Terminal device, base station device, control method for terminal device, and control method for base station device

Abstract

The present invention improves mobility management performance between a terminal device and a base station device. The terminal device comprises a reception unit, a prediction unit, and a transmission unit. The reception unit receives information about measurement settings that include a measurement event for measuring the reception quality of a cell and information that indicates permission to use cell prediction results from the base station device. The prediction unit outputs a reception quality for the cell as cell prediction results. The transmission unit reports the measurement event, a first reception quality that was actually measured with respect to the measurement event, and a second reception quality that is based on the cell prediction results to the base station device on the basis of the information that indicates permission to use cell prediction results.

Description

Terminal device, base station device, terminal device control method, and base station device control method

[0001] The present invention relates to a terminal device, a base station device, a method for controlling a terminal device, and a method for controlling a base station device.

[0002] The standardization project 3GPP (3rd Generation Partnership Project (registered trademark)) is studying technical specifications for communication standards that meet the requirements of NR (New Radio (also referred to as "5G")), which is the fifth generation of mobile communications, including eMBB (Enhanced Mobile Broadband), MTC (Massive Machine Type Communications), and URLLC (Ultra-Reliable and Low Latency Communications).

[0003] 3GPP is studying a method for optimizing signaling, reporting values, etc. by using AI / ML (Artificial Intelligence / Machine Learning). Specifically, the 3GPP is studying a technology in which a terminal device or a network (i.e., a base station device, a core network device, etc.) is provided with a learning model trained by machine learning (ML), which is a field of AI, and an output value obtained by inputting a predetermined input value into the learned learning model is used as a substitute for, complement to, or verification of an actual measurement value (Non-Patent Document 1).

[0004] 3GPP is also planning to study the use of AI / ML in mobility management. For example, studies are planned to be conducted with the aim of improving the performance and reliability of mobility management by predicting (inferring) the future quality of a cell using a trained learning model and determining the evaluation of events such as handovers in advance based on the predicted results (Non-Patent Document 2).

[0005] 3GPP TR 38.843 V18.0.0 (2023-12) RP-234055

[0006] However, the various parameters in conventional mobility management are determined by network operators (base station devices) based on the actual surrounding environments of cells and terminal devices, and are not designed to conform to the cell quality predicted by terminal devices. Furthermore, measurement events are determined based on the results of actual cell measurements, and therefore are not considered when evaluations are made using predicted values, as with AI / ML. Therefore, there is a problem that predicting the cell reception quality (cell quality) using AI / ML and simply using it for mobility management may actually degrade the performance of conventional mobility management. To date, no specific solution has been proposed to this problem.

[0007] In view of this problem, an object of one aspect of the present invention is to improve the performance of mobility management between a terminal device and a base station device by predicting the reception quality of a cell using a trained model.

[0008] A terminal device according to one aspect of the present invention is a terminal device that communicates with a base station device, and includes a receiving unit that receives information regarding measurement settings including a measurement event for measuring the reception quality of a cell and information indicating permission to use the cell prediction result from the base station device, a prediction unit that outputs fluctuations in the reception quality of the cell as a cell prediction result, and a transmitting unit that reports to the base station device each of the measurement event, a first reception quality actually measured for the measurement event, and a second reception quality based on the cell prediction result, based on the information indicating permission to use the cell prediction result.

[0009] In addition, a base station device according to one aspect of the present invention is a base station device that communicates with a terminal device, and includes: a transmitting unit that transmits to the terminal device information regarding measurement settings including a measurement event for measuring the reception quality of a cell and information indicating permission to use the cell prediction result; a prediction unit that performs control regarding the prediction of fluctuations in the reception quality of the cell, which is output by the terminal device as the cell prediction result; and a receiving unit that receives a measurement report message that includes the measurement event transmitted based on the information indicating permission to use the cell prediction result, a first reception quality actually measured by the terminal device related to the measurement event, and a second reception quality based on the cell prediction result.

[0010] According to the above-described aspect, by predicting the reception quality of a cell using a trained model, it is possible to improve the performance of mobility management between a terminal device and a base station device.

[0011] 1 is a diagram showing an example of the configuration of a wireless communication system according to an embodiment. FIG. 2 is a diagram showing an example of the functional configuration of a terminal device according to an embodiment. FIG. 3 is a diagram showing an example of the functional configuration of a base station device according to an embodiment. FIG. 4 is a diagram showing an example of reporting a prediction result of cell quality according to an embodiment. FIG. 5 is a diagram showing another example of reporting a prediction result of cell quality according to an embodiment. FIG. 6 is a diagram showing an example of the relationship between input data and output data of a trained model according to an embodiment. FIG. 7 is a sequence diagram showing an example of an RRC message according to an embodiment. FIG. 8 is a diagram showing a framework of AI / ML for air interface. FIG. 9 is a diagram showing an example of the hardware configuration of a terminal device. FIG. 10 is a diagram showing an example of the hardware configuration of a base station device.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The problems and embodiments in this specification are merely examples and do not limit the scope of the present invention. In particular, even if the expressions used are different, the technology of the present invention can be applied as long as they are technically equivalent, and do not limit the scope of the present invention. Furthermore, each embodiment can be appropriately combined within the scope of the processing content. For example, an inactive period may be referred to as an inactive period.

[0013] Publicly known technologies may be used as appropriate in the wireless communication system according to the embodiment of the present invention. Applicable publicly known technologies may be, for example, 5G (NR), Beyond 5G, 5G-Advanced, 6G, or other wireless communication methods. The wireless communication system according to the embodiment of the present invention is mainly targeted at NR, but is not limited thereto. For example, the embodiment of the present invention can also be applied to LTE (Long Term Evolution) and LTE-Advanced. It can also be applied to a wireless communication system that uses NR as part of the wireless communication system.

[0014] Furthermore, the embodiments of the present invention are applicable to any wireless communication system including at least a terminal device and a base station device, and are also applicable to future wireless communication systems. In the following description, LTE and LTE-Advanced are also referred to as E-UTRA (Evolved Universal Terrestrial Radio Access), but the meaning is the same.

[0015] Hereinafter, embodiments of a base station apparatus, a terminal apparatus, and a wireless communication system disclosed in the present application will be described with reference to the drawings. Note that the disclosed technology is not limited to the following embodiments.

[0016] <Wireless Communication System> Fig. 1 is a diagram showing an example of the configuration of a wireless communication system 1 according to an embodiment of the present invention. The wireless communication system 1 according to the embodiment is configured from, for example, a terminal device 10, base station devices 20A and 20B, and a core network 30. Note that when there is no need to distinguish between the base station devices 20A and 20B, they will simply be referred to as base station device 20. Furthermore, there may be multiple terminal devices 10.

[0017] The terminal device 10 may be a wireless terminal such as a mobile phone, a smartphone, a PDA (Personal Digital Assistant), a tablet, a wearable device, a personal computer, a vehicle, or any other device or equipment (sensor device, etc.) having a wireless communication function. The terminal device 10 may also be referred to as a wireless communication device, a communication device, a receiving device, a mobile station, a UE (User Equipment), a user device, etc.

[0018] A wireless communication service is provided to a terminal device 10 by a base station device 20 and a core network 30 in a wireless communication system 1. The core network 30 has functions such as managing service subscriber information, managing sessions such as voice calls, and managing location registration of the terminal device 10. The core network 30 also transmits control data and / or user data to the terminal device 10 via the base station device 20.

[0019] The core network 30 may be a 5G Core (5GC) in 5G (NR) or an Evolved Packet Core (EPC) in 4G (E-UTRA). The connection method between the core network 30 and the base station device 20 may be a Non-Stand Alone (NSA) method or a Stand Alone (SA) method.

