JP2014042183A - Radio communication device and radio communication method - Google Patents

Abstract

[PROBLEMS] To suppress the possibility of communication trouble accompanying switching of communication frequency of cognitive radio communication.
A first vacant frequency list indicating vacant frequencies at a current position, and a second vacant frequency list indicating vacant frequencies at a radio wave non-reachable position set outside an area where radio waves from the current position can reach. And get. When selecting a communication frequency from the first vacant frequency list, the second vacant frequency list is also referred to so that the vacant frequencies included in the second vacant frequency list are also included in the vacant frequencies not included in the second vacant frequency list. Select with priority on frequency. In this way, even when moving while cognitive wireless communication is performed, switching of the communication frequency does not occur as long as it moves toward a radio wave non-arrival position whose communication frequency is included in the second vacant frequency list. For this reason, it is possible to suppress the possibility of hindering cognitive radio communication as the communication frequency is switched.
[Selection] Figure 6

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.

  However, since cognitive radio communication is a technology that uses a frequency (vacant frequency) that does not happen to be used due to time or location factors, it is not possible to continue using the communication frequency in use. In particular, when communicating with cognitive radio while moving at high speed, such as in an automobile, it is necessary to switch the communication frequency as the location moves. There is a possibility that communication may be hindered during switching of the communication frequency, and in order to reduce such time as much as possible, a technique for quickly searching for and switching to a new communication frequency to be used has been proposed ( Patent Document 1).

JP 2010-136291 A

  However, even in the proposed technology, switching of the communication frequency occurs as the location moves, and there is a possibility that cognitive radio communication may be hindered due to the switching of the communication frequency. there were.

  The present invention has been made in view of the above-described problems of the prior art, and is a technique capable of suppressing as much as possible the possibility of hindering communication due to switching of the communication frequency of cognitive radio communication. For the purpose of provision.

  In order to solve the above-described problem, when the wireless communication device and the wireless communication method of the present invention acquire information related to the current position, a first free frequency list indicating a free frequency at the current position and a radio wave from the current position are displayed. A second vacant frequency list indicating vacant frequencies at radio wave non-reaching positions set outside the reachable area is acquired. Then, a communication frequency for cognitive radio communication is selected from the free frequencies in the first free frequency list. At this time, referring to not only the first free frequency list but also the second free frequency list, priority is given to the free frequencies included in the second free frequency list over the free frequencies not included in the second free frequency list. To select. Note that “selecting a free frequency included in the second free frequency list with priority over a free frequency not included in the second free frequency list” means selecting as follows. First, there is an empty frequency (referred to as the first empty frequency here) that is included in the first empty frequency list but not included in the second empty frequency list, and the second empty frequency list also includes the second empty frequency list. When there is a free frequency (also referred to as a common free frequency here) included in the frequency list, the common free frequency is always selected. Further, when there is no common free frequency, it means selecting one of the first free frequencies.

  In this way, if the communication frequency moves toward the radio wave non-reachable position included in the second vacant frequency list even when moving while cognitive wireless communication is performed using the selected communication frequency, the communication frequency is Can continue to use. For this reason, it can suppress that switching of a communication frequency generate | occur | produces, As a result, it becomes possible to suppress a possibility that a cognitive radio | wireless communication may be interfered with the switching of a communication frequency.

  In the above-described wireless communication apparatus of the present invention, the second vacant frequency list may be acquired for a plurality of radio wave non-arrival positions. When selecting a communication frequency, the plurality of second free frequency lists are also referred to, and the free frequencies included in many second free frequency lists are given priority over free frequencies included in the second free frequency list. May be selected.

  In this way, a free frequency that can be used at more radio wave non-arrival positions can be selected as a communication frequency, so that switching of communication frequencies can be suppressed even when moving while cognitive wireless communication is performed. It is possible to suppress a situation in which communication is hindered due to switching of the communication frequency.

  Further, in the above-described wireless communication device of the present invention, that is, the wireless communication device of the present invention that acquires the second vacant frequency list for a plurality of radio wave non-arrival positions, the radio wave set within a predetermined distance from the current position. The second vacant frequency list may be acquired for the arrival position.

  Although a detailed reason will be described later, when a communication frequency is selected with reference to the second vacant frequency list acquired for a plurality of radio wave non-arrival positions, the second vacant frequency at a radio non-arrival position that is too far from the current position. Referring to the list, it becomes easy to select specific free frequencies in the first free frequency list in a concentrated manner. Therefore, if the second vacant frequency list for the radio wave non-arrival position within a predetermined distance from the current position is acquired, a specific vacant frequency in the first vacant frequency list is not intensively selected. It becomes possible to improve the utilization efficiency of the vacant frequency.

  In addition, the above-described wireless communication apparatus of the present invention, that is, wireless communication of the present invention that selects, as communication frequencies, free frequencies included in more second free frequency lists among the free frequencies in the first free frequency list. In the apparatus, there may be a case where there are a plurality of empty frequencies having the same number of second empty frequency lists included. In such a case, the available frequencies included in the second available frequency list for the radio wave non-arrival position in the predetermined direction from the current position may be preferentially selected from the plurality of available frequencies. In addition, the radio wave non-arrival position at this time is not necessarily one, and may be a plurality of radio wave non-arrival positions included in a predetermined direction having a certain width.

  When the wireless communication device is mounted on a transportation means such as a vehicle, the traveling direction of the vehicle or the like is a predetermined direction for the wireless communication device. Therefore, when there are a plurality of free frequencies having the same number of second free frequency lists included, the free frequencies included in the free frequency list for the radio non-arrival position in the predetermined direction from the current position are changed to other free frequencies. If the priority is selected, it is possible to suppress a situation where the communication frequency needs to be switched due to movement.

  Alternatively, in the wireless communication device of the present invention described above, that is, the wireless communication device of the present invention that acquires the second vacant frequency list for a plurality of radio wave non-arrival positions, a plurality of radio wave inconsistencies in a predetermined direction range from the current position. The second vacant frequency list may be acquired for the arrival position.

