Control device and control method

Abstract

To provide a technique capable of quickly and appropriately performing beam update.SOLUTION: A control device of a base station includes a control unit configured to execute a step of transmitting a plurality of beams, a step of acquiring a measurement result of the plurality of beams from a mobile station, a step of acquiring a direction of the mobile station with respect to the base station, and a beam management step of determining from which subprocedure a beam determination procedure including a plurality of subprocedures is started on the basis of the measurement result and the direction of the mobile station.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to beam management in wireless communications. [Background technology]

[0002] Beamforming is used in wireless communications such as the 5th Generation Mobile Communication System (5G), especially in wireless communications using high-frequency radio waves. Beamforming narrows the range of radio waves and concentrates power in a narrow area, making it possible to expand the communication range.

[0003] Non-Patent Document 1 states that the Beam Management procedure has three sub-procedures, P1 to P3. It is described that the procedures include: 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.

[0004] 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 the CSI-RS (Channel State Information Reference Signal) signal. The base station updates the beam to be used based on the measurement results. The base station determines whether it is necessary to update the beam, and if so, updates the beam, allowing the base station and mobile station to continue communication using an appropriate beam. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] 3GPP TR 38.802 V14.2.0 (2017-09) Summary of the Invention [Problem to be solved by the invention]

[0006] 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 possible to start from the middle (P2 or P3 subprocedure). Skipping some subprocedures enables quick beam update. On the other hand, skipping necessary subprocedures can cause the problem of not being able to select the optimal beam.

[0007] One aspect of the present disclosure aims to provide a technology that can quickly and appropriately perform beam updates. [Means for solving the problem]

[0008] 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.

[0009] 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: [Effects of the Invention]

[0010] According to the present 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 beam currently in use, and by performing a beam determination procedure from an appropriate sub-procedure based on the evaluation results, it is possible to quickly and appropriately update the beam. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a control device according to an embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of a functional configuration of a control device according to an embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a functional configuration of a base station according to an embodiment. [Figure 5] FIG. 5 is a flowchart showing the overall processing flow of beam management according to an embodiment. [Figure 6] FIG. 6 is a flowchart showing a detailed flow of the beam determination process according to an embodiment. [Figure 7] 7A to 7C are diagrams illustrating a beam determination process according to one embodiment. [Figure 8] FIG. 8 is a flowchart showing the flow of a start phase determination process for a beam update process according to an embodiment. [Figure 9] 9(A) to 9(C) are diagrams for explaining a method for calculating the distance and direction of a mobile station. [Figure 10] FIG. 10 is a flowchart showing the flow of a start phase determination process for a beam update process according to another embodiment. [Figure 11] FIG. 11 is a flowchart showing the flow of a start phase determination process for a beam update process according to yet another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Embodiment 1) Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The following embodiments are merely examples for the purpose of explanation, 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.

[0013] [System Overview] FIG. 1 is a diagram showing an example of a 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.

[0014] A distributed base station has one or more antennas. The antenna is, for example, an adaptive array antenna. 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 the control device 1.

[0015] The mobile station 3 is, for example, a smartphone, a tablet terminal, a wearable terminal, or an in-vehicle data communication device. However, the mobile station 3 is not limited to these, and may also be a stationary terminal device. The mobile station 3 is also called a terminal station or a user terminal.

[0016] 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 in the figure, mobile station 3 is communicating using beam b1. It is possible that the communication quality of beam b1 will deteriorate as mobile station 3 moves or as the radio wave propagation environment changes. In that case, the control device 1 will change the beam used for communication with mobile station 3.

[0017] 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 an update is necessary, which sub-procedure of the beam determination procedure should be started from, and starts the beam determination procedure from the determined sub-procedure. Note that the control device 1 determines whether the beam needs to be updated and the start phase, taking into account 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.

[0018] [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), etc. may be included. The CPU 101 may also be linked to a hardware circuit such as a field programmable gate array (FPGA).

[0019] 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 executed by the CPU 101, data processed by the CPU 101, etc. The main memory device 102 may be a dynamic random access memory (DRAM), a static random access memory (SRRAM), or a The auxiliary storage device 103 is, for example, a hard disk drive, a solid state drive (SSD), or a read only memory (ROM). 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, and the like. The auxiliary storage device 103 is, for example, a hard disk drive, a solid state drive (SSD), or the like. 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."

