JP2014013531A - On-vehicle apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel uplink multi-rate adaptive on-vehicle apparatus that can communicate properly with new and old optical beacons.SOLUTION: An on-vehicle apparatus 2 performs wireless communication using an optical signal with an optical beacon 4 installed on a road. The on-vehicle apparatus 2 includes: an optical transmission unit 23 capable of performing electro-optical conversion at two types of high and low transmission speeds; an optical reception unit 24 capable of performing optical-electro conversion at a given transmission speed; a communication control unit (on-vehicle controller) 21 that causes a priority frame being an uplink frame U1 of a low speed storing priority information that should be informed preferentially to the optical beacon 4 to be included in plural in uplink frame groups U1 to U7 that are transmitted by the optical transmission unit 23.

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. 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.

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.

  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; An optical receiver capable of photoelectric conversion at a predetermined transmission rate, and an upstream that causes the optical transmitter to transmit a priority frame that is a low-speed uplink frame storing priority information to be preferentially notified to the optical beacon. And a communication control unit included in the frame group.

According to the in-vehicle device of the present invention, the communication control unit includes the priority frame, which is a low-speed uplink frame storing priority information to be preferentially notified to the optical beacon, in the uplink frame group. The optical beacon can receive the priority frame regardless of whether the type is new or old.
For this reason, regardless of the old and new types of optical beacons, the optical beacon can execute a predetermined process (for example, downlink switching) triggered by acquisition of priority information.

Further, according to the in-vehicle apparatus of the present invention, the communication control unit includes a plurality of priority frames in the upstream frame group, so that the priority frame can be more reliably compared to the case where only one priority frame is included in the upstream frame group. Can be sent to optical beacons.
For this reason, the optical beacon can reliably execute a predetermined process (for example, downlink switching) triggered by acquisition of priority information, which is necessary regardless of the old and new types of optical beacons. Can communicate properly.

(2) In the in-vehicle device of the present invention, more specifically, the priority information includes only the following first information, the following first information and the second or third information, or the following first information: It is preferable that all the first to third information is included.
First information: Trigger information that triggers downlink switching by old and new optical beacons Second information: Subsystem key information used by old and new optical beacons to determine the type of provided information after downlink switching Information: Type information indicating the new and old of the in-vehicle device

The reason why the first information is always included in the priority information is that if the first information is not provided to the optical beacon, the optical beacon does not perform the downlink switching, and the provision information scheduled to be transmitted in the downlink after the switching is provided. This is because the vehicle-mounted device of the present invention cannot be acquired.
The reason why the second information should be included in the priority information is that if the second information is not notified to the optical beacon, the optical beacon cannot determine the type of information to be provided after downlink switching, and the provision other than the desired type is provided. This is because the vehicle-mounted device of the present invention can acquire only information.

  The reason why the third information should be included in the priority information is that if the third information is notified to the optical beacon, the new optical beacon changes the content of the provided information according to the new and old types of the vehicle-mounted devices. This is because it becomes possible to provide appropriate information according to the new and old types of in-vehicle devices.

(3) In the in-vehicle device of the present invention, it is preferable that the communication control unit sets an uplink frame other than the priority frame in the uplink frame group as a non-priority frame that does not store the first information.
The reason is that, since the communication time that can be uplinked to one optical beacon is limited, the number of uplink frames included in the uplink frame group is also limited. This is because the degree of freedom of data contents to be uplinked by the in-vehicle device should be secured.

(4) In the in-vehicle device according to the present invention, the communication control unit causes the optical transmission unit to uplink transmit the priority frame at a low speed, and uplinks other uplink frames to the optical transmission unit at a high speed. It is preferable to make it.
In this case, when the communication partner is a new optical beacon, the new optical beacon can receive an upstream frame other than the priority frame at a high speed, so that the communication in the uplink direction can be speeded up.

  (5) By the way, most of the in-vehicle devices currently in operation have a structure in which an optical transmission unit and an optical reception unit are housed in a single head, and the light transmitted from the optical transmission unit of the own device is transmitted inside the head. A half-duplex communication method is employed in which transmission and reception are alternately performed in order to avoid a situation in which communication is disabled due to reflection on the windshield and the like that wraps around the optical receiver.

  Therefore, for example, when an in-vehicle device continuously transmits an upstream frame group including a plurality of priority frames, a downstream frame (hereinafter also referred to as a “turn-back frame”) transmitted by an optical beacon to notify the acquisition of the vehicle ID. The vehicle-mounted device arrives at the vehicle-mounted device during the transmission period of the upstream frame (hereinafter also referred to as “subsequent frame”) following the last priority frame, and the vehicle-mounted device does not detect that the optical beacon has already recognized the vehicle ID. There is a possibility that the in-vehicle device may continue transmission (retransmission) of the uplink frame group in the uplink region.

