JP5995316B2 - Light beacon - Google Patents

Description

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

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

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

  On the other hand, as part of the safe driving support system (DSSS) using optical beacons, the reference position of the communication area of the optical beacon, the stop line position of the downstream intersection, the uplink position (the optical beacon has been received) “UL position correction information” (hereinafter sometimes referred to simply as “position correction information”) up to link information (uplink frame transmission position), and cumulative transmission frames of downlink information (downlink frames) after downlink switching The number of “DL transmission frames” that is the number and “signal information” that is the scheduled number of seconds of the signal at the intersection may be included in the downlink frame as “safe driving support information”.

The vehicle-mounted device provided with such information subtracts the distance obtained from the distance of the position correction information and the number of DL transmission frames from the distance from the reference position to the stop line position, thereby obtaining the stop line position from the current vehicle position. Can be obtained accurately.
In this case, since the distance to the stop line position can be accurately obtained, it is possible to accurately execute the assist control for safe driving such as urging the driver to prevent the vehicle from entering the intersection immediately before the red signal. .

JP 2005-268925 A

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

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

  Therefore, in order to ensure upward compatibility of the new vehicle-mounted device, a conventional vehicle-mounted device that performs only low-speed uplink transmission (hereinafter referred to as “old vehicle-mounted device”) before the new vehicle-mounted device transmits high-speed uplink information. Similarly, if the communication protocol of transmitting low-speed uplink information storing vehicle identification information (hereinafter also referred to as “vehicle ID”) is adopted, the old optical beacon can also perform downlink switching. The new in-vehicle device can communicate with the old optical beacon.

  By the way, when a plurality of uplink information is transmitted by one road-to-vehicle communication, such as when a new in-vehicle device transmits high-speed uplink information after low-speed uplink information, a subsequent uplink is performed. When “position correction information” that is dynamically updated each time the transmission position (uplink position) of information is obtained is included in downlink information regardless of the timing of downlink switching based on the first low-speed uplink information The relationship between the “position correction information” and the “number of DL transmission frames” is lost, and there is a problem that it is impossible to accurately calculate the actual distance using these pieces of information.

  In the above, the relationship between the “position correction information” and the “number of DL transmission frames” is broken. Specifically, the “number of DL transmission frames” is based on the uplink information at the time of downlink switching. In contrast, “position correction information” refers to a case where uplink information at the time of downlink switching is not a reference.

  In order to eliminate such inconvenience, downlink switching is performed not only when low-speed uplink information is received but also when subsequent high-speed uplink information is received. If the starting point of “the number of frames” is made to correspond to the time when high-speed uplink information is received, it is possible to achieve consistency with “position correction information”.

  However, if the transmission time becomes longer or the number of transmission frames increases due to the increase in capacity of the high-speed uplink information, it is a problem at which point in time during transmission the “position correction information” is generated using the uplink position. It becomes. The time difference between the uplink information transmission time at the uplink position, which is the reference for the “position correction information”, and the downlink information transmission time, which is the starting point for the number of DL transmission frames, is the distance from the vehicle position to the stop line position. Since this is an error in obtaining it, it is desirable to make the error as small as possible in order to accurately perform safe driving support.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a DSSS-compatible optical beacon that can provide accurate safe driving support information to an in-vehicle device.

(1) The present invention is an optical beacon that performs wireless communication with an in-vehicle device of a running vehicle by an optical signal,
An optical receiver including a light receiving element that converts an upstream optical signal constituting uplink information into an electrical signal;
An optical transmission unit including a light emitting element that converts an electrical signal into a downlink optical signal constituting downlink information;
A communication control unit capable of executing downlink switching triggered by reception of the uplink information and generating an uplink position that is a transmission position of the uplink information;
The communication control unit includes a transmission position of a final frame of the uplink information including a plurality of frames as the uplink position in the downlink information after downlink switching.

According to the present invention, the transmission position of the last frame among the uplink information composed of a plurality of frames can be included in the downlink information after downlink switching as the uplink position , so that it becomes the reference for “position correction information”. The time difference between the transmission point of uplink information at the link position and the transmission point of downlink information that becomes the starting point of the number of DL transmission frames after downlink switching triggered by this uplink information can be made as small as possible. it can. Therefore, distance information (such as the distance between the vehicle position and the stop line position) for safe driving support can be accurately obtained using the “position correction information” and the “number of DL transmission frames”.
In the present invention, as an example of “including the uplink position in the downlink information”, when the uplink position is included in the downlink information as it is, or “position correction information calculated using the uplink position” In some cases, it is included in downlink information.

(2) Moreover, this invention is an optical beacon which performs radio | wireless communication with the vehicle-mounted apparatus of the vehicle in driving | running | working by an optical signal,
An optical receiver including a light receiving element that converts an upstream optical signal constituting uplink information into an electrical signal;
An optical transmission unit including a light emitting element that converts an electrical signal into a downlink optical signal constituting downlink information;
A communication control unit capable of executing downlink switching triggered by reception of the uplink information and generating an uplink position that is a transmission position of the uplink information;
It said communication control unit includes a feature to include transmission position of the last frame of the uplink information of a single frame of data size exceeding 74 bytes, to the downlink information after downlink switching as the uplink position To do.

According to the “near infrared interface standard” of the current optical vehicle detector (optical beacon), an in-vehicle device adopting the half-duplex method takes one frame of uplink information having a data size of up to 74 bytes. Only supposed to send. On the other hand, in the present invention, in order to maintain the compatibility with the conventional optical beacon while increasing the capacity of the uplink information, after the transmission of the conventional uplink information (old uplink information), the capacity is continuously increased. It is conceivable to transmit normalized uplink information (new uplink information). In this case, new uplink information exceeding 74 bytes, which is the maximum size of the old uplink information, may be transmitted in a single frame. In the present invention, when uplink information of a single frame exceeding 74 bytes different from the old uplink information is received, the frame itself becomes the final frame, and the transmission position of the final frame is acquired as the uplink position. can do.

(3) It is preferable that the communication control unit includes the uplink position acquired from the second half part of the final frame in the downlink information.
With such a configuration, the time difference between the time when uplink information serving as a reference of “position correction information” is transmitted and the time when downlink information serving as the starting point of the number of DL transmission frames is transmitted is more reliably reduced. be able to.

(4) The communication control unit may include the uplink position adopted with reference to the end side of the last frame in the downlink information.
(5) In this case, the uplink position to be included in the downlink information is acquired from the last plurality of uplink positions acquired for the last frame before the n1th (however, n1: a predetermined constant). It is preferable to be in the uplink position.

  The communication control unit converts the optical signal (uplink light) received by the optical receiving unit into an electrical signal, and acquires the plurality of uplink positions in time series by reading the electrical signal at a predetermined sampling period. On the other hand, when the uplink light received by the optical receiver is converted into an electrical signal, the generation of the electrical signal may not be stopped immediately even if the uplink light is terminated depending on the tracking performance (response performance) of the conversion circuit. is there. In this case, the electrical signal is generated even after the end of the uplink light, and the uplink position can be obtained from the electrical signal generated after the end of the uplink light. Thus, since the uplink position acquired after the end of the uplink light is different from the actual uplink position, it is desired not to include it in the downlink information.

  Therefore, in the present invention, for example, “n1” is set in advance as a value that does not include the uplink position acquired after the end of the uplink light, and the uplink position acquired from the last n1 before the last frame is reduced. By including in the link information, it is possible to exclude the uplink position acquired after the end of the uplink light, and more reliably include the actual uplink information transmission position as the uplink position in the downlink information.

