Terminal device, base station device, control method, and program suitable for beam selection in wireless communication using artificial intelligence (AI) / machine learning (ML)

Abstract

This terminal device measures, at a plurality of timings, a reference signal transmitted from a base station device using a prescribed beam, acquires a plurality of measurement results pertaining to wireless quality of the prescribed beam and including a first measurement result for a first timing and a second measurement result for a second timing, and transmits, to the base station device, a report message containing at least the differential value between the value of the second measurement result and the report value of the first measurement result.

Description

Terminal device, base station device, control method, and program suitable for beam selection in wireless communication using artificial intelligence (AI) / machine learning (ML)

[0001] The present invention relates to a technology for reporting wireless quality measurement results in beam selection for wireless communication using artificial intelligence (AI) / machine learning (ML).

[0002] In the standardization work of the Third Generation Partnership Project (3GPP (registered trademark)), the use of artificial intelligence (AI) / machine learning (ML) is being considered for a communication device capable of forming multiple beams to perform wireless communication, in order to determine which of the multiple beams to use to communicate with a partner device. Non-Patent Document 1 describes an AI / ML model in which a terminal device measures reference signal received power (RSRP) for some beams included in multiple beams with narrow beam widths that can be formed in a network (base station device), and selects a beam to use for communication from all of the multiple beams based on the RSRP.

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

[0004] The beam selection method in the AI / ML model requires feedback of wireless quality measurement results, which differs from conventional beam selection methods.

[0005] The present invention provides a technique for reporting wireless quality from a terminal device to a base station device that is suitable for a beam selection method using an AI / ML model for the beam used by the base station device.

[0006] A terminal device according to one aspect of the present invention has a measurement means for measuring a reference signal transmitted from a base station device using a predetermined beam at multiple timings and obtaining multiple measurement results of radio quality for the predetermined beam, including a first measurement result for a first timing and a second measurement result for a second timing, and a transmission means for transmitting a report message to the base station device, including at least a difference value between the value of the second measurement result and the reported value of the first measurement result.

[0007] A base station device according to one aspect of the present invention is a base station device that repeatedly transmits a reference signal using a predetermined beam, and has: an acquisition means that acquires from a terminal device multiple measurement results of radio quality based on measurements of the reference signal at multiple timings, the first measurement result and a difference value between the value of the second measurement result and the reported value of the first measurement result via a report message for reporting the multiple measurement results, the measurement results including a first measurement result for a first timing and a second measurement result for a second timing; a restoration means that restores the second measurement result from the first measurement result and the difference value; and a control means that controls the beam to be used for communication with the terminal device based on the first measurement result and the second measurement result.

[0008] According to the present invention, it becomes possible for a terminal device to report to a base station device wireless quality suitable for a selection method based on an AI / ML model for beams used by the base station device.

[0009] 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.

[0010] The accompanying drawings are incorporated into 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. 1A is a diagram illustrating an example of the configuration of a wireless communication system. FIG. 1B is a diagram illustrating an example of the configuration of a wireless communication system. FIG. 2A is a diagram illustrating an example of machine learning for beam determination. FIG. 2B is a diagram illustrating an example of machine learning for beam determination. FIG. 3 is a diagram illustrating an example of information reported as a conventional measurement result. FIG. 4 is a diagram illustrating an example of information reported as a measurement result according to an embodiment. FIG. 5 is a diagram illustrating an example of information reported as a measurement result according to an embodiment. FIG. 6A is a diagram illustrating an example of the contents of a measurement report. FIG. 6B is a diagram illustrating an example of the contents of a measurement report. FIG. 6C is a diagram illustrating an example of the contents of a measurement report. FIG. 7 is a diagram illustrating an example of the flow of processing executed in a wireless communication system. FIG. 8 is a diagram illustrating an example of the flow of processing executed in a wireless communication system. FIG. 9 is a diagram illustrating an example of the hardware configuration of an apparatus. FIG. 10 is a diagram illustrating an example of the functional configuration of a terminal apparatus. FIG. 11 is a diagram illustrating an example of the functional configuration of a base station apparatus.

[0011] 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.

[0012] 1A and 1B show an example configuration of a wireless communication system according to this embodiment. This wireless communication system is, for example, a cellular communication system conforming to the 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 102. The base station device 101 can form multiple first beams 111 and selectively uses one of these beams to communicate with the terminal device 102. The selection of the beam to be used is performed, for example, based on the results of measuring the reception quality of reference signals transmitted by all beams in the terminal device 102. This selection is particularly effective in the downlink where signals are transmitted from the base station device 101 to the terminal device 102. The reference signal here is, for example, a synchronization signal / physical broadcast channel (SS / PBCH) block (SSB) or a channel state information reference signal (CSI-RS). Furthermore, the reception quality may be, for example, reference signal received power (RSRP), reference signal received quality (RSRQ), signal-to-interference-and-noise ratio (SINR), etc. For example, the terminal device 102 measures the reception quality of the reference signal transmitted in each of the multiple first beams 111 and notifies the base station device 101 of the measurement results. Based on the measurement results, the base station device 101 determines, for example, a beam with high reception quality as the beam to be used for communication with the terminal device 102.

