Terminal device, base station device, control method, and program for measuring and reporting wireless quality to improve handover efficiency

Abstract

To prevent a decrease in handover efficiency due to wireless quality measurement and reporting.SOLUTION: A terminal device receives, from a connected base station device, setting information related to measuring wireless quality for each of multiple beams formed by other base station devices and reporting the measurement results, the setting information including information on a group of two or more beams from the multiple beams, on the basis of the setting information, observes reference signals transmitted from each of the multiple beams, measures the wireless quality for each of the multiple beams, on the basis of the wireless quality for each of the multiple beams and information on the beam group, identifies wireless quality statistical values for the group, and on the basis of the setting information, reports the statistical values to the base station device.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technique for measuring and reporting radio quality by a terminal device in a cellular communication system. [Background technology]

[0002] In a cellular communication system, handover is performed in which a terminal device switches a cell or beam to which it is connected due to the movement of the terminal device or changes in the communication environment. During handover, the terminal device measures each cell / beam, and the cell to which the terminal device is connected is determined based on the measurement results. Non-Patent Document 1 describes that if the best value of the measured wireless quality is equal to or less than a predetermined threshold, the best value is treated as the quality of the cell corresponding to that beam. If there is a beam whose wireless quality exceeds the predetermined threshold, the linear average value of the wireless qualities of the beam is treated as the quality of the cell corresponding to that beam. That is, if the number of beams whose measured wireless quality exceeds the predetermined threshold is one or less, the measured quality of the best beam is treated as the quality of the cell corresponding to that beam. If the number of beams whose measured wireless quality exceeds the predetermined threshold is two or more, the linear average value of the qualities exceeding the threshold is treated as the quality of the cell corresponding to that beam. In one example, the terminal device notifies the base station device of the quality as the quality of a candidate cell to which it is to handover, and the base station device transmits an instruction to the terminal device to hand over to one of the cells. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP(registered trademark) TS 38.331 Summary of the Invention [Problem to be solved by the invention]

[0004] When using conventional standards, even if the quality of many beams of a cell is significantly below a threshold, the cell may be selected as a handover destination cell if the quality of a specific beam that exceeds the threshold is good. In this case, only a small number of beams may be able to communicate with good communication quality in the handover destination cell, which may result in a decrease in handover efficiency, such as an increase in the probability that another handover will be required in a short period of time when the terminal device is moving. [Means for solving the problem]

[0005] The present invention provides a technique for reporting radio quality measurement results that makes it possible to prevent a decrease in handover efficiency.

[0006] A terminal device according to one embodiment of the present invention has a receiving means for receiving, from a base station device to which it is connected, configuration information regarding measurement of wireless quality for each of a plurality of beams formed by another base station device and reporting of the results of the measurement, the configuration information including information on a group of beams consisting of two or more beams from the plurality of beams; a measuring means for observing a reference signal transmitted from each of the plurality of beams based on the configuration information and measuring the wireless quality for each of the plurality of beams; an identifying means for identifying a statistical value of wireless quality for the group based on the wireless quality for each of the plurality of beams and information on the group of beams; and a reporting means for reporting the statistical value to the base station device based on the configuration information.

[0007] A base station device according to one embodiment of the present invention has a notification means for notifying a connected terminal device of setting information regarding measurement of wireless quality for each of a plurality of beams formed by another base station device and reporting of the results of the measurement, the setting information including information on a group of beams consisting of two or more beams from the plurality of beams, a receiving means for receiving from the terminal device a report of wireless quality statistics determined from the wireless quality for each of the beams belonging to the group from the plurality of beams, and a decision means for deciding whether to hand over the terminal device to the other base station device based on the report. [Effects of the Invention]

[0008] According to the present invention, it is possible to prevent a decrease in handover efficiency caused by a measurement report of wireless quality. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Figure 2] FIG. 1 is a diagram illustrating an example of the flow of communication processing executed by a wireless communication system. [Figure 3] FIG. 1 is a diagram illustrating an example of the flow of communication processing executed by a wireless communication system. [Figure 4] A diagram illustrating an example of an event based on wireless quality per beam group. [Figure 5] FIG. 1 is a diagram illustrating an example of the flow of communication processing executed by a wireless communication system. [Figure 6] A diagram illustrating an example of an event based on wireless quality per beam group. [Figure 7] FIG. 1 is a diagram illustrating an example of the flow of communication processing executed by a wireless communication system. [Figure 8] FIG. 1 is a diagram illustrating an example of the flow of communication processing executed by a wireless communication system. [Figure 9] FIG. 1 is a diagram illustrating an example of the flow of communication processing executed by a wireless communication system. [Figure 10] FIG. 2 is a diagram illustrating an example of the hardware configuration of a base station device and a terminal device. [Figure 11] FIG. 2 is a diagram illustrating an example of a functional configuration of a base station device. [Figure 12] FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any desired manner. Furthermore, the same reference numerals are used to designate identical or similar components, and redundant descriptions will be omitted.

[0011] Fig. 1 shows an example of the configuration of a wireless communication system according to this embodiment. The wireless communication system is, for example, a cellular communication system that complies with the 5th generation (5G) cellular communication standard of the 3rd Generation Partnership Project (3GPP), and is configured to include base station devices 101 to 102 and a terminal device 111. Note that Fig. 1 shows only two base station devices and one terminal device, but it goes without saying that a large number of base station devices and a large number of terminal devices may exist.

[0012] Base station device 101 is a base station device connected to terminal device 111. Base station device 102 is a base station device that is a candidate for handover from base station device 101. Base station device 102 can form multiple beams and use some of the multiple beams to provide communication services to terminal device 111. Note that, like base station device 102, base station device 101 can also form multiple beams and use some of the beams to connect to terminal device 111 and provide communication services to terminal device 111.

[0013] The terminal device 111 measures the reception quality of a predetermined reference signal (e.g., a synchronization signal (SS) / physical broadcast channel (PBCH) block (SSB) or a channel state information-reference signal (CSI-RS)) transmitted by another surrounding base station device (e.g., the base station device 102) while connected to the base station device 101. Each reference signal is associated with a transmission configuration indicator (TCI) in the base station device. For example, in FIG. 1, TCI0 ​​to TCI8 are associated with different CSI-RS resources, and TCI9 to TCI11 are associated with different SSB indexes. Based on this information, the terminal device 111 can measure radio quality by observing reference signals for each of multiple beams, which are at least a portion of the many beams formed by base station devices other than the base station device 101. Note that in the following description, unless otherwise specified, "multiple beams" formed by other base station devices means beams designated as measurement targets, and does not mean all beams formed by other base station devices. Here, the wireless quality includes, for example, reference signal received power (RSRP), reference signal received quality (RSRQ), received signal strength, signal-to-noise ratio (SNR), signal-to-noise and interference ratio (SINR), interference power, etc. The terminal device 111 observes the resources of each reference signal, measures the wireless quality, and reports the measurement results to the connected base station device 101. For example, when the base station device 101 receives information on the measurement results, it determines, based on the information, whether or not to hand over the terminal device 111 to a cell constituted by another base station device.

