JP2009211397A - Radio communication method and vehicle communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain safety even when the number of terminals on vehicles is increased by giving priority to the terminal on the vehicle with high risk in allotting communication resources in a radio communication method in which communication between road and the vehicle and the communication between the vehicles are shared. <P>SOLUTION: The radio communication method in a vehicle communication system carries out multiplexed communication by having vehicle loaded terminals and roadside machines and uses one radio transmission path. The method includes: a process in which the vehicle loaded terminal acquires information on its own vehicle; a process in which the vehicle loaded terminal calculates the degree of risk expressing the degree of risk of the own vehicle on the basis of the acquired information on its own vehicle; a process in which the vehicle loaded terminal notifies the calculated degree of risk to the roadside machine; and a process in which the roadside machine allots the communication resources by giving priority to the vehicle loaded terminal for the vehicle with the high degree of risk. It is preferable to have the calculation for the degree of risk calculated also based on information regarding notified surrounding vehicles. As the information of the vehicles, it is preferable to have behavior of the vehicle, operation of the vehicle and a state of a driver included. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless communication technique in a vehicle communication system.

  Development of Intelligent Transport System (ITS) that integrates roads and vehicles using information and communication technology for the purpose of improving safety, transport efficiency, and comfort. It has been. In the ITS, the above-described object is achieved by road-to-vehicle communication between a roadside device installed on the road and a vehicle-mounted device mounted on the vehicle and vehicle-to-vehicle communication between the vehicle-mounted devices.

  As described above, an in-vehicle device mounted on a vehicle needs to perform both road-to-vehicle communication and vehicle-to-vehicle communication. Here, when different wireless communication methods are used for road-to-vehicle communication and vehicle-to-vehicle communication, the frequency resource utilization efficiency is lowered, and the in-vehicle device is complicated and the cost is increased. Therefore, it is preferable that the modulation system, the frequency, and the like be the same in the road-to-vehicle communication and the vehicle-to-vehicle communication so that the wireless circuit can be shared.

  As a communication method for achieving both road-to-vehicle communication and vehicle-to-vehicle communication, a method of temporally dividing road-to-vehicle communication and vehicle-to-vehicle communication has been proposed (for example, Patent Document 1). In such a system, the ratio of time allocated to road-to-vehicle communication and vehicle-to-vehicle communication is fixed or assigned to the requested node, but overflows when the number of nodes increases. In road-to-vehicle communication and vehicle-to-vehicle communication, information related to safety is exchanged. Therefore, if communication with high urgency cannot be transmitted, an accident or the like may occur.

In addition, as a frequency channel allocation method in inter-vehicle communication, a method of capturing an image of a vehicle entering an intersection, predicting a collision risk based on the image, and preferentially allocating a frequency channel to a vehicle with a high risk level Has been proposed (Patent Document 2). According to this method, since the frequency channel is assigned with priority to a vehicle having a high degree of danger, safety can be improved even when the number of vehicles increases.
JP 2000-165313 A Japanese Patent Laid-Open No. 2005-32010

  In the wireless communication system that shares road-to-vehicle communication and vehicle-to-vehicle communication, the present invention preferentially allocates communication resources to in-vehicle terminals with a high degree of danger, so that safety can be ensured even when the number of in-vehicle terminals increases. The purpose is to keep.

  The present invention is a wireless communication method in a vehicle communication system that includes a plurality of in-vehicle terminals and at least one roadside device, and these nodes perform multiplexed communication using one wireless transmission path. As multiplexed communication using one wireless transmission path, methods such as time division multiple access, frequency division multiple access, code division multiple access, and the like can be adopted.

In order to achieve the above object, the wireless communication method according to the present invention includes a step in which an in-vehicle terminal acquires information about the own vehicle, and a degree of danger of the own vehicle based on the information about the own vehicle acquired by the in-vehicle terminal. A step of calculating a risk level indicating the risk level, a step in which the in-vehicle terminal notifies the calculated risk level to the roadside device, and a step in which the roadside device preferentially allocates communication resources from the in-vehicle terminal of the vehicle having a high risk level. And including.

