Network control device and program

Abstract

This network control device for controlling a wireless communication network in which terminal devices perform wireless communication with each other via a plurality of distributed access points comprises: an AP cluster identification unit for identifying an AP cluster indicating one or more access points for performing wireless communication with a terminal device; and a CPU selection unit for selecting, for each AP cluster for each terminal device, a CPU connected to the access point included in the AP cluster.

Description

Network control device and program

[0001] This application claims priority to Japanese Patent Application No. 2024-025555, filed on Feb. 22, 2024, the contents of which are incorporated herein by reference.

[0002] Conventionally, technology related to CF-m MIMO (Cell-Free massive Multi-Input Multi-Output) is known. According to CF-m MIMO, each base station distributes multiple antennas and links these antennas to suppress the effects of interference between a terminal and multiple base stations. In addition, the base station transmits a reference signal to the terminal while sweeping a downlink beam in multiple directions. The terminal receives the reference signal and notifies the base station of the identifier of the best downlink beam that maximizes the received signal power. CF-m MIMO is disclosed, for example, in Non-Patent Document 1.

[0003] Emil Bjornson, Luca Sanguinetti, "Scalable Cell-Free Massive MIMO Systems" arXiv:1908.03119v2 [cs.IT] 8 May 2020

[0004] In the architecture shown in Non-Patent Document 1, an external controller calculates the cluster of access points and transmits it to the CPU. However, there is no description of a specific control scheme or interface, making it difficult for even those skilled in the art to realize it.

[0005] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a network control device and a program that can realize suitable wireless communication throughout the RAN.

[0006] (1) One aspect of the present invention is a network control device that controls a wireless communication network in which terminal devices wirelessly communicate with each other via multiple distributed access points, the network control device comprising: an AP cluster identification unit that identifies an AP cluster indicating one or more of the access points that wirelessly communicate with the terminal device; and a CPU selection unit that selects, for each AP cluster for each terminal device, a CPU to be connected to the access point included in the AP cluster. (2) Another aspect of the present invention is the network control device of (1) above, wherein the AP cluster identification unit and the CPU selection unit are included in a RAN Intelligent Controller (RIC) that controls the multiple CPUs, and the RIC acquires transmission path and computer resource information from a distributed unit (O-DU) and then updates policy information for the AP cluster according to the usage status of the transmission path and the computer. (3) Another aspect of the present invention is the network control device of (2) above, wherein the RIC identifies the AP cluster after updating the policy information for the AP cluster and notifies the distributed unit of the newly identified AP cluster. (4) In another aspect of the present invention, in the network control device of any of (1) to (3) above, an upper limit of the access points that form the AP cluster is predetermined, and the AP cluster identification unit identifies the AP cluster within a range that does not exceed the predetermined upper limit of the access points. (5) In another aspect of the present invention, in the network control device of any of (1) to (4) above, a lower limit of wireless quality between the access points and the terminal device that can be used as the AP cluster is predetermined, and the AP cluster identification unit does not identify the access points as the AP cluster if the wireless quality is below the predetermined lower limit. (6) In another aspect of the present invention, in the network control device of (5) above, the terminal device and the access points perform beamforming with each other, and the wireless quality is the quality of a best beam that maximizes received signal power as a result of beamforming.(7) According to another aspect of the present invention, in the network control device of (5) above, the terminal device and the access point perform beamforming with each other, and the wireless quality is determined based on received signal power for each combination of the beam of the terminal device and the beam of the access point as a result of the beamforming. (8) According to another aspect of the present invention, in the network control device of (6) or (7) above, the terminal device has multiple antennas that can be used simultaneously, and the multiple antennas included in the terminal device can output beams in different directions, and the AP cluster identification unit identifies the AP cluster based on the antennas that can be used simultaneously by the terminal device. (9) According to another aspect of the present invention, in the network control device of any of (1) to (8) above, the AP cluster identification unit and the CPU selection unit are included in a RAN Intelligent Controller (RIC) that controls the multiple CPUs, and the RIC recalculates the AP cluster and related parameters after obtaining wireless quality information and service information from a distributed unit (O-DU). (10) According to another aspect of the present invention, in the network control device of (9) above, a list of the access points to be used in the AP cluster is predetermined, and the AP cluster identification unit identifies the AP cluster according to the predetermined list of access points. (11) According to another aspect of the present invention, in the network control device of (10) above, a list of the terminal devices to be used in the AP cluster is predetermined, and the AP cluster identification unit identifies the AP cluster according to the predetermined list of terminal devices. (12) According to another aspect of the present invention, in the network control device of any of (1) to (11) above, the AP cluster identification unit and the CPU selection unit are included in a RAN Intelligent Controller (RIC) that controls the multiple CPUs, and the RIC obtains transmission power information indicating the power of the transmission path and the beams transmitted by the terminal devices from a distributed unit (O-DU) at a different site, and performs pilot allocation calculations based on the obtained information.(13) Another aspect of the present invention is a program for executing a network control device that controls a wireless communication network in which terminal devices communicate wirelessly with each other via a plurality of distributed access points, the program executing an AP cluster identification step that identifies an AP cluster indicating one or more access points that communicate wirelessly with the terminal device, and a CPU selection step that selects, for each AP cluster for each terminal device, a CPU to be connected to the access point included in the AP cluster.

[0007] According to the present invention, it is possible to provide a network control device and a program that can realize suitable wireless communication throughout the RAN.

[0008] 1 is a diagram for explaining the configuration of a wireless communication network according to a first embodiment. FIG. 2 is a diagram for explaining the logical configuration of a wireless communication network according to the first embodiment. FIG. 3 is a functional configuration diagram showing an example of the functional configuration of a network control device according to the first embodiment. FIG. 4 is a sequence diagram showing a sequence when an AP cluster is calculated using Near-RT RIC in the network control device according to the first embodiment. FIG. 5 is a sequence diagram showing a sequence when an AP cluster is calculated using O-DU in the network control device according to the first embodiment. FIG. 6 is a diagram showing the logical configuration of a wireless communication network according to the first embodiment. FIG. 7 is a diagram showing an example of an upper limit value of the number of access points forming an AP cluster according to the first embodiment. FIG. 8 is a diagram showing an example of a lower limit value of wireless quality according to the first embodiment. FIG. 9 is a diagram showing a first example of beamforming between a terminal device and an access point according to the first embodiment. FIG. 10 is a diagram showing an example of a case where only the best beam is considered as wireless quality according to the first embodiment. FIG. 11 is a diagram showing an example of a case where multiple beams are considered as wireless quality according to the first embodiment. FIG. 12 is a diagram showing a second example of beamforming between a terminal device and an access point according to the first embodiment. FIG. 13 is a sequence diagram showing an example of an interface for information related to an AP cluster change according to the first embodiment. FIG. 14 is a diagram showing the logical configuration of a wireless communication network according to the first embodiment. FIG. 15 is a diagram showing an example of a list of access points used in an AP cluster for each user according to the first embodiment. Fig. 1 is a diagram showing an example of a list of spatially multiplexed users according to the first embodiment. Fig. 2 is a diagram showing an example of optimization of an AP cluster in accordance with a RAN resource situation according to the first embodiment. Fig. 3 is a diagram showing an example of optimization of an AP cluster in accordance with user movement according to the first embodiment. Fig. 4 is a diagram for explaining a processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to a second embodiment. Fig. 5 is a sequence diagram showing details of the processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the second embodiment.30 is a first diagram showing a logical configuration of a wireless communication network for explaining a processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to a second embodiment. FIG. 31 is a first detailed sequence diagram showing details of the processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the second embodiment. FIG. 32 is a second diagram showing a logical configuration of a wireless communication network for explaining a processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the second embodiment. FIG. 33 is a second detailed sequence diagram showing details of the processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the second embodiment. FIG. 34 is a configuration diagram showing beamforming in a first example according to a third embodiment. FIG. 35 is a functional configuration diagram of a terminal in a first example according to the third embodiment. FIG. 36 is a communication quality table in a first example according to the third embodiment. FIG. 37 is a beam table in a first example according to the third embodiment. FIG. 38 is a sequence diagram in a first example according to the third embodiment. FIG. 39 is a configuration diagram showing a combination of beams that can be simultaneously used by terminals in a first example according to the third embodiment. FIG. 39 is a beam table based on FIG. 30. FIG. 31 is a configuration diagram showing beamforming in a second example according to the third embodiment. FIG. 39 is a functional configuration diagram of a base station in a second example according to the third embodiment. FIG. 10 is a communication quality table in a second example according to the third embodiment. FIG. 11 is a beam table in a second example according to the third embodiment. FIG. 12 is a diagram for explaining the configuration of a wireless communication network according to the prior art. FIG. 13 is a diagram for explaining a processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the prior art.

[0009] A network control device and a program according to an aspect of the present invention will be described in detail below with reference to preferred embodiments and the accompanying drawings. Note that the aspects of the present invention are not limited to these embodiments and include various modifications and improvements. In other words, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially identical, and the components described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the present invention. Furthermore, in the drawings below, the scale and number of components may differ from the scale and number of the actual components to make each configuration easier to understand.