[0014] Conventionally, for each cell formed by a base station device other than the currently connected base station device 101, if the number of reference signals (beams) whose wireless quality exceeds a predetermined threshold is one or less, the terminal device 111 notifies the base station device 101 of the best wireless quality. Here, the predetermined threshold is notified in advance from the base station device 101 to the terminal device 111, and can be given by the value absThreshSS-BlocksConsolidation for SSB and the value absThreshCSI-RS-Consolidation for CSI-RS. Furthermore, if the number of reference signals (beams) whose wireless quality exceeds the predetermined threshold exceeds a predetermined number, the terminal device 111 notifies the base station device 101 of the average value of a number of measurement values ​​that does not exceed the predetermined number. Note that this predetermined number is notified in advance from the base station device 101 to the terminal device 111, and can be given by the value nrofSS-BlocksToAverage for SSB and the value nrofCSI-RS-ResourcesToAverage for CSI-RS. These values ​​are all set to 2 or greater.

[0015] Based on such a report, the base station device 101 may handover the terminal device 111 to, for example, a cell having a beam with sufficiently good wireless quality. For example, the base station device 101 initiates handover when the wireless quality of a neighboring cell measured by the terminal device 111 is better than the wireless quality of the cell formed by the terminal device 111 by a predetermined offset (Event A3), or when the wireless quality of the neighboring cell becomes better than a predetermined threshold (Event A4). However, if the wireless quality of the neighboring cell used as the reference at this time is determined as described above, it is expected that the efficiency of handover may decrease. That is, in the conventional method, even if there is only one beam whose wireless quality exceeds the predetermined threshold, the terminal device 111 determines whether or not to perform handover based on the wireless quality of that one beam. Here, if the wireless quality is accidentally very high but is good only under extremely limited conditions, the probability that the state of the terminal device 111 will deviate from that condition within a short period of time is high. If the terminal device 111 falls outside of this condition, it may be necessary to perform a handover to another cell again. In other words, in a conventional method, if a first cell exists in which the radio quality is very good only for a specific beam, a handover to the first cell may be triggered even if a second cell exists that has many beams whose radio quality is good on average but not better than that of the specific beam. As a result, the probability of a second handover being required within a short period of time may increase. The same applies when the radio quality of only a few beams corresponding to significantly different geographical areas in the same cell exceeds a predetermined threshold. In other words, if the radio quality of a handover destination cell deteriorates after connecting to the handover destination cell via one beam, it is expected that the terminal device 111 may fall into a state in which there are no candidate beams to switch to in the vicinity. In this case, the terminal device 111 cannot switch to another beam with good quality without handing over, and it may be necessary to switch the destination cell by handover.

[0016] In this embodiment, in view of such circumstances, a plurality of beams are grouped, and statistical information such as the average value of the wireless quality in each group is reported from the terminal device 111 to the base station device 101. For example, in FIG. 1 , TCI0 ​​to TCI2 are grouped as a first group, TCI3 to TCI5 as a second group, and TCI6 to TCI8 as a third group. This grouping can be defined, for example, in relation to TCI9 to TCI11 corresponding to the SSB index. That is, as an example, it can be determined that a group of beams, each associated with a CSI-RS and covering a part of an area covered by a beam corresponding to each SSB index, belong to one group. After measuring the wireless quality of each beam, the terminal device 111 statistically processes the measurement values ​​of the wireless quality for the beams belonging to each group and reports the statistical values ​​to the base station device 101. The terminal device 111 can report, for example, the (linear) mean, variance, median, minimum value, etc. of the measurement values ​​to the base station device 101. Furthermore, the terminal device 111 may report, for example, a weighted average of measurement values ​​for multiple beams to the base station device 101. For example, if TCI0 ​​to TCI2 are considered as one group, a value such as (measurement value of TCI0) × 0.1 + (measurement value of TCI1) × 0.8 + (measurement value of TCI2) × 0.1 may be reported to the base station device 101. In other words, a weighted addition may be performed such that, among beams in a group, emphasis is placed on measurement values ​​for beams that correspond to the vicinity of the center of the range covered by those beams. Note that this is just one example, and any weight may be used. Note that, in the following description, the radio quality for a group refers to a value after the above-described statistical processing has been performed on the radio quality for the group, unless otherwise specified.

[0017] By reporting such statistical values, the base station device 101 can grasp the trend of the wireless quality for each of the first to third groups described above, for example. Then, the base station device 101 can make a handover decision based on the trend. That is, in the past, if the wireless quality of only one beam was significantly high, a decision to handover to that beam could be made based on that wireless quality. However, in this embodiment, the base station device 101 can decide not to perform a handover to that beam if, for example, the statistical values ​​for multiple beams are not good to a certain extent. Note that this is just one example, and the base station device 101 can perform any control based on the acquired information.

[0018] In one example, the beam groups may be selected such that each beam is adjacent to at least other beams in the group, as in the first to third groups described above. Also, the beam groups may be configured such that TCIs at every predetermined number of TCIs, such as TCI0, TCI2, TCI4, TCI6, and TCI8 in FIG. 1 are one group, and TCI1, TCI3, TCI5, and TCI7 are another group. Alternatively, the beams may be grouped based on any criteria, such as TCI0, TCI1, TCI6, and TCI7 being one group, TCI2, TCI3, and TCI8 being another group, and TCI4 and TCI5 being yet another group. Furthermore, if the base station device 102 has multiple transmission / reception points (TRPs), a group may be set for each beam group belonging to the TRP. Furthermore, while the above example describes grouping of TCI0 ​​to TCI8, each associated with a separate resource of CSI-RS, it is of course also possible to group beams associated with SSB indices, for example, grouping TCI9 and TCI10 into one group.

[0019] By grouping multiple beams corresponding to adjacent or mutually close geographical areas (directions) into one group, it is expected that sufficient wireless quality can be ensured in the area corresponding to that group. Therefore, even if the communication quality of the terminal device 111 deteriorates after the terminal device 111 is handed over to one of the beams belonging to that group, communication services with sufficient wireless quality can be provided to the terminal device 111 by changing the connection destination to another beam in the same group. Furthermore, by grouping beams covering non-adjacent geographical areas into one group, if the wireless quality of the group is good, it is expected that a certain degree of good wireless quality can be obtained in a wide area where those beams are formed. Therefore, by handing over the terminal device 111 to a base station device 102 that forms that group of beams, even if the wireless quality of the connection destination beam deteriorates, communication services with sufficient wireless quality can be provided to the terminal device 111 by changing the connection destination to another beam formed by the base station device 102. As a result, unnecessary handovers can be prevented, and handover efficiency can be improved.

