JP4203832B2 - Wireless communication apparatus, wireless communication system, and wireless communication method - Google Patents

Description

The present invention relates to a wireless communication apparatus , a wireless communication system, and a wireless communication method that perform data communication wirelessly.

In Japan and Europe, when building an RFID system using radio waves in the UHF band, the usable frequency band is narrow. FIG. 8 is a diagram showing an example of channel arrangement in the UHF band. As shown in the figure, nine channels obtained by dividing a 2 MHz band from 952.0 to 954.0 MHz by a 200 kHz width are arranged in Japan. In Europe, 10 channels obtained by dividing a 2 MHz band of 865.6 to 867.6 MHz by a 200 kHz width are arranged. In a region where the usable frequency band is narrow, when a plurality of wireless communication devices such as reader / writers are installed close to each other, so-called carrier sense is used to avoid radio wave interference between reader / writers. Mandatory by law.

Carrier sense is also called LBT (Listen Before Talk), and the frequency at which communication is possible by measuring (sense) the received power intensity of the carrier (carrier) before communicating between the reader / writer and the RFID tag. It is to confirm whether the radio wave is. That is, for the radio wave transmitted from the reader / writer to the RFID tag, the received power intensity of the channel in the frequency band is measured . If the measured received power intensity is equal to or higher than a predetermined level, it is determined that the channel is in use and waits for transmission, and if it is lower than the predetermined level, it is determined that the channel is unused and transmission is performed. . This process prevents interference with adjacent reader / writers.

As described above, it is specified that the available state of a usable channel is checked before the reader / writer starts communication by performing carrier sense, and if there is an available channel, radio waves of that frequency are transmitted . However, there is no particular restriction as to which channel is selected and used when there are a plurality of empty channels. Thus, for example, the following method has been proposed as a free channel selection method.

(A) As soon as a free channel is found, that channel is selected. When there are a plurality of empty channels, the priority order is determined in advance.
(B) Search all channels and select the channel with the lowest measured received power intensity.
(C) Search all channels, evaluate the level of the neighboring channels of the free channel, and weight it. Further, weighting based on the importance of the application is performed at the time of channel level evaluation, and a channel is selected according to the weighting (see, for example, Patent Document 1 below).

  In the conventional channel selection method, the channel evaluation is complicated in the order of (A) ⇒ (B) ⇒ (C). As a result, the total communication amount in the carrier sense system can be increased. .

JP 2006-197233 A

The present invention has been made to increase the total communication amount by devising a channel evaluation method. That is, in a radio communication apparatus and radio communication system having a carrier sense function, and a radio communication method performing carrier sense, a channel to be used is selected in consideration of the influence of an interference wave of an adjacent channel when searching for an empty channel, and the selected use An object of the present invention is to improve communication efficiency between a wireless communication device and a data carrier by performing communication at an optimal communication speed for a channel.

  In order to achieve the above object, a wireless communication apparatus of the present invention performs wireless data communication with a data carrier by using one or a plurality of channels on a plurality of frequency bands. Before wireless communication with a data carrier, the device searches an odd number of free channels with continuous frequency bands based on the received power intensity measured in units of channels in a continuous channel group within a predetermined range. The communication speed with the data carrier is started by setting the communication speed higher as the frequency bandwidth of the entire odd number of consecutive empty channels extracted by the search is wider.

Further, in the wireless communication apparatus of the present invention, the reception power equal to or lower than the first threshold is determined based on the reception power intensity measured in units of channels in a continuous channel group within a predetermined range before wireless communication with the data carrier. searches a free channel is the intensity extracting one free channel, the received signal strength of a channel adjacent to the high frequency side of the extracted said one free channel, to the low frequency side of the extracted said one free channel If the received power strengths of adjacent channels are both equal to or lower than the second threshold value, which is greater than the first threshold value, it may be possible to use a continuous odd number of empty channels.

Furthermore, the wireless communication device of the present invention is a wireless communication device that performs wireless data communication with a data carrier by using one or a plurality of channels on a frequency band divided into a plurality of data bands. Before wireless communication with the carrier, in a continuous channel group within a predetermined range, based on the received power intensity measured in units of channels, a search is made for an empty channel having a received power intensity equal to or less than a first threshold, and It is characterized in that reception power intensity data for each channel is accumulated every time an empty channel is searched, and a communication speed is set by estimating an empty channel state based on a past received power intensity when searching for an empty channel.

