JP2008099070A - Road-to-vehicle communication device and road-to-vehicle communication method - Google Patents

Abstract

Information distribution according to vehicle position information is performed in consideration of cost and installation space.
A roadside wireless communication device (not shown) is connected to a directivity variable antenna AN1. By changing the directivity of the variable directivity antenna AN1 between Pa1 and Pa2, the communication area can be controlled, and different information services are provided to the vehicles V2 and V3 and V1 in each communication area. can do. In the vehicles V2 and V3 approaching the intersection Crs from a distance, the driver is notified by voice or the like how many seconds later the green signal changes to the yellow signal. In the vehicle V1 reaching the area close to the intersection Crs, for example, it can be confirmed whether or not there is a vehicle entering the intersection from an area that has become a blind spot due to a building. In the vehicle V1, it can be predicted that a vehicle ignoring a red light or an emergency vehicle will enter the intersection.
[Selection] Figure 1

Description

  The present invention relates to a road-to-vehicle communication method using a communication device mounted on a vehicle and a communication device fixedly installed along a road, and the road-to-vehicle communication device fixedly installed.

  In recent years, various attempts have been made to reduce the number of traffic accidents. One of them is a collision prevention system with an object located in the traveling direction of the vehicle by mounting a radar or an imaging sensor on the vehicle. In order for these systems to operate effectively, the object of interest must be in line of sight from the vehicle.

  On the other hand, many accidents are caused by the rapid approach of unforeseen vehicles. “Out of sight” refers to vehicles such as curves, intersections, and other vehicles and other obstacles in the direction of travel of the vehicle, other vehicles that join or cross the region, road side walls, buildings, and other obstacles. Says that it is not fully visible. In order to reduce these accidents that occur outside the line of sight, safety systems using wireless communication are being studied. One of them is a road-to-vehicle communication system that is performed between a communication device installed on the roadside and a communication device mounted on a vehicle. Such a road-vehicle communication system has been reported in Non-Patent Document 1 and the like.

  Road-to-vehicle communication systems aim to prevent accidents by providing information. As an example, it is conceivable to distribute the presenting information of the intersection to the vehicle heading to the intersection, or to distribute the image information of the position that becomes the blind spot of the driver near the intersection. That is, a vehicle that enters the intersection from the left or right direction, and that is a blind spot due to the building at the intersection, or whether the signal that is the blind spot ahead of the curve is red, yellow, blue (green), etc. is there. In addition, it is considered to distribute information not only for safety system purposes but also for entertainment purposes.

By the way, in such a road-to-vehicle communication system, Patent Literature 1 reports an idea of realizing high-quality communication by using an adaptive array to follow a vehicle that moves an antenna pattern.
Japanese Patent Laying-Open No. 2005-020792 Tsukawa, Sadayuki, “Communications in Intelligent Transportation Systems,” Science (B), vol. 82-B, no. 11, pp. 1958-1965, 1999.

In the road-to-vehicle communication system, a greater effect can be achieved by providing different information depending on the position of the vehicle that is the target of information distribution. For example, image transmission is being conducted to convey the details of the blind spot near the intersection, but from the viewpoint of system communication capacity, large capacity information such as images is transmitted to all vehicles. Therefore, it is realistic to distribute vehicle position information, intersection display information, etc. with a small amount of information to vehicles far from the intersection.
At this time, in order to distribute different information according to the position of the target vehicle using a conventional roadside communication device with a fixed antenna pattern, the number of roadside communication devices is required accordingly. Since road-to-vehicle communication systems are assumed to be implemented in major accident occurrence areas throughout the country, it is a big problem that the cost and installation space of communication devices become enormous.

  In such a road-to-vehicle communication system, since the system is established only within the range covered by the roadside communication device installed on the roadside, the degree of infrastructure penetration is very important for the establishment of the system. However, since it is not possible to maintain all roadside communication devices at once, infrastructure will be improved in stages. The problem here is that when a roadside communication device is added, it must be matched with a roadside communication device that has been arranged. For example, overlapping of areas covered by roadside communication devices must be avoided from the viewpoint of radio wave interference and infrastructure efficiency.