  When the wireless communication device is mounted on a vehicle such as a vehicle, it is unlikely that the vehicle will continue to move in the direction of retreating, so the necessity of referring to the second free frequency list in such a direction is It becomes lower than the second free frequency list in the other direction. Therefore, if the second vacant frequency list for the radio wave non-arrival position in the predetermined direction range excluding such a direction is acquired, it is possible to reduce the processing load of the wireless communication device.

  Further, in the above-described wireless communication apparatus of the present invention, the following may be performed. First, information regarding the moving direction of the wireless communication device is acquired. Then, the presence / absence of a communication frequency is determined with reference to the second vacant frequency list for the radio wave non-arrival position in the moving direction. As a result, when a communication frequency is not included in the second vacant frequency list, a new communication frequency may be selected.

  In this way, while the communication frequency is included in the second free frequency list in the moving direction, communication can be performed using the communication frequency, and therefore the frequency of switching of the communication frequency can be suppressed.

  Further, in the above-described wireless communication apparatus of the present invention, that is, when a communication frequency is not included in the second vacant frequency list in the moving direction, the wireless communication apparatus of the present invention that selects a new communication frequency is as follows. Anyway. First, when it is determined that the communication frequency is not included in the second free frequency list in the moving direction, a distance that can be communicated using the communication frequency (communication possible distance) when moving in the same direction. Is detected. Then, it may be switched to a new communication frequency at a timing according to the communicable distance.

  In this way, the communication frequency can be switched at an appropriate timing.

  In the above-described wireless communication apparatus of the present invention that switches the communication frequency at a timing according to the communicable distance, the communicable distance may be detected as follows. First, when it is determined that a communication frequency is not included in the second empty frequency list in the moving direction, an intermediate position is set between the radio wave non-arrival position and the current position corresponding to the second empty frequency list. Then, a list of vacant frequencies for the intermediate position is acquired. Then, the communicable distance may be detected with reference to a list of vacant frequencies at the intermediate position.

  By doing this, in addition to the second empty frequency list of the radio wave non-arrival position and the first empty frequency list of the current position, it is possible to refer to the list of empty frequencies at the intermediate position. Can be detected.

  Further, in the above-described wireless communication device of the present invention that detects a communicable distance, information on the moving speed of the wireless communication device is acquired, and communication possible time that is communication possible time using a communication frequency can be communicated. It may be acquired based on the distance and the moving speed, and information regarding the acquired communicable time may be transmitted.

  In this way, it is possible to notify the timing when the current communication frequency becomes unusable, so that it is possible to avoid troubles in communication due to switching of the communication frequency.

  In the above-described wireless communication apparatus of the present invention, when a communication frequency is selected, the communication frequency may be transmitted to a server connected via wireless communication.

  In this way, it is possible to start wireless communication with the wireless communication apparatus of the present invention by reading the communication frequency from the server.

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. It is explanatory drawing which illustrated the predetermined location which acquires the empty frequency list | wrist about the outside of a communication area. It is explanatory drawing which showed a mode that the vacant frequency list | wrist in the present position and a communication area | region outside in order to start cognitive radio | wireless communication was acquired. It is a flowchart of the communication frequency selection process which selects the communication frequency used for cognitive radio communication based on an idle frequency list. It is explanatory drawing which illustrated the empty frequency list outside a present position and a communication area. It is a flowchart of the first half part of the communication frequency switching process which switches a communication frequency during cognitive radio communication. It is a flowchart of the latter half part of a communication frequency switching process. It is explanatory drawing which illustrated a mode that the boundary of the present communication frequency was detected during cognitive radio | wireless communication. It is explanatory drawing which shows a mode that a new communication frequency is determined based on a moving direction and the idle frequency list of the front. It is explanatory drawing which illustrated the predetermined | prescribed location where the radio | wireless communication apparatus 100 of a modification acquires the empty frequency list | wrist outside a communication area.

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. Each television station is assigned a unique frequency, and each television station uses the assigned frequency to broadcast a television program within its own area. In this embodiment, the description will be made on the assumption that cognitive radio communication is performed using an unoccupied frequency for television broadcasting. The example wireless communication apparatus 100 can be applied.

FIG. 1 conceptually shows a plurality of television stations A to C and areas RA to RC in which each television station broadcasts a television program. For example, the television station A broadcasts a television program in the region RA, the television station B broadcasts a television program in the region RB, and the television station C broadcasts a television program in the region RC. Each television station A to C broadcasts using a unique frequency assigned in advance. Accordingly, the frequency assigned to the television station B or the television station C is not used in the region RA, and the frequency assigned to the television station A or the television station C is not used in the region RB. Similarly, in the area RC, the frequency assigned to the television station A or the television 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 station A-C broadcasts a television program is a vast thing which has a radius of several + Km. On the other hand, the area (communication area) in which the vehicle 10 can communicate with other vehicles is about 100 m to 200 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 using a mobile phone line. 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. In addition, the wireless communication device 100 can acquire necessary data by exchanging data with the vehicle control unit 12 that controls the vehicle 10 and the car navigation system 14.

FIG. 3 shows a detailed configuration of the wireless communication apparatus 100. As illustrated, the wireless communication device 100 according to the present embodiment is centered on a communication control unit 102 that controls the overall operation of the wireless communication device 100, a wireless communication unit 104, a communication frequency selection unit 106, and a storage unit. 108, a GPS unit 110, an external interface unit 112, and the like are connected by a bus 114 so as to exchange data with each other.
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 communication frequency selection unit 106 manages a process of selecting a communication frequency to be used when cognitive wireless communication is performed with another vehicle. The storage unit 108 stores various data obtained with communication. The GPS unit 110 receives a GPS signal from a GPS satellite (not shown) and detects the current position. The external interface unit 112 manages the exchange of data with other devices (such as the vehicle control unit 12 and the car navigation system 14) mounted on the vehicle 10.