[0013] However, if the terminal device 102 measures reference signals for all of the first beams 111 to determine reception quality and notify the base station device 101 of the reception quality, the need to perform multiple measurements increases the time required to determine the beam. Furthermore, multiple notifications for multiple beams may waste radio resources. In response to this, for example, by selecting some beams that are expected to provide good quality in the terminal device 102 and having the terminal device 102 measure and report only those beams, it is possible to simplify the measurements and reduce the amount of information to be reported. However, this process does not allow for the selection of a beam to be used from all of the first beams 111. In response to this, the use of artificial intelligence (AI) / machine learning (ML) to select a beam to be used is being considered. For example, at least a portion of the measurement results by the terminal device 102 of reference signals transmitted in second beams that are fewer than the first beam 111 are input into a trained model obtained by machine learning. Then, as an output of the trained model, a small number of candidates for beams to be used by the base station device 101 for communication (e.g., downlink, and in some cases, also uplink) with the terminal device 102 may be output. After that, the terminal device 102 measures the reception quality of the reference signal for each of the small number of candidates, and the beam to be used for communication may be determined based on the measurement results. Also, the beam to be used for communication may be determined all at once, rather than the candidates, based on the output of the trained model.

[0014] The second beam, the reception quality of which is input to the trained model, may be, for example, a part of the first beam 111, as shown by beam 112 in FIG. 1A . That is, a part of the many first beams 111 that the base station device 101 can form (e.g., one beam 112 is set for each predetermined number of first beams 111) is set as the second beam, and the reception quality of the reference signal transmitted via the second beam is measured in the terminal device 102. Then, at least a part of the measurement results is input to the trained model, thereby determining the beam to be used in the base station device 101 for communication with the terminal device 102. Also, a beam with a wider beam width than the first beam 111, such as beam 113 in FIG. 1B , may be used as the second beam. For example, when SSB is transmitted by beam 113 and CSI-RS is transmitted by the first beam 111, the terminal device 102 transmits the measurement results of the SSB to the base station device 101, and the beam that the base station device 101 uses to communicate with the terminal device 102 is determined from the first beam 111 by inputting the measurement results into the trained model.

[0015] In this way, beam selection based on artificial intelligence / machine learning makes it possible to determine a beam suitable for communication between the base station device 101 and the terminal device 102 from among all of the first beams 111, without the terminal device 102 measuring and reporting the radio quality of all of the first beams 111. Note that beam selection based on artificial intelligence / machine learning can be performed in the base station device 101, but may also be performed in, for example, another network node. In that case, the base station device 101 can provide information received from the terminal device 102 to that network node and obtain information on the beam determined based on that information from the network node. In this way, beam selection does not necessarily have to be performed in the base station device 101.

[0016] An example of machine learning for beam determination will now be described with reference to Figures 2A and 2B. Figure 2A shows an example of the learning phase in machine learning, and Figure 2B shows an example after the learning phase is completed and a trained model for beam determination processing has been obtained. Note that these are merely examples, and the beams to be used may be determined by other configurations.

[0017] In the learning phase shown in the example of FIG. 2A , machine learning is performed using information about the reception quality at the terminal device 102 of reference signals transmitted from each of the first beams 111 as training data 203, and information about the reception quality at the terminal device 102 of reference signals transmitted from each of the second beams as input 202. Here, the training data may be, for example, data about the reception quality itself corresponding to each of the first beams 111, or data specifying a beam to be selected when that reception quality is obtained. Furthermore, although the reception quality of the second beam is represented as RSRP in FIG. 2A , it may also be other index values ​​such as RSRQ, SINR, or signal-to-noise ratio (SNR). The reception quality of the second beam is input to a learning model 201, and information in a format corresponding to the training data 203 is output from that information. Then, the difference value between that output and the training data 203 is fed back to the learning model 201, and the learning model 201 is updated. This process is repeated until the difference value remains sufficiently small, or until the process has been repeated a predetermined number of times, at which point the machine learning ends and the learned model at that time is output as the trained model.

[0018] 2B , an input 212 relating to the reception quality for the second beam, which is the same as the input 202 in the learning phase, is supplied to the trained model 211. Based on the input 212, the trained model 211 infers and outputs a beam 213 (or a candidate beam in some cases) to be used for communication with the terminal device 102 in the base station device 101. In this way, based on measurement results of reference signals transmitted by fewer beams than the first beam 111, a beam to be used for communication with the terminal device 102 can be determined from all of the first beams 111.

[0019] For example, the reception quality input 202 / 212 for the second beam may be adjusted to a predetermined level for values ​​below that level. For example, if the predetermined level for RSRP is set to -60 dBm, all reception quality information below -60 dBm may be input to the learning model 201 / trained model 211 as -60 dBm. In other words, reception quality values ​​low enough that they are expected to have little impact on learning and inference may all be treated as having the same quality. In the examples of Figures 2A and 2B, the input multiple reception qualities are distinguished by the input port as to which beam of the second beam each corresponds. For example, into a port labeled RSRP #1, the RSRP for one beam corresponding to that RSRP #1 is always input, and RSRPs for other beams are not input. This is because if this order is not fixed, learning will not be completed or the accuracy of inference will deteriorate.

