JP2026017238A - Control device and control method - Google Patents

Abstract

A technology is provided that enables beam updating to be performed quickly and appropriately.
[Solution] A control device for a base station includes a control unit that executes the steps of transmitting multiple beams, acquiring measurement results of the multiple beams from a mobile station, acquiring the direction of the mobile station relative to the base station, and a beam management step of determining which sub-procedure to start from in a beam determination procedure consisting of multiple sub-procedures based on the measurement results and the direction of the mobile station.
[Selected figure] Figure 8

Description

This disclosure relates to beam management in wireless communications.

Beamforming is used in wireless communications such as the 5th Generation Mobile Communication System (5G), particularly in wireless communications using high-frequency radio waves. Beamforming narrows the range of radio waves and concentrates power in a small area, making it possible to expand the communication range.

Non-Patent Document 1 describes that the Beam Management procedure includes three sub-procedures, P1 to P3. P1 is a coarse adjustment using a wide beam on the transmitting side, P2 is a fine adjustment using a narrow beam on the transmitting side, and P3 is a fine adjustment using a narrow beam on the receiving side.

Furthermore, while communicating using the determined beam, the mobile station measures the received strength of the beam and reports the measurement results to the base station. The measured value is typically the Reference Signal Received Power (RSRP) of a CSI-RS (Channel State Information Reference Signal) signal. The base station determines whether the beam to be used needs to be updated based on the measurement results, and updates the beam if necessary. This allows the base station and mobile station to continue communication using an appropriate beam.

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

When it is determined that a beam update is necessary, it is not necessary to start from the beginning of the beam determination procedure (i.e., the P1 subprocedure), but it is conceivable that it could start midway (the P2 or P3 subprocedure). Skipping some subprocedures allows for quick beam updates. On the other hand, skipping necessary subprocedures can result in the problem of being unable to select the optimal beam.

One aspect of the present disclosure aims to provide technology that can perform beam updates quickly and appropriately.

One aspect of the present disclosure is
A control device of a base station,
transmitting a plurality of beams;
acquiring measurement results of the plurality of beams from a mobile station;
obtaining a direction of the mobile station relative to the base station;
a beam management step of determining which sub-procedure to start from among a plurality of sub-procedures of a beam determination procedure based on the measurement result and the direction of the mobile station;
The base station control device is provided with a control unit that executes the above.

Another aspect of the present disclosure is
A method for controlling a base station, comprising:
transmitting a plurality of beams;
acquiring measurement results of the plurality of beams from a mobile station;
obtaining a direction of the mobile station relative to the base station;
a beam management step of determining which sub-procedure to start from among a plurality of sub-procedures of a beam determination procedure based on the measurement result and the direction of the mobile station;
The control method includes:

According to this disclosure, by taking into account not only the beam measurement results but also the direction of the mobile station, it is possible to evaluate the stability of the currently used beam, and by performing the beam determination procedure from the appropriate sub-procedure based on the evaluation results, it is possible to quickly and appropriately update the beam.

FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment. FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device according to an embodiment. FIG. 3 is a diagram illustrating an example of a functional configuration of a control device according to an embodiment. FIG. 4 is a diagram illustrating an example of a functional configuration of a base station according to an embodiment. FIG. 5 is a flowchart showing the overall processing flow of beam management according to an embodiment. FIG. 6 is a flowchart showing a detailed flow of a beam determination process according to an embodiment. 7A to 7C are diagrams illustrating a beam determination process according to one embodiment. FIG. 8 is a flowchart showing the flow of a start phase determination process for a beam update process according to an embodiment. 9A to 9C are diagrams for explaining a method for calculating the distance and direction of a mobile station. FIG. 10 is a flowchart showing the flow of a start phase determination process for a beam update process according to another embodiment. FIG. 11 is a flowchart showing the flow of a start phase determination process for a beam update process according to yet another embodiment.

(Embodiment 1)
Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The following embodiments are merely examples for explanatory purposes, and the present disclosure is not limited to the configurations of the embodiments. For example, an example using mobile communication, particularly 5G standard cellular communication (mobile communication), will be described below, but the technology of the present disclosure may be applied to cellular communication other than the 5G standard or wireless communication other than cellular communication.

[System Overview]
Fig. 1 is a diagram showing an example of the system configuration of a 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. A distributed base station, together with other distributed base stations in the same communication area, provides wireless access to a mobile station 3 located within the communication area. It is assumed that the two distributed base stations shown in Fig. 1 are located in the same communication area. Each of the distributed base stations is connected to the control device 1.

A distributed base station is equipped with one or more antennas. The multiple antennas equipped in a distributed base station are, for example, adaptive array antennas. An adaptive array antenna is an array antenna in which multiple antenna elements are arranged. An adaptive array antenna can adaptively control the weighting of each antenna element according to the radio wave propagation environment and electrically change the beam pattern. The beam pattern can also be said to be the directivity of the beam formed by the adaptive array antenna. The beam pattern of the distributed base station is controlled by a control device 1.

