A wireless communication system that uses a relay device as an extended antenna for a terminal device, a terminal device, a control method, and a program.

Abstract

To provide a wireless communication system in which a terminal device uses a relay device having an RF relay function as an extended antenna to communicate with a base station device.SOLUTION: In a wireless communication system, a terminal device sends out a search signal for a relay device at at least one of a first frequency and a second frequency, detects a frequency-converted search signal at the second frequency when the search signal is sent at the first frequency, and detects a frequency-converted search signal at the first frequency when the search signal is sent at the second frequency, and determines that a relay device is present when the frequency-converted search signal is detected, and when it is determined that a relay device is present, communicates with a base station device using the relay device as a virtual antenna.SELECTED DRAWING: Figure 7

Description

Technical Field

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[0001] The present invention relates to a wireless communication system in which a relay device is used as an extended antenna of a terminal device.

Background Art

[0007] According to the present invention, a terminal device can communicate with a base station device by using a relay device having an RF relay function as an extended antenna. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating an example of a wireless communication system configuration. [Figure 2] This diagram shows an example of the process flow for a terminal device to acquire capability information from a relay device. [Figure 3] This diagram shows an example of the process flow in which a terminal device proactively notifies a base station device of capability information. [Figure 4] This diagram shows an example of the process flow for a terminal device to identify the detailed state of the transmission path between the terminal device and the base station device and the relay device. [Figure 5]This figure shows one configuration of a relay device that converts the frequency of a signal received from a terminal device to one of several frequencies. [Figure 6] This figure shows an example of the processing flow for controlling the destination of the frequency conversion of wireless signals in a relay device. [Figure 7] This diagram shows an example of the process flow for a terminal device to detect a relay device that only has relay functionality. [Figure 8] This figure shows some hardware configuration examples for terminal devices and relay devices. [Figure 9] This figure shows an example of the functional configuration of a terminal device. [Figure 10] This figure shows some examples of the functional configuration of a relay device. [Modes for carrying out the invention]

[0009] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the features described in the embodiments may be combined in any way. Furthermore, identical or similar configurations will be given the same reference numeral, and redundant descriptions will be omitted.

[0010] (System Configuration) Figure 1 shows an example configuration of a wireless communication system according to this embodiment. In this wireless communication system, terminal device 101 is connected to multiple relay devices 121 and 122, and relay devices 121 and 122 relay communication between terminal device 101 and base station device 151. Terminal device 101 and base station device 151 are wireless communication devices that comply with, for example, the 5th generation (5G) or later cellular communication standards of the 3rd Generation Partnership Project (3GPP®). Although Figure 1 shows an example of one terminal device 101 and one base station device 151, it is naturally assumed that there are many of these communication devices.

[0011] In this embodiment, relay devices 121 and 122 are connected to the terminal device 101 and operate to function as pseudo-antennas extending from the terminal device 101 by relaying only communications involving the terminal device 101. That is, relay devices 121 and 122 function as extension antennas (extended antennas) of the terminal device 101, and the connection between them and the terminal device 101 is configured to use wireless communication instead of cables. As a result, the terminal device 101 uses relay devices 121 and 122 as antennas provided in its own device to communicate with the base station device 151. The base station device 151 does not recognize relay devices 121 and 122 individually. That is, the terminal device 101 and relay devices 121 and 122 are combined to operate as a virtual terminal device. Hereafter, since relay devices 121 and 122 function as antennas for the virtual terminal device, these devices may be referred to as virtual antennas. More precisely, each of the one or more antennas of relay devices 121 and 122 is used as a virtual antenna. However, when there is no particular need to distinguish between them, relay devices 121 and 122 that perform relay transmission are sometimes referred to as virtual antennas (meaning that relay devices 121 and 122 function as virtual antennas). Relay devices 121 and 122 are configured to relay only communications involving terminal device 101 and do not relay communications from other terminal devices. Relay devices 121 and 122 may be, for example, wireless devices held by the user, such as a smartwatch, but are not particularly limited.

[0012] The relay devices 121 and 122 amplify the radio signal transmitted from the terminal device 101 and relay it to the base station device 151, and also amplify the radio signal transmitted from the base station device 151 and relay it to the terminal device 101. The relay devices 121 and 122 do not demodulate or decode the radio signals transmitted and received between the terminal device 101 and the base station device 151. In other words, the relay devices 121 and 122 have a radio frequency (RF) relay function (function as a radio repeater). Here, the signal 111 transmitted and received between the terminal device 101 and the relay devices 121 and 122 is transmitted via a short-distance communication line using a high-frequency band (terahertz (THz) band), such as the 300GHz band. On the other hand, the signal 141 transmitted and received between the relay devices 121 and 122 and the base station device 151 is transmitted via a relatively long-distance communication line using a relatively low-frequency band (millimeter wave band), such as the 39GHz band. In other words, relay devices 121 and 122 convert signals received in a first frequency band (THz band) for communication with terminal device 101 to a second frequency band (millimeter wave band) for communication with base station device 151 and relay them, and also convert signals received in the second frequency band to the first frequency band and relay them.

[0013] The relay devices 121 and 122, as wireless repeaters, only perform amplification and frequency conversion for communication between the terminal device 101 and the base station device 151, but also have a communication function to accept control from the terminal device 101. In this embodiment, the relay devices 121 and 122 are assumed to have the function of wireless repeaters, but the following discussion may also apply if they are configured to perform regenerative relay, as necessary. As shown in Figure 1, for example, the relay devices 121 and 122 have a communication function unit 131, which is a communication function to accept control from the terminal device 101, and a relay function unit 132. The communication function unit 131 has, for example, the function to perform Sidelink communication with the terminal device 101 in accordance with the 3GPP cellular communication standard. This is just one example, and the communication function unit 131 may be configured to communicate with the terminal device 101 by a communication function such as a wireless local area network (LAN) or Bluetooth®. The terminal device 101, for example, uses a side-link communication function to discover relay devices 121 and 122 that communicate with the communication function unit 131, and connects with the relay devices 121 and 122 through communication with the communication function unit 131.

[0014] The relay function unit 132 has a wireless repeater function that amplifies and frequency-converts the signal received from the terminal device 101 or the base station device 151 and outputs the amplified and frequency-converted signal. Note that the relay function unit 132 can operate in a frequency band different from that of the communication function unit 131. For example, the terminal device 101 may perform communication for controlling the relay devices 121 and 122 in a relatively low predetermined frequency band, and perform communication with the base station device 151 via the relay devices 121 and 122 in a high frequency band such as the THz band or the millimeter wave band. Note that this is an example, and for example, the communication function unit 131 may also use the frequency band used by the relay function unit 132, such as the THz band or the millimeter wave band. Then, the communication function unit 131 and the relay function unit 132 are each configured to operate in a frequency band corresponding to the operation of the terminal device 101. Note that the terminal device 101 only performs control communication regarding communication with the relay devices 121 and 122. Further, since the terminal device 101 uses the relay devices 121 and 122 existing at positions where the distance from the own device is short, it is not necessary to transmit a signal to the base station device 151 with a large power, so that the power consumption can be suppressed.

[0015] Hereinafter, on the premise that such a system configuration is used, various types of information to be transmitted and received and various types of processing to be executed among the terminal device 101, the relay devices 121 and 122, and the base station device 151 according to the present embodiment will be described.

