JP2018055547A - Optical beacon and on-vehicle device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical beacon with a high possibility of appropriately receiving a high speed frame transmitted by an on-vehicle after a low speed frame.SOLUTION: An optical beacon 4 performs radio communication with an on-vehicle device of a vehicle that is traveling by using an optical signal.The optical beacon comprises: an optical receiving unit 14 capable of photoelectric conversion at two sorts of high and low transmission rates ; an optical transmitting unit 13 capable of electrical/optical conversion at a predetermined transmission rate; and a communication control unit 7 for performing processing of causing a sophisticated on-vehicle unit to re-execute a transmission sequence of a low speed frame and a high speed frame when a predetermined condition is established, which indicates that the high speed frame transmitted after the low speed frame is not normally received by the sophisticated on-vehicle unit operable in high speed up-link transmission.SELECTED DRAWING: Figure 1

Description

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

  In road-to-vehicle communication systems where optical beacons and in-vehicle devices communicate optically, optical beacons that support high-speed uplink reception (hereinafter also referred to as “new optical beacons”) and in-vehicle devices that support high-speed uplink transmission ( Hereinafter, introduction of “new vehicle-mounted device”) is being studied (for example, see Patent Document 1).

The new optical beacon can communicate with an in-vehicle device that performs only low-speed uplink transmission (hereinafter also referred to as “old in-vehicle device”). It is also necessary to be able to communicate with an optical beacon.
Therefore, in Patent Document 1, a new in-vehicle device transmits a low-speed frame storing vehicle identification information (hereinafter referred to as “vehicle ID”) before a high-speed frame, and a new-type device that supports high-speed uplink communication. Even in this case, a communication procedure for performing communication using a low-speed frame first has been proposed.

When the new vehicle-mounted device transmits a high-speed frame after a low-speed frame, an area that can receive the low-speed frame but cannot receive the high-speed frame depending on the traveling speed of the vehicle (insensitive area F in FIG. 11 of Patent Document 1). ), A new in-vehicle device may transmit a high-speed frame.
When a high-speed frame is transmitted in such a dead zone, the new optical beacon cannot receive the high-speed frame, and in the case of a communication standard that does not allow retransmission of the high-speed frame, there is no possibility that the new optical beacon can acquire the high-speed frame.

Therefore, in Patent Document 1, a high-speed frame is received so as to be upstream or substantially at the same position as the upstream end (hereinafter referred to as “first uplink upstream end”) of an area where low-speed frames can be received. It has been proposed to set the position (hereinafter referred to as “uplink position setting”) of the upstream end of the possible area (hereinafter referred to as “second uplink upstream end”).
As a result, the insensitive area does not occur in the new light beacon, and the new light beacon can appropriately receive the high speed frame transmitted after the low speed frame.

JP 2014-016973 A

In the above-described new optical beacon, the downlink region may be set up to a portion (hereinafter referred to as “downlink upstream portion”) that extends upstream from the second uplink upstream end.
When the new in-vehicle device enters the inside of the above-described downlink upstream portion, the new in-vehicle device starts transmission of the low-speed frame including the vehicle ID of the own vehicle, triggered by reception of the downlink frame.

On the other hand, the uplink region is defined as a region where the bit error rate satisfies a predetermined communication quality (for example, 10 ⁻⁵ or less). Therefore, even if the new in-vehicle device transmits a low-speed frame in the downlink upstream portion, the communication quality is rarely satisfied, and normally, the new optical beacon cannot receive the low-speed frame.
However, since the low-speed frame transmitted first by the new in-vehicle device has a relatively small data size and is often only one frame, the probability is not high, but the new optical beacon receives the low-speed frame transmitted in the upstream of the downlink. there's a possibility that.

In this case, since the new light beacon transmits a downstream frame storing the vehicle ID of the new in-vehicle device, the new in-vehicle device starts transmitting a high-speed frame in response to the reception of the downstream frame.
Since the high-speed frame has a relatively large data size and a large number of frames, if the position of the new in-vehicle device in the vehicle traveling direction has not reached the upstream end of the second uplink at the start of transmission of the high-speed frame, The beacon may not receive all high speed frames properly.

As described above, even if the above-described uplink position setting is performed, the new optical beacon may not be able to appropriately receive the high-speed frame depending on the position condition and installation condition of the optical beacon and the vehicle-mounted device.
In view of such circumstances, in the road-to-vehicle communication performed between the multi-rate compatible optical beacon and the vehicle-mounted device in the uplink direction, the present invention provides a high-speed frame transmitted by the vehicle-mounted device after the low-speed frame. The purpose is to increase the possibility of receiving properly.

  (1) An optical beacon according to an aspect of the present invention is an optical beacon that performs wireless communication using an optical signal with an in-vehicle device of a traveling vehicle, and is capable of photoelectric conversion at two high and low transmission speeds. Check that the receiver, the optical transmitter capable of electro-optical conversion at a predetermined transmission rate, and the advanced vehicle that supports high-speed uplink transmission are not normally receiving the high-speed frame transmitted after the low-speed frame. A communication control unit that executes processing for causing the advanced vehicle-mounted device to re-execute the transmission sequence of the low-speed frame and the high-speed frame when a predetermined condition to be expressed is satisfied.

  (9) An in-vehicle device according to an aspect of the present invention is an in-vehicle device that performs wireless communication using an optical beacon and an optical signal installed on a road, and is an optical receiver that can perform photoelectric conversion at a predetermined transmission speed. And a communication control unit capable of executing a transmission sequence for transmitting a high-speed frame after a low-speed frame, and a communication control unit capable of executing a transmission sequence for transmitting a high-speed frame after a low-speed frame. The unit can execute memory control for holding the uplink data for a predetermined time after completing the transmission of the uplink data by the high-speed frame.

  ADVANTAGE OF THE INVENTION According to this invention, possibility that an optical beacon will receive appropriately the high-speed flame | frame which an onboard equipment transmits after a low-speed flame | frame can be raised.

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 of the road which shows the communication area | region and incident area of an optical beacon. It is a frame configuration diagram of an upstream frame. It is a frame configuration diagram of a downstream frame. It is a sequence diagram which shows an example of the road-vehicle communication performed in a communication area. It is explanatory drawing which shows an example of the downlink upstream part located in the upstream of an uplink area | region. It is a timing chart which shows an example of the road-vehicle communication in case transmission of a high-speed frame is started in the upstream vicinity of an uplink area. It is a calculation table which shows the example of calculation of the receiving rate for every high speed frame. It is a calculation table which shows the example of calculation of the reception omission rate for every high-speed frame. It is a time chart which shows the suitable timing example of the re-execution of the transmission sequence by vehicle equipment.

<Outline of Embodiment of the Present Invention>
Hereinafter, an outline of embodiments of the present invention will be listed and described.
(1) An optical beacon according to the present embodiment is an optical beacon that performs wireless communication with an on-vehicle device of a running vehicle using an optical signal, and an optical receiver that can perform photoelectric conversion at two high and low transmission speeds. An optical transmitter capable of electro-optical conversion at a predetermined transmission rate, and a predetermined high-speed frame transmitted by an advanced vehicle-mounted device that supports high-speed uplink transmission are not normally received. A communication control unit that executes processing for causing the advanced vehicle-mounted device to re-execute the transmission sequence of the low-speed frame and the high-speed frame when the condition is satisfied.

According to the optical beacon of the present embodiment, the communication control unit executes a process for causing the advanced vehicle-mounted device to re-execute the transmission sequence of the low-speed frame and the high-speed frame when the predetermined condition is satisfied. Even if the high-speed frame cannot be normally received, the optical beacon can re-receive the high-speed frame by re-execution of the transmission sequence by the in-vehicle device.
Therefore, it is possible to increase the possibility that the optical beacon appropriately receives the high-speed frame that the in-vehicle device transmits after the low-speed frame.

(2) In the optical beacon of the present embodiment, the predetermined condition includes that a frame number number value included in the plurality of high-speed frames transmitted continuously has a jump greater than or equal to a predetermined threshold value. It is preferable that
The reason is that if the frame number has the above jump, it is clear that the optical beacon 4 has not received a part of the series of high-speed frames, and it cannot be said to be normal reception. is there.

  (3) In the optical beacon of the present embodiment, the predetermined condition is that a reception rate at the time of reception of the final frame among the plurality of high-speed frames transmitted continuously is equal to or less than a predetermined threshold. It may be included.

  The reason is that when the reception rate at the time of receiving the final frame is low, it is clear that the optical beacon has not received a part of the series of high-speed frames, and it cannot be said that it is normal reception. is there.

  (4) In the optical beacon of the present embodiment, the predetermined condition is that a reception rate at the time of receiving a plurality of the high-speed frames transmitted continuously is below a predetermined threshold defined for each frame number. May be included.

  The reason is that even if the reception rate at the time of receiving each high-speed frame is low, it is clear that the optical beacon has not received a part of the series of high-speed frames, and it cannot be said to be normal reception. It is.

