Base station device, terminal device, communication method, and program in wireless communication system in which communication using plurality of transmission / reception points (TRP) is performed

Abstract

This base station device communicates with a terminal device using a plurality of transmission / reception points (TRPs) including a first TRP and a second TRP. The base station device notifies the terminal device of information indicating a characteristic, among characteristics of a channel estimated on the basis of a channel state information-reference signal (CSI-RS) transmitted from the first TRP when calibration is not performed between the first TRP and the second TRP, that can be used for signal reception when the frequency or transmission timing of the first TRP is adjusted by calibration between the first TRP and the second TRP.

Description

Base station device, terminal device, communication method, and program in a wireless communication system in which communication is performed using multiple transmission / reception points (TRPs)

[0001] The present invention relates to an operation technique for a wireless communication system in which a base station device performs communication using a plurality of transmission / reception points (TRPs).

[0002] A system is being considered in which a base station device communicates using multiple transmission / reception points (TRPs) located at geographically distant locations. In such a system, the base station device may select one of the multiple TRPs to communicate with a terminal device, and may also simultaneously use two or more TRPs to communicate with a terminal device.

[0003] 3GPP (registered trademark) Contribution, R1-2203142

[0004] The present invention provides an efficient operation technique for a system in which a base station device communicates using multiple TRPs.

[0005] A base station device according to one aspect of the present invention is a base station device that communicates with a terminal device using multiple TRPs including a first transmission / reception point (TRP) and a second TRP, and has a notification means for notifying the terminal device of information indicating characteristics that can be used to receive signals when the frequency or transmission timing of the first TRP is adjusted by the calibration between the first TRP and the second TRP, among channel characteristics estimated based on the channel state information-reference signal (CSI-RS) transmitted from the first TRP when no calibration is performed between the first TRP and the second TRP.

[0006] A terminal device according to one aspect of the present invention has a receiving means for receiving information from a base station device that communicates with the terminal device using multiple TRPs including a first transmission / reception point (TRP) and a second TRP, the information indicating channel characteristics estimated based on a channel state information-reference signal (CSI-RS) transmitted from the first TRP when calibration is not performed between the first TRP and the second TRP, which characteristics can be used to receive a signal when the frequency or transmission timing of the first TRP is adjusted by the calibration between the first TRP and the second TRP; and an execution means configured to perform reception processing of a signal in a state in which the calibration is performed between the first TRP and the second TRP using the information and the result of estimating the channel characteristics based on the CSI-RS transmitted from the first TRP when the calibration is not performed.

[0007] According to the present invention, it is possible to efficiently operate a system in which a base station device communicates with a terminal device using a plurality of transmission / reception points (TRPs).

[0008] 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.

[0009] The accompanying drawings are included in and constitute a part of the specification, illustrate embodiments of the present invention, and are used, together with the description, to explain the principles of the present invention. FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. FIG. 2 is a diagram illustrating the TCI-state notified to a terminal device. FIG. 3 is a diagram illustrating an example of the flow of communication processing executed in the wireless communication system. FIG. 4 is a diagram illustrating the TCI-state notified to a terminal device. FIG. 5 is a diagram illustrating an example of the flow of communication processing executed in the wireless communication system. FIG. 6 is a diagram illustrating an example of the flow of communication processing executed in the wireless communication system. FIG. 7 is a diagram illustrating qcl-Type. FIG. 8 is a diagram illustrating the TCI-state notified to a terminal device. FIG. 9 is a diagram illustrating an example of the flow of communication processing executed in the wireless communication system. FIG. 10 is a diagram illustrating NZP-CSI-RS-Resource notified to a terminal device. FIG. 11 is a diagram illustrating an example of the flow of frequency and timing synchronization and adjustment processing. FIG. 12 is a diagram illustrating an example of the flow of processing related to measurement and reporting by a terminal device. FIG. 13 is a diagram illustrating an example of settings for measurement and reporting by a terminal device. Fig. 14 is a diagram illustrating an example of settings for measurement and reporting by a terminal device. Fig. 15 is a diagram illustrating an example of a process flow related to measurement and reporting by a terminal device. Fig. 16 is a diagram illustrating an example of a process flow related to measurement and reporting by a terminal device. Fig. 17 is a diagram illustrating an example of the hardware configuration of a base station device and a terminal device. Fig. 18 is a diagram illustrating an example of the functional configuration of a base station device. Fig. 19 is a diagram illustrating an example of the functional configuration of a terminal device.

[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. This wireless communication system is, for example, a cellular communication system conforming to a cellular communication standard standardized for the fifth generation (5G) or later, and is configured to include a base station device (gNB 101) and terminal devices 121 and 122. The gNB 101 establishes a connection with the terminal devices 121 and 122 using at least one of multiple transmission / reception points (TRPs, e.g., a first TRP 111 and a second TRP 112) located at geographically separate locations, and communicates with them. Here, a single TRP may include multiple antenna elements. In this case, adjustment (calibration) is performed within the TRP to roughly match the frequencies, timing, etc. between the multiple antenna elements. When this calibration is performed within the TRP, the processing is performed within the TRP device, so the terminal device does not need to be involved in the calibration. For example, the frequencies of each of the multiple antenna elements are identified within the TRP, and a control unit within the TRP controls the frequencies to match. In addition, clock adjustments can be performed so that radio signals are output from each antenna element at approximately the same timing. When radio signals are transmitted from each of the multiple antenna elements included in one TRP at approximately the same timing, the distances between the antenna elements and the terminal device are approximately equal, so it is assumed that the radio signals will be received by the terminal device within a certain period of time. This certain period is, for example, a period corresponding to the length of the cyclic prefix of orthogonal frequency division multiplexing (OFDM). As a result, the radio signals transmitted from the antenna elements are received by the terminal device within a certain frequency difference range and a certain time difference range, and the terminal device can successfully decode the radio signals without being particularly aware of calibration.

[0012] On the other hand, when multiple TRPs are used for communication with a single terminal device, calibration between those TRPs may be required, for example, to receive radio signals from the terminal device. Even if the gNB101 takes the lead in performing calibration across multiple TRPs, it is not easy to accurately synchronize the timing due to differences in the cable length from the gNB101 to each TRP. Furthermore, depending on the location of the terminal device, the distance between the terminal device and the first TRP and the distance between the terminal device and the second TRP are expected to vary significantly. Even if the first TRP and the second TRP can transmit signals at the same time, the reception timing of those signals in the terminal device may be significantly different, and the terminal device may not be able to properly decode those signals. Furthermore, even if the frequencies between multiple TRPs are roughly the same, there may be gradual deviations in the operating frequencies due to temperature changes in each TRP.

[0013] Therefore, calibration across multiple TRPs can be performed using feedback such as measurement results by the terminal device of signals transmitted from each TRP. For example, when the terminal device establishes frequency synchronization based on a radio signal from the first TRP 111, it performs channel estimation using a radio signal (reference signal) from the second TRP 112, using the frequency at which synchronization with the first TRP 111 is established as a reference. The terminal device further performs channel estimation after a certain period of time has elapsed to determine the amount of phase rotation of the channel. If there is a frequency shift, its effect appears as a phase rotation of the channel. Here, the magnitude of the frequency shift corresponds to the amount of phase rotation of the channel per certain period of time. Therefore, by repeatedly performing such channel estimation to determine the amount of phase rotation per unit time of the channel (the direction and magnitude of the phase rotation), the frequency shift between the first TRP 111 and the second TRP 112 can be determined. The terminal device feeds back information indicating the phase rotation amount or frequency shift to the gNB 101, for example, via at least one of the first TRP 111 and the second TRP 112. Then, based on the feedback, the gNB 101 adjusts, for example, the frequency (or signal phase) of the second TRP 112 so as to suppress the phase rotation amount of the channel in the terminal device. For example, the gNB 101 transmits an instruction to the control unit of the second TRP 112 to adjust the frequency or to rotate the phase of the transmission signal in the opposite direction to the feedback phase rotation direction and transmit it. This allows the frequencies of the radio signals transmitted from the first TRP 111 and the second TRP 112 to be roughly the same.

