JP4432656B2 - Traffic survey system - Google Patents

Description

  The present invention relates to a traffic survey system, and more particularly to a traffic survey system using a wireless network.

As a conventional traffic volume survey system, for example, a system is known in which a dedicated device equipped with a sensor is installed on the road side of a road, and the passage of the vehicle is detected by the sensor to automatically count the vehicle (patent) Reference 1). According to this system, since it is not necessary to manually count the vehicles, the traffic volume can be easily investigated.
JP-A-11-015943

  However, in the conventional traffic volume survey system described above, a dedicated device equipped with a sensor must be installed at the location where the traffic volume survey is to be performed. Moreover, a total of two such dedicated devices must be installed, one on the upstream side and one on the downstream side of the road. When conducting traffic volume surveys at multiple locations, more dedicated equipment is required. As described above, since the conventional traffic survey system requires installation of many dedicated devices, there is a problem that the traffic survey takes a lot of time and cost. In order to solve this problem, it is considered desirable to conduct traffic surveys using general-purpose devices used for other purposes, not special devices for traffic surveys.

  Therefore, an object of the present invention is to provide a system capable of conducting a traffic volume survey without installing special equipment.

  The object of the present invention includes an access point for connecting to the Internet installed near the road and a wireless terminal mounted on a vehicle, the access point including means for connecting the wireless terminal to the Internet, and the wireless It is achieved by a traffic survey system comprising means for counting the vehicles passing on the road based on the number of connected terminals. According to the present invention, since the traffic volume is investigated using an Internet connection access point that will be installed near the road in the near future, it is possible to investigate the traffic volume without using special equipment. Can do. The “means” herein includes both those realized by hardware and those realized by software, and single hardware and single software are realized by the above two means. It does not matter even if it has the function to be.

  The object of the present invention also includes at least one access point for internet connection installed near the road, the access point comprising means for connecting a wireless terminal mounted on a vehicle to the internet, and the wireless terminal It is also achieved by a traffic survey system characterized by comprising means for counting the vehicles passing on the road based on the number of connections.

  In a preferred embodiment of the present invention, the access point includes a directional antenna, a change in received signal strength of a signal from the wireless terminal mounted on the vehicle approaching the access point, and the vehicle moving away from the access point. Means for determining a traveling direction of the vehicle passing on the road based on a difference from a change in received signal strength of a signal from the mounted wireless terminal. According to this, there is no need to install a total of two dedicated devices, one on the upstream side and one on the downstream side of the road, and it is possible to determine whether to go up or down with only one device.

  In a preferred embodiment of the present invention, a plurality of the access points are provided, and a traveling direction of the vehicle passing on the road is determined based on an order in which the wireless terminal connects to each access point. . According to this, it is possible to reliably determine the traveling direction of the vehicle.

  In a further preferred embodiment of the present invention, the access point is a wireless LAN access point. According to this, a traffic survey system can be constructed using a highly versatile system.

  The object of the present invention is also provided with an access point for Internet connection installed near the road, a wireless terminal mounted on a vehicle, and a server connected to the access point via the Internet. The point comprises means for connecting the wireless terminal to the Internet, and means for transferring information relating to the connection of the wireless terminal to the access point to the server, wherein the server connects the wireless terminal to the access point. The present invention is also achieved by a traffic survey system comprising means for counting the vehicles passing on the road based on connection. According to this, the processing load of the access point can be reduced.

  According to the present invention, it is possible to investigate the traffic volume without using special equipment. In addition, it is possible to determine whether the vehicle travels in the upward or downward direction using a single access point.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram for explaining an outline of a traffic volume survey system according to a preferred embodiment of the present invention.

  The traffic volume survey system according to the present invention surveys traffic volume using an access point for Internet connection. As shown in FIG. 1, an access point (AP) 11 installed on a road serving as a survey point. And a wireless terminal 13 mounted on the vehicle 12.

  The access point 11 counts the number of vehicles passing through the survey point by counting the number of connection nodes, and at the same time, determines the traveling direction of the vehicle, that is, whether the vehicle is an ascending vehicle or a descending vehicle. Hereinafter, a method for determining the traveling direction of the vehicle will be described.

