Terminal, base station and wireless communication method

Abstract

Provided is a terminal including: a reception unit which receives, from a base station, a measurement setting for associating information indicating a target cell in which predetermined processing is to be performed with a condition setting indicating a condition for starting the predetermined processing; a measurement unit which measures the reception quality of a cell; and a control unit which starts the predetermined processing corresponding to the condition setting when the measured cell is included in the target cell and the reception quality of the measured cell satisfies the condition for starting the predetermined processing.

Description

[Technical field]

[0001] The present invention relates to a terminal, a base station, and a wireless communication method. [Background technology]

[0002] 3GPP (3rd Generation Partnership Project), an international standardization organization, is studying NR (New Radio), a new radio access technology for 5th generation (5G) cellular systems. NR is a technology that is being studied to realize a wider variety of services than LTE and LTE-Advanced, which are 4th generation (4G) cellular systems (Non-Patent Document 1).

[0003] For example, NR defines different usage scenarios as requirements for realization, such as eMBB (enhanced Mobile Broadband) which realizes high-speed, large-capacity communications, URLLC (Ultra-Reliable and Low Latency Communication) which realizes ultra-reliable, low-latency communications, and mMTC (massive Machine Type Communication) which realizes simultaneous connections of multiple Internet of Things (IoT) devices.

[0004] A wireless communication system is provided with a handover procedure for moving between cells without disconnecting communication. Also, a conditional handover procedure is being considered for setting cell information of the handover destination in advance, with the aim of increasing the robustness (stability) of handover. The conditional handover procedure currently being considered differs from the LTE handover procedure in that the terminal decides to start handover (Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] 3GPP TS38.300 v15.6.0, Internet<URL:https: / / www.3gpp.org / ftp / Specs / archive / 38_series / 38.300 / 38300-f60.zip> [Non-Patent Document 2] 3GPP R2-1700544, Internet<URL:https: / / www.3gpp.org / ftp / TSG_RAN / WG2_RL2 / TSGR2_AHs / 2017_01_NR / Docs / R2-1700544.zip> Summary of the Invention [Problem to be solved by the invention]

[0006] The introduction of the conditional handover procedure is expected to improve the probability of successful handover. On the other hand, the conditional handover procedure currently under consideration has a problem that it imposes restrictions on mobility procedures other than handover to the handover candidate cell.

[0007] For example, assume that there are cells A and B, cell A is designated as a handover candidate cell, and cell B is not designated as a handover candidate cell. If cell A satisfies the condition for starting a conditional handover, the terminal performs a handover to cell A. On the other hand, if cell A does not satisfy the condition for starting a conditional handover and cell B satisfies the condition for starting a conditional handover, the terminal ends the process without performing a handover to cell B.

[0008] In addition, when considering an actual network configuration, it may be preferable to add a cell with good quality as a secondary cell group, rather than performing a conditional handover to the cell. However, currently, no consideration has been given to a method of adding a secondary cell group in a procedure similar to the conditional handover procedure.

[0009] The present disclosure has been made in consideration of the above points, and aims to provide a flexible mobility procedure. [Means for solving the problem]

[0010] A terminal according to one embodiment of the present disclosure has a receiving unit that receives from a base station a measurement setting that matches information indicating a target cell for which a specified processing is to be performed with a condition setting that indicates a condition for starting the specified processing, a measurement unit that measures the reception quality of the cell, and a control unit that starts the specified processing corresponding to the condition setting when the measured cell is included in the target cells and the reception quality of the measured cell satisfies the condition for starting the specified processing.

[0011] A base station according to one embodiment of the present disclosure includes a receiving unit that receives a measurement report indicating the reception quality of a cell from a terminal, a generating unit that generates a measurement setting that matches information indicating a target cell for which a specified processing is to be performed with a condition setting indicating a condition for starting the specified processing based on the received measurement report, and a transmitting unit that transmits the generated measurement setting to the terminal. Effect of the Invention

[0012] According to the present disclosure, flexible mobility procedures can be provided. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating an example of a configuration of a wireless communication system according to an embodiment of the present invention. [Diagram 2] FIG. 13 illustrates an example of a measurement event. [Diagram 3] FIG. 1 is a diagram for explaining the basic procedure of handover. [Figure 4] FIG. 1 is a diagram for explaining the basic procedure of conditional handover. [Diagram 5] FIG. 11 is a diagram for explaining a basic procedure for adding a secondary cell group. [Figure 6] FIG. 2 is a diagram illustrating an example of a hardware configuration of a terminal and a base station. [Figure 7] FIG. 2 is a diagram illustrating an example of a functional block configuration of a terminal. [Figure 8] FIG. 2 is a diagram illustrating an example of a functional block configuration of a base station. [Figure 9] FIG. 2 is a diagram showing an example of a conditional handover procedure according to the present embodiment. [Figure 10] FIG. 2 is a diagram showing an example of fluctuation in cell quality according to the present embodiment. [Figure 11] A figure showing an example of a secondary cell group addition procedure related to this embodiment. [Figure 12] FIG. 1 is a diagram showing a specific example (part 1) of measurement settings. [Figure 13] FIG. 13 is a diagram showing a specific example (part 2) of measurement settings. [Figure 14] FIG. 13 is a diagram showing a specific example (part 3) of measurement settings. [Figure 15] FIG. 11 is a diagram showing a specific example (part 4) of measurement settings. [Figure 16] FIG. 11 is a diagram showing an example (part 1) of a method for specifying a measurement target cell based on a measurement configuration. [Figure 17] FIG. 13 is a diagram showing an example (part 2) of a method for specifying a measurement target cell based on a measurement configuration. [Figure 18] 11 is a flowchart illustrating an example of a processing procedure performed by a terminal. [Figure 19] 13 is a flowchart illustrating an example of a processing procedure performed by a base station. [Figure 20] FIG. 13 is a diagram showing a modification of the standard specification according to the embodiment. [Figure 21] FIG. 13 is a diagram showing a modification of the standard specification according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings, in which the same reference numerals denote the same or similar configurations.

[0015] <System configuration> A wireless communication system according to this embodiment will be described. The wireless communication system according to this embodiment is for NR, but is not limited thereto. For example, it is also applicable to LTE and LTE-Advanced. It is also applicable to a wireless communication system that partially uses NR. More generally, this embodiment is applicable to any wireless communication system that includes at least a terminal and a base station, including future wireless communication systems. In the following description, LTE and LTE-Advanced are also referred to as EUTRA, but have the same meaning.

[0016] An area (coverage area) formed by a base station is called a cell. EUTRA and NR are cellular communication systems constructed by multiple cells. The wireless communication system according to this embodiment may apply either TDD (Time Division Duplex) or FDD (Frequency Division Duplex), or a different method may be applied to each cell.

