JP7596824B2 - Vehicle communication system and communication control method - Google Patents

Description

This disclosure relates to technology for sharing data received from an external device through vehicle-to-vehicle communication.

Patent Document 1 discloses a technology for generating and updating traffic information, in which a center sets a vehicle group consisting of multiple vehicles and a representative vehicle based on probe information uploaded from each of the multiple vehicles. In Patent Document 1, probe information refers to vehicle position, driving speed, fuel efficiency, and wiper operation status. The configuration disclosed in Patent Document 1 aims to reduce communication volume by regarding the probe information from the representative vehicle as the probe information for the entire vehicle group.

Patent Document 2 also discloses technology that uses vehicle-to-vehicle communication as a configuration for reducing the amount of communication when a vehicle obtains specified content data from a center. That is, the center divides the content data into multiple partial data and distributes them, and each vehicle interpolates and integrates the partial data that it has not obtained by obtaining it from other vehicles through vehicle-to-vehicle communication. Note that the configuration disclosed in Patent Document 2 does not have the concept of a vehicle group, and whether or not vehicle-to-vehicle communication with a vehicle that has unobtained data is possible is a matter of chance.

JP 2012-89088 A JP 2010-220050 A Patent No. 2019-41179

To put autonomous driving into practical use and realize a safer traffic society, it is preferable to wirelessly distribute dynamic maps from a center to each vehicle via roadside units or wide-area wireless base stations such as 4G. A dynamic map here refers to data on dynamic map elements, such as information on moving objects in blind spots on the road and the status of traffic lights.

However, in a configuration in which data is distributed from a wide-area wireless base station to each vehicle, there is a concern that wireless resources may become strained. In addition, in a configuration in which data is distributed individually from a roadside unit to each vehicle, the connection time between the roadside unit and each vehicle is short, which may limit the amount of data that can be transmitted from the roadside unit to the vehicle. This is because the communication range of a roadside unit is finite, such as within a few hundred meters. Furthermore, the faster the vehicle is traveling, the shorter the time that the vehicle spends within the communication range of the roadside unit. Therefore, the available communication time may be insufficient for the time required to transmit data.

With this in mind, the developers of this disclosure have considered a technology that forms a vehicle group based on vehicle position information, etc., and has each vehicle in the vehicle group share the task of receiving a dynamic map from a roadside unit, which is then shared and complemented within the vehicle group. With this configuration, data communication is performed on a vehicle group basis, which is expected to reduce the risk of insufficient communication time with the roadside unit and the risk of wireless resources becoming strained.

However, after further investigation, the developers discovered that, depending on the data size of the dynamic map, there could be cases where communication time was insufficient, even when each vehicle in the fleet shared the data reception.

This disclosure was made based on these circumstances, and its purpose is to provide a vehicle communication system and communication control method that can reduce the risk that a vehicle will not be able to receive data from a roadside unit.

The vehicle communication system for achieving the object is a vehicle communication system in which each of a plurality of vehicles (M) configured to be able to perform vehicle-to-vehicle communication receives distribution data distributed from a roadside unit (3), and includes a central control unit (4, 5) configured to be able to communicate with the vehicles via the roadside unit or a wireless base station, and the central control unit includes an individual information acquisition unit (J1) that acquires a control plan created in each of the plurality of vehicles from each of the plurality of vehicles via the roadside unit or a wireless base station, a vehicle group organization unit (J6) that organizes a vehicle group, which is a group of a plurality of vehicles, based on the control plans of each of the plurality of vehicles, and a vehicle group speed acquisition unit (J63) that acquires the moving speed of the vehicle group in the communication area of the roadside unit based on the control plans of the vehicles that constitute the vehicle group. ), a connected vehicle setting unit (J62) that sets, for each time period, connected vehicles that will perform data communication with the roadside unit among the multiple vehicles that make up the vehicle group based on a control plan for each vehicle, a notification processing unit (J8) that distributes vehicle group setting data indicating a combination of vehicles that make up the vehicle group set by the vehicle group formation unit to at least one vehicle related to the vehicle group, and a data size acquisition unit (J41) that acquires the size of the distributed data, wherein, when the connected vehicles receive a part or all of the distributed data from the roadside unit, they are configured to share the received data with general vehicles that are vehicles other than the connected vehicles that make up the vehicle group through vehicle-to-vehicle communication, and the vehicle group formation unit adjusts the length of the vehicle group based on the size of the distributed data and the movement speed of the vehicle group.

According to the above configuration, the length of the vehicle group is adjusted according to the size of the distribution data and the moving speed of the vehicle group. Therefore, in a configuration in which data communication with a roadside unit is performed on a vehicle group basis, it is possible to reduce the risk that the communication time between the vehicle group and the roadside unit will be insufficient for the time required for data distribution. In turn, it is possible to reduce the risk that the vehicle will not be able to receive data from the roadside unit.

The communication control method for achieving the above object is a communication control method for each of a plurality of vehicles (M) configured to be able to perform vehicle-to-vehicle communication to receive predetermined distribution data distributed from a roadside unit (3), the method comprising the steps of: a central control device (4, 5) configured to be able to communicate with the plurality of vehicles via the roadside unit or a wireless base station acquiring, from each of the plurality of vehicles, a control plan created in each of the plurality of vehicles , via the roadside unit or the wireless base station (S102a); forming a vehicle group that is a group of the plurality of vehicles based on the control plans of the respective vehicles (S106); acquiring, by the central control device, the moving speed of the vehicle group in the communication area of the roadside unit based on the control plans of the vehicles that constitute the vehicle group (S404); The method includes the device setting, for each time period, connected vehicles, which are vehicles that will communicate data with the roadside unit, among the multiple vehicles that make up the vehicle group, based on a control plan for each vehicle (S109) ; the central control unit distributing vehicle group setting data indicating a combination of vehicles that make up the vehicle group to at least one vehicle related to the vehicle group (S106b); the central control unit acquiring the size of the distributed data (S401) ; when the connected vehicle receives some or all of the distributed data from the roadside unit, sharing the received data with general vehicles, which are vehicles other than the connected vehicles that make up the vehicle group, via vehicle-to-vehicle communication (S111); and the central control unit adjusting the length of the vehicle group based on the size of the distributed data and the movement speed of the vehicle group (S408).

The above communication control method corresponds to the above-mentioned vehicle communication system, and has the same effect as the above-mentioned vehicle communication system.

Note that the reference characters in parentheses in the claims indicate the correspondence with the specific means described in the embodiments described below as one aspect, and do not limit the technical scope of this disclosure.

1 is a diagram showing an overall configuration of a vehicle communication system Sys; 2 is a diagram conceptually showing the relationship between a roadside unit 3, a network device 4, and a server 5. FIG. 1 is a block diagram showing a configuration of an in-vehicle device 1. FIG. FIG. 2 is a block diagram for explaining the function of the vehicle-mounted device 1. 2 is a block diagram for explaining the configuration and functions of a wireless base station 2. FIG. FIG. 2 is a block diagram for explaining the configuration and functions of a roadside unit 3. FIG. 13 is a conceptual diagram for explaining segmentation of distribution data. FIG. 2 is a block diagram for explaining the configuration and functions of a network device 4. FIG. 11 is a diagram for explaining a method for setting a vehicle group. 11A and 11B are diagrams for explaining the effect of the vehicle group setting method of the present disclosure. FIG. 13 is a diagram for explaining the operation of the plan correction unit J61. FIG. 2 is a block diagram for explaining the configuration and functions of a server 5. FIG. 2 is a sequence diagram for explaining the operation of each device related to the formation of a group of vehicles. FIG. 4 is a diagram showing an example of vehicle group setting data. FIG. 4 is a sequence diagram for explaining the operation of each device involved in the distribution of static map data. FIG. 4 is a sequence diagram for explaining the operation of each device involved in the distribution of dynamic map data. FIG. 2 is a diagram illustrating an example of a vehicle fleet. 18 is a diagram showing a transition of communication quality between each vehicle constituting the vehicle group shown in FIG. 17 and the roadside unit 3. FIG. FIG. 11 is a diagram showing an example of a shared route corresponding to a case where vehicles A to C are connected vehicles. 11 is a flowchart corresponding to a resource allocation related process. 13 is a flowchart corresponding to a vehicle group length adjustment process. 11 is a conceptual diagram for explaining the operation of a vehicle group length adjustment process. FIG. FIG. 13 is a diagram showing an example of a combination of vehicles connected in each time slot. FIG. 2 is a diagram showing an example of a manner in which radio resources are allocated to each vehicle; 4 is a sequence diagram showing a detailed procedure of data communication between a roadside unit 3 and a vehicle group. FIG. FIG. 11 is a diagram illustrating an example of a method for setting a connected vehicle. FIG. 11 is a diagram illustrating an example of a method for setting a connected vehicle. FIG. 11 is a diagram illustrating an example of a method for setting a vehicle group. FIG. 13 is a diagram for explaining how to handle a vehicle that is about to turn right or left. FIG. 2 is a diagram showing a scene in which a roadside unit 3 performs short-range communication in parallel with a group of multiple vehicles. 11 is a diagram showing an example of a manner of allocation of wireless resources when a roadside unit 3 performs short-range communication in parallel with a plurality of vehicle groups. FIG. FIG. 11 is a diagram showing an example of setting a communication schedule taking into account vehicle-side traffic volume.

Embodiments of the present disclosure will now be described with reference to the drawings. FIG. 1 is a diagram showing an example of a schematic configuration of a vehicle communication system Sys according to the present disclosure. Note that "NW" in each drawing is an abbreviation for network.

<Overall composition>
1, the vehicle communication system Sys may include an in-vehicle device 1, a wireless base station 2, a roadside device 3, a network device 4, and a server 5. The network device 4 is a component of a core network CN, which is a wide-area communication network.

In FIG. 1, only two on-board vehicles M, which are vehicles equipped with the on-board device 1, are shown, but in reality, there may be three or more vehicles in the entire system. Hereinafter, for a certain on-board device 1, the vehicle in which the on-board device 1 is mounted will be referred to as the subject vehicle, and vehicles other than the subject vehicle will be referred to as other vehicles. The on-board vehicle M is a vehicle that runs on a road. The on-board vehicle M may be a four-wheeled vehicle, a two-wheeled vehicle, a three-wheeled vehicle, etc. Two-wheeled vehicles also include motorized bicycles. In this embodiment, as an example, the on-board vehicle M as the subject vehicle is a four-wheeled vehicle. Hereinafter, the term "vehicle" will basically refer to the on-board vehicle M, except for the shielded vehicle NM.

There may also be multiple wireless base stations 2, roadside units 3, and network devices 4. For example, as shown in FIG. 2, multiple network devices 4 are connected to a server 5, and multiple roadside units 3 are also connected to each of the multiple network devices 4. For each vehicle and each vehicle-mounted device 1, the wireless base stations 2, roadside units 3, network devices 4, and servers 5 correspond to external devices.

The vehicle-mounted device 1 is an automated driving device equipped with a function for wireless communication with other vehicles, roadside devices 3, and wireless base stations 2. The vehicle-mounted device 1 is configured to be able to perform wireless communication with the wireless base stations 2 in accordance with standards such as LTE (Long Term Evolution). The vehicle-mounted device 1 corresponds to user equipment (UE) for the wireless base stations 2 and the core network CN. The vehicle-mounted device 1 is also configured to be able to perform direct wireless communication with the roadside devices 3 and other vehicles. In other words, each mounted vehicle is configured to be able to perform direct wireless communication with each other (so-called vehicle-to-vehicle communication) via the vehicle-mounted device 1. The vehicle-mounted device 1 creates a control plan for autonomously driving the vehicle based on data acquired through road-to-vehicle communication or vehicle-to-vehicle communication.

The wireless base station 2 is wireless equipment that provides a mobile communication system that complies with the standards of, for example, LTE (Long Term Evolution), 4G, or 3G. Here, as an example, the wireless base station 2 and the vehicle-mounted device 1 are configured to be able to perform wireless communication that complies with 4G and LTE as wide-area communication. The wireless base station 2 is also called an eNB (evolved NodeB).

Here, wide-area communication refers to wireless communication in a manner that allows communication distances of 500 m or 1 km or more. Parts that are not described in the embodiments are assumed to be performed by methods defined in the LTE or 4G standards. The wireless base station 2 may provide wireless communication conforming to the 3G standard. In addition, the wireless base station 2 may be a facility that performs wireless communication conforming to 5G (so-called gNB: next generation NodeB) when the communication range can be formed in a relatively wide area. Hereinafter, LTE, 3G, 4G, 5G, etc. are collectively referred to as LTE, etc. The wireless base station 2 transmits and receives wireless signals conforming to LTE, etc., with the vehicle-mounted device 1. The following embodiments can be modified as appropriate to conform to communication architectures such as 3G, 4G, and 5G defined by 3GPP (Third Generation Partnership Project).

The wireless base station 2 is arranged for each predetermined cell. A cell refers to the communication range covered by one wireless base station 2. The wireless base station 2 itself may also be called a cell. Cell types according to size include macrocells, microcells, nanocells, picocells, etc. A macrocell is a cell with a cell radius of, for example, 500 m to several km. Some macrocells have a cell radius of more than 10 km. A microcell is a cell with a cell radius of several hundred meters. Nanocells and picocells are cells with a cell radius of several tens of meters to 100 meters. Nanocells are also called small cells. There is no clear definition of the names of cells according to their size, and the radii of the various cells mentioned above are merely examples. The actual size and shape of a cell may vary depending on the radio wave environment of a building, etc.

Here, as an example, the wireless base station 2 is configured as a macrocell. The dashed line in FIG. 1 indicates the communication range of the wireless base station 2 as a macrocell. The wireless base station 2 is connected to the core network CN via an access line such as an IP (Internet Protocol) network. The wireless base station 2 relays traffic between the vehicle-mounted device 1 and the core network CN. The wireless base station 2 is also connected to the roadside device 3 via wired or wireless communication so that they can communicate with each other.

The roadside unit 3 is a wireless communication device arranged along the road. The roadside unit 3 is also called an RSU (Road Side Unit). The roadside unit 3 is set to form a communication range that is relatively narrower than that of the wireless base station 2. The roadside unit 3 is a facility that forms a communication area with a radius of about 50 m to 300 m. For example, the communication distance of the roadside unit 3 is set to about 250 m. The two-dot chain line in FIG. 1 conceptually shows the communication area of the roadside unit 3. For convenience, communication with the roadside unit 3 is also called short-range communication. Each vehicle can carry out short-range communication with the roadside unit 3 when the vehicle is within the communication area of the roadside unit 3.

The standard for the short-range communication performed by the roadside unit 3 can be any standard, such as the WAVE (Wireless Access in Vehicular Environment) standard disclosed in IEEE 1509 or the DSRC (Dedicated Short Range Communications) standard. The short-range communication method may be Wi-Fi (registered trademark). That is, the roadside unit 3 may be a Wi-Fi access point/router. Alternatively, the roadside unit 3 may perform communication in accordance with the 5G standard. For example, the roadside unit 3 may be a gNB. Note that in one aspect, a system configuration in which the roadside unit 3 is a gNB can be considered as a non-standalone system configuration in which the entire network is a combination of a 4G/LTE core network CN and a 5G base station.

The core network CN is what is known as an EPC (Evolved Packet Core). The core network CN provides functions such as user authentication, contract analysis, setting of data packet forwarding paths, and QoS (Quality of Service) control. The core network CN may include public communication networks provided by telecommunications carriers, such as IP networks and mobile phone networks.

The core network CN includes, for example, MME, S-GW, P-GW, PCRF, etc. MME is an abbreviation for Mobility Management Entity, and is responsible for managing UEs in a cell and controlling the radio base station 2. S-GW is an abbreviation for Serving Gateway, and is a configuration equivalent to a gateway for data from a UE. P-GW is an abbreviation for Packet Data Network Gateway, and is equivalent to a gateway for connecting to a PDN (Packet Data Network) such as the Internet. The P-GW assigns IP addresses and transfers packets to the S-GW. PCRF is an abbreviation for Policy and Charging Rules Function, and is a logical node that controls the QoS and charging of user data transfer. Elements that constitute QoS include the priority of data transfer, the presence or absence of bandwidth guarantee, the required bandwidth, and the allowable delay time. The PCRF includes a database that has network policies and charging rules. The core network CN may include a Home Location Register (HLR)/Home Subscriber Server (HSS), etc. The names and combinations of the devices constituting the core network CN can be changed as appropriate to correspond to the communication standards adopted by the vehicle communication system Sys, such as 3G and 5G. For example, EPC can be replaced with 5GC (5th Generation Core network). In addition, the functional arrangement in the core network CN can be changed as appropriate. For example, the functions provided by the PCRF may be provided by another device.

The network device 4 refers to a device that executes a V2X edge application, which will be described later, among the facilities that constitute the core network CN, such as an MME or an S-GW. The network device 4 is arranged, for example, for each predetermined management area. The management area may correspond to a map tile, which is a division unit of a map, or may be an administrative division unit such as a prefecture, or may be another division unit. For example, the network device 4 may be arranged for each base node that constitutes the core network CN. The base node is, for example, a data center of a wide area communication network. In one aspect, the network device 4 plays a role of aggregating information acquired by the roadside device 3 and transmitting it to the server 5. In other words, the network device 4 aggregates reports from the roadside devices 3 under its management and reports them to the server 5. The management area corresponds to an area in which the network device 4 can collect information. Details of the network device 4 will be described separately later.

The server 5 is a device that generates data for vehicles by executing data communication with the network device 4 and the vehicles. For example, the server 5 cooperates with the network device 4 to execute a process for distributing static map data showing detailed road structures with high accuracy to each vehicle. The static map data can also be called high-accuracy map data. The static map data can also be called road data. In addition, hereinafter, map elements whose positions and existence status do not change, for example, over a period of several minutes to several hours, such as road structures, are also called static map elements. In contrast, map elements whose positions and existence status change with time changes over a period of several minutes to several hours are called dynamic map elements. Examples of dynamic map elements include congested sections, construction sections, broken-down vehicles, fallen objects, accident locations, lane restriction sections, traffic volume, weather, road surface conditions, and the like. In addition, the average trajectory for each lane, which is obtained by integrating the driving trajectories of multiple vehicles, can also be adopted as a dynamic map element. In addition, the average trajectory for each lane can be used for setting a target trajectory during automatic driving.

The static map data is managed in the server 5, for example, divided into multiple map tiles. Management here includes not only storage but also data updates and distribution to the in-vehicle device 1, roadside device 3, and network device 4. Each map tile corresponds to map data for a different area in the real world. In other words, a map tile refers to multiple small areas obtained by dividing a map according to certain rules. A map tile can also be called a mesh. The range of a map tile may be defined by a data size. For example, each map tile is set so that the amount of data is less than a predetermined value. According to such an embodiment, the data size in one distribution can be kept below a certain value.

The server 5 may be configured to update the static map data based on the probe data uploaded from the vehicle, as described below. The probe data here is a data set indicating the observation positions of features identified by, for example, the surroundings monitoring sensor 7 of the vehicle. The probe data may include, for example, source information, travel trajectory information, route information, and feature information. Travel trajectory information is information indicating the trajectory traveled by the vehicle. Feature information indicates the observation coordinates of features such as landmarks. Examples of landmarks include road markings such as signs, commercial signs, stop lines, poles, and utility poles. The probe data may also include vehicle behavior information such as vehicle speed, steering angle, yaw rate, turn signal operation information, and wiper operation information.

The server 5 also cooperates with the network device 4, which will be described later, to generate and distribute dynamic map data indicating dynamic, semi-dynamic, and semi-static traffic information that is useful for controlling the vehicle. The dynamic map data includes, for example, the average vehicle speed and traffic volume for each link, which is the management unit of the road. A link can also be called a road segment. The dynamic map data can also be data indicating the current position, moving speed, and traveling direction of each other moving object that exists near an intersection on a general road or a branching/merging point on a highway. The dynamic map data can also be information indicating the position and lighting status of a traffic light in front of the vehicle, or information indicating a driving trajectory according to the traveling direction within the intersection. The information indicating the lighting status indicates the current lighting status, the remaining time, the next lighting status, etc.

The dynamic map data may also be information about semi-dynamic map elements that indicate the location or type of obstacles on the road, such as sections where traffic is restricted, the end of a traffic jam, or the location of objects that have fallen on the road. The dynamic map data may also include local weather information. As described above, the dynamic map data can be understood as data that indicates relatively real-time (i.e., dynamic) traffic conditions. Data that indicates traffic conditions corresponds to traffic information.

The server 5 also transfers data such as traffic conditions for a certain area acquired from a certain network device 4 to a network device 4 corresponding to an adjacent area. In terms of the division of roles between the network devices 4 and the server 5, the network device 4 manages relatively narrow dynamic/static maps, while the server 5 manages wider dynamic/static maps. Wide-area traffic information collected by the server 5 is distributed to each network device 4, each of which has a different jurisdiction. For example, the server 5 provides each network device 4 with information such as vehicles entering from areas adjacent to the area managed by a certain network device 4 and their scheduled arrival times. Such information on adjacent areas can be used by the network device 4 for processing such as organizing a vehicle fleet in advance.

