JP2007060410A - Device and method for wireless communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform efficient communication when recognition wireless communication is carried out. <P>SOLUTION: A device for wireless communication is a wireless communication device which detects a free frequency band among a plurality of frequency bands and communicates data by using the detected frequency band, and is equipped with an antenna which transmits and receives radio signals; a communication processing unit which communicates through the antenna; and a control processing unit which selects a frequency band out of the plurality of frequency bands, inspects whether the selected frequency band is usable for a first time, communicates data for a second time the total of which and the first time is constant by using the communication processing unit when the selected frequency band is usable, and determines the first time and second time according to the selected frequency band. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus and a wireless communication method, and more particularly to a technique for efficiently detecting a vacant frequency band from a plurality of frequency bands.

  In a conventional radio communication system, a radio frequency band assigned for radio communication is divided into a plurality of radio frequency channels having a certain bandwidth, and these channels are temporarily assigned to radio communication devices. Establishing wireless communication between wireless communication devices is generally performed.

  In the above technique, a channel once assigned to a wireless communication device has a precondition that the wireless communication device has a right to use until communication is completed, and is not used by other systems or other wireless communication devices. is there. Therefore, whether or not a frequency band to be used in wireless communication is vacant only needs to first determine a used / unused detection result when assigning a channel.

In the above technique, the radio communication system only considers using only the radio frequency band assigned to the communication system. However, recently, even in a frequency band other than the radio frequency band assigned to the radio communication system, the radio frequency channel being used by another system is avoided by carrier sense, and the radio communication system is used. Cognitive radio technology that dynamically allocates and temporarily shares has been proposed (see, for example, Non-Patent Document 1).
J.Mitola III et al., “Cognitive Radio; Making Software Radios More Personal” (IEEE Personal Communications Magazine (Aug, 1999) Volume: 6 Issue: 4 Page (s): 13-18)

  In this cognitive wireless communication, it is assumed that the frequency band used by another system / wireless communication apparatus is temporarily shared, and therefore, the wireless communication channel to be used is not always in an environment where it can be used. Moreover, it is a precondition that interference should not be given to a wireless communication system or a wireless communication apparatus to which the frequency band is originally assigned.

  Therefore, when performing cognitive radio communication, in addition to performing own communication, it is necessary to periodically inspect whether the frequency band used in cognitive radio communication is being used. Since interference with an existing system is not allowed, the ratio of the time required for inspection is inevitably increased compared with the communication time. Therefore, when the communication time ratio is small, it is not efficient for the wireless communication device.

  The present invention provides a wireless communication apparatus and a wireless communication method that enable efficient communication in the case of cognitive wireless communication.

  A wireless communication device according to an aspect of the present invention is a wireless communication device that performs data communication using a vacant frequency band detected from a plurality of frequency bands, and includes an antenna that transmits and receives a wireless signal, and the antenna A communication processing unit that performs communication, and a frequency band is selected from among the plurality of frequency bands, and whether or not the selected frequency band is available is checked for a first time, and the selected frequency band Can be used, the first time and the second time during which data communication is performed for a second time in which the total with the first time is constant using the communication processing unit. And a control processing unit that determines according to the selected frequency band.

  A wireless communication device according to an aspect of the present invention is a wireless communication device that performs data communication using a vacant frequency band detected from a plurality of frequency bands, and includes an antenna that transmits and receives a wireless signal, and the antenna A communication processing unit that performs communication, and a frequency band is selected from among the plurality of frequency bands, and whether or not the selected frequency band is available is checked for a first time, and the selected frequency band And a control processing unit that performs data communication for a second time in which the total with the first time is constant using the communication processing unit, and the control processing unit Is characterized in that when the same frequency band is available for a predetermined number of times, the first time is shortened in the next inspection.

  A wireless communication method as one aspect of the present invention is a wireless communication method for performing data communication using an empty frequency band detected from a plurality of frequency bands, and selects a frequency band from the plurality of frequency bands, The sum of the first time as the time for checking whether or not the selected frequency band is available and the first time as the time for performing data communication when the selected frequency band is available A second time in which the frequency is constant is determined according to the selected frequency band, and the selected frequency band is used during the first time, and the selected frequency band can be used. In this case, the data communication is performed during the second time.