  First, the access point 11 includes a directional antenna, has an output of f [dBm] in one direction of the road (for example, the upward direction), and is larger in the reverse direction (downward direction) b. It has an output of [dBm]. FIG. 2 is a graph showing an example of the horizontal characteristic of such a directional antenna. As shown in FIG. 2, the gain of this directional antenna is maximum in the 0 ° direction and minimum in the 180 ° direction.

  When a signal with an output A [dBm] is transmitted from the wireless terminal 13 to the access point 11 having such a directional antenna, the access point 11 receives a signal from the wireless terminal 13, but FIG. Thus, when the vehicle 12 is located on the upstream side of the access point 11, the reception gain of the transmission signal is (A + f) [dBm], and when the vehicle 12 is located on the downstream side of the access point 11, (A + b ) [DBm].

As shown in the figure, when the vehicle 12 travels in the downward direction at a speed v [m / s] and gradually approaches the access point 11, a signal transmitted from the vehicle 12 at a distance L from the access point 11. The received signal strength (RSSI) can be expressed as follows.
RSSI∝ (A + f) / (L−vt) (1)

On the other hand, when the vehicle 12 traveling in the downward direction at the speed v [m / s] passes through the installation point of the access point 11 and gradually moves away from the access point 11, the vehicle 12 at a position away from the access point 11 by the distance L. The received signal strength (RSSI) of the signal transmitted from can be expressed as follows.
RSSI∝ (A + b) / (L−vt) (2)

  3 and 4 are graphs showing changes in received signal strength (RSSI).

  As shown in FIG. 1, when the vehicle 12 traveling at a speed v [m / s] passes near the installation point of the access point 11, the received signal strength (RSSI) increases as the vehicle 12 approaches the access point 11. It gradually increases, reaches a peak when it is closest to the access point 11, and gradually decreases as it moves away from the access point 11. Here, when the vehicle 12 travels in the downward direction, the change in RSSI becomes a graph as shown in FIG. 3 based on the above formulas (1) and (2), and the vehicle 12 travels in the upward direction. In this case, the RSSI changes as shown in FIG. Therefore, it is possible to determine whether the vehicle is going up or down from the difference in the RSSI pattern.

  FIG. 5 is a block diagram schematically showing the configuration of a traffic volume survey system according to a preferred embodiment of the present invention.

  As shown in FIG. 5, this traffic survey system 10 includes a plurality of access points 11 installed on the road, wireless terminals 13 mounted on vehicles 12 traveling on the road, and access points via the Internet 14. 11 is connected to the server 15.

  The access point 11 is a relay device for connecting the wireless terminal 13 to the Internet 14, and relays packets from a node on the wireless network to a node on the wired network and from a node on the wired network to a node on the wireless network. To do. The access point 11 is installed at predetermined intervals along the road so that a plurality of wireless terminals can be simultaneously connected and an Internet connection can be provided as a roaming service. As the access point 11, for example, a wireless LAN access point based on the IEEE802.11 standard can be used, but other network devices can also be used. When a wireless LAN access point based on the IEEE802.11 standard is used, a traffic survey system based on a highly versatile system can be constructed. As a result, the user can connect to the Internet 14 from the wireless terminal 13 via the access point 11 while the vehicle 12 is traveling, and receive services such as a navigation system and traffic jam information. In addition, the access point 11 has the connection node counting function described above, and thus has a function of counting the number of vehicles passing on the road and examining the traffic volume.

  The wireless terminal 13 is a vehicle-mounted wireless device for connecting to the Internet 14 via the access point 11 and is a node connected to the network. The wireless terminal 13 has hardware necessary for realizing a navigation system and a traffic jam information providing system. For example, a personal computer or PDA equipped with a network device corresponding to the access point 11 can be used. The wireless terminal 13 is preferably mounted on all vehicles traveling on the road, but may be mounted only on a specific vehicle to be investigated. If all vehicles are equipped with wireless terminals, a complete traffic survey can be conducted.

  The server 15 performs overall management of each access point 11 and aggregates and manages traffic volume. The server 15 can be configured using a general computer and is connected to each access point 11 via the Internet 14. The server 15 counts the vehicles passing on the road based on the information sent from the access point 11, and determines the traveling direction of the vehicles.

