Communication terminal, communication device, and program

Abstract

This communication terminal is for sidelink communication with another communication terminal, and comprises: a reception means for receiving a reference signal included in the sidelink communication; a calculation means for calculating a predetermined index on the basis of the reference signal; and a transmission means for transmitting feedback information to the other communication terminal when a cast type included in control information received in the sidelink communication is group cast.

Description

Communication terminal, communication device and program

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

[0002] V2X (Vehicle to Everything) is a vehicle communication technology that enables network connections and interoperability between vehicles, vehicles and roadside devices, and vehicles and pedestrians. V2X is expected to be used to support safe driving by alerting drivers to hidden dangers that cannot be detected by conventional in-vehicle devices such as cameras and LiDAR.

[0003] In V2X, a transmitter can communicate directly with a receiver via a sidelink. Unlike the Uu link (air interface between a network device and a user device) of a cellular network, sidelink communication is performed via a newly defined PC5 interface (air interface between V2X devices) for V2X. The frequency band used for V2X communication is defined as Band 47 (5855 MHz to 5925 MHz) in the 3GPP (3rd Generation Partnership Project) (registered trademark) specifications.

[0004] The 3GPP specifications define three types of sidelink communication formats: broadcast, unicast, and groupcast, each of which targets different types of terminals. Broadcast targets all terminals within a transmission distance, unicast targets one specific terminal, and groupcast targets multiple specific terminals.

[0005] Among these, GroupCast is expected to be used in vehicle platooning. When vehicles are platooning, the formation and management of the platoon and the adjustment of vehicle spacing within the platoon are carried out while driving, and the information required for this is exchanged between devices within the platoon via GroupCast communication.

[0006] Because V2X is expected to be used for safety-related applications, high reliability is required in wireless communications, and there is a demand for a method to reduce the interference that a communicating terminal causes to other wireless communications taking place in the vicinity of the terminal itself.

[0007] In wireless communication, methods such as transmission power control and precoding are used to reduce interference caused by a communicating terminal to other wireless communications taking place in the vicinity of the terminal. These methods are realized by feedback control.

[0008] Special Publication No. 2022-526741

[0009] Conventionally, in Uu communication conforming to the 3GPP standard, for example, feedback information is transmitted and received using a CSI report (channel state information report). Furthermore, Patent Literature 1 describes a technique in which a first device transmits a CSI report to a second device based on a reference signal in sidelink communication.

[0010] However, Patent Document 1 describes a technique related to unicast communication and does not consider sending and receiving feedback information via groupcast. Furthermore, in the past, sending and receiving feedback information via groupcast has not been implemented between terminals that comply with the 3GPP standard.

[0011] Therefore, in groupcast, it is not possible to apply interference avoidance techniques such as transmission power control and precoding, which are realized by feedback control.As a result, when other wireless communication terminals are present around a V2X terminal traveling in a convoy, there is a concern that groupcast communication performed by the V2X terminal may interfere with other wireless communication terminals.

[0012] In view of the above-described problems, the present invention aims to provide a mechanism for transmitting and receiving feedback information in groupcast communication performed by a V2X terminal.

[0013] The communication device of the present invention that achieves the above-mentioned object is a communication terminal that performs sidelink communication with another communication terminal, and is characterized by comprising: a receiving means for receiving a reference signal included in the sidelink communication; a calculating means for calculating a predetermined indicator based on the reference signal; and a transmitting means for transmitting feedback information including the predetermined indicator to the other communication terminal when the cast type included in the control information received in the sidelink communication is groupcast.

[0014] According to the present invention, it is possible to provide a mechanism for transmitting and receiving feedback information in groupcast communication performed by V2X terminals.

[0015] It is a diagram showing an example of the configuration of a communication system in this embodiment. It is a diagram showing an example of the configuration of a communication system in this embodiment. It is a block diagram showing an example of the functional configuration of a terminal (UE) in this embodiment. It is a sequence diagram of a first embodiment. It is an example of the data structure of SCI.

[0016] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0017] [First embodiment] (System configuration) Fig. 1 is a diagram showing an example of the system configuration of a communication device according to this embodiment. As shown in Fig. 1, the system is made up of terminal A 101, terminal B 102, terminal C 103, and terminal D 104. In Fig. 1, connection processing for Sidelink communication between terminals (UEs, communication terminals) has been completed, and terminal A 101 is in a state where Sidelink communication is possible between terminal B 102, terminal C 103, and terminal D 104.

