JP2014112753A - Optical beacon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical beacon that can differentiate the content of supply information in accordance with new and old types of on-vehicle devices.SOLUTION: An optical beacon 4 for performing radio communication based on optical signals with an on-mount device 2 of a running vehicle comprises: a light receiving unit 11 that can perform light-to-electricity conversion at two types of (high and low) transmission rates; a light transmitting unit 10 that can perform electricity-to-light conversion at a predetermined transmission rate; and a communication controller (beacon controller 7) that can perform the following two types of down-link switching. First down-link switching is down-link switching in which with up-link reception of low-rate frame UL1 as a condition, a down-link frame having first supply information D1 stored therein is contained in a first down frame group DL2-2 to be subsequently transmitted. Second down-link switching is down-link switching in which with up-link reception of high-rate frame UL2 as a condition, a down frame having second supply information D2 stored therein is contained in a second down frame group DL2-2 to be subsequently transmitted.

Description

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

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

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

JP 2005-268925 A

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

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

  Therefore, an optical beacon (hereinafter referred to as “Old Hikari”) that allows the new in-vehicle device to receive an uplink low-speed frame not only from a high-speed frame but also from an in-vehicle device that performs only low-speed uplink transmission (hereinafter also referred to as “old in-vehicle device”). If a communication protocol that transmits a low-speed frame storing vehicle identification information (hereinafter also referred to as “vehicle ID”) that can be recognized by a beacon ”is used, downlink switching to the old optical beacon is performed. Can be performed, and upward compatibility of the new in-vehicle device can be ensured.

  Also, assuming that the new vehicle-mounted device transmits a high-speed frame after transmitting a low-speed frame, lane notification information storing a vehicle ID between the first low-speed frame and a high-speed frame scheduled to be transmitted thereafter By adopting a communication protocol that provides a transmission interruption period for receiving a downstream frame including the new in-vehicle device, by retransmitting a plurality of high-speed frames without noticing the downstream frame storing its own vehicle ID, Loss of the opportunity to receive downstream frames can be prevented.

On the other hand, considering the upward compatibility of the new optical beacon, as with the old optical beacon, if the downlink switching corresponding to the uplink reception of the low-speed frame is performed once, the new optical beacon can be used regardless of whether the in-vehicle device is new or old. Conventional downlink data can be provided.
However, if the new optical beacon only performs downlink switching as before, the new in-vehicle device can transmit a high-speed frame including a large amount of data such as probe data in the uplink, as in the case of the old in-vehicle device. Only downlink data can be obtained.

Therefore, in a system in which the new optical beacon performs downlink switching only once in response to uplink reception of low-speed frames, the incentive to uplink as many high-speed frames as possible does not work, and the uplink speed There is a possibility that it cannot be achieved at an early stage.
In view of the conventional problems, an object of the present invention is to provide a new light beacon capable of differentiating the contents of provided information depending on whether the in-vehicle device is new or old.

  (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 performing electro-optical conversion at a predetermined transmission rate and a communication control unit capable of executing the following two types of downlink switching are provided.

First downlink switching: Downlink switching including a downlink frame storing first provision information in a downlink frame group to be transmitted thereafter on condition that uplink reception of a low-speed frame is a condition. Second downlink switching: high-speed frame Downlink switching that includes the downlink frame storing the second provision information in the downlink frame group to be transmitted thereafter on condition that the uplink reception of

  According to the optical beacon of the present invention, the communication control unit provides a second provision to the second downlink frame group to be transmitted thereafter on the condition that the second downlink switching, that is, uplink reception of a high-speed frame is performed. Since it is possible to perform downlink switching that includes downlink frames that store information, the second provision information can be provided only to new in-vehicle devices that have actually transmitted uplinks of high-speed frames. The second provision information does not pass to the old in-vehicle device that does not transmit.

Therefore, the contents of the provided information can be differentiated depending on whether the in-vehicle device is new or old, and the object of the present invention is achieved.
Examples of the second provision information include “signal offset information” that is assumed to be provided to a new in-vehicle device that uplinks probe data using a high-speed frame. “Offset” means the deviation of the starting point of the green signal between adjacent intersections under system control, and “Signal offset information” is information that expresses the deviation in a format that can be specified on the vehicle side. is there.

(2) In the optical beacon of the present invention, in the case of a communication protocol that allows the in-vehicle device to perform uplink transmission of a plurality of the high-speed frames, uplink reception of the high-speed frames is performed by the plurality of high-speed frames. It is preferable that reception of the predetermined high-speed frame is completed.
The reason is that when a plurality of high-speed frames are transmitted in the uplink, it is impossible to specify the time point when the second downlink switching condition is satisfied unless the condition is satisfied upon completion of reception of one of the high-speed frames. Because.

(3) As the completion of reception of the predetermined high-speed frame, for example, reception completion of the high-speed frame that can be received first can be adopted.
In this case, the second downlink switching condition establishment (trigger generation) is the earliest, and there is an advantage that the processing time until the data switching after the condition is established can be afforded and the processing load can be reduced. The high-speed frame that can be received first is usually the first frame. However, in consideration of communication errors, the high-speed frames after two frames can be the high-speed frames that can be received first.

(4) As the completion of reception of the predetermined high-speed frame, reception completion of the final frame among the plurality of high-speed frames may be adopted.
As described above, when the completion of the reception of the last frame is satisfied as the second downlink switching condition, the data contents of other high-speed frames received so far can be detected in advance. For this reason, more detailed communication control described later, such as changing the content of the second provision information according to the data content of the high-speed frame, becomes possible.

(5) As described above, when the completion of reception of the last frame is set as the second downlink switching condition, if the last frame is missed due to a communication error or the like, the second downlink switching is performed at any time. May not be done.
Therefore, the uplink reception of the high-speed frame further includes the elapse of a predetermined time from the completion of reception of the high-speed frame received first, or the predetermined time from the completion of reception of the high-speed frame finally received. It is preferred to include a course or both courses.
If these are included in the establishment of the condition, it is possible to prevent the optical beacon from performing the second downlink switching because the final frame is unknown.

(6) (7) In the optical beacon of the present invention, in the case of a communication protocol that allows the in-vehicle device to perform uplink transmission of the plurality of high-speed frames, a plurality of the uplink transmissions of the high-speed frames are performed. The elapse of a predetermined time from completion of reception of the predetermined high-speed frame among the high-speed frames may be adopted alone.
In this case, as the predetermined high-speed frame, for example, the high-speed frame that can be received first can be employed.

(8) In the present invention, the communication control unit may determine the second downlink switching time point (the transmission start time point of the second downlink frame group) after this time when viewed from the uplink reception of the high-speed frame. It is preferable to set after the end of the downlink cycle of the first downlink frame group.
In this way, it is easy to afford time from the establishment of the second downlink switching condition to the actual start of transmission of the second downlink frame group, and the processing load on the communication control unit can be reduced. There are advantages.

The “downlink cycle” refers to the transmission time of a group of downlink frames composed of downlink frames that are repeatedly transmitted after an optical beacon is switched after downlink.
The number of frames included in one downlink frame group is variable (up to 79 frames according to the communication protocol), and the communication control unit of the optical beacon configures the downlink frame group according to the data amount of provided information to be downlinked. The number of frames to be performed is determined, and the provided information is stored by dividing into the determined number of downlink frames.

(9) In the optical beacon of the present invention, prior to this transmission of the first frame group, a return frame including lane notification information is repeatedly transmitted, and prior to transmission of the second frame group. It is preferable not to repeatedly transmit the return frame.
The reason is that the repeated transmission of the return frame is usually performed at the time of the first downlink switching, and there is no problem even if it is not performed again at the time of the second downlink switching. This is because if the repeated transmission of the return frame at the time of switching is stopped, useless communication time can be saved.

(10) However, in the optical beacon of the present invention, the transmission control unit repeatedly transmits a return frame including lane notification information prior to the transmission of the first frame group, and the second frame group. Also in this transmission, prior to this, the return frame may be repeatedly transmitted.
In this case, since the second downlink switching process is the same process as the first downlink switching, the software implementation on the communication control unit is simplified.

(11) In the optical beacon of the present invention, it is preferable that the communication control unit includes the second provision information a plurality of times in the second downlink frame group.
In this way, it is possible to reliably ensure two or more downlink transmissions for the second provided information, which is the number of times required by the conventional communication protocol.

(12) For the same reason, the communication control unit may include the second provision information on the first half side of the second downlink frame group.
The “first half side” of the downstream frame group refers to a range from the first frame of the downstream frame group to the frame located at the center. For example, in the case of a 79-frame downlink frame group, the first frame is from the first frame to 40 frames. Therefore, if the second provision information is included in the first half of the downlink frame group, even in the case of the second downlink frame group having a large number of frames such that two downlink cycles cannot be secured within a predetermined time, the conventional communication protocol is used. In this case, it is possible to increase the possibility that the second provision information can secure two or more downlink transmissions, which is the number of times required for the second provision information.