(5) In the optical beacon of this embodiment, the predetermined condition may include not receiving the high-speed frame even if a predetermined time elapses after receiving the low-speed frame.
The reason is that, in the above case, it can be estimated that the in-vehicle device has not transmitted a series of high-speed frames from the beginning, so that it can be determined that the optical beacon has not normally received the high-speed frames.

(6) In the optical beacon of this embodiment, it is preferable that the process for re-executing the transmission sequence includes a process of stopping transmission of a downstream frame for a predetermined time after receiving the low-speed frame.
The reason is that if the above processing is executed, the in-vehicle device determines that road-to-vehicle communication with another optical beacon is newly started, and re-executes the transmission sequence of the low-speed frame and the high-speed frame. is there.

(7) In the optical beacon of this embodiment, the process for re-executing the transmission sequence is a process of clearing the identification value of the vehicle ID of the lane notification information included in the downstream frame transmitted after receiving the low-speed frame. May be included.
The reason is that even when the above processing is executed, the in-vehicle device determines that road-to-vehicle communication with another optical beacon is newly started, and it is considered that the transmission sequence of the low-speed frame and the high-speed frame is re-executed. It is.

(8) In the optical beacon of the present embodiment, the transmission start point of the low-speed frame due to the re-execution of the transmission sequence is immediately before the advanced vehicle-mounted device moving downstream at a predetermined assumed speed is immediately before the uplink upstream end. When it is assumed that the optical beacon has not received the transmitted low-speed frame, it is preferable that the advanced vehicle-mounted device is before the time point when the re-transmission sequence starts.
In this way, it is possible to secure a downlink communication amount that is almost equivalent to the current worst case case (see FIG. 10), and it is possible to execute downlink communication that satisfies the requirements of the standard.

  (9) The in-vehicle device of the present embodiment is an in-vehicle device that performs wireless communication using an optical beacon and an optical signal installed on a road, and includes an optical receiving unit capable of photoelectric conversion at a predetermined transmission speed, An optical transmission unit capable of electro-optical conversion at two types of transmission rates, and a communication control unit capable of executing a transmission sequence for transmitting a high-speed frame after a low-speed frame, and the communication control unit includes: After completing the transmission of the uplink data by the high-speed frame, it is possible to execute a memory control for holding the uplink data for a predetermined time.

  According to the vehicle-mounted device of the present embodiment, the communication control unit can execute the memory control for holding the uplink data for a predetermined time after completing the transmission of the uplink data by the high-speed frame. When the transmission sequence of the frame and the high-speed frame is re-executed, it is possible to prevent the transmission sequence from being re-executed because there is no uplink data stored in the high-speed frame.

  (10) In the in-vehicle device of the present embodiment, the predetermined time is set to a time (for example, 250 to 500 ms) sufficient for the on-vehicle device to complete road-to-vehicle communication with one optical beacon. That's fine.

<Details of Embodiment of the Present Invention>
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the present embodiment, an uplink frame transmitted from the in-vehicle device 2 toward the optical beacon 4 or information transmitted thereby may be referred to as “uplink information” or “uplink signal”. Further, the downlink frame transmitted from the optical beacon 4 toward the in-vehicle device 2 or information transmitted thereby may be referred to as “downlink information” or “downlink signal”.

[Overall system configuration]
FIG. 1 is a block diagram showing a schematic configuration of a road-vehicle communication system according to the present embodiment. 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. 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 (see FIG. 3) traveling on a road R.

The traffic control system 1 includes a central device 3 provided in a traffic control room or the like, and a large number of optical beacons (optical vehicle detectors) 4 installed at various locations on the road R. The optical beacon 4 can perform wireless communication with the in-vehicle device 2 by optical communication using near infrared as a communication medium.
The optical beacon 4 includes a beacon controller (communication controller) 7 that performs communication control and the like, and a plurality (four in the example of FIG. 1) of beacon heads (transmit / receive) connected to the sensor interface of the beacon controller 7. 8).

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 simultaneously performs transmission control in the downlink direction for the light emitting unit 13 for optical communication and reception control in the uplink direction for the light receiving unit 14 for optical communication.
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 (see FIG. 3) 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.

[Overall configuration of optical beacon]
The beacon head 8 of the optical beacon 4 includes a transmission / reception unit 11 (optical transmission / reception unit) for optical communication and a sensor unit 12 for vehicle detection in a housing 9 (see FIGS. 1 and 3).
As described above, in the optical beacon 4 of the present embodiment, the optical communication function and the vehicle detection function are obtained by incorporating the units 11 and 12 for optical communication and vehicle detection in the housing 9 of one beacon head 8, respectively. It has a structure with both.

The optical communication transceiver unit 11 is an optical transceiver that wirelessly transmits and receives optical signals to and from the in-vehicle device 2.
As shown in FIG. 1, the transmission / reception unit 11 receives a light emitting unit 13 for optical communication that transmits a downlink light DO (see FIG. 3) and an uplink light UO (see FIG. 3) and converts them into electrical signals. And a light receiving unit 14 for optical communication.

A light emitting unit 13 for optical communication (hereinafter also referred to as “communication light emitting unit 13”) includes a transmission circuit that converts a downstream frame transmitted from the beacon controller 7 into a serial transmission signal having a predetermined transmission rate; And a light emitting element composed of a light emitting diode (LED) that converts the output transmission signal into an optical signal in the downlink direction.
The light emitting element of the communication light emitting unit 13 sends the downlink light DO, which is a near infrared light signal, obliquely downward toward the upstream side.

The light receiving unit 14 for optical communication (hereinafter also referred to as “communication light receiving unit 14”) amplifies a light receiving element such as a photodiode (PD) and an electric signal output from the light receiving element. A receiving circuit for generating a digital signal.
The light receiving element of the communication light receiving unit 14 receives the uplink light UO, which is a near-infrared optical signal transmitted by the vehicle-mounted device 2 before the beacon head 8, and converts it into an electrical signal. The reception circuit of the communication light receiving unit 14 sends a digital signal generated from the converted electrical signal to the beacon controller 7.

The sensor unit 12 is a light detection sensor for detecting the presence of the vehicle 20 passing almost directly below the beacon head 8 without contact.
As shown in FIG. 1, the sensor unit 12 includes a vehicle sensing light emitting unit 15 that transmits incident light IO (see FIG. 3), and a vehicle that receives reflected light RO (see FIG. 3) and converts it into an electrical signal. And a light receiving unit 16 for sensing.

The vehicle-sensing light-emitting unit 15 (hereinafter also referred to as “sensing light-emitting unit 15”) transmits incident light IO, which is an optical pulse signal having a predetermined cycle, downward.
The vehicle sensing light receiving unit 16 (hereinafter also referred to as “sensing sensing light receiving unit 16”) receives the reflected light RO of the incident light IO on the road R and the vehicle 20, and uses the received reflected light RO as an electrical signal. Convert and send to the beacon controller 7.

The beacon controller 7 includes a computer device having a signal processing unit, a CPU, a memory, and the like. And a function as a sensing control unit of the vehicle 20.
The beacon controller 7 stores a computer program for communication control and sensing control in a storage device (not shown), and the CPU reads out and executes the program so that the CPU performs the communication control. Functions as a control unit and a sensing control unit.

For example, the beacon controller 7 may include a downlink signal (first downlink frame) including lane notification information in which an identification value of a vehicle ID (hereinafter also referred to as “ID value”) is not stored, or predetermined provision information. Is transmitted to the communication light-emitting unit 13 at a predetermined cycle.
The beacon controller 7 continues to transmit the downlink signal, and receives the uplink signal (uplink frame) including the ID value that the vehicle-mounted device 2 will transmit when receiving the downlink signal. Judgment is made.

  When the beacon controller 7 detects the reception of the uplink signal by the communication light receiving unit 14, the lane notification information storing the ID value and the lane number value extracted from the uplink signal, the provision information for the vehicle 20, and And one or a plurality of downlink signals (second downlink frames) including the generated information are transmitted to the communication light emitting unit 13 for a predetermined time (for example, 250 to 350 ms).

Then, when the predetermined time elapses, the beacon controller 7 restores the content of the provision information included in the downlink signal and waits for reception of the uplink signal from the in-vehicle device 2 of the vehicle 20 that comes next. .
Note that the beacon controller 7 transfers information included in the uplink signal, such as probe data including a travel locus such as the position and time of the vehicle 20, to the central device 3.

The beacon controller 7 always sends the incident light IO of a predetermined wavelength to the sensing light emitting unit 15 at a constant intensity and pulse period, and whether the received light intensity of the reflected light RO received by the sensing light receiving unit 16 is equal to or greater than a threshold value. The presence of the vehicle 20 is sensed depending on whether or not.
That is, the beacon controller 7 generates a sensing signal of the vehicle 20 and transmits the sensing signal to the central device 3 when the light receiving intensity of the reflected light RO that is equal to or greater than the threshold value is detected in the sensing light receiving unit 16. This threshold value is not limited to a fixed value, and may vary depending on, for example, a follow-up process according to the received light intensity of the reflected light RO.

