JP2002204198A - Link establishment method, mobile station and on-vehicle apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent or suppress the influence of a gray zone in a low-speed movement without increasing a response-judgment received signal level Lth. SOLUTION: When a reception level is the response-judgment received signal level Lth or more (200) and when data from a road-side antenna can be normally received and decoded (202), a reception-counter comparison value N is selected (210) according to the detection result of a vehicle speed (208). At a point of time when a state that the data from the road-side antenna can be normally received and decoded is continued in the number of frames corresponding to the reception-counter comparison value N in a stat that the reception level is the level Lth or more (204, 206), ht transmission of a link establishment request is permitted. Since the comparison value N is set at a large value when the vehicle speed is low, it is possible to prevent the phenomenon that a link is erroneously established in the gray zone appearing before an intrinsic communication region, that the number of times of retransmission of exceeded due to data error, and that a data transmission cannot be completed inside the intrinsic communication region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for establishing a wireless link between a fixed station (for example, roadside equipment) and a mobile station (for example, a vehicle-mounted device), and a mobile station (for example, a vehicle-mounted device) suitable for implementing this method. Machine).

[0002]

2. Description of the Related Art An automatic toll collection system (ETC: Electr)
onic Toll Collection system) enables automatic charging, by allowing the vehicle on the road (including other places where the vehicle can run such as a parking lot in the present application) to be promptly charged. This is a kind of road-to-vehicle communication system aiming at quick settlement and congestion elimination. As shown in FIG.
In TC, a roadside antenna 10 having a shaped beam is installed on a bridge-like or beam-like structure so as to cover a predetermined area on a road. On the other hand, the in-vehicle device 12 is mounted on each vehicle 14 traveling on the road. The roadside antenna 10 and the on-vehicle device 12 are means for road-vehicle communication between a roadside facility (not shown) and the vehicle 14.

[0003] The roadside facility is a facility that executes processing related to billing. It is assumed that a vehicle enters the roadside antenna communication area from the roadside antenna 10 at all times or by a vehicle sensor or camera provided in the roadside facility. If determined, a signal for interrogation is wirelessly transmitted. Roadside antenna 10
The vehicle 14 located far from the roadside cannot receive the signal transmitted by the roadside antenna 10, but the vehicle 14 located sufficiently close to the roadside antenna 10 can receive the signal by the vehicle-mounted device 12. The in-vehicle device 12 is a kind of an automatic response recording device, and responds to a signal received from the roadside antenna 10 when it receives an inquiry signal. That is, first, a link establishment request is wirelessly transmitted so that data related to billing can be transmitted to and from the roadside facility via a wireless link with the roadside antenna 10.
The roadside equipment side receives and decodes a predetermined signal wirelessly transmitted by the roadside antenna 10 in response to this, so that the onboard unit 1
The two sides determine that the link establishment is successful. After the link is established, data transmission related to billing and the like is performed, and the link is released with the termination.

[0004] In addition, the area in which the signal transmitted by radio from the roadside antenna 10 can be received by the vehicle-mounted device 12, that is, the communication area of the roadside antenna 10, depends on the design of the roadside antenna 10 and
It is determined by the wireless function of the vehicle-mounted device 12.

First, the installation position and the directivity of the roadside antenna 10 are appropriately designed in consideration of a road cover situation as shown in FIG. 6, for example. The horizontal axis in FIG. 6 is the traveling direction of the vehicle 14,
That is, the position of the vehicle 14 is shown along the direction from the upstream to the downstream along the length of the road. The vertical axis in FIG.
The reception level of the signal from the roadside antenna 10 in the vehicle-mounted device 12 is shown. In the reception level design shown in FIG. 6, the reception level monotonously increases as the vehicle 14 approaches the roadside antenna 10, and after the reception level reaches a peak, the reception level increases as the vehicle 14 moves away from the roadside antenna 10. The level drops monotonically. In this way, by appropriately designing the installation position and directivity of the roadside antenna 10, a change curve of the reception level with respect to the position of the vehicle-mounted device 12 can be substantially determined.