[0020] The 5G base station device 20 connected to the 5GC is a gNB, and the 4G base station device 20 connected to the EPC is an eNB. The 5G base station devices are connected to each other via an Xn interface, and the 4G base station devices are connected to each other via an X2 interface.

[0021] An area (coverage area) formed by a base station device 20 may be called a "cell." E-UTRA and 5G are cellular communication systems constructed by multiple cells. As a wireless communication system according to an embodiment of the present invention, either a time division duplex (TDD) or a frequency division duplex (FDD) method may be applied, and different methods may be applied to each cell.

[0022] The base station device 20 may be configured, for example, as being divided into a CU (Centralized Unit), a DU (Distributed Unit), and an RU (Radio Unit). The CU is connected to a core network. The DU is connected to the terminal device 10, for example, via the RU. The communication path between the CU and the DU is realized, for example, by a fronthaul interface (F1 interface). Multiple DUs may be connected to one CU. A part of the base station device 20 may be configured by a program executable on a cloud network.

[0023] In the example shown in Figure 1, data (DL data, downlink data) transmitted from the core network 30 to the terminal device 10 is transmitted from the core network 30 to the base station device 20, and then transmitted (forwarded) from the base station device 20 to the terminal device 10.

[0024] Data (UL data, uplink data) transmitted from the terminal device 10 to the core network 30 is transmitted from the terminal device 10 to the base station device 20 and then transmitted (transferred) from the base station device 20 to the core network 30 .

[0025] The terminal device 10 and the base station device 20 transmit and receive RRC messages (also called RRC signaling) in a Radio Resource Control (RRC) layer. Also, the terminal device 10 and the base station device 20 transmit and receive MAC control elements (MAC CEs) in a Medium Access Control (MAC) layer.

[0026] The RRC message is transmitted as an RRC Protocol Data Unit (PDU), and the logical channel (LCH) to which it is mapped may be a common control channel (CCCH), a dedicated control channel (DCCH), a paging control channel (PCCH), a broadcast control channel (BCCH), a multicast control channel (MCCH), or the like.

[0027] The MAC CE is transmitted as a MAC PDU (or MAC subPDU). A MAC subPDU is equivalent to a service data unit (SDU) in the MAC layer plus, for example, 8 bits of header information, and the MAC PDU includes one or more MAC subPDUs.

[0028] Next, the physical channels and physical signals according to the embodiment include at least a synchronization signal (Primary Synchronization Signal, Secondary Synchronization Signal), a physical broadcast channel (PBCH), a physical random access channel (PRACH), a physical downlink control channel (PDCCH), a channel state information-reference signal (CSI-RS), a physical uplink control channel (PUCCH), a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), a scheduling reference signal (SRS), and a demodulation reference signal (DMRS), but detailed description thereof will be omitted.

[0029] <Terminal Device> Fig. 2 is a diagram showing an example of the functional configuration of a terminal device 10 according to an embodiment. As shown in Fig. 2, the terminal device 10 includes, for example, a processing unit 11, a control unit 13, a receiving unit 15, a transmitting unit 17, and a transmitting / receiving antenna unit 19. The processing unit 11 includes, for example, a radio resource processing unit 111 and a prediction unit 113. Note that the functional configuration of the terminal device 10 shown in Fig. 2 is merely an example, and the functional divisions and names of each functional block may be different as long as the operations according to the embodiment can be performed. Furthermore, one or more blocks that realize other functions may be present.

[0030] The processing unit 11 generates, for example, control information for controlling the receiving unit 15 and the transmitting unit 17, and outputs the control information to the control unit 13. The processing unit 11 executes processes related to, for example, a radio resource control layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control layer.

[0031] The radio resource processing unit 111 manages various setting information (RRC parameters, information elements (IEs)) of the terminal device 10. For example, the radio resource processing unit 111 generates information to be allocated to each channel of the physical uplink and outputs the information to the transmission unit 17. Furthermore, based on instructions from the base station device 20, the radio resource processing unit 111 performs measurements of the serving cell and neighboring cells, start and stop of transmission and reception processing, DL synchronization procedure (cell search), UL synchronization procedure (random access procedure), reacquisition of system information, event evaluation related to mobility management, a series of processes related to mobility management, and the like.

[0032] The prediction unit 113 has at least one trained learning model (a machine-learned model, hereinafter also referred to as a trained model) and performs control processing to output a predetermined predicted value based on input data. That is, the prediction unit 113 uses the trained model to calculate and process specific input information according to its intended use, and outputs the result as a predicted value. The prediction unit 113 performs (executes) activation, deactivation, switching, fallback (stopping use of the trained model), etc. of the trained model based on instructions from the radio resource processing unit 111 or instructions from the base station device 20, and performs (executes) prediction of cell measurements and / or prediction of event evaluation.

[0033] The control unit 13 performs various controls in the terminal device 10. For example, the control unit 13 generates control signals or control data for controlling the receiving unit 15 and the transmitting unit 17 based on control information from the processing unit 11. Furthermore, the control unit 13 controls uplink transmission to the base station device 20, scheduling request transmission, and downlink reception from the base station device 20 based on the prediction result from the prediction unit 113.

[0034] The receiving unit 15 separates, demodulates, and decodes various signals received from the base station device 20 via the transmitting / receiving antenna unit 19 based on a control signal provided by the control unit 13. The receiving unit 15 outputs the decoded information to the processing unit 11.

[0035] The transmitter 17 generates, for example, a physical uplink signal based on a control signal provided from the controller 13, and performs encoding and modulation on the physical uplink signal or the physical uplink channel provided from the processor 11. The transmitter 17 multiplexes various signals and transmits them to the base station device 20 via the transmitter-receiver antenna unit 19.

[0036] The processing unit 11 and the control unit 13 are realized, for example, by a processor system including a processor and a memory. In this case, the processor provides the functions of the processing unit 11 and the control unit 13 by executing a program that describes the operation of the terminal device 10, which will be described later. The processing unit 11 and the control unit 13 may be realized by a single processor system or by multiple processor systems. Alternatively, the processing unit 11 and the control unit 13 may be realized by a DSP (Digital Signal Processor), a hardware circuit, or the like.

[0037] <Base Station Device> Fig. 3 is a diagram illustrating an example of the functional configuration of the base station device 20 according to the embodiment. As shown in Fig. 3, the base station device 20 includes, for example, a processing unit 21, a control unit 23, a receiving unit 25, a transmitting unit 27, and a transmitting / receiving antenna unit 29. The processing unit 21 illustratively includes a radio resource processing unit 211 and a prediction unit 213. Note that the functional configuration of the base station device 20 illustrated in Fig. 3 is merely an example, and the names of the functional divisions and functional blocks may be different as long as the operations according to the embodiment can be performed. Furthermore, one or more blocks that realize other functions may be present.

[0038] The processing unit 21 generates, for example, control information for controlling the receiving unit 25 and the transmitting unit 27, and outputs the control information to the control unit 23. The processing unit 21 executes processes relating to, for example, the radio resource control layer, the packet data integration protocol layer, the radio link control layer, and the medium access control layer.

[0039] The radio resource processing unit 211 generates, for example, downlink data, an RRC message, and a MAC control element to be allocated to the physical downlink shared channel PDSCH, and outputs these to the transmission unit 27. The radio resource processing unit 211 also generates a control signal or control data to be allocated to the physical downlink control channel PDCCH, and outputs this to the transmission unit 27. Furthermore, the radio resource processing unit 211 manages various setting information of the terminal device 10. Based on a signal from the terminal device 10 or a notification by an RRC message, the radio resource processing unit 211 executes start and stop of transmission and reception processing, start of a UL synchronization procedure (random access procedure), update of system information, adjustment of the beam transmission angle, cell setting related to mobility management, and pre-setting of parameters related to measurement event types (measurement event identifiers).

