JP2012235334A - Roadside communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a road-to-vehicle communication system capable of suppressing interference between identical slots while ensuring a required communication area.SOLUTION: A roadside communication apparatus, transmitting information to a vehicle with a predetermined time slot, includes: service area storage means that stores a service area of the roadside communication apparatus; transmission means that transmits information to a vehicle; reception means that receives position information of the vehicle and communication quality of communication with the roadside communication apparatus from the vehicle; and communication control means that identifies a vehicle existing around a service area edge of the roadside communication apparatus from the position information of the received vehicle, narrows the communication area of the transmission means if the communication quality of the vehicle is higher than a threshold, or widens the communication area of the transmission means when the communication quality of the vehicle is lower than the threshold.

Description

  The present invention relates to communication area control in road-to-vehicle communication.

In recent years, as part of Intelligent Transport System (ITS),
Development of a driving support system that transmits driving support information to a vehicle using road-to-vehicle communication is underway. In road-to-vehicle communication, it is assumed that a time slot is assigned to each roadside device and broadcast communication is performed in a time division manner using the same frequency band. In the ITS driving support system in which the use of a plurality of time slots is being considered, when the time occupation ratio of road-to-vehicle communication is arbitrarily defined, for example, a slot configuration as shown in FIG. 2 can be considered.

  Here, there may be a situation in which communication cannot be secured because radio waves do not reach the service area of the roadside machine due to the arrangement of the roadside machine and the influence of the environment such as terrain. On the other hand, when radio waves from the roadside device fly too much, it is possible that communication cannot be performed successfully due to interference between the same slots. Therefore, it is necessary to transmit information to the entire service area of the roadside machine and to suppress unnecessary radio wave transmission.

JP 2007-110633 A JP-A-11-266194

  An object of the present invention is to reduce interference between the same slots while securing a necessary communication area in a road-to-vehicle communication system.

  To achieve the above object, a roadside communication device according to the present invention is a roadside communication device that transmits information to a vehicle in a predetermined time slot, and stores a service area of the roadside communication device. From the storage means, the transmission means for transmitting information to the vehicle, the reception means for receiving the position information of the vehicle and the communication quality of communication with the roadside communication device from the vehicle, and the received position information of the vehicle The vehicle existing near the service area edge of the roadside communication device is identified, and if the communication quality of the vehicle is higher than a threshold, the communication area of the transmission means is narrowed, and if the communication quality of the vehicle is lower than the threshold, the Communication control means for expanding the communication area of the transmission means.

  Here, the communication area may be controlled by controlling the transmission power. If the antenna is a directional antenna that can change the tilt angle of the transmission beam, the width of the communication area may be controlled by controlling the beam tilt angle.

  As described above, the communication area is specified based on the position information obtained from the vehicle, so that the vehicle existing near the end of the service area is identified and the vehicle becomes the end of the communication area based on the communication quality information obtained from the vehicle. By controlling the range, it is possible to prevent radio waves from flying unnecessarily far while securing a service area.

Further, in the present invention, a time slot different from that of the adjacent roadside communication device is assigned, and the same information as the information transmitted by the adjacent roadside communication device is transmitted in the time slot assigned to the adjacent roadside communication device. It is also preferable to transmit by the transmission means.

  In this way, for example, even when the radio wave does not reach the entire service area from the roadside communication device due to environmental influences such as terrain and large vehicles, the vehicle can acquire information from the adjacent roadside communication device. it can.

  In addition, although the roadside communication apparatus may always transmit information on the adjacent roadside communication apparatus (intersection), sending unnecessary radio waves may cause inconvenience and cause inconvenience. Therefore, it is preferable to transmit information to be transmitted by the adjacent roadside communication device only when it is necessary to support the adjacent roadside communication device. This situation determination may be performed by the roadside communication device to be supported, or the supported side may determine and notify the adjacent roadside communication device to that effect.

  When the roadside communication device to be supported makes a determination, the roadside communication device preferably adopts the following configuration. That is, the service area storage unit also stores a service area of the adjacent roadside communication device, and the reception unit receives the position information of the vehicle and the communication quality with the adjacent roadside communication device from the vehicle. The communication control means, when the vehicle is located within a service area of the adjacent roadside communication device and communication quality with the adjacent roadside communication device is lower than a predetermined value, the transmission means In the time slot assigned to the roadside communication device to be transmitted, the same information as the information transmitted by the adjacent roadside communication device is transmitted by the transmission means.

