9, characterized in that, when the first mode is adopted, the beam change request includes the measurement results of the beams among the beamsets instructed to be measured by the base station that satisfy the reporting conditions notified by the base station, and when the second mode is adopted, the beam change request includes information indicating that the beam update conditions notified by the base station are met.

12. The user terminal according to claim 9, characterized in that, when the first mode is adopted, the beam change request is created before the resource allocation request is created, and the resource allocation request requests a resource amount according to the amount of data of the beam change request.

13. A base station control method comprising: a mode selection step of adopting one of a plurality of modes, including at least a first mode in which resources are allocated each time a beam change request is made by a user terminal, and a second mode in which resources are allocated periodically in advance, in response to a beam change request transmitted by a user terminal; a mode notification step of notifying the user terminal of the selected mode; and a beam change step of changing the beam used for communication with the user terminal in response to a beam change request from the user terminal, wherein if the first mode is adopted, the beam change step comprises: receiving a resource allocation request from the user terminal for transmitting a beam change request; allocating resources for transmitting a beam change request and notifying the user terminal; receiving a beam change request from the user terminal via the allocated resources; changing the beam used for communication; and notifying the user terminal of the changed beam, wherein if the second mode is adopted, the beam change step comprises: receiving a beam change request from the user terminal via the pre-allocated communication resources; changing the beam used for communication; and notifying the user terminal of the changed beam. A method for controlling a base station, characterized by the features described above.

14. A user terminal control method comprising: a mode notification step of receiving notification from a base station of which of a plurality of modes to adopt in response to a beam change request, which includes at least a first mode of allocating resources each time a request is made and a second mode of allocating resources periodically in advance; and a change request step of transmitting a beam change request to the base station according to the beam measurement result, wherein if the first mode is adopted, the change request step includes a step of transmitting a resource allocation request to the base station for transmitting a beam change request, a step of receiving notification of resource allocation for transmitting a beam change request, a step of transmitting a beam change request to the base station via the allocated resources, and a step of receiving notification of the changed beam from the base station, wherein if the second mode is adopted, the change request step includes a step of transmitting a beam change request to the base station via the pre-allocated communication resources, and a step of receiving notification of the changed beam from the base station.

15. A program for causing a computer to perform each step of the method described in claim 13.

16. A program for causing a computer to perform each step of the method according to claim 14.

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