[0020] In each group, beams to be used for processes such as calculation of radio quality for the group and handover determination may be determined, and beams not to be used for such processes may be determined. For example, if it is known in advance that the quality of a specific beam in the group is low due to the operating conditions of surrounding base station devices (e.g., when transmission is not performed using a specific beam), the measurement results for that beam may not be used for calculation of radio quality for the group and handover determination. Furthermore, for example, a beam whose measurement results tend to show a unique value (e.g., a value significantly higher or lower than that of other adjacent beams) may be determined not to be used for calculation of radio quality for the group. The number of beams to be considered in each group may also be set. For example, a minimum value for the number of beams to be considered in each group may be set. According to this, for example, if a certain beam is suitable as a connection destination because the radio quality of multiple beams is good but the radio quality of other beams is low, the radio quality of (at least some of) the beams with low radio quality may not be considered in calculation of radio quality for the group. Therefore, by reducing the influence of the beam with low wireless quality, it is possible to prevent handover from becoming difficult to be performed to a base station device having a group suitable as a connection destination. In this case, since the statistical value of wireless quality for a minimum number of beams is calculated, even if the wireless quality of only one specific beam is high, the statistical value of wireless quality of the group to which that beam belongs will be lowered by the wireless quality of the other beams, so it is still possible to make it difficult to select that beam as a handover destination.

[0021] The base station device 101 transmits configuration information for causing the above-described report to be made to the terminal device 111. For example, the base station device 101 transmits the above-described configuration information to the terminal device 111 using a radio link control (RRC) message (for example, an RRC Reconfiguration message). The configuration information includes measurement configuration (for example, layer 1 or layer 3) (for example, information specified by MeasObjectNR) and measurement result reporting configuration (for example, information specified by ReportConfigNR). For example, the measurement configuration includes a list of beams including information identifying beams to be measured (for example, beam identifiers or TCI indexes). The reporting configuration includes, for example, information specifying reporting of radio quality information on a group-by-group basis, in addition to or instead of information similar to that in a conventional measurement report regarding radio quality measurement. Furthermore, at least one of the measurement configuration and the reporting configuration, or separately from these information, includes information indicating the group to which each beam included in the list belongs. The base station device 101 may notify the terminal device 111 of configuration information including information about a large number of beams and groups, and may activate or deactivate measurement and reporting for beams to be measured and reported separately from the configuration information. For example, the base station device 101 may notify the terminal device 111 of information specifying some beams, of which the configuration information has been notified, that are to be used by the terminal device 111 to actually perform measurements and reports, separately from the configuration information. In one example, configuration information for a large number of beams corresponding to a wide geographical area may be notified by an RRC message as described above, and activation information specifying some beams to be used by the terminal device 111 may be transmitted via a medium access control (MAC) control element (CE). In this way, the MAC CE of the MAC layer may activate or deactivate configuration information for beams to be actually measured according to changes in the state of the terminal device 111, eliminating the need to transmit and receive RRC layer messages each time.

[0022] The terminal device 111 measures beams formed by surrounding base station devices (e.g., the base station device 102) based on the configuration information (and the activation information), and calculates statistical values ​​of the measurement results for each group to which the beam belongs. The terminal device 111 may also transmit information on the measurement results for each beam to the base station device 101, as in the past. The terminal device 111 then transmits the statistical values ​​of the measurement results to the base station device 102. The terminal device 111 may periodically report the statistical values ​​of the measurement results to the base station device 101, or may transmit the statistical values ​​of the measurement results to the base station device 101 in response to receiving a predetermined instruction from the base station device 101. The base station device 101 may notify the terminal device 111, for example, of an instruction to report a single measurement result or an instruction to report periodic measurement results as a reporting configuration. This instruction may be transmitted from the base station device 101 to the terminal device 111, for example, using downlink control information (DCI) or MAC CE. Furthermore, when a periodic measurement result report is instructed, the period can be specified together with the instruction. Note that information indicating the period may be notified to the terminal device 111 together with the above-mentioned setting information.

[0023] When the base station device 101 receives a report of the measurement result from the terminal device 111, the base station device 101 can determine whether to hand over the terminal device 111 to a cell provided by another base station device based on the result. In one example, the base station device 101 can decide to hand over the terminal device 111 to another base station device when a predetermined condition is met, such as the statistical value of the wireless quality for each group of beams formed by the other base station device (base station device 102) being higher than a predetermined level, as described above.

[0024] An example of the processing flow in this case will be described with reference to Figures 2 and 3. The processing in this embodiment is performed in the same manner as conventional processing, except for changes in the processing related to measurement and reporting. That is, the base station device 101 currently connected to the terminal device 111 measures reference signals (SSB or CSI-RS) transmitted from surrounding base station devices (such as the base station device 102), and transmits cell identifiers of the surrounding base station devices and report configuration information to the terminal device 111 so as to report the radio quality of the reference signals (S201). At this time, the base station device 101 also notifies the terminal device 111 of information on the identifiers of beams to be measured, which are at least a part of multiple beams formed by base station devices that provide neighboring cells. Furthermore, in this embodiment, at least the multiple beams to be measured are grouped into one or more groups, and the base station device 101 notifies the terminal device 111 of information on the groups. Note that this information may be included in one or two of the measurement configuration of the communicating cell (information specified by servingcellMO or the like), the measurement configuration of the candidate cell (information specified by MeasObjectNR or the like), and the reporting configuration (information specified by ReportConfigNR, for example), or may be included in all of them. Also, information on groups may be prepared separately from these. In this case, at least one of the measurement configuration and the reporting configuration indicates that measurement reports of radio quality for each group should be performed. Then, when the terminal device 111 receives configuration information including an instruction indicating that measurement reports of radio quality for each group should be performed, the terminal device 111 can refer to the information on the groups and confirm the group of beams specified as the measurement target. Furthermore, when reporting measurement results, the measurement values ​​of the reference signals of the communicating cell measured for beam failure detection may be used depending on the measurement configuration of the communicating cell.

[0025] The base station device 101 may use an RRC message to notify the terminal device 111 of configuration information designating a large number of beams as candidates for measurement targets. Then, the base station device 101 may transmit information to the terminal device 111, for example, via MAC CE or DCI, to enable some beams among the candidate measurement targets as measurement targets. In this case, it is not necessary to transmit an RRC message again when the measurement target is changed. Note that the group to which each beam belongs may be set in advance, and the information may be transmitted via an RRC message. Alternatively, the groups may be reorganized each time the beams to be measured are updated, and information about the groups may be transmitted using MAC CE or the like together with information to enable the beams to be measured. Also, the beams to be enabled as measurement targets may be specified by information specifying a group. That is, when the relationship between groups and beams is set in advance (for example, via an RRC message), a specific group may be specified by MAC CE or the like, and the terminal device 111 may be instructed to measure the radio quality of each beam belonging to the group.