  As described above, even when a communication resource is preferentially assigned to a vehicle with a high degree of risk, the number of vehicles increases, and even if a vehicle that cannot perform communication occurs, the degree of urgency is high. Communication resources can be reliably allocated to vehicles that perform communication. Therefore, safety can be maintained even when the number of vehicles increases.

  In the present invention, risk calculation processing is performed in each vehicle, and the calculation processing is distributed. Therefore, there is also an advantage that the processing efficiency is improved as compared with the case where the risk level is calculated with a single device such as a roadside device.

  Here, the present invention further includes a step in which the in-vehicle terminal notifies other in-vehicle terminals of information about the acquired own vehicle, and in the step of calculating the degree of risk, in addition to the information about the own vehicle, the notified other It is preferable that the degree of risk is calculated based on information related to the vehicle.

  In this way, the degree of danger of the host vehicle can be calculated more accurately using not only the information about the host vehicle but also information about the other vehicle.

  Note that the information related to the vehicle includes information related to the behavior of the vehicle, information related to the operation of the vehicle, and information related to the state of the driver of the vehicle.

  The information related to the behavior of the vehicle is information indicating what behavior the vehicle will exhibit as a result of an operation by the driver and other external factors (road surface condition, wind, etc.). This information can be obtained by measuring the behavior of the vehicle with a sensor. A typical example of the information related to the behavior of the vehicle is a vehicle speed and acceleration.

  The information regarding the operation of the vehicle is information indicating what operation the driver has performed on the vehicle. This information can be obtained by acquiring the operation status of the interface with the user such as a handle or a pedal. As an example of the information regarding operation of a vehicle, the information regarding the operation condition, such as a steering wheel, an accelerator, a brake, a blinker, and a horn, can be mentioned.

  The information regarding the state of the driver of the vehicle includes the physiological / biological information of the driver. This information can be obtained by measuring the driver's physiological information, taking and analyzing the driver's image, or recognizing the voice of the driver. Examples of information regarding the state of the driver of the vehicle include the driver's heart rate, blood pressure, sweating state, brain waves, and the driver's facial expression and utterance.

  In the present invention, the degree of risk is preferably calculated as follows. In other words, it is preferable that information related to the vehicle is composed of a plurality of pieces of information, and a score representing danger is calculated for each of the information based on the content of the information, and the degree of risk is obtained as the sum of the plurality of calculated scores. For each piece of information regarding the vehicle, it is possible to employ a configuration in which the relationship between the contents of the information and the score representing the danger is stored in advance as a table, and the score is obtained with reference to this table. Further, although the risk level is obtained as the sum of a plurality of scores, the average of the plurality of scores is substantially equivalent to obtaining the sum of the plurality of scores. The sum of the scores may be a simple sum (simple sum) or a weighted sum (weighted sum).

As described above, even when a plurality of pieces of information relating to the vehicle are used, if only the score is calculated and the sum is obtained, the processing load is not so much. Therefore, even when the risk level is calculated on the vehicle side, the risk level can be calculated at high speed.

  In the present invention, communication resources allocated to a vehicle or a roadside machine include the following. When the multiplexing communication method is a time division multiple access method, the communication resource is a time slot. When the multiplex communication method is a frequency division multiple access method, the communication resource is a frequency channel (frequency slot). When the multiplexed communication method is a code division multiple access method, the communication resource is a spreading code. A plurality of communication resources (time slots, frequency channels, spreading codes, etc.) may be allocated to one vehicle. A vehicle to which a plurality of time slots and the like are assigned can communicate at a higher speed. Therefore, it is also preferable to assign a plurality of time slots to a vehicle with a high degree of danger.

  The present invention can be understood as a wireless communication method including at least a part of the above processing. The present invention can also be understood as a vehicle communication system that executes at least a part of the above processing. Each of the above processes can be combined with each other as much as possible to constitute the present invention.

