JP2016126394A - Wireless tag communication system and tag reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless tag communication system configured to allow a tag reader to read information from an intended wireless tag in a short time even when there are a wireless tag to be read and a wireless tag not to be read in a service area.SOLUTION: A tag reader sets a partial ID, which is a part of a tag ID of an intended wireless tag, as a tag ID specification condition (S11), and transmits a read instruction including the partial ID (S12). A wireless tag having received the read instruction transmits a response signal when a tag ID of the tag includes the partial ID. The tag reader analyzes a result of reception (S13), and transmits a reception success to the wireless tag when the reception is successful. Until an additional response suppression period elapses, the same read instruction is repeatedly transmitted. When a determination is made that the additional response suppression period has elapsed, the partial ID is changed (S24). When no end instruction is issued, a read instruction including the changed partial ID is transmitted.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a wireless tag communication system including a wireless tag and a tag reader, a tag reader included in the wireless tag communication system, and more particularly to a technique for improving reading efficiency.

  Conventionally, there is a system in which a wireless tag is attached to a product or device in a store, a warehouse, etc., and the ID of the wireless tag is read using a tag reader to perform inventory or inventory management. By using the wireless tag, the presence or absence of many articles can be confirmed in a short time.

  However, in a system in which a wireless tag responds to a read command from a tag reader, if there are a large number of wireless tags in the communication range of the tag reader, the wireless tag that does not need to be read transmits a response signal, and the wireless tag that needs to be read The speed of reading information is reduced.

  Therefore, in Patent Document 1, the wireless tag to be communicated is selected by changing the communication range by changing the strength of the radio wave radiated from the communication antenna provided in the wireless tag reader / writer.

JP 2009-17291 A

  However, if a wireless tag that needs to be read and a wireless tag that does not need to be read are mixed in a narrow range, even if the communication range is narrowed, only the wireless tag that needs to be read cannot be selected.

  Initially, even if all of the wireless tags in the communication range are the wireless tags to be read, the tag reader communicates with the wireless tag one by one, and the read wireless tag is no longer the wireless tag to be read. . Therefore, when there are a plurality of wireless tags in the communication range, a wireless tag that needs to be read in the communication range and a wireless tag that does not need to be read are always mixed.

  The present invention has been made based on this circumstance, and the purpose of the present invention is to shorten the time required even if there is a wireless tag that needs to be read in the communication range and a wireless tag that does not need to be read. Thus, an object of the present invention is to provide a wireless tag communication system in which a tag reader can read information from a wireless tag that needs to be read, and a tag reader provided in the wireless tag communication system.

  The above object is achieved by a combination of the features described in the independent claims, and the subclaims define further advantageous embodiments of the invention. Reference numerals in parentheses described in the claims indicate a correspondence relationship with specific means described in the embodiments described later as one aspect, and do not limit the technical scope of the present invention. .

  In order to achieve the above object, a first aspect of the present invention relates to a tag reader (1) that transmits a read command including a partial ID that is a part of a tag ID included in a wireless tag to be responded and receives a response signal from the wireless tag. 1A) and a wireless tag including a wireless tag (100) that receives a read command and transmits a response signal based on the fact that its own tag ID includes a partial ID included in the read command. It is a tag communication system.

  According to the present invention, the read command includes a partial ID that is a part of the tag ID of the wireless tag to which the response signal is to be transmitted, and the wireless tag has its own tag even when the read command is received. If the ID does not include a partial ID, no response signal is transmitted. Therefore, the tag reader limits the wireless tag that transmits the response signal to the wireless tag that needs to be read by including the partial ID included in the tag ID of the wireless tag that needs to be read in the read command. be able to. Therefore, even if there are a wireless tag that needs to be read in the communication range and a wireless tag that does not need to be read, information can be read from the wireless tag that needs to be read in a short time.

  In the invention according to claim 2, the read command includes information indicating the number of slots included in the tag reading period, and the wireless tag is randomly selected from the slots included in the tag reading period when transmitting a response signal. When the response signal is transmitted in the selected slot and the tag reader has succeeded in receiving the response signal and the predetermined re-response suppression time has not elapsed, the response signal is transmitted even if the read command is received. The tag reader sets the partial ID to a different value when or before it is determined that the time during which the reading command including the same partial ID is repeatedly transmitted exceeds the re-response suppression time. Change and send a read command.

  In the EPCglobal standard specification, “UHF Class 1 Gen 2 Standard v.2.0.0” defines the following. That is, it is specified that the read command transmitted from the tag reader includes the number of slots, and that the wireless tag selects a slot for transmitting a response signal at random from the slots described in the read command. . By providing a plurality of slots, response signals from a plurality of wireless tags can be received with a single read command.

  However, in a system in which a wireless tag responds to a read command from a tag reader, if a large number of wireless tags exist within the communication range of the tag reader, response signals simultaneously transmitted from complicated wireless tags collide with each other, Cannot receive correctly.

  Therefore, the EPCglobal standard specification stipulates that a response suppression function is installed so that a response signal is not transmitted even if a read command is received after a response signal is transmitted to the wireless tag.

  However, when there are many wireless tags in a range where radio waves from the tag reader can reach, there is a possibility that the reresponse suppression time elapses before information is read from all the wireless tags. When the reresponse suppression time elapses, the read wireless tag responds again. As a result, the response signal transmitted from the unread wireless tag and the response signal transmitted from the already read wireless tag collide, and communication between the unread wireless tag and the tag reader may be hindered. If the communication between the unread wireless tag and the tag reader is hindered, the reading efficiency is lowered accordingly.

  Therefore, in the present invention, the partial ID is changed to a different value when it is determined that the period during which the read command including the same partial ID is transmitted exceeds the re-response suppression time. Thereby, it is suppressed that the already read radio | wireless tag transmits a response signal again. For this reason, the read radio tag transmits a response signal, and the response signal collides with the response signal transmitted by the unread radio tag, so that the response signal transmitted by the unread radio tag cannot be received correctly. Is suppressed. As a result, the tag reader improves the efficiency of reading information from the wireless tag that needs to be read even when there are many wireless tags that need to be read in the reading range.

  In the invention according to claim 3, the partial ID designates one of a plurality of tag IDs included in the wireless tag to be read, and the tag reader includes the same partial ID. Based on the fact that the number of reception failures within the time during which the read command is repeatedly sent or the value related to reception failure, which is a value that changes according to the number of reception failures, exceeds the division number increase threshold, the partial ID is read. All the tag IDs included in the wireless tag are changed to a value that is divided into a larger number of sections than before.

  When the number of reception failures within the time during which the read command including the same partial ID is transmitted exceeds the division number increase threshold, the read command responds with the division number by the partial ID included in the read command. This means that there are too many wireless tags.

  Therefore, the partial ID is changed to a value that divides all tag IDs of the wireless tag to be read into a larger number of sections than before. As a result, among the wireless tags that have received the read command including the partial ID, the number of wireless tags having the partial ID decreases, so the number of wireless tags that respond to the read command decreases. Therefore, since the number of reception failures is reduced, information can be read more efficiently from a plurality of radio tags that are read.

  In the invention according to claim 4, the partial ID designates one of a plurality of tag IDs included in the wireless tag to be read, and the tag reader includes the same partial ID. While sending the read command repeatedly, based on the fact that the read command is sent but no response signal is received, the partial ID is assigned to all the tag IDs of the wireless tag to be read than before. Change to a value that divides into smaller numbers.