[0016] (Acquisition of capability information regarding the wireless repeater portion of the relay device) As described above, the terminal device 101 can perform control communication to control the relay devices 121 and 122, but in doing so, it is necessary to be aware of the capabilities of the relay devices 121 and 122. In particular, it is important for the terminal device 101 to be aware of the relay communication function of the relay function unit 132 for communication with the base station device 151. In this embodiment, in view of these circumstances, the relay devices 121 and 122 use the communication function unit 131 to notify the terminal device 101 of capability information regarding the relay function unit 132. For example, the relay devices 121 and 122 transmit to the terminal device 101 information indicating whether or not they have a relay function unit 132 as capability information. Alternatively, the relay devices 121 and 122 may transmit to the terminal device 101 information indicating whether or not the relay function unit 132 can function as a virtual antenna for the terminal device 101 as capability information. By obtaining this information, the terminal device 101 can search for a relay device that can be used as a virtual antenna.

[0017] In addition, relay devices 121 and 122 can notify the terminal device 101 of information indicating, as capability information, for example, a frequency band available on the terminal device 101 side. That is, relay devices 121 and 122 can notify the terminal device 101 of information on a first frequency band (for example, the THz band) to which the radio signal transmitted from the base station device 151 is to be converted when relaying it to the terminal device 101 as a wireless repeater. The terminal device 101 can determine that it can use relay devices 121 and 122 as virtual antennas on the condition that, for example, the frequency band available to the terminal device itself matches the frequency band available to relay devices 121 and 122. Further, relay devices 121 and 122 can notify the terminal device 101 of information indicating, as capability information, a second frequency band (for example, the millimeter wave band) available for signal transmission and reception with the base station device 151. The terminal device 101 can determine that it can use relay devices 121 and 122 as virtual antennas on the condition that, for example, the frequency band available to the base station device 151 matches the frequency band available to relay devices 121 and 122 on the base station device 151 side. These frequency bands may be notified to the terminal device 101, for example, as a list of frequency bands available to the relay function unit 132. The terminal device 101 can identify the frequency band to be used in communication performed by the terminal device itself using relay devices 121 and 122 by acquiring information on the frequency bands corresponding to the relay function unit 132 in relay devices 1, 21 and 122. Note that relay devices 121 and 122 can notify the terminal device 101 of information on at least one of the above-described first frequency band and second frequency band. That is, relay devices 121 and 122 do not necessarily have to notify the terminal device 101 of information on both the first frequency band and the second frequency band, and may notify the terminal device 101 of only information on either the first frequency band or the second frequency band.

[0018] Furthermore, relay devices 121 and 122 may notify terminal device 101 of the number and configuration of physical antennas available in the relay function unit 132 as capability information. The information on the number of antennas may include, for example, the number of antennas available as antennas on the terminal device 101 side and the number of antennas available as antennas on the base station device 151 side. The information on the number of antennas may also include, for example, information indicating the number of antennas corresponding to each frequency band available to relay devices 121 and 122. The information on the antenna configuration may include information on the positional relationship of the antennas. The information on the antenna configuration may also include information on the number of streams that can be transmitted and received with the base station device 151. Based on this information, terminal device 101 may transmit multiple streams to relay devices 121 and 122, for example, using polarization or multiple frequency bands. Relay devices 121 and 122 may separate the multiple streams by polarization or frequency band and transmit these multiple streams in parallel using multiple antennas (and multiple frequency bands as necessary) on the base station device 151 side. In this way, the terminal device 101 can determine what form communication can be performed via the relay devices 121 and 122 based on information about the number and configuration of the antennas.

[0019] Figure 2 shows an example of the processing flow when capability information of relay devices 121 and 122 is provided to terminal device 101. Terminal device 101 sends a message to each of relay devices 121 and 122 to inquire about capability information (S201), and each of relay devices 121 and 122 provides its own capability information to terminal device 101 (S202). Terminal device 101 may also send an inquiry message that includes information indicating whether or not its own device is a terminal device capable of using a virtual antenna. If terminal device 101 is capable of using a virtual antenna, relay devices 121 and 122 may notify terminal device 101 of information indicating whether their own devices function as virtual antennas. Terminal device 101 may also send an inquiry message that includes information on the frequency band (e.g., THz band) that its own device can use with relay devices that function as virtual antennas. Terminal device 101 may also send an inquiry message that includes information on the frequency band used by base station device 151 for communication. In these cases, relay devices 121 and 122 may notify terminal device 101 of the frequency bands available to their own devices as capability information, or they may notify information indicating whether the frequency bands included in the inquiry message are available. Terminal device 101 may also send an inquiry message that includes information about the number and configuration of antennas that its own devices have. As described above, relay devices 121 and 122 notify terminal device 101 of the number and configuration of antennas that their own devices have as capability information.

[0020] Furthermore, terminal device 101 may obtain capability information regarding the wireless repeater portion (relay function unit 132) from relay devices 121 and 122, for example, by using the provisions for sidelink communication in the 3GPP standard. In this case, the communication function unit 131 of relay devices 121 and 122 is configured to operate in accordance with the provisions for sidelink communication. In this case, for example, capability information for sidelink communication can be reused. In sidelink communication, terminal device sends a UECapabilityEnquirySidelink message to inquire about obtaining capability information from other terminal devices, and other terminal devices send a UECapabilityinformationSidelink message containing their own capability information. For example, in S201 described above, terminal device 101 sends a first message, which is an extension of the UECapabilityEnquirySidelink message, to relay devices 121 and 122. Furthermore, when the communication function unit 131 of the relay devices 121 and 122 receives a message that is an extended version of the UECapabilityEnquirySidelink message, it may, in S202 described above, transmit capability information regarding the wireless repeater portion (relay function unit 132) to the terminal device 101 using a message that is an extended version of the UECapabilityinformationSidelink message.

[0021] Terminal device 101 may send information to relay devices 121 and 122 indicating that it is inquiring about capability information regarding the wireless repeater portion in a message that is an extension of the UECapabilityEnquirySidelink message. This message may also include information inquiring whether relay devices 121 and 122 have the functionality of a wireless repeater (i.e., whether they can operate as a virtual antenna). Conventional UECapabilityEnquirySidelink messages include frequencyBandListFilterSidelink, which inquires about the frequency band corresponding to sidelink communication and the combination of frequency bands that can be used in combination in sidelink communication. This information includes only information about the frequency band for sidelink and does not include information unrelated to sidelink communication, such as wireless repeaters. Therefore, in this embodiment, this information can be extended to allow inquiring about information about frequency bands that can be used for the wireless repeater portion. Terminal device 101 may also send ue-CapabilityInformationSidelink, which includes its own capability information, to relay devices 121 and 122, similar to conventional UECapabilityEnquirySidelink messages. This is just one example, and capability information does not necessarily have to be transmitted from terminal device 101 to relay devices 121 and 122. Furthermore, the extended UECapabilityEnquirySidelink message may include information querying the number and configuration of antennas in the wireless repeater portions of relay devices 121 and 122.