[0018] As shown in Fig. 2, in this embodiment, terminal A101, terminal B102, terminal C103, and terminal D104 are mounted on vehicles traveling in a convoy. Terminal A101 transmits and receives information necessary for organizing and managing the convoy and for adjusting inter-vehicle distances between terminals B102, C103, and D104 using groupcast communication. It is assumed that information indicating which group each terminal belongs to (e.g., a group ID) is set in advance for each terminal. It is also assumed that information indicating that terminal B102, terminal C103, and terminal D104 are included in at least terminal A101's group (e.g., the IDs of terminal B102, terminal C103, and terminal D104) is set in advance for at least terminal A101.

[0019] (Functional Configuration of Device) Next, the functional configuration of the communication device according to this embodiment will be described with reference to Fig. 3. Note that the configuration of the functional blocks described below is merely an example.

[0020] Some (or in some cases all) of the functional blocks described below may be replaced with other functional blocks that perform similar functions, some functional blocks may be omitted, or additional functional blocks may be added. Furthermore, one functional block described below 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, with the remaining functions configured in software. When the functional blocks are configured in software, a processor constituting the control unit 201 described below executes a control program for realizing the functions stored in the storage unit 202 described below. This provides the functions of each functional block.

[0021] FIG. 3 is a block diagram showing an example of the functional configuration of terminal A101, terminal B102, terminal C103, and terminal D104 in this embodiment. In FIG. 3, 201 denotes a control unit that controls the operation of the terminals. 202 denotes a storage unit that stores information used by the control unit 201 for control and information related to communication. 203 denotes a reception quality measurement unit that measures reception quality from a reference signal received from a remote terminal. 204 denotes a communication setting unit that performs communication setting reflecting feedback information such as a channel state information report received from the remote terminal. 205 denotes a feedback information generation unit that generates feedback information such as a channel state information report to be transmitted to the remote terminal. 206 denotes a feedback information processing unit that processes feedback information such as a channel state information report received from the remote terminal. 207 denotes a wireless communication unit that transmits and receives information to and from other terminals using side link communication. 208 denotes a control information processing unit that processes side link control information received by 207. The communication setting unit, control information processing unit, and wireless communication unit are examples of a receiving means and a transmitting means. The reception quality measurement unit is an example of a calculating means.

[0022] (Processing Example) The operation of this embodiment will be described using the operation sequence diagram shown in Fig. 4. In Fig. 4, terminal A101 is connected to terminal B102, terminal C103, and terminal D104 by Sidelink communication via wireless communication unit 207 (F301).

[0023] Terminal A101 transmits sidelink control information (hereinafter, SCI), and terminal B102, terminal C103, and terminal D104 receive the SCI transmitted from terminal A101 (F302).

[0024] Here, the SCI defines a first stage SCI (1st-stage SCI) and a second stage SCI (2nd-stage SCI). The first stage SCI is transmitted on a PSCCH (Physical Sidelink Control Channel). The second stage SCI is transmitted on a PSSCH (Physical Sidelink Shared Channel). The first stage SCI includes information on scheduling of the PSSCH, such as the frequency and time resources of the PSSCH, the format of the second stage SCI, and information on resource reservation. The second stage SCI includes information indicating the destination of data included in the PSSCH, information necessary for decoding the PSSCH, such as a HARQ (Hybrid Automatic Repeat reQuest) process number, etc.

[0025] FIG. 5 is a diagram illustrating an example of SCI on a PSSCH according to an embodiment of the present invention. Specifically, FIG. 5 illustrates 'SCI format 2-A' used in the first and second modes of V2X communication. Note that SCI format 2-A is second-stage SCI. The first mode is a mode in which a base station allocates (schedules) radio resources to be used for sidelink communication to a terminal. The second mode is a mode in which the terminal itself selects radio resources to be used for sidelink communication from a pre-configured resource pool.

[0026] An example of 'SCI format 2-A' is shown below. In HARQ operation, SCI format 2-A is used for decoding PSSCH in the following cases: when HARQ-ACK information includes ACK or NACK, when HARQ-ACK information includes only NACK, or when there is no feedback of HARQ-ACK information.

[0027] The following information is transmitted using SCI format 2-A: HARQ process number - 4 bits, New Data indicator - 1 bit, Redundancy version - 2 bits, Source ID - 8 bits, Destination ID - 16 bits, HARQ feedback enabled / disabled indicator - 1 bit, Cast type indicator - 2 bits, and CSI request - 1 bit.

[0028] The cast type is defined in the 'Cast type indicator' (F07) of the SCI described above. That is, terminal B102, terminal C103, and terminal D104 can identify the cast type of data transmitted by terminal A101 based on the 'Cast type indicator' included in the SCI received via the PSSCH. Returning to Fig. 4, the explanation will be continued. The cast type is set to one of unicast, groupcast, and broadcast.