  If a read command including the same partial ID is repeatedly transmitted, the number of wireless tags that transmit a response signal in response to the read command is equal to the number of times the read command is transmitted until the reresponse suppression time elapses. Decrease depending on

  When a read command was sent but no response signal was received, it was sent from all the wireless tags having the partial ID included in the read command by a read command sent before that. This means that the response signal has been successfully received.

  This means that the current partial ID has too few wireless tags having the partial ID and can receive response signals from more wireless tags with the same reresponse suppression time.

  Therefore, the partial ID is changed to a value that divides all tag IDs of the wireless tag to be read into a smaller number of sections than before. Thereby, since the number of the radio | wireless tags which can be read within re-response suppression time can be increased, information can be read more efficiently from the some radio | wireless tag made into reading object.

  In the invention according to claim 5, when the tag reading period ends, if the reception success rate within the tag reading period is higher than the reference success rate range where the reading efficiency is good, the next tag While the number of slots in the reading period is reduced more than before, if the reception success rate in the tag reading period is lower than the reference success rate range, the number of slots in the next tag reading period is increased more than before. .

  In this way, when the number of slots in the next tag reading period is increased or decreased based on the reception success rate in each tag reading period, the slot so that the reception success rate falls within the reference success range regardless of the number of wireless tags. Will be adjusted.

  When the reception success rate is too high, the ratio of empty slots is large and the reading efficiency is lowered. Of course, when the reception success rate is too low, the reading efficiency also decreases. The reference success range is a range in which reading efficiency is good, and the reading efficiency in one tag reading period is improved by adjusting the number of slots so as to fall within the reference success rate range. Therefore, the time for reading information from a plurality of wireless tags can be shortened.

  In the invention according to claim 6, the tag reader stores a reading ID list that is a list of tag IDs of the RFID tags that need to be read, and transmits a reading command including the partial ID, so that the tag reading period During the execution of the partial ID designation mode, which is a mode for receiving a response signal from the wireless tag, the number of wireless tags that have not been successfully received, or the second or more reception of successful response signals Tag ID designation mode for transmitting a read command by including one tag ID selected from the read ID list in the read command based on the fact that the transition condition set based on the ratio of response signals to be successful is satisfied Migrate to

  If the tag reader stores a read ID list that is a list of tag IDs of wireless tags that need to be read, one wireless tag that transmits a response signal by including one tag ID in the read command Can be specified.

  In addition, when the number of wireless tags that need to be read decreases, a read command including a partial ID is transmitted and a response signal is received from a plurality of wireless tags. The tag ID designation mode in which the command is transmitted has better reading efficiency.

  The reason is that, in the tag ID designation mode, it is necessary to send a read command by the number of radio tags that have not been successfully received. The reading efficiency is worse than the ID designation mode.

  However, even in the partial ID designation mode, if there are many wireless tags with the partial ID included in the read command, all wireless tags with the partial ID included in the read command are within one reresponse suppression time. In some cases, the response signal cannot be read. In this case, if the response signal is read from all the wireless tags in the partial ID mode, a read command including the partial ID included in the tag ID of the wireless tag that could not be read again after the re-response suppression time has elapsed. Must be sent. When the read command is transmitted again, the wireless tag that has already been read also transmits a response signal. When a response signal is transmitted from a wireless tag that has already been read, the efficiency of reading the response signal from a wireless tag that has not been read yet decreases.

  This decrease in reading efficiency is high when the number of radio tags that have already been successfully received is large, in other words, when the number of radio tags that have not yet been successfully received is small. In addition, when the number of already received wireless tags is relatively large, the ratio of response signals that have been successfully received for the second time or more of the response signals that have been successfully received in the tag reading period after the transmission of one read command Is also expensive.

  Therefore, in the invention according to this claim, the transition condition is set based on the number of wireless tags that have not been successfully received and the ratio of response signals that have been successfully received for the second time or more of the response signals that have been successfully received. Set. Then, based on the establishment of this transition condition, the mode shifts to the tag ID designation mode. Accordingly, information can be read from the wireless tag that needs to be read in a shorter time.

  The invention according to claim 7 is based on a tag reader (1) for transmitting a read command including information indicating the number of slots included in a tag read period for a number of wireless tags, and receiving the read command. And a wireless tag communication system including a wireless tag (100) for transmitting a response signal, and when transmitting a response signal, the wireless tag responds with a slot randomly selected from a slot included in a tag reading period. After the tag reader succeeds in receiving the response signal and receiving the response signal, the response signal is transmitted again based on the reception of the read command after a predetermined reresponse suppression time has elapsed. The tag reader stores a reading ID list that is a list of tag IDs of wireless tags that need to be read, and targets a plurality of wireless tags. The number of radio tags that have not been successfully received and received while executing the multiple tag read mode, which is a mode in which a response command is received from the radio tag during the tag read period One tag ID selected from the reading ID list is read based on the fact that the transition condition set based on at least one of the ratios of the response signals that have been successfully received for the second time or more among the response signals that have been successfully received. It shifts to the tag ID designation mode in which it is included in the command and transmits the read command.

  In the multiple tag reading mode, as in the partial ID designation mode, response signals from a plurality of wireless tags can be received by transmitting a single read command.

  On the other hand, in the multiple tag reading mode, a wireless tag that has already been successfully read also transmits a response signal in response to the read command again after the reresponse suppression time has elapsed. As a result, a response signal from a wireless tag that has not been successfully received collides with a response signal from a wireless tag that has already been successfully received, and a response signal from a wireless tag that has not been successfully received yet. There is a possibility that reading will be impossible.

  The possibility that a response signal from a wireless tag that has not been successfully received cannot be read due to a collision of response signals is that the number of wireless tags that have already been successfully received is large, in other words, reception is still successful. It becomes high when the number of wireless tags that are not used is small.

  In addition, when the number of radio tags that have already been successfully received is large, among the response signals that have been successfully received in the tag reading period after the transmission of one read command, the response signals that have been successfully received for the second time or more increase. .

  Therefore, as in the invention according to this claim, at least one of the number of wireless tags that have not been successfully received and the ratio of response signals that have been successfully received for the second time or more among the response signals that have been successfully received. Based on this, set the migration conditions. Then, based on the establishment of this transition condition, the mode shifts to the tag ID designation mode. Accordingly, information can be read from the wireless tag that needs to be read in a shorter time.

  In the invention according to claim 8, the tag ID includes an area ID indicating the area where the wireless tag is located, and the tag reader transmits a read command including the area ID as a partial ID.

  Wireless tags are widely used for inventory management by being affixed to merchandise or items that contain it. In inventory management, there is a case where it is desired to check products stored in a certain area. In this case, the tag reader wants to communicate only with a wireless tag that exists in a certain area.

  Here, it is conceivable that the output intensity of the radio wave transmitted by the tag reader is weakened so that the radio wave intensity does not become so high that the wireless tag responds to an area that does not need to be read. However, if the output intensity of the radio wave is weakened, it becomes difficult to communicate with the wireless tag existing in the area to be read.

  Therefore, in the present invention, the area ID indicating the area where the wireless tag is located is included in the tag ID. Then, the tag reader transmits a read command including the area ID as the partial ID. As a result, only the wireless tag with the tag ID having the area ID included in the read command transmits the response signal. Therefore, information can be read in a short time from a wireless tag that exists in an area that needs to be read.

  In the invention according to claim 9, the tag reader (1A) includes a position detection unit (60) for detecting its own position and includes an area ID indicating an area determined based on the position detected by the position detection unit. Send instructions.

  In this way, the tag reader acquires its own position, automatically determines an area determined based on the position, and transmits a reading command including an area ID indicating the area. This eliminates the need for the user to input the area to be read.

  The invention according to claim 10 includes a display section (1d) for displaying at least one of the position determined by the position detection section and the area determined based on the position.