[0020] Note that only a portion of the second beams may be input to the learning model 201 and the trained model 211. For example, even if a large number of measurement results, such as measurement results for all second beams, are acquired from the terminal device 102, only a portion of the measurement results is used as the input 202 to the learning model 201 to perform machine learning. Note that the teacher data 203 is the same as when all measurement results are used. Similarly, only a portion of the measurement results of the second beams may be used as the input 212 for the trained model 211. Note that the number of measurement results included in the input 202 and the input 212 is the same. That is, if, for example, eight measurement result values ​​are input as the input 202 in the learning phase, eight measurement result values ​​are also input as the input 212 in the inference phase. Note that if only the measurement result values ​​are used as the input 202 and the input 212 here, it becomes unclear which of the second beams the value relates to, which may result in a decrease in learning efficiency and inference performance. Therefore, input 202 and input 212 may include information indicating which beam the value relates to. That is, a combination of a beam ID for each second beam and the reception quality (e.g., RSRP) of the corresponding reference signal may be used as input 202 and input 212.

[0021] Note that the learning model 201 and the trained model 211 may use, as the input 202 and the input 212, the value of one wireless quality measurement result acquired at a specific timing for each second beam, but this is not limited thereto. For example, multiple wireless quality values ​​measured at multiple timings may be used as the input 202 and the input 212. That is, for each second beam, a repeatedly transmitted reference signal may be measured at multiple timings, and multiple pieces of wireless quality data obtained by the measurements may be used as the input. For example, when wireless quality data measured at M different timings for each of N beams is used as the input, the learning model 201 and the trained model 211 use the input 202 and the input 212 containing M × N elements. By using multiple pieces of wireless quality data measured at multiple timings as inputs in this way, for example, changes in wireless quality due to changes over time in the environment in which the terminal device 102 is located can be learned, and a beam suitable for subsequent environmental changes of the terminal device 102 can be selected. Furthermore, by using multiple pieces of wireless quality data measured at multiple times as input, the amount of input data increases, making it possible to select an appropriate beam with higher accuracy.

[0022] Here, an increase in the amount of data used as input 202 or input 212 means an increase in the amount of data to be fed back from the terminal device 102 to the base station device 101. Furthermore, for example, if the values ​​of the measurement results to be fed back could be reported in detail, it is expected that more accurate beam selection would be possible, but even when such highly accurate data is transmitted, the amount of data to be fed back may similarly increase. For this reason, even if a beam can be selected with high accuracy, the frequency utilization efficiency of the entire system may decrease.

[0023] In view of these circumstances, the present embodiment provides a technique for reducing the amount of data to be fed back. In one example, when a reference signal from the same beam is measured multiple times within a certain short period of time, it is assumed that no significant changes will occur in the measurement results. Therefore, for example, when reporting a value of radio quality measured at short intervals not exceeding a predetermined time length, the value may be reported as a differential value from other reported values. Conventionally, as shown in FIG. 3 , identification information 301 (CRI or SSBRI) that identifies one or more beams and measurement results 302 of radio signals for each of the one or more beams are reported. Note that CRI is an acronym for CSI-RS (Channel State Information-Reference Signal) Resource Indicator. Furthermore, SSBRI is an acronym for SSB (Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) Block) Resource Indicator. That is, a beam is associated with a resource on which a CSI-RS or SSB is transmitted, and the beam used to transmit the reference signal is identified according to the resource on which the reference signal is measured. Here, when measurement results 302 for multiple beams are reported, a first value of RSRP is reported for one beam (e.g., the beam with the best radio quality), and the RSRPs for the other beams are expressed by differential values ​​from the first value.

