JP6015428B2 - Wireless communication apparatus and wireless communication method - Google Patents

Description

  The present invention relates to a radio communication apparatus that performs cognitive radio communication while moving, and more particularly, to a technique for selecting a communication frequency used for cognitive radio communication.

  A system (wireless communication system) in which a plurality of wireless communication apparatuses communicate using radio is premised on communication using a frequency assigned in advance. Further, different frequencies are assigned to different wireless communication systems so that communication in the system does not interfere with communication in other systems. However, since the frequency range that can be used for wireless communication is limited, if the number of wireless communication systems increases, there may be a shortage of allocated frequencies. Therefore, a communication technology called cognitive radio communication has been attracting attention today, and research and development are being actively promoted.

  Cognitive radio communication is the following communication technology. Most wireless communication systems do not always use the assigned frequency continuously for 24 hours. Therefore, there is a time zone that is not actually used in the frequency allocated to the radio communication system. In addition, when a wireless communication system targets a certain area such as a television broadcasting station, the frequency allocated to the wireless communication system is not used outside the target area. The cognitive radio communication is a technique for performing radio communication using a frequency (called “free frequency” or “white space”) that is not used in time or place.

  In order for the wireless communication apparatus to perform cognitive wireless communication, it is necessary to acquire an available frequency. Therefore, the following techniques have been proposed. First, a communication method other than cognitive radio communication is used to connect to the nearest radio base station, and information on available frequencies that can be used at the location where the radio base station exists is acquired. And the technique which starts a cognitive radio communication based on the information of the acquired vacant frequency is proposed (patent document 1).

JP 2012-134650 A

  However, when the proposed technology is applied to a wireless communication device that performs cognitive wireless communication while moving, such as a wireless communication device mounted on an automobile, there are the following problems. That is, since the position where the wireless communication device that performs cognitive wireless communication exists and the position where the free frequency for performing cognitive wireless communication is acquired (the position of the wireless base station) do not match, the acquired free frequency is There is a problem that it cannot be used at the destination and the cognitive radio communication cannot be continued. In addition, when the wireless communication device moves outside the area that can communicate with the wireless base station, it becomes impossible to acquire a vacant frequency from the wireless base station, and it becomes impossible to continue cognitive wireless communication. It was.

  The present invention has been made in view of the above-described problems of conventional techniques, and an object thereof is to provide a cognitive radio communication technique in which communication is not easily interrupted even when a radio communication apparatus moves.

In order to solve the above-described problem, the wireless communication device and the wireless communication method of the present invention can be used when the vehicle is in a base station communication area and is in a position near the wireless base station (first area). The first cognitive radio communication is performed using the “free frequency available for cognitive radio communication in the base station communication area ”. On the other hand, if the vehicle is in the base station communication area and located at a position far away from the radio base station (second area), the current position of the vehicle can be used for cognitive radio communication at its own position. performing a second cognitive radio communication with such a free frequency. " Note that the “free frequency available for cognitive radio communication in the base station communication area ” may be stored in advance in each radio base station, but can communicate with the radio base station instead of the radio base station. The database may be stored in advance in association with each radio base station. In addition, the “free frequency available for cognitive radio communication at its own location” is stored in advance in the radio base station or database in association with each point in the second area, and a vacant frequency near the self location is stored. The frequency may be “free frequency available for cognitive radio communication at its own location”, but when starting the second cognitive radio communication, the radio base station or database is based on the self location and the available area of each free frequency. You may calculate.

In this way, when cognitive radio communication is started within the base station communication area and at a position close to the radio base station (first area), the position from the position where the vacant frequency is acquired (position of the radio base station) to the vehicle Therefore, it is highly possible that the cognitive radio communication using the “free frequency available for the cognitive radio communication in the base station communication area ” can be continued even when the vehicle moves from there. On the other hand, when cognitive radio communication is started at a position within the base station communication area and far from the radio base station (second area), the vehicle is started from the position (radio base station position) from which the vacant frequency is acquired. When the vehicle moves from there, the distance to the position where the vacant frequency was acquired (the position of the radio base station) further increases, and “ can be used for cognitive radio communication within the base station communication area. There is a high possibility that cognitive radio communication using "free frequency" cannot be continued. In this regard, in the wireless communication device and the wireless communication method of the present invention, when a vehicle is present at a position far away from the wireless base station (second region), the “free frequency available for cognitive wireless communication at its own position” is set. The used cognitive radio communication is started. For this reason, even if it is a position from which the vehicle has moved, the distance between the position where the vacant frequency is acquired and the position of the vehicle can be kept small, and the possibility that cognitive radio communication can be continued is increased. Is possible.

  In the wireless communication apparatus of the present invention described above, in addition to the second vacant frequency information, information indicating a range in which the vacant frequency indicated by the second vacant frequency information can be used may be acquired.

  In this way, when starting the second cognitive radio communication, the radio communication device can recognize the range in which the free frequency used for the second cognitive radio communication can be used. The use of the vacant frequency can be prevented. Further, when there are a plurality of idle frequencies indicated by the second idle frequency information, the second cognitive radio communication is continued for a longer time without switching the idle frequency to be used by selecting the second idle frequency having a wider usable range. It becomes possible to do.