(13) In the optical beacon of the present invention, when each uplink reception is detected in the order of the following a) to d), the communication control unit is the following regardless of the following c) and d): It is preferable to continue transmission of the second downstream frame group corresponding to b).
a) Uplink reception of a low speed frame including a first vehicle ID b) Uplink reception of a high speed frame including a first vehicle ID c) Within a predetermined time from a) of a low speed frame including a second vehicle ID Uplink reception d) Uplink reception of high-speed frame including second vehicle ID

In this case, the second provision information for the new vehicle-mounted device of the first vehicle ID (hereinafter also referred to as “preceding vehicle-mounted device”) continues to be provided after c), and the second vehicle ID It is also provided for new in-vehicle devices (hereinafter also referred to as “subsequent in-vehicle devices”).
Therefore, assuming that the second provision information is dynamic information such as the signal offset information, the information that is slightly older for the subsequent vehicle-mounted device is provided. There is an advantage that the provided information can be surely provided.

  (14) In the optical beacon of the present invention, when the uplink reception is detected in the order of the above a) to d), the communication control unit performs the second down on the condition of the above d). The second downlink frame group corresponding to the above d) may be transmitted after the second downlink frame group corresponding to the above b) is continuously transmitted until the link is switched. .

In this case, the second provision information for the preceding vehicle-mounted device is provided until d), and the second provision information for the subsequent vehicle-mounted device is provided after d).
Therefore, the transmission time of the second provided information can be extended until the preceding in-vehicle device detects the high-speed uplink reception from the subsequent in-vehicle device. Can provide information.

(15) Further, in the optical beacon of the present invention, the communication control unit newly performs the first downlink switching on condition of the following c), and newly performs the second downlink on condition of the following d). Switching may be performed.
In this case, so-called post-winning processing is performed, and the second provision information for the preceding vehicle-mounted device is provided only up to c) above, but it is sufficient to perform the first and second downlink switching as usual. Therefore, it is easy to implement software for the communication control unit.

(16) In the optical beacon of the present invention, the communication control unit includes the second provision included in the second downlink frame group depending on whether the high-speed frame or the data content satisfies a predetermined condition. It is preferable to change the content of the information.
In this way, it is possible to provide the second provision information of a predetermined amount of data only to a high-speed frame satisfying a predetermined condition or a new in-vehicle device that has uplinked data contents, and a high-speed uplink using a high-speed frame. Incentives for transmission can be increased.

(17) In the optical beacon of the present invention, in the case of a communication protocol that allows the in-vehicle device to perform uplink transmission of the plurality of high-speed frames, the communication control unit defines the total number of high-speed frames as It is preferable that the content of the second provision information included in the second downlink frame group is changed according to the comparison result with the number of frames.
In this way, it is possible to provide the second provision information of a predetermined amount of data only to the new in-vehicle device that has uplinked the high-speed frame of the specified number of frames or more, and the high-speed uplink transmission using a plurality of high-speed frames. Incentives can be increased.

(18) In the optical beacon according to the aspect of the invention, the communication control unit may include the second downlink frame group to be included in the second downlink frame group according to a comparison result between the number of trajectories of probe data included in the high-speed frame and the predetermined number of trajectories. You may decide to change the content of 2 provision information.
In this way, it is possible to provide the second provision information of a predetermined amount of data only to the new in-vehicle device that has uplinked the high-speed frame more than the specified number of trajectories, and incentives for high-speed uplink transmission of probe data Can be increased.

(19) Further, in the optical beacon of the present invention, in the case of a communication protocol that allows the in-vehicle device to perform uplink transmission of the plurality of high-speed frames, the communication control unit is not the last high-speed frame. The content of the second provision information included in the second downlink frame group may be changed according to the comparison result between the frame size and the specified size.
In this way, it is possible to provide the second provision information of a predetermined amount of data only to the new in-vehicle device that has uplinked a high-speed frame that is equal to or larger than the specified size, and high-speed uplink transmission by a plurality of high-speed frames Incentives can be increased.

(20) In the optical beacon of the present invention, the communication control unit may not perform the second downlink switching when the high-speed frame or the data content thereof does not satisfy a predetermined condition.
In this way, since the second provision information is provided only to a high-speed frame that satisfies a predetermined condition or a new in-vehicle device that has uplinked the data content, the incentive for high-speed uplink transmission by the high-speed frame is increased. be able to.

  (21) In the optical beacon of the present invention, the second provided information may be either static information or dynamic information, but as an example of dynamic information, a green signal between adjacent intersections that are system-controlled The signal offset information in which the deviation of the start time is expressed in a format that can be specified on the vehicle side can be employed.

(22) In the optical beacon of the present invention, the communication control unit performs the first operation until the end time of the downlink cycle of the first downlink frame group after this time as viewed from the time of uplink reception of the high-speed frame. It is preferable to complete creation of downlink data included in the second downlink frame group.
In this way, compared with the case where the downlink data is generated after detecting the uplink reception of the high-speed frame, the generation time can be advanced, and the transmission timing of the downlink data can be delayed. Can be prevented.

(23) In the optical beacon of the present invention, the communication control unit may complete creation of downlink data to be included in the second downlink frame group before receiving the uplink of the high-speed frame.
Even in this case, compared with the case where the downlink data is created after detecting the uplink reception of the high-speed frame, the creation time can be advanced, and the transmission timing of the downlink data can be prevented from being delayed. can do.

(24) However, when the memory for storing the downlink data included in the first downlink frame group and the memory for the downlink data included in the second downlink frame group are shared, the communication control unit It is necessary to complete the creation of downlink data to be included in the second downlink frame group before the start of transmission of the first downlink frame group.
The reason is that when the memory is shared, the content of the downlink data included in the second downlink frame group needs to be determined before the start of transmission of the downlink data included in the first downlink frame group. is there.

  In (22) to (24) above, the creation start timing of the downlink data included in the second downlink frame group may be, for example, the time when uplink reception of a low-speed frame is detected.

  As described above, according to the present invention, a new optical beacon capable of differentiating information provided to an in-vehicle device according to whether the in-vehicle device is new or old is 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 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 sequence diagram which shows the road-vehicle communication in the case of performing 2nd downlink switching. It is a sequence diagram which shows the road-vehicle communication in the case of performing 2nd downlink switching. It is explanatory drawing which shows the example of the switching process of 2nd downlink switching. It is explanatory drawing of downlink data in case a some new vehicle equipment communicates with a new light beacon by another lane. It is explanatory drawing of downlink data in case a some new vehicle equipment communicates with a new light beacon by another lane. It is explanatory drawing which shows the specific example of the preparation timing of the downlink data by a prior | preceding preparation system. It is explanatory drawing which shows the other specific example of the preparation timing of the downlink data by a prior | preceding preparation system.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[Definition of terms, etc.]
Here, terms used in this specification are defined.
Downstream frame DL: A generic term for frames transmitted by the optical beacon 4 in the downlink. The downlink frame DL includes a downlink frame DL1 and a downlink frame DL2 described later.
Up frame UL: A generic term for frames transmitted by the in-vehicle device 2 through uplink. The upstream frame UL includes an upstream frame UL1 and an upstream frame UL2, which will be described later.

In this specification, “continuous transmission” of frames is synonymous with “repetitive transmission”, and not only when there is no interval between frames, but also when burst transmission is performed with an interval of a predetermined time length between each frame. including.
In this specification, a series of frames that are continuously transmitted (repeatedly transmitted) with a predetermined number of frames is referred to as a “frame group”. For example, in the case of “transmission of a downlink frame group”, it means continuous transmission (repeated transmission) of each downlink frame DL constituting the group.

In this specification, a downlink frame group including a plurality of downlink frames DL may be referred to as a “downlink frame group DL”.
The same applies to downstream frames DL1, DL2, DL2-1, DL2-2, and upstream frames UL1, UL2, which will be described later.

Downlink frame DL1: A downlink frame DL that is repeatedly transmitted toward the downlink area DA before the optical beacon 4 performs downlink switching described later (the first downlink switching when downlink switching is performed twice). Say.
Uplink frame UL1: An uplink frame UL that is transmitted by the vehicle-mounted device 2 in response to reception of the downlink frame DL1 and that has a low transmission rate. Also referred to as “low speed frame UL1”.

Uplink frame UL2: An uplink frame UL having a high transmission rate transmitted by the new in-vehicle device 2A. Also referred to as “high-speed frame UL2”.
In the case of the new in-vehicle device 2A that supports high-speed uplink transmission (see FIG. 5), both the low-speed frame UL1 and the high-speed frame UL2 can be transmitted as the uplink frame UL, and the old in-vehicle device 2B that does not support high-speed uplink transmission. In the case of (see FIG. 5), only the low-speed frame UL1 can be transmitted as the uplink frame UL.

Downstream frame DL2: This refers to the downlink frame DL that the optical beacon 4 repeatedly transmits after downlink switching described later (the first downlink switching when downlink switching is performed twice).
When downlink switching is performed twice, the downlink frame DL2 is composed of the next downlink frame DL2-1 and downlink frame DL2-2.