[0026] Based on the received measurement and reporting configuration, the terminal device 111 measures the reception quality of a predetermined reference signal (SSB or CSI-RS) transmitted from the beam targeted for measurement (S202). Then, the terminal device 111 uses the measurement result to identify the reception quality (statistical value) for each group (S203). Then, the terminal device 111 reports the identified reception quality for each group to the base station device 101 (S204). Note that the terminal device 111 may report the reception quality for each beam in addition to the reception quality for each group to the base station device 101. Upon receiving the report, the base station device 101 decides to perform a handover as necessary (S205) and transmits a handover instruction to the terminal device 111 (S206). In response to the instruction, the terminal device 111 executes a handover from the base station device 101 to another base station device (for example, the base station device 102) (S207).

[0027] For example, after deciding to have the terminal device 111 execute a handover, the base station device 101 transmits a HANDOVER REQUEST message to a handover destination base station device (e.g., the base station device 102), and when a HANDOVER REQUEST ACKNOWLEDGE message indicating acceptance of the handover is received, the base station device 101 can transmit a message (e.g., an RRC Reconfiguration message) to start the handover to the terminal device 111. In this case, communication parameters to be used by the terminal device 111 are specified in the HANDOVER REQUEST ACKNOWLEDGE message, and the base station device 101 can transmit the communication parameters together with a handover instruction.

[0028] Note that this is just one example, and the base station device 101 may, for example, notify the terminal device 111 of post-handover configuration information between the terminal device 111 and the handover destination base station device at a timing before the actual handover is performed (for example, at the time of S201 or at an earlier timing). Then, for example, before receiving a handover instruction to the base station device 102, the terminal device 111 may receive configuration information for communication with the base station device 102 and perform processes such as establishing synchronization of the uplink and downlink with the base station device 102 in advance. Then, for example, the terminal device 111 may measure the wireless quality at Layer 1 of the reference signal transmitted from the base station device 102 and report the results to the base station device 101, and the base station device 101 may decide whether or not to hand over the terminal device 111 to the base station device 102 based on the report. After determining to handover the terminal device 111 to the base station device 102, the base station device 101 can instruct the terminal device 111 to execute the handover without performing processing such as transmitting a HANDOVER REQUEST message to the base station device 102. In this case, since the connection setup with the base station device 102 has already been completed, the time from receiving the handover instruction to starting communication of user data with the base station device 102 can be shortened. Note that a procedure for shortening such a handover period is called Layer 1 / Layer 2 Triggered Mobility (LTM). In one example, the measurement configuration for this LTM can be notified to the terminal device 111 by an information element called LTM-Config, and the reporting configuration can be notified by an information element called LTM-CSI-ReportConfigToAddModList.

[0029] In this embodiment, regardless of whether pre-configuration for handover is performed, the terminal device 111 identifies wireless quality information for a group of beams and reports it to the base station device 101. Then, based on the results of the report, the base station device 101 may determine, for example, to execute a handover to another base station device with good wireless quality for the group, but not to another base station device with poor wireless quality for the group. That is, when a specific base station device forms multiple beams, if the wireless quality of only one or a few beams among the multiple beams is particularly high, it is assumed that the wireless quality of the group is not high. In this case, if the terminal device 111 moves slightly or the surrounding environment changes, another handover may be necessary within a short period after the handover. In contrast, the base station device 101 according to this embodiment may avoid a handover to a base station device with insufficient wireless quality for almost all of the multiple beams, and may encourage a handover to a base station device that forms multiple beams belonging to a group with good statistical wireless quality. This makes it possible to prevent handovers from being repeatedly performed within a short period of time due to changes in circumstances such as the movement of the terminal device 111.

[0030] In the above example, the base station device 101 determines whether to cause the terminal device 111 to perform a handover. However, the terminal device 111 may also determine whether to perform a handover autonomously. That is, the terminal device 111 may perform a conditional handover. The processing flow in this case is shown in FIG. 3. The base station device 101 notifies the terminal device 111 of information indicating beams to be measured and the group to which each beam belongs (S301), similar to S201 in FIG. 2. In this case, the configuration information for reporting does not need to be notified. For example, the base station device 101 transmits a HANDOVER REQUEST message to a base station device (e.g., base station device 102) that is a candidate for the handover destination, at a timing prior to S301, and receives a HANDOVER REQUEST ACKNOWLEDGE message including configuration information for the terminal device 111 after the handover. Then, the base station device 101 notifies the terminal device 111 of configuration information to be used after handover to the candidate base station device as the handover destination, for example, in a message of S301. FIG. 3 shows an example in which the configuration information for this conditional handover is notified from the base station device 101 to the terminal device 111 in S301 using an information element called "conditional LTM config." Note that this configuration information may be notified before S301 or after S301. The terminal device 111 holds configuration information for connection with the candidate base station device as the handover destination, and performs pre-configuration such as executing uplink and downlink synchronization establishment processing as necessary (S302). Thereafter, the terminal device 111 measures the wireless quality of predetermined reference signals transmitted from other surrounding base station devices (S303) and, similar to S203, identifies the wireless quality for each group (S304). Then, the terminal device 111 determines whether to perform a handover based on the wireless quality for each identified group (S305), and if it decides to perform a handover, it performs handover processing to the base station device to which the handover is to be performed (S306).

[0031] As described above, in this embodiment, when the decision on whether to perform handover is made in the base station device 101, the radio quality for each group is reported to the base station device 101, and when the decision is made in the terminal device 111, the radio quality for each group is not transmitted to the base station device 101, and the terminal device 111 may independently decide to perform handover based on the radio quality. In either case, by using the radio quality for each group, the terminal device 111 can handover to a base station device having multiple beams with good radio quality (due to the existence of a group with good statistical radio quality) without handing over to a base station device having insufficient radio quality in almost all of the multiple beams. This makes it possible to avoid a situation where there is no beam with good radio quality among the beams formed by the connected base station device, even if the radio quality significantly deteriorates in a short period after the terminal device 111 performs handover, and to prevent unnecessary handover from occurring.

[0032] Note that the terminal device 111 not only measures the wireless quality of a beam formed by another base station device (e.g., base station device 102) other than the currently connected base station device 101, but also measures the wireless quality of a beam formed by the base station device 101. Then, the terminal device 111 may, for example, switch the beam to use a beam that can provide better wireless quality than the beam currently being used. In one example, the terminal device 111 may determine a beam to use based on the measurement result and request communication using that beam from the base station device 101. Furthermore, the terminal device 111 may, for example, transmit information indicating the TCI corresponding to the beam to be used to the base station device 101 when transmitting uplink user data, as control information.

