JP6357373B2 - Spectrum sensing method and wireless communication apparatus - Google Patents

Description

  The present invention relates to spectrum sensing, and more particularly to spectrum sensing when white space information cannot be acquired from a white space information providing apparatus.

  In order to increase the frequency use efficiency, research on cognitive radio in which the radio communication device adaptively changes the frequency and radio scheme used for radio communication by recognizing and recognizing the surrounding radio wave environment is underway. In particular, a form in which the unlicensed person (secondary user) uses a frequency allocated to the licensee (primary user) but not actually used can be considered. Such a frequency is referred to as a secondary usable frequency or white space. When the secondary user uses such a white space, it is necessary to detect an available frequency (channel).

  As a method of acquiring a usable frequency by a secondary user, a method of acquiring from a white space database is being studied. The white space database (white space information providing device) is a device that acquires frequencies available to the secondary user at each location and notifies the secondary user. It is considered that the frequency that can be used in each location is determined based on information (primary location, frequency, transmission power, etc.) on the primary user, terrain information, and the like.

  However, a situation in which communication between the secondary user and the white space database cannot be performed is assumed. In order to continue secondary communication without interfering with the primary user even when the white space database cannot be accessed, the secondary user must perform spectrum sensing by himself and continue communication based on the sensing result.

  Here, since spectrum sensing takes time, if sensing is repeated in order for all frequencies, a large amount of time is required only for sensing processing.

Special table 2013-530608 gazette Special table 2012-529196 gazette

  As described above, if all frequencies (channels) are sensed, the processing time becomes long. Therefore, it is desirable to narrow down the frequency to be sensed and perform sensing.

  An object of the present invention is to reduce the time required for sensing processing by narrowing down the frequency to be sensed when white space information cannot be acquired from the white space information providing apparatus.

In order to achieve the above object, the first aspect of the present invention provides:
A spectrum sensing method performed by a wireless communication device,
A white space information acquisition step for acquiring white space information representing a usage situation for each frequency from the white space information providing device;
A sensing step of performing spectrum sensing when the white space information cannot be obtained from the white space information providing device;
Including
The sensing step includes
A first step of setting at least a part of frequencies not used by the primary user as sensing target frequencies based on the white space information acquired most recently;
A second step of adding a part of the frequencies used by the primary user to the sensing target frequency based on the white space information acquired most recently;
A third step of performing spectrum sensing for the sensing target frequency determined in the first step and the second step;
It is characterized by including.

  According to such a method, the wireless communication apparatus can determine the sensing target based on the white space information acquired from the white space database most recently, so that it is not necessary to sense all frequencies.

  In this case, all or at least a part of the frequencies not used by the primary user are set as sensing targets because the frequencies that are known to be secondary usable from the white space information can be used continuously. This is to confirm that there is. In addition, although it is preferable to make all the frequencies which the primary user is not using as a sensing object, it is good also considering only a part of the frequency which the primary user is not using as a sensing object. When only a part is to be sensed, it is preferable to include in the sensing target the frequency that the wireless communication device is secondary using.

  The reason why a part of the frequency used by the primary user is also a sensing target is that the use of the frequency by the primary user may end with the movement of the wireless communication device or the passage of time. If only the frequency that is not used by the primary user is set as a sensing target, a frequency that can be newly used for secondary use cannot be detected, and there is a concern that the frequency utilization efficiency may be reduced. Therefore, even if the frequency is being used by the primary user, the frequency utilization efficiency can be increased by setting some of the frequencies as sensing targets.

  In the second step of the present invention, it is also preferable to add a predetermined number of frequencies among the frequencies used by the primary user to the sensing target frequency. Here, the number of frequencies to be added to the sensing target (predetermined number) may be a predetermined fixed value, may be a value determined based on other factors, or may be determined randomly. It may be a value to be set.

  In the second step of the present invention, it is also preferable that some of the frequencies used by the primary user are randomly selected and added to the sensing target frequency. Or you may make it add to a sensing object preferentially as a frequency with a long period which is not a sensing object.