(6) In addition, the uplink position included in the downlink information is a predetermined number that satisfies the n2th or later from the last among a plurality of uplink positions acquired for the last frame (however, n2: (n2 ≧ n1)) It may be the uplink position acquired in (constant).
In the case of the above (5), since only the rear boundary value of the uplink position that can be included in the downlink information among the plurality of uplink positions acquired for the last frame is defined, There is a possibility that the uplink position acquired on the front side may be adopted as the uplink position included in the downlink information. For this reason, in the present invention, “n2” which is the boundary value on the front side is set in advance so that the uplink position acquired on the rear side of the last frame can be adopted.

  Note that by setting n2 = n1, the n1 (= n2) th specific uplink position from the end can be adopted as the uplink position included in the downlink information. In addition, when the electrical signal conversion circuit in the optical receiving unit has high tracking performance with respect to the optical signal, the communication control unit can discard the uplink position acquired after the uplink light is terminated. In the case of the configuration, it is also possible to adopt the uplink position acquired last (n1 = n2 = 1) as an uplink position to be included in the downlink information as it is.

(7) Uplink positions to be included in the downlink information are more than t1 hours before completion of reception of the last frame among a plurality of uplink positions acquired for the last frame (however, t1: a predetermined constant) ) May be the uplink position acquired.
In this case as well, the uplink position acquired after the end of the uplink light is reduced by presetting a time “t1” that does not include the uplink position acquired after the end of the uplink light. It can be excluded from the link information.

(8) Uplink positions included in the downlink information are t2 hours before the reception completion time of the last frame among a plurality of uplink positions acquired for the last frame (however, t2: (t2 ≧ It may be the uplink position acquired at a predetermined constant satisfying t1).
In the case of (7) above, only the rear boundary value of the uplink position that can be included in the downlink information among the plurality of uplink positions acquired for the last frame is defined. There is a possibility that an uplink position acquired at an earlier time may be adopted as an uplink position included in the downlink information. Therefore, in the present invention, by setting “t2” as the front boundary value in advance, the uplink position acquired at a later time of the final frame can be adopted.
In the case of t2 = t1 (or t1≈t2), a specific uplink position acquired before time t1 (= t2) from the reception completion time of the last frame can be adopted. Also, when the electrical signal conversion circuit in the optical receiver has high follow-up performance with respect to the optical signal, or when the communication controller can accurately recognize when the uplink light ends (reception completion time) Is the last acquired uplink by setting t1 as the end time of the uplink light and t2 as the time immediately before that (for example, a time equivalent to the sampling period of the uplink position). The position can be adopted as an uplink position to be included in the downlink information as it is.

(9) The communication control unit may include an uplink position adopted with reference to a head side of the last frame in the downlink information.
(10) In this case, the uplink position included in the downlink information is acquired from the first N1 or later (where N1: a predetermined constant) among the plurality of uplink positions acquired for the last frame. It may be an uplink position.
In the header portion of the frame constituting the uplink information, a description regarding the data length of the frame is made, and when the reception of the frame is started, the reception completion time of the frame can be predicted. Therefore, the uplink position acquired at a position close to the reception completion time of the final frame by adopting the uplink position after the predetermined number (N1) from the beginning in consideration of the predicted reception completion time of the final frame. Can be included in the downlink.

(11) The uplink position included in the downlink information is N2 before the first among a plurality of uplink positions acquired for the last frame (however, N2: a predetermined constant that satisfies (N2 ≧ N1)) May be the uplink position acquired.
In the case of (10) above, only the front boundary value of the uplink position that can be included in the downlink information among the plurality of uplink positions acquired for the last frame is defined. There is a possibility that the uplink position acquired after the end point is adopted. Therefore, in the present invention, by setting “N2” as the rear boundary value in advance, the actual uplink information transmission position can be more reliably included in the downlink information as the uplink position.

(12) The uplink position to be included in the downlink information is after a time T1 from the reception start time of the final frame among a plurality of uplink positions acquired for the final frame (where T1: a predetermined constant). It may be the acquired uplink position.
In this case as well, in the same manner as described above, by adopting an uplink position after a predetermined time (T1) from the reception start time in consideration of the predicted reception completion time of the last frame, the reception of the final frame is completed. The uplink position acquired at a close position can be included in the downlink information.

(13) The uplink position included in the downlink information is T2 hours before the reception start time of the final frame among the plurality of uplink positions acquired for the final frame (provided that T: (T2 ≧ The uplink position acquired at a predetermined constant satisfying T1) may be used.
In the case of (12) above, only the front boundary value of the uplink position that can be included in the downlink information among the plurality of uplink positions acquired for the last frame is defined. There is a possibility that the uplink position acquired after the end point is adopted. Therefore, in the present invention, by setting in advance “T2” that is the rear boundary value, the transmission position of the actual uplink information can be more reliably included in the downlink information as the uplink position.

  According to the optical beacon of the present invention, it is possible to provide a DSSS-compliant optical beacon that can provide accurate safe driving support information to the in-vehicle device.

It is a block diagram which shows schematic structure of a road-vehicle communication system. It is the top view of the road which looked at the installation part of an optical beacon from the top. It is a side view which shows the communication area | region of an optical beacon. It is a sequence diagram which shows the conventional communication procedure. It is a figure which shows the mixed state of the old and new optical beacons and vehicle equipment. It is a flowchart which shows upward compatible control of a new light beacon. It is a frame block diagram of uplink information. It is a frame block diagram of downlink information. It is a sequence diagram which shows the road-to-vehicle communication when not providing a transmission interruption period. It is a sequence diagram which shows the road-to-vehicle communication in the case of providing a transmission interruption period. It is explanatory drawing which shows an example of the provision information in a safe driving assistance system. It is a circuit block diagram of the new light beacon which concerns on 1st Embodiment. It is explanatory drawing of the measurement principle of an uplink position using a position detection element. It is a sequence diagram which shows the communication procedure of 1st Embodiment. It is a time chart which shows the example of a timing of the communication procedure of 1st Embodiment. It is a time chart for demonstrating the acquisition method of an uplink position. It is a flowchart which shows an example of the process which acquires an uplink position by main CPU. It is a flowchart which shows an example of a process in case an uplink position is acquired by a communication process part. It is a circuit block diagram of the new light beacon which concerns on 2nd Embodiment. It is explanatory drawing of the measurement principle of an uplink position using division | segmentation PD. It is a circuit block diagram of the new light beacon which concerns on 3rd 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 includes a light emitting element that transmits downlink light (downlink direction (downlink) optical signal) made of near infrared rays to the downlink area DA (see FIG. 3). Has a light receiving element that receives uplink light (uplink direction (upstream) optical signal) made of near infrared rays from the vehicle-mounted device 2 in the uplink area UA (see FIG. 3).

The optical transmission unit 10 converts a downlink information (downlink frame) transmitted from the beacon controller 7 into a serial transmission signal having a predetermined transmission rate, and the output transmission signal is an optical signal in the downlink direction. It is comprised from the light emitting element which consists of a light emitting diode etc. which convert into.
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.
When the uplink area UA is set to be wider in this way, 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 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 converts an uplink information (uplink frame) output from the in-vehicle controller 21 into a serial transmission signal having a predetermined transmission rate, and the output transmission signal is an optical signal in the uplink direction. It is comprised from the light emitting element which consists of a light emitting diode etc. which convert into.
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 travel data of the host vehicle (for example, probe information that is travel trajectory data in which passage positions and passage times are arranged in time series) as uplink information, and the optical transmission unit 23. It also has a function of transmitting to the uplink.
In this case, by increasing the transmission speed of the uplink information, more probe information (such as a road section that records the travel locus is lengthened, or the recording density of the passing position and passing time in the same road section is increased. Information) can be transmitted.

