Communication device, terminal device, communication system, and communication method

Abstract

[Problem] To provide a communication device, a terminal device, a communication system, and a communication method that achieve both mobility management and communication quality for the terminal device. [Solution] A communication device according to the present disclosure comprises: a communication unit that is connected to one of a plurality of first communication points and transmits a paging message to a terminal device in an idle mode via the one first communication point; and a control unit that selects one or more second communication points from a plurality of second communication points on the basis of the position or propagation environment of the terminal device in a connected mode and establishes a connection with the selected one or more second communication points. The first communication points constitute a static or semi-static communication area, the second communication points constitute a dynamic communication area through spatial multiplexing or diversity, and the communication unit communicates with the terminal device in the connected mode via the one or more second communication points with which the connection has been established.

Description

Communication device, terminal device, communication system, and communication method

[0001] The present disclosure relates to a communication device, a terminal device, a communication system, and a communication method.

[0002] The fifth-generation mobile communication system, so-called 5G, which has features such as high-speed large-capacity (eMBB: enhanced Mobile BroadBand), low latency and high reliability (URLLC: Ultra-Reliable and Low Latency Communications), and a large number of simultaneous connections (mMTC: massive Machine Type Communication), was first standardized as Rel-15 in 2018, and services compatible with 5G were also launched in Japan in March 2020. In 5G, the use of the millimeter-wave band, which is expected to easily secure a wide frequency band to achieve ultra-high speed, is expected.

[0003] In 5G, the millimeter-wave band is used as a capacity booster cell to enhance capacity, and the use of subterahertz waves is also expected for the next-generation system (e.g., 6G). On the other hand, it has been pointed out that in the case of millimeter waves and subterahertz waves, the propagation distance is short, so small cell formation may cause deterioration of communication quality at the cell boundary. Regarding this problem, attention is being paid to a technology called self-free, which dynamically forms virtual cells individually for each user, as shown in Patent Document 1 below.

[0004] International Publication No. 2023 / 112702

[0005] On the other hand, it is common for a wireless terminal to support an idle mode in order to reduce power consumption during non-communication. The network manages the mobility of wireless terminals in the idle mode at the granularity of a registration area composed of one or more cells so that it can transmit paging to wireless terminals in this idle mode. When it is assumed that the network operates to form only cells that are dynamically and virtually configured individually for each user, it becomes difficult to set a registration area for managing the mobility of wireless terminals in the idle mode.

[0006] Furthermore, reducing the number of base stations required for smaller cells raises concerns about increased installation costs. Therefore, 5G employs an architecture that divides base station functions into CUs (Central Units) and DUs (Distributed Units), allowing only the DU functions to be distributed. Additionally, there is discussion about introducing an open interface to separate the RU (Radio Unit) from the DU functions, enabling some DU functions to be implemented in the cloud. One such open interface, CPRI (Common Public Radio Interface), raises concerns that the increased number of MIMO layers and wider channel bandwidths will drastically increase the throughput required for the fronthaul connecting the RU and DU.

[0007] This disclosure provides a communication device, a terminal device, a communication system, and a communication method that can improve the communication quality of terminal devices.

[0008] The communication device of this disclosure comprises: a communication unit connected to one of a plurality of first communication points, which transmits a paging message to an idle-mode terminal device via the first communication point; and a control unit which selects one or more second communication points from a plurality of second communication points based on the location or propagation environment of the connected-mode terminal device, and establishes a connection with the selected one or more second communication points, wherein the first communication point constitutes a static or quasi-static communication area, the second communication points constitute a dynamic communication area by spatial multiplexing or diversity, and the communication unit communicates with the connected-mode terminal device via the one or more second communication points with which the connection has been established.

[0009] A diagram showing an example of conventional distributed control of base stations. A diagram showing an example of the architecture configuration of 5GS. A diagram showing each option for functional division between CU (Central Unit) and DU (Distributed Unit). A diagram showing an example of the architecture of a base station. A diagram showing an example of a communication system according to this embodiment. A diagram showing an example of dynamically generating a communication area (second communication area). A diagram showing another example of dynamically generating a communication area (second communication area). A diagram showing an example of the handover procedure for a wireless terminal in connected mode. A diagram showing an example of the procedure following Figure 8. A diagram showing an example of the procedure following Figure 9. A block diagram showing an example of the configuration of an information processing device according to this embodiment. A diagram showing an example of clustering processing of the second communication point performed in the central device unit. A diagram showing an example of the required amount of data for each interface.

[0010] Embodiments of the present invention will be described below with reference to the drawings.

[0011] <1. Conventional Base Station Distributed Control> The coverage of base stations operating as capacity booster cells that utilize higher frequencies such as the millimeter wave band is expected to be reduced to smaller cells depending on the propagation characteristics of that frequency band. To provide wide coverage, many base stations must be installed. Recently, with the need to work towards the SDGs (Sustainable Development Goals), reducing network power consumption (energy saving) has become an important issue. Therefore, in addition to basic coverage cells that are controlled statically, capacity booster cells are used that can be dynamically controlled to a lower power consumption state (inactive state) by switching on or off in an on-demand manner according to traffic demand. This capacity booster cell is composed of one or more distributed communication points that make up the base station.

[0012] Figure 1 shows an example of a conventional distributed control system for base stations. The first communication point 200-1 provides the first basic coverage cell (cell 1), and the second communication points 210-1, 210-2, and 210-3 provide capacity booster cells for the first basic coverage cell. Similarly, the first communication point 200-2 provides the second basic coverage cell (cell 2), and the second communication points 210-4, 210-5, and 210-6 provide capacity booster cells for the second basic coverage cell.

[0013] The capacity booster cell shown is an example consisting of three second communication points 210, but the number of second communication points 210 is not limited to three. The number of second communication points 210 may be one or more.

[0014] The first communication points 200-1 to 200-2, which provide basic coverage cells, operate in frequency bands known as the low band and mid-band, while the second communication point 210, which provides capacity booster cells, operates in frequency bands known as the mid-band and high band.

[0015] The low band is, for example, the frequency band included in FR1 (410 MHz - 7.125 GHz). The mid-band is, for example, the frequency band included in FR1 (410 MHz - 7.125 GHz) and FR3 (7.125 GHz - 24.25 GHz). The high band is, for example, the frequency band included in FR3 (7.125 GHz - 24.25 GHz) and FR2 (24.25 GHz - 71.0 GHz), as well as the sub-telehertz band.

[0016] The wireless terminal 100 is connected to the first communication point 200-1 within the first basic coverage cell (cell 1), and further connected to the second communication points 210-1, 210-2, and 210-3 which constitute the capacity booster cell. Connection means wireless connection, and means that a state is reached where signals can be transmitted and received or communication can be achieved through parameter exchange, etc. The wireless terminal 100 communicates using the second communication points 210-1, 210-2, and 210-3 in addition to the first communication point 200-1.

[0017] When wireless terminal 100 moves from the first basic coverage cell (cell 1) to the second basic coverage cell (cell 2), wireless terminal 100 disconnects from the second communication points 210-1, 210-2, and 210-3 that constitute the capacity booster cell, and performs a handover from the first communication point 200-1 that provides the first basic coverage cell (cell 1) to the first communication point 200-2 that provides the second basic coverage cell (cell 2). At the cell edge where this handover is performed, wireless terminal 100 disconnects the capacity booster cell.

[0018] When the wireless terminal 100 completes the handover to the second basic coverage cell (cell 2) and moves into the capacity booster cell consisting of the second communication points 210-4, 210-5, and 210-6, it connects with the second communication points 210-4, 210-5, and 210-6. The wireless terminal 100 communicates using the second communication points 210-4, 210-5, and 210-6 in addition to the first communication point 200-2.

[0019] Thus, in conventional distributed base station control, when a handover is performed at the cell edge, the wireless terminal 100 releases the capacity booster cell, resulting in a deterioration of communication quality. Embodiments of the present invention introduce a technology based on distributed base station control that can resolve this problem.

[0020] <2.5G System Architecture> Figure 2 shows an example of the configuration of a 5GS architecture. The 5G core network (CN) 30 is also called 5GC (5G Core) / NGC (Next Generation Core), or simply the network.

[0021] Hereinafter, the 5G core network 30 will also be referred to as 5GC / NGC. The core network 30 is connected to the UE (User Equipment) 10 via the RAN (Radio Access Network) / AN (Access Network) 20. The RAN / AN 20 corresponds to the base station 20. The UE 10 corresponds to a wireless terminal 100, which is an example of a terminal device according to this embodiment.

[0022] In the example shown in Figure 2, RAN / AN20 is not included in the core network 30, but it can be considered as a device belonging to the core network 30.

[0023] An application server (AS) 40, which processes applications, is connected to 5GS via the internet. The application server 40 is a device also called a server or cloud server, and it executes some or all of the processing of the application. This enables the user interface (UE) 10 to use applications via 5G services.

[0024] If the entity providing the application has a contract such as an SLA (Service Level Agreement) with a PLMN (Public Land Mobile Network) operator providing 5G services, the application server 40 can also be placed within the core network 30 as a DN (Data Network) 340. The application server 40 may also be provided in the form of an edge server.

[0025] The 5GS control plane functions are composed of multiple NFs (Network Functions). The multiple NFs in the control plane functions include, for example, AMF (Access and Mobility Management Function) 301, NEF (Network Exposure Function) 302, NRF (Network Repository Function) 303, NSSF (Network Slice Selection Function) 304, PCF (Policy Control Function) 305, SMF (Session Management Function) 306, UDM (Unified Data Management) 307, AF (Application Function) 308, AUSF (Authentication Server Function) 309, UCMF (UE radio Capability Management Function) 310, and LMF (Location Management Function) 311.

[0026] The UDM307 includes a UDR (Unified Data Repository) that holds and manages subscriber information, and an FE (Front End) unit that processes subscriber information.

[0027] The AMF301 performs mobility management.

[0028] The SMF306 handles session management.

[0029] The UCMF310 holds UE Radio Capability Information corresponding to all UE Radio Capability IDs in the Public Land Mobile Network (PLMN). The UCMF310 is responsible for assigning each PLMN-assigned UE Radio Capability ID.

[0030] In UE-Based mode, the LMF311 provides UE10 with assistance data for positioning. Using the assistance data acquired from the LMF311, UE10 can perform GNSS (Global Navigation Satellite System) measurements and position calculations. For example, UE10 can use a widely known method called Assisted-GNSS.

[0031] In UE-Assisted mode, the LMF311 acquires GNSS-related measurements such as Code Phase, Doppler, and Carrier Phase from the UE10, which is equipped with a GNSS receiver, and calculates the position of the UE10.

[0032] Furthermore, for UE10s that are equipped with a GNSS receiver but cannot receive signals from GNSS, or that are not equipped with GNSS, the LMF311 acquires information related to the position of the UE10 using positioning techniques called: -OTDOA (Observed Time Difference Of Arrival) -Multi-RTT (Round Trip Time) -DL AoD (Downlink Angle-of-Departure) -DL TDOA (Downlink Time Difference Of Arrival) -UL TDOA (Uplink Time Difference Of Arrival) -UL AoA (Angle of Arrival).

[0033] Namf is a service-based interface provided by AMF301. Nsmf is a service-based interface provided by SMF306. Nnef is a service-based interface provided by NEF302. Npcf is a service-based interface provided by PCF945. Nudm is a service-based interface provided by UDM307. Naf is a service-based interface provided by AF308. Nnrf is a service-based interface provided by NRF303. Nnssf is a service-based interface provided by NSSF304. Nausf is a service-based interface provided by AUSF309. Nucmf is a service-based interface provided by UCMF310. Nlmf is a service-based interface provided by LMF311. Each NF exchanges information with other NFs via its respective service-based interface.

[0034] Each Network Function (NF) can request or subscribe to services provided by other network functions, and receive responses or notifications from those services. In other words, each NF exchanges information with other NFs through request / response or subscription / notification means via its respective service-based interface.

[0035] The DN (Data Network) 340 has the functionality to enable connections to MNO (Mobile Network Operator) proprietary services, the internet, and third-party services.

[0036] The UPF (User Plane Function) 330 has the function of processing user plane data. The UPF 330 functions as a data transfer processing unit for user plane data processed by the application server 40. The UPF 330 also functions as a gateway connected to the RAN / AN 20.

[0037] Here, each NF of the core network 30 can be configured using virtualization or containers. Each NF can be implemented on a cloud server. In 5GS, each NF can be configured dynamically and reconfigurably using SDN (Software Defined Network).

[0038] In a 5G core network 30 configured according to a service-based architecture, new NFs (Network Functions) can be introduced by defining new services and service-based interfaces for those services. Furthermore, in the next generation (i.e., 6G) and beyond, the core network 30 may involve aggregation, subdivision, or transfer of specific services to other NFs, depending on the services provided by each NF. Therefore, the NFs supported by the core network 30 are not limited to the types of NFs in the 5G core network 30 exemplified above.

[0039] RAN / AN20 has the function of enabling connection to RANs and to ANs other than RANs. RAN / AN20 includes base stations called gNBs or ng-eNBs. RANs are sometimes called NG (Next Generation)-RANs.

[0040] Information is exchanged between UE10 and AMF301 via reference point N1. Information is exchanged between RAN / AN20 and AMF301 via reference point N2. Information is exchanged between SMF306 and UPF330 via reference point N4.

[0041] The SMF 306 performs QoS (Quality of Service) control for each service data flow. The QoS control of the SMF 306 can be applied to both IP and Ethernet type service data flows. By performing QoS control for each service data flow, the SMF 306 provides QoS that is authorized for each specific service.

[0042] The SMF 306 can utilize metrics such as QoS subscriber information in conjunction with service-based, subscription-based, or predefined PCF internal policy rules.

[0043] The SMF 306 determines the QoS to be authorized for the QoS flow using the PCC (Policy and Charging Control) rules related to the QoS flow, that is, the data flow controlled by QoS.

[0044] When the QoS flow is deleted, the SMF 306 can notify the PCF 305 that the QoS flow has been deleted. Also, when the SMF 306 cannot guarantee the bit rate guaranteed by the QoS flow, that is, the GFBR (Guaranteed Flow Bit Rate), it can notify the PCF 305 that the GFBR cannot be guaranteed.

[0045] As a QoS reservation process for the QoS flow, the establishment of a UE-initiated QoS flow is possible. Also, as part of the QoS flow change process, downgrading or upgrading of QoS is possible.

[0046] In addition, in mobile communication systems after the next generation (i.e., 6G), it is assumed that not only control plane function groups but also user plane functions (e.g., UPF 330) and RAN / AN 20 will support service-based architectures. Therefore, each node constituting the mobile communication system can be implemented and / or configured / reconfigured in an information processing device including a cloud server in a dynamic and re-configurable manner by utilizing technologies such as virtualization, container, and / or SDN (Software Defined Network).

[0047] <3. Functional Split between CU (Central Unit) and DU (Distributed Unit)> Figure 3 is a diagram showing each option of the functional split between CU (Central Unit) and DU (Distributed Unit) discussed in 5G, excerpted from 3GPP TR38.801 "Study on new radio access technology: Radio access architecture and interfaces".

