JP6424520B2 - Wireless tag communication device - Google Patents

Description

  The technology disclosed herein relates to a wireless tag communication device that transmits a carrier signal to communicate with a wireless tag.

  Patent Document 1 discloses a reader / writer device that communicates with an RFID (Radio Frequency IDentification) tag. Before the reader / writer device transmits the carrier signal to the RFID tag, whether or not the scheduled channel (frequency) to be used for transmitting the carrier signal can be used (ie, by the other reader / writer device) Perform carrier sense processing to determine whether or not it is being used. Thereafter, a carrier signal is transmitted to the RFID tag using a channel determined to be usable by the carrier sense process.

JP, 2013-219458, A

  In the technique of Patent Document 1, the reader / writer apparatus transmits a first carrier signal to execute a first process, and then transmits a second carrier signal to perform a second process. Carrier sense processing is performed before execution of the first processing and before execution of the second processing. There is a need for a technique that can reduce the time required to continuously execute the first process and the second process.

  The present specification provides a technique that can reduce the time required to continuously execute the first process and the second process, as compared to the prior art.

  The wireless tag communication device disclosed in the present specification is a wireless tag communication device that transmits a carrier signal to communicate with the wireless tag. The wireless tag communication device transmits the first carrier signal to execute the first process for communicating with the wireless tag, and (a) the first carrier is transmitted during a first predetermined period. Execute carrier sense processing to confirm that a specific channel to be used for signal transmission is not used by another wireless tag communication device, and (b) in the carrier sensing process, the specific channel is determined by the other wireless tag communication device The first carrier signal is transmitted using the specific channel when it is confirmed that it is not in use. The wireless tag communication device transmits a second carrier signal to communicate with the wireless tag continuously in a preset second period after the end of the transmission of the first carrier signal in (b). When processing 2 is to be performed, (A) the second carrier signal is transmitted using the specific channel used for transmitting the first carrier signal without performing the carrier sense processing. .

  The above wireless tag communication device does not perform the carrier sense processing when the second processing is continuously performed in the second period after the end of the first processing, the identification used in the first processing The second carrier signal is transmitted using the channel. Therefore, when the second process is continuously performed after the end of the first process, compared to the conventional technique in which the carrier sense process is performed before the execution of the first process and before the execution of the second process. , The number of times of carrier sense processing can be reduced. Therefore, according to the above-described wireless tag communication device, the time required to continuously execute the first process and the second process can be shortened, as compared with the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the structure of a communication system typically. The flowchart which shows the reading processing which the control section of the radio tag communication device executes. The flowchart which shows the write-in processing which the control part of a wireless tag communication apparatus performs. The time chart which compares and shows the writing processing by the RFID tag communication device of a comparative example, and the writing processing by the RFID tag communication device of this embodiment.

  The main features of the embodiment described below are listed. The technical elements shown below are technical elements that are independent of one another and exhibit technical usefulness by themselves or various combinations, and are not limited to the combinations described in the claims at the time of filing. .

(Feature 1) The second period may be shorter than the first period.

  As described above, the carrier sense process confirms whether or not a channel scheduled to be used for transmitting a carrier signal is not being used by another wireless tag communication device during a preset first period. Processing. Usually, the minimum value of the length of the first period is determined by the law. Therefore, according to the above configuration, since the second period is shorter than the first period, the second carrier signal is continuously transmitted in the second period after the end of transmission of the first carrier signal. Between the end of transmission of the first carrier signal and the start of transmission of the second carrier signal, the other RFID tag communication device starts using the specific channel used for transmission of the first carrier signal It can suppress that a situation occurs.

(Feature 2) The first process may be a process for acquiring identification information from a wireless tag. The second process may be one of a process of reading information stored in the wireless tag and a process of writing information in the wireless tag.

(System configuration; Fig. 1)
A communication system 2 illustrated in FIG. 1 includes a wireless tag communication device 10, a plurality of wireless tags 50a and 50b, and the like. Although only the wireless tags 50 a and 50 b are illustrated in FIG. 1, in reality, many other wireless tags exist around the wireless tag communication device 10. Hereinafter, in the present specification, the wireless tags represented by the wireless tags 50a and 50b may be collectively referred to as the wireless tag 50.

