JP6565768B2 - Optical communication device - Google Patents

Description

  The disclosure according to this specification relates to an optical communication device that is mounted on a moving body such as a vehicle and transmits / receives information to / from an optical communication roadside device installed on a road.

  Conventionally, for example, Patent Document 1 discloses a vehicle road provided with a receiving unit that receives a downlink signal from an optical communication path side unit such as an optical beacon, and a transmission unit that transmits an uplink signal toward the optical communication path side unit. An inter-vehicle communication device is disclosed. The road-to-vehicle communication apparatus determines that the communication unit has entered the communication area with the optical communication roadside device based on the reception state of the downlink signal by the reception unit, and starts transmission of the uplink signal from the transmission unit. According to such control, transmission of an unnecessary uplink signal before entering the communication area can be suppressed.

Japanese Patent Application Laid-Open No. 2014-119956

  Now, in the road-to-vehicle communication device disclosed in Patent Document 1, the optical communication roadside unit enters the communication area based on the reception state of the downlink signal by the receiving unit. Therefore, the determination that the communication area has been entered is not necessarily accurate, and even an uplink signal transmitted after the determination that the communication area has been entered may not be reliably received by the optical communication path side device. Therefore, in the road-to-vehicle communication device, in order to ensure communication reliability, uplink signal transmission is repeated at a substantially constant transmission cycle after determining that the communication area has been entered.

  However, the transmission cycle of the uplink signal is set to be relatively short so that the uplink signal is reliably received by the optical communication roadside unit even from a vehicle traveling at high speed. Therefore, for example, when the vehicle is traveling at a low speed, even if transmission of the uplink signal is suppressed before entering the communication area, the number of times the uplink signal is transmitted after entering the communication area is not It could increase as needed.

  The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide an optical signal capable of suppressing transmission of an unnecessary uplink signal while ensuring reliability of communication with an optical communication path side unit. It is to provide a communication device.

In order to achieve the above object, the disclosed first aspect is an optical communication that transmits and receives information by optical communication with an optical communication roadside unit (110) that is mounted on a mobile body (A) and installed on a road. A receiving unit (81) that receives a downlink signal from an optical communication path side unit, a transmission unit (82) that transmits an uplink signal toward the optical communication path side unit, and a reception state of the receiving unit A communication area determination unit (72) for determining that the reception unit has entered the stable communication area (SCA) with the optical communication roadside device, a speed acquisition unit (71) for acquiring the traveling speed of the mobile object, and a communication area A transmission control unit that starts transmission of an uplink signal by the transmission unit based on the determination that the determination unit is within the stable communication area, and sets the transmission interval (ti) of the uplink signal to be shorter as the traveling speed increases. And running speed is slow Transmission control section for setting a long transmission distance Ruhodo uplink signal (73), comprising a transmission control unit is acquired at a speed acquisition unit after the communication area determining unit determines that a stable communication area that the running speed used to set the transmission interval corresponding to the travel speed, are optical communication device that initiates the transmission of the uplink signal.

  According to this aspect, the transmission interval of the uplink signal that is started after it is determined that the vehicle has entered the stable communication area is shortened as the traveling speed of the mobile body increases. Therefore, even when the moving body is traveling at a high speed, the number of times that the uplink signal is transmitted to the optical communication path side device is secured. As described above, the uplink signal can be reliably received by the optical communication path side unit.

  On the other hand, when the moving body is traveling at a low speed, the transmission interval of the uplink signal is lengthened. Therefore, coupled with the control that does not transmit the uplink signal until it is determined that the stable communication area has been entered, the number of uplink signal transmissions to one optical communication path side device can be accurately suppressed. According to the above, the optical communication device transmits an unnecessary uplink signal while ensuring the reliability of communication with the optical communication roadside device for road-to-vehicle communication that starts based on the determination to enter the stable communication area. Can be suppressed.

  Note that the reference numbers in the parentheses merely show an example of a correspondence relationship with a specific configuration in an embodiment described later, and do not limit the technical scope at all.

