Communication UE, communication method, and program

Abstract

Provided is a communication UE that performs sidelink communication with another communication UE in a mode for selecting a wireless resource, the communication UE comprising: a transmission unit that transmits, to the other communication UE, first sidelink control information including information pertaining to a wireless resource that is used for the other communication UE to transmit feedback information pertaining to a channel state; and a reception unit that receives the feedback information from the other communication UE.

Description

Communication Terminal, Communication Method, and Program

[0001] The present invention relates to a communication terminal, a communication method, and a program.

[0002] V2X (Vehicle to Everything) is a vehicle communication technology that can realize network connections and mutual cooperation between vehicles, between a vehicle and a roadside unit, and between a vehicle and a pedestrian. V2X is expected to be used to support safe driving by warning a driver of hidden dangers that cannot be detected by conventional in-vehicle devices such as cameras and LiDAR.

[0003] In V2X, a transmitting device can communicate directly with a receiving device via a sidelink. Different from the Uu link (air interface between a network device and a user device) of a cellular network, a device using a sidelink communicates as follows. That is, communication is performed via a newly defined PC5 interface (air interface between V2X devices) for V2X. The frequency band used for sidelink communication is defined in the specifications of 3GPP (3rd Generation Partnership Project) (registered trademark) as Band47 (5855 MHz to 5925 MHz).

[0004] Also, in the 3GPP specifications, three types of sidelink communication forms, broadcast, unicast, and groupcast, are defined, and the forms of terminals to be communicated with are different for each. Broadcast targets all terminals within the transmission distance. Unicast targets a specific single terminal. Groupcast targets a specific plurality of terminals.

[0005] Japanese Patent No. 7230815

[0006] Situations requiring communication with specific vehicles, such as unicast or groupcast, include adaptive cruise control following other vehicles and truck platooning. When vehicles are following or platooning, each vehicle needs to maintain a constant distance from the vehicle in front. To achieve this, it is expected that each vehicle will send and receive information about its status, such as vehicle speed, accelerator, brakes, and steering, via unicast or groupcast communication.

[0007] Because V2X is intended for use in safety-related applications, high reliability is required in wireless communication, and methods are needed to reduce interference that a communicating terminal causes to other wireless communications taking place in its vicinity.

[0008] In wireless communication, techniques such as transmit power control and precoding are used to reduce interference that a communicating terminal causes to other wireless communications taking place in its vicinity. These techniques are implemented through feedback control.

[0009] Conventionally, in Uu communication compliant with the 3GPP standard, feedback information is sent and received using CSI Report. Furthermore, Patent Document 1 describes a technique for securing wireless resources for ACK / NACK transmitted by other terminals and notifying the resource information of these resources using Sidelink Control Information (SCI).

[0010] However, the technology described in Patent Document 1 focuses primarily on acquiring feedback information for retransmission control and does not consider the transmission and reception of feedback information regarding channel status between V2X terminals. Furthermore, conventionally, the transmission and reception of feedback information regarding channel status has not been implemented between terminals performing sidelink communication compliant with the 3GPP standard.

[0011] In other words, interference avoidance techniques such as transmit power control and precoding, which are implemented through feedback control of channel state, cannot be applied to unicast and groupcast communications between V2X terminals. Therefore, there is a concern that unicast and groupcast communications performed by V2X terminals may interfere with other wireless communications when other wireless communication terminals are present around V2X terminals that are following or traveling in a convoy.

[0012] The present invention has been made in view of at least one of the above-mentioned problems. One aspect of the present invention is to provide a means for sending and receiving feedback information regarding the channel state at any time in sidelink communication.

[0013] A communication device as one aspect of the present invention is a communication terminal that performs sidelink communication with another communication terminal in a mode for selecting a wireless resource, and is characterized by comprising: a transmitting unit that transmits first sidelink control information to the other communication terminal, which includes information about a wireless resource for the other communication terminal to transmit feedback information regarding the channel state; and a receiving unit that receives the feedback information from the other communication terminal.

[0014] According to one aspect of the present invention, it is possible to provide a means for sending and receiving feedback information regarding the channel state at any time in sidelink communication.

[0015] This is a diagram showing an example of the configuration of the communication system in this embodiment. This is a block diagram showing an example of the functional configuration of a terminal (UE) in this embodiment. This is a diagram showing an example of the configuration of the communication system in the first embodiment. This is a sequence diagram of the first embodiment. This is an example of the data structure of the SCI in this embodiment. This is a diagram showing an example of the allocation of feedback resources to a terminal (UE) in the first embodiment. This is an example of the data structure of the SCI in the first embodiment. This is an example of the data structure of the SCI in the first embodiment. This is a diagram showing an example of the configuration of the communication system in the second embodiment. This is a sequence diagram of the second embodiment. This is a diagram showing an example of the allocation of feedback resources to a terminal (UE) in the second embodiment. This is an example of the data structure of the SCI in the second embodiment. This is an example of the data structure of the SCI in the second embodiment. This is an example of the data structure of the SCI in the second embodiment. This is a sequence diagram of the third embodiment. This is a diagram showing an example of the allocation of feedback resources to a terminal (UE) in the third embodiment. This is an example of the data structure of the SCI in the third embodiment. This is an example of the data structure of the SCI in the third embodiment.

[0016] The following describes each embodiment in detail with reference to the attached drawings. In the following description, “number ***” in TS*** represents the Technical Specification number in the 3GPP standard. The following embodiments do not limit the invention to the claims. Multiple features are described in the embodiments, but not all of these features are essential to the invention, and the multiple features may be combined arbitrarily. Furthermore, in the attached drawings, the same or similar configurations are given the same reference numeral, and redundant descriptions are omitted. Also, the terminal is also called UE (User Equipment) and communication terminal.

