JP2007150427A - Communication apparatus and communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication apparatus and a communication system which decrease the possibility of carrier collision due to a hidden terminal problem. <P>SOLUTION: An on-vehicle apparatus 10a is the communication apparatus which transmitts a time T required for the transmission of carriers to be transmitted to a mobile terminal 12 for another on-vehicle apparatus 10b and executes transmission by an omnidirectional antenna, and thereafter completes the transmission to the mobile terminal 12 within the time T by using a directional antenna. It is characterized in that a transmission reception area 40a by the omnidirectional antenna of the on-vehicle apparatus 10a with the on-vehicle apparatus 10b is wider than a transmission reception area 50a by the directional antenna of the on-vehicle apparatus 10a with the on-vehicle apparatus 10b. The on-vehicle apparatus 10b transmits the carriers to the mobile terminal 12 for a time other than the time T. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless transmission technology between movable communication devices.

Conventionally, an inter-vehicle communication apparatus using a CSMA (Carrier Sense Multiple Access) method is known (see, for example, Patent Document 1). The CSMA method detects the channel usage status by trying to receive once before each communication device starts communication (carrier sense), starts transmission of a packet when the channel is idle, and transmits a packet when the channel is busy. It is a method to make up for. This inter-vehicle communication device sets a maximum waiting time from the time when the packet transmission is stopped to the time when the next carrier sense is started in order to maximize the number of vehicles successfully transmitting the packet. The next carrier sense start time is set at a random time.
JP 2001-45013 A

  By the way, even when the CSMA scheme in the above-described prior art is adopted, in order to avoid a communication collision, each communication apparatus must detect a carrier transmitted by all other communication apparatuses. However, if communication devices that cannot detect each other's carriers transmit simultaneously to a common communication partner, both transmissions may not be normally received (collision), and so-called hidden terminal problems may occur. . For this reason, it is considered that it is not easy to detect carriers transmitted by all other communication apparatuses.

  Therefore, an object of the present invention is to provide a communication device and a communication system that can reduce the possibility of carrier collision due to the hidden terminal problem.

The object is as described in claim 1.
First transmission means for transmitting a period during which other communication devices are prohibited from transmitting carriers;
A communication device comprising a second transmission means for transmitting a carrier within the period,
The transmission area of the first transmission means is achieved by a communication device characterized by being wider than the transmission area of the second transmission means.

In addition, the object is as described in claim 6.
A communication system comprising a first communication device, a second communication device, and a third communication device,
The first communication device includes first transmission means for transmitting a period during which transmission of a carrier is prohibited to the second communication device, and second transmission means for transmitting the carrier to the third communication device within the period,
The second communication device includes third transmission means for transmitting the carrier to the third communication device outside the period,
The transmission area of the first transmission means is achieved by a communication system characterized by being wider than the transmission area of the second transmission means.

  In the first and sixth aspects of the invention, carrier transmission by another communication device is prohibited in an area wider than the transmission area of the second transmission means. In such a configuration, since it is possible to prohibit another communication apparatus from transmitting a carrier before the second transmission unit transmits the carrier, the possibility of carrier collision due to a hidden terminal problem can be reduced.

In this case, as described in claim 2, the communication device according to claim 1 is an in-vehicle communication device, an object to which the first transmission means transmits a carrier is an in-vehicle communication device, and the second transmission means is If the target to transmit the carrier is a portable communication device,
According to a seventh aspect of the present invention, in the communication system according to the sixth aspect, the first communication device and the second communication device are in-vehicle communication devices, and the third communication device is a portable communication device. In communication, it is possible to reduce the possibility that carriers transmitted from in-vehicle communication devices to portable communication devices collide with each other.

Furthermore, as described in claim 3, in the communication device according to claim 1 or 2, the maximum communicable distance of the transmission area of the first transmission unit is twice the maximum communicable distance of the transmission area of the second transmission unit. If it is above,
As described in claim 8, in the communication device according to claim 6 or 7, the maximum communicable distance of the transmission area of the first transmission means is the communication between the transmission area of the second transmission means and the transmission area of the third transmission means. If it is larger than the sum of the maximum possible distances, ideally, collision of carriers transmitted by the second transmission means can be eliminated.