[0029] In F303, when terminal B102, terminal C103, and terminal D104 determine that the cast type of the data transmitted by terminal A101 is groupcast (F303), they perform the following. That is, they receive the reference signal transmitted from terminal A101 and measure information related to reception quality (F304). The reference signal may be, for example, a CSI-RS (Channel State Information-Reference Signal) or a DM-RS (Demodulation Reference Signal). Terminal B102, terminal C103, and terminal D104 transmit feedback information including information related to the measured reception quality to terminal A101 (F305). Note that the information related to reception quality is an example of a predetermined index.

[0030] Here, the feedback information may include information for identifying a terminal group performing groupcast communication (e.g., a group ID). The feedback information may further include information for identifying a terminal in the group (e.g., a terminal ID) and information related to the reception quality measured in the processing procedure of F305. The feedback information may also be a channel state information report (CSI report). Examples of the data structure of a channel state information report are shown in Tables 1 to 3.

[0031]

[0032]

[0033]

[0034] As shown in Tables 1 to 3, the information on reception quality may include, for example, a CRI (CSI-RS resource indicator) and a signal quality indicator (CQI: Channel Quality Indicator). The information on reception quality may further include a rank indicator (RI: Rank indicator) and / or a precoding matrix indicator (PMI: Precoding matrix indicator). The information on reception quality may also include reference signal received power (RSRP), reference signal received quality (RSRQ), and / or received signal strength (RSSI), which are obtained by measuring the reference signal. RSRP is an abbreviation for Reference Signal Received Power. RSRQ is an abbreviation for Reference Signal Received Quality. RSSI is an abbreviation for Received Signal Strength Indicator. RSRP, RSRQ, and RSSI may be PSSCH-RSRP, PSCCH-RSRP, and SL RSSI (SideLink RSSI), respectively. In addition, the information on reception quality may include a signal-to-interference-plus-noise ratio (SINR).

[0035] Terminal B102, terminal C103, and terminal D104 may transmit feedback information to terminal A101 using a MAC CE (Medium Access Control Element) transmitted on a PSSCH. Alternatively, terminal B102, terminal C103, and terminal D104 may transmit feedback information to terminal A101 using a PSFCH (Physical Sidelink Feedback Channel).

[0036] Furthermore, terminal B102, terminal C103, and terminal D104 may transmit all or part of the feedback information using a measurement report (Measurement Report) specified in an RRC message. For example, the measurement report may include information on reception quality. More specifically, the measurement report may include PSSCH-RSRP, PSCCH-RSRP, and / or SL RSSI (SideLink RSSI). Furthermore, in addition to information on reception quality, the measurement report may include information for identifying a terminal group performing groupcast communication (e.g., a group ID) and information for identifying a terminal within the group (e.g., a terminal ID).

[0037] By including information for identifying the terminal group in the feedback information, terminal A101 can identify the group that is the sender of the feedback information even if there are multiple terminal groups performing groupcast communication. Furthermore, by including information for identifying a terminal within the group in the feedback information, terminal A101 can do the following: Namely, it can identify the terminal that was unable to receive the feedback information among all terminals performing groupcast communication, i.e., terminal B102, terminal C103, and terminal D104.

[0038] Upon receiving the feedback information in F305, terminal A101 sets precoding information based on the feedback information received from each terminal (performs precoding configuration). Terminal A101 may also perform transmission power configuration based on RSRP or the like included in the feedback information received from each terminal (F306). Terminal A101 may also perform beamforming configuration based on the feedback information.

[0039] Thereafter, terminal A101 transmits signals to terminal B102, terminal C103, and terminal D104 in accordance with the precoding setting, transmission power setting, and / or precoding setting (F307). At this time, terminal A101 may transmit precoded signals to terminal B102, terminal C103, and terminal D104 in accordance with the precoding setting. Terminal A101 may also control the transmission power of signals to be transmitted to terminal B102, terminal C103, and terminal D104 in accordance with the transmission power setting. Terminal A101 may also perform beamforming in accordance with the beamforming setting when transmitting signals.

[0040] In this embodiment, the operation is described in the case where terminal A101 mainly transmits and receives feedback information, but terminal B102, terminal C103, and terminal D104 may also perform the same operation as terminal A101. Also, in this embodiment, terminal B102, terminal C103, and terminal D104 transmit feedback information, but this is not limited to this. In other words, instead of all of terminal B102, terminal C103, and terminal D104 transmitting feedback information, some of the terminals performing groupcast communication may transmit feedback information.

