JP4528716B2 - Base station and radio communication method - Google Patents

Description

The present invention relates to a base station and a wireless communication method for efficiently detecting a frequency in a wireless communication system in which wireless communication is performed in an arbitrary frequency band.

  Conventionally, a wireless communication system realizes wireless communication using a predetermined frequency band assigned in advance. In addition, when there are a plurality of predetermined frequency bands, for example, the wireless communication apparatus performs frequency detection for the purpose of specifying the frequency band to be used when starting wireless communication.

  When there are multiple radio frequency channels that can be used for communication in this way, for example, the received signal strength for each channel is measured in the radio communication device, and it is detected whether the radio frequency is used in order from the lowest or highest radio frequency. After that, a method of using an available channel is usually performed.

  In particular, in the case of wireless communication between a fixed station and a mobile station, a frequency list created based on the frequency at which the mobile station has performed wireless communication in the past, with the position and time at which the fixed station and the mobile station exist as units. The frequency list is preferentially detected by referring to the frequency list based on the position and time when the mobile station starts the wireless communication, and preferentially detecting the frequency band with a high frequency of wireless communication in the past. (For example, refer to Patent Document 1).

  In addition, it is considered that the availability of all channels is grasped even during communication, and the channel assignment is changed when interference with other wireless communication devices occurs (see, for example, Patent Document 2). .

  In the technique described above, a radio communication system usually takes into account a radio frequency band (license band) uniquely assigned to the communication system. However, recently, even in a frequency band other than the radio frequency band assigned to a specific communication system, a radio frequency channel already used by carrier sense is avoided, and a radio frequency is dynamically allocated and shared. A study of cognitive radio technology has been started (see Non-Patent Document 1, for example).

Recently, the allocation of frequency bands to wireless communication systems is very tight. Under such circumstances, it is desirable to share a frequency band assigned to a wireless communication system other than the own wireless communication system and effectively use limited frequency resources. Therefore, the wireless communication devices constituting the wireless communication system can be used from any frequency region that can be shared in consideration of the frequency usage situation that changes every moment depending on the location where the wireless communication device exists. It is necessary to detect possible frequency bands. In this case, since the frequency region to be frequency-detected is very wide, it is required to perform frequency detection efficiently.
In addition, since a frequency band pre-assigned to another radio communication system is shared, it is avoided to interfere with a radio communication device configuring another radio communication system that already uses the frequency band. Therefore, frequency detection requires high reliability. In particular, if only a radio frequency band licensed for a conventional radio communication system is used, the bandwidth of each frequency channel is constant even when there are a plurality of frequency channels that can be used. Not so difficult.
JP, 2000-36975, A FIG. 2 and FIG. JP 2002-300630 A J.Mitola III et al., “Cognitive Radio; Making Software Radios More Personal”, Source: IEEE Personal Communications Magazine, (Aug, 1999)

  However, when performing the above-described cognitive wireless communication, generally, unless the frequency bandwidth to be used is defined in advance, the wireless communication device transmits data necessary for communication when a request for communication occurs. A wireless communication channel having a wireless communication bandwidth determined by conditions such as rate and quality is required. There is no particular limitation as to which frequency is used as long as it is a radio frequency band that can be transmitted and received by the wireless communication device, but it is necessary to ensure that a necessary frequency bandwidth can be used. Furthermore, in the cognitive radio, since the frequency band used by other existing systems is usually temporarily shared, it is essential not to interfere with the existing system. Therefore, it is necessary to secure after detecting whether or not the radio frequency to be used is empty.

  Further, in the conventional frequency detection method, depending on the location and time of the wireless communication device when starting wireless communication, a frequency band with a high frequency of wireless communication in the past is preferentially detected. The frequency detection efficiency is increased by determining frequency band candidates for frequency detection and the detection order thereof by the method. This is based on the background that there is a high probability that a specific frequency band is available at a specific time in a specific place.

  However, when sharing a plurality of arbitrary frequency bands, it is necessary to consider the frequency usage situation that changes from moment to moment as described above, and determining the frequency detection target according to a specific time is It cannot be said that it is efficient and reliable. This is because the frequency band to be shared is not always in the same usage form at a specific time. Furthermore, considering that the location of the wireless communication device changes due to the movement of the wireless communication device, it is also efficient and highly reliable to determine the frequency detection target according to the place when the wireless communication is started. I can't say that. This is because the frequency band to be shared is likely to be in a different usage form in different places.

  The frequency band handled by the wireless communication apparatus that performs the cognitive wireless communication is expected to be wider than before, and the frequency bandwidth of the channel to be used is diversified. For this reason, the time for detecting the vacant frequency band is greatly increased, and the processing amount and power consumption of the wireless communication apparatus are increased accordingly.

Therefore, the present invention has been made to solve the above-described problem, and a base capable of efficiently and reliably detecting an available frequency band for a wide range of arbitrary frequency regions. An object is to provide a station and a wireless communication method.

The base station of the present invention comprises a notifying means for notifying contained in the frequency domain to be used for wireless communication with multiple mobile stations, the frequency band of the frequency detected on the plurality of mobile stations, said frequency band Means for acquiring a base station detection result indicating whether or not is used in another radio communication system, and detecting whether or not the frequency band is used in another radio communication system from each of the mobile stations Receiving means for receiving a mobile station detection result, each mobile station detection result, a storage means for storing the base station detection result, and a frequency utilization rate in the frequency band based on the stored detection result And calculating means for selecting a frequency band to be frequency-detected based on the frequency utilization rate for a frequency region used for radio communication with the plurality of mobile stations. And wherein the Rukoto.

