JP2013164830A - Optical beacon and on-vehicle machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new optical beacon multi-rate compatible in an uplink direction that can reliably provide a new on-vehicle machine with counter value service information provided after downlink switching.SOLUTION: An optical beacon 4 performs radio communication by an optical signal with an on-vehicle machine 2 of a vehicle under traveling. The optical beacon 4 includes: an optical reception unit 11 that is capable of photoelectric conversion at two high and low transfer rates; an optical transmission unit 10 that is capable of electro-optical conversion at a given transfer rate; a communication control unit (beacon controller) 7 that can adopt the following two conditions as a condition for performing downlink switching: the first condition being reception completion of a lower rate frame UL1; and the second condition being reception completion of a higher rate frame UL2.

Description

  The present invention relates to an optical beacon that performs wireless communication using an optical signal and an in-vehicle device.

As a traffic information service using a road-to-vehicle communication system, so-called VICS (Vehicle Information and Communication System) 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. The loss of the opportunity to receive the downlink frame can be prevented by repeating the retransmission of a plurality of uplink frames without the vehicle-mounted device noticing the downlink frame storing its own vehicle ID.

However, most of the new in-vehicle devices are considered to adopt a half-duplex communication method in which transmission and reception are alternately performed. The new in-vehicle device cannot receive the downlink frame that has arrived at the aircraft.
Accordingly, for the consideration service information stored in the downlink frame in the first half of the downlink frame group in which the optical beacon is continuously transmitted after downlink switching of the downlink frame, it is twice as many times as required by the conventional communication protocol. May not be received.

In view of the above-described conventional problems, the first object of the present invention is to provide a multi-rate compatible new optical beacon in the uplink direction that can reliably provide the value-added service information provided after downlink switching to the new vehicle-mounted device. And
In addition, a second object of the present invention is to provide a new in-vehicle device that supports multirate in the uplink direction, which can more reliably acquire the value service information provided after downlink switching.

(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 adopting the following two types of conditions as conditions for downlink switching are provided. .
First condition: Completion of low-speed frame reception Second condition: Completion of reception of high-speed frame

According to the optical beacon of the present invention, the communication control unit can perform downlink switching even when the second condition (high-speed frame reception completion) is established, and therefore the downlink frame group continuously transmitted after downlink switching. By making the transmission start time close to the timing of completion of reception of the high-speed frame, it is possible to increase the possibility that the new in-vehicle device can receive the value service information included in the head side of the downlink frame group twice.
Accordingly, the value service information provided after downlink switching can be reliably provided to the new in-vehicle device, and the first object described above is achieved.

  (2) In the in-vehicle device of the present invention, the communication control unit performs downlink switching with continuous transmission of a downlink frame including lane notification information storing vehicle identification information when the first condition is satisfied. When the second condition is satisfied, it is preferable to perform downlink switching without continuous transmission of the downlink frame including the lane notification information.

The reason is that the loopback of the vehicle ID to the in-vehicle device is often completed by the continuous transmission of the downlink frame including the lane notification information executed according to the first condition (reception of the low-speed frame). This is because it is considered unnecessary to further perform continuous transmission of a downlink frame (turned frame) including lane notification information corresponding to the second condition (complete reception of a high-speed frame).
In this case, since the return frames are not continuously transmitted according to the second condition, there is an advantage that the transmission opportunities of other useful downlink frames can be increased accordingly.

(3) In the optical beacon of the present invention, in the case of a communication protocol that allows continuous transmission of a plurality of the high-speed frames, the second condition is that reception of any high-speed frame among the plurality of high-speed frames is completed. It is possible to adopt that a predetermined time has passed since.
(4) More specifically, the predetermined time may be set to a predetermined fixed time, for example. In this case, there is an advantage that the load on the communication control unit can be reduced by setting the fixed time value relatively long.