[0017] FIG. 1 is a diagram showing an example of the configuration of a wireless communication system 1 according to the present embodiment. A terminal 10 is wirelessly connected to a base station 20-1 or a base station 20-2. Hereinafter, when the base station 20-1 and the base station 20-2 are not distinguished from each other, they are referred to as a base station 20. In addition, the terminal 10 can be wirelessly connected to the base station 20-1 and the base station 20-2 at the same time. The base station 20-1 and the base station 20-2 can use EUTRA or NR. For example, the base station 20-1 may use NR and the base station 20-2 may use EUTRA, or vice versa. The base station 20 in EUTRA is referred to as an eNB (evolved NodeB), and the base station 20 in NR is referred to as a gNB (g-NodeB). Hereinafter, when the base station 20 is referred to, it includes both eNB and gNB. In addition, the terminal 10 in EUTRA and NR is referred to as a UE (User Equipment). The base station 20, which is a gNB, may be connected to the terminal 10 using a part (BWP: bandwidth part) of the frequency band it uses. Hereinafter, when the cell is referred to, it includes BWP.

[0018] The terminal 10 is connected to the base station 20 on a cell-by-cell basis. The terminal 10 may be connected to the base station 20 using a plurality of cells (carrier aggregation). When the terminal 10 is connected via a plurality of base stations 20 (dual connectivity), the base station 20 to which the terminal 10 is initially connected is called a master node (MN), and the base station 20 to which the terminal 10 is additionally connected is called a secondary node (SN). Among the plurality of cells to which the terminal 10 is connected, one or more cells provided by the master node are called a master cell group (MSG). Also, among the plurality of cells to which the terminal 10 is connected, one or more cells provided by the secondary node are called a secondary cell group (SCG).

[0019] The base stations 20 are connected to each other via a base station interface. The base stations 20 and the core network device 40 are also connected to each other via a core network interface. The base station interface is used to exchange control signals necessary for handover and coordinated operations between the base stations 20. The core network device 40 has the base stations 20 under its control, and mainly handles load control between the base stations 20, calling (paging) the terminal 10, and mobility control such as location registration.

[0020] The terminal 10 and the base station 20 transmit and receive RRC messages in the Radio Resource Control (RRC) layer. The terminal 10 and the base station 20 also transmit and receive MAC Control Elements (MAC CEs) in the Medium Access Control (MAC) layer. The RRC messages are transmitted as RRC Protocol Data Units (PDUs), and the logical channels to which they are mapped include a Common Control Channel (CCCH), a Dedicated Control Channel (DCCH), a Paging Control Channel (PCCH), a Broadcast Control Channel (BCCH), or a Multicast Control Channel (MCCH). The MAC CEs are transmitted as MAC PDUs (or MAC subPDUs). The MAC subPDUs are equivalent to a Service Data Unit (SDU) in the MAC layer plus an 8-bit header, and the MAC PDUs include one or more MAC subPDUs.

[0021] Next, the physical channels and physical signals according to this embodiment will be described. Among the physical channels according to this embodiment, the physical broadcast channel (PBCH: Physical Broadcast Channel), the physical random access channel (PRACH: Physical Random Access Channel), the physical downlink control channel (PDCCH: Physical Downlink Control Channel), and the channel state information estimation reference signal (CSI-RS: Channel State Information-Reference Signal) will be described below. Note that in this system, at least a synchronization signal (Primary Synchronization Signal, Secondary Synchronization Signal), a physical uplink control channel (PUCCH: Physical Uplink Control Channel), a physical downlink shared channel (PDSCH: Physical Downlink Shared Channel), a physical uplink shared channel (PUSCH: Physical Uplink Shared Channel), a scheduling reference signal (SRS: Scheduling Reference Signal), and a demodulation reference signal (DMRS: Demodulation Reference Signal) are also present, but detailed description thereof will be omitted.

[0022] (Physical Broadcast Channel PBCH) The physical broadcast channel PBCH is transmitted from the base station 20 to the terminal 10 and is used to notify common parameters (broadcast information, system information) in the cells under the control of the base station 20. The system information is further classified into a master information block (MIB) and a system information block (SIB). The system information block is further subdivided and transmitted, such as SIB1, SIB2, etc. The system information includes information required for connecting to a cell, and for example, the MIB includes a system frame number and information indicating whether camping on a cell is possible. The SIB1 includes parameters (cell selection parameters) for calculating the quality of the cell, cell-common channel information (random access control information, PUCCH control information, PUSCH control information), scheduling information of other system information, and the like. The PBCH is periodically transmitted as a set with a synchronization signal as a synchronization signal block (SSB: Synchronization Signal Block (or SS / PBSH)). By receiving the SSB, the terminal 10 can obtain cell identifier (cell ID) information and reception timing, as well as measure the quality of the signal of the cell.

[0023] (Physical Random Access Channel PRACH) The physical random access channel PRACH is used by the terminal 10 to transmit a random access preamble to the base station 20. The PRACH is generally used in a state where uplink synchronization is not established between the terminal 10 and the base station 20, and is used for transmission timing adjustment information (timing advance) and uplink radio resource requests. Information indicating radio resources capable of transmitting the random access preamble is transmitted to the terminal using broadcast information or an RRC message.

[0024] (Physical Downlink Control Channel PDCCH) The physical downlink control channel PDCCH is transmitted from the base station 20 to the terminal 10 to notify the terminal 10 of downlink control information (DCI). The downlink control information includes uplink radio resource information (uplink grant (UL grant)) that the terminal 10 can use, or downlink radio resource information (downlink grant (DL grant)). The downlink grant is information indicating the scheduling of the physical downlink shared data channel PDSCH. The uplink grant is information indicating the scheduling of the physical uplink shared data channel PUSCH. When the PDCCH is transmitted as a response to a PRACH (random access preamble), the PDSCH indicated by the PDCCH is a random access response, and includes index information of the random access preamble, transmission timing adjustment information, uplink grant, etc.

[0025] (Channel State Information Estimation Reference Signal - CSI-RS) A reference signal CSI-RS for estimating channel state information is transmitted from the base station 20 to estimate the state of the downlink. For the CSI-RS, a transmission resource (CSI-RS resource) indicating a position where the CSI-RS is transmitted can be set for each terminal 10, and further, a CSI-RS resource can be set for each antenna port. The terminal 10 uses the CSI-RS as a measurement signal for frequency-time tracking, mobility management, or beam management.

[0026] Next, we will briefly explain the settings and procedures related to mobility, such as cell quality measurement and handover, as specified in the conventional EUTRA and NR specifications.

[0027] (Measurement Settings) The base station 20 notifies the terminal 10 in the connected mode of a measurement configuration including information for performing measurements of neighboring cells (signals) and a measurement result report. The measurement configuration is notified to the terminal using dedicated signaling (RRC message), for example, an RRCReconfiguration message.

[0028] The base station 20 notifies the terminal 10 of the measurement configuration, thereby causing the terminal 10 to perform measurements on NR and / or EUTRA frequencies.

[0029] In addition, base station 20 sets measurement configurations to report to terminal 10 on the SSB identifier, the quality for each SSB, and the cell quality based on the SSB, or the CSI-RS identifier, the quality for each CSI-RS resource, and the cell quality based on the CSI-RS resource.