  In addition, it is conceivable that spots where radio waves do not reach may be formed even within the service area depending on radio wave propagation conditions, and adjustment of the roadside communication device is important. It is expected that a great amount of man-hours will be required for this adjustment.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to implement information distribution according to the position area of a vehicle in a road-to-vehicle communication system in consideration of cost and installation space. Is to provide. Another object is to provide a practical means in infrastructure development and management of roadside communication devices.

The invention according to claim 1 is an antenna installed at a predetermined height above the road in a road-to-vehicle communication apparatus fixedly installed to communicate with a communication device mounted on a vehicle traveling on the road. Thus, the road-to-vehicle communication device includes a variable directivity antenna capable of forming a beam pattern corresponding to a plurality of road regions in different distance ranges.
As the directivity variable antenna, an adaptive array antenna can be used in addition to the antenna using the variable reactance element described in the following embodiments.

The invention according to claim 2 is characterized in that communication is periodically and sequentially established in a plurality of road areas in different distance ranges.
In the invention according to claim 3, the road area can be continuously adjusted with respect to the distance range, and the adjustment is applied to the road range between the two communication areas by the two communication devices installed in advance. It is possible to do this.

  According to a fourth aspect of the present invention, the directivity variable antenna includes one feed element, a plurality of parasitic elements provided at a predetermined distance from the feed element, and a plurality of variable reactances loaded on the parasitic element. It is comprised from an element, and directivity can be controlled by changing the reactance value of a variable reactance element.

  In the invention according to claim 5, the directivity variable antenna includes a main loop wiring arranged on a single reference plane with a power feeding unit including a pair of two feeding points, a main loop wiring, An antenna element having at least one secondary loop wiring that is arranged in parallel or on the same plane and that does not have a feeding point, and each loop wiring does not have a crossing point and a contact with each other. The center point of the enclosed plane area is located on one vertical section perpendicular to the reference plane that passes through the center point of the plane area surrounded by the main loop wiring, and is surrounded by any one loop wiring. When viewed from the normal direction of the reference plane, the planar area that appears is partially overlapped with another planar area that is surrounded by other adjacent loop wirings, and the secondary loop wiring has two locations on the vertical section. Each with variable rear The main loop wiring has a variable reactance element at one location on the vertical cross section and a power feeding portion at the other location on the vertical cross section. Directivity can be changed by changing the reactance values of multiple variable reactance elements by considering half of the loop wiring as feed elements, the main loop wiring around the variable reactance elements and the secondary loop wiring as multiple parasitic elements. It is characterized by changing.

According to a sixth aspect of the present invention, in a road-to-vehicle communication method using a communication device mounted on a vehicle traveling on a road and a communication device fixedly installed, a directivity variable antenna is connected to the communication device fixedly installed. A variable antenna is installed at a predetermined height above the road, and a beam pattern can be formed corresponding to a plurality of road areas in different distance ranges, and periodically switched to a plurality of road areas in different distance ranges. A road-to-vehicle communication method characterized by sequentially establishing communication.
Here, the information that is periodically switched in a plurality of regions in different distance ranges and sequentially communicates may be the same information, or may be different information for each region. The latter case means different information depending on the distance range from the fixedly installed communication device.

  According to the first means, in the road-to-vehicle communication system, by controlling the antenna beam pattern of the roadside communication device, a flexible response meeting the system requirements can be performed with one directivity variable antenna. Compared to the case of using an antenna whose pattern cannot be controlled, the cost and installation space can be greatly reduced.

  According to the second and sixth means, by distributing different information according to the position area of the target vehicle for communication, it is possible to distribute information effectively within the communication capacity of the system. That is, it becomes possible to provide different road information according to the position area of the target vehicle or to provide different services including entertainment.

  According to the third means, when the infrastructure is added, it is possible to match the existing infrastructure only by changing the antenna beam pattern, so that the maintenance man-hours can be reduced. In addition, when adjusting the radio wave propagation environment in order to secure an area to be covered by each roadside communication device, the antenna beam pattern can be controlled to some extent, so that there is a cost merit as well.

  According to the fourth means, the number of antennas and the number of high-frequency circuits of the transmitter or the receiver can be reduced to one system each compared with the case where an array antenna by digital beam forming is used. An antenna device can be realized.

