Communication Method

Abstract

A communication method of the present invention includes: a carrier sensing step (S10) of performing carrier sensing at predetermined time intervals; a transmission step (S11) of, when a signal transmitted by another radio tag to an access point is not detected during performance of the carrier sensing and when not in a transmission suspended state, transmitting first data including ID information of an own radio tag to the access point; a command interpretation step (S12) of, when a signal is detected during performance of the carrier sensing and the signal is not a signal transmitted by another radio tag to the access point, regarding the detected signal as a signal transmitted from the access point and interpreting a command included in the signal; and a frequency changing step (S13) of, when it is interpreted that the signal includes a command instructing a frequency change, changing the radio frequency of a signal transmitted by the own radio tag.

Description

[Technical Field]

[0001] The present disclosure relates to a communication method and a wireless tag, and more particularly to a communication method for an active wireless tag, a communication method for an access point that receives radio waves from an active wireless tag, and an active wireless tag. [Background technology]

[0002] There are wireless tags that are attached to products and used to track their location. Wireless tags are also called electronic tags, IC (Integrated Circuit) tags, wireless IC tags, contactless IC tags, and RFID (Radio Frequency Identification) tags. Wireless tags are divided into passive types that are powered by electricity from an external device and emit radio waves, and active types that are powered by a built-in battery and emit radio waves themselves.

[0003] For example, Patent Document 1 proposes a system that can track containers using active wireless tags, and discloses that this makes it possible to provide a real-time wireless tracking system within a limited area with a fixed boundary. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-529049 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the frequencies available for active RFID tags may vary from region to region. For example, the available frequency in Japan is 920 MHz. Meanwhile, the available frequency in China is 830 MHz, the available frequency in Europe is 868 MHz, and the available frequency in the United States is 915 MHz.

[0006] In other words, when tracking across regions where the available frequencies for wireless tags are different, it is necessary to change the frequency.

[0007] Furthermore, in many cases, costs cannot be spent on RF tags used for tracking, etc., and relatively inexpensive RF tags without a means for receiving data are used, which means that the initially set frequency cannot be changed.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a communication method and a wireless tag that can change the frequency of an active wireless tag that does not have a means for receiving data. [Means for solving the problem]

[0009] A communication method in one embodiment of the present disclosure is a communication method performed by one of a plurality of wireless tags in a communication system consisting of an access point and a plurality of wireless tags, and includes: a carrier sensing step of performing carrier sensing at predetermined intervals; a transmission step of transmitting first data to the access point including ID information that is information for uniquely identifying the one wireless tag, if a signal transmitted to the access point by a wireless tag other than the one wireless tag is not detected during the carrier sensing and if the transmission is not stopped; a command interpretation step of detecting a signal during the carrier sensing and if the signal is not a signal transmitted to the access point by a wireless tag other than the one wireless tag, interpreting a command included in the signal transmitted from the access point, assuming that the detected signal is a signal transmitted from the access point; and a frequency change step of changing the radio frequency of the signal transmitted by the one wireless tag, if the command interpretation step interprets the signal to include a command instructing a frequency change.

[0010] This allows an active wireless tag that does not have the means to receive data to use the carrier sense function to interpret commands sent by an access point, thereby allowing the frequency used by the wireless tag to be changed.

[0011] Here, for example, in the transmitting step, if the command interpretation step interprets the signal as including a command instructing to stop transmission and change frequency, and if a signal transmitted from the different wireless tag to the access point is not detected during the carrier sensing, second data in which information indicating that the command has been received is added to the first data and transmitted to the access point, and in the frequency changing step, if the command interpretation step interprets the signal as including a command instructing to stop transmission and change frequency, after the second data is transmitted, the wireless frequency of the signal transmitted from the one wireless tag is changed, and the communication method may further include a control step of stopping only the execution of the transmitting step after the second data is transmitted in the transmitting step until the command interpretation step interprets that the signal transmitted from the access point detected during the carrier sensing includes a command instructing to resume transmission.

[0012] This allows the wireless tag to use the carrier sense function to interpret the commands sent by the access point, thereby changing the frequency used by the wireless tag and stopping signal transmission.

[0013] Also, for example, in the transmitting step, if the command interpretation step interprets that the signal includes a command to stop transmission, and if the signal transmitted by the different wireless tag to the access point is not detected during the carrier sensing, second data in which information indicating that the command has been received is added to the first data is transmitted to the access point, and the communication method may further include a control step of stopping only the execution of the transmitting step after the second data has been transmitted in the transmitting step.

[0014] This allows the wireless tag to use the carrier sense function to interpret the command sent by the access point, thereby stopping signal transmission from the wireless tag.

[0015] Also, for example, in the frequency change step, if the command interpretation step interprets that the signal includes a command instructing a frequency change, the radio frequency of the signal transmitted by the one wireless tag is changed, and in the control step, when the radio frequency of the signal transmitted by the one wireless tag is changed in the frequency change step, execution of the transmission step may be resumed.

[0016] This allows the wireless tag to use the carrier sense function to interpret the commands sent by the access point, allowing the frequency used by the wireless tag to be changed and signal transmission that has been stopped to be resumed.

[0017] Furthermore, for example, the information indicating that the command has been received is an ACK (Acknowledgement).

[0018] Furthermore, for example, the carrier sensing step may include an intensity calculation step of calculating the intensity of a signal received while the carrier sensing is being performed, a first detection step of determining that a signal transmitted by a wireless tag other than the one wireless tag is being detected during a period in which a first average intensity, obtained by dividing the intensity calculated in the intensity calculation step by a first period and averaging the intensity, exceeds a first threshold value, and a second detection step of determining that a signal other than a signal transmitted by a wireless tag other than the one wireless tag is being detected by determining a pattern consisting of a number of times that exceeds a second threshold value and a number of times that is equal to or less than the second threshold value, obtained by dividing the intensity calculated in the intensity calculation step by a second period that is shorter than the first period and averaging the intensity.

[0019] This allows the wireless tag to use the carrier sense function to simultaneously perform normal carrier sense and carrier sense used to interpret commands sent by the access point.

[0020] Furthermore, for example, the carrier sensing step may include an intensity calculation step of calculating the intensity of a signal received while the carrier sensing is being performed, and a first detection step of determining that a signal transmitted by a wireless tag other than the one wireless tag is being detected during a period in which a first average intensity, obtained by dividing the intensity calculated in the intensity calculation step by a first period and averaging the intensity, exceeds a first threshold; and the second carrier sensing step may include an intensity calculation step of calculating the intensity of a signal received while the carrier sensing is being performed, and a second detection step of determining that a signal other than a signal transmitted by a wireless tag other than the one wireless tag is being detected by determining a pattern in which a second averaging period, obtained by dividing the intensity calculated in the intensity calculation step by a second period shorter than the first period and averaging the intensity, exceeds a second threshold and a second threshold or less.

[0021] This allows the wireless tag to use the carrier sense function to alternately perform normal carrier sense and carrier sense used to interpret commands sent by the access point.

[0022] Also, for example, in the command interpretation step, the command contained in the signal transmitted from the access point may be interpreted based on a combination of the number of second averaging periods that exceed a second threshold and the number that are less than or equal to the second threshold, which constitute the pattern determined in the second detection step.

[0023] Furthermore, a communication method in one embodiment of the present disclosure is a communication method performed by an access point of a communication system consisting of the access point and a plurality of wireless tags, and includes an ID information collection step of collecting ID information, which is information for uniquely identifying each of the plurality of wireless tags; a signal transmission step of broadcasting to the plurality of wireless tags at predetermined intervals a signal including a command instructing the plurality of wireless tags to change a first frequency currently being used by the plurality of wireless tags to a second frequency; and a signal stopping step of stopping broadcasting the signal including the command when it is confirmed that information indicating that the command has been received has been received from all of the plurality of wireless tags.

[0024] With this, the access point can send commands to a plurality of active wireless tags that it manages and that do not have a means for receiving data, and change the frequency used by the wireless tags.

[0025] Here, for example, the method may further include a recognition step of recognizing that the multiple wireless tags are moving to an area where the second frequency different from the first frequency currently being used by the multiple wireless tags is required, and recognizing that the multiple wireless tags have started moving to the area, and a confirmation step of confirming that the multiple wireless tags have entered the area, wherein in the signal transmission step, if it is recognized in the recognition step that the multiple wireless tags have started moving to the area, a signal instructing the multiple wireless tags to change the first frequency currently being used by the multiple wireless tags to the second frequency and including a command instructing them to stop transmitting may be broadcast at predetermined intervals, and further, if it is confirmed in the confirmation step that the multiple wireless tags have entered the area, a signal including a command instructing them to resume transmission may be broadcast at predetermined intervals to the multiple wireless tags.