  According to the present invention, efficient communication can be performed in the case of cognitive radio communication.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a wireless communication apparatus according to the first embodiment of the present invention. The radio communication apparatus of FIG. 1 down-converts a signal received by an antenna 101 into a baseband signal by an RF (Radio Frequency) analog signal processing unit 102, converts the signal to a digital signal by an A / D converter 103, The digital signal processing unit 106 digitally processes the signal to obtain reception information. In transmission, transmission information from the digital signal processing unit 106 is converted into an analog baseband signal by the D / A converter 105, up-converted to a transmission frequency band by the RF analog signal processing unit 104, and transmitted from the antenna 101. . Blocks 102, 103, 104, 105, and 106 correspond to, for example, a communication processing unit. The control processing unit 107 controls transmission processing and reception processing, and exchanges control signals with the respective blocks 102, 103, 104, 105, 106. Although one antenna is shown in FIG. 1, a plurality of antennas may be arranged.

  Here, the control processing unit 107 has a function of checking whether or not a frequency band for performing wireless communication is free (unused). Specifically, it is checked whether or not the frequency band is vacant depending on whether or not the signal power input to the digital signal processing unit 106 is greater than or equal to a certain threshold Th1. Alternatively, the inspection is performed based on whether or not the power value of the received analog signal in the RF analog signal processing unit 102 is greater than or equal to a certain threshold Th2. In the inspection, various known methods can be used in addition to the example shown here.

  FIG. 2 shows a state in which the wireless communication apparatus of FIG. 1 performs wireless communication while periodically detecting whether or not a frequency band for performing wireless communication is free (unused). The wireless communication apparatus repeatedly performs a repetition unit 205 composed of the idle frequency detection time 203 and the data communication time 204. In the vacant frequency detection time 203, it is confirmed whether or not this frequency band is vacant by continuously observing signals in the frequency band for performing wireless communication (empty frequency detection process). As a result of confirmation, when this frequency band is vacant (when use by another system is not detected), data communication is performed in the data communication time 204 using this frequency band. If the use of a frequency band by another system is detected in the free frequency detection process, the communication in that frequency band is given up and another frequency band is selected, and the free frequency detection process is performed again.

  Here, in the conventional wireless communication apparatus, the idle frequency detection time and the data communication time are generally constant. On the other hand, the control processing unit 107 of the wireless communication apparatus according to the present embodiment controls the ratio of the idle frequency detection time 203 and the data communication time 204 in FIG. 2, and the ratio depends on the frequency band to be used. Can be changed. However, the sum of the idle frequency detection time 203 and the data communication time 204 is constant. Hereinafter, the reason why the ratio is changed according to the frequency band to be used will be described.

  The wireless communication apparatus according to the present embodiment assumes cognitive wireless (cognitive wireless) communication. In general, in cognitive radio communication, a frequency band that is not originally assigned to a radio communication device is used. Therefore, it is necessary to consider so as not to cause interference with a radio communication system that is officially assigned a frequency. is there. Therefore, in the idle frequency detection time 203 and the data communication time 204 in FIG. 2, the ratio of the idle frequency detection time 203 must be increased. Increasing the ratio of the vacant frequency detection time 203 can improve the accuracy of detecting whether or not the frequency band is vacant, but the data communication time is shortened and the efficiency is reduced accordingly.

  Therefore, in the present embodiment, each frequency band that can be used in cognitive radio communication depends on what form is used by the existing system (the radio communication system to which the frequency band is originally assigned). The ratio between the idle frequency detection time 203 and the data communication time 204 for the frequency band is determined in advance. Then, idle frequency detection processing and data communication are performed at a ratio according to the frequency band to be used. This enables efficient data communication. This will be described in more detail below.

  FIG. 4 is a table (ratio determination information) showing the frequency usage mode of the existing system for each frequency band used in cognitive radio communication and the ratio applied to each frequency band. This table is stored in the storage device 108 of FIG. However, the frequency usage form is arbitrary information and does not necessarily need to be saved.

  In this example, there are two ratios, ratio 1 and ratio 2. However, the ratio may be a multistage configuration having three or more stages. Specific examples of the ratio 1 and the ratio 2 are shown in FIG. The ratio 2 is set so that the idle frequency detection time is shorter than the ratio 1, and the data communication time is set longer.

  As shown in FIG. 4, for example, when the usage form of a frequency band is “broadcast”, it is sufficient to determine whether there is a broadcast in a place where the wireless communication device is present. A ratio 2 with a short frequency detection time is applied. On the other hand, when the frequency band usage mode is “cellular wireless communication” or “wireless LAN”, the ratio of the free frequency detection time to the frequency band is long so as not to affect the communication performed in other systems. 1 is applied.

  When performing the free frequency detection process, the control processing unit 107 in FIG. 1 first selects a frequency band, and detects a ratio to be applied to the selected frequency band from the table in FIG. Based on the detected ratio, the idle frequency detection time and the data communication time are calculated from the repetition unit time specified in advance. However, when the ratio includes the free frequency detection time and the data communication time directly, for example, when the ratio is stored in the format of “free frequency detection time: data communication time”, this calculation process is unnecessary.

