JP5655752B2 - Wireless tag system - Google Patents

Description

  The present invention relates to a wireless tag system including a wireless tag and a wireless tag reader, and particularly to a technique for suppressing power consumption of a wireless tag when a plurality of wireless tag readers are provided.

  In a wireless tag system including a wireless tag and a plurality of wireless tag readers, communication areas of a plurality of wireless tag readers often partially overlap each other in order to eliminate communication leakage. When a wireless tag exists in a place where communication areas of a plurality of wireless tag readers overlap, it is possible to prevent communication between the wireless tag and the wireless tag reader from being disabled due to collision of signals from the plurality of wireless tag readers. There is a need. Therefore, in Patent Document 1, each tag reader has a signal transmission function at a specific timing for each tag reader in advance, and uses a signal from the tag to synchronize the time and transmit at a specific timing held in advance. By doing so, the signal transmission timing is not overlapped with each other, and the signal is transmitted to the tag. Thereby, even if the tag is within the communication area of a plurality of tag readers, the tag reader can be identified and communicated.

Japanese Patent No. 4037421

  However, in the technique of Patent Document 1, the wireless tag needs to maintain a receivable state until a signal may be transmitted from a wireless tag reader whose signal transmission time is the latest among a plurality of wireless tag readers. There is. For example, when there are four wireless tag readers, the wireless tags must be able to communicate with any of them, so the period for which one wireless tag reader is ready must be secured for the period transmitted by the four wireless tag readers. Don't be. Then, the wireless tag determines whether it is within the communication range or out of the communication range of the wireless tag reader based on the reception result of the period corresponding to the number of the wireless tag readers.

  The wireless tag is carried by a person. Therefore, the wireless tag is overwhelmingly long when it exists in a place that is not within the communication range of any wireless tag reader, and even if it is in a receivable state, it does not receive any signal from any wireless tag reader after all. Too many.

  However, the wireless tag in the conventional system determines whether the wireless tag reader is within the communication range of the wireless tag reader or out of the communication range based on the reception result in a period corresponding to the number of wireless tag readers. Therefore, even when the wireless tag reader is outside the communication range of the wireless tag reader, the length of one receivable state is the same as that when the wireless tag reader is within the communication range of the wireless tag reader. In addition, since the receivable state is periodically repeated, the time in which the signal can be received without receiving a signal from the wireless tag reader becomes a longer time due to integration, and the power consumption of the wireless tag can be sufficiently reduced. There wasn't.

  The present invention has been made based on this situation, and an object thereof is to provide a wireless tag system capable of reducing power consumption of the wireless tag.

In order to achieve the object, the invention described in claims 1 and 2 is a wireless tag system including a wireless tag and a plurality of wireless tag readers communicating with the wireless tag, wherein the plurality of wireless tag readers are wirelessly connected. When a signal from the tag is received, radio waves are transmitted to the wireless tag at a common transmission time determined based on the reception time and common to the plurality of wireless tag readers. Further, after transmitting the radio wave at the common transmission time point, transmission data capable of identifying the wireless tag reader is transmitted to the wireless tag at the second transmission time point set at a different timing for each wireless tag reader.

On the other hand, after a signal is transmitted to the wireless tag reader, the wireless tag is set in a receivable state during a first reception period in which radio waves that may be transmitted from the wireless tag reader at a common transmission time point. When it is determined that no radio wave has been received, the standby state is set based on the elapse of the first reception period. In addition, when it is determined that additional reception is necessary based on the determination that radio waves from the wireless tag reader have been received during the first reception period, and when it is determined that additional reception is necessary, the second transmission time point from the wireless tag reader to receive the transmission data to be transmitted in, to add a period of receiving.

  As described above, in the present invention, the wireless tag is in a receivable state during the first reception period in order to receive the radio wave transmitted from the wireless tag reader at the common transmission time after transmitting the signal. The first reception period in the present invention is a period for determining whether radio waves from at least one of the plurality of radio tag readers have been received or radio waves from any of the radio tag readers have not been received. Even if radio waves from a plurality of wireless tag readers overlap in the same period, this determination is possible. Therefore, each of the plurality of wireless tag readers is determined based on the time when the signal from the wireless tag is received, and transmits a radio wave to the wireless tag at a common transmission time common to the plurality of wireless tag readers, that is, at the same timing. I am doing so. When a plurality of wireless tag readers transmit radio waves at a common transmission point, the plurality of wireless tag readers transmit radio waves from at least one of the plurality of wireless tag readers, rather than when the plurality of wireless tag readers transmit radio waves at a transmission timing at which the signals do not overlap each other. Is likely to be transmitted for a shorter period. Therefore, the first reception period of the wireless tag may be shorter than the reception period when a plurality of wireless tag readers transmit the signals so that they do not overlap each other. For example, the first reception period is one wireless tag reader. Is substantially the same as the period during which the signal is transmitted.

  And when it is judged that the radio tag did not receive the radio wave from the radio tag reader during the first reception period, the radio tag is set in a standby state based on the elapse of the first reception period. As described above, the wireless tag is overwhelmingly located in a place that is not within the communication range of any wireless tag reader, so the case where the wireless tag enters a standby state after the first reception period has elapsed is overwhelming. Many. Therefore, by shortening one first reception period, it is possible to greatly shorten the total period in which reception is possible, thereby reducing power consumption.

Further, the plurality of wireless tag readers transmit the transmission data to the wireless tag at the second transmission time set at a different timing for each wireless tag reader after transmitting the radio wave at the common transmission time. On the other hand, the wireless tag determines whether additional reception is necessary based on determining that the radio wave from the wireless tag reader has been received in the first reception period. To determine the required additional receiver in the case of communication error (claim 1) and the reception intensity is equal to or greater than distance determination strength (claim 2). If it is determined that additional reception is necessary, a period in which reception is possible is added to receive transmission data transmitted from the wireless tag reader at the second transmission time point. By adding a period in which reception is possible, transmission data can be received from the wireless tag reader without any data collision. Based on this transmission data, the wireless tag identifies the wireless tag reader as in Patent Document 1. can do.

In the these inventions, when the added received was determined to be necessary, but will add the duration of the reception state, since the wireless tag is intended to be portable to a person actually Is overwhelmingly long when it is located outside the communication range of the wireless tag reader. For this reason, there are few cases where a period in which reception is possible is added. Thus, power consumption of the wireless tag can be sufficiently reduced. In addition, in the present invention, the wireless tag reader can be specified as described above.