[0048] In 4G, Option 8, which uses the CPRI / OBSAI protocol, is adopted, defining a configuration that divides the network into RRH (Remote Radio Head) which processes RF (Radio Frequency) and BBU (BaseBand Unit) which processes other L1 / L2 / L3 functions. Since the fronthaul connecting the BBU and RRH requires a transmission speed proportional to the number of antenna ports and channel bandwidth, in 5G, where the use of Massive MIMO (Multiple-Input Multiple-Output) and wider channel bandwidths are envisioned, there was a need to introduce a division option that could alleviate this transmission speed requirement. Therefore, in 5G, a configuration is defined in which the system is divided into a DU that processes L2 / L1 functions below the RLC (Radio Link Control) sublayer and a CU that processes L2 / L3 functions above the PDCP (Packet Data Convergence Protocol) sublayer, that is, an F1 interface based on Option 2.

[0049] 5G supports three distinct communication modes: eMBB, URLLC, and mMTC. Beyond 5G (B5G), the demand for support for other communication modes with different characteristics is expected to increase, making the introduction of adaptive communication processing mechanisms tailored to each mode desirable. Furthermore, depending on the communication mode, dynamic control of the division of functions other than Option 2 is also conceivable.

[0050] In 5G, an SDAP (Service Data Adaptation Protocol) sublayer (not shown) is added as a higher sublayer above the user plane of the PDCP sublayer. The SDAP sublayer provides QoS (Quality of Service) flows to 5GC and handles functions or services such as mapping QoS flows to Data Radio Bearers (DRBs) and marking QFI (QoS Flow Identifier) ​​packets for downlink (DL) and uplink (UL) packets.

[0051] <4. Base Station Architecture> Figure 4 shows an example of the architecture of the base station 20. In the configuration shown in Figure 4(a), the functions of the base station 20 (RAN / AN20) are divided into a CU (Central Unit) 21 that handles L2 / L3 functions above the PDCP (Packet Data Convergence Protocol) sublayer and a DU (Distributed Unit) 22 that handles L2 / L1 functions below the RLC (Radio Link Control) sublayer. The functions of the RAN / AN20 can be distributed and arranged via the F1 interface corresponding to Option 2.

[0052] In the configuration shown in Figure 4(b), the Radio Unit (RU) 24, which handles the radio portion of the DU22's functions, is separated. More specifically, the functions of the DU22 can be distributed between the DU23, which is the DU22 with the radio processing removed, and the RU24, which handles the radio processing, via a fronthaul compliant with the Common Public Radio Interface (CPRI), corresponding to option 8. Here, the RU24 is also called the Remote Radio Head (RRH). The RU24 and DU23 are connected via the fronthaul. The configuration of the fronthaul is not limited to a specific one, but examples include fiber optic cables or an all-optical network.

[0053] In the configuration shown in Figure 4(c), the RU26, which processes the LOW PHY sublayer and the radio unit, is separated from the functions of the DU22. More specifically, the functions of the DU22 can be distributed between the DU25, which is the DU22 with the processing of the LOW PHY sublayer and the radio unit removed, and the RU26, which processes the processing of the LOW PHY sublayer and the radio unit, via a fronthaul compliant with eCPRI (evolved Common Public Radio Interface), which corresponds to option 7.

[0054] In the examples shown in Figures 4(a) to 4(c), an example of an F1 interface is shown in which a CU21 that processes L2 / L3 functions above the PDCP sublayer and a DU22 that processes L2 / L1 functions below the RLC sublayer. However, the configuration of separating the CU21 and DU22 is not limited to this. For example, a configuration corresponding to option 4, in which a CU21 that processes L2 / L3 functions above the RLC sublayer and a DU22 that processes L2 / L1 functions below the MAC (Media Access Control) sublayer, is also possible. Furthermore, a configuration corresponding to option 6, in which a CU21 that processes L2 / L3 functions above the MAC sublayer and a DU22 that processes L1 functions below the PHY sublayer, is also possible. Other configurations corresponding to other options are also possible.

[0055] Furthermore, one or more DU22s, one or more DU23s, and / or one or more DU25s can be connected to one CU21.

[0056] Furthermore, the CU21 can be separated into a control plane section and a user plane section via the E1 interface. One or more user plane sections of the CU21 can be configured for each DU (e.g., DU22, DU23, or DU25). The control plane section of one CU21 is connected to one or more user plane sections of the CU21 via the E1 interface. The control plane section of one CU21 and each DU are connected via the F1-C interface, and the user plane sections of the CU21 and each DU are connected via the F1-U interface.

[0057] <5. Base Station Distributed Control> <5-1. Basic Configuration and Operation> Figure 5 is a diagram showing an example of a communication system according to this embodiment. This communication system realizes base station distributed control according to this embodiment. Multiple first communication points, 510-1 and 510-2, are arranged in the target area, and multiple second communication points, 520-1 to 520-12, are arranged as second communication points. The first communication points 510-1 and 510-2 constitute a static or quasi-static communication area, and the second communication points 520-1 to 520-12 constitute a dynamic communication area by spatial multiplexing or diversity.

[0058] The first central device unit 500-1 corresponding to the communication device according to this embodiment is connected to the first communication point 510-1 and is also connectable to or connected to the second communication points 520-1 to 520-7.

[0059] The second central device unit 500-2, corresponding to the communication device according to this embodiment, is connected to the first communication point 510-2 and is also connectable to or connected to the second communication points 520-6 to 520-12. In this example, the second communication points 520-6 and 520-7 are connectable to or connected to both the first central device units 500-1 and 500-2, respectively.

[0060] In the following description, unless otherwise specified, the first central device units 500-1 and 500-2 will be referred to as the central device unit 500. Unless otherwise specified, the first communication points 510-1 and 510-2 will be referred to as the first communication point 510. Unless otherwise specified, the second communication points 520-1 to 520-12 will be referred to as the second communication point 520.

[0061] A first communication point 510-1 connected to a first central unit 500-1 provides a first basic coverage cell (cell 1) corresponding to a first communication area. A first communication point 510-2 connected to a second central unit 500-2 provides a second basic coverage cell (cell 2) corresponding to a first communication area. In the example shown in Figure 5, the wireless terminal 100, which is UE10, is located within cell 1.

[0062] One of the processes that the wireless terminal 100 (see Figure 1), which is the UE10, performs when in standby mode (idle mode) is paging monitoring. The size of the registration area is determined by a trade-off between the wireless resources consumed by paging and the burden of updating the registration area of ​​the wireless terminal 100.

[0063] The registered area is the area used for mobility management, also called the tracking area, and is identified by TAI (Tracking Area Identity). The network (PLMN) manages the location of the wireless terminal 100 within the range of the set of tracking areas to which the wireless terminal 100 is camped, so that messages or data can be sent to the wireless terminal 100 when it is in standby mode (idle mode).

[0064] The wireless terminal 100 requests registration with the network by sending a registration request to the first communication point 510 of the cell where it is located. When the wireless terminal 100 is registered with the network, the AMF 301 assigns a set of tracking areas included in the TAI list as the area (registration area) for registering the wireless terminal 100. In other words, the network manages that the registered wireless terminal 100 is located within one of the tracking areas in the TAI list.

[0065] If the wireless terminal 100 detects a more optimal cell according to the cell reselection criteria, it reselects that cell and camps on to it. If the selected cell does not belong to any tracking area in the TAI list registered by the wireless terminal 100, a location registration process, that is, a process to update the TAI list, is performed on the base station side or the terminal 100 side.

[0066] A TAI is assigned to the first basic coverage cell (cell 1) and the second basic coverage cell (cell 2), and a registration area is set by one or more cells including the first basic coverage cell (cell 1) and / or the second basic coverage cell (cell 2).

[0067] The first communication point 510-1, which is connected to the first central unit 500-1, can send paging notifications (paging messages) to wireless terminals 100 in standby mode (idle mode) within a registered area including the first basic coverage cell (cell 1). In other words, the communication unit of the first central unit 500-1 is connected to the first communication point 510-1 and can send paging messages to the wireless terminals 100 (terminal devices) in idle mode via the first communication point 510-1. After receiving the paging message, the wireless terminals 100 initiate a procedure to transition from idle mode to connected mode. The transition to connected mode is triggered when the terminal device recognizes that there is a message addressed to it by receiving the Physical Downlink Control Channel (PDCCH) (specifically, Downlink Control Information (DCI)).

[0068] The first communication point 510-2, which is connected to the second central unit 500-2, can send paging notifications (paging messages) to wireless terminals 100 in standby mode (idle mode) within a registered area including the second basic coverage cell (cell 2). In other words, the communication unit of the first central unit 500-2 is connected to the first communication point 510-2 and can send paging messages to wireless terminals 100 (terminal devices) in idle mode via the first communication point 510-2. After receiving the paging message, the wireless terminal 100 initiates a procedure to transition from idle mode to connected mode.

[0069] Second communication points 520-1, 520-2, and 520-3, connected to the first central unit 500-1, provide a first capacity booster cell for the first basic coverage cell (cell 1), or a second communication area 531 as a substitute therefor. The second communication area 531 may consist of coverage provided by one or more antennas of one or more second communication points, or one or more beams. The operating frequency band of the second communication area 531 is the same as or higher than that of cell 1, and the communication speed of the second communication area 531 may be the same as or higher than that of cell 1. The second communication area 531 is smaller (narrower) than the area of ​​cell 1 (first communication area).

[0070] In connected mode, the wireless terminal 100 can send and receive user plane data (e.g., PDSCH (Physical Data Shared Channel) or PUSCH (Physical Uplink Shared Channel)) within the second communication area 531 via the first communication point 510-1 which provides the first basic coverage cell (cell 1) and the second communication points 520-1, 520-2, and 520-3 which provide the second communication area 531. For example, a wireless terminal 100 that has transitioned from idle mode to connected mode acquires (receives) information (first information) relating to the second communication points 520-1, 520-2, and 520-3 from the first communication point 510-1, establishes a connection with the second communication points 520-1, 520-2, and 520-3 based on the acquired information, and communicates (for example, sending and receiving user plane data) with the first central device unit 500-1 (communication device) that has already been established via the second communication points 520-1, 520-2, and 520-3.

[0071] Similarly, the second communication points 520-4, 520-5, and 520-6 connected to the first central unit 500-1 provide a second communication area 532 for the first basic coverage cell (cell 1). The operating frequency band of the second communication area 532 is the same as or higher than that of cell 1, and the communication speed of the second communication area 532 may be the same as or higher than that of cell 1. The second communication area 532 is smaller (narrower) than the area of ​​cell 1 (first communication area).

[0072] In connected mode, the wireless terminal 100 can send and receive user plane data (e.g., PDSCH or PUSCH) within the second communication area 532 via the first communication point 510-1, which provides the first basic coverage cell (cell 1), and the second communication points 520-4, 520-5, and 520-6, which provide the second communication area 532. For example, when the wireless terminal 100 transitions from idle mode to connected mode, it acquires (receives) information (first information) related to the second communication points 520-4, 520-5, and 520-6 from the first communication point 510-1, and based on the acquired information, it communicates (e.g., sends and receives user plane data) with the first central unit 500-1 (communication device) which has been established via the connection with the second communication points 520-4, 520-5, and 520-6.

[0073] The second communication points 520-7, 520-8, and 520-9, connected to the second central unit 500-2, provide a second communication area 533 for the second basic coverage cell (cell 2). The operating frequency band of the second communication area 533 is the same as or higher than that of cell 2, and the communication speed of the second communication area 533 may be the same as or higher than that of cell 1. The second communication area 533 is smaller (narrower) than the area of ​​cell 2 (first communication area).

[0074] In connected mode, the wireless terminal 100 can send and receive user plane data (e.g., PDSCH or PUSCH) within the second communication area 533 via the first communication point 510-2, which provides a second basic coverage cell (cell 2), and the second communication points 520-7, 520-8, and 520-9, which provide the second communication area 533. For example, when the wireless terminal 100 transitions from idle mode to connected mode, it acquires (receives) information (first information) related to the second communication points 520-7, 520-8, and 520-9 from the first communication point 510-2, and based on the acquired information, it communicates (e.g., sends and receives user plane data) with the second central unit 500-2 (communication device) which has been established via the connection with the second communication points 520-7, 520-8, and 520-9.

[0075] Similarly, the second communication points 520-10, 520-11, and 520-12 connected to the second central unit 500-2 provide a second communication area 534 for the second basic coverage cell (cell 2). The operating frequency band of the second communication area 534 is the same as or higher than that of cell 2, and the communication speed of the second communication area 534 may be the same as or higher than that of cell 2. The second communication area 534 is smaller (narrower) than the area of ​​cell 2 (first communication area).

[0076] In connected mode, the wireless terminal 100 can send and receive user plane data (e.g., PDSCH or PUSCH) within the second communication area 534 via the first communication point 510-2, which provides the second basic coverage cell (cell 2), and the second communication points 520-10, 520-11, and 520-12, which provide the second communication area 534. For example, when the wireless terminal 100 transitions from idle mode to connected mode, it acquires (receives) information (first information) related to the second communication points 520-10, 520-11, and 520-12 from the first communication point 510-2, and based on the acquired information, it communicates (e.g., sends and receives user plane data) with the second central unit 500-2 (communication device) which has been established via the connection with the second communication points 520-10, 520-11, and 520-12.

[0077] The central unit 500 can schedule the resources of a second communication point 520 that provides a second communication area using a physical downlink control channel (PDCCH) via the first communication point 510 in cross-carrier scheduling using a carrier indicator field (CIF).

[0078] The central unit 500 uses the RRC IE (Radio Resource Control Information Element) CrossCarrierSchedulingConfig to set parameters for cross-carrier scheduling on the wireless terminal 100. When CrossCarrierSchedulingConfig for a serving cell, for example, the first communication point 510, is set on the wireless terminal 100, the value of the carrier indicator field corresponds to the value indicated by CrossCarrierSchedulingConfig.

[0079] Figure 5 shows an example of one central unit 500 for each basic coverage cell, but the configuration of the central unit 500 is not limited to this. For example, it is possible to distribute the functions of the central unit 500 to multiple devices and operate them in a coordinated manner. It can be distributed as one central unit connected to one first communication point 510 and one or more central units connected to one or more second communication points.

[0080] Furthermore, the central unit 500 can provide basic coverage cells to the wireless terminal 100, which is a UE, via a non-terrestrial network (NTN).

[0081] The non-terrestrial payload, transmitted via the non-terrestrial gateway (NTN Gateway) and feeder link, operates as a base station 20 of the non-terrestrial network, providing non-terrestrial NR access to the wireless terminal 100 as a service link via the non-terrestrial payload.

[0082] The central unit 500 is connected to a non-terrestrial gateway, and the non-terrestrial payload can operate as a first communication point 510. Here, the non-terrestrial gateway can operate as DU23 or DU25, and the first communication point 510 can operate as RU24 via the CPRI interface on the Satellite Radio Interface (SRI), or as RU26 via the eCPRI interface on the Satellite Radio Interface.

[0083] Furthermore, the central unit 500 can operate as a non-terrestrial gateway or as part of a non-terrestrial gateway, and the non-terrestrial payload can operate as a first communication point 510. Here, the first communication point 510 can operate as a DU22 via the F1 interface on the satellite radio interface.

[0084] A wireless terminal 100 in connected mode can establish simultaneous connections to both non-terrestrial NR access via a non-terrestrial payload providing a basic coverage cell and terrestrial NR access via one or more second communication points 520 providing a second communication area.

[0085] Non-ground payloads are deployed on satellites in low-earth orbit (LEO), medium-earth orbit (MEO), geostationary earth orbit (GEO), unmanned aerial systems (UAS) platforms, and high-elliptical orbit (HEO) satellites, among others.

