JP2008092197A - Vehicle-to-vehicle communication system, and vehicle and repeater used in the vehicle-to-vehicle communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the probability that a repeater receives a packet from each vehicle more than in the conventional practice. <P>SOLUTION: Each vehicle 300 comprises: a packet receiving part 325 for receiving a first transmission packet 220a transmitted from a repeater 200; a vehicle information generating part 305 for generating vehicle information 305a about one's own vehicle; a packet generating part 310 for generating a second packet 310a to be a base of a second transmission packet 315a to be transmitted to the repeater on the basis of vehicle information generated by the vehicle information generating part; a traveling direction detecting part 335 for detecting a traveling direction of the one's own vehicle; a transmission start time determining part 320 for determining a transmission start time on the basis of the traveling direction of the one's own vehicle detected by the traveling direction detecting part by defining a time between a receiving time of the first transmission packet and a transmission start time of the second transmission packet 315a as a transmission start time; and a packet transmitting part 315 for generating a second transmission packet by performing predetermined processing of the second packet on the basis of the transmission start time determined by the transmission start time determining part and transmitting the second transmission packet 315a to the repeater. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a vehicle-to-vehicle communication system that performs communication between vehicles by wireless communication via a repeater, and a vehicle and a repeater used in the vehicle-to-vehicle communication system.

  2. Description of the Related Art Conventionally, there is an inter-vehicle communication system that performs communication between vehicles (hereinafter referred to as “between vehicles” or “between vehicles”) by wireless communication via a repeater (for example, Patent Document 1).

  The inter-vehicle communication system is used for, for example, an application for preventing an encounter accident at an intersection. In this application, each vehicle generates a packet based on the vehicle information at regular intervals and sends the generated packet to the other vehicle in order to notify the other vehicle of vehicle information such as the position of the own vehicle. , Exchanging information between vehicles.

  This inter-vehicle communication system may use, for example, a CSMA (Carrier Sense Multiple Access) method for packet transmission. The “CSMA method” is a method in which each vehicle senses a carrier to determine the channel usage status before transmitting a packet, and determines whether to transmit a packet or make a matching transmission according to the channel usage status. is there. In this CSMA scheme, each vehicle transmits a packet if the channel is idle, while each vehicle repeats the packet transmission until the channel becomes idle if the channel is busy. Sense your career.

By the way, in a vehicle-to-vehicle communication system, a state where communication cannot be performed directly between vehicles may occur due to the influence of a building or the like. Such a state occurs particularly at an intersection and around the intersection (hereinafter referred to as “intersection etc.”). Therefore, in the inter-vehicle communication system, a repeater is installed at an intersection or the like, and the repeater transmits packets received from each vehicle to other vehicles, thereby enabling information exchange even between vehicles that cannot communicate directly. .
Japanese Patent Laid-Open No. 2001-45013 (FIG. 1)

  However, the inter-vehicle communication system using the conventional repeater has the following problems.

  That is, between vehicles that cannot communicate directly with each other, the vehicles are in a so-called hidden terminal relationship. Each vehicle having such a relationship, when only sensing the carrier, starts the timing of sensing the carrier of the other vehicle (hereinafter referred to as “carrier sense start timing”) and the transmission of the packet of the other vehicle. The timing (hereinafter referred to as “packet transmission start timing”) cannot be monitored. Therefore, in each vehicle, the start timing of the carrier sense of the own vehicle may overlap with the timing of the other vehicle, or the start timing of packet transmission of the own vehicle may overlap with the timing of the other vehicle. In such a case, the conventional inter-vehicle communication system may not be able to receive a packet from each vehicle when the packet transmission start timing overlaps between the vehicles.

  In order to solve such a problem, the present invention starts the packet transmission based on the parameter determined by the relative relationship between the repeater and the own vehicle, thereby determining the packet transmission start timing. An object of the present invention is to provide a vehicle-to-vehicle communication system that can prevent overlap.

  Further, according to the present invention, each vehicle determines a carrier sense start time based on a parameter determined by a relative relationship between the repeater and the host vehicle, and senses a carrier according to the carrier sense start time. Another object of the present invention is to provide an inter-vehicle communication system capable of preventing overlapping of carrier sense timings by starting packet transmission when a channel is in an idle state.

  In order to solve the above-described problem, the inter-vehicle communication system according to the first invention includes a repeater and one or more vehicles, and the repeater and each vehicle have the following configurations.

  The repeater is predetermined for each fixed period, based on arbitrary information, the packet generation unit on the repeater side that generates the first packet and the first packet generated by the packet generation unit on the repeater side Packet transmission means on the repeater side that generates the first transmission packet by performing processing and transmits the first transmission packet to each vehicle, and packet reception on the relay side that receives the second transmission packet transmitted from each vehicle Means.

  On the other hand, each vehicle has a vehicle side packet receiving means for receiving the first transmission packet transmitted from the repeater, a vehicle information generating means for generating vehicle information relating to the host vehicle, and a vehicle generated by the vehicle information generating means. Based on the information, the reception time of the first transmission packet received by the vehicle-side packet generation means for generating the second packet, the traveling direction detection means for detecting the traveling direction of the host vehicle, and the vehicle-side packet reception means A transmission start time determining means for determining a transmission start time based on the traveling direction of the host vehicle detected by the traveling direction detecting means, with the time from the start of transmission of the second transmission packet as the transmission start time. Based on the transmission start time determined by the transmission start time determining means, a second transmission packet is generated by performing a predetermined process on the second packet; And a packet transmitting means for transmitting a second transmission packet to the repeater. The packet transmission means performs a predetermined process on the second packet in advance to generate a second transmission packet, and performs the second transmission based on the transmission start time determined by the transmission start time determination means. The packet may be transmitted to the repeater.

  The inter-vehicle communication system according to the second invention includes a repeater and one or more vehicles, and each of the repeater and each vehicle has the following configuration.

  The repeater is configured to generate a first packet on the basis of arbitrary information including position information of the repeater and a packet generator generated on the repeater side by a packet generation unit on the repeater side, at regular intervals. Predetermined processing is performed on one packet to generate a first transmission packet, a packet transmission means on the relay side that transmits the first transmission packet to each vehicle, and a second transmission packet transmitted from each vehicle is received Packet receiving means on the repeater side.

  On the other hand, each vehicle has a vehicle side packet receiving means for receiving the first transmission packet transmitted from the repeater, a vehicle information generating means for generating vehicle information relating to the host vehicle, and a vehicle generated by the vehicle information generating means. Included in the first transmission packet received by the vehicle-side packet generating means for generating the second packet based on the information, the vehicle position detecting means for detecting the position of the host vehicle, and the vehicle-side packet receiving means. Distance calculating means for calculating the relative distance from the repeater to the own vehicle based on the position information of the repeater and the position of the own vehicle detected by the vehicle position detecting means, and from the reception time of the first transmission packet (2) The transmission start time is determined based on the relative distance detected by the distance calculation means, with the time until the transmission start time of the transmission packet as the transmission start time. Based on the transmission start time determined by the start time determination means and the transmission start time determination means, a predetermined process is performed on the second packet to generate a second transmission packet, and the second transmission packet is transmitted to the repeater. Vehicle-side packet transmitting means for transmitting. The packet transmission means performs a predetermined process on the second packet in advance to generate a second transmission packet, and performs the second transmission based on the transmission start time determined by the transmission start time determination means. The packet may be transmitted to the repeater.

  In 1st invention, each vehicle determines the transmission start time of a 2nd transmission packet based on the traveling direction of the own vehicle. Here, the traveling direction of the host vehicle is a parameter determined by the relative relationship between the repeater and the vehicle. Therefore, the transmission start time is determined by the relative relationship between the repeater and the vehicle.

  Such a transmission start time has a different value between vehicles having different traveling directions. Therefore, according to 1st invention, the transmission start time of a 2nd transmission packet can be varied between vehicles from which a traveling direction differs. Therefore, it is possible to prevent overlapping of packet transmission timings between vehicles.

  Further, according to the first invention, each vehicle determines a carrier sense start time based on the traveling direction of the host vehicle, senses a carrier according to the carrier sense start time, and the channel is in an idle state. At this time, the transmission start time of the second transmission packet may be determined. As a result, the first invention can also prevent overlapping of carrier sense timings.

  Therefore, according to 1st invention, the case where a carrier is simultaneously sensed and the case where a packet is transmitted simultaneously can be reduced between vehicles in the relationship of the hidden terminal which cannot communicate directly. As a result, according to the first aspect, it is possible to reduce the probability that the repeater will not be able to receive packets from each vehicle as compared to the prior art.

  In 2nd invention, each vehicle determines the transmission start time of a 2nd transmission packet based on the relative distance from a repeater to the own vehicle. Here, the relative distance is a parameter determined by the relative relationship between the repeater and the vehicle. Therefore, the transmission start time is determined by the relative relationship between the repeater and the vehicle.

  Such a transmission start time has a different value between vehicles having different relative distances from the repeater. Therefore, according to 2nd invention, the transmission start time of a 2nd transmission packet can be varied between vehicles from which the relative distance from a repeater differs. Therefore, it is possible to prevent overlapping of packet transmission timings between vehicles.

  Furthermore, according to the second invention, each vehicle determines the carrier sense start time based on the relative distance from the repeater to the host vehicle, senses the carrier according to the carrier sense start time, When the channel is in an idle state, the transmission start time of the second transmission packet may be determined. As a result, the second invention can also prevent overlapping of carrier sense timings.

  Therefore, according to the second invention, as in the first invention, between the vehicles in the relationship of the hidden terminal that cannot communicate directly, the case where the carrier is simultaneously sensed or the case where the packet is simultaneously transmitted is Can also be reduced. As a result, according to the second invention, similarly to the first invention, it is possible to reduce the probability that the repeater will not be able to receive packets from each vehicle as compared to the prior art.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, common components and similar components are denoted by the same reference numerals, and redundant description thereof is omitted.