Next, in the vehicle-mounted device 12, the roadside antenna 10
Is detected by monitoring the received signal. As a method of this detection, first, there is a threshold determination of the reception level. That is, the in-vehicle device 12 has a function of monitoring and detecting the reception level. When the reception level detected by using this function is sufficiently high, the vehicle-mounted device 12 enters the communication area of one of the roadside antennas 10 (or enters the communication area). There is a possibility). Whether the reception level is sufficiently high is determined by checking whether the reception level is equal to or higher than a predetermined threshold. This threshold is one of the factors that determine the sensitivity of the in-vehicle device 12 as a receiver, and the in-vehicle device 12 establishes a link only when it is determined that the reception level is sufficiently high by comparison with the threshold. A transmission operation including transmission of a request is performed. In FIG. 6, this threshold is described as a response determination reception signal level Lth. As is clear from the description of FIG. 6, the spread (set length) of the communication area of the roadside antenna 10 for each vehicle-mounted device 12 depends not only on its installation position and directivity design but also on the parameters used in the vehicle-mounted device 12. Is also affected by the response determination signal level Lth.

Further, since the communication between the roadside equipment and the on-vehicle device 12 is digital communication using framed signals, error detection / correction is also used as a method for detecting entry into the communication area of the roadside antenna 10. it can. That is, as shown in FIG. 7, when the frames wirelessly transmitted from the roadside antenna 10 can be normally received and decoded continuously over the number of frames equal to or greater than the predetermined reception counter comparison value N, the communication area of the roadside antenna 10 Can be determined. Since a signal transmitted from the roadside antenna 10 includes an error detection / correction code such as a CRC (Cyclic Redundancy Code), a received signal is a signal from the roadside antenna 10 by using the code. And that it has been successfully received and decoded. In the in-vehicle device 12, usually, the determination based on the reception level and the determination based on the number of consecutive normal reception frames are used together in order to obtain reliability. That is, when a change from a state in which the result of “out of the communication area” is obtained in at least one of the two determinations to a state in which the result of “inside the communication area” is obtained in both determinations is detected, The vehicle-mounted device 12 transmits a link establishment request, which is a signal for establishing a wireless link with the roadside antenna 10.

The vehicle-mounted device 12 establishes a charge (the vehicle 14 or its owner / user) via a connection via the roadside antenna 10 when establishing a link or at a predetermined time after the link is established and before the link is released. Various types of information including identification information to be specified are exchanged with roadside equipment. These pieces of information need to be stored in the vehicle-mounted device 12. In order to satisfy these requirements, the in-vehicle device 12 has, for example, the configuration shown in FIG. FIG.
In the example shown in FIG. 1, the on-vehicle device 12 includes a wireless unit 16 for wireless communication with roadside facilities via the roadside antenna 10, an HMI 18 which is an interface for a vehicle occupant and the like, an IC card storing identification information and the like. IC card reader / writer 20, which is a device for accessing the device, SAM 22, which is a security unit for protecting personal information such as identification information at the time of this access, and a control unit for controlling the operation of the above components 24.

FIG. 9 and FIG. 10 show the radio unit 1 of the vehicle-mounted device 12.
6 or the procedure executed by the control unit 24, it is checked whether or not a wireless link with the roadside antenna 10 can be established. If it is determined that the link can be established, a procedure for establishing the link, that is, a link establishment procedure Is shown.

[0010] As shown in FIG.
If no wireless link is established, the in-vehicle device 12 checks whether or not a link establishment request can be transmitted by executing a link establishment start procedure (100). As shown in FIG. 10, in the link establishment start procedure, first, it is checked whether or not the roadside antenna 10 is provided sufficiently close by continuous or intermittent electromagnetic wave monitoring by the wireless unit 16 (200, 202). In particular, in step 200, the reception level at the radio unit 16 is set to the response determination reception signal level L
In step 202, it is checked whether data from the roadside equipment can be normally decoded from the signal received by the radio unit 16. If it is determined in step 200 that the reception level is insufficient, or if it is determined in step 202 that normal decoding is not possible, the reception counter is reset to an initial value, and monitoring and determination are repeated.