[0086] Low Earth orbit satellites orbit at altitudes of 300 to 1500 km, and their typical beam footprint size is 100 to 1000 km.

[0087] Medium Earth orbit satellites orbit at altitudes of 7,000 to 25,000 km, and their typical beam footprint size is 100 to 1,000 km.

[0088] Geostationary satellites orbit at an altitude of 35,786 km, and their typical beam footprint size is between 200 and 3,500 km.

[0089] Unmanned aerial system platforms fly at altitudes of 8 to 50 km, with typical beam footprint sizes ranging from 5 to 200 km. These include stratospheric platforms (HAPS: High Altitude Platform Stations) that fly at altitudes of 20 km.

[0090] Highly elliptical orbit satellites fly at altitudes of 400 to 50,000 km, and their typical beam footprint size is 200 to 3,500 km.

[0091] Furthermore, the above-mentioned geostationary orbit (GEO) satellites can also be classified as geostationary orbit (GSO) satellites, while other low Earth orbit (LEO) satellites and medium Earth orbit (MEO) satellites can be classified as non-geosynchronous orbit (NGSO) satellites.

[0092] Furthermore, the aforementioned service links are defined as three types: Earth-fixed service links, which are provided by beams that continuously cover the same geographical area; Quasi-Earth-fixed service links, which are provided by beams that cover one geographical area for a limited period and another geographical area for a different period; and Earth-moving service links, which are provided by beams with a coverage area that moves along the Earth's surface.

[0093] In other words, non-terrestrial payloads carried on geostationary satellites can provide Earth-fixed service links or quasi-Earth-fixed service links, while non-terrestrial payloads carried on non-geostationary satellites can provide quasi-Earth-fixed service links or Earth-mobile service links.

[0094] <5-2. Base Station Distributed Control> Each central unit 500, or the network function of the core network 30, for example, the AMF 301, can dynamically configure a communication area (second communication area) using one or more second communication points 520 according to the location of the wireless terminal 100 in connected mode and the traffic demand. That is, some or all of the second communication points 520 for configuring the second communication area can be controlled to be on or off according to the location of the wireless terminal 100 in connected mode and the traffic demand. In other words, although the example in Figure 5 above shows an example of setting four second communication areas, this is only one example, and in this embodiment, the central unit 500 or the AMF 301 can dynamically configure a second communication area by arbitrarily combining one or more second communication points 520 according to the location of the wireless terminal 100. The central unit 500 then provides the wireless terminal 100 with information (first information) relating to a second communication point in the determined second communication area, enabling the wireless terminal 100 to communicate with the central unit 500 via the second communication point.

[0095] More specifically, the dynamic communication area is comprised of one or more clustered second communication points 520, providing a dynamically configured second communication area for the wireless terminal 100. For example, depending on the location of the wireless terminal 100 in connected mode, second communication points 520-6 and 520-7 can provide a dynamic second communication area A, and second communication points 520-6 and 520-8 can provide a dynamic second communication area B.

[0096] Figure 6 shows an example of dynamically configuring a second communication area A. In this case, it is assumed that the wireless terminal 100 is located within the second communication area A. Figure 7 shows an example of dynamically configuring a second communication area B. In this case, it is assumed that the wireless terminal 100 is located within the second communication area B.

[0097] Clustering is the process of determining one or more combinations of second communication points to be assigned to the wireless terminal 100 to constitute a communication area, and may further include assigning the determined one or more second communication points to the wireless terminal 100.

[0098] Furthermore, the AMF 301 may cluster one or more second communication points 520 to constitute a dynamic communication area, taking into account not only the location of the wireless terminal 100 in connected mode, but also the mobility state, which indicates the degree of mobility. For example, for wireless terminals 100 in a higher mobility state, more second communication points 520 can be clustered to create a wider communication area. Mobility management according to this embodiment includes managing the location of the wireless terminal 100, and may further include managing the mobility state.

[0099] Here, the mobility state can be an index with a granularity of normal, medium, or high, or an even finer granularity (for example, 0 to 2 of X bits). X It may be set as an index of an integer value of -1. Alternatively, the mobility state may be an index of the movement speed of the wireless terminal 100, or an index corresponding to the movement speed of the wireless terminal 100. For example, the wireless terminal 100 or AMF 301 may set an index of normal, medium, or high granularity according to a pre-set threshold for movement speed and the movement speed of the wireless terminal 100.

[0100] Alternatively, a network function for processing statistical information, such as a Network Data Analytics Function (NWDAF), or a network function for managing location information, such as an LMF 311, may calculate the mobility status of each wireless terminal 100, and another network function, such as an AMF 301, may acquire the mobility status of each wireless terminal 100 via a service-based interface.

[0101] Furthermore, if there are multiple candidate second communication points 520 operating in different frequency bands, the wireless terminals 100 with a higher mobility state (e.g., mobility state: high) can be clustered to include second communication points 520 operating in a lower frequency band, while the wireless terminals 100 with a lower mobility state (e.g., mobility state: normal) can be clustered to include second communication points 520 operating in a higher frequency band.

[0102] Here, the AMF 301 may be configured with information relating to the operating frequency band range of the second communication point 520 for each mobility state for clustering. According to this configured information, the AMF 301 can identify the frequency band range for each mobility state and cluster the second communication point 520 that operate in the frequency band included in the corresponding range.

[0103] When the AMF301 detects a change in the mobility status of the wireless terminal 100 in connected mode, it can perform a reclustering process of the second communication point 520 in order to update the dynamic communication area.

[0104] The AMF 301 can, for example, use the AMF Configuration Update, which is one of the NGAP (NG Application Protocol) procedures, to notify the central unit 500 of information relating to a dynamic communication area. The AMF 301 can include information relating to one or more second communication points 520 that constitute the dynamic communication area in the AMF CONFIGURATION UPDATE message.

[0105] Furthermore, the AMF 301 may generate candidate configurations (clustering candidates) for a second communication point 520 that constitute a dynamic communication area, depending on the location of the wireless terminal 100 in connected mode, the speed of movement of the wireless terminal 100, or at least one of its mobility status, and provide the generated candidate configurations for the second communication point 520 to the first central unit 500-1 (when the wireless terminal 100 belongs to cell 1). Here, the candidate configurations for the second communication point 520 may be, for example, a list containing candidates for the second communication point 520.

[0106] For example, the AMF 301 may include in the AMF CONFIGURATION UPDATE message a configuration of one or more candidate second communication points 520 that constitute a dynamic communication area.

[0107] The following are various operational examples 1 to 5 for configuring a dynamic communication area. (Example 1) The central unit 500 instructs the wireless terminal 100 in connected mode to measure the communication quality of the second communication point 520 included in the received candidate configuration and to report the measured communication quality. The central unit 500 obtains the measurement results from the wireless terminal 100 in connected mode and sets up a dynamic communication area (second communication area) according to the measurement results. That is, the central unit 500 selects one or more second communication points 520 that constitute the communication area based on the measurement results obtained from the wireless terminal 100, in other words, clusters one or more second communication points.

[0108] Furthermore, the central unit 500 may transmit to the connected wireless terminal 100 instructions for measuring the communication quality of the second communication point 520 included in the received candidate configuration, and criteria for setting the communication area. The wireless terminal 100 may set a dynamic communication area according to the measurement results and the criteria for setting. That is, the wireless terminal 100 selects one or more second communication points 520 that constitute the communication area based on the measurement results and the criteria for setting; in other words, it clusters one or more second communication points.

[0109] Here, the criterion for setting is a threshold related to reception quality, and the communication quality (reception quality) is the reception strength of the reference signal transmitted from the second communication point at the wireless terminal 100. The reception strength at the wireless terminal 100 is, for example, SS Reference Signal Received Power (SS-RSRP), CSI Reference Signal Received Power (CSI-RSRP), DL PRS Reference Signal Received Power (DL PRS-RSRP), etc.

[0110] (Example 2) The central unit 500 also obtains the above-mentioned mobility state from the wireless terminal 100 in connected mode or from the AMF 301, and selects one or more second communication points 520 that constitute the communication area according to the mobility state of each wireless terminal 100. For example, for wireless terminals 100 with a higher mobility state, more second communication points 520 can be selected to make the communication area wider.

[0111] Furthermore, if there are multiple candidate second communication points 520 operating in different frequency bands, a second communication point 520 operating in a lower frequency band can be selected for wireless terminals 100 with a higher mobility state (e.g., mobility state: high), and a second communication point 520 operating in a higher frequency band can be selected for wireless terminals 100 with a lower mobility state (e.g., mobility state: normal).

[0112] Here, the central unit 500 may be configured with information relating to the operating frequency band range of the second communication point 520 for each mobility state for selection. For example, different priorities may be set for each mobility state in each range of the operating frequency band of the second communication point 520. The central unit 500 can identify the frequency band range for each mobility state according to this configured information and select the second communication point 520 that operates in the frequency band included in the corresponding range.

[0113] (Example 3) When a wireless terminal 100 or AMF 301 in connected mode detects a change in mobility status, it can transmit the updated mobility status to the central unit 500.

[0114] When the central unit 500 receives an updated mobility status from the wireless terminal 100 in connected mode or from the AMF 301, or when it detects a change in mobility status according to a preset threshold for movement speed and the movement speed of the wireless terminal 100, it can perform a reselection process of the second communication point 520 in order to update the dynamic communication area.

[0115] (Example 4) The central unit 500 may set the wireless terminal 100 by transmitting to the wireless terminal 100 in connected mode information relating to the operating frequency band range of the second communication point 520, which has different priorities corresponding to the mobility status of the wireless terminal 100 in connected mode, as a criterion for measuring the communication quality for the second communication point 520 or setting the communication area.

[0116] The wireless terminal 100 measures the communication quality of the second communication point 520 operating in a higher priority frequency band range, according to the information relating to the operating frequency band range of the configured second communication point 520. Based on the measurement results and the criteria for configuration, the wireless terminal 100 can select one or more second communication points 520 that constitute the communication area.

[0117] Furthermore, the central unit 500 may set information relating to the operating frequency band range of the second communication point 520 for each mobility state, which has different priorities set for each mobility state, as a criterion for measuring the communication quality of the second communication point 520 or setting the communication area, by transmitting this information to the wireless terminal 100 in connected mode.

[0118] The wireless terminal 100 measures the communication quality of the second communication point 520 operating in a higher priority frequency band range corresponding to the mobility status of the wireless terminal 100, according to the information relating to the operating frequency band range of the set second communication point 520. Based on the measurement results and the criteria for setting, the wireless terminal 100 can select one or more second communication points 520 that constitute the communication area.

[0119] Examples 1-4 have been explained above, but other examples are possible as long as a dynamic communication area can be configured.

[0120] (Example of using communication with both the first communication point 510 and the second communication point 520) The central unit 500 can set up carrier aggregation for a wireless terminal 100 in connected mode, with the first communication point 510 providing the first basic coverage cell (cell 1) designated as PCell (Primary Cell), and one or more second communication points 520 providing a dynamic communication area designated as SCell (Secondary Cell).

[0121] The central unit 500 adjusts the frame timing and SFN (System Frame Number) between the first communication point 510 and one or more second communication points 520. Alternatively, if there is an offset of multiple slots between the first communication point 510 and one or more second communication points 520, this offset is set for the wireless terminal 100 in connected mode.

[0122] Furthermore, the central unit 500 can configure dual / multi-connectivity for wireless terminals 100 in connected mode, designating a first communication point 510 that provides a first basic coverage cell (cell 1) as an MN (Master Node) and one or more second communication points 520 that provide a dynamic communication area as SN (Secondary Node).

[0123] <5-3. Base station distributed control associated with handover between basic coverage> In this embodiment, when the wireless terminal 100 performs a handover of the first communication point 510, the wireless terminal 100 maintains a connection to at least one of the second communication points related to the second communication area to which the wireless terminal 100 belongs before and after the handover (even during the handover process), thereby suppressing a decrease in communication quality at the cell edge. On the central equipment side, the central equipment unit that is the source of the handover (for example, the first central equipment unit 500-1) processes the transfer of the connection to the at least one second communication point from the central equipment unit that is connected to the target first communication point to which the handover is to take over (for example, the first central equipment unit 500-2). The procedure for performing such a handover will now be described.

[0124] Figure 8 shows an example of the handover procedure for a wireless terminal 100 in connected mode. Figure 9 shows an example of the procedure following Figure 8, and Figure 10 shows an example of the procedure following Figure 9.

[0125] As a prerequisite, the wireless terminal 100 in connected mode is assumed to be located within the second communication area 532, which is defined by the second communication points 520-4, 520-5, and 520-6 in Figure 6.

[0126] Upon receiving user plane data addressed to the wireless terminal 100, which is UE10, the UPF330 transfers the received data to the first central unit 500-1 (S600-1).

[0127] The first central device unit 500-1 transfers the received data to the first communication point 510-1 which provides the first basic coverage cell (cell 1), and to the second communication points 520-4, 520-5, and 520-6 which provide the second communication area 532 (S600-2).

[0128] In connected mode, the wireless terminal 100 receives user plane data transferred from the UPF 330 via the first communication point 510-1 and the second communication points 520-4, 520-5, and 520-6.

[0129] The first central unit 500-1 acquires mobility control information (for example, information regarding roaming and / or access restrictions) from the AMF 301 (step S601). This mobility control information is updated when the TA (Tracking Area) is updated. The AMF 301 may also provide the first central unit 500-1 with candidate configurations of the second communication point 520 that constitute the dynamic communication area described above, as mobility control information.

[0130] The first central unit 500-1, which is the source, sets or instructs the wireless terminal 100, which is in connected mode, to perform a communication quality measurement procedure (step S602). Here, the first central unit 500-1 can set the measurement procedure according to the information related to mobility control that it has acquired. The wireless terminal 100, which is in connected mode, then performs a communication quality measurement according to the set measurement procedure and reports the measurement result to the first central unit 500-1, which is the source (same step S602). The target of the communication quality measurement may, for example, be the second communication point 520 to which the wireless terminal 100 is currently connected, and the candidate second communication point 520. As another example, the wireless terminal 100 may decide to measure the second communication point 520 to which it is currently connected and a second communication point within a certain range in the vicinity. Information regarding the target of the communication quality measurement may be included in the set measurement procedure described above, or it may be determined autonomously by the wireless terminal 100.

[0131] The first central unit 500-1 decides to perform a handover of the connected wireless terminal 100 based on the reported measurement results (Measurement Report) and RRM (Radio Resource Management) information (step S603). In this example, the handover is specifically from the first basic coverage cell (cell 1) provided by the first communication point 510-1 to the second basic coverage cell (cell 2) provided by the first communication point 510-2. Here, the RRM information is, for example, information regarding the RRM configuration. For example, suppose both types of measurements, SSB (SS / PBCH block) and CSI-RS (Channel State Information Reference Signal), are available. In this case, the RRM configuration may include information regarding beam measurements related to SSB and CSI-RS for the reporting cell. Furthermore, the RRM setting may include a list of the best cells (e.g., a first communication point 510 and a second communication point 520) at each frequency for which measurement information is available.

[0132] Furthermore, when a wireless terminal 100 in connected mode is handed over to a second basic coverage cell (cell 2), the first central unit 500-1 selects at least one second communication point 520 from among the second communication points 520-4, 520-5, and 520-6 that constitute the second communication area to which it currently belongs, according to the measurement information, so as not to cause deterioration of communication quality at the cell edge (step S604). In this example, it is assumed that the second communication point 520-6 is selected. The method for selecting the second communication point 520 can be anything, such as selecting one or more second communication points with the highest communication quality, selecting the second communication point closest to or furthest from the cell edge, selecting the second communication point with the highest or lowest operating carrier frequency, or arbitrarily selecting one or more second communication points.

