Distributed base station device, base station control device, terminal device, communication control method for distributed base station device, communication control method for base station control device, and communication control method for terminal device

Abstract

A distributed base station device comprising a communication unit that communicates with a terminal device, wherein the terminal device performs cooperative communication with a plurality of said distributed base station devices, and the communication unit transmits, to the terminal device, list information relating to a list of the distributed base station devices that are included in a device group comprising one or more of the distributed base station devices.

Description

Distributed base station device, base station control device, terminal device, communication control method for distributed base station device, communication control method for base station control device, and communication control method for terminal device

[0001] The present disclosure relates to a distributed base station device, a base station control device, a terminal device, a communication control method for a distributed base station device, a communication control method for a base station control device, and a communication control method for a terminal device.

[0002] Radio access methods and radio networks for cellular mobile communications (hereinafter also referred to as "Long Term Evolution (LTE)," "LTE-Advanced (LTE-A)," "LTE-Advanced Pro (LTE-A Pro)," "New Radio (NR)," "New Radio Access Technology (NRAT)," "Evolved Universal Terrestrial Radio Access (EUTRA)," or "Further EUTRA (FEUTRA)") are being considered by the 3rd Generation Partnership Project (3GPP (registered trademark)).

[0003] In the following description, LTE includes LTE-A, LTE-A Pro, and EUTRA, and NR includes NRAT and FEUTRA. In LTE, a base station (base station device) is referred to as an eNodeB (evolved NodeB), in NR, a base station (base station device) is referred to as a gNodeB, and in LTE and NR, a terminal device (mobile station, mobile station device, terminal) is referred to as a UE (User Equipment). LTE and NR are cellular communication systems in which multiple areas covered by a base station are arranged in the form of cells. A single base station may manage multiple cells.

[0004] 5G NR is a next-generation radio access technology (RAT) different from LTE, and is a next-generation radio access method for LTE. NR is an access technology that can support various use cases, including eMBB (Enhanced mobile broadband), mMTC (Massive machine type communications), and URLLC (Ultra reliable and low latency communications). NR has been standardized to support a technical framework that corresponds to the usage scenarios, requirements, and deployment scenarios of those use cases.

[0005] In recent years, discussions on next-generation wireless communications have been progressing, and there are demands for even higher speed communications beyond 5G NR, low-latency and highly reliable communications, large numbers of high-density communications, and simultaneous support of multiple of these. To achieve these requirements, further improvements in frequency utilization efficiency are required.

[0006] One possible technique for improving frequency utilization efficiency is to have multiple base station devices (distributed base station devices) cooperate to communicate with terminal devices, thereby enabling efficient communication with terminal devices. Non-Patent Document 1 below describes a technique for cooperative transmission from multiple transmission points.

[0007] R1-2400753, “CSI enhancements for large antenna arrays and CJT”, Ericsson, 3GPP RAN1 #116, February-March 2024.

[0008] In the technology related to cooperative transmission disclosed in Non-Patent Document 1, multiple base station devices cooperate to communicate with terminal devices, thereby enabling further improvement in frequency utilization efficiency. In such cooperative transmission, it is necessary to support the cooperative transmission means of multiple base station devices and the mobility of terminal devices.

[0009] Therefore, the present disclosure proposes a distributed base station device, a base station control device, a terminal device, a communication control method for a distributed base station device, a communication control method for a base station control device, and a communication control method for a terminal device that can improve communication quality even when the terminal device moves and performs cooperative communication with multiple distributed base station devices.

[0010] In order to solve the above problems, the distributed base station device of the present disclosure is a distributed base station device having a communication unit that communicates with a terminal device, wherein the terminal device is performing cooperative communication with a plurality of the distributed base station devices, and the communication unit transmits list information to the terminal device regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices.

[0011] 1 is a diagram illustrating an example of a cell-based communication system. FIG. 1 is a diagram illustrating an example configuration of a communication system according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example operation of a communication system according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example operation of a communication system according to an embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example operation of a communication system according to an embodiment of the present disclosure. FIG. 5 is a diagram illustrating an example operation of a communication system according to an embodiment of the present disclosure. FIG. 6 is a diagram illustrating an example configuration of a base station according to an embodiment of the present disclosure. FIG. 7 is a diagram illustrating an example configuration of a terminal device according to an embodiment of the present disclosure. FIG. 8 is a diagram illustrating an example control of a communication system according to an embodiment of the present disclosure. FIG. 9 is a diagram illustrating an example control of a communication system according to an embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example operation of a communication system according to an embodiment of the present disclosure. FIG. 11 is a diagram illustrating an example control of a communication system according to an embodiment of the present disclosure.

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiments, the same components are designated by the same reference numerals, and redundant description will be omitted.

[0013] The present disclosure will be described in the following order of items: 1. Overview 1-1. Issues 2. Configuration Example of Communication System of This Embodiment 2-1. Overall Configuration Example of Communication System 2-2. Operation Example of Communication System 2-2-1. Operation Example Relating to Data Transmission Function 2-2-2. Operation Example Relating to Control Information Transmission Function 2-2-3. Index Information 2-2-4. Mobility Management 2-2-5. Operation Example Relating to Cooperative Communication 2-2-6. Operation Example Relating to Multiple Terminal Devices 2-2-7. Operation Example Relating to Cooperative Communication of Multiple Terminal Devices 2-3. Configuration Example of Base Station 2-4. Configuration Example of Terminal Device 2-4-1. Measurement 2-4-2. Feedback 2-4-3. Report 3. Operation Example of Communication System of This Embodiment 3-1. Notification of List Information 3-2. Notification of Index Information 3-3. Notification of Setting Change 3-4. Determination of Distributed Base Station Device Based on QCL Information 3-5. Handover of device group 3-6. Conditional handover of device group 3-7. Trigger evaluation 4. Modifications 4-1. Configuration example of base station 5. Other embodiments 6. Effects 7. Hardware configuration

[0014] <<1. Overview>> <1-1. Problems> Figure 1 is a diagram showing an example of a cell-based communication system. Conventionally, in cell-based cellular mobile communications such as LTE and NR, one or more base stations 30A form a communication cell, and a terminal device 40 communicates with the base station 30A. For example, as shown in Figure 1, the terminal device 40 belongs to a cell formed by two base stations 30A and performs communication.

[0015] 2 is a diagram illustrating a configuration example of a communication system according to an embodiment of the present disclosure. On the other hand, assuming a distributed antenna environment as shown in FIG. 2, it is assumed that multiple distributed base station devices (which may also be referred to as Transmission and Reception Points: TRPs) cooperate to provide communications to terminal devices 40. Note that a communication system 1 including a distributed base station device 302 will be described later.

[0016] The distributed base station devices 302 that communicate with the terminal device 40 may be divided into those that communicate and those that do not, depending on the location or communication request of the terminal device 40. For example, taking the location of the terminal device 40 as an example, a distributed base station device 302 that is close to the terminal device 40 may communicate with the terminal device 40, while a distributed base station device 302 that is far from the terminal device 40 may not communicate with the terminal device 40. Also, taking a communication request as an example, the distributed base station device 302 may differ depending on whether more reliable communication is required or not. In this case, the terminal device 40 needs to determine which distributed base station device group to communicate with depending on the communication function.

[0017] <<2. Example of Configuration of Communication System of Present Embodiment>> <2-1. Example of Overall Configuration of Communication System> A communication system 1 of this embodiment will be described with reference to FIG.

[0018] 2, the communication system 1 includes a core network 20, a base station 30, and a terminal device 40. The communication system 1 provides users with a wireless network (mobile network) that enables mobile communication by the wireless communication devices constituting the communication system 1 operating in cooperation with each other.

[0019] The wireless network of this embodiment may be, for example, a cellular network configured with a radio access network (RAN) and a core network (CN) 20. The mobile network may include a terminal device 40.

[0020] The core network 20 manages the base stations 30. The core network 20 manages subscriber information for each terminal device 40 (hereinafter also referred to as UE (User Equipment) 40) and manages sessions for each UE 40. The core network 20 may be located on a cloud, for example.

[0021] The base station (RAN) 30 controls and manages all aspects of wireless communication, including managing frequency and time resources for wireless communication. The base station 30 includes a central unit (CU), a distributed unit (DU), and a radio unit (RU) having a distributed antenna. The base station 30 includes not only terrestrial base station equipment, but also non-terrestrial base station equipment that operates as communication devices such as satellite stations, drones, balloons, and airplanes.

