Terminal device for performing efficient beam control, base station device, control method, and program

Abstract

This terminal device receives, from a base station device that forms a plurality of beams and performs communication, first configuration information relating to measurement of channel state information (CSI) for determining which of the plurality of beams is to be enabled, and second configuration information relating to selection of the plurality of beams, executes measurement of the CSI on the basis of the first configuration information, determines an effective beam from the plurality of beams on the basis of the measurement result of the CSI and the second configuration information, notifies the base station device of information indicating the beam determined to be enabled, and enables the beam determined to be enabled.

Description

Terminal device, base station device, control method, and program for performing efficient beam control

[0001] The present invention relates to beam control techniques in cellular communication systems.

[0002] In a fifth-generation (5G) cellular communication system, a base station device and a terminal device can form beams to perform high-capacity communication. The 5G cellular communication standard specifies that a base station device uses a transmission configuration indication (TCI) to control a downlink beam. The base station device receives a channel state information (CSI) report from a UE and determines the TCI based on the report.

[0003] Here, CSI reporting is performed in one of periodic, aperiodic, and semi-persistent modes. Among these, in semi-persistent CSI reporting, the base station device notifies the terminal device of parameters necessary for CSI measurement using a radio resource control (RRC) message, and then notifies the terminal device of information instructing the start and end of measurement result reporting. This notification is performed, for example, using a medium access control control element (MAC CE) when reporting is to be performed on a physical uplink control channel (PUCCH), and using downlink control information (DCI) when reporting is to be performed on a physical uplink shared channel (PUSCH). In accordance with this notification, the terminal device performs measurement and reporting at regular intervals from when it is instructed to start reporting until it is instructed to end reporting. Also, in aperiodic CSI reporting, the base station device notifies the terminal device of parameters necessary for measuring CSI using an RRC message, and instructs the terminal device to report the measurement result using, for example, DCI. In the case of aperiodic CSI reporting, the terminal device reports the CSI measurement result to the base station device only once in response to the instruction.

[0004] Based on the reported CSI, the base station device determines some of the many available beams as beams to be used in the downlink, and notifies the terminal device of the result of the determination using a TCI state indicating whether the many beams are enabled or disabled. Separate identification information (TCI state ID) is assigned to each of the many beams, and information indicating whether the beams are enabled or disabled corresponding to the respective identification information is notified to the terminal device. This notification is performed so that which beam is being used can be specified using a limited number of DCI bits. The base station device notifies the terminal device of which of the enabled TCIs to use to transmit a downlink signal, using the DCI transmitted together with the transmission of the signal. The terminal device performs reception processing of the downlink signal based on the TCI specified in the DCI.

[0005] The TCI that is enabled for a terminal device is changed depending on the status of the terminal device. For example, when the terminal device moves, the corresponding TCI state is enabled so that a beam appropriate for the moved position becomes enabled. For such processing, the base station device needs to transmit a control message to the terminal device as described above to cause the terminal device to report CSI. The base station device can, for example, monitor the communication status of the terminal device and transmit an instruction to report such CSI depending on the result.

[0006] However, in such a procedure, after the base station device determines that CSI reporting is necessary, it transmits an instruction to report CSI to the terminal device, the terminal device reports the CSI in accordance with the reporting instruction, and then the base station device instructs the terminal device to switch the beam to be activated, which may result in a long time being required to complete the setting of the appropriate beam.

[0007] The present invention provides a technique for shortening the time required for beam control and improving the efficiency of control.

[0008] A terminal device according to one aspect of the present invention has a receiving means for receiving, from a base station device that forms multiple beams and communicates, first setting information regarding measurement of channel state information (CSI) for determining which of the multiple beams to enable, and second setting information regarding selection of the multiple beams; an execution means for performing measurement of the CSI based on the first setting information; a determination means for determining which of the multiple beams to enable based on the CSI measurement results and the second setting information; a notification means for notifying the base station device of information indicating the beam that has been determined to be enabled; and an activation means for activating the beam that has been determined to be enabled.

[0009] A base station device according to one aspect of the present invention is a base station device that forms multiple beams and communicates, and has: a notification means that notifies a terminal device of first setting information regarding measurement of channel state information (CSI) for determining which of the multiple beams to enable, and second setting information regarding selection of the multiple beams; a receiving means that receives information indicating a beam from the multiple beams that the terminal device has decided to enable based on the results of measurement of the CSI in the terminal device using the first setting information and the second setting information; and a transmitting means that transmits a downlink signal to the terminal device using one of the beams that has been decided to enable.

[0010] According to the present invention, the time required for beam control can be reduced, and the control can be made more efficient.

[0011] Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which the same or similar elements are designated by the same reference numerals.

[0012] The accompanying drawings are included in and constitute a part of the specification, illustrate embodiments of the present invention, and together with the description are used to explain the principles of the present invention. Figure 1 is a diagram showing an example of the configuration of a wireless communication system. Figure 2 is a diagram showing a conventional example of processing for setting beams that can be used to transmit downlink signals to terminal devices. Figure 3 is a diagram showing an example of the processing flow of a first method. Figure 4 is a diagram showing an example of the processing flow of a second method. Figure 5 is a diagram showing an example of the hardware configuration of devices. Figure 6 is a diagram showing an example of the functional configuration of a base station device. Figure 7 is a diagram showing an example of the functional configuration of a terminal device.

[0013] 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.

[0014] 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 conforming to the fifth generation (5G) cellular communication standard of the Third Generation Partnership Project (3GPP (registered trademark)), and is configured to include a base station device 101 and a terminal device 111. Note that Fig. 1 shows only one base station device 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.

