JP2006148258A - Rfid system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance accuracy of data communication in an RFID system comprising a larger number of wireless communication apparatus than the number of frequency division. <P>SOLUTION: A wireless communication apparatus being assigned, in one and one correspondence, with a frequency band obtained by dividing a frequency band for use in wireless communication is altered every predetermined time so that the divided frequency bands are assigned sequentially to all wireless communication apparatus and that processing is repeated. The communication apparatus performs wireless communication only when the divided frequency band is assigned and uses the divided frequency band thus assigned in that wireless communication. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an RFID (Radio Frequency Identification) system including a plurality of wireless communication devices that perform wireless communication with an RF tag.

  As this type of RFID system, for example, there is an RFID system used in a library (see, for example, Patent Document 1). In a library where an RFID system is introduced, for example, an RF tag reader / writer unit, which is a wireless communication device, is installed in a book lending counter, a book return counter, a theft prevention gate, and the like. Then, a book lending process, a return process, and an anti-theft process are executed using wireless communication with an RF tag provided in a book performed by those RF reader / writer units and storing the book information.

  As described above, the RFID system used in a library or the like is mainly used for data communication by electromagnetic induction in a 13.56 MHz band having a relatively short communication distance.

JP 2003-126744 A

  By the way, the electromagnetic induction method has a short communication distance, the size of the RF tag is large and the price is high, and therefore the library uses a 2.4 GHz band or UHF band, and the radio wave method has a long communication distance and a small RF tag size. RFID is considered to be the mainstream in the future.

  However, since the radio wave RFID system has a long communication distance, there is a problem that a plurality of RF reader / writers use the same frequency at the same time, thereby causing crosstalk. For example, data transmitted from an RF tag that is in data communication with an RF tag reader / writer unit installed in a book lending counter is read by an RF reader / writer installed in a book return counter or an anti-theft gate.

  In order to solve this, it is conceivable to divide the frequency band into a plurality of parts and assign the divided frequency band to each RF tag reader / writer unit. There is a limit to the number of divisions. Therefore, depending on the number of RF tag reader / writer units, the number of RF tag reader / writer units is larger than the number of frequency divisions. In this case, one frequency band must be assigned to a plurality of RF tag reader / writer units. However, it is conceivable that crosstalk will occur.

  An object of the present invention is to improve the accuracy of data communication in an RFID system including radio communication apparatuses having a larger number than the frequency division number.

  The RFID system of the present invention is provided with a larger number than the number of divisions of the frequency band used for wireless communication, and a wireless communication device that performs wireless communication with the RF tag, and a divided frequency band obtained by dividing the frequency band Means for changing the wireless communication devices to be assigned in a one-to-one relationship at regular time intervals, and repeatedly performing the process of sequentially assigning the divided frequency bands to all the wireless communication devices, the communication device comprising: Wireless communication is executed only when the divided frequency band is assigned by the means, and the assigned divided frequency band is used for the wireless communication.

  ADVANTAGE OF THE INVENTION According to this invention, the precision of the data communication in the RFID system provided with the radio | wireless communication apparatus with more numbers than frequency division | segmentation can be improved.

  An embodiment of the present invention will be described with reference to the drawings. This embodiment is an application example to an RFID system used in the library system A.

  FIG. 1 is a system configuration diagram schematically showing the configuration of a library system A including an RFID system 1 of the present embodiment. As shown in FIG. 1, the library system A includes a book lending processing device 3 set in the first to third lending counters 2, a book return processing device 5 installed in the return counter 4, and an exit. An anti-theft gate 6 for anti-theft processing installed in the vicinity, a system server (not shown) and the like are connected via a LAN. The book lending processing device 3 is a book lending PC (Personal Computer) 7 and RF tag reader / writer units 8a, 8b and 8c which are wireless communication devices. The book return processing device 5 is a book return PC and an RF tag reader / writer unit 8d. The anti-theft gate 6 is provided with six RF tag reader / writer units 8e, 8f, 8g, 8h, 8i and 8j.

