Base station device, terminal device, and control method for switching cells on basis of inference of event success / failure

Abstract

This base station device, which communicates with terminal devices on the basis of the cellular communication standard of the 3rd generation partnership project (3GPP): issues, to a terminal device connected to the base station device, an instruction that causes the terminal device to measure the reception power of a signal received from each of a first cell provided by the base station device and a second cell provided by another base station device, infer, using the measurement values acquired by the measurement, whether or not a predetermined condition relating to the reception power is satisfied at a specific timing after the measurement or within a range of a period having a certain length after the measurement, and make a report when it is inferred that the predetermined condition is satisfied, the instruction including information for the terminal device to identify the specific timing or the period having the certain length; receives the report when it is inferred that the predetermined condition is satisfied; and notifies the terminal device, on the basis of the reception of the report from the terminal device, that processing for switching a connection destination of the terminal device from the first cell to the second cell should be executed.

Description

Base station apparatus, terminal apparatus, and control method for performing cell switching based on estimation of event success or failure

[0001] The present invention relates to a cell switching technology for a connected terminal in a mobile communication system.

[0002] In the 3rd Generation Partnership Project (3GPP (registered trademark)), LTM cell switching (LTM Cell Switch) is specified to more efficiently perform switching of a cell connected to a terminal, compared to conventional handover in layer 3. LTM is an abbreviation for L1 / L2 Triggered Mobility. In cell switching by LTM, cell switching is performed at a lower layer compared to handover in layer 3, so that cell switching can be performed quickly.

[0003] On the other hand, in 3GPP, utilization of artificial intelligence (AI) and machine learning (ML) for control in mobile communication systems is under study. Non-Patent Document 1 describes AI / ML for Mobility, which uses AI and ML for the handover function.

[0004] 3rd Generation Partnership Project, "TR 38.744 Study on Artificial Intelligence (AI) / Machine Learning (ML) for mobility in NR; (Release 19)"

[0005] The present invention provides a technique for improving connection stability when a terminal performs cell switching in a mobile communication system.

[0006] A base station device according to one aspect of the present invention is a base station device that communicates with a terminal device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), and comprises: an instruction means that gives an instruction to the terminal device connected to the base station device, which causes the terminal device to measure the received power of signals received from a first cell provided by the base station device and a second cell provided by another base station device, and uses the measured value obtained from the measurement to estimate whether predetermined conditions regarding the received power are met at a specific timing after the measurement or within a certain period of time after the measurement, and reports if it is estimated that the predetermined conditions are met, the instruction means which includes information for the terminal device to specify the specific timing or the certain period of time; a receiving means that receives the report when it is estimated that the predetermined conditions are met; and a notification means that, based on the receipt of the report from the terminal device, notifies the terminal device that it should perform a process to switch the connection destination of the terminal device from the first cell to the second cell.

[0007] A terminal device according to one aspect of the present invention is a terminal device that communicates with a base station device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), and comprises: a receiving means that measures the received power of signals received from a first cell provided by the base station device connected to the terminal device and a second cell provided by another base station device, and uses the measured value obtained by the measurement to estimate whether predetermined conditions regarding the received power are met at a specific timing after the measurement or for a certain period of time after the measurement, and receives an instruction indicating that a report should be made if it is estimated that the predetermined conditions are met, the instruction including information for the terminal device to specify the specific timing or the certain period of time; an estimation means that makes the estimation of whether the predetermined conditions are met in accordance with the instruction; a reporting means that makes the report based on the fact that the predetermined conditions are met; and an execution means that executes a process when it receives a notification from the base station device indicating that it should perform a process to switch the connection destination of the terminal device from the first cell to the second cell.

[0008] According to the present invention, the stability of the connection when a terminal switches cells in a mobile communication system can be improved.

[0009] Other features and advantages of this disclosure will become apparent from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar components are given the same reference numeral.

[0010] The attached drawings are included in the specification and constitute part thereof, illustrating embodiments of the present disclosure and are used together with the description to explain the principles of the present disclosure. Figure 1 is a diagram showing an example configuration of a mobile communication system. Figure 2 is a diagram showing an example sequence of messages exchanged between communication devices. Figure 3 is a diagram showing an example hardware configuration of a communication device. Figure 4 is a diagram showing an example functional configuration of a base station. Figure 5 is a diagram showing an example functional configuration of a terminal. Figure 6 is a diagram showing an example operation performed by a base station and a terminal. Figure 7 is a diagram showing an example sequence of messages exchanged between communication devices. Figure 8 is a diagram showing an example sequence of messages exchanged between communication devices.

[0011] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the features described in the embodiments may be combined in any way. Furthermore, identical or similar configurations will be given the same reference numeral, and redundant descriptions will be omitted.

[0012] (System Configuration) Figure 1 shows an example of the configuration of a mobile communication system according to this embodiment. The mobile communication system of this embodiment is, for example, a cellular communication system compliant with the cellular communication standard of the Third Generation Partnership Project (3GPP®). The cellular communication standard may be Long Term Evolution (LTE), Fifth Generation Mobile Communication System (5G), Beyond 5G, 6G, etc. However, it is not limited to these, and the following discussion can be applied to a mobile communication system compliant with any wireless communication standard. This mobile communication system is composed of, for example, a base station 101, a base station 102, and a terminal 111. Base stations 101 and 102 are sometimes referred to as base station 100 without distinction. Base station 100 exchanges wireless signals with terminal 111 via a wireless medium. Base station 100 includes, for example, gNB (next Generation Node B), eNB (evolved Node B), etc. Base station 100 is connected to a core network (not shown). The core network may be, for example, an Evolved Packet System (EPS) or a 5G Core Network (5GC). Terminal 111 is a terminal used by a user and exchanges radio signals with base station 100 via a radio medium. Terminal 111 may be called User Equipment (UE). Terminal 111 includes, for example, a smartphone, mobile phone, personal computer, tablet terminal, wearable device, IoT (Internet of Things) terminal, etc. For example, base station 100 and terminal 111 can communicate in the cell provided by each base station 100 using the connection established between terminal 111 and base station 100. In Figure 1, base station 101 provides cell 121, and base station 102 provides cell 122. Figure 1 shows an example where there are two base stations 100 and one terminal 111, but in a mobile communication system, there may be three or more base stations 101, or two or more terminals 111. In this case, multiple terminals 111 may be connected to one base station 100, or one terminal 111 may be connected to multiple base stations 100.

[0013] Base stations 101 and 102 may be interconnected by a network 131. Network 131 may be a wired or wireless network. For example, base stations 101 and 102 may communicate over network 131 using an X2 interface or an Xn interface. The X2 interface may be used for communication between eNBs. The Xn interface may be used for communication between gNBs. For example, when base station 101 causes a terminal 111 connected to its device to switch from a cell 121 provided by its device to a cell 122 provided by base station 102, it may exchange information necessary for the switch with base station 102 using an X2 interface or an Xn interface.