In addition, as the number of subsequent frames to be uplink-transmitted increases, it is more likely that the in-vehicle device will continue to transmit (retransmit) uplink frames in the uplink region without noticing the return frame.
Therefore, an in-vehicle device that tries to uplink more data to the new optical beacon loses the opportunity to receive the downstream frame significantly, or passes through the communication area without receiving the downstream frame. May result.

  The road-to-vehicle communication system according to the present invention is a road-to-vehicle communication system including the vehicle-mounted device according to the present invention described in (1) to (4) and the optical beacon. The optical beacon performs continuous transmission of a downlink frame storing downlink vehicle identification information and downlink switching on condition that the last uplink frame in the uplink frame group is received. To do.

In this case, since the optical beacon performs continuous transmission of the return frame and downlink switching on condition that the last uplink frame is received, the in-vehicle device can receive the return frame after the transmission of the subsequent frame is completed.
Therefore, the in-vehicle device can detect that the optical beacon has already recognized the vehicle identification information after transmitting the uplink frame group, and the in-vehicle device continuously transmits (retransmits) the uplink frame group. Loss of reception opportunities can be prevented.

  (6) Another road-to-vehicle communication system of the present invention corresponds to the same problem, and is a road provided with the in-vehicle device of the present invention according to (1) to (4) and the optical beacon. In the inter-vehicle communication system, the optical beacon includes a downlink transmission and a downlink in which the identification information of the vehicle included in the uplink frame is stored after a predetermined time has elapsed since the reception of the predetermined uplink frame in the uplink frame group. It is characterized by switching.

In this case, since the optical beacon performs continuous transmission of the return frame and downlink switching after a predetermined time has elapsed since the reception of the predetermined uplink frame, the in-vehicle device transmits the return frame after completion of transmission of the uplink frame group. Can be received.
Therefore, the in-vehicle device can detect that the optical beacon has already recognized the vehicle identification information after transmitting the uplink frame group, and the in-vehicle device continuously transmits (retransmits) the uplink frame group. Loss of reception opportunities can be prevented.

  (7) Still another road-to-vehicle communication system of the present invention includes the in-vehicle device (in-vehicle device including “first information” in priority information) according to the present invention described in (2) above, and the optical beacon. In the road-vehicle communication system, the optical beacon performs downlink transmission and downlink switching in which the identification information of the vehicle included in the uplink frame is stored on condition that the priority frame is received. And

  Even in this case, if the number of subsequent frames after the last priority frame is set to be small on the in-vehicle device side, the optical beacon has already recognized the vehicle identification information even when transmitting the upstream frame group. Can be detected by the in-vehicle device after transmitting the upstream frame group.

(8) On the other hand, when the optical beacon is implemented to perform continuous transmission of return frames and downlink switching on condition that the priority frame is received, depending on the number of priority frames included in the upstream frame group and the time interval, There is a possibility that the beacon repeats downlink switching at a relatively short time interval and the processing load of communication control on the optical beacon side becomes excessive.
Therefore, when the optical beacon receives the priority frame having the same transmission source within a predetermined time, the optical beacon does not perform continuous transmission of the downlink frame storing downlink vehicle identification information and downlink switching. Is preferred.

(9) It should be noted that the conditions for continuous transmission of the return frame and downlink switching may be employed in the same optical beacon.
That is, the optical beacon that receives the priority frame as a condition for continuous transmission of the return frame and downlink switching is further configured to perform continuous transmission of the return frame on condition that the last uplink frame is received in the uplink frame group. Downlink switching may be performed.

  In this way, if the conditions for performing downlink switching, etc. are duplicated, the new in-vehicle device can be used regardless of the transmission processing even at the initial stage of operation where new in-vehicle devices performing various transmission processes coexist. It becomes easy to detect a loopback.

  (10) Further, after the optical beacon whose priority frame is received as a condition for continuous transmission of a return frame and downlink switching is after a predetermined time has elapsed since reception of the predetermined upstream frame in the upstream frame group Alternatively, continuous transmission of return frames and downlink switching may be performed. In this case as well, the same effect as in the case (9) can be obtained.

  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 frame block diagram of uplink information. It is a frame block diagram of downlink information. It is a sequence diagram which shows the communication procedure of 1st Embodiment. 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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[Definition of terms, etc.]
Here, terms used in this specification are defined.
Downlink frame DL1: A downlink frame that the optical beacon 4 repeatedly transmits toward the downlink area DA before downlink switching described later.
Uplink frame UL1: An uplink frame 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: “Low speed” generated by the in-vehicle device 2 by writing the value of the vehicle ID of the host vehicle in a predetermined storage area (for example, “Vehicle ID” (see FIG. 7) in the header of the uplink information). This is the uplink frame UL1.