[0017] (System Configuration) Figure 1 is a diagram showing an example of the system configuration of a communication device according to this embodiment. The system shown in Figure 1 may be a 5G system or a system other than 5G (for example, 5G Advanced, 6G, and 6G or later). As shown in Figure 1, terminals A101 and B102 are mounted on the vehicle that follows another vehicle. Terminals C103, D104, E105, and F106 are mounted on the vehicle that travels in a convoy. Terminals G107 and H108 are mounted on the vehicle that travels alone. Terminal A101 transmits and receives information about vehicle speed and the state of the accelerator, brakes, steering, etc., with terminal B102 using unicast communication in order to maintain a constant distance between vehicles.

[0018] Furthermore, terminal C103 transmits and receives information necessary for the formation and management of the convoy and for adjusting the distance between vehicles within the group using groupcast communication with terminals D104, E105, and F106. Terminals G107 and H108 transmit and receive information using broadcast communication to inform other vehicles of information necessary for driving. Each terminal is pre-configured with information indicating which group it belongs to (e.g., a group ID). In addition, at least terminal C103 is pre-configured with information indicating that terminals D104, E105, and F106 are included in its group (e.g., the IDs of terminals D104, E105, and F106).

[0019] (Functional Configuration of the Device) Next, the functional configuration of the communication device according to this embodiment will be described. Note that the configuration of the functional blocks described below is merely an example.

[0020] Some (and sometimes all) of the functional blocks described may be replaced by other functional blocks that perform similar functions, some functional blocks may be omitted, or further functional blocks may be added. Also, one functional block shown in the following description may be divided into multiple functional blocks, or multiple functional blocks may be integrated into one functional block. Furthermore, only some of the functional blocks may be configured in hardware, while the other functions are configured in software. When a functional block is configured in software, the processor constituting the control unit 201 described later executes a control program to realize the function stored in the storage unit 202 described later. This provides the function of that functional block.

[0021] Figure 2 is a block diagram showing an example of the functional configuration of terminals A101, B102, C103, D104, E105, and F106 in this embodiment. In Figure 2, 201 is a control unit that controls the operation of the terminal. 202 is a storage unit that stores information used by the control unit 201 for control and information related to communication. 203 is a reception quality measurement unit that measures reception quality from a reference signal received from the other terminal. 204 is a communication setting unit that performs communication settings that reflect feedback information such as channel status information reports received from the other terminal. 205 is a feedback information generation unit that generates feedback information such as channel status information reports to be transmitted to the other terminal. 206 is a feedback information processing unit that processes feedback information such as channel status information reports received from the other terminal. 207 is a wireless communication unit that sends and receives information with other terminals using sidelink communication. 208 is a control information processing unit that processes sidelink control information received by 207. The communication setting unit 204, the control information processing unit 208, and the wireless communication unit 207 are examples of a receiving unit and a transmitting unit. Furthermore, the feedback information processing unit 206 is an example of a determination unit.

[0022] [First Embodiment] (System Configuration) Figure 3 is a diagram showing an example of the configuration of the communication system in the first embodiment. As shown in Figure 3, the system is configured with terminal A101 and terminal B102. In Figure 3, the connection process for sidelink communication between the terminals has been completed, and terminal A101 is in a state where sidelink communication with terminal B102 is possible.

[0023] (Processing Example) The operation of this embodiment will be explained using the operation sequence diagram shown in Figure 4.

[0024] In Figure 4, terminals A101 and B102 are connected via Sidelink communication through their respective wireless communication units 207 (F301).

[0025] Terminal A101 is receiving SCI and receives SCI transmitted from terminals B102 to H108 (F302).

[0026] Here, SCI is defined as having a first-stage SCI and a second-stage SCI. The first-stage SCI is transmitted via PSCCH (Physical Sidelink Control Channel). The second-stage SCI is transmitted via PSSCH (Physical Sidelink Shared Channel). The first-stage SCI includes information related to PSSCH scheduling, such as frequency and time resources for PSSCH, the format of the second-stage SCI, and resource reservation information. The second-stage SCI includes information necessary for decoding PSSCH, such as information indicating the destination of the data contained in PSSCH and the HARQ (Hybrid Automatic Repeat reQuest) process number.

[0027] Figure 5 shows an example of SCI on PSCCH according to this embodiment. Specifically, Figure 5 shows 'SCI format 1-A' used in the first and second modes of V2X communication. Note that SCI format 1-A is the first stage SCI. The first mode (mode 1) is a mode in which the base station allocates (schedules) radio resources to be used for sidelink communication to the terminal. The second mode (mode 2) is a mode in which the terminal itself selects the radio resources to be used for sidelink communication from a pre-configured resource pool.

[0028] The following is an example of information transmitted in 'SCI format 1-A'.・Priority -(F01) ・Frequency resource assignment -(F02) ・Time resource assignment -(F03) ・Resource reservation period - (F04) ・DMRS pattern - (F05) ・2nd-stage SCI format - (F06) ・Beta_offset indicator - (F07) ・Number of DMRS port -(F08) ・Modulation and coding scheme -(F09) ・Additional MCS table indicator - (F10) ・PSFCH overhead indication - (F11) ・Reserved - (F12)

[0029] The PSSCH resource configuration is defined by the second to fourth fields (F02 to F04) of the SCI described above. These second to fourth fields (F02 to F04) constitute resource reservation information. Therefore, in this embodiment, available wireless resources can be identified based on the resource reservation information contained in the SCI received by the PSSCH.

[0030] In F303 of Figure 4, terminal A101 checks whether there are any available free resources based on the resource reservation information included in the SCI received from terminals B102 to H108. For example, terminal A101 selects several wireless resources that are expected to have good line quality based on the measurement results of the RSRP (Reference Signal Received Power) of unreserved resources, and then decides which wireless resource to use from among them.

[0031] In F304, terminal A101 reserves the wireless resource determined in F303 using the SCI explained with reference to Figure 5. The SCI transmitted in F304 is an example of second sidelink control information.

