JP4872817B2 - Roadside communication apparatus and communication method - Google Patents

Description

  The present invention relates to a roadside communication device installed on a road side and a communication method thereof in a communication system for realizing an intelligent transport system (ITS).

  In recent years, for the purpose of promoting traffic safety and preventing traffic accidents, advanced road traffic systems that improve the safety of vehicles by receiving information from infrastructure devices installed on the road and utilizing this information have been studied. (For example, refer to Patent Document 1). Such a system is mainly realized by a plurality of roadside communication devices as communication devices on the infrastructure side and an in-vehicle communication device that is a communication device mounted on each vehicle. As a combination of communication, there are road-to-road communication between roadside communication devices, road-to-vehicle (or roadway) communication between roadside communication devices and vehicle-mounted communication devices, and vehicle-to-vehicle communication between vehicle-mounted communication devices. .

  In the above-described intelligent road traffic system, multiple access is used in order to perform communication between roads, between roads, and between cars within a limited frequency band. There are frequency division multiplexing (FDMA) and code division multiplexing (CDMA) as multi-access methods, but considering multi-access in communication including many in-vehicle communication devices, multi-access including time-division multiplexing is effective. is there.

Japanese Patent No. 2806801

However, in a competitive access method in which communication is performed autonomously in time division multiplex communication, transmission signals may collide from an in-vehicle communication device in inter-vehicle communication as the traffic volume increases. When such transmission signal collision occurs, there arises a problem that reception cannot be performed due to mutual interference. On the other hand, in non-competitive access in which time slot multiplex communication assigns a time slot to each in-vehicle communication device, the problem of signal collision can be avoided, but the number of time slots to be assigned becomes insufficient as the number of vehicles increases. is there.
In such a situation, information transmitted from one in-vehicle communication device may not be transmitted to other in-vehicle communication devices, and the safety of road traffic cannot be sufficiently increased.

  In view of the conventional problems as described above, the present invention provides a roadside communication device that reliably transmits information transmitted from an in-vehicle communication device to the surroundings within a communication area of the roadside communication device to enhance road traffic safety. And it aims at providing the communication method.

The present invention is a roadside communication device that is installed on a roadside and that can communicate with an in-vehicle communication device mounted on a vehicle traveling on a road in its own monitoring area, wherein the in-vehicle communication device transmits data to other devices. If the data includes information on the position of the in-vehicle communication device, the monitoring means for acquiring the information and the information on the position of each in-vehicle communication device A determination means for determining the importance of transmitting information by each communication device for each in-vehicle communication device, and when assigning time slots to each in-vehicle communication device, the importance is relatively ranked, those but it is the most high allocating time slots at a predetermined frequency, which as a relatively importance decreases, and a communication control means for reducing long to transmission frequency periodic assign A.

  In such a roadside communication device, information from vehicles with higher importance than information from vehicles with low importance is obtained by performing communication control according to the importance of each vehicle-mounted communication device transmitting information. Can be preferentially recognized by the in-vehicle communication device of another vehicle.

Also, based on the relative importance of information transmission, the transmission from each in-vehicle communication device is treated differently (differential communication control), resulting in a limited resource time. Slots can be used effectively .

In the roadside communication device, the communication control means may retransmit information related to a vehicle having a higher importance level than a predetermined level through road-to-vehicle communication.
In this case, in competitive access, information from a vehicle with high importance is retransmitted, and it becomes possible to preferentially let other vehicles know the information.

In the roadside communication apparatus, the monitoring unit can predict the behavior of the vehicle, and the determination unit can determine the importance level using the behavior as an element of the determination.
In this case, based on the prediction of the behavior, the vehicle information that is predicted to be dangerous can be notified to the in-vehicle communication device of another vehicle, and the danger can be avoided.

In the roadside communication device, the monitoring unit can acquire signal information related to lighting of the traffic light, and the determination unit can determine the importance level using the signal information as one element of the determination.
In this case, in consideration of the current display of the traffic light and the change thereof, the vehicle information that is predicted to be dangerous can be notified to the in-vehicle communication device of another vehicle, and the danger can be avoided.

