JP2011227724A - On-vehicle terminal and safety driving support system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which is used to set the receiving sensitivity properly to an on-vehicle terminal for executing road-to-vehicle communication and vehicle-to-vehicle communication in accordance with the target of communication.SOLUTION: The on-vehicle terminal includes: a communication unit by which road-to-vehicle communication with a roadside machine and vehicle-to-vehicle communication with another vehicle are carried out; and a control unit which controls to switch the communication unit to the road-to-vehicle communication or the vehicle-to-vehicle communication and to set the receiving sensitivity of the communication unit. The control unit sets the receiving sensitivity so that the receiving sensitivity of the vehicle-to-vehicle communication performed by the communication unit becomes higher than that of the road-to-vehicle communication performed by the communication unit.

Description

  The present invention relates to an in-vehicle terminal and a safe driving support system that perform road-to-vehicle communication and vehicle-to-vehicle communication.

Research and development of Intelligent Transport Systems (ITS) are underway in order to provide safety and convenience to users by transmitting and receiving information on vehicles and roads by wireless communication (see Non-Patent Document 1). reference). In ITS, the safe driving support system obtains traffic information, etc. that is not directly visible from the vehicle by wireless communication between the vehicle and infrastructure equipment such as roadside units and other vehicles, and provides information to the driver as necessary. By doing this, traffic accidents will be reduced. Wireless systems classified as safe driving support systems include a vehicle-to-vehicle communication system and a road-to-vehicle communication system.

  The inter-vehicle communication system is a system in which the in-vehicle terminal wirelessly communicates with other vehicles, obtains information on surrounding vehicles (position, speed, vehicle control information, etc.), and provides safe driving support to the user as necessary. is there. On the other hand, the road-to-vehicle communication system is a system in which an in-vehicle terminal wirelessly communicates with a roadside device to obtain information (signal information, regulation information, road information, etc.) and provides safe driving support to a user as necessary. Safe driving support methods include driving control of the vehicle such as collision avoidance and braking based on the obtained information, and providing information in a form that is easy for the user to understand, such as screen display and voice, to call attention Can be considered.

  Whether the information used for safe driving support is obtained by vehicle-to-vehicle communication or road-to-vehicle communication is irrelevant for the user receiving the service, and the difference is not conscious. Conversely, providing the information obtained by the vehicle-to-vehicle communication and the road-to-vehicle communication without distinction increases the opportunity for the user to receive the service. Furthermore, from the viewpoint of the system configuration, if one on-vehicle terminal can be used for both vehicle-to-vehicle communication and road-to-vehicle communication, cost performance increases. For this reason, in a safe driving support system, it is desired to share an in-vehicle terminal for vehicle-to-vehicle communication and road-to-vehicle communication from the viewpoint of providing information to the user and rationalizing the configuration.

  Patent Document 1 describes a vehicle wireless communication system that performs road-to-vehicle communication and vehicle-to-vehicle communication. The vehicle-mounted device that constitutes the vehicle wireless communication system includes a wireless device that performs road-to-vehicle communication and a wireless device that performs vehicle-to-vehicle communication, and the vehicle-mounted control device switches between which information is received. Do.

JP 2009-128976 A

Ministry of Internal Affairs and Communications “Study Group on ITS Wireless System Advancement” report published in June 2009

As described above, although it is desirable to share the in-vehicle terminal in the inter-vehicle communication and the road-to-vehicle communication, a suitable reception sensitivity setting differs depending on the communication environment between the two. Therefore, care must be taken when actually sharing the device. Hereinafter, an example will be described.

  The characteristics of communication performed during road-to-vehicle communication will be described using the example of FIG. The road-to-vehicle communication service is provided within a range where communication with the device is possible at a place where the roadside device is located. For example, in the case of providing signal information, a tall communication device is installed in a place with good visibility near an intersection to communicate with the vehicle.

FIG. 1A is a plan view of an intersection. In the figure, a road-to-vehicle communication area 20 in which the vehicle 1 can communicate with the roadside machine 2 is indicated by a dotted line. Note that the width of the road-to-vehicle communication area varies depending on the transmission power of the roadside device and the reception sensitivity on the vehicle side.
FIG. 1B is a diagram showing received power when the vehicle 1 traveling from left to right on the road of FIG. 1A performs wireless communication with the roadside device 2. The horizontal axis corresponds to the position on the road, and the vertical axis represents the received power. In addition, a range in which communication between the vehicle and the roadside machine should be established is shown as an assumed communication area in consideration of a time margin for keeping the information provided to the vehicle in time for safe driving support.