In the first aspect of the invention, the wireless tag reader transmits transmission data to the wireless tag at the common transmission time point, and the wireless tag requires additional reception when the radio wave received during the first reception period is a reception error. It is judged that. If it is a reception error, it can be determined that the communication is within the communication range of a plurality of wireless tag readers, and therefore it is determined that additional reception is necessary.
In the invention according to claim 2, the radio tag receives the radio wave from the radio tag reader during the first reception period if the reception intensity of the radio wave received during the first reception period is lower than a preset area judgment strength. If the first reception period has passed and the standby state is set, and the reception strength of the radio wave received during the first reception period is equal to or greater than the coverage determination strength, additional reception is necessary. to decide.
If the reception strength of the radio wave received during the first reception period is lower than the coverage determination strength, it is determined that it is not within the communication range of any wireless tag reader, and the standby state is set based on the passage of the first reception period. is there. On the other hand, when the reception intensity of the radio wave received during the first reception period is equal to or greater than the area determination intensity, it is determined that the communication area is within at least one of the wireless tag readers, and additional reception is performed. The range determination strength is a strength determined based on the reception strength that the wireless tag can receive from the wireless tag reader when the communication range is at least one of the wireless tag readers.
Depending on the circuit, there is a circuit in which data signals from a plurality of wireless tag readers are duplicated and communication with the wireless tag reader cannot be performed simply as noise and does not cause a communication error. However, in this way, when additional reception is determined based on the reception intensity of radio waves, such a circuit can also be used, so that the range of component selection is widened.

  In the invention according to claim 3, when it is determined that the radio tag is successfully received based on the radio wave received during the first reception period, the radio tag is based on the transmission data that has been successfully received without adding a period in which reception is possible. The process determined by

  In the third aspect of the present invention, the wireless tag does not add a period in which reception is possible when it is determined that reception is successful based on the radio wave received in the first reception period. can do. It is also possible to quickly execute processing determined based on transmission data that has been successfully received.

  In the third aspect, the wireless tag reader transmits the transmission data by transmission at the common transmission time point (first transmission), so that the wireless tag is connected to the wireless tag reader in the first reception period (first reception period). The communication is configured to be successful. Instead, it can be configured as in the following claim 4.

  According to a fourth aspect of the present invention, the wireless tag reader is characterized in that the transmission time of the radio wave transmitted at the common transmission time is shorter than the transmission time of the transmission data transmitted at the second transmission time. According to the fourth aspect of the present invention, the first transmission / reception is intended only for the wireless tag to determine whether it is within the communication range of at least one wireless tag reader or within the communication range of any wireless tag reader. In this case, the radio waves transmitted by the wireless tag reader at the common transmission point need only be known to be present from the wireless tag reader. Therefore, the transmission time of the radio wave transmitted at the common transmission time is made shorter than the transmission time of the transmission data transmitted at the second transmission time. According to the invention described in claim 4, since the transmission time of the radio wave transmitted at the common transmission time is shorter than the transmission time of the transmission data transmitted at the second transmission time, the first reception period of the wireless tag is shortened. can do.

When determining the need for additional received by reception strength, the wireless tag reader does not need to send the transmission data is first transmission. Therefore, it can also be as claimed in claim 5 . In the invention according to claim 5 , the wireless tag reader transmits an unmodulated wave to the wireless tag at the common transmission time.

According to the sixth aspect of the present invention, the wireless tag sequentially determines whether or not the reception is successful during the period of the added receivable state, and ends the receivable state when the reception is successful. In this way, since the period of the additional receivable state can be shortened, the power consumption of the wireless tag can be further reduced.

The invention according to claim 7 is the receivable state in which the wireless tag adds the second transmission time point of the plurality of wireless tag readers when there are a plurality of wireless tag readers that transmitted radio waves at the common transmission time point in claim 6 . The second transmission time point determining means for determining a plurality of transmission time points different from each other within the period of time. Further, the second transmission time point determination means determines the second transmission time points of the plurality of wireless tag readers in order from the earliest time point among the plurality of transmission time points set in advance within the period in which reception is possible. The plurality of wireless tag readers transmit the transmission data at the second transmission time determined by the second transmission time determination means.

In the invention according to claim 7 , the second transmission time point of each wireless tag reader is set in order from the earliest transmission time point among a plurality of transmission time points set in advance within the period of the receivable state added by the wireless tag. Yes. Therefore, it is more likely that any wireless tag reader will transmit the transmission data at a time earlier in the receivable period added by the wireless tag than when the second transmission time is predetermined for each wireless tag reader. Become. In addition, the wireless tag ends the receivable state when it is determined that reception is successful. As a result, the period during which the wireless tag can be received can be shortened. Thus, the wireless tag can further reduce power consumption.

According to an eighth aspect of the present invention, a reader control device that controls a plurality of wireless tag readers is provided. In addition, when a plurality of wireless tag readers receive a signal from the wireless tag, notification information for notifying the reception is transmitted to the reader control device. In addition, the reader control device includes a second transmission time point determining unit, and further includes a transmission time point indicating unit that instructs a plurality of wireless tag readers on the second transmission time point determined by the second transmission time point determining unit.

In a wireless tag system including a plurality of wireless tag readers, a reader control device that controls the plurality of wireless tag readers is often provided. Therefore, according to the eighth aspect , the RFID tag system including the second transmission time point determination means can be obtained by utilizing the reader control device.

However, the present invention is not limited to the above aspect of the eighth aspect, and the reader control device can be made unnecessary as in the ninth aspect. According to the ninth aspect of the present invention, any one of the plurality of wireless tag readers includes the second transmission time point determination means. Then, among the plurality of wireless tag readers, the wireless tag reader that does not include the second transmission time point determining unit receives notification information for notifying the second transmission time point determining unit when receiving a signal from the wireless tag. It transmits to the wireless tag reader provided. Further, the wireless tag reader provided with the second transmission time point determination means transmits to the other wireless tag reader the second transmission time point for the other wireless tag reader among the second transmission time points determined by the second transmission time point determination means. Time point indicating means is provided.

According to the ninth aspect of the present invention, since the reader control device is not required to include the second transmission time point determination means in the wireless tag system, a wireless tag system without the reader control device is possible. Therefore, there is a possibility that the installation area of the entire system can be reduced and the cost can be reduced.

In the invention 請 Motomeko 10, wherein a plurality of radio tag reader, the notification information is transmitted by including the received signal strength of a signal received from the wireless tag. The second transmission time point determination means sets the second transmission time points of the plurality of wireless tag readers in advance in the period of the receivable state in descending order of the received signal strength of the signals received by the plurality of wireless tag readers from the wireless tags. It is determined as an earlier transmission time among the set transmission times.

  In this way, the wireless tag reader that receives the signal from the wireless tag with a high received signal strength determines the second transmission time as the earlier transmission time. In addition, a wireless tag reader that can receive a signal from a wireless tag with a high received signal strength is likely to succeed in communication with the wireless tag. Therefore, the wireless tag is more likely to be successfully received at an early point in the added receivable period. Therefore, the possibility that the second reception period of the wireless tag can be shortened is further improved.

The reader controller is not required even in the following claims 1 1. In the invention of the claim 1 1, wherein, the plurality of radio tag readers, when receiving a signal from the wireless tag, the reception, and a notification information including priority information indicating the priority, other radio tag reader Send to. The plurality of wireless tag readers include a transmission reader number determination unit and a second transmission time point determination unit. The transmission reader number determination means determines whether or not there are a plurality of wireless tag readers that transmitted radio waves at the common transmission time point based on notification information from other wireless tag readers and whether or not they received signals from wireless tags. To do. The second transmission time point determination means is preset within the period of the receivable state added by the wireless tag when it is determined by the transmission reader number determination means that there are a plurality of wireless tag readers that have transmitted radio waves at the common transmission time point. Among the plurality of transmission time points, a transmission time point different from the second transmission time point of the other RFID tag reader and the earliest possible time point is determined as its second transmission time point, Based on the priority order information included in the notification information, the second transmission time point of itself is determined from a plurality of transmission time points. Each wireless tag reader transmits the transmission data at the second transmission time determined by the second transmission time determination means.