The wireless communication apparatus of the present invention can be suitably applied to a reader / writer used in an RFID system that requires countermeasures against interference due to carrier sense, such as a reader / writer in a high-power UHF band or a low-power UHF band.
A wireless communication system according to the present invention includes any one of the wireless communication devices described above and a data carrier capable of data communication with the wireless communication device.
The present invention is also a wireless communication method for performing wireless data communication with a data carrier by using one or a plurality of channels on a frequency band divided into a plurality, and wirelessly communicates with the data carrier. Before communication, in a continuous channel group in a predetermined range, a search step for searching for an odd number of empty channels having continuous frequency bands based on the received power intensity measured in units of channels, and extracted by the search step A setting step of setting a higher communication speed as the frequency bandwidth of the entire odd number of consecutive empty channels is wider, and communication with the data carrier is started at the communication speed set in the setting step. It is characterized by doing.
The search step includes an empty channel having a received power intensity equal to or less than a first threshold based on a received power intensity measured in units of channels in a continuous channel group within a predetermined range before wireless communication with a data carrier. To search for one vacant channel, and the received power intensity in both the channel adjacent to the extracted vacant channel on the high frequency side and the channel adjacent on the low frequency side is the first threshold value. If it is less than or equal to the second threshold value, the search may be made as a continuous odd number of empty channels.
The present invention is also a wireless communication method for performing wireless data communication with a data carrier by using one or a plurality of channels on a frequency band divided into a plurality, and wirelessly communicates with the data carrier. An empty channel search step for searching for an empty channel having a received power intensity equal to or lower than a first threshold based on the received power intensity measured in units of channels in a continuous channel group within a predetermined range before communication; An accumulation step of accumulating received power intensity data in units of channels each time a channel is searched; a communication speed setting step of estimating a vacant channel state based on a past received power intensity when searching for an empty channel and setting a communication speed; The communication with the data carrier is started at the communication speed set in the communication speed setting step.

According to the wireless communication device , the wireless communication system, and the wireless communication method of the present invention, when the used channel is selected from the free channels searched at the time of carrier sense, the used channel is selected according to the free state of the adjacent channel. I did it. In addition, the communication speed in the selected use channel is set to the maximum speed at which communication is possible according to the use status of the adjacent channel, and communication is performed. For this reason, by communicating at high speed when there are many free channels and communicating at low speed when there are few free channels, it is possible to suppress the effects of communication errors and increased communication time due to radio wave interference of adjacent channels. . In addition, communication efficiency can be significantly increased as compared with a fixed channel selection method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a reader / writer which is a wireless communication apparatus of the present invention.

As shown in the figure, the reader / writer 1 of this embodiment is a device that performs wireless data communication with an RFID tag that is a data carrier using radio waves. More specifically, the reader / writer 1 selects and uses radio waves of one channel frequency selected from the nine channels in the UHF band shown in FIG. 8, and stores it in the memory for the RFID tag. Ru der to perform reading and writing of data stored. The reader / writer 1 includes a control unit 2, a transmitter 3, a transmission unit 4, a reception unit 5, a circulator 6, and an antenna 7 described below.

The control unit 2 controls transmission / reception between the reader / writer 1 and the RFID tag, generates and outputs a transmission signal S ₁ mainly transmitted to the RFID tag, and receives a reception signal S ₂ received from the RFID tag. To process. The configuration of the control unit 2 will be described in detail with reference to FIG.

The transmitter 3 sets the carrier frequency of the transmission signal S ₁ based on the control signal S ₃ from the control unit 2, and is configured by a PLL circuit in this embodiment.

The transmitter 4 outputs a read signal or a write signal to the RFID tag as a transmission signal S ₁ , and includes a digital / analog converter 41, a modulator 42, and a high frequency amplifier 43. First digital-to-analog converter 41 outputs the transmission data outputted from the control unit 2 as a baseband signal S ₄ is converted into an analog signal from a digital signal. Next, the modulator 42 modulates the carrier wave f ₀ having a predetermined frequency set by the transmitter 3 with the baseband signal S ₄ input from the digital-analog converter 41, and transmits the readout signal when the carrier signal f ₀ is transmitted. ₀ means no modulation. Further, the high frequency amplifier 43 performs power amplification of the RF signal input from the modulator 42. The transmission signal S ₁ output from the high frequency amplifier 43 is radiated from the antenna 7 through the circulator 6 and the low-pass filter 8.