<Configuration of the vehicle-mounted device 1>
The vehicle-mounted device 1 is a device that creates a control plan for autonomously driving the vehicle based on data received from a network device 4 or a server 5 via a wireless base station 2 or a roadside device 3. In other words, the vehicle-mounted device 1 corresponds to a so-called automatic driving device that provides an automatic driving function. In one aspect, the vehicle-mounted device 1 corresponds to a UE for the core network CN. The vehicle-mounted device 1 corresponds to a vehicle communication device. Note that the vehicle-mounted device 1 does not need to have all of the functions exemplified below. Furthermore, functions related to automatic driving, such as the function of creating a control plan, may be provided by another device.

As shown in FIG. 3, the vehicle-mounted device 1 is used by being connected to a vehicle condition sensor 6, a surroundings monitoring sensor 7, a locator 8, and a vehicle control ECU 9 via an in-vehicle network IvN, which is a communication network constructed within the vehicle. The ECU in the component names is an abbreviation for Electronic Control Unit and refers to an electronic control device. The vehicle-mounted device 1 can also be considered a type of ECU. Here, the configuration including the vehicle-mounted device 1 and the devices connected to the vehicle-mounted device 1 is also referred to as the vehicle-mounted system IvS.

The vehicle state sensor 6 is a sensor that detects state quantities related to the driving control of the vehicle. The vehicle state sensor 6 includes a shift sensor, a vehicle speed sensor, a steering angle sensor, an acceleration sensor, etc. The type of sensor to be connected to the vehicle-mounted device 1 as the vehicle state sensor 6 can be designed as appropriate, and it is not necessary to have all of the sensors described above.

The perimeter monitoring sensor 7 is a sensor that detects the environmental conditions around the vehicle. The perimeter monitoring sensor 7 is, for example, a perimeter monitoring camera that captures an image of a predetermined range around the vehicle, a millimeter wave radar that transmits a search wave to a predetermined range around the vehicle, a sonar, a LIDAR (Light Detection and Ranging/Laser Imaging Detection and Ranging) sensor, or the like. As an example, the in-vehicle system IvS is equipped with a front camera arranged at the top end of the windshield or the front end of the roof to capture an image of the front of the vehicle as the perimeter monitoring sensor 7. The front camera has a function of identifying objects using, for example, CNN (Convolutional Neural Network) or DNN (Deep Neural Network) technology that applies deep learning. The perimeter monitoring sensor 7 detects objects around the vehicle, such as moving objects such as pedestrians and other vehicles, and stationary objects such as objects that have fallen on the road. In addition, the perimeter monitoring sensor 7 detects road markings such as lane markings around the vehicle. The detection results of the perimeter monitoring sensor 7 are input sequentially to the in-vehicle device 1.

The locator 8 is a device that sequentially calculates (in other words, identifies) the position of the vehicle in which the locator 8 is used (i.e., the vehicle itself). For example, the locator 8 includes a GNSS receiver that receives positioning signals transmitted by positioning satellites that constitute the Global Navigation Satellite System (GNSS), and calculates the position using the positioning signals received by the GNSS receiver. Note that the locator 8 may determine the position by combining the positioning results of the GNSS receiver with the measurement results of a gyro sensor, a vehicle speed sensor, and the like. Furthermore, the locator 8 may correct the position by performing so-called map matching processing, in which the trajectory of the determined position is superimposed on the road shape indicated by the map data. The position information indicating the current position sequentially identified by the locator 8 is provided to the vehicle-mounted device 1.

The vehicle control ECU 9 is an electronic control device that performs acceleration/deceleration control and/or steering control of the vehicle based on instruction signals input from the vehicle-mounted device 1 or operation by a passenger in the driver's seat. Examples of the vehicle control ECU 9 include a steering ECU, a power unit control ECU, and a brake ECU. The steering ECU performs steering control. The power unit control ECU performs acceleration/deceleration control. The brake ECU performs deceleration control. The vehicle control ECU 9 acquires detection signals output from each sensor mounted on the vehicle, such as an accelerator position sensor, a brake stroke sensor, a steering angle sensor, and a vehicle speed sensor. The vehicle control ECU 9 outputs control signals to each driving control device, such as an electronically controlled throttle, a brake actuator, and an EPS (Electric Power Steering) motor, based on operation commands based on the driver's driving operation or control commands from the vehicle-mounted device 1.

Note that some or all of the various devices described above may be directly connected to the in-vehicle device 1 without going through the in-vehicle network IvN. Furthermore, the devices connected to the in-vehicle device 1 are not limited to those exemplified above. A variety of ECUs may be connected to the in-vehicle device 1. The configuration of the in-vehicle system IvS can be changed as appropriate. For example, the function of the locator 8 may be provided by the in-vehicle device 1, or may be provided by a forward camera serving as a surroundings monitoring sensor 7.

The vehicle-mounted device 1 includes a control unit 11, an in-vehicle communication unit 12, a wide-area communication unit 13, and a short-range communication unit 14. The control unit 11 is mainly configured as a computer. The control unit 11 includes a processor 111, a RAM 112, and a storage 113. The processor 111 is hardware for arithmetic processing that is coupled to the RAM 112. The processor 111 includes at least one arithmetic core such as a CPU. The processor 111 executes various processes by accessing the RAM 112. The storage 113 includes a non-volatile storage medium such as a flash memory. The storage 113 stores a vehicle communication control program as a program executed by the processor 111. The processor 111 executing the program corresponds to executing a vehicle communication control method, which is a method corresponding to the vehicle communication control program.

The in-vehicle communication unit 12 is a circuit module for communicating with other devices via the in-vehicle network IvN. The in-vehicle communication unit 12 is realized using analog circuit elements, ICs, and PHY chips that comply with the communication standards of the in-vehicle network IvN. A variety of data is input to the in-vehicle communication unit 12, such as vehicle speed data detected by a vehicle speed sensor.

The in-vehicle communication unit 12 includes a buffer, which is a storage area that temporarily holds data for external transmission input from other in-vehicle devices such as the vehicle control ECU 9 until the data is wirelessly transmitted to the wireless base station 2 or the roadside unit 3. Data for external transmission is data destined for, for example, the network device 4, the server 5, or another vehicle. The buffer may be realized using a rewritable storage medium such as a RAM. The in-vehicle communication unit 12 also has a function of monitoring the amount of data stored in the buffer and the information stored in the headers of the data. The data in the buffer is sequentially transmitted to the destination server 5 via a communication path according to the data input source. Components of the communication path here may include a frequency, a modulation method, etc.

The wide-area communication unit 13 is a communication module that wirelessly connects to the wireless base station 2 and enables the vehicle-mounted device 1 to communicate with external devices, which are other communication devices, via the core network CN. The wide-area communication unit 13 includes, as smaller elements, a wide-area communication antenna and a wide-area communication transceiver.

The wide-area communication antenna is an antenna for transmitting and receiving radio waves in a specific frequency band used for wireless communication with the wireless base station 2. The wide-area communication transceiver demodulates signals received by the wide-area communication antenna and provides them to the control unit 11, and also modulates data input from the control unit 11 and outputs it to the wide-area communication antenna for wireless transmission. Through cooperation between the wide-area communication antenna and the wide-area communication transceiver, the wide-area communication unit 13 functions as a communication module that outputs received data to the communication control unit F1, and modulates data input from the communication control unit F1 and transmits it to an external device.

The short-range communication unit 14 is a communication module for performing direct wireless communication (i.e., short-range communication) with other in-vehicle devices 1 and roadside devices 3 using radio waves in a specified frequency band. In other words, the short-range communication unit 14 is a communication module for realizing vehicle-to-vehicle communication and road-to-vehicle communication. This short-range communication unit 14 includes, as smaller elements, a short-range communication antenna and a short-range communication transceiver. The short-range communication antenna is an antenna for transmitting and receiving radio waves in the frequency band used for short-range communication. The short-range communication transceiver modulates data input from the communication control unit F1, outputs it to the short-range communication antenna, and transmits it wirelessly. In addition, the short-range communication transceiver demodulates the signal received by the short-range communication antenna and provides it to the communication control unit F1.

The short-range communication unit 14 includes a reception strength detection unit 141 that detects the signal strength (RSSI: Received Signal Strength Indication) of a signal received by a short-range communication antenna. The RSSI corresponds to the received signal strength. The RSSI detected by the reception strength detection unit 141 is output to the communication control unit F1 in association with the received data. The short-range communication unit 14 may be configured to calculate the signal-to-noise ratio, bit error rate (BER: Bit Error Rate), packet loss rate, etc. of the received signal and provide them to the communication control unit F1 in association with the received data. The signal-to-noise ratio is a parameter indicating the ratio or difference between a signal and noise. The signal-to-noise ratio may also be expressed as SNR (Signal-to-Noise Ratio), SN ratio, S/N, etc. The higher the signal-to-noise ratio, the better the quality. The packet loss rate corresponds to the rate of data failure to be received per certain time. The short-range communication unit 14 may be configured to calculate some or all of these quality indicators. Additionally, the control unit 11 may have the functionality to calculate the various quality indicators described above.

In this embodiment, as an example, road-to-vehicle communication and vehicle-to-vehicle communication are performed using the same communication method, but this is not limited to the above. Road-to-vehicle communication and vehicle-to-vehicle communication may be performed using different communication methods. Accordingly, a communication module for road-to-vehicle communication may be provided separately from a communication module for vehicle-to-vehicle communication. For example, vehicle-to-vehicle communication may be performed according to the WAVE standard, while road-to-vehicle communication may be performed using 5G.

<Functions of the in-vehicle device 1>
Here, the functions and operations of the vehicle-mounted device 1 will be described. The vehicle-mounted device 1 has various functional units shown in Fig. 4 as functional units realized by the processor 111 executing the vehicle communication control program. That is, the vehicle-mounted device 1 has a communication control unit F1, a vehicle information acquisition unit F2, a driving environment acquisition unit F3, a control plan unit F4, a communication status acquisition unit F5, a report processing unit F6, a vehicle group information acquisition unit F7, a data acquisition unit F8, and a control execution unit F9. Note that some of the functions of the vehicle-mounted device 1 may be provided by other ECUs.

The communication control unit F1 is configured to control the operation of the wide area communication unit 13 and the narrow area communication unit 14. The communication control unit F1 performs mobility management such as selecting a serving cell based on, for example, the reception strength of a reference signal transmitted from the wireless base station 2. In addition, the communication control unit F1 receives a specific control signal emitted from the roadside unit 3 to detect the presence of the roadside unit 3 and establish a communication connection with the roadside unit 3. The signal used to detect the roadside unit 3 can be a beacon or advertisement signal transmitted using a specific control channel.

The communication control unit F1 generates data to be transmitted to other vehicles, etc., based on requests from the report processing unit F6, etc., which will be described later, and transmits it from the wide area communication unit 13 or the narrow area communication unit 14. In addition, the communication control unit F1 performs processing such as sequence control on the data received by the wide area communication unit 13 or the narrow area communication unit 14 to restore the original data, and provides it to the data acquisition unit F8, etc.

The communication control unit F1 also periodically transmits a predetermined advertising signal from the short-range communication unit 14. The advertising signal is a signal for notifying other vehicles and the roadside unit 3 of the presence of the vehicle, and includes at least source information indicating the vehicle that transmitted the signal (i.e., the source vehicle). Of course, the advertising signal may include information other than the source information.

The source information is identification information (so-called vehicle ID) that is assigned in advance to the source vehicle to distinguish it from other on-board vehicles. The source information may be identification information (i.e. device ID) that is assigned in advance to the on-board device 1 as the source to distinguish it from other on-board devices 1. Note that since the on-board device 1 and the vehicle correspond one-to-one here, the expression "vehicle" as the source/destination of the wireless signal/data can be read as "on-board device 1". Additional information of the source information may be stored, for example, in the header of the communication packet.

The advertising signal may include information such as the time of transmission at the transmission source. Furthermore, the advertising signal may include vehicle information of the transmission source vehicle, such as the current position, direction of travel, traveling speed, and acceleration of the transmission source vehicle. In other words, the advertising signal may be configured to periodically transmit a vehicle information packet, which is a communication packet including vehicle information of the transmission source vehicle. The advertising signal may be periodically transmitted in a so-called broadcast mode, without specifying an individual destination.

The communication control unit F1 also acquires information indicating communication quality, such as the RSSI and S/N ratio of the received data, from the short-range communication unit 14, in association with the received data, which is data corresponding to the received signal. Since the received data includes source information, the above configuration corresponds to acquiring communication quality information for each source. In other words, the communication control unit F1 acquires an index indicating the communication quality for each communication partner, such as another vehicle or roadside unit 3. The information indicating the communication quality for each short-range communication partner is output to the communication status acquisition unit F5.

The vehicle information acquisition unit F2 acquires various information indicating the vehicle state from the vehicle state sensor 6, the locator 8, the vehicle control ECU 9, etc., as vehicle information. Examples of vehicle information include the state of the vehicle power supply (on/off), vehicle speed, acceleration, steering angle, accelerator depression amount, brake depression amount, wiper operation state, shift position, turn signal operation state, etc.

The driving environment acquisition unit F3 acquires driving environment information, which is information indicating the environment around the vehicle, in other words the driving environment, from the surrounding monitoring sensor 7 and the locator 8. The driving environment information here includes the current position of the vehicle, the driving lane, the type of road on which the vehicle is traveling, the speed limit, the curvature, the remaining distance to an intersection/branch/merging point, and relative position information such as traffic lights and stop lines. The driving environment can also include the positions and moving speeds of other moving bodies, the shapes and sizes of surrounding objects, and the like. For example, the driving environment acquisition unit F3 acquires the inter-vehicle distance and collision margin time between the vehicle and other vehicles in front of the vehicle. The acquisition here also includes generating the target information by performing calculation processing based on predetermined information. The surroundings of the vehicle are assumed to be, for example, an area within 100 m of the vehicle.

The driving environment acquisition unit F3 may acquire detection results from each of the multiple surrounding monitoring sensors 7 and combine them to recognize the position and type of objects present around the vehicle. In other words, the driving environment acquisition unit F3 may be configured to recognize the driving environment by performing sensor fusion processing that combines sensing information from multiple types of sensors. In addition, the driving environment acquisition unit F3 may identify the driving environment using other vehicle information received from other vehicles by the short-range communication unit 14, dynamic map data received from the roadside unit 3 or wireless base station 2, etc. The dynamic map data that can be acquired from the roadside unit 3 or wireless base station 2 may include road construction information, traffic regulation information, congestion information, weather information, speed limits, etc.

The control planning unit F4 creates a vehicle control plan based on the driving environment information acquired by the driving environment acquisition unit F3. The control plan can also be called a driving plan. The control plan can be classified into a long-term plan, a medium-term plan, and a short-term plan depending on the detail of the plan content and the scope of application. The long-term plan corresponds to information that roughly indicates the driving route from the current position to the destination, for example. The medium-term plan is a control plan that is more detailed/specific than the long-term plan, and includes, for example, the driving lane and driving speed in the range that is scheduled to be passed within 5 to 10 minutes. The short-term plan is a control plan that is even more detailed/specific than the medium-term plan, and indicates a control plan for a road section that is scheduled to be passed within 1 minute or within 500 m. Each control plan can include the driving point and driving speed for each time. Hereinafter, the long-term control plan will be simply referred to as the long-term plan. Similarly, the medium-term and short-term control plans will also be referred to as the medium-term plan and the short-term plan, respectively.

The control planning unit F4 generates a driving route from the vehicle's position to the destination as a long-term plan, for example. The driving route set as the long-term plan corresponds to route information at the road level, such as which roads to take and which intersections to turn at. The driving route set as the long-term plan is calculated by a route search process that inputs the current position and destination of the vehicle. The control planning unit F4 reports the generated long-term plan data to the network device 4 in cooperation with the communication control unit F1. The network device 4 creates and returns a medium-term plan for the vehicle corresponding to the upload source based on the long-term plan uploaded from the vehicle and the traffic conditions on the driving route shown in the long-term plan. As described above, the traffic conditions include the degree of road congestion and the average driving speed. Note that, in this example, the control planning unit F4 generates a long-term plan for the vehicle and transmits it to the network device 4, but this is not limited to this. The vehicle may transmit its current position and destination to the network device 4, and the network device 4 may generate a long-term to medium-term control plan.

The control planning unit F4 also receives data indicating the mid-term plan from the network device 4 in cooperation with the communication control unit F1. Note that, as an example here, the network device 4 generates and distributes a mid-term plan for the vehicle based on a long-term plan provided by the vehicle, but this is not limited to this. The server 5 may provide the vehicle with data necessary for creating a mid-term plan based on the long-term plan transmitted from the vehicle, and the control planning unit F4 may generate the mid-term plan.

In addition, the control planning unit F4 generates a short-term plan based on the mid-term plan distributed from the network device 4 and on the positional relationship with the features and moving objects around the vehicle acquired by the driving environment acquisition unit F3. The short-term plan corresponds to a plan that has been modified from the mid-term plan based on the detection results of the surrounding monitoring sensor 7, etc.

For example, when the presence of an obstacle in front of the vehicle is confirmed based on the detection results of the forward camera as the perimeter monitoring sensor 7 or dynamic map data, the control planning unit F4 may generate a driving plan to pass by the side of the obstacle. In addition, it may also plan emergency avoidance actions to avoid collisions with other objects, such as avoiding objects that have fallen on the road and controlling the vehicle to stop in front of pedestrians. In addition, medium-term or short-term driving plans may include information such as schedule information for acceleration and deceleration to adjust speed on the calculated route, schedule information for steering angle control, information on points for lane changes, and timing for notifying the driver of vehicle behavior.

In this example, the control plan generated by the control planning unit F4 is a plan for driving the vehicle autonomously, but is not limited to this. The control plan generated by the control planning unit F4 may also be a control plan for assisting the driving operation of the driver's seat occupant (the so-called driver). In other words, the vehicle-mounted device 1 may be a driving assistance device.

The communication status acquisition unit F5 is configured to manage the status of short-range communication with other vehicles (so-called vehicle-to-vehicle communication) and the status of short-range communication with the roadside device 3 (so-called road-to-vehicle communication). When the communication status acquisition unit F5 receives an advertising signal transmitted from another vehicle, it associates the source information indicated in the advertising signal with communication quality information such as the reception strength of the advertising signal and stores them in the RAM 112. That is, the communication quality information is stored separately for each vehicle. Communication quality information acquired at different times for a certain other vehicle may be sorted and stored in chronological order, for example, so that the latest communication quality information is at the top. In addition, data that has been stored for a certain period of time may be sequentially discarded. Only the latest data may be stored as communication quality information for one other vehicle. Note that the signal for evaluating the communication quality of another vehicle is not limited to a broadcast advertising signal, and may be a data signal exchanged by unicast.

When the communication status acquisition unit F5 receives a wireless signal emitted by a roadside unit 3 in short-range communication, it stores information indicating the communication quality with the roadside unit 3 in association with an ID indicating the source of the signal. In a situation in which the vehicle is capable of communicating with multiple roadside units 3, the communication status acquisition unit F5 manages and stores communication quality information for each roadside unit 3.

The report processing unit F6 generates a communication status report, which is a communication packet indicating the communication status between the vehicle and other vehicles, at a predetermined period and transmits it to the network device 4 in cooperation with the communication control unit F1. For example, when road-to-vehicle communication is possible, the report processing unit F6 transmits the communication status report to the network device 4 via a route that passes through the roadside unit 3. When road-to-vehicle communication is not possible, the report processing unit F6 transmits the communication status report to the network device 4 via the wireless base station 2 (i.e., by wide area communication). When road-to-vehicle communication is possible, this refers to a state in which the vehicle is within the communication area of the roadside unit 3 and a communication connection with the roadside unit 3 is established.

The communication status report can be, for example, a data set indicating the communication quality of each other vehicle that is performing vehicle-to-vehicle communication. The information for each vehicle is configured so that it can be identified by the vehicle ID. The communication status report includes source information. This enables the roadside unit 3 or network device 4, which is the recipient of the information, to identify the communication status between vehicles that are in a positional relationship where vehicle-to-vehicle communication can be performed, such as combinations of vehicles with good/poor communication quality, or combinations where communication is difficult/unstable.

The communication status report may also include vehicle status information such as the current position, driving speed, traveling direction, and driving lane ID of the sending vehicle as reference information. The driving lane ID indicates which lane from the left or right edge of the road the vehicle is driving in. Furthermore, the communication status report may also include information such as the lighting status of the turn signal of the vehicle and whether the vehicle is driving across a lane boundary line. A communication packet indicating the driving status of the vehicle may also be called a vehicle status report. The communication status report and the vehicle status report may be sent as separate communication packets or may be integrated.

