JP2011071630A - Interference avoidance device and mobile communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interference avoidance device capable of avoiding interference of a transmission signal from a roadside communication device on the occurrence of the interference. <P>SOLUTION: The interference avoidance device 10 causes a transmission signal from a first roadside communication device 2 to avoid interference with a transmission signal from a second roadside communication device when an on-board communication device 3 receives the transmission signal from the first roadside communication device 2. The interference avoidance device includes an interference decision unit 13 for determining the presence of interference and a characteristic changing unit 14 for changing distance-level characteristics being propagation distance characteristics of a transmission signal level from the roadside communication device 2, on the basis of the decision results of the interference decision unit 13. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an interference avoidance device and a mobile communication device used in, for example, an intelligent transport system (ITS).

In recent years, for the purpose of promoting traffic safety and preventing traffic accidents, terminals have received information from infrastructure devices installed on the road, and this information has been used to improve the safety of advanced road traffic systems. (For example, refer patent document 1).
Such an intelligent road traffic system is mainly composed of a plurality of roadside communication devices which are wireless communication devices on the infrastructure side and a plurality of in-vehicle communication devices which are wireless communication devices mounted on each vehicle.

  In this case, a combination of communication performed between communication subjects includes road-to-road communication between road-side communication devices, road-to-vehicle (or vehicle-road) communication between road-side communication devices and vehicle-mounted communication devices, and vehicle-mounted communication. Vehicle-to-vehicle communication performed between aircraft.

Japanese Patent No. 2806801

  In the above-mentioned intelligent road traffic system, what kind of communication control is to be carried out by effectively using the band in coexistence of each communication including road-to-road communication, road-to-vehicle communication and vehicle-to-vehicle communication? It becomes important. In view of this, it has been studied that multiple access is used to perform communication between roads, road vehicles, and vehicles within a limited frequency band.

For example, an autonomous random access method represented by CSMA (Carrier Sense Multiple Access) is adopted as a multi-access method for inter-vehicle communication in which communication with only a small number of in-vehicle communication devices is assumed in mountainous areas. Is preferred.
On the other hand, road-to-road communication, road-to-vehicle communication, and vehicle-to-vehicle communication coexist in an area where roadside communication devices exist. In this case, since the priority of the information handled by the roadside communicator that is the infrastructure side is generally high, a mechanism that gives priority to road-to-vehicle communication and road-to-road communication over vehicle-to-vehicle communication is required. .

Therefore, in order to preferentially transmit information of the roadside communication device, time division multiplexing (TDMA: Time Division) in which the frequency used for communication is time-divided at regular intervals and a time slot dedicated to transmission of the roadside communication device is provided. Multiple access by Multiple Access is enabled.
Therefore, for example, assuming a communication system composed of a plurality of roadside communication device groups installed at each intersection, a time slot transmitted by each roadside communication device is assigned by the TDMA method, and the remaining time slot is assigned to a vehicle by the CSMA method. It is considered to be a rational communication system to be used for inter-vehicle communication.

  Further, when road-to-vehicle communication is performed by a plurality of roadside communication devices in the same time slot assigned by the TDMA system as described above, roadside communication is performed so that transmission signals transmitted from the roadside communication devices do not interfere with each other. The communication area of each machine is set. This is because if there is an area where transmission signals from a plurality of roadside communication devices interfere with each other, a mobile communication device existing in the area can accurately receive a signal from the roadside communication device. This is because communication is not established.

In this way, the communication area of the roadside communicator is initially set so that the transmission signals do not interfere with each other, but the surrounding communication environment changes due to, for example, increase or decrease of buildings, etc. while the system operation is continued. In this case, the transmission signal from the roadside communication device may reach a wide range unexpectedly, and may interfere with transmission signals from other roadside communication devices.
Therefore, the present invention provides an interference avoidance device capable of avoiding interference when there is interference of a transmission signal from a roadside communication device, and mobile communication preferable for causing the interference avoidance device to function. The purpose is to provide a machine.

  (1) In order to achieve the above object, the present invention provides a transmission signal from the first roadside communication device and a transmission signal from the second roadside communication device when the mobile communication device receives the transmission signal from the first roadside communication device. An interference avoidance device that avoids interference, an interference determination unit that determines presence or absence of interference, and a propagation distance characteristic of a transmission signal level from the roadside communication device based on a determination result by the interference determination unit And a characteristic changing unit that changes the distance-level characteristic.

According to the present invention, when the interference determination unit determines the presence or absence of interference between the transmission signals from the first and second roadside communication devices, the characteristic changing unit is configured to determine whether the roadside communication device is based on the determination result. The distance-level characteristic which is the propagation distance characteristic of the transmission signal level from is changed. The change of the distance-level characteristic can be, for example, one or both of the first and second roadside communication devices.
That is, if it is determined that there is interference, the distance-level characteristic is reduced by the characteristic changing unit so that the reception level of the transmission signal from the roadside communication apparatus received by the mobile communication apparatus at a certain position is lowered. The reception level of the transmission signal from the roadside communication device in the mobile communication device can be lowered, and the generated interference can be avoided.

  (2) Since the environment for wireless transmission from a mobile communication device present at a certain position to a roadside communication device is equivalent to the environment for wireless transmission from the roadside communication device to the mobile communication device, the interference The determination unit may be configured to estimate the distance-level characteristic based on a position of the mobile communication device and a reception level at the roadside communication device of a transmission signal transmitted from the mobile communication device at the position. In this case, the interference determination unit may be configured to determine the presence or absence of the interference based on the estimated distance-level characteristic.

(3) Further, in this configuration, when the transmission level (transmission output) of the signal from the mobile communication device is variable, even if the mobile communication device exists at a certain position, the transmission signal of the mobile communication device The reception level in the roadside communication device is indefinite. In this case, the interference determination unit may be configured to further estimate the distance-level characteristic based on transmission level information of a transmission signal transmitted from the mobile communication device.
Thereby, the interference determination unit can estimate the distance-level characteristic by acquiring the transmission level information of the mobile communication device.