The base station of the present invention includes a notifying means for notifying contained in the frequency domain to be used for wireless communication with multiple mobile stations, the frequency band of the frequency detected on the plurality of mobile stations, wherein An acquisition means for acquiring a base station detection result indicating whether or not a frequency band is used in another radio communication system; and whether or not the frequency band is used in another radio communication system from each of the mobile stations. receiving means for receiving location information at the time of the retrieved mobile station detection result and the mobile station detection result, and each of the mobile stations detection result and each of said position information, storing means for storing the base station detection result And a calculation means for calculating a frequency utilization rate in the frequency band based on the stored detection result and position information, and a frequency region used for wireless communication with the plurality of mobile stations. Based on the frequency utilization, characterized by comprising selecting means for selecting a frequency band of frequencies detected, the.

According to the base station and the wireless communication method of the present invention, it is possible to efficiently and reliably detect an available frequency band for an arbitrary frequency region over a wide range.

Hereinafter, a wireless communication apparatus, system, and method according to embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
A wireless communication apparatus according to this embodiment will be described with reference to FIG. FIG. 1 shows an example of the configuration of a wireless communication apparatus according to this embodiment.
As shown in FIG. 1, the wireless communication apparatus of this embodiment includes a transmission / reception antenna 101, an analog processing unit 102, a digital signal processing unit 103, and a control device 108. The analog processing unit 102 includes a wireless reception unit 104, an A / D conversion unit 105, a wireless transmission unit 106, and a D / A conversion unit 107. Further, the digital signal processing unit 103 includes a processing determination unit 109 and a detection result storage device 110.

The transmission / reception antenna 101 transmits and receives radio signals.
The wireless reception unit 104 receives a high-frequency wireless signal received by the transmission / reception antenna 101, converts it into a baseband signal, and supplies the baseband signal to the A / D conversion unit 105. The A / D conversion unit 105 converts the baseband signal into a digital signal and supplies the digital signal to the digital signal processing unit 103. The wireless transmission unit 106 converts the baseband signal received from the D / A conversion unit 107 into a high-frequency wireless signal and transmits it from the transmission / reception antenna 101. The D / A conversion unit 107 converts the digital signal received from the digital signal processing unit 103 into an analog baseband signal and supplies the analog baseband signal to the wireless transmission unit 106.

  The digital signal processing unit 103 performs processing of a digital signal received in communication and processing of a digital signal to be transmitted. Further, the processing determination unit 109 and the detection result storage device 110 in the digital signal processing unit 103 are mainly used in the free frequency detection processing of this embodiment.

In the idle frequency detection process performed in the present embodiment, the control device 108 outputs an instruction signal to the wireless reception unit 104 and the A / D conversion unit 105 so that the narrowband block is received. In addition, the control device 108 divides the entire bandwidth that can be received by the wireless communication device into a plurality of narrowband blocks having a narrow bandwidth.
The digital signal processing unit 103 determines whether or not the narrowband block is “free” with respect to the signal received by the narrowband block. The detection result storage device 110 stores the determination result. The process determination unit 109 selects a narrowband block to be detected based on the determination result stored in the detection result storage device 110. The narrowband block will be described later with reference to FIG.

  In the example of the wireless communication apparatus shown in FIG. 1, when performing the vacant frequency detection process, it is determined whether or not the received signal is vacant after converting the received signal into a digital signal. However, the conversion to the digital signal is not performed. In addition, it may be configured to determine whether or not there is a vacancy based on the received power at the time of the analog signal.

  Next, the narrowband block will be described with reference to FIG. FIG. 2 is a diagram illustrating that the receivable frequency band W of the wireless communication device is divided into a plurality of narrowband blocks 201 in the narrowband in the vacant frequency detection method of the present embodiment. It is assumed that the wireless communication apparatus of this embodiment can measure received power for each narrowband block in FIG. For example, the wireless reception unit 104 measures received power. The narrow band block is about several hundred kHz, for example, 200 kHz.

  Next, how each narrow band block is received will be described with reference to FIG. As shown in FIG. 2, a selection filter 301 for selecting a narrowband block having a bandwidth Wn is prepared. The selection filter 301 is provided in the wireless reception unit 104, for example. The structure may be such that the setting of the local frequency synthesizer of the wireless reception unit 104 is changed so that the selection filter 301 selects a specific narrow band block. In addition, information is not actually extracted at reception, but only for measuring whether or not the frequency band of the narrow band block is used. Therefore, it is only necessary to measure received power. The received power can be measured by either analog processing or digital processing, and can be held as a numerical value, and is not particularly limited as long as it can be compared with a certain threshold value.

Next, a method for determining the period of the narrowband block that is actually subjected to the detection process when the vacant frequency is detected will be described with reference to FIG.
As shown in FIG. 4, the minimum value L (L is an integer) of the number of narrowband blocks in which all the necessary frequency bandwidth D that is desired to be secured for wireless communication is included is used to detect the free frequency in the first embodiment. It is set as the period 402 of the narrowband block to be performed. This setting is performed by the control device 108, for example.

Next, a processing example in which detection processing is performed for each period of the narrowband block determined in FIG. 4 will be described with reference to FIGS. 5 and 6. FIG. 5 shows a processing example, and FIG. 6 shows a detection processing flow.
As shown in FIG. 5, a narrowband block period 502 for detecting a vacant frequency is set (step S601). Then, the narrowband block 501 having the lowest frequency is selected (step S602). Reception processing is performed on the narrowband block 501 selected for each cycle (step S603). For example, if the received power is less than the threshold value X [dBm], it is determined as “free”, otherwise “in use” is determined, and these results are held (step S604). Here, for the result of performing the detection process for each narrowband block, for example,
(1) Detection processing: “performed” / “not implemented” / “not implemented”
(2) Detection result: “Free” / “In use”
Such flag information may be held for each narrowband block. These are held in the detection result storage device 110, for example. As a realization method, a method of preparing a register capable of holding a state in hardware implementation, a method of preparing a state table or the like in software, and the like can be considered.

