JP2014016973A - Optical beacon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical beacon which is multi-rate compatible in the uplink direction and is capable of properly receiving high-speed frames transmitted after low-speed frames.SOLUTION: The present invention is related to an optical beacon 4 which wirelessly communicates with on-vehicle devices 2 of traveling vehicles 20 using optical signals. The optical beacon 4 includes: an optical receiver unit 11 capable of making photoelectric conversion at high and low two transmission rates; an optical transmitter unit 10 capable of making electro-optical conversion at a predetermined transmission rate; and a communication control unit (beacon controller) 7 capable of reproducing low-speed frames UL1 or high-speed frames UL2 from an electrical signal output from the optical receiver unit 11. Position setting is also done to place a next second upstream end on the upstream of a next first upstream end or at substantially the same position as the next first upstream end. The first upstream end is a physically or logically most upstream end P1, P1' of an area AR1 in which low-speed frames UL1 can be received. The second upstream end is a physically or logically most upstream end P2, P2' of an area AR2 in which high-speed frames UL2 can be received.

Description

  The present invention relates to an optical beacon that performs wireless communication using an optical signal with an in-vehicle device of a traveling vehicle.

As a traffic information service using a road-to-vehicle communication system, so-called VICS (Vehicle Information and Communication System: registered trademark of Road Traffic Information Communication System Center) using optical beacons, radio beacons or FM multiplex broadcasting has already been developed. ing.
Among these, the optical beacon employs optical communication using near infrared rays as a communication medium, and is capable of bidirectional communication with the in-vehicle device. Specifically, uplink information including travel time information between beacons held by the vehicle is transmitted from the in-vehicle device to the infrastructure-side optical beacon.

On the other hand, downlink information including traffic jam information, section travel time information, event regulation information, lane notification information, and the like is transmitted from the optical beacon to the in-vehicle device (see, for example, Patent Document 1).
For this reason, the optical beacon includes a beacon head (projector / receiver) that transmits / receives an optical signal to / from the vehicle-mounted device, and the transmitter / receiver inputs the transmission signal input from the beacon controller to the light emitting diode. An optical transmitter that transmits downlink light and an optical receiver that converts an optical signal received by the photodiode into an electrical signal and outputs the electrical signal to the beacon controller are mounted.

JP 2005-268925 A

Between 1993 and the present, about 54,000 heads of optical beacons have been deployed on roads throughout the country, but the communication capacity has been expanded compared to conventional optical communication systems using such existing optical beacons. It is being considered to improve the system.
As measures for expanding the communication capacity, there are measures such as increasing the transmission rate for each of the uplink and downlink, expanding the communication area, or changing the communication protocol. Among these, if the uplink speed is increased from the current level (64 kbps), a large amount of probe data can be collected from the in-vehicle device without greatly expanding the communication area, which can be used for the advancement of traffic signal control. .

As described above, in order to realize a higher uplink speed, an optical beacon (hereinafter also referred to as “new optical beacon”) corresponding to high-speed uplink reception and an in-vehicle device (hereinafter referred to as “high-speed uplink transmission”). , Also referred to as “new in-vehicle device”).
However, even if new optical beacons and new in-vehicle devices are introduced, these new devices will not be compatible with existing road-to-vehicle communication systems unless they are compatible with conventional devices that can only perform low-speed uplink communication. Increase in link speed is hindered.

  Therefore, in order to ensure upward compatibility of the new in-vehicle device, an optical beacon that can receive uplinks only from low-speed frames from in-vehicle devices that perform only low-speed uplink transmission (hereinafter also referred to as “old in-vehicle devices”) Adopt a communication protocol that uplinks a low-speed frame storing vehicle identification information (hereinafter also referred to as “vehicle ID”) that can be recognized by “old optical beacon”) before the high-speed frame. For example, the old optical beacon can perform downlink switching, and the new in-vehicle device can communicate with the old optical beacon.

  Furthermore, if a communication protocol is adopted that provides a transmission interruption period for receiving a downstream frame including lane notification information storing a vehicle ID between a low-speed frame to be transmitted first and a high-speed frame to be transmitted thereafter. By repeating the retransmission of a plurality of uplink frames without the vehicle-mounted device noticing the downlink frame storing its own vehicle ID, it is possible to prevent the loss of the downlink frame reception opportunity.

Note that, as will be described in detail in a later embodiment, a basic communication procedure performed by the new in-vehicle device that provides the transmission interruption period is, for example, as follows.
1) Wait until the downstream frame DL1 is received.
2) If the downstream frame DL1 (information type may or may not be considered) is received, the low-speed frame UL1 including the vehicle ID is transmitted.

3) Wait for the downlink frame DL2 (ID storage frame including lane notification information in which the vehicle ID is stored) from the optical beacon.
4) If the lane notification information in which the vehicle ID is stored within a certain time is not received, the low-speed frame UL1 is retransmitted.
5) If the lane notification information in which the vehicle ID is stored within a certain time is received, the retransmission of the low speed frame UL1 is stopped and the transmission of the high speed frame UL2 is started.

  By the way, in the new optical beacon that supports high-speed uplink reception, in order to separate the upstream electrical signal from disturbance (the electrical signal generated when the light receiving element senses downlink light or reflected sunlight), An electrical filter that passes electrical signals (for example, 64 kbps and 256 kbps) but blocks a band component of about 500 kHz or more including a downstream band electrical signal (for example, 1024 kbps) (for example, a low-pass filter having a cutoff frequency of about 500 kHz: Is not an optical filter) in the receiving circuit of the optical receiving unit.

When such a receiving circuit is employed, the high-speed frame close to the cutoff frequency is slightly less transparent to the filter than the low-speed frame, and as a result, the high-speed frame reception performance is slightly worse than the low-speed frame reception performance. Become.
This difference in reception performance due to the difference in transmission speed appears as the difference between areas that can receive low-speed frames and high-speed frames as it is, and the most upstream end of the area that can receive low-speed frames can receive high-speed frames. It is upstream from the most upstream end.

  On the other hand, as in the communication procedure described above, for example, a new in-vehicle device that supports high-speed uplink transmission first transmits a low-speed frame, and then confirms the return of its vehicle ID and then transmits a high-speed frame. When the rules are adopted, depending on the traveling speed of the vehicle, the new in-vehicle device may receive the high-speed frame in an area where the low-speed frame can be received but the high-speed frame cannot be received (see “dead area F” in FIG. 11) May be sent.

And if a high-speed frame is transmitted in such a dead zone, the new optical beacon cannot receive the high-speed frame, and if the communication protocol does not allow retransmission of the high-speed frame, there is no possibility that the new optical beacon can acquire the high-speed frame. End up.
The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an optical beacon compatible with multirate in the uplink direction, which can appropriately receive a high-speed frame transmitted after a low-speed frame.

  (1) The optical beacon of the present invention is an optical beacon that performs wireless communication with an in-vehicle device of a traveling vehicle using an optical signal, and an optical receiver capable of photoelectric conversion at two types of high and low transmission speeds; An optical transmission unit capable of electro-optical conversion at a predetermined transmission rate and a communication control unit capable of reproducing a low-speed frame or a high-speed frame from an electric signal output from the optical reception unit are defined as follows. The second upstream end is positioned upstream or substantially at the same position as the first upstream end defined below.

First upstream end: the physical or logical most upstream end of the area that can receive the low-speed frame Second upstream end: the physical or logical most upstream end of the area that can receive the high-speed frame In this specification, , "Substantially the same position" means that the difference in distance between the first upstream end and the second upstream end is such that it can be regarded as within an error range (for example, 5 cm) from the viewpoint of vehicle position measurement. To do.

  Also, in this specification, “physical uppermost stream end” means the uppermost stream end of the area that can be received by the optical receiver, and “logical uppermost stream end” means communication control. This means that it is the apparent uppermost end that can be set by the information processing of the part.

According to the optical beacon of the present invention, since the above-described position setting is performed, there is no region where the low-speed frame can be received but the high-speed frame cannot be received (“dead region F” in FIG. 11), and the low-speed frame If it is received, then the subsequent high-speed frame can be received without fail.
Therefore, it is possible to obtain an optical beacon that supports multirate in the uplink direction and can appropriately receive a high-speed frame transmitted after a low-speed frame.

(2) In the optical beacon of the present invention, the optical receiver does not pass the light receiving element that receives the upstream optical signal, the amplifier that amplifies the electrical signal output from the light receiving element, and the downstream band amplified signal. In the case of including a filter that allows the amplified signal in the upstream band to pass through and a comparator that binarizes the filtered electric signal, the position setting may be performed by the following circuit design.
Circuit design: Circuit design that determines the constants of the circuit elements included in the optical receiver so that the gain of the electrical signal in the comparator is larger in the high-speed frame than in the low-speed frame.

(3) The circuit design may be performed on the circuit element constituting at least one of the amplifier and the filter, for example.
With this circuit design, the second upstream end, which is the “physical” uppermost stream end, can be set upstream or substantially at the same position as the first upstream end, which is the “physical” uppermost stream end. .
In this case, the circuit design for determining the constants of the circuit elements takes a certain amount of time, but the circuit scale can be reduced as compared with an optical setting described later that requires two receiving systems for low speed and high speed. There is an advantage.

(4) In the optical beacon of the present invention, when the communication control unit can measure the uplink position of the low-speed frame from the electrical signal output from the optical reception unit, the position setting is performed by the communication control. This can be performed by the next reception restriction process by the unit.
Reception restriction processing: processing for performing downlink switching based on the low-speed frame only when the uplink position of the low-speed frame is downstream of the fixed point position defined as the threshold value representing the second upstream end.

In this case, since the communication control unit performs the above-described reception restriction process, the second upstream end as the “physical” or “logical” uppermost stream end is used as the first “logical” uppermost stream end. It can be set upstream or substantially the same position as the upstream end.
Further, in this case, since the position can be set only by changing the computer program executed by the communication control unit, the present invention is relatively easy as compared with the case where the position is set by the above-described circuit design or optical setting described later. There is an advantage that it can be implemented.

(5) In the case of an optical beacon whose position is set by reception-restricting processing, the in-vehicle device that is the communication partner transmits a low-speed frame at high speed in one road-to-vehicle communication with the optical beacon. It is preferable that the transmission is performed before the frame.
The reason for this is, for example, assuming that the optical beacon performs downlink switching in response to reception of a low-speed frame, and the in-vehicle device transmits a high-speed frame according to the content of the downlink frame after downlink switching. If the low-speed frame is transmitted before the high-speed frame, the in-vehicle device does not transmit the high-speed frame unless the optical beacon performs downlink switching, so that the in-vehicle device transmits the high-speed frame in the dead area. This is because it can be effectively prevented.

(6) Further, in the case of an optical beacon where the position is set by the reception-restricting process, the above-mentioned “fixed position” is, for example, the second position that is further upstream from the upstream end of the uplink region in the regulations What is necessary is just to select from the range (including both end positions) to the upstream end.
The reason for this is that the physical first and second upstream ends are not located downstream of the upstream end of the uplink region in terms of regulations, so if a fixed point position is selected from the above range. This is because the reception limiting process can be appropriately executed.

(7) In the optical beacon of the present invention, when the optical receiver includes a low-speed reception system for receiving a low-speed frame and a high-speed reception system for receiving a high-speed frame, the position setting is performed. May be performed by the following optical setting.
Optical setting: The physical uppermost end of the area where the low-speed receiving system can receive the low-speed frame is upstream or substantially higher than the physical uppermost end of the area where the high-speed receiving system can receive the high-speed frame. Setting to determine the receiving direction (light receiving direction) of both receiving systems

With this optical setting, the second upstream end, which is the “physical” uppermost stream end, is set upstream or substantially at the same position as the first upstream end, which is the “physical” uppermost stream end. it can.
In this case, since the position setting is performed by optical setting that determines the receiving directions of both receiving systems, there is an advantage that the position setting can be performed more reliably than the position setting by the reception limiting process or the circuit design. is there.

(8) The road-to-vehicle communication system of the present invention includes an on-vehicle device of a traveling vehicle, and the optical beacon according to any one of the above (1) to (7) that performs wireless communication with the on-vehicle device using an optical signal. It is characterized by having.
Therefore, the road-to-vehicle communication system of the present invention has the same effects as the optical beacon of the present invention described in any of the above (1) to (7).

  As described above, according to the present invention, since there is no region in which a low-speed frame can be received but a high-speed frame cannot be received, a high-speed frame transmitted after the low-speed frame can be appropriately received. A rate-enabled optical beacon can be provided.