(4) As another means for determining the presence or absence of the interference, the interference determination unit determines the distance-level characteristics based on the position of the mobile communication device and the roadside communication received by the mobile communication device at the position. It is possible to adopt a configuration in which the estimation is based on the reception level of the transmission signal from the machine and the presence / absence of the interference is determined based on the estimated distance-level characteristic.
In this case, since the distance-level characteristic is estimated based on the reception level of the transmission signal from the roadside communication device received by the mobile communication device, and the presence or absence of interference is determined, whether interference occurs at the position of the mobile communication device. A configuration for directly determining whether or not is obtained.

(5) As another means for determining the presence or absence of the interference, the interference determination unit receives the transmission signal from the roadside communication device received by the mobile communication device at the position and the position of the mobile communication device. It can be set as the structure which determines the presence or absence of the said interference based on the information with an error generation rate.
In this case, if there is interference between the transmission signals from the roadside communication devices, the reception error occurrence rate becomes high in the mobile communication device existing in the interference area. Based on the position information of the machine, it can be determined whether or not interference occurs at the position.

(6) As another means for determining the presence or absence of the interference, the interference determination unit transmits a plurality of second roadside communication devices in the vicinity of the first roadside communication device, with transmission times overlapping. The presence or absence of the interference can be determined based on the reception error occurrence rate of the signal received by the first roadside communication device.
When the first roadside communication device receives transmission signals from a plurality of second roadside communication devices and the transmission signals interfere with each other, the first roadside communication device has a high reception error rate. Therefore, according to the above configuration, it is possible to determine whether or not interference occurs at the position of the first roadside communication device and the position in the vicinity thereof.

(7) Further, in the interference avoidance device, the characteristic changing unit may use the first and second characteristics based on a threshold of the distance-level characteristic that can secure a minimum communication service area that should maintain necessary communication performance. It is preferable to have a function of preferentially selecting a side having a margin in the roadside communication device and reducing the distance-level characteristic.
In this case, even when interference occurs and the distance-level characteristic of the roadside communication device is deteriorated, it is possible to secure the minimum communication service area.

(8) In the interference avoidance device, the roadside communication device includes an output adjustment unit that adjusts a signal transmission output, and the characteristic changing unit is determined to have interference by the interference determination unit. Preferably, the request signal for reducing the transmission output from the roadside communication device by the output adjusting unit is generated.
In this case, when the interference determination unit determines that there is interference, the characteristic changing unit generates a request signal, and when the request signal is given to the output adjustment unit of the roadside communication device, the output adjustment unit reduces the transmission output. Therefore, it is possible to reduce the distance-level characteristic in the roadside communication device.

(9) Further, the present invention is a mobile communication device that is capable of wireless communication with a roadside communication device, and obtains its position and a reception level of a transmission signal received from the roadside communication device received at the position. And a communication unit capable of wirelessly transmitting the information to give the information acquired by the acquisition unit to the interference determination unit of the interference avoidance apparatus.
According to the present invention, the communication unit wirelessly transmits the information on the own position acquired by the acquisition unit and the information on the reception levels of the transmission signals from the first and second roadside communication devices received at the position. By providing the interference determination unit of the interference avoidance device, the interference determination unit can determine the distance-level characteristics of the first and second roadside communication devices by using the position of the mobile communication device (the own communication device). Position) and the reception level of the transmission signal from the first and second roadside communication devices received by the mobile communication device at the position, and the estimated distance between the first and second roadside communication devices − The presence or absence of the interference can be determined based on the level characteristic.

According to the interference avoidance device of the present invention, when interference of a transmission signal from a roadside communication device occurs, transmission from the roadside communication device is reduced by reducing the distance-level characteristic of the roadside communication device. The reception level of the signal in the mobile communication device can be lowered, and the interference that has occurred can be avoided.
Further, according to the mobile communication device of the present invention, it is possible to give the information on the own position and the information on the reception level of the transmission signal received from the roadside communication device received at the position to the interference determination unit of the interference avoidance device. It becomes possible and becomes a preferable configuration when the interference avoidance device functions as described above.

It is a schematic perspective view which shows the whole structure of an intelligent road traffic system (ITS). It is a road top view which shows a part of jurisdiction area of an intelligent road traffic system. It is a block diagram which shows the internal structure of a roadside communication apparatus and a vehicle-mounted communication apparatus. (A) is a schematic explanatory diagram illustrating the communication area between the parent device and the child device in plan view, and (b) is an arbitrary distance away from the parent device (child device). The graph which shows the relationship between a position and the reception level of the transmission signal from the main | base station (slave machine) in the said position is shown. It is a flowchart of the process by the determination method (1) of the presence or absence of interference, and a characteristic change part. It is a flowchart of the process by the determination method (2) of the presence or absence of interference, and a characteristic change part. It is a flowchart of the process by the determination method (3) of the presence or absence of interference, and a characteristic change part. It is a flowchart of the process by the determination method (4) of the presence or absence of interference, and a characteristic change part.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Overall system configuration]
FIG. 1 is a schematic perspective view showing an overall configuration of an intelligent road traffic system (ITS). FIG. 2 is a road plan view showing a part of the jurisdiction area of this intelligent road transportation system.
This intelligent road traffic system includes a traffic signal 1, a roadside communication device 2, an in-vehicle communication device 3 (see FIG. 2) as a mobile communication device, a central device 4, a vehicle 5 equipped with the in-vehicle communication device 3, and the like.
The traffic signal 1 and the roadside communication device 2 are installed at each of a plurality of intersections Ci (i = 1 to 12 in the figure), and are connected to the router 8 via a communication line 7 such as a telephone line. . This router 8 is connected to the central device 4 in the traffic control center.

  FIG. 3 is a block diagram showing an internal configuration of the roadside communication device 2 and the in-vehicle communication device 3. In the present embodiment, the roadside communication device 2 includes one parent device 2A and a plurality of child devices 2B. And the interference avoidance apparatus 10 which concerns on embodiment of this invention is installed in 2 A of main | base stations.