Furthermore, as described in claim 4, in the communication device according to any one of claims 1 to 3, the first transmitting means transmits with an omnidirectional antenna, and the second transmitting means transmits with a directional antenna. Then, again
According to a ninth aspect of the present invention, in the communication system according to any one of the sixth to eighth aspects, the first transmitting means transmits by an omnidirectional antenna, and the second transmitting means and the third transmitting means are directional antennas. If the transmission is performed, it is possible to prohibit other communication devices existing around the device from transmitting the carrier, and to accurately transmit the carrier to be transmitted to the communication partner existing in a specific direction. can do.

Further, as described in claim 5, in the communication device according to any one of claims 1 to 3, the period during which the carrier transmission is prohibited is determined based on the transmission time of the second transmission means. And again
As described in claim 10, in the communication system according to any one of claims 6 to 9, if the period during which the carrier is prohibited from transmission is determined based on the transmission time of the second transmission means, By appropriately setting the carrier transmission prohibition period of other communication devices with respect to the time required for the carrier transmission by the second transmission means, carrier collision can be effectively prevented without occupying the communication line wastefully. it can.

  According to the present invention, the possibility of carrier collision due to the hidden terminal problem can be reduced.

  The best mode for carrying out the present invention will be described below. FIG. 1 is a diagram showing a configuration of an approach notification system that is an embodiment of a communication system of the present invention. As shown in FIG. 1, the approach notification system includes an in-vehicle device 10 that is an embodiment of the communication device of the present invention and a portable terminal 12 that a pedestrian has. The approach notification system notifies the vehicle (driver) side or the owner side of the mobile terminal 12 that a vehicle carrying the vehicle-mounted device 10 and a pedestrian carrying the mobile terminal 12 are approaching each other. is there. A person who rides a motorcycle such as a light vehicle including a bicycle or a motor-driven bicycle may carry the portable terminal 12.

[Outline of this approach notification system]
FIG. 4 is a diagram for explaining an overview of an approach notification system that is an embodiment of the communication system of the present invention. FIG. 4 shows a situation where two opposing vehicles are approaching a pedestrian carrying the mobile terminal 12. The vehicle-mounted device 10a is mounted on one vehicle, and the vehicle-mounted device 10b is mounted on the other vehicle. Reference numeral 40a denotes a transmission / reception area with another in-vehicle device using the omnidirectional antenna of the in-vehicle device 10a (hereinafter referred to as “to-in-vehicle device transmission / reception area 40a”). Reference numeral 40b denotes a transmission / reception area with another in-vehicle device using the omnidirectional antenna of the in-vehicle device 10b (hereinafter referred to as “to-in-vehicle device transmission / reception area 40b”). Reference numeral 50a denotes a transmission / reception area with the mobile terminal 12 by the directional antenna of the in-vehicle device 10a (hereinafter, referred to as “to-mobile terminal transmission / reception area 50a”). Reference numeral 50b denotes a transmission / reception area with the mobile terminal 12 by the directional antenna of the in-vehicle device 10b (hereinafter referred to as “vs. mobile terminal transmission / reception area 50b”).

  In the situation shown in FIG. 4, when two vehicles that are separated from each other approach each other, the vehicle-mounted devices 10 a and 10 b enter the other vehicle-mounted device transmission / reception area 40, and receive the carrier transmitted by the partner. Ready to go. On the other hand, since the mobile terminal 12 is not included in any of the mobile terminal transmission / reception areas 50 of the in-vehicle devices 10a and 10b, the mobile device 12 cannot receive the carrier transmitted by the in-vehicle devices 10a and 10b. In this situation, consider a case where the in-vehicle device 10a transmits a carrier (for example, an activation signal or vehicle approach information) to be transmitted to the mobile terminal 12.

  The in-vehicle device 10a transmits the time T necessary for transmitting the carrier to be transmitted to the mobile terminal 12 to another in-vehicle device using the omnidirectional antenna, and then uses the directional antenna to carry it within the time T. The transmission to the terminal 12 is completed. The time T is set in consideration of the time required until the mobile terminal 12 is included in the mobile terminal transmission / reception area 50a when the vehicle on which the vehicle-mounted device 10a is mounted approaches the mobile terminal 12. It is desirable. On the other hand, when the vehicle-mounted device 10b existing in the vehicle-mounted device transmission / reception area 40a receives this time T, even if the transmission from the omnidirectional antenna of the vehicle-mounted device 10a ends, the directional antenna of the vehicle-mounted device 10a also ends. Even if the carrier cannot be received from the mobile terminal 12 toward the portable terminal 12, the carrier is not transmitted during T. After the elapse of time T, if there is a carrier to be transmitted to the mobile terminal 12, the in-vehicle device 10b starts transmitting the carrier.