[0014] In addition, the terminal device can determine how much the reception timing of the signal from the second TRP 112 deviates from the reception timing of the signal from the first TRP 111, based on the timing at which the signal from the first TRP 111 is received. For example, the terminal device measures a predetermined signal such as a synchronization signal from the second TRP 112, determines the deviation in the reception timing, and feeds back the amount of deviation to the gNB 101 via at least one of the first TRP 111 and the second TRP 112. As a result, the gNB 101, for example, instructs the second TRP 112 to shift the transmission timing by the amount of deviation when transmitting a signal to the terminal device (for example, if the signal from the second TRP 112 arrives late at the terminal device, the transmission timing is advanced, and if the signal from the second TRP 112 arrives early at the terminal device, the transmission timing is delayed). As a result, in the terminal device, the signals (or their main components) transmitted from the first TRP 111 and the second TRP 112 arrive within the time length of the cyclic prefix, for example.

[0015] Here, the timing at which a radio signal should be transmitted at each TRP and the combination of TRPs used for communication of a terminal device depend on the location of the terminal device. Therefore, calibration can be performed individually for each terminal device. For example, if the combination of TRPs used for a first terminal device is different from the combination of TRPs used for a second terminal device, the TRPs used as the basis for frequency adjustment may also differ. Furthermore, even if the same combination of TRPs is used for calibration of the first terminal device and calibration of the second terminal device, the appropriate transmission timing of the radio signal may differ depending on the location of each terminal device. Therefore, calibration between TRPs is not always performed, and whether calibration is performed may be determined depending on which terminal device is communicating with which device. For example, when communicating with a terminal device located sufficiently close to one TRP, communication may be performed only via that one TRP. In this case, calibration between TRPs is not performed.

[0016] At this time, the characteristics of the radio signal arriving at the terminal device differ when inter-TRP calibration is performed and when such calibration is not performed. For example, when the second TRP 112 performs calibration based on the radio signal arriving at the terminal device from the first TRP 111, the second TRP 112 transmits a signal at a frequency and transmission timing different from when calibration is not performed. Therefore, for example, compared to when a signal is transmitted only from the second TRP 112, the average delay and frequency of the received signal at the terminal device will be different. For example, the frequency correction value of the terminal device assuming that inter-TRP calibration is performed may be different from the frequency correction value to be used when demodulating a signal in a state where inter-TRP calibration is not performed. In addition, the channel estimation value obtained by the terminal device by measuring, for example, a channel state information-reference signal (CSI-RS) or a synchronization signal (SS) / physical broadcast channel (PBCH) block (SSB) while calibration is being performed is different from the channel estimation value when calibration is not performed. Therefore, if the terminal device does not perform demodulation processing corresponding to whether or not the calibration between TRPs is performed, the terminal device may perform demodulation processing using an inappropriate frequency correction value or channel estimation value. As a result, the demodulation performance of the terminal device may be degraded due to the difference in frequency or channel estimation value.

[0017] For this reason, in this embodiment, a technology is provided that enables a terminal device to perform demodulation processing appropriate for each TRP depending on whether or not calibration between TRPs has been performed.

[0018] In this embodiment, for example, each TRP is configured to notify the terminal device whether it performs calibration (adjustment of frequency or transmission timing) with other TRPs or does not perform such calibration. For example, each TRP transmits information corresponding to whether the signal transmitted to the terminal device is a signal for which inter-TRP calibration has been performed in the downlink control information (DCI) of the signal transmitted to the terminal device. In this embodiment, as an example, a Transmission Configuration Indicator (TCI) state is used as information corresponding to whether inter-TRP calibration has been performed.

[0019] Here, the TCI state will be explained using FIG. 2. FIG. 2 shows part of the TCI state setting information notified from the gNB101 to the terminal device. As shown in FIG. 2, each TCI state includes a TCI-state ID and QCL (Quasi Co-Location)-Info, which are identifiers of that state. Then, in QCL-Info, an NZP (Non Zero Power)-CSI-RS-ResourceSetId or SSB index is specified to indicate the CSI-RS resource. Note that here, we will focus on CSI-RS and omit a description of SSB. In this way, the TCI state is associated with the resource from which the reference signal (CSI-RS) is transmitted. For example, the terminal device measures the reference signal associated with each TCI state, and based on the measurement results, performs reception settings for signal demodulation and the like for each TCI state. Then, when a TCI state identifier (TCI-state ID) is specified in the DCI during subsequent communication, the terminal device performs reception processing such as signal demodulation using the reception settings associated with the TCI-state identified by that identifier. Note that, for example, one TCI state is set for each beam having different characteristics. For this reason, the gNB101 will specify different TCI-state IDs at least when transmitting radio signals only via the first TRP111 and when transmitting radio signals only via the second TRP112.

[0020] Here, in this embodiment, a TCI-state is further prepared for the case where calibration is performed between TRPs (for example, between the first TRP 111 and the second TRP 112). In one example, TCI-state ID = 0 is assigned to the TCI state when a signal is transmitted only using the first beam formed by the first TRP 111 without performing inter-TRP calibration, and TCI-state ID = 1 is assigned to the TCI state when a signal is transmitted only using the second beam formed by the second TRP 112 without performing inter-TRP calibration. Then, in this embodiment, for example, TCI-state ID = 2 is assigned to the TCI state when a signal after inter-TRP calibration is transmitted from both the first TRP 111 and the second TRP 112 using the first beam and the second beam. That is, even when the same beam is used, different TCI states may be prepared depending on whether or not calibration between TRPs is performed. Note that different beams may be formed when calibration between TRPs is performed and when such calibration is not performed. The first TRP 111 and the second TRP 112 transmit reference signals without calibration in resources corresponding to TCI-state ID = 0, 1, respectively, and transmit reference signals after calibration in resources corresponding to TCI-state ID = 2. The terminal device measures these reference signals and determines reception settings corresponding to each TCI state. Then, for example, when the second TRP 112 transmits a radio signal without performing calibration with other TRPs, the gNB 101 specifies TCI-state ID = 1 in the DCI and transmits a signal (physical downlink shared channel (PDSCH)). This allows the terminal device to receive the radio signal using reception settings based on the reference signal transmitted without calibration in the second TRP 112.On the other hand, when the first TRP 111 and the second TRP 112 perform calibration and transmit radio signals, the gNB 101 transmits a signal by specifying TCI-state ID = 2 in the DCI. As a result, the terminal device can receive the radio signal using reception settings based on the reference signals transmitted from each TRP while calibration is being performed between the first TRP 111 and the second TRP 112.

[0021] An example of the processing flow in this case is shown in Figure 3. In this processing example, the second TRP 112 transmits an uncalibrated CSI-RS using resources identified by NZP-CSI-RS-ResourceSetID = 1 corresponding to TCI-state ID = 1 (S301). The terminal device (UE) measures the CSI-RS and determines the reception setting corresponding to TCI-state ID = 1. Note that the second TRP 112 periodically transmits this CSI-RS, and the terminal device (UE) can measure the CSI-RS multiple times. Furthermore, the first TRP 111 transmits an uncalibrated CSI-RS using resources identified by NZP-CSI-RS-ResourceSetID = 0 corresponding to TCI-state ID = 0 (S302). The terminal device performs the measurement and determines the reception setting corresponding to TCI-state ID = 0. Note that the first TRP 111 periodically transmits this CSI-RS, and the terminal device can measure the CSI-RS multiple times. Then, the gNB 101 transmits to the terminal device a DCI (including a downlink control channel (PDCCH)) in which information corresponding to TCI state ID = 1, which corresponds to only the second TRP 112 transmitting data without calibration, is set (S303). Here, in the DCI, an index of 0 to 7 is assigned to each enabled TCI state, and the index indicates information indicating the TCI state ID. In the following, the fact that the index value corresponding to that ID is included (set) in the DCI is expressed as "the TCI state ID is included (set)." 3 shows an example in which the gNB 101 transmits DCI to the UE using the first TRP 111, but for example, the DCI may be transmitted using the second TRP 112, or the DCI may be transmitted using both the first TRP 111 and the second TRP 112. When the terminal device recognizes the value of the TCI state ID indicated in this DCI, it receives subsequent data using the reception setting determined based on the CSI-RS transmitted from the second TRP 112 without calibration.As a result, the terminal device performs communications such as receiving a signal (PDSCH) transmitted from the second TRP 112 without calibration, and transmitting a composite automatic repeat request acknowledgement (HARQ-ACK) for that PDSCH (S304).