  Next, the control device 108 determines whether or not the narrowband block can be shifted to the higher frequency by the detection period T. If it can be shifted, the process proceeds to step S605; otherwise, the process proceeds to step S607 (step S605). If it can be shifted, the narrow band block number is shifted to the higher frequency by T (step S608).

As a result of performing the free frequency detection process on the selected narrowband block, as shown in the example of the result of FIG. 5, when two or more narrowband blocks determined to be “in use” continue (a plurality In the case of continuous use over a period (in FIG. 5, “in use” blocks continue over 2 periods), detection processing is still performed between the narrowband blocks determined to be “in use”. Information that “not detected” is stored for each narrowband block so that the detection process is not performed on the narrowband block that has not been performed (step S607). The reason for doing this is that the period of the narrowband block for performing the detection process is the minimum frequency bandwidth that just enters the frequency bandwidth D that is desired to be ensured for wireless communication, and therefore continuously in this period. This is because if there is no space, the frequency bandwidth D cannot be secured in the meantime.
Since a free frequency search is performed with a period of the frequency bandwidth D that is desired to be used in wireless communication, the frequency bandwidth D is included in a block section in which two or more detected blocks are determined to be “no free” continuously. Can never be ensured. Therefore, it is possible to omit the detection processing of the blocks that have not yet been detected with the empty frequency sandwiched between those blocks, thereby reducing the amount of empty frequency detection processing. As a result, it is possible to significantly reduce the processing amount / power consumption of the wireless communication device.

An example different from FIG. 1 of the present embodiment will be described with reference to FIG. In the following, the same parts as those already described are designated by the same reference numerals and the description thereof is omitted.
In FIG. 1, the vacant frequency detection process is performed using the reception unit that receives communication information in the wireless communication device. However, as shown in FIG. 7, the wireless reception unit (detection) that performs a separate reception process for the vacant frequency detection process ) And A / D converter 702 may be prepared separately.

(Second Embodiment)
The first embodiment is effective when a plurality of narrowband blocks determined to be “in use” are continuous, but for example, “in use” and “empty” appear alternately as shown in FIG. In many situations, there are fewer parts to omit the detection process. The second embodiment is effective in such a case.

  Processing in the second embodiment will be described with reference to FIG. In the present embodiment, it is the same as in the first embodiment that the cycle of the narrowband block for detecting the vacant frequency is set to the minimum frequency bandwidth in which the frequency bandwidth D that is desired to be ensured for wireless communication is entered. (Step S601). The same holds for the detection result stored in the wireless communication apparatus.

  As shown in FIG. 9, the first embodiment differs from the first embodiment in that a plurality of stages are prepared, and a narrowband block for detecting a vacant frequency in a certain stage has been detected up to the stage before it. One located near the middle of the narrowband block is selected (step S903). However, if the middle cannot be selected, the block closest to the middle is selected. This is illustrated in FIG. Further, all the detection results of the narrowband blocks selected for each stage are held (step S904).

  A method of selecting a narrowband block that omits the detection process in the next step S905 will be described. As shown in FIG. 10, in the results of all narrowband blocks in which vacant frequency detection has been performed up to Stage N with Stage N + 1, there is no gap between two narrowband blocks detected as “in use”. If there is a detection block, the difference between the block numbers is calculated, and it is checked whether or not the difference is smaller than the narrow band block period for detecting the free frequency of Stage 0. Here, if the period is smaller than the narrow band block period in which the vacant frequency detection of Stage 0 is performed, the detection process is “not executed” for all the undetected blocks in between (step S905). In this way, the detection process can be omitted for each stage.

  The omission of the frequency detection process will be described with reference to FIG. In FIG. 11, the initial detection period at the time of the first detection (Stage 0) is 20. For example, in Stage 2, it is assumed that block number 19 and block number 36 have been detected and are “in use”. Here, when the absolute value of the difference between the block number 19 and the block number 36 is calculated to be 17 and is smaller than the initial detection period 20, the detection process is not performed for all the blocks existing between the block number 19 and the block 36. It can be. As a result, the number of blocks for which detection processing can be omitted can be selected for each stage, and processing can be reduced.

Another example of omitting the frequency detection process will be described mainly with reference to FIG. FIG. 12 shows an example in the case of Stage 2.
As shown in FIG. 10, there are two narrowband blocks P and Q that are detected as “in use” as shown in FIG. If the number of narrowband blocks detected so far between P and Q is less than ^2N , all narrowband blocks existing between them that have not yet been detected are executed. Information indicating that the detection process is not performed is held (step S905).

In the example of FIG. 12, there are two narrowband blocks detected as “in use” in the stage 2, and there are two narrowband blocks that have been detected between them. ^{Since 2} = 4 or less, all the narrowband blocks that have not been subjected to detection processing between them can be “not performed”, and unnecessary detection processing can be omitted. In this way, it is possible to significantly reduce the amount of free frequency detection processing by advancing the detection processing while omitting the detection processing at each stage. The number of Stages to which this process is repeated is not particularly limited here. For example, the following procedure can be considered.

   (1) It is determined in advance that a certain number of stages will be executed.

   (2) Repeat for each stage until one or more frequency band candidates for which the bandwidth D can be secured are seen.

  Further, if the result of the detection process is “not implemented” for all narrowband blocks up to a certain stage, it is determined that a desired bandwidth cannot be secured.

(Third embodiment)
In the first embodiment, once the period of a narrowband block for which idle frequency detection is performed is determined, idle detection is performed over all narrowband blocks that can be received by the wireless communication apparatus. Also in the second embodiment, vacancy detection is performed over all narrowband blocks that can be received by the wireless communication apparatus in each stage.
At this time, if there is a plurality of narrowband blocks that are detected as “vacant” in the intermediate result, even if it does not perform vacancy detection over all the narrowband blocks that can be received by the wireless communication device, the details are focused on only that portion. There is a possibility that the detection process can be further omitted by performing the process. The third embodiment relates to such a detection process.

