JP2009065296A - Radio ic tag read system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To select a channel to be used to read a radio IC tag while monitoring a plurality of channels almost in real time to always monitor use states of the respective channels. <P>SOLUTION: A radio IC tag read system comprises a first variable-frequency oscillation unit which generates a signal of frequency corresponding to a unit radio channel, a transmission unit and a reception unit which perform transmission to and reception from a radio IC tag using the signal, a carrier-sense-by-channel execution unit which measures reception radio wave intensities of the plurality of unit radio channels simultaneously and repeatedly to output RSSIs indicative of measurement results, a carrier sense control unit which generates a carrier sense result table showing whether the plurality of unit radio channels are usable based upon the reception radio wave intensities, and stores it, and a transmission/reception control unit which controls the first variable-frequency oscillation unit to generate a signal of frequency corresponding to a unit radio channel that the transmission unit and reception unit are made to use. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless IC tag reading system, and more particularly to a wireless IC tag reading system for reading a so-called wireless IC tag (also referred to as an electronic tag or RFID).

  A so-called wireless IC tag reader may cause interference between both readers or a reader that should not respond to the wireless IC tag if another reader is present in the vicinity. There is a case where the radio wave read from the radio wave or the reflected radio wave interferes, and there is a possibility that the radio IC tag cannot be read normally.

  As one of the techniques for avoiding such inconvenience, it is indispensable to mount an LBT (Listen before Talk) function in the reading device (for example, Non-Patent Document 1). The LBT function is a certain time (carrier sense time) for a unit radio channel (carrier sense band) from which the reading device intends to emit radio waves, a certain level of strength from other reading devices and other wireless stations. This is a method for avoiding interference between the reading device and the radio station by emitting radio waves after confirming that no radio waves of the (carrier sense level) are transmitted.

Further, in order to avoid that normal radio IC tag reading cannot be performed due to interference between radio waves radiated from other readers and radio waves for reading, a plurality of bands allocated to the radio IC tag readers In general, a radio wave for reading is divided into channels and transmitted for each channel (for example, Patent Document 1 and Patent Document 2).
“Information and Communication Council, Information and Communication Technology Subcommittee, Power Saving Wireless System Committee Report (draft)”, [online], [searched on November 8, 2006], Internet <http://www.soumu.go.jp /s-news/2005/pdf/051005_2_2.pdf> Japanese Unexamined Patent Publication No. 2000-20651 Japanese Unexamined Patent Publication No. 2003-60652

  However, when the wireless band assigned to the wireless IC tag reader is limited, the number of channels is limited. For example, in the United States, a band of 902 MHz to 928 MHz (bandwidth 26 MHz) is allocated to the wireless IC tag reader, whereas in Japan, 950 MHz to 956 MHz (bandwidth 6 Mz), and in Korea, 910 MHz to 914 MHz (bandwidth 4 MHz). In fact, the frequency band at both ends is a guard band for preventing interference with the adjacent frequency band, and thus the bandwidth is further limited.

  In such an environment, when a large number of wireless IC tag readers are arranged within the communication range of each other (for example, when a plurality of wireless IC tag devices are arranged in the same warehouse), the channel There may be frequent communication collisions.

  An object of the present invention is to appropriately select a channel to be used for reading a wireless IC tag while monitoring each of a plurality of channels that can be used by the wireless IC tag reader in almost real time and constantly monitoring the usage status of each channel. It is an object of the present invention to provide a wireless IC tag reading technique that can be performed in the same manner.

  One typical aspect of the present invention is proposed as a wireless IC tag reading system that reads a wireless IC tag that can use a plurality of unit wireless channels.

  The wireless IC tag reading system includes a first oscillating unit (for example, a first frequency variable oscillating unit of a reader / writer) that generates a signal having a frequency corresponding to a unit wireless channel used for transmission / reception with the wireless IC tag, Transmission / reception means (for example, a transmitter / receiver of a reader / writer) that performs transmission / reception with the wireless IC tag using the signal generated by the first oscillating means, and the received radio wave intensity at each of the plurality of unit radio channels Based on the carrier sense means (for example, the carrier sense execution unit for each channel of the reader / writer) that outputs the information (for example, RSSI) indicating the measurement result simultaneously and repeatedly, and the received radio wave intensity measured by the carrier sense means Information indicating whether or not each of the unit radio channels can be used (for example, a carrier sense result table). Units to be used by the transmission / reception means based on the first control means to be configured and stored (for example, the carrier sense control unit of the reader / writer control device) and information indicating whether or not each of the plurality of unit radio channels can be used And a second control unit (for example, a transmission / reception control unit of the reader / writer control device) that controls the first oscillation unit so as to generate a signal having a frequency corresponding to the radio channel.