[0022] Here, the gNB101 requests the terminal device to provide auxiliary information, for example, to perform calibration between the first TRP111 and the second TRP112 (S305). For example, the gNB101 transmits a control signal (PDCCH) to the terminal device requesting the measurement results of the CSI-RS from the first TRP111 and the measurement results of the CSI-RS from the second TRP112. Then, the terminal device transmits the auxiliary information (UE assistance information) to the gNB101 (S306). According to the information on these measurement results, the phase of the channel estimation value and the rotation speed per time of that phase are identified, and the gNB101 can identify the frequency deviation when receiving each TRP based on this information. Then, the gNB101 identifies the frequency of each TRP based on the difference between the frequency when calibration is not performed on each TRP and the frequency used as the reference for reception in the terminal device, and during calibration, the frequencies between the TRPs are matched based on the identified frequency difference. The terminal device may also notify the gNB101 of information specifying the reception timing of signals from each TRP. In this case, the gNB101 adjusts the transmission timing of signals from each TRP during calibration according to the difference in the reception timing of signals from each TRP. Note that FIG. 2 shows an example in which the gNB101 transmits a control signal using the first TRP111 and the terminal device transmits auxiliary information to the second TRP112, but this is not limited to this. That is, the control signal may be transmitted via the second TRP112, or the auxiliary information may be transmitted to the first TRP111. In addition, both the first TRP 111 and the second TRP 112 may be used to transmit and receive control signals and auxiliary information.

[0023] Then, based on the auxiliary information, the gNB101 transmits the CSI-RS after calibration between the first TRP111 and the second TRP112 from both the first TRP111 and the second TRP112 (S307, S308). At this time, the first TRP111 and the second TRP112 transmit the CSI-RS in a resource identified by NZP-CSI-RS-ResourceSetID = 2 corresponding to the TCI state (TCI-state ID = 2) after calibration between the TRPs. In this case, the first TRP111 and the second TRP112 periodically transmit this CSI-RS, and the terminal device can measure the CSI-RS multiple times. Thereafter, the gNB101 transmits to the terminal device a DCI (including a PDCCH) in which the TCI state ID is set to 2, corresponding to the first TRP111 and the second TRP112 transmitting data in a calibrated state (S309). Note that the gNB101 may transmit DCI to the UE using only the first TRP111, or, for example, may transmit DCI using only the second TRP112, or using both the first TRP111 and the second TRP112. When the terminal device recognizes the value of the TCI state ID indicated in this DCI, it receives subsequent data using the reception setting determined based on the CSI-RS transmitted from the first TRP111 and the second TRP112 in a calibrated state. As a result, the terminal device performs communications such as receiving signals (PDSCH) transmitted from the first TRP 111 and the second TRP 112 in a calibrated state and transmitting a composite automatic repeat request (HARQ-ACK) for the PDSCH between the first TRP 111 and the second TRP 112. This prevents the terminal device from receiving the PDSCH transmitted from the second TRP 112 in S304, for example, using a reception setting based on the CSI-RS calibrated between the TRPs.It is also possible to prevent the terminal device from receiving the PDSCH transmitted from the first TRP 111 and the second TRP 112 in S310 and S311 using a reception setting based on CSI-RS for which calibration between TRPs has not been performed.

[0024] In addition, in FIG. 3, an example was described in which the TCI state ID is used to indicate whether to use a reception setting based on a CSI-RS in which inter-TRP calibration has been performed, or whether to use a reception setting based on a CSI-RS in which inter-TRP calibration has not been performed. However, this is just an example, and other information may be used. For example, as shown in FIG. 4, for one TCI state, information on a reference signal in the case where inter-TRP calibration is not performed and information on a reference signal in the case where inter-TRP calibration is performed are prepared. In FIG. 4, "referenceSignal" indicates information on a reference signal in the state in which inter-TRP calibration has not been performed, and "referenceSignal-cal" indicates information on a reference signal in the state in which inter-TRP calibration has been performed. For example, NZP-CSI-RS-ResourceSetID=0 and NZP-CSI-RS-ResourceSetID=2 are associated with TCI state ID=0. Furthermore, NZP-CSI-RS-ResourceSetID=1 and NZP-CSI-RS-ResourceSetID=2 are associated with TCI state ID=1. That is, in the examples of Figures 2 and 3, an example is shown in which a TCI state with TCI state ID=2 corresponding to NZP-CSI-RS-ResourceSetID=2 is prepared, but here, such a TCI state is not prepared.

[0025] Then, the gNB101 uses the resources for each reference signal to transmit the CSI-RS after inter-TRP calibration has been performed and the CSI-RS in a state where inter-TRP calibration has not been performed, and the terminal device measures each of these reference signals and prepares each reception setting. Then, the gNB101 includes information indicating whether inter-TRP calibration has been performed or not in the DCI together with information indicating the TCI state, and transmits this to the terminal device. An example of the processing flow in this case is shown in FIG. 5. Note that in FIG. 5, the same reference symbols are used for processes similar to those in FIG. 3. In the processing example of FIG. 5, the first TRP 111 and the second TRP 112 each transmit a CSI-RS in a state where inter-TRP calibration has not been performed (S301, S302) and a CSI-RS in a state where inter-TRP calibration has been performed (S307, S308), and the terminal device performs the measurement and determines the reception setting. In this processing example, gNB101 then transmits information (cal_flg) indicating whether or not signaling is performed in a state where calibration between TRPs has been performed, together with the TCI state ID, in a DCI (S501, S502).

[0026] Here, in the example of Figure 5, for TCI state ID = 1, cal_flg = 0 (no calibration) is associated with NZP-CSI-RS-ResourceSetID = 1, and cal_flg = 1 (with calibration) is associated with NZP-CSI-RS-ResourceSetID = 2. Then, in S501, gNB101 transmits TCI state ID = 1 and cal_flg = 0 in DCI, thereby indicating that subsequent signals will be transmitted without calibration between the second TRP 112 and the TRP. Further, in S502, the gNB101 transmits the DCI including TCI state ID = 1 and cal_flg = 1, thereby indicating that subsequent signals will be transmitted from the first TRP111 and the second TRP112 in a state after inter-TRP calibration. In this way, by using information (flag) other than the TCI state ID in combination with the TCI state ID, when the number of TCI states enabled in the terminal device is limited to a small number, it is possible to prevent a portion of the small number of TCI states from being used to transmit a signal corresponding to whether or not inter-TRP calibration is being performed. For example, when inter-TRP calibration is being performed, a DCI including cal_flg information may be transmitted, and in each of the states where calibration is not being performed, a DCI not including cal_flg information may be transmitted. In other words, whether or not cal_flg information is included may correspond to whether or not inter-TRP calibration is being performed. It is also possible to increase the number of TCI states (number of bits for specifying the TCI state in the DCI) that are valid in the terminal device without using the cal_flg information, and perform the processing shown in FIG. 3 .