It is a block diagram which shows schematic structure of a road-vehicle communication system. It is the top view of the road which looked at the installation part of an optical beacon from the top. It is a side view which shows the communication area | region of an optical beacon. It is a sequence diagram which shows the conventional communication procedure. It is a figure which shows the mixed state of the old and new optical beacons and vehicle equipment. It is a flowchart which shows upward compatible control of a new light beacon. It is a frame block diagram of uplink information. It is a frame block diagram of downlink information. It is a sequence diagram which shows the road-to-vehicle communication when not providing a transmission interruption period. It is a sequence diagram which shows the road-to-vehicle communication in the case of providing a transmission interruption period. It is explanatory drawing which shows an example of the dead area of a high-speed flame | frame. It is a circuit block diagram of the new light beacon which concerns on 1st Embodiment. It is explanatory drawing of the measurement principle of an uplink position using a position detection element. It is a flowchart which shows an example of the reception restriction process by main CPU. It is a circuit block diagram of the new optical beacon which concerns on the modification of 1st Embodiment. It is explanatory drawing of the measurement principle of an uplink position using division | segmentation PD. (A) is a figure which shows the circuit structural example of the filter used for the new optical beacon concerning 2nd Embodiment, (b) is a graph which shows the frequency characteristic of a filter. It is a graph which shows an example of the frequency characteristic of the amplifier used for the new optical beacon concerning 2nd Embodiment. It is a circuit block diagram of the new light beacon which concerns on 3rd Embodiment. It is a side view which shows the area which can receive the low-speed receiving system and the high-speed receiving system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overall system configuration]
FIG. 1 is a block diagram showing an overall configuration of a road-vehicle communication system according to an embodiment of the present invention. As shown in FIG. 1, the road-to-vehicle communication system of the present embodiment includes an infrastructure-side traffic control system 1 and an in-vehicle device 2 mounted on a vehicle 20 traveling on a road R.

The traffic control system 1 includes a central device 3 provided in a traffic control room and the like, and a large number of optical beacons (optical vehicle detectors) 4 installed in various places on the road R. The optical beacon 4 transmits near infrared rays. Wireless communication can be performed with the in-vehicle device 2 by optical communication as a communication medium.
The optical beacon 4 includes a beacon controller 7 and a plurality (four in FIG. 1) of beacon heads (also referred to as projectors / receivers) 8 connected to the sensor interface of the beacon controller 7. .

The beacon controller 7 is connected to a communication unit 6 on the infrastructure side, and the communication unit 6 is connected to the central apparatus 3 by a communication line 5 such as a telephone line.
The communication unit 6 can be configured by, for example, a traffic signal controller that controls the color of a signal lamp, an information relay device that performs a relay process of traffic information on the infrastructure side, and the like.

The optical beacon 4 of this embodiment employs a full-duplex communication method. That is, the beacon controller 7 to be described later can simultaneously perform transmission control in the downlink direction for the optical transmission unit 10 and reception control in the uplink direction for the optical reception unit 11.
On the other hand, the in-vehicle device 2 of the present embodiment employs a half-duplex communication method. That is, the below-described vehicle-mounted controller 21 does not simultaneously perform uplink direction transmission control for the optical transmission unit 23 and downlink direction reception control for the optical reception unit 24.

  The uplink direction transmission control for the optical transmission unit 23 and the downlink direction reception control for the optical reception unit 24 may be performed at the same time, but as a matter of fact, only one of them is configured to function. It shall be. That is, it is difficult to receive the downlink during uplink transmission.

[Configuration of optical beacon]
The beacon head 8 of the optical beacon 4 has an optical transmitter 10 capable of electro-optical conversion and an optical receiver 11 capable of photoelectric conversion inside the casing.
Among these, the optical transmission unit 10 has a light emitting element that transmits downlink light (optical signal in the downlink direction) made of near infrared rays to the downlink area DA (see FIG. 3), and the optical reception unit 11 is up It has a light receiving element that receives uplink light (an optical signal in the uplink direction) made of near infrared rays from the vehicle-mounted device 2 in the link area UA (see FIG. 3).

The optical transmitter 10 transmits a downstream frame transmitted from the beacon controller 7 into a serial transmission signal having a predetermined transmission rate, and converts the output transmission signal into an optical signal in the downlink direction. It is comprised from the light emitting element which consists of diodes.
In the optical beacon 4 of the present embodiment, the transmission speed of the optical signal transmitted by the optical transmitter 10 is 1024 kbps as in the conventional old optical beacon.

The light receiving unit 11 includes a light receiving element such as a photodiode and a receiving circuit that amplifies an electric signal output from the light receiving element and generates a digital reception signal.
In the optical beacon 4 of the present embodiment, the optical receiver 11 is multi-rate capable of photoelectric conversion at two types of transmission rates, high and low, and the lower transmission rate is 64 kbps as in the conventional old optical beacon. It is. The higher transmission speed may be 128 kbps, 192 kbps, 256 kbps, 384 kbps, 512 kbps, 1024 kbps, etc., but in this embodiment, it is assumed to be 256 kbps.

FIG. 2 is a plan view of the road R when the installation portion of the optical beacon 4 of this embodiment is viewed from above.
As shown in FIG. 2, the optical beacon 4 of the present embodiment is installed on a road R having a plurality of (four in the illustrated example) lanes R1 to R4 in the same direction, and corresponds to the lanes R1 to R4. A plurality of beacon heads 8 provided, and one beacon controller 7 serving as a control unit that collectively controls these beacon heads 8 are provided.

The beacon controller 7 is composed of a computer device having a signal processing unit, a CPU, a memory, and the like. It has a function as a communication control part which performs.
The beacon controller 7 stores a computer program for communication control in a storage device, and the CPU functions as the communication control unit when the CPU reads and executes the program.

The beacon controller 7 is installed on a support column 13 standing on the side of the road. Each beacon head 8 is attached to an erection bar 14 installed horizontally on the road R side from the support column 13 and is disposed immediately above each lane R1 to R4 of the road R.
The light emitting element of the beacon head 8 emits near infrared rays toward the upstream side in the vehicle traveling direction from directly below the lanes R <b> 1 to R <b> 4, thereby performing road-to-vehicle communication with the in-vehicle device 2. A communication area A is set on the upstream side of the head 8.

[Communication area of optical beacons]
FIG. 3 is a side view showing the communication area A of the optical beacon 4.
As shown in FIG. 3, the communication area A of the optical beacon 4 includes a downlink area (area provided with solid hatching in FIG. 3) DA and an uplink area (area provided with dashed hatching in FIG. 3) UA. It consists of.

Among these, the downlink area DA is an area in which an in-vehicle head 22 that is a projector / receiver of the in-vehicle device 2 can receive an optical signal in the downlink direction transmitted from the beacon head 8. d, a range indicated by Δdac having apexes at positions a and c at a height of 1 m above the ground.
The uplink area UA is an area where the beacon head 8 can receive an optical signal in the uplink direction transmitted from the in-vehicle head 22, and the light projecting / receiving position d and the positions b and c at a height of 1 m above the ground. This is the range indicated by Δdbc as the apex.

Accordingly, the upstream end c of the downlink area DA and the uplink area UA coincide with each other, and the uplink area UA overlaps with the upstream portion of the downlink area DA in the vehicle traveling direction (the right side portion in FIG. 3). Further, the vehicle traveling direction length of the downlink area DA coincides with the same direction length of the entire communication area A.
In the case of the old optical beacon (optical vehicle sensor), the formal area dimensions of the downlink area DA and the uplink area UA are defined by the regulations.

For example, in the case of an old optical beacon for general roads, the downstream end a of the downlink area DA is located 1.0 to 1.3 m upstream immediately below the beacon head 8, and from the downstream end a of the downlink area DA. The distance to the downstream end b of the uplink area UA is defined as 2.1 m.
Further, the distance from the downstream end b of the uplink area UA to the upstream end c of the area UA is defined as 1.6 m. Accordingly, the total length of the official communication area A in the vehicle traveling direction (the length between ac) is 3.7 m.

  On the other hand, in the optical beacon 4 (new optical beacon) of the present embodiment, the downstream end a of the downlink area DA is extended to a position immediately below the beacon, and the upstream end c is extended to the upstream side of the above-mentioned regulation, thereby reducing the downlink area DA. The vehicle traveling direction range is set wider than in the case of an old optical beacon that does not support high-speed uplink reception.

As a specific numerical example, when the area directly below the beacon head 8 is 0 m (origin) and the upstream direction is a positive direction, the range of the downlink area DA of this embodiment (position from position a in FIG. 3) The range up to c) is 0.70 to 6.04 m.
When the downlink area DA is set wider in this way, the reliability of the in-vehicle device 2 receiving the optical signal in the downlink direction is increased and the communication time is increased, so that the communication capacity in the downlink direction can be increased. .

In addition, the range of the uplink area UA (the range from the position b to the position c in FIG. 3) of the present embodiment is 3.04 to 6.04 m, and the position of the upstream end c is 1. It is extended upstream by 04m.
Thus, if the uplink area UA is set wider, the reliability of the optical beacon 4 to receive the optical signal in the uplink direction is increased and the communication time is increased, so that the communication capacity in the uplink direction can be expanded. .

[Configuration of in-vehicle device]
As shown in FIG. 3, the in-vehicle device 2 of the present embodiment includes an in-vehicle controller 21 and an in-vehicle head 22, and an optical transmitter 23 and an optical receiver 24 are accommodated in the in-vehicle head 22. ing.
Among these, the optical transmission unit 23 has a light emitting element that emits uplink light (uplink direction optical signal) made of near infrared, and the optical reception unit 24 uses near infrared transmitted to the downlink area DA. A light receiving element that receives downlink light (an optical signal in the downlink direction).

The optical transmission unit 23 is a light emitting circuit that converts an upstream frame output from the in-vehicle controller 21 into a serial transmission signal having a predetermined transmission rate, and converts the output transmission signal into an optical signal in the uplink direction. It is comprised from the light emitting element which consists of diodes.
In the in-vehicle device 2 of the present embodiment, the optical transmission unit 23 is multi-rate capable of electro-optical conversion at two types of high and low transmission rates, and the lower transmission rate is 64 kbps as in the conventional old in-vehicle device. It is. The higher transmission speed may be 128 kbps, 192 kbps, 256 kbps, 384 kbps, 512 kbps, 1024 kbps, etc., but in this embodiment, it is assumed to be 256 kbps.

The light receiving unit 24 includes a light receiving element such as a photodiode and a receiving circuit that amplifies an electric signal output from the light receiving element and generates a digital reception signal.
In the in-vehicle device 2 of the present embodiment, the transmission speed of the optical signal received by the optical receiving unit 24 is 1024 kbps as in the conventional old in-vehicle device.

The in-vehicle controller 21 includes a computer device having a signal processing unit, a CPU, a memory, and the like, and has a function as a communication control unit that performs road-to-vehicle communication with the optical beacon 4.
The in-vehicle controller 21 stores a computer program for communication control in a storage device, and the CPU functions as the communication control unit when the CPU reads and executes the program.

Furthermore, the in-vehicle controller 21 generates traveling data of the host vehicle (for example, probe information that is traveling locus data in which passing positions and passing times are arranged in time series) as uplink data, and the optical transmission unit 23. It also has a function of transmitting to the uplink.
In this case, by increasing the uplink speed, more probe information (information that lengthens the road section that records the travel trajectory or increases the recording density of the passing position and the passing time in the same road section) Can be sent.

In addition, the vehicle-mounted controller 21 of this embodiment may have a circuit configuration in which a simple control unit including an ASIC (Application Specific Integrated Circuit) is provided separately from the main body control unit including the CPU.
This simple control unit, for example, has a function of generating a low-speed uplink frame including identification information (hereinafter referred to as “vehicle ID”) of the own vehicle 20 when the optical receiver 24 receives some downlink frame. Have

[Definition of terms, etc.]
Here, terms used in this specification are defined.
Downlink frame DL1: A downlink frame that the optical beacon 4 repeatedly transmits toward the downlink area DA before downlink switching described later.
Uplink frame UL1: An uplink frame transmitted by the in-vehicle device 2 in response to reception of the downlink frame DL1 is a transmission frame having a low transmission rate. Also referred to as “low speed frame UL1”.

Uplink frame UL2: An uplink frame transmitted by the in-vehicle device 2 in response to reception of the downlink frame DL1 is a frame having a high transmission rate. Also referred to as “high-speed frame UL2”.
When the in-vehicle device 2 is a new in-vehicle device 2A (see FIG. 5) that supports high-speed uplink transmission, both the low-speed frame UL1 and the high-speed frame UL2 can be transmitted as an upstream frame, and the in-vehicle device 2 can perform high-speed uplink transmission. In the case of the incompatible old vehicle-mounted device 2B (see FIG. 5), only the low-speed frame UL1 can be transmitted as the upstream frame.

