JP5204060B2 - Wireless communication base station and control method thereof - Google Patents

Description

  The present invention relates to a radio communication technique for controlling a radio wave transmission range.

  In recent years, in the field of ITS (Intelligent Transport System), wireless communication systems for vehicles have been studied worldwide for the purpose of providing various services such as safe driving support and provision of advanced traffic information.

  These services are not provided by one-to-one communication for specific vehicles, but are often provided by one-to-many communication for vehicles existing in a specific area. For example, a radio base station is installed at an intersection with poor visibility and no traffic light, and a service for distributing road images in each direction of the intersection from this radio base station is being studied. Each vehicle that is about to enter the intersection receives the road image in the left and right direction of the intersection, which is the blind spot of the driver, and displays it on the navigation screen, etc., to inform the driver of the presence of other vehicles in the left and right direction of the intersection. Recognize and support safe driving at intersections. In the case of this service, a road image in a certain direction is distributed in an area where the direction of the road image is a blind spot of the driver. That is, in the case of a crossroad intersection, the direction of the road orthogonal to the shooting direction of the road video is the distribution target area. As described above, in the vehicular wireless communication system, the distribution target area is often different depending on the content of the service.

  In wireless communication, when a non-directional antenna such as a dipole antenna installed vertically is used, radio waves are emitted uniformly in all directions, so that radio waves are emitted to areas that are not targeted for distribution. . This not only consumes unnecessary power, but also causes radio wave interference with communications of other services such as inter-vehicle communications, which may cause a reduction in wireless communication efficiency. For this reason, it is desirable that radio waves emitted from the radio base station be emitted only within the distribution target area requested by the service.

  In order to solve the above problem, a directional antenna such as a Yagi antenna that can limit the radio wave transmission range is conventionally used. For example, a radio base station of a cellular phone divides a service area called a cell into sub-areas called sectors by directional antennas, thereby limiting the radio wave transmission range when communicating with individual mobile terminals. The capacity is increased (see Non-Patent Document 1). In addition, the development of antennas using a technique called adaptive beam forming that adaptively controls the radio wave transmission range, such as adaptive array antennas, is also underway. Adaptive beam forming is a technology that adaptively directs the antenna directing surface in the direction of a communication target based on the direction of arrival of a received wave from the communication target. Since radio waves are emitted only for communication targets, radio wave interference with other communications can be minimized.

  In the technique described in Patent Document 1, the distribution of vehicles is detected by a sensor such as a camera, the area to be distributed is calculated, and the radio wave transmission range is controlled by an adaptive array antenna. When one-to-many communication is performed using an adaptive array antenna, it is necessary to calculate the direction in which all target vehicles exist and generate an integrated beam pattern that covers those directions. However, as the number of vehicles increases, the processing time becomes enormous and difficult to realize. Therefore, in Patent Document 1, the communication area is divided into several subareas in advance, and the beam is subdivided in units of subareas based on the detected vehicle distribution. The pattern is controlled. As a result, even in one-to-many communication, it is possible to control so as to transmit radio waves only in an area where the vehicle exists without requiring much processing time.

JP 2007-228196 A

Supervised by Yoshiyuki Takeda, “Radio / Frequency Textbooks in the Wireless Broadband Era”, Impress R & D, published on March 4, 2008, pages 123-124.

  However, the technology described in Non-Patent Document 1 detects and manages in which sector or in which direction each wireless terminal unit, and controls the radio wave transmission range based on it. Therefore, it is difficult to apply to one-to-many communication for an unspecified large number within a distribution target area and to control a radio wave transmission range according to a request for specifying a distribution area for each service (hereinafter referred to as a distribution area request). .

  Moreover, since the technique described in Patent Document 1 controls the radio wave transmission range in a unified manner according to the vehicle distribution, the radio wave transmission range cannot be controlled according to the distribution area request for each service.

  That is, the conventional technology has a problem that it is impossible to control the radio wave transmission range according to the distribution area request for each service.

  In order to solve the above problems, the disclosed radio base station is connected to a plurality of directional antennas, and the directional antenna for transmitting radio waves and the transmission power of the directional antenna can be switched during data transmission.

The radio base station and the control method thereof include a distribution target area stored in a storage device in association with a service application in response to a data transmission request from a service application, and a distribution target area included in the data transmission request A wireless transmission control unit that acquires one of the distribution target areas,
A directional antenna having a communication area corresponding to the acquired distribution target area is referred to a communication area including a plurality of transmission powers for each of the plurality of directional antennas stored in the storage device. A wireless transmission pattern calculation unit that selects the transmission power of the selected directional antenna from a plurality of transmission powers, and the transmission power selected from the selected directional antennas to respond to data transmission requests from service applications According to another aspect of the disclosed radio base station, the service application distributes data corresponding to the data transmission request to the vehicles existing in the acquired distribution target area. Distribution area calculation that is a service and obtains the distribution target area where the vehicle exists from the acquired distribution target area The wireless transmission pattern calculation unit sets a distribution target area obtained by the distribution area calculation unit as a distribution target area for selecting a directional antenna and transmission power.

  Yet another aspect of the disclosed radio base station is that a plurality of directional antennas each having a communication area on the road from the intersection to each direction are connected, and the road conditions from the intersection to each direction are determined from the intersection. Service communication area management table for storing a distribution target area including a distribution target distance, antenna communication area management table for storing a communication area including transmission power corresponding to a plurality of communication distances for each of a plurality of directional antennas, and service communication A wireless transmission control unit that acquires an area subject to distribution of road conditions by referring to the area management table, and an antenna communication area management table, and refers to the directional antenna having a communication area corresponding to the acquired area to be distributed having a plurality of directivities. Select the transmission power corresponding to the communication distance selected from the antenna and satisfying the distribution target distance of the acquired distribution target area. Wireless transmission pattern calculation section that selects the transmission power corresponding to a plurality of communication distance, and, with the transmission power selected from the selected directional antenna, and a wireless communication unit for transmitting the road conditions.