[Optical beacon installation status]
As shown in FIG. 2, the optical beacon 4 of the present embodiment is installed on a road R having a plurality (four in the illustrated example) of lanes R1 to R4 in the same direction.
The optical beacon 4 includes a plurality of the beacon heads 8 provided corresponding to the respective lanes R1 to R4, and one beacon controller 7 that is a communication control unit that collectively controls these beacon heads 8. Prepare.

The beacon controller 7 is installed on a support column 17 erected on the left side of the road R. Each beacon head 8 is attached to an erection bar (beam member) 18 that is laid horizontally on the road R side from the column 17 and is disposed immediately above the center position of each lane R1 to R4.
The communication light emitting unit 13 of the beacon head 8 emits the downlink light DO toward the upstream side in the vehicle traveling direction from directly below the own device. Thereby, the communication area A for performing road-to-vehicle communication with the vehicle-mounted device 2 is set on the upstream side of the beacon head 8.

  The sensing light emitting unit 15 of the beacon head 8 emits the incident light IO almost directly below the own device. As a result, the incident area B, which is the sensing area of the vehicle 20 passing through the predetermined lanes R1 to R4 on the road R, is set almost directly below the beacon head 8.

[Communication area and incident area of optical beacons]
FIG. 3 is a side view of the road R showing the communication area A and the incident area B of the optical beacon 4.
As shown in FIG. 3, the communication area A of the transmission / reception unit 11 includes a downlink area DA (solid hatched portion) that is a receivable range of the downlink light DO by the in-vehicle device 2 and an uplink light UO by the beacon head 8. And an uplink area UA (broken line hatched portion) which is a light receiving range.

According to the UTMS (Universal Traffic Management Systems) Association “Optical Vehicle Detector Near-Infrared Interface Standard Version 2” (hereinafter referred to as “Old Interface Standard”) established on August 3, 2001, each area DA, UA The standard values of the upstream / downstream end positions are as follows.
Downstream area DA downstream end position a0: +1.3 m
Downstream end position b0 of the uplink area UA: a0 + 2.1 m (= 3.4 m)
Upstream end position c0 of both areas DA and UA: b0 + 1.6 m (= 5.0 m)

In the “Advanced Optical Beacon Near-Infrared Interface Standard Version 4” (hereinafter referred to as “New Interface Standard”) developed by the UTMS Association, which was formulated on January 28, 2016, the standard value of the upstream end position of each area DA, UA ( For general roads):
Downstream area DA downstream end position a0: +0.70 m
Downstream end position b0 of the uplink area UA: a0 + 2.70 m (= 3.40 m)
Upstream end position c0 of both areas DA and UA: b0 + 2.64 m (= 6.04 m)
The standard values of the positions a0 to c0 are values when the upstream direction is a positive number from the position immediately below the light emitter / receiver 8 (origin O) on the reference plane having a height H of 1.0 m from the road surface. .

In the old interface standard, the transmission rate of the uplink optical UO transmitted by the vehicle-mounted device 2 is only 64 kbit / s, and the transmission rate of the downlink optical DO received by the vehicle-mounted device 2 is only 1024 kbit / s.
On the other hand, in the new interface standard, the transmission speed of the downlink optical DO is the same as the conventional one, but the transmission speed of the uplink optical UO is two types of high and low (low speed is 64 kbit / s and high speed is 256 kbit / s. s).

Therefore, the optical beacon 4 according to the new interface standard is called a multi-rate compatible optical beacon (a “new optical beacon” or an “advanced optical beacon”) capable of receiving a conventional low-speed uplink reception and a new high-speed uplink reception. ).
The in-vehicle device 2 conforming to the new interface standard is called a multi-rate in-vehicle device capable of performing conventional low-speed uplink transmission and new high-speed uplink transmission (referred to as “new in-vehicle device” or “advanced in-vehicle device”). .)

In the present embodiment, it is assumed that both the optical beacon 4 and the vehicle-mounted device 2 are devices that support high-speed uplink communication.
That is, in this embodiment, it is assumed that the optical beacon 4 is a new optical beacon (advanced optical beacon) and the in-vehicle device 2 is a new in-vehicle device (advanced optical in-vehicle device).

The incident area B of the sensor unit 12 is an irradiation range of the incident light IO on which the sensing light emitting unit 15 enters the road R.
The center of the incident area B in the road width direction is at a position substantially equal to the center of the lanes R1 to R4 corresponding to the beacon head 8 in the road width direction. The emission direction V1 of the incident light IO is normally directed upstream (plus side) by a predetermined angle α (for example, 4.5 °) with respect to the vertical direction, but is downstream by a predetermined angle with respect to the vertical direction. It may be directed to the side (minus side).

[Configuration of in-vehicle device]
As shown in FIG. 3, the in-vehicle device 2 of the present embodiment includes an in-vehicle controller (communication control unit) 21 and an in-vehicle head (optical transmission / reception unit) 22. An optical transmitter 23 and an optical receiver 24 are accommodated in the in-vehicle head 22.
The optical transmitter 23 has a light emitting element that emits an uplink light UO (uplink direction optical signal) made of near infrared rays, and the optical receiver 24 has a downlink light UO (downlink direction made of near infrared rays). A light receiving element for receiving an optical signal).

The optical transmission unit 23 is a light emitting circuit that converts an upstream frame output from the in-vehicle controller 21 into a serial transmission signal having a predetermined transmission rate, and converts the output transmission signal into an optical signal in the uplink direction. And a light emitting element made of a diode or the like.
The optical receiver 24 includes a light receiving element such as a photodiode that photoelectrically converts an optical signal in the downlink direction and outputs an electric signal, and a receiving circuit that amplifies the output electric signal and generates a digital received signal. Have

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 (not shown), and the CPU reads and executes the program, so that the CPU functions as the communication control unit. To do.

The in-vehicle controller 21 generates traveling data of the host vehicle (for example, probe information that is traveling locus data in which passing positions and passing times are arranged in time series) as uplink data, and uploads it to the optical transmitter 23. It also has a function to transmit a link.
In this case, if the uplink speed is increased as in the new interface standard, more probe information (longer road sections that record the travel trajectory, higher recording density of passing positions and passing times in the same road section) Information can be transmitted.

The in-vehicle 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.
For example, when the optical receiving unit 24 receives any downlink frame, the simple control unit transmits only one uplink frame (conventional uplink frame having a transmission rate of 64 kbit / s) including the vehicle ID of the host vehicle. The unit 23 has a function of causing uplink transmission.

[Frame structure of upstream frame]
FIG. 4 is a frame configuration diagram of the upstream frame.
As shown in FIG. 4, in the upstream frame storage area, in order from the top, a transmission control unit for synchronization (hereinafter referred to as “synchronizing unit”) for recognizing frame delimiters, a header unit, and an actual data unit And a CRC (Cyclic Redundancy Check) transmission control unit (hereinafter referred to as “CRC unit”).

In the upstream frame, 1 byte is assigned to the synchronization part, 10 bytes are assigned to the header part, 59 bytes at maximum are assigned to the real data part, and 4 bytes (1 byte idle part + 2 bytes CRC + 1 byte) are assigned to the CRC part. Of the last synchronization part).
In the header part of the upstream frame, storage areas such as “number of subsystem key information”, “vehicle ID”, “vehicle equipment type”, “information type”, “last frame flag”, and “frame number within the same information type” Is 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 a downlink of a public vehicle priority system (PTPS), a vehicle operation management system (MOCS), a field express support system (FAST), and a safe driving support system (DSSS). This is key information for selecting 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.

  The data format of the “subsystem key information” is different depending on the standard of each system, so the details are omitted. For example, in the case of a safe driving support system (DSSS), the brake state, the turn signal state, the hazard state, Information such as vehicle speed, traveling direction, acceleration / deceleration, and accelerator pedal position is included.

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 provides information according to the standard of the system. Is transmitted in a downlink frame. This provided information is called “special information” in the standard.
In this way, the optical beacon 4 determines the type of “special information” to be included in the downlink information after uplink reception based on the type of “subsystem key information”.

“Vehicle ID” is an area for storing a vehicle ID identification value (which may be a numerical value or a symbol) generated by the vehicle-mounted device 2 itself or automatically generated by the optical beacon 4 and notified to the vehicle-mounted device 2. . The in-vehicle device 2 stores the value of the vehicle ID stored at the time of uplink transmission in the vehicle ID of the header portion of the uplink frame.
“In-vehicle device type” is an area in which the type of the in-vehicle device 2 is stored. “Information type” is an area for storing the type of uplink information. In the new interface standard, the values of these areas indicate whether the uplink transmission subject is new or old, and whether the uplink information is high speed or low speed.

Specifically, when transmitting a low-speed uplink frame, the in-vehicle device 2 stores a predetermined value (for example, “6”) indicating the new in-vehicle device in the “in-vehicle device type” and the predetermined in the “information type”. A value (for example, “1”) is stored.
Further, when transmitting the high-speed uplink frame, the in-vehicle device 2 stores a predetermined value (for example, “6”) indicating the new in-vehicle device in the “in-vehicle device type” and a predetermined value (for example, in the “information type”). , “4”).