[0022] The base station 30 also includes a base station control device 301 and a plurality of distributed base station devices 302. In the following description, a case will be described in which a CU is applied to the base station control device 301 and a DU / RU is applied to the distributed base station device 302. Note that the base station 30 may have a configuration different from that described above, and other configurations will be described later.

[0023] The plurality of distributed base station devices 302 are defined as a device group consisting of one or more distributed base station devices 302 according to the communication function. That is, the device group is a group of distributed base station devices, and is called, for example, a group of multi-TRP, a GM-TRP, a set of mTRP, a cluster of mTRP, etc. Note that the device group is not particularly limited to these names.

[0024] The communication functions include, for example, a data transmission function, a control information transmission function, and a quality management function for managing the quality of communication services. The data transmission function is, for example, a Physical Data Shared Channel (PDSCH) or a Physical Uplink Shared Channel (PUSCH). The control information transmission function is, for example, a Physical Downlink Control Channel (PDCCH) or a PUSCH. The quality management function is, for example, Quality of Service (QoS).

[0025] <2-2. Operational Example of Communication System> <2-2-1. Operational Example Related to Data Transmission Function> Fig. 3 is a diagram showing an operational example of a communication system according to an embodiment of the present disclosure. The device group in Fig. 3 is a group defined when a data transmission function (PDSCH) is applied as the communication function. The multiple distributed base station devices 302 included in the device group defined by the data transmission function (PDSCH) have the same channel characteristics.

[0026] Device groups with the same channel characteristics include groups with the same delay between each distributed base station device 302 and the terminal device 40, groups with the same Doppler shift, groups with the same antenna orientation, etc. The antenna 313 included in the distributed base station device 302 may be used in duplicate between device groups.

[0027] In such equipment groups with the same channel characteristics, the terminal device 40 moves between equipment groups while switching the equipment group to which it is connected for communication, as shown in Fig. 3. At this time, the equipment group switching may be performed by the base station control device 301 or by the terminal device 40. Furthermore, the terminal device 40 may execute Measurement and Measurement report (described later) for information required for forming equipment groups and switching equipment groups.

[0028] <2-2-2. Operation Example Related to Control Information Transmission Function> Fig. 4 is a diagram showing an operation example of a communication system according to an embodiment of the present disclosure. The device group in Fig. 4 is a group defined when a control information transmission function (PDCCH) is applied as a communication function. The multiple distributed base station devices 302 included in the device group defined by the control information transmission function (PDCCH) have different channel characteristics.

[0029] Device groups with different channel characteristics include groups with different Doppler shifts, groups with different antenna orientations, etc. The antenna 313 included in the distributed base station device 302 may be used in duplicate between device groups.

[0030] In such equipment groups with different channel characteristics, the terminal device 40 moves between equipment groups while switching the equipment group to which it is communicatively connected, as shown in Fig. 4. At this time, the switching of the equipment group may be performed by the base station control device 301, as described above, or by the terminal device 40. Furthermore, the terminal device 40 may execute Measurement and Measurement report, which will be described later, for information required for forming an equipment group and switching the equipment group.

[0031] <2-2-3. Index Information> The index information is information that associates list information (first list information) related to a list of distributed base station devices 302 included in an equipment group with list information (second list information) related to a list of distributed base station devices 302 included in another equipment group. The list information is generated for each communication function and is information that lists one or more distributed base station devices 302 included in an equipment group. When the above-mentioned equipment group for the data transmission function (PDSCH) and the equipment group for the control information transmission function (PDCCH) are different, the association may be performed using index information. That is, index information indicating the association between the equipment group for the data transmission function (PDSCH) and the equipment group for the control information transmission function (PDCCH) is generated in advance, and the generated index information is notified from the distributed base station device 302 to the terminal device 40. The index information may be notified in advance by RRC signaling at the time of handover, for example. Furthermore, the index information may include information indicating the equipment group for the corresponding PDSCH in a control signal transmitted from the equipment group for the PDCCH.

[0032] <2-2-4. Mobility Management> An apparatus group is a group defined when a mobility management function (terminal management function) that manages terminal apparatuses 40 is applied as a communication function. With the mobility management function, all distributed base station apparatuses 302 connected to the base station control apparatus 301 may cooperate to manage the terminal apparatuses 40. On the other hand, for example, if there is an anchor base station 30 that can form a wide-area cell such as a macrocell, the distributed base station apparatus 302 may not need to perform mobility management. Furthermore, apparatus groups with the mobility management function may also be associated with other apparatus groups using index information.

[0033] Fig. 11 is a diagram showing an example of index information. As shown in Fig. 11, the index information L may associate, for example, device groups each consisting of a plurality of distributed base station devices 302 listed for each communication function with each other. The index information L in Fig. 11 defines, for example, index information corresponding to a PDSCH device group as device group ID 1, index information corresponding to a PDSCH device group as device group ID 2, index information corresponding to a PDCCH device group as device group ID 3, index information corresponding to a PDCCH device group as device group ID 4, etc.

[0034] 2-2-5. Operational Example of Cooperative Communication FIG. 5 is a diagram illustrating an operational example of a communication system according to an embodiment of the present disclosure. As illustrated in FIG. 5, multiple distributed base station devices 302 execute cooperative communication with a terminal device 40. The cooperative communication may be, for example, communication using one or a combination of four transmission means described below. The first of the four transmission means is a transmission means in which each distributed base station device 302 adjusts its transmission timing and transmits signals so that they are received by the terminal device 40 at the same timing. The second of the four transmission means is a transmission means in which each distributed base station device 302 adjusts the phase of a transmission signal and transmits signals so that they are combined in phase at the terminal device 40. The third of the four transmission means is a transmission means in which each distributed base station device 302 adjusts frequency shift due to Doppler and transmits signals so that they are received by the terminal device 40 without frequency shift. The fourth of the four transmission means is a transmission means in which each distributed base station device 302 selects one or more distributed base station devices 302 from among the distributed base station devices 302 belonging to a device group and transmits the signals.

[0035] <2-2-6. Operation Example Relating to Multiple Terminal Devices> Figure 6 is a diagram illustrating an operation example of a communication system according to an embodiment of the present disclosure. As shown in Figure 6, the communication system 1 according to the embodiment includes multiple terminal devices 40. The multiple terminal devices 40 include a first terminal device 40a and a second terminal device 40b, and the first terminal device 40a and the second terminal device 40b belong to different device groups. In other words, there is a device group for the first terminal device 40a and a device group for the second terminal device 40b.

[0036] In this case, the device group for the first terminal device 40a and the device group for the second terminal device 40b may be a combination of the same distributed base station device 302, or a combination of different distributed base station devices 302. In the case of a combination of different distributed base station devices 302, one or more distributed base station devices 302 may be the same, or all of the distributed base station devices 302 may be different distributed base station devices 302.

[0037] 7 is a diagram illustrating an example of operation of a communication system according to an embodiment of the present disclosure. As shown in FIG. 7, a communication system 1 according to the embodiment includes a plurality of terminal devices 40, and each of the plurality of terminal devices 40 performs cooperative communication.

[0038] The operation of the communication system 1 shown in Fig. 7 is similar to the cooperative communication in the communication system 1 in Fig. 5, and similar to the communication with the multiple terminal devices 40 in the communication system 1 in Fig. 6. Furthermore, any of the operation examples of the communication system 1 of the present embodiment can be applied to the communication system 1 of the present embodiment even if multiple terminal devices 40 are present.

[0039] 2-3. Example Configuration of Base Station> Figure 8 is a diagram showing an example configuration of a base station according to an embodiment of the present disclosure. The base station 30 includes a wireless communication unit 31, a storage unit 32, and a control unit 33. Note that the configuration shown in Figure 8 is a functional configuration, and the hardware configuration may be different. In other words, as described above, the base station 30 includes a base station control device 301 and a distributed base station device 302, and the base station control device 301 and the distributed base station device 302 are realized by the wireless communication unit 31, the storage unit 32, and the control unit 33.

[0040] The wireless communication unit 31 is a signal processing unit for wireless communication with other wireless communication devices (for example, terminal device 40). The wireless communication unit 31 includes the antenna 313 and operates under the control of the control unit 33. The wireless communication unit 31 supports one or more wireless access methods and performs transmission and reception processing.

[0041] The storage unit 32 is a data readable / writable storage device such as a dynamic random access memory (DRAM), a static random access memory (SRAM), a flash memory, a hard disk, etc. The storage unit 32 functions as a storage means of the base station 30.