  According to still another aspect of the disclosed radio base station, when there is no vehicle on the road of the acquired distribution target area, the acquired distribution target area is excluded from the selection target of the directional antenna.

  In another aspect of the disclosed radio base station, the road condition distribution target area includes a road in the direction from the intersection where the road in the direction of the road condition becomes a blind spot.

  According to still another aspect of the disclosed radio base station, the road condition is a road image obtained by photographing the road in each direction from the intersection.

  According to still another aspect of the disclosed radio base station, the road condition is vehicle information notification from a vehicle approaching an intersection.

  According to the radio communication base station of the present invention, it is possible to control a communication area for transmitting radio waves in response to a distribution area request for each service, thereby reducing the influence of radio wave interference on other communications in non-service target areas. , Power consumption can be reduced.

1 is a configuration diagram of a wireless communication system according to a first embodiment. It is a figure which shows the example of installation of a radio | wireless communications system. It is a block diagram of a radio base station. It is an example of a structure of an antenna communication area management table. It is a structural example of a service communication area management table. It is a sequence diagram which shows operation | movement of a wireless base station. It is a flowchart which shows the operation | movement of a wireless transmission pattern calculation process. 6 is a diagram illustrating an example of a wireless communication system according to a second embodiment. FIG. FIG. 10 is a sequence diagram illustrating an operation of the radio base station according to the second embodiment. FIG. 10 is a configuration diagram of a radio base station according to a third embodiment. It is a structural example of a vehicle information management table. It is a structural example of a service communication area management table. FIG. 10 is a sequence diagram illustrating an operation of the radio base station according to the third embodiment. It is a flowchart which shows the operation | movement of a delivery area calculation process.

  Hereinafter, specific examples according to the present invention will be described with reference to the drawings.

  FIG. 1 shows a system configuration of a wireless communication system according to the present embodiment. For example, the wireless communication system provides an ITS (Intelligent Transport System) service to a vehicle. As shown in FIG. 1, this wireless communication system is installed in each vehicle and receives a plurality of wireless terminals 200 for receiving ITS service data and wirelessly communicates with each wireless terminal 200 via an antenna such as a directional antenna 101. Wireless base station 100 and a network 1 for providing an ITS service via the wireless base station 100. As equipment for providing an ITS service, an ITS service center 2 is connected to the network 1, and a plurality of cameras 3 are connected to a specific radio base station 100.

  The wireless base station 100 is a communication facility for wirelessly communicating with the wireless terminal 200, and is installed at a service providing location. The radio base station 100 is connected to facilities providing ITS services such as the ITS service center 2 via the network 1 and plays a role as an access point for providing the ITS service to the radio terminal 200. ing. As shown in FIG. 2, the radio base station 100 uses a plurality of directional antennas 101-1, 101-2,... To configure a plurality of communication areas along the road direction. For example, as shown in FIG. 2, when the radio base station 100 is installed at a crossroad intersection, the communication area 102 corresponding to the road in each direction using four directional antennas 101-1,. -1,..., 102-4 are configured. In this embodiment, the individual directional antennas 101 are assigned to the roads in the respective directions. For example, the roads A100 and A101 and the roads B50 and B51, which are the same road, are assigned one directivity. A single directional antenna may be used to handle roads in multiple directions, such as using an antenna.

  The wireless terminal 200 is a wireless communication device mounted on a vehicle such as a DSRC (Dedicated Short Range Communication) vehicle-mounted device, and can access an ITS service by performing wireless communication with a nearby wireless base station 100.

  The network 1 is a communication network composed of, for example, a circuit switching network or a packet switching network, and is connected to a plurality of radio base stations 100 and facilities providing ITS services such as the ITS management center 2.

  The ITS management center 2 is a facility for an ITS service provider or country to provide and control an ITS service such as a traffic information distribution service such as a traffic jam or an intersection video distribution service.

  For example, as shown in FIG. 2, the camera 3 is installed in the vicinity of an intersection or a T-junction with poor visibility, and shoots a road image showing the situation on the road at the intersection or the T-junction. The camera 3 provides a service for distributing road images to the wireless terminal 200 via the connected wireless base station 100. For example, in FIG. 2, cameras 3-1,..., 3-4 that shoot road images in the directions of the roads at the intersection are installed, and the directional antenna 101-1 connected to the radio base station 100 is installed. ,..., 101-4, the captured road image is distributed to the communication area in the road direction orthogonal to the shooting direction. The wireless terminal 200 displays the received road image on, for example, a monitor of an in-vehicle navigation system, thereby assisting the driver to safely drive and turn left and right at intersections and T-junctions. In the present embodiment, the camera 3 is directly connected to the radio base station 100, but may be connected to the network 1.

  As shown in FIG. 3, each wireless base station 100 is connected to the network 1 and communicates with the ITS service center 2 and the like, and a plurality of directional antennas 101-1, 101-2,. A wireless communication unit 120 for performing wireless communication with the wireless terminal 200 and the like, a processor 130 for executing various arithmetic processes, and an external storage device 140 such as a hard disk drive device in which various data and programs are stored. , A ROM 150 in which various data and programs are stored in advance, a RAM 160 serving as a work area of the processor 130, and an input / output interface 170 which is an interface of the camera 3 and other input / output devices.