[0040] The prediction unit 213 performs processing to manage the prediction unit 113 of the terminal device 10. Based on information related to mobility management, such as the state of the cell, the reported predicted value, and information for determining the accuracy and error of the predicted value, the prediction unit 213 determines whether activation, deactivation, switching, or fallback of the trained model of the terminal device 10 is necessary, and determines whether to cause the terminal device 10 to perform cell measurement prediction and / or event evaluation prediction.

[0041] The control unit 23 performs various controls in the base station device 20. For example, the control unit 23 generates a control signal or control data for controlling the receiving unit 25 and the transmitting unit 27 based on control information from the processing unit 21. Furthermore, the control unit 23 controls downlink transmission to the terminal device 10 and uplink reception from the terminal device 10 based on determination information from the prediction unit 213.

[0042] The receiving unit 25 separates, demodulates, and decodes various signals received from the terminal device 10 or the core network 30 via the transmitting / receiving antenna unit 29 based on a control signal provided by the control unit 23. The receiving unit 25 outputs the decoded information to the processing unit 21.

[0043] The transmitter 27 generates, for example, a downlink reference signal based on the control signal provided by the controller 23. The transmitter 27 encodes, modulates, multiplexes, and so on various pieces of information provided by the processor 21, and transmits the signal to the terminal device 10 via the transmitting / receiving antenna unit 29.

[0044] Furthermore, the transmitter 27 transmits data to the terminal device 10, another base station device 20, or the core network 30. The receiver 25 receives data from the terminal device 10, another base station device 20, or the core network 30.

[0045] The processing unit 21 and the control unit 23 are realized, for example, by a processor system including a processor and a memory. In this case, the processor provides the functions of the processing unit 21 and the control unit 23 by executing a program that describes the operation of the base station device 20, which will be described later. The processing unit 21 and the control unit 23 may be realized by a single processor system or by multiple processor systems. Alternatively, the processing unit 21 and the control unit 23 may be realized by a DSP, a hardware circuit, or the like.

[0046] <AI / ML for NR air interface> The AI ​​(artificial intelligence) / ML (machine learning) for air interface framework discussed by 3GPP will be briefly explained using Figure 8. This framework consists of Data Collection (300), Model Training (301), Management (302), Inference (303), and Model Storage (304). A machine learning model generated and trained using the framework of Figure 8 is referred to as an AI / ML model, or simply as a trained model.

[0047] Data Collection (300) has the function of collecting data and providing training data to Model Training (301), management data to Management (302), and inference data to Inference (303).

[0048] Model Training (301) has the function of training, verifying, and testing an AI / ML model. Model Training may also generate performance indicators for the model performance testing procedure. Furthermore, it may perform pre-processing, cleaning, formatting, and transformation of training data. Note that building an AI / ML model itself while training is sometimes referred to as learning, but in the present invention, the terms are used interchangeably. Model Training has the function of storing trained, verified, and tested AI / ML models, or updated AI / ML models, in Model Storage (304).

[0049] Management (302) has the function of managing and monitoring the execution of AI / ML models, including activation, deactivation, switching, and fallback. Monitoring an AI / ML model means performance monitoring to ensure that appropriate inferences (predictions) are being made based on data input from Data Collection and Inference. In other words, Management evaluates the degree of discrepancy between the output data from Inference and the correct data.

[0050] Management outputs information (Management Instructions) necessary for the function management of Inference (303) to Inference. Management Instructions are commands that indicate, for example, activation, deactivation, switching, and fallback of AI / ML models. It also outputs Model Transfer / Delivery Requests to Model Storage (304) to request the transfer / delivery of AI / ML models. It also outputs Performance Feedback / Retraining Requests to Model Training (301) to train (retrain) and update AI / ML models.

[0051] Inference (303) has the function of providing output from a process that applies an AI / ML model when inference data provided by Data Collection (300) is used as input. It may also perform pre-processing, cleaning, formatting, and transformation of the inference data. It also outputs data (Inference Output) to Management, which is used by Management to monitor the AI / ML model.

[0052] Model Storage (304) has the function of storing trained / updated AI / ML models used in Inference. Model Storage (304) also has the function of delivering AI / ML models to Inference (303) (Model Transfer / Delivery).

[0053] Here, any method for generating the trained model performed in Model Training (301) may be used. For example, a trained model may acquire data on cell measurement values, fluctuations in measurement values ​​over time, frequency information, the mobile speed of the terminal, and the like as training data, and output the measurement results (i.e., reception quality) of the cell after a certain time has elapsed as a predicted value using these as training data. The trained model used may be generated by a device other than the terminal device 10 (e.g., a base station device 20 or other external computing device) and transferred to the terminal device 10. Furthermore, the learning algorithm applied to the training, education, and reinforcement of the learning model may be any method as long as it obtains the expected output. For example, it may be a machine learning algorithm implemented using a convolutional neural network, a multilayer neural network, a deep neural network, or distributed computing. Supervised learning is preferable as the learning method, but unsupervised learning may also be used.

[0054] Note that some or all of the functions shown in Figure 8 can be executed by the terminal device 10, the base station device 20, or other devices. That is, Figure 8 illustrates an outline of each function and its relationship with respect to the life cycle of a machine learning model, and does not impose any restrictions on the location where the function is executed, nor does it impose any restrictions on the input and output of data.

[0055] <Measurement Configuration / Measurement Report> The base station device 20 notifies (configures, specifies, transmits) information regarding the measurement configuration to the terminal device 10, thereby causing the terminal device 10 to measure frequencies (e.g., NR and / or EUTRA frequencies). Note that the information regarding the measurement configuration is notified, for example, by an RRC message (e.g., RRCReconfiguration). Note that the information regarding the measurement configuration may be referred to as the measurement configuration, and hereinafter, the information regarding the measurement configuration will be referred to as the measurement configuration.

[0056] The measurement configuration includes at least the following parameters: (1) Measurement object(s) The measurement object(s) includes information about the object(s) on which the terminal device 10 performs measurements, and multiple objects can be set in list format. The base station device 20 can indicate intra-frequency measurements, inter-frequency measurements, and inter-RAT (Radio Access Technology) E-UTRA measurements as measurement objects. In the case of inter-system EUTRA measurements, the EUTRA frequency is set as the measurement object.

[0057] Furthermore, the base station device 20 can include a list of cells to which a cell-specific offset is assigned, a block cell list, and an allowed cell list in the measurement objects. The cell-specific offset is an offset value added to the measurement result during measurement, the block cell list is a list indicating cells that are not applicable (non-target) for event evaluation (described later) or measurement reporting, and the allowed cell list is a list indicating cells that are applicable (target) for event evaluation or measurement reporting. To manage measurement objects, the base station device 20 sets a measurement object identifier (measObjectId) for each measurement object.

[0058] (2) Reporting configuration(s) The reporting configuration includes information related to a measurement report, and one or more reporting configurations are set for each measurement target in a list format. To manage the reporting configurations, the base station device 20 sets a reporting configuration identifier (reportConfigId) for each reporting configuration.

[0059] (3) Measurement identity(ies) The measurement identifier (measId) is an identifier for linking (associating, relating) one measurement object identifier (measObjectId) with one reporting configuration identifier (reportConfigId). Multiple measurement identifiers can be set in a list format. The measurement identifier may link multiple reporting configurations to one measurement object, or multiple measurement objects may be linked to the same reporting configuration. The measurement identifier is transmitted in a measurement report to report a measurement event that satisfies a trigger condition to the base station device 20.

[0060] Regarding measurement targets for NR, the terminal device 10 measures and reports on the serving cell (also referred to as the serving cell), listed cells, and detected cells. Listed cells are cells included in a list notified by the base station device 20. Detected cells refer to other cells that the terminal device 10 has independently detected.