  The library system A is provided with a PC (hereinafter referred to as a control PC) 10 for controlling the RF tag reader / writer unit 8, which is a control device for controlling all the RF tag reader / writer units 8 (8a to 8j). . Each RF tag reader / writer unit 8 is connected to the control PC 10 via a LAN cable 11 and a hub 12. The RFID system 1 is configured by the control PC 10 and the RF tag reader / writer unit 8 connected to the LAN. In this library system A, a well-known book rental is performed using data communication executed by the RF tag reader / writer unit 8 with respect to an RF tag (not shown) provided for a book and storing book data such as identification data of the book. Processing, book return processing and anti-theft processing are executed.

  FIG. 2 is an explanatory diagram for explaining a frequency band used by the RFID system 1. In the RFID system 1 of the present embodiment, the wireless communication performed between the RF tag reader / writer unit 8 and the RF tag is a radio communication using a 2.4 GHz band, a UHF band, or the like as a frequency band. In the present embodiment, the frequency band is divided into four to obtain four divided frequency bands, which will be described in detail later, but these four divided frequency bands are sequentially assigned to the ten RF tag reader / writer units 8. I have to. Here, the number of divisions of the frequency band is set to such a size that the divided frequency bands after division do not affect each other. These four divided frequency bands are channel 1 to channel 4 (ch1 to ch4 in the figure).

  Next, the RFID system 1 will be described.

  FIG. 3 is a block diagram showing electrical connection of each part provided in the control PC 10. As shown in FIG. 3, the control PC 10 is provided with a microcomputer (hereinafter referred to as a microcomputer) 30. The microcomputer 30 includes a ROM (Read Only Memory) 33 for storing fixed data such as a startup program in advance through a bus line 32 in a CPU (Central Processing Unit) 31 that performs drive control of each unit and various calculations, A RAM (Random Access Memory) 34 functioning as a work area for storing data in a rewritable manner and a timer 35 for measuring time are connected. Further, a LAN interface 36 for executing data communication with each RF tag reader / writer unit 8 and the system server via the LAN cable 11 is connected to the microcomputer 30 via the bus line 32. ing.

  Further, a display 39 and a keyboard 40 are connected to the microcomputer 30 via a bus line 32 and an I / O device control unit 38. Further, an HDD (Hard Disk Drive) 41 is connected to the microcomputer 30 via a bus line 32. The HDD 41 stores a computer program for operating the microcomputer 30 and a channel assignment table T1. The computer program or the like stored in the HDD 41 is copied to the RAM 34 when the control PC 10 is activated, and thus the microcomputer 30 can perform drive control of each unit and various calculations.

  FIG. 4 is a schematic diagram showing the channel assignment table T1. The channel assignment table T1 is a table for defining the RF tag reader / writer unit 8 to which the channels ch1 to ch4 are assigned every specified time t. In the present embodiment, time slots for channel assignment are set in the order of 1-5. The holding time of one time slot is the specified time t described above. Here, the antenna 52 in the table indicates an antenna 52 described later included in the RF tag reader / writer unit 8, and the antenna ID is identification information for identifying each antenna 52.

  FIG. 5 is an external perspective view schematically showing the RF tag reader / writer unit 8. The RF tag reader / writer unit 8 (8a to 8j) has the same configuration and differs only in identification information. As shown in FIG. 5, the RF tag reader / writer unit 8 includes an RF tag reader / writer 51 and an antenna 52 connected to the RF tag reader / writer 51. The RF tag reader / writer unit 8 radiates radio waves from the antenna 52 and executes an information read / write operation on the RF tag provided in the book.

  FIG. 6 is a block diagram showing the electrical connection of each part of the RF tag reader / writer unit 8. The RF tag reader / writer unit 8 includes a microcomputer 60. The microcomputer 60 is configured by connecting a CPU 61 to a memory unit 64 including a ROM and a RAM and a timer 65 via a bus line 62.

