Vehicle-mounted apparatus, communication method of vehicle-mounted apparatus, and program
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-02-05
- Publication Date
- 2026-08-13
Smart Images
Figure JP2025003762_13082026_PF_FP_ABST
Abstract
Description
In-vehicle device, communication method for the in-vehicle device, and program
[0001] This disclosure relates to an in-vehicle device, a communication method for the in-vehicle device, and a program.
[0002] When the in-vehicle unit receives a signal from the roadside antenna, it measures the signal strength (RSSI value), and if the measured RSSI value exceeds a predetermined threshold, the in-vehicle unit determines that it has entered the communication range of the roadside antenna and starts sending a reply to the roadside antenna (see, for example, Patent Document 1).
[0003] Figure 8 is a diagram illustrating a conventional in-vehicle unit. As shown in Figure 8, the mounting height (height from the ground to the in-vehicle unit 9) of the in-vehicle unit 9 differs depending on the type of vehicle V on which it is installed. Figure 8 shows an example in which an in-vehicle unit 9a mounted on a small vehicle Va (e.g., a passenger car) and an in-vehicle unit 9b mounted on a large vehicle Vb (e.g., a large truck) each receive signals from a roadside antenna ANT. Generally, the roadside antenna ANT is installed such that when the small vehicle Va arrives at a predetermined position X1 (a predetermined distance upstream from the installation position X0 of the roadside antenna ANT), the in-vehicle unit 9a can receive radio waves WA with a signal strength (RSSI value) above a predetermined threshold. However, the mounting heights of the in-vehicle units 9a and 9b differ between the small vehicle Va and the large vehicle Vb. Therefore, even if the horizontal distance from the roadside antenna ANT to the on-board units 9a and 9b is the same, the RSSI values of the signals received by the on-board units 9a and 9b will be different. As shown in the example in Figure 8, since the roadside antenna ANT is installed assuming a small vehicle Va, when the RSSI value is measured at the same position X1, the RSSI value of the large vehicle Vb will be smaller than that of the small vehicle Va.
[0004] At this time, if the threshold value of the RSSI value is set to the same value for the large vehicle Vb and the small vehicle Va, the in-vehicle device 9a of the small vehicle Va can receive the radio wave WA whose RSSI value is equal to or greater than the threshold value at the position X1, but the in-vehicle device 9b of the large vehicle Vb cannot receive the radio wave WA whose RSSI value is equal to or greater than the threshold value until it reaches the position X2 on the downstream side (road-side antenna ANT side) from the position X1. That is, the communication available time Ta (or the communication available distance La) of the in-vehicle device 9b of the large vehicle Vb is shorter than the communication available time Ta (or the communication available distance La) of the in-vehicle device 9a of the small vehicle Va when comparing from the start of the reply from the in-vehicle device 9a of the small vehicle Va until passing through the communication range of the road-side antenna ANT (for example, the installation position X0 of the road-side antenna).
[0005] Therefore, in the conventional in-vehicle device 9, in order to suppress the shortening of the communication available time (or the communication available distance) of the large vehicle Vb in this way, the in-vehicle device 9b mounted on the large vehicle Vb sets an RSSI correction value for large vehicles, and starts a reply when the value obtained by adding the RSSI correction value to the measured RSSI value becomes larger than the threshold value. For example, when the difference in the RSSI values between the radio wave WA and the radio wave WB with a smaller signal intensity than the radio wave WA is set as the RSSI correction value, as shown in FIG. 8, the in-vehicle device 9b of the large vehicle Vb can start a reply to the road-side antenna ANT at the timing of receiving the radio wave WB. Thereby, the in-vehicle devices 9a and 9b of the small vehicle Va and the large vehicle Vb can reply to the road-side antenna ANT at the same timing.
[0006] Japanese Patent No. 5258690
[0007] Conventional in-vehicle devices only classify vehicle types into two categories: large vehicles and small vehicles, and set a uniform RSSI correction value for large vehicles. However, in reality, the mounting height of the in-vehicle device varies depending on the vehicle shape for both large and small vehicles. That is, in conventional in-vehicle devices, the fine differences in the mounting height for each vehicle are not reflected in the RSSI correction value, so it is difficult to suppress the variation in the communication available time for each vehicle. Also, due to differences in the mounting angle of the in-vehicle device and individual differences in the communication module performance of the in-vehicle device, there may be differences in the RSSI values measured by individual in-vehicle devices, further increasing the variation in the communication available time for each vehicle.
[0008] The purpose of this disclosure is to provide an in-vehicle device, a communication method for the in-vehicle device, and a program that can individually set communication correction values to ensure sufficient communication time with a roadside antenna, regardless of mounting position or individual differences.
[0009] According to one aspect of the present disclosure, the in-vehicle device is an in-vehicle device capable of communicating with a roadside antenna, and includes: a correction information acquisition unit that acquires the antenna number of a correction roadside antenna and a signal strength reference value set for the correction roadside antenna; a signal strength recording unit that samples and records the signal strength of a received signal when the antenna number included in the signal received from the roadside antenna matches the antenna number of the correction roadside antenna; a correction value setting unit that sets a communication correction value based on the difference between a representative value of the sampled signal strength and the signal strength reference value; and a communication processing unit that starts sending a reply to the roadside antenna when the sum of the signal strength of the signal received from the roadside antenna and the communication correction value exceeds a threshold.