[0030] The measurement configuration includes at least the following parameters:

[0031] (1) Measurement object(s) The measurement object includes information about the object on which the terminal 10 performs measurement, and a plurality of objects can be set in the form of a list. In intra-frequency measurements and inter-frequency measurements, the measurement object indicates frequency and time resource information and subcarrier spacing information of the reference signal to be measured by the terminal 10. For example, in the case of inter-system EUTRA measurements (inter-RAT (Radio Access Technology) E-UTRA measurements), the EUTRA frequency is set as the measurement object. In addition, the base station 20 can include a list of cells that give a cell-specific offset, a black cell list, and a white cell list as the measurement object. The cell-specific offset is an offset value added to the measurement result during measurement, the black cell list is a list indicating cells that are not applicable (not applicable) for event evaluation (described later) or measurement report, and the white cell list is a list indicating cells that are applicable (applicable) for event evaluation or measurement report. In order to manage the measurement objects, the base station 20 sets a measurement object identifier (measObjectId) for each measurement object.

[0032] (2) Reporting configuration(s) The report configuration includes information about a measurement report, and one or more report configurations are set for each measurement target in the form of a list. In order to manage the report configuration, the base station 20 sets a report configuration identifier (reportConfigId) for each report configuration. Each report configuration includes at least the following information: Reporting criterion: A trigger condition (criterion) for the terminal 10 to transmit a measurement report. Either single event or periodic event reporting is set. RS type (reference signal type): RS used by terminal 10 for beam measurement results or cell measurement results. Either SSB or CSI-RS is specified. · Reporting format: Information about the quantity per cell or per beam to include in the measurement reports (e.g. what to report (RSRP / RSRQ / SINR) and what the maximum number of beams or cells to report is).

[0033] (3) Measurement identity(ies) The measurement identifier (measId) is used to link (associate, associate) one measurement object with one reporting configuration. In other words, the measurement identifier (measId) corresponds to one measurement object identifier (measObjectId) and one reporting configuration identifier (reportConfigId). A plurality of measurement identifiers can be set in a list format. A measurement identifier may link a plurality of reporting configurations to a single measurement object, or may link a plurality of measurement objects to the same reporting configuration. The measurement identifier is transmitted in a measurement report in order to report an event that satisfies a trigger condition to the base station 20.

[0034] (4) Quantity configuration(s) Define the filter (weighting) settings for the measurement results. The measurement results are averaged by specifying a filter coefficient for each measurement value. The base station 20 may set different filter coefficients for different report contents of different RS types.

[0035] (5) Measurement gap(s) Defines a gap period during which the terminal 10 can interrupt communication and perform measurements (especially inter-frequency measurements and inter-system measurements).

[0036] In addition, the measurement configuration can include (1) Measurement object(s), (2) Reporting configuration(s), and (3) Measurement identity(ies), which can each include settings for NR and settings for other RATs (e.g., EUTRA).

[0037] Regarding measurement targets for NR, the terminal 10 measures and reports on the serving cell, list cells, and detected cells. Regarding measurement targets for EUTRA, the terminal 10 measures and reports on the list cells and detected cells. The list cells are cells included in a list notified by the base station 20. The detected cells are other cells that the terminal 10 has detected independently.

[0038] (Measurement event(s)) The condition (measurement type) indicating the transmission trigger of a Measurement Report message is specified by the base station 20 as either periodic reporting or event triggered reporting. As event triggered reporting in NR, multiple measurement events shown in Fig. 2 are defined. The measurement events are specified in the report configuration and managed by an event identifier (eventId).

[0039] (Applicable cell) For each measurement event, the applicable cell to be evaluated is defined. For example, the applicable cell for measurement in Event A1 is the serving cell. Also, the applicable cell for measurement in Event A3 is a cell (neighboring cell) detected at the measurement frequency that is linked to the reporting configuration including Event A3. However, if a black cell list is notified, the cells in the list are excluded. Also, if a white cell list is configured, the applicable cell for measurement is a cell in the white cell list.

[0040] (Measurement report triggering) The terminal 10 initiates the measurement reporting procedure when the measurement type is an event triggered report and the measurement result meets the condition indicated by the measurement event. In other words, the measurement report procedure is initiated when the measurement result of the measurement target cell meets the event condition corresponding to the event identifier specified in the reporting configuration included in the measurement configuration. At this time, the terminal 10 reports the measurement result of the cell corresponding to the measurement identifier that meets the condition.

[0041] (HO: Handover Procedure) Next, the basic procedure of handover will be described with reference to Fig. 3. The terminal 10 (UE) is in communication (Connected Mode) with the base station 20-1 (Source gNB). A measurement configuration for notifying the condition (trigger condition) of a measurement event is set in the terminal 10. The terminal 10 evaluates the measurement event for a measurement target cell corresponding to a specified measurement event among neighboring cells (for example, Event A3) (S10).

[0042] Here, when a measurement event occurs in one of the measurement target cells (Cell-X) (i.e., when the measurement result of the measurement target cell (Cell-X) satisfies the condition of the measurement event specified in the report configuration), the terminal 10 starts the measurement report procedure and transmits a measurement report message (MeasurementReport) to the base station 20-1 (S11). The measurement report message includes at least a measurement identifier (measID) corresponding to the established measurement event and information of the measurement target cell related to the measurement event (e.g., the cell ID of the cell where the event occurred and the measurement result).

[0043] The base station 20-1 that has received the measurement report message determines whether the terminal 10 should execute handover based on the received measurement result, and starts the handover procedure if necessary (S12). Typically, the base station 20-1 requests handover preparation from the base station 20-2 (Target gNB) to which the cell (Cell-X) that satisfies the trigger condition belongs, and exchanges information between the base stations 20 to enable the terminal 10 to access the base station 20-2 (S13). Then, the base station 20-1 transfers an RRC message (RRCReconfiguration) including information required for handover transmitted from the base station 20-2 to the terminal 10.

[0044] The terminal 10 executes handover based on the received RRC message, and attempts synchronization and random access to the base station 20-2. If the random access procedure with the base station 20-2 is successful, the terminal 10 transmits a response message (RRCReconfigurationComplete) corresponding to the received RRC message to the base station 20-2, and completes the handover procedure.

[0045] (Conditional Handover (CHO) Procedure) Next, the basic procedure of the conditional handover will be explained with reference to FIG.

[0046] A measurement configuration including a measurement event for notifying the start of a conditional handover procedure to the base station 20 is configured in the terminal 10. The terminal 10 evaluates the measurement event for a measurement target cell corresponding to the specified measurement event among neighboring cells.

[0047] Here, if a measurement event occurs in one of the measurement target cells (Cell-X) (i.e., if the measurement result of the measurement target cell (Cell-X) satisfies the condition of the measurement event specified in the reporting configuration), the terminal 10 starts the measurement report procedure and transmits a measurement report message (MeasurementReport) to the base station 20-1 (S20).