In FIG. 1, the central device 4 constitutes a LAN with the traffic signal 1 and the roadside communication device 2 of each intersection Ci included in the area under its control, and the central device 4 includes the traffic signal 1 and each roadside communication. Bidirectional communication with the machine 2 is possible. The central device 4 may be installed on the road instead of the traffic control center.
The central device 4 has a control unit including a workstation (WS), a personal computer (PC), and the like. This control unit collects, processes (calculates), records various information from the roadside communication device 2, The signal control of the traffic signal 1 and the control of information provision to the roadside communication device 2 are performed in an integrated manner.

[Wireless transmission method, etc.]
In FIG. 2, this intelligent road traffic system includes a plurality of roadside communication devices 2 capable of wireless communication with an in-vehicle communication device 3, and mobile wireless that performs wireless communication with other communication devices 2 and 3 using a carrier sense method. It is equipped with the vehicle-mounted communication device 3 which is a kind of transceiver. Each roadside communication device 2 (master device 2A, slave device 2B-1) has a communication area (a1, a2) that extends in a specific route, and the vehicle 5 that travels in its own communication area (a1, a2). Wireless communication with the in-vehicle communication device 3 is possible. Each roadside communication device 2 can also perform wireless communication (inter-road communication) with another roadside communication device 2 set at an adjacent intersection.

Each roadside communication device 2 is assigned a time slot for wireless transmission by itself by the master unit 2A in the TDMA system, and wireless transmission is not performed in a time zone other than this roadside time zone. A time zone other than the road time zone is opened as a transmission time by the CSMA method for the in-vehicle communication device 3.
Each roadside communication device 2 has a time synchronization function with other roadside communication devices 2 in order to control its own transmission timing. The time synchronization of the roadside communication device 2 is performed by, for example, GPS synchronization that adjusts its own clock to the GPS time, air synchronization that adjusts its own clock to a transmission signal from another roadside communication device 2, or the like.

[Roadside communication device]
In FIG. 3, the roadside communication device 2 includes one parent device 2A and a plurality of child devices 2B. However, in the following, these are not matters specific to the parent device 2A and the child devices 2B, but both When a matter common to the two is described, it is simply referred to as “roadside communication device 2”.
The roadside communication device 2 includes a wireless communication unit 21 having a transmission / reception circuit and the like connected to an antenna 20 for wireless communication, a wired communication unit 22 having a transmission / reception circuit and the like for bidirectional communication with the central device 4, and these communications A control unit 23 including a CPU that performs control and a storage unit 24 including a storage device such as a ROM and a RAM connected to the control unit 23 are provided. The storage unit 24 stores a computer program for communication control executed by the control unit 23, communication device IDs of the communication devices 2 and 3, and the like.

The control unit 23 of the roadside communication device 2 includes a data transfer unit 23A as a functional unit achieved by executing the computer program. Further, the control unit 23 of the parent device 2A includes a slot generation unit 23B. I have.
Further, the wireless communication unit 21 of the roadside communication device 2 includes an output adjustment unit 21B that adjusts the transmission output of the transmission signal. The output adjustment unit 21B can be a variable attenuator provided in the RF circuit of the wireless communication unit 21. The variable attenuator can be adjusted by a control signal from the control unit 23 to adjust the wireless transmission output. It becomes possible.

The slot generation unit 23B included in the control unit 23 of the parent device 2A not only transmits the transmission time of the own device but also the transmission times of a plurality of child devices 2B belonging to the management group managed by the own device. And has a function of generating the assigned information. The generated allocation information is notified to each slave unit 2B belonging to the management group, and the master unit 2A and each slave unit 2B broadcast the allocation information to its own communication area.
Master unit 2A and each slave unit 2B wirelessly transmit the allocation information and various types of information described later in the time slot for roadside communication unit 2 described in the allocation information generated by base unit 2A, and receive the allocation information The in-vehicle communication device 3 performs wireless transmission in a time zone other than the time slot described in the allocation information. The in-vehicle communication device 3 transmits various information such as position information described later in a time zone other than the time slot.

  The data transfer unit 23A included in the roadside communication device 2 temporarily stores the information from the central device 4 and other roadside communication devices 2 received by the wired communication unit 22 in the storage unit 24 to perform wireless communication. It can be transmitted to the in-vehicle communication device 3 via the unit 21. In addition, the data transfer unit 23A temporarily stores the information from the in-vehicle communication device 3 received by the wireless communication unit 21 in the storage unit 24, and the central device 4 and other roadside communication via the wired communication unit 22. It can also be transferred to the machine 2, and in the case of the parent machine 2A, it can also be transferred to the interference avoidance device 10.

[Interference avoidance device]
In the present embodiment, the interference avoidance device 10 is provided together with the master unit 2A.
As described above, a time slot is allocated for the roadside communication device 2 to perform wireless transmission, but a plurality of roadside communication devices 2 may transmit signals in the same time slot. For this reason, the communication areas are initially set so that the roadside communication devices 2 (for example, 2A and 2B-1) whose transmission timing is at least partially overlapped in time do not interfere with each other's transmission signals.

However, as shown in FIG. 2, a change in a building in which one or both of the communication area a1 of the parent device 2A and the communication area a2 of the child device 2B-1 are provided along the road, for example. In some cases, the initial setting is widened. In FIG. 2, the communication area a1 of the parent device 2A and the communication area a2 of the child device 2B-1 partially overlap, and the parent device 2A and the child device 2B-1 have overlapping signal transmission timings. Therefore, the area where the communication areas a1 and a2 overlap (the cross hatch portion existing at the intersection C2) is an interference area b where the transmission signal from the base unit 2A interferes with the transmission signal from the handset 2B. Become.
Therefore, the interference avoidance device 10 transmits the transmission signal from the parent device 2A (or the child device 2B-1) which is the first roadside communication device 2 to the in-vehicle communication device 3 (in-vehicle communication mounted on the vehicle 5A in FIG. 2). When the device 3-1) receives, the transmission signal avoids interference with the transmission signal transmitted from the child device 2B-1 (or the parent device 2A) as the second roadside communication device 2 (reduction) ).