[0010] According to one aspect of the present disclosure, a communication method is a communication method for an in-vehicle device capable of communicating with a roadside antenna, comprising the steps of: acquiring the antenna number of a corrective roadside antenna and a signal strength reference value set for the corrective roadside antenna; sampling and recording the signal strength of a received signal when the antenna number included in a signal received from the roadside antenna matches the antenna number of the corrective roadside antenna; setting a communication correction value based on the difference between a representative value of the sampled signal strength and the signal strength reference value; and starting a reply to the roadside antenna when the sum of the signal strength of the signal received from the roadside antenna and the communication correction value exceeds a threshold.
[0011] According to one aspect of the present disclosure, the program causes an in-vehicle device capable of communicating with a roadside antenna to perform the following steps: acquire the antenna number of a corrective roadside antenna and a signal strength reference value set for the corrective roadside antenna; sample and record the signal strength of a received signal when the antenna number included in the signal received from the roadside antenna matches the antenna number of the corrective roadside antenna; set a communication correction value based on the difference between a representative value of the sampled signal strength and the signal strength reference value; and start sending a reply to the roadside antenna when the sum of the signal strength of the signal received from the roadside antenna and the communication correction value exceeds a threshold.
[0012] According to the above embodiment, by individually setting the communication correction value, it is possible to ensure sufficient communication time with the roadside antenna regardless of the mounting position or individual differences.
[0013] This is a diagram showing the overall configuration of the communication system according to the first embodiment. This is a first flowchart showing an example of processing by an in-vehicle device according to the first embodiment. This is a second flowchart showing an example of processing by an in-vehicle device according to the first embodiment. This is a diagram showing an example of correction information. This is a first diagram showing an example of signal strength reference values and representative values. This is a second diagram showing an example of signal strength reference values and representative values. This is a schematic block diagram showing the configuration of a computer. This is a diagram for explaining a conventional in-vehicle device.
[0014] <First Embodiment> The embodiments will be described in detail below with reference to the drawings.
[0015] (Overall Configuration of the Communication System) Figure 1 is a diagram showing the overall configuration of the communication system according to the first embodiment. As shown in Figure 1, the communication system 1 comprises an in-vehicle unit 10, a terminal device 20, a server 30, and a roadside antenna 40.
[0016] The on-board unit 10 is mounted in the vehicle and communicates wirelessly (e.g., via DSRC communication) with the roadside antenna 40 to process charges for toll roads, parking fees, etc. This charging process is the same as conventional charging processes. As an example of charging for toll roads, the on-board unit 10 uses its GNSS function to identify the vehicle's route, calculates the toll based on the distance traveled on the toll road, and processes the charge of the calculated toll via wireless communication with the roadside antenna 40. The on-board unit 10 may also perform charging for road pricing aimed at curbing traffic congestion in urban areas. In this case, charging points are set up at the entrances to roads (general roads) or areas where congestion occurs. The on-board unit 10 uses its GNSS function to identify when the vehicle has passed these charging points and processes the charge according to the road and area.
[0017] Furthermore, the in-vehicle unit 10 of this embodiment sets a communication correction value based on the signal strength (RSSI value) of the signal received from the correction roadside antenna 42, which will be described later. Details of how to set the communication correction value will be described later. By using the communication correction value, the in-vehicle unit 10 can start responding to the signal received from the roadside antenna 40 at an appropriate timing depending on the mounting position, individual differences, and mounting environment of the in-vehicle unit 10. Note that the mounting position of the in-vehicle unit 10 includes the mounting height and mounting angle according to the vehicle type and shape of the vehicle. Individual differences of the in-vehicle unit 10 include variations in the performance of the communication module, etc. The mounting environment of the in-vehicle unit 10 includes external factors that affect the wireless communication of the in-vehicle unit 10, such as film attached to the windshield, equipment installed near the in-vehicle unit 10 (e.g., a drive recorder), and changes in the mounting position due to modifications such as changes in vehicle height.
[0018] The terminal device 20 is operated by the installer who installs the in-vehicle unit 10 into the vehicle. The installer connects the terminal device 20 to the in-vehicle unit 10 so that it can communicate wirelessly or via a wired connection, and performs setup to configure the in-vehicle unit 10 with vehicle identification information, vehicle type information, etc.
[0019] The server 30 communicates wirelessly with the in-vehicle unit 10 (for example, via cellular communication) and transmits correction information to the in-vehicle unit 10 for setting the communication correction value. The server 30 may also be a billing server that processes toll road fees and parking fees, with added functionality.
[0020] The roadside antenna 40 includes a roadside antenna 41 for charging and a roadside antenna 42 for correction.
[0021] The roadside antenna 41 for charging is installed at charging points (entrances and exits) of toll roads, entrances and exits of parking lots, drive-throughs, etc., and transmits and receives various information (signals) for charging processing with the on-board unit 10. The roadside antenna 41 for charging is the same as conventional roadside antennas used on toll roads and parking lots.
[0022] The correction roadside antenna 42 transmits correction signals to the vehicle. The correction roadside antenna 42 may be installed, for example, on a test road within the installation company's facilities or in a location where GNSS positioning is possible (a location without obstructions that block satellite signals), such as a public road. The in-vehicle unit 10 sets the communication correction value based on the correction signals received from the correction roadside antenna 42 while the vehicle is in motion.