  Moreover, when the side to be supported judges, it is preferable that the roadside communication apparatus adopts the following configuration. That is, when the communication quality of the vehicle does not exceed the threshold value even when the communication control means performs control to expand the communication area, the communication control means further has an adjacent roadside unit cooperation means for notifying the adjacent roadside communication device to that effect. When the communication control means receives the notification from the adjacent roadside communication device by the adjacent roadside device cooperation means, the adjacent roadside device transmits in the time slot assigned to the adjacent roadside communication device. The same information as the information to be transmitted is transmitted by the transmission means.

  Thus, unnecessary interference can be prevented by transmitting the same information as the information transmitted by the adjacent road side communication device only when it is necessary to support the adjacent road side communication device.

  The present invention can be understood as a roadside communication device including at least a part of the above means. Further, the present invention can also be understood as a road-to-vehicle communication method for performing the above-described processing, and a program for realizing these methods. It can also be understood as a road-to-vehicle communication system including the above means and processing. Each of the above means and processes can be combined with each other as much as possible to constitute the present invention.

  According to the present invention, it is possible to reduce interference between the same slots while securing a necessary communication area in a road-to-vehicle communication system.

It is a figure which shows the functional block of the vehicle-mounted terminal and roadside machine concerning 1st Embodiment. It is a figure explaining arrangement | positioning of a roadside machine, and time slot allocation. It is a flowchart which shows the process of the communication area control which the roadside machine in 1st Embodiment performs. It is a figure for demonstrating the communication area control in 1st Embodiment. It is a figure for demonstrating the communication area control in 1st Embodiment. It is a figure explaining an adjacent roadside machine supporting information provision when a roadside machine cannot provide information with respect to the whole service area. It is a figure which shows the functional block of the roadside machine concerning 2nd Embodiment. It is a flowchart which shows the information provision assistance process with respect to the adjacent roadside machine which the roadside machine in 2nd Embodiment performs.

(First embodiment)
In the road-to-vehicle communication system according to the present embodiment, a roadside device (roadside communication device) is provided at an intersection, and transmits information for assisting driving to a vehicle located in a service area determined for each roadside device. Examples of the driving support information include information on signals, information on vehicles entering an intersection, obstacle information on roads, traffic jam tail information, and the like. In road-to-vehicle communication according to the present embodiment, the same information is given to all vehicles in the service area by broadcast communication. Of course, individual information may be given to each vehicle. The road-to-vehicle communication system uses a single frequency band of 700 MHz, and its service area is set to about several tens to several hundreds of meters. The use frequency band may be a 5.8 GHz band or the like.

  Moreover, in this embodiment, vehicles also exchange information using the same frequency band as road-to-vehicle communication. Since road-to-vehicle communication and vehicle-to-vehicle communication use the same frequency band, road-to-vehicle communication and vehicle-to-vehicle communication are used in a time-sharing manner. In road-to-vehicle communication, time slots are allocated to each roadside machine in a time-sharing manner in the road-to-vehicle priority area, and broadcast communication is performed from the roadside machine to the vehicle.

Roadside machines are placed at each intersection. FIG. 2 shows an arrangement image of roadside devices (base stations) and slot assignment when nine time slots are used. In this way, different time slots are assigned to adjacent roadside units. Here, the size of the service area may be determined for each intersection (roadside machine). The area of the service area should be within the range where radio waves reach from the roadside machine, but it is considered that radio waves do not reach the service area due to environmental effects such as obstacles. Further, in a situation where intersections (roadside units) are dense, it is conceivable that radio waves from the roadside units fly too much and cause interference between the same slots. In the example of FIG. 2, interference between the same slots can occur at the intersection A due to radio waves from the intersection J.

  FIG. 1 is a diagram showing functional blocks of an in-vehicle terminal (in-vehicle communication device) 10 and a roadside machine (roadside communication device) 20 in the present embodiment.

  The in-vehicle terminal 10 includes an antenna 11, a transmission unit 12, a reception unit 13, a communication quality acquisition unit 14, and a GPS device 15. The receiving unit 13 receives information transmitted from the roadside device 20 and other in-vehicle terminals. The communication quality acquisition unit 14 measures the carrier-to-noise ratio (CN ratio) of the received signal as the communication quality of road-to-vehicle communication and vehicle-to-vehicle communication. The GPS device 15 is a device that specifies the position information of the own vehicle by two-dimensional or three-dimensional coordinate data based on information received from GPS satellites. In response to reception from the roadside device, the transmission unit 12 transmits the in-vehicle terminal ID, the position information, and the CN ratio of the received signal from the roadside device.