Therefore, the optical beacon 4 can be determined as a low-speed frame from the new in-vehicle device when the in-vehicle device type value of the received upstream frame is “6” and the information type value is “1”. When the value of the in-vehicle device type of the upstream frame is “6” and the value of the information type is “4”, it can be determined that the high-speed frame is from the new in-vehicle device.
In the case of an old vehicle-mounted device, the value of the vehicle-mounted device type is set to a value other than “6”. Therefore, when the optical beacon 4 receives an uplink frame having a value of “vehicle-mounted device type” other than “6”, It can be determined that the communication partner is an old vehicle-mounted device that does not support high-speed uplink transmission.

The “last frame flag” is a storage area for indicating which is the last frame among one or a plurality of uplink frames transmitted by the in-vehicle device 2.
For example, when continuously transmitting a plurality of uplink frames, the in-vehicle device 2 stores a predetermined flag value (for example, “1”) only in the “final frame flag” of the last uplink frame, and other than that The flag value is not stored in the upstream frame. Further, when transmitting only one uplink frame, the vehicle-mounted device 2 sets a final frame flag for the uplink frame.

The “frame number within the same information type” is the order number of the uplink frame when the information of the same information type is transmitted in one uplink frame or divided into a plurality of uplink frames and continuously transmitted.
The maximum number of uplink frames that can be continuously transmitted by the in-vehicle device 2 is defined as 16 frames. Accordingly, when the in-vehicle device 2 continuously transmits, for example, 16 uplink frames, the number values 1 to 16 are sequentially stored in the “frame number within the same information type” from the top uplink frame. Even in the case of one frame transmission, a number value is added to the frame number.

[Frame structure of downstream frame]
FIG. 5 is a frame configuration diagram of a downstream frame.
As shown in FIG. 5, the downlink frame storage area also includes a synchronization part, a header part, an actual data part, and a CRC part in order from the top, as in the case of the frame structure of the upstream frame (FIG. 4). .

In the downstream frame, 1 byte is allocated to the synchronization section, 5 bytes are allocated to the header section, 123 bytes are allocated to the real data section, and 4 bytes are allocated to the CRC section (1 byte idle section + 2 bytes CRC + 1 byte final). Synchronous part) is assigned.
The header portion of the downstream frame includes storage areas such as “information type”, “last frame flag”, and “frame number within the same information type”.

  “Information type” is an area in which the type of downlink information provided to the vehicle 20 by the optical beacon 4 is stored. In “Information Type”, numerical values from 1 to 63, which are ID values set in advance according to the type of provided information, are stored.

The “last frame flag” is a storage area for indicating which one or the number of downlink frames of the same information type transmitted by the optical beacon 4 is the last frame.
For example, the optical beacon 4 has a predetermined flag value (for example, “1” only in the “final frame flag” of the last downlink frame among a plurality of downlink frames of the same information type transmitted continuously in one downlink cycle. ”), And the flag value is not stored in other downlink frames of the same information type. Further, when transmitting only one downlink frame, the optical beacon 4 sets a final frame flag for the downlink frame.

The “frame number within the same information type” is the order number of the downlink frame when information of the same type is transmitted in one downlink frame or divided into a plurality of downlink frames and continuously transmitted.
When the optical beacon 4 continuously transmits one piece of provision information, the number of downlink frames is defined as 80 frames at the maximum (including the first frame storing lane notification information). Accordingly, when the optical beacon 4 continuously transmits, for example, 80 downlink frames of the same information type, the number values 1 to 80 in order from the first downlink frame are stored in the “frame number in the same information type”. Even in the case of one frame transmission, a number value is added to the frame number.

The type of information provided to the in-vehicle device 2 included in the actual data portion of the downstream frame may change before and after the optical beacon 4 receives a low-speed upstream frame from the in-vehicle device 2.
That is, the optical beacon 4 can switch the content of the information provided to the in-vehicle device 2 before and after receiving a low-speed uplink frame.

  More specifically, the optical beacon 4 receives January 2016 in a downstream frame (hereinafter referred to as “first downstream frame”) transmitted before receiving a low-speed uplink frame (before low-speed uplink reception). In the UTMS Association's “Advanced Optical Beacon Near-Infrared AMIS Communication Application Standard Version 3” (hereinafter referred to as “Communication Application Standard (Version 3)”), the provision of uplink information is a condition. Information that is specified not to be included (such as “current position information”) can be included in the actual data portion.

  In addition, the optical beacon 4 uses a communication application standard (version 3) for a downstream frame (hereinafter referred to as “second downstream frame”) transmitted after receiving a low-speed uplink frame (after receiving a low-speed uplink). In addition to information stipulated that the provision of uplink information is not a condition, the information specified as a condition for the provision of uplink information in the communication application standard (version 3) (such as "route signal information") Can also be included in the real data part.

The optical beacon 4 provides the provision information to the in-vehicle device 2 by one downlink frame when the provision information of the single information type to the in-vehicle device 2 fits in the capacity of the actual data part (123 bytes).
The optical beacon 4 is divided into a plurality of downlink frames (downstream frame groups) when the provision information of the single information type to the in-vehicle device 2 does not fit in the capacity of the actual data part (123 bytes), The provided information is provided to the in-vehicle device 2.

As shown in FIG. 5, examples of the provision information included in the first downlink frame include, for example, “lane notification information” (where the identification value of the vehicle ID is not stored), “current position information”, and the like. There is. The “lane notification information” is information for notifying the lane number on which the vehicle 20 travels, and the “current position information” is the position information (latitude and longitude) of the installation location of the beacon head 8.
The storage area of “lane notification information” includes “vehicle ID”, “lane number”, “beacon identification flag”, and the like. The optical beacon 4 does not store an identification value (ID value) in “vehicle ID” in the lane notification information included in the first downlink frame before uplink reception.

When the optical beacon 4 receives a low-speed uplink frame including the identification value (ID value) of the vehicle ID from the in-vehicle device 2, the second beacon frame (in which the acquired ID value is stored in the “vehicle ID” of the lane notification information) Hereinafter, this downstream frame is also referred to as a “turnback frame”), and the generated return frame is continuously transmitted.
Therefore, the in-vehicle device 2 can determine communication establishment with the optical beacon 4 based on whether or not the ID value of the host vehicle is included in the received lane notification information of the 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” of the lane notification information included in the return frame.
Therefore, the in-vehicle device 2 can determine which lane the host vehicle is traveling from the lane number value included in the received lane notification information of the return frame.

The “beacon identification flag” is a storage area indicating whether or not the own device is a device that supports high-speed uplink reception.
The optical beacon 4 corresponding to the high speed uplink reception stores a predetermined flag value (for example, “01”) in the “beacon identification flag” of the downlink frame, and the old optical beacon not corresponding to the high speed uplink reception is Other values (for example, “00”) are stored in the “beacon identification flag” of the downstream frame.

  Therefore, the in-vehicle device 2 determines whether the optical beacon of the communication partner is the new optical beacon 4 corresponding to the high-speed uplink reception according to the value of the “beacon identification flag” included in the “lane notification information” of the downlink frame. It can be determined whether the old optical beacon.

The type of the downlink frame that turns on the flag field of the lane notification information (beacon identification flag = 01) may be both the first and second downlink frames, or only the second downlink frame. However, as shown in FIG. 5, the latter case is assumed in this embodiment.
That is, in the optical beacon 4 of the present embodiment, the flag field of the first downlink frame is set to off (beacon identification flag = 00), and the flag field of the second downlink frame is set to on (beacon identification flag = 01). Set.

The downlink frame group that is repeatedly transmitted by the transmission / reception unit 11 of the optical beacon 4 after receiving the low-speed uplink is composed of 1 to 80 downlink frames. In the case of the old interface standard, the transmission time of the repeated transmission is 250 ms. is there.
Further, the downlink frame 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 above-described transmittable time range, and the downlink frame transmission period is about 1 ms.

Therefore, for example, when one significant data (provided information) is constituted by three downstream frames, the transmission cycle is about 3 ms, so that the data is about 80 times within a predetermined transmittable time (250 ms). It will be sent repeatedly.
However, in the optical beacon of the new interface standard, the downlink area DA is expanded to the vicinity immediately below the beacon head 8, so that the number of times of repeatedly transmitting a downlink frame group composed of 1 to 80 downlink frames is increased. be able to.

As shown in FIG. 5, examples of the provision information included in the second downlink frame include, for example, “lane notification information” (where the identification value of the vehicle ID is stored), “route signal information”, and “ Travel speed link information ".
The “lane notification information” is as described above. The “route signal information” is route signal information of an intersection located downstream of the installation point of the optical beacon 4. “Travel speed link information” is travel speed information of provided links preset for each optical beacon 4.

[Road-to-vehicle communication in the communication area]
FIG. 6 is a sequence diagram illustrating an example of road-to-vehicle communication performed in the communication area A.
In FIG. 6, a downlink frame DL1 is a downlink frame (first downlink frame) that is repeatedly transmitted by the optical beacon 4 in an initial state before low-speed uplink reception.
The downlink frame DL2 is a downlink frame (second downlink frame) that the optical beacon 4 repeatedly transmits after receiving the low-speed uplink.