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

Even if the optical beacon 4 receives the ID storage frame, there is a case where the ID return or the downlink switching is not immediately performed (for example, see FIGS. 10 and 11).
Loopback of vehicle ID: the vehicle-mounted device 2 generates an ID storage frame, uplink-transmits the generated ID storage frame, and the optical beacon 4 performs ID loopback to loop the vehicle ID to the vehicle-mounted device 2 that is the transmission source. This is a series of processing to be backed up.

Priority frame: When the in-vehicle device 2 transmits an upstream frame group composed of a plurality of upstream frames UL1, regardless of the new and old types, the low-speed upstream frame UL1 that stores the priority information to be preferentially notified to the optical beacon 4 is stored. That means.
Non-priority frame: Among a plurality of uplink frames UL1 constituting the uplink frame group, an uplink frame UL1 other than the priority frame (upstream frame UL1 having no first information among first to third information described later) I mean.

Subsequent frame: Refers to one or a plurality of upstream frames UL1 following the last priority frame among non-priority frames.
The in-vehicle device 2 according to the present embodiment includes the following first to third information as a specific example of the “priority information” in the low-speed uplink frame UL1.

First information: Trigger information that triggers downlink switching by old and new optical beacons 4 Second information: Subsystem key information used by old and new optical beacons 4 to determine the type of provision information after downlink switching Third information: Type information indicating the new and old of the vehicle-mounted device. Specific contents of the trigger information, subsystem key information, and type information will be described later.

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

Such information is also provided to old in-vehicle devices that do not support high-speed uplink transmission.
However, in the optical beacon 4 (new optical beacon) of the present embodiment, for example, the signal information including the switching timing of the signal lamp color at the intersection as the provision information for the vehicle equipped with the new in-vehicle device corresponding to the high-speed uplink transmission, It is also possible to provide dedicated information predetermined for a new vehicle-mounted device, such as charging station information indicating a route to the nearest charging station, which is useful information when the vehicle 20 is an electric vehicle (see FIGS. 9 to 12). ).

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

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

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

In the “number of subsystem key information” (hereinafter sometimes abbreviated as “number of information”), the number of “subsystem key information” stored in order from the top of the actual data portion is stored.
That is, when the number of information is zero, the “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 n 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.
As described above, the “subsystem key information” constitutes the above-described second information used by the old and new optical beacons 4 to determine the type of provision information after downlink switching.

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

For example, when the value of “vehicle equipment type” is “6”, it indicates that the transmission subject is the new vehicle equipment 2A, and when the value of “vehicle equipment type” is “other than 6”, the transmission subject is old. It shows that it is vehicle equipment 2B.
Further, when the “information type” value is “4”, it indicates that the uplink information is “high-speed”, and when the “information type” value is “other than 4” including “1”, uplink is performed. Indicates that the information is “slow”.

Therefore, when the in-vehicle device 2 (new in-vehicle device 2A) of the present embodiment transmits the “low-speed” uplink frame UL1, “6” is stored in the “in-vehicle device type” and “1” in the “information type”. Is stored.
Further, in the case of transmitting the “high-speed” uplink frame UL1, the in-vehicle device 2 (new in-vehicle device 2A) of the present embodiment stores “6” in the “in-vehicle device type” and “4” in the “information type”. Is stored.
On the other hand, when the old vehicle-mounted device 2B transmits the “low-speed” uplink frame U1, the value “other than 6” is stored in the “vehicle device type”, and the value “other than 4” is stored in the “information type”. .

Accordingly, the optical beacon 4 determines whether the transmission subject of the upstream frame UL1 is the new in-vehicle device 2A or the old in-vehicle device 2B depending on whether the value of the “on-vehicle device type” of the received upstream frame UL1 is “6” or “other than 6”. Can be determined.
Thus, the values of “6” and “other than 6” stored in the “vehicle equipment type” constitute the above-described third information that is type information for indicating whether the vehicle equipment 2 is new or old.

  The optical beacon 4 determines whether the transmission rate of the upstream frame UL1 is “high speed” or “low speed” depending on whether the value of the “information type” of the received upstream frame UL1 is “4” or “other than 4”. Can do. Then, when the optical beacon 4 receives the upstream frame UL1 having the value of “information type” other than “4”, the reception of the upstream frame UL1 triggers the reception of the vehicle ID included in the header portion of the upstream frame UL1. A return frame in which the value is stored in the lane notification information is generated, and the return frame is continuously transmitted and downlink switching is performed.

  Therefore, in this embodiment, the value of “other than 4” stored in the “information type” constitutes the above-described trigger information (first information) that triggers downlink switching by the old and new optical beacons 4.

The “last frame flag” is a storage area for indicating which of the uplink frame groups is the final frame when the in-vehicle device 2 transmits the uplink frame group including the plurality of uplink frames UL1.
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 the plurality of uplink frames UL1 constituting the uplink frame group, and other uplink frames UL1. The flag value is not stored in the frame UL1.