[0010] [Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, as a premise for the description of the present embodiment, in a wireless communication network according to the present embodiment, terminal devices communicate wirelessly with each other via access points. In the present embodiment, it is assumed that Cell-Free massive MIMO (CF-mMIMO) is used, which cooperatively utilizes a large number of antennas arranged in a wide communication area. Furthermore, in the present embodiment, it is assumed that a mechanism is used in which signals from a plurality of distributed access points are processed using MU-MIMO (Multi-User MIMO) or the like at a base where the access points are aggregated.

[0011] Fig. 36 is a diagram illustrating the configuration of a wireless communication network according to a conventional technique. First, with reference to the diagram, the configuration of a wireless communication network 9 according to a conventional technique and problems therewith will be described. The wireless communication network 9 includes access points AP1 to AP8 and CPUs (Central Processing Units) 1 to CPU2. The diagram also illustrates terminal devices UE1 to UE4. Each terminal device performs wireless information communication with other terminal devices via a nearby access point.

[0012] By performing beamforming, the terminal device and the access point search for a suitable beam (best beam) and perform concentrated information communication using a beam with a narrow wide-angle range. This configuration makes it possible to compensate for propagation loss. In the following description, a beam transmitted from a terminal device to an access point may be referred to as an uplink beam. Also, a beam transmitted from an access point to a terminal device may be referred to as a downlink beam. In the illustrated example, each terminal device transmits beams in four azimuths. Also, each access point transmits beams in eight azimuths. The reference signal contains the identifier # of that beam.

[0013] An AP cluster is configured as a group of access points consisting of one terminal device and one or more access points. In other words, an AP cluster includes one or more access points determined for each terminal device, and is a group of access points that transmit and receive wireless signals. In the example shown in the figure, AP clusters APC1 to APC4 are configured.

[0014] Specifically, in AP cluster APC1, terminal device UE1 transmits beam #1 and access point AP1 transmits beam #5 to communicate with each other, and terminal device UE1 transmits beam #3 and access point AP2 transmits beam #8 to communicate with each other. Also, in AP cluster APC2, terminal device UE2 transmits beam #4 and access point AP2 transmits beam #4 to communicate with each other, and terminal device UE2 transmits beam #2 and access point AP4 transmits beam #5 to communicate with each other. Also, in AP cluster APC3, terminal device UE3 transmits beam #1 and access point AP5 transmits beam #8 to communicate with each other, and terminal device UE3 transmits beam #2 and access point AP6 transmits beam #8 to communicate with each other. In addition, in AP cluster APC4, terminal device UE4 transmits beam #3 and access point AP6 transmits beam #3, thereby communicating information with each other; terminal device UE4 transmits beam #1 and access point AP7 transmits beam #8, thereby communicating information with each other; terminal device UE4 transmits beam #2 and access point AP8 transmits beam #8, thereby communicating information with each other.

[0015] Here, terminal devices include information and communication devices such as smartphones, tablet devices, and wearable devices used by users. In other words, terminal devices are likely to move as users move. Therefore, as users move, the relative positional relationship between the terminal device and access points is likely to change dynamically. However, with conventional technology, it has been difficult to dynamically switch access points included in an AP cluster as users move.

[0016] Furthermore, according to the prior art, when a terminal device exists between access points controlled by different CPUs, cooperation between CPU1 and CPU2 is not performed properly, resulting in a problem of degraded communication quality.

[0017] [First Embodiment] Fig. 1 is a diagram for explaining the configuration of a wireless communication network according to a first embodiment. The configuration of a wireless communication network 1 according to the first embodiment will be explained with reference to the same figure. In this embodiment, the wireless communication network 1 differs from a wireless communication network 9 according to the conventional technology in that it includes a RAN Intelligent Controller (RIC) that controls the multiple CPUs. In the example shown in the figure, the RIC controls CPU1 and CPU2.

[0018] In the connection between the terminal device UE and the access point AP, according to this embodiment, the connection destination of the terminal device UE3 is different. Specifically, in the AP cluster APC3, the terminal device UE3 further transmits beam #4, and the access point AP4 transmits beam #2, thereby performing information communication with each other. In other words, the terminal device UE3 performs information communication with the access points AP4, AP5, and AP6.

[0019] Here, the access point AP4 is controlled by a CPU 1, and the access points AP5 and AP6 are controlled by a CPU 2. That is, the terminal device UE3 is capable of communicating information with a plurality of access points controlled by different CPUs.

[0020] 2 is a diagram illustrating the logical configuration of a wireless communication network according to the first embodiment. In this embodiment, a terminal device connects to multiple access points, so it is necessary for each terminal device to determine which access point to transmit and receive data to. Furthermore, because the location of a terminal device changes from moment to moment, it is necessary to appropriately update the AP cluster.

[0021] As shown in the figure, wireless quality varies depending on how an AP cluster is formed. Wireless quality is significantly affected by the relative distance and orientation between the terminal device and the access point. For example, if an AP cluster is formed using terminal devices and access points with unsuitable relative distances and orientations, wireless quality may be degraded (even though a different combination could actually provide better wireless quality).

[0022] Furthermore, the transmission bandwidth changes depending on which CPU controls which access point due to the relationship between the CPUs and the access points. In other words, it can be said that the transmission bandwidth changes depending on how the AP cluster is formed.

[0023] Furthermore, if access is concentrated on an access point controlled by a CPU, the load may be unevenly distributed to that CPU. In other words, the amount of computer resource consumption may change depending on how the AP cluster is formed.

[0024] According to this embodiment, by forming an AP cluster appropriately, it becomes possible to achieve various KPIs (Key Performance Indicators) such as wireless quality, transmission path bandwidth, computer resource consumption, etc. Furthermore, according to this embodiment, by controlling both the network and wireless on a per-user basis, it becomes possible to ensure communication quality for each user in any location.

[0025] 3 is a functional configuration diagram showing an example of the functional configuration of a network control device according to the first embodiment. An example of the functional configuration of the network control device 10 according to this embodiment will be described with reference to the same figure. The network control device 10 controls a wireless communication network 1. The network control device 10 may be included as part of the functions of an Open Radio Access Network (Open RAN, O-RAN, or ORAN) architecture. The part of the functions of the O-RAN architecture may be, for example, a RAN Intelligent Controller (RIC).

[0026] The network control device 10 includes an AP cluster identification unit 11 and a CPU selection unit 12. The network control device 10 may include a CPU (not shown), a storage device such as a ROM (Read only memory) or a RAM (Random access memory), etc., connected by a bus, and may function as a device including the AP cluster identification unit 11 and the CPU selection unit 12 by executing a network control program. Note that all or part of the functions of the network control device 10 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field-Programmable Gate Array).

[0027] The AP cluster identification unit 11 identifies an AP cluster. An AP cluster is identified for each terminal device. An AP cluster indicates one or more access points that communicate wirelessly with the terminal device. The number of access points included in an AP cluster may be, for example, approximately one to three. The AP cluster identification unit 11 identifies an AP cluster based on information acquired from the terminal device or the access points, for example.

[0028] The CPU selection unit 12 selects, for each AP cluster, a CPU to be connected to the access points included in the AP cluster. Here, the CPU may be a distributed unit (O-DU) in the O-RAN architecture. In the O-RAN architecture, the RIC uses a controller such as a non-real time (RT) RIC that controls at a period of 1 [sec] or more, or a near-real time (RT) RIC that controls at a period of 10 [msec] to 1 [sec], to instruct the O-DU on massive MIMO parameter information. The CPU selection unit 12 selects, for each AP cluster, which CPU (O-DU) the access points included in the AP cluster will be connected to.

[0029] In this embodiment, it is desired to control Massive MIMO so that various KPIs can be achieved in the entire wireless communication network 1, but currently there is a lack of an interface for collecting the necessary information and issuing control instructions.

[0030] For example, there is a lack of an interface for AP cluster information. Currently, O-RAN does not define policy information or instruction formats, such as constraints and prerequisites for AP cluster formation based on the computer and transmission path resource status of each site. Therefore, it is difficult to form an AP cluster taking into account the computer resources and transmission path resources of each site. This may result in a shortage of transmission paths and resources. Furthermore, when a terminal device performs beamforming, in CF-m MIMO, the beam of the terminal device connects to multiple access points with different received signal powers at the access points and different best beams at that time. In such cases, it is not easy to appropriately determine beams between multiple combinations of access points and terminal devices simply by combining the best beams between the access points and terminal devices.

[0031] In addition, there is a lack of an interface for information related to AP cluster changes. Currently, O-RAN does not define the configuration information for AP cluster changes or the instruction format for them. Therefore, it is not possible to change the AP cluster using Near-RT RIC or related MIMO parameter information in response to user movement or service changes, which may result in degradation of wireless quality.

[0032] Considering the wide-area deployment of CF-m MIMO, the computational complexity of transmission and reception processing and the transmission path load between the access point and the CPU are concentrated on a single CPU, posing a challenge in terms of scalability. Therefore, a method of distributing CPUs is being considered. In a distributed CPU environment, interference occurs between terminal devices connected to different CPUs (hereinafter, sometimes referred to as inter-site UE interference), which may degrade the wireless quality of terminal devices located near CPU boundaries. To continuously provide the communication quality required for each application in every location where users are present, it is necessary to suppress this inter-site interference.

[0033] Hereinafter, an example of a specific implementation means when the network control device according to this embodiment is incorporated into the O-RAN architecture will be described with reference to the drawings.