  As a result, even if the mobile terminal 12 is included in the mobile terminal transmission / reception area 50 of both the in-vehicle devices 10 due to further elapse of time, the in-vehicle devices 10 do not transmit carriers at the same time. The mobile terminal 12 does not miss the activation signal from the in-vehicle device 10 or the vehicle approach information. As a result, the mobile terminal 12 can be reliably started, and the pedestrian carrying the mobile terminal 12 can be reliably notified of the approach of the vehicle, so that the safety of the pedestrian is ensured.

  The size (maximum communicable distance) of the on-vehicle device transmission / reception area 40 is desirably larger than the sum of the maximum communicable distances of the portable terminal transmission / reception area 50a and the portable terminal transmission / reception area 50b. Even if the boundary corresponding to the maximum communicable distance portion of each other's mobile terminal transmission / reception area 50 has a facing positional relationship as shown in FIG. 4, other in-vehicle devices 10 are in the in-vehicle device transmission / reception area 40. It is because it is included and the carrier transmission of the other vehicle equipment 10 can be stopped exactly. As a specific method, for example, when the reception sensitivity of the in-vehicle device 10 and the reception sensitivity of the portable terminal 12 are the same, and the gain of the omnidirectional antenna of the in-vehicle device 10 and the maximum gain of the directional antenna are the same, there is no What is necessary is just to make the transmission output of a directional antenna more than twice the transmission output of a directional antenna. Alternatively, when the gain of the omnidirectional antenna of the in-vehicle device 10 and the maximum gain of the directional antenna are the same and the transmission output is also the same, the reception sensitivity of the in-vehicle device 10 is set to be at least twice that of the mobile terminal 12. That's fine.

  Then, the structure of the portable terminal 12 and the vehicle equipment 10 which implement | achieve the above-mentioned approach alerting | reporting system is demonstrated below.

[Configuration of mobile terminal 12]
FIG. 2 is an example of a system configuration of the mobile terminal 12. The portable terminal 12 has an antenna 6 for transmitting / receiving radio waves having a predetermined frequency (for example, 2.4 GHz) to / from the outside. The receiving unit 7 receives a radio wave (that is, a carrier) transmitted by the vehicle-mounted device 10 via the antenna 6 (hereinafter, the radio wave transmitted by the vehicle-mounted device 10 is referred to as “vehicle-mounted device transmission wave”).

  The ID addition / detection unit 8 detects an activation signal from information obtained by the reception unit 7 demodulating the vehicle-mounted device transmission wave. The ID addition / detection unit 8 that has detected the activation signal adds the terminal ID given to each portable terminal 12 to the transmission data, and the transmission unit 5 performs modulation to detect the presence of the portable terminal 12 via the antenna 6. Start radio transmission to receive. Hereinafter, the radio wave transmitted by the mobile terminal 12 via the antenna 6 is referred to as “terminal transmission wave”. The terminal transmission wave is transmitted intermittently at a constant output.

  The ID adding / detecting unit 8 detects an ID from information obtained by the receiving unit 7 demodulating the vehicle-mounted device transmission wave. When the terminal ID is included in the ID detected by the ID addition / detection unit 8, it is known that the vehicle is approaching the pedestrian carrying the mobile terminal 12 via the information providing unit 9. Is done. That is, in order for the vehicle-mounted device 10 that has received the terminal transmission wave including the terminal ID to inform the mobile terminal 12 that has the terminal ID that the vehicle is approaching, the vehicle approach including the terminal ID is performed. The in-vehicle device transmission wave is transmitted as information. If the terminal ID is included, the information providing unit 9 provides the pedestrian that the vehicle is approaching by voice information, visual display information, vibration, or the like. The vehicle-mounted device transmission wave transmitted by the vehicle-mounted device 10 includes vehicle ID information given to each vehicle-mounted device 10 or each vehicle on which the vehicle-mounted device 10 is mounted so that the transmission source can be specified. May be. Further, specific examples of the mobile terminal 12 include a mobile phone and a personal digital assistance (PDA) in terms of being portable.