The reception level is the response determination reception signal level Lt.
h, and when it is determined that the data from the roadside equipment can be normally decoded from the signal received by the radio unit 16, the count value of the reception counter is incremented by 1 (204), and the steps to repeat the monitoring and the determination are continued. Return to 200. Therefore, the count value of the reception counter indicates the number of consecutive frames that can be decoded normally in a state where a reception level equal to or higher than the response determination reception signal level Lth is obtained. As shown in FIG. 9, since the received signal is formed into a (constant length) frame, the count value indicates that a signal having a reception level equal to or higher than the response determination reception signal level Lth and capable of normal reception decoding is received. It can also be said that it represents the duration of the state of being made. Therefore,
In the procedure shown in FIG. 10, when the count value of the reception counter becomes equal to or more than a predetermined reception counter comparison value N (N = normal reception determination duration / frame length) (206), it is determined that the transmission of the link establishment request can be permitted. Then, the reception counter is reset to the initial value, and at the same time as the step 102 shown in FIG.
Move to

In the procedure shown in FIG. 9, when the transmission of the link establishment request is permitted in the procedure shown in FIG. 10 (102), the link establishment request is wirelessly transmitted (10).
4). When the road-side facility responds to this link establishment request via the road-side antenna 10 and the link can be considered to be established (106), the road-side facility / vehicle device related to charging in a road-to-vehicle communication routine (not shown). 1
Communication between the two and various information processing are executed.

On the other hand, when it can be considered that link establishment has failed, for example, when a response signal from the roadside equipment to the link establishment request cannot be normally received, the count value of the link establishment request counter is incremented by 1 (108). Then, the procedure returns to the link establishment start procedure. However, this is limited to when the count value of the link establishment request counter exceeds the set value (110). That is, even if the link establishment fails once, the link establishment request can be repeatedly transmitted until the count value of the link establishment request counter exceeds the set value, so that the electromagnetic wave environment temporarily deteriorates. However, a link can be suitably established.

When the count value of the link establishment request counter exceeds a set value, the link establishment request counter is reset to an initial value and a re-link establishment request timer is started (112). Until the re-link establishment request timer measures a predetermined time, the vehicle-mounted device 12 does not execute transmission of a signal such as a link establishment request. When the predetermined time is reached, that is, when the re-link establishment request timer times out (114), the procedure returns to the link establishment start procedure. Therefore, if the link cannot be established despite the trials corresponding to the set number of times, a link establishment request or the like is waited for a change in the surrounding conditions during the time required for the relink establishment request timer to time out. Is prohibited.

[0015]

However, according to the above-described procedure, when the vehicle 14 is moving at a very low speed due to traffic congestion, an accident, or the like, the road-vehicle communication routine is performed due to a so-called gray zone. May not be able to complete data transmission normally.

As shown in FIG. 11A, the gray zone is an area which is generated outside the communication area of the roadside antenna 10, usually before (upstream) the communication area. This is an area where the reception level at the device 12 is equal to or higher than the response determination reception signal level Lth. The gray zone is generally caused by unnecessary radiation, reflection, propagation, and the like.
For example, such a gray zone occurs when a signal transmitted by the roadside antenna 10 is reflected by a road surface, a surrounding building, a hood of the vehicle 14, or the like. In addition, the position where the gray zone appears, the spread of the gray zone,
The reception level in the gray zone depends on the surface shape / material and vehicle type of the vehicle 14 on which the on-vehicle device 12 is mounted and other vehicles existing around the vehicle 14 and the weather at that time. Is also not constant for each charging gate.

If the vehicle 14 is moving at a speed within a predetermined range (for example, within a speed range having a margin in the legal speed range), the vehicle 14
This gray zone has no significant effect on wireless transmission between the on-board unit 12 and the roadside antenna 10 mounted on the vehicle. In other words, if a suitable communication area design is performed, the gray zone is only an area that passes in a relatively short time for the vehicle 14 moving within the speed range, and therefore, the passage of the gray zone is difficult. Whether the conditions for transmitting the link establishment request are not satisfied in the required short time (see FIG. 10), or if the transmission of the link establishment request fails, the link establishment fails (steps 106 to 114 in FIG. 9).
Is one of Therefore, as shown in FIG. 11B, the link can be correctly established after entering the original communication area, and the data transmission by the road-to-vehicle communication routine can be completed.