Downlink frame DL2: A downlink frame (including a case of a series of frames) that the optical beacon 4 repeatedly transmits toward the downlink area DA after downlink switching described later.
ID storage frame: “Low speed” generated by the in-vehicle device 2 by writing the value of the vehicle ID of the host vehicle in a predetermined storage area (for example, “Vehicle ID” (see FIG. 7) in the header of the uplink information). This is the uplink frame UL1.

Loop frame: When the optical beacon 4 receives an ID storage frame, it refers to the downlink frame DL2 generated by writing the same value as the vehicle ID included in the frame in a predetermined storage area.
ID loopback: When the optical beacon 4 receives an ID storage frame, it refers to a process of generating a loopback frame and performing downlink transmission.

In addition, when the optical beacon 4 receives the ID storage frame, the downlink switching may be performed without continuously transmitting the return frame.
Loopback of vehicle ID: the vehicle-mounted device 2 generates an ID storage frame, uplink-transmits the generated ID storage frame, and the optical beacon 4 performs ID loopback to loop the vehicle ID to the vehicle-mounted device 2 that is the transmission source. This is a series of processing to be backed up.

Downlink switching: Refers to changing the substantial data contents included in the downlink frames DL1 and DL2 repeatedly transmitted by the optical beacon 4 before and after the switching.
In the present embodiment, the downlink frame DL2 after downlink switching includes a turn-back frame and a downlink frame DL2 including provision information for the vehicle corresponding to the vehicle ID. The provided information can include information such as traffic jam information, section travel time information, and event regulation information.

Such information is also provided to old in-vehicle devices that do not support high-speed uplink transmission.
However, in the optical beacon 4 (new optical beacon) of the present embodiment, for example, the signal information including the switching timing of the signal lamp color at the intersection as the provision information for the vehicle equipped with the new in-vehicle device corresponding to the high-speed uplink transmission, It is also possible to provide dedicated information predetermined for a new vehicle-mounted device, such as charging station information indicating a route to the nearest charging station, which is useful information when the vehicle 20 is an electric vehicle (see FIGS. 9 and 10). ).

As the data storage area of the vehicle ID in the upstream frame UL1 and the downstream frames DL1 and DL2, any area may be used. For example, a “header part” or “lane notification information” may be used.
The lane notification information of the downlink frames DL1 and DL2 includes a field for storing a vehicle ID for each lane R1 to R4 (FIG. 2), and a lane number can be assigned to each vehicle ID. For this reason, the vehicle-mounted device 2 of the vehicle 20 traveling in different lanes R1 to R4 reads which lane R1 to R4 the host vehicle is traveling by reading which of the vehicle IDs of the host vehicle is included in the storage field. Can be determined.

[Frame structure of upstream frame]
FIG. 7 is a frame configuration diagram of uplink information (uplink frame).
As shown in FIG. 7, the uplink frame UL1 is sequentially transmitted from the head in synchronization with a transmission control unit for synchronization (hereinafter referred to as “synchronization unit”), a header unit, an actual data unit, and a CRC (for CRC). Cyclic Redundancy Check) transmission control unit (hereinafter referred to as “CRC unit”).

As shown in FIG. 7, in the case of the uplink frame UL1, 1 byte is allocated to the synchronization section, 10 bytes are allocated to the header section, 59 bytes are allocated to the actual data section, and 4 bytes ( 1 byte idle part + 2 bytes CRC + 1 byte final synchronization part).
The header portion of the uplink information includes storage areas such as “number of subsystem key information”, “vehicle ID”, “vehicle equipment type”, “information type”, and “last frame flag”.

In the “number of subsystem key information” (hereinafter sometimes abbreviated as “number of information”), the number of “subsystem key information” stored in order from the top of the actual data portion is stored.
That is, when the number of information is zero, “subsystem key information” is not included in the actual data portion, and when the number of information is “1”, one “subsystem key information” is included in the actual data portion. When the number of information is “n”, n “subsystem key information” is included in the actual data part.

The above-mentioned “subsystem key information” indicates that the optical beacon 4 is downlink information such as public vehicle priority system (PTPS), vehicle operation management system (MOCS), field express support system (FAST), and safe driving support system (DSSS). Key information for selecting the additional information.
The in-vehicle device 2 determines the contents of “subsystem key information” and “subsystem key information” according to which system of the UTMS standard the host vehicle is compatible with.

For example, the in-vehicle device 2 sets the value of the “number of subsystem key information” in the header part to “1” when the host vehicle corresponds to one system of the UTMS standard, and follows the standard of the one system. The “subsystem key information (1)” of the contents is stored in the actual data part.
In addition, when the host vehicle is compatible with two systems of the UTMS standard, the in-vehicle device 2 sets the value of the “number of subsystem key information” in the header part to “2”, and sets the standard of the two systems respectively. The “subsystem key information (1)” and “subsystem key information (2)” having the contents are stored in the actual data part.

  Note that the data format of the “subsystem key information” differs depending on the standard of each system and will not be described in detail. For example, in the case of a safe driving support system (DSSS), the brake state, the turn signal state, the hazard Information such as state, vehicle speed, traveling direction, acceleration / deceleration, and accelerator pedal position is included.

On the other hand, the optical beacon 4 determines which system included in the in-vehicle device 2 is included in the UTMS standard according to the type of “subsystem key information” included in the uplink information, and conforms to the standard of the system. The provided information is stored in the downlink frame DL2 after downlink switching and transmitted in downlink. This provided information may be referred to as “value service information” in the sense that it is provided as a price for subsystem key information.
Thus, the “subsystem key information” is used by the old and new optical beacons 4 to determine the type of provision information after downlink switching.

“Vehicle ID” is an area for storing a vehicle ID value generated by the in-vehicle device 2 by itself or automatically generated by the optical beacon 4. The in-vehicle device 2 stores the vehicle ID stored at the time of uplink transmission. Is stored in the vehicle ID of the header portion of the upstream frame UL1.
“In-vehicle device type” is an area for storing the type of the in-vehicle device 2, and “Information type” is an area for storing the type of uplink information. Indicates whether the link transmission subject is new or old and whether the uplink information is high speed or low speed.

Specifically, when the in-vehicle device 2 (new in-vehicle device 2A) of the present embodiment transmits the low-speed uplink frame UL1, a predetermined value (eg, “6” ”) And a predetermined value (for example,“ 1 ”) indicating low speed is stored in“ Information Type ”.
Further, when the new in-vehicle device 2A transmits the high-speed uplink frame UL2, the new in-vehicle device 2A stores a predetermined value (for example, “6”) indicating the new in-vehicle device 2A in the “in-vehicle device type” and the high-speed in the “information type”. A predetermined value (for example, “4”) is stored.

Therefore, the optical beacon 4 (new optical beacon 4A) of the present embodiment is received from the new in-vehicle device 2A when the in-vehicle device type value of the received uplink frame UL is “6” and the information type value is “1”. If the value of the on-vehicle device type of the received uplink frame UL is “6” and the value of the information type is “4”, it is the high-speed frame UL2 from the new on-vehicle device 2A. Can be determined.
In the case of the old vehicle-mounted device 2B, since the value of the vehicle-mounted device type is set to other than “6”, the new light beacon 4A receives an uplink frame UL having a value of “vehicle-mounted device type” other than “6”. Can be determined to be the low-speed frame UL1 from the old vehicle-mounted device 2B.

When the new light beacon 4A completes reception of the low-speed frame UL1 from the new in-vehicle device 2A and the old in-vehicle device 2B, it generates a return frame in which the value of the vehicle ID included in the header part is stored in the lane notification information. Perform downlink switching with continuous transmission.
On the other hand, in this embodiment, the new light beacon 4A does not perform downlink switching when the reception of the high-speed frame UL2 from the new in-vehicle device 2A is completed. However, it is possible to adopt a protocol for performing downlink switching in response to the completion of reception of the high-speed frame UL2.

As described above, in this embodiment, the completion of the reception of the low-speed frame UL1 from the new in-vehicle device 2A and the old in-vehicle device 2B is a condition for the new optical beacon 4A to perform downlink switching with continuous transmission of the return frame (the opportunity or Trigger).
The completion of the reception of the high-speed frame UL2 from the new in-vehicle device 2A is not a condition (an opportunity or a trigger) for the new light beacon 4A to continuously transmit the return frame or perform downlink switching.

The “final frame flag” is used to indicate which of the uplink frame groups is the final frame when the in-vehicle device 2 (which may be new or old) transmits an uplink frame group including a plurality of uplink frames UL. Storage area.
That is, the in-vehicle device 2 stores a predetermined flag value (for example, “1”) only in the “final frame flag” of the last frame among a plurality of uplink frames UL constituting the uplink frame group, and other uplink frames UL The flag value is not stored in the frame UL.

[Frame structure of downstream frame]
FIG. 8 is a frame configuration diagram of downlink information (downlink frame).
As shown in FIG. 8, the frame configurations of the downlink frames DL1 and DL2 are similar to the frame configuration of the uplink frame UL1 (FIG. 7), in order from the top, the synchronization unit, the header unit, the actual data unit, and the CRC unit. Consists of.

In the case of the downlink frames DL1 and DL2, 1 byte is assigned to the synchronization part, 5 bytes are assigned to the header part, 123 bytes are assigned to the actual data part, and 4 bytes (1 byte idle part + 2 bytes) are assigned to the CRC part. CRC + 1 byte final synchronization part) is allocated.
In the actual data part of the downlink frames DL1 and DL2, any one of various information shown in FIG. 9 is stored as provision information for the vehicle 20.

Specifically, the optical beacon 4 (which may be old or new) includes “lane notification information” in the actual data portion of the downlink frame DL1 before downlink switching.
The optical beacon 4 corresponds to the subsystem key information uplinked from the vehicle-mounted device 2 in the actual data portion of the downlink frame DL2 after downlink switching, except when the downlink frame DL2 is a folded frame. The provided information is selected, and the selected provided information is included in the actual data part.

  The optical beacon 4 transmits the provision information in one downlink frame DL2 when the provision information fits in the capacity (123 bytes) of the actual data part. If the provision information does not fit, the optical beacon 4 is provided in a plurality of downlink frames DL2. Information may be sent.

As shown in FIG. 8, the storage area of “lane notification information” includes “vehicle ID”, “lane number”, “beacon identification flag”, and the like.
In the case of the downlink frame DL1 before downlink switching, the optical beacon 4 does not store a value in the “vehicle ID” of the “lane notification information”, but includes an ID storage frame from the in-vehicle device 2 and is included in the header portion thereof. The value of the vehicle ID to be stored is stored in the “vehicle ID” of the “lane notification information” to generate a return frame. The optical beacon 4 writes the lane number value corresponding to the beacon head 8 that acquired the uplink information in “lane number”.

The “beacon identification flag” is a storage area indicating whether or not the own device supports high-speed uplink reception.
That is, the optical beacon 4 stores a predetermined flag value (for example, “01”) in the “beacon identification flag” of the downlink frames DL1 and DL2 in the case of the new optical beacon 4A corresponding to the high-speed uplink reception by the own device. However, when the own optical beacon 4B does not support high-speed uplink reception, other values (for example, “00”) are stored in the “beacon identification flag” of the downlink frames DL1 and DL2.

  Therefore, the vehicle-mounted device 2 (new vehicle-mounted device 2A) of the present embodiment that supports high-speed uplink transmission uses the value of the “beacon identification flag” included in the “lane notification information” of the downlink frames DL1 and DL2 to determine the communication partner. Whether the optical beacon 4 is the new optical beacon 4A or the old optical beacon 4B can be determined.

The downlink frame group that is repeatedly transmitted from the optical transmission unit 10 of the optical beacon 4 after downlink switching is composed of 1 to 80 downlink frames DL2, and the repeatable transmission time is 250 ms.
The downlink frame DL2 is composed of an arbitrary number of frames corresponding to the amount of data to be transmitted in the downlink direction, and is repeatedly transmitted within the range of the transmittable time. Further, the transmission period of the downstream frame DL2 is about 1 ms.

Therefore, for example, when one significant data is constituted by three downlink frames DL2, the transmission cycle is about 3 ms, so that the data is repeatedly transmitted about 80 times within a predetermined transmittable time (250 ms). Will be.
However, if the downlink area DA is expanded to the vicinity immediately below the beacon head 8 as in this embodiment (see FIG. 3), the number of downlink frames DL2 to be repeatedly transmitted can be increased up to about 200.