A wireless communication apparatus and method according to this embodiment will be described with reference to FIG.
In FIG. 13, in the first embodiment, two consecutively detected “empty” continues, so that the detection processing is not performed in the narrowband block that performs the free frequency detection performed thereafter. There is a possibility that the detection process can be further omitted by proceeding with the empty frequency search process while paying attention to the two consecutive portions. This process can also be applied to the second embodiment. Specifically, if there are a plurality of items detected as “free” in each stage, and the total of the consecutive numbers is larger than the frequency bandwidth D to be secured for wireless communication, pay attention to that portion. To do.

  Further, if there are a plurality of narrowband blocks detected as “vacant” in the intermediate result, the following three examples can be considered as specific methods for performing processing while paying attention only to that portion.

   (1) When two blocks detected as “free” at Stage 0 are consecutive, detection processing is performed for all the narrowband blocks between and around the two detected narrowband blocks.

   (2) When two blocks detected as “free” in Stage 0 are consecutive, the processing of the second embodiment is performed between the two detected narrowband blocks and the periphery thereof. Here, the maximum stage number is cut off at about 2 or 3. When the number of stages is 3, the frequency bandwidth D desired to be secured is detected evenly by narrow-band blocks with equal intervals of 5 and 9 divisions.

   (3) When two blocks detected as “free” in Stage 0 are consecutive, the processing of the second embodiment is performed between and around the two detected narrowband blocks. The processing of the second embodiment is continued until all blocks between and around the two narrowband blocks detected as “free” are detected.

(Fourth embodiment)
In the third embodiment, the vacant frequency detection processing is performed in the direction from the narrow band block in the low frequency band to the narrow band block in the high frequency band. In the fourth embodiment, the narrow band block in the high frequency band is performed. The detection process will proceed.
As in this embodiment and the third embodiment, by determining that the detection process is always started from a narrowband block having a high frequency or a low frequency, it is possible to successively use frequencies from the high frequency portion or the low frequency portion. Becomes higher. From such a detection method, communication with higher frequency utilization efficiency can be realized by securing a necessary frequency band.

(Fifth embodiment)
In the fifth embodiment, if the frequency bandwidth D that is desired to be secured for wireless communication is less than a certain bandwidth R, the detection processing is performed from the narrow-band block having a lower frequency, and D is equal to or greater than R. For example, detection processing is performed from the narrow band block of higher frequency.

If the third embodiment is performed by the method of the fourth embodiment, for example, a bandwidth wider than the bandwidth R can be secured in a higher frequency band. However, it is possible to increase the rate at which a narrow band is secured at a low frequency. As a result, it is possible to bias the ratio of ensuring the lower or higher frequency band with respect to each of the wide band and the narrow band. From such a detection method, communication with higher frequency utilization efficiency can be realized by securing a necessary frequency band.
(Sixth embodiment)
The present embodiment is a case where the frequency detection method described above is applied to a radio communication system including a base station and a mobile station.
The wireless communication system of the present embodiment includes, for example, a base station (BS) 1401 and three mobile stations (MS) 1403 as shown in FIG. The base station 1401 performs radio communication using a plurality of mobile stations 1403 and radio channels 1404 and 1405 within the communication area 1402. In addition to the example shown here, for example, the following description holds true for wireless communication between base stations and between mobile terminals, and wireless communication in which the base station and the mobile station are in a one-to-one relationship.
In the case of FIG. 14, the frequency band previously assigned to the radio communication system is used for the radio channel 1404, and control data such as a frequency detection request and a frequency detection result report are mainly communication targets. The radio channel 1405 uses a frequency band assigned to another radio communication system, and information data such as application data is mainly a communication target. Therefore, the wireless channel 1405 for communicating information data shares the frequency band with other wireless communication systems. Note that the radio channel 1405 can use the same frequency band for radio communication between the base station 1401 and all mobile stations 1403, or can use any frequency band for radio communication with each mobile station 1403. .

Next, the base station of this embodiment will be described with reference to FIG.
The base station of this embodiment includes a plurality of antennas 1501-1, 1501-2, 1501-3, 1501-4, 1501-5, and a plurality of radio processing circuits 1502-1, 1502-2, 1502-3, 1502-. 4, 1502-5, a plurality of modulation circuits 1503-1 and 1503-2, a plurality of demodulation circuits 1504-1 and 1504-2, a frequency detection circuit 1505, a frequency detection result storage unit 1506, and a control unit 1507.

(When sending and receiving information data such as application data)
<For transmission>
Based on the frequency detection result stored in the frequency detection result storage unit 1506, the control unit 1507 specifies the frequency band for transmitting the determined information data, to the wireless processing circuit 1502-1.

  The modulation circuit 1503-1 adds an error detection code to the input information data and performs error correction coding, and modulates the information by a predetermined modulation method and outputs the result to the radio processing circuit 1502-1.

  The radio processing circuit 1502-1 receives the modulated information data, and performs predetermined radio processing such as D / A conversion, quadrature modulation, up-conversion, band limitation, and power amplification on the input information data. And generate a radio signal. The radio processing circuit 1502-1 generates a radio signal according to the frequency band specified by the control unit 1507. The radio signal is transmitted from the antenna 1501-1.

<When receiving>
The control unit 1507 designates a frequency band for receiving the information data determined based on the frequency detection result stored in the frequency detection result storage unit 1506 to the radio processing circuit 1502-2.

  The radio processing circuit 1502-2 receives a radio signal received by the antenna 1501-2. The radio processing circuit 1502-2 performs predetermined radio processing such as power amplification, band limitation, down-conversion, orthogonal demodulation, A / D conversion, and the like on the input radio signal according to the frequency band specified by the control unit 1507. The digital signal is generated, and this digital signal is output to the demodulation circuit 1504-1.