On the other hand, if the vehicle 14 is moving at a lower speed than the above speed range, the time required for the vehicle 14 to pass through the gray zone is sufficient for the link establishment permission determination. There may be situations where link establishment is not sufficient, or situations where link establishment is sufficient but data transmission by the road-to-vehicle communication routine is insufficient. If the time required for passage is sufficient for link establishment permission determination but not enough for link establishment, the operation including steps 106, 108 and 110 in FIG. 9 is repeated, and more specifically, a relink establishment request timer is started. Link establishment is forbidden for a while. If the link is allowed to be established again, and if it has penetrated deep into the communication area (or has passed the communication area), the data communication required for charging cannot be executed or completed in the communication area. It can be. Also, in order to reliably receive data, the in-vehicle device 12, particularly the wireless unit 16, normally requests the roadside antenna 10 to retransmit data when a signal from the roadside antenna 10 cannot be normally received and decoded. Or a function of automatically repeating the data retransmission request for a predetermined limit number of times, or executing a link establishment procedure for a predetermined period when a normal signal is not received even if the request is repeated (when the number of retransmissions is exceeded). It has a relink prohibition timer function to prohibit. Therefore, FIG.
As shown in FIG. 1 (C), it is possible that the link establishment prohibited by the road-to-vehicle communication routine is permitted after the user has entered deep into the original communication area (or passed by). In such a case, even if the link establishment procedure is executed, the link cannot be established in the communication area or the data transmission by the road-to-vehicle communication routine cannot be normally completed.

One of the means for solving this problem is as follows.
There is a method in which the response determination reception signal level Lth is set to be higher so that a gray zone cannot be generated in the first place. However, the response determination reception signal level Lth
Is a parameter for determining the sensitivity of the in-vehicle device 12 as a receiver, as described above. If the parameter is set to a higher value, the original communication area (that is, not the gray zone) also becomes smaller. Considering that the appearance of the gray zone differs for each roadside antenna 10 (for example, for each toll gate through which the vehicle 14 passes) and changes depending on surrounding facilities, traffic and weather conditions, etc., it is necessary to avoid the influence of the gray zone. It is realistic to set the response determination reception signal level Lth to a value with a considerable margin, that is, a very high value.
In practice, this makes it difficult to establish a link and complete data transmission in the original communication area.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is intended to reduce the influence of the gray zone during low-speed movement without changing the response determination reception signal level Lth and, consequently, the reception sensitivity. The reduction is one of the purposes.

[0021]

SUMMARY OF THE INVENTION According to the present invention, a mobile station moves along a predetermined direction with a fixedly installed fixed station through a procedure in which a mobile station transmits a link establishment request in response to a call transmitted from the fixed station. The present invention can be expressed as an invention relating to a link establishment method for establishing a wireless link with a mobile station which is undergoing a communication. One of the prerequisites of the link establishment method according to the present invention is that, after the level of a received signal from a fixed station in a mobile station reaches a predetermined response determination reception signal level Lth or more, a predetermined normal reception determination duration (= Receive counter comparison value N ×
Frame length. However, for example, when the frame is formed into a fixed length frame, the mobile station becomes the fixed station only when the reception level is kept higher and the data can be normally decoded from the received signal. The point is that a link establishment request is transmitted by recognizing that the user has entered the communication area.

One of the features of the link establishment method according to the present invention is that transmission of a link establishment request in the gray zone is prevented or suppressed or link establishment fails.
A mobile station automatically changes the normal reception determination duration according to the moving speed of the mobile station. In the link establishment method according to the present invention, the level of the received signal generated outside the original communication area of the fixed station due to unnecessary radiation, reflection, or propagation is the same as that in the original communication area. The frequency of occurrence of a phenomenon in which a link is erroneously established in a gray zone which is equal to or larger than Lth but whose spread is not sufficient to complete communication between fixed and mobile stations,
Has been reduced. When practicing the present invention, it is not necessary to set the response determination reception signal level Lth higher.