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 frame of downlink information that the optical beacon 4 repeatedly transmits toward the downlink area DA before downlink switching described later.
Up frame UL1: A frame having a low transmission rate among frames of uplink information transmitted by the in-vehicle device 2 in response to reception of the downlink frame DL1. Also referred to as “low speed frame UL1”.

Uplink frame UL2: A frame having a high transmission rate among uplink information frames (including a case of a series of frame groups) transmitted by the vehicle-mounted device 2 in response to reception of the downlink frame DL1. Also referred to as “high-speed frame UL2”.
When the vehicle-mounted device 2 is a new vehicle-mounted device 2A (see FIG. 5) that supports transmission of the high-speed frame UL2, both the low-speed frame UL1 and the high-speed frame UL2 can be transmitted as the upstream frame, and the vehicle-mounted device 2 can transmit the high-speed frame UL2. In the case of the old vehicle-mounted device 2B that does not support transmission (see FIG. 5), only the low-speed frame UL1 can be transmitted as an upstream frame.

Downlink frame DL2: A frame of downlink information (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: Up-link frame UL1, which is generated by 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” in the header portion of the uplink information (see FIG. 7)) It refers to UL2.

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

When the optical beacon 4 receives the ID storage frame, there is a case where the downlink switching is performed without continuously transmitting the return frame (for example, refer to the second downlink switching shown in FIG. 14).
Loopback of vehicle ID: the vehicle-mounted device 2 generates an ID storage frame, uplink-transmits the generated ID storage frame, and the optical beacon 4 performs ID loopback to loop the vehicle ID to the vehicle-mounted device 2 that is the transmission source. This is a series of processing to be backed up.

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

These pieces of information are also provided to old in-vehicle devices that are not compatible with transmission of the high-speed frame UL2.
However, in the optical beacon 4 (new optical beacon) of the present embodiment, for example, a signal including a signal lamp color switching timing at an intersection is provided as information provided for a vehicle equipped with a new in-vehicle device that supports transmission of a high-speed uplink frame UL2. It is also possible to provide dedicated information predetermined for a new vehicle-mounted device, such as information and charging station information indicating a route to the nearest charging station, which is useful information when the vehicle 20 is an electric vehicle (FIG. 9 and FIG. 9). (See FIG. 10).

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

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

As shown in FIG. 7, in the case of the uplink frame UL1, 1 byte is allocated to the synchronization section, 10 bytes are allocated to the header section, 59 bytes are allocated to the actual data section, and 4 bytes ( 1 byte idle part + 2 bytes CRC + 1 byte final synchronization part). Therefore, the maximum data size of the upstream frame UL1 is 74 bytes. For example, a data string of 0x7E (= 01111110) is stored in the head synchronization unit and the last synchronization unit of the uplink frame UL1, and the header portion of the uplink information includes “number of subsystem key information”, “vehicle ID”, Storage areas such as “vehicle equipment type”, “information type”, and “last frame flag” are included.

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

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

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

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

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

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

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

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

In addition, when the new light beacon 4A of the present embodiment completes reception of the low-speed frame UL1 from the new in-vehicle device 2A, it generates a return frame in which the value of the vehicle ID included in the header portion is stored in the lane notification information, and this frame Downlink switching with continuous transmission of.
Furthermore, the new light beacon 4A also performs downlink switching when the reception of the high-speed frame UL2 from the new in-vehicle device 2A is completed. In this case, continuous transmission of the return frame may be further performed, or the continuous transmission may not be performed.

Thus, the completion of reception of the low-speed frame UL1 from the new in-vehicle device 2A is a condition for the new light beacon 4A to perform downlink switching with continuous transmission of the return frame. The completion of reception of the high-speed frame UL2 from the new in-vehicle device 2A is also a condition for the new light beacon 4A to perform downlink switching with or without continuous transmission of the return frame.
Note that when the communication partner of the new optical beacon 4A is the old in-vehicle device 2B, the high-speed frame UL2 is not received, so that the downlink switching according to the completion of the reception of the high-speed frame UL2 is not naturally performed.

The “last frame flag” is used to indicate which of the uplink frames is the final frame when the in-vehicle device 2 (which may be new or old) transmits an uplink frame group including a plurality of uplink frames UL2. Storage area.
That is, the in-vehicle device 2 stores a predetermined flag value (for example, “1”) only in the “final frame flag” of the last frame among a plurality of uplink frames UL constituting the uplink frame group, and other uplink frames UL The flag value is not stored in the frame UL.

  In the present embodiment, the low-speed frame UL1 transmitted by the new and old vehicle-mounted devices 2 is composed of a single upstream frame having a maximum of 74 bytes. The high-speed frame UL2 transmitted by the new vehicle-mounted device 2A is composed of a single upstream frame having a data size larger than the low-speed frame UL1 (exceeding 74 bytes), or a plurality of upstream frames (upstream frames). Consists of. In the latter case, the total data size of the plurality of upstream frames UL2 is not necessarily larger than the maximum data size of the low-speed frame UL1, and may be the same as or smaller than this.

[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 portion of the downlink frames DL1 and DL2, any one of various information shown in FIG. 8 is stored as provision information for the vehicle 20.

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

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

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

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

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

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

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

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

[Conventional road-to-vehicle communication]
FIG. 4 is a sequence diagram showing a conventional communication procedure performed in the communication area A.
Here, in FIG. 4, a frame with a white circle indicates that the frame does not include a vehicle ID (a frame having lane notification information without a vehicle ID), and a frame with a black circle indicates an ID loopback between road vehicles. Indicates that the frame is used (upstream “ID storage frame” or downstream “folding frame”). The same applies to FIGS. 9 to 11.

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

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

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

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

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

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

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

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

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

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

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

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

Specifically, as described above, the old and new optical beacons 4 are included in the “lane notification information” (see FIG. 8) (refer to FIG. 8) of the downlink frames DL1 and DL2 to be transmitted by the optical transmission unit 10 in the downlink. A flag field indicating the type is defined in advance.
When the beacon controller 7 operates as the new optical beacon 4A, the beacon controller 7 turns on the flag fields of all the downlink frames DL1 and DL2 to be repeatedly transmitted or the downlink frames DL1 and DL2 for each predetermined period. Is operated as the old optical beacon 4B, the flag fields of the downstream frames DL1 and DL2 are turned off.

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

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

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

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

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

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

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

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

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

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

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

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

In FIG. 9, U0 to U3 indicate a plurality of upstream frames (upstream frame groups) UL1 and UL2 that are transmitted by the new vehicle-mounted device 2A that has detected the downstream frame DL1.
In FIG. 9, the number of frames in the upstream frame group is 4, but the number of frames is not limited to 4, for example, 3 or more high-speed frames UL2 may be transmitted, There may be a case where only one high-speed frame UL2 having a relatively long data length is transmitted.

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

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

In the present embodiment, since it is assumed that the new in-vehicle device 2A does not determine whether the communication partner is new or old, continuous transmission of the low-speed frame U0 and the high-speed frames U1 to U3 is performed by the communication partner of the new in-vehicle device 2A. It is executed regardless of whether the beacon 4A or the old optical beacon 4B.
The optical beacon 4 of the communication partner of the new in-vehicle device 2A extracts the vehicle ID value from its header part upon completion of reception of the low-speed frame U0 included in the upstream frame group, and stores the value in the lane notification information. Perform frame continuous transmission and downlink switching.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[Contents provided by DSSS and their problems]
FIG. 11 is an explanatory diagram illustrating an example of provision information in the safe driving support system (DSSS).
In FIG. 11, P0 is a “reference position” representing a representative point of the uplink area UA, and P1 is a predetermined object (for example, a stop line at an intersection) that is located downstream from the uplink area UA. A “predetermined position” representing a representative point is shown.