[0014] In the 3GPP cellular communication standard, LTM Cell Switching is defined as a cell switching method that switches cells at a lower layer than the conventional Layer 3 (L3) handover. LTM is an abbreviation for L1 / L2 Triggered Mobility. LTM cell switching allows for efficient switching of the cell to which a terminal is connected. Figure 2 shows an example of the sequence exchanged between communication devices when performing LTM cell switching. In Figure 2, the source base station 101 connected to terminal 111 instructs terminal 111 to measure and report the radio quality of cell 121 and surrounding cells provided by its device. This instruction can be made via a setting using the Layer 3 RRC Reconfiguration message. RRC is an abbreviation for Radio Resource Control. Terminal 111 performs a measurement report according to the settings made by source base station 101 (S201). This measurement report may also be performed using a Measurement Report message at Layer 3. Based on the measurement report, source base station 101 selects one or more candidate cells (LTM candidate cells) to be used as the switching destination for cell switching (S202). Source base station 101 notifies terminal 111 of the selected LTM candidate cells (S203). This notification may include configuration information (LTM candidate settings) for terminal 111 to communicate with the selected LTM candidate cells. Source base station 101 also notifies terminal 111 of the settings to measure and report the radio quality of each LTM candidate cell at Layer 1 (L1). These notifications may be performed using an RRC reconfiguration message. An LTM candidate cell may include multiple cells provided by a single base station 100. For example, a single base station 100 can constitute a cell at each of several different frequencies. Furthermore, each cell composed of each beam formed by a single base station 100 can be distinguished.For example, in Figure 1, if the area of ​​cell 122 provided by base station 102 is covered by a collection of multiple beams formed by base station 102, each of the distinguishable individual cells provided by each beam may be included in the LTM candidate cells as a distinct cell from one another. Thus, the term cell in this embodiment includes each cell provided by one base station at multiple different frequencies, and each distinguishable cell provided by each beam formed by one base station. Terminal 111 responds with an RRC reconfiguration complete message. This completes the preparation phase for performing LTM.

[0015] Terminal 111 performs synchronization processing for each cell notified as an LTM candidate cell (S205, S206). For example, terminal 111 may perform processes such as activating the TCI state and synchronizing with the LTM candidate cell as downlink (DL) synchronization. TCI is an abbreviation for Transmission Configuration Indication. Terminal 111 prepares for communication with the LTM candidate cell by activating the TCI state corresponding to the candidate beam used for communication with the LTM candidate cell. Terminal 111 may also perform DL direction synchronization by receiving the synchronization signal transmitted by the LTM candidate cell. Terminal 111 may also perform processes such as TA adjustment for uplink (UL) synchronization. TA is an abbreviation for Timing Advance. TA adjustment can adjust the timing at which the signal transmitted by terminal 111 reaches base station 100, which provides the LTM candidate cell. In this way, pre-synchronization is performed between terminal 111 and the base station providing the LTM candidate cell, enabling efficient cell switching. This completes the Early Sync phase.

[0016] Terminal 111 measures the L1 level radio quality of each LTM candidate cell based on the settings notified by source base station 101 and transmits a measurement report to source base station 101 (S207). In measuring the L1 level radio quality, the radio quality of each beam from which the signal is transmitted may be measured for each signal transmitted from each base station 100. In addition, the report of the L1 level radio quality measurement may report each of the measured radio quality values. Reporting to source base station 101 may be done periodically or based on the fulfillment of predetermined conditions included in the settings. For example, predetermined conditions include the beam quality of the serving cell provided by source base station 101 falling below a threshold (event 2), the beam quality of the LTM candidate cell becoming higher than the beam quality of the serving cell by an offset value (event 3), the beam quality of the LTM candidate cell becoming higher than a threshold (event 4), and the beam quality of the serving cell falling below a first threshold and the beam quality of the LTM candidate cell becoming higher than a second threshold (event 5). Beam quality is, for example, received power. Values ​​indicating received power include RSRP, RSRQ, RSSI, SINR, etc. RSRP is an abbreviation for Reference Signal Received Power. RSRQ is an abbreviation for Reference Signal Received Quality. RSSI is an abbreviation for Received Signal Strength Indicator. SINR is an abbreviation for Signal to Interference plus Noise Ratio. The source base station 101 can set one or more of the above events 2 to 5 as predetermined conditions. Terminal 111 measures the radio quality of the beams of the serving cell and LTM candidate cell, uses the measured values ​​to determine whether predetermined conditions notified by the source base station 101 are met, and reports to the source base station 101 if the predetermined conditions are met. This reporting by terminal 111 to the source base station 101 triggered by the fulfillment of predetermined conditions indicated in the settings can be called an event-triggered report.

[0017] When the source base station 101 receives a measurement report from the terminal 111, it decides whether or not to perform a cell switch (S208). If it is decided to perform a cell switch, the source base station 101 notifies the terminal 111 that it should perform a cell switch (S209). For example, the source base station 101 may give instructions to the terminal 111 by transmitting a MAC CE that includes an LTM Cell Switch Command. MAC CE is an abbreviation for Medium Access Control Control Element. When the terminal 111 receives the notification that it should perform a cell switch, it disconnects from the source base station 101 and applies the settings for communication with the target base station 102 (S210). The target base station 102 is a base station that provides the cell selected as the switching destination from among the LTM candidate cells. Terminal 111 establishes a connection with the target base station 102 using a random access procedure (S211). This completes the LTM cell switching. In this way, by using LTM cell switching, procedures at Layer 3 are unnecessary, and the processing time during switching is shortened by early synchronization with one or more LTM candidate cells, making it possible to perform cell switching efficiently.

[0018] As described above, LTM cell switching reduces the time required for cell switching, thereby improving connection stability. However, if terminal 111 is moving at high speed, cell switching may still fail even with LTM cell switching. For example, when an event trigger is reported, terminal 111 determines whether predetermined conditions for reporting are met each time it measures the radio quality of each LTM candidate cell. If the predetermined conditions are met, terminal 111 sends a measurement report to source base station 101. Upon receiving the measurement report, source base station 101 decides whether to perform cell switching based on the measurement report, and if it decides to perform cell switching, it sends a cell switching instruction to terminal 111. In this way, a certain amount of time elapses between the meeting of the predetermined conditions for reporting and the transmission of the cell switching instruction. If terminal 111 is moving at high speed, terminal 111 may move outside the source base station 101's cell during this time. In this case, the cell switching instruction transmitted by source base station 101 is not received by terminal 111, and cell switching fails. Furthermore, if the terminal 111 is moving at an even faster speed, there is a possibility that the measurement report transmitted by the terminal 111 may not be received by the source base station 101. Also, if the frequency band used in the cell is a high frequency band such as the millimeter wave band, the measurement report from the terminal 111 and the cell switching instructions from the source base station 101 may not be received if the terminal 111 moves out of the line of sight of the source base station 101.