Mobile station 3 is, for example, a smartphone, tablet terminal, wearable terminal, or in-vehicle 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.

The example shown in Figure 1 includes two transmission points: distributed base stations RU#1 and RU#2. Three beams, b0, b1, and b2, are transmitted from distributed base station RU#1. Two beams, b3 and b4, are transmitted from distributed base station RU#2. In the example shown, mobile station 3 communicates using beam b1. It is possible that the communication quality of beam b1 will deteriorate as mobile station 3 moves or the radio wave propagation environment changes, in which case control device 1 will change the beam used for communication with mobile station 3.

The mobile station 3 receives from the control device 1 the specification of multiple beams, including communication beams and measurement beams, measures the received signal strength of the reference signal for the multiple beams at a predetermined interval, and reports the measurement results to the control device 1. Alternatively, the mobile station 3 may report the measurement results to the control device 1 when requested by the control device 1. Upon receiving the measurement results from the mobile station 3, the control device 1 determines whether the currently used beam needs to be updated, and if so, which sub-procedure of the beam determination procedure should be started from, and starts the beam determination procedure from the determined sub-procedure. The control device 1 determines whether the beam needs to be updated and the start phase based on the beam measurement results (received signal strength) and the direction of the mobile station 3 relative to the distributed base station (transmission point). Details of the beam determination procedure will be described later.

[composition]
2 is a diagram illustrating an example of the hardware configuration of the control device 1. The control device 1 includes a CPU 101, a main memory device 102, an auxiliary memory device 103, an input device 104, an output device 105, and a communication device 106. The CPU 101 is also called a processor or an arithmetic unit. The CPU 101 is not limited to a single processor, and may have a multi-processor configuration. In addition to the CPU 101, a graphics processing unit (GPU), a digital signal processor (DSP), or the like may be included. The CPU 101 may also be linked to a hardware circuit such as a field programmable gate array (FPGA).

The CPU 101 executes a computer program that has been loaded in an executable manner into the main memory device 102, and provides processing for the control device 1. The main memory device 102 stores the computer program that the CPU 101 executes, data that the CPU 101 processes, etc. The main memory device 102 may be a dynamic random access memory (DRAM), a static random access memory (SRRAM), or the like.
The auxiliary storage device 103 is, for example, a hard disk drive, a solid state drive (SSD), etc. Furthermore, the auxiliary storage device 103 is used as a storage area that supports the main storage device 102, and stores computer programs executed by the CPU 101, data processed by the CPU 101, etc. The auxiliary storage device 103 is, for example, 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. The removable storage medium is, for example, a Blu-ray disc, a Digital Versatile Disc (DVD), a Compact Disc (CD), a flash memory card, etc. The CPU 101 is an example of a "control unit" of a "control device."

The input device 104 is a device that allows the operator to input information to the control device 1, and is, for example, a keyboard, a mouse, or a touch panel with a touch sensor overlaid on a display. The output device 105 is a device that displays information to the outside, particularly to the operator, and is, for example, a display device such as an LCD display or an electroluminescence panel. The output device 105 may also include a speaker or other device that outputs sound. The communication device 106 communicates with other devices via a communication interface, either wirelessly or via wired communication. The control device 1 is configured to be able to communicate with the base station 2 and core network 4 via the communication device 106.

Figure 3 shows an example of the functional configuration of the control device 1. The control device 1 includes a control unit 10, and its sub-functional units include a measurement result acquisition unit 11, a mobile station information acquisition unit 12, a beam update determination unit 13, and a beam determination unit 14. The measurement result acquisition unit 11 acquires beam measurement results for the mobile station 3. The mobile station information acquisition unit 12 acquires information about the mobile station 3, including the distance between the base station 2 and the mobile station 3 and the direction of the mobile station 3 relative to the base station 2. The beam update determination unit 13 determines whether the beam used by the mobile station 3 needs to be updated, and if so, which sub-procedure of the beam determination procedure should be started from. The beam determination unit 14 determines the beam that the mobile station 3 will use for communication. The functions of the control unit 10 and its sub-functional units are realized by the CPU 101 executing programs loaded into the main memory device 102, but some or all of the functions may be realized by dedicated hardware circuits.

4 is a diagram showing an example of the functional configuration of the base station 2. The base station 2 includes an RU (Radio Unit) 21, a DU (Distributed Unit) 22, and a CU (Centralized Unit) 23. The RU 21 is a functional unit that controls an antenna array to communicate with the mobile station 3 by radio waves, and also controls MIMO, beamforming, etc. The antenna array of the RU 21 is also called a transmission reception point (TRP). The RU 21
The antenna array in the base station 2 may be referred to as a transmission point or a reception point. In this disclosure, the position of the base station 2 refers to the position of the antenna array (i.e., a transmission/reception point, a transmission point, or a reception point). The DU 22 is a functional unit that performs signal modulation/demodulation, MAC layer communication control, etc. The CU 23 is a functional unit that controls the DU 22 and the RU 21, connects to the core network (CN) 4, performs PDCP protocol processing such as packet encryption, and RRC protocol processing such as radio resource management. Note that multiple RUs 21 may be connected to one DU 22, and multiple DUs 22 may be connected to one CU 23. The respective functional units of the RU 21, DU 22, and CU 23 may be located in geographically separate locations, or may be located in the same location or within the same device. The RU 21, DU 22, and CU 23 are communicatively connected to the control device 1 and perform control based on commands from the control device. The control device 1 may be located at a location geographically separated from the RU 21, DU 22, and CU 23, or may be located at the same location or within the same device.