[0042] The control unit 33 is a controller that controls each unit of the base station 30 and functions as the base station control device 301. The control unit 33 is realized by a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). For example, the control unit 33 is realized by a processor executing various programs stored in a storage device inside the base station 30 using RAM or the like as a working area. The control unit 33 may also be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). A CPU, an MPU, an ASIC, and an FPGA can all be considered controllers. The control unit 33 may also be realized by a GPU (Graphics Processing Unit) in addition to or instead of a CPU.

[0043] 2-4. Example Configuration of Terminal Device FIG. 9 is a diagram illustrating an example configuration of a terminal device according to an embodiment of the present disclosure. The terminal device 40 wirelessly communicates with other communication devices, such as a base station 30. The terminal device 40 is, for example, a mobile phone, a smart device (smartphone or tablet), a PDA (Personal Digital Assistant), or a personal computer. The terminal device 40 may be a device such as a commercial camera equipped with a communication function, or may be a motorcycle or mobile broadcast vehicle equipped with a communication device such as an FPU (Field Pickup Unit). The terminal device 40 may also be an M2M (Machine to Machine) device or an IoT (Internet of Things) device.

[0044] Furthermore, the terminal device 40 is capable of cooperative communication with the base station 30. The terminal device 40 receives signals cooperatively transmitted by a plurality of distributed base station devices 302. Furthermore, the terminal device 40 communicates with the distributed base station devices 302 of the device group.

[0045] The terminal device 40 includes a wireless communication unit 41, a storage unit 42, and a control unit 43. Note that the configuration shown in Fig. 9 is a functional configuration, and the hardware configuration may be different from this. Furthermore, the functions of the terminal device 40 may be distributed and implemented in multiple physically separated components.

[0046] The wireless communication unit 41 is a signal processing unit for wireless communication with other wireless communication devices (for example, the base station 30 and other terminal devices 40). The wireless communication unit 41 includes an antenna 413 and operates under the control of the control unit 43. The wireless communication unit 41 may be the same as the wireless communication unit 31 of the base station 30. The wireless communication unit 41 supports one or more wireless access methods capable of cooperative communication, and performs transmission and reception processing.

[0047] The storage unit 42 is a data readable / writable storage device such as a DRAM, an SRAM, a flash memory, a hard disk, etc. The storage unit 42 functions as a storage means of the terminal device 40.

[0048] The control unit 43 is a controller that controls each unit of the terminal device 40. The control unit 43 is realized by a processor such as a CPU or an MPU. For example, the control unit 43 is realized by a processor executing various programs stored in a storage device inside the terminal device 40 using RAM or the like as a work area. The control unit 43 may also be realized by an integrated circuit such as an ASIC or an FPGA. A CPU, an MPU, an ASIC, and an FPGA can all be considered as controllers. The control unit 43 may also be realized by a GPU in addition to or instead of a CPU.

[0049] <2-4-1. Measurement> The terminal device 40 may receive a synchronization signal or a reference signal transmitted from each distributed base station device 302 belonging to the device group, and measure the amount of radio wave propagation delay, the amount of phase variation, the Doppler shift, etc. Here, the objects to be measured (CSI Measurement) are not limited to the amount of radio wave propagation delay, the amount of phase variation, and the Doppler shift, and other items may also be measured.

[0050] Here, the synchronization signal may be a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a Tertiary Synchronization Signal (TSS), a Synchronization Signal Block (SSB), etc. Note that the names of the synchronization signals are not limited to these. Also, the reference signal may be a Channel State Information-Reference Signal (CSI-RS), a De-Modulation Reference Signal (DMRS), a Phase Tracking Reference Signal (PTRS), a Tracking Reference Signal (TRS), etc. Note that the names of the reference signals are not limited to these.

[0051] The synchronization signal or reference signal may be transmitted from each distributed base station device 302 belonging to the device group at different frequencies or at different times, or may be transmitted at the same frequency or at the same time.

[0052] The execution cycle of the CSI measurement of the terminal device 40 may be periodic or aperiodic (for example, event triggered).

[0053] When performing measurement periodically, the terminal device 40 receives a synchronization signal or a reference signal transmitted at a predetermined timing and performs CSI measurement. The period may be a combination of multiple periods. Furthermore, the terminal device 40 may continuously perform CSI measurement.

[0054] When measurement is performed aperiodically, the terminal device 40 performs CSI measurement at the timing when a CSI measurement execution request is received from the distributed base station device 302. Furthermore, the terminal device 40 measures a CSI measurement execution trigger that has been notified or determined in advance, and performs CSI measurement at the timing when the trigger occurs. Examples of the trigger include when a predetermined time is reached, when the reception quality falls below a certain level, when the movement speed of the terminal device 40 increases, when the terminal device 40 starts moving, etc. Note that the trigger is not limited to these.

[0055] <2-4-2. Feedback> The terminal device 40 performs feedback (CSI Feedback) of the measurement results (CSI Measurement) to each distributed base station device 302 or base station control device 301 belonging to the device group at a predetermined timing.

[0056] The information to be fed back may be any one or more of the amount of radio wave propagation delay, the amount of phase variation, and the Doppler shift, but is not limited to these.

[0057] Furthermore, the information to be fed back may be specified by the base station 30. For example, when feedback of the amount of radio wave propagation delay is specified, the terminal device 40 feeds back only the amount of radio wave propagation delay to the base station 30. The information to be fed back may be notified from the base station 30 to the terminal device 40 by control information such as DCI or MAC CE. The information to be fed back may be included in a synchronization signal or a reference signal transmitted for CSI measurement and notified from the base station 30 to the terminal device 40.

[0058] For example, when CSI measurement is performed using a reference signal, the information to be fed back may be determined in association with the frequency resource, time resource, or orthogonal code or sequence on which the reference signal is transmitted.

[0059] Resources include Frequency, Time, Resource Element (including REG, CCE, and CORESET), Resource Block, Bandwidth Part, Component Carrier, Symbol, Sub-Symbol, Slot, Mini-Slot, Non-slot, Subslot, Subframe, Frame, PRACH occasion, Occasion, Code, Multi-access physical resource, Multi-access signature, and Subcarrier Spacing (Numerology).

[0060] The execution cycle of the feedback of the terminal device 40 may be periodic or aperiodic (for example, event triggered).

[0061] When feedback is performed periodically, the terminal device 40 transmits CSI feedback to the device group (source base station device group) that is the source before switching at a predetermined timing.

[0062] When feedback is performed aperiodically, the terminal device 40 transmits the CSI measurement result at the timing when a request for notification of the CSI measurement result is received from the source base station device group. The terminal device 40 measures a trigger for performing CSI measurement that is notified or determined in advance, and transmits CSI feedback at the timing of the trigger.

[0063] An example of a trigger is when the measured communication quality (e.g., RSRP: Reference Signal Received Power) of a candidate device group (target base station device group) that will be a target after switching becomes equal to or greater than a threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of a candidate target base station device group becomes equal to or less than a threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of a source base station device group becomes equal to or greater than a threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of a candidate source base station device group becomes equal to or less than a threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of a candidate target base station device group becomes better or worse than the measured communication quality (e.g., RSRP) of a candidate source base station device group. Another example of a trigger is when the measured communication quality (e.g., RSRP) of the target base station device group candidate becomes equal to or lower than a first threshold and the measured communication quality (e.g., RSRP) of the source base station device group becomes equal to or higher than a second threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of the target base station device group candidate becomes equal to or higher than a first threshold and the measured communication quality (e.g., RSRP) of the source base station device group becomes equal to or lower than a second threshold. Another example of a trigger is when the movement speed of the terminal device 40 becomes equal to or higher than a threshold. Another example of a trigger is when the movement speed of the terminal device 40 becomes equal to or lower than a threshold. Another example of a trigger is when a time synchronization error between the antennas 313 (hereinafter also referred to as distributed antennas 313) of the distributed base station devices 302 included in the measured source base station device group exceeds a predetermined value.Another example of a trigger is when the time synchronization deviation between the distributed antennas 313 included in the measured source base station device group becomes larger than the time synchronization deviation between the distributed antennas 313 included in the measured target base station device group. Another example of a trigger is when the time synchronization deviation between the distributed antennas 313 included in the measured source base station device group becomes larger than the time synchronization deviation between the distributed antennas 313 included in the measured target base station device group by at least Offset. Another example of a trigger is when the time synchronization deviation between the distributed antennas 313 included in the measured target base station device group becomes equal to or smaller than a predetermined value. Another example of a trigger is when the time synchronization deviation between the distributed antennas 313 included in the measured target base station device group becomes smaller than the time synchronization deviation between the distributed antennas 313 included in the measured source base station device group. Another example of a trigger is when the time synchronization deviation between the distributed antennas 313 included in the measured target base station device group becomes smaller than the time synchronization deviation between the distributed antennas 313 included in the measured source base station device group by at least Offset. Another example of a trigger is when a frequency synchronization error between the distributed antennas 313 included in the measured source base station device group exceeds a predetermined value. Another example of a trigger is when a frequency synchronization error between the distributed antennas 313 included in the measured source base station device group becomes larger than a frequency synchronization error between the distributed antennas 313 included in the measured target base station device group. Another example of a trigger is when a frequency synchronization error between the distributed antennas 313 included in the measured source base station device group becomes larger than a frequency synchronization error between the distributed antennas 313 included in the measured target base station device group by at least Offset. Another example of a trigger is when a frequency synchronization error between the distributed antennas 313 included in the measured target base station device group becomes equal to or smaller than a predetermined value. Another example of a trigger is when a frequency synchronization error between the distributed antennas 313 included in the measured target base station device group becomes smaller than a frequency synchronization error between the distributed antennas 313 included in the measured source base station device group.Another example of a trigger is when the frequency synchronization deviation between the distributed antennas 313 included in the target base station device group that has been measured becomes smaller by at least Offset than the frequency synchronization deviation between the distributed antennas 313 included in the source base station device group that has been measured.

