JP4844511B2 - Vehicle communication system - Google Patents

Description

  The present invention relates to a vehicle communication system with improved communication traffic utilization efficiency.

  The conventional BroadCast type CSMA communication has a drawback that the amount of communication decreases when traffic is concentrated. This is because the number of waiting users increases rapidly due to communication collisions, and the increased waiting users perform communication one after another, resulting in a further increase in collisions and a rapid increase in invalid communication.

  In the case of a vehicle communication system that uses the BroadCast CSMA method to communicate between vehicles and between roadside units and vehicles, road traffic is increased near intersections where vehicles are concentrated, especially in the vicinity of intersections. There is a risk that the communication speed from the terminal may decrease or communication may not be possible. Therefore, in order to prioritize communication from the roadside machine, time synchronization communication is performed to provide a vehicle (on-board machine) transmission prohibition period during which only the roadside machine can transmit, or to limit transmission according to the communication control information from the roadside machine. ing.

However, this method is effective in the communication area of roadside units, but it cannot be controlled from roadside units for vehicles outside the area, so it is effective for outgoing calls from vehicles outside the area. There is no. Therefore, the vehicle that has received the communication control information in the area is to copy and transmit this communication control information when transmitting application data (see, for example, Patent Document 1).
JP 2004-304655 A

  However, the above method has a problem that, for example, when there is no application data for transmitting traffic information, communication control information for controlling communication is not transferred. In addition, when the communication control information received from the roadside machine is transferred to another vehicle, it is transferred every predetermined distance or every predetermined time, so communication control is ensured when the radio wave condition is bad. Information could not be transferred.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a vehicle communication system that can efficiently and accurately transmit information from a roadside machine to a vehicle.

  The vehicle communication system according to claim 1, which has been made in order to solve such a problem (1: In this column, in order to facilitate understanding of the invention, “the best mode for carrying out the invention” is necessary as necessary. The reference numerals used in the columns are attached, but it does not mean that the claims are limited by the reference numerals.) Are receiving means (20), transfer means (40, 50), and radio wave intensity detection means (30). And a transfer frequency control means (40).

Receiving means (20) is installed in the roadside, roadside device for transmitting information including the communication control information (10), or, receiving information from the first other vehicle for transmitting information including the communication control information (60) To do. The transfer means (40, 50) is transferred to the first other vehicle (60) other than the second other vehicle by extracting the communication control information from the information received by the receiving means (20) (60), The radio wave intensity detection means (30) detects the transmission radio wave intensity of the roadside machine (10).

The transfer frequency control means (40) determines the frequency at which the communication control information is transferred to the second other vehicle (60) by the transfer means (40, 50) according to the radio wave intensity detected by the radio wave intensity detection means (30). Control.
In such a vehicle communication system (1), information transmitted from the roadside machine (10) installed on the roadside or the first other vehicle (60) that transmits information including communication control information is received by the receiving means (20 The communication control information is extracted from the received information. Then, the extracted communication control information is transferred to the second other vehicle (60). Furthermore, the transfer frequency at the time of transfer is controlled according to the radio field intensity of the roadside machine (10).

Usually, if the radio field intensity from the roadside machine (10) or the first other vehicle (60) decreases, the possibility that radio waves cannot be received and information cannot be transferred increases. Therefore, for example, when the radio wave intensity is reduced, if the transfer frequency of information is increased, the transfer frequency is increased even if the radio wave intensity is low, so that the information can be transferred to the second other vehicle (60).

Conversely, when the radio field intensity is high, the possibility of receiving radio waves is high, and thus the possibility of transmitting information is high. Therefore, when the radio field intensity is high, the information can be transferred to the second other vehicle (60) even if the information transfer frequency is reduced.

Thus, if the transfer frequency of transferring the communication control information to the second other vehicle (60) is controlled in accordance with the radio field intensity from the roadside machine (10), the communication control information is efficiently and reliably transmitted . It can be transmitted to two other vehicles (60).

By the way, for example, when transferring traffic information or information for improving the convenience of the vehicle occupant to the second other vehicle (60), communication control information for performing communication control is transmitted together with the information. However, such information is transmitted under the control of application software executed by an in-vehicle electronic device such as a car navigation device.