  For example, a vehicle communication system as one aspect of the present invention includes a plurality of in-vehicle terminals and at least one roadside device, and these nodes perform multiplexed communication using a single wireless transmission path. The in-vehicle terminal includes an information acquisition unit that acquires information about the host vehicle, a risk level calculation unit that calculates a risk level indicating the degree of danger of the host vehicle based on the acquired information about the host vehicle, and a calculation A risk notification means for notifying a roadside device of a given risk level, and the roadside device has a communication resource allocation means for preferentially allocating communication resources from an in-vehicle terminal with a high risk level. .

  Here, the in-vehicle terminal further includes information notifying means for notifying other in-vehicle terminals of information related to the own vehicle acquired by the information acquiring means, and the risk level calculating means includes the information related to the own vehicle. It is preferable to calculate the degree of risk based on the notified information about the other vehicle.

  According to the present invention, since communication resources can be preferentially allocated to in-vehicle terminals with a high degree of risk, safety can be maintained even when the number of in-vehicle terminals increases.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings.

(First embodiment)
[Overview]
An outline of the communication method in this embodiment will be described. In the present embodiment, TDMA-TDD (Time Division Multiple Access-Time Division Duplex) is adopted as a wireless access method. The roadside machine centrally controls access control. FIG. 1 shows a frame configuration used in this embodiment. The TDMA frame is divided into a plurality of time slots, and each is assigned to each node. In the frame configuration shown in FIG. 1, an uplink communication period, a downlink communication period, and a vehicle-to-vehicle communication period for road-to-vehicle communication are provided in a TDMA frame at intervals of 2 ms, and each time slot is assigned to each node. The time slot is dynamically assigned by the roadside device for each TDMA frame.

Note that the length of the up-and-down period and the down-to-vehicle communication period of road-to-vehicle communication are not fixed, and after assigning the time slots necessary for road-to-vehicle communication, the remaining time slots are Assign to communication. Therefore, the length of each period can change dynamically every TDMA frame. Here, if the number of vehicles is large, there may be a shortage of time slots for inter-vehicle communication, but it is necessary to communicate urgently by assigning time slots preferentially from vehicles with a high degree of risk (described later). Time slots are preferentially assigned to vehicles.

[Constitution]
<Whole system>
FIG. 2 is a diagram showing a system configuration of the vehicle communication system according to the present embodiment. As shown in the figure, the present vehicle communication system includes an in-vehicle terminal and roadside devices mounted on a plurality of vehicles.

  Each vehicle communicates with roadside equipment to provide traffic information such as traffic jams and accidents, to receive danger information such as the danger of colliding with other vehicles and obstacles, music, etc. Receive content such as video and video, or provide an Internet connection. This road-to-vehicle communication may be a form in which information is exchanged bidirectionally between roads and cars, or a form in which information is sent only from the roadside machine to the vehicle direction (information shower).

  Each vehicle performs inter-vehicle communication between vehicles. In inter-vehicle communication, for example, a warning is issued to a partner vehicle when the vehicle interval is too close, or attention is given to surrounding vehicles when a lane change is to be made. In addition, it notifies the following vehicle that there is an obstacle ahead, or warns the following vehicle when the host vehicle suddenly brakes. In addition, communication such as voice communication and exchange of music and videos may be performed between vehicles. Even if communication regarding the exchange of music or the like is not possible, no safety problem will occur, but if a collision warning or the like cannot be communicated, a safety problem will occur.

<In-vehicle terminal>
Next, the functional configuration of the in-vehicle terminal 10 mounted on the vehicle will be described.

  The in-vehicle terminal 10 includes a wireless transmission / reception unit 11, a vehicle information acquisition unit 12, a risk level calculation unit 13, and a risk level table 14. The wireless transmission / reception unit 11 performs wireless communication (transmission / reception) according to time slot assignment from the roadside device.