(Wireless tag communication device 10)
The wireless tag communication device 10 is a communication device for communicating with a plurality of wireless tags 50a and 50b present in the vicinity. The wireless tag communication device 10 can read data stored in the wireless tag 50 and write (or store) data in the wireless tag 50 by communicating with the wireless tag 50. The wireless tag communication device 10 includes an operation unit 12, a display unit 14, a control unit 16, a memory 18, a transmission circuit 20, a reception circuit 22, and an antenna 24.

  The operation unit 12 includes a plurality of keys. The user can input various instructions to the wireless tag communication device 10 by operating the operation unit 12. The display unit 14 is a display for displaying various information.

  The control unit 16 executes various processes in accordance with the program in the memory 18. The memory 18 stores various information.

  The transmission circuit 20 is a circuit for transmitting a carrier signal via the antenna 24. The carrier signal transmitted from the transmission circuit 20 includes various requests (for example, an inventory request, a read request, a write request, etc. described later) and various information (identification information of the wireless tag 50 described later, written content information, Etc. are included. Although not shown, the transmission circuit 20 includes an encoding unit, a modulation unit, an oscillator, an amplifier, and the like. In the present embodiment, the transmission circuit 20 uses one channel specified by the control unit 16 from among a plurality of channels (frequencies) allocated as channels available for transmission of a carrier signal. Send. A method for the control unit 16 to specify a channel will be described later.

  The receiving circuit 22 is a circuit for receiving a carrier signal from each wireless tag 50 via the antenna 24. The carrier signal received by the receiving circuit 22 includes various information (for example, identification information described later, target information, and the like) that each wireless tag 50 transmits in response to a request. Although not shown, the receiving circuit 22 includes an amplifier, a demodulation unit, a binarization processing unit, a decoding unit, and the like.

  The antenna 24 radiates the carrier signal output from the transmission circuit 20 to space, and catches the carrier signal output from each wireless tag 50.

(Wireless tag 50)
The wireless tag 50 is a known RFID tag. Although not illustrated, the wireless tag 50 includes an antenna, a control circuit, a memory, and the like. In the memory of the wireless tag 50, identification information unique to the wireless tag 50 is stored. For example, the identification information of the wireless tag 50a of FIG. 1 is "TA". Similarly, the identification information of the wireless tag 50b is "TB". Furthermore, in the memory of the wireless tag 50, target information to be read by the wireless tag communication device 10 is stored. The target information includes, for example, arbitrary information such as price and quantity.

(Reading process; Fig. 2)
Next, the contents of the reading process performed by the control unit 16 of the wireless tag communication device 10 according to the present embodiment will be described with reference to FIG. When the user of the wireless tag communication device 10 inputs a predetermined reading instruction on the operation unit 12, the control unit 16 starts the reading process of FIG.

  In S10, the control unit 16 randomly specifies one channel from among a plurality of channels (for example, 10 frequencies) allocated as channels (frequencies) available for transmitting a carrier signal.

  Next, in step S12, the control unit 16 determines whether the channel specified in step S10 is in use by another wireless tag communication device (hereinafter sometimes referred to as "other device"). Specifically, the control unit 16 receives the carrier signal of the channel specified in S10 (that is, the carrier signal transmitted by the other device) during the first period (for example, 5 ms). Monitor whether or not The minimum value of the length of the first period is predetermined by the law (for example, 5 ms). If the carrier signal of the channel specified in S10 is not received within the first period, the control unit 16 determines NO in S12, and proceeds to S14. That is, in the case of NO at S12, it is determined that the channel specified at S10 is not being used by another device. On the other hand, when the carrier signal of the channel specified in S10 is received within the first period, the control unit 16 determines YES in S12, and proceeds to S13. That is, in the case of YES in S12, it is determined that the channel specified in S10 is being used by another device. When the channel specified in S10 is used by another device, the wireless tag communication device 10 which is the own device can not transmit a carrier signal using that channel. This is because when two or more wireless tag communication devices transmit carrier signals simultaneously using the duplicated channel, normal communication with the wireless tag 50 can not be performed.