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 acquires information on the current position using the GPS unit 110 (S100).
In the present embodiment, description will be made assuming that information on the current position is acquired using the GPS unit 110 built in the wireless communication device 100. However, as shown in FIG. Can be used to connect to the radio base station 2, and the current position may be acquired based on information from the radio base station 2. Alternatively, the current position may be acquired from the car navigation system 14 via the external interface unit 112. In this embodiment, the GPS unit 110 corresponds to the “current position acquisition unit” in the present invention.

When the current position is acquired, by connecting to the database 4 via the radio base station 2 and the public communication network 3, the free frequency list for the current position and the predetermined position set outside the communication area of the vehicle 10 A free frequency list is acquired (S102).
Here, the “free frequency list” is a list listing frequencies (free frequencies) that are allocated for wireless communication but are not used. 1, the vehicle 10 is in the area RA of the television station A, and therefore the frequency assigned to the television station B or the television station C and the frequency not assigned to any of the television stations A to C. And becomes an empty frequency. Therefore, when the vehicle 10 acquires the free frequency list in the region RA, the free frequency list is described in the list.
In this embodiment, the free frequency list at the current position P0 corresponds to the “first free frequency list” in the present invention. In addition, the communication control unit 102 that executes control for acquiring the free frequency list corresponds to the “first acquisition unit” in the present invention.
Further, in the wireless communication apparatus 100 according to the present embodiment, such an empty frequency list is acquired not only for the current position but also for the following multiple positions set outside the communication area.

FIG. 5 illustrates a position (list acquisition position) where the wireless communication apparatus 100 according to the present embodiment acquires the free frequency list. As shown in the drawing, the list acquisition positions are set at a total of eight locations that are separated from each other by a distance L in the front-rear and left-right directions in the moving direction of the vehicle 10 with the current position of the vehicle 10 as the center. This distance L is set to a distance that is at least twice (typically several times to about 10 times) the radius of the communication area of the vehicle 10. However, for the reason described later, it is not preferable to set the distance L too large, and the distance L is limited to a value equal to or less than a predetermined value.
Note that the current position P0 is not different from the eight list acquisition positions P1 to P8 in that the free frequency list is acquired. However, in this specification, when it is referred to as “list acquisition position”, it is set outside the communication area of the vehicle 10. It is assumed that the current position P0 is not included. Therefore, the “list acquisition position” in the present embodiment corresponds to the “radio wave non-arrival position” in the present invention.
In the present embodiment, the description is given assuming that eight list acquisition positions P1 to P8 are set, but more list acquisition positions may be set in a grid pattern with a finer pitch.
Furthermore, in the present embodiment, the description will be made assuming that the free frequency list is acquired by connecting to the database 4 via the radio base station 2 and the public communication network 3, but the database is built in the radio communication apparatus 100 in advance. In addition, a free frequency list may be acquired from this database.
In this embodiment, the free frequency list for the list acquisition positions P1 to P8 corresponds to the “second free frequency list” in the present invention, and the communication control unit 102 executes control for acquiring these free frequency lists. Corresponds to “second acquisition means” in the present invention.

  In the communication control process of FIG. 4, when the current position P0 is acquired from the GPS unit 110, eight list acquisition positions set with reference to the current position P0 and free frequency lists for nine positions of the current position P0 are stored in the database 4. (S102). The free frequency list acquired in this way is stored in the storage unit 108. In the following, the free frequency list may be simply referred to as “list”.

  Subsequently, it is determined whether or not cognitive radio communication is already being performed (S104). As described above, since the communication control process is started in response to a request from the driver of the vehicle 10 or the vehicle control unit 12, the cognitive radio communication is not yet performed immediately after the process is started. Therefore, in this case, it is determined that the cognitive radio communication is not being performed (S104: no), and the process proceeds to the process for starting the cognitive radio communication as follows.

In the process for starting the cognitive radio communication, first, it is determined whether or not all the empty frequency lists acquired for the current position P0 and the list acquisition positions P1 to P8 match (S106).
For example, as illustrated in FIG. 6A, when the vehicle 10 exists at a position far from the boundary of the region RA, the current position P0 and the list acquisition positions P1 to P8 are all within the region RA. Therefore, in such a case, all the acquired free frequency lists are the same list. Note that, as described above with reference to FIG. 1, the regions RA to RC are much wider than the communication region of the vehicle 10, and in many cases this is the state.
On the other hand, as illustrated in FIG. 6B, when the vehicle 10 is present near the boundary of the region RA, a part of the list acquisition position enters another region (region RB or region RC). . The free frequency list acquired at such a list acquisition position is different from other lists.

As a result, if all the acquired free frequency lists match (S106: yes), it is considered that the situation does not change even if any free frequency in the list is selected. Therefore, an arbitrary free frequency is selected from the list as a communication frequency (S108), and cognitive radio communication is started using the selected communication frequency (S110). Note that specific control for cognitive wireless communication is controlled by the wireless communication unit 104. Accordingly, the wireless communication unit 104 of this embodiment corresponds to “communication means” in the present invention.
On the other hand, when not all free frequency lists match (S106: no), after selecting a communication frequency by referring to all the free frequency lists (S200), the selected communication is performed. Cognitive radio communication is started using the frequency (S110). Processing for selecting a communication frequency (communication frequency selection processing) will be described in detail later.