[0022] The relay devices 121 and 122 use messages that extend the UECapabilityinformationSidelink message to notify the terminal device 101 of information such as whether it has the functionality of a wireless repeater. Furthermore, the relay devices 121 and 122 can notify the terminal device 101 of the supported frequency bands (and combinations of supported frequency bands) of the wireless repeater portion using information similar to that of the conventional supportedBandCombinationListSidelink and supportedBandListSidelink. The relay devices 121 and 122 also notify the terminal device 101 of the number and configuration of antennas in the wireless repeater portion.

[0023] Furthermore, the capability information described above may be notified from relay devices 121 and 122 to terminal device 101 without adhering to the provisions of sidelink communication. For example, capability information may be notified using a Bluetooth® profile. That is, the communication function units 131 of terminal device 101 and relay devices 121 and 122 may be configured to perform Bluetooth communication. Then, in S202 described above, relay devices 121 and 122 may notify terminal device 101 of information such as whether or not they have the function of a virtual antenna, the supported frequency band, the number and configuration of antennas, using a Generic Attribute Profile (GATT). The terminal device 101 may also notify relay devices 121 and 122 of its own device information using GATT. In addition, the communication function units 131 of terminal device 101 and relay devices 121 and 122 may send and receive capability information using a wireless LAN.

[0024] The terminal device 101 identifies, for example, relay devices 121 and 122 that can operate as virtual antennas, based on the capability information of the relay devices 121 and 122 that it has acquired. Then, the terminal device 101 recognizes the configuration of the virtual antenna based on the frequency band, the number and configuration of antennas that relay devices 121 and 122 can use on the base station device 151 side, and can communicate with the base station device 151 using that configuration. Relay devices 121 and 122 may transmit their own capability information without receiving an inquiry message from the terminal device 101. For example, relay devices 121 and 122 may spontaneously transmit their own capability information in response to, for example, when the power is turned on or when a user operation to turn on the function as a virtual antenna is received. By detecting such capability information, the terminal device 101 can recognize that there are devices with virtual antenna functionality in the vicinity.

[0025] (Updating terminal device capability information) As described above, terminal device 101 can communicate with base station device 151 by using relay devices 121 and 122 as virtual antennas. Terminal device 101 notifies base station device 151 of capability information such as the number of antennas, assuming that such virtual antennas exist. For example, if relay devices 121 and 122 each have two antennas on the base station device 151 side, terminal device 101 can be said to have four virtual antennas because the two relay devices each have two antennas. Therefore, in such a case, terminal device 101 can notify base station device 151 of capability information that it has four antennas. On the other hand, in such an environment, the number of virtual antennas in terminal device 101 may change, for example, if either relay device 121 or 122 is powered off or if a connection with a new relay device is established.

[0026] Furthermore, for example, when the terminal device 101 transmits channel status information (CSI) to the base station device 151, it can compress the CSI using artificial intelligence (AI) / machine learning (ML). For example, by using ML with the uncompressed CSI as input, a first trained model is obtained for acquiring a compressed CSI that can obtain a compression ratio determined by a predetermined criterion, such as the lowest compression ratio or a compression ratio below a standard value, and a second trained model is obtained by using the compressed CSI as input to acquire the uncompressed CSI. At this time, the first trained model is held in the terminal device 101, and the second trained model is held in the base station device 151. For example, the terminal device 101 can acquire the CSI by channel estimation in its own device, and by performing ML based on that information, generate the first and second trained models, and notify the base station device 151 of the second trained model. This second trained model is provided from the terminal device 101 to the base station device 151, for example, as capability information. Furthermore, the capability information may only indicate whether or not the CSI can be compressed and decompressed by the first and second trained models, and the second trained model may be notified to the base station device 151 separately from the capability information. In this way, when the terminal device 101 obtains a CSI by channel estimation, it compresses the CSI using the first trained model and transmits it to the base station device 151, and the base station device 151 inputs the received compressed CSI into the second trained model to obtain the channel estimation result at the terminal device 101. On the other hand, if, for example, the communication environment between the terminal device 101 and the base station device 151 changes significantly, it is expected that the trained model will no longer be suitable for that communication environment. In this case, the terminal device 101 can update the second trained model that was notified to the base station device 151 as capability information.

[0027] Furthermore, the terminal device 101 can control the beam to be used for communication between the terminal device 101 and the base station device 151 using AI / ML. For example, the terminal device 101 and the base station device 151 can measure radio quality using only a portion of the many available beams, and use the measurement results as input to perform ML to select the optimal beam from all available beams and generate a trained model. In one example, the base station device 151 transmits measurement signals using all available beams, and the terminal device 101 selects the optimal beam from the measurement results of those signals. Meanwhile, it can use the measurement results of signals transmitted with some beams as input and generate a trained model using ML with the selected optimal beam as training data. At this time, the terminal device 101 can notify the base station device 151 as capability information that it can perform beam selection using the trained model. Even in this case, if the communication environment between the terminal device 101 and the base station device 151 changes significantly, it is expected that the trained model will no longer be suitable for that communication environment. In this case, it is conceivable that the terminal device 101 will be unable to perform beam selection using a trained model, even though it has notified the base station device 151 that it can perform beam selection using a trained model as capability information.

[0028] Thus, the capability information of terminal device 101 is expected to change dynamically when a virtual antenna is used or when AI / ML is used. Conventionally, terminal device 101 cannot provide its capability information to base station device 151 unless it is inquired about by base station device 151. As a result, base station device 151 may end up communicating with terminal device 101 according to inaccurate capability information. Here, base station device 151 acquires the capability information of terminal device 101 when it establishes a connection with terminal device 101. As a result, terminal device 101 can disconnect and reconnect each time its capability information changes. However, in this case, the signaling overhead can increase significantly because the connection will be repeatedly disconnected and reconnected each time the configuration of the virtual antenna or the communication status of terminal device 101 changes.

[0029] In this embodiment, in view of these circumstances, the terminal device 101 is made capable of voluntarily transmitting capability information to the base station device 151 while maintaining a connection with the base station device 151. Figures 3(A) and 3(B) show an example of this processing flow. For example, when the terminal device 101 detects the need to change the capability information (S301), it decides to transmit the capability information to the base station device 151 (S302). Then, the terminal device 101 voluntarily transmits the capability information to the base station device 151. The terminal device 101 transmits UECapabilityInformation to the base station device 151 without receiving an inquiry message from the base station device 151. Alternatively, the terminal device 101 may request the base station device 151 to transmit an inquiry message (S311). That is, the terminal device 101 transmits a message to the base station device 151 requesting the transmission of a UECapabilityEnquiry message. When terminal device 101 receives a UECapabilityEnquiry sent from base station device 151 in response to this request message (S312), it sends UECapabilityInformation to base station device 151 in response (S313). In this way, terminal device 101 sends a signal to base station device 151 to transmit capability information even when it has not received an inquiry for capability information from base station device 151. Then, by notifying base station device 151 of the modified capability information from terminal device 101 using that signal, base station device 151 becomes able to control the communication of terminal device 101 using accurate capability information.