  As can be seen from this figure, the received power in road-to-vehicle communication depends on the distance from the transmitter, with the peak directly below the roadside unit (shown by the dotted line connecting FIG. 1 (a) and FIG. 1 (b)). Value is easy to predict. In addition, since the roadside device is installed at a high position where the line of sight is good, the received power is larger than the vehicle-to-vehicle communication described later. Therefore, the receiving sensitivity of the in-vehicle terminal can be set lower than the vehicle-to-vehicle communication. For example, if communication sensitivity with a roadside device is possible in all of the assumed communication areas in the figure and reception sensitivity is set with some margin, set the received power P1 as a threshold value and ignore signals below it. It ’s fine.

  The characteristics of communication performed during inter-vehicle communication will be described with reference to the example of FIG. In vehicle-to-vehicle communication, services are provided by exchanging information between vehicles, so that not only the own vehicle but also other vehicles need to have in-vehicle terminals. The vehicles described in the following description have the equipment necessary for vehicle-to-vehicle communication.

FIG. 2A is a plan view of an intersection. There is no roadside machine installed at this intersection. In the figure, the host vehicle 1 performs inter-vehicle communication with another vehicle 3. Here, it is assumed that the other vehicle 3 is stopped before the intersection. In addition, there is a building in the lower left block of this intersection, which shields radio waves between the own vehicle and other vehicles.
FIG. 2B is a diagram illustrating received power when the host vehicle 1 traveling from the left to the right in FIG. 2A performs wireless communication with another vehicle 3. The horizontal axis corresponds to the position on the road, and the vertical axis represents the received power. The scale of the graph is the same as in FIG. In addition, a range in which communication with other vehicles is to be established is shown as an assumed communication area in consideration of a time margin for keeping the information provided to the vehicle in time for safe driving support.

  As can be seen from this figure, in the inter-vehicle communication, in the period of non-line-of-sight communication in which there is an obstacle between both vehicles, radio waves reach only by wraparound or the like, so the received power is low. Then, when the line-of-sight communication period in which both vehicles can communicate linearly without being affected by the shielding object (indicated by the dotted line connecting FIG. 2 (a) and FIG. 2 (b)), the received power suddenly appears. Becomes higher. Thereafter, the strength gradually decreases as the distance between the vehicles increases. Moreover, since the position of the transmitter is lower than that in the road-to-vehicle communication described above, the received power is reduced as a whole.

However, considering the purpose of vehicle-to-vehicle communication, which is to obtain information on other vehicles in the vicinity and support the user's safe driving, such as preventing encounter accidents, it is the period of unforeseen communication in which the user cannot directly see the other vehicle. It is required to establish communication. Therefore, reception power P2 lower than road-to-vehicle communication is set as a threshold value so that communication with other vehicles is possible in all of the assumed communication areas in the figure.

  Considering the above-mentioned difference in communication environment between road-to-vehicle communication and vehicle-to-vehicle communication, we will examine issues when sharing in-vehicle terminals. When setting the reception sensitivity of the in-vehicle terminal, it can be said that in road-to-vehicle communication, the reception sensitivity can be set relatively low as described above. On the other hand, in vehicle-to-vehicle communication, it can be said that it is necessary to increase the reception sensitivity especially when there are shielding objects such as buildings.

However, in a vehicle-mounted terminal that is commonly used for road-to-vehicle communication and vehicle-to-vehicle communication that has been proposed in the past, the reception sensitivity is single, and the same value is set for both road-to-vehicle and vehicle-to-vehicle. FIG. 3 shows reception sensitivity set by a conventional in-vehicle terminal. FIG. 3A is a diagram illustrating a communication partner and reception sensitivity of the in-vehicle terminal when the vehicle is in the road-to-vehicle communication area. As can be seen from the figure, a road-to-vehicle communication period and a vehicle-to-vehicle communication period are provided by time division. The time division method can be variously determined, but may be a method of repeating a communication period (for example, 100 msec) between the road and the vehicle according to the synchronization timing from the roadside machine. In this case, if the ratio between road and vehicle is specified in the header, the allocation of the communication period can be changed according to the situation. The reception sensitivity is a value that matches the vehicle-to-vehicle communication.
On the other hand, since the vehicle-to-vehicle communication is always performed when the vehicle is not in the road-to-vehicle communication area, the reception sensitivity suitable for the vehicle-to-vehicle communication is set as shown in FIG.

  As described above, when a conventional in-vehicle terminal is used, it is necessary to set the reception sensitivity high in accordance with the inter-vehicle communication side. On the other hand, in road-to-vehicle communication, although the reception sensitivity can be set low originally, communication is performed with excessive performance with high reception sensitivity that meets the requirements of vehicle-to-vehicle communication. As a result, the in-vehicle terminal may receive radio waves from a range equal to or greater than the service providing area (road-to-vehicle communication area) of the roadside device, and communication efficiency may be reduced. It also leads to increased power consumption and noise.