  As shown in road-to-vehicle communication in FIG. 10 described later, when the optical beacon 4 performs downlink switching according to the ID storage frame, the uplink transmission time of the subsequent frame and the downlink after the downlink switching are performed. Since transmission times may overlap, it is preferable that the transmittable period of the downlink frame DL2 after downlink switching is (250 + α) ms (for example, 350 ms).

[Conventional road-to-vehicle communication]
FIG. 4 is a sequence diagram showing a conventional communication procedure performed in the communication area A.
Here, in FIG. 4, a frame with a white circle indicates that the frame does not include a vehicle ID (a frame having lane notification information without a vehicle ID), and a frame with a black circle indicates an ID loopback between road vehicles. Indicates that the frame is used (upstream “ID storage frame” or downstream “folding frame”). The same applies to FIGS. 9 and 10.

  In the following description of road-to-vehicle communication, it is assumed that the operation subject is the optical beacon 4 and the in-vehicle device 2, but the actual communication control is performed by the beacon controller (communication control unit) 7 of the optical beacon 4 and the in-vehicle device. The in-vehicle controller (communication control unit) 21 of the machine 2 executes. This also applies to the road-to-vehicle communication shown in FIGS.

As shown in FIG. 4, the optical beacon 4 (the old optical beacon 4B in the case of FIG. 4) continues to transmit the downlink frame DL1 at a predetermined transmission cycle from the beacon head 8 provided for each of the lanes R1 to R4. Yes. At this stage, the vehicle ID is not stored in the lane notification information.
When the vehicle 20 enters the downlink area DA, the vehicle-mounted device 2 (the old vehicle-mounted device 2B in the case of FIG. 4) receives the downlink frame DL1 including the lane notification information (no vehicle ID) or the other downlink frame DL1, It is detected that 20 has entered the communication area A of the optical beacon 4.

At this time, the in-vehicle device 2 generates a low-speed uplink frame UL1 (the ID storage frame U1 in FIG. 4) in which the vehicle ID is stored in the header portion, and switches the communication of the own device from reception to transmission once. Uplink frame UL1 is transmitted in uplink, and then the communication of the own device is returned from transmission to reception.
When there is information to be provided to the optical beacon 4 such as travel time information, the information is stored in the actual data portion of the ID storage frame U1.

When the ID storage frame U1 is properly received by the optical beacon 4 through the CRC check of the received frame, etc., the optical beacon 4 starts to repeatedly transmit the downlink frame DL2 after switching the downlink within 10 milliseconds at the latest. To do.
A plurality of downlink frames DL2 repeatedly transmitted after downlink switching includes a plurality of loopback frames (downlink frames DL2 with black circles) continuously transmitted at the head portion, and downlink frames including predetermined provision information repeatedly transmitted thereafter. It consists of DL2.

This repeated transmission of the downlink frame DL2 is repeated as much as possible within the predetermined time.
Also, as shown in FIG. 4, the return frame (downlink frame DL2 with a black circle) is a series of a plurality of downlink frames DL2 (for example, five downlink frames DL2) that constitute downlink information during the transmission period of provided information. Conventionally, it is included only at the beginning of a series of a plurality of downlink frames DL2, and is repeatedly transmitted (every 5 frames in the example of FIG. 4).

In addition, since a series of downlink frames DL2 constituting the downlink information can be stored up to 80, the return frames (downlink frames DL2 with black circles) are stored at a rate of one in 80 frames in the least frequent case. Will be.
The in-vehicle device 2 receives a plurality of downlink frames DL2 from the optical beacon 4, and determines whether or not any of the plurality of downlink frames DL2 includes lane notification information in which the vehicle ID of the host vehicle is written. To do.

When the determination result is affirmative, the in-vehicle device 2 confirms that the loopback of the vehicle ID of the own vehicle has been successful, and maintains the communication of the own device as received at this time.
Conversely, while the determination result is negative, the in-vehicle device 2 determines that the loopback of the vehicle ID of the host vehicle is not successful, switches the communication of the host device from reception to transmission, Retransmit UL1. In this case, for example, the in-vehicle device 2 transmits the uplink frame UL1 again after a predetermined time (for example, 30 ms) after transmission of the previously transmitted uplink frame U1. The in-vehicle device 2 repeats this retransmission operation until the vehicle ID loopback is successful.

[Problems in mixed situations]
FIG. 5 is a diagram illustrating a mixed state of old and new optical beacons 4A and 4B and in-vehicle devices 2A and 2B.
As shown in FIG. 5, the new optical beacon 4A supports uplink reception not only at a low transmission rate (64 kbps) but also at a high transmission rate (for example, 256 kbps). The optical beacon 4 of this embodiment corresponds to the new optical beacon 4A.
Similarly, the new in-vehicle device 2A supports uplink transmission not only at a low transmission rate (64 kbps) but also at a high transmission rate (for example, 256 kbps). The in-vehicle device 2 of the present embodiment corresponds to the new in-vehicle device 2A.

In contrast, the old optical beacon 4B is an optical beacon that performs only uplink reception at a low transmission rate (64 kbps), that is, an optical beacon that does not support uplink reception at a high transmission rate (for example, 256 kbps). It is.
Similarly, the old in-vehicle device 2B is an in-vehicle device that performs only uplink transmission at a low transmission rate (64 kbps), that is, an in-vehicle device that does not support uplink transmission at a high transmission rate (for example, 256 kbps). .

As described in the definition of terms above, “DL1” in FIG. 5 indicates a downlink frame transmitted by the old and new optical beacons 4A and 4B before downlink switching, and “UL1” in FIG. 5 indicates the downlink frame DL1. In response to reception, the old and new vehicle-mounted devices 2A and 2B indicate low-speed frames that can be transmitted, and “UL2” in FIG. 5 indicates a high-speed frame that can be transmitted only by the new vehicle-mounted device 2A.
Further, “DL2” in FIG. 5 indicates a downlink frame transmitted by the old and new optical beacons 4A and 4B after downlink switching.

Here, it is assumed that the new light beacon 4A and the new in-vehicle device 2A perform road-to-vehicle communication. When the new and old types of the optical beacon 4 cannot be discriminated, the new in-vehicle device 2A performs uplink transmission at a low speed in order to reliably receive and receive the uplink frame.
In this case, since the transmission speed in the downlink direction is “1024 kbps” in both the old and new cases, the new in-vehicle device 2A only receives the downlink frame DL1 from the new optical beacon 4A, and the communication partner is the new optical beacon 4A. I can't detect that.

As described above, if the new vehicle-mounted device 2A cannot recognize that it is communicating with the new optical beacon 4A while passing through the downlink area DA of the new optical beacon 4A, it is possible to perform high-speed uplink transmission. The in-vehicle device 2A performs uplink transmission at a low speed for the new optical beacon 4A, and the uplink speed cannot be increased.
Therefore, in the present embodiment, beacon identification information (for example, “beacon identification flag” in FIG. 8) indicating that the own apparatus is a new optical beacon 4A corresponding to high-speed uplink reception, It can be included in DL2.

Specifically, as described above, the flag field indicating the new and old types of the optical beacon 4 in the “lane notification information” (or “header portion”) of the downlink frames DL1 and DL2 to be transmitted by the optical transmission unit 10 in the downlink. Is defined in advance.
When the beacon controller 7 operates as the new optical beacon 4A, the beacon controller 7 turns on the flag fields of all the downlink frames DL1 and DL2 to be repeatedly transmitted or the downlink frames DL1 and DL2 for each predetermined period. Is operated as the old optical beacon 4B, the flag fields of the downstream frames DL1 and DL2 are turned off.

  Therefore, the new vehicle-mounted device 2A can determine that the communication partner is the new optical beacon 4A when the flag field of the received downlink frames DL1 and DL2 is on, and cannot detect the flag field when it is off. If it is determined that the communication partner is the old optical beacon 4B.

However, if the low-speed frame UL1 is always included in the upstream frame group, communication with both types of optical beacons 4 is possible without determining the new and old types of the optical beacon 4 of the communication partner.
The reason is that if the low-speed frame UL1 is used, both the old and new optical beacons 4A and 4B can communicate with each other as usual, and the old optical beacon 4B is able to communicate with other frames in the upstream frame group evenly as the high-speed frame UL2. This is because there is no particular problem.

  In this embodiment, it is assumed that the new in-vehicle device 2A is a type that does not perform the new / old determination of the optical beacon 4, but the new in-vehicle device 2A performs the new / old determination of the optical beacon 4 based on the flag field of the downlink frame DL1. As a result, the high-speed frame UL2 may be transmitted only when the communication partner is found to be the new light beacon 4A.

[Upward compatibility control of Shinko beacon]
FIG. 6 is a flowchart showing the upward compatible control performed by the beacon controller 7 of the new optical beacon 4A, which is the optical beacon 4 of the present embodiment.
As shown in FIG. 6, the beacon controller 7 of the new light beacon 4A repeatedly transmits a downlink frame DL1 with the flag field set to ON in a predetermined cycle (step ST1 in FIG. 6), so that the own device becomes a new light. It notifies the outside that it is a beacon 4A.

In this state, the beacon controller 7 determines whether or not the uplink frame UL1 has been received (step ST2 in FIG. 6), and continues the downlink transmission in step ST1 until the reception is detected.
When detecting the reception of the upstream frame UL1, the beacon controller 7 determines whether or not the transmission subject of the received upstream frame UL1 is the new in-vehicle device 2A corresponding to a high transmission rate (256 kbps in this embodiment). Determination is made (step ST3 in FIG. 6).

The determination in step ST3 can be made, for example, depending on whether the transmission rate of the upstream frame UL1 received by the optical receiver 11 is high or low. In this case, if the received upstream frame UL1 is high speed, it can be determined that the transmission subject is the new in-vehicle device 2A, and if it is low speed, it can be determined that the transmission subject is the old in-vehicle device 2B.
In addition, the vehicle-mounted controller 21 of the new vehicle-mounted device 2A may adopt a rule for including vehicle-mounted device identification information indicating that the device is the new vehicle-mounted device 2A compatible with high-speed uplink transmission in the uplink frame UL1.

Specifically, a flag field (for example, “vehicle equipment type” in FIG. 7) indicating the new and old types of the in-vehicle device 2 is defined in advance in the header portion of the uplink frame UL1 that the optical transmission unit 23 performs uplink transmission. .
When the in-vehicle controller 21 of the new in-vehicle device 2A operates the own device as the new in-vehicle device 2A, the on-vehicle controller 21 turns on the flag field of the uplink frame UL1 that is transmitted at high speed, and operates the own device as the old in-vehicle device 2B. In this case, the flag field of the upstream frame UL1 is turned off.

  Therefore, if such a rule is adopted, the beacon controller 7 can determine that the transmission subject is the new in-vehicle device 2A when the flag field of the received upstream frame UL1 is on, and the upstream frame UL1 When the flag field is off or when the flag field cannot be detected, it can be determined that the transmission subject is the old vehicle-mounted device 2B.

When the determination result of step ST3 is affirmative, that is, when the transmission subject of the uplink frame UL1 is the new in-vehicle device 2A, the beacon controller 7 performs downlink transmission for the new in-vehicle device after downlink switching ( Step ST4 in FIG. 6).
Downlink transmission for new in-vehicle equipment includes provision information for new in-vehicle equipment such as signal information and charging station information in addition to provision information for old in-vehicle equipment such as traffic jam information, section travel time information and event regulation information This is done by repeatedly transmitting the downstream frame DL2.

When the determination result of step ST3 is negative, that is, when the transmission subject of the uplink frame UL1 is the old vehicle-mounted device 2B, the beacon controller 7 performs downlink transmission for the old vehicle-mounted device after downlink switching ( Step ST5 in FIG. 6).
This downlink transmission for the old in-vehicle device is performed by repeatedly transmitting only the downlink frame DL2 including provision information for the old in-vehicle device such as traffic jam information, section travel time information, and event regulation information.

  As described above, downlink transmission of the downlink frame DL2 in steps ST4 and ST5 performed after downlink switching is performed until a predetermined time (for example, 250 ms) elapses from the downlink switching time point.

[Road-to-vehicle communication when no transmission interruption period is provided]
FIG. 9 is a sequence diagram showing road-to-vehicle communication when the new in-vehicle device 2A fails in the ID confirmation because the new in-vehicle device 2A transmits the upstream frames UL1 and UL2 without providing the “transmission interruption period”.