Also it is of the claims 1 1, since the reader controller is not required to include the second transmission time determination means in the wireless tag system, it is possible to radio tag system that does not include a reader control unit. Therefore, there is a possibility that the installation area of the entire system can be reduced and the cost can be reduced.

As the claim 1 1, in the invention each wireless tag reader determines respectively the second transmission time of the own priority, for example, it can be determined by different reader ID for each wireless tag reader. Further, as the following claims 1 2, it is also possible to determine the priority to the received signal strength.

In the invention of the claim 1 wherein, the plurality of radio tag readers, the received signal strength of a signal received from the wireless tag, be included in the notification information as the priority information, so as to transmit to the other wireless tag reader When the signal itself is received from the wireless tag, the second transmission time determination means determines the received signal strength included in the notification information received from the other wireless tag reader and the received signal of the signal received from the wireless tag. Compared with the strength, the higher the received signal strength, the higher the priority, and the second transmission time of itself is determined from a plurality of transmission times.

In this way, as in the tenth aspect , the wireless tag reader that receives the signal from the wireless tag with a high received signal strength determines the second transmission time as the earlier transmission time. Accordingly, the wireless tag is more likely to be successfully received at an early point in the added receivable period, so that the possibility of shortening the second reception period of the wireless tag is further improved.

1 is a diagram illustrating an example of a system configuration of a wireless tag system 1. FIG. 2 is a diagram illustrating an arrangement of wireless tag readers 100 and a communication area 101 of each wireless tag reader 100. FIG. 1 is a diagram illustrating a configuration of a wireless tag reader 100. FIG. 2 is a diagram showing a configuration of a wireless tag 200. FIG. It is a figure which illustrates the communication sequence of the radio | wireless tag 200 and radio | wireless tag readers 100A-D. It is a figure explaining the effect of an embodiment. It is a flowchart which shows the 2nd transmission time determination process which the controller 300 performs in 2nd Embodiment. In 2nd Embodiment, it is a figure which illustrates the communication sequence of the wireless tag 200 and the wireless tag reader 100. FIG. It is a flowchart which shows the 2nd transmission time determination process performed in the modification 2 of 2nd Embodiment. It is a flowchart which shows the 2nd transmission time determination process which the controller 300 performs in the modification 3 of 2nd Embodiment.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the first embodiment will be described. FIG. 1 is an example of a system configuration of a wireless tag system 1 according to the present invention. As shown in the figure, the wireless tag system 1 includes a plurality (four in this case) of wireless tag readers 100A, 100B, 100C, and 100D, and a wireless tag 200. Note that although one wireless tag 200 is shown in FIG. 1, a plurality of wireless tags 200 may be provided. The wireless tag system 1 also includes a controller 300 (see FIG. 3) that controls a plurality of wireless tag readers 100.

  FIG. 2 is a diagram illustrating the arrangement of the wireless tag reader 100 and the communication area 101 of each wireless tag reader 100. The wireless tag system 1 is a system that detects the presence of a person in a certain monitoring area (for example, the site of a house and its surroundings) by allowing the person to carry the wireless tag 200 and detecting the wireless tag 200. Therefore, the entire communication area formed by the communication areas 101A to 101D of the plurality of wireless tag readers 100A to 100D needs to cover the monitoring area without omission. Moreover, the site serving as the center of the monitoring area has many polygons such as a rectangle, while the communication areas 101A to 101D of the wireless tag readers 100A to 100D are circular. Therefore, the wireless tag readers 100A to 100D are arranged so that the communication areas 101A to 101D of the wireless tag readers 100A to 100D partially overlap with the communication areas 101A to 101D of the other wireless tag readers 100A to 100D. Yes.

  FIG. 3 is a diagram illustrating a configuration of the wireless tag reader 100. As shown in FIG. 3, the wireless tag reader 100 includes a control unit 110, a transmission unit 120, a reception unit 130, and an antenna 140. The control unit 110 transmits a signal to be transmitted wirelessly to the outside to the transmission unit 120, and obtains a signal received by the antenna 140 and demodulated / decoded by the reception unit 130 from the reception unit 130. The control unit 110 includes a memory 111 and a timer 112 inside.

  The memory 111 stores the ID and delay time of the wireless tag reader 100. The delay time is the time from the transmission of the first transmission data to the transmission of the second transmission data, and is set to a different time for each wireless tag reader 100. Also, the difference in delay time of each wireless tag reader 100 is the same as or slightly larger than the transmission time of transmission data so that transmission data from a plurality of wireless tag readers 100 does not collide. The timer 112 is used for measuring the delay time.

  The transmission unit 120 includes a coding unit 121, a modulation unit 122, and an amplification unit 123. The encoding unit 121 encodes the signal supplied from the control unit 110. This signal includes the ID of the wireless tag reader 100. The encoding unit 121 outputs the encoded signal to the modulation unit 122. The modulation unit 122 converts the signal encoded by the encoding unit 121 into an electrical digital signal, and then uses a predetermined communication channel to perform a predetermined modulation method such as phase shift keying or frequency shift keying. Modulate with The amplification unit 123 amplifies the signal modulated by the modulation unit 122. The amplified signal is transmitted from the antenna 140 as a radio wave.

  Further, the antenna 140 receives a radio wave transmitted from the wireless tag 200. The received radio wave is demodulated by the demodulator 131. The demodulated signal is encoded by the decoding unit 132, and the encoded signal is sent to the control unit 110.

  When the control unit 110 determines that the tag data has been received from the wireless tag 200 based on the signal supplied from the reception unit 130, the wireless tag reader 100 has a fixed transmission time determined based on the reception time of the tag data. The reader data including the ID and the predetermined command is transmitted to the wireless tag 200. The fixed transmission time point is common to all the wireless tag readers 100 and corresponds to the common transmission time point in the claims. The reader data corresponds to the transmission data in the claims.

  When the RFID tag reader 100 transmits reader data at a fixed transmission time point, the RFID tag reader 100 is further set at a different timing for each RFID tag reader 100 and set not to overlap with the second transmission period of other RFID tag readers 100. The reader data is transmitted to the wireless tag 200 also at the time of the second transmission. The second transmission time is also determined based on the tag data reception time.

  FIG. 4 is a diagram illustrating a configuration of the wireless tag 200. The wireless tag 200 is carried by a person. The wireless tag 200 is an active wireless tag and includes a built-in power supply 210. In addition to the built-in power supply 210, the wireless tag 200 includes a transmission unit 220, a reception unit 230, an antenna 240, a vibration sensor 250, and a control unit 260. The built-in power supply 210 supplies power to them.

  The transmission unit 220 includes a coding unit 221, a modulation unit 222, and an amplification unit 223. The encoding unit 221 encodes the signal transmitted from the control unit 260 and sends the encoded signal to the modulation unit 222. The modulation unit 222 modulates the code from the code unit 221 by a modulation method such as amplitude displacement modulation, for example. The amplification unit 223 amplifies the signal modulated by the modulation unit 222 and transmits the amplified signal from the antenna 240.