  As an example of dealing with this problem, it is conceivable to reduce the transmission power from the roadside device. Thereby, even if the reception sensitivity of the in-vehicle terminal is kept constant at the level of vehicle-to-vehicle communication, it is possible to suppress a decrease in efficiency during road-to-vehicle communication to some extent. However, even in road-to-vehicle communication, there is a possibility that radio waves during communication may be blocked by the occurrence of shadowing, that is, the presence of large vehicles, buildings, etc., so the transmission power is not necessarily reduced.

  Moreover, in patent document 1, since the radio | wireless machine used by vehicle-to-vehicle communication and road-to-vehicle communication is switched, the wireless communication suitable for each characteristic can be performed. However, since the scale of the apparatus becomes large, the design is restricted by taking up a large space, and the waste of the configuration also increases.

  The present invention has been made in view of the above circumstances, and the purpose of the present invention is for an in-vehicle terminal that performs road-to-vehicle communication and vehicle-to-vehicle communication to appropriately set reception sensitivity according to a communication target. Is to provide the technology.

In order to achieve the above object, the present invention adopts the following configuration. That is,
A communication unit that performs road-to-vehicle communication with a roadside machine and vehicle-to-vehicle communication with other vehicles,
A control unit that controls whether the communication unit performs road-to-vehicle communication or vehicle-to-vehicle communication, and a control unit that performs control to set reception sensitivity of the communication unit;
The said control part is a vehicle-mounted terminal characterized by setting reception sensitivity so that the reception sensitivity which performs vehicle-to-vehicle communication becomes higher than the reception sensitivity which the said communication part performs road-to-vehicle communication.

In the in-vehicle terminal having such a configuration, the control unit performs control so that reception sensitivity when performing vehicle-to-vehicle communication is higher than that during road-to-vehicle communication. As a result, while performing vehicle-to-vehicle communication, the probability of establishing communication with other vehicles that are out of line of sight increases, so it is possible to provide information to the user and control the vehicle appropriately Therefore, safe driving support is performed well. In addition, during the road-to-vehicle communication, the reception sensitivity necessary to establish communication with the roadside device is set, so that an efficient in-vehicle terminal can be operated.

The control unit of the in-vehicle terminal repeats switching between road-to-vehicle communication and vehicle-to-vehicle communication when the host vehicle is in a road-to-vehicle communication area that can receive data from a roadside device with the set reception sensitivity. If the vehicle is outside the road-to-vehicle communication area, the communication unit may be controlled to perform only vehicle-to-vehicle communication.
In an in-vehicle terminal having such a configuration, road-to-vehicle communication and vehicle-to-vehicle communication are alternately repeated within a range where communication with a roadside machine is possible, and information from other vehicles and information from roadside machines can be received. As a result, the amount of information that can be used for safe driving support increases. In addition, since only vehicle-to-vehicle communication is performed in a range where communication with the roadside machine is not possible, a lot of information on other vehicles can be collected, and the accuracy of safe driving support is improved.

The control unit of the in-vehicle terminal may be configured to control the communication unit by repeating a road-to-vehicle communication period and a vehicle-to-vehicle communication period for a predetermined time when the host vehicle is in the road-to-vehicle communication area. good.
By adopting such a configuration, the control unit can regularly switch the period of road-to-vehicle communication and vehicle-to-vehicle communication, and can efficiently acquire information from roadside units and other vehicles. .

The communication unit tries to establish communication with the roadside device,
The control unit may be configured to determine whether the host vehicle is in a road-to-vehicle communication area based on a result of the trial.
Alternatively, the in-vehicle terminal further includes a position acquisition unit that acquires position information of the host vehicle,
The control unit may be configured to determine whether the host vehicle is in a road-to-vehicle communication area based on the acquired position information.
In an in-vehicle terminal having such a configuration, the control unit can grasp whether the own vehicle is in the road-to-vehicle communication area based on the communication trial result or the position information of the own vehicle. The communication period can be appropriately switched.

The present invention includes a vehicle including the above-described vehicle-mounted terminal;
Including a vehicle in the road-to-vehicle communication area and a roadside machine for road-to-vehicle communication,
The roadside device delivers the reception sensitivity that the in-vehicle terminal should set when communicating with the roadside device,
After receiving the distributed reception sensitivity, the control unit can be regarded as a safe driving support system that sets the distributed reception sensitivity as reception sensitivity of road-to-vehicle communication.
In the safe driving support system having such a configuration, the user of the vehicle can enjoy the benefit of setting the reception sensitivity appropriately by using the in-vehicle terminal. In addition, since the reception sensitivity when performing road-to-vehicle communication is set to an optimal value for the roadside device, it is possible to efficiently use communication resources.