(5) However, if the predetermined time is set to a predetermined fixed time, even if the actual transmission time of the high-speed frame from the new vehicle-mounted device is smaller than the fixed time, the fixed time does not elapse. The second condition is not satisfied, and the start of downlink switching using a high-speed frame is unnecessarily delayed.
Therefore, the predetermined time may be a predicted time that can be calculated from the number of frames of the remaining high-speed frames that can be received subsequent to the high-speed frame after reception completion among the plurality of high-speed frames.

The number of remaining high-speed frames can be calculated, for example, by subtracting the number of received high-speed frames from the total number of high-speed frames recorded in the low-speed frame or the top frame of the high-speed frame.
In this case, it is necessary to calculate the predicted time when the second condition is satisfied. However, even if the number of high-speed frames transmitted by the new vehicle-mounted device varies, the second condition depends on the number of frames of the remaining high-speed frames. Can be accurately calculated, and downlink switching using high-speed frames can be performed accurately.

(6) In the optical beacon of the present invention, in the case of a communication protocol that allows continuous transmission of a plurality of the high-speed frames, the second condition includes information indicating a final frame among the plurality of high-speed frames. The reception of the high-speed frame may be completed.
In this case, since the reception completion of the high-speed frame including information indicating the final frame is set as the second condition, even if the number of uplink frames transmitted by the new vehicle-mounted device fluctuates, the second condition according to the number of frames Can be accurately determined, and downlink switching using high-speed frames can be performed accurately.

  (7) The in-vehicle device of the present invention is an in-vehicle device that performs wireless communication using an optical beacon and an optical signal installed on a road, and an optical transmission unit capable of electro-optical conversion at two high and low transmission speeds; An optical receiving unit capable of photoelectric conversion at a predetermined transmission rate, and a communication control unit for transmitting one or a plurality of high-speed frames by providing a transmission interruption period after transmission of the low-speed frame. The uplink period from the start of transmission of the low-speed frame to the start of reception of the downlink frame is a length of time during which the consideration service information provided by the optical beacon can be received at least twice in a plurality of downlink frames that can be received after that period. It is characterized by being set to.

According to the vehicle-mounted device of the present invention, the uplink period is set to a length of time at which the consideration service information provided from the optical beacon in a plurality of downlink frames that can be received after that period can be received at least twice. In the communication time in the limited downlink area, the new in-vehicle device can reliably receive the consideration service information twice.
Therefore, according to the new vehicle-mounted device of the present invention, the consideration service information provided after downlink switching can be reliably acquired, and the above-described second object is achieved.

(8) Assuming that a low-speed frame is retransmitted, the uplink period includes first to fourth times defined below.
First time: Transmission period of the low-speed frame when retransmitting a low-speed frame Second time: Transmission interruption time Third time: Transmission time of one or a plurality of high-speed frames Fourth time: Transmission of a high-speed frame is completed Switching time from receiving to receiving

(9) Therefore, if at least one of the first to fourth times is set to a time length defined next, the value service information provided after downlink switching is more reliably acquired from the Shinko beacon. become able to.
First time: time length selected from a range of 10 to 29.5 msec in 0.5 msec increments Second time: selected from a range of 10 to 23.5 msec in 0.5 msec increments Time length Third time: Transmission time length of one or a plurality of high-speed frames generated by the number of common frame portions selected from 1 to 8 Fourth time: 0.5 to 4 in 0.5 msec increments . Length of time selected from the range up to 5 ms

In the above first to fourth times, the lower limit of the first and second times is 10 milliseconds because the time required for downlink switching is approximately 10 milliseconds.
That is, when the first and second times are shortened to less than 10 milliseconds, the lane notification information transmitted by the optical beacon at the time of downlink switching performed according to the first condition (reception of the low-speed frame) is included. This is because the new in-vehicle device cannot receive the downstream frame, and the new in-vehicle device cannot properly communicate with the optical beacon.

(10) In the in-vehicle device of the present invention, the communication control unit includes a storage area for vehicle identification information in the header part of the low-speed frame, and a storage area for the identification information in the header part of the high-speed frame. It is preferable not to do so.
In this way, the frame length of one or a plurality of high-speed frames can be reduced by an amount not including the vehicle ID storage area in the header portion of the high-speed frame. Therefore, the start timing of downlink switching accompanying the second condition (completion of high-speed frame reception) is advanced, and more downlink claims can be provided to the new in-vehicle device.