In FIG. 11, h1 is also referred to as a transmission position (hereinafter referred to as “first uplink position”) of the upstream frame UL1 detected by the optical beacon 4 as infrared light (thus, it is not necessary to extract data contents). H2 indicates the transmission position of the upstream frame UL2 detected by the optical beacon 4 as infrared light (hereinafter also referred to as “second uplink position”).
h3 indicates the reception start position (hereinafter also referred to as “downlink position”) of the downlink frame DL2 successfully received by the in-vehicle device 2.

Furthermore, in FIG. 11, L0, Lh1, Lh2, Ln, and L represent the following distances, respectively.
L0: Distance from the reference position P0 to the predetermined position P1 Lh1: Distance from the reference position P0 to the first uplink position h1 Lh2: Distance from the reference position P0 to the second uplink position h2 Ln: First up Distance from link position h1 to downlink position h3 L: Actual distance from downlink position h3 to predetermined position P1

In DSSS, the optical beacon 4 includes “safe driving support information” in a part of a real data part of a plurality of downlink frames DL2 repeatedly transmitted after downlink switching.
The “safe driving support information” includes static information (fixed) including the coordinates of the positions P0 and P1 so that the in-vehicle device 2 can perform safe driving support control such as urging the driver to brake before the intersection. Value) and "signal information" which is dynamic information indicating the estimated number of seconds of the signal at the intersection.

However, as shown in FIG. 11, it is the downlink position h3 that the in-vehicle device 2 actually acquires the downlink frame DL2 including the safe driving support information.
For this reason, even if only the reference position P0 and the predetermined position P1 are provided to the vehicle-mounted device 2, the vehicle-mounted device 2 cannot obtain the actual distance L shortened by the movement to the downlink position h3. The distance from the current position of the vehicle 20 to the predetermined position P1 becomes inaccurate, and safe driving support cannot be performed correctly.

  Therefore, in DSSS, the following “UL position correction information” and “DL transmission frame number” are used as dynamic information calculated by the optical beacon 4 for each communication with the in-vehicle device 2 as well as the fixed value road linear information. Include in safe driving support information.

"UL position correction information"
The “UL position correction information” is information indicating a difference between the uplink position h1 where the positional deviation occurs due to individual differences in light amount for each in-vehicle device 2 or communication timing (communication cycle) and the fixed reference position P0. The distance Lh1 in FIG. 11 corresponds to this. That is, the “position correction information” expresses the uplink position h1 as a distance value in the vehicle traveling direction starting from the reference position P0.
When the optical beacon 4 detects the upstream frame UL1 as infrared light, the optical beacon 4 measures the transmission position of the optical signal to generate the position correction information Lh1, and includes the generated position correction information Lh1 in the safe driving support information.

"Number of DL transmission frames"
When the optical beacon 4 receives the uplink frame UL1, it performs downlink switching immediately (10 ms or less), and therefore the moving distance Ln from the uplink position h1 to the downlink position h3 is usually relatively small.
However, there is a case where the in-vehicle device 2 fails to receive the downlink frame DL2 due to the shielding caused by the wiper operation of the vehicle 20 or direct sunlight, and in this case, the moving distance Ln cannot be ignored. Become bigger.

Therefore, in DSSS, in order to be able to correct the actual distance L by calculating the moving distance Ln on the in-vehicle device 2 side, it is the cumulative number of transmission frames accumulated from the start of downlink transmission of the downlink frame DL2. The number of DL transmission frames ”is included in the safe driving support information.
The transmission time for one frame of the downstream frame UL2 is about 1 ms. Therefore, when the number of DL transmission frames is n and the vehicle speed is V, the moving distance Ln from the uplink position h1 to the downlink position h3 can be obtained by a calculation formula of Ln = V × n × 1 msec.

In the above-mentioned DSSS communication protocol, it is an implicit premise that only one uplink frame UL1 is transmitted assuming the case of the old vehicle-mounted device 2B.
In this case, the vehicle-mounted device 2 can correctly calculate the actual distance L using the calculation formula L = L0−Lh1−Ln.

  On the other hand, when the new in-vehicle device 2A transmits the high-speed frame UL2 after the low-speed frame UL1 as in the present embodiment, the new light beacon 4A ensures compatibility with the old in-vehicle device 2B. If downlink switching is performed in response to reception of frame UL1, but downlink switching is not performed in high-speed frame UL2, "DL transmission frame count" is based on uplink frame UL1 at the time of downlink switching. On the other hand, since the “position correction information” is not based on the uplink frame UL1 at the time of downlink switching, the relationship between the “position correction information” and the “number of DL transmission frames” is lost. There is a problem that the actual distance L cannot be accurately calculated using.

That is, in the example of FIG. 11, the “number of DL transmission frames” is provided in response to the reception of the uplink frame UL1 accompanied by downlink switching, but the “position correction information” is sequentially updated regardless of downlink switching. Is done.
For this reason, when the new optical beacon 4A updates the position correction information from Lh1 to Lh2 and provides it to the new in-vehicle device 2A by the high-speed frame UL2 received later, the new in-vehicle device 2A is L = L0−Lh2-Ln. Thus, the actual distance L is calculated by the erroneous calculation formula, and the actual distance L cannot be calculated accurately.

  Therefore, in this embodiment, the new light beacon 4A performs downlink switching not only when the low-speed frame UL1 is received but also when the high-speed frame UL2 is received, and the criterion of the “number of DL transmission frames” is determined. In addition to the high-speed frame UL2, position correction information Lh2 regarding the transmission position of the high-speed frame UL2 is included in the downlink frame DL2. Thereby, the new vehicle-mounted device 2A can calculate the accurate actual distance L ′ (= L0−Lh2−Ln ′) using the new position correction information Lh2 and the number of DL transmission frames, and can appropriately operate the DSSS.

Further, when the transmission time of the high-speed frame UL2 becomes long or the number of frames increases due to the increase in capacity, it becomes a problem which position in the transmission period is set as the uplink position h2. That is, if the uplink position h2 is not properly set, the time difference between the transmission time of the high-speed frame UL2 and the transmission time of the downlink frame DL2 that is the starting point of the number of DL transmission frames after downlink switching increases. This time difference becomes an error in obtaining the actual distance L ′. Therefore, in the present embodiment, more appropriate DSSS operation is enabled by appropriately acquiring the uplink position h2 that is the transmission position of the high-speed frame UL2.
Hereinafter, a configuration example of the new optical beacon 4A that employs the above-described concept and can appropriately operate the DSSS will be described.

[First Embodiment]
FIG. 14 is a sequence diagram illustrating a communication procedure according to the first embodiment.
As shown in FIG. 14, in the communication procedure of the first embodiment, when the new in-vehicle device 2A continuously transmits the high-speed frames U1 to U3 after the transmission interruption period, the new optical beacon is also received when the reception of the high-speed frames U1 to U3 is completed. When 4A performs downlink switching, the above-described problems associated with the operation of DSSS are solved.

  In FIG. 14, the new optical beacon 4A that has received the low-speed frame UL1 performs the first downlink switching, and transmits a return frame and a downlink frame DL2 including predetermined provision information. When the new in-vehicle device 2A confirms the success of the loopback of the vehicle ID by receiving the downlink frame DL2 during the transmission interruption period, the new in-vehicle device 2A next transmits the high-speed frame UL2. When the new optical beacon 4A confirms the completion of the reception of the high-speed frame UL2, it switches the downlink again. Then, the starting point of the number of DL transmission frames is reset in correspondence with the second downlink switching time, and the number of DL transmission frames is included in the safe driving support information of the downlink frame DL2.