The vehicle group information acquisition unit F7 is configured to acquire vehicle group setting data transmitted from the network device 4. The vehicle group setting data may be acquired via the roadside unit 3, or may be received from the wireless base station 2. A vehicle group here is a group of multiple vehicles. Vehicles belonging to one vehicle group share and complement each other's content data, which is distributed in a multiple-part split state from the roadside unit 3, by vehicle-to-vehicle communication. The content data here refers to, for example, static map data or dynamic map data.

The vehicle group setting data includes information indicating connected vehicles at each time point within a specified period and a shared route of data within the vehicle group. In one vehicle group, general vehicles other than the connected vehicles communicate with the roadside unit 3 via the connected vehicles. The connected vehicles correspond to vehicles that relay communication between the general vehicles and the roadside unit 3. The connected vehicles are representative of the vehicle group in one respect, and therefore can also be called representative vehicles. As will be described later, the connected vehicles can be changed over time among the vehicles belonging to the same vehicle group. Information on connected vehicles at each time point is notified to the roadside unit 3 from the network device 4 as the above-mentioned vehicle group setting data. The vehicle group information acquisition unit F7 stores the acquired vehicle group setting data in RAM 112. Details of the vehicle group setting will be described later.

The data acquisition unit F8 is configured to acquire static map data and dynamic map data through road-to-vehicle communication with the roadside unit 3 and vehicle-to-vehicle communication with other vehicles belonging to the same vehicle group. Details of the operation of the data acquisition unit F8 will be described separately below. The data acquired by the data acquisition unit F8 can be used by the control plan unit F4 to create a short-term control plan. For example, it can be used to create a control plan for driving through an intersection, a control plan for stopping depending on the status of traffic lights, a path plan after turning right or left, and a path plan for branching out or merging.

The control execution unit F9 outputs an instruction signal corresponding to the control plan determined by the control planning unit F4 to the vehicle control ECU 9. The vehicle control ECU 9 controls the driving control device to be controlled based on the instruction signal. The control execution unit F9 may have the functions of the vehicle control ECU 9. In that case, the control execution unit F9 may output control signals to various actuators. The controlled objects of the control planning unit F4 and the control execution unit F9 include not only actuators but also information presentation devices such as displays and speakers. For example, the control execution unit F9 displays a turn-by-turn image showing the route on a head-up display, or provides visual or audio warning of deceleration or lane changes based on the control plan.

<Configuration of wireless base station 2>
Next, the configuration of the wireless base station 2 will be described with reference to Fig. 5. As shown in Fig. 5, the wireless base station 2 includes a wide-area communication device 21, a network connection device 22, and a base station control unit 23. The wide-area communication device 21 and the network connection device 22 are connected to the base station control unit 23 so as to be able to communicate with each other.

The wide-area communication device 21 is a communication module for performing wide-area communication with the vehicle. The basic configuration of the wide-area communication device 21 can be the same as that of the wide-area communication unit 13. The wide-area communication device 21 outputs received data to the base station control unit 23. In addition, the wide-area communication device 21 transmits data input from the base station control unit 23 using radio resources instructed by the base station control unit 23.

Radio resources (in other words, bearers) for wide-area communication can be controlled using the concept of resource blocks. A resource block is a control unit of radio resources that is divided using time slots and frequency slots. The length of a time slot can be made to correspond to TTI (Transmission Time Interval), which is the smallest unit of scheduling. The control unit of radio resources in the time domain may be a subframe or a frame. The description of a time slot in this disclosure can be replaced with a subframe or a frame. In addition, the description of a time slot can also be replaced with a symbol used in LTE, etc. The number of carriers that define a frequency slot can be, for example, 6 to 20. Of course, the number of carriers can be changed appropriately depending on the frequency interval. The description of a resource block can be replaced with a resource element. Note that other modulation methods can be adopted as components of radio resources. For example, radio resources may be subdivided into resource blocks using three items: time slots, frequency slots, and modulation methods.

The network connection device 22 is equipment for communicating with the network device 4 and the roadside unit 3. The network connection device 22 is configured to be able to communicate with each of the network device 4 and the roadside unit 3 using, for example, optical fiber. The network connection device 22 outputs data input from the network device 4 and the roadside unit 3 to the base station control unit 23. In addition, the network connection device 22 outputs data input from the base station control unit 23 to the roadside unit 3 or the network device 4 depending on the destination of the data.

The base station control unit 23 is mainly configured as a computer including a processor 231, a RAM 232, and a storage 233. A base station control program is stored in the storage 233 as a program executed by the processor 231. The execution of the program by the processor 231 corresponds to the execution of a base station control method, which is a method corresponding to the base station control program.

The base station control unit 23 includes various functional units shown in FIG. 5 as functional units that are realized when the processor 231 executes the base station control program. That is, the base station control unit 23 includes, as functional units, a connection control unit H1, a communication control unit H2, and a transfer processing unit H3.

The connection control unit H1 is configured to manage and control vehicles as UEs connected to the wireless base station 2. For example, the connection control unit H1 performs handovers and other operations associated with the movement of the vehicle.

The communication control unit H2 is configured to control the operation of the wide area communication device 21. The communication control unit H2 controls the allocation state of radio resources for each vehicle-mounted device 1 based on a control signal from, for example, an MME. Based on the allocation of radio resources determined by the communication control unit H2, the wide area communication device 21 transmits data to the vehicle-mounted device 1 and receives data from the vehicle-mounted device 1. Processing related to data communication is performed in cooperation with the transfer processing unit H3, which will be described next.

The forwarding processing unit H3 is configured to perform processing for forwarding data input from the network device 4 and the vehicle to an appropriately specified destination. The mode of distribution may be either unicast or multicast, and may be selected, for example, according to the destination or the type of transmission data. Note that unicast refers to a method of transmitting data by specifying a single destination, and multicast refers to a method of transmitting data by specifying multiple destinations. Compared to multicast and broadcast, unicast has the advantage that it is possible to perform acknowledgement and retransmission, and reliability is easily guaranteed. Broadcast refers to a method of transmitting data to an unspecified number of destinations (all destinations). Note that other modes of data transmission, such as geocast, can also be adopted. Geocast is a communication mode of a flooding method in which a destination is specified by location information. In geocast, vehicles present within a range specified as a geocast area receive the data. According to geocast, it is possible to transmit information without specifying the identification information of vehicles present in the area to which the information is to be distributed.

For example, the transfer processing unit H3 transmits the vehicle group setting data generated by the network device 4 to each vehicle that constitutes the vehicle group. The vehicle group setting data can be distributed by, for example, geocast or broadcast. The destination of the vehicle group setting data may be one of the multiple vehicles that constitute the vehicle group. In that case, the vehicle that receives the vehicle group setting data distributes the vehicle group setting data to the relevant vehicles by vehicle-to-vehicle communication. The transfer processing unit H3 may also unicast the medium-term control plan data for each vehicle input from the network device 4 to each vehicle. In addition, the transfer processing unit H3 transfers communication packets such as communication status reports transmitted from each of the multiple vehicles to the network device 4.

<Configuration of road-side unit 3>
Here, the configuration of the roadside unit 3 will be described. The roadside unit 3 is arranged, for example, near an intersection or near a branching/merging point of a highway. The roadside unit 3 may also be arranged in the middle of a curve or on an uphill road. The roadside unit 3 is preferably arranged in a position where the traffic situation ahead is difficult to see. Of course, the roadside unit 3 may also be arranged in the middle between intersections.

The roadside unit 3 may be formed integrally with structures installed along the road, such as traffic lights, lighting equipment, and toll gates (gates) for toll roads. Here, along the road includes not only the sides of the road, but also the air above the road surface. The roadside unit 3 may also be installed as a marker buried in the road surface. Note that multiple roadside units 3 may be installed at one intersection. For example, a roadside unit 3 may be installed for each road connected to the intersection, such as on the entrance and exit sides of the intersection.

As shown in FIG. 6, the roadside unit 3 includes a short-range communication device 31, a network connection device 32, an area monitoring device 33, and a roadside control unit 34. Each of the short-range communication device 31, the network connection device 32, and the area monitoring device 33 is connected to the roadside control unit 34 so as to be able to communicate with each other.

The short-range communication device 31 is a communication module for performing short-range communication with the vehicle. The basic configuration of the short-range communication device 31 can be the same as that of the short-range communication unit 14. The short-range communication device 31 also includes a reception strength detection unit 311 that detects the RSSI of the received signal. The short-range communication device 31 outputs information indicating communication quality, such as the RSSI detected by the reception strength detection unit 311, to the roadside control unit 34 in association with the received data. As described above, in addition to the RSSI, the information indicating communication quality can also include the S/N ratio of the received signal, the BER, and the packet loss rate.

The network connection device 32 is equipment for communicating with the wireless base station 2 and the network device 4. The network connection device 32 is configured to be able to communicate with each of the wireless base station 2 and the network device 4 using, for example, optical fiber. Of course, a relay device (so-called router) may be interposed between the roadside unit 3 and the wireless base station 2 or the network device 4. The network connection device 32 outputs data input from the wireless base station 2 and the network device 4 to the roadside control unit 34. It also outputs data input from the roadside control unit 34 to the wireless base station 2 or the network device 4 depending on the destination of the data.

The area monitoring device 33 is a device that monitors the traffic conditions in a monitoring target area that is preset for the roadside unit 3. For example, the area monitoring device 33 detects the positions, sizes, and movement status of moving objects and obstacles that exist within the monitoring target area. Moving objects can include vehicles, bicycles, pedestrians, animals, etc. Obstacles mainly refer to fallen objects, construction zones, and parked vehicles. Obstacles can also include the moving objects mentioned above. Components of the movement status include the presence or absence of movement, the movement speed, and the movement direction.

The monitoring area is set for each roadside unit 3. For example, the monitoring area of a roadside unit 3 installed near an intersection is the inside of the intersection or its vicinity. For example, a roadside unit 3 installed at an intersection detects pedestrians waiting for a traffic light, pedestrians crossing the road, bicycles and pedestrians approaching the intersection, automobiles, and vehicles planning to turn right or left. A roadside unit 3 installed at an intersection can also detect obstacles such as parked vehicles near the entrance and exit of the intersection. In addition, the monitoring area of a roadside unit 3 installed near a branching/merging point of an expressway is set to include the branching/merging point. A roadside unit 3 installed at a branching/merging point of an expressway can detect the position and speed information of vehicles traveling on the main road of the road, and the position and speed of vehicles traveling on the side road that is the branching/merging road.

A camera, LiDAR, millimeter wave radar, etc. can be used as the area monitoring device 33. Here, as an example, the area monitoring device 33 is a camera that is installed so that the monitoring target area is included in its imaging range. The roadside camera, which is a camera serving as the area monitoring device 33, is installed above the road near the intersection so that it can capture images of cars entering the intersection. The roadside camera may also be installed above the sidewalk around the intersection so that it can capture images of the crosswalk around the intersection. The roadside unit 3 may be equipped with one camera as the area monitoring device 33, or may be equipped with multiple cameras. The images captured by the roadside camera are output to the roadside control unit 34. The roadside unit 3 may be equipped with multiple types of sensors, such as a camera and LiDAR, as the area monitoring device 33.

The roadside control unit 34 is mainly configured as a computer including a processor 341, a RAM 342, and a storage 343. A roadside unit control program is stored in the storage 343 as a program executed by the processor 341. The execution of the above program by the processor 341 corresponds to the execution of a roadside unit control method, which is a method corresponding to the roadside unit control program.

The roadside control unit 34 has various functional units shown in FIG. 6 as functional units that are realized when the processor 341 executes the roadside device control program. That is, the roadside control unit 34 has a short-range communication control unit G1, a traffic condition acquisition unit G2, a communication condition acquisition unit G3, and a network processing unit G4.

The short-range communication control unit G1 is configured to control the operation of the short-range communication device 31. The short-range communication control unit G1 detects the presence of an unconnected vehicle by receiving a specific wireless signal, such as an advertising signal, emitted from the vehicle, and performs processing related to a communication connection with the vehicle. The processing related to the communication connection includes the exchange of keys used for encrypted communication.

The short-range communication control unit G1 acquires data received by the short-range communication device 31 and outputs it to the traffic condition acquisition unit G2 and the communication condition acquisition unit G3. The short-range communication control unit G1 also divides the original data, which is data for distribution provided by the network device 4, into multiple segment data and unicasts it to specific vehicles. The segments sent to each vehicle are some or all of a series of segments. The roadside unit 3 unicasts different segments to each vehicle that makes up the vehicle group so that all segments are present for the entire vehicle group. The original data for distribution is dynamic map data or static map data.

As shown in FIG. 7, segment data corresponds to partial data obtained by dividing original data so that each data piece has a specified data size. Segment data can also be called segment data or partial data. Each piece of segment data includes, for example, an original data ID for identifying the original data, and a segment ID for identifying each piece of segment data in the original data. The segment ID is an identifier that indicates the order of the segments, and can also be called a segment number. The segment ID can be used by each vehicle-mounted device 1 to identify segments that have not yet been acquired. Note that the original data ID and segment ID in each segment are optional elements and may be omitted.

The segmentation of the original data may be real or virtual. For example, the segment data may be the result of dividing the main body of the original data (the so-called payload) and packetizing it. Segment data may also be called segment packets. Segment data may also be a set of communication packets corresponding to the original data, divided into a predetermined number of packets. The example shown in FIG. 7 illustrates an example in which the original data is divided into 90 pieces of segment data. FIG. 7 also illustrates an example in which the 90 segment packets that make up the original data are divided into three destination groups according to the destination.

The process of dividing the original data into segment data may be performed by the roadside device 3 or by the network device 4. The size of each segment may be constant or may be set to a different value depending on the amount of wireless resources allocated to each vehicle. In other words, the size of each segment may be set to a value according to the capacity with which the connected vehicle can communicate with the roadside device 3 in a short-range manner. The short-range communication capacity between the vehicle-mounted device 1 and the roadside device 3 is determined according to the length of time during which the two devices can communicate with each other in a short-range manner, in other words, the estimated value of the time the vehicle-mounted device 1 stays in the communication area of the roadside device 3. The communication time and therefore the communication capacity between the vehicle-mounted device 1 and the roadside device 3 are determined by the vehicle's traveling speed, etc. Therefore, the short-range communication capacity between the vehicle-mounted device 1 and the roadside device 3 can be calculated from the planned value of the vehicle's traveling speed, that is, the control plan. Here, as an example, the roadside device 3 performs segmentation according to the amount of wireless resources allocated to each vehicle, which will be described later. Of course, the network device 4 is configured to provide the original data to the roadside device 3 in a state in which the data is divided into multiple segment data.

As with wide area communication, radio resources for short range communication can also be controlled using the concept of resource blocks that are divided using time slots and frequency slots. In other words, short range communication is controlled using the concept of time slots. For example, the target of segment data delivery can be switched at the boundary of a time slot. The length of one time slot can be, for example, 1 millisecond, 10 milliseconds, or 50 milliseconds. The length of a time slot may be 0.25 milliseconds, 0.5 milliseconds, or less than 1 millisecond. As mentioned above, a time slot can be set to correspond to a TTI. Note that a time slot is a control unit of radio resources in the time domain, and the specific length can be changed depending on the communication specifications. The length of a time slot in short range communication may be the same as the length of a time slot in wide area communication, or may be different.

The number of carriers defining the frequency slots for short-range communication can be, for example, 6 to 12. Of course, the number of carriers can be changed as appropriate. The frequencies used in short-range communication can be different from the frequencies used in wide-range communication. Note that the radio resources for short-range communication can also be divided into resource blocks using time slots and frequency slots, as well as a modulation method.

Based on instructions from the network device 4, the roadside unit 3 sequentially unicasts multiple pieces of segment data to connected vehicles that make up the vehicle group. The distribution targets for each piece of segment data can be appropriately set by the network device 4 from within the vehicle group. As described separately below, each connected vehicle wirelessly transmits the received segment data to other general vehicles that make up the same vehicle group via a specified shared route. In this way, multiple pieces of segment data are shared in sequence within the vehicle group, and the dynamic map data as the original data is restored in each vehicle. In other words, each vehicle-mounted device 1 within the vehicle group can reconstruct and use the content data as the original data by sharing each piece of segment data via short-range communication.

In addition, by dividing data into segments and transmitting/receiving it in this manner, the amount of communication in each vehicle-mounted device 1 can be reduced. In addition, because the size of the data transmitted and received is reduced, the time required to transmit and receive one piece of data is shortened. As a result, the possibility of successful transmission and reception of data can be increased even in a relatively short time. In addition, because data is shared within the vehicle group, even if the leading vehicle of the vehicle group goes outside the communication area of the roadside unit 3, the leading vehicle can also communicate with the roadside unit 3 as long as the following vehicles of the same vehicle group are within the communication area of the roadside unit 3.

The traffic condition acquisition unit G2 acquires the traffic conditions in a specified monitoring target area based on data input from the area monitoring device 33. The traffic conditions here include, for example, the positions, sizes, and movement conditions of moving objects and obstacles present in the monitoring target area. The traffic conditions can also include road surface conditions, such as whether the road surface is wet due to rain or snow, and weather conditions, such as whether it is raining or not. In addition, as described above, the traffic conditions can include traffic volume, average vehicle speed, and the presence or absence of congestion. The traffic condition acquisition unit G2 may specify the traffic conditions using position information acquired from the vehicle by road-to-vehicle communication. The traffic condition data, which is information indicating the traffic conditions acquired by the traffic condition acquisition unit G2, is output to the network processing unit G4.

The communication status acquisition unit G3 is configured to acquire and manage the implementation status of road-to-vehicle communication with a vehicle. When the communication status acquisition unit G3 receives a wireless signal from a vehicle, it stores information indicating the communication quality with the vehicle in association with the vehicle ID indicating the source of the signal. When communication with multiple vehicles is possible, it manages and stores communication quality information for each vehicle. The communication status information indicating the communication quality for each vehicle acquired by the communication status acquisition unit G3 is output to the network processing unit G4. The communication status acquisition unit G3 may be configured to receive information indicating the quality of vehicle-to-vehicle communication between the vehicles from each vehicle via the connected vehicle. In addition, the communication status acquisition unit G3 calculates the degree of communication load and the usage rate of wireless resources available for short-range communication (so-called congestion degree), and outputs them to the network processing unit G4.

The network processing unit G4 is configured to control communication with the network device 4 and the wireless base station 2. The network processing unit G4 acquires data input from the network device 4. The network processing unit G4 has an aggregated reporting unit G41 that aggregates information acquired by the traffic condition acquisition unit G2 and the communication condition acquisition unit G3 and reports it to the network device 4. The aggregated reporting unit G41 transmits information indicating the traffic conditions acquired by the traffic condition acquisition unit G2 within a certain period of time to the network device 4. The aggregated reporting unit G41 also transmits information indicating the traffic conditions acquired by the communication condition acquisition unit G3 within a certain period of time to the network device 4. The traffic condition data aggregated and reported by the roadside unit 3 can be used when the network device 4 generates dynamic map data.

<Configuration of Network Device 4>
Next, the configuration of the network device 4 will be described with reference to Fig. 8. As shown in Fig. 8, the network device 4 includes a network connection device 41, a vehicle management database 42, and an edge control unit 43. The network connection device 41 and the vehicle management database 42 are each connected to the edge control unit 43 so as to be able to communicate with each other.

The network connection device 41 is equipment for communicating with the wireless base station 2, the roadside unit 3, and the server 5. The network connection device 41 is configured to be able to communicate with each of the wireless base station 2, the roadside unit 3, and the server 5 using, for example, optical fiber. The network connection device 41 outputs data input from the wireless base station 2, the roadside unit 3, and the server 5 to the edge control unit 43. For example, the network connection device 41 acquires the vehicle's long-term control plan and the communication status with other vehicles, etc. from the wireless base station 2 and the roadside unit 3, and outputs them to the edge control unit 43. In addition, the network connection device 41 acquires traffic condition data collected by another network device 4 from the server 5 and outputs them to the edge control unit 43.

The network connection device 41 also outputs data input from the edge control unit 43 to the wireless base station 2, the roadside unit 3, or the server 5 depending on the destination of the data. In one aspect, the wireless base station 2 and the roadside unit 3 in this disclosure correspond to elements that configure a path for the network device 4 to communicate data with the vehicle. Whether the wireless base station 2 or the roadside unit 3 is used as the means of communication between the network device 4 and the vehicle can be changed as appropriate in consideration of communication efficiency, cost, and confidentiality.

The vehicle management database 42 is a database realized by using a rewritable non-volatile storage medium. The vehicle management database 42 is configured so that data can be written, read, deleted, etc. by the edge control unit 43. The vehicle management database 42 stores data (hereinafter, individual situation data) indicating the current position, control plan, implementation status of short-range communication with other vehicles and roadside units 3, etc. for each vehicle-mounted unit 1 in association with the vehicle ID. For example, the individual situation data for each vehicle-mounted unit 1 may be held in any data structure, such as a list format. The individual situation data may include information such as the current travel speed, driving lane, traveling direction, and planned points for changing the driving position.