  In addition, it is preferable to repeatedly execute the sensing step while white space information cannot be acquired from the white space information providing apparatus. At this time, in the first sensing step of the iterative process, the sensing target is determined based on the white space information most recently acquired from the white space database. In the second and subsequent sensing steps in the iterative process, the previous sensing result is determined. Based on this, it is preferable to implement the first step and the second step. By doing so, efficient sensing can be performed using the latest sensing results.

  The present invention can also be understood as a spectrum sensing method that executes at least a part of the above processing. The present invention can be understood as a wireless communication device provided with a means for executing at least a part of the above processing or a mobile body provided with the wireless communication device. The present invention can also be understood as a computer program for causing a computer to execute this method, or a computer-readable storage medium in which this computer program is stored non-temporarily. Each of the above means and processes can be combined with each other as much as possible to constitute the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, when white space information cannot be acquired from a white space information provision apparatus, the frequency required for sensing can be narrowed down and the time required for sensing processing can be shortened.

The figure which shows the outline | summary of the communication system which concerns on this embodiment. The figure which shows the functional block of the vehicle-mounted radio | wireless communication apparatus in this embodiment. The flowchart which shows the flow of the spectrum sensing process in this embodiment.

<System overview>
FIG. 1 is a diagram showing an outline of a vehicle communication system according to the present embodiment. The vehicle communication system includes a vehicle 1 equipped with an in-vehicle wireless communication device 10 and a white space database (WSDB) 2. The WSDB knows whether or not the primary user is using each frequency (channel) (that is, whether or not the secondary user is available), and sends information about the usage status of the primary user to the vehicle 1. Send. The vehicle 1 determines a channel to be used for secondary communication based on the usage status of the primary user transmitted from the WSDB device 2.

  Hereinafter, information indicating the usage status of the primary user for each channel (that is, information indicating availability of secondary communication) is referred to as white space information (WS information).

  Here, while the WS information can be acquired from the WSDB device 2 at the time A, the communication between the vehicle 1 and the WSDB device 2 is cut off at the time B, and the vehicle 1 becomes the WSDB device 2. Assume that the WS information can no longer be acquired. In order for the vehicle 1 to continue the secondary communication, it is necessary to perform spectrum sensing so as not to interfere with the primary user. Here, if sensing is performed for all channels, the processing takes time. Therefore, the vehicle 1 stores the WS information acquired from the WSDB device 2 most recently, and based on the stored WS information. Determine the channels to be sensed and perform spectrum sensing on some channels. A specific method for determining the sensing target channel will be described in detail later.

<Device configuration and processing details>
Here, the configuration of the in-vehicle wireless communication device 10 will be described. The in-vehicle wireless communication device 10 is an information processing device (computer) having a wireless communication function. The in-vehicle wireless communication device 10 includes a central processing unit, a storage device such as a RAM and a ROM, an input / output device, a communication interface, and the like, and the functions shown in FIG. 2 are realized by the central processing unit executing a program. To do. That is, the in-vehicle wireless communication device 10 functions as a wireless communication unit 11, a WS information acquisition unit 12, a WS information storage unit 13, a sensing target channel determination unit 14, a sensing unit 15, and a channel determination unit 16. Note that some or all of these functions may be realized by a dedicated hardware circuit.

  The wireless communication unit 11 is a functional unit that performs wireless communication with the WSDB device 2 and other vehicles (on-vehicle wireless communication devices). The wireless communication method of the wireless communication unit 11 is not particularly limited, and any existing communication method can be adopted. For example, DSRC (Dedicated Short Range Communication), wireless LAN (IEEE 802.11 system), millimeter wave communication, mobile WiMAX (IEEE 802.16e, m), mobile phone communication, and the like can be employed. Note that the wireless communication unit 11 may perform communication with the WSDB device 2 and communication with another vehicle by using different wireless communication methods having different communication interfaces.

  The WS information acquisition unit 12 is a functional unit that acquires WS information from the WSDB device 2 via the wireless communication unit 11. The WS information obtained from the WSDB device 2 includes the usage status of the primary user for each channel. Note that the format of the WS information is not particularly limited in the present invention, and may be expressed in an arbitrary format. For example, the WS information may include only the channel usage status of each channel at the current location, or may include the channel usage status for a plurality of areas.