[0032] In F305, terminal A101, after transmitting the SCI in F304, determines whether or not feedback information regarding the channel status from terminal B102 is required. This determination may be made by setting predetermined thresholds for the received signal strength (RSSI), reference signal received power (RSRP), and / or reference signal received quality (RSRQ) of the signal received from terminal B102. RSSI stands for Received Signal Strength Indicator. RSRP stands for Reference Signal Received Power. RSRQ stands for Reference Signal Received Quality. RSSI, RSRP, and RSRQ may be SL RSSI (SideLink RSSI), PSSCH-RSRP, and PSCCH-RSRP, respectively. Alternatively, the determination may be made as long as the number of times terminal A101 transmits data to terminal B102 is below a predetermined threshold. Alternatively, the determination may be made as long as the elapsed time since terminal A101 started communicating with terminal B102 is below a predetermined threshold.

[0033] In F306, terminal A101 determines that it needs feedback information regarding the channel status from terminal B102. In this case, terminal A101 selects (allocates) a wireless resource from the wireless resources reserved in F304 for terminal B102 to transmit feedback information regarding the channel status. Terminal A101 also transmits an SCI containing information about the said wireless resource to terminal B102 (F307). This SCI is an example of first sidelink control information.

[0034] Figure 6 shows an example of the allocation of feedback resources to a terminal (UE) in the first embodiment. In Figure 6, 401 is a wireless resource that terminal A101 periodically reserved at F304 in Figure 4. Also in Figure 6, terminal A101 is assumed to have selected wireless resource 402 as the resource to transmit a reference signal. Furthermore, terminal A101 is assumed to have selected wireless resource 403, which is the resource for the next period based on the resource that transmits the reference signal, as a resource for feedback transmission for terminal B102 to transmit feedback information regarding the channel state. Note that one time interval in the time direction in Figure 6 may be one slot.

[0035] In F307, terminal A101 transmits an SCI using PSSCH that includes information identifying the terminal transmitting feedback information regarding the channel state and information identifying the radio resource used to transmit the feedback information. Specifically, the information identifying the terminal transmitting feedback information regarding the channel state may be the ID information of terminal B102. The information identifying the radio resource used to transmit the feedback information may be information related to at least one of the frequency and time of the radio resource 403 in Figure 6.

[0036] Furthermore, a Resource Reservation Indicator may be used as information to identify the wireless resource for transmitting feedback information.

[0037] Furthermore, PSCCH may be used for transmitting SCI as explained in F307.

[0038] Figures 7, 8, and 9 show examples of the data structure of the SCI in the first embodiment, transmitted via F307. Figure 7 corresponds to SCI format 2-A, which is the second-stage SCI. Figure 8 corresponds to SCI format 2-B, which is the second-stage SCI. Figure 9 corresponds to SCI format 2-C, which is the second-stage SCI. The 9th to 11th fields (F09 to F11) of this SCI define the terminal that transmits feedback information regarding the channel status and the radio resources used for transmitting the feedback. Specifically, the 'CSI feedback transmission UE ID' (F09) defines information that identifies the terminal that transmits feedback information regarding the channel status. In other words, terminal A101 uses the 'CSI feedback transmission UE ID' included in the SCI transmitted via PSSCH to identify (specify) terminal B102, which transmits feedback information regarding the channel status.

[0039] Furthermore, 'CSI feedback resource frequency assignment' (F10) defines information relating to the frequency position of the radio resource for transmitting feedback information. Also, 'CSI feedback resource time assignment' (F11) defines information relating to the time position of the radio resource for transmitting feedback information. In other words, terminal B102 can identify the radio resource 403 for transmitting feedback information based on the following included in the SCI received by PSSCH. The following are 'CSI feedback resource frequency assignment' and 'CSI feedback resource time assignment'.

[0040] Furthermore, 'CSI feedback resource frequency assignment' (F10), included in the SCI of F307, contains information indicating the frequency position of the radio resource from which feedback information is transmitted. Additionally, 'CSI feedback resource time assignment' (F11), also included in the SCI of F307, sets information indicating the time position of the radio resource to be reserved.

[0041] Furthermore, the radio resource to which terminal A101 transmits the reference signal may be predetermined to be a radio resource of the same frequency as the radio resource for transmitting feedback information, but a predetermined period earlier (for example, the previous period). In other words, terminal B102 may recognize the radio resource to which the reference signal is transmitted based on the location of the radio resource for transmitting feedback information specified in the SCI received at F307 in Figure 4. Alternatively, terminal A101 may include information to identify the radio resource to which the reference signal is transmitted in the SCI transmitted at F307 (i.e., the SCI shown in Figures 7 to 9). In other words, terminal B102 may recognize the radio resource to which the reference signal is transmitted based on the information to identify the radio resource to which the reference signal is transmitted. Returning to Figure 4, the explanation continues.

[0042] In F308, terminal A101 transmits a reference signal using the wireless resource 402. Here, the reference signal may be, for example, CSI-RS, DM-RS, or PRS. CSI-RS is an abbreviation for Channel state information-reference signal. DM-RS is an abbreviation for Demodulation Reference Signal. PRS is an abbreviation for Positioning Reference Signal. In F309, terminal B102 receives the reference signal transmitted from terminal A101 and measures information regarding reception quality. In F310, terminal B102 transmits feedback information, including the measured information regarding reception quality, to terminal A101 using the feedback transmission resource 403.

[0043] Note that the information regarding reception quality is an example of a predetermined index. Here, the feedback information may include information (e.g., terminal ID) for identifying the terminal that transmitted the feedback information.

[0044] By including information for identifying the terminal in the feedback information, even when there are multiple terminals performing unicast communication and / or terminal groups performing group cast communication, the terminal A101 can identify the terminal that is the transmission source of the feedback information.

[0045] The feedback information may further include information regarding the reception quality measured in the processing procedure of F309. Also, the feedback information may be a channel state information report (CSI report). Examples of the data structure of the channel state information report are as shown in Tables 1 to 3.