The network communication unit 110 is configured by a network card conforming to a wired LAN standard such as Ethernet (registered trademark), for example, and accesses the network 1 and is based on, for example, various IP (Internet Protocol) communication protocols. Send and receive the data generated. The connection form with the network 1 is not limited to a wired connection such as Ethernet, but is a wireless connection such as WiMAX (Worldwide Interoperability for Microwave Access (registered trademark)) or LTE (Long Term Evolution). There may be.

  The wireless communication unit 120 is composed of, for example, a wireless communication device compliant with a communication standard such as IEEE 802.11, and uses a wireless medium access control method such as CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance). Thus, data generated based on various communication protocols is transmitted and received. Further, a plurality of directional antennas 101-1, 101-2,... Are connected to the wireless communication unit 120, and a radio wave transmission antenna switching unit 121 that switches a directional antenna that transmits radio waves, and each directional antenna. A transmission power switching unit 122 that switches the transmission power to be output. Note that the wireless communication unit 120 is assumed to have a plurality of RF (Radio Frequency) circuits corresponding to each directional antenna, but the plurality of directional antennas share one RF circuit, The output antenna may be switched electronically by the radio wave transmission antenna switching unit 121.

  The processor 130 functionally selects a directional antenna 101 for transmitting radio waves and calculates a suitable transmission power in accordance with a request for specifying a distribution area of each ITS service (hereinafter referred to as a distribution area request). A transmission pattern calculation unit 131, a wireless transmission control unit 132 that controls the wireless communication unit 120 based on a result derived by the wireless transmission pattern calculation unit 131 at the time of data transmission, and cameras 3-1, 3-2,. And an input / output control unit (not shown) for performing input / output control on the display device, the input device, and the like.

  The external storage device 140 includes an antenna communication area management table 141 that stores information related to a communicable area of each directional antenna 101, and a service communication area management table that stores information related to a distribution area request for each ITS service. 142. The data in each of the tables 141 and 142 are manually input from the outside using a GUI (Graphical User Interface) or the like via an input / output device (not shown) such as a keyboard or the network communication unit 110. Alternatively, it may be automatically input from a specific program via an API (Application Program Interface) or the like. The external storage device 140 further stores various programs 143 executed by the processor 130 in advance. Each processing unit 131, 132 of the processor 130 functions by executing various programs 143 stored in the external storage device 140. The various programs 143 also include an ITS service program that operates in the radio base station 100.

  As shown in FIG. 4, the antenna communication area management table 141 of the external storage device 140 includes an antenna ID 1411 that is an ID for identifying each of a plurality of antennas installed in the radio base station 100, and the communication direction of the antenna. Communication direction 1412, road ID 1413 which is the ID of the road corresponding to the communicable direction of the antenna, transmission power 1414 which is a reference value of the transmission power of the antenna, and communication which is a communicable distance corresponding to the transmission power The distance 1415 and a transmission power default value 1416 that is a default value of the transmission power of the antenna are stored. In this embodiment, both the antenna communication direction 1412 and the road ID 1413 are designated, but only one of them may be designated.

  The antenna communication direction 1412 includes, for example, a front direction (direction of the main lobe of the directional antenna) in which the directional antenna faces and an angle at which communication is possible with respect to the front direction of the directional antenna. Here, for example, the direction is represented by an angle obtained clockwise from the north. For example, when the directional antenna is facing east and the communicable angle is ± 30 degrees like the directional antenna 101-2 in FIG. 2, the communication direction area 1412 of the antenna communication area management table 141 includes A value of 90 degrees meaning the east direction and a communicable angle of 30 degrees are added (corresponding to an entry with antenna ID 2 in FIG. 4). Note that these directions may be automatically acquired using a sensor such as a digital compass, or may be manually set on a setting screen or the like from an input / output device such as a keyboard.

  As the road ID 1413, for example, an identifier of a road used in a digital map used for a navigation system or the like is used. The road information of a digital map is generally composed of a “node” that means a point such as an intersection and an “arc” that means a one-way road that connects the two points as the start and end points. The radio base station 100 is installed on a node or an arc. In either case, the arc ID (arc individual number) and the node ID (node individual number) that is the end point of the arc are used. By the combination, the road in each direction as seen from the installation location of the radio base station 100 can be uniquely specified including the course direction of the vehicle. That is, the combination of the arc ID and the arc end point (node) ID corresponds to the road ID 1413. If the road ID 1413 is a bidirectional road, it can be distinguished by the traveling direction, but in this embodiment, the traveling direction is not distinguished.

  The transmission power 1414 means, for example, output power that the wireless communication unit 120 supplies to the directional antenna 101, and the output power is switched by switching the gain of the power amplifier by the transmission power switching unit 122 of the wireless communication unit 120. The value of can be switched. As transmission power increases, radio waves reach longer distances and the communicable distance also changes. For this reason, each antenna ID entry in the antenna communication area management table 141 includes a plurality of communication distance entries corresponding to the transmission power value. These values may be set, for example, by measuring the communicable distance at each transmission power value at the time of installation, or may be set adaptively by receiving feedback of the reception status from the wireless terminal 200 while operating. Also good.

  As shown in FIG. 5, the service communication area management table 142 of the radio base station 100 includes a service ID 1421 that is an ID for identifying the type of the ITS service, a distribution target direction 1422 that is a distribution target direction of the ITS service, A distribution target road ID 1423, which is road information targeted for distribution by the ITS service of the corresponding ID, is stored.

  The service ID 1421 is, for example, a port number defined in the transport layer of TCP / IP (Transmission Control Protocol / Internet Protocol). In the operation of the lower layer such as the wireless transmission control unit 132, the ITS service of the upper layer Used to identify the application.