[First Embodiment]
Hereinafter, the first embodiment will be described in the order of “configuration of inter-vehicle communication system”, “determination method of transmission start time of second transmission packet”, and “operation of inter-vehicle communication system”.

<Configuration of inter-vehicle communication system>
Hereinafter, the configuration of the first embodiment to which the present invention is applied will be described with reference to FIG. FIG. 1 is a block diagram for explaining a configuration of a repeater and a vehicle in a vehicle-to-vehicle communication system according to the first embodiment.

  An inter-vehicle communication system 100 to which the present invention is applied includes a repeater 200 and an in-vehicle computer (hereinafter simply referred to as “vehicle”) 300 mounted on each vehicle. Although only one vehicle 300 is shown in FIG. 1, there are actually a plurality of vehicles 300.

  First, the configuration of the repeater 200 will be described.

  The repeater 200 receives a main operation unit 202 configured by a CPU, a main storage unit 204 configured by a RAM, a register, and the like, a transmission antenna 245 that transmits a first transmission packet 220a, and a second transmission packet 315a. An antenna 250 is included. The first transmission packet 220a is information transmitted from the repeater 200 to each vehicle 300. The second transmission packet 315a is information transmitted from each vehicle 300 to the repeater 200.

  The main calculation unit 202 of the repeater 200 is a functional unit that performs various calculations. The main arithmetic unit 202 is formed on a single chip together with the main storage unit 204. The main calculation unit 202 includes a timer 205, a reference signal information generation unit 210, a packet generation unit 215, a packet transmission unit 220, a carrier sense unit 225, a packet reception unit 230, and a vehicle information extraction unit 235. In FIG. 1, each component of the main arithmetic unit 202 is depicted so as to directly output various signals and data to the subsequent components. However, in practice, each component outputs various signals and data to the subsequent components via the main storage unit 204. That is, the former stage component stores various signals and data in the main storage unit 204, and the subsequent stage component reads the signal and data from the main storage unit 204. A series of these operations is defined by the program. Hereinafter, description of this point is omitted.

  The timer 205 is a functional unit that measures time.

  The reference signal information generation unit 210 is a functional unit that generates reference signal information 210a. The reference signal information 210a is information for synchronizing the operation timing between the devices constituting the inter-vehicle communication system 100, that is, between the repeater 200 and one or more vehicles 300. The reference signal information generation unit 210, for example, from current time information representing the current time, measurement time information representing the time measured at regular intervals by the timer 205 of the repeater 200, and the reception time of the first transmission packet 220a. The reference signal information 210a can be used as criterion signal information 210a, which is a criterion for determining the time until the time to start transmission of the second transmission packet 315a (hereinafter referred to as “transmission start time”).

  In this embodiment, the reference signal information generation unit 210 uses information combining measurement time information and determination reference information as the reference signal information 210a.

  In this embodiment, the determination criterion information includes “information in which the traveling direction of the vehicle 300 is associated with the transmission mode start time of the second transmission packet 315a” (see FIG. 2A), which will be described later. And “transmission mode time” (see FIG. 2C). Here, “transmission mode” means a state in which a signal can be transmitted to the outside. The “transmission mode start time” means the time from the reference time (hereinafter referred to as “reference time”) to the start of the transmission mode. In this embodiment, the “transmission mode start time of the second transmission packet 315a” is a time at which each vehicle 300 receives the first transmission packet 220a from the repeater 200 as a reference time, and from this reference time, It is time to start the transmission mode. The “transmission mode time” means the time during the transmission mode.

  The packet generation unit 215 is a functional unit that generates the first packet 215a representing the arbitrary information based on the arbitrary information. In this embodiment, the reference signal information 210a generated by the reference signal information generation unit 210 is used as arbitrary information.

  The packet transmission unit 220 performs a predetermined process on the first packet 215a generated by the packet generation unit 215 to generate a first transmission packet 220a, and transmits the first transmission packet 220a to each vehicle 300. Means. In this embodiment, a process such as modulation is performed as a predetermined process.

  The carrier sense unit 225 is a functional unit that determines the channel usage status.

  The packet receiving unit 230 is a functional unit that receives the second transmission packet 315a transmitted from each vehicle 300 and generates the first reception packet 230a based on the received second transmission packet 315a. Note that the second transmission packet 315a and the first reception packet 230a each include vehicle information 305a of the vehicle 300 that transmitted the second transmission packet 315a.

  The vehicle information extraction unit 235 is a functional unit that extracts the vehicle information 305 a of the vehicle 300 from the first reception packet 230 a generated by the packet reception unit 230.

  The main storage unit 204 of the repeater 200 is a storage unit that stores various types of information. The main storage unit 204 is provided with a storage area for storing various programs and data according to operation. One of them is a vehicle information storage unit 240.

  The vehicle information storage unit 240 is a storage area provided for storing the vehicle information 305 a of the vehicle 300 extracted by the vehicle information extraction unit 235.

  In addition, the vehicle information 305a of the vehicle 300 stored in the vehicle information storage unit 240 is different from the other vehicle, that is, the vehicle 300 that transmitted the second transmission packet 315a including the vehicle information 305a at regular intervals. Sent to the vehicle.

  Next, the configuration of the vehicle 300 will be described.

  The vehicle 300 includes a main calculation unit 302 configured by a CPU, a main storage unit 304 configured by a RAM, a register, and the like, a transmission antenna 345 that transmits a second transmission packet 315a, and a reception antenna that receives a first transmission packet 220a. 350.

  The main calculation unit 302 of the vehicle 300 is a functional unit that performs various calculations. The main arithmetic unit 302 is formed on a single chip together with the main storage unit 304. The main calculation unit 302 includes a vehicle information generation unit 305, a packet generation unit 310, a packet transmission unit 315, a transmission start time determination unit 320, a packet reception unit 325, a reference signal information extraction unit 330, a traveling direction detection unit 335, and a vehicle. A position detection unit 340 is provided. In FIG. 1, each component of the main arithmetic unit 302 is depicted so as to directly output various signals and data to the subsequent components. However, in practice, each component outputs various signals and data to the subsequent component via the main storage unit 304. That is, the former stage component stores various signals and data in the main storage unit 304, and the subsequent stage component reads the signal and data from the main storage unit 304. A series of these operations is defined by the program. Hereinafter, description of this point is omitted. The main calculation unit 302 has a timer (not shown), and each component of the main calculation unit 302 operates according to the time measured by the timer (not shown).

  The vehicle information generation unit 305 is a functional unit that generates vehicle information 305a related to the host vehicle.

  The packet generation unit 310 is a functional unit that generates a second packet 310 a representing the vehicle information 305 a based on the vehicle information 305 a generated by the vehicle information generation unit 305.

  The packet transmission unit 315 performs a predetermined process on the second packet 310a generated by the packet generation unit 310 to generate a second transmission packet 315a, and transmits the second transmission packet 315a to the repeater 200. Means. In this embodiment, as predetermined processing, for example, processing such as modulation by a plurality of code sequences and conversion from a digital signal to an analog signal is performed.

  The transmission start time determination unit 320 is a functional unit that determines the transmission start time of the second transmission packet 315a. In this embodiment, the “transmission start time” is the time from the reception time of the first transmission packet 220a to the time when transmission of the second transmission packet 315a is started. Details of the method for determining the transmission start time will be described in the section “Method for determining the transmission start time of the second transmission packet” described later.

  In this embodiment, the transmission start time determination unit 320 includes a carrier sense unit 322 and a carrier sense start timing determination unit 324. The carrier sense unit 322 is a functional unit that determines the channel usage status. On the other hand, the carrier sense start timing determination unit 324 is a functional unit that determines the start timing of carrier sense. The carrier sense unit 322 and the carrier sense start timing determination unit 324 cooperate to sense a carrier at the later-described carrier sense start timing and start transmission of the second transmission packet 315a when the channel is in an idle state. The signal (hereinafter referred to as “transmission start signal”) 320a is output to the packet transmission unit 315, thereby determining the transmission start time of the second transmission packet 315a. Note that the carrier sense unit 322 and the carrier sense start timing determination unit 324 are not essential components, but are provided because the transmission of the second transmission packet 315a can be prevented when the channel is busy. preferable.

  The packet receiving unit 325 is a functional unit that receives the first transmission packet 220a transmitted from the repeater 200 and generates the second reception packet 325a based on the received first transmission packet 220a. Each of the first transmission packet 220a and the second reception packet 325a includes reference signal information 210a generated by the repeater 200 that has transmitted the first transmission packet 220a.

  The reference signal information extraction unit 330 is a functional unit that extracts the reference signal information 210 a generated by the reference signal information generation unit 210 of the repeater 200 from the second received packet 325 a generated by the packet reception unit 325.

  The traveling direction detection unit 335 is a functional unit that detects the traveling direction of the host vehicle using a known method for detecting the traveling direction. As a method of detecting the traveling direction, for example, a method of detecting using an azimuth angle sensor or a geomagnetic sensor, and various other methods are known, and any of these known methods can be adopted. Is omitted.

  The vehicle position detection unit 340 is a functional unit that detects the position of the host vehicle using a known method for detecting a position. As for the method of detecting the position, for example, a method of detecting using a radio wave emitted from a position beacon and various other methods are known, and any of these known methods can be adopted. Omitted.

  The main storage unit 304 of the vehicle 300 is a storage unit that stores various types of information. The main storage unit 304 is provided with a storage area for storing various programs and data according to operation.

<Determination Method of Transmission Start Time of Second Transmission Packet in First Embodiment>
Hereinafter, a method for determining the transmission start time of the second transmission packet 315a in this embodiment will be described with reference to FIG. 1 and FIGS. In this embodiment, the transmission start time of second transmission packet 315a is determined based on the traveling direction of vehicle 300.

  FIGS. 2A to 2C are diagrams for explaining a method of determining the transmission start time of the second transmission packet 315a. FIG. 2A shows information in which the traveling direction of the vehicle 300 is associated with the transmission mode start time of the second transmission packet 315a. FIG. 2B shows a range in the traveling direction of the vehicle 300. FIG. 2C shows the relationship between the traveling direction of the vehicle 300 and the transmission start time of the second transmission packet 315a.

