JP6007661B2 - In-vehicle machine - Google Patents

Description

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

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. Of these, if the uplink speed is increased from the current level (64 kbps), a large amount of probe data can be collected from the optical beacon without greatly expanding the communication area, which can be used to enhance 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.

For example, a new in-vehicle device can transmit a high-speed optical signal for a new optical beacon, but a low-speed optical signal for an optical beacon that performs only low-speed uplink reception (hereinafter also referred to as “old optical beacon”). If transmission is not possible, uplink information cannot be provided to the old optical beacon.
Also, in this case, since the old optical beacon cannot detect the new in-vehicle device, it is not possible to perform downlink switching triggered by the uplink transmission of the new in-vehicle device, and to provide information for vehicles equipped with the new in-vehicle device. Can not. For this reason, the incentive to newly install a new in-vehicle device is reduced, and the increase in the uplink speed does not progress.

  On the other hand, in communication between a new optical beacon that supports multi-rate in the uplink direction and a new in-vehicle device, if the new in-vehicle device cannot recognize that it is communicating with the new optical beacon while passing through the downlink region of the new optical beacon, The new in-vehicle device that is capable of high-speed uplink transmission always performs uplink transmission at a low speed even for a new optical beacon, and it is not possible to increase the uplink speed.

  In view of the conventional problems, an object of the present invention is to provide a new in-vehicle device that can appropriately communicate with old and new optical beacons and supports multirate in the uplink direction.

(1) The in-vehicle device of the present invention is an in-vehicle device that performs wireless communication using an optical beacon and an optical signal installed on a road, and an optical transmission unit capable of electro-optical conversion at two types of high and low transmission speeds; Based on an optical receiver capable of photoelectric conversion at one transmission rate different from the two transmission rates, and beacon identification information included in a downstream frame transmitted at the one transmission rate, the optical Determine whether the beacon is a new optical beacon that supports high-speed uplink reception or an old optical beacon that does not support it, and perform uplink transmission at a high transmission rate or uplink transmission at a low transmission rate according to the determination result. And a communication control unit for switching whether to set to non-transmission.

According to the vehicle-mounted device of the present invention, when the communication partner is a new optical beacon, uplink transmission is performed at a high transmission rate, and when the communication partner is an old optical beacon, uplink transmission is performed at a low transmission rate. Is set to non-transmission, it is possible to appropriately communicate with the old and new optical beacons.
Therefore, a new in-vehicle device that can appropriately communicate with the old and new optical beacons and supports multirate in the uplink direction can be obtained.

(2) In the in-vehicle device according to the present invention, the communication control unit causes the optical beacon to transmit a downlink transmission including a downlink frame including signal information for a new in-vehicle device corresponding to high-speed uplink transmission. It is preferable that the identification information can be included in the upstream frame.
In this way, it is possible to reliably prevent the downlink frame including the signal information for the new in-vehicle device from being erroneously downlink transmitted to the old in-vehicle device.

  As described above, according to the present invention, it is possible to obtain a new in-vehicle device that can appropriately communicate with old and new optical beacons and that supports multi-rate in the uplink direction.

It is a block diagram which shows schematic structure of a road-vehicle communication system. It is the top view of the road which looked at the installation part of an optical beacon from the top. It is a side view which shows the communication area | region of an optical beacon. It is a sequence diagram which shows the conventional communication procedure. It is a figure which shows the mixed state of the old and new optical beacons and vehicle equipment. It is a flowchart which shows upward compatible control of a new light beacon. It is a flowchart which shows the upward compatible control of a new vehicle equipment. It is a sequence diagram which shows the communication procedure of 1st Embodiment. In the communication procedure of 1st Embodiment, it is a sequence diagram which shows the case where a new vehicle equipment fails in ID confirmation. It is a sequence diagram which shows the communication procedure of 2nd Embodiment. It is a sequence diagram which shows the communication procedure of 3rd Embodiment. It is a sequence diagram which shows the communication procedure of 4th Embodiment. It is a sequence diagram which shows the communication procedure of 5th Embodiment. It is a sequence diagram which shows the communication procedure of 6th Embodiment. It is a sequence diagram which shows the communication procedure of 7th Embodiment. It is a sequence diagram which shows the communication procedure of 8th Embodiment. It is a sequence diagram which shows the communication procedure of 9th Embodiment.

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

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

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

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

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

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

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

The light receiving unit 11 includes a light receiving element such as a photodiode and a receiving circuit that amplifies an electric signal output from the light receiving element and generates a digital reception signal.
In the optical beacon 4 of the present embodiment, the optical receiver 11 is multi-rate capable of photoelectric conversion at two types of transmission rates, high and low, and the lower transmission rate is 64 kbps as in the conventional old optical beacon. It is. The higher transmission speed may be 128 kbps, 192 kbps, 256 kbps, 384 kbps, 512 kbps, 1024 kbps, etc., but in this embodiment, it is assumed that it is 128 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. The beacon controller 7 communicates with the central device 3 via the communication unit 6 (see FIG. 1) and road-to-vehicle communication with the in-vehicle device 2. 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 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 to 6.0 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. .

Further, 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 3.4 to 6.0 m, and the position of the upstream end c is 1. It is extended upstream by 0m.
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 that it is 128 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.
The simple control unit has a function of causing the optical transmission unit 23 to perform uplink transmission of only one low-speed uplink frame including the vehicle ID of the host vehicle when the optical reception unit 24 receives any downlink frame, for example. .

[Definition of terms, etc.]
Here, terms used in this specification are defined.
Downlink frame DL1: A downlink frame that the optical beacon 4 repeatedly transmits toward the downlink area DA before downlink switching described later.
Uplink frame UL1: An uplink frame that the in-vehicle device 2 repeatedly transmits in response to the reception of the downlink frame DL1.

Downlink frame DL2: A downlink frame (including a case of a series of frames) that the optical beacon 4 repeatedly transmits toward the downlink area DA after downlink switching described later.
ID storage frame: An uplink frame UL1 generated by the in-vehicle device 2 in which the identification information (hereinafter referred to as “vehicle ID”) of the vehicle 20 of its own device is written in a predetermined storage area.

Loop frame: When the optical beacon 4 receives an ID storage frame, it refers to the downlink frame DL2 generated by writing the same value as the vehicle ID included in the frame in a predetermined storage area.
When the optical beacon 4 does not perform downlink switching even when receiving the ID storage frame (see, for example, FIG. 12 and FIG. 14), the downlink frame DL1 may become a return frame.