In the above-described wireless communication apparatus of the present invention, it may be determined whether the vehicle is present in the first area or the second area based on the information on the self position and the information on the position of the radio base station. Good.

In this way, since it is determined whether the vehicle exists in the first area or the second area based on the position where the vehicle and the radio base station actually exist, the cognitive radio communication to be started (first cognitive radio communication) Alternatively, the second cognitive radio communication) can be accurately selected.

In the above-described radio communication apparatus of the present invention, it may be determined whether the vehicle is present in the first area or the second area according to the reception level of the signal received from the radio base station. .

In this way, it is possible to determine whether the vehicle exists in the first area or the second area by determining the reception level of the signal transmitted from the radio base station. Therefore, even at a position close to the radio base station, if the reception level of the beacon is low due to an external factor such as a shielding object, it is determined as the second area and the second cognitive radio communication is started. Then, even if the beacon cannot be received thereafter, the second cognitive radio communication is continued as it is. That is, it is possible to continue the second cognitive radio communication even at a position where the beacon cannot be received due to an external factor such as a shield although it is close to the radio base station.

  In addition, in the above-described wireless communication device of the present invention, when there are a plurality of free frequencies indicated by the second free frequency information when starting the second cognitive wireless communication, the wireless communication device is adjacent to a wireless base station that can currently communicate. The idle frequency that can be used also in the radio base station may be preferentially selected and the second cognitive radio communication may be started.

  In this way, in the state where the second cognitive radio communication is performed, when moving away from the currently communicable radio base station toward another adjacent radio base station, the vacant frequency being used is continued. Can be used. In addition, the radio base station that can communicate with the radio base station that is currently communicable is a radio base station that is communicable with or intersects with a radio base station that is currently communicable, or within a predetermined distance between communicable ranges. An example is a radio base station.

  In the above-described wireless communication apparatus of the present invention, when switching from the first cognitive wireless communication to the second cognitive wireless communication, there are a plurality of free frequencies indicated by the second free frequency information, and the plurality of free frequencies. If the idle frequency used in the first cognitive radio communication before switching is included, the idle frequency may be selected to start the second cognitive radio communication.

  If it carries out like this, when switching from 1st cognitive radio communication to 2nd cognitive radio communication, it will become possible to continue using the idle frequency in use.

It is explanatory drawing which showed notionally the mode that the vehicle 10 performed cognitive radio | wireless communication using the idle frequency of television. It is explanatory drawing which shows the rough radio | wireless communications system 1 for the vehicle 10 to perform cognitive radio | wireless communication. It is explanatory drawing which shows the structure of the radio | wireless communication apparatus 100 of a present Example. It is a flowchart of the communication control process which the vehicle 10 of a present Example performs at the time of cognitive radio | wireless communication. 2 is an explanatory diagram conceptually showing a base station communication area of a radio base station 2. FIG. It is explanatory drawing which shows the effect when the "area | region which can use the same idle frequency" switches in the vicinity of a base station communication area. 10 is an explanatory diagram conceptually showing a method of selecting “free frequency corresponding to self position” in Modification 1. FIG. 10 is a flowchart showing a second cognitive radio communication stop process of Modification 1; FIG. 10 is an explanatory diagram conceptually showing a method of selecting “an empty frequency corresponding to a self-position” in Modification 2; 12 is an explanatory diagram conceptually showing a method of selecting “free frequency corresponding to self position” in Modification 3. FIG.

Hereinafter, examples will be described in order to clarify the contents of the present invention described above.
A. Device configuration :
First, an outline of cognitive radio communication performed in the vehicle 10 equipped with the radio communication device 100 of the present embodiment will be briefly described. In this embodiment, cognitive radio communication is performed using a television broadcast frequency. A unique frequency is assigned to each television broadcast station, and each television broadcast station transmits a television signal toward each area using the assigned frequency. In this embodiment, the description will be made assuming that cognitive radio communication is performed using a vacant frequency for television broadcasting, but of course, the present embodiment is performed in exactly the same manner when cognitive radio communication is performed using a vacant frequency other than for TV broadcasting. The example wireless communication apparatus 100 can be applied.

  FIG. 1 conceptually shows a plurality of television broadcasting stations A to C and areas RA to RC in which the television broadcasting stations transmit television signals. For example, the television broadcast station A transmits a television signal to the region RA, the television broadcast station B transmits a television signal to the region RB, and the television broadcast station C transmits a television signal to the region RC. In addition, each of the television broadcast stations A to C transmits a television signal using a unique frequency assigned in advance. Therefore, in the area RA, the frequency assigned to the television broadcast station B or the television broadcast station C is not used, and in the area RB, the frequency assigned to the television broadcast station A or the television broadcast station C is not used. . Similarly, in the area RC, the frequency allocated to the television broadcast station A or the television broadcast station B is not used. The vehicle 10 performs cognitive radio communication with other vehicles (not shown) using these unused frequencies (vacant frequencies). In addition, each area | region RA-RC where each television broadcasting station A-C transmits a television signal is a vast thing which has a radius of several tens Km. On the other hand, the range in which the vehicle 10 can communicate with other vehicles is typically about 100 m to 150 m in radius. As described above, the areas RA to RC, the communication area of the vehicle 10, and the size of the vehicle 10 are greatly different in digit, but for convenience of display, they are displayed at a ratio different from the actual ratio in FIG. Yes.