[0061] The measured cell quality (reception quality, measurement quality) is calculated by measuring a synchronization signal block (SSB) or a channel state information reference signal (CSI-RS). The cell quality can be expressed using any of RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength Indicator), SINR (Signal to Interference plus Noise Ratio), and path loss.

[0062] The measurement event(s) to be evaluated by the terminal device 10 are specified by the base station device 20. The measurement event is specified in the report configuration and managed by an event identifier (eventId). When a measurement event is triggered (established), the terminal device 10 generates a measurement report message (Measurement Report) and transmits it to the base station device 20. The condition (measurement type) indicating the trigger for transmitting the measurement report message is either a periodic report or an event triggered report, and either one of them is specified by the base station device 20.

[0063] For each measurement event, an applicable cell to be evaluated is defined. For example, the applicable cell for event A1 is the serving cell. The applicable cell for event A3 is a cell (neighbor cell) detected at the frequency to be measured and linked to the reporting configuration including event A3.

[0064] The terminal device 10 initiates the measurement reporting procedure when the measurement type is an event-triggered report, the measurement result meets the conditions indicated by the measurement event, and continues to meet the conditions for a predetermined period of time thereafter. In other words, the measurement reporting procedure is initiated when the measurement result of the measurement target cell satisfies (establishes) a measurement event corresponding to an event identifier specified in a reporting configuration included in the measurement configuration, and continues to satisfy the measurement event for a predetermined period of time. At this time, the terminal device 10 reports the measurement result of the cell corresponding to the measurement identifier that satisfies the measurement event.

[0065] Here, the reception quality of the serving cell is defined as Mp, the reception quality of the neighboring cell as Mn, the frequency offset corresponding to the serving frequency as Ofp, the frequency offset corresponding to the frequency of the neighboring cell as Offn, the cell-specific offset corresponding to the serving cell as Ocp, the cell-specific offset corresponding to the neighboring cell as Ocn, the event-specific offset value as Off, the hysteresis value as Hys, and the quality-based threshold as Thresh (Thresh1, Thresh2). The base station device 20 transmits these parameters as part of the measurement configuration to the terminal device 10 using an RRC message. Note that the base station device sets a parameter TTT (Time To Trigger) indicating the length of a predetermined time related to the establishment of a measurement event in the terminal device 10.

[0066] The terminal device 10 determines that the entering condition of event A3 is satisfied when the cell measurement result after filtering (L3 filtering) for averaging / smoothing the measurement result satisfies Equation 1. Similarly, the terminal device 10 determines that the leaving condition of event A3 is satisfied when the measurement result satisfies Equation 2.

[0067] [Formula 1] Mn + Ofn + Ocn - Hys > Mp + Ofp + Ocp + Off

[0068] [Formula 2] Mn+Ofn+Ocn+Hys<Mp+Ofp+Ocp+Off

[0069] <Conditional Handover> A terminal device 10 in a communication state moves within a cell formed by a base station device 20 using handover or conditional handover (CHO). In conditional handover, cell setting information specifying a candidate cell (target cell) as a handover destination and a trigger condition for handover (conditional handover) (measurement event type (measurement event, measurement report event)) are notified to the terminal device 10 in advance from the base station device 20. The measurement event (trigger condition) specified in the conditional handover setting is also referred to as an event condition (Conditional Event).

[0070] At this time, the base station device 20 can configure a maximum of eight candidate cells (i.e., a maximum of eight candidate cell configurations) for the terminal device 10. The terminal device 10 measures the serving cell and neighboring cells. Furthermore, the terminal device 10 evaluates measurement events based on trigger conditions notified from the base station device 20. Hereinafter, one or more pieces of cell configuration information and trigger conditions are collectively referred to as a conditional handover configuration. The conditional handover configuration includes candidate cells and other necessary cell configurations, and is specified in the form of one or more lists. Here, the measurement target cell is a candidate cell included in the conditional handover configuration, and is identified by a physical cell identifier (PCI). In other words, the terminal device 10 considers a cell having a physical cell identifier specified in an RRC message (RRCReconfiguration) included in the conditional handover configuration to be the measurement target cell.

[0071] The base station device 20 and the terminal device 10 each identify and manage conditional handover configurations using a handover condition reconfiguration identifier (CondReconfigId). The base station device 20 and the terminal device 10 can add, delete, or change each conditional handover configuration corresponding to a handover condition reconfiguration identifier. In addition, the handover condition reconfiguration identifier (CondReconfigId) can specify an event condition by linking it to a measurement identifier (measId) included in the measurement configuration.

[0072] When the trigger condition is met (the conditional handover condition is continuously satisfied for the TTT interval), the terminal device 10 applies the cell configuration of the candidate cell corresponding to the event condition as the handover destination cell. That is, after the conditional handover is successful, the cell configuration corresponding to other cells becomes unnecessary. Therefore, the terminal device in which the conditional handover is successful autonomously deletes the cell configuration corresponding to cells other than the destination cell.

[0073] Other examples of conditional handover events include quality-based event condition A3, event condition A4, and event condition A5. The establishment and departure conditions of event condition A3 are the same as those of the corresponding measurement event, event A3, and the establishment and departure conditions of event condition A4 and event condition A5 are the same as those of the corresponding events A4 and A5, respectively.

[0074] Taking the above into consideration, the following embodiments of the present invention will be described with reference to the drawings. In the description of the embodiments of the present invention, if a specific description of well-known functions or configurations related to the embodiments of the present invention makes the gist of the embodiments of the present invention unclear, the detailed description will be omitted.

[0075] 4 and 5 are diagrams showing an example of fluctuations in cell reception quality predicted by the prediction unit 113 of the terminal device 10 according to the first embodiment and the corresponding relationship between the corresponding measurement reports. The horizontal axis represents the fluctuations over time, and the vertical axis represents the fluctuations in reception quality.

[0076] FIG. 6 is a diagram showing an example of the relationship between the input data and output data of the prediction unit 113 of the terminal device 10 and the trained model executed by the prediction unit 113. A trained model (trained model) that has already been trained is input to the prediction unit 113. The input trained model may be selected and set (notified, specified) by the base station device 20, or may be selected autonomously by the terminal device 10. At this time, multiple trained models may be selected, or a suitable trained model may be selected. If a trained model has already been selected, the prediction unit 113 may switch the trained model.

[0077] Furthermore, the terminal device 10 activates / deactivates the trained model. The activation / deactivation of the trained model may be selected and set (notified, specified) by the base station device 20, or may be selected autonomously by the terminal device 10. The terminal device 10 and the base station device 20 may assign model identifiers (Model IDs) to the trained models, respectively, and manage them. The terminal device 10 may use different trained models for each measurement event and / or measurement quantity (RSRP, RSRQ, etc.). The base station device 20 may instruct the terminal device 10 to use different trained models for each measurement event and / or measurement quantity (RSRP, RSRQ, etc.).

[0078] The prediction unit 113 receives input of data (cell measurement results) representing the cell reception quality measured by the terminal device 10. The trained model activated and operating in the prediction unit 113 outputs data (cell prediction results) representing a predicted value of the fluctuation in reception quality after a predetermined time (e.g., time t) has elapsed for each of the input cell reception qualities. For example, if the measurement results corresponding to cell 0, cell 1, ..., cell n (n is a natural number) are m0, m1, ..., mn, the output predicted values ​​are e0, e1, ..., en. The predicted value may be a signed difference value from the input indicating the degree of fluctuation in the cell reception quality, or may be the absolute value of the same measurement quantity, or may be the absolute value of a measurement quantity different from the predicted value. For example, RSRP may be input as the cell reception quality, and a predicted value of RSRQ may be output as the output.