[0034] First, specific means for solving the problem of insufficient interfaces for AP cluster information will be described with reference to Figures 4 to 12. Specifically, in this embodiment, a message instructing a change to policy information required when the Near RT RIC determines an AP cluster, and that policy information, are added to the interfaces between the Non-RT-RIC and the Near RT RIC (A1) and between the Non-RT-RIC and the O-DU (O1).

[0035] 4 is a sequence diagram showing the sequence for calculating an AP cluster using Near-RT RIC in the network control device according to the first embodiment. The diagram shows the processing of Non-RT RIC (SMO), Near-RT RIC, and O-DU. The processing at each step will be explained below.

[0036] (Step S11) First, the O-DU transmits a data collection (O1) to the Non-RT RIC. The transmitted information includes information on the transmission path and computer resources.

[0037] (Step S12) After acquiring the transmission path and computer resource information from the O-DU, the Non-RT RIC changes the policy information of the AP cluster according to the usage status of the transmission path and computer.

[0038] (Step S13) Next, the Non-RT RIC sends an Updated Configuration (A1) to the Near RT RIC. The Updated Configuration (A1) includes new messages and additional information. The information sent here includes AP cluster policy information and change instructions.

[0039] (Step S14) Upon receiving the Updated Configuration (A1) from the Non-RT RIC, the Near RT RIC recalculates the AP cluster based on the new AP cluster policy information.

[0040] (Step S15) After the AP cluster is recalculated, the Near RT RIC transmits an Updated Configuration (E2) to the O-DU, which includes information indicating the recalculated AP cluster.

[0041] 5 is a sequence diagram showing the sequence when calculating an AP cluster using O-DU in the network control device according to the first embodiment. As with FIG. 4, the diagram illustrates the processing of Non-RT RIC (SMO), Near-RT RIC, and O-DU. In the explanation given with reference to FIG. 5, steps similar to those in FIG. 4 are denoted by similar reference numerals, and explanations thereof may be omitted. Specifically, steps S11 and S12 are similarly processed, and therefore explanations thereof will be omitted.

[0042] (Step S16) The Non-RT RIC sends an Updated Configuration (O1) to the O-DU. The Updated Configuration (O1) includes new messages and additional information. The information sent here includes AP cluster policy information and change instructions.

[0043] (Step S17) When the O-DU receives the Updated Configuration (O1) from the Non-RT RIC, it recalculates the AP cluster based on the new AP cluster policy information.

[0044] 4 and 5, the AP cluster policy information is changed according to the usage status of the resources (transmission path and computer) of the entire RAN, and the Near RT RIC or O-DU (CPU) recalculates the AP cluster, thereby making it possible to control the amount of resource consumption. Therefore, according to this embodiment, it is possible to prevent quality degradation due to resource shortages.

[0045] 6 is a diagram showing the logical configuration of a wireless communication network according to the first embodiment. This diagram shows a logical configuration similar to that of the wireless communication network 1 shown in FIG. 2. Here, the greater the total number of access points forming an AP cluster, the greater the amount of transmission path usage and computer resource usage. Therefore, in this embodiment, it is preferable to set an upper limit on the number of access points that can be used as an AP cluster. In this case, the upper limit of the number of access points that form an AP cluster is set in advance, and the AP cluster identification unit 11 can identify an AP cluster within a range that does not exceed the predetermined upper limit of access points.

[0046] By setting an upper limit on the number of access points that transmit and receive signals as an AP cluster, it is possible to prevent the total number of access points that form an AP cluster from increasing too much, which in turn prevents an increase in the amount of transmission lines used and computer resources used, which would otherwise be caused by an excessive increase in the total number of access points that form an AP cluster.

[0047] 7 is a diagram showing an example of the upper limit of the number of access points that form an AP cluster according to the first embodiment. In the diagram, an upper limit of the number of access points that form an AP cluster is set for each of CPU1 to CPU3. Specifically, the upper limit of the number of access points for CPU1 is 3, the upper limit of the number of access points for CPU2 is 3, and the upper limit of the number of access points for CPU3 is 3. In the example shown, the upper limit is the same regardless of the CPU, but may be different for each CPU.

[0048] Returning to FIG. 6 , in this embodiment, there are cases where the quality between the access points forming the AP cluster and the terminal devices is below the expected quality. It is preferable to eliminate such connections below the expected quality. Therefore, in this embodiment, it is preferable to set a lower limit for the wireless quality between the access points and the terminal devices forming the AP cluster. In this case, a lower limit for the wireless quality between the access points and the terminal devices that can be used as an AP cluster is predetermined, and the AP cluster identification unit 11 may not identify an access point as an AP cluster if the wireless quality falls below the predetermined lower limit. Specifically, the signal-to-noise ratio (SINR) may be used as the wireless quality.

[0049] According to this embodiment, by setting a lower limit value for wireless quality between the access points and terminal devices that form an AP cluster, it is possible to prevent the wireless quality between the access points and terminal devices from falling below an expected quality. Furthermore, according to this embodiment, it is possible to eliminate connections that are below the expected quality, thereby reducing the consumption of computer resources and transmission path resources.

[0050] 8 is a diagram showing an example of a lower limit value of wireless quality according to the first embodiment. In the diagram, a lower limit value of wireless quality between the access points forming an AP cluster and the terminal devices is set for each of CPU1 to CPU3. Specifically, the lower limit value of wireless quality for CPU1 is 10 dB, the lower limit value of wireless quality for CPU2 is 5 dB, and the lower limit value of wireless quality for CPU3 is 10 dB. As in the example shown in the figure, the lower limit value of wireless quality may be different for each CPU, or may be the same for each CPU.

[0051] Here, the beam transmitted from the terminal device is taken into consideration when determining the wireless quality between the access points forming the AP cluster and the terminal device. Regarding the beam transmitted from the terminal device, only the best beam may be considered, or multiple candidates may be considered. Hereinafter, with reference to Figures 9 to 12, an example of a beam considered when determining the wireless quality between the access points forming the AP cluster and the terminal device will be described.

[0052] 9 is a diagram showing a first example of beamforming between a terminal device and an access point according to the first embodiment. The diagram shows a terminal device UE1 and access points AP1 to AP3 located near the terminal device UE1. The access points AP1 to AP3 each sweep their own beams. In the example shown, each access point AP outputs beams #1 to #8. The terminal device UE1 measures the received signal power of the beams output from the access point AP while changing its own beam. The terminal device UE1 identifies the received signal power of the beams from the access point AP for each beam it outputs.

[0053] First, it is possible to consider only the best beam as the wireless quality. That is, the terminal device UE and the access point AP perform beamforming with each other, and in this case, the wireless quality can be said to be the quality of the best beam that maximizes the received signal power as a result of beamforming. The terminal device UE1 notifies the best beam of each access point AP as many times as the number of beams it outputs, and at that time associates it with the index number of the beam it outputs. Each access point AP can know the best beam for the beam output by the terminal device UE1 and its received signal power. Through this processing, the beam between the terminal device UE1 and the access points AP1 to AP3 is determined.

[0054] 10 is a diagram showing an example of a case where only the best beam is considered as the wireless quality according to the first embodiment. In the diagram, each access point AP is associated with the best beam (the index of the beam output by the access point AP) for each beam output by the terminal device UE1, and the received signal power. Specifically, when the terminal device UE1 outputs beam #1, the best beam is beam #4 in relation to access point AP1, beam #4 in relation to access point AP2, and beam #7 in relation to access point AP3. Furthermore, when the terminal device UE1 outputs beam #2, the best beam is beam #3 in relation to access point AP1, beam #4 in relation to access point AP2, and beam #7 in relation to access point AP3. Furthermore, when the terminal device UE1 outputs beam #3, the best beam is beam #4 in relation to access point AP1, beam #5 in relation to access point AP2, and beam #1 in relation to access point AP3. Furthermore, when the terminal device UE1 outputs beam #3, the best beam is beam #4 in relation to access point AP1, beam #5 in relation to access point AP2, and beam #1 in relation to access point AP3. Furthermore, when the terminal device UE1 outputs beam #4, the best beam is beam #3 in relation to access point AP1, beam #2 in relation to access point AP2, and beam #4 in relation to access point AP3.

[0055] Returning to FIG. 9 , it is next possible to consider multiple beams as the wireless quality. That is, the terminal device UE and the access point perform beamforming with each other, and the wireless quality can be determined based on the received signal power for each combination of the beam of the terminal device UE and the beam of the access point AP as a result of the beamforming. When multiple beams are considered as the wireless quality, the access points AP1 to AP3 each sweep their own beams. Next, each access point AP transmits an instruction regarding the number of beam candidates returned by the terminal device UE1 via a physical broadcast channel (PBCH) or the like. The terminal device UE1 measures the received signal power of the beam output from the access point AP while changing the beam it outputs. The terminal device UE1 identifies the received signal power of the beam from the access point AP for each beam it outputs.

[0056] The terminal device UE1 notifies the beam candidates of each access point AP based on the conditions instructed by the access point AP, for the number of beams it outputs. At that time, the terminal device UE1 associates the index of the beam it outputs with the beam candidate of each access point AP. Through this process, each access point AP can know the beam candidate for the beam output by the terminal device UE1 and its received signal power.

