Patent Publication Number: US-2023162606-A1

Title: In-vehicle apparatus, roadside apparatus, and communication method

Description:
TECHNICAL FIELD 
     The present disclosure relates to an in-vehicle apparatus, a roadside apparatus, and a communication method. 
     BACKGROUND ART 
     Dedicated Short Range Communications (DSRC) are examples of radio communication used in Intelligent Transport System (ITS). In IEEE 802.11p, a technology based on radio local area network (LAN) technology is studied as a standard compatible with DSRC. 
     Patent Literature (hereinafter, referred to as PTL) 1 discloses a method in which a roadside camera is installed at an intersection for transmitting a video to a right-turning vehicle by a radio signal, thereby displaying a video of a blind spot. 
     CITATION LIST 
     Patent Literature 
     PTL 1 
     Japanese Patent Application Laid-Open No. 2007-086964 
     SUMMARY OF INVENTION 
     In road-to-vehicle communication, however, there are no specifications for providing distribution services of a video of a road (herein also simply referred to as “road video”) shot by cameras installed at places such as intersections (herein, examples of the video of an object include videos and images of the object). 
     One non-limiting and exemplary embodiment of the present disclosure facilitates providing an in-vehicle apparatus that can receive a distribution service of a road video (herein also simply referred to as “road video distribution service”), and providing a roadside apparatus and a communication method. 
     An in-vehicle apparatus according to one exemplary embodiment of the present disclosure includes: receiving circuitry, which, in operation, receives, from a roadside apparatus providing a distribution service of a road video, an advertisement message indicating that the distribution service is provided; message generating circuitry, which, in operation, generates, based on reception of the advertisement message, a message regarding transmission of the road video to the roadside apparatus; and transmitting circuitry, which, in operation, transmits the message regarding the transmission of the road video to the roadside apparatus. 
     A roadside apparatus according to one exemplary embodiment of the present disclosure includes: transmitting circuitry, which, in operation, transmits an advertisement message indicating provision of a distribution service of a road video; receiving circuitry, which, in operation receives a message regarding transmission of the road video from an in-vehicle apparatus; message generating circuitry, which, in operation, generates, based on receipt of the message regarding the transmission of the road video, a video distribution message including identification information, an installation position, and a shooting direction of a camera capturing the road video, and transmits the video distribution message to the in-vehicle apparatus. 
     A roadside apparatus according to one exemplary embodiment of the present disclosure includes: transmitting circuitry, which, in operation, transmits an advertisement message that indicates provision of a distribution service of a road video and includes pieces of identification information, installation positions, and shooting directions of a plurality of cameras each shooting a road; and receiving circuitry, which, in operation, receives a message regarding transmission of the road video from an in-vehicle apparatus. In the roadside apparatus, the transmitting circuitry transmits, based on reception of the message regarding the transmission of the road video, a video signal of the road video captured by at least one camera among the plurality of cameras to the in-vehicle apparatus. 
     A communication method according to one exemplary embodiment of the present disclosure is used by an in-vehicle apparatus and includes: receiving, from a roadside apparatus providing a distribution service of a road video, an advertisement message indicating that the distribution service is provided; generating, based on the receiving of the advertisement message, a message regarding transmission of the road video to the roadside apparatus; and transmitting the message regarding the transmission of the road video to the roadside apparatus. 
     A communication method according to one exemplary embodiment of the present disclosure is used by a roadside apparatus and includes: transmitting an advertisement message indicating provision of a distribution service of a road video; receiving a message regarding transmission of the road video from an in-vehicle apparatus; generating, based on the receiving of the message regarding the transmission of the road video, a video distribution message including identification information, an installation position, and a shooting direction of a camera capturing the road video; and transmitting the video distribution message to the in-vehicle apparatus. 
     A communication method according to one exemplary embodiment of the present disclosure is used by a roadside apparatus and includes: transmitting an advertisement message that indicates provision of a distribution service of a road video and includes pieces of identification information, installation positions, and shooting directions of a plurality of cameras each shooting a road; receiving a message regarding transmission of the road video from an in-vehicle apparatus; and transmitting, based on the receiving of the message regarding the transmission of the road video, a video signal of the road video captured by at least one camera among the plurality of cameras to the in-vehicle apparatus. 
     It should be noted that general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof 
     According to one exemplary embodiment of the present disclosure, an in-vehicle apparatus can receive a road video distribution service. 
     Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the specification and drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    illustrates an exemplary configuration of a road-vehicle cooperation system for driving assistance (herein also simply referred to as “road-vehicle cooperation driving assistance system”); 
         FIG.  2    is a sequence diagram schematically illustrating an exemplary operation of the road-vehicle cooperation driving assistance system; 
         FIG.  3    illustrates an exemplary block configuration of a roadside apparatus; 
         FIG.  4    illustrates an exemplary block configuration of an in-vehicle apparatus; 
         FIG.  5    illustrates a format of WSA; 
         FIG.  6    is a diagram for explaining exemplary elements included in a video distribution message; 
         FIG.  7 A  is a sequence diagram illustrating an exemplary operation of the road-vehicle cooperation driving assistance system; 
         FIG.  7 B  is a sequence diagram illustrating the exemplary operation of the road-vehicle cooperation driving assistance system; 
         FIG.  7 C  is a sequence diagram illustrating the exemplary operation of the road-vehicle cooperation driving assistance system; 
         FIG.  7 D  is a sequence diagram illustrating the exemplary operation of the road-vehicle cooperation driving assistance system; 
         FIG.  8    illustrates a variation of the elements included in the video distribution message; 
         FIG.  9    is a diagram for explaining a variation of a method for setting the shooting direction of a camera; 
         FIG.  10 A  is a sequence diagram illustrating a variation of the operation of the road-vehicle cooperation driving assistance system; 
         FIG.  10 B  is a sequence diagram illustrating the variation of the operation of the road-vehicle cooperation driving assistance system; 
         FIG.  10 C  is a sequence diagram illustrating the variation of the operation of the road-vehicle cooperation driving assistance system; and  FIG.  10 D  is a sequence diagram illustrating the variation of the operation of the road-vehicle cooperation driving assistance system. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, one or more embodiments of the present disclosure will be described in detail with reference to the drawings. However, a detailed description more than necessary may be omitted, such as a detailed description of a well-known matter and a duplicate description for a substantially identical configuration, to avoid unnecessary redundancy of the following description and to facilitate understanding by a person skilled in the art. 
     The accompanying drawings and the following description are provided for a person skilled in the art to understand the present disclosure sufficiently, and are not intended to limit the subject matter recited in the claims. 