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

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

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

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

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

The “beacon identification flag” is a storage area indicating whether or not the own device supports high-speed uplink reception.
That is, when the optical beacon 4 is a new optical beacon 4A that 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 frames DL1 and DL2. 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 frames DL1 and DL2.

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

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

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

  As shown in road-to-vehicle communication in FIG. 9 described later, when the optical beacon 4 performs downlink switching according to the ID storage frame, the uplink transmission time of the subsequent frame and the downlink after the downlink switching are performed. Since transmission times may overlap, it is preferable that the transmittable period of the downlink frame DL2 after downlink switching is (250 + α) ms (for example, 350 ms).

[Conventional road-to-vehicle communication]
FIG. 4 is a sequence diagram showing a conventional communication procedure performed in the communication area A.
Here, in FIG. 4, a frame with a white circle indicates that the frame does not include a vehicle ID (a frame having lane notification information without a vehicle ID), and a frame with a black circle indicates an ID loopback between road vehicles. Indicates that the frame is used (upstream “ID storage frame” or downstream “folding frame”). The same applies to 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 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 transmits the low-speed uplink frame UL1 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 U1 in 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 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. 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 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 low-speed priority frames are included in the upstream frame groups U1 to U7, communication with both types of optical beacons 4 is possible without determining the old and new types of the optical beacon 4 of the communication partner.
The reason is that if the priority frame is used, the old and new optical beacons 4A and 4B can communicate with each other as usual, and even if other frames in the upstream frame group are uniformly transmitted at high speed, the old optical beacons 4B. This is because there is no particular problem just because it cannot receive it. The new in-vehicle device 2 </ b> A of the present embodiment is of a type that does not determine whether the optical beacon 4 is new or old.

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

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

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

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

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

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

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

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

[Road-to-vehicle communication according to the first embodiment]
FIG. 9 is a sequence diagram illustrating a communication procedure according to the first embodiment.
Here, U1 to U7 indicate a plurality of uplink frames (uplink frame groups) UL1 that the new vehicle-mounted device 2A that has detected the downlink frame DL1 transmits by uplink. In the example of FIG. The number is 8 frames.

However, the number of frames in the uplink frame group is arbitrary as long as transmission is possible during the uplink information transmission possible time (for example, about 130 milliseconds).
For example, as shown in FIG. 12, the uplink frame group transmitted by the in-vehicle device 2 may be configured with 11 frames, may be configured with the number of frames exceeding 11 frames, or may be configured with less than 8 frames. In some cases, the number of frames is relatively small.

In FIG. 9, an uplink frame U1 with hatching indicates a “priority frame” with a low transmission rate (64 kbps in this embodiment), and uplink frames U2 to U7 (subsequent frames) without hatching. Indicates a “non-priority frame” with a high transmission rate (256 kbps in this embodiment).
The distinction in the figure between the priority frame and the non-priority frame is the same in the road-to-vehicle communication shown in the drawings after FIG.

Note that FIG. 9 illustrates a case where the uplink transmission period of the subsequent frames U5 to U7 after the last (second in the example) priority frame U1 is relatively short.
For this reason, before the vehicle ID stored in the last priority frame U1 is first looped back from the optical beacon 4, that is, before the continuous transmission of the ID storage frame immediately after downlink switching reaches the new in-vehicle device 2A, The new in-vehicle device 2A completes the uplink transmission of the subsequent frames U5 to U7.

As shown in FIG. 9, when the new in-vehicle device 2A of the first embodiment receives the downlink frame DL1 in the downlink area DA, the priority frame U1 is immediately uplink transmitted at a low speed, and subsequently, the non-priority frame U2 Uplink transmission of ~ U4 at high speed.
Further, the new in-vehicle device 2A transmits the priority frame U1 again at a low speed after the non-priority frames U2 to U4, and then uplinks the non-priority frames U5 to U7 at a high speed.

That is, the new in-vehicle device 2A is a low-speed uplink frame UL1 storing priority information when uplink transmission of a series of uplink frames composed of a plurality of uplink frames UL1 is triggered by reception of the first downlink frame DL1. Communication control is performed to include a plurality of priority frames U1 in an upstream frame group to be transmitted to the optical transmission unit 23.
The uplink transmission of the uplink frame group is executed 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.

The new optical beacon 4A that has received the upstream frame group extracts the vehicle ID value from the header portion of the priority frame U1 triggered by the reception of the priority frame U1 included in the upstream frame group, and stores the value in the lane notification information. Perform frame continuous transmission and downlink switching.
In other words, when the new light beacon 4A detects that the value of the “information type” of the priority frame U1 is other than a predetermined value (for example, a value other than “4”), it performs continuous transmission of the return frame and downlink switching.