  The reason for including the vehicle ID storage area in the header portion of the low-speed frame is that if there is no storage area, both the old and new optical beacons will switch the downlink according to the first condition (reception of the low-speed frame). This is because the new in-vehicle device cannot properly communicate with both the old and new optical beacons.

As described above, according to the present invention, it is possible to obtain a new optical beacon that supports multi-rate in the uplink direction and can reliably provide the value service information provided after downlink switching.
Furthermore, according to the present invention, a new in-vehicle device that supports multi-rate in the uplink direction and that can reliably acquire the value service information provided after downlink switching can be obtained.

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 a time chart which shows the example of a timing in the case of providing a transmission interruption period, (a) is when an optical beacon succeeds in reception of the first low-speed frame, (b) is an optical beacon failing in reception of the first low-speed frame. Show the case. It is a sequence diagram which shows the communication procedure of 1st Embodiment. It is a time chart which shows the example of a timing of the communication procedure of 1st Embodiment. It is a time chart which shows the example of a timing of the communication procedure of 2nd Embodiment.

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 portion 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.

When the optical beacon 4 receives the ID storage frame, the optical beacon 4 may perform downlink switching without continuously transmitting the return frame (for example, refer to the second downlink switching illustrated in FIG. 11).
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 the 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 to 11). ).

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”. Determines that the communication partner is the old vehicle-mounted device 2B that does not support high-speed uplink transmission.

When the new light beacon 4A completes the reception of the low-speed frame UL1 from the new in-vehicle device 2A, 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, and is accompanied by continuous transmission of this frame. Perform link switching.
The new light beacon 4A also performs downlink switching even when the reception of the high-speed frame UL2 from the new in-vehicle device 2A is completed. In this case, the return frame may be further continuously transmitted, or the continuous transmission may be performed. You may decide not to do.

Thus, the completion of the reception of the low-speed frame UL1 from the new vehicle-mounted device 2A is a condition (first condition) for the new optical beacon 4A to perform downlink switching with continuous transmission of return frames.
The completion of reception of the high-speed frame UL2 from the new in-vehicle device 2A is a condition (second condition) for the new optical beacon 4A to perform downlink switching with or without continuous transmission of the return frame. .

Further, the new optical beacon 4A does not support high-speed uplink reception when receiving an uplink frame UL in which the value of “vehicle equipment type” is a predetermined value (“6” in the present embodiment) indicating the new vehicle equipment 2A. Similarly to the case of the old optical beacon 4B, on the condition that reception of the uplink frame UL is completed, downlink switching with continuous transmission of the return frame is performed.
Note that when the communication partner of the new optical beacon 4A is the old in-vehicle device 2B, the high-speed frame UL2 is not received, and therefore downlink switching according to the second condition is not performed.

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 to 11.

  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 that are repeatedly transmitted or the downlink frames DL1 and LD2 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 the present embodiment, it is assumed that the new in-vehicle device 2 </ b> A is a type that does not determine whether the optical beacon 4 is new or old.

[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.

[Problems when there is no transmission interruption period]
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 shown in FIGS.

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 2A retransmits the large-capacity uplink frame groups U0 to U1 including the low-speed frame U0 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 problems 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 U0 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 vehicle ID included in U0 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 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 at least 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 U0 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.

[Problems when resending low-speed frames]
FIG. 11 is a time chart illustrating an example of timing when a transmission interruption period is provided.
11A shows a case where the optical beacon 4 succeeds in receiving the first low-speed frame UL1, and FIG. 11B shows a case where the optical beacon 4 fails to receive the first low-speed frame UL1. Show.