Therefore, if the application software is not executed, the communication control information is not transferred to the second other vehicle (60). Therefore, as described in claim 2, the transfer frequency control means (40) transfers the communication control information to the second other vehicle (60) at a predetermined frequency independent of the frequency of transferring information other than the communication control information . ).

In this way, the communication control information is transmitted at a frequency independent of the transmission frequency controlled by the application software. Therefore, even when the application software is not operating, the communication control information is reliably transmitted to the second other vehicle (60 ).

  By the way, in order to transfer information by the transfer means (40, 50), it becomes a problem whether the information is received by the receiving means (20). That is, it is necessary to receive information by the receiving means (20), extract communication information from the received information, and transfer it.

  Therefore, when the radio field intensity detection means (30) receives the transmission radio field intensity of the roadside machine (10), the radio field intensity detection means (30) is provided from the roadside machine (10) as described in claim 3. If the information is received by the receiving means (20), the transmission radio wave intensity can be detected. When the information is received by the receiving means (20), the radio wave intensity can be detected.

In other words, if the receiving means (20) knows the radio wave intensity when the information is received, it can be known whether the receiving means (20) has received the information, so the communication control is efficiently performed according to the radio wave intensity. Information can be transferred to the second other vehicle (60).
Further, as described in claim 4, when the radio field intensity detected by the radio field intensity detecting unit (30) decreases, the transfer frequency control unit (40) transmits the communication control information by the transfer unit (40, 50). Control may be performed so that the frequency of transfer to the second other vehicle (60) increases.
In this way, even if the radio field intensity is small, the possibility that information can be transferred is very high compared to the conventional method. Therefore, information can be accurately transferred to the second other vehicle (60).
Conversely, when the radio field intensity is high, there is a high possibility that radio waves can be received, and thus the possibility that information can be transferred is increased. Therefore, as described in claim 5, when the radio wave intensity detected by the radio wave intensity detecting means (30) increases, the transfer frequency control means (40) sends the communication control information by the transfer means (40, 50). If control is performed so that the frequency of transfer to the second other vehicle (60) is low, the information can be transferred to the second other vehicle (60) with the frequency of information transfer being reduced.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. The embodiment of the present invention is not limited to the following embodiment, and can take various forms as long as they belong to the technical scope of the present invention.

  FIG. 1 is a block diagram showing a schematic configuration of the vehicle communication system 1. As shown in FIG. 1, the vehicle communication system 1 includes an in-vehicle device 5 and a roadside device 10, and the in-vehicle device 5 includes a receiver 20, a radio wave intensity detector 30, a control unit 40, and a transmitter 50.

  The roadside machine 10 is installed on the roadside and transmits information including communication control information to the vehicle 7, and includes a signal processing unit, a transmitter, an antenna, or the like (not shown). The roadside device 10 is installed at a traffic light or the like provided at an intersection as shown in FIG. 3, and transmits information with transmission power capable of transmitting information from the intersection to a predetermined range as shown in FIG.

  The communication method of the roadside device 10 is a BroadCast type CSMA / CA (Carieer Sense Multiple Access / Collision Avoidance) method. This method is a communication method that checks if there is a host (vehicle, etc.) that is currently communicating by trying to receive once before starting communication. Multiple terminals share the same line, If other people are not communicating, start their own communication. Further, when a plurality of communications are performed simultaneously, it is detected, and after waiting for a random time, the transmission procedure is performed again.

  This communication system has a drawback that the amount of communication is reduced because many communication collisions occur when traffic is concentrated. That is, in the case of a vehicle communication system, communication traffic increases in the vicinity of intersections where vehicles are concentrated, and there is a possibility that the communication speed from a roadside device installed in the vicinity of the intersection may be slow or communication may not be possible.

  The receiver 20 receives information from the roadside machine 10, and includes an antenna that receives radio waves from the roadside machine 10, a demodulator that demodulates radio waves received by the antenna, and an A / A that converts the demodulated signals into digital data. D converter etc. are provided.

The radio wave intensity detector 30 detects the transmission radio wave intensity of the roadside machine 10 and detects the instantaneous intensity of the radiowave transmission of the roadside machine 10 when received by the receiver 20.
The control unit 40 extracts communication control information from the information received by the receiver 20, and uses the extracted communication control information for the other vehicle 60 via the transmitter 50 according to the radio wave intensity detected by the radio wave intensity detector 30. Is controlled by a CPU, a ROM, a RAM, and an I / O (not shown).

