Control device, control method, and control program

Abstract

To solve the problem in which since there are multiple sidelink communication schemes and communication devices may support different communication schemes, it is difficult to establish sidelink communication between appropriate communication devices.SOLUTION: A communication device that communicates using a sidelink communication function in a Third Generation Partnership Project (3GPP) cellular communication standard sends a discovery message containing information indicating a predetermined function to be performed using the sidelink communication function to search for other communication devices that can perform the predetermined function.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a control device, a control method, and a control program. [Background technology]

[0002] Wireless communication standards such as Long Term Evolution (LTE) and New Radio (NR) have been established as cellular communication standards by the Third Generation Partnership Project (3GPP (registered trademark)). These standards include provisions for sidelink communication (3GPP standards, TS36.300, TS38.300, etc.), which allow direct communication between terminal devices (UE) without going through a mobile communication network (core network).

[0003] In communication via a base station, communication between the base station and the UE is performed under the control of the base station. Therefore, communication between a UE and another UE can be performed under the control of the base station in a communication method according to the functions between the UEs. On the other hand, in Sidelink communication, since a base station is not involved, it is assumed that processing such as identifying a partner device and determining a communication method is performed between UEs. For example, Patent Document 1 describes a method of employing an appropriate communication method for communication by exchanging Sidelink capability information between user devices. Patent Document 2 describes a method of connecting a UE outside the communication range of a base station to a relay device installed within the communication range via Sidelink, thereby enabling communication with the base station. Patent Document 3 describes a communication device that transmits a search request message to surrounding devices and performs network settings for another device selected by the user from among devices that have sent responses to the message. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-071153 [Patent Document 2] Patent Publication No. 2021-078140 [Patent Document 3] JP 2002-236628 A Summary of the Invention [Problem to be solved by the invention]

[0005] Sidelink communication can be used in various ways. In this case, whether or not the UE can perform sidelink communication in a way requested by the UE depends on the state of the other UE to which the UE is connected. Even if the user selects the other UE to which the UE is connected as in Patent Document 3, it is not easy to make an appropriate selection if the user does not know whether the other UE can perform the desired sidelink communication. As a result, the efficiency of sidelink communication may decrease.

[0006] The present invention provides a technique that enables sidelink communication to be performed efficiently. [Means for solving the problem]

[0007] A communication device according to one embodiment of the present invention has a communication means for communicating using a sidelink communication function in the cellular communication standard of the Third Generation Partnership Project (3GPP), and a search means for transmitting a discovery message including information indicating a specified function performed using the sidelink communication function, and searching for other communication devices capable of performing the specified function. Effect of the Invention

[0008] According to the present invention, it is possible to efficiently execute sidelink communication. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Diagram 2] FIG. 2 is a diagram illustrating an example of a hardware configuration of a communication device (UE). [Diagram 3] A diagram showing an example of the functional configuration of a communication device (UE). [Figure 4] FIG. 13 is a diagram illustrating an example of a message format. [Diagram 5] FIG. 13 is a diagram illustrating an example of the configuration of information elements in a message. [Figure 6] FIG. 11 is a diagram illustrating an example of a process flow executed by a UE that transmits a discovery message. [Figure 7] FIG. 11 is a diagram illustrating an example of a process flow executed by a UE receiving a discovery message. [Figure 8] FIG. 1 is a diagram illustrating an example of an operation related to D2D communication. [Figure 9] FIG. 11 is a diagram illustrating an example of a processing flow related to D2D communication. [Figure 10] FIG. 11 is a diagram for explaining an example of operation related to UE Relay communication. [Figure 11] A diagram showing an example of a processing flow related to UE Relay communication. [Figure 12] FIG. 11 is a diagram illustrating an example of an operation related to Network Relay communication. [Figure 13] FIG. 11 is a diagram illustrating an example of a process flow related to Network Relay communication. [Figure 14] FIG. 13 is a diagram illustrating an example of a message format. [Figure 15] FIG. 13 is a diagram illustrating services and related information stored in a message. [Figure 16] FIG. 11 is a diagram illustrating an example of a processing flow executed by a UE that receives a discovery message. [Figure 17] FIG. 1 is a diagram for explaining a use case of the system. [Figure 18] FIG. 2 is a diagram illustrating an example of a flow of processing executed in the system. [Figure 19] FIG. 11 is a diagram illustrating an example of a process flow executed by a UE that transmits a discovery message. [Figure 20]FIG. 11 is a diagram illustrating an example of a process flow executed by a UE receiving a discovery message. [Figure 21] FIG. 13 is a diagram illustrating an example of a message format. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0011] [Embodiment 1] (System Configuration) 1 shows an example of the configuration of a wireless communication system according to this embodiment. This wireless communication system is a system in which wireless communication is performed according to a cellular communication standard such as LTE or NR of the Third Generation Partnership Project (3GPP (registered trademark)), and includes a base station 101 and terminals (UE 111 to UE 117). Here, the UE 111 to UE 117 are configured to be able to perform sidelink communication defined in those wireless communication standards.

[0012] The UE 111 to the UE 117 can communicate in various formats using the sidelink communication. For example, the UE 111 can directly communicate with the UE 112 without the base station 101. For example, TS23.304 of the 3GPP (registered trademark) also includes a provision that allows the UE 113, which can directly communicate with the base station 101, to relay communication between the UE 114, which cannot directly communicate with the base station 101, and the base station. Furthermore, in the technical report TR23.752 of the 3GPP (registered trademark), it is reported that a configuration in which another UE 116 relays communication between the UE 115 and the UE 117, which cannot directly communicate with each other, is a major item of consideration. In this way, using the sidelink communication, (1) direct communication between UEs, (2) relay between a UE outside the communication range of the base station and a network, and (3) relay of communication between UEs existing outside the range in which they can directly communicate with each other can be performed. In the following, (1) may be referred to as D2D communication, Network Relay, or UE Relay.

[0013] The UE detects other UEs that are candidates for connection destinations, and selects another UE to connect to from among the candidates. Here, for example, a case will be considered where UE 114 that exists outside the communication range of base station 101 attempts to connect to base station 101 using Network Relay. In this case, UE 114 connects to UE 113 that is connected to base station 101, and is able to communicate with base station 101 via UE 113. On the other hand, it is assumed that UE 114 discovers UE 115 that exists nearby, for example, as a candidate for connection destination of Sidelink communication. Here, UE 115 is not connected to base station 101 and cannot provide Network Relay. However, conventionally, UE 114 cannot know whether UE 115 can provide Network Relay or not until connection with UE 115 is established. As a result, UE 114 recognizes that UE 115 cannot provide Network Relay after connecting with UE 115, and disconnects Sidelink. Then, the UE 114 needs to perform the process again, starting from the process for detecting other UEs that can provide the Network Relay. In this way, since the UE cannot know the status of the other UEs to which it is connected, the process may become complicated. Also, with regard to D2D communication and UE Relay, conventionally, the UE cannot know in advance whether other UEs can perform such communication.

[0014] In consideration of such circumstances, this embodiment provides a method for enabling a UE to determine in advance whether other UEs that are potential connection destinations are capable of performing sidelink communication in the manner required by the UE itself.

[0015] In this embodiment, a UE transmits a discovery message used to detect another UE or to enable detection by another UE, including additional information such as information indicating a mode of sidelink communication requested by the UE itself and a communication status in the UE itself. For example, the UE may transmit a discovery message including information indicating which communication method the UE itself is searching for a sidelink communication partner in, among D2D communication, Network Relay, and UE Relay. The UE may transmit a discovery message including information that can specify whether the UE itself can perform D2D communication, whether Network Relay, and whether UE Relay can be performed as information indicating the communication status, etc., in the discovery message. Note that such information may be included in a response message for responding to the discovery message. In one example, a UE that transmits a discovery message may transmit the discovery message including information indicating a requested sidelink communication method. On the other hand, a UE that transmits a response message may transmit the response message including information indicating a communication method that can be performed by the UE as information indicating the communication status. The other UE may transmit a response message only when sidelink communication is possible in the communication method requested by the UE. By receiving such a discovery message from the UE, the other UE can determine which communication method, D2D communication, Network Relay, or UE Relay, is requested to be used. By receiving a response message from the other UE, the UE can identify the other UE that is possible to communicate in the communication method requested by the own device. Only the UE that is possible to perform sidelink communication in the mode requested by the source UE, which is indicated in the discovery message, may transmit a response message to the discovery message.

[0016] In the following, the configuration and operation of a terminal (UE) performing sidelink communication in a cellular communication standard will be described, but the following discussion can be applied to a wireless communication device performing similar communication, which is a more generalized version of a UE. Also, the following configuration and operation are merely examples, and any changes and modifications can be made without departing from the spirit of the invention.