  The repeater 200 stores “information that associates the traveling direction of the vehicle 300 with the transmission mode start time of the second transmission packet 315a” (see FIG. 2A) in the main storage unit 204. This “information in which the traveling direction of the vehicle 300 is associated with the transmission mode start time of the second transmission packet 315a” is set in advance according to the operation. In the example shown in FIG. 2A, the traveling direction of the vehicle 300 is divided into four ranges Da to Dd. In this embodiment, the range Da is a range of 90 ° from the northwest to the northeast as shown in FIG. Similarly, the range Db is a range of 90 ° from northeast to southeast, the range Dc is a range of 90 ° from southeast to southwest, and the range Dd is 90 ° from southwest to northwest. The range of the range. The transmission mode start times Ta to Td shown in FIG. 2A are set in advance to different values corresponding to the traveling directions Da to Dd of the vehicle 300.

  Further, the repeater 200 stores the value t (see FIG. 2C) as the “transmission mode time” in the main storage unit 204. The value “t” of “transmission mode time” is set in advance according to the operation. In this embodiment, the “transmission mode time” value t is set as a fixed value.

  The repeater 200 is in a transmission mode at a certain period, that is, a mode in which the first transmission packet 220a is transmitted to the vehicle 300.

  At this time, in the repeater 200, first, the reference signal information generation unit 210 reads from the main storage unit 204 "information in which the traveling direction of the vehicle 300 is associated with the transmission mode start time of the second transmission packet 315a" and " A value t of “transmission mode time” is read. These pieces of information are information serving as determination criterion information. When the reference signal information generation unit 210 reads out these pieces of information, in response thereto, the reference signal information 210a is generated by combining these pieces of information and the measurement time information, and is output to the packet generation unit 215.

  When the reference signal information 210a is input from the reference signal information generation unit 210, the packet generation unit 215 generates a first packet 215a based on the reference signal information 210a in response to the reference signal information 210a, and sends it to the packet transmission unit 220. Output.

  When the first packet 215a is input from the packet generation unit 215, the packet transmission unit 220 modulates the first packet 215a in response to the first packet 215a and generates the first transmission packet 220a and transmits it to each vehicle 300. .

  On the other hand, in each vehicle 300, the travel direction detection unit 335 detects the travel direction of the host vehicle at regular intervals, and generates information 335a indicating the travel direction of the host vehicle (hereinafter referred to as “travel direction information”). And stored in the main storage unit 304.

  Next, each vehicle 300 enters the reception mode at regular intervals. Here, the “reception mode” means a state in which a signal transmitted from an external device can be received. At this time, in each vehicle 300, the packet receiver 325 receives the first transmission packet 220a transmitted from the repeater 200.

  When receiving the first transmission packet 220a transmitted from the repeater 200, the packet reception unit 325 responds to this by converting the first transmission packet 220a from an analog signal to a digital signal, or a plurality of codes. The second received packet 325 a is generated by performing processing such as demodulation by the sequence, and is output to the reference signal information extraction unit 330.

  When the second received packet 325a is input from the packet receiver 325, the reference signal information extractor 330 extracts the reference signal information 210a from the second received packet 325a in response to the input, and the transmission start time determiner 320 is output to the carrier sense start timing determination unit 324.

  When the reference signal information 210a is input from the reference signal information extraction unit 330, the carrier sense start timing determination unit 324 is included in the reference signal information 210a as the determination reference information from the reference signal information 210a in response to the input. "Information in which the traveling direction of the vehicle 300 is associated with the transmission mode start time of the second transmission packet 315a" is extracted, as shown in FIG. 2C, the "traveling direction of the vehicle 300 and the second transmission packet The transmission mode start times Ta to Td are set for each of the travel directions Da to Dd based on the information associated with the transmission mode start times of 315a. The transmission mode start times Ta to Td are set as times after the reference time, with the time when the first transmission packet 220a is received as the reference time.

  Further, the carrier sense start timing determination unit 324 extracts “transmission mode time” included in the reference signal information 210a as the determination reference information from the reference signal information 210a, and as shown in FIG. Based on the “transmission mode time”, the transmission mode time t is set for each of the traveling directions Da to Dd. Note that the value t of the transmission mode time is set as a time after the transmission mode start time Ta to Td has elapsed as a reference time.

  In addition, the total value (t × 4) of the transmission mode time corresponding to each of the ranges Da to Dd is a value equal to or less than the reception mode time Tr of the repeater 200. Here, “reception mode time” means the time during the reception mode. For example, the value t of the transmission mode time is preferably set to about 5 to 20 mS when each vehicle 300 enters the reception mode and the transmission mode during about 100 mS.

  The carrier sense start timing determination unit 324 sets the transmission mode start times Ta to Td and the transmission mode time t for each of the traveling directions Da to Dd, and in response to this, reads the traveling direction information 335a from the main storage unit 304. Based on the traveling direction information 335a, the transmission mode start time and the transmission mode time t of the second transmission packet 315a in the host vehicle are determined.

  At this time, when the traveling direction of the host vehicle is within the range Da, the carrier sense start timing determination unit 324 uses Ta (FIGS. 2A and 2C) as the value of the transmission mode start time of the second transmission packet 315a. )). Similarly, the carrier sense start timing determination unit 324 determines Tb as the transmission mode start time of the second transmission packet 315a when the traveling direction of the host vehicle is within the range Db, and the traveling direction of the host vehicle is within the range. When it is within Dc, Tc is determined as the transmission mode start time of the second transmission packet 315a, and when the traveling direction of the host vehicle is within the range Dd, as the transmission mode start time of the second transmission packet 315a, Td is determined.

  When the carrier sense start timing determination unit 324 determines the transmission mode start time and the transmission mode time t of the second transmission packet 315a in the host vehicle, in response to this, the carrier sense start timing determination unit 324 determines the carrier mode within the range of the transmission mode time t of the host vehicle. Determine the sense start timing.

  When the carrier sense start timing determination unit 324 determines the carrier sense start timing, the carrier sense start timing determination unit 324 waits until the elapsed time from the reception time of the first transmission packet 220a reaches the carrier sense start timing.

  When the elapsed time reaches the carrier sense start timing, the carrier sense start timing determination unit 324 generates a carrier sense start signal 324a in response to this and outputs it to the carrier sense unit 322. The carrier sense start signal 324a is a signal for instructing the carrier sense unit 322 to start carrier sense.

  When the carrier sense start signal 324a is input from the carrier sense start timing determination unit 324, the carrier sense unit 322 starts carrier sense in response thereto. At this time, the carrier sense unit 322 determines the channel usage status based on the channel status signal 325b input from the packet reception unit 325. The carrier sense unit 322 generates a transmission start signal 320a and outputs the transmission start signal 320a to the packet transmission unit 315 when it is determined that the channel is in an idle state. Thereby, the transmission start time of the second transmission packet 315a is determined.

  Thus, each vehicle 300 determines the transmission start time of the second transmission packet 315a in the own vehicle.

  In this embodiment, since the transmission start time determination unit 320 is configured to perform carrier sense, the transmission start time of the second transmission packet 315a is determined after determining the carrier sense start timing. ing. However, when the transmission start time determination unit 320 has a configuration in which carrier sense is not performed, that is, a configuration in which the carrier sense start timing determination unit 324 and the carrier sense unit 322 are not included, the carrier sense start timing is determined. Without determining the transmission start time of the second transmission packet 315a.

  Note that the value of the direction range can be changed as appropriate. For example, in the example shown in FIG. 2, the number of directions that divide 360 ° is four. Therefore, the range in one direction is 90 °. However, the number of directions that divide 360 ° may be three or less, and conversely, five or more. Therefore, the value of the direction range is changed by changing the number of directions dividing 360 °. In addition, when the value of the direction range is changed, the transmission mode start time corresponding to the traveling direction is also changed accordingly.

<Operation of inter-vehicle communication system>
The operation of the first embodiment will be described below with reference to FIG. FIG. 3 is a flowchart illustrating the operation of the repeater and the vehicle in the vehicle-to-vehicle communication system according to the first embodiment. In the communication between the two devices (here, between the repeater 200 and the vehicle 300), information received by the communication on the receiving device is temporarily stored in the main storage unit and then read. A series of these operations is defined by the program. Hereinafter, description of this point is omitted.

  The repeater 200 repeats the following operation at a cycle of about 100 mS.

  In the repeater 200, the timer 205 constantly measures the elapsed time, generates an elapsed time signal 205a representing the elapsed time each time a predetermined elapsed time elapses, and outputs it to the reference signal information generation unit 210. (S105).

  When the elapsed time information 205a is input from the timer 205, the reference signal information generation unit 210 responds to the reference signal information 210a by changing the reference signal information 210a at regular intervals based on the elapsed time signal 205a and the determination reference information. It is generated and output to the packet generator 215 (S110). In this embodiment, the criterion information includes “information in which the traveling direction of the vehicle 300 is associated with the transmission mode start time of the second transmission packet 315a” (see FIG. 2A), and “transmission mode”. This information includes “time” (see FIG. 2C).

  When the reference signal information 210a is input from the reference signal information generation unit 210, the packet generation unit 215 responds to the header to specify a transmission destination (here, the vehicle 300) in the reference signal information 210a, and A unique word or the like that defines the configuration of the signal to be generated (here, the first packet 215a) is added to generate the first packet 215a and output it to the packet transmitter 220 (S115). The packet transmitter 220 to which the first packet 215a is input stops its operation and enters a standby state until the transmission start signal 225a is input. The transmission start signal 225a is a signal for instructing the packet transmission unit 220 to transmit the first transmission packet 220a.

  When the first packet 215a is output to the packet transmission unit 220, the packet reception unit 230 is activated in response thereto.

  When the packet reception unit 230 is activated, in response to this, the reception of the second transmission packet 315a is started via the reception antenna 250 at regular intervals (S120).