[0027] Although the above example describes the case where two TRPs are used, the number of TRPs may be three or more. An example of the processing in this case is shown in FIG. 6. FIG. 6 shows the processing flow when a third TRP (not shown in FIG. 1) is used in addition to the first TRP 111 and the second TRP 112. Here, the third TRP is used alone or together with the second TRP 112. When the third TRP is used together with the second TRP 112, calibration is performed between these TRPs. At this time, for example, a CSI-RS in an uncalibrated state is transmitted from the third TRP using a resource identified by NZP-CSI-RS-ResourceSetID=3 (S601). Furthermore, the CSI-RS in a state in which calibration has been performed between the second TRP 112 and the third TRP is transmitted from the second TRP 112 and the third TRP using resources identified by NZP-CSI-RS-ResourceSetID=4 (S602, S603).

[0028] At this time, these NZP-CSI-RS-ResourceSetIDs may be associated with separate TCI states, or may be associated with one TCI state. For example, for TCI state ID = 1, in addition to the "referenceSignal" and "referenceSignal-cal" in FIG. 4, information such as "referenceSignal-cal2" may be added. Then, NZP-CSI-RS-ResourceSetID = 4 may be specified as the "referenceSignal-cal2" information. In this case, for example, by transmitting DCI including TCI state ID = 1 and cal_flg = 0, the gNB101 indicates that subsequent signals are transmitted from the second TRP112 without inter-TRP calibration. Further, gNB101 indicates that subsequent signals will be transmitted from the first TRP111 and the second TRP112 with inter-TRP calibration performed by transmitting DCI including TCI state ID = 1 and cal_flg = 1 (S502, S310, S311). Further, gNB101 indicates that subsequent signals will be transmitted from the first TRP111 and the second TRP112 with inter-TRP calibration performed by transmitting DCI including TCI state ID = 1 and cal_flg = 2 (S604, S605, S606). In addition, when each NZP-CSI-RS-ResourceSetID is associated with a separate TCI state, as shown in FIG. 3, for example, the TCI state ID associated with the resource to which the CSI-RS in the state in which calibration is performed between the second TRP 112 and the third TRP should be transmitted can be included in the DCI and transmitted in S604. In this case, for example, the TCI state ID when communication is performed without calibration in each TRP and the TCI state ID when calibration is performed between TRPs in any combination of TRPs are set to be different from each other.Then, gNB101 may select one TRP or a combination of two or more TRPs to use for communication and transmit a DCI with a TCI state ID corresponding to the selected TRP or combination of TRPs.

[0029] As in the above example, reference signal information for the case where calibration is performed between three or more TRPs can be defined. In this case, a separate TCI state or a combination of information such as TCI state and cal_flg is associated with any combination of TRPs. Each TRP transmits a calibrated CSI-RS and an uncalibrated CSI-RS using separate resources. The gNB 101 then transmits a DCI specifying a TCI state ID or a combination of TCI state ID and cal_flg to the terminal device according to the TRP used when transmitting data to the terminal device. In this way, when three or more TRPs are used, if any one or more of the three or more TRPs are used, the terminal device can perform reception processing corresponding to whether or not calibration between the TRPs has been performed.

[0030] In addition, the calibration between TRPs can be performed based on the frequency used in one TRP and the reception timing of the signal transmitted from that TRP in the terminal device. That is, the calibration between the first TRP 111 and the second TRP 112 can be performed by, for example, adjusting the frequency of the second TRP 112 to match the frequency used in the first TRP 111. In addition, the transmission timing of the signal from the second TRP 112 is adjusted based on the reception timing of the main wave of the signal transmitted from the first TRP 111 in the terminal device so that the main wave of the signal from the second TRP 112 is received by the terminal device at that timing. This is just an example, and the reference frequency and timing may be specified separately.

[0031] In addition, the terminal device can reuse, for example, the channel estimation results when inter-TRP calibration is not performed when inter-TRP calibration is performed. For example, when only transmission timing calibration is performed for a specific TRP, the frequency characteristics can be considered to be common to those when inter-TRP calibration is not performed. In this case, the delay spread can also be considered to be common between cases when inter-TRP calibration is performed and when inter-TRP calibration is not performed. In addition, for example, when only frequency calibration is performed for a specific TRP, the delay characteristics can be considered to be common to those when inter-TRP calibration is not performed. In this case, the Doppler spread can also be considered to be common between cases when inter-TRP calibration is performed and when inter-TRP calibration is not performed. Therefore, based on these characteristics that can be considered to be common, the terminal device can use the CSI-RS measurement results when inter-TRP calibration is not performed to perform signal reception processing when inter-TRP calibration is performed. For example, by using a channel estimation value based on CSI-RS when inter-TRP calibration is not performed, it is possible to improve the accuracy of channel estimation when inter-TRP calibration is performed. In some cases, the transmission of CSI-RS may be omitted when calibration is performed.

[0032] As information that notifies a terminal device that such predetermined characteristics are common, there is information indicating the type of QCL (qcl-Type). qcl-Type is associated with the TCI state as shown in FIG. 2. Type A to type D shown in FIG. 7 are already set in the standard as qcl-Type. In this embodiment, as shown in FIG. 7, type E, which relates to the case where only transmission timing calibration is performed for a predetermined TRP, and type F, which relates to the case where only frequency calibration is performed for a predetermined TRP, are newly defined. Note that "type E" and "type F" are merely for explanation purposes, and any name of information indicating that a value indicating the characteristics of a channel obtained from a reference signal such as CSI-RS in a state where calibration is not performed can be used in a state where calibration is performed, can be used. By notifying the terminal device of this information, the gNB 101 can indicate the commonalities between the channel characteristics when inter-TRP calibration is not performed and the channel characteristics when inter-TRP calibration is performed. Based on this information, the terminal device can determine whether to use the measurement results of the reference signal when inter-TRP calibration is not performed and how to use the measurement results. For example, the terminal device can use the measurement results of the reference signal when calibration is not performed in the reception processing of the signal when inter-TRP calibration is performed. Furthermore, the terminal device can, for example, use the measurement results of the reference signal when calibration is not performed to improve the accuracy of channel estimation when calibration is performed and determine the reception settings. Note that, based on this information, the terminal device may use the measurement results of the reference signal when calibration is performed when calibration is not performed.

[0033] 8 shows an example of information notified from gNB101 to a terminal device. The example of FIG. 8 shows an example in which two QCL-Info are included in the information (TCI-state) about the TCI state when calibration between TRPs is performed. Each of these two QCL-Info contains information about the reference signal transmitted without calibration between TRPs for one TRP.

[0034] For example, the resource from which the first TRP 111 transmits a reference signal in a state where calibration between TRPs is not performed is indicated by NZP-CSI-RS-ResourceSetID = 0. Also, the resource from which the second TRP 112 transmits a reference signal in a state where calibration between TRPs is not performed is indicated by NZP-CSI-RS-ResourceSetID = 1. At this time, when calibration is performed between the first TRP 111 and the second TRP 112, the TCI state includes QCL-Info1 for the first TRP 111 and QCL-Info2 for the second TRP 112.