[0026] Furthermore, for example, the method may further include a recognition step of recognizing that the multiple wireless tags have started to move into an area where it is necessary to use the second frequency different from the first frequency currently being used by the multiple wireless tags, and a confirmation step of confirming that the multiple wireless tags have entered the area, wherein the signal transmission step may further include, if it is recognized in the recognition step that the multiple wireless tags have started to move into the area, broadcasting to the multiple wireless tags at predetermined intervals a signal including a command instructing them to stop transmitting, and if it is confirmed in the confirmation step that the multiple wireless tags have entered the area, broadcasting to the multiple wireless tags at predetermined intervals a signal including a command instructing them to change from the first frequency currently being used by the multiple wireless tags to the second frequency.

[0027] In addition, a wireless tag in one embodiment of the present disclosure is one of a plurality of wireless tags in a communication system consisting of an access point and a plurality of wireless tags, and includes: a carrier sense unit that performs carrier sensing at predetermined intervals; an output control unit that, when a signal transmitted to the access point by a wireless tag other than the one wireless tag is not detected during the carrier sensing and when the transmission is not stopped, transmits first data to the access point including ID information that is information for uniquely identifying the one wireless tag; an interpretation unit that detects a signal during the carrier sensing and, when the signal is not a signal transmitted to the access point by a wireless tag other than the one wireless tag, interprets a command included in the signal transmitted from the access point, assuming that the detected signal is a signal transmitted from the access point; and a frequency control unit that, when the interpretation unit interprets the command to include an instruction to change the frequency, changes the radio frequency of the signal transmitted by the one wireless tag.

[0028] These comprehensive or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0029] According to the communication method etc. of the present disclosure, it is possible to change the frequency of an active type wireless tag that does not have a means for receiving data. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a communication system according to an embodiment. [Figure 2] FIG. 2 is a block diagram illustrating a functional configuration of the AP according to the embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of a hardware configuration of a computer that realizes the functions of the AP according to the embodiment by software. [Figure 4] FIG. 4 is a diagram conceptually illustrating an example of a signal including a command broadcast by a signal transmitting unit according to the embodiment. [Figure 5] FIG. 5 is a block diagram showing the functional configuration of the wireless tag according to the embodiment. [Figure 6] FIG. 6 is a diagram for conceptually explaining the execution of the first carrier sense according to the embodiment. [Figure 7] FIG. 7 is a diagram for conceptually explaining the execution of the second carrier sense according to the embodiment. [Figure 8A] FIG. 8A is a diagram illustrating an example of execution of the first carrier sense according to the embodiment. [Figure 8B] FIG. 8B is a diagram illustrating an example of execution of the second carrier sense according to the embodiment. [Figure 9] FIG. 9 is a diagram showing an example of detailed functional blocks of a control circuit included in the LSI unit shown in FIG. [Figure 10A] FIG. 10A is an example of the first data according to the embodiment. [Figure 10B] FIG. 10B is an example of the second data according to the embodiment. [Figure 11A] FIG. 11A is a diagram illustrating an example of an operation sequence of a communication system according to a comparative example. [Figure 11B] FIG. 11B is a diagram illustrating an example of an operation sequence of the communication system according to the embodiment. [Figure 12A] FIG. 12A is a diagram for explaining the operation of an AP and a plurality of wireless tags according to CASE 1. In FIG. [Figure 12B] FIG. 12B is a diagram for explaining the operation of the AP and multiple wireless tags according to CASE 1. [Figure 12C] FIG. 12C is a diagram for explaining the operation of the AP and multiple wireless tags according to CASE 1. [Figure 12D] FIG. 12D is a diagram for explaining the operation of the AP and multiple wireless tags according to CASE 1. [Figure 12E] FIG. 12E is a diagram for explaining the operation of the AP and multiple wireless tags according to CASE 1. [Figure 12F] FIG. 12F is a diagram for explaining the operation of the AP and multiple wireless tags according to CASE 1. [Figure 13A] FIG. 13A is a diagram for explaining the operation of the AP and multiple wireless tags according to CASE 3. [Figure 13B] FIG. 13B is a diagram for explaining the operation of the AP and multiple wireless tags according to CASE 3. [Figure 14] FIG. 14 is a flowchart showing an outline of the operation of the wireless tag according to the embodiment. [Figure 15] FIG. 15 is a flowchart showing an example of detailed operation of the wireless tag according to the embodiment. [Figure 16] FIG. 16 is a flowchart showing an outline of the operation of the AP according to the embodiment. [Figure 17]FIG. 17 is a flowchart illustrating an example of detailed operation of the AP according to the embodiment. [Figure 18] FIG. 18 is a flowchart illustrating an example of detailed operation of the AP according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. The numerical values, shapes, materials, components, component placement and connection configurations, usage procedures, communication procedures, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in the independent claims that represent the highest concept of the present disclosure will be described as optional components. Furthermore, each figure is not necessarily an exact illustration. In each figure, substantially identical components are assigned the same reference numerals, and redundant explanations are omitted or simplified.

[0032] (Embodiment) Hereinafter, a wireless tag and an AP (access point) according to an embodiment will be described with reference to the drawings.

[0033] [1 Communication System] FIG. 1 is a diagram illustrating an example of the configuration of a communication system 1 according to an embodiment. As illustrated in FIG. 1, the communication system 1 includes a plurality of wireless tags 10 and an AP 20 that can change the frequencies used by the plurality of wireless tags 10 under its management. For example, the communication system 1 can be used in a system that identifies, manages, or tracks the locations of items to which the wireless tags 10 are assigned. The wireless tags 10 are described in detail below, but they are active wireless tags that do not have a data reception function and only have a carrier sense function. The AP 20 is described in detail below, but the AP 20 may be capable of using a global positioning system (GPS).

[0034] Each device will be described below.

[0035] [1.2 AP20] The configuration of the AP 20 according to this embodiment will be described below. Fig. 2 is a block diagram showing the functional configuration of the AP 20 according to this embodiment.

[0036] The AP 20 is implemented by a computer or the like and is a wireless base station that manages multiple wireless tags 10. The AP 20 also functions as an end point of a communication network and can be connected to the communication network wirelessly. In the following description, the AP 20 will be described as being capable of using GPS, but this is not limiting and it is sufficient if the area in which the AP 20 is located can be recognized via the communication network.

[0037] In this embodiment, the AP 20 includes an information collection unit 201, a recognition unit 202, a confirmation unit 203, a signal output control unit 204, and a memory 205, as shown in FIG.

[0038] Before describing the functional configuration of the AP 20 according to this embodiment, an example of the hardware configuration of the AP 20 according to this embodiment will be described with reference to FIG.

[0039] [1.2.1 Hardware Configuration] FIG. 3 is a diagram showing an example of the hardware configuration of a computer 1000 that realizes the functions of the AP 20 according to the embodiment by software.

[0040] 3, the computer 1000 is a computer including an input device 1001, an output device 1002, a CPU 1003, an internal storage 1004, a RAM 1005, a reading device 1007, a transmitting / receiving device 1008, and a bus 1009. The input device 1001, the output device 1002, the CPU 1003, the internal storage 1004, the RAM 1005, the reading device 1007, and the transmitting / receiving device 1008 are connected by the bus 1009.

[0041] The input device 1001 is a user interface device such as an input button, a touch pad, a touch panel display, etc., and accepts user operations. Note that the input device 1001 may be configured to accept voice operations, remote operations using a remote control, etc., in addition to accepting user touch operations.

[0042] The output device 1002 is also used as the input device 1001, and is configured by a touch pad or a touch panel display, etc., and notifies the user of information that should be made known to the user.

[0043] The internal storage 1004 is a flash memory, etc. The internal storage 1004 may also store in advance at least one of a program for realizing the functions of the AP 20 and an application that uses the functional configuration of the AP 20.

[0044] The RAM 1005 is a random access memory, and is used to store data and the like when a program or application is executed.

[0045] The reading device 1007 reads information from a recording medium such as a USB (Universal Serial Bus) memory. The reading device 1007 reads the above-mentioned programs and applications from a recording medium on which the programs and applications are recorded, and stores the programs and applications in the built-in storage 1004.