[0024] In this embodiment, in one example, measurement results corresponding to multiple times are transmitted in a manner similar to such conventional reports. Fig. 4 shows an example of the configuration of a measurement result report transmitted from the terminal device 102 to the base station device 101 in this embodiment. This report includes beam identification information 401, as in the past. However, in conventional reports, information on the wireless quality measured for each of multiple beams is included, and therefore identification information 301 for each of the multiple beams is included. However, in this embodiment, wireless quality corresponding to multiple timings for a single beam is indicated, and therefore only identification information 401 for one beam may be included. For example, a value 402 indicating the initial first measurement result is expressed in 7 bits, as in the conventional RSRP, and a value 403 indicating the second measurement result at the next timing is expressed as a difference value from the value 402 indicating the first measurement result. A value 404 indicating the third measurement result at the next timing is expressed as a difference value from the value 403 indicating the second measurement result, and a value 405 indicating the fourth measurement result at a subsequent timing is expressed as a difference value from the value 404 indicating the third measurement result. Note that the differential value of the conventional measurement results needs to be able to express a certain wide range of values ​​due to quality variations between beams. In contrast, the differential value of the present embodiment indicates the time change of the measurement value for one beam, and the amount of change is expected to be relatively small. Therefore, while the differential value of the conventional measurement results is expressed using four bits, the differential value of the measurement results of the present embodiment can be expressed using a smaller number of bits (e.g., two or three bits). Furthermore, when using the same number of bits as in the conventional method, the range of the time change amount of the wireless quality for one beam is expected to be relatively narrower than the range of the difference in wireless quality between multiple beams, so the time change amount can be expressed in detail. Note that while FIG. 4 shows an example in which information about only one beam is transmitted, information about multiple beams may also be transmitted. Note that information about each of the multiple beams may be included in a separate report message and transmitted.That is, one report message may include a measurement result for one beam at a first time and a difference value between a measurement result for another time and the other measurement result. Also, for example, a plurality of pieces of information as shown in Fig. 4 may be concatenated, and one report may be notified from the terminal device 102 to the base station device 101. Also, one measurement report may be configured to report up to four wireless quality measurement results as in the conventional case, and if more than four measurement values ​​are to be reported, multiple report messages may be transmitted.

[0025] Furthermore, for example, measurement results corresponding to multiple timings may be reported at different timings. In this case, for example, as shown in FIG. 5 , measurement results may be reported to the base station device 101 each time a measurement is performed, such as a first report 501 including a first measurement value 503, a second report 511 including a second measurement value 513, and a third report 521 including a third measurement value 523. In this case, identification information 502, 512, and 522 indicating which beam the report is for are included in each report. Then, for example, the first measurement value 503 is expressed without using a differential value, the second measurement value 513 is expressed by a differential value from the first measurement value 503, and the third measurement value 523 is expressed by a differential value from the second measurement value 513. When measurement results are reported using the method shown in FIG. 4 , identification information for identifying the beam is reported only once for multiple measurement result values, making it possible to report with a smaller amount of data than the method shown in FIG. 5 . On the other hand, when the method shown in FIG. 5 is used, information on the measurement results is notified to the base station device 101 without waiting until a predetermined number (e.g., four) of measurement results are aggregated, so that the terminal device 102 does not need to retain the measurement results for a long period of time. In particular, when measurement results for multiple beams are to be reported, there is no need to continue retaining the measurement results for each of the multiple beams until a predetermined number of measurement results are aggregated, which can reduce waste of resources such as memory for storing information. Note that while FIG. 5 shows information on only one beam, information aggregating measurement results corresponding to one timing (common period) for multiple beams may be reported from the terminal device 102 to the base station device 101. That is, the measurement result values ​​themselves for each of the multiple beams corresponding to a first time point may be transmitted in one report message, and the difference values ​​between the measurement result values ​​for each of the multiple beams corresponding to a second time point and the reported value of the measurement result immediately before that may be transmitted in another report message.

[0026] In the above example, each reported value is represented by a difference value from the value of the immediately preceding measurement result, but this is not limited to this. For example, a difference value from the value of the first measurement result may be reported. That is, in the example of FIG. 4 , not only the value 403 indicating the second measurement result, but also the value 404 indicating the third measurement result and the value 405 indicating the fourth measurement result may be expressed by a difference value from the value 402 indicating the first measurement result. The same applies to the example of FIG. 5 .

[0027] Here, examples of information reported in this embodiment will be described in comparison with conventional reporting examples using Figures 6A to 6C. Figure 6A shows, as an example, the change over time in RSRP values ​​measured for three beams. For example, the RSRP (RSRP #1) obtained by measuring the reference signal from beam 1 at a first time (TIME #1) is shown to be 40 dBm. Similarly, the RSRPs (RSRP #2 and RSRP #3) obtained by measuring the reference signals from beam 2 and beam 3 at TIME #1 are shown to be 30 dBm and 0 dBm, respectively. Furthermore, it is shown that RSRP #1, RSRP #2, and RSRP #3 are 35 dBm, 25 dBm, and 5 dBm, respectively, at a second time (TIME #2), and 35 dBm, 20 dBm, and 10 dBm, respectively, at a third time (TIME #3). The first to third times are given for convenience and do not mean that the measurement results were measured simultaneously. For example, when a reporting method such as that shown in FIG. 5 is used, the most recent measurement results obtained at the time of reporting are sufficient. Even when a reporting method such as that shown in FIG. 4 is used, it is sufficient that measurements are performed during a predetermined period including each time. Furthermore, in this embodiment, it is sufficient to capture the change in radio quality over time for each beam. In this case, it is sufficient to perform measurements according to a predetermined rule, such as starting measurement of beam 2 after multiple measurements of beam 1, and it is not necessary for measurements of each beam to be performed at the corresponding time.