  Further, the microcomputer 60 is connected to a radio unit 66 that includes a berth band unit 66a and an RF unit 66b, and transmits and receives radio waves from the antenna 52. The radio unit 66 is also controlled by the microcomputer 60.

  Further, the microcomputer is connected with a LAN interface 67 for connecting the control PC 10 via the LAN cable 11 and the hub 12 to execute data communication with the control PC 10. Specifically, the LAN interface 67 includes a LAN connector 68 and a LAN controller 69 to which the LAN connector 68 is connected. In the RF tag reader / writer unit 8, a power supply circuit 70 is connected to the LAN connector 68, and the power supply circuit 70 supplies power supplied from the LAN connector 68 to each part of the RF tag reader / writer unit 8.

  The hub 12 has a power supply function. With this power supply function, power is supplied from the HUB to the RF tag reader / writer unit 8 via each LAN cable 11. Specifically, for power supply, lines (4, 5, 7, 8 pins) that are not used for data transmission among a plurality of lines of the LAN cable 11 are used as power supply lines.

  Next, data communication processing performed by the RFID system 1 will be described with reference to FIGS.

  First, the outline of the data communication process will be described based on the time chart shown in FIG. In the data communication process, first, channel assignment defined in the time slot 1 is executed according to the channel assignment table T1. That is, the channels 1, 2, 3, and 4 are assigned to the RF tag reader / writer unit 8 having the antenna 52 with the antenna IDs 1, 2, 3, and 4. Then, radio wave output is performed using the channel to which the RF tag reader / writer unit 8 is assigned. At this time, the RF tag reader / writer unit 8 transmits the data read from the RF tag to the control PC 10. This process is executed for a specified time t.

  After the specified time t has elapsed, the channel assignment specified in the time slots 2, 3, 4 and 5 is sequentially executed every specified time t. At that time, the RF tag reader / writer unit to which the channel is assigned is executed. 8 performs data communication. Specifically, in time slot 2, channels 1, 2, 3, and 4 are assigned to RF tag reader / writer unit 8 having antenna 52 with antenna IDs of 5, 6, 7, and 8. In the time slot 3, channels 1, 2, 3, and 4 are assigned to the RF tag reader / writer unit 8 having the antennas 52 with antenna IDs 9, 10, 1, and 2. In the time slot 4, channels 1, 2, 3, and 4 are assigned to the RF tag reader / writer unit 8 having the antennas 52 with antenna IDs of 3, 4, 5, and 6. In the time slot 5, channels 1, 2, 3, and 4 are assigned to the RF tag reader / writer unit 8 having the antenna 52 with the antenna IDs of 7, 8, 9, and 10. After the time slot 5, the process returns to the time slot 1, and thereafter the above processing is repeated. That is, in this embodiment, time slots 1 to 5 are set as one cycle, and this cycle is repeatedly executed thereafter. In this one cycle, there is a time zone in which a certain channel is assigned to all the RF tag reader / writer units 8.

  Next, processing performed by each device in this data communication processing will be described in detail. First, channel assignment processing executed by the CPU 31 of the control PC 10 according to a computer program will be described with reference to FIGS. 8 is a flowchart showing the flow of channel assignment processing in the control PC 10, FIG. 9 is a schematic diagram showing various storage areas formed in the RAM 34, and FIG. 10 is a schematic diagram showing the data structure of control data. 11 is a flowchart showing the flow of timer interrupt processing in the control PC 10.

  In the channel assignment process shown in FIG. 8, as shown in FIG. 9, a time slot value n area 81 and an end flag area 82 for storing the value n of the time slot formed in the RAM 34 are used.

  In the channel allocation process, first, the time slot value n of the time slot value n area 81 is set to 1 as initialization of the time slot value n area 81 (step S1). Next, the timer 35 is initialized, and the initial time of the timer 35 is set to 0 (step S2).