Further, the link establishment method according to the present invention
It can be executed by an on-board device in a road-to-vehicle communication system represented by TC. For example, consider a system including a roadside facility having a directivity and a roadside antenna installed near a road and a vehicle-mounted device mounted on a vehicle, which is designed so that a predetermined area on the road is a communication area. As an example,
There is an ETC having a roadside facility for executing communication for charging or confirming a vehicle traveling on a road, and an on-vehicle device for transmitting a signal including identification information for specifying a charging target to the roadside facility. . In such a road-to-vehicle communication system, the roadside equipment corresponds to the above fixed station,
The on-vehicle device corresponds to the above-described mobile station. In this type of system, a signal for a speedometer mounted on the vehicle (for example, a vehicle speed pulse generated according to rotation of a driven wheel) and a signal for controlling a drive system of the vehicle (for example, an engine speed and a transmission Control signal), the output of a positioning device mounted on the vehicle (for example, a change or speed of a position detected by a GPS receiver), or the output of a wireless detection device mounted on the vehicle (for example, the output speed of a radar or Time change of the distance information) can be given to the in-vehicle device as a signal indicating the moving speed or a signal for deriving the moving speed in the information used to determine the start of link establishment, so that it is relatively simple. Implementation is possible.

Further, the present invention can be expressed as an invention relating to a mobile station. Mobile station according to the present invention, means for receiving a call wirelessly transmitted from the fixed station, and means for determining whether the level of the received signal from the fixed station is equal to or higher than a predetermined response determination received signal level, Means for determining whether or not data can be normally decoded from the received signal; and receiving the signal for a predetermined period of time for normal reception determination after the level of the received signal reaches the level of the response determination received signal or more. A means for determining whether or not the state in which the level is maintained and data can be normally decoded from the received signal has continued, and only when it is determined that the state has been continued, it is determined that it has entered the communication area of the fixed station and a link establishment request is made. Means for wirelessly transmitting the radio signal to the fixed station in response to a call wirelessly transmitted from the fixed station, carried or carried by a mobile object such as a person or a vehicle moving in a predetermined direction. A means for automatically changing the normal reception determination duration according to the moving speed of the mobile station so that the transmission of the link establishment request in the gray zone is prevented or suppressed or the link establishment fails in the mobile station establishing the network. Unnecessary radiation, reflection or propagation occurs outside the original communication area of the fixed station, and the level of the received signal becomes equal to or higher than the response determination reception signal level as in the original communication area, but the spread of the received signal is larger than that of the fixed station. The frequency of occurrence of a phenomenon in which a link is erroneously established in a gray zone where communication is not completed is reduced.

The present invention can be expressed as an invention relating to a vehicle-mounted device. The in-vehicle device according to the present invention is a means for receiving a call wirelessly transmitted from the roadside equipment, and a means for determining whether the level of a reception signal from the roadside equipment is equal to or higher than a predetermined response determination reception signal level, Means for determining whether or not data can be normally decoded from the received signal; and receiving the signal for a predetermined period of time for normal reception determination after the level of the received signal reaches the level of the response determination received signal or more. Means for determining whether or not the state where the level is maintained and data can be normally decoded from the received signal has continued, and only when it is determined that the state has been continued, it is determined that it has entered the communication area of the roadside equipment and a link establishment request is made. Means for wirelessly transmitting the roadside equipment, which is mounted on a vehicle moving along a predetermined direction, and establishes a wireless link with the roadside equipment in response to a call wirelessly transmitted from the roadside equipment. A means for automatically changing the normal reception determination duration according to the moving speed of the own vehicle so that transmission of the link establishment request in the gray zone is prevented or suppressed or the link establishment fails in the on-board machine; The level of the received signal becomes higher than the response determination received signal level as in the original communication area due to reflection or propagation and occurs outside the original communication area of the roadside equipment, but the spread completes the communication with the roadside equipment. The frequency of occurrence of a phenomenon in which a link is erroneously established in a gray zone that is not enough is reduced.