It is a block diagram which shows the whole structure of the optical communication apparatus relevant to road-to-vehicle communication, a navigation apparatus, and an optical beacon. It is a figure which shows typically the stable communication area | region and unstable communication area | region of an optical beacon. It is a figure which shows typically the stable communication area | region and unstable communication area | region of an optical beacon. FIG. 6 is a diagram illustrating that an uplink signal transmission interval is set to be shorter when the traveling speed of the vehicle is higher than that in FIG. 5. FIG. 5 is a diagram showing that an uplink signal transmission interval is set to be longer when the vehicle traveling speed is lower than that in FIG. 4. It is a flowchart which shows the detail of the transmission process implemented by the transmission / reception processing circuit.

  An optical communication device 100 according to an embodiment of the present disclosure is mounted on a vehicle A together with a navigation device 10 as illustrated in FIG. The optical communication device 100 performs bidirectional road-to-vehicle communication with various optical beacons 110 installed on the road by optical communication using near infrared rays. The various optical beacons 110 include optical beacons for DSS (Driving Safety Support Systems) and VICS (Vehicle Information and Communication System (registered trademark)).

  The optical beacon 110 is connected to a central device installed in a traffic control center or the like via a communication line such as a telephone line. The optical beacon 110 repeatedly transmits a downlink signal toward the optical communication apparatus 100 and receives an uplink signal transmitted from the optical communication apparatus 100.

  Information transmitted by the downlink signal (hereinafter, “downlink information”) includes traffic information regarding the road in the traveling direction of the vehicle A, scheduled travel time information, and the like. The information transmitted by the uplink signal (hereinafter, “uplink information”) includes probe information such as travel time and road trajectory of the road on which the vehicle A has traveled. The optical beacon 110 transmits probe information collected from a number of vehicles to the central device. The uplink information includes unique ID information assigned to each optical communication device 100. When receiving the uplink signal from the specific vehicle A, the optical beacon 110 intermittently transmits a downlink signal including the received ID information.

  The optical beacon 110 includes a beacon control unit 111 and at least one light projecting / receiving unit 112. The beacon control unit 111 is mainly configured by a microcontroller having a processor, a RAM, and a storage medium. The beacon control unit 111 integrally controls wired communication with the central device and optical communication with the optical communication device 100.

  The light projecting / receiving unit 112 shown in FIGS. 2 and 3 is attached to an erection bar that is laid horizontally from a column provided on the side of the roadway. The light projecting / receiving unit 112 is located above a road through which the vehicle A can pass. The communication area in which road-to-vehicle communication can be performed is set in the upstream direction of the light projecting / receiving unit 112 depending on the installation posture of the light projecting / receiving unit 112 with the light receiving surface and the irradiation surface facing upstream from directly below. The upstream direction of the light projecting / receiving unit 112 is the direction opposite to the traveling direction of the vehicle A.

  The communication area of the optical beacon 110 is different between the downlink signal and the uplink signal. The communication area (hereinafter referred to as “DL communication area”) in which the optical communication apparatus 100 transmits a downlink signal is 0.7 to upstream from the reference position RP according to the standard, assuming that the reference position RP is directly below the light projecting / receiving unit 112. The range is 6.0 m. On the other hand, an area where the optical beacon 110 can receive an uplink signal (hereinafter referred to as “UL communication area”) is a range of 3.4 to 6.0 m upstream of the reference position RP according to the standard.

  As described above, the upstream ends of the DL communication area and the UL communication area are generally set wider than the above standards. In addition, the upstream end of the DL communication area does not necessarily match the upstream end of the UL communication area. For example, when the upstream end of the DL communication area is located upstream of the upstream end of the UL communication area, the “unstable communication area UCA” is defined from the upstream end of the UL communication area to the upstream end of the DL communication area. Then, the “stable communication area SCA” is defined from the upstream end of the UL communication area to the downstream end of the DL communication area.

  Since the unstable communication area UCA can be irradiated with near-infrared light that is a downlink signal, the optical communication device 100 can receive the downlink signal while being unstable. However, the success rate of downlink signal reception in the unstable communication area UCA is lower than the success rate of downlink signal reception in the stable communication area SCA. In addition, since the unstable communication area UCA is outside the UL communication area, an uplink signal transmitted from the optical communication device 100 located in the unstable communication area UCA is difficult to be received by the light projecting / receiving unit 112. Therefore, the unstable communication area UCA is an area that can succeed in downlink communication but fails in uplink communication.

  The light projecting / receiving unit 112 includes at least one light emitting diode and one photodiode. A light emitting diode irradiates the downlink signal which consists of near-infrared light toward DL communication area. The photodiode can receive an uplink signal composed of near-infrared light output from the optical communication device 100 located in the UL communication area.