  The receiving unit 230 includes a demodulating unit 231 that demodulates radio waves received by the antenna 240 and a decoding unit 232 that decodes a signal demodulated by the demodulating unit 231. The decoding unit 232 supplies the decoded signal to the control unit 260.

  The vibration sensor 250 is a sensor whose conduction state changes mechanically, and is turned on when there is no vibration, and turned off when there is vibration. The on / off state of the vibration sensor 250 is input to the control unit 260.

  The control unit 260 controls the transmission unit 220 and the reception unit 230. In addition, the control unit 260 includes a timer 261 and a memory 262. The timer 261 measures time by counting clocks of a clock oscillator (not shown). The control unit 260 shifts from the standby state to the activated state when the ON signal from the vibration sensor 250 is input. Then, when a certain time has elapsed after the signal is input, or when it is determined that data from the wireless tag reader 100 cannot be received as described later, the process returns to the standby state. And while starting, predetermined tag data, such as ID signal, are output to the transmission part 220 with a fixed period. The transmission unit 220 encodes, modulates and amplifies the tag data, and transmits it from the antenna 240.

  Therefore, the wireless tag 200 transmits the tag data to the outside periodically (for example, every 2.0 seconds) while the vibration sensor 250 detects vibrations at a certain interval or less. In addition, after transmitting the tag data, the control unit 260 supplies power to the receiving unit 230 from the built-in power supply 210 to make it ready for reception. The periods in which reception is possible are the first reception period and the second reception period. However, for the second reception period, as will be described later, it is determined whether or not the reception is possible depending on the reception result of the first reception period.

  During the first reception period, when the wireless tag 200 is located within the communication area of at least one wireless tag reader 100 and the tag data transmitted by the wireless tag 200 can be received, the wireless tag reader 100 Is a period during which reader data is transmitted for the first time. Therefore, the first reception period is a period determined according to the data length of the reader data from the wireless tag reader 100. However, since all the wireless tag readers 100 transmit the reader data at the same fixed transmission time, the first reception period is the same as the period when the reader data is received from one wireless tag reader 100. The first reception period starts immediately after the tag data is transmitted.

  If no reader data is received from any of the RFID tag readers 100 during this first reception period, the reception ready state is immediately terminated when the first reception period elapses, and a transition is made to a standby state. . In the present embodiment, it is determined that the reader data has not been received when the reception is not successful and the reception error is not determined. On the other hand, if reception is successful or a reception error occurs, it is determined that reader data has been received.

  Here, “successful reception” refers to a case where the final code is correctly recognized based on the signal supplied from the decoding unit 232. On the other hand, the reception error is a case where some commands such as the first command and some codes can be recognized from the signal supplied from the decoding unit 232, but not all of them can be recognized. If reception is successful, the reception ready state is terminated, and processing based on the command acquired by successful reception is performed. As this process, for example, there is an authentication process with the wireless tag reader 100.

  On the other hand, if it is determined that there is a reception error, it is determined to add a period in which reception is possible, and the reception is possible in the second reception period. The second reception period is a period for receiving the reader data transmitted by the wireless tag reader 100 at the second transmission time. As described above, the second transmission time point of the wireless tag reader 100 is set so as not to overlap with the second transmission period of the other wireless tag readers 100. Therefore, the second reception period is longer than the time obtained by adding the second transmission period of one wireless tag reader 100 by the number of wireless tag readers 100. However, it is not necessary to continue the receivable state until the second reception period ends. If reception of reader data from any one of the RFID tag readers 100 is successful even during the second reception period, the receivable state is terminated. Note that when the receivable state is terminated due to successful reception, processing based on the command acquired by successful reception is performed.

  FIG. 5 is a diagram illustrating a communication sequence between the wireless tag 200 and the wireless tag readers 100A to 100D. The reception period of the wireless tag 200 will be described with reference to FIG. In FIG. 5, the tag means the wireless tag 200, and the readers A to D mean the wireless tag readers 100A to 100D, respectively.

  At time t1, the wireless tag 200 is transmitting tag data. In the wireless tag 200, a pulse waveform rising from the time point t1 indicates a tag data transmission period. The tag data transmitted at time t1 is not received by any of the wireless tag readers 100A to 100D. Therefore, none of the RFID tag readers 100A to 100D transmits the reader data at the fixed transmission time. In each of the readers 100A to 100D, the pulse waveform rising from the time t2 is a broken line, which indicates that the reader data is not transmitted although it is the fixed transmission time. Since the reader data is not transmitted, the wireless tag 200 does not receive the reader data during the first reception period. In the wireless tag 200, the pulse waveform starting from the time point t2 is indicated by a broken line, which indicates that the reader data was not received during the first reception period. Since the wireless tag 200 has not received the reader data during the first reception period, the wireless tag 200 immediately shifts to a standby state after the first reception period has elapsed.

  Further, as indicated by the broken line in the period of t3, each wireless tag reader 100 does not transmit reader data even at the second transmission time.

  The wireless tag 200 transmits the tag data again at time t4 after 2 seconds have elapsed from time t1. This time, only the RFID tag reader 100A receives this tag data, and the other RFID tag data 100B to 100D do not receive the tag data. Therefore, the wireless tag reader 100A transmits reader data at a fixed transmission time (time t5), but the other wireless tag readers 100B to 100D do not transmit reader data. In the wireless tag reader 100A, the pulse waveform rising from the time point t5 is a solid line, whereas in the other wireless tag readers 100B to 100D, the pulse waveform rising from the time point t5 is a broken line. This is shown.

  Further, upon receiving the tag data, the wireless tag reader 100A transmits the reader data not only at the fixed transmission time but also at the second transmission time (time t6). However, since only one wireless tag reader 100A transmits tag data, data collision does not occur, so the wireless tag 200 determines that communication is successful. Therefore, the wireless tag 200 does not enter the second reception period in a receivable state. Further, the other RFID tag readers 100B to 100D do not transmit the reader data even at the second transmission time as indicated by the broken line in the pulse waveform during the period t7.

  At the next tag data transmission time (time t8) after time t4, the wireless tag 200 transmits the tag data again. This time, the tag data is received by the two wireless tag readers 100A and 100B. Therefore, the wireless tag readers 100A and 100B both transmit reader data at a fixed transmission time (time t9). On the other hand, the remaining two wireless tag readers 100C and 100D do not transmit reader data. In the wireless tag readers 100A and 100B, the pulse waveform rising from the time point t9 is a solid line, while in the remaining wireless tag readers 100C and 100D, the pulse waveform rising from the time point t9 is a broken line. Shows this.

  Since the two wireless tag readers 100A and 100B transmit reader data at time t9, the wireless tag 200 determines that a reception error has occurred (time t9). Therefore, it is set in a receivable state in the second reception period starting from time t10.

  The wireless tag readers 100A and 100B that have received the tag data also transmit the reader data at the second transmission time. However, as described above, the second transmission time point is set to a different time point for each wireless tag reader 100, and the data transmission time is set not to overlap. In the example of FIG. 5, the wireless tag reader 100A sets the start time (time t10) of the second reception period of the wireless tag 200 as the second transmission time. On the other hand, the wireless tag reader 100B transmits the reader data from time t11 after the second reader data transmission of the wireless tag reader 100A is completed. In this way, in order to prevent the data transmission times from overlapping, for example, in the time slot method, different slots may be used. A slot is a unit time for transmitting data.