  The control processing unit 107 performs idle frequency detection processing for the selected frequency band during the idle frequency detection time. For example, the reception power of the received signal in the selected frequency band is acquired from the RF analog signal processing unit 102, and it is determined whether or not the selected frequency band is available based on the acquired reception power.

  When the selected frequency band is available, the control processing unit 107 controls the blocks 102 to 106 to perform data communication during the data communication time. The control processing unit 107 may synchronize with the communication partner by using a control channel prepared in advance before performing data communication. For example, when the selected frequency band is different from the frequency band in the previous data communication, the frequency band to be used is newly notified, and when the ratio is changed, the ratio after the change is also notified. . When the communication is continued after performing the data communication, the control processing unit 107 performs the free frequency detection process again for the same frequency band as the selected frequency band.

  On the other hand, if the selected frequency band is not available, the control processing unit 107 selects another frequency band and performs the free frequency detection process again.

  As described above, according to the present embodiment, since the ratio between the free frequency detection time and the data communication time is changed according to the frequency band where it is to be detected whether or not the data can be used, efficient data can be obtained. Communication can be realized.

(Second Embodiment)
In the second embodiment, when “free” continuously reaches a predetermined number of times as the determination result in the free frequency detection process, the ratio of the free frequency detection time to the data communication time is used in the next free frequency detection process. Is changed to a ratio that the idle frequency detection time is further shortened, that is, a ratio that the data communication time is further increased.

  For example, assume that there are two ratios (ratio 1 and ratio 2) as shown in FIG. As shown in FIG. 5, initially, the idle frequency detection process and data communication are repeated at a ratio of 1, but the number of times that “empty” is detected (frequency usage by other systems has not been detected) continues. If N (N is a positive integer) times or more, the ratio 2 is used, which is one step shorter in the free frequency detection time after the next repetition unit. In this embodiment as well, as in the first embodiment, the ratio between the idle frequency detection time and the data communication time is set in two stages, ratio 1 and ratio 2, but the ratio is set to three or more stages. Therefore, the data communication time may be increased. In this example, the number of stages is increased by one, but a plurality of stages may be increased.

  FIG. 6 is a flowchart showing the flow of processing in the present embodiment. This process is performed by the control processing unit 107.

  It is assumed that the control processing unit 107 selects a frequency band from among a plurality of frequency bands and selects a ratio 1 as an initial value for the selected frequency band (S601). Note that the ratio to the selected frequency band may be selected from the table of FIG. Subsequently, the undetected number of times parameter D is initialized with D = 0 (S602). A free frequency detection process is performed for the selected frequency band (S603). If the selected frequency band is not “vacant”, that is, if the frequency usage of this frequency band by another system is detected (NO in S604), another frequency band is searched (S606). On the other hand, when the selected frequency band is “vacant”, that is, when frequency use of this frequency band is not detected (YES in S604), each block 102 to 106 is controlled to perform data communication, The detection frequency parameter D is increased by 1 (S605). When the undetected frequency parameter D is less than the threshold value N (NO in S607), the free frequency detection process is performed again for the same frequency band. On the other hand, when the undetected number of times parameter D is equal to or greater than the threshold value N (YES in S607), the ratio is changed from ratio 1 to ratio 2 (S608).

  In the above, when the number of times judged as “free” exceeds the threshold, the ratio was changed to a ratio that the data communication time is longer, but conversely, the number of times that was not judged as “free” exceeded the threshold. In such a case, the ratio may be changed to a ratio in which the idle frequency detection time is longer by one or more stages.

  As described above, according to the present embodiment, when the number of times determined to be “free” is equal to or greater than the threshold value, the data communication time is changed to a longer ratio. Communication can be realized.

(Third embodiment)
In the third embodiment, the ratio used at the end of cognitive radio communication in the second embodiment is stored as history information for each frequency band, and the ratio in the history information is used when performing new communication. By using this, more efficient communication is performed.

  FIG. 7 shows an example of history information. The history information is stored in the storage device 108. For the frequency band for which cognitive wireless communication has been successful in the past, the control processing unit 107 stores the ratio of the free frequency detection time and the data communication time used at the end of the communication in the storage device 108 as shown in FIG. . FIG. 7 shows a case where the two ratios (ratio 1 and ratio 2) shown in FIG. 3 are used. Of course, in this embodiment, the ratio may be a multi-stage configuration having three or more stages. When performing cognitive wireless communication, the control processing unit 107 determines an initial value of the ratio based on the history information of FIG.