[0133] The source first central unit 500-1 issues and transmits a Handover Request message to the target second central unit 500-2 (step S605). The Handover Request message contains information necessary for the target second central unit 500-2 to prepare for the handover. This information may include, for example, instructions to maintain the connection between the at least one second communication point 520 (i.e., second communication point 520-6) that the terminal device will maintain connection with (not switch over) during the handover, and the wireless terminal 100 in connected mode. In other words, when a connected wireless terminal 100 hands over to a second central unit 500-2 (another first communication point or other communication device), the first central unit 500-1 can select at least one second communication point from among the second communication points with which a connection has already been established to maintain a connection with the wireless terminal 100, and can send a handover request message that includes an instruction to maintain a connection between the selected second communication point and the wireless terminal 100. The handover request message may also include the measurement results of the communication quality at the wireless terminal 100 for the candidate second communication point 520 that constitute the dynamic communication area.

[0134] Here, the source first central unit 500-1 may notify the target second central unit 500-2 of the TCI (Transmission Configuration Indicator) state of the second communication point 520 to be maintained, in addition to the instruction to maintain the connection with at least one second communication point 520, as information necessary to prepare for the handover. The second central unit 500-2 applies the notified TCI state to each of the at least one second communication point 520 (i.e., the second communication point 520-6) that does not switch over during the handover. In other words, the target second central unit 500-2 applies the same TCI state to the at least one second communication point 520 that does not switch over as the source first central unit 500-1. Details of the TCI state will be described later.

[0135] Therefore, the target second central unit 500-2 applies the same TCI-state as the source first central unit 500-1 to the second communication point 520, which does not undergo switching. As a result, the wireless terminal 100 in connected mode continues to use the same downlink reference signal and pseudo-collocation relationship with the second communication point 520, which does not undergo switching, when handing over from the first basic coverage cell (cell 1) to the second basic coverage cell (cell 2).

[0136] Furthermore, the source first central unit 500-1 may include, for example, information regarding instructions for connecting (referred to as a second connection) between the at least one second communication point 520 (i.e., the second communication point 520-6) that does not switch during the handover and the second central unit 500-2, as necessary for preparing the handover. This information may further include instructions to use the second communication point 520 to communicate with the wireless terminal 100 after connecting to the at least one second communication point 520 (i.e., the second communication point 520-6). The instruction for the second connection is, for example, an instruction to switch from the connection between the second communication point 520-6 and the first central unit 500-1 (referred to as the first connection) to the second connection between the second communication point 520-6 and the second central unit 500-2. Alternatively, the instruction for the second connection may be an instruction to add a second connection between the second communication point 520-6 and the second central device unit 500-2 to the first connection between the second communication point 520-6 and the first central device unit 500-1.

[0137] The second central unit 500-2, in accordance with instructions to maintain connection with the second communication point 520-6, sets up or clusters a second communication area A (see Figure 6), which is a dynamic communication area formed by the second communication points 520-6 and 520-7 (step S606). The selection of the second communication point 520-7 to be combined with the second communication point 520-6 may be based on the measurement results of the wireless terminal 100 for the candidate second communication point to be switched to, or the second central unit 500-2 or AMF 301 may make the selection based on the location of the wireless terminal 100 and / or the surrounding geographic environment. As the measurement results of the wireless terminal 100 depend on the location of the wireless terminal 100, any method of selecting the second communication point is acceptable as long as the selection is based on the location of the wireless terminal 100 or the propagation environment.

[0138] In this way, when handing over from the first basic coverage cell (cell 1) to the second basic coverage cell (cell 2), a dynamic communication area including at least one of the second communication points 520-4, 520-5, and 520-6 that constitute the original second communication area (i.e., the second communication point 520-6) is clustered as a new second communication area A. As a result, the wireless terminal 100 in connected mode can continue to send and receive user plane data (e.g., PDSCH or PUSCH) via the second communication point 520-6 before and after the handover (even during the handover process). In other words, by not switching at least one second communication point 520 when handing over from the first basic coverage cell (cell 1) to the second basic coverage cell (cell 2), the degradation of communication quality at the cell edge can be improved.

[0139] The second central device unit 500-2 transmits a connection establishment request message to the second communication point 520-6 in accordance with the second connection instruction (step S607), thereby establishing a second connection between the second communication point 520-6 and the second central device unit 500-2.

[0140] Here, the first connection between the first central unit 500-1 and the second communication point 520, and the second connection between the second central unit 500-2 and the second communication point 520 are controlled for each wireless terminal 100 in connected mode.

[0141] Therefore, the first central device unit 500-1 can assign unique identification information within the first central device unit 500-1 to the first connection, and the second central device unit 500-2 can assign unique identification information within the second central device unit 500-2 to the second connection.

[0142] Furthermore, the source first central unit 500-1 can request a DAPS (Dual Active Protocol Stack) handover from one or more DRBs (Data Radio Bearers). Here, a DAPS handover is a handover in which the wireless terminal 100 maintains its connection with the source base station (the first central unit 500-1 and the first communication point 510-1) even after receiving an RRC (Radio Resource Control) message for the handover. More specifically, a DAPS handover is a handover in which the wireless terminal 100 maintains its connection with the source base station even after receiving an RRC message for the handover, until it successfully gains random access to the target base station (the second central unit 500-2 and the first communication point 510-2) and releases its connection with the source base station.

[0143] The target second central unit 500-2 prepares for the handover and sends a HANDOVER REQUEST ACKNOWLEDGE message to the source first central unit 500-1 (step S608). This message contains a transparent container that is sent to the connected wireless terminal 100 as an RRC message for performing the handover.

[0144] The source, the first central unit 500-1, initiates a handover by sending an RRC Reconfiguration message to the connected wireless terminal 100 via the first communication point 510-1 (step S609). The RRC Reconfiguration message includes, at a minimum, the ID of the target cell, a new C-RNTI (Cell Radio Network Temporary Identifier), and information regarding the target BS security algorithm for the selected security algorithm, as information necessary to access the target cell (i.e., the target base station, in this example, the second central unit 500-2 and the first communication point 510-2). Furthermore, the RRC Reconfiguration message may include a set of dedicated RACH (Random Access Channel) resources, information indicating the relationship between the RACH resources and the SSB(s), information indicating the relationship between the RACH resources and the UE-specific CSI-RS configuration, information on common RACH resources, and system information of the target cell, etc.

[0145] Furthermore, the RRC reset message transmitted to the wireless terminal 100 includes information (second information) necessary to access at least one of the second communication points 520-7 (in this example, second communication points 520-6, 520-7) that provide a dynamic communication area which becomes the second communication area A, other than the second communication point 520-6 that is not switched over during handover. Here, the RRC reset message may also include information indicating the second communication point 520-6 that is not switched over during handover, among the one or more second communication points 520 (in this example, second communication points 520-6, 520-7) that provide a dynamic communication area which becomes the second communication area A.

[0146] The first central unit 500-1, which is the source, continues to transmit downlink packets using the DRB(s) configured for DAPS handover until it receives a HANDOVER SUCCESS message from the second central unit 500-2, which is the target, in step S616 (step S610). That is, the first central unit 500-1, which is the source, continues to transmit downlink data to the wireless terminal 100, including data buffered internally and new data received from the UPF for the wireless terminal 100. This downlink transmission uses at least one of the first communication point 510 and the second communication point 520-6, which does not undergo switching.

[0147] The source first central unit 500-1 sends an Early Status Transfer message to the target second central unit 500-2 for the DRB(s) on which DAPS handover has been configured (step S611). Here, the DL COUNT value included in the Early Status Transfer message is, for example, the PDCP SN (Packet Data Convergence Protocol Sequence Number) and HFN (Hyper Frame Number) of the first PDCP SDU (Packet Data Convergence Protocol Service Data Unit) that the source first central unit 500-1 transfers to the target second central unit 500-2. The source first central unit 500-1 continues to assign SNs to the downlink PDCP SDUs until it sends an SN Status Transfer message to the target second central unit 500-2 in step S617.

[0148] Furthermore, the source first central unit 500-1 transmits an SN status transfer message to the target second central unit 500-2 for DRB(s) to which DAPS handover is not configured (step S612). The SN status transfer message includes the uplink PDCP SN reception status and the downlink PDCP SN transmission status for DRBs to which PDCP status retention applies (i.e., RLC AM (Acknowledged Mode)).

[0149] The uplink PDCP SN reception status includes at least the PDCP SN of the first missing UL PDCP SDU. If there are out-of-sequence UL PDCP SDUs that the connected wireless terminal 100 needs to retransmit to the target cell (target base station), the uplink PDCP SN reception status may include a bitmap of those reception statuses.

[0150] The downlink PDCP SN transmission status is information indicating the next PDCP SN that the second central unit 500-2 must assign to a new PDCP SDU that has not yet been assigned a PDCP SN.

[0151] User data transmitted to the source, the first central device unit 500-1, is transferred to the target, the second central device unit 500-2 (step S613-1). The target, the second central device unit 500-2, buffers the transferred user data (step S613-2).

[0152] The wireless terminal 100 in connected mode detaches from the old basic coverage cell (the first communication point 510-1 providing the first basic coverage cell (cell 1)) and synchronizes with the new basic coverage cell (the first communication point 510-2 providing the second basic coverage cell (cell 2)) (step S614). Furthermore, the wireless terminal 100 in connected mode maintains its connection to the second communication point 520-6 while connecting (synchronizing) with the second communication point 520-7 (switching the second communication points 520-4 and 520-5 to the second communication point 520-7). The wireless terminal 100 may also establish a connection with the second communication point 520-7 by transmitting a connection request to the second central unit 500-2 via the first communication point 510-2 providing cell 2. Furthermore, if there is one or more second communication points (or candidates thereof) other than the second communication point 520-6 that maintains the connection, the wireless terminal 100 may target all of these one or more second communication points for connection, or it may select at least one second communication point from among them for connection.

[0153] However, in the case of a DAPS handover, the wireless terminal 100 in connected mode will not detach from the source cell (the first communication point 510-1 providing the first basic coverage cell (cell 1)) until it receives an RRC configuration message. Then, upon receiving an explicit release notification from the target second central unit 500-2, the wireless terminal 100 in connected mode releases its resources and configuration to the source cell (the first communication point 510-1 providing the first basic coverage cell (cell 1)). As a result, the wireless terminal 100 stops receiving downlink data from the source cell and / or transmitting uplink data to the source cell.

[0154] In the case of a DAPS handover and RLC AM, the first central unit 500-1, which is the source, may transmit the uplink PDCP SN reception status and downlink PDCP SN transmission status of a DRB that is not configured for DAPS using the SN status transfer message in step S617, rather than the SN status transfer message in step S612.

[0155] The source first central unit 500-1 may additionally send an early status transfer message to the DRBs configured with DAPS between steps S610 and S617 to instruct them to discard PDCP SDUs that have already been transferred. The target second central unit 500-2 does not transmit PDCP SDUs (downlink PDCP SDUs transferred from the first central unit 500-1) whose COUNT is smaller than the transmitted DL COUNT value to the connected wireless terminal 100. The target second central unit 500-2 discards PDCP SDUs that have not been attempted to be transmitted.

[0156] The wireless terminal 100, which is in a connected state (connected mode) synchronized with the target cell (the first communication point 510-2 that provides the second basic coverage cell (cell 2)), completes the RRC handover procedure by sending an RRCReconfigurationComplete message to the target cell (step S615).

[0157] In the case of a DAPS handover, the target second central unit 500-2 transmits a handover success message to the source first central unit 500-1 to notify that the connected wireless terminal 100 has successfully accessed the target cell (the first communication point 510-2 providing the second basic coverage cell (cell 2)) (step S616). In response, the source first central unit 500-1 transmits an SN status transfer message for the DRBs configured with DAPS to the target second central unit 500-2, as described above (step S617).

[0158] The source, the first central unit 500-1, continues transmitting the uplink QoS flow to the UPF 330 using DRBs configured with DAPS until it sends an SN status transfer message to the target, the second central unit 500-2, in step S617. The target, the second central unit 500-2, does not transfer the received uplink PDCP SDUs to the UPF 330 until it receives the SN status transfer message. This SN status transfer message indicates the beginning of the uplink PDCP SDUs to be transferred to the UPF 330. For example, the UL HFN and the first missing SN in the uplink PDCP SN reception status indicate the beginning of the uplink PDCP SDUs to be transferred to the UPF 330. The target second central unit 500-2 does not transmit uplink PDCP SDUs that have a UL COUNT lower than the provided UL COUNT.

[0159] The target second central unit 500-2 sends a path switch request message to the AMF 301 (step S618). This message triggers the core network (CN) to switch the downlink data path (DL data path) to the target second central unit 500-2 and to establish an NG-C interface instance toward the target second central unit 500-2.

[0160] The core network switches the downlink data path to the target second central unit 500-2 (step S619). The UPF 330 sends a packet indicating the "end marker" for each PDU session / tunnel on the old path to the source first central unit 500-1 (step S620), and the UPF 330 may release all U-plane / TNL (Transport Network Layer) resources destined for the source first central unit 500-1.

[0161] When the target second central unit 500-2 receives a packet indicating an "end marker" via user data transferred from the source first central unit 500-1, it transfers the buffered user data from step S613-2 onward to the first communication point 510-2, which provides the second basic coverage cell (cell 2), and to the second communication points 520-6 and 520-7, which provide the second communication area A, which is a dynamic communication area (step S621).

[0162] In connected mode, the wireless terminal 100 can receive user plane data transferred from the second central unit 500-2 via the first communication point 510-2 and the second communication points 520-6 and 520-7.

[0163] From this point onward, the UPF 330, having received user plane data addressed to the wireless terminal 100, which is UE10, forwards the received data to the second central unit 500-2 (S622).

[0164] The second central device unit 500-2 transfers the received data to the first communication point 510-2, which provides a second basic coverage cell (cell 2), and to the second communication points 520-6 and 520-7, which provide a second communication area A, which is a dynamic communication area (S623).

[0165] In connected mode, the wireless terminal 100 can receive user plane data transferred from the UPF 330 via the first communication point 510-2 and the second communication points 520-6 and 520-7.

[0166] As a response to the path switching request message in step S618, the AMF 301 sends a path switching request acknowledgment message to the target second central unit 500-2 (step S624).

[0167] When the target second central unit 500-2 receives a path switching request response message from the AMF 301, it sends a UE context release message to the source first central unit 500-1 to notify it of a successful handover (step S625). Upon receiving the UE context release message, the source first central unit 500-1 releases resources related to the UE context (e.g., radio resources and control plane (C-plane) related resources).

[0168] The following describes modifications of the procedure shown in Figures 8 to 10, or other examples of operation.

[0169] (Example 1) In step S606, when the wireless terminal 100 in connected mode moves from the second communication area of ​​the second communication points 520-4, 520-5, and 520-6 within the first basic coverage cell (cell 1) to the second basic coverage cell (cell 2), the second central device unit 500-2 sets up a second communication area B (see Figure 7), which is a dynamic communication area of ​​the second communication points 520-6 and 520-8, different from the second communication area A, according to the position of the wireless terminal 100 in connected mode.