The receiving unit 5 inputs a signal returned from the RFID tag as a received signal S ₂ , and includes a band limiting filter 51, a low noise amplifier 52, a demodulator 53, an amplifier 54, and an analog / digital converter 55. Since the received signal S ₂ input through the band limiting filter 51 is a weak radio wave due to the reflected wave of the RFID tag, it is amplified by the low noise amplifier 52 and output to the demodulator 53. Here, the demodulator 53 demodulates the input received signal S ₂ into a baseband signal S ₄ by a carrier wave f ₀ of a predetermined frequency from the transmitter 3. Next, the demodulated baseband signal S ₄ is input to the amplifier 54 to be amplified. Further analog-to-digital converter 55 outputs a baseband signal S ₄ which is amplified from an analog signal into a digital signal. Then, the reception signal S ₂ output from the analog-digital converter 55 is input to the control unit 2 and processed.

In this embodiment, a passive tag that does not incorporate a power source is used in the RFID tag . For this reason, the communication method between the reader / writer 1 and the RFID tag is a half-duplex method, the antenna 7 is shared for transmission and reception, and the circulator 6 separates the transmission signal S ₁ and the reception signal S ₂ . It is supposed to be. That is, at the time of transmission, the transmission signal S ₁ output from the transmission unit 4 is guided from the circulator 6 to the antenna 7 through the low-pass filter 8 and radiated from the antenna 7 toward the external RFID tag. On the other hand, at the time of reception, the received signal S ₂ from the RFID tag received by the antenna 7 is guided from the circulator 6 to the receiving unit 5 through the low-pass filter 8.

  FIG. 2 is a diagram illustrating a configuration of a control unit in the reader / writer.

As shown in the figure, the control unit 2 includes a transmission data generation unit 21 and an encoding unit 22. The transmission data generated by the transmission data generation unit 21 is encoded by the encoding unit 22, and the encoded data is encoded. The transmission data is output to the digital / analog converter 41 as a digital signal. The control unit 2 and the decoding section 23 includes a reception data processing section 24, decoded by the decoding unit 23 a digitized received signal S ₂ is inputted from the analog digital converter 55, the decoding The received data is processed by the received data processing unit 24.

Further, the control unit 2 includes an FFT processing unit 25, a channel selection processing unit 26, and a FIFO memory 27. First, the FFT processing unit 25 performs a fast Fourier transform process using a digital signal input from the analog-digital converter 55 during carrier sensing. That is, the FFT processing unit 25 executes a fast Fourier transform process on the digital amount data input from the analog-digital converter 55 . By this fast Fourier transform processing, the FFT processing unit 25 extracts each frequency component included in the digital signal, and acquires and outputs received power intensity distribution data for each frequency band as shown in FIG.

Next, the channel selection processing unit 26 causes the FIFO memory 27 to store distribution power intensity distribution data for each frequency band input from the FFT processing unit 25 during carrier sensing . The channel selection processing unit 26 evaluates an empty channel based on the received power intensity distribution data read from the FIFO memory 27. If there are a plurality of continuous empty channel groups of one or more channels, the channel selection processing unit 26 optimizes the channel. A process of selecting a correct channel group is performed. Further, the channel selection processing unit 26 sets the carrier frequency of the transmission signal S ₁ to the transmitter 3 in order to change the transmission speed (communication speed) of the carrier wave f ₀ in the selected use channel to the maximum communication speed. A control signal S ₃ to be set is output. The channel selection process will be described in detail with reference to FIG.

  FIG. 3 is a diagram illustrating a passive RFID communication method and a spectrum state in each communication period.

  As described above, the reader / writer 1 according to the present embodiment employs a passive RFID communication method, and radio waves transmitted from the reader / writer 1 to the RFID tag serve to supply electromotive force for operating the RFID tag. Therefore, it is radiated at a high output from the antenna 7. As shown in the figure, a read command is transmitted as a modulated wave from the antenna 7 of the reader / writer 1 during the communication period from the reader / writer 1 to the RFID tag. At this time, the RFID tag demodulates and analyzes the read command. In addition, an option for designating the transmission rate of a signal to the RFID tag can be added at the time of command transmission, and the transmission rate can be changed for each communication. FIG. 2B shows the modulated wave spectrum of the reader / writer 1 whose band is limited in the channel.