[0035] For example, when the transmission timing of the second TRP 112 is adjusted based on the timing at which the signal transmitted from the first TRP 111 reaches the terminal device, the QCL-Info2 for the second TRP 112 is specified as NZP-CSI-RS-ResourceSetID = 1 and qcl-Type = type E. That is, when transmitting a signal when calibration between TRPs is performed, in the second TRP 112, information about CSI-RS in a state where calibration between TRPs is not performed (NZP-CSI-RS-ResourceSetID = 1) is specified, and the characteristics of the channel that can be used in common with the channel estimation value obtained by measuring the CSI-RS are indicated by qcl-Type. On the other hand, since the first TRP 111 does not perform any special adjustment, the QCL-Info1 for the first TRP 111 is specified as NZP-CSI-RS-ResourceSetID = 0 and qcl-Type = type A. That is, for signals transmitted from the first TRP 111, it is indicated that the same channel characteristics can be used as when transmitting CSI-RS without inter-TRP calibration. Similarly, when the frequency of the second TRP 112 is adjusted based on the frequency of the signal transmitted from the first TRP 111, in QCL-Info2, NZP-CSI-RS-ResourceSetID = 1 and qcl-Type = typeF are specified, and in QCL-Info1, NZP-CSI-RS-ResourceSetID = 0 and qcl-Type = typeA are specified. Note that, for example, when calibration is performed between three or more TRPs and communication is performed, one TCI-state can include QCL-Info according to the number of TRPs. That is, for each TRP, information regarding the reference signal when inter-TRP calibration has not been performed (NZP-CSI-RS-ResourceSetID) and QCL-Info storing qcl-Type can be prepared.

[0036] An example of the processing flow in this case is shown in Figure 9. Note that processes similar to those in Figure 3 are assigned common reference symbols with Figure 3 and will not be described again. In this processing example, the terminal device measures reference signals transmitted by the first TRP 111 and the second TRP 112 when calibration is not performed (S301, S302). Then, when a signal is subsequently transmitted in a state where calibration is performed, a DCI with TCI state ID set to "2" is transmitted from the gNB 101 to the terminal device. Note that the TCI-state corresponding to TCI state ID = 2 includes the above-mentioned QCL-Info1 and QCL-Info2, and this information is assumed to have been notified to the UE in advance. Based on this TCI-state information, the terminal device uses the results of measuring the CSI-RS in S301 and S302 to communicate with the first TRP 111 and the second TRP 112 in a state where inter-TRP calibration has been performed (S901, S902). In this way, by newly defining the qcl-Type information, it is possible to use the results of channel estimation using a reference signal transmitted in a state where calibration has not been performed between multiple TRPs for processing such as receiving a signal transmitted in a state where calibration has been performed. Note that the terminal device can use the qcl-Type information in reception processing, but it is not necessarily required to use it. In other words, it is sufficient for the terminal device to have a reception processing function configured to be able to use the information.

[0037] In the above example, a qcl-Type was described that enables the measurement results of the CSI-RS when calibration between TRPs is not performed to be used in communication when calibration between TRPs is performed. Separately, a qcl-Type may be defined that enables timing synchronization, timing correction, frequency synchronization, frequency correction, etc. to be performed using the SSB. For example, the qcl-Type between the SSB and the CSI-RS typically transmitted from one TRP is type C. As shown in FIG. 10, the SSB and the CSI-RS are associated by including the TCI-state identifier (TCI-StateId) of the SSB in information about the CSI-RS resource (NZP-CSI-RS-ResourceSet associated with the NZP-CSI-RS-ResourceSet). Then, for example, typeG or typeH shown in FIG. 7 is specified as qcl-Type in QCL-Info of CSI-RS. For example, the channel when CSI-RS is transmitted after transmission timing calibration is performed does not maintain delay characteristics between the channel when SSB is transmitted, but frequency characteristics are maintained. For this reason, typeG is specified as qcl-Type in this case. Also, for example, the channel when CSI-RS is transmitted after frequency calibration is performed does not maintain frequency characteristics between the channel when SSB is transmitted, but delay characteristics are maintained. For this reason, typeH is specified as qcl-Type in this case. Then, the terminal device can perform timing correction and frequency correction by, for example, combining channel estimation values ​​by SSB and channel estimation values ​​by CSI-RS. For example, in order to establish and correct frequency synchronization for a specific TRP, a terminal device can use an SSB and a CSI-RS with a qcl-Type of type C between that SSB (e.g., a CSI-RS in a state where no calibration has been performed between TRPs), as well as a CSI-RS that has undergone timing-related calibration between TRPs.In addition, in order to establish synchronization and correct timing for a specific TRP, the terminal device can use the CSI-RS in which the qcl-Type between the SSB and the SSB is type C, as well as the CSI-RS in which frequency-related calibration between TRPs has been performed. In this way, in the synchronization and correction of frequency and timing in the terminal device, in addition to the SSB and the CSI-RS before calibration, the CSI-RS after calibration can be used. By indicating to the terminal device that it is possible to improve the synchronization accuracy between the terminal device and the gNB101, for example.

[0038] 11 shows an example of a procedure for frequency / timing synchronization / adjustment using SSB and CSI-RS. In this processing example, when the first TRP 111 and the second TRP 112 perform inter-TRP calibration, the second TRP 112 operates to adjust the frequency and timing of the signal transmitted by the first TRP 111. That is, even when inter-TRP calibration is performed, the first TRP 111 does not particularly change the frequency or timing. The first TRP 111 and the second TRP 112 transmit SSB without performing inter-TRP calibration (S1101, S1102). In addition, the first TRP 111 and the second TRP 112 transmit CSI-RS without performing inter-TRP calibration (S1103, S1104). The terminal device receives the SSB and establishes synchronization of the frequency and reception timing for each of the first TRP 111 and the second TRP 112 (S1106, S1107). The terminal device can also perform channel estimation based on the SSB. Here, the SSB and CSI-RS in a state where calibration between TRPs has not been performed have a common reference frequency and transmission timing, and the qcl-Type of this CSI-RS is type C in relation to the SSB. Therefore, the terminal device can further adjust the frequency and reception timing between the first TRP 111 and the second TRP 112 based on the assumption that the channel estimated by the CSI-RS has a common Doppler shift and average delay with the channel estimated using the SSB (S1106, S1107).

[0039] In addition, for the CSI-RS from the first TRP 111, even after the calibration between TRPs is performed, the channel characteristics can be treated as the same as the CSI-RS in an uncalibrated state, except that the transmitted resources are different. For this reason, although not shown in FIG. 11, the terminal device can adjust the frequency and reception timing based on the CSI-RS transmitted from the first TRP 111 after the calibration, in the same way as the CSI-RS in an uncalibrated state. On the other hand, the frequency and timing of the CSI-RS from the second TRP 112 can be changed by performing the calibration between TRPs. For this reason, if the terminal device adjusts the frequency and timing using the calibrated CSI-RS transmitted from the second TRP 112 in the same way as the CSI-RS in an uncalibrated state, it may end up adjusting to a frequency and timing different from the frequency and timing between the second TRP 112. Therefore, when adjusting the frequency and timing for the second TRP 112, the terminal device treats the CSI-RS after inter-TRP calibration has been performed differently from the CSI-RS in an uncalibrated state.

[0040] For example, if the transmission timing is adjusted in the second TRP 112 by calibration between TRPs and the frequency is not adjusted, the terminal device treats the qcl-Type of the adjusted CSI-RS as type G in relation to the SSB. In this case, the gNB 101 may, for example, notify the terminal device in advance that the qcl-Type in relation to the NZP-CSI-RS-ResourceSetID = 2 and the SSB index of the SSB transmitted from the second TRP 112 is type G. Also, for example, if the frequency is adjusted in the second TRP 112 by calibration between TRPs and the transmission timing is not adjusted, the terminal device treats the qcl-Type of the adjusted CSI-RS as type H in relation to the SSB. In this case, the gNB101 may, for example, notify the terminal device in advance that the qcl-Type in the relationship between the NZP-CSI-RS-ResourceSetID = 2 and the SSB index of the SSB transmitted from the second TRP112 is typeH. In this way, by defining a new qcl-Type, it is possible to specify the relationship between the SSB and the CSI-RS after calibration between the TRPs has been performed. Then, by notifying the terminal device of this qcl-Type information from the gNB101, the terminal device can recognize that it can use the CSI-RS after calibration between the TRPs has been performed in synchronization and adjustment of the frequency and timing of each TRP.