  The wireless transmission / reception unit 11 transmits information on the own vehicle acquired by the vehicle information acquisition unit 12 and the risk level of the own vehicle to the roadside machine and other vehicles. Moreover, the radio | wireless transmission / reception part 11 receives the information regarding the vehicle which the surrounding vehicle is transmitting.

  The vehicle information acquisition unit 12 acquires information related to the own vehicle. Here, information on the behavior of the vehicle is mainly acquired. That is, the vehicle speed of the host vehicle is acquired by the vehicle speed sensor 12a, and the acceleration of the host vehicle is acquired by the acceleration sensor 12b. The GPS device 12c acquires the current position of the host vehicle.

The risk level calculation unit 13 calculates a risk level indicating the degree of danger of the host vehicle based on the information about the host vehicle and the information about the surrounding vehicles and the risk level table 14. In the present embodiment, the degree of risk is calculated based on the speed and acceleration of the host vehicle, the distance from the surrounding vehicle, and the relative speed and relative acceleration with the surrounding vehicle. Specifically, the risk level table 14 stores a risk level score corresponding to each of the above information. An example of the risk level table 14 is shown in FIG. In the example of FIG. 3, for example, if the speed of the host vehicle is 10 km / h, the corresponding risk score is “1”. In the risk table of FIG. 3, absolute values are used for speed and acceleration. The risk level calculation unit 13 refers to the risk level table 14 for each of the five items of the speed of the host vehicle, the acceleration of the host vehicle, the distance to the surrounding vehicle, the relative speed with the surrounding vehicle, and the relative acceleration with the surrounding vehicle. To extract the risk score. And the risk level acquisition part 13 is made into the risk level of the own vehicle by summing up the extracted five risk level scores. According to this calculation method, the maximum value (most dangerous) of the risk level is “20”, and the minimum value (most safe) is “0”.

  In the above description, the risk is obtained as the sum (simple sum) of the risk scores obtained from the individual information. However, the risk may be obtained as a sum (weighted sum) obtained by weighting each risk score. Here, the weighting coefficient may be a fixed value, or the weighting coefficient may be changed according to the situation. For example, it is conceivable to change the weighting coefficient of the risk score regarding other information based on the content of certain information. Specifically, when the speed of the host vehicle is high, the risk score for the relative distance to the other vehicle is increased, while when the host vehicle speed is low, the risk score for the relative distance to the other vehicle is weighted. It may be possible to reduce the size.

  In the present embodiment, the risk level is calculated periodically. When there is a risk transmission request from the roadside device 20, the wireless transmission / reception unit 11 transmits the calculated risk to the roadside device 20. Further, even when there is no risk level transmission request from the roadside device 20, if the calculated risk level is equal to or greater than the threshold value, it is transmitted to the roadside device 20 via the wireless transmission / reception unit 11.

<Roadside machine>
Next, the functional configuration of the roadside machine 20 will be described.

  The roadside machine 20 includes a wireless transmission / reception unit 21, a risk transmission request unit 22, a risk storage unit 23, and a time slot allocation unit 24. The wireless transmission / reception unit 21 performs wireless communication with the vehicle.

  The danger level transmission request unit 22 periodically requests the surrounding vehicles to transmit the danger level. The degree of risk transmitted as a response from the vehicle is stored in the degree of risk storage unit 23. The time slot allocation unit 24 dynamically allocates time slots for each TDMA frame. In the present embodiment, road-to-vehicle communication is treated with the highest priority, and even if road-to-vehicle communication is performed, if there is a margin in the time slot, a time slot is allocated for vehicle-to-vehicle communication preferentially from a vehicle with a high degree of danger. Detailed processing contents of the time slot allocation unit 24 will be described below.

[Processing flow]
<In-vehicle terminal>
Next, the process which the vehicle-mounted terminal 10 performs is demonstrated with reference to the flowchart of FIG.