[0028] 6B shows an example of value information notified from the terminal device 102 to the base station device 101 in a conventional measurement report when measurement values ​​such as those shown in FIG. 6A are obtained. In conventional measurement reports, a first measurement result for one beam, such as the best measurement result for multiple beams, is expressed as information indicating the value itself using 7 bits, and a second measurement result for another beam is expressed as information indicating a difference value from the first measurement result using 4 bits. For example, the report for the first time (TIME #1) in FIG. 6B includes information indicating the measurement result itself (40 dBm) for RSRP #1, and information indicating the difference value from RSRP #1 for RSRP #2 and RSRP #3. That is, since RSRP #2 is 30 dBm and the difference from RSRP #1 is 10 dB, information indicating this "10 dB" is included in the report. Similarly, RSRP #3 is 0 dBm, and the difference from RSRP #1 is 40 dB, so information indicating "40 dB" is included in the report. Furthermore, information regarding the second time (TIME #2) includes the RSRP #1 value "35 dBm" and the difference values ​​between RSRP #2 and RSRP #3 and RSRP #1 "10 dB" and "30 dB". Similarly, information regarding the third time (TIME #3) includes the RSRP #1 value "35 dBm" and the difference values ​​between RSRP #2 and RSRP #3 and RSRP #1 "15 dB" and "25 dB".

[0029] 6C shows an example of value information reported from the terminal device 102 to the base station device 101 in a measurement report of this embodiment when measurement values ​​such as those in FIG. 6A are obtained. In this embodiment, in the first report (at a first time (TIME #1)), information indicating the measurement results for each beam itself is reported from the terminal device 102 to the base station device 101. That is, in the report at the first time (TIME #1), information indicating "40 dBm," "30 dBm," and "0 dBm," which respectively indicate RSRP #1, RSRP #2, and RSRP #3, is reported from the terminal device 102 to the base station device 101. Then, at a second time (TIME #2), a difference value from the reported value at the first time is reported for each beam. For example, for beam 1, a calculation of 35-40=-5 is performed to subtract the RSRP#1 value for TIME#1 from the RSRP#1 value for TIME#2, and the resulting "-5 dB" is reported from the terminal device 102 to the base station device 101 as the difference value. Similarly, for beam 2, since 25-30=-5, a difference value of "-5 dB" is reported, and for beam 3, since 5-0=5, a difference value of "5 dB" is reported. Furthermore, at a third time (TIME#3), a difference value from the reported value at the second time is reported for each beam. For example, for beam 1, a calculation of 35-35=0 is performed to subtract the RSRP#1 value for TIME#2 from the RSRP#1 value for TIME#3, and the resulting "0 dB" is reported from the terminal device 102 to the base station device 101 as the difference value. Similarly, for beam 2, a difference value of "-5 dB" is reported since 20-25=-5, and for beam 3, a difference value of "5 dB" is reported since 10-5=5.

[0030] It is expected that the differential value for the same beam will have a narrower dynamic range than the differential value of the measurement results between beams. Therefore, for example, the differential value in FIG. 6C can be expressed in 2 or 3 bits, which is fewer than the 4 bits that indicate the conventional differential value between beams. For example, if the measurement result value itself is expressed in 7 bits and the differential value is expressed in 3 bits, at time #1, the conventional method requires 7 + 4 × 2 = 15 bits, while the method of this embodiment requires 7 × 3 = 21 bits. Meanwhile, for the total from time #1 to time #3, the conventional method requires 15 × 3 = 45 bits, while the method of this embodiment requires 21 + 3 × 3 × 2 = 39 bits, thereby reducing the number of bits. Furthermore, for example, if the differential value is expressed in 4 bits, it is expected that the dynamic range of the differential value will be narrower than the dynamic range of the differential value in the conventional report, allowing more detailed information to be fed back. In this case, 45 bits of information are transmitted and received by both the conventional method and the method of this embodiment at time #1 to time #3. On the other hand, when considering up to TIME #4 (not shown), the conventional method requires 15 × 4 = 60 bits, while the method of this embodiment requires 21 + 4 × 3 × 3 = 57 bits. This means that even if the differential value is transmitted using 4 bits, the number of bits transmitted and received can be reduced. In the initial report, for example, a differential value based on the value of one measurement result may be used, as in the conventional method. That is, the report value at TIME #1 in FIG. 6C may be the same as the report value at TIME #1 in FIG. 6B. This results in 15 bits at TIME #1 for both the conventional method and the method of this embodiment, preventing a short-term increase in the number of bits. Furthermore, in this embodiment, only the differential value is transmitted from TIME #2 onwards, thereby reducing the number of bits. This allows the terminal device 102 to report the measurement results of wireless quality to the base station device 101 using fewer bits than when a report using a differential value between beams is performed as in the conventional method. Furthermore, the differential value may be expressed using more than 4 bits, such as 5 bits.Even in this case, it is possible to express the quality of the radio signal with fewer bits than when expressing the quality of the radio signal itself, and furthermore, by using a relatively large number of bits, it is possible to express the quality of the radio signal with high accuracy.

[0031] Fig. 7 shows an example of the flow of processing executed in a wireless communication system. In the example of Fig. 7, the terminal device 102 measures the wireless quality of each beam at multiple measurement occasions and reports the measurement results together using the difference value as described with reference to Fig. 6C.