A configuration of the interference avoidance device 10 for realizing this function will be described.
In the embodiment of FIG. 3, the interference avoidance device 10 has the wireless communication unit 21 and the wired communication unit 22 in common with the roadside communication device 2. Further, the interference avoidance device 10 includes a control unit 11 including a CPU that controls interference avoidance processing using the communication units 21 and 22, and a storage device such as a ROM and a RAM connected to the control unit 11. And a storage unit 12. The storage unit 12 stores a computer program for control executed by the control unit 11.
The control unit 11 of the interference avoidance device 10 includes an interference determination unit 13 and a characteristic change unit 14 as functional units achieved by executing the computer program. Note that each functional unit included in the interference avoidance device 10 will be described later.

[In-vehicle communication device]
In FIG. 3, an in-vehicle communication device 3 includes a communication unit 31 having a transmission / reception circuit connected to an antenna 30 for wireless communication, a control unit 32 including a processor for performing communication control on the communication unit 31, and the like. And a storage unit 33 including a storage device such as a ROM or a RAM connected to the control unit 32. The storage unit 33 stores a computer program for communication control executed by the control unit 32, communication device IDs of the communication devices 2 and 3, and the like.
The in-vehicle communication device 3 can wirelessly communicate with the roadside communication device 2 and other in-vehicle communication devices 3, and the communication unit 31 can execute wireless communication by the carrier sense method. For this reason, the communication unit 31 constantly senses the reception level of a predetermined carrier frequency, and does not perform wireless transmission when the value is equal to or higher than a certain threshold value, and performs wireless transmission only when the value is less than the threshold value. Is supposed to do.

In addition, the control part 32 of the vehicle-mounted communication apparatus 3 has the acquisition part 32a as a function part achieved by running the said computer program, and the vehicle 5 (vehicle-mounted communication apparatus 3) acquires the acquisition part 32a. It is possible to acquire various information such as its own position and speed, and it is possible to acquire various information received by the communication unit 31 from other in-vehicle communication devices 3 and roadside communication devices 2 by wireless communication. The control unit 32 can store the information acquired by the acquisition unit 32 a in the storage unit 24 and can wirelessly transmit the information to the outside via the communication unit 31.
In particular, the acquisition unit 32a can acquire the position of itself (the vehicle-mounted communication device 3) and the reception level of the transmission signal from the roadside communication device 2 received by the communication unit 31 at the position. And the communication part 31 can transmit the said information on radio in order to give the various information which the acquisition part 32a acquired to the interference determination part 13 of the interference avoidance apparatus 10 (via the roadside communication apparatus 2).

Among the information acquired by the vehicle 5 (the in-vehicle communication device 3), the position and direction of the self (the in-vehicle communication device 3) can be acquired by autonomous measurement by sensors on the vehicle 5 side such as GPS. Although it can be obtained from the infrastructure side such as an optical beacon. The speed of the vehicle 5 can be acquired based on a speed sensor provided in the vehicle 5.
For this reason, in the other vehicle 5 or the roadside communication device 2 that has received the vehicle information including the position, speed, and the like, for example, it is possible to perform safe driving support control for avoiding, for example, a right-hand collision or a head-on collision.

[Interference judgment unit of interference avoidance device]
The interference determination unit 13 included in the interference avoidance device 10 has a function of determining whether transmission signals wirelessly transmitted from the plurality of roadside communication devices 2 interfere with each other. That is, it has a function of determining the presence or absence of interference between a transmission signal wirelessly transmitted from the parent device 2A and a transmission signal wirelessly transmitted from the child device 2B-1.
FIG. 4A is a schematic explanatory diagram illustrating the communication area a1 of the parent device 2A and the communication area a2 of the child device 2B-1 in plan view, and FIG. 4B is a parent device. A graph K1 showing the relationship between an arbitrary position X separated by a certain distance from 2A and the reception level P of the transmission signal from the parent device 2A at the position X, and a certain distance from the child device 2B-1 The graph K2 which shows the relationship between the arbitrary position Y which left | separated and the reception level P of the transmission signal from the subunit | mobile_unit 2B-1 in the said position Y is shown.

<Method for determining presence / absence of interference (1)>
The outline of the determination method (1) of presence / absence of interference will be described. The interference determination unit 13 includes a “distance-level characteristic” included in the parent device 2A and a “distance” included in the child device 2B-1. “Level characteristic” is estimated, and the presence or absence of interference is determined based on the estimated “distance-level characteristic”.
The “distance-level characteristic” possessed by the master unit 2A (slave unit 2B-1) is a propagation distance characteristic of a transmission signal from the master unit 2A (slave unit 2B-1), and is transmitted and received. Represents the relationship between distance and signal level. Specifically, the base unit 2A (slave unit 2B-1) with respect to the position X (position Y) of the in-vehicle communication device 3 and the base device that can be received by the in-vehicle communication device 3 at the position X (position Y). This is a characteristic regarding the relationship with the reception level P of the transmission signal from 2A (slave unit 2B-1), and is expressed as the graph K1 (K2) in FIG. 4B.
As shown in the graph K1 (graph K2), the distance-level characteristic of the parent device 2A (slave device 2B-1) increases as the distance from the parent device 2A (slave device 2B-1) increases. The reception level P of the transmission signal from (child device 2B-1) has a characteristic of decreasing.

FIG. 5 is a flowchart of a process (1) for determining the presence / absence of interference by the interference determination unit 13 and a process by the characteristic changing unit 14. A method (1) for determining the presence or absence of interference will be described with reference to FIG.
The control unit 32 of the in-vehicle communication device 3 can include information on its own position at the time of transmission (hereinafter referred to as position information) in a signal to be wirelessly transmitted.
Therefore, each of the plurality of in-vehicle communication devices 3 wirelessly transmits a signal including position information (steps S11a and S11b). The wireless communication unit 21 of the parent device 2A and the child device 2B-1 receives a transmission signal transmitted from each of the in-vehicle communication devices 3, and is transmitted from the position information of each of the in-vehicle communication devices 3 and the position indicated by the position information. The information on the reception level of each transmission signal is acquired, and the data transfer unit 23A stores the information in the storage unit 24 (steps S12a and S12b). The reception level is a level value of a signal that can be correctly demodulated in the wireless communication unit 21.