On the other hand, the present invention is a communication method in a roadside communication device that is installed on a roadside and can communicate with a vehicle-mounted communication device mounted on a vehicle traveling on a road in its own monitoring area. Whether or not to transmit data to the device, if the data includes information about the position of the in-vehicle communication device, obtain the information, based on the information about the position of each in-vehicle communication device, The importance of transmitting information by each in-vehicle communication device is determined for each in-vehicle communication device, and when assigning time slots to each in-vehicle communication device, the importance is ranked relative to each other. Time slots are assigned to the highest one at a predetermined frequency, but as the importance decreases, the assigned period is lengthened to reduce the transmission frequency .

In such a communication method, each vehicle-mounted communication device performs communication control according to the importance of transmitting information, so that information from vehicles with higher importance is received than information from vehicles with low importance. It becomes possible to make the vehicle-mounted communication device of another vehicle know with priority. Also, based on the relative importance of information transmission, the transmission from each in-vehicle communication device is treated differently (differential communication control), resulting in a limited resource time. Slots can be used effectively.

According to the roadside communication device or the communication method of the present invention, in the communication area of the road-side communication device, the information transmitted from the in-vehicle communication apparatus of high importance vehicle by reliably transmitted around the road traffic safety Can be increased. In addition, time slots, which are limited resources, can be used effectively.

  FIG. 1 is a plan view of a road on which a roadside communication device according to an embodiment of the present invention is installed. In the figure, it is assumed that each of two roads intersecting each other is, for example, an up / down 1 lane. The roadside communication device 1 is installed on the roadside, for example, near an intersection. The said roadside communication apparatus 1 is attached to the support | pillar of the signal apparatus 2, for example. On the other hand, each vehicle traveling on the road is equipped with an in-vehicle communication device. The roadside communication device 1 in the center of the figure can communicate with the vehicle-mounted communication devices of the vehicles A to J in the monitoring area X, and can also communicate with other roadside communication devices 1 on the right side of the figure, for example. .

  The roadside communication device 1 is connected to the central control unit 4 of the traffic control center. The central control unit 4 and the roadside communication device 1 are connected by wire (however, wireless is also possible), and the roadside communication devices 1 (communication between roads, however, wired is also possible), the roadside communication device 1 and in-vehicle communication. Wireless communication between devices (road-to-vehicle communication from “road” to “car” or road-to-vehicle communication from “car” to “road”) and between vehicle-mounted communication devices (vehicle-to-vehicle communication) Communication is used.

  FIG. 2 is a block diagram showing the internal configuration of the roadside communication device 1 and the in-vehicle communication device 3. The roadside communication device 1 includes a communication unit (transmission / reception unit) 11 connected to an antenna 10, a control unit 12 that performs control related to communication, and a storage unit 13 connected to the control unit 12.

  The control unit 12 monitors, as an internal function, whether or not the in-vehicle communication device 3 mounted on a vehicle traveling on a road in the monitoring area X transmits data to other devices, and the data When information about the position of the in-vehicle communication device is included, the importance of each in-vehicle communication device 3 transmitting information based on the monitoring unit 12a for acquiring the information and the information about the position of each in-vehicle communication device 3 Is determined for each in-vehicle communication device, and a communication control unit 12c that performs communication control with each in-vehicle communication device 3 according to importance.

  On the other hand, the in-vehicle communication device 3 includes a communication unit (transmission / reception unit) 31 connected to the antenna 30, a control unit 32 that performs control related to communication, and a storage unit 33 that stores unique information such as an ID. .

  In the roadside communication device 1 and the vehicle-mounted communication device 3 as described above, communication between roads, roads and vehicles, between roads, and between vehicles is performed by a time division multiplexing method within a limited frequency band. FIG. 3 shows an example of a frame configuration. One frame is constituted by roads, road vehicles, roadways, and time slots of vehicles.