  When receiving the second transmission packet 315a transmitted from any of the vehicles 300, the packet reception unit 230 performs a process such as demodulation on the received second transmission packet 315a in response to the first transmission packet 315a. 230a is generated and output to the vehicle information extraction unit 235, and a channel status signal 230b representing a value corresponding to the channel usage status is generated based on the received voltage level or received power level of the received second transmission packet 315a. Then, the data is output to the carrier sense unit 225 (S125). Note that the second transmission packet 315a and the first reception packet 230a each include vehicle information 305a of the vehicle 300 that transmitted the second transmission packet 315a, as described above.

  When the first reception packet 230a is input from the packet reception unit 230, the vehicle information extraction unit 235 responds to the vehicle information 305a of the vehicle 300 that has transmitted the second transmission packet 315a from the first reception packet 230a. Is extracted and output to the vehicle information storage unit 240 (S130).

  When the vehicle information 305a is input from the vehicle information extraction unit 235, the vehicle information storage unit 240 stores the input vehicle information 305a in response to the input (S135).

  When the channel status signal 230b is input from the packet receiving unit 230, the carrier sense unit 225 responds to the carrier sense based on the channel status signal 230b input from the packet receiving unit 230 in S125, that is, Then, the channel usage status is determined (S140), and it is determined whether the channel is in an idle state (S145).

  In S145, when the carrier sense unit 225 determines that the channel is in an idle state, the carrier sense unit 225 generates a transmission start signal 225a and outputs the transmission start signal 225a to the packet transmission unit 220 (S150). The transmission start signal 225a is a signal for instructing the packet transmission unit 220 to transmit the first transmission packet 220a as described above.

  On the other hand, in S145, when the carrier sense unit 225 determines that the channel is not in an idle state, that is, the channel is in a busy state, the operation of S140 and S145, that is, “carrier sense” is performed for a predetermined time. And “determination of whether or not the channel is idle” is performed. In this embodiment, the predetermined time is, for example, a time within a range of about 100 mS from the execution time of S105. The carrier sense unit 225 ends the operation when a predetermined time has elapsed. In this case, the repeater 200 repeats the operations after S105 again.

  When the transmission start signal 225a is input from the carrier sense unit 225, the packet transmission unit 220 performs a process such as modulation on the first packet 215a input from the packet generation unit 215 in S115. Then, the first transmission packet 220a is generated and transmitted to each vehicle 300 via the transmission antenna 245 (S155). The operation from S140 to S155, that is, the operation from “carrier sense” to “generation / transmission of the first transmission packet” is performed before the operation of S130, that is, the operation of “vehicle information extraction”. May be.

  On the other hand, the vehicle 300 repeatedly performs the following operation at a cycle of about 100 mS.

  In the vehicle 300, the vehicle position detection unit 340 is activated at regular intervals, detects the position of the host vehicle, generates vehicle position information 340a, and outputs it to the vehicle information generation unit 305 (S205). The vehicle position information 340a is information representing the position of the host vehicle.

  When the vehicle position information 340a is input from the vehicle position detection unit 340, the vehicle information generation unit 305 generates vehicle information 305a such as the position of the own vehicle based on the vehicle position information 340a in response to the input. The packet is output to the packet generator 310 (S210).

  When the vehicle information 305a is input from the vehicle information generation unit 305, the packet generation unit 310 generates a header that specifies the transmission destination (here, the repeater 200) and the vehicle information 305a in response thereto. A unique word or the like that defines the configuration of the signal (here, the second packet 310a) is added to generate the second packet 310a and output it to the packet transmission unit 315 (S215). The packet transmission unit 315 to which the second packet 310a is input stops its operation and enters a standby state until the transmission start signal 320a is input. The transmission start signal 320a is a signal for instructing the packet transmission unit 315 to transmit the second transmission packet 315a.

  Also, in the vehicle 300, the traveling direction detection unit 335 is activated at regular intervals, detects the traveling direction of the host vehicle, generates traveling direction information 335a representing the traveling direction of the host vehicle, and transmits the transmission start time. It outputs to the carrier sense start timing determination part 324 of the determination part 320 (S220). The operation of S220 may be performed before the operation of S205, that is, the operation of “vehicle position information generation”.

  The operations from S205 to S220 described above, that is, the operations from “vehicle position information generation” to “traveling direction information generation” are performed asynchronously with the operation of the repeater 200.

  Thereafter, the packet receiving unit 325 is activated. When activated, the packet receiver 325 starts receiving the first transmission packet 220a transmitted from the repeater 200 via the reception antenna 350 at regular intervals in response to the activation (S225).

  When receiving the first transmission packet 220a transmitted from the repeater 200, the packet reception unit 325 performs a process such as demodulation on the received first transmission packet 220a in response to the first transmission packet 220a. Is generated and output to the reference signal information extraction unit 330, and based on the received voltage level or received power level of the received first transmission packet 220a, a channel status signal 325b representing a value corresponding to the channel usage status is generated. The data is output to the carrier sense unit 322 of the transmission start time determination unit 320 (S230). Note that the first transmission packet 220a and the second reception packet 325a each include the reference signal information 210a generated by the repeater 200 that transmitted the first transmission packet 220a, as described above.

  When the second received packet 325a is input from the packet receiver 325, the reference signal information extractor 330 extracts the reference signal information 210a from the second received packet 325a in response to the input, and the transmission start time determiner 320 is output to the carrier sense start timing determination unit 324 (S235). The reference signal information 210a is information generated by the reference signal information generation unit 210 of the repeater 200 in S110. In this embodiment, the reference signal information 210a is information that combines measurement time information and determination reference information as described above. Further, in this embodiment, the determination criterion information is information in which the traveling direction and the carrier sense start timing are associated with each traveling direction of the vehicle 300 centering on the repeater 200 as described above. .

  When the reference signal information 210a is input, the carrier sense start timing determination unit 324 determines the carrier sense start timing in response to the input (S240). This determination is performed by the method described in the section “Method for determining the transmission start time of the second transmission packet in the first embodiment” described above.

  When the carrier sense start timing determination unit 324 determines the carrier sense start timing of the host vehicle, in response to this, the carrier sense start timing determination unit 324 waits until the carrier sense start timing of the host vehicle is reached (S245), and sets the carrier sense start timing of the host vehicle. Then, the carrier sense start signal 324a is generated and output to the carrier sense unit 322 (S250).

  In response to the carrier sense start signal 324a input from the carrier sense start timing determination unit 324, the carrier sense unit 322 responds to this based on the channel status signal 325b input from the packet reception unit 325 in S230. Carrier sense is performed (S255), and it is determined whether or not the channel is in an idle state (S260).

  In S260, when the carrier sense unit 322 determines that the channel is in an idle state, the carrier sense unit 322 generates a transmission start signal 320a and outputs the transmission start signal 320a to the packet transmission unit 315 (S265). The transmission start signal 320a is a signal for instructing the packet transmission unit 315 to transmit the second transmission packet 315a as described above.

  On the other hand, in S260, when the carrier sense unit 322 determines that the channel is not in an idle state, that is, the channel is in a busy state, the operation of S255 and S260, that is, “carrier sense” is performed for a predetermined time. And “determination of whether or not the channel is idle” is performed. In this embodiment, the predetermined time is, for example, a time within a range of about 5 to 20 mS. In addition, the carrier sense part 322 complete | finishes operation | movement, when predetermined time passes. In this case, the vehicle 300 repeats the operations after S205 again.

  When the transmission start signal 320a is input from the carrier sense unit 322 of the transmission start time determination unit 320, the packet transmission unit 315 responds to the second packet 310a input from the packet generation unit 310 in S215. Then, the second transmission packet 315a is generated by performing processing such as modulation and transmitted to the repeater 200 via the transmission antenna 345 (S270).

  In this embodiment, the time when the transmission start signal 320a is output from the transmission time start determination unit 320 to the packet transmission unit 315 has a different value between the vehicles 300 having different traveling directions. Therefore, according to this embodiment, the transmission start time of the second transmission packet 315a can be made different between the vehicles 300 having different traveling directions. Therefore, it is possible to prevent the transmission timing of the second transmission packet 315a from overlapping between the vehicles 300, and also prevent the timing of carrier sense from overlapping.

[Second Embodiment]
In the first embodiment, each vehicle 300 determines the transmission start time of the second transmission packet 315a based on the traveling direction of the host vehicle. On the other hand, in 2nd Embodiment, each vehicle 300A determines the transmission start time of the 2nd transmission packet 315a based on the position of the own vehicle.

  Hereinafter, the second embodiment will be described in the order of “configuration of inter-vehicle communication system”, “determination method of transmission start time of second transmission packet”, and “operation of inter-vehicle communication system”.

<Configuration of inter-vehicle communication system>
Hereinafter, the configuration of the second embodiment to which the present invention is applied will be described with reference to FIG. FIG. 4 is a block diagram for explaining the configuration of the repeater and the vehicle in the inter-vehicle communication system according to the second embodiment.

  First, the configuration of the repeater 200 will be described.

  The configuration of the repeater 200 of this embodiment is the same as that of the first embodiment. However, in this embodiment, the main storage unit 204 stores relay device position information representing the installation position of the own device in advance. Further, the packet generation unit 215 reads the repeater position information stored in advance in the main storage unit 204, and generates the first packet 215a so that the repeater position information is included. In this embodiment, the criterion information included in the first packet 215a includes information in which the relative distance from the repeater 200 to the vehicle 300A and the transmission mode start time are associated with each other (FIG. 5A )reference). Further, the determination criterion information includes information that designates the start timing of carrier sense and the value of the transmission mode time t for each vehicle 300A.

  Next, the configuration of the vehicle 300A of this embodiment will be described.

  The vehicle 300A according to this embodiment includes a distance calculation unit 342A in addition to the components of the vehicle 300 according to the first embodiment. The distance calculation unit 342A is a functional unit that calculates a relative distance from the repeater 200 to the host vehicle.