[0046] The transmitting / receiving device 1008 is a communication circuit for performing wireless or wired communication. The transmitting / receiving device 1008 may communicate with, for example, a server device or a cloud connected to a network, download the above-mentioned programs and applications from the server device or the cloud, and store them in the built-in storage 1004.

[0047] The CPU 1003 is a central processing unit that copies programs and applications stored in the internal storage 1004 to the RAM 1005 and sequentially reads and executes instructions contained in the programs and applications from the RAM 1005. Note that the instructions may also be executed directly from the internal storage 1004.

[0048] Next, each functional configuration of the AP 20 according to this embodiment will be described.

[0049] [1.2.2 Information Collection Unit 201] The information collection unit 201 collects ID information, which is information for uniquely identifying each of the multiple wireless tags 10. In this embodiment, the information collection unit 201 collects ID information of all wireless tags under the management of the AP 20 via a communication network and stores the ID information in the memory 205. Here, the communication network is, for example, a cellular wireless communication network.

[0050] [1.2.3 Recognition unit 202] The recognition unit 202 recognizes that the multiple wireless tags 10 have started to move to an area where it is necessary to use a second frequency different from the first frequency currently being used by the multiple wireless tags 10. In this embodiment, the recognition unit 202 may recognize that the wireless tags 10 have started to move, for example, from the location information of the multiple wireless tags 10 under the management of the AP 20. Alternatively, the recognition unit 202 may recognize that the multiple wireless tags 10 have started to move by acquiring information about departure, such as departure time, acquired from the ID information of the multiple wireless tags 10 via a communication network.

[0051] The recognition unit 202 may recognize that the multiple wireless tags 10 are moving to an area where a second frequency different from the first frequency currently being used by the multiple wireless tags 10 is required. In this embodiment, the recognition unit 202 may acquire, for example, via a communication network, information on the area to which the wireless tags 10 are moving from the ID information of the wireless tags 10 under the management of the AP 20. This allows the recognition unit 202 to recognize that the multiple wireless tags 10 are moving to an area where a frequency different from the frequency currently being used is used.

[0052] [1.2.4 Confirmation Section 203] The confirmation unit 203 confirms (recognizes) that multiple wireless tags 10 have come under the control of the AP 20. The confirmation unit 203 also confirms (recognizes) the area where the AP 20 is located using a GPS or the like. In the present embodiment, the following description will be given assuming that the AP 20 accompanies the movement of multiple wireless tags 10. Therefore, the confirmation unit 203 confirms the position of the AP 20 using a GPS and confirms that the position of the AP 20 has entered the area, thereby being able to confirm that multiple wireless tags 10 have entered the area. Even when the AP 20 does not use a GPS but recognizes the area where the AP 20 is located via a communication network, the operation of the confirmation unit 203 is similar, and therefore a description thereof will be omitted.

[0053] The AP 20 is not limited to accompanying the movement of the multiple wireless tags 10, and the AP 20 does not have to accompany the movement of the multiple wireless tags 10. In this case, the wireless tags 10 may be managed by the APs 20 present in the area from which the multiple wireless tags 10 move and the area to which they move.

[0054] [1.2.5 Signal output control unit 204] The signal output control unit 204 controls the output of a signal (radio wave of a specific frequency). The signal output control unit 204 includes a signal transmitting unit 2041 and a signal stopping unit 2042, as shown in FIG.

[0055] [1.2.5.1 Signal Transmitter 2041] The signal transmitting unit 2041 broadcasts, at predetermined intervals, a signal including a command to instruct the plurality of wireless tags 10 to change the first frequency currently being used by the plurality of wireless tags 10 to the second frequency.

[0056] For example, suppose that the recognition unit 202 recognizes that multiple wireless tags 10 have started to move into the area. In this case, the signal transmission unit 2041 broadcasts, at predetermined intervals, a signal that instructs the multiple wireless tags 10 to change the first frequency that the multiple wireless tags 10 are using to the second frequency and that includes a command to stop transmission.

[0057] Then, when the confirmation unit 203 confirms that multiple wireless tags 10 have entered the area, the signal transmission unit 2041 broadcasts a signal including a command to the multiple wireless tags 10 to resume transmission at predetermined intervals.

[0058] In this way, the signal transmission unit 2041 may cause the multiple wireless tags 10 to change the frequency (radio frequency) they use and stop transmitting when the multiple wireless tags 10 start moving (depart) to the area.

[0059] Note that when the recognition unit 202 recognizes that multiple wireless tags 10 have started to move into the area, the signal transmission unit 2041 does not have to broadcast a signal including a command instructing the multiple wireless tags 10 to change from the first frequency currently in use to the second frequency. That is, the signal transmission unit 2041 may broadcast a signal including a command instructing the multiple wireless tags 10 to stop transmission at predetermined intervals. Then, when the confirmation unit 203 confirms that multiple wireless tags 10 have entered the area, the signal transmission unit 2041 may broadcast a signal including a command instructing the multiple wireless tags 10 to change from the first frequency currently in use to the second frequency at predetermined intervals.

[0060] In this way, the signal transmitting unit 2041 may simply cause the multiple wireless tags 10 to stop transmitting signals when the multiple wireless tags 10 start moving (depart) toward the area, and may change the frequency (radio frequency) used after the multiple wireless tags 10 enter the area.

[0061] 4 is a diagram conceptually illustrating an example of a signal including a command broadcast by the signal transmitting unit 2041 according to the embodiment. The signal including the command is broadcast via the antenna of the AP 20.

[0062] Commands to change the frequency, stop transmission, or resume transmission can be included in the signal and broadcast using on-off keying (OOK), which periodically changes the signal strength, as shown in Figure 4, for example.

[0063] The method of including these commands in the signal is not limited to the example shown in Fig. 4. To create a pattern signal corresponding to a specific command, the signal strength may be changed to a threshold or less at regular intervals a predetermined number of times by on-off modulation.

[0064] [1.2.5.2 Signal Stop 2042] When the signal stopping unit 2042 confirms that it has received information indicating that the command has been received from all of the wireless tags 10, it stops broadcasting the signal including the command.

[0065] [1.2.6 Memory 205] The memory 205 is an example of a storage medium, and is configured, for example, by a rewritable nonvolatile memory such as a hard disk drive or a solid state drive. A storage medium equivalent to the memory 205 may exist on the cloud.

[0066] [1.3 Wireless tag 10] Next, the configuration of the wireless tag 10 according to this embodiment will be described below. Fig. 5 is a block diagram showing the functional configuration of the wireless tag 10 according to this embodiment.

[0067] The wireless tag 10 is an active type wireless tag that is powered by a built-in battery and emits radio waves by itself, and has only a carrier sense function without a data reception function. The wireless tag 10 is attached (attached) or assigned to an item such as a product. In this embodiment, the wireless tag 10 can apply the carrier sense function to obtain a signal (interpret a command) instructing a change in frequency (radio frequency), etc. As shown in FIG. 5, the wireless tag 10 includes a battery 11, a sensor 12 that senses the state of the item, and an LSI (Large Scale Integration) unit 13.

[0068] The battery 11 is built into the wireless tag 10 and supplies power to the LSI unit 13 .

[0069] The sensor 12 senses the state of the article to which the wireless tag 10 is attached or attached, and transmits the sensing result to the LSI unit 13. Note that the sensor 12 is not essential.

[0070] The LSI unit 13 will be described later.

[0071] [1.3.1 LSI part 13] The LSI unit 13 is composed of an IC chip or the like that is driven by the battery 11. The LSI unit 13 is connected to an antenna, and when wireless tags 10 other than its own wireless tag 10 (hereinafter referred to as other wireless tags 10) are not emitting radio waves (signals), the LSI unit 13 can transmit radio waves (signals) to the AP 20 by emitting radio waves (signals) itself. The LSI unit 13 is realized by a CPU, a memory 134, and the like.

[0072] In this embodiment, the LSI unit 13 includes an RF (Radio Frequency) unit 130 , a radio wave intensity measurement unit 131 , a carrier sense unit 132 , a control circuit 133 , a memory 134 , and a data modulation unit 135 .