  The information stored in the storage unit 24 of the base unit 2A is sent to the interference determination unit 13 of the interference avoidance device 10 by the data transfer unit 23A (step S13a). The information stored in the storage unit 24 of the slave unit 2B-1 is sent by the data transfer unit 23A to the interference determination unit 13 of the interference avoidance device 10 in the master unit 2A via the wired communication unit 22 (step S13b).

And the interference determination part 13 estimates the distance-level characteristic which each of the main | base station 2A and the subunit | mobile_unit 2B-1 has based on each said sent information. That is, the interference determination unit 13 includes the position X of each of the plurality of in-vehicle communication devices 3 wirelessly communicating with the parent device 2A and the parent device 2A (wireless communication unit) of the transmission signal transmitted by each of the in-vehicle communication devices 3 at each position X. Based on the reception level in 21), the distance-level characteristic possessed by base unit 2A is estimated (step S14).
Furthermore, the interference determination unit 13 includes a position Y of each of the plurality of in-vehicle communication devices 3 wirelessly communicating with the child device 2B-1, and a child device 2B-1 of a transmission signal transmitted by each of the in-vehicle communication devices 3 at each position Y. Based on the reception level in (wireless communication unit 21), the distance-level characteristic of slave unit 2B-1 is estimated (step S14).
The estimation process in step S14 includes the wireless transmission environment from the in-vehicle communication device 3 existing at a certain position to the parent device 2A (child device 2B-1) and the parent device 2A (child device 2B-1). This is possible because the environment for wireless transmission to the in-vehicle communication device 3 is the same.

  And the interference determination part 13 determines the presence or absence of interference based on the distance-level characteristic of the main | base station 2A estimated, and the distance-level characteristic of the subunit | mobile_unit 2B-1 (step S15). That is, the interference determination unit 13 can acquire information on the distance-level characteristics of the parent device 2A and the child device 2B-1 shown in the graphs K1 and K2 in FIG. An area in which the reception level of the transmission signal and the reception level of the transmission signal from the slave unit 2B-1 are both equal to or greater than the threshold value α1 and the difference (DU ratio) in the reception level is within the threshold value α2 (for example, 15 dB). In Z, it can be determined that interference occurs, and a region Z in which interference occurs can be determined as an interference area.

  Further, as described above, since the time slot for the roadside communication device 2 is allocated by the parent device 2A, the interference determination unit 13 provides information on the timing of signal transmission from each of the communication devices 2 and 3, It can be acquired from the master unit 2A. For this reason, when the interference determination part 13 estimates the presence or absence of interference based on the received signal from the vehicle-mounted communication apparatus 3, it is also possible to acquire the information of the time when interference has occurred.

[Characteristic change part of interference avoidance device]
And the said characteristic change part 14 with which the interference avoidance apparatus 10 is provided is based on the said determination result by the interference determination part 13, The said distance-level characteristic which the main | base station 2A and / or the subunit | mobile_unit 2B-1 have The process which changes is performed (step S16). Note that the distance-level characteristic can be changed in one or both of the parent device 2A and the child device 2B-1.

This change process will be described in detail. When the interference determination unit 13 determines that there is interference (in the case of “Yes” in step S15), one or both of the parent device 2A and the child device 2B-1 The distance-level characteristic of one or both of the signals is reduced by the characteristic changing unit 14 so that the reception level of the transmission signal transmitted from the mobile communication device 3 decreases (step S16).
In the case of FIG. 4B, only the distance-level characteristic of the child device 2B-1 is reduced as shown by the two-dot chain line graph K2. As a result, in the mobile communication device 3-1 existing at the position where the interference occurs in the region Z (interference area), the reception level of the transmission signal transmitted from the child device 2 </ b> B- 1 is lowered, which is generated. It is possible to avoid interference.

In addition, the vehicle-mounted communication device 3 may adjust the transmission level (transmission output) of a transmission signal by control by its control part 32 (refer FIG. 3) as needed. Thus, when the transmission level of the signal from the in-vehicle communication device 3 is variable, even if the in-vehicle communication device 3 exists at a fixed position, the reception levels in the parent device 2A and the child device 2B-1 are indefinite. Become.
Therefore, even in this case, the transmission signal of the in-vehicle communication device 3 includes the distance-level characteristics (step S14 in FIG. 5), Information on the transmission level of the transmission signal (hereinafter referred to as transmission level information) can also be included. The interference determination unit 13 can acquire the transmission level information together with the position information, and can further estimate the distance-level characteristic based on the transmission level information. That is, by comparing the reference transmission level information with the acquired reception level information, the relative reception level value and the reception level attenuation ratio can be obtained, and the distance-level characteristic can be estimated. It becomes possible.

  A specific process (step S16) executed by the characteristic changing unit 14 will be described. As described above, each of the parent device 2A and the child device 2B-1 includes the output adjustment unit 21B including a variable attenuator that adjusts the transmission output of the signal. Therefore, when the interference determination unit 13 determines that there is interference (in the case of “Yes” in step S15), the characteristic changing unit 14 is transmitted from one or both of the parent device 2A and the child device 2B-1. A request signal for reducing the transmission output of the signal is reduced by the variable attenuator. And this characteristic change part 14 transmits the produced | generated request signal to one or both of the control part 23 of the main | base station 2A, and the control part 23 of the subunit | mobile_unit 2B-1, and the control part which received this request signal 23 outputs a control signal to the variable attenuator to autonomously lower the transmission output.

It should be noted that the processing of steps until the transmission output is reduced is repeatedly executed until the level at which interference can be avoided is reached.
Further, the request signal generated by the characteristic changing unit 14 also includes an adjustment amount signal for the degree to which the transmission output is reduced (decrease amount), and the transmission output is gradually increased from the current transmission output with respect to a predetermined value. Can be lowered.

