JP2024050080A - Message control device and message control method - Google Patents

Abstract

[Problem] To provide a message control device that improves the reliability of communication while suppressing the use of wireless resources. [Solution] A message control device according to one aspect of the present disclosure includes a control unit that determines whether or not multi-hop communication is necessary for sending a message, and a communication unit that transmits the message using multi-hop communication when it is determined that multi-hop communication is necessary. This makes it possible to determine to use multi-hop communication when there is a high need for multi-hop communication, and to determine to use single-hop communication when a message can be transmitted using single-hop communication. This makes it possible to improve the reliability of communication while suppressing the use of wireless resources. [Selected Figure] Figure 4

Description

This disclosure relates to a message control device and a message control method that can transmit messages via both single-hop and multi-hop communication.

For autonomous driving, safe driving assistance, and the like, it is being considered to wirelessly share information acquired by vehicles with other vehicles or roadside devices. In addition, the use of single-hop or multi-hop communication in vehicle-to-vehicle and road-to-vehicle communication is being considered. In single-hop communication, a packet is sent directly from a source node to a destination node. In multi-hop communication, a packet is sent from a source node to a destination node or area via one or more nodes. For example, if an in-vehicle communication device is outside the range of the roadside communication device's radio waves, the in-vehicle communication device communicates with the roadside communication device using multi-hop communication (Patent Document 1).

Japanese Patent No. 5909960

The heavy use of multi-hop communication results in excessive communication capacity and puts strain on the communication bandwidth. In other words, the heavy use of multi-hop communication uses a lot of wireless resources. For this reason, the use of single-hop communication for most communications is being considered. However, there are cases where the reliability of single-hop communication is lower than that of multi-hop communication.

Therefore, one of the objectives of the present disclosure is to provide a message control device and a message control method that improves the reliability of communications while reducing the use of wireless resources.

A message control device according to one aspect of the present disclosure includes a control unit that determines whether or not multi-hop communication is required to transmit a message, and a communication unit that transmits the message using multi-hop communication when it is determined that multi-hop communication is required.

A message control method according to one aspect of the present disclosure includes determining whether multi-hop communication is required to transmit a message, and transmitting the message using multi-hop communication if it is determined that multi-hop communication is required.

According to one aspect of the present disclosure, it is possible to improve the reliability of communication while suppressing the use of wireless resources.

FIG. 1 is a diagram illustrating an example of a schematic configuration of an intelligent road transport system according to an embodiment. FIG. 2A is a diagram showing an example of a GUC. FIG. 2B is a diagram showing an example of a GAC. FIG. 2C is a diagram showing an example of a GBC. FIG. 3 shows an example of a single-hop communication failure. FIG. 4 is a diagram illustrating an example of the operation of the control unit. FIG. 5 is a diagram illustrating another example of the operation of the control unit. FIG. 6 illustrates an example of multi-hop communication and destination determination according to the first embodiment. FIG. 7 shows an example of determining whether to use multi-hop communication or single-hop communication according to the first embodiment. FIG. 8 illustrates an example of multi-hop communication and destination determination according to the third embodiment. FIG. 9 illustrates an example of multi-hop communication and destination determination according to the fourth embodiment. FIG. 10 illustrates an example of multi-hop communication and destination determination by a vehicle according to the seventh embodiment. FIG. 11 illustrates an example of multi-hop communication and destination determination by an RSU according to the seventh embodiment. FIG. 12 is a diagram illustrating an example of a vehicle according to an embodiment. FIG. 13 is a diagram illustrating an example of an RSU according to an embodiment.

The following describes in detail an embodiment of the present disclosure with reference to the accompanying drawings. In the following description, identical parts are given the same reference numerals. Since identical parts have the same names, functions, etc., detailed descriptions will not be repeated.

(Intelligent Transport Systems)
Fig. 1 is a diagram showing an example of a schematic configuration of an intelligent transport system according to an embodiment. The intelligent transport system 1 shown in Fig. 1 may include a vehicle 10, a roadside unit 20, and an ITS server 30. The intelligent transport system 1 may be interchangeably read as an Intelligent Transport System (hereinafter, ITS), a road transport system, a transport system, and the like. The roadside unit 20 may be called a RoadSide Unit (hereinafter, RSU) 20.

ITS1 may be called a system (so-called Cooperative ITS (CITS)) in which information (e.g., traffic information, information for autonomous driving, etc.) is shared among multiple vehicles. In ITS1, communication is performed using any one or a combination of the message control methods according to each embodiment of the present disclosure described later.

Vehicle 10 is a vehicle that travels on a roadway. Vehicle 10 may be a car, or a vehicle that does not move autonomously (e.g., a bicycle). A car may be one or both of a four-wheeled vehicle and a two-wheeled vehicle.

The vehicle 10 has an on-board communication device and can communicate with other vehicles 10, the RSU 20, the ITS server 30, etc., via wireless communication. Examples of wireless communication methods include Long Term Evolution (LTE), 5th generation mobile communication system (5G), and Wi-Fi (registered trademark).

Direct communication between vehicles 10 may be referred to as vehicle-to-vehicle (V2V) communication. Communication between vehicles 10 and RSUs 20 may be referred to as vehicle-to-infrastructure (V2I) communication. V2V and V2I communication may be referred to as vehicle-to-everything (V2X) communication.

The messages transmitted between the vehicles 10 may include, for example, at least one of the following:
Cooperative Awareness Message (CAM), which periodically transmits vehicle position, speed, etc.
Decentralized Environmental Notification Message (DENM), which notifies when certain events occur;
- Collective Perception Message (CPM) for sharing the environment perceived based on perception sensors.

CAM is a message sent in the Cooperative Awareness (CA) service proposed by ETSI (European Telecommunications Standards Institute). Cooperative awareness in road traffic means that road users and roadside infrastructure can know each other's location, movement and attributes. Road users refer to all users on and around the road who are responsible for road safety and control, such as cars, trucks, motorbikes, bicycles, pedestrians, etc., and roadside infrastructure refers to facilities such as road signs, traffic lights, barriers, entrances, etc.

CPM is a message sent in the CP service proposed by ETSI. The CP service is a service that notifies the surrounding area of the positions, behavior, and attributes of surrounding road users and other targets detected by the vehicle sending the CPM.

The RSU 20 collects information on surrounding road conditions, surrounding traffic lights, etc. Traffic light information can include the color of the traffic lights. The RSU 20 also has a function of communicating the collected information with the vehicle 10, other RSUs 20, the ITS server 30, etc. Traffic lights may be called traffic lights. Traffic light information may be called information indicating the traffic light status. The RSU 20 may be equipped with a sensor and collect information using the sensor. This sensor may include a camera. Examples of road conditions are road congestion, the presence or absence of fallen objects, and the condition of the road surface.

The RSU 20 may relay communications between the vehicle 10 and the ITS server 30. The RSU 20 may be connected to one or both of the traffic lights and the sensors so as to be able to communicate with each other via wires or wirelessly.

A mobile communication terminal may be used as the communication unit of the RSU 20. The mobile communication terminal is, for example, a mobile terminal such as a mobile phone, a smartphone, or a tablet terminal. The communication terminal is equipped with one or more sensors such as a camera, and is therefore expected to contribute to providing useful information.

The ITS server 30 may provide traffic information, driving assistance information, etc. to the vehicle 10, and may control the color of traffic lights based on information received from the vehicle 10, the RSU 20, etc. The ITS server 30 may be a cloud server or an on-premise server. An example of the functional configuration and hardware configuration of each device such as the vehicle 10 will be described later.

Note that the system configuration of ITS 1 shown in FIG. 1 is an example, and the configuration of ITS system 1 is not limited to the configuration shown in FIG. 1. Naturally, the number of vehicles 10 is not limited to the number shown in FIG. 1. Furthermore, the number of RSUs 20 and ITS servers 30 is not limited to the number shown in FIG. 1.

(V2X communication)
In the European V2X standard, GeoNetworking, which performs routing using vehicle position information, is being considered. GeoNetworking includes forwarding methods (geographical addressing methods and forwarding algorithms) in point-to-point communication and point-to-multipoint communication. As forwarding methods for GeoNetworking, Single Hop Broadcast (SHB), GeoUnicast (Geographically-Scoped Unicast (GUC)), GeoAnycast (Geographically-Scoped AnyCast (GAC)), GeoBroadcast (Geographically-Scoped BroadCast (GBC)), and Topologically Scoped Broadcast (TSB) are being considered.

The sending communication device and the receiving communication device may be called nodes. Since forwarding involves both receiving and transmitting, the forwarding communication device may also be called a node. As in the example of Figure 2A, in GUC, the sending vehicle specifies the location where one vehicle exists as the destination and transmits a message to surrounding vehicles. The message arrives at the destination vehicle by being forwarded closer to the destination. The location is specified, for example, by coordinates.

As shown in the example of FIG. 2B, in GAC, a source vehicle specifies one area as a destination and transmits a message to surrounding vehicles. Area may be interpreted as range. The shape of the destination area may be, for example, a circle, a rectangle, or an ellipse. The message transmitted by the source vehicle is forwarded so as to approach the area specified as the destination, and reaches one of the vehicles within the destination area.

As in the example of Figure 2C, in GBC, the sending vehicle specifies one area as the destination and sends a message to surrounding vehicles. The message is forwarded so as to approach the destination area. In GBC, the shape of the destination area can also be, for example, circular, rectangular, or elliptical. When any vehicle in the destination area receives the message, that vehicle broadcasts the message to the destination area. When any vehicle in the area specified by the message receives the broadcasted message, it broadcasts the message again. A vehicle that has broadcast a message once will not broadcast the message again, even if it receives the message thereafter. In this way, the message is transmitted to all vehicles in the destination area.

TSB has n hops, and each hop broadcasts a message to the surroundings. SHB can be thought of as TSB with 1 hop.

SHB may also be called single-hop communication or single-hop type communication. GUC, GAC, GBC, and TSB may also be called multi-hop communication or multi-hop type communication.