[0020] The input device 104 is a device through which an operator inputs 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 for displaying information to the outside, particularly to the operator, and is, for example, a display device such as a liquid crystal display or an electroluminescence panel. The output device 105 may also include a speaker or other device for outputting sound. The communication device 106 communicates with other devices via a communication interface by wireless or wired communication. The control device 1 is configured to be able to communicate with the base station 2 and the core network 4 via the communication device 106.

[0021] FIG. 3 illustrates an example of the functional configuration of the control device 1. The control device 1 includes a control unit 10, and sub-functional units of the control unit 10 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 a program loaded in the main memory device 102, but some or all of the functions may be realized by dedicated hardware circuits.

[0022] 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 radio waves with the mobile station 3, 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 this embodiment can also 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 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 in geographically separate locations from the RU 21, DU 22, and CU 23, or may be located in the same location or within the same device.

[0023] The mobile station 3 includes a CPU, a main memory device, an auxiliary memory device, an output device, an operation device, a wireless communication device, and an antenna. The wireless communication device of the mobile station 3 connects to a wireless access network via the 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 the measurement results to the base station, and performs communication using the beams notified from the base station.

[0024] [process] (1) Overall processing of the beam determination procedure 5 is a flowchart showing the flow of processing performed by the control device 1 when the base station 2 communicates with the mobile station 3. At the start of this processing, the mobile station 3 is in an idle state. 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.

[0025] 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. Fig. 6 is a flowchart showing the details of the beam determination procedure S11 in step S11. Fig. 7 is a diagram explaining the beam determination procedure. The beam determination procedure will be explained below with reference to Figs. 6 and 7.

[0026] 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 is also a process in which a mobile station 3 in an idle state (RRC_IDLE) establishes a connection based on an SSB (Synchronization Signal Block). As shown in FIG. 7(A), the base station 2 sweeps the SSB beam in multiple different directions (beam sweeping). The mobile station 3 performs coarse adjustment of the transmission beam using a transmission beam with low angular resolution. The mobile station 3 receives an SSB beam (wide beam) using a receiving beam with a low reception strength. The mobile station 3 measures the reception strength (e.g., RSRP) of the SSB of each SSB beam and transmits a signal on a Random Access Channel (RACH) at the transmission timing associated with the SSB with the highest reception strength. The mobile station 3 may also sweep the receiving beam to determine the optimum pair of transmitting and receiving beams. The beam determined in this procedure is a wide beam with low angular resolution and is not the optimum beam for transmitting and receiving data, so beam refinement is performed in the following procedure. The wide beam corresponds to a base station beam of the first angular resolution.

[0027] 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 FIG. 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 received 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 received 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.

[0028] In step S113, fine adjustment of the receive beam is performed using a receive beam with high angular resolution. The processing in step S113 corresponds to the P3 subprocedure (third subprocedure). As shown in FIG. 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 receive beams with higher angular resolution than those in the P1 and P2 subprocedures, and determines the receive beam with the highest reception strength (e.g., RSRP).

[0029] The above process determines a pair of transmission and reception beams to be used in communication between the base station 2 and the mobile station 3. The base station 2 determines not only the beam to be used in communication (communication beam), but also the beam to be measured by the mobile station 3 during communication (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 has an intensity above the threshold in the P1 sub-procedure or P2 sub-procedure, or the runner-up beam may be selected.

[0030] In step S12, the base station 2 notifies the mobile station 3 of the communication beam and measurement beam determined in step S11, and performs communication using the communication beam. The mobile station 3 measures the communication beam and the measurement beam and reports the measurement results to the base station 2. The timing of measurement and reporting at the mobile station 3 may be specified by the base station 2 or may be determined by the mobile station 3 itself.

[0031] In step S13, the base station 2 receives the beam measurement result (measurement report) from the mobile station 3. The beam measurement result includes information on the reception strength of the beam at the mobile station 3, such as the reference signal received power (RSRP).

[0032] In step S14, the base station 2 determines whether or not it is necessary to change the beam used for communication with the mobile station 3. The determination of whether or not it is necessary to change the beam is made based on, for example, whether or not 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 equal to or less than a threshold, or whether there is another beam with a higher reception strength than the currently used beam. If it is determined that it is not necessary to change the beam (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 it is necessary to change the beam, the process proceeds to step S15.