  Further, the vehicle 300A includes a transmission start time determination unit 320A instead of the transmission start time determination unit 320 of the first embodiment. Similar to the transmission start time determination unit 320, the transmission start time determination unit 320A is a functional unit that determines the transmission start time of the second transmission packet 315a. However, the transmission start time determination unit 320 of the first embodiment determines the transmission start time of the second transmission packet 315a based on the traveling direction of the host vehicle. On the other hand, the transmission start time determination unit 320A of this embodiment determines the transmission start time of the second transmission packet 315a based on the position of the host vehicle.

  Further, the vehicle 300A includes a carrier sense start timing determination unit 324A instead of the carrier sense start timing determination unit 324 of the first embodiment. The carrier sense start timing determination unit 324A is a functional unit that determines the start timing of carrier sense, similarly to the carrier sense start timing determination unit 324. However, the carrier sense start timing determination unit 324 according to the first embodiment determines the carrier sense start timing based on the traveling direction of the host vehicle. On the other hand, the carrier sense start timing determination unit 324A of this embodiment determines the start timing of carrier sense based on the position of the host vehicle.

<Determination Method of Transmission Start Time of Second Transmission Packet in Second Embodiment>
Hereinafter, a method for determining the transmission start time of the second transmission packet in this embodiment will be described with reference to FIG. 4 and FIGS. In this embodiment, the transmission start time of the second transmission packet 315a is determined based on the relative distance from the repeater 200 to the vehicle 300A.

  FIGS. 5A and 5B are diagrams for explaining a method of determining the transmission start time of the second transmission packet 315a. FIG. 5A shows information associating the relative distance from the repeater 200 to the vehicle 300A and the transmission mode start time, which is used as determination criterion information in this embodiment. FIG. 5B shows the relationship between the relative distance from the repeater 200 to the vehicle 300A and the transmission start time of the second transmission packet 315a.

  The repeater 200 stores “information that associates the relative distance from the repeater 200 to the vehicle 300 </ b> A and the transmission mode start time” (see FIG. 5A) in the main storage unit 204. This “information in which the relative distance from the repeater 200 to the vehicle 300A is associated with the transmission mode start time” is set in advance according to the operation. In the example shown in FIG. 5A, the relative distance from the repeater 200 to the vehicle 300A ranges from “L1a to L1b”, “L2a to L2b”, “L3a to L3b”, “L4a to L4b”, “L5a to L5b ",... The transmission mode start times “T1a”, “T2a”, “T3a”, “T4a”, “T5a”, etc. shown in FIG. 5A correspond to the relative distance from the repeater 200 to the vehicle 300A in advance. It is set to a different value.

  Further, the repeater 200 stores the value t (see FIG. 5B) in the main storage unit 204 as “transmission mode time”. The value “t” of “transmission mode time” is set in advance according to the operation. In this embodiment, the “transmission mode time” value t is set as a fixed value.

  The repeater 200 stores the repeater position information indicating the position of the repeater 200 in the main storage unit 204.

  The repeater 200 is in a transmission mode, that is, a mode in which the first transmission packet 220a is transmitted to the vehicle 300A at regular intervals.

  At this time, in the repeater 200, first, the reference signal information generation unit 210 associates the relative distance from the main storage unit 204 to the “repeater position information”, “the repeater 200 to the vehicle 300A, and the transmission mode start time. "Information" and "transmission mode time" value t. These pieces of information are information serving as determination criterion information. When the reference signal information generation unit 210 reads out these pieces of information, in response thereto, the reference signal information 210a is generated by combining these pieces of information and the measurement time information, and is output to the packet generation unit 215.

  When the reference signal information 210a is input from the reference signal information generation unit 210, the packet generation unit 215 generates a first packet 215a based on the reference signal information 210a in response to the reference signal information 210a, and sends it to the packet transmission unit 220. Output.

  When the first packet 215a is input from the packet generation unit 215, the packet transmission unit 220 modulates the first packet 215a to generate the first transmission packet 220a and transmits it to each vehicle 300A. .

  On the other hand, in each vehicle 300A, the vehicle position detection unit 340 detects the position of the host vehicle at regular intervals, generates vehicle position information 340a, and stores it in the main storage unit 304.

  Next, each vehicle 300A enters the reception mode at regular intervals. At this time, in each vehicle 300A, the packet receiving unit 325 receives the first transmission packet 220a transmitted from the repeater 200.

  When receiving the first transmission packet 220a transmitted from the repeater 200, the packet reception unit 325 responds to this by converting the first transmission packet 220a from an analog signal to a digital signal, or a plurality of codes. The second received packet 325 a is generated by performing processing such as demodulation by the sequence, and is output to the reference signal information extraction unit 330.

  When the second received packet 325a is input from the packet receiver 325, the reference signal information extractor 330 extracts the reference signal information 210a from the second received packet 325a in response to the input, and the transmission start time determiner The data is output to the carrier sense start timing determination unit 324A of 320A and also output to the distance calculation unit 342A.

  When the reference signal information 210a is input from the reference signal information extraction unit 330, the distance calculation unit 342A extracts the repeater position information from the reference signal information 210a in response to the input, and the relay represented by the repeater position information The position of the vessel 200 is specified. Further, the distance calculation unit 342A reads the vehicle position information 340a from the main storage unit 304, specifies the position of the host vehicle represented by the vehicle position information 340a, and calculates the relative distance from the repeater 200 to the host vehicle.

  When the distance calculation unit 342A calculates the relative distance from the repeater 200 to the own vehicle, in response to this, the distance calculation unit 342A generates relative distance information 342a that represents the calculated relative distance from the repeater 200 to the own vehicle, and transmits the information. This is output to the carrier sense start timing determination unit 324A of the start time determination unit 320A.

  When the reference signal information 210a is input from the reference signal information extraction unit 330, the carrier sense start timing determination unit 324A is included in the reference signal information 210a as the determination reference information from the reference signal information 210a in response thereto. "Information in which the relative distance from the repeater 200 to the vehicle 300A is associated with the transmission mode start time" is extracted, and as shown in FIG. 5B, the "relative distance from the repeater 200 to the vehicle 300A Based on the information associated with the transmission mode start time, transmission mode start times T1a to T5a are set for each relative distance. The transmission mode start times T1a to T5a are set as times after the reference time, which is the time when the first transmission packet 220a is received.

  Further, the carrier sense start timing determination unit 324A extracts the “transmission mode time” included in the reference signal information 210a as the determination reference information from the reference signal information 210a, and as shown in FIG. Based on the “transmission mode time”, the transmission mode time t is set for each relative distance. Note that the value t of the transmission mode time is set as a time after the transmission mode start times T1a to T5a have passed, as a reference time.

  Note that the total value of the transmission mode times corresponding to each of the relative distances is equal to or less than the reception mode time Tr of the repeater 200. The value t of the transmission mode time is preferably set to about 5 to 20 mS, for example, when each vehicle 300A enters the reception mode and the transmission mode during about 100 mS.

  The carrier sense start timing determination unit 324A sets the transmission mode start times T1a to T5a and the transmission mode time t for each relative distance, and based on the relative distance information 342a input from the distance calculation unit 342A in response thereto. Thus, the transmission mode start time and the transmission mode time t of the second transmission packet 315a in the host vehicle are determined.

  At this time, when the vehicle position of the host vehicle is within the range L1a to L1b, the carrier sense start timing determination unit 324A uses T1a (FIG. 5A) as the value of the transmission mode start time of the second transmission packet 315a. (Refer to (B)). Similarly, the carrier sense start timing determination unit 324A determines T2a as the transmission mode start time of the second transmission packet 315a when the vehicle position of the host vehicle is within the range L2a to L2b, and the vehicle position of the host vehicle Is within the range L3a to L3b, T3a is determined as the transmission mode start time of the second transmission packet 315a, and when the vehicle position of the host vehicle is within the range L4a to L4b, the second transmission packet 315a T4a is determined as the transmission mode start time, and when the vehicle position of the host vehicle is within the range L5a to L5b, T5a is determined as the transmission mode start time of the second transmission packet 315a.

  The carrier sense start timing determination unit 324A determines the transmission mode start time and the transmission mode time t of the second transmission packet 315a in the own vehicle, and in response, within the range of the transmission mode time t of the own vehicle, Determine the sense start timing.

  When the carrier sense start timing determination unit 324A determines the carrier sense start timing, the carrier sense start timing determination unit 324A waits until the elapsed time from the reception time of the first transmission packet 220a reaches the carrier sense start timing.

  When the elapsed time reaches the carrier sense start timing, the carrier sense start timing determination unit 324A generates a carrier sense start signal 324a in response to this and outputs it to the carrier sense unit 322.

  When the carrier sense start signal 324a is input from the carrier sense start timing determination unit 324A, the carrier sense unit 322 starts carrier sense in response thereto. At this time, the carrier sense unit 322 determines the channel usage status based on the channel status signal 325b input from the packet reception unit 325. The carrier sense unit 322 generates a transmission start signal 320a and outputs the transmission start signal 320a to the packet transmission unit 315 when it is determined that the channel is in an idle state. Thereby, the transmission start time of the second transmission packet 315a is determined.

  Thus, each vehicle 300A determines the transmission start time of the second transmission packet 315a in its own vehicle.

  In this embodiment, the transmission start time determination unit 320A is configured to perform carrier sense. Therefore, after determining the carrier sense start timing, the transmission start time determination unit 320A determines the transmission start time of the second transmission packet 315a. ing. However, when the transmission start time determination unit 320A has a configuration that does not perform carrier sense, that is, a configuration that does not include the carrier sense start timing determination unit 324A and the carrier sense unit 322, the carrier sense start timing Without determining the transmission start time of the second transmission packet 315a.

  Note that the value of the relative distance range can be changed as appropriate. However, when the value of the relative distance range is changed, the value of the transmission mode start time corresponding to the relative distance is also changed accordingly.