Mobile station 3 includes a CPU, main memory device, auxiliary memory device, output device, operation device, wireless communication device, and antenna. Mobile station 3 connects to a wireless access network via antenna 107 using a mobile wireless communication method such as 5G, and performs wireless communication via a base station. The wireless communication device also measures base station beams, reports measurement results to the base station, and performs communications using beams notified by the base station.

[process]
(1) Overall Processing of Beam Determination Procedure Fig. 5 is a flowchart showing the flow of processing performed by the control device 1 when the base station 2 and the mobile station 3 communicate with each other. At the start of this processing, the mobile station 3 is in an idle state, and no connection has been established with the base station 2. The following processing is performed between the base station 2 and the mobile station 3. The processing of the base station 2 is performed under the control of the control device 1, but in the following explanation, the base station 2 may be described as being the subject of the operation.

In step S11, a beam determination procedure is performed between the base station 2 and the mobile station 3 to determine the beam to be used for communication between the base station 2 and the mobile station 3 and the beam to be used for measurement. Figure 6 is a flowchart showing the details of the beam determination procedure S11 in step S11. Figure 7 is a diagram explaining the beam determination procedure. The beam determination procedure will be explained below with reference to Figures 6 and 7.

In step S111, coarse adjustment of the transmission beam is performed using a transmission beam with low angular resolution. The process of step S111 corresponds to the P1 subprocedure (first subprocedure). This procedure also involves a mobile station 3 in an idle state (RRC_IDLE) establishing a connection based on SSBs (Synchronization Signal Blocks). As shown in FIG. 7A, the base station 2 sweeps SSB beams in multiple different directions (beam sweeping). The mobile station 3 receives SSB beams (wide beams) using reception beams with low angular resolution. The mobile station 3 measures the SSB reception strength (e.g., RSRP) of each SSB beam and transmits a preamble via a Random Access Channel (RACH) at the transmission timing associated with the SSB with the highest reception strength, thereby establishing a connection. The mobile station 3 may also sweep reception beams to determine an optimal pair of transmission and reception beams. The beam determined in this procedure is a wide beam with low angular resolution and is not the optimal beam for transmitting and receiving data, so beam refinement is performed in the following procedure. Note that the wide beam used in this sub-procedure corresponds to a base station beam with the first angular resolution.

In step S112, fine adjustment of the transmission beam is performed using a transmission beam with high angular resolution. The processing of step S112 corresponds to the P2 subprocedure (second subprocedure). As shown in Figure 7 (B), the base station 2 transmits CSI-RS beams (narrow beams) with higher angular resolution in multiple different directions within the angular range of the beam determined in the P1 subprocedure. The mobile station 3 measures the reception strength (e.g., RSRP) of the CSI-RS signal contained in each beam and reports the measurement results to the base station 2. The base station 2 determines the CSI beam with the highest reception strength as the transmission beam to be used for communication between the base station 2 and the mobile station 3. The narrow beam used in this subprocedure corresponds to a base station beam with a second angular resolution, which is higher than the first angular resolution.

In step S113, fine adjustment of the receiving beam is performed using a receiving beam with high angular resolution. The processing in step S113 corresponds to the P3 subprocedure (third subprocedure). As shown in Figure 7(C), the base station 2 repeatedly transmits CSI-RS using the narrow beam determined in the P2 subprocedure, and the mobile station 3 sweeps and receives receiving beams with higher angular resolution than those used in the P1 and P2 subprocedures, and determines the receiving beam with the highest reception strength (e.g., RSRP).

The above process determines the pair of transmit and receive beams to be used in communications between the base station 2 and the mobile station 3. The base station 2 determines not only the beam to be used for communications (communication beam), but also the beam to be measured by the mobile station 3 during communications (measurement beam). When determining the measurement beam, for example, a beam adjacent to the angle of the communication beam may be selected, or a beam that achieved an intensity above the threshold in the P1 or P2 subprocedure, or the runner-up beam, may be selected.

In step S12, the base station 2 notifies the mobile station 3 of the communication beams and measurement beams determined in step S11, and performs communication using the communication beams. During communication, the mobile station 3 measures the communication beams and measurement beams and reports the measurement results to the base station 2. The timing of measurement and reporting in the mobile station 3 may be specified by the base station 2, or may be determined by the mobile station 3 itself.

In step S13, the base station 2 receives beam measurement results (measurement report) from the mobile station 3. The beam measurement results include information regarding reception strength, such as the reference signal received power (RSRP) of the beam at the mobile station 3.