The present invention can also be expressed as a communication program for link establishment executed on the vehicle-mounted device. The communication program for establishing a link according to the present invention is configured such that after the level of the reception signal related to the call wirelessly transmitted from the roadside equipment reaches the predetermined response determination reception signal level or higher, the predetermined level is equal to or longer than the predetermined normal reception determination duration. A set of instructions for determining whether or not the reception level of the received signal has been maintained and whether or not a state in which data can be normally decoded from the received signal has been continued. A command set for wirelessly transmitting a link establishment request, and having a device mounted on a vehicle moving along a predetermined direction, a wireless link between the roadside equipment in response to a call wirelessly transmitted from the roadside equipment. In the link establishment program executed for establishing, the transmission of the link establishment request in the gray zone is prevented or suppressed, or the link is established. It has a command set to automatically change the normal reception determination duration according to the moving speed of the own vehicle so that it fails, unnecessary radiation, reflection or propagation occurs outside the original communication area of the roadside equipment and the original communication A phenomenon in which the link is erroneously established in the gray zone where the level of the received signal is equal to or higher than the response determination received signal level as in the area, but the spread is not enough to complete the communication between the roadside equipment on-board equipment. The frequency of occurrence of is reduced.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The same or corresponding components as those of the related art shown in FIGS. 5 to 11 are denoted by the same reference numerals, and redundant description will be omitted. In addition, the present invention provides an in-vehicle device 12 shown in FIG. 8 under the environment shown in FIG.
In particular, since it can be executed by the radio unit 16 and the control unit 24, the following description is based on the configuration shown in FIGS. Further, the present invention can be implemented as a modification of the link establishment procedure shown in FIG. 9, in particular, the link establishment start procedure which is step 100 thereof, so that the following description also assumes the link establishment procedure shown in FIG. 9.

FIG. 1 shows a flow of a link establishment start procedure in one embodiment of the present invention. As shown in this figure, in the present embodiment, when executing the link establishment start procedure, the speed of the mounting destination vehicle (own vehicle) 14, that is, the vehicle speed is detected (208). If it is determined in step 200 that the reception level is equal to or higher than the response determination reception signal level Lth, and if it is detected in step 202 that the signal from the roadside antenna 10 can be normally received and decoded, the reception counter comparison value N is set to step 208 Is automatically set to a value corresponding to the detected vehicle speed (210). What is compared with the count value of the reception counter in step 206 is the reception counter comparison value N thus set according to the vehicle speed.

The reception counter comparison value N is set to a large value when the vehicle speed is low. For example, as shown in FIG. 2, when the vehicle speed V is sufficiently low and it can be considered that the road is congested or the like, the reception counter comparison value N at the normal time is used.
In step 210, a reception counter comparison value N = N2 larger than N = N1 is automatically selected. By setting the reception counter comparison value N to a large value N2 at a low speed in this way, transmission of a link establishment request in the gray zone or link establishment corresponding thereto can be prevented, or frequent occurrence thereof can be prevented. It is possible to more reliably establish a normal link within the original communication area and complete the data transmission by the road-to-vehicle communication routine.

Further, the reception counter comparison value N1 in the normal state and the reception counter comparison value N2 in the low speed state are both set to natural numbers between A / VT and B / VT. Here, A and B are the expected length of the gray zone and the set length of the link establishment area in the communication area, respectively, as shown in FIG. The expected length A of the gray zone is set empirically. The link establishment area included in the communication area is an area in which a link should be established prior to execution of data transmission by the road-to-vehicle communication routine in the first communication area. The design length can be determined in combination with the set lengths C and D. The second communication area includes the link establishment area and the first communication area, and has a set length with a margin.