Here, in the example of FIG. 11, it is assumed that the installation height of the in-vehicle head 22 is “1.5 m” (for example, a large vehicle). Therefore, the communication time during traveling in the communication area A is shorter than when the height is “1.0 m” (for example, in the case of a medium-sized vehicle or a small vehicle).
In this case, for example, if the vehicle 20 passes through the communication area A in FIG. 3 at a vehicle speed of 70 km / hour, the in-vehicle device 2 passes through the time point ts of the start point of the downlink area DA (also the start point of the uplink area UA). The communication time from the end point to the passing point te is 243.7 msec.

In FIG. 11, the upper time zone indicated by “DL2” indicates the transmission time of the downstream frame DL2 by the new optical beacon 4A, and the lower time zone indicated by “UL” indicates the low speed frame UL1 and the high speed frame by the new vehicle-mounted device 2A. The transmission time of UL2 is shown.
In the example of FIG. 11, only the first downlink frame DL2 of the series of downlink frame groups configured with 80 frames is configured with a folded frame.

The optical beacon 4 transmits “value service information” from the head of the downstream frame group to 54 frames (this number of frames is required in the “near infrared interface standard” of the optical beacon). As described above, this “value service information” is predetermined provision information (service information) to be downlinked by the optical beacon 4 corresponding to the subsystem key information uplinked by the in-vehicle device 2.
“Continuous transmission time” in FIG. 11 is a transmission time length of a return frame continuously transmitted before downlink frame group transmission of 80 frames after downlink switching.

In the example of FIG. 11, it is assumed that the required transmission time of the low-speed frame UL1 is 4.0 msec, and the required transmission time of the high-speed frame UL2 is 37.9 msec for 16 frames.
Furthermore, in the example of FIG. 11, the transmission interruption period between the low speed frame UL1 and the high speed frame UL2 is set to 20.0 msec, and the transmission cycle when retransmitting the low speed frame UL1 is set to 30.0 msec. It is assumed that 5.0 msec is assigned as the switching time from the time when the new in-vehicle device 2A returns from the completion of transmission of the high-speed frame to the reception state tr.

Therefore, as shown in FIG. 11B, when the uplink timing is bad and the low-speed frame UL1 has to be retransmitted, the “uplink” from the start of transmission of the first low-speed frame U1 to the start of reception of the downlink frame DL2 The “period UT” includes the following first to fourth times excluding the transmission time of the low-speed frame UL1.
First time: Transmission period of the low-speed frame UL1 when the low-speed frame UL1 is retransmitted (30.0 ms in the example of FIG. 11)
Second time: transmission interruption period (20.0 msec in the example of FIG. 11)

Third time: transmission time of the high-speed frame UL2 (in the example of FIG. 11, 37.9 milliseconds in the case of 16 frames)
Fourth time: switching time from the completion of transmission of the high-speed frame UL2 to the time tr at which the new vehicle-mounted device 2A returns to the receiving state (5.0 ms in the example of FIG. 11)

As shown in FIG. 11A, when the transmission start of the first low-speed frame UL1 is after the start point passage time ts (in the example shown, a delay of 2.0 msec), the low-speed frame UL1 is appropriately selected by the optical beacon 4. Can be received.
Accordingly, the optical beacon 4 performs downlink switching when the reception of the first low-speed frame UL1 is completed, continuously transmits the return frame during the continuous transmission time, and repeats the downlink frame group (80 frame unit). Send downlink.

  As described above, when downlink switching is appropriately performed by the first low-speed frame UL1, the receivable time (time from the return time tr to the end point passage time ts) by the new vehicle-mounted device 2A is 174. 9 milliseconds, and the time for receiving the service information for two times, which is the number of times requested in the contract, is secured.

On the other hand, as shown in FIG. 11B, for example, the optical beacon 4 may not be able to receive the first low-speed frame UL1 because the head of the first low-speed frame UL1 slightly overlaps the start point passage time ts. .
In this case, the downlink switching is performed by the second low-speed frame UL2, but the receivable time (time from the return time tr to the end point passage time ts) by the new in-vehicle device 2A is 146.9 ms. Shorten.