[0046]

[0047]

[0048]

[0049] As shown in Tables 1-3, information regarding reception quality may include, for example, CRI (CSI-RS resource indicator) and Channel Quality Indicator (CQI). Furthermore, information regarding reception quality may also include Rank Indicator (RI) and / or Precoding Matrix Indicator (PMI). Additionally, information regarding reception quality may include Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and / or Received Signal Strength (RSSI), which are obtained by measuring a reference signal. RSRP stands for Reference Signal Received Power. RSRQ stands for Reference Signal Received Quality. RSSI stands for Received Signal Strength Indicator. RSRP, RSRQ, and RSSI may also be PSSCH-RSRP, PSCCH-RSRP, and SL RSSI (SideLink RSSI), respectively. The information regarding received quality may also include the signal-to-interference-plus-noise ratio (SINR). The information regarding received quality may also include information for identifying the terminal that transmitted the feedback information (Feedback UE ID).

[0050] Furthermore, terminal B102 may transmit all or part of the feedback information using a Measurement Report defined in the RRC message. For example, the Measurement Report may include information regarding reception quality. More specifically, the Measurement Report may include PSSCH-RSRP, PSCCH-RSRP and / or SL RSSI (SideLink RSSI).

[0051] In F311, terminal A101 sets precoding information (performs precoding settings) based on feedback information received from terminal B102. Terminal A101 may also set the transmit power based on RSRP, etc., included in the feedback information received from terminal B102. Terminal A101 may also perform beamforming settings based on the feedback information.

[0052] Subsequently, terminal A101 transmits a signal to terminal B102 according to the precoding settings and transmit power settings, or according to the precoding settings (F312). Specifically, terminal A101 may control the transmit power of the signal transmitted to terminal B102 according to the transmit power settings. Also, when transmitting a signal, terminal A101 may perform beamforming according to the beamforming settings.

[0053] In this embodiment, the operation of sending and receiving feedback information is described, mainly using terminal A101. However, terminal B102 may also perform the same operation as terminal A101.

[0054] [Second Embodiment] In the second embodiment, the configuration of the wireless communication system, the functional configuration of the terminal device, and the data structure of the SCI on the PSCCH may be the same as those shown in Figures 1, 2, and 5, as in the first embodiment.

[0055] In the first embodiment, terminal A101 determines whether it needs feedback information regarding the channel status from terminal B102. If terminal A101 determines that it needs feedback information regarding the channel status, it selects a wireless resource from the wireless resources reserved by terminal A101 for terminal B102 to transmit the feedback information. Terminal A101 also controls the transmission of the feedback information via SCI. On the other hand, in the second embodiment, terminal C103 determines whether it needs feedback information regarding the channel status from terminals D104, E105, and F106, which are communicating via groupcast. Suppose terminal C103 determines that it needs feedback information regarding the channel status from terminals D104 and E105 among terminals D104, E105, and F106. In this case, terminal C103 selects a wireless resource from the wireless resources reserved by terminal C103 for terminals D104 and E105 to transmit the feedback information regarding the channel status, and controls the transmission of the feedback information using SCI.

[0056] Figure 10 shows an example of the configuration of the communication system in the second embodiment. The example of the communication system configuration shown in Figure 10 differs from the same figure (see Figure 3) in the first embodiment described above in that the number of terminals performing Sidelink communication is different.

[0057] In Figure 10, terminal C103 is connected to terminals D104, E105, and F106 via Sidelink communication through the wireless communication unit 207 (F301).

[0058] Terminal C103 receives SCI transmitted via PSCCH from terminals D104, E105, and F106, and identifies available wireless resources based on the resource reservation information contained in the received SCI. The method for identifying available wireless resources and the method for reserving wireless resources used by terminal C103 may be the same as the method described in F301 to F304 of Figure 4.

[0059] The operation of this embodiment will be explained using the operation sequence diagram shown in Figure 11.

[0060] In F401, terminal C103 determines whether or not feedback information regarding the channel status of terminals D104 and E105 is necessary. The method for determining whether or not feedback information regarding the channel status is necessary may be the same as the method described in F305 of Figure 4.

[0061] In F402, assume that terminal C103 determines that it needs feedback information regarding the channel status from terminals D104 and E105. In this case, terminal C103 selects a resource from among the radio resources reserved by terminal C103 for terminals D104 and E105 to transmit feedback information regarding the channel status, and notifies terminals D104 and E105 using SCI (F403).

[0062] Figure 12 shows an example of the allocation of feedback resources to terminals (UEs) in the second embodiment. The example of feedback resource allocation shown in Figure 12 differs from the same figure (see Figure 6) in the first embodiment described above in that feedback resources are allocated to multiple terminals.

[0063] In Figure 12, 501 is a radio resource periodically reserved by terminal C103. Also in Figure 12, terminal C103 selects radio resource 502 as the resource to transmit a reference signal to terminal D104. Also, terminal C103 selects radio resource 504 as the resource to transmit a reference signal to terminal E105. Furthermore, terminal C103 selects radio resource 503, which is the resource for the next cycle based on the resource that transmits the reference signal, as a resource for feedback transmission for terminal B104 to transmit feedback information regarding the channel state. Also, terminal C103 selects radio resource 505, which is the resource for the next cycle based on the resource that transmits the reference signal, as a resource for feedback transmission for terminal E105 to transmit feedback information regarding the channel state. Note that one time interval in the time direction in Figure 12 may be one slot.

[0064] In F403, terminal C103 transmits an SCI containing the following information using PSSCH. This information includes the number of terminals that transmit feedback information regarding the channel status, information identifying the terminals that transmit the feedback information, and information identifying the radio resources for transmitting the feedback information. Specifically, the information identifying the terminals that transmit feedback information regarding the channel status may be the ID information of terminal C103 and the ID information of terminal D104. The information identifying the radio resources for transmitting the feedback information may be information related to the time and frequency of radio resources 503 and 505 in Figure 12.