  Next, details of the navigation device 10 and the optical communication device 100 mounted on the vehicle A will be described in order based on FIG.

  The navigation device 10 provides route information to the destination, road information acquired through road-to-vehicle communication, and the like to the driver of the vehicle A by display and voice. The navigation device 10 includes a position detection unit 30, a display 21, an audio output unit 22, an external memory 23, a navigation control unit 20, and the like.

  The position detection unit 30 includes a GNSS receiver 31, an inertial sensor 32, and a vehicle speed signal input unit 33. The GNSS receiver 31 receives positioning signals from a plurality of artificial satellites, and measures the current position of the vehicle A based on the received positioning signals. The inertial sensor 32 is a gyro sensor or the like, and measures the acceleration acting on the vehicle A. The vehicle speed signal input unit 33 is electrically connected to a vehicle speed sensor 40 mounted on the vehicle A. A vehicle speed pulse corresponding to the rotational speed of the wheel of the vehicle A is input to the vehicle speed signal input unit 33. Based on the vehicle speed pulse input to the vehicle speed signal input unit 33, the traveling speed and the travel amount of the vehicle A can be calculated.

  The position detection unit 30 integrates the information acquired in each configuration (31 to 33) to generate current position information of the vehicle A and speed information indicating the current traveling speed of the vehicle A, and navigation Sequentially provided to the control unit 20. The position detection unit 30 may further include a geomagnetic sensor capable of detecting a traveling direction from geomagnetism and an acquisition unit for acquiring steering angle information of a steering as a configuration for acquiring position information and speed information. Good.

  The display 21 includes a liquid crystal display capable of displaying color. The display 21 displays the route information to the destination set by the driver and various information related to the vehicle A such as VICS information and DSSS information provided by the optical beacon 110 to the driver by images displayed on the screen. Can present.

  The audio output unit 22 includes a speaker that can reproduce audio. The audio output unit 22 reproduces predetermined information sounds and audio messages set in advance in the vehicle interior, so that various information related to the vehicle A such as route information, VICS information, and DSSS information is given to the driver. Can present.

  The external memory 23 includes a writable nonvolatile storage medium such as an HDD and a flash memory. The external memory 23 stores map data displayed on the display 21, audio data reproduced by the audio output unit 22, and the like. In addition, the external memory 23 stores optical beacon information indicating the type of each optical beacon 110, the installed latitude and longitude, and the like.

  The navigation control unit 20 is mainly configured by a microcontroller having a processor, a RAM, a storage medium, an input / output interface, and a bus line for connecting them. The navigation control unit 20 executes a program stored in a storage medium by a processor, thereby presenting processing such as route information, VICS information, and DSSS information, and transmitting and receiving information to and from the optical communication device 100. I do. For example, the navigation control unit 20 sequentially transmits the speed information of the vehicle A acquired by the position detection unit 30 toward the optical communication device 100. Further, the navigation control unit 20 sequentially acquires information received by the optical communication device 100.

  The optical communication device 100 is attached to, for example, the upper surface of the dashboard of the vehicle A so as to facilitate optical communication with the light projecting / receiving unit 112 installed above the road. The optical communication device 100 has a function of receiving a downlink signal transmitted from the optical beacon 110 and a function of transmitting an uplink signal toward the optical beacon 110. The optical communication device 100 includes a receiving unit 81, a transmitting unit 82, a transmission / reception processing circuit 70, and the like.

  The receiving unit 81 includes at least one photodiode that can detect near-infrared light. The light receiving surface of the photodiode is directed upward in the traveling direction of the vehicle A. The receiving unit 81 receives the downlink signal by detecting near infrared light emitted from the light projecting / receiving unit 112 as a downlink signal. The receiving unit 81 converts a downlink signal received by optical communication into an electric signal, and sequentially outputs it to the transmission / reception processing circuit 70.

  The transmission unit 82 includes at least one light emitting diode capable of emitting near infrared light. The irradiation surface of the light emitting diode is directed upward in the traveling direction of the vehicle A, similarly to the light receiving surface of the receiving unit 81. The transmission unit 82 converts the uplink signal output as an electrical signal from the transmission / reception processing circuit 70 into a near-infrared pulse signal, and sequentially transmits the pulse signal toward the upper side in the traveling direction where the light projecting / receiving unit 112 is located.