On the other hand, in the communication period from the RFID tag to the reader / writer 1, the reader / writer 1 transmits an unmodulated continuous carrier wave CW from the antenna 7. The radio wave returned from the RFID tag to the reader / writer 1 with a slight delay from the continuous carrier wave CW changes the antenna impedance of the RFID tag according to the data in the memory inside the tag. As a result, the amount of reflection of the radio wave from the reader / writer 1 changes according to the change in the antenna impedance of the tag, and is returned as a weak signal modulated by the tag data. The impedance modulation speed of the RFID tag is determined by the transmission speed specified in the transmission command. FIG. 4C shows a modulated wave spectrum of a weak signal due to a change in impedance between the continuous carrier wave CW of the reader / writer 1 and the RFID tag.

  FIG. 4 is a diagram showing the relationship between the communication speed and the frequency band.

  As shown in the figure, when the data transmission speed from the reader / writer 1 to the RFID tag is increased, the affected frequency band is widened. That is, when the communication speed is high, the occupied band of the upper and lower sidebands extends to the channel adjacent to the used channel, and is easily affected by the carrier wave used in the adjacent channel.

For example the illustrated example, Ru der those carriers f ₀ from the reader-writer 1 showed modulated wave spectrum for RFID tags when n-channel. When the data transmission speed is 40 kbps (low speed), the occupied bandwidths of the upper sideband (USB: Upper Side Band) and the lower sideband (Lower Side Band) are each expanded to 80 kHz by encoding, and 80 kbps (medium speed). In this case, it can be seen that the same bandwidth is expanded to 160 kHz by encoding, and in the case of 160 kbps (high speed), the same bandwidth is expanded to 320 kHz. In particular, when the transmission speed is set to a high speed, if there is an interference wave spectrum in the adjacent n + 1 channels, the frequency band is covered, and the communication reliability between the reader / writer 1 and the RFID tag is lowered.

  Therefore, the reader / writer 1 of the present embodiment statistically checks the intensity of the interference wave of the adjacent reader / writer at the time of channel evaluation by carrier sense, and changes the communication speed to the optimum value according to the intensity of the interference wave. Thus, the communication efficiency between the reader / writer 1 and the RFID tag is increased.

  FIG. 5 is a diagram showing the relationship between received power intensity distribution data and empty channels.

As described above, FFT processing unit 25 of the control unit 2 executes the fast Fourier transform processing using a digital signal supplied from the analog-digital converter 55 during carrier sensing, on a per-channel basis, such as in the figure The measured received power intensity distribution data is acquired. In the figure, the horizontal axis shows nine channels (CH) that can be used in the UHF band, and the vertical axis shows the received power intensity (dBm) level divided into three threshold levels, Th1, Th2, and Th3. is there.

  Here, the threshold value Th1 is set to −74 dBm defined as the carrier sense level of the high-power UHF band. In the illustrated example, the channel whose measured received power intensity is less than the threshold Th1, that is, the four channels CH2, CH3, CH6, and CH9 are free channels that can be communicated. When there are a plurality of vacant channels as in the received power intensity distribution data, the channel selection processing unit 26 evaluates the vacant channels as follows and then selects the optimum channel and selects the used channel. Determine the communication speed at.

  FIG. 6 is a flowchart showing an example of channel selection processing in the control unit.

In the figure, the reader / writer 1 first stops the transmission of radio waves from the antenna 7 and performs carrier sense prior to communication with the RFID tag (step 601). That is, the reader / writer 1 measures the received power intensity on all channels (CH1 to CH9) in the UHF band via the antenna 7 and the receiving unit 5 . Based on the received power intensity distribution data from the FFT processor 25 , the channel selection processor 26 searches for an empty channel whose received power intensity is less than the carrier sense level (−74 dBm) of the threshold Th1. In the example of FIG. 5, four channels CH2, CH3, CH6, and CH9 correspond to empty channels.

  Next, the channel selection processing unit 26 checks whether or not there is an empty channel of a medium level or higher among the empty channels searched by carrier sense (step 602). Here, “empty channel of medium level or higher” refers to a channel that satisfies the condition that the received power intensity of at least one adjacent channel on both the upper and lower sides is less than the threshold Th2 among the empty channels. The example in FIG. 5 will be described as follows.