In FIG. 9, U1 to U4 indicate a plurality of uplink frames (uplink frame groups) UL1 and UL2 that are transmitted by the new vehicle-mounted device 2A that has detected the downlink frame DL1 in uplink.
In FIG. 9, the number of frames in the upstream frame group is 4, but the number of frames is not limited to 4, for example, 3 or more high-speed frames UL2 may be transmitted, There may be a case where only one high-speed frame UL2 having a relatively long data length is transmitted.

Further, the uplink frame U0 without hatching indicates a “low-speed frame” with a low transmission rate (64 kbps in this embodiment), and the uplink frames U2 to U4 with hatching have a high transmission rate. This indicates a “high-speed frame” of (256 kbps in the present embodiment).
Note that the illustrated distinction between the low-speed frame U0 and the high-speed frames U1 to U3 is the same in the road-to-vehicle communication in FIG.

When transmitting a large amount of data such as probe information in the uplink, the data cannot often be stored in the low-speed frame U0. Therefore, in the example of FIG. 9, the new in-vehicle device 2A transmits a total of three high-speed frames U1 to U3 following the low-speed frame U0.
Specifically, when the new in-vehicle device 2A receives the downlink frame DL1 in the downlink area DA, the new vehicle-mounted device 2A immediately uplinks the low speed frame U0 at a low speed, and subsequently uplinks the high speed frames U1 to U3.

In the present embodiment, since it is assumed that the new in-vehicle device 2A does not determine whether the communication partner is new or old, continuous transmission of the low-speed frame U0 and the high-speed frames U2 to U4 means that the communication partner of the new in-vehicle device 2A It is executed regardless of whether the beacon 4A or the old optical beacon 4B.
The optical beacon 4 of the communication partner of the new in-vehicle device 2A extracts the vehicle ID value from its header part upon completion of reception of the low-speed frame U0 included in the upstream frame group, and stores the value in the lane notification information. Perform frame continuous transmission and downlink switching.

That is, when the optical beacon 4 is the new optical beacon 4A, when it is detected that the value of “vehicle equipment type” in the low-speed frame U0 is “6” and the value of “information type” is “1”, Perform continuous transmission and downlink switching.
In addition, when the optical beacon 4 is the old optical beacon 4B, the type determination as described above cannot be performed. Therefore, when the reception of the low-speed frame U0 is completed, the return frame is continuously transmitted and downlinked immediately as usual. Do.

As described above, when the old optical beacon 4B receives the low-speed frame U0, which is an ID storage frame, under the assumption that large-capacity uplink transmission is not performed, it can immediately switch the downlink by continuously transmitting the return frame. The new light beacon 4A also immediately switches the downlink when the reception of the low-speed frame U0 is completed in order to maintain compatibility with the old vehicle-mounted device 2B.
Therefore, as shown in FIG. 9, depending on the transmission period of the high-speed frames U1 to U3 (U3 in the example of FIG. 9), the return frame may reach the new in-vehicle device 2A during the transmission.

In this case, when the new in-vehicle device 2A adopts the half-duplex communication method, the new light beacon 4A has already recognized the vehicle ID even though the return frame has arrived at the light receiving unit 24. Cannot be detected by the new in-vehicle device 2A.
In this case, as indicated by a broken line in FIG. 9, the new in-vehicle device 2 </ b> A retransmits the large-capacity uplink frame groups U <b> 0 to U <b> 3 including the low-speed frame U <b> 0 that is the ID storage frame.

This phenomenon is more likely to occur as the amount of provision information other than the lane notification information to be included in the downlink information increases.
The reason is that, as the amount of data of the provided information increases, the frequency of including the return frame in the downlink frame DL2 repeatedly transmitted by the new optical beacon 4A decreases, and thus the probability that the new in-vehicle device 2A cannot recognize the loopback increases. is there.

Therefore, for the return frame that is downlink transmitted periodically after every downlink switching (every 5 frames in the example of FIG. 9), the new in-vehicle device 2A has a timing that overlaps with the transmission period of the uplink frame groups U0 to U3. The possibility of receiving may be reduced.
In this case, even after retransmitting the uplink frame groups U0 to U3, the new in-vehicle device 2A does not notice the return frame, and uplink transmission (retransmission) of the uplink frame groups U0 to U3 is continued unnecessarily.

Then, as the number of frames transmitted by the new in-vehicle device 2A increases, the possibility that transmission of the uplink frame groups U0 to U3 is continued in the uplink area UA without noticing the return frame increases.
Therefore, the new in-vehicle device 2A that attempts to uplink more data to the new optical beacon 4A greatly loses the opportunity to receive the downlink frame DL2 that is transmitted only for a limited period (eg, 250 ms), or in an extreme case. May result in an unreasonable result of passing through the communication area A without receiving the downlink frame DL2.

[Road-to-vehicle communication when there is a transmission interruption period]
FIG. 10 is a sequence diagram showing road-to-vehicle communication when the new in-vehicle device 2A succeeds in ID confirmation because the new in-vehicle device 2A transmits the upstream frames UL1 and UL2 with a “transmission interruption period”.
In the example of FIG. 10, when the new in-vehicle device 2A continuously transmits the high-speed frames U1 to U3 after the low-speed frame U0, by providing a “transmission interruption period” between the first low-speed frame U0 and the high-speed frame U1, The above-mentioned problems associated with the failure of the return frame are solved.

This “transmission interruption period” is set to a predetermined time length necessary for the new in-vehicle device 2A to confirm the success of the loopback of the vehicle ID performed by the own device and to prepare for transmission of the high-speed frame U1. The
For example, it is assumed that the new light beacon 4A takes about 5 to 10 milliseconds from the reception of the ID storage frame U0 to the start of transmission of the downlink frame DL2, and the new in-vehicle device 2A confirms the loopback of the vehicle ID of the own vehicle, Assuming that the delay time required to start transmission of the high-speed frame U1 is 10 milliseconds, the transmission interruption period may be set in a range of approximately 15 to 20 milliseconds.

If this transmission interruption period is provided, the return frame continuously transmitted after downlink switching reaches the optical receiver 24 of the new in-vehicle device 2A during the period, and the new in-vehicle device 2A receives the received return frame. By determining whether or not the included vehicle ID matches that of the own device, the success of the loopback of the vehicle ID can be confirmed.
After the above confirmation, the new in-vehicle device 2A continuously transmits the high-speed frames U1 to U3, and after the continuous transmission ends, switches the communication of the own device to reception.

Thus, according to the new vehicle-mounted device 2A that provides the transmission interruption period between the low-speed frame U0 and the high-speed frame U1, the new light beacon 4A has recognized the vehicle ID by the return frame received from the new light beacon 4A during the transmission interruption period. It can be surely detected.
For this reason, it is possible to prevent the loss of the opportunity to receive the downlink frame DL2 due to the new in-vehicle device 2A continuing uselessly transmitting a plurality of uplink frames U0 to U3.

As a method for setting the transmission interruption period, a method in which the in-vehicle controller 21 continues to output a signal indicating the light-off state to the optical transmission unit 23 during the period, or the light transmission element 23 of the optical transmission unit 23 at the beginning of the period is set. There is a method in which power supply is stopped and extinguished, and power supply to the light emitting element is restarted and light is emitted again at the end of the period.
Moreover, you may employ | adopt the method of reducing the power of a light emitting element to such an extent that an optical signal cannot reach | attain the optical beacon 4. In this way, there is an advantage that power at the time of re-emission of the light emitting element can be quickly returned and disturbance of the synchronization part on the head side of the upstream frame U1 can be suppressed.

On the other hand, if the low-speed frame U0 that is the ID storage frame does not reach the new light beacon 4A for some reason (such as the windshield of the vehicle 20 being clouded), the light beacon 4 does not return the return frame. The in-vehicle device 2A cannot confirm the success of the loopback.
Therefore, if the new in-vehicle device 2A fails to confirm the success of the loopback during the transmission interruption period, only the low-speed frame U0 that is the ID storage frame is retransmitted to the optical transmission unit 23 as shown by the broken line in FIG. The transmission interruption period is after the low-speed frame U0 that is transmitted and retransmitted.

  Accordingly, when the new light beacon 4A can properly receive the retransmitted low-speed frame U0, the success of the vehicle ID loopback is confirmed by the return frame received from the new light beacon 4A during the transmission interruption period, as described above. be able to.

In the example of FIG. 10, it is preferable that the data size of the low-speed frame U0 that is the first upstream frame is as small as possible. For example, it is preferably smaller than any one of the high speed frames U1 to U4.
More preferably, for example, the data size of the low-speed frame U0 is reduced by minimizing the data stored in the low-speed frame U0 such as vehicle ID information, travel time between beacons, and the service type supported by the new in-vehicle device 2A. Is preferably set to the minimum (for example, about 5 bytes in the actual data portion) among the plurality of upstream frames U0 to U3 transmitted in one communication.

  The reason for this is that if the frame length of the low-speed frame U0 that can be retransmitted is long, the remaining time in which uplink transmission can be performed when the low-speed frame U0 is retransmitted is reduced accordingly, and uplink transmission is performed. This is because, for example, the last high-speed frame U3 among the plurality of high-speed frames U1 to U3 to be performed may not normally reach the new light beacon 4A.

  In the example of FIG. 10, the new in-vehicle device 2A receives a new optical beacon corresponding to high-speed uplink reception by the communication partner based on the beacon identification flag included in the downlink frame DL1 or the downlink frame DL2 received during the transmission interruption period. It may be determined whether the old optical beacon 4B is 4A or non-compliant, and whether to transmit the high-speed frames U1 to U3 after the transmission interruption period may be determined according to the determination result.

As described above, the communication partner of the new optical beacon 4A is preferably the new in-vehicle device 2A (FIG. 10) that performs uplink transmission with a transmission interruption period between the low-speed frame U0 and the high-speed frames U1 to U3. The new vehicle-mounted device 2A (FIG. 9) that continuously transmits the upstream frames U0 to U3 without providing a transmission interruption period may be used.
The reason for this is that if the number of frames and the transmission time of the high-speed frame UL2 are set to be small, the new in-vehicle device 2A displays the folded frame that is downlinked corresponding to the low-speed frame UL1, even without providing a transmission interruption period. It is because it can receive appropriately.

[Problems due to insensitive areas of high-speed frames]
FIG. 11 is an explanatory diagram showing an example of a dead area of the high-speed frame UL2.
In FIG. 11, a solid line area RA1 indicates an area where the optical receiver 11 can actually receive the low-speed frame UL1, and a virtual line area RA2 indicates an area where the optical receiver 11 can actually receive the high-speed frame UL2. Is shown.

In FIG. 11, P1 is the most upstream end (hereinafter referred to as “first upstream end”) at a predetermined height H (for example, H = 1.0 m) of the area RA1 in which the low-speed frame UL1 can be received. , P2 is the most upstream end (hereinafter referred to as “second upstream end”) at a predetermined height H of the area RA2 in which the high-speed frame UL2 can be received.
In this case, “receivable” means that the upstream frames UL1 and UL2 can be received at a predetermined bit error rate (for example, 10 ^{−5 in the} standard value) or less.

Here, as shown in FIG. 11, the range of the area RA1 in the vehicle traveling direction is wider than the range of the area RA2 in the same direction.
In other words, the difference in range is expressed by the positional relationship between the first upstream end P1 and the second upstream end P2, and in the normal optical receiver 11 that uses the same lens for receiving the upstream frames UL1 and UL2, the first upstream end P1. Is located upstream of the second upstream end P2. The reason is as follows.

  That is, in the filter 34 (see FIG. 12) of the optical receiver 11 mounted on the new optical beacon 4A, the upstream electrical signal is disturbed (electrical signal generated when the light receiving element senses downlink light or reflected sunlight). In order to separate the signal, the upstream band electrical signal (64 kbps and 256 kbps in this embodiment) is allowed to pass through, but the frequency characteristic that blocks the band component of about 500 kHz or more including the downstream band electrical signal (1024 kbps in this embodiment) is cut off. Need to be used.

Therefore, the high-speed frame UL2 close to the cutoff frequency is slightly less transmissive to the filter 34 than the low-speed frame UL1, and as a result, the low-speed frame UL1 has a slightly lower reception performance than the high-speed frame UL2 in terms of reception performance of the new optical beacon 4A. Deteriorate.
The difference in reception performance due to the difference in transmission speed appears as it is in the wide range of the receivable range of the low-speed frame UL1 and the high-speed frame UL2, and at the “physical” uppermost end that can actually receive the low-speed frame UL1. A certain first upstream end P1 is upstream of the second upstream end P2, which is the “physical” most upstream end that can actually receive the high-speed frame UL2.