[0065] Furthermore, PSCCH may be used for transmitting SCI as described in F403.

[0066] Figures 13, 14, and 15 show examples of the SCI data structure in the second embodiment. The 9th to 18th fields (F09 to F18) of this SCI define the number of terminals that transmit feedback information regarding the channel status, the terminals that transmit the feedback information, and the wireless resources used to transmit the feedback information.

[0067] Figures 13, 14, and 15 differ from the same figures (see Figures 7, 8, and 9) in the first embodiment in that they include information on the number of terminals that transmit feedback information regarding the channel status. Specifically, the number of terminals that transmit feedback information regarding the channel status is defined in 'Feedback number of UE' (F09). That is, terminal C103 can use the 'Feedback number of UE' included in the SCI transmitted via PSSCH to notify how many terminals are transmitting feedback information regarding the channel status.

[0068] Furthermore, the 'CSI feedback transmission UE ID #1' (F10) defines information that identifies the first terminal to send feedback information regarding the channel status. That is, terminal C103 can identify (specify) terminal D104 to send feedback information regarding the channel status using the 'CSI feedback transmission UE ID #1' included in the SCI transmitted via PSSCH.

[0069] Furthermore, the following is defined for 'CSI feedback resource frequency assign #1' (F11) and 'CSI feedback resource time assign #1' (F12), respectively. That is, information relating to the time and frequency of the radio resource used by the first terminal that transmits feedback information regarding the channel state is defined. Terminal D104 can identify the radio resource 503 for transmitting feedback information based on the following. The following refers to 'CSI feedback resource frequency assign #1' and 'CSI feedback resource time assign #1' included in the SCI received by PSSCH.

[0070] Furthermore, the 'CSI feedback transmission UE ID #2' (F13) defines information that identifies the second terminal to which feedback information regarding the channel status will be sent. In other words, terminal C103 can use the 'CSI feedback transmission UE ID #2' included in the SCI transmitted via PSSCH to identify (specify) terminal E105 to which feedback information regarding the channel status will be sent.

[0071] Furthermore, the following is defined in 'CSI feedback resource frequency assignment #2' (F14). The following is defined in 'CSI feedback resource time assignment #2' (F15). The following are information relating to the time and frequency of the radio resource used by the second terminal that transmits feedback information regarding the channel state. That is, terminal E105 can identify the radio resource 505 for transmitting feedback information based on the following. The following are 'CSI feedback resource frequency assignment #2' and 'CSI feedback resource time assignment #2' included in the SCI received by PSSCH.

[0072] Furthermore, the radio resource to which terminal C103 transmits the reference signal may be predetermined to be a radio resource of the same frequency as the radio resource for transmitting feedback information, but a predetermined period earlier (for example, the previous period). In other words, terminals D104 and E105 may recognize the radio resource to which the reference signal is transmitted based on the location of the radio resource for transmitting feedback information specified in the SCI received at F403 in Figure 11. Alternatively, terminal C103 may include information to identify the radio resource to which the reference signal is transmitted in the SCI transmitted at F408 (i.e., the SCI shown in Figures 13 to 15). In other words, terminals D104 and E105 may recognize the radio resource to which the reference signal is transmitted based on information to identify the radio resource to which the reference signal is transmitted. Returning to Figure 11, the explanation continues.

[0073] In F404, terminal C103 transmits a reference signal using wireless resource 502. Here, the reference signal may be the same type of signal as described in F308 of Figure 4.

[0074] In step F405, terminal D104 receives a reference signal transmitted from terminal C103 and measures information regarding reception quality. In step F406, terminal D104 transmits feedback information, including the measured reception quality information, to terminal C103 using the feedback transmission resource 503. Here, the measured reception quality information may be the same as the information described in step F310 of Figure 4.

[0075] Furthermore, the feedback information may also be a Channel Status Information Report (CSI report). Examples of the data structure of a Channel Status Information Report are shown in Tables 4 to 6.

[0076]

[0077]

[0078]

[0079] Furthermore, the data structure of the channel status information report differs from that of the first embodiment in that it includes information for identifying the terminal group performing groupcast communication (Feedback Group ID).

[0080] By including information to identify the terminal group in the feedback information, terminal C103 can identify the group that sent the feedback information, even if there are multiple terminal groups performing groupcast communication. Furthermore, by including information to identify the terminals within the group in the feedback information, terminal C103 can do the following: it can identify the terminal that has determined that feedback information regarding the channel status is necessary, that is, the terminal among terminals D104 and E105 that was unable to correctly receive the feedback information.

[0081] In F407, terminal C103 sets precoding information (performs precoding settings) based on feedback information received from terminal D104. Terminal C103 may also set the transmit power based on RSRP, etc., included in the feedback information received from terminal D104. Terminal C103 may also set the beamforming settings based on the feedback information.

[0082] Subsequently, terminal C103 transmits a signal to terminal D104 according to the precoding settings and transmit power settings, or according to the precoding settings (F408). Specifically, terminal C103 may control the transmit power of the signal to be transmitted to terminal D104 according to the transmit power settings. Also, when transmitting a signal, terminal C103 may perform beamforming according to the beamforming settings.

[0083] In F409, terminal C103 transmits a reference signal using wireless resource 504. Here, the reference signal may be the same type of signal as described in F308 of Figure 4.

[0084] In F410, terminal E105 receives a reference signal transmitted from terminal C103 and measures information regarding reception quality. In F411, terminal E105 transmits feedback information, including the measured reception quality information, to terminal C103 using the feedback transmission resource 505. Here, the measured reception quality information may be the same as the information described in F310 of Figure 4.

[0085] In F412, terminal C103 sets precoding information (performs precoding settings) based on feedback information received from terminal E105. Terminal C103 may also set the transmit power based on RSRP, etc., included in the feedback information received from terminal E105. Terminal C103 may also set the beamforming settings based on the feedback information.