[0041] In addition to the relationship between the SSB and the CSI-RS after calibration, the relationship between the CSI-RS in an uncalibrated state and the CSI-RS in a calibrated state can also be used for synchronization and adjustment of the frequency and timing related to the second TRP 112. That is, the relationship between the CSI-RS in an uncalibrated state and the CSI-RS in a calibrated state can be specified as described above, such that qcl-Type is type E or type F. Based on this information, the terminal device can improve the accuracy of synchronization and adjustment of the frequency and timing related to the second TRP 112.

[0042] As described above, calibration between TRPs is performed based on UE assistance information (S306 in FIG. 3) from the terminal device. Here, the UE assistance information is assumed to include, for example, information indicating time changes in the amplitude and phase of the channel estimated based on the CSI-RS for each of the multiple TRPs. According to this, when the terminal device uses a common frequency to receive the CSI-RS corresponding to each TRP, the gNB101 or each TRP can determine the error between the common frequency and the frequency used in each TRP from the phase rotation amount of the channel estimation value obtained based on the CSI-RS. Furthermore, the gNB101 or each TRP can determine the frequency difference between the TRPs to be calibrated based on the frequency error. An example of such a processing flow is shown in FIG. 12.

[0043] In the process of FIG. 12, the gNB 101 notifies the terminal device, for example, via the first TRP 111, of setting information for reporting aperiodic measurement results of channel state information (CSI) (S1201). This setting information may include, for example, a list (CSI-AperiodicTriggerStateList) of information (CSI-AperiodicTriggerState) regarding measurement reports for each of a plurality of TRPs. Figure 13 schematically shows the information notified to the terminal device. The CSI-AperiodicTriggerStateList includes, for example, multiple (two in the example of FIG. 13) CSI-AperiodicTriggerState. Then, CSI-AperiodicTriggerState includes an identifier for reporting (CSI-ReportConfigId), information on the resource to which CSI-RS is transmitted (NZP-CSI-RS-ResourceSetID), and information indicating the TCI state to be used by the terminal device (TCI-StateId). This setting information is transmitted individually to the terminal device using, for example, a radio resource control (RRC) message (e.g., an RRC Reconfiguration message). For example, when the number of CSI-AperiodicTriggerState included in this setting information exceeds a predetermined number, the gNB101 selects a portion of the many CSI-AperiodicTriggerStates and notifies the terminal device that the selected setting information should be enabled (S1202). The predetermined number is determined according to the number of bits used to specify which setting is used for reporting in the DCI. For example, if a 3-bit field is provided in the DCI to specify which setting is used and the CSI-AperiodicTriggerStateList includes nine or more CSI-AperiodicTriggerStates, up to eight CSI-AperiodicTriggerStates can be selected and enabled from the nine or more CSI-AperiodicTriggerStates.Note that in cases where all settings in the CSI-AperiodicTriggerStateList should be valid, such as when the number of CSI-AperiodicTriggerStates is equal to or less than a predetermined number, the process of S1202 can be omitted.

[0044] The terminal device measures the CSI-RS, for example, in the resource indicated by the NZP-CSI-RS-ResourceSetID included in the enabled reporting configuration, and using the reception setting of the TCI state included in the reporting configuration. For example, the terminal device measures the CSI-RS transmitted from the second TRP 112 in the resource corresponding to NZP-CSI-RS-ResourceSetID = 1 using the reception setting of the TCI state of TCI-stateId = 1 (S1203). Also, the terminal device measures the CSI-RS transmitted from the first TRP 111 in the resource corresponding to NZP-CSI-RS-ResourceSetID = 0 using the reception setting of the TCI state of TCI-stateId = 0 (S1206). Note that the CSI-RS is repeatedly transmitted from each TRP, and the terminal device can repeatedly measure the repeatedly transmitted CSI-RS. Then, the gNB101 transmits an instruction to the terminal device, for example, via the first TRP111, to perform a CSI measurement report based on CSI-AperiodicTriggerState:1 (S1204). This instruction is transmitted, for example, using DCI (including PDCCH). Furthermore, the fact that a CSI measurement report based on CSI-AperiodicTriggerState:1 should be performed can be indicated by specifying an associated CSI-ReportConfigId. In accordance with this instruction, the terminal device transmits UE assistance information including the measurement results of the CSI-RS transmitted from the second TRP112 to the gNB101 (S1205). 12 shows an example in which the UE assistance information is transmitted to the second TRP 112, but this information may be transmitted to the first TRP 111. For example, information about the first TRP 111 may be transmitted to the first TRP 111, and information about the second TRP 112 may be transmitted to the second TRP 112, or, for example, the DCI of S1204 may specify which TRP the information should be transmitted to. Also, for example, a primary TRP may be set in advance, and control information may always be transmitted to that primary TRP.In addition, the base station device may request the terminal device to report not only the second TRP 112 but also the measurement results of CSI-RS related to the first TRP 111 (S1207). Then, based on this request, the terminal device transmits the measurement report results related to CSI-RS transmitted from the first TRP 111 to the gNB 101 (via at least one of the first TRP 111 and the second TRP 112) (S1208).

[0045] According to this processing, based on the measurement results of the CSI-RS transmitted from multiple TRPs in the terminal device, the gNB101 can identify the error between the frequency used to receive signals in the terminal device and the frequency used to transmit signals in each TRP. As a result, the gNB101 can identify the frequency difference between the multiple TRPs to be calibrated, and when calibration between the TRPs is required, it can perform control to adjust the frequency of at least one of the TRPs so that the frequency difference is eliminated. For example, if the frequency used to receive signals from each TRP is not common in the terminal device, the gNB101 can be notified of the frequency information used to receive signals from each TRP. This makes it possible to identify the frequency at which the multiple TRPs transmit signals, even if the terminal device performs reception processing using different frequencies for each TRP.

[0046] On the other hand, in order to calibrate the frequency between TRPs, it is sufficient to be able to identify the frequency difference between the TRPs, and it is not necessary to identify the CSI-RS measurement results for each TRP. For this reason, for example, in this embodiment, only information that enables the frequency difference to be identified is transmitted. For example, a terminal device measures the CSI-RS from each TRP using a common reception setting (reception frequency), and the differential value of the channel estimation value (e.g., phase on the I (in-phase) -Q (quadrature) plane) indicated by the measurement result is reported to the gNB 101. Also, for example, instead of the differential value of the phase of the channel estimation value, the differential value of the rotation speed of the phase of the channel estimation value may be reported to the gNB 101. In other words, the reference frequency used for reception in the terminal device and the reference frequency used for transmission in each of the first TRP 111 and the second TRP 112 rarely completely coincide. It is assumed that the channel estimate value between the first TRP111 and the second TRP112 rotates due to the frequency difference between the first TRP111 and the second TRP112, and that the channel estimate value between the first TRP111 and the second TRP112 also rotates due to the frequency difference between the second TRP112. If the difference in the rotation speed of the phase of the channel estimate value between each of these TRPs can be identified, the frequency difference between the first TRP111 and the second TRP112 can be sufficiently reduced by adjusting, for example, the frequency of the second TRP112 or the phase of the signal by the frequency difference corresponding to the rotation speed difference. Then, the terminal device adjusts the frequency used for reception according to, for example, the phase rotation speed of the channel estimate value between the first TRP111 and the second TRP112, or performs demodulation processing taking into account the phase rotation, thereby enabling high-accuracy reception and demodulation of signals in a calibrated state. This reduces the amount of information, or makes it possible to notify the gNB101 of information that can identify the frequency difference in more detail.