In step S14, the base station 2 determines whether it is necessary to change the beam used for communication with the mobile station 3. The determination of whether a beam change is necessary is made based on, for example, whether the measurement results of the mobile station 3 satisfy certain conditions, such as whether the reception strength included in the measurement results of the currently used beam is below a threshold, or whether there is another beam with a higher reception strength than the currently used beam. If it is determined that a beam change is not necessary (S14-NO), the process returns to step S13 and waits for the next measurement result from the mobile station 3. On the other hand, if it is determined that a beam change is necessary, the process proceeds to step S15.

In step S15, base station 2 determines whether the starting phase of the beam update will be sub-procedure P1, P2, or P3. Details of this process will be described later.

In step S16, the base station 2 executes the beam determination procedure from the subprocedure determined in step S15 and determines the beam to be used for communication and measurement. This process is similar to the process of step S11 described with reference to Figures 6 and 7, but depending on the start phase, the processes of steps S111 and S112 may be omitted.

In step S17, the base station 2 notifies the mobile station 3 of the communication beam and measurement beam determined in step S16, and performs communication using the communication beam. From this point on, the processing from step S13 to step S17 is repeated until communication between the base station 2 and the mobile station 3 is completed.

(2) Start Phase Determination Process S15
8 is a flowchart showing details of the start phase determination process of the beam determination procedure in step S15. The process of step S15 will be described with reference to FIG.

In step S151, the control device 1 acquires the beam measurement results and position information of the mobile station 3. For example, the control device 1 stores the measurement results received in memory when it receives the measurement results in step S13, and in step S151, the measurement result acquisition unit 11 acquires these measurement results from memory. The position information of the mobile station 3 may be acquired in any manner, for example, by acquiring from the mobile station 3 the position information acquired by the mobile station 3 using a GPS device or other GNSS device. The position information transmitted from the mobile station 3 may be included in a measurement report or in another signal. Alternatively, the position information of the mobile station 3 may be determined based on the time difference of arrival (TDOA) of radio waves from the mobile station 3 at multiple base stations 2 (RUs or transmitting/receiving points).

In step S152, the control device 1 calculates the direction θ ₀ and distance d _UE,RS of the mobile station 3 relative to the base station 2. Here, relative to the base station 2 means, more precisely, relative to the transmitting/receiving point (TRP) of the beam.

Figure 9(A) is a diagram showing an example of the positional relationship between a base station 2 and a mobile station 3. In Figure 9(A), it is assumed that a building 902 is present in a direction 904 of the mobile station 3 as seen from the base station 2, preventing radio waves from reaching the mobile station 3, and that communication between the base station 2 and the mobile station 3 is carried out using radio waves reflected by the building 903 in a direction 905. Figure 9(B) is a diagram showing the positional relationship in Figure 9(A) projected onto a horizontal plane and viewed from above.

In step S152, the mobile station information acquisition unit 12 can calculate the direction θ ₀ and the distance d _UE,BS according to the following formula, as shown in FIG. 9(B).

Here, (x _UE , y _UE ) and (x _BS , y _BS ) are the x and y coordinates of the mobile station 3 and base station 2 (transmission and reception points), respectively. The coordinate system may be a global coordinate system such as latitude and longitude, or a local coordinate system based on a specific base station.

In step S153, the beam update determination unit 13 determines whether or not a beam exceeding the intensity threshold Th1 is present in the measurement report from the mobile station 3. The intensity threshold Th1 corresponds to the first threshold in this disclosure. The intensity threshold Th1 may be determined as appropriate. For example, the intensity threshold Th1 is a value that allows stable communication to continue using that beam if the reception intensity is equal to or greater than that value. If no beam exceeds the intensity threshold Th1 (S153-NO), the process proceeds to step S157, and the beam update determination unit 13 determines to start the beam determination procedure from the P1 sub-procedure (S111). On the other hand, if a beam exceeding the intensity threshold Th1 is present (S153-YES), the process proceeds to step S154.

In step S154, the beam update determination unit 13 determines whether there is a beam whose direction matches the direction of the mobile station 3 among the beams that exceed the intensity threshold Th1.

Here, whether or not the beam direction matches the direction of the mobile station 3 is determined, for example, as follows. In one example, if the direction _θ0 of the mobile station 3 is within the range of the half-width of the beam, the beam direction can be determined to be that of the mobile station 3. More specifically, if the beam direction exceeding the intensity threshold Th1 is defined as θ _OK and the beam width (half-width) of this beam is defined as φ, it is determined that the beam matches the direction of the mobile station 3 if θ _OK -φ/2 < θ ₀ < θ _OK +φ/2 is satisfied. Note that if there are multiple beams exceeding the intensity threshold Th1, the above determination is made for each beam.