[0017] (Device configuration) Fig. 2 shows an example of the hardware configuration of a communication device that operates as a UE according to this embodiment. Note that the configuration shown in Fig. 2 is merely an example, and the UE may be realized by a hardware configuration different from the hardware configuration shown in Fig. 2. For example, the UE may not have a part of the hardware configuration shown in Fig. 2, or may include additional configuration. The UE has, for example, a storage unit 201, a control unit 202, a function unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207.

[0018] The storage unit 201 includes memories such as a Read Only Memory (ROM) and a Random Access Memory (RAM), and stores various information such as programs for performing various operations described below and communication parameters for wireless communication. In addition to memories such as ROM and RAM, the storage unit 201 may include storage media such as a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a non-volatile memory card, and a DVD. The storage unit 201 may also include multiple memories.

[0019] The control unit 202 is configured with, for example, a processor such as a CPU or MPU, an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA), etc. Here, CPU is an acronym for Central Processing Unit, and MPU is an acronym for Micro Processing Unit. The control unit 202 controls the entire UE, for example, by executing a program stored in the storage unit 201. The control unit 202 may control the UE in cooperation with the program stored in the storage unit 201 and an OS (Operating System). The control unit 202 may also include multiple processors such as a multi-core processor.

[0020] Moreover, the control unit 202 can control the functional unit 203 to realize a predetermined function such as an impact detection function, an imaging function, a printing function, and a projection function. The functional unit 203 is configured to include hardware for the UE to execute a predetermined process. For example, when the functional unit 203 has an imaging function, the functional unit 203 has an optical lens unit, an optical system that controls an aperture, a zoom, a focus, and the like, and an imaging element for converting light (image) introduced through the optical lens unit into an electrical image signal. The imaging element generally uses a complementary metal oxide semiconductor (CMOS) or a charge coupled device (CCD). Under the control of the control unit 202, the functional unit 203 converts the subject light imaged by a lens included in the functional unit 203 into an electrical signal by the imaging element, performs noise reduction processing, and outputs the digital data as image data. The image data is recorded in the storage unit 201 according to the DCF (Design Rule for Camera File system) standard. Furthermore, when the functional unit 203 has an impact detection function, it includes a sensor, and when the sensor detects an impact or vibration of a certain level or more, it notifies the control unit 202 of the detection result. In this embodiment, the UE may be a smartphone, a digital still camera, a network camera, a printer, an in-vehicle device, or the like having an imaging function. However, the UE is not limited to these, and may be, for example, a projector that projects an image onto a projection unit, or a head-mounted display that provides a user with an image based on data received from the outside. In addition, the UE may be a wearable device such as wearable glasses or a smart watch that has a function of projecting an image onto a projection surface such as the user's retina or glass. The in-vehicle device means a control device that is standardly installed in a vehicle such as an automobile, a car navigation device installed in a vehicle such as an automobile, a drive recorder device installed in a vehicle such as an automobile for recording images during driving, or the like.

[0021] The input unit 204 receives various operations from the user. The output unit 205 outputs various types of information to the user. Here, the output by the output unit 205 includes at least one of display on a screen, audio output by a speaker, vibration output, and the like. Note that both the input unit 204 and the output unit 205 may be realized by one module, such as a touch panel.

[0022] The communication unit 206 is configured to include hardware (e.g., a radio frequency (RF) chip, a baseband chip, etc.) for performing wireless communication conforming to the 3GPP (registered trademark) cellular communication standard. The communication unit 206 controls a corresponding antenna 207 to transmit and receive wireless signals for wireless communication. Note that while FIG. 2 shows a configuration with one antenna 207, multiple antennas may be used. The communication unit 206 is configured to be able to perform sidelink communication with other UEs, in addition to communication with a base station, for example.

[0023] FIG. 3 is a block diagram showing an example of a functional configuration of a communication device (UE). A part (in some cases, all) of the functional blocks described in the communication device may be replaced with other functional blocks that perform similar functions, some functional blocks may be omitted, or further functional blocks may be added. In addition, one functional block described in the following description may be divided into multiple functional blocks, or multiple functional blocks may be integrated into one functional block. The UE includes a function control unit 301, a storage control unit 302, a discovery message generation unit 303, a discovery message analysis unit 304, and a communication control unit 305. The function control unit 301 controls the operation of each function of the UE, for example, by causing the control unit 201 to execute a program stored in the storage unit 202. The storage control unit 302 executes various controls related to the storage of information, such as, for example, storing information in the storage unit 202 and retrieving information from the storage unit 202. The discovery message generation unit 303 generates a discovery message to be sent in order to detect other UEs. Furthermore, the discovery message generating unit 303 generates a response message to a discovery message received from another UE in some cases. The discovery message analyzing unit 304 analyzes a discovery message sent from another UE. The communication control unit 305 controls the wireless communication unit 203 and the antenna control unit 204 to perform communication with a base station and sidelink communication with another UE. The communication control unit 305 is configured to send out a discovery message generated by the discovery message generating unit 303, or to supply a discovery message sent out and received from another UE to the discovery message analyzing unit 304.

[0024] (Discovery message configuration) Next, configuration examples of a discovery message and a response message will be described with reference to FIG. 4 and FIG. 5. FIG. 4 shows formats of an exemplary discovery message and a response message. In the following, the discovery message will be described, but the response message may include similar contents unless otherwise specified. The discovery message is a message transmitted when a UE performs a process of detecting other UEs, and the response message is a message for other UEs that receive the discovery message to detect the presence of the device. In this embodiment, it is assumed that the discovery message and the response message used in the procedure of 5G ProSe Direct Discovery are in the formats shown in FIG. 4 and FIG. 5. Each message is used to discover other nearby UEs that support 5G Prose by direct wireless transmission between two UEs using 5G NR (New Radio) technology. ProSe is an abbreviation for Proximity Service.

[0025] In the message 401, the Destination Layer-2 ID stores a Layer-2 ID indicating the destination of the message. In one example, the Destination Layer-2 ID of the discovery message does not store information indicating an individual other UE as the destination, but may store information indicating a broadcast, for example. On the other hand, the Destination Layer-2 ID of the response message may store an ID of the UE that is the source of the discovery message. The Source Layer-2 ID stores a Layer-2 ID indicating the source of the message. The Frame type stores information indicating the type of this message. For example, information indicating whether the message is a discovery message or a response message is stored in the Frame type. The Frame type of the discovery message is set to "Prose Direct Discovery".

[0026] In the Connection Capability 402, information indicating the mode of sidelink communication requested by the UE that has transmitted the discovery message 401 (the UE that detects other UEs) is set. For example, as shown in FIG. 4, bits for setting the sidelink communication methods "Network Relay", "UE Relay", and "D2D" may be prepared as information indicating the mode of sidelink communication. Among these communication methods, a bit corresponding to the communication method requested by the UE that has transmitted the discovery message is set to "1", and a bit corresponding to the communication method that is not requested is set to "0". Note that this is only an example, and bits corresponding to modes other than these communication methods may be prepared, or a bit corresponding to the requested mode may be set to "0", and a bit corresponding to the not requested mode may be set to "1". Note that, when the UE wants to acquire all information of other UEs around the UE, it is not necessary to set anything in the Connection Capability (for example, all bits are set to "0").

[0027] When another UE receives a discovery message in which nothing is set in Connection Capability 402, the other UE may return a response message in which a sidelink communication method that the UE can execute is set. When another UE receives a discovery message, the other UE transmits a response message in which the ID of the UE that sent the message is specified in Destination Layer-2 ID. In this case, the sidelink communication method that the UE that sends the response message can execute may be set in Connection Capability 402 of the response message. For example, a bit corresponding to a sidelink communication method that the UE can execute may be set to "1", and a bit corresponding to a sidelink communication method that the UE cannot execute may be set to "0". A sidelink communication method that can be executed may be indicated by "0", and a sidelink communication method that cannot be executed may be indicated by "1". When a UE is capable of executing a plurality of communication methods, the UE may set the bits corresponding to the plurality of methods to values ​​indicating that the communication methods are executable. On the other hand, when a UE receives a discovery message in which a requested communication method is specified, the UE may return a similar response message if the UE can execute sidelink communication of the communication method. In this case, nothing may be set in Connection Capability 402 of the response message. In this case, the UE that transmitted the discovery message can estimate that it can execute sidelink communication in the requested communication method in response to receiving a response message in which the ID of the own device is specified in the Destination Layer-2 ID. In addition, the UE may not return a response message when it cannot execute sidelink communication in the requested communication method specified in the discovery message.