[0048] The base station 20-1 that has received the measurement report message determines whether or not handover is possible based on the received measurement result, and starts a conditional handover procedure if necessary. Typically, it requests handover preparation from the base station 20-2 to which the notified cell (Cell-X) belongs, and exchanges information for accessing the base station 20-2 between the base stations 20 (S21). Then, the base station 20-1 transfers an RRC message (RRCReconfiguration) including information required for conditional handover, which is transmitted from the base station 20-2, to the terminal 10 (S22).

[0049] The terminal 10 measures the handover candidate cell based on the measurement configuration included in the received RRC message. That is, the terminal 10 evaluates the measurement event by regarding the notified handover candidate cell as a measurement target cell (applicable cell(s)) (S23). Then, if a measurement event is established in the measurement target cell (S23: Yes), the terminal 10 executes handover based on the notified configuration information (S24), and attempts to acquire synchronization and random access to the base station 20-2 (S25). If the random access procedure with the base station 20-2 is successful, the terminal 10 transmits a response message (RRCReconfigurationComplete) corresponding to the received RRC message to the base station 20-2 (S26), and completes the conditional handover procedure.

[0050] (Secondary Cell Group (SCG) Addition Procedure) Next, a basic procedure for adding a secondary cell group will be described with reference to Fig. 5. The terminal 10 (UE) is in communication with the base station 20-1 (MN gNB) (Connected Mode). The terminal 10 evaluates a measurement event for a measurement target cell corresponding to a specified measurement event among neighboring cells (for example, Event A4).

[0051] Here, when a measurement event occurs in one of the measurement target cells (Cell-X) (i.e., when the measurement result of the measurement target cell (Cell-X) satisfies the condition of the measurement event specified in the report configuration), the terminal 10 starts the measurement report procedure and transmits a measurement report message (MeasurementReport) to the base station 20-1 (S30). The measurement report message includes at least a measurement identifier (measID) corresponding to the established measurement event and information on the measurement target cell related to the measurement event (e.g., the cell ID of the cell where the event occurred and the measurement result).

[0052] The base station 20-1 that has received the measurement report message judges whether the terminal 10 should add the secondary cell group based on the received measurement result, and starts the secondary cell group addition procedure if necessary. Typically, the base station 20-1 requests the base station 20-2 (SN gNB) to which the cell (Cell-X) that satisfies the trigger condition belongs to add the secondary cell group, and the base station 20 exchanges information for the terminal 10 to add the cell under the base station 20-2 as a secondary cell group (S31, S32). Then, the base station 20-1 transmits an RRC message (RRCConnectionReconfiguration) including information required for adding the secondary cell group to the terminal 10 (S33). Also, the terminal 10 transmits a response message (RRCConnectionReconfigurationComplete) to the received RRC message (S34).

[0053] The terminal 10 attempts to acquire synchronization and perform random access to the base station 20-2 based on the received RRC message. If the random access procedure with the base station 20-2 is successful, various processes related to the addition of a secondary cell group are performed with the base station 20-2 (S35).

[0054] <Overview of the Technology According to the Present Embodiment> In this embodiment, for example, as shown in the processing procedure of step S22 in Figure 4, when base station 20 notifies the base station 20 of a candidate cell for conditional handover, other candidate cells other than the candidate cell, and a measurement configuration including a trigger condition related to the conditional handover procedure, if the trigger condition is not satisfied for the candidate cell (i.e., handover is not initiated) but the trigger condition is satisfied for the other candidate cells, a measurement report message including at least the cell quality of the other candidate cells is transmitted to base station 20.

[0055] Also, depending on the moving direction of the terminal 10, it may be appropriate to add a candidate cell as a secondary cell group in addition to the serving cell, rather than necessarily performing handover. Therefore, in this embodiment, the base station 20 notifies the terminal 10 of the candidate cell of the secondary cell group, etc., so that the terminal 10 can initiate a procedure for adding the candidate cell as a secondary cell group by itself.

[0056] <Hardware configuration> 6 is a diagram showing an example of the hardware configuration of the terminal 10 and the base station 20. The terminal 10 and the base station 20 each include a processor 11, a memory 12, a storage device 13, a communication device 14 for performing wired or wireless communication, an input device 15 for accepting input operations, an output device 16 for outputting information, and an antenna 17.

[0057] The processor 11 is, for example, a CPU (Central Processing Unit), and controls the terminal 10 and the base station 20.

[0058] The memory 12 is composed of, for example, a Read Only Memory (ROM), an Erasable Programmable ROM (EPROM), an Electrically Erasable Programmable ROM (EEPROM), and / or a Random Access Memory (RAM).

[0059] The storage device 13 is configured by storage such as a hard disk drive (HDD), a solid state drive (SSD), and / or an embedded multi media card (eMMC).

[0060] The communication device 14 is a device that communicates via a wired and / or wireless network, and is, for example, a network card, a communication module, etc. The communication device 14 may also include an amplifier, an RF (Radio Frequency) device that performs processing related to wireless signals, and a BB (BaseBand) device that performs baseband signal processing.

[0061] The RF device performs, for example, D / A conversion, modulation, frequency conversion, power amplification, etc. on the digital baseband signal received from the BB device to generate a radio signal to be transmitted from the antenna 17. The RF device also performs frequency conversion, demodulation, A / D conversion, etc. on the radio signal received from the antenna 17 to generate a digital baseband signal and transmit it to the BB device. The BB device performs a process of converting the digital baseband signal to an IP packet, and a process of converting the IP packet to a digital baseband signal.

[0062] The input device 15 is, for example, a keyboard, a touch panel, a mouse, and / or a microphone, etc. The output device 16 is, for example, a display and / or a speaker, etc.

[0063] <Function block configuration> (Terminal) FIG. 7 is a diagram showing an example of a functional block configuration of the terminal 10. The terminal 10 includes a transmitting unit 100, a receiving unit 101, a measuring unit 102, and a control unit 103. FIG. 7 shows the functional blocks required in this embodiment. The transmitting unit 100 and the receiving unit 101 may be realized by, for example, the communication device 14, or may be realized by the processor 11 executing a program stored in the storage device 13 in addition to the communication device 14. The measuring unit 102 and the control unit 103 may be realized by the processor 11 executing a program stored in the storage device 13. The program can be stored in a storage medium. The storage medium storing the program may be a non-transitory computer readable storage medium. The non-transitory storage medium is not particularly limited, and may be, for example, a storage medium such as a USB memory or a CD-ROM.

[0064] The transmitter 100 generates and transmits an uplink signal to be transmitted to the base station 20 .

[0065] The receiving unit 101 receives a downlink signal from the base station 20. The receiving unit 101 also receives from the base station 20 measurement setting information (e.g., measurement configuration) in which information indicating a target cell for which a predetermined process is performed (e.g., measurement object) is associated with a condition setting (e.g., reporting configuration) indicating a condition for starting the predetermined process. The predetermined process includes at least one of starting a conditional handover procedure, starting a secondary cell group addition procedure, and starting a measurement report procedure. For example, the predetermined process may include starting a conditional handover and starting a measurement report procedure, may include adding a secondary cell group and starting a measurement report procedure, or may include starting a conditional handover, adding a secondary cell group, and starting a measurement report procedure.