  Here, “simultaneously” means that one execution does not hinder the other execution, and does not necessarily mean that it must be executed at the same time. For example, “simultaneously” includes that the carrier sense execution unit for each channel measures the received radio wave intensity and outputs the measurement result while shifting the timing every 0.1 msec.

  According to the present invention, it is possible to monitor whether or not all unit radio channels can be used continuously. Therefore, when a free channel is generated, the free channel can be used quickly and effectively. Can do.

  In the above wireless IC tag reading system, the carrier sense means comprises a plurality of channel-specific carrier sense means provided for each unit radio channel, and the received radio wave intensity in the unit radio channel to which each channel-specific carrier sense means corresponds is determined. It is good also as a structure which outputs the information shown.

According to the above configuration, since it is possible to perform carrier sense individually for each unit radio channel, compared with the case where all unit radio channels are performed using a single carrier sense means, It is possible to shorten the carrier sense execution interval and constantly monitor the availability of the channel.
Until now, when using a technique such as LBT, generally, the channel selection method has been to sequentially shift to the next channel or channel by random numbers or the like. In addition to such a channel selection method (algorithm), the carrier sense result for each unit channel is reflected in real time, so that a channel already used by another reader is selected once and the LBT operation is performed. Since unnecessary time can be eliminated, channel selection can be performed effectively and appropriately.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless IC tag reading technique which can perform the selection of the channel used for radio | wireless IC tag reading appropriately and at high speed, always monitoring the usage condition of each channel can be provided.

  First, an example of a basic configuration of the wireless IC tag reading system in this embodiment will be described.

[1. Wireless IC tag reading system]
FIG. 1 is a functional block diagram showing an example of a basic configuration of a wireless IC tag reading system according to an embodiment of the present invention.

  The wireless IC tag reading system 1 includes a reader / writer control device 10, a reader / writer 20 connected to the reader / writer control device 10, and an antenna unit 30 connected to the reader / writer 20. Hereinafter, each component of the wireless IC tag reading system 1 will be described.

[1.1. Reader / Writer Control Device]
The reader / writer control device 10 performs reading processing of the reader / writer 20, that is, transmission / reception processing with the wireless IC tag 40, transmission time control associated therewith, determination of the presence / absence of an empty channel based on the result of carrier sense (LBT), transmission / reception The unit radio channel to be used is determined and commanded. In other words, the reader / writer control device 10 reads the reader / writer 20 (transmitting a carrier wave for setting the wireless IC tag in a receiving state, transmitting a modulated wave with a question command, supplying power to the wireless IC tag. To transmit a carrier wave to be continued, reception of a response from the wireless IC tag), and to instruct the reader / writer 20 to transmit the data read from the wireless IC tag 40. Data received from the writer 20 is stored, a function of performing predetermined information processing (for example, generation of a list of unique IDs of wireless IC tags), and designation of a unit wireless channel used by the reader / writer 20 for transmission / reception , And storage of the carrier sense execution result, determination of the channel to be used based on the carrier sense result, and transmission time control.

  The reader / writer control device 10 is an information processing device including an arithmetic processing device such as a CPU and a storage device such as a ROM and a RAM, and is, for example, a computer or various controllers. FIG. 2 is a block diagram illustrating a hardware configuration example of the reader / writer control device 10. In the configuration example shown in FIG. 2, the reader / writer control device 10 converts a user input such as a CPU 201, a RAM 202 that is a temporary storage unit, a ROM 203 that stores programs and fixed data, and a keyboard and a pointing device. An input device 204 provided to the CPU 201, a screen display device 205 (for example, a liquid crystal display device) for showing the processing result of the CPU 201 to the user, and a communication control device 206 (for example, for communicating with the reader / writer 20) LAN board etc.).