[0086] Subsequently, terminal C103 transmits a signal to terminal E105 according to the precoding settings and transmit power settings, or according to the precoding settings (F413). Specifically, terminal C103 may control the transmit power of the signal to be transmitted to terminal E105 according to the transmit power settings. Also, when transmitting a signal, terminal C103 may perform beamforming according to the beamforming settings.

[0087] As a result, terminal C103 can select terminals D104 and E105 from among terminals D104, E105, and F106 that are communicating via Groupcast, and send and receive feedback information between these two terminals.

[0088] In this embodiment, the operation of sending and receiving feedback information is described, mainly using terminal C103. However, terminals D104, E105, and F106 may also be configured to perform the same operations as terminal C103. Furthermore, in this embodiment, terminal C103 selects terminals D104 and E105 to control the transmission of feedback information, but this is not limited to this. That is, instead of selecting some of the terminals communicating in groupcast to perform feedback control, all terminals, including terminals D104, E105, and F106, may be selected to perform feedback control.

[0089] In this embodiment, precoding is used for processing after sending and receiving feedback information in groupcast communication, that is, for communication settings that reflect the feedback information. However, a method that does not perform precoding may also be adopted. For example, methods that do not perform precoding may include transmit power control or beamforming.

[0090] [Third Embodiment] In the third embodiment, the configuration of the wireless communication system, the functional configuration of the terminal device, and the data structure of the SCI on the PSCCH may be the same as those shown in Figures 1, 2, and 5, as in the first and second embodiments. Furthermore, the configuration of the wireless communication system may be the same as that shown in Figure 10, as in the second embodiment.

[0091] In the third embodiment, terminal C103 determines whether ACK or NACK feedback information regarding the decoding results of received data from terminals D104, E105, and F106, which are communicating via groupcast, is necessary. Let's assume that terminal C103 determines that ACK or NACK feedback information regarding the decoding results of received data from terminals D104 and E105 is necessary.

[0092] In this case, terminal C103 selects a wireless resource from among the wireless resources reserved by its terminal for terminals D104 and E105 to transmit the ACK or NACK feedback information, and controls the transmission of the feedback information via SCI.

[0093] The configuration of the communication system in the third embodiment is the same as that shown in the figure of the second embodiment described above (see Figure 10). That is, in Figure 10, terminal C103 is connected to terminals D104, E105, and F106 via Sidelink communication through the wireless communication unit 207.

[0094] Terminal C103 receives SCI transmitted via PSCCH from terminals D104, E105, and F106, and identifies available wireless resources based on the resource reservation information contained in the received SCI. The method for identifying available wireless resources and the method for reserving wireless resources used by terminal C103 may be the same as the method described in F301 to F304 of Figure 4.

[0095] The operation of this embodiment will be explained using the operation sequence diagram shown in Figure 16.

[0096] In F501, terminal C103 determines whether ACK or NACK feedback information is required regarding the decoding results of data received from terminals D104, E105, and F106. This determination may be made, for example, by determining whether the cast type when terminal C103 transmits data is unicast or groupcast. Alternatively, it may be determined by setting a predetermined threshold for the priority of the data that terminal C103 plans to transmit in unicast or groupcast communication. For example, terminal C103 may determine that ACK or NACK feedback information is required if the priority is above a predetermined threshold.

[0097] In F502, it is assumed that terminal C103 has determined that ACK or NACK feedback information regarding the decoding results of the received data from terminals D104 and E105 is necessary.

[0098] In this case, terminal C103 selects a resource for transmitting ACK or NACK feedback information from among the wireless resources reserved by terminal C103, and notifies terminals D104 and E105 using SCI (F503).

[0099] Figure 17 shows an example of the allocation of feedback resources to a terminal (UE) in the third embodiment. The example of feedback resource allocation shown in Figure 17 differs from the second embodiment in that the wireless resources immediately after data transmission to the designated terminal are allocated as feedback resources.

[0100] In Figure 17, 601 is a wireless resource periodically reserved by terminal C103. Also in Figure 17, terminal C103 selects wireless resources 602 and 604, respectively, as wireless resources to transmit data to designated terminals D104 and E105. Furthermore, terminal C103 selects wireless resources 603 and 605, which will be the resources for the next cycle based on the resource to which data is transmitted, as resources to which terminals D104 and E105 transmit ACK or NACK feedback information, respectively.

[0101] In F503, terminal C103 transmits an SCI using PSSCH that includes the following: information on the number of terminals transmitting ACK or NACK feedback information, information identifying the terminals transmitting the feedback information, and information identifying the wireless resources for transmitting the feedback information.

[0102] Furthermore, PSCCH may be used for transmitting the SCI as described above.

[0103] Figures 18, 19, and 20 show examples of the data structure of the SCI in the third embodiment. The 9th to 18th fields (F09 to F18) of this SCI define the following: the number of terminals that transmit ACK or NACK feedback information regarding the decoding result of the received data, the terminals that transmit the feedback information, and the wireless resources used to transmit the feedback information.

[0104] Figures 18, 19, and 20 differ from the second embodiment in that, instead of including a field defining a radio resource for transmitting ACK or NACK feedback information, they include a field defining a radio resource for transmitting ACK or NACK feedback information. The 'Feedback number of UE' (F09) of the SCI described above defines the number of terminals to which ACK or NACK feedback information regarding the decoding result of the received data is transmitted. That is, terminal C103 can use the 'Feedback number of UE' included in the SCI transmitted via PSSCH to notify how many terminals are transmitting ACK or NACK feedback information regarding the decoding result of the received data.

[0105] Furthermore, the ACK / NACK feedback transmission UE ID #1 (F10) defines information that identifies the first terminal to transmit ACK or NACK feedback information. That is, terminal C103 can identify (specify) terminal D104 to transmit ACK or NACK feedback information regarding the decoding result of the received data using the following. The following is the ACK / NACK feedback transmission UE ID #1 included in the SCI transmitted by PSSCH.