[0033] In step S15, the base station 2 determines which of the sub-procedures P1, P2, and P3 should be the starting phase of the beam update. Details of this process will be described later.

[0034] 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 the processes of steps S111 and S112 may be omitted depending on the start phase.

[0035] 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. After this, the processes from step S13 to step S17 are repeated until communication between the base station 2 and the mobile station 3 is completed.

[0036] (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.

[0037] In step S151, the control device 1 acquires the beam measurement results and location information of the mobile station 3. For example, the control device 1 stores the measurement results received in memory when receiving the measurement results in step S13, and in step S151, the measurement result acquisition unit 11 acquires the measurement results from the memory. The location information of the mobile station 3 may be acquired in any manner, for example, by acquiring from the mobile station 3 the location information acquired by the mobile station 3 using a GPS device or other GNSS device. The location information transmitted from the mobile station 3 may be included in a measurement report or in another signal. Alternatively, the location 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).

[0038] In step S152, the control device 1 calculates the direction θ0 and distance d of the mobile station 3 relative to the base station 2. UE,RS Here, using base station 2 as a reference means, more precisely, using the transmitting / receiving point (TRP) of the beam as a reference.

[0039] 9A is a diagram showing an example of the positional relationship between a base station 2 and a mobile station 3. In FIG. 9A, 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. Communication between the base station 2 and the mobile station 3 is performed using a wave reflected by the building 903 of a radio wave in a direction 905. 9(B) is a diagram showing the positional relationship of FIG. 9(A) projected onto a horizontal plane and viewed from above.

[0040] In step S152, the mobile station information acquisition unit 12 acquires the direction θ0 and the distance d UE,BS As shown in FIG. 9(B), it can be calculated according to the following formula:

number

[0041] 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 the present disclosure. The intensity threshold Th1 may be determined as appropriate. For example, the intensity threshold Th1 is a value at which stable communication can be continued using that beam if the reception intensity is equal to or greater than that value. If there is no beam exceeding 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 there is a beam exceeding the intensity threshold Th1 (S153-YES), the process proceeds to step S154.

[0042] In step S154, the beam update determination unit 13 determines whether or not there is a beam having a direction that matches the direction of the mobile station 3 among the beams exceeding the intensity threshold Th1.

[0043] Here, whether or not the beam direction and the direction of the mobile station 3 coincide 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, a beam direction exceeding an intensity threshold Th1 is determined as θ OK Let the beam width (half width) of this beam be φ, and θ OK -φ / 2<θ0<θ OK If +φ / 2 is satisfied, it is determined that the beam matches the direction of the mobile station 3. If there are multiple beams that exceed the intensity threshold Th1, the above determination is made for each beam.

[0044] In another example, the beam direction exceeding the intensity threshold Th1 is determined as θ OK Let D be the maximum Fresnel diameter of this beam, and then θ OK -D / d UE,BS <θ0<θ OK +D / d UE,BS If the above equation is satisfied, it may be determined that the beam and the direction of the mobile station 3 coincide with each other. UE,BS is the base Distance d from station 2 UE,BSWhen the beam is separated by a distance of 1 / 2, the maximum Fresnel diameter D is It is an approximation of the angle between the distant point. When the wavelength of the radio wave is λ, the maximum Fresnel diameter is D = (λd UE,BS ) 1 / 2 Therefore, the above determination formula can be expressed as follows:

number

[0045] 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. If it is determined that a corresponding beam exists (YES in S154), the process proceeds to step S156.

[0046] In step S155, the beam update determination unit 13 calculates the distance d UE,BS is the distance Threshold d TH Determine whether the distance is greater than or equal to the distance threshold d TH corresponds to the second threshold value in the present disclosure. UE,BS is the distance threshold d TH If it is less than (S155-NO), the process returns to step The process proceeds to step S157, where the beam update determination unit 13 determines to start the beam determination procedure from the P1 sub-procedure (S111). UE,BS is the distance threshold d TH If it is greater than or equal to (S1 If the result is 55-YES, 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).