  FIG. 6 is a block diagram schematically showing the configuration of the access point 11.

  As shown in FIG. 6, the access point 11 includes a wireless network interface unit 21, a wired network interface unit 22, a system controller 23, and a memory 24. The wireless network interface unit 21 is an interface for connecting to a wireless network, and realizes network connection with the wireless terminal 13. The wireless network interface unit 21 includes a directional antenna 21X. The wired network interface unit 22 is an interface for connecting to a wired network, and realizes Internet connection. The system controller 23 controls the wireless network interface unit 21 and the wired network interface unit 22 to control packet relay processing. The memory 24 serves as a normal memory and a buffer memory, and records software and various data.

  The access point 11 realizes a bridge function for connecting the wireless terminal 13 to the Internet 14 in cooperation with the hardware and software described above, and realizes a function for counting the number of connected nodes. As described above, reception signal strength (RSSI) monitoring / recording, node connection processing, counting of the number of nodes, recording of count values, and the like are performed.

  FIG. 7 is a flowchart showing a vehicle counting procedure by the access point 11.

  As shown in FIG. 7, the access point 11 broadcasts a beacon (S71), and when the wireless terminal 13 detects a beacon when the vehicle 12 enters the communication area of the access point 11 (S72Y), the wireless terminal An RTS (Request To Send) signal is transmitted from 13 (S73). When the access point 11 receives the RTS signal from the wireless terminal 13 (S74Y) and transmits a CTS (Clear To Send) signal in response (S75), the wireless terminal 13 that has received the CTS signal receives an ACK (Acknowledge). A signal is transmitted (S76Y, S77). Then, when the access point 11 receives the ACK signal, a network connection is established and communication is started (S78Y, S79). At this time, the access point 11 constantly monitors the RSSI during communication, and records the RSSI from the start to the end of the network connection in the memory (S80).

  Thereafter, when the vehicle 12 moves out of the communication area and the RSSI becomes weak and communication becomes difficult, the access point 11 disconnects the network connection of the wireless terminal 13 and ends the communication (S81). Then, the access point 11 reads the RSSI pattern from the start to the end of the network connection by the wireless terminal 13 from the memory, and compares the RSSI change with the patterns of the ascending vehicle and the descending vehicle (S82). As a result, when it is an ascending vehicle pattern, the count value of the ascending vehicle is counted up (S83), and when it is a descending vehicle pattern, the count value of the descending vehicle is counted up (S84). The count values of the ascending vehicle and the descending vehicle are transferred to the server 15 in response to a request from the server 15 or periodically (S85).

  As described above, according to the present embodiment, it is possible to investigate the traffic volume using an access point for connecting to the Internet, and use only one access point equipped with a directional antenna. Since it is possible to judge the passage of vehicles, there is no need to prepare two dedicated devices, one on the upstream side and one on the downstream side, as in the past. it can.

  In the above embodiment, only one access point is used, and the directional antenna is used as the access point antenna to determine whether it is up or down, but two or more access points are used. Up / down discrimination may be performed.

  FIG. 8 is a schematic diagram for explaining an outline of a traffic volume survey system according to another preferred embodiment of the present invention.

  As shown in FIG. 8, in this system, two access points including a first access point 11X and a second access point 11Y installed on the road are used. Access points 11X and 11Y are arranged at a certain distance along the road so that their communication areas do not overlap each other.

  As shown in the figure, when the vehicle 12 is traveling in the downward direction, the wireless terminal 13 mounted on the vehicle 12 is first connected to the first access point 11X, and then connected to the second access point 11Y. Therefore, it can be determined that the vehicle 12 is traveling in the downward direction. On the other hand, when the vehicle 12 is traveling in the upward direction, the vehicle is traveling in the upward direction because it is first connected to the second access point 11Y and then to the first access point 11X. Can be judged. As described above, the connection status of the wireless terminal 13 and the data of the time are transferred from the access points 11X and 11Y to the server 15 and processed by the server 15, and the vehicle uphill at the installation point of the access point 11X or the access point 11Y.・ Descent is judged.