     In intersections in right-hand traffic such as in the United States, right turns may be possible even at red lights. For turning a vehicle right, the driver stops the vehicle before making a right turn and check for possible collisions with another vehicle entering the intersection from the left. A vehicle in the lane on the left side of the right-turning vehicle may make difficult to visually recognize another vehicle entering the intersection from the left because the left view is blocked from the driver. In addition, for turning a vehicle left at an intersection, a vehicle waiting for a left turn in the oncoming lane may make difficult to visually recognize another vehicle coming straight in the oncoming lane to enter the intersection. 
       FIG.  1    illustrates an exemplary configuration of a road-vehicle cooperation driving assistance system according to the present disclosure. Intersection  900  illustrated in  FIG.  1    includes roads  910 ,  920 ,  930 ,  940 ,  950 ,  960 ,  970 , and  980 . In the example of  FIG.  1   , vehicles are kept to the right side of a road. 
     Roadside apparatuses are installed at intersection  900 . Each roadside apparatus performs radio communication with an in-vehicle apparatus (not illustrated) of a vehicle entering intersection  900  (see the following examples). At intersection  900 , installed is roadside apparatus  100   a  for performing radio communication with an in-vehicle apparatus of a vehicle (not illustrated) traveling on road  950  to enter intersection  900 . At intersection  900 , installed is roadside apparatus  100   b  for performing radio communication with an in-vehicle apparatus of a vehicle (not illustrated) traveling on road  970  to enter intersection  900 . At intersection  900 , installed is roadside apparatus  100   c  for performing radio communication with in-vehicle apparatuses of vehicles  300  and  500  traveling on road  910  to enter intersection  900 . At intersection  900 , installed is roadside apparatus  100   d  for performing radio communication with in-vehicle apparatuses of vehicles  400  traveling on road  930  to enter intersection  900 . 
     Hereinafter, when roadside apparatuses  100   a  to  100   d  are not distinguished from each other, they may be referred to as roadside apparatuses  100 . In  FIG.  1   , roadside apparatuses  100  are illustrated on the roads for simplification of the drawing; however, roadside apparatus  100  may be installed on, for example, a structure such as a traffic light or a utility pole. Roadside apparatuses  100  may be interconnected by, for example, wired or radio backhaul lines. 
     At intersection  900 , roadside cameras for shooting vehicles entering intersection  900  are installed. For example, roadside camera  200   a  for shooting road  950  is installed at intersection  900 . Roadside camera  200   b  for shooting road  970  is installed at intersection  900 . Roadside camera  200   c  for shooting road  910  is installed at intersection  900 . Roadside camera  200   d  for shooting road  930  is installed at intersection  900 . 
     Hereinafter, when roadside cameras  200   a  to  200   d  are not distinguished from each other, they may be referred to as roadside cameras  200 . 
     Roadside cameras  200  a to  200   d  are connected to each of roadside apparatuses  100 . For example, roadside cameras  200   a  to  200  d are connected to roadside apparatus  100   c  as illustrated in  FIG.  1   . In  FIG.  1   , the illustration of how roadside apparatuses  100   a,    100   b,  and  100   d  are connected to roadside cameras  200  is omitted for simplification of the drawing. 
     Roadside camera  200  may be connected to neighboring roadside apparatus  100  and connected to the other roadside apparatuses  100  via a backhaul line connecting roadside apparatuses  100 . For example, roadside camera  200   a  may be connected to neighboring roadside apparatus  100   a  and connected to the other roadside apparatuses  100   b  to  100   d  via a backhaul line of roadside apparatuses  100 . 
     Roadside apparatus  100  performs radio communication with an in-vehicle apparatus mounted in a vehicle by using millimeter waves. For example, directional beam  600 —with millimeter waves—of roadside apparatus  100   c  is steered toward road  910 . This configuration allows roadside apparatus  100   c  to perform radio communication with the in-vehicle apparatuses of vehicles  300  and  500  traveling on road  910  to enter intersection  900 . In a similar manner, roadside apparatuses  100   a,    100   b,  and  100   d  perform radio communication with the in-vehicle apparatuses of vehicles entering intersection  900  by using directional beams with millimeter waves. The communication area of directional beam  600  with millimeter waves is inside intersection  900  in  FIG.  1   ; however, the communication area may reach road  910  or  920 . 
     As described below, roadside apparatus  100  may perform radio communication with the in-vehicle apparatus by using microwaves when transmitting a service advertisement message such as Wave Service Advertisement (WSA). 
     In addition, roadside apparatus  100  and an in-vehicle apparatus to be mounted in a vehicle may perform radio communication according to a wireless system conforming to IEEE802.11p (also referred to as “Wireless Access in Vehicular Environments (WAVE)”), for example. 
     Vehicle  300  illustrated in  FIG.  1    is in a process of a right turn from road  910  to road  980 . A large vehicle  500  is stopped in the lane on the left side of vehicle  300 . Therefore, road  930  on the left side may be poorly visible for the driver of vehicle  300 . For example, vehicle  400  travelling straight on road  930  to enter intersection  900  may be difficult for the driver of vehicle  300  to see. 
     Roadside apparatus  100  advertises to the in-vehicle apparatus (notifies the in-vehicle apparatus of) provision of a road video distribution service—the road video is captured by roadside camera  200  installed at intersection  900 —by using, for example, a service advertisement message such as WSA. This configuration, for example, allows the in-vehicle apparatus of vehicle  300  to recognize the road video distribution service at intersection  900 , and to receive the video of road  930  captured by roadside camera  200   d.  Therefore, the visibility for the driver of vehicle  300  in the left direction is improved. 
       FIG.  2    is a sequence diagram schematically illustrating an exemplary operation of the road-vehicle cooperation driving assistance system.  FIG.  2    illustrates a sequence example when vehicle  300  traveling on road  910  enters intersection  900 . 
     Roadside camera  200  transmits captured video data (e.g., data of a video captured by the camera) to roadside apparatus  100   c  (S 1 ). 
     Roadside apparatus  100   c  transmits a service advertisement message indicating provision of a video distribution service for advertising to (notifying) vehicle  300  (in-vehicle apparatus mounted in vehicle  300 ) that the video distribution service is provided (S 2 ). 
     The service advertisement message includes service IDs (identifications) which identify various services provided by roadside apparatus  100   c.  Vehicle  300  reads a service ID, indicating the video distribution service, included in the received service advertisement message, thereby determining that roadside apparatus  100   c  provides the road video distribution service. 
     When vehicle  300  reads the service ID indicating the video distribution service, vehicle  300  confirms the connection of the millimeter wave communication with roadside apparatus  100   c  (S 3 ). 
     When vehicle  300  confirms the connection of the millimeter wave communication, vehicle  300  transmits a service application message including a service ID corresponding to the video distribution service to roadside apparatus  100   c  in order to apply for the video distribution service to roadside apparatus  100   c  (S 4 ). 