  The transmission / reception processing circuit 70 is electrically connected to the navigation device 10 and can transmit / receive information to / from the navigation device 10 through wired communication. The transmission / reception processing circuit 70 is mainly configured by a microcontroller including a processor, a RAM, a storage medium, and the like. In addition, the transmission / reception processing circuit 70 includes a reception port that acquires downlink information received by the reception unit 81 and a transmission port that outputs uplink information transmitted from the transmission unit 82. The transmission / reception processing circuit 70 constructs a data processing unit 71, an area determination unit 72, and a transmission / reception control unit 73 as functional units that process optical communication with the optical beacon 110 by executing a program stored in a storage medium.

  The data processing unit 71 rearranges the various types of downlink information received from the optical beacon 110 based on a preset priority order and transfers the information to the navigation control unit 20. In addition, the data processing unit 71 acquires probe information and the like transmitted to the optical beacon 110 from the navigation control unit 20. Further, the data processing unit 71 acquires speed information indicating the traveling speed of the vehicle A from the navigation control unit 20. The data processing unit 71 repeatedly acquires speed information while the vehicle A is traveling. The data processing unit 71 may simply acquire the value of the traveling speed calculated by the navigation control unit 20 as speed information, or obtain the average of these values after acquiring the traveling speed for a plurality of consecutive times. It is good also as speed information.

  The area determination unit 72 determines whether or not the reception unit 81 has entered the stable communication area SCA of the optical beacon 110 based on the reception state of the downlink signal in the reception unit 81. The area determination unit 72 determines the reception state based on whether or not the reception unit 81 has continuously received the downlink signal transmitted from the light projecting / receiving unit 112. For example, if the number of downlink signal receptions within a predetermined time exceeds a predetermined threshold, the region determination unit 72 determines that the reception unit 81 is continuously receiving the downlink signal, and performs stable communication. It is determined that the receiving unit 81 is in the area SCA. On the other hand, when the number of downlink signal receptions within a predetermined time is less than the threshold, the region determination unit 72 determines that the reception unit 81 is outside the stable communication region SCA.

  The transmission / reception control unit 73 performs an acquisition process of the downlink signal received by the reception unit 81 and an output process of the uplink signal transmitted from the transmission unit 82. The transmission / reception control unit 73 starts transmission of an uplink signal by the transmission unit 82 based on the determination that the region determination unit 72 is the stable communication region SCA (see FIGS. 4 and 5). 4 and 5, a leftward arrow from the optical beacon 110 to the optical communication device 100 indicates a downlink signal, and a rightward arrow from the optical communication device 100 to the optical beacon 110 indicates an uplink signal. .

  The transmission / reception control unit 73 sets the uplink signal transmission interval ti to be shorter as the traveling speed of the vehicle A acquired by the data processing unit 71 increases. As a result, the uplink signal transmission cycle is shortened, and the number of uplink signal transmissions per predetermined time is increased (see FIG. 4). On the other hand, the transmission / reception control unit 73 sets the transmission interval ti of the uplink signal longer as the traveling speed becomes slower. As a result, the transmission cycle of the uplink signal is extended, and the number of uplink signal transmissions per predetermined time is reduced (see FIG. 5).

  Further, the transmission / reception control unit 73 adjusts the uplink signal transmission interval ti based on the latest traveling speed acquired by the data processing unit 71 even after starting transmission of the uplink signal. Specifically, every time an uplink signal is transmitted, the transmission / reception control unit 73 sets an interval until the next uplink signal is transmitted based on the latest traveling speed. Therefore, even if the traveling speed of the vehicle A largely fluctuates after the determination with the stable communication area SCA, the transmission / reception control unit 73 transmits the uplink signal at the transmission interval ti corresponding to the traveling speed after the variation. Let

  The transmission / reception control unit 73 determines that the communication with the optical beacon 110 is completed when the downlink signal is not received from the optical beacon 110 for a predetermined time (for example, about 3 seconds). Further, the transmission / reception control unit 73 can end the transmission of the uplink signal based on the reception of the uplink signal by the optical beacon 110 before the communication with the optical beacon 110 is ended.