  According to the fifth means, an antenna having a planar structure can be realized while maintaining high beamforming performance. Considering that an enormous number of roadside communication devices are installed throughout the country, the installation space constraints can be greatly relaxed.

  Hereinafter, the present invention will be described based on specific examples.

  FIG. 1 is a schematic diagram showing an example of the configuration of a road-to-vehicle communication system for the purpose of providing information near an intersection using the variable directivity antenna according to the present embodiment.

  In the present embodiment, a roadside radio communication apparatus (not shown) is connected to the directivity variable antenna AN1 shown in FIG. As shown in FIG. 1, the communication area can be controlled by changing the directivity of the directivity variable antenna AN1 between Pa1 and Pa2, and different services can be switched and provided. At this time, it is assumed that communication is established with a plurality of surrounding vehicles to which information is provided by a multiple access protocol such as TDMA, CDMA, or FDMA.

  When the directivity of the directivity variable antenna AN1 is set to Pa1, a roadside wireless communication apparatus (not shown) transmits, for example, the intersection Crs to the vehicles V2 and V3 approaching the intersection Crs from a distance via the variable directivity antenna AN1. The signal state at is transmitted. In the vehicles V2 and V3 approaching the intersection Crs from a distance, it is also possible to receive the data as a data transmission without continuously viewing the signal state. For example, it is also possible to notify the driver by voice or the like how many seconds later the blue signal changes to the yellow signal.

  When the directivity of the directivity variable antenna AN1 is set to Pa2, a roadside wireless communication apparatus (not shown) passes the directivity variable antenna AN1 to the vehicle V1 reaching the area close to the intersection Crs as Data2, for example, the intersection Crs. Send nearby vehicle status. In the vehicle V1 that has reached the area close to the intersection Crs, for example, it can be confirmed whether or not there is a vehicle or a pedestrian entering the intersection from an area that has become a blind spot due to a building. Thereby, it can be foreseen that vehicles, pedestrians, and emergency vehicles that ignore the red light will enter the intersection. As a result, for example, immediately before the signal in the straight traveling direction, which is the traveling direction of the vehicle, changes from red to blue, it is possible to avoid a collision with a vehicle or a pedestrian entering the intersection from the lateral direction.

FIG. 2 shows a configuration example of a directivity variable antenna that can be used in this embodiment. The antenna 10 of FIG. 2 corresponds to a specific embodiment of a variable directivity antenna constituting the invention according to claim 5. The planar shape of each loop wiring of the feeding element A11, the parasitic element P11a, and the parasitic element P11b included in the antenna 10 of FIG. 2 is circular. This feeding element A11 corresponds to the main loop wiring. Further, the parasitic element P11a and the parasitic element P11b correspond to the secondary loop wiring. Feed element A11 is disposed on the reference plane sigma ₀ parallel to the yz plane of Fig. Also, the parasitic element P11a and the parasitic element P11b are respectively disposed on a plane parallel sigma ₂ on the reference plane sigma _0. Here, the symbol d2 indicates the distance between the reference plane Σ ₀ and the plane Σ ₂ .

A plane Σ _{1 in} FIG. 2 is a plane that passes through the center point C ₀ of the power feeding element A 11 and is perpendicular to the plane Σ ₀ (hereinafter referred to as a vertical section Σ ₁ ). The vertical cross section Σ ₁ is a plane parallel to the xy plane, intersects perpendicularly to the plane region surrounded by the main loop wiring, and the center point C _{a of the} secondary loop wiring (the parasitic element P11a and the parasitic element P11b). , C _b both are arranged on the vertical section sigma _1.
Code d1a of FIG. 2 shows the distance to the center point C ₀ of the main loop line from the center point C _a parasitic element P11a. Similarly, reference numeral d1b is a distance to the center point C ₀ of the center point C _b parasitic element P11b. More specifically, with respect to the feeding element A11, each of the slave loop wirings (the parasitic element P11a and the parasitic element P11b) is d1a = in the y-axis direction with respect to a predetermined wavelength λ. d1b = lambda / 4 and are arranged so made, and, in the z-axis direction is placed away from the reference plane sigma ₀ as a d2 = 0.0064λ.