[0170] Similar to the case of the second communication area A, when a connected wireless terminal 100 hands over from the first basic coverage cell (cell 1) to the second basic coverage cell (cell 2), the second central unit 500-2 clusters a dynamic communication area including at least one of the second communication points 520-4, 520-5, and 520-6 (second communication point 520-6) that constitute the second communication area as the second communication area B. This allows the connected wireless terminal 100 to continue sending and receiving user plane data (e.g., PDSCH or PUSCH) via the second communication point 520-6. In other words, by not switching at least one second communication point 520 when handing over from the first basic coverage cell (cell 1) to the second basic coverage cell (cell 2), the degradation of communication quality at the cell edge can be improved.

[0171] (Example 2) In step S604 of Figure 8, instead of selecting the second communication point 520-6 as at least one second communication point 520 to maintain the connection when the wireless terminal 100 in connected mode is handed over to the second basic coverage cell (cell 2), the first central unit 500-1 may set up or cluster a second communication area. That is, the first central unit 500-1 may set up or cluster a second communication area A (or a second communication area B, which is a dynamic communication area formed by the second communication points 520-6 and 520-7) so as to maintain the connection with the second communication point 520-6. In this case, the first central device unit 500-1 can transmit information relating to the second communication point 520, including the second communication points 520-6 and 520-7 that constitute the second communication area A (or the second communication points 520-6 and 520-8 that constitute the second communication area B), to the second central device unit 500-2 via a handover request message as information necessary to prepare for the handover. As a result, the second central device unit 500-2 can omit step S606.

[0172] (Example 3) In step S604, the first central device unit 500-1 may set LTM (L1 / L2 Triggered Mobility). Since LTM is controlled by lower layers such as the media access control (MAC) layer, faster switching can be expected compared to conventional L3 mobility handover. For this reason, LTM is set at least for dynamic communication areas where the coverage is narrow due to the use of high frequencies and switching becomes more frequent, thereby increasing capacity. In other words, LTM may be set for basic coverage cells and dynamic communication areas, or it may be set only for dynamic communication areas.

[0173] When LTM is set for one or more second communication points 520 that constitute a dynamic communication area, the first central unit 500-1 transmits an RRCReconfiguration message to the connected wireless terminal 100, which includes candidate configurations for the second communication points 520. Here, the first central unit 500-1 can set candidate configurations for the second communication points 520 according to the mobility status of the wireless terminal 100 and / or information relating to the range of operating frequency bands of the second communication points 520, which have different priorities set corresponding to the mobility status of the wireless terminal 100.

[0174] The wireless terminal 100, which is UE10, saves the configuration of the received candidate for the second communication point 520 and responds with an RRCReconfigurationComplete message.

[0175] Before receiving a switching command to the second communication point 520, the wireless terminal 100 synchronizes with a candidate second communication point 520 on the downlink. Alternatively, before receiving a switching command to the second communication point 520, the wireless terminal 100 may perform a UE-based timing advance measurement to synchronize with a candidate second communication point 520 on the uplink.

[0176] The wireless terminal 100 performs an L1 measurement on the set candidate second communication point 520 and transmits the L1 measurement report to the first central device unit 500-1. Here, the L1 measurement is, for example, the SS Reference Signal Received Power (SS-RSRP), CSI Reference Signal Received Power (CSI-RSRP), DL PRS Reference Signal Received Power (DL PRS-RSRP), etc.

[0177] The wireless terminal 100 can transmit this L1 measurement report to the first central unit 500-1 via UCI (Uplink Control Information) or MAC CE (Control Element).

[0178] The first central device unit 500-1 may also instruct the wireless terminal 100 whether to report using UCI or MAC CE in the reporting configurations included in the measurement settings using RRC signaling.

[0179] In step S604, the first central unit 500-1 can select at least one second communication point 520 from among the second communication points 520-4, 520-5, and 520-6 constituting the second communication area, according to the results of the L1 measurement included in the received L1 measurement report, to maintain the connection (i.e., not switch) during the handover from the first basic coverage cell (cell 1) to the second basic coverage cell (cell 2) of the wireless terminal 100. That is, the first central unit 500-1 can select the second communication point 520-6 as the at least one second communication point 520 from among the second communication points 520-4, 520-5, and 520-6 constituting the second communication area to maintain the connection (i.e., not switch), so as not to cause deterioration of communication quality at the cell edge.

[0180] The first central device unit 500-1 selects the second communication points 520-6 and 520-7 as the second communication area A, which is a dynamic communication area, and decides to switch to the second communication point 520 (i.e., the second communication point 520-7) other than the second communication point 520-6, which does not switch connections.

[0181] The first central unit 500-1 transmits a switching command, for example, a MAC (Media Access Control) CE, to the wireless terminal 100, which triggers the switching by including a target configuration ID indicating an index of the configuration of a candidate target second communication point 520, a beam indicated by TCI (Transmission Configuration Indicator)-state, and, if available, the timing advance of the target second communication point 520. Here, the first central unit 500-1, AMF 301, or network data analysis function (not shown) may calculate the timing advance of each candidate target second communication point 520 from the location information of the wireless terminal 100, the timing advance and location information of the second communication point 520 connected to the wireless terminal 100 (for example, the second communication point 520-6), and the location information of each candidate target second communication point 520.

[0182] Upon receiving the switching command, the wireless terminal 100 executes the operation to switch the second communication point 520-4 or 520-5, other than the second communication point 520-6 which is the second communication point 520 that will not be switched, to the second communication point 520-7.

[0183] The system can detect a Physical Downlink Control Channel (PDCCH) containing Downlink Control Information (DCI) for the wireless terminal 100 and any serving cell, and configure the wireless terminal 100 with a list of up to M TCI-State configurations in the PDSCH-Config, a parameter of the upper layer, so that the wireless terminal 100 can decode the Physical Downlink Shared Channel (PDSCH) according to the detected Physical Downlink Control Channel. Here, M depends on maxNumberConfiguredTCIstatesPerCC of the UE capability.

[0184] The list of TCI-State configurations in PDSCH-Config may include a TCI-State configuration for each candidate second communication point 520. In other words, the wireless terminal 100 can select one TCI-State configuration for each second communication point 520.

[0185] Furthermore, if a non-terrestrial payload providing a ground-mobile service link operates as a first communication point 510 providing a basic coverage cell, a feeder link switchover for the non-terrestrial payload and / or a handover of the service link provided by the non-terrestrial payload may occur even if the wireless terminal 100 does not move. Therefore, even if either a feeder link switchover or a service link handover occurs, the first central unit 500-1 can decide to maintain one or more second communication points that provide a dynamic communication area to the wireless terminal 100.

[0186] Furthermore, if a non-terrestrial payload providing a quasi-terrestrial service link that maintains the same PCI (Physical Cell ID) in a geographic area covered by a quasi-terrestrial beam operates as a first communication point 510 providing a basic coverage cell, a feeder link switchover for the non-terrestrial payload and / or a satellite switchover for the wireless terminal 100 may occur even if the wireless terminal 100 does not move. Therefore, even if either a feeder link switchover or a satellite switchover occurs, the first central unit 500-1 can decide to maintain one or more second communication points that provide a dynamic communication area to the wireless terminal 100.

[0187] In particular, resynchronization is necessary during soft or hard satellite switchovers that maintain the same SSB frequency and PCI.

[0188] In the event of a soft satellite switchover, the wireless terminal 100 can initiate synchronization with the first communication point 510-2 of the target satellite for resynchronization before the first communication point 510-1 of the source satellite terminates cell provision.

[0189] In the event of a hard satellite switchover, the wireless terminal 100 can only begin synchronizing with the target satellite's first communication point 510-2 for resynchronization after the switchover to the target satellite's first communication point 510-2 has begun.

[0190] Here, the first central device unit 500-1 can acquire the offset during resynchronization from the first communication point 510-1 of the source satellite to the first communication point 510-2 of the target satellite, and use it to adjust the frame timing and SFN with the second communication point 520, or to adjust the offset of multiple slots set in the wireless terminal 100.

[0191] As described above, according to this embodiment, it is possible to set up a dynamic communication area for each wireless terminal 100, which is composed of one or more second communication points 520 that act as capacity booster cells for a basic coverage cell composed of a first communication point 510, without depending on the basic coverage cell. Furthermore, during handover between basic coverage cells, by not switching at least one of the one or more second communication points 520 connected to the wireless terminal 100, the deterioration of communication quality at the cell edge can be reduced.

[0192] <5-4. Configuration of various devices such as the central unit 500, wireless terminal 100, DU22, DU23, NF, and second communication point>

[0193] The second communication point 520 may be an antenna device including an antenna, array antenna, antenna panel, etc., or it may be an antenna port corresponding to a beam formed by one or more antenna elements. Alternatively, the second communication point 520 may be a device called a TRP (Transmit / Receive Point).

[0194] Furthermore, the second communication point 520 may be a device including a DU (Distributed Unit) 22 (see Figure 4(a)) that is connected to the central unit 500 via a front hole conforming to the F1 interface. Here, the DU 22 may include the antenna device and antenna port described above. Multiple DU 22s can be connected to one central unit 500.

[0195] The central unit 500, the DU23 excluding the processing of the wireless unit, the DU25 excluding the processing of the LOW PHY sublayer and the wireless unit, the NF of the core network 30 (for example, AF308), the application server 40, and various other devices such as the OAM (Operations, Administration and Maintenance) described later are all composed of information processing devices that realize their respective functions.

[0196] Figure 11 is a block diagram showing an example configuration of the information processing device 700 according to this embodiment. The information processing device 700 is a device that implements the functions of the central unit 500, the DU23 excluding the processing of the wireless unit, the DU25 excluding the processing of the LOW PHY sublayer and the wireless unit, the NF of the core network 30 (e.g., AF308), the application server 40, and the OAM (Operations, Administration and Maintenance) described later. In other words, the NF, application server 40, OAM, central unit 500, DU23, and DU25 can each be implemented by the configuration of the information processing device 700. The information processing device 700 is, for example, a server device. The information processing device 700 may also be a device collectively referred to as a cloud server or an edge server.

[0197] As shown in Figure 11, the information processing device 700 comprises a communication unit 71, a storage unit 72, and a control unit 73. Naturally, the information processing devices 700 that realize the central device unit 500, DU23, DU25, NF, application server 40, and OAM, respectively, share the same basic configuration of the communication unit 71, storage unit 72, and control unit 73, but the operation of the communication unit 71, storage unit 72, and control unit 73 differs according to the respective roles of the central device unit 500, DU23, DU25, NF, application server 40, and OAM. Note that the configuration shown in Figure 11 is a functional configuration, and the hardware configuration may differ from this. Furthermore, the functions of the information processing device 700 may be distributed and implemented across multiple physically separated configurations. For example, the information processing device 700 may be composed of multiple server devices.

[0198] The communication unit 71 is a communication interface for communicating with other devices. The communication unit 71 may be a network interface or an equipment connection interface. For example, the communication unit 71 may be a LAN (Local Area Network) interface such as a NIC (Network Interface Card), or a USB interface consisting of a USB (Universal Serial Bus) host controller, USB port, etc. Furthermore, the communication unit 71 may be a wired interface or a wireless interface. The communication unit 71 functions as a communication means for the information processing device 700. The communication unit 71 communicates with the base station 20 and other NF nodes, AN nodes, and wireless terminals according to the control of the control unit 73.

[0199] The memory unit 72 is a data read / write storage device such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), flash memory, or hard disk. The memory unit 72 functions as a storage means for the information processing device 700.

[0200] The control unit 73 is a controller that controls each part of the information processing device 700. The control unit 73 is implemented by a processor such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), or GPU (Graphics Processing Unit). For example, the control unit 63 is implemented by the processor executing various programs stored in the storage device inside the information processing device 700 using RAM (Random Access Memory) or the like as a working area. The control unit 73 may also be implemented by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array). A CPU, MPU, GPU, ASIC, and FPGA can all be considered controllers.

[0201] The processing performed in at least one of the first central device unit 500-1 or the second central device unit 500-2 according to this embodiment is performed by a control unit 73 provided in at least one of the first central device unit 500-1 or the second central device unit 500-2. Communication with other devices (first communication point, second communication point, first central device unit, second central device unit, AMF, UPF, etc.) performed in at least one of the first central device unit 500-1 or the second central device unit 500-2 according to this embodiment is performed by a communication unit 71 provided in at least one of the first central device unit 500-1 or the second central device unit 500-2. The data or information used in the processing and communication of the first central device unit 500-1 or the second central device unit 500-2 according to this embodiment is temporarily or permanently stored in a storage unit 72 provided in the first central device unit 500-1 or the second central device unit 500-2.

[0202] The processing performed by at least one of the AMF 301 or UPF 330 according to this embodiment is carried out by a control unit 73 provided in at least one of the AMF 301 or UPF 330. Communication with other devices (first central device unit, second central device unit, UPF, etc.) performed by at least one of the AMF 301 or UPF 330 according to this embodiment is carried out by a communication unit 71 provided in at least one of the AMF 301 or UPF 330. The data or information used in the processing and communication of the AMF 301 or UPF 330 according to this embodiment is temporarily or permanently stored in a storage unit 72 provided in the AMF 301 or UPF 330.

[0203] The processing performed by the wireless terminal 100 according to this embodiment is carried out by the control unit 73 provided in the wireless terminal 100. Communication with other devices (first communication point, second communication point, first central device unit, second central device unit, etc.) performed by the wireless terminal 100 according to this embodiment is carried out by the communication unit 71 provided in the wireless terminal 100. The data or information used in the processing and communication of the wireless terminal 100 according to this embodiment is temporarily or permanently stored in the storage unit 72 provided in the wireless terminal 100.

[0204] The following provides supplementary explanations regarding the central device unit 500 (first central device unit 500-1 or second central device unit 500-2), the DU (Distributed Unit) 22, the second communication point 520, and the wireless terminal 100.

[0205] The second communication point 520 may be a device that includes at least a Radio Unit (RU) 24 (see Figure 4(b)) that processes the radio, which is connected to a DU 23 (see Figure 4(b)) via a fronthaul compliant with the Common Public Radio Interface (CPRI). Here, the RU 24 may include the antenna device and antenna port described above. Multiple RU 24s can be connected to a single DU 23.

[0206] Furthermore, the second communication point 520 may be a device that includes at least an RU 26 (see Figure 4(c)) which processes the LOW PHY sublayer and the radio section (Radio), and is connected to a DU 25 (see Figure 4(c)) via a fronthaul compliant with eCPRI (evolved Common Public Radio Interface). Here, the RU 26 may include the antenna device and antenna port described above. Multiple RU 26s can be connected to one DU 25.

[0207] The central unit 500 processes the functions of the RRC sublayer and PDCP sublayer in the control plane, and processes the functions of the SDAP sublayer and PDCP sublayer in the user plane.

[0208] For example, in step S604, the central unit 500 can cluster two or more second communication points 520 that are not perceived by the wireless terminal 100 as being in the same location, i.e., are perceived as being in different locations, to form a dynamic communication area as a capacity booster cell or a substitute thereof. Here, the wireless terminal 100 can determine whether or not it is in the same location using a QCL (Quasi Co Location) type parameter provided by TCI-State, which will be described later. By transmitting data to the wireless terminal 100 from multiple second communication points 520 that are not in the same location using a diversity or spatial multiplexing method, the central unit 500 can obtain the effects of diversity or spatial multiplexing.