[0015] The base station device 101 can form multiple beams and provide communication services to the terminal device 111 using some of the multiple beams. The base station device 101 selects one of the multiple beams and transmits a downlink signal to the terminal device 111 using the selected beam. Note that if a different beam is used, the characteristics of the transmission path between the terminal device 111 and the base station device 101 will differ, and the decoding process of the downlink signal to be performed in the terminal device 111 will also differ. For this reason, when transmitting a downlink signal, the base station device 101 notifies the terminal device 111 of which beam the signal was transmitted using, using downlink control information (DCI). Here, since the base station device 101 can configure multiple beams, in a situation where all of the beams can be used, it is not possible to uniquely identify the beam used to transmit the downlink signal using the limited number of DCI bits. For this reason, a beam that can be used to transmit a downlink signal to the terminal device 111 can be selected from the multiple beams available to the base station device 101 and configured in advance in the terminal device 111. The flow of this process will be described using FIG. 2.

[0016] The base station device 101 notifies the terminal device 111 of setting information for the terminal device 111 to measure and report the radio quality (channel state information (CSI)) of signals transmitted by the base station device 101 using each beam (S201). This setting information is notified using, for example, a radio resource control (RRC) message such as an RRC Reconfiguration message. Here, in the example of FIG. 2, it is assumed that the CSI is reported aperiodic or semi-persistently. In this case, the base station device 101 instructs the terminal device 111 to report the CSI using, for example, a medium access control control element (MAC CE) or DCI (S203). In addition, in the case of aperiodic reporting, the base station device 101 transmits an instruction to the terminal device 111 using DCI, and the terminal device 111 measures the CSI-reference signal (CSI-RS) transmitted from the base station device 101 in accordance with this instruction and reports the CSI only once. On the other hand, in the case of semi-persistent reporting, the start and end of measurement and reporting are instructed using MAC CE or DCI. The terminal device 111 starts CSI-RS measurement reporting in response to receiving a start instruction, and also ends CSI-RS measurement reporting when an end instruction is received while performing semi-persistent CSI reporting. In semi-persistent CSI reporting, CSI measurement reporting is performed periodically between the start instruction and the end instruction. When aperiodic or semi-persistent CSI measurement reporting is used, the base station device 101 transmits this instruction, for example, when a specific condition is met. That is, when the base station device 101 determines that a CSI measurement report is necessary (S202), it transmits an instruction to report the CSI measurement to the terminal device 111. For example, the base station device 101 may determine that a CSI measurement report is necessary when the terminal device 111 fails to receive a downlink signal transmitted by a specific beam consecutively, or when it is assumed that the radio quality of a specific beam is significantly better than the previously reported CSI. The terminal device 111 measures the CSI-RS transmitted from the base station device 101 (S204) and reports the measurement result to the base station device 101 (S205).

[0017] The base station device 101 uses the result of the report received in S205 to determine one or more beams to be enabled (made available) for downlink signal transmission to the terminal device 111 from among multiple beams that the base station device 101 can use for transmitting downlink signals (S206). Each of the multiple beams that the base station device 101 can form is associated with a Transmission Configuration Indication (TCI). Then, the beams that can be used for transmitting downlink signals to the terminal device 111 are set by enabling a TCI state that indicates the state of the TCI. For example, the TCI state of a beam heading in a direction significantly different from the direction of the terminal device 111 is disabled, and the TCI state of at least some of the beams heading toward the direction of the terminal device 111 is enabled. Each TCI can be associated with a reference signal to be measured. For example, in the example of FIG. 1 , TCI0 ​​to TCI8 may be associated with CSI-RS, and TCI9 to TCI11 may be associated with synchronization signal / physical broadcast channel (SS / PBCH) blocks (SSBs). Note that TCIn means TCI stateid=n. Different reference signals are associated with multiple TCIs having different TCI stateids. That is, CSI-RSs based on different radio resources (frequency and time resources) or sequences may be associated with TCI0 ​​to TCI8, and SSBs based on different radio resources or sequences may be associated with TCI9 to TCI11. The base station device 101 notifies the terminal device 111 of configuration information for these reference signals, and the terminal device 111 can measure these reference signals based on the configuration information. Furthermore, when the base station device 101 and the terminal device 111 communicate using a plurality of cells, the TCIs used by the respective cells may be associated with reference signals provided by other cells, rather than with reference signals provided by the respective cells. In this case, information for identifying which cell's reference signal is associated with which cell's TCI may be notified to the terminal device 111.

[0018] Then, the base station device 101 transmits to the terminal device 111 a MAC CE including information specifying one or more beams determined to be enabled for downlink signal transmission to the terminal device 111 (S207). The base station device 101 may notify the terminal device 111 of a TCI stateid specifying one or more beams to be enabled. The base station device 101 may notify the terminal device 111 of information such as a bitmap indicating enabled or disabled as the TCI state corresponding to each of multiple beams formed by the base station device 101. Thereafter, when transmitting a downlink signal (e.g., a physical downlink shared channel (PDSCH) or a physical downlink control channel (PDCCH)) to the terminal device 111, the base station device 101 selects a beam to be used from the one or more beams determined to be enabled in S206. Then, the base station device 101 includes information specifying the beam to be used in DCI in the PDCCH to be transmitted when transmitting the downlink signal, and transmits the DCI to the terminal device 111 (S208).

[0019] In this way, to set a downlink beam, the terminal device 111 needs to receive a CSI measurement report instruction from the base station device 101, report the CSI, and receive designation of one or more beams that have been determined to be activated based on the results of the report. Therefore, a certain amount of time is required for transmitting a downlink signal between the base station device 101 and the terminal device 111 using an appropriate beam, which may prevent signal transmission from being performed in a timely manner.