Downstream frame DL2-1: This refers to the downstream frame DL2 that is repeatedly transmitted after the “first downlink switching” described later, by the new optical beacon 4A (see FIGS. 10 and 11) that can perform downlink switching twice.
Downstream frame DL2-2: This refers to the downstream frame DL2 that is repeatedly transmitted after the “second downlink switching” described later by the new optical beacon 4A (see FIGS. 10 and 11) that can perform the downlink switching twice.

When downlink switching is performed only once, the contents of the downlink data included in the downlink frame group DL2 are not changed thereafter. In this case, it can also be said that the downlink frame DL2 = the downlink frame DL2-1.
On the other hand, when the downlink switching is performed twice, part or all of the contents of the downlink data included in the downlink frame group DL2-1 (a part in the present embodiment) is changed by the second downlink switching, The downlink frame group DL2-2 is configured with the changed downlink data.

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. 6) in the header portion of the uplink information). This is the uplink frame UL1.
Return frame: When the optical beacon 4 receives an ID storage frame, the same value as the vehicle ID included in the frame is stored in a predetermined storage area (for example, “lane notification information” in the actual data portion of the downlink information (see FIG. 7) refers to the downlink frame DL2 generated as described in (7)).

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.
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 content (provided information) included in the downlink frame group DL repeatedly transmitted by the optical beacon 4 before and after the switching.
First downlink switching: When the new light beacon 4A performs downlink switching twice, it refers to downlink switching performed on condition that the low-speed frame UL1 is received.
Second downlink switching: When the new light beacon 4A performs downlink switching twice, it refers to downlink switching performed on condition that the high-speed frame UL2 is received.

The downlink frame groups DL2 and DL2-1 after downlink switching (first downlink switching if performed twice) correspond to the communication partner of this road-to-vehicle communication corresponding to subsystem key information, vehicle ID, etc. The provision information for the vehicle 20 (hereinafter also referred to as “first provision information”) is included.
The first provision information is provision information that is also provided to the old in-vehicle device 2B that does not support high-speed uplink transmission, such as traffic jam information, section travel time information, and event regulation information.

In the downlink frame group DL2-2 after the second downlink switching, provision information (hereinafter also referred to as "second provision information") for the vehicle 20 equipped with the new in-vehicle device 2A that supports high-speed uplink transmission. .) Is included.
The second provided information includes, for example, “signal offset information” expressed in a format that allows the in-vehicle device 2 of the vehicle 20 to specify an offset that is a deviation of the blue start time between adjacent intersections, or the vehicle 20 is an electric vehicle “Charging station information” indicating the route to the nearest charging station, which is useful information in some cases.

Any area may be used as the data storage area of the vehicle ID of the uplink frame UL and the downlink frame DL, but for example, a “header part” or “lane notification information” can be used.
The lane notification information in the downlink frame DL includes a field for storing a vehicle ID for each lane R1 to R4 (see 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.

In addition, only the conventional downlink switching based on the low-speed frame UL1 is referred to as “downlink switching”, and the change in the content of the downlink data accompanying the subsequent uplink reception of the high-speed frame UL2 is referred to as “downlink switching”. It may be defined by other terms that are not.
As other terms, for example, “data change”, “data change”, “data change”, “data update”, “data insertion”, “data addition”, and the like of the downstream frame group can be considered.

[Frame structure of upstream frame]
FIG. 6 is a frame configuration diagram of uplink information (uplink frame).
As shown in FIG. 6, the uplink frame UL is sequentially transmitted from the top in order to synchronize with the receiving side, a transmission control unit for synchronization (hereinafter referred to as “synchronizing unit”), a header unit, an actual data unit, and a CRC ( Cyclic Redundancy Check) transmission control unit (hereinafter referred to as “CRC unit”).

In the uplink frame UL, 1 byte is assigned to the synchronization part, 10 bytes are assigned to the header part, 59 bytes at the maximum 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.
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 the value of the vehicle ID generated by the in-vehicle device 2 by itself or automatically generated by the optical beacon 4 and notified to the in-vehicle device 2. The value of the vehicle ID stored sometimes 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 new in-vehicle device 2A transmits the low-speed uplink frame UL1, 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”. Is stored a predetermined value (for example, “1”) indicating that the speed is low.
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 new optical beacon 4A can determine that the received in-frame UL is the low-speed frame UL1 from the new in-vehicle device 2A when the in-vehicle device type value of the received upstream frame UL is “6” and the information type value is “1”. When the value of the on-vehicle device type of the received upstream frame UL is “6” and the value of the information type is “4”, it can be determined that the high-speed frame UL2 is from the new on-vehicle device 2A.
In the case of the old vehicle-mounted device 2B, since the value of the vehicle-mounted device type is set to other than “6”, the new light beacon 4A receives an uplink frame UL having a value of “vehicle-mounted device type” other than “6”. Can determine 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 of the present embodiment completes 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 this frame is repeated. Perform “first downlink switching” with transmission.
In addition, the new optical beacon 4A of the present embodiment performs “second downlink switching” in response to the reception of the high-speed frame UL2 from the new in-vehicle device 2A. In this case, the repeated transmission of the return frame is further performed. Alternatively, the repeated transmission may not be performed.

Thus, the uplink reception of the low-speed frame UL1 from the new in-vehicle device 2A is a condition for the first optical beacon 4A to perform the first downlink switching accompanied by the repeated transmission of the return frame.
The uplink reception of the high-speed frame UL2 from the new in-vehicle device 2A is a condition for the second optical beacon 4A to perform the second downlink switching with or without the repeated transmission of the return frame.

Note that the new optical beacon 4A is not capable of high-speed uplink reception when it receives an uplink frame UL in which the value of the “on-vehicle device type” is a predetermined value (other than “6” in the present embodiment) indicating the old on-vehicle device 2B. Similarly to the case of the corresponding old optical beacon 4B, on the condition that reception of the uplink frame UL is completed, downlink switching with repeated transmission of the return frame is performed.
Note that when the communication partner of the new light beacon 4A is the old vehicle-mounted device 2B, the high-speed frame UL2 is not received, so the second downlink switching 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. 7 is a frame configuration diagram of downlink information (downlink frame).
As shown in FIG. 7, the frame configuration of the downlink frame DL is also composed of a synchronization portion, a header portion, an actual data portion, and a CRC portion in order from the top, as in the case of the frame configuration of the uplink frame UL (FIG. 6). .

In the downlink frame DL, 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 are assigned to the CRC part (1 byte idle part + 2 bytes CRC + 1 byte). Of the last synchronization part).
In the actual data portion of the downlink frame DL, for example, any one of various types of provision information illustrated in FIGS. 10 and 11 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 of the actual data part (123 bytes). If the provision information does not fit, the optical beacon 4 transmits a plurality of downlink frames DL2 (downlink frames). Group) may send the provided information.

As shown in FIG. 7, 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.
The optical beacon 4 stores a predetermined flag value (for example, “01”) in the “beacon identification flag” of the downlink frame DL in the case of the “new optical beacon 4A” corresponding to high-speed uplink reception. In the case of the old optical beacon 4B that does not support high-speed uplink reception, other values (for example, “00”) are stored in the “beacon identification flag” of the downlink frame DL.

  Therefore, the new in-vehicle device 2A corresponding to the high-speed uplink transmission determines whether the communication beacon optical beacon 4 is the new optical beacon 4A based on the value of the “beacon identification flag” included in the “lane notification information” of the downlink frame DL. Whether it is 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. 9 to be described later, when the new vehicle-mounted device 2A continuously transmits the subsequent high-speed frames U1 to U3 with a transmission interruption period after the preceding low-speed frame U0, Since the uplink transmission time of the frames U1 to U3 and the downlink transmission time after downlink switching may overlap, the transmission possible period of the downlink frame DL2 after downlink switching is (250 + α) ms (for example, 350 ms) It is preferable to do.

[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”). This is the same in the road-to-vehicle communication shown in FIGS.

  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 distinguished, the new in-vehicle device 2A performs uplink transmission at a low speed in order to receive and receive the uplink frame UL with certainty.
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 new in-vehicle device 2A has a communication protocol that always includes the low-speed frame UL1 in the upstream frame group, communication with both types of optical beacons 4 can be performed without determining the old and new types of the optical beacon 4 of the communication partner. Is possible.
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.

  Therefore, as a mode of the new vehicle-mounted device 2A, the “first type” that performs the new / old determination of the optical beacon 4 and transmits the high-speed frame UL2 only when the communication partner is the new optical beacon 4A, and the old and new of the optical beacon 4 are used. The “second type” that transmits the low-speed frame UL1 and the high-speed frame UL2 without making a determination may be employed.