     When roadside apparatus  100   c  receives the service application message, roadside apparatus  100   c  transmits a video distribution message including the camera ID, installation position, and shooting direction of the at least one roadside camera  200  installed at intersection  900  (S 5 ). In the example of  FIG.  1   , roadside apparatus  100   c  transmits a video distribution message including camera IDs, installation positions, and shooting directions of four cameras (roadside cameras  200   a  to  200   d ). The video distribution message will be described in detail in the description regarding  FIG.  6   . 
     Vehicle  300  determines the camera ID of roadside camera  200  shooting (in other words, capturing a video of) the road on which a blind spot may occur based on the following: the installation positions and shooting directions of roadside cameras  200  included in the received video distribution message, the position information of vehicle  300 , and the direction in which vehicle  300  is going to travel (S 6 ). For example, during a process of a right turn from road  910  to road  980 , vehicle  300  illustrated in  FIG.  1    determines the camera ID of roadside camera  200   d  shooting road  930 , on which a blind spot may occur. Vehicle  300  may acquire position information of vehicle  300  by using the Global Positioning System (GPS). Vehicle  300  may acquire the direction in which vehicle  300  is going to travel by using the signal of the direction indicator. 
     For requesting the distribution of the road video corresponding to the determined camera ID, vehicle  300  transmits a video distribution request message including the determined camera ID to roadside apparatus  100   c  (S 7 ). 
     Roadside apparatus  100   c  transmits a video signal including video data from roadside camera  200  corresponding to the camera ID included in the received video distribution request message to vehicle  300  (S 8 ). For example, roadside apparatus  100   c  transmits to vehicle  300  a video signal including video data from roadside camera  200   d.    
     For cancelling the video distribution service, vehicle  300  transmits a service cancellation message including the service ID corresponding to the video distribution service to roadside apparatus  100   c  (S 9 ). For example, vehicle  300  may transmit the service cancellation message to roadside apparatus  100   c  when vehicle  300  completes the right turn (for example, when the direction indicator indicating the right turn is turned off). 
     As described in S 20  of  FIG.  7 B , vehicle  300  may omit the confirmation of the millimeter wave connection in S 3 . 
       FIG.  3    illustrates an exemplary block configuration of roadside apparatus  100 . Roadside apparatus  100  includes local server  101 , message generator  102 , radio processor  103 , antenna  104 , and controller  105 . Roadside apparatus  100  is connected to one or more roadside cameras  200 . 
     Local server  101  receives video data transmitted from roadside cameras  200 . Local server  101  stores information regarding each roadside camera  200  such as the camera ID, camera installation position, and shooting direction, and associates the received video data with the information regarding roadside camera  200  that have transmitted the video data. Local server  101  transmits the video signal including the video data to an in-vehicle apparatus via radio processor  103 . 
     Message generator  102  generates a service advertisement message and a video distribution message. The service advertisement message includes the service ID corresponding to the video distribution service. The video distribution message includes information regarding each roadside camera  200  such as the ID, installation position, and shooting direction of the camera. Message generator  102  transmits the generated service advertisement message and video distribution message to the in-vehicle apparatus via radio processor  103 . 
     Radio processor  103  performs radio communication by using millimeter waves via antenna  104 . Radio processor  103  may use microwaves for transmitting the service advertisement message. 
     Controller  105  controls the entire roadside apparatus  100 . Controller  105  may include a processor such as a central processing unit (CPU) or a digital signal processor (DSP). 
     Controller  105  may implement a predetermined function, for example, according to a program stored in a storage device. For example, controller  105  assigns a camera ID to each roadside camera  200 . Controller  105  stores, in local server  101 , the camera ID and the information regarding the installation position, and shooting direction of roadside camera  200  having the camera ID. Controller  105  associates the video data transmitted from local server  101  with information (camera ID, installation position, and shooting direction) regarding roadside camera  200 . Controller  105  instructs message generator  102  to generate a service advertisement message and a video distribution message. Controller  105  executes video distribution start processing and video distribution end processing. 
       FIG.  4    illustrates an exemplary block configuration of in-vehicle apparatus  700 . In-vehicle apparatus  700  includes antenna  701 , radio processor  702 , controller  703 , message generator  704 , GPS processor  705 , map data storage  706 , direction indicator  707 , and display  708 . 
     Radio processor  702  performs radio communication by using millimeter waves via antenna  701 . Radio processor  702  may use microwaves for receiving the service advertisement message. 
     Controller  703  controls the entire in-vehicle apparatus  700 . Controller  703  may include a processor such as a CPU or a DSP. 
     Controller  703  may implement a predetermined function, for example, according to a program stored in a storage device. For example, controller  703  determines the camera ID of roadside camera  200  shooting the road on which a blind spot may occur based on the following: the installation positions and shooting directions of the cameras included in the received video distribution message, the position information of vehicle  300  acquired by GPS processor  705 , map data stored in map data storage  706 , and a state of direction indicator  707 . Controller  703  instructs message generator  704  to generate a service application message, a video distribution request message, and a service cancellation message. 
     Message generator  704  generates the service application message and the video distribution request message. The service application message includes the service ID corresponding to the video distribution service. The video distribution request message includes the camera ID of roadside camera  200  for which the video distribution is requested. Message generator  704  transmits the generated service application message and video distribution request message to roadside apparatus  100 . 
     GPS processor  705  receives a GPS signal transmitted from a GPS satellite and acquires the current position of vehicle  300 . 
     Map data storage  706  stores map data such as terrain information, road centerline information, and road edge information. 
     Direction indicator  707  informs whether vehicle  300  is in the process of right or left turn. 
     Display  708  displays video data received from roadside apparatus  100  via radio processor  702 . 
       FIG.  5    illustrates a format of WSA. The format of WSA illustrated in  FIG.  5   , for example, may be used for the service advertisement message transmitted by roadside apparatus  100  to in-vehicle apparatus  700 . As illustrated in  FIG.  5   , WSA includes fields of WSA header  1001 , service information segment  1002 , channel information segment  1003 , and WAVE routing advertisement  1004 . 
     Service information segment  1002  includes fields of service information count  1005 , Provider Service Identifier (PSID)  1006 , channel index  1007 , reserve  1008 , service information option indicator  1009 , and WAVE information element extension  1010 . 
     PSID  1006  is a service ID represented by an integer from 0 to 270549119 according to the service. PSID  1006  is assigned to an organization authorized to use the PSID. Therefore, a value that has not yet been associated with any service and has not been assigned to any organization is assigned to the PSID of the road video distribution service. 
       FIG.  6    is a diagram for explaining exemplary elements included in a video distribution message. The video distribution message transmitted by roadside apparatus  100  to in-vehicle apparatus  700  includes elements of the ID, installation position, and shooting direction of a camera as illustrated in  FIG.  6   . 