[0079] As described above, the output predicted value is the reception quality of each cell after the time t of each input value. Here, the time t may be the TTT set for the measurement event, a time specified by the base station device 20, or a uniquely determined fixed value (e.g., 100 microseconds). Alternatively, the time t may be scaled at the speed of the terminal device 10, or may be a different value for each cell. Furthermore, by specifying multiple values, multiple predicted values ​​with different prediction times may be output for one input.

[0080] The terminal device 10 in Figures 4 and 5 measures multiple cells (cell A, cell B, cell C) belonging to one or multiple base station devices 20. Figures 4 and 5 show an example in which the cell measurement results in the terminal device 10 are input into a trained model, and the output result, which is a graph of the temporal fluctuation of the cell prediction result, is illustrated. The trained model used by the terminal device 10 is generated, for example, from teacher data such as information on physical cell IDs, fluctuations in the reception quality of multiple cells, frequency information of the cells to be measured, the moving speed of the terminal device 10, position information of the terminal device 10 and the base station device 20, physical cell IDs that are outside the line of sight (NON-LINE OF SIGHT), the transmission power of the base station device 20, weather, and the amount of interference between the terminal devices 10. The trained model inputs the reception quality of a cell and outputs the reception quality of the input cell after a predetermined time has elapsed, or the amount of fluctuation in the reception quality.

[0081] 4 and 5, the terminal device 10 is in connected mode (connected state) and is communicating with the base station device 20, with cell A as the serving cell. Cells B and C are neighboring cells that are the subject of measurement. The base station device 20 also sets, as the measurement configuration, a setting in the terminal device 10 for evaluating a measurement event for cell B or cell C. At least event A3, which compares the reception quality of the serving cell with that of the neighboring cell, is set as the measurement event.

[0082] The terminal device 10 in Fig. 4 is instructed by the base station device 20 whether or not to perform event evaluation using the cell prediction result, which is the output of the trained model. In other words, the base station device 20 instructs the terminal device 10 whether or not to activate the trained model and trigger a measurement event using the output cell prediction result. The base station device 20 determines whether or not to perform event evaluation using the cell prediction result in the terminal device 10 based on the UE Capability message received from the terminal device 10.

[0083] By using the cell prediction results obtained from the trained model, the terminal device 10 can notify the evaluation results of the measurement event before actually measuring the cell, making it possible to prevent handover failures due to delays or failures in reporting measurement events related to handover, and is expected to improve the handover success rate.The base station device 20 can receive reports of the establishment of measurement events based on the cell prediction results earlier than actually occurring, and by receiving reports of future cell prediction results, it can accurately determine whether or not to perform a handover, and is expected to improve the handover success rate.

[0084] When using the cell prediction result, the terminal device 10 adds information indicating whether the measurement event is a report using the cell prediction result and reports (transmits) the result when reporting the established measurement event to the base station device 20. For example, the terminal device 10 may transmit a measurement report message different from the conventional one, may add a 1-bit identifier to the measurement report message, or may add other identifiable information and then report.

[0085] For example, the terminal device 10 may add a predicted cell reception quality (second reception quality, cell prediction result) to the measurement report message in addition to the actually measured cell reception quality (first reception quality, cell measurement result) and report it. The predicted cell reception quality to be added is any one of the measurement target cell of the measurement event, the serving cell, or a neighboring cell, or a combination of these. Alternatively, the base station device 20 may specify cell information (e.g., a physical cell ID) to be predicted. The predicted cell reception quality is the cell reception quality after a predetermined time has elapsed from the current time. The predetermined time may be the same as the TTT set in the measurement event, or may be a value specified by the base station device 20.

[0086] Time T01 indicates the time when the reception quality of cell A becomes lower than the reception quality of cell C based on the cell prediction result. In other words, it indicates the time when the entering condition of event A3 is satisfied for cell C. Note that each reception quality takes into consideration various parameters used to evaluate the measurement event, such as the frequency offset notified in the measurement configuration, the cell-specific offset, the offset value for each event, and the hysteresis value.

[0087] Time T02 indicates the time at which the terminal device 10 determines that the event establishment condition for event A3 has been satisfied for a predetermined time period from time T01. That is, as the output of the trained model, the cell prediction result for cell C exceeds the cell prediction result for cell A between time T01 and time T02, and the terminal device 10 predicts that event A3 will be established for cell C. The predetermined time period may be, for example, TTT, or may be based on information indicating a time length specified by the base station device 20. Here, if the terminal device 10 at time T01 can output (predict) the reception quality of each cell at time T02 using the trained model, it triggers a corresponding measurement event at time T01 without waiting for time T02, and transmits a measurement report message to the base station device 20.

[0088] At this time, when the terminal device 10 predicts the reception quality of the cell from time T02 onwards from the output result of the trained model, additional prediction information regarding the reception quality of the cell may be included in the measurement report message and transmitted. The additional prediction information includes, for example, information indicating that handover of the source cell (cell A) may occur again after handover to the target cell (cell C) (so-called ping-pong), information indicating the possibility of handover failure or the magnitude of the possibility of handover failure, information indicating the time when the event leaving condition of the target cell will be satisfied, information indicating the predicted stay time in the target cell after handover, etc. The base station device 20 may individually configure the terminal device 10 as to which prediction information to additionally report.

[0089] Furthermore, the terminal device 10 evaluates the degree of deviation between the predicted value and the actual measurement value, and verifies the prediction accuracy. As a result, if it is determined that the predicted value included in the measurement report message (first measurement report message) transmitted at time T01 is incorrect (the deviation of the predicted value is within an acceptable range), it may transmit a measurement report message (second measurement report message) based on the actual measurement result. At this time, the terminal device 10 transmits the second measurement report message including at least the measurement result of the cell ID that is the same as the measurement identifier reported in the first measurement report message.

[0090] The determination of deviation of the predicted value may be made when the difference between the predicted value and the actual measurement value is equal to or greater than a certain threshold, or when the cumulative difference between the predicted value and the actual measurement value is equal to or greater than a certain threshold. In this case, the threshold may be set in advance as an evaluation parameter by the base station device 20 to the terminal device 10. When the terminal device 10 determines that the predicted value included in the measurement report message transmitted at time T01 is correct (the deviation of the predicted value is outside the allowable range), it does not take any particular action and continues making judgments based on the prediction.

[0091] The terminal device 10 may constantly monitor the predicted value and transmit the second measurement report message when it determines that the predicted value is incorrect, or may make this determination for each measurement report message transmission, or may make this determination based on information set by the base station device 20. For example, the terminal device 10 may transmit the second measurement report message periodically according to a set time interval, may transmit the second measurement report message based on the number of times the first measurement report message has been transmitted (for example, transmit the second measurement report message after transmitting the first measurement report message n times (n is a value set by the base station device 20)), or may transmit the second measurement report message non-periodically based on an instruction from the base station device 20.

[0092] The non-periodic instruction from the base station device 20 may be notified by downlink control information included in L1 signaling (PDCCH), by a MAC control element, or by an individual or common RRC message.

[0093] Time T03 indicates the time when the reception quality of cell A falls below that of cell B based on the cell prediction result. In other words, it indicates the time when the event establishment condition (entering condition) of event A3 is satisfied for cell B. Furthermore, time T04 indicates the time when the terminal device 10 determines that the event establishment condition of event A3 has been satisfied continuously for a predetermined time from time T03. In other words, this means that, as the output of the trained model, the cell prediction result of cell B exceeds the cell prediction result of cell A from time T03 to time T04, and the terminal device 10 predicts that event A3 will be established for cell B.

[0094] At this time, when the terminal device 10 predicts the reception quality of the cell from time T04 onwards from the output result of the trained model, additional prediction information regarding the reception quality of the cell may be included in the measurement report message and transmitted. The additional prediction information may be the same as that described above. Alternatively, as shown in FIG. 4, when the predicted stay time after handover to cell B continues for a certain period of time, the terminal device 10 may not transmit the additional prediction information.

