JP2012205110A - Communication device, communication method and communication program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide communication device, communication method and communication program, capable of appropriate channel assignment.SOLUTION: The communication device includes: detection unit for detecting a command from a reception signal of a channel; determination unit for determining from the command a communication scheme being in use; and a communication unit for, based on the channel and the communication scheme, communicating through a communicable channel. In the communication method, a command is detected from a reception signal of a channel, and a communication scheme being in use is determined from the command, and based on the channel and the communication scheme, communication is performed through a communicable channel. The communication program allows a computer to execute: a detection step for detecting a command from a reception signal of a channel; a determination step for determining a communication scheme being in use; and based on the channel and the communication scheme, a communication step for communicating through a communicable channel.

Description

  The present invention relates to a communication device, a communication method, and a communication program.

  As a data encoding technique when the IC tag returns a response signal to the reader / writer device, an FM (Frequency Modulation) 0 (zero) method, a mirror subcarrier (MS) method, or the like can be used. When a plurality of reader / writers are adjacent to each other, normal communication may be disturbed by radio wave interference. As an interference avoidance method in such MS system or FM0 system, the techniques of Patent Documents 1 and 2 are disclosed.

  Patent Document 1 assigns channels 1 to 3 and 7 to 9 to MS machines, assigns channels 4 to 6 to FM0 machines, and uses FM0 and MS systems based on arbitrarily set interference level judgments. Disclosure technology is disclosed. Patent Document 2 discloses a technique for avoiding interference by changing a channel on the MS device side.

JP 2009-33473 A JP 2010-21684 A

  However, in the technique of Patent Document 1, when a remote FM0 machine interferes with the channel of the MS machine, accurate use determination cannot be performed. Further, in the technique of Patent Document 2, there is a possibility that the FM0 machine may select a tag response channel, and there is a possibility of repeating interference errors.

  SUMMARY An advantage of some aspects of the invention is that it provides a communication apparatus, a communication method, and a communication program capable of performing appropriate channel assignment.

  In order to solve the above-described problem, a communication device disclosed in the specification includes a detection unit that detects a command from a received signal of a channel, a determination unit that determines a communication method used from the command, the channel, and the channel And a communication unit that communicates through a communicable channel based on the communication method.

  In order to solve the above problems, a communication method disclosed in the specification detects a command from a received signal of a channel, determines a communication method used from the command, and based on the channel and the communication method. Communicate over a communicable channel.

  In order to solve the above problem, a communication program disclosed in the specification includes a detection step of detecting a command from a received signal of a channel in a computer, a determination step of determining a communication method used from the command, And a communication step of performing communication using a communicable channel based on the channel and the communication method.

  According to the communication device, the communication method, and the communication program disclosed in the specification, appropriate channel assignment can be performed.

(A) And (b) is a figure for demonstrating the radio wave interference in RFID. 1 is a device configuration diagram of a communication system according to Embodiment 1. FIG. (A) represents data stored in the memory as a table, and (b) is a diagram for explaining an example of a query command. (A) And (b) is a figure for demonstrating the interference level of each channel. It is a flowchart for demonstrating an example of operation | movement of a communication apparatus. FIG. 10 is a block diagram for explaining a hardware configuration of part of a communication apparatus according to a second embodiment.

  Prior to the description of the embodiments, radio wave interference in RFID (Radio Frequency Identification) will be described. Referring to FIG. 1A, it is assumed that a plurality of reader / writers RW1 to RW3 are arranged. The reader / writer RW1 transmits a command signal to the tag TG1 wirelessly and receives a response signal from the tag TG1 wirelessly. The reader / writer RW2 transmits a command signal to the tag TG2 wirelessly and receives a response signal from the tag TG2 wirelessly. When the reader / writers RW1 to RW3 are adjacent to each other, radio waves when the reader / writers RW1 to RW3 transmit / receive signals to / from the tag may interfere with each other.

  In the FM0 system, radio wave interference is avoided by using an LBT (Listen Before Talk) function. Specifically, a channel (CH) of a predetermined carrier sense level (as an example, -74 dBm) or less is used for signal transmission and reception, and interference is avoided by time division communication. However, since the transmission channel of the reader / writer and the response channel of the tag in time division communication are the same, a standby time occurs. Therefore, the FM0 system is difficult to use for high-speed reading.