  (A) of FIG. 3 is an example of non-competitive access in which a road, a road car, a road, and a car are all configured as a reservation system slot and one frame. If there are n vehicles, There are n reserved seat slots for inter-vehicle communication. FIG. 3 (b) shows that one frame is composed of a reservation method slot for road, road and vehicle communication, and a contention (competition) method slot (empty slot) for inter-vehicle communication. This is an example of competitive access for vehicle communication. In this example, all vehicle-to-vehicle communication is competing access. However, some inter-vehicle communication can be mixed with access methods, such as assigning time slots and non-competing access. .

  FIG. 4 is an example of a data format transmitted from the in-vehicle communication device 3 and includes a header, reception quality, vehicle position, direction (traveling direction), speed, mode, and data. The header includes a preamble, an ID, and the like. The reception quality is C / N (Carrier to Noise Ratio), RSSi (Receive Signal Strength Indication), etc. as seen from the in-vehicle communication device. The position and direction of the vehicle are information obtained from GPS, a vehicle-side sensor, and the like, and are based on information acquired on the vehicle side. The speed is information based on a speed sensor. The mode means that transmission from the in-vehicle communication device is in a state of non-competing access with a time slot assigned under the control of the roadside communication device, or competing access that performs transmission autonomously. It is information indicating whether or not.

<< First Embodiment: Non-competing Access >>
First, the case where inter-vehicle communication by the in-vehicle communication device 3 of each vehicle in the monitoring area X is in a non-competitive access state will be described.
The roadside communication device 1 constantly monitors the transmission of the vehicle in its own monitoring area X from the in-vehicle communication device 3, and when a new vehicle is detected, assigns a time slot to the in-vehicle communication device 3. The assigned time slot is notified to the in-vehicle communication device 3. Accordingly, the in-vehicle communication device 3 can perform communication between vehicles and between roads by non-competitive access.

  By assigning time slots in this way to the in-vehicle communication devices 3 of all vehicles in the monitoring area X, each in-vehicle communication device 3 can perform transmission without causing a signal collision. . When the vehicle goes out of the monitoring area, the time slot assigned to the in-vehicle communication device is released to be an empty slot and can be assigned to another in-vehicle communication device.

  Here, the roadside communication device 1 does not assign time slots to the in-vehicle communication devices 3 in the monitoring area X in the same manner, but performs differential communication control. Specifically, for example, when a collision prevention service is desired at an intersection, the risk of the vehicle based on the position, traveling direction, and speed of each vehicle, in other words, information transmitted from the in-vehicle communication device of the vehicle Is determined to be transmitted to an in-vehicle communication device or a roadside communication device of another vehicle.

  In the example of FIG. 1, vehicles A, B, C, and D are about to enter an intersection, the degree of danger is high, and the importance of transmitting the information to the in-vehicle communication device of another vehicle is high. On the contrary, the vehicle E that is moving toward the intersection but is still far from the intersection and has a low speed, and the vehicles F, G, H, I, and J that have already passed through the intersection are low in risk. Is less important to communicate.

  As described above, the roadside communication device 3 performs relative ranking of the importance levels when assigning the time slots to the in-vehicle communication devices 3, and assigns the time slots at a predetermined frequency to those having the highest importance levels. Allocation is performed, but as the importance decreases relatively, the allocation period is lengthened to reduce the transmission frequency. Thereby, the frequency of transmission changes to high / low according to the high / low importance of each vehicle (each in-vehicle communication device).

For example, in the above example, as shown in FIG. 5, of high importance vehicles A, B, C, allocated time slots between the inter-vehicle-Kurumaji a relatively short predetermined period T _S for D, For the less important vehicles F, G, H, I and J, time slots are assigned with a relatively long period _TL . Thus, based on the relative importance of information transmission, the transmission from each in-vehicle communication device is treated differently (differential communication control), resulting in a time that is a limited resource. Slots can be used effectively.

In FIG. 1, the frequency of the assigned period is controlled by determining the degree of risk in the monitoring area X including one intersection. However, when the monitoring area covers a plurality of intersections, a plurality of intersections are considered. The degree of risk may be judged.
For example, when the vehicle H is determined to have a high degree of risk in relation to an adjacent intersection, and the information can be obtained from another roadside communication device installed at the adjacent intersection, the importance of the vehicle H is increased. can do.