  The in-vehicle terminal 10 detects information related to the own vehicle via the vehicle information acquisition unit 12 (S10). Here, the speed of the host vehicle is acquired from the speed sensor 12a, the acceleration of the host vehicle is acquired from the acceleration sensor 12b, and the position information of the host vehicle is acquired from the GPS device 12c. In addition, information about surrounding vehicles is detected (S11). Here, the information about the surrounding vehicle may be acquired by the own vehicle using a millimeter wave radar, a camera, or the like, or may be notified by wireless communication from another vehicle. In the case of notification, for example, the host vehicle information may be transmitted from the vehicle to all other vehicles, or when transmitting data to the roadside machine, the host vehicle information is stored together and the surrounding vehicles store this data. You may notify by receiving. Then, the relative speed, relative acceleration, and relative distance with respect to the surrounding vehicle are acquired from the speed, acceleration, and position of the surrounding vehicle and the speed, acceleration, and position of the host vehicle.

Next, the risk level calculation unit 13 extracts a risk level score with reference to the risk level table 14 for each information of the speed and acceleration of the own vehicle and the relative distance, relative speed, and relative acceleration with the surrounding vehicle. (S12). Then, the obtained individual risk scores are summed to calculate the vehicle risk (S13). For example, when the risk table shown in FIG. 3 is used, own vehicle speed: 80 km / h, own vehicle acceleration: 0.15 G, relative distance: 20 m, relative speed: 10 k
If m / h and relative acceleration: 0.12G, the risk score corresponding to each is 4, 2, 3, 1, 1, and the risk of the vehicle is 11 in total.

  Next, it is determined whether or not the calculated degree of risk is greater than or equal to a predetermined threshold value (S14). The threshold value can be set as appropriate. For example, when the maximum value of the risk is 20, as described above, the threshold value may be about 15. Here, when the degree of danger is equal to or greater than a predetermined threshold (S14-YES), the process proceeds to step S16 and the degree of danger is transmitted to the roadside machine 20.

  If the degree of risk is less than the threshold value (S14-NO), it is determined whether a request for risk level transmission is received from the roadside device 20 (S15). If transmission of the risk level is requested (S15-YES), the process proceeds to step S16, and the risk level is transmitted to the roadside machine 20. On the other hand, if the transmission of the risk level is not requested (S15-NO), the process is terminated.

  Through such processing by the in-vehicle terminal, the roadside device 20 can periodically acquire and grasp the risk of each vehicle. And when the danger level of a vehicle is more than a predetermined threshold value, the new danger degree will be notified to the roadside machine 20 rapidly.

<Roadside machine>
First, the processing performed by the roadside machine 20 will be described with reference to the flowchart of FIG.

  The roadside machine 20 first grasps the amount of data used in road-to-vehicle communication (S20). The roadside machine 20 can grasp how many vehicles are in the communication area, and can grasp the entire data amount by multiplying the data amount per vehicle by the number of communication vehicles. Here, as shown in FIG. 1, consider an example in which the roadside machine 20 performs one-to-one communication with three vehicles.

  Next, the roadside device 20 calculates the number of time slots Si required for road-to-vehicle communication (S21). When the roadside machine 20 performs one-to-one bi-directional communication with three vehicles, the time slots of the three vehicles are assigned to the up and down time slots, so a total of six time slots are required.

  Next, the roadside device 20 calculates a time slot Sv necessary for vehicle-to-vehicle communication (S22). This may be calculated from the number of vehicles for which there is a communication request (allocation request), or from the number of surrounding vehicles if all vehicles only broadcast to surrounding vehicles. good.

  Note that time slot assignment does not require assignment of only one time slot to one node, and a plurality of time slots may be assigned as necessary. By assigning a plurality of time slots, the node can communicate at high speed.