[0106] Furthermore, the following is defined in 'ACK / NACK feedback resource frequency assignment #1' (F11). This refers to information relating to the time and frequency of the radio resource used by the first terminal transmitting ACK or NACK feedback information. Furthermore, the following is defined in 'ACK / NACK feedback resource time assignment #1' (F12). This refers to information relating to the time and frequency of the radio resource used by the first terminal transmitting ACK or NACK feedback information. In other words, terminal D104 can identify the radio resource 603 for transmitting feedback information based on the following. The following is 'ACK / NACK feedback resource frequency assignment #1' included in the SCI received by PSSCH. Furthermore, the following is 'ACK / NACK feedback resource time assignment #1'.

[0107] Furthermore, the 'ACK / NACK feedback transmission UE ID #2' (F13) defines information that identifies a second terminal that transmits ACK or NACK feedback information regarding the decoding result of the received data. That is, terminal C103 can identify (specify) terminal E105 that transmits ACK or NACK feedback information regarding the decoding result of the received data using the following. The following is the 'ACK / NACK feedback transmission UE ID #2' included in the SCI transmitted by PSSCH.

[0108] Furthermore, the following is defined in 'ACK / NACK feedback resource frequency assignment #2' (F14): This refers to information relating to the time and frequency of the radio resources used by the second terminal that transmits ACK or NACK feedback information regarding the decoding result of the received data. The following is defined in 'ACK / NACK feedback resource time assignment #2' (F15): This refers to information relating to the time and frequency of the radio resources used by the second terminal that transmits ACK or NACK feedback information regarding the decoding result of the received data. In other words, terminal E105 can identify the radio resource 505 for transmitting feedback information based on the following. The following is 'ACK / NACK feedback resource frequency assignment #2' included in the SCI received by PSSCH. Furthermore, the following is 'ACK / NACK feedback resource time assignment #2'. Return to Figure 16 and continue the explanation.

[0109] In F504, terminal C103 transmits the SCI and data to designated terminal D104 using the PSSCH via the wireless resource 502. Here, the SCI transmitted by terminal C103 may be the same as the SCI shown in Figure 18, Figure 19, or Figure 20 described above. At this time, terminal D104 can identify that the data is intended for terminal D104 based on the 'Destination ID' (F505) included in the SCI received via the PSSCH.

[0110] In F505, terminal D104 receives data transmitted from terminal C103 and attempts to decode the data. Subsequently, terminal D104 transmits ACK or NACK feedback information regarding the decoded result of the received data to terminal C103 using the feedback transmission resource 603 (F506). Here, the ACK or NACK feedback information regarding the decoded result of the received data may include information for identifying the terminal that sent the feedback information (e.g., terminal ID). Also, similar to the second embodiment described above, it may include information for identifying the terminal group performing groupcast communication (e.g., group ID) and information for identifying terminals within the group (e.g., terminal ID).

[0111] By including information to identify the terminal group in the feedback information, terminal C103 can identify the group that sent the feedback information, even if there are multiple terminal groups performing groupcast communication. Furthermore, by including information to identify terminals within the group in the feedback information, terminal C103 can do the following: it can identify terminals that have determined that ACK or NACK feedback information regarding the decoding result of the received data is necessary, i.e., terminals D104 and E105 that were unable to correctly receive the feedback information.

[0112] When F506 receives feedback information, terminal C103 makes a decision to retransmit based on the feedback information received from terminal D104 (F507).

[0113] In F507, if terminal C103 receives feedback information from terminal D104 that is NACK, it retransmits the data sent to terminal D104 via wireless resource 602 (F508).

[0114] In F509, terminal C103 transmits the SCI and data to designated terminal E105 via the PSSCH using the wireless resource 604. Here, the SCI transmitted by terminal C103 may be the same as the SCI in Figure 18, Figure 19, or Figure 20 described above. At this time, terminal E105 can identify that the data is intended for terminal E105 based on the 'Destination ID' (F505) contained in the SCI received by the PSSCH.

[0115] In F510, terminal E105 receives data transmitted from terminal C103 and attempts to decode the data. Subsequently, terminal E105 transmits ACK or NACK feedback information regarding the decoded result of the received data to terminal C103 using the feedback transmission resource 605 (F511).

[0116] When F511 receives feedback information, terminal C103 makes a decision to retransmit based on the feedback information received from terminal E105 (F512).

[0117] In F512, if terminal C103 receives feedback information from terminal E105 that is NACK, it retransmits the data that it sent to terminal E105 using wireless resource 604 (F513).

[0118] As a result, terminal C103 can select terminals D104 and E105 from among terminals D104, E105, and F106 that are communicating via Groupcast, and send and receive feedback information between these two terminals.

[0119] In this embodiment, the operation of sending and receiving feedback information is described, mainly using terminal C103. However, terminals D104, E105, and F106 may also be configured to perform the same operations as terminal C103. Furthermore, in this embodiment, terminal C103 selects terminals D104 and E105 to control the transmission of feedback information, but this is not limited to this. That is, instead of selecting some of the terminals communicating in groupcast to perform feedback control, all terminals, including terminals D104, E105, and F106, may be selected to perform feedback control.

[0120] [Other Embodiments] The present invention may also involve supplying a recording medium containing program code for software that realizes the above-described functions to a system or device, and having the computer (CPU, MPU) of the system or device read and execute the program code stored on the recording medium. In this case, the program code read from the storage medium itself realizes the functions of the above-described embodiments, and the storage medium containing that program code constitutes the present invention.

[0121] For storing program code, storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, ROMs, and DVDs can be used.

[0122] Furthermore, the aforementioned functions may be realized not only by the computer executing the program code it reads, but also by the operating system (OS) running on the computer performing some or all of the actual processing based on the instructions of that program code. OS stands for Operating System.