[0041] In this embodiment, terminal A101 receives all of the feedback information transmitted by terminal B102, terminal C103, and terminal D104, but this is not limiting. In this embodiment, terminal A101 may receive feedback information only from some of the terminals that are performing groupcast communication, rather than receiving feedback information from all of the terminals.

[0042] The above process enables terminal A101 to transmit and receive feedback information to and from terminal B102, terminal C103, and terminal D104 with which it is performing groupcast communication.

[0043] [Other Embodiments] The present invention may be configured such that a recording medium on which program code for software that realizes the above-described functions is recorded is supplied to a system or device, and a computer (CPU, MPU) of the system or device reads and executes the program code stored on the recording medium. In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiments, and the recording medium on which the program code is stored constitutes the present invention.

[0044] Examples of storage media that can be used to supply the program code include flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, ROMs, and DVDs.

[0045] Furthermore, the above-mentioned functions may be realized not only by the computer executing the read program code, but also by the OS running on the computer performing some or all of the actual processing based on the instructions of the program code. OS is an abbreviation for Operating System.

[0046] Furthermore, the program code read from the storage medium may be written to a memory provided in a function expansion board inserted into a computer or a function expansion unit connected to the computer, and a CPU provided in the function expansion board or function expansion unit may then perform some or all of the actual processing based on the instructions of the program code to realize the above-mentioned functions.

[0047] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0048] This application claims priority based on Japanese Patent Application No. 2024-101011, filed June 24, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A communication terminal that performs sidelink communication with another communication terminal, comprising: a receiving means for receiving a reference signal included in the sidelink communication; a calculating means for calculating a predetermined indicator based on the reference signal; and a transmitting means for transmitting feedback information including the predetermined indicator to the other communication terminal when the cast type included in control information received in the sidelink communication is groupcast.

2. A communication terminal that performs sidelink communication with another communication terminal, comprising: a transmitting means that transmits control information including information indicating that the cast type is groupcast and a reference signal to the other communication terminal through the sidelink communication; and a receiving means that receives feedback information including a predetermined indicator included in the sidelink communication from the other communication terminal.

3. The communication terminal according to claim 1 or 2, wherein the reference signal is a Channel State Information-Reference signal.

4. The communication terminal according to claim 1 or 2, characterized in that the predetermined index is a precoding matrix index (PMI), a signal-to-interference-plus-noise ratio (SINR), a signal quality index (CQI) or a received signal strength indicator (RSSI).

5. The communication terminal according to claim 1 or 2, wherein the feedback information includes information for identifying a group that transmits and receives the feedback information.

6. The communication terminal according to claim 1 or 2, wherein the feedback information includes information for identifying a terminal within a group that transmits and receives the feedback information.

7. The communication terminal according to claim 2, wherein the transmitting means, when receiving the feedback information, performs precoding setting based on the feedback information.

8. The communication terminal according to claim 2, wherein said transmitting means, when receiving said feedback information, sets transmission power based on said feedback information.

9. The communication terminal according to claim 2, wherein the transmitting means, when receiving the feedback information, performs beamforming settings for the terminal itself based on the feedback information.

10. The communication terminal according to claim 1 or 2, wherein the control information is SCI (Sidelink Control Information) information transmitted via a PSSCH (Physical Sidelink Shared Channel).

11. A communication method performed by a communication terminal that performs sidelink communication with another communication terminal, comprising: a step of receiving a reference signal included in the sidelink communication; a step of calculating a predetermined indicator based on the reference signal; and a step of transmitting feedback information including the predetermined indicator to the other communication terminal when the cast type included in the control information received in the sidelink communication is groupcast.

12. A communication method performed by a communication terminal that performs sidelink communication with another communication terminal, comprising: a step of transmitting control information including information indicating that the cast type is groupcast and a reference signal to the other communication terminal through the sidelink communication; and a step of receiving feedback information from the other communication terminal that is included in the sidelink communication and includes a predetermined indicator.

13. A program for causing a computer of a communication terminal that performs sidelink communication with another communication terminal to execute the following steps: receiving a reference signal included in the sidelink communication; calculating a predetermined indicator based on the reference signal; and, if the cast type included in the control information received in the sidelink communication is groupcast, transmitting feedback information including the predetermined indicator to the other communication terminal.

14. A program for causing a computer of a communication terminal that performs sidelink communication with another communication terminal to execute the following steps: transmitting control information including information indicating that the cast type is groupcast and a reference signal to the other communication terminal through the sidelink communication; and receiving feedback information including a predetermined indicator that is included in the sidelink communication from the other communication terminal.

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