[0047] In this embodiment, as shown in FIG. 14, information on the resource from which CSI-RS from each TRP is transmitted (NZP-CSI-RS-ResourceSetID) and the TCI-StateId corresponding to the reception setting to be used are associated with one CSI-AperiodicTriggerState. Then, for this CSI-AperiodicTriggerState, for example, an identifier (CSI-ReportConfigId) different from the identifier of the setting information as shown in FIG. 13 is assigned. 14, the resource from which the CSI-RS from the first TRP 111 is transmitted (NZP-CSI-RS-ResourceSetID = 0), the resource from which the CSI-RS from the second TRP 112 is transmitted (NZP-CSI-RS-ResourceSetID = 1), and, for example, the CSI-AperiodicTriggerState of CSI-ReportConfigId = 2 including the TCI state (TCI-StateId = 0) associated with the reception processing of the signal from the first TRP 111 are shown. Then, the gNB 101 can request information on the difference value from the terminal device by transmitting DCI specifying the CSI-ReportConfigId.

[0048] 15 shows the flow of processing when UE assistance information is provided from a terminal device to a gNB101 when such configuration information is used. In this processing, the gNB101 provides configuration information including information such as that shown in FIG. 14 to the terminal device, for example, via the first TRP111 (S1501). Then, the gNB101 notifies the terminal device of the information on the configuration information to be enabled as necessary (S1502). Then, the terminal device measures the CSI-RS transmitted from the first TRP111 and the second TRP112 (S1503, S1504). Then, the gNB101 transmits DCI specifying CSI-ReportConfigId = 2 and requests the terminal device for information on the phase difference value between the channel between the first TRP111 and the channel between the second TRP112 (S1505). Then, in response to the request, the terminal device provides the gNB101 with information on the difference value (for example, for the second TRP 112) (S1506). In this way, by reporting the difference value, it is no longer necessary to report separate information for each TRP, so the amount of information to be reported can be reduced. In addition, by using the reduced amount of information to increase the number of bits of the reported information, the granularity of the reported information can be refined, and the accuracy of control can be improved. For example, when phase difference information is represented using 4 bits, the phase difference can only be expressed in units of 360 / 16 = 22.5 °. However, by using 6 bits, for example, it becomes possible to express the phase difference in units of approximately 6 °, making it possible to accurately determine the rate of increase or decrease of the phase difference and to accurately determine the frequency difference. Note that the setting for reporting the phase difference can coexist with the setting for CSI-RS measurement reporting for each TRP. For example, in the processing of Figure 15, by transmitting a DCI with CSI-ReportConfigId = 0 or 1 specified as in Figure 12, it is possible to transmit the measurement results of the CSI-RS transmitted from each TRP, rather than the differential value, from the terminal device to gNB101.

[0049] 15 shows an example of a process for identifying the frequency difference between TRPs. Alternatively or in addition to this, a process may be performed in which the terminal device reports the difference in the reception timing of the CSI-RS. For example, in multiple TRPs to be calibrated, the resources from which the CSI-RS is transmitted from each TRP are set so that the CSI-RS is transmitted at the same timing. For example, the resources to be used are set so that the resources from which the CSI-RS from the second TRP 112 is transmitted are the same as the resources from which the CSI-RS from the first TRP 111 is transmitted. Furthermore, the gNB 101 transmits setting information such as that shown in FIG. 14 to the terminal device. Then, the terminal device measures the difference in reception timing and reports the time difference to the base station device. For example, as shown in FIG. 16, CSI-RS is transmitted simultaneously from the first TRP 111 and the second TRP 112 (S1601, S1602), and the terminal device measures these CSI-RS. Then, in response to receiving an instruction from the gNB 101 (S1505), the terminal device reports the measurement results of the reception time difference of these CSI-RS to the gNB 101 (S1603). This allows the gNB 101 to identify the time difference until signals transmitted simultaneously from each TRP reach the terminal device. For example, if the CSI-RS from the first TRP 111 is received earlier than the CSI-RS from the second TRP 112 by ΔT, and calibration is performed between the first TRP 111 and the second TRP 112, the transmission timing of the signal from the second TRP 112 is advanced by ΔT. This allows the signals transmitted from the first TRP 111 and the second TRP 112 to be received simultaneously by the terminal device. Note that the terminal device can also measure and report the frequency difference along with measuring and reporting this time difference. That is, in the process of FIG. 15, by making the resource for transmitting the CSI-RS of S1503 the resource with the same timing as the resource for transmitting the CSI-RS of S1504, the terminal device can measure the time difference and frequency difference at the same time.

[0050] FIG. 17 shows an example of the hardware configuration of a base station device (gNB101) and terminal devices (terminal device 121, terminal device 122) according to this embodiment. In one example, the base station device and terminal device are configured to include a processor 1701, a ROM 1702, a RAM 1703, a storage device 1704, and a communication circuit 1705. The processor 1701 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 1702 and storage device 1704. The ROM 1702 is a read-only memory that stores information such as programs and various parameters related to the processing performed by the base station device and terminal device. The RAM 1703 functions as a workspace when the processor 1701 executes a program and is also a random access memory that stores temporary information. The storage device 1704 is configured, for example, by a removable external storage device. The communication circuit 1705 is configured, for example, by a circuit for wireless communication of 5G or a successor standard. While FIG. 17 illustrates one communication circuit 1705, the base station apparatus and the terminal apparatus may have multiple communication circuits. For example, the base station apparatus and the terminal apparatus may have wireless communication circuits for 5G and a successor standard, respectively, and a common antenna for these circuits. The base station apparatus and the terminal apparatus may also have separate antennas suitable for each standard. The base station apparatus may also have a wired communication circuit used when communicating with other base station apparatuses or core network nodes. The terminal apparatus may also have a communication circuit conforming to a wireless communication standard other than the cellular communication standard, such as a wireless local area network (LAN) or Bluetooth (registered trademark). The base station apparatus and the terminal apparatus may have separate communication circuits 1705 for each of multiple available frequency bands, or may have a common communication circuit 1705 for at least some of these frequency bands.

[0051] FIG. 18 shows an example of the functional configuration of a base station device. The base station device includes, for example, a setting unit 1801, a report receiving unit 1802, a calibration control unit 1803, and a communication control unit 1804. Note that FIG. 18 only shows functions particularly related to this embodiment, and various other functions that the base station device may have are omitted from the illustration. For example, the base station device naturally has other functions that base station devices compliant with 5G and subsequent standards generally have. Furthermore, the functional blocks in FIG. 18 are shown schematically, and the respective functional blocks may be realized by being integrated together or may be further subdivided. Furthermore, each function in FIG. 18 may be realized, for example, by the processor 1701 executing a program stored in the ROM 1702 or the storage device 1704, or may be realized, for example, by a processor within the communication circuit 1705 executing predetermined software. Note that the details of the processing performed by each functional unit will not be described here, and only their general functions will be outlined.

[0052] The setting unit 1801, for example, prepares a resource setting for transmitting a reference signal (e.g., CSI-RS) when calibration between TRPs is performed and a resource setting for transmitting a reference signal when calibration is not performed separately, and notifies the terminal device of setting information including information that enables the setting to be distinguished, such as a TCI state ID. The setting unit 1801 may generate the setting information described above using, for example, FIG. 2, FIG. 4, etc., and notify the terminal device of the setting information. In addition, the setting unit 1801 may transmit to the terminal device setting information such as that shown in FIG. 8, which includes information indicating whether or not a channel estimation result based on another reference signal, such as qcl-Type as shown in FIG. 7, can be used. In addition, the setting unit 1801 may generate setting information such as that shown in FIG. 13 or FIG. 14 when causing the terminal device to perform measurements to identify the frequency difference or timing difference for performing calibration, and transmit the setting information to the terminal device. The report receiving unit 1802 receives UE assistance information from, for example, a terminal device. Note that, for example, the report receiving unit 1802 uses the setting information notified to the terminal device by the setting unit 1801 to determine whether to report the frequency difference or time difference information as described using FIG. 15 or FIG. 16, or the measurement results of the CSI-RS from each TRP. Then, the report receiving unit 1802 transmits an instruction to the terminal device that sets an identifier of the report setting corresponding to the decision, thereby receiving a report according to the decision. For example, when calibration between TRPs is performed, the calibration control unit 1803 adjusts the frequency and transmission timing of each TRP, and performs control so that the frequencies and reception timing (for example, of the main wave) of signals from multiple TRPs are approximately the same in the terminal device. The communication control unit 1804 transmits DCI including information such as TCI state ID and cal_flg to the terminal device based on the information set in the setting unit 1801, depending on whether calibration between TRPs is performed when transmitting a signal, and controls communication.