  FIG. 3 is a functional block diagram of the reader / writer control device. The reader / writer control device 10 controls transmission and reception operations of the reader / writer 20, and also uses a unit radio channel (that is, a carrier frequency) used when the reader / writer 20 performs transmission / reception with the wireless IC tag 40. A transmission / reception control unit 211 for designating a carrier sense, a carrier sense result received from the reader / writer 20 and stored therein, and a carrier sense control unit 212 for instructing a unit radio channel (frequency) targeted for carrier sense, and a carrier A carrier sense result storage unit 213 for storing and storing sense results.

  FIG. 4 is a diagram illustrating an example of the contents stored in the carrier sense result storage unit 213. FIG. 4 shows a data configuration example of a carrier sense result table that is a storage content of the carrier sense result storage unit. In this example, the carrier sense result table 400 has one record 401 for each unit radio channel assigned as the usable frequency band of the reader / writer 20, and each record 401 has a flag storage field 402. In the flag storage field 402, information indicating whether or not the unit radio channel is usable, for example, information indicating whether or not the intensity of the interference wave in the unit radio channel is less than or less than a predetermined value. Is written. For example, if the measurement result received by the carrier sense control unit 212 indicates that the intensity of the interference wave of the unit radio channel is equal to or less than a predetermined value of −74 dBm, the carrier sense control unit 212 is applicable. In a flag storage field 402 of the record 401, “0” that is a flag indicating that the unit radio channel can be used is stored. On the other hand, if the measurement result received by the carrier sense control unit 212 indicates that the intensity of the interference wave of the unit radio channel exceeds a predetermined value of −74 dBm, the flag storage field of the corresponding record 401 402 stores “1” which is a flag indicating that the unit radio channel cannot be used. The information written in the flag storage field 402 is a result of the latest carrier sense in the unit radio channel, and is rewritten to the latest information every time carrier sense in the unit radio channel is executed.

In the present embodiment, a carrier sense result table 400 is provided for each reader / writer 20.
The operations of these units 211 to 213 of the reader / writer control device 10 and the reader / writer control device 10 will be described later.

[1.2. Reader / Writer]
Next, the reader / writer 20 according to the present embodiment will be described.
The reader / writer 20 is a device that performs wireless transmission and reception with the wireless IC tag 40 and reads information stored in the wireless IC tag 40 (for example, a unique ID). The reader / writer 20 can selectively use a plurality of unit radio channels (frequency bands) that can be used when transmitting and receiving with the wireless IC tag 40. For example, taking a reader / writer that reads a so-called high-power 950 MHz band passive tag as an example, the reader / writer 20 divides nine unit radio channels obtained by dividing a radio band 952 to 954 MHz allocated for transmission and reception by a 200 KHz width. It can be used selectively.

  Further, the reader / writer 20 continuously monitors the plurality of unit radio channels for carrier sensing in order to monitor the use of frequency bands by other radio stations such as another reader / writer for each of the unit radio channels. To do. For example, in the reader / writer 20 according to the present embodiment, the carrier sense time in each unit radio channel is carrier sensed every 1 ms for each unit radio channel.

  The reader / writer 20 continuously and cyclically executes carrier sense even during radio wave transmission for reading the wireless IC tag 40 and during a stop time after transmission. Of course, the carrier sense is continuously and cyclically executed even outside the transmission time and the stop time (for example, during the standby time).

  The reader / writer 20 passes the carrier sense result to the reader / writer control device 10. Receiving the carrier sense result from the reader / writer 20, the reader / writer control apparatus 10 records a carrier sense result table 400, which is data indicating whether each unit radio channel can be used.

  When reading the wireless IC tag 40, the reader / writer 20 designates according to the control command from the reader / writer control device 10, more specifically, the transmission / reception control unit 211, according to the result of the carrier sense. The command / data transmission / reception to / from the wireless IC tag 40 is performed using the unit radio channel.

  The reader / writer 20 performs carrier sense of each unit radio channel, and performs transmission / reception for reading the radio IC tag 40 in the unit radio channel designated in accordance with a command from the reader / writer control device 10. This transmission / reception can be continued up to the maximum continuous transmission time. When it is necessary to continue transmission after the end of the continuous transmission time, the reader / writer 20 refers to the latest result of carrier sense that has been continuously performed until the end of the continuous transmission time. Search for a unit radio channel that is a channel, and if there is a unit radio channel that is an empty channel, transition to the unit radio channel and elapse of transmission stop time, carrier sense time, and backoff time in the unit radio channel Continue to send immediately without waiting.