[Problems when there is no transmission interruption period]
FIG. 8 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. 8, U0 to U3 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 FIG. 8, the number of frames in the upstream frame group is 4, but the number of frames is not limited to four. For example, three 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 U1 to U3 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 of 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. 8, 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 example of FIG. 8, it is assumed that the new in-vehicle device 2A does not determine whether the communication partner is new or old, and continuous transmission (repetitive transmission) of the low-speed frame U0 and the high-speed frames U1 to U3 is performed by the new in-vehicle device 2A. It is executed regardless of whether the communication partner is the new optical 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, in the old optical beacon 4B, under the assumption that large-capacity uplink transmission is not performed, when the low-speed frame U0 that is an ID storage frame is received, the return frame can be immediately transmitted to perform downlink switching. Therefore, 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. 8, depending on the transmission period of the high-speed frames U1 to U3 (U3 in the example of FIG. 8), 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. 8, 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, the return time of the return frame periodically transmitted after downlink switching (every 5 frames in the example of FIG. 8) 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. 9 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. 9, 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 is set. There is a method in which power supply is stopped and extinguished, and power supply to the light emitting element is restarted and light is emitted again at the end of the period.
Moreover, you may employ | adopt the method of reducing the power of a light emitting element to such an extent that an optical signal cannot reach | attain the optical beacon 4. In this way, there is an advantage that power at the time of re-emission of the light emitting element can be quickly returned and disturbance of the synchronization part on the head side of the upstream frame U1 can be suppressed.

On the other hand, if the low-speed frame U0, which is an ID storage frame, does not reach the new light beacon 4A due to some reason (such as fogging of the windshield of the vehicle 20 or light shielding by the wiper), the light beacon 4 returns a return frame. Therefore, the new in-vehicle device 2A cannot confirm the success of the loopback.
Therefore, if the new in-vehicle device 2A cannot 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. 9, 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 U3.
More preferably, for example, the data size of the low-speed frame U0 is reduced by minimizing the data stored in the low-speed frame U0 such as vehicle ID information, travel time between beacons, and the service type supported by the new in-vehicle device 2A. Is preferably set to the minimum (for example, about 5 bytes in the actual data portion) among the plurality of upstream frames U0 to U3 transmitted in one communication.

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

  In the example of FIG. 9, the new in-vehicle device 2 </ b> A has a new optical beacon whose communication partner supports high-speed uplink reception based on the beacon identification flag included in the downlink frame DL <b> 1 or the downlink frame DL <b> 2 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 switching downlink once]
As shown in FIGS. 8 and 9, if the new optical beacon 4A performs the conventional downlink switching according to the uplink reception of the low-speed frame UL1 in the same manner as the old optical beacon 4B, the new in-vehicle device 2A In contrast, conventional downlink data (such as traffic jam information) can be provided.

However, if the new optical beacon 4A performs only conventional downlink switching, the new in-vehicle device 2A transmits the high-speed frame UL2 including a large amount of data such as probe data in the uplink, but the old in-vehicle device 2B. Only the same downlink data can be obtained.
Accordingly, in a system in which the new optical beacon 4A performs downlink switching only once in response to uplink reception of the low-speed frame UL1, there is no incentive for the new in-vehicle device 2A to try to uplink as many high-speed frames UL2 as possible. .

Conversely, if the new in-vehicle device 2A that transmits probe data in the high-speed frame UL2 is provided with useful new information such as signal offset information suitable for the information provision, the new in-vehicle device 2A Use of the high-speed frame UL2 is promoted.
Therefore, as a measure for providing new information such as signal offset information to the vehicle 20 that uplinks probe data in the high-speed frame UL2, the new in-vehicle device 2A reports the transmission schedule of the high-speed frame UL2 in the low-speed frame UL1. "Method" can be considered.

The operation of this reporting method is as follows, for example.
1) The new in-vehicle device 2A stores “6” in “in-vehicle device type” of the low-speed frame UL1 when the uplink transmission of the high-speed frame UL2 is scheduled.
2) When there is no plan for uplink transmission of the high-speed frame UL2, the new vehicle-mounted device 2A stores other than “6” in the “vehicle-device type” of the low-speed frame UL1.

3) When the new light beacon 4A receives the low-speed frame UL1 whose “vehicle equipment type” is “6”, it adds new information such as signal offset information to generate downlink data, and performs downlink switching.
4) When the new light beacon 4A receives the low-speed frame UL1 whose “vehicle equipment type” is “other than 6”, it generates downlink data of only conventional information not including new information such as signal offset information, and performs downlink switching. Do.

  However, in the above-described reporting method, it is determined whether or not new information is to be entered in the downlink data in response to the reporting of the new in-vehicle device 2A. For example, impersonation that performs reporting even though there is no plan to transmit the high-speed frame UL2 New information is uniformly provided to the new vehicle-mounted device 2A, which is not an appropriate operation from the viewpoint of fairness.

[Road-to-vehicle communication when switching to the second downlink]
FIG.10 and FIG.11 is a sequence diagram which shows the road-vehicle communication in the case of performing 2nd downlink switching.
In the example of FIG. 10 and FIG. 11, in addition to “first downlink switching” (downlink switching 1) based on the low speed frame UL1, “second downlink switching” (downlink switching 2) based on the high speed frame UL2. ) Is used.

And the problem of the above-mentioned report system is solved by carrying out operation which includes the 2nd offer information, such as signal offset information, in downlink frame group DL2-2 transmitted after the 2nd downlink change. .
That is, in this case, the second provision information is given only to the new in-vehicle device 2A that actually transmitted the high-speed frame UL2 in the uplink, and is not provided to the camouflaged new in-vehicle device 2A. It can be said that this is a more appropriate operation.

Hereinafter, with reference to FIG. 10 and FIG. 11, the content of the “double switching method” road-to-vehicle communication will be described more specifically.
10 and 11, the new optical beacon 4A adopts the following first condition as a condition for performing the first downlink switching, and the following condition as a condition for performing the second downlink switching. The second condition is adopted.
First condition: uplink reception of low-speed frame UL1 Second condition: uplink reception of high-speed frame UL2

Then, when the first condition is satisfied, the new light beacon 4A performs “first downlink switching” similar to the case where the communication partner is the old vehicle-mounted device 2B, and after the repeated transmission of the return frame, The downlink frame group DL2-1 including the first provision information is repeatedly transmitted.
Further, when the second condition is satisfied, the new light beacon 4A performs “second downlink switching” and transmits the downlink frame group DL2-2 including the second provision information such as signal offset information.

  In the case of the second downlink switching, the return frame in which the vehicle ID is stored in the lane notification information may be continuously transmitted (see FIG. 10) or may not be performed ( This point will be described later.

[Uplink reception detection method]
The establishment of the first condition can be detected when the CRC check of the low-speed frame UL1 is normally performed.
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.

However, in the case of a communication protocol that allows the new in-vehicle device 2A to transmit a plurality of high-speed frames UL2 in the uplink, which is assumed in the present embodiment, it is considered that the condition is satisfied when reception of the predetermined high-speed frame UL2 is completed. Unless this is the case, the point in time when the second condition is satisfied cannot be specified.
Therefore, the new optical beacon 4A of the present embodiment performs the following detection methods 1 to 3 as the uplink reception detection method when there are a plurality of high-speed frames UL2.

(Detection method 1)
In the detection method 1, the completion of the reception of the high-speed frame UL2 that can be received first is satisfied as the second condition.
Specifically, the new light beacon 4A regards the time point when the CRC check of the high speed frame UL2 in which the same vehicle ID as that of the low speed frame UL1 is stored first becomes normal as the uplink reception for the plurality of high speed frames UL2. .

In the detection method 1, the completion of the reception of the first frame U1 shown in FIG. 10 normally satisfies the second condition. Of course, if there is a communication error (such as when the optical signal does not reach due to fogging of the windshield or light shielding by the wiper) in the first frame U1, reception after the second frame U2 can be completed.
According to this detection method 1, since the establishment of the second condition is the earliest, and the second downlink switching performed after the condition is established, the processing time until the data switching can be afforded, so the CPU of the beacon controller 7 There is an advantage that the processing load can be reduced.

That is, 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 establishment of the second condition to the start of the second downlink switching is as long as possible.
In this regard, in the detection method 2 described later, the time from the completion of reception of the final frame U3 to the second downlink switching cannot be taken too long, whereas in the detection method 1, not the final frame U3 but mainly the head. Since the completion of reception of the frame U1 is a trigger, the time until switching can be made relatively long, and the processing load on the CPU can be reduced.

(Detection method 2)
In the detection method 2, the completion of the reception of the final frame U3 among the plurality of high-speed frames UL2 is satisfied as the second condition.
Specifically, the new optical beacon 4A detects the time when the high-speed frame UL2 (the final frame U3 in FIG. 11) in which the final frame flag is set to “1” is detected as uplink reception for a plurality of high-speed frames UL2. Consider.