Therefore, the area from the first upstream end P1 to the second upstream end P2 in FIG. 11 is an area that can receive the low-speed frame UL1 but cannot receive the high-speed frame UL2 (hereinafter referred to as “insensitive area”) F. It becomes.
By the way, as in the road-to-vehicle communication of FIG. 10, for example, the new vehicle-mounted device 2A first transmits the low-speed frame UL1, confirms its own vehicle ID with the return frame received thereafter, and then transmits the high-speed frame UL2. When the rules are adopted, the new in-vehicle device 2A may transmit the high-speed frame UL2 in the dead zone F depending on the traveling speed of the vehicle 20.

  In particular, when the vehicle 20 passes through the communication area A at a low speed of, for example, 10 km / h or less, the new in-vehicle device 2A receives the downlink transmission of the return frame after switching the uplink of the low-speed frame UL1 to the downlink. → A series of transmission and reception up to the uplink transmission of the high-speed frame UL2 may be performed in the insensitive area F.

Thus, when the new in-vehicle device 2A transmits the high-speed frame UL2 in the dead zone F, the new optical beacon 4A cannot receive the high-speed frame UL2.
In addition, in order to secure the time for the new in-vehicle device 2A to receive the downlink, when adopting a communication protocol that does not give a retransmission opportunity to the high-speed frame UL2, the high-speed frame UL2 transmitted by the new in-vehicle device 2A in the dead area F If the new light beacon 4A misses, there is no possibility of acquiring the high-speed frame UL2.

Therefore, in this embodiment, the second upstream end P2 is positioned upstream or substantially at the same position as the first upstream end P1 (or may be an apparent first upstream end P1 ′ described later). By doing so, the generation of the dead area F is prevented, and the new light beacon 4A can reliably receive the high-speed frame UL2.
Hereinafter, there are some specific examples of the position setting method. Hereinafter, the embodiment of the new light beacon 4A will be described for each specific example.

[First Embodiment]
In the first embodiment, by executing “reception restriction processing” that prohibits downlink switching by the low-speed frame UL1 transmitted in the insensitive area F, the first upstream end P1 that is the “physical” most upstream end Instead of this, the apparent first upstream end P1 ′, which is the “logical” uppermost stream end downstream, is adopted, and the above-described position setting is performed.

FIG. 12 is a circuit configuration diagram of the new optical beacon 4A according to the first embodiment.
As shown in FIG. 12, in the new optical beacon 4A of the first embodiment, the optical receiver 11 includes a first light receiving system 26 that is a communication light receiving system (light receiving circuit) and a measurement light receiving system (light receiving circuit). And a second light receiving system 27.
The beacon controller 7 includes a communication IC (communication processing unit) 28, a position IC (position processing unit) 29, and a main CPU (determination processing unit) 30.

Although not shown in FIG. 12, the beacon controller 7 also includes a memory that temporarily stores “position data” and “upstream data” output from the ICs 28 and 29.
The first light receiving system 26 includes a communication conversion element 32, an amplifier 33, a filter 34, and a comparator 35 in order from the left side of FIG. The communication conversion element 32 includes a light receiving element (for example, a photodiode (hereinafter also referred to as “PD”)) that converts the received optical signal in the uplink direction into an electrical signal.

The amplifier 33 includes a high-speed amplifier circuit that operates in a high-speed band (in this embodiment, 256 kbps). The amplifier 33 operates and amplifies the electrical signal converted by the PD 32 in a high-speed band, and outputs the amplified electrical signal to the subsequent filter 34.
The filter 34 is a low-pass filter that can extract at least a component in the high-speed band (in this embodiment, 256 kbps). The filter 34 may be a bandpass filter that covers from low speed components to high speed components.

The filter 34 extracts a low-speed component or a high-speed component from the amplified electrical signal, and outputs the extracted low-speed signal or high-speed signal to a comparator 35 at the subsequent stage.
The comparator 35 is composed of a high speed comparator capable of comparing a high speed signal with a threshold value. The comparator 35 compares the input low-speed signal or high-speed signal with a threshold value, and outputs a digital reception signal (bit data) extracted by this comparison to the communication IC 28 in the subsequent stage.

  The communication IC 28 determines the transmission rate of the received signal using the idle pattern of the first 5 bytes, samples the bit data at the determined transmission rate, and reproduces the upstream data included in the upstream frames UL1 and UL2. The communication IC 28 sends the reproduced upstream data to the main CPU 30 at the subsequent stage.

The second light receiving system 27 includes a conversion element 36 for measurement, an amplifier 37, and a peak hold circuit 38 in order from the left side of FIG.
The communication conversion element 36 includes a position detection element (hereinafter also referred to as “PSD”) that outputs an electrical signal corresponding to the input position in the light receiving surface of the upstream frames UL1 and UL2. Note that the principle of measuring the uplink position using the PSD 36 (FIG. 13) will be described later.

The PSD 36 of the present embodiment is a two-dimensional PSD, and can output four current values necessary for calculating the two-dimensional coordinates of the spot light incident on the light receiving surface.
The current values output from the four output terminals of the PSD 36 are amplified by the amplifier 37 at the subsequent stage. The electric signal amplified by the amplifier 37 is input to the peak hold circuit 38 at the subsequent stage. The peak hold circuit 38 generates measurement data by holding the maximum amplitude of the amplified signal for a predetermined time, and sends the generated measurement data to the subsequent position IC 29.

The position IC 29 measures the uplink position using the measurement data (the current value of each output terminal of the PSD 36) input from each peak hold circuit 38. The position IC 29 sends position data that is the measurement result to the main CPU 30.
The position data output from the position IC 29 may be based on either coordinates (x, y) on the light receiving surface of the PSD 36 or coordinates (X, Y) on the road side (see FIG. 13).

In this embodiment, the position data is based on coordinates (x, y). In this case, the main CPU 30 needs to perform an operation for converting the coordinates (x, y) to the coordinates (X, Y).
The main CPU 30 determines the low-speed frame UL1 depending on whether or not the uplink position of the low-speed frame UL1 represented by the “position data” from the position IC 29 is downstream of the threshold value (fixed position) indicating the second upstream end P2. A “reception limited process” is performed to determine whether or not to perform downlink switching. Details of this reception restriction process (the flowchart in FIG. 14) will be described later.

[Measurement principle of uplink position]
FIG. 13 is an explanatory diagram of the principle of measuring the uplink position using the position detection element (PSD) 36.
As shown in FIG. 13, the coordinates (X, Y) on the road side are two-dimensional coordinates within a plane having a predetermined height H (for example, H = 1.0 m) from the road surface of the road R. Along the R extending direction (vehicle traveling direction), the Y direction is along the width direction of the road R.

The two-dimensional PSD 36 is arranged inside the beacon head 8 so that the x direction of the light receiving surface corresponds to the X direction on the road side and the y direction of the light receiving surface corresponds to the Y direction on the road side. .
In the two-dimensional PSD 36, assuming that the current values of the output terminals x1, x2, y1, and y2 are Ix1, Ix2, Iy1, and Iy2, respectively, the coordinates (x, y) of the incident position of the spot light incident on the light receiving surface are obtained. And can be calculated by the following relational expression.
2x / Lx = {(Ix2 + Iy1)-(Ix1 + Iy2)} / (Ix1 + Ix2 + Iy1 + Iy2)
2y / Ly = {(Ix2 + Iy2)-(Ix1 + Iy1)} / (Ix1 + Ix2 + Iy1 + Iy2)

In the above relational expression, Lx is the length of the light receiving surface in the x direction, and Ly is the length of the light receiving surface in the y direction.
Therefore, when the value of the measurement data Ix1, Ix2, Iy1, Iy2 obtained from the peak hold circuit 38 of the optical receiver 24 exceeds a predetermined threshold, the position IC 29 substitutes these values into the above relational expression, The value of the coordinate (x, y) of the incident position of the spot light is calculated. In the present embodiment, this coordinate value is position data.

On the other hand, as shown in FIG. 13, the optical signal transmitted toward the beacon head 8 at an arbitrary position (X, Y) in the uplink area UA is condensed by the lens and is within the light receiving surface of the PSD 36. Spot light is incident on any one position (x, y).
Therefore, the incident position (x, y) of the upstream optical signal (uplink light) transmitted in the uplink area UA has a one-to-one correspondence with the transmission position (X, Y) on the road side. If the value of the position (x, y) is found, the transmission position (X, Y) of the optical signal (the coordinate value on the road side of the uplink position) can be obtained by coordinate conversion based on a geometric linear relationship. it can.

Therefore, when the main CPU 30 acquires the position data from the position IC, the main CPU 30 converts the value of the coordinate (x, y) of the position data into the value of the coordinate (X, Y) on the road side by the above coordinate conversion, and the uplink position. Ask for.
When obtaining the road side coordinates (X, Y) at the position IC29, the position IC29 also performs the coordinate conversion described above. In this case, the position data output from the position IC 29 is a value based on the coordinates (X, Y) on the road side.

[Reception limited processing by the main CPU]
FIG. 14 is a flowchart illustrating an example of reception restriction processing by the main CPU 30.
As shown in FIG. 14, the main CPU 30 always determines whether or not uplink data has been acquired from the communication IC 28 (step ST11), and if uplink data has been acquired, further acquires position data from the position IC 29. It is determined whether or not (step ST12).

When the determination result of step ST12 is negative, the main CPU 30 returns the process to step ST11.
If the determination result of step ST12 is affirmative, the main CPU 30 determines whether or not the acquired uplink data is the high-speed frame UL2 (step ST13). This determination is made based on whether the value of the in-vehicle device type in the uplink frame is “6” and the value of the information type is “4”.

  If the determination result in step ST13 is negative, that is, if the uplink frame is the low-speed frame UL1 that triggers downlink switching, the main CPU 30 stores the latest position data stored in the memory at that time. After adopting the coordinate value (X, Y) (step ST14), it is determined whether or not the uplink position of the low-speed frame UL1 indicated by the coordinate value (X, Y) is downstream of the “fixed point position”. (Step ST16).

The “fixed point position” is a position defined in advance as a threshold representing the second upstream end P2 (see FIG. 11).
Further, the “fixed point position” is, for example, a range (both ends) from the upstream end of the uplink area UA (a position 6.04 m from immediately below the beacon) to the second upstream end P2 further upstream than that. Including location). Since the physical first and second upstream ends P1 and P2 are not located downstream of the upstream end of the uplink area according to the regulations, if a fixed point position is selected from such a range, reception is limited. This is because the process can be appropriately executed.

If the determination result in step ST16 is negative, that is, if the uplink position of the low-speed frame UL1 is upstream or at the same position as the fixed point position, the process returns to step ST11.
Accordingly, the low speed frame UL1 in this case is not received in the information processing in the main CPU 30.

If the determination result of step ST16 is affirmative, that is, if the uplink position of the low speed frame UL1 is downstream of the fixed point position, the main CPU 30 generates the downlink frame DL2 (step ST17).
In this case, in order to respond to the reception of the low-speed frame UL1 that triggers the downlink switching, the main CPU 30 performs the downlink switching and the continuous transmission of the return frame, and then the sub-frame described in the low-speed frame UL1 acquired this time. Provided information corresponding to the system key information is included in the downlink frame DL2.

If the determination result in step ST13 is affirmative, that is, if the uplink frame is the high-speed frame UL2 that does not trigger downlink switching, the main CPU 30 coordinates the position data stored in the memory at that time. After discarding (X, Y) (step ST15), the downlink frame DL2 is generated (step ST17).
In this case, in order to respond to reception of the high-speed frame UL2 that does not trigger downlink switching, the main CPU 30 includes provision information corresponding to the subsystem key information acquired last time in the downlink frame DL2 without performing downlink switching. .

[Effects of First Embodiment]
As described above, according to the new light beacon 4A of the present embodiment, the main CPU 30 is concerned only when the uplink position of the low-speed frame UL1 is downstream from the fixed point position (threshold value indicating the second upstream end P2). A reception limitation process (FIG. 14) for performing downlink switching based on the low-speed frame UL1 is executed.

That is, when the new in-vehicle device 2A transmits the low-speed frame UL1 in the dead zone F, the downlink switching is not performed, and the new in-vehicle device 2A transmits the low-speed frame UL1 at the second upstream end P2 or downstream thereof. As long as downlink switching is performed.
By executing the reception limiting process, the uppermost stream end of the area that can receive the low-speed frame UL1 is not the first upstream end P1 that is the “physical” uppermost stream end but the “upstream” of the second upstream end P2. The first upstream end P1 ′, which is the “logical” uppermost stream end, is set (see FIG. 11).