[0020] In this embodiment, a technique is provided for shortening the period for setting a beam to be enabled for transmitting a downlink signal to a terminal device 111 from among multiple beams formed by a base station device 101.

[0021] In a first technique in this embodiment, the terminal device 111 autonomously determines whether or not a situation exists in which measurement should be performed, and when the situation dictates that measurement should be performed, performs measurement without waiting for an instruction from the base station device 101, and reports the measurement results to the base station device 101. Note that the measurement and reporting here may be aperiodic or quasi-permanent CSI measurement and reporting, but the terminal device 111 may, for example, autonomously change the period of periodic CSI measurement and reporting.

[0022] In the first technique, the base station device 101 notifies the terminal device 111 of information indicating a condition for starting or ending CSI reporting, in addition to the measurement and reporting configuration information such as that of S201. For example, the condition for starting CSI reporting may include the strength of a predetermined reference signal exceeding a predetermined value (becoming equal to or greater than the predetermined value), and the information indicating the condition notified from the base station device 101 to the terminal device 111 may include, as information indicating the condition for starting reporting, information indicating the predetermined reference signal and information indicating the predetermined value. Furthermore, the condition for ending reporting may include the strength of the predetermined reference signal falling below a predetermined value (becoming equal to or less than the predetermined value), and the information indicating the condition notified from the base station device 101 to the terminal device 111 may include, as information indicating the condition for ending reporting, information indicating the predetermined reference signal and information indicating the predetermined value. The information indicating the predetermined reference signal may include, for example, an SS / PBCH Resource Indicator (SSBRI) that identifies an SSB, or a CSI Reference Signal Resource Indicator (CRI) that identifies a CSI-RS. That is, based on the information indicating this condition, when the strength of the SSB or CSI-RS identified by the SSBRI or CRI exceeds a predetermined value (is equal to or greater than a predetermined value), the terminal device 111 can start quasi-persistent or aperiodic CSI measurement and reporting based on the setting information notified from the base station device 101 without receiving any further instructions from the base station device 101. Furthermore, based on the information indicating this condition, if the strength of the SSB or CSI-RS identified by the SSBRI or CRI falls below a predetermined value (is greater than or equal to a predetermined value), for example, if quasi-permanent CSI measurement and reporting is being performed, the terminal device 111 terminates further measurement and reporting.

[0023] Note that the above conditions are merely examples, and other conditions may be used. For example, in the state shown in FIG. 1, when the terminal device 111 moves in the direction of the beam of TCI11 and the radio quality of the beam of TCI9 deteriorates, CSI reporting may be initiated. That is, quasi-permanent or aperiodic CSI measurement and reporting may be initiated on the condition that the strength of the SSB or CSI-RS specified by the SSBRI or CRI falls below a predetermined value. Furthermore, as the conditions here, for example, conditions related to the channel quality information (CQI, PMI, RI) of the CSI-RS may be used. Note that CQI is a channel quality indicator, PMI is a precoding matrix indicator, and RI is a rank indicator.

[0024] The base station device 101 can notify the terminal device 111 of multiple pieces of configuration information regarding measurement and reporting of CSI. For example, separate configuration information is notified to the terminal device 111 for each TCI. In one example, first configuration information indicating that a CSI report for a first TCI should be transmitted and second configuration information indicating that a CSI report for a second TCI should be transmitted are notified to the terminal device 111. Note that multiple pieces of configuration information may be notified to the terminal device 111 for one TCI. For example, for one specific TCI, third configuration information indicating that a CSI report should be transmitted at 50 millisecond intervals and fourth configuration information indicating that a CSI report should be transmitted at 500 millisecond intervals may be notified to the terminal device 111. In this case, the third setting information and the fourth setting information may be setting information for periodic CSI measurement and reporting, and the terminal device 111 may switch the setting information used for periodic CSI measurement and reporting between the third setting information and the fourth setting information when a specific condition is satisfied. Each setting information is assigned identification information (reportConfigID) that identifies the setting information. For example, when a specific condition is satisfied, the base station device 101 may notify the terminal device 111 of information indicating the condition so that CSI measurement and reporting based on the specific setting information is started or ended. That is, the information indicating the condition may include information indicating which of multiple setting information the start or end of CSI measurement and reporting is related to.

[0025] The base station device 101 may separately define the conditions and the processes to be executed, and notify the terminal device 111 of the information indicating the combination of the conditions and the processes, in addition to the information on the conditions and the processes. For example, the following information may be notified to the terminal device 111: Condition 1: L1-RSRP of SSBRI 1 is A or higher Condition 2: L1-RSRP of SSBRI 2 is B or lower Condition 3: L1-RSRP of CRI 1 is C or higher ... Execution instruction 1: Start CSI reporting for reportConfigID=1, 2 Execution instruction 2: End CSI reporting for reportConfigID=1, 2 Execution instruction 3: Start CSI reporting for reportConfigID=3, 4 Execution instruction 4: Execute CSI reporting once for reportConfigID=5, 6 ... Instruction setting 1: Condition 1, execution instruction 1 Instruction setting 2: Condition 2, execution instruction 2 Instruction setting 3: Condition 1, execution instruction 3 Instruction setting 4: Condition 3, execution instruction 4 ... According to this notification method, for example, it is not necessary to prepare information indicating conditions individually for multiple execution instructions, and signaling overhead due to notifications can be reduced. Furthermore, according to this notification method, when changing the combination of conditions and execution instructions in some instruction settings, it is sufficient to update only the information in the instruction settings, and therefore signaling overhead can be reduced even when updating the information indicating the conditions. Furthermore, for example, when a specific instruction setting is released, the terminal device 111 may delete the instruction setting while maintaining the information on the conditions and execution instructions. By maintaining the information on the conditions and execution instructions, the base station device 101 can subsequently notify the terminal device 111 to activate an instruction setting including at least one of the conditions and execution instructions. According to this, when the same conditions and execution instructions can be reused, the base station device 101 can instruct the terminal device 111 to measure and report CSI under specific conditions with minimal signaling.