[0066] The measurement unit 102 measures the reception quality (cell quality) of a cell. The reception quality may be, for example, Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), received signal strength indicator (RSSI), or Reference Signal-Signal to Interference and Noise Ratio (RS-SINR).

[0067] The control unit 103 performs various processes related to, for example, the RRC layer. In addition, when a cell measured by the measurement unit 102 is included in the target cells of the predetermined process and the reception quality of the cell measured by the measurement unit 102 satisfies a condition setting indicating a condition for starting the predetermined process, the control unit 103 executes the predetermined process corresponding to the condition setting. For example, when a condition for transmitting a measurement report (such as the above-mentioned Event A1) is set in the reporting configuration, the control unit 103 transmits a measurement report message including the measurement result of the cell to the base station 20.

[0068] In addition, the specified processing includes at least the initiation of a conditional handover procedure and the initiation of a measurement report procedure, the information indicating the target cell of the specified processing includes information indicating the target cell of the conditional handover and information indicating the target cell of the measurement report (frequency, black cell list, white cell list, etc.), and the condition setting indicating the conditions for starting the specified processing may include a condition setting indicating the conditions for starting the conditional handover procedure.

[0069] In this case, the control unit 103 executes the conditional handover procedure if the cell measured by the measurement unit 102 is included in the target cells for the conditional handover and the reception quality of the measured cell satisfies the condition setting indicating the conditions for starting the conditional handover procedure.

[0070] In addition, when the cell measured by the measurement unit 102 is not included in the target cells for conditional handover, the measured cell is included in the target cells for the measurement report, and the reception quality of the measured cell satisfies the condition setting indicating the condition for starting the conditional handover procedure, the control unit 103 transmits a measurement report message including the reception quality of the measured cell to the base station 20.

[0071] In addition, the specified processing may include at least the initiation of a secondary cell group addition, the information indicating a target cell of the specified processing may include information indicating a target cell of the secondary cell group, and the condition setting indicating a condition for starting the specified processing may include a condition setting indicating a condition for starting a secondary cell group addition procedure.

[0072] In this case, if the measured cell is included in the target cells of the secondary cell group and the reception quality of the measured cell satisfies the condition setting indicating the condition for starting the secondary cell group addition procedure, the control unit 103 executes a process of adding the measured cell to the secondary cell group.

[0073] In addition, the specified processing includes initiating a secondary cell group addition procedure and initiating a measurement report procedure, the information indicating a target cell for the specified processing includes information indicating a target cell for the secondary cell group and information indicating a target cell for the measurement report, and the condition setting indicating a condition for starting the specified processing may include a condition setting indicating a condition for starting the secondary cell group addition procedure.

[0074] In this case, if the measured cell is not included in the target cells of the secondary cell group, the measured cell is included in the target cells of the measurement report, and the reception quality of the measured cell satisfies the condition setting indicating the condition for starting the secondary cell group addition procedure, the control unit 103 transmits a measurement report message including the reception quality of the measured cell to the base station 20.

[0075] (base station) FIG. 8 is a diagram showing an example of a functional block configuration of the base station 20. The base station 20 includes a transmitting unit 200, a receiving unit 201, and a control unit 202. FIG. 8 shows the functional blocks required in this embodiment. The transmitting unit 200 and the receiving unit 201 may be realized by, for example, the communication device 14, or may be realized by the processor 11 executing a program stored in the storage device 13 in addition to the communication device 14. The control unit 202 may be realized by the processor 11 executing a program stored in the storage device 13. The program can be stored in a storage medium. The storage medium storing the program may be a computer-readable non-transient storage medium. The non-transient storage medium is not particularly limited, and may be, for example, a storage medium such as a USB memory or a CD-ROM.

[0076] The transmitter 200 generates and transmits a downlink signal to be transmitted to the terminal 10 .

[0077] The receiver 201 receives an uplink signal from the terminal 10. For example, the receiver 201 receives from the terminal 10 a measurement report message indicating the reception quality of the cell.

[0078] The control unit 202 performs various processes related to the RRC layer, for example. The control unit 202 also includes a generation unit 203 that generates an RRC message.

[0079] The generating unit 203 generates measurement configuration information (e.g., measurement configuration) including information indicating a target cell for which a predetermined process is performed (e.g., measurement object) and a condition setting indicating a condition for starting the predetermined process (e.g., reporting configuration) based on the measurement report received by the receiving unit 201. The measurement configuration information generated by the generating unit 203 is transmitted from the transmitting unit 200 to the terminal 10.

[0080] <Processing Procedure> Next, a process performed by the wireless communication system 1 according to the present embodiment will be specifically described.

[0081] (Conditional Handover Procedure) 9 is a diagram showing an example of a conditional handover procedure according to the present embodiment. First, a measurement configuration including a measurement event (here, EventX1) that triggers transmission of a measurement report message is configured in the terminal 10. The terminal 10 evaluates the measurement event for a cell corresponding to the specified measurement event (EventX1) among neighboring cells.

[0082] Here, if a measurement event occurs in one of the measurement target cells (Cell-X1) (i.e., if the measurement result of the measurement target cell (Cell-X) satisfies the condition of EventX1), the terminal 10 transmits a measurement report message to the base station 20-1 (S40).

[0083] The base station 20-1 that has received the measurement report message determines that the terminal 10 has detected Cell-X1 that satisfies the condition of EventX1, and transmits a message (e.g., a Handover Request message) indicating the start of preparation for conditional handover to the base station 20-2 that provides Cell-X1 (S41). The base station 20-2 generates an RRC message including information necessary for the terminal 10 to execute a conditional handover process, and transmits a handover response (e.g., a Handover Request Acknowledge) message including the generated RRC message to the base station 20-1 (S42). Note that the RRC message includes a measurement object including information explicitly indicating a target cell for the conditional handover (here, Cell-X1), and a measurement configuration including a reporting configuration including a trigger condition related to the conditional handover procedure (here, EventY1). Here, the terminal 10 regards measurement target cells other than the conditional handover target cell (Cell-X1) among the measurement target cells based on the measurement object and reporting configuration as target cells for the measurement report (here, assumed to be Cell-Y1 and Cell-Z1).

[0084] The base station 20-1, which has received the handover response message from the base station 20-2, transmits an RRC message (RRCReconfiguration) including the measurement configuration included in the received handover response message to the terminal 10 (S43).

[0085] The terminal 10 measures (determines) whether or not Cell-X1 satisfies Event Y1 based on the measurement configuration included in the received RRC message, and determines whether or not to start a conditional handover procedure (S44). If Event Y1 is satisfied, the terminal 10 acquires synchronization with Cell-X1 and attempts random access to the base station 20-2 (S45). If the random access procedure with the base station 20-2 is successful, the terminal 10 transmits a response message (e.g., RRCReconfigurationComplete) corresponding to the RRC message received in the processing procedure of step S43 to the base station 20-2 (S46). Thereafter, the base station 20-2 transmits a message (UEContextRelease) to the base station 20-1 to instruct it to delete the UE context (terminal-related information related to connection) of the terminal 10 (S47).