The upstream frame UL1 is a low-speed upstream frame transmitted by the vehicle-mounted device 2 in response to the reception of the downstream frame DL1. The low-speed uplink frame UL1 is also referred to as “low-speed frame UL1”.
The upstream frame UL2 is a high-speed upstream frame that is transmitted by the in-vehicle device 2 in response to the reception of the downstream frame DL2. The high-speed upstream frame UL2 is also referred to as “high-speed frame UL2”.
A frame with a white circle indicates a frame in which the ID value is not stored in the vehicle ID, and a frame with a black circle indicates that the frame has an ID value stored in the vehicle ID.

In FIG. 6, U0 to U3 indicate a plurality of uplink frames (uplink frame groups) UL1 and UL2 that the in-vehicle device 2 performs uplink transmission.
Although FIG. 6 illustrates the case where the number of frames in the uplink frame group is four, the number of frames is not limited to four. For example, in the uplink frame group, three or more high-speed frames UL2 may be transmitted (maximum of 16 frames in the standard), or only one high-speed frame UL2 having a relatively long data length may be transmitted. .

An uplink frame U0 without hatching indicates a low-speed frame UL1 with a low transmission rate (64 kbitp / s), and an uplink frame U1 to U3 with hatching is a high-speed frame UL2 with a high transmission rate (256 kbps). It shows that.
In the following description of road-to-vehicle communication, the operation main body 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 2. The in-vehicle controller (communication control unit) 21 executes.

As shown in FIG. 6, the optical beacon 4 transmits a downlink frame DL1 including lane notification information whose ID value is not stored in the vehicle ID from all the beacon heads 8 corresponding to the lanes R1 to R4 (see FIG. 2). The transmission continues toward the road R at a predetermined transmission cycle.
When the vehicle 20 traveling in one of the lanes R1 to R4 on the road R enters the downlink area DA, the in-vehicle device 2 receives the downlink frame DL1 including the lane notification information (no ID value) or the other downlink frame DL1. . Thereby, the vehicle equipment 2 detects that the own vehicle has entered the communication area A of the optical beacon 4.

At this time, the in-vehicle device 2 stores the ID value of the host vehicle in the vehicle ID and the low-speed frame UL1 (hereinafter also referred to as “ID storage frame U0”) in which the in-vehicle device type value is “6”. It generates and switches its own communication from reception to transmission once, and uplinks the generated low-speed frame UL1. Thereafter, the vehicle-mounted device 2 returns its own communication from transmission to reception.
When there is information to be provided to the optical beacon 4 such as travel time information, the in-vehicle device 2 stores the information in the actual data part of the low-speed frame UL1 (ID storage frame U0).

The optical beacon 4 includes the lane notification information in which the acquired ID value is included in the vehicle ID and the value of the beacon identification flag is “1” when the low-speed frame UL1 is properly received through the CRC check of the received frame. Downlink frames DL2 (hereinafter also referred to as “turnback frames”) are continuously transmitted.
The optical beacon 4 is a downstream frame that includes other provision information after the elapse of a period of continuous transmission of the above lane notification information (defined as 8 ± 2 ms in the interface standard; hereinafter referred to as “continuous transmission period”). DL2 repeated transmission is executed every predetermined downlink period.

A plurality of downlink frames DL2 included in a single downlink cycle includes a leading one folded frame (downlink DL2 including lane notification information with an ID value) and subsequent lane notification information that is continuously transmitted. It consists of one or a plurality of downlink frames DL2 including link information.
The repeated transmission of the downlink frame DL2 performed after the continuous transmission period is repeated as much as possible within a predetermined time (for example, 350 ms).

Since the downlink frame DL2 included in one downlink cycle is composed of a maximum of 80 frames, the lane notification information transmitted by the first frame of the downlink cycle is one in 80 frames in the case of the least frequency. It becomes.
When the in-vehicle device 2 transmits the high-speed frames U1 to U3 after the low-speed frame U0, the “transmission interruption period” (a maximum of 20 ms is defined in the new interface standard) between the low-speed frame U0 and the high-speed frame U1. ) Is provided, and a return frame is received during this transmission interruption period.

The in-vehicle device 2 determines whether there is a downlink frame DL2 received from the optical beacon 4 that includes lane notification information in which the ID value of the host vehicle is stored in the vehicle ID.
If the above determination result is affirmative, the in-vehicle device 2 determines that the loopback of the ID value of the own vehicle is successful, and receives the communication state of the own device until the transmission interruption period elapses. Keep it.

While the above determination result is negative, the in-vehicle device 2 determines that the loopback of the ID value of the own vehicle is not successful, switches the communication state of the own device from reception to transmission, and transmits the uplink frame UL1. Is retransmitted (see the upstream frame U0 indicated by the broken line in FIG. 6).
In this case, the in-vehicle device 2 transmits the low-speed frame UL1 again after a predetermined time (for example, 30 milliseconds) has elapsed after transmission of the low-speed frame UL1 transmitted previously. The in-vehicle device 2 repeats this retransmission operation until the loopback of the ID value of the host vehicle is successful.

The in-vehicle device 2 determines whether the communication partner supports high-speed uplink reception or not based on the beacon identification flag included in the downlink frame DL2 received during the transmission interruption period, and according to the determination result It is determined whether to transmit the high-speed frames U1 to U3.
That is, the in-vehicle device 2 transmits the high-speed frame UL2 (U1 to U3) after the transmission interruption period when the above determination result is affirmative, and the high-speed frame when the above determination result is negative. Do not send UL2.

[High-speed uplink transmission before the uplink area]
FIG. 7 is an explanatory diagram showing an example of the downlink upstream section DA0 located on the upstream side of the uplink area UA.
In FIG. 7, an alternate long and short dash boundary line DB0 is an upstream boundary of the downlink area DA in which the in-vehicle device 2 can receive the first downlink frame DL1 before the content of the provision information transmitted by the optical beacon 4 in the downlink is switched. Indicates.

A broken boundary line UB1 indicates the upstream boundary of the uplink area UA in which the optical beacon 4 can receive the low-speed frame UL1 transmitted by the in-vehicle device 2 in the uplink. A solid boundary line UB2 indicates an upstream boundary of the uplink area UA in which the optical beacon 4 can receive the high-speed frame UL2 that the vehicle-mounted device 2 performs uplink transmission. “Receivable” in this case means that an uplink signal or a downlink signal having a light amount corresponding to the minimum reception sensitivity can be received at a predetermined bit error rate (for example, 10 ^{−5 in the} standard value) or less.

In FIG. 7, P0 is an intersection position (hereinafter referred to as “downlink upstream end”) between the upstream boundary DB0 and a predetermined installation height H (for example, H = 1.0 m) of the vehicle-mounted device 2.
In FIG. 7, P1 is the intersection position (= first uplink upstream end) of the upstream boundary UB1 and the installation height H, and P2 is the intersection position (= second) of the upstream boundary UB2 and the installation height H. Upstream upstream end).

In the optical beacon 4 of the present embodiment, it is assumed that the second uplink upstream end P2 is set to be upstream (may be coincident) with respect to the first uplink upstream end P1.
The reason is that if the first uplink upstream end P1 is upstream of the second uplink upstream end P2, the range between the upstream ends P1 and P2 indicates that the optical beacon 4 can receive the low-speed frame UL1, but the high-speed frame This is because the “insensitive area” (see FIG. 11 of Patent Document 1) in which UL2 cannot be received, and the optical beacon 4 cannot properly receive the high-speed frame UL2.

  As shown in FIG. 7, the downlink upstream end P0 of the optical beacon 4 is connected to the uplink upstream end (example of FIG. 11) in order to ensure uplink transmission when the vehicle-mounted device 2 approaches the uplink area UA. Then, the position may be set upstream of the second uplink upstream end P2).

In this case, a downlink upstream portion DA0, which is a portion of the downlink region DA located on the upstream side of the upstream boundary UB2 of the uplink region UA, is formed.
Therefore, when the in-vehicle device 2 enters the downlink upstream part DA0, the in-vehicle device 2 receives the downlink frame DL1 and starts transmitting the low-speed frame UL1.

On the other hand, the uplink area UA is an area satisfying communication quality with a bit error rate of 10 ⁻⁵ or less. Therefore, even if the in-vehicle device 2 transmits the low speed frame UL1 in the downlink upstream part DA0, the optical beacon 4 cannot normally receive the low speed frame UL1.
However, the low-speed frame UL1 that is first transmitted by the in-vehicle device 2 has a relatively small data size and is often only one frame. For this reason, although the probability is not so high, there is a possibility that the optical beacon 4 receives the low-speed frame UL1 transmitted in the downlink upstream part DA0.

In this case, since the optical beacon 4 switches the provided information to be transmitted in the downlink and transmits the downlink frame DL2 storing the vehicle ID of the vehicle-mounted device 2, the vehicle-mounted device 2 responds to the reception of the downlink frame DL2 with the high-speed frame UL2 Start sending.
However, since the high-speed frame UL2 has a relatively large data size and a large number of frames, the position of the vehicle-mounted device 2 in the vehicle traveling direction has not reached the second uplink upstream end P2 at the start of transmission of the high-speed frame UL2. There is a possibility that the optical beacon 4 cannot properly receive all the high-speed frames UL2.