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.

Preceding frame: When the vehicle-mounted device 2 transmits a plurality of uplink frames UL1, it means one or a plurality of uplink frames UL1 that are uplinked in advance, including at least the first uplink frame UL1.
Subsequent frame: When the in-vehicle device 2 transmits a plurality of uplink frames UL1, it means one or a plurality of uplink frames UL1 that are uplink-transmitted after the preceding frame.

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

Such information is also provided to old in-vehicle devices that do not support high-speed uplink transmission.
However, in the optical beacon 4 of the present embodiment, for example, signal information including the timing of switching the signal lamp color at an intersection or the vehicle 20 is an electric signal as information provided for a vehicle equipped with a new in-vehicle device that supports high-speed uplink transmission. It is also possible to provide dedicated information predetermined for a new vehicle-mounted device, such as charging station information indicating a route to the nearest charging station, which is useful information in the case of an automobile (see FIGS. 8 to 17).

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

Although not shown, the uplink frame UL1 and the downlink frames DL1 and DL2 are in order from the top, a synchronization part for synchronizing with the receiving side, a header part, an actual data part, and a CRC (Cyclic Redundancy Check). Part.
In the case of the uplink frame UL1, 1 byte is assigned to the synchronization part, 10 bytes are assigned to the header part, 59 bytes are assigned to the actual data part, and 2 bytes are assigned to the CRC part.

In the case of downlink frames DL1 and DL2, 1 byte is assigned to the synchronization part, 5 bytes are assigned to the header part, 123 bytes are assigned to the actual data part, and 2 bytes are assigned to the CRC part. Yes. This embodiment also follows the frame structure on this rule.
Further, the downlink frame group repeatedly transmitted from the optical transmission unit 10 after downlink switching is composed of 1 to 80 downlink frames DL2, and the transmittable time for the repeated transmission is 250 ms.

The downlink frame DL2 is composed of an arbitrary number of frames according to the amount of data to be transmitted in the downlink direction, and is repeatedly transmitted within the range of the transmittable time. Further, the transmission period of the downstream frame DL2 is about 1 ms.
Therefore, for example, when one significant data is constituted by three downlink frames DL2, the transmission cycle is about 3 ms, so that the data is repeatedly transmitted about 80 times within a predetermined transmittable time (250 ms). Will be.

However, if the downlink area DA is expanded to the vicinity immediately below the beacon head 8 as in this embodiment (see FIG. 3), the number of downlink frames DL2 to be repeatedly transmitted can be increased up to about 200.
As shown in road-to-vehicle communication in FIG. 10 described later, when the optical beacon 4 performs downlink switching according to the ID storage frame, the uplink transmission time of the subsequent frame and the downlink after the downlink switching are performed. Since transmission times may overlap, it is preferable that the transmittable period of the downlink frame DL2 after downlink switching is (250 + α) ms.

[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 a frame that includes a vehicle ID. (Frame having lane notification information with vehicle ID). The same applies to the drawings after FIG.

  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 described with reference to FIG.

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 an uplink frame UL1 (the ID storage frame U1 in FIG. 4) in which the vehicle ID is stored in the lane notification information, and transmits the uplink frame U1 in the uplink.
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.

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 switches the communication of the own device from transmission to reception at this point.
On the contrary, while the determination result is negative, the in-vehicle device 2 determines that the loopback of the vehicle ID of the own vehicle is not successful and keeps the communication of the own device as transmitted.
In this case, for example, the in-vehicle device 2 transmits the upper frame UL1 again after a predetermined time (for example, 30 ms) after transmission of the upstream frame U1 transmitted previously. 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, 128 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, 128 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, 128 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, 128 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. The upstream frames transmitted by the new and old vehicle-mounted devices 2A and 2B are shown in response to reception.
“DL2” indicates a downlink frame transmitted by the old and new optical beacons 4A and 4B after downlink switching.

Here, it is assumed that the new light beacon 4A and the new in-vehicle device 2A perform road-to-vehicle communication. When the new and old types of the optical beacon 4 cannot be discriminated, the new vehicle-mounted device 2A performs uplink transmission at a low speed in order to receive and receive the uplink frame UL1 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 this embodiment, it is assumed that the beacon controller 7 can include beacon identification information indicating that the own apparatus is the new optical beacon 4A corresponding to high-speed uplink reception in the downlink frames DL1 and DL2.

Specifically, a flag field indicating the new and old types of the optical beacon 4 is defined in advance in the header part of the downlink frames DL1 and DL2 to be transmitted by the optical transmission unit 10 in the downlink.
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.
Hereinafter, upward compatible control performed by the new optical beacon 4A and the new in-vehicle device 2A on the assumption that the beacon identification information described above is included in the downlink frames DL1 and DL2 will be described.

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

In this state, the beacon controller 7 determines whether or not the uplink frame UL1 has been received (step ST2 in FIG. 6), and continues the downlink transmission in step ST1 until the reception is detected.
When detecting the reception of the upstream frame UL1, the beacon controller 7 determines whether or not the transmission subject of the received upstream frame UL1 is the new in-vehicle device 2A corresponding to a high transmission speed (128 kbps in the present embodiment). Determination is made (step ST3 in FIG. 6).

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

Specifically, a flag field indicating the new and old types of the in-vehicle device 2 is defined in advance in the header portion of the uplink frame UL1 transmitted by the optical transmission unit 23 in the uplink.
Then, when the in-vehicle controller 21 of the new in-vehicle device 2A operates the own device as the new in-vehicle device 2A, it turns on the flag field of all or part of the uplink frame UL1 for uplink transmission, When operating as the in-vehicle device 2B, the flag field of the uplink frame UL1 is turned off.

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

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

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

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

[Upward compatibility control of new in-vehicle equipment]
FIG. 7 is a flowchart showing the upward compatible control performed by the in-vehicle controller 21 of the new in-vehicle device 2A that is the in-vehicle device 2 of the present embodiment.
As shown in FIG. 7, the in-vehicle controller 21 of the new in-vehicle device 2A always determines whether or not the downlink frame DL1 has been received (step ST11 in FIG. 7). Then, it is determined whether or not the flag field of the downstream frame DL1 is ON (step ST12 in FIG. 7).