[0032] First, the base station device 101 notifies the terminal device 102 of configuration information for reporting measurement results (S701). The base station device 101 can notify the terminal device 102 of this configuration information using, for example, a message of a radio resource control (RRC) layer (e.g., an RRC Reconfiguration message). This configuration information can include information specifying, for example, the number of measurement results to be reported for each beam, how many measurement results to include in each report message, and the number of report messages to be transmitted from the terminal device 102. Note that this configuration information may also include information indicating that multiple measurement results for one beam should be reported in one report message. Here, for example, the configuration information can specify that four measurements should be performed for each beam at different timings, that information on the four measurement results should be included in one report message, and that one report message should be transmitted for each beam. Note that, for multiple reports for one beam, information indicating that a difference value indicating time fluctuation should be included in the message may be explicitly included. Furthermore, when multiple measurement results are to be reported for one beam, it may be predetermined, for example, by being specified in a standard, that a difference value between the measurement results be reported. In this case, indicating that multiple measurement results are to be reported for one beam may implicitly indicate that a difference value regarding the change over time in the measurement results for that one beam will be reported.

[0033] Then, the terminal device 102 measures the reference signal (CSI-RS in the example of FIG. 7) transmitted from the base station device 101 the number of times specified for each beam (S702 to S705). After the measurement, the terminal device 102 generates a measurement report based on the setting information specified in S701 and transmits the measurement report to the base station device 101 (S706). Here, the terminal device 102 generates a report message (CSI report) including a value indicating the result of the first measurement itself and values ​​indicating the results of the second to fourth measurements by difference values ​​from the reported value of the previous measurement result, and transmits this to the base station device 101.

[0034] Upon receiving the report message, the base station device 101 extracts the first measurement value as is, adds the difference value corresponding to the second measurement report to the first measurement value to obtain the second measurement value, adds the difference value corresponding to the third measurement report to the second measurement value to obtain the third measurement value, and adds the difference value corresponding to the fourth measurement report to the third measurement value to obtain the fourth measurement value. The base station device 101 then inputs the first to fourth measurement values ​​into a trained model, selects one or more candidate beams expected to be suitable for communication with the terminal device 102 from all beams available for communication (S707), and notifies the terminal device 102. Thereafter, the base station device 101 selects the beam to be actually used for communication by, for example, transmitting a reference signal using the candidate beam and having the terminal device 102 measure the reference signal (S708). 7 , the trained model used in S707 is obtained by acquiring measurement results of reference signals for all second beams, such as the first beam 111 and beams 112 and 113, that can be used for communication, and performing machine learning using the beam selected based on the measurement results of the first beam 111 as training data and the measurement results of the second beam as input. The selection criteria for the beam to be used for communication (i.e., training data) based on the measurement results of the first beam 111 can be arbitrarily selected depending on how the beam to be selected in the environment in which actual communication will be performed thereafter should be selected. For example, in training to obtain a trained model suitable for an environment in which a vehicle moves along a fixed track, such as a train, the training data can be selected so that a beam that provides good communication quality at the destination is selected.

[0035] The processing in Fig. 7 corresponds to the processing when, for example, information as shown in Fig. 4 is reported from the terminal device 102 to the base station device 101. Next, with reference to Fig. 8, the processing when information as shown in Fig. 5 is reported from the terminal device 102 to the base station device 101 will be described.

[0036] First, the base station device 101 notifies the terminal device 102 of configuration information for reporting measurement results (S801). This configuration information may include the same information as in S701, but here may include information indicating that one report message should include one measurement result for each of multiple beams and that multiple (e.g., four) report messages should be transmitted for each beam. Note that the configuration information may include information explicitly indicating that a differential value of the radio quality for each beam should be reported in the second or subsequent report message. Furthermore, the fact that a differential value of the radio quality for each beam should be reported in the second or subsequent report message may be implicitly specified, for example, by indicating that multiple radio qualities should be reported for each beam. In other words, it may be determined that a differential value is always transmitted when multiple measurement results of the radio qualities for each beam are reported.

[0037] Thereafter, the terminal device 102 measures reference signals transmitted from, for example, the base station device 101 for each of one or more beams (S802, S804, S806, S808), and reports information indicating the wireless quality of the measurement results to the base station device 101 (S803, S805, S807, S809). In S803, the terminal device 102 reports a value indicating the measurement result itself to the base station device 101 to make the first report. Then, in S805, the terminal device 102 reports a difference value from the value of the measurement result reported in S803, in S807, reports a difference value from the value of the measurement result reported in S805, and in S809, reports a difference value from the value of the measurement result reported in S807. When the base station device 101 receives the report message, it extracts the first measurement value as is, adds the difference value corresponding to the second measurement report to the first measurement value to obtain the second measurement value, adds the difference value corresponding to the third measurement report to the second measurement value to obtain the third measurement value, and adds the difference value corresponding to the fourth measurement report to the third measurement value to obtain the fourth measurement value. The subsequent processing (S810 and S811) is the same as S707 and S708 in Figure 7.