  Four channels, CH2, CH3, CH6, and CH9, are searched as empty channels. Of these, the received power intensity of CH3 on the adjacent side is less than the threshold Th2, but the received power intensity of CH1 on the adjacent lower side exceeds the threshold Th2, so it does not correspond to an empty channel of the middle level or higher and is at a low level. Evaluated as a free channel. Since CH3 and CH4 received power intensity are both lower than the threshold Th2, CH3 corresponds to an empty channel of the medium level or higher. Since the received power strengths of CH5 and CH7 on both upper and lower sides of the CH6 exceed the threshold Th2, CH6 is evaluated as being a low-level empty channel, not corresponding to a medium-level or higher empty channel. Since CH9 has no channel on the adjacent side and the received power intensity is less than the threshold Th2, and the received power intensity of the adjacent lower CH8 is also less than the threshold Th2, it corresponds to an empty channel of the middle level or higher.

  Next, the channel selection processing unit 26 checks whether or not there is a high level free channel among the free channels of the medium level or higher (step 603). Here, the “high level free channel” means a channel satisfying the condition that the received power intensity of at least two adjacent channels on both the upper and lower sides is less than the threshold Th3 among the empty channels of the medium level or higher. . The example in FIG. 5 will be described as follows.

  Two channels, CH3 and CH9, were searched as idle channels of the medium level or higher. Of these, for CH3, the reception power strengths of the two adjacent CH1 and CH2 are both less than the threshold Th3, and the reception power strengths of the two adjacent CH4 and CH5 are both less than the threshold Th3. Corresponds to an empty channel. On the other hand, although there is no channel 9 having a received power intensity equal to or higher than the threshold Th3 on the upper side, the received power intensity of the second CH7 adjacent to the upper side exceeds the threshold Th3. Instead, it is evaluated as a medium level free channel.

  As described above, the channel selection processing unit 26 evaluates which level of low, medium and high corresponds to all the empty channels, and then selects a channel to be used according to the following procedure and determines its communication speed. .

  First, it is determined whether there is a high level free channel (step 604). Here, if there is a high-level empty channel, the channel to be used is selected from among them (step 609). For the high-level empty channels, even if the data transmission rate is set to a high speed (160 kbps) and the occupied bandwidth of the upper and lower sidebands is expanded to 320 kHz as described in FIG. Since the received power intensity of each channel is less than the threshold value Th3, radio wave interference with an adjacent channel does not occur. Therefore, when a high-level vacant channel is used, communication is possible by weighting the Lo signal of the transmitter 3 by LBF (Local Beam Forming) and weighting the RF signal output from the modulator 42. Communication is started by setting the maximum speed to a high speed (step 607). Note that the carrier sense in step 601 is always executed before communication is completed and new communication is performed.

  In the example of FIG. 5, since there is a high-level vacant channel CH3, it is selected as a use channel, and communication is performed with a high communication speed. Although there may be a plurality of high-level vacant channels, in this case, the received power intensity of all the channels is less than the threshold Th1, and any channel may be selected.

  On the other hand, if there is no high level free channel, it is determined whether there is a medium level free channel (step 605). If there is a medium level empty channel, a channel to be used is selected from those channels (step 608). Since the received power intensity of one channel on both the upper and lower sides is lower than the threshold Th2 in the middle level empty channel, even if the data transmission rate is set to the medium speed (80 kbps) as shown in FIG. The occupied bandwidth extends only up to 160 kHz, and radio wave interference with adjacent channels does not occur. Therefore, when using a medium level free channel, the communication speed is set to the medium speed and communication is started (step 607).

  Further, when there is no medium level empty channel, a use channel is selected from the low level empty channels (step 606). Since the low-level empty channel has the received power intensity of both the upper and lower adjacent channels equal to or higher than the threshold Th2, if the data transmission speed is set to a low speed (40 kbps) as shown in FIG. No radio wave interference with adjacent channels. Therefore, when a low-level empty channel is used, the communication speed is set to a low speed and communication is started (step 607).