As the status of short-range communication between each vehicle and other vehicles, at least one of various items indicating communication quality, such as the RSSI of the signal from the other vehicle as the communication partner, the S/N ratio, the BER, the packet loss rate, etc., is registered. The communication quality for each communication partner is stored in association with the identification information of the communication partner.

The edge control unit 43 is mainly configured as a computer including a processor 431, a RAM 432, and a storage 433. The storage 433 stores an edge program as a program executed by the processor 431. The processor 431 executes the program, which corresponds to the edge program, by executing a vehicle group control method. The edge program can be called a V2X edge application. The V2X edge application corresponds to a V2X application implemented by a device in a communication architecture defined by 3GPP, such as LTE. The storage 433 also stores data related to the installation position and communication area of the roadside unit 3.

The edge control unit 43 includes various functional units shown in FIG. 8 as functional units that are realized when the processor 431 executes the edge program. That is, the edge control unit 43 includes, as functional units, an individual information acquisition unit J1, a traffic condition acquisition unit J2, a traffic condition prediction unit J3, a distribution data generation unit J4, a medium-term plan unit J5, a vehicle group formation unit J6, a resource control unit J7, and a notification processing unit J8. The distribution data generation unit J4 includes, as more specific functional units, a data size acquisition unit J41 and a data size adjustment unit J42. The vehicle group formation unit J6 includes, as more specific functional units, a plan correction unit J61, a connected vehicle setting unit J62, a vehicle group speed acquisition unit J63, and a shared route setting unit J64.

The individual information acquisition unit J1 acquires communication status data provided by multiple roadside units 3 and wireless base stations 2. That is, it acquires the vehicle-to-vehicle communication status between vehicles, the road-to-vehicle communication status, the communication load and congestion level at the roadside unit 3, and the like. The individual information acquisition unit J1 also acquires long-term plans, position information, driving speed, and the like reported by each vehicle. That is, the individual information acquisition unit J1 acquires the communication status, driving state, and driving plan for each vehicle. The driving plan includes the current position and current driving speed. The individual information acquisition unit J1 can also acquire not only long-term plans as driving plans, but also medium-term plans created by the medium-term planning unit J5 described below. The data indicating the individual status of the vehicle is not limited to that transmitted from the vehicle or roadside unit 3, but can also include information generated inside the network device 4.

Furthermore, the individual information acquisition unit J1 acquires from the server 5 communication status data of vehicles present near the border with the own area, collected by other network devices 4. The own area here refers to the management area associated with the network device 4 itself. The data for each vehicle acquired by the individual information acquisition unit J1 is stored in the vehicle management database 42, separated by vehicle.

The traffic condition acquisition unit J2 acquires traffic condition data transmitted from multiple roadside units 3. The traffic condition acquisition unit J2 also transmits the traffic condition data collected from multiple roadside units 3 to the server 5. The traffic condition acquisition unit J2 also acquires traffic condition data near the border of the managed area collected by other network devices 4 from the server 5. For example, the traffic condition acquisition unit J2 acquires information on vehicles entering its own area from other areas provided by the server 5. The other areas here refer to areas managed by other network devices 4 adjacent to its own area.

The traffic condition prediction unit J3 predicts the traffic conditions after a predetermined prediction time in each road section in the time area based on the traffic condition data acquired by the traffic condition acquisition unit J2. Note that the traffic condition prediction may use a long-term control plan provided by each vehicle or a medium-term plan for each vehicle created by the medium-term planning unit J5 described later.

The road section to be predicted may be the area monitored by the roadside unit 3. The traffic condition prediction unit J3 may be configured to predict the traffic conditions for each road section having a predetermined length. As an example, the traffic conditions after a predetermined time are predicted for each road section. The prediction time may be a period corresponding to dynamic data such as 1 second, 10 seconds, or 30 seconds, or may be a period corresponding to semi-dynamic data such as 5 minutes, 10 minutes, or 30 minutes.

The distribution data generation unit J4 generates dynamic map data for the roadside unit 3 to distribute to each vehicle group, for example, based on the prediction results of the traffic condition prediction unit J3. The dynamic map data for the roadside unit 3 to distribute to each vehicle group can be, for example, a data set showing the predicted results of traffic conditions for an area within a certain range from the roadside unit 3. That is, it includes the average vehicle speed and traffic volume for each road section. As described above, the dynamic map data can include meteorological information such as the amount of rainfall for each point, road surface conditions, and the presence or absence of fog. The dynamic map data can include road construction information, traffic regulation information, road obstacle information, congestion information, speed limits, traffic light information, target driving trajectory data, etc.

The distribution data generation unit J4 also generates static map data for the roadside unit 3 to distribute to each vehicle group, and distributes it to the roadside unit 3. The static map data for the roadside unit 3 can be, for example, a data set for an area within a certain range from the roadside unit 3. Alternatively, it can be a data set that extracts only information about the road section that each vehicle group is scheduled to pass through.

The data size acquisition unit J41 is configured to evaluate/acquire the size of data to be distributed to the vehicle group. If the vehicle group communication capacity cannot be set larger than the size of the distribution data even after performing the vehicle group length adjustment process described below, the data size adjustment unit J42 performs a process to thin out the distribution data so that the distribution data fits within the vehicle group communication capacity. Details of the data size adjustment unit J42 will be described separately below.

The medium-term planning unit J5 creates a medium-term control plan based on the long-term control plans provided by each vehicle and the traffic conditions at each point predicted by the traffic condition prediction unit J3. As described above, the medium-term control plan includes the driving lanes and driving speeds for road sections that are scheduled to be passed within a specified time, for example, 5 to 10 minutes. The medium-term planning unit J5 creates a medium-term control plan based on the traffic conditions for the road sections related to the long-term driving plan uploaded from the vehicle.

The vehicle group organizing unit J6 is configured to organize a vehicle group based on the individual situation data for each vehicle acquired by the individual information acquisition unit J1 and registered in the vehicle management database 42. For example, as shown in FIG. 9, the vehicle group organizing unit J6 sets vehicles whose RSSI is equal to or greater than a predetermined grouping strength to the same group (in other words, a vehicle group). In FIG. 9, the solid bidirectional arrows represent combinations in which the RSSI of the signal in both directions is equal to or greater than the grouping strength. Also, the dashed bidirectional arrows represent combinations in which the RSSI of the wireless signal in at least one direction is less than the grouping strength. In the embodiment shown in FIG. 9, vehicles M1 to M5 form the same vehicle group Gr1, and vehicles M6 to M7 form another vehicle group Gr2.

The grouping strength may be set to a value that allows stable vehicle-to-vehicle communication, and may be changed according to the standard value of transmission power defined in the vehicle-to-vehicle communication standard. The grouping strength may be set to a value that, for example, provides an expected packet delivery rate of 95% or more. A stable communication state may be, for example, a state in which the packet loss rate is less than 5%. The required communication quality may be determined according to the purpose of communication, etc.

The grouping strength depends on the transmission power value specified in the vehicle-to-vehicle communication standard, but can be, for example, -60 dBm, -50 dBm, -40 dBm, -30 dBm, etc. The grouping strength can be set based on the simulation results of RSSI in an environment where communication is stable (hereinafter, good environment). A good environment is assumed to be a situation where the inter-vehicle distance is 25 m and there are no obstacles between the vehicles. An environment where communication is unstable (hereinafter, bad environment) is assumed to be a situation where the inter-vehicle distance is 50 m and there is an obstacle such as a large truck that does not have inter-vehicle communication function between the vehicles. If the RSSI observed in a good environment is -40 dBm to -50 dBm and the RSSI observed in a bad environment is -60 dBm to -80 dBm, the grouping strength can be -55 dBm, which is located on the boundary between their distributions.

Note that the RSSI does not need to be equal to or greater than the grouping strength for all combinations of vehicles that make up a vehicle group. A vehicle can belong to a vehicle group based on the RSSI of communication with at least one of the vehicles that make up the vehicle group being equal to or greater than the grouping strength. For example, the RSSI of communication between the leading vehicle M1 of the vehicle group and the vehicle M5 located at the rear of the vehicle group may be less than the grouping strength. For example, if the RSSI of communication between the leading vehicle M1 and the rearmost vehicle M5 and the vehicle M3 located in the middle is equal to or greater than the grouping strength, they can belong to the same vehicle group.

The RSSI used to organize the vehicle group may be the most recent observation value, or the average, median, maximum, or minimum value of the observation value within a fixed time period. Note that, as an example here, RSSI is used to select vehicles to be included in the same vehicle group, but this is not limiting. The signal-to-noise ratio may be a specified value or higher, or the packet loss rate within a fixed time period may be less than a specified value, etc., may be adopted as a grouping condition. The threshold value for each item that specifies the grouping condition is also referred to as a grouping threshold. The grouping strength mentioned above is also an example of a grouping threshold.

The size of the vehicle group may be adjusted so that the required communication quality is guaranteed for data communication between the network device 4 or server 5 and the vehicle. If the number of vehicles constituting the vehicle group is too large, the time required to complete data sharing increases. In addition, if the number of hops from the general vehicle to the connected vehicle increases, the communication delay time and packet loss rate may increase. In addition, considering that the wireless resources available for short-range communication are limited, the more the number of vehicles constituting the vehicle group increases, the less communication bandwidth available per vehicle and the lower the communication speed may be. The communication delay time may be evaluated as the time (so-called latency) required for data transmitted by a general vehicle as a leaf node (described later) to reach the roadside unit 3 via the connected vehicle, or the time for data transmitted by the roadside unit 3 to reach the leaf node via the connected vehicle. Other indicators for adjusting the size of the vehicle group may include round-trip latency (RTT) and throughput.

The vehicle group formation unit J6 can adjust the size of the vehicle group in terms of the number of hops and the number of vehicles so that the communication delay time and the like meet the desired communication conditions/requirements. For example, if the number of hops from the connecting vehicle to the terminal is four or more, the size of the vehicle group is reduced and adjusted so that the maximum hop number is three or less. The size of the vehicle group can be expressed mainly by the number of vehicles that make up the vehicle group, that is, the number of constituent members. Note that here, as a more preferable example, the maximum hop number is limited to three, but this is not limited to this. The maximum hop number may be allowed up to five. Note that if the delay time required for driving assistance or automatic driving when turning right or left at an intersection is 10 milliseconds, the maximum hop number is specified so that the delay time is less than 10 milliseconds.

The vehicle group organizing unit J6 may also reduce the number of vehicles constituting the vehicle group when the communication delay time between the end vehicle and the server 5 via the connected vehicle exceeds a predetermined threshold. The vehicle group organizing unit J6 may also reduce the number of vehicles constituting the vehicle group when the communication speed between the general vehicle and the roadside unit via the connected vehicle falls below a predetermined allowable threshold. Hereinafter, the vehicle group that is the target of processing among multiple vehicle groups is also referred to as the target vehicle group.

As described above, the vehicle group organizing unit J6 organizes the vehicle group taking into consideration the communication quality between the vehicles. This makes it easier to ensure communication quality within the vehicle group compared to organizing the vehicle group based only on the vehicle distance and position information. For example, as shown in FIG. 10, when a large truck/trailer exists as a shielding vehicle NM between vehicles with a small spatial distance, in a configuration in which the vehicle group is organized based only on distance, vehicle M6, whose success rate of inter-vehicle communication is unstable, may be included in vehicle group Gr1. In contrast, when organizing a vehicle group as in the configuration disclosed herein, in other words, when setting a gap in the vehicle group, vehicle M6 located in the shadow of the shielding vehicle NM can be set to another vehicle group Gr2 according to a configuration using inter-vehicle communication quality such as RSSI. Note that the shielding vehicle NM here refers to a vehicle that does not have an inter-vehicle communication function.

Of course, the vehicle group formation unit J6 may be configured to set a vehicle group using at least one parameter indicating the communication quality between vehicles, as well as the vehicle distance. For example, the condition for belonging to the same vehicle group may be that the RSSI is equal to or greater than the grouping strength, and the vehicle distance is less than a predetermined grouping distance. The grouping distance may be, for example, 50 mm, 100 m, or 150 m. The grouping distance may be different for general roads and expressways. In other words, it may be changed according to the travel speed limit or road type. Naturally, the higher the speed limit, the wider the vehicle distance should be set, and therefore the grouping distance may be set accordingly. For example, the grouping distance for general roads may be 50 m, while the grouping distance for expressways may be 200 m or 300 m.

The grouping distance may be defined as the number of seconds until passing the same point (so-called inter-vehicle time). Inter-vehicle time corresponds to the time from when a leading vehicle passes a landmark, which is a specific structure that serves as a marker on the road, such as a signpost, until the following vehicle passes the landmark. Inter-vehicle time roughly corresponds to the value obtained by dividing the inter-vehicle distance by the traveling speed of the following vehicle. Of course, inter-vehicle time may also be calculated by taking into account the acceleration of the following vehicle, etc.

The plan correction unit J61 adjusts the positional relationship of the vehicles constituting the vehicle group so as to ensure the quality of the inter-vehicle communication. In other words, the relative running position of each vehicle is adjusted so as to ensure an appropriate inter-vehicle distance for inter-vehicle communication. The plan correction unit J61 corresponds to a configuration that corrects the mid-term plan for each vehicle so that the distance between the vehicles in the vehicle group falls within a predetermined range suitable for inter-vehicle communication. The distance range suitable for inter-vehicle communication can be designed in advance based on simulations, etc. The distance range suitable for inter-vehicle communication may be set to different values for general roads with large curvature and expressways with relatively small curvature. For example, the inter-vehicle distance suitable for inter-vehicle communication on general roads may be set to 50 m or less, while the inter-vehicle distance suitable for inter-vehicle communication on expressways may be set to 250 m or less. The inter-vehicle distance suitable for inter-vehicle communication may be defined in terms of the inter-vehicle time.

Furthermore, when an isolated vehicle Ma that does not belong to any vehicle group exists, the plan correction unit J61 adjusts the medium-term travel plan of the isolated vehicle Ma so that the isolated vehicle Ma belongs to any vehicle group close to the isolated vehicle Ma. For example, as shown in FIG. 11, when an isolated vehicle Ma exists between the first vehicle group Gr1 and the second vehicle group Gr2, the plan correction unit J61 creates a control plan as a medium-term plan for the isolated vehicle Ma, in which a period is set to accelerate the isolated vehicle Ma so that the isolated vehicle Ma belongs to the first vehicle group Gr1. Of course, a control plan may be created in which a period is set to decelerate the isolated vehicle Ma so that the isolated vehicle Ma can join the second vehicle group Gr2. However, deceleration control may impair the convenience of the user riding in the isolated vehicle Ma. Therefore, it is preferable that the plan correction unit J61 incorporates the isolated vehicle Ma into a vehicle group located ahead by setting an acceleration period, as long as the speed limit and other traffic conditions allow. In addition, the vehicle group formation unit J6 may adjust the control plan for each vehicle so that the isolated vehicle Ma belongs to one of the vehicle groups by using acceleration/deceleration, lane changes, etc.

In addition, if it is difficult to incorporate the isolated vehicle Ma into the vehicle group located ahead due to circumstances such as the speed limit, a control plan may be created to incorporate the isolated vehicle Ma into the vehicle group located behind by introducing a deceleration period. When the plan correction unit J61 corrects the medium-term plan for the isolated vehicle Ma, the vehicle group formation unit J6 updates the vehicle group setting information based on the correction result so as to incorporate the isolated vehicle Ma into an existing vehicle group. In addition, the isolated vehicle Ma may be incorporated into either vehicle group by decelerating vehicle group Gr1 or accelerating vehicle group Gr2.

The plan correction unit J61 may control the traveling speed for each vehicle group. For example, the speed plan of each vehicle constituting the vehicle group is adjusted so that the vehicle group does not split at an intersection or a branching/merging point. The plan correction unit J61 also shortens or lengthens the inter-vehicle distance so that the desired level of inter-vehicle communication quality is ensured within the vehicle group. In addition, the plan correction unit J61 adjusts the length of the entire vehicle group or suppresses the traveling speed so that the road-to-vehicle group communication time described later is equal to or longer than the required reception time. The road-to-vehicle group communication time here is the communication time with the roadside unit 3 for the entire vehicle group. The road-to-vehicle group communication time can be, for example, the time from when the leading vehicle of the vehicle group enters the communication area of the roadside unit 3 to when the rearmost vehicle of the vehicle group leaves the communication area of the roadside unit 3. The required reception time corresponds to the time required to receive all of the segmented series of data from the roadside unit 3.

The connected vehicle setting unit J62 is configured to set the vehicles (i.e., connected vehicles) that will perform short-range communication with the roadside unit 3 from among the vehicle group for each time period. The connected vehicle setting unit J62 changes the connected vehicles over time based on the relative position of each vehicle with respect to the roadside unit 3. Details of the connected vehicle setting unit J62 will be described separately later.

The vehicle group speed acquisition unit J63 is configured to acquire the moving speed in the communication area of the roadside unit 3 through which the vehicle group will next pass, based on the driving plan of each vehicle constituting the vehicle group. The planned value of the moving speed of the vehicle group near the roadside unit 3 acquired by the vehicle group speed acquisition unit J63 can be used for calculating the vehicle group communication capacity, etc.

The shared route setting unit J64 creates a shared route, which is a communication route from a general vehicle in the vehicle group to a connecting vehicle, based on the communication status between each vehicle in the vehicle group and other vehicles. Note that, since vehicles in the vehicle group communicate with each other bidirectionally using unicast, the communication route as a shared route is reversible. In other words, the shared route corresponds to a communication route from a connecting vehicle to each general vehicle, and also corresponds to a communication route from each general vehicle to a connecting vehicle. In one aspect, the shared route can also be called a forwarding route. The method of setting a shared route will be described in detail later.

For each vehicle group, the resource control unit J7 sets a communication schedule between the roadside unit 3 and each vehicle that constitutes the vehicle group. In a scene where multiple vehicle groups can communicate with the roadside unit 3, the resource control unit J7 allocates radio resources for road-to-vehicle communication to each vehicle group to prevent interference between the vehicle groups. This configuration reduces the risk of communication interruptions due to interference. The resource control unit J7 also controls the allocation state of radio resources for wide-area communication with vehicles at the wireless base station 2.

The notification processing unit J8 is configured to notify the corresponding roadside unit 3 and each vehicle of the mid-term planning data of each vehicle, the vehicle group setting data generated by the vehicle group formation unit J6, the communication schedule for each vehicle group set by the resource control unit J7, etc. Various information may be distributed via the roadside unit 3 or via the wireless base station 2. The destination of the vehicle group setting data, etc. may be all vehicles that make up the vehicle group, or just one vehicle. If the destination of the vehicle group setting data, etc. is only one of the vehicles that make up the target vehicle group, the vehicle that receives the vehicle group setting data simply forwards the vehicle group setting data to the other vehicles that make up the vehicle group that are indicated in the vehicle group setting data.

<Configuration of Server 5>
The configuration of the server 5 will be described below with reference to Fig. 12. As shown in Fig. 12, the server 5 includes a server communication device 51, a road data storage unit 52, a dynamic data storage unit 53, and a server control unit 54. The server control unit 54 is connected to each of the server communication device 51, the road data storage unit 52, and the dynamic data storage unit 53 so as to be able to communicate with each other.

The server communication device 51 is equipment for communicating with the network device 4. The server communication device 51 can also be understood as a device for performing data communication with the wireless base station 2, the roadside device 3, and the vehicle-mounted device 1 via the network device 4. The server communication device 51 is configured to be able to communicate with the network device 4 using, for example, optical fiber. The server communication device 51 outputs data input from the network device 4 to the server control unit 54. For example, the server communication device 51 outputs probe data, traffic condition data, and the like from the network device 4.

The server communication device 51 also outputs data input from the server control unit 54 to the network device 4 according to the destination of the data. For example, the server communication device 51 transmits traffic condition data provided from a certain network device 4 to another network device 4 adjacent to the network device 4 under the control of the server control unit 54. The server communication device 51 also outputs at least a portion of weather forecast information, construction plan information, etc. acquired from another server as traffic condition supplement data to the network device 4 under the control of the server control unit 54. The traffic condition supplement data acquired from an external server and distributed can also include traffic light lighting schedule information, bus operation information, and emergency vehicle location information.

The road data storage unit 52 is a database in which high-precision map data is stored as static map data. The road data storage unit 52 can also be called a static map database. The road data storage unit 52 is realized using a rewritable non-volatile storage medium. The road data storage unit 52 is configured so that data can be written, read, deleted, etc. by the server control unit 54. The map data stored in the road data storage unit 52 can be updated, for example, based on probe data uploaded from multiple vehicles.