  The roadside machine 20 includes an antenna 21, a transmission unit 22, a reception unit 23, a communication control unit 24, and a service area storage unit 25. The antenna 21 may be an omnidirectional antenna or a directional antenna as long as it can transmit radio waves to the service area. Note that when a directional antenna is used, it is preferable to use an antenna capable of adjusting the beam tilt angle.

  The transmission unit 22 acquires information to be notified to the vehicle from a data processing unit (not shown), performs modulation processing, and transmits the information. The transmission timing is performed in a time slot assigned to the roadside device 20.

  The receiving unit 23 acquires information transmitted from the vehicle, performs demodulation processing and the like, and acquires position information included in the received information and communication quality between road vehicles. The acquired position information and communication quality are sent to the communication control unit 24.

  The communication control unit 24 specifies a transmission parameter to be given to the transmission unit 22 and controls an area (communication area) where a radio wave transmitted from the roadside device 20 reaches. In order to adjust the width of the communication area, the power of the transmission radio wave may be adjusted, the beam tilt angle of the transmission radio wave may be adjusted, or both of them may be adjusted. Hereinafter, the processing content when the communication control part 24 adjusts a communication area is demonstrated. The communication control unit 24 compares the vehicle position information obtained from the receiving unit 24 with the service area of the roadside machine 20 stored in the service area storage unit 24, and identifies the vehicle located at the end of the service area. To do. There are various methods for determining the position in the service area as the service area edge. For example, an area within a predetermined distance from the boundary of the stored service area can be considered as the service area edge. Then, referring to the communication quality (CN ratio) sent from the vehicle determined to be located at the end of the service area, the transmission power is reduced or the beam tilt angle is increased if the communication quality is higher than the communicable CN ratio threshold. Thus, the communication area is narrowed, and if it is lower than the threshold, the communication area is widened by increasing the transmission power or decreasing the beam tilt angle. This adjustment is performed until the transmission power and the beam tilt angle are stabilized. Further, even after stabilization, adjustment is performed at a predetermined interval.

  FIG. 3 is a flowchart showing a communication area control process performed by the roadside machine according to the present embodiment. FIG. 4 shows the roadside machine 20 and its service area 31. Hereinafter, an operation example of communication area control performed by the roadside machine will be described with reference to FIGS. 3 and 4.

  The roadside device 20 transmits information in the assigned time slot, and the vehicles a to d that have acquired the information from the roadside device 20 transmit information including position information and communication quality (CN ratio) to the roadside device 20. doing. The roadside device 20 receives position information and communication quality included in information transmitted from the vehicle in the service area 31 (S102). And the vehicle located in the edge part of the service area 31 is specified based on the positional information received from the vehicle (S104). In the example of FIG. 4, it is assumed that the roadside device 20 uses an omnidirectional antenna, so the service area 31 extends on both sides of the roadside device 20. Accordingly, the area 32 and the area 33 correspond to the service area edge. For example, the area 32 and the area 33 can be stored in the service area storage unit 25. In the situation shown in FIG. 4, the vehicle a located in the region 32 and the vehicle d located in the region 33 are specified as vehicles located at the end of the service area.

  Next, for the vehicle located at the end of the service area, the CN ratio measured value (Rdb) transmitted by the vehicle is compared with the communicable CN ratio threshold (Xdb) (S106). When the CN ratio measured value Rdb is equal to the threshold value Xdb (X−R = 0), the communication area is not changed. When the CN ratio measured value Rdb is smaller than the threshold value Xdb (X−R> 0), the communication area is widened by increasing the transmission power (S108). When the CN ratio measured value Rdb is larger than the threshold value Xdb (X−R <0), the communication area is narrowed by reducing the transmission power (S110). Here, in the comparison between the CN ratio measured value and the threshold value, if the difference between the two is within a predetermined range, it may be determined that they match.

It is determined whether or not the transmission power is stable, that is, whether or not the reception power has changed within the most recent predetermined period (S112). If the transmission power is not stable, the process returns to step S102 to continue the adjustment of the communication area. On the other hand, if the transmission power is stable, the process ends. In the example of FIG. 4, the transmission power is controlled so that the communication quality of the vehicles a and d located at the end of the service area is about the communicable CN ratio. In this way, information can be transmitted throughout the service area 31 and unnecessary radio waves can be prevented from reaching the outside of the service area 31 and causing interference.