  In this way, the user can check whether the area designated by the reading command transmitted by the tag reader is the area intended by the user by looking at the area or position displayed on the display unit. Can be confirmed.

  The invention according to claim 11 is a tag reader (1, 1A) that transmits a read command including a partial ID that is a part of a tag ID included in a wireless tag to respond and receives a response signal from the wireless tag.

  This tag reader is a tag reader provided in the wireless tag communication system according to claim 1.

1 is a perspective view showing an external appearance of a tag reader 1. FIG. 2 is a block diagram showing an internal configuration of a tag reader 1. FIG. 2 is a block diagram showing an internal electrical configuration of the wireless tag 100. FIG. 5 is a flowchart illustrating processing executed by the control unit 128 of the wireless tag 100. It is a flowchart which shows the process which the control part 20 of the tag reader 1 performs. 2 is a diagram conceptually showing signals transmitted by a tag reader 1 and a plurality of wireless tags 100. FIG. It is a figure which shows the time change of the tag reading number in a comparative example. It is a figure which shows the time change of the tag reading number in 1st Embodiment. It is a figure which shows notionally the reading ID list which the tag reader 1 of 2nd Embodiment has memorize | stored. It is a flowchart which shows the process in the normal reading mode which the control part 20 of the tag reader 1 performs in 2nd Embodiment. It is a flowchart which shows the process in the tag ID designation | designated mode which the control part 20 of the tag reader 1 performs in 2nd Embodiment. It is a flowchart which shows the process in the partial ID designation | designated mode which the control part 20 of the tag reader 1 performs in 3rd Embodiment. It is a figure explaining the area divided in 4th Embodiment. It is a block diagram which shows the electrical structure inside the tag reader 1A of 4th Embodiment. It is a flowchart which shows the process which the control part 20 of 1 A of tag readers of 4th Embodiment performs. It is a flowchart which shows the process in the normal reading mode which the control part 20 of the tag reader 1 performs in 5th Embodiment.

<First Embodiment>
(Configuration of tag reader 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an appearance of a tag reader 1 provided in the wireless tag communication system of the first embodiment. The wireless tag communication system includes a tag reader 1 and a wireless tag 100 (see FIG. 3).

  The tag reader 1 is a portable type and has a function of reading information stored in the wireless tag 100 by communicating with the wireless tag 100 (see FIG. 3). In the present embodiment, this function is executed when a predetermined trigger button provided in the tag reader 1 is pressed by the user. Details of this function will be described later with reference to FIG. Further, the tag reader 1 includes a display unit 1d that displays a reading result and the like.

  The internal configuration of the tag reader 1 includes an antenna 10, a control unit 20, and a communication unit 30, as shown in a block diagram in FIG. Moreover, although not shown, a battery etc. are also provided. The communication unit 30 includes a transmission unit 40 and a reception unit 50.

  The transmitter 40 includes an encoder 41, a modulator 42, and an amplifier 43. The encoding unit 41 encodes the signal supplied from the control unit 20 and outputs the encoded signal to the modulation unit 42. The modulation unit 42 converts the signal encoded by the encoding unit 41 into an electrical digital signal, and then modulates by a modulation method based on a predetermined communication method using a predetermined communication channel. To do. The amplification unit 43 amplifies the signal modulated by the modulation unit 42. The amplified signal is transmitted from the antenna 10 as a radio wave.

  The receiving unit 50 includes a demodulating unit 51 and a decoding unit 52. The demodulator 51 demodulates the radio wave received by the antenna 10 and sends it to the decoder 52. The decoding unit 52 decodes the demodulated signal and sends the decoded signal to the control unit 20.

  The control unit 20 is a computer including a CPU, a ROM, a RAM, and the like. The CPU executes a program stored in the ROM and the like while using a temporary storage function of the RAM, and will be described later with reference to FIG. Execute the process. Note that some or all of the functions executed by the control unit 20 may be configured by hardware using one or a plurality of ICs.

(Configuration of wireless tag 100)
The wireless tag 100 is an RFID tag, and includes an antenna 110 and one IC chip 120 as shown in FIG. The antenna 110 has an electrical length suitable for the frequency used.

  The IC chip 120 includes a rectifier 122, a demodulator 124, a memory 126, a controller 128, and a modulator 130.

  When the antenna 110 receives the radio wave transmitted from the tag reader 1, the rectifying unit 122 smoothes and rectifies the electric signal generated by the antenna 110 by the radio wave, and supplies operating power to other elements in the IC chip 120. The rectifying unit 122 also includes a charging capacitor (not shown), and charges the charging capacitor with radio waves received by the antenna 110. The electric charge charged in the charging capacitor serves as a power source for the wireless tag 100 when it is not receiving radio waves.

  The demodulator 124 demodulates a signal such as a read command transmitted from the tag reader 1 from the radio wave received by the antenna 110 and outputs the demodulated signal to the controller 128. The memory 126 is nonvolatile, and stores an ID of the wireless tag 100 (hereinafter, tag ID) and the like.

  When the control unit 128 acquires a signal such as a read command, the control unit 128 executes a process determined based on the acquired signal. The processing executed by the control unit 128 includes reading data from the memory 126 and outputting transmission data to the modulation unit 130. The processing executed by the control unit 128 will be described later in detail.

  Modulation section 130 is connected to antenna 110, modulates transmission data such as a response signal output from control section 128, and outputs the result to antenna 110. When the transmission data modulated by the antenna 110 is output, the transmission data is radiated as a radio wave.

(Processing of the control unit 128)
The control unit 128 periodically executes the process illustrated in FIG. 4 while receiving power from the rectification unit 122. In step S1, it is determined whether a read command has been received. The read command is a command transmitted when the tag reader 1 executes step S12 of FIG. If this determination is NO, the process of FIG. 4 is terminated.

  If a read command is received, step S1 becomes YES, and the process proceeds to step S2. In step S2, it is determined whether there is an ID designation in the read command. The specified ID is a partial ID in the first embodiment. That is, in the first embodiment, in step S2, it is determined whether or not a partial ID is included. The partial ID is a signal that designates a part of the tag ID included in the wireless tag 100 that should respond, and the wireless tag 100 that transmits the response signal needs to have this partial ID.

  If the determination in step S2 is YES, the process proceeds to step S3. In step S3, its own tag ID is read from the memory 126, and it is determined whether or not the tag ID has an ID specified by the read command, that is, whether or not it has a partial ID in the first embodiment. .

  If the determination in step S3 is NO, the process of FIG. 4 ends without transmitting a response signal. If judgment of step S3 is YES, it will progress to step S4. Also, if the determination in step S2 is NO, that is, if the partial ID is not specified in the read command, the process proceeds to step S4.

  In step S4, it is determined whether or not re-response is being suppressed. In the next step S5, when a response signal is transmitted to the tag reader 1 and a reception success signal is received from the tag reader 1, reresponse suppression is started. Thereafter, when a preset re-response suppression time (for example, 1 second) has not elapsed, the re-response is being suppressed. If the re-response is being suppressed (S4: YES), the processing in FIG. 4 is terminated without transmitting a response signal. If the re-response is not being suppressed (S4: NO), the process proceeds to step S5.

  The read command includes information indicating the number of slots included in the tag reading period, which is a period in which the tag reader 1 receives the response signal. In step S5, one slot is randomly selected from the plurality of slots constituting the tag reading period and a response signal is transmitted. The response signal is generated according to a predetermined protocol, and the generated response signal is output to modulation section 130. This response signal includes its own tag ID.