For this reason, even if the low-speed frame UL1 is transmitted in an area where the low-speed frame UL1 can be received but the high-speed frame UL2 cannot be received (“dead area F” in FIG. 11), the main CPU 30 ignores the low-speed frame UL1. Only when it is the low-speed frame UL1 transmitted in a place past the dead zone F, downlink switching is performed.
Therefore, if the low-speed frame UL1 can be received, the high-speed frame UL2 can also be received, and the new optical beacon 4A can appropriately receive the high-speed frame UL2 transmitted after the new in-vehicle device 2A follows the low-speed frame UL1.

Further, according to the new light beacon 4A of the present embodiment, the physical uppermost stream end P1 is changed to the logical uppermost stream end only by changing the computer program so that the main CPU 30 executes the reception restriction process (FIG. 14). The position setting to switch to P1 ′ can be performed.
Therefore, the circuit design of the second embodiment and the optical setting of the third embodiment have an advantage that the mounting can be relatively easily performed as compared with the case where the position of the most upstream end P1 is set.

Furthermore, according to the new optical beacon 4A of the present embodiment, downlink switching is performed in response to reception of the low-speed frame UL1, regardless of whether the communication partner of the new optical beacon 4A is the new in-vehicle device 2A or the old in-vehicle device 2B. Road-to-vehicle communication can be performed appropriately.
In addition, since the downlink switching is not performed in the high-speed frame UL2, the processing load of the new optical beacon 4A can be reduced even when the downlink switching is performed when the high-speed frame UL2 is received, and the timing of the downlink switching There is an advantage that it is possible to prevent the reception opportunity of the downlink frame DL2 transmitted in the downlink thereafter from being reduced.

Further, according to the new light beacon 4A of the present embodiment, the PD 32 is adopted as the light receiving element of the first light receiving system 26 for communication, and the measurement light separate from the PD 32 is used as the light receiving element of the second light receiving system 27 for measurement. The PSD 36, which is a conversion element, is employed.
For this reason, as in a modified example (FIGS. 15 and 16) to be described later, the position determination resolution can be increased as compared with the case of the second light receiving system 27 using the divided PD 40.

Further, in the second light receiving system 27 using the PSD 36, the alignment with the uplink area UA on the road side becomes easier than in the second light receiving system 27 using the divided PD 40, and the installation work of the optical beacon 4 is reduced. There is also an advantage that it can be reduced.
That is, in the light receiving element composed of the divided PDs, it is necessary to align the beacon head 8 so that the light receiving surfaces of the plurality of PD1 to PD4 correspond to the divided areas UA1 to UA4. There is a disadvantage that it takes.

  On the other hand, in the PSD 36, the correction coefficient of the conversion equation between the coordinates (x, y) of the light receiving surface and the coordinates (X, Y) on the road side is adjusted by a computer program, thereby associating with the road side. Can be finely adjusted, so that it is not necessary to align the beacon head 8 so strictly. Therefore, it is possible to save the trouble of installing the beacon head 8 as compared with the case of the divided PD that cannot be finely adjusted on the software.

Further, according to the new light beacon 4A of the present embodiment, the light receiving unit 11 uses separate conversion elements 32 and 36 for the first light receiving system 26 and the second light receiving system 27. In addition, even if a conversion element having relatively poor followability in the high-speed band is employed in the second light receiving system 27, the quality of the electrical signal output from the first light receiving system 26 is not affected.
Therefore, in the case of configuring the optical beacon 4 capable of measuring the uplink position, it is possible to appropriately cope with the increase in the speed of the uplink frame UL2 and to obtain a new optical beacon 4A excellent in reception performance in the uplink direction.

[Modification of First Embodiment]
In the first embodiment described above, a two-dimensional PSD is adopted as the position measurement PSD 36. However, a one-dimensional PSD in which the x direction of the light receiving surface is arranged along the vehicle traveling direction is adopted. Also good.
This is because the uplink position of the uplink frame necessary for the reception restriction process is an uplink position in the vehicle traveling direction, and the position in the road width direction (Y direction) is not particularly problematic.

However, if the two-dimensional PSD is used, it is also possible to measure the uplink position in the road width direction (Y direction), so that position data that deviates from a predetermined range in the predetermined Y direction travels in another lane. It can be determined that the light is uplink light from the vehicle 20, and more accurate operations such as discarding the position data can be performed.
In the first embodiment, the reason why the PSD 36 is used only for measurement and the output signal is not input to the first light receiving system 26 for communication is as follows.

That is, at present, there is no PSD that satisfactorily follows a high-speed (256 kbps) optical signal, and if the output signal of the PSD 36 is also used for measurement, a new optical beacon 4A corresponding to high-speed uplink reception cannot be configured. It is.
Therefore, if a high-performance PSD that does not slow down the rise and fall of a high-speed (256 kbps) optical signal is realized, a circuit configuration that uses the output of the PSD 36 also for the first light receiving system 26 is adopted. , PD32 can be omitted.

  In the first embodiment described above, the second upstream end is not only the “physical” most upstream end P2 (see FIG. 11) that can actually receive the high-speed frame UL2, but also the uplink position of the high-speed frame UL2. It may be the “logical” uppermost stream end P2 ′ based on the orientation result.

[Other Modifications of First Embodiment]
FIG. 15 is a circuit configuration diagram of a new optical beacon 4A according to a modification of the first embodiment.
The main difference between the modification of FIG. 15 and the first embodiment of FIG. 12 is that a divided PD 40 is employed instead of the PSD 36 as a conversion element for measurement.
Hereinafter, the functional units substantially the same as those in the first embodiment will be denoted by the same reference numerals in FIG. 15, and detailed description thereof will be omitted, and differences from the first embodiment will be mainly described.

As shown in FIG. 15, the divided PD 40 of the second light receiving system 27 has a uniform light receiving surface by joining four PD1 to PD4 in the width direction.
The output terminals of the PD1 to PD4 are connected to the subsequent amplifier 37, and the electric signals photoelectrically converted by the PD1 to PD4 are amplified by the amplifier 37 and input to the peak hold circuit 38. The peak hold circuit 38 generates measurement data by holding the maximum amplitude of the amplified signal for a predetermined time, and sends the generated measurement data to the subsequent position IC 29.

The position IC 29 measures the uplink position using the measurement data (voltage values at the output terminals of the PD1 to PD4) input from the peak hold circuits 38. The position IC 29 sends position data that is the measurement result to the main CPU 30.
In addition, the measurement principle (FIG. 16) in the case of measuring an uplink position from the voltage value (measurement data) of the output terminal of PD1-PD4 which comprises division | segmentation PD40 is mentioned later.

As shown in FIG. 15, the first light receiving system 26 has an adder 41. Each amplifier 37 is connected to an output terminal adder 41, and the output terminal of the adder 41 is connected to a subsequent filter 34.
That is, in the case where the light receiving element is a PD, it has a follow-up performance with good rise and fall even for a relatively high speed optical signal (256 kpbs in this embodiment). Therefore, in the present embodiment, a circuit configuration is employed in which the sum signal obtained by adding the amplified signals of PD1 to PD4 is sent to the filter 34 of the first light receiving system 26, and the divided PD 40 is also used as a communication conversion element. ing.

As described above, when the conversion element 40 including the divided PD is employed, the light receiving elements used in the first light receiving system 26 and the second light receiving system 27 can be shared by one type of conversion element 40.
For this reason, compared with the case of 1st Embodiment (FIG. 12) which employ | adopts different conversion elements 32 and 36 about the 1st and 2nd light-receiving systems 26 and 27, a circuit scale can be reduced and a mounting board | substrate can be reduced. There is an advantage that the size can be reduced.

The functions of the filter 34 and the comparator 35 in the first light receiving system 26 and the function of the communication IC 28 of the beacon controller 7 are the same as those in the first embodiment of FIG. .
The determination process performed by the main CPU 30 of the beacon controller 7 is also the same as that in the first embodiment in FIG.

[Measurement principle of uplink position]
FIG. 16 is an explanatory diagram of the measurement principle of the uplink position using the divided PD.
As shown in FIG. 16, the road-side divided areas UA1 to UA4 are areas obtained by dividing a plane having a predetermined height H (for example, H = 1.0 m) from the road surface of the road R substantially equally along the vehicle traveling direction. Yes, PD1 to PD4 constituting the divided PD 40 are arranged inside the beacon head 8 so that the light receiving areas thereof substantially correspond to the divided areas UA1 to UA4.

Therefore, for example, as shown in FIG. 16, when spot light incident on the divided PD 40 is detected on the light receiving surface of the PD 1, the spot light transmission position is the divided area UA1 of the uplink area UA. It turns out that there was.
Similarly, if the irradiation position of the spot light is PD2, PD3 or PD4, it is found that the transmission position is the divided area UA2, UA3 or UA4.

Therefore, when the value of the measurement data V1, V2, V3, V4 obtained from the peak hold circuit 38 of the optical receiver 24 exceeds a predetermined threshold, the position IC 29 determines which PDi (i = 1 to 1) In step 4), it is determined whether or not it has occurred, and the reference position of the divided area UAi corresponding to the determined PDi is set as the uplink position of the optical signal.
Therefore, in the present embodiment, a reference position predetermined as a representative point of each divided area UAi is position data output from the position IC 29.

  In addition, as shown in JP 2012-84072 A by the same inventor as the present application, if a finer divided region corresponding to the voltage value ratio between adjacent ones of PD1 to PD4 is set in advance. The uplink position of the optical signal can be specified by the number of regions in the vehicle traveling direction that exceeds the number of divisions of the division PD 40 (four in this embodiment).

[Second Embodiment]
In the new optical beacon 4A of the second embodiment, a circuit for setting constants for circuit elements constituting the receiving circuit of the optical receiving unit 11 instead of setting the apparent first upstream end P1 ′ in the information processing of the main CPU 30. By design, the upstream ends P1, P2 of the second upstream end P2, which is the “physical” uppermost end, are upstream of the first downstream end P1, which is the “physical” uppermost end. The position is set.

FIG. 17A is a diagram illustrating a circuit configuration example of the filter 34 used in the new optical beacon 4A of the second embodiment, and FIG. 17B is a graph illustrating the frequency characteristics of the filter 34.
In addition, also in the new optical beacon 4A of 2nd Embodiment, the circuit structure similar to FIG.12 and FIG.15 which are the types which measure an uplink position is employable. However, in the second embodiment, the positions of the upstream ends P1 and P2 are set by setting the constants of the circuit elements, so it is not always necessary to measure the uplink position. For this reason, the optical receiver 11 having a circuit configuration having only the first light receiving system 26 for communication may be used.

The filter 34 of this embodiment has a function of removing signal components in the bands of the downlink frames DL1 and DL2 from the amplified signal output from the amplifier 33. As shown in FIG. The first trap circuit 43 is composed of one capacitor C1, and the second trap circuit 44 is composed of a second coil L2 and a second capacitor C2.
The first and second trap circuits 43 and 44 constitute a parallel LC circuit, respectively.

  The first trap circuit 43 has one end connected to the amplifier 33 and the other end connected to the second trap circuit 44. The second trap circuit 44 has one end connected to the first trap circuit 43 and the other end connected to the comparator 35. Accordingly, the first trap circuit 43 and the second trap circuit 44 are connected to each other in series.

  The filter 34 has a third capacitor C3 having one end connected to the previous stage of the first trap circuit 43 and the other end grounded, and a fourth capacitor whose one end is connected to the connecting portion of both the trap circuits 43 and 44 and whose other end is grounded. It further includes a capacitor C4 and a fifth capacitor C5 having one end connected to the subsequent stage of the second trap circuit 44 and the other end grounded.

The third to fifth capacitors C3 to C5 and the coils L1 and L2 constitute a fifth-order Butterworth low-pass filter.
That is, the filter 34 of the present embodiment has a circuit configuration further including a low-pass filter circuit 45 configured by the third to fifth capacitors C3 to C5 and both the coils L1 and L2. That is, the filter 34 includes a low-pass filter circuit 45 and both trap circuits 43 and 44 that are superposed so as to serve as the coils L1 and L2.

According to the filter 34 having the above circuit configuration, for example, an analog filter having frequency characteristics shown in FIG. 17B can be configured by setting the inductances of the coils L1 and L2 and the capacitances of the capacitors C1 to C5 to appropriate values. .
In the frequency characteristic of FIG. 17B, the gain is extremely small in the portion of about 600 kHz and the portion of about 1.1 MHz, and a sharp decrease in gain is seen in the vicinity of about 500 kHz, and the gain is higher in the frequency band higher than 500 kHz. It appears at a low value and the power is cut off.