Next, the roadside device 20 determines whether the total number of time slots required for road-to-vehicle communication and the number of time slots required for vehicle-to-vehicle communication is within the total number of time slots (S23). If the required number of time slots is less than the total number of time slots (S23-YES), even after assigning time slots for road-to-vehicle communication, the time slot assignment unit 24 is used for vehicle-to-vehicle communication for all vehicles. Can be assigned a time slot (S24). On the other hand, if the required number of time slots is larger than the total number of time slots (S23-NO), time slots cannot be assigned to some vehicles. Therefore, the roadside machine 20 acquires the risk level of the surrounding vehicle (S25). This may be acquired as a response by the roadside device 20 transmitting a risk information transmission request. Alternatively, the risk level already acquired may be acquired from the risk level storage unit 23. The time slot allocating unit 24 first allocates time slots for road-to-vehicle communication, and then preferentially allocates time slots for vehicle-to-vehicle communication from vehicles with a high degree of danger (S26).

[Operation / Effect of Embodiment]
In this way, it is possible to perform efficient communication by performing multiplexed communication using one wireless transmission path for road-to-vehicle communication and vehicle-to-vehicle communication, and dynamically assigning time slots in TDMA frames. .

  In addition, when the number of vehicles increases, vehicles that cannot be assigned time slots will occur. However, since time slots are preferentially assigned according to the degree of danger, vehicles that are trying to perform safety-related communications such as collision warnings. Are preferentially assigned time slots, and are unlikely to cause safety problems.

  In addition, since the calculation of the risk is a distributed process performed by each vehicle, the process does not concentrate on the roadside machine. In addition, the calculation of the risk level for each vehicle is a simple process of extracting the risk score corresponding to each piece of information related to the vehicle from the risk level table and summing them, and can therefore be executed at high speed. is there.

  In this embodiment, the risk level is calculated based on the speed / acceleration of the host vehicle and the relative distance / relative speed / relative acceleration with the surrounding vehicle, but the risk level is calculated based on other information. It may be broken.

Information such as speed and acceleration can be said to be information obtained by a sensor, which is information on the behavior of the vehicle, that is, information on how the vehicle behaves as a result of the driving operation by the driver. In addition to the speed and acceleration, the vehicle behavior information includes yaw rate, airbag operation status information, ABS (Antilock Brake System)
) And the like regarding the operating status.

(Second Embodiment)
In the second embodiment, the degree of risk is calculated based on information other than information related to the behavior of the vehicle.

  FIG. 6 is a diagram illustrating an example of a functional configuration of the in-vehicle terminal according to the present embodiment. According to the in-vehicle terminal shown in FIG. 6, the vehicle information acquisition unit 12 acquires information regarding the operation of the vehicle by the driver as information regarding the own vehicle. Specifically, it is detected how much the steering wheel is turned by the steering sensor 12d and how much the accelerator and the brake are depressed by the accelerator opening sensor 12e and the brake pedal force sensor 12f. When the steering wheel is turned off, it is more dangerous than when the steering wheel is not cut, and as the accelerator or brake is stepped on, the danger is higher. Further, not focusing on the current value alone, it may be determined that the risk is more dangerous when the fluctuation range of the operation of the steering wheel, the accelerator, or the brake is large based on the history of operation. Further, as information related to the operation of the vehicle other than those shown in the drawing, an operating state of a winker (direction indicator), an operating state of a horn, and the like can be given. The operation of the blinker means a change of course (turns left or right) or a lane change, and the degree of danger increases. Since the horn is used when the driver recognizes the danger, it can be determined that the danger is great during the operation.