As described above, the reception counter comparison value N1 at normal time and the reception counter comparison value N2 at low speed
Is determined according to the expected length A of the gray zone and the set length B of the link establishment area, it is possible to cope with a typical situation of the charging gate where the vehicle 14 may pass. Note that the range in which the vehicle speed V can be taken is limited based on the performance of the vehicle 14, laws and regulations, and the like, so that there is no particular problem even in two-stage switching as shown in FIG. 2, but more preferably as shown in FIG. It is desirable to perform multi-stage switching or the like.

Further, regarding the vehicle speed V, the vehicle 1
4 can be obtained from a device generally mounted. For example, a normal vehicle 14 is equipped with a vehicle speedometer. A signal for displaying the vehicle speed on the vehicle speed meter, for example, a vehicle speed pulse generated every time the driven wheel rotates by a predetermined angle is counted to obtain the vehicle speed V, and based on this, the reception counter comparison value N according to step 210 is switched. can do. Alternatively, the vehicle speed V may be derived from a signal for controlling the drive system of the vehicle 14, for example, information on the engine speed or transmission control. Alternatively, when a positioning device such as a GPS receiver is mounted on the vehicle 14, the vehicle speed V detected by the positioning device is
May be used, or the current position detected by the positioning device may be input, and the amount of time change thereof may be obtained as the vehicle speed V. Alternatively, when a radar device is mounted on the vehicle 14, the vehicle speed V may be obtained based on the Doppler shift appearing in an echo from an object around the vehicle received by the radar device. From the amount of time change of the distance to the object around the detected vehicle,
The vehicle speed V may be obtained. In order to easily obtain information on the vehicle speed V, it is desirable to configure the on-vehicle device 12 according to the present embodiment in an integrated manner with a navigation system including a positioning device.

The application of the present invention is not limited to the vehicle-mounted device 12 in ETC. For example, the present invention can be applied to a vehicle-mounted device in a road-vehicle communication system having a purpose other than charging. Further, the present invention can be applied to a system for providing information from a fixed station such as a roadside facility to a mobile body other than a vehicle, for example, a human.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a flow of a link establishment start procedure according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of switching contents of a reception counter comparison value in the present embodiment.

FIG. 3 is a diagram for explaining a principle of setting a reception counter comparison value in the embodiment.

FIG. 4 is a diagram for explaining another example of setting of a reception counter comparison value in the present embodiment.

FIG. 5 is a conceptual diagram showing a schematic configuration of an ETC.

FIG. 6 is a diagram showing a change in the reception level of the vehicle-mounted device along the traveling direction position and a flow of operation of the vehicle-mounted device accompanying the movement of the vehicle.

FIG. 7 is a conceptual diagram showing a configuration of a signal exchanged between a roadside antenna and a vehicle-mounted device.

FIG. 8 is a block diagram illustrating a functional configuration of the vehicle-mounted device.

FIG. 9 is a flowchart showing a flow of a link establishment procedure.

FIG. 10 is a flowchart showing a flow of a conventional link establishment start procedure.

FIG. 11 is a diagram for explaining a conventional problem.
In particular, (A) shows the change according to the traveling direction position of the in-vehicle device reception level when the gray zone occurs, and (B) shows the operation flow of the in-vehicle device when the vehicle is moving at the normal speed. (C) is a diagram showing a flow of operation of the vehicle-mounted device when the vehicle is moving at a low speed due to traffic congestion or the like.

[Explanation of symbols]

10 Roadside antenna, 12 On-board unit, 14 Vehicle, 16
Radio unit, 24 control unit, Lth response determination reception signal level, N, N1, N2 reception counter comparison value, V vehicle speed.