The dynamic data storage unit 53 is a database that stores traffic condition data, which is data that indicates the traffic conditions at each point. Because the traffic conditions at each point correspond to dynamic map elements, the dynamic data storage unit 53 can also be called a dynamic map database. The dynamic data storage unit 53 can also store weather information for each point, road construction information, traffic regulation information, road obstacle information, congestion information, speed limits, traffic light information, and target driving trajectory data.

The dynamic data storage unit 53 is also realized using a rewritable non-volatile storage medium. The dynamic data storage unit 53 is configured so that data can be written, read, deleted, etc. by the server control unit 54. The traffic condition data for each point stored in the dynamic data storage unit 53 can be updated based on traffic condition data provided by the network device 4, for example.

The server control unit 54 is mainly configured as a computer including a processor 541, a RAM 542, and a storage 543. The processor 541 is hardware for arithmetic processing coupled with the RAM 542. The processor 541 includes at least one arithmetic core such as a CPU. The processor 541 executes various processes by accessing the RAM 542. The storage 543 includes a non-volatile storage medium such as a flash memory. The storage 543 stores a server program as a program executed by the processor 541. The processor 541 executing the program corresponds to executing a distribution data update method, which is a method corresponding to the server program. The server program can be called a V2X application.

The server control unit 54 has various functional units shown in FIG. 12 as functional units that are realized when the processor 541 executes the server program. That is, the server control unit 54 has the following functional units: a road data management unit K1, a traffic data management unit K2, and a traffic control unit K3.

The road data management unit K1 is configured to manage the map data stored in the road data storage unit 52. The road data management unit K1 updates the map stored in the road data storage unit 52 based on integrated map data obtained by, for example, integrating probe data uploaded from multiple vehicles. The road data management unit K1 may also update the map stored in the road data storage unit 52 based on map data provided by a specified map vendor. The update interval for the map data may be, for example, daily, weekly, or monthly.

The road data management unit K1 also transmits to each of the multiple network devices 4, from among the map data stored in the road data storage unit 52, data on areas related to each network device 4 in map tile units. The network device 4 transmits, from among the received map data, data on the range corresponding to the roadside device 3 to the multiple roadside devices 3. The roadside device 3 distributes the distribution map data to each vehicle by road-to-vehicle communication.

The traffic data management unit K2 is configured to manage the traffic condition data stored in the dynamic data storage unit 53. The traffic data management unit K2 sequentially updates the data stored in the dynamic data storage unit 53 based on, for example, traffic condition data observed by the roadside unit 3 and input from the network device 4. The update interval may be, for example, 1 second, 5 seconds, 30 seconds, or 5 minutes, 10 minutes, 30 minutes, etc. In addition, the traffic data management unit K2 may update the weather information for each point stored in the dynamic data storage unit 53 based on weather information obtained from an external server, for example the contents of a raincloud radar. The traffic data management unit K2 can be called a dynamic data management unit.

The traffic control unit K3 is configured to control the communication between the vehicle-mounted device 1 and the wireless base station 2, and the communication between the vehicle-mounted device 1 and the roadside device 3. For example, when the amount of wide-area communication performed by the vehicle-mounted device 1 exceeds a predetermined threshold, it transmits an instruction signal to restrict the implementation of wide-area communication. In addition, an instruction signal to stop the transmission of probe data is transmitted to the vehicle-mounted device 1 in an area/period where the collection of probe data is not required. Conversely, an instruction signal requesting the transmission of probe data is transmitted to the vehicle-mounted device 1 in an area/period where the collection of probe data is required. Similarly, the traffic control unit K3 controls whether or not to transmit traffic condition data, taking into account the cumulative value of the communication volume, the data collection status, etc. In addition, the traffic control unit K3 can also execute processing such as limiting the amount of data to be transmitted by the roadside device 3, taking into account the communication load status of the roadside device 3.

<Interactions between devices related to vehicle convoy formation>
Here, the operation of each device related to the formation of a vehicle group and data distribution using the set vehicle group information will be described with reference to the sequence diagram shown in FIG.

First, the network device 4 acquires data indicating traffic conditions from the roadside device 3 and the server 5 at a predetermined timing (step S101). The vehicle-mounted device 1 also creates a long-term plan at any time (step S102) and transmits the long-term plan data including the current position and traveling speed to the network device 4 (step S102a). Such step S102a corresponds to a vehicle information acquisition step for the network device 4.

The vehicle-mounted device 1 also generates data indicating the status of short-range communication with other vehicles and the roadside device 3 (step S103) and transmits the data to the roadside device 3 and the network device 4 (step S103a). Step S103a corresponds to a communication status acquisition step for the network device 4. The observation data in the vehicle-mounted device 1 may be acquired by the roadside device 3 and then transmitted to the network device 4, or the vehicle-mounted device 1 may transmit the data to the network device 4 via wide-area communication. The roadside device 3 collects the communication status with other vehicles reported by the vehicle-mounted device 1 and the communication quality with the vehicle-mounted device 1 observed by the roadside device 3 itself (step S104). Then, the roadside device 3 transmits a data set indicating various communication statuses to the network device 4 as needed (step S104a).

The network device 4 creates a medium-term plan for each vehicle based on the traffic condition data acquired in step S101 and the long-term plan for each vehicle (step S105). The created medium-term plan is distributed to the corresponding vehicle by the notification processing unit J8 at any time. The medium-term plan may be unicast to each vehicle-mounted device 1 using wide area communication. However, in that case, the load on the wireless base station 2 may increase and wireless resources may become tight. In view of such circumstances, the medium-term plan for each vehicle may be configured to be first distributed to the roadside device 3, and then unicast from the roadside device 3 to each vehicle. When the vehicle-mounted device 1 receives the data of the medium-term plan generated by the network device 4, it creates a short-term plan based on the medium-term plan.

In this way, the network device 4 collects or internally generates various data for determining the vehicle fleet prior to the vehicle fleet organization process. The data for determining the vehicle fleet generated internally by the network device 4 is, for example, a medium-term plan for each vehicle. The medium-term plan also includes the target speed for each location.

In this specification, various data that are used to determine a vehicle group are also referred to as context data. The context data includes at least information indicating the quality of wireless communication between vehicles. As described above, the information indicating the quality of wireless communication between vehicles includes at least a portion of various indicators such as RSSI, SNR, and packet loss rate. Furthermore, as a more preferred aspect of this embodiment, the context data may also include information on long-term/medium-term control plans for each vehicle, including the current location and driving speed.

Then, the network device 4 organizes a vehicle group based on the medium-term control plan for each vehicle and the communication status of each vehicle with other vehicles (step S106). The vehicle group organization process can be repeated a predetermined number of times or until the number of isolated vehicles Ma falls below a predetermined value in conjunction with the medium-term planning process in step S105 so as to suppress the number of isolated vehicles Ma or to prevent a shortage of road-vehicle group communication time.

Note that, if the presence of isolated vehicles Ma or the insufficient road-to-vehicle group communication time relative to the required reception time is acceptable, it is not necessary to repeatedly perform steps S105 to S106. Also, after forming a group of vehicles, a medium-term plan for each vehicle may be created so that the group can be maintained. In other words, the order of performing steps S105 and S106 may be reversed.

In addition, as the vehicle group is organized, the network device 4 sets a shared route with each vehicle in the vehicle group as the starting point (in other words, the root node) and creates a communication schedule between each vehicle and the roadside unit 3 (step S106x). Step S106x corresponds to a supply route setting step.

When the vehicle group formation is complete, the network device 4 distributes setting information regarding the vehicle group that is scheduled to pass through the communication area of the roadside device 3 to the roadside device 3 (step S106a). The network device 4 also distributes vehicle group setting data, which is a data set indicating the vehicle group setting, to each vehicle (step S106b). Step S106b corresponds to a vehicle group setting distribution step.

As with the mid-term plan, the vehicle group setting data may be unicast to each vehicle by wide area communication, or may be distributed to each vehicle via the roadside unit 3. However, in order to carry out data communication with the roadside unit 3 on a vehicle group basis from the time when the leading vehicle of the vehicle group enters the communication area of the roadside unit 3, it is preferable that each vehicle is able to obtain vehicle group information before the leading vehicle of the vehicle group enters the communication area of the roadside unit 3. Therefore, as an example, the vehicle group setting data is assumed to be unicast to each vehicle by wide area communication. When the vehicle-mounted unit 1 receives the vehicle group setting data, it updates the data related to the vehicle group setting that it holds (step S108).

As shown in FIG. 14, for example, the vehicle group setting data includes a vehicle group ID, constituent member data, and data indicating the setting of a shared route for each time period. The vehicle group ID is an identifier for distinguishing a vehicle group from other vehicle groups, and can be set for each vehicle group by the network device 4. The constituent member data is list data of vehicle IDs that belong to the same vehicle group. Note that communication address information may be used as identification information instead of a vehicle ID.

The shared route can be formed in a tree format with the connecting vehicle at each time point as the starting point (root), as described separately below. The shared route data can be expressed as table data indicating the input source and transfer destination for each time period. The time period here is defined as the time when the connecting vehicle switches. The shared route data for each time period includes data indicating the connecting vehicle at each time slot (each time). In other words, the vehicle group setting data indicates the setting of the connecting vehicle at each time. Time periods during which multiple vehicles are set as connecting vehicles may be provided. Note that FIG. 14 shows data indicating the shared route from time t1 to t6 for a vehicle group whose constituent members are vehicles A to D.

The vehicle group setting data may include data indicating the period during which the vehicle group is valid, in other words, the period during which the vehicle group setting is maintained. In addition, to facilitate the association of the other party in the vehicle-to-vehicle communication with the recognition results of the surrounding monitoring sensor 7 (e.g., a camera), the vehicle group setting data may include data indicating the external characteristics and position information of each member. External characteristics refer to, for example, the vehicle type, color, and size. Note that, in order to reduce the processing load of the wireless base station 2 and the like and to reduce the wireless resource usage rate, it is preferable that the vehicle group setting data be set to 10 to 100 kilobytes or less. For example, it is preferable that the information indicating the external characteristics is compressed in data size by being symbolized, etc.

Then, the network device 4 creates a communication schedule based on the predicted communication conditions with the roadside unit 3, which are determined according to the control plan for each vehicle (step S109). As will be described later, creating the communication schedule includes a process of setting the connected vehicles in each time slot. Therefore, step S109 can be called the connected vehicle setting step. Then, each vehicle group transmits the schedule to the roadside unit 3 and each vehicle that is scheduled to pass through.

Based on the communication schedule data received from the network device 4, the roadside unit 3 sequentially distributes segment data to each connected vehicle using the designated short-range communication wireless resources (step S110). Each vehicle-mounted unit 1 transfers and shares the segment data distributed from the roadside unit 3 according to the sharing route included in the vehicle group setting data (step S111). Step S111 can be called the vehicle group sharing step. When each vehicle-mounted unit 1 completes sharing of a series of segment data, it combines them to restore the original data.

<Interactions related to distribution of static map data>
Here, the operation of each device involved in the distribution process of high-precision map data showing road structures, in other words, static map data, will be described with reference to FIG.

The server 5 updates the map data based on information provided by the map vendor at any time, information provided by the road management company, probe data uploaded from the vehicle, etc. (step S201). For example, the server 5 performs an update process for the static map data stored in the road data storage unit 52 at a predetermined time, such as 1:00 AM every day. After updating the static map data, the server 5 transmits the updated map data to the network device 4. The transmitted data may be all data or differential data.

The network device 4 updates the map data stored therein based on the map data provided by the server 5 (step S202). The network device 4 also distributes the updated map data to each of the multiple roadside units 3.

The roadside device 3 updates the map data it holds based on the map data provided by the network device 4 (step S203). The roadside device 3 further segments the map data for each map tile that it is to distribute, for example, and prepares it for distribution to the vehicle. Note that the segmentation of the static map data itself may be performed by the network device 4 or the server 5.

As described in step S109, the network device 4 creates a communication schedule for each vehicle group and each vehicle, and notifies the roadside device 3 (step S204). Note that, as an example, the network device 4 creates the communication schedule here, but this is not limited to this. The roadside device 3 or the server 5 may create a communication schedule for each vehicle based on the vehicle group setting data notified from the network device 4.

Based on the communication schedule data received from the network device 4, the roadside device 3 sequentially distributes the segmented static map data to each connected vehicle using the designated short-range communication wireless resources (step S205). Each vehicle-mounted device 1 transfers and shares the segmented map data distributed from the roadside device 3 according to the sharing route included in the vehicle group setting data (step S206). When each vehicle-mounted device 1 completes sharing of a series of segment data, it combines them to restore the original static map data and updates the map data it holds (step S207).

<Interactions related to distribution of dynamic map data>
Here, the operation of each device involved in the generation and distribution of dynamic map data will be described with reference to FIG.

The roadside unit 3 transmits data indicating the observed traffic conditions to the network device 4 at any time (step S301). The network device 4 aggregates the traffic condition data reported from each roadside unit 3 and transmits it to the server 5 (step S302). The server 5 updates the registered contents of the dynamic data storage unit 53 based on the traffic condition data provided by the network device 4, and transmits data indicating the update results to the network device 4 (step S303). The vehicle-mounted device 1 transmits the long-term plan data to the network device 4 at a predetermined timing (step S304).

Prior to predicting the traffic conditions at each point, the network device 4 collects various data for predicting the traffic conditions from each device such as the roadside unit 3 or generates it internally. Then, based on the data provided by each device, the network device 4 predicts the traffic conditions at each point after a predetermined time (step S305). For example, the traffic conditions at a certain target point are estimated based on the traffic volume at a point a certain distance ahead of the target point and the status of the traffic lights at the intersection. Here, the closer side refers to the opposite side in the direction of travel. The network device 4 generates dynamic map data based on the predicted traffic conditions (step S306). The dynamic map data may also be generated in a form divided into predetermined road sections like map tiles. The dynamic map data may have an expiration date or the like set. In addition, the network device 4 creates a communication schedule for each vehicle group and each vehicle based on the control plan of each vehicle, and notifies the roadside device 3 (step S307).

Based on the communication schedule data received from the network device 4, the roadside device 3 sequentially distributes the segmented dynamic map data to each connected vehicle using the designated short-range communication wireless resources (step S308). Each vehicle-mounted device 1 transfers and shares the segmented dynamic map data distributed from the roadside device 3 according to the shared route included in the vehicle group setting data (step S309). When each vehicle-mounted device 1 completes sharing of a series of segment data, it combines them to restore the original dynamic map data, and appropriately modifies the short-term control plan based on the dynamic map data (step S310).

<Method of selecting connected vehicles and data sharing routes within a fleet>
Here, an example of a procedure for setting a data sharing route in a vehicle group will be described with reference to FIG. 17, FIG. 18, and FIG. 19. Here, a case where a data sharing route is set for a vehicle group GrX including vehicles A to F will be described as an example. As shown in FIG. 17, vehicle A corresponds to the leading vehicle of the vehicle group GrX, and vehicle F corresponds to the trailing vehicle. Although FIG. 17 shows a two-lane road, the number of lanes of the road may be one or three or more. The roadside unit 3 is disposed on the shoulder or the like on the first lane side. That is, here, the first lane corresponds to the nearest lane, which is the lane closest to the roadside unit 3. The roadside unit 3 may be disposed directly above the road. Here, as an example, the lane on the right side of the traveling direction is called the first lane, assuming that the system is used in an area where traffic is on the right side, but this is not limited thereto. As another aspect, the lane on the left side of the traveling direction may be the first lane.

Figure 18 conceptually shows the transition of the RSSI between the roadside unit 3 and each vehicle in the vehicle group configuration shown in Figure 17. Ra to Rf in Figure 18 represent the transition of the RSSI of the signal from vehicles A to F observed by the roadside unit 3. For example, Rb indicates the change over time of the RSSI of the signal from vehicle B. Basically, the RSSI increases as the vehicle approaches the roadside unit 3, and decreases as the vehicle moves away from the roadside unit 3. In addition, the RSSI peak is more likely to be higher for vehicles traveling in the first lane, which is closer to the roadside unit 3, than for vehicles traveling in the second lane. In addition, the signal from a vehicle traveling in the first lane, which has no other lanes between it and the roadside unit 3, is less likely to be blocked by other vehicles or affected by multipath. In other words, it can be expected that the communication quality with the roadside unit 3 will be better for vehicles traveling in the first lane than for vehicles traveling in the second lane.

Focusing on such a tendency, the connected vehicle setting unit J62 of this embodiment sets vehicles A to C traveling in the first lane as connected vehicles in order, as an example. For example, the vehicle group formation unit J6 sets vehicles traveling in the first lane and having an RSSI equal to or greater than a predetermined connection threshold Pth as connected vehicles. Of course, the state in which the RSSI is equal to or greater than the predetermined connection threshold Pth is temporary, so connected vehicles are dynamically switched within the vehicle group. For example, the period during which vehicle A is set as the connected vehicle is from time t1 to time t3 when the RSSI is equal to or greater than the predetermined connection threshold Pth. Furthermore, vehicle B is set as the connected vehicle between times t2 and t5. Furthermore, vehicle C is set as the connected vehicle between times t4 and t6. In this way, the connected vehicle setting unit J62 estimates the time when the RSSI will be equal to or greater than the connection threshold Pth based on the control plan of each vehicle and the installation position of the roadside unit 3, and can determine the timing to switch connected vehicles within the vehicle group based on the estimation result.

The connection threshold Pth may be set to a value that allows stable road-to-vehicle communication and may be changed according to the standard value of transmission power defined in the standards for road-to-vehicle communication. The connection threshold Pth may be set to a value that, for example, results in an expected packet delivery rate of 95% or more. The connection threshold Pth depends on the default value of transmission power, but may be set to, for example, -55 dBm, -40 dBm, -30 dBm, etc.

The length of time during which the RSSI is equal to or greater than the connection threshold Pth corresponds to the individual communication available time during which the vehicle can stably communicate with the roadside unit 3 in short-range communication. The length of time during which the RSSI is equal to or greater than the connection threshold Pth, i.e., the individual communication available time, is determined based on the distance range in which the signal transmitted by the roadside unit 3 can be received at or greater than the RSSI and the vehicle's traveling speed. The distance range in which the signal transmitted by the roadside unit 3 can be received at or greater than the RSSI is determined according to the transmission power of the roadside unit 3 and the receiving sensitivity of the vehicle. In addition, the start and end times of the individual communication available time can be calculated from the position of the vehicle relative to the communication area of the roadside unit 3 and the control plan for the traveling speed. The above configuration corresponds to a configuration in which a connected vehicle is selected at each time point based on a predicted value of the transition of the RSSI of each vehicle relative to the roadside unit 3. The RSSI is determined by the relative position of the vehicle relative to the roadside unit 3. Therefore, from another perspective, the above configuration corresponds to a configuration in which a connected vehicle is selected at each time based on a predicted value of the relative position of each vehicle with respect to the roadside unit 3, which is determined by a control plan for each vehicle. Note that the individual communication available time does not have to be based on RSSI, but may simply be the time during which the vehicle is capable of short-range communication with the roadside unit 3, that is, the time during which the vehicle is within the communication area of the roadside unit 3.

In the example shown in FIG. 18, between times t2 and t3, vehicles A and B may exist in parallel as connected vehicles. Furthermore, between times t4 and t5, vehicles B and C may exist in parallel as connected vehicles. During such a period when multiple connected vehicles exist, the roadside unit 3 performs data communication with each vehicle. Furthermore, a general vehicle performs data communication with the server 5, etc., via the connected vehicle that is closer to the connected vehicle on the shared route. Of course, the switching of connected vehicles may be planned so that there is always only one connected vehicle. In one aspect, the connected vehicle setting unit J62 corresponds to a configuration that creates a switching schedule for connected vehicles based on a control plan for each vehicle.

The above rules for setting connected vehicles are merely examples and can be changed as appropriate. For example, the connected vehicles may be set from vehicles D to F traveling in the second lane. For example, a time period may be set in which vehicles D and E are connected vehicles. Connected vehicles may be determined based not only on RSSI but also on SNR, packet loss rate, the presence or absence of radio wave obstacles such as large vehicles in the vicinity, and the like.

Figure 19 shows an example of a shared route setting mode when each of vehicles A to C is a connecting vehicle. The vehicle group formation unit J6 creates a communication route with the connecting vehicle as the root node. General vehicles with which the connecting vehicle as the root node directly communicates data are preferentially selected from those with high communication quality with the connecting vehicle. As mentioned above, the communication quality can be evaluated, for example, by RSSI. For example, the general vehicles with which the connecting vehicle as the root node directly communicates data are the general vehicles with the highest and second highest RSSI values of the signals transmitted by the connecting vehicle (i.e. the top two). General vehicles with which the connecting vehicle as the root node directly communicates data correspond to nodes with a depth of 1.

The forwarding destination for a general vehicle located at a depth of 1 is selected from among the general vehicles that have not yet been selected as tree components and have the best communication quality with the node in question. The forwarding destination for general vehicles located at depths 2 and 3 is selected in the same way.