  In S13, the control unit 16 determines whether the processes of S10 and S12 have been performed for all of the plurality of channels assigned as channels available for transmission of the carrier signal. When the processes of S10 and S12 have not been executed for all the channels, the control unit 16 determines NO in S13, and returns to S10. At S10 after the return, the control unit 16 newly identifies one channel among the unspecified channels, and makes the determination at S12 again.

  At S14, the control unit 16 causes the memory 18 to store channel information indicating the channel identified at S10. Below, each processing of S10 to S14 may be collectively called "carrier sense processing".

  In S16, the control unit 16 starts transmission of a carrier signal via the transmission circuit 20 and the antenna 24 using the channel indicated by the channel information stored in S14. The carrier signal transmitted in S16 includes an inventory request for requesting the wireless tag 50 to transmit identification information. When each wireless tag 50 receives a carrier signal including an inventory request, it generates and transmits a carrier signal including its identification information (TA, TB, etc. in FIG. 1). The control unit 16 receives a carrier signal transmitted from the wireless tag 50 and including identification information of the wireless tag 50 via the antenna 24 and the receiving circuit 22.

  Next, in S18, when the control unit 16 receives a carrier signal including identification information from the wireless tag 50, the control unit 16 acquires identification information included in the carrier signal.

  Next, in S20, when the predetermined carrier signal transmission period (for example, 100 ms) ends, the control unit 16 ends the transmission of the carrier signal started in S16. Hereinafter, the processes of S16 to S20 may be collectively referred to as “inventory process”. When the inventory process is completed, the control unit 16 can grasp what kind of identification information the wireless tag 50 has in the communication range of the wireless tag communication device 10.

  Next, at S22, the control unit 16 restarts transmission of the carrier signal using the channel indicated by the channel information stored at S14. The carrier signal transmitted in S22 includes the identification information of one of the one or more pieces of identification information acquired in S18, and the wireless tag 50 to which the identification information is assigned (in the following, the specific wireless tag 50). , And a read request for requesting transmission of target information stored in the memory. In the present embodiment, after the transmission of the carrier signal is completed in S20 (that is, after the inventory process is completed), the control unit 16 performs a second period (for example, 2 ms) shorter than the first period described above. The transmission of the carrier signal of S22 is started using the channel indicated by the channel information stored in S14. When the specific wireless tag 50 receives the carrier signal transmitted in S22, it generates and transmits a carrier signal including target information stored in the memory. The control unit 16 receives a carrier signal transmitted from the specific wireless tag 50 and including target information via the antenna 24 and the receiving circuit 22. Even if the wireless tag 50 other than the specific wireless tag 50 (hereinafter referred to as a normal wireless tag 50) receives the carrier signal, the received carrier signal includes the identification information attached to the normal wireless tag 50. It is not done. Therefore, the wireless tag 50 normally does not generate and transmit a carrier signal including target information.

  Next, in S24, when the control unit 16 receives the carrier signal including the target information from the specific wireless tag 50, the control unit 16 acquires the target information included in the carrier signal.

  When the target information is to be acquired from the plurality of specific wireless tags 50, the control unit 16 acquires the identification information to be included in the carrier signal for each predetermined period after the start of transmission of the carrier signal in S22 in S18. By replacing with one of the one or more pieces of identification information, the target information can be sequentially obtained from each of the plurality of specific wireless tags 50.

  Next, when the predetermined carrier signal transmission period (for example, 100 ms) ends in S26, the control unit 16 ends the transmission of the carrier signal started in S22. Hereinafter, the processes of S22 to S26 may be collectively referred to as a "read process". When the reading is completed in S26, the control unit 16 ends the reading process of FIG.