<Operation of inter-vehicle communication system>
Hereinafter, the operation of the second embodiment will be described with reference to FIG. FIG. 6 is a flowchart illustrating the operation of the repeater and the vehicle in the inter-vehicle communication system according to the second embodiment. In the communication between the two devices (here, between the repeater 200 and the vehicle 300A), the information received by the communication on the receiving device is temporarily stored in the main storage unit and then read. A series of these operations is defined by the program. Hereinafter, description of this point is omitted.

  The repeater 200 of this embodiment repeats the same operation as that of the first embodiment at a cycle of about 100 mS. However, in this embodiment, the determination criterion information used when generating the reference signal information 210a in S110 is information that associates the relative distance from the repeater 200 to the vehicle 300A and the transmission mode start time. .

  On the other hand, the vehicle 300A of this embodiment repeatedly performs the following operations at a cycle of about 100 mS.

  The vehicle 300A of this embodiment performs the operations of S205 to S215 and S225 to S235 as in the first embodiment. Note that the vehicle 300A does not include the traveling direction detection unit 335, unlike the vehicle 300 of the first embodiment. Therefore, the vehicle 300A does not perform the operation of S220 of the first embodiment, that is, the operation of “traveling direction information generation”. However, in S205, the vehicle position detection unit 340 of the vehicle 300A outputs the generated vehicle position information 340a to the vehicle information generation unit 305 and also to the distance calculation unit 342A. In addition, when the second reception packet 325a is input from the packet reception unit 325 in S230, the reference signal information extraction unit 330 of the vehicle 300A responds to the reference signal information from the second reception packet 325a in S235. 210a is extracted and output to the carrier sense start timing determination unit 324A of the transmission start time determination unit 320A and also output to the distance calculation unit 342A.

  When the reference signal information 210a is input from the reference signal information extraction unit 330 in S235, the distance calculation unit 342A extracts the repeater position information from the reference signal information 210a in response to this (S236). Based on the extracted repeater position information and the vehicle position information 340a input from the vehicle position detection unit 340 in S205, the relative distance from the repeater 200 to the host vehicle is calculated, and the relative distance information 342a is generated. The transmission start time determining unit 320A outputs the carrier sense start timing determining unit 324A (S237).

  The carrier sense start timing determination unit 324A responds when the reference signal information 210a is input from the reference signal information extraction unit 330 in S235 and the relative distance information 342a is input from the distance calculation unit 342A in S237. Then, the carrier sense start timing is determined (S240). This determination is performed by the method described in the section “Method for determining the transmission start time of the second transmission packet in the second embodiment” described above.

  When the carrier sense start timing determination unit 324A determines the carrier sense start timing of the host vehicle, in response to this, the carrier sense start timing determination unit 324A waits until the carrier sense start timing of the host vehicle is reached (S245), and sets the carrier sense start timing of the host vehicle. Then, the carrier sense start signal 324a is generated and output to the carrier sense unit 322 (S250).

  Hereinafter, the vehicle 300A of this embodiment performs the operations of S255 to S270 as in the first embodiment.

  In this embodiment, the time when the transmission start signal 320a is output from the transmission time start determination unit 320A to the packet transmission unit 315 has a different value between the vehicles 300A having different relative distances from the repeater 200. Therefore, according to this embodiment, the transmission start time of the second transmission packet 315a can be made different between the vehicles 300A having different relative distances from the repeater 200. Therefore, the inter-vehicle communication system 100 can prevent the timing of the transmission of the second transmission packet 315a from overlapping between the vehicles 300A, and can also prevent the timing of the carrier sense from overlapping.

  Note that the inter-vehicle system 100 may cause a communication failure if the number of vehicles 300A performing communication significantly increases.

  For example, from the relationship between the data transmission speed and the packet size transmitted by each vehicle 300A, when the limit of the number of vehicles 300A that can transmit data at a cycle of 100 mS is 100, the communication vehicle 300A present at an intersection or the like. There are times when there are more than 100 units. At this time, it is physically impossible for all the vehicles 300A to communicate. Accordingly, at this time, a communication failure occurs in the inter-vehicle system 100A.

  In order to solve such a problem, the vehicle 300A of the second embodiment is preferably configured as, for example, the following (1) or (2).

  (1) The vehicle 300A having a low communication priority may be configured not to transmit a transmission packet. In addition, as the vehicle 300A having a low communication priority, for example, a vehicle 300A having a relative distance to an intersection where the repeater 200 is installed is larger than a predetermined distance.

  In such a configuration, for example, the carrier sense start timing determination unit 324A of the transmission time start determination unit 320A has a relative distance from the repeater 200 to the host vehicle calculated by the distance calculation unit 342A larger than a predetermined distance. If it is larger, it can be realized by canceling the subsequent processing without setting the timing, and by causing the packet transmission unit 315 to discard the packet.

  (2) The vehicle 300A may be configured to be capable of changing the transmission cycle of the transmission packet arbitrarily long (for example, changing the transmission cycle from normal 100 mS to 200 mS).

  In such a configuration, for example, the repeater 200 transmits a transmission packet indicating a traffic jam according to the traffic jam situation around the relay device 200. When each vehicle 300A receives this transmission packet, the transmission time start determination unit The carrier sense start timing determination unit 324A of 320A is designated by “information associating the relative distance from the repeater 200 to the vehicle 300A and the transmission mode start time” included in the reference signal information 210a as the determination reference information. This can be achieved by adding an arbitrary time value to the transmission mode start time of the own device. In addition, it is preferable that an arbitrary time value is added to the transmission mode start time of the own device, preferably, the relative distance from the repeater 200 calculated by the distance calculation unit 342A to the own vehicle is larger than a predetermined distance. If you want to do it. Further, the time value to be added is preferably a time value of 100 mS intervals such as 100 mS, 200 mS,... When the transmission cycle is 100 mS.

[Third Embodiment]
In the third embodiment, a vehicle 300 that exists in a place with a large number of vehicles can acquire a transmission mode time longer than a vehicle 300 that exists in a place with a small number of vehicles.

  In this embodiment, the configurations of the repeater 200 and the vehicle 300 are the same as those in the first embodiment.

  However, in this embodiment, the repeater 200 detects the position of each vehicle 300 based on the vehicle information 305a included in the second transmission packet 315a transmitted from each vehicle 300, and the repeater 200 is Identify how busy the vehicle is in each direction, centered. Then, the repeater 200 determines the transmission mode time t and the transmission mode start time of the vehicle for each direction according to the degree of congestion of the vehicle, and includes the determined transmission mode time t and the transmission mode start time of the vehicle. In addition, determination criterion information is generated. The repeater 200 generates reference signal information 210a based on the determination reference information, generates a first packet 215a, and further generates a first transmission packet 220a based on the reference signal information 210a. To each vehicle 300. Thereby, the repeater 200 gives the transmission mode time longer than the vehicle 300 which exists in a place with few vehicles to the vehicle 300 which exists in a place with many vehicles.

  Hereinafter, a method for determining the transmission start time according to the third embodiment will be described with reference to FIG. 1 and FIGS.

  7A to 7C are diagrams for explaining a method for determining the transmission start time. FIG. 7A shows information in which the degree of vehicle congestion is associated with the transmission mode start time. Information in which the degree of congestion of the vehicle and the transmission mode time are associated with each other is stored in advance in the main storage unit 204 of the repeater 200. Note that the transmission mode time t of the vehicle is set to be longer as the degree of congestion of the vehicle is higher. FIG. 7B illustrates an example of the position of the vehicle 300 that exists around the repeater 200 with the repeater 200 as the center. FIG. 7C shows the relationship between the degree of congestion of the vehicle and the transmission mode time of the vehicle.

  In this embodiment, the repeater 200 sequentially receives the second transmission packet 315a from each vehicle 300 existing around the repeater 200 by the packet receiving unit 230.

  When the repeater 200 sequentially receives the second transmission packet 315a from each vehicle 300, in response to this, the vehicle information extraction unit 235 is activated to extract the vehicle information 305a from the second transmission packet 315a. Based on 305a, the position of each vehicle 300 is detected (see FIG. 7B), and the number of vehicles is counted for each direction. Thereby, the repeater 200 identifies the degree of vehicle congestion in each direction with the repeater 200 as the center.

  When the repeater 200 identifies the degree of congestion of the vehicle in each direction, the reference signal information generation unit 210 generates reference signal information 210a in response thereto. The generation of the reference signal information 210a is performed as follows.

  First, the reference signal information generation unit 210 reads information that associates the degree of congestion of the vehicle and the transmission mode time shown in FIG. 7A from the main storage unit 204, and based on this information, for each direction, The transmission mode time t of the vehicle is determined. Here, for example, the reference signal information generation unit 210 determines t2 (see FIG. 7A) as the transmission mode time of the vehicle corresponding to the direction within the range Da (see FIG. 7B). To do. Similarly, the reference signal information generation unit 210 determines t4 as the transmission mode time of the vehicle corresponding to the direction in the range Db, and determines t3 as the transmission mode time of the vehicle corresponding to the direction in the range Dc. T1 is determined as the transmission mode time of the vehicle corresponding to the direction in the range Dd. In this way, the reference signal information generation unit 210 determines the vehicle transmission mode time t corresponding to each direction. In addition, the total value of the transmission mode time t of the vehicle corresponding to each direction is a value less than or equal to the reception mode time Tr of the repeater 200.

  Next, the reference signal information generation unit 210 determines the transmission mode start times Ta to Td so as to have the relationship shown in FIG. 7C for each direction based on the determined transmission mode time t of the vehicle. . At this time, the reference signal information generation unit 210 first determines the transmission mode start time Ta of the vehicle corresponding to the direction in the range Da with reference to the transmission time of the first transmission packet 220a. The value of the transmission mode start time Ta has a fixed length and is stored in the main storage unit 204 in advance. Next, the reference signal information generation unit 210 adds the transmission mode time t2 of the vehicle corresponding to the direction in the range Da and a predetermined blank time to the transmission mode start time Ta of the vehicle, and within the range Db The transmission mode start time Tb of the vehicle corresponding to the direction is determined. Next, the reference signal information generation unit 210 adds the transmission mode time t4 of the vehicle corresponding to the direction in the range Db and a predetermined blank time to the transmission mode start time Tb of the vehicle, and within the range Dc. The transmission mode start time Tc of the vehicle corresponding to the direction is determined. Next, the reference signal information generation unit 210 adds the transmission mode time t3 of the vehicle corresponding to the direction in the range Dc and a predetermined blank time to the transmission mode start time Tc of the vehicle, and within the range Dd The transmission mode start time Td of the vehicle corresponding to the direction is determined. In this manner, the reference signal information generation unit 210 determines the vehicle transmission mode start times Ta to Td corresponding to the respective directions.