[0073] [1.3.1.1 RF section 130] The RF unit 130 includes a TX 1301 and an RX 1302, and transmits and receives signals (radio waves) via an antenna. The TX 1301 is a transmitting circuit, and converts a signal modulated by the data modulation unit 135 into radio waves in the frequency band used by the wireless tag 10 via the antenna, thereby transmitting the signal via radio waves. The RX 1302 is a receiving circuit, and converts radio waves in the frequency band used by the wireless tag 10 received by the antenna into a signal (received signal), and transmits the signal to the radio wave intensity measurement unit 131.

[0074] [1.3.1.2 Radio wave intensity measurement unit 131] The radio wave intensity measurement unit 131 calculates the intensity of a signal received while carrier sensing is being performed. In this embodiment, the radio wave intensity measurement unit 131 measures the intensity of the radio wave received by the RF unit 130 by calculating the intensity of the received signal in the frequency band used by the wireless tag 10, which is transmitted from the RF unit 130 while carrier sensing is being performed. The radio wave intensity measurement unit 131 calculates RSSI (Received Signal Strength Indication) as the intensity of the received signal.

[0075] [1.3.1.3 Carrier sense unit 132] The carrier sense unit 132 performs carrier sensing at predetermined intervals. More specifically, the carrier sense unit 132 monitors the radio wave intensity measured by the radio wave intensity measurement unit 131 while performing carrier sensing, thereby checking whether the frequency band used by the wireless tag 10 itself (wireless tag 10) is occupied by radio waves from other wireless tags or the like. The carrier sense unit 132 transmits the check result to the control circuit 133.

[0076] In this embodiment, the carrier sense unit 132 monitors the strength of the received signal calculated by the radio wave intensity measurement unit 131 while performing carrier sensing, and detects whether other wireless tags 10 are transmitting signals and whether the AP 20 is transmitting signals. Hereinafter, normal carrier sense for detecting whether other wireless tags 10 are transmitting radio waves will be referred to as "first carrier sense," and pattern recognition carrier sense for detecting whether the AP 20 is transmitting a signal will be referred to as "second carrier sense." The carrier sense unit 132 may simultaneously perform the first carrier sense and the second carrier sense while performing carrier sensing at predetermined intervals, or may alternate between the first carrier sense and the second carrier sense when performing carrier sensing at predetermined intervals. The following description will be given taking as an example a case where the first carrier sense and the second carrier sense are alternately performed.

[0077] Fig. 6 is a diagram for conceptually explaining the execution of first carrier sense according to the embodiment. As shown in Fig. 6(a), when another wireless tag 10 is transmitting radio waves, the radio wave intensity as shown in Fig. 6(b) is measured by the radio wave intensity measurement unit 131. Then, as long as the measured radio wave intensity as shown in Fig. 6(b) exceeds the first threshold, the carrier sense unit 132 detects that the other wireless tag 10 is in a busy state, transmitting a signal.

[0078] 6(b), that is, while the radio wave intensity measured by the radio wave intensity measurement unit 131 is equal to or lower than the threshold, the carrier sense unit 132 detects that the other wireless tag 10 is in an idle state where the other wireless tag 10 is not transmitting a signal. When the other wireless tag 10 is in an idle state, the control circuit 133, which will be described later, can transmit radio waves in the frequency band used by the wireless tag 10. In other words, by performing the first carrier sense, the wireless tag 10 can transmit radio waves while avoiding radio wave collision with other wireless tags 10.

[0079] FIG. 7 is a diagram conceptually illustrating the execution of second carrier sense according to an embodiment. As shown in (a) of FIG. 7, when AP 20 broadcasts a signal including a command, the radio wave intensity measurement unit 131 measures the radio wave intensity (not shown). Then, when there is a period in which the radio wave intensity measured by the radio wave intensity measurement unit 131 exceeds a second threshold, the carrier sense unit 132 detects a repetitive pattern (reception intensity pattern) of the radio wave intensity, as shown in (b) of FIG. 7. Note that, as shown in (b) of FIG. 7, the repetitive pattern can be defined by the number of periods per fixed cycle in which the radio wave intensity measured by the radio wave intensity measurement unit 131 is equal to or less than the second threshold. The second threshold may be different from or the same as the first threshold.

[0080] Next, a specific example of the execution of the first carrier sense will be described with reference to FIG. 8A.

[0081] FIG. 8A is a diagram illustrating an example of execution of the first carrier sense according to the embodiment.

[0082] During carrier sensing, suppose that the radio wave intensity measurement unit 131 receives a received signal from the RX 1302, as shown in (a) of FIG. 8A, and calculates the strength of the received signal (signal strength) as shown in (b) of FIG. 8A. Then, as shown in (c) of FIG. 8A, the carrier sense unit 132 divides the calculated received signal strength by a first period and averages it. The carrier sense unit 132 determines a period in which the averaged first average strength exceeds a first threshold as a busy state, and determines a period in which it does not exceed a first threshold as an idle state. The carrier sense unit 132 then transmits the determination result to the control circuit 133 as a first carrier sense result.

[0083] Next, a specific example of the execution of the second carrier sense will be described with reference to FIG. 8B.

[0084] FIG. 8B is a diagram illustrating an example of execution of the second carrier sense according to the embodiment.

[0085] During carrier sensing, suppose that the radio wave intensity measurement unit 131 receives a received signal from the RX 1302, as shown in (a) of FIG. 8B, and calculates the strength of the received signal (signal strength) as shown in (b) of FIG. 8B. Then, as shown in (c) of FIG. 8B, the carrier sense unit 132 divides and averages the calculated received signal strength by a second period shorter than the first period, and determines a pattern (received strength pattern) consisting of the number of times the averaged second averaged strength exceeds a second threshold and the number of times it is equal to or less than the second threshold. Then, the carrier sense unit 132 transmits the determination result to the control circuit 133 as a second carrier sense result.

[0086] 1.3.1.4 Control Circuit 133 When the control circuit 133 receives the first carrier sense result from the carrier sense unit 132, it transmits the ID information of the control circuit 133 (wireless tag 10) stored in memory 134 to the data modulation unit 135. When the control circuit 133 receives the second carrier sense result from the carrier sense unit 132, it stores the pattern (reception intensity pattern) included in the second carrier sense result in a partial area (pattern buffer 134a) of the memory 134. If the control circuit 133 can interpret a command using the transmitted second carrier sense result, it adds information indicating that the command has been received, such as an ACK (Acknowledgement), to the ID information of the control circuit 133 (wireless tag 10) stored in memory 134 and transmits the added information to the data modulation unit 135. The control circuit 133 executes an operation according to the interpreted command.

[0087] FIG. 9 is a diagram showing an example of detailed functional blocks of the control circuit 133 included in the LSI unit 13 shown in FIG.

[0088] 9, the control circuit 133 includes a pattern match determination unit 1331, an interpretation unit 1332, an RF frequency control unit 1333, and an RF output control unit 1334. The control circuit 133 uses a control program stored in the memory 134 to execute the functions of the pattern match determination unit 1331, the interpretation unit 1332, the RF frequency control unit 1333, and the RF output control unit 1334. The pattern match determination unit 1331, the interpretation unit 1332, the RF frequency control unit 1333, and the RF output control unit 1334 may be implemented by hardware.

[0089] [1.3.1.4.1 Pattern Matching Determination Unit 1331] The pattern match determination unit 1331 performs a matching determination on a repeating pattern (reception intensity pattern) included in the second carrier sense result transmitted from the carrier sense unit 132 and stored in the pattern buffer 134a, which is a partial area of ​​the memory 134. More specifically, the pattern match determination unit 1331 determines whether or not the repeating pattern (reception intensity pattern) included in the second carrier sense result corresponds to any one of a plurality of preset patterns.

[0090] [1.3.1.4.2 Interpretation Section 1332] When the interpretation unit 1332 detects a signal during carrier sensing and the detected signal is not a signal transmitted from another wireless tag to the AP 20, the interpretation unit 1332 determines that the detected signal is a signal transmitted from the AP 20 and interprets the command contained in the signal transmitted from the AP 20. More specifically, the interpretation unit 1332 interprets the command contained in the signal transmitted from the AP 20 based on a combination of the number of times the second averaging period constituting the repeating pattern contained in the second carrier sense result exceeds the second threshold and the number of times it is equal to or less than the second threshold. For example, the interpretation unit 1332 interprets the command contained in the signal as a command to stop transmission and change the frequency, or as a command to resume transmission. The interpretation unit 1332 also interprets the command contained in the signal as a command to stop transmission or a command to change the frequency.