[0064] <2-4-3. Measurement and Measurement Report for Determining Distributed Base Station Apparatus> Furthermore, the terminal device 40 may perform measurement and measurement report for information required for determining the distributed base station device 302 of the device group that will perform cooperative transmission.

[0065] A terminal device 40 connected to an apparatus group (herein described as a source base station apparatus group) to which multiple distributed base station apparatuses 302 belong may measure the downlink signal quality of the source base station apparatus group. Also, a terminal device 40 connected to the source base station apparatus group may measure the downlink signal quality of another apparatus group (herein described as one or more target base station apparatus group candidates).

[0066] The downlink signal quality is any one of RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength Indicator), and SINR (Signal to Interference plus Noise Ratio), but is not limited to these.

[0067] The downlink signal quality may be measured using synchronization signals (PSS, SSS, TSS, SSB) or reference signals (CSI-RS, DMRS, PTRS, TRS), etc. However, the measurement of the downlink signal quality is not limited to these.

[0068] In addition, the downlink signal quality may be measured by receiving signals cooperatively transmitted by the device group to which the distributed base station device 302 belongs, or may be measured for each distributed base station device 302 by receiving signals transmitted by each distributed base station device 302 belonging to the device group.

[0069] The execution cycle of the measurement of the terminal device 40 may be periodic or aperiodic (for example, event triggered).

[0070] When measurements are performed periodically, the terminal device 40 performs measurements at predetermined timing. The period may be a combination of multiple periods. Alternatively, the terminal device 40 may perform measurements continuously.

[0071] When measurements are performed aperiodically, the terminal device 40 performs measurements at the timing when it receives a measurement execution request from the source base station device group. Also, the terminal device 40 measures a measurement execution trigger that has been notified or determined in advance, and performs measurements at the timing when the trigger occurs. Examples of triggers include when a predetermined time arrives, when the reception quality falls below a certain level, when the moving speed of the terminal device 40 increases, when the terminal device 40 starts moving, etc.

[0072] The terminal device 40 feeds back, at a predetermined timing, a measurement report that is a measurement result of the downlink signal quality of the source base station device group that performed the measurement to the source base station device group. The terminal device 40 also feeds back, at a predetermined timing, a measurement report that is a measurement result of the downlink signal quality of one or more target base station device groups that performed the measurement to the source base station device group.

[0073] Examples of information in a Measurement report are described below. The following information may be reported as separate information for the measurement results of downlink signal quality of a source base station device group and the measurement results of downlink signal quality of a target base station device group, or may be reported at separate times. The information in the Measurement report includes SS-RSRP, CSI-RSRP, SS-RSRQ, CSI-RSRQ, SS-RSSI, CSI-RSSI, SS-SINR, CSI-SINR, etc.

[0074] The reporting cycle of the measurement report of the terminal device 40 may be periodic or aperiodic (for example, event triggered).

[0075] When the measurement report is executed periodically, the terminal device 40 transmits the measurement result to the source base station device group at a predetermined timing.

[0076] When measurement reports are executed aperiodically, the terminal device 40 transmits the measurement results at the timing when a request for notification of the measurement results is received from the source base station device group. The terminal device 40 measures a notified or determined trigger for measurement execution, and transmits a measurement report at the timing of the trigger.

[0077] An example of a trigger is when the measured communication quality (e.g., RSRP) of the target base station device group candidate becomes equal to or greater than a threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of the target base station device group candidate becomes equal to or less than a threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of the source base station device group becomes equal to or greater than a threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of the source base station device group becomes equal to or less than a threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of the target base station device group candidate becomes better or worse than the measured communication quality (e.g., RSRP) of the source base station device group. Another example of a trigger is when the measured communication quality (e.g., RSRP) of the target base station device group candidate becomes equal to or lower than a first threshold and the measured communication quality (e.g., RSRP) of the source base station device group becomes equal to or higher than a second threshold. Another example of a trigger is when the measured communication quality (e.g., RSRP) of the target base station device group candidate becomes equal to or higher than a first threshold and the measured communication quality (e.g., RSRP) of the source base station device group becomes equal to or lower than a second threshold. Another example of a trigger is when the movement speed of the terminal device 40 becomes equal to or higher than a threshold. Another example of a trigger is when the movement speed of the terminal device 40 becomes equal to or lower than a threshold. Another example of a trigger is when the time synchronization deviation between the distributed antennas 313 included in the measured source base station device group exceeds a predetermined value. Another example of a trigger is when the time synchronization deviation between the distributed antennas 313 included in the measured source base station device group becomes larger than the time synchronization deviation between the distributed antennas 313 included in the measured target base station device group.Another example of a trigger is when the time synchronization error between the distributed antennas 313 included in the measured source base station device group becomes larger by at least Offset than the time synchronization error between the distributed antennas 313 included in the measured target base station device group. Another example of a trigger is when the time synchronization error between the distributed antennas 313 included in the measured target base station device group becomes smaller than the time synchronization error between the distributed antennas 313 included in the measured source base station device group. Another example of a trigger is when the time synchronization error between the distributed antennas 313 included in the measured target base station device group becomes smaller than the time synchronization error between the distributed antennas 313 included in the measured source base station device group by at least Offset. Another example of a trigger is when the frequency synchronization error between the distributed antennas 313 included in the measured source base station device group exceeds a predetermined value. Another example of a trigger is when the frequency synchronization error between the distributed antennas 313 included in the measured source base station device group becomes larger than the frequency synchronization error between the distributed antennas 313 included in the measured target base station device group. Another example of a trigger is when the frequency synchronization error between the distributed antennas 313 included in the measured source base station device group becomes larger by at least Offset than the frequency synchronization error between the distributed antennas 313 included in the measured target base station device group. Another example of a trigger is when the frequency synchronization error between the distributed antennas 313 included in the measured target base station device group becomes equal to or smaller than a predetermined value. Another example of a trigger is when the frequency synchronization error between the distributed antennas 313 included in the measured target base station device group becomes smaller than the frequency synchronization error between the distributed antennas 313 included in the measured source base station device group. Another example of a trigger is when the frequency synchronization error between the distributed antennas 313 included in the measured target base station device group becomes smaller by at least Offset than the frequency synchronization error between the distributed antennas 313 included in the measured source base station device group.

[0078] <<3. Operation Example of Communication System According to Present Embodiment>> <3-1. Notification of List Information> Fig. 10 is a diagram illustrating an example of control of the communication system according to an embodiment of the present disclosure. The distributed base station device 302 of the device group notifies the terminal device 40 in advance of list information of the distributed base station devices 302 included in the device group. The list information is, for example, index information L shown in Fig. 11 .

[0079] 10 , the source base station device group connected to the terminal device 40 notifies the terminal device 40 of list information. After that, the terminal device 40 receives the notified list information and configures the distributed base station device 302 of the device group based on the list information. Then, the terminal device 40 notifies the source base station device group that the configuration of the distributed base station device 302 of the device group has been completed.

[0080] 12 is a diagram illustrating an example of control of the communication system according to an embodiment of the present disclosure. The distributed base station device 302 of the device group notifies the terminal device 40 of the ID information of the device group in advance. The ID information is, for example, the index information L shown in FIG. 11.