In the embodiment of FIG. 2, the master unit 2 and the slave unit 2 </ b> B- 1 are configured to have a communication area in a direction along the road by a directional antenna, and each of a plurality of roads extending from one intersection. A plurality of directional antennas are provided at one intersection so as to have a communication area. In FIG. 2, there are four roads and four directional antennas are provided at one intersection, but only two are shown for ease of explanation.
As described above, a plurality of directional antennas having different directivities are provided at one intersection, and the request signal generated by the characteristic changing unit 14 causes interference among the plurality of directional antennas. Information indicating that the signal output by the directional antenna of the route determined to be reduced is reduced.

  In addition, as a process for reducing the distance-level characteristics of one or both of the master unit 2A and the slave unit 2B-1, the directivity and beam width of the antenna 20 are changed so that the communication area is narrowed. Alternatively, the tilt angle of the antenna 20 may be lowered so that the communication area is narrowed. However, since the variable attenuator only has to be adjusted when the transmission output is reduced as in this embodiment, the processing is simpler than the case of changing the directivity, the beam width, or the tilt angle. .

Moreover, although the characteristic change part 14 demonstrated as the case where the distance-level characteristic which one or both of the main | base station 2A and the subunit | mobile_unit 2B-1 have had reduced in the said embodiment, distance-level characteristic was demonstrated. It is preferable that the roadside communication device 2 that lowers is selectively performed by a predetermined processing procedure.
That is, the characteristic changing unit 14 compares the current distance-level characteristic of the parent device 2A estimated in step S14 with the "threshold-level characteristic threshold value α3", and further, the child device 2B-1 estimated in step S14. The current distance-level characteristic is compared with the “distance-level characteristic threshold value α3”, and the distance-level characteristic is selected by preferentially selecting the side having a margin in the parent device 2A and the child device 2B-1. It has a function to lower. The “distance-level characteristic threshold α3” is a distance-level characteristic that can secure a minimum communication service area in which necessary communication performance should be maintained.

  That is, in FIG. 2, for example, when the distance-level characteristic of the slave unit 2B-1 is reduced, the communication area a2 of the slave unit 2B-1 becomes narrower, and the road-to-road communication with the adjacent slave unit 2B-2 And the characteristic changing unit 14 generates a request signal so as to reduce the distance-level characteristic of the base unit 2A, in a case where the necessary road-to-road communication performance may not be maintained. Transmit to base unit 2A. For this purpose, a condition that can ensure the performance of the road-to-road communication between the parent device 2A and the adjacent child device 2B-2 is necessary.

According to such a processing procedure, even when interference occurs between transmission signals and the distance-level characteristic of any roadside communication device 2 is reduced, the minimum communication service area is reduced. The roadside communication between the adjacent roadside communication devices 2 can be ensured.
In the above description, the case where only the distance-level characteristic of the parent device 2A is reduced by lowering the transmission output of the parent device 2A has been described. While reducing the level characteristic, the distance-level characteristic of the other (slave unit 2B-1) may also be reduced. That is, the required amount of decrease in distance-level characteristics may be distributed among the plurality of roadside communication devices 2.

<Method for determining presence / absence of interference (2)>
FIG. 6 is a flowchart of processing by the determination method (2) of presence / absence of interference and the characteristic changing unit 14. Also in this determination method (2), the interference determination unit 13 estimates the “distance-level characteristics” possessed by each of the plurality of roadside communication devices 2, and performs interference based on these estimated “distance-level characteristics”. Determine presence or absence.

That is, the master unit 2A and the slave unit 2B-1 transmit signals to the plurality of in-vehicle communication devices 3 existing at the respective positions in the communication areas a1 and a2 (step S21a, step S21b), and each in-vehicle communication. When the device 3 receives the signal, the vehicle-mounted communication device 3 acquires information on the reception level of the signal (Step S22a, Step S22). The reception level is a level value of a signal that can be correctly demodulated in the communication unit 31.
Then, each in-vehicle communication device 3 includes information on its own position when receiving the signal (hereinafter referred to as position information) together with the information on the reception level in the transmission signal, and the parent device 2A and the child device 2B. -1 (step S23a, step S23b).

When the wireless communication unit 21 of the parent device 2A and the child device 2B-1 receives a transmission signal transmitted from each of the in-vehicle communication devices 3, the in-vehicle communication device 3 is included in the position indicated by the position information included in the transmission signal. The received information on the reception level of the transmission signal from the roadside communication device 2 and the position information are acquired, and the data transfer unit 23A stores them in the storage unit 24 (steps S24a and S24b).
The information stored in the storage unit 24 of the base unit 2A is sent to the interference determination unit 13 of the interference avoidance device 10 by the data transfer unit 23A (step S25a). The information stored in the storage unit 24 of the slave unit 2B-1 is sent to the interference determination unit 13 of the interference avoidance device 10 in the master unit 2A via the wired communication unit 22 by the data transfer unit 23A (step S25b).

And the interference determination part 13 estimates the distance-level characteristic which each of the main | base station 2A and the subunit | mobile_unit 2B-1 has based on each said sent information.
That is, the interference determination unit 13 includes the position X of each of the plurality of in-vehicle communication devices 3 wirelessly communicating with the parent device 2A, and the reception level of the transmission signal from the parent device 2A received by each of the in-vehicle communication devices 3 at each position X. Based on the above, the distance-level characteristic of the base unit 2A is estimated (step S26).
Further, the interference determination unit 13 transmits the position Y of each of the plurality of in-vehicle communication devices 3 wirelessly communicating with the child device 2B-1 and the transmission from the child device 2B-1 received by each of the in-vehicle communication devices 3 at each position Y. Based on the reception level of the signal, the distance-level characteristic possessed by the slave unit 2B-1 is estimated (step S26).