[Configuration of in-vehicle device 10]
FIG. 3 is an example of a system configuration of the in-vehicle device 10. The in-vehicle device 10 has an omnidirectional antenna 15 for receiving radio waves from the outside and a directional antenna 14 for transmitting in-vehicle device transmission waves to the outside. In the present embodiment, three directional antennas 14 are provided, and each of the three directional antennas 14a, 14b, and 14c has directivity in different directions within a predetermined angle range in the traveling direction. Is installed. In general, a directional antenna has a property that the directivity becomes sharper as the antenna gain increases. That is, the directional antennas 14a, 14b, and 14c arranged to have directivity in different directions are different in the direction in which the gain is maximum. On the other hand, the omnidirectional antenna 15 has almost uniform antenna gain in all directions.

  The carrier sending time detection compatible reception unit 16 (hereinafter, referred to as “reception unit 16”) uses the omnidirectional antenna 15 switched by the directivity switching unit 22 to be described later to determine whether or not there is a carrier of another in-vehicle device. Is determined (carrier sense). When detecting the carrier of the other in-vehicle device, the receiving unit 16 acquires the carrier transmission time Tt1 for the mobile terminal 12 of the other in-vehicle device from the carriers of the other in-vehicle device, and transmits the carrier transmission time setting corresponding transmission unit 30 ( Hereinafter, it is referred to as “transmitting unit 30”. The transmission unit 30 that has acquired the carrier transmission time Tt1 stops carrier transmission to the mobile terminal 12 for (Tt1 + α) time. Note that by setting α to a random value, even if there are other in-vehicle devices other than the other in-vehicle devices, there is a high possibility that collision with the carrier transmitted by the other in-vehicle devices can be avoided.

  If the receiving unit 16 further detects a carrier of another in-vehicle device while the transmitting unit 30 stops transmission for (Tt1 + α) time, the mobile unit of the other in-vehicle device is detected from the detected carriers of the other in-vehicle device. 12 is acquired and sent to the transmission unit 30. The transmission unit 30 that has acquired the carrier transmission time Tt2 further extends the carrier transmission stoppage for the mobile terminal 12 by an α time considering Tt2. This is repeated until no other on-vehicle carrier is detected.

  When the carrier transmission stop time elapses, the transmission unit 30 sets the carrier transmission time Tj1 necessary for transmitting the activation signal transmitted from the self-vehicle device to the mobile terminal 12 via the omnidirectional antenna 15 to the other vehicle devices. To send. Then, within the carrier transmission time Tj1, the directivity switching unit 22 switches to the directional antenna 14 having directivity in the traveling direction of the vehicle, and the transmission unit 30 transmits an activation signal to the portable terminal 12. The mobile terminal 12 that has received the activation signal starts transmission of a terminal transmission wave that is intermittently transmitted at a constant output, as described above.

  The receiving unit 16 receives the terminal transmission wave received by the directional antenna 14 and acquires information obtained by demodulating the terminal transmission wave. The reception level detection unit 18 connected to the reception unit 16 detects the reception level indicating the reception sensitivity of the terminal transmission wave received by the reception unit 16 and is obtained by the reception unit 16 demodulating the terminal transmission wave. A terminal ID is detected from the information. Information on the reception level detected by the reception level detection unit 18 is supplied to the direction / distance estimation unit 20.

  A directivity switching unit 22 that controls the directivity of the directional antenna 14 is connected to the direction / distance estimating unit 20. The direction / distance estimator 20 sends azimuth direction information to be received to the vehicle. The directivity switching unit 22 switches the directivity of the directional antenna 14 according to the azimuth angle direction supplied from the direction / distance estimation unit 20. When the reception level for all azimuth directions is supplied from the reception level detection unit 18 by switching the directivity of the directional antenna 14, the direction / distance estimation unit 20 receives the radio wave arrival direction and distance, that is, the mobile terminal 12. Estimate the direction in which the person who owns the person exists and the distance to the person. For example, when the reception level of the terminal transmission wave when the directional antenna 14a is used is the maximum among the reception levels of the terminal transmission wave when each directional antenna 14 is used, the directivity of the directional antenna 14a is provided. It is presumed that there is a pedestrian carrying the portable terminal 12 in the direction of the sex, and the walking carried by the portable terminal 12 at a distance away according to the value of the reception level of the terminal transmission wave when the directional antenna 14a is used. Presumably exist. Since the value of the reception level of the terminal transmission wave changes according to the distance between the vehicle and the portable terminal 12, the direction / distance estimation unit 20 is a map value that defines the relationship between the value of the reception level of the terminal transmission wave and the distance. The distance to the pedestrian carrying the mobile terminal 12 is estimated using the above. In addition, the directivity switching unit 22 can be controlled so that radio waves are transmitted toward the estimated direction of the mobile terminal 12. Furthermore, the directivity switching unit 22 sets a region where radio waves are transmitted based on vehicle speed, turn signal information, and navigation information, which will be described later. In order to set a region where radio waves are transmitted, a plurality of directional antennas 14 having different directivity directions may be selectively switched as described above, or one directional antenna may be controlled. The 14 directivities may be controlled.