[0026] Note that L1-RSRP indicates reference signal received power in the physical layer. Furthermore, the configuration information can use conventional reportConfig (CSI-ReportConfig), and reportConfigID is identification information that identifies the configuration information. Note that in CSI-ReportConfig, which indicates an execution instruction set together with the conditions for starting and ending semi-persistent CSI measurement and reporting, reportConfigType can be set to semiPersistent (OnPUCCH or OnPUSCH). On the other hand, in CSI-ReportConfig, which indicates an execution instruction set together with the conditions for starting aperiodic CSI measurement and reporting, reportConfigType can be set to aperiodic. The existing settings of reportConfig (CSI-ReportConfig) include information on the settings of CSI-RS resources used for reporting semi-persistent or aperiodic CSI and the timing of reporting to the base station device 101.

[0027] In one example, the base station device 101 may notify the terminal device 111 of the index of the SSB or CSI-RS as information for identifying the SSB or CSI-RS used in determining the above-mentioned conditions. Furthermore, a reference signal associated with a beam currently being used for condition determination (e.g., a reference signal associated with an enabled TCI) or a reference signal associated with a beam not currently being used (e.g., a reference signal associated with a disabled TCI) may be specified. Furthermore, multiple reference signals may be used for determining the conditions. For example, when one cell is composed of multiple TRPs, the average value of multiple reference signals transmitted by each TRP may be used for condition determination. In this case, the base station device 101 notifies the terminal device 111 of a list of reference signals used to calculate the average value (a list of SSB or CSI-RS indices). Furthermore, the terminal device 111 may calculate the average value of measurement results for reference signals that exceed or fall below a threshold specified by the base station device 101. Furthermore, the terminal device 111 may select measurement results of reference signals, in order of quality or quality, equal to the number of reference signals specified by the base station device 101, and calculate an average value using the selected samples. Furthermore, the terminal device 111 may set a weighting coefficient for the measurement results of each reference signal and then calculate a weighted average value. Furthermore, when determining that the conditions are satisfied, the terminal device 111 may send a notification including the measurement results of the reference signals to the base station device 101, and the base station device 101, upon receiving the notification, may instruct the terminal device 111 to start or end quasi-persistent or aperiodic CSI measurement and reporting.

[0028] When the base station device 101 receives a report of the results of CSI measurement performed by the terminal device 111 because the above-mentioned conditions are satisfied, the base station device 101 determines, from among the multiple beams formed by the base station device 101, beams to be usable for downlink communications with the terminal device 111. The base station device 101 then transmits information indicating whether each beam is enabled or disabled to the terminal device 111. This information may be, for example, information indicating whether the TCI state corresponding to each beam is enabled or disabled. Each enabled beam is assigned an index, for example, from 0 to 15. After transmitting this information, the base station device 101 may use the index to indicate, in the DCI, the beam used when transmitting the downlink signal. When receiving the downlink signal, the terminal device 111 may check the index indicating the TCI in the DCI and perform a decoding process compatible with the TCI corresponding to the index.

[0029] The processing flow of the first technique described above will be outlined using Fig. 3. First, the base station device 101 notifies the terminal device 111 (for example, using an RRC message) of information indicating conditions under which the measurement and reporting of CSI should be performed, in addition to configuration information for CSI measurement and reporting (S301). Note that the example of Fig. 3 shows an example in which the configuration information for CSI measurement and reporting and the information indicating conditions under which the measurement and reporting should be performed are notified in a single RRC message, but this is just an example, and these pieces of information may be notified from the base station device 101 to the terminal device 111 by separate messages. Furthermore, after transmitting the message of S301, the base station device 101 can also notify the terminal device 111 of a message that updates only the conditions (for example, at least one of the above-mentioned conditions and instruction settings).

[0030] When the terminal device 111 determines that the notified condition is satisfied (S302), it measures the radio quality (CSI) using the setting information associated with the condition (S303) and reports the measurement result to the base station device 101 (S304). The subsequent processing of S305 to S307 is the same as the processing of S206 to S208 described above. According to this processing, the terminal device 111 can measure and report the CSI without waiting for a measurement and report instruction such as S203 in FIG. 2. Therefore, in S305 to S306, the base station device 101 can determine a beam to be enabled for downlink communication of the terminal device 111 and notify the terminal device 111, thereby shortening the time until downlink communication can be performed using an appropriate beam.

[0031] In the second technique, the terminal device 111 determines a beam to be enabled for the terminal device 111's downlink communication. The terminal device 111, for example, receives configuration information for measuring and reporting CSI and performs measurements based on the configuration information. Then, instead of providing the measurement results to the base station device 101, the terminal device 111 uses the measurement results to select a beam that can be used for transmitting a downlink signal to the terminal device 111. This eliminates the need for the terminal device 111 to notify the base station device 101 of the measurement results and the base station device 101 to notify the terminal device 111 of the beam to be enabled that the base station device 101 has determined, thereby shortening the time until downlink communication can be performed using an appropriate beam.