[0033] In the above-described embodiment, an example has been described in which the terminal device 111 transmits a measurement report to the base station device 101 periodically or in response to an instruction from the base station device 101. In contrast to this, an event may be set for determining whether or not to report the measurement result of the wireless quality of a reference signal measured by the terminal device 111, based on the wireless quality of the reference signal. For example, as shown in FIG. 4, Events A3a, A4a, and A5a similar to conventional Events A3, A4, and A5 may be defined. That is, in the conventional Event A3, it is determined that an event has occurred when the wireless quality (q2) of a neighboring cell becomes better than the wireless quality (q1) of the currently connected cell by more than a predetermined offset (Offset) (q2≧q1+Offset), whereas in Event A3a, this is applied to a group of beams. That is, Event A3a may be defined so that an event is determined to have occurred when the statistical value of the wireless quality of any of the groups of beams of a neighboring cell exceeds a value obtained by adding a predetermined offset value to the statistical value of the wireless quality of the group of beams used in the currently connected cell (or the wireless quality value of one beam currently in use). While the conventional Event A4 requires the wireless quality of the neighboring cell to exceed a predetermined threshold, Event A4a requires the wireless quality of any of the groups of beams of the neighboring cell to exceed a predetermined threshold. While Event A5 requires the wireless quality of the currently connected cell to fall below a first threshold and the wireless quality of the neighboring cell to be better than a second threshold, Event A5a requires the wireless quality statistical value of the group of beams currently connected (or the wireless quality value of one beam currently in use) to fall below the first threshold and the wireless quality of any of the groups of beams of the neighboring cell to be higher than the second threshold. Here, the group of beams used to determine the event may be determined by the terminal device. For example, the terminal device performs measurements on all beams and determines the group of beams in connection. In this case, if the measurement value of the reference signal in the terminal device changes, the group used to determine the event also changes.On the other hand, when the base station device determines the group to be used for determining the event, the group may be changed by the setting in the RRC layer. In this case, the group of the beam related to the cell in communication used for determining the event is not changed by the change in the measurement value. Note that these are just examples, and another event may be newly defined.

[0034] Furthermore, a condition (TimeToTrigger) regarding the period during which it has been determined that each event has occurred may be applied as a condition for making a report corresponding to each event. That is, the terminal device 111 may transmit a measurement report to the base station device 101 not at the time when any of the above-mentioned Events A3a, A4a, and A5a occurs, but at the time when the event continues to occur from the first occurrence of the event until the time length indicated by TimeToTrigger has elapsed.

[0035] An example of the processing flow in this case is shown in Figure 5. Note that, although Figure 5 shows an example of the processing flow when LTM is performed, similar processing can be performed when Layer 3 measurement reporting is performed, except for processing related to LTM. In this processing, first, the base station device 101 to which the terminal device 111 is currently connected notifies the terminal device 111 of setting information, measurement settings, reporting settings, group information, and event information related to a base station device (cell) that is a candidate for LTM handover destination (S501). Here, the setting information related to the candidate base station device that is a candidate for LTM handover destination includes setting information (for example, of the RRC layer) for the terminal device 111 to communicate with the candidate base station device. After receiving this information, the terminal device 111, as necessary, performs uplink and downlink synchronization establishment processing with the candidate base station device in advance for LTM handover (S502). Note that the measurement settings and reporting settings here include information for performing measurements and reporting on beams formed by the candidate base station device that is a candidate for LTM handover destination. Furthermore, group information may be included in these pieces of information or may be notified separately from these pieces of information. Event information may be transmitted, for example, included in a report setting. Note that information defining each event may be notified separately to the terminal device 111, and the report setting may include only an event ID for identifying which event is the basis for transmitting a measurement result report.

[0036] The terminal device 111 measures the (layer 1) wireless quality (such as L1-RSRP) of a reference signal transmitted from a base station device that is a candidate for handover (S503), and performs statistical processing of the wireless quality for each beam group (S504). Then, the terminal device 111 determines whether an event specified in S501 has occurred based on the wireless quality for each group (S505). If the terminal device 111 determines that an event has occurred, it reports information indicating the wireless quality for each group to the base station device 101. Thereafter, the base station device 101 determines whether to perform handover based on the report (S507), and transmits information instructing handover to the terminal device 111 by, for example, a Cell Switch Command (S508). In accordance with the instruction, the terminal device 111 disconnects from the currently connected base station device 101, and performs processing to connect to the handover destination base station device (S509).

[0037] In this way, by specifying the conditions for transmitting measurement reports, reports are transmitted only in situations where there is a high probability that a handover will be required, thereby reducing overhead compared to when measurement reports are transmitted periodically.

[0038] In the above embodiment, an example has been described in which the terminal device 111 executes a handover in response to a handover command from the base station device 101. Alternatively, an event may be set for the terminal device 111 to determine whether or not to perform a handover on its own initiative, based on the radio quality of a reference signal measured by the terminal device 111. For example, as shown in FIG. 6, CondEvents A3a, A4a, and A5a similar to the conventional CondEvents A3, A4, and A5 may be defined. That is, the conventional CondEvent A3 determines that an event has occurred when the radio quality (q2) of a neighboring cell becomes better than the radio quality (q1) of the currently connected cell by more than a predetermined offset (Offset) (q2≧q1+Offset), whereas CondEvent A3a applies this to a group of beams. That is, CondEvent A3a can be defined so that an event is determined to have occurred when the statistical value of the wireless quality of any of the groups of beams of a neighboring cell exceeds a value obtained by adding a predetermined offset value to the statistical value of the wireless quality of the group of beams used in the connected cell (or the wireless quality value of one beam currently in use). While the conventional CondEvent A4 requires the wireless quality of the neighboring cell to exceed a predetermined threshold, CondEvent A4a requires the wireless quality of any of the groups of beams of a neighboring cell to exceed a predetermined threshold. While CondEvent A5 requires the wireless quality of the currently connected cell to fall below a first threshold and the wireless quality of the neighboring cell to be better than a second threshold, CondEvent A5a requires the wireless quality of the statistical value of the group of beams currently connected (or the wireless quality value of one beam currently in use) to fall below the first threshold and the wireless quality of any of the groups of beams of a neighboring cell to be higher than a second threshold. Here, the group of beams used to determine an event may be determined by the terminal device. For example, the terminal device performs measurements on all beams and determines the group of connected beams. In this case, if the measurement value of the reference signal in the terminal device changes, the group used to determine an event also changes.On the other hand, when the base station device determines the group to be used for determining the event, the group may be changed by the setting in the RRC layer. In this case, the group of the beam related to the cell in communication used for determining the event is not changed by the change in the measurement value. Note that these are just examples, and another event may be newly defined.