  That is, when the in-vehicle device 2 starts transmission of the high-speed frame UL2 in the vicinity of the upstream side of the second uplink upstream end P2 (see the bar graph UL on the lower side of FIG. 8), the upstream frame composed of a plurality of high-speed frames UL2 Although a plurality of high-speed frames UL2 in the latter half of the group may be received, there is a high possibility that the optical beacon 4 cannot receive the high-speed frames UL2 for the first few frames.

As described above, when the downlink upstream portion DA0 exists in the communication area A and transmission of the high-speed frame UL2 is started in the downlink upstream portion DA0, the second uplink upstream end P2 is changed to the first uplink upstream end. There is a possibility that the optical beacon 4 cannot normally receive a part of the high-speed frame UL2 even if the position is set to be upstream or coincident with P1.
Therefore, in the optical beacon 4 of the present embodiment, the following measures are taken in order to increase the reception rate of the high-speed frame UL2.

That is, in the optical beacon 4 of the present embodiment, the beacon controller 7 executes a process (hereinafter referred to as “reception monitoring process”) for monitoring the reception state of the high-speed frame UL2 transmitted after the low-speed frame UL1.
In addition, when the beacon controller 7 determines that the high-speed frame UL2 is not normally received as a result of the reception monitoring process, the beacon controller 7 causes the vehicle-mounted device 2 to re-execute the transmission sequence of the low-speed frame UL1 and the high-speed frame UL2. Processing (hereinafter referred to as “initialization processing”) is executed.

As a result, even when the optical beacon 4 cannot normally receive the high-speed frame UL2 because the transmission of the high-speed frame UL2 is started in the downlink upstream part DA0, the in-vehicle device 2 re-executes the transmission sequence. The optical beacon 4 can re-receive the high-speed frame UL2. Therefore, the reception rate of the high-speed frame UL2 can be increased.
Hereinafter, an outline of “reception monitoring processing” and “initialization processing” executed by the optical beacon 4 (specifically, the beacon controller 7) of the present embodiment and specific examples of each processing will be described.

[Outline of reception monitoring processing and initialization processing]
FIG. 8 is a timing chart showing an example of road-to-vehicle communication when transmission of the high-speed frame UL2 is started near the upstream side of the uplink region.
In FIG. 8, “distance x” is a coordinate representing a distance with the origin immediately below the beacon head 8 on the road R and a positive value in the upstream direction (left direction in FIG. 8) from the origin.

The point where x = 0.7 m is the downstream end position of the downlink area DA in the new interface standard (position a0 in FIG. 3). The point where x = 3.4 m is the downstream end position (position b0 in FIG. 3) of the uplink area UA in the same standard.
The point where x = 6.04 m is the upstream end position (position c0 in FIG. 3) of the uplink area UA in the same standard. Here, it is assumed that the point where x = 6.04 m is the above-described second uplink upstream end P2 (see FIG. 7).

“Time t” is a coordinate representing an elapsed time when the vehicle 20 travels in the downstream direction (right direction in FIG. 8) from the point c0 with the passing point of the point c0 as the origin. Therefore, the time t proceeds from the left side to the right side. The time value at the point b0 (= 135.8 ms) and the time value at the point a0 (= 274.6 ms) are time values when the assumed speed of the vehicle 20 is 70 km / h.
In FIG. 8, the lower bar graph UL is a time chart of the transmission timing of the upstream frames UL1 and UL2. An upper bar graph DL is a time chart of transmission timings of the downstream frames DL1 and DL2.

As shown in the legend of FIG. 8, in the lower bar graph UL, the “solid hatched hatched” portion means the low-speed frame UL1. The portion of “horizontal line hatching” means the high-speed frame UL2.
In the upper bar graph DL, the “blank” portion means the first downstream frame DL1. The portion of “check pattern hatching” means a continuous transmission period of lane notification information.

In the upper bar graph DL, the “black fill” portion means the first frame in which the lane notification information is stored in the second downstream frame DL2 of 80 frames. The portion of “broken diagonal hatching” means the remaining 79 frames excluding the head of the second downstream frame DL2 of 80 frames.
In the upper bar graph DL, a portion “hatched hatching including thin lines and thick lines” means a period during which the optical beacon 4 executes “initialization processing”.

The time chart of road-to-vehicle communication in FIG. 8 assumes a case where the following sequences 1) to 3) are performed on the upstream side of the uplink upstream end c0.
1) Uplink transmission of the first low-speed frame UL1 2) Continuous transmission of lane notification information and downlink transmission of the first lane notification information of 80 frames 3) Uplink transmission of the first high-speed frame UL2 in this case There is a high possibility that the optical beacon 4 cannot receive a series of high-speed frames UL2 that start transmission on the upstream side of c0 (x> 6.04m).

Therefore, in the optical beacon 4 of the present embodiment, as shown in the flowchart of FIG. 8, the beacon controller 7 transmits the low-speed frame UL1 from the advanced vehicle-mounted device 2 (the low-speed frame of the vehicle-mounted device type = 6 and the information type = 1). ) Is received (step ST1), the “reception monitoring process” regarding the high-speed frame UL2 is executed (step ST2).
Specifically, the reception monitoring process is a process for determining whether or not a predetermined condition (hereinafter, also referred to as “reception failure condition”) indicating that the high-speed frame UL2 is not normally received is satisfied. That is.

The beacon controller 7 executes an initialization process if the reception failure condition is satisfied (Yes in step ST3) (step ST4), and if the reception failure condition is not satisfied (No in step ST3), the initialization process. Is not executed (step ST5).
Specifically, the above-described initialization process is a process for causing the vehicle-mounted device 2 to re-execute the transmission sequence of the low-speed frame UL1 and the high-speed frame UL2.

When the optical beacon 4 executes the initialization process, the in-vehicle device 2 re-executes the sequence of the low-speed frame UL1 and the high-speed frame UL2 as shown in the lower bar graph UL. That is, the in-vehicle device 2 restarts the uplink transmission sequence from the beginning.
For this reason, the optical beacon 4 can re-receive the high-speed frame UL2 that the in-vehicle device 2 transmits after the low-speed frame UL1, and the reception rate of the high-speed frame UL2 by the optical beacon 4 can be increased.

[Specific example of reception monitoring processing]
As the “reception failure condition” in the reception monitoring process, that is, a predetermined condition indicating that the high-speed frame UL2 is not normally received, for example, the following first condition to fourth condition can be employed. In addition, only one of these may be employ | adopted for the following 1st condition-4th condition, and you may decide to employ | adopt combining any at least 2 conditions arbitrarily.

(First condition)
The first condition is that the number of frame numbers (specifically, “frame number within the same information type” in the header part) included in a plurality of high-speed frames UL2 that are transmitted continuously is greater than or equal to a predetermined threshold value. Is that there is.
The reason is that if the frame number has the above jump, it is clear that the optical beacon 4 has not received a part of the series of high-speed frames UL2, and it cannot be said that the reception is normal. It is.

For example, the beacon controller 7 may determine that the first condition is satisfied when the number value of the frame number included in the first received high-speed frame UL2 is equal to or greater than a predetermined threshold (for example, “6”). .
This process is a process of determining a reception failure from the first frame among a plurality of high-speed frames UL2 that can transmit a maximum of 16 frames.

Also, the beacon controller 7 determines that the difference between the frame number number value included in the previously received high-speed frame UL2 and the frame number number value included in the currently received high-speed frame UL2 is a predetermined threshold (for example, “6 ]) In the above case, it may be determined that the first condition is satisfied.
This process is a process for determining a reception failure of an intermediate frame excluding the top frame among a plurality of high-speed frames UL2 that can transmit a maximum of 16 frames. The number value (initial value is 0) of the frame number included in the previously received high-speed frame UL2 is held, and each time the high-speed frame UL2 is received, the number value of the currently received high-speed frame and the previously received high-speed frame If the number of skipped frames is calculated from the number value, it is possible to determine by the same calculation whether the leading frame is included or not. However, the threshold value may be different depending on whether the head frame is included or not.

(Second condition)
The second condition is a reception rate at the time of reception of the final frame (specifically, the high-speed frame whose value of the “final frame flag” in the header part is 1) among the plurality of high-speed frames UL2 transmitted continuously. Is below a predetermined threshold (for example, 70%).
The reason is that when the reception rate at the time of reception of the final frame is low, it is clear that the optical beacon 4 has not received a part of the series of high-speed frames UL2, which is not normal reception. Because.

In the above second condition, instead of the “reception rate” at the time of reception of the final frame, the “number of receptions” of the high-speed frame UL2 at the time of reception may be adopted.
In other words, the second condition is that the “number of receptions” at the time of reception of the final frame among a plurality of high-speed frames UL2 transmitted continuously is a predetermined threshold value (for example, a reception number value corresponding to a reception rate of 70%). It may be the following. When the number of receptions is used, the predetermined threshold value may be made different for each number value (or each number value range) of the frame number of the last frame.