[0028] In the Connection Capability Info 403, necessary information is set according to the executable Sidelink communication method. For example, base station information such as an identifier related to the base station to which the UE transmitting this message is connected, information indicating the carrier, and received radio wave strength of a signal from the base station, and a terminal identifier of the UE are stored in the Connection Capability Info 403. The identifier related to the base station may be, for example, a physical cell identifier. The information indicating the carrier may be information capable of identifying a network such as a Public Land Mobile Network (PLMN) identifier. The information indicating the carrier may be information capable of identifying a frequency band used such as an Absolute Radio Frequency Channel Number (ARFCN). The carrier information may be information on a communication carrier that operates the base station. Note that the base station information may be configured to include at least any one of the above-mentioned identifiers, carrier (used frequency band / communication carrier) information, and received radio wave strength, and may additionally or alternatively include information other than these. The terminal identifier may be, for example, an identifier such as Temporary Mobile Subscriber Identities (TMSI) related to communication with the base station. The terminal identifier may be any other identifier capable of identifying the UE. Note that these pieces of information are merely examples, and for example, information that enables identification of other connected UEs may be set in Connection Capability Info 403 as information related to UE Relay.

[0029] Here, an example of information set in Connection Capability Info 403 will be described with reference to FIG. 5. FIG. 5 (A) shows an example of information items set in Connection Capability Info 403. As an example, Connection Capability Info 403 is set with an operation state identifier, a base station identifier, a connected terminal identifier, a base station signal strength, connected base station information, and the like. Each of these pieces of information is assigned an index of 1 to 5, and the index is used in Connection Capability Info 403 to declare which information is to be transmitted. For example, by setting "01" in item 501 in FIG. 5 (B), it is specified that the operation state identifier follows in the subsequent item 502. In this case, for example, "01" indicating that a function for executing Network Relay is being activated is set as item 502. Note that whether or not a function is being activated is specified separately from whether or not the function is supported. That is, if Network Relay is supported but not activated, the corresponding information in Connection Capability can be set to "01" and the operation state identifier can be set to "02". In item 503, a base station identifier is written thereafter. The base station identifier may be, for example, fixed length or variable length. When variable length information is used, the length of the information is indicated, for example, as indicated by "06" in item 504, and then the base station identifier "XXXXXX" is set in item 505. Also, in item 506, "05" indicating the connected base station information is set, and the length of the information is indicated as "04" in item 507. Here, the connected base station information is configured so that further information can be represented by an extended index. For example, "01" is set in item 508, and "01" is set in the following item 509, indicating that the UE that transmitted this message is connected to the base station of company A. Also, "02" is set in item 510, and "51" is set in the following item 511, indicating that the frequency band being used is n78.Note that these pieces of information are merely examples, and other types of information may be set as Connection Capability Info 403.

[0030] Returning to Figure 4, the Frame Payload stores the main body of information exchanged between devices using messages.

[0031] (Processing flow) Next, an example of the flow of processing executed by a UE that transmits a discovery message will be described with reference to Fig. 6. Note that this processing is executed, for example, by using discovery message generating unit 303. Also, the processing in Fig. 6 is merely an example, and for example, some processing steps may be omitted, or processing steps not shown may be added.

[0032] First, the UE generates a discovery message as described above and transmits it to the surroundings (S601). In one example, when the UE acquires all information of the surrounding UEs, the UE transmits it without setting anything to Connection Capability. Also, when the UE detects only other UEs capable of performing D2D communication (supporting the D2D communication function), for example, the UE sets a bit corresponding to D2D communication to a predetermined value in Connection Capability. Similarly, when the UE detects other UEs capable of performing UE Relay or Network Relay, the UE sets a corresponding bit of Connection Capability to a predetermined value. Note that the UE may set a corresponding bit of a second communication method to be used, among one or more first communication methods supported by the UE, to a predetermined value. That is, the UE may not set a corresponding bit to a predetermined value for a communication method not supported by the UE. After that, the UE waits for reception of a response message from the other UE (S602). When the UE receives a response message from the other UE, the UE checks the value of Connection Capability in the message (S603). As described above, the Connection Capability in the response message stores information indicating whether the other UE that has transmitted the response message is capable of D2D communication, UE Relay, or Network Relay. Therefore, the UE can identify in which communication method the other UE that has transmitted the response message is capable of performing Sidelink communication by analyzing the Connection Capability.

[0033] Here, for example, a process when a UE desires to perform D2D communication with another UE will be described. The UE confirms that there is another UE capable of performing D2D communication in the vicinity (S604). If there is no other UE capable of performing D2D communication in the vicinity, the UE may end the process as it is. If there is a surrounding UE capable of performing D2D communication in the vicinity, the UE determines whether to perform D2D communication with the surrounding UE. For example, when the UE and the surrounding UE are both connected to the same base station, there are cases where communication via the base station can perform faster communication without performing D2D communication. For example, this is the case when the frequency band used for connecting to the base station is a frequency band such as a millimeter wave that can secure a sufficiently wide signal bandwidth and can use a large amount of resources. For this reason, in this embodiment, when the UE is connected to the same base station as the other UE, it is determined not to perform D2D communication.

[0034] If the UE is not in the communication range of any base station (YES in S605), the UE is not connected to the same base station as the surrounding UEs, and therefore performs D2D communication (S607). If the UE is connected to any base station (or is in the cell provided by the base station), the UE checks the Connection Capability Info in the response message. The UE then acquires the base station identifier to which the other UE that transmitted the response message is connected (or is in the cell), and determines whether the other UE is in the communication range of the same base station as the UE (S606). If the UE and the other UE are in the communication range of the same base station (YES in S606), the UE does not perform D2D communication, and otherwise (NO in S606), the UE performs D2D communication (S607). Note that, for example, if the frequency band used in the connected (or in-service) base station is not a predetermined frequency band such as a millimeter wave band, the UE may determine to perform D2D communication even if the other UE is connected to (or in-service) the same base station. Also, the UE may determine to perform D2D communication when, for example, the wireless quality between the UE and a base station to which the UE is connected (or is located) falls below a predetermined value. Even if the UE is connected to a base station different from the other UE, the UE may determine not to perform D2D communication when both the UE and the other UE can perform high-volume communication with the base station. In this way, whether or not to perform D2D communication can be determined based on various criteria, and is not limited to the determination based on whether or not the UE is connected to the same base station as described above.

[0035] Next, a process will be described for a case where, for example, a UE desires that another UE relays communication between the UE and a communication partner UE by UE Relay communication. The UE confirms the presence of another UE capable of performing UE Relay communication in the vicinity by confirming the Connection Capability of the received response frame (S608). In one example, a UE that has established a connection with another UE by Sidelink communication or a UE that belongs to a group including another UE for performing Sidelink communication transmits a response frame indicating that it is capable of performing UE Relay communication. If such another UE does not exist, the UE ends the process as it is. On the other hand, if such another UE exists in the vicinity, the UE analyzes the Connection Capability Info in the response frame transmitted from the other UE. Then, the UE determines whether there is another UE capable of performing Sidelink communication with the communication partner UE of the UE itself among the other UEs that have transmitted the response frame (S609). If there is another UE in the vicinity that can perform Sidelink communication with the communication partner UE of the UE (YES in S609), the UE establishes a connection with the other UE and performs UE Relay communication using Sidelink communication (S610). On the other hand, if there is no other UE in the vicinity that can perform sidelink communication with the communication partner UE (NO in S609), the UE ends the process (S610).

[0036] Finally, for example, a process in the case where a UE desires that another UE relays communication between the UE and a base station by Network Relay communication will be described. The UE confirms that there is another UE in the vicinity that can perform Network Relay communication by checking the Connection Capability of the received response frame (S611). Then, the UE analyzes the Connection Capability Info in the response frame transmitted from such another UE. The Connection Capability Info stores information such as an identifier of the base station to which the UE is to connect, the reception strength of radio waves from the base station, the carrier that operates the base station, and the frequency band used for communication. Based on this information, the UE determines which UE among the other UEs that can perform Network Relay is to be connected to. Here, the UE places importance on good wireless quality with the base station, and selects another UE with good reception strength with the base station as the connection destination (S612). Note that this is just an example, and the UE may allow connection only to other UEs that are connected to a specific carrier (for example, a carrier with which the UE has a contract). Also, the UE may determine to preferentially connect to another UE that is connected to a base station that has a received radio wave strength equal to or greater than a predetermined value and uses a high frequency band that allows wideband transmission. Also, the UE may select another UE to connect to according to a priority order obtained by inputting information stored in the Connection Capability Info to a predetermined function. Then, the UE connects to the selected other UE and executes Network Relay communication (S613). Note that the other UE may be in a state of being connected to a base station or in a state of waiting. When the other UE is in a state of waiting, it may establish a connection with the base station in a state of waiting in response to the UE receiving a connection request for Network Relay communication.

[0037] Next, an example of the flow of processing executed by a UE that receives a discovery message and returns a response message will be described with reference to Fig. 7. Note that this processing is executed, for example, by using discovery message analysis unit 304. Also, the processing in Fig. 7 is merely an example, and for example, some processing steps may be omitted, or processing steps not shown may be added.