In the above safe driving support system, the in-vehicle terminal further includes a storage unit that stores an entry that associates the roadside device with the distributed reception sensitivity,
The control unit may be configured to control the communication unit to perform road-to-vehicle communication with entry reception sensitivity when communicating with a roadside device having an entry in the storage unit.
Since the vehicle-mounted terminal having such a configuration stores an appropriate reception sensitivity with the roadside machine that has once performed roadside-to-vehicle communication, when the vehicle enters the communication area of the roadside machine again, the road-to-vehicle terminal efficiently Communication can be performed.

The safe driving support system may include a plurality of roadside machines. In that case, the in-vehicle terminal performs road-to-vehicle communication with a plurality of roadside units and reception sensitivities suitable for each by dividing the road-to-vehicle communication period.
According to the safe driving support system having such a configuration, since the in-vehicle terminal can obtain traffic information from a plurality of roadside devices, an area to be covered as an information source when providing information to the user is widened. As a result, the amount of information serving as a basis for judgment increases, and it becomes possible to further improve safety.

The present invention provides the above-described in-vehicle terminal,
A roadside machine that performs road-to-vehicle communication with vehicles in the road-to-vehicle communication area;
A roadside device, and a management device that stores an entry that associates a reception sensitivity to be set by the in-vehicle terminal when communicating with the roadside device,
The management device distributes the entry to the in-vehicle terminal,
When the control unit communicates with a roadside device that has received an entry, the control unit can be regarded as a safe driving support system that controls the communication unit to perform road-to-vehicle communication with the reception sensitivity of the entry. .
By providing such a management device, it is possible to store the optimum reception sensitivity to be set for each roadside device and distribute it to the vehicle. As a result, each vehicle can perform efficient road-to-vehicle communication.

In the above safe driving support system, the in-vehicle terminal estimates the optimum reception sensitivity when communicating with the roadside device, sets the reception sensitivity, and uploads it to the management device. The management device is uploaded The reception sensitivity can also be stored as an entry associated with the roadside device.
According to the safe driving support system having such a configuration, since the optimum receiving sensitivity to be set for the roadside device can be collected from each vehicle in the management device, it is more efficient by distributing it to other vehicles. Road-to-vehicle communication can be realized.

In the above safe driving support system, the transmission power from the roadside device can be reduced during the period in which road-to-vehicle communication is performed.
In such a roadside device, in addition to reducing the reception sensitivity of the in-vehicle terminal during road-to-vehicle communication, the transmission power when information is distributed decreases, so the efficiency of communication resources is reduced on the roadside device side. Can be used effectively.

  ADVANTAGE OF THE INVENTION According to this invention, the vehicle-mounted terminal which performs road-to-vehicle communication and vehicle-to-vehicle communication can set a receiving sensitivity appropriately according to the object of communication.

It is a figure which shows the change of the received power in road-vehicle communication. It is a figure which shows the change of the received electric power in vehicle-to-vehicle communication. It is a figure which shows the receiving sensitivity in the conventional road-to-vehicle communication and vehicle-to-vehicle communication. It is a figure which shows the structure of the vehicle-mounted terminal of Embodiment 1. 3 is a flowchart illustrating an entire process according to the first exemplary embodiment. 4 is a flowchart illustrating reception sensitivity setting for road-to-vehicle communication according to the first exemplary embodiment. It is a figure which shows the reception sensitivity in the road-to-vehicle communication of Embodiment 1, and vehicle-to-vehicle communication. It is a figure which shows the roadside communication period which communicates with several roadside machines. It is a figure which shows a mode that a roadside machine delivers reception sensitivity. It is a figure which shows a mode that the receiving sensitivity of a roadside machine is memorize | stored in a management apparatus. 10 is a flowchart illustrating an entire process according to the third embodiment.

<Embodiment 1>
Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. The main components of the safe driving support system described below include a host vehicle 1, a roadside device 2, and another vehicle 3.

(Configuration of in-vehicle terminal)
FIG. 4 is a block diagram showing the configuration of the in-vehicle communication terminal mounted on the host vehicle 1. The control unit 101 is a device that gives instructions to each block to control the contents and order of processing, and is configured by a program that operates on the ECU, for example. The communication unit 102 is a wireless communication device that performs road-to-vehicle communication and vehicle-to-vehicle communication. The storage means 103 is a database that stores an entry that associates a roadside device and a reception sensitivity to be set to the roadside device, and an HDD, a semiconductor nonvolatile memory, or the like can be used. The position data acquisition unit 102 is a device that acquires the current position of the host vehicle as position data. For example, a device that receives a signal from a GPS satellite and identifies the current position is used. Moreover, you may make it have an autonomous positioning function in addition to GPS.

  Here, the degree of reception sensitivity with which the communication unit receives data transmitted from a roadside machine or another vehicle is determined by a threshold value of reception power set on the communication unit side. For example, in FIG.1 (b), the electric power value smaller than P1 set as a threshold value is disregarded, and only the part beyond it is processed by the control part as data from a roadside machine. On the other hand, in FIG. 2B, since P2 is set as the threshold value, a portion with lower received power than that in FIG. 1B is also processed by the control unit as data from the roadside device. As described above, the reception sensitivity can be increased by setting the threshold value, but on the other hand, the ratio of noise is increased.