(Modification of second condition)
In the second condition, instead of the “reception rate” at the time of reception of the last frame, the “reception omission rate” of the high-speed frame UL2 at the time of reception (= number of frames that failed to be received / frame number of the last frame) is adopted. Also good.
In other words, as the second condition, the “reception omission rate” at the time of reception of the final frame among the plurality of high-speed frames UL2 transmitted continuously is not less than a predetermined threshold (for example, 30%). May be.

In the modified example of the second condition described above, not the “reception omission rate” at the time of reception of the last frame but the “reception omission number” (= the number of frames for which reception failed) of the high-speed frame UL2 at the time of reception is adopted. Also good.
That is, the second condition is that the “reception occlusion frequency” at the time of reception of the final frame among a plurality of high-speed frames UL2 transmitted continuously is a reception threshold corresponding to a predetermined threshold (for example, a reception omission rate of 30%). (Numerical value) or more. Similar to the number of receptions, this threshold value may be different for each frame number number value (or each number value range).

(Third condition)
The third condition is a predetermined condition in which the reception rate at the time of receiving a plurality of high-speed frames UL2 transmitted continuously is determined for each frame number (specifically, “frame number in the same information type” in the header part). It is below the threshold value.
The reason is that even when the reception rate at the time of receiving each high-speed frame UL2 is low, it is clear that the optical beacon 4 has not received a part of the series of high-speed frames UL2, and what is normal reception? I can't say that.

FIG. 9 is a calculation table showing an example of calculating the reception rate for each high-speed frame UL2.
In FIG. 9, “frame number” is a frame number within the same information type in the header portion of the high-speed frame UL2. The “monitoring threshold value” is a threshold value of a reception rate set in advance in the beacon controller 7 for each frame number number value i (i = 1 to 16).

The criteria for selecting the monitoring threshold value are, for example, as follows.
Criteria 1) When the denominator of the monitoring threshold is “n _i ” (i = 1 to 16), the natural number satisfying n _i = i (the same value as the number value i) is set.
Criterion 2) When the monitoring threshold numerator is “m _i ” (i = 1 to 16), it is a natural number that satisfies m _i ≦ i, m _i−1 ≦ m _i , and m ₁₆ <16.

“Reception example” is a determination column indicating reception success or reception failure for each number i of frame numbers, “◯” means reception success, and “×” means reception failure.
The “reception rate” is a reception rate calculated for each number value i of the frame number, and is calculated by a calculation formula of “reception rate = current number of successful receptions / current number value i”.
In the numerical example of FIG. 9, since the reception rate (= 4/8) is lower than the monitoring threshold (= 5/8) at the number value i = 8, the beacon is received when the eighth high-speed frame UL2 is received. The controller 7 executes the initialization process.

In the above third condition, instead of the “reception rate” at the time of receiving a plurality of high speed frames UL2, the “number of receptions” of the high speed frame UL2 at the time of reception may be adopted.
That is, the third condition is that the “number of receptions” at the time of receiving a plurality of high-speed frames UL2 transmitted continuously is a predetermined threshold (for example, the numerator of “monitoring threshold” in FIG. 9). Value).

(Modification of the third condition)
In the third condition, not the “reception rate” at the time of receiving a plurality of high-speed frames UL2, but the “reception omission rate” of the high-speed frame UL2 at the time of reception (= number of frames that failed to be received / current frame number value) It may be adopted.

FIG. 10 is a calculation table illustrating a calculation example of the reception leakage rate for each high-speed frame UL2.
In FIG. 10, the “frame number” is a frame number within the same information type of the header portion of the high-speed frame UL2. The “monitoring threshold value” is a threshold value of a reception omission rate preset in the beacon controller 7 for each frame number number value i (i = 1 to 16). The selection criteria for the monitoring threshold value are the same as the criteria 1 and 2 described above.

The “reception omission rate” is a reception omission rate calculated for each number value i of the frame number, and is calculated by a calculation formula of “reception omission rate = current number of reception omissions / current number value i”.
In the numerical example of FIG. 10, since the reception omission rate (= 4/8) exceeds the monitoring threshold (= 3/8) at the number value i = 8, when the eighth high-speed frame UL2 is received, The beacon controller 7 executes the initialization process.

The current number of reception omissions can be calculated by the following steps 1 and 2. In the next steps 1 and 2, “ip (initial value = 0)” is the frame number for the previous reception, “ic” is the frame number for the current reception, and “GT (initial value = 0)” is the number of reception omissions. Cumulative value.
Step 1: Every time the high-speed frame UL2 is received, a process of adding (ic-ip-1) to GT and a process of updating ip to ic are executed.
Step 2: The GT value obtained by the addition process in Step 1 is output as the current number of reception omissions.

Applying the above processing to the reception example up to frame number 9 in FIG. 10 is as follows.
When receiving frame 2 UL2: Cumulative value GT = 0 + “1-0−1” = 0
When receiving frame 2 UL2: Cumulative value GT = 0 + “4-1-1” = 2
When receiving frame number 5 UL2: Cumulative value GT = 2 + “5-4-1” = 2
When receiving frame 2 UL2: Cumulative value GT = 2 + “8-5-1” = 4
When receiving frame number 9 UL2: Cumulative value GT = 4 + “8-7-1” = 4

In the modified example of the third condition described above, not the “reception omission rate” at the time of receiving a plurality of high speed frames UL2, but the “number of omissions in reception” (= the number of frames for which reception failed) at the time of the reception. It may be adopted.
That is, the third condition is that the “number of reception omissions” at the time of receiving a plurality of high-speed frames UL2 transmitted continuously is a predetermined threshold (for example, the “monitoring threshold” in FIG. 10). It may be less than (molecular value). The beacon controller 7 may execute the initialization process when the number of reception omissions is not determined for each frame number and the number of reception omissions exceeds a certain threshold.

  By the way, when the second condition is adopted, the reception rate, the number of receptions, the reception omission rate, or the number of omissions at the time of reception of the final frame are required. Therefore, the reception monitoring process cannot be performed if the final frame cannot be received. Since the determination of whether or not the reception is bad (step ST3 in FIG. 8) is after the reception of the final frame, the output of the determination result is delayed.

  On the other hand, if the third condition is adopted, it is determined whether or not there is a reception failure using the reception rate, the number of receptions, the reception omission rate, or the number of omissions at the time of receiving each high-speed frame UL2 (step in FIG. 8). Since ST3) can be performed, the reception monitoring process can be executed even if the final frame cannot be received, and the determination result can be output more quickly than in the case of the second condition.

(4th condition)
The fourth condition is that even after a predetermined time (for example, 30 ms = 20 ms + α) has elapsed after receiving the low-speed frame UL1 (the low-speed frame with the on-vehicle device type = 6 and the information type = 1) from the advanced on-vehicle device 2, The high-speed frame UL2 is not received.
The reason is that if the above condition is satisfied, it can be estimated that the vehicle-mounted device 2 has not transmitted a series of high-speed frames UL2 from the beginning, so that the optical beacon 4 has not received the high-speed frame UL2 normally. Because it can.

[Specific example of initialization processing]
The “initialization process” executed by the beacon controller 7, that is, the process for causing the vehicle-mounted device 2 to re-execute the transmission sequence of the low-speed frame UL 1 and the high-speed frame UL 2 includes, for example, the following first process and second process: Can be adopted.

(First process)
In the first process, transmission of the second downlink frame DL2 after reception of the low-speed frame UL1 (the low-speed frame with the on-vehicle device type = 6 and the information type = 1) from the advanced on-vehicle device 2 is performed for a predetermined time (for example, 20 (30 ms).
More specifically, after the elapse of the predetermined time, the beacon controller 7 may switch downlink transmission to transmission of the first downlink frame DL1.

  The reason is that if the beacon controller 7 executes the first process, the vehicle-mounted device 2 determines that the road-vehicle communication with another optical beacon 4 has been newly started, and the low-speed frame UL1 and the high-speed frame UL2 are determined. This is because it is considered that the transmission sequence is re-executed.

(Second process)
In the second process, the lane notification information included in the second downlink frame DL2 is transmitted after receiving the low-speed frame UL1 (the low-speed frame of the vehicle-mounted device type = 6 and the information type = 1) from the advanced vehicle-mounted device 2. This is processing for clearing the identification value of the vehicle ID.
The reason is that even when the beacon controller 7 executes the second process, the in-vehicle device 2 determines that the road-vehicle communication with another optical beacon 4 is newly started, and the low-speed frame UL1 and the high-speed frame are determined. This is because it is considered that the UL2 transmission sequence is re-executed.

[Example of suitable timing for re-execution]
FIG. 11 is a time chart illustrating a suitable timing example of re-execution of the transmission sequence by the in-vehicle device 2.
In FIG. 11, the road-to-vehicle communication on the upper stage side (current worst condition) is that the uplink transmission of the first low-speed frame UL1 is performed immediately before the point x = 6.04m (uplink upstream end c0). A case where the optical beacon 4 cannot receive the low-speed frame UL1 is shown.