If the flag field is turned on as a result of the determination, the in-vehicle controller 21 sets the transmission rate of the subsequent frame to be uplink-transmitted by the optical transmission unit 23 after the preceding frame (step ST13 in FIG. 7). ).
Conversely, when the flag field is off or when the field itself does not exist, the in-vehicle controller 21 sets the transmission rate of the subsequent frame to be uplink transmitted to the optical transmission unit 23 after the preceding frame, or Alternatively, transmission of the subsequent frame is stopped (step ST14 in FIG. 7).

  As described above, the uplink transmission of the uplink frame UL1 in steps ST13 and ST14 is performed until the vehicle ID loopback (detection of the return frame) is confirmed.

[Road-to-vehicle communication according to the first embodiment]
FIG. 8 is a sequence diagram illustrating a communication procedure according to the first embodiment.
Here, a frame DL1 with a white triangle indicates a downstream frame in which the new and old type flag fields of the optical beacon 4 are on. The same applies to the drawings after FIG.
In FIG. 8, U1 to U4 indicate a plurality of uplink frames (uplink frame group) UL1 that the in-vehicle device 2 performs uplink transmission, and the first uplink frame U1 is a “preceding frame” and is transmitted thereafter. Assume that the upstream frames U2 to U4 are “following frames”.

  Further, the uplink frame U1 (preceding frame) without hatching indicates that the transmission speed is low (64 kbps in this embodiment), and the uplink frames U2 to U4 (subsequent frames) with hatching are transmitted. It shows that the speed is high speed (128 kbps in this embodiment). This also applies to road-to-vehicle communication shown in FIG. 9 and subsequent figures.

  In FIG. 8, since the uplink transmission period of the high-speed subsequent frames U2 to U4 (with hatching) is relatively short, before the vehicle ID stored in the preceding frame U1 is first looped back from the optical beacon 4, That is, the case where the new in-vehicle device 2A completes the uplink transmission of the subsequent frames U2 to U4 is illustrated before the continuous transmission of the ID storage frame immediately after the downlink switching reaches the new in-vehicle device 2A.

As shown in FIG. 8, when the new in-vehicle device 2A according to the first embodiment receives the downlink frame DL1 for the first time in the downlink area DA, the low-speed preceding frame U1 is immediately uplink transmitted in response to the reception. Let
That is, the new in-vehicle device 2A (specifically, the simple control unit of the in-vehicle controller 21) sets the transmission speed of the preceding frame U1 to a low speed in advance, and receives the first downlink frame DL1 as a trigger. The transmission unit 23 causes the preceding frame U1 to be uplink transmitted at a low speed.

The uplink transmission of the low-speed preceding frame U1 is performed regardless of whether the communication partner of the new in-vehicle device 2A is the new optical beacon 4A or the old optical beacon 4B.
Next, the new in-vehicle device 2A determines whether or not the flag field of the received downlink frame DL1 is on, and if the flag field is on, determines that the communication partner is the new optical beacon 4A. The high-speed subsequent frames U2 to U4 are continuously transmitted after the preceding frame U1.

That is, the new in-vehicle device 2A (specifically, the main body control unit of the in-vehicle controller 21) sends the subsequent frames U2 to U4 to the optical transmission unit 23 when it is determined that the communication partner is the new optical beacon 4A. Make uplink transmission at high speed.
Conversely, if the flag field is off or the flag field cannot be detected, the new in-vehicle device 2A determines that the communication partner is the old optical beacon 4B and sets the subsequent frame to non-transmission. To do.

  However, as indicated by a virtual line (broken line) in FIG. 8, the new in-vehicle device 2A uplinks one or a plurality of subsequent frames U2 and U3 at a low speed when it is determined that the communication partner is the old optical beacon 4B. You may decide to transmit.

  In this case, depending on the frame length of the low-speed subsequent frames U2 and U3, it may not be possible to receive the return frame continuously transmitted by the old optical beacon 4B immediately after the downlink switching. If the new in-vehicle device 2A can confirm the loopback by the return frame transmitted in downlink every 5 frames in the example), the new in-vehicle device 2A will not retransmit the preceding frame U1, and may enter the receiving state of the downlink frame DL2. it can.

In the road-to-vehicle communication of FIG. 8, when the flag field can be detected but either on / off is unknown, the new in-vehicle device 2A may not know which type of communication partner should be new or old. possible.
In this case, the new in-vehicle device 2A may perform high-speed uplink transmission by setting the transmission rate of the subsequent frames U2 to U4 to be high, or may set the subsequent frame to non-transmission or the subsequent frames U2 and U3. The transmission rate may be set to a low speed and low-speed uplink transmission may be performed.

The reason is that even if high-speed subsequent frames U2 to U4 are erroneously transmitted to the old optical beacon 4B, the old optical beacon 4B determines that the subsequent frames U2 to U4 as noise and does not receive it. It is.
Conversely, even if the low-speed subsequent frames U2 and U3 are erroneously transmitted to the new optical beacon 4A, the new optical beacon 4A can receive the subsequent frames U2 and U3 without any problem, so that there is no particular problem.

As described above, according to the new vehicle-mounted device 2A of the first embodiment (FIG. 8), the preceding process for setting the transmission speed of the preceding frame U1 to a low speed is executed. Even so, the optical beacon 4 can receive the preceding frame U1.
In this case, since the low-speed preceding frame U1 is an ID storage frame including a vehicle ID, the optical beacon 4 can execute a predetermined process such as downlink switching regardless of the old and new types of the optical beacon 4.

Further, according to the new in-vehicle device 2A of the first embodiment, when the communication partner is the new optical beacon 4A, the transmission rate of the subsequent frames U2 to U4 is set to a high speed, and the communication partner is the old optical beacon 4B. Performs non-transmission or transmission of the subsequent frames U2 and U3, and executes subsequent processing for setting the transmission rate of the subsequent frames U2 and U3 to a low speed.
Therefore, for the new optical beacon 4A, it is possible to perform high-speed uplink transmission in which the subsequent frames U2 to U4 are set at a high speed, and for the old optical beacon 4B, non-transmission of the subsequent frames U2 and U3 or the subsequent frame U2 , U3 is set to a low speed, low-speed uplink transmission is possible, and communication with the old and new optical beacons 4A and 4B can be performed appropriately.

[Problems when sending subsequent frames continuously]
FIG. 9 is a sequence diagram showing a case where the new in-vehicle device 2A fails in the ID confirmation in the communication procedure of the first embodiment (FIG. 8).
As described above, when transmitting a large amount of data such as probe information in the uplink, it is often impossible to store data in the preceding frame U1. Therefore, in the examples of FIGS. 8 and 9, the new in-vehicle device 2A continuously transmits subsequent frames including a total of three upstream frames U2 to U4 at a high speed.