  When the tag reader 1 can receive the transmitted response signal, the tag reader 1 transmits a reception success signal to the wireless tag 100 in step S14 of FIG. In step S6, it is determined whether or not the reception success signal has been received. If this judgment becomes YES, it will progress to Step S7 and will start re-response suppression. On the other hand, if the reception success signal is not received within a certain time after the response signal is transmitted, the re-response suppression is not started and the process of FIG. 4 is terminated.

(Processing of tag reader 1)
When the trigger button is pressed, the control unit 20 of the tag reader 1 executes the process shown in FIG. In step S11, tag ID designation conditions are set. The tag ID designation condition is a condition for limiting a part of the wireless tag 100 that responds to the read command among the plurality of wireless tags 100, and specifically, sets a partial ID. In the present embodiment, the partial ID indicates one or a plurality of bits on the lowest side of the tag ID, and the number of bit digits changes in step S13 described later. It is assumed that the initial digit number of the partial ID is 2 digits. Therefore, there are four types of partial IDs “00”, “10”, “01”, and “11”. When executing step S1 for the first time after the trigger button is pressed, “00” is set.

  With these four types of partial IDs, all tag IDs included in the wireless tag 100 to be read are divided into four sections. In the first embodiment, all the wireless tags 100 existing in the communication range are to be read.

  In step S <b> 12, a read command is transmitted from the antenna 10 via the transmission unit 40. The read command is a command for instructing transmission of a response signal to the wireless tag 100 that has received the read command, and includes the partial ID set in step S11 and the number of slots provided in the tag reading period.

  FIG. 6 conceptually shows signals transmitted by the tag reader 1 and the plurality of wireless tags 100. In the example of FIG. 6, a read command is transmitted between times t1 and t2. When the wireless tag 100 receives the read command transmitted by the tag reader 1, as described above, the wireless tag 100 randomly selects a slot and transmits a response signal when its tag ID has a partial ID. To do. In the example of FIG. 6, the wireless tag 100a transmits a response signal in the first slot in the period from time t2 to t3, and the wireless tags 100b and 100c transmit the response signal in the second slot in the period from time t3 to t4. The wireless tag 100n transmits a response signal in slot n during the period from time t6 to time t7. On the other hand, the third slot from time t4 to t5 is an empty slot. In addition, the round shown in FIG. 6 means transmission of one reading command and subsequent tag reading period.

  In step S13, the reception result is analyzed. Since the response signal is generated according to a predetermined protocol, the signal received by the decoding unit 52 according to the protocol is acquired, and if a signal that can be recognized as a tag ID is included, it is determined that the reception is successful. The analysis of the reception result is performed for each slot constituting the tag reading period.

  In the example of the first round of FIG. 6, in the first slot, only the wireless tag 100a transmits a response signal, so that reception is successful. Also, slot n is successfully received. On the other hand, since the wireless tags 100b and 100c transmit response signals in the second slot, these two response signals interfere with each other and the signal level is high, but the response signal cannot be read. In this case, reception fails. If the signal itself is not acquired, neither reception success nor reception failure occurs.

  In step S14, the tag ID that has been successfully received is stored in a predetermined memory, and a reception success signal indicating that reception has been successful is transmitted to the wireless tag 100 that has been successfully received.

  In step S15, it is determined whether all slots have been completed. If this determination is NO, the process returns to step S13, and steps S13 and S14 are executed for the next slot. If judgment of step S15 is YES, it will progress to step S16.

  In step S16, it is determined whether or not the reading is completed, that is, whether or not the response signals from all the wireless tags 100 existing in the range where the reading command can be received are successfully received. More specifically, this determination is made when all partial IDs are set, and when there is no reception failure in reading with each partial ID set.

  If judgment of step S16 is YES, it will progress to step S17. In step S17, the end flag is turned on. Then, it progresses to step S25 mentioned later. If judgment of step S16 is NO, it will progress to step S18.

  In step S18, it is determined whether the reception success rate is within the reference success rate range, higher than that, or lower than that. The reception success rate is the number of slots successfully received with respect to the total number of slots. Alternatively, instead of the total number of slots, the number of successful slots and the number of failed slots may be used as the denominator.

  If the reception success rate is higher than the reference success rate range, the process proceeds to step S19. In step S19, the number of slots is decreased by a predetermined number (for example, one). If the reception success rate is medium, that is, if the reception success rate is within the reference success rate range, it is determined to proceed to step S20 and maintain the number of slots. If the reception success rate is lower than the reference success rate range, step S21 is performed. Go to and increase the number of slots by a predetermined number.

  In step S22, it is determined whether or not the reresponse suppression time has elapsed since the reading command was transmitted in step S12. If this judgment is NO, it will return to Step S12 and will perform Step S12 and subsequent steps again. If so far the first round shown in FIG. 6, the second round shown in FIG. 6 is executed.

  By executing step S12 in the second round, in the example of FIG. 6, a read command is transmitted during the period from time t8 to t9. Then, the response signal can be received in the subsequent first slot to n. In the example of FIG. 6, since the communication with the wireless tag 100a and the wireless tag 100n is successful in the first round, the wireless tags 100a and 100n transmit the response signal even when receiving the reading command in the second round. do not do. On the other hand, since the wireless tags 100b and 100c both transmitted the response signal in the second slot in the first round, the communication has not yet been successful. Therefore, the wireless tags 100b and 100c again select a responding slot at random and transmit a response signal.

  In the example of FIG. 6, in the second round, the wireless tag 100b transmits a response signal in the second slot, and the wireless tag 100c transmits a response signal in the third slot. Therefore, the tag reader 1 succeeds in communication with the wireless tags 100b and 100c in the second round.

  If the re-response time elapses while repeating steps S12 to S22, the determination in step S22 is YES and the process proceeds to step S23.

  In step S23, the number of divisions is updated. The number of divisions is a number in which all tag IDs are divided by partial IDs. If the number of bit digits of the partial ID is two digits, the number of divisions is four. The number of divisions is set so that the number of wireless tags 100 that exist within the reading range of the tag reader 1 and have a partial ID is close to the upper limit that the tag reader 1 can read within the tag reading period. Is preferred.

  Therefore, the division number is changed using the reading result of each slot. Specifically, in the repetition of steps S12 to S22, when the number of reception failures is equal to or greater than the division number increase threshold, there are too many wireless tags 100 that transmit response signals with the current division number. Therefore, the number of bits of the partial ID is increased by one digit. On the other hand, if all the reading results of each slot become empty slots in one round, it can be determined that the division is excessive and that there are too few wireless tags 100 that transmit response signals. Therefore, the number of bits of the partial ID is reduced by one digit. The number of bits of the partial ID is maintained unless the number of reception failures is equal to or greater than the division number increase threshold and the reading results of each slot are not all empty slots in one round.

  Note that the number of reception failures may be a total value of the reception failures in all slots or an average value of the number of reception failures in one slot. Further, the median value of the number of reception failures for each slot may be used. This number of reception failures corresponds to a reception failure related value in the claims. The division number increase threshold is appropriately set according to a specific calculation method for the number of reception failures. When the number of divisions is updated, the process proceeds to step S24.

  In step S24, the tag ID designation condition is updated to the next partial ID. The next partial ID is a partial ID obtained by adding 1 bit to the partial ID included in the read command in step S12 when the number of bits of the partial ID is increased in step S23. For example, if the partial ID included in the read command in step S12 is “00”, the next partial ID is “001”.

  When the bit number of the partial ID is maintained in step S23, the partial ID has the same number of digits as the partial ID included in the read command in step S12. For example, if the partial ID included in the read command in step S12 is “00”, the next partial ID is “01”.