FIG. 7 is a diagram illustrating another example of the functional configuration of the in-vehicle terminal according to the present embodiment. According to the in-vehicle terminal shown in FIG. 7, the vehicle information acquisition unit 12 acquires information related to the driver's state as information related to the own vehicle. Specifically, the heart rate of the driver is acquired by the heart rate measuring device 12g, the amount of the driver's sweat is measured by the sweat measuring device 12h, or the drowsiness state of the driver is acquired by the dozing detection device 12i. Or The heart rate measuring device 12g is installed, for example, at a handle grip portion. When the driver's heart rate suddenly increases, it can be determined that the situation is dangerous. The sweat measurement device 12h is also installed at the grip portion of the handle. When the amount of sweating by the driver increases, it can be determined that the driver is in a dangerous state. The doze detection device 12i captures the driver's facial expression with a camera provided on the steering wheel, dashboard, etc., and analyzes the image (such as eyelid opening, gaze behavior, number of blinks, etc.) to analyze driving. The degree of sleepiness of the person is determined. When the driver is sleepy, it can be determined that the driver is in a dangerous state. Further, as information related to the state of the driver other than those shown in the drawing, blood pressure, brain waves, voice of the driver, line of sight, and the like can be given. Blood pressure and brain waves are the driver's biological information, and it can be determined from the waveform whether or not danger has been detected. The voice information can determine the content of the utterance by voice recognition, or can analyze the waveform of the voice to determine the driver's psychological state (irritated, etc.). Further, by looking at the driver's line of sight, it is possible to detect a sideward driving.

  As described above, the information related to the vehicle is roughly classified into three types: information related to the behavior of the vehicle, information related to the operation of the vehicle, and information related to the state of the driver. In the above description, only an example of using these three types of information individually is used, but it can be easily understood that these may be used in combination.

  Thus, by calculating the risk level of the vehicle using various information, the risk level can be determined with higher accuracy.

(Third embodiment)
In the first embodiment, time slots are always assigned to road-to-vehicle communication, and time slots are also assigned to vehicle-to-vehicle communication when there is a margin after assigning time slots to road-to-vehicle communication. However, both road-to-vehicle communication and vehicle-to-vehicle communication may be preferentially assigned from a vehicle with a high degree of danger.

  That is, in step S16 of the flowchart shown in FIG. 5, the time slot assigning unit 24 of the roadside machine 20 assigns time slots for road-to-vehicle communication and vehicle-to-vehicle communication in order from the vehicle with the highest degree of danger. In this way, emergency communication from a high-risk vehicle can be preferentially performed, and safety can be improved.

(Fourth embodiment)
In the first embodiment, as a communication method, as shown in FIG. 1, the roadside device 20 and each in-vehicle terminal 10 communicate on a one-to-one basis, and the in-vehicle terminals 10 directly communicate with each other. is doing. However, the communication method is not limited to the above, and various methods can be employed.

  For example, in road-to-vehicle communication, one-way communication may be performed from the roadside device 20 to the in-vehicle terminal 10. As an example, a mode in which the roadside device 20 delivers traffic information and the like to the in-vehicle terminal 10 can be cited as an example. Moreover, the system (vehicle-to-vehicle communication) which relays the roadside machine 20 between the vehicle-mounted terminals 10 can also be used. As described above, various types of communication can be considered, but any method may be adopted.

(Fifth embodiment)
In the first embodiment, a time division multiple access method (TDMA) is described as an example of a multiplexed communication method. However, the multiplexed communication method is not limited to TDMA.

  In addition to TDMA (see FIG. 8) divided in the time direction, frequency division multiple access (FDMA, see FIG. 9) may be adopted for one radio channel to a plurality of frequency channels (frequency slots). When the FDMA method is adopted, the roadside device 20 allocates frequency slots, not time slots, to the in-vehicle terminal 10 as communication resources.

Also, code division multiple access (CDMA, see FIG. 10) for multiplexing using spreading codes may be employed. When the CDMA system is adopted, the roadside device 20 assigns a spread code, not a time slot, to the in-vehicle terminal 10 as a communication resource.

  Further, TDMA, FDMA, and CDMA may be used in combination. For example, as shown in FIG. 11, the frequency band is divided by the FDMA method to use a plurality of frequency slots, and each frequency slot is divided into time slots by the TDMA method. In the example of FIG. 11, one frame is divided into five frequency slots and seven time slots, and is divided into 35 channels as a whole. The roadside device 20 allocates these individual channels to the in-vehicle terminal 10.