[0023] Furthermore, at least some of the roadside charging antennas 41 installed at locations where vehicles are required to stop, such as parking lot entrances and exits or drive-throughs, may be used as correction roadside antennas 42. In this case, the in-vehicle unit 10 uses the charging processing signals received from the roadside charging antennas 41 while approaching and stopping at parking lot entrances and exits as correction signals to set the communication correction values.
[0024] (Functional configuration of the in-vehicle unit) As shown in Figure 1, the in-vehicle unit 10 includes a correction information acquisition unit 101, a signal strength recording unit 102, a correction value setting unit 103, a communication processing unit 104, and a memory 105.
[0025] The correction information acquisition unit 101 acquires the antenna number of the correction roadside antenna 42 and the signal strength reference value set for the correction roadside antenna 42.
[0026] The signal strength recording unit 102 samples the signal strength (RSSI value) of the received signal and records it in the memory 105 when the antenna number included in the signal received from the roadside antenna 40 matches the antenna number of the correction roadside antenna 42.
[0027] The correction value setting unit 103 sets a communication correction value based on the difference between the representative value of the sampled signal strength (RSSI value) and the signal strength reference value.
[0028] The communication processing unit 104 has a communication module that performs wireless communication with the roadside antenna 40. The communication processing unit 104 starts sending a reply to the roadside antenna 40 when the value obtained by adding a communication correction value to the signal strength (RSSI value) of the signal received from the roadside antenna 40 exceeds a threshold.
[0029] The memory 105 stores information acquired and generated by each part of the in-vehicle unit 10 (antenna number, signal strength reference value, measured signal strength, communication correction value, etc.).
[0030] (Processing Example 1 for On-board Device) Figure 2 is a first flowchart showing a processing example for an on-board device according to the first embodiment. An example of the processing when the on-board device 10 is installed in a vehicle will be explained with reference to Figure 2.
[0031] First, the installer connects the terminal device 20 to the in-vehicle unit 10 and inputs identification information and vehicle type information of the vehicle to which the in-vehicle unit 10 is installed. Then, the correction information acquisition unit 101 of the in-vehicle unit 10 acquires the vehicle type information that the installer has entered into the terminal device 20 (step S101).
[0032] Next, the correction value setting unit 103 performs initial setup of the communication correction value based on the vehicle type information acquired by the correction information acquisition unit 101. Specifically, the correction value setting unit 103 determines whether the vehicle to which the in-vehicle unit 10 is installed is a motorcycle, a passenger car, or a large vehicle (step S102). If the vehicle type information indicates a motorcycle, the correction value setting unit 103 sets the motorcycle correction value as the communication correction value (initial value) (step S103). If the vehicle type information indicates a passenger car, the correction value setting unit 103 sets the passenger car correction value as the communication correction value (initial value) (step S104). If the vehicle type information indicates a large vehicle, the correction value setting unit 103 sets the large vehicle correction value as the communication correction value (initial value) (step S105). The set communication correction value is recorded in the memory 105.
[0033] The correction values for motorcycles, passenger cars, and large vehicles are values determined by the manufacturer of the on-board unit 10 based on simulations, tests, etc. Note that the correction values for motorcycles and passenger cars may be zero. In other words, the RSSI value of the signal received from the roadside antenna 40 may be corrected with the communication correction value only when the on-board unit 10 is mounted on a large vehicle.
[0034] Furthermore, Figure 2 shows an example where vehicle types are classified into three categories: motorcycles, passenger cars, or large vehicles, but the system is not limited to this. In other embodiments, vehicle types may be classified into only two categories (for example, passenger cars and large vehicles), or into four or more categories.
[0035] (Processing Example 2 of the In-Vehicle Device) Figure 3 is a second flowchart showing a processing example of the in-vehicle device according to the first embodiment. Figure 4 is a diagram showing an example of correction information. Figure 5 is a first diagram showing an example of signal strength reference value and representative value. Figure 6 is a second diagram showing an example of signal strength reference value and representative value. Referring to Figures 3 to 6, an example of processing to be performed after the installation of the in-vehicle device 10 and while the in-vehicle device 10 is operating will be described.
[0036] First, when the vehicle engine is turned on, the in-vehicle unit 10 is activated. The communication processing unit 104 of the in-vehicle unit 10 reads the communication correction value from the memory 105 and sets it in the communication module (step S201). Immediately after installation of the in-vehicle unit 10, the memory 105 contains the communication correction value (initial value) corresponding to the vehicle information set in Figure 2. Therefore, for a while after installation of the in-vehicle unit 10, the communication processing unit 104 uses the communication correction value corresponding to the vehicle information. Furthermore, as the in-vehicle unit 10 is used continuously, the communication correction value is updated according to the installation location, installation environment, individual differences, etc. of the in-vehicle unit 10 through the processing described later (steps S207 to S215). From thereafter, the communication processing unit 104 can use the communication correction value adjusted to suit each individual in-vehicle unit 10.
[0037] Next, the correction information acquisition unit 101 of the in-vehicle unit 10 acquires correction information 11 (Figure 4) from the server 30, which includes the antenna number of the correction roadside antenna 42 and the signal strength reference value of the correction roadside antenna 42 (step S202). For example, the correction information acquisition unit 101 may transmit vehicle location information to the server 30, and the server 30 may transmit only the correction information 11 for the correction roadside antennas 42 that are within a predetermined range from the vehicle's location. Alternatively, the server 30 may transmit the correction information 11 for all correction roadside antennas 42 regardless of the vehicle's location.