Specifically, when vehicle A is the connected vehicle, for example, vehicles B and D are set as communication partners of vehicle A based on the communication quality with vehicle A. Then, a route is set so that vehicle B directly communicates with vehicle C, vehicle C directly with vehicle F, and vehicle D directly with vehicle E. As a result, the data received by vehicle A from the roadside unit 3 is transferred to vehicles B and D, and the data is transferred and shared in sequence for each system of vehicle B → C → F and vehicle D → E. Note that transfer from vehicle A to vehicles B and D can be performed in the same time slot (i.e., simultaneously) by, for example, allocating different frequency slots. In addition, each node does not simply transfer data, but also executes a process of receiving data addressed to its own vehicle when the destination is not limited to other vehicles. Data communication between vehicles and between roads and vehicles is performed by unicast. When the receiving side successfully receives data, it returns a reception success response (so-called Ack), which is a signal indicating that the data was successfully received, to the transmitting side. In addition, when reception fails, control signals such as a retransmission request are exchanged.

Here, as an example, the number of branches extending from each node is set to 2 or less. The number of branches extending from a certain node corresponds to the number of vehicles to which the received data is to be transferred. Even if a certain vehicle is surrounded by other vehicles, it is expected that it can directly communicate with eight vehicles that are in the front, back, left, right, and diagonal directions. In other words, the maximum number of other vehicles within line of sight is assumed to be about eight. It is expected that communication quality will be guaranteed with vehicles within line of sight. In light of this situation, the number of branches extending from the root node may be allowed to be up to eight. In addition, as a shared route, the number of vehicles to which each vehicle transfers received data may be set to a value corresponding to the number of lanes on the travel route. The vehicle group formation unit J6 creates a shared route based on the communication quality between the vehicles that make up the vehicle group so that the tree depth (height) is 5 or less, in other words, so that data reaches the end within 5 hops. The shared route is expressed in the form of a routing table or the like.

However, since vehicle C is located at the rear of the vehicle group, if a failure occurs in receiving segment data between the roadside unit 3 and vehicle C, the vehicle group will have no way of acquiring the missing data through short-range communication. In light of this situation, when formulating a segment data distribution schedule, instead of allocating traffic evenly to multiple connected vehicles, the size (in other words, weight) and type of traffic to be assigned may be changed depending on the position within the vehicle group. For example, a communication schedule may be created so that more data is distributed to connected vehicles located in the front half of the vehicle group than to vehicles located in the rear half of the vehicle group. Also, a communication schedule may be created so that less important traffic, in other words, traffic that is tolerable for loss, is distributed to connected vehicles located in the rear half of the vehicle group, for example.

More specifically, when delivering 10 pieces of segment data to vehicle group GrX as shown in FIG. 17, etc., a plan may be created to deliver the first to fourth segments to vehicle A, the fifth to eighth segments to vehicle B, and the ninth to tenth segments to vehicle C. By making the delivery data size smaller in this way in the latter half compared to the first half, it becomes easier to ensure sufficient time to perform retransmission control, etc. As a result, the risk of data being missed can be reduced.

The shared route for each vehicle group is updated when the members of the vehicle group change. As another aspect, the shared route may be changed for each roadside unit 3. However, if a shared route is set for each roadside unit 3, the processes involved in creating, distributing, and receiving the shared route may become complicated. Therefore, it is preferable to modify the shared route when the members of the vehicle group change, rather than changing the shared route for each roadside unit 3.

As the shared route, a tree pattern is prepared in which each of the multiple vehicles constituting the vehicle group is the root node. Specifically, in the above example, a shared route may be created in which vehicle D, vehicle E, and vehicle F are each the root node. This is because there may be a pattern in which vehicles D, E, and F are preferentially set as connecting vehicles depending on the position of the roadside unit 3. While the shared route for each vehicle is set in advance, which vehicle is actually selected as the connecting vehicle may be dynamically changed for each roadside unit 3. For example, the combination of vehicles used as connecting vehicles may be appropriately selected depending on whether the roadside unit 3 is set on the left or right side of the road.

The shared route can be applied not only when receiving data from the roadside unit 3, but also when a general vehicle performs data communication with the server 5, etc. For example, if vehicle C wants to perform data communication with the server 5 during a time period when vehicle A is the connected vehicle, vehicle C first unicasts a communication packet addressed to the server 5 to vehicle B. If the communication packet received from vehicle C is addressed to the server 5, vehicle B forwards it to vehicle A according to the routing table as the shared route. If the communication packet received from vehicle B is addressed to the server 5, vehicle A forwards it to the roadside unit 3, which then transmits it to the server 5. In this way, the shared route can be applied not only to downstream communication from the roadside unit 3 to the vehicle, but also to upstream communication from the vehicle to the roadside unit 3, server 5, and network device 4.

<Resource allocation method within a fleet>
Here, an example of allocation of wireless resources used by the network device 4 for data communication between connected vehicles and the roadside device 3 will be described. As an example, a case will be described in which wireless resources are allocated over time to vehicles A to C, assuming the vehicle group configuration shown in Fig. 17 described above.

As shown in FIG. 20, the network device 4 executes steps S401 to S408 as a preparation process for allocating wireless resources (step S409). The series of processes shown in the flowchart in FIG. 20 can be called resource allocation-related processes. The number of steps and the processing order of the resource allocation-related processes can be changed as appropriate. For example, the flowchart shown in FIG. 20 may include a step of checking the combination of available frequencies, and a loop process of allocating resources to different traffic types requiring different QoS.

In step S401, the network device 4 acquires the amount of traffic to be transmitted to the vehicle group to be processed. Step S401 corresponds to a data size acquisition step. Step S401 is performed by the cooperation of the resource control unit J7 and the data size acquisition unit J41. Note that, as an example, a case where resources are allocated for downstream communication from the roadside unit 3 to the vehicle is illustrated here, but the same can be performed for upstream communication from the vehicle to the roadside unit 3. The amount of traffic that is retained in the transmission buffer of each vehicle, which corresponds to the amount of traffic for upstream communication, can be acquired, for example, using a buffer status report (BSR). Note that in normal LTE, the BSR is transmitted to the wireless base station 2. Each vehicle may be configured to transmit a control signal equivalent to the LTE BSR to the network device 4 via the wireless base station 2 or the roadside unit 3.

The traffic that the roadside unit 3 transmits to each vehicle group is, for example, a group of segment data of static map data or a group of segment data of dynamic map data. Of course, the type of traffic is not limited to this, and may include, for example, video signals of the monitored area captured by a roadside camera, audio signals, etc. Traffic types can be broadly categorized into video, audio, still images, and others. The QoS required may differ depending on the type of traffic. The QoS for each traffic may be determined by an application, etc.

In step S402, if there are multiple types of traffic, the transmission priority is determined according to the QoS. For example, the traffic is sorted so that traffic with the shortest allowable delay time is transmitted first. Note that if there is only one type of traffic, step S402 may be omitted. Step S402 is an optional element.

In step S403, the vehicle group speed acquisition unit J63 refers to the installation location information of the roadside unit 3 stored in the storage 433, and acquires data indicating the communication area of the roadside unit 3 through which the target vehicle group will next pass. In step S404, the vehicle group speed acquisition unit J63 acquires the moving speed of the vehicle group when passing through the communication area of the roadside unit 3 through which the target vehicle group will next pass, based on the control plan for each vehicle belonging to the target vehicle group. The moving speed of the vehicle group may be the traveling speed of the leading vehicle, or may be the average value of the speeds of all the vehicles that make up the vehicle group. It may also be the average value of the traveling speeds of the leading vehicle and the trailing vehicle. Step S404 can be called a vehicle group speed acquisition unit step. When step S404 is completed, the process proceeds to step S405.

In step S405, the start time, end time, and length of the individual communication available time are calculated based on information such as the lane and speed of each connected vehicle, the communication area of the roadside unit 3, and the road-to-vehicle communication quality.

In step S406, based on the calculation result in step S405, the road-vehicle group communication available time is calculated as the time from when vehicle A becomes able to communicate with the roadside unit 3 until when vehicle C becomes unable to communicate. Note that, as an example, the vehicle that constitutes the vehicle group and is at the front of the vehicles traveling in the nearest lane is treated as the effective leading vehicle, and vehicle C is treated as the effective trailing vehicle. In other words, the road-vehicle group communication available time is the time from when the vehicle at the front of the nearest lane among the vehicles constituting the vehicle group becomes able to communicate with the roadside unit 3 until when the vehicle at the rear of the nearest lane becomes unable to communicate with the roadside unit 3.

In another aspect, the road-vehicle group communication available time may be the time from when the leading vehicle in the vehicle group becomes able to communicate with the roadside unit 3 to when the trailing vehicle in the vehicle group becomes unable to communicate with the roadside unit 3, regardless of the driving lane. Specifically, the time when the vehicle F located at the very end of the entire vehicle group leaves the communication area of the roadside unit 3 may be regarded as the end time of the road-vehicle group communication available time. With this configuration, the road-vehicle group communication time can be relatively long.

In step S407, it is determined whether the road-to-vehicle group communication available time estimated in the above step is sufficient for the traffic volume obtained in step S401. Determining whether the road-to-vehicle group communication available time is sufficient for the traffic volume to be transmitted corresponds to determining whether the vehicle group communication capacity, which is the amount of data that can be transmitted/received during the road-to-vehicle group communication available time, exceeds the traffic volume to be transmitted/received. The vehicle group communication capacity is determined according to the number of time slots included in the road-to-vehicle group communication available time and the number of frequency resources available in each time slot. In other words, it is determined according to the total number of resource blocks available during the road-to-vehicle group communication available time. A method for calculating the vehicle group communication capacity will be described separately below.

If the available time for road-to-vehicle group communication is insufficient for the amount of traffic to be transmitted, step S407 is judged as negative, the process proceeds to step S408, and the vehicle group length adjustment process is executed. On the other hand, if the available time for road-to-vehicle group communication is sufficient for the amount of traffic to be transmitted, step S407 is judged as positive, and the process proceeds to step S409.

The vehicle group length adjustment process in step S408 includes steps S501 to S505 as shown in FIG. 21. In step S501, it is determined whether there are any vehicles around the target vehicle group that could potentially be incorporated into the target vehicle group. A vehicle that could potentially be incorporated into the target vehicle group can be, for example, a vehicle whose inter-vehicle communication quality with at least one of the vehicles belonging to the target vehicle group satisfies a predetermined incorporation condition.

The incorporation condition may be, for example, that the RSSI of two-way or one-way communication is equal to or greater than a predetermined incorporation threshold. Of course, the incorporation condition may also include that the vehicle is within a certain distance from the vehicle group. The incorporation threshold may be set to be the same as the grouping strength or a predetermined amount smaller than the grouping strength. The processing of steps S501 to S502 is a temporary process to extend the length of the vehicle group when the vehicle group communication capacity is insufficient, so the incorporation threshold is set to a value, for example, about 5 dBm smaller than the grouping strength. With this setting, vehicles that are normally incorporated into another vehicle group can be included in the target vehicle group. The incorporation condition is set to be easier to satisfy (i.e., looser) than the grouping condition so that the size of the vehicle group can be expanded.

If there is a vehicle that satisfies the incorporation condition in the vicinity of the vehicle group to be processed, the vehicle is incorporated into the target vehicle group. For example, as shown in FIG. 22, if there is a vehicle G in the rear of the target vehicle group GrX, the RSSI of the signal from the tail vehicle F of the target vehicle group GrX or the vehicle C located at the sub-tail is equal to or greater than the incorporation threshold, the vehicle group formation unit J6 adds the vehicle G to the target vehicle group GrX. If the vehicle G is a member of another vehicle group GrZ, the vehicle G may be removed from the vehicle group GrZ or may belong to both vehicle groups. In other words, the vehicle G may maintain its membership in the vehicle group GrZ to which it originally belonged. In this way, the vehicle group formation unit J6 is configured to be able to set a vehicle group so that one vehicle temporarily belongs to multiple vehicle groups. Here, the mode of adding a new vehicle to the tail of the vehicle group has been described, but the position at which the new vehicle is incorporated may be the front of the vehicle group. In other words, a vehicle located in front of the target vehicle group may be incorporated. Once the vehicle fleet reorganization process in step S502 is complete, return to step S404.

If there is no vehicle that satisfies the inclusion conditions in the vicinity of the vehicle group to be processed in step S501, step S501 is judged as negative and the process proceeds to step S503. In step S503, it is determined from the viewpoint of communication quality between the vehicles whether the inter-vehicle distance of the target vehicle group can be increased by a predetermined distance. For example, if there is a combination of vehicles in which the RSSI falls below a predetermined allowable lower limit value if the current inter-vehicle distance is increased, it is determined that the inter-vehicle distance cannot be increased. On the other hand, if the communication quality between the constituent members can be maintained even if the inter-vehicle distance in the longitudinal direction of each vehicle is increased by a certain amount, step S503 is judged as positive and the process proceeds to step S504.

In step S504, the plan correction unit J61 corrects the control plan for each vehicle in the vehicle group so as to increase the inter-vehicle distance by a predetermined amount. Note that, from the viewpoint of extending the length of the vehicle group, it is not necessary to change the speed of the leading vehicle. The vehicles whose control plans are corrected in step S504 are the second vehicle from the front of the vehicle group onwards.

The adjustment amount of the distance between each vehicle may be a constant value such as 1 m, 3 m, or 5 m. Since it is sufficient to extend the length of the vehicle group as a whole, the adjustment amount of the distance between each vehicle may be different for each vehicle. The adjustment amount of the distance between each vehicle may be dynamically set to a length according to the shortage of the vehicle group communication capacity. For example, if the shortage of the vehicle group communication capacity is two time slots, the length of the vehicle group may be extended so that the communication time for two time slots is secured. In that case, the adjustment amount of the distance between each vehicle may be a value obtained by dividing the required extension amount, which is a length determined by multiplying the time for two time slots by the traveling speed of the vehicle group, by the number of constituent members minus 1. Note that in a configuration in which only vehicles traveling in the nearest lane are used as connecting vehicles, the required extension amount divided by the number of vehicles traveling in the nearest lane minus 1 becomes the adjustment amount of the distance between the vehicles traveling in the nearest lane. Vehicles traveling in lanes other than the nearest lane can also increase the distance between themselves and the preceding vehicle to the same extent in order to maintain their positional relationship with the vehicle traveling in the nearest lane. When the control plan correction process in step S504 is completed, the process returns to step S404. Step S408, which includes steps S501 to S504, can be called the vehicle group length adjustment step.

In step S505, the speed control plan for all vehicles that make up the target vehicle group is modified so that the traveling speed of the entire vehicle group is suppressed by a predetermined amount. The vehicle speed suppression amount can be, for example, 1 km/h, 2 km/h, 4 km/h, etc. The vehicle group formation process can be repeated until it is determined in step S407 of FIG. 20 that the road-vehicle group communication time is sufficient. Therefore, the final traveling speed suppression amount can be 6 km/h, 8 km/h, etc.

However, since suppressing the driving speed may lead to a decrease in user convenience, when the cumulative value of the suppression amount is equal to or greater than a predetermined upper limit, the suppression amount of the vehicle speed may be set to the upper limit, and the data size adjustment unit J42 may execute an adjustment process to reduce the traffic volume. The reduction in the traffic volume by the data size adjustment unit J42 may be achieved by deleting data with low importance based on a preset importance level. In other words, when the vehicle group communication capacity is insufficient for the traffic volume even after performing the vehicle group length adjustment process, the data size adjustment unit J42 may narrow down the distribution data to information that is important for driving control. Information that is important for driving control includes objects that have a collision possibility of a vehicle constituting the vehicle group equal to or greater than a predetermined threshold, the position of a stop line, the lighting status of a traffic light, etc. Information with a relatively low importance includes information about objects that have a low possibility of collision with a vehicle.

A variety of methods can be used to evaluate the possibility of a collision between a vehicle and another object, such as calculating the time to collision based on the direction and speed of movement of each object and their acceleration, so detailed explanations will be omitted here. Data size can also be reduced by lowering the resolution of the video/image data. Once the processing in step S505 is complete, the process returns to step S404.

In step S409, the allocation of resource blocks for each vehicle constituting the vehicle group is planned. Figures 23 and 24 show an example of an allocation mode in which vehicles A to C are used as connected vehicles in sequence/temporarily in parallel from time t1 to t6. Figure 23 conceptually shows connected vehicles at each time, in other words, at each time slot, and Figure 24 shows an example of a specific resource block allocation mode based on the general communication schedule shown in Figure 23. Radio resources are divided and controlled based on the concepts of time and frequency as shown in Figure 24. In other words, they are controlled in resource block units. Each frame in Figure 24 represents a resource block. Here, as an example, six frequencies from the first frequency f1 to the sixth frequency f6 are configured to be available as frequency resources.

In FIG. 24, resource blocks hatched with a diagonal line pattern represent resource blocks for communication with vehicle A, and resource blocks hatched with a horizontal dashed line pattern represent resource blocks for communication with vehicle B. Resource blocks hatched with a dot pattern represent resource blocks for communication with vehicle C. As shown in FIG. 24, in time slots (#1 to #3 in the figure) in which vehicle A is the only connected vehicle, all frequencies are assigned to vehicle A. On the other hand, in time slots (#4 to #5 in the figure) in which vehicles A and B act as connected vehicles, different frequencies are used for vehicles A and B. For example, in the fourth time slot, the first frequency f1 and the second frequency f2 are assigned to vehicle A, while the third frequency f3 to the sixth frequency f6 are assigned to vehicle B. Similarly, in periods in which vehicle B is the only connected vehicle or vehicle C is the only connected vehicle, all frequencies are assigned to vehicles B and C. On the other hand, in time slots (#8-9 in the figure) in which vehicles B and C act as connected vehicles, the frequencies used are shared between vehicles B and C. Note that all frequencies here refer to frequencies available to the vehicle group, and do not necessarily refer to all frequencies used in short-range communication. When multiple vehicle groups access the same roadside unit 3, the frequencies are shared among the multiple vehicle groups. Also, when vehicle-to-vehicle communication and road-to-vehicle communication are implemented using the same communication method, resource blocks are shared between road-to-vehicle communication and vehicle-to-vehicle communication.

As shown in FIG. 24, the result of the allocation of radio resources includes an allocated frequency for each vehicle for each time slot. The number of resource blocks allocated to each vehicle is preferably set to be greater than the amount of traffic to be transmitted to each vehicle. If the first segment shown in FIG. 7 is to be delivered to vehicle A, at least the number of resource blocks that can transmit the first segment are allocated. If the second segment shown in FIG. 7 is to be delivered to vehicle B, at least the number of resource blocks that can transmit the second segment are allocated. Similarly, resource blocks are allocated to vehicle C so that it can accommodate the transmission data for vehicle C.

The amount of data that one resource block can accommodate may vary depending on the frequency. Also, if the time slot is different, the distance between the roadside unit 3 and the vehicle will also vary, so even if the frequency is the same, the amount of data that one resource block can accommodate may vary depending on the time slot. In addition, if the communication performance, such as the reception processing speed, differs from vehicle to vehicle, the data size that can be transmitted by one resource block may differ from vehicle to vehicle.

The allocation of radio resources is based on the characteristics of each frequency, each time slot, and each vehicle, and estimates the amount of data that can be transmitted by each resource block, and determines the allocation mode of the resource blocks. Note that resource allocation for each vehicle may be performed using an approximate value of the capacity of each resource block. The approximate value of the capacity of each resource block may be a value registered in advance for each frequency, or may be calculated from a past actual value according to the distance from the roadside unit 3. The method of calculating communication capacity will be described separately later.

When the network device 4 completes the allocation of wireless resources to each vehicle, it notifies the roadside unit 3 of a communication schedule including the allocation results (step S410). If the vehicle group composition is changed as a result of the vehicle group length adjustment process, the network device 4 distributes updated vehicle group setting data to the related vehicles. If the control plan of each vehicle is changed as a result of the vehicle group length adjustment process, the network device 4 distributes the updated control plan to the related vehicles. Here, the related vehicles refer to the vehicles that use the data related to the updated vehicle group setting and control plan.

<Calculation method for individual communication capacity and vehicle group communication capacity>
Here, an example of a method for calculating individual communication capacity and vehicle group communication capacity will be described using various parameters. The vehicle group communication capacity may be calculated by the vehicle group organization unit J6 or the resource control unit J7. The functional layout for calculating the communication capacity can be changed as appropriate. α(M) described below refers to a set of time slots assigned to a certain mounted vehicle M. β(M, τ) refers to a set of frequencies assigned to a certain mounted vehicle M in a certain time slot τ. In addition, r(M, τ, f) refers to a communication rate (bps) when a mounted vehicle M uses a certain frequency f in a certain time slot τ. Δτ indicates the length of time per one time slot.

The individual communication capacity C(M), which is the capacity with which a vehicle can communicate with the roadside unit 3, is expressed by the following equation (1) using the above parameters.