[0091] In this embodiment, if the repeating pattern (reception intensity pattern) included in the second carrier sense result corresponds to one of multiple pre-set patterns, the interpretation unit 1332 interprets the command corresponding to the corresponding pattern as the command included in the signal transmitted from AP20.

[0092] [1.3.1.4.3 RF frequency control unit 1333] When the interpretation unit 1332 interprets that the signal transmitted from the AP 20 includes a command instructing a frequency change, the RF frequency control unit 1333 changes the radio frequency of the signal transmitted by itself (the wireless tag 10).

[0093] In addition, if the interpretation unit 1332 interprets that the signal transmitted from the AP 20 includes a command to stop transmission and change the frequency, the RF frequency control unit 1333 changes the radio frequency of the signal it transmits after the second data containing the ID information plus an ACK is transmitted.

[0094] As described above, ACK is an example of information indicating that a command has been received.

[0095] [1.3.1.4.4 RF output control unit 1334] The RF output control unit 1334 controls the output of a signal to be transmitted to the AP 20, and controls the stopping or restarting (starting) of signal transmission to the AP 20.

[0096] For example, if the RF output control unit 1334 does not detect a signal transmitted from another wireless tag 10 to the AP 20 while performing carrier sensing and if no instruction to stop transmission has been given, it transmits first data including its own (wireless tag 10's) ID information to the AP 20.

[0097] Fig. 10A is an example of the first data according to the embodiment. As shown in Fig. 10A, the first data according to the embodiment is ID information of the wireless tag 10 included in the data field.

[0098] Furthermore, for example, when the interpretation unit 1332 interprets that the signal transmitted from the AP 20 includes a command instructing to stop transmission and change the frequency and when the RF output control unit 1334 does not detect a signal transmitted from another wireless tag 10 to the AP 20 during carrier sensing, the RF output control unit 1334 may transmit second data, which is the first data plus an ACK, to the AP 20. In this case, after the second data is transmitted, the RF output control unit 1334 stops transmitting signals to the AP 20 until the interpretation unit 1332 interprets that the signal transmitted from the AP 20 detected during carrier sensing includes a command instructing to resume transmission. Then, when the RF frequency control unit 1333 changes the radio frequency of the signal transmitted by the RF output control unit 1334 (wireless tag 10), the RF output control unit 1334 may resume transmitting signals to the AP 20.

[0099] Fig. 10B is an example of the second data according to the embodiment. As shown in Fig. 10B, the second data according to the embodiment has an ACK added to the ID information (first data) of the wireless tag 10 included in the data field. The ACK may be added to an empty area in the data field.

[0100] For example, if the interpretation unit 1332 interprets that the signal transmitted from the AP 20 includes a command to stop transmission, and if no signal transmitted from another wireless tag 10 to the AP 20 is detected during carrier sensing, the RF output control unit 1334 may transmit second data in which an ACK is added to the first data to the AP 20. In this case, the RF output control unit 1334 stops transmitting signals to the AP 20 after the second data is transmitted.

[0101] [1.3.1.5 Memory 134] The memory 134 is an example of a storage medium such as a flash memory. The memory 134 is not limited to being arranged inside the control circuit 133 as shown in FIG. 5 , but may be arranged outside the control circuit 133 and inside or outside the LSI unit 13.

[0102] In this embodiment, memory 134 stores a control program that causes LSI unit 13 to operate radio wave intensity measurement unit 131, carrier sense unit 132, and data modulation unit 135. Memory 134 also stores a control program that causes control circuit 133 to operate pattern match determination unit 1331, interpretation unit 1332, RF frequency control unit 1333, and RF output control unit 1334. A portion of memory 134 is also used by control circuit 133 as a buffer (pattern buffer 134a).

[0103] [1.3.1.6 Data Modulation Unit 135] The data modulation unit 135 performs modulation to transmit data onto the radio waves. More specifically, the data modulation unit 135 performs modulation to transmit the ID information of its own wireless tag 10, transmitted from the control circuit 133, onto the radio waves.

[0104] [2 Operation of Communication System 1] Next, the operation of the communication system 1 configured as above, which is made up of a plurality of wireless tags 10 and the AP 20, will be described.

[0105] [2.1 Operation sequence of communication system 1] First, before explaining the operation sequence of the communication system 1 according to this embodiment, as a comparative example, we will explain the operation sequence of a communication system according to the comparative example having wireless tags 90A and 90B that can only perform normal carrier sensing (first carrier sensing).

[0106] FIG. 11A is a diagram illustrating an example of an operation sequence of a communication system according to a comparative example.

[0107] 11A, in the communication system according to the comparative example, each of the wireless tag 90A and the wireless tag 90B performs carrier sensing at predetermined intervals. More specifically, the wireless tag 90A performs normal carrier sensing (corresponding to first carrier sensing) at predetermined intervals, and when it detects that the other wireless tag 90B is in an idle state where it is not transmitting radio waves, it transmits ID information (corresponding to first data) of the wireless tag 90A to the AP 91. Similarly, the wireless tag 90B performs normal carrier sensing (corresponding to first carrier sensing) at predetermined intervals, and when it detects that the other wireless tag 90A is in an idle state where it is not transmitting radio waves, it transmits ID information (corresponding to first data) of the wireless tag 90B to the AP 91.

[0108] FIG. 11B is a diagram showing an example of an operation sequence of the communication system 1 according to the embodiment.

[0109] 11B, in the communication system 1 according to the present embodiment, the wireless tag 10A and the wireless tag 10B each perform normal carrier sensing and carrier sensing for pattern recognition at predetermined intervals. More specifically, the wireless tags 10A and 10B alternately perform first carrier sensing (normal carrier sensing) and second carrier sensing (carrier sensing for pattern recognition) at predetermined intervals. Here, it is assumed that the AP 20 broadcasts a signal including a command to stop transmission and change the frequency for a fixed period at predetermined intervals.

[0110] When the wireless tag 10A performs a first carrier sense and detects that the other wireless tag 10B is in an idle state not transmitting radio waves, it transmits the ID information (first data) of the wireless tag 10A to the AP 20. Similarly, when the wireless tag 10B performs a first carrier sense and detects that the other wireless tag 10A is in an idle state not transmitting radio waves, it transmits the ID information (first data) of the wireless tag 10B to the AP 20.

[0111] Furthermore, when the wireless tag 10A performs a second carrier sense and detects a repeating pattern (reception intensity pattern) from the received signal, it interprets the command contained in the signal from the detected repeating pattern (reception intensity pattern). If the wireless tag 10A can interpret the command contained in the signal, it performs the next transmission timing, i.e., a first carrier sense, and if it detects an idle state, it transmits second data, which is the ID information of the wireless tag 10A plus an ACK, to the AP 20.

[0112] Similarly, when the wireless tag 10B performs a second carrier sense and detects a repeating pattern (reception intensity pattern) from the received signal, it interprets the command contained in the signal from the detected repeating pattern. If the wireless tag 10B can interpret the command contained in the signal, it performs the next transmission timing, i.e., a first carrier sense, and if it detects an idle state, it transmits second data, which is the ID information of the wireless tag 10B plus an ACK, to the AP 20.

[0113] [2.2 Usage scenarios of communication system 1] Next, a usage scenario in which the communication system 1 is used for logistics will be described. A usage scenario in which the AP 20 accompanies the movement of a plurality of wireless tags 10 under its management, i.e., the movement of the wireless tags 10 attached to articles, will be referred to as CASE 1 and will be described with reference to Figs. 12A to 12F.

[0114] <case1> 12A and 12B are diagrams for explaining the operation of the AP 20 and the multiple wireless tags 10 according to CASE 1. FIG.

[0115] FIG. 12A is a diagram showing an example of the operation of the AP 20 and a plurality of wireless tags 10 in a scene where the communication system 1 according to the embodiment is used for logistics within an area A. In FIG.

[0116] 12A, each of the plurality of wireless tags 10 alternately performs first carrier sensing and second carrier sensing, and transmits first data including ID information at regular intervals (every predetermined period). Here, each of the plurality of wireless tags 10 is used for logistics within area A, and therefore transmits a signal at the radio frequency (first frequency) used in area A.

[0117] Meanwhile, the AP 20 collects and stores ID information of multiple wireless tags 10 under its management. The AP 20 is also connected to a cellular wireless communication network in area A. The AP 20 stores the ID information, but if the ID information is lost when the power is turned off, the stored ID information may be uploaded to a specific server or cloud.