[0057] 11 is a diagram showing an example of a case where multiple beams are considered as wireless quality according to the first embodiment. In the diagram, each access point AP is associated with multiple beams (two in this case) output by the terminal device UE1, and received signal power. Specifically, when the terminal device UE1 outputs beam #1, the best beams are beam #4 and beam #5 in relation to access point AP1, beam #4 and beam #8 in relation to access point AP2, and beam #7 and beam #1 in relation to access point AP3. Furthermore, when the terminal device UE1 outputs beam #2, the best beams are beam #3 and beam #1 in relation to access point AP1, beam #4 and beam #5 in relation to access point AP2, and beam #7 and beam #8 in relation to access point AP3. Furthermore, when the terminal device UE1 outputs beam #3, the best beam is beam #4 in relation to access point AP1, beam #5 in relation to access point AP2, and beam #1 in relation to access point AP3. Furthermore, when the terminal device UE1 outputs beam #4, the best beam is beam #3 in relation to access point AP1, beam #2 in relation to access point AP2, and beam #4 in relation to access point AP3.

[0058] 12 is a diagram showing a second example of beamforming between a terminal device and an access point according to the first embodiment. The illustrated example shows an example in which the terminal device UE1 can use multiple beams simultaneously. In the second example, the terminal device UE1 is equipped with an antenna capable of outputting beams #1 and #2, and an antenna capable of outputting beams #3 and #4. That is, in the second example, the terminal device UE1 is equipped with multiple antennas capable of simultaneously outputting multiple beams. The multiple antennas equipped in the terminal device UE1 are each capable of outputting beams in different directions. In the illustrated example, the number of beams that the terminal device UE1 can use simultaneously is two, and the simultaneously usable combinations are beams #1 and #3, beams #1 and #4, beams #2 and #3, and beams #2 and #4. In this case, the AP cluster identification unit 11 identifies an AP cluster based on the antennas that the terminal device UE1 can use simultaneously.

[0059] Hereinafter, even when the terminal device UE1 can use multiple beams simultaneously, the processing procedures will be described for both the case where the best beam is considered as the wireless quality and the case where multiple beams are considered as the wireless quality.

[0060] A case will be described in which the best beam is considered as wireless quality. The access point AP sweeps its own beam. The terminal device UE1 measures the received signal power of the beam output from the access point AP while changing its own beam. The terminal device UE1 identifies the received signal power of the beam from the access point AP for each beam it outputs. The terminal device UE1 notifies each access point AP of the best beam for the number of beams it outputs, and associates it with the index number of the beam it outputs. Furthermore, the terminal device UE1 also notifies the number of beams it can use simultaneously and their combinations. Each access point AP can know the best beam for the beam output by the terminal device UE1, its received signal power, and the beams that the terminal device UE1 can use simultaneously. Through this process, the beams between the terminal device UE1 and the access points AP1 to AP3 are determined.

[0061] A case will be described in which multiple beams are considered as wireless quality. The access point AP sweeps its own beams. Each access point AP transmits an instruction regarding the number of beam candidates returned by the terminal device UE1 via a physical broadcast channel (PBCH) or the like. The terminal device UE1 notifies each access point AP of the best beam for the number of beams it outputs, and associates them with the index numbers of the beams it outputs. Furthermore, the terminal device UE1 also notifies the number of beams it can use simultaneously and their combinations. Each access point AP can know the best beam for the beams output by the terminal device UE1, its received signal power, and the beams that the terminal device UE1 can use simultaneously. Through this process, beams between the terminal device UE1 and the access points AP1 to AP3 are determined.

[0062] Next, specific means for solving the problem of a lack of an interface for information related to AP cluster changes will be described with reference to Figures 13 to 16. Specifically, in this embodiment, an instruction message for changing the AP cluster and related MIMO parameter information, as well as the AP cluster and parameter information, are added to the interface between Near-RT-RIC and O-DU (E2).

[0063] 13 is a sequence diagram showing an example of an interface for information related to an AP cluster change according to the first embodiment. The diagram shows the processing of Non-RT RIC (SMO), Near-RT RIC, and O-DU. The processing at each step will be explained below.

[0064] (Step S21) First, the O-DU transmits a data collection (O1) to the Near-RT RIC. The transmitted information includes the user's wireless quality information, service information, and so on.

[0065] (Step S22) After acquiring the wireless quality information and service information, the Near-RT RIC recalculates the AP cluster and related parameters.

[0066] (Step S23) Next, the Near-RT RIC transmits an Updated Configuration (E2) to the O-DU. The Updated Configuration (E2) includes new messages and additional information. The transmitted information includes AP cluster information and change instructions.

[0067] (Step S24) After receiving the Updated Configuration (E2), the O-DU calculates the weights of MU-MIMO based on the new AP cluster and related parameters.

[0068] By adopting such a configuration, it is possible to change the AP cluster and MIMO parameters required for signal processing calculations in response to user movement and changes in services. It is also possible to provide wireless quality appropriate for the environment after movement and the service currently being used. Furthermore, it is possible to continuously ensure the communication quality desired by the user.

[0069] 14 is a diagram showing the logical configuration of a wireless communication network according to the first embodiment. This diagram shows a logical configuration similar to that of the wireless communication network 1 shown in FIG. 2. Here, an example of information related to an AP cluster change is a list of access points used in the AP cluster for each user. In the example shown in the figure, the access points used in the AP cluster of the terminal device UE4 are access point AP5, access point AP6, and access point AP7. That is, according to this embodiment, a list of access points AP used in the AP cluster is predetermined, and the AP cluster identification unit 11 identifies the AP cluster according to the predetermined list of access points AP.

[0070] In this way, by defining a list of access points used in the AP cluster for each user as information related to AP cluster changes, the AP cluster used for transmitting and receiving data to and from the terminal device UE can be changed to an AP cluster that can ensure the required wireless quality in response to user movement or changes in services. Therefore, according to this embodiment, it is possible to continuously provide the communication quality desired by the user. Note that the wireless quality between the access point AP and the terminal device UE can be obtained using the methods described with reference to Figures 9 to 12.

[0071] 15 is a diagram showing an example of a list of access points used in an AP cluster for each user according to the first embodiment. In the diagram, a list of access points forming an AP cluster is associated with each of the terminal devices UE1 to UE4. Specifically, the terminal device UE1 is associated with access points AP1 and AP2, the terminal device UE2 is associated with access points AP2 and AP4, the terminal device UE3 is associated with access points AP4, AP5, and AP6, and the terminal device UE4 is associated with access points AP6, AP7, and AP8.

[0072] Returning to Figure 14, information related to AP cluster change can be exemplified by a list of users who are spatially multiplexed in the same PRB (Physical Resource Block) during the same MU-MIMO signal processing. In the example shown in the figure, terminal apparatus UE1 and terminal apparatus UE2 are spatially multiplexed, and terminal apparatus UE3 and terminal apparatus UE4 are spatially multiplexed. That is, according to this embodiment, a list of terminal apparatuses UE to be used in an AP cluster is predetermined, and the AP cluster identification unit 11 can also be said to identify an AP cluster according to the predetermined list of terminal apparatuses UE.

[0073] In this way, by defining a list of spatially multiplexed users as information related to an AP cluster change, it becomes possible to control the combination of users to be spatially multiplexed in MU-MIMO in accordance with changes in the interference situation between users due to changes in the positional relationships between multiple users, etc. Therefore, according to this embodiment, continuous communication quality for users can be ensured.

[0074] 16 is a diagram showing an example of a list of spatially multiplexed users according to the first embodiment. In the figure, spatial multiplexing IDs are associated with a list of user IDs. Specifically, spatial multiplexing ID 1 is associated with terminal devices UE1 and UE2, and spatial multiplexing ID 2 is associated with terminal devices UE3 and UE4.

[0075] Next, a specific example of AP cluster optimization using the above-described embodiment will be described with reference to FIGS.

[0076] Fig. 17 is a diagram showing an example of optimization of an AP cluster depending on the RAN resource situation. An example of optimization of an AP cluster depending on the RAN resource situation will be described with reference to the same figure. Fig. 17(A) is a diagram showing an example of the logical configuration of a wireless communication network 1, and Fig. 17(B) is a diagram showing an example of the functional configuration of an O-RAN architecture.

[0077] First, wireless quality information between the access point AP and the terminal device UE, RAN transmission path resource usage rate, computer resource usage rate, user spatial distribution, service usage status, etc. are acquired via the O1 interface. Next, Non-RT RIC determines AP cluster policy information using mathematical programming or machine learning according to KPIs based on the collected RAN resource information and user service information. Here, examples of KPIs include the total throughput of each user, each user's throughput satisfaction level, wireless resource usage rate, computer resource usage rate, and transmission path bandwidth usage rate.

[0078] Furthermore, the Non-RT RIC transmits AP cluster policy information and a change instruction to the Near-RT RIC using the AP cluster policy information interface described above. The Near-RT RIC then updates the AP cluster for each user using the updated AP cluster policy. Furthermore, the Near-RT RIC transmits a setting change instruction to the O-DU using the AP cluster change-related interface described above, and starts communication using the updated AP cluster.

[0079] In this way, the AP cluster is updated according to the RAN resource situation, and the usage situation of the computer and the usage situation of the transmission path are optimized. Here, users who operate the terminal apparatus UE may be present in different locations during the day and at night (for example, the density increases in business districts where many workplaces are located during the day, and the density increases in residential areas at night). Therefore, the distribution of terminal apparatuses UE during the day and the distribution of terminal apparatuses UE at night may differ from each other. According to this embodiment, the AP cluster can be updated in real time to a suitable AP cluster according to each distribution situation. Therefore, according to this embodiment, suitable wireless communication can be realized throughout the RAN.