[0038] As shown in Figure 4, the correction information 11 includes, for example, the antenna number, type, and signal strength reference value for each of the correction roadside antennas 42. The type indicates whether the antenna is a correction roadside antenna 42 dedicated to correction, or a correction roadside antenna 42 used for both billing and correction (some billing roadside antennas 41 that can be used for correction). Note that the correction information 11 does not include the antenna numbers of billing roadside antennas 41 that cannot be used for correction (billing-only).
[0039] For the correction-dedicated roadside antenna 42, the signal strength reference value is threshold A. Threshold A is the threshold used to determine whether or not the in-vehicle unit 10 will start sending a reply to the roadside antenna 40.
[0040] For the roadside antenna 42 used for both charging and correction, the signal strength reference value includes the design RSSI maximum value D of the roadside antenna 42. The RSSI maximum value D is the maximum RSSI value of the signal received from the roadside antenna 40 by a standard in-vehicle unit. A standard in-vehicle unit is an in-vehicle unit installed in a specified mounting location and environment, and having the performance expected in the design. This RSSI maximum value D is a value determined, for example, by the manufacturer of the in-vehicle unit 10 based on simulations, tests, etc.
[0041] Next, let's assume that the vehicle receives a signal from the roadside antenna 40 while it is in motion (step S203). Then, the communication processing unit 104 of the in-vehicle unit 10 determines from the antenna number included in the signal from the roadside antenna 40 whether this roadside antenna 40 is a toll roadside antenna 41 or a correction roadside antenna 42 (step S204).
[0042] If the antenna number included in the signal of roadside antenna 40 does not match the antenna number of the correction roadside antenna 42 included in the correction information 11, the communication processing unit 104 determines that this roadside antenna 40 is a billing roadside antenna 41 used exclusively for billing. In this case, the in-vehicle unit 10 does not update the communication correction value and only performs billing processing. Specifically, the communication processing unit 104 determines whether the value obtained by adding the communication correction value set at startup to the RSSI value of the signal of the billing roadside antenna 41 exceeds a predetermined threshold A (step S205). This threshold A is the same as the threshold A included in the signal strength reference value of the correction information 11.
[0043] If the value obtained by adding the RSSI value to the communication correction value does not exceed threshold A (step S205; NO), the communication processing unit 104 determines that it is not within the communication range of the billing roadside antenna 41 and waits until it receives the next signal. On the other hand, if the value obtained by adding the RSSI value to the communication correction value exceeds threshold A (step S205; YES), the communication processing unit 104 determines that it has entered the communication range of the billing roadside antenna 41 and starts sending a reply to the billing roadside antenna 41 to perform billing (step S206). The content of the billing process is the same as the conventional process, so the explanation is omitted.
[0044] Also, after the charging process is completed, when the vehicle engine is turned off (step S215; YES), the in-vehicle device 10 ends a series of processes. When the vehicle engine remains ON (step S215; NO), the in-vehicle device 10 returns to step S203 and waits until the next signal from the roadside antenna 40 is received.
[0045] When the antenna number included in the signal from the roadside antenna 40 matches the antenna number of the correction-use roadside antenna 42 included in the correction information 11, the communication processing unit 104 determines that this roadside antenna 40 is the correction-use roadside antenna 42. When the roadside antenna 40 of the in-vehicle device 10 is the correction-dedicated correction-use roadside antenna 42, only the update of the correction value for communication is performed. When the roadside antenna 40 is the correction-use roadside antenna 42 that is shared for charging / correction, both the charging process and the update of the correction value for communication are performed.
[0046] First, a case where the roadside antenna 40 is the correction-dedicated correction-use roadside antenna 42 will be described. In this case, while the signal strength recording unit 102 of the in-vehicle device 10 is receiving a signal from the correction-dedicated correction-use roadside antenna 42, the RSSI value (measured value) of the signal is sampled and recorded in the memory 105 (step S207).
[0047] When the vehicle passes the correction-use roadside antenna 42 and stops receiving the signal, the correction value setting unit 103 of the in-vehicle device 10 obtains a representative value of the RSSI value from the time series of the RSSI values recorded in the memory 105 (step S208).
[0048] FIG. 5 illustrates the change in RSSI value according to the distance to the installation position X0 of the roadside antenna 40. The graph M1 in FIG. 5 is a graph illustrating the change in RSSI value measured (or simulated) by a standard in-vehicle unit, and the graph M2 is a graph illustrating the change in RSSI value actually measured by the in-vehicle unit 10. As described above, when the RSSI value of the received signal exceeds the threshold value A, the in-vehicle unit 10 starts a reply to the roadside antenna 40. Therefore, as shown in the graph M1 of FIG. 5, it is ideal that the in-vehicle unit 10 can continuously receive a signal with an intensity exceeding the threshold value A while moving the distance (prescribed communication distance L) required until the communication between the in-vehicle unit 10 and the roadside antenna 40 is completed. However, since the actual mounting position of the in-vehicle unit 10 is different from that of a standard in-vehicle unit, as shown in the graph M2 of FIG. 5, the distance L' where the RSSI value exceeds the threshold value A may be less than the prescribed communication distance L. Then, when the in-vehicle unit 10 does not reply until the RSSI value of the received signal exceeds the threshold value A, there is a possibility that the vehicle will pass through the communication range of the roadside antenna 40 (the installation position X0 of the roadside antenna 40) before the communication is completed.