  In order to determine the importance, not only the location, the traveling direction, and the speed, but also the behavior of the vehicle including dangerous driving acts such as reverse running and meandering can be considered. In this case, the monitoring unit 12a of the roadside communication device 1 may predict a future behavior from the current behavior of the vehicle, and the determination unit 12b may determine the importance based on the predicted behavior. If importance is determined using such behavior as an element of determination, vehicle information that is predicted to be dangerous can be notified to in-vehicle communication devices of other vehicles, and danger can be avoided. .

  Further, in the case of a plurality of lanes, the road can be estimated by including information on road lanes in the “place”, and therefore, a right turn with a high degree of danger can be used as an element for determining the importance. If vehicle type information is also acquired, for example, emergency vehicles (ambulances, fire engines, police cars, etc.) are judged to be highly important, and in some cases information on the vehicles that can be dangerous vehicles is also obtained. The in-vehicle communication device of another vehicle can be informed and danger can be avoided.

  Moreover, in determining the importance, it is possible to consider signal information regarding lighting of traffic lights at intersections. For example, the monitoring unit 12a of the roadside communication device 1 determines whether the vehicle suddenly enters the intersection or stops suddenly based on the color of the signal and the position / speed of the vehicle. It can be taken into the degree judgment. In this case, in consideration of the current display of the traffic light and its change, the vehicle information that is predicted to be dangerous can be notified to the in-vehicle communication device of another vehicle to avoid danger. it can.

  In the above embodiment, the transmission frequency is adjusted according to the importance. However, not only the transmission frequency is adjusted, but time slots may not be assigned to vehicles with low importance.

<< Second Embodiment: Competitive Access >>
Next, a roadside communication device suitable for a case where inter-vehicle communication by the in-vehicle communication device 3 of each vehicle in the monitoring area X is in a competitive access state will be described.
In FIG. 6, the roadside communication device 1 has a plurality (four in this example) of antennas 10-1, 10-2, 10-3, and 10-4. The roadside communication device 1 can communicate with the in-vehicle communication devices 3A, 3B, 3C, 3D mounted on the vehicles A to D, for example. In addition, when not distinguishing several vehicle-mounted communication apparatus 3A-3D individually, it is only called vehicle-mounted communication apparatus 3. FIG.

  FIG. 7 is a block diagram illustrating details of functions of the roadside communication device 1 and the in-vehicle communication device 3. The roadside communication device 1 includes a communication unit (transmission / reception unit) 11 connected to an antenna 10 (individual codes are 10-1, 10-2, 10-3, and 10-4), and a control unit that performs control related to communication. 12 and a storage unit 13 connected to the control unit 12. Note that the communication unit 11 actually has a transmission unit and a reception unit separately, but is simplified and shown in common.

  The communication unit 11 as a transmission unit of the roadside communication device 1 has a transmission function of a plurality of systems (4 systems) corresponding to the number of antenna elements for spatial multiplexing. Each system includes a signal processing unit 11b that performs processing such as inverse discrete Fourier transform, and an RF unit 11c that performs frequency conversion. The spatial multiplexing processing unit (multi-antenna processing unit) 11a performs spatial multiplexing processing on a signal to be transmitted, and simultaneously transmits a plurality of signal sequences from a plurality of antennas 10-1, 10-2, 10-3, 10-4. To do.

  In addition, the communication unit 11 as a receiving unit of the roadside communication device 1 receives a plurality of systems (four systems) corresponding to the number of antennas 10 in order to separate a plurality of signal sequences transmitted from the transmission path. It has a function. Each system includes an RF unit 11c that performs frequency conversion, a signal processing unit 11b that performs processing such as discrete Fourier transform, and the like. The spatial multiplexing processing unit 11a separates a plurality of signal sequences received by the plurality of antennas 10-1, 10-2, 10-3, 10-4.