In the example of FIG. 9, since two priority frames U1 are included, the new optical beacon 4A (same as in the case of the old optical beacon 4B) performs repeated frame return and downlink switching twice. .
In the case of the non-priority frames U2 to U4 and U5 to U7, the value of “information type” is a predetermined value (for example, “4”) and does not include the trigger information for the continuous transmission and downlink switching. Therefore, even if the new optical beacon 4A receives the non-priority frames U2 to U4 and U5 to U7, the return optical frame is not continuously transmitted and the downlink is not switched.

Since the priority frame U1 is uplink-transmitted at a low speed, even when the communication partner of the new in-vehicle device 2A is the old optical beacon 4B, the old optical beacon 4B transmits the return frame continuously when the priority frame U1 is received. And downlink switching.
Conversely, the non-priority frames U2 to U4, U5 to U7 are uplink-transmitted at a high speed, so the old optical beacon 4B cannot receive the non-priority frames U2 to U4 and U5 to U7. For this reason, the old optical beacon 4B does not perform continuous transmission of the return frame and downlink switching triggered by reception of the non-priority frames U2 to U4 and U5 to U7.

In the road-to-vehicle communication shown in FIG. 9, depending on the frame length of the high-speed subsequent frames U5 to U7, it may be impossible to receive the return frame continuously transmitted by the old optical beacon 4B immediately after the second downlink switching. .
However, if the new in-vehicle device 2A can confirm the loopback by the return frame transmitted by downlink at predetermined intervals thereafter (every 5 frames in the example of FIG. 9), the new in-vehicle device 2A does not retransmit the uplink frame group. In this manner, it is possible to enter a receiving state for the downstream frame DL2.

  As described above, according to the new vehicle-mounted device 2A of the first embodiment (FIG. 9), the priority frame U1 which is the low-speed uplink frame UL1 storing the priority information to be notified to the optical beacon 4 with priority is transmitted to the uplink frame group. Therefore, the optical beacon 4 can receive the priority frame U1 regardless of whether the optical beacon 4 of the communication partner is old or new.

The priority information includes trigger information (first information) that triggers downlink switching by the old and new optical beacons 4A and 4B. Can be executed by the optical beacon 4.
Further, since the priority information includes subsystem key information (second information) used by the old and new optical beacons 4A and 4B to determine the type of provision information after downlink switching, the optical beacon Regardless of the new and old type 4, the type of provision information desired by the vehicle 20 can be properly detected by the optical beacon 4.

  Furthermore, according to the new in-vehicle device 2A of the first embodiment, since the priority information includes type information (third information) indicating whether the in-vehicle device 2 is new or old, steps ST3 to ST5 in FIG. As shown, when the communication partner of the new in-vehicle device 2A is the new light beacon 4A, an operation of changing the content of the provided information according to the new and old types of the in-vehicle device 2 can be adopted. Therefore, it is possible to provide appropriate information according to the new and old types of the in-vehicle device 2.

Further, according to the new in-vehicle device 2A of the first embodiment, since a plurality of priority frames U1 are included in the upstream frame group, the priority frame U1 is compared with a case where only one priority frame U1 is included in the upstream frame group. Can be transmitted to the optical beacon 4 more reliably.
For this reason, the optical beacon 4 can surely execute a predetermined process (downlink switching or determination of the type of provided information) that is necessary regardless of the new or old type of the optical beacon 4. And can communicate appropriately with the old and new optical beacons 4.

In the first embodiment described above, the priority frame U1 includes all of the first to third information. However, the priority frame U1 includes at least the first information. It is sufficient that the second and third information are not included.
Therefore, the priority frame U1 includes only the first information, the first information and the second or third information, and the first to third information. (The same applies to the following modified examples and other embodiments).

[Modification of First Embodiment]
By the way, when the new in-vehicle device 2A includes a plurality of priority frames U1 in the upstream frame groups U1 to U7, when the priority frame U1 is received as in the first embodiment (FIG. 9), the return frame is always transmitted continuously. When downlink switching is performed, the optical beacon 4 (which may be old or new) repeats its continuous transmission and downlink switching by the number of priority frames U1 included in the upstream frame groups U1 to U7. Become.

  For this reason, the new in-vehicle device 2A sets a relatively large number of priority frames U1 to be included in one upstream frame group U1 to U7. For this reason, when the time interval between the priority frames U1 is short The optical beacon 4 has to repeat downlink switching in a relatively short cycle, which may increase the processing load of communication control and prevent downlink switching at an appropriate timing.

Thus, in the first embodiment (FIG. 9), the priority frame (the source is the same) U1 after the same vehicle ID is received within a predetermined time T0 (see FIG. 9) from the reception of the previous priority frame U1. In this case, it is preferable to adopt communication control for the optical beacon 4 that does not perform continuous transmission of the return frame and downlink switching for the subsequent priority frame U1.
In this way, it is possible to prevent an increase in processing load due to the optical beacon 4 repeating the downlink switching within a relatively short time, and it is possible to reliably perform the return frame continuous transmission and the downlink switching.