[0209] The wireless terminal 100 receives a CSI-RS, which is a reference signal for estimating channel state information transmitted from the second communication point, and measures the CSI parameters. The CSI parameters are, for example, CQI (Channel quality indicator), PMI (Precoding Matrix Indicator), and RI (Rank Indicator). The wireless terminal 100 reports CSI feedback, including the CSI parameters, to the RAN / AN 20 function, for example, via the first communication point 510 or the second communication point 520. The RAN / AN 20 function determines settings for transmitting downlink data from the second communication point 520 to the wireless terminal 100 according to the received CSI parameters, such as the modulation scheme, coding rate, number of layers, MIMO precoding, etc. CQI, PMI, and RI will be described below.

[0210] CQI is an indicator of channel quality and is an integer value ranging from 0 to 15. The CQI value corresponds to the highest Modulation and Coding Scheme (MCS) that is suitable for downlink transmission to achieve the required Block Error Rate (BLER) under given channel conditions.

[0211] The PMI consists of a set of indices corresponding to the precoding matrix, and the function of RAN / AN20 is to apply this precoding matrix to downlink data transmitted from the second communication point 520. The construction of the precoding matrix may include a matrix representing a Discrete Fourier Transform (DFT) based beam or group of beams with respect to two polarizations. The construction of the precoding matrix may further include a matrix representing at least one of the phase adjustment components between the two polarizations for beam selection, beam weighting, and co-phasing.

[0212] A codebook is provided as a precoding matrix, and the codebook corresponding to PMI can be identified depending on the number of antenna ports and the codebook type set by the higher layer.

[0213] Codebook types include Type I Single-Panel Codebook, Type I Multi-Panel Codebook, Type II Codebook, and Enhanced Type II Codebook.

[0214] In a Type I codebook, a specific beam is selected from a group of beams for each layer, while in a Type II codebook, a group of beams is selected for each layer, and all beams within the group are linearly combined.

[0215] RI is an index indicating the number of layers that can be used for downlink data transmission under specific channel conditions, and also corresponds to the maximum number of paths that can be treated as uncorrelated and usable for spatial multiplexing of downlink data. In a distributed data center that can utilize computing resources via an optical network, the DU23, which excludes the processing of the wireless section, or the DU25, which excludes the processing of the LOW PHY sublayer and the wireless section, can be dynamically implemented within the data center, as included in the central equipment unit 500 or the second communication point 520. Connections can be made via the fronthaul on the optical network to the DU22, the RU24 which processes the wireless section, and the RU26 which processes the LOW PHY sublayer and the wireless section, as included in the first communication point 510 and / or the second communication point 520.

[0216] Furthermore, the DU23 units, excluding the processing of the radio section included in multiple second communication points 520, can be integrated and implemented as a single unit. Similarly, the DU25 units, excluding the processing of the LOW PHY sublayer and radio section included in multiple second communication points 520, can be integrated and implemented as a single unit. In other words, one DU23 unit, excluding the processing of the radio section, can be connected to the RU24 units, which process the radio section and are included in multiple second communication points 520. Likewise, one DU25 unit, excluding the processing of the LOW PHY sublayer and radio section, can be connected to the RU26 units, which process the LOW PHY sublayer and radio section and are included in multiple second communication points 520.

[0217] Switching the connection between the central unit 500 and the second communication point 520 can also be done by changing the address of the destination on the optical network.

[0218] <5-5. TCI (Transmission Configuration Indicator) - State> Antenna ports are defined such that the channel on which a symbol on an antenna port is transmitted can be inferred from the channel on which another symbol on the same antenna port is transmitted.

[0219] Two antenna ports can be considered quasi-co-located if the channel characteristics on which symbols are transmitted on one antenna port can be inferred from the channel on which symbols are transmitted on the other antenna port. Channel characteristics include at least one of the following: delay spread, Doppler spread, Doppler shift, average gain, average delay, and spatial Rx parameters. For example, if the channel characteristics corresponding to two different antenna ports are recognized as being in a quasi-co-location relationship with respect to Doppler shift, the wireless terminal 100, which is a UE, can determine the Doppler shift of one antenna port and apply the result to both antenna ports to perform channel estimation.

[0220] Each TCI-State includes parameters for establishing a quasi-co-location relationship between one or two downlink reference signals and the demodulation reference signal (DM-RS) ports of the physical downlink shared channel (antenna ports for the demodulation reference signal of the physical downlink shared channel), the demodulation reference signal ports of the physical downlink control channel (antenna ports for the demodulation reference signal of the physical downlink control channel), or the CSI-RS (Channel State Information Reference Signal) ports of the CSI-RS resource (antenna ports for the CSI-RS resource).

[0221] The pseudo-collocation relationship is defined by parameters of the upper layer, for example, qcl-Type1 for the first downlink reference signal and, if set, qcl-Type2 for the second downlink reference signal.

[0222] For the case of two downlink reference signals, the type of quasi-co-location (QCL) must not be the same, regardless of whether the reference signals are on the same downlink or different downlinks.

[0223] The type of pseudo-collocation corresponding to each downlink reference signal is given by a parameter in the upper layer, for example, qcl-Type in QCL-Info.

[0224] The type of pseudo-collocation can be one of the following values:

[0225] typeA : {Doppler shift, Doppler spread, average delay, delay spread} typeB : {Doppler shift, Doppler spread} typeC : {Doppler shift, average delay} typeD : {Spatial Rx parameter}

[0226] The wireless terminal 100, which is the UE, can be configured using a list of up to 128 TCI-State configurations within the dl-OrJointTCI-StateList of the PDSCH-Config parameter, which is a parameter of the upper layer. Here, the dl-OrJointTCI-StateList of PDSCH-Config notifies the wireless terminal 100 of reference signals for pseudo-collocation of the Bandwidth Part (BWP) or demodulated reference signal (DM-RS) of the physical downlink shared channel and the demodulated reference signal (DM-RS) of the physical downlink control channel, and reference signals for pseudo-collocation of the CSI-RS. Where applicable, it also notifies the wireless terminal 100 of reference signals with qcl-Type set to "typeD" to determine the resources of the BWP or component carrier dynamic-grant and configured-grant-based physical downlink shared channel and physical downlink control channel, and the uplink transmit space filter (UL TX spatial filter) for the Sounding Reference Signal (SRS).

[0227] After receiving an initial configuration of a dl-OrJointTCI-StateList from a higher layer, which consists of one or more TCI-States that can be used as a designated TCI-State, the wireless terminal 100 assumes, where applicable, that the DM-RS of the physical downlink shared channel and the DM-RS of the physical downlink control channel, which are not received during the RACH (Random Access Channel) procedure, and the CSI-RS to which the designated TCI-State is applied, are in a pseudo-collocation relationship, i.e., pseudo-same location, with the reference signal of the candidate TCI-State indicated by the LTM cell switch command via MAC CE.

[0228] Otherwise, the wireless terminal 100 assumes that the DM-RS of the physical downlink shared channel, the DM-RS of the physical downlink control channel, and the CSI-RS to which the instructed TCI-State is applied are in a pseudo-collocation relationship with the SSB identified by the wireless terminal 100 during the initial access procedure.

[0229] Furthermore, after receiving an initial setting of a dl-OrJointTCI-StateList from a higher layer, which consists of one or more TCI-States that can be used as one designated TCI-State, or an initial setting of an ul-TCI-StateList from a higher layer, which consists of one or more TCI-UL-States that can be used as one designated TCI-State, and before applying the designated TCI-State from the configured TCI-State, the wireless terminal 100, if applicable, uses a dynamic-grant-based physical uplink sharing channel that is not transmitted during the RACH procedure, a configured-grant-based physical uplink sharing channel and a physical uplink control channel that are not transmitted during the RACH procedure, and MAC For an SRS to which a TCI-State is selected from among the candidate TCI-States or candidate TCI-UL-States indicated by a cell switch command of the LTM via the CE is applied, the transmit space filter is determined.

[0230] Otherwise, the wireless terminal 100 assumes, where applicable, that the transmit space filter for the SRS to which dynamic-grant and configured-grant-based physical uplink shared channels and physical uplink control channels apply, and the instructed TCI-State, is the same as the transmit space filter for physical uplink shared channel transmissions scheduled by RAR (Random Access Response) uplink grants during the initial access procedure, or for physical uplink shared channel transmissions in MsgA (Message A).

[0231] As part of the synchronization reset procedure, after receiving a dl-OrJointTCI-StateList configuration from a higher layer, which consists of one or more TCI-States that can be used as a designated TCI-State, the wireless terminal 100 assumes that the DM-RS of the physical downlink shared channel, the DM-RS of the physical downlink control channel, and the CSI-RS to which the designated TCI-State is applied are in a pseudo-collocation relationship with the SSB or CSI-RS resources identified by the wireless terminal 100 during the random access procedure initiated as part of the synchronization reset procedure.

[0232] As part of the synchronization reset procedure, after receiving a dl-OrJointTCI-StateList setting from a higher layer consisting of one or more TCI-States that can be used as a single designated TCI-State, or an ul-TCI-StateList setting from a higher layer consisting of one or more TCI-UL-States that can be used as a single designated TCI-State, the wireless terminal before applying the designated TCI-State from the configured TCI-State 100 assumes, where applicable, that the transmit space filter for the SRS applying dynamic-grant and configured-grant based physical uplink shared channels and physical uplink control channels, and the indicated TCI-State, is the same as the transmit space filter for physical uplink shared channel transmissions scheduled by RAR uplink grants during random access procedures initiated as synchronization reconfiguration procedures, or for physical uplink shared channel transmissions in MsgA.

[0233] When the wireless terminal 100 receives a dl-OrJointTCI-StateList setting from a higher layer, which consists of only one TCI-State that can be used as the one TCI-State to be instructed, the wireless terminal 100 determines the pseudo-collocation relationship from the DM-RS of the physical downlink shared channel, the DM-RS of the physical downlink control channel, and the TCI-State for the CSI-RS to which the instructed TCI-State is applied.

[0234] When the wireless terminal 100 receives a dl-OrJointTCI-StateList setting from a higher layer consisting of only one TCI-State that can be used as one designated TCI-State, or a ul-TCI-StateList setting from a higher layer consisting of only one TCI-UL-State that can be used as one designated TCI-State, the wireless terminal 100, if applicable, determines a dynamic-grant and configured-grant based physical uplink shared channel and physical uplink control channel, and a transmit space filter for the SRS to which the designated TCI-State is applied.

[0235] If the wireless terminal 100 is not provided with dl-OrJointTCI-StateList-r17, and the physical downlink shared channel is scheduled by the DCI (Downlink Control Information) format in which the TCI field exists, the TCI field in the DCI of the scheduling component carrier indicates the activated TCI-State in the scheduling component carrier or the downlink's BWP (Bandwidth Part), and the wireless terminal 100, which is the UE, must use the TCI-State according to the value of the 'Transmission Configuration Indication' field in the physical downlink control channel detected in the DCI to determine the pseudo-collocation of the antenna ports of the physical downlink shared channel.

[0236] The wireless terminal 100 can assume that, with respect to the parameters of the QCL type given in the indicated TCI-State, the DM-RS port of the serving cell's physical downlink shared channel is in the same position as the reference signal(s) in the TCI-State, if the time offset between the reception of the downlink DCI and the corresponding physical downlink shared channel is greater than or equal to a threshold (timeDurationForQCL). Here, the threshold is based on the reported UE capability.

[0237] For a single-slot physical downlink shared channel, the specified TCI-State must be based on the activated TCI-State of the slot with the scheduled physical downlink shared channel. For a multi-slot physical downlink shared channel, or if the wireless terminal 100 is configured with the higher-layer parameter (pdsch-TimeDomainAllocationListForMultiPDSCH), the specified TCI-State must be based on the activated TCI-State of the first slot with the scheduled physical downlink shared channel, and the wireless terminal 100 assumes that the activated TCI-State is the same across all slots with the scheduled physical downlink shared channel.

[0238] <6. Details of Clustering Process> Figure 12 shows an example of clustering process for the second communication point 520 in the central device unit 500 (first central device unit 500-1 or second central device unit 500-2).

[0239] The control unit 73 of the central device unit 500 acquires information relating to the second communication point via the communication unit 71 (step S801). The acquired information relating to the second communication point is stored in the storage unit 72 of the central device unit 500.

[0240] The information relating to the second communication point includes, for example, at least one of the following: the maximum number of MIMO layers that the second communication point can support, and the maximum channel bandwidth (maximum frequency bandwidth). Here, the information relating to the maximum number of MIMO layers that the second communication point can support and the maximum channel bandwidth can be obtained from the second communication point or from the OAM (Operations, Administration and Maintenance) equipment. The number of MIMO layers may also be the number of MIMO spatial streams or the number of antenna ports.

[0241] Furthermore, the control unit 73 of the central device unit 500 acquires information relating to the front hole connected to the second communication point from the second communication point or OAM, etc., via the communication unit 71 (step S802). The acquired information relating to the front hole connected to the second communication point is stored in the storage unit 72 of the central device unit 500.

[0242] Information related to the fronthaul includes, for example, the fronthaul interface and at least one piece of information related to the maximum communication speed. Examples of fronthaul interfaces include the F1 interface, CPRI, eCPRI, etc.

[0243] As described in the explanations of Figures 8 and 9 above, the control unit 73 of the central unit 500 sets a dynamic communication area with one or more second communication points 520 according to the location of the wireless terminal 100 in connected mode.

[0244] The control unit 73 of the central unit 500 can cluster one or more second communication points 520 from among candidates for the second communication point 520 to provide a dynamic communication area, depending on the location of the wireless terminal 100 in connected mode. Here, the location of the wireless terminal 100 in connected mode can be obtained from the network function of the core network 30, for example, from the LMF 311. This can be obtained directly from the LMF 311 or via the AMF 301.

[0245] Furthermore, candidates for the second communication point 520 that constitute the dynamic communication area may be obtained from the AMF 301 as information related to mobility control. The AMF 301 can generate candidate configurations for the second communication point 520 according to the location of the wireless terminal 100 in connected mode, and / or information related to the network slice (e.g., S-NSSAI (Single Network Slice Selection Assistance Information)) and information related to the data network (e.g., DNN (Data Network Name)). In other words, the AMF 301 can generate different candidate configurations for the second communication point 520 depending on the network slice used by the wireless terminal 100 in connected mode. Here, DNN corresponds to APN (Access Point Name) used in systems prior to 4G. The DNN / APN identifies the gateway device, which is the DN (Data Network) / AP (Access Point). S-NSSAI and DNN can be included in the session establishment request message transmitted from the wireless terminal 100 to the AMF 301.

[0246] Furthermore, the control unit 73 of the central unit 500 can cluster second communication points 520 that provide a dynamic communication area from among candidates, according to information relating to the communication quality of one or more second communication points 520. Here, the information relating to the communication quality of the second communication points is, for example, the received signal strength at the wireless terminal 100 of the reference signal transmitted from the second communication point, and the central unit 500 acquires the received signal strength at the wireless terminal 100 included in the measurement report transmitted from the wireless terminal 100. The received signal strength at the wireless terminal 100 is, for example, SS Reference Signal Received Power (SS-RSRP), CSI Reference Signal Received Power (CSI-RSRP), DL PRS Reference Signal Received Power (DL PRS-RSRP), etc.

[0247] The control unit 73 of the central device unit 500 starts clustering processing of the second communication point 520 according to the location of the wireless terminal 100 in the above-mentioned connected state (connected mode), or information relating to the communication quality of one or more candidate second communication points 520 (step S803).