[0081] 12 , the source base station device group connected to the terminal device 40 notifies the terminal device 40 of ID information. After that, the terminal device 40 configures the distributed base station device 302 of the device group associated with the ID based on the notified ID information. Then, the terminal device 40 notifies the source base station device group that the configuration of the distributed base station device 302 of the device group has been completed.

[0082] 13 is a diagram illustrating an example of control of a communication system according to an embodiment of the present disclosure. The distributed base station device 302 of the device group reconfigures the distributed base station device 302 in the terminal device 40 at a predetermined timing or when a notification of reconfiguration of the distributed base station device 302 is received.

[0083] 13 , the source base station device group connected to the terminal device 40 notifies the terminal device 40 of information related to a setting change of the distributed base station device 302. After that, the terminal device 40 reconfigures the distributed base station device 302 of the device group based on the notified information related to the setting change. Then, the terminal device 40 notifies the source base station device group that the reconfiguration of the distributed base station device 302 of the device group has been completed.

[0084] <3-4. Determination of Distributed Base Station Devices Based on QCL Information> The distributed base station devices 302 included in an device group may be determined based on Quasi Co-Location (QCL) information (which may also be referred to as quasi-co-location, TCI (Transmission Configuration Indication), etc., but is not particularly limited to this). In other words, the list information may list the distributed base station devices 302 grouped based on the QCL information as device groups.

[0085] The QCL information may be information indicating that one or more of the following are the same channel characteristics: Doppler Shift, Doppler Spread, Average Delay, Delay Spread, Spatial Receiver Parameter, etc.

[0086] 17 and 18 are diagrams showing examples of information on channel characteristics included in the QCL information. As the QCL information, for example, information as shown in FIGS. 17 and 18 may be notified from the base station 30 to the terminal device 40. Furthermore, the QCL information notified from the base station 30 to the terminal device 40 may be one or more pieces of information included in the diagrams shown in FIGS. 17 and 18.

[0087] In the QCL information shown in Fig. 17, QCL-TypeA includes Doppler Shift, Doppler Spread, Average Delay, and Delay Spread, QCL-TypeB includes Doppler Shift and Doppler Spread, QCL-TypeC includes Average Delay and Doppler Shift, QCL-TypeD includes Spatial Receiver Parameter, QCL-TypeE includes Average Delay, and QCL-TypeF includes Doppler Shift. In the QCL information shown in Fig. 18, QCL-TypeA includes Doppler Shift, QCL-TypeB includes Doppler Spread, QCL-TypeC includes Average Delay, and QCL-TypeD includes Delay Spread.

[0088] For example, in the QCL information shown in FIG. 18, when QCL-TypeA and QCL-TypeC are notified from the base station 30 to the terminal device 40, the terminal device 40 determines that the channel characteristics of Doppler Shift and Average Delay can be considered to be the same.

[0089] 3.5. Handover of Device Groups In the communication system 1 according to the embodiment, the terminal device 40 moves between device groups as shown in Fig. 3. At this time, the terminal device 40 executes handover processing to switch device groups.

[0090] Hereinafter, the handover process accompanying the movement of the terminal device 40 will be described.

[0091] 14 is a diagram illustrating an example of control of the communication system according to an embodiment of the present disclosure, specifically, a sequence diagram for explaining an example of a flow of handover. FIG. 14 illustrates a case where a terminal device 40 performs handover from a source base station device group, which is a handover source, to a target base station device group, which is a handover destination.

[0092] As shown in FIG. 14, the terminal device 40 performs measurement (measurement control) to measure the state of communication quality and the like, and transmits a measurement report to the source base station device group and the target base station device group.

[0093] The source base station device group determines whether or not handover of the terminal device 40 is necessary, i.e., whether or not switching of the base station device group is necessary, based on a measurement report of communication quality, etc. If the source base station device group determines that handover is necessary, it transmits a switching notification regarding a switching request to the target base station device group, i.e., requests handover.

[0094] Upon receiving the handover request, the target base station device group performs admission control and notifies the source base station device group of an acknowledgement for the handover request.

[0095] Next, the source base station device group transmits an RRC Reconfiguration including a handover command to the terminal device 40, notifying it of the execution of handover.

[0096] Upon receiving the RRC Reconfiguration, the terminal device 40 detaches from the source base station device group (cancels the communication connection) and executes an initial access procedure with the target base station device group. For example, the terminal device 40 transmits a PRACH (Physical Random Access Channel) to the target base station device group.

[0097] The target base station device group transmits a Random Access response to the terminal device 40. Thereafter, the terminal device 40 transmits an RRC reconfiguration complete to the target base station device group, and when the target base station device group receives the RRC reconfiguration complete, the initial access procedure is completed, and when communication connection is established, the handover process is completed.

[0098] 14, the terminal device 40 starts handover at the timing when it receives a handover command from the source base station device group. In other words, this is a base station device group-initiated handover sequence.

[0099] 15 is a diagram illustrating an example of operation of a communication system according to an embodiment of the present disclosure. As illustrated in FIG. 15, in the communication system 1 according to the embodiment, a terminal device 40 moves between device groups. At this time, if a switching condition is satisfied, the terminal device 40 executes a handover process to switch device groups.

[0100] Hereinafter, a conditional handover process accompanying movement of the terminal device 40 will be described.

[0101] 16 is a diagram illustrating an example of control of a communication system according to an embodiment of the present disclosure, specifically, a sequence diagram for explaining an example of a handover flow. Fig. 16 illustrates a case where a terminal device 40 performs handover from a source base station group, which is a handover source, to a first target base station group #1 or a second target base station group #2, which is a handover destination.

[0102] As shown in FIG. 16, the terminal device 40 performs measurement (measurement control) to measure the state of communication quality and the like, and transmits a measurement report to the source base station device group.

[0103] The source base station device group determines whether a conditional handover of the terminal device 40 is necessary, i.e., whether a base station device group switch is necessary, based on a measurement report of communication quality, etc. If the source base station device group determines that a handover is necessary, it transmits a switch notification regarding a switch request to the first target base station device group #1 and the second target base station device group #2, i.e., requests a handover.

[0104] Upon receiving the handover request, each of the first target base station device group #1 and the second target base station device group #2 performs admission control and notifies the source base station device group of an acknowledgement for the handover request.

[0105] Subsequently, the source base station device group notifies the terminal device 40 of the execution of handover by transmitting an RRC Reconfiguration including a handover command to the terminal device 40. This RRC Reconfiguration includes, for example, information related to handover for evaluating a switching condition.

[0106] Upon receiving the RRC Reconfiguration, the terminal device 40 transmits an RRC Reconfiguration complete to the source base station device group, and evaluates a trigger for performing a conditional handover (an execution trigger).

[0107] The terminal device 40 evaluates the implementation trigger, and when the implementation trigger is detected to determine that the switching condition is satisfied, the terminal device 40 detaches from the source base station device group and starts an initial connection procedure with the handover destination base station device group. Note that in Fig. 16, it is assumed that the first target base station device group #1 is detected as the handover destination base station.

[0108] The terminal device 40 transmits a PRACH (Physical Random Access Channel) to the first target base station device group #1.

[0109] The first target base station device group #1 transmits a Random Access response to the terminal device 40. Thereafter, the terminal device 40 transmits an RRC Reconfiguration complete to the first target base station device group #1, and when the first target base station device group #1 receives the RRC Reconfiguration complete, the initial access procedure and handover processing are completed.

[0110] The first target base station device group #1, which has completed the initial connection procedure and connected to the terminal device 40, notifies the source base station device group of "Handover Success," indicating that the handover was successful. The source base station device group, which has received the "Handover Success" notification, cancels the handover to the second target base station device group #2, which was not selected as the handover destination, by notifying "Handover Cancel" to the second target base station device group #2.

[0111] 16, the source base station device group does not determine the target base station device group as the handover destination, but notifies the terminal device 40 of the candidate target base station device groups. As a result, the terminal device 40 selects the target base station device group that can be connected at the time of the handover and performs the handover. In other words, this is a terminal device-driven handover sequence.

[0112] Trigger Evaluation The trigger used in the conditional handover described above includes handover-related information for evaluating a switching condition for a source base station group, and also includes handover-related information for evaluating a switching condition for a target base station group candidate.