According to the detection method 2, as shown in FIG. 11, the new in-vehicle device 2A can receive the downlink frame DL2-2 that is continuously transmitted after the second downlink switching from the first frame.
As described above, when the reception of the final frame U3 is completed as the second condition is satisfied, the new light beacon 4A can detect the data contents of the other high-speed frames U1 and U2 received so far. For this reason, there exists an advantage that the detailed communication control mentioned later, such as changing the content of 2nd provision information according to the data content of the high-speed frames U1-U3, becomes possible.

(Detection method 3)
In the detection method 3, the passage of the predetermined time T1 (see FIG. 11) from the completion of reception of an arbitrary high-speed frame UL2 is regarded as the establishment of the second condition.
Specifically, the new optical beacon 4A indicates a time when a predetermined fixed time (for example, 35.5 milliseconds) has elapsed from the time when the reception of the high-speed frame UL2 is first completed (the first CRC check is completed). The second condition is considered to be satisfied.

Alternatively, the new optical beacon 4A determines whether the second fixed time (for example, 3.0 milliseconds) has elapsed from the time when reception of the high-speed frame UL2 is completed (the last CRC check is completed). Is considered to be true.
In the detection method 2 described above, if the last frame U3 is missed due to a communication error or the like, there is a possibility that the second downlink switching is not performed no matter what time. Therefore, when the detection method 2 is adopted, it is preferable to use the detection method 3 together. Only the detection method 3 may be adopted.

  The detection method 3 is particularly effective when the transmission time of the high-speed frame UL2 is set to a fixed length, and the value of the fixed time can be set relatively long according to the transmission time of the high-speed frame UL2. For this reason, there is an advantage that the processing load of the beacon controller 7 can be reduced.

(Detection method 4)
However, in the detection method 3, 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 (detection method 4) 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.

According to the detection method 4, it is necessary for the new optical beacon 4A to detect the total number of frames of the high-speed frame UL2. For this, the new in-vehicle device 2A may write the total number of frames of the high speed frame UL2 in the head frame of the low speed frame UL1 or the high speed frame UL2.
According to the detection method 4, it is necessary to calculate the predicted time when the second condition is satisfied for each different communication partner. However, even if the number of high-speed frames UL2 transmitted by the new in-vehicle device 2A varies, the remaining time remains. The time when the second condition is satisfied can be accurately calculated according to the number of frames of the high-speed frame UL2, and downlink switching using the high-speed frame UL2 can be performed accurately.

  Although the above-described detection methods 1 to 4 may be employed independently for each new light beacon 4A, a plurality of methods that can be selected from the detection methods 1 to 4 are employed in combination with one new light beacon 4A. It may be.

[Downlink switching processing]
Next, a variation of the switching process in the second downlink switching will be described.
The switching processes that the new light beacon 4A of the present embodiment can employ at the time of the second downlink switching include the following switching processes 1 to 3.

(Switching process 1)
In the switching process 1, even when the second condition (uplink reception of the high-speed frame UL2) is established, the return frame is repeated as the downlink frame DL including the lane notification information as in the case of the first downlink switching. Transmission is performed (see FIG. 10).
That is, the new light beacon 4A repeatedly transmits the return frame, and then transmits the downlink frame group DL2-2 including the second provision information.

The new light beacon 4A returns the process to the initial state and switches to transmission of the downlink frame DL1 after 250 msec from the establishment of the second condition.
According to the switching process 1, since the second downlink switching process is the same process as the first downlink switching, there is an effect that the software implementation for the beacon controller 7 is simplified.

(Switching process 2)
However, since the loopback of the vehicle ID for the in-vehicle device 2 is often completed by the repeated transmission of the return frame executed at the time of the first downlink switching, the same repeated transmission is performed at the time of the second downlink switching. It seems that there is no problem even if it is not performed.
Therefore, as shown in FIG. 11, in the second downlink switching, “switching process 2” that does not involve repeated transmission of the return frame may be performed.

According to the switching process 2, the repeated transmission of the return frame according to the second condition (reception completion of the high-speed frame UL2) is not performed, and therefore a wasteful communication time due to the repeated transmission of the downlink frame DL which is not so necessary. Therefore, it is possible to prevent other useful downlink frame DL transmission opportunities from being taken away.
Even in the switching process 2, the new light beacon 4A returns the process to the initial state after 250 msec from the establishment of the second condition, and switches to transmission of the downlink frame DL1.

(Switching process 3)
FIG. 12 is an explanatory diagram showing the contents of the switching process 3.
As shown in the legend of FIG. 12, “D” indicates the data before the first downlink switching (downlink data of the downlink frame group DL1), and “C” indicates the continuous transmission of the lane notification information including the vehicle ID. (Repeated frame return transmission).

“D1” is data (first provision information) provided after the first downlink switch, and “D2” is data (second provision) provided only after the second downlink switch. Information).
As shown in FIG. 12, the new optical beacon 4A of the present embodiment includes only the first provision information D1 in the downlink frame group DL2-1 after the first downlink switching, and after the second downlink switching. In the downstream frame group DL2-2, the first provision information D1 and the second provision information D2 are included.

As indicated by the arrow in FIG. 12, when the uplink process of the high-speed frame UL2 is detected, the switching process 3 does not immediately switch to the downlink frame group DL2-2 but instead transmits the downlink frame group DL2- After transmission of 1 is completed, transmission of the downlink frame group DL-2 is started.
That is, in this case, the new optical beacon 4A determines the transmission start time of the downlink frame group DL2-2 as the end time of the downlink cycle of the downlink frame group DL2-1 after this time as seen from the uplink reception of the high-speed frame UL2. Set to.

Here, the “downlink cycle” refers to the transmission time of a group of downlink frames DL composed of a predetermined number of downlink frames that the optical beacon 4 repeatedly transmits after downlink switching.
The number of frames included in one downlink frame group DL is variable (a maximum of 79 frames in terms of communication protocol), and the beacon controller 7 of the optical beacon 4 determines the downlink frame according to the data amount of provided information to be downlinked. The number of frames constituting the group DL is determined, and the provision information is stored by being divided into the determined number of downlink frames DL.

Therefore, in the case of the switching process 3, as shown in the upper and lower stages of FIG. 12, the transmission start of the downlink frame group DL2-2 varies depending on the number of frames of the downlink frame group DL2-1, and the downlink frame group DL2- 1 may be the end time tm of the current cycle or the start time tn of the next cycle.
For example, in the case of the upper stage in FIG. 12, the number of downlink frames to be downlinked is large, and the time from uplink reception to the end time tm of the current cycle exceeds the processing delay Td. Transmission of the group DL2-2 is started.

On the other hand, in the lower side of FIG. 12, the number of downlink frames to be downlinked is small, and the time from uplink reception to the end time tm of the current cycle does not exceed the processing delay Td. At time tn, transmission of the downlink frame group DL2-2 is started.
According to the switching process 3, it is easy to afford time from the establishment of the second condition (reception of the high-speed frame UL2) until the transmission of the downlink frame group DL2-2 is actually started, and the beacon controller 7 There is an advantage that the processing load can be reduced.

As described above, the purpose of the switching process 3 is to secure a time margin for the start of transmission of the downlink frame group DL2-2.
Therefore, the transmission start time of the downlink frame group DL2-2 does not necessarily have to be strictly adjusted to the end time tm, tn of the downlink cycle of the downlink frame DL2-1, and may be after the end time tm, tn. .

As shown in “data array 1” in FIG. 12, it is preferable to include the second provision information D2 on the first half side of the downlink frame group DL2-2 transmitted in one downlink cycle.
In this way, it is possible to increase the possibility that two or more downlink transmissions, which are the number of times required by the communication protocol, can be secured for the second provision information D2. The arrangement of the second provision information D2 on the first half side can be realized by arranging the information D1 before and after the “subsystem information”.

  The “first half side” of the downlink frame group DL2-2 refers to a range from the first frame of the downlink frame group DL2-2 to the frame located at the center. Therefore, for example, in the case of the 79 frame downlink frame group DL2-2, the first frame to the 40th frame are the first half side.

Further, as shown in “data array 2” in FIG. 12, the second provision information D2 may be included at least twice in the downlink frame group DL2-2 transmitted in one downlink cycle.
In this way, it is possible to reliably ensure the downlink transmission of two times or more, which is the number of times required by the communication protocol, for the second provision information D2. In this case, the plurality of second provision information D2 may be arranged apart from each other as illustrated or may be continuous.

[Method of providing signal offset information, etc.]
Even in the operation of providing the second provision information such as the signal offset information by the second downlink switching on the condition that the high-speed frame UL2 is received, for example, the probe for one trajectory is always in one high-speed frame UL2. If all the information is provided also to the semi-disguised new in-vehicle device 2A that only uplinks the data, the fairness with the new in-vehicle device 2A that uplinks the probe data that has been measured upright is lacking.

  Therefore, in order to ensure the fairness of the new in-vehicle device 2A, the content of the second provision information (eg, “detail level” in the case of signal offset information) is changed according to the content of the plurality of high-speed frames UL2. It is desirable to employ a providing method that determines whether to provide the second providing information or not. As such providing methods, for example, the following providing methods 1 to 4 are conceivable.