[0086] In the processing procedure of step S44, it is assumed that the terminal 10 determines that Cell-X1 does not satisfy Event Y1, but Cell-Y1 satisfies Event Y1. In this case, the terminal 10 transmits a measurement report message (Measurement Report) indicating that Cell-Y1 satisfies Event Y1 to the base station 20-1. Thereafter, the base station 20-1 may perform, for example, a processing procedure similar to the processing procedure of steps S41 to S43 between the base station 20 that provides Cell-Y1 and the terminal 10. The terminal 10 can perform a handover to Cell-Y1 by executing a conditional handover procedure.

[0087] It is preferable that EventX1 is different from a measurement event corresponding to a condition for starting a conventional handover procedure. For example, if the condition of the conventional measurement event EventA3 is "the quality of the neighboring cell is 3 dB higher than the quality of the serving cell for 3 seconds," then it is preferable that EventX1 is a measurement event in which (a) the quality of the neighboring cell is 3 dB higher than the quality of the serving cell for 1 second, or (b) the quality of the neighboring cell is 2 dB higher than the quality of the serving cell for 3 seconds. The above is merely an example, and other conditions may be used, but it is preferable that the measurement event used by the base station 20 to determine the start of a conditional handover is more relaxed than the measurement event (EventA3, etc.) used to start a conventional handover procedure.

[0088] This is because the measurement report message in the conventional handover procedure is used to notify the base station 20 of the "cell that satisfies the trigger condition for handover", whereas the measurement report message in the conditional handover procedure is used to notify the base station 20 of the "cell that is likely to be the handover destination".

[0089] FIG. 10 is a diagram showing an example of cell quality fluctuation according to the present embodiment. At the start of FIG. 10, the terminal 10 performs measurement by regarding adjacent cells (Cell A, Cell B) as cells to be measured. At time t1, the cell quality of Cell A satisfies a measurement event (EventX1) for the base station 20 to determine whether to start a conditional handover. In this case, the terminal 10 notifies the base station 20 of a measurement report message indicating that Cell A has satisfied the measurement event. Between times t1 and t2, the terminal 10 receives an RRC message from the base station 20 including a designation of a conditional handover target cell (Cell A) and a condition for starting a conditional handover procedure (EventY1). At this time, the terminal 10 regards Cell A as a target cell for EventY1 (i.e., conditional handover) and Cell B as a measurement target cell for the measurement report. Here, if the terminal 10 moves away from Cell A and the cell quality of Cell A does not satisfy Event Y1 even at time t2 (the cell quality of Cell A does not exceed the cell quality of the serving cell by a certain amount), the terminal 10 does not perform handover to Cell A (does not initiate a conditional handover procedure). On the other hand, if the cell quality of Cell B satisfies Event Y1 after time t2 (the cell quality of Cell B exceeds the cell quality of the serving cell by a certain amount), the terminal 10 notifies the base station 20 of a measurement report message indicating that the cell quality of Cell B satisfies Event Y1. Thereafter, the base station 20 may transmit to the terminal 10 an RRC message including a designation of a cell to be subjected to conditional handover (Cell B) and a condition for starting the activation of a conditional handover procedure (Event Y1). Alternatively, the base station 20 may transmit to the terminal 10 an RRC message indicating a conventional handover procedure for Cell B. This allows the terminal 10 to perform a conditional handover (or handover) to Cell B.

[0090] (Secondary cell group addition procedure) FIG. 11 is a diagram showing an example of a secondary cell group addition procedure according to the present embodiment.

[0091] First, a measurement configuration including a measurement event (here, EventX2) that is a trigger for transmitting a measurement report message is configured in the terminal 10. The terminal 10 evaluates the measurement event for a measurement target cell corresponding to the specified measurement event (EventX2) among neighboring cells.

[0092] Here, if a measurement event occurs in one of the measurement target cells (Cell-X2) (i.e., if the measurement result of the measurement target cell (Cell-X2) satisfies the condition of EventX2), the terminal 10 transmits a measurement report message to the base station 20-1 (S50).

[0093] The base station 20-1 that has received the measurement report message determines that the terminal 10 has detected Cell-X2 that satisfies the conditions of EventX2, and transmits a secondary gNB addition request (SgNB Addition Request) message to the base station 20-2 that provides Cell-X2 (S51). The base station 20-2 determines whether or not Cell-X2 can be added based on the radio resource occupancy status of Cell-X2, and transmits a secondary gNB addition request acknowledgement (SgNB Addition Request Acknowledge) message indicating the determination result to the base station 20-1 (S52).

[0094] The base station 20-1 that has received the secondary gNB addition request response from the base station 20-2 transmits an RRC message (RRCConnectionReconfiguration) including a measurement object (Measurement Object) including information indicating a secondary cell group addition target cell (here, Cell-X2) and information indicating target cells for the measurement report (here, Cell-Y2, Cell-Z2), and a measurement configuration (Measurement Configuration) including a reporting configuration (Reporting configuration) including a condition for starting the secondary cell group addition process (here, EventY2) to the terminal 10 (S53). The terminal 10 transmits an RRC message (RRCConnectionReconfigurationComplete) to the base station 20-1 (S54).

[0095] The terminal 10 measures whether or not Cell-X2 satisfies Event Y2 based on the measurement configuration included in the received RRC message, and determines whether or not to start a secondary cell group addition process (S55). If Event Y2 is satisfied, the terminal 10 performs synchronization acquisition with Cell-X2 and attempts random access to the base station 20-2. If the random access procedure with the base station 20-2 is successful, the terminal 10 performs a process related to the addition of a secondary cell group with the base station 20-2 (S56).

[0096] In the processing procedure of step S55, it is assumed that the terminal 10 determines that Cell-X2 does not satisfy Event Y2, but Cell-Y2 satisfies Event Y2. In this case, the terminal 10 transmits a measurement report message (Measurement Report) indicating that Cell-Y2 satisfies Event Y2 to the base station 20-1 (S57). After that, the base station 20-1 may perform, for example, processing procedures similar to the processing procedures of steps S51 to S54 between the base station 20 that provides Cell-Y2 and the terminal 10. The terminal 10 can add Cell-Y2 as a secondary cell group.

[0097] The above-described processing procedures of Fig. 9 and Fig. 11 may be combined. The terminal 10 may execute a conditional handover procedure when a target cell of the conditional handover procedure satisfies a trigger condition of a measurement event, and execute a secondary cell group addition procedure when a target cell of a secondary cell group satisfies a measurement event. The terminal 10 may also execute a secondary cell group change procedure instead of the secondary cell group addition procedure.

[0098] (Example of Measurement Configuration) Next, a specific example of the measurement configuration according to this embodiment will be described.

[0099] 12 is a diagram showing a specific example (part 1) of a measurement configuration. In the measurement configuration, a measurement object and a reporting configuration are associated with each other by a measurement identifier (measId), as in conventional EUTRA and 5G (NR).