  The control unit 12 of the roadside communication apparatus 1 performs control for time division multiplexing, control of processing in the spatial multiplexing processing unit 11a, and other control. The time division multiplexing here is time division multiplexing for each communication of road-to-road communication, vehicle-to-vehicle communication, road-to-vehicle communication, and road-to-vehicle communication. Moreover, the control part 12 has the monitoring means 12a, the determination means 12b, and the communication control means 12c as an internal function similarly to 1st Embodiment.

  On the other hand, as in the first embodiment, the in-vehicle communication device 3 stores a communication unit (transmission / reception unit) 31 connected to the antenna 30, a control unit 32 that performs control related to communication, and unique information such as an ID. And a storage unit 33.

  FIG. 8 shows an example of using time slots in the second embodiment. In FIG. 8, “road” indicates road-to-road communication, “vehicle” indicates vehicle-to-vehicle communication, “road car” indicates road-to-vehicle communication, and “vehicle” indicates road-to-vehicle communication. .

  In FIG. 8, a time slot for road-to-road communication is shared by a plurality (four) of road-to-road communication. In addition, a time slot for inter-road communication is shared by a plurality (four) of road communication. Furthermore, one time slot is shared by road-to-road communication and road-to-vehicle communication. Such sharing is performed by space division multiplexing (SDM), details of which will be described later.

  By sharing one time slot in time-division multiplexing by communication involving the roadside communication device 1 (inter-road communication and inter-road communication), the occupation time of the communication involving the roadside communication device 1 is reduced, Can be used effectively. And since occupation time, such as road-to-road communication, becomes short, it becomes possible to ensure much occupation time of vehicle-to-vehicle communication.

  Therefore, even if the number of in-vehicle communication devices 3 increases, the frequency of collision of transmission timings of inter-vehicle communication can be suppressed. And since the vehicle-mounted communication apparatus 3 is not a multi-antenna system, the increase in the cost of the vehicle-mounted communication apparatus 3 which a general user purchases can also be avoided.

Now, when performing spatial multiplexing in the road-to-road communication, the control unit 12 and the spatial multiplexing processing unit 11a perform the following processing.
First, when there are a plurality of roadside communication devices 1 that are communication partners of one roadside communication device 1, a plurality of time slots for communication between roads are required only by time division multiplexing. When communication is performed only by time division multiplexing, the roadside communication device 1 that attempts to transmit a signal for road-to-road communication has a different timing (different time slot) with respect to a plurality of roadside communication devices that are communication partners. It is necessary to perform road-to-road communication.

On the other hand, in this embodiment, since the roadside communication device 1 is a multi-antenna, the roadside communication is multiplexed by spatial multiplexing (SDM) using the fact that the communication between roads is MIMO communication (Multiple Input Multiple Output). To do.
Specifically, in the time division multiplexing process, the control unit 12 secures time slots corresponding to the number of communication partners for communication between a plurality of roads to a plurality of roadside communication devices 1 that are communication partners. Instead, the number of time slots for communication between roads is less than the number of one or the number of communication partners that can be shared by a plurality of road communication.

  The spatial multiplexing processing unit 11a spatially multiplexes and transmits data of a plurality of systems to be transmitted to a plurality of other roadside communication devices 1 that are communication partners in the time slot for roadside communication. By the spatial multiplexing, the time slot for road-to-road communication is shared by a plurality of road-to-road communication.

  As described above, by spatially multiplexing road-to-road communication, installing a large number of roadside communication devices 1 in urban areas where there is a lot of traffic, even if the communication frequency of road-to-road communication increases, The occupation time of the communication between the roads does not increase so much, and radio resources (time slots) can be used efficiently.

Next, processing in the spatial multiplexing processing unit 11a of the in-vehicle communication device 3 and the roadside communication device 1 when performing spatial multiplexing in inter-road communication will be described.
For example, when a plurality of in-vehicle communication devices 3A to 3D simultaneously perform inter-road communication with the roadside communication device 1A, a plurality of vehicle routes can be obtained only by time division processing by competitive access using the slotted aloha method or the like. Inter-communication will collide.