(Provision method 1)
In the providing method 1, when the second providing information is signal offset information, the detail level of the information is changed according to the “total number of frames” of the high-speed frame UL2.
Specifically, the new light beacon 4A has a simple signal offset information with a small number of intersections (if the total number of frames (for example, 16 frames at the maximum) of the high-speed frame UL2 is less than a predetermined number of frames (for example, 3 frames)). For example, the information for two intersections is provided, and if the number of frames is equal to or greater than the prescribed number, the full version signal offset information (for example, the information for five intersections) is provided.

The specified number of frames may be set to a common value for all new light beacons 4A, or may be set to a unique value for each point. When the eigenvalue is set, it is preferably set according to the number of frames of the high-speed frame UL2 corresponding to the distance to the optical beacon 4 upstream of the optical beacon 4.
In the case of the optical beacon 4 that can communicate with the central device 3 of the traffic control center, the specified number of frames may be specified by communication from the central device 3.

In addition, when the provision method 1 is adopted, it is necessary to specify the number of frames of the plurality of high-speed frames UL2 that are actually uplinked. Therefore, the above-described “detection method 2” is adopted as the uplink reception detection method. There is a need to.
According to the providing method 1, since it is not necessary to read the data content of the high-speed frame UL2, the processing is easier than the following providing methods 2 and 3 that require reading.

(Provision method 2)
In the providing method 2, when the second providing information is signal offset information, the detail level of the information is changed according to the “frame size” of the high-speed frame UL2.
Specifically, if the frame size of any high-speed frame UL2 excluding the final frame is less than the specified size, the new light beacon 4A provides simple signal offset information with a small number of intersections and should be larger than the specified size. For example, it provides full version signal offset information.

The specified size may be set to a common value for all new light beacons 4A, or may be a unique value for each point.
In the case of the optical beacon 4 that can communicate with the central device 3 of the traffic control center, the specified size may be specified by communication from the central device 3.

In addition, when the providing method 2 is adopted, it is necessary to specify the frame size of each uplink high-speed frame UL2 that is actually uplinked. In this case as well, the above-described “detection method 2” is used as the uplink reception detection method. Need to be adopted.
According to the providing method 2, since it is necessary to read the frame size of the high-speed frame UL2, the processing is more complicated than the providing method 1, but the following providing information 3 that needs to specify the number of trajectories of probe data is required. Easy to process.

(Provision method 3)
In the providing method 3, when the second providing information is signal offset information, the detail level of the information is changed according to the “total number of trajectories” of the probe data included in the high-speed frame UL2.
Specifically, the new light beacon 4A provides simple signal offset information with a small number of intersections if the total number of trajectories is less than the specified number of trajectories, and if the total number of trajectories is greater than the specified number of trajectories, the full version signal offset information is provided. provide.

The specified number of trajectories may be set to a common value for all the new light beacons 4A, or may be set to a unique value for each point. When the eigenvalue is set, it is preferably set according to the number of frames of the high-speed frame UL2 corresponding to the distance to the optical beacon 4 upstream of the optical beacon 4.
In the case of the optical beacon 4 that can communicate with the central device 3 of the traffic control center, the specified number of trajectories may be specified by communication from the central device 3.

In addition, when the providing method 3 is adopted, it is necessary to specify the number of trajectories from the probe data included in the plurality of high-speed frames UL2 that are actually uplinked. It is necessary to employ the “detection method 2” described above.
According to the providing method 3, since it is necessary to specify the number of trajectories of probe data, the processing is more complicated than that of the providing method 2, but the determination is based on the number of actually uplinked trajectories. Compared to 1 and 2, more accurate determination is possible.

Note that the contents of the high-speed frame UL2 may be compressed for the purpose of downsizing the uplink data. In this case, there is a possibility that the total number of trajectories cannot be easily confirmed unless the data is decompressed with a predetermined decompression logic.
Therefore, when the providing method 3 is adopted, when the new in-vehicle device 2A compresses the uplink data to be included in the high-speed frame UL2, the “number of trajectories” is not compressed, and other data is compressed. It is preferable to adopt.

  In the above providing methods 1 to 3, assuming that the second providing information is signal offset information, the detail level is changed. However, the “content change” relating to the “second providing information” is changed. "" Is not limited thereto, and includes addition / change / deletion of information contents that can substantially change the contents of downlink information according to the uplink amount on the vehicle side.

(Provision method 4)
In the providing methods 1 to 3 described above, the high-speed frame UL2 or the data content thereof (specifically, the total number of frames, the frame size, the total number of trajectories of probe data in the high-speed frame UL2) does not satisfy a predetermined condition. Is to provide signal offset information with a lower level of detail than if it is satisfied, but if the high-speed frame UL2 or its data content does not satisfy a predetermined condition, the signal offset information itself is not downlinked, that is, An implementation that does not execute the second downlink switching may be adopted.

For example, when determining whether the predetermined condition is correct or not by “total number of frames”, if the total number of frames (for example, a maximum of 16 frames) of the high-speed frame UL2 is less than a specified number of frames (for example, 3 frames), the second It is only necessary not to execute downlink switching.
In addition, when determining whether the predetermined condition is correct or not by “frame size”, if the frame size of any high-speed frame UL2 excluding the final frame is less than the specified size, the second downlink switching is not executed. You can do it.

Furthermore, when determining whether the predetermined condition is correct or not based on the “total number of trajectories” of the probe data, the total number of trajectories that the new in-vehicle device 2A has uplinked in one or a plurality of high-speed frames UL2 is less than the specified number of trajectories If so, the second downlink switching may not be executed.
Although it depends on how much the predetermined value (threshold value) of the predetermined condition is set, for example, when the predetermined condition is not satisfied, it can be regarded that the uplink transmission itself of the high-speed frame UL2 is not performed. In such a case, it is considered that there is no particular problem even if the implementation as in the providing method 4 is performed.

[Downlink switching for multiple lanes]
FIG. 13 is an explanatory diagram of downlink switching when a plurality of new in-vehicle devices 2A communicate with the new light beacon 4A in different lanes R1, R2.
In the legend of FIG. 13, “D”, “C”, and “D1” are the same as those in FIG. “D2a” is data (second provision information) provided only after the second downlink switching for the new in-vehicle device 2A of the vehicle 20 (vehicle IDa) passing through the lane R1, and “D2b” This is data (second provision information) provided only after the second downlink switching for the new in-vehicle device 2A of the vehicle 20 (vehicle IDb) passing through the lane R2.

  In the example of FIG. 13, a new in-vehicle device 2A (hereinafter also referred to as “preceding in-vehicle device”) of the vehicle 20 (vehicle IDa) passing through the lane R1 enters the communication area A in advance, and the second down While receiving the downlink frame group D2-2 after the link switching, the new in-vehicle device 2A (hereinafter also referred to as “subsequent in-vehicle device”) of the vehicle 20 (vehicle IDb) passing through the lane R2 during the reception. However, it is assumed that it is time to enter the communication area A and start road-to-vehicle communication with the same new light beacon 4A.

Here, when the new optical beacon 4A does not receive a new low-speed frame UL1 within a predetermined time T (= 350 msec) from the uplink reception of the low-speed frame UL1, the downlink is switched to the downlink frame UL1 to the initial state. Return.
Therefore, in order to establish the above assumption, it is a condition that the uplink reception of the low-speed frame UL1 of the succeeding vehicle-mounted device is detected within the predetermined time T from the uplink reception of the low-speed frame UL1 of the preceding vehicle-mounted device.

If the communication timing of FIG. 13 is put together in the itemized list, the new optical beacon 4A detects each uplink reception in the following order a) to d).
a) Uplink reception of low speed frame UL1 including vehicle IDa detected by beacon head 8 in lane R1 b) Uplink reception of high speed frame UL2 including vehicle IDa detected in beacon head 8 of lane R1

c) Uplink reception within a predetermined time T from a) of the low speed frame UL1 including the vehicle IDb detected by the beacon head 8 in the lane R2 d) Vehicle IDb detected by the beacon head 8 in the lane R2 Uplink reception of high-speed frame UL2 including

  In the example of FIG. 13, when the uplink reception of the high-speed frame UL2 is detected, the second downlink is immediately switched, but the continuous transmission C of the lane notification information is not performed (the above-described “switching process 2”). ) Is assumed.

(Pattern 1)
In “Pattern 1” shown in FIG. 13, the new light beacon 4A newly performs the first downlink switching on the condition of the above c), and newly performs the second downlink switching on the condition of the above d). Is.
That is, the new light beacon 4A performs a so-called post-winning process in which all road-to-vehicle communication for the preceding vehicle IDa is canceled, triggered by the uplink reception of the low-speed frame UL1 of the subsequent vehicle IDb.