  The second reception period of the wireless tag 200 is set to a period in which the reader data can be received even when the wireless tag reader 100D that has set the second transmission time at the latest time transmits the second time (t12). Time). However, the wireless tag 200 does not continue the reception state until the second reception period ends, but ends the receivable state if any one of the reader data is successfully received. Therefore, when the wireless tag reader 100A successfully receives the data transmission starting from time t9, the wireless tag 200 ends the receivable state.

  After t13, the tag data is received by the three wireless tag readers 100A to 100C. Although details are omitted, in this case as well, when a reception error occurs, the wireless tag 200 sets the second reception period, and the three wireless tag readers 100A to 100C perform the second transmission set at different timings. At the time, the reader data is transmitted for the second time.

  The effects of the present embodiment described above will be described with reference to FIG. 6A is a diagram illustrating a communication sequence of the wireless tag 200 and the wireless tag readers 100A to 100D when the present embodiment is applied, and FIG. 6B is a wireless communication when the conventional technology is applied. It is a figure which illustrates the communication sequence of tag 200 and radio | wireless tag readers 100A-D.

  In the present embodiment, the wireless tag 200 is in a receivable state during the first reception period so that the reader data transmitted from the wireless tag reader 100 can be received after transmitting the tag data. On the other hand, when receiving the tag data, the four wireless tag readers 100A to 100D transmit the reader data to the wireless tag 200 at the same fixed transmission time. Therefore, as shown in FIG. 6A, the first reception period of the wireless tag 200 is the same as the period when the reader data from one wireless tag reader 100 is received. When it is determined that the reader data has not been received during the first reception period, the wireless tag 200 immediately enters a standby state when the first reception period has elapsed.

  On the other hand, in the related art shown in FIG. 6B, the wireless tag 200 always transmits the reader data from all the wireless tag readers 100A to 100D after transmitting the tag data. Receivable state. As can be seen from the comparison between FIGS. 6A and 6B, according to the present embodiment, the period during which the wireless tag 200 is in a receivable state can be shortened, so that power consumption can be reduced.

  Further, after the RFID tag readers 100A to 100D transmit the reader data at the fixed transmission time point, the RFID tag readers 100A to 100D transmit the reader data also at the second transmission time point set at a different timing for each of the wireless tag readers 100A to 100D. On the other hand, the wireless tag 200 determines that it has received the reader data from the wireless tag reader 100 during the first reception period. If the data is a reception error, the wireless tag 200 makes the second reception period receivable. By setting the second reception period to a receivable state, reader data can be received without any data collision. Based on this reader data, the wireless tag 200 identifies the wireless tag reader 100 as in Patent Document 1. can do.

  Further, in the present embodiment, when the wireless tag 200 determines that the reception is successful based on the reader data received during the first reception period, the wireless tag 200 does not add the period in which reception is possible, A process determined based on this is executed. Therefore, the process based on the reader data can also be executed promptly.

  Further, in the present embodiment, if the wireless tag 200 determines that the reception is successful even during the second reception period, the wireless tag 200 ends the receivable state at that time. As a result, the period of the receivable state can be shortened, and a process based on successful data can be executed promptly.

  In addition, when the second reception period is set to the receivable state, the total receivable time becomes long. However, since the wireless tag 200 is carried by a person, the wireless tag 200 is out of the communication range of the wireless tag reader 100. The time that is located in is overwhelmingly long. Therefore, in the first place, when adding the second reception period.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the first embodiment described above, the second transmission time point when each wireless tag reader 100 starts transmitting tag data for the second time is a preset fixed time point. In contrast, in the second embodiment, the second transmission time point of each wireless tag reader 100 is determined each time based on whether or not the radio wave from the wireless tag 200 has been received in the first reception period (this determination). The process for the following is referred to as a second transmission time point determination process). Other configurations are the same as those in the first embodiment.

  The second transmission time determination process is performed by the controller 300 in the second embodiment. Therefore, in the second embodiment, the controller 300 corresponds to the reader control device in the claims.

  FIG. 7 is a flowchart showing the second transmission time point determination process executed by the controller 300. In the second embodiment, when each wireless tag reader 100 receives tag data from the wireless tag 200, the wireless tag reader 100 notifies the controller 300 together with its own ID (hereinafter referred to as reader ID). Note that the reader ID includes different numerical values. The contents to be notified are hereinafter referred to as notification information. When the notification information is acquired from at least one of the wireless tag readers 100, the controller 300 starts the second transmission time determination process in FIG.

  In step S1, notification information from another wireless tag reader 100 is acquired. In this step S1, if other wireless tag readers 100 have also received tag data, notification information can be acquired from the tag readers 100 as well.

  In subsequent step S2, it is determined whether or not the number of RFID tag readers 100 notified in step S1 is two or more. If this determination is negative, the second transmission time point determination process is terminated. On the other hand, if this determination is affirmative, the process proceeds to step S3. When the process proceeds to step S3, the plurality of wireless tag readers 100 transmit the reader data for the second time. In the second embodiment, the second transmission time of each wireless tag reader 100 is determined each time by executing steps S3 and S4.

  First, in step S <b> 3, the transmission order of the second reader data of each wireless tag reader 100 is determined. Since the reader data is transmitted when tag data is received from the wireless tag 200, in this step S3, the transmission order is determined for the plurality of wireless tag readers 100 that have received the notification information. In the second embodiment, the transmission order is determined from 1 in the order determined by the numerical value of the reader ID included in the notification information.

  In the subsequent step S4, the second reader data transmission time point (second time transmission) is stored by using the correspondence table that defines the correspondence between the transmission time points and the transmission order and the transmission order determined in step S3. Time). The transmission time points in the correspondence table are set as many as the number of wireless tag readers 100. Each transmission time point is a time point within the second reception period of the wireless tag 200 and different time points. In addition, the tag data started to be transmitted at the transmission time point is the second reception period of the wireless tag 200. Is set to end transmission. A table in which the transmission points set in this way correspond to the transmission order in order from the earliest transmission point is the transmission point correspondence table. From the transmission time correspondence table and the transmission order determined in step S3, the second transmission time of each wireless tag reader 100 is determined. The transmission time is a time when the tag data reception start time or reception end time is determined as a time measurement start.

  In subsequent step S5, the wireless tag reader 100 specified by the reader ID included in the notification information is instructed at the second transmission time determined in step S4.

  The wireless tag reader 100 instructed at the second transmission time in step S5 starts transmitting the second reader data at the instructed second transmission time. Similarly to the first embodiment, the wireless tag 200 ends the receivable state when reception from any one of the wireless tag readers 100 is successful.

  FIG. 8 is a diagram corresponding to FIG. 6 of the first embodiment, that is, a diagram illustrating a communication sequence between the wireless tag 200 and the wireless tag reader 100 in the second embodiment. However, FIG. 8A is a communication sequence diagram when the first embodiment is applied, and is shown for comparison with the second embodiment (FIGS. 8B and 8C).