  Next, control data to be transmitted to all the RF tag reader / writer units 8 is generated (step S3). Specifically, the contents of the channel assignment table T1, the radio wave transmission start time, the radio wave transmission end time, etc. corresponding to the time slot value n stored in the time slot value area of the RAM 34 are used as control data. The contents of the channel assignment table T1 include an antenna ID indicating the RF tag reader / writer unit 8 to which each channel is assigned. The initial time of the timer 35 is used as the radio wave transmission start time. For example, in the first routine of this process, it is 0 set in step S2. In the second and subsequent routines, the end time (count time) of the timer 35 in the previous routine becomes the initial time in the routine. The radio wave transmission end time is a time obtained by adding the specified time t to the radio wave transmission start time. Here, FIG. 9 shows the data structure of the control data.

  Next, the generated control data is broadcasted to all the RF tag reader / writer units 8 (step S4), the flag in the end flag area 82 is cleared, the end time of the timer 35 is set, and the timer 35 is started. (Step S5). The end time of the timer 35 is a time obtained by adding the specified time t to the initial time of the timer 35. At the same time, timer interrupt processing is enabled.

  Here, when the timer 35 is started, the timer interruption process shown in FIG. 11 is started. In the timer interrupt process, when the count time of the timer 35 reaches the end time set in step S5 (Y in step S21), a flag is set in the end flag area 82 of the RAM 34 (step S22). At this time, the count time of the timer 35 is stopped at the end time.

  Next, in the channel assignment process, the process proceeds to step S6, waits for reception of RF tag data from the RF tag reader / writer unit 8 that has started data communication (step S6), and receives RF tag data from the RF tag reader / writer unit 8. If so (Y in step S6), the received RF tag data is transmitted to the system server (step S7). The processes in steps S6 and S7 are repeated while the flag is not set in the end flag area 82 (N in step S8).

  If the flag is set in the end flag area 82 by the timer interrupt process (Y in step S8), the timer 35 is prohibited from being interrupted, and 1 is added to the time slot value n in the time slot value n area 81. (Step S9).

  Next, it is determined whether or not the time slot value n in the time slot value n area 81 is greater than 5 (step S10). If it is 5 or less (N in step S10), the process returns to step S3 and returns to step S3. Steps S3 to S10 are repeatedly executed. Thereby, channel allocation processing corresponding to the time slot values 1 to 5 is executed.

  On the other hand, when the time slot value n is larger than 5 (Y in step S10), the time slot value n in the time slot value n area 81 is set to 1 (step S11), and the process returns to step S3. Thereby, the channel allocation process corresponding to the time slot values 1 to 5 is repeatedly executed.

  Next, data communication processing executed by the CPU 61 of each RF tag reader / writer unit 8 in accordance with the computer program will be described with reference to FIGS. Here, FIG. 12 is a flowchart showing a flow of data communication processing in the RF tag reader / writer unit 8, FIG. 13 is a schematic diagram showing a storage area formed in the RAM of the RF tag reader / writer unit 8, and FIG. 14 is an RF tag reader / writer unit. 9 is a flowchart showing the flow of timer interrupt processing in FIG.

  In the data communication process shown in FIG. 12, the end flag area 83 formed in the memory unit 64RAM is used as shown in FIG.

  In the data communication process, first, it waits until reception of control data transmitted from the control PC 10 (N in step S31). If control data is received (Y in step S31), the received control data is transmitted to the own antenna. It is determined whether or not there is an ID (step S32). If there is no antenna ID of the own device in the control data (N in step S32), the process returns to step S31.

  If the control data has its own antenna ID (Y in step S32), the flag in the end flag area 83 is cleared, and the radio wave transmission start time and radio wave transmission end time in the control data are set to the initial time of the timer 65 and The timer 65 is started by setting the end time (step S33). At the same time, timer interrupt processing is enabled.