[0248] The control unit 73 of the central device unit 500 calculates an index related to the amount of data for all second communication points 520 included in the configuration (cluster) that constitutes a dynamic communication area (step S804). Details of the process for calculating the index related to the amount of data will be described later.

[0249] The control unit 73 of the central device unit 500 determines whether or not the indicator related to the amount of data for each second communication point 520 falls within the characteristics of the front hole connected to the second communication point 520 (step S805). Details of the determination of whether or not it falls within the characteristics of the front hole will be described later.

[0250] If the data volume indicators for all second communication points 520 included in the configuration (cluster) are within the characteristics of the fronthaul connected to the second communication point 520, the control unit 73 of the central device unit 500 transmits the configured configuration (cluster) information to the wireless terminal 100 in connected mode via the communication unit 71 and the first communication point (step S806), and terminates the process.

[0251] On the other hand, in step S805, if the indicator related to the amount of data at the second communication point 520 does not fall within the characteristics of the front hole connected to the second communication point 520, the control unit 73 of the central device unit 500 changes the settings of the second communication point 520 (for example, at least one of the number of MIMO layers or the channel bandwidth (frequency bandwidth)) (step S807), and the processing from step S804 onwards is executed.

[0252] <6-1. Calculation of an Indicator Related to the Amount of Data for the Second Communication Point> Figure 13 is a diagram showing an example of the amount of data required for each interface. Here, an example of the relationship between the number of MIMO layers and channel bandwidth and the throughput required for the fronthaul (CPRI) is shown. In step S802, the control unit 73 of the central unit 500 can acquire information related to the amount of data required for each interface as part of the information related to the fronthaul connected to the second communication point.

[0253] The information regarding the required amount of data is information in which at least one of the number of MIMO layers and channel bandwidth supported by the second communication point is a variable. For example, in the case of a CPRI interface, the required amount of data is proportional to the number of MIMO layers and channel bandwidth supported by the second communication point, as shown in Figure 13.

[0254] If the control unit 73 of the central unit 500 sets the number of MIMO layers supported by a second communication point connected via a CPRI interface corresponding to option 8 of the RAN / AN 20 functional division to 2, and sets the channel bandwidth to 20 MHz, it calculates 2 Gbps (X = 1 Gbps) as an index for the amount of data to this second communication point, according to the information relating to the amount of data required for the CPRI interface. Here, the set channel bandwidth is, for example, the active BWP (Bandwidth Part).

[0255] In the eCPRI interface, which corresponds to option 7 of the RAN / AN20 functional division, the I / Q sample sequence of OFDM (Orthogonal Frequency-Division Multiplexing) signals is transmitted via fronthaul for each MIMO spatial stream or MIMO layer, and the IFFT (Inverse Fast Fourier Transform) / FFT processing is handled by the RU24 side. Therefore, the required fronthaul transmission speed can be reduced compared to the CPRI interface.

[0256] The control unit 73 of the central unit 500 sets the number of MIMO layers supported by the second communication point connected via the eCPRI interface to 8, and sets the channel bandwidth to 100 MHz. In this case, it calculates, for example, 2 Gbps as an indicator of the amount of data to be transmitted to this second communication point, according to the information relating to the required amount of data to the eCPRI interface. Here, the channel bandwidth to be set is, for example, the active BWP (Bandwidth Part).

[0257] <6-2. Determination of whether or not the characteristics of the front hole are met> In step S802, the control unit 73 of the central device unit 500 acquires information on the maximum communication speed of the front hole as part of the information relating to the front hole connected to the second communication point. The maximum communication speed is an example of the characteristics of the front hole, and the characteristics of the front hole may be defined by indicators other than the maximum communication speed.

[0258] The information regarding the maximum communication speed of the fronthaul includes values ​​that are set according to, for example, the specifications and distance of the optical cable.

[0259] Furthermore, the information regarding the maximum communication speed of the front hall may include the value of the maximum communication speed guaranteed by the optical fiber service to the front hall.

[0260] The control unit 73 of the central device unit 500 determines whether the indicator related to the amount of data to the second communication point is less than or equal to the maximum communication speed of the fronthaul. For example, as described above, if the number of MIMO layers supported by the second communication point connected by the CPRI interface is set to 2 and the channel bandwidth is set to 20 MHz, the indicator related to the amount of data to the second communication point is 2 Gbps. Therefore, if the maximum communication speed of the fronthaul is 2 Gbps or more, it is determined that the data is within the characteristics of the fronthaul. On the other hand, if the maximum communication speed of the fronthaul is less than 2 Gbps, it is determined that the data is not within the characteristics of the fronthaul.

[0261] Furthermore, as mentioned above, if the number of MIMO layers supported by the second communication point connected via the eCPRI interface is set to 8 and the channel bandwidth is set to 100 MHz, the indicator for the amount of data to the second communication point is 2 Gbps. Therefore, if the maximum fronthaul communication speed is 2 Gbps or higher, it is determined that the data is within the characteristics of the fronthaul. On the other hand, if the maximum fronthaul communication speed is less than 2 Gbps, it is determined that the data is not within the characteristics of the fronthaul.

[0262] <6-3. Changing the settings of the second communication point> Suppose that in step S805, for example, it is determined that the second communication point, which is set to have 8 MIMO layers and a channel bandwidth of 100 MHz, does not fit within the characteristics of the fronthaul. In this case, in step S807, the control unit 73 of the central unit 500 changes the MIMO layer count to 4 or changes the channel bandwidth to 80 MHz in order to reduce the indicator related to the amount of data for the second communication point. Here, the channel bandwidth that is changed is, for example, the active BWP (Bandwidth Part).

[0263] Furthermore, the control unit 73 of the central unit 500 may decide not to include the target second communication point in the configuration (cluster) for the new connected state (connected mode) wireless terminal 100 if the target second communication point is already included in the configuration (cluster) of another connected state (connected mode) wireless terminal 100 and a sufficient number of MIMO layers, for example, 4 or more, cannot be set.

[0264] For example, the number of wireless terminals 100 in connected mode that can be included in the configuration (cluster) simultaneously may be pre-configured for each set number of MIMO layers or channel bandwidth.

[0265] <6-4. Wireless Resource Allocation for Second Communication Points in a Cluster> The control unit 73 of the central unit 500 can allocate wireless resources of the second communication point included in the configuration (cluster) set for each wireless terminal 100 in connected mode, according to the number of MIMO layers and channel bandwidth set for the second communication point. That is, based on the fronthaul characteristics (e.g., maximum communication speed) and interface-related information (interface type, etc.), the control unit 73 sets the upper limit of the number of MIMO layers and the upper limit of the frequency bandwidth (channel bandwidth) that can be set for the second communication point so as to satisfy the fronthaul characteristics. The number of MIMO layers and channel bandwidth can be allocated to one or more wireless terminals so as to be within a range less than or equal to these upper limits set for the second communication point.

[0266] More specifically, if the second communication point is clustered to only one wireless terminal 100 in connected mode, the control unit 73 of the central unit 500 allocates wireless resources to this wireless terminal 100 with a number of layers less than or equal to the upper limit of the MIMO layer count set, and a channel bandwidth less than or equal to the upper limit of the channel bandwidth set.

[0267] Furthermore, if the second communication point is clustered with multiple wireless terminals 100 in connected mode, the control unit 73 of the central unit 500 allocates wireless resources with a channel bandwidth below the set upper limit of the channel bandwidth so that the total number of multi-user MIMO layers for the multiple wireless terminals 100 is below the set upper limit of the MIMO layer count.

[0268] Furthermore, the control unit 73 of the central unit 500 can set a PMI (Precoding Matrix Indicator) corresponding to the precoding matrix applied by the second communication point included in the configuration (cluster) set for each wireless terminal 100 in connected mode, according to the number of MIMO layers set for the second communication point. The control unit 73 of the central unit 500 allocates wireless resources for the second communication point according to the set PMI.

[0269] As described above, the base station distributed control of this embodiment allows for clustering of one or more second communication points 520 that constitute a dynamic communication area according to the fronthaul interface and fronthaul characteristics. Furthermore, the number of MIMO layers and channel bandwidth of each clustered second communication point 520 can be set according to the fronthaul interface and fronthaul characteristics. Therefore, by allocating wireless resources to the wireless terminal 100 with a number of layers less than or equal to the set MIMO layer count and a channel bandwidth less than or equal to the set channel bandwidth, it becomes possible to give any interface fronthaul characteristics.

[0270] The embodiments described above are merely examples of how to implement this disclosure, and it is possible to implement this disclosure in various other forms. For example, various modifications, substitutions, omissions, or combinations thereof are possible without departing from the gist of this disclosure. Such modified, substituted, or omission forms are also included within the scope of the invention described in the claims and its equivalents, as are included within the scope of this disclosure.

[0271] Furthermore, the effects described herein are merely illustrative, and other effects may also occur.

[0272] Furthermore, this disclosure may also take the following configurations: [Item 1] A communication device comprising: a communication unit connected to one of a plurality of first communication points, which transmits a paging message to an idle-mode terminal device via the one first communication point; and a control unit which selects one or more second communication points from a plurality of second communication points based on the location or propagation environment of the connected-mode terminal device, and establishes a connection with the selected one or more second communication points, wherein the first communication point constitutes a static or quasi-static communication area, the second communication points constitute a dynamic communication area by spatial multiplexing or diversity, and the communication unit communicates with the connected-mode terminal device via the one or more second communication points with which the connection has been established. [Item 2] The communication device according to Item 1, wherein the first communication point provides the terminal device with a first communication area, and the one or more second communication points provide the terminal device with a second communication area narrower than the first communication area. [Item 3] The communication device according to Item 1 or 2, wherein the control unit obtains information including one or more candidates for the second communication point from a device that manages the mobility of the terminal device, and selects one or more second communication points from the candidates based on the information including the candidates. [Item 4] The communication device according to any one of Items 1 to 3, wherein when the terminal device in connected mode is handed over to a target communication device connected to another first communication point among the plurality of first communication points, the control unit selects at least one second communication point from the one or more second communication points on which the connection has been established to maintain a connection with the terminal device, the communication unit transmits information relating to the selected at least one second communication point to the target communication device, and the information relating to the selected at least one second communication point includes a request to the target communication device to establish a connection with the selected at least one second communication point.[Item 5] The communication device according to Item 4, wherein the request is to establish the connection with the target communication device while maintaining the connection with the communication device for the selected at least one second communication point. [Item 6] The communication device according to Item 4, wherein the request is to switch the connection from the connection with the communication device to the connection with the target communication device for the selected at least one second communication point. [Item 7] The communication device according to any one of Items 4 to 6, wherein the information relating to the selected at least one second communication point includes a TCI (Transmission Configuration Indicator) state for each selected at least one second communication point and instructions to apply each of the TCI states for each selected at least one second communication point. [Item 8] The communication device according to Item 7, wherein the TCI-state includes one or two downlink reference signals and parameters for setting a quasi co-location relationship between a demodulated reference signal port of a physical downlink shared channel, a demodulated reference signal port of a physical downlink control channel, or a CSI (Channel State Information Reference Signal)-RS (Reference Signal) port. [Item 9] The communication device according to any one of Items 1 to 8, wherein the one or more second communication points are RUs (Radio Units), the communication unit is connected to a DU (Distributed Unit) via an F1 interface, and the fronthaul between the DU and the second communication points is connected via a specific interface. [Item 10] The communication device according to Item 9, wherein the control unit sets at least one of the MIMO layer number limit and frequency bandwidth limit for each of the one or more second communication points based on information relating to the characteristics of the fronthaul.[Item 11] The communication device according to Item 10, wherein the control unit sets at least one of the upper limit of the MIMO layer count and the upper limit of the frequency bandwidth for each of the one or more second communication points, based on further information relating to the specific interface. [Item 12] The communication device according to Item 10 or 11, wherein the control unit determines whether each of the one or more second communication points has been assigned to another terminal device in connected mode other than the terminal device, and if it has not been assigned to any other terminal device, assigns to the terminal device a first MIMO layer count less than or equal to the upper limit of the MIMO layer count and a bandwidth less than or equal to the upper limit of the frequency bandwidth. [Item 13] The control unit determines whether each of the one or more second communication points has been assigned to another connected mode terminal device other than the terminal device, and if it has been assigned to another terminal device, it assigns to the terminal device a second number of MIMO layers such that the total number of MIMO layers to be assigned to the terminal device and the one or more other terminal devices is less than or equal to the upper limit of the number of MIMO layers, and wireless resources with a bandwidth less than or equal to the upper limit of the frequency bandwidth, according to any one of items 10 to 12. [Item 14] A terminal device comprising: a communication unit that, in idle mode, receives a paging message from a communication device connected to one of a plurality of first communication points via one of a plurality of first communication points; and a control unit that, in connected mode, acquires first information relating to one or more second communication points from a plurality of second communication points, depending on the location or propagation environment of the terminal device, via one of the first communication points, wherein the first communication point constitutes a static or quasi-static communication area, the second communication point constitutes a dynamic communication area by spatial multiplexing or diversity, and the communication unit communicates with the communication device that has established a connection with the one or more second communication points via the one or more second communication points based on the acquired first information.[Item 15] The terminal device according to Item 14, wherein the first communication point provides a first communication area to the terminal device, and the one or more second communication points provide the terminal device with a second communication area narrower than the first communication area. [Item 16] The terminal device according to Item 14 or 15, wherein the communication unit receives information including one or more candidates for the second communication point and conditions relating to measuring the communication quality of the one or more candidates for the second communication point and reporting the measurement results, and the control unit performs the measurement of the communication quality of the candidates for the second communication point and reports the measurement results of the communication quality according to the conditions included in the information. [Item 17] The terminal device according to any one of items 14 to 16, wherein the control unit controls a handover from one first communication point to another first communication point among the plurality of first communication points connected to the target communication device, and the communication unit receives information that identifies at least one second communication point among the one or more second communication points that maintains a connection with the terminal device during the handover, and continues to use the second communication point indicated by the identifying information during the handover. [Item 18] The terminal device according to item 17, wherein the control unit acquires second information relating to one or more second communication points different from the at least one second communication point that maintains a connection with the terminal device during the handover, and the communication unit communicates with the target communication device after the handover via the second communication point indicated by the identifying information and the one or more second communication points relating to the second information.[Item 19] A communication system comprising a communication device and a terminal device, wherein the communication device comprises: a communication unit connected to one of a plurality of first communication points and transmitting a paging message to the terminal device in idle mode via the one first communication point; and a control unit that selects one or more second communication points from a plurality of second communication points based on the location or propagation environment of the terminal device in connected mode and establishes a connection with the selected one or more second communication points, wherein the terminal device comprises a communication unit that receives the paging message via the one first communication point in idle mode, wherein the first communication point constitutes a static or quasi-static communication area, the second communication point constitutes a dynamic communication area by spatial multiplexing or diversity, and the communication unit of the terminal device in connected mode communicates with the communication unit of the communication device via the one or more second communication points. [Item 20] A communication method comprising: sending a paging message to an idle terminal device via one of a plurality of first communication points; selecting one or more second communication points from a plurality of second communication points based on the location or propagation environment of the connected terminal device; establishing a connection with the selected one or more second communication points; communicating with the connected terminal device via the one or more second communication points with which the connection has been established; the first communication points constitute a static or quasi-static communication area; and the second communication points constitute a dynamic communication area by spatial multiplexing or diversity.