  FIG. 2 shows a rough wireless communication system 1 for the vehicle 10 to perform cognitive wireless communication. As shown in the figure, the vehicle 10 is equipped with the wireless communication device 100 of the present embodiment and can be connected to the wireless base station 2. The radio base station 2 is connected to the database 4 through the public communication line network 3. The database 4 stores a large amount of information relating to vacant frequencies. The wireless communication device 100 can acquire necessary data by exchanging data with the vehicle control unit 12 that controls the vehicle 10. The radio base stations 2 are installed in various locations according to the output intensity, population density, and the like of each radio base station 2.

  FIG. 3 shows a detailed configuration of the wireless communication apparatus 100. As shown in the figure, a wireless communication device 100 according to the present embodiment includes a GPS unit 108 and a communication control unit connected to the communication control unit 102 around a communication control unit 102 that controls the overall operation of the wireless communication device 100. The wireless communication unit 104 and the storage unit 106 are connected to the terminal 102 via the bus 110. Among them, the wireless communication unit 104 controls processing of performing wireless communication with the wireless base station 2 (see FIG. 2), other vehicles, and the like under the control of the communication control unit 102. In addition, the storage unit 106 stores the processing result of the communication control unit 102 and various data obtained along with the communication. The GPS unit 108 receives a GPS signal from a GPS satellite (not shown) and detects the current position.

B. Communication control processing:
FIG. 4 shows a flowchart of communication control processing executed when the wireless communication apparatus 100 performs cognitive wireless communication. This process is started by the communication control unit 102 by the operation of the driver of the vehicle 10 or in response to a request from the vehicle control unit 12. When the communication control process is started, first, the communication control unit 102 determines whether or not it is time to confirm reception of a beacon (S100).

  The beacon is a signal periodically broadcast from the radio base station 2, and the beacon is used for information indicating the address (destination information) of the radio base station 2 that is the transmission source and for communication with the radio base station 2. Information indicating the frequency to be used is included. In the wireless communication apparatus 100 according to the present embodiment, after confirming reception of a beacon as the communication control process is activated, reception of a beacon is confirmed every time a predetermined time (for example, 60 seconds) elapses.

  Immediately after the communication control process is activated, it is determined that it is time to confirm reception of a beacon (S100: yes). In this case (S100: yes), it is determined whether the wireless communication unit 104 has received a beacon (S102). Of course, since the beacon transmitted from the radio base station 2 reaches only a predetermined distance (for example, 200 m) from the radio base station 2, the radio communication device 100 (the vehicle 10) is ultimately determined in the determination process of S102. It is determined whether or not the wireless base station 2 is in an area where communication is possible. Hereinafter, an area where the radio base station 2 can communicate with the radio communication apparatus 100 is referred to as a “base station communication area”. Instead of the determination process of whether or not the beacon is received in S102, the wireless communication apparatus 100 (vehicle 10) is determined by performing the determination process whether or not the reception level of the beacon is the minimum reception level (for example, −82 dBm) or more. ) May exist in the base station communication area.

  If the wireless communication device 100 is present in the base station communication area as a result of the determination processing in S102 (S102: yes), “beacon reception level”, “wireless base station address” based on the beacon received from the wireless base station 2 (Destination information) ”and“ Frequency for communication with radio base station ”are specified and stored in the storage unit 106. The “beacon reception level” is the intensity of the radio wave received by the wireless communication unit 104 as a beacon, and generally (if there are few external factors such as a shielding object), Larger and smaller the further away from the radio base station 2. The “radio base station address (destination information)” is information for designating a specific radio base station 2 when transmitting a signal from the radio communication device 100, such as the MAC address of the radio base station 2. In other words, by specifying “address of radio base station (destination information)”, it is possible to specify the radio base station 2 with which the radio communication apparatus 100 can communicate. The “frequency for communication with the radio base station” is a frequency used when the radio communication apparatus 100 communicates with the radio base station 2, unlike the idle frequency used for cognitive radio communication.

  When the “beacon reception level”, “address of the wireless base station (destination information)”, and “frequency for communication with the wireless base station” are specified based on the beacon received from the wireless base station 2 in this way, It is determined whether or not the “beacon reception level” is equal to or greater than a predetermined value (eg, −70 dBm) (S106). As described above, since the reception level of the beacon corresponds to the distance from the wireless base station 2 to the wireless communication device 100, the wireless communication device 100 (vehicle 10) is determined to be wireless in the determination process in S106. It is determined whether or not it exists in a position within a predetermined distance from the base station 2 (an area including the position of the wireless communication device 2, hereinafter referred to as “first area”). As the above-described predetermined value (threshold value for determining the beacon reception level), a value obtained by adding a certain margin to the reception sensitivity of the wireless communication device 100 or the like is used.

  FIG. 5 conceptually shows the base station communication area of the radio base station 2. In FIG. 5, an outer solid circle indicates an area where a beacon can be received, that is, a base station communication area. The inner solid line circle indicates a region where the reception level of the beacon is equal to or higher than a predetermined value, that is, a “first region” which is the base station communication region and includes the position of the radio base station 2. Also, the area between the inner solid circle and the outer solid circle (hatched hatched pattern) is the area where the beacon can be received but the reception level is less than the predetermined value, that is, the base station communication area. An area outside one area (hereinafter referred to as “second area”) is shown. In the determination process of S106 in FIG. 4, it is determined whether the wireless communication device 100 (vehicle 10) exists in the first area or the second area set in this way.