  When the number of bits of the partial ID is decreased in step S23, the next partial ID is determined as follows. First, consider a partial ID obtained by reducing the number of bits by one digit from the partial ID included in the read command in step S12. For example, if the partial ID before decreasing the number of bits is “00”, the partial ID whose number of bits is decreased by one digit is “0”. If all types of partial IDs having one more digit than the partial ID are included in the read command and transmitted, the partial ID with the number of bits reduced by one digit is set as the next partial ID. If the partial ID obtained by reducing the number of bits by one digit is “0”, the next partial ID is determined to be “1”. On the other hand, if there is a partial ID that is not included in the read command among the partial IDs whose number of bits is one digit greater than the partial ID after the bit number reduction, the partial ID that is not included in the read command is set as the next partial ID. And For example, when the read command including the partial ID “00” is transmitted but the read command including the partial ID “01” is not transmitted, the number of bits of the partial ID is reduced in step S23. Even if it is decided, the next partial ID is “01”.

  In a succeeding step S25, it is determined whether or not there is an end command. There are two types of termination commands. One is that the trigger button is turned off. The other is that the end flag is on. If the determination in step S25 is YES, after outputting a sound signifying the end, the process of FIG. 5 is ended. On the other hand, if determination of step S25 is NO, it will return to step S12. When returning to step S12, step S12 and subsequent steps are executed with the read command including the partial ID updated in step S24.

(Effect of 1st Embodiment)
When receiving a reception success signal from the tag reader 1 (S6: YES), the wireless tag 100 does not transmit a response signal even if it receives a read command during the re-response suppression time (S4, S7). ). However, when there are a large number of wireless tags 100 in the communication range of the tag reader 1, the reresponse suppression time may elapse before the tag reader 1 successfully communicates with all the wireless tags 100. . When the re-response suppression time elapses, the wireless tag 100 that has already been successfully received transmits a response signal again in response to the read command. The response signal collides with a response signal transmitted by the wireless tag 100 that has not been successfully received, and the tag reader 1 may not be able to read the response signal from the wireless tag 100 that has not been successfully received. If communication between the wireless tag 100 and the tag reader 1 that has not been successfully received is hindered, the time until the tag reader 1 reads response signals from all the wireless tags 100 becomes longer.

  FIG. 7 is a diagram illustrating a change over time in the number of read tags in the comparative example. In this comparative example, when the tag reader 1 does not include a partial ID in the read command, and the wireless tag 100 receives the read command, the wireless tag 100 selects a slot that responds at random from the slots constituting the read period, unless the reresponse is suppressed. Then, a response signal is transmitted.

  When the re-response suppression time elapses after the first reading command is transmitted, the wireless tag 100 that has been successfully read also transmits the response signal again. For this reason, the number of wireless tags 100 that can read the response signal hardly changes, whereas the number of wireless tags 100 that can newly read the response signal decreases with the passage of time. In other words, with the passage of time, the number of reading response signals from the wireless tag 100 that need not be read increases. Therefore, reading efficiency is bad.

  On the other hand, in the first embodiment, the tag reader 1 transmits a reading command including a partial ID (S12), and the wireless tag 100 receives its reading command and receives its tag ID. If the partial ID is provided, a response signal is transmitted (S1 to S3, S5). However, even if a read command is received (S1: YES), a response signal is not transmitted unless its own tag ID has a partial ID (S3: NO).

  Therefore, even when a large number of wireless tags 100 exist in the communication range, the tag reader 1 may limit the wireless tag 100 that transmits the response signal to a part of the wireless tags 100 that have received the read command. it can.

  If it is determined that the period during which the read command including the same partial ID is transmitted exceeds the re-response suppression time (S22: YES), the partial ID included in the read command is different from the previous one. To the next partial ID which is the value of (S24). As a result, the wireless tag 100 that has already been successfully received is prevented from transmitting a response signal again in response to the read command.

  Therefore, as shown in FIG. 8, in this embodiment, even when time elapses, most of the wireless tags 100 that read the response signal become wireless tags 100 that newly read the response signal. In addition, the possibility that the response signal transmitted by the wireless tag 100 that has not been successfully received will fail to be read due to signal collision is reduced. Therefore, information can be read from the wireless tag 100 that needs to be read in a short time.

  Furthermore, in this embodiment, the read command including the same partial ID is repeatedly transmitted until the reresponse suppression time elapses (S12, S22), and the number of reception failures in that period exceeds the division number increase threshold. In this case, the number of bits of the partial ID is increased by one digit (S23). When the number of bits of the partial ID is increased by one digit, all tag IDs are divided into twice as many as before.

  As a result, among the wireless tags 100 that have received the read command including the partial ID, the number of wireless tags 100 having the partial ID decreases, and therefore the number of wireless tags 100 that respond to the read command decreases. Therefore, since the number of reception failures is reduced, the time for reading response signals from the plurality of wireless tags 100 can be shortened.

  In addition, when all the reading results of each slot become empty slots in one round, it can be determined that the current partial ID has too few wireless tags 100 having the partial ID. . Therefore, when all slot read results become empty slots in one round, the number of bits of the partial ID is reduced by one digit (S23). Thereby, although the read command is transmitted, it is suppressed that all the slots become empty slots, so that the time for reading the response signals from the plurality of wireless tags 100 can be further shortened.

  In addition, when it is determined that the period in which the reading command including the same partial ID is repeatedly transmitted has passed the re-response reading time, not only the number of divisions is updated, but also when the tag reading period ends. Then, the number of slots in the next reading period is determined (S18 to S21).

  Since the number of slots is increased or decreased based on the comparison between the reception success rate and the reference success rate range in each tag reading period, the reception success rate does not depend on the number of wireless tags present in the communication range of the tag reader 1. The number of slots will be adjusted to fall within the reference success range.

  When the reception success rate is too high, the ratio of empty slots is large, and the reading efficiency is lowered. When the reception success rate is too low, the reading efficiency is also lowered. Therefore, by adjusting the number of slots so as to fall within the reference success rate range, the reading efficiency in one tag reading period is improved. This also shortens the time for reading response signals from the plurality of wireless tags 100.

Second Embodiment
Next, a second embodiment will be described. In the following description of the second embodiment, elements having the same reference numerals as those used so far are the same as elements having the same reference numerals in the previous embodiments unless otherwise specified. Further, when only a part of the configuration is described, the above-described embodiment can be applied to the other parts of the configuration.

  In the second embodiment, the tag reader 1 stores a read ID list conceptually shown in FIG. 9 in, for example, a nonvolatile memory provided in the control unit 20. The reading ID list is a list of tag IDs of the wireless tags 100 that need to be read, and includes tag IDs of all the wireless tags 100 that need to be read and a read flag of each tag ID.

(Processing in normal reading mode)
When the trigger button is pressed, the control unit 20 of the tag reader 1 according to the second embodiment first executes the normal reading mode process shown in FIG. Comparing FIG. 10 with FIG. 5, FIG. 10 includes step S26 instead of not including steps S11, S22, S23, and S24. Also, step S14-1 is executed instead of step S14 in FIG.

  Steps S11, S22, S23, and S24 in FIG. 5 are processes related to designation of a partial ID and update of a partial ID. That is, in the normal reading mode illustrated in FIG. 10, the wireless tag 100 that transmits the response signal is not limited using the partial ID. Therefore, in step S12 of FIG. 10, a read command that does not include the partial ID is transmitted.

  The read command transmitted in step S12 in FIG. 10 is the same as the read command transmitted in the first embodiment except that the partial ID is not included, and includes information indicating the number of slots included in the tag reading period. . This read command is intended to send back a response signal to all the wireless tags 100 that receive the read command, and the normal read mode corresponds to the multiple tag read mode in the claims.