     The “camera ID” is a unique ID that identifies roadside camera  200 . 
     The “camera installation position” indicates the installation position of roadside camera  200 . The camera installation position may be indicated by latitude and longitude, for example. 
     The “shooting direction of camera” indicates the shooting direction of roadside camera  200 . The shooting direction may be indicated by absolute azimuth angles, for example, with roadside camera  200  as a reference, with due north at 0 degrees or 360 degrees, due east at 90 degrees, due south at 180 degrees, and due west at 270 degrees. 
     The video distribution message transmitted by roadside apparatus  100  to in-vehicle apparatus  700  includes the elements of all the roadside cameras  200  capturing the road videos to be distributed by roadside apparatus  100 . In the example of  FIG.  1   , for example, the video distribution message transmitted by roadside apparatus  100  to in-vehicle apparatus  700  includes the elements of roadside camera  200   a,  the elements of roadside camera  200   b,  the elements of roadside camera  200   c,  and the elements of roadside camera  200   d.    
       FIGS.  7 A to  7 D  are sequence diagrams illustrating the exemplary operation of the road-vehicle cooperation driving assistance system. The circled A, B, and C in  FIG.  7 A  lead to the circled A, B, and C in  FIG.  7 B . The circled D in  FIG.  7 B  leads to the circled D in  FIG.  7 C . The circled E and F in  FIG.  7 C  lead to the circled E and F in  FIG.  7 D . 
     Roadside cameras  200  transmit captured video data to local server  101  (S 11 ). Local server  101  receives the video data transmitted from roadside cameras  200 . 
     Controller  105  sets a different camera ID for each roadside camera  200 , associates the installation position, and shooting direction of each roadside camera  200  with the video data received by local server  101 , and stores the data in the local server  101  (S 12  to S 14 ). 
     Controller  105  outputs a service advertisement instruction to message generator  102  for advertising to vehicle  300  that the video distribution service is provided (S 15 ). 
     Controller  105  outputs a service ID (PSID) corresponding to the video distribution service to message generator  102  (S 16 ). 
     Message generator  102  generates a service advertisement message including the service ID output in S 16 , and transmits the message to in-vehicle apparatus  700  via radio processor  103  and antenna  104  (S 17 ). 
     When vehicle  300  enters the communication area of roadside apparatus  100 , controller  703  of in-vehicle apparatus  700  illustrated in  FIG.  7 B  receives the service advertisement message via antenna  701  and radio processor  702  (S 18 ). The received service advertisement message includes a service ID indicating that the video distribution service is being provided. 
     Controller  703  reads the service ID included in the service advertisement message (S 19 ). By reading the service ID of the video distribution service included in the service advertisement message, controller  703  recognizes that the road video distribution service is provided at intersection  900 . 
     When controller  703  receives the service advertisement message of S 18  with microwaves, the controller confirms the connection of the millimeter wave communication with roadside apparatus  100  (S 20 ). For example, controller  703  confirms whether or not roadside apparatus  100 , the transmission source of the service advertisement message received by using microwaves, matches roadside apparatus  100  connected by using millimeter waves. For example, the matching confirmation can be carried out as follows: controller  703  compares information for identifying roadside apparatus  100  included in a packet, which includes a service advertisement message, with information for identifying roadside apparatus  100  included in a packet, which is used for millimeter wave connection. 
     Controller  703  may omit the processing of S 20  when the service advertisement message is received by using millimeter waves. 
     In order to apply for the video distribution service to roadside apparatus  100 , controller  703  outputs a service application instruction and the service ID read in S 19  to message generator  704  (S 21 , S 22 ). 
     Message generator  704  generates a service application message including the service ID output in S 22 , and transmits the message to roadside apparatus  100  via radio processor  702  and antenna  701  (S 23 ). When the service advertisement message is received by using microwaves, radio processor  702  may transmit the service application message by using microwaves. 
     As illustrated in  FIG.  7 A , controller  105  of roadside apparatus  100  receives the service application message for video distribution via antenna  104  and radio processor  103  (S 24 ). 
     Controller  105  reads the service ID included in the service application message (S 25 ). By reading the service ID of the video distribution service included in the service application message, controller  105  recognizes that in-vehicle apparatus  700  has applied for the road video distribution service at intersection  900 . 
     When controller  105  recognizes the application of the video distribution service, controller  105  acquires, from local server  101 , the ID, installation position, and shooting direction of the at least one camera stored in local server  101 , and outputs the acquired data to message generator  102  (S 26 , S 27 , S 28 ). For example, controller  105  acquires data from local server  101  and outputs the acquired data to message generator  102 . The acquired data include the ID, installation position, and shooting direction of each of roadside cameras  200   a  to  200   d  installed at intersection  900 . 
     For providing vehicle  300  with the content of the video distribution service (the IDs, installation positions, and shooting directions of roadside cameras  200  installed at intersection  900 ), controller  105  outputs a video distribution instruction to message generator  102  (S 29 ). 
     In response to the video distribution instruction in S 29 , message generator  102  generates a video distribution message including the IDs, installation positions, and shooting directions of the cameras output in S 26 , S 27 , and S 28 , and transmits the message to in-vehicle apparatus  700  via radio processor  103  and antenna  104  (S 30 ). 
     Controller  703  of in-vehicle apparatus  700  illustrated in  FIG.  7 B  receives the video distribution message via antenna  701  and radio processor  702  (S 31 ). 
     Controller  703  receives a direction indicating signal from direction indicator  707  (S 32 ). For example, when vehicle  300  illustrated in  FIG.  1    is in a process of a right turn from road  910  to road  980 , controller  703  receives a direction indicating signal indicating the right turn from direction indicator  707 . 
     Controller  703  receives map data from map data storage  706  (S 33 ). 
     Controller  703  receives the current position information of the vehicle from GPS processor  705  (S 34 ). 
     Controller  703  determines the camera ID of roadside camera  200  shooting the road on which a blind spot may occur based on the following (S 35 ): the installation positions and shooting directions of roadside cameras  200  included in the video distribution message received in S 31 , the direction indicated by the direction indicating signal received in S 32  (direction in which the vehicle is going), the map data received in S 33 , and the current position information of the vehicle received in S 34 . 
     For example, in the case of vehicle  300  in  FIG.  1   , controller  703  determines the entrance of vehicle  300  into intersection  900  based on the current position information of vehicle  300  acquired by GPS processor  705  and the map data. In addition, controller  703  determines from the direction indicating signal output from direction indicator  707  that vehicle  300  is about to turn right to road  980 . 
     Based on the installation positions and shooting directions of roadside cameras  200  included in the video distribution message received in S 31 , controller  703  determines roadside camera  200   d  shooting road  930  located opposite to road  980 , onto which vehicle  300  is to turn right. Controller  703  then determines the camera ID of the determined roadside camera  200   d.  In this manner, controller  703  determines the camera ID of roadside camera  200   d  shooting road  930 , on which a blind spot from the right-turning vehicle  300  may occur. 