  As a result, when the wireless communication device 100 exists in the first area (S106: no), the “radio base station address” specified in the process of S104 is set to the radio base station 2 specified in the process of S104. In addition, a “first free frequency list request signal for base stations” requesting a list of “free frequencies corresponding to the position of the radio base station” (hereinafter referred to as “first free frequency list”) is transmitted (S108). ). Of course, the first free frequency list request signal for the base station is transmitted from the radio communication unit 104 using the “frequency for communication with the radio base station” specified in the process of S104. When the first free frequency list request signal for the base station is transmitted to the radio base station 2 in this way, it waits until the first free frequency list is received (S110).

When the radio base station 2 receives the first free frequency list request signal for base stations from the radio communication device 100, the radio base station 2 stores the radio base station position information indicating the position of the radio base station 2 with respect to the database 4 shown in FIG. A “first free frequency list request signal for DB” requesting one free frequency list is transmitted. Here, in the database 4, the “location of the television broadcast station”, “frequency used for transmission of the television signal”, and “frequency used for transmission of the television signal” are associated with each television broadcast station. Is stored in a range that is prohibited from being used (hereinafter referred to as “prohibited range”). When the database 4 receives the first free frequency list request signal for DB from the radio base station 2, the database 4 specifies the position of the radio base station 2 based on the radio base station position information included in the signal. Subsequently, it is determined whether or not the position of the wireless base station 2 is included in the prohibited range over a preset frequency range, and the frequency where the position of the wireless base station 2 is not included in the prohibited range is determined. It is specified as “free frequency corresponding to the position of the radio base station”. Then, the specified list of “free frequencies corresponding to the position of the wireless base station” (including the case where there is one free frequency) is transmitted to the wireless base station 2 as the first free frequency list. When receiving the first free frequency list from the database 4, the wireless base station 2 transmits the received first free frequency list to the wireless communication device 100 that has transmitted the first free frequency list request signal for the base station.
The database 4 may store in advance a first vacant frequency list associated with each wireless base station 2. In this case, when the database 4 receives the first free frequency list request signal for DB from the radio base station 2, the database 4 searches the first free frequency list corresponding to the radio base station 2 and searches for the first free frequency list searched. Is transmitted to the radio base station 2.

  When the communication control unit 102 of the wireless communication device 100 receives the first free frequency list (S110: yes), any “free frequency corresponding to the position of the wireless base station” from the received first free frequency list. Is selected (S112). Then, cognitive radio communication with another vehicle is started using the selected “free frequency corresponding to the position of the radio base station” (S114). In the present embodiment, such cognitive radio communication using the “free frequency corresponding to the position of the radio base station” is referred to as “first cognitive radio communication”.

  Here, as shown in FIG. 5, when the first cognitive radio communication is started when the radio communication device 100 (vehicle 10) exists in the “first region”, the radio communication device 100 starts from the radio base station 2. Since the wireless communication apparatus 100 moves from there (possibly within a predetermined distance), there is a possibility that the wireless communication apparatus 100 exists in the base station communication area, that is, “free frequency corresponding to the position of the wireless base station”. There is a high possibility that the first cognitive radio communication using is located at a position where the first cognitive radio communication is permitted. Therefore, when the first cognitive radio communication is started when the radio communication apparatus 100 exists in the “first region”, the first cognitive radio communication using the “free frequency corresponding to the position of the radio base station” is continued. It is highly possible.

  On the other hand, when the first cognitive wireless communication is started when the wireless communication device 100 (vehicle 10) exists in the “second region”, the wireless communication device 100 is far from the wireless base station 2 (a predetermined distance). If the wireless communication device 100 moves from there, the possibility of being outside the base station communication area, that is, the “first frequency using the“ free frequency corresponding to the position of the wireless base station ”” is used. There is a high possibility of entering a region where cognitive radio communication is prohibited (portion indicated by hatching in the figure). Therefore, when the first cognitive radio communication is started when the radio communication apparatus 100 exists in the “second region”, the first cognitive radio communication using the “free frequency corresponding to the position of the radio base station” is continued. There is a risk that it will not be possible.

  Therefore, when the wireless communication device 100 (vehicle 10) is present in the “second region”, the wireless communication device 100 according to the present embodiment uses cognitive wireless communication using “free frequency corresponding to its own position” (this embodiment). In the example, it is referred to as “second cognitive radio communication”. That is, the communication control unit 102 first identifies its own position (the position of the wireless communication device 100) when it is determined in step S104 of FIG. 4 that the wireless communication device 100 exists in the second area (S106: no). (S120). This process is performed in the following procedure. The communication control unit 102 transmits a signal instructing the GPS unit 108 to detect the current position. When the GPS unit 108 receives this signal, it receives a GPS signal from a GPS satellite to detect the current position, and transmits the current position to the communication control unit 102. When receiving the current position from the GPS unit 108, the communication control unit 102 stores the received current position in the storage unit 106 as its own position.