[0113] The trigger may include, for example, the following information. An example of a trigger is information that the measured communication quality (e.g., RSRP) of the target base station device group candidate is equal to or higher than a threshold. An example of a trigger is information that the measured communication quality (e.g., RSRP) of the source base station device group candidate is equal to or lower than a threshold. An example of a trigger is information that the measured communication quality (e.g., RSRP) of the source base station device group candidate is equal to or lower than an offset from the measured communication quality (e.g., RSRP) of the target base station device group candidate. An example of a trigger is information that the measured communication quality (e.g., RSRP) of the target base station device group candidate is equal to or higher than an offset from the measured communication quality (e.g., RSRP) of the source base station device group. An example of a trigger is information that the measured communication quality (e.g., RSRP) of the source base station device group is worse in reception quality than the measured communication quality (e.g., RSRP) of the target base station device group candidate. An example of a trigger is information that the measured communication quality (e.g., RSRP) of the target base station device group candidate is better in reception quality than the measured communication quality (e.g., RSRP) of the source base station device group. An example of a trigger is information that a time synchronization error between the distributed antennas 313 included in the source base station device group has exceeded a predetermined value.An example of a trigger is information that a time synchronization error between the distributed antennas 313 included in the source base station device group has become larger than a time synchronization error between the distributed antennas 313 included in the target base station device group.An example of a trigger is information that a time synchronization error between the distributed antennas 313 included in the source base station device group has become larger than a time synchronization error between the distributed antennas 313 included in the target base station device group by at least Offset.An example of a trigger is information that a time synchronization error between the distributed antennas 313 included in the target base station device group has become equal to or smaller than a predetermined value.An example of a trigger is information that a time synchronization error between the distributed antennas 313 included in the target base station device group has become smaller than a time synchronization error between the distributed antennas 313 included in the source base station device group.An example of a trigger is information that the time synchronization error between the distributed antennas 313 included in the target base station device group has become smaller by at least Offset than the time synchronization error between the distributed antennas 313 included in the source base station device group. An example of a trigger is information that the frequency synchronization error between the distributed antennas 313 included in the source base station device group has exceeded a predetermined value. An example of a trigger is information that the frequency synchronization error between the distributed antennas 313 included in the source base station device group has become larger than the frequency synchronization error between the distributed antennas 313 included in the target base station device group. An example of a trigger is information that the frequency synchronization error between the distributed antennas 313 included in the source base station device group has become larger by at least Offset than the frequency synchronization error between the distributed antennas 313 included in the target base station device group. An example of a trigger is information that the frequency synchronization error between the distributed antennas 313 included in the target base station device group has become smaller than the frequency synchronization error between the distributed antennas 313 included in the source base station device group. An example of the trigger is information that the frequency synchronization error between the distributed antennas 313 included in the target base station device group has become smaller than the frequency synchronization error between the distributed antennas 313 included in the source base station device group by at least Offset.

[0114] For the communication quality, time synchronization, or frequency synchronization error of at least one of the source base station device group and the target base station device group, a reference resource for measurement may be defined, and measurement may be performed at a predetermined time and frequency.

[0115] In addition, in a conditional handover, information required at the time of or after switching may be notified to the terminal device 40 from the source base station device group.

[0116] Examples of information required for conditional handover may include one or more of the following information:

[0117] The information relating to the procedure for conditional handover to the target base station device group includes, for example, the following information: The information relating to the procedure for conditional handover includes a PRACH transmission resource of the target base station device group candidate, a PRACH transmission preamble sequence of the target base station device group candidate, a cell ID of the target base station device group candidate, an uplink / downlink carrier frequency of the target base station device group candidate, a bandwidth of the target base station device group candidate, a terminal-specific ID (C-RNTI) after handover to the target base station device group, a radio resource configuration after handover to the target base station device group, a condition for updating the information set relating to handover to the target base station device group, trigger information for performing handover to the target base station device group, timing advance information of the target base station device group candidate, an SSB index of the target base station device group candidate, information relating to the transmission weight, and information relating to 2-STEP initial access.

[0118] The trigger-related information used for the conditional handover to the target base station group includes, for example, the following information: The trigger-related information includes RSRP information of the target base station group candidate, RSRQ information of the target base station group candidate, RSSI information of the target base station group candidate, timer information related to the execution of base station group switching handover of the target base station group candidate, information related to the start time of the execution of base station group switching handover of the target base station group candidate, information related to the start time of the execution of the base station group switching handover execution trigger detection operation of the target base station group candidate, information related to the operation after the timer related to the execution of base station group switching handover of the target base station group candidate expires, the operation when a synchronization signal of a cell other than the target base station group candidate is received, information related to the time synchronization of the target base station group, information related to the frequency synchronization of the target base station group, and information related to the transmission power of the target base station group.

[0119] The information relating to the execution of detachment from the source base station device group includes, for example, the following information: The information relating to the execution of detachment includes RSRP information of the source base station device group, RSRQ information of the source base station device group, RSSI information of the source base station device group, information relating to the timer for executing detachment from the source base station device group, information relating to the time for executing detachment from the source base station device group, information relating to the time synchronization of the source base station device group, information relating to the frequency synchronization of the source base station device group, and information relating to the transmission power of the source base station device group.

[0120] <<4. Modifications>> <4-1. Example of Base Station Configuration> The functions of the base station 30 of this embodiment may be separated into multiple functions, such as a CU (Central Unit), a DU (Distributed Unit), and an RU (Radio Unit). In this case, the base station control device 301 and the distributed base station device 302 have hardware configurations according to the separated functions. The following describes the CU / DU / RU separation of the functions of the base station 30.

[0121] 19 is a diagram showing an example of CU / DU / RU separation of the functions of a base station 30. In the current standard, the functions of a base station (e.g., gNB) are separated into two, a CU (Central Unit) and a DU (Distributed Unit). Here, the DU may include some or all of the functions known as RRH (Radio Remote Head), RRU (Remote Radio Unit), and RU (Radio Unit), as they were called in 3GPP LTE.

[0122] The boundary between the CU and DU (also called the split point or division point) is set between the Packet Data Convergence Protocol (PDCP) layer and the Radio Link Control (RLC) layer (Option 2) in the 3GPP protocol stack, as shown by F1 in FIG. 19 . To establish communication between the CU and DU, 3GPP defines "F1" as the interface between these units. This interface is a logical interface. Communication between the CU and DU is established by IP packets passing through, for example, Ethernet (registered trademark) (IEEE 802.3).

[0123] The base station 30 processes the MAC layer (Media Access Control Layer) and above by, for example, making a central control entity (e.g., CU or DU) function as a base station control device 301. The base station 30 may also process the PHY layer and below by, for example, making a group of transmitting antennas serving as transmission points function as a distributed base station device 302.

[0124] As an example, separation such as Option A to Option E shown in Fig. 19 can be considered. Note that the separation of functions is not limited to the examples shown below. Option A: An example of separating CU and DU / RU using Option 2 Option B: An example of separating CU / DU and RU using Option 7 Option C: An example of separating CU / DU and RU using Option 8 Option D: An example of separating CU and DU using Option 2, and DU and RU using Option 7 Option E: An example of separating CU and DU using Option 2, and DU and RU using Option 8

[0125] 19 , the CU functions as the base station control device 301, and the DU / RU functions as the distributed base station device 302. In Option B and Option C, the CU / DU functions as the base station control device 301, and the RU functions as the distributed base station device 302. In Option D and Option E, the DU functions as the base station control device 301, and the RU functions as the distributed base station device 302.

[0126] <<5. Other Embodiments>> The processing according to each of the above-described embodiments may be executed in various different forms other than the above-described embodiments.

[0127] For example, among the processes described in the above embodiments, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically using a known method. Furthermore, the information including the processing procedures, specific names, various data, and parameters shown in the above documents and drawings can be changed as desired unless otherwise specified. For example, the various information shown in each drawing is not limited to the information shown in the drawings.

[0128] Furthermore, the components of each device shown in the figure are conceptual functional components and do not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each device is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0129] Furthermore, the above-described embodiments and modifications can be combined as appropriate within the scope of not causing any contradiction in the processing content.

[0130] Furthermore, the effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0131] <<6. Effects>> As described above, the distributed base station device (distributed base station device 302 in the embodiment) according to the present disclosure is a distributed base station device including a communication unit (wireless communication unit 31 in the embodiment) that communicates with a terminal device (terminal device 40 in the embodiment), the terminal device performing cooperative communication with a plurality of the distributed base station devices, and the communication unit transmits list information regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices to the terminal device.

[0132] In this way, the distributed base station device of the present disclosure can connect the terminal device to an appropriate device group by notifying the terminal device of list information, even when the terminal device moves and performs cooperative communication with multiple distributed base station devices, thereby improving communication quality.