Of these, the preceding frame U1 is an ID storage frame, and the subsequent frames U2 to U4 are data frames storing the probe information and the like.
Here, in the conventional road-to-vehicle communication, when the optical beacon 4 receives the ID storage frame U1 under the assumption that the large-capacity uplink transmission as described above is not performed, the return frame is immediately transmitted continuously and is down. It is an operation to perform link switching as quickly as possible.

  For this reason, in the case of the new light beacon 4A as well, as described above, when downlink switching is performed triggered by reception of the ID storage frame U1, the ID storage frame immediately after downlink switching arrives as shown in FIG. The uplink transmission of the high-speed subsequent frames U2 to U4 (with hatching) only needs to be completed by the time, but the transmission period of each subsequent frame U2 to U4 is relatively long as shown in FIG. The same applies to the case where the number of frames is large.) When the return frame reaches the new in-vehicle device 2A during the transmission period (U4 in the example of FIG. 9), the return frame arrives at the optical receiver 24. Nevertheless, the new in-vehicle device 2A may not be able to detect that the new light beacon 4A has already recognized the vehicle ID.

In this case, as indicated by a broken line in FIG. 9, the new in-vehicle device 2A retransmits the large-capacity uplink frame groups U1 to U4 including the preceding frame U1 that is an ID storage frame.
As described above, this phenomenon is more likely to occur as the number of a plurality of series of downlink frames DL2 constituting the downlink information increases. This is because the frequency with which the new optical beacon 4A transmits the return frame is low, and thus the probability that the new in-vehicle device 2A cannot recognize the loopback increases.

As described above, the turn-on frame periodically transmitted after downlink switching (every 5 frames in the example of FIG. 9) also overlaps with the transmission period of the uplink frame groups U1 to U4. The possibility that 2A can be received is reduced.
In this case, even after retransmitting the uplink frame groups U1 to U4, the new in-vehicle device 2A does not notice the return frame, and uplink transmission (retransmission) of the uplink frame groups U1 to U4 is continued in vain.

Then, as the number of frames transmitted by the new in-vehicle device 2A increases, the possibility that transmission of the uplink frame groups U1 to U4 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 (for example, 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 according to the second embodiment]
FIG. 10 is a sequence diagram illustrating a communication procedure according to the second embodiment.
As shown in FIG. 10, in the second embodiment, when the new in-vehicle device 2A continuously transmits the high-speed subsequent frames U2 to U4 after the preceding frame U1, between the first preceding frame U1 and the subsequent frame U2, “ By providing the “transmission interruption period”, the problem of the first embodiment described above is 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.
For example, it is assumed that the reception process of the ID storage frame U1 received by the new light beacon 4A from the vehicle 20 takes about 5 to 10 milliseconds, and further, the new light beacon 4A is necessary for starting the ID return process of the ID storage frame U1. Assuming that the delay time (delay time required for downlink switching in the example of FIG. 10) is 10 milliseconds, the transmission interruption period may be set in the range of 15 to 20 milliseconds.

If this transmission interruption period is provided, the return frame continuously transmitted after downlink switching reaches the optical receiver 24 of the new in-vehicle device 2A during the period, and the new in-vehicle device 2A receives the received return frame. By determining whether or not the included vehicle ID matches that of the own device, the success of the loopback of the vehicle ID can be confirmed.
After the above confirmation, the new in-vehicle device 2A continuously transmits the second and subsequent subsequent frames U2 to U4, and after the continuous transmission is completed, switches the communication of the own device to reception.

Thus, according to the new vehicle-mounted device 2A of the present embodiment, it is possible to reliably detect that the new light beacon 4A has already recognized the vehicle ID from the return frame received from the new light beacon 4A during the transmission interruption period. .
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 U1 to U4.

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 can be quickly restored at the time of re-emission of the light emitting element, and disturbance of the synchronization part of the second upstream frame U2 can be suppressed.

On the other hand, if the ID storage frame U1 does not reach the new light beacon 4A due to some cause (such as fogging of the windshield of the vehicle 20), the optical beacon 4 does not return the return frame, so the new in-vehicle device 2A is a loop. Unable to confirm back success.
Therefore, if the new in-vehicle device 2A cannot confirm the success of the loopback during the transmission interruption period, only the preceding frame U1 that is the ID storage frame is retransmitted to the optical transmission unit 23 as shown by the broken line in FIG. After the preceding frame U1, the transmission is interrupted.

  Therefore, if the new light beacon 4A can properly receive the retransmitted previous frame U1, the loopback received from the new light beacon 4A during the transmission interruption period confirms the successful loopback of the vehicle ID, as described above. can do.

In the second embodiment, the frame length of the preceding frame U1, which is the first upstream frame, is preferably as short as possible. For example, it is preferably shorter than at least one of the subsequent frames U2 to U4.
More preferably, the frame length of the first upstream frame U1 may be set to the shortest (for example, about 5 bytes in the actual data portion) among all the upstream frames U1 to U4 constituting the upstream frame group. That is, it is desirable that the data stored in the first upstream frame U1 is limited to the necessary data, for example, only vehicle ID information, travel time between beacons, information on the type of service supported by the in-vehicle device, and the like. .

  The reason is that, as described above, if the frame length of the first uplink frame U1 that is likely to be retransmitted is long, the remaining time in which uplink transmission can be performed when the uplink frame U1 is retransmitted is correspondingly reduced. This is because, for example, the last uplink frame U4 among a plurality of uplink frames U2 to U4 scheduled to be uplink-transmitted cannot be transmitted (the new optical beacon 4A cannot be normally reached).

As shown in FIG. 10, the turn-back frame, which is the downlink frame DL2 continuously transmitted after the downlink switching, stores the vehicle ID acquired from the new vehicle-mounted device 2A, and also has a flag field set to ON. It is preferable that
In this way, based on the flag field included in the downlink frame DL2 received by the new in-vehicle device 2A during the transmission interruption period, the optical beacon 4 is a new optical beacon 4A that supports high-speed uplink reception or an old non-compatible one. Whether it is the optical beacon 4B can be determined, and the content of the subsequent processing can be determined according to the determination result.