[0038] When a UE receives a discovery message sent from another surrounding UE (S701), the UE analyzes the Connection Capability contained therein and checks the Sidelink communication method requested by the other UE (S702).

[0039] When another UE requests D2D communication (S703), the UE includes information indicating whether the UE itself can execute (supports) D2D communication in the Connection Capability of the response message (S704). For example, when the UE itself supports D2D communication, the UE sets a bit corresponding to D2D communication in the Connection Capability to "1". Similarly, when another UE requests UE Relay communication (S706), the UE includes information indicating whether the UE itself supports UE Relay communication in the Connection Capability of the response message (S707). Furthermore, when another UE requests Network Relay communication (S709), the UE includes information indicating whether the UE itself supports Network Relay communication in the Connection Capability of the response message (S710). Furthermore, when the UE receives a discovery message that does not specify a specific Sidelink communication method from another UE (S712), the UE includes a function supported by the UE itself in the Connection Capability (S713).

[0040] The UE also includes associated information related to the communication method that is indicated in the Connection Capability to be supported in the Connection Capability Info (S705, S708, S711, S714). For example, when the UE includes information indicating that the UE supports D2D communication in the response message, the UE sets the base station identifier of the base station in which the UE is located or connected in the Connection Capability Info (S705). When the UE includes information indicating that the UE supports UE Relay communication in the response message, the UE sets the terminal identifier capable of identifying other connected UE in the Connection Capability Info (S708). When the UE includes information indicating that the UE supports Network Relay communication in the response message, the UE sets the base station information of the base station in which the UE is connected or located in the Connection Capability Info (S711). Note that the base station information includes, for example, information such as a base station identifier, received signal strength, carrier information, and band. When the UE receives a discovery message that does not specify a specific Sidelink communication method, the UE sets all associated information related to functions supported by the UE in the Connection Capability Info (S714). Although the UE can generate and transmit one response message including information related to a plurality of communication methods, the UE may also generate and transmit a separate response message for each communication method.

[0041] (Example of operation) Next, some operation examples in the above-mentioned system will be described. First, an example of processing when a UE requests D2D communication will be described. Fig. 8(A) to Fig. 8(C) show some situations in which D2D communication is required, and Fig. 9(A) to Fig. 9(C) show examples of processing flows in each situation. D2D communication can be used, for example, for vehicles including UEs with sidelink communication function to exchange information between the vehicles and travel in a convoy. D2D communication can also be used when such vehicles directly communicate with roadside devices (such as traffic lights) including UEs with sidelink communication function to exchange information about road information.

[0042] In FIG. 8A, for example, it is assumed that UE801 is about to perform D2D communication. Here, UE802 and UE803 exist around UE801. Also, it is assumed that UE803 is staying within the range of cell 805 formed by base station 804 and can communicate with base station 804. Here, UE801 transmits a discovery message to the surroundings without specifying a specific communication method in Connection Capability, and UE802 and UE803 receive the message (F901). In response to the discovery message, UE802 transmits a response message to UE801 in which a value indicating that D2D communication is possible and that it is not within the range of any base station is set (F902). Also, UE803 sets that Network Relay communication is possible and base station information related to base station 804, and transmits the response message to UE801 (F903). Here, UE801 desires D2D communication, and therefore determines whether or not to perform D2D communication with UE802 as a communication partner. When using the processing example of FIG. 6, since the UE 801 is not present within the communication range of any base station (YES in S605), the UE 801 determines to perform D2D communication with the UE 802 and executes connection processing (F904). Note that the UE 802 and the UE 803 may include in the associated information whether or not the communication function they support is activated. This enables the UE 801 to identify whether or not each UE can immediately start communication using the communication function it supports.

[0043] In FIG. 8B, for example, it is assumed that UE811 is about to perform D2D communication. Here, UE812 exists around UE811. Also, it is assumed that UE811 is staying within the range of cell 815 formed by base station 813 and can communicate with base station 813. Furthermore, it is assumed that UE812 is staying within the range of cell 816 formed by base station 814 and can communicate with base station 814. Here, UE811 transmits a discovery message to the surroundings without specifying a specific communication method in Connection Capability, and UE812 receives the message (F911). In response to the discovery message, UE812 transmits a response message to UE811 in which a value indicating that D2D communication is possible and that UE812 is within the range of base station 814 is set (F912). As a result, UE811 recognizes that D2D communication with UE812 can be performed, and determines whether or not to perform D2D communication with UE812 as a communication partner. When using the processing example of FIG. 6, the UE 811 determines to perform D2D communication with the UE 812 because the UE 811 is present within the communication range of the base station 813 and the UE 812 is present within the communication range of the base station 815 different from the base station 813 (NO in S606). Then, the UE 811 executes a connection process with the UE 812 (F913). Note that the UE 812 may include in the associated information whether or not the supported D2D communication function is activated. This enables the UE 811 to determine whether or not the D2D communication can be started immediately.

[0044] In FIG. 8C, for example, it is assumed that UE821 is about to perform D2D communication. Here, UE822 exists around UE821. Also, it is assumed that both UE821 and UE822 are staying within the range of cell 824 formed by base station 823 and can communicate with base station 823. Here, UE821 transmits a discovery message to the surroundings without specifying a specific communication method in Connection Capability, and UE822 receives the message (F921). In response to the discovery message, UE822 transmits a response message to UE821 in which a value indicating that D2D communication is possible and that it is within the range of base station 823 is set (F922). As a result, UE821 recognizes that D2D communication with UE822 can be performed, and determines whether or not to perform D2D communication with UE822 as a communication partner. 6, the UE 821 determines not to perform D2D communication with the UE 822 because the UE 821 is present within the communication range of the base station 823 and the UE 822 is also present within the communication range of the same base station 823 (YES in S606). Then, the UE 821 does not perform connection processing with the UE 822 (F923) and performs communication via the base station 823, for example.

[0045] In this way, the UE can easily identify other UEs capable of performing D2D communication and perform D2D communication with the other UEs. Also, the UE can appropriately determine whether to perform D2D communication, for example, not to perform D2D communication with other UEs connected to the same base station, based on associated information included in the response message.

[0046] Next, an example of processing will be described when a UE requests a first other UE supporting a UE Relay communication function to relay communication with a second other UE. FIG. 10 shows a situation in which UE Relay communication is requested, and FIG. 11 shows an example of a processing flow in this situation. Note that UE Relay can be used, for example, when a vehicle including a UE with a sidelink communication function outside the communication range of a base station uses UE Relay to exchange road information between the vehicles. In addition, a roadside device (such as a traffic light device) including a UE with a sidelink communication function can support communication between vehicles including a UE with a sidelink communication function outside the communication range of a base station by supporting UE Relay.

[0047] In Fig. 10, it is assumed that UE 1001 is attempting to communicate with UE 1003. It is assumed that UE 1002 and UE 1004 exist around UE 1001, and UE 1003 and UE 1005 exist within a range to which UE 1001 cannot directly connect. Note that UE 1002 can directly communicate with UE 1003, and UE 1004 can directly communicate with UE 1005. It is also assumed that UE 1002 and UE 1004 support UE Relay communication.

[0048] UE 1001 transmits a discovery message with UE Relay set in Connection Capability in order to search for other UEs capable of relaying communication with UE 1003 using the UE Relay communication function (F1101). When UE 1002 and UE 1004 receive this discovery message, they transmit response messages indicating that they support the UE Relay communication function to UE 1001 (F1102, F1103). In addition, UE 1002 may include a terminal identifier of UE 1003 as associated information in Connection Capability Info in the response message. In addition, UE 1004 may include a terminal identifier of UE 1005 as associated information in Connection Capability Info in the response message. When UE 1001 receives these response messages, it may identify that it is capable of communicating with UE 1003 through UE Relay communication of UE 1002 and that it is capable of communicating with UE 1005 through UE Relay communication of UE 1004. Then, since UE 1001 desires to communicate with UE 1003, UE 1002 that can communicate with UE 1003 by UE Relay communication is selected as a connection destination, and connection establishment processing is performed (F1104). Note that UE 1002 and UE 1004 may include in the associated information whether or not the supported UE Relay communication function is activated. This enables UE 1001 to immediately identify whether or not it is possible to start communication with a desired counterpart device by the UE Relay communication function.

[0049] In this way, the UE can easily identify other UEs capable of performing UE Relay communication and can receive UE Relay communication from the other UEs. The UE can appropriately select other UEs capable of communicating with an appropriate counterpart device based on the associated information in the response message. This allows the UE to appropriately select other devices supporting the UE Relay communication function and communicate with the desired counterpart device.