  The demodulation circuit 1504-1 demodulates the digital signal input from the wireless processing circuit 1502-2, performs error correction decoding, and outputs the result to the control unit 1507.

  The control unit 1507 performs error detection on the input data, and if there is no error, outputs it as information data such as application data.

(When transmitting / receiving control data such as frequency detection request and frequency detection result)
<For transmission>
The control unit 1507 outputs control data to be transmitted to the modulation circuit 1503-2.

  The modulation circuit 1503-2 adds an error detection code and error correction coding to the control data input from the control unit 1507, modulates the data with a predetermined modulation method, and outputs the modulated data to the radio processing circuit 1502-3. .

  The radio processing circuit 1502-3 performs predetermined radio processing such as D / A conversion, quadrature modulation, up-conversion, band limitation, and power amplification on the modulated information data input from the modulation circuit 1503-2. The wireless signal is generated, and the wireless signal is transmitted from the antenna 1501-3.

<When receiving>
The radio processing circuit 1502-4 inputs a radio signal received by the antenna 1501-4, and performs predetermined amplification such as power amplification, band limitation, down-conversion, quadrature demodulation, A / D conversion on the input radio signal. Wireless processing is performed to generate a digital signal, and the digital signal is output to the demodulation circuit 1504-2.

  The demodulation circuit 1504-2 demodulates the input digital signal, performs error correction decoding, and outputs the result to the control unit 1507.

  When the frequency detection result is input, the control unit 1507 stores the frequency detection result in the frequency detection result storage unit 1506.

(When performing frequency detection processing)
The radio processing circuit 1502-5 inputs a radio signal received by the antenna 1501-5, and performs predetermined amplification such as power amplification, band limitation, down-conversion, quadrature demodulation, A / D conversion on the input radio signal. Radio processing is performed to generate a digital signal, and the digital signal is output to the frequency detection circuit 1505.

  The frequency detection circuit 1505 performs power measurement or the like as frequency detection processing on the input digital signal and stores the result in the frequency detection result storage unit 1506. Note that a frequency band that is a frequency detection target determined based on the frequency detection result stored in the frequency detection result storage unit 1506 is designated from the control unit 1507 to the radio processing circuit 1502-5, and the radio processing circuit 1502-5 The processing circuit 1502-5 generates a radio signal according to the frequency band.

Next, the mobile station of this embodiment will be described with reference to FIG.
The mobile station of this embodiment includes a plurality of antennas 1501-1, 1501-2, 1501-3, 1501-4, 1501-5, and a plurality of radio processing circuits 1502-1, 1502-2, 1502-3, 1502-. 4, 1502-5, a plurality of modulation circuits 1503-1 and 1503-2, a plurality of demodulation circuits 1504-1 and 1504-2, a frequency detection circuit 1505, and a control unit 1601.

(When sending and receiving information data such as application data)
<For transmission>
The control unit 1601 inputs information data and outputs the input information data to the modulation circuit 1503-1.

  The modulation circuit 1503-1 adds an error detection code to the input information data and performs error correction coding, and modulates the information by a predetermined modulation method and outputs the result to the radio processing circuit 1502-1.

  The radio processing circuit 1502-1 performs predetermined radio processing such as D / A conversion, quadrature modulation, up-conversion, band limitation, and power amplification on the input modulated information data to generate a radio signal. The radio signal is transmitted from the antenna 1501-1.

  Note that a frequency band for transmitting information data is specified from the control unit 1601 to the wireless processing circuit 1502-1, and the wireless processing circuit 1502-1 generates a wireless signal according to the frequency band. The control unit 1601 can perform the above-described control by notifying the frequency band using control data from the base station.

<When receiving>
The radio processing circuit 1502-2 receives a radio signal received by the antenna 1501-2, and performs predetermined amplification such as power amplification, band limitation, down-conversion, quadrature demodulation, A / D conversion on the input radio signal. Wireless processing is performed to generate a digital signal, and the generated digital signal is output to the demodulation circuit 1504-1.

  The demodulation circuit 1504-1 demodulates the input digital signal, performs error correction decoding, and outputs the result to the control unit 1601.

  The control unit 1601 performs error detection on the input data, and if there is no error, outputs it as information data such as application data.

  Note that a frequency band for receiving the information data is designated from the control unit 1601 to the radio processing circuit 1502-2, and the radio processing circuit 1502-2 generates a radio signal according to the frequency band.

(When transmitting / receiving control data such as frequency detection request and frequency detection result)
<For transmission>
The control unit 1601 outputs control data to the modulation circuit 1503-2.

  The modulation circuit 1503-2 adds an error detection code and error correction coding to the input control data, modulates the data by a predetermined modulation method, and outputs the modulated data to the radio processing circuit 1502-3.

  The radio processing circuit 1502-3 performs predetermined radio processing such as D / A conversion, quadrature modulation, up-conversion, band limitation, and power amplification on the input modulated control data to generate a radio signal. The generated radio signal is transmitted from the antenna 1501-3.

<When receiving>
The radio processing circuit 1502-4 inputs a radio signal received by the antenna 1501-4, and performs predetermined amplification such as power amplification, band limitation, down-conversion, quadrature demodulation, A / D conversion on the input radio signal. Wireless processing is performed to generate a digital signal, and the generated digital signal is output to the demodulation circuit 1504-2.

  Demodulation circuit 1504-2 demodulates the input digital signal, performs error correction decoding, and outputs the result to control unit 1601.

(When a frequency detection request is notified from the base station using control data)
The radio processing circuit 1502-5 inputs a radio signal received by the antenna 1501-5, and performs predetermined radio such as power amplification, band limitation, down-conversion, quadrature demodulation, A / D conversion on the input radio signal. Processing is performed to generate a digital signal, and the generated digital signal is output to the frequency detection circuit 1505.

  The frequency detection circuit 1505 performs power measurement or the like as frequency detection processing on the input digital signal and notifies the control unit 1601 of the result.