  The distribution target direction 1422, the distribution target road ID 1423, and the distribution target distance 1424 are the direction, road, and distance corresponding to the distribution target area of the ITS service, respectively, and the data formats are the communication direction 1412 and the road of the antenna communication management table 141, respectively. This is the same as ID 1413 and communicable distance 1415. In this embodiment, both the distribution target direction 1422 and the road ID 1423 are specified, but only one of them may be specified.

The operation of the radio communication base station will be described with reference to FIG. When the ITS service application 300 operating in the radio base station 100 transmits data,
The data transmission request is output to the wireless transmission control unit 132 (S301). The data transmission request includes the service ID (S) of the ITS service application 300 in addition to the transmission data (D).

  When receiving the data transmission request, the wireless transmission control unit 132 refers to the service communication area management table 142, searches for an entry with the service ID 1421 = S, and obtains distribution target area information (R) (S302). At this time, if an entry matching service ID = S is not found, a default value in which service ID 1421 is written as “default” in service communication area management table 142 is acquired as distribution target area information (R). . Here, the distribution target area information (R) is a list of the distribution target direction 1422, the distribution target road ID 1423, and the distribution target distance 1424 of the corresponding service ID in the service communication area management table 142. For example, the distribution target area information (R) with the service ID “1000” is R = {[0, N / A, 120], [180, N / A, 120]} (where [distribution target direction, distribution Expressed as “target road ID, distribution target distance]”.

  Next, the wireless transmission control unit 132 outputs a wireless transmission pattern calculation request including the acquired distribution target area information (R) to the wireless transmission pattern calculation unit 131 (S303). The wireless transmission pattern calculation unit 131 executes a wireless transmission pattern calculation process, which will be described in detail later (S304), and obtains a wireless transmission pattern (P). Here, the wireless transmission pattern (P) is a list of antenna IDs and transmission powers of antennas that are radio wave transmission targets calculated based on the distribution target area information (R). For example, when the calculated antenna IDs of the antennas to be transmitted are “1” and “3” and the respective transmission powers are “10 dBm” and “15 dBm”, the wireless transmission pattern (P) is P = {[1 , 10], [3, 15]} (represented as [antenna ID, transmission power]). If the wireless transmission pattern (P) that satisfies the conditions of the distribution target area information (R) cannot be obtained in the wireless transmission pattern calculation process, a value (error code) indicating an error is set in the wireless transmission pattern (P). Set (eg, P = {0, 0}, etc.).

  Next, the wireless transmission pattern calculation unit 131 responds to the wireless transmission control unit 132 with the obtained wireless transmission pattern (P) (S305). Upon receiving the response, the wireless transmission control unit 132 checks whether the acquired wireless transmission pattern (P) is a normal value (is not an error) (S306). In the case of an error, a data transmission error indicating that the data transmission has not ended normally is notified to the ITS service application 300 that is the data transmission request source (S307). On the other hand, if the wireless transmission pattern (P) is a normal value, a wireless transmission request including the wireless transmission pattern (P) and transmission data (D) is output to the wireless communication unit 120 (S308). The radio communication unit 120 selects an antenna by the radio wave transmission antenna switching unit 121 and the transmission power switching unit 122 according to the radio transmission pattern (P), sets the transmission power (S309), and transmits via the directional antenna 101. A radio wave carrying data (D) is transmitted (S310).

  Through the above processing, the radio wave transmission range is controlled based on the distribution area request when each ITS service application is transmitted.

  The wireless transmission pattern calculation process (S304 in FIG. 6) will be described with reference to the flowchart shown in FIG.

  The wireless transmission pattern calculation unit 131 sets the wireless transmission pattern (P) that is the output of this processing to be null (S350), and the distribution target area (R) included in the wireless transmission pattern calculation request in step 351 is It is checked whether it is empty (Null) (S351). If it is empty, go to Step 362. In this case, since the wireless transmission pattern (P) remains empty, a value indicating an error is set in the wireless transmission pattern (P), assuming that the wireless transmission pattern (P) is not normally obtained (S363), The process ends.

  If the distribution target area (R) is not empty in step 351, the distribution target area entry (r) is extracted from the distribution target area (R) list (S352). It is checked whether or not a distribution target road ID 1423 is specified in the extracted distribution target area entry (r) (S353). If it is designated, the antenna communication area management table 141 is referred to obtain a list of antenna IDs corresponding to the designated distribution target road ID 1413 (S354), and the process proceeds to step 357. For example, when the distribution target road ID is “A100”, since the antenna ID 1411 corresponds to “1” in the antenna communication area management table 141, the list of acquired antenna IDs is {1}.

  On the other hand, if the distribution target road ID is not specified, it is checked whether the distribution target direction is specified in the distribution target area entry (r) (S355). If specified, the antenna communication area management table 141 is referred to obtain a list of antenna IDs corresponding to the designated distribution target direction (S356), and the process proceeds to step 357. For example, when the distribution target direction is “90 °”, the antenna ID corresponds to “2” in the antenna communication area management table 141, so the list of acquired antenna IDs is {2}.

  If step 354 is passed, step 356 is passed, or if the delivery target direction is not specified in step 355, the process proceeds to step 357. Here, it is checked whether or not a list of antenna IDs has been acquired. If there is no corresponding antenna ID in step 354 or step 356, or if neither the distribution target road ID nor the distribution target direction is specified in the distribution target area entry (r), the list of antenna IDs cannot be acquired. Therefore, the process proceeds to step 363. In this case, it means that an invalid value has been passed as the distribution target area (R), so a value indicating an error is set in the wireless transmission pattern (P) (S363), and the process is terminated.