In the frequency characteristics of FIG. 17B, the gain at 64 kbps, which is the transmission rate of the low-speed frame UL1, is smaller than the gain at 256 kbps, which is the transmission rate of the high-speed frame UL2.
For this reason, the low-speed frame UL1 is slightly less transparent to the filter 34 than the high-speed frame UL2, and as a result, the reception performance of the low-speed frame UL1 is slightly worse than the reception performance of the high-speed frame UL2.

The difference in reception performance due to the difference in transmission speed appears as a difference between areas where the low speed frame UL1 and the high speed frame UL2 can be received.
Therefore, if the filter 34 of FIG. 17A having the frequency characteristics of FIG. 17B is employed, the positional relationship between P1 and P2 shown in FIG. 11 is reversed, and the area RA2 in which the high-speed frame UL2 can be actually received. The second upstream end P2 that is the most upstream end of the upstream side is upstream of the first upstream end P1 that is the most upstream end of the area R1 in which the low-speed frame UL1 can actually be received.

  As described above, according to the new optical beacon 4A of the second embodiment, by appropriately setting the constants of the circuit elements constituting the receiving circuit of the optical receiving unit 11, the second “physical” most upstream end is set. Since the upstream end P1 is set upstream (or substantially at the same position) from the first upstream end P1, which is the “physical” uppermost stream end, the low speed frame UL1 can be received but the high speed is high. A dead area F in which the frame UL2 cannot be received does not occur.

  Therefore, by transmitting the low-speed frame UL1 in the insensitive area F, it is possible to prevent the subsequent high-speed frame UL2 from becoming unreceivable, and it is possible to appropriately receive the high-speed frame UL2 transmitted after the low-speed frame UL1. The new optical beacon 4A corresponding to the multi-rate in the uplink direction is obtained.

  In addition, according to the new optical beacon 4A of the second embodiment, although it takes a certain amount of time to design a circuit for determining the constants of the circuit elements constituting the filter 34, etc., it does not measure the uplink position. When adopting a type that does not include the second light receiving system 27 (for example, in the circuit configuration of FIG. 12, a type in which the light receiving unit 11 is configured only from the first light receiving system 26), two types for low speed and high speed are used. Compared to the case of a third embodiment (FIGS. 19 and 20) described later that requires the receiving systems 26A and 26B, there is an advantage that the circuit scale can be reduced.

FIG. 18 is a graph showing an example of frequency characteristics of the amplifier 33 used in the new optical beacon 4A according to the second embodiment.
Even if the amplifier 33 having the frequency characteristics shown in FIG. 18 is employed instead of the filter 34 shown in FIG. 17, the same effect as described above can be obtained. That is, as shown by a solid line in FIG. 18, in the multi-rate compatible amplifier 33, circuit elements that constitute the amplifier so that substantially the same gain can be obtained in a frequency band including a low speed range (64 kbps) to a high speed range (256 kbps). It is normal to set a constant of.

In this regard, in the amplifier 33 according to the present embodiment, as indicated by a virtual line, the constants of circuit elements constituting the amplifier are set such that the gain in the low speed region (64 kbps) is smaller than the gain in the high speed region (256 kbps). Is set.
Therefore, also in this case, regarding the electric signal input to the comparator 35, the reception performance of the low-speed frame UL1 is slightly worse than the reception performance of the high-speed frame UL2, so the area AR1 of the low-speed frame UL1 is changed to the area of the high-speed frame UL2. It can be narrower than AR2.

  The feature of the second embodiment is that the high-speed frame UL2 increases the gain of the electric signal in the comparator 35 compared to the low-speed frame UL1, and thus constitutes one of the filter 34 and the amplifier 33. In addition to setting the constants of the circuit elements, the gain of the comparator 35 may be differentiated by appropriately setting the constants of both circuit elements.

[Third Embodiment]
In the new optical beacon 4A of the third embodiment, the apparent first upstream end P1 ′ is not set in the information processing of the main CPU 30, but the optical system for the two systems of receiving systems 26A and 26B provided in the optical receiving unit 11 is used. By performing the setting, the second upstream end P2 that is the “physical” uppermost stream end is located upstream from the first downstream end P1 that is the “physical” uppermost stream end. The positions of P1 and P2 are set.

FIG. 19 is a circuit configuration diagram of the new optical beacon 4A according to the third embodiment.
As shown in FIG. 19, in the new optical beacon 4A of the present embodiment, the optical receiver 11 receives the low speed reception system 26A for receiving the low speed frame UL1, and the high speed reception system 26B for receiving the high speed frame UL2. The receiving systems 26A and 26B of the optical receiving unit 11 are two systems for low speed and high speed.

Of the two receiving systems 26A and 26B, the low-speed receiving system 26A includes a lens 31A, a conversion element 32A composed of a PD, an amplifier 33A, a filter 34A, and a comparator 35A in order from the left side of FIG.
The amplifier 33A includes a low-speed amplifier circuit that operates in a low-speed band (in this embodiment, 64 kbps), the filter 34A includes a filter circuit that can extract a low-speed band component, and the comparator 35A includes a low-speed signal and a threshold value. It consists of a low-speed comparator that can be compared.

The high-speed receiving system 26B includes a lens 31B, a conversion element 32B composed of a PD, an amplifier 33B, a filter 34B, and a comparator 35B in order from the left side of FIG.
The amplifier 33B is composed of a high-speed amplifier circuit that operates in a high-speed band (in this embodiment, 256 kbps), the filter 34B is composed of a filter circuit that can extract a component in the high-speed band, and the comparator 35B It consists of a high-speed comparator that can be compared.

FIG. 20 is a side view showing areas RA1 and RA2 in which both receiving systems 26A and 26B can receive uplink frames UL1 and UL2, respectively.
As shown in FIG. 20, the low-speed lens 31A is attached to the beacon head 8 in a state of facing the light receiving surface of the PD 32A, and similarly, the high speed lens 31B is a beacon in the state of facing the light receiving surface of the PD 32B. It is attached to the head 8.

  The lenses 31A and 31B are attached to the beacon head 8 so that their optical axis directions are obliquely downward, and their optical axis directions are set non-parallel to each other. By employing lenses 31A and 31B having different focal lengths, the inclination angle of the upstream oblique side of area RA1 is larger than the inclination angle of the upstream oblique side of area RA2.

Therefore, the lenses 31A of the receiving systems 26A and 26B are arranged so that the most upstream end P2 of the area RA2 of the high speed receiving system 26B is upstream of the most upstream end P1 of the RA1 of the area of the low speed receiving system 26A. , 31B is optically set.
It should be noted that the uppermost stream end P2 of the area RA2 does not necessarily have to be upstream of the uppermost stream end P1 of the area RA1, and the optical setting is performed so as to be substantially the same position as the uppermost stream end P1. It may be. However, it is not necessary to match the downstream ends of the areas RA1 and RA2.

  As described above, according to the new optical beacon 4A of the third embodiment, the above-described optical setting is performed on the low-speed reception system 26A and the high-speed reception system 26B, thereby providing a “physical” uppermost end. Since the second upstream end P2 is set upstream (or substantially at the same position) from the first upstream end P1, which is the “physical” uppermost stream end, the low-speed frame UL1 can be received. Does not generate the dead zone F in which the high-speed frame UL2 cannot be received.

  Therefore, by transmitting the low-speed frame UL1 in the insensitive area F, it is possible to prevent the subsequent high-speed frame UL2 from becoming unreceivable, and it is possible to appropriately receive the high-speed frame UL2 transmitted after the low-speed frame UL1. The new optical beacon 4A corresponding to the multi-rate in the uplink direction is obtained.

  Further, according to the new optical beacon 4A of the third embodiment, the position setting of the upstream ends P1 and P2 of the respective areas RA1 and RA2 is performed by optical setting that determines the light receiving directions of the lenses 31A and 32B of both receiving systems 26A and 26B. Therefore, the position setting can be performed more reliably than the position setting by the reception restriction process of the first embodiment and the position setting by the circuit design of the second embodiment.

[Other variations]
The embodiments (including modifications) disclosed herein are illustrative and non-restrictive in every respect. The scope of rights of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope equivalent to the configurations described in the claims.

For example, in the above-described embodiment, the new in-vehicle device 2A continuously transmits a plurality of high-speed frames U1 to U3, but burst transmission is performed with an interval of a predetermined time length between frames. Also good.
In addition, in this specification, the “on-vehicle device” includes those that are always fixed in that state after being mounted on the vehicle 20, and are brought into the vehicle 20 only when the driver wants to use it, and temporarily. The thing mounted in the vehicle 20 is also included.

2 Onboard unit 2A New onboard unit 2B Old onboard unit 4 Optical beacon 4A New optical beacon 4B Old optical beacon 7 Beacon controller (communication control unit)
8 Beacon head 20 Vehicle 23 Optical transmitter 24 Optical receiver 26 First light receiving system (light receiving system for communication)
26A Low-speed reception system 26B High-speed reception system 27 Second light-receiving system (light-receiving system for measurement)
30 Main CPU
32 Conversion element (PD) for communication
33 Amplifier 34 Filter 35 Comparator 36 Measurement Conversion Element (PSD)

First upstream end: the most upstream end of the area that can receive the low-speed frame Second upstream end: the most upstream end of the area that can receive the high-speed frame In this specification, “substantially the same position” This means that the distance difference between the first upstream end and the second upstream end is such that it can be regarded as within an error range (for example, 5 cm) from the viewpoint of vehicle position measurement.

The present invention relates to an optical beacon that performs wireless communication using an optical signal with an in-vehicle device of a traveling vehicle, and a road-to-vehicle communication system including the optical beacon .

(7) In the optical beacon of the present invention, when the optical receiver includes a low-speed reception system for receiving a low-speed frame and a high-speed reception system for receiving a high-speed frame, the position setting is performed. May be performed by the following optical setting.
Optical setting: The physical uppermost end of the area where the high- speed receiving system can receive the high-speed frame is upstream or substantially higher than the physical uppermost end of the area where the low- speed receiving system can receive the low-speed frame. Setting to determine the receiving direction (light receiving direction) of both receiving systems

The present invention relates to an optical beacons that performs wireless communication by the in-vehicle device and an optical signal of a moving vehicle.

Claims (8)

An optical beacon that performs wireless communication with an in-vehicle device of a running vehicle using an optical signal,
An optical receiver capable of photoelectric conversion at two transmission speeds, high and low;
An optical transmitter capable of electro-optical conversion at a predetermined transmission rate;
A communication control unit capable of reproducing a low-speed frame or a high-speed frame from the electrical signal output by the optical receiver, and
An optical beacon characterized in that the second upstream end defined below is positioned upstream or substantially at the same position as the first upstream end defined below.
First upstream end: Physical or logical uppermost end of area capable of receiving low-speed frames Second upstream end: Physical or logical uppermost end of area capable of receiving high-speed frames The optical receiver includes a light receiving element that receives an upstream optical signal, an amplifier that amplifies an electrical signal output from the light receiving element, a filter that does not pass a downstream amplified signal but passes an upstream amplified signal, A comparator that binarizes the filtered electrical signal,
The optical beacon according to claim 1, wherein the position setting is performed by the following circuit design.
Circuit design: Circuit design that determines the constants of the circuit elements included in the optical receiver so that the gain of the electrical signal in the comparator is larger in the high-speed frame than in the low-speed frame.   The optical beacon according to claim 2, wherein the circuit design is performed on the circuit element constituting at least one of the amplifier and the filter. The communication control unit can measure the uplink position of the low-speed frame from the electrical signal output by the optical receiving unit,
The optical beacon according to claim 1, wherein the position setting is performed by a next reception restriction process performed by the communication control unit.
Reception restriction processing: processing for performing downlink switching based on the low-speed frame only when the uplink position of the low-speed frame is downstream of the fixed point position defined as the threshold value representing the second upstream end.   The optical vehicle beacon according to claim 4, wherein the in-vehicle device transmits the low speed frame before the high speed frame in one road-to-vehicle communication performed with the optical beacon.   5. The fixed point position is selected from a range (including both end positions) from an upstream end of an uplink region according to a rule to a second upstream end further upstream. 5. An optical beacon according to 5. The optical receiver includes a low-speed receiving system for receiving a low-speed frame and a high-speed receiving system for receiving a high-speed frame. The position setting is performed by the following optical setting. The optical beacon according to 1.
Optical setting: The physical uppermost end of the area where the low-speed receiving system can receive the low-speed frame is upstream or substantially higher than the physical uppermost end of the area where the high-speed receiving system can receive the high-speed frame. Setting to determine the receiving direction of both receiving systems An in-vehicle device of a running vehicle,
A road-to-vehicle communication system comprising: the optical beacon according to claim 1, 2, 4, and 7 that performs wireless communication with the in-vehicle device using an optical signal.

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