  Specifically, as described above, the optical beacon 110 that has received the uplink signal adds unique ID information included in the uplink signal to the downlink signal. The transmission / reception control unit 73 determines whether or not ID information addressed to the vehicle is included in the downlink signal after the transmission of the uplink signal is started. When the downlink signal does not include the ID information addressed to the own vehicle, the transmission / reception control unit 73 determines that the uplink signal is not received by the optical beacon 110 and continues to transmit the uplink signal. On the other hand, when the ID addressed to the vehicle is included in the downlink signal, the transmission / reception control unit 73 determines that the uplink signal is received by the optical beacon 110 and ends the transmission of the uplink signal (FIG. 4). And FIG. 5).

  The details of the process of changing the uplink signal transmission interval ti in accordance with the traveling speed of the vehicle A as described above will be described based on FIG. 6 and with reference to FIGS. The transmission processing illustrated in FIG. 6 is started by the transmission / reception processing circuit 70 based on the start of power supply to the optical communication device 100.

  Note that such transmission processing may be started by the transmission / reception processing circuit 70 based on a command signal from the navigation control unit 20 that detects the approach to the optical beacon 110 based on the position information. Further, the flowchart of FIG. 6 mainly shows contents for starting transmission of an uplink signal based on reception of a downlink signal and contents for adjusting a transmission interval ti. For example, communication with the optical beacon 110 is terminated. Description of the processing to be performed is omitted.

  In S101, a process of receiving a downlink signal is performed, and the process proceeds to S102. In S102, based on the reception state of the downlink signal received in S101, it is determined whether or not the reception unit 81 is in the stable communication area. In S102, when the downlink signal can be continuously received, it is determined that the receiving unit 81 is in the stable communication area SCA (S102: YES), and the process proceeds to S103. On the other hand, when the downlink signal is not continuously received, it is determined that the receiving unit 81 is outside the stable communication area SCA (S102: NO), and the process returns to S101. By repeating S101 and S102, the receiver 81 (vehicle A) waits for entry into the stable communication area SCA.

  In S103, the latest speed information is acquired, and the process proceeds to S104. In S104, based on the latest speed information acquired in S103, a transmission interval ti corresponding to the speed information is set, and the process proceeds to S105. In S105, an uplink signal is transmitted, and the process proceeds to S106. In S106, the timer which measures the elapsed time after transmitting an uplink signal is started, and it progresses to S107.

  In S107, it is determined whether or not a downlink signal including ID information addressed to the own vehicle has been received. If it is determined in S107 that a downlink signal including ID information addressed to the host vehicle has been received (S107: YES), it is estimated that the uplink signal has been received by the optical beacon 110, and a series of transmission processes is terminated. To do. As described above, the transmission / reception processing circuit 70 is in a state of waiting for the end of communication with the optical beacon 110 accompanying the passage of the stable communication area SCA.

  On the other hand, if it is determined in S107 that a downlink signal including ID information addressed to the vehicle has not been received (S107: NO), the process proceeds to S108. In S108, the elapsed time of the timer started in S106 is compared with the transmission interval ti set in S104, and it is determined whether or not the elapsed time exceeds the transmission interval ti. If it is determined in S108 that the elapsed time of the timer is less than the transmission interval ti and before the timeout (S108: NO), the process returns to S107. And by repeating determination of S107 and S108, reception of the downlink signal containing ID information addressed to the own vehicle is waited.

  On the other hand, if it is determined in S108 that the elapsed time of the timer is equal to or greater than the transmission interval ti and the timeout has elapsed (S108: YES), the process returns to S103. Then, by performing S103 to S106, the uplink signal is transmitted after resetting the next transmission interval ti based on the latest speed information. Furthermore, according to repetition of S103 to S108, the uplink signal is repeatedly transmitted while adjusting the transmission interval ti until the reception of the downlink signal including the ID information addressed to the own vehicle.

  According to the present embodiment described so far, the transmission interval of the uplink signal that is started after the determination that the vehicle has entered the stable communication area SCA becomes shorter as the traveling speed of the vehicle A becomes higher. Therefore, even when the vehicle A is traveling at a high speed, the number of times the uplink signal is transmitted from the stable communication area SCA is secured. As described above, the uplink signal can be reliably received by the optical beacon 110.