[0019] In light of these circumstances, the source base station 101 in this embodiment causes the terminal 111 to measure the received power from its own device and LTM candidate cells, and to estimate whether predetermined conditions are met using the measured values, and to report if it is estimated that the predetermined conditions are met. The source base station 101 then, based on receiving the report from the terminal 111, executes a process to switch the terminal 111's connection destination from the first cell provided by its own device to the second LTM candidate cell reported by the terminal 111. For example, the source base station 101 causes the terminal 111 to measure the received power of signals received from the first cell and the second cell, and to estimate whether predetermined conditions regarding the received power are met using the acquired measured values ​​at a specific timing after the measurement, or within a certain length of time after the measurement, and to report if it is estimated that the predetermined conditions are met. The instructions from the source base station 101 include information for the terminal 101 to specify that specific timing or certain length of time. Terminal 111 makes an inference as to whether predetermined conditions are met, in accordance with instructions received from source base station 101, and makes a report based on the inference that the predetermined conditions are met. Furthermore, terminal 111 executes a process when it receives a notification from source base station 101 indicating that it should perform a process to switch terminal 111's connection destination from the first cell to the second cell. With this configuration, LTM cell switching is performed based on the inference that predetermined conditions are met, so the stability of the connection provided to terminal 111 can be improved even when terminal 111 is moving at high speed.

[0020] The specific timing after the measurement and the fixed period after the measurement may be determined based on the speed of the terminal 111. For example, the source base station 101 may cause the terminal 111 to make predictions about whether predetermined conditions will be met at a specific timing further in the future or at a longer fixed period, as the speed of the terminal 111 increases. This not only improves the stability of the connection provided to the terminal 111 even when the speed of the terminal 111 is high, but also avoids situations where cell switching occurs too early when the speed of the terminal 111 is low.

[0021] The source base station 101 may, when it is estimated that a predetermined condition is met, instruct the base station to report if it is estimated that the predetermined condition is met for a predetermined period of time from the time the estimation was made. This confirms that the estimation that the predetermined condition is met continues for a predetermined period of time, thereby increasing the reliability of cell switching based on estimation.

[0022] Furthermore, if the source base station 101 includes information to specify a particular timing in its instructions to the terminal 111, it may instruct the terminal 111 to report a predetermined length of time before this specific timing. Similarly, if the source base station 101 includes information to specify a certain length of time in its instructions to the terminal 111, it may further estimate the timing at which a predetermined condition will be met within that certain length of time, and instruct the terminal 111 to report a predetermined length of time before the estimated timing at which the predetermined condition will be met. With this configuration, the source base station 101 will receive a predetermined length of time before the timing at which the predetermined condition will be met. As a result, the source base station 101 can issue a cell switching instruction to the terminal 111 at an earlier timing, thereby improving the stability of the connection provided to the terminal 111, even when the terminal 111 is moving at high speed.

[0023] Examples of the configuration and operation of the base station 101 and terminal 111 that operate in this manner are described below.

[0024] (Circuit Configuration) An example configuration of the base station 101 and terminal 111 will be described. Figure 3 is a diagram showing the hardware configuration of the base station 101 and terminal 111. In one example, the base station 101 and terminal 111 are configured to include a processor 301, ROM 302, RAM 303, storage device 304, and communication circuit 305. The processor 301 is a computer configured to include one or more processing circuits, such as a general-purpose CPU (Central Processing Unit) or ASIC (Application-Specific Integrated Circuit). The processor 301 performs the overall processing of the device and the above-mentioned processing by reading and executing programs stored in the ROM 302 and storage device 304. The ROM 302 is a read-only memory in which information such as programs and various parameters related to the processing performed by the base station 101 is recorded. The RAM 303 functions as a workspace when the processor 301 executes programs and is a random access memory in which temporary information is recorded. The storage device 304 is configured, for example, by a removable external storage device. The communication circuit 305 is configured to include, for example, circuits for wired or wireless communication between the base station 101 and the terminal 111. For example, the base station 101 can communicate with the terminal 111 using the communication circuit 305 for LTE or 5G and an antenna (not shown). The base station 101 can also communicate with other base stations and network equipment (not shown) using the communication circuit 305 for wired communication. The terminal 111 can communicate with the base station 101 using the communication circuit 305 for LTE or 5G and an antenna (not shown).

[0025] (Functional Configuration) Figure 4 shows an example of the functional configuration of the base station 101. The base station 101 is configured to include, for example, a wireless communication control unit 401, a condition determination instruction unit 402, a report receiving unit 403, a cell switching notification unit 404, and an information acquisition unit 405. Figure 4 shows the functional configuration of the base station 101 in this embodiment, and the general configuration of the base station 101 is omitted. These functional units can be realized, for example, by the processor 301 executing a program stored in the ROM 302 or storage device 304 and controlling the communication circuit 305 as needed. However, it is not limited to this, and dedicated hardware for realizing each function may be provided, for example.

[0026] The wireless communication control unit 401 performs communication with the terminal 111. For example, the wireless communication control unit 401 can allocate wireless resources to be used for transmission to the terminal 111, wireless resources to be used by the terminal 111 when it transmits, wireless resources to which reference signals for measuring wireless quality are transmitted by the terminal 111, and wireless resources to be used by the terminal 111 when it transmits reports. The wireless communication control unit 401 can use the allocated wireless resources to communicate with the terminal 111.

[0027] The condition determination instruction unit 402 instructs the terminal 111 to make an inference as to whether or not predetermined conditions are met. For example, the condition determination instruction unit 402 may instruct the terminal 111 to include information that identifies LTM candidate cells for which wireless quality measurement should be performed, predetermined conditions to be determined by inference, information that identifies an inference model to be used for inference, and information that identifies a specific timing or period of a certain length after measurement for which the predetermined conditions should be inferred to be met. The condition determination instruction unit 402 also instructs the terminal 111 to make a report when predetermined conditions are met. For example, the condition determination instruction unit 402 may instruct the terminal 111 to include information that should be reported when predetermined conditions are met, and information indicating the timing at which the report should be made.

[0028] The report receiving unit 403 receives reports transmitted from terminal 111. The cell switching notification unit 404 notifies terminal 111 to perform cell switching if it is determined to do so based on the reports received from terminal 111 by the report receiving unit 403. The information acquisition unit 405 acquires information from terminal 111. For example, the information acquisition unit 405 may acquire information indicating the movement speed of terminal 111 and the accuracy of the estimation.

[0029] Figure 5 shows an example of the functional configuration of terminal 111. Terminal 111 is configured to include, for example, a wireless communication control unit 501, an instruction receiving unit 502, a wireless quality measurement unit 503, a condition determination unit 504, a report transmission unit 505, a cell switching execution unit 506, and an information provision unit 507. Figure 5 shows the functional configuration of terminal 111 in this embodiment, and omits, for example, the general configuration of terminal 111. These functional units can be realized, for example, by a processor 301 executing a program stored in ROM 302 or storage device 304 and controlling the communication circuit 305 as needed. However, it is not limited to this, and for example, dedicated hardware for realizing each function may be provided.