[0118] 12B and 12C are diagrams illustrating an example of the operation of the AP 20 and the multiple wireless tags 10 when the communication system 1 according to the embodiment departs from an area A toward another area B. In FIG.

[0119] 12B, the AP 20 recognizes that the multiple wireless tags 10 have started moving by acquiring information about departure from the location information of the multiple wireless tags 10 it manages or from the ID information of the multiple wireless tags 10 via a wireless communication network. Here, the AP 20 accesses a specific server or cloud via the wireless communication network, for example, and acquires area information (area B) to which the wireless tags 10 are to move from the ID information of the wireless tags 10 it manages. Then, as shown in FIG. 12B, the AP 20 broadcasts a signal including a command to instruct the multiple wireless tags 10 to change from the first frequency to the second frequency and to stop transmission.

[0120] Meanwhile, each of the multiple wireless tags 10 alternately performs first carrier sense and second carrier sense, and transmits first data including ID information at regular intervals (at predetermined intervals). The multiple wireless tags 10 perform second carrier sense, interpret the command contained in the signal, and operate in accordance with the interpreted command. As shown in FIG. 12B, the multiple wireless tags 10 transmit an ACK at the next transmission timing in accordance with the interpreted command, and then stop transmitting signals thereafter. After transmitting the ACK, the multiple wireless tags 10 change the wireless frequency they use from the first frequency to the second frequency in accordance with the interpreted command.

[0121] 12C shows a state in which all of the multiple wireless tags 10 change their wireless frequencies from the first frequency to the second frequency and stop transmitting signals, and a state in which the AP 20 stops broadcasting as a result of receiving ACKs from all of the multiple wireless tags 10. Note that even if the AP 20 is unable to receive ACKs from all of the multiple wireless tags 10, the AP 20 may stop broadcasting if it is unable to receive signals from other wireless tags 10 even after a certain period of time has passed since it last received an ACK from one of the multiple wireless tags 10.

[0122] FIG. 12D is a diagram showing an example of the operation of the AP 20 and the multiple wireless tags 10 when the communication system 1 according to the embodiment enters area B.

[0123] 12D, each of the multiple wireless tags 10 alternately performs only the first carrier sense and the second carrier sense at the radio frequency (second frequency) used in area B. Meanwhile, when the AP 20 confirms that it has entered area B using GPS or the like, it broadcasts a signal including a command to start transmission to the multiple wireless tags 10 at the second frequency. Note that if the AP 20 is powered off after leaving area A and the ID information stored at the time of departure is lost, the AP 20 may access a specific server or cloud to acquire the ID information.

[0124] 12E and 12F are diagrams showing an example of the operation of the AP 20 and the plurality of wireless tags 10 until all of the wireless tags 10 under the management of the AP 20 start transmitting in the communication system 1 according to the embodiment in area B. FIG.

[0125] The example shown in Fig. 12E shows how each of the multiple wireless tags 10 starts (resumes) signal transmission of the first data in accordance with a command interpreted by executing the second carrier sense. Meanwhile, the AP 20 continues broadcasting until it acquires the first data from all of the multiple wireless tags 10. Meanwhile, the example shown in Fig. 12F shows how the AP 20 acquires the first data from all of the multiple wireless tags 10, and then stops broadcasting.

[0126] <case2> In CASE 1, it has been described that at the time of departure, the AP 20 recognizes that the destination of the multiple wireless tags 10 under its management is area B, but this is not limited to this. The AP 20 does not have to recognize that the destination of the multiple wireless tags 10 under its management is area B, and a case in which the AP 20 cannot recognize that the destination is area B will be described as CASE 2. In other words, CASE 2 is a usage scenario in which the AP 20 accompanies the movement of the multiple wireless tags 10 under its management, but cannot recognize that the destination of the multiple wireless tags 10 is area B. The following description will be made with reference to Figures 12A to 12F. Descriptions of operations similar to those in CASE 1 will be omitted, and only the differences will be described.

[0127] 12B in CASE 2, the AP 20 recognizes that the multiple wireless tags 10 have started moving by acquiring information about departure from the ID information of the multiple wireless tags 10 via the wireless communication network or the location information of the multiple wireless tags 10 it manages. Note that the AP 20 in CASE 2 cannot acquire area information (area B) to which the wireless tags 10 are moving. Therefore, the AP 20 broadcasts a signal including a command to stop transmission to the multiple wireless tags 10. In this way, the AP 20 in CASE 2 does not broadcast a signal including a command to change from the first frequency to the second frequency.

[0128] Meanwhile, each of the multiple wireless tags 10 alternately performs first carrier sense and second carrier sense and transmits first data including ID information at regular intervals. In CASE 2, in Fig. 12B, the multiple wireless tags 10 transmit ACK at the next transmission timing in accordance with the interpreted command and then stop transmitting signals thereafter.

[0129] 12D in CASE 2, each of the multiple wireless tags 10 alternately performs only first carrier sense and second carrier sense at not only the first frequency but also at a wireless frequency used in another area such as area B. On the other hand, when the AP 20 confirms using GPS or the like that it has entered area B, it broadcasts a signal at the second frequency to the multiple wireless tags 10, the signal including a command to change from the first frequency to the second frequency. In this way, the AP 20 in CASE 2 does not broadcast a signal including a command to start transmission.

[0130] 12E in CASE 2, each of the multiple wireless tags 10 changes its wireless frequency from the first frequency to the second frequency in accordance with the command interpreted by executing the second carrier sense, and starts (resumes) signal transmission of the first data at the second frequency. Meanwhile, the AP 20 continues broadcasting until it has acquired the first data from all of the multiple wireless tags 10. The subsequent process is the same as in CASE 1, and therefore will not be described further.

[0131] <case3> In CASE 1 and CASE 2, the AP 20 is described as accompanying the movement of the multiple wireless tags 10 that it manages, but this is not limited to this. The AP 20 that manages the multiple wireless tags 10 may change for each region. Below, a usage scenario will be described as CASE 3, in which the AP 20 does not accompany the movement of the multiple wireless tags 10 that it manages and is used in the region at the time of departure, and is unable to recognize that the destination of the multiple wireless tags 10 is region B.

[0132] 13A and 13B are diagrams for explaining the operation of the AP 20 and the multiple wireless tags 10 according to CASE 3. Fig. 13A shows an example of the operation of the AP 20 and the multiple wireless tags 10 in a scene where the communication system 1 according to the embodiment is used for logistics within an area A. Note that the example of the operation shown in Fig. 13A is the same as that explained in Fig. 12A, and therefore explanation thereof will be omitted.

[0133] FIG. 13B shows an example of the operations of the AP 20 and the multiple wireless tags 10 when the communication system 1 according to the embodiment prepares to depart from the area A.

[0134] In FIG. 13B, the AP 20 broadcasts a signal including a command to stop transmission upon receiving an instruction that multiple wireless tags 10 are leaving area A. As described above, the AP 20 in CASE 3 does not broadcast a signal including a command to change the first frequency to the second frequency. Meanwhile, each of the multiple wireless tags 10 alternately performs first carrier sense and second carrier sense, and transmits first data including ID information at regular intervals. In FIG. 13B, the multiple wireless tags 10 transmit an ACK at the next transmission timing in accordance with the interpreted command, and then stop transmitting signals thereafter. Since the subsequent operations are similar to those in CASE 2 except for the scene in FIG. 12D, a description thereof will be omitted.

[0135] 12D in CASE 3, each of the multiple wireless tags 10 alternately performs only first and second carrier senses at not only the first frequency but also the wireless frequencies used in other regions. Meanwhile, when AP 20 in region B receives an indication that multiple wireless tags 10 have entered region B, it accesses a specific server or cloud and acquires their ID information. Then, AP 20 in region B broadcasts a signal at the second frequency that includes a command to instruct the multiple wireless tags 10 to change from the first frequency to the second frequency. In this way, AP 20 in region B in CASE 3 does not broadcast a signal that includes a command to start transmission.

[0136] [2.3 Operation of the wireless tag 10] Next, the operation of the wireless tag 10 according to this embodiment will be described.

[0137] FIG. 14 is a flowchart showing an outline of the operation of the wireless tag 10 according to the embodiment.

[0138] First, the wireless tag 10 performs carrier sensing at predetermined intervals (S10).

[0139] Next, if the wireless tag 10 does not detect a signal transmitted from another wireless tag 10 to the AP 20 while performing carrier sensing and is not in a transmission stop state, it transmits first data including its own (wireless tag 10) ID information to the AP 20 (S11).