The use of a transmission method according to the type of message is being considered. For example, the use of GBC for DENM is being considered. DENM is a message that conveys environmental information such as icy roads and obstacles on the road, and it is necessary to convey this environmental information to multiple following vehicles. For this reason, broadcasting is used for DENM, and multi-hop communication is often preferable.

Multi-hop communication can send messages to vehicles farther away than SHB by passing them from the source vehicle to the destination vehicle via a relay vehicle. Multi-hop communication may also be able to send messages to areas where it is difficult to send messages using SHB due to radio wave obstructions. However, heavy use of multi-hop communication uses a lot of wireless resources.

For this reason, V2X communication often uses SHB. For example, the use of SHB for messages that are sent periodically, such as CAM, CPM, and Basic Safety Message (hereinafter, BSM), is being considered. BSM is a message proposed by the Society of Automotive Engineers (SAE), and has the same uses as CAM. Like CAM, BSM may also include the vehicle's position, speed, etc.

Using SHB reduces problems such as communication capacity pressure. However, with SHB, there is a risk that messages will not be delivered to the required destination. For example, with SHB, as in the example of Figure 3, radio waves may not reach the destination from the sender due to obstructions. In the example of Figure 3, there are structures around the intersection. The structures and obstructions may be referred to as radio wave obstructions or radio wave impediments. A vehicle is traveling on a road toward an intersection, and uses SHB to send a message to other vehicles on the crossroads. However, the radio waves representing the message may not travel sufficiently around obstructions, resulting in failure to send or receive the message.

If the transmission of periodically sent messages such as CAM is performed using multi-hop communication, the message sent by the vehicle in the example shown in Figure 3 will be more likely to reach other vehicles at the intersection. However, using multi-hop communication frequently will use a lot of wireless resources.

The inventors therefore came up with a method to achieve more reliable V2X communication while reducing the problems that arise from the heavy use of multi-hop communication.

Note that in the following description of the embodiments, the messages communicated by the V2X communication device may be any of CPM, CAM, DENM, and BSM, or may be messages defined in the Basic System Profile (BSP) of the CAR 2 CAR Communication Consortium (C2CCC) or other standards. The messages in the following embodiments are messages that are transmitted periodically. However, the messages in the embodiments may be messages that are not transmitted periodically. Furthermore, the messages in the embodiments may include messages that are transmitted periodically and messages that are not transmitted periodically.

The V2X communication device is mounted on the vehicle 10. The V2X communication device may be mounted on the RSU 20. The V2X communication device may correspond to an ITS station (ITS-S) or may be included in the ITS-S. The ITS-S is a device that exchanges information, and may be an OBU (On-Board Unit), an RSU, or a mobile terminal, or may be included in any of them. The mobile terminal is, for example, a PDA (Personal Digital Assistant) or a smartphone. The OBU may be called an in-vehicle device.

(Message Control Method)
A message control method according to an embodiment of the present disclosure is described below. Each message control method may be applied to the above-mentioned ITS1.

As described below with reference to FIG. 12, the vehicle 10 may include a control unit 11, a sensor 12, a locator 13, an input/output unit 14, and a communication unit 15.

The communication unit 15 may perform V2X communication. The control unit 11 may acquire information obtained by V2X communication. The information obtained by V2X communication may be a V2X reception result. The V2X reception result may be information indicating a V2X communication state.

The V2X communication state may indicate the quality of the V2X communication. The quality of the V2X communication may indicate a reception situation. The V2X communication state may indicate, for example, successful or unsuccessful transmission, or successful or unsuccessful reception. The V2X communication state may also indicate successful or unsuccessful reception of an ACKnowledgement (ACK) and/or a Negative ACKnowledgement (NACK). The V2X reception state may be at least one of a measurement result of a received signal, an error rate, and a signal to noise ratio (SNR). The error rate may be represented by a packet error rate (PER), a block error rate (BLER), a bit error rate (BER), etc.

The V2X communication state may be information included in a message received by V2X communication. This message may be communicated in packet units. The message may be interpreted as data. The message received by V2X communication may include at least one of the state of other vehicles (hereinafter, other vehicle state), the state of the RSU (hereinafter, RSU state), the state of a traffic signal (hereinafter, traffic signal state), traffic information, the position of a node (hereinafter, node position), and a request for multi-hop communication (hereinafter, multi-hop communication request). The communication request may be a communication instruction.

The message from the vehicle may include at least one of the following: other vehicle state, node position, and multi-hop communication request. The other vehicle state may include at least one of the other vehicle's position (hereinafter, other vehicle position), the other vehicle's speed, and the other vehicle's braking state. The message from the RSU 20 may include at least one of the RSU state, node position, traffic signal state, traffic information, and multi-hop communication request. The traffic signal state may include the state of a traffic signal connected or linked to the RSU 20. The traffic signal state may include the light color of the traffic signal. The traffic signal state may include information indicating whether passage is permitted or not permitted. The communication unit 15 may acquire traffic information by broadcasting and/or V2X communication. The traffic information may include information regarding congestion (e.g., the location of the congestion).

The communication unit 15 may transmit a message using a communication method determined by the control unit 11. The control unit 11 determines whether the communication method is multi-hop communication or single-hop communication. When the control unit 11 determines to use multi-hop communication, it also determines a forwarding method and communication parameters determined according to the forwarding method determined. The communication parameters include the number of hops, the destination, etc. The communication parameters may be read as communication settings. When the destination is a point, the destination may include a position. The position may be represented by latitude and longitude. When the destination is a point, the forwarding method may be GUC. When the destination is an area, the destination may include the shape of the area and the position of the area. The shape of the area may indicate one of a plurality of candidate shapes including one or more of a circle, a rectangle, and an ellipse. When the destination is an area, the forwarding method may be GAC or GBC. The position of the area may include one or more of the center position of the area, the size of the area, and the angle of the area. The center position of the area may be represented by latitude and longitude. When the shape of the area is circular, the size of the area may be the radius. When the shape of the area is rectangular, the size of the area may be the length of the long side and the length of the short side, and the angle of the area may be the azimuth angle of the long side. When the shape of the area is elliptical, the size of the area may be the length of the long axis and the length of the short axis, and the angle of the area may be the azimuth angle of the long axis. The destination area may be read as a destination area, an estimated area, an area where non-line-of-sight communication is performed, an area where single-hop communication is difficult, an area where multi-hop communication is required, and the like. The control unit 11 may estimate the destination, and when the destination is a point, determine the transfer method as GUC. The control unit 11 may estimate the destination, and when the destination is an area, determine the transfer method as GAC or GBC. When the destination is an area, the control unit 11 may approximate the estimated area to one of a plurality of candidate shapes and determine the shape and position of the area. The shape of the area may differ depending on the embodiment described later, or may differ depending on the information used to determine the necessity of multi-hop communication.

The sensor 12 may detect the environment (surrounding environment information) around the vehicle 10 on which the sensor 12 is mounted. Detection may be interpreted as recognition or location. The vehicle 10 on which the sensor 12 is described may be referred to as the host vehicle. The sensor 12 may detect at least one of the following: the road shape around the host vehicle, the traffic signal state of the traffic lights around the host vehicle, the status of obstacles present around intersections located around the host vehicle, and the detection status of the preceding vehicle closest to the host vehicle. The surroundings of the host vehicle preferably include the area ahead of the host vehicle. An obstacle detected by the sensor 12 may be interpreted as an obstruction. An obstacle detected by the sensor 12 may include a building.

The control unit 11 may acquire vehicle position information (hereinafter, vehicle position information) based on information from the locator 13. Acquire may be interpreted as any of measurement, detection, and calculation. The vehicle position information may be one or both of the vehicle's position and information related to a change in the vehicle's position. The vehicle's position may be expressed, for example, by latitude and longitude. Information related to a change in the vehicle's position may include, for example, at least one of the vehicle's traveling direction and speed.

The memory 112 in the control unit 11 may store map information. The communication unit 15 may receive the map information. The map information includes the positions of roads and intersections. The map information may include the road structure. The road structure may include the shapes of roads and intersections. The shape of the road may be represented by information indicating the curvature of the road. The map information may include the positions of buildings. The positions of buildings may indicate the range in which the buildings exist, rather than a single coordinate indicating the position where the building is located. The range in which the building is located may be rephrased as the arrangement of structures. The map information may include the average vehicle speed for at least some of the roads.

The control unit 11 may acquire the vehicle state from at least one of the sensor 12, the drive unit, and the operation unit. The vehicle state may include one or more of the vehicle speed, acceleration, braking state, traveling direction of the vehicle, and steering angle.

The memory 112 in the control unit 11 may store the vehicle's travel trajectory (history of vehicle position information) from a certain period of time in the past to the present. The travel trajectory is determined by the control unit 11 based on information from one or both of the locator 13 and the sensor 12.

The control unit 11 may store the execution status of coordinated driving with surrounding vehicles (coordinated driving state) and may control coordinated driving. The communication unit 15 may receive the coordinated driving state. The coordinated driving may be platooning of the vehicle itself and surrounding vehicles. The coordinated driving state may include whether platooning is enabled or disabled, and may include the positions of the platoon members.

The control unit 11 may control multi-hop communication or single-hop communication in V2X communication based on information indicating at least one state of the vehicle and the environment (hereinafter, state information). The state information may include one or more of map information, vehicle position information, V2X communication state, vehicle state, driving trajectory, coordinated driving state, and surrounding environment information. The control unit 11 may determine at least one of the necessity of multi-hop communication, the destination, and the maximum number of hops for multi-hop communication based on the state information. Depending on the determination of the necessity of multi-hop communication, it is determined whether the communication method is SHB or multi-hop communication. The destination may be one of the location and the area.

As described below, the RSU 20 includes a control unit 21 and a communication unit 25. The control unit 21 may have the same functions as the control unit 11. The memory 212 in the control unit 21 may store the position information of the RSU 20, or may store map information. The communication unit 25 may receive the map information. The map information may include the shapes of roads and intersections around the RSU 20. The map information may include the positions of buildings around the RSU 20. The map information may include the average vehicle speed for at least some of the roads.