  First, FIG. 8A will be described. At time t1, the wireless tag 200 is transmitting tag data. In the wireless tag 200, a pulse waveform rising from the time point t1 indicates a tag data transmission period. The two RFID tag readers 100B and 100D have received the tag data transmitted at time t1, but the other two RFID tag readers 100A and 100C have not received it. Therefore, the wireless tag readers 100B and 100D transmit the reader data at a fixed transmission time (time t2). On the other hand, the remaining two wireless tag readers 100A and 100C do not transmit reader data.

  Since the two wireless tag readers 100B and 100D transmit the reader data at time t2, the wireless tag 200 determines that a reception error has occurred in the first reception period (time t2). For this reason, the reception is enabled in the second reception period starting from time t3.

  The wireless tag readers 100B and 100D that have received the tag data also transmit the reader data at the second transmission time. In the first embodiment described above, the second transmission time point is set in advance to a different time point for each wireless tag reader 100. Specifically, in the wireless tag reader 100B, the time t4 that is the second transmission time point in the second reception period is set as the second transmission time point, and the wireless tag reader 100D is the time point t6 that is the fourth transmission time point. Is set at the time of the second transmission.

  Therefore, in the case of the first embodiment, the wireless tag 200 needs to continue at least in a receivable state from the time t4 to the time when the reception of the data to be transmitted by the wireless tag reader 100B is successful. Further, if the data reception from the wireless tag reader 100B is not successful, it is necessary to continue the receivable state from the time t6 to the time when the data reception started by the wireless tag reader 100D is successful.

  Next, FIG. 8B will be described. FIG. 8B is also the same as FIG. 8A. At time t1, the wireless tag 200 transmits tag data, and the two wireless tag readers 100B and 100D receive the tag data. Therefore, at the time t2, the two wireless tag readers 100B and 100D transmit the reader data, so that the wireless tag 200 determines that a reception error has occurred in the first reception period, and starts from the time t3. The reception period is in a receivable state.

  However, in 2nd Embodiment, it is set as the 2nd transmission time of each wireless tag reader 100 which transmits 2nd reader | reader data in order from the thing with an early transmission time among several transmission time candidates. That is, as shown in FIG. 8B, when the two RFID tag readers 100B and 100D transmit the reader data for the second time, the time t3, which is the first transmission time in the second reception period, and 2 The time t4 that is the first transmission time is set as the second transmission time of the wireless tag readers 100B and 100D, respectively. Considering this in comparison with the first embodiment, the second transmission time of the wireless tag reader 100B is advanced from the time t4 to the time t3, and the second transmission time of the wireless tag reader 100D is from the time t6 to the time t4. It will be early.

  When the wireless tag reader 100B starts transmitting the reader data for the second time from time t3 and the wireless tag 200 succeeds in receiving this reader data, the wireless tag reader 100B receives the wireless tag 200 in a short period of time as shown in FIG. 8B. The possible state ends.

  Next, FIG. 8C will be described. In FIG. 8C as well, the wireless tag 200 transmits tag data at time t1. However, in the example of FIG. 8C, the three wireless tag readers 100A, 100C, and 100D receive the tag data, and at the time t2, the three wireless tag readers 100A, 100C, and 100D transmit the reader data. doing. As a result, the wireless tag 200 determines that a reception error has occurred in the first reception period, and is in a receivable state for the second reception period starting from time t3.

  In the example of FIG. 8C, since the three RFID tag readers 100A, 100C, and 100D transmit the reader data for the second time, the time t3, which is the first transmission time in the second reception period, and the second time The transmission time point t4 and the third transmission time point t5 are set as the second transmission time points of the wireless tag readers 100A, 100C, and 100D, respectively. Considering this in comparison with the first embodiment, the second transmission time of the wireless tag reader 100C is advanced from the time t5 to the time t4, and the second transmission time of the wireless tag reader 100D is from the time t6 to the time t5. It will be early.

  If the wireless tag reader 100A starts transmitting reader data for the second time from time t3 and the wireless tag 200 succeeds in receiving this reader data, the wireless tag 200 receives the wireless tag 200 in a short period of time as shown in FIG. 8C. The possible state ends. Even if the reader data transmitted by the wireless tag reader 100A is not successfully received for some reason, the wireless tag readers 100C and 100D continuously read the reader data from the second transmission time t4 and t5. Since transmission is performed, reception succeeds early.

  As described above, according to the second embodiment described above, when the wireless tag 200 determines that the reception is successful even within the second reception period, the wireless tag 200 ends the receivable state at that time. In addition, as the second transmission time point of each wireless tag reader 100 that transmits the reader data for the second time, a plurality of transmission time point candidates (t3 to t6 in FIG. 8) are used in order from the earliest transmission time point. As a result, the time during which the wireless tag 200 is in a receivable state in the second reception period can be shortened. Therefore, the wireless tag 200 can further reduce power consumption.

(Modification 1 of 2nd Embodiment)
In the second embodiment described above, the controller 300 executes the second transmission time point determination process of FIG. 7, but any one wireless tag reader 100 may execute the process. In this case, when receiving the tag data, the wireless tag reader 100 that does not execute the second transmission time determination process transmits the above notification information to the wireless tag reader 100 that executes the second transmission time determination process. In this way, since a wireless tag system without the controller 300 is possible, there is a possibility that the installation area of the entire system can be reduced and the cost can be reduced.

(Modification 2 of the second embodiment)
In the second modification of the second embodiment, when the four wireless tag readers 100 receive the tag data, they are notified to all other wireless tag readers 100 together with their own IDs (hereinafter referred to as reader IDs). To do. Each wireless tag reader 100 executes the second transmission time point determination process shown in FIG. 9 in order to determine its own second transmission time point. This process is executed at regular intervals.

  In step S11, it is determined whether or not a signal (that is, tag data) is received from the wireless tag 200. If this determination is negative, the process in FIG. 9 ends. On the other hand, if it is affirmation determination, it will progress to step S12. In step S12, notification information is transmitted to the other wireless tag reader 100. This notification information is the same as that in the second embodiment, and is information that includes reception of tag data and a reader ID.

  In step S13, notification information is acquired from another wireless tag reader 100. In the following step S14, it is determined whether or not the number of the RFID tag readers 100 that have acquired the notification information in step S13 is 1 or more (that is, whether or not there is a notification from at least one other RFID tag reader 100). This step S14 is executed when the tag data itself is received from the wireless tag 200. Therefore, step S14 determines whether or not there are a plurality of wireless tag readers 100 that have received tag data including themselves. This step S14 corresponds to the transmission reader number judging means in the claims. Even when the determination in step S14 is a negative determination, the processing in FIG. 9 ends.

  On the other hand, if step S14 is affirmative, the process proceeds to step S15. In the case of proceeding to step S15, a plurality of wireless tag readers 100 including itself transmit the reader data for the second time. Therefore, by executing the following steps S15 and S16, the second transmission time of itself is determined each time.

  In step S15, the second reader data transmission order is determined. Specifically, the priority order of the other RFID tag reader 100 that has received the notification information is compared with its own priority order, and the transmission order is determined in the order of priority. Here, it is assumed that the priority order is determined by the reader ID. For example, if the reader ID is 2 and the reader ID of another wireless tag reader 100 that has received the notification information is 4, the transmission order of the wireless tag reader 100 with the reader ID 4 is 1 and the transmission order of the wireless tag reader 100 with the reader ID 4 is 2. .