  The processing executed by the control unit 128 of the wireless tag 100 is the same as that in the first embodiment. Since the partial ID is not included in the read command, the determination in step S2 in FIG. 4 is NO. Therefore, in this normal reading mode, when receiving a read command, the wireless tag 100 transmits a response signal unless reresponse suppression is in progress.

  The tag reader 1 analyzes the analysis of the reception result based on this response signal (S13). In subsequent step S14-1, the read ID list is updated based on the analysis result in step S13. That is, the read flag corresponding to the tag ID of the wireless tag 100 that has been successfully received is changed to read. Similarly to step S <b> 14, the reception success signal is transmitted to the wireless tag 100.

  After step S14-1 is executed, as in the first embodiment, reading completion is determined (S16), and the number of slots is increased or decreased based on the reception success rate (S18 to S21). If it is determined in step S25 that there is no termination command, the process proceeds to step S26.

  In step S26, it is determined whether or not to shift to the tag ID designation mode. This determination is to determine whether or not the transition condition is satisfied. There are two transition conditions, and the first transition condition is that the number of wireless tags 100 that have not been successfully received is equal to or less than the first transition threshold. Whether or not the first transition condition is satisfied is determined by comparing the number of read flags whose read flag is unread in the read ID list with the first transition threshold.

  The second transition condition is that the ratio of response signals that have been successfully received for the second time or more out of the response signals that have been successfully received in the current round is equal to or greater than the second transition threshold value. Whether or not the second transition condition is satisfied is determined from the execution results of steps S13 and S14-1 that are repeatedly executed until step S15 becomes YES.

  If neither the first transition condition nor the second transition condition is satisfied, the determination in step S26 is NO and the process returns to step S12. Therefore, a read command that does not limit the wireless tag 100 that transmits the response signal is transmitted again.

  On the other hand, if either the first transition condition or the second transition condition is satisfied, the determination in step S26 is YES, and the process proceeds to the tag ID designation mode shown in FIG.

(Processing in tag ID designation mode)
When the mode is shifted to the tag ID designation mode, as shown in FIG. 11, in step S31, the read ID list is referred to, and one tag ID whose read flag is unread is selected, and this is designated as the designated tag ID. And

  In step S32, a read command including the designated tag ID determined in step S31 is transmitted. This read command includes information indicating that the number of slots included in the tag reading period is one.

  When the wireless tag 100 receives the read command, steps S1 and S2 in FIG. 4 are YES. The determination in step S3 is YES only for the wireless tag 100 with the tag ID included in the read command. Therefore, only the wireless tag 100 with the tag ID included in the read command transmits a response signal, and the tag reader 1 receives this response signal.

  In step S33, the response signal received from the wireless tag 100 is analyzed. In step S34, it is determined whether the reception is successful as a result of the analysis in step S33. If this judgment is NO, it will progress to Step S39, and if it is YES, it will progress to Step S35.

  In step S35, the tag ID successfully received is compared with the read ID list. If the tag ID that has been successfully received is in the read ID list, the read flag corresponding to the tag ID is updated to read in step S36.

  In step S37, it is determined whether reading has been completed. When all the read flags for all tag IDs included in the read ID list are already read, the reading is completed. If it is determined that the reading is completed (S37: YES), the process proceeds to step S38, and the end flag is turned on. Thereafter, the process proceeds to step S39.

  If it is determined that the reading has not been completed (S37: NO), the process proceeds to step S39 without executing step S38. In step S39, it is determined whether or not an end command has been issued. This determination is the same as step S25 of the first embodiment. When the trigger button is turned off or when the end flag is turned on, it is determined that there is an end command (S39: YES). If judgment of step S39 is YES, the process of FIG. 11 will be complete | finished.

  If it is determined that there is no termination command (S39: NO), the process proceeds to step S40. In step S40, it is determined whether or not to shift to the normal reading mode. As a first condition for shifting to the normal reading mode, there is a condition that the time during which the tag ID designation mode is executed exceeds the designated mode end time. Further, as a second condition for shifting to the normal reading mode, there is a condition that the number of times this tag ID designation mode is repeated exceeds the designated mode end count. If any of the conditions is satisfied, the determination in step S40 is YES, and the process proceeds to the normal reading mode shown in FIG. Accordingly, it is possible to avoid the inconvenience of continuing the tag ID designation mode even though the wireless tag 100 that has not been read in the reading ID list does not exist in the communication range. If the determination in step S40 is no, the process returns to step S31 and continues reading with the tag ID specified.

(Effect of 2nd Embodiment)
In the second embodiment, since the tag reader 1 stores the read ID list, the wireless tag 100 that transmits the response signal can be specified by including one tag ID in the read command and transmitting it. .

  However, the tag ID is not included in the read command from the beginning, but initially the normal read mode (FIG. 10) in which the read command not including the tag ID is transmitted is executed. In the normal reading mode, response signals can be received from the plurality of wireless tags 100 by transmitting a single reading command.

  And if the transfer conditions which transfer to tag ID designation | designated mode are satisfied (S26: YES), it will transfer to tag ID designation | designated mode which transmits the read command which included tag ID.

  The tag ID designation mode is a normal reading mode in which a plurality of wireless tags 100 transmit response signals in one reading command in that it is necessary to transmit reading commands by the number of wireless tags 100 that have not been successfully read. The reading efficiency is worse than that.

  However, in the normal reading mode, the wireless tag 100 that has already been successfully read transmits the response signal again, and the response signal may collide with the response signal transmitted by the wireless tag 100 that has not been successfully read. is there. On the other hand, in the tag ID designation mode, there is no possibility that a plurality of response signals will collide.

  Therefore, a decrease in reading efficiency due to a collision between a response signal from the wireless tag 100 that has not been successfully read and a response signal from the wireless tag 100 that has already been successfully read designates the wireless tag 100 one by one. In a situation where the reading efficiency is lower than the reduction in reading efficiency, the reading efficiency is improved in the tag ID designation mode.

  It cannot be directly determined that the response signal from the wireless tag 100 that has not been successfully read has collided with the response signal from the wireless tag 100 that has already been successfully read. This is because when a plurality of response signals collide, the response signals cannot be read. However, there is a correlation between the ratio of response signals that have already been successfully read out of response signals that have been successfully read and the ratio of response signals that have not yet been successfully received among response signals that have collided. When the ratio of response signals that have already been successfully read out of the response signals that have been successfully read is large, the response signal from the wireless tag 100 that has already been successfully read and the wireless tag 100 that has not yet been successfully read. This is because there will be many collisions with response signals from. Therefore, in the second embodiment, when the second transition condition is satisfied, the mode shifts to the tag ID designation mode.

  If the number of wireless tags 100 that have not been successfully read decreases, the number of wireless tags 100 that have been successfully read increases. Therefore, the response signal from the wireless tag 100 that has not been successfully read often collides with the response signal from the wireless tag 100 that has already been successfully read. Therefore, even when the first transition condition is satisfied, the mode shifts to the tag ID designation mode.

  In the second embodiment, a normal reading mode in which response signals from a plurality of wireless tags 100 can be read with a single read command is executed until the first transition condition or the second transition condition is satisfied. When the first transition condition or the second transition condition is satisfied, the mode shifts to the tag ID designation mode, so that a response signal can be received from the wireless tag 100 that needs to be read in a short time.

<Third Embodiment>
Also in the third embodiment, the tag reader 1 stores a reading ID list. Then, the tag reader 1 of the third embodiment executes a partial ID designation mode shown in FIG. 12 instead of the normal reading mode shown in FIG. This partial ID designation mode is a combination of the process shown in FIG. 5 and the process shown in FIG.