Claims (5)

[Claims] 1. A method according to claim 1, wherein the mobile station transmits a link establishment request in response to a call transmitted from the fixed station, and the communication between the fixed station and the mobile station moving in a predetermined direction. A link establishment method for establishing a wireless link, wherein after a level of a received signal from a fixed station at a mobile station reaches a predetermined response determination reception signal level or more, the level of the received signal exceeds a predetermined normal reception determination duration. Only when the above reception level is maintained and the state in which data can be normally decoded from the received signal continues, the mobile station identifies itself as having entered the communication area of the fixed station and transmits a link establishment request. In the establishment method, the mobile station automatically normalizes according to its own moving speed so that transmission of the link establishment request in the gray zone is prevented or suppressed or the link establishment fails. By changing the signal determination duration, unnecessary radiation, reflection or propagation occurs outside the fixed station's original communication area, and the received signal level is equal to or greater than the response judgment received signal level as in the original communication area. A link establishment method characterized in that the frequency of occurrence of a phenomenon in which a link is erroneously established in a gray zone whose spread is not sufficient to complete communication between a fixed station and a mobile station is reduced. 2. A roadside facility having a directivity designed such that a predetermined area on a road is a communication area and having a roadside antenna installed near the road is defined as the fixed station, and along a predetermined traveling direction. 2. A road-vehicle communication system in which an in-vehicle device mounted on a moving vehicle is the mobile station.
The link establishment method according to claim 1, wherein a signal for a speedometer mounted on the vehicle, a signal for controlling a drive system of the vehicle, an output of a positioning device mounted on the vehicle, or a signal mounted on the vehicle A link establishment method, wherein an output of a wireless detection device is provided to a vehicle-mounted device as a signal indicating a moving speed or a signal for deriving the moving speed. 3. The link establishment method according to claim 2, wherein the road-side facility is provided for executing communication for charging or confirming the vehicle passing on the road, and a signal including identification information for specifying a charging target. A link establishment method which is executed in an automatic toll collection system provided with the above-mentioned on-board unit as a device for transmitting a link to a roadside facility. 4. A means for receiving a call wirelessly transmitted from a fixed station, a means for determining whether the level of a signal received from the fixed station is equal to or higher than a predetermined response determination reception signal level, and Means for judging whether or not data can be decoded normally from the receiver, and after the level of the received signal reaches or exceeds the response determination received signal level, the received level is maintained for a predetermined normal reception determination duration or longer. Means for determining whether or not the state in which data can be normally decoded from the received signal has continued, and means for assuming that the mobile station has entered the communication area of the fixed station and wirelessly transmitting a link establishment request only when it is determined that the state has been continued. And establishes a wireless link with the fixed station in response to a call wirelessly transmitted from the fixed station, carried or carried by a mobile object such as a person or a vehicle moving in a predetermined direction. The mobile station has means for automatically changing the normal reception determination duration according to the moving speed of its own station so that transmission of a link establishment request in the gray zone is prevented or suppressed or link establishment fails. Although the level of the received signal is higher than the response determination received signal level as in the original communication area due to radiation, reflection or propagation outside the fixed station's original communication area, its spread completes communication with the fixed station. A mobile station characterized in that the frequency of occurrence of a phenomenon in which a link is erroneously established in a gray zone that is not sufficient is reduced. 5. A means for receiving a call wirelessly transmitted from the roadside equipment, a means for determining whether the level of a signal received from the roadside equipment is equal to or higher than a predetermined response determination reception signal level, and Means for judging whether or not data can be decoded normally from the receiver, and after the level of the received signal reaches or exceeds the response determination received signal level, the received level is maintained for a predetermined normal reception determination duration or longer. Means for determining whether or not a state in which data can be normally decoded from a received signal has continued, and means for wirelessly transmitting a link establishment request by assuming that the vehicle has entered the communication area of the roadside equipment only when it is determined that the state has been continued. And a vehicle-mounted device that is mounted on a vehicle that moves along a predetermined direction and that establishes a wireless link with the roadside facility in response to a call wirelessly transmitted from the roadside facility. Means for automatically changing the normal reception determination duration according to the moving speed of the own vehicle so that transmission of the link establishment request in the gray zone is prevented or suppressed or the link establishment fails, and unnecessary radiation and reflection are provided. Alternatively, the level of the received signal becomes higher than or equal to the response determination received signal level as in the original communication area due to propagation outside the original communication area of the roadside equipment, but its spread is required to complete communication with the roadside equipment. An in-vehicle device characterized by reducing the frequency of occurrence of a phenomenon in which a link is erroneously established in a missing gray zone.