In this case, the new in-vehicle device 2A has a chance to receive the consideration service information twice for the hatched portion corresponding to 28 frames from the head and the black portion corresponding to 4 frames from the end. However, for the white intermediate portion corresponding to 22 frames in the meantime, the new vehicle-mounted device 2A is given a chance to receive it only once.
As described above, in the case of the uplink transmission timing at which the optical beacon 4 cannot receive the first low-speed frame UL1, the new in-vehicle device 2A is requested by the contract for a part of the downlink frame group in which the consideration service information is stored. In some cases, it is not possible to ensure two receptions.

[First Embodiment]
FIG. 12 is a sequence diagram illustrating a communication procedure according to the first embodiment.
As shown in FIG. 12, in the communication procedure of the first embodiment, when the new in-vehicle device 2A continuously transmits the high-speed frames U1 to U3 after the transmission interruption period, even if the reception of the high-speed frames U1 to U3 is completed, the new light The beacon 4A performs downlink switching to solve the above-described problems caused by retransmission of the low-speed frame UL1.

In other words, in the first embodiment (FIG. 12), the new optical beacon 4A executes downlink switching not only when reception of the low speed frame UL1 but also completion of reception of the high speed frame UL2 is detected. In other words, the new light beacon 4A employs the following two types of conditions as conditions for performing downlink switching.
First condition: Completion of low-speed frame reception Second condition: Completion of reception of high-speed frame

Of the above two conditions, the establishment of the first condition can be detected by the normal CRC check of the low-speed frame UL1. The establishment of the second condition can be detected when the CRC check of the single high-speed frame UL2 is normally performed when there is a single high-speed frame UL2.
On the other hand, in the case of a communication protocol that allows continuous transmission of a plurality of high-speed frames UL2, the passage of a predetermined time T1 (see FIG. 12) from the completion of reception of any high-speed frame UL2 is regarded as the second condition being satisfied. I can do that.

For example, after a CRC check of an arbitrary frame (for example, the top frame) of the plurality of high-speed frames UL2 is completed, a predetermined fixed time (for example, a transmission time of 15 frames from the completion of reception of the top frame) It is possible to adopt a method (first method) that considers that the second condition is satisfied when a certain 35.5 milliseconds have elapsed.
The first method is particularly effective when the transmission time of the high-speed frame UL2 is set to a fixed length. Since the value of the fixed time can be set relatively long according to the transmission time of the high-speed frame UL2, the beacon controller 7 There is an advantage that can reduce the load.

  However, in the first method, when the transmission time of the high-speed frame UL2 is variable according to the data amount, the actual transmission time of the high-speed frame UL2 is smaller than the fixed time set on the beacon side. However, if the fixed time has not elapsed, the second condition is not satisfied, and the start of downlink switching using the high-speed frame UL2 is unnecessarily delayed.

Therefore, the establishment of the second condition is determined by the elapse of a predicted time that can be received from the number of frames of the remaining high-speed frame UL2 that can be received subsequent to the high-speed frame UL2 after completion of reception among the plurality of high-speed frames UL2. A method (second method) may be adopted.
The predicted time can be calculated from, for example, the number of remaining frames obtained by subtracting the number of received high-speed frames UL2 from the total number of high-speed frames UL2, and the communication speed of the high-speed frames UL2. In this case, the new optical beacon 4A needs to know the total number of frames of the high-speed frame UL2, but for this, for example, the new vehicle-mounted device 2A has the total number of high-speed frames UL2 as the first frame of the low-speed frame UL1 or the high-speed frame UL2. What is necessary is just to describe the number of frames.

  According to the second method, it is necessary to calculate the predicted time when the second condition is satisfied for each different communication partner, but even if the number of high-speed frames UL2 transmitted by the new in-vehicle device 2A varies, There is an advantage that the time when the second condition is satisfied can be accurately calculated according to the number of frames of the remaining high-speed frame UL2, and downlink switching using the high-speed frame UL2 can be performed accurately.