  On the other hand, if a list of applicable antenna IDs can be acquired in step 354 or step 356, the process proceeds to step 358.

  Note that the steps so far correspond to processing for selecting an antenna that is a radio wave transmission target of the wireless transmission pattern (P), and the processing from step 358 described below corresponds to processing for determining transmission power of each antenna. .

  The distribution target area entry (r) is referred to and it is checked whether or not a distribution target distance is designated (S358). If it is designated, the process proceeds to step 359, and the antenna communication area management table 141 is referenced to obtain the minimum transmission power value satisfying the distribution target distance for each antenna ID in the obtained antenna ID list. For example, when the acquired antenna ID list is {1} and the distribution target distance is 120 m, the minimum transmission power that satisfies the distribution target distance is 15 dBm (communication distance: 140 m) with reference to the antenna communication area management table 141 It becomes. If the transmission target distance cannot be satisfied even with the maximum transmission power value, the maximum transmission power value is set. On the other hand, if not specified, the antenna communication area management table 141 is referred to, and the default value 1416 of the transmission power is acquired for each antenna ID in the acquired antenna ID list (S360). In this way, at step 359 or 360, a list of antenna IDs and transmission power values of antennas that are radio wave transmission targets is obtained.

  The list is merged with the current value of the wireless transmission pattern (P) (S361). Returning to step 351, the same processing is executed for the other distribution target area entries.

  Returning to step 351 and executing the same processing for other distribution target area entries, for example, the following results are obtained. If the distribution target road ID 1423 is “A100” or “A101” in step 353, the antenna ID 1411 corresponds to “1” or “3” in the antenna communication area management table 141 in step 354. The list of IDs is {1, 3}. When the acquired antenna ID list is {1, 3} and each distribution target distance is 120 m, the minimum transmission power satisfying the distribution target distance is 15 dBm (communication) in all cases with reference to the antenna communication area management table 141. Distance: 140m).

  Here, merging means taking a union. That is, the merge processing in step 361 corresponds to obtaining the union of the wireless transmission patterns (p) obtained from the respective distribution target area entries (r). For example, the wireless transmission pattern (p1) obtained from the distribution target area entry (r1) is p1 = {[1, 15 dBm]} (where expressed as [antenna ID, transmission power]), the distribution target area entry (r2) When the wireless transmission pattern (p2) obtained from p2 = {[1, 10 dBm]} and the wireless transmission pattern (p3) obtained from the distribution target area entry (r3) is p3 = {[3, 15 dBm]} , P1, p2, and p3 are merged as follows. First, when antenna ID = “1” is compared between p1 and p2, since the transmission power value is p1> p2, the value of p1 remains when the union is taken. Next, when p3 is seen, antenna ID = “3” and is not included in p1 and p2, and therefore the value of p3 remains when the union is taken. Therefore, the result of merging p1, p2, and p3 is p1∪p2∪p3 = {[1,15 dBm], [3,15 dBm]}. In this way, it is possible to obtain a wireless transmission pattern (P) that satisfies the requests of all distribution target area entries (r).

  Returning to step 351, when there is no entry of the distribution target area information (R), the process proceeds to step 362. If the given distribution target area information (R) is not empty, since the value is set in the wireless transmission pattern (P) in step 361, the process ends. Through the above processing, the wireless transmission pattern (P) can be acquired in response to the request for the distribution target area (R).

  In this description, the ITS service application 300 calculates the wireless transmission pattern every time data is transmitted. However, the distribution target area information (R) set in the service communication area management table 142 is used. ) May be calculated in advance and stored in the external storage device 140 or cached in the RAM 160 and referred to during data transmission processing to replace the wireless transmission pattern calculation processing.

  As described above, in this embodiment, the distribution target area information of each ITS service specified in the service communication area management table 142 and the communication area of each directional antenna 101 specified in the antenna communication area management table 141. Based on the information, the radio wave transmission direction and distance of data transmission by the ITS service application 300 operating in the radio base station 100 are controlled. Therefore, by setting the distribution area request for each ITS service in the service communication area management table 142 in advance, the radio wave transmission direction and distance according to the distribution area request for each ITS service can be controlled. The influence of radio wave interference on other communications in the area can be reduced.

  FIG. 8 shows a wireless communication system in the present embodiment. The system configuration of the wireless communication system is the same as that shown in FIG. In FIG. 8, the same reference numerals as those in FIG.

  In the wireless communication system of the present embodiment, the wireless terminal 200 periodically transmits vehicle information to the surroundings (vehicle information notification 400). The vehicle information notification 400 includes, for example, a vehicle ID for identifying the vehicle, a time when the vehicle information is acquired, position information / speed / traveling direction of the vehicle, a road ID, and the like. Each vehicle receives vehicle information notifications 400 from other vehicles in the vicinity, thereby recognizing the running status of other vehicles in the vicinity of its own vehicle, and warns the driver or controls the running when there is a collision risk. . Thus, the vehicle information notification 400 is information indicating the situation on the road. On the other hand, at places with poor visibility, such as intersections and curves, radio waves are blocked by the presence of buildings and the like between vehicles, and the vehicles cannot communicate with each other and cannot recognize the presence of other vehicles. Therefore, a radio base station 100 is installed at an intersection or a curve where the vehicles cannot communicate directly, and the radio base station 100 detects the approach of the vehicle instead and approaches another vehicle located in the blind spot direction. By notifying the presence of the vehicle (vehicle approach notification 401), a collision accident is prevented. In the case of such a service, the target area of the vehicle approach notification 401 changes depending on which road the approaching vehicle is traveling on, so the ITS service application needs to dynamically specify the distribution target area. .

  The operation of the wireless communication system in the present embodiment will be described.