[0049] For this reason, the correction value setting unit 103 obtains, as a representative value, an RSSI value C that can be continuously maintained while moving the prescribed communication distance L, which is the distance required until the communication with the roadside antenna 40 is completed, from the time series of the RSSI values (measured values) sampled in step S207 (step S208). Specifically, the correction value setting unit 103 obtains the time required to move the communication distance L based on the speed of the vehicle measured by the GNSS function of the in-vehicle unit 10, and obtains an RSSI value C in the time series of the RSSI values, in which the continuously maintainable time matches the time required to move the communication distance L.
[0050] Further, the correction value setting unit 103 records the difference (A - C) between the threshold value A, which is the signal intensity reference value of the correction dedicated roadside antenna 42, and the RSSI value C obtained in step S208 in the memory 105 as the latest correction value (step S209). At this time, the correction value setting unit 103 may delete the time series of the RSSI values recorded in the memory 105.
[0051] The correction value setting unit 103 reads n correction values from the memory 105, starting with the most recent ones, and calculates the average value. The correction value setting unit 103 sets (updates) the calculated average as the communication correction value and records it in the memory 105 (step S210). If the in-vehicle unit 10 has just been installed and n correction values have not yet been recorded, the correction value setting unit 103 may skip step S210.
[0052] Furthermore, the correction value setting unit 103 may perform the processing in steps S208 to S210 when the GNSS function of the in-vehicle unit 10 determines that the vehicle has passed the installation location of the correction roadside antenna 42. This allows the in-vehicle unit 10 to discard the signal from the correction roadside antenna 42 installed on an adjacent road if it mistakenly receives the signal, instead of using it to set the communication correction value.
[0053] Next, we will describe the case where the roadside antenna 40 is a combined charge / correction roadside antenna 42 (charge roadside antenna 41). The signal strength recording unit 102 of the in-vehicle unit 10 samples the RSSI value (measured value) of the signal and records it in the memory 105 while receiving a signal from the combined charge / correction roadside antenna 42 (step S211).
[0054] Furthermore, the communication processing unit 104 of the in-vehicle unit 10 determines whether the sum of the RSSI value of the signal from the correction roadside antenna 42 (charging roadside antenna 41) and the communication correction value set at startup exceeds a predetermined threshold A (step S212). This process is the same as the process in step S205.
[0055] If the value obtained by adding the RSSI value to the communication correction value does not exceed threshold A (step S212; NO), the communication processing unit 104 determines that it is not within the communication range of the billing roadside antenna 41 and waits until it receives the next signal. On the other hand, if the value obtained by adding the RSSI value to the communication correction value exceeds threshold A (step S212; YES), the communication processing unit 104 determines that it has entered the communication range of the billing roadside antenna 41 and starts sending a reply to the billing roadside antenna 41 to perform the billing process (step S213). In the case of a parking lot entrance / exit, the billing process includes parking lot entry / exit processing.
[0056] When the vehicle passes the roadside correction antenna 42 and stops receiving signals, the correction value setting unit 103 of the in-vehicle unit 10 determines a representative value of the RSSI value from the time series of RSSI values recorded in the memory 105 (step S214).
[0057] Figure 6 illustrates the change in RSSI value according to the distance to the installation position X0 of the roadside antenna 40. Graph M3 in Figure 6 is an example of the change in RSSI value measured (or simulated) by a standard in-vehicle device, and graph M4 is an example of the change in RSSI value actually measured by the in-vehicle device 10. The correction value setting unit 103 determines the maximum value E of the RSSI value as a representative value from the time series of actually measured RSSI values (step S214).
[0058] Furthermore, the correction value setting unit 103 records the difference (D-E) between the design RSSI maximum value D, which is the signal strength reference value of the combined charge / correction roadside antenna 42, and the RSSI maximum value E obtained in step S214, as the latest correction value in the memory 105 (step S215). In the case of the combined charge / correction roadside antenna 42, the vehicle is temporarily stopped at a stopping position near the correction roadside antenna 42 (e.g., before the vehicle stop bar) to perform communication, so the RSSI value measured at this stopping position is designed to be the maximum value. Therefore, the design RSSI maximum value D is the RSSI maximum value of the signal that a standard in-vehicle unit can receive at this stopping position.
[0059] The correction value setting unit 103 reads n correction values from the memory 105, starting with the most recent ones, and calculates the average value. The correction value setting unit 103 sets (updates) the calculated average as the communication correction value and records it in the memory 105 (step S210). If the in-vehicle unit 10 has just been installed and n correction values have not yet been recorded, the correction value setting unit 103 may skip step S210.
[0060] Furthermore, once the update of the communication correction value is complete and the vehicle engine is turned OFF (step S215; YES), the on-board unit 10 terminates the series of processes. If the vehicle engine remains ON (step S215; NO), the on-board unit 10 returns to step S203 and waits until it receives the next signal from the roadside antenna 40.
[0061] The in-vehicle unit 10 executes the series of processes shown in Figure 3 each time it is started up.