  For this reason, the new in-vehicle device 2A can determine whether the optical beacon 4 is new or old even after the transmission of the preceding frame U1, and the optical beacon is based only on the downlink frame DL1 received before the transmission of the preceding frame U1. Compared with the case where the new and old types of 4 are determined, the determination can be reliably performed.

[Road-to-vehicle communication according to the third embodiment]
FIG. 11 is a sequence diagram illustrating a communication procedure according to the third embodiment.
The road-to-vehicle communication of the third embodiment (FIG. 11) is different from that of the second embodiment (FIG. 10) in that when the new light beacon 4A receives the preceding frame U1, which is an ID storage frame, only ID return is performed. The downlink switching is executed on condition that the last uplink frame U4 is detected after that.

In the second embodiment (FIG. 10), the new optical beacon 4A performs downlink switching in response to the reception of the uplink frame U1 that is an ID storage frame, so that the new in-vehicle device 2A completes transmission of the last uplink frame U4. Immediately after that, there is an advantage that the downlink frame DL2 including the provision information for the own vehicle can be received early.
However, if provision information useful for the host vehicle is stored biased toward the heads of the plurality of downlink frames DL2, it may be advantageous to delay downlink switching.

  Further, in the second embodiment, since the new in-vehicle device 2A that has performed many uplinks that are beneficial to the roadside cannot receive because of the half-duplex method during that period, a predetermined downlink frame DL2 is included accordingly. There is a possibility that the opportunity to receive downlink information may be lost, and the motivation for transmitting a large number of uplinks may be reduced.

Therefore, in the third embodiment (FIG. 11), the new optical beacon 4A performs downlink switching on condition that the last uplink frame U4 in the uplink frame groups U1 to U4 is received.
For this reason, the new in-vehicle device 2A can receive the downlink frame DL2 after downlink switching in order from the top, and even if information useful for the host vehicle is biased and stored on the head side of the downlink frame DL2, the beneficial effect is obtained. It is possible to reduce the possibility of missing information.

In the third embodiment (FIG. 11), when the new in-vehicle device 2A continuously transmits the subsequent frames U2 to U4, a final frame flag (hereinafter referred to as “final frame”) is displayed in a predetermined field of the header portion of the last upstream frame U4. Abbreviated as “flag”). In FIG. 11, an upstream frame U4 indicated by a black triangle indicates that the final flag is written in the frame (the same applies to FIGS. 12 to 15).
Therefore, the optical beacon 4 that has received the upstream frame U4 can determine that it is the last upstream frame if the final flag is present in the predetermined field.

The identification information of the last uplink frame U4 can be performed by not only the final flag as described above but also the total frame number and frame number written in the uplink frame groups U1 to U4.
In this case, the new optical beacon 4A can determine the uplink frame in which the value of the total number of frames and the value of the frame number (that is, the value of “4” in the present embodiment) match as the last uplink frame U4.

[Road-to-vehicle communication according to the fourth embodiment]
FIG. 12 is a sequence diagram illustrating a communication procedure according to the fourth embodiment.
As in the third embodiment (FIG. 11), when the new optical beacon 4A performs downlink switching on condition that the last uplink frame U4 is received, the last uplink beacon, for example, as indicated by a cross in FIG. If the frame U4 ends undelivered, the downlink switching is not performed no matter what time the new light beacon 4A passes, and the new in-vehicle device 2A cannot acquire the downlink frame DL2 including the provided information.

Therefore, in the fourth embodiment (FIG. 12), when the new optical beacon 4A cannot determine which of the upstream frame groups U1 to U4 is the last, the downlink switching is performed after elapse of predetermined times T1 and T2. Is supposed to run.
Of the two types of predetermined times T1 and T2 shown in FIG. 12, the first predetermined time T1 starts from the time when the uplink frame was last received (the reception time of the uplink frame U3 in FIG. 12). The predetermined time T2 starts from the reception time point of the first upstream frame U1, which is an ID storage frame.

  As described above, when the preset predetermined times T1 and T2 have elapsed (either one of the predetermined times T1 or T2 has elapsed or both have elapsed), downlink switching is performed. Then, it is possible to prevent the new optical beacon 4A from performing the downlink switching because it is unknown which is the last uplink frame U4.

[Road-to-vehicle communication according to the fifth embodiment]
FIG. 13 is a sequence diagram illustrating a communication procedure according to the fifth embodiment.
As shown in FIG. 13, in the fifth embodiment, when the new in-vehicle device 2A continuously transmits the subsequent frames U2 to U4 after the preceding frame U1, the new light beacon 4A includes an ID storage frame (upstream frame U1). By performing downlink switching on condition that the optical receiver 11 has received the last upstream frame U4 in the upstream frame groups U1 to U4, the problem of the first embodiment is solved. Yes.

  The feature of the fifth embodiment (FIG. 13) compared with the third and fourth embodiments (FIGS. 11 and 12) is that the ID wrapping ( In the fifth embodiment (FIG. 13), the ID return (transmission of the return frame) is not performed in the fifth embodiment (FIG. 13), whereas the timing of downlink switching is different from the timing of downlink switching. And the downlink switching timing are the same.

In this way, if the new optical beacon 4A executes downlink switching on condition that the last uplink frame U4 has been received, the new in-vehicle device 2A is returned at the beginning after the downlink switching. The frame can be received after transmission of subsequent frames U2-U4 is complete.
Therefore, as shown in FIG. 13, even if the new in-vehicle device 2A transmits the upstream frame groups U1 to U4 without providing the “transmission interruption period” in the second embodiment (FIG. 10), the new optical beacon The new in-vehicle device 2A can easily detect that 4A has recognized the vehicle ID, which is preferable.

  However, in the fifth embodiment of FIG. 13, the new in-vehicle device 2A that is the communication partner of the new optical beacon 4A stores frame identification information (for example, the above-mentioned final flag) indicating which is the last upstream frame U4. If so, it may be a new vehicle-mounted device 2A of a type that provides a “transmission interruption period” after the preceding frame U1.

That is, the new in-vehicle device 2A that is the communication partner of the new optical beacon 4A in FIG. 13 employs both the transmission interruption period and the frame identification information indicating which is the final frame. For example, the new in-vehicle device of the third embodiment (FIG. 11) The in-vehicle device 2A may be used.
Note that the determination method of the last uplink frame U4 by the new optical beacon 4A is the same as that in the third embodiment (FIG. 11), and thus the description thereof is omitted.