  When the self-location is identified in this way (S120), the wireless base station 2 identified in the processing of S104 (with the “radio base station address” identified in the processing of S104) is added. A “second free frequency list request signal” requesting a list of “free frequencies” (hereinafter referred to as “second free frequency list”) is transmitted (S122). Of course, the second empty frequency list request signal includes information indicating the self-location specified in the processing of S120 (hereinafter referred to as “self-location information”). Similarly to the case where the first free frequency list request signal for the base station is transmitted, the second free frequency list request signal is transmitted using the “frequency for communication with the wireless base station” specified in the process of S104. It is transmitted from the communication unit 104. When the second free frequency list request signal is transmitted to the radio base station 2 in this way, the process waits until the second free frequency list is received (S110).

When receiving the second vacant frequency list request signal from the wireless communication apparatus 100, the radio base station 2 transmits the received second vacant frequency list request signal to the database 4 shown in FIG. 2 as it is. That is, since the second empty frequency list request signal received from the wireless communication apparatus 100 already includes information indicating the position for requesting the empty frequency (here, self-position information), it is transmitted to the database 4 as it is. . When the database 4 receives the second vacant frequency list request signal from the radio base station 2, the database 4 specifies the position of the radio communication device 100 based on the self-location information included in the signal. Subsequently, it is determined whether or not the position of the wireless communication device 100 is included in the prohibited range over a preset frequency range, and the frequency where the position of the wireless communication device 100 is not included in the prohibited range is determined. It is specified as “free frequency corresponding to the self position”. Then, the specified list of “free frequencies corresponding to the self position” (including the case where there is one free frequency) is transmitted to the radio base station 2 as a second free frequency list. When receiving the second free frequency list from the database 4, the wireless base station 2 transmits the received second free frequency list to the wireless communication device 100 that has transmitted the second free frequency list request signal.
Note that the database 4 may store a second free frequency list associated with each of a plurality of points in the second region. In this case, when the database 4 receives the second vacant frequency list request signal from the radio base station 2, the database 4 identifies the position of the radio communication apparatus 100 and is associated with the point closest to the identified position of the radio communication apparatus 100. The second free frequency list is searched, and the searched second free frequency list is transmitted to the radio base station 2.

  Upon receiving the second free frequency list (S110: yes), the communication control unit 102 of the wireless communication device 100 selects any “free frequency corresponding to its own position” from the received second free frequency list. (S112). Then, the second cognitive radio communication with another vehicle is started using the selected “free frequency corresponding to the self position” (S114). When selecting any “free frequency corresponding to the self-location” from the second free frequency list, the free frequency used in the first cognitive radio communication performed immediately before in the second free frequency list. Is present, the free frequency is selected. If it carries out like this, when switching from 1st cognitive radio communication to 2nd cognitive radio communication, it will become possible to continue using the idle frequency in use.

  As described above, there is a possibility that the first cognitive radio communication using the “free frequency corresponding to the position of the radio base station” may enter the area where the first cognitive radio communication is prohibited (outside the base station communication area) than the first area. When the wireless communication device 100 (vehicle 10) is present in the higher “second region”, the second cognitive wireless communication using the “free frequency corresponding to the self-location” is started. The “free frequency corresponding to the self position” is a free frequency that the wireless communication apparatus 100 can use within a predetermined distance from the self position. Therefore, even when the wireless communication device 100 enters the outside of the base station communication area, the second cognitive wireless communication can be continued at least until the wireless communication device 100 moves a predetermined distance.

The above describes the process when it is determined that the beacon is received in the determination process of S102 (S102: yes). On the other hand, when the beacon is not received (S102: no), it is determined whether or not the first cognitive wireless communication is being performed (S130). If the first cognitive radio communication is being performed (S130: yes), after stopping the first cognitive radio communication (S132), the process returns to the head of the communication control process and the above-described series of processes is repeated. That is, when the beacon cannot be received even though the first cognitive radio communication is being performed, the radio communication device 100 may have moved outside the base station communication area without switching to the second cognitive radio communication. Therefore, the first cognitive radio communication is stopped because there is a possibility that it has moved to an area where the use of an unused frequency in use is not permitted.
On the other hand, when the first cognitive radio communication is not being performed (S130: no), that is, when the second cognitive radio communication is being performed, and when any cognitive radio communication is not performed, the head of the communication control process Returning to the above, the above-described series of processing is repeated. In particular, when the second cognitive radio communication is being performed, the “vacant frequency corresponding to the self position” (the idle frequency that the radio communication apparatus 100 can use within a predetermined distance from the self position) is used. Since this frequency can be used even outside the base station communication area, communication is not stopped even if a beacon cannot be received.

  In addition, when returning to the head of the communication control process during the first cognitive radio communication, when the “radio base station address” specified based on the newly received beacon is the same (the process of S104), that is, the previous time When a beacon is received from the same radio base station 2 as the radio base station 2 that received the beacon, the first cognitive radio communication that is being executed is continued without newly starting the cognitive radio communication.