[0133] In addition, in a distributed base station device, the device group is formed according to a communication function, the list information is generated for each communication function, and the communication function includes at least one of a data transmission function for transmitting data to the terminal device, a control information transmission function for transmitting control information to the terminal device, a quality control function for managing the quality of communication services, and a terminal management function for managing the terminal device.

[0134] In this way, distributed base station devices are divided into device groups according to their communication functions, so that terminal devices can be connected to device groups that have the communication functions required for the terminal devices, thereby improving communication quality.

[0135] Further, in the distributed base station device, the device group is formed according to a communication function, the list information is generated for each of the communication functions, and includes first list information associated with the first of the communication functions and second list information associated with the second of the communication functions, and the communication unit transmits index information associating the distributed base station device included in the first list information with the distributed base station device included in the second list information to the terminal device.

[0136] In this way, by notifying the terminal device of index information, the distributed base station device can connect the terminal device to a device group that has the communication functions required by the terminal device, thereby improving communication quality.

[0137] In addition, in the distributed base station device, the plurality of distributed base station devices included in the device group have the same channel characteristics.

[0138] In this way, the distributed base station device has the same channel characteristics as the other distributed base station devices included in the device group, so that an appropriate device group corresponding to the communication function can be formed, thereby improving communication quality.

[0139] Furthermore, in the distributed base station device, the plurality of distributed base station devices included in the device group have different channel characteristics.

[0140] In this way, since the distributed base station device has different channel characteristics from the other distributed base station devices included in the device group, it is possible to form an appropriate device group corresponding to the communication function, thereby improving communication quality.

[0141] In addition, in a distributed base station device, the terminal device performs cooperative communication with multiple distributed base station devices included in the device group and performs measurements related to the cooperative communication, and the communication unit receives measurement results related to the cooperative communication measured in the terminal device.

[0142] In this way, the distributed base station device can receive the measurement results of the cooperative communication, and therefore can obtain information necessary for connection with the terminal device.

[0143] In addition, in the distributed base station device, when it is determined to switch to another device group based on the received measurement results, the communication unit transmits a switching notification regarding a switching request to the other device group that is the target.

[0144] In this way, the distributed base station device can appropriately switch and connect the terminal device to another device group by transmitting a switch notification to the other device group.

[0145] In addition, in the distributed base station device, the list information is information in which the distributed base station devices are grouped based on QCL information, which is information on quasi-colocation, and are listed as device groups.

[0146] In this way, the distributed base station devices are grouped into appropriate device groups based on the QCL information.

[0147] In addition, the base station control device (in the embodiment, base station control device 301) according to the present disclosure is a base station control device that includes a control unit (in the embodiment, control unit 33) that controls distributed base station devices that communicate with terminal devices, and the control unit transmits list information that lists the distributed base station devices by dividing them into multiple device groups based on their functions, each group consisting of one or more of the distributed base station devices, to the terminal device via the distributed base station device.

[0148] In this way, the base station control device of the present disclosure can connect the terminal device to an appropriate device group by notifying the terminal device of list information, even when the terminal device moves and performs cooperative communication with multiple distributed base station devices, thereby improving communication quality.

[0149] In addition, a terminal device (terminal device 40 in an embodiment) according to the present disclosure is a terminal device equipped with a control unit (control unit 43 in an embodiment) that performs cooperative communication with a plurality of distributed base station devices, and the control unit receives list information from the distributed base station device regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices.

[0150] In this way, even when a terminal device according to the present disclosure is moving and performing cooperative communication with multiple distributed base station devices, it can connect to an appropriate device group based on list information, thereby improving communication quality.

[0151] Furthermore, in the terminal device, the control unit executes measurements related to the cooperative communication, acquires measurement results, and transmits the acquired measurement results to the distributed base station device.

[0152] In this way, the terminal device can transmit the measurement results of the cooperative communication to the distributed base station device, and the distributed base station device can obtain information necessary for connection with the terminal device.

[0153] In addition, in the terminal device, when the control unit receives a switching notification regarding a switching request sent from the distributed base station device, it terminates the communication connection with the distributed base station device that is the source of the switching and establishes a communication connection with the distributed base station device that is the destination of the switching based on the received switching notification.

[0154] In this way, the terminal device can switch to and connect to another more appropriate device group, thereby improving communication quality.

[0155] In addition, in the terminal device, when the control unit receives a switching notification regarding a switching request transmitted from the distributed base station device, it determines whether the switching conditions for switching to the distributed base station device to be switched to are met, and if it determines that the switching conditions are met, it terminates the communication connection with the distributed base station device to be switched to and establishes a communication connection to the distributed base station device to be switched to.

[0156] In this way, the terminal device can switch to and connect to another more appropriate device group based on the switching conditions, thereby improving communication quality.

[0157] In the terminal device, the switching conditions include at least one of communication quality, time synchronization deviation, and frequency synchronization deviation.

[0158] In this way, the terminal device can switch to another device group taking into consideration communication quality, time synchronization deviation, and frequency synchronization deviation.

[0159] In addition, the communication control method for a distributed base station device according to the present disclosure is a communication control method for a distributed base station device executed by a distributed base station device that communicates with a terminal device, wherein the terminal device is engaged in cooperative communication with a plurality of the distributed base station devices, and the distributed base station device transmits list information to the terminal device regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices.

[0160] In this way, the communication control method for a distributed base station device according to the present disclosure can connect a terminal device to an appropriate device group by notifying the terminal device of list information, even when the terminal device moves and performs cooperative communication with multiple distributed base station devices, thereby improving communication quality.

[0161] In addition, the communication control method for a base station control device according to the present disclosure is a communication control method for a base station control device executed by a base station control device that controls a distributed base station device that communicates with a terminal device, in which the base station control device generates list information that lists a plurality of the distributed base station devices by grouping them into a plurality of device groups based on function, each group consisting of one or more of the distributed base station devices, and transmits the generated list information to the terminal device via the distributed base station device.

[0162] In this way, the communication control method of the base station control device according to the present disclosure can connect the terminal device to an appropriate device group by notifying the terminal device of list information, even when the terminal device moves and performs cooperative communication with multiple distributed base station devices, thereby improving communication quality.

[0163] In addition, the communication control method for a terminal device according to the present disclosure is a communication control method for a terminal device executed by a terminal device that performs cooperative communication with a plurality of distributed base station devices, in which the terminal device receives list information from the distributed base station device regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices.

[0164] In this way, the communication control method for a terminal device according to the present disclosure can improve communication quality by connecting to an appropriate device group based on list information, even when performing cooperative communication with multiple distributed base station devices while moving.

[0165] <<7. Hardware Configuration>> Information devices such as the base station 30, base station control device 301, and distributed base station device 302 according to each of the above-described embodiments are realized by a computer 1000 configured as shown in FIG. 20, for example. The following description will be given using a communication system 1 according to the embodiments as an example. FIG. 20 is a hardware configuration diagram showing an example of the computer 1000 that realizes the functions of the base station 30. The computer 1000 has a CPU 1100, a RAM 1200, a ROM (Read Only Memory) 1300, a HDD (Hard Disk Drive) 1400, a communication interface 1500, and an input / output interface 1600. The components of the computer 1000 are connected by a bus 1050.

[0166] The CPU 1100 operates and controls each component based on programs stored in the ROM 1300 or the HDD 1400. For example, the CPU 1100 loads the programs stored in the ROM 1300 or the HDD 1400 into the RAM 1200 and executes processing corresponding to the various programs.

[0167] The ROM 1300 stores boot programs such as a Basic Input Output System (BIOS) that is executed by the CPU 1100 when the computer 1000 is started, and programs that depend on the hardware of the computer 1000 .

[0168] HDD 1400 is a computer-readable recording medium that non-temporarily records programs executed by CPU 1100 and data used by such programs. Specifically, HDD 1400 is a recording medium that records a program according to the present disclosure, which is an example of program data 1450.

[0169] The communication interface 1500 is an interface for connecting the computer 1000 to an external network 1550 (e.g., the Internet). For example, the CPU 1100 receives data from other devices and transmits data generated by the CPU 1100 to other devices via the communication interface 1500.

[0170] The input / output interface 1600 is an interface for connecting the input / output device 1650 and the computer 1000. For example, the CPU 1100 receives data from an input device such as a keyboard or a mouse via the input / output interface 1600. The CPU 1100 also transmits data to an output device such as a display, a speaker, or a printer via the input / output interface 1600. The input / output interface 1600 may also function as a media interface for reading programs and the like recorded on a predetermined recording medium. Examples of media include optical recording media such as a DVD (Digital Versatile Disc) or a PD (Phase Change Rewritable Disc), magneto-optical recording media such as an MO (Magneto-Optical Disk), tape media, magnetic recording media, and semiconductor memories.