  On the other hand, the MS method is a method in which two channels (usually channels of transmission channel ± 1), which are sidebands of a transmission channel, are used as response channels dedicated to tags using mirror coding. Therefore, standby time is unlikely to occur in the MS system. Therefore, the MS method is advantageous for high-speed reading. As an example of the MS system, one transmission channel (CH8) and its sideband response channels (CH7, CH9), and another transmission channel (CH14) and its sideband response channels (CH13, CH15). ) Is used as a channel for MS.

  From the above, radio wave interference is suppressed in each communication method. However, the actual radio wave environment is changing every moment. For example, even if the MS system can be used when the RFID system is installed, the radio wave environment changes due to the installation of another RFID system in the vicinity. In this case, there is a possibility that the MS system cannot be used after the installation of the RFID system.

  In particular, when the MS-type reader / writer and the FM0-type reader / writer are adjacent to each other, the transmission channels may overlap. In this case, communication failure may occur. Here, the command signal from the FM0 reader / writer can be determined by carrier sense. Therefore, the MS reader / writer can recognize the transmission channel of the FM0 reader / writer by carrier sense.

However, it is difficult for the FM0 reader / writer to correctly recognize the MS-use channel. For example, referring to FIG. 1 (b), it is assumed that the MS reader / writer transmits a command signal for transmission channel CH8 and receives response signals for response channels CH7 and CH9 from the tag. The response signal level received by the MS reader / writer from the tag is as weak as 1/10 ¹⁰ to 1/10 ⁶ of the command signal level. Therefore, it is difficult for the FM0 reader / writer to recognize whether the channels CH7 and CH9 are used in the MS method. Therefore, the FM0 reader / writer may transmit a command signal using the channels CH7 and CH9. In this case, the FM0 command signal interferes with the MS response signal, which may cause a communication error in the MS method.

  In the technology of Patent Document 1, channels CH1 to 3 and CH7 to 9 are assigned to the MS machine, channels CH4 to 5 are assigned to the FM0 machine, and the FM0 system and the MS system are determined based on the arbitrarily set interference level judgment. The channel usage is determined. If the interference level of the command signal is equal to or higher than the set value, it is determined that the command signal channel is the used channel. However, the usage status of the response signal channel cannot be grasped. For example, when a signal having an interference level equal to or higher than a predetermined value is received on the channel CH2, it is determined that the MS device normally uses the channels CH1 to CH3. However, since a signal having an interference level equal to or higher than a predetermined value may be a signal from a remote FM0 reader / writer, it is difficult to accurately determine the channel to be used. In addition, since the interference level of the signals of the response channels (CH1, CH3, CH7, CH9) of the MS machine is weak, it is difficult to accurately determine the channel to be used using the MS response signal.

  The technique of Patent Document 2 includes an interference determination unit that determines the presence or absence of an interference signal of a response channel, and a frequency switching unit that switches the frequency of the carrier wave between the first frequency (CH2) and the second frequency (CH8). ing. For example, when the interference radio wave of FM0 machine is detected, the interference is avoided by changing the channel on the MS machine side. However, the FM0 machine side does not determine the usage status of channels CH1 to CH3 and CH7 to CH9 in the MS machine. When the FM0 machine automatically selects a channel, the tag response channel may be selected. In this case, an interference error may be repeated.

  In the following embodiments, a communication device, a communication method, and a communication program that can perform appropriate channel assignment even when other reader / writers are arranged nearby will be described. Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 2 is an apparatus configuration diagram of the communication system 300 according to the first embodiment. The communication system 300 according to the present embodiment employs an RFID system as an example. Referring to FIG. 2, communication system 300 includes communication device 100 and tag 200. The communication device 100 is a reader / writer that transmits a command signal to the tag 200 wirelessly and receives a response signal from the tag 200 wirelessly. The command signal may be referred to as a question signal. The communication device 100 may be an FM0 communication device, an MS communication device, or a composite communication device that supports both methods. The tag 200 is a device that transmits a response signal in response to a command signal received from the communication device 100.