Thereafter, it is determined whether or not an instruction to end the cognitive radio communication is instructed by the driver of the vehicle 10 or by a request from the vehicle control unit 12 (S112). When the end of communication is not instructed (S112: no) It is determined whether or not there is a boundary in the moving direction of the vehicle 10 at which the current communication frequency cannot be used (S114). As shown in FIG. 5, since the list acquisition position P2 is set in the moving direction of the vehicle 10, the communication currently being used in the list is referred to with reference to the empty frequency list acquired for the list acquisition position P2. If the frequency is not included, it can be determined that there is a communication frequency boundary. Of course, when the destination is set in the car navigation system 14, the empty frequency list of the list acquisition position closest to the direction of the destination or the guidance route may be referred to. Alternatively, it is possible to detect the moving direction of the vehicle 10 based on the history of the current position acquired in the past and refer to the empty frequency list of the list acquisition position existing in the detected moving direction.
Note that the communication control unit 102 executes processing for detecting the moving direction of the vehicle 10 based on information from the car navigation system 14 or a history of the current position. Therefore, the communication control unit 102 of this embodiment corresponds to the “movement direction acquisition unit” in the present invention. In this embodiment, the communication control unit 102 also determines whether or not a communication frequency is included in the free frequency list for the list acquisition position in the moving direction. Therefore, the communication control unit 102 of the present embodiment also corresponds to the “determination unit” in the present invention.

As a result, when the current communication frequency is included in the referenced free frequency list, it can be determined that there is no communication frequency boundary in the moving direction of the vehicle 10 (S114: no). Returning and acquiring a new current position (S100), a free frequency list for the current position P0 and the list acquisition positions P1 to P8 is acquired (S102). That is, since the vehicle 10 performs cognitive radio communication while moving, there is a possibility that the vacant frequency lists at the current position P0 and the list acquisition positions P1 to P8 are always changed. For this reason, during the cognitive radio communication, the vacant frequency list at the current position P0 and the list acquisition positions P1 to P8 of the vehicle 10 is continuously acquired.
Then, following the acquisition of these lists in S102, it is determined in S104 that “cognitive radio communication is in progress (S104: yes)”, so it is determined whether or not to end the cognitive radio communication (S112). If not (S112: no), it is determined whether there is a communication frequency boundary in the moving direction (S114). Then, when there is no communication frequency boundary (S114: no), the process returns to the top again, and the above-described processing (S100 to 104, S112, S114) is repeated.

  On the other hand, when a communication frequency boundary exists in the moving direction of the vehicle 10 (S114: yes), that is, when the current communication frequency is not included in the empty frequency list in the moving direction. Starts communication frequency switching processing to switch the current communication frequency to a new communication frequency (S300). The communication frequency switching process will be described in detail later.

  And after switching to a new communication frequency, it returns to the head of processing, acquires the present position of vehicle 10, and after acquiring the empty frequency list about current position P0 and list acquisition positions P1-P8 (S100, S102), the subsequent series of processing (104, S112, S114) is repeated. If it is instructed to end communication by the driver of the vehicle 10 or the vehicle control unit 12 while repeating such processing, it is determined that the cognitive wireless communication is ended (S112: yes), and FIG. The communication control process is terminated.

C. Communication frequency selection processing:
FIG. 7 shows a flowchart of the communication frequency selection process (S200). As described above, when the wireless communication apparatus 100 starts cognitive wireless communication, this process includes at least one list different from the other lists in the free frequency list of the current position P0 and the list acquisition positions P1 to P8. (If it is determined “no” in S106 of FIG. 4), the process is started. This process is executed by the communication frequency selection unit 106 under the control of the communication control unit 102. Therefore, the communication frequency selection unit 106 of the present embodiment corresponds to “communication frequency selection means” in the present invention.

  When the communication frequency selection process is started, first, all the free frequencies included in the free frequency list at the current position P0 are read, and each free space outside the communication area (that is, the list acquisition positions P1 to P8) is read. The number included in the frequency list is detected (S202). This is the following process.

FIG. 8 is an explanatory diagram showing how the number of free frequencies included in the free frequency list outside the communication area is detected for each free frequency included in the free frequency list at the current position P0. In the figure, an empty frequency list acquired for the current position P0 and eight empty frequency lists acquired for outside the communication area (list acquisition positions P1 to P8) are illustrated.
In the illustrated example, the five frequencies of ch2, ch3, ch5, ch7, and ch9 are described as empty frequencies in the empty frequency list at the current position P0. Also, empty frequencies are described in each of the eight empty frequency lists outside the communication area.
In S202 of the communication frequency selection process in FIG. 7, the number of five free frequencies (ch2, ch3, ch5, ch7, ch9) described in the list of the current position P0 included in the eight lists outside the communication area. Is detected. That is, if cognitive radio communication is started at the current position P0, a communication frequency must be selected from these five free frequencies. Therefore, it is evaluated whether or not each of these five vacant frequencies can be used at a position other than the current position P0.
For example, the empty frequency ch2 at the current position P0 is included in three lists: a list of the list acquisition position P1, a list of the list acquisition position P4, and a list of the list acquisition position P7. Therefore, the number of vacant frequencies ch2 is three. Similarly, other free frequencies at the current position P0 are included in the four lists of the list acquisition position P2, the list acquisition position P3, the list acquisition position P5, and the list acquisition position P6. It becomes. There are two for the empty frequency ch5, two for the empty frequency ch7, and four for the empty frequency ch9.

  As described above, when the number of free frequencies included in the list of the current position P0 is detected in the list outside the communication area (S202), the free frequency with the largest number of detected frequencies is selected (S204).

Subsequently, it is determined whether or not a plurality of empty frequencies are selected (S206). As a result, when a plurality of free frequencies have been selected (S206: yes), the free frequency with the larger number included in the list of the front list acquisition positions is selected (S208).
Here, the “front list acquisition positions” are three list acquisition positions that are a combination of the list acquisition positions closest to the moving direction of the vehicle 10 and the list acquisition positions on both sides thereof. For example, in the example shown in FIG. 5, the list acquisition position P2 in the moving direction of the vehicle 10 and the list acquisition positions P1. P3 is applicable. In addition, when a destination is set in the car navigation system 14, the list acquisition position closest to the direction of the destination or the guide route and the list acquisition positions on both sides correspond to the front list acquisition position. . In the example shown in FIG. 8, the number of free frequencies ch3 and ch9 is the largest with all four, but if only the list for the front list acquisition position is detected, the free frequency ch3 has two free frequencies. Since ch9 is one, vacant frequency ch3 is selected.
On the other hand, if it is determined in S206 that only one free frequency has been selected (S206: no), the process of selecting the free frequency having the larger number in the front list (S208) is not required. It becomes. If it is determined in S206 that there is no common free frequency, an arbitrary free frequency is selected from the list of current positions.