  Note that the frequency band targeted for frequency detection notified from the base station is specified to the radio processing circuit 1502-5 from the control unit 1601, and the radio processing circuit 1502-5 generates a radio signal according to the frequency band. To do. The frequency detection result notified to the control unit 1601 is transmitted to the base station as control data.

  As described above, in the radio communication between the base station and the mobile station, an arbitrary frequency band can be used between the mobile stations.

Next, an example of the frequency detection method will be described with reference to FIGS. FIG. 17 is a sequence chart of the frequency detection method of this embodiment.
When starting the frequency detection, the control unit 1507 of the base station determines a target frequency detection range (S1701). In step S1701, as shown in FIG. 18, in the area where the base station exists, it can be used except for the frequency band that is always used by other wireless communication systems and the frequency band that is used for highly urgent applications. That is, a frequency band that can be shared with other wireless communication systems is identified, and its center frequency and band are determined. In the example of FIG. 18, the center frequency is determined from F1 to Fn, and the band is determined to be 20 MHz. In the example of FIG. 18, the same band is determined at all the center frequencies, but different bands can be determined.

  The control unit 1507 determines a frequency band to be a frequency detection target from the determined frequency detection range (S1702), and notifies the mobile station as control data. In the examples of FIGS. 17 and 18, the center frequency F1 and the band of 20 MHz are notified.

  Receiving the notification, the control unit 1601 of the mobile station uses the frequency detection circuit 1505 to detect whether or not this frequency band is used (S1703), and notifies the detection result to the base station as control data. Similarly, the control unit 1507 of the base station uses the frequency detection circuit 1505 to detect whether this frequency band is used (S1704).

  In the base station, the detection result notified from the mobile station and the detection result performed by the mobile station are stored in the frequency detection result storage unit 1506, whereby the frequency detection result is updated (S1705). Thereafter, steps S1701 to S1705 are repeatedly executed in a predetermined cycle.

Next, an example of the contents of the frequency detection result storage unit 1506 will be described with reference to FIGS. 19, 20, and 21.
In the example of FIGS. 19 and 20, the frequency detection result calculated using the frequency detection result of the past N times (N is an arbitrary integer, 5 in the examples of FIGS. 19 and 20) for the frequency band. A timer and a timer maximum value used in the control of the control unit 1507 are stored.
As the frequency detection result, in the detection results in the base station and all mobile stations, 1 is detected when at least one detection result indicates that the frequency is used. If the result indicates that the frequency is not used, 0 is stored.
Further, as the frequency utilization rate, a ratio of 1 in the past N frequency detection results for the frequency band is stored.
The timer is a value used to determine whether or not to perform frequency detection processing for the frequency band, and the timer maximum value is a timer that is used after the frequency detection processing is executed for the frequency band. The value to be reset. Therefore, the timer is sequentially subtracted from the timer maximum value, and when it becomes 0, the frequency detection process is executed. Also, a small timer maximum value means that the frequency detection processing frequency is large, and conversely a large timer maximum value means that the frequency detection processing frequency is small.

  In the example of FIG. 19, the timer maximum value is determined according to the above-described frequency utilization rate. When the frequency utilization rate is small, the timer maximum value is also set small. When the frequency utilization rate is large, the timer maximum value is also set large. ing. In this case, when the frequency utilization rate is small, that is, when there is a high possibility that the frequency band can be used, the detection frequency of the frequency band is increased, and as a result, the reliability of the frequency detection process is improved.

  In the example of FIG. 20, the timer maximum value is determined according to the frequency utilization rate described above, the timer maximum value is set large when the frequency utilization rate is large and small, and the timer maximum value is set when the frequency utilization rate is medium. The value is set low. In this case, when the frequency usage rate is moderate, that is, it is difficult to determine whether or not the frequency band can be used, the frequency of detection of the frequency band is increased, and as a result, the efficiency of the frequency detection process is improved. Will be allowed to.

  FIG. 21 shows a modification of the configuration example shown in FIG. In the example of FIG. 21, the frequency detection result calculated using the frequency detection result in the past N times (N is an arbitrary integer, 5 in the example of FIG. 21) for the frequency band, and other control units A timer and a timer maximum value used in the control 1507 are stored. Here, as the frequency detection result, a ratio indicating that the frequency is used in the detection results in the base station and all the mobile stations is stored. That is, when it is detected that 5 mobile stations are used by one base station and 9 mobile stations, 50 is stored as a detection result. Further, as the frequency utilization rate, an average of the past N frequency detection results for the frequency band is stored. Note that the timer and the timer maximum value are the same as those in the example of FIG. 19, but the timer maximum value can also be determined in the same manner as in the example shown in FIG.

Next, details of the frequency detection target determination method in step S1702 will be described with reference to FIG. FIG. 22 is a flowchart of frequency detection target determination processing performed by the control unit 1507 of the base station. In addition, this process shall be implemented with progress of a predetermined period as mentioned above.
When a predetermined period elapses, the control unit 1507 of the base station refers to the frequency detection result storage unit 1506 and selects a frequency at which the timer is minimized at that time (step S2201). If there is only one selected frequency, this frequency is set as a detection target (steps S2202 and S2203). When two or more frequencies are selected (step S2202), it is determined whether the selected frequency is M or less (step S2204). When it is M or less, all the selected frequencies are determined. The detection target is set (step S2205). Here, M is an arbitrary integer and means the maximum number of frequencies that can be included in one frequency detection request for the mobile station. When the selected frequency is higher than M (step S2204), the frequency of M is selected from the frequencies having a low frequency detection rate at this time (step S2206). For the selected frequency, the timer is reset to the timer maximum value (step S2207).