  Here, when the timer 65 is started, the timer interruption process shown in FIG. 14 is started. In the timer interrupt processing, when the count time of the timer 65 reaches the end time of the timer 65 set in step S33 (Y in step S41), a flag is set in the end flag area 83 of the RAM of the memory unit 64 ( Step S42). At this time, the count time of the timer 65 is stopped at the end time.

  Next, in the data communication process, the process proceeds to step S34, where transmission of an RF tag data read command to the RF tag is started by radio waves on the channel specified by the control data. If RF tag data is received from the RF tag (Y in step S35), the received RF tag data is transmitted to the control PC 10 (step S36). The processes in steps S35 and S36 are repeated while the flag is not set in the end flag area 83 (N in step S37).

  If the flag is set in the end flag area 83 by the timer interrupt process (Y in step S37), the timer 65 is prohibited from being interrupted and the radio wave output is stopped (step S38).

  As described above, in the present embodiment, the number of RF tag reader / writer units 8 that are wireless communication devices (the present embodiment) is more than the number of frequency band divisions used in wireless communication (5 in the present embodiment). Then, in a configuration with many 10), the RF tag reader / writer unit 8 to which channels (divided frequency bands) are assigned in a one-to-one relationship is changed at every predetermined time t, and the divided frequency bands are assigned to all the RF tag reader / writer units 8. The RF tag reader / writer unit 8 performs the wireless communication only when the divided frequency band is assigned, and uses the assigned divided frequency band for the wireless communication. Since only one RF tag reader / writer unit 8 uses one channel, RFI It is possible to prevent the occurrence of crosstalk in the system 1. Therefore, it is possible to improve the accuracy of data communication in the RFID system 1 including the RF tag reader / writer unit 8 having a larger number than the frequency division number.

  In the present embodiment, a control PC 10 that is a control device that controls the RF tag reader / writer unit 8 that is a wireless communication device, and a hub that connects each RF tag reader / writer unit 8 and the control PC 10 via the LAN cable 11. 12, and the power is supplied from the hub 12 to each RF tag reader / writer unit 8 via the LAN cable 11, so that the LAN cable 11 also serves as a power supply line, thereby simplifying the configuration of the RFID system 1. Can do.

1 is a system configuration diagram schematically showing a configuration of a library system including an RFID system according to an embodiment of the present invention. It is explanatory drawing for demonstrating the frequency band which an RFID system uses. It is a block diagram which shows the electrical connection of each part with which control PC is provided. It is a schematic diagram which shows a channel allocation table. 1 is an external perspective view schematically showing an RF tag reader / writer unit. It is a block diagram which shows the electrical connection of each part with which an RF tag reader / writer unit is provided. It is a time chart which shows the flow of a data communication process. It is a flowchart which shows the flow of the channel allocation process in control PC. It is a schematic diagram which shows the storage area formed in RAM of control PC10. It is a schematic diagram which shows the data structure of control data. It is a flowchart which shows the flow of the timer interruption process in control PC. It is a flowchart which shows the flow of the data communication process in a RF tag reader / writer unit. It is a schematic diagram which shows the storage area formed in RAM of RF tag reader / writer unit. It is a flowchart which shows the flow of the timer interruption process in a RF tag reader / writer unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... RFID system 8 ... Wireless communication apparatus 10 ... Control apparatus 11 ... LAN cable 12 ... Hub

Claims (2)

A wireless communication device that is provided in a number greater than the number of divisions of the frequency band used for wireless communication and performs wireless communication with the RF tag;
A process of changing the wireless communication device to which the divided frequency band obtained by dividing the frequency band is assigned in a one-to-one relationship at a predetermined time, and sequentially assigning the divided frequency band to all the wireless communication devices. Repetitive means,
With
The RFID system, wherein the communication device performs wireless communication only when the divided frequency band is assigned by the means, and uses the assigned divided frequency band for the wireless communication. A control device provided with the means for controlling the wireless communication device;
A hub for connecting each wireless communication device and the control device via a LAN cable;
With
The RFID system according to claim 1, wherein power is supplied from the hub to each wireless communication device via a LAN cable.

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