  Further, the straight line distance (ie, the width of the second area) from the “boundary between the first area and the second area” to the “boundary between the inside and the outside of the base station communication area” is a confirmation interval of beacon reception (for example, 60 It is preferable that the distance is longer than the distance traveled by the wireless communication device 100 (vehicle 10) during (second). This is because, when the wireless communication device 100 starts the first cognitive wireless communication in the first region, it has already passed the second region and moved to the outside of the base station communication region at the timing when the reception of the beacon is confirmed next. This is to suppress what has been done. In this way, when the radio communication device 100 moves outside the base station communication area, the second cognitive radio communication is started in the second area, so that the first cognitive radio communication is performed and the outside of the base station communication area is performed. Compared to the case of moving to, it is possible to perform cognitive radio communication for a long time.

  As described above, when the wireless communication device 100 (vehicle 10) starts in the first cognitive wireless communication when the wireless communication device 100 (vehicle 10) exists in the “first region”, the wireless communication device 100 Since the wireless communication device 100 is located near (within a predetermined distance) from the wireless base station 2, even if the wireless communication device 100 moves from there, there is a possibility that the wireless communication device 100 exists in the base station communication area, that is, “in the position of the wireless base station. There is a high probability that the first cognitive radio communication using the “corresponding idle frequency” is in a position where the first cognitive radio communication is permitted. Therefore, when the first cognitive radio communication is started when the radio communication apparatus 100 exists in the “first region”, the first cognitive radio communication using the “free frequency corresponding to the position of the radio base station” is continued. It is highly possible.

  On the other hand, when the first cognitive wireless communication is started when the wireless communication device 100 (vehicle 10) exists in the “second region”, the wireless communication device 100 is far from the wireless base station 2 (a predetermined distance). If the wireless communication device 100 moves from there, the possibility of being outside the base station communication area, that is, the “first frequency using the“ free frequency corresponding to the position of the wireless base station ”” is used. There is a high possibility of entering a region where cognitive wireless communication is prohibited (portion indicated by hatching of the dot pattern in FIG. 5). Therefore, when the first cognitive radio communication is started when the radio communication apparatus 100 exists in the “second region”, the first cognitive radio communication using the “free frequency corresponding to the position of the radio base station” is continued. There is a risk that it will not be possible.

  Therefore, when the wireless communication device 100 exists in the “second region”, the wireless communication device 100 according to the present embodiment starts the second cognitive wireless communication using the “free frequency corresponding to the self-location”. The “free frequency corresponding to the self position” is a free frequency that the wireless communication apparatus 100 can use within a predetermined distance from the self position. Therefore, even when the wireless communication device 100 enters the outside of the base station communication area, the second cognitive wireless communication can be continued at least until the wireless communication device 100 moves a predetermined distance. For example, as shown in FIG. 6, when moving from the first area to the outside of the base station communication area via the second area, the vacant frequency is switched (here, the vacant frequencies are changed from “ch1, ch2, ch3”). In the case of switching to “ch1, ch2”, the available frequency (available frequency corresponding to the self position, here ch1 or ch2) is used in the second area, so the first frequency is also outside the base station communication area. 2 cognitive radio communication can be continued.

  In addition, the beacon reception level is generally large at the peripheral position of the wireless base station 2 and decreases as the distance from the wireless base station 2 increases. However, if there is an external factor such as a shielding object, There is a possibility that the reception level of the beacon becomes low or the beacon cannot be received even at the peripheral position (position near the radio base station 2). In this regard, the wireless communication device 100 according to the present embodiment is a position where the reception level of the beacon is low due to an external factor such as a shield, even in the peripheral position of the wireless base station 2 (even in the vicinity of the wireless base station 2) Then, it judges that it is the 2nd field and starts the 2nd cognitive radio communication. Then, even if the beacon cannot be received thereafter, the second cognitive radio communication is continued as it is. That is, the second cognitive radio communication is continued even at a position where the beacon cannot be received due to an external factor such as an obstruction, although the position is in the vicinity of the radio base station 2 (position near the radio base station 2). Is possible.

C. Modified example:
Next, a modification of the present embodiment will be described.

C-1. Modification 1
FIG. 7 conceptually shows a selection method of “free frequency corresponding to self position” in the first modification. As shown in FIG. 7, when there are “ch1, ch2” as vacant frequencies in the second vacant frequency list, a vacant frequency with a wider usable range may be selected. That is, when the wireless communication device 100 receives the second free frequency list, it also receives information indicating an area where each free frequency (here, “ch1, ch2”) included in the second free frequency list can be used. To do. Then, the communication control unit 102 calculates a direction in which the wireless communication device 100 (vehicle 10) moves, and an available frequency (here “ch2”) having a longer usable distance in the direction is calculated from the second available frequency list. select. This makes it possible to continue the second cognitive radio communication for a longer time. In addition, it is good also as a structure which selects a common free frequency in the whole predetermined range including the radio | wireless communication apparatus 100 (10) from the 2nd free frequency list.

  Furthermore, when it is configured to receive information indicating an area where each free frequency included in the second free frequency list can be used, the second cognitive radio communication may be stopped as follows.