[Road-to-vehicle communication according to the sixth embodiment]
FIG. 14 is a sequence diagram illustrating a communication procedure according to the sixth embodiment.
As in the fifth embodiment (FIG. 13), when the new optical beacon 4A performs downlink switching on condition that the last uplink frame U4 is received, the last uplink beacon, for example, as indicated by a cross in FIG. If the frame U4 ends undelivered, the downlink switching is not performed no matter what time the new light beacon 4A passes, and the new in-vehicle device 2A cannot acquire the downlink frame DL2 including the provided information.

Therefore, also in the sixth embodiment (FIG. 14), when the new optical beacon 4A cannot determine which of the upstream frame groups U1 to U4 is the last, the downlink after a predetermined time T1, T2 has elapsed. Switching is to be executed.
Of the two types of predetermined times T1 and T2 shown in FIG. 14, the first predetermined time T1 starts from the time when the uplink frame was last received (the reception time of the uplink frame U3 in FIG. 14). The predetermined time T2 starts from the reception time point of the first upstream frame U1, which is an ID storage frame.

  As described above, when the preset predetermined times T1 and T2 have elapsed (either one of the predetermined times T1 or T2 has elapsed or both have elapsed), downlink switching is performed. Then, it is possible to prevent the optical beacon 4 from performing the downlink switching because it is unknown which is the last uplink frame U4.

In the sixth embodiment of FIG. 14 as well, the new in-vehicle device 2A that is the communication partner of the new optical beacon 4A stores frame identification information (for example, the above-mentioned final flag) indicating which is the last upstream frame U4. If it is a thing, the new vehicle equipment 2A of the type which provides a "transmission interruption period" after the preceding frame U1 may be sufficient.
That is, the new in-vehicle device 2A, which is the communication partner of the new optical beacon 4A in FIG. 14, employs both the transmission interruption period and the frame identification information indicating which is the last frame. For example, in-vehicle in the third embodiment (FIG. 11). Machine 2 may be used.

[Road-to-vehicle communication according to the seventh embodiment]
FIG. 15 is a sequence diagram illustrating a communication procedure according to the seventh embodiment.
The seventh embodiment (FIG. 15) differs from the fifth embodiment (FIG. 13) in that the new light beacon 4A performs only ID return on the upstream frame (preceding frame) U1 that is an ID storage frame, and thereafter The downlink switching is performed when the reception of the last uplink frame U4 among the subsequent frames U2 to U4 transmitted continuously is detected.

  As shown in FIG. 15, in the seventh embodiment, since the new in-vehicle device 2A continuously transmits all the upstream frames U1 to U4 without interruption, even if the new optical beacon 4A performs ID return, reception of the return frame is performed. The timing may overlap with the transmission period of the subsequent frames U2 to U4, and the new vehicle-mounted device 2A may not be able to properly receive the return frame.

However, when the new optical beacon 4A detects the reception of the last uplink frame U4, it performs downlink switching and continuously transmits the return frame immediately after the switching.
Therefore, the new in-vehicle device 2A can appropriately confirm the success of the loopback by the above-described return frame transmitted in downlink after downlink switching.
In this way, even when the in-vehicle devices 2 that implement various types of transmission processing are mixed, the in-vehicle device 2 can easily detect the loopback regardless of the transmission processing. It becomes possible to increase the efficiency of inter-vehicle communication.

[Road-to-vehicle communication according to the eighth embodiment]
FIG. 16 is a sequence diagram illustrating a communication procedure according to the eighth embodiment.
The difference between the eighth embodiment (FIG. 16) and the first embodiment (FIG. 8) is that the new in-vehicle device 2A is not the preceding process for fixing the transmission speed of the preceding frame U1 to a low speed, but the old and new types of the optical beacon 4 Accordingly, the preceding process for setting the transmission rate of the preceding frame U1 to high speed or low speed is executed.

That is, the new in-vehicle device 2A of the eighth embodiment (FIG. 16) determines whether or not the flag field of the received downlink frame DL1 is on, and when the flag field is on, The new light beacon 4A is determined and the transmission speed of the preceding frame U1 is set to a high speed.
In addition, when the flag field is off or the flag field cannot be detected, the new in-vehicle device 2A determines that the communication partner is the old optical beacon 4B and reduces the transmission rate of the preceding frame U1. Set to.

On the other hand, the subsequent processing performed by the new vehicle-mounted device 2A of the eighth embodiment (FIG. 16) is the same as that of the first embodiment (FIG. 8).
That is, when the communication partner is the new optical beacon 4A, the new in-vehicle device 2A continuously transmits the high-speed subsequent frames U2 to U4 following the preceding frame U1.
Further, when the communication partner is the old optical beacon 4B, the new in-vehicle device 2A sets the subsequent frames U2 and U3 to non-transmission, or sets the transmission speed of the subsequent frames U2 and U3 to low when transmitting. To do.

In the road-to-vehicle communication of FIG. 16, when the flag field can be detected but either on / off is unknown, the new in-vehicle device 2A may not know which of the new and old types of the communication partner should be determined. possible.
In this case, the new in-vehicle device 2A sets the transmission rate of the preceding frame U1 to low speed and sets the subsequent frames U2 and U3 to non-transmission, or sets the transmission rate of the subsequent frames U2 and U3 to low speed.

The reason is that if the high-speed preceding frame U1 and the high-speed subsequent frames U2 to U4 are erroneously transmitted to the old optical beacon 4B, the old optical beacon 4B cannot receive any upstream frame, and the downlink switching is performed. This is because is no longer performed.
Conversely, even if the low-speed preceding frame U1 and the low-speed subsequent frames U2 and U3 are erroneously transmitted to the new optical beacon 4A, the new optical beacon 4A can receive the preceding frame U1 and the subsequent frames U2 and U3 without any problem. This is because there is no problem.

As described above, according to the new in-vehicle device 2A of the eighth embodiment (FIG. 16), the transmission speed of the preceding frame U1 is set to high speed or low speed according to the old and new types of the communication partner, so the optical beacon 4 of the communication partner Regardless of the new and old types, the optical beacon 4 can receive the preceding frame U1.
In this case, since the high-speed or low-speed preceding frame U1 is an ID storage frame including the vehicle ID, the optical beacon 4 can execute predetermined processing such as downlink switching regardless of the old and new types of the optical beacon 4. it can.