[0030] Messages that cause the terminal device 101 to send capability information or capability information inquiry messages to the base station device 151 are transmitted using, for example, radio resource control (RRC) messages, physical uplink control channel (PUCCH) messages, and media access control control elements (MAC CE). When the terminal device 101 voluntarily transmits capability information, it may transmit all of the modified capability information of the terminal device 101 to the base station device 151, or it may transmit only the modified parts of the capability information to the base station device 151. Furthermore, in a message that causes the base station device 151 to send a capability information inquiry message, the terminal device 101 may transmit only a request for the transmission of an inquiry message, or it may transmit information indicating, for example, which items of the capability information will be changed.

[0031] The capability information transmitted from the terminal device 101 to the base station device 151 may include, for example, MIMO (Multiple Input Multiple Output) related information and corresponding frequency band information. The MIMO related information may include, for example, sounding reference signal (SRS) setting information (SRSConfig), beam setting information (SpatialrelationInfo), and the number of MIMO layers for the downlink and uplink, respectively (maxNumberMIMOLayersPDSCH, maxNumberMIMO-LayersCBPUSCH). Furthermore, as mentioned above, information necessary to perform the function, such as AI / ML model information, may be included in the capability information.

[0032] The terminal device 101 may determine, for example, that a change in capability information is necessary when the connection to the relay device used as a virtual antenna is lost, or when a new connection is made to the relay device used as a virtual antenna. The terminal device 101 may also determine, for example, whether the original CSI has been restored after inputting the compressed CSI obtained by inputting the CSI into a first trained model for compression into a second trained model for decompression, and if it has not been restored accurately (if the error exceeds a predetermined value), it may determine that a change in capability information (retraining of the model) is necessary. Furthermore, the terminal device 101 may input the measurement results of only a portion of the available beams into the trained model and determine whether the beam identified as the beam to be used is the optimal beam among the entirety of the available beams. That is, the terminal device 101 may, for example, periodically perform measurements on the entirety of the available beams and determine whether the beam to be used determined according to the measurement results matches the beam identified using the trained model. Furthermore, if the beams do not match, the terminal device 101 may determine that a change in capability information (model retraining) is necessary. In one example, if the terminal device 101 determines that model retraining is necessary, it may send a request to the base station device 151 to send capability information or a capability information inquiry message once the retraining is complete. As a result, since a retrained model exists at the time the message is sent, it becomes possible to perform communication using the retrained model in a short amount of time.

[0033] Furthermore, terminal device 101 may send a request to base station device 151 to send capability information or a capability information inquiry message if it determines that the model needs to be retrained. In this case, base station device 151 can immediately stop using the trained model for decompressing CSI that has become unsuitable for the communication conditions, for example. Until terminal device 101 updates the trained model and provides it to base station device 151, and until base station device 151 receives the updated trained model, CSI may be provided from terminal device 101 to base station device 151 using the conventional procedure. This prevents communication control based on inaccurate CSI due to the use of an inappropriate trained model. In addition, base station device 151 may, for example, send measurement signals on all available beams to cause terminal device 101 to perform retraining in order to update the trained model for beam control that has become unsuitable for the communication conditions.

[0034] (Reporting of wireless quality to terminal devices by relay devices) When communication between the terminal device 101 and the base station device 151 is performed using the relay devices 121 and 122 described above, both the radio quality associated with the first transmission path (e.g., in the THz band) between the terminal device 101 and the relay devices 121 and 122, and the radio quality associated with the second transmission path (e.g., in the millimeter-wave band) between the relay devices 121 and 122 and the base station device 151, affect the communication quality of the communication between the terminal device 101 and the base station device 151. For example, it is assumed that a radio signal transmitted from the base station device 151 is received by the relay devices 121 and 122 at low power, and that the signal-to-noise ratio (SNR) becomes low due to the addition of noise originating from the relay devices 121 and 122 to the radio signal. When this low-SNR radio signal is amplified, not only the signal component but also the noise component is greatly amplified, so even if the received power of the radio signal at the terminal device 101 is sufficient, the SNR of the radio signal remains low. Similarly, if the signal-to-noise ratio (SNR) of the radio signal transmitted from terminal device 101 and received by relay devices 121 and 122 is low, the SNR of the radio signal transmitted from relay devices 121 and 122 and received by base station device 151 will remain low even if the received power of the radio signal will be sufficient. In other words, if the power of the signal reaching relay devices 121 and 122 is low, the SNR will be low due to noise originating from relay devices 121 and 122, and when the radio signal is amplified, the SNR of the radio signal may remain low even if the received power of the radio signal at terminal device 101 and base station device 151 is sufficient.

[0035] In such a case, it is conceivable that communication between the terminal device 101 and the base station device 151 may not be able to properly transmit and receive radio signals, even though the radio quality (received power) at the terminal device 101 appears to be good. To address this, the terminal device 101 can ensure sufficiently high communication quality for communication between the terminal device 101 and the base station device 151 by using, for example, a relay device as a virtual antenna that can achieve a predetermined quality level for both the radio quality in the first and second transmission paths described above. On the other hand, while the terminal device 101 and the base station device 151 can recognize the communication quality of communication via the entire transmission path between the terminal device 101 and the base station device 151 using existing methods such as channel estimation, they cannot recognize the communication quality of the first and second transmission paths separately. Therefore, the terminal device 101 cannot select an appropriate relay device to ensure sufficiently high communication quality for communication between the terminal device 101 and the base station device 151.

[0036] In this embodiment, in view of these circumstances, the relay devices 121 and 122 identify the radio quality of the first transmission path and the radio quality of the second transmission path in the relay function unit 132, and notify the terminal device 101 of the results of this identification. For example, the relay function unit 132 of the relay devices 121 and 122 measures predetermined signals transmitted from the terminal device 101 and the base station device 151 to measure the radio quality of the first transmission path and the second transmission path, respectively. The relay function unit 132 then provides the measurement results to the communication function unit 131, and the communication function unit 131 notifies the terminal device 101 of the provided measured values ​​of radio quality. Here, the predetermined signal may be, for example, a reference signal or a synchronization signal generated using a known sequence, and the radio quality may be, for example, the received power of the signal or the signal-to-noise and interference ratio (SINR). The relay function unit 132 can measure the radio quality, for example, by correlation detection using a known sequence used to generate the predetermined signal. Furthermore, the relay function unit 132 may measure the received power of the radio signal using power detectors connected to antennas on the terminal device 101 side and the base station device 151 side, for example. The power detectors may also be arranged to be accessible by the communication function unit 131, in which case the relay function unit 132 does not need to have a correlation detection function or an information provision function to the communication function unit 131. In other words, the relay function unit 132 may consist only of functions as a radio repeater, such as amplification of the received signal and frequency conversion. Note that at least one of the radio quality of the first transmission path and the second transmission path may be measured and reported to the terminal device 101. That is, only the radio quality of the first transmission path may be measured and reported, only the radio quality of the second transmission path may be measured and reported, or both may be measured and reported.

[0037] The relay devices 121 and 122 may, for example, periodically measure the radio quality of the first and second transmission paths, respectively, or they may perform measurements in response to receiving instructions from the terminal device 101. In one example, the base station device 151 may send a predetermined notification to the terminal device 101 if the received power of the signal from the terminal device 101 is sufficient, but its quality, such as SNR, is insufficient. Upon receiving this predetermined notification, the terminal device 101 may send instruction signals to the relay devices 121 and 122 to perform measurements. Similarly, the terminal device 101 may send instruction signals to the relay devices 121 and 122 to perform measurements if the received power of the signal from the base station device 151 is sufficient, but its quality, such as SNR, is insufficient.