  The communication system 300 can communicate using a plurality of channels, and channels CH1 to CH15 are used as an example. A channel is a specific frequency or frequency band. In this embodiment, a higher frequency is set as the channel number is larger.

  The communication device 100 includes an antenna 10, a reception unit 20, a demodulation unit 30, a clock 40, a communication control unit 50, a modulation unit 60, and a transmission unit 70. The communication control unit 50 is configured as one chip as an example, and includes a command detection unit 51, a control unit 52, a memory 53, and a switching unit 54. The tag 200 includes two antennas 81, a diode 82, capacitors 83a and 83b, a switching element 84, a demodulator 85, a clock 86, a controller 87, a memory 88, and a modulator 89. The diode 82, the capacitors 83a and 83b, the switching element 84, the demodulation unit 85, the clock 86, the control unit 87, the memory 88, and the modulation unit 89 may be configured by a single IC (Integrated Circuit) chip.

  Next, the operation of the communication system 300 will be described with reference to FIG. The receiving unit 20 receives a signal corresponding to each channel via the antenna 10. For example, the receiving unit 20 receives a response signal from the tag 200 and also receives a command signal from a communication device other than the communication device 100. The demodulator 30 demodulates a signal received via the antenna 10 and generates a demodulated signal. The demodulated signal is sent to the command detection unit 51 and the control unit 52.

  The control unit 52 performs carrier sense. Specifically, controller 52 uses the demodulated signal received from demodulator 30 to measure the interference level of the signals received on channels CH1 to CH15. The control unit 52 stores the interference level obtained by the measurement in the memory 53 in association with each channel. FIG. 3A shows the data stored in the memory 53 as a table.

  Here, in RFID communication, a command for identifying a communication method is included in a command signal. FIG. 3B is a diagram for explaining an example of a query command defined in the EPCglobal Class-1 Generation-2 standard. Referring to FIG. 3B, the query command includes an M value. The M value is a value given according to the communication method. In the FM0 command signal, M value = 1 is set. In the MS command signal, either M value = 2, 4, or 8 is set. Therefore, by detecting the M value, it is possible to detect whether the command signal including the query command is an FM0 command signal or an MS command signal.

  The control unit 52 identifies a channel having an interference level equal to or higher than a predetermined value among the interference levels stored in the memory 53. As the predetermined value in this case, for example, a carrier sense level can be used. As an example, the carrier sense level is -74 dB. The control unit 52 sends the identified channel to the command detection unit 51. The command detection unit 51 detects a query command from the channel signal received from the control unit 52, detects an M value from the query command, and sends the M value to the control unit 52.

  The control unit 52 determines which channel is in use by detecting the communication method from the M value detected by the command detection unit 51. For example, referring to FIG. 4A, it is assumed that the interference level of the signal of channel CH8 is equal to or higher than the carrier sense, and the M value of the signal received through the channel is other than 1. In this case, it can be determined that the channel CH8 is used as an MS transmission channel and the channels CH7 and CH9 are used as MS response channels. Also, referring to FIG. 4B, it is assumed that the interference level of the signal on channel CH8 is equal to or higher than the carrier sense, and the M value of the signal received on the channel is 1. In this case, it can be determined that the channel CH8 is used as an FM0 transmission channel and a response channel.

  Next, the control unit 52 selects a transmission channel so that the channel used in any communication method and the channel used in the communication method of the communication apparatus 100 do not overlap, and the result is sent to the switching unit 54. send. The switching unit 54 switches the channel of the transmission command generated by the modulation unit 60 to the channel selected by the control unit 52. The clock 40 generates a clock signal in accordance with an instruction from the control unit 52. The modulation unit 60 generates a transmission command using the frequency of the clock signal generated by the clock 40 and transmits the transmission command via the antenna 10.

  It is preferable that the control unit 52 selects a channel having the lowest interference level as a transmission channel among channels not used in any communication method. This is because radio wave interference can be further suppressed.

  The tag 200 receives a command signal via the antenna 81. The diode 82 rectifies the command signal and generates a DC voltage. Capacitor 83b holds the electric power generated by this DC voltage. Each device operates using the electric power held in the capacitor 83b. The demodulation unit 85 generates a demodulated signal from the command signal by demodulation. The controller 87 reads tag information stored in the memory 88.