  FIG. 5 is a block diagram showing a configuration example of the reader / writer 20. Hereinafter, a configuration example of the reader / writer 20 will be described with reference to FIG. The reader / writer 20 includes a transmission unit 501, a reception unit 502, a first variable frequency oscillation unit 503, a channel-specific carrier sense execution unit 504 provided for each unit radio channel, a main control unit 506, and a communication control unit. 507.

  In this embodiment, there is one channel-specific carrier sense execution unit 504 for each of the nine unit radio channels, channel 1 (CH1) to channel 9 (CH9). Of course, it is needless to say that one carrier sense execution unit can execute a carrier sense while switching channels at regular intervals.

[1.2.1. Transmitter]
The transmission unit 501 wirelessly transmits a carrier wave or a modulated wave to the wireless IC tag 40 via the antenna unit 30. FIG. 5 is a block diagram illustrating a circuit configuration example of the transmission unit 501. Hereinafter, a configuration example of the transmission unit 501 will be described with reference to FIG.

  In the configuration example illustrated in FIG. 6, the transmission unit 501 includes a modulation circuit 601, an amplification circuit 602 connected to the output side of the modulation circuit 601, a first low-pass filter 603 connected to the output of the amplification circuit 602, A coupler 604 connected to the output of one low-pass filter 603, a second low-pass filter 605 connected to the output of the coupler 604, and a power detector 606 connected to another output of the coupler 604. Yes.

The modulation circuit 601 uses the command output from the main control unit 506 as a baseband signal, and modulates the carrier wave signal output from the first frequency variable oscillation unit 503 by a predetermined modulation method (for example, Direct UP Converter method). , Output a modulated wave. The amplification circuit 602 receives the modulated wave from the modulation circuit 601 and amplifies the modulated wave to a level at which it can be emitted in the air. The first low-pass filter 603 and the second low-pass filter 605 serve to remove spurious signals included in the amplified modulated wave. The coupler 604 receives the amplified modulated wave from the first low-pass filter 603, distributes the modulated wave, and outputs it to the power detector 606. The power detector 606 receives the distributed modulated wave, detects the transmission output, and outputs it to the main control unit 506. Further, the power detector 606 can detect whether or not the antenna is connected indirectly because the detected value varies depending on whether or not the antenna is connected when transmitting the radio wave. This difference can be determined by the main control unit 506, and the output with high power when the antenna is not connected can be suppressed, or the higher-order side controlling the reading apparatus can be notified. (The figure is omitted)
The output of the first variable frequency oscillator 503 is connected to the modulation circuit 601, and modulation is performed using the signal output from the first variable frequency oscillator 503 as a carrier wave.

[1.2.2. Receiver]
Next, the receiving unit 502 will be described. FIG. 7 is a block diagram illustrating a circuit configuration example of the receiving unit 502. The receiving unit 502 illustrated in FIG. 7 includes a demodulation circuit 701 and an amplification circuit 702. The demodulation circuit 701 is supplied with radio waves received by the antenna unit. Further, the output of the first frequency variable oscillation unit 503 is connected to the demodulation circuit 701, and a response from the wireless IC tag 40 is transmitted using the same unit wireless channel as the unit wireless channel used by the transmission unit. Receive. The demodulation circuit 701 is configured by a demodulator using, for example, a direct conversion method.

  The amplification circuit 702 amplifies the output of the demodulation circuit 701 to a level at which an analog signal can be digitally converted. For example, the amplifier circuit 702 includes a first differential amplifier connected to the output of the demodulation circuit 701, an active filter connected to the output, and a second differential amplifier connected to the output of the active filter. Is done. The output of the amplifier circuit 702 is converted into a digital signal via an AD converter (not shown) and passed to the main control unit 506.

[1.2.3. First frequency variable oscillator]
The first variable frequency oscillating unit 503 generates a carrier wave signal having a frequency corresponding to the unit radio channel designated by the reader / writer control device 10, and supplies this to the transmitting unit 501 and the receiving unit 502. The first variable frequency oscillation unit 503 is a module on which, for example, a PLL (Phase Lock Loop) IC and a VCO (Voltage Control Oscillator) IC are mounted.