  The WS information acquired by the WS information acquisition unit 12 from the WSDB device 2 is stored in the WS information storage unit 13. Since the WS information acquisition unit 12 stores the WS information in the WS information storage unit 13 every time it acquires the WS information from the WSDB device 2, the WS information storage unit 13 stores the WS information received from the WSDB device 2 most recently.

  WS information is stored in the WS information storage unit 13. The WS information stored in the WS information storage unit 13 is referred to by the channel determination unit 16 when determining a channel used for secondary communication, and is also referred to when the sensing target channel determination unit 14 determines a sensing target channel. The

  The sensing target channel determination unit 14 is a functional unit that determines a sensing target channel when the in-vehicle wireless communication device 10 performs spectrum sensing by itself when communication with the WSDB device 2 is disconnected. The sensing target channel determination unit 14 determines a sensing target channel based on the latest WS information stored in the WS information storage unit 13. Details of the method for determining the sensing target channel will be described later.

The sensing unit 15 is a functional unit that performs spectrum sensing on the sensing target channel determined by the sensing target channel determination unit 14 and detects whether or not the primary user is using the channel. Any sensing algorithm can be adopted. Depending on the wireless communication method to be detected, for example, by energy detection, wavelet decomposition technique, pilot-based spectrum sensing, eigenvalue-based sensing, feature detection, matched filter method, etc.
It can be determined whether or not the channel is in use.

  Hereinafter, spectrum sensing processing including sensing target channel determination processing will be described with reference to the flowchart of FIG. The spectrum sensing process by the in-vehicle wireless communication device 10 is started when the connection with the WSDB device 2 is disconnected or the WS information cannot be acquired within the time (S10).

In step S11, the sensing target channel determination unit 14 acquires the latest WS information stored in the WS information storage unit 13, and excludes the channel used by the primary user from the sensing target (adds to the exclusion list). Other channels not used by the primary user are set as sensing target channels. As described above, the sensing target channel determination unit 14 determines a sensing target channel based on the WS information acquired from the WSDB device 2 most recently. Hereinafter, the WS information acquired from the WSDB apparatus is also referred to as DB information in order to distinguish it from the WS information acquired by sensing itself.

  In step S11, all channels not used by the primary user may be added to the sensing target, or only some of them may be added to the sensing target. When only a part is set as a sensing target, a predetermined number of channels may be set as sensing targets. Moreover, about the channel which the vehicle-mounted radio | wireless communication apparatus 10 is currently using for secondary communication, or a channel with high possibility of using in the future, adding to a sensing object is preferable.

  In step S12, the sensing target channel determination unit 14 selects a predetermined number (N) from the excluded channels registered in the exclusion list and adds the selected channel to the sensing target channel. The predetermined number N may be a predetermined value or may be determined based on other factors. For example, the channels to be added to the sensing target can be randomly selected from the channels in the exclusion list.

  In step S13, the sensing unit 15 performs spectrum sensing for the sensing target channel determined in step S12. The sensing result is stored as the latest WS information in the WS information storage unit 13 and is notified to the channel determination unit 16.

  In step S14, the channel determination unit 16 determines a channel to be used for secondary communication. For example, if communication of the primary user is detected in the channel that has been used so far, the use of this channel is immediately stopped, and the use channel is determined according to any criteria from the other available channels. . If the primary user's communication is not detected in the channel being used, the use of that channel may be continued.

  In step S <b> 15, it is determined whether or not the connection with the WSDB apparatus 2 is restored and the WS information can be acquired from the WSDB apparatus 2. If communication with the WSDB device 2 is impossible (S15-NO), the process proceeds to step S16. If communication with the WSDB apparatus 2 is possible (S15-YES), the spectrum sensing process is stopped, and the process returns to the channel determination process based on the WS information acquired from the WSDB apparatus 2 (step S17).

  In step S16, based on the spectrum sensing result in step S13, the sensing target channel determination unit 14 adds a channel that is being used by the primary user to the exclusion list, and sets a channel that is not being used by the primary user as a sensing target. .

After step S16, the process returns to step S12, and the processes of steps S12 to S15 are repeated. This repeated process continues until the connection with the WSDB device 2 is restored. The sensing target channel determination process for the second and subsequent iterations determines the sensing target based on the WS information acquired by sensing itself rather than the WS information acquired from the WSDB device 2 as compared with the first process. The other points are basically the same. However, in step S12, when selecting the sensing target channel from the excluded channel, it may be simply selected at random, but the frequency that is not the target of spectrum sensing is preferentially added to the sensing target, etc. You may choose according to the criteria of.