[0062] (Computer Configuration) Figure 7 is a schematic block diagram showing the configuration of the computer. The computer 900 comprises a processor 901, main memory 902, auxiliary memory 903, and interface 904. The above-mentioned in-vehicle device 10 is implemented in the computer 900. The operation of each of the above-mentioned processing units is stored in the auxiliary memory 903 in the form of a program. The processor 901 reads the program from the auxiliary memory 903, expands it into the main memory 902, and executes the above processing according to the program. The processor 901 also allocates memory area in the main memory 902 to be used for the above processing according to the program.
[0063] The program may be for implementing a part of the functions to be performed by the computer 900. For example, the program may perform functions in combination with other programs already stored in the auxiliary storage device 903, or in combination with other programs implemented in other devices. In other embodiments, the computer may be equipped with a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), FPGA (Field Programmable Gate Array), etc. In this case, some or all of the functions implemented by the processor may be implemented by the integrated circuit.
[0064] Examples of auxiliary storage devices 903 include HDDs (Hard Disk Drives), SSDs (Solid State Drives), magnetic disks, magneto-optical disks, CD-ROMs (Compact Disc Read Only Memory), DVD-ROMs (Digital Versatile Disc Read Only Memory), and semiconductor memory. The auxiliary storage device 903 may be an internal medium directly connected to the bus of the computer 900, or it may be an external medium (external storage device 910) connected to the computer 900 via an interface 904 or a communication line. Furthermore, if this program is distributed to the computer 900 via a communication line, the computer 900 that receives the distribution may expand the program into the main memory 902 and execute the above processing. In at least one embodiment, the auxiliary storage device 903 is a tangible storage medium that is not temporary.
[0065] (Effects) As described above, the in-vehicle unit 10 according to this embodiment includes: a correction information acquisition unit 101 that acquires the antenna number of the correction roadside antenna 42 and a signal strength reference value set for the correction roadside antenna 42; a signal strength recording unit 102 that samples and records the RSSI value of the received signal when the antenna number included in the signal received from the roadside antenna 40 matches the antenna number of the correction roadside antenna 42; a correction value setting unit 103 that sets a communication correction value based on the difference between a representative value of the sampled RSSI value and the signal strength reference value; and a communication processing unit 104 that starts sending a reply to the roadside antenna 40 when the sum of the RSSI value of the signal received from the roadside antenna 40 and the communication correction value exceeds a threshold A.
[0066] In this way, the in-vehicle unit 10 can set an appropriate communication correction value for each in-vehicle unit based on the RSSI value of the signal received from the correction roadside antenna 42. Furthermore, by adding the communication correction value set for each in-vehicle unit 10 to the RSSI value of the signal received from the roadside antenna 40 and making a determination, the difference in RSSI values of the signals received by each in-vehicle unit 10 from the roadside antenna 40 at the same location can be reduced. Therefore, regardless of the mounting position, mounting environment, individual differences, etc. of the in-vehicle unit 10, the reply start timing can be appropriately adjusted to ensure sufficient communication time (communication distance) with the roadside antenna 40.
[0067] Furthermore, the correction value setting unit 103 sets a communication correction value based on the difference between a representative value, which is the maximum value E among the sampled signal intensities, and a signal intensity reference value, which is the design maximum value D of the RSSI value of the signal that can be received from the correction roadside antenna 42.
[0068] For example, if the correction roadside antenna 42 is installed in a parking lot or drive-through, where vehicles are required to stop temporarily, the vehicle will stop at the designated stopping point to communicate, making it easy to determine the maximum RSSI value D (reference value) of the signal that a standard in-vehicle unit can receive. Therefore, if the actually measured maximum RSSI value E deviates from the maximum RSSI value D of a standard in-vehicle unit, the in-vehicle unit 10 can adjust the timing of the response start so that it can secure the same communication time as a standard in-vehicle unit by setting a communication correction value based on that difference. In addition, each time the in-vehicle unit 10 arrives at a location where the correction roadside antenna 42 is installed, such as a parking lot or drive-through, it can appropriately learn and update the communication correction value in response to changes in the mounting position and environment of the in-vehicle unit 10, as well as performance degradation due to aging.
[0069] Furthermore, the correction value setting unit 103 determines a representative value for the maximum RSSI value C that can be continuously maintained while traveling a predetermined communication distance L, which is the distance required to complete communication with the roadside antenna 40, from the time series of sampled signal strengths. Based on the difference between the representative value, the maximum RSSI value C, and the threshold value A, which is the signal strength reference value, the unit sets a communication correction value.
[0070] In this way, if the RSSI maximum value C obtained from the actually measured RSSI value deviates from the threshold A, the in-vehicle unit 10 sets a communication correction value based on that difference, thereby adjusting the reply start timing so that it can ensure the same communication time as a standard in-vehicle unit. Furthermore, each time the in-vehicle unit 10 passes a location where the correction roadside antenna 42 is installed, it can appropriately learn and update the communication correction value in response to changes in the mounting position and environment of the in-vehicle unit 10, as well as performance degradation due to aging. In addition, by installing the correction roadside antenna 42 on roads such as public roads, it becomes possible to update the communication correction value at any time even in the in-vehicle unit 10 of vehicles that do not use parking lots or drive-throughs.
[0071] Furthermore, the correction value setting unit 103 records the difference between the representative value and the signal strength reference value, and sets the average of a predetermined number of differences (n values) from the most recent as the communication correction value.