[0050] Next, an example of processing when a UE requests a first other UE supporting a Network Relay communication function to relay communication with a second other UE will be described. FIG. 12 shows a situation in which Network Relay communication is requested, and FIG. 13 shows an example of a processing flow in this situation. The Network Relay function can be used, for example, to extend the communication range of a base station. For example, a vehicle including a UE with a Sidelink communication function and located outside the communication range of a base station can connect to the base station by relaying communication of a roadside device that includes a UE with a Sidelink communication function and supports the Network Relay function. This allows a vehicle located outside the communication range of a base station to access the Internet, etc., and obtain road information, etc.

[0051] In Fig. 12, it is assumed that UE 1201 searches for other UEs that support the Network Relay function in order to connect to a base station. Here, it is assumed that UE 1202, UE 1203, and UE 1204 exist around UE 1201. It is also assumed that UE 1202 and UE 1203 exist within a communication range 1206 of base station 1205 and support Network Relay. On the other hand, it is assumed that UE 1204 exists outside the communication range 1206 and does not support Network Relay. It is also assumed that the radio wave strength from base station 1205 at UE 1202 is higher than the radio wave strength from base station 1205 at UE 1203.

[0052] In order to search for other UEs that support the Network Relay communication function, the UE 1201 transmits a discovery message with Network Relay set in Connection Capability (F1301). Since the UE 1202 and the UE 1203 support the Network Relay function, they return a response message including information indicating that they support the Network Relay function to the UE 1201 (F1302, F1303). The UE 1202 and the UE 1203 transmit the response message including associated information such as the base station identifier of the connected or located base station 1205, the received signal strength, carrier information, and the frequency band used. The UE 1202 and the UE 1203 may include in the associated information whether or not the supported Network Relay function is activated. This allows the UE 1201 to determine whether or not it can immediately start communication with a base station using the Network Relay function. On the other hand, the UE 1204 does not support the Network Relay function, so it does not return a response message.

[0053] Upon receiving the response messages from UE 1202 and UE 1203, UE 1201 can identify that each of them supports the Network Relay function. Then, UE 1201 identifies information on the base stations to which UE 1202 and UE 1203 are connected from those response messages, selects UE 1202 having good received radio wave strength as a connection destination, and executes connection processing with UE 1202 (F1304).

[0054] In this way, the UE can easily identify other UEs capable of performing Network Relay communication and can receive Network Relay communication from the other UEs. The UE can appropriately select other UEs that can communicate with the base station with better wireless quality, for example, based on associated information in the response message. This allows the UE to appropriately select other devices that support the Network Relay communication function and communicate with the base station.

[0055] In the above embodiment, a method has been described in which a UE that has received a discovery message returns a response message in which a supported communication method is set. However, the present invention is not limited to this. For example, a UE may periodically transmit a signal such as a broadcast signal in which a supported communication method is set even if the UE has not received a discovery message. In an environment in which such a signal is transmitted, a UE can easily identify other UEs that can perform sidelink communication in a communication method requested by the UE by detecting the signal transmitted by other UEs in the vicinity.

[0056] [Embodiment 2] In the above embodiment, a method has been described in which a UE can identify other UEs in the vicinity that can execute a sidelink communication method in a communication method requested by the UE itself. In this embodiment, a method is provided in which a UE identifies other UEs that can provide a service requested by the UE itself and execute sidelink communication, and executes the service. The device configuration is the same as in the first embodiment.

[0057] In this embodiment, a discovery message in a format as shown in FIG. 14 is used. In this format, the Destination Layer-2 ID, the Source Layer-2 ID, and the Frame type are the same as those described in FIG. 4. That is, in this embodiment, it is assumed that the discovery message used in the procedure of 5G ProSe Direct Discovery has the format shown in FIG. 14. The discovery message used in this embodiment includes a "Service" field after the Frame type. The Service field stores information indicating a service that the UE that is the source of the discovery message wants other UEs to execute. Then, the Frame Payload stores information according to the Service. In this embodiment, the UE may generate and transmit a discovery message that stores, for example, "Recording" in the Service and the location information acquired by the UE in the Frame Payload. In addition, the UE that has received the discovery message may generate and return a response frame using the format as shown in FIG. 14 as necessary. In one example, the UE that has received the discovery message returns a response frame that stores information indicating a service that the UE can execute (a service requested by the UE that transmitted the discovery message) in Service. The UE can also store information corresponding to the service in the Frame Payload of the response frame. That is, in this embodiment, information indicating a service that the UE can execute is stored in the response frame of the discovery message used in the 5G ProSe Direct Discovery procedure.

[0058] FIG. 15 shows an example of information to be set in a discovery message. In the example of FIG. 15, record, rescue, platoon group formation, and junction approach detection are shown as examples of values ​​indicating services that can be set in the Service field. The following describes information set by the first UE on the transmission side of the discovery message when each of these services is stored in the Service field. Furthermore, the conditions for the second UE on the receiving side to respond to the message, the process to be executed together with the response, and information to be set in the response message are also described. The contents of the services are not limited to the above four, and values ​​indicating services other than these may be set in the Service field. For example, since the above four services are services for the case where the UE is mounted on the vehicle, services for the case where the UE is not mounted on the vehicle may be specified. In addition, the information stored in the discovery message, the conditions for the response in the receiving UE, the process to be executed, and the information to be included in the response message are not limited to the example of FIG. 15. That is, even if the service is, for example, "record", the information may be different from those shown in FIG. 15 and described later. First, a case where "record" is set in the Service field will be described. In this case, the first UE that transmits the discovery message stores location information of the device itself (the first UE) in the discovery message. Then, the second UE that receives this message returns a response message to the first UE when, for example, all of the following four conditions are satisfied. The first condition is that the device itself (the second UE) is performing shooting using the shooting function it has at the time of receiving the discovery message. This is based on the condition that when a phenomenon such as a traffic accident occurs, there is a possibility that the phenomenon is being shot. In other words, when a discovery message is transmitted after the occurrence of such a phenomenon, if the second UE is not performing shooting at that time, it is estimated that the video desired to be recorded has not been shot in the second UE. Therefore, if the second UE is not performing shooting at the time of receiving the discovery message, the second UE does not transmit a response message to the first UE. The second condition is that the second UE is present in an area within a certain range of distance from the first UE. The communication distance of the sidelink communication between UEs is, for example, about 500 meters. Therefore, the certain range can be set to be equal to or shorter than this communication distance. In the case of a recording service, for example, an image taken by a second UE located close to the scene (the location where the first UE is located) is more useful for identifying the situation. Therefore, when the second UE is far away from the first UE and it is estimated that useful image cannot be taken, the second UE does not transmit a response message to the first UE. The above-mentioned certain range can be set so that such useful image can be obtained. Note that this certain range may be a fixed value or a dynamically settable value. The third condition is that the posture of the own device (second UE) is such that the position of the UE (first UE) that transmitted the discovery message can be photographed by the photographing function of the own device. In other words, when the second UE is in a posture that does not allow it to photograph an object to be recorded, such as an accident scene, the response message is not transmitted to the first UE even if the distance to the first UE is sufficiently close.The fourth condition is that the second UE permits the provision of the recorded video to others. Recorded video, such as images captured by a drive recorder, is the property of the photographer, and therefore the video must not be given to others without the owner's permission. For this reason, if the second UE does not permit the provision of the stored video to others, it does not transmit a response message to the first UE. A second UE that satisfies the above-mentioned first to fourth conditions may transmit a response message to the first UE.

[0059] When the second UE decides to send a response message, it saves the video captured by its own image capturing function (and does not discard the video for at least a certain period of time). In addition, the second UE includes identification information used for Sidelink communication, such as an International Mobile Equipment Identity (IMEI), in the response message and transmits it to the first UE. This enables the first UE to subsequently request the communication device that recorded the video to transmit the video, using the IMEI as the destination.

[0060] Next, a case where "rescue" is set in the Service field will be described. In this case, the first UE stores its own location information and the rescue target requested by its own device in a discovery message and transmits it. Here, information indicating what kind of rescue is needed, such as "breakdown," "out of gasoline," "distress," and "approach of a tailgating vehicle," is stored in the discovery message as information on the rescue target. In one example, information indicating a more detailed rescue target, such as "engine failure" or "flat tire," may be indicated as the "breakdown" information. The second UE transmits a response message to the discovery message on the condition that its own device can head for rescue or that communication via the core network is possible at the time of receiving the discovery message. In addition, when the second UE transmits a response message because its own device can head for rescue, it heads for the position of the first UE without performing any particular processing within the device. In this case, the second UE may transmit information on the scheduled time when its own device will arrive at the position of the first UE in the response message. On the other hand, when the second UE transmits a response message because communication via the core network is possible, the second UE performs relay communication to another rescuer via the core network. In this case, the second UE may not transmit a response message generated by itself, but may forward a response message generated by the other rescuer to the first UE. This response message may include information on the estimated time when the other rescuer will arrive at the location of the first UE.