[0030] The wireless communication control unit 501 performs communication with the base station 100. For example, the wireless communication control unit 501 communicates with the source base station 101 using the radio resources allocated by the source base station 101 connected to its own device. The instruction receiving unit 502 receives instructions from the source base station 101. For example, the instruction receiving unit 502 may receive instructions indicating that it should measure the received power of the source base station 101 or LTM candidate cell to which its own device is connected, and use the measured values ​​to estimate whether predetermined conditions are met. The wireless quality measurement unit 503 measures the wireless quality according to the instructions received by the instruction receiving unit 502. The condition determination unit 504 uses the measured values ​​of the received power of the source base station 101 or LTM candidate cell to which its own device is connected, measured by the wireless quality measurement unit 503, to estimate whether predetermined conditions are met. For example, the condition determination unit 504 may use the measured values ​​of the received power to estimate the received power at a specific timing or for a certain period of time after the measurement, and use the estimated values ​​to determine whether predetermined conditions are met. The condition determination unit 504 may directly estimate whether predetermined conditions are met using the measured value of the received power, without performing estimation of the received power at a specific timing or for a certain period of time after measurement using the measured value of the received power. The report transmission unit 505 transmits a report to the source base station 101 when it is estimated that predetermined conditions are met. The cell switching execution unit 506 performs LTM cell switching based on instructions from the source base station 101. The information provision unit 507 provides the source base station 101 with information regarding the terminal 111. For example, the information provision unit 507 may provide the source base station 101 with information indicating the movement speed of the terminal 111 and the accuracy of the estimation.

[0031] (Processing Flow) The operation of the source base station 101 and the terminal 111 when a terminal 111 connected to the source base station 101 performs cell switching to the target base station 102 will be described. Figure 6 shows an example of the operation performed by each device when a terminal 111 connected to the source base station 101 performs cell switching to the target base station 102. In Figure 6, it is assumed that the LTM candidate cell for terminal 111 to perform LTM cell switching has been identified in advance by the source base station 101. For example, the source base station 101 may identify the LTM candidate cell based on the radio quality of signals received by terminal 111 from its own device and surrounding cells, as provided by terminal 111. In this case, the source base station 101 may instruct terminal 111 to measure and report the radio quality of signals received from its own device and from surrounding cells. For example, the source base station 101 may give instructions using measurement settings (Measurement Configuration, MeasConfig). In response, terminal 111 may perform measurements according to the measurement settings and transmit a measurement report. The measurement report may include information indicating the received power of signals received by terminal 111 from source base station 101 and surrounding base stations. Based on the measurement report, source base station 101 may identify LTM candidate cells.

[0032] The source base station 101 instructs the terminal 111 to infer whether predetermined conditions are met based on the radio quality of signals received from its own device and LTM candidate cells (S601). This instruction may be included, for example, in the information for configuring LTM candidates included in the RRC Reconfiguration message. The information for configuring LTM candidates may be called LTM Candidate Configuration. For example, the source base station 101 may instruct the terminal 111 to measure the Layer 1 radio quality of signals received from its own device and LTM candidate cells. Radio quality is, for example, a value indicating received power. The measured value (L1 measured value) in the measurement of Layer 1 radio quality may be a measured value indicating the individual radio quality measured. For example, the measured value indicating the individual radio quality may be so-called raw data. In addition, in the report of Layer 1 measured values, each beam formed by the target base station 102 may be reported separately. On the other hand, the measured value in the measurement of radio quality at Layer 3 (L3 measurement value) can be a statistical value of the measured values ​​that represent the individual radio quality measured. For example, the statistical value can be the mean, maximum, median, weighted mean, etc. As an example, in the reporting of L3 measurement values, the average value of the measured values ​​in each beam composed of the target base station 102 may be reported as a value that represents the radio quality of that target base station 102. The source base station 101 may be instructed to estimate whether predetermined conditions are met using the measured value that represents the radio quality. The predetermined conditions include, for example, events 2 to 5 described above.

[0033] The source base station 101 may include information that the terminal 111 should use for measurement and estimation in its instructions to the terminal 111. For example, the source base station 101 may include in its instructions information related to measurement and estimation, such as information identifying candidate LTM cells for which radio quality should be measured, information specifying predetermined conditions to be determined by estimation, information specifying an inference model to be used for estimation, and information specifying a specific timing after measurement or a certain length of time after measurement for which it should be determined by estimation whether the predetermined conditions are met. The information specifying predetermined conditions to be determined by estimation may be information that identifies one or more of the events 2 to 5 described above. If the instructions include information specifying a specific timing after measurement for which it should be determined whether the predetermined conditions are met, the terminal 111 will estimate, at the time the measurement was performed, whether the predetermined conditions will be met when the time indicated by that specific timing has elapsed since the measurement. As an example, the terminal 111 will estimate, using the measured value, whether the predetermined conditions will be met X seconds after the time the measurement was performed. On the other hand, if the instructions include information that specifies a certain period of time after measurement during which it should be determined by estimation whether a predetermined condition is met, the terminal 111 can estimate whether the predetermined condition is met during a certain period of time from the moment the measurement was taken. For example, the terminal 111 uses the measured value to estimate whether the predetermined condition is met within X seconds starting from the moment the measurement was taken. If the predetermined condition is met, the terminal 111 can identify the timing at which the predetermined condition is met and report information indicating that identified timing to the source base station 101.

[0034] The source base station 101 can determine a specific timing after measurement at which it should estimate whether predetermined conditions are met, based on the speed of the terminal 111. For example, the source base station 101 can determine a specific timing such that the time from the measurement timing to the specific timing becomes longer, so that it can estimate a future timing further ahead, as the value indicating the speed of the terminal 111 is larger (faster speed). In other words, the "X seconds" mentioned above can be determined to be larger, as the speed of the terminal 111 is faster. This increases the likelihood of successful cell switching even when the speed of the terminal 111 is fast. Similarly, the source base station 101 can determine a fixed length of period after measurement at which it should estimate whether predetermined conditions are met, based on the speed of the terminal 111. For example, the source base station 101 can determine a fixed length of period such that the fixed length of period becomes longer, so that it can estimate a future timing further ahead, as the value indicating the speed of the terminal 111 is larger (faster speed). In other words, the faster the terminal 111 moves, the longer the aforementioned "X seconds" can be determined. Furthermore, if the terminal 111's moving speed is below a predetermined threshold, the source base station 101 does not need to make estimations regarding the predetermined conditions. This improves the stability of the connection to terminals with high moving speeds while reducing power consumption for terminals with low moving speeds. The source base station 101 can obtain information indicating the terminal 111's moving speed from the terminal 111. The source base station 101 can also estimate the terminal 111's moving speed based on other information obtained from the terminal 111. For example, the source base station 101 can cause the terminal 111 to periodically transmit a reference signal and estimate the terminal 111's moving speed based on the received power of the received reference signal. The reference signal may be a Sounding Reference Signal.

[0035] Terminal 111 can make inferences about whether predetermined conditions are met by using artificial intelligence (AI) or machine learning (ML) for inference. When inference using AI or ML is performed in terminal 111, source base station 101 may include information identifying the AI ​​model in its instructions as information that identifies the inference model to be used for inference. The AI ​​model may be a trained model generated by performing machine learning using training data. For example, terminal 111 can use a measured value indicating the measured wireless quality and a specific timing after the measurement to be inferred as input to the AI ​​model, and obtain the inferred result of the wireless quality at the input specific timing after the measurement as the output of the AI ​​model. Also, terminal 111 can use a value indicating the measured wireless quality and a specific timing after the measurement to be inferred as input to the AI ​​model, and obtain the inferred result of whether predetermined conditions are met at the input specific timing after the measurement as the output of the AI ​​model. For example, the AI ​​model may be identified by its configuration and parameters. The configuration of the AI ​​model may be rules, mathematical formulas, neural network configurations, etc., used to output inference results based on the input data. Furthermore, the parameters of the AI ​​model may be, for example, the weight coefficients of a trained model generated by performing machine learning using training data. For example, by notifying the source base station 101 of the mathematical formula that constitutes the AI ​​model and the values ​​of each coefficient included in the formula, the terminal 111 can identify the AI ​​model to be used for inference. Also, by notifying the source base station 101 of the configuration of the neural network used in the AI ​​model and the weights of each neuron, the terminal 111 can identify the AI ​​model to be used for inference. If identification information exists between the source base station 101 and the terminal 111 to identify each AI model, the terminal 111 can identify the AI ​​model to be used for inference by notifying the source base station 101 of that identification information.