Further, according to the new in-vehicle device 2A of the eighth embodiment, when the communication partner is the new optical beacon 4A, the transmission rate of the subsequent frames U2 to U4 is set to a high speed, and the communication partner is the old optical beacon 4B. Performs non-transmission or transmission of the subsequent frames U2 and U3, and executes subsequent processing for setting the transmission rate of the subsequent frames U2 and U3 to a low speed.
Therefore, for the new optical beacon 4A, it is possible to perform high-speed uplink transmission in which the subsequent frames U2 to U4 are set at a high speed, and for the old optical beacon 4B, non-transmission of the subsequent frames U2 and U3 or the subsequent frame U2 , U3 is set to a low speed, low-speed uplink transmission is possible, and communication with the old and new optical beacons 4A and 4B can be performed appropriately.

[Modification of Eighth Embodiment]
The new in-vehicle device 2A of the eighth embodiment (FIG. 16) also transmits the subsequent frames U2 to U4 after the preceding frame U1 to the new light beacon 4A. (FIG. 9) can occur as well.

Thus, the new in-vehicle device 2A of the eighth embodiment can be improved in the same communication procedure as in the second embodiment (FIG. 10) to the seventh embodiment (FIG. 15).
That is, the improvement of the communication procedure of the second embodiment (FIG. 10) to the seventh embodiment (FIG. 15) can be similarly applied to the new in-vehicle device 2A of the eighth embodiment (FIG. 16). it can.

[Road-to-vehicle communication according to the ninth embodiment]
FIG. 17 is a sequence diagram illustrating a communication procedure according to the ninth embodiment.
The ninth embodiment (FIG. 17) differs from the first embodiment (FIG. 8) in that not only the preceding process for fixing the transmission rate of the preceding frame U <b> 1 to a low speed but also the new in-vehicle device 2 </ b> A is an optical beacon 4. Regardless of the new or old type, the subsequent processing for fixing the transmission rate of the subsequent frames U2 to U4 at a high speed is performed.

That is, the new in-vehicle device 2A of the ninth embodiment (FIG. 17) always performs uplink transmission of the preceding frame U1 at a low speed without determining the new and old types of communication partners, and uplink transmission of the subsequent frames U2 to U4. Always do it at high speed.
For this reason, the new optical beacon 4A with which the new in-vehicle device 2A of the ninth embodiment is a communication partner does not need to provide a flag field in the downlink frame DL1 for notifying that the own device supports high-speed uplink reception.

As described above, according to the new vehicle-mounted device 2A of the ninth embodiment (FIG. 17), the preceding process for setting the transmission rate of the preceding frame U1 to a low speed is executed. Even so, the optical beacon 4 can receive the preceding frame U1.
In this case, since the low-speed preceding frame U1 is an ID storage frame including a vehicle ID, the optical beacon 4 can execute a predetermined process such as downlink switching regardless of the old and new types of the optical beacon 4.

Further, according to the new in-vehicle device 2A of the ninth embodiment, the subsequent process for setting the transmission rate of the subsequent frames U2 to U4 to a high speed is executed.
For this reason, when the communication partner is the new optical beacon 4A, high-speed uplink transmission in which the subsequent frames U2 to U4 are set at high speed is possible. When the communication partner is the old optical beacon 4B, the subsequent frames U2 to U4 are transmitted. Since it is determined that the noise is not received and only the low-speed preceding frame U1 is properly received, it is possible to appropriately communicate with the old and new optical beacons 4A and 4B.

[Modification of Ninth Embodiment]
The new in-vehicle device 2A of the ninth embodiment (FIG. 17) also transmits the subsequent frames U2 to U4 after the preceding frame U1 to the new light beacon 4A. (FIG. 9) can occur as well.

Therefore, the new in-vehicle device 2A of the ninth embodiment can be improved in the same communication procedure as that of the second embodiment (FIG. 10) to the seventh embodiment (FIG. 15).
That is, the improvement of the communication procedure of the second embodiment (FIG. 10) to the seventh embodiment (FIG. 15) can be similarly applied to the new in-vehicle device 2A of the ninth embodiment (FIG. 17). it can.

[Modified example of transmission interruption period]
In the second embodiment (FIG. 10) to the fourth embodiment (FIG. 12), the transmission interruption period of the upstream frames U1 to U4 is set between the first upstream frame U1 and the second upstream frame U2. Yes. However, the optimal transmission period between which frames in the uplink frame groups U1 to U4 can vary depending on the performance of the optical beacon 4 and the uplink speed.

Therefore, in the above-described second to fourth embodiments, for example, a transmission interruption period is provided between the second and third upstream frames U2 and U3, or a transmission interruption period is provided between the subsequent upstream frames U3 and U4. You may decide to do.
For example, when the new optical beacon 4A requires a certain processing time (for example, about 10 milliseconds) from the time when the first upstream frame U1 is received until the transmission of the downstream frame including the identification information (turned frame) is started. In the meantime, even if the in-vehicle device 2 switches to the receiving state, the return frame cannot be received.

Therefore, if it is possible to finish transmission of the next and subsequent uplink frames U2 to U4 during the processing time, it is possible to increase the efficiency of road-to-vehicle communication.
For example, when the uplink speed is the current 64 kbps, according to the current standard for road-to-vehicle communication, about 10 milliseconds are required to transmit one uplink frame (the actual data portion has a maximum size of 59 bytes). in the case of).

  If it takes 10 milliseconds or more for the optical beacon 4 that has received the first upstream frame U1 to start transmitting the return frame, the second upstream frame U2 is transmitted during that time. It can be expected that the communication efficiency will be higher if the reception frame is switched to the reception state after the transmission of the upstream frame U2. In this case, a transmission interruption period may be provided between the second frame and the third frame.

  From the above viewpoint, the new in-vehicle device 2A excludes the last included in the upstream frame groups U1 to U4 when transmitting the upstream frame groups U1 to U4 including the vehicle ID in the first upstream frame U1 to the optical beacon 4. It can be said that after the transmission of the upstream frames U1 to U3, it is temporarily switched to the reception state and waits for a return frame that is a downstream frame including the vehicle ID.

In the new in-vehicle device 2A, if the timing for switching to the reception state can be set variably, even if the transmission time of the return frame from the new optical beacon 4A varies due to changes in the rules, the in-vehicle device 2 can deal flexibly.
For example, if the uplink speed can be improved to 128 kbps, it takes 5 msec to transmit one frame (in the case where the actual data part is the maximum size of 59 bytes). Until the start of frame transmission, the second and third frames may be transmitted, and a transmission interruption period may be provided between the third and fourth frames.