  As described above, according to the present embodiment, it is possible to efficiently reduce the time required for the vacant frequency detection process, thereby realizing efficient data communication.

(Fourth embodiment)
In the fourth embodiment, the frequency usage mode and ratio (see FIG. 4) to be stored in the storage device 108 in FIG. 1 are acquired from outside the wireless communication device by wireless communication.

  As shown in FIG. 8, the wireless communication device receives information on the frequency usage mode and information on the ratio from the external information providing server 801 by wireless communication, and stores the information in the storage device 802. This reception is performed periodically, for example, and the storage device 802 is updated with the received information after the second time. Thus, for example, an appropriate ratio can be selected even when the wireless communication device is moved to a geographical area having a different frequency usage form.

  Here, the case of acquiring frequency usage information and ratio information from an external server by wireless communication has been shown. However, such information may be acquired via an external storage device that can be connected to the wireless communication device. It is also possible to obtain from a device connected by wire.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

It is a block diagram which shows the structure of the radio | wireless communication apparatus according to embodiment of this invention. It is the figure which showed a mode that an idle frequency detection process and data communication were repeated. It is a figure which shows the content of a ratio. It is a figure which shows an example of a frequency utilization form and ratio for every frequency band. It is a figure explaining changing a ratio, when the frequency | count judged as "vacant" continues continuously N times or more. It is a flowchart which shows the flow of the process which changes a ratio. It is a figure which shows an example of log | history information. It is a figure which shows the example which acquires frequency utilization form information and ratio information from an external information provision server.

Explanation of symbols

Reference Signs List 101 antenna 102 RF analog signal processing unit 103 A / D converter 104 RF analog signal processing unit 105 D / A converter 106 digital signal processing unit 107 control processing unit 108, 802 storage device 801 information providing server

Claims (9)

A wireless communication device that performs data communication using an empty frequency band detected from a plurality of frequency bands,
An antenna for transmitting and receiving radio signals;
A communication processing unit for performing communication via the antenna;
Selecting a frequency band from the plurality of frequency bands, and checking whether the selected frequency band is available for a first time,
When the selected frequency band is available, the communication processing unit is used to perform data communication for a second time that is constant with the first time.
A control processing unit for determining the first time and the second time according to the selected frequency band;
A wireless communication device comprising: A storage device storing ratio determination information in which each of the plurality of frequency bands is associated with a ratio between the first time and the second time;
The wireless communication apparatus according to claim 1, wherein the control processing unit determines the first time and the second time based on the ratio determination information.   The wireless communication apparatus according to claim 2, wherein the control processing unit acquires ratio determination information from an external device, and updates the ratio determination information in the storage device with the acquired ratio determination information. A wireless communication device that performs data communication using an empty frequency band detected from a plurality of frequency bands,
An antenna for transmitting and receiving radio signals;
A communication processing unit for performing communication via the antenna;
Selecting a frequency band from the plurality of frequency bands, and checking whether the selected frequency band is available for a first time,
A control processing unit configured to perform data communication for a second time in which the total with the first time is constant using the communication processing unit when the selected frequency band is available; ,
When the same frequency band is available for a predetermined number of times in succession, the control processing unit shortens the first time in the next inspection.
A wireless communication apparatus. A storage device that holds a plurality of ratios of the first time and the second time;
The control processing unit determines the first and second times using a ratio given as an initial value among the plurality of ratios, and the same frequency band can be used continuously for the predetermined number of times. In this case, the wireless communication apparatus according to claim 4, wherein a ratio of the first time being shorter by a predetermined number of steps is used in the next inspection. The storage device has history information that holds the changed ratio for each frequency band,
The wireless communication apparatus according to claim 5, wherein the control processing unit uses a ratio held in the history information as the initial value.   The said control process part performs the test | inspection of whether the said selected frequency band is available based on the power value of the received signal received by the said antenna, The Claim 1 thru | or 6 characterized by the above-mentioned. Wireless communication device.   8. The control processing unit according to claim 1, wherein when the selected frequency band is not available, the control processing unit selects another frequency band and performs the inspection on the selected other frequency band. A wireless communication device according to claim 1. A wireless communication method for performing data communication using an empty frequency band detected from a plurality of frequency bands,
Selecting a frequency band from the plurality of frequency bands;
The sum of the first time as the time for checking whether or not the selected frequency band is available and the first time as the time for performing data communication when the selected frequency band is available A second time for which is constant according to the selected frequency band;
Performing the inspection during the first time for the selected frequency band;
When the selected frequency band is available, the data communication is performed during the second time.
A wireless communication method.

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