However, in this embodiment, although the in-vehicle communication device 3 is a single antenna, the roadside communication device 1 is a multi-antenna. Therefore, when simultaneously transmitting from a plurality of in-vehicle communication devices 3 to the roadside communication device 1, a plurality of SIMOs are used. It can be regarded as MIMO communication combining (Single Input Multiple Output).
Therefore, the roadside communication device 1 regards a plurality of inter-roadway communication as MIMO communication, and separates a plurality of inter-roadway communication performed simultaneously by spatial multiplexing processing.

  Specifically, each of the in-vehicle communication devices 3A to 3D is a single antenna, but transmits a training symbol for MIMO channel estimation (a training symbol for signal separation processing) as a preamble or the like during inter-road communication. To do. The training symbol for MIMO channel estimation is also transmitted during inter-vehicle communication.

  Now, it is assumed that a plurality of in-vehicle communication devices 3A to 3D simultaneously perform inter-road communication with the roadside communication device 1A and signals collide with each other. Even in this case, the spatial multiplexing processing unit 11a of the roadside communication device 1A performs channel estimation using the training symbols for MIMO channel estimation transmitted from the in-vehicle communication devices 3A to 3D, and each in-vehicle communication device The signals transmitted by 3A to 3D are separated. Note that the spatial multiplexing processing unit 11a of the roadside communication device 1A can separate signals even when performing inter-road communication at the same time as long as the vehicle-mounted communication devices 3 are equal to or less than the number of antenna elements of the roadside communication device 11. .

  In the time division process, the control unit 12 of the roadside communication device 1 secures a time slot for inter-vehicle communication, and the time slot is assigned to the in-vehicle communication device 10 having the number of antenna elements equal to or less than that of the roadside communication device 1. Communication control to be assigned may be performed. In this case, it is ensured that the number of in-vehicle communication devices 10 that communicate simultaneously in one time slot for inter-road communication is equal to or less than the number of antennas of the roadside communication device 1, and signal separation can be performed reliably.

Next, vehicle-to-vehicle communication will be described.
As described above, the training symbol for MIMO channel estimation is transmitted from the in-vehicle communication device 3 also during inter-vehicle communication. Since the inter-vehicle communication is SISO (Single Input Single Output), the training symbol for MIMO channel estimation is not used for inter-vehicle communication, but when the roadside communication device 1 monitors the inter-vehicle communication. Used. By monitoring the vehicle-to-vehicle communication, the roadside communication device 1 can use the monitoring result for centralized control of vehicle-to-vehicle communication in the communication area and other processes.

  However, as shown in FIG. 9, in the case of inter-vehicle communication, a plurality of inter-vehicle communication signals may compete and collide. In the illustrated example, the signal transmitted from the vehicle A and the signal transmitted from the vehicle C collide with each other in the time slot 1. In the time slot 5, the signal transmitted from the vehicle A and the signal transmitted from the vehicle F collide with each other. In such a case, the vehicle-to-vehicle communication fails, but the roadside communication device 1 monitoring it performs channel estimation using the training symbol for MIMO channel estimation, and each of the plurality of in-vehicle communication devices that have collided The signals transmitted by 3A to 3D are separated.

  Therefore, the roadside communication device 1 can monitor even when a plurality of vehicle-to-vehicle communications collide, and can efficiently monitor the vehicle-to-vehicle communication. In addition, the roadside communication device 1 that monitors the vehicle-to-vehicle communication that has collided separates the signal and then retransmits the vehicle-to-vehicle communication, thereby preventing important information on vehicle-to-vehicle communication from being lost. it can.

  As described above, the spatial multiplexing processing unit 11a of the roadside communication device 1 performs signals from other roadside communication devices 1 (signals for roadside communication) and signals from the in-vehicle communication device 3 (signals for communication between roadways and vehicles). When receiving any of the signals of the inter-vehicle communication), it is assumed that the communication is a MIMO communication, and a spatially multiplexed signal separation process is performed.