  On the other hand, when the vehicle A is traveling at a low speed, the uplink signal transmission interval ti is increased. Therefore, coupled with the control that does not start transmission of the uplink signal until it is determined that the mobile communication device has entered the stable communication area SCA, the number of uplink signal transmissions to one optical beacon 110 can be accurately suppressed. According to the above, the optical communication device 100 can suppress transmission of unnecessary uplink signals while ensuring the reliability of communication with the optical beacon 110 that is started based on the determination of entering the stable communication area SCA. As a result, reduction of power consumption of the optical communication device 100, extension of the life of the light emitting diode of the transmission unit 82, and the like are realized.

  In addition, in the present embodiment, even if the traveling speed of the vehicle A largely fluctuates after determining that the vehicle has entered the stable communication area SCA, the uplink signal transmission interval ti is adjusted as appropriate based on the latest traveling speed. obtain. Therefore, the optical communication device 100 can continue the transmission of the uplink signal at the appropriate transmission interval ti. According to the above, it becomes easier to realize both ensuring of the reliability of road-to-vehicle communication and suppression of unnecessary uplink signal transmission.

  Further, the transmission / reception processing circuit 70 of this embodiment adjusts the transmission interval ti every time an uplink signal is transmitted. Therefore, even when the traveling speed is remarkably lowered after the start of uplink transmission, the uplink signal transmission interval ti can be adjusted more accurately according to the traveling speed. Therefore, it is easier to achieve both ensuring of road-to-vehicle communication reliability and suppression of unnecessary uplink signal transmission.

  In the present embodiment, the area determination unit 72 determines that the reception unit 81 is in the stable communication area SCA based on the continuous reception of downlink signals. Based on such a reception state of the downlink signal, the optical communication device 100 can start transmission of the uplink signal without delay at a timing at which reception by the optical beacon 110 is possible. Therefore, the optical communication device 100 can minimize the number of uplink signal transmissions while reliably performing road-to-vehicle communication with the optical beacon 110.

  In addition, in the present embodiment, the optical communication device 100 can end the transmission of the uplink signal by acquiring the downlink signal including the ID information addressed to the own vehicle. According to the above, since unnecessary transmission continuation toward the optical beacon 110 that has received the uplink signal is not performed, the number of uplink signal transmissions can be reliably reduced.

  In the first embodiment, the data processing unit 71 corresponds to a “speed acquisition unit”, the region determination unit 72 corresponds to a “communication region determination unit”, and the transmission / reception control unit 73 corresponds to a “transmission control unit”. The optical beacon 110 corresponds to an “optical communication roadside device”, and the vehicle A corresponds to a “moving object”.

(Other embodiments)
Although one embodiment of the present disclosure has been described above, the present disclosure is not construed as being limited to the above-described embodiment, and can be applied to various embodiments and combinations without departing from the scope of the present disclosure. be able to.

  In the first modification of the above embodiment, the approach of the receiving unit to the stable communication area SCA is determined based on the strength of the downlink signal. Specifically, the area determination unit according to the first modification determines that the reception unit is in the stable communication area SCA based on the fact that the light intensity of the downlink signal transmitted from the optical beacon exceeds a predetermined intensity threshold. . Also by the above determination method, the area determination unit can ensure the estimation accuracy of the positional relationship between the stable communication area SCA and the reception unit. As a result, the optical communication apparatus can start transmission of an uplink signal without delay at a timing at which reception by an optical beacon is possible.

  In addition, the region determination unit according to the second modification of the above embodiment combines the determination whether the downlink signal is continuously received and the determination whether the strength of the down link signal exceeds the threshold strength. The approach of the receiving unit to the stable communication area is estimated. Specifically, the region determination unit according to the second modified example is configured such that the intensity of all continuously received down link signals exceeds the threshold intensity, or the average value of continuously received down link signal intensity is the threshold value. When the strength is exceeded, it is determined that the receiving unit is in the stable communication area SCA. According to the above determination method, the optical communication device can further increase the estimation accuracy of entering the stable communication area SCA of the optical beacon.

  The optical communication device according to the third modification of the above embodiment is configured as a part of the navigation device. That is, in Modification 3, the navigation device has the function of the optical communication device according to the present disclosure. Therefore, each functional unit constructed in the transmission / reception processing circuit 70 of the above embodiment is constructed in the navigation control unit in the third modification.

  The optical communication device according to the fourth modification of the above embodiment is connected to, for example, a communication bus provided in the vehicle A, and can acquire speed information without using a navigation device. As in the fourth modification, the optical communication device may not be configured to accompany the navigation device.