[0036] Furthermore, the source base station 101 may include in its instructions information related to reporting, such as information that identifies the timing for reporting and information that should be included in the report. For example, the timing for reporting may be the timing at which it is presumed that a predetermined condition will be met. By promptly reporting when it is presumed that a predetermined condition will be met, the likelihood of successful cell switching can be increased even when the terminal 111 is moving at high speed. The timing for reporting may be the timing after a predetermined period of time has elapsed from the time at the terminal 111 that it is presumed that a predetermined condition will be met. The terminal 111 can presum that the predetermined condition will continue to be met during this predetermined period of time. This can increase the reliability of the presumed predetermined condition being met. In this case, the source base station 101 may include in its instructions information that identifies this predetermined period of time. Also, the timing for reporting may be a predetermined period of time before the timing identified by the presumed timing at which the predetermined condition will be met. As a result, the source base station 101 receives a report earlier than the actual timing when the predetermined conditions are met, allowing the source base station 101 to instruct the terminal 111 to perform cell switching at an earlier time.

[0037] The information to be included in the report may include information identifying LTM candidate cells that meet predetermined conditions, predetermined conditions that are presumed to be met, the presumed timing at which the predetermined conditions will be met, an estimated value of the radio quality, and information indicating the probability that the predetermined conditions will be met. If the probability of the predetermined conditions being met is output based on the estimation, the source base station 101 may include in the instructions that a report should be made if the probability of the predetermined conditions being met exceeds a predetermined threshold. In this case, information indicating the predetermined threshold may be included in the instructions. The information that the source base station 101 includes in the instructions is not limited to the above, and may include only a part of the above.

[0038] When terminal 111 receives instructions from source base station 111, it measures the radio quality according to the instructions and makes an inference as to whether predetermined conditions are met (S602). For example, based on the information contained in the instructions, terminal 111 may identify the serving cell and LTM candidate cell provided by source base station 101 as cells whose radio quality should be measured. Also, based on the information contained in the instructions, terminal 111 may identify the conditions that should be determined by inference. Furthermore, based on the information contained in the instructions, terminal 111 may identify the inference model to be used for inference and a specific timing or period of a certain length after measurement for which it should infer whether predetermined conditions are met. If the instructions do not contain this information, terminal 111 may obtain the information necessary for measurement and inference using other methods. For example, terminal 111 may use information that has been pre-set in its own device. As an example, if the AI ​​model to be used for inference has been pre-identified, terminal 111 may perform inference using that AI model.

[0039] Terminal 111 can use measured radio quality values ​​to estimate radio quality at specific timings or for a certain period of time after measurement as instructed by source base station 101, and use the estimated radio quality values ​​to estimate whether predetermined conditions instructed by source base station 101 are met. For example, if terminal 111 is instructed by source base station 101 to estimate whether event 3 is met at a timing X seconds after the timing of measurement, terminal 111 measures the received power from source base station 101 and the received power from LTM candidate cells, respectively, and estimates the received power X seconds after the timing of measurement for each received power. Terminal 111 can periodically measure the received power and keep each measurement result as a history. For example, terminal 111 can obtain estimated values ​​of received power from source base station 101 and estimated values ​​of received power from LTM candidate cells as the output (inference results) of the AI ​​model specified by source base station 101 by inputting the measurement results it holds and information indicating the timing to be estimated. As an example, terminal 111 may use one or more measured values ​​of received power held as measurement results for source base station 101. Also, terminal 111 may use one or more measured values ​​of received power held as measurement results for LTM candidate cells. For example, terminal 111 may use one or more measured values ​​of received power from source base station 101 and one or more measured values ​​of received power from LTM candidate cells to estimate the received power for source base station 101. Also, terminal 111 may use one or more measured values ​​of received power from source base station 101 and one or more measured values ​​of received power from LTM candidate cells to estimate the received power for LTM candidate cells. The data that terminal 111 uses to estimate the received power is not limited to these. Any information that terminal 111 can use to estimate the received power of the source base station 101 and the LTM candidate cell may be used as input to the AI ​​model. For example, the speed of terminal 111 may be used as input to the AI ​​model. Terminal 111 uses the estimated received power of the source base station 101 and the estimated received power of the LTM candidate cell X seconds after performing the measurement to determine whether event 3 is met.For example, if terminal 111 determines that the estimated value of the received power of the LTM candidate cell exceeds a predetermined offset value and is greater than the estimated value of source base station 101, terminal 111 may determine that event 3 is met at a specific timing after measurement as instructed by source base station 101. Also, if terminal 111 determines that the estimated value of the received power of the LTM candidate cell is less than or equal to the sum of the estimated value of source base station 101 and the predetermined offset value, terminal 111 may determine that event 3 is not met. Furthermore, if the instructions from source base station 101 indicate that terminal 111 should report if the predetermined conditions are continuously met for a predetermined period after it is estimated that the predetermined conditions are met, terminal 111 may continue to measure radio quality for a predetermined period after it is estimated that the predetermined conditions are met, and estimate whether the predetermined conditions continue to be met. In this case, terminal 111 reports if the predetermined conditions are continuously met for a predetermined period after it is estimated that the predetermined conditions are met. Furthermore, terminal 111 will not report if the predetermined conditions are no longer met during a predetermined period after it is presumed that the predetermined conditions are met. In this way, the predetermined period during which a report is made when the predetermined conditions are continuously met can be called TTT. TTT is an abbreviation for Time To Trigger.

[0040] On the other hand, for example, if terminal 111 is instructed by source base station 101 to estimate whether event 3 is met during a period of X seconds from the time the measurement was performed, terminal 111 measures the received power from source base station 101 and the received power from LTM candidate cells, respectively, and estimates the received power for each received power during a period of X seconds from the time the measurement was performed. As an example, terminal 111 divides the period of X seconds from the time the measurement was performed into predetermined unit time intervals and estimates the received power at each interval. Then, terminal 111 determines whether event 3 is met at each interval using the respective estimated values. The estimation of received power at each interval and the determination of whether event 3 is met can be performed in the same way as the estimation of received power at a specific interval and the determination of whether event 3 is met at each interval described above. That is, for each measurement performed, terminal 111 estimates the received power for multiple intervals included in the period of X seconds from the time the measurement was performed, and determines whether event 3 is met at each interval. Terminal 111 reports to source base station 101 if it determines that event 3 is met at one or more timings. Terminal 111 does not report to source base station 101 if it determines that event 3 is not met at any timing. If the instructions from source base station 101 indicate that terminal 111 should report if the predetermined conditions are continuously met for a predetermined period after it is presumed that the predetermined conditions are met, terminal 111 may measure the radio quality for a predetermined period after it is presumed that the predetermined conditions are met, and estimate whether the predetermined conditions are continuously met. In this case, terminal 111 reports if the predetermined conditions are continuously met for a predetermined period after it is presumed that the predetermined conditions are met. That is, for each measurement, terminal 111 estimates the received power for multiple timings included in the X-second period from the timing of the measurement, and determines whether event 3 is met at each timing.Terminal 111 reports to source base station 101 if it is determined that event 3 is met at one or more timings for a predetermined period of time. If terminal 111 determines that event 3 is met at one or more timings, it may then confirm in subsequent estimations that the predetermined conditions are expected to continue to be met at the timing in which event 3 was determined to be met.