The predetermined time T0 may be set to be approximately equal to or slightly longer than the time required for the optical beacon 4 to complete the downlink switching (for example, 8 ± 2 milliseconds).
The reason is that if the predetermined time T0 is set to be approximately equal to or longer than the time necessary for completing the downlink switching, the subsequent priority frame is set before the downlink switching started by the reception of the preceding priority frame U1. This is because it is possible to prevent an increase in processing load due to the start of downlink switching upon reception of U1.

[Problems when the transmission time of subsequent frames is long]
As described above, when transmitting a large amount of data such as probe information in the uplink, the data cannot often be stored in the priority frame U1. Therefore, in the example of FIG. 9, the new in-vehicle device 2A stores uplink data in a total of six non-priority frames U2 to U7 and continuously transmits them at a high speed. It is assumed that the data frame has a relatively large capacity in which information is stored.

In the conventional road-to-vehicle communication, if the optical beacon 4 receives one ID storage frame under the assumption that the large-capacity uplink transmission as described above is not performed, the return frame can be continuously transmitted and the downlink can be switched as much as possible. It is a quick operation.
For this reason, when the new optical beacon 4A performs downlink switching triggered by the reception of the priority frame U1, for example, as shown by a broken line in FIG. 9, when the transmission period of the subsequent frames U5 to U7 is relatively long (the number of frames In some cases, the return frame may reach the new vehicle-mounted device 2A during the transmission period of the subsequent frame.

In this case, the new in-vehicle device 2 </ b> A cannot detect that the new light beacon 4 </ b> A has recognized the vehicle ID even though the return frame has arrived at the light receiving unit 24. In this case, the new in-vehicle device 2A retransmits the large capacity uplink frame groups U1 to U7 including the priority frame U1 and the non-priority frames U2 to U7.
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 return 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 U7. The possibility that 2A can be received may be reduced.
Therefore, even after retransmitting the uplink frame groups U1 to U7, the new vehicle-mounted device 2A does not notice the return frame, and uplink transmission (retransmission) of the uplink frame groups U1 to U7 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 U1 to U4 is continued in the uplink area UA without noticing the return frame increases.
For this reason, as the new in-vehicle device 2A trying to uplink more data to the new optical beacon 4A, the reception opportunity of the downlink frame DL2 that is transmitted only for a limited period (for example, 250 ms) is greatly lost, In such a case, there is a possibility that an unreasonable result may occur such as 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 2 </ b> A continuously transmits the upstream frame groups U <b> 1 to U <b> 7, the event that the optical beacon 4 performs continuous transmission of the return frame and downlink switching is the final. By changing to reception of the frame U7, the problem of the first embodiment is solved.

That is, in the second embodiment (FIG. 10), the new optical beacon 4A performs downlink switching on condition that the last upstream frame U7 of the upstream frame groups U1 to U7 is received. For this reason, the new in-vehicle device 2A can always receive the return frame after completing the transmission of the upstream frame groups U1 to U7, and confirm that the new optical beacon 4A has recognized the vehicle ID after transmitting the upstream frame groups U1 to U7. It can be detected reliably.
Therefore, 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 (retransmitting) the uplink frame groups U1 to U7.

In the second embodiment (FIG. 10), when the new in-vehicle device 2A continuously transmits the subsequent frames U5 to U7, 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 U7. Abbreviated as “flag”). In FIG. 10, an upstream frame U7 indicated by a black triangle indicates that the final flag is written in the frame (the same applies to FIGS. 11 and 12).
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.

In addition, as identification information indicating that the upstream frame UL1 is the last, not only the final flag as described above but also the total number of frames and the frame number are described in the upstream frames constituting the upstream frame groups U1 to U7. Can also be done.
In this case, the new optical beacon 4A determines that the uplink frame in which the value of the total number of frames and the value of the received frame number (that is, the value of “8” in the present embodiment) match is the last uplink frame U7. Can do.

[Road-to-vehicle communication according to the third embodiment]
FIG. 11 is a sequence diagram illustrating a communication procedure according to the third embodiment.
As in the second embodiment (FIG. 10), assuming that the reception of the last uplink frame U7 is a condition for downlink switching, for example, as shown by a cross in FIG. No matter how many times the beacon 4A elapses, continuous transmission of the return frame and downlink switching are not performed, and the new in-vehicle device 2A cannot acquire the downlink frame DL2 including the provided information.

Therefore, in the third embodiment (FIG. 11), the new optical beacon 4A continues to send back and return frames after a predetermined time T1, T2 has elapsed from a predetermined frame in the upstream frame group U1 to U7. Link switching is executed.
Of the two types of predetermined times T1 and T2 shown in FIG. 11, the first predetermined time T1 starts from the time when the uplink frame was last received (the reception time of the uplink frame U6 in FIG. 11). The predetermined time T2 starts from the reception time point of the first upstream frame U1.