The communication unit 25 may have the same functions as the communication unit 15. In addition to the functions of the communication unit 15, the communication unit 25 may be connected to a wired network (e.g., an optical fiber network) and communicate with the wired network, or may be connected to traffic lights and communicate with the traffic lights. The RSU 20 may transmit information detected by sensors including a camera from the communication unit 25 to at least one of the vehicle 10, another RSU 20, and the ITS server 30.

Figure 4 shows an example of the operation of the control unit 11. First, in S120, the control unit 11 acquires state information. Then, in S130, the control unit 11 determines whether multi-hop communication is necessary for transmitting a message based on the acquired state information. That is, the control unit 11 determines whether the communication method for transmitting the message is multi-hop communication or single-hop communication. If it is determined in S130 that multi-hop communication is necessary (Y), in S140, the control unit 11 determines the communication settings for multi-hop communication based on the state information acquired in S120. The communication settings to be determined include the destination. The communication settings to be determined may also include the maximum number of hops. If the destination is the position of the vehicle, the forwarding method can be GUC. The forwarding method may also be one of the communication settings. An example of the forwarding method when the destination is an area is GAC or GBC.

Then, in S150, the control unit 11 transmits the message using multi-hop communication according to the communication settings determined in S140. On the other hand, if it is determined in S130 that multi-hop communication is not necessary (N), in S160, the control unit 11 transmits the message using single-hop communication. The operation shown in FIG. 4 may be repeated periodically, or may be executed each time a message to be transmitted is generated.

Figure 5 shows another example of the operation of the control unit 11. The operation example shown in Figure 5 is an operation example related to message transfer. First, in S210, the control unit 11 acquires a message received by the communication unit 15. Then, in S220, the control unit 11 acquires status information. Then, in S230, the control unit 11 determines whether multi-hop communication is required to transmit the message based on the message acquired in S210 and the status information acquired in S220. In other words, it determines whether the communication method for transmitting the message should be multi-hop communication or single-hop communication.

In this S230, the state information may not be used, and the message acquired in S210 may be analyzed to determine whether multi-hop communication is necessary (in other words, whether forwarding is necessary). If location information is specified by the message acquired in S210 and the vehicle is not present at the location indicated by the location information, the control unit 11 determines that multi-hop communication is necessary. In this case, the forwarding method becomes GUC.

In addition, even if a destination area is specified by the message acquired in S210 and the vehicle is not present in that area, the control unit 11 determines that multi-hop communication is necessary. In this case, the forwarding method is GAC or GBC. Even if a destination area is specified by the message acquired in S210 and the vehicle is present in that area, if GBC is specified as the forwarding method, it may be determined that the message is to be forwarded. For example, if there is a vehicle in the area that has not yet received the message, it is determined that the message is to be forwarded.

If it is determined in S230 that multi-hop communication is necessary (Y), then in S240 the control unit 11 determines the communication settings for multi-hop communication based on one or both of the message acquired in S210 and the status information acquired in S220. Then, in S250, the control unit 11 transmits, i.e., forwards, the message received in S210. On the other hand, if it is determined in S230 that multi-hop communication is not necessary (N), the control unit 11 ends this operation without forwarding the message received in S210. This operation may be performed every time the communication unit 15 receives a message, or may be repeated periodically.

The message that performs the operation of FIG. 5 may be a message that is sent periodically. Periodically may be read as cyclically. An example of periodicity is a transmission frequency (rate) between 10 Hz and 1 Hz, i.e., a transmission interval between 100 ms and 1000 ms. For example, the operation of FIG. 5 may be performed for one or more of the aforementioned CAM, CPM, and DENM messages.

In this disclosure, the operation of the control unit 11 may be read as the operation of the control unit 21. In this disclosure, the operation of the communication unit 15 may be read as the operation of the communication unit 25.

First Embodiment
The control unit 11 may determine the necessity of multi-hop communication based on at least one of map information and vehicle position information. If the control unit 11 determines that multi-hop communication is necessary, the communication unit 15 may transmit a message using multi-hop communication. If the control unit 11 determines that multi-hop communication is not necessary, the communication unit 15 may transmit a message using single-hop communication.

The control unit 11 may determine whether or not an intersection exists ahead of the vehicle based on the map information and the vehicle position information. The ahead of the vehicle may be within the communication distance by SHB. Alternatively, the ahead of the vehicle may be within a judgment distance set to less than several hundred meters. The communication distance and the judgment distance are examples of a predetermined distance. The judgment distance may be changed according to the speed of the vehicle. The judgment distance may be a distance that the vehicle can travel in a certain time. The ahead is not limited to the road on which the vehicle is traveling, but may include roads on which the vehicle can travel by turning right or left. This determination may be performed in S130 of FIG. 4. When it is determined that an intersection exists ahead of the vehicle, the control unit 11 may determine that multi-hop communication is necessary regardless of whether or not there is a structure around the intersection. This is because there are often structures around intersections. However, the presence of a structure may be taken into consideration as described below.

The control unit 11 may acquire the arrangement of structures present around the intersection ahead of the vehicle based on the map information and the vehicle position information. The control unit 11 may estimate whether single-hop communication with a vehicle on the crossroad is difficult, that is, whether the communication quality of single-hop communication with a vehicle on the crossroad is poor, based on the arrangement of the structures. The control unit 11 may also estimate whether communication with a vehicle on the crossroad is line of sight (LOS) communication or non-line of sight (NLOS) communication, based on the arrangement of the structures. The control unit 11 may estimate, as an area where single-hop communication is difficult, an area that is blocked from the vehicle by a structure (an area where line of sight communication occurs) among areas on the crossroad and areas where single-hop communication is possible when structures are not taken into consideration. The control unit 11 may not estimate that single-hop communication is difficult when there are few areas where line of sight communication occurs, taking into consideration radio wave wraparound. Therefore, when the angle at which non-line-of-sight communication occurs and the ratio of the angle at which non-line-of-sight communication occurs to the angle at which line-of-sight communication occurs are equal to or greater than the threshold values set for those angles, the control unit 11 may estimate that single-hop communication is difficult. The leakage of radio waves differs depending on the frequency of the radio waves. The frequency of the radio waves at which the message is transmitted may be in various frequency bands such as the 5 GHz band or the 700 MHz band. When it is estimated that single-hop communication is difficult, the control unit 11 may determine that multi-hop communication is necessary.

The control unit 11 may determine whether or not there is a traffic light at the intersection ahead of the vehicle. Whether or not there is a traffic light may be determined from map information and vehicle position information. In addition, whether or not there is a traffic light may be determined by communication with a roadside device, or may be determined based on a signal provided by a sensor 12 such as a camera. If there is a traffic light at the intersection, the control unit 11 may determine that multi-hop communication is not necessary. This is because problems are less likely to occur when communication is unavailable, since the traffic light controls which vehicles can enter the intersection.

[Communication settings]
Next, communication setting will be described. The control unit 11 may set a destination area including an area where SHB is estimated to be difficult. Furthermore, when the control unit 11 estimates that SHB with a vehicle on an intersection is difficult, the control unit 11 may estimate an area on the intersection ahead of the vehicle that is the destination of multi-hop communication based on map information, vehicle position information, and the speed of the vehicle. The destination area may be a range that satisfies at least one of a range on the intersection within a certain distance from the vehicle, a range on the intersection within a certain angle from the traveling direction of the vehicle, and a range on the intersection that is hidden by a structure as seen from the vehicle. Furthermore, the destination area may be an area where the time when a vehicle traveling on the intersection enters the intersection may overlap with the time when the vehicle enters the intersection.

In the example of FIG. 6, the vehicle is traveling on a road toward an intersection. If it is determined that single-hop communication to the intersection on the road on which the vehicle is traveling is difficult due to a structure, the vehicle determines that multi-hop communication is necessary. The destination area in multi-hop communication may be an area where the time at which a vehicle traveling on the intersection enters the intersection may overlap with the time at which the vehicle enters the intersection. The time at which the vehicle enters the intersection can be estimated from the vehicle speed of the vehicle and the distance to the intersection. Whether or not the vehicle traveling on the intersection will enter the intersection at this time can be calculated from the position and speed of the vehicle traveling on the intersection. If the speed of the vehicle traveling on the intersection is within a preset speed range, the vehicle can calculate the area in which a vehicle on the intersection that can enter the intersection at the same time as the vehicle is located.

The estimated area shown in Figure 6 illustrates the area calculated in this manner. The shape of the estimated area shown in Figure 6 is a rectangular area along an intersection. The vehicle may specify this estimated area as the destination of multi-hop communication and send a message using multi-hop communication. Since an area is specified, GAC or GBC can be used as the forwarding method. In Figure 6, a message sent by the vehicle setting up multi-hop communication is forwarded to the estimated area by another vehicle that is closer to the estimated area than the vehicle and traveling in the same lane as the vehicle.

The control unit 11 may determine the maximum number of hops depending on the distance to the destination area. The maximum number of hops may also be a fixed value set in advance.

The example in FIG. 7 is an example in which multi-hop communication and single-hop communication are used together. In the example shown in FIG. 7, the structures located around the intersection are smaller than in the example shown in FIG. 6. Therefore, SHB is possible between vehicles located in estimated area b. Estimated area b may be an area where line-of-sight communication is possible. The position and speed of the vehicle shown in FIG. 7 are assumed to be the same as those in FIG. 6. Estimated area a may be the estimated area shown in FIG. 6 excluding estimated area b.

In the example of FIG. 7, the vehicle determines the estimated area a as the destination in the communication settings determined in S140 of FIG. 4, and transmits a message in S150. Furthermore, the vehicle may determine that multi-hop communication is not necessary for estimated area b, which is an area on the intersection and where SHB is possible, and may transmit a message to estimated area b or other vehicles within estimated area b using single-hop communication such as SHB. Note that the vehicle may first transmit a message to estimated area b, and then transmit the message to estimated area a.