  4 shows an example in which the roadside unit 20 uses an omnidirectional antenna. However, as shown in FIG. 5, the roadside unit 20 uses a directional antenna, and its service area 34 is one side of the roadside unit 20. It can be considered that it exists only on the side. In this case, the end of the service area 34 is the portion farthest from the roadside machine 20 as shown as a region 35 in the figure. The communication area range is controlled so that the CN ratio of the vehicle located at the end of this service area of the roadside machine 20 becomes the threshold value Xdb. Here, since the directional antenna is used, the communication area range can be controlled not only by changing the transmission output but also by changing the tilt angle of the transmission beam.

  According to the present embodiment, it is possible to provide information to the entire service area defined for the roadside device, and to suppress unnecessary radio waves from reaching the outside of the service area and causing interference between the same slots.

(Second Embodiment)
In the present embodiment, a situation in which radio waves transmitted from roadside devices do not reach the entire service area due to environmental influences such as topography is dealt with. Radio waves transmitted from roadside devices are designed to reach the entire service area, but depending on environmental changes, radio waves may not arrive as designed. In this embodiment, an adjacent roadside machine assists in providing information in such a situation.

  Specifically, in the roadside unit arrangement and slot allocation as shown in FIG. 2, the roadside unit located at the intersection A transmits safe driving information regarding the intersection A at the timing of the slot 1, and the roadside unit located at the intersection B is The safe driving information regarding the intersection B is transmitted at the timing of the slot 2. Here, as shown in FIG. 6, a situation is considered in which the roadside device 61 at the intersection A cannot distribute information to the entire service area 63. At this time, the roadside unit 62 at the intersection B transmits the same safe driving information as the intersection A at the timing of the slot 1 to secure the service area of the intersection A. Each roadside unit may always transmit traffic safety information about adjacent intersections at the slot timing of the adjacent roadside unit. However, to prevent interference due to unnecessary radio wave transmission, one roadside unit can use the entire service area. Only when the roadside cannot be covered, the adjacent roadside machine supports.

  FIG. 7 is a diagram showing a functional configuration of the roadside machine according to the present embodiment. Compared to the first embodiment (FIG. 1), an adjacent roadside machine cooperation unit 26 is provided. The adjacent roadside machine cooperation unit 26 is a functional part for exchanging various information with the adjacent roadside machine. For example, information such as whether information can be provided to the entire service area with the adjacent roadside machine, Exchange safe driving information to be transmitted.

  In the present embodiment, the service area storage unit 25 stores not only its own service area but also the service area of an adjacent roadside machine (intersection).

  Further, the communication control unit 24 includes the same function (FIG. 3) as that of the first embodiment, but further includes the following function in the present embodiment. That is, a function for determining whether an adjacent roadside machine can provide information for the entire service area, and a function for transmitting safe driving information of an adjacent intersection at the slot timing of the adjacent roadside machine when information is not provided including.

The antenna 21 is preferably a directional antenna in order to limit the reach of the transmission radio wave. For example, a plurality of antennas having different directivities may be provided and the antenna to be used may be switched.

  Here, in FIG. 6, a method for determining whether the roadside device 62 at the intersection B needs to support the roadside device 61 at the intersection A, in other words, whether the roadside device 61 can transmit information to the entire service area 63. There are two possible ways. One is a method in which an adjacent roadside device 62 makes a determination, and the other is a method in which a roadside device 61 that provides information makes a determination.

  FIG. 8 is a flowchart showing the process of determining whether the roadside machine on the side supporting the entire service area of the adjacent roadside machine is covered. Therefore, the example of FIG. 6 shows processing performed by the roadside device 62. The flowchart of FIG. 8 will be described below with reference to FIG. The roadside device 62 intercepts information transmitted from the vehicle to the roadside device 61 (S202). This information includes the vehicle position information and the CN ratio of the received radio wave from the roadside unit 61. Therefore, if the CN ratio of the received radio wave from the roadside device 61 is low even though the vehicle is located in the service area 63, it can be determined that the vehicle has not received the safe driving support information from the roadside device 61. (S204). When determining in this way, the roadside device 62 transmits the safe driving information transmitted by the roadside device 61 at the timing of the time slot assigned to the roadside device 61 (S206).