[0038] Figure 4 shows an example of this process flow. In this process, relay devices 121 and 122 measure the radio quality, such as the received power, of the downlink radio signal transmitted from the base station device 151 (S401, S402), and also measure the radio quality, such as the received power, of the uplink radio signal transmitted from the terminal device 101 (S403, S404). Relay devices 121 and 122 are connected to the terminal device 101 and function as virtual antennas, so that signals transmitted from the base station device 151 are relayed to the terminal device 101, and signals transmitted from the terminal device 101 are relayed to the base station device 151. Relay devices 121 and 122 notify the terminal device 101 of the measurement results of at least one of S402 and S404 (S405). The notification in S405 can be made using, for example, sidelink communication, Bluetooth, or wireless LAN. Furthermore, when sidelink communication is used, notification S405 may be made using the physical sidelink control channel (PSCCH) or the physical sidelink shared channel (PSSCH). Also, relay devices 121 and 122 may perform measurements and reports periodically, or they may perform measurements and reports aperiodicly in accordance with measurement instructions (S406) from the terminal device 101. The terminal device 101 may also instruct, for example, the communication function units 131 of relay devices 121 and 122 to report the measurement results on the condition that predetermined conditions are met. In this way, the terminal device 101 can obtain measurement results of the radio quality of the first transmission path between the terminal device 101 and the relay devices 121 and 122, and measurement results of the radio quality of the second transmission path between the terminal device 101 and the base station device 151.

[0039] When terminal device 101 receives measurement results of the radio quality at relay devices 121 and 122, it transmits these measurement results to base station device 151, for example. Based on these measurement results, base station device 151 may perform actions such as transmit power control. For example, if the radio quality related to the second transmission path (e.g., received power at relay devices 121 and 122) is low, base station device 151 may control the transmission power of the downlink signal to increase. Also, if the received measurement results of the radio quality indicate that the radio quality related to the first transmission path is low (e.g., below a predetermined value), terminal device 101 may control the transmission power of the uplink signal to increase. Furthermore, if terminal device 101 is using a relay device as a virtual antenna where the radio quality is insufficient (radio quality is below a predetermined value) for at least one of the first or second transmission paths, terminal device 101 may stop using that relay device. Terminal device 101 may also switch the relay device being used. The terminal device 101 may also instruct relay devices not currently being used as virtual antennas to measure and report their wireless quality. This allows the terminal device 101 to select a relay device with good wireless quality from among the unused relay devices and use it as a new virtual antenna.

[0040] (Frequency conversion in relay devices) As described above, terminal device 101 transmits signals to relay devices 121 and 122 by multiplexing them using polarization and multiple frequency channels (e.g., in the THz band), and relay devices 121 and 122 convert these signals into signals on a single frequency channel and relay them to base station device 151. In this case, if the converted frequency channels in relay devices 121 and 122 are fixed, many terminal devices using virtual antennas will use those frequency channels, making it difficult to secure sufficient resources for those frequency channels. Note that "frequency channels" here may be set in multiples for a single frequency band, or only one may be set for a single frequency band. That is, a frequency channel may be a partial band of a single frequency band, or it may be the entirety of a single frequency band.

[0041] Therefore, in this embodiment, the relay devices 121 and 122 are configured to use multiple different frequency channels included in the frequency band available for relaying radio signals to the base station device 151. The relay devices 121 and 122 then set the frequency channel to be used when relaying signals to the base station device 151 according to instructions from the terminal device 101. This prevents the communication of numerous terminal devices using the relay devices from being concentrated on a specific frequency channel and improves the flexibility of frequency resource allocation.

[0042] Figure 5 shows an example configuration of relay devices 121 and 122 according to this embodiment. For example, terminal device 101 transmits wireless signals containing separate data on frequency channel A and frequency channel B, respectively. When relay devices 121 and 122 receive these wireless signals, they separate them using band-pass filters (BPFs) 502 that allow only the bandwidth of frequency channel A to pass through and BPFs that allow only the bandwidth of frequency channel B to pass through. Relay devices 121 and 122 then perform frequency conversion of the frequencies of these wireless signals to frequency C or frequency D, for example, using the waveform output by oscillator 503. The frequency-converted wireless signals are supplied to switch 504 so that they are input to either BPF 505 for frequency C or BPF 506 for frequency D. Switch 504 switches the output destination so that, for example, if the wireless signal should be output at frequency C, the wireless signal is input to BPF 505, and the wireless signal is not input to BPF 506. Furthermore, switch 504 switches the output destination so that, for example, if the wireless signal should be output at frequency D, the wireless signal is input to BPF 506, while the wireless signal is not input to BPF 505. Then, if the frequency of the relayed wireless signal is frequency C, the wireless signal that has passed through BPF 505 is amplified and relayed (output from the antenna), and if the frequency of the relayed wireless signal is frequency D, the wireless signal that has passed through BPF 506 is amplified and relayed (output from the antenna).

[0043] Figure 5 shows an example where two frequency bands (frequency C and frequency D) can be used to relay radio signals to the base station device 151, but the relay devices 121 and 122 may be configured to use three or more frequency bands. Also, the example shows that the radio signals transmitted from the terminal device 101 to the relay devices 121 and 122 are frequency multiplexed, but they may be multiplexed using polarization or time, for example. In this case, the relay devices 121 and 122 can separate signals transmitted with different polarizations or times and perform radio signal conversion processing so that these signals are transmitted at the same frequency and time using multiple antennas. However, in any case, when the relay function unit 132 operates as a radio repeater, it is not necessary to perform processes such as signal demodulation and decoding, and re-encoding and re-modulation.

[0044] The relay devices 121 and 122 receive instruction information from the terminal device 101, for example, using the communication function unit 131. This instruction information includes the changed frequency. When the communication function unit 131 receives the instruction information from the terminal device 101, it supplies the instruction content to the control unit 501. The control unit 501 then controls the frequency of the oscillator 503 and the switch 504 in the relay devices 121 and 122 so that a radio signal of the instructed frequency is output. In other words, the control unit 501 controls the transmission frequency of the oscillator 503 and sets the output destination of the switch 504 so that the radio signal with the changed frequency is input to the appropriate BPF. As described above, the relay devices 121 and 122 notify the terminal device 101 of the available frequency bands (frequency channels) as capability information. The terminal device 101 transmits the information of the frequency bands indicated as available by this capability information to the base station device 151 as its own capability information. The base station device 151 then selects one of the available frequency bands indicated in its capability information and allocates the frequency resources included in the selected frequency band to the terminal device 101. The terminal device 101 instructs the relay devices 121 and 122 to use the allocated frequency band. The control units 501 of the relay devices 121 and 122 then convert the radio signal arriving from the terminal device 101 into a radio signal of that frequency band and relay it.