As described above, when one vacant frequency is selected from the list of the current position P0 (S204 or S208), a response request is transmitted to the outside of the vehicle 10 using the vacant frequency (S210). That is, it is desirable to establish communication in advance in order to exchange data with the other party (such as another vehicle) to communicate with. Therefore, in order to take a so-called “handshake”, a signal requesting transmission of a response signal (response request) is transmitted to the other party to communicate.
Then, after transmitting the response request, it is determined whether a response signal from the other party has been received until a predetermined time elapses (S212). If no response signal has been received (S212: no) Then, it is determined whether or not the number of times the response request has been transmitted at the idle frequency has reached a predetermined number (S214). As a result, if the predetermined number of times has not been reached (S214: no), whether or not a response signal has been received after a predetermined time has elapsed after transmitting a response request again using the available frequency (S210). Is determined (S212).
If a response signal is received while repeating such processing (S212: yes), communication is established. Therefore, the idle frequency is selected as the communication frequency (S218), and the communication frequency selection processing of FIG. After completing the above, the communication control process of FIG. 4 is resumed.

On the other hand, when the number of times the response request has been transmitted reaches a predetermined number without receiving a response signal (S214: yes), the use of the free frequency is abandoned and the free frequency with the next largest number is selected ( S216). In the example shown in FIG. 8, the idle frequency ch9 is selected next to the idle frequency ch3.
Then, after a response request is transmitted again using the newly selected idle frequency (S210), the following series of processes (S212 to S216) are repeated. If the number of transmissions reaches the predetermined number without receiving a response signal while repeating such processing (S214: yes), the next highest available frequency is selected (S216), and then the process goes to S210. Return and repeat the series of processes described above. On the other hand, when the response signal can be received (S212: yes), the idle frequency at that time is selected as the communication frequency (S218), and then the communication frequency selection process of FIG.
When broadcast transmission is performed without specifying a communication partner, processing for handshaking (S210 to S216) is not necessary. Therefore, in this case, after selecting a free frequency having a large number (S204 or S208), the free frequency may be immediately selected as a communication frequency (S218).

  As described above, the wireless communication device 100 according to the present embodiment is the highest in the free frequency list at the list acquisition positions P1 to P8 outside the communication area, out of the free frequencies listed in the free frequency list at the current position P0. A free frequency that is often described is selected as a communication frequency. In this way, even when the wireless communication device 100 is mounted on a transportation means that moves at a relatively high speed, such as the vehicle 10, there is a situation where the communication frequency must be switched during cognitive wireless communication for the following reason. Generation | occurrence | production can be suppressed.

  First, since the transportation means such as the vehicle 10 can travel a relatively long distance even during the cognitive radio communication, it may occur that the vehicle 10 enters another area during the communication. However, when a communication frequency is selected from the list of free frequencies at the current position P0, if a free frequency that can be used in another area is selected, there is no need to switch the communication frequency even if it enters that area. . Therefore, in the wireless communication device 100 according to the present embodiment, when a communication frequency is selected from the free frequencies included in the free frequency list at the current position P0, the wireless communication device 100 includes the largest number in the free frequency list outside the communication area. Select a free frequency. In this way, even if the vehicle 10 or the like moves during cognitive radio communication, there is a high possibility that the communication frequency in use will continue to be used, so that the occurrence of a situation that requires switching of the communication frequency can be suppressed.

  In addition, when selecting a communication frequency, priority is given to the free frequency included in the free frequency list ahead of the vehicle 10, so that the communication frequency being used can be selected even by movement during cognitive wireless communication. The possibility to continue using it as it is increased. As a result, it is possible to further suppress the occurrence of a situation that requires switching of the communication frequency.

From the viewpoint of suppressing the occurrence of a situation that requires switching of the communication frequency with the movement of the vehicle 10, a free frequency list at a position as far as possible from the current position P0 of the vehicle 10 is acquired (accordingly, It is preferable that the distance L in FIG. However, if the distance L is too large, the utilization efficiency of the vacant frequency is lowered. This is due to the following reason.
For example, as shown in FIG. 6 (a), even when the vehicle 10 is located approximately in the center of the region RA, if the distance L is increased, a free frequency list in another region around the region RA is acquired. become. Then, wherever the vehicle 10 is in the area RA, a free frequency list having the same contents is acquired, and a similar free frequency is selected from the free frequency list at the current position P0. Become. As a result, the communication frequency is concentrated on a part of the vacant frequencies and only a part of the vacant frequencies are used, so that the utilization efficiency is lowered.

  On the other hand, in the wireless communication apparatus 100 of the present embodiment, the distance L is set to a value that is not excessively large (typically, several tens times the radius of the communication area). For this reason, a part of the list acquisition positions P1 to P8 enters the other area only when the vehicle 10 is present near the boundary of the area (see FIG. 6B). The list acquisition positions P1 to P8 also exist in the same area as the current position P0 (see FIG. 6A). In this case, any free frequency is selected from the free frequency list at the current position P0 (see S106 and S108 in FIG. 4). For this reason, since the free frequency list at the current position P0 is selected as a communication frequency without bias, all the free frequencies can be used efficiently.

  Of course, even when the communication frequency is selected in this way, if the cognitive radio communication is continued for a long time, the vehicle 10 moves to the vicinity of the boundary of the region, and as a result, the boundary of the communication frequency in the moving direction. Can be detected. Alternatively, even when cognitive radio communication is started near the boundary of the region, the boundary of the communication frequency may be detected in the moving direction depending on the route on which the vehicle 10 has traveled thereafter. In such a case, “yes” is determined in S114 of the communication control process shown in FIG. 4, and the following communication frequency switching process is started.