<Advantageous effects of this embodiment>
When the in-vehicle wireless communication device 10 performs spectrum sensing by itself, if all channels are targeted, the time cost becomes high, but the time required for sensing by narrowing down the sensing target channels based on recent WS information. Can be shortened. At this time, by sensing a channel that can be used for secondary communication, it is possible to detect whether or not a channel that has been usable up to that point can be used continuously. Further, by selecting and sensing several channels that cannot be used for secondary communication, it is possible to detect a channel in which communication of the primary user is lost as the vehicle moves or time elapses. If only the channels that can be used so far are targeted for sensing, the number of channels that can be used is reduced, but the number of channels that can be used may increase by sensing channels that are not usable until then. .

<Modification>
The above description is illustrative of the present invention and is not intended to limit the present invention. The present invention can be variously modified within the scope of its technical idea.

  For example, in the above embodiment, the wireless communication device mounted on the vehicle is described as an example, but the secondary user is not limited to the in-vehicle wireless communication device. The secondary user in the present invention may be any movable wireless communication device other than the in-vehicle wireless communication device. A movable wireless communication device is a wireless communication device installed in a vehicle, airplane, ship, etc., a wireless communication apparatus that is brought into a vehicle, airplane, ship, etc., and moves as they move, and can be carried by humans Such as a wireless communication device.

DESCRIPTION OF SYMBOLS 10 In-vehicle wireless communication apparatus 11 Wireless communication part 12 WS information acquisition part 13 WS information storage part 14 Sensing object channel determination part 15 Sensing part 16 Channel determination part

Claims (11)

A spectrum sensing method performed by a wireless communication device,
A white space information acquisition step for acquiring white space information representing a usage situation for each frequency from the white space information providing device;
A sensing step of performing spectrum sensing when the white space information cannot be obtained from the white space information providing device;
Including
The sensing step includes
A first step of setting at least a part of frequencies not used by the primary user as sensing target frequencies based on the white space information acquired most recently;
A second step of adding a part of the frequencies used by the primary user to the sensing target frequency based on the white space information acquired most recently;
A third step of performing spectrum sensing for the sensing target frequency determined in the first step and the second step;
A spectrum sensing method comprising: In the second step, a predetermined number of frequencies among the frequencies used by the primary user are added to the sensing target frequency.
The spectrum sensing method according to claim 1. In the second step, a part of the frequencies used by the primary user is randomly selected and added to the sensing target frequency.
The spectrum sensing method according to claim 1 or 2. While the white space information cannot be acquired from the white space information providing device, the sensing step is repeatedly executed.
The spectrum sensing method of any one of Claims 1-3. In the second and subsequent sensing steps in the iterative process, the first step and the second step are performed based on the previous sensing result.
The spectrum sensing method according to claim 4. An acquisition means for acquiring white space information representing a usage situation for each frequency from the white space information providing device;
Sensing means for performing spectrum sensing when the white space information cannot be obtained from the white space information providing device,
The sensing means sets at least a part of the frequencies not used by the primary user as sensing target frequencies based on the white space information acquired most recently, and further selects one of the frequencies used by the primary user. Part frequency is added to the sensing target frequency, and spectrum sensing is performed for the sensing target frequency.
A wireless communication apparatus. The sensing means adds a predetermined number of frequencies among the frequencies used by the primary user to the sensing target frequency.
The wireless communication apparatus according to claim 6. The sensing means randomly selects some of the frequencies used by the primary user and adds them to the sensing target frequency.
The wireless communication apparatus according to claim 6 or 7. The sensing means repeatedly executes determination of sensing target frequency and spectrum sensing while white space information cannot be acquired from the white space information providing apparatus.
The wireless communication apparatus according to any one of claims 6 to 8. In the second and subsequent processes in the iterative process, the sensing means determines a sensing target frequency based on the previous sensing result.
The wireless communication apparatus according to claim 9.   The program for making a computer perform each step of the method of any one of Claims 1-5.

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