The control unit 11 may determine the complexity of the route to the destination based on map information and vehicle position information. The route to the destination is the route when traveling on roads. The complexity may be determined based on the number of turns at intersections, etc. on the route. This is because radio waves tend to travel in a straight line, so the more turns there are, the higher the possibility that a message cannot be transmitted using single-hop communication. Of course, the presence or absence of structures may be taken into consideration based on map information. However, since areas with a high number of turns are often areas where structures are likely to exist, such as urban areas, it may be assumed that structures exist in a straight line to the destination.

In addition, the longer the distance, the more difficult it becomes to transmit a message using single-hop communication. The control unit 11 may determine the complexity based on the number of turns on the route to the destination and the distance to the destination. The control unit 11 may set the complexity to a higher value the more turns there are on the route and the longer the distance.

The control unit 11 may determine or change the maximum number of hops in multi-hop communication based on the complexity. Also, as described above, the longer the distance, the more difficult it becomes to transmit a message using single-hop communication, so the control unit 11 may determine or change the maximum number of hops in multi-hop communication depending on the distance. The control unit 11 may determine or change the maximum number of hops in multi-hop communication when it is determined that multi-hop communication is necessary.

When the complexity is higher than or equal to the threshold, the control unit 11 may increase the value of the maximum hop count more than when the complexity is equal to or lower than the threshold. When the complexity is higher than or equal to the threshold, the control unit 11 may change the maximum hop count from a first value to a second value and use the second value for multi-hop communication. The control unit 11 may calculate the second value by adding a constant number to the first value. The first value may be a value specified in the specifications, or may be a value that has been previously determined or set. The second value may be a value specified in the specifications. The first value and the second value may be values that change depending on the vehicle situation and the surrounding situation.

According to this embodiment, the vehicle determines whether to communicate a message by multi-hop communication or single-hop communication based on at least one of map information and vehicle position information. This allows the vehicle to determine to use multi-hop communication when there is a high need for multi-hop communication, and to determine to use single-hop communication when a message can be transmitted using single-hop communication. This makes it possible to improve the reliability of communication while suppressing the use of wireless resources.

Second Embodiment
The control unit 11 may determine the necessity of multi-hop communication based on information obtained by V2X communication. When the control unit 11 determines that multi-hop communication is necessary, the control unit 11 may determine communication settings for the multi-hop communication based on information obtained by V2X communication. The control unit 11 may include one or both of a destination and a maximum number of hops in the multi-hop communication in the communication settings for the multi-hop communication to be determined.

If the control unit 11 determines that multi-hop communication is necessary, the communication unit 15 may transmit the message using multi-hop communication. If the control unit 11 determines that multi-hop communication is not necessary, the communication unit 15 may transmit the message using single-hop communication.

The control unit 11 may acquire the position of the other vehicle from a received message received from the other vehicle by V2X communication, or may estimate the other vehicle passage area based on the other vehicle state in the received message. The other vehicle passage area is an area where it can be estimated that the other vehicle will pass within a certain time. The other vehicle passage area can be estimated based on the position, traveling direction, and speed of the other vehicle. The control unit 11 may determine whether or not an intersection (e.g., an intersection in front of the host vehicle) exists ahead of the other vehicle in the traveling direction based on the other vehicle position or the other vehicle passage area. The control unit 11 may determine the necessity of multi-hop communication based on the existence of the intersection. The meaning of "ahead" may be the same as that of the host vehicle. For example, when it is determined that an intersection exists ahead of the other vehicle, the control unit 11 may determine that multi-hop communication is necessary. Furthermore, when it is determined that an intersection existing ahead of the other vehicle is also an intersection existing ahead of the host vehicle, the control unit 11 may determine that multi-hop communication is necessary for the message transmitted by the host vehicle.

The control unit 11 may determine whether or not single-hop communication with an area in which other vehicles exist is difficult based on the reception status of messages from other vehicles. The reception status may be replaced with communication quality. The reception status may be determined based on the V2X reception status described above, such as PER. If it is determined that the communication is difficult, the control unit 11 may determine that multi-hop communication is necessary. The multi-hop communication here may be GUC if the position of the other vehicles is known based on messages from the other vehicles.

The control unit 11 may determine whether or not there is a high possibility that the other vehicle will approach the own vehicle based on the state of the other vehicle and the state of the own vehicle. When the traveling direction of the other vehicle and the traveling direction of the own vehicle intersect, and the predicted time when the other vehicle will arrive at the intersection point and the predicted time when the own vehicle will arrive are close, the control unit 11 may determine that there is a high possibility that the other vehicle will approach the own vehicle. The predicted times being close may mean, for example, that the difference between the two predicted times is about several seconds. Since the other vehicle and the own vehicle travel on a road, the control unit 11 may further use map information when determining whether or not there is a high possibility that the other vehicle will approach the own vehicle. In addition to the positions and speeds of the own vehicle and the other vehicle, the acceleration of the own vehicle and the other vehicle may also be used to calculate the predicted time. If the acceleration is negative, the vehicle is decelerating. The vehicle can be decelerated by braking. Therefore, the control unit 11 may determine the acceleration based on the brake state.

When it is determined that there is a high possibility that another vehicle will approach the own vehicle, the control unit 11 may determine that multi-hop communication is necessary. This is because, when there is a high possibility that another vehicle will approach the own vehicle, there is a high need to deliver the own vehicle's message to the other vehicle. Note that even when there is a high possibility that another vehicle will approach the own vehicle, if it can be determined that there is a high possibility that communication can be performed by single-hop communication, for example, because there are no structures between the other vehicle and the own vehicle, the control unit 11 may not need to determine that multi-hop communication is necessary.

The control unit 11 may also determine, based on the state of the other vehicle, that multi-hop communication is necessary when the other vehicle is moving at a high speed or the situation of the other vehicle is highly urgent. The control unit 11 may also determine, based on the state of the vehicle itself, that multi-hop communication is necessary when the vehicle is moving at a high speed or the situation of the vehicle is highly urgent.

The control unit 11 may determine whether or not the message transmitted or forwarded by the vehicle is to be multi-hop communication based on a message received from the RSU 20 by V2X communication. For example, based on the traffic signal state included in the message received from the RSU 20, it may determine whether or not the light color of a traffic signal (e.g., a traffic signal at an intersection in front of the vehicle) is a color indicating passage (e.g., blue or green). If it is determined that the light color of the traffic signal is a color indicating passage, the control unit 11 may determine that multi-hop communication is necessary. If the traffic signal at the intersection in front of the vehicle indicates passage, it is considered that the vehicle will enter the intersection. Therefore, the control unit 11 can determine that multi-hop communication is necessary in order to transmit the message transmitted by the vehicle to other vehicles present in the vicinity of the vehicle with a higher probability. The multi-hop communication here can be a forwarding method in which the destination is an area on an intersection intersecting the road on which the vehicle is traveling and in the direction toward the intersection, for example, the estimated area shown in FIG. 6. This forwarding method may be GAC or GBC. The forwarding method may also be GUC, where the destination is the position of a specific other vehicle, such as the leading vehicle at an intersection heading toward an intersection.

The RSU 20 has a fixed position. Therefore, the RSU 20 can determine whether or not communication is difficult using single-hop communication due to surrounding structures. Therefore, the RSU 20 may transmit a signal to instruct or request multi-hop communication to the surroundings. When an instruction or request for multi-hop communication is received from the RSU 20, the control unit 11 may determine that multi-hop communication is necessary.

The other vehicle can determine the communication quality of V2X communication at any time while traveling. If the other vehicle determines that multi-hop communication is necessary, it is highly likely that the following vehicle also requires multi-hop communication. Therefore, the other vehicle may transmit a message including an instruction or request for multi-hop communication to the surrounding area. When the control unit 11 receives an instruction or request for multi-hop communication from the other vehicle, it may determine that multi-hop communication is necessary.

Similar to the other vehicles described above, when the host vehicle determines that a message sent by a surrounding vehicle requires multi-hop communication, the control unit 11 may transmit a multi-hop communication request to the other vehicles and the RSU 20. The other vehicles that receive the multi-hop communication request sent by the host vehicle may transmit the message sent by the other vehicles via multi-hop communication. Furthermore, the RSU 20 that receives the multi-hop communication request sent by the host vehicle may transmit a signal to instruct or request multi-hop communication to the surroundings. The control unit 11 may use multi-hop communication to transmit the multi-hop communication request. Note that when the message sent by the host vehicle is to be multi-hop communication, the control unit 11 sets the communication setting for the message to be multi-hop communication.

The control unit 11 may determine whether or not multi-hop communication is required for a message transmitted by the vehicle based on the communication state of a message received from another vehicle through V2X communication. For example, the control unit 11 may determine whether or not multi-hop communication is required for a message transmitted by the vehicle based on whether or not a message that is scheduled to be received from another vehicle has been received. The control unit 11 may determine that a message is scheduled to be received from another vehicle when a message is periodically received from the other vehicle, or when a message is transmitted to the other vehicle and a response thereto is required. When a message that is scheduled to be received from the other vehicle is not received, the control unit 11 may determine that multi-hop communication is required. The control unit 11 may acquire the position of the other vehicle (other vehicle position) based on the most recently received message from the other vehicle.

When the control unit 11 determines that multi-hop communication is necessary, the control unit 11 may specify the other vehicle position as the destination of the multi-hop communication. When the other vehicle position is the destination, GUC may be used as the multi-hop communication. When the control unit 11 determines that multi-hop communication is necessary, the control unit 11 may perform multi-hop communication of a message with the other vehicle presence area, where the other vehicle may exist, as the destination. When the estimation accuracy of the other vehicle's position is low, it is preferable to set the other vehicle presence area as the destination. An example of a case in which the estimation accuracy of the other vehicle's position decreases is when the communication state with the other vehicle is poor and messages periodically transmitted by the other vehicle cannot be received. The other vehicle presence area may be a circular area within a certain distance from the other vehicle position. The other vehicle presence area may also be an area on an intersection within a certain distance from the other vehicle position. The worse the estimation accuracy of the other vehicle's position, the larger the other vehicle presence area may be. GAC or GBC may be used as the multi-hop communication with the other vehicle presence area as the destination.