Further, on the power supply element A11 is feeding part F0 on the vertical section sigma ₁ is arranged, a variable reactance element X1 is disposed on the opposite side of the loop line. Other also each variable reactance elements X2~X5 of are disposed one each on the vertical cross section sigma ₁ on each loop line.
With these configurations, the effective length of each loop, including the action of each reactance in each loop wiring, is based on the variable control of each reactance value of each reactance element X1 to X5. It can be variably controlled so as to match one wavelength of the electromagnetic wave.

The variable reactance elements X1 to X5 are constituted by chip components such as varicap diodes, chip capacitors, chip inductors, chip resistors, and the reactance values are changed by applying a DC voltage to the varicap diodes.
In addition, the feeding element A11 and the parasitic elements P11a and P11b have a multi-layer structure. However, the elements need not have an intersection, and may be configured in the same plane, for example, configured to have no intersection using a bridge. Also good.

The antenna 10 in FIG. 2 can be formulated by expressing the directivity as a product of an array factor and an equivalent weight vector by regarding the power feeding unit F0 and the variable reactance elements X1 to X5 as approximate dipoles. For example, the reactance domain algorithm in the conventional ESPAR antenna can be easily applied by such a formulation.
Moreover, you may change arbitrarily the magnitude relationship of each length d1a, d1b, r of FIG. Accordingly, in the first embodiment, r (= λ / 2π) <d1a = d1b is set. However, for example, d1a <r <d1b (asymmetric) or d1a ≦ d1b <r is set. Also good. From the viewpoint of ease of control, it is desirable that the physical loop lengths of the respective loop wirings coincide with each other. The effective length of the main loop wiring is the wavelength of the electromagnetic wave handled. Each loop is not limited to a circle but may be a polygon.

  The antenna 10 in FIG. 2 can control the variable reactance elements X1 to X5 with, for example, DC voltages, respectively, and the directivity variable antenna can control the directivity while keeping the transmitter as one system. . That is, since it is not necessary to prepare a plurality of transmitters for each directivity, a wireless communication apparatus that transmits different information to a plurality of areas can be realized at low cost. Moreover, although the antenna 10 of FIG. 2 has some thickness (d2), since it is comprised by the planar structure, the freedom degree with respect to installation space is large.

As an example of an antenna pattern that can be realized by the antenna 10, two types of beam patterns of a broad side direction (a, equivalent to Pa1 in FIG. 1) and an endfire direction (b, equivalent to Pa2 in FIG. 1) are shown in FIG. . Further, the reactance values of the reactance circuits at this time are shown in Table 1.

  In the present embodiment, for vehicles far from the intersection (V2, V3 in FIG. 1), the directivity of the variable directivity antenna is set to Pa1, and the intersection display information (Data 1 in FIG. 1) with a small capacity is provided. For a vehicle in the vicinity of the intersection (V1 in FIG. 1), large-capacity image information (Data 2 in FIG. 1) is provided with the directivity of the variable directivity antenna as Pa2. In the first place, it is not realistic from the viewpoint of system establishment to provide data of large capacity such as image information to all vehicles. For this reason, in this embodiment, by providing detailed information only to vehicles near the intersection (V1 in FIG. 1) with a high degree of danger, a great effect can be achieved with realistic communication capacity. Incidentally, when it is desired to obtain the same effect using a conventional roadside communication device whose antenna pattern is not variable, the same number of sets of roadside communication devices and antennas as the number of areas to be divided is required, which greatly increases the cost.

  In the first embodiment, the method of providing two types of information services using the two patterns Pa1 and Pa2 has been described. However, the present invention is not limited to this, and three or more types of patterns and three or more types of information services are provided. Information services can be provided as well. In addition, the directivity variable antenna is not limited to the above-described shape, and may be any configuration as long as the antenna pattern can be changed, such as an adaptive array antenna, a directivity switching antenna, and a reactance loaded antenna.

In addition, a synchronization signal in the inter-vehicle communication can be provided from the roadside communication device.
Moreover, although the present Example described road-to-vehicle communication, it cannot be overemphasized that it is effective similarly when performing unidirectional broadcasting from a roadside communication apparatus to a surrounding vehicle.

  The location where this service is provided is not limited to the vicinity of the intersection, but is valid at any point where other accidents can occur.

  FIG. 4 is a schematic diagram showing an example of the present embodiment for the purpose of simplifying the adjustment of the infrastructure system in road-to-vehicle communication using the directivity variable antenna.