FIG. 15 is a time chart illustrating a timing example of the communication procedure according to the first embodiment. In the example shown in FIG. 15, the number of frames of the high-speed frame UL2 and the number of frames of the downlink frame DL2 are set larger than those shown in FIG. 14, and the high-speed frame UL2 is set to 16 frames, and the downlink frame DL2 is set to 80 frames. It is a frame.
Also in the example shown in FIG. 15, when the first low-speed frame UL1 transmitted from the new vehicle-mounted device 2A is received by the new optical beacon 4A, the new optical beacon 4A performs downlink switching and transmits the downlink frame DL2. Start. On the other hand, the new in-vehicle device 2A starts transmission of the high-speed frame UL2 after confirming the success of the loopback. When the new optical beacon 4A completes reception of all the high-speed frames UL2, it performs the second downlink switching and transmits the downlink frame DL2 again.

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

The beacon controller 7 also includes a memory 31 that temporarily stores “upstream data” and “position data” output from the communication processing unit 28 and the position CPU 29.
The first light receiving system 26 includes a communication conversion element (first conversion element) 32, an amplifier 33, a filter 34, and a comparator 35 in order from the left side of FIG. The communication conversion element 32 includes a light receiving element (for example, a photodiode (hereinafter also referred to as “PD”)) that converts the received optical signal in the uplink direction into an electrical signal.

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

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

  The communication processing unit 28 includes a programmable logic device (PLD) such as an FPGA (Field Programmable Gate Array), and among the bit data input from the comparator 35, the transmission speed of the received signal is determined using an idle pattern of the first 5 bytes. The bit data is sampled at the determined transmission rate, and the uplink data included in the uplink frames UL1 and UL2 is reproduced. Then, the communication processing unit 28 temporarily stores the reproduced uplink data in the memory 31.

The second light receiving system 27 includes a measurement conversion element (second conversion element) 36, an amplifier 37, and a peak hold circuit 38 in order from the left side of FIG.
The conversion element 36 for measurement is composed of a position detection element (hereinafter also referred to as “PSD”) that outputs an electrical signal corresponding to the input position in the light receiving surface of the upstream frames UL1 and UL2. The measurement principle of the uplink positions h1 and h2 using the PSD 36 will be described later with reference to FIG.

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

  The position CPU 29 measures the uplink position using the measurement data (the current value of each output terminal of the PSD 36) input from each peak hold circuit 38. Specifically, the position CPU 29 samples the measurement data input from the peak hold circuit 38 at a predetermined period (for example, 0.3 msec), and generates a plurality of position data in time series. The plurality of position data generated by the position CPU 29 is read into the communication processing unit 28 and temporarily stored in the memory 31.

Note that the position data output by the position CPU 29 may be based on either coordinates (x, y) on the light receiving surface of the PSD 36 or coordinates (X, Y) on the road side (see FIG. 13). In this embodiment, the position data is based on coordinates (x, y). In this case, the main CPU 30 needs to perform an operation for converting the coordinates (x, y) to the coordinates (X, Y).
The main CPU 30 reads “upstream data” and a plurality of “position data” stored in the memory 31, and position correction information Lh 1, Lh 2 from the plurality of “position data” according to the contents of the “upstream data”. The position data used for calculation is selected. A method for selecting the position data will be described later with reference to FIGS.

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

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

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

On the other hand, as shown in FIG. 13, the optical signal transmitted toward the beacon head 8 at an arbitrary position (X, Y) in the uplink area UA is condensed by the lens and is within the light receiving surface of the PSD 36. Spot light is incident on any one position (x, y).
Therefore, the incident position (x, y) of the upstream optical signal (uplink light) transmitted in the uplink area UA has a one-to-one correspondence with the transmission position (X, Y) on the road side. If the value of the position (x, y) is found, the road side of the optical signal transmission position (X, Y) (uplink positions h1, h2 (see FIG. 11)) by coordinate conversion based on a geometric linear relationship. Coordinate value) can be obtained.

[Uplink position acquisition processing by main CPU 30]
FIG. 17 is a flowchart illustrating an example of an uplink position acquisition process performed by the main CPU 30.
As shown in FIG. 17, the main CPU 30 determines whether or not uplink data has been acquired from the communication processing unit 28 (whether or not uplink data has been read from the memory 31) (step ST11), and when the uplink data has been acquired. Further, it is determined whether or not position data has been acquired from the position CPU 29 (whether or not position data has been read from the memory 31) (step ST12).

If the determination result in step ST12 is negative, there is no need to adopt position data, so the main CPU 30 generates a downlink frame DL2 storing predetermined provision information without performing the process in step ST13 ( Step ST14).
If the determination result in step ST12 is affirmative, the main CPU 30 determines position data to be adopted as the uplink position from among a plurality of position data sampled by the position CPU 29 (step ST13). Then, the main CPU 30 obtains the coordinate values (X, Y) of the adopted position data, and then generates the downlink frame DL2 (step ST14).

  In step ST13, the main CPU 30 selects position data satisfying a predetermined condition from a plurality of position data, and adopts it as an uplink position. Specifically, in the present embodiment, the selection condition is that the position data is acquired based on the last frame of the uplink information. For example, when the uplink information is composed of 16 high-speed frames UL2, the position data acquired from the 16th high-speed frame UL2 is adopted as the uplink position and included in the downlink frame DL2. .

  By adopting position data acquired based on the last frame among a plurality of high-speed frames UL2 as an uplink position, when the high-speed frame UL2 is transmitted at this uplink position, and downlink switching by the high-speed frame UL2 The time difference from the transmission point of the downstream frame DL2, which is the starting point for the number of subsequent DL transmission frames, can be made as small as possible. Therefore, the actual distance L ′ shown in FIG. 11 can be calculated more accurately based on the position correction information calculated using the uplink position and the number of DL transmission frames. In addition, it is preferable to select an uplink position acquired from the latter half of the last frame in order to obtain an accurate actual distance L ′.

Hereinafter, some examples of a method for selecting position data to be used as an uplink position from among a plurality of position data will be described.
[First method]
FIG. 16 is a time chart for explaining a method of selecting an uplink position.
In FIG. 16, a total of 16 frames of uplink frames (high-speed frames) UL2 are transmitted. At the beginning and the end of each frame, a synchronization unit indicated by “7E” is provided. The communication processing unit 28 of the new optical beacon 4A detects the head and tail synchronization units of each uplink frame UL2, and extracts the uplink data stored in the uplink frame UL2. The main CPU 30 can grasp the timing at which the upstream frame UL2 is received by reading the upstream data extracted by the communication processing unit 28, particularly when the head and tail synchronization units are detected.

On the other hand, the measurement data S acquired by amplifying and peak-holding the output of the PSD 36 from the second light receiving system 27 is input to the position CPU 29. The position CPU 29 samples the measurement data S at a predetermined cycle, and generates and acquires a plurality of position data. In the example illustrated in FIG. 16, the position CPU 29 sequentially acquires position data D _i (i = 1 to n) at a predetermined sampling period ta.

Here, the electric signal converted into the DC component by the peak hold circuit 38 of the second light receiving system 27 is held for the time constant of the peak hold circuit 38 even after the uplink light is terminated at the time tue in FIG. Data S may be generated. As described above, even if the measurement data S is output after the end of the uplink light, the normal position data _Di is obtained if there is an output equal to or higher than a predetermined threshold (for example, the position data in FIG. 16). D reference _{n-1, D n).} However, since such position data D _n−1 and D _n do not indicate the actual uplink light transmission position, it is preferable to employ the position data as the uplink position included in the downlink frame DL2 after downlink switching. Absent.