  Then, the interference determination unit 13 determines the presence or absence of interference based on the estimated distance-level characteristic of the parent device 2A and the distance-level characteristic of the child device 2B-1 (step S27). That is, the interference determination unit 13 acquires information on the distance-level characteristics of the parent device 2A and the child device 2B-1 shown in the graphs K1 and K2 in FIG. 4B, similarly to the determination method (1). The reception level of the transmission signal from the parent device 2A and the reception level of the transmission signal from the child device 2B-1 are both equal to or greater than the threshold value α1, and the difference between the reception levels (DU ratio) is In the region Z within the threshold α2 (for example, 15 dB), it can be determined that interference occurs, and the region Z in which interference occurs can be determined as the interference area.

And the said characteristic change part 14 with which the interference avoidance apparatus 10 is provided is based on the said determination result by the interference determination part 13, The said distance-level characteristic which the main | base station 2A and / or the subunit | mobile_unit 2B-1 have The process which changes is performed (step S28). The processing by the characteristic changing unit 14 is the same as the determination method (1).
In the case of this determination method (2), the parent device 2A and the child device 2B-1 need a step for acquiring information on the reception level in the in-vehicle communication device 3, but the parent device received by the in-vehicle communication device 3 Since the distance-level characteristic is estimated based on the reception level of the transmission signal from 2A and the slave unit 2B-1, and the presence / absence of interference is determined, a configuration for directly determining the presence / absence of interference is obtained.

<Method for determining presence / absence of interference (3)>
FIG. 7 is a flowchart of processing by the determination method (3) of presence / absence of interference and the characteristic changing unit 14. This determination method (3) will be described.
As road-to-vehicle communication, the master unit 2A and the slave unit 2B-1 transmit signals to the plurality of in-vehicle communication devices 3 existing at the respective positions in the communication areas a1 and a2 (step S31a, step S31b), When each in-vehicle communication device 3 receives the signal, the in-vehicle communication device 3 obtains a reception error occurrence rate of the signal (step S32a, step S32). The reception error can be a demodulation error in the communication unit 31. In this determination method (3), only one of the parent device 2A and the child device 2B-1 can function and can be determined. However, in the present embodiment, a case where both function will be described.
Then, each in-vehicle communication device 3 includes information on its own position when the reception error occurs (hereinafter referred to as position information) in the transmission signal together with the information on the reception error occurrence rate. It transmits to the subunit | mobile_unit 2B-1 (step S33a, step S33b).

When the wireless communication unit 21 of the parent device 2A and the child device 2B-1 receives a transmission signal transmitted from each of the in-vehicle communication devices 3, the in-vehicle communication device 3 is included in the position indicated by the position information included in the transmission signal. The information of the reception error occurrence rate of the transmission signal from the roadside communication device 2 that has been received and the position information are acquired, and the data transfer unit 23A stores them in the storage unit 24 (steps S34a and S34b).
The information stored in the storage unit 24 of the base unit 2A is sent to the interference determination unit 13 of the interference avoidance device 10 by the data transfer unit 23A (step S35a). The information stored in the storage unit 24 of the slave unit 2B-1 is sent by the data transfer unit 23A to the interference determination unit 13 of the interference avoidance device 10 in the master unit 2A via the wired communication unit 22 (step S35b).

Note that if the transmission signals from the roadside communication device 2 interfere with each other, the in-vehicle communication device 3 existing in the interference area has a high reception error occurrence rate. Based on the position information of the communication device 3, it can be determined whether or not interference occurs at the position.
Therefore, the interference determination unit 13 includes information on the position of the in-vehicle communication device 3 and the reception error occurrence rate of the transmission signal transmitted from the parent device 2A received by the in-vehicle communication device 3 at the position, and / or in-vehicle communication. By acquiring information on the position of the machine 3 and the reception error occurrence rate of the transmission signal transmitted from the slave unit 2B-1 received by the vehicle-mounted communication apparatus 3 at the position, each vehicle-mounted communication is based on the information. It is determined whether or not interference occurs at the position of the machine 3 (step S36). That is, when the reception error occurrence rate acquired as information exceeds the threshold α4, it can be determined that interference has occurred at the position of the in-vehicle communication device 3 that is the transmission source of the information. Thereby, the area where interference occurs can be determined as the interference area.

And the said characteristic change part 14 with which the interference avoidance apparatus 10 is provided is based on the said determination result by the interference determination part 13, The said distance-level characteristic which the main | base station 2A and / or the subunit | mobile_unit 2B-1 have The process which changes is performed (step S37). The processing by the characteristic changing unit 14 is the same as the determination method (1).
The steps (S31 to S36) until the determination of the presence or absence of interference in this determination method (3) may be an additional condition when determining the presence or absence of interference by the determination method (1) or the determination method (2). . That is, interference occurs when the determination of “with interference” is made in step S15 of FIG. 5 of the determination method (1) and the determination of “with interference” is made in step S36 of the determination method (3). May be determined.

<Method for determining presence / absence of interference (4)>
FIG. 8 is a flowchart of the process by the determination method (4) of presence / absence of interference and the characteristic changing unit 14. In the determination method (3), the presence / absence of interference is determined based on the rate of occurrence of reception errors in the in-vehicle communication device 3, but in the determination method (4), interference is determined based on the rate of occurrence of reception errors in the roadside communication device 2. Determine presence or absence.
As shown in FIG. 2, another (second) slave unit 2B-2 exists next to (in between) both the master unit 2A and the slave unit 2B-1. As the inter-road communication, the master unit 2A and the slave unit 2B-1 transmit signals to the slave unit 2B-2 (steps S41a and S41b in FIG. 8), and when the slave unit 2B-2 receives the signal, The child device 2B-2 obtains a reception error occurrence rate of the signal (step S42). The reception error can be a demodulation error in the wireless communication unit 21.
And the subunit | mobile_unit 2B-2 sends the information of this reception error occurrence rate to the interference determination part 13 of the interference avoidance apparatus 10 in the main | base station 2A via the wired communication part 22 by the data transfer part 23A (step S43). .