D. Communication frequency switching processing:
9 and 10 show a flowchart of the communication frequency switching process executed by the wireless communication apparatus 100 of this embodiment for switching the communication frequency.
As shown in the figure, when the communication frequency switching process (S300) is started, a free frequency list is acquired at an intermediate position between the position (list acquisition position) where the communication frequency boundary is detected and the current position P0 (S302).

FIG. 11 illustrates a state in which an empty frequency list at an intermediate position is acquired. In the example shown in FIG. 11A, the vehicle 10 moves toward the list acquisition position P2. Except when the destination is set in the car navigation system 14, in most cases, the moving direction of the vehicle 10 is the direction of the list acquisition position P2. If the currently used communication frequency is not included in the free frequency list for the list acquisition position P2, the boundary of the communication frequency is detected (S114 of FIG. 4: yes). Subsequently, an intermediate position is set between the position where the boundary is detected (in this case, the list acquisition position P2) and the current position P0, and an empty frequency list at the intermediate position is acquired. The white square mark shown in FIG. 11 represents the intermediate position set in this way. The free frequency list at the intermediate position is also acquired by connecting to the database 4 via the radio base station 2 and the public communication line network 3.
Further, when the destination is set in the car navigation system 14, the moving direction of the vehicle 10 is not necessarily the direction of the list acquisition position P2. For example, as illustrated in FIG. 11B, when the moving direction of the vehicle 10 is the direction of the list acquisition position P1, the position where the communication frequency boundary is detected is the list acquisition position P1. Therefore, in this case, an empty frequency list is acquired by setting an intermediate position indicated by a white square between the list acquisition position P1 and the current position P0.

When the free frequency list at the intermediate position is acquired as described above (S302 in FIG. 9), it is determined whether or not a communication frequency currently in use exists in the list (S304). As a result, when there is no communication frequency in use in the free frequency list at the intermediate position (S304: no), the intermediate position also exists outside the boundary.
Therefore, a new intermediate position is set between the intermediate position and the current position P0, and a free frequency list at the new intermediate position is acquired (S306). In the example shown in FIG. 11 (a) or FIG. 11 (b), a new intermediate position (illustration is shown) between the intermediate position indicated by a white square mark in the drawing and the current position P0 of the vehicle 10. (Omitted) is set to obtain a free frequency list. Then, for the newly set intermediate position, it is determined whether there is a communication frequency currently in use in the free frequency list (S304).
If such a determination is repeated, it is determined that the communication frequency currently in use exists in the free frequency list at the intermediate position (S304: yes). Incidentally, in the example illustrated in FIG. 11, “yes” is determined in the first determination in S <b> 304.

Here, if there is a communication frequency currently in use in the free frequency list at the intermediate position (S304: yes), it can be considered that the current communication frequency can be used up to the intermediate position. Furthermore, it is considered better to switch the communication frequency when the intermediate position is reached.
Therefore, the communicable distance is detected based on the distance to the intermediate position (S308). The communicable distance is detected as follows. First, the linear distance can be immediately calculated from the position information of the current position P0 and the intermediate position. However, it does not actually move linearly. Therefore, a simple communicable distance is calculated by multiplying the linear distance by a coefficient larger than 1. Alternatively, the communicable distance may be calculated using an actual travel route with reference to map information registered in the car navigation system 14.

Subsequently, the moving speed (or average moving speed) of the vehicle 10 is acquired from the vehicle control unit 12 (see FIG. 2) mounted on the vehicle 10, and the communicable distance previously detected is determined by the acquired moving speed. By dividing, a time during which communication can be continued at the current communication frequency (communication available time) is calculated (S310).
Then, the communicable distance and the communicable time (or any one of them) are transmitted toward the other party that is cognitively communicating (S312). When broadcast transmission is performed without specifying a communication partner, the communication possible distance and communication possible time may be broadcast.
As described above, when the communicable distance and communicable time are determined and transmitted toward the communication partner (S308 to S312), a new communication frequency to be switched from the current communication frequency is determined as follows.
The processing so far (S302 to S312) is mainly executed by the communication control unit 102. Therefore, the communication control unit 102 according to the present embodiment corresponds to the “usable distance detecting unit”, “movement speed acquiring unit”, and “communication available time acquiring unit” in the present invention.

When determining a new communication frequency, first, referring to the empty frequency list at the current position P0 and the empty frequency list in the moving direction, the empty frequencies included in any empty frequency list are newly set. It is extracted as a vacant frequency (hereinafter referred to as “candidate frequency”) that is a candidate for the communication frequency (S314).
The reason why the candidate frequency is not a free frequency included in the moving direction list but a free frequency included in the current position P0 list and the moving direction list will be described later. Also, the free frequency list at the current position P0 and the free frequency list in the moving direction are already acquired in S102 of the communication control process of FIG. 4 before starting the communication frequency switching process of FIGS. 108.

FIG. 12 shows how candidate frequencies are extracted with reference to the empty frequency list at the current position P0 and the empty frequency list in the moving direction. In the illustrated example, the five free frequencies ch1, ch3, ch6, ch7, and ch9 are described in the free frequency list at the current position P0. Of these, ch3 is the communication frequency currently in use. Also, the four empty frequencies ch1, ch4, ch6, and ch9 are described in the empty frequency list at the list acquisition position P1 in the moving direction. Note that the fact that the list acquisition position P1 is in the movement direction corresponds to the case shown in FIG.
As the candidate frequency, a free frequency included in the list of moving directions is extracted from the free frequencies included in the free frequency list at the current position P0. In the example shown in FIG. 12, three free frequencies ch1, ch6, and ch9 are candidate frequencies.

  When candidate frequencies are extracted in this manner (S314 in FIG. 9), it is then determined whether or not the extracted candidate frequencies exist (S316 in FIG. 10). In the example shown in FIG. 12, three frequencies are extracted, but there are cases where candidate frequencies cannot be extracted.