In another example, the beam direction exceeding the intensity threshold Th1 may be defined as θ _OK , and the maximum Fresnel diameter of this beam may be defined as D. If θ _OK - D/d _UE,BS < θ ₀ < θ _OK + D/d UE _,BS is satisfied, it may be determined that the direction of the beam matches that of the mobile station 3. Here, D/d _UE,BS is an approximation of the angle between the beam central axis and a point that is the maximum Fresnel diameter D when the base station 2 is a distance d _UE,BS /2 away from the beam central axis. When the wavelength of the radio wave is λ, the maximum Fresnel diameter is given as D = (λd _UE,BS ) ^1/2 , so the above determination formula can be expressed as follows:

In the determination of step S154, if it is determined that there is no beam that matches the direction of the mobile station 3 among the beams that exceed the intensity threshold Th1 (S154-NO), the process proceeds to step S155. On the other hand, if it is determined that there is a beam that matches the direction of the mobile station 3 among the beams that exceed the intensity threshold Th1 (S154-YES), the process proceeds to step S156.

In step S155, the beam update determination unit 13 determines whether the distance d _UE,BS of the mobile station 3 is equal to or greater than the distance threshold d _TH . The distance threshold d _TH corresponds to the second threshold in the present disclosure. If the distance d _UE,BS is less than the distance threshold d _TH (S155-NO), the process proceeds to step S157, and the beam update determination unit 13 determines to start the beam determination procedure from the P1 sub-procedure (S111). On the other hand, if the distance d _UE,BS is equal to or greater than the distance threshold d _TH (S1
If the result is YES (S115-55), the process proceeds to step S158, and the beam update determination unit 13 determines to start the beam determination procedure from the P2 sub-procedure (S112).

The distance threshold d _TH can be determined, for example, as follows: When a beam with beam width φ is used, the width of the communication area (footprint) at distance d _UE,BS is d _UE,BS ·φ. From the moving speed v _UE of the mobile station 3 and the processing delay τ _BM required for the beam update process, the distance L _BM traveled by the mobile station 3 during the beam update process is v _UE ·τ _BM . If L _BM is allowed to be up to half of d _UE,BS ·φ, the distance threshold d _TH can be set to 2v _UE τ _BM /φ as shown in the following formula.

If the distance d _UE,BS is less than the distance threshold d _TH , the mobile station 3 may move outside the beam footprint during the beam update process, so the beam determination process starts from an earlier sub-procedure (P1 sub-procedure). On the other hand, if the distance d _UE,BS is equal to or greater than the distance threshold d _TH , the mobile station 3 remains within the beam footprint, so the beam determination process can start from a later sub-procedure (P2 sub-procedure).

The control device 1 may acquire the moving speed v _UE of the mobile station 3 in any way. For example, if the mobile station 3 notifies the base station 2 of its moving speed v _UE , this can be used. If the mobile station 3 does not report its moving speed v _UE , the moving speed v UE of the mobile station 3 can be estimated from the angular change of the beam with the maximum intensity, provided that the intensity measurement values of each beam are reported in the beam measurement results at the most recent measurement timings. Specifically, the moving speed v _UE can be estimated by: moving speed v _UE = (distance d _UE,BS to the mobile station) × (angle change) / (beam measurement time interval). Furthermore, if the beam intensity measurement values are not reported, a predetermined value may be used as the moving speed of the mobile station 3.

The distance threshold dTH may be determined by further considering the beam lifetime _τLT (the maximum time for which the same beam can be continuously used). In this case, the lifetime _τLT can be added to determine _dTH = _2vUE ( _τBM + _τLT )/φ.

In step S156, the beam update determination unit 13 performs the same determination as in step S155. The determination content is the same as in step S155, so repeated explanation will be omitted. Note that the distance threshold _dTH in steps S155 and S156 may be the same or may be different values.

If the distance d _UE,BS is less than the distance threshold d _TH (S156-NO), the process proceeds to step S158, and the beam update determination unit 13 determines to start the beam determination procedure from the P2 sub-procedure (S112). On the other hand, if the distance d _UE,BS is equal to or greater than the distance threshold d _TH (S1
If the result is YES (56-YES), the process proceeds to step S159, and the beam update determination unit 13 determines to start the beam determination procedure from the P3 subprocedure (S113). If the distance d _UE,BS is less than the distance threshold d _TH , there is a possibility that the mobile station 3 will move outside the footprint of the beam during the beam update process, so the beam update process starts from an earlier subprocedure (P2 subprocedure). On the other hand, if the distance d _UE,BS is equal to or greater than the distance threshold d _TH , the mobile station 3 will remain within the footprint of the beam, so the beam update process can start from a later subprocedure (P3 subprocedure).

[Advantageous Effects]
According to the technique disclosed herein, when it becomes necessary to change the beam used for communication between the base station 2 and the mobile station 3, the beam determination (update) procedure, which is made up of multiple subprocedures, can be started from an intermediate subprocedure rather than from the beginning, thereby enabling rapid beam updating. Furthermore, the start phase of the beam determination procedure is determined taking into consideration not only the received strength of the beam at the mobile station 3 but also information such as the direction and distance between the base station 2 and the mobile station 3. Therefore, by executing the necessary subprocedures without omitting them, it is possible to more reliably update to an appropriate beam.