[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 upstream frames U1 to U4 are transmitted continuously, but burst transmission may be performed with an interval of a predetermined time length provided between the frames.

However, in the fourth embodiment (FIG. 12) and the sixth embodiment (FIG. 14) described above, it is necessary to set the interval between frames within a range in which the predetermined time T1 is secured.
This is because if the interval equal to or longer than the predetermined time T1 is left, the new optical beacon 4A may determine that some kind of trouble has occurred in the uplink and may perform downlink switching or the like.

  In addition, the “on-vehicle device” of the present invention 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 vehicle 20. Also included in the.

In a situation where the new in-vehicle device 2A can perform either an operation that does not provide a transmission interruption period (for example, FIG. 8) or an operation that provides a transmission interruption period (for example, FIG. 10), the new optical beacon 4A Downlink switching including continuous transmission of loopback frames is performed when frame U1 is received, and further downlink switching including continuous transmission of loopback frames is performed once the last uplink frame U4 is received. Anyway.
In this way, it becomes easy to recognize the success of the loopback in any type of new vehicle-mounted device 2A.

Further, as shown in FIG. 8 and FIG. 10, when downlink switching including continuous transmission of the return frame is performed immediately after reception of the first uplink frame U1, the new in-vehicle device 2A cannot receive the continuous transmission of the return frame. After that, the new in-vehicle device 2A can recognize the loopback only by receiving a return frame sent at a constant frequency in the downlink frame DL2.
Therefore, it is possible to include more folded frames than the conventional frame as the downlink frame DL2.

  For example, in addition to inserting one folded frame at the beginning of a series of downlink frames DL2 constituting downlink information as usual, the second folded frame is also used, or one or three folded frames are provided. For example, it is possible to adopt a method such that the ratio is one. Further, if the total number of downstream frames DL2 is N, a method of inserting one or a plurality of folded frames before or after the N / 2th or before or after the N / 3th may be used.

  In addition, if the transmission interval (for example, 20 ms) of the uplink transmission process that is repeated until the in-vehicle device 2 can confirm the loopback is defined in advance, the return frame is always transmitted at a cycle shorter than the uplink transmission interval. Thus, the folded frames may be inserted at a rate of about 10 to 15 frames (corresponding to a time of about 10 to 15 ms).

In general, in a computer device, when downlink information is transmitted continuously and repeatedly, a transmission mode such as a mode for repeatedly transmitting a downlink frame DL2 after downlink switching or a mode in which a return frame is continuously transmitted is used. Changing the mode is advantageous because it requires a processing load and a CPU having a high processing capacity to be employed, so that the number of switching of the transmission mode is smaller.
From such a point of view, as described above, the downlink frame DL2 after downlink switching includes a larger number of folded frames than before, for example, to increase the probability that the in-vehicle device recognizes loopback success and to change the transmission mode. It is promising to reduce the number of times.

Here, an example is shown in which the reception of the first uplink frame and the reception of the last uplink frame are used as triggers for operations such as downlink switching and continuous transmission of return frames, but the present invention is not limited to such a configuration. .
This is because it is considered that there is a case where it is more convenient for the in-vehicle device 2 to specify at what timing the optical beacon 4 should perform downlink switching.

  Therefore, “uplink frame UL1” is provided with “DL switching request information (for example, a flag provided at a predetermined position such as a header)” for requesting downlink switching for the optical beacon 4, and the DL switching request information is received from the in-vehicle device 2. The optical beacon 4 may perform operations such as downlink switching and continuous transmission of return frames at the timing of receiving the signal.

  For example, if the total number of uplink frames transmitted by the new vehicle-mounted device 2A is two, the new vehicle-mounted device 2A may have two again after transmitting the first uplink frame U1 and stopping transmission for a predetermined time. It is easier to process two frames in succession than to transmit the uplink frame U2 of the eye. Even if the uplink does not reach the optical beacon 4 and retransmits it, The impact of a decrease in communication efficiency is small. In such a case, DL switching request information may be stored in the second frame.

  In addition, even when the total number of uplink frames transmitted by the new in-vehicle device 2A is about 10, for example, it takes a predetermined time (for example, 10 ms) until the optical beacon 4 performs downlink switching. Is known, the DL switching request information may be transmitted when the period required for transmitting the uplink frame UL1 becomes equal to or shorter than the predetermined time (for example, 10 ms). For example, if it takes 5 ms to transmit one frame, the DL switching request information may be included in the eighth frame.

  Then, after the eighth frame is received and the DL switching request information is confirmed, the optical beacon 4 that shifts to the downlink switching mode is actually switched to the downlink (for example, 10 ms). Since the new vehicle-mounted device 2A can finish transmission of the ninth frame and the tenth frame, road-to-vehicle communication can be performed more efficiently by that amount.

  In this way, by introducing a communication protocol that allows the in-vehicle device 2 to specify at what timing the optical beacon 4 wants to perform downlink switching and continuous transmission of return frames, it is possible for the in-vehicle device 2 and the road device. This makes it possible to realize flexible and more convenient road-to-vehicle communication.

  In this case, if the optical beacon 4 cannot receive the uplink frame in which the DL switching request information is stored in the uplink frame UL1 transmitted from the vehicle-mounted device 2, the timing when the optical beacon 4 performs downlink switching. In this case, downlink switching may be performed at the timing when the final uplink frame U4 is received. Furthermore, as shown in FIG. 14, a method of performing downlink switching after elapse of a predetermined time T1 since the last reception of the uplink frame U4 may be used in combination.

2 In-vehicle device 4 Optical beacon 7 Beacon controller (communication controller)
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 (2)

An in-vehicle device that performs wireless communication with an optical beacon and an optical signal installed on a road,
An optical transmitter capable of electro-optical conversion at two transmission speeds, high and low,
An optical receiver capable of photoelectric conversion at one transmission rate different from the two transmission rates ;
Based on the beacon identification information included in the downlink frame transmitted at the one type of transmission rate, it is determined whether the optical beacon is a new optical beacon corresponding to high-speed uplink reception or an unsupported old optical beacon, and the determination result And a communication control unit that switches between uplink transmission at a high transmission rate, uplink transmission at a low transmission rate, or non-transmission. The communication control unit may include in-vehicle unit identification information for causing the optical beacon to perform downlink transmission including downlink signal transmission including signal information for a new in-vehicle device corresponding to high-speed uplink transmission in the upstream frame. The in-vehicle device according to claim 1 which can be performed.

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