  Next, the reference signal information generation unit 210 determines the criterion so as to include the transmission mode time t of the vehicle corresponding to each determined direction and the transmission mode start times Ta to Td of the vehicle corresponding to each determined direction. Generate information.

  Next, the reference signal information generation unit 210 generates the reference signal information 210a by combining the measurement time information and the determination reference information.

  In this way, the repeater 200 generates the reference signal information 210a. The generated reference signal information 210a is output from the reference signal information generation unit 210 to the packet generation unit 215.

  When the repeater 200 generates the reference signal information 210a, the packet generator 215 generates the first packet 215a in response to the reference signal information 210a. At this time, the packet generation unit 215 includes, in the reference signal information 210a, a header that specifies the transmission destination (here, the vehicle 300), a unique word that defines the configuration of the signal to be generated (here, the first packet 215a), and the like. Is added to generate the first packet 215a. The generated first packet 215a is output from the packet generator 215 to the packet transmitter 220.

  When the repeater 200 generates the first packet 215a, the packet transmitter 220 generates the first transmission packet 220a in response to the first packet 215a. At this time, the packet transmission unit 220 performs a predetermined process on the first packet 215a to generate the first transmission packet 220a. The generated first transmission packet 220a is transmitted to each vehicle 300 by the packet transmission unit 220 via the transmission antenna 245.

  In this way, the repeater 200 transmits the first transmission packet 220a to each vehicle 300. The first transmission packet 220a includes reference signal information 210a. The reference signal information 210a is a criterion that indicates the transmission mode time t and the transmission mode start time of the vehicle determined according to the degree of congestion of the vehicle. Contains information. Therefore, each vehicle 300 that has received the first transmission packet 220a can determine the transmission mode start time and the transmission mode time of the second transmission packet 315a according to the position of the host vehicle. The transmission mode start time and transmission mode time determined at this time correspond to each direction centering on the repeater 200. In addition, the transmission mode time is a value corresponding to the degree of congestion of the vehicle, and is a relatively long value if the degree of congestion of the vehicle is high. Therefore, in this embodiment, the vehicle 300 that exists in a place with a large number of vehicles can acquire the transmission mode time longer than the vehicle 300 that exists in a place with a small number of vehicles. Thereby, the inter-vehicle communication system 100 of this embodiment can prevent the overlapping of the transmission timing of the second transmission packet 315a between the vehicles 300 more efficiently than the first embodiment. Overlap of carrier sense timing can also be prevented.

[Fourth Embodiment]
In the fourth embodiment, each vehicle 300A of the second embodiment is provided with the traveling direction detection unit 335 of the first embodiment.

  In the second embodiment, each vehicle 300A determines the transmission start time of the second transmission packet 315a based on the position of the host vehicle. On the other hand, in this embodiment, each vehicle 300B determines the transmission start time of the second transmission packet 315a based on the traveling direction of the own vehicle and the position of the own vehicle.

  The configuration of the fourth embodiment to which the present invention is applied will be described below with reference to FIG. FIG. 8 is a block diagram for explaining a configuration of a repeater and a vehicle in the inter-vehicle communication system according to the fourth embodiment.

  The configuration of the repeater 200 of this embodiment is the same as that of the second embodiment. However, in this embodiment, the determination criterion information included in the first packet 215a is “information in which the relative distance from the repeater 200 to the vehicle 300A and the transmission mode start time are associated with each other” in the second embodiment. In addition to (see FIG. 5 (A)), “information in which the traveling direction of the vehicle 300 and the transmission mode start time of the second transmission packet 315a are associated” (see FIG. 2 (A)) of the first embodiment is included. (See FIG. 5A).

  A vehicle 300 according to this embodiment includes a traveling direction detection unit 335 according to the first embodiment, in addition to the components of the vehicle 300A according to the second embodiment.

  In addition, the carrier sense start timing determination unit 324A of the transmission start time determination unit 320A according to the present embodiment determines that the reference signal information 210a includes “the traveling direction and the first direction of the vehicle 300 included in the reference signal information 210a as the determination reference information. 2 ”information that associates the transmission mode start time of the transmission packet 315a” and “information that associates the relative distance from the repeater 200 to the vehicle 300A and the transmission mode start time” are extracted, and based on these information The transmission mode start times T1a to T5a are set for each relative distance in each traveling direction. The transmission mode start times T1a to T5a are set as times after the reference time, which is the time when the first transmission packet 220a is received.

  The configuration of the fourth embodiment to which the present invention is applied will be described below with reference to FIG. FIG. 9 is a flowchart illustrating the operation of the repeater and the vehicle in the inter-vehicle communication system according to the fourth embodiment.

  The repeater 200 of this embodiment repeats the same operation as that of the second embodiment at a cycle of about 100 mS.

  Further, the vehicle 300B of this embodiment repeatedly performs the same operation as that of the second embodiment at a cycle of about 100 mS.

  However, as shown in FIG. 9, the vehicle 300B of this embodiment is configured between the operation of S215 and the operation of S225, that is, the “second packet generation” step and the “first transmission packet reception start” step. In the same manner as in the first embodiment, the operation of S220, that is, the operation of the “running direction information generation” step is performed.

  In addition, the vehicle 300B of this embodiment is the operation of S240, that is, the operation of the “carrier sense start timing determination” step. 2 ”information that associates the transmission mode start time of the transmission packet 315a” and “information that associates the relative distance from the repeater 200 to the vehicle 300A and the transmission mode start time” are extracted, and based on these information The transmission mode start times T1a to T5a are set for each relative distance in each traveling direction.

  Thereby, vehicle 300B of this embodiment can determine the transmission start time for each relative distance in each traveling direction based on the traveling direction of the own device and the traveling direction of the own vehicle.

  In the second embodiment, the transmission start time of the second transmission packet 315a can be made different between the vehicles 300A having different relative distances from the repeater 200 in each traveling direction. On the other hand, in this embodiment, the transmission start time of the second transmission packet 315a can be made different between the vehicles 300A having different relative distances from the repeater 200 for each traveling direction. Therefore, according to the inter-vehicle communication system 100 of this embodiment, it is possible to prevent the overlapping of the transmission timings of the second transmission packet 315a between the vehicles 300A better than in the second embodiment. Further, overlapping of carrier sense timings can also be prevented.

  The vehicle 300B of the fourth embodiment is preferably configured as in the following (1) or (2), for example, similarly to the vehicle 300A of the second embodiment.

  (1) The vehicle 300B having a low communication priority may be configured not to transmit a transmission packet.

  Such a configuration is similar to the case of the second embodiment, for example, when the carrier sense start timing determination unit 324A of the transmission time start determination unit 320A determines that the vehicle from the repeater 200 calculated by the distance calculation unit 342A. When the relative distance is larger than a predetermined distance, it is possible to realize the configuration by canceling the subsequent processing without setting the timing and discarding the packet by the packet transmission unit 315. .

  (2) The vehicle 300B may be configured to be capable of changing the transmission cycle of the transmission packet arbitrarily long (for example, changing the transmission cycle from normal 100 mS to 200 mS).

  Such a configuration is similar to the case of the second embodiment. For example, the relay device 200 transmits a transmission packet indicating a traffic jam according to the traffic jam situation around the relay device 200. When this transmission packet is received, the carrier sense start timing determination unit 324A of the transmission time start determination unit 320A receives the vehicle 300A from the repeater 200 included in the reference signal information 210a as the determination reference information (however, in this embodiment, This is realized by adding an arbitrary time value to the transmission mode start time of the own device specified by the “information that associates the relative distance to the vehicle 300B) and the transmission mode start time”. Can do.

  As described above, according to the present invention, the probability that the repeater cannot receive a packet from each vehicle can be reduced as compared with the prior art. That is, the probability that the repeater receives a packet from each vehicle can be improved as compared with the prior art.

(Usage form)
The present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the gist of the present invention.

  For example, in the first and second embodiments, the component that outputs a signal to the subsequent component in the main arithmetic unit 202 of the repeater 200 receives a signal from the previous component. In response to this, a signal to be output to a subsequent component is generated. Similarly, in the main arithmetic unit 302 of the vehicle 300 (300A), a component that outputs a signal to a subsequent component also receives a signal from the previous component, and in response, A signal to be output to the component is generated. However, these components generate a signal to be output to the subsequent component in advance, store it in the main storage unit, and generate a signal in response to the signal input from the previous component. The stored signal may be read from the storage unit and output to a subsequent component.

  Further, the criterion information may be stored in advance in the main storage unit 304 of each vehicle 300. Thereby, the repeater 200 does not need to include the determination reference information in the first transmission packet 220a.

  Further, in the first embodiment, the range in the traveling direction of the vehicle is fixed to the ranges Da to Dd. However, the repeater 200 includes information for determining the range of the traveling direction of the vehicle in the determination criterion information, generates the first transmission packet 220a so as to include the determination criterion information, and transmits the first transmission packet 220a to each vehicle 300. As a result, each vehicle 300 can be set to a range in an arbitrary traveling direction.