  Specifically, in the partial ID designation mode, as shown in FIG. 12, step S14 in FIG. 5 is replaced with step S14-1 in FIG. 10, and the same processing as step S26 in FIG. 10 is performed before step S23. Step S22-1 is executed.

  Therefore, when the number of wireless tags 100 that have not been successfully received is equal to or less than the first transition threshold value, the first transition condition is satisfied, and the process proceeds to the tag ID designation mode. Further, in the current round, when the ratio of response signals that have been successfully received for the second time or more among the response signals that have been successfully received is equal to or greater than the second transition threshold, the second transition condition is satisfied, and the tag Transition to ID designation mode.

  If the tag ID designation mode is not entered and if the determination in step S25 is NO, step S12 and subsequent steps are executed again. At this time, since the re-response suppression time has elapsed, the wireless tag 100 that has already been successfully read is again a response signal if its own tag ID includes the partial ID included in the read command. Send.

  Therefore, a response signal that has already been successfully read may collide with a response signal that has not yet been successfully read, and a response signal that has not yet been successfully read may not be read. When the number of wireless tags that have not been successfully read is small, there is a high possibility that an unread response signal cannot be read due to a collision between the read response signal and the unread response signal.

  In addition, when the number of wireless tags that have not been successfully read is small, the ratio of response signals that have been successfully received for the second time or more among the response signals that have been successfully received in one round is high. On the other hand, in the tag ID designation mode, there is no collision of response signals.

  Therefore, also in the third embodiment, when either the first transition condition or the second transition condition is satisfied, the mode shifts to the tag ID designation mode. Accordingly, information can be read from the wireless tag that needs to be read in a shorter time.

  Further, the partial ID designation mode has higher reading efficiency than the normal reading mode, as described with reference to FIGS. 7 and 8 in the first embodiment. Therefore, in the third embodiment, the reading efficiency is further improved as compared with the second embodiment.

<Fourth embodiment>
In the fourth embodiment, the wireless tag 100 includes an area ID representing an area where each wireless tag 100 is located as a part of the tag ID. For example, assume that the entire area is divided into three areas A to C as shown in FIG. In this case, the wireless tag 100 located in the A area includes an area ID (for example, A) indicating the A area as a part of the tag ID. Similarly, the wireless tag 100 located in the B area includes an area ID representing the B area as a part of the tag ID, and the wireless tag 100 located in the C area represents the C area as a part of the tag ID. An area ID is provided. The area ID is described at a predetermined position of the tag ID, such as the head of a UID (Unique Item Identifier) of the tag ID.

  In the fourth embodiment, the tag reader 1A only needs to read the response signal only from the wireless tag 100 in the area where the tag reader 1A is located. As a situation where it is only necessary to read a response signal from the wireless tag 100 in a certain area, for example, there is a situation in which it is desired to grasp a product in a certain area in inventory management.

  As shown in FIG. 14, the tag reader 1 </ b> A of the fourth embodiment includes a position detection unit 60, and the position detection unit 60 detects the current position of the tag reader 1 </ b> A. The position detection unit 60 is, for example, a GPS receiver.

  A predetermined storage unit such as a memory provided in the control unit 20 stores a relationship for determining an area and an area ID from the coordinates. The storage unit also stores a read ID list. This read ID list includes a read flag corresponding to each tag ID as in the second embodiment.

  When the trigger button is pressed, the control unit 20 of the tag reader 1A executes the process shown in FIG. In step S51, the current position is detected using the position detection unit 60. This current position is expressed in coordinates. In step S52, the area and area ID are determined from the coordinates representing the current position detected in step S51 and the correspondence relationship for determining the area and area ID from the coordinates.

  In step S53, the coordinates representing the current position detected in step S51 and the area determined in step S52 are displayed on the display unit 1d of the tag reader 1A.

  In step S54, a read command including the area ID determined in step S52 is transmitted. For example, as shown in FIG. 13, when the tag reader 1A is located in the A area, a reading command including the area ID of the A area is transmitted. The area ID included in the read command corresponds to the partial ID. This read command also includes information indicating the number of slots provided in the tag reading period.

  FIG. 13 also illustrates the communication range 1r of the tag reader 1A. Like the communication range 1r illustrated in FIG. 13, the communication range 1r may exceed the area where the tag reader 1A is located. Therefore, the read command is also received by the wireless tag 100 located in the B area or the C area.

  Also in the fourth embodiment, the control unit 128 of the wireless tag 100 executes the processing shown in FIG. When the area ID of the A area is included in the read command, the wireless tag 100 located in the B area or the C area does not transmit a response signal because the determination in step S3 is NO, and the wireless tag 100 is in the A area. Only the wireless tag 100 that is located transmits a response signal.

  In step S55, the response signal received from the wireless tag 100 is analyzed. In step S56, it is determined whether the reception is successful as a result of the analysis in step S55. If this judgment is NO, it will progress to Step S60, and if it is YES, it will progress to Step S57. In step S57, the read flag in the read ID list is updated based on the response signal that has been successfully received.

  In step S58, it is determined by referring to the reading ID list whether reading has been completed. If it is determined that the reading is completed (S58: YES), the process proceeds to step S59, and the end flag is turned on. Thereafter, the process proceeds to step S60.

  If it is determined that the reading has not been completed (S58: NO), the process proceeds to step S60 without executing step S59. In step S60, it is determined whether an end command has been issued. When the trigger button is turned off or when the end flag is on, it is determined that there is an end command (S60: YES). If the determination in step S60 is YES, the process of FIG. 15 is terminated, and if NO, the process returns to step S54.

(Effect of 4th Embodiment)
In the fourth embodiment, the tag ID includes an area ID indicating the area where the wireless tag 100 is located. Then, the tag reader 1A transmits a read command including the area ID (S54). Accordingly, only the wireless tag having the tag ID having the area ID included in the read command transmits a response signal and receives the read command, but does not have the area ID included in the read command. The wireless tag 100 with the tag ID does not transmit a response signal. Therefore, a response signal can be received in a short time from the wireless tag 100 existing in an area that needs to be read.

  In the fourth embodiment, the position of the tag reader 1 is automatically detected (S51), and the area ID is automatically determined based on the current position (S52). This saves the user from having to input the area to be read.

  Further, the area corresponding to the area ID and the coordinates representing the current position are displayed on the display unit 1d (S53). Thereby, whether the area designated by the reading command transmitted by the tag reader 1 is an area intended by the user by the user viewing the area or the current position displayed on the display unit 1d. Can be confirmed.

<Fifth Embodiment>
In the fifth embodiment, the control unit 20 of the tag reader 1 executes the process of FIG. 16 instead of the process of FIG. The process of FIG. 16 is different from the process of FIG. 5 only in that the number of slots for each round is not changed. Note that the number of slots is two or more and is set in advance.

  Since the number of slots for each round is not changed, the processing in FIG. 16 is the same as the processing in FIG. 5 in steps S1 to S18 and S22. Instead of steps S19 to S21 in FIG. S21-1 is executed. Further, step S23 is not provided.

  While steps S19 to S21 in FIG. 5 decrease, maintain, and increase the number of slots, steps S19-1 to S21-1 decrease, maintain, and increase the number of divisions. Specifically, in step S19-1, the number of bit digits of the partial ID is reduced by one digit, in step S20-1, the number of bit digits of the partial ID is maintained, and in step S21-1, the number of bit digits of the partial ID is reduced by one digit. increase.