[0045] Figure 6 shows an example of the frequency setting process flow for relay devices 121 and 122. In this process, first, relay devices 121 and 122 transmit capability information to terminal device 101, including the frequency bands available for relaying radio signals to base station device 151 (S601). Then, terminal device 101 notifies base station device 151 (for example, via relay devices 121 and 122, or directly without going through relay devices 121 and 122) of capability information indicating that the frequency bands available to relay devices 121 and 122 are available to its own devices (S602). Then, base station device 151 selects one of the frequency bands indicated by the capability information, allocates resources for uplink communication in that frequency band, and notifies terminal device 101 (for example, via relay devices 121 and 122, or directly without going through relay devices 121 and 122) of information indicating the allocated resources (S603). The base station device 151 may notify the terminal device 101 of a combination of information about the frequency band to be used and information indicating which resource within that frequency band is allocated. However, if the frequency band containing the frequency resource is identified by the information specifying the frequency resource, the frequency band information does not need to be notified to the terminal device 101. The terminal device 101 sends instructions to relay devices 121 and 122 to relay the uplink signal to the base station device 151 using the frequency band corresponding to the allocated frequency resource (S604). Then, relay devices 121 and 122, in accordance with the instructions, control, for example, the oscillator 503 and the switch 504 to configure themselves to relay the uplink signal to the base station device 151 using the instructed frequency band (S605).

[0046] The base station device 151 may also notify the terminal device 101 of information indicating which frequency band to use in which time slot. In this case, the terminal device 101 similarly notifies the relay devices 121 and 122 of information associating the time slot with the frequency band to be used, and the control units 501 of the relay devices 121 and 122 can perform control processing to change the frequency band to be used as time progresses according to that information. This makes it possible to switch the frequency band to be used at the appropriate timing, and to use a large number of frequency bands more flexibly. Alternatively, information associating multiple time slots with the corresponding frequency bands to be used may be notified to the relay devices 121 and 122. The relay devices 121 and 122 control themselves to use the corresponding frequency band in each of the multiple time slots. In this way, by notifying information that specifies the time changes of the frequency band to be used, the number of instruction signals to be transmitted can be reduced, and the frequency band to be used can be switched frequently and flexibly. The terminal device 101 may individually send instructions regarding the frequency band to be used to multiple relay devices 121 and 122, or it may send them simultaneously via multicast.

[0047] Subsequently, the terminal device 101 transmits the uplink signal using the time and frequency range in the frequency band before conversion by the relay devices 121 and 122, which corresponds to the resources allocated in S603 (for example, a specific time and frequency range in the frequency band used, indicated by the resource block). For example, if the lower end of the frequency band used when relaying radio signals from relay devices 121 and 122 to the base station device 151 (for example, frequency C or frequency D in Figure 5) is f2, the lower end of the allocated frequency resource is f2+Δ, and the lower end of the frequency band when transmitting radio signals from the terminal device 101 to relay devices 121 and 122 (for example, frequency A in Figure 5) is f0, then the terminal device 101 transmits the uplink signal in the frequency resource with f0+Δ as its lower end. Furthermore, as shown in Figure 5, when the terminal device 101 transmits wireless signals to the relay devices 121 and 122 using multiple frequency bands, for example, if the lower ends of two frequency bands (for example, frequency A and frequency C in Figure 5) are f0 and f1 respectively, the terminal device 101 transmits the uplink signal in the frequency resources with f0+Δ and f1+Δ as the lower ends. In this way, for example, the base station device 151 can flexibly allocate wireless resources, making it possible to avoid congestion in only specific frequency bands.

[0048] (Identification of relay devices that have only analog functionality) In the example described above, the terminal device 101 uses a sidelink communication function or the like to discover and connect to relay devices 121 and 122, which have a communication function unit 131, and uses the connected relay devices 121 and 122 as a virtual antenna. The terminal device 101's (virtual) capabilities, such as the number of MIMO layers, are determined by recognizing relay devices that can be used as virtual antennas. Therefore, when using a virtual antenna, it is necessary to recognize those relay devices. On the other hand, if relay devices 121 and 122 only have a relay function unit 132 and do not have a communication function unit 131, the sidelink communication function or the like cannot be used, and it is assumed that the terminal device 101 will not be able to discover those relay devices 121 and 122.

[0049] In this embodiment, in view of these circumstances, in order to find a relay device having only the relay function unit 132, the terminal device 101 sends out at least one of the signals in the first frequency band (e.g., THz band) used when communicating with the base station device 151 using a virtual antenna, and the signals in the second frequency band (e.g., millimeter wave band) after conversion by the relay device, and detects radio waves in the frequency band after frequency conversion (which occurs when a relay device is present). That is, when a relay device is nearby, the radio signal sent by the terminal device 101 is frequency converted by that relay device and output, so the terminal device 101 can determine that a relay device is nearby if it can detect the radio signal after frequency conversion. In other words, the terminal device 101 can determine that a relay device is nearby if it detects the signal in the second frequency band after sending out the signal in the first frequency band, or if it detects the signal in the first frequency band after sending out the signal in the second frequency band.

[0050] The terminal device 101 may periodically transmit at least one of the signals in the first frequency band and the signals in the second frequency band to perform signal detection processing in the converted frequency band. However, it is not limited to this, and the terminal device 101 may transmit a signal and perform detection processing when a predetermined event is detected. For example, the terminal device 101 may transmit a signal and perform detection processing when, for example, detection is instructed to start by a user operation on the terminal device 101. For example, the relay device is a wireless device held by the user, such as a smartwatch, and the user is expected to turn on the switch of the device and instruct the detection of the device to start.

[0051] Here, the relay device is assumed to have a constant amplification factor, for example. In this case, the terminal device 101 transmits a signal with sufficiently weak power. This prevents strong interference with signals from other terminal devices at the base station device 151, even if, for example, the signal transmitted by the terminal device 101 in the first frequency band is amplified by the relay device and output in the second frequency band. Similarly, the terminal device 101 transmits a signal in the second frequency band with sufficiently weak power and detects the signal in the first frequency band. It should be noted that signals in the THz band undergo significant distance attenuation, and even when amplified and output, the range of the radio waves is limited, and it is assumed that they will not interfere with other signals.

[0052] For example, frequency and time resources for searching for relay devices may be provided in the form of a resource pool. For example, resources are set up that the terminal device 101 can use to transmit a search signal, and corresponding resources are set up for the terminal device 101 to receive the signal after it has been frequency converted and relayed. For example, a THz band frequency and time resource is provided as a first resource, and a millimeter-wave band frequency and time resource corresponding to that first resource is provided as a second resource. Furthermore, a millimeter-wave band frequency and time resource is provided as a third resource, and a THz band frequency and time resource corresponding to that third resource is provided as a fourth resource. The terminal device 101 determines whether a relay device exists by transmitting a signal in the first or third resource and determining whether the frequency-converted signal is detected in the second or fourth resource. For example, the first resource may be set up during periods when the base station device 151 does not transmit millimeter-wave band signals. For example, the first resource may be set up in a time slot where uplink resources are allocated. Furthermore, a second resource corresponding to the first resource may also be set in the same time slot. If a relay device exists, the signal transmitted on the first resource in the THz band is converted to a signal on the second resource in the millimeter-wave band and relayed by that relay device. According to the above setting, since no millimeter-wave signals are transmitted from the base station equipment 151, the terminal device 101 can measure the millimeter-wave signals relayed by the relay device under interference-free conditions. In addition, the third resource described above may also be set at a time when the base station equipment 151 does not transmit millimeter-wave signals, that is, in a time slot allocated to the uplink. The terminal device 101 sends a millimeter-wave signal on the third resource where the base station equipment 151 does not transmit millimeter-wave signals, and performs detection processing of THz band signals on the fourth resource.According to the above configuration, since no millimeter-wave signals are transmitted from the base station device 151, the relay device does not relay those millimeter-wave signals, and therefore the terminal device 101 can measure the millimeter-wave signals relayed by the relay device under interference-free conditions. Although it is assumed that THz signals are transmitted between other terminal devices and their corresponding relay devices, interference from these signals to the signals transmitted between the terminal device 101 and the relay device can be ignored due to their high frequency.