  In the control unit 40, communication control information is extracted from various information such as traffic information and entertainment information transmitted from the roadside device 10, and extracted at a predetermined frequency independent of the frequency of transmitting information such as traffic information. The communication control information thus transmitted is transferred to the other vehicle 60 via the transmitter 50.

  That is, when traffic information such as traffic jam information or information that improves the convenience of a vehicle occupant is transferred by a VICS or car navigation device, communication control information for performing communication control is transmitted together with the information. However, the information is controlled and transmitted by application software executed by an in-vehicle electronic device such as a car navigation device, but the control unit 40 differs from the information transfer frequency in the device that executes the application software. The communication control information is transferred to the other vehicle 60 at an independent transfer frequency.

The transmitter 50 performs D / A conversion on communication control information, which is digital data, using a D / A converter (not shown), then modulates it using a modulator (not shown) and transmits it to the other vehicle 60 from the antenna. )
Next, the content of the control process executed in the control unit 40 will be described based on FIG. FIG. 2 is a flowchart showing the flow of the control process.

  In the control process, as shown in FIG. 2, information is acquired from the receiver 20 in S100, and in subsequent S105, it is determined whether or not the information acquired in S100 is valid information.

  That is, it is determined whether or not the information acquired in S100 is information used in application software, or whether or not it is simply noise. If the information is valid (S105: Yes), the process proceeds to S110. If the information is not valid (S105: No), the process returns to S100, and information reception is repeated.

  In subsequent S110, communication control information is acquired from the information acquired in S100. The communication control information varies depending on the application software, but includes an ID indicating the roadside device of the communication partner, a header indicating the length of information to be communicated, and the number of transfers.

  In subsequent S115, the radio wave intensity is acquired from the radio wave intensity detector 30. That is, the radio field intensity when valid information is acquired in S100 is acquired. In subsequent S120, it is determined whether or not the radio wave intensity acquired in S110 is equal to or greater than a predetermined value.

  When the radio wave intensity is smaller than the predetermined value (S120: No), the process proceeds to S125, and after the transmission interval time is set short, the process proceeds to S135. On the other hand, when the field intensity is equal to or higher than the predetermined value (S120: Yes), the process proceeds to S130, and after the transmission interval time is set longer, the process proceeds to S135.

Thus, in S125 and S130, the transmission frequency of the communication control information can be controlled by changing the time of the transmission interval.
In subsequent S135, it is determined whether or not a predetermined time has elapsed since the transmission of the previous communication control information. When the predetermined time has elapsed (S135: Yes), the process proceeds to S140. When the predetermined time has not elapsed (S135: No), the process waits until the predetermined time elapses.

  In S140, the communication control information acquired in S110 is transmitted from the transmitter 50 to the other vehicle 60. Then, after the transmission is completed, the process is returned to S100, and the control process is repeated.

(Features of the vehicle communication system 1)
Such characteristics of the vehicle communication system 1 will be described with reference to FIGS. 3, 4, and 5. FIG. 3 is a diagram showing the state of communication frequency when the roadside device 10 is installed near the intersection, and FIG. 4 is the state of communication frequency when there is a large vehicle near the intersection where the roadside device 10 is installed. FIG. FIG. 5 is a diagram conceptually showing how the communication control information is transferred between the roadside machine 10 and the plurality of vehicles 7.

  In the vehicle communication system 1, information transmitted from the roadside device 10 is received by the receiver 20, and communication control information is extracted from the received information. Then, the extracted communication control information is transferred to the other vehicle 60. And the transfer frequency at the time of transfer is controlled according to the radio wave intensity when information is received from the roadside device 10.

  Usually, as shown in FIG. 3 (a), when the distance from the roadside machine 10 becomes large, or as shown in FIG. In such a case, since the radio wave intensity from the roadside device 10 becomes small, there is a high possibility that radio waves cannot be received and information cannot be transferred.

  At this time, in the conventional method, as shown in FIGS. 3B and 4B, the information transfer frequency from the vehicle 7 to the other vehicle 60 is constant. On the other hand, in the vehicle communication system 1, when the radio field intensity decreases, the transfer frequency of information transferred from the vehicle 7 to the other vehicle 60 increases as shown in FIGS. 3 (b) and 4 (b). Therefore, even if the radio field intensity is small, the possibility of transferring information is very high compared to the conventional method. Therefore, information can be accurately transferred to the other vehicle 60.