  As described above, when the predetermined time T1 and T2 set in advance elapses (either one of the predetermined time T1 or T2 elapses or both may elapse), the return frame is continuously transmitted and the downlink. If switching is to be performed, it is possible to prevent the new optical beacon 4A from performing the continuous transmission and downlink switching because it is unknown which is the last uplink frame U7. it can.

Therefore, when the condition for performing downlink switching is the reception of the last uplink frame U7, it is preferable that the passage of the predetermined times T1 and T2 from the predetermined frame is also set as the condition.
However, in the third embodiment (FIG. 11), the new optical beacon 4A does not adopt the reception of the last uplink frame U7 as a condition for performing downlink switching, but only the passage of the predetermined times T1 and T2 from the predetermined frame. It may be adopted.

  Note that, in the third embodiment (FIG. 11), when the implementation in which the total number of frames and the frame number are written in each uplink frame UL1 constituting the uplink frame group is adopted, the first uplink frame U1 or the last uplink frame is used. The elapse of “predetermined time” from the start of reception of an arbitrary upstream frame UL1 as well as U7 can be triggered by continuous transmission of downlink frames and downlink switching.

[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 shown in FIG. 12, in the fourth embodiment, when the new optical beacon 4A receives the priority frame U1, the communication control of the first embodiment (FIG. 9) that performs downlink switching and the second frame when the final frame U10 is received. Both of the communication control of the embodiment (FIG. 10) are executed.

In the example of FIG. 12, since the two priority frames U1 are included in the uplink frame groups U1 to U10, the new optical beacon 4A performs downlink switching twice in response to the reception, and the last uplink frame U10. In response to this reception, downlink switching is performed once, and downlink switching is performed three times in total.
In this way, if the new optical beacon 4A overlaps the conditions for downlink switching, the new in-vehicle device can be used regardless of the transmission processing even if the new in-vehicle device 2A that implements various types of transmission processing is mixed. There is an advantage that the machine 2A can easily detect the loopback of the vehicle ID.

  Also in the fourth embodiment (FIG. 12), in order to prevent an increase in processing load due to repeated switching of the downlink by the new optical beacon 4A in a relatively short time, a predetermined time from the reception of the previous priority frame U1. In Ta (see FIG. 12), if a priority frame U1 with the same vehicle ID (and hence the same transmission source) U1 is received, a return frame is continuously transmitted and downlink switching is performed for the subsequent priority frame U1. The communication control that does not exist may be adopted for the new light beacon 4A.

  For the same reason, when the last frame U10 is received within a predetermined time Tb (see FIG. 12) from the reception of the last priority frame U1, the return frame is continuously transmitted and the downlink is switched for the last frame U10. Communication control that is not performed may be adopted in the new light beacon 4A.

[Modification of Fourth Embodiment]
In the fourth embodiment (FIG. 12), when the new optical beacon 4A receives the priority frame U1, the second embodiment (FIG. 9) performs communication control in the first embodiment (FIG. 9) in which downlink switching is performed and the final frame U10 is received. Although both communication control of FIG. 10) is performed, you may decide to use together the communication control of 1st Embodiment (FIG. 9), and 3rd Embodiment (FIG. 11).

  That is, the new optical beacon 4A receives the priority frame U1 and performs communication control in the first embodiment (FIG. 9) that performs downlink switching, and a predetermined time T1, from a predetermined frame in the uplink frame groups U1 to U7. You may decide to perform both communication control of 3rd Embodiment (FIG. 11) which performs downlink switching after progress of T2.

[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 new in-vehicle device 2A continuously transmits a plurality of uplink frames U1 to U7, but burst transmission is performed with an interval of a predetermined time length between frames. Also good.

However, in the above-described third embodiment (FIG. 11), it is necessary to set intervals between a plurality of uplink 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.

  The “in-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 mounted on the vehicle 20. Is included.

As in the first embodiment (FIG. 9) described above, when the downlink switching including continuous transmission of the return frame is performed immediately after receiving the plurality of priority frames U1, the new in-vehicle device 2A performs continuous transmission of the return frame. If it cannot be received, the new in-vehicle device 2A can recognize the loopback only by receiving a return frame sent at a constant frequency in the downstream 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.

In the first embodiment (FIG. 9) described above, the new in-vehicle device 2A may be able to specify at what timing the new light beacon 4A wants to perform downlink switching.
That is, for example, a storage area for requesting downlink switching is provided in the uplink frame UL1, and at the timing when the uplink frame U1 with the flag of the storage area is received, the new optical beacon 4A You may make it perform operation | movement, such as a continuous transmission of a return | turnback frame.