It is a figure which shows the structural example of the TDMA frame used by 1st Embodiment. It is a figure which shows the system configuration | structure of the vehicle communication system in 1st Embodiment, and the function structure of a vehicle-mounted terminal and a roadside machine. It is a figure which shows the example of the risk degree table in 1st Embodiment. It is a flowchart which shows the flow of the process which a vehicle-mounted terminal performs in 1st Embodiment. It is a flowchart which shows the flow of the process which a roadside machine performs in 1st Embodiment. It is a figure which shows the example of a function structure of the vehicle-mounted terminal in 2nd Embodiment. It is a figure which shows the example of a function structure of the vehicle-mounted terminal in 2nd Embodiment. It is a figure explaining a time division multiple access system (TDMA). It is a figure explaining a frequency division multiple access system (FDMA). It is a figure explaining a code division multiple access system (CDMA). It is a figure explaining a FDMA + TDMA system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 In-vehicle terminal 11 Wireless transmission / reception part 12 Vehicle information acquisition part 13 Risk level calculation part 14 Risk level table 20 Roadside machine 21 Wireless transmission / reception part 22 Risk level transmission request part 23 Risk level storage part 24 Time slot allocation part

Claims (11)

A wireless communication method in a vehicle communication system that includes a plurality of in-vehicle terminals and at least one roadside device, and these nodes perform multiplexed communication using one wireless transmission path,
The in-vehicle terminal acquires information about the vehicle;
A step in which the in-vehicle terminal calculates a risk level representing the degree of danger of the host vehicle based on the acquired information on the host vehicle;
An in-vehicle terminal notifying the roadside device of the calculated degree of risk;
The roadside machine preferentially allocates communication resources from the in-vehicle terminal of a high-risk vehicle;
A wireless communication method comprising: The vehicle-mounted terminal further includes a step of notifying the other vehicle-mounted terminal of information about the acquired own vehicle,
In the step of calculating the risk level, the risk level is calculated based on the notified information about the other vehicle in addition to the information about the own vehicle.
The wireless communication method according to claim 1. The information on the vehicle includes information on the behavior of the vehicle.
The wireless communication method according to claim 1 or 2. The information related to the vehicle includes information related to the operation of the vehicle.
The wireless communication method according to any one of claims 1 to 3. The information about the vehicle includes information about the state of the driver of the vehicle,
The wireless communication method according to any one of claims 1 to 4, wherein: The information about the vehicle is composed of a plurality of information,
The risk level is calculated as a sum of a plurality of calculated scores in the step of calculating the risk level, and a risk level is calculated as a sum of a plurality of calculated scores. The wireless communication method according to any one of claims. The multiplexing communication method is a time division multiple access method,
The communication resource allocated to the in-vehicle terminal is a time slot.
The wireless communication method according to any one of claims 1 to 6. The multiplexing communication scheme is a frequency division multiple access scheme,
The communication resource allocated to the in-vehicle terminal is a frequency channel.
The wireless communication method according to any one of claims 1 to 6. The multiplexed communication method is a code division multiple access method,
The communication resource allocated to the in-vehicle terminal is a spreading code,
The wireless communication method according to any one of claims 1 to 6. A vehicle communication system that includes a plurality of in-vehicle terminals and at least one roadside unit, and these nodes perform multiplexed communication using one radio transmission path,
The in-vehicle terminal includes an information acquisition unit that acquires information about the host vehicle, a risk level calculation unit that calculates a risk level indicating the degree of danger of the host vehicle based on the acquired information about the host vehicle, and a calculated risk level. And a risk notification means for notifying the roadside machine,
The roadside machine has a communication resource allocation means for preferentially allocating communication resources from a vehicle terminal having a high degree of risk. The in-vehicle terminal further includes information notification means for notifying other in-vehicle terminals of information related to the own vehicle acquired by the information acquisition means,
11. The vehicle communication system according to claim 10, wherein the risk level calculation unit calculates the risk level based on the notified information about the other vehicle in addition to the information about the own vehicle.

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