[0047] Distance threshold d TH can be determined, for example, as follows: When a beam with a beam width φ is used, the distance d UE,BS The width of the communication area (footprint) in UE,BSφ. The moving speed of the mobile station 3 is v UE and the processing delay τ required for beam update processing BM From this, the distance L that the mobile station 3 travels during the beam update process is BM is v UE ·τ BM It becomes. L BM d UE,BS If half of φ is allowed, the distance threshold d TH is 2v UE τ BM / φ.

number

[0048] Distance d UE,BS is the distance threshold d TH If the distance d is less than 0.05, the mobile station 3 may move outside the footprint of the beam during the beam update process, so the beam determination process starts from an earlier sub-procedure (P1 sub-procedure). UE,BS is the distance threshold d TH In the above cases, the mobile station 3 remains within the footprint of the beam, and therefore can start the beam determination process from a later sub-procedure (P2 sub-procedure).

[0049] The control device 1 detects the moving speed v of the mobile station 3. UE For example, when the mobile station 3 moves at a speed v UE If the base station 2 has notified the base station 2 of the moving speed v UE If there is no report of the beam intensity measurement value of each beam in the beam measurement results of the most recent measurement timings, the moving speed v of the mobile station 3 can be calculated from the angle change of the beam with the maximum intensity. UE Specifically, the moving speed v UE = (distance of the mobile station d UE,BS ) × (angle change) / (beam measurement time interval) Furthermore, if the measured beam intensity value is not reported, a predetermined value may be used as the moving speed of the mobile station 3.

[0050] The distance threshold dTH is further determined by the beam lifetime (the maximum time that the same beam can be used) τ LT In this case, the lifetime τ LT Add d TH =2v UE (τ BM +τ LT ) / φ.

[0051] 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 a repeated explanation will be omitted. Note that the distance threshold d TH may be the same in step S155 and step S156, or may be different values.

[0052] Distance d UE,BS is the distance threshold d TH If it is less than (S156-NO), the process returns to step The process proceeds to step S158, and the beam update determination unit 13 determines the beam from the P2 sub-procedure (S112). Decide to start the procedure. Meanwhile, distance d UE,BS is the distance threshold d TH If it is greater than or equal to (S1 If the result is YES (S156), the process proceeds to step S159, and the beam update determination unit 13 determines to start the beam determination procedure from the P3 sub-procedure (S113). UE,BS is the distance threshold d TH If the distance d is less than d, the mobile station 3 may move outside the footprint of the beam during the beam update process, so the beam update process starts from an earlier sub-procedure (P2 sub-procedure). UE,BS is the distance threshold d TH In the above cases, mobile station 3 remains within the footprint of the beam, and therefore can start the beam update process from a later sub-procedure (P3 sub-procedure).

[0053] [Beneficial Effects] According to the technique of the present disclosure, 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 sub-procedures, can be started from an intermediate sub-procedure 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, so by executing the necessary sub-procedures without skipping them, it becomes possible to update to an appropriate beam more reliably.

[0054] [Variations] In the above example, two-dimensional coordinates are used to calculate the direction and distance of the mobile station 3, but three-dimensional coordinates may also be used, as shown in Figure 9(C). In the case of three-dimensional coordinates, the direction of the mobile station 3 is specified by the azimuth angle θ0 and the zenith angle φ0. The azimuth angle θ0, the zenith angle φ0, and the distance d UE,RS can be calculated based on the following formula:

number

[0055] (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.

[0056] 10 is a flowchart showing the beam update start phase determination process (step S15) in this embodiment. Compared to embodiment 1 (FIG. 8), the determination processes of steps S155 and S156 are omitted. If it is determined in step S154 that no beam matching the direction of the mobile station 3 exists among the beams exceeding the 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 sub-procedure. On the other hand, if it is determined in step S154 that a beam matching the direction of the mobile station 3 exists among the beams exceeding the 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 sub-procedure.

[0057] In this embodiment, as in embodiment 1, when it becomes necessary to change the beam used for communication between base station 2 and 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 effect of enabling rapid beam updating.

[0058] (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.

[0059] 11 is a flowchart showing the beam update start phase determination process (step S15) in this embodiment. Compared to the first embodiment (FIG. 8), this embodiment differs in that, depending on the determination result of step S154, the processes of steps S201 and S202 are performed instead of the processes of steps S155 and S156.