  When the number of divisions is reduced, that is, the number of digits of the partial ID is reduced, the number of wireless tags 100 having the partial ID is increased. Accordingly, since the reception success rate can be lowered as in the case of reducing the number of slots, instead of reducing the number of slots, in the fifth embodiment, the number of divisions is reduced in step S19-1.

  Further, when the number of divisions is increased, that is, the number of digits of the partial ID is increased, the number of the wireless tags 100 having the partial ID is decreased. Therefore, as in the case of increasing the number of slots, the reception success rate can be increased. Therefore, instead of increasing the number of slots, in the fifth embodiment, the number of divisions is increased in step S21-1.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, The following modification is also contained in the technical scope of this invention, Furthermore, the summary other than the following is also included. Various modifications can be made without departing from the scope.

<Modification 1>
For example, in the above-described embodiment, the lowermost bit of the tag ID and the area ID are shown as the partial ID, but the partial ID may be other than these. For example, an ID indicating the type of product may be used as the partial ID. Also, a plurality of types of partial IDs may be combined, for example, both the area ID and the lowermost bit of the tag ID are used as the partial ID.

<Modification 2>
The area ID stored in the wireless tag 100 may be a plurality of digits, and the number of divisions based on the area ID may be variable as in the first, third, and fifth embodiments. When an example in which the area ID is a plurality of digits is shown based on the fourth embodiment, the A area may be divided into, for example, four areas A00, A01, A10, and A11, respectively. In this way, the A area can be divided into two by including either A0 or A1 as the partial ID in the read command. Also, by including any of A00, A01, A10, and A11 as the partial ID in the read command, the A area can be divided into four.

<Modification 3>
Regardless of the processing result of step S23, in step S24, the next partial ID used when it is determined to maintain the division number in step S23 is used as a reference, and the bit number of the reference partial ID is increased, maintained, or decreased. The determined partial ID may be determined as the next partial ID.

<Modification 4>
In 4th Embodiment, although the GPS receiver was illustrated as the position detection part 60, the position detection part 60 is not restricted to a GPS receiver. The position of the tag reader 1 may be detected using a beacon from a wireless LAN access point or a Bluetooth beacon. Bluetooth is a registered trademark.

<Modification 5>
In step S23, instead of the number of reception failures, the number of slots may be used to determine increase or decrease in the number of divisions. Since the number of slots is changed according to the reception success rate, the number of slots changes according to the number of reception failures. Therefore, the increase or decrease in the number of divisions can be determined using the number of slots instead of the number of reception failures. In this case, the number of slots corresponds to the reception failure related value in the claims.

<Modification 6>
In the above-described embodiment, when it is determined that the re-response suppression time has elapsed (S22: YES), the division number is updated (S23). However, even before it is determined that the re-response suppression time has elapsed, the number of divisions may be updated if the condition for increasing or decreasing the number of divisions in step S23 is satisfied.

1: tag reader, 1A: tag reader, 1d: display unit, 1r: communication range, 10: antenna, 20: control unit, 30: communication unit, 40: transmission unit, 41: encoding unit, 42: modulation unit, 43: amplification Unit: 50: reception unit 51: demodulation unit 52: decoding unit 60: position detection unit 100: wireless tag 110: antenna 120: IC chip 122: rectification unit 124: demodulation unit 126: memory 128: Control unit 130: Modulation unit

Claims (11)

A tag reader (1, 1A) that transmits a read command including a partial ID that is a part of a tag ID included in a wireless tag to respond, and receives a response signal from the wireless tag;
The wireless tag (100) that receives the read command and transmits the response signal based on the fact that its own tag ID includes the partial ID included in the read command is provided. A wireless tag communication system. In claim 1,
The read command includes information indicating the number of slots included in the tag reading period,
When transmitting the response signal, the wireless tag transmits the response signal in a slot randomly selected from the slots provided in the tag reading period,
And, if the predetermined re-response suppression time has not elapsed since the tag reader succeeded in receiving the response signal, the response signal is not transmitted even if the read command is received. ,
The tag reader changes the partial ID to a different value when or before determining that the time during which the read command including the same partial ID is repeatedly transmitted exceeds the re-response suppression time. And transmitting the read command. In claim 2,
The partial ID designates one of a plurality of tag IDs included in the wireless tag to be read,
The tag reader has a reception failure related value that is a value that changes according to the number of reception failures or the number of reception failures within a time during which the read command including the same partial ID is repeatedly transmitted, and the division number increase threshold is set. The wireless tag communication system according to claim 1, wherein the partial ID is changed to a value that divides all the tag IDs of the wireless tag to be read into a larger number of divisions than before, based on the fact that the number is exceeded. In claim 2 or 3,
The partial ID designates one of a plurality of tag IDs included in the wireless tag to be read,
While the tag reader repeatedly transmits the read command including the same partial ID, the tag reader reads the partial ID based on transmitting the read command but not receiving the response signal. A wireless tag communication system, wherein all tag IDs included in a target wireless tag are changed to values that are divided into a smaller number of sections than before. In claim 3 or 4,
The tag reader, when the reception success rate in the tag reading period is higher than a reference success rate range in which reading efficiency is good when the tag reading period ends, the slot in the next tag reading period. If the reception success rate in the tag reading period is lower than the reference success rate range, the number of slots in the next tag reading period is increased more than before. A wireless tag communication system. In any one of Claims 2-5,
The tag reader is
Storing a read ID list that is a list of tag IDs of the wireless tags that need to be read;
Sending a reading command including the partial ID and receiving the response signal from the wireless tag during the tag reading period is still being successfully received while executing the partial ID designation mode. From the read ID list, based on the number of the wireless tags that are not present or the transition condition set based on the ratio of response signals that have been successfully received for the second time or more among the response signals that have been successfully received. The RFID tag communication system, wherein the selected tag ID is included in the read command, and the mode is shifted to a tag ID designation mode in which the read command is transmitted. A tag reader (1) for transmitting a read command including information indicating the number of slots included in the tag reading period for a plurality of wireless tags;
A wireless tag communication system comprising a wireless tag (100) that transmits a response signal based on receiving the read command,
When transmitting the response signal, the wireless tag transmits the response signal in a slot randomly selected from the slots provided in the tag reading period,
And after the tag reader succeeds in receiving the response signal, the response signal is transmitted again based on the reception of the read command after a predetermined reresponse suppression time has elapsed. ,
The tag reader is
Storing a read ID list that is a list of tag IDs of the wireless tags that need to be read;
Sending a reading command for the plurality of wireless tags, and receiving the response signal from the wireless tag during the tag reading period, while still executing the multiple tag reading mode, the reception is still successful. Based on the fact that a transition condition set based on at least one of the number of the wireless tags that have not been received and the ratio of response signals that have been successfully received for the second time or more among the response signals that have been successfully received is satisfied, One tag ID selected from the read ID list is included in the read command, and the mode is shifted to a tag ID designation mode in which the read command is transmitted. In any one of Claims 1-6,
The tag ID includes an area ID indicating an area where the wireless tag is located,
The RFID tag communication system according to claim 1, wherein the tag reader transmits the reading command including the area ID as the partial ID. In claim 8,
The tag reader (1A)
A position detector (60) for detecting its own position;
The RFID tag communication system, wherein the read command including an area ID indicating an area determined based on a position detected by the position detection unit is transmitted. In claim 9,
A wireless tag communication system comprising a display unit (1d) for displaying at least one of a position detected by the position detection unit and an area determined based on the position.   A tag reader (1, 1A) that transmits a read command including a partial ID that is a part of a tag ID included in a wireless tag to respond and receives a response signal from the wireless tag.

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