なお、図２４に示す例においては、第４タイムスロットにおける車両Ａが利用可能な周波数の集合βは｛ｆ１、ｆ２｝であり、第５タイムスロットにおける車両Ａが利用可能な周波数の集合βは｛ｆ１｝である。また、第４タイムスロットにおける車両Ｂが利用可能な周波数の集合βは｛ｆ３、ｆ４、ｆ５、ｆ６｝であり、第５タイムスロットにおける車両Ａが利用可能な周波数の集合βは｛ｆ２、ｆ３、ｆ４、ｆ５、ｆ６｝となる。

In the example shown in Fig. 24, the set β of frequencies available to vehicle A in the fourth time slot is {f1, f2}, and the set β of frequencies available to vehicle A in the fifth time slot is {f1}. The set β of frequencies available to vehicle B in the fourth time slot is {f3, f4, f5, f6}, and the set β of frequencies available to vehicle A in the fifth time slot is {f2, f3, f4, f5, f6}.

The number of time slots Nτ in α(M) can be expressed by the following equation (2), where φ is the distance in the road extension direction of the communication area of the roadside unit 3 and v(M) is the average driving speed of vehicles in that communication area. Since φ is constant, as shown in equation (2), the number of elements in set α(M), i.e., the number of time slots Nτ, increases as the vehicle speed decreases. Therefore, if we ignore cases where frequencies are shared with other vehicles, the communication capacity can basically be increased.

また、車群通信容量Ｃｇｒは、１つの側面において車群を構成する各車両での個別通信容量Ｃ（Ｍ）の合算値と解する事ができる。そのため、車群通信容量Ｃｇｒは、車群を構成する車両の集合である車群集合μを用いて次の式（３）で表現可能である。なお、車両Ｍ１～Ｍ６を構成メンバとして備える車群Ｇｒの車群集合μは｛Ｍ１，Ｍ２，Ｍ３，Ｍ４，Ｍ５，Ｍ６｝として表現される。

In addition, the vehicle group communication capacity Cgr can be interpreted as the sum of the individual communication capacities C(M) of the vehicles constituting the vehicle group in one aspect. Therefore, the vehicle group communication capacity Cgr can be expressed by the following formula (3) using a vehicle group set μ, which is a set of vehicles constituting the vehicle group. Note that the vehicle group set μ of the vehicle group Gr, which has vehicles M1 to M6 as its members, is expressed as {M1, M2, M3, M4, M5, M6}.

なお、車速を抑制すれば車群全体として使用可能なタイムスロットの数が伸びるため、車群通信容量を伸ばすことができる。また、車間距離を空けることで、複数の車両が並列的に通信する時間を短縮でき、それにより、各車両が使用可能な周波数リソースが増大しうる。その結果、車群通信容量を増大できる。

In addition, by suppressing vehicle speed, the number of time slots available for the entire vehicle group can be increased, which increases the vehicle group communication capacity. In addition, by increasing the distance between vehicles, the time that multiple vehicles communicate in parallel can be shortened, which can increase the frequency resources available to each vehicle. As a result, the vehicle group communication capacity can be increased.

Note that, although a method of calculating a specific communication capacity taking into account the variations in the specific communication rates for each frequency, each time slot, and each vehicle has been disclosed above, this is not limiting. Using the communication rate r(τ) of the unit resource block for each time slot, which ignores/includes the amount of variation due to frequency and vehicle, the individual communication capacity C(M) can be expressed by the following formula (4). Note that Nb(M, τ) in the formula refers to the number of resource blocks assigned to the vehicle in each time slot τ.

さらに、タイムスロットによる通信レートの変動成分を無視／包含した単位リソースブロックの通信レートｒを用いて個別通信容量Ｃ（Ｍ）は次の式（５）でも概算可能である。なお、Ｃｕは、リソースブロック当りのデータ容量であって、Ｃｕ＝ｒ・Δτの関係を有する。Ｃｕは、過去の通信実績に基づいて算出されても良いし、設計値であってもよい。Ｃｕは、直近所定時間以内における複数の周波数での通信レートの平均値に、Δτを乗じた値に設定されうる。ｔＲＢ（Ｍ）は、車両に割り当てているリソースブロックの総数を示す。例えば図２４に示す例では、車両Ａに割り当てているリソースブロックの総数ｔＲＢ（Ａ）は、２１となる。

Furthermore, the individual communication capacity C(M) can be roughly calculated by the following formula (5) using the communication rate r of the unit resource block ignoring/including the fluctuation component of the communication rate due to the time slot. Cu is the data capacity per resource block, and has the relationship of Cu=r·Δτ. Cu may be calculated based on past communication results, or may be a design value. Cu may be set to a value obtained by multiplying the average value of the communication rates at multiple frequencies within a fixed time by Δτ. tRB(M) indicates the total number of resource blocks assigned to the vehicle. For example, in the example shown in FIG. 24, the total number tRB(A) of resource blocks assigned to vehicle A is 21.

さらに、路車群通信可能時間Ｔｇｒは、車群の先頭車両が路側機３の通信エリアに入ってから、末尾車両が路側機３の通信エリアを退出するための期間として算出することができる。車群の長さをＬｇｒとし、車群の平均速度をＶｇｒとすると、路車群通信可能時間Ｔｇｒ＝（φ＋Ｌｇｒ）／Ｖｇｒとなる。

Furthermore, the road-vehicle group communication available time Tgr can be calculated as the period from when the leading vehicle of the vehicle group enters the communication area of the roadside device 3 until the trailing vehicle exits the communication area of the roadside device 3. If the length of the vehicle group is Lgr and the average speed of the vehicle group is Vgr, then the road-vehicle group communication available time Tgr = (φ + Lgr) / Vgr.

Here, if the total number of resource blocks available in one time slot is Nb, and the number of time slots available to the entire vehicle group is Nτ, the vehicle group communication capacity Cgr is expressed by the following equation (6). Note that Nb corresponds to the number of frequencies available to the target vehicle group. Nτ corresponds to the integer part of Tgr/Δτ, and can be written as [Tgr/Δτ] using Gaussian symbols, for example. Nτ can be expressed using Gaussian symbols or floor functions. tRB(gr) indicates the total number of resource blocks available to the entire vehicle group.

例えば図２４に示す例では、車群ＧｒＸが使用可能なキャリア数が６であるためリソースブロックの総数Ｎｂ＝６となる。また、タイムスロット数Ｎτが１１であるため、ｔＲＢ（ｇｒ）は、６×１１＝６６となる。なお、ここでは説明を簡単にするために、対象車群が使用可能な周波数の数が通信期間中一定としている。

24, the number of carriers available to the vehicle group GrX is 6, so the total number of resource blocks Nb = 6. Also, the number of time slots Nτ is 11, so tRB(gr) is 6 x 11 = 66. For simplicity of explanation, it is assumed here that the number of frequencies available to the target vehicle group is constant during the communication period.

When radio resources are divided into resource blocks based on three parameters, time, frequency, and modulation method, the total number of resource blocks available in one time slot is equal to the product of the number of frequencies and the number of modulation methods. However, it is expected that the communication rate will vary significantly for each modulation method. Therefore, when a modulation method is also used as a component of a resource block, it is preferable to calculate the individual communication capacity and vehicle group communication capacity using the communication rate r for each modulation method.

In addition, the network device 4 may estimate the individual communication capacity and vehicle group communication capacity based on the past communication performance, according to the current traveling speed and the number of vehicles that make up the vehicle group. The vehicle group communication capacity may also be estimated according to the traveling speed of the vehicle group and the length of the vehicle group.

<Operation when receiving segment data>
Here, an example of the operation of the roadside device 3 and the connected vehicles when the roadside device 3 segments the original data and distributes it to each vehicle will be described with reference to Fig. 25. First, when the roadside device 3 receives distribution data, such as static map data or dynamic map data, from the network device 4 (step S601), the roadside device 3 generates a plurality of segment data by dividing the data into predetermined sizes (step S602). As described above, the network device 4 or the server 5 may perform segmentation of the distribution data. Here, as an example, the case where the distribution data is divided into three segments, 1st to 3rd segments, is illustrated. Also, the case where the vehicle group with which the communication is performed is the vehicle group GrX including vehicles A to F, which was mentioned in the explanations of Figs. 17, 23, 24, etc., is illustrated.

After that, when the roadside device 3 detects that at least a part of the vehicle group has entered the communication area, it starts short-range communication with the vehicle group. Specifically, it unicasts the first segment to vehicle A, which corresponds to the leading vehicle (step S603).

When the vehicle-mounted device 1 of vehicle A receives the first segment sent from the roadside device 3 to its own vehicle, it returns an Ack to the roadside device 3 as a reception response (step S604). This allows the roadside device 3 to confirm that at least vehicle A was able to successfully send the first segment.

The vehicle-mounted device 1 of vehicle A also distributes the first segment to other vehicles in the vehicle group via a preset shared route (step S605). The shared route is as described with reference to FIG. 19 etc. For example, vehicle A unicasts the first segment to vehicles B and D. Vehicles B and D each return an Ack to vehicle A and unicast the first segment to vehicles C and E. Vehicles C and E return an Ack to the sender. Vehicle C unicasts the first segment to vehicle F.

When sharing of the first segment within the vehicle group is completed, vehicle A, as a connected vehicle, transmits a sharing completion report to the roadside unit 3 (step S606). Completion of data sharing within the vehicle group can be detected, for example, by vehicles E and F, which are terminal nodes (in other words, leaf nodes) of the shared route, transmitting a completion message to vehicle A, as the root node, indicating that the first segment has been received. The completion message from the leaf node may reach the root node via internal nodes such as vehicles B and C.

Note that sending a sharing completion report from the connected vehicle to the roadside unit 3 is an optional element and can be omitted. In other words, the above-mentioned step S606 and steps S613 and S623 described below can be omitted. However, a configuration in which the connected vehicle sends a sharing completion report has the advantage that the roadside unit 3 can grasp the progress of whether or not the sharing of the delivered segment has been completed normally.

Next, when it is time for vehicle B to become a connected vehicle, the roadside unit 3 unicasts the second segment to vehicle B as a connected vehicle (step S610). When the vehicle-mounted unit 1 of vehicle B receives the second segment sent from the roadside unit 3 to its own vehicle, it returns an Ack to the roadside unit 3 as a reception response (step S611). This allows the roadside unit 3 to confirm that at least vehicle B was able to successfully send the second segment. In addition, the vehicle-mounted unit 1 of vehicle B distributes the second segment to other vehicles in the vehicle group via a preset shared route (step S612). When vehicle B as a connected vehicle completes sharing the second segment within the vehicle group, it transmits a sharing completion report to the roadside unit 3 (step S613).

Furthermore, when the time comes for vehicle C to become a connected vehicle, the roadside unit 3 unicasts the third segment to vehicle C as the connected vehicle (step S620). When the vehicle-mounted unit 1 of vehicle C receives the third segment sent from the roadside unit 3 to its own vehicle, it returns an Ack to the roadside unit 3 as a reception response (step S621). This allows the roadside unit 3 to confirm that at least vehicle C was able to successfully send the third segment. In addition, the vehicle-mounted unit 1 of vehicle C distributes the third segment to other vehicles in the vehicle group via the previously set shared route (step S622). When vehicle C as the connected vehicle completes sharing the third segment within the vehicle group, it transmits a sharing completion report to the roadside unit 3 (step S623).

Furthermore, each vehicle in the vehicle group including vehicle C restores the original data by combining the multiple segment data received from the roadside unit 3 or other vehicles in the vehicle group (step S624). If the restoration of the original data is successful, for example, vehicle C, which is the connected vehicle at that time, sends to the roadside unit 3 a restoration success report, which is a control signal indicating that the restoration of the original data has been successful (step S625).

Such a configuration for transmitting a restoration success report allows the roadside unit 3 to recognize that the target vehicle group has successfully received and shared a series of segment data. Note that transmitting the restoration success report is an optional element and may be omitted.

<Effects of the above configuration>
Introduction:
In order to perform autonomous driving or advanced driving assistance, it is assumed that a dynamic map showing blind spots on the road, traffic conditions outside the detection area of the vehicle-mounted sensor, and detailed road structures is required. The dynamic map here can be interpreted as map data including the static map data and dynamic map data described above. In the above assumption, if the vehicle cannot acquire the dynamic map, a so-called fallback control may be executed, which restricts the function, such as suppressing the driving speed to a predetermined value or lower or switching to manual driving, in order to ensure safety. If the driving speed is suppressed, the convenience of the user is impaired.

If the dynamic map has a small capacity, each vehicle may be able to obtain the data individually from the roadside unit 3 or wireless base station 2, but in order to achieve more advanced, highly accurate, or flexible autonomous driving, it is expected that the dynamic map will need to be made larger in capacity.

In a configuration in which each vehicle obtains a dynamic map from the roadside unit 3 through unicast communication, the connection time between the roadside unit 3 and each vehicle is short, limiting the amount of data that can be transmitted. This is because the communication range of the roadside unit 3 is finite, such as within a few hundred meters. In addition, the faster the vehicle is traveling, the shorter the time the vehicle stays within the communication range of the roadside unit 3. This can lead to a situation in which the available communication time is insufficient for the time required for data transmission. In addition, in a configuration in which each vehicle obtains a dynamic map individually from the wireless base station 2, there are concerns about an increase in the processing load on the wireless base station 2 and a shortage of wireless resources.

With this in mind, the developers of this disclosure have considered a technology that forms a vehicle group based on the vehicle's position information and driving speed, and each vehicle in the vehicle group receives a dynamic map in a shared manner, which is then shared and supplemented within the vehicle group. With this configuration, data communication is performed on a vehicle group basis, reducing the risk of communication time shortages and wireless resource congestion.

Furthermore, as the developers continued their research, they discovered that when a vehicle group is configured with location information and driving speed as the main parameters, the vehicles that make up the group are not necessarily able to communicate stably with each other. For example, if there is a radio wave obstruction between two vehicles, such as a large trailer that prevents inter-vehicle communication, it can become difficult for the two to communicate. Naturally, if communication between vehicles in a group is unstable, it will be impossible to properly share data within the group to complement and restore the data.

In response to the above-mentioned problems, according to the above disclosure, first, the network device 4 manages the vehicle group using context data including the vehicle-to-vehicle communication status. Since the network device 4 forms a vehicle group based on the vehicle-to-vehicle communication quality, it is possible to reduce the risk of including vehicles that are actually difficult to communicate with in the same vehicle group. In other words, it becomes easier to ensure communication quality within the vehicle group.

In addition, in the proposed configuration, vehicles that are likely to run side by side for a certain period of time are grouped together as a group based on the travel plan of each vehicle. This configuration makes it easier to maintain the group settings, and reduces the processing load on the network device 4 related to group organization.

Furthermore, the network device 4 allocates radio resources for road-to-vehicle communication to each vehicle to prevent interference between the vehicles. This configuration can reduce the risk of communication failure due to interference.

Note that another possible configuration is to give vehicles the ability to form a vehicle group. However, in such a configuration, overhead may occur for forming a vehicle group when vehicles are replaced. Therefore, in this configuration, this overhead may cause delays in data communication and control delays before the vehicle group can function. Note that overhead here refers to the exchange of control signals to determine communication paths within the vehicle group and connected vehicles.

In contrast to such an assumed configuration, the proposed configuration allows the network device 4 to set up a vehicle group through centralized control and notify each vehicle in advance, thereby suppressing communication delays and control delays due to the overhead. In other words, it becomes possible to seamlessly realize changes in the vehicle group configuration and transitions to another vehicle group. In addition, since each vehicle does not need to exchange route control messages, which are control signals for setting up communication routes within the vehicle group, the processing load of the vehicle-mounted device 1 can also be reduced. Therefore, it is possible to realize the vehicle-mounted device 1 using a processor or communication module with relatively low processing power. As a result, it is possible to suppress the introduction cost of the vehicle-mounted device 1 into the vehicle.

In addition, in the above configuration, large volumes of data are segmented and distributed to the vehicle group. Specifically, the roadside unit 3 transmits different segments to each of the multiple vehicles in the vehicle group by unicast communication, and the data received in fragments by the multiple vehicles is shared and combined within the vehicle group. With this configuration, by using the concept of a vehicle group to ensure a communication connection with the roadside unit 3 on an area basis, the communication time with the roadside unit 3 can be extended compared to when each vehicle communicates with the roadside unit 3 individually. Furthermore, as a result, vehicles can obtain large volumes of data through short-range communication that are too large for each vehicle to receive on its own. For example, large-capacity dynamic maps of intersections, interchanges, and junctions can be distributed in real time.

In other words, according to the present disclosure, even if the dynamic map becomes so large that it cannot be received within the individual communication time, data can be sent and received by ensuring surface connections between individual vehicle groups. Furthermore, because unicast communication is performed between the roadside unit 3 and the vehicle, the roadside unit 3 can confirm that each segment has reached the vehicle group normally.

As a first comparative configuration, which is another configuration related to the distribution of dynamic maps, a configuration can be assumed in which the wireless base station 2 as a macrocell distributes dynamic maps to each vehicle by unicast. However, since the number of vehicles included in a macrocell can be enormous, it is practically difficult to distribute dynamic maps to each vehicle by unicast, given that the processing load and wireless resources of the wireless base station 2 are finite.

As a second comparative configuration, a configuration in which the wireless base station 2 multicasts or broadcasts the dynamic map to vehicles within the area is also possible. However, with multicast and broadcast, the receiving terminal, the vehicle, does not return an ACK as a reception completion report, so the distributing device is unclear as to whether the destination (i.e., the vehicle) was able to deliver the data successfully. As a result, the dynamic map cannot be resent to vehicles that have failed to receive the data, making it difficult to guarantee the quality of the system as a whole.

In contrast to the first and second comparative configurations, the proposed configuration allows the distribution device to confirm that the vehicle has received the data normally, and also reduces problems with processing/radio resources. In other words, the proposed configuration uses the concept of a vehicle group to indirectly achieve multicast communication that can be confirmed as reaching the destination by combining unicast communication with connected vehicles in the vehicle group with data sharing within the vehicle group.

Patent Document 2 suggests a configuration in which segment data is shared and combined via vehicle-to-vehicle communication to restore the original data. However, in the configuration disclosed in Patent Document 2, whether or not a vehicle encounters another vehicle that has data that the vehicle does not have is determined by chance, so it may take a relatively long time to gather all the data. In contrast, with the proposed configuration, segment data is quickly shared among vehicles based on a shared route that has been set in advance. Therefore, it is expected that data sharing will be completed within a few seconds of data distribution.

In addition, the above configuration creates a plan to deliver as much data/segments as possible to vehicles traveling in the first half of the vehicle group, and reduce the amount of data delivered as the vehicle approaches the end of the vehicle group. By weighting the size of the data delivered in this way according to the vehicle's position within the vehicle group, it is possible to increase the reliability of communication with the roadside unit 3 for the entire vehicle group.

In addition, with the above configuration, vehicles traveling in the nearest lane are given priority as connected vehicles. With such a configuration, the effects of shadowing by other vehicles and multipath fading can be reduced, improving communication quality.

The shared path setting unit J64 sets a tree-shaped communication path with a depth of 5 or less as a shared path within the vehicle group, with the connected vehicle as the root node. With this configuration, information can be shared quickly within the vehicle group. For example, even if the maximum communication time required per hop is 200 milliseconds, the time required for data to be expanded to a leaf node in 5 hops can be suppressed to 1 second or less. Therefore, with the above configuration, even if the information contained in the dynamic map data is dynamic data that changes every second, it is expected that data sharing can be completed before the validity of the data is lost. Of course, the depth of the shared path may be set to 4 or less, or 3 or less. The depth of the shared path, in other words, the maximum number of hops within the vehicle group, can be set based on the time required per hop and the duration of validity of the distributed data.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-mentioned embodiments, and the various modified examples described below are also included in the technical scope of the present disclosure. Furthermore, in addition to the following, various modifications can be implemented without departing from the gist of the present disclosure. For example, the various modified examples described below can be implemented in appropriate combinations as long as no technical contradictions arise. Note that components having the same functions as those described in the above-mentioned embodiments are given the same reference numerals, and their description is omitted. Furthermore, when only a portion of the configuration is mentioned, the configuration of the previously described embodiment can be applied to the other portions.

<Example of driving speed control>
According to the above formulas (1) to (6), the road-vehicle group communication available time capable of accommodating the traffic to be transmitted, in other words, the number of required time slots, can be derived. The network device 4 may be configured to determine the traveling speed of the vehicle group when passing through the communication area of the roadside device 3 using the relational expressions, and to reflect the traveling speed in the control plan. The target speed can be roughly calculated based on the traffic volume to be transmitted and received, the diameter φ of the communication area of the roadside device 3, the vehicle group length Lgr, and the expected value of the communication rate r. When the inter-vehicle distance is constant, the vehicle group length Lgr can be expressed by the number of vehicles constituting the vehicle group. In other words, the target speed can be calculated based on the number of vehicles constituting the vehicle group and the traffic volume. Note that the QoS of the communication may be used instead of/in parallel with the traffic volume.