  As described above, according to the present embodiment, the traveling direction of the vehicle is determined from the difference in timing at which the wireless terminal is connected to the plurality of access points installed on the road, so the traveling direction of the vehicle is reliably determined. In addition, it is not always necessary to employ a directional antenna as in the above embodiment.

  The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

  For example, in the above embodiment, the case where the access point is installed on the road has been described. However, the present invention is not limited to this. For example, the access point is located near the road such as a roadside (roadside) or a median. It only has to be installed.

  In the above embodiment, the case where the access point includes means for counting the passage of the vehicle and means for determining the traveling direction of the vehicle has been described. However, such a function may be provided on the server side. Absent. In other words, by sending necessary information from the access point to the server, the server counts up and down vehicles. As information to be sent from the access point to the server at this time, for example, information on connection to the access point of the wireless terminal, such as data notifying that there is a node connection, received field strength (RSSI) data over time, etc. . In this way, since the main processing relating to the traffic volume survey is performed on the server side, the access point only needs to perform processing relating to the Internet connection of the wireless terminal, and the processing load on the access point can be reduced.

FIG. 1 is a schematic diagram for explaining an outline of a traffic volume survey system according to a preferred embodiment of the present invention. FIG. 2 is a graph showing an example of the horizontal characteristic of such a directional antenna. FIG. 3 is a graph showing changes in received signal strength (RSSI). FIG. 4 is a graph showing changes in received signal strength (RSSI). FIG. 5 is a block diagram schematically showing the configuration of a traffic volume survey system according to a preferred embodiment of the present invention. FIG. 6 is a block diagram schematically showing the configuration of the access point 11. FIG. 7 is a flowchart showing a vehicle counting procedure by the access point 11. FIG. 8 is a schematic diagram for explaining an outline of a traffic volume survey system according to another preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Traffic survey system 11 Access point 11X Access point 11Y Access point 12 Vehicle 13 Wireless terminal 14 Internet 15 Server 21 Wireless network interface part 21X Directional antenna 22 Wired network interface part 23 System controller 24 Memory

Claims (6)

An access point for Internet connection installed near the street,
With a wireless terminal mounted on the vehicle,
The access point is
Means for connecting the wireless terminal to the Internet;
Means for counting the vehicles passing on the road based on the connection of the wireless terminals ;
A directional antenna,
Difference between change in received signal strength of signal from the wireless terminal mounted on the vehicle approaching the access point and change in received signal strength of signal from the wireless terminal mounted on the vehicle moving away from the access point And a means for determining a traveling direction of the vehicle passing on the road based on the traffic volume. Including at least one access point for internet connection installed near the road,
The access point is
Means for connecting a wireless terminal mounted on a vehicle to the Internet;
Means for counting the vehicles passing on the road based on the connection of the wireless terminals ;
A directional antenna,
Difference between change in received signal strength of signal from the wireless terminal mounted on the vehicle approaching the access point and change in received signal strength of signal from the wireless terminal mounted on the vehicle moving away from the access point And a means for determining a traveling direction of the vehicle passing on the road based on the traffic volume.   The traffic survey system according to claim 1, wherein the access point counts a vehicle traveling in the upward direction and a vehicle traveling in the downward direction on the road. A plurality of the access points, the wireless terminal to any one of claims 1 to 3, characterized in that to determine the traveling direction of the vehicle passing through the road based on the order to connect to each access point The traffic survey system described. The traffic survey system according to any one of claims 1 to 4, wherein the access point is a wireless LAN access point. An access point for Internet connection installed near the street,
A wireless terminal mounted on the vehicle;
A server connected to the access point via the Internet,
The access point is
Means for connecting the wireless terminal to the Internet;
Means for transferring information relating to the connection of the wireless terminal to the access point to the server,
The server
Means for counting the vehicles passing on the road based on connection of the wireless terminal to the access point ;
Difference between change in received signal strength of signal from the wireless terminal mounted on the vehicle approaching the access point and change in received signal strength of signal from the wireless terminal mounted on the vehicle moving away from the access point And a means for determining a traveling direction of the vehicle passing on the road based on the traffic volume.

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