[0032] In the second technique, the base station device 101 notifies the terminal device 111 of first setting information related to CSI measurement and second setting information related to selection of a beam to be activated by the terminal device 111. The terminal device 111 then performs CSI measurement based on the first setting information, and determines which of multiple beams formed by the base station device 101 to activate based on the CSI measurement result and the second setting information. The terminal device 111 then notifies the base station device 101 of information indicating the beam decided to be activated, and also performs processing to activate the beam. The terminal device 111 can, for example, notify the base station device 101 that it will activate the TCI state corresponding to the beam to be activated. Note that the terminal device 111 may also notify the base station device 101 of a bitmap indicating whether the TCI state corresponding to each of the multiple beams formed by the base station device 101 is enabled or disabled. Furthermore, the terminal device 111 may notify the base station device 101 of information capable of identifying a CSI-RS or SSB corresponding to the beam to be enabled. That is, since a CSI-RS or SSB generated using different radio resources or sequences is transmitted in each beam, the terminal device 111 can identify the corresponding beam by identifying the CSI-RS or SSB. In response to receiving a notification from the terminal device 111, the base station device 101 identifies the beam indicated by the notification that has been determined to be enabled in the terminal device 111, and uses the identified beam in subsequent downlink communications.

[0033] The second setting information described above may include information indicating the number of beams that can be enabled. For example, the base station device 101 may notify the terminal device 111 of second setting information indicating that a maximum of two beams may be enabled. When the terminal device 111 receives such second setting information, it determines to enable a number of beams that does not exceed the number indicated by the second setting information. For example, in a DCI including information for transmitting a downlink signal after a selected beam is enabled, the number of beams that can be enabled may be determined according to the number of bits available for notifying information specifying the beams to be used for transmitting the signal. For example, when three bits are provided for specifying beams in the DCI, the number of beams that can be enabled may be determined to be eight, and when four bits are provided for specifying beams in the DCI, the number of beams that can be enabled may be determined to be 16. Note that the terminal device 111 may notify the base station device 101 of the maximum number of beams that can be enabled in the terminal device 111. In this case, the terminal device 111 may enable a number of beams that does not exceed the maximum number of beams. In addition, the base station device 101 may determine the number of beams that the terminal device 111 may consider valid, provided that the number does not exceed the maximum number of beams that may be considered valid as notified by the terminal device 111, and notify the terminal device 111 of that number.

[0034] Furthermore, the above-mentioned second setting information may include, for example, information specifying beams that should always be enabled (i.e., that should not be disabled). Conversely, the second setting information may include information specifying beams that the terminal device 111 is allowed to determine whether to enable or disable. For example, in the example of FIG. 1, the base station device 101 may notify the terminal device 111 of second setting information that specifies TCI9 to TCI11 as beams that should not be disabled. The terminal device 111 may determine whether to enable or disable each beam that is not a beam that should not be disabled. Note that, when the number of beams that can be enabled is specified, the terminal device 111 determines which beams to enable so that the number of beams that should not be disabled and the number of beams that are enabled among the other beams do not exceed the specified number of beams. According to such settings, for example, by always enabling beams with wide beam widths that enable minimum communication, a certain communication service can be provided to the terminal device 111 even if communication quality deteriorates in beams with narrow beam widths.

[0035] Furthermore, the second setting information may include, for example, information indicating the wireless quality that the enabled beams must satisfy. The base station device 101 can specify, for example, the wireless quality according to the type of communication service (communication application) to be provided to the terminal device 111. The terminal device 111 selects enabled beams from among beams that satisfy the specified wireless quality. Specifying such wireless quality can prevent the unnecessary selection of beams that cannot be used to provide the communication service to the terminal device 111 due to insufficient wireless quality. The terminal device 111 can enable a predetermined number of beams (a number determined by the capabilities of the terminal device 111 or not exceeding the number of enabled beams specified by the base station device 101) from among beams that exceed the specified wireless quality. Note that, at this time, the predetermined number of beams may be selected in order of best wireless quality, or may be selected randomly (from a group of beams that can achieve the specified wireless quality). Note that, if the terminal device 111 is not notified of information indicating the wireless quality that the enabled beams must satisfy, it can enable a predetermined number of beams from among beams with good wireless quality.

[0036] The base station device 101 and the terminal device 111 may, for example, execute the process of activating the beam determined to be activated after a predetermined period has elapsed since the terminal device 111 notified the base station device 101 of the beam determined to be activated (since the base station device 101 received the notification). That is, if the terminal device 111 activates the beam determined to be activated at the time of transmitting the beam, the base station device 101 may not be able to activate the beam at that timing due to a propagation delay of the notification or a delay due to processing such as decoding, and it is assumed that inconsistency occurs between the base station device 101 and the terminal device 111. For this reason, for example, the base station device 101 and the terminal device 111 may simultaneously activate the selected beam after a predetermined period has elapsed, such as a predetermined number of slots after the time slot in which the terminal device 111 notified the base station device 101 of the beam determined to be activated. This makes it possible to prevent inconsistency between the base station device 101 and the terminal device 111.

[0037] The base station device 101 may notify the terminal device 111 of third setting information indicating information indicating the length of this predetermined period. That is, the length of the predetermined period may be set by the base station device 101. The base station device 101 may also notify the terminal device 111 of third setting information indicating multiple candidates for the length of the predetermined period. In this case, the terminal device 111 selects a period of any length from the multiple candidates and activates the beam determined to be activated after the period has elapsed. The terminal device 111 may also notify the base station device 101 of information indicating the length of the selected period in addition to information indicating the beam determined to be activated. After the notified period has elapsed, the base station device 101 executes a process to activate the beam determined by the terminal device 111 to be activated. According to this process, the terminal device 111 can determine the length of the predetermined period (from among the candidates presented by the base station device 101). If the length of the predetermined period is clearly defined, for example, by a standard, signaling of information regarding the length of the period may be omitted altogether.