  In this embodiment, when a roadside communication device is added and installed, the entire system is matched by adjusting the antenna pattern of the roadside communication device to be added without making a significant change to the already installed device. Can take. ANa1, ANa2 and Ar1, Ar2 respectively indicate an antenna connected to the installed roadside communication device and its communicable area. Here, in order to enable communication in the area Ar3 between the communication areas Ar1 and Ar2 of ANa1 and ANa2, a roadside communication device is newly added and connected to the antenna ANp1. However, if there is an overlap in the communication areas Ar1, Ar2, and Ar3 of ANa1, ANa2, and ANp1 as shown in FIG. 4, there is a possibility that interference will occur in that section. In order to avoid this interference, conventionally, it has been necessary to adjust the position, power, etc. of all antennas, which has been a heavy burden. Here, it is possible to reduce overlap by applying a directivity variable antenna as each antenna and electronically adjusting the antenna pattern. For this reason, the degree of freedom for adjustment is greatly increased, and the infrastructure cost can be reduced. At least, if the antenna pattern of the antenna ANp1 connected to the newly added roadside communication device is electronically adjusted, the new area Ar3 does not interfere with the communication areas Ar1 and Ar2 by the already provided roadside communication device. .

When a synchronization signal in vehicle-to-vehicle communication is provided from a roadside communication device, a plurality of synchronization signals can be easily avoided from being transmitted from a plurality of roadside communication devices to one vehicle.
Further, in addition to the adjustment based on the antenna pattern, a greater effect can be obtained by combining with the adjustment based on the transmission power or arrangement of the communication device.

[Other directivity variable antenna]

  An ESPAR antenna (Electronically Steerable Passive Array Radiator antenna), which is one of simple directivity control antennas, is reported in Japanese Patent Application Laid-Open No. 2004-134873. An example of the ESPAR antenna configuration is shown in FIG. The directivity control method is also reported in the above-mentioned publications.

  The configuration of the ESPAR antenna 20 of FIG. 5 will be briefly described. FIG. A is a perspective view showing a configuration of an ESPAR antenna 10 having a feeding element A0 and six parasitic elements A1 to A6 each having a variable reactance element connected thereto. The feeder element A0 and the parasitic elements A1 to A6 are linear conductors provided in the vertical direction, and are connected to the ground conductor 11 through the seven holes 110 to 116 of the ground conductor 11 arranged horizontally. It is provided upward without touching. As for the arrangement of the seven holes 110 to 116, the hole 110 is provided at the center, and the holes 111 to 116 are provided at the positions of the apexes of the regular hexagon around the hole 110. Thus, the feed element A0 and the parasitic elements A1 to A6 are provided, for example, with the same length through the seven holes 110 to 116 of the ground conductor 11.

  FIG. B shows a sectional view of the feeding element A0 and the parasitic elements A1 and A4 formed on a single plane. Under the hole 110 of the ground conductor 11, the feed element A0 is connected to the core wire of the coaxial cable 5 and connected to the receiver. Under the holes 111 and 114 of the ground conductor 11, the parasitic elements A1 and A4 are connected to variable reactance elements 12-1 and 12-4 whose other ends are grounded. Exactly in the same manner, the six parasitic elements A1 to A6 are variable reactance elements 12-1 to 12-6 (all shown) having the other ends grounded under the holes 111 to 116 of the ground conductor 11. Not connected).

  FIG. C is a circuit diagram illustrating an example of a variable reactance element and a control method thereof. FIG. As in C, the negative electrodes of the varactor diodes 12-1 to 12-6 are connected to the parasitic elements A1 to A6 which are linear conductors. The positive electrodes of the varactor diodes 12-1 to 12-6 are grounded. By adjusting the potential applied from the adaptive controller C to the negative electrodes of the varactor diodes 12-1 to 12-6 via the resistors 14-1 to 14-6, the varactor diodes 12-1 to 12-6 are made variable reactances. It can act as an element. The connection points between the adaptive controller C and the resistors 14-1 to 14-6 are connected to capacitors 15-1 to 15-6 whose other ends are grounded. By changing the potential applied from the adaptive controller C to the negative electrodes of the varactor diodes 12-1 to 12-6 via the resistors 14-1 to 14-6, the varactor diodes 12-1 to 12-6 are changed. It can act as a variable reactance element.