As described above, according to the reader / writer 1 having the above-described function, after the level evaluation is performed for all the empty channels, the transmission rate is changed according to the empty state of the adjacent channel. Thereby, when there are many empty channels, data is transmitted at a high speed, and when there are few free channels, data is transmitted at a low speed, so that it is possible to suppress influences such as communication errors due to radio wave interference of adjacent channels and increase in communication time . For this reason, it is possible to significantly increase the communication efficiency as compared with the fixed channel selection method. Note that the following channel selection process may be employed instead of the channel selection process described in FIG.

  FIG. 7 is a flowchart showing another example of channel selection processing in the control unit.

In the figure, the reader / writer 1 first stops carrier wave transmission from the antenna 7 and performs carrier sense prior to communication with the RFID tag (step 701). That is, the reader / writer 1 measures the received power intensity on all channels (CH1 to CH9) in the UHF band via the antenna 7 and the receiving unit 5 . Then, the channel selection processing unit 26 searches for a free channel whose received power intensity is less than the carrier sense level (−74 dBm) of the threshold Th1 based on the received power intensity distribution data from the FFT processing unit 25 (step 702). Note that this empty channel search by carrier sense is the same as in FIG.

  Next, the channel selection processing unit 26 accumulates free channel information (step 703). That is, the channel selection processing unit 26 stores the received power intensity data of each channel searched by carrier sense in the FIFO memory 27. The empty channel information is accumulated every time carrier sense is performed, and the latest amount of data of each channel is accumulated in the FIFO memory 27 by a specified amount.

  Next, the channel selection processing unit 26 checks the channel history information (step 704). Here, “channel history information” refers to an average value of the number of empty channels calculated using the history of past channel information stored in the FIFO memory 27. For the past channel information, it is preferable to adopt data that can reflect the radio wave interference state of each recent channel depending on the number of times and time, such as the latest n data or data within n minutes from the present.

  Then, the channel selection processing unit 26 determines whether there are three or more past average free channels by checking the channel history information (step 705). If there are 3 or more past average free channels, it is next determined whether there are 5 or more past average free channels (step 708). As a result, when there are five or more average free channels in the past, a used channel is selected from the free channels searched by the current carrier sense (step 710). If there are 5 or more average free channels in the past, it can be estimated that the number of other reader / writers that have recently performed communication is small. Therefore, the communication speed is set to the maximum high speed (160 kbps) by LBF. Is started (step 707). Note that the carrier sense in step 701 is always executed before communication is completed and new communication is performed.

  On the other hand, in step 708, even when the average number of free channels in the past does not exist 5 or more, the channel to be used is selected from the free channels searched by the current carrier sense. The lowered medium speed (80 kbps) is set (step 709). Then, by setting the transmission speed to medium speed, the occupied bandwidth of the upper and lower sidebands is narrowed so that radio wave interference with the adjacent channel does not occur, and communication is started (step 707).

  Further, in step 705, even when there is no past average free channel number of 3 or more, the used channel is selected from the free channels searched by the current carrier sense. In this case, the transmission rate is minimized. Is set to a low speed (40 kbps) (step 706). Then, by setting the transmission speed to a low speed, the occupied bandwidth of the upper and lower sidebands is further narrowed so that radio wave interference with the adjacent channel does not occur, and communication is started (step 707).

As described above, in the channel selection process shown in FIG. 7, the past channel use history is held and accumulated every time carrier sense is performed, so that the radio wave state of each latest channel can be referred to before communication. As a result, the ratio of idle channels is estimated from accumulated past statistics, not the instantaneous idle channel status measured by carrier sense, and the number of reader / writers that may cause radio wave interference is estimated, and the transmission speed corresponding to that is estimated. Is to decide . For this reason, the effect according to the actual environment can be exhibited. In particular, it is suitable in an environment where the number of installed reader / writers in the system increases or decreases in operation .

In the above-described embodiment, an example in which the wireless communication apparatus of the present invention is applied to a high-power UHF band reader / writer has been described. However, the present invention is not limited to this . As long as it is used in a system that requires countermeasures against interference by carrier sense, it can be similarly applied to a low-output UHF band reader / writer and other frequency band communication devices.

1 is a diagram showing a configuration of a reader / writer which is a wireless communication apparatus of the present invention. The figure which shows the structure of the control part in a reader / writer. The figure which shows the communication state of a passive type RFID, and the spectrum state of each communication period. The figure which shows the relationship between a communication speed and a frequency band. The figure which shows the relationship between received power intensity distribution data and an empty channel. The flowchart figure which shows an example of the channel selection process in a control part. The flowchart figure which shows the other example of the channel selection process in a control part. The figure which shows the channel arrangement | positioning example of a UHF band.