[0095] The period from time T04 to time T05 shows a state in which the serving cell of the terminal device 10 is cell B, and the neighboring cells are cell A and cell C. Time T05 indicates the time when the reception quality of cell B falls below the reception quality of cell A based on the cell prediction result. In other words, it indicates the time when the event establishment condition (entering condition) of event A3 is satisfied for cell A. Furthermore, time T06 indicates the time at which the terminal device 10 determines that the event establishment condition of event A3 has been satisfied for a predetermined period of time from time T05. In other words, this means that, as the output of the trained model, the cell prediction result of cell A exceeds the cell prediction result of cell B from time T05 to time T06, and the terminal device 10 predicts that event A3 will be established for cell A.

[0096] At this time, in the terminal device 10, when the reception quality of the cell from time T06 onwards is predicted from the output result of the trained model, additional prediction information regarding the reception quality of the cell may be included in the measurement report message and transmitted. The additional prediction information may be the same as that described above. Furthermore, as shown in Figure 4, the additional prediction information may include information indicating that the reception quality of another surrounding cell (cell C) will exceed that of the target cell after handover to the target cell (cell A), information indicating the predicted time at which the reception quality of the other surrounding cell (cell C) will exceed that of the target cell, information indicating the predicted time at which the reception quality of the other surrounding cell (cell C) will exceed that of the source cell (cell B), and the like.

[0097] The terminal device 10 in Fig. 5 differs from Fig. 4 in that the base station device 20 instructs the terminal device 10 whether or not to additionally report a cell prediction result for a measurement event to be reported. In other words, the base station device 20 instructs the terminal device 10 to perform event evaluation based on the actually measured reception quality of the cell, while activating a trained model and instructing the terminal device 10 whether or not to add the output cell prediction result when reporting the measurement event. The base station device 20 determines whether or not to report a cell prediction result in the terminal device 10 based on the UE Capability message received from the terminal device 10.

[0098] By notifying the terminal device 10 of the cell prediction result obtained from the trained model, it becomes possible for the base station device 20 to perform appropriate mobility management, which is expected to improve the handover success rate. In addition to the report of the establishment of a measurement event, the base station device 20 receives from the terminal device 10 determination information that can be used for mobility management of the base station device 20, which enables the base station device 20 to accurately determine whether or not to perform a handover, which is expected to improve the handover success rate.

[0099] The terminal device 10 reports the predicted cell reception quality in addition to the actually measured cell reception quality in a measurement report message. The predicted cell reception quality to be added is either the measurement target cell of the measurement event, the serving cell, or a neighboring cell, or a combination of these. The predicted cell reception quality is the cell reception quality after a predetermined time has elapsed from the current time. The predetermined time may be the same as the TTT set in the measurement event, or may be based on information indicating a time length specified by the base station device 20.

[0100] Time T11 indicates the time when the reception quality of cell A becomes lower than the reception quality of cell C based on the actually measured reception quality of the cells. In other words, it indicates the time when the entering condition of event A3 is satisfied for cell C. Note that each reception quality takes into consideration various parameters used to evaluate the measurement event, such as the frequency offset notified in the measurement configuration, the cell-specific offset, the offset value for each event, and the hysteresis value.

[0101] Time T12 indicates the time at which the terminal device 10 determines that the event establishment condition for event A3 has been satisfied for a predetermined period of time from time T11. That is, from time T11 to time T12, the reception quality of cell C exceeds the reception quality of cell A, and the terminal device 10 determines that event A3 has been established for cell C. The predetermined period of time is, for example, TTT.

[0102] Here, if the terminal device 10 at time T12 can output (predict) the reception quality of each cell at time T13 using the trained model, the measurement report message triggered and reported at time T12 includes the cell prediction result at time T13 and transmits it to the base station device 20. The time interval from time T12 to time T13 (e.g., time t2) may be, for example, TTT, or may be based on information indicating a time length specified by the base station device 20. The added cell prediction result may be reported as a predicted value, may be calculated and reported as a difference value from the reception quality of the cell being reported, may be reported as the result of other detected neighboring cells with a certain quality or higher, or may be reported together with granularity information indicating the range of error in the cell prediction result.

[0103] Alternatively, when the terminal device 10 predicts the reception quality of the cell from time T12 onward from the output result of the trained model, additional prediction information regarding the reception quality of the cell may be included in the measurement report message and transmitted. The additional prediction information may be, for example, information indicating that handover of the source cell (cell A) may occur again after handover to the target cell (cell C) (so-called ping-pong), information indicating the possibility of handover failure or the magnitude of the possibility of handover failure, information indicating the time when the event leaving condition of the target cell will be satisfied, information indicating the predicted stay time in the target cell after handover, etc. The base station device 20 may individually configure the terminal device 10 as to which prediction information to additionally report.

[0104] Furthermore, the terminal device 10 may determine, based on the predicted value predicted at time T13, that it should not transmit a measurement report message based on the actual measurement result. The determination of whether to transmit a measurement report message may be based on the additional prediction information described above. When the additional prediction information is used, threshold information (such as a threshold indicating a time or a ratio) used for the determination is set in the terminal device 10 by the base station device 20. When it is determined that it should not transmit a measurement report message, the terminal device 10 may cancel the transmission of the measurement report message, suppress the transmission of the measurement report message, suspend the measurement identifier corresponding to the measurement event, stop evaluating the reporting setting corresponding to the measurement event, or consider the measurement event to not satisfy the event establishment condition (not be triggered).

[0105] The terminal device 10 may constantly monitor the predicted value and transmit a measurement report message based on the actual measurement result when it determines that the predicted value is incorrect. The determination of the accuracy of the predicted value may be the same as the method described above. If the measurement report message was not transmitted based on the determination of whether to transmit the measurement report message, the measurement report message may further include information on the time when the measurement event actually occurred and the reception quality of the cell. Furthermore, the terminal device 10 may transmit information indicating that it has determined that the predicted value is incorrect to the base station device 20.

[0106] The terminal device 10 that has determined not to transmit a measurement report message reports information about the unreported measurement event to the base station device 20. For example, the terminal device 10 may use a UE assistance information message, which is an RRC message. The information included in the RRC message may include, in addition to information indicating the unreported event, information about the measurement event (measurement identifier), information about the actual time when the measurement event occurred, or the reception quality of the cell, and the reason for determining that the measurement event was not transmitted.

[0107] Time T14 indicates the time when the reception quality of cell A falls below that of cell B based on the actually measured reception quality of the cells. In other words, it indicates the time when the event establishment condition (entering condition) of event A3 for cell B is satisfied. Furthermore, time T15 indicates the timing at which the terminal device 10 determines that the event establishment condition of event A3 has been satisfied continuously for a predetermined time from time T14. In other words, this means that from time T14 to time T15, the reception quality of cell B exceeds the reception quality of cell A, and the terminal device 10 determines that event A3 has been established for cell B. The predetermined time is, for example, TTT.

[0108] Here, if the terminal device 10 at time T15 can output (predict) the reception quality of each cell at time T16 using the trained model, the measurement report message triggered and reported at time T15 includes the cell prediction result at time T16 and transmits it to the base station device 20. The time interval from time T15 to time T16 (e.g., time t2) may be, for example, TTT, or may be based on information indicating a time length specified by the base station device 20. The added cell prediction result may be the same as that described above.

[0109] If the predicted value included in the measurement report message transmitted at time T15 is correct, the terminal device 10 continues making judgments based on the prediction without doing anything in particular. As shown in Fig. 5, if the predicted stay time after handover to cell B continues for a certain period of time (for example, until time T16), the terminal device 10 may stop making judgments about the correctness of the predicted value included in the measurement report message and resume normal operation.