[0038] In this way, in this embodiment, it is possible to suppress an increase in the amount of data when the terminal device 102 feeds back the time variation in wireless quality for some of the multiple beams formed by the base station device 101.

[0039] FIG. 9 shows an example of the hardware configuration of the base station device 101 and the terminal device 102 according to this embodiment. In one example, the base station device 101 and the terminal device 102 are configured to include a processor 901, a ROM 902, a RAM 903, a storage device 904, and a communication circuit 905. The processor 901 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 902 or the storage device 904. The ROM 902 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 102. The RAM 903 functions as a workspace when the processor 901 executes a program and is also a random access memory that stores temporary information. The storage device 904 is configured, for example, by a removable external storage device. The communication circuit 905 is configured, for example, by a circuit for wireless communication of 5G or a successor standard. While FIG. 9 illustrates one communication circuit 905, the base station device 101 and the terminal device 102 may have multiple communication circuits. For example, the base station device 101 and the terminal device 102 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 102 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 102 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 102 may have separate communication circuits 905 for each of the multiple available frequency bands, or may have a common communication circuit 905 for at least some of the frequency bands.

[0040] FIG. 10 shows an example of the functional configuration of the terminal device 102. The terminal device 102 includes, for example, a measurement unit 1001, a report generation unit 1002, and a reporting unit 1003. Note that FIG. 10 only shows functions particularly related to this embodiment, and various other functions that the terminal device 102 may have are omitted from the illustration. For example, the terminal device 102 naturally has other functions that terminal devices compliant with 5G or subsequent standards generally have. The functional blocks in FIG. 10 are shown schematically, and the respective functional blocks may be integrated or further subdivided. Each function in FIG. 10 may be realized, for example, by the processor 901 executing a program stored in the ROM 902 or the storage device 904, or may be realized, for example, by a processor within the communication circuit 905 executing predetermined software. Since the details of the processing performed by each functional unit are as described above, only the general functions of the terminal device 102 will be outlined here.

[0041] The measurement unit 1001 measures wireless quality by observing reference signals transmitted from a large number of first beams 111 formed in the base station device 101 and from second beams, such as beams 112 and 113, that are fewer than the first beams 111. The measurement unit 1001 acquires multiple wireless quality measurement results by observing reference signals transmitted at multiple timings for each of one or more second beams. The report generation unit 1002 generates a report message for reporting the wireless quality measured by the measurement unit 1001. As shown in FIGS. 4 and 5 , the report message here includes a difference value from a previously reported measurement result for each beam, if such a measurement result exists. The report unit 1003 transmits the report message generated by the report generation unit 1002 to the base station device 101. The terminal device 102 may measure all of the first beams 111 and the second beams for the purpose of processing the learning phase of machine learning, and notify the base station device 101 of the results. Even in this case, the terminal device 102 can perform measurements at least for the second beam at multiple timings as described above, and can notify the base station device 101 of the measurement results expressed using differential values.

[0042] FIG. 11 shows an example of the functional configuration of the base station device 101. The base station device 101 includes a report receiving unit 1101, a measurement result reconstruction unit 1102, and a beam control unit 1103. Note that FIG. 11 only shows functions particularly related to this embodiment, and omits 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. The functional blocks in FIG. 11 are shown only schematically, and the respective functional blocks may be integrated or further subdivided. Each function in FIG. 11 may be realized, for example, by the processor 901 executing a program stored in the ROM 902 or the storage device 904, or by a processor within the communication circuit 905 executing predetermined software. Since the details of the processing performed by each functional unit are as described above, only the general functions of the base station device 101 will be outlined here.

[0043] The report receiving unit 1101 receives one or more report messages described above from the terminal device 102. This report message has a configuration as shown in FIG. 4 or FIG. 5. The measurement result reconstruction unit 1102 reconstructs the measurement result based on the information of the difference value acquired by the report message. That is, when the measurement result at the second time is indicated by a difference value from the measurement result at the first time, the measurement result reconstruction unit 1102 reconstructs the measurement result at the second time by adding the measurement result at the first time and the difference value. The beam control unit 1103 inputs the measurement result reconstructed by the measurement result reconstruction unit 1102 into a trained model to, for example, identify candidate beams to be actually used for communication. Then, the beam control unit 1103 notifies the terminal device 102 of the candidate beams, transmits a reference signal using the candidate beams, and causes the terminal device 102 to measure the reference signal. The beam control unit 1103 then receives the measurement results from the terminal device 102 and determines the beam to actually be used based on the results. Then, the beam control unit 1103 performs subsequent communication with the terminal device 102 using the determined beam. Furthermore, in the learning phase of machine learning, the beam control unit 1103 repeatedly updates the learning model based on information on measurement results for each of the first beam 111 and the second beam from the terminal device 102. Here, the measurement results for at least the second beam include measurement results for multiple timings, and the measurement results can be reported using differential values. In this case, the measurement result reconstruction unit 1102 reconstructs the measurement results for each of the second beams and inputs them to the beam control unit 1103. This allows the beam control unit 1103 to perform machine learning using the reconstructed information.