As a result, if candidate frequencies have been extracted (S316: yes), it is determined whether or not there are a plurality of candidate frequencies (S318).
If there are a plurality of candidate frequencies (S318: yes), the number of candidates included in the free frequency list ahead of the moving direction is acquired for each candidate frequency (S320). As described above, the front free frequency list is a free frequency list in the movement direction and a free frequency list at the list acquisition positions on both sides of the list acquisition position in the movement direction. Therefore, the free frequency lists ahead of the moving direction are two free frequency lists acquired at the list acquisition positions on both sides in the moving direction. In the example shown in FIG. 12, the free frequency list in the moving direction is a list of the list acquisition position P1, and therefore, the list of the list acquisition position P4 and the list of the list acquisition position P2 are applicable. These vacant frequency lists are also already acquired in S102 of the communication control process of FIG. 4 and stored in the storage unit 108 before the communication frequency switching process of FIGS. 9 and 10 is started.
In S320, the number included in these two free frequency lists is acquired for each candidate frequency. Describing in accordance with the example of FIG. 12, the candidate frequency ch1 is not included in the list of the list acquisition position P4 or the list acquisition position P1, so the number is zero. Further, since the candidate frequency ch6 is included in any list, the number is two, and the candidate frequency ch9 is included only in the list at the list acquisition position P2, so the number is one. Become.

  When the number of frequencies included in the free frequency list ahead of the moving direction is acquired for each candidate frequency in this way (S320), the candidate frequency with the larger acquired number is selected (S322), and then the frequency of the selected candidate is selected. Is determined as the communication frequency after switching (S324). In the example shown in FIG. 12, the candidate frequency ch6 is determined as the communication frequency after switching.

  The above has described the process of determining the communication frequency after switching when a plurality of candidate frequencies have been extracted (S318: yes). On the other hand, when only one candidate frequency is extracted (S318: no), the candidate frequency is determined as the communication frequency after switching (S324).

If no candidate frequency is extracted (S316: no), the communication frequency after switching is determined as follows. First, for each vacant frequency included in the vacant frequency list in the moving direction, the number included in the vacant frequency list ahead is acquired (S326). In this process, the process performed on the list of the current position P0 and the list of the list acquisition positions P1 to P8 in S202 of the communication frequency selection process described above with reference to FIG. It is a process to apply to.
Then, among the free frequencies included in the moving direction list, the free frequency with the larger number included in the front list is determined as the communication frequency after switching (S328).
The processing for determining the communication frequency after switching (S314 to S328) as described above is mainly executed by the communication frequency selection unit 106 under the control of the communication control unit 102.

When the communication frequency after switching is determined as described above (S324 or S328), information on the communication frequency is transmitted to the communication partner (S330). When broadcast transmission is performed, transmission is performed without specifying the other party.
Then, the switched communication frequency is registered in the database 4 via the radio base station 2 and the public communication network 3 (S332).

Thereafter, it is determined whether or not the vehicle 10 has reached the switching position for the communication frequency (S334). The communication frequency switching position refers to the case where it is determined that the current communication frequency exists in the free frequency list at the intermediate position after the communication frequency switching process of FIGS. 9 and 10 is started (S304 in FIG. 9: yes). ) Intermediate position.
As a result, when it is determined that the communication frequency switching position has not been reached (S334: no), the same determination is repeated and the apparatus enters a standby state. When it is determined that the switching position has been reached (S334: yes), the communication frequency used so far is switched to the determined communication frequency after switching (S336), and then the communication shown in FIGS. 9 and 10 is performed. The frequency switching process is terminated, and the process returns to the communication control process of FIG.
Note that the communication control unit 102 executes the process of switching the communication frequency (S336). Therefore, the communication control unit 102 of this embodiment corresponds to the “switching unit” in the present invention.

As described above, in the communication frequency switching process according to the present embodiment, after switching from the free frequencies (candidate frequencies) included in the free frequency list at the current position P0 and the free frequency list in the moving direction. Is selected (S314 in FIG. 9). For this reason, even if the communication frequency is switched at a position before the position where the current communication frequency can no longer be used, the communication frequency after switching can be used from that position. Absent. In other words, since it is only necessary to switch slightly before the boundary of the communication frequency in use, there is no need to specify the exact boundary position. For this reason, it becomes possible to greatly simplify the process for switching the communication frequency of cognitive radio communication.
As shown in S314 of FIG. 9, when the communication frequency switching process of the present embodiment extracts the candidate frequencies of the communication frequency, the list of the current position P0 and the movement, not the vacant frequencies included in the movement direction list, are extracted. This is the reason why the vacant frequencies included in the list of directions are extracted in common.

  Further, in the communication frequency switching process according to the present embodiment, when there are a plurality of candidate frequencies (S318: yes in FIG. 10), the list of free frequencies other than the moving direction is also referred to and the list is displayed. The communication frequency after switching is determined as the one with the larger number (S322 and S324). For this reason, even when the moving direction of the vehicle 10 is changed after the communication frequency after switching is determined, it is possible to avoid disconnection of communication.

  In addition, when a boundary between communication frequencies in use is detected, a distance (communication distance) in which the communication frequency can be used and a time in which the communication frequency can be used (communication time) are transmitted in advance (see FIG. 9 (S312), and after determining the communication frequency after switching, information on the communication frequency is transmitted in advance (S330 in FIG. 10). For this reason, since it is possible for the communication partner side to predict when the communication frequency is switched, it is possible to avoid a situation in which the communication is disturbed due to the switching.

  In addition, the switched communication frequency is registered in the database 4 connected to the public communication network 3 (S332). For this reason, even if the communication partner fails to receive the information regarding the communication frequency after switching, it is possible to connect to the database 4 and read out, so that a situation in which communication is disturbed due to switching of the communication frequency is avoided. It becomes possible to do.