[0041] Furthermore, for example, terminal 111 can directly use the measured wireless quality to infer whether predetermined conditions are met at a specific timing or for a certain period of time after the measurement, without inferring the wireless quality at a specific timing or for a certain period of time after the measurement using the measured wireless quality. In this case, for example, if terminal 111 is instructed by source base station 101 to infer whether event 3 is met at a timing X seconds after the timing of the measurement, terminal 111 can measure the received power from source base station 101 and the received power from LTM candidate cells, respectively, and input the measured received power and information indicating the timing to be inferred to the AI ​​model specified by source base station 101. In this case, terminal 111 can obtain whether event 3 is met at the input timing to be inferred as the output (inference result) of the AI ​​model. For example, terminal 111 can periodically measure the received power and keep each measurement result as a history. Terminal 111 may use one or more measured values ​​of the received power of the source base station 101, one or more measured values ​​of the received power of LTM candidate cells, and information indicating the timing to be estimated as input to the AI ​​model. For example, if terminal 111 outputs an estimate that event 3 will be met at a timing X seconds after the timing of the measurement, it will report to the source base station 101. If terminal 111 outputs an estimate that event 3 will not be met at a timing X seconds after the timing of the measurement, it will not report to the source base station 101. Terminal 111 may also obtain the probability that event 3 will be met at the input estimated timing as output to the AI ​​model. In this case, if the outputted probability exceeds a predetermined threshold indicated in the instructions of the source base station 101, terminal 111 will report to the source base station 101. If the outputted probability is less than or equal to the predetermined threshold indicated in the instructions of the source base station 101, terminal 111 will not report to the source base station 101.

[0042] Furthermore, if the terminal 111 receives instructions from the source base station 101 to estimate whether event 3 will be met during a period of X seconds from the time the measurement was performed, the terminal 111 measures the received power from the source base station 101 and the received power from the LTM candidate cell, respectively, and estimates whether event 3 will be met at each of the predetermined unit time intervals within the X-second period from the time the measurement was performed. In this case, for each measurement performed, the terminal 111 estimates whether event 3 will be met at each of the multiple timing intervals included in the X-second period from the time the measurement was performed. The determination of whether event 3 will be met at each timing interval can be performed in the same way as the determination of whether event 3 will be met at a specific timing interval as described above. If the terminal 111 determines that event 3 will be met at one or more timing intervals, it reports this to the source base station 101. If the terminal 111 determines that event 3 will not be met at any of the timing intervals, it does not report this to the source base station 101.

[0043] If it is presumed that the predetermined conditions are met, terminal 111 makes a report to source base station 101 (S603). Terminal 111 may make a report that includes information specified in the instructions from source base station 101. For example, terminal 111 may report information that identifies an LTM candidate cell that meets the predetermined conditions, the predetermined conditions that are presumed to be met, the timing that is presumed to be when the predetermined conditions are met, an estimated value of radio quality, information indicating the probability that the predetermined conditions are met, etc. For example, if the instructions include multiple events from events 2 to 5 as predetermined conditions, terminal 111 may presumed whether the conditions are met for each event and report information indicating the event that is presumed to be met. Also, if the instructions from source base station 101 include information that specifies a certain length of time after measurement during which it should be presumed whether the predetermined conditions are met, terminal 111 may identify the timing during which the predetermined conditions are met and report information indicating that timing. Furthermore, if the AI ​​model used for prediction outputs a probability that a predetermined condition is met, terminal 111 may report information indicating the probability that the predetermined condition is met. Also, if terminal 111 predicts that the predetermined condition is met at multiple timings within a certain period, it may report information indicating each timing, and may report the probability that the predetermined condition is met at each timing. Note that the information indicating the probability that the predetermined condition is met included in the report may be limited to those timings in which the probability of exceeding a predetermined threshold included in the instructions of source base station 101 is indicated within a certain period. This may reduce the amount of information included in the report.

[0044] The source base station 101 determines to execute cell switching based on the report from the terminal 111 (S604). For example, the source base station 101 can determine to execute cell switching based on receiving the report from the terminal 111. In this case, the source base station 101 can instruct the terminal 111 to switch to an LTM candidate cell based on information that identifies the LTM candidate cell satisfying a predetermined condition included in the report (S605). Furthermore, the source base station 101 does not have to determine to execute cell switching immediately after receiving the report from the terminal 111. For example, if the report from the terminal 111 includes information indicating a timing at which a predetermined condition is estimated to be satisfied, the source base station 101 can adjust the timing of issuing a cell switching instruction to the terminal 111 based on the moving speed of the terminal 111. For example, when the source base station 101 receives a report from the terminal 111 and the moving speed of the terminal 111 is higher than a predetermined threshold, the source base station 101 can transmit a cell switching instruction immediately. On the other hand, when the source base station 101 receives a report from the terminal 111 and the moving speed of the terminal 111 is lower than a predetermined threshold, the source base station 101 does not instruct cell switching immediately, and can transmit the cell switching instruction to the terminal 111 at a timing determined according to the moving speed of the terminal 111, which is before the timing estimated that the predetermined condition will be satisfied. In this way, by adjusting the timing of issuing the cell switching instruction in the source base station 101, the cell to which the terminal 111 connects can be changed at an appropriate timing according to the moving speed of the terminal 111.

[0045] (Processing Example) This section describes a processing example involving the source base station 101, terminal 111, and target base station 102 when terminal 111 connected to source base station 101 performs cell switching to target base station 102. Figure 7 shows an example of a sequence exchanged between communication devices when terminal 111 connected to source base station 101 performs LTM cell switching to target base station 102. In Figure 7, source base station 101, connected to terminal 111, instructs terminal 111 to measure and report the radio quality of cell 121 and surrounding cells provided by its device. This instruction can be made via a setting using the Layer 3 RRC Reconfiguration message. Terminal 111 makes a measurement report according to the setting (S701). This measurement report can also be made using the Layer 3 Measurement Report message. Based on the measurement report, source base station 101 selects one or more cells that will be candidates for connection destinations (LTM candidates) (S702). The source base station 101 notifies the terminal 111 of the selected LTM candidate cell (S703). This notification may include configuration information (LTM candidate settings) for the terminal 111 to communicate in the selected LTM candidate cell. For example, the LTM candidate settings may include information that identifies the LTM candidate cell and communication parameters that the terminal 111 should use for communication after switching to each LTM candidate cell. Each LTM candidate cell setting may be assigned an identifier to identify it. For example, each LTM candidate cell setting may be assigned a different target setting ID. The target setting ID may be used by the source base station 101 to specify the settings that the terminal 111 should apply when switching cells. For example, by receiving the LTM candidate settings, the terminal 111 may activate the TCI state corresponding to each LTM candidate cell. Furthermore, by receiving an LTM Cell Switch Command from the source base station 101, terminal 111 can enable the TCI state corresponding to the cell or configuration information specified by the LTM Cell Switch Command while disabling the TCI state corresponding to other cells or configuration information.Furthermore, the source base station 101 instructs the terminal 111 to infer whether predetermined conditions are met based on the radio quality of signals received from its own device and LTM candidate cells (S703). This instruction may be included in the LTM or LTM candidate settings contained in the RRC reconfiguration message. The terminal 111 responds using the RRC reconfiguration complete message. This completes the preparation phase for executing LTM.