[1.2.4. Carrier sense execution unit by channel]
Each channel-specific carrier sense execution unit 504 performs carrier sense of a unit radio channel corresponding to the channel-specific carrier sense execution unit 504 (hereinafter, referred to as “assigned unit radio channel”), and receives radio waves in the corresponding unit radio channel. Measure and output the signal intensity of (interfering radio waves). FIG. 8 shows a circuit configuration example of the carrier sense execution unit 504 for each channel.

  In the configuration example illustrated in FIG. 8, the channel-specific carrier sense execution unit 504 receives the reception signal received by the antenna unit 30 and the reference signal output from the second frequency oscillation unit 804 (the center frequency of the designated unit radio channel). Are mixed to output an IF signal, a low-pass filter 802 for removing a reference signal (PLL_LO signal) and noise from the output of the mixer 801, and an output until the output of the low-pass filter 802 can be converted at a DC level. It comprises an amplifier circuit (for example, log amplifier) 803 and a second frequency oscillator 804 that generates a reference signal corresponding to the center frequency of the assigned unit radio channel.

  The output of the amplifier circuit 803 is passed to the main control unit 506 as RSSI (Received Signal Strength Indicator).

[1.2.5. Main control unit]
Returning to FIG. 5, the description of the components of the reader / writer 20 will be continued.
The main control unit 506 receives a control command from the reader / writer control device 10, interprets it, causes the transmission unit to transmit a modulated wave carrying an unmodulated carrier wave or command, and reacts to the transmitted modulated wave. The output of the receiving unit 502 that has received the response signal from the wireless IC tag 40 is transferred to the reader / writer control device 10 as data (unique ID). Further, the main control unit 506 instructs the first frequency variable oscillation unit 503 for the frequency of the reference signal separately. The main control unit 506 receives the RSSI output from the carrier sense execution unit 504 for each channel, passes it to the reader / writer control device 10 and stores it as the carrier sense execution result described above.

[1.2.7. Communication control unit]
The communication control unit 507 is a device that communicates with the reader / writer control device 10 and is, for example, a LAN board.

[1.3. Antenna unit]
Returning to FIG. 1, the description of the components of the wireless IC tag reading system 1 in the present embodiment will be continued.
The antenna unit 30 radiates a carrier wave or modulated wave received from the reader / writer 20, more specifically, the transmission unit 501, in the air, radiates the carrier wave or modulated wave toward the wireless IC tag 40, and the wireless IC tag 40. Is received, and this response is supplied to the reader / writer 20, more specifically to the receiving unit 502. Further, the antenna unit 30 supplies a received signal (including interference radio waves) to the reader / writer 20, more specifically to the carrier sense execution unit 504.

  As an example, the antenna unit 30 includes a transmitting antenna, a receiving antenna (for example, a pole antenna, a patch antenna, etc.) and a case (for example, a resin molded case) for housing and protecting the antenna. In the present embodiment, the antenna unit 30 is a separate device from the reader / writer 20, and the antenna unit 30 is connected to the reader / writer 20 by a LAN cable or the like. Therefore, the antenna unit 30 can be installed even at a place away from the reader / writer 20.

  Further, the antenna for transmitting and the antenna for receiving included in the antenna unit 30 may be separate types (a transmitting antenna and a receiving antenna are provided separately), or an integrated type (one antenna for transmitting and receiving). Any of the above may be used.

  Further, as another configuration example that can be adopted by the present invention, the antenna unit 30 is not separated from the reader / writer 20, and the whole of the plurality of antenna units 30 or the transmission antenna / reception antenna is connected to the reader / writer 20. The present embodiment is also established as a configuration to be incorporated therein.

  Further, the number of antenna units 30 connected to the reader / writer 20 is not limited to one. A plurality of antenna units 30 may be connected to one reader / writer 20, and the reader / writer 20 may perform a transmission / reception process and a carrier sense execution process while switching the plurality of antenna units 30. For example, antennas / units 30 are installed in four directions in a closed space such as a warehouse, and these four antenna units 30 are connected to one reader / writer 20 via a cable or the like. The reader / writer 20 may connect these four antenna units 30 by switching means such as a switch so as to perform transmission / reception and / or carrier sense from four different directions and positions.