  In step S16, using the same correspondence table as in the second embodiment and the transmission order determined in step S15, the second reader data transmission time is determined.

  After executing step S16, the wireless tag reader 100 starts transmitting the reader data for the second time at the second transmission time determined in step S16.

  When each wireless tag reader 100 executes the above processing, a plurality of transmission time point candidates are set as the second transmission time point of each wireless tag reader 100 that transmits the second reader data, as in the second embodiment described above. Among these, it can be used in order from the earliest transmission point. Therefore, since the time during which the wireless tag 200 is in the receivable state in the second reception period can be shortened, the power consumption of the wireless tag 200 can be further reduced.

  Further, even in the second modification of the second embodiment, since the controller 300 is not necessary, a wireless tag system that does not include the controller 300 is possible. Therefore, the installation area of the entire system can be reduced, and the cost can be reduced. There is a possibility that it can be reduced.

(Modification 3 of 2nd Embodiment)
In the third modification of the second embodiment, the controller 300 performs the second transmission time point determination process as in the second embodiment. However, in the second embodiment, the transmission order is determined based on the reader ID. In the third modification of the second embodiment, the transmission order is determined based on the received radio wave intensity. The wireless tag reader 100 also includes the received radio wave intensity when the tag data is received in addition to the fact that the tag data has been received and the reader ID in the notification information.

  FIG. 10 is a flowchart showing the second transmission time determination process executed by the controller 300 in the third modification of the second embodiment. 10, steps that perform the same processing as in FIG. 7 are assigned the same step numbers as in FIG. That is, the second transmission time point determination process shown in FIG. 10 is the same as that in FIG. 7 except for step S3-1.

  In step S3-1, the transmission order of the second reader data of each wireless tag reader 100 is determined. Specifically, in this step S3-1, the received signal strength included in the notification information acquired from each wireless tag reader 100 is compared, and the higher the received signal strength is, the higher the priority is. The transmission order is determined in order from 1 in descending order.

  In the third modification of the second embodiment, the wireless tag reader 100 that has received a signal from the wireless tag 200 with high received signal strength determines that the second transmission time is the earlier transmission time. Further, the more wireless tag reader 100 that can receive tag data with a higher received signal strength, the easier it is to communicate with the wireless tag 200. Therefore, the wireless tag 200 is more likely to be successfully received early in the second reception period, and as a result, the wireless tag 200 may be able to reduce the time during which reception is possible in the second reception period. More improved.

(Other modifications of the second embodiment)
In the second embodiment described above, the second transmission time is always determined using the correspondence table. However, the present invention is not limited to this mode. Similarly to the first embodiment, in the second embodiment, each wireless tag reader 100 stores the second transmission time in advance, and uses the correspondence table only when a change is necessary. The second transmission time may be changed.

  In this case, as long as all the wireless tag readers 100 can receive the tag data, it is not necessary to change the second transmission time of each wireless tag reader 100. Accordingly, in step S2 of FIG. 7 executed by the controller 300 (or any one of the wireless tag readers 100), when n is the number of readers notified and x is the total number of wireless tag readers 100, 2 ≦ n ≦ x−1. May be judged.

  Moreover, in 2nd Embodiment other than the modification 3 mentioned above, the transmission order was determined using the priority order decided from reader ID. However, the present invention is not limited to this, and when each wireless tag reader 100 stores a second transmission time point similar to that of the first embodiment, the second transmission time points are set so as not to overlap each other. Therefore, the transmission order may be determined on the assumption that the earlier the second transmission time is, the higher the priority is.

  Also, in the second modification of the second embodiment in which each wireless tag reader 100 determines its second transmission time point, the priority order is determined by the received signal strength as in the third modification of the second embodiment. It may be.

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

(Modification 1 common to the first and second embodiments)
For example, in the above-described embodiment, the wireless tag reader 100 transmits the same reader data for the first transmission and the second transmission. However, the first transmission can be data intended only to cause a reception error. In this case, it is only necessary to know the presence or absence of radio waves from the wireless tag reader 100, and there is no need to make the reception successful with the data transmitted at the first time. That is, there is no need to send a regular command. Therefore, it is possible to make the data shorter than the data transmitted at the second time within the range of the data amount that can cause a reception error. Accordingly, the first reception period of the wireless tag 200 can be made shorter than that in the above-described embodiment.

  If the wireless tag reader 100 does not transmit a regular command in the first transmission, the wireless tag 200 is always in the second transmission if it is located within the communication range of at least one of the wireless tag readers 100. Need to be received. However, also in the above-described embodiment, when the communication areas of the plurality of wireless tags 200 are present in overlapping areas, it is necessary to perform the second reception. As described above, in the first modification, the first reception period can be shortened. Therefore, when the ratio of overlapping areas is high, the first modification is effective. Conversely, when the ratio of overlapping areas is low, the aspect of the above-described embodiment is preferable.

(Modification 2 common to the first and second embodiments)
Further, in the above-described embodiment, the wireless tag 200 is in a receivable state in the second reception period when it is determined as a reception error as a result of demodulating and decoding the radio wave received in the first reception period. Instead of this, the reception strength of the radio wave received during the first reception period may be compared with a predetermined range judgment strength to determine whether or not the second reception period is in a receivable state.

  More specifically, if the reception intensity of the radio wave received during the first reception period is lower than the range determination intensity, it is determined that the radio wave from the wireless tag reader 100 has not been received during the first reception period. In this case, the wireless tag reader 100 is determined not to be within the communication range, and immediately enters a standby state when the first reception period has elapsed. On the other hand, if the reception intensity of the radio wave received during the first reception period is equal to or greater than the range determination intensity, it is determined that the radio wave is transmitted from at least one of the RFID tag readers 100. That is, it is determined that the communication area is within at least one of the wireless tag readers 100. In this case, in order to receive a command from the wireless tag reader 100, the second reception period is set to a receivable state.

  Depending on the type of circuit, there is a circuit in which data from a plurality of RFID tag readers 100 are duplicated, and a situation in which the RFID tag reader 100 cannot be specified and cannot be communicated is simply noise and does not cause a communication error. However, in this way, when it is determined whether or not the communication area is within the range based on the reception intensity, such a circuit can be used, so that the range of component selection is widened. In addition, since the reception intensity of the non-modulated wave is determined, there is an advantage that demodulation and decoding are not required when determining whether or not the second reception period is in a receivable state.

  In this case, the wireless tag reader 100 may transmit an unmodulated wave (a transmission wave that does not superimpose modulated data on a carrier wave) without transmitting data in the first transmission.

(Other variations)
In the above-described embodiment, as illustrated in FIG. 5, the first reception period and the second reception period are not continuous. That is, the second reception period is provided separately from the first reception period. However, the second reception period may not be provided separately from the first reception period, and the first reception period may be extended so that the second data from the wireless tag reader 100 can be received.