[0046] Terminal 111 performs synchronization processing for each cell notified as an LTM candidate (S705, S706). For example, as DL synchronization, terminal 111 may perform processes such as activating the TCI state and synchronizing with the LTM candidate cell. Terminal 111 prepares for communication with the LTM candidate cell by activating the TCI state corresponding to the candidate beam to be used with the LTM candidate cell. Terminal 111 may also perform DL direction synchronization by receiving the synchronization signal transmitted by the LTM candidate cell. Terminal 111 may also perform processes such as TA adjustment for UL synchronization. This completes the Early Sync phase.

[0047] Terminal 111 measures the radio quality based on instructions from source base station 101 and makes an inference as to whether predetermined conditions are met (S707). The radio quality may be measured at L1 level. If terminal 111 infers that the predetermined conditions are met, it reports this to source base station 101 (S708). The report may be made at Layer 1. For example, terminal 111 may use MAC CE or UCI (Uplink Control Information) to report that it infers that the predetermined conditions are met.

[0048] When the source base station 101 receives a report from the terminal 111, the source base station 101 determines whether to perform cell switching (S709). If it is determined to perform cell switching, the source base station 101 instructs the terminal 111 to perform cell switching (S710). For example, the source base station 101 may give the instruction to the terminal 111 by transmitting a MAC CE including an LTM Cell Switch Command. The LTM Cell Switch Command message may include information indicating an LTM candidate cell to be a cell switching target. For example, the source base station 101 may notify the terminal 111 of the LTM candidate cell to be the cell switching target by specifying a target configuration ID notified in the LTM candidate configuration. Note that, if the L1 measurement report by the terminal 111 includes information indicating the quality of each beam of each LTM candidate cell, the LTM Cell Switch Command message may include information indicating which beam corresponding to the LTM candidate cell to be the cell switching target should be used. When the terminal 111 receives the instruction to perform cell switching, the terminal 111 releases the connection with the source base station 101 and applies configuration for communication with the target base station 102 (S711). The terminal 111 establishes a connection with the target base station 102 using a random access procedure (S712). As described above, in LTM cell switching, by estimating whether a predetermined condition is satisfied by the terminal 111, the stability of the connection provided to the terminal 111 can be improved even when the terminal 111 is moving at high speed.

[0049] (Modification 1) In the above example, a MAC CE including an LTM Cell Switch Command is transmitted from the source base station 101 to the terminal 111 based on the terminal 111's inference that a predetermined condition is met (S710), and the terminal 111 performs an LTM cell switch (S711, S712). The operation that the source base station 101 causes the terminal 111 to perform based on the terminal 111's inference that a predetermined condition is met is not limited to an LTM cell switch. For example, the source base station 101 may cause the terminal 111 to perform an Early Sync based on the terminal 111's inference that a predetermined condition is met. Figure 8 shows an example sequence when the source base station 101 causes the terminal 111 to perform an Early Sync based on the terminal 111's inference that a predetermined condition is met. In Figure 8, the same reference numbers are used for operations similar to those in Figure 7, and their explanations are omitted. Once the preparation phase for executing LTM is complete, terminal 111 measures the radio quality according to instructions from source base station 101 and makes an inference as to whether predetermined conditions are met (S707). If terminal 111 infers that the predetermined conditions are met, it reports this to source base station 101 (S708).

[0050] When the source base station 101 receives a report from the terminal 111, it decides whether or not to have the terminal 111 perform early synchronization for LTM candidate cells that meet predetermined conditions included in the report (S801). If the source base station 101 decides to have the terminal 111 perform early synchronization, it instructs the terminal 111 to perform early synchronization (S802). For example, the source base station 101 may instruct the terminal 111 by transmitting a MAC CE that includes Candidate Cell TCI States Activation. When the terminal 111 receives the instruction to perform early synchronization, it performs early synchronization with the target base station 102 (S705, 706).

[0051] Terminal 111 continues to measure the radio quality of the LTM candidate cell that performed early synchronization and determines whether predetermined conditions are met (S803). For example, terminal 111 may use measured values, rather than estimated values, to determine whether predetermined conditions are met. If terminal 111 determines that predetermined conditions are met, it reports to source base station 101 (S804). The report may be performed at Layer 1. For example, terminal 111 may use MAC CE or UCI to report that predetermined conditions have been met. When source base station 101 receives the report from terminal 111, it decides whether to perform cell switching (S709). If it is decided to perform cell switching, source base station 101 instructs terminal 111 to perform cell switching (S710). For example, source base station 101 can issue instructions to terminal 111 by transmitting a MAC CE containing an LTM Cell Switch Command. When terminal 111 receives instructions to perform cell switching, it disconnects from source base station 101 and applies settings for communication with target base station 102 (S711). Terminal 111 establishes a connection with target base station 102 using a random access procedure (S712). In this way, by predicting whether predetermined conditions will be met before having terminal 111 perform early synchronization, terminal 111 can be made to perform early synchronization when the likelihood of LTM cell switching being performed increases.

[0052] (Modification 2) Terminal 111 may evaluate the accuracy of the estimation and notify source base station 101 of the evaluation result. For example, if terminal 111 has estimated the received power at a specific timing after measurement, it can evaluate the accuracy of the estimation by performing a measurement of the received power at that specific timing and calculating the error between the estimated value and the measured value. For example, the error between the estimated value and the measured value may be the absolute value of the difference between the estimated value and the measured value. Terminal 111 may also calculate a statistical value (average value, etc.) of the error between the estimated value and the measured value. For example, terminal 111 may notify source base station 101 if the error between the estimated value and the measured value or its statistical value exceeds a predetermined threshold. Based on the notification from terminal 111, source base station 101 may instruct terminal 111 to stop estimating whether predetermined conditions are met. Also, if terminal 111 estimates that predetermined conditions are met, it may provide a report including a value indicating the error between the estimated value and the measured value. The source base station 101 can decide whether or not to have terminal 111 perform cell switching or early synchronization based on a notification from terminal 111. For example, if the error between the estimated value notified by terminal 111 and the measured value is greater than a predetermined threshold, the source base station 101 may decide not to perform cell switching or early synchronization. In this way, by having terminal 111 evaluate the accuracy of the estimation and the source base station 101 make decisions on cell switching etc. based on the evaluation result, the source base station 101 can have terminal 111 perform LTM cell switching based on a more reliable estimation. Terminal 111 may evaluate the accuracy of the estimation using the received power of the cell with the strongest received power among the source base station 101 and LTM candidate cells, or it may evaluate the accuracy of the estimation using the received power of K cells in order from the cell with the strongest received power.