[Modification]
In the above example, two-dimensional coordinates are used to calculate the direction and distance to the mobile station 3, but three-dimensional coordinates may also be used, as shown in Fig. 9(C). In the case of three-dimensional coordinates, the direction of the mobile station 3 is specified by an azimuth angle θ ₀ and a zenith angle φ _0. The azimuth angle θ ₀ , zenith angle φ _0, and distance d _UE,RS can be calculated based on the following equations.

(Embodiment 2)
This embodiment differs from embodiment 1 in the process of determining the start phase of beam update (step S15). As the rest is the same as embodiment 1, only the differences will be mainly described.

Figure 10 is a flowchart showing the beam update start phase determination process (step S15) in this embodiment. Compared to embodiment 1 (Figure 8), the determination processes of steps S155 and S156 are omitted. If it is determined in step S154 that there is no beam matching the direction of mobile station 3 among the beams exceeding intensity threshold Th1 (S154-NO), the process proceeds to step S158, where it is determined that the beam determination procedure will start from the P2 subprocedure. On the other hand, if it is determined in step S154 that there is a beam matching the direction of mobile station 3 among the beams exceeding intensity threshold Th1 (S154-YES), the process proceeds to step S159, where it is determined that the beam determination procedure will start from the P3 subprocedure.

In this embodiment, as in embodiment 1, when it becomes necessary to change the beam used for communication between the base station 2 and the mobile station 3, the beam determination (update) procedure, which consists of multiple sub-procedures, can be started from an intermediate sub-procedure rather than from the beginning, thereby achieving the advantage of enabling rapid beam updating.

(Embodiment 3)
This embodiment differs from embodiment 1 in the process of determining the start phase of beam update (step S15). As the rest is the same as embodiment 1, only the differences will be mainly described.

Figure 11 is a flowchart showing the beam update start phase determination process (step S15) in this embodiment. Compared to embodiment 1 (Figure 8), this embodiment differs in that, depending on the determination result of step S154, steps S201 and S202 are performed instead of steps S155 and S156.

In step S201, a determination is made using past history. More specifically, it is determined whether the beam duration of a beam selected under the same or similar conditions in the past is sufficiently long. The determination of whether it is sufficiently long can be made by comparing the beam duration with a duration threshold. The duration threshold can be determined as appropriate, and can be, for example, the lifetime required for the beam. If the beam duration is less than the duration threshold, processing proceeds to step S157, where the beam update determination unit 13 determines to start the beam determination procedure from the P1 subprocedure (S111). On the other hand, if the beam duration is equal to or greater than the duration threshold, processing proceeds to step S158, where the beam update determination unit 13 determines to start the beam determination procedure from the P2 subprocedure (S112).

The determination process in step S202 is the same as that in step S201, so a repeated explanation will be omitted. Note that the duration threshold may be the same in steps S201 and S202, or may be different values. In step S202, if the beam duration is less than the duration threshold, processing proceeds to step S158, where the beam update determination unit 13 determines to start the beam determination procedure from the P2 subprocedure (S112). On the other hand, if the beam duration is equal to or greater than the duration threshold, processing proceeds to step S159, where the beam update determination unit 13 determines to start the beam determination procedure from the P3 subprocedure (S113).

In steps S201 and S202, past selections included in the history that satisfy the following conditions can be considered to be selections under the same or similar conditions as the current selection. Criteria for determining identity include one or more of the following: whether the same beam as the beam currently being used for communication was selected; whether the location information of the mobile station 3 is the same; whether the moving speed of the mobile station 3 is the same; and whether the orientation of the mobile station 3 is the same. Here, "the location information of the mobile station 3 is the same" means that the distance between the current location information of the mobile station 3 and the location information of the mobile station 3 in the past selection is within a predetermined threshold, which can be determined as appropriate. The same applies to the orientation and moving speed. As an example, the beam update determination unit 13 searches the history for a selection in which the location information and moving speed of the mobile station 3 are the same as those currently used for communication and which selected the same beam. The beam update determination unit 13 then performs the determination in steps S201 and S202 by comparing the beam duration of the selected beam with the duration threshold. If there are multiple beam selections that meet the conditions, the statistical values (average, mode, median, minimum, maximum, etc.) of the beam durations of these selections may be compared with the duration threshold. One example of a statistical value is a weighted average, with more weight given to the most recent value. Alternatively, the beam duration of the most recent selection may be compared with the duration threshold.

In order to make a history-based determination as in this embodiment, the control device 1 stores in memory the measurement results of the mobile station 3, information such as the position, orientation, and movement speed of the mobile station 3, the selected beam, and the beam duration of the selected beam each time it performs a beam update process.