[0038] Furthermore, when the base station device 101 receives, from the terminal device 111, a notification of information indicating a beam determined to be valid, the base station device 101 may transmit an acknowledgement (ACK) to the terminal device 111. For example, the terminal device 111 may notify the base station device 101 of information indicating the beam determined to be valid using an RRC message or a MAC CE included in an uplink data signal. Then, the base station device 101 may transmit an ACK to the terminal device 111 using an RRC message or a MAC CE included in a downlink data signal. Then, after notifying the base station device 101 of information indicating the beam determined to be valid, the terminal device 111 may perform an activation process for the beam determined to be valid based on receiving an ACK in response to the notification. In other words, the terminal device 111 may not perform an activation process for the beam determined to be valid unless it receives an ACK from the base station device 101. If the terminal device 111 does not receive an ACK even after waiting for a predetermined length of time, the terminal device 111 may retransmit a notification of the beam determined to be valid to the base station device 101. The base station device 101 may always return an ACK when it successfully receives a notification of information indicating the beam determined to be valid, or may determine whether or not to accept the content of the notification and return an ACK only if it determines to accept it. This can prevent inconsistencies in the beams to be validated between the base station device 101 and the terminal device 111. The notification from the terminal device 111 to the base station device 101 may be assigned identification information that can uniquely identify the notification. In this case, the base station device 101 may assign the identification information to the ACK and transmit it.

[0039] Furthermore, the base station device 101 may periodically transmit information about a beam that is determined to be valid for the terminal device 111 from among the multiple beams that it forms. For example, the terminal device 111 may notify the base station device 101 of information indicating a beam that has been determined to be valid using uplink control information (UCI). In this case, the base station device 101 cannot return an ACK, but by periodically transmitting information about a beam that has been determined to be valid for the terminal device 111, the terminal device 111 can recognize whether the information about the beam that has been determined to be valid is consistent with the beam that the terminal device 111 has determined to be valid. That is, upon receiving this information, the terminal device 111 determines whether the beam that has been determined to be valid by the terminal device 111 matches the beam that the terminal device 111 has notified the base station device 101. Then, if the beam indicated by the information received from the base station device 101 does not match the beam that the terminal device 111 has notified the base station device 101, the terminal device 111 may retransmit to the base station device 101 a notification of the beam that it has determined to be valid. That is, when a beam recognized in the base station device 101 and activated for the terminal device 111 does not match a beam recognized in the terminal device 111 that should be activated, the terminal device 111 may determine that a notification of the beam determined to be activated has not correctly reached the base station device 101, and may retransmit the notification. This makes it possible to correct a mismatch in the beams determined to be activated between the base station device 101 and the terminal device 111. Note that the terminal device 111 may suspend the activation process of the beam determined to be activated until the mismatch is corrected.

[0040] It is possible that the terminal device 111 receives allocation of radio resources for the physical downlink shared channel (PDSCH) and the physical uplink shared channel (PUSCH) from the base station device 101 when the terminal device 111 and the base station device 101 have inconsistent recognition of the enabled beams (TCI state inconsistency). In this case, the terminal device 111 may notify the base station device 101 that it cannot accept the notified resource allocation (or that it is in a state where resource allocation is not possible). Furthermore, the base station device 101 may allocate resources for the PDSCH and PUSCH signals in two or more beams for transmitting those signals, assuming that the TCI state is inconsistent. If the two or more beams to which the resources are allocated include a beam that is not enabled by the terminal device 111, the terminal device 111 may perform data communication using enabled beams without using that beam. This allows communication to continue even when a period in which TCI state inconsistency may occur occurs.

[0041] The processing flow of the second method described above will be outlined using FIG. 4 . First, the base station device 101 notifies the terminal device 111 of first setting information related to CSI measurement and second setting information related to beam selection, for example, using an RRC message (S401). While the example in FIG. 4 shows an example in which the first setting information and the second setting information are notified in a single message, these setting information may also be notified in separate messages. The terminal device 111 performs radio quality (CSI) measurement based on the first setting information (S402), and selects a valid beam from among multiple beams formed by the base station device 101 based on the measurement results (S403). Then, the terminal device 111 transmits a notification including the beam selection result to the base station device 101 (S404). Here, the base station device 101 may return an ACK in response to this notification (S405). The base station device 101 may periodically transmit information about beams that are enabled for the terminal device 111 to the terminal device 111. The base station device 101 and the terminal device 111 execute a process for enabling the beams notified by the terminal device 111, for example, after a predetermined period has elapsed since the transmission and reception of the notification in S404 (S406, S407). This enabling process, for example, a process for associating and storing a predetermined index with each enabled beam, enables the base station device 101 to specify a beam to be used by DCI in subsequent communications. After completing this process, the base station device 101 selects a beam to be used from the beams that are enabled for the terminal device 111 when transmitting a downlink signal, and transmits DCI including information indicating the selected beam to the terminal device 111 (S408).

[0042] In this way, in the second technique, after the terminal device 111 measures the wireless quality, the terminal device 111 determines the beam to be activated without notifying the base station device 101 of the measurement result and without the base station device 101 determining the beam to be activated and notifying the same. This makes it possible to reduce the number of times signaling occurs between the terminal device 111 and the base station device 101, and shortens the time required for the terminal device 111 to determine the beam to be activated and activate it.