[0140] Next, if the wireless tag 10 detects a signal while performing carrier sensing and the signal is not a signal transmitted from another wireless tag 10 to the AP 20, the wireless tag 10 determines that the detected signal is a signal transmitted from the AP 20 and interprets the command contained in the signal transmitted from the AP 20 (S12).

[0141] Next, if the signal is interpreted as including a command to change the frequency, the wireless tag 10 changes the wireless frequency of the signal that it transmits (S13).

[0142] FIG. 15 is a flowchart showing an example of detailed operation of the wireless tag 10 according to the embodiment.

[0143] First, the wireless tag 10 periodically (at every predetermined period) performs carrier sensing (S101). For example, the wireless tag 10 periodically alternates between first carrier sensing and second carrier sensing, but may also simultaneously perform first carrier sensing and second carrier sensing.

[0144] Next, the wireless tag 10 checks whether or not it has detected a signal from another wireless tag 10 during the carrier sense and whether or not it has received a transmission stop instruction (S102).

[0145] In step S102, if a signal from another wireless tag 10 is detected or a stop signal is received (No in step S102), the wireless tag 10 checks whether the detected signal can be received correctly (S103).

[0146] In step S103, if the wireless tag 10 can correctly receive the detected signal (No in step S103), it checks whether it is detecting signals from other wireless tags 10 (S104). Note that the case where the wireless tag 10 cannot correctly receive the detected signal (Yes in step S103) corresponds to the case where signals from other wireless tags 10 overlap, or the case where signals from other wireless tags 10 and the AP 20 overlap.

[0147] In step S104, if the wireless tag 10 has not detected a signal from another wireless tag 10 (No in step S104), it determines that it has detected a signal from the AP 20 (Yes in S105) and interprets the command included in the signal from the AP 20 (S106). When the wireless tag 10 interprets the command included in the signal from the AP 20, it changes, for example, the command reception status (ACK) stored in its internal memory (memory 134) to a status indicating that it has received a command from the AP. The command included in the signal from the AP 20 may be a command to stop signal transmission from itself (wireless tag 10) (transmission disabled), a command to change the wireless frequency used by itself (wireless tag 10) to a specific wireless frequency, etc.

[0148] The process of step S105 may be omitted. If the answer is Yes in step S103, Yes in step S104, or No in step S105, the process returns to step S101.

[0149] In step S102, if no signal is detected from another wireless tag 10 and no stop signal is received (Yes in step S102), the wireless tag 10 checks whether the command was interpreted in the previous carrier sense (second carrier sense) (S107).

[0150] In step S107, if the command was not interpreted in the previous execution of the second carrier sense (No in step S107), the wireless tag 10 transmits the ID information to the AP 20 (S108).

[0151] In step S107, if the command was interpreted in the previous execution of the second carrier sense (Yes in step S107), the wireless tag 10 adds an ACK to the ID information and transmits it to the AP 20 (S109).

[0152] Next, the wireless tag 10 executes an operation according to the command interpreted in the previous execution of the second carrier sense (S110). After execution, the wireless tag 10 returns to step S101.

[0153] In step S110, for example, if the command included in the signal from the AP 20 is a command to stop (disable) signal transmission from the wireless tag 10 itself (wireless tag 10), the wireless tag 10 stops subsequent signal transmission after transmitting ACK to the AP 20. Then, the wireless tag 10 changes, for example, the transmission enable / disable status (TxStop) stored in the internal memory (memory 134) to a status indicating that signal transmission from the wireless tag 10 itself has been stopped.

[0154] Also, in step S110, for example, if the command included in the signal from the AP 20 is a command instructing the wireless tag 10 to change the wireless frequency used by itself (the wireless tag 10) to a specific wireless frequency, the wireless tag 10 changes the wireless frequency used to the specific wireless frequency after transmitting ACK to the AP 20. Then, the wireless tag 10 may change, for example, the frequency selection state (Freq) stored in the internal memory (memory 134) to a state indicating that the specific wireless frequency is selected.

[0155] [2.4 AP20 Operation] Next, the operation of the AP 20 according to this embodiment will be described.

[0156] FIG. 16 is a flowchart showing an outline of the operation of the AP 20 according to the embodiment.

[0157] First, the AP 20 collects (S20) ID information for each of the wireless tags 10. More specifically, the AP 20 collects ID information that is information for uniquely identifying each of the wireless tags 10 that it manages.

[0158] Next, the AP 20 broadcasts, at predetermined intervals, a signal including a command to instruct the plurality of wireless tags 10 to change the first frequency being used by the plurality of wireless tags 10 to the second frequency (S21).

[0159] Next, when the AP 20 confirms that it has received the command from all of the wireless tags 10, it stops broadcasting the signal including the command (S22).

[0160] Figures 17 and 18 are flowcharts showing an example of detailed operation of the AP 20 according to the embodiment. In Figures 17 and 18, it is assumed that the AP 20 and a plurality of wireless tags 10 under its management are used in logistics, and that the wireless tags 10 move from area A to area B, where the wireless tags 10 can use different radio frequencies. Figure 17 shows the operation of the AP 20 in area A, and Figure 18 shows the operation of the AP 20 in area B.

[0161] First, as shown in FIG. 17, the AP 20 recognizes (confirms) that it is in area A using a GPS or the like (S201).

[0162] Next, the AP 20 collects all ID information of the wireless tags 10 under its management (S202). For example, the AP 20 connects to a cellular wireless communication network in area A to collect and store ID information of multiple wireless tags 10 under its management.

[0163] Next, while in area A, the AP 20 recognizes that the wireless tag 10 will move to area B, which uses a different frequency (radio frequency) for signal transmission (S203). For example, the AP 20 accesses a specific server or cloud via a wireless communication network and acquires area B, the destination of the wireless tag 10, from the ID information of the wireless tag 10 it manages, thereby recognizing that the wireless tag 10 it manages will move to area B.

[0164] Next, the AP 20 transmits a signal including a command to change the frequency and stop transmission to the wireless tags 10 that it manages (S204). In this embodiment, the AP 20 broadcasts a signal including a command to instruct a plurality of wireless tags 10 to change the first frequency to the second frequency and to stop transmission, thereby transmitting the signal including the command to the wireless tags 10 that it manages. Note that the AP 20 may transmit a signal including a command to stop transmission without including a command to change the frequency.

[0165] Next, if the AP 20 can confirm that all wireless tags 10 have received the command (Yes in S205), it stops sending the command to the wireless tags it manages (S206). In this embodiment, the AP 20 stops sending the command to the wireless tags it manages by stopping broadcasting as a result of receiving ACKs from all of the wireless tags 10 it manages. Note that if it cannot confirm that all wireless tags 10 have received the command in step S205 (No in S205), it executes step S205 again to check whether it has confirmed that all wireless tags 10 have received the command.

[0166] Next, the operation of the AP 20 will be described with reference to FIG.

[0167] First, as shown in FIG. 18, the AP 20 recognizes (confirms) that it is in area B using a GPS or the like (S301). When the AP 20 moves from area A to area B together with the wireless tag 10 managed by the AP 20, the AP 20 can recognize that it has entered area B by recognizing that it is in area B using a GPS or the like. Note that when the AP 20 does not move together with the wireless tag 10 managed by the AP 20, the AP 20 may recognize (confirm) that the wireless tag 10 under its management has entered area B upon receiving an instruction from the user of the AP 20 or the like. The AP 20 may also obtain ID information of the wireless tag 10 under its management from a specific server or cloud uploaded by the AP 20 in area A via a wireless communication network.

[0168] Next, the AP 20 transmits a signal including a command to instruct the wireless tags 10 under its management to resume transmission (S302). In this embodiment, the AP 20 broadcasts a signal including a command to start transmission to the multiple wireless tags 10 under its management at the frequency of area B. In addition, in Fig. 17, when the AP 20 transmits a signal including a command to stop transmission without including a command to change the frequency, it can transmit a signal including a command to change the frequency instead of a command to resume transmission.

[0169] Next, if the AP 20 can confirm that all wireless tags 10 have received the command (Yes in S303), it stops sending the command to the wireless tags it manages (S304). In this embodiment, the AP 20 stops sending the command to the wireless tags it manages by stopping broadcasting as a result of receiving ACKs from all of the wireless tags 10 it manages. Note that if it cannot confirm that all wireless tags 10 have received the command in step S303 (No in S303), it executes step S303 again to check whether it has confirmed that all wireless tags 10 have received the command.