[0061] Next, a case where "platooning group formation" is set in the Service field will be described. In this case, a group name that serves as an identifier for forming a platoon is set in the discovery message. The second UE may determine whether to transmit a response message by manual operation by a user. When transmitting a response message, the second UE transmits the response message to the first UE, including a password for joining the group and an identifier of the device itself. The second UE may use, for example, a nickname of the device itself as an identifier. By receiving the response message, the first UE may obtain a password and an identifier related to the second UE and determine whether to allow the second UE to join the group. A plurality of vehicles including UEs that belong to the group formed in this way may be controlled to perform automatic platooning using, for example, a known automatic driving technology.

[0062] Finally, a case where "Meeting point approach detection" is set in the Service field will be described. In this case, the discovery message includes the location information of the first UE and information indicating the traveling direction. The second UE transmits a response message when the distance to the first UE is within a certain range and the second UE is traveling in a direction approaching the meeting point. In one example, the second UE does not perform any particular process other than transmitting the response message. The second UE transmits the location information of its own device (the second UE) and information indicating the traveling direction to the first UE, including the response message. This allows the first UE to detect the approach of the second UE at the meeting point ahead of the first device.

[0063] FIG. 16 shows an example of a flow of processing executed by a second UE that receives a discovery message in this embodiment. When the second UE receives a discovery message sent from another UE (S1601), it checks the service included in the discovery message (S1602). If "record" is set in the Service field of the discovery message (S1603), the second UE executes processing related to "record" (S1604). On the other hand, if "rescue" is set in the Service field of the discovery message (S1605), the second UE executes processing related to "rescue" (S1606). If "platooning group formation" is set in the Service field of the discovery message (S1607), the second UE executes processing related to "platooning group formation" (S1608). If "junction approach detection" is set in the Service field of the discovery message (S1609), the second UE executes processing related to "junction approach detection" (S1610). The processing related to each service has been described above and will not be repeated here.

[0064] Next, a use case of the system will be described with reference to FIG. 17. In this example, it is assumed that a vehicle 1701, a vehicle 1702, a network camera 1703, a vehicle 1704, a vehicle 1705, and a Road Side Unit (RSU 1706) are present within a certain range. Here, a situation will be considered in which the vehicle 1701 and the vehicle 1702 collide, and the UE mounted on the vehicle 1701 requests other UEs in the vicinity to provide captured images. In this case, the UE mounted on the vehicle 1701 transmits a discovery message. In the following, this UE is simply referred to as "vehicle 1701". Similarly, in the following, the UEs in those devices are referred to as vehicle 1702, network camera 1703, vehicle 1704, vehicle 1705, and RUS 1706. The vehicle 1701 sets "record" in the Service field in the discovery message, and sets the location information of the vehicle 1701 in the Frame Payload as information according to the service. It should be noted that vehicle 1702 also performs the above-mentioned processing, but since this is similar to the processing performed by vehicle 1701, only vehicle 1701 will be described here, and a description of vehicle 1702 will be omitted.

[0065] Here, vehicle 1702 has a photographing function and can photograph only in the traveling direction, but does not permit provision of the recorded video. In FIG. 17, the arrow indicates the photographing direction. Network camera 1703 has a photographing function and can record in all directions (at least the entire area within the lane in which vehicle 1701 etc. is traveling), and permits provision of the recorded video. Vehicle 1704 has a photographing function and can photograph in the traveling direction and the opposite direction, and permits provision of the recorded video. Vehicle 1705 has a photographing function and can photograph only in the traveling direction, and permits provision of the recorded video. RSU 1706 does not have a photographing function.

[0066] Vehicle 1701 is assumed to be capable of performing sidelink communication with, for example, vehicle 1702, network camera 1703, vehicle 1704, vehicle 1705, and RUS 1706. That is, the communication range of vehicle 1701 includes the position of RSU 1706. On the other hand, vehicle 1701 may use a range different from the communication range as a range for searching for other UEs using a discovery message, for example, as shown in the hatched area in Fig. 17. Fig. 17 illustrates a situation in which vehicle 1701 uses a search range that includes the positions of vehicle 1702, network camera 1703, vehicle 1704, and vehicle 1705, but does not include the position of RSU 1706.

[0067] Fig. 18 shows an example of operations executed by the system in the situation as shown in Fig. 17. Note that, in this example, vehicle 1701 transmits a discovery message requesting a "recording" service to other UEs in the vicinity upon collision with vehicle 1702.

[0068] First, when vehicle 1701 detects an impact of a certain level or more (F1801), it sets the Service field to “record”, generates a discovery message in which its own device's location information is stored in the Frame Payload, and transmits it to the surroundings (F1802). Note that the location information of vehicle 1701 can be acquired, for example, using a GPS function mounted on vehicle 1701. Vehicle 1702, network camera 1703, vehicle 1704, vehicle 1705, and RSU 1706 receive the discovery message and identify that the Service field is set to “record”. Then, vehicle 1702, network camera 1703, vehicle 1704, vehicle 1705, and RSU 1706 decide whether to send a response message to the discovery message.

[0069] Vehicle 1702 is taking pictures using its own device, but has not permitted video provision, so vehicle 1702 decides not to transmit a response message (F1803) and ends the process.

[0070] The network camera 1703 is taking pictures in the direction of the vehicle 1701, the distance from the vehicle 1701 is within a certain range, and the provision of pictures is permitted, so it decides to return a response message (F1804). In this case, the network camera 1703 stores the taken picture (F1805), and returns a response message including its own device's IMEI to the vehicle 1701 (F1806). The vehicle 1701 then stores the IMEI of the network camera 1703 in order to obtain pictures from the network camera 1703 thereafter (F1807). Similarly, the vehicle 1704 also decides to return a response message (F1808), stores the taken picture (F1809), and returns a response message including its own device's IMEI to the vehicle 1701 (F1810). The vehicle 1701 then stores the IMEI of the vehicle 1704 (F1811).

[0071] Vehicle 1705 is taking pictures with its own device, has permission to provide the pictures, and is within a certain distance from vehicle 1701, but is not taking pictures in the direction of vehicle 1701. Therefore, vehicle 1705 decides not to send a response message (F1812), and ends the process.

[0072] In addition, the RSU 1706 does not have an image capturing function, and the distance from the vehicle 1701 is not within a certain range. Therefore, the RSU 1706 decides not to transmit a response message (F1813), and ends the process.

[0073] Thereafter, the vehicle 1701 requests the network camera 1703 to transmit the video stored therein, with the IMEI of the network camera 1703 stored in F1807 as the destination (F1814). When the network camera 1703 receives the request message from the vehicle 1701, it transmits the video stored in F1805 to the vehicle 1701 (F1815). When the vehicle 1701 receives the video from the network camera 1703, it stores the video (F1816). Furthermore, the vehicle 1701 requests the vehicle 1704 to transmit the video stored therein, with the IMEI of the vehicle 1704 stored in F1811 as the destination (F1817). When the vehicle 1704 receives the request message from the vehicle 1701, it transmits the video stored in F1809 to the vehicle 1701 (F1818). When vehicle 1701 receives the image from vehicle 1704, it stores the image (F1819).

[0074] Next, an example of a process flow executed by a UE requesting the "recording" service, such as a UE mounted in vehicle 1701, will be described with reference to Fig. 19. In the following, the UE requesting the "recording" service may be referred to as a first UE, and the UE that is requested to perform the "recording" service may be referred to as a second UE.

[0075] First, the first UE monitors whether an impact (collision) of a certain level or more has occurred (S1901). Note that this monitoring is for determining a trigger for transmitting a discovery message requesting a service, and when another trigger is used, state monitoring corresponding to that trigger may be performed. For example, when a discovery message is transmitted in response to receiving a predetermined user operation, the first UE may monitor whether the predetermined user operation has been received. For example, when there is another vehicle driving dangerously around the vehicle 1701, a discovery message may be transmitted when a user operation is performed to request a recording from the surrounding vehicles. When the first UE detects a trigger for transmitting a discovery message (here, a collision) (YES in S1901), the first UE generates a discovery message in which a requested service (here, "recording") is set, and broadcasts the message (S1902). Then, the first UE waits for a response message from other surrounding UEs (S1903). For example, the first UE may transmit the discovery message multiple times at regular intervals, or may retransmit the discovery message when it does not receive a response message for a certain period of time. Also, the first UE may end the process when it does not receive a response message for a certain period of time.

[0076] When the first UE receives the response message (YES in S1903), it acquires and stores the IMEI of the second UE that is the sender of the response message, which is included in the response message (S1904).Then, the first UE requests the second UE to provide the stored video, addressed to the stored IMEI (S1905), and acquires the video from the second UE (S1906).