  FIG. 9 shows a flow when the ITS service application 301 operating in the radio base station 100 transmits data. The part which attached | subjected the same code | symbol as FIG. 6 of Example 1 represents the same thing.

The difference from FIG. 6 of the first embodiment is that the data transmission request (S320) of the ITS service application 301 includes the distribution target area information (R). That is, the ITS service application 301 directly specifies distribution target area information such as a distribution target direction, a distribution target road ID, and a distribution target distance at the time of request. Upon receiving the data transmission request, the wireless transmission control unit 132 extracts the distribution target area information (R), and in step 303, the wireless transmission pattern calculation unit 131 uses the acquired distribution target area information (R) as a wireless transmission pattern calculation request. To pass. In FIG. 6 of the first embodiment, it is necessary to obtain the distribution target area information (R) by referring to the service communication area management table 142 based on the service ID, but in the second embodiment, the distribution target directly from the ITS service application 301 is obtained. Since the area information (R) is passed, the processing in step 302 in FIG. 6 is not necessary. The subsequent processing is the same as in FIG.
As in the first embodiment, the correspondence relationship between the distribution target area information (R) and the wireless transmission pattern (P) is cached on the RAM 160 or the like and referenced so that the wireless transmission pattern calculation process S304 is performed. It may be omitted.

  As described above, in this embodiment, since the ITS service application 301 can designate the distribution target area (R) for each data transmission, the ITS service application 301 dynamically distributes the distribution target area (R) according to the situation. R) can be changed.

  Therefore, in this embodiment, since the distribution target area can be specified for each data transmission, it is possible to cope with the case where the distribution target area dynamically changes depending on the situation, and radio wave interference with other communications in the non-service target area. Can reduce the effects of

  In the vehicle approach notification 401 in FIG. 8 according to the second embodiment, the blind spot direction of the approaching vehicle is the distribution target area, but even the vehicle located in the distribution target area moves away from the radio base station 100 installed at the intersection. It is not necessary to distribute the vehicle traveling in the direction, and only the vehicle traveling in the direction approaching the intersection where the radio base station 100 is originally installed is targeted for distribution. That is, when there is only a vehicle traveling in a direction away from the intersection on the distribution target area, it is not necessary to distribute the vehicle approach notification 401 from the radio base station 100. Conversely, it may cause interference with other communications such as the vehicle information notification 400, and it is desirable to avoid unnecessary delivery as much as possible. In the wireless communication system according to the present embodiment, unnecessary distribution is prevented based on the state of the vehicle on the distribution target area.

  As shown in FIG. 10, the radio base station 100 according to the present embodiment includes a vehicle information management unit that manages peripheral vehicle information acquired by the vehicle information notification 400 from the radio terminal 200 in the processor 130 in addition to the configuration of FIG. 3. 133 and a distribution area calculation unit 134 that calculates an actual distribution area according to the vehicle distribution and the like, and vehicle information in which peripheral vehicle information managed by the vehicle information management unit 133 is stored in the external storage device 140 A management table 144 is provided. Note that in this embodiment, items are added to the service communication area management table 142 of FIG. 3 as described later, so that the service communication area management table 145 is shown in FIG.

  As shown in FIG. 11, the vehicle information management table 144 of the external storage device 140 includes, for example, a vehicle ID 1441 that is an ID of a target vehicle of vehicle information, and a time stamp 1442 that is a time when the vehicle information is acquired by the transmission source vehicle. Latitude 1443 / longitude 1444 which is the position (latitude / longitude) of the vehicle at the acquisition time of the vehicle information, speed 1445 which is the speed of the vehicle at the acquisition time of the vehicle information, and at the acquisition time of the vehicle information The traveling direction 1446 that is the traveling direction of the vehicle and the road ID 1447 that is the ID of the road on which the vehicle is traveling at the time when the vehicle information is acquired are stored. Here, the vehicle ID 1441 is a unique number assigned to the vehicle such as a chassis number, for example.

  As shown in FIG. 12, the service communication area management table 145 of the external storage device 140 is to be distributed in addition to the information 1451 to 1454 corresponding to the information 1421 to 1424 of the service communication area management table 142 of FIG. The target vehicle traveling direction area 1455 which is the traveling direction of the vehicle is stored. In the first embodiment, the target road ID 1423 is handled in a form that does not distinguish the traveling direction. In the present embodiment, the target road ID 1423 is treated in a form that distinguishes the traveling direction. That is, different road IDs are given depending on the traveling direction of the vehicle, even if the road is a bidirectional road located in the same direction as seen from the installation point (intersection) of the radio base station 100. Specifically, for example, as described above, it is expressed by a combination of an arc individual number (arc ID) meaning a one-way road and an individual node number (node ID) which is an end point of the arc in the corresponding direction. Accordingly, the notation method of the target road ID in FIG. 12 is also changed to clearly indicate the traveling direction. For example, the notation A100-S means a road whose traveling direction corresponds to the road A100 in FIG. 2 is south (S).

  The operation of the wireless communication system in the present embodiment will be described.

  When the vehicle information management unit 133 of the radio base station 100 receives the vehicle information notification 400 from a nearby vehicle, the vehicle information management unit 133 refers to the vehicle ID 1441 in the vehicle information management table 144 and searches for a corresponding entry. If there is a corresponding entry, the information is updated based on the contents of the received vehicle information notification 400. If there is no corresponding entry, a new entry is created based on the contents of the received vehicle information notification 400. In addition, the vehicle information management unit 133 monitors the time stamp 1442 and discards (deletes) an entry whose information is not updated even after a certain period of time has elapsed from the vehicle information management table 144. Through the above processing, the vehicle information management table 144 is managed so that new vehicle information is always stored.