Next, the details of the frequency detection result update method in step S1705 will be described with reference to FIG. FIG. 23 is a flowchart of frequency detection result update processing performed under the control of the control unit 1507 of the base station. Here, the update of the frequency detection result is performed after the frequency detection result in the mobile station and the base station is completed and the detection result is notified from the mobile station.
First, the control unit 1507 of the base station updates the frequency utilization rate (step S2301). For example, if the frequency detection result storage unit 1506 is configured as shown in FIG. 19 and FIG. 20, the oldest frequency detection result is deleted and a new detection result is stored. This is done by recalculating the stored ratio. If configured as in the example shown in FIG. 21, the oldest frequency detection result is deleted, the new detection result is stored, and the average is calculated again.

  Subsequently, if it is necessary to change the maximum timer value according to the updated frequency utilization rate, this is changed (step S2302). When the timer maximum value is changed, if the timer exceeds the timer maximum value at this point (step S2303), the timer is reset to the timer maximum value (step S2304). When a plurality of frequencies are included in the frequency detection request for the mobile station, the above processing is repeated for all frequencies (step S2305).

  In the frequency detection method of the sixth embodiment described above, when detecting whether or not the frequency band targeted for wireless communication is being used by another wireless communication system, the base station and the base station and the wireless All mobile stations existing in a communicable communication area perform detection, and control the frequency detection frequency for each frequency band according to the frequency utilization rate in the communication area calculated using the detection result. For example, the frequency detection frequency is set so that the frequency detection frequency is higher than the other frequency bands for a frequency band whose frequency utilization rate is smaller than a certain value. In addition, the frequency detection frequency is set so that the frequency detection frequency is lower than the other frequency bands for a frequency band having a frequency utilization rate larger than a certain value. Thereby, the ratio of the place where the said frequency band is utilized by the other radio | wireless communications system, and the ratio of time will be considered in the said communication area. As a result, even when the frequency usage state changes from moment to moment or when the mobile station is moving, it is possible to detect the available frequency band efficiently and with high reliability.

(Seventh embodiment)
Hereinafter, a seventh embodiment of the present invention will be described in detail with reference to the drawings. A mobile station that implements the frequency detection method of the seventh embodiment will be described with reference to FIG.
According to FIG. 24, a position information detection unit 2402 is added to the configuration example of the mobile station of FIG. 16 described in the sixth embodiment. The position information detection unit 2402 acquires position information at the time point when performing frequency detection processing using GPS (Global Positioning System) or the like.

Next, the frequency detection method in this embodiment will be described with reference to FIG. Hereinafter, the same steps as those already described are denoted by the same reference numerals and description thereof is omitted.
According to the sequence chart of the frequency detection method shown in FIG. 25, in step S2501, the mobile station notifies the base station of the position information detection result together with the frequency detection result as control data.

Next, a configuration example of the frequency detection result storage unit 1506 in the present embodiment will be described. In the seventh embodiment, the control unit 1507 of the base station divides the communication area into a plurality of sub areas as shown in FIG. In the example shown in FIG. 26, the vicinity of the base station is divided into subarea A, and the periphery thereof is divided into subarea B to subarea E.
In this case, as shown in FIGS. 27 and 28, the frequency detection result storage unit 1506 stores the past N times (N is an arbitrary integer, 5 in the examples of FIGS. 27 and 28) corresponding to each sub-area. Frequency detection result, frequency usage rate corresponding to each sub-area calculated using the frequency detection result, frequency usage rate corresponding to all communication areas calculated from frequency usage rate corresponding to each sub-area, control The timer used in the control of the unit 1507 and the timer maximum value are stored.
Here, the frequency detection result is obtained in the same manner as in the sixth embodiment, FIG. 27 is the same as the example shown in FIGS. 19 and 20, and FIG. 28 is the same as the example shown in FIG. Further, the timer and the timer maximum value are the same as in the sixth embodiment. The frequency usage rate corresponding to the entire communication area can be obtained by averaging the frequency usage rates corresponding to the sub areas.

  As described above, since the base station is notified of the location information at the time of acquiring the frequency detection result from each mobile station together with the frequency detection result, it is possible to grasp the subarea to which each mobile station belongs. is there.

  The frequency detection target determination method in step S1702 and the frequency detection result update method in step S1705 may be performed in the same manner as the method described with reference to FIGS. 22 and 23 in the sixth embodiment.

  In the frequency detection method of the seventh embodiment described above, when detecting whether or not the frequency band to be applied to wireless communication is being used by another wireless communication system, the base station and the base station and the wireless Every mobile station in a communicable communication area performs detection, and for each frequency band according to the frequency utilization rate in the communication area calculated using the detection result and position information at the time of detection. The frequency detection frequency is controlled. Thereby, the ratio of the place where the said frequency band is utilized by the other radio | wireless communications system, and the ratio of time will be considered in the said communication area. As a result, even when the frequency usage state changes from moment to moment or when the mobile station is moving, it is possible to detect the available frequency band efficiently and with high reliability.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements 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.