[0060] 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 the beam duration is sufficiently long can be made by comparing the beam duration with a duration threshold. The duration threshold may be determined as appropriate, for example, the lifetime required for the beam. If the beam duration is less than the duration threshold, the process 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, the process proceeds to step S158, where the beam update determination unit 13 determines to start the beam determination procedure from the P2 subprocedure (S112).

[0061] The determination process in step S202 is the same as that in step S201, and therefore 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, the process proceeds to step S158, where 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 beam duration is equal to or greater than the duration threshold, the process proceeds to step S159, where the beam update determination unit 13 determines to start the beam determination procedure from the P3 sub-procedure (S113).

[0062] In steps S201 and S202, past selections included in the history that satisfy the following conditions can be determined 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 appropriately. The same applies to the orientation and moving speed. As an example, the beam update determination unit 13 searches the history for a beam that has the same location information and moving speed of the mobile station 3 as the current one and that selected the same beam as the beam currently being used for communication. 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 a 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 multiple selections may be compared with the duration threshold. As an example of the statistical value, a weighted average, in which the most recent value is given a greater weight, may be used. Alternatively, the beam duration of the most recent selection may be compared with the duration threshold.

[0063] In order to make a judgment based on history 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 moving 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.

[0064] In this embodiment, as in the first embodiment, the beacon used for communication between the base station 2 and the mobile station 3 is When it becomes necessary to change the beam system, the beam determination (update) procedure, which is made up of multiple sub-procedures, can be started from an intermediate sub-procedure rather than from the beginning, which has the effect of enabling rapid beam update. In this embodiment, the stability of the beam currently in use is evaluated based on the past history, and an appropriate start phase for beam update can be determined based on the beam stability.

[0065] Instead of making a decision by directly referencing past history, a machine learning model may be trained using the past history as training data, with each situation as input and the duration of the selected beam as output, and the beam duration in the current situation may be determined by the machine learning model. The estimated beam duration may then be compared with a duration threshold to determine the start phase of the beam determination procedure. This approach also achieves the same effect.

[0066] (Other variations) 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.

[0067] Although the above embodiment illustrates an example of application to 5G cellular communication, the present disclosure can also be applied to cellular communication of other 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.

[0068] The present disclosure can also be realized by providing a computer program implementing 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. [Explanation of symbols]

[0069] 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

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

7. In the second determination step, the direction of the mobile station is determined as θ ０ , the direction of the beam whose received signal strength is higher than the first threshold is defined as θ ＯＫ , where φ is the beam width of the beam, and θ ＯＫ −φ / 2<θ ０ < θ ＯＫ +φ / 2, it is determined that the direction of the beam matches that of the mobile station.

7. The control device according to claim 6.

8. In the second determination step, the direction of the mobile station is determined as θ ０ , the direction of the beam whose received signal strength is higher than the first threshold is defined as θ ＯＫ , the distance between the base station and the mobile station is d ＵＥ，ＢＳ , where D is the maximum Fresnel diameter of the beam, and θ ＯＫ -D / d ＵＥ，ＢＳ <θ ０ <θ ＯＫ +D / d ＵＥ，ＢＳ If the above condition is satisfied, it is determined that the direction of the beam and the mobile station coincide.

7. The control device according to claim 6.

9. 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.

10. The second threshold is defined as the beam width of the beam with the highest received signal strength, φ, and the moving speed of the mobile station, v. ＵＥ , the processing delay required for the beam determination procedure is τ ＢＭ As a result, 2v ＵＥ τ ＢＭ / φ, The control device according to claim 9 .

11. The second threshold is defined as the beam width of the beam with the highest received signal strength, φ, and the moving speed of the mobile station, v. ＵＥ , the processing delay required for the beam management sub-procedure is τ ＢＭ , the lifetime of the beam with the highest received intensity is τ ＬＴ As a result, 2v ＵＥ (τ ＢＭ +τ ＬＴ ) / φ, The control device according to claim 9 .

12. the control unit further executes a step of acquiring a moving speed of the mobile station. The control device according to claim 10 .

13. 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 .

14. 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.

15. 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.

16. 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:

17. 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.

18. 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.

19. 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.

20. 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:

21. 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.

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