[1.5. Wireless IC tag]
Next, a general configuration example of the wireless IC tag 40 will be described.
The wireless IC tag 40 includes a memory 41, a control unit 42, a transmission / reception unit 43, and an antenna 44. The memory 41 is a storage device that stores information to be read such as identification information such as product information and shipper information. The control unit 42 interprets commands, requests, commands, etc. from the reader / writer 20 and executes operations in response thereto. The transmission / reception unit 43 includes a modulation unit (not shown) and a demodulation unit (not shown), and modulates / demodulates signals in order to communicate with the reader / writer 20. The antenna 44 receives a carrier wave from the reader / writer 20, feeds it to the transmission / reception unit 43, receives a modulated signal from the transmission / reception unit 43, and radiates it in the air so that the reader / writer 20 receives it.
Above, description of the structural example of the radio | wireless IC tag reading system 1 is complete | finished.

[2. Example of operation of wireless IC tag reading system]
Next, an operation example of the wireless IC tag reading system 1 will be described.
[2.1. Send / receive (read) processing]
When the reader / writer control device 10 requests the reader / writer 20 to read the wireless IC tag 40, the reader / writer control device 10 refers to the carrier sense result table 400, which is the latest carrier sense execution result, to read another wireless station (reader / writer). A unit wireless channel that is not used is selected, and a command is sent to the reader / writer 20 to read the wireless IC tag 40 using this unit wireless channel. In accordance with this instruction, the reader / writer 20 reads the wireless IC tag 40 using the designated unit wireless channel. This reading is performed within a predetermined continuous transmission possible time (for example, within 4 seconds). If reading of the wireless IC tag 40 is not completed within the predetermined continuous transmission time, the reader / writer 20 finishes transmission / reception on the unit wireless channel, and unit wireless usable for the reader / writer control device 10 is completed. Inquires about the channel or waits for a command from the reader / writer control device 10.

  The reader / writer control device 10 determines whether or not there is a channel (empty channel) that can be used in other unit radio channels except for the unit radio channel used by the reader / writer 20. The determination is made with reference to the carrier sense execution result stored in 213. As a result of the determination, if there is a usable unit radio channel (that is, a vacant channel), the reader / writer 20 is instructed to continue transmission / reception using the unit radio channel that is the vacant channel.

  In the wireless IC tag reading system 1 according to the present invention, the change of the unit radio channel used due to the arrival of the continuously transmittable time is performed without generating a time interval as much as possible. For example, when the reader / writer 20 starts reading a wireless IC tag using a certain unit wireless channel and then the continuous transmission time expires, the reader / writer 20 expires, and then the transmission stop time, carrier sense time Without waiting for the elapse of the back-off time, it immediately operates using another unit radio channel, which is another empty channel, to resume reading of the radio IC 40 tag.

  In the conventional reader / writer, when the continuous transmission possible time arrives, the reader / writer has a predetermined transmission stop time (for example, 50 milliseconds), and then a carrier sense time for determining whether or not the unit radio channel can be used. (For example, 5 ms), and subsequent back-off time (a time for avoiding transmission collision after the lapse of the carrier sense time, a period of a length that is randomly determined by random numbers after the lapse of the carrier sense time (for example, , 0 to 5 msec)), transmission / reception is stopped in the unit wireless channel, that is, the reading operation of the wireless IC tag 40 is stopped. As a result, the wireless IC tag 40 cannot be read during the transmission stop time, carrier sense time, and backoff time, and the wireless IC tag 40 reading efficiency (the number of wireless IC tags read per unit time). However, the wireless IC tag reading system 1 according to the present invention can continue reading the wireless IC tag 40 without inserting such time loss.

FIG. 9 is a flowchart showing an example of transmission / reception (reading) processing of the wireless IC tag reading system 1 according to the present embodiment.
First, in the wireless IC tag reading system 1, when reading the wireless IC tag 40, the reader / writer control device 10 instructs the reader / writer 20 to start transmission / reception (reading). At this time, the reader / writer control device 10 designates a unit radio channel used for transmission / reception. The unit radio channel is selected and determined by the reader / writer control device 10 based on a carrier sense execution result (specifically, the carrier sense result table 400) obtained as a result of carrier sense processing described later.