[0080] Fig. 18 is a diagram showing an example of optimization of an AP cluster accompanying user movement according to the first embodiment. With reference to the same figure, an example of optimization of an AP cluster accompanying user movement will be described. Fig. 18(A) is a diagram showing an example of the logical configuration of a wireless communication network 1, and Fig. 18(B) is a diagram showing an example of the functional configuration of an O-RAN architecture.

[0081] First, wireless quality information and user service information between the access point AP and the terminal device UE are acquired via the O1 interface. Next, in Near-RT RIC, based on the collected wireless quality information and user service information, etc., AP cluster policy information and a user list to be spatially multiplexed using MU-MIMO are calculated using mathematical programming or machine learning according to the KPI. Here, examples of KPIs include the total throughput of each user, the throughput satisfaction of each user, the utilization rate of wireless resources, the utilization rate of computer resources, and the utilization rate of transmission path bandwidth.

[0082] Next, the AP cluster information is transmitted from the Near-RT RIC to the O-DU. This transmission is performed using the interface related to the AP cluster change described above. Optimal communication is initiated after the user moves using a new AP cluster for each user and MU-MIMO parameters. Therefore, according to this embodiment, even if the user moves, the AP cluster can be updated in real time to a suitable AP cluster. Therefore, according to this embodiment, suitable wireless communication can be realized throughout the RAN.

[0083] [Second Embodiment] A second embodiment will be described with reference to Fig. 19 to Fig. 24. In the second embodiment, a processing procedure for suppressing interference between terminal devices UE present at different sites will be described. The second embodiment aims to continuously provide communication quality required for each application at any location where users are present. To achieve this aim, it is necessary to suppress interference between terminal devices UE at different sites (hereinafter, sometimes referred to as interference between different site UEs) that occurs to users near the boundary between distributed CPUs.

[0084] According to conventional technology, there is a method for suppressing interference between UEs at different sites by duplicating and transferring a main signal (IQ signal) to a CPU at another site and forming an AP cluster across the CPUs at different sites. However, because the main signals (IQ signals) transmitted and received by each terminal device UE are aggregated at one site for wireless signal processing, the IQ signals must be transmitted to the BH between the CPUs at different sites, which places a heavy load on the BH. For this reason, it is necessary to limit the size of the AP cluster across the sites so as not to exceed the BH capacity, and there is a possibility that interference between UEs at different sites cannot be completely eliminated. When the terminal device UE also performs beamforming, there is a problem that when connecting to multiple access points APs, such as CF-m MIMO, where the beam of the terminal device UE affects the received signal power of the access point AP and the best beam at that time, the beam cannot be appropriately determined simply by combining the best beam between the access point AP and the terminal device UE.

[0085] 37 is a diagram for explaining a processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the conventional technology. With reference to the same figure, problems with the processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network 9 according to the conventional technology will be explained. In the same figure, the AP cluster of terminal device UE1 includes access points AP1 to AP6, and the AP cluster of terminal device UE2 includes access points AP7 to AP9. Here, there is an interference signal from terminal device UE1 to terminal device UE2 (access points AP7 and AP8).

[0086] According to the conventional technology, the RIC first calculates an AP cluster based on the wireless quality required by the user, within a range that does not exceed the BH capacity. Here, the RIC controls the AP cluster that receives the main signal for each terminal device UE. In this case, IQ signals from access points AP5 and AP6 included in the AP cluster of the terminal device UE1 are transferred to and aggregated by the CPU1. The CPU1 performs channel estimation and signal processing for the terminal device UE1. Signals to access points AP not included in the AP cluster of the terminal device UE1, i.e., interference signals from the terminal device UE1 to access points AP7 and AP8, are treated as noise. Therefore, when the CPU2 calculates the weight for the terminal device UE2, it is unable to separate the interference signal from the terminal device UE1, resulting in degradation of wireless quality.

[0087] Therefore, in this embodiment, each terminal device UE starts up a CPU that performs only channel estimation of same-site and different-site UE interference signals at a plurality of local sites to which an access point AP that causes different-site UE interference is directly connected, and simultaneously performs channel estimation of the different-site UE interference signals at each site. Next, using this estimated channel of the different-site UE interference signals, a weight calculation is performed to suppress the different-site UE interference with the terminal device UE that performs main signal processing at the CPU of its own site.

[0088] Pilot allocation information of terminal devices UE that are sources of inter-site interference, which are necessary for channel estimation of inter-site interference signals between multiple sites, and a list of access points APs that perform channel estimation of inter-site interference between UEs are calculated by an external controller and transmitted to the CPU of each site. Note that the list of access points APs that perform channel estimation of inter-site interference between UEs is limited to access points APs that are sufficiently affected by the interference, and is not performed for access points APs whose interference is weak and unnecessary. Note that the wireless quality between the access points APs and the terminal devices UEs can be obtained using the methods described with reference to Figures 9 to 12.

[0089] 19 is a diagram for explaining a processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the second embodiment. With reference to the diagram, a method for solving the above-mentioned problems will be explained.

[0090] First, the RIC calculates the control objects. The control objects include an AP cluster that transmits and receives a main signal for each terminal device UE, pilot allocation information, beam information transmitted by the terminal device UE, an AP cluster that performs only channel estimation for each terminal device UE, and an instruction to start up an estimation CPU. After the calculation, the RIC issues an instruction to each CPU.

[0091] Next, IQ signals of the access points AP5 and AP6 included in the AP cluster of the terminal device UE1 are transferred and aggregated to the CPU 1. Subsequently, the CPU 1 performs channel estimation and signal processing for the terminal device UE1.

[0092] Furthermore, a channel estimation CPU1' for different-site UE interference signals from the terminal device UE1 is started up at the local site, and channel estimation is performed. Subsequently, channel information is shared from the channel estimation CPU1' to the CPU2. The CPU2 calculates the weight of the terminal device UE2 using estimated channels between the terminal device UE1 and the access point AP7 and between the terminal device UE1 and the access point AP8. A minimum mean squared error (MMSE) criterion may be used in this calculation process. By separating the different-site UE interference signals from the terminal device UE1, it is possible to suppress interference from the terminal device UE1.

[0093] That is, according to this embodiment, there are access points AP (in the illustrated example, access points AP7 and AP8) that perform only channel estimation for the terminal device UE1. The access points AP use the estimated channels to calculate the weights for the terminal device UE2. Note that in the illustrated example, the interference from the terminal device UE1 to the access point AP9 is weak, so channel estimation is not performed.

[0094] It is also assumed that the terminal device UE2 also starts up a CPU 2′ for channel estimation in site #1 in order to reduce interference with the terminal device UE1. However, in the explanation given with reference to the same figure, the explanation is omitted to avoid complicating the description.

[0095] According to this embodiment, channel estimation of an inter-site UE interference signal from a terminal device UE is simultaneously performed at multiple local sites to which the interfered access point AP is connected, and weight calculations for suppressing inter-site UE interference are performed at each local site using the estimated channel, thereby making it possible to suppress inter-site UE interference without transmitting IQ signals to the BH between sites. In other words, inter-site UE interference can be suppressed over a wide area without expanding the AP cluster or increasing the BH load that accompanies this. Therefore, according to this embodiment, it is possible to know the best beam of the access point AP for the beam transmitted by the terminal device UE, and to select an appropriate beam. Therefore, according to this embodiment, it is possible to improve the quality of wireless communication.

[0096] 20 is a sequence diagram showing details of a processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the second embodiment. The diagram shows the processing of Non-RT RIC or Near-RT RIC (i.e., RIC), and O-DU. The processing at each step will be explained below.

[0097] (Step S31) First, a data collection (O1) is transmitted from an O-DU of a different site to an RIC. The information transmitted here includes information on the transmission power of the terminal device UE, propagation path information, and information on the beam of the terminal device UE. If multiple O-DUs exist, each O-DU transmits a data collection (O1).

[0098] (Step S32) The RIC performs pilot allocation calculation based on the data collection (O1) acquired from multiple O-DUs of different sites. Details of this calculation will be described later with reference to FIGS. 21 and 22.

[0099] (Step S33) After calculating the pilot allocation, the RIC transmits an Updated Configuration (O1 or E2) to the O-DU. Here, the transmitted information includes pilot allocation information, information on the transmission power of the terminal apparatus UE, a change instruction, information on the beam of the terminal apparatus UE, etc. If there are multiple O-DUs, the RIC transmits an Updated Configuration (O1 or E2) for each O-DU.

[0100] (Step S34) Next, the RIC calculates the range of channel estimation for each user. Details of this calculation will be described later with reference to FIGS. 23 and 24.

[0101] (Step S35) After calculating the pilot allocation, the RIC transmits an Updated Configuration (O1 or E2) to the O-DU. Here, the transmitted information includes a list of access points AP whose channels have been estimated for each user, a change instruction, information about the beam of the terminal device UE, etc. If multiple O-DUs exist, the RIC transmits an Updated Configuration (O1 or E2) to each O-DU.

[0102] (Step S36) The O-DU performs channel estimation based on the new pilot information and the list of access points AP. If there are multiple O-DUs, each O-DU performs channel estimation.

[0103] Next, the pilot allocation calculation in step S32 will be described in detail with reference to FIGS.