     When there are a plurality of roads on which blind spots may occur, controller  703  may determine a plurality of camera IDs. 
     In addition, for example, when vehicle  500  illustrated in  FIG.  1    is in a process of a left turn to road  940 , the road on which a blind spot may occur is road  950 , which is the oncoming lane ahead of vehicle  500 . Therefore, in-vehicle apparatus  700  to be mounted in vehicle  500  may determine the camera IDs of roadside cameras  200   a  and  200   b  as the camera IDs of roadside cameras  200  shooting roads  950  and  970 , on which blind spots may occur when vehicle  500  is in a process of a left turn. 
     Controller  703  outputs a video distribution request instruction and the determined camera ID to message generator  704  for requesting distribution of the video corresponding to the determined camera ID (S 36 , S 37 ). 
     Message generator  704  generates a video distribution request message including the camera ID output in S 35  in response to the video distribution request instruction in S 36 , and transmits the message to roadside apparatus  100  via radio processor  702  and antenna  701  (S 38 ). When the service advertisement message is received by using microwaves, radio processor  702  may transmit the video distribution request message by using microwaves. 
     As illustrated in  FIG.  7 C , controller  105  of roadside apparatus  100  receives the video distribution request message via antenna  104  and radio processor  103  (S 39 ). 
     Controller  105  reads the camera ID included in the video distribution request message received in S 39  (S 40 ). 
     Controller  105  outputs a video distribution start instruction and the camera ID read in S 40  to local server  101  (S 41 , S 42 ). 
     Local server  101  transmits a video signal including video data corresponding to the camera ID output in S 42  to in-vehicle apparatus  700  via radio processor  103  and antenna  104  (S 43 ). Radio processor  103  transmits the video signal by using millimeter waves. The video distribution may be transmitted according to a protocol such as Real Time Streaming Protocol (RTSP) or Real-time Transport Protocol (RTP). 
     As illustrated in  FIG.  7 D , display  708  of in-vehicle apparatus  700  receives the video signal via antenna  701 , radio processor  702 , and controller  703 , and displays the road video (S 44 ). For example, display  708  displays a road video captured by roadside camera  200   d.    
     Direction indicator  707  outputs a direction indicating signal to controller  703  (S 45 ). For example, when vehicle  300  illustrates in  FIG.  1    completes a right turn onto road  980 , direction indicator  707  outputs an off-state direction indicating signal to control unit  703 . 
     When controller  703  receives the off-state direction indicating signal from direction indicator  707 , controller  703  outputs a service cancellation instruction and the service ID of the video distribution service to be canceled to message generator  704 , for cancelling the video distribution service (S 46 , S 47 ). 
     Message generator  704  generates a service cancellation message including the service ID output in S 47  in response to the service cancellation instruction in S 46 , and transmits the message to roadside apparatus  100  via radio processor  702  and antenna  701  (S 48 ). When the service advertisement message is received by using microwaves, radio processor  702  may transmit the service cancellation message by using microwaves. 
     As illustrated in  FIG.  7 C , controller  105  of roadside apparatus  100  receives the service cancellation message via antenna  104  and radio processor  103  (S 49 ). 
     When controller  105  receives the service cancellation message in S 49 , the controller outputs a video distribution end instruction to local server  101  (S 50 ). Local server  101  ends the transmission of the video signal in response to the video distribution end instruction in S 50 . 
     As described above, roadside apparatus  100  includes radio processor  103  and message generator  102 . Radio processor  103  transmits a service advertisement message indicating the provision of a road video distribution service and receives a service application message indicating transmission request of the road video from in-vehicle apparatus  700 . Message generator  102 , based on the receipt of the service application message, generates a video distribution message including the ID, installation position, and shooting direction of roadside camera  200  capturing the road video, and transmits the message to in-vehicle apparatus  700  via radio processor  103 . 
     In-vehicle apparatus  700  includes radio processor  702  and message generator  704 . Radio processor  702  receives, from roadside apparatus  100  providing the road video distribution service, a service advertisement message indicating that the road video distribution service is provided. Message generator  704  generates, based on the receipt of the service advertisement message, the service application message indicating transmission request of the road video to be transmitted to roadside apparatus  100 . Radio processor  702  further transmits the service application message to roadside apparatus  100 . 
     This configuration allows in-vehicle apparatus  700  to recognize that roadside apparatus  100  is providing a road video distribution service by receiving the service advertisement message, which indicates the provision of a road video distribution service and is transmitted from roadside apparatus  100 . In-vehicle apparatus  700  thus can receive the road video distribution service. 
     In addition, roadside apparatus  100  transmits a video signal to in-vehicle apparatus  700  by using millimeter wave communication. This configuration allows in-vehicle apparatus  700  to receive a high-quality video signal, for example, with a resolution of 1920×1080 pixels, a frame rate of 30 fps, and a color space of RGB24. 
     In-vehicle apparatus  700  determines the camera ID of roadside camera  200  shooting a road that is blind from the vehicle based on the position of the vehicle, the direction in which the vehicle is going to travel, map data, and installation positions and shooting directions of the cameras. Even when the directivity of millimeter wave communication limits the target roadside apparatus  100  for radio communication, this configuration allows in-vehicle apparatus  700  to receive, from roadside apparatus  100  performing the millimeter wave communication, a road video captured by roadside camera  200  shooting the blind road. 
     Roadside apparatus  100  may use microwave communication for transmission of a service advertisement message. This configuration allows the service advertisement message to be transmitted to a wider communication area than when transmitted by using millimeter wave communication. 
     Variation 1 
       FIG.  8    illustrates a variation of the elements included in the video distribution message. The video distribution message may further include an intersection ID, a lane ID, and a Uniform Resource Locator (URL) in addition to the elements illustrated in  FIG.  6   . 
     The intersection ID is a unique ID that identifies intersection  900  where roadside apparatuses  100  and roadside cameras  200  are installed. The intersection ID is also included in map data stored in map data storage  706  of in-vehicle apparatus  700 . For example, intersection  900  on the map data is associated with the intersection ID assigned to intersection  900 . 
     As roadside apparatus  100  adds the intersection ID to the video distribution message, in-vehicle apparatus  700  can reduce erroneous selection of the camera ID of roadside camera  200 . For example, when vehicle  300  illustrated in  FIG.  1    enters intersection  900 , in-vehicle apparatus  700  compares the intersection ID included in the received video distribution message with the intersection ID corresponding to intersection  900  included in the map data. If the intersections IDs are not the same, in-vehicle apparatus  700  discards the received video distribution message and does not determine the camera ID. This configuration allows in-vehicle apparatus  700  to reduce erroneous selection of the camera ID. 