In the present embodiment, the following method is used so that the position data D _n−1 and D _n acquired after the end of the uplink light is not adopted as the uplink position.
Specifically, the main CPU30 is to last at n1-th earlier, and n2-th and subsequent among the plurality of position data _{D i} acquired by the position CPU 29 (n1, n2 are predetermined constants, n2 ≧ n1) is obtained employing the position data D _i was as uplink position.

n1 is set as a number that does not include the position data D _n−1 and D _n acquired after the end of the uplink light. For example, in the example of FIG. 16, since the last position data from the last is acquired after the end of the uplink light, a numerical value satisfying n1 ≧ 3 is set. Accordingly, the position data that can be selected is the position data before Dn _-2 .
Also, n2 is set to a numerical value that does not include the position data acquired in the first half of the final frame UL2, for example. In this way, by adopting the position data acquired between n1 and n2 from the end as the uplink position, the position data acquired in the latter half of the final frame UL2 and before the end of the uplink light can be reliably obtained. It can be adopted as the uplink position.

  Note that n1 and n2 may be the same value. In this case, since one piece of position data is selected, this can be adopted as an uplink position as it is. When there are a plurality of position data included in the n1 to n2th ranges, for example, an average value of the plurality of position data may be adopted as the uplink position.

[Second method]
In the selection method described above, the position data to be adopted as the uplink position is selected based on the order in which the position data is acquired by the position CPU 29. However, as described below, the time at which the position data was acquired The position data to be adopted as the uplink position can be selected based on the above.
That is, as shown in FIG. 16, the main CPU 30 employs the position data acquired at tx for at least t1 hours before and after t2 hours before the reception completion time tue of the final frame UL2 as the uplink position. (T1 and t2 are predetermined constants, t2 ≧ t1).

The reception completion time tue of the final frame UL2 can be grasped from the uplink data acquired from the communication processing unit 28 at the same time. However, since the reception completion time tue of the final frame UL2 that can be grasped by the main CPU 30 is based on uplink data obtained from the communication processing unit 28, there is a possibility that a slight delay occurs from the actual completion of reception of the uplink light. There is sex. For this reason, the time t1 is set as a time when position data (for example, D _n−1 , D _n ) acquired after the uplink light ends is not adopted as the uplink position.

  Further, the time t2 is set as a time not including the position data acquired in the first half of the final frame UL2, for example. Thus, by adopting the position data acquired at tx for t1 to t2 hours before the reception completion time tue as the uplink position, it is acquired in the latter half of the final frame UL2 and before the end of the uplink light. The position data can be reliably included in the downlink frame DL2 as an uplink position.

  Note that t1 and t2 may be set to the same time, or set to a time (a time including at least one position data) between which the time difference between the two is extremely short. In this case, since one piece of position data is selected, this can be adopted as an uplink position as it is. In addition, when there are a plurality of position data included in tx between times t1 and t2, an average value of the plurality of position data may be adopted as the uplink position.

[Third method]
Both the first and second methods described above are employed as the uplink position with reference to the end side of the last frame UL2, such as the position data acquired last for the last frame UL2 or the reception completion time of the last frame UL2. Although the method of selecting position data has been described, it is also possible to select position data to be adopted as an uplink position with reference to the head side of the last frame as described below.

Specifically, the main CPU30, among the plurality of position data _{D i} obtained for the final frame UL2, from the beginning N1 -th, and N2-th previous (N1, N2 is a predetermined constant, N2 ≧ N1) to The acquired position data can be adopted as the uplink position. The reception start time tus of the final frame UL2 can be grasped from “uplink data” acquired from the communication processing unit. In addition, since the data length is described in the header portion of the final frame UL2, the reception completion time of the final frame UL2 can be predicted based on the data length.

N1 is set to a numerical value not including position data acquired in the first half of the final frame UL2, for example, taking into account the time from the reception start time of the final frame UL2 to the predicted reception completion time. N2 does not include the position data D _n−1 and D _n acquired after the end of the uplink light in consideration of the predicted reception completion time, and is acquired at a time as close as possible to the reception completion time Set to a numeric value that contains position data. Thus, by adopting the position data acquired between N1 and N2 from the beginning as the uplink position, the position data acquired surely in the second half of the final frame UL2 and before the end of the uplink light. Can be adopted as the uplink position.

  N1 and N2 may be the same value. In this case, since one piece of position data is selected, this can be adopted as an uplink position as it is. When there are a plurality of position data included in the N1 to N2th ranges, an average value of the plurality of position data can be adopted as the uplink position.

[Fourth method]
A fourth method to be described next is a method of selecting an uplink position based on the time when position data is acquired by the position CPU 29. As shown in FIG. 16, the main CPU 30 may employ position data acquired at tx after the time T1 from the reception start time tus of the final frame UL2 and before time T2 as the uplink position. (T1 and T2 are predetermined constants, T2 ≧ T1). T1 is set to a time that does not include the position data acquired in the first half of the final frame UL2 in consideration of the time from the reception start time of the final frame UL2 to the predicted reception completion time. T2 does not include the position data D _n−1 and D _n acquired after the end of the uplink light in consideration of the predicted reception completion time, and is acquired at a time as close as possible to the reception completion time Set to the time at which position data is included. As described above, the position data acquired at time t1 from the reception start time at tx is used as the uplink position, so that the position acquired in the second half of the final frame UL2 and before the end of the uplink light. Data can be reliably adopted as the uplink position.

  In the first and second methods described above, since the position data to be used as the uplink position is selected based on the position data acquired last and the reception completion time of the last frame UL2, the main CPU 30 Needs to read all of the position data acquired by the position CPU 29 and obtain the position data to be adopted as the uplink position retroactively from the last position data or the reception completion time of the last frame UL2. On the other hand, in the third and fourth methods, the position data to be adopted as the uplink position is selected on the basis of the head side of the last frame UL2, and therefore the main CPU 30 needs to read all the position data. The processing burden can be reduced.

[Uplink position acquisition processing by the communication processing unit 28]
In the above, the main CPU 30 has selected the position data to be used as the uplink position, but the communication processing unit 28 can also select the position data. Details of this case will be described below.
FIG. 18 is a flowchart illustrating an example of processing when the communication processing unit 28 acquires an uplink position. In the example illustrated in FIG. 18, the communication processing unit 28 selects position data to be adopted as the uplink position and stores it in the memory 31. The main CPU 30 is configured to read the uplink position from the memory 31 in order to obtain the position correction information.

  In FIG. 18, the communication processing unit 28 always determines whether or not the heads of a plurality of high-speed frames UL2 have been detected (step ST21). Specifically, it is determined whether or not a 5-byte idle pattern attached to the top of the high-speed frame UL2 is detected. If this determination is affirmative, the position CPU 29 also starts sampling of position data, so the communication processing unit 28 sequentially acquires the position data sampled by the position CPU 29 (step ST22).

  Next, the communication processing unit 28 determines whether or not the final frame UL2 in the plurality of high-speed frames UL2 has been detected (step ST23). Specifically, the header portion of the final frame UL2 is provided with a “final frame flag” (see FIG. 7), which is a storage area indicating that the frame is the final frame. Whether or not is turned on is detected (step ST23). If this determination is negative, the process returns to step ST22. If the determination is affirmative, acquisition of position data from the position CPU 29 is stopped when reception of the final frame UL2 is completed (step ST24). ).

  Next, the communication processing unit 28 stores the last acquired position data in the memory 31 (step ST25). Since the communication processing unit 28 reproduces the uplink data from the digital reception signal (bit data) extracted by the first light receiving system 26, the communication processing unit 28 always grasps the reception status of the high-speed frame UL2. Accordingly, the communication processing unit 28 can accurately grasp the reception completion time of the final frame UL2, that is, the end time of the uplink light, and do not acquire the position data from the position CPU 29 after the uplink light ends. It has become.