[0104] Fig. 21 is a first diagram showing a logical configuration of a wireless communication network for explaining a processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to a second embodiment. Fig. 22 is a first detailed sequence diagram showing details of the processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the second embodiment. A detailed processing procedure for calculating pilot allocation will be explained with reference to Figs. 21 and 22 .

[0105] Here, it is preferable that the indication form for the pilot allocation information and the transmission power information of the terminal device UE be defined for the channel estimation across the sites of the interference signal from the terminal device UE that is the source of the interference between different site UEs. However, currently, there is no definition for these in the O-RAN architecture. Therefore, the CPU of the different site cannot distinguish the pilot signal of the terminal device UE that causes the interference between different site UEs. In other words, currently, there is a problem that the channel estimation of the interference signal cannot be performed.

[0106] In addition, when the terminal device UE also performs beamforming, it is possible to connect to a plurality of access points AP such as CF-m MIMO, in which the received signal power of the access point AP and the best beam at that time are different depending on the beam of the terminal device UE. In such a case, there is a problem that it is not easy to appropriately determine the beam between the plurality of access points AP and the terminal device UE by only combining the best beam between the access point AP and the terminal device UE.

[0107] Therefore, in this embodiment, a message instructing addition and modification of pilot allocation information and transmission power information for each terminal device UE and its parameter information are added to the interface between Near-RT-RIC and O-DU (E2) or between Non-RT-RIC and O-DU (O1) (which can be considered as RIC and O-DU in the illustrated example). By such an interface, user transmission power and pilot allocation information for each terminal device UE are transmitted from the RIC to each site.

[0108] According to this embodiment, O-DU2' (vCPU2) performs channel estimation of the terminal device UE2 and access points AP1 to AP4, and O-DU1' (vCPU1) performs channel estimation of the terminal device UE1 and access points AP5 to AP8. That is, according to this embodiment, channel estimation across sites is realized. In this way, it is possible to calculate a weight that suppresses interference between UEs of different sites using the estimated channel.

[0109] Below, specific examples of the interface between Near-RT-RIC and O-DU (E2) and specific examples of the interface between Non-RT-RIC and O-DU (O1) will be described.

[0110] First, a specific example of the interface between Near-RT-RIC and O-DU (E2) will be described. In this case, it is required to reduce the overhead due to pilot resource expansion while preventing pilot contamination. Therefore, Non-RT-RIC calculates the pilot sequence length according to the user density in the area so as to balance the degree of pilot contamination and the overhead of the pilot signal (including beam information of the terminal device UE). In this way, an interface is added to instruct the O-DU as the sequence length for each area.

[0111] By adding an interface that instructs the O-DU as the sequence length for each area, for example, in a certain area, during periods of high user density, the pilot sequence length can be extended, improving the directivity of the pilots and preventing degradation of wireless quality due to pilot contamination. Conversely, during periods of low user density, the pilot sequence length can be shortened, increasing the proportion of wireless resources allocated to the main signal and improving frequency utilization efficiency. Since large changes in user density are expected to occur in periods of minutes to hours, it is preferable to utilize Non-RT-RIC, which is suitable as a controller for the same period.

[0112] Next, a specific example of the interface between Non-RT-RIC and O-DU (O1) will be described. In this case, there is a problem that the interference situation of pilot signals between users changes due to user movement, and pilot contamination occurs between users to which the same pilot is assigned. Therefore, Near RT-RIC calculates pilot allocation information (including beam information of the terminal apparatus UE) each time to reduce pilot contamination based on the interference situation between users according to the user's movement. Furthermore, the pilot allocation information for each terminal apparatus UE obtained as a result of the calculation is shared with all O-DUs that accommodate other terminal apparatuses UE that may cause interference from that terminal apparatus UE.

[0113] By adopting such a configuration, pilot contamination can be reduced by instructing optimal pilot allocation according to changes in the interference situation between users due to user movement. Also, channel estimation can be performed independently in all O-DUs that are subject to inter-site interference. Since channel fluctuations due to user movement are expected to occur in periods from milliseconds to seconds, it is preferable to utilize Near RT-RIC, which is suitable as a controller with the same period.

[0114] By defining the above-described interface, pilot allocation information is shared among a plurality of sites. Therefore, it is possible to perform channel estimation of an interference signal of a terminal apparatus UE, which is a source of interference between different-site UEs, at a plurality of sites. By using this estimated channel of interference between different-site UEs to perform MIMO weight calculation for suppressing the interference signal at each site, it is possible to suppress interference between different-site UEs. That is, according to this embodiment, it is possible to know the best beam of the access point AP for the beam of the terminal apparatus UE. Therefore, according to this embodiment, it is possible to select an appropriate beam for each of the access point AP and the terminal apparatus UE, and it is possible to achieve quality improvement.

[0115] Next, the calculation of the range of channel estimation for each user in step S34 described above will be described in detail with reference to FIGS.

[0116] Fig. 23 is a second diagram showing the logical configuration of a wireless communication network for explaining the processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the second embodiment. Fig. 24 is a second detailed sequence diagram showing details of the processing procedure for suppressing interference between terminal devices at different sites using a wireless communication network according to the second embodiment. With reference to Figs. 23 and 24 , the detailed processing procedure for calculating the channel estimation range for each user will be explained.

[0117] Here, in a situation where the O-DU (CPU) is distributed across multiple sites, it is preferable to define list information of access points APs that perform only channel estimation for each terminal device UE, and the instruction form thereof. However, currently, there is no definition of these in the O-RAN architecture. Therefore, there is a problem that the amount of calculation of the O-DU may increase due to channel estimation between the access point AP and the terminal device UE where interference between different sites UE is weak and interference removal is not required.

[0118] In addition, when the terminal device UE also performs beamforming, it is possible to connect to a plurality of access points AP such as CF-m MIMO, in which the received signal power of the access point AP and the best beam at that time are different depending on the beam of the terminal device UE. In such a case, there is a problem that it is not easy to appropriately determine the beam between the plurality of access points AP and the terminal device UE by only combining the best beam between the access point AP and the terminal device UE.

[0119] Therefore, in this embodiment, a message instructing each site to change the list information of the access point AP that only performs channel estimation for each terminal device UE, and its parameter information, are added to the interface between Near-RT-RIC and O-DU (E2) or between Non-RT-RIC and O-DU (O1) (which can be considered as RIC and O-DU in the example shown).

[0120] The O-DU1' performs channel estimation of interference between different-site UEs only between the designated access point AP and terminal device UE. In this way, it is possible to calculate a weight for suppressing interference between different-site UEs using the estimated channel.

[0121] Furthermore, according to this embodiment, it is also possible to perform only channel estimation by A-DU2 between the terminal device UE1 and the access point AP7, and between the terminal device UE1 and the access point AP8. In other words, by narrowing down to only between the access point AP and the terminal device UE where interference between different site UEs occurs, it is also possible to obtain an effect of suppressing the amount of calculation.

[0122] According to this embodiment, the O-DU (CPU) performs channel estimation for only the terminal apparatus UE and the access point AP for which interference should be removed according to the interference situation between users, and can be used for weight calculation to suppress interference. Also, according to this embodiment, it is possible to prevent an increase in the amount of O-DU calculation due to channel estimation between the access point AP and the terminal apparatus UE E where the interference signal is weak and interference removal is not required. Also, according to this embodiment, it is possible to know the best beam of the access point AP for the beam of the terminal apparatus UE. Therefore, according to this embodiment, it is possible to select an appropriate beam for each of the access point AP and the terminal apparatus UE, thereby achieving quality improvement.

[0123] [Third Embodiment] A third embodiment will be described with reference to Figures 25 to 34. In the third embodiment, a specific aspect of the method for acquiring wireless quality between an access point AP and a terminal device UE, as described with reference to Figures 9 to 12, will be described. The third embodiment can also be said to be a specific method for ensuring wireless quality, as described with reference to Figures 9 to 12. Note that in the description of the third embodiment, reference numerals are newly assigned, and therefore may overlap with the reference numerals of the above-mentioned embodiments.

[0124] The third embodiment will be described in the following two examples. Example 1: When one terminal communicates with multiple base stations at the same time, a combination of multiple uplink beams from the terminal and multiple downlink beams from each of the multiple base stations. Example 2: When one base station communicates with multiple terminals at the same time, a combination of multiple downlink beams from the base station and multiple uplink beams from each of the multiple terminals.

[0125] Example 1 FIG. 25 is a configuration diagram showing beamforming in a first example according to the third embodiment of the present invention.

[0126] According to Figure 25, when one terminal communicates with multiple base stations simultaneously, the diagram shows a combination of multiple uplink beams from the terminal and multiple downlink beams from each of the multiple base stations. The system of Figure 25 includes terminal 1, three base stations 21 to 23, and a base station control device 3. Terminal 1 has a beamforming-compatible multi-antenna capable of transmitting uplink beams in multiple directions, and communicates simultaneously with multiple base stations 2. Here, the transmission beam from terminal 1 is referred to as an "uplink beam." According to Figure 25, the multi-antenna of terminal 1 is capable of transmitting uplink beams #1 to #4 in each of four directions. The multi-antenna transmits reference signals for the uplink beams in different directions while performing beam sweeping. The reference signal includes an identifier # for that uplink beam.