  In the above embodiment, the speed information acquisition step (S103) and the transmission interval setting step (S104) are performed prior to the uplink signal transmission step (S105) and the timer start step (S106). However, in the transmission processing of the optical communication apparatus according to the modified example 5, after the uplink signal transmission step and the timer start step are performed, the speed information acquisition step and the transmission interval setting step are performed. Even in the above processing order, the transmission interval of the uplink signal can be adjusted more accurately according to the traveling speed.

  In Modification 6 of the above embodiment, the uplink signal transmission interval is set only once before and after the start of uplink signal transmission. That is, even if the traveling speed of the vehicle fluctuates after it is determined that the vehicle has entered the stable communication area, the uplink signal continues to be transmitted at the transmission cycle that is initially set. Even in the modified example 6 as described above, the traveling speed before and after it is determined that the vehicle has entered the stable communication region can be reflected in the transmission cycle, so it is possible to ensure the reliability of road-to-vehicle communication and unnecessary uplink signals. Coexistence with transmission suppression is possible.

  The method for setting the transmission interval ti with respect to the traveling speed of the vehicle A can be changed as appropriate. For example, the transmission interval ti may be set as a function that is inversely proportional to the traveling speed, or may be set as a linear or nonlinear function that decreases in value as the traveling speed increases. In addition, the change in the transmission interval ti with respect to the traveling speed may not be continuous. For example, as the traveling speed increases, a function or table that sets the transmission interval ti in a stepwise manner may be defined in advance. Furthermore, the transmission interval ti may be a constant value in a speed range lower than a preset low speed range value. Similarly, the transmission interval ti may be a constant value in a speed range higher than a preset high speed range value.

  The mobile body on which the optical communication device is mounted is not limited to the vehicle A as in the above embodiment. The optical communication device can be mounted on various moving bodies traveling on a roadway such as a passenger car, a truck (truck), a motorcycle (two-wheeled vehicle), a bus, and a construction machine.

A vehicle (mobile body), ti transmission interval, UCA unstable communication area, 71 data processing section (speed acquisition section), 72 area determination section (communication area determination section), 73 transmission / reception control section (transmission control section), 81 reception , 82 transmitter, 100 optical communication device, 110 optical beacon (optical communication roadside machine)

Claims (6)

An optical communication device that is mounted on a mobile body (A) and transmits / receives information by optical communication with an optical communication roadside device (110) installed on a road,
A receiving unit (81) for receiving a downlink signal from the optical communication path side unit;
A transmission unit (82) for transmitting an uplink signal toward the optical communication path side unit;
A communication region determination unit (72) for determining that the reception unit has entered a stable communication region (SCA) with the optical communication roadside device based on a reception state of the reception unit;
A speed acquisition unit (71) for acquiring the traveling speed of the mobile body;
A transmission control unit that starts transmission of an uplink signal by the transmission unit based on the determination that the communication region determination unit is within the stable communication region, and the transmission interval of the uplink signal as the traveling speed increases A transmission control unit (73) that sets (ti) short, and sets the transmission interval of the uplink signal longer as the traveling speed becomes slower ,
The transmission control unit sets a transmission interval corresponding to the travel speed using the travel speed acquired by the speed acquisition unit after the communication area determination unit determines that the communication area determination unit is within the stable communication area. , optical communication devices you start the transmission of the uplink signal. The speed acquisition unit repeats acquisition of the traveling speed,
The optical communication device according to claim 1, wherein the transmission control unit adjusts an uplink signal transmission interval based on the traveling speed after starting transmission of an uplink signal.   3. The optical communication device according to claim 2, wherein the transmission control unit sets a transmission interval until a next uplink signal is transmitted based on the traveling speed every time an uplink signal is transmitted.   The said communication area determination part determines with the said receiving part being in the said stable communication area based on the said receiving part having received continuously the downlink signal transmitted from the said optical communication roadside machine. 4. The optical communication device according to claim 3.   The communication area determination unit is configured to determine that the reception unit is in the stable communication area based on a light intensity of a downlink signal transmitted from the optical communication path side unit exceeding a predetermined intensity threshold. The optical communication apparatus as described in any one of 1-4.   The transmission control unit sets a next transmission interval using the latest traveling speed acquired by the speed acquisition unit at a timing when an elapsed time after transmitting an uplink signal exceeds a transmission interval. Item 6. The optical communication device according to any one of Items 1 to 5.

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