(Writing process; Fig. 3)
Next, with reference to FIG. 3, the contents of the writing process performed by the control unit 16 of the wireless tag communication device 10 of the present embodiment will be described. When the user of the wireless tag communication device 10 specifies the write content information to be written to the wireless tag 50 in the operation unit 12 and inputs a predetermined write instruction, the control unit 16 starts the write process of FIG. 3. At this time, if the user desires to write different pieces of written content information to each of the plurality of wireless tags 50, the wireless tag 50 writes the written content information out of the plurality of wireless tags 50 for each of the written content information. Specify identification information of

  The control unit 16 first executes the carrier sense process and the inventory process of S10 to S20. The contents of the carrier sense process and the inventory process of S10 to S20 are the same as the carrier sense process and the inventory process of FIG. When the transmission of the carrier signal is completed at S20, the control unit 16 proceeds to S40.

  At S40, the control unit 16 restarts transmission of the carrier signal using the channel indicated by the channel information stored at S14. The carrier signal transmitted in S40 is assigned the write content information input when the write instruction is input, one identification information of the one or more identification information acquired in S18, and the identification information And a write request for the specific wireless tag 50. The write request is a command for requesting the wireless tag 50 to write the write content information in the memory. Even in the process of FIG. 3, the control unit 16 uses the channel indicated by the channel information stored in S14 in the second period after the transmission of the carrier signal is completed in S20 (ie, after the inventory process is completed). Then, the transmission of the carrier signal of S40 is started. When the specific wireless tag 50 receives the carrier signal transmitted in S40, the specific wireless tag 50 stores (that is, writes) the write content information in the memory. Note that even if the normal wireless tag 50 other than the specific wireless tag 50 receives the carrier signal, the carrier signal does not include the identification information attached to the normal wireless tag 50, so the normal wireless tag 50 does not , Write content information is not stored in the memory.

  When the write content information is to be written to the plurality of specific wireless tags 50, the control unit 16 acquires the identification information to be included in the carrier signal in each predetermined period after the start of transmission of the carrier signal in S40 in S18. By replacing the written content information included in the carrier signal with the written content information corresponding to the one other identification information while replacing with the other one of the one or more identification information, a plurality of specific wireless tags 50 The write content information corresponding to each can be written.

  Next, in S42, when the predetermined carrier signal transmission period (for example, 200 ms) ends, the control unit 16 ends the transmission of the carrier signal started in S40. Hereinafter, the processes of S40 and S42 may be collectively referred to as a "write process". When the write process ends in S42, the control unit 16 proceeds to S44.

  In S44 to S48, the control unit 16 performs the read process as in S22 to S26 in FIG. However, in S44, the control unit 16 uses the channel indicated by the channel information stored in S14 in the second period after the transmission of the carrier signal is completed in S42 (that is, after the write process is completed). Then, transmission of the carrier signal of S44 (ie, read processing) is started. In the process of FIG. 3, the control unit 16 proceeds to S50 when S48 ends.

  In S50, the control unit 16 determines whether the writing of the writing content information to the specific wireless tag 50 is normally completed. Specifically, in S50, the control unit 16 checks whether the target information acquired from the specific wireless tag 50 in S46 matches the written content information to be written to the specific wireless tag 50. . If the target information acquired from all the specific wireless tags 50 matches the write content information input to the wireless tag communication device 10, the control unit 16 determines YES in S50, and the write process of FIG. 3 is performed. finish. That is, in the case of YES in S50, the write content information is normally stored in the memory in all the specific wireless tags 50. On the other hand, when the target information acquired from at least one specific wireless tag 50 does not match the input write content information, the control unit 16 determines NO in S50, and the write processing in FIG. 3 ends in error. Do.

(Comparison between the comparative example and the present embodiment; FIG. 4)
Here, in order to sufficiently explain the function and effect of the wireless tag communication device 10 of the present embodiment, a conventional wireless tag communication device (hereinafter sometimes referred to as a conventional device) performs write processing as a comparative example. The operation of the case will be described.