[0127] Each of the base stations 21 to 23 also has a beamforming-compatible multi-antenna capable of transmitting downlink beams in multiple directions, and communicates simultaneously with the terminal 1. Here, the transmission beam from each of the base stations 21 to 23 is referred to as a "downlink beam." According to FIG. 25, the multi-antenna of each of the base stations 21 to 23 is capable of transmitting downlink beams #1 to #8 in each of eight directions. The multi-antenna transmits the reference signal of the downlink beam in different directions while performing beam sweep. The reference signal includes the identifier # of the downlink beam.

[0128] The base station control device 3 controls each of the base stations 21 to 23 by determining the best downlink beam for communication with the terminal 1. The base station control device 3 also manages the uplink beam for the terminal 1.

[0129] FIG. 26 is a functional configuration diagram of a terminal in a first example according to the third embodiment of the present invention.

[0130] 26, terminal 1 has, in addition to multi-antenna 100, a communication quality measurement unit 101, a downlink best beam selection unit 102, an uplink best beam selection unit 103, an uplink beam control unit 104, a beam table notification unit 105, and an uplink beam notification unit 106. These functional components other than the multi-antenna are realized by executing a program that causes a computer installed in the terminal to function. Furthermore, the processing flow of these functional components can also be understood as a beam selection method in a terminal having multi-antennas.

[0131] [Communication Quality Measurement Unit 101] The communication quality measurement unit 101 measures the communication quality of a plurality of downlink beams from each base station 2 for each uplink beam in a different direction at the terminal 1. The communication quality may be, for example, received signal power.

[0132] Fig. 27 is a communication quality table in a first example according to the third embodiment of the present invention. According to Fig. 27, the received signal power (communication quality) for downlink beams #1 to #8 of each base station 21 to 23 is shown for each uplink beam #1 to #4 of terminal 1.

[0133] [Best Downlink Beam Selection Unit 102] The best downlink beam selection unit 102 selects a "best downlink beam" whose communication quality meets or exceeds a predetermined condition among multiple downlink beams at each base station for each uplink beam in a different direction at the terminal 1. The "predetermined condition" for selecting the best downlink beam may be, for example, selecting the downlink beam with the highest communication quality.

[0134] 27, for example, for the uplink beam #1 of terminal 1, downlink beam #1, which has the highest communication quality, is selected as the best downlink beam among downlink beams #1 to #8 in base station 21. Similarly, next, for the uplink beam #1 of terminal 1, downlink beam #4, which has the highest communication quality, is selected as the best downlink beam among downlink beams #1 to #8 in base station 22. Furthermore, for the uplink beam #2 of terminal 1, downlink beam #3, which has the highest communication quality, is selected as the best downlink beam among downlink beams #1 to #8 in base station 21.

[0135] [Uplink best beam selection unit 103] The uplink best beam selection unit 103 selects the "uplink best beam" from among the multiple uplink beams in the terminal 1 such that the sum of the communication qualities of the downlink best beams in all base stations 2 is equal to or exceeds a predetermined condition. The "predetermined condition" for selecting the uplink best beam may be, for example, selecting the downlink beam with the highest communication quality.

[0136] According to Figure 27, for example, among multiple uplink beams #1 to #4 in terminal 1, the sum of the communication qualities of the best downlink beams in all base stations 2 is calculated. For uplink beam #1 of terminal 1, the sum of the communication qualities of downlink beam #1 of base station 21, downlink beam #4 of base station 22, and downlink beam #7 of base station 23 is calculated as the best downlink beam. Similarly, for uplink beam #2 of terminal 1, the sum of the communication qualities of downlink beam #3 of base station 21, downlink beam #4 of base station 22, and downlink beam #4 of base station 23 is calculated as the best downlink beam. Ultimately, uplink beam #2 of terminal 1, which has the highest sum of communication qualities of the best downlink beams in all base stations 2, is selected as the "best uplink beam."

[0137] [Uplink Beam Control Unit 104] The uplink beam control unit 104 controls the multi-antenna 100 so as to communicate with a plurality of base stations 2 simultaneously using the "uplink best beam."

[0138] [Beam Table Notification Unit 105] The beam table notification unit 105 creates a "beam table" that associates the identifiers of multiple uplink beams of the terminal 1 with the identifiers of the best downlink beams of each base station.

[0139] The beam table can be used for beam management, for example. Based on the technical specifications for beam management, the following controls are defined: Beam determination: Selection of transmitting beam / receiving beam Beam measurement: Communication quality of received signal of beam Beam reporting: Reporting of beam information Beam sweeping: Sweeping of a spatial area (e.g., 360 degrees)

[0140] FIG. 28 shows a beam table in a first example according to the third embodiment of the present invention.

[0141] According to FIG. 28, multiple uplink beams #1 to #4 for terminal 1 are arranged in a vertical column. Each uplink beam is associated with an identifier of the best downlink beam for each base station 21 to 23. According to FIG. 28, for example, the following beam table is created: The uplink beam #1 for terminal 1 is associated with the identifier of the best downlink beam #1 with the highest received signal strength among the best downlink beams received from base station 21. The uplink beam #2 for terminal 1 is associated with the identifier of the best downlink beam #3 with the highest received signal strength among the best downlink beams received from base station 21. The uplink beam #3 for terminal 1 is associated with the identifier of the best downlink beam #4 with the highest received signal strength among the best downlink beams received from base station 21. The uplink beam #4 for terminal 1 is associated with the identifier of the best downlink beam #2 with the highest received signal strength among the best downlink beams received from base station 21. ... In this way, similar associations can be made for the other base stations 21 and 23 as viewed from terminal 1.

[0142] In addition, the beam table notification unit 105 may further associate the ``communication quality'' of the best downlink beam from each base station 2 with each of the identifiers #1 to #4 of the uplink beam of the terminal 1 in the beam table.

[0143] Then, the beam table notification unit 105 notifies the base station control device 3 of the beam table via the base station 2. The base station control device 3 can know which of the best downlink beams of each of the base stations 21 to 23 should be selected to improve communication quality, depending on the uplink beam selected by the terminal 1.

[0144] [Uplink beam notification unit 106] The uplink beam notification unit 106 notifies each base station 2 of the identifier of the uplink beam of the terminal 1 and the identifier of the best downlink beam of the base station corresponding to the identifier of the uplink beam.

[0145] FIG. 29 is a sequence diagram of a first example according to the third embodiment of the present invention.

[0146] The uplink beam notification unit 106 notifies each base station 2 of the identifier of the best uplink beam selected for the terminal 1.

[0147] FIG. 30 is a configuration diagram showing a combination of beams that can be used simultaneously by a terminal in a first example according to the third embodiment of the present invention.

[0148] According to FIG. 30, it is assumed that terminal 1 has multiple multi-antennas 100. The number of uplink beams that terminal 1 can transmit simultaneously is also multiple. In this case, the beam table notification unit 105 further notifies combinations of identifiers of uplink beams that can be transmitted simultaneously from among the multiple uplink beams of terminal 1. Number of beams that can be used simultaneously: 2 Simultaneously usable combinations (uplink beam #1, uplink beam #3) (uplink beam #1, uplink beam #4) (uplink beam #2, uplink beam #3) (uplink beam #2, uplink beam #4)

[0149] FIG. 31 is a beam table based on FIG.

[0150] The downlink best beam selection unit 102 described above may select one or more downlink best beams whose communication quality meets or exceeds a predetermined condition. For example, if the communication quality is received signal power, the following predetermined conditions can be set to select multiple downlink best beams: (Predetermined condition 1) Up to xx downlink beams in descending order of received signal power (Predetermined condition 2) Downlink beams with received signal power of yy dBm or more (Predetermined condition 3) Up to xx downlink beams with received signal power of yy dBm or more As a result, the beam table in Figure 31 is different from the beam table in Figure 28 in that one or more downlink best beams are associated with each uplink beam of terminal 1.

[0151] The beam table in Fig. 31 also includes combinations of beams that can be used simultaneously by the terminal 1 in Fig. 30. This allows the base station control device 3, which has received the beam table, to know the best downlink beam with high communication quality for the base station 2 for each beam that can be used simultaneously by the terminal 1.

[0152] Example 2 FIG. 32 is a configuration diagram showing beamforming in a second example according to the third embodiment of the present invention.

[0153] 32, in comparison with FIG. 25, shows a combination of multiple downlink beams from the base station and multiple uplink beams from each of the multiple terminals when one base station 2 simultaneously communicates with multiple terminals. The terminal 1 has a beamforming-compatible multi-antenna capable of transmitting uplink beams in multiple directions. The functions of the terminal 1, base station 2, and base station control device 3 are exactly the same as those in FIG. 1.

[0154] FIG. 33 is a functional configuration diagram of a base station in a second example according to the third embodiment of the present invention.

[0155] According to Figure 33, the base station 2 has a multi-antenna 200, as well as a communication quality measurement unit 201, an uplink best beam selection unit 202, a downlink best beam selection unit 203, a downlink beam control unit 204, a beam table notification unit 205, and a downlink beam notification unit 206. These functional components other than the multi-antenna are realized by executing a program that causes a computer installed in the base station to function. Furthermore, the processing flow of these functional components can also be understood as a beam selection method in a base station having multiple antennas. Comparing Figure 33 with the above-mentioned Figure 26, the following functions are relatively the same. <Terminal side in FIG. 26> <-> <Base station side in FIG. 33> Communication quality measurement unit 101 Communication quality measurement unit 201 Downlink best beam selection unit 102 Uplink best beam selection unit 202 Uplink best beam selection unit 103 Downlink best beam selection unit 203 Uplink beam control unit 104 Downlink beam control unit 204 Beam table notification unit 105 Beam table notification unit 205 Uplink beam notification unit 106 Downlink beam notification unit 206

[0156] [Multi-antenna 200] The multi-antenna 200 is a beamforming-compatible antenna capable of transmitting downlink beams in a plurality of directions.