As in the first embodiment, this embodiment also provides the advantage of enabling rapid beam updating when it becomes necessary to change the beam used for communication between the base station 2 and the mobile station 3, because it is possible to start from an intermediate sub-procedure rather than starting from the beginning of the beam determination (update) procedure consisting of multiple sub-procedures. In this embodiment, the stability of the beam currently in use is evaluated based on past history, and an appropriate start phase for beam updating can be determined based on the stability of the beam.

Instead of making a decision by directly referencing past history, it is also possible to use past history as training data to train a machine learning model that takes each situation as input and outputs the duration of the selected beam, and then use this machine learning model to determine the beam duration in the current situation.The estimated beam duration can then be compared with a duration threshold to determine the start phase of the beam determination procedure. This approach can also achieve the same effect.

(Other Modifications)
The above-described embodiment is merely an example, and the present disclosure can be modified and implemented as appropriate within the scope that does not deviate from the gist of the disclosure.

The above embodiment illustrates an example of application to 5G cellular communication, but it can also be applied to other cellular communication standards such as 3G, 4G, and 6G, as well as wide-area 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 802.6). Examples of narrow-area wireless communication include wireless LAN (IEEE 802.11/a/b/g/n/ac/ax), Bluetooth (registered trademark), DSRC, and ZigBee (registered trademark). Furthermore, while the above embodiment illustrates communication between a base station and a mobile station, the technique of the present disclosure can be applied to communication between any wireless communication devices.

The present disclosure can also be realized by supplying a computer program that implements the functions described in the above embodiments 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 via a non-transitory computer-readable storage medium connectable to the computer's system bus, or via a network. Non-transitory computer-readable storage media include, for example, any type of disk, such as a magnetic disk (e.g., a floppy disk, a hard disk drive (HDD), etc.), an optical disk (e.g., a CD-ROM, a DVD disk, a Blu-ray disk), a read-only memory (ROM), a random access memory (RAM), an EPROM, an EEPROM, a magnetic card, a flash memory, an optical card, or any type of medium suitable for storing electronic instructions.

1: Control device 2: Base station 3: Mobile station 10: Control unit 11: Measurement result acquisition unit 12: Mobile station information acquisition unit 13: Beam update determination unit 14: Beam determination unit

Claims (21)