The above configuration corresponds to a configuration in which the communication capacity between the vehicle group and the roadside unit 3 is estimated based on the moving speed of the vehicle group, and the moving speed of the vehicle group, in other words the travel speed of each vehicle constituting the vehicle group, is set so that the estimated value exceeds the planned traffic volume by a predetermined amount. With the above configuration, it is possible to pass through intersections and branching/merging points without changing the composition of the vehicle group, i.e., the constituent members. Note that not needing to change the composition of the vehicle group means that there is no need to update the shared route within the vehicle group. With the above configuration, the processing load associated with updating the shared route can also be reduced.

<Additional information on how to set up connected vehicles>
In the above embodiment, the configuration in which only the vehicle traveling in the nearest lane is set as the connecting vehicle is disclosed, but this is not limited thereto. Vehicles traveling in other lanes can also be adopted as the connecting vehicle. For example, all vehicles may be adopted as the connecting vehicle. Also, as shown in FIG. 26, the leading vehicle, the trailing vehicle, and the vehicle traveling in the nearest lane may be adopted as the connecting vehicle. As shown in FIG. 27, when there is a section in which the distance Dm between the vehicles traveling in the nearest lane is equal to or greater than a predetermined threshold value DTh, the vehicle traveling in the second or third closest lane from the roadside device 3 may be adopted as the connecting vehicle. In FIG. 26 and FIG. 27, the vehicles hatched in a diagonal line pattern represent the vehicles set as the connecting vehicle. In addition, the connecting vehicle may be switched over time so that all the vehicles become the connecting vehicles. In FIG. 26 and FIG. 27, the vehicles hatched in a diagonal line pattern represent the candidates for the connecting vehicle. The candidates for the connecting vehicle refer to the vehicles that are set as the connecting vehicle at a certain point in time as time changes.

Also, the connected vehicles for upstream communication and the connected vehicles for downstream communication may be set separately. Generally, communication modules are equipped with antennas for both reception and transmission, but there are few cases where an antenna for transmission is equipped. In view of such circumstances, it is difficult to transmit data to the roadside unit 3 and receive data from the roadside unit 3 in parallel if there is only one connected vehicle. When the amount of data transmitted from the vehicle group to the roadside unit 3 is relatively large, there is a concern about a lack of communication time/communication capacity. In response to such concerns, by providing a separate connected vehicle for transmitting data to the roadside unit 3 in addition to the connected vehicle for downstream communication that receives data from the roadside unit 3, it becomes possible to perform transmission and reception in parallel. The connected vehicle for upstream communication corresponds to the transmission person in charge, and the connected vehicle for downstream communication corresponds to the reception person in charge.

As mentioned above, data transmitted and received in downstream communication refers to static/dynamic map data, etc. Data transmitted and received in upstream communication includes, for example, probe data, data showing self-diagnosis results, and operation record data during autonomous driving. Examples of operation record data to be uploaded include the system operation status and camera footage within a specified time before and after the occurrence of a specified recording event. Data transmitted from a vehicle/vehicle group to the roadside unit 3 also includes data to be transmitted to the network device 4 or server 5 via the roadside unit 3. In other words, data transmitted from a vehicle/vehicle group to the roadside unit 3 also includes communication packets whose final destination is the network device 4 or server 5.

<Additional information on how to set up a convoy>
The vehicle group organizing unit J6 may divide the vehicle group according to the traveling direction. For example, as shown in FIG. 28, the vehicle group may be divided into vehicles planning to turn right, vehicles planning to turn left, and vehicles planning to go straight through the intersection. The vehicle group Gr1 shown in FIG. 28 is a group of vehicles planning to go straight through the intersection, specifically, vehicles traveling in the straight lane. The vehicle group Gr2 is a group of vehicles planning to turn right at the intersection, specifically, vehicles traveling in the right turn lane. The vehicle group Gr3 is a group of vehicles planning to turn left at the intersection, specifically, vehicles traveling in the left turn lane. The information required by the vehicles may differ depending on whether they turn right, turn left, or go straight through the intersection.

As described above, the vehicle group is set according to the direction of travel at the lane level, so that necessary data according to the direction of travel can be preferentially distributed. In addition, the distribution of unnecessary data can be suppressed. Note that data that is unnecessary for right-turning vehicles is, for example, traffic condition data for roads extending from an intersection in the straight-ahead direction and in the left-turn direction. Additionally, the vehicle group formation unit J6 may divide the vehicle group by lane. This is because it is expected that the average speed will differ for each lane on expressways.

<Regarding belonging to multiple vehicle convoys>
As shown in FIG. 29, a right-turning vehicle may be allowed to temporarily belong to multiple vehicle groups. When turning right, the positional relationship with the following vehicle changes significantly, so that communication with other vehicles in the same vehicle group is more likely to be interrupted than when the vehicle is traveling along the road. Therefore, by making the vehicle planning to turn right belong to a separate vehicle group in addition to the main vehicle group, the possibility that the vehicle will momentarily become an isolated vehicle Ma can be reduced. A similar treatment may be performed for a left-turning vehicle. Note that the example shown in FIG. 29 illustrates a case where vehicle J belongs to both vehicle group Gr4 and vehicle group Gr5. Vehicles K and L belong to both vehicle group Gr5 and vehicle group Gr6.

<About two-channel distribution>
In the above-described embodiment, an aspect in which each segment is distributed to one vehicle in one vehicle group has been disclosed, but this is not limiting. Each segment may be distributed to two vehicles at a time. For example, the first segment may be distributed to vehicle A and vehicle D. Such a configuration in which two systems are shared makes it possible to provide redundancy to the shared route within the vehicle group. For example, even if vehicle A fails to communicate with the roadside unit 3, other members including vehicle A can obtain the first segment through the shared route with vehicle D as the root node.

<Operation of the resource control unit>
In a scene in which one roadside unit 3 communicates with a plurality of vehicle groups Gr7 to Gr9 simultaneously as shown in FIG. 30, the network device 4 allocates radio resources for road-to-vehicle communication to each vehicle group as shown in FIG. 31. This configuration can reduce the risk of communication failure due to interference. FIG. 31 discloses an aspect in which frequencies f1 to f2 are allocated to vehicle group Gr7, frequencies f3 to f4 to vehicle group Gr8, and frequencies f5 to f6 to vehicle group Gr9. In FIG. 30, resource blocks hatched with diagonal lines represent radio resources for vehicle group Gr7, and resource blocks hatched with vertical dashed lines represent radio resources for vehicle group Gr8. Resource blocks hatched with dot patterns represent radio resources for vehicle group Gr9.

The resource control unit J7 may also create a communication schedule for short-range communication by taking into account vehicle-side traffic volume, which is an estimate of the amount of wireless resources used for inter-vehicle communication within the vehicle group and data transmission from the vehicles to the roadside unit 3, when the vehicle group passes through the communication area of the roadside unit 3.

The vehicle-side traffic volume includes traffic related to the transfer (sharing) of received data from the roadside unit 3. Furthermore, the vehicle-to-vehicle traffic may include camera images from a see-through application. The see-through application is an application that wirelessly transmits camera images from a leading vehicle to a following vehicle. The see-through application, for example, enables a following vehicle to recognize the traffic conditions in an area blocked by the leading vehicle. The leading vehicle here refers to a vehicle traveling relatively ahead, and a following vehicle corresponds to a vehicle located relatively behind. The see-through application may also be called a visual sharing or camera image sharing application. Furthermore, the vehicle-side traffic volume may include probe data for uploading, etc.

The amount of inter-vehicle traffic required for data sharing at each time can be roughly calculated based on the size of the distribution data and the sharing route. In addition, a predetermined estimated value can be used as the traffic volume of the see-through application. The traffic volume of the upload data can be obtained from the vehicle using a BSR or the like.

The resource control unit J7 may use a resource map to create communication schedules for road-to-vehicle communication and inter-vehicle communication, for example, as shown in FIG. 32. Note that resource blocks enclosed in curly brackets in FIG. 32 indicate road-to-vehicle communication, and for example, the resource block indicated by {R, A} indicates a resource block for data distribution from the roadside unit 3 to vehicle A. Also, resource blocks enclosed in parentheses in FIG. 32 indicate resource blocks for inter-vehicle communication, and for example, (A, B) indicates a resource block used for communication between vehicle A and vehicle B. Note that (A, X) indicates a resource block used for broadcasting or geocasting by A.

<Pre-check process when changing vehicle groups>
Each vehicle may be configured to receive vehicle group setting data related to a new vehicle group a predetermined time before the time when the members of the vehicle group actually change. In this case, each vehicle may be configured to verify whether or not vehicle-to-vehicle communication is established with other vehicles located in front of and behind the vehicle on the shared route indicated in the new vehicle group setting data before the configuration of the vehicle group actually changes. If vehicle-to-vehicle communication with the target vehicle is not established even before a predetermined final confirmation time from the vehicle group change time, which is the time when the configuration of the vehicle group actually changes, an error message indicating this may be transmitted to the network device 4. The final confirmation time may be, for example, 500 milliseconds or 1 second. When the network device 4 receives the error message, it recalculates the shared route based on the latest communication status data.

As described above, by checking whether vehicle-to-vehicle communication is possible before actually switching the vehicle group setting, the risk of discovering that communication is not possible after changing the vehicle group setting can be reduced. In other words, if a shared route that is difficult to implement in practice is set by the network device 4 based on the difference between the communication environment for each vehicle as understood by the network device 4 and the actual communication environment, it becomes possible to correct the route before it is actually put into operation.

The network device 4 may be configured to change parameters such as the grouping threshold based on the frequency of receiving error messages. With this configuration, a vehicle group is formed with a threshold according to the actual communication environment, which can improve the stability of communication within the vehicle group.

<Functional layout>
Some or all of the functions of the network device 4, such as the vehicle group organizing unit J6, may be provided by the wireless base station 2, the roadside unit 3, or the server 5. The functions of the network device 4 may be distributed among the wireless base station 2, the roadside unit 3, and the server 5. For example, the function of organizing a vehicle group provided by the network device 4 may be provided by the server 5. The network device 4 or the server 5 corresponds to a central control device. The same applies to the functions provided by the server 5. In other words, the functional arrangement can be changed as appropriate. For the vehicle-mounted device 1, the wireless base station 2, the roadside unit 3, the network device 4, and the server 5 correspond to external devices.

<About the distribution data>
The dynamic map data and static map data correspond to common data to be shared among a plurality of vehicles. Of course, the distribution data from an external device to be shared among a plurality of vehicles is not limited to dynamic map data and static map data. The distribution data may be software update data, etc. The present disclosure is applicable to the distribution of various data. However, it can be said that the present disclosure is particularly suitable for transmitting and receiving large amounts of data that require relatively real-time performance, such as dynamic maps.

<Configuration of Data Transmitted from Roadside Unit 3 to Vehicle>
Data transmitted from the roadside device 3 to the vehicle can be divided into data to be shared by the entire vehicle group and data addressed only to a specific vehicle. For this reason, it is preferable that a header or the like of data transmitted from the roadside device 3 to the vehicle by short-range communication includes a sharing flag indicating whether the data is to be shared by the vehicle group. The sharing flag may be expressed by one bit or several bits. When each vehicle receives data with the sharing flag set to on, the vehicle also acquires the contents of the data and performs a transfer process according to the sharing route. On the other hand, when each vehicle receives data with the sharing flag set to off, it is sufficient to perform only a transfer process according to the sharing route without referring to the payload. According to this configuration, it is possible to execute a process according to the data to be shared by the entire vehicle group and the data addressed only to a specific vehicle.

<Additional remarks (1)>
The device, system, and method described in the present disclosure may be realized by a dedicated computer that configures a processor programmed to execute one or more functions embodied by a computer program. The device and method described in the present disclosure may also be realized using a dedicated hardware logic circuit. Furthermore, the device and method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor that executes a computer program and one or more hardware logic circuits. The computer program may also be stored in a computer-readable non-transient tangible recording medium as instructions executed by the computer. In other words, the means and/or functions provided by the network device 4 and the like can be provided by software recorded in a substantial memory device and a computer that executes the software, software only, hardware only, or a combination thereof. For example, some or all of the functions provided by the network device 4 may be realized as hardware. Aspects in which a certain function is realized as hardware include aspects in which it is realized using one or more ICs, etc. The network device 4 may be realized using an MPU, GPU, or DFP (Data Flow Processor) instead of a CPU. The network device 4 may be realized by combining a plurality of types of arithmetic processing devices, such as a CPU, an MPU, and a GPU. The network device 4 may be realized as a system-on-chip (SoC). Furthermore, the various processing units may be realized using a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC). The various programs may be stored in a non-transitive tangible storage medium. As a storage medium for the programs, various storage media such as a hard-disk drive (HDD), a solid state drive (SSD), a flash memory, and a secure digital (SD) card can be adopted. The non-transitive tangible storage medium also includes a ROM such as an erasable programmable read only memory (EPROM).

The multiple functions possessed by one component in the above embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Furthermore, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. In addition, part of the configuration of the above embodiments may be omitted. Furthermore, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

In addition to the network device 4 described above, various forms, such as a system that includes the network device 4 as a component, are also included in the scope of this disclosure. For example, forms such as a program for causing a computer to function as the network device 4, and a non-transient physical recording medium such as a semiconductor memory on which this program is recorded are also included in the scope of this disclosure.

<Additional remarks (2)>
The present disclosure also includes the following configurations. Note that methods corresponding to the following devices and systems including the following devices as components are also included in the scope of the present disclosure.
A device that sets a target speed for a vehicle group when passing through the communication area of the roadside unit based on the volume of traffic to be transmitted and received, the diameter φ of the communication area of the roadside unit, the vehicle group length Lgr, and an estimated communication rate r.
A device that creates and distributes a control plan for each vehicle to drive within the communication area of the roadside unit at the target speed set above.
A device that adjusts the number of vehicles in a vehicle fleet based on the size of the distribution data and the average moving speed of the vehicles passing through the communication area of the roadside unit.
A device that adjusts the size of a vehicle fleet based on at least one of the latency and communication speed of indirect data communication between general vehicles as leaf nodes and roadside units via connected vehicles.
A connected vehicle is a device configured to relay communication between a general vehicle, which is a vehicle other than the connected vehicle that constitutes the vehicle group, and the roadside unit.
A device that organizes a group of vehicles based on at least one of the RSSI and SNR of signals exchanged in vehicle-to-vehicle communication.

1 Vehicle-mounted device, 2 Radio base station, 3 Roadside device, 4 Network device (Central control device), 5 Server (Central control device), F1 Communication control unit, F6 Report processing unit, F7 Vehicle group information acquisition unit, J1 Individual information acquisition unit, J41 Data size acquisition unit, J42 Data size adjustment unit, J6 Vehicle group formation unit, J61 Plan correction unit, J62 Connected vehicle setting unit, J63 Vehicle group speed acquisition unit, J64 Shared route setting unit, J7 Resource control unit, J8 Notification processing unit, S102a Vehicle information acquisition step, S103a Communication status acquisition step, S106 Vehicle group formation step, S106b Vehicle group setting distribution step, S106x Shared route setting step, S109 Connected vehicle setting step, S111 Vehicle group sharing step, S401 Data size acquisition step, S404 Vehicle group speed acquisition step, S408 Vehicle group length adjustment step.

Claims (10)

A vehicle communication system for receiving distribution data from a roadside device (3) in each of a plurality of vehicles (M) configured to be able to perform vehicle-to-vehicle communication,
A central control device (4, 5) configured to be able to communicate with a vehicle via the roadside device or the wireless base station,
The central control device
an individual information acquisition unit (J1) that acquires a control plan created in each of the plurality of vehicles from each of the plurality of vehicles via the roadside device or the wireless base station ;
A vehicle group organizing unit (J6) that organizes a vehicle group, which is a group of the plurality of vehicles, based on the control plan for each of the plurality of vehicles;
a vehicle group speed acquisition unit (J63) that acquires a moving speed of the vehicle group in a communication area of the roadside device based on the control plan of the vehicles that constitute the vehicle group;
a connection vehicle setting unit (J62) that sets, for each time period, a connection vehicle that performs data communication with the roadside device among the plurality of vehicles constituting the vehicle group based on the control plan for each vehicle;
a notification processing unit (J8) that distributes vehicle group setting data indicating a combination of the vehicles that constitute the vehicle group set by the vehicle group formation unit to at least one of the vehicles related to the vehicle group;
a data size acquisition unit (J41) for acquiring the size of the distribution data;
the connected vehicle is configured, when receiving a part or all of the distribution data from the roadside device, to share the received data with general vehicles that are the vehicles other than the connected vehicle constituting the vehicle group through vehicle-to-vehicle communication;
The vehicle group forming unit is a vehicular communication system that adjusts the length of the vehicle group based on the size of the distribution data and the moving speed of the vehicle group. 2. The vehicle communication system according to claim 1,
The vehicle group formation unit includes:
calculating a vehicle group communication capacity, which is a traffic volume that the vehicle group can transmit and receive via wireless communication with the roadside device, based on the length of the vehicle group and the moving speed of the vehicle group;
A vehicle communication system that increases the length of the vehicle group when the vehicle group communication capacity is smaller than the size of the distribution data. 3. The vehicle communication system according to claim 2,
The vehicle group organization unit increases the length of the vehicle group by including vehicles outside the vehicle group, either in front of or behind the vehicle group, in the vehicle group based on the fact that the vehicle group communication capacity is smaller than the size of the distribution data. 4. The vehicle communication system according to claim 3,
The vehicle group formation unit is a vehicle communication system that increases the length of the vehicle group by decelerating the vehicle located at the end of the vehicle group by a predetermined amount when there are no vehicles in front of or behind the vehicle group. 5. The vehicle communication system according to claim 3,
A vehicle communication system comprising a data size adjustment unit (J42) that performs a process of thinning out the distribution data, on the condition that the vehicle group communication capacity does not become greater than the size of the distribution data even when the vehicle group formation unit adjusts the length of the vehicle group. 5. A vehicle communication system according to claim 2, further comprising:
A vehicle communication system comprising: a plan modification unit (J61) that modifies the control plan of each of the vehicles so that the movement speed of the vehicle group in the communication area is reduced by a predetermined amount based on the fact that the vehicle group communication capacity is smaller than the size of the distribution data. 7. A vehicle communication system according to claim 1,
the individual information acquisition unit acquires information indicating a communication status between each of the plurality of vehicles and other vehicles;
the information indicating the communication status with the other vehicle includes at least one of a received signal strength of a signal from the other vehicle and a signal-to-noise ratio which is a ratio of a strength of a signal from the other vehicle to noise,
The vehicle group formation unit is a vehicle communication system that causes vehicles whose received signal strength is equal to or greater than a predetermined threshold, or vehicles whose signal-to-noise ratio is equal to or greater than a predetermined threshold, to belong to the same vehicle group. 8. The vehicle communication system according to claim 7 ,
the central control device is configured to be able to communicate with the roadside device,
The central control device also transmits the vehicle group setting data for each vehicle group to the roadside device;
The roadside unit is configured to communicate with the connected vehicles based on the vehicle group setting data notified from the central control device. 9. The vehicle communication system according to claim 8 ,
The vehicle group formation unit creates a shared route, which is a communication route from the general vehicle to the connecting vehicle within the vehicle group, based on a communication status between each of the vehicles and the other vehicles;
The vehicle communication system is configured such that the notification processing unit transmits a data set including information about the shared route as the vehicle group setting data to the vehicle. A communication control method for each of a plurality of vehicles (M) configured to be able to perform vehicle-to-vehicle communication to receive predetermined distribution data distributed from a roadside device (3), comprising:
A central control device (4, 5) configured to be able to communicate with the plurality of vehicles via the roadside device or the wireless base station acquires a control plan created in each of the plurality of vehicles from each of the plurality of vehicles via the roadside device or the wireless base station (S102a);
The central control device organizes a vehicle fleet, which is a group of the plurality of vehicles, based on the control plan for each of the plurality of vehicles (S106);
The central control device acquires a moving speed of the vehicle group in a communication area of the roadside device based on the control plan of the vehicles constituting the vehicle group (S404);
The central control device sets, for each time period, a connection vehicle that is a vehicle that performs data communication with the roadside device among the plurality of vehicles constituting the vehicle group based on the control plan for each vehicle (S109);
The central control device distributes vehicle group setting data indicating a combination of the vehicles that constitute the vehicle group to at least one of the vehicles related to the vehicle group (S106b);
The central control device acquires a size of the distribution data (S401) ;
When the connected vehicle receives a part or all of the distribution data from the roadside device, the connected vehicle shares the received data with general vehicles that are the vehicles other than the connected vehicle that constitute the vehicle group through vehicle-to-vehicle communication (S111);
The central control device adjusts the length of the vehicle fleet based on the size of the distribution data and the moving speed of the vehicle fleet (S408).

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