[0157] [Communication Quality Measuring Unit 201] The communication quality measuring unit 201 measures the communication quality of a plurality of uplink beams from each of the terminals 11 to 13 for each downlink beam in a different direction in the base station 2.

[0158] Fig. 34 shows a communication quality table in a second example according to the third embodiment of the present invention. According to Fig. 34, the received signal power (communication quality) of multiple uplink beams #1 to #4 from each of the terminals 11 to 13 is associated with each of downlink beams #1 to #8 in different directions in the base station 2.

[0159] [Uplink Best Beam Selector 202] The uplink best beam selector 202 selects, for each downlink beam in a different direction, a best uplink beam from among multiple uplink beams for each terminal 11-13, whose communication quality meets or exceeds a predetermined condition. According to FIG. 34, for example, for downlink beam #1 of base station 2, uplink beam #1 with the highest communication quality is selected as the best uplink beam from among uplink beams #1-#4 for terminal 11. Similarly, for downlink beam #1 of base station 2, uplink beam #4 with the highest communication quality is selected as the best uplink beam from among downlink beams #1-#4 for terminal 12. Furthermore, for downlink beam #2 of base station 2, uplink beam #3 with the highest communication quality is selected as the best uplink beam from among uplink beams #1-#4 for terminal 11. The uplink best beam selector 202 may select one or more best uplink beams whose communication quality meets or exceeds a predetermined condition.

[0160] [Downlink Best Beam Selector 203] The downlink best beam selector 203 selects, from among the multiple downlink beams in the base station 2, a downlink best beam whose sum of the communication qualities of the uplink best beams for all terminals 1 is equal to or exceeds a predetermined condition. According to FIG. 34 , for example, among the multiple uplink beams #1 to #8 in the base station 2, the sum of the communication qualities of the downlink best beams for all terminals 1 is calculated. According to the downlink beam #1 of the base station 2, the sum of the communication qualities of the uplink beam #1 for terminal 11, the uplink beam #4 for terminal 12, and the uplink beam #3 for terminal 13 is calculated as the best uplink beam. Similarly, according to the downlink beam #2 of the base station 2, the sum of the communication qualities of the uplink beam #3 for terminal 11, the uplink beam #4 for terminal 12, and the uplink beam #4 for terminal 13 is calculated as the best uplink beam. Finally, the downlink beam #2 of the base station 2, which has the highest sum of the communication qualities of the downlink best beams for all terminals 11 to 13, is selected as the "downlink best beam."

[0161] The downlink beam control unit 204 controls the multi-antenna 200 with the selected best downlink beam.

[0162] [Beam Table Notification Unit 205] The beam table notification unit 205 notifies the base station control device 3 of a beam table that associates the identifier of the downlink beam of the base station with the identifier of the best uplink beam of each terminal.

[0163] FIG. 35 shows a beam table in a second example according to the third embodiment of the present invention.

[0164] According to Figure 35, for example, the following beam table is created. Downlink beam #1 of base station 2 is associated with the identifier of best uplink beam #1, which has the highest received signal strength among the best uplink beams received from terminal 11. Downlink beam #2 of base station 2 is associated with the identifier of best uplink beam #3, which has the highest received signal strength among the best uplink beams received from terminal 11. Downlink beam #8 of base station 2 is associated with the identifier of best uplink beam #2, which has the highest received signal strength among the best uplink beams received from terminal 11.

[0165] The beam table notification unit 205 may also associate the identifiers of one or more best uplink beams for each terminal with the beam table. Furthermore, the beam table notification unit 205 may further associate the communication quality of the best uplink beam for each terminal with each identifier of the downlink beam of the base station in the beam table. Furthermore, the beam table notification unit 205 may further notify a combination of identifiers of downlink beams that can be transmitted simultaneously from among multiple downlink beams in the base station.

[0166] [Downlink beam notification unit 206] The downlink beam notification unit 206 notifies each terminal 1 of the identifier of the downlink beam of the base station 2 and the identifier of the best uplink beam for the terminal corresponding to the identifier of the downlink beam.

[0167] As described above in detail, according to the terminal, base station, and program of the present invention, when multiple connections are made simultaneously between the terminal and the base station, the optimal combination of uplink beams and downlink beams in beamforming can be selected.

[0168] Furthermore, the above-described embodiment makes it possible to, for example, "effectively utilize wireless resources between a terminal and a base station," thereby contributing to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote sustainable industrialization, and foster innovation."

[0169] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present invention.

[0170] Furthermore, a computer program for implementing the functions of each of the above-described devices may be recorded on a computer-readable recording medium, and the program may be read and executed by a computer system. The term "computer system" may also include hardware such as an OS and peripheral devices. The term "computer-readable recording medium" refers to a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a DVD (Digital Versatile Disc), or a storage device such as a hard disk built into a computer system.

[0171] Furthermore, the term "computer-readable recording medium" also includes a storage medium that stores a program for a certain period of time, such as a volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within a computer system that serves as a server or client when the program is transmitted via a network such as the Internet or a communication line such as a telephone line. The program may also be transmitted from a computer system that stores the program in a storage device or the like to another computer system via a transmission medium or by transmission waves within the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has the function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may also be a program that realizes part of the aforementioned functions. Furthermore, the program may be a so-called differential file (differential program) that can realize the aforementioned functions in combination with a program already recorded in the computer system.

[0172] According to the present invention, it is possible to realize suitable wireless communication throughout the RAN.

[0173] REFERENCE SIGNS LIST 1 wireless communication network, AP access point, UE terminal device, 10 network control device, 11 AP cluster identification unit, 12 CPU selection unit

Claims

1. A network control device that controls a wireless communication network in which terminal devices communicate wirelessly with each other via a plurality of distributed access points, comprising: an AP cluster identification unit that identifies an AP cluster indicating one or more of the access points that communicate wirelessly with the terminal devices; and a CPU selection unit that selects, for each of the AP clusters for each of the terminal devices, a CPU to be connected to the access point included in the AP cluster.

2. The network control device according to claim 1, wherein the AP cluster identification unit and the CPU selection unit are included in a RAN Intelligent Controller (RIC) that controls a plurality of the CPUs, and the RIC acquires transmission path and computer resource information from a distribution unit (O-DU), and then updates policy information of the AP cluster according to the usage status of the transmission path and the computer.

3. The network control device according to claim 2, wherein the RIC identifies the AP cluster after updating the policy information of the AP cluster, and notifies the distributed unit of the identified new AP cluster.

4. The network control device according to claim 1, wherein an upper limit of the number of access points forming the AP cluster is determined in advance, and the AP cluster identification unit identifies the AP cluster within a range that does not exceed the predetermined upper limit of the number of access points.

5. The network control device according to claim 1, wherein a lower limit value of wireless quality between the access point and the terminal device that can be used as the AP cluster is predetermined, and the AP cluster identification unit does not identify the access point as the AP cluster if the wireless quality falls below the predetermined lower limit value.

6. The network control device according to claim 5, wherein the terminal device and the access point perform beamforming with each other, and the wireless quality is the quality of the best beam that maximizes received signal power as a result of beamforming.

7. The network control device according to claim 5, wherein the terminal device and the access point perform beamforming with each other, and the wireless quality is determined based on the received signal power for each combination of the beam of the terminal device and the beam of the access point as a result of the beamforming.

8. A network control device as described in claim 6 or claim 7, wherein the terminal device is equipped with multiple antennas that can be used simultaneously, the multiple antennas equipped on the terminal device are each capable of outputting beams in different directions, and the AP cluster identification unit identifies the AP cluster based on the antennas that can be used simultaneously by the terminal device.

9. The network control device according to claim 1, wherein the AP cluster identification unit and the CPU selection unit are included in a RAN Intelligent Controller (RIC) that controls a plurality of the CPUs, and the RIC recalculates the AP cluster and related parameters after obtaining radio quality information and service information from a distribution unit (O-DU).

10. The network control device according to claim 9, wherein a list of the access points to be used in the AP cluster is determined in advance, and the AP cluster identification unit identifies the AP cluster according to the predetermined list of access points.

11. The network control device according to claim 9, wherein a list of the terminal devices to be used in the AP cluster is determined in advance, and the AP cluster identification unit identifies the AP cluster in accordance with the predetermined list of the terminal devices.

12. The network control device according to claim 1, wherein the AP cluster identification unit and the CPU selection unit are included in a RAN Intelligent Controller (RIC) that controls a plurality of the CPUs, and the RIC acquires transmission power information indicating the transmission path and the power of the beam transmitted by the terminal device from a distribution unit (O-DU) at a different site, and performs pilot allocation calculations based on the acquired information.

13. A program for executing a network control device that controls a wireless communication network in which terminal devices communicate with each other wirelessly via multiple distributed access points, the program executing an AP cluster identification step that identifies an AP cluster indicating one or more access points that communicate wirelessly with the terminal device, and a CPU selection step that selects, for each AP cluster for each terminal device, a CPU to be connected to the access point included in the AP cluster.

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