[0100] The measurement object includes a CHO cell list, which is information indicating a target cell of the conditional handover. The CHO cell list can include one or more physical cell IDs (PCI: Physical Cell Identifier) ​​of the target cell of the conditional handover. Note that the measurement object may include information indicating frequency / time resource information and subcarrier spacing information of the reference signal to be measured by the terminal 10, which is specified in the conventional specifications, and information indicating the cell to be reported in the measurement report message, such as a black cell list, a white cell list, etc.

[0101] The reporting configuration includes a "measurement event" which is a condition setting indicating a condition for starting a conditional handover procedure. The measurement event may be the same as the measurement event shown in Fig. 2, or may be a measurement event (such as the above-mentioned Event Y1) associated with a condition for the terminal 10 to start a conditional handover procedure.

[0102] The reporting configuration may include a flag (useCHOcellList) indicating whether the CHO cell list is valid or invalid. The reporting configuration may include "HO type", which is a flag indicating whether the cell included in the CHO cell list is a conditional handover target or a secondary cell group addition target. When the HO type is included, the CHO cell list may be called a "cell list" or a "CHO / SCG add cell list". For example, when addSCG is set in the HO type, the cell included in the CHO cell list is a secondary cell group addition target cell. When the HO type is addSCG, the CHO cell list corresponds to "information indicating a secondary cell group target cell". The cell included in the CHO cell list may be a target cell for secondary cell group change.

[0103] When the HO type is addSCG, the reporting configuration may include a "measurement event" that is a condition setting indicating a condition for starting the secondary cell group addition procedure. The measurement event may be the same as the measurement event shown in Fig. 2, or may be a measurement event (for example, the above-mentioned Event Y2) that corresponds to a condition for the terminal 10 to start the secondary cell group addition process.

[0104] FIG. 13 is a diagram showing a specific example (part 2) of the measurement configuration. In the specific example (part 2) of the measurement configuration, the reporting configuration includes a flag (useCHOcell) indicating a cell in the CHO cell list for which the conditional handover target cell is valid. For example, when useCHOcell is set to cells #0 and #3, this indicates that only cells #0 and #3 are conditional handover target cells among cells #0 to #3 included in the CHO cell list. Other points not mentioned are the same as the specific example (part 1) of the measurement configuration.

[0105] 14 is a diagram showing a specific example (part 3) of the measurement configuration. In the specific example (part 3) of the measurement configuration, the measurement object includes, in addition to the CHO cell list, a CHO cell group that groups cells that are targets of conditional handover.

[0106] Also, the reporting configuration includes information (useCHOgroup) indicating which group in the CHO cell group is to be designated as the conditional handover target cell. For example, when useCHOgroup is set to Group#1, Cell#1 and Cell#2 included in Group#1 in the CHO cell group become the conditional handover target cells. Other points not mentioned are the same as those in the specific example (part 1) of the measurement configuration.

[0107] FIG. 15 is a diagram showing a specific example (part 4) of the measurement configuration. In the specific example (part 4) of the measurement configuration, each cell included in the CHO cell list is associated with an HO type indicating whether it is a conditional handover target cell or a secondary cell group addition target cell. Unlike the specific examples (parts 1 to 3) of the measurement configuration, the specific example (part 4) of the measurement configuration allows for setting each cell as a conditional handover target cell or a secondary cell group addition target cell. Other points not mentioned are the same as the specific example (part 1) of the measurement configuration.

[0108] FIG. 16 is a diagram showing an example (part 1) of a method for specifying a measurement target cell based on a measurement configuration. In the example of FIG. 16, based on one measurement object and one reporting configuration, cells A to X are considered as measurement target cells, and further, among the measurement target cells, cells A and B are specified as conditional handover target cells. Furthermore, the reporting configuration includes a measurement event corresponding to a conditional handover procedure and / or a measurement event corresponding to a measurement report. Furthermore, the measurement object and the reporting configuration are associated with each other by the same measurement identifier (measID#0). Cells A to X may be cells that can be measured as adjacent cells among cells of a frequency indicated by the measurement object, or may be cells specified by a white cell list included in the measurement object. Furthermore, when a black cell list is included in the measurement object, cells A to X may be cells excluding the cells specified by the black cell list.

[0109] FIG. 17 is a diagram showing an example (part 2) of a method for specifying a measurement target cell based on a measurement configuration. In the example of FIG. 17, based on one measurement object and one reporting configuration, cells A to X are regarded as measurement target cells, and further, among the measurement target cells, cell A is designated as a conditional handover target cell, and cell B is designated as a secondary cell group addition target cell. The method by which the terminal 10 regards cells A to X as measurement target cells may be the same as the example of FIG. 16. Moreover, the reporting configuration includes at least one of a measurement event corresponding to a conditional handover procedure, a measurement event corresponding to a secondary cell group addition, and a measurement event corresponding to a measurement report. Moreover, the measurement object and the reporting configuration are associated with each other by the same measurement identifier (measID#0).

[0110] The above-described setting examples of the measurement configuration are merely examples, and the present embodiment is not limited to these examples. For example, the designation of the secondary cell group addition target cell may be defined by a list separate from the CHO cell list. For example, the SCG addition cell list may be defined in the measurement object. Also, the SCG addition cell list may be defined in an IE (Information Element) different from the measurement object. For example, it may be defined in an IE (CellGroupConfig) that configures the master cell group and the secondary cell group.

[0111] (Terminal processing procedure) FIG. 18 is a flowchart showing an example of a processing procedure performed by the terminal 10. The terminal 10 in which the measurement configuration is set determines a measurement target cell based on a measurement object and a reporting configuration, and measures the cell quality of the neighboring cell considered as the measurement target cell (S100). Next, it is determined whether or not the measured cell quality satisfies a measurement event (the above-mentioned Event A3, Event Y1, Event Y2, etc.) corresponding to a conditional handover procedure or a secondary cell group addition process included in the reporting configuration (S101). If it does not satisfy, it returns to the processing procedure of step S100, and if it does satisfy, it proceeds to step S102. Next, the terminal 10 determines whether or not the physical cell ID of the cell satisfying the measurement event is included in the CHO cell list (S102). If it does not satisfy, it proceeds to step S103, and if it does, it proceeds to step S104.

[0112] The terminal 10 transmits a measurement report message including the measured cell quality of the neighboring cell (also called a concerned cell) to the base station 20 (S103).

[0113] When the HO type is specified, the terminal 10 checks whether it is CHO or SCG add (S104). If the HO type is CHO, the process proceeds to step S105, and if it is SCG add, the process proceeds to step S106. Alternatively, the terminal 10 may check whether it is CHO or SCG add based on the established measurement event (EventY1, EventY2). In this case, information indicating which measurement event corresponds to CHO or SCG add may be included in the measurement configuration, or may be statically defined in the standard specification.

[0114] The terminal 10 initiates a conditional handover procedure for the neighboring cell (S105). The terminal 10 initiates a secondary cell group addition procedure for the neighboring cell (S106).