In the slave unit 2B-2, if interference occurs due to transmission signals from the master unit 2A and the slave unit 2B-1, the reception error occurrence rate increases in the slave unit 2B-2. Based on the occurrence rate and the location information of the slave unit 2B-2, it is possible to determine whether or not interference occurs at the location of the slave unit 2B-2 and a location near the slave unit 2B-2.
Therefore, the reception error occurrence rate of the signal received by the slave unit 2B-2 that is transmitted by overlapping a part or all of the transmission time from the master unit 2A and the slave unit 2B-1 in the vicinity of the slave unit 2B-2, Whether the interference determination unit 13 obtains from the slave unit 2B-2, based on the information on the reception error occurrence rate, whether or not interference is occurring at the location of the slave unit 2B-2 and the vicinity thereof. Determination is made (step S44). That is, when the reception error occurrence rate acquired as information exceeds the threshold value α5, it is determined that interference occurs at the position of the slave unit 2B-2 and a position in the vicinity thereof. Thereby, the area where interference occurs can be determined as the interference area.

And the said characteristic change part 14 with which the interference avoidance apparatus 10 is provided is based on the said determination result by the interference determination part 13, The said distance-level characteristic which the main | base station 2A and / or the subunit | mobile_unit 2B-1 have The process which changes is performed (step S45). The processing by the characteristic changing unit 14 is the same as the determination method (1).
It should be noted that the steps (S41 to S44) up to the determination of the presence or absence of interference in the determination method (4) are performed when the presence or absence of interference is determined by the determination method (1), the determination method (2), or the determination method (3). Additional conditions may be used. That is, it is determined that interference has occurred when the determination of “with interference” is made at step S15 of the determination method (1) and the determination of “with interference” is made at step S44 of the determination method (4). You may do it.

According to the interference avoidance device 10 of each of the embodiments described above, when interference of transmission signals from a plurality of roadside communication devices 2 occurs, the plurality of roadside communication devices 2 have a plurality of these or some of them. By reducing the distance-level characteristic, the reception level in the mobile communication device 3 of the transmission signal from the roadside communication device 2 having the reduced distance-level characteristic can be reduced, and the generated interference can be avoided. It becomes possible to do.
As a result, the in-vehicle communication device 3 can accurately receive information from the roadside communication device 2, and a vehicle equipped with the in-vehicle communication device 3 can prevent accidents such as collision prevention at a front intersection. It is possible to implement safe driving support that prevents accidents.

Further, the configuration of the present invention is not limited to the illustrated form, and may be other forms within the scope of the present invention. In the above-described embodiment, the case where the transmission signals of the two roadside communication devices 2 (the parent device 2A and the child device 2B-1) interfere with each other, but even when the transmission signals of three or more roadside communication devices 2 interfere, The interference avoidance device 10 of the present invention can be applied. Moreover, although the case where the transmission signals of the parent device 2A and the child device 2B-1 interfere with each other has been described, the transmission signals from the plurality of child devices 2B may interfere.
As shown in FIG. 2, the antenna is a directional antenna, but may be an omnidirectional antenna.
Moreover, although the said embodiment demonstrated the case where the interference avoidance apparatus 10 was provided with 2 A of main | base stations, you may provide the interference avoidance apparatus 10 separately from the roadside communication apparatus 2 in a communication system.

  2: roadside communication device, 2A: parent device, 2B: child device, 3: in-vehicle communication device (mobile communication device), 10: interference avoidance device, 13: interference determination unit, 14: characteristic changing unit, 21B: output adjusting unit 31: Communication unit 32a: Acquisition unit

Claims (9)

When a mobile communication device receives a transmission signal from a first roadside communication device, an interference avoidance device that avoids interference between the transmission signal and a transmission signal from a second roadside communication device,
An interference determination unit for determining presence or absence of the interference;
An interference avoidance apparatus comprising: a characteristic changing unit that changes a distance-level characteristic that is a propagation distance characteristic of a transmission signal level from the roadside communication device based on a determination result by the interference determination unit; .   The interference determination unit estimates the distance-level characteristic based on a position of the mobile communication device and a reception level of the transmission signal transmitted from the mobile communication device at the position at the roadside communication device. The interference avoidance apparatus according to claim 1, wherein presence or absence of the interference is determined based on the distance-level characteristic.   The interference avoidance apparatus according to claim 2, wherein the interference determination unit further estimates the distance-level characteristic based on transmission level information of a transmission signal transmitted from the mobile communication device.   The interference determination unit estimates the distance-level characteristic based on a position of the mobile communication device and a reception level of a transmission signal from the roadside communication device received by the mobile communication device at the position. The interference avoidance apparatus according to claim 1, wherein presence or absence of the interference is determined based on the distance-level characteristic.   The interference determination unit determines presence / absence of the interference based on information on a position of the mobile communication device and a reception error occurrence rate of a transmission signal from the roadside communication device received by the mobile communication device at the position. The interference avoidance device according to any one of claims 1 to 4.   The interference determination unit is configured to receive a reception error rate of a signal transmitted by a plurality of second roadside communication devices in the vicinity of the first roadside communication device and transmitted by overlapping the transmission time and received by the first roadside communication device. The interference avoidance device according to any one of claims 1 to 5, wherein the presence or absence of the interference is determined based on the information.   The characteristic changing unit has a margin in the first and second roadside communication devices based on a threshold of the distance-level characteristic that can secure a minimum communication service area in which necessary communication performance should be maintained. The interference avoidance device according to claim 1, wherein the interference avoidance device has a function of preferentially selecting and reducing the distance-level characteristic. The roadside communication device has an output adjustment unit that adjusts the transmission output of a signal,
The said characteristic change part produces | generates the request signal which reduces the transmission output from the said roadside communication apparatus by the said output adjustment part, when it determines with the interference determination part having interference. The interference avoidance device according to item. A mobile communication device capable of wireless communication with a roadside communication device,
An acquisition unit that acquires its own position and a reception level of a transmission signal received from the roadside communication device received at the position;
In order to give the information acquired by the acquisition unit to the interference determination unit of the interference avoidance device according to claim 1, a mobile communication unit comprising a communication unit capable of wirelessly transmitting the information Machine.

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