[0053] As described above, the terminal device 101 can recognize a relay device that does not have a communication function unit 131 and use that relay device as a virtual antenna. In the above example, a case was described in which the terminal device 101 transmits a signal for searching for a relay device during a period when the base station device 151 is not transmitting millimeter-wave signals, but this is not the only example. For example, the terminal device 101 may notify the base station device 151 that it is searching for a relay device and receive a resource allocation for searching from the base station device 151. In this case, the terminal device 101 can transmit a search signal while the base station device 151 is transmitting a signal in the millimeter-wave band. However, the base station device 151 will not transmit a signal in the millimeter-wave band radio resources used by the relay device when relaying its signal, corresponding to the radio resources used by the terminal device 101 to transmit the millimeter-wave signal for searching and the THz band radio resources used by the terminal device 101 to transmit the search signal. This prevents interference from signals from the base station device 151 from occurring in the radio resources used by the terminal device 101 to search for a relay device. Furthermore, as mentioned above, it is assumed that a relay device can relay wireless signals in multiple frequency bands. For this reason, the terminal device 101 may perform signal detection processing in those multiple frequency bands. That is, the terminal device 101 may perform relay device detection processing using a combination of multiple frequency bands. In addition, since the terminal device 101 knows the signal it has transmitted, it may detect the signal from the relay device by performing correlation detection using the waveform obtained by frequency conversion of that signal, or it may simply detect the signal from the relay device by performing power detection in the resources after frequency conversion.

[0054] Furthermore, if multiple relay devices exist, the terminal device 101 can perform detection processing to detect each of them. For example, by forming multiple beams and performing detection processing for each beam, the terminal device 101 can detect relay devices located in the direction a beam is pointed, and detect relay devices located in other directions using other beams. In other words, by performing detection processing for each beam, the terminal device 101 can detect relay devices located in different directions by separating them by beam. It is possible, but not limited to, changing the beam used over time to identify which beam has detected a relay device. For example, the terminal device 101 may use different signal sequences for each beam and perform relay device detection processing using multiple beams in parallel. In other words, the terminal device 101 can identify which beam direction a relay device is located in based on which signal sequence has been detected. Also, for example, if all relay devices to be searched perform the same frequency conversion, the terminal device 101 may use different frequency resources for each beam and perform relay device detection processing using multiple beams in parallel. In other words, the terminal device 101 can determine which beam direction the relay device is located in based on which frequency resource the signal was detected on.

[0055] Figure 7 shows an example of the processing flow for a terminal device 101 to search for a relay device that does not have a communication function unit 131. The terminal device 101 periodically or in response to a predetermined event sends a search signal in a first resource (or a third resource) (S701). The relay device, for example, after being powered on by a user operation, converts the frequency of the signal to a second resource (or a fourth resource if it receives a search signal transmitted using the third resource) (S702), amplifies it, and outputs it (S703). The terminal device 101 detects the relay device in response to receiving a radio signal transmitted from the relay device in the second resource (S704). For example, the terminal device 101 can determine whether the received signal is a signal that has been frequency-converted from a radio signal transmitted by itself, and then determine whether a relay device exists based on the result of that determination. However, this is not limited to the above; for example, the presence of a relay device may be determined when a predetermined level or higher of power is detected in the second resource. Then, the terminal device 101, having determined that a relay device exists, uses that relay device as a virtual antenna to communicate with the base station device 151.

[0056] In this way, if there is a relay device that does not have a communication function unit 131, the terminal device 101 can detect that relay device and use that relay device as a virtual antenna to communicate with the base station device 151.

[0057] (Device configuration) Next, we will describe an example configuration of the terminal device 101 and relay devices 121 and 122 configured to perform the above-described process. Since the functions that the terminal device 101 and relay devices 121 and 122 should have are as described above, we will only describe the general configuration of the terminal device 101 and relay devices 121 and 122 below. The base station device 151 has roughly the same functions as a conventional base station device, so it will not be described here. The detailed operation of the base station device 151 is as described above.

[0058] Figure 8 shows an example of the hardware configuration of the communication function unit 131 and control unit 501 of the terminal device 101 and relay devices 121 and 122 according to this embodiment. In the following, the communication function unit 131 and control unit 501 of the relay device may be simply referred to as the relay device. In one example, the terminal device 101 and relay devices 121 and 122 are configured to include a processor 801, ROM 802, RAM 803, storage device 804, and communication circuit 805. The processor 801 is a computer configured to include one or more processing circuits, such as a general-purpose CPU (Central Processing Unit) or ASIC (Application-Specific Integrated Circuit), and executes the overall processing of the device and the above-mentioned processing by reading and executing programs stored in the ROM 802 and storage device 804. The ROM 802 is a read-only memory that stores information such as programs and various parameters related to the processing executed by the terminal device 101 and relay devices 121 and 122. RAM 803 functions as a workspace for the processor 801 to execute programs and is a random access memory that stores temporary information. The storage device 804 is composed of, for example, a removable external storage device. The communication circuit 805 is composed of, for example, a circuit for wireless communication of 5G or its successor standards. Although one communication circuit 805 is shown in Figure 8, the terminal device 101 and relay devices 121 and 122 may have multiple communication circuits. For example, the terminal device 101 and relay devices 121 and 122 may have wireless communication circuits for 5G and its successor standards, respectively, and a common antenna for those circuits, and may be configured to perform side-link communication functions. The terminal device 101 and relay devices 121 and 122 may also have separate antennas suitable for each standard. Furthermore, the terminal device 101 may also have communication circuits compliant with wireless communication standards other than cellular communication standards, such as Wi-Fi or Bluetooth®. Furthermore, relay devices 121 and 122 may have, in addition to or instead of, communication circuits for cellular communication, wireless LAN or Bluetooth communication circuits.

[0059] Figure 9 shows an example of the functional configuration of the terminal device 101. The terminal device 101 includes a first communication unit 901, a second communication unit 902, a virtual antenna control unit 903, and an AI / ML function unit. These functions can be implemented, for example, by the processor 801 executing a program stored in the ROM 802 or storage device 804, or by the communication circuit 805. However, this is just one example, and the functions shown in Figure 9 may be realized by other configurations. Furthermore, the functions shown in Figure 9 are just one example, and the various processes described above may be realized by other function units.