[0043] Note that the first method and the second method may be selectively executed, or the first method and the second method may be used in combination. When the first method and the second method are selectively executed, for example, when notifying the terminal device 111 of the configuration information for the initial measurement, the base station device 101 may also notify the terminal device 111 of information indicating which method to use. Note that, for example, the notification may be made implicitly depending on whether the information on the condition (S301) or the configuration information regarding beam selection (S401) is transmitted. Also, when the first method and the second method are used in combination, the base station device 101 may notify the terminal device 111 of both the information indicating the condition under which measurement should be performed and the configuration information regarding beam selection. The terminal device 111 may perform measurement when the notified condition is satisfied and select a beam based on the measurement result. That is, in the second technique, the terminal device 111 can perform wireless quality measurement and beam selection, for example, in response to receiving first setting information regarding measurement and second setting information regarding beam selection in S401, but by being notified of the conditions for starting the processing, the terminal device 111 can autonomously start the processing in response to determining that the conditions are satisfied.

[0044] Although the above description focuses on the setting of beams for transmitting and receiving downlink signals, the setting of beams used for transmitting and receiving uplink signals can be performed in a similar manner. That is, when the same frequency channel is used for the downlink and the uplink, it is assumed that the downlink channel characteristics and the uplink channel characteristics are common. Therefore, uplink communication can also be performed using the beam selected for transmitting downlink signals as described above.

[0045] FIG. 5 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 501, a ROM 502, a RAM 503, a storage device 504, and a communication circuit 505. The processor 501 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 502 or the storage device 504. The ROM 502 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 503 functions as a workspace when the processor 501 executes a program and is also a random access memory that stores temporary information. The storage device 504 is configured, for example, by a removable external storage device. The communication circuit 505 is configured, for example, by a circuit for wireless communication of 5G or a successor standard. While FIG. 5 illustrates one communication circuit 505, 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. 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 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 505 for each of the multiple available frequency bands, or may have a common communication circuit 505 for at least some of the frequency bands.

[0046] FIG. 6 shows an example of the functional configuration of the base station device 101 according to this embodiment. The base station device 101 includes, as its functions, a measurement report setting designator 601, a condition designator 602, a selection setting designator 603, an information notification unit 604, an information receiver 605, a beam selector 606, an activation processor 607, and a data communication unit 608. Note that FIG. 6 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 base station devices compliant with 5G and subsequent standards generally have. Furthermore, the functional blocks in FIG. 6 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. 6 may be realized, for example, by the processor 501 executing a program stored in the ROM 502 or the storage device 504, or by a processor present within the communication circuit 505 executing predetermined software. The details of the processes executed by each functional unit have been described above, so the description will not be repeated here, and only the general functions will be outlined.

[0047] The measurement report setting designation unit 601 designates setting information related to CSI measurement and reporting for the terminal device 111. This setting information is similar to measurement information related to conventional CSI measurement and reporting. The condition designation unit 602 designates conditions for the terminal device 111 to autonomously start and end CSI measurement and reporting in the above-described first method. The selection setting designation unit 603 designates setting information used when the terminal device 111 autonomously determines a beam to be activated in the above-described second method. The information notification unit 604 notifies the terminal device 111 of the setting information designated by the measurement report setting designation unit 601 and information designated by at least one of the condition designation unit 602 and the selection setting designation unit 603. The information receiving unit 605 receives various information notified from the terminal device 111. For example, in the first method, the information receiving unit 605 receives a report of the CSI measurement results. Furthermore, in the second method, the information receiving unit 605 receives information designating a beam to be activated. In the first technique, the beam selection unit 606 determines a beam to be activated in communication with the terminal device 111 based on the CSI measurement results received by the information receiving unit 605. Note that when the second technique is used, the beam selection unit 606 is not used. The activation processing unit 607 executes processing to activate a beam that has been notified by the terminal device 111 or selected by the beam selection unit 606 and that has been determined to be activated in communication with the terminal device 111. The data communication unit 608 uses one of the beams activated by the activation processing unit 607 to communicate with the terminal device 111.

[0048] FIG. 7 shows an example of the functional configuration of the terminal device 111 according to this embodiment. The terminal device 111 includes, as its functions, a setting receiving unit 701, a condition determining unit 702, a measuring unit 703, a beam selecting unit 704, a reporting unit 705, an activation processing unit 706, and a data communication unit 707. Note that FIG. 7 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. 7 are shown schematically, and each functional block may be realized as an integrated unit or may be further subdivided. Furthermore, each function in FIG. 7 may be realized, for example, by the processor 501 executing a program stored in the ROM 502 or the storage device 504, or by a processor within the communication circuit 505 executing predetermined software. The details of the processes executed by each functional unit have been described above, so the description will not be repeated here, and only the general functions will be outlined.

[0049] The setting receiver 701 receives, from the base station device 101, information including setting information for CSI measurement and reporting, and at least one of information indicating conditions for starting and ending measurement and reporting, and setting information for selecting a beam. Furthermore, for example, when the base station device 101 determines a beam to be enabled for communication with the terminal device 111, the setting receiver 701 receives information indicating the beam from the base station device 101. When the first technique is used, the condition determiner 702 determines whether a condition included in the information received by the setting receiver 701 is satisfied. The measurement unit 703 measures the radio quality of a signal transmitted from the base station device 101 based on the setting information for CSI measurement received by the setting receiver 701. When the first technique is used, for example, the measurement unit 703 measures the radio quality in response to the condition determiner 702 determining that the condition is satisfied. When the second technique is used, the beam selector 704 uses the setting information for beam selection received by the setting receiver 701 to determine which of the multiple beams formed by the base station device 101 is to be usable (enabled) for communication with the base station device 101 based on the measurement results of the measurement unit 703. Note that when the second technique is not used, the beam selector 704 is not used. The report unit 705, for example, reports the wireless quality measured by the measurement unit 703 to the base station device 101. Furthermore, when the second technique is used, the report unit 705 reports information on the beam determined to be enabled by the beam selector 704 to the base station device 101. The activation processor 706, for example, performs processing to activate the beam received by the setting receiver 701 and determined to be enabled in the base station device 101. Furthermore, when the second technique is used, the activation processor 706 performs processing to activate the beam determined to be enabled by the beam selector 704. The data communication unit 707 communicates with the base station device 101 using one of the beams activated by the activation processing unit 706 .