As the storage area, for example, “type information” (see FIG. 7) in the header can be used.
As described above, if the information type value is an uplink frame other than a predetermined value, the new light beacon 4A determines that the uplink frame is low speed and performs downlink switching, and the information type value is a predetermined value. In this case, it is determined that the uplink frame is high speed, and downlink switching is not performed.

  For this reason, when the new in-vehicle device 2A transmits a plurality of priority frames U1 at a low speed, the information type value of only one priority frame U1 is set to a value other than a predetermined value among the plurality of priority frames U1. If the value of the information type of the other priority frame U1 is set to a predetermined value, it is possible to cause the new light beacon 4A to perform downlink switching by one priority frame U1 arbitrarily selected on the in-vehicle device 2 side.

  Further, when the number of priority frames U1 transmitted by the new in-vehicle device 2A is two in total, for example, the new in-vehicle device 2A has a transmission interval from the first priority frame U1 to the second priority frame U1. If it is relatively long, the downlink switching by the first priority frame U1 can be omitted by requesting the downlink switching only by the second priority frame U1.

  In addition, even when the total number of uplink frames transmitted by the new in-vehicle device 2A is about 10, for example, the optical beacon 4 needs a predetermined time (for example, 10 ms) to perform downlink switching. If it is known, the priority frame U1 including downlink switching request information may be transmitted when the period required for transmitting the uplink frame UL1 is 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 by the in-vehicle device 2, the timing when the optical beacon 4 performs downlink switching. In this case, downlink switching may be executed at the timing when the final uplink frame U7 is received. Further, as shown in FIG. 11, a method of performing downlink switching after elapse of a predetermined time T1 after the last reception of the uplink frame U4 may be used in combination.

2 Onboard unit 2A New onboard unit 2B Old onboard unit 4 Optical beacon 4A New optical beacon 4A Old optical beacon 7 Beacon controller (communication control unit)
8 Beacon head 10 Optical transmission unit 11 Optical reception unit 20 Vehicle 21 In-vehicle controller (communication control unit)
22 On-vehicle head 23 Optical transmitter 24 Optical receiver

Claims (10)

An in-vehicle device that performs wireless communication with an optical beacon and an optical signal installed on a road,
An optical transmitter capable of electro-optical conversion at two transmission speeds, high and low,
An optical receiver capable of photoelectric conversion at a predetermined transmission rate;
A communication control unit including a plurality of priority frames, which are low-speed uplink frames storing priority information to be preferentially notified to the optical beacon, in an uplink frame group to be transmitted to the optical transmission unit;
An in-vehicle device characterized by comprising: The priority information includes only the following first information, the following first information and the second or third information, or all the following first to third information. In-vehicle machine.
First information: Trigger information that triggers downlink switching by old and new optical beacons Second information: Subsystem key information used by old and new optical beacons to determine the type of provided information after downlink switching Information: Type information indicating the new and old of the in-vehicle device   The in-vehicle device according to claim 2, wherein the communication control unit sets an uplink frame other than the priority frame in the uplink frame group as a non-priority frame that does not store the first information.   The communication control unit causes the optical transmission unit to uplink transmit the priority frame at a low speed, and causes the optical transmission unit to uplink transmit other uplink frames at a high speed. The in-vehicle device described. A road-to-vehicle communication system comprising the in-vehicle device according to claim 1 and the optical beacon,
The optical beacon performs continuous transmission of a downlink frame storing downlink vehicle identification information included in the uplink frame and downlink switching on condition that the last uplink frame in the uplink frame group is received. Road-to-vehicle communication system. A road-to-vehicle communication system comprising the in-vehicle device according to claim 1 and the optical beacon,
The optical beacon performs continuous transmission of a downlink frame and downlink switching after storing a predetermined time from reception of a predetermined uplink frame in the uplink frame group and storing vehicle identification information included in the uplink frame. A road-vehicle communication system characterized by the above. A road-to-vehicle communication system comprising the in-vehicle device according to claim 2 and the optical beacon,
The road-to-vehicle communication system, wherein the optical beacon performs continuous transmission and downlink switching of a downlink frame storing vehicle identification information included in an uplink frame on condition that the priority frame is received.   6. The optical beacon does not perform continuous transmission of a downlink frame and downlink switching in which identification information of a vehicle included in an uplink frame is stored when the same priority frame is received within a predetermined time. The road-to-vehicle communication system described in 1.   The optical beacon performs continuous transmission and downlink switching of a downlink frame storing vehicle identification information included in the uplink frame on condition that the last uplink frame in the uplink frame group is received. The road-to-vehicle communication system described in 1.   The optical beacon performs continuous transmission and downlink switching of a downlink frame storing vehicle identification information included in the uplink frame after a predetermined time has elapsed since the reception of the predetermined uplink frame in the uplink frame group. The road-to-vehicle communication system according to claim 7 or 8.

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