Therefore, as illustrated in FIG. 16, the communication processing unit 28 does not acquire the position data D _n−1 and D _n sampled after the uplink light is terminated, and the position data generated immediately before the uplink is terminated. D _n−2 is acquired last and stored in the memory 31. The main CPU 30 generates position correction information by reading the last position data D _n−2 stored in the memory 31. As a result, the time difference between the transmission time point of the uplink information UL2 at the uplink position and the transmission time point tds of the downlink frame DL2 that is the starting point of the number of DL transmission frames can be minimized, and this uplink position is used. The actual distance L ′ shown in FIG. 11 can be obtained more accurately based on the position correction information calculated in this way and the number of DL transmission frames.

  As described above, even when the position data to be adopted as the uplink position is selected by the communication processing unit 28, the predetermined position data from the last or the beginning is used as in the first to fourth methods described above. It is also possible to select the position data acquired before or after a predetermined time from the reception completion time or the reception start time. That is, in the example illustrated in FIG. 18, the position data acquired last among the plurality of position data is selected as the uplink position, but the n1 to n2th position data from the end and the N1 to N2th position data from the beginning are selected. It is also possible to select position data, position data of tx for t1 to t2 time before the reception completion time tue, or position data of tx for time T1 to T2 after the reception start time tus.

[Modification of First Embodiment]
In the first embodiment described above, a two-dimensional PSD is adopted as the position measurement PSD 36. However, a one-dimensional PSD in which the x direction of the light receiving surface is arranged along the vehicle traveling direction is adopted. Also good.
The reason is that the optical beacon 4 only needs to be able to measure the uplink position in the vehicle traveling direction in order to generate the position correction information Lh1, Lh2, and the position in the road width direction (Y direction) is not particularly problematic. .

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

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

[Second Embodiment]
FIG. 19 is a circuit configuration diagram of the new optical beacon 4A according to the second embodiment.
The main difference between the second embodiment shown in FIG. 19 and the first embodiment shown in FIG. 12 is that a divided PD 40 is used instead of the PSD 36 as a conversion element for measurement.
Hereinafter, the functional units substantially the same as those in the first embodiment will be denoted by the same reference numerals in FIG. 19, and detailed description thereof will be omitted. Differences from the first embodiment will be mainly described.

As shown in FIG. 19, the divided PD 40 of the second light receiving system 27 has a uniform light receiving surface by joining four PD1 to PD4 in the width direction.
The output terminals of the PD1 to PD4 are connected to the subsequent amplifier 37, and the electric signals photoelectrically converted by the PD1 to PD4 are amplified by the amplifier 37 and input to the peak hold circuit 38. The peak hold circuit 38 generates the measurement data while holding the maximum amplitude of the amplified signal for a predetermined time, and sends the generated measurement data to the subsequent position CPU 29.

The position CPU 29 measures the uplink position using the measurement data (voltage values at the output terminals of the PD1 to PD4) input from the peak hold circuits 38. The position CPU 29 sends position data that is the measurement result to the main CPU 30. That is, in this embodiment, the position CPU 29 sends position data to the main CPU 30 directly (or via a memory) without going through the communication processing unit 28.
In addition, the measurement principle (FIG. 20) in the case of measuring an uplink position from the voltage value (measurement data) of the output terminal of PD1-PD4 which comprises division | segmentation PD40 is mentioned later.

As shown in FIG. 19, the first light receiving system 26 has an adder 41. The output terminal of each amplifier 37 is connected to the adder 41, and the output terminal of the adder 41 is connected to the subsequent filter 34.
That is, in the case where the light receiving element is a PD, it has a follow-up performance with good rise and fall even for a relatively high speed optical signal (256 kpbs in this embodiment). Therefore, in the present embodiment, a circuit configuration is employed in which the sum signal obtained by adding the amplified signals of PD1 to PD4 is sent to the filter 34 of the first light receiving system 26, and the divided PD 40 is also used as a communication conversion element. ing.

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

The functions of the filter 34 and the comparator 35 in the first light receiving system 26 and the function of the communication processing unit 28 of the beacon controller 7 are the same as those in the first embodiment of FIG. Omitted.
The uplink position acquisition processing by the main CPU 30 is also the same as in the case of the first embodiment described with reference to FIGS. 16 and 17, and thus detailed description thereof is omitted. However, in this embodiment, since position data is not sent from the position CPU 29 to the communication processing unit 28, the uplink position acquisition process cannot be performed by the method shown in FIG.

[Measurement principle of uplink position]
FIG. 20 is an explanatory diagram of the measurement principle of the uplink position using the divided PD.
As shown in FIG. 20, the road-side divided areas UA1 to UA4 are areas obtained by dividing a plane having a predetermined height H (for example, H = 1.0 m) from the road surface of the road R substantially equally along the vehicle traveling direction. Yes, PD1 to PD4 constituting the divided PD 40 are arranged inside the beacon head 8 so that the light receiving areas thereof substantially correspond to the divided areas UA1 to UA4.

Therefore, for example, as shown in FIG. 20, when spot light incident on the divided PD 40 is detected on the light receiving surface of the PD 1, the spot light transmission position is the divided area UA1 of the uplink area UA. It turns out that there was.
Similarly, if the irradiation position of the spot light is PD2, PD3 or PD4, it is found that the transmission position is the divided area UA2, UA3 or UA4.

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

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

[Third Embodiment]
FIG. 21 is a circuit configuration diagram of the new optical beacon 4A according to the third embodiment.
As shown in FIG. 21, in the new optical beacon 4A of the third embodiment, the optical receiver 11 includes a first light receiving system 26 that is a communication light receiving system (light receiving circuit) and a measurement light receiving system (light receiving circuit). And a second light receiving system 27. Hereinafter, the functional units substantially the same as those in the first embodiment will be denoted by the same reference numerals in FIG. 21, and detailed description thereof will be omitted, and differences from the first embodiment will be mainly described.

The second light receiving system 27 has the same configuration as the second light receiving system 27 (see FIG. 12) of the first embodiment, and includes a conversion element 36 made of PSD, an amplifier 37, and a peak hold circuit 38. The principle of measuring the uplink position in the second light receiving system 27 is as described with reference to FIG.
On the other hand, the first light receiving system 26 includes substantially the same configuration as the first light receiving system 26 (see FIG. 12) of the first embodiment, and includes a conversion element 32 made of PD, an amplifier 33, a filter 34, and a comparator 35. doing. Then, the electrical signal output from the PD 32 is processed by the same procedure as in the first embodiment, and the digital reception signal (bit data) is output from the comparator 35 to the communication processing unit 28.

  Further, in the present embodiment, the PSD 36 used in the second light receiving system 27 is also used as a conversion element for the first light receiving system 26 (for communication). More specifically, the first light receiving system 26 further includes a PSD 36, an adder 41, a filter 34, and a comparator 35 in addition to the above configuration. The adder 41 is connected to the output terminal of the amplifier 37. The output terminal of the adder 41 is connected to the filter 34. The signal output from the PSD 36 is amplified by the amplifier 37 and then added in the adder 41. The signal generated by the adder 41 is output to the comparator 35 after a predetermined speed component is extracted by the filter 34. The comparator 35 compares the input signal with a threshold value, and outputs a digital received signal (bit data) extracted by this comparison to the communication processing unit 28. In FIG. 21, the first light receiving system including the PD 32 is denoted by reference numeral 26A, and the first light receiving system including the PSD 36 is denoted by reference numeral 26B.

As described in the first embodiment, the PSD 36 has relatively poor tracking performance in the high-speed band (256 kbps), and it is difficult to reproduce uplink data from the received optical signal in the high-speed band, but the low-speed band (64 kbps). Therefore, it is possible to reproduce uplink data from the received optical signal in the low-speed band.
Therefore, in the present embodiment, the PSD 36 is used not only for measurement but also for communication with respect to an optical signal in a low-speed band (64 kbps), that is, the low-speed frame UL1, and the communication light receiving system 26A, 26B is duplexed.