[0050] As described above, the base station device 101 and terminal device 111 according to this embodiment can quickly determine and activate one or more beams that can be used for communication by the terminal device 111 from among multiple beams formed by the base station device 101. This makes it possible to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote sustainable industrialization, and foster innovation."

[0051] 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.

[0052] This application claims priority based on Japanese Patent Application No. 2023-161689, filed September 25, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A terminal device comprising: a receiving means for receiving, from a base station device which forms multiple beams and communicates, first setting information regarding measurement of channel state information (CSI) for determining which of the multiple beams to enable, and second setting information regarding selection of the multiple beams; an execution means for performing measurement of the CSI based on the first setting information; a determination means for determining which of the multiple beams to enable based on the CSI measurement results and the second setting information; a notification means for notifying the base station device of information indicating the beam that has been determined to be enabled; and an enabling means for enabling the beam that has been determined to be enabled.

2. A terminal device as described in claim 1, wherein the second setting information includes information indicating the number of beams that can be enabled, and the determination means enables a number of beams out of the plurality of beams that does not exceed that number.

3. A terminal device as described in claim 1 or 2, wherein the second setting information includes information specifying beams that must not be disabled.

4. A terminal device as described in any one of claims 1 to 3, wherein the second setting information includes information indicating a wireless quality that a beam to be enabled must satisfy, and the determination means determines a beam to be enabled from among beams that satisfy the wireless quality.

5. A terminal device as claimed in any one of claims 1 to 4, wherein the activation means activates the beam that has been determined to be activated after a predetermined period has elapsed since the notification means notifies the base station device.

6. The terminal device according to claim 5, wherein said receiving means receives third setting information indicating the length of said predetermined period from said base station device.

7. The terminal device of claim 5, wherein the receiving means receives third setting information indicating a plurality of candidates for the length of the specified period from the base station device, the enabling means selects a period of any length from the plurality of candidates for the length of the specified period and enables the beam that has been determined to be enabled after the period has elapsed, and the notifying means notifies the base station device of information indicating the length of the selected period in addition to information indicating the beam that has been determined to be enabled.

8. A terminal device as described in any one of claims 1 to 7, further comprising means for periodically receiving information on a beam among the plurality of beams that is determined to be valid for the terminal device from the base station device, wherein the notification means retransmits information indicating the beam determined to be valid to the base station device when the beam determined to be valid indicated in the information received from the base station device does not match the beam determined to be valid indicated in the information notified to the base station device.

9. A base station device that forms multiple beams for communication, comprising: a notification means for notifying a terminal device of first setting information regarding measurement of channel state information (CSI) for determining which of the multiple beams to activate, and second setting information regarding selection of the multiple beams; a receiving means for receiving information indicating a beam among the multiple beams that has been determined to be active by the terminal device based on the results of measurement of the CSI in the terminal device using the first setting information and the second setting information; and a transmitting means for transmitting a downlink signal to the terminal device using one of the beams that has been determined to be active.

10. The base station device according to claim 9, wherein the second setting information includes information indicating a number of beams that can be enabled.

11. A base station device as described in claim 9 or 10, wherein the second setting information includes information specifying beams that must not be disabled.

12. A base station device as described in any one of claims 9 to 11, wherein the second setting information includes information indicating a radio quality that a beam to be enabled must satisfy.

13. A base station device as described in any one of claims 9 to 12, wherein the transmitting means transmits a downlink signal to the terminal device using one of the beams indicated by the information after a predetermined period has elapsed since the terminal device transmitted information indicating a beam determined to be valid.

14. The base station device according to claim 13, wherein said notification means notifies said terminal device of third setting information indicating the length of said predetermined period.

15. The base station device of claim 13, wherein the notification means notifies the terminal device of third setting information indicating a plurality of candidates for the length of the specified period, and the receiving means receives information indicating the length of one of the plurality of candidates for the length of the specified period selected in the terminal device in addition to information indicating the beam that has been determined to be valid.

16. A base station device as claimed in any one of claims 9 to 15, further comprising means for periodically transmitting to said terminal device information on a beam among said plurality of beams which is valid for said terminal device.

17. A control method executed by a terminal device, comprising: receiving, from a base station device that forms multiple beams and communicates, first setting information regarding measurement of channel state information (CSI) for determining which of the multiple beams to activate, and second setting information regarding selection of the multiple beams; measuring the CSI based on the first setting information; determining which of the multiple beams to activate based on the CSI measurement results and the second setting information; notifying the base station device of information indicating the beam determined to be activated; and enabling the beam determined to be activated.

18. A control method executed by a base station device that forms multiple beams for communication, comprising: notifying a terminal device of first setting information for measuring and reporting channel state information (CSI) for determining which of the multiple beams to activate, and second setting information for selecting the multiple beams; receiving information indicating a beam among the multiple beams that has been determined to be activated by the terminal device based on the result of measuring the CSI in the terminal device using the first setting information and the second setting information; and transmitting a downlink signal to the terminal device using one of the beams that has been determined to be activated.

19. A program for causing a computer installed in a terminal device to execute the control method according to claim 17.

20. A program for causing a computer installed in a base station device to execute the control method according to claim 18.

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