[0072] In this way, the in-vehicle unit 10 can suppress the significant change in the communication correction value caused by, for example, an abnormality in the correction roadside antenna 42 or a temporary communication failure.
[0073] Furthermore, when the in-vehicle unit 10 is installed in the vehicle, the correction information acquisition unit 101 acquires vehicle type information from the terminal device 20 that sets up the in-vehicle unit 10, and the correction value setting unit 103 sets the correction value corresponding to the vehicle type information as the communication correction value when it acquires the vehicle type information.
[0074] In this way, when the in-vehicle unit 10 performs its first communication with the roadside antenna 40 immediately after being installed in the vehicle, it can adjust the response timing based on a communication correction value corresponding to the vehicle type information. This prevents insufficient communication time with the roadside antenna 40 during the first communication.
[0075] <Other Embodiments> Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made. In other embodiments, the order of the above-described processes may be changed as appropriate. Also, some processes may be executed in parallel.
[0076] <Note> The above-described embodiment can be understood, for example, as follows.
[0077] (1) According to the first embodiment, the in-vehicle unit 10 is an in-vehicle unit 10 capable of communicating with a roadside antenna 40, and includes a correction information acquisition unit 101 that acquires the antenna number of a correction roadside antenna 42 and a signal strength reference value set for the correction roadside antenna 42, a signal strength recording unit 102 that samples and records the signal strength (RSSI value) of the received signal when the antenna number included in the signal received from the roadside antenna 40 matches the antenna number of the correction roadside antenna 42, a correction value setting unit 103 that sets a communication correction value based on the difference between the sampled representative value of the signal strength and the signal strength reference value, and a communication processing unit 104 that starts sending a reply to the roadside antenna 40 when the value obtained by adding the communication correction value to the signal strength of the signal received from the roadside antenna 40 exceeds a threshold A.
[0078] In this way, the in-vehicle unit 10 can set an appropriate communication correction value for each in-vehicle unit based on the RSSI value of the signal received from the correction roadside antenna 42. Furthermore, by adding the communication correction value set for each in-vehicle unit 10 to the RSSI value of the signal received from the roadside antenna 40 and making a determination, the difference in RSSI values of the signals received by each in-vehicle unit 10 from the roadside antenna 40 at the same location can be reduced. Therefore, regardless of the mounting position, mounting environment, individual differences, etc. of the in-vehicle unit 10, the reply start timing can be appropriately adjusted to ensure sufficient communication time (communication distance) with the roadside antenna 40.
[0079] (2) According to the second embodiment, in the in-vehicle device 10 according to the first embodiment, the correction value setting unit 103 sets a communication correction value based on the difference between a representative value which is the maximum value (RSSI maximum value E) among the sampled plurality of signal intensities and a signal intensity reference value which is the design maximum value (RSSI maximum value D) of the signal intensity of the signal that can be received from the correction roadside antenna 42.
[0080] For example, if the correction roadside antenna 42 is installed in a parking lot or drive-through, where vehicles are required to stop temporarily, the vehicle will stop at the designated stopping point to communicate, making it easy to determine the maximum RSSI value D (reference value) of the signal that a standard in-vehicle unit can receive. Therefore, if the actually measured maximum RSSI value E deviates from the maximum RSSI value D of a standard in-vehicle unit, the in-vehicle unit 10 can adjust the timing of the response start so that it can secure the same communication time as a standard in-vehicle unit by setting a communication correction value based on that difference. In addition, each time the in-vehicle unit 10 arrives at a location where the correction roadside antenna 42 is installed, such as a parking lot or drive-through, it can appropriately learn and update the communication correction value in response to changes in the mounting position and environment of the in-vehicle unit 10, as well as performance degradation due to aging.
[0081] (3) According to the third embodiment, in the in-vehicle device 10 according to the first or second embodiment, the correction value setting unit 103 determines a representative value of the signal strength (RSSI value) that can be continuously maintained while traveling a predetermined communication distance L, which is the distance required to complete communication with the roadside antenna 40, from the time series of sampled signal strength (RSSI value), and sets a communication correction value based on the difference between the representative value and a signal strength reference value which is a threshold A.
[0082] In this way, if the RSSI value C obtained from the actually measured RSSI value deviates from the threshold A, the in-vehicle unit 10 sets a communication correction value based on that difference, thereby adjusting the reply start timing so that it can ensure the same communication time as a standard in-vehicle unit. Furthermore, each time the in-vehicle unit 10 passes a location where a correction roadside antenna 42 is installed, it can appropriately learn and update the communication correction value in response to changes in the mounting position and environment of the in-vehicle unit 10, as well as performance degradation due to aging. In addition, by installing the correction roadside antenna 42 on roads such as public roads, it becomes possible to update the communication correction value at any time even in the in-vehicle unit 10 of vehicles that do not use parking lots or drive-throughs.
[0083] (4) According to the fourth embodiment, in the in-vehicle device 10 according to any one of the first to third embodiments, the correction value setting unit 103 records the difference between the representative value and the signal strength reference value, and sets the average value of a predetermined number of differences from the most recent as the communication correction value.
[0084] In this way, the in-vehicle unit 10 can suppress the significant change in the communication correction value caused by, for example, an abnormality in the correction roadside antenna 42 or a temporary communication failure.