     The lane ID is a unique ID that identifies the lane shot by roadside camera  200 . The lane ID is also included in the map data stored in map data storage  706  of in-vehicle apparatus  700 . For example, road  910  on the map data is associated with the lane ID assigned to road  910 . 
     As roadside apparatus  100  adds the lane ID to the video distribution message, in-vehicle apparatus  700  can reduce erroneous selection of the camera ID of roadside camera  200 . For example, in-vehicle apparatus  700  acquires the lane ID of a road on which a blind spot may occur, and determines the camera ID of roadside camera  200  shooting the road with the acquired lane ID. This configuration allows in-vehicle apparatus  700  to reduce erroneous selection of the camera ID. 
     A URL indicates an access destination of video data in local server  101 . In-vehicle apparatus  700  transmits an HTTP request to the URL included in the video distribution message, and roadside apparatus  100  returns the video of the specified URL as an HTTP response. This configuration allows in-vehicle apparatus  700  to display the road video on a web browser. 
     When in-vehicle apparatus  700  receives video data by using a URL, in-vehicle apparatus  700  does not have to transmit the video distribution request message in S 38  of  FIG.  7 B  to roadside apparatus  100 . In other words, in-vehicle apparatus  700  may transmit the URL corresponding to the determined camera ID to roadside apparatus  100  in place of the video distribution request message of S 38 . 
     In addition, roadside apparatus  100  may omit transmission of the installation positions and shooting directions of the cameras, the intersection ID, and the URL. For example, roadside apparatus  100  may transmit a video distribution message including the camera ID and the lane ID to in-vehicle apparatus  700 . 
     Variation 2 
       FIG.  9    is a diagram for explaining a variation of the method for setting the shooting direction of a camera in the description for  FIGS.  6  and  8   . In  FIG.  9   , the same components as in  FIG.  1    are given the same reference numerals. 
     With the installation position of the roadside apparatus  100  as a reference, roadside apparatus  100  assigns numbers to the roads forming intersection  900  according to a predetermined rule. For example, roadside apparatus  100   c  illustrated in  FIG.  9    assigns number  0  to the road on which roadside apparatus  100   c  is installed as a reference, and assigns numbers  1 ,  2 , and  3  clockwise to the other roads forming intersection  900 . Roadside apparatus  100   d  assigns number  0  (indicated in parentheses in  FIG.  9   ) to the road on which roadside apparatus  100   d  is installed as a reference, and assigns numbers  1 ,  2 , and  3  (indicated in parentheses in  FIG.  9   ) clockwise to the other roads forming intersection  900 . 
     With the road on which roadside apparatus  100  is installed as a reference, roadside apparatus  100  indicates the shooting direction of roadside camera  200  by a number attached to the road shot by the camera. As illustrated in  FIG.  9   , for example, roadside apparatus  100   c  assigns the number  0  without parentheses to the road, on which roadside apparatus  100   c  is installed, therefore indicates the shooting direction of roadside camera  200   d  by the number “ 3 ” without parentheses. Roadside apparatus  100   c  indicates the shooting direction of roadside camera  200   a  by the number “ 0 ” without parentheses. Roadside apparatus  100   c  indicates the shooting direction of roadside camera  210   b  by the number “ 1 ” without parentheses. Roadside apparatus  100   c  indicates the shooting direction of roadside camera  220   c  by the number “ 2 ” without parentheses. Roadside apparatus  100   c  transmits a video distribution message including the camera IDs of roadside cameras  200  and the shooting directions (the numbers assigned to the roads) of roadside cameras  200  corresponding to the respective camera IDs. 
     In a similar manner, for example, roadside apparatus  100   d  assigns the number  0  with parentheses to the road, on which roadside apparatus  100   d  is installed, therefore indicates the shooting direction of roadside camera  200   a  by the number “ 3 ” with parentheses as illustrated in  FIG.  9   . Roadside apparatus  100   d  indicates the shooting direction of roadside camera  200   b  by the number “ 0 ” with parentheses. Roadside apparatus  100   d  indicates the shooting direction of roadside camera  210   c  by the number “ 1 ” with parentheses. Roadside apparatus  100   d  indicates the shooting direction of roadside camera  200   d  by the number “ 2 ” with parentheses. Roadside apparatus  100   d  transmits a video distribution message including the camera IDs of roadside cameras  200  and the shooting directions (the numbers assigned to the roads) of roadside cameras  200  corresponding to the respective camera IDs. 
     In-vehicle apparatus  700  recognizes in advance the rule of the shooting directions of roadside cameras  200 . Therefore, for example, when a vehicle is in a process of a right turn at crossroads intersection  900  illustrated in  FIG.  9   , in-vehicle apparatus  700  may determine the ID of the camera shooting the road of number  3  as a camera shooting a road on which a blind spot may occur. In addition, for example, when a vehicle is in a process of a left turn at crossroads intersection  900  illustrated in  FIG.  9   , in-vehicle apparatus  700  may determine the ID of the camera shooting the road of number  0  as a camera shooting a road on which a blind spot may occur. 
     As described above, the shooting direction of roadside cameras  200  may be indicated by a number assigned to the road according to a predetermined rule, with the installation position of the roadside apparatus  100  as a reference. This configuration allows in-vehicle apparatus  700  to reduce the amount of calculation required to determine the camera ID, thus allows speedy determination of the camera ID. 
     Variation 3 
     Roadside apparatus  100  may collectively transmit a service advertisement message and a video distribution message by adding the elements of the video distribution message illustrated in  FIG.  6    or  FIG.  8    to the field of WAVE information element extension  1010  in the format of WSA illustrated in  FIG.  5   . In this case, in-vehicle apparatus  700  may collectively transmit a service application message and a video distribution request message, or may separately transmit the service application message and the video distribution request message. 
       FIGS.  10 A to  10 D  are sequence diagrams illustrating an exemplary operation of a road-vehicle cooperation driving assistance system in variation 3. In  FIGS.  7 A to  7 D , roadside apparatus  100  separately transmits the service advertisement message and the video distribution message. In  FIGS.  10 A to  10 D , roadside apparatus  100  collectively transmits the service advertisement message and the video distribution message. 
     The circled A in  FIG.  10 A  leads to the circled A in  FIG.  10 B . The circled B in  FIG.  10 B  leads to the circled B in  FIG.  10 C . The circled E and F in  FIG.  10 C  lead to the circled E and F in  FIG.  10 D . Descriptions of parts the same as those in  FIGS.  7 A to  7 D  are omitted. 