In the example of Figure 8, the host vehicle is traveling on a road toward an intersection. At the intersection that intersects with the road on which the host vehicle is traveling, another vehicle 10a, also a vehicle 10, is traveling toward the same intersection as the host vehicle. There are structures around the intersection. If the host vehicle and the other vehicle 10a are in a positional relationship that makes them out of the line of sight due to these structures, SHB may be difficult.

At time t = t1, the vehicle and the other vehicle 10a are in a positional relationship where they are not blocked by structures, and can communicate with each other via single-hop communication. At time t = t1, the vehicle receives a message from the other vehicle 10a and obtains the position, speed, and direction of travel of the other vehicle.

At time t=t2, the vehicle and the other vehicle 10a are out of line of sight due to structures. Therefore, the vehicle switches from SHB to multi-hop communication to transmit the message. The destination area is determined based on the position of the other vehicle 10a at time t=t2, which is determined based on the speed and position of the other vehicle 10a acquired at time t1, and taking into account the range in which the speed of the other vehicle 10a may change after time t=t1. In FIG. 8, the dashed square illustrates the destination area determined in this way. The vehicle may also transmit a message using GUC, with the position of the other vehicle 10a at time t=t2 as the destination.

In the example of Figure 8, at time t = t2, there is another vehicle 10b that is closer to the destination than the own vehicle and traveling in the same lane as the own vehicle, and this other vehicle 10b forwards the message sent by the own vehicle to another vehicle 10a traveling at the intersection.

In this example, the judgment conditions in S130 in FIG. 4 are that the vehicle is aware of the presence of another vehicle 10a on the intersection, that it has been determined that there is a possibility that the vehicle and the other vehicle 10a will approach each other, and that it has been determined that communication between the vehicle and the other vehicle via SHB is difficult due to structures.

If this determination condition is met, the vehicle transmits a message via multi-hop communication, and if this determination condition is not met, the vehicle transmits a message via single-hop communication. In this way, it is possible to improve the reliability of communication while suppressing the use of wireless resources.

Third Embodiment
The control unit 11 may determine the necessity of multi-hop communication based on at least one of a travel trajectory (a route traveled by the vehicle in the past) and a vehicle state. The travel trajectory may be information indicating the location where the vehicle was located at a certain time or distance in the past. If the control unit 11 determines that multi-hop communication is necessary, the communication unit 15 may transmit a message using multi-hop communication. If the control unit 11 determines that multi-hop communication is not necessary, the communication unit 15 may transmit a message using single-hop communication.

The control unit 11 may determine whether or not multi-hop communication is necessary based on the state of the vehicle. For example, if sudden braking of the vehicle is detected based on the state of the vehicle, if a failure or abnormality of the vehicle is detected, or if it is estimated that there is a high possibility that a following vehicle will approach the vehicle, the control unit 11 may determine that multi-hop communication is necessary.

Sudden braking can also be referred to as sudden deceleration or sudden braking. Sudden braking means negative acceleration where the absolute value of the acceleration is greater than a preset threshold. The malfunction or abnormality may be a malfunction or abnormality in a driving system device. An example in which it is estimated that there is a high possibility that a following vehicle will approach the vehicle is when sudden braking of the vehicle is detected and the following vehicle exists or is likely to exist within a certain distance behind the vehicle. Whether or not a following vehicle exists within a certain distance behind the vehicle can be determined by vehicle-to-vehicle communication with the following vehicle. If the vehicle is traveling on a road with heavy traffic, it may be determined that there is a high possibility that a following vehicle exists within a certain distance behind the vehicle.

The control unit 11 may determine whether or not multi-hop communication is necessary based on the driving trajectory. If the driving trajectory is set to be equal to the communication distance by SHB and includes a right or left turn, it may determine that multi-hop communication is necessary.

The control unit 11 may also take into consideration the presence of structures and determine whether or not multi-hop communication is necessary based on the vehicle state, the driving trajectory, and the range in which structures are present. The control unit 11 may determine that multi-hop communication is necessary based on the vehicle state, and also based on the driving trajectory, and may further determine that multi-hop communication is necessary when it determines that message communication is difficult using SHB due to structures. The range of the structures can be determined based on map information. The range of the structures may also be detected by a sensor provided in the vehicle.

When the control unit 11 determines that multi-hop communication is necessary, the control unit 11 may determine the destination of the multi-hop communication based on the driving trajectory. For example, when sudden braking of the host vehicle is detected, the control unit 11 may determine an area (following vehicle area) where a following vehicle is likely to exist based on the driving trajectory, and specify the following vehicle area as the destination of the multi-hop communication. The following vehicle area can also be said to be an area where a message transmitted by the host vehicle should be transmitted to the following vehicle. The following vehicle area may include an area where a message transmitted by the host vehicle should be transmitted to the following vehicle, where it is difficult to transmit the message using SHB.

If the following vehicle area includes an area where it is difficult to transmit messages using SHB, the message can be sent to the following vehicle with a high probability by using multi-hop communication to send the message to the following vehicle area.

In the example of Figure 9, the vehicle suddenly brakes after turning right at an intersection. The sudden braking of the vehicle can be detected based on the state of the vehicle. In addition, it can be determined that the vehicle has just turned right based on the travel trajectory. Around the intersection, there are structures adjacent to the road on which the vehicle is currently traveling and the road on which it was previously traveling. Therefore, the vehicle determines that multi-hop communication is required for the message to be sent.

The vehicle determines the following vehicle area based on the travel trajectory. The following vehicle area shown in FIG. 9 is a road identified by the travel trajectory included in the range to be transmitted by SHB, and is an area on a road that connects at an intersection to the road on which the vehicle is currently traveling. The vehicle may then specify the following vehicle area as the destination of multi-hop communication and transmit a message using multi-hop communication. The forwarding method in the communication settings for multi-hop communication may be GAC or GBC. In addition, if the position of the following vehicle to which a message should be transmitted can be identified by V2X communication before the vehicle turns at the intersection, the forwarding method may be GUC.

In Figure 9, there are other vehicles near the intersection. There are no structures blocking communication between the vehicle and the other vehicles at the intersection. The message sent by the vehicle is forwarded by the other vehicles at the intersection and transmitted to other vehicles in the following vehicle area.

By using the driving trajectory to determine whether multi-hop communication is necessary, it is possible to improve the reliability of communication while reducing the use of wireless resources.

Fourth Embodiment
The control unit 11 may determine at least one of the necessity of multi-hop communication, the destination, and the maximum hop number of multi-hop communication based on the coordinated operation state. If the control unit 11 determines that multi-hop communication is necessary, the communication unit 15 may transmit a message using multi-hop communication. If the control unit 11 determines that multi-hop communication is not necessary, the communication unit 15 may transmit a message using single-hop communication.

If platooning is enabled, the vehicle is in a coordinated driving state. If the control unit 11 determines that platooning is enabled, i.e., the vehicle is in a coordinated driving state, the control unit 11 may determine that multi-hop communication is necessary. During platooning, the vehicles traveling in the platoon may communicate their recognition that they are in a platooning state to some or all of the other vehicles traveling in the platoon. Thus, the vehicle can recognize whether or not it is in a platooning state by communicating with other vehicles.

When the vehicle is traveling in a platoon, other vehicles in the platoon that are relatively close to the vehicle may be radio wave shielded, and the vehicle may not be able to send a message to other vehicles that are relatively far from the vehicle using single-hop communication. Therefore, when the control unit 11 determines that the vehicle is traveling in a platoon, it may determine that the message to be sent from the vehicle requires multi-hop communication.

When in a coordinated driving state, the control unit 11 may determine the destination of the multi-hop communication based on the coordinated driving information. For example, the control unit 11 may set the position of the leading vehicle or the trailing vehicle of the convoy that includes the vehicle itself as the destination of the multi-hop communication, and transmit a message by multi-hop communication with the transfer method being GUC.

According to this embodiment, by using the coordinated driving state of the vehicles to determine whether multi-hop communication is necessary, it is possible to improve the reliability of communication while suppressing the use of wireless resources.

Fifth embodiment
The control unit 11 may determine at least one of the necessity of multi-hop communication, the destination, and the maximum number of hops in the multi-hop communication based on the surrounding environment information. As described above, the surrounding environment information is the environment around the vehicle 10. The environment may include the shape of the road, the position and size of an obstacle, and the state of a traffic signal.

If the control unit 11 determines that multi-hop communication is necessary, the communication unit 15 may transmit the message using multi-hop communication. If the control unit 11 determines that multi-hop communication is not necessary, the communication unit 15 may transmit the message using single-hop communication.

For example, the control unit 11 may obtain the road shape ahead of the vehicle based on the sensor 12, and determine whether or not an intersection exists ahead of the vehicle based on the road shape. If it is determined that an intersection exists ahead of the vehicle, the control unit 11 may determine that multi-hop communication is necessary.

The control unit 11 may use the detection results of the sensor 12 instead of the map information in the first embodiment. For example, instead of recognizing the shape of the road ahead from the map information, the control unit 11 may recognize the shape of the road ahead from the detection results of the sensor 12. Also, instead of recognizing the presence or absence of a building around the intersection ahead and the range of the building from the map information, the control unit 11 may recognize the presence or absence of a building around the intersection ahead and the range of the building from the detection results of the sensor 12.

The control unit 11 may also use a combination of map information and the detection results of the sensor 12. The control unit 11 may also use the detection results of a sensor other than the vehicle itself received via V2X communication, or may use a combination of the detection results of a sensor other than the vehicle itself received via V2X communication and the detection results of the sensor 12.