[0123] Furthermore, the program code read from the storage medium is written to the memory of a function expansion board inserted into the computer or a function expansion unit connected to the computer. Then, based on the instructions of that program code, the CPU of the function expansion board or function expansion unit may perform some or all of the actual processing to realize the aforementioned functions.

[0124] The present invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are attached to make the scope of the invention public.

[0125] This application claims priority based on Japanese Patent Application No. 2024-160513, filed on 17 September 2024, and all of its contents are incorporated herein by reference.

Claims

1. A communication terminal that performs sidelink communication with another communication terminal in a mode for selecting a wireless resource, comprising: a transmitting unit that transmits to the other communication terminal first sidelink control information, which includes information about a wireless resource for the other communication terminal to transmit feedback information regarding the channel state; and a receiving unit that receives the feedback information from the other communication terminal.

2. The communication terminal according to claim 1, characterized in that the transmitting unit transmits information relating to the radio resource, which includes at least one of the frequency of the radio resource and the time of the radio resource.

3. The communication terminal according to claim 1 or 2, characterized in that the transmitting unit includes the ID information of the other communication terminal that transmits the feedback information in the first side link control information.

4. The communication terminal according to any one of claims 1 to 3, characterized in that the receiving unit receives the feedback information which includes the ID information of the other communication terminal.

5. The communication terminal according to any one of claims 1 to 4, characterized in that the receiving unit receives the feedback information including terminal group ID information of the other communication terminal.

6. The communication terminal according to any one of claims 1 to 5, characterized in that the transmitting unit includes in the first side link control information the number of other communication terminals that transmit the feedback information.

7. The communication terminal according to any one of claims 1 to 6, characterized in that the transmitting unit selects and allocates the wireless resource for the other communication terminal to transmit the feedback information from among the reserved wireless resources.

8. A communication terminal according to any one of claims 1 to 7, wherein after transmitting second sidelink control information including information indicating that the wireless resources used by the communication terminal are reserved, the transmission unit has a determination unit that determines whether or not the feedback information is required from the other communication terminal, and the transmission unit transmits the first sidelink control information to the other terminal when the determination unit determines that the feedback information is required from the other communication terminal.

9. The receiving unit receives the feedback information via the wireless resource used by the other communication terminal to transmit the feedback information, according to any one of claims 1 to 8.

10. The communication terminal according to any one of claims 1 to 9, characterized in that the transmitting unit selects a radio resource that is available at a later time than the radio resource that transmits a reference signal to the other communication terminal as the radio resource for the other communication terminal to transmit the feedback information.

11. The communication terminal according to claim 10, wherein the receiving unit receives the measurement result of the reference signal as feedback information from the other communication terminal.

12. The receiving unit receives feedback information from the other communication terminal, which includes information identifying the other communication terminal that transmitted the feedback information, according to any one of claims 1 to 11.

13. A communication method performed by a communication terminal that performs sidelink communication with another communication terminal in a mode for selecting a wireless resource, comprising the steps of: transmitting first sidelink control information to the other communication terminal, which includes information about a wireless resource for which the other communication terminal transmits feedback information regarding the channel state; and receiving the feedback information from the other communication terminal.

14. A program for causing a communication terminal that performs sidelink communication with another communication terminal in a mode that selects a wireless resource to transmit first sidelink control information to the other communication terminal, which includes information about the wireless resource for which the other communication terminal transmits feedback information regarding the channel state; and receiving the feedback information from the other communication terminal.

15. A communication terminal that performs sidelink communication with another communication terminal in a mode for selecting a wireless resource, comprising: a receiving unit that receives first sidelink control information from the other communication terminal, which includes information about a wireless resource for transmitting feedback information regarding the channel state; and a transmitting unit that transmits the feedback information to the other communication terminal.

16. The communication terminal according to claim 15, characterized in that the receiving unit receives information relating to the radio resource, which includes at least one of the frequency of the radio resource and the time of the radio resource.

17. The communication terminal according to claim 15 or 16, characterized in that the receiving unit receives the first sidelink control information which includes the ID information of the communication terminal transmitting the feedback information.

18. The communication terminal according to any one of claims 15 to 17, characterized in that the transmitting unit transmits the feedback information including the ID information of the communication terminal.

19. The communication terminal according to any one of claims 15 to 18, characterized in that the transmitting unit transmits the feedback information including the terminal group ID information of the communication terminal.

20. The communication terminal according to any one of claims 15 to 19, characterized in that the receiving unit receives the first sidelink control information, which includes the number of communication terminals that transmit the feedback information.

21. The communication terminal according to any one of claims 15 to 20, wherein the transmitting unit transmits the feedback information via the wireless resource for the communication terminal to transmit the feedback information.

22. The communication terminal according to any one of claims 15 to 21, wherein the transmitting unit transmits the measurement result of the reference signal received from the other communication terminal to the other communication terminal as feedback information.

23. The communication terminal according to any one of claims 15 to 22, wherein the transmitting unit transmits the feedback information, which includes information identifying the communication terminal that transmits the feedback information, to the other communication terminal.

24. A communication method performed by a communication terminal that performs sidelink communication with another communication terminal in a mode for selecting a wireless resource, comprising: a receiving step of receiving first sidelink control information from the other communication terminal, which includes information about a wireless resource for transmitting feedback information regarding the channel state; and a transmitting step of transmitting the feedback information to the other communication terminal.

25. A program for causing a communication terminal to perform sidelink communication with another communication terminal in a mode that selects a wireless resource to receive first sidelink control information from the other communication terminal, which includes information about a wireless resource for transmitting feedback information about the channel state; and a program for causing a communication terminal to perform sidelink communication with another communication terminal in a mode that selects a wireless resource to perform sidelink communication with the other communication terminal to perform sidelink communication with the other communication terminal to transmit the feedback information.

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