[0110] The period from time T16 to time T17 shows a state in which the serving cell of the terminal device 10 is cell B, and the surrounding cells are cell A and cell C. Time T17 shows the time when the reception quality of cell B falls below that of cell A. In other words, it shows the time when the event establishment condition (entering condition) of event A3 is satisfied for cell A. Furthermore, time T18 shows the timing at which the terminal device 10 determines that the event establishment condition of event A3 has been satisfied for a predetermined period of time from time T16. In other words, this means that the reception quality of cell A exceeds the reception quality of cell B from time T17 to time T18, and the terminal device 10 determines that event A3 is established for cell A.

[0111] Here, if the terminal device 10 at time T18 can output (predict) the reception quality of each cell at time T19 using a trained model, the measurement report message triggered and reported at time T18 may include the cell prediction result at time T19 or additional prediction information and transmit it to the base station device 20. The additional prediction information may be the same as that described above. Furthermore, as shown in FIG. 5 , the additional prediction information may include information indicating that the reception quality of another neighboring cell (cell C) will exceed that of the target cell after handover to the target cell (cell A), information indicating the predicted time at which the reception quality of another neighboring cell (cell C) will exceed that of the target cell, information indicating the predicted time at which the reception quality of another neighboring cell (cell C) will exceed that of the source cell (cell B), and a cell ID recommended as the target cell (cell C in the case of time T19).

[0112] 7 is a sequence diagram for explaining an example of an RRC message exchanged between the terminal device 10 and the base station device 20. Although not shown, the sequence starts from a state in which the wireless connection (RRC setup) procedure between the terminal device 10 and the base station device 20 is completed and the state of the terminal device 10 has transitioned to a communicating state (connected state, also referred to as an RRC Connected state). Also, it is assumed that the terminal device 10 generates an RRC message (UE Capability message) and transmits it to the base station device 20 in order to notify the base station device 20 of its own wireless capabilities.

[0113] The terminal device 10 may transmit information such as the location information accuracy of the terminal device 10 (positioning support information), information indicating the maximum time that can be predicted when using a trained model, and the maximum number of cells that can be predicted in the UE Capability message.

[0114] The base station device 20 transmits a first RRC message (RRC message 1 in the figure) to the terminal device 10 (step S100). The first RRC message may be an individual RRC message, such as an RRCReconfiguration message. The first RRC message is transmitted including a measurement configuration for setting a measurement event for the terminal device 10. The first RRC message may also include a trained model configuration for instructing activation, deactivation, switching, or fallback of a trained model used by the terminal device 10. When instructing activation, deactivation, or switching of a trained model, the base station device 20 notifies the terminal device 10 of the identifier (Model ID) of the trained model. The base station device 20 may also instruct activation or deactivation simultaneously with switching of a trained model.

[0115] In response to the first RRC message, the terminal device 10 transmits a second RRC message (RRC message 2 in the figure) to the base station device 20 (step S101). The second RRC message is, for example, an RRCReconfigurationComplete message. The second RRC message is also used by the base station device 20 to notify that activation, deactivation, switching, or fallback of a trained model specified by the base station device 20 has been successfully completed.

[0116] The terminal device 10, in which the measurement configuration is set and the trained model is activated, transmits a third RRC message (RRC message 3 in the figure) to the base station device 20 based on the measurement configuration (step S102). The third RRC message is, for example, a measurement report message. The transmission timing of the third RRC message and the information included in the third RRC message of the terminal device 10 are the same as those described in FIGS. 4 and 5 .

[0117] Alternatively, the terminal device 10 and the base station device 20 may be configured to operate by combining the operations of Figures 4 and 5. For example, the operation of Figure 4 (i.e., evaluating a measurement event using a cell prediction result) may be performed when determining an event establishment condition, and the operation of Figure 5 (i.e., evaluating a measurement event using a cell measurement result and adding the cell prediction result to a report) may be performed when determining an event departure condition, or vice versa. Alternatively, the operation of Figure 4 may be normally continued, and if it is determined that the cell prediction result is incorrect, it may be switched to the operation of Figure 5. That is, if it is determined that the accuracy of the output of the trained model being used is low, the terminal device 10 and the base station device 20 fall back to conventional operation using actual cell measurement values ​​when evaluating measurement events.

[0118] Alternatively, the base station device 20 may explicitly specify which operation to perform in an RRC message, or the operation may be configured to be switched using downlink control information or MAC control elements included in L1 signaling (PDCCH).

[0119] Thus, according to the first embodiment, the terminal device 10 and the base station device 20 can improve the performance of mobility management between the terminal device 10 and the base station device 20 by predicting the reception quality of the cell using a learned model and sending and receiving measurement report messages including the predicted results of the reception quality of the cell.

[0120] Second Embodiment A second embodiment will be described. Note that a description of configurations, functions, or procedures common to the first and second embodiments will be omitted. In other words, the following mainly describes the differences from the first embodiment.

[0121] The terminal device 10 and base station device 20 of the second embodiment use a cell prediction result, which is the output of a trained model, to evaluate a measurement event (event condition (Conditional Event)) used to trigger a conditional handover (CHO). The terminal device 10 is instructed by the base station device 20 whether or not to evaluate the event condition using the cell prediction result, which is the output of the trained model. In other words, the base station device 20 instructs the terminal device 10 whether or not to activate the trained model and perform a conditional handover using the output cell prediction result. The base station device 20 determines whether or not to evaluate the event condition using the cell prediction result in the terminal device 10 based on the UE Capability message received from the terminal device 10.

[0122] The base station device 20 may instruct the terminal device 10 whether or not to perform either or both of (1) evaluation of a measurement event using a cell prediction result and (2) evaluation of an event condition using a cell prediction result. The method of instructing may be to use downlink control information included in L1 signaling (PDCCH), a MAC control element, or an individual or common RRC message.

[0123] By using the cell prediction results obtained from the trained model, the terminal device 10 can evaluate the event conditions before actually measuring the cell, which is expected to improve the conditional handover success rate.In addition, the terminal device 10 can accurately determine whether or not to perform a conditional handover, which is expected to improve the conditional handover success rate and reduce the frequency of radio link failures after a conditional handover.

[0124] For example, the terminal device 10 evaluates an event condition using the reception quality of the target cell after a predetermined time has elapsed from the current time (cell prediction result), and if the event condition set based on the cell prediction result is met, executes a conditional handover to the target cell. The predetermined time may be the same as the TTT set in the measurement event, or may be a value specified by the base station device 20.

[0125] When the terminal device 10 executes the conditional handover using the cell prediction result, the terminal device 10 reports (transmits) information indicating whether or not the cell prediction result was used to the base station device 20. For example, the terminal device 10 may add information indicating whether or not the cell prediction result was used to an RRC message (RRCReconfigurationComplete) that notifies completion of the execution of the conditional handover.

[0126] Alternatively, the terminal device 10 may evaluate the event condition based on the actually measured reception quality of the target cell (first reception quality, cell measurement result), and when the set event condition is met, determine whether to perform conditional handover based on the predicted reception quality of the target cell (second reception quality, cell prediction result).The cell prediction result used is the cell prediction result obtained after a predetermined time has elapsed since the time the event condition was met.The predetermined time may be the same as the TTT set in the event condition, or may be a value specified by the base station device 20.

[0127] The terminal device 10 may determine not to perform conditional handover based on the cell prediction result when a radio link failure is predicted after the conditional handover, more specifically, when the reception quality of other surrounding cells is predicted to exceed that of the target cell within a short time after handover to the target cell, when handover of the source cell is executed again after handover to the target cell, when the reception quality of the target cell falls below a predetermined value after a predetermined time, when an event leaving condition of the target cell is satisfied, or when the predicted stay time in the target cell after handover is less than a predetermined time. Each parameter used for the above determination may be notified to the terminal device 10 in advance from the base station device 20.