  The control unit 87 generates response data based on the tag information read from the memory 88. The clock 86 generates a basic clock signal having a basic period from the demodulated signal generated by the demodulation unit 85 by demodulation. The clock 86 generates a carrier clock signal obtained by multiplying the basic clock signal. The modulation unit 89 generates a response signal from the response data using the carrier clock signal. The switching element 84 is repeatedly turned on and off using the response signal. Thereby, a response signal is transmitted from the antenna 81. A capacitor 83a may be provided in order to match impedance.

  According to the present embodiment, the channel being used can be detected by detecting a command for identifying the communication method. Therefore, even in an environment where a plurality of reader / writers interfere with each other, appropriate channel allocation can be performed so that interference errors are suppressed.

  FIG. 5 is a flowchart for explaining an example of the operation of the communication apparatus 100. The flowchart in FIG. 5 is an example that is executed in an environment where channels CH8 and CH14 are used as MS transmission channels. Hereinafter, an example of the operation of the communication apparatus 100 will be described with reference to FIGS. 2 and 5. First, the control unit 52 measures the interference levels of all channels (channel CH1 to channel CH15) and stores them in the memory 53 (step S1).

  Next, the control unit 52 determines whether or not the interference level of at least one of the channels CH8 and CH14 is equal to or higher than the carrier sense level (step S2). If it is determined as “Yes” in step S <b> 2, the channel higher than the carrier sense level among the channels CH <b> 8 and CH <b> 14 is sent to the command detection unit 51. Thereby, the command detection unit 51 detects a query command from the channel signal received from the control unit 52, and detects an M value from the query command (step S3). The controller 52 determines whether or not the M value detected in step S3 exceeds 1 (step S4).

  When it is determined as “Yes” in step S4, the control unit 52 prohibits the use of the transmission channel and the response channel used in the MS system and stores the information in the memory 53 (step S5). Next, the control unit 52 refers to the memory 53 and determines an available channel other than the channel used in the MS system and below the carrier sense level (step S6). Next, the control unit 52 refers to the memory 53 and selects a channel having the lowest interference level from the usable channels obtained in step S6 (step S7).

  Next, the control unit 52 controls the switching unit 54 so that communication with the tag 200 is started using the channel selected in step S7. Thereby, the transmission unit 70 starts communication with the tag 200 using the channel selected in step S7. The receiving unit 20 receives a response signal from the tag 200 (step S8). Thereafter, the execution of the flowchart ends. In addition, when it determines with "No" at step S2, and when it determines with "No" at step S4, step S6 is performed.

  In the second embodiment, an example in which the function of each device is realized by executing a communication program will be described. FIG. 6 is a block diagram for explaining a partial hardware configuration of the communication apparatus 100a according to the second embodiment. Referring to FIG. 6, the communication device 100a may include a CPU 101, a RAM 102, a storage device 103, an interface 104, and the like. Each of these devices is connected by a bus or the like.

  A CPU (Central Processing Unit) 101 is a central processing unit. The CPU 101 includes one or more cores. A RAM (Random Access Memory) 102 is a volatile memory that temporarily stores programs executed by the CPU 101, data processed by the CPU 101, and the like. The storage device 103 is a nonvolatile storage device. As the storage device 103, for example, a ROM (Read Only Memory) or the like can be used. The communication program according to the present embodiment is stored in the storage device 103. The interface 104 is a device for transmitting and receiving signals to and from the demodulator 30 and the modulator 60.

  The communication program stored in the storage device 103 is expanded in the RAM 102 so as to be executable. The CPU 101 executes a communication program expanded on the RAM 102. Thereby, the communication control unit 50 of FIG. 2 is realized. As described above, the function of each device may be realized by executing the communication program.

(Other examples)
In each of the above embodiments, an RFID system conforming to the C1G2 standard is adopted, but the present invention is not limited to this. For example, in each of the above embodiments, the FM0 method and the MS method are detected from the M value. When the M value includes another communication method, the M value is detected and used in the other communication method. Channels may be detected. In each of the above embodiments, a query command based on the C1G2 standard is detected as a command for identifying a communication method, but the present invention is not limited to this. For example, when another command for identifying a communication method is used in a standard other than the C1G2 standard, the channel of the communication method used can be detected by detecting the other command. .