  Upon receiving this transmission / reception start command, the reader / writer 20 starts transmission / reception processing execution using the designated unit radio channel (S901). That is, the reader / writer 20 generates a reference wave having a frequency corresponding to the center frequency of the designated unit radio channel by the first frequency variable oscillation unit 503 and supplies the reference wave to the transmission unit 501. The transmitter 501 generates a carrier wave in this frequency band and a modulated wave obtained by modulating the carrier wave using the reference wave, and supplies the carrier wave and the modulated wave to the antenna unit 30. The response from the wireless IC tag 40 is also demodulated by the receiving unit 502 based on this reference wave, and the data obtained as a result of the demodulation is passed to the reader / writer control device 10.

  Next, the wireless IC tag reading system 1 determines whether or not the continuous transmission time has elapsed since the start of transmission / reception processing (S902). This determination may be made by the reader / writer control device 10 or by the main control unit 506 of the reader / writer 20.

  As a result of determining whether or not the continuous transmittable time has elapsed, if it is determined that the continuous transmittable time has not expired (No in S902), the wireless IC tag reading system 1 returns to step S901 and continues transmission / reception processing. . On the other hand, when it is determined that the continuous transmission time has expired (S902, Yes), the reader / writer 20 stops the transmission / reception process (S903). After the transmission / reception is stopped, the wireless IC tag reading system 1 determines whether a transmission / reception end condition is satisfied (S904). As the transmission / reception establishment conditions, it can be considered that the repetition of the transmission / reception processing has reached a predetermined number of times and the number of wireless IC tags successfully read has reached the assumed man-hours. The transmission / reception end condition can be freely determined by the operation of the wireless IC tag reading system 1, and there is no limitation on what end condition is used in the present invention.

  When the reader / writer 20 determines that the transmission / reception end condition is satisfied (S904, Yes), the wireless IC tag reading system 1 ends the transmission / reception process. On the other hand, when the reader / writer 20 determines that the transmission / reception end condition is not satisfied (S904, No), the wireless IC tag reading system 1 is stored in the carrier sense result storage unit 213 of the reader / writer control device 10. The carrier sense result table 400 is referred to (S905).

  Next, the wireless IC tag reading system 1 determines whether there is a usable unit wireless channel based on the contents of the carrier sense result table 400 (S906). As a result, when it is determined that there is no unit radio channel that can be used, the radio IC tag reading system 1 returns to step S905 and the unused unit radio channel is stored in the carrier sense result table. wait. On the other hand, if it is determined that there is an unused unit wireless channel, the wireless IC tag reading system 1 uses the usable unit wireless channel to continue the transmission / reception process so that the reader / The writer 20 is commanded (S907).

  Thereafter, the wireless IC tag reading system 1 returns to step S901, and continues the transmission / reception process using the designated usable unit wireless channel.

  By the above-described transmission / reception processing, the wireless IC tag reading system 1 according to the present invention continues the transmission / reception processing immediately after the continuous transmission time expires without waiting for the transmission stop time, carrier sense time, and back-off time to elapse. Will be able to.

[2.2. Carrier sense processing]
Next, carrier sense processing according to the present embodiment will be described. The wireless IC tag reading system 1 employs a method of executing carrier sense in each unit wireless channel in real time.

  Each of the channel-specific carrier sense execution units 504 executes carrier sense of the assigned unit radio channel every predetermined period (for example, 1 msec), and outputs an RSSI as an execution result. The main control unit 506 that has received the RSSI from the channel-specific carrier sense execution unit 504 communicates information (for example, availability flag “0” or “1”) according to the RSSI or the value of RSSI for each radio unit channel. The data is transmitted to the reader / writer control device 10 via the control unit 507.

  The RSSI carrier sense control unit 212 for each unit radio channel stores a flag indicating “in use” or “unusable” for the unit radio channel in the carrier sense result table 400 corresponding to the reader / writer 20.

  According to the carrier sense process, it is possible to constantly monitor whether each unit radio channel can be used for a channel, and to know a usable (empty) channel that can be used immediately. The carrier sense result is stored in the carrier sense result storage unit 213, and the carrier sense control unit 212 refers to the stored contents of the carrier sense result storage unit 213 so that the reader / writer 20 It is possible to designate a unit radio channel that can immediately start or continue transmission / reception without stopping transmission / reception by carrier sense time and back-off time.