[0039] The above-described events can also be applied to conditional handover. For example, as shown in FIG. 7, the base station device 101 notifies the terminal device 111 of a conditional handover configuration (conditional LTM config), as well as measurement configuration, group information, and event information therefor (S701). Note that the conditional handover configuration includes, for example, an RRC layer configuration for communication with a base station device that is a candidate for handover destination, and further includes information indicating that the terminal device 111 may autonomously switch its connection destination. The measurement configuration, group configuration, and event information are the same as those in S501 described above. The terminal device 111 performs uplink and downlink synchronization establishment processing with the base station device that is a candidate for handover destination, as necessary (S702). Furthermore, the terminal device 111 measures the radio quality of reference signals transmitted from at least some of the multiple beams formed by each base station device that is a candidate for handover destination (S703). The terminal device 111 then identifies the radio quality for each group from the radio quality of the measured reference signal (S704), and determines whether to perform handover depending on whether the event specified in S701 has occurred based on the radio quality for each group (S705). That is, when it is determined that an event has occurred, the terminal device 111 performs handover to another base station device that is the target of the event (S706). In this way, by defining an event related to a group of beams for which a conditional handover should be performed, when the terminal device 111 performs handover, the terminal device 111 can reliably connect to a beam with good radio quality on a group-by-group basis. Note that the terminal device 111 may select a beam to use for communication with the currently connected base station device using the above-mentioned event related to the group.

[0040] In the above-described embodiment, an example has been described in which, at the time of handover (or change of beam within the same cell), the radio quality corresponding to a plurality of beams formed by a base station device that is a candidate for the handover destination is grouped, and the radio quality for each group is identified. However, this is merely an example, and, for example, when adding or changing a secondary cell, the connection destination may be determined based on the radio quality for each group of beams as described above.

[0041] Furthermore, in the above-described embodiment, an example has been described in which a group of beams is set and the radio quality for that group is identified. However, without specifying a group, for example, statistical values ​​for two or more of a plurality of beams formed by a specific base station device may be specified as the radio quality for that specific base station device. Conventionally, when there is one or fewer beams whose radio quality exceeds a predetermined value, it has been specified that the terminal device reports the measurement results for the beam with the best radio quality to the serving base station device. In contrast, in this embodiment, the base station device may notify the terminal device of configuration information instructing the terminal device to report the radio quality as a statistical value, such as an average value, for a predetermined minimum number of beams or more. For example, by setting this minimum number, the influence of the unique radio quality on the reported radio quality for a base station device with only one beam corresponding to a uniquely good radio quality and the radio quality of the other beams being poor can be suppressed. In this way, by selecting a base station device to which a terminal device is to be connected based on statistical values ​​of measurement results for a predetermined minimum number or more of beams formed by candidate base stations without specifying a group, the probability that the terminal device will have to change its connection destination again within a short period of time after connecting to that base station device can be reduced.

[0042] An example of the processing flow in this case is shown in Figure 8. Note that Figure 8 shows the processing flow in which the terminal device 111 reports measurement results to the base station device 101 in response to the occurrence of an event. In Figure 8, parts that perform the same processing as in Figure 5 are assigned the same reference numerals, and descriptions thereof will be omitted. In this processing, the base station device 101 notifies the terminal device 111 of information indicating the minimum number of beams to be measured or reported, in addition to setting information, measurement setting, reporting setting, and event information related to a base station device (cell) that is a candidate for handover by LTM (S801). Here, the information indicating the minimum number of beams may be included in, for example, only one of the measurement setting and the reporting setting, or may be included in both, as in the group information in the above-mentioned embodiment. Furthermore, the information indicating the minimum number of beams may be transmitted separately from the measurement setting and the reporting setting, and information such as an index for identifying the minimum number of beams may be included in at least one of the measurement setting and the reporting setting.

[0043] The terminal device 111 then observes reference signals transmitted from each of the multiple beams formed by the base station device that is a candidate for handover and measures the wireless quality (S503). The terminal device 111 then identifies statistical values ​​(such as average values) of the wireless quality for a number of beams equal to or greater than the notified minimum number (S802). Conventionally, the terminal device 111 notifies the base station device 101 of the best value of the wireless quality when there is one or fewer beams whose wireless quality exceeds a predetermined threshold, or of the linear average value of the wireless qualities when there are multiple beams whose wireless quality exceeds the predetermined threshold. For this reason, when there is only one beam corresponding to an exceptionally high wireless quality and the wireless qualities of the other beams are extremely low, the terminal device 111 reports the exceptionally high wireless quality. On the other hand, by specifying the minimum number of beams (two or more) as in this processing example, the wireless quality is identified taking into account not only the exceptionally high wireless quality but also the extremely low wireless qualities of the other beams. The terminal device 111, for example, identifies the fewest number of beams designated in descending order of wireless quality and calculates statistical values ​​of the wireless qualities of reference signals transmitted from those beams. Note that, for example, if there are more than the minimum number of beams corresponding to wireless qualities exceeding a predetermined threshold, the terminal device 111 may calculate statistical values ​​by considering all of those beams. In this case, as in the past, an upper limit on the number of beams to be considered may be specified, and beams exceeding that number may not be considered even if their corresponding wireless qualities exceed the predetermined threshold. Furthermore, for example, even if there are more than the minimum number of beams corresponding to wireless qualities exceeding the predetermined threshold, the terminal device 111 may calculate statistical values ​​by considering only the fewest number of beams. The statistical values ​​calculated here may be, for example, a linear average value or other statistical values ​​such as the median of the wireless qualities of the fewest number of beams in descending order of wireless quality. Furthermore, other calculation methods may be used, such as the average value of the wireless qualities of the fewest number of beams in descending order of wireless quality, excluding the highest value, among the fewest number of beams in descending order of wireless quality.

[0044] Thereafter, the terminal device 111 determines whether an event has occurred based on the wireless qualities identified for a number of beams equal to or greater than a specified minimum value (S803). If the terminal device 111 determines that an event has occurred, it reports information on the wireless qualities identified in S802 to the base station device 101 (S506). Note that the event here is determined, for example, by treating the "number of beams equal to or greater than a minimum value" as a "group" of Events A3a, A4a, and A5a shown in FIG. 4. That is, if (statistical values ​​of) the wireless qualities of beams equal to or greater than a specified minimum number among multiple beams formed in a base station device providing a neighboring cell exceed a value obtained by adding a predetermined offset value to the wireless quality of the currently connected beam or the statistical value of the wireless quality of a group including that beam, it may be determined that Event A3a has occurred. Furthermore, if statistical values ​​of the wireless qualities of beams equal to or greater than a specified minimum number among multiple beams formed in a base station device providing a neighboring cell exceed a predetermined threshold, it may be determined that Event A4a has occurred. Furthermore, when the wireless quality of the currently connected beam or the statistical value of the wireless quality of a group including that beam falls below a first predetermined threshold, and (the statistical value of) the wireless quality for a specified minimum number or more of beams formed in a base station device that provides a neighboring cell exceeds a second predetermined threshold, it may be determined that Event A5a has occurred. Note that the wireless quality of the currently connected base station device may take into account only the beam in use, or may be the statistical value of the wireless quality for a specified minimum number or more of beams formed by the base station device. Furthermore, the terminal device 111 may report the statistical value of the wireless quality, regardless of an event, for example, periodically or when receiving a predetermined instruction from the base station device 101, in response to the predetermined instruction.