  An adaptive array antenna configured using a plurality of such simple directivity control antenna elements is reported in Japanese Patent Application Laid-Open No. 2004-066473. In order to form a beam pattern for each area on a straight road as shown in FIG. 1, the ESPAR antenna 10 in FIG. 5 does not use, for example, all six parasitic elements A1 to A6. Obviously, only the feed elements A1 and A4 need be used with the feed element A0. The plane formed by these parasitic elements A1 and A4 and the feeder element A0 (the paper surface in FIG. 5.B) may be parallel to the road direction in which it is arranged.

1 is a schematic diagram illustrating an example of a configuration of a road-to-vehicle communication system according to a first embodiment. The top view and side view of an antenna used for Example 1. FIG. The broad-side direction beam pattern (a) and endfire direction beam pattern (b) of the antenna of FIG. The figure which shows an example of the road-vehicle communication system infrastructure adjustment method of Example 2. Explanatory drawing of the conventional variable reactance element loading directivity control antenna.

Explanation of symbols

AN1: Directional variable antenna device used for roadside communication device Pa1, Pa2: Antenna pattern to be switched Data1, Data2: Data transmitted by antenna pattern Pa1, Pa2 A11: Metal loop wiring including feeding point P11a, P11b: Parasitic metal loop wiring F0: Feed points x1 to x5: Variable reactance elements ANa1, ANa2: Antennas connected to installed roadside communication devices Ar1, Ar2: Areas communicable corresponding to ANa1, ANa2 ANp1: Connected to additional roadside communication devices Antenna Ar3: Communication area corresponding to ANp1

Claims (6)

In a road-to-vehicle communication device fixedly installed to communicate with a communication device mounted on a vehicle traveling on a road,
An antenna installed at a predetermined height above the road,
A road-to-vehicle communication device having a variable directivity antenna capable of forming a beam pattern corresponding to a plurality of road regions in different distance ranges. The road-to-vehicle communication apparatus according to claim 1, wherein communication is periodically and sequentially established in a plurality of road areas in the different distance ranges. The road area is continuously adjustable for the distance range,
The road-to-vehicle communication device according to claim 1, wherein the adjustment is made possible in order to apply to a road range between two communication areas by two previously installed communication devices. The directivity variable antenna is
One feeding element, a plurality of parasitic elements provided at a predetermined interval from the feeding element, and a plurality of variable reactance elements loaded on the parasitic element,
The road-to-vehicle communication device according to any one of claims 1 to 3, wherein directivity can be controlled by changing a reactance value of the variable reactance element. The directivity variable antenna is
One main loop wiring arranged on one reference plane with a power feeding unit composed of two sets of two feeding points, and a feeding point arranged parallel or on the same plane as the main loop wiring An antenna element having at least one secondary loop wiring not provided,
Each of the loop wirings has no intersection and no contact with each other,
The center point of the plane area surrounded by the secondary loop wiring is located on one vertical section perpendicular to the reference plane, passing through the center point of the plane area surrounded by the main loop wiring.
A planar region surrounded by any one of the loop wirings, when viewed from the normal direction of the reference plane, partially overlaps with another planar region surrounded by the other adjacent loop wirings,
The slave loop wiring has variable reactance elements at two locations on the vertical section,
The main loop wiring has a variable reactance element at one location on the vertical cross section, and has the power feeding unit at another location on the vertical cross section,
Half of the main loop wiring centering on the feeding point is regarded as the feeding element, the main loop wiring centering on the variable reactance element and the secondary loop wiring are regarded as the plurality of parasitic elements,
4. The road-to-vehicle communication device according to claim 1, wherein directivity is changed by changing reactance values of the plurality of variable reactance elements. 5. In a road-to-vehicle communication method using a communication device mounted on a vehicle traveling on a road and a communication device fixedly installed,
Connect a directional variable antenna to the fixedly installed communication device,
Installing the directivity variable antenna at a predetermined height above the road;
A beam pattern can be formed corresponding to multiple road areas of different distance ranges.
A road-to-vehicle communication method characterized in that communication is established by sequentially switching to a plurality of road regions in different distance ranges.