[0044] The terminal device 102 may perform a conventional measurement report. That is, a report such as that shown in FIG. 6B may be performed. The terminal device 102 may also transmit capability information to the base station device 101 indicating whether or not it is possible to perform a report using a temporal difference value as in this embodiment. The terminal device 102 may also determine whether or not to perform a report using a temporal difference value. In this case, the terminal device 102 may transmit, for example, information that enables it to determine whether to perform a report using a temporal difference value as in FIG. 6C or a report using a difference value between beams as in FIG. 6B, in a report message. Based on this information, the base station device 101 may identify whether the measurement result includes a temporal difference value, and based on this identification result, reconstruct the measurement result from the remaining information. The terminal device 102 may also notify the base station device 101 of the type of report to be performed, and then autonomously determine the number of measurement results to include in the report, whether or not to perform a report, etc. For example, measurement results below a predetermined level may not be reported.

[0045] As described above, in this embodiment, it is possible to reduce the amount of feedback data transmitted from the terminal device 102 to the base station device 101 or to increase the accuracy of the data. This makes it possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, which is to "Develop resilient infrastructure, promote sustainable industrialization, and foster innovation."

[0046] 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.

[0047] This application claims priority based on Japanese Patent Application No. 2024-042223, filed on March 18, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A terminal device having: a measurement means for measuring a reference signal transmitted from a base station device using a predetermined beam at multiple timings and obtaining multiple measurement results of wireless quality for the predetermined beam, including a first measurement result for a first timing and a second measurement result for a second timing; and a transmission means for transmitting a report message to the base station device, the report message including at least a difference value between the value of the second measurement result and the reported value of the first measurement result.

2. The terminal device according to claim 1, wherein the transmitting means transmits to the base station device one report message including identification information for identifying the specified beam, the first measurement result for the specified beam, and the difference value.

3. The terminal device according to claim 2, wherein the transmitting means generates a report message including the identification information, the first measurement result, and the difference value separately for each of the plurality of specified beams and transmits the report message to the base station device.

4. The terminal device according to claim 1, wherein the transmitting means transmits to the base station device a first report message including identification information for identifying the specified beam and the first measurement result for the specified beam, and a second report message different from the first report message including the identification information and the difference value.

5. The terminal device according to claim 1, wherein the transmitting means transmits to the base station device a first report message including the first measurement results for a plurality of the specified beams and a second report message including the difference value between the second measurement results for the plurality of the specified beams and the first measurement results.

6. A base station device that repeatedly transmits a reference signal using a predetermined beam, comprising: an acquisition means that acquires from a terminal device a plurality of measurement results of radio quality based on measurements of the reference signal at a plurality of timings, the first measurement result and a difference value between the value of the second measurement result and the reported value of the first measurement result via a report message for reporting the plurality of measurement results, the measurement results including a first measurement result for a first timing and a second measurement result for a second timing; a restoration means that restores the second measurement result from the first measurement result and the difference value; and a control means that controls a beam to be used for communication with the terminal device based on the first measurement result and the second measurement result.

7. The base station device according to claim 6, wherein the acquisition means receives from the terminal device one report message including identification information identifying the specified beam, the first measurement result for the specified beam, and the difference value.

8. The base station device according to claim 7, wherein the acquisition means receives from the terminal device a plurality of report messages including the identification information, the first measurement result, and the difference value for each of the plurality of predetermined beams.

9. The base station device of claim 6, wherein the acquisition means receives from the terminal device a first report message including identification information for identifying the specified beam and the first measurement result for the specified beam, and a second report message different from the first report message including the identification information and the difference value.

10. The base station device of claim 6, wherein the acquisition means receives from the terminal device a first report message including the first measurement results for a plurality of the specified beams, and a second report message including the difference value between the second measurement results for the plurality of the specified beams and the first measurement results.

11. A control method executed by a terminal device, comprising: measuring a reference signal transmitted from a base station device using a predetermined beam at multiple timings, and obtaining multiple measurement results of radio quality for the predetermined beam, including a first measurement result for a first timing and a second measurement result for a second timing; and transmitting a report message to the base station device, including at least a difference value between the value of the second measurement result and the reported value of the first measurement result.

12. A control method executed by a base station device, comprising: repeatedly transmitting a reference signal using a predetermined beam; acquiring from a terminal device, via a report message for reporting a plurality of measurement results of radio quality based on measurements of the reference signal at a plurality of timings, the plurality of measurement results including a first measurement result for a first timing and a second measurement result for a second timing, the first measurement result and a difference value between the value of the second measurement result and the reported value of the first measurement result; restoring the second measurement result from the first measurement result and the difference value; and controlling a beam to be used for communication with the terminal device based on the first measurement result and the second measurement result.

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

14. A program for causing a computer installed in a base station device to execute the control method set forth in claim 12.

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