  Next, a description will be given of a process for determining whether or not the roadside device 61 itself providing information reaches the entire service area 63. The roadside device 61 controls the communication area according to the flowchart of FIG. 3 as in the first embodiment. Here, when the communication quality of the vehicle existing in the service area 63 is low, control is performed to increase the communication area by increasing the transmission power or reducing the beam tilt angle (S108). If the communication quality does not exceed the threshold even if the transmission power is increased or the beam tilt angle is decreased within the allowable range, the roadside device can determine that the radio wave has not reached the vehicle in the service area. In addition, it can be determined which area the radio wave does not reach. In such a case, a request is made to transmit radio waves to an area where radio waves do not reach the adjacent roadside machine via the adjacent roadside machine cooperation unit 26.

  When the roadside device supports the service area of the adjacent roadside device, the communication area is controlled so that the transmission radio wave does not fly to an unnecessary range by any of the above methods. For example, it is desired to transmit with a transmission power that can be received at a minimum by a vehicle located in the area to be supported in the service area of the adjacent roadside machine. Further, the roadside device need only transmit radio waves in the direction in which the roadside device to be supported is located. When a plurality of antennas having different directivities are used, it is only necessary to transmit from an antenna having directivity with respect to the adjacent roadside direction.

  According to the present embodiment, even when a single roadside device cannot provide information to the entire service area due to environmental changes or the like, the adjacent roadside device supports the provision of information to the entire service area. Information can be provided. In addition, it is possible to suppress unnecessary transmission of radio waves by determining whether information can be provided to the entire service area and providing support only when the information is not provided. Furthermore, even when providing information support, radio wave interference can be suppressed by limiting the communication area to the area to be supported.

DESCRIPTION OF SYMBOLS 10 In-vehicle terminal 20 Roadside machine 21 Antenna 22 Transmission part 23 Reception part 24 Communication control part 25 Service area memory | storage part 26 Adjacent roadside machine cooperation part 31, 34 Service area 32, 33, 35 Service area edge part

Claims (7)

A roadside communication device that transmits information to a vehicle at a predetermined time slot,
Service area storage means for storing the service area of the roadside communication device;
Transmitting means for transmitting information to the vehicle;
Receiving means for receiving from the vehicle position information of the vehicle and communication quality of communication with the roadside communication device;
A vehicle existing near the service area end of the roadside communication device is identified from the received vehicle position information, and if the communication quality of the vehicle is higher than a threshold, the communication area of the transmission means is narrowed, and the communication quality of the vehicle Communication control means for expanding the communication area of the transmission means if is lower than the threshold;
A roadside communication device. The communication control unit controls a communication area by controlling transmission power from the transmission unit;
The roadside communication apparatus according to claim 1. The transmitting means has a directional antenna capable of changing the beam tilt angle,
The communication control means controls a communication area by controlling a beam tilt angle of the directional antenna;
The roadside communication apparatus according to claim 1 or 2. The communication control means stops control of the communication area when the communication quality of the vehicle existing near the service area end of the roadside communication device is stable, and resumes control of the communication area after a predetermined period of time.
The roadside communication apparatus according to any one of claims 1 to 3. A different time slot from the adjacent roadside communication device is assigned,
In the time slot allocated to the adjacent roadside communication device, the same information as the information transmitted by the adjacent roadside communication device is transmitted by the transmission means.
The roadside communication apparatus in any one of Claims 1-4. The service area storage means also stores a service area of the adjacent roadside communication device,
The receiving means receives from the vehicle the position information of the vehicle and the communication quality with the adjacent roadside communication device,
When the vehicle is located in a service area of the adjacent roadside communication device and the communication quality with the adjacent roadside communication device is lower than a predetermined value, the communication control unit is In the time slot assigned to the roadside communication device, the same information as the information transmitted by the adjacent roadside communication device is transmitted by the transmission means.
The roadside communication device according to claim 5. If the communication quality of the vehicle does not exceed the threshold even if the communication control means expands the communication area, it further has an adjacent roadside machine cooperation means for notifying the adjacent roadside communication device to that effect,
When the communication control unit receives the notification from the adjacent roadside communication device by the adjacent roadside device cooperation unit, the adjacent roadside communication device transmits in a time slot assigned to the adjacent roadside communication device. Transmitting the same information as the information by the transmitting means;
The roadside communication device according to claim 5.

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