  FIG. 13 shows a flow when the ITS service application 302 operating in the radio base station 100 transmits data in this embodiment. In addition, since the location which attached | subjected the same code | symbol as FIG. 6 of Example 1 represents the same thing, description is abbreviate | omitted. The difference from FIG. 6 of the first embodiment is that steps 330 to 332 for calculating an actual distribution area are inserted between step 302 and step 303 according to the vehicle distribution and the like.

  After acquiring the distribution target area information (R) of the ITS service application 302 in step 302, the wireless transmission control unit 132 sends a distribution area calculation request including the distribution target area information (R) to the distribution area calculation unit 134. Output (S330). Here, the distribution target area information means a list of the distribution target direction 1452, distribution target road ID 1453, distribution target distance 1454, and vehicle traveling direction 1455 of the corresponding service ID in the service communication area management table 145. The distribution area calculation unit 134 performs a distribution area calculation process (to be described later) based on the delivered distribution area information (R) (S331), and sends the calculated new distribution area information (R ′) to the distribution area calculation response. Is returned to the wireless transmission control unit 132 (S332). The wireless transmission control unit 132 checks the distribution target area information (R ′) (S333), and if the content is empty, returns a data transmission error notification to the ITS service application 302 (S334). If the contents are set, the same processing as in FIG. 6 is performed using the distribution target area information (R ′).

  Next, the process of the distribution area calculation process (S331) by the distribution area calculation unit 134 will be described using the flow of FIG.

  The distribution area calculation unit 134 first sets the distribution target area information (R ′) that is the output of this processing to be empty (S370), and the distribution target area (R) included in the received distribution area calculation request is not empty. Is checked (S371). If it is empty, the distribution area calculation process is terminated. In this case, since the delivery target area information (R ′) that is an output remains empty, a data transmission error notification is returned to the ITS service application 302 by the check in step 333 in FIG. 13, and application data is not transmitted.

  On the other hand, if the distribution target area (R) is not empty (S371: No), the process proceeds to step 372, and the distribution target area entry (r) is extracted from the distribution target area (R).

  Next, it is checked whether or not a road ID is specified in the distribution target area entry (r) (S373). If it is designated, the vehicle information management table 144 is referred to obtain a list of vehicle information entries whose road ID 1447 matches the designated road ID (S374), and the process proceeds to step 379.

  If the road ID is not specified (S373: No), it is checked whether the distribution target direction is specified in the distribution target area entry (r) (S375). If it is not specified, it means that there is no information for specifying the distribution target area, so the distribution target area information (R ′) is set to empty (S384), and the distribution area calculation process is terminated. Also in this case, a data transmission error notification is returned to the ITS service application 302, and application data is not transmitted.

  When the distribution target direction is designated (S375: Yes), the vehicle information management table 144 is referred to obtain a list of vehicle information entries located in the designated direction (S376). Specifically, vehicle position information (latitude / longitude) obtained by referring to the latitude 1443 and longitude 1444 of the vehicle information entry and the position information of the installation location of the wireless base station 100 given in advance are used. Thus, the relative distance and the relative direction are calculated. The vehicle information entry whose relative direction is the designated direction is acquired. Strict angle information is obtained as the relative direction obtained from the vehicle position information, but when it can be determined that the road direction is the same as the specified direction (for example, within ± 30 ° of the specified direction), the relative direction is It is assumed that the direction is specified.

  In step 377, the distribution target area entry (r) is referred to and it is checked whether the traveling direction of the target vehicle is specified. If not specified, the process proceeds to step 379. If it is designated, the list of the acquired vehicle information entries is referred to, only those whose traveling direction 1446 matches the designated traveling direction are extracted, and the process proceeds to step 379.

  It is checked whether the obtained list of vehicle information entries is empty (S379). If it is empty, it means that there is no vehicle to be distributed in the distribution target area entry (r), so the process returns to step 371 without adding to the output distribution target area information (R ′). On the other hand, when it is not empty, it progresses to the step (S380-S383) which determines object distance.

  The distribution target area entry (r) is referred to and it is checked whether the target distance is designated (S380). If not specified, the process proceeds to step 381 to calculate the relative distance from the radio base station 100 given in advance for each entry in the obtained list of vehicle information entries to obtain the maximum value Dmax (S381). ). In the case where it is designated, the relative distance between the radio base station 100 and each vehicle information entry is calculated in the same manner, but the maximum value Dmax below the target distance is obtained (S383). This is because when the target distance is specified, vehicles that are farther than the specified target distance are not targeted. Then, the obtained Dmax is set as the target distance of the distribution target area entry (r) and merged with the distribution target area information (R ′) (S382).

  Thereafter, the process returns to step 371 and the same processing is performed. Eventually, the distribution target area information (R) becomes empty, and the distribution area calculation process ends by the branching of step 371.

  Based on the above processing, the unnecessary area where the target vehicle does not exist is determined based on the distribution state of the surrounding vehicles obtained from the vehicle information management table 144 from the distribution target area information of the ITS service application 302 specified by the service communication area management table 145. Can be removed.

  This can also be applied to the case where the ITS service application side specifies the distribution target area information when requesting data transmission, as in the second embodiment.

  Similarly to the first embodiment, the correspondence relationship between the distribution target area information (R) and the wireless transmission pattern (P) is cached on the RAM 160 or the like and referred to so that the wireless transmission pattern calculation process (FIG. 13 S304) may be omitted.

  In this embodiment, the wireless base station recognizes the distribution state of the surrounding vehicles by transmitting the position information from the vehicle to the wireless base station. However, a sensor such as a camera is installed on the road or its surroundings. Thus, the distribution state of the vehicle may be recognized.