As an example of a combination of the sensor 12 and map information, a case where the detection result of the sensor 12 is used to acquire the traffic signal state can be considered. The control unit 11 recognizes the existence of an intersection from the map information. The control unit 11 may acquire the traffic signal state ahead of the vehicle based on the sensor 12, and may determine whether or not the traffic signal light color indicates that passage is permitted based on the traffic signal state. If it is determined that the traffic signal light color indicates that passage is permitted, the control unit 11 may determine that multi-hop communication is necessary. The control unit 11 may use the detection result of the sensor 12 instead of the reception result of the V2X communication in the second embodiment (e.g., the traffic signal state from the RSU 20), or may use a combination of the reception result of the V2X communication and the detection result of the sensor 12.

For example, the control unit 11 may sequentially acquire the position of a vehicle preceding the host vehicle based on the detection results of the sensor 12, and when it determines from the detection results of the sensor 12 that the vehicle preceding has been lost, it may determine that multi-hop communication is necessary. Lost may also be expressed as being lost or not being detected. The vehicle preceding may be the vehicle closest to the host vehicle among the vehicles traveling ahead of the host vehicle. However, the vehicle preceding may also be a vehicle ahead of the host vehicle whose distance from the host vehicle is less than the preceding vehicle determination distance. The preceding vehicle determination distance may be set to the communication distance of single-hop communication or less.

When the control unit 11 determines that multi-hop communication is necessary due to the loss of the preceding vehicle, the control unit 11 may execute multi-hop communication with an area that includes the location where the preceding vehicle was lost and extends in the direction in which the preceding vehicle is estimated to have traveled. The direction in which the preceding vehicle is estimated to have traveled can be determined from the direction of movement of the preceding vehicle immediately before it was lost.

By setting the destination area for multi-hop communication to an area extending in the direction in which the preceding vehicle is estimated to have traveled, it is possible to improve the reliability of communication while reducing the use of wireless resources, even if the preceding vehicle is lost due to the preceding vehicle making a right or left turn.

Sixth embodiment
In the above embodiments, the vehicle that transmits a message determines that multi-hop communication is necessary and transmits the message including information indicating that it is multi-hop communication. In contrast, in the sixth embodiment, the vehicle that receives the message determines whether or not to forward the received message.

This determination may be performed by the control unit 11 mounted on the vehicle 10, or by the control unit 21 provided in the RSU 20. When the control unit 11 performs the determination, the control unit 11 controls the communication unit 15. When the control unit 21 performs the determination, the control unit 21 controls the communication unit 25. In the following description, the control unit 11 can be read as the control unit 21. When the control unit 11 is read as the control unit 2, the communication unit 15 is read as the communication unit 25.

The sixth embodiment describes a case where the control unit 11 executes the process shown in FIG. 5. When the control unit 11 acquires a message received by the communication unit 15, the control unit 11 determines the necessity of multi-hop communication based on the state information. In this embodiment, the necessity of multi-hop communication can also be referred to as the necessity of message forwarding.

The following can be given as examples of status information. That is, the status information may include one or more of map information, vehicle position information, V2X communication status, vehicle status, driving trajectory, coordinated driving status, surrounding environment information, and road information.

When the control unit 11 determines that multi-hop communication is necessary, the control unit 11 may determine communication settings based on the state information. The communication settings are, for example, at least one of the destination and the maximum number of hops for multi-hop communication.

If the control unit 11 determines that multi-hop communication is necessary, the communication unit 15 may forward the message using multi-hop communication. If the control unit 11 determines that multi-hop communication is not necessary, the communication unit 15 may not forward the message.

If the received message was a single-hop communication message, but the control unit 11 determines that the message needs to be forwarded, the control unit 11 may change the message to multi-hop communication and the communication unit 15 may forward the message. Even if the received message is a multi-hop communication message, if the control unit 11 determines that the message does not need to be forwarded, the communication unit 15 may not need to forward the message. For example, if the destination is the vehicle's position or the vehicle is in the destination area, the control unit 11 may determine that the received message does not need to be forwarded.

Since a message may include the location of the sender, the control unit 11 may obtain the location of the sender based on the received message. The sender of the message may be, for example, another vehicle or the RSU 20. If the location of the sender of the received message can be obtained, it becomes easier to determine whether or not the received message needs to be forwarded. For example, if a message needs to arrive at an intersection with the sender, but it is difficult to receive the message at the intersection, the control unit 11 determines that the received message needs to be forwarded. For example, if there is a structure around the intersection, or if there is an area on the intersection with the sender that is out of the line of sight from the sender, it is difficult to receive the message at the intersection. If the message needs to arrive in that area, the control unit 11 determines that the received message needs to be forwarded. If there is a destination in the above area that requires a message, it means that the message needs to arrive at the above area.

The control unit 11 may also determine that it is necessary to forward the received message if there is a high possibility that the source vehicle will approach a vehicle on an intersection. The possibility that the source vehicle will approach a vehicle on an intersection may have the same meaning as the possibility that another vehicle will approach the vehicle described in the second embodiment. The control unit 11 may determine that it is necessary to forward the message if the source and destination are out of line of sight.

When the control unit 11 determines that the message needs to be forwarded, it may determine the destination of the multi-hop communication, i.e., the transmission destination, based on the state information. The control unit 11 may determine the destination to be an area on an intersection with the sender where it is difficult to receive the message. The control unit 11 may also determine the destination to be an area on an intersection with the sender that is out of line of sight from the sender. The control unit 11 may also determine the destination to be an area where a vehicle that requires the message is present.

A specific example of a vehicle forwarding a message will be described with reference to FIG. 10. In the example of FIG. 10, the vehicle receives a message by single-hop communication from a source vehicle on the travel path. If the vehicle determines that it is necessary to forward the message, the vehicle may estimate an area on an intersection with the travel path of the source vehicle where it will be difficult to receive the message. The vehicle may then designate the estimated area as the destination of multi-hop communication and forward the message using multi-hop communication.

Based on the information contained in the received message, the vehicle determines whether the received message also needs to be received at an intersection that intersects with the road on which the vehicle is traveling. If the received message is transmitted by SHB, the range in which the received message needs to be received can be determined from the position of the transmitting vehicle and the communication range of the SHB. If the determined range includes an intersection, the vehicle may determine that the received message also needs to be received at the intersection.

In the example of Figure 10, there are structures around the intersection that make it difficult to receive a message sent by the source vehicle via SHB. The vehicle can recognize the presence of these structures from map information or from sensor detection results when the vehicle passes near the structures. Therefore, the vehicle determines that it is necessary to forward the received message.

Destinations of messages to be forwarded are shown by dashed lines in FIG. 10. The destination area is an area where a vehicle traveling on an intersection toward an intersection may enter the intersection at the same time as the sending vehicle. The vehicle recognizes the location and speed of the sending vehicle and the location of the intersection from the received message, and can predict the time required for the sending vehicle to enter the intersection. The speed range of vehicles traveling on the intersection can also be predicted in advance based on the speed limit, etc. The size of the destination area can be determined from this speed range and the above-mentioned required time. The vehicle may also obtain the speed of vehicles traveling on the intersection through vehicle-to-vehicle communication, sensors, etc. If the speed can be obtained, the speed change range in which the speed changes due to acceleration and deceleration based on the obtained speed may be used instead of the speed range predicted in advance.

The vehicle forwards the received message including the destination determined in this way. The vehicle forwards the message only when it is necessary to forward the message, which reduces the use of wireless resources and improves the reliability of communication.

The destination is set to an area on an intersection that intersects with the road on which the sending vehicle is traveling. The use of wireless resources can also be reduced by not setting the destination to an area where forwarding is not required.

Next, a specific example of RSU 20 forwarding a message will be described. For example, in an RSU 20 installed at an intersection with poor visibility, when the communication unit 25 receives a single-hop communication message from a source vehicle, the control unit 21 may change the message to multi-hop communication and specify a destination position on the intersection for the source vehicle.

In the example of FIG. 11, RSU 20 is installed at an intersection with poor visibility. That is, in communication between a vehicle located on the road that RSU 20 faces and a vehicle located on an intersection that intersects with that road, there is a non-line-of-sight area due to structures around the intersection. At the position of the sending vehicle shown in FIG. 11, there is a non-line-of-sight area on the intersection.

In this example, the RSU 20 receives a single-hop communication message from the source vehicle. The RSU 20 may be configured to forward all received messages based on the environment in which the RSU 20 is installed, such as an environment in which the RSU 20 is surrounded by an environment in which communication using SHB is difficult.

The RSU 20 may also determine whether there is an area where reception is difficult in the area where the received message should be received, and if there is an area where reception is difficult, determine to forward the received message. The presence or absence of an area where reception is difficult may be determined based on the position of the source vehicle included in the received message and map information acquired or stored by the RSU 20. For example, in the example shown in FIG. 11, there is an area where reception is difficult at the intersection where the message sent by the source vehicle intersects with the road on which the source vehicle is traveling due to a structure. On the other hand, in the example shown in FIG. 11, there is no structure at the upper side of the intersection in FIG. 11. Therefore, if the position of the source vehicle is at the upper side of the intersection in FIG. 11, the RSU 20 does not need to determine to forward the received message.

When the RSU 20 determines that it is necessary to forward the received message, it may estimate an area in which it is difficult to receive the message. The area in which it is difficult to receive the message may be an area on an intersection with the driving path of the sending vehicle, which may be a preset area. The position of the structure can be obtained in advance. It is possible to calculate the range of the sending vehicle where an area where reception is difficult on the intersection due to the structure will occur, and the size of that area. The RSU 20 may set the area in which reception is difficult to a fixed area that includes all of the areas calculated while changing the position of the sending vehicle. Alternatively, the RSU 20 may calculate the area in which reception is difficult each time from the position of the sending vehicle and map information included in the received message. The RSU 20 may specify the area in which reception is difficult as the destination of multi-hop communication, and forward the message using multi-hop communication.