Explanation of symbols

1 Reader / Writer (wireless communication device)
2 Control Unit 21 Transmission Data Generation Unit 22 Encoding Unit 23 Decoding Unit 24 Reception Data Processing Unit 25 FFT Processing Unit 26 Channel Selection Processing Unit 27 FIFO Memory 3 Transmitter 4 Transmitting Unit 41 Digital Analog Converter 42 Modulator 43 High Frequency Amplifier 5 Receiving Unit 51 Band Limit Filter 52 Low Noise Amplifier 53 Demodulator 54 Amplifier 55 Analog to Digital Converter 6 Circulator 7 Antenna 8 Low-Pass Filter S ₁ Transmitted Signal S ₂ Received Signal S ₃ Control Signal S ₄ Baseband Signal f ₀ Carrier

Claims (7)

A wireless communication device for performing wireless data communication with a data carrier by using one or a plurality of channels on a frequency band divided into a plurality,
Before wireless communication with the data carrier, in a predetermined range of continuous channel groups, based on the received power intensity measured in units of channels, search for an odd number of free channels with continuous frequency bands,
A wireless communication apparatus, wherein a communication speed with a larger data rate is set as the frequency bandwidth of the entire odd number of consecutive free channels extracted by the search is increased, and communication with a data carrier is started. Before wireless communication with the data carrier, in a continuous channel group within a predetermined range, an empty channel having a received power intensity equal to or less than the first threshold is searched based on the received power intensity measured in units of channels. Extract two free channels,
The received power intensity of the channel adjacent to the high frequency side of the extracted one empty channel and the received power intensity of the channel adjacent to the low frequency side of the extracted one empty channel are both from the first threshold value. 2. The wireless communication apparatus according to claim 1, wherein an odd number of continuous idle channels are set when the second threshold is less than or equal to a second threshold value. A wireless communication device for performing wireless data communication with a data carrier by using one or a plurality of channels on a frequency band divided into a plurality,
Before the wireless communication with the data carrier, in a continuous channel group in a predetermined range, based on the received power intensity measured in units of channels, search for an empty channel having a received power intensity equal to or lower than the first threshold,
The received power intensity data for each channel is accumulated every time the empty channel is searched, and the communication speed is set by estimating the empty channel status based on the past received power intensity when searching for an empty channel. Wireless communication device. A wireless communication system comprising the wireless communication device according to claim 1 and a data carrier capable of data communication with the wireless communication device. A wireless communication method for performing wireless data communication with a data carrier using one or a plurality of channels on a frequency band divided into a plurality,
A search step of searching for an odd number of free channels having continuous frequency bands based on the received power intensity measured in units of channels in a predetermined range of continuous channel groups before wireless communication with the data carrier;
A setting step of setting a higher communication speed as the frequency bandwidth of the entire odd number of consecutive free channels extracted by the search step is wider, and
A wireless communication method, wherein communication with the data carrier is started at a communication speed set in the setting step. The search step includes
Before wireless communication with the data carrier, in a continuous channel group within a predetermined range, an empty channel having a received power intensity equal to or less than the first threshold is searched based on the received power intensity measured in units of channels. Extract two free channels,
When the received power intensity in both the channel adjacent to the extracted one free channel on the high frequency side and the channel adjacent on the low frequency side is equal to or lower than the second threshold value that is larger than the first threshold value. 6. The wireless communication method according to claim 5, wherein the search is performed as a continuous odd number of empty channels. A wireless communication method for performing wireless data communication with a data carrier using one or a plurality of channels on a frequency band divided into a plurality,
An empty channel that searches for an empty channel having a received power intensity equal to or less than a first threshold based on the received power intensity measured in units of channels in a continuous channel group within a predetermined range before wireless communication with a data carrier. The search process;
An accumulation process for accumulating received power intensity data in units of channels every time an empty channel is searched;
A communication speed setting step for estimating a free channel state based on the past received power intensity when searching for a free channel and setting a communication speed,
A wireless communication method, wherein communication with the data carrier is started at a communication speed set in the communication speed setting step.

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