[3. Modified example]
In the above embodiment, the reader / writer 20 having a plurality of second frequency oscillating units 804 that oscillate a reference signal corresponding to the corresponding unit radio channel is used. However, one carrier sense executing unit is used. Thus, the present invention is also realized as a configuration using the reader / writer 20 that performs carrier sense processing for all unit radio channels.

  FIG. 10 shows a configuration example of the reader / writer 20A that performs carrier sense processing for all unit radio channels with one carrier sense execution unit.

  The reader / writer 20A has substantially the same configuration as that of the reader / writer 20 described in the above embodiment, and the same components are denoted by the same reference numerals and detailed description thereof is omitted.

  The reader / writer 20A receives a reference signal from the second frequency variable oscillation unit 505 that can switch the frequency of the reference signal at high speed for carrier sense processing, and receives the reference signal from the second frequency variable oscillation unit 505, and responds to the reference signal. The carrier sense execution unit 504A executes carrier sense in the unit radio channel.

  The second variable frequency oscillating unit 505 generates a reference signal (PLL_LO signal) at a frequency corresponding to each unit radio channel, and supplies this to the carrier sense executing unit 504. The second variable frequency oscillator 505 is a module on which, for example, a PLL (Phase Lock Loop) IC and a VCO (Voltage Control Oscillator) IC are mounted.

  The main control unit 506 instructs the second frequency variable oscillating unit 505 to switch and output a reference signal having a frequency corresponding to each unit radio channel. For example, the main control unit 506 may output a timing signal instructing the timing for changing the frequency to the second variable frequency oscillation unit 505, or output a channel number designation signal for designating a unit radio channel. You may do it. Alternatively, a configuration may be adopted in which a timing signal instructing the timing of changing the frequency is generated by a counter or timer provided separately from the main control unit 506 and output to the second variable frequency oscillation unit 505.

  The reader / writer control device 10 and the antenna unit 30 are the same as those in the above-described embodiment.

Block diagram showing a configuration example of a wireless IC tag reading system Block diagram showing a hardware configuration example of a reader / writer control device Functional block diagram of reader / writer control device The figure which shows the example of a carrier sense result table Block diagram showing a configuration example of a reader / writer Block diagram showing a circuit configuration example of a transmitter of a reader / writer Block diagram showing a circuit configuration example of a receiving unit of a reader / writer Block diagram showing a circuit configuration example of a carrier sense execution unit of a reader / writer The flowchart which shows the example of the transmission / reception process which a radio | wireless IC tag reading system performs Block diagram showing a configuration example of a reader / writer according to a modified example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wireless IC tag reading system 10 ... Reader / writer control apparatus 20 ... Reader / writer 30 ... Antenna unit 40 ... Wireless IC tag 501 ... Transmission part 502 ... Reception part 503 ... First frequency variable oscillation part 504 ... Carrier sense by channel Execution unit 506 ... main control unit

Claims (2)

A wireless IC tag reading system for reading a wireless IC tag that can use a plurality of unit wireless channels,
First oscillating means for generating a signal having a frequency corresponding to a unit radio channel used for transmission / reception with the radio IC tag;
Transmission / reception means for performing transmission / reception with the wireless IC tag using the signal generated by the first oscillation means;
Carrier sense means for simultaneously and repeatedly measuring the received radio wave intensity in each of the plurality of unit radio channels and outputting information indicating the measurement results;
First control means for generating and storing information indicating whether or not each of the plurality of unit radio channels can be used based on the received radio wave intensity measured by the carrier sense means;
A second oscillating unit configured to control the first oscillating unit to generate a signal having a frequency corresponding to the unit radio channel to be used by the transmitting / receiving unit, based on information indicating availability of each of the plurality of unit radio channels; And a wireless IC tag reading system.   The carrier sense means comprises a plurality of channel-specific carrier sense means provided for each unit radio channel, and each channel-specific carrier sense means outputs information indicating the received radio wave intensity in the corresponding unit radio channel. The wireless IC tag reading system according to claim 1, wherein:

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