Further, a method of determining whether the second condition is satisfied by the completion of reception of the high-speed frame UL2 including information indicating the last frame (for example, the above-mentioned “final frame flag”) among the plurality of high-speed frames UL2 (third Method) may be adopted.
Even in the case of the third method, even when the number of uplink frames transmitted by the new in-vehicle device 2A fluctuates, the time when the second condition is established according to the number of frames can be accurately determined, and the high-speed frame UL2 is used. Downlink switching can be performed accurately.

In order to reduce the processing load of the new light beacon 4A as much as possible, it is preferable that the time from the trigger of the second condition to the start of downlink switching is as long as possible.
In this regard, in the third method, the time from reception of the last frame to downlink switching cannot be taken too long, whereas in the first and second methods, reception of the first frame instead of the last frame is triggered. Therefore, there is an advantage that it is possible to take a relatively long time until the downlink switching, and to reduce the processing load as compared with the third method.

  The first to third methods described above may be employed independently for the new optical beacon 4A, but a plurality of methods selectable from the first to third methods are combined into one new optical beacon 4A. May be adopted.

[Effects of First Embodiment]
FIG. 13 is a time chart illustrating a timing example of the communication procedure according to the first embodiment.
In the case of FIG. 13 as well, as in the example of FIG. 11B, reception of the first low-speed frame UL1 fails and downlink switching is performed in the second low-speed frame UL1, but the high-speed frame UL2 Even when reception is completed, since the new optical beacon 4A performs downlink switching, the transmission start time of the downstream frame group in units of 80 frames is adjusted to the vicinity of the return time tr of the reception status of the new vehicle-mounted device 2A.

For this reason, as shown in FIG. 13, the new in-vehicle device 2 </ b> A has a limited downlink frame group receivable time (time from the return event tr to the end point passage time ts: 146.9 msec). The consideration service information arranged on the head side can be received twice, which is the number of times requested in the contract.
Therefore, according to the new light beacon 4A of the present embodiment, the value service information provided after downlink switching can be more reliably provided to the new in-vehicle device 2A.

[Continuous sending of folded frames according to high-speed frames]
In the time chart of FIG. 13, “continuous transmission time” is also provided when downlink switching is performed in response to the completion of reception of the high-speed frame UL2. That is, the new light beacon 4A continuously transmits the return frame that is the downlink frame DL2 including the lane notification information even when the second condition (reception of the high-speed frame UL2 is completed) is established.

  However, the loopback of the vehicle ID to the in-vehicle device 2 is often completed by the continuous transmission of the down frame including the lane notification information executed according to the first condition (reception of the low speed frame UL1). It is considered that there is little need for further continuous transmission of downlink frames including lane notification information corresponding to the above condition (completion of reception of the high-speed frame UL2).

Therefore, as shown in the communication procedure of FIG. 12, when the second condition is satisfied, downlink switching without continuous transmission of loopback frames may be performed.
By adopting such an implementation, continuous transmission according to the second condition (reception completion of the high-speed frame UL2) is not performed, so that it is possible to prevent a transmission opportunity of another downlink frame from being taken away by unnecessary continuous transmission. Can do.

[Second Embodiment]
FIG. 14 is a time chart illustrating a timing example of a communication procedure according to the second embodiment.
As shown in FIG. 14, in the second embodiment, the first to fourth times included in the uplink period UT are shortened compared to the case of FIG. To solve the problem.

  That is, in the new in-vehicle device 2A according to the second embodiment (FIG. 14), the uplink period UT from the start of transmission of the first low-speed frame UL1 to the start of reception of the downlink frame is reduced by shortening the first to fourth times. However, it is set to be a time length in which the consideration service information provided from the optical beacon 4 in a plurality of downlink frames DL2 that can be received after the period UT can be received at least twice.

Specifically, as apparent from a comparison between FIG. 11B and FIG. 14, the transmission period of the low-speed frame UL1 is changed from 30.0 msec to 20.0 msec, so that the transmission period is 10.0 m. Seconds are shortened.
In addition, the transmission interruption period is shortened by 4.0 msec by changing the transmission interval (interval from the head to the top) of the first high-speed frame UL2 from the low-speed frame UL1 to 20.0 msec. .