[0128] When the terminal device 10 determines not to execute the conditional handover, it may transmit a measurement report message including the established measurement identifier to the base station device 20. Alternatively, it may transmit information indicating non-execution of the conditional handover and the reason for the determination using another RRC message (e.g., UE assistance information).

[0129] Thus, according to the second embodiment, the terminal device 10 and the base station device 20 can improve the performance of mobility management between the terminal device 10 and the base station device 20 by predicting the reception quality of the cell using a trained model and performing a conditional handover based on the predicted result of the reception quality of the cell.

[0130] The above-described embodiments are intended to facilitate understanding of the present invention and are not to be construed as limiting the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention also includes equivalents thereof.

[0131] <Hardware Configuration of Each Device in Each Embodiment> The hardware configuration of each device in the wireless communication system of each embodiment will be described with reference to FIGS.

[0132] 9 is a diagram illustrating an example of the hardware configuration of the terminal device 10. As illustrated in FIG. 9, the terminal device 10 includes, as hardware components, a radio frequency (RF) circuit 32 including an antenna 31, a central processing unit (CPU) 33, and a memory 34. The terminal device 10 may further include a display device such as a liquid crystal display (LCD) connected to the CPU 33. The memory 34 includes at least one of a random access memory (RAM) such as a synchronous dynamic random access memory (SDRAM), a read only memory (ROM), and a flash memory, and stores programs, control information, and data signals.

[0133] The correspondence between the functional configuration of the terminal device 10 shown in Fig. 2 and the hardware configuration of the terminal device 10 shown in Fig. 9 will be described. The transmitting / receiving antenna unit 19, the transmitter unit 17, and the receiver unit 15 are realized by, for example, an RF circuit 32, or an antenna 31 and an RF circuit 32. The control unit 13 and the processing unit 11 are realized by, for example, a CPU 33, a memory 34, a digital electronic circuit (not shown), etc. Examples of the digital electronic circuit include an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), and a large scale integration (LSI).

[0134] Fig. 10 is a diagram illustrating an example of the hardware configuration of the base station device 20. As shown in Fig. 10, the base station device 20 includes, as hardware components, an RF circuit 42 equipped with an antenna 41, a CPU 43, a DSP 44, a memory 45, and a network IF (Interface) 46. The CPU 43 is connected via a bus to enable input and output of various signals and data signals. The memory 45 includes at least one of a RAM such as an SDRAM, a ROM, and a flash memory, and stores programs, control information, and data signals.

[0135] The correspondence between the functional configuration of the base station device 20 shown in Fig. 3 and the hardware configuration of the base station device 20 shown in Fig. 10 will be described. The transmitting / receiving antenna unit 29, the transmitter 27, and the receiver 25 are realized by, for example, an RF circuit 42, or an antenna 41 and an RF circuit 42. The control unit 23 and the processing unit 21 are realized by, for example, a CPU 43, a DSP 44, a memory 45, a digital electronic circuit (not shown), etc. Examples of the digital electronic circuit include an ASIC, an FPGA, and an LSI.

[0136] REFERENCE SIGNS LIST 1 Wireless communication system 10 Terminal device 20 Base station device 30 Core network 11, 21 Processing unit 13, 23 Control unit 15, 25 Receiving unit 17, 27 Transmitting unit 19, 29 Transmitting / receiving antenna unit 31, 41 Antenna 32, 42 RF circuit 33, 43 CPU 34, 45 Memory 44 DSP 46 Network IF 111, 211 Radio resource processing unit 113, 213 Prediction unit 300 Data Collection 301 Model Training 302 Management 303 Inference 304 Model Storage

Claims

1. A terminal device that communicates with a base station device, comprising: a receiving unit that receives information regarding measurement settings including a measurement event for measuring the reception quality of a cell and information indicating permission to use the cell prediction result from the base station device; a prediction unit that outputs a prediction of fluctuations in the reception quality of the cell as a cell prediction result; and a transmitting unit that reports to the base station device each of the measurement event, a first reception quality actually measured for the measurement event, and a second reception quality based on the cell prediction result based on the information indicating permission to use the cell prediction result.

2. A terminal device as described in claim 1, comprising a prediction unit that obtains the second reception quality of the cell from a trained learning model that has undergone machine learning to predict fluctuations in the reception quality of the cell by inputting the first reception quality of the cell into the trained learning model.

3. The terminal device according to claim 1, wherein, when use of the cell prediction result is permitted and when the first reception quality satisfies the establishment condition of the measurement event for a predetermined time, the terminal device transmits each of the first reception quality and the second reception quality of the cell related to the measurement event in a measurement report message.

4. A terminal device as described in claim 3, which suppresses the establishment of the measurement event if it predicts that handover to the cell is not appropriate even if the first reception quality satisfies the establishment condition of the measurement event for a predetermined time.

5. The terminal device according to claim 1, wherein, when the use of the cell prediction result is permitted, the measurement event is not evaluated using the first reception quality, and when the second reception quality satisfies the establishment condition of the measurement event for a predetermined time, the first reception quality and the second reception quality of the cell related to the measurement event are included in a measurement report message and transmitted.

6. A terminal device as described in claim 1, wherein, when a conditional handover setting corresponding to the measurement event is set and the second reception quality in the measurement target cell for the conditional handover setting satisfies the establishment condition of the measurement event for a predetermined time, the terminal device executes a conditional handover procedure corresponding to the measurement event.

7. A base station device that communicates with a terminal device, comprising: a transmitting unit that transmits to the terminal device information regarding measurement settings including a measurement event for measuring the reception quality of a cell and information indicating permission to use the cell prediction result; a prediction unit that controls the prediction of fluctuations in the reception quality of the cell, which is output by the terminal device as a cell prediction result; and a receiving unit that receives a measurement report message that includes the measurement event, a first reception quality actually measured by the terminal device for the measurement event, and a second reception quality based on the cell prediction result, transmitted based on the information indicating permission to use the cell prediction result.

8. A base station device as described in claim 7, wherein the second reception quality of the cell is obtained from a trained learning model that has undergone machine learning to predict fluctuations in the reception quality of the cell equipped in the terminal device by inputting the first reception quality of the cell into the trained learning model.

9. The base station device according to claim 7, wherein an evaluation parameter is set in the terminal device for evaluating the degree of deviation between the first reception quality actually measured by the terminal device and the second reception quality based on the cell prediction result.

10. The base station device according to claim 7, wherein a conditional handover setting corresponding to the measurement event is configured in the terminal device, and execution of the conditional handover procedure based on the cell prediction result is permitted.

11. A control method for a terminal device that communicates with a base station device, comprising the steps of: receiving information regarding measurement settings including a measurement event for measuring the reception quality of a cell and information indicating permission to use the cell prediction result from the base station device; outputting a prediction of fluctuations in the reception quality of the cell as a cell prediction result; and reporting to the base station device each of the measurement event, a first reception quality actually measured for the measurement event, and a second reception quality based on the cell prediction result, based on the information indicating permission to use the cell prediction result.

12. A control method for a base station device that communicates with a terminal device, comprising the steps of: transmitting to the terminal device information regarding measurement settings including a measurement event for measuring the reception quality of a cell and information indicating permission to use the cell prediction result; controlling the prediction of fluctuations in the reception quality of the cell, which is output by the terminal device as the cell prediction result; and receiving a measurement report message transmitted based on the information indicating permission to use the cell prediction result, the measurement report message including the measurement event, a first reception quality actually measured by the terminal device for the measurement event, and a second reception quality based on the cell prediction result.

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