[0273] Furthermore, this disclosure can also be structured in the following way from another perspective.

[0274] <Communication device (base station)> (1) A communication device that provides the functions of a base station, comprising one or more communication points and one central unit, wherein the central unit includes a connection unit with a first communication point that transmits paging messages to terminal devices in idle mode, a selection unit that selects at least one second communication point for each terminal device in connected mode, and a connection control unit that establishes a connection between the selected one or more second communication points and the central unit.

[0275] (2) The communication device according to (1), wherein the first communication point provides basic coverage and at least one of the second communication points provides a communication area that enhances capacity.

[0276] (3) The connection between the central unit and each of the second communication points is set for each of the terminal devices in connected mode, as described in (1).

[0277] (4) The communication device according to (3), wherein the connection control unit assigns a unique identification information within the central unit to the connection set for each terminal device in connected mode.

[0278] (5) The communication device according to (1), wherein the central device unit includes an acquisition unit that acquires information relating to the location of the terminal device in connected mode, and the selection unit selects at least one second communication point for the terminal device in connected mode according to the information relating to the location.

[0279] (6) The communication device according to (1), wherein the central device unit includes an acquisition unit that acquires information relating to the communication quality between the terminal device in connected mode and at least one of the second communication points, and the selection unit selects at least one of the second communication points for the terminal device in connected mode according to the information relating to the communication quality.

[0280] (7) The communication device according to any one of (1) to (6), wherein the central device unit includes an acquisition unit that acquires a configuration from another device that includes at least one candidate for the second communication point for the terminal device in connected mode, and the selection unit selects at least one of the candidates for the second communication point for the terminal device in connected mode from among the configurations.

[0281] (8) The communication device according to (7), wherein the other device generates the configuration according to the information relating to the position of the terminal device in connected mode.

[0282] (9) The communication device according to (1), wherein the central device unit includes an acquisition unit that acquires information relating to the mobility state of the terminal device in connected mode, and the selection unit selects at least one second communication point for the terminal device in connected mode according to the information relating to the mobility state.

[0283] (10) The communication device according to (9), wherein the information relating to the mobility state is one of normal, medium, or high.

[0284] (11) The communication device according to (9), wherein the information relating to the mobility state is information corresponding to the movement speed of the terminal device in connected mode.

[0285] (12) A communication device according to any one of (9) to (11), comprising: an acquisition unit for acquiring from another device a configuration including at least one candidate for the second communication point for the terminal device in connected mode, wherein the candidate for the second communication point includes a plurality of second communication points operating in different frequency bands, and the selection unit selects the second communication point operating in a lower frequency band for the terminal device in a higher mobility state, and the second communication point operating in a higher frequency band for the terminal device in a lower mobility state, according to the information relating to the mobility state.

[0286] (13) The communication device according to (1), wherein the central device unit includes a setting unit for setting a QCL (Quasi Co Location) type parameter for the second communication point, and the selection unit selects at least two of the second communication points for the connected mode terminal device according to the QCL type parameter.

[0287] (14) The communication device according to (11), wherein the selection unit selects at least two second communication points that indicate the parameter is in a different position.

[0288] (15) The communication device according to (1), wherein the central device unit includes a transmitting unit that transmits information for determining whether or not the terminal device in idle mode is within the registration area via the first communication point.

[0289] (16) The communication device according to (1), wherein when the connected terminal device, which is connected to the source communication device, is handing over to a target second communication device including other first communication points, the selection unit selects at least one of the second communication points from one or more of the second communication points which have established a connection with the central device unit, and the connection control unit transmits a request to establish a second connection between the selected at least one second communication point and the second central device unit of the target second communication device.

[0290] (17) The communication device according to (16), wherein the request is a request to instruct a switch from the connection with the central device unit to the second connection with the second central device unit.

[0291] (18) The communication device according to (16), wherein the request is a request to maintain the connection with the central device unit and to instruct the establishment of the second connection with the second central device unit.

[0292] (19) The communication device according to any one of (16) to (18), wherein the central device unit includes a transmitting unit that transmits information relating to at least one selected second communication point to the second central device unit of the target second communication device.

[0293] (20) The communication device according to (19), wherein the information relating to the second communication point includes an instruction not to switch the second communication point.

[0294] (21) The communication device according to (19) or (20), wherein the information relating to the second communication point includes a TCI (Transmission Configuration Indicator) state for each of the selected second communication points and an instruction to apply each of the selected second communication points.

[0295] (22) The communication device according to (21), wherein the TCI-state includes one or two downlink reference signals and parameters for establishing a quasi co-location relationship between a demodulation reference signal port of a physical downlink shared channel, a demodulation reference signal port of a physical downlink control channel, or a CSI (Channel State Information Reference Signal)-RS (Reference Signal) port.

[0296] (23) The communication device according to (1), wherein the second communication point is a Distributed Unit, and the front hole between the central unit and the second communication point is connected via an F1 interface.

[0297] (24) The communication device according to (1), wherein the second communication point is a Radio Unit, and the fronthaul between the Distributed Unit, which is connected to the central unit via an F1 interface, and the second communication point is connected via a specific interface.

[0298] (25) The communication device described in (24), wherein the specific interface is a CPRI (Common Public Radio Interface) interface.

[0299] (26) The communication device described in (24), wherein the specific interface is an eCPRI (evolved Common Public Radio Interface) interface.

[0300] (27) The communication device according to any one of (23) to (26), wherein the central device unit includes a second acquisition unit for acquiring information relating to the characteristics of the front hole, and a setting unit for setting at least one of the number of layers and the operating bandwidth of the second communication point for the connected terminal device according to the acquired information relating to the performance of the front hole.

[0301] (28) The communication device according to (27), wherein the second acquisition unit further acquires information relating to the specific interface from the Distributed Unit, and the setting unit sets at least one of the number of layers and the operating bandwidth of the second communication point for the terminal device in connected mode according to the information relating to the performance of the fronthaul and the information relating to the specific interface.

[0302] (29) The communication device according to (28), wherein the central unit includes a resource allocation unit that, when the second communication point is selected for one of the connected mode terminal devices, allocates a first number of layers less than or equal to the number of layers set for the terminal device, and a first channel bandwidth less than or equal to the set channel bandwidth.

[0303] (30) The communication device according to (27), wherein the setting unit sets at least one of the number of layers and the operating bandwidth of the second communication point for two or more connected mode terminal devices.

[0304] (31) The communication device according to (30), wherein the central unit includes a resource allocation unit that, when the second communication point is selected for two or more wireless terminals in connected mode, allocates wireless resources within a second channel bandwidth less than or equal to the set channel bandwidth so that the total number of multi-user MIMO layers for the two or more wireless terminals becomes less than or equal to the set number of layers.

[0305] (32) The communication device according to (27) or (28), wherein the number of terminal devices in the selectable connected mode is set for each number of layers or each operating bandwidth set at the second communication point.

[0306] <Wireless terminal> (1) A terminal device including a control unit, the control unit including, in idle mode, a first selection unit for selecting or re-selecting a first communication point, a transmission unit for transmitting a registration request to the selected first communication point, and in connected mode, a receiving unit for acquiring information relating to one or more second communication points that are the connection destination via the first communication point, wherein the transmission unit transmits a connection request to one or more of the second communication points according to the information.

[0307] (2) The terminal device according to (1), wherein the receiving unit further acquires a candidate including one or more of the second communication points, and second information including the conditions for measurement and reporting of the second communication points included in the candidate.

[0308] (3) The terminal device described in (2), wherein the conditions for the report are a report of measurements at Layer 1, and the information is a switching command via a Control Element (CE) in a sublayer lower than the Radio Resource Control (RRC) sublayer.

[0309] (4) The terminal device according to (1), wherein the receiving unit further acquires a candidate including one or more of the second communication points, and second information including conditions for measuring and selecting the second communication points included in the candidate.

[0310] (5) The terminal device according to (1), wherein when a handover occurs from the first communication point which is the source to another first communication point which is the target, the receiving unit receives second information indicating one or more second communication points which are not to be switched from one or more connected second communication points.

[0311] (6) The terminal device according to (5), wherein the control unit includes a selection unit that, upon receiving the second information, selects a second communication point other than the second communication point indicated by the second information from among one or more second communication points included in the information, and the transmission unit transmits a connection request to the selected second communication point.

[0312] <Communication System> (1) A communication system comprising a communication device and a terminal device, wherein the communication device provides the function of a base station comprising one or more communication points and one central unit, the central unit includes a connection unit with a first communication point that transmits paging messages to terminal devices in idle mode, a selection unit that selects at least one second communication point for each terminal device in connected mode, and a connection control unit that establishes a connection between the selected one or more second communication points and the central unit, and the terminal device including the control unit, the control unit includes, in idle mode, a first selection unit that selects or re-selects a first communication point, a transmission unit that transmits a registration request to the selected first communication point, and in connected mode, a receiving unit that acquires information relating to one or more second communication points that are connection destinations via the first communication point, and the transmission unit transmits a connection request to one or more second communication points according to the information, the communication system.

[0313] 10: UE (User Equipment) 20: Base station equipment 30: Core network 40: Application server 71: Communication unit 72: Memory unit 73: Control unit 500: Central unit 510: First communication point 520: Second communication point 700: Information processing device

Claims

1. A communication device comprising: a communication unit connected to one of a plurality of first communication points, which transmits a paging message to an idle-mode terminal device via the first communication point; and a control unit which selects one or more second communication points from a plurality of second communication points based on the location or propagation environment of the connected-mode terminal device, and establishes a connection with the selected one or more second communication points, wherein the first communication point constitutes a static or quasi-static communication area, the second communication points constitute a dynamic communication area by spatial multiplexing or diversity, and the communication unit communicates with the connected-mode terminal device via the one or more second communication points with which the connection has been established.

2. The communication device according to claim 1, wherein the first communication point provides a first communication area to the terminal device, and the one or more second communication points provide the terminal device with a second communication area that is narrower than the first communication area.

3. The communication device according to claim 1, wherein the control unit obtains information including one or more candidates for a second communication point from a device that manages the mobility of the terminal device, and selects one or more second communication points from the candidates based on the information including the candidates.

4. The communication device according to claim 1, wherein when the terminal device in connected mode is handed over to a target communication device connected to another first communication point among the plurality of first communication points, the control unit selects at least one second communication point from the one or more second communication points on which the connection has been established to maintain a connection with the terminal device, the communication unit transmits information relating to the selected at least one second communication point to the target communication device, and the information relating to the selected at least one second communication point includes a request to the target communication device to establish a connection with the selected at least one second communication point.

5. The communication device according to claim 4, wherein the requirement is to establish the connection with the target communication device while maintaining the connection with the selected second communication point.

6. The communication device according to claim 4, wherein the request is a request for switching the connection of the selected at least one second communication point from the connection with the communication device to the connection with the target communication device.

7. The communication device according to claim 4, wherein the information relating to the selected at least one second communication point includes a TCI (Transmission Configuration Indicator) state for each selected at least one second communication point and an instruction to apply each of the TCI states for each selected at least one second communication point.

8. The communication device according to claim 7, wherein the TCI-state includes one or two downlink reference signals and parameters for establishing a quasi co-location relationship between a demodulation reference signal port of a physical downlink shared channel, a demodulation reference signal port of a physical downlink control channel, or a CSI (Channel State Information Reference Signal)-RS (Reference Signal) port.

9. The communication device according to claim 1, wherein the one or more second communication points are RUs (Radio Units), the communication unit is connected to a DU (Distributed Unit) via an F1 interface, and the fronthaul between the DU and the second communication points is connected via a specific interface.

10. The communication device according to claim 9, wherein the control unit sets at least one of the MIMO layer number and frequency bandwidth limits for each of the one or more second communication points based on information relating to the characteristics of the front hole.

11. The communication device according to claim 10, wherein the control unit sets at least one of the upper limit of the MIMO layer count and the upper limit of the frequency bandwidth for each of the one or more second communication points, based on further information relating to the specific interface.

12. The communication device according to claim 10, wherein the control unit determines whether each of the one or more second communication points has been assigned to another connected mode terminal device other than the terminal device, and if it has not been assigned to another terminal device, assigns to the terminal device a first MIMO layer count of less than or equal to the upper limit of the MIMO layer count, and a bandwidth of less than or equal to the upper limit of the frequency bandwidth.

13. The control unit determines whether each of the one or more second communication points has been assigned to another connected mode terminal device other than the terminal device, and if it has been assigned to another terminal device, it assigns to the terminal device a second number of MIMO layers such that the total number of MIMO layers to be assigned to the terminal device and the one or more other terminal devices is less than or equal to the upper limit of the number of MIMO layers, and wireless resources with a bandwidth less than or equal to the upper limit of the frequency bandwidth, according to claim 10.

14. A terminal device comprising: a communication unit that, in idle mode, receives a paging message from a communication device connected to one of a plurality of first communication points via one of a plurality of first communication points; and a control unit that, in connected mode, acquires first information relating to one or more second communication points from a plurality of second communication points, depending on the location or propagation environment of the terminal device, via the one first communication point, wherein the first communication point constitutes a static or quasi-static communication area, the second communication point constitutes a dynamic communication area by spatial multiplexing or diversity, and the communication unit communicates with the communication device that has established a connection with the one or more second communication points via the one or more second communication points based on the acquired first information.

15. The terminal device according to claim 14, wherein the first communication point provides a first communication area to the terminal device, and the one or more second communication points provide the terminal device with a second communication area that is narrower than the first communication area.

16. The terminal device according to claim 14, wherein the communication unit receives information including one or more candidates for second communication points and conditions relating to the measurement of communication quality for the one or more candidates for second communication points and the reporting of the measurement results, and the control unit performs the measurement of communication quality for the candidates for second communication points and reports the measurement results of the communication quality in accordance with the conditions included in the information.

17. The terminal device according to claim 14, wherein the control unit controls a handover from one first communication point to another first communication point among the plurality of first communication points that is connected to a target communication device, and the communication unit receives information that identifies at least one second communication point among the one or more second communication points that maintains a connection with the terminal device during the handover, and continues to use the second communication point indicated by the identifying information during the handover.

18. The terminal device according to claim 17, wherein the control unit acquires second information relating to one or more second communication points different from the at least one second communication point that maintains connection with the terminal device during the handover, and the communication unit communicates with the target communication device after the handover via the second communication point indicated by the identifying information and the one or more second communication points relating to the second information.

19. A communication system comprising a communication device and a terminal device, wherein the communication device includes a communication unit connected to one of a plurality of first communication points and transmitting a paging message to the terminal device in idle mode via the one first communication point, and a control unit that selects one or more second communication points from a plurality of second communication points based on the location or propagation environment of the terminal device in connected mode and establishes a connection with the selected one or more second communication points, and the terminal device includes a communication unit that receives the paging message via the one first communication point in idle mode, wherein the first communication point constitutes a static or quasi-static communication area, the second communication point constitutes a dynamic communication area by spatial multiplexing or diversity, and the communication unit of the terminal device in connected mode communicates with the communication unit of the communication device via the one or more second communication points.

20. A communication method comprising: transmitting a paging message to an idle terminal device via one of a plurality of first communication points; selecting one or more second communication points from a plurality of second communication points based on the location or propagation environment of the connected terminal device; establishing a connection with the selected one or more second communication points; and communicating with the connected terminal device via the one or more second communication points with which the connection has been established; wherein the first communication points constitute a static or quasi-static communication area, and the second communication points constitute a dynamic communication area by spatial multiplexing or diversity.

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