A control device of a base station,
transmitting a plurality of beams;
acquiring measurement results of the plurality of beams from a mobile station;
obtaining a direction of the mobile station relative to the base station;
a beam management step of determining which sub-procedure to start from among a plurality of sub-procedures of a beam determination procedure based on the measurement result and the direction of the mobile station;
A control device comprising a control unit that executes the above. In the beam management step, a sub-procedure to start from among a plurality of sub-procedures of a beam determination procedure is determined based on the distance between the base station and the mobile station in addition to the measurement result and the direction of the mobile station.
2. The control device according to claim 1. The control unit
further performing the step of obtaining information from the mobile station regarding the location of the mobile station;
In the step of acquiring the direction of the mobile station relative to the base station, the direction of the mobile station relative to the base station is obtained from a position of the mobile station and a position of the base station.
2. The control device according to claim 1. The beam determination procedure includes:
a first sub-procedure of adjusting a base station beam using a base station beam of a first angular resolution;
a second sub-procedure of adjusting a base station beam using a base station beam with a second angular resolution higher than the first angular resolution;
a third sub-procedure, which is the adjustment of the mobile station beam;
in this order,
In the beam management step, it is determined which of the first subprocedure, the second subprocedure, and the third subprocedure to start based on the measurement result and the direction of the mobile station.
2. The control device according to claim 1. The beam management step includes a first determination step of determining whether or not there is a beam whose received signal strength is higher than a first threshold in the measurement result, and if there is no beam whose received signal strength is higher than the first threshold, determining to start from the first sub-procedure.
5. The control device according to claim 4. The beam management step includes a second determination step of determining whether or not there is a beam that matches the direction of the mobile station among beams whose received signal strength is higher than the first threshold;
If there are beams whose received signal strength is higher than a first threshold and none of the beams coincides with the direction of the mobile station, start from the first subprocedure or the second subprocedure;
If there are beams whose received signal strength is higher than a first threshold and if any of those beams coincides with the direction of the mobile station, start the second subprocedure or the third subprocedure.
6. The control device according to claim 5. In the second determination step, the direction of the mobile station is θ ₀ , the direction of the beam having a received signal strength higher than the first threshold is θ _OK , and the beam width of the beam is φ, and θ _OK −φ/2<θ ₀ <
If θ _OK +φ/2 is satisfied, it is determined that the direction of the beam matches that of the mobile station.
7. The control device according to claim 6. In the second determination step, when the relationship θ OK -D/d UE,BS < θ ₀ < θ _OK +D/d _UE,BS is satisfied, where θ 0 is the direction of the mobile station, θ _OK is the direction of the beam whose received signal strength is higher than the first threshold, d _{UE,BS is} the distance between the base _station and the mobile _station, and D is the maximum Fresnel diameter of the beam, it is determined that the direction of the beam and the mobile station coincide.
7. The control device according to claim 6. the beam management step includes a third determination step of determining whether a distance between the base station and the mobile station is greater than a second threshold;
If there are beams whose received signal strength is higher than a first threshold, and none of the beams coincides with the direction of the mobile station, and the distance between the base station and the mobile station is greater than the second threshold, start from the first subprocedure;
If there are beams whose received signal strength is higher than a first threshold, and none of the beams coincides with the direction of the mobile station, and the distance between the base station and the mobile station is less than the second threshold, start from the second subprocedure;
If there are beams whose received signal strength is higher than a first threshold, and among those beams there is a beam that matches the direction of the mobile station, and the distance between the base station and the mobile station is greater than the second threshold, start from the second subprocedure;
If there are beams whose received signal strength is higher than a first threshold, and among those beams there is a beam that matches the direction of the mobile station, and the distance between the base station and the mobile station is smaller than the second threshold, start from the third subprocedure.
7. The control device according to claim 6. The second threshold is 2v _UE τ _BM /φ, where φ is the beam width of the beam with the highest received signal strength, v _UE is the moving speed of the mobile station, and τ _BM is the processing delay required for the beam determination procedure.
The control device according to claim 9 . The second threshold is 2v UE (τ BM +τ LT )/φ, where φ is the beam width of the beam with the highest received signal strength, v _UE is the moving speed of the mobile station, τ _BM is the processing delay required for the beam management sub- _procedure , _and τ _LT is the lifetime of the beam with the highest _received signal strength.
The control device according to claim 9 . the control unit further executes a step of acquiring a moving speed of the mobile station.
The control device according to claim 10 . the control unit further executes a step of calculating a moving speed of the mobile station based on an angular change in a beam direction at which the received signal strength is maximized at different measurement timings and a measurement time interval between the different measurement timings.
The control device according to claim 10 . The beam management step includes a second determination step of determining whether or not there is a beam that matches the direction of the mobile station among beams whose received signal strength is higher than the first threshold;
If there are beams whose received signal strength is higher than the first threshold and none of these beams coincides with the direction of the mobile station, start from the second subprocedure;
If there are beams whose received signal strength is higher than the first threshold and if there is a beam among those beams that matches the direction of the mobile station, start from the third subprocedure.
6. The control device according to claim 5. The beam management step further includes a step of acquiring a duration of a beam selected based on a measurement result under the same conditions from a past history, and determining from which sub-procedure of the beam determination procedure to start based on a comparison between the duration of the beam and a duration threshold.
5. The control device according to claim 4. A method for controlling a base station, comprising:
transmitting a plurality of beams;
acquiring measurement results of the plurality of beams from a mobile station;
obtaining a direction of the mobile station relative to the base station;
a beam management step of determining which sub-procedure to start from among a plurality of sub-procedures of a beam determination procedure based on the measurement result and the direction of the mobile station;
A control method comprising: The beam determination procedure includes:
a first sub-procedure of adjusting a base station beam using a base station beam of a first angular resolution;
a second sub-procedure of adjusting a base station beam using a base station beam with a second angular resolution higher than the first angular resolution;
a third sub-procedure, which is the adjustment of the mobile station beam;
in this order,
In the beam management step, it is determined which of the first subprocedure, the second subprocedure, and the third subprocedure to start based on the measurement result and the direction of the mobile station.
17. The control method according to claim 16. The beam management step includes a first determination step of determining whether or not there is a beam whose received signal strength is higher than a first threshold in the measurement result, and if there is no beam whose received signal strength is higher than the first threshold, determining to start from the first sub-procedure.
18. The control method according to claim 17. the beam management step includes a third determination step of determining whether a distance between the base station and the mobile station is greater than a second threshold;
If there are beams whose received signal strength is higher than a first threshold, and none of the beams coincides with the direction of the mobile station, and the distance between the base station and the mobile station is greater than the second threshold, start from the first subprocedure;
If there are beams whose received signal strength is higher than a first threshold, and none of the beams coincides with the direction of the mobile station, and the distance between the base station and the mobile station is less than the second threshold, start from the second subprocedure;
If there are beams whose received signal strength is higher than a first threshold, and among those beams there is a beam that matches the direction of the mobile station, and the distance between the base station and the mobile station is greater than the second threshold, start from the second subprocedure;
If there are beams whose received signal strength is higher than a first threshold, and among those beams there is a beam that matches the direction of the mobile station, and the distance between the base station and the mobile station is smaller than the second threshold, start from the third subprocedure.
18. The control method according to claim 17. obtaining, from the mobile station, information relating to the location of the mobile station;
determining a direction of the mobile station relative to the base station or a distance between the mobile station and the base station from the position of the mobile station and the position of the base station;
17. The control method of claim 16, further comprising: transmitting a plurality of beams;
acquiring measurement results of the plurality of beams from a mobile station;
obtaining a direction of the mobile station relative to a base station;
a beam management step of determining which sub-procedure to start from among a plurality of sub-procedures of a beam determination procedure based on the measurement result and the direction of the mobile station;
A computer program for causing an information processing device to execute the above.