  FIG. 8 shows a flowchart showing the second cognitive radio communication stop process of the first modification. This process is executed by the communication control unit 102 every predetermined time. When the second cognitive radio communication stop process is started, the communication control unit 102 determines whether or not the second cognitive radio communication is being performed (S200). If the second cognitive radio communication is not being performed (S200: no), the second cognitive radio communication stop process is terminated as it is. On the other hand, when the second cognitive wireless communication is being performed (S200: yes), the current position (self-position) of the wireless communication device 100 (vehicle 10) is specified (S202). When the self-position is specified, it is determined whether or not the self-position is included in an area where the available vacant frequency can be used (S204). As a result, when the self-position is included in an area where the available unused frequency can be used (S204: yes), the second cognitive radio communication stop process is terminated as it is, and the second cognitive radio communication is continued. On the other hand, when the self-position is not included in the area where the available free frequency can be used (S204: no), the second cognitive radio communication is stopped (S206). In this way, it is possible to prevent an unused frequency from being used outside the usable range.

C-2. Modification 2
FIG. 9 conceptually shows a method of selecting “free frequency corresponding to self position” in the second modification. In the second modification, a case will be described in which a radio base station 2b different from the radio base station 2a that can currently communicate exists within a predetermined distance from the radio communication device 100 (or the radio base station 2a that can currently communicate). . In this case, when the wireless communication device 100 receives the second free frequency list from the database 4 via the wireless base station 2a, the wireless communication device 100 also includes available frequencies that can be used until the wireless base station 2b can communicate. Receive.

  In the second vacant frequency list (“ch1, ch2” in the figure) acquired when starting the second cognitive radio communication, there are vacant frequencies that can be used until communication with the radio base station 2b becomes possible. In this case, the frequency (“ch2” in the figure) is selected. In this way, in the state of performing the second cognitive radio communication, when moving to the direction of another radio base station 2b existing within a predetermined distance away from the currently communicable radio base station 2a, It becomes possible to continuously use the vacant frequency (“ch2” in the figure).

C-3. Modification 3
FIG. 10 conceptually shows a method of selecting “free frequency corresponding to self position” in the third modification. In the third modification, a case where there is a radio base station 2b adjacent to the currently communicable radio base station 2a (including a case where the radio base station 2a and the radio base station 2b exist within a predetermined distance) will be described. . In this case, when the wireless communication device 100 receives the second free frequency list from the database 4 via the wireless base station 2a, the wireless communication device 100 can use a free frequency (wireless base station 2b) that can be used in the base station communication area of the wireless base station 2b. The idle frequency corresponding to the position 2b) is also received.

  When there is a free frequency that can be used in the base station communication area of the wireless base station 2b in the second free frequency list ("ch1, ch2" in the figure) acquired when starting the second cognitive wireless communication. Selects the frequency ("ch2" in the figure). In this way, when moving from the currently communicable radio base station 2a to the radio base station 2b while performing the second cognitive radio communication, the unused frequency ("ch2" in the figure) in use is continued. Can be used.

C-4. Modification 4
In the above-described embodiment, if the reception level of the beacon received from the radio base station 2 is equal to or higher than a predetermined value, the first cognitive radio communication is started (determined to be the first area), and the reception level is predetermined. If it is less than the value, the second cognitive radio communication is started (determined to be the second region). However, the present invention is not limited to this configuration.

  In the fourth modification, a plurality of signals including signals other than beacons received from the radio base station 2 are measured. Then, for each of the plurality of signals, it is determined whether the reception level is equal to or higher than a predetermined value (whether it is in the first area or the second area). As a result, when the reception level of a predetermined number or more (for example, 10%) of a plurality of signals is less than a predetermined value, it is determined as the second region and the second cognitive radio communication is started. This can improve the accuracy of the start determination of the second cognitive radio communication. The plurality of signals including signals other than beacons preferably have the same transmission cycle. This can reduce the difference between the reception timings of the plurality of signals (the reception timing is the same), so whether or not the plurality of signals are equal to or more than a predetermined value when the wireless communication device 100 is present at the same position. This is because the probability that the determination can be made increases, and as a result, the accuracy of the start determination of the second cognitive radio communication can be further improved.

C-5. Modification 5:
In the above-described embodiment, which of the first cognitive radio communication and the second cognitive radio communication is started based on the beacon received from the radio base station 2 (whether it is in the first area or the second area). It was set as the structure which judges. Not limited to this, it may be configured to determine which of the first cognitive radio communication and the second cognitive radio communication is started based on the self position.

  In the fifth modification, the self position is periodically received using the GPS unit 108. Then, every time the self position is received, the distance between the radio base station 2 and the self position is calculated, and it is determined whether or not this distance is equal to or less than a preset threshold value. As a result, if the distance between the radio base station 2 and its own position is equal to or smaller than the threshold value, it is determined that the area is the first area and the first cognitive radio communication is started. Is larger than the threshold value, it is determined that it is the second area, and the second cognitive radio communication is started. The position of the radio base station 2 is specified based on a beacon transmitted by the radio base station 2. Further, as the threshold value, from the communication range of the radio base station 2 calculated in advance based on the transmission level of the radio base station 2, the reception sensitivity of the radio communication device 100, and an arbitrary radio wave propagation model (for example, a free space model). A value obtained by subtracting a certain value (for example, the distance traveled by the wireless communication device 100 (vehicle 10) during the reception interval (for example, 60 seconds) of the vacant frequency list) can be exemplified.