[0045] FIG. 9 shows a processing flow when the terminal device 111 performs a conditional handover in which the terminal device 111 autonomously changes the base station device to which it is connected in response to the occurrence of an event. In FIG. 9, parts that perform the same processing as in FIG. 7 are denoted by the same reference numerals, and descriptions thereof will be omitted. In this processing, the base station device 101 notifies the terminal device 111 of the conditional handover configuration, the measurement configuration therefor, event information, and information indicating the minimum number of beams to be measured or reported (S901). Here, the information indicating the minimum number of beams may be included in the measurement configuration, for example, as with the group information in the above-described embodiment, or may be transmitted separately from the measurement configuration, and information such as an index for identifying the minimum number of beams may be included in the measurement configuration. Then, as with S802, the terminal device 111 calculates statistical values ​​of wireless quality for beams equal to or greater than the specified minimum number (S902) and determines whether an event has occurred based on the calculated values ​​(S903). If the terminal device 111 determines that an event has occurred, it executes a handover (S706).

[0046] As described above, even when groups are not formed, by specifying the minimum number of beams to be considered when obtaining measurement results, it is possible to prevent a base station device that obtains specifically high wireless quality only for one or a very small number of beams from being highly evaluated for its wireless quality.

[0047] FIG. 10 shows an example of the hardware configuration of the base station device 101 and the terminal device 111 according to this embodiment. In one example, the base station device 101 and the terminal device 111 are configured to include a processor 1001, a ROM 1002, a RAM 1003, a storage device 1004, and a communication circuit 1005. The processor 1001 is a computer configured to include one or more processing circuits, such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and performs the overall processing of the device and each of the above-mentioned processes by reading and executing programs stored in the ROM 1002 or the storage device 1004. The ROM 1002 is a read-only memory that stores information such as programs and various parameters related to the processing executed by the base station device 101 and the terminal device 111. The RAM 1003 functions as a workspace when the processor 1001 executes a program, and is also a random access memory that stores temporary information. The storage device 1004 is configured, for example, by a removable external storage device. The communication circuit 1005 is configured by, for example, a circuit for wireless communication of 5G or a successor standard. Note that while one communication circuit 1005 is illustrated in FIG. 10 , the base station device 101 and the terminal device 111 may have multiple communication circuits. For example, the base station device 101 and the terminal device 111 may have wireless communication circuits for 5G and a successor standard, respectively, and a common antenna for these circuits. Note that the base station device 101 and the terminal device 111 may also have separate antennas suitable for each standard. The base station device 101 may also have a wired communication circuit used when communicating with other base station devices (e.g., the base station device 102) or nodes in the core network. The terminal device 111 may also have a communication circuit compliant with a wireless communication standard other than a cellular communication standard, such as a wireless local area network (LAN) or Bluetooth (registered trademark). The base station device 101 and the terminal device 111 may have separate communication circuits 1005 for each of the multiple available frequency bands, or may have a common communication circuit 1005 for at least some of the frequency bands.

[0048] FIG. 11 shows an example of the functional configuration of a base station device 101. The base station device 101 includes, for example, a measurement configuration unit 1101, a report configuration unit 1102, a beam group configuration unit 1103, a configuration notification unit 1104, and a handover control unit 1105. Note that FIG. 11 only shows functions particularly related to this embodiment, and does not illustrate various other functions that the base station device 101 may have. For example, the base station device 101 naturally has other functions that a base station device compliant with 5G or a subsequent standard generally has. Also, the functional blocks in FIG. 11 are shown schematically, and the respective functional blocks may be realized as an integrated unit or may be further subdivided. Also, each function in FIG. 11 may be realized, for example, by the processor 1001 executing a program stored in the ROM 1002 or the storage device 1004, or may be realized, for example, by a processor present in the communication circuit 1005 executing predetermined software. The details of the processes executed by each functional unit will not be described here, but only the general functions thereof will be outlined.

[0049] The measurement setting unit 1101 generates measurement setting information for causing the terminal device 111 to measure radio signals transmitted from beams formed by other base station devices. The report setting unit 1102 generates report setting information for the terminal device 111 to report results of measuring radio signals based on the measurement setting information by the measurement setting unit 1101. Note that the report setting unit 1102 may, for example, set event information for reporting the measurement results and include it in the report setting information. The beam group setting unit 1103, for example, groups beams to be measured. Furthermore, the beam group setting unit 1103 may, for example, determine the minimum number of beams to be considered when reporting the measurement results. Information on the groups of beams set by the beam group setting unit 1103 or the minimum number of beams to be considered is provided to the measurement setting unit 1101 or the report setting unit 1102, and the provided information may be included in at least one of the measurement setting information and the reporting setting information. Furthermore, setting information including information on the group of beams set by the beam group setting unit 1103 or the minimum number of beams to be considered may be generated separately from the measurement setting unit 1101 and the report setting unit 1102. The setting notification unit 1104 notifies the terminal device 111 of the setting information generated via the measurement setting unit 1101, the report setting unit 1102, and the beam group setting unit 1103.

[0050] The handover control unit 1105 executes control for handing over the terminal device 111 to another base station device. The handover control unit 1105 receives measurement results for a group of beams from the terminal device 111, and determines to execute handover of the terminal device 111 when a predetermined condition is met, such as the wireless quality indicated by the measurement results being higher by a predetermined offset than the wireless quality of the beam to which the terminal device 111 is currently connected (or a group of beams including that beam). After making this determination, the handover control unit 1105 transmits and receives control messages for handover with other base station devices forming the group of beams whose wireless quality was good, and can notify the terminal device 111 of setting information for communication with other base station devices and instruct the handover. The handover control unit 1105 may also acquire communication setting information for base station devices that are candidates for handover destinations, and notify the terminal device 111 of the communication setting information before receiving a report of the measurement results. Then, based on the measurement result, the handover control unit 1105 may notify the terminal device 111 of a cell switching command specifying a destination cell, and cause the terminal device 111 to perform handover. Also, the handover control unit 1105 may perform setting of a conditional handover.