[0085] (5) According to the fifth embodiment, in the in-vehicle device 10 according to any one of the first to fourth embodiments, the correction information acquisition unit 101 acquires vehicle type information from the terminal device 20 that sets up the in-vehicle device 10 when the in-vehicle device 10 is installed in the vehicle, and the correction value setting unit 103 sets the correction value corresponding to the vehicle type information as the communication correction value when the vehicle type information is acquired.
[0086] In this way, when the in-vehicle unit 10 performs its first communication with the roadside antenna 40 immediately after being installed in the vehicle, it can adjust the response timing based on a communication correction value corresponding to the vehicle type information. This prevents insufficient communication time with the roadside antenna 40 during the first communication.
[0087] (6) According to the sixth aspect, the communication method is a communication method for an in-vehicle unit 10 that can communicate with a roadside antenna 40, and includes the steps of: acquiring the antenna number of a corrective roadside antenna 42 and a signal strength reference value set for the corrective roadside antenna 42; sampling and recording the signal strength of the received signal when the antenna number included in the signal received from the roadside antenna 40 matches the antenna number of the corrective roadside antenna 42; setting a communication correction value based on the difference between a representative value of the sampled signal strength and the signal strength reference value; and starting a reply to the roadside antenna 40 when the value obtained by adding the communication correction value to the signal strength of the signal received from the roadside antenna 40 exceeds a threshold A.
[0088] (7) According to the seventh aspect, the program causes the in-vehicle unit 10, which can communicate with the roadside antenna 40, to perform the following steps: to obtain the antenna number of the corrective roadside antenna 42 and the signal strength reference value set for the corrective roadside antenna 42; to sample and record the signal strength of the received signal when the antenna number included in the signal received from the roadside antenna 40 matches the antenna number of the corrective roadside antenna 42; to set a communication correction value based on the difference between the sampled representative value of the signal strength and the signal strength reference value; and to start sending a reply to the roadside antenna 40 when the value obtained by adding the communication correction value to the signal strength of the signal received from the roadside antenna 40 exceeds threshold A.
[0089] According to the above embodiment, by individually setting the communication correction value, it is possible to ensure sufficient communication time with the roadside antenna regardless of the mounting position or individual differences.
[0090] 1 Communication system 10 In-vehicle unit 101 Correction information acquisition unit 102 Signal strength recording unit 103 Correction value setting unit 104 Communication processing unit 105 Memory 20 Terminal device 30 Server 40 Roadside antenna 41 Roadside antenna for charging 42 Roadside antenna for correction V Vehicle
Claims
1. An in-vehicle device capable of communicating with a roadside antenna, comprising: a correction information acquisition unit that acquires the antenna number of a correction roadside antenna and a signal strength reference value set for the correction roadside antenna; a signal strength recording unit that samples and records the signal strength of a received signal when the antenna number included in the signal received from the roadside antenna matches the antenna number of the correction roadside antenna; a correction value setting unit that sets a communication correction value based on the difference between the sampled representative value of the signal strength and the signal strength reference value; and a communication processing unit that starts sending a reply to the roadside antenna when the sum of the signal strength of the signal received from the roadside antenna and the communication correction value exceeds a threshold.
2. The in-vehicle device according to claim 1, wherein the correction value setting unit sets the communication correction value based on the difference between the representative value, which is the maximum value among the sampled plurality of signal intensities, and the signal intensity reference value, which is the design maximum value of the signal intensity of the signal that can be received from the correction roadside antenna.
3. The in-vehicle device according to claim 1, wherein the correction value setting unit determines a representative value of the signal strength that can be continuously maintained while traveling a predetermined communication distance, which is the distance required to complete communication with the roadside antenna, from the time series of the sampled signal strength, and sets the communication correction value based on the difference between the representative value and the signal strength reference value which is the threshold.
4. The in-vehicle device according to any one of claims 1 to 3, wherein the correction value setting unit records the difference between the representative value and the signal strength reference value, and sets the average value of a predetermined number of the differences, starting from the most recent, as the communication correction value.
5. The in-vehicle device according to any one of claims 1 to 3, wherein the correction information acquisition unit acquires vehicle type information from a terminal device that sets up the in-vehicle device when the in-vehicle device is installed in a vehicle, and the correction value setting unit sets a correction value corresponding to the vehicle type information as the communication correction value when the vehicle type information is acquired.
6. A communication method for an in-vehicle device capable of communicating with a roadside antenna, comprising: a step of acquiring the antenna number of a corrective roadside antenna and a signal strength reference value set for the corrective roadside antenna; a step of sampling and recording the signal strength of a received signal when the antenna number included in the signal received from the roadside antenna matches the antenna number of the corrective roadside antenna; a step of setting a communication correction value based on the difference between a representative value of the sampled signal strength and the signal strength reference value; and a step of starting a reply to the roadside antenna when the sum of the signal strength of the signal received from the roadside antenna and the communication correction value exceeds a threshold.
7. A program that causes an in-vehicle unit capable of communicating with a roadside antenna to execute the following steps: acquiring the antenna number of a corrective roadside antenna and a signal strength reference value set for the corrective roadside antenna; sampling and recording the signal strength of a received signal when the antenna number included in the signal received from the roadside antenna matches the antenna number of the corrective roadside antenna; setting a communication correction value based on the difference between the sampled representative value of the signal strength and the signal strength reference value; and starting a reply to the roadside antenna when the sum of the signal strength of the signal received from the roadside antenna and the communication correction value exceeds a threshold.