[0053] As described above, according to this embodiment, the source base station 101 causes the terminal 111 to measure the received power from its own device and LTM candidate cells, and to estimate whether predetermined conditions are met using the measured values, and to report if it is estimated that the predetermined conditions are met. Based on the report received from the terminal 111, the source base station 101 causes the terminal 111 to execute a process to switch the terminal 111's connection destination from the first cell provided by its own device to the second LTM candidate cell. On the other hand, the terminal 111 makes an estimation as to whether predetermined conditions are met according to the instructions received from the source base station 101, and makes a report based on the estimation that the predetermined conditions are met. Furthermore, the terminal 111 executes the process when it receives a notification from the source base station 101 indicating that it should perform the process to switch the terminal 111's connection destination from the first cell to the second cell. With this configuration, LTM cell switching is performed based on the assumption that predetermined conditions are met, thereby improving the stability of the connection provided to terminal 111, even when terminal 111 is moving at high speed. Thus, it becomes possible to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0054] The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist of the invention.

[0055] This application claims priority based on Japanese Patent Application No. 2025-030313, filed on 27 February 2025, and all of its contents are incorporated herein by reference.

Claims

1. A base station device that communicates with a terminal device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: an instruction means that gives an instruction to the terminal device connected to the base station device, which causes the terminal device to measure the received power of signals received from a first cell provided by the base station device and a second cell provided by another base station device, and uses the measurement value obtained from the measurement to estimate whether predetermined conditions regarding the received power are met at a specific timing after the measurement or within a certain period of time after the measurement, and reports if it is estimated that the predetermined conditions are met, the instruction means which gives the instruction which includes information for the terminal device to specify the specific timing or the certain period of time; a receiving means that receives the report when it is estimated that the predetermined conditions are met; and a notification means that, based on the receipt of the report from the terminal device, notifies the terminal device that it should perform a process to switch the connection destination of the terminal device from the first cell to the second cell.

2. The base station device according to claim 1, further comprising an acquisition means for acquiring information indicating the moving speed of the terminal device, wherein the instruction means determines the specific timing or the fixed-length period based on the moving speed of the terminal device and gives the instruction including information for specifying the determined specific timing or the fixed-length period.

3. The base station device according to claim 1 or 2, wherein the instruction means provides an instruction that further includes information indicating that the report should be made if it is presumed that the predetermined conditions are met over a period of a predetermined length from the time when it is presumed that the predetermined conditions are met.

4. The base station device according to any one of claims 1 to 3, wherein the instruction means further includes information indicating that the report should be made a predetermined length before the specific timing if the instruction includes information for specifying the specific timing, and further includes information indicating that the report should be made a predetermined length before the estimated timing when the predetermined conditions are met if the instruction includes information for specifying a certain length of time.

5. The base station device according to any one of claims 1 to 4, wherein the measurement value is an L1 measurement value, and the process includes switching the connection destination of the terminal device from the first cell to the second cell using L1 / L2 Triggered Mobility (LTM).

6. The base station device according to claim 1, wherein the process comprises the terminal device activating a Transaction Configuration Indication (TCI) state for communication with the second cell.

7. A terminal device that communicates with a base station device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: a receiving means that measures the received power of signals received from a first cell provided by the base station device connected to the terminal device and a second cell provided by another base station device, uses the measured value obtained by the measurement to estimate whether predetermined conditions regarding the received power are met at a specific timing after the measurement or for a certain period of time after the measurement, and receives an instruction indicating that a report should be made if it is estimated that the predetermined conditions are met, the instruction including information for the terminal device to specify the specific timing or the certain period of time; an estimation means that makes the estimation of whether the predetermined conditions are met in accordance with the instruction; a reporting means that makes the report based on the fact that the predetermined conditions are met; and an execution means that executes a process when it receives a notification from the base station device indicating that it should perform a process to switch the connection destination of the terminal device from the first cell to the second cell.

8. The terminal device according to claim 7, further comprising a means for providing information indicating the moving speed of the terminal device.

9. The terminal device according to claim 7 or 8, wherein the instruction further includes information indicating that the report should be made if it is presumed that the predetermined conditions are met over a period of predetermined length from the time when it is presumed that the predetermined conditions are met, and the reporting means makes the report if it is presumed that the predetermined conditions are met over a period of predetermined length from the time when it is presumed that the predetermined conditions are met.

10. The terminal device according to any one of claims 7 to 9, wherein the instruction includes information for identifying the specific timing, and further includes information indicating that the report should be made a predetermined length before the specific timing, and the reporting means makes the report a predetermined length before the specific timing.

11. The terminal device according to any one of claims 7 to 9, wherein the estimation means, when it is estimated that the predetermined conditions are met, further estimates the timing at which the predetermined conditions are met, and the instruction, if it includes information for specifying a period of a certain length, further includes information indicating that the report should be made a period of a predetermined length before the estimated timing at which the predetermined conditions are met, and the reporting means makes the report a period of a predetermined length before the estimated timing at which the predetermined conditions are met.

12. The terminal device according to any one of claims 7 to 11, wherein the measurement value is an L1 measurement value, the process includes switching the connection destination of the terminal device from the first cell to the second cell using L1 / L2 Triggered Mobility (LTM), and the execution means executes the process of switching the connection destination of the terminal device from the first cell to the second cell using LTM based on the receipt of the instruction.

13. The terminal device according to any one of claims 7 to 11, wherein the process includes the terminal device activating a Transaction Configuration Indication (TCI) state for communication with the second cell, and the execution means performs the process of the terminal device activating a TCI state for communication with the second cell based on the receipt of the instruction.

14. A control method performed by a base station device that communicates with a terminal device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: an instruction to a terminal device connected to the base station device to measure the received power of signals received from a first cell provided by the base station device and a second cell provided by another base station device, to use the measured value obtained from the measurement to estimate whether predetermined conditions regarding the received power are met at a specific timing after the measurement or within a certain period of time after the measurement, and to report if it is estimated that the predetermined conditions are met, the instruction includes information for the terminal device to specify the specific timing or the certain period of time; the report is received when it is estimated that the predetermined conditions are met; and the terminal device is notified that it should perform a process to switch the connection destination of the terminal device from the first cell to the second cell based on the receipt of the report from the terminal device.

15. A control method performed by a terminal device that communicates with a base station device based on the cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: measuring the received power of signals received from a first cell provided by the base station device connected to the terminal device and a second cell provided by another base station device; using the measured value obtained by the measurement, making an estimation of whether predetermined conditions regarding the received power are met at a specific timing after the measurement or for a certain period of time after the measurement; and receiving an instruction indicating that a report should be made if it is estimated that the predetermined conditions are met, the instruction including information for specifying the specific timing or the certain period of time; making the estimation of whether the predetermined conditions are met in accordance with the instruction; making the report based on the fact that the predetermined conditions are met; and executing a process when the terminal device receives a notification indicating that it should perform a process to switch the connection destination of the terminal device from the first cell to the second cell.

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