E. Modified example:
In the above-described embodiment, the description has been given assuming that the plurality of list acquisition positions P1 to P8 are set without deviating from the current position P0 in a specific direction. However, a plurality of list acquisition positions may be set so as to be biased in a specific direction.
For example, when the wireless communication device 100 is mounted on a transportation means such as the vehicle 10, it is unlikely that the wireless communication device 100 continues to move backward for a long time. Therefore, as illustrated in FIG. 13, a plurality of list acquisition positions P1 to P5 are provided so as to be biased forward and sideward with respect to the vehicle 10, and a communication frequency is determined with reference to the empty frequency list for these positions. You may do it.

  In the above-described embodiment or modification, the current position P0 and the plurality of list acquisition positions are described as being arranged in a grid pattern. However, these are not necessarily arranged in a grid pattern, and may be arranged, for example, on the circumference or arc with the current position P0 as the center, with an equiangular interval.

  The wireless communication apparatus 100 of the present embodiment has been described above, but the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the scope of the present invention.

1 ... wireless communication system, 2 ... wireless base station, 3 ... public communication network,
4 ... database, 10 ... vehicle, 12 ... vehicle control unit,
14 ... car navigation system, 100 ... wireless communication device,
102: Communication control unit 104: Wireless communication unit 106: Communication frequency selection unit,
108 ... Storage unit 110 ... GPS unit,
112 ... External interface unit 114 ... Bus

Claims (11)

A wireless communication device that performs cognitive wireless communication using a vacant frequency that is not used by a party who has been assigned a frequency used for wireless communication,
Current position acquisition means for acquiring information about the current position;
First acquisition means for acquiring a first free frequency list that is a list indicating the free frequencies at the current position;
Second acquisition means for acquiring a second vacant frequency list that is a list of vacant frequencies at a radio wave non-reachable position set outside an area where radio waves of the wireless communication device can reach from the current position;
A communication frequency selection means for selecting a communication frequency that is a frequency used for wireless communication from among the free frequencies shown in the first free frequency list;
Communication means for performing the cognitive radio communication using the communication frequency,
The communication frequency selection means refers to the second free frequency list when selecting the communication frequency, and includes the free frequency that is not included in the second free frequency list. A wireless communication apparatus which is means for preferentially selecting the idle frequency. The wireless communication device according to claim 1,
The second acquisition means is means for acquiring the second vacant frequency list for a plurality of radio wave non-arrival positions,
The communication frequency selection means also refers to a plurality of second empty frequency lists when selecting the communication frequency, and includes the empty frequencies included in a number of the second empty frequency lists. A wireless communication device which is a means for selecting with priority over the free frequency with less. The wireless communication device according to claim 2,
The wireless communication apparatus, wherein the second acquisition unit is a unit that acquires the second vacant frequency list for the radio wave non-arrival position within a predetermined distance from the current position. The wireless communication apparatus according to claim 2 or claim 3, wherein
The second acquisition means is a means for selecting a plurality of radio wave non-arrival positions within a predetermined direction range from the current position and acquiring the free frequency list for the plurality of radio wave non-arrival positions. . A wireless communication device according to any one of claims 2 to 4,
When there are a plurality of idle frequencies having the same number of the second idle frequency lists included in the communication frequency selection means, the communication frequency selection means is added to the idle frequency list for the radio wave non-arrival position in a predetermined direction from the current position. A wireless communication apparatus which is means for preferentially selecting the free frequency included. The wireless communication device according to claim 3 or 4, wherein
A moving direction acquisition means for acquiring information relating to the moving direction of the wireless communication device;
Judging means for judging the presence or absence of the communication frequency with reference to the second vacant frequency list for the radio wave non-arrival position in the moving direction;
The communication frequency selection means is a wireless communication apparatus which is means for selecting a new communication frequency when it is determined that the communication frequency is not included in the second vacant frequency list in the moving direction. The wireless communication device according to claim 6,
When it is determined that the communication frequency is not included in the second free frequency list in the movement direction, a communicable distance that is a communicable distance using the communication frequency along the movement direction is detected. Communicable distance detecting means;
A wireless communication apparatus comprising: switching means for switching to the newly selected communication frequency at a timing according to the communicable distance. The wireless communication device according to claim 7,
If it is determined that the communication frequency is not included in the second vacant frequency list in the moving direction, the second acquisition unit and the radio wave non-reachable position corresponding to the second vacant frequency list Means for setting an intermediate position between the current position and obtaining a list of the free frequencies for the intermediate position;
The communicable distance detecting means is a means for detecting the communicable distance with reference to a list of idle frequencies at the intermediate position. The wireless communication device according to claim 7 or 8,
Moving speed acquisition means for acquiring information relating to the moving speed of the wireless communication device;
A communicable time acquisition means for acquiring a communicable time that is a communicable time using the communication frequency based on the communicable distance and the moving speed;
The said communication means is a radio | wireless communication apparatus which is a means to transmit the information regarding the said communication possible time. A wireless communication apparatus according to any one of claims 1 to 9,
The communication means is a wireless communication device which is means for transmitting the selected communication frequency to a server connected via the wireless communication when the communication frequency selection means selects the communication frequency. A wireless communication method for performing cognitive wireless communication using a vacant frequency that is not used by a party who has been assigned a frequency used for wireless communication,
Acquiring information about the current position;
Obtaining a first free frequency list which is a list indicating the free frequencies at the current position;
Obtaining a second vacant frequency list that is a list of the vacant frequencies at a radio wave non-reachable position set outside an area where radio waves of the wireless communication device can reach from the current position;
Selecting a communication frequency, which is a frequency used for wireless communication, from among the free frequencies included in the first free frequency list;
Performing the cognitive radio communication using the communication frequency,
The step of selecting the communication frequency refers to the second vacant frequency list with reference to the second vacant frequency list when selecting the communication frequency, so that the vacant frequencies not included in the second vacant frequency list are included in the second vacant frequency list. A wireless communication method which is a step of preferentially selecting the free frequency included.

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