  An information provision determination unit 24 is also connected to the direction / distance estimation unit 20. Information on the presence direction and distance of the person holding the mobile terminal 12 estimated by the direction / distance estimation unit 20 is sent to the information provision determination unit 24. The information provision determination unit 24 includes information on the speed (vehicle speed) of the host vehicle detected using a vehicle speed sensor, vehicle turn signal information detected using a turn signal indicator, and a navigation system mounted on the vehicle. Navigation information such as road shape, road width, intersection shape, and lane number information in the vicinity of the current position of the vehicle detected by using the vehicle (particularly in the forward direction) is supplied. The navigation information is stored in advance in the map database of the navigation system.

  A pedestrian presence information provision area table 26 is connected to the information provision determination unit 24. In the pedestrian presence information provision area table 26, information on a pedestrian presence information provision area in which different areas are set with parameters such as a steering angle, vehicle speed, blinker information, and navigation information is written in advance. The information provision determination unit 24 uses information on the steering angle of the host vehicle detected using the steering angle sensor, information on the speed (vehicle speed) of the host vehicle detected using the vehicle speed sensor, and a blinker indicator. Obtain navigation information such as the detected vehicle blinker information and the road shape, road width, intersection shape, and lane number information of the road near the current position of the vehicle detected using the navigation system mounted on the vehicle, The pedestrian presence information provision area corresponding to the acquired information is read from the pedestrian presence information provision area table 26. The navigation information is stored in advance in the map database of the navigation system. And the information provision determination part 24 was read based on the position of the pedestrian carrying the mobile terminal 12 estimated by the direction / distance estimation part 20 (information on the direction of existence and the distance to the pedestrian). It is determined whether or not there is a pedestrian carrying the mobile terminal 12 in the pedestrian presence information providing area. In addition, the pedestrian presence information provision area information is not previously stored in the pedestrian presence information provision area table 26, but the pedestrian presence information provision areas corresponding to these parameters are sequentially derived according to a predetermined calculation formula. May be.

  The information providing determination unit 24 is connected to an information providing unit 28 that visually or audibly provides information to the driver of the host vehicle using a display or a speaker. When it is determined that there is a pedestrian who has the mobile terminal 12 in the pedestrian presence information provision area, the information provision determination unit 24 determines that the pedestrian is present in the pedestrian presence information provision area. The information providing unit 28 is instructed to notify the person. When the information providing unit 28 receives an information providing instruction from the information providing determining unit 24, the information providing unit 28 operates the display and the speaker, so that the pedestrian exists in the pedestrian presence information providing area for the own vehicle and the own vehicle Inform the vehicle driver that there is a possibility of contact with the pedestrian.

  Furthermore, when the information provision determination unit 24 determines that there is a pedestrian carrying the mobile terminal 12 in the pedestrian presence information provision area, the information provision determination unit 24 includes the terminal ID of the mobile terminal 12 acquired by the reception unit 16. To identify the terminal ID of the mobile terminal 12 in the pedestrian presence information provision area and to transmit the vehicle-mounted device transmission wave toward the mobile terminal 12 in the pedestrian presence information provision area The number 14 is selected from 14a to 14c. Then, the information provision determination unit 24 transmits the terminal ID of the mobile terminal 12 in the pedestrian presence information provision area to the transmission unit 30 and transmits the number of the specified directional antenna 14 to the directivity switching unit 22. . The directivity switching unit 22 switches the three directional antennas 14a, 14b, and 14c according to the number of the directional antenna 14 received from the information provision determination unit 24, and the transmission unit 30 selects the selected directional antenna. Then, the radio wave modulated with respect to the terminal ID of the mobile terminal 12 in the pedestrian presence information provision area received from the information provision determination unit 24 and the own vehicle ID is transmitted as an in-vehicle device transmission wave. The mobile terminal 12 that has received the in-vehicle device transmission wave detects the terminal ID included in the in-vehicle device transmission wave by the ID addition / detection unit 8 (see FIG. 2), and includes its own terminal ID in the terminal ID. Is included, the pedestrian is notified that the vehicle is approaching via the information providing unit 9 (see FIG. 2).