In the present embodiment, the roadside device performs communication without changing the transmission power. Therefore, the range in which road-to-vehicle communication is established depends on the setting of the reception sensitivity of the communication unit. In addition, the wireless communication capability of other vehicles is unified according to the specification of inter-vehicle communication, and description will be made assuming that the transmission power is constant regardless of the vehicle. Therefore, the range in which vehicle-to-vehicle communication is established basically depends on the setting of the reception sensitivity of the communication unit, and changes depending on the presence or absence of an obstacle.
Note that, under actual traffic conditions, there may be variations in power on the transmission side and differences in capabilities of communication devices on the reception side. Even in such a case, it is possible to handle the setting of reception sensitivity uniformly by absorbing the difference for each apparatus by a coefficient or the like.

(Processing flow)
FIG. 5 is a flowchart showing an outline of the processing of this embodiment. This flow starts from the time when the system is activated by the engine start of the vehicle.
In step S101, the position data acquisition unit receives a signal from a GPS satellite, acquires the current position, and sets it as position data of the host vehicle. And the communication part 102 tries communication with a roadside machine.
In step S102, the control unit determines whether the host vehicle is in a road-to-vehicle communication area where communication with the roadside machine is possible. This determination is made by determining whether or not the data packet distributed by the roadside device can be received based on the trial result of the communication unit. If it is in the road-to-vehicle communication area, the process proceeds to S103, and if not, the process proceeds to S105.
In step S103, the control unit determines whether or not it is the current road-vehicle communication period. This determination is made with reference to the control data included in the header because the data packet of the roadside machine has been received in the previous step. If it is the current road-to-vehicle communication period, proceed to S104.
Otherwise, the process proceeds to S105. At this time, the roadside machine with which communication has been established is specified by an ID or the like.
In step S104, the control unit sets reception sensitivity during road-vehicle communication. This process will be described later.
In step S105, the control unit sets the reception sensitivity at the time of inter-vehicle communication. As for the reception sensitivity at the time of inter-vehicle communication, a default value is determined in advance based on the specification of inter-vehicle communication.
In step S106, the communication unit performs wireless communication according to the reception sensitivity set in S104 or S105. In the case of road-to-vehicle communication, infrastructure information can be obtained from a roadside machine, and information on the vehicle side may be uploaded as necessary. If it is a vehicle-to-vehicle communication period, a communication part communicates between vehicles and exchanges information.
In step S107, the control unit performs various safe driving support operations based on the information obtained in the previous step.
The number and timing of executing the processes of S106 to S107 can be variously set. For example, as indicated by a looped arrow in the flowchart, communication with each circuit side unit may be attempted. Alternatively, communication may be performed a plurality of times with the reception sensitivity once set in S104 and S105, and the process may return to S101 when a predetermined number of times or time has elapsed.

The reception sensitivity setting process for road-to-vehicle communication in step S104 will be further described. FIG. 6 is a flowchart for explaining this process.
In step S201, the control unit refers to the storage unit. The storage means stores the reception sensitivity to be set for each roadside device as an entry. Therefore, the control unit searches for an entry using the ID of the roadside device with which communication has been established as a key (S202).
If there is an entry, the process proceeds to step S204, and the stored value is set as the reception sensitivity. On the other hand, if there is no entry, the process proceeds to step S203, and a default reception sensitivity lower than a predetermined value normally used for inter-vehicle communication is set.

  FIG. 7 shows the result of the reception sensitivity set by the in-vehicle terminal of the host vehicle according to the flowcharts shown in FIGS. FIG. 7A is a diagram illustrating communication periods and reception sensitivities of road-to-vehicle and vehicle-to-vehicle communication when the vehicle is in a road-to-vehicle communication area. Each communication period is time-divided into road-to-vehicle and vehicle-to-vehicle communication periods as in the conventional method. Looking at the reception sensitivity, a relatively low reception sensitivity is set in the road-to-vehicle communication period, and a higher reception sensitivity is set in the vehicle-to-vehicle communication period. On the other hand, when the vehicle is not in the road-vehicle communication area, as shown in FIG. 7B, high reception sensitivity suitable for vehicle-to-vehicle communication is always set.

  As described above, according to the in-vehicle terminal of the present embodiment, the communication unit depends on the position of the vehicle (within a range where communication with the roadside device can be performed) and the communication time zone (communication period between road and vehicle). Reception sensitivity is controlled. As a result, it is possible to improve the use efficiency of communication resources by setting the reception sensitivity according to the communication target while acquiring information necessary for assisting the user's safe driving.