     After S 14 , controller  105  in roadside apparatus  100  illustrated in  FIG.  10 A  acquires, from local server  101 , the ID, installation position, and shooting direction of the at least one camera stored in local server  101 , and outputs the acquired data to message generator  102  (S 49 , S 50 , S 51 ). For example, controller  105  acquires data from local server  101  and outputs the acquired data to message generator  102 . The acquired data include the ID, installation position, and shooting direction of each of roadside cameras  200   a  to  200   d  installed at intersection  900 . 
     Controller  105  outputs a service advertisement instruction to message generator  102  for advertising the following to vehicle  300 : the content of the video distribution service (the IDs, installation positions, and shooting directions of roadside cameras  200  installed at intersection  900 ); and that the video distribution service is provided (S 52 ). 
     Message generator  102  generates a service advertisement message including the IDs, installation positions, and shooting directions of the cameras output in S 49 , S 50 , and S 51 , and the service ID output in S 16 , and transmits the message to in-vehicle apparatus  700  via radio processor  103  and antenna  104  (S 53 ). 
     When vehicle  300  enters the communication area of roadside apparatus  100 , controller  703  of in-vehicle apparatus  700  illustrated in  FIG.  10 B  receives the service advertisement message via antenna  701  and radio processor  702  (S 54 ). The received service advertisement message includes the following: a service ID indicating that the video distribution service is being provided; and the content of the video distribution service (the IDs, installation positions, and shooting directions of roadside cameras  200  installed at intersection  900 ). 
     When controller  703  receives the service advertisement message of S 54  with microwaves, the controller confirms the connection of the millimeter wave communication with roadside apparatus  100  (S 20 ). 
     Controller  703  determines the camera ID of roadside camera  200  shooting a road on which a blind spot may occur based on the following (S 55 ): the installation positions and shooting directions of roadside cameras  200  included in the service advertisement message received in S 54 , the direction indicated by the direction indicating signal received in S 32  (direction in which the vehicle is going), map data received in S 33 , and the current position information of the vehicle received in S 34 . 
     In order to apply for the video distribution service to roadside apparatus  100 , controller  703  outputs a service application instruction, the service ID read in S 19 , and the camera ID determined in S 55  to message generator  704  (S 21 , S 22 , S 56 ). 
     Message generator  704  generates a service application message including the service ID output in S 22  and the camera ID output in S 56 , and transmits the message to roadside apparatus  100  via radio processor  702  and antenna  701  (S 57 ). When the service advertisement message is received by using microwaves, radio processor  702  may transmit the service application message by using microwaves. 
     Controller  105  in roadside apparatus  100  illustrated in  FIG.  10 C  receives the service application message for video distribution via antenna  104  and radio processor  103  (S 58 ). 
     Controller  105  reads the service ID and the camera ID included in the service application message (S 25 , S 59 ). By reading the service ID of the video distribution service included in the service application message, controller  105  recognizes that in-vehicle apparatus  700  has applied for the road video distribution service at intersection  900 . 
     Controller  105  outputs a video distribution start instruction and the camera ID read in S 59  to local server  101  (S 41 , S 42 ). 
     The processing after S 44  in  FIG.  10 D  is the same as that in  FIG.  7 D , thus the description thereof is omitted. 
     As described above, roadside apparatus  100  may collectively transmit a service advertisement message and a video distribution message, and in-vehicle apparatus  700  may collectively transmit a service application message and a video distribution request message. 
     This configuration reduces the number of times signals are exchanged between in-vehicle apparatus  700  and roadside apparatus  100  during the period after the in-vehicle apparatus receives the service advertisement message and before the in-vehicle apparatus receives the video signal. The in-vehicle apparatus thus can receive the video signal more quickly. 
     In the above-described embodiments, the expressions “processor,” “-er,” “-or,” and “-ar” used for the component elements may be replaced with other expressions such as “circuit (circuitry),” “assembly,” “device,” “unit,” or “module.” 
     The description has been given of embodiments with reference to the accompanying drawings, but the present disclosure is not limited to the embodiments. It is apparent that variations or modifications in the category recited in the claims may be conceived of by a person skilled in the art. It is to be understood that such variations or modifications also fall within the technical scope of the present disclosure. In addition, the component elements in the embodiments may be optionally combined without departing from the spirit of the present disclosure. 
     The present disclosure can be realized by software, hardware, or software in cooperation with hardware. Each functional block used in the description of each embodiment described above can be partly or entirely realized by an LSI such as an integrated circuit, and each process described in the each embodiment may be controlled partly or entirely by the same LSI or a combination of LSIs. The LSI may be individually formed as chips, or one chip may be formed so as to include a part or all of the functional blocks. The LSI may include a data input and output coupled thereto. The LSI here may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on a difference in the degree of integration. 
     However, the technique of implementing an integrated circuit is not limited to the LSI and may be realized by using a dedicated circuit, a general-purpose processor, or a special-purpose processor. In addition, a FPGA (Field Programmable Gate Array) that can be programmed after the manufacture of the LSI or a reconfigurable processor in which the connections and the settings of circuit cells disposed inside the LSI can be reconfigured may be used. The present disclosure can be realized as digital processing or analogue processing. 
     If future integrated circuit technology replaces LSIs as a result of the advancement of semiconductor technology or other derivative technology, the functional blocks could be integrated using the future integrated circuit technology. Biotechnology can also be applied. 
     The present disclosure can be realized by any kind of apparatus, device or system having a function of communication, which is referred to as a communication apparatus. The communication apparatus may comprise a transceiver and processing/control circuitry. The transceiver may comprise and/or function as a receiver and a transmitter. The transceiver, as the transmitter and receiver, may include an RF (radio frequency) module including amplifiers, RF modulators/demodulators and the like, and one or more antennas. Some non-limiting examples of such a communication apparatus include a phone (e.g., cellular (cell) phone, smart phone), a tablet, a personal computer (PC) (e.g., laptop, desktop, netbook), a camera (e.g., digital still/video camera), a digital player (digital audio/video player), a wearable device (e.g., wearable camera, smart watch, tracking device), a game console, a digital book reader, a telehealth/telemedicine (remote health and medicine) device, and a vehicle providing communication functionality (e.g., automotive, airplane, ship), and various combinations thereof. 
     The communication apparatus is not limited to be portable or movable, and may also include any kind of apparatus, device or system being non-portable or stationary, such as a smart home device (e.g., an appliance, lighting, smart meter, control panel), a vending machine, and any other “things” in a network of an “Internet of Things (IoT)”. 
     The communication may include exchanging data through, for example, a cellular system, a wireless LAN system, a satellite system, etc., and various combinations thereof. 
     The communication apparatus may comprise a device such as a controller or a sensor which is coupled to a communication device performing a function of communication described in the present disclosure. For example, the communication apparatus may comprise a controller or a sensor that generates control signals or data signals which are used by a communication device performing a communication function of the communication apparatus. 