  In addition, when notifying a pedestrian that the vehicle is approaching by transmitting the vehicle-mounted device transmission wave as vehicle approach information including the terminal ID as described above, switching of the directional antenna 14 by the directivity switching unit 22 is performed. And before transmission of the in-vehicle device transmission wave by the transmission unit 30, the directivity switching unit 22 switches to the omnidirectional antenna 15, and the reception unit 16 determines whether there is a carrier of another on-vehicle device (carrier sense). ). When detecting the carrier of the other in-vehicle device, the receiving unit 16 acquires the carrier transmission time Tt3 for the portable terminal 12 of the other in-vehicle device from the carriers of the other in-vehicle device, and sends it to the transmitting unit 30. The transmission unit 30 that has acquired the carrier transmission time Tt3 stops carrier transmission to the mobile terminal 12 for (Tt3 + β) time. Note that, by setting β to a random value, there is a high possibility that a collision with a carrier transmitted by another in-vehicle device can be avoided even if there is another in-vehicle device in addition to the other in-vehicle device.

  When the receiving unit 16 further detects a carrier of another in-vehicle device while the transmission unit 30 stops transmission for (Tt3 + β) time, the mobile unit of the other in-vehicle device is detected from the detected carriers of the other in-vehicle device. 12 is transmitted to the transmission unit 30. The transmitting unit 30 that has acquired the carrier transmission time Tt4 further extends the carrier transmission stoppage to the mobile terminal 12 by a β time considering Tt4. This is repeated until no other on-vehicle carrier is detected.

  When the carrier transmission stop time elapses, the transmission unit 30 transmits to the other vehicle-mounted device the carrier transmission time Tj2 necessary for transmitting the vehicle approach information transmitted from the vehicle-mounted device to the mobile terminal 12 via the omnidirectional antenna 15. Send to. Then, within the carrier transmission time Tj2, the directivity switching unit 22 switches the three directional antennas 14a, 14b, and 14c according to the number of the directional antenna 14 received from the information provision determination unit 24, and the transmission unit 30 is selected. The radio wave modulated with respect to the terminal ID of the portable terminal 12 and its own vehicle ID in the pedestrian presence information provision area received from the information provision determination unit 24 via the directivity antenna is transmitted as vehicle approach information.

  In addition, what is necessary is just to set the above-mentioned pedestrian presence information provision area similarly to the setting method of the alarm area disclosed by Unexamined-Japanese-Patent No. 2005-202893.

[Operation of this approach notification system]
Then, the operation | movement flow of the vehicle equipment 10 which implement | achieves the above approach alerting | reporting systems is demonstrated. FIG. 5 is a flowchart of an example of a control routine executed by the in-vehicle device 10 of the present embodiment. When a carrier (for example, an activation signal or vehicle approach information) to be transmitted to the mobile terminal 12 is generated, the routine shown in FIG. 5 is activated, and the process of step 1 is first executed. The receiving unit 16 instructs the directivity switching unit 22 to switch to the omnidirectional antenna 15 (step 1), and determines whether or not the carrier of the other in-vehicle device can be detected (step 2). When detecting the carrier of the other in-vehicle device (step 2; Yes), the receiving unit 16 acquires the carrier transmission time Tt to the mobile terminal 12 from the carriers of the other in-vehicle device, and sends it to the transmitting unit 30 ( Step 3). The transmission unit 30 that has acquired the carrier transmission time Tt determines whether or not the transmission of the carrier to the mobile terminal 12 is stopped for (Tt + α) time (step 5). If it has not stopped for (Tt + α) time (step 5; No), the receiving unit 16 determines again whether or not the carrier of the other in-vehicle device is detected (step 6). When the carrier of the other on-vehicle device is further detected (step 6; Yes), the reception unit 16 repeats the processes of steps 3 and 5, and further, the carrier of the other on-vehicle device is not detected (step 6; In No), the process of step 5 is repeated.