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

(Appendix)
(Appendix 1)
A detection unit for detecting a command from the received signal of the channel;
A determination unit for determining a communication method used from the command;
A communication apparatus comprising: a communication unit that communicates with a communicable channel based on the channel and the communication method.
(Appendix 2)
The communication apparatus according to appendix 1, wherein the detection unit detects the command on a predetermined channel.
(Appendix 3)
Detect commands from the received signal of the channel,
From the command, determine the communication method used,
A communication method comprising performing communication using a communicable channel based on the channel and the communication method.
(Appendix 4)
4. The communication method according to appendix 3, wherein the command is detected on a predetermined channel when the command is detected.
(Appendix 5)
On the computer,
A detection step of detecting a command from the received signal of the channel;
A determination step of determining a communication method used from the command;
And a communication step of performing communication on a communicable channel based on the channel and the communication method.
(Appendix 6)
The communication program according to appendix 5, wherein the command is detected in a predetermined channel in the detection step.
(Appendix 7)
A command detection unit for detecting a command for identifying a communication method from a received signal having an interference level equal to or higher than a predetermined value;
A channel detection unit for detecting a channel used in a communication method corresponding to the command from the command detected by the command detection unit;
A communication unit that communicates using a channel other than the channel detected by the channel detection unit.
(Appendix 8)
There are a plurality of channels through which the communication unit can communicate,
8. The communication apparatus according to claim 7, wherein the communication unit uses a channel having an interference level equal to or lower than a predetermined value as the transmission channel among the plurality of channels.
(Appendix 9)
There are a plurality of channels through which the communication unit can communicate,
The communication apparatus according to appendix 7, wherein the communication unit uses a channel having the lowest interference level among the plurality of channels as a channel for transmission.
(Appendix 10)
10. The communication device according to any one of appendices 7 to 9, wherein the communication method is an FM0 (Frequency Modulation zero) method or an MS (Miller Mixed Sub-carrier) method.
(Appendix 11)
The communication device according to any one of appendices 7 to 10, wherein the communication device is a reader / writer of an RFID system.
(Appendix 12)
The communication device according to any one of appendices 7 to 11, wherein the command is a query command defined in the C1G2 standard.
(Appendix 13)
A command for identifying a communication method is detected from a received signal having an interference level equal to or higher than a predetermined value,
From the command, a channel used in a communication method corresponding to the command is detected,
Communication using a channel other than the channel.
(Appendix 14)
On the computer,
A command detection step of detecting a command for identifying a communication method from a received signal having an interference level equal to or higher than a predetermined value;
A channel detection step of detecting a channel used in a communication method corresponding to the command from the command detected in the command detection step;
And a communication step of performing communication using a channel other than the channel detected in the channel detection step.

DESCRIPTION OF SYMBOLS 10 Antenna 20 Receiving part 30 Demodulation part 40 Clock 50 Communication control part 51 Command detection part 52 Control part 53 Memory 54 Switching part 60 Modulation part 70 Transmission part 81 Antenna 82 Diode 83 Capacitor 84 Switching element 85 Demodulation part 86 Clock 87 Control part 88 Memory 89 Modulation unit 100 Communication device 200 Tag 300 Communication system

Claims (6)

A detection unit for detecting a command from the received signal of the channel;
A determination unit for determining a communication method used from the command;
A communication device comprising: a communication unit that communicates through a communicable channel based on the channel and the communication method.   The communication device according to claim 1, wherein the detection unit detects the command using a predetermined channel. Detect commands from the received signal of the channel,
From the command, determine the communication method used,
A communication method comprising performing communication using a communicable channel based on the channel and the communication method.   4. The communication method according to claim 3, wherein the command is detected on a predetermined channel when the command is detected. On the computer,
A detection step of detecting a command from the received signal of the channel;
A determination step of determining a communication method used from the command;
And a communication step of performing communication on a communicable channel based on the channel and the communication method.   6. The communication program according to claim 5, wherein, in the detection step, the command is detected on a predetermined channel.

Images