According to the pattern 1, the second provision information D2a for the preceding vehicle-mounted device with the vehicle IDa is provided only up to c) above, which may be unreasonable for the preceding vehicle-mounted device.
However, since it is sufficient to perform the normal first and second downlink switching for the beacon heads 8 in any lanes R1 to R4, the control logic set in the beacon controller 7 is simplified, and the software There is an advantage that the mounting becomes easy.

(Pattern 2)
“Pattern 2” shown in FIG. 13 indicates that the new optical beacon 4A transmits the downlink frame group DL2-2 including the downlink data (D1 + D2a) corresponding to the above b) regardless of the above c) and d). It will continue.
However, continuous transmission C of lane notification information corresponding to the above c) is performed. If this continuous transmission C is not performed, the new optical beacon 4A cannot notify the subsequent vehicle-mounted device that the subsequent vehicle-mounted device has been recognized, and the subsequent vehicle-mounted device continues to perform uplink transmission.

According to the pattern 2, the second provision information D2a for the preceding vehicle-mounted device with the vehicle IDa continues to be provided after c) and is also provided to the subsequent vehicle-mounted device with the vehicle IDb. Therefore, there is an advantage that the second provision information D2a can be reliably provided to both of the new in-vehicle devices 2A.
When the second provision information D2a is dynamic information such as signal offset information, the provision information D2a for the preceding vehicle-mounted device is slightly old information for the subsequent vehicle-mounted device, but is on the order of 100 milliseconds. There is no particular problem because it is only a delay.

(Pattern 3)
“Pattern 3” shown in FIG. 13 is a group of downlink frames of downlink data (D1 + D2a) corresponding to the above b) until the new optical beacon 4A performs the second downlink switching under the above condition d). After the transmission of DL2-2 is continued, the transmission is switched to the transmission of downlink data (D1 + D2b) corresponding to the above d).

In this case, the second provision information D2a for the preceding in-vehicle device of the vehicle IDa is provided until d) above, and the second provision information D2b for the subsequent in-vehicle device of the vehicle IDb is after the above d). Provided to.
According to Pattern 3, for the preceding in-vehicle device, the transmission time of the second provision information D2a can be extended until a high-speed uplink reception from the following in-vehicle device is detected. The latest second provision information D2b can be provided. For this reason, it is possible to provide appropriate information compromised on both vehicles 20.

[Modified example of downlink switching in the case of multiple lanes]
FIG. 14 is an explanatory diagram showing a modification example of downlink switching when a plurality of new in-vehicle devices 2A communicate with the new optical beacon 4A in different lanes R1, R2.
The modification of FIG. 14 differs from the example of FIG. 13 in that the new optical beacon 4A performs “switching process 3” (transmission of the downlink frame group DL2-1 being transmitted) as the switching process in the second downlink switching. And the process of starting transmission of the downlink frame group DL-2) is adopted.

Therefore, in the modification of FIG. 14, in each of the patterns 1 to 3, the reception of the high-speed frame UL2 detected in each lane R1, R2 is completed, and the transmission of the downlink frame group DL2-2 including the provision information D2a or D2b is started. A time lag Δt exists between the time points.
Since the other points are the same as in the example of FIG. 13, the same effects as those of the patterns 1 to 3 shown in FIG. 13 can be obtained in the case of the patterns 1 to 3 shown in FIG.

[Downlink data creation method]
As one example of a downlink data creation method in the case of performing downlink switching corresponding to uplink reception of the low-speed frame UL1 and the high-speed frame UL2 as in the above-described embodiment, for example, the beacon controller 7 The CPU detects the reception of the high-speed frame UL2 not only for the creation of the downlink data D1 triggered by the reception of the low-speed frame UL1, but also for the creation of the downlink data (D1 + D2) triggered by the reception of the high-speed frame UL2. In such a case, it is conceivable that the method is performed after the fact and stored in the memory (hereinafter referred to as the “post-preparation method”).

However, in the post-creation method, when the reception of the high-speed frame UL2 is detected, the downlink data (D1 + D2) is created again from the beginning, and the high-speed frame UL2 is transmitted after the low-speed frame UL1 in one road-to-vehicle communication. When communicating with the new vehicle-mounted device 2A, the CPU of the beacon controller 7 must always create the downlink data twice.
For this reason, a processing delay of the CPU is likely to occur, and there is a possibility that downlink data (D1 + D2) corresponding to the high-speed frame UL2 cannot be transmitted at an appropriate timing.

  Therefore, before detecting the uplink reception of the high-speed frame UL2, a method in which downlink data (D1 + D2) necessary when the reception is detected is created in advance and stored in a memory (hereinafter referred to as “previous creation method”). It is preferable to transmit the stored downlink data (D1 + D2) when uplink reception of the high-speed frame UL2 is actually detected.

In this way, the creation time can be advanced compared to the case where the creation of the downlink data (D1 + D2) is started after the reception of the high-speed frame UL2 is detected, and the downlink data D1 and the downlink data (D1 + D2) Can be created in parallel.
Therefore, compared to the post-creation method in which the creation of the downlink data (D1 + D2) corresponding to the high-speed frame UL2 is started after the reception of the high-speed frame UL2 is detected, the processing delay of the CPU is less likely to occur. There is an advantage that the transmission timing of D1 + D2) can be prevented from being delayed.

(Specific example 1 of the pre-creation method)
FIG. 15 is an explanatory diagram showing a specific example of the creation timing of downlink data by the advance creation method.
FIG. 15 shows a specific example of the downlink data creation timing performed by the CPU of the beacon controller 7 in the case of “pattern 2” in FIG.

“Data creation period 1” in FIG. 15 indicates that the beacon controller 7 has the downlink data D1 transmission buffer B1 and the downlink data (D1 + D2) transmission buffer B2 individually. This is the creation period.
In addition, “data creation period 2” in FIG. 15 is a period during which downlink data can be created when the beacon controller 7 shares the same transmission buffer B for downlink data D1 and downlink data (D1 + D2). It is.

The beacon controller 7 is a program-controlled “CPU” that operates by software, a “memory” that stores predetermined data (including the above-described transmission buffer), and a downlink of the optical transmitter 10 that operates by wired logic. "Communication IC" that controls transmission.
The communication IC transmits the data in the transmission buffer according to the control signal of the CPU. The CPU manages the “UL2 reception flag”. When the reception of the high-speed frame UL2 is detected, the CPU turns on the flag (for example, sets the value to “1”). When it has elapsed, the flag is turned off (for example, the value is set to “0”). The communication IC may manage the “UL2 reception flag”.

As shown in “data creation period 1” in FIG. 15, when the beacon controller 7 has two dedicated transmission buffers B1 and B2, the CPU of the beacon controller 7 receives the uplink of the low-speed frame UL1. As a trigger, creation of the downlink data D1 is started.
The CPU ends the creation of the downlink data D1 at the latest by the completion of the continuous transmission C of the lane notification information (= the transmission start time of the downlink data D1; the same applies hereinafter), and transmits the created downlink data D1. Store in buffer B1.

Further, when the CPU of the beacon controller 7 detects the uplink reception of the low speed frame UL1, the CPU of the beacon controller 7 starts to generate the downlink data (D1 + D2a) regardless of whether the uplink reception of the high speed frame UL2 is detected.
The CPU finishes creating the downlink data (D1 + D2a) at the latest by detecting the uplink reception of the high-speed frame UL2, and stores the created downlink data (D1 + D2a) in the transmission buffer B2.

When the CPU (when the communication IC manages the flag, the communication IC) actually detects uplink reception of the high-speed frame UL2, the CPU turns on the UL2 reception flag.
When the UL2 reception flag is “off”, the communication IC reads the data from the transmission buffer B1 for the downlink data D1, causes the optical transmission unit 10 to perform downlink transmission, and the UL2 reception flag is “on”. In this case, data is read from the transmission buffer B2 for downlink data (D1 + D2), and the optical transmission unit 10 is caused to perform downlink transmission.

As shown in “data creation period 2” in FIG. 15, when one transmission buffer B is shared, the CPU of the beacon controller 7 receives the low-speed frame UL1 as a trigger and receives a down link corresponding to the high-speed frame UL2. Creation of link data (D1 + D2a) is started.
The CPU ends the creation of the downlink data (D1 + D2a) at the latest by the end of the continuous transmission C of the lane notification information, and stores the created downlink data (D1 + D2a) in the predetermined storage area of the transmission buffer B, respectively. .

In the example of FIG. 15, the storage area for the downlink data D2 is set on the top side of the transmission buffer B, and the area after the downlink data D2 is the storage area for the downlink data D1.
Therefore, the CPU stores the downlink data D2 from the beginning of the transmission buffer B to a predetermined address value corresponding to the data amount, and the downlink data D1 after the next address value of the predetermined address value. To store.

When the CPU (when the communication IC manages the flag, the communication IC) actually detects uplink reception of the high-speed frame UL2, the CPU turns on the UL2 reception flag.
When the UL2 reception flag is “off”, the communication IC reads data from the address value subsequent to the predetermined address value in the transmission buffer B, causes the optical transmission unit 10 to perform downlink transmission, and transmits the UL2 reception flag. Is “on”, data is read from the head of the transmission buffer B, and the optical transmission unit 10 is caused to perform downlink transmission.