<Modification 1>
The method for setting the reception sensitivity has been described above by giving a specific example. However, when implementing the present invention, a part of the above flow can be changed.
For example, the modification which judges whether it is in a road-to-vehicle communication area by a method different from Embodiment 1 can be considered. In step S102 of the flow of FIG. 5, this determination is made based on whether or not a trial of communication with the roadside device has been established.

Here, a configuration is conceivable in which the in-vehicle terminal stores in the storage means whether or not the point is included in the road-to-vehicle communication area using the position data on the map as a key. And a control part can judge whether it is in road-to-vehicle communication by referring a memory | storage means based on the position data of the own vehicle acquired by S101.

<Modification 2>
Moreover, the case where the own vehicle can communicate with a plurality of roadside devices is conceivable. In other words, this is a case where the vehicle exists in a region where road-to-vehicle communication areas of a plurality of roadside devices overlap. In such a case, there has conventionally been a method of time-sharing the road-to-vehicle communication period. This is shown in FIG. When the two roadside devices 2A and 2B are within the communicable range of the vehicle, the control unit performs time-division of one road-vehicle communication period and performs wireless communication with each roadside device.

  According to the method of Fig.8 (a), the vehicle-mounted terminal can collect the information from a some roadside machine. However, since high reception sensitivity is set in accordance with the vehicle-to-vehicle communication period in both the road-to-vehicle and vehicle-to-vehicle communication periods, the communication performance is excessive during the road-to-vehicle communication period. Further, even when the reception sensitivity suitable for the roadside devices 2A and 2B is different due to the influence of the topography and the shielding object, the reception sensitivity is set uniformly.

In order to deal with this problem, the reception sensitivity in the road-to-vehicle communication period is set as shown in FIG. That is, communication with the roadside devices 2A and 2B is performed in a time division manner, and reception sensitivity suitable for the communication side roadside device is set in each divided period.
As described above, if the road-to-vehicle communication period is time-divided for each roadside device and reception sensitivity suitable for each is set, it is possible to receive any information distributed by each roadside device. As a result, the information base used for the user's safe driving support is increased, and the accuracy of vehicle control and information provision is improved. Furthermore, since the receiving sensitivity during the road-to-vehicle communication period is generally set lower than the vehicle-to-vehicle communication period, it is possible to efficiently use communication resources.

<Embodiment 2>
Another embodiment of the present invention will be described. This embodiment is different from the above-described example in that the reception sensitivity set in the road-to-vehicle communication period by the control unit is determined according to the instruction value distributed from the roadside device.

  The concept of reception sensitivity setting in this embodiment will be described with reference to FIG. The host vehicle 1 is traveling in a direction approaching the roadside machine 2 installed at the intersection. The area 20A is a range in which the roadside device and the vehicle can communicate when the in-vehicle terminal is set with reception sensitivity with the received power PA as a threshold. Hereinafter, this state is also referred to as a state where the reception sensitivity is set as PA. The area 20B is a communicable range when the reception sensitivity is set with the reception power PB lower than the PA as a threshold.

  The in-vehicle terminal first tries to receive a packet from the roadside device 2 as in the first embodiment. It is assumed that the reception sensitivity at this time is PA. Then, when the vehicle enters the area 20A, communication between the two is first established (circled number 1).

In this embodiment, PB is stored in a predetermined data area in the packet as appropriate reception sensitivity when the in-vehicle terminal communicates with the roadside device 2. Therefore, the control unit changes the reception sensitivity from PA to PB. At this point in time, the vehicle side cannot obtain information from the roadside machine. Then, the vehicle travels to the right side of the drawing while periodically trying to communicate with the reception sensitivity PB of the in-vehicle terminal (circle numeral 2).
When the vehicle enters the area 20B, communication with the roadside machine is established (circle numeral 3). Thereafter, the communication unit acquires distribution information with this reception sensitivity.

According to such a safe driving support system, the in-vehicle communication terminal is instructed by the roadside device with an appropriate reception sensitivity, and performs communication with the reception sensitivity lowered according to the reception sensitivity, so that communication resources can be used efficiently. Become. Also, since the road-to-vehicle communication is not performed until the road-to-vehicle communication is established again (area 20B) after changing the reception sensitivity (a period corresponding to the circled number 2), the vehicle-to-vehicle communication takes time during that period. It becomes possible to assign and it becomes easy to acquire the information regarding other vehicles.

  In the present embodiment, the received reception sensitivity PB may be stored in the storage unit of the in-vehicle terminal in association with the roadside device 2. As a result, when the vehicle tries to enter the intersection with the roadside device 2 again, it is possible to improve communication efficiency by setting the reception sensitivity PB from the beginning.