[0170] [3 Effects, etc.] As described above, before moving to an area where a different frequency is used, the wireless tag 10 according to this embodiment receives a command from an access point using the carrier sense function, changes the frequency setting, and then stops transmission to the access point. The command reception operation continues at the new frequency, and resumes transmission to the access point when an instruction to resume transmission is received from the access point.

[0171] As described above, according to this embodiment, by simply changing the control program stored in the memory of an active-type wireless tag that does not have a means for receiving data, the frequency of the wireless tag can be changed using the carrier sense function of the wireless tag.Furthermore, according to this embodiment, the wireless tag can use the carrier sense function to simultaneously or alternately perform normal carrier sense and carrier sense used to interpret commands sent by an access point.

[0172] More specifically, the access point according to this embodiment manages an active type wireless tag that has no means for receiving data, and by recognizing the area in which the wireless tag is currently located, can send a command to the wireless tag and change the frequency used by the wireless tag. On the other hand, although the wireless tag according to this embodiment is an active type wireless tag that has no means for receiving data, it can use its carrier sense function to interpret commands sent by the access point, and therefore can change the frequency used by the wireless tag.

[0173] While the wireless tag and AP according to aspects of the present disclosure have been described above based on the embodiments, the present disclosure is not limited to these embodiments. For example, the present disclosure may be embodied in another embodiment realized by any combination of the components described in this specification or by excluding some of the components. Furthermore, the present disclosure also includes variations obtained by applying various modifications to the above embodiments that would occur to those skilled in the art without departing from the spirit of the present disclosure, i.e., the meaning of the wording set forth in the claims.

[0174] The following aspects may also be included within the scope of one or more aspects of the present disclosure.

[0175] (1) Some of the components constituting the AP may be a computer system consisting of a microprocessor, ROM, RAM, hard disk unit, display unit, keyboard, mouse, etc. A computer program is stored in the RAM or hard disk unit. The microprocessor operates in accordance with the computer program to achieve its functions. Here, the computer program is composed of a combination of multiple instruction codes that indicate commands to a computer to achieve a predetermined function.

[0176] (2) Some of the components constituting the AP may be configured as a single system LSI (Large Scale Integration). A system LSI is an ultra-multifunctional LSI manufactured by integrating multiple components on a single chip, and specifically, is a computer system configured including a microprocessor, ROM, RAM, etc. A computer program is stored in the RAM. The system LSI achieves its functions when the microprocessor operates in accordance with the computer program.

[0177] (3) Some of the components constituting the AP may be configured as an IC card or a standalone module that can be attached to or detached from each device. The IC card or module may be a computer system composed of a microprocessor, ROM, RAM, etc. The IC card or module may include the ultra-multifunctional LSI. The IC card or module achieves its functions when the microprocessor operates according to a computer program. The IC card or module may be tamper-resistant.

[0178] (4) Furthermore, some of the components constituting the AP may be the computer program or digital signal recorded on a computer-readable recording medium, such as a flexible disk, hard disk, CD-ROM, MO, DVD, DVD-ROM, DVD-RAM, BD (Blu-ray (registered trademark) Disc), semiconductor memory, etc. Alternatively, they may be the digital signal recorded on such a recording medium.

[0179] In addition, some of the components constituting the above AP may transmit the computer program or the digital signal via a telecommunications line, a wireless or wired communication line, a network such as the Internet, data broadcasting, etc.

[0180] (5) The present disclosure may be embodied as the methods described above, a computer program for implementing these methods on a computer, or a digital signal comprising the computer program.

[0181] (6) The present disclosure may also be a computer system having a microprocessor and a memory, the memory storing the computer program, and the microprocessor operating in accordance with the computer program.

[0182] (7) The program or the digital signal may also be implemented by another independent computer system by recording it on the recording medium and transferring it, or by transferring the program or the digital signal via the network, etc.

[0183] (8) The above-described embodiments and modifications may be combined with each other. [Industrial Applicability]

[0184] The present disclosure can be used for active wireless tags that do not have a means for receiving data and access points that manage them. [Explanation of symbols]

[0185] 1. Communication Systems 10. Radio tag 11 Batteries 12 sensors 13 LSI section 20 AP 130 RF section 131 Radio wave intensity measurement unit 132 Career Sense Department 133 Control circuit 134, 205 memory 134a Pattern Buffer 135 Data Modulation Unit 201 Information Gathering Department 202 Recognition part 203 Verification Department 204 Signal output control section 205 memory 1301 TX 1302 RX 1331 Pattern Matching Decision Unit 1332 Interpretation Department 1333 RF frequency control section 1334 RF output control section 2041 Signal Transmitter 2042 Signal Stop

Claims

1. A communication method performed by one of a plurality of wireless tags in a communication system including an access point and a plurality of wireless tags, comprising: a carrier sensing step of performing carrier sensing at predetermined intervals; a transmitting step of transmitting first data to the access point, the first data including ID information being information for uniquely identifying the one wireless tag, when a signal transmitted from a wireless tag other than the one wireless tag to the access point is not detected during the execution of the carrier sensing and when the wireless tag is not in a transmission stop state; a command interpretation step of detecting a signal during the execution of the carrier sensing and, if the signal is not a signal transmitted to the access point by a wireless tag different from the one wireless tag, interpreting a command included in the signal transmitted from the access point, assuming that the detected signal is a signal transmitted from the access point; a frequency changing step of changing the radio frequency of the signal transmitted by the one wireless tag when the command interpreting step interprets the signal as including a command for instructing a frequency change; In the transmitting step, If the command interpretation step interprets the signal as including a command to stop transmission and change frequency, and if the signal transmitted from the different wireless tag to the access point is not detected during the carrier sensing, transmitting second data to the access point, the second data being the first data plus information indicating that the command has been received; In the frequency changing step, If the command interpretation step determines that the signal contains a command to stop transmission and change the frequency, after the second data is transmitted, the radio frequency of the signal transmitted by the one wireless tag is changed; The communication method further includes a control step of stopping only the execution of the transmission step until it is interpreted in the command interpretation step that a signal transmitted from the access point detected during the execution of the carrier sensing includes a command instructing to resume transmission, after the second data is transmitted in the transmission step. Communication method.

2. A communication method performed by one of a plurality of wireless tags in a communication system including an access point and a plurality of wireless tags, comprising: a carrier sensing step of performing carrier sensing at predetermined intervals; a transmitting step of transmitting first data to the access point, the first data including ID information being information for uniquely identifying the one wireless tag, when a signal transmitted from a wireless tag other than the one wireless tag to the access point is not detected during the execution of the carrier sensing and when the wireless tag is not in a transmission stop state; a command interpretation step of detecting a signal during the execution of the carrier sensing and, if the signal is not a signal transmitted to the access point by a wireless tag different from the one wireless tag, interpreting a command included in the signal transmitted from the access point, assuming that the detected signal is a signal transmitted from the access point; a frequency changing step of changing the radio frequency of the signal transmitted by the one wireless tag when the command interpreting step interprets the signal as including a command for instructing a frequency change; In the transmitting step, If the command interpretation step interprets the signal as including a command to instruct to stop transmission, and if the signal transmitted from the different wireless tag to the access point is not detected during the carrier sensing, transmitting second data to the access point, the second data being the first data plus information indicating that the command has been received; the communication method further includes a control step of stopping only the execution of the transmission step after the second data is transmitted in the transmission step. Communication method.

3. In the frequency changing step, If the signal is interpreted in the command interpretation step to include a command for instructing a frequency change, the radio frequency of the signal transmitted by the one wireless tag is changed; In the control step, when the radio frequency of the signal transmitted by the one wireless tag is changed in the frequency change step, execution of the transmission step is resumed. The communication method according to claim 2 .

4. The information indicating that the command has been received is an ACK (Acknowledgement).

3. The communication method according to claim 1 or 2.

5. In the carrier sensing step, a strength calculation step of calculating a strength of a signal received during the carrier sensing; a first detection step of determining that a signal transmitted from a wireless tag other than the one wireless tag to the access point is being detected during a period in which a first averaged intensity obtained by dividing the intensity calculated in the intensity calculation step by a first period and averaging the divided intensity exceeds a first threshold; a second detection step of determining that a signal other than a signal transmitted to the access point by a wireless tag different from the first wireless tag is detected by determining a pattern of a second averaging period obtained by dividing the intensity calculated in