  As described above, the communication control unit 102 acquires first vacant frequency information indicating the vacant frequency corresponding to the position of the radio base station with which the radio communication apparatus can communicate. Therefore, the communication control unit 102 corresponds to the “first acquisition unit” in the present invention. Further, the communication control unit 102 acquires information regarding the self-position that is the current position of the wireless communication device, and acquires second free frequency information indicating a free frequency corresponding to the self-position. Accordingly, the communication control unit 102 corresponds to the “self-position acquisition unit” and the “second acquisition unit” in the present invention. In addition, the communication control unit 102 determines in which region the wireless communication device exists between the first region including the position of the wireless base station and the second region adjacent to the first region. Therefore, the communication control unit 102 corresponds to the “determination unit” in the present invention. In addition, when the wireless communication device exists in the first region, the communication control unit 102 performs first cognitive wireless communication that is cognitive wireless communication using the free frequency indicated by the first free frequency information, and the wireless communication device When it exists in the 2nd field, the 2nd cognitive radio communication which is the cognitive radio communication using the idle frequency which the 2nd idle frequency information shows is performed. Therefore, the communication control unit 102 corresponds to “communication means” in the present invention.

  As described above, the wireless communication device 100 according to the present embodiment and the modification has been described. However, the present invention is not limited to the above-described embodiment and the modification, and may be implemented in various modes without departing from the gist thereof. it can.

  For example, the wireless communication device 100 according to the present embodiment uses the “frequency for communication with the wireless base station” when transmitting signals requesting the first free frequency list and the second free frequency list to the wireless base station 2. However, it may be configured to use “the same frequency as the beacon”.

1 ... wireless communication system, 2 ... wireless base station, 3 ... public communication network,
4 ... database, 10 ... vehicle, 12 ... vehicle control unit,
DESCRIPTION OF SYMBOLS 100 ... Wireless communication apparatus, 102 ... Communication control part, 104 ... Wireless communication part,
106: Storage unit 108: GPS unit 110: Bus

Claims (7)

A wireless communication device that is provided in a vehicle and performs cognitive wireless communication with another vehicle using a vacant frequency that is not used by a party who has been assigned a frequency used for wireless communication,
First free frequency information indicating the free frequency that can be used for the cognitive wireless communication in a base station communication area in which communication is possible between the wireless communication device and the wireless base station is acquired from the wireless base station . First acquisition means;
Self-position acquisition means for acquiring information on the self-position that is the current position of the vehicle ;
Second acquisition means for acquiring, from the radio base station, second idle frequency information indicating the idle frequency that can be used for the cognitive radio communication at the self-position;
A first region including the position of the radio base station to a said base station communication area, of the second region adjacent the A base station communication area to said first area, said in any area Determining means for determining whether a vehicle exists;
When the vehicle exists in the first area, the first cognitive radio communication that is the cognitive radio communication using the idle frequency indicated by the first idle frequency information is performed, and the vehicle exists in the second area. And a communication means for performing second cognitive radio communication that is the cognitive radio communication using the idle frequency indicated by the second idle frequency information. The wireless communication device according to claim 1,
The said 2nd acquisition means is a radio | wireless communication apparatus which is a means to acquire the information which shows the range which can use the said idle frequency which this 2nd idle frequency information shows in addition to the said 2nd idle frequency information. The wireless communication apparatus according to claim 1 or 2,
The determination unit is a unit that determines a region where the vehicle is present among the first region and the second region based on the information on the self-location and the information on the location of the radio base station. apparatus. The wireless communication apparatus according to claim 1 or 2,
The said determination means is a radio | wireless communication apparatus which is a means to determine the area | region where the said vehicle exists among the said 1st area | region and the said 2nd area | region according to the reception level of the signal received from the said radio base station. A wireless communication device according to any one of claims 1 to 4,
The communication means, when starting the second cognitive radio communication, if there are a plurality of the idle frequencies indicated by the second idle frequency information, the radio base station adjacent to the radio base station that is currently communicable Wireless communication means for preferentially selecting the available frequency that can be used in the communicable range of the wireless base station existing within a predetermined distance from the vehicle , and starting the second cognitive wireless communication apparatus. A wireless communication device according to any one of claims 1 to 4,
When the communication means switches from the first cognitive radio communication to the second cognitive radio communication, there are a plurality of idle frequencies indicated by the second idle frequency information, and the idle frequencies are included in the idle frequencies. A wireless communication device that is means for starting the second cognitive wireless communication by selecting the free frequency when the free frequency used in the first cognitive wireless communication is included. A wireless communication method in which a vehicle performs cognitive wireless communication with another vehicle using a vacant frequency that is not used by a party who has been assigned a frequency to be used for wireless communication,
First vacant frequency information indicating the vacant frequency that can be used for the cognitive radio communication in a base station communication area where communication between a radio communication device provided in the vehicle and a radio base station is possible , Acquiring from the base station ;
Obtaining information about the current position of the vehicle ,
Obtaining from the radio base station second vacant frequency information indicating the vacant frequency available for the cognitive radio communication at the self-position;
A first region including the position of the radio base station to a said base station communication area, of the second region adjacent the A base station communication area to said first area, said in any area Determining whether a vehicle is present;
When the vehicle exists in the first area, the first cognitive radio communication that is the cognitive radio communication using the idle frequency indicated by the first idle frequency information is performed, and the vehicle exists in the second area. And performing a second cognitive radio communication that is the cognitive radio communication using the idle frequency indicated by the second idle frequency information.

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