  The method of setting the reception sensitivity according to the instruction from the roadside device as in the present embodiment is effective, for example, when there is no entry corresponding to the roadside device in the storage unit of the in-vehicle terminal. That is, if the default reception sensitivity is PA and the optimum reception sensitivity for the roadside device is PB, the optimum reception sensitivity PB can be set by an instruction from the roadside device, and PB is stored in the storage means. Can be used for subsequent communications.

  The method of the present embodiment is also effective in preventing the road-to-vehicle communication areas of the two roadside machines from overlapping when roadside machines are added as traffic volume increases. That is, when high reception sensitivity before expansion is stored in the storage means of the in-vehicle terminal, road-to-vehicle communication can be performed with appropriate reception sensitivity by lowering the reception sensitivity according to the reception sensitivity change instruction from the roadside device. And the reception sensitivity can be stored again.

<Embodiment 3>
Another embodiment of the present invention will be described. Here, in addition to road-to-vehicle and vehicle-to-vehicle communication, communication is performed between the vehicle and a management device connected via a network, and reception sensitivity information is accumulated in the management device.

  The components of this embodiment are shown in FIG. The in-vehicle terminal of the host vehicle 1 has the same configuration as that described with reference to FIG. 4, and performs road-to-vehicle communication with the roadside device 2. Further, vehicle-to-vehicle communication is performed with other vehicles not shown. The management device 4 is connected to the network by the communication device 401 and transmits / receives information to / from the vehicle. In the reception sensitivity DB 402 of the management device, an entry that associates a roadside device with a reception sensitivity appropriate for the roadside device is stored.

The outline of the processing flow of this embodiment is as shown in FIG.
Steps S301 to S302 are processes performed by the vehicle 1 and correspond to the lower left part of FIG. In S301, the in-vehicle terminal of the vehicle 1 evaluates the communication quality based on the communication result with the actual roadside device 2, and estimates the optimum reception sensitivity. In S <b> 302, the in-vehicle terminal of the vehicle 1 transmits the estimated reception sensitivity to the management device 4.
Steps S303 to S304 are processes performed by the management apparatus 4 and correspond to the upper part of FIG. In S303, the management apparatus stores an entry of the roadside device and the optimum reception sensitivity in the reception sensitivity DB. In S304, the management device distributes the entry of the reception sensitivity DB to the vehicle 3 entering the area of the roadside device 2.
Step S305 is a process performed by the vehicle 3, and corresponds to the lower right portion of FIG. In S305, the vehicle 3 sets the distributed reception sensitivity to the in-vehicle terminal, and uses it in the subsequent road-to-vehicle communication.

Note that the communication unit of the in-vehicle terminal also communicates with the management device in the present embodiment. In that case, you may communicate with the same apparatus as road-to-vehicle / vehicle-to-vehicle communication. Alternatively, a cellular data communication system (such as a mobile phone, PHS, or WiMAX) or a hot spot communication system (such as a wireless LAN) may be used as a communication device suitable for communication with the management apparatus.
Further, when information is distributed from the reception sensitivity DB of the management device to the vehicle, it may be in an on-demand format according to an inquiry from the vehicle, or may be broadcast within a predetermined area. In that case, a data communication channel such as one channel of an in-vehicle radio or a character broadcast of a TV broadcasting system can be used.

A method for setting the reception sensitivity by the in-vehicle terminal of the vehicle 1 will be described. The in-vehicle terminal first sets a default reception sensitivity PA. And when passing the road-to-vehicle communication area of the roadside machine 2, communication quality is analyzed and the optimal receiving sensitivity which should be set is estimated.
This reception sensitivity estimation will be described by taking as an example a case in which signal information is transmitted from the roadside device 2 installed at the intersection to the vehicle. Here, it is assumed that a condition that “a data packet of signal information transmitted from a roadside device can be received 200 m before an intersection” is set as a communication quality standard.

The in-vehicle terminal sets the reception sensitivity PA and periodically tries to communicate with the roadside device. When the communication is established and the data packet can be received, the current position is acquired by the position data acquisition unit. Then, by comparing with map data (not shown) previously stored in a storage device such as a ROM, it is determined how far the current position where communication has been established is from the intersection.
When the distance between the communication establishment point and the intersection is greater than 200 m, the communication quality standard is satisfied even if the reception sensitivity is set to a value lower than PA. Therefore, a calculation based on the distance between the intersection and the communication establishment point is performed to estimate the optimum reception sensitivity and upload to the management device via the communication unit. On the other hand, when the distance between the communication establishment point and the intersection is smaller than 200 m, the reception sensitivity is changed to a value higher than PA and uploaded to the management device.