  Further, when the radio wave intensity is high, the possibility of receiving radio waves is high, and thus the possibility that information can be transferred is increased. Therefore, when the radio field intensity is high, the information can be transferred to the other vehicle 60 with a low information transfer frequency as shown in FIGS. 3 (b) and 4 (b).

  As described above, since the transfer frequency of transferring the communication control information to the other vehicle 60 is controlled according to the radio wave intensity from the roadside machine 10, the communication control information is transmitted to the roadside machine as shown in FIG. The communication control information transmitted from 10 to the vehicle 7 is sequentially transferred to a plurality of other vehicles 60. Therefore, the communication control information can be transmitted to the other vehicle 60 efficiently and reliably.

  Moreover, when transferring traffic information or information that improves the convenience of the vehicle occupant to the other vehicle 60, communication control information for performing communication control is transmitted together with the information. However, such information is transmitted under the control of application software executed by an in-vehicle electronic device such as a car navigation device.

  Therefore, in the conventional method, if the application software is not executed, the communication control information is not transferred to the other vehicle 60. However, in the vehicle communication system 1, the communication control information is transmitted at a predetermined frequency independent of the information transfer frequency. Transferred to another vehicle 60.

Therefore, since the communication control information is transmitted at a frequency independent of the transmission frequency controlled by the application software, the communication control information can be reliably transmitted to the other vehicle 60.
Moreover, since the transmission radio wave intensity when the information from the roadside machine 10 is received is detected, the communication control information can be efficiently transferred to the other vehicle 60 according to the radio wave intensity.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, A various aspect can be taken.

  For example, in the above embodiment, the communication method between the roadside device 10, the receiver 20, and the transmitter 50 is the CSMA / CA method, but the communication method may be a CSMA / CD method.

1 is a block diagram showing a schematic configuration of a vehicle communication system 1. FIG. It is a flowchart which shows the flow of a process of a control process. It is a figure which shows the condition of the communication frequency at the time of installing the roadside machine 10 in the intersection vicinity. It is a figure which shows the condition of the communication frequency in case a large vehicle exists in the vicinity of the intersection where the roadside machine 10 was installed. It is the figure which showed notionally the mode that communication control information is transferred between the roadside machine 10 and the some vehicles 7. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle communication system, 5 ... Onboard equipment, 7 ... Vehicle, 10 ... Roadside machine, 20 ... Receiver, 30 ... Radio wave intensity detector, 40 ... Control part, 50 ... Transmitter, 60 ... Other vehicle.

Claims (5)

A receiving unit that is installed on the roadside and receives information from a roadside machine that transmits information including communication control information , or a first other vehicle that transmits information including communication control information ;
Transfer means extracts the communication control information from the received information, and transfers to the second other vehicle other than the first of the other vehicle by the receiving means,
Radio field intensity detecting means for detecting the transmission radio field intensity of the roadside machine;
Transfer frequency control means for controlling the frequency of transferring the communication control information to the second other vehicle by the transfer means according to the radio wave intensity detected by the radio wave intensity detection means;
A vehicle communication system comprising: The vehicle communication system according to claim 1,
The transfer frequency control means includes
A vehicle communication system, wherein the communication control information is transferred to the second other vehicle at a predetermined frequency independent of a frequency of transferring information other than the communication control information. In the vehicle communication system according to claim 1 or 2,
The radio wave intensity detecting means includes
A vehicle communication system, wherein a transmission radio wave intensity is detected when information from the roadside device is received by the receiving means. In the vehicle communication system according to any one of claims 1 to 3,
The transfer frequency control means includes
A vehicle communication system, wherein when the radio field intensity detected by the radio field intensity detection means becomes small, the transfer means controls the frequency of transferring the communication control information to the second other vehicle. . In the vehicle communication system according to any one of claims 1 to 4,
The transfer frequency control means includes
A vehicle communication system, wherein when the radio field intensity detected by the radio field intensity detection means increases, the transfer means controls so as to reduce the frequency of transferring the communication control information to the second other vehicle. .

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