  As shown in the upper part of FIG. 4, the conventional apparatus first transmits a carrier signal using a channel determined to be usable by carrier sense processing to perform inventory processing. When the transmission of the carrier signal is finished (that is, the inventory process is finished), the conventional device waits without starting the transmission of the next carrier signal for a predetermined waiting period (50 ms). The conventional device executes carrier sense processing again after the elapse of the standby period, and transmits a carrier signal using a channel determined to be usable by the carrier sense processing to perform write processing. When the transmission of the carrier signal is finished (that is, the writing process is finished), the conventional device stands by without starting transmission of the next carrier signal for a predetermined waiting period (50 ms). The conventional apparatus executes carrier sense processing again after the elapse of the waiting period, and transmits a carrier signal using a channel determined to be usable by the carrier sense processing to perform read processing. When the transmission of the carrier signal is completed (that is, when the reading process is completed), the conventional apparatus confirms that the writing of the write information to the wireless tag is normally performed, and ends the writing process.

  As described above, the conventional apparatus has a standby period after the end of the inventory process and the write process. In addition, the conventional apparatus performs carrier sense processing before each processing of the inventory processing, the write processing, and the read processing. Therefore, according to the conventional device, the carrier sense process, the inventory process, the standby, the second carrier sense process, the write process, the second standby, and the third carrier sense are performed between the start and the completion of the write process. It takes time to sequentially perform each processing of the processing, the read processing, and the confirmation that the writing has been normally performed.

  Also, although not shown in FIG. 4, when the conventional device executes the reading process, as in the case of the writing process described above, the carrier sense process is performed between the start and the completion of the reading process. It takes time for the inventory process, the standby process, the second carrier sense process, and the read process to be sequentially performed.

  On the other hand, as shown in the lower part of FIG. 4, the wireless tag communication device 10 of this embodiment first transmits a carrier signal using a channel determined to be usable by carrier sense processing to perform inventory processing. (See S10 to S20 in FIG. 3). When the wireless tag communication device 10 ends transmission of the carrier signal (ie, ends the inventory processing), the wireless tag communication device 10 does not wait for a predetermined waiting period (50 ms) and does not re-execute the carrier sense processing. The carrier signal is transmitted using the channel used in the inventory process to perform the write process (see S40 and S42 in FIG. 3). At this time, after the wireless tag communication device 10 ends transmission of the carrier signal for the inventory process, a second period (for example, 2 ms) shorter than the above-described first period (that is, a period necessary for the carrier sense process). Start transmitting carrier signals for write processing. When the wireless tag communication device 10 ends transmission of the carrier signal (ie, ends the write process), the wireless tag communication device 10 continues without waiting for a predetermined waiting period and without re-executing the carrier sense process. The carrier signal is transmitted using the channel used in the inventory process and the write process to perform the read process (see S44 to S48 in FIG. 3). In this case as well, after the wireless tag communication device 10 finishes transmitting the carrier signal for the write process, it starts transmitting the carrier signal for the read process within the second period. When the wireless tag communication device 10 ends the read process, it confirms that the writing of the write information to the wireless tag 50 is normally performed (YES in S50 of FIG. 3), and ends the write process (FIG. 3). .

  As described above, after the end of the inventory processing, the wireless tag communication device 10 of this embodiment is used in the inventory processing without waiting for a predetermined waiting period and without re-executing the carrier sense processing. The carrier signal is transmitted using the above channel to perform write processing. Similarly, after the end of the write process, the wireless tag communication device 10 uses the channel used in the inventory process without providing a waiting period and without re-executing the carrier sense process, and uses the carrier signal. Send and perform write processing. Therefore, according to the wireless tag communication device 10 of this embodiment, the carrier sense process, the inventory process, the write process, the read process, and the writing are normally performed between the start and the completion of the write process. It takes time to perform each process in order to confirm that.

  Further, although not shown in FIG. 4, when the RFID tag communication device 10 of this embodiment executes the reading process, as in the case of the writing process described above, the process from when the reading process is started until when the process is completed. In the meantime, it takes time for the carrier sense process, the inventory process, and the read process to be performed sequentially (see FIG. 2).