[0060] The first communication unit 901 is a functional unit for communicating with, for example, the communication function units 131 of the relay devices 121 and 122. The first communication unit 901 has, for example, a sidelink communication function. Alternatively, the first communication unit 901 may have a Bluetooth communication function or a wireless LAN communication function in addition to or instead of the sidelink communication function. Control communication with the relay devices 121 and 122 is performed using the first communication unit 901. The second communication unit 902 communicates with the base station device 151. Communication of user data and control data with the base station device 151 is performed via the second communication unit 902. When the virtual antenna is not used, the second communication unit 902 can, for example, directly transmit millimeter-wave signals to the base station device 151. When the virtual antenna is used, the second communication unit 902 transmits, for example, THz signals. The THz band signal is converted to a millimeter-wave band signal via relay devices 121 and 122 and transmitted to the base station equipment 151. The second communication unit 902 also receives, for example, a millimeter-wave band signal transmitted from the base station equipment 151 directly, or receives the signal converted from the THz band signal by relay devices 121 and 122.

[0061] The virtual antenna control unit 903 performs various controls necessary for using the relay devices 121 and 122 as virtual antennas, and while they are being used as virtual antennas. For example, the virtual antenna control unit 903 detects the relay devices using the first communication unit 901 or the second communication unit 902, and performs connection processing with those relay devices in order to use them as virtual antennas. The virtual antenna control unit 903 also performs the various control communications associated with using the virtual antennas, for example, via the first communication unit 901 or the second communication unit 902. The AI / ML function unit 904 performs various processes using AI and ML. For example, the AI / ML function unit 904 can perform CSI compression and beam selection as described above. The AI / ML function unit 904 also generates and updates trained models using machine learning as needed. For example, the AI / ML function unit 904 updates the trained model if it becomes inappropriate due to environmental changes or other reasons. Furthermore, the AI / ML function unit 904 performs the various control communications associated with using AI / ML, for example, via the second communication unit 902. For example, if it becomes necessary to update the trained model for CSI compression and decompression, the AI / ML function unit 904 can notify the base station device 151 of changes in the capability information of the terminal device 101.

[0062] Figure 10 shows an example of the functional configuration of the communication function unit 131 and control unit 501 (i.e., the part other than the relay function unit 132) of the relay devices 121 and 122. The part of the relay devices 121 and 122 other than the relay function unit 132 includes, as its function, a communication unit 1001, a capability information notification unit 1002, and a measurement result notification unit 1003. These functions can be implemented, for example, by the processor 801 executing a program stored in the ROM 802 or storage device 804, or by the communication circuit 805. However, this is just an example, and the functions in Figure 10 may be realized by other configurations. Also, the functions shown in Figure 10 are just an example, and the various processes described above may be realized by other functional units.

[0063] The communication unit 1001 has functions corresponding to the first communication unit 901 of the terminal device 101. That is, if the first communication unit 901 performs communication using the sidelink communication function, the communication unit 1001 also has the sidelink communication function. The capability information notification unit 1002 notifies the terminal device 101, via the communication unit 1001, of information about the capabilities of the relay function unit 132, for example. For example, the capability information notification unit 1001 notifies the terminal device 101 of whether or not it has a relay function unit 132, the frequency band that the relay function unit 132 can use, and the number and configuration of antennas that can be used in the relay function unit 132. The measurement result notification unit 1003 measures the radio quality of the signal received by the relay function unit 132, for example, and notifies the terminal device 101 of the measurement result. The measurement result notification unit 1003 is configured to obtain radio quality by monitoring the received power of the signal at each antenna of the relay function unit 132, for example.

[0064] As described above, the terminal device 101 according to this embodiment can communicate with the base station device 151 by using a relay device having an RF relay function as an extended antenna through appropriate control. Therefore, it becomes possible to contribute to Goal 9 of the United Nations Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0065] The invention is not limited to the embodiments described above, and various modifications and changes are possible within the scope of the gist of the invention.

Claims

1. A wireless communication system comprising a terminal device, a base station device to which the terminal device is connected, and a relay device that converts a signal of a first frequency transmitted by the terminal device to a second frequency, amplifies it and relays it to the base station device, and converts a signal of the second frequency transmitted by the base station device to a first frequency, amplifies it and relays it to the terminal device, and which can use multiple frequencies as the second frequency, wherein the terminal device A transmission means for transmitting a signal for searching for the relay device at at least one of the first frequency and the second frequency, A detection means for detecting the search signal whose frequency has been converted to the second frequency when the search signal is transmitted at the first frequency, and when the search signal is transmitted at the second frequency, at the first frequency. A determination means for determining that the relay device exists when the frequency-converted search signal is detected, If it is determined that the relay device exists, a communication means for using the relay device as a virtual antenna to communicate with the base station device, A terminal device characterized by having the following features.

2. The terminal device according to claim 1, characterized in that the transmitting means transmits the search signal in a first resource configured to transmit the search signal at a first frequency, and the detection means detects the search signal in a second resource configured to correspond to the first resource at a second frequency, or the transmitting means transmits the search signal in a third resource configured to transmit the search signal at a second frequency, and the detection means detects the search signal in a fourth resource configured to correspond to the third resource at a first frequency.

3. The terminal device according to claim 1, characterized in that the transmission means transmits the search signal during a period when the base station device does not transmit a downlink signal at the second frequency.

4. The transmission means transmits the search signal at a plurality of frequencies that can be used as the first frequency or a plurality of frequencies that can be used as the second frequency. The terminal device according to claim 1, characterized in that the detection means detects the frequency-converted search signal in each of the plurality of frequencies that can be used as the first frequency when the search signal is transmitted in each of the plurality of frequencies that can be used as the second frequency corresponding to the plurality of frequencies, and in each of the plurality of frequencies that can be used as the second frequency when the search signal is transmitted in each of the plurality of frequencies that can be used as the first frequency corresponding to the plurality of frequencies.

5. The system further comprises forming means for forming multiple beams directed in different directions, In each of the plurality of beams, the transmission means transmits the search signal, and the detection means detects the frequency-converted search signal. The terminal device according to feature 1.

6. The transmission means transmits the search signal generated using a different sequence in each of the plurality of beams. The detection means detects the search signal using the sequence, thereby identifying which of the plurality of beams the search signal was detected in. The determination means determines, based on the detection result, which of the plurality of beams the relay device was detected in. The terminal device according to feature 5.

7. The transmission means transmits the search signal using different frequency resources in each of the plurality of beams. The detection means detects the search signal in the frequency resource after the frequency resource has been frequency-converted, thereby identifying which of the plurality of beams the search signal was detected in. The determination means determines, based on the detection result, which of the plurality of beams the relay device was detected in. The terminal device according to feature 5.

8. A control method performed by a terminal device in a wireless communication system, the system comprising: a terminal device; a base station device to which the terminal device is connected; a relay device that converts a signal of a first frequency transmitted by the terminal device to a second frequency, amplifies it, and relays it to the base station device; and a relay device that converts a signal of the second frequency transmitted by the base station device to a first frequency, amplifies it, and relays it to the terminal device, and which can use multiple frequencies as the second frequency, wherein Sending a signal for searching for the relay device at at least one of the first frequency and the second frequency, When the search signal is transmitted at the first frequency, the frequency of the search signal is converted to the second frequency, and when the search signal is transmitted at the second frequency, the frequency of the search signal is converted to the first frequency. When the frequency-converted search signal is detected, it is determined that the relay device exists, If it is determined that the relay device exists, the relay device is used as a virtual antenna to communicate with the base station equipment, A control method characterized by including

9. A program for causing a computer installed in a terminal device to execute the control method described in claim 8.

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