[0077] Next, an example of a flow of a process executed by a UE that requests the "recording" service, such as the UEs mounted on the vehicle 1702, the network camera 1703, the vehicle 1704, the vehicle 1705, and the RSU 1706, will be described with reference to FIG. 20. Here again, the UE that requests the "recording" service may be called the first UE, and the UE that requests the "recording" service may be called the second UE. Note that the first UE that executes the process of FIG. 19 can naturally execute the process of FIG. 20 in parallel, and similarly, the second UE that executes the process of FIG. 20 can execute the process of FIG. 19 in parallel. That is, a UE can function as either a first UE or a second UE depending on the situation in which the UE is placed.

[0078] When the second UE receives a discovery message from the first UE (YES in S2001), it determines whether or not to respond to the discovery message (S2002). That is, the second UE determines whether or not the condition for responding to the discovery message is satisfied, for example, as described in relation to FIG. 15. When the second UE determines that the condition is not satisfied (NO in S2002), it ends the process without transmitting a response message. For example, the vehicle 1702, the vehicle 1705, and the RSU 1706 do not transmit a response message because they do not satisfy the above-mentioned condition. On the other hand, when the second UE determines that the condition is satisfied (YES in S2002), it stores the video (S2003), generates a response message including the IMEI of the device, and transmits it to the first UE (S2004). For example, the network camera 1703 and the vehicle 1704 satisfy the above-mentioned condition, so they store the video and transmit a response message. After transmitting the response message, if the second UE receives a video acquisition request addressed to the IMEI of the first UE from the first UE (YES in S2005), the second UE transmits the video stored in S2003 to the first UE (S2006). Note that, for example, if the second UE does not receive a video acquisition request for a certain period of time (NO in S2005), the second UE may delete the video stored in S2003 and end the process.

[0079] In this way, using Sidelink communication, vehicle 1701 can request other UEs in the vicinity to store and provide video images in response to detecting a collision, for example, and can acquire the stored video images.

[0080] Note that the above-mentioned operation example is related to "recording", but for example, the processes of S1606, S1608, and S1610 in FIG. 16 are executed according to a table such as that in FIG. 15. For example, the vehicle 1701 may send a discovery message in which "rescue" is set in addition to or instead of the above-mentioned "recording". In this case, for example, the vehicle 1705 is moving in a direction away from the vehicle 1701 and cannot go to rescue. For this reason, the vehicle 1705 may not transmit a response message when, for example, communication via the core network is not possible. In addition, the network camera 1703 and the RSU 1706 cannot perform rescue but relay a discovery message to other rescuers when, for example, communication via the core network is possible. In one example, the network camera 1703 and the RSU 1706 may forward the discovery message to a contact such as the police. Then, the network camera 1703 and the RSU 1706 may forward response messages from other rescuers to the vehicle 1701. In this case, the expected arrival time of the other rescuer may be set in the response message. Furthermore, vehicle 1704 is traveling in a direction approaching vehicle 1701, and therefore is able to head to provide rescue. Therefore, vehicle 1704 may transmit a response message in which the expected arrival time is set, for example, based on the distance between vehicle 1704 and vehicle 1701. Note that vehicle 1702 is the party involved in the collision, and therefore is unable to head to provide rescue, and therefore does not transmit a response message.

[0081] Furthermore, when a discovery message with "platooning group formation" set is transmitted, the vehicle that receives the discovery message notifies the driver that the message has been received. Then, when the vehicle receives approval from the driver to form a platooning group, it may notify the vehicle that sent the discovery message of a response message. Furthermore, when a discovery message with "junction approach detection" set is transmitted, other vehicles approaching the junction transmit a response message including their own device's position information and traveling direction.

[0082] In this way, by using a sidelink discovery message and a response message thereto, a service requested by a UE that transmits a discovery message can be appropriately provided to that UE.

[0083] [Embodiment 3] The above-described first and second embodiments may be combined. For example, a discovery message 2101 may be configured as shown in FIG. 21. The discovery message 2101 is obtained by adding the "Service" field described with reference to FIG. 14 immediately after the "Connection Capability Info" in the discovery message in FIG. 4. Note that the order of these fields is not limited to this, and a field such as Connection Capability may be placed after the Service field. Also, information corresponding to the Service is stored in the Frame Payload in FIG. 4.

[0084] By using such a configuration, for example, a first UE that transmits a discovery message can identify a second UE that can perform D2D communication and can perform "Service". For example, in FIG. 17, a vehicle 1701 searches for other UEs that can perform D2D communication as in the first embodiment in response to detecting an impact of a certain magnitude or more, and further searches for other UEs that can support the "record" service as in the second embodiment. That is, the vehicle 1701 transmits a discovery message in which the bit for D2D communication in the Connection Capability is set to 1 and "record" is set in the Service field. The vehicle 1701 also sets information corresponding to the service (location information in this case) in the Frame Payload field. When other UEs in the vicinity receive this discovery message, they transmit a response message if they support D2D communication and meet the conditions for the "record" service. For example, if the vehicle 1704 in FIG. 17 does not support D2D communication, the vehicle 1704 may not transmit a response message even though it meets the conditions for the record service. In this manner, the first UE can discover the second UE that can perform, for example, subsequent video request and acquisition through D2D communication. Note that when the vehicle 1702, the network camera 1703, the vehicle 1704, the vehicle 1705, and the RSU 1706 all satisfy the D2D communication requirements, the same operations as those described in the second embodiment are performed.

[0085] This is just an example, and various modes may be taken. For example, when a discovery message with a "rescue" service set is transmitted, a UE that satisfies the condition that communication via a core network is possible may transmit a response message if Network Relay is also possible. That is, even if communication via a core network is possible, a UE that is not capable of executing Network Relay may not transmit a response message. On the other hand, a UE that can go to rescue may transmit a response message even if Network Relay is not possible. In this way, whether or not a response message should be transmitted may be determined according to a combination of the conditions satisfied for the service and the supported Sidelink communication method.

[0086] Furthermore, the above-described embodiments can be used in any combination unless otherwise specified.

[0087] (Summary of the embodiment) At least some of the above-described embodiments can be summarized as follows.

[0088] [Item 1] 1. A communication device, comprising: A communication means for communicating using a Sidelink communication function in the cellular communication standard of the Third Generation Partnership Project (3GPP); a search means for transmitting a discovery message including information indicating a predetermined function performed using the sidelink communication function to search for another communication device capable of executing the predetermined function; A communication device comprising:

[0089] [Item 2] the information indicating the predetermined function is information indicating a communication method supported by the communication device, the searching means searches for the other communication device capable of executing the predetermined function based on a response transmitted by the other communication device when the other communication device supporting the communication method receives the discovery message; 2. The communication device according to item 1,

[0090] [Item 3] The information indicating the communication method is information indicating a second communication method to be used among the first communication methods supported by the communication device. 3. The communication device according to item 2,

[0091] [Item 4] The communication device described in item 2 or 3, characterized in that the communication method includes a first communication method for directly communicating between the communication device and the other communication device, a second communication method for relaying communication between the communication device and a communication partner of the communication device having a Sidelink communication function, and a third communication method for relaying communication between the communication device and a base station.

[0092] [Item 5] the information indicating the predetermined function is information indicating a service that the communication device requests another device to execute, the searching means, when the other communication device that satisfies a condition corresponding to the service receives the discovery message, searches for the other communication device that can execute the predetermined function based on a response transmitted by the other communication device; 5. The communication device according to any one of items 1 to 4,

[0093] [Item 6] the communication device is a vehicle; The communication device described in item 5, characterized in that the information indicating the service includes at least one of recording and providing information photographed by the other device, rescuing the vehicle, forming a group for platooning with the vehicle, and detecting a junction point where the vehicle is approaching.

[0094] [Item 7] The communication device described in item 6, characterized in that when the information indicating the service indicates recording and providing information captured by the other device, the discovery message further includes location information of the communication device.

[0095] [Item 8] 8. The communication device according to item 7, characterized in that, when the information indicating the service indicates recording and providing information photographed by the other device, the communication means obtains an identification number of the other communication device from the response and uses the identification number to communicate to obtain the information photographed by the other communication device.

[0096] [Item 9] A communication device described in any one of items 6 to 8, characterized in that when the information indicating the service indicates rescue of the vehicle, the discovery message further includes location information of the communication device and information indicating what type of rescue is requested.

[0097] [Item 10] A communication device described in any one of items 6 to 9, characterized in that when the information indicating the service indicates forming a group for platooning with the vehicle, the discovery message further includes information indicating a group name.

[0098] [Item 11] 11. The communication device according to any one of claims 6 to 10, characterized in that, when the information indicating the service indicates detection of a junction point approaching the vehicle, the discovery message further includes information indicating the position information and direction of travel of the vehicle.