1: wireless tag system, 100: wireless tag reader, 101: communication area, 110: control unit, 111: memory, 112: timer, 120: transmission unit, 121: encoding unit, 122: modulation unit, 123: amplification unit, 130 : Receiver, 131: demodulator, 132: decoder, 140: antenna, 200: wireless tag, 210: built-in power supply, 220: transmitter, 221: encoder, 222: modulator, 223: amplifier, 230: Receiving unit, 231: demodulating unit, 232: decoding unit, 240: antenna, 250: vibration sensor, 260: control unit, 261: timer, 262: memory, 300: controller

Claims (12)

A wireless tag system comprising a wireless tag and a plurality of wireless tag readers communicating with the wireless tag,
When the plurality of wireless tag readers receive a signal from the wireless tag, the plurality of wireless tag readers are determined based on a reception time point and transmit a radio wave to the wireless tag at a common transmission time point common to the plurality of wireless tag readers. After transmitting the radio wave at the time, at the second transmission time set at a different timing for each wireless tag reader, transmit transmission data that can identify the wireless tag reader to the wireless tag,
The wireless tag is
After transmitting a signal, the first reception period during which radio waves that may be transmitted from the wireless tag reader at the time of the common transmission can be received is set to a receivable state, and radio waves from the wireless tag reader are not received during the first reception period. If it is determined that the first reception period has elapsed, the standby state is entered,
Based on the determination that the radio wave from the wireless tag reader has been received during the first reception period, the necessity for additional reception is determined, and if it is determined that additional reception is necessary, the second transmission time point from the wireless tag reader to receive the transmission data to be transmitted in, and add the period of the reception state,
The wireless tag reader transmits the transmission data to the wireless tag at the common transmission time point,
The wireless tag system according to claim 1, wherein the wireless tag determines that additional reception is necessary when a radio wave received during the first reception period is a reception error. A wireless tag system comprising a wireless tag and a plurality of wireless tag readers communicating with the wireless tag,
When the plurality of wireless tag readers receive a signal from the wireless tag, the plurality of wireless tag readers are determined based on a reception time point and transmit a radio wave to the wireless tag at a common transmission time point common to the plurality of wireless tag readers. After transmitting the radio wave at the time, at the second transmission time set at a different timing for each wireless tag reader, transmit transmission data that can identify the wireless tag reader to the wireless tag,
The wireless tag is
After transmitting a signal, the first reception period during which radio waves that may be transmitted from the wireless tag reader at the time of the common transmission can be received is set to a receivable state, and radio waves from the wireless tag reader are not received during the first reception period. If it is determined that the first reception period has elapsed, the standby state is entered,
Based on the determination that the radio wave from the wireless tag reader has been received during the first reception period, the necessity for additional reception is determined, and if it is determined that additional reception is necessary, the second transmission time point from the wireless tag reader to receive the transmission data to be transmitted in, and add the period of the reception state,
The wireless tag determines that it has not received the radio wave from the radio tag reader during the first reception period if the reception intensity of the radio wave received during the first reception period is lower than a preset area determination strength, Based on the elapse of the first reception period, a standby state is established, and when the reception strength of the radio wave received during the first reception period is equal to or greater than the range determination strength, it is determined that additional reception is necessary. A featured wireless tag system. In claim 1 ,
If the wireless tag determines that the reception is successful based on the radio wave received during the first reception period, the wireless tag executes a process that is determined based on the transmission data that has been successfully received without adding a period in which reception is possible. A wireless tag system characterized by that. In claim 2 ,
The wireless tag reader is characterized in that a transmission time of radio waves transmitted at the common transmission time is shorter than a transmission time of transmission data transmitted at the second transmission time. In claim 2 or 4 ,
The wireless tag system, wherein the wireless tag reader transmits an unmodulated wave to the wireless tag at the common transmission time. In any one of Claims 1-5 ,
In the wireless tag system, the wireless tag sequentially determines whether or not reception is successful during the period of the additional reception enabled state, and ends the reception enabled state when reception is successful. In claim 6 ,
When there are a plurality of wireless tag readers that transmitted radio waves at the common transmission time point, the second transmission time points of the plurality of wireless tag readers are a plurality of transmission time points that are different from each other within the period of the receivable state added by the wireless tag. A second transmission time determination means for determining
The second transmission time point determination means determines the second transmission time points of the plurality of RFID tag readers in order from the earliest time point among the plurality of transmission time points set in advance within the period of the receivable state,
The wireless tag system, wherein the plurality of wireless tag readers transmit the transmission data at a second transmission time determined by the second transmission time determination means. In claim 7 ,
A reader control device for controlling the plurality of wireless tag readers;
When the plurality of wireless tag readers receive a signal from the wireless tag, notification information for notifying the reception is transmitted to the reader control device,
The reader control device includes the second transmission time point determination means, and further includes a transmission time point instruction means for instructing the plurality of wireless tag readers to determine a second transmission time point determined by the second transmission time point determination means. A featured wireless tag system. In claim 7 ,
Any one of the plurality of wireless tag readers comprises the second transmission time point determining means,
Among the plurality of wireless tag readers, the wireless tag reader that does not include the second transmission time point determination means determines that the second transmission time point determination information is received when a signal from the wireless tag is received. To a wireless tag reader equipped with means,
In addition, the wireless tag reader including the second transmission time point determination unit instructs the other wireless tag reader of the second transmission time point to the other wireless tag reader among the second transmission time points determined by the second transmission time point determination unit. A wireless tag system comprising transmission time instruction means for performing transmission. In claim 8 or 9 ,
The plurality of wireless tag readers are configured to transmit the notification information including a received signal strength of a signal received from the wireless tag,
The second transmission time point determination means presets the second transmission time points of the plurality of wireless tag readers within the period of the receivable state in descending order of received signal strength of signals received from the wireless tags by the plurality of wireless tag readers. A wireless tag system that determines an earlier transmission time among a plurality of transmitted transmission times. In claim 6 ,
The plurality of wireless tag readers are:
When receiving a signal from the wireless tag, notification information including priority information indicating that it has been received and priority order is transmitted to another wireless tag reader,
Number of transmission readers that determine whether there are a plurality of wireless tag readers that transmitted radio waves at the time of the common transmission based on the notification information from other wireless tag readers and whether or not they received a signal from the wireless tag Judgment means,
When it is determined by the transmission reader number determination means that there are a plurality of wireless tag readers that have transmitted radio waves at the common transmission time point, a plurality of transmission time points set in advance within a period of a receivable state added by the wireless tag. Among them, a second transmission time point determination means for determining a time point that is different from the second transmission time point of the other RFID tag reader and that is as early as possible as its second transmission time point,
The second transmission time point determination means determines its second transmission time point from the plurality of transmission time points based on its own priority and priority information included in the notification information,
The wireless tag system, wherein the transmission data is transmitted at a second transmission time determined by the second transmission time determination means. In claim 11 ,
The plurality of wireless tag readers include the received signal strength of the signal received from the wireless tag as the priority information in the notification information, and transmits the information to another wireless tag reader.
In the case where the device itself also receives a signal from the wireless tag, the second transmission time determination means determines the received signal strength included in the notification information received from the other wireless tag reader and the received signal strength of the signal received from the wireless tag by itself. And the second transmission time point is determined from the plurality of transmission time points, assuming that the higher the received signal strength is, the higher the priority is.

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