The block diagram which shows an example of the radio | wireless communication apparatus of 1st to 5th embodiment. The figure for demonstrating a narrow-band block. The figure for demonstrating the selection filter for selecting a certain narrow-band block. The figure which shows the reference | standard which determines the period of the narrowband block which performs frequency detection. The figure which shows an example of the idle frequency detection in 1st Embodiment. The flowchart of the process in 1st Embodiment. The block diagram which shows the example different from FIG. 1 of the radio | wireless communication apparatus of 1st-5th embodiment. The figure for demonstrating the condition where "in use" and "vacant" appear alternately when a detection process is performed for every period of a narrow-band block. The flowchart of the process in 2nd Embodiment. The figure which shows an example of selection of the narrow band block which performs the free frequency detection in each Stage, and the detection process with respect to the selected block The figure for demonstrating the method of omission of a frequency detection process. The figure which shows an example which selects the narrow-band block which does not perform the detection process in the case of Stage2. FIG. 10 is a diagram illustrating that when a portion detected as “free” continues continuously a plurality of times and there is a portion that is continuously detected as “free”, the subsequent periodic detection processing is interrupted. The figure which shows a radio | wireless communications system provided with the base station and 6th mobile station in 6th and 7th embodiment. The block diagram which shows an example of the base station of FIG. The block diagram which shows an example of the mobile station of FIG. The sequence chart of the frequency detection method of 6th Embodiment. The figure which shows utilization of the frequency band in a certain area. The figure which shows the 1st example of the content of the frequency detection result memory | storage part of FIG. The figure which shows the 2nd example of the content of the frequency detection result memory | storage part of FIG. The figure which shows the 3rd example of the content of the frequency detection result memory | storage part of FIG. 18 is a flowchart showing the operation in step S1702 of FIG. 18 is a flowchart showing the operation of step S1705 in FIG. The block diagram which shows an example of the mobile station in the 7th Embodiment of this invention. The sequence chart of the frequency detection method of the 7th Embodiment of this invention. The figure which shows the communication area around a base station. The figure which shows the 1st example of the content of the frequency detection result memory | storage part in the base station in the 7th Embodiment of this invention. The figure which shows the 2nd example of the content of the frequency detection result memory | storage part in the base station in the 7th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Transmission / reception antenna, 102 ... Analog processing part, 103 ... Digital signal processing part, 104 ... Wireless reception part, 105, 702 ... A / D conversion part, 106 ... Wireless transmission part, 107 ... D / A conversion part, 108 ... Control device 109 ... Processing determination unit 110 ... Storage device for detection result storage, 201, 501 ... Narrowband block, 301 ... Select filter, 402,502 ... Narrowband block cycle, 1401 ... Base station, 1402 ... Communication area, 1403 ... Mobile station, 1404, 1405 ... Radio channel, 1501-1 to 5 ... Antenna, 1502-1 to 5 ... Radio processing circuit, 1503-1 to 2 ... Modulation circuit, 1504-1 to 2 ... Demodulation circuit, 1505 ... Frequency detection circuit, 1506 ... frequency detection result storage unit, 1507, 1601 ... control unit, 2402 ... position information detection unit

Claims (10)

A notification means for notifying the plurality of mobile stations of a frequency band that is included in a frequency region used for wireless communication with the plurality of mobile stations;
Obtaining means for obtaining a base station detection result indicating whether or not the frequency band is used in another wireless communication system;
Receiving means for receiving a mobile station detection result for detecting whether or not the frequency band is used in another wireless communication system from each of the mobile stations;
Storage means for storing each mobile station detection result and the base station detection result;
Calculation means for calculating a frequency utilization rate in the frequency band based on the stored detection results;
A base station comprising: selection means for selecting a frequency band to be a frequency detection target based on the frequency utilization factor for a frequency region used for wireless communication with the plurality of mobile stations. A notification means for notifying the plurality of mobile stations of a frequency band that is included in a frequency region used for wireless communication with the plurality of mobile stations;
Obtaining means for obtaining a base station detection result indicating whether or not the frequency band is used in another wireless communication system;
Receiving means for receiving from each mobile station the position information at the time of acquiring the mobile station detection result and the mobile station detection result detected whether or not the frequency band is used in another wireless communication system;
Each of the mobile station detection results and each of the location information, storage means for storing the base station detection results;
Calculation means for calculating a frequency utilization rate in the frequency band based on the stored detection result and position information;
A base station comprising: selection means for selecting a frequency band to be a frequency detection target based on the frequency utilization factor for a frequency region used for wireless communication with the plurality of mobile stations.   3. The base station according to claim 1, wherein the calculation unit calculates the frequency utilization rate based on a plurality of times of the mobile station detection results and a plurality of times of the base station detection results. .   The calculation means calculates the frequency utilization rate based on whether or not at least one of the mobile station detection result and the base station detection result indicates that it is used in another radio communication system. The base station according to claim 1 or 2, wherein the base station is characterized.   The said calculation means calculates the said frequency utilization factor based on the ratio which shows that the said mobile station detection result and the said base station detection result are used for the other radio | wireless communications system. The base station according to claim 1 or 2.   The said selection means sets so that the frequency which performs a frequency detection with respect to the frequency band in which the said frequency utilization factor is smaller than a certain value may become higher than another frequency band. Item 3. The base station according to Item 2.   The said selection means is set so that the frequency which performs a frequency detection with respect to the frequency band where the said frequency utilization factor is larger than a certain value becomes lower than another frequency band. Item 3. The base station according to Item 2. The base station according to claim 1, wherein the frequency domain includes a frequency band that is allocated in advance to another wireless communication system. Notifying the plurality of mobile stations of the frequency band that is included in the frequency region used for radio communication with the plurality of mobile stations,
Obtaining a base station detection result indicating whether or not the frequency band is used in another wireless communication system;
Receiving from each mobile station a mobile station detection result that detects whether or not the frequency band is used in another radio communication system;
Storing each mobile station detection result and the base station detection result;
Based on the stored detection results, calculate the frequency utilization rate in the frequency band,
A radio communication method, wherein a frequency band to be a frequency detection target is selected based on the frequency utilization rate for a frequency region used for radio communication with the plurality of mobile stations. Notifying the plurality of mobile stations of the frequency band that is included in the frequency region used for radio communication with the plurality of mobile stations,
Obtaining a base station detection result indicating whether or not the frequency band is used in another wireless communication system;
Receiving position information at the time of acquiring the mobile station detection result and the mobile station detection result detected whether or not the frequency band is used in another wireless communication system from each of the mobile stations,
Storing each mobile station detection result and each position information, and the base station detection result;
Based on the stored detection result and position information, calculate the frequency utilization rate in the frequency band,
A radio communication method, wherein a frequency band to be a frequency detection target is selected based on the frequency utilization rate for a frequency region used for radio communication with the plurality of mobile stations.

Images