[0053] FIG. 19 shows an example of the functional configuration of a terminal device. The terminal device includes, for example, a setting receiving unit 1901, a report transmitting unit 1902, and a communication control unit 1903. Note that FIG. 19 only shows functions particularly related to this embodiment, and various other functions that the terminal device may have are omitted from the illustration. For example, the terminal device naturally has other functions that terminal devices compliant with 5G or subsequent standards generally have. The functional blocks in FIG. 19 are shown only schematically, and the respective functional blocks may be integrated or further subdivided. Each function in FIG. 19 may be realized, for example, by the processor 1701 executing a program stored in the ROM 1702 or the storage device 1704, or by a processor within the communication circuit 1705 executing predetermined software. The details of the processes performed by each functional unit will not be described here, and only their general functions will be outlined.

[0054] The setting receiver 1901 receives setting information generated by the setting unit 1801 of the base station device. The report transmitter 1902 measures the CSI-RS transmitted from each TRP according to the setting information, and reports the channel estimation value or information on the phase difference and reception timing difference to the base station device in response to instructions from the base station device. The communication controller 1903 controls communication. For example, the communication controller 1903 establishes and adjusts frequency synchronization and timing synchronization with each TRP by measuring reference signals. Furthermore, the communication controller 1903 establishes and adjusts frequency synchronization and timing synchronization when communicating simultaneously with multiple TRPs by measuring reference signals transmitted by the multiple TRPs (with inter-TRP calibration performed). At this time, the communication controller 1903 may recognize that the measurement results of reference signals transmitted using different resources can be mutually utilized based on the qcl-Type information transmitted from the base station device. Then, the communication control unit 1903 may establish frequency and timing synchronization and perform reception processing based on the qcl-Type information. Furthermore, the communication control unit 1903 configures reception settings individually for each reference signal based on measurement results of the reference signals transmitted using different resources. That is, a reception setting is configured for each reference signal resource. Then, when the communication control unit 1903 receives DCI transmitted from the base station device that includes information identifying the reference signal resource, it receives the signal from the base station device using the reception setting corresponding to the resource.

[0055] As described above, the terminal device in this embodiment prepares reception settings for each of the states in which inter-TRP calibration is performed and the state in which inter-TRP calibration is not performed, using different reference signal settings. Then, the base station device transmits DCI containing identification information that specifies the corresponding reference signal setting depending on whether calibration is performed when communication is performed. The terminal device can perform reception processing appropriate for each of the states in which calibration is performed and the state in which calibration is not performed by using the reception setting corresponding to the identification information to perform reception processing of signals from the base station device. In addition, the base station device can notify the terminal device of newly defined qcl-Type information so that, for example, channel characteristic values ​​obtained from measurement results of reference signals in a state in which calibration is not performed can be used in reception in a state in which calibration is performed. By this notification, the terminal device can effectively utilize the channel characteristics and efficiently receive signals in a state in which calibration is performed. In addition, by defining new qcl-Type information, it is possible to also use CSI-RS information after inter-TRP calibration is performed when establishing frequency and timing synchronization in each TRP. Furthermore, by transmitting the phase difference and reception timing difference of the channel estimation values ​​between TRPs as UE assistance information, it is possible to reduce the amount of information or provide more detailed information. As such, according to this embodiment, it is possible to efficiently operate a system in which a base station device simultaneously uses multiple TRPs to transmit signals to a terminal device. Therefore, it is possible to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0056] 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.

[0057] This application claims priority based on Japanese Patent Application No. 2024-022352, filed February 16, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A base station device that communicates with a terminal device using multiple TRPs including a first transmission / reception point (TRP) and a second TRP, the base station device having a notification means for notifying the terminal device of information indicating characteristics that can be used to receive signals when the frequency or transmission timing of the first TRP is adjusted by the calibration between the first TRP and the second TRP, among channel characteristics estimated based on the channel state information-reference signal (CSI-RS) transmitted from the first TRP when no calibration is performed between the first TRP and the second TRP.

2. The base station device of claim 1, wherein when the frequency calibration is performed between the first TRP and the second TRP, the information indicates that, among the channel characteristics, Doppler spread, average delay, and delay spread can be used to receive signals when the calibration is performed.

3. A base station device as described in claim 1 or 2, wherein when the calibration regarding transmission timing is performed between the first TRP and the second TRP, the information indicates that, among the characteristics of the channel, Doppler shift, Doppler spread, and delay spread can be used to receive signals when the calibration is performed.

4. The base station device according to any one of claims 1 to 3, wherein the information indicates a type of Quasi Co-Location (QCL).

5. A terminal device comprising: a receiving means for receiving, from a base station device that communicates with the terminal device using multiple TRPs including a first transmission / reception point (TRP) and a second TRP, information indicating channel characteristics that can be used to receive a signal when the frequency or transmission timing of the first TRP is adjusted by the calibration between the first TRP and the second TRP, among channel characteristics estimated based on the channel state information-reference signal (CSI-RS) transmitted from the first TRP when calibration is not performed between the first TRP and the second TRP; and an execution means configured to perform reception processing of a signal in a state in which the calibration is performed between the first TRP and the second TRP, using the information and the result of estimating the channel characteristics based on the CSI-RS transmitted from the first TRP when the calibration is not performed.

6. A terminal device as described in claim 5, wherein when the frequency calibration is performed between the first TRP and the second TRP, the information indicates that, among the channel characteristics, Doppler spread, average delay, and delay spread can be used to receive signals when the calibration is performed.

7. A terminal device as described in claim 5 or 6, wherein when the calibration regarding transmission timing is performed between the first TRP and the second TRP, the information indicates that, among the characteristics of the channel, Doppler shift, Doppler spread, and delay spread can be used to receive the signal when the calibration is performed.

8. The terminal device according to any one of claims 5 to 7, wherein the information is information indicating a type of Quasi Co-Location (QCL).

9. A communication method executed by a base station device that communicates with a terminal device using multiple TRPs including a first transmission / reception point (TRP) and a second TRP, comprising notifying the terminal device of information indicating characteristics that can be used to receive a signal when the frequency or transmission timing of the first TRP is adjusted by the calibration between the first TRP and the second TRP, among channel characteristics estimated based on the channel state information-reference signal (CSI-RS) transmitted from the first TRP when no calibration is performed between the first TRP and the second TRP.

10. A communication method executed by a terminal device, comprising receiving, from a base station device that communicates with the terminal device using multiple TRPs including a first transmission / reception point (TRP) and a second TRP, information indicating characteristics that can be used to receive a signal when the frequency or transmission timing of the first TRP is adjusted by the calibration between the first TRP and the second TRP, among channel characteristics estimated based on a channel state information-reference signal (CSI-RS) transmitted from the first TRP when no calibration is performed between the first TRP and the second TRP; wherein the terminal device is configured to use the information and the result of estimating the channel characteristics based on the CSI-RS transmitted from the first TRP when the calibration is not performed to perform reception processing of a signal in a state where the calibration is performed between the first TRP and the second TRP.

11. A program for causing a computer to function as each of the means possessed by the base station device according to any one of claims 1 to 4.

12. A program for causing a computer to function as each of the means possessed by the terminal device according to any one of claims 5 to 8.

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