[0171] For example, when the computer 1000 functions as the base station control device 301 according to the embodiment, the CPU 1100 of the computer 1000 executes a program loaded onto the RAM 1200 to realize functions such as the control unit 33. The HDD 1400 stores various programs used by the base station control device 301 according to the present disclosure and data in the storage unit 32. The CPU 1100 reads and executes program data 1450 from the HDD 1400, but as another example, the CPU 1100 may obtain these programs from another device via an external network 1550.

[0172] As described above, the present disclosure can also take the following configurations. (1) A distributed base station device including a communication unit that communicates with a terminal device, wherein the terminal device is performing cooperative communication with a plurality of the distributed base station devices, and the communication unit transmits, to the terminal device, list information relating to a list of the distributed base station devices included in a device group made up of one or more of the distributed base station devices. (2) The device group is formed according to communication functions, and the list information is generated for each of the communication functions, and the communication functions include at least one of a data transmission function that transmits data to the terminal device, a control information transmission function that transmits control information to the terminal device, a quality management function that manages the quality of communication services, and a terminal management function that manages the terminal device. (3) The distributed base station device according to (1) or (2), wherein the device group is formed according to communication functions, the list information is generated for each of the communication functions and includes first list information associated with the first communication function and second list information associated with the second communication function, and the communication unit transmits index information associating the distributed base station devices included in the first list information with the distributed base station devices included in the second list information to the terminal device. (4) The distributed base station device according to any one of (1) to (3), wherein the multiple distributed base station devices included in the device group have the same channel characteristics. (5) The distributed base station device according to any one of (1) to (3), wherein the multiple distributed base station devices included in the device group have different channel characteristics. (6) The distributed base station device according to any one of (1) to (5), wherein the terminal device performs cooperative communication with the multiple distributed base station devices included in the device group and performs measurements related to the cooperative communication, and the communication unit receives measurement results related to the cooperative communication measured in the terminal device.(7) The distributed base station device according to (6), wherein, when it is determined to switch to another device group based on the received measurement result, the communication unit transmits a switch notification regarding a switch request to the other device group as a target. (8) The distributed base station device according to any one of (1) to (7), wherein the list information is information that lists the distributed base station devices grouped based on QCL information that is information about pseudo collocation, as the device groups. (9) A base station control device comprising a control unit that controls distributed base station devices that communicate with a terminal device, wherein the control unit transmits list information that lists the plurality of distributed base station devices grouped into a plurality of device groups for each function, each group consisting of one or more of the distributed base station devices, to the terminal device via the distributed base station device. (10) A terminal device that performs cooperative communication with a plurality of distributed base station devices, wherein the control unit receives list information regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices from the distributed base station device. (11) The terminal device according to (10), wherein the control unit performs measurements related to the cooperative communication, acquires measurement results, and transmits the acquired measurement results to the distributed base station device. (12) The terminal device according to (10) or (11), wherein, upon acquiring a switching notification related to a switching request transmitted from the distributed base station device, the control unit terminates a communication connection with the distributed base station device that is a switching source, and establishes a communication connection with the distributed base station device that is a switching destination based on the acquired switching notification. (13) The terminal device according to (10) or (11), wherein, upon acquiring a switching notification related to a switching request transmitted from the distributed base station device, the control unit determines whether a switching condition for switching to the distributed base station device that is a switching destination is satisfied, and, upon determining that the switching condition is satisfied, terminates the communication connection with the distributed base station device that is a switching source, and establishes a communication connection with the distributed base station device that is a switching destination. (14) The terminal device according to (13), wherein the switching condition includes at least one of communication quality, time synchronization deviation, and frequency synchronization deviation.(15) A communication control method for a distributed base station device executed by a distributed base station device that communicates with a terminal device, wherein the terminal device is performing cooperative communication with a plurality of the distributed base station devices, and the distributed base station device transmits list information regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices to the terminal device. (16) A communication control method for a base station control device executed by a base station control device that controls a distributed base station device that communicates with a terminal device, wherein the base station control device generates list information that lists the plurality of distributed base station devices by grouping them into a plurality of device groups each consisting of one or more of the distributed base station devices, and transmits the generated list information to the terminal device via the distributed base station device. (17) A communication control method for a terminal device executed by a terminal device that performs cooperative communication with a plurality of distributed base station devices, wherein the terminal device receives list information regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices from the distributed base station device.

[0173] REFERENCE SIGNS LIST 1 Communication system 20 Core network 30 Base station 301 Base station control device 302 Distributed base station device 40 Terminal device

Claims

1. A distributed base station device having a communication unit that communicates with a terminal device, wherein the terminal device is engaged in cooperative communication with a plurality of the distributed base station devices, and the communication unit transmits list information to the terminal device regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices.

2. The distributed base station device of claim 1, wherein the device groups are formed according to communication functions, the list information is generated for each of the communication functions, and the communication functions include at least one of a data transmission function for transmitting data to the terminal device, a control information transmission function for transmitting control information to the terminal device, a quality management function for managing the quality of communication services, and a terminal management function for managing the terminal device.

3. The distributed base station device of claim 1, wherein the device group is formed according to a communication function, the list information is generated for each of the communication functions, and includes first list information associated with the first of the communication functions and second list information associated with the second of the communication functions, and the communication unit transmits index information associating the distributed base station device included in the first list information with the distributed base station device included in the second list information to the terminal device.

4. The distributed base station device according to claim 1, wherein the plurality of distributed base station devices included in the device group have the same channel characteristics.

5. The distributed base station device according to claim 1, wherein the plurality of distributed base station devices included in the device group have different channel characteristics.

6. The distributed base station device of claim 1, wherein the terminal device performs cooperative communication with multiple distributed base station devices included in the device group and performs measurements related to the cooperative communication, and the communication unit receives measurement results related to the cooperative communication measured in the terminal device.

7. The distributed base station device of claim 6, wherein the communication unit, when it determines to switch to another device group based on the received measurement results, transmits a switching notification regarding a switching request to the other device group that is the target.

8. The distributed base station device according to claim 1, wherein the list information is information that lists the distributed base station devices grouped based on QCL information, which is information about pseudo-colocation, as device groups.

9. A base station control device comprising a control unit that controls a distributed base station device that communicates with a terminal device, wherein the control unit transmits list information that lists a plurality of the distributed base station devices by grouping them into a plurality of device groups each consisting of one or more of the distributed base station devices to the terminal device via the distributed base station device.

10. A terminal device that performs cooperative communication with multiple distributed base station devices and is equipped with a control unit, wherein the control unit receives list information from the distributed base station device regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices.

11. The terminal device according to claim 10, wherein the control unit performs measurements related to the cooperative communication, acquires measurement results, and transmits the acquired measurement results to the distributed base station device.

12. The terminal device of claim 10, wherein, when the control unit receives a switching notification regarding a switching request transmitted from the distributed base station device, it terminates the communication connection with the distributed base station device that is the source of the switching and establishes a communication connection with the distributed base station device that is the destination of the switching based on the received switching notification.

13. The terminal device according to claim 10, wherein, when the control unit receives a switching notification regarding a switching request transmitted from the distributed base station device, it determines whether or not the switching conditions for switching to the distributed base station device to be switched to are met, and if it determines that the switching conditions are met, it terminates the communication connection with the distributed base station device to be switched to and establishes a communication connection with the distributed base station device to be switched to.

14. The terminal device according to claim 13, wherein the switching conditions include at least one of communication quality, time synchronization deviation, and frequency synchronization deviation.

15. A communication control method for a distributed base station device executed by a distributed base station device that communicates with a terminal device, wherein the terminal device is performing cooperative communication with a plurality of the distributed base station devices, and the distributed base station device transmits list information regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices to the terminal device.

16. A communication control method for a base station control device executed by a base station control device that controls distributed base station devices that communicate with terminal devices, in which the base station control device generates list information that lists multiple distributed base station devices by grouping them into multiple device groups for each function, each group consisting of one or more distributed base station devices, and transmits the generated list information to the terminal devices via the distributed base station device.

17. A communication control method for a terminal device executed by a terminal device that performs cooperative communication with multiple distributed base station devices, wherein the terminal device receives list information from the distributed base station device regarding a list of the distributed base station devices included in a device group consisting of one or more of the distributed base station devices.

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