  Therefore, in the present embodiment, in the distribution target area for each ITS service, only the range where the service distribution target vehicle exists is extracted and the radio wave is transmitted, so that the influence of the radio wave interference on other communication in the non-service target area. Can be further reduced. In addition, when there is no service delivery target vehicle, radio wave transmission can be suppressed, so that power consumption can be minimized.

  The embodiment described above is an example, and the present invention is not limited to this. That is, various applications are possible, and all the embodiments are included in the scope of the present invention.

  For example, in the above embodiment, each process of the radio base station is realized by executing a predetermined operation program using a processor and a RAM, but may be realized by original hardware as necessary. Is possible.

  In this embodiment, the radio base station is described, but the radio terminal side may have a similar function. For example, a directional antenna facing forward and a directional antenna facing backward can be mounted on the vehicle, and the transmission direction can be switched according to the distribution area request of the in-vehicle ITS application.

  In this embodiment, only a directional antenna is used as an antenna, but an omnidirectional antenna can also be used for omnidirectional transmission. The antenna communication area management table can also represent an omnidirectional antenna by setting “omnidirectional (0 ± 360)” in the communication direction area.

  1: infrastructure network 2: ITS management center 3: camera 100: wireless base station 101: directional antenna 102: communication area 110: network communication unit 120: wireless communication unit 121: radio wave transmission antenna switching Unit: 122: transmission power switching unit, 130: processor, 131: wireless transmission pattern calculation unit, 132: wireless transmission control unit, 133: vehicle information management unit, 134: distribution area calculation unit, 140: external storage device, 141: Antenna communication area management table, 142: service communication area management table, 143: program, 144: vehicle information management table, 150: ROM, 160: RAM, 170: input / output interface, 200: wireless terminal, 300, 301, 302: ITS service application.

Claims (12)

Connect multiple directional antennas,
In response to the data transmission request from the service application, either the distribution target area stored in the storage device in association with the service application or the distribution target area included in the data transmission request A wireless transmission control unit for acquiring
A directional antenna having the communication area corresponding to the acquired distribution target area is referenced with reference to a communication area including a plurality of transmission powers for each of the plurality of directional antennas stored in the storage device. A radio transmission pattern calculating unit that selects from a plurality of directional antennas and selects transmission power of the selected directional antennas from the plurality of transmission powers;
A radio communication base station comprising: a radio communication unit that transmits data corresponding to the data transmission request from the service application with the transmission power selected from the selected directional antenna. The service application is a service that distributes data corresponding to the data transmission request to vehicles obtained in the acquired distribution target area,
A distribution area calculation unit for obtaining a distribution target area where the vehicle exists from the acquired distribution target area;
The wireless transmission pattern calculation unit sets the distribution target area obtained by the distribution area calculation unit as the distribution target area for selecting the directional antenna and the transmission power. Wireless communication base station. Connect multiple directional antennas with each communication area on the road from the intersection to each direction,
A service communication area management table for storing a distribution target area including a distribution target distance from the intersection of road conditions from the intersection to each direction;
An antenna communication area management table for storing a communication area including transmission power corresponding to a plurality of communication distances for each of the plurality of directional antennas;
A wireless transmission control unit that refers to the service communication area management table and acquires a distribution target area of the road condition;
With reference to the antenna communication area management table, a directional antenna having the communication area corresponding to the acquired distribution target area is selected from the plurality of directional antennas, and the distribution target distance of the acquired distribution target area is determined. A radio transmission pattern calculation unit that selects a transmission power corresponding to the communication distance to be satisfied from transmission powers corresponding to the plurality of communication distances; and
A radio communication base station, comprising: a radio communication unit that transmits the road condition with the transmission power selected from the selected directional antenna.   The radio communication base station according to claim 3, wherein when there is no vehicle on the acquired road of the distribution target area, the acquired distribution target area is excluded from selection targets of the directional antenna. The radio communication base station according to claim 3, wherein the distribution target area of the road condition includes a road in a direction from the intersection where a road in the direction of the road condition becomes a blind spot. 4. The radio communication base station according to claim 3, wherein the road condition is a road image obtained by photographing a road in each direction from the intersection. The radio communication base station according to claim 3, wherein the road condition is vehicle information notification from a vehicle approaching the intersection. A plurality of directional antennas each having a communication area on the road from the intersection to each direction are connected, and the distribution target area including the distribution target distance from the intersection of the road condition from the intersection to each direction is stored. And a communication communication control method in a wireless communication base station having a service communication area management table for storing communication areas including transmission power corresponding to a plurality of communication distances for each of the plurality of directional antennas Because
Refer to the service communication area management table, obtain the distribution target area of the road condition,
Referencing the antenna communication area management table, selecting a directional antenna having the communication area corresponding to the acquired distribution target area from the plurality of directional antennas,
A transmission power corresponding to the communication distance satisfying the distribution target distance of the acquired distribution target area is selected from transmission power corresponding to the plurality of communication distances;
A radio communication control method, wherein the road condition is transmitted with the transmission power selected from the selected directional antenna.   9. The wireless communication control method according to claim 8, wherein when there is no vehicle on the acquired road of the distribution target area, the acquired distribution target area is excluded from selection targets of the directional antenna. 9. The wireless communication control method according to claim 8, wherein the distribution target area of the road condition includes a road in a direction from the intersection where a road in the direction of the road condition becomes a blind spot. 9. The wireless communication control method according to claim 8, wherein the road condition is a road image obtained by photographing a road in each direction from the intersection. 9. The wireless communication control method according to claim 8, wherein the road condition is a vehicle information notification from a vehicle approaching the intersection.

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