It is a figure which shows the structure of 1st Embodiment. (A)-(C) is a figure which shows the determination method of the transmission start time of 1st Embodiment, respectively. It is a flowchart which shows operation | movement of 1st Embodiment. It is a figure which shows the structure of 2nd Embodiment. (A) And (B) is a figure which shows the determination method of the transmission start time of 2nd Embodiment, respectively. It is a flowchart which shows operation | movement of 2nd Embodiment. (A)-(C) are the figures which respectively show the determination method of the transmission start time of 3rd Embodiment. It is a figure which shows the structure of 4th Embodiment. It is a flowchart which shows operation | movement of 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Inter-vehicle communication system 200 ... Repeater 202 ... Main operation part (CPU)
204 ... Main storage (RAM)
205 ... timer 210 ... reference signal information generation unit 215 ... packet generation unit 220 ... packet transmission unit 225 ... carrier sensing unit 230 ... packet reception unit 235 ... vehicle information extraction unit 240 ... vehicle information storage unit 245 ... transmission antenna 250 ... reception antenna 300, 300A ... Vehicle (on-vehicle computer)
302 ... main arithmetic unit (CPU)
304: Main storage unit (RAM)
305 ... Vehicle information generation section 310 ... Packet generation section 315 ... Packet transmission section 320, 320A ... Transmission start time determination section 322 ... Carrier sense section 324, 324A ... Carrier sense start timing determination section 325 ... Packet reception section 330 ... Reference signal information Extraction unit 335 ... travel direction detection unit 340 ... vehicle position detection unit 342A ... distance calculation unit 345 ... transmission antenna 350 ... reception antenna 205a ... elapsed time signal 210a ... reference signal information 215a ... first packet 220a ... first transmission packet 225a ... Transmission start signal 230a ... first reception packet 230b ... channel status signal 305a ... vehicle information 310a ... second packet 315a ... second transmission packet 320a ... transmission start signal 324a ... carrier sense start signal 325a ... second reception packet 325b ... Channel status signal 335a ... Traveling direction information 340a ... Vehicle position information

Claims (14)

In the inter-vehicle communication system that communicates between vehicles by wireless communication via a repeater,
The repeater is
A packet generation means on the repeater side that generates the first packet based on arbitrary information at fixed intervals;
A repeater side that performs a predetermined process on the first packet generated by the packet generation means on the repeater side to generate a first transmission packet, and transmits the first transmission packet to each vehicle Packet transmission means,
A relay-side packet receiving means for receiving a second transmission packet transmitted from each of the vehicles,
Each said vehicle
Vehicle-side packet receiving means for receiving the first transmission packet transmitted from the repeater;
Vehicle information generating means for generating vehicle information relating to the own vehicle;
Vehicle-side packet generation means for generating a second packet based on the vehicle information generated by the vehicle information generation means;
Traveling direction detection means for detecting the traveling direction of the host vehicle;
The time from the reception time of the first transmission packet received by the packet reception means on the vehicle side to the time to start transmission of the second transmission packet is defined as a transmission start time, and the time detected by the traveling direction detection means Transmission start time determining means for determining the transmission start time based on the traveling direction of the host vehicle;
Based on the transmission start time determined by the transmission start time determination means, a predetermined process is performed on the second packet to generate the second transmission packet, and the second transmission packet is transmitted to the repeater. A vehicle-to-vehicle communication system comprising: vehicle-side packet transmitting means for transmitting. In the inter-vehicle communication system that communicates between vehicles by wireless communication via a repeater,
The repeater is
Based on any information including the position information of the repeater at a certain period, packet generating means on the repeater side for generating the first packet;
A repeater side that performs a predetermined process on the first packet generated by the packet generation means on the repeater side to generate a first transmission packet, and transmits the first transmission packet to each vehicle Packet transmission means,
A relay-side packet receiving means for receiving a second transmission packet transmitted from each of the vehicles,
Each said vehicle
Vehicle-side packet receiving means for receiving the first transmission packet transmitted from the repeater;
Vehicle information generating means for generating vehicle information relating to the own vehicle;
Vehicle-side packet generation means for generating a second packet based on the vehicle information generated by the vehicle information generation means;
Vehicle position detecting means for detecting the position of the host vehicle;
Based on the position information of the repeater included in the first transmission packet received by the packet reception means on the vehicle side and the position of the own vehicle detected by the vehicle position detection means, the relay Distance calculating means for calculating a relative distance from the vessel to the host vehicle;
The time from the reception time of the first transmission packet to the time to start transmission of the second transmission packet is defined as a transmission start time, and the transmission start time is determined based on the relative distance detected by the distance calculation means. A transmission start time determining means to perform,
Based on the transmission start time determined by the transmission start time determination means, a predetermined process is performed on the second packet to generate the second transmission packet, and the second transmission packet is transmitted to the repeater. A vehicle-to-vehicle communication system comprising: vehicle-side packet transmitting means for transmitting. In a vehicle used for a vehicle-to-vehicle communication system that performs communication between vehicles by wireless communication via a repeater,
Packet receiving means for receiving a first transmission packet transmitted from the repeater;
Vehicle information generating means for generating vehicle information relating to the own vehicle;
Packet generating means for generating a second packet based on the vehicle information generated by the vehicle information generating means;
Traveling direction detection means for detecting the traveling direction of the host vehicle;
The traveling direction detection is performed by setting a time from the reception time of the first transmission packet received by the packet reception means to the time to start transmission of the second transmission packet generated based on the second packet, as a transmission start time. Transmission start time determining means for determining the transmission start time based on the traveling direction of the host vehicle detected by the means;
Based on the transmission start time determined by the transmission start time determination means, a predetermined process is performed on the second packet to generate the second transmission packet, and the second transmission packet is transmitted to the repeater. And a packet transmission means for transmitting the vehicle. The vehicle according to claim 3, wherein
The transmission start time determining unit is configured when the first transmission packet received by the packet receiving unit on the vehicle side includes determination criterion information serving as a reference for determining the transmission start time. The transmission start time is determined based on the determination criterion information and the traveling direction of the host vehicle detected by the traveling direction detection means. The vehicle according to claim 4, wherein
The transmission start time determining means has a function of sensing a carrier,
When the first transmission packet received by the vehicle-side packet receiving means includes determination reference information serving as a reference for determining the transmission start time, the determination reference information, and the Based on the traveling direction of the host vehicle detected by the traveling direction detection means, a carrier sense start time is determined, the carrier is sensed according to the carrier sense start time, and when the channel is in an idle state, A vehicle characterized by determining a transmission start time. In a vehicle used for a vehicle-to-vehicle communication system that performs communication between vehicles by wireless communication via a repeater,
Packet receiving means for receiving a first transmission packet transmitted from the repeater;
Vehicle information generating means for generating vehicle information relating to the own vehicle;
Packet generating means for generating a second packet based on the vehicle information generated by the vehicle information generating means;
Vehicle position detecting means for detecting the position of the host vehicle;
Based on the position information of the repeater included in the first transmission packet received by the packet reception means and the position of the own vehicle detected by the vehicle position detection means, A distance calculating means for calculating a relative distance to the vehicle;
The time from the reception time of the first transmission packet to the time of starting transmission of the second transmission packet generated based on the second packet is defined as the transmission start time, and the relative distance detected by the distance calculation means Based on the transmission start time determining means for determining the transmission start time,
Based on the transmission start time determined by the transmission start time determination means, a predetermined process is performed on the second packet to generate the second transmission packet, and the second transmission packet is transmitted to the repeater. A vehicle-side packet transmitting means for transmitting the vehicle. The vehicle according to claim 6, wherein
The transmission start time determining unit is configured when the first transmission packet received by the packet receiving unit on the vehicle side includes determination criterion information serving as a reference for determining the transmission start time. The transmission start time is determined based on the determination criterion information and the relative distance detected by the distance calculation means. The vehicle according to claim 7, wherein
The transmission start time determining means has a function of sensing a carrier,
When the first transmission packet received by the vehicle-side packet receiving means includes determination reference information serving as a reference for determining the transmission start time, the determination reference information, and the Based on the relative distance detected by the distance calculation means, a carrier sense start time is determined, a carrier is sensed according to the carrier sense start time, and the transmission start time is set when the channel is in an idle state. A vehicle characterized by deciding. In a repeater for use in a vehicle-to-vehicle communication system that communicates between vehicles by wireless communication via a repeater,
Packet generating means for generating the first packet based on arbitrary information at regular intervals;
Packet transmission means for generating a first transmission packet by performing a predetermined process on the first packet generated by the packet generation means on the repeater side, and transmitting the first transmission packet to each of the vehicles When,
Packet receiving means for receiving a second transmission packet transmitted from each of the vehicles,
The said packet generation means produces | generates a said 1st packet so that the criteria information used as the reference | standard for making the said vehicle determine the transmission start time of a said 2nd transmission packet may be included. The repeater characterized by the above-mentioned. The repeater according to claim 9,
Furthermore, based on the second transmission packet received by the packet receiving means, vehicle position identification means for identifying the position of the vehicle that transmitted the second transmission packet,
The packet generation means identifies the degree of vehicle congestion in each direction based on the position of each vehicle identified by the vehicle position identification means, and the determination is made according to the identified degree of vehicle congestion in each direction. The repeater characterized by determining reference information and generating the first packet so as to include the determined determination reference information. The inter-vehicle communication system according to claim 2,
Furthermore, it has traveling direction detection means for detecting the traveling direction of the host vehicle,
The transmission start time determining means uses a time from the reception time of the first transmission packet to the time of starting transmission of the second transmission packet as a transmission start time, and the transmission start time determining means The vehicle-to-vehicle communication system, wherein the transmission start time is determined based on a traveling direction and a traveling direction of the host vehicle detected by the traveling direction detecting means. The vehicle according to claim 6, wherein
Furthermore, it has traveling direction detection means for detecting the traveling direction of the host vehicle,
The transmission start time determining means uses a time from the reception time of the first transmission packet to the time of starting transmission of the second transmission packet as a transmission start time, and the transmission start time determining means The transmission start time is determined based on the traveling direction and the traveling direction of the host vehicle detected by the traveling direction detecting means. The vehicle according to claim 6 or 12,
The vehicle according to claim 1, wherein the transmission start time determining means does not transmit a packet when the communication priority is low. The vehicle according to claim 6 or 12,
The transmission start time determining means changes a packet transmission cycle longer.

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