Further, the transmission time of the high-speed frame UL2 is shortened by 5.6 milliseconds by changing the configuration of the upstream frame group including the plurality of high-speed frames UL2 from 16 frames to 4 frames. That is, the maximum data length of the actual data part is expanded from 59 bytes to 236 bytes, which is four times larger, and the data amount of the frame common part such as the header part is reduced to shorten the transmission time.
Further, the switching time from the completion of transmission of the high-speed frame UL2 to the reception state is changed from 5.0 ms to 2.0 ms, thereby shortening the switching time by 3.0 ms.

In the new in-vehicle device 2A of the second embodiment, the uplink period UT is shortened by a total of 22.6 milliseconds due to the above-mentioned time reduction, so that the reception time of the downlink frame group by the new in-vehicle device 2A (return time tr To the end point passage time ts) is extended to a time during which a downstream frame group of 80 frames can be received twice.
For this reason, according to the new in-vehicle device 2A of the present embodiment, the consideration service information can be reliably received twice, and the consideration service information provided after downlink switching can be more reliably acquired.

  In addition, since the said effect by the new vehicle equipment 2A which concerns on 2nd Embodiment is based on adjustment of the uplink period UT of the new vehicle equipment 2A, it succeeds irrespective of the new and old types of the optical beacon 4 which is a communication partner. It is.

[Numerical range variations]
The first to fourth time lengths in the second embodiment (FIG. 14) are merely examples, and can be set to various time lengths within a predetermined range.
For example, the “first time” may be a time length selected from a range of 10 to 29.5 msec in 0.5 msec increments. Further, the “second time” may be a time length selected from a range of 10 to 23.5 msec in 0.5 msec increments.

The reason for the lower limit of the first and second times being 10 milliseconds is that the time required for downlink switching is approximately 10 milliseconds.
That is, when the first and second times are shortened to less than 10 milliseconds, the lane notification information transmitted by the optical beacon 4 at the time of downlink switching performed according to the first condition (reception of the low-speed frame) is changed. The new in-vehicle device cannot receive the included downstream frame, and the new in-vehicle device 2A cannot appropriately communicate with the optical beacon 4.

Further, the “third time” may be a transmission time length of one or a plurality of high-speed frames generated by the number of common frame portions selected from 1 to 8.
In addition, in the standard (for example, “U-shaped communication application common standard”) relating to communication between the optical beacon 4 and a host device such as the central device of the traffic control center, the data amount of the actual data portion is defined as 246 bytes or less. Therefore, in order to allow the optical beacon 4 to uplink the amount of data exceeding it to the host device, it is necessary to change the standard.

Therefore, it is preferable to select the number of frame common parts so that the size of the actual data part generated by the optical beacon 4 is 59 × 4 = 236 bytes or less.
Therefore, the “third time” is preferably a transmission time length of one or a plurality of high-speed frames generated by the number of frame common parts selected from 4 to 8.
Furthermore, the “fourth time” may be a time length selected from a range of 0.5 to 4.5 msec in 0.5 msec increments.

In the second embodiment, the total time of the uplink period UT is shortened by shortening all of the first to fourth times. However, by shortening at least one of them, the time is increased. The total time of the link period UT may be shortened.
In the second embodiment, the new in-vehicle device 2A includes a vehicle ID storage area (see FIG. 7) in the header portion of the low speed frame UL1, but the vehicle ID storage area is included in the header portion of the high speed frame UL2. You may decide not to include it.

  In this case, the frame length of one or a plurality of high-speed frames UL2 is reduced by the amount not including the vehicle ID storage area in the header portion of the high-speed frame UL2. Accordingly, there is an advantage that the downlink switching start time associated with the second condition (reception of the high-speed frame) is advanced, and more downlink claims can be provided to the new in-vehicle device 2A.