[0115] In the above-described processing procedure, if the reporting configuration does not include a measurement event related to a secondary cell group addition process, the procedures of steps S104 and S106 do not exist.

[0116] (Base station processing procedure) Fig. 19 is a flowchart showing an example of a processing procedure performed by the base station 20. The base station 20 receives a measurement report message indicating the reception quality of the cell from the terminal 10 (S200). Then, the base station 20 generates an RRC message including, for example, the measurement configuration described in Figs. 12 to 15 (S201). Then, the base station 20 transmits the generated RRC message to the terminal 10 (S202).

[0117] <Specification change example> Fig. 20 is a diagram showing a modified example of the standard specification (3GPP TS38.331) according to this embodiment. The example of Fig. 20 is a modified example of the standard specification corresponding to the processing procedure other than step S104 and step S106 in Fig. 18.

[0118] 21 is a diagram showing a modified example of the standard specification (3GPP TS38.331) according to this embodiment. The example in FIG. 21 is a modified example of the standard specification corresponding to the processing procedure shown in FIG.

[0119] <Summary> According to the embodiment described above, when a measurement object satisfies a measurement event specified in a measurement report, a conditional handover procedure, a secondary cell group addition procedure, and transmission of a measurement report message can be flexibly performed, thereby making it possible to provide a flexible mobility procedure.

[0120] Furthermore, according to the present embodiment, when a target cell for a conditional handover procedure does not satisfy a measurement event for starting the conditional handover procedure, and another cell satisfies the measurement event, the terminal 10 can transmit a measurement report message including the measured cell quality of the other cell to the base station 20. This allows the base station 20 to instruct the terminal 10 to perform a conditional handover to the other cell, making it possible to provide more flexible mobility control.

[0121] Furthermore, according to the present embodiment, when it is more appropriate to add a measured cell as a secondary cell group rather than to perform handover, it is possible to instruct the terminal 10 to add the secondary cell group. This makes it possible to provide more flexible mobility control and to further improve the communication speed between the terminal 10 and the base station 20.

[0122] <Supplementary explanation of the embodiment> The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The flow charts, sequences, elements included in the embodiments, and their arrangements, materials, conditions, shapes, sizes, etc. are not limited to those illustrated, and can be changed as appropriate. In addition, configurations shown in different embodiments can be partially replaced or combined with each other.

[0123] The terminal 10 and / or the base station 20 may include hardware such as integrated circuits such as a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), and a system-on-a-chip (SoC). Some or all of the functional blocks may be realized by the hardware. Furthermore, the processor 11 may be at least one of the hardware.

[0124] The order of the sequences and flowcharts described in the embodiments may be changed as long as no inconsistency occurs in the processing. [Explanation of symbols]

[0125] 1...wireless communication system, 10...terminal, 11...processor, 12...memory, 13...communication device, 14...storage device, 14...communication device, 15...input device, 16...output device, 17...antenna, 20...base station, 20-1...base station, 20-2...base station, 40...core network device, 100...transmitting unit, 101...receiving unit, 102...measuring unit, 103...control unit, 200...transmitting unit, 201...receiving unit, 202...control unit, 203...generating unit

Claims

1. A receiving unit that receives, from a base station, information indicating a target cell in which a predetermined process is to be performed and a condition setting indicating a condition for starting the predetermined process; A measurement unit that measures the cell; a control unit that starts the predetermined process corresponding to the condition setting when the measured cell is included in the target cells and the measurement result of the measured cell satisfies a condition for starting the predetermined process; having The predetermined process includes at least initiating a secondary cell group addition procedure; The information indicating the target cell includes information indicating a target cell to be added to a secondary cell group, The condition setting includes a condition setting indicating a condition for starting the secondary cell group addition procedure, The information indicating the target cell including information indicating a target cell to be added to the secondary cell group and the condition setting including a condition for starting the secondary cell group addition procedure are associated with each other by a predetermined identifier; When the measured cell is included in the target cell to be added to the secondary cell group, and the measurement result of the measured cell satisfies a condition setting indicating a condition for starting the secondary cell group addition procedure, the control unit starts a process of adding the measured cell to the secondary cell group between the base station of the measured cell and the base station of the measured cell. Terminal.

2. The predetermined process includes at least starting a conditional handover procedure and starting a measurement report procedure, The information indicating the target cell includes information indicating a target cell in which a conditional handover is performed and information indicating a target cell in which a measurement report is performed, The condition setting includes a condition setting indicating a condition for starting a conditional handover procedure. The terminal according to claim 1.

3. The predetermined process includes initiating a cell change procedure of at least a secondary cell group; The information indicating the target cell includes information indicating a target cell to be changed to a secondary cell group, The condition setting includes a condition setting indicating a condition for starting a cell change procedure of the secondary cell group, The control unit starts a process of changing the measured cell in the secondary cell group when the measured cell is included in the target cell to be changed to the secondary cell group and the measurement result of the measured cell satisfies a condition setting indicating a condition for starting a cell change procedure of the secondary cell group. A terminal according to claim 1 or 2.

4. A wireless communication method performed by a terminal, receiving, from a base station, information indicating a target cell in which a predetermined process is to be performed and a condition setting indicating a condition for starting the predetermined process; Measuring the cell; starting the predetermined process corresponding to the condition setting when the measured cell is included in the target cells and a measurement result of the measured cell satisfies a condition for starting the predetermined process; Including, The predetermined process includes at least initiating a secondary cell group addition procedure; The information indicating the target cell includes information indicating a target cell to be added to a secondary cell group, The condition setting includes a condition setting indicating a condition for starting the secondary cell group addition procedure, The information indicating the target cell including information indicating a target cell to be added to the secondary cell group and the condition setting including a condition for starting the secondary cell group addition procedure are associated with each other by a predetermined identifier; The step of starting the predetermined process includes, when the measured cell is included in the target cells to be added to the secondary cell group, and the measurement result of the measured cell satisfies a condition setting indicating a condition for starting the secondary cell group addition procedure, starting a process of adding the measured cell to the secondary cell group between the base station of the measured cell and the base station of the measured cell. A wireless communication method.

5. The predetermined process includes at least starting a conditional handover procedure and starting a measurement report procedure, The information indicating the target cell includes information indicating a target cell in which a conditional handover is performed and information indicating a target cell in which a measurement report is performed, The condition setting includes a condition setting indicating a condition for starting a conditional handover procedure. The wireless communication method according to claim 4.

6. The predetermined process includes initiating a cell change procedure of at least a secondary cell group; The information indicating the target cell includes information indicating a target cell to be changed to a secondary cell group, The condition setting includes a condition setting indicating a condition for starting a cell change procedure of the secondary cell group, The step of starting the predetermined process includes starting a process of changing the measured cell in the secondary cell group when the measured cell is included in the target cell to be changed to the secondary cell group and the measurement result of the measured cell satisfies a condition setting indicating a condition for starting a cell change procedure of the secondary cell group.

6. The wireless communication method according to claim 4 or 5.

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