  When the carrier of the other in-vehicle device is not detected in Step 2 (Step 2; No), or when it is determined that the time has been stopped for (Tt + α) in Step 5 (Step 5; Yes), the transmitting unit 30 Based on the amount of information that the in-vehicle device transmits to the portable terminal 12, the carrier transmission time Tj of the own in-vehicle device is set (step 7), and the carrier transmission time Tj is transmitted to the other in-vehicle device (step 8). Within the carrier transmission time Tj, the directivity switching unit 22 switches to the directional antenna 14 by the above-described method, and the transmission unit 30 transmits a carrier such as vehicle approach information to the mobile terminal 12 (step 9).

  In addition, the portable terminal 12 which implement | achieves the above approach alerting | reporting systems should just transmit a terminal transmission wave, when a carrier sense is performed and a carrier is not detected.

  As described above, according to the approach notification system described above, since the other in-vehicle device can be prohibited from transmitting the carrier before the own in-vehicle device transmits the carrier, the own in-vehicle device and the other in-vehicle device are connected to the mobile terminal 12. On the other hand, the collision of the transmitted carrier is prevented, and the mobile terminal 12 does not miss the activation signal or the vehicle approach information from the in-vehicle device 10. As a result, the mobile terminal 12 can be reliably started, and the pedestrian carrying the mobile terminal 12 can be reliably notified of the approach of the vehicle, so that the safety of the pedestrian is ensured.

  In addition, according to the approach notification system described above, it is possible to notify only the pedestrian who has the mobile terminal 12 present in the pedestrian presence information provision area, and the mobile terminal existing outside the area. A pedestrian carrying 12 can be informed of the approach of the vehicle. As a result, a pedestrian who needs to be notified of the approach of the vehicle can surely be notified of this, and a pedestrian who does not need much notification of the approach of the vehicle (particularly a position that is not related to the approach of the vehicle (for example, a straight-ahead vehicle) It is possible to reduce the annoyance felt by the pedestrian by the notification to the subject who is in the back).

  Furthermore, according to the above approach notification system, pedestrian presence information can be provided to the vehicle driver only when there is a pedestrian who has the mobile terminal 12 in the pedestrian presence information provision area, When there is no pedestrian carrying the portable terminal 12 in the area, it is possible not to provide pedestrian presence information to the vehicle driver. As a result, when there is a pedestrian at a position that should be notified to the vehicle driver during vehicle driving, the vehicle driver can be surely notified of this, and the vehicle driver need not be informed so much. When there are pedestrians, it is possible to reduce the annoyance felt by the driver by providing the pedestrian presence information.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above embodiment, the intermittent transmission wave transmitted by the mobile terminal 12 is received by the directional antenna 14 of the in-vehicle device 10 and the position of the pedestrian carrying the mobile terminal 12 is estimated based on the reception level. However, the portable terminal 12 receives the radio wave transmitted from the in-vehicle device 10 via the directional antenna 14 and sends the reception level back to the in-vehicle device 10 to estimate the position of the pedestrian carrying the portable terminal 12. May be.

  That is, the gain of the directional antenna is high only in a specific direction, and the gain of the omnidirectional antenna is constant in almost all directions, and the direction in which the mobile terminal 12 exists can be determined using the difference. The in-vehicle device 10 cannot grasp where the mobile terminal 12 is present with respect to the vehicle only by receiving the terminal transmission wave via the omnidirectional antenna 15. This is because if the distance from the vehicle is the same, the reception level is the same even if the location is different. However, when the in-vehicle device 10 transmits a radio wave via the directional antenna 14 having a high gain only in a specific direction, the portable terminal 12 existing in the direction having the directivity receives the in-vehicle device transmission wave. The reception level is higher than the reception level when the mobile terminal 12 that does not exist in the direction having the directivity receives the vehicle-mounted device transmission wave. Therefore, the reception level of the terminal transmission wave received by the in-vehicle device 10 via the omnidirectional antenna 15 and the reception level of the in-vehicle device transmission wave transmitted by the in-vehicle device 10 via the directional antenna 14 on the portable terminal 12 side are determined. By comparing, the direction in which the mobile terminal 12 exists can be determined. And since the vehicle equipment transmission wave is transmitted via the directional antenna 14, based on the reception level by the side of the portable terminal 12 of a vehicle equipment transmission wave, the detail of the portable terminal 12 which exists in the determined direction is shown. The direction and distance (that is, the location of a pedestrian who has the mobile terminal 12) can be estimated.