According to the method as described above, the communication quality is evaluated based on the result of the vehicle actually performing the road-to-vehicle communication. When the management device distributes the reception sensitivity estimated based on the evaluation result to each vehicle, the communication efficiency of each vehicle is improved.
For example, when the safe driving support system has just started, or when a roadside unit has been added, the default setting value can be corrected by acquiring communication quality from the vehicle that actually performed road-to-vehicle communication. Operation according to the actual situation of the area becomes possible. In addition, the reception sensitivity can be updated or fine-tuned in accordance with changes in shielding such as buildings or traffic conditions. In addition, as the operation period becomes longer and information from many vehicles gathers, the estimation accuracy of the reception sensitivity improves.
Even if the reception sensitivity is already stored in the storage means of the in-vehicle terminal, the above-described reception sensitivity estimation method can be finely adjusted to suit the latest situation.

  In each of the above embodiments, communication efficiency is improved by reducing the reception sensitivity of the in-vehicle terminal during the period of road-to-vehicle communication. In combination with this, it is possible to adopt a configuration in which the transmission power on the roadside device side is lowered. For example, when the optimum reception sensitivity uploaded from each vehicle to the management device is significantly lower than the value entered as the optimum value in the current reception sensitivity DB, in addition to lowering the reception sensitivity, the roadside machine It seems that there is no problem even if the transmission power on the side is lowered. By reducing the transmission power in this way, power consumption can be reduced. In addition, it is possible to reduce the size when updating the device.

1: Own vehicle 100: In-vehicle terminal 101: Control unit 102: Communication unit 2: Roadside machine

Claims (11)

A communication unit that performs road-to-vehicle communication with a roadside machine and vehicle-to-vehicle communication with other vehicles,
A control unit that controls whether the communication unit performs road-to-vehicle communication or vehicle-to-vehicle communication, and a control unit that performs control to set reception sensitivity of the communication unit;
The in-vehicle terminal, wherein the control unit sets reception sensitivity so that reception sensitivity for performing vehicle-to-vehicle communication is higher than reception sensitivity for performing communication between the vehicle and the vehicle. The control unit controls the communication unit to repeat switching between road-to-vehicle communication and vehicle-to-vehicle communication when the host vehicle is in a road-to-vehicle communication area where data from a roadside device can be received with the set reception sensitivity. The in-vehicle terminal according to claim 1, wherein the communication unit is controlled to perform only vehicle-to-vehicle communication when the host vehicle is outside the road-to-vehicle communication area. The said control part controls the said communication part by repeating the road-to-vehicle communication period and the vehicle-to-vehicle communication period of predetermined time, respectively, when the own vehicle exists in the road-to-vehicle communication area. The in-vehicle terminal described. The communication unit tries to establish communication with the roadside device,
The in-vehicle terminal according to claim 2 or 3, wherein the control unit determines whether or not the own vehicle is in a road-to-vehicle communication area based on a result of the trial. It further has a position acquisition unit that acquires position information of the host vehicle,
The in-vehicle terminal according to claim 2, wherein the control unit determines whether the host vehicle is in a road-to-vehicle communication area based on the acquired position information. A vehicle comprising the in-vehicle terminal according to any one of claims 1 to 5,
Including a vehicle in the road-to-vehicle communication area and a roadside machine for road-to-vehicle communication,
The roadside device delivers the reception sensitivity that the in-vehicle terminal should set when communicating with the roadside device,
The control unit, after receiving the distributed reception sensitivity, sets the distributed reception sensitivity as the reception sensitivity of road-to-vehicle communication. The in-vehicle terminal further includes a storage unit that stores an entry in which a roadside device and a distributed reception sensitivity are associated with each other,
The said control part controls the said communication part so that road-to-vehicle communication may be performed with the receiving sensitivity of an entry, when communicating with the roadside machine in which the entry exists in the said memory | storage means. Safe driving support system. Including multiple roadside machines,
The control unit of the in-vehicle terminal performs the road-to-vehicle communication with the plurality of roadside devices in a time-sharing manner during the road-to-vehicle communication period, and controls the communication unit to set the reception sensitivity for each roadside device. The safe driving support system according to claim 6 or 7, characterized in that A vehicle comprising the in-vehicle terminal according to any one of claims 1 to 5,
A roadside machine that performs road-to-vehicle communication with vehicles in the road-to-vehicle communication area;
A roadside device, and a management device that stores an entry that associates a reception sensitivity to be set by the in-vehicle terminal when communicating with the roadside device,
The management device distributes the entry to the in-vehicle terminal,
The said control part controls the said communication part to perform the road-vehicle communication with the receiving sensitivity of an entry, when communicating with the roadside machine which received the entry, The safe driving assistance system characterized by the above-mentioned. The in-vehicle terminal estimates the optimum reception sensitivity when communicating with the roadside device, sets the reception sensitivity, and uploads it to the management device.
The safe driving support system according to claim 9, wherein the management device stores the uploaded reception sensitivity as an entry associated with a roadside device. The safe driving support system according to any one of claims 6 to 10, wherein transmission power from a roadside device is reduced during a period in which road-vehicle communication is performed.

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