Such duplication of the communication light receiving systems 26A and 26B can increase the certainty in acquiring "upstream data" and can also be used for early discovery of malfunctions such as failures in the PD 32 and PSD 36. .
That is, when the uplink data is reproduced by the PSD 36, it is possible to determine that the uplink frame received at that time is the low-speed frame UL1, but at this time, if the uplink data is not reproduced by the PD 32, the PD 32 has a failure. It can be recognized that there is a problem such as. Conversely, when the uplink data is reproduced only by the PD 32, the uplink frame received at that time can be estimated to be the high-speed frame UL2, but at this time, it is included in the header portion of the uplink frame. If the value of “Information Type” (see FIG. 7) indicates the low-speed frame UL1, the low-speed frame UL1 that should be received by the PSD 36 has not been received. Can be recognized. Therefore, it is possible to detect and deal with problems in the PD 32 and PSD 36 at an early stage.

The uplink position acquisition processing by the main CPU 30 or the communication processing unit 28 is the same as that in the first embodiment described with reference to FIGS. 16 to 18, and thus detailed description thereof is omitted.
[Other variations]
The embodiments (including modifications) disclosed herein are illustrative and non-restrictive in every respect. The scope of rights of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope equivalent to the configurations described in the claims.

  For example, in the above-described embodiment, the case where the present invention is applied to the multi-rate compatible new optical beacon 4A in the uplink direction is illustrated, but the present invention is an optical beacon 4 (only corresponding to a single rate in the uplink direction ( For example, the old optical beacon 4B) capable of receiving only the low-speed frame UL1 can be employed.

  That is, in the communication between the old optical beacon 4B and the old in-vehicle device 2B, the old in-vehicle device 2B can transmit a plurality of low-speed uplink information through one road-to-vehicle communication, and the uplink information received first by the old optical beacon 4B. In the case where only downlink switching is performed, the relationship between the “position correction information” and the “number of DL transmission frames” included in the safe driving support information provided by the old optical beacon 4B in accordance with DSSS is broken. The problem of is applied as it is.

Therefore, even in the case of the old optical beacon 4B, not only when the first low-speed uplink information is received, but also with respect to the low-speed uplink information received thereafter, downlink switching is performed, and the position correction information Lh2 at the time of reception is changed. And the number of DL transmission frames may be included in the downlink frame DL2.
In this case, an appropriate actual distance L ′ can be calculated by the old in-vehicle device 2B, and the DSSS can be appropriately operated.

Further, in the communication between the new optical beacon 4A and the new in-vehicle device 2A, when the new in-vehicle device 2A transmits a plurality of high-speed uplink information, not only when the first high-speed uplink information is received, For the high-speed uplink information received at the same time, by performing downlink switching, the position correction information Lh2 at the time of reception and the number of DL transmission frames may be included in the downlink frame DL2.
Also in this case, an appropriate actual distance L ′ can be calculated by the new in-vehicle device 2A, and the DSSS can be appropriately operated.

  Further, the present invention acquires an uplink position based on the final frame even when the uplink information transmitted first is composed of a plurality of frames regardless of whether it is high speed or low speed, and uses this uplink position. If the calculated position correction information Lh2 and the number of DL transmission frames are included in the downlink frame DL2, the in-vehicle device 2 can calculate an appropriate actual distance L.

In the above-described embodiment, the uplink positions h1 and h2 are defined as “position correction information” represented by the distances Lh1 and Lh2 in the vehicle traveling direction starting from the reference position P0, but the uplink positions h1 and h2 May be represented by a coordinate value on the map, and the coordinate value may be notified to the in-vehicle device 2.
In this case, since the uplink positions h1 and h2 can be grasped even if the coordinates of the reference position P0 are unknown, the reference position P0 may not be included in the safe driving support information.

2 Onboard unit 2A New onboard unit 2B Old onboard unit 4 Optical beacon 4A New optical beacon 4B Old optical beacon 7 Beacon controller (communication control unit)
8 Beacon head 20 Vehicle 23 Optical transmission unit 24 Optical reception unit 28 Communication processing unit 29 Position CPU
30 Main CPU

Claims (13)

An optical beacon that performs wireless communication with an in-vehicle device of a running vehicle using an optical signal,
An optical receiver including a light receiving element that converts an upstream optical signal constituting uplink information into an electrical signal;
An optical transmission unit including a light emitting element that converts an electrical signal into a downlink optical signal constituting downlink information;
A communication control unit capable of executing downlink switching triggered by reception of the uplink information and generating an uplink position that is a transmission position of the uplink information;
The optical control beacon, wherein the communication control unit includes a transmission position of a final frame of the uplink information including a plurality of frames as the uplink position in the downlink information after downlink switching. An optical beacon that performs wireless communication with an in-vehicle device of a running vehicle using an optical signal,
An optical receiver including a light receiving element that converts an upstream optical signal constituting uplink information into an electrical signal;
An optical transmission unit including a light emitting element that converts an electrical signal into a downlink optical signal constituting downlink information;
A communication control unit capable of executing downlink switching triggered by reception of the uplink information and generating an uplink position that is a transmission position of the uplink information;
It said communication control unit includes a feature to include transmission position of the last frame of the uplink information of a single frame of data size exceeding 74 bytes, to the downlink information after downlink switching as the uplink position Light beacon.   The optical beacon according to claim 1 or 2, wherein the communication control unit includes an uplink position acquired from a second half part of the final frame in the downlink information.   The optical communication beacon according to any one of claims 1 to 3, wherein the communication control unit includes, in the downlink information, an uplink position adopted with reference to a tail side of the final frame.   The uplink position included in the downlink information is the uplink position acquired before the n1th (however, n1: predetermined constant) from the last among the plurality of uplink positions acquired for the last frame. The optical beacon according to claim 4.   Uplink positions to be included in the downlink information are acquired at the n2th and subsequent positions from the last among a plurality of uplink positions acquired for the last frame (however, n2: a predetermined constant that satisfies (n2 ≧ n1)). The optical beacon according to claim 5, wherein the optical beacon is at an uplink position.   The uplink position included in the downlink information is acquired at least t1 hours before the completion of reception of the final frame among the multiple uplink positions acquired for the final frame (however, t1: a predetermined constant). The optical beacon according to claim 4, wherein the optical beacon is at a designated uplink position.   Uplink positions to be included in the downlink information are t2 hours before the completion of reception of the final frame among a plurality of uplink positions acquired for the final frame (however, t2: (t2 ≧ t1)) The optical beacon according to claim 7, wherein the uplink position is acquired at a predetermined constant to be satisfied.   The optical communication beacon according to any one of claims 1 to 3, wherein the communication control unit includes, in the downlink information, an uplink position adopted with reference to a head side of the final frame.   The uplink position included in the downlink information is the uplink position acquired from the first N1 onward (where N1: a predetermined constant) among the plurality of uplink positions acquired for the last frame. The optical beacon according to claim 9.   The uplink position to be included in the downlink information is acquired from the beginning of the plurality of uplink positions acquired for the last frame before the N2th (however, N2: a predetermined constant that satisfies (N2 ≧ N1)). The optical beacon according to claim 10, wherein the optical beacon is at an uplink position.   Uplink positions to be included in the downlink information are acquired after a time T1 from the reception start time of the final frame among a plurality of uplink positions acquired for the final frame (where T1: a predetermined constant). The optical beacon according to claim 9, which is an uplink position.   Uplink positions included in the downlink information satisfy T2 hours before the reception start time of the final frame among a plurality of uplink positions acquired for the final frame (provided that T2: (T2 ≧ T1)) The optical beacon according to claim 12, wherein the uplink position is a predetermined constant).

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