  As shown in FIG. 4, according to the RFID tag communication device 10 of the present embodiment, the second and subsequent carrier sense processes can be omitted, so this is compared with the case where the conventional device executes the write process (or read process). Thus, the number of carrier sense processes can be reduced. Moreover, according to the wireless tag communication device 10, the standby period is not provided. Therefore, according to the wireless tag communication device 10, the time required to execute the writing process (or the reading process) can be shortened compared to the case of the conventional device (see FIG. 4).

  Also, in the writing process (FIG. 3), after the end of transmission of the carrier signal for the inventory process, the wireless tag communication device 10 performs a second period which is shorter than the first period (ie, the period required for the carrier sensing process). Then, transmission of a carrier signal for write processing is started (see S40 in FIG. 3). The minimum value of the length of the first period required for the wireless tag communication device to perform the carrier sense process is determined by the law. Therefore, according to the wireless tag communication device 10 of the present embodiment, since the second period is shorter than the first period, the transmission of the carrier signal for the write process is started after the transmission of the carrier signal for the inventory process is completed. Until then, it is possible to suppress the occurrence of a situation where the use of the channel used for the inventory process is started by another device. Similarly, after completing the transmission of the carrier signal for the write process, the wireless tag communication device 10 of this embodiment starts the transmission of the carrier signal for the read process within the second period (FIG. 3). See S44). Also, when the RFID tag communication device 10 performs the reading process (FIG. 2), after the transmission of the carrier signal for the inventory process is completed, the transmission of the carrier signal for the reading process is performed within the second period (See S22 of FIG. 2). Also in these cases, the wireless tag communication device 10 can suppress the occurrence of a situation where the channel used for the above processing (write processing, inventory processing) is used by another device.

(Correspondence relationship)
The inventory process and the read process or the write process performed after the inventory process are examples of the “first process” and the “second process”, respectively. The channel stored at S14 of FIGS. 2 and 3 is an example of the “specific channel”.

  As mentioned above, although the specific example of this invention was described in detail, these are only an illustration and do not limit a claim. The art set forth in the claims includes various variations and modifications of the specific examples described above.

  The technical elements described in the present specification or the drawings exhibit technical usefulness singly or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the techniques illustrated in the present specification or the drawings simultaneously achieve a plurality of purposes, and achieving one of the purposes itself has technical utility.

2: communication system 10: wireless tag communication device 12: operation unit 14: display unit 16: control unit 18: memory 20: transmission circuit 22: reception circuit 24: antenna 50a, 50b: wireless tag

Claims (2)

A wireless tag communication device that transmits a carrier signal to communicate with a wireless tag,
A first process of transmitting a first carrier signal to communicate with the wireless tag, and performing the first process for acquiring identification information from the wireless tag ,
(A) Perform carrier sense processing to confirm that a specific channel scheduled to be used for transmission of the first carrier signal is not used by another RFID tag communication device during a preset first period ,
(B) transmitting a first carrier signal using the specific channel when it is confirmed in the carrier sense processing that the specific channel is not being used by another wireless tag communication device;
A second process of transmitting a second carrier signal and communicating with the wireless tag continuously in a preset second period after the end of the transmission of the first carrier signal of (b), When the second process , which is one of the process of reading information stored in the wireless tag and the process of writing information in the wireless tag, is to be performed,
(A) without performing the carrier sense process
(B) transmitting a second carrier signal using the particular channel used to transmit the first carrier signal ;
(C) In the case where the second process is a process of reading information stored in the wireless tag, if information should be read from a plurality of wireless tags, after the start of transmission of the second carrier signal, every predetermined period , By changing the identification information included in the second carrier signal, the information stored in the wireless tag is read from each of the plurality of wireless tags,
(D) In the case where the second process is a process of writing information in the wireless tag, if the information should be written in the plurality of wireless tags, the second process is performed every predetermined period after the start of transmission of the second carrier signal. By replacing the identification information included in the second carrier signal and replacing the information to be written with the content corresponding to the identification information, the information corresponding to the wireless tag is written in each of the plurality of wireless tags.
Wireless tag communication device.   The wireless tag communication device according to claim 1, wherein the second period is shorter than the first period.

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