  In addition, the mobile terminal 12 that has received the activation signal from the in-vehicle device 10 detects its own position by GPS or the like, and transmits the position information to the in-vehicle device 10, so that the in-vehicle device 10 possesses the mobile terminal 12. You may estimate the position of a pedestrian. Therefore, the present invention determines whether or not it is dangerous based on the relative positional relationship between the pedestrian and the vehicle obtained by GPS or the like, and if it is determined to be dangerous, the driver side of the vehicle or the owner of the portable terminal 12 It is also applicable to a system that provides information to the side.

  By the way, desirably, the information providing unit 9 of the mobile terminal 12 specifically notifies which vehicle is approaching from which direction as well as the fact of the approach. The information provision part 9 determines the content to alert | report based on the information contained in a vehicle equipment transmission wave.

  Further, instead of selectively switching the plurality of directional antennas 14, the directionality of the directional antennas 14 may be controlled so as to cover a predetermined azimuth angle. Further, the directional antenna 14 may be a directional antenna having directivity in only one direction in front of the vehicle, or may be a directional antenna having directivity in two directions in front of the vehicle and rear of the vehicle. As a result, even when the vehicle moves backward instead of when the vehicle moves forward, the pedestrian in the backward direction (that is, the traveling direction) can be informed of the presence of the vehicle, and the pedestrian can be notified to the driver. The presence of

  In the above embodiment, the road environment such as the road shape and the number of lanes is acquired based on the navigation information sent from the navigation system. It is good also as acquiring based on communication data.

It is the figure which showed one structure of the approach alerting | reporting system which is embodiment of the communication system of this invention. It is an example of the system configuration | structure of the portable terminal 12. FIG. 2 is an example of a system configuration of the in-vehicle device 10. It is a figure for demonstrating the outline | summary of the approach alerting | reporting system which is embodiment of the communication system of this invention. It is a flowchart of an example of the control routine which the vehicle equipment 10 of a present Example performs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Transmitting part 6,15 Omnidirectional antenna 7 Receiving part 8 ID addition / detection part 9,28 Information provision part 10,10a, 10b In-vehicle apparatus 12 Portable terminal 14,14a, 14b, 14c Directional antenna 16 Carrier transmission time detection Corresponding receiver 18 Reception level detector 19 Pedestrian position determination unit 20 Direction / distance estimation unit 22 Directivity switching unit 24 Information provision determination unit 26 Pedestrian presence information provision area table 30 Carrier transmission time setting correspondence transmission unit 40, 40a, 40b Transmission / reception area for in-vehicle devices 50, 50a, 50b Transmission / reception area for portable terminal

Claims (10)

First transmission means for transmitting a period during which other communication devices are prohibited from transmitting carriers;
A communication device comprising a second transmission means for transmitting a carrier within the period,
A communication apparatus characterized in that the transmission area of the first transmission means is wider than the transmission area of the second transmission means.   The communication device according to claim 1, wherein the first transmission unit transmits a carrier is an in-vehicle communication device, and the second transmission unit transmits a carrier is a portable communication device.   The communication apparatus according to claim 1 or 2, wherein the maximum communicable distance of the transmission area of the first transmission means is at least twice the maximum communicable distance of the transmission area of the second transmission means.   The communication apparatus according to any one of claims 1 to 3, wherein the first transmission means transmits by an omnidirectional antenna, and the second transmission means transmits by a directional antenna.   The communication apparatus according to claim 1, wherein the period is determined based on a transmission time of the second transmission unit. A communication system comprising a first communication device, a second communication device, and a third communication device,
The first communication device includes first transmission means for transmitting a period during which transmission of a carrier is prohibited to the second communication device, and second transmission means for transmitting the carrier to the third communication device within the period,
The second communication device includes third transmission means for transmitting the carrier to the third communication device outside the period,
A communication system characterized in that the transmission area of the first transmission means is wider than the transmission area of the second transmission means.   The communication system according to claim 6, wherein the first communication device and the second communication device are vehicle-mounted communication devices, and the third communication device is a portable communication device.   The communication system according to claim 6 or 7, wherein the maximum communicable distance of the transmission area of the first transmission means is larger than the sum of the maximum communicable distances of the transmission area of the second transmission means and the transmission area of the third transmission means.   The communication system according to any one of claims 6 to 8, wherein the first transmission means transmits by an omnidirectional antenna, and the second transmission means and the third transmission means transmit by a directional antenna.   The communication system according to claim 6, wherein the period is determined based on a transmission time of the second transmission unit.

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