[0051] FIG. 12 shows an example of the functional configuration of the terminal device 111. The terminal device 111 includes, for example, a setting receiving unit 1201, a quality measuring unit 1202, a beam group quality identifying unit 1203, a report transmitting unit 1204, and a handover processing unit 1205. Note that FIG. 12 only shows functions particularly related to this embodiment, and various other functions that the terminal device 111 may have are omitted from the illustration. For example, the terminal device 111 naturally has other functions that terminal devices compliant with 5G and subsequent standards generally have. Furthermore, the functional blocks in FIG. 12 are shown schematically, and the respective functional blocks may be realized as an integrated unit or may be further subdivided. Furthermore, each function in FIG. 12 may be realized, for example, by the processor 1001 executing a program stored in the ROM 1002 or the storage device 1004, or may be realized, for example, by a processor present in the communication circuit 1005 executing predetermined software. The details of the processes executed by each functional unit will not be described here, but only the general functions thereof will be outlined.

[0052] The setting receiver 1201 receives setting information generated via the measurement setting unit 1101, the report setting unit 1102, and the beam group setting unit 1103 from the base station device 101. The setting receiver 1201 may also receive, from the base station device 101, pre-setting information for conditional handover settings and communication with a base station device that is a candidate for handover for LTM. Based on the measurement setting information received by the setting receiver 1201, the quality measurement unit 1202 observes a radio signal (reference signal) transmitted by another base station device other than the base station device 101 that is a candidate for handover, and measures its radio quality. The quality measurement unit 1202 observes reference signals transmitted from each of multiple beams formed by the other base station device, and measures the radio quality of each beam. The quality measurement unit 1202 may also measure the radio quality of one or more beams formed by the base station device 101, including the currently connected beam, as necessary. The beam group quality specifying unit 1203 calculates statistical values ​​of wireless quality obtained for a group of beams or for more than the minimum number of beams, based on beam group information (information indicating a group of beams or a minimum number of beams to be considered) received by the setting receiving unit 1201. The report transmitting unit 1204 reports the calculated statistical values ​​of wireless quality (and, if necessary, measurement results of wireless quality for individual beams) to the base station device 101 based on the report setting information. Note that if an event is specified in the report setting information, the report transmitting unit 1204 reports the statistical values ​​to the base station device 101 when it determines that an event based on the statistical values ​​of wireless quality has occurred. For example, when the handover processing unit 1205 receives a handover instruction from the base station device 101, it executes handover from the base station device 101 to another base station device in accordance with the instruction. Furthermore, when the setting receiving unit 1201 receives a setting for a conditional handover, the handover processing unit 1205 autonomously executes a handover when a predetermined condition is satisfied, without relying on an instruction from the base station device 101. Note that the handover processing unit 1205 may autonomously change the destination beam from the currently connected beam to another beam, for example, without changing the destination base station device, based on the same criteria as in the case of a handover.

[0053] As described above, in this embodiment, whether or not to perform a handover is determined by taking into consideration the statistical values ​​of wireless quality for at least two groups of beams, rather than the individual wireless quality for each of multiple beams formed by a candidate base station device as a handover destination (beams designated as measurement targets among the many beams formed by that base station device). This reduces the probability that a terminal device will handover to a base station device that has a particularly high wireless quality for an extremely small number of beams, and increases the probability that a base station device that reduces the probability of a re-handover occurring even if the environment in which the terminal device is located changes is selected as a handover destination. As a result, it is possible to improve the stability of communication in the terminal device and prevent a decrease in handover efficiency in wireless communication systems. This makes it possible to contribute to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

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

Claims

1. A terminal device, a receiving means for receiving, from a connected base station device, setting information relating to measurement of radio quality for each of a plurality of beams formed by another base station device and a report of the measurement results, the setting information including information on a group of beams consisting of two or more beams from the plurality of beams; a measurement means for measuring a radio quality of each of the plurality of beams by observing a reference signal transmitted from each of the plurality of beams based on the setting information; a determination means for determining a statistical value of wireless quality for the group based on wireless quality for each of the plurality of beams and information on the group of beams; reporting means for reporting the statistical value to the base station device based on the setting information; A terminal device comprising:

2. 2. The terminal device according to claim 1, wherein said reporting means periodically reports said statistical value to said base station device.

3. 2. The terminal device according to claim 1, wherein the reporting means, when receiving a predetermined instruction from the base station device, reports the statistical value to the base station device in response to the predetermined instruction.

4. The terminal device described in claim 1, characterized in that the setting information includes measurement setting information regarding the measurement of the wireless quality and report setting information regarding the reporting of the results of the measurement, and at least one of the measurement setting information and the report setting information includes information on the group of the beam.

5. A base station device, a notification means for notifying a currently connected terminal device of setting information related to measurement of radio quality for each of a plurality of beams formed by another base station device and reporting of the measurement results, the setting information including information on a group of beams consisting of two or more beams from the plurality of beams; a receiving means for receiving from the terminal device a report of a statistical value of wireless quality determined from the wireless quality of each of the beams belonging to the group among the plurality of beams; a decision means for deciding whether to hand over the terminal device to the other base station device based on the report; A base station device comprising:

6. 6. The base station apparatus according to claim 5, wherein said receiving means periodically receives a report of said statistical value from said terminal apparatus.

7. 6. The base station device according to claim 5, wherein the receiving means transmits a predetermined instruction to the terminal device to cause the terminal device to report the statistical value, and receives a report of the statistical value transmitted from the terminal device in response to the predetermined instruction.

8. the setting information includes measurement setting information related to measurement of the radio quality and report setting information related to reporting a result of the measurement; The base station device according to claim 5, wherein the notification means generates the setting information by including information on the group of the beam in at least one of the measurement setting information and the reporting setting information.

9. A control method executed by a terminal device, comprising: receiving, from a connected base station device, configuration information related to measurement of radio quality for each of a plurality of beams formed by another base station device and reporting of the measurement results, the configuration information including information on a group of beams consisting of two or more beams from the plurality of beams; observing a reference signal transmitted from each of the plurality of beams based on the setting information, and measuring a radio quality for each of the plurality of beams; determining a radio quality statistic for the group based on information about the group of beams and the radio quality for each of the plurality of beams; reporting the statistical value to the base station device based on the setting information; A control method comprising:

10. A control method executed by a base station device, notifying the currently connected terminal device of setting information related to measurement of radio quality for each of a plurality of beams formed by another base station device and reporting of the measurement results, the setting information including information on a group of beams consisting of two or more beams from the plurality of beams; receiving, from the terminal device, a report of a statistical value of wireless quality determined from the wireless quality of each of the beams belonging to the group among the plurality of beams; determining whether to hand over the terminal device to the other base station device based on the report; A control method comprising:

11. A program for causing a computer provided in a terminal device to execute the control method according to claim 9.

12. A program for causing a computer provided in a base station device to execute the control method according to claim 10.

Images