Furthermore, the control unit 11 or the control unit 21 (hereinafter, simply the control unit 11) may determine that the message received by the SHB is to be forwarded by multi-hop communication when a traffic jam is detected. When a traffic jam occurs, the speed of the vehicle connected to the end of the traffic jam may suddenly decrease, so the following vehicle needs to be careful, as in the case of detecting sudden braking. Therefore, when the control unit 11 detects a traffic jam, the message is to be multi-hop communication. In addition to detecting a traffic jam, the control unit 11 may determine whether to use multi-hop communication by taking into account the shape of the road where the traffic jam occurs. For example, the control unit 11 may determine that the message is to be forwarded when, in addition to detecting a traffic jam, the end of the traffic jam is near the exit of an intersection, or in the middle of or near the exit of a sharp curve. Whether or not the curve is sharp may be determined, for example, by comparing a preset threshold value with the degree of curvature of the road. When using multi-hop communication based on the detection of a traffic jam, the control unit 11 may set an area on the road toward the traffic jam as the destination.

When driving around a sharp curve, the driver must be cautious, just as when driving near an intersection. Therefore, when the vehicle is driving around a sharp curve, the control unit 11 may decide to perform multi-hop communication of a message regardless of whether a traffic jam is detected.

For example, the control unit 11 may detect a congestion state based on the V2X communication. When the communication unit 15 receives a message for multi-hop communication and a congestion state is detected, the control unit 11 may stop forwarding in the multi-hop communication. Furthermore, when a congestion state is detected, the control unit 11 may set the message to single-hop communication even if it can be determined to perform multi-hop communication according to the conditions and the like described above. Setting the communication to single-hop communication may mean changing the multi-hop communication to single-hop communication. When the communication unit 15 receives a message for single-hop communication and a congestion state is detected, the control unit 11 may determine that multi-hop communication is unnecessary even if it can be determined to change to multi-hop communication and forward the message according to the conditions and the like described above.

(Additional Note)
The following is noted regarding one embodiment of the present disclosure.

[Appendix 1]
a control unit that determines whether multi-hop communication is required for transmitting a message;
and a communication unit that transmits a message using multi-hop communication when it is determined that multi-hop communication is necessary.
[Appendix 2]
The control unit determines whether multi-hop communication is necessary to transmit a message based on whether or not there is an area in at least a portion of the communication area of a message via single-hop communication where single-hop communication is difficult due to radio interference.
[Appendix 3]
The message control device is used in a vehicle,
2. The message control device according to claim 1, wherein the control unit determines whether or not multi-hop communication is required for transmitting the message based on a road structure around the vehicle.
[Appendix 4]
The message control device according to claim 3, wherein the control unit determines whether multi-hop communication is required to transmit a message based on whether the vehicle is traveling at a position where an intersection is located within a predetermined distance ahead.
[Appendix 5]
The message control device according to claim 4, wherein the control unit determines that multi-hop communication is required to transmit the message based on the presence of an electromagnetic interference between the vehicle and an intersection that intersects with the road on which the vehicle is traveling at the intersection.
[Appendix 6]
The message control device described in Appendix 4, wherein when the vehicle is traveling at a position where there is an intersection within a specified distance ahead, the control unit determines that multi-hop communication is required to send a message, regardless of whether there is an electromagnetic interference between the vehicle and an intersection that intersects with the road on which the vehicle is traveling at the intersection.
[Appendix 7]
The control unit determines whether multi-hop communication is required to send a message based on whether the vehicle is traveling at a location where there is an intersection within a specified distance ahead, and whether there is a traffic light at the intersection.
[Appendix 8]
The message control device according to claim 7, wherein the control unit determines that multi-hop communication is required to transmit the message based on the color of the traffic light allowing the vehicle to enter the intersection.
[Appendix 9]
The message control device according to claim 3, wherein the control unit determines whether multi-hop communication is required for transmitting the message based on whether the vehicle is traveling around a sharp curve.
[Appendix 10]
2. The message control device according to claim 1, wherein the control unit determines whether or not multi-hop communication is required to transmit the message based on a reception status of a signal transmitted from a communication partner.
[Appendix 11]
2. The message control device according to claim 1, wherein the control unit determines whether or not multi-hop communication is required for transmitting the message based on whether or not a signal requesting multi-hop communication has been received.
[Appendix 12]
The message control device according to claim 2, wherein when the control unit determines that multi-hop communication is necessary, the communication unit transmits a message to a destination area including an area where single-hop communication is difficult due to radio interference.
[Appendix 13]
A message control device as described in Appendix 4, wherein when the control unit determines that multi-hop communication is necessary, the communication unit transmits a message to an area where at least a portion of the destinations include an intersection that intersects with the road on which the vehicle is traveling at the intersection.
[Appendix 14]
A message control device as described in Appendix 13, wherein the shape of the destination area is a rectangle along an intersection.
[Appendix 15]
determining whether multi-hop communication is required for transmitting a message;
if it is determined that multi-hop communication is necessary, transmitting the message using multi-hop communication.

(Hardware configuration)
FIG. 12 is a diagram showing an example of a vehicle 10 according to an embodiment. The vehicle 10 includes a control unit 11, a sensor 12, a locator 13, an input/output unit 14, and a communication unit 15. The block diagram shown in this example shows functional blocks. Each of these functional blocks (components) is realized by any combination of at least one of hardware and software. Note that the "vehicle" described in the above embodiment may be read as any one or more functional blocks (e.g., the control unit 11, the communication unit 15) in the vehicle 10.

Figure 12 shows only the parts necessary for explaining the present disclosure. The vehicle 10 includes parts necessary for driving, such as a drive unit and an operating unit. The drive unit is, for example, one or both of an engine and a motor. The operating unit is, for example, a steering wheel.

The control unit 11 is composed of a microprocessor (hereinafter simply referred to as the processor) 111, a memory 112, and a communication interface 113. The communication interface 113 is, for example, an input/output (IO) port. The control unit 11 may be called an electronic control unit (ECU), or may be composed of a central processing unit (CPU) including interfaces with peripheral devices, a control device, an arithmetic unit, registers, etc.

The control unit 11 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and the processing of the processor 111 may be realized using the hardware. For example, the processor 111 may be implemented using at least one of these pieces of hardware.

Each function of the vehicle 10 (e.g., message generation, processing based on information from the sensor 12) may be realized, for example, by loading a specific software (program) onto hardware such as the processor 111 and memory 112, so that the processor 111 performs calculations, controls communication via the communication unit 15, and controls at least one of reading and writing data in the memory 112.

The processor 111 may, for example, operate an operating system to control the entire in-vehicle computer. The processor 111 may also read programs, software modules, data, etc. into the memory 112 and execute various processes according to these. The program may be a program for causing the computer to execute at least a portion of the operations described in the above-mentioned embodiments. The program may be read as program code.

The memory 112 is a computer-readable recording medium and may be composed of at least one of, for example, a Read Only Memory (ROM), an Erasable Programmable ROM (EPROM), an Electrically EPROM (EEPROM), a Random Access Memory (RAM), or other suitable storage medium. The memory 112 may also be called a register, a cache, a main memory, or the like. The memory 112 may store executable programs, software modules, and the like for implementing a method according to an embodiment of the present disclosure.

The control unit 11 may include a storage (auxiliary storage device) that is a computer-readable recording medium with a larger capacity than the memory 112. The control unit 11 may read and write data to and from the memory 112 to the storage. The storage is not limited to being provided in the control unit 11, and may be independent of the control unit 11 and connected to the control unit 11 via a communication line.

The communication interface 113 may be called an input/output port, and may be used to exchange information between the control unit 11 and other blocks. The other blocks are, for example, blocks used for operation. The control unit 11 may obtain signals from the sensors 12 via the communication interface 113.

The control unit 11 may provide driving assistance functions, autonomous driving functions, etc., based on an Inertial Navigation System (INS), an Artificial Intelligence (AI) chip, an AI processor, AI functions, etc.

The sensor 12 may include, for example, a current sensor, a wheel rotation speed sensor, a tire pressure sensor, a vehicle speed sensor, an acceleration sensor, an angular velocity sensor, an object detection sensor, and the like. Each sensor may provide a signal (on-off signal, analog signal, digital signal, etc.) obtained by measurement to the control unit 11 via the communication interface 113. For example, the object detection sensor may generate a detection signal when it detects a target such as an obstacle, a vehicle, or a pedestrian.

The sensor 12 may include a device capable of providing information on the environment surrounding the vehicle 10, such as a millimeter wave radar, a Light Detection and Ranging (LiDAR), a camera, or a gyro system (e.g., an Inertial Measurement Unit (IMU)). A plurality of sensors 12 may be mounted on the vehicle 10, and a plurality of sensors 12 of the same type may be mounted on the vehicle. For example, cameras serving as the sensor 12 may be mounted on the front, rear, and both sides of the vehicle 10.

The locator 13 acquires location information of the vehicle 10. The locator 13 may acquire the location information based on a positioning system (e.g., a satellite positioning system (Global Navigation Satellite System (GNSS), Global Positioning System (GPS), etc.)), map information (e.g., a High Definition (HD) map, an Autonomous Vehicle (AV) map, etc.), and the speed, acceleration, angular velocity, etc. obtained from the sensor 12 described above.

The input/output unit 14 includes an input device that accepts input from the outside and an output device that performs output to the outside. The input device is, for example, a keyboard, a mouse, a microphone, a switch, a button, or a sensor. The output device is, for example, a display, a speaker, or a Light Emitting Diode (LED) lamp. The input device and the output device may be integrated into one structure (for example, a touch panel).

The input/output unit 14 may be composed of various devices for providing various information such as driving information, such as a car navigation system, an audio system, a television, a radio, etc., and one or more ECUs for controlling these devices. The input/output unit 14 may provide various information/services to the occupants of the vehicle 10 by using information acquired from an external device (e.g., an ITS server 30) via the communication unit 15.

The input/output unit 14 may receive input through user operation, or may be connected to a specific device, storage medium, etc. to receive data input. The input/output unit 14 may output the input result to, for example, the control unit 11.