In this case, according to the new interface standard, the vehicle-mounted device 2 retransmits the low-speed frame UL1 after 30 ms has elapsed since the uplink transmission of the first low-speed frame UL1.
When the optical beacon 4 receives the second low-speed frame UL1, the sequence of road-to-vehicle communication is started. That is, from the standpoint of the in-vehicle device 2 side, uplink transmission of the low-speed frame UL1 → downlink reception of the continuous frame and the first frame of the downlink cycle → uplink transmission of the high-speed frame UL2 → remaining frames of the downlink cycle Road-to-vehicle communication proceeds in the order of the downlink reception.

As described above, when the road-vehicle communication sequence is started by the second low-speed frame UL1, the number of frames of the downlink frame DL2 that can be received by the in-vehicle device 2 after the uplink transmission of the high-speed frame UL2 is “183 frames”. "
The new interface standard stipulates that the number of frames of the second downlink frame DL2 provided to the in-vehicle device 2 is 160 frames or more. Therefore, the time chart of road-to-vehicle communication on the upper side of FIG. 11 satisfies the requirements in the standard.

In FIG. 11, the road-to-vehicle communication (re-execution timing) on the lower side is performed before the point where x = 6.04 m (uplink upstream end c0), and uplink transmission of the first low-speed frame UL1 is performed. The case where the optical beacon 4 has received the low-speed frame UL1 and a plurality of high-speed frames UL2 are uplinked across the point where x = 6.04 m is shown.
In this case, when the optical beacon 4 of the present embodiment performs the initialization process, the in-vehicle device 2 re-executes the transmission sequence of the low speed frame UL1 and the high speed frame UL2.

  However, if the re-execution start time (second transmission start time of the low-speed frame UL1) ts is delayed by the in-vehicle device 2, the transmission end time te of the high-speed frame UL2 is also delayed, and after this transmission end time te, the in-vehicle device There is a possibility that the number of frames of the downlink frame DL2 that can be received by 2 does not satisfy “160 frames or more” in the standard.

Therefore, the transmission start time point ts of the low-speed frame UL1 due to the re-execution of the in-vehicle device 2 is the case where the reception of the first low-speed frame UL1 is unsuccessful (the road-to-vehicle communication on the upper stage in FIG. 11), It is preferable to be before the time point (t = 30 ms).
In other words, the transmission start time point ts is obtained by transmitting the low-speed frame UL1 transmitted immediately before the uplink upstream end c0 by the vehicle-mounted device 2 moving downstream at a predetermined assumed speed (for example, 70 km / h) to the optical beacon 4. Is assumed to be before the time point (t = 30 ms) when the in-vehicle device 2 starts a retransmission sequence.

In this way, it is possible to secure downlink traffic (183 frames) that is almost equivalent to the road-to-vehicle communication (current worst condition) on the upper side of FIG. 11, and execute downlink communication that satisfies the requirements of the new interface standard. become able to.
In addition, in the lower-level road-to-vehicle communication (re-execution timing) in FIG. 11, if the execution period of the initialization process by the optical beacon 4 can be about 20 ms, the transmission start time ts of the low-speed frame UL1 is adjusted to 30 ms. It will be possible.

[Need for improvement of in-vehicle equipment]
By the way, when a reception failure of the high-speed frame UL2 is detected after the low-speed frame UL1 is received, the optical beacon 4 receives the “retransmission request” for the required high-speed frame UL2 as a means for improving the reception rate of the high-speed frame UL2. It is conceivable that the in-vehicle device 2 retransmits the predetermined high-speed frame UL2 in response to the retransmission request.
However, with this means, it is necessary to improve the control function of the in-vehicle controller 21 so that the in-vehicle device 2 can respond to the retransmission request for the high-speed frame UL2.

On the other hand, the initialization process of the present embodiment is, in other words, a process for causing the in-vehicle device 2 to redo the transmission sequence according to the new interface standard related to the uplink transmission of the low speed frame UL1 and the high speed frame UL2. I can say that.
Therefore, from the standpoint of the in-vehicle device 2 side, there is an effect that it is not necessary to improve the control function of the in-vehicle controller 21 in accordance with the new interface standard such as software executed by the CPU of the in-vehicle controller 21 and a control circuit such as ASIC. is there.

However, in order to prevent an increase in memory capacity, the in-vehicle device 2 adopts memory control that immediately erases large-capacity uplink data such as probe data when uplink transmission by the high-speed frame UL2 is completed. There is a possibility.
In this case, because the in-vehicle device 2 re-executes the transmission sequence of the low-speed frame UL1 and the high-speed frame UL2 by the initialization process of the present embodiment, there is no uplink data to be stored in the high-speed frame UL2. The in-vehicle device 2 cannot re-execute the transmission sequence.

Therefore, the in-vehicle controller 21 of the in-vehicle device 2 that re-executes the transmission sequence of the low-speed frame UL1 and the high-speed frame UL2 transmits the uplink data for a predetermined time after completing the transmission of the uplink data by the high-speed frame UL2. It is preferable that the retained memory control be executable.
The predetermined time may be set to a time (for example, 250 to 500 ms) sufficient for the in-vehicle device 2 to complete road-vehicle communication with one optical beacon 4.

  The embodiments disclosed herein are illustrative in all respects and should be considered not restrictive. The scope of the right of the present invention is shown not by the contents of the above-described embodiment but by the scope of claims, and is intended to include meanings equivalent to the scope of claims and all modifications within the scope.

DESCRIPTION OF SYMBOLS 1 Traffic control system 2 Vehicle equipment 3 Central apparatus 4 Optical beacon 5 Communication line 6 Communication part 7 Beacon controller (communication control part, light emission control part)
8 Beacon head 9 Housing 11 Transmission / reception unit 12 Sensor unit 13 Light-emitting unit for optical communication (light transmission unit)
14 Light receiving unit for optical communication (light receiving unit)
DESCRIPTION OF SYMBOLS 15 Light-emitting unit for detection 16 Light-receiving unit for detection 17 Support | pillar 18 Construction bar 20 Vehicle 21 Vehicle-mounted controller 22 Vehicle-mounted head 23 Light transmitter 24 Light receiver R Road R1-R4 Lane

Claims (10)

An optical beacon that performs wireless communication with an in-vehicle device of a running vehicle using an optical signal,
An optical receiver capable of photoelectric conversion at two transmission speeds, high and low;
An optical transmitter capable of electro-optical conversion at a predetermined transmission rate;
When a predetermined condition indicating that a high-speed frame transmitted by an advanced in-vehicle device corresponding to high-speed uplink transmission is not normally received after a low-speed frame is satisfied, a transmission sequence of the low-speed frame and the high-speed frame is determined. An optical beacon comprising: a communication control unit that executes processing for causing the advanced vehicle-mounted device to re-execute. The predetermined condition includes
2. The optical beacon according to claim 1, wherein the number value of the frame number included in the plurality of high-speed frames transmitted continuously includes a jump that is equal to or greater than a predetermined threshold. The predetermined condition includes
The optical beacon according to claim 1 or 2, wherein a reception rate at the time of reception of a final frame among the plurality of high-speed frames transmitted continuously is not more than a predetermined threshold. The predetermined condition includes
4. The reception rate according to claim 1, wherein a reception rate at the time of receiving a plurality of the high-speed frames transmitted continuously is less than a predetermined threshold defined for each frame number. 5. Light beacon. The predetermined condition includes
The optical beacon according to any one of claims 1 to 4, wherein the high-speed frame is not received even if a predetermined time elapses after the low-speed frame is received. In the process for re-executing the transmission sequence,
The optical beacon according to any one of claims 1 to 5, further comprising a process of stopping transmission of a downlink frame for a predetermined time after receiving the low-speed frame. In the process for re-executing the transmission sequence,
The optical beacon according to any one of claims 1 to 5, including a process of clearing an identification value of a vehicle ID of lane notification information included in a downstream frame transmitted after receiving the low-speed frame. The transmission start time of the low-speed frame by re-execution of the transmission sequence is:
When it is assumed that the optical beacon has not received the low-speed frame transmitted immediately before the uplink upstream end by the advanced on-vehicle device moving downstream at a predetermined assumed speed, the advanced on-vehicle device retransmits the low-speed frame. The optical beacon according to any one of claims 1 to 7, wherein the optical beacon is before a time point when the sequence is started. An in-vehicle device that performs wireless communication with an optical beacon and an optical signal installed on a road,
An optical receiver capable of photoelectric conversion at a predetermined transmission rate;
An optical transmitter capable of electro-optical conversion at two transmission speeds, high and low,
A communication control unit capable of executing a transmission sequence for transmitting a high-speed frame after a low-speed frame, and
The communication control unit is an in-vehicle device capable of executing memory control for holding the uplink data for a predetermined time after completing transmission of the uplink data by the high-speed frame.   The on-vehicle device according to claim 9, wherein the predetermined time is set to a time sufficient for the on-vehicle device to complete road-to-vehicle communication with one optical beacon.

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