[Other variations]
The embodiment disclosed this time (including the above-described modifications) is illustrative in all respects and not restrictive. 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 second embodiment described above, the uplink service UT is shortened and the reception time of the downlink information is increased to ensure reception of the service information twice. Even if a rule for reducing the number of frames of the frame DL2 from the current level (for example, a rule for reducing the number of frames DL2 from 54 frames to 28 frames) is adopted, it is possible to ensure reception of the value service information twice.
However, in this case, since the number of frames that the optical beacon 4 can downlink as the consideration service information decreases, there is a demerit that an operational limitation occurs.

In the above-described embodiment, the new vehicle-mounted device 2A continuously transmits a plurality of high-speed frames U1 to U3. However, burst transmission may be performed by providing an interval of a predetermined time length between frames. .
In addition, in this specification, the “on-vehicle device” includes those that are always fixed to the 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 New optical beacon 7 Beacon controller (communication control unit)
8 Beacon head 10 Optical transmission unit 11 Optical reception unit 20 Vehicle 21 In-vehicle controller (communication control unit)
22 On-vehicle head 23 Optical transmitter 24 Optical receiver

Claims (10)

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;
An optical beacon comprising: a communication control unit capable of adopting the following two types of conditions as conditions for performing downlink switching.
First condition: Completion of low-speed frame reception Second condition: Completion of reception of high-speed frame   When the first condition is satisfied, the communication control unit performs downlink switching with continuous transmission of a downlink frame including lane notification information storing vehicle identification information, and the second condition is satisfied. In this case, the optical beacon according to claim 1, wherein downlink switching is performed without continuous transmission of the downlink frame including the lane notification information. In the case of a communication protocol that allows continuous transmission of a plurality of the high-speed frames,
3. The optical beacon according to claim 1, wherein the second condition is that a predetermined time has elapsed from completion of reception of an arbitrary high-speed frame among the plurality of high-speed frames.   The optical beacon according to claim 3, wherein the predetermined time is a predetermined fixed time.   4. The optical beacon according to claim 3, wherein the predetermined time is an estimated time that can be calculated from the number of frames of the remaining high-speed frames that can be received following an arbitrary high-speed frame after completion of reception among the plurality of high-speed frames. . In the case of a communication protocol that allows continuous transmission of a plurality of the high-speed frames,
The optical beacon according to any one of claims 1 to 5, wherein the second condition is completion of reception of the high-speed frame including information indicating a final frame among the plurality of high-speed frames. An in-vehicle device that performs wireless communication with an optical beacon and an optical signal installed on a road,
An optical transmitter capable of electro-optical conversion at two transmission speeds, high and low,
An optical receiver capable of photoelectric conversion at a predetermined transmission rate;
A communication control unit that transmits one or more high-speed frames with a transmission interruption period after transmission of the low-speed frame, and
The uplink service period from the start of transmission of the first low-speed frame to the start of reception of the downlink frame can receive at least twice the value service information provided from the optical beacon in a plurality of downlink frames that can be received after that period. An in-vehicle device characterized in that the time length is set. The in-vehicle device according to claim 7, wherein the uplink period includes first to fourth times defined below.
First time: Transmission period of the low-speed frame when retransmitting a low-speed frame Second time: Transmission interruption time Third time: Transmission time of one or a plurality of high-speed frames Fourth time: Transmission of a high-speed frame is completed Switching time from receiving to receiving The in-vehicle device according to claim 8, wherein at least one of the first to fourth times is set to a time length defined next.
First time: time length selected from a range of 10 to 29.5 msec in 0.5 msec increments Second time: selected from a range of 10 to 23.5 msec in 0.5 msec increments Time length Third time: Transmission time length of one or a plurality of high-speed frames generated by the number of common frame portions selected from 1 to 8 Fourth time: 0.5 to 4 in 0.5 msec increments . Length of time selected from the range up to 5 ms   10. The communication control unit according to any one of claims 7 to 9, wherein the header part of the low-speed frame includes a storage area for vehicle identification information, and the header part of the high-speed frame does not include the storage area for the identification information. The in-vehicle device described.

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