In performing the retransmission, as in the case of non-competing access, the roadside communication device 3 does not retransmit to each in-vehicle communication device 3 in a fair manner but treats it differently.
Specifically, the roadside communication device 3 performs the relative ranking of the above-mentioned importance on the information transmitted from each in-vehicle communication device 3, and retransmits the information whose importance is equal to or higher than a predetermined level. If it is less than the predetermined level, it will not be retransmitted. As a result, whether or not to perform retransmission is discriminated depending on whether or not the importance of each in-vehicle communication device is equal to or higher than a predetermined level.

  For example, in the above example, as shown in FIG. 5, re-transmission is performed for vehicles A, B, C, and D having high importance, and vehicles F, G, H, I, J and others having low importance are others. Is not retransmitted. Thus, based on the relative importance of information transmission, the time slot which is a limited resource can be effectively used by discriminating the transmission from each in-vehicle communication device.

  In each of the above embodiments, the roadside communication device 1 is installed on the support column of the traffic light 2. However, the installation mode is not limited to this, and the support device may be installed with a support column or the like standing alone. . Further, it may be combined with a control device (not shown) of the traffic light 2 and configured as a part of the traffic light 2.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined not by the above-mentioned meaning but by the scope of claims for patent, and is intended to include all modifications within the scope and meaning equivalent to the scope of claims for patent.

It is a top view of the road where the roadside communication apparatus by embodiment of this invention was installed. It is a block diagram which shows the internal structure of the roadside communication apparatus by 1st Embodiment, and a vehicle-mounted communication apparatus. It is an example of a frame structure. It is an example of the data format transmitted from a vehicle-mounted communication apparatus. It is a figure which shows an example of allocation of a time slot. It is a figure which shows the roadside communication apparatus and vehicle-mounted communication apparatus of a multi-antenna by 2nd Embodiment. It is a block diagram which shows the internal structure of the roadside communication apparatus by 2nd Embodiment, and a vehicle-mounted communication apparatus. It is a usage example of a time slot. It is a figure which shows the collision and transmission success in the time slot of the signal in a slotted aloha.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Roadside communication apparatus 3 In-vehicle communication apparatus 12a Monitoring means 12b Determination means 12c Communication control means AJ Vehicle X Monitoring area

Claims (5)

A roadside communication device installed on the roadside and capable of communicating with an in-vehicle communication device mounted on a vehicle traveling on a road in its own monitoring area,
Monitoring means for monitoring whether or not the in-vehicle communication device transmits data to another device, and when the data includes information on the position of the in-vehicle communication device;
Based on information on the position of each in-vehicle communication device, a determination unit that determines the importance of each in-vehicle communication device transmitting information for each in-vehicle communication device;
When assigning time slots to each in-vehicle communication device, relative importance ranking is performed, and time slots are assigned at a predetermined frequency to those having the highest importance, but the importance decreases relatively. And a communication control means for reducing the transmission frequency by extending the assigned period . The roadside communication device according to claim 1, wherein the communication control unit retransmits information related to a vehicle having the importance level higher than a predetermined level by road-to-vehicle communication . The monitoring means predicts the behavior of the vehicle,
The roadside communication device according to claim 1 , wherein the determination unit determines the importance degree using the behavior as an element of determination . The monitoring means acquires signal information related to lighting of a traffic light ,
The roadside communication device according to claim 1 or 2, wherein the determination unit determines the importance degree using the signal information as one element of determination. A communication method in a roadside communication device that is installed on a roadside and can communicate with an in-vehicle communication device mounted on a vehicle traveling on a road in its own monitoring area,
Monitor whether the in-vehicle communication device transmits data to other devices, and if the data includes information on the position of the in-vehicle communication device, obtain the information,
Based on the information on the position of each in-vehicle communication device, determine the importance of each in-vehicle communication device transmitting information for each in-vehicle communication device,
When assigning time slots to each in-vehicle communication device, relative importance ranking is performed, and time slots are assigned at a predetermined frequency to those having the highest importance, but the importance decreases relatively. Accordingly, the communication method is characterized in that the frequency of allocation is lengthened to reduce the transmission frequency .

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