  In addition, in the data creation period 2 in FIG. 15, the reason that the creation end time of the downlink data (D1 + D2a) is the end time of the continuous transmission C of the lane notification information is that all the data stored in the shared transmission buffer B are This is because the content of the downlink data (D1 + D2a) needs to be determined before the start of transmission of the downlink data D1.

  As described above, according to the preceding creation method of FIG. 15, the downlink data (D1 + D2a) corresponding to the high-speed frame UL2 is created in advance before the reception of the high-speed frame UL2 is detected. In comparison with the case where creation of downlink data (D1 + D2a) is started (in the case of the above-mentioned “post-creation method”), the processing delay of the CPU accompanying the creation is less likely to occur, and the downlink data (D2 + D2a) It is possible to prevent the transmission timing from being delayed.

  In FIG. 15, a specific example of the pre-creation method has been described by taking “Pattern 2” in FIG. 13 as an example, but in the case of “Pattern 1” and “Pattern 3” in FIG. 13, or passing through one lane R <b> 1. Even when only communicating with one new in-vehicle device 2A, the preceding creation method similar to the above can be adopted.

(Specific example 2 of the pre-creation method)
FIG. 16 is an explanatory diagram illustrating another specific example of downlink data creation timing according to the preceding creation method.
FIG. 16 shows a specific example of the downlink data creation timing performed by the CPU of the beacon controller 7 in the case of “pattern 2” in FIG.

In the “data creation period 1” in FIG. 16, the beacon controller 7 also includes the downlink data D1 transmission buffer B1 and the downlink data (D1 + D2) transmission buffer B2. This is the creation period.
Also, in “data creation period 2” in FIG. 16, the beacon controller 7 has only one transmission buffer B, and the same transmission buffer B is used for the downlink data D1 and the downlink data (D1 + D2). This is the period during which downlink data can be created when sharing.

16 differs from that of FIG. 15 in that “data creation period 1” in the case where there are two transmission buffers B1 and B2, the creation end point of the downlink data (D1 + D2a) is the downlink data D1. It can be extended to the point of completion of transmission.
That is, the CPU of the beacon controller 7 starts creating downlink data (D1 + D2a) triggered by the uplink reception of the low-speed frame UL1, but before the transmission of the downlink data D1 that is already being transmitted is completed. The creation of (D1 + D2a) is terminated.

In other words, the CPU ends the downlink data (D1 + D2a) at the end of the downlink cycle of the downlink frame group DL2-1 after the current time when the end of the downlink data (D1 + D2a) can be generated from the time of receiving the uplink of the high-speed frame UL2. Set to.
The other contents of the advance creation method of FIG. 16 are the same as those of the advance creation method of FIG. Therefore, the advance creation method of FIG. 16 has the same effect as the advance creation method of FIG.

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

2 Onboard unit 2A New onboard unit 2B Old onboard unit 4 Optical beacon 4A New optical beacon 4B 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 (24)

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 performing the following two types of downlink switching.
First downlink switching: Downlink switching including a downlink frame storing the first provision information in a first downlink frame group to be transmitted thereafter on condition that uplink of a low-speed frame is received Second downlink switching : Downlink switching that includes the downlink frame storing the second provision information in the second downlink frame group to be transmitted thereafter on condition that uplink reception of the high-speed frame is received In the case of a communication protocol that allows the in-vehicle device to transmit a plurality of the high-speed frames as uplinks,
The optical beacon according to claim 1, wherein the uplink reception of the high-speed frame is completion of reception of the predetermined high-speed frame among the plurality of high-speed frames.   The optical beacon according to claim 2, wherein the reception completion of the predetermined high-speed frame is reception completion of the high-speed frame that can be received first.   The optical beacon according to claim 2, wherein the reception completion of the predetermined high-speed frame is completion of reception of a final frame among the plurality of high-speed frames.   In the uplink reception of the high-speed frame, elapse of a predetermined time from completion of reception of the high-speed frame received first, or elapse of a predetermined time from completion of reception of the high-speed frame received last, or The optical beacon according to claim 4, including both of the processes. In the case of a communication protocol that allows the in-vehicle device to transmit a plurality of the high-speed frames as uplinks,
2. The optical beacon according to claim 1, wherein the uplink reception of the high-speed frame is a lapse of a predetermined time from completion of reception of the predetermined high-speed frame among the plurality of high-speed frames.   The optical beacon according to claim 6, wherein the predetermined high-speed frame is the high-speed frame that can be received first.   The communication control unit sets the second downlink switching time after the end of the downlink cycle of the first downlink frame group after the current time when the uplink of the high-speed frame is received. The optical beacon according to any one of 1 to 7.   Prior to this, the communication control unit repeatedly transmits a return frame including lane notification information, and transmits the second frame group prior to the transmission of the first frame group. The optical beacon according to any one of claims 1 to 8, wherein the optical beacon is not repeatedly transmitted.   The communication control unit repeatedly transmits a return frame including lane notification information prior to the transmission of the first frame group, and prior to this the transmission of the return frame also includes the return frame. The optical beacon according to any one of claims 1 to 8, wherein the frame is repeatedly transmitted.   The optical communication beacon according to any one of claims 1 to 10, wherein the communication control unit includes the second provision information in the second downlink frame group a plurality of times.   The optical communication beacon according to any one of claims 1 to 11, wherein the communication control unit includes the second provision information on a first half side of the second downlink frame group. When each uplink reception is detected in the order of a) to d) below,
The optical beacon according to any one of claims 1 to 12, wherein the communication control unit continues transmission of the second downlink frame group corresponding to the following b) regardless of the following c) and d). .
a) Uplink reception of a low speed frame including a first vehicle ID b) Uplink reception of a high speed frame including a first vehicle ID c) Within a predetermined time from a) of a low speed frame including a second vehicle ID Uplink reception d) Uplink reception of high-speed frame including second vehicle ID When each uplink reception is detected in the order of a) to d) below,
The communication control unit continues the transmission of the second downlink frame group corresponding to the following b) until the second downlink switching is performed on the condition that the following d) is satisfied. The optical beacon according to any one of claims 1 to 12, wherein the corresponding second downlink frame group is transmitted.
a) Uplink reception of a low speed frame including a first vehicle ID b) Uplink reception of a high speed frame including a first vehicle ID c) Within a predetermined time from a) of a low speed frame including a second vehicle ID Uplink reception d) Uplink reception of high-speed frame including second vehicle ID When each uplink reception is detected in the order of a) to d) below,
The communication control unit newly performs a first downlink switching on condition of the following c), and newly performs a second downlink switching on condition of the following d). The optical beacon described in the item.
a) Uplink reception of a low speed frame including a first vehicle ID b) Uplink reception of a high speed frame including a first vehicle ID c) Within a predetermined time from a) of a low speed frame including a second vehicle ID Uplink reception d) Uplink reception of high-speed frame including second vehicle ID   The communication control unit changes the content of the second provision information included in the second downlink frame group according to whether the high-speed frame or the data content satisfies a predetermined condition. The optical beacon according to any one of 15. In the case of a communication protocol that allows the in-vehicle device to transmit a plurality of the high-speed frames as uplinks,
The communication control unit changes content of the second provision information included in the second downlink frame group according to a comparison result between the total number of high-speed frames and the specified number of frames. Light beacon.   The communication control unit changes the content of the second provision information included in the second downlink frame group according to a comparison result between the number of trajectories of probe data included in the high-speed frame and the number of predetermined trajectories. Item 17. The optical beacon according to Item 16. In the case of a communication protocol that allows the in-vehicle device to transmit a plurality of the high-speed frames as uplinks,
The communication control unit changes the content of the second provision information included in the second downlink frame group according to a comparison result between a frame size other than the last high-speed frame and a specified size. Light beacon as described.   The optical communication beacon according to any one of claims 1 to 15, wherein the communication control unit does not perform the second downlink switching when the high-speed frame or the data content thereof does not satisfy a predetermined condition.   21. The light according to claim 1, wherein the second provision information is signal offset information that expresses a deviation of a start point of a green signal between adjacent intersections under system control in a format that can be specified on the vehicle side. beacon.   The communication control unit includes the downlink data included in the second downlink frame group before the end of the downlink cycle of the first downlink frame group after the current time when the uplink of the high-speed frame is received. The optical beacon according to any one of claims 1 to 21, which completes the creation of.   The optical communication beacon according to any one of claims 1 to 21, wherein the communication control unit completes the creation of downlink data to be included in the second downlink frame group before receiving the uplink of the high-speed frame. When sharing a memory for storing downlink data included in the first downlink frame group and a memory for downlink data included in the second downlink frame group,
The optical communication beacon according to claim 22 or 23, wherein the communication control unit completes the creation of downlink data to be included in the second downlink frame group by the start of transmission of the first downlink frame group.

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