     The communication apparatus also may include an infrastructure facility, such as a base station, an access point, and any other apparatus, device or system that communicates with or controls apparatuses such as those in the above non-limiting examples. 
     Summary of the Present Disclosure 
     An in-vehicle apparatus according to the present disclosure includes: receiving circuitry, which, in operation, receives, from a roadside apparatus providing a distribution service of a road video, an advertisement message indicating that the distribution service is provided; message generating circuitry, which, in operation, generates, based on reception of the advertisement message, a message regarding transmission of the road video to the roadside apparatus; and transmitting circuitry, which, in operation, transmits the message to the roadside apparatus. 
     In the in-vehicle apparatus according to the present disclosure, a format of Wave Service Advertisement (WSA) is used as a format of the advertisement message. 
     In the in-vehicle apparatus according to the present disclosure, when the transmitting circuitry transmits the message, the receiving circuitry receives, from the roadside apparatus, identification information, installation positions, and shooting directions of a plurality of cameras each shooting a road. 
     The in-vehicle apparatus according to the present disclosure further includes, control circuitry, which, in operation, determines at least one piece of identification information among the pieces of identification information of the plurality of cameras each shooting the road, based on a position of a vehicle in which the in-vehicle apparatus is mounted, a direction in which the vehicle is going to travel, map data, the installation positions and the shooting directions. 
     In the in-vehicle apparatus according to the present disclosure, the transmitting circuitry transmits, to the roadside apparatus, the at least one piece of identification information, and the receiving circuitry receives, from the roadside apparatus, a video signal of a road video from at least one camera of the plurality of camera, the at least one camera corresponding to the at least one piece of identification information. 
     In the in-vehicle apparatus according to the present disclosure, the road includes a plurality of lanes; the receiving circuitry further receives intersection identification information of an intersection where the plurality of cameras are installed and lane identification information of at least one lane among the plurality of lanes shot by the plurality of cameras; and the control circuitry further determines, based on the intersection identification information and the lane identification information, identification information of a camera among the plurality of cameras each shooting the road. 
     In the in-vehicle apparatus according to the present disclosure, the advertisement message includes the pieces of identification information, the installation positions, and the shooting directions of the plurality of cameras each shooting the road. 
     In the in-vehicle apparatus according to the present disclosure, the message generating circuitry generates a second application message including the at least one piece of identification information that has been determined as the message regarding the transmission of the road video; and the receiving circuitry receives, from the roadside apparatus, a video signal of the road video captured by at least one camera among the plurality of cameras, the at least one camera corresponding to the at least one piece of identification information that has been determined. 
     In the in-vehicle apparatus according to the present disclosure, the road includes a plurality of lanes; the advertisement message further includes intersection identification information of an intersection where the plurality of cameras are installed and lane identification information of at least one lane among the plurality of lanes shot by the plurality of cameras; and the control circuitry further determines, based on the intersection identification information and the lane identification information, the at least one piece of identification information among the pieces of identification information of the plurality of cameras each shooting the road. 
     In the in-vehicle apparatus according to the present disclosure, at least one of the shooting directions is indicated by an absolute azimuth angle with a camera capturing the road video among the plurality of cameras as a reference. 
     In the in-vehicle apparatus according to the present disclosure, at least one of the shooting directions is indicated by a number assigned to the road with an installation position of the roadside apparatus as a reference, according to a predetermined rule. 
     A roadside apparatus according to the present disclosure includes: transmitting circuitry, which, in operation, transmits an advertisement message indicating provision of a distribution service of a road video from an in-vehicle apparatus; receiving circuitry, which, in operation, receives the message regarding transmission of the road video; message generating circuitry, which, in operation, generates, based on receipt of the service application message, a video distribution message including identification information, an installation position, and a shooting direction of a camera capturing the road video, and transmits the video distribution message to the in-vehicle apparatus. 
     A roadside apparatus according to the present disclosure includes: transmitting circuitry, which, in operation, transmits an advertisement message that indicates provision of a distribution service of a road video and includes pieces of identification information, installation positions, and shooting directions of a plurality of cameras each shooting a road; and receiving circuitry, which, in operation, receives the message regarding the transmission of the road video from an in-vehicle apparatus. In the roadside apparatus, the transmitting circuitry transmits, based on reception of the message regarding the transmission of the road video, a video signal of the road video captured by at least one camera among the plurality of cameras to the in-vehicle apparatus. 
     A communication method according to the present disclosure is used by an in-vehicle apparatus and includes: receiving, from a roadside apparatus providing a distribution service of a road video, an advertisement message indicating that the distribution service is provided; generating, based on the receiving of the advertisement message, a message regarding transmission of the road video to the roadside apparatus; and transmitting the message regarding the transmission of the road video to the roadside apparatus. 
     A communication method according to the present disclosure is used by a roadside apparatus and includes: transmitting an advertisement message indicating provision of a distribution service of a road video; receiving the message regarding the transmission of the road video from an in-vehicle apparatus; generating, based on the receiving of the message regarding the transmission of the road video, a video distribution message including identification information, an installation position, and a shooting direction of a camera capturing the road video; and transmitting the video distribution message to the in-vehicle apparatus. 
     A communication method according to the present disclosure is used by a roadside apparatus and includes: transmitting an advertisement message that indicates provision of a distribution service of a road video and includes pieces of identification information, installation positions, and shooting directions of a plurality of cameras each shooting a road; receiving the message regarding the transmission of the road video from an in-vehicle apparatus; and transmitting, based on the receiving of the message regarding the transmission of the road video, a video signal of the road video captured by at least one camera among the plurality of cameras to the in-vehicle apparatus. 
     This application is entitled to and claims the benefits of Japanese Patent Application No. 2020-124499 filed on Jul. 21, 2020 and Japanese Patent Application No. 2020-181293 filed on Oct. 29, 2020, the disclosures of which including the specifications, drawings and abstracts are incorporated herein by reference in its entirety. 
     INDUSTRIAL APPLICABILITY 
     The present disclosure is particularly advantageous for, for example, radio communication between a roadside apparatus and an in-vehicle apparatus. 
     REFERENCE SIGNS LIST 
       100 ,  100   a,    100   b,    100   c,    100   d  Roadside apparatus 
       200 ,  200   a,    200   b,    200   c,    200   d  Roadside camera 
       300 ,  400 ,  500  Vehicle 
       600  Directional beam 
       900  Intersection 
       910 ,  920 ,  930 ,  940 ,  950 ,  960 ,  970 ,  980  Road 
       1001  WSA header 
       1002  Service information segment 
       1003  Channel information segment 
       1004  WAVE routing advertisement 
       1005  Service information count 
       1006  PSID 
       1007  Channel index 
       1008  Reserve 
       1009  Service information option indicator 
       1010  WAVE information element extension