The input/output unit 14 may output data, content, etc. in a format that is perceptible to the user.

The communication unit 15 is hardware for wirelessly communicating with an external device (e.g., another vehicle 10, an ITS server 30, etc.), and is also referred to as, for example, a transmission/reception device, a network device, a network controller, a network card, a communication module, etc. The communication unit 15 may be configured to include a high-frequency switch, a duplexer, a filter, an amplifier, a frequency synthesizer, an antenna, etc. The communication unit 15 may be configured with a transmitter, a receiver, a transmission/reception circuit, or a transmission/reception device that are described based on a common understanding in the technical field to which the present disclosure relates.

The communication unit 15 supports, for example, Long Term Evolution (LTE), LTE-Advanced (LTE-A), LTE-Beyond (LTE-B), SUPER 3G, IMT-Advanced, 4th generation mobile communication system (4G), 5th generation mobile communication system (5G), 6th generation mobile communication system (6G), xth generation mobile communication system (xG (x is, for example, an integer or decimal)), Future Radio Access (FRA), New-Radio Access Technology (RAT), New Radio (NR), New radio access (NX), Future generation radio access (FX), Global System for Mobile communications (GSM (registered trademark)), CDMA2000, Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE Communication may be performed using 802.20, Ultra-WideBand (UWB), Bluetooth (registered trademark), or other wireless communication methods, or wireless communication methods that are expanded, modified, created, or defined based on these.

The communication unit 15 may be controllable by the processor 111 of the control unit 11, and the communication unit 15 may be included in the control unit 11.

The communication unit 15 may transmit at least one of the signal from the sensor 12, information obtained based on the signal, information based on the input from the input/output unit 14, etc., to an external device via wireless communication.

The communication unit 15 may receive various information (traffic information, signal information, vehicle distance information, etc.) from an external device and provide it to the control unit 11. This information may be output via the input/output unit 14. The control unit 11 may perform control based on this information.

The method of realizing each functional block is not particularly limited. That is, each functional block may be realized using one device that is physically or logically combined, or may be realized using two or more devices that are physically or logically separated and connected directly or indirectly (e.g., using wires, wirelessly, etc.). The functional block may be realized by combining the one device or the multiple devices with software.

For example, although only one processor 111 is shown, there may be multiple processors. Furthermore, processing may be performed by one processor, or processing may be performed by two or more processors simultaneously, sequentially, or using other techniques. Furthermore, processor 111 may be implemented by one or more chips.

The hardware of each functional block may be connected by a bus for communicating information. The bus may be configured using a single bus, or may be configured using different buses between each device. The bus may be realized by a wired or wireless system.

The RSU 20, ITS server 30, etc. may also have the same configuration as the vehicle 10. A person skilled in the art would be able to understand the descriptions related to the vehicle 10 by appropriately interpreting them.

In addition, the configuration of the vehicle 10 that includes the control unit 11 or the configuration that includes the control unit 11 and the communication unit 15 may be called a message control device.

Figure 13 is a diagram showing an example of an RSU according to an embodiment. The RSU 20 includes a control unit 21 and a communication unit 25. The control unit 21 may include a microprocessor (hereinafter simply referred to as a processor) 211, a memory 212, and a communication interface 213.

The control unit 21 may have the same functions as the control unit 11. The communication unit 25 may have the same functions as the communication unit 15. The processor 211, the memory 212, and the communication interface 213 may be the same as the processor 111, the memory 112, and the communication interface 113, respectively.

In addition, the configuration of the RSU 20 that includes the control unit 21 or the configuration that includes the control unit 21 and the communication unit 25 may be called a message control device.

The message control device may execute the message control method described above.

(Modification)
In addition, terms explained in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings.

In this disclosure, terms such as apparatus, circuit, device, section, and unit may be read interchangeably.

The term "vehicle" in the present disclosure may be interpreted as any moving object. Examples of moving objects include, but are not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcarts, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones, multicopters, quadcopters, balloons, and objects mounted thereon.

The moving body may be a moving body that travels autonomously based on an operating command. The moving body may be a moving body that moves with a person on board, in other words a vehicle (e.g., a car, an airplane, etc.), or it may be an unmanned moving body (e.g., a drone, an autonomous vehicle, etc.). The moving body may be a robot. The robot may be manned or unmanned.

The information, parameters, etc. described in this disclosure may be represented using absolute values, may be represented using relative values from a predetermined value, or may be represented using other corresponding information. For example, a radio resource may be indicated by a predetermined index.

The names used for parameters and the like in this disclosure are not limiting in any way. Furthermore, the formulas and the like that use these parameters may differ from those explicitly disclosed in this disclosure.

The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

The input and output information, signals, etc. may be stored in a specific location (e.g., memory) or may be managed using a management table. The input and output information, signals, etc. may be overwritten, updated, or added to. The output information, signals, etc. may be deleted. The input information, signals, etc. may be transmitted to another device.

Notification of information is not limited to the aspects/embodiments described in this disclosure and may be performed using other methods.

In addition, notification of specific information (e.g., notification that "X is the case") is not limited to explicit notification, but may be implicit (e.g., by not notifying the specific information or by notifying other information).

Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

Software, instructions, information, etc. may also be transmitted and received via a transmission medium. For example, if the software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and/or wireless technologies (such as infrared, microwave), then these wired and/or wireless technologies are included within the definition of a transmission medium.

Each aspect/embodiment described in this disclosure may be used alone, in combination, or switched between depending on the implementation. In addition, the processing procedures, sequences, flow charts, etc. of each aspect/embodiment described in this disclosure may be rearranged as long as there is no inconsistency. For example, the methods described in this disclosure present elements of various steps using an exemplary order, and are not limited to the particular order presented.

As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

Any reference to elements using designations such as "first," "second," etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient way to distinguish between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must precede the second element in some way.

In this disclosure, "A/B" and "at least one of A and B" may be interpreted as interchangeable. Also, in this disclosure, "A/B/C" may mean "at least one of A, B, and C."

In this disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "combined" may also be interpreted in the same way as "different."

When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, similar to the term "comprising." Additionally, the term "or," as used in this disclosure, is not intended to be an exclusive or.

In this disclosure, where articles have been added through translation, such as a, an, and the in English, this disclosure may include that the nouns following these articles are in the plural form.

In this disclosure, terms such as "less than", "less than", "greater than", "more than", "equal to", etc. may be read as interchangeable. In addition, in this disclosure, terms meaning "good", "bad", "big", "small", "high", "low", "fast", "slow", "wide", "narrow", etc. may be read as interchangeable, not limited to positive, comparative and superlative. In addition, in this disclosure, terms meaning "good", "bad", "big", "small", "high", "low", "fast", "slow", "wide", "narrow", etc. may be read as interchangeable, not limited to positive, comparative and superlative, as expressions with "ith" (i is any integer) (for example, "best" may be read as "ith best").

In this disclosure, the terms "of," "for," "regarding," "related to," "associated with," etc. may be read interchangeably.

Although the invention according to the present disclosure has been described in detail above, it is clear to those skilled in the art that the invention according to the present disclosure is not limited to the embodiments described herein. The invention according to the present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the invention as determined based on the description of the present disclosure. Therefore, the description of the present disclosure is intended as an illustrative example and does not have any restrictive meaning on the invention according to the present disclosure.

Claims (15)

a control unit that determines whether multi-hop communication is required for transmitting a message;
a communication unit that transmits the message using the multi-hop communication when it is determined that the multi-hop communication is necessary. The message control device according to claim 1, wherein the control unit determines whether multi-hop communication is necessary to transmit the message based on whether there is an area in at least a part of the communication area of the message by single-hop communication where the single-hop communication is difficult due to radio wave obstructions. The message control device is used in a vehicle,
The message control device according to claim 1 , wherein the control unit determines whether or not multi-hop communication is required for transmitting the message based on a road structure around the vehicle. The message control device according to claim 3, wherein the control unit determines whether multi-hop communication is required to transmit the message based on whether the vehicle is traveling at a position where an intersection is located within a predetermined distance ahead. The message control device according to claim 4, wherein the control unit determines that multi-hop communication is required to transmit the message based on the presence of a radio wave obstruction between the vehicle and an intersection that intersects with the road on which the vehicle is traveling at the intersection. The message control device according to claim 4, wherein, when the vehicle is traveling at a position where an intersection is located within a predetermined distance ahead, the control unit determines that multi-hop communication is required to transmit the message, regardless of whether or not a radio wave obstruction exists between the vehicle and an intersection that intersects with the road on which the vehicle is traveling at the intersection. The message control device according to claim 4, wherein the control unit determines whether multi-hop communication is required to transmit the message based on whether the vehicle is traveling at a position where there is an intersection within a predetermined distance ahead, and whether there is a traffic light at the intersection. The message control device according to claim 7, wherein the control unit determines that multi-hop communication is required to transmit the message based on the light color of the traffic light permitting the vehicle to enter the intersection. The message control device according to claim 3, wherein the control unit determines whether multi-hop communication is required to transmit the message based on whether the vehicle is traveling around a sharp curve. The message control device according to claim 1, wherein the control unit determines whether or not multi-hop communication is required to transmit the message based on a reception status of a signal transmitted from a communication partner. The message control device according to claim 1, wherein the control unit determines whether or not multi-hop communication is required to transmit the message based on whether or not a signal requesting multi-hop communication has been received. The message control device according to claim 2, wherein, when the control unit determines that the multi-hop communication is necessary, the communication unit transmits the message to a destination area that includes an area in which the single-hop communication is difficult due to radio wave obstructions. The message control device according to claim 4, wherein, when the control unit determines that the multi-hop communication is necessary, the communication unit transmits the message to an area in which at least some of the destinations include an intersection that intersects with the road on which the vehicle is traveling at the intersection. The message control device according to claim 13, wherein the shape of the destination area is a rectangle along the intersection. determining whether multi-hop communication is required for transmitting a message;
If it is determined that the multi-hop communication is necessary, transmitting the message using the multi-hop communication.

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