[0099] [Item 12] the information indicating the predetermined function is information indicating a communication method that the communication device requests to use and a service that the communication device requests another device to execute, the searching means searches for the other communication device capable of executing the predetermined function based on a response transmitted by the other communication device when the other communication device that supports the communication method and satisfies a condition corresponding to the service receives the discovery message; 2. The communication device according to item 1,

[0100] [Item 13] 1. A communication device, comprising: A communication means for communicating using a Sidelink communication function in the cellular communication standard of the Third Generation Partnership Project (3GPP); a transmitting means for transmitting a response including information indicating a predetermined function performed using the sidelink communication function to the other communication device when the other communication device receives a discovery message from the other communication device for searching for a partner with which to perform sidelink communication; A communication device comprising:

[0101] [Item 14] When the discovery message includes information indicating the predetermined function and when the communication device supports the predetermined function, the transmission means transmits the response including the information indicating the predetermined function to the other communication device. Item 14. The communication device according to item 13,

[0102] [Item 15] 15. The communication device according to item 13 or 14, wherein the information indicating the predetermined function is information indicating a communication method supported by the communication device.

[0103] [Item 16] The communication device described in item 15, characterized in that the communication methods include a first communication method for directly communicating between the communication device and the other communication device, a second communication method for relaying communication between the other communication device and a communication partner of the communication device having a sidelink communication function, and a third communication method for relaying communication between the other communication device and a base station.

[0104] [Item 17] Item 17. The communication device according to item 16, characterized in that, when information indicating the first communication method is included in the response, the transmission means further includes an identifier of a base station to which the communication device is connected or located in the response and transmits the response.

[0105] [Item 18] 18. The communication device according to item 16 or 17, wherein when the response includes information indicating the second communication method, the transmission means further includes an identifier of the communication partner in the response and transmits the response.

[0106] [Item 19] 19. The communication device according to any one of claims 16 to 18, characterized in that, when information indicating the third communication method is included in the response, the transmission means further includes information about the base station in the response and transmits it.

[0107] [Item 20] The communication device described in item 19, characterized in that the information about the base station includes at least one of the following information: an identifier of the base station to which the communication device is connected, a frequency used by the base station, a received radio wave strength of the signal from the base station, and a telecommunications carrier that operates the base station.

[0108] [Item 21] The discovery message includes information indicating the predetermined function, the information indicating the predetermined function is information indicating a service that the other communication device requests the other device to execute, based on the communication device satisfying the condition corresponding to the service, the transmitting means transmits the response including information indicating the predetermined function to the other communication device; Item 14. The communication device according to item 13,

[0109] [Item 22] the other communication device is a vehicle; The communication device described in item 21, characterized in that the information indicating the service includes at least one of recording and providing information photographed by the other device, rescuing the vehicle, forming a group for platooning with the vehicle, and detecting a junction point where the vehicle is approaching.

[0110] [Item 23] The communication device described in item 22, characterized in that when the information indicating the service indicates recording and providing information photographed by the other device, the transmitting means, based on the satisfaction of the condition, includes an identifier of the communication device in the response and transmits the response to the other communication device.

[0111] [Item 24] The communication device described in item 22 or 23, characterized in that when the information indicating the service indicates rescue of the vehicle, the transmitting means, based on the satisfaction of the condition, includes information on the estimated time when the communication device will arrive at the vehicle's location in the response and transmits the response to the other communication device.

[0112] [Item 25] 25. The communication device of any one of items 22 to 24, characterized in that when the information indicating the service indicates the formation of a group for platooning with the vehicle, the transmission means, based on the satisfaction of the condition, includes in the response an identifier and password of the communication device for joining the group and transmits the response to the other communication device.

[0113] [Item 26] the communication device is a vehicle; 26. The communication device according to any one of claims 22 to 25, characterized in that, when the information indicating the service indicates detection of a junction where the vehicle is approaching, the transmission means, based on the satisfaction of the condition, includes in the response the location information and information indicating the direction of travel of the communication device and transmits the response to the other communication device.

[0114] [Item 27] A control method executed by a communication device that communicates using a Sidelink communication function in a cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: A control method comprising: transmitting a discovery message including information indicating a specified function to be performed using the Sidelink communication function, and searching for other communication devices capable of executing the specified function.

[0115] [Item 28] A control method executed by a communication device that communicates using a Sidelink communication function in a cellular communication standard of the Third Generation Partnership Project (3GPP), comprising: A control method characterized by including, when another communication device receives a discovery message from the other communication device searching for a partner for sidelink communication, transmitting a response to the other communication device including information indicating a specified function performed using the sidelink communication function.

[0116] [Item 29] A program for causing a computer to function as each of the means possessed by the communication device described in any one of items 1 to 26.

[0117] <Other embodiments> The present invention provides a program for implementing one or more of the functions of the above-described embodiments to a system or device via a network or a storage medium. It can also be implemented by a process in which one or more processors in a computer of the system or device read and execute the program. It can also be implemented by a circuit (e.g., ASIC) that implements one or more of the functions.

[0118] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0119] 303: Discovery message generation unit, 304: Discovery message analysis unit

Claims

1. A communication device, A communication means for communicating using a Sidelink communication function in the Third Generation Partnership Project (3GPP) communication standard; a search means for transmitting a discovery message including information indicating a predetermined function performed using the Sidelink communication function to search for other communication devices capable of executing the predetermined function; A communication device comprising:

2. the information indicating the predetermined function is information indicating a communication method supported by the communication device, the searching means searches for the other communication device capable of executing the predetermined function based on a response transmitted by the other communication device when the other communication device supporting the communication method receives the discovery message; 2. The communication device according to claim 1.

3. the information indicating the communication method is information indicating a second communication method that is requested to be used among first communication methods supported by the communication device; 3. The communication device according to claim 2.

4. 3. The communication device according to claim 2, wherein the communication methods include a first communication method for directly communicating between the communication device and the other communication device, a second communication method for relaying communication between the communication device and a communication partner of the communication device having a Sidelink communication function, and a third communication method for relaying communication between the communication device and a base station.

5. the information indicating the predetermined function is information indicating a service that the communication device requests another device to execute, the searching means searches for the other communication devices that can execute the predetermined function based on a response transmitted by the other communication devices when the other communication devices that satisfy the conditions corresponding to the service receive the discovery message; 2. The communication device according to claim 1.

6. the communication device is a vehicle; 6. The communication device according to claim 5, wherein the information indicating the service includes at least one of recording and providing information photographed by the other device, rescuing the vehicle, forming a group for platooning with the vehicle, and detecting a merging point where the vehicle is approaching.

7. The communication device according to claim 6, wherein when the information indicating the service indicates recording and providing information captured by the other device, the discovery message further includes location information of the communication device.

8. The communication device described in claim 7, characterized in that when the information indicating the service indicates recording and providing information photographed by the other device, the communication means obtains an identification number of the other communication device from the response and uses the identification number to communicate to obtain the information photographed by the other communication device.

9. 7. The communication device according to claim 6, wherein, when the information indicating the service indicates rescue of the vehicle, the discovery message further includes location information of the communication device and information indicating what type of rescue is requested.

10. The communication device according to claim 6, characterized in that, when the information indicating the service indicates the formation of a group for platooning with the vehicle, the discovery message further includes information indicating a group name.

11. A communication device capable of communicating with other communication devices using a Sidelink communication function in the Third Generation Partnership Project (3GPP) standard, a transmitting means for transmitting a discovery message including information regarding relay communication in order to search for a relay device that relays communication with the other communication device; a receiving means for receiving a response message from the relay device after transmitting the discovery message; a connection processing means for connecting to the relay device; A communication device comprising:

12. The communication device described in Claim 11, characterized in that the discovery message includes an identifier of the communication device and an identifier of the other communication device.

13. The communication device of claim 11, wherein the response message includes an identifier of the other communication device.

14. The communication device described in Claim 11, characterized in that the communication device further has a selection means for selecting one relay device from multiple relay devices when the response message is received from multiple relay devices.

15. A control method executed by a communication device that communicates using a Sidelink communication function in a Third Generation Partnership Project (3GPP) communication standard, comprising: A control method characterized by including transmitting a discovery message including information indicating a predetermined function to be performed using the Sidelink communication function, and searching for other communication devices that can perform the predetermined function.

16. A control method executed by a communication device that communicates using a Sidelink communication function in a Third Generation Partnership Project (3GPP) communication standard, comprising: a transmission step of transmitting a discovery message including information regarding relay communication in order to search for a relay device that relays communication with another communication device; a receiving step of receiving a response message from the relay device after transmitting the discovery message; a connection processing step of connecting to the relay device; A control method comprising:

17. A program for causing a computer to function as each of the means included in the communication device according to any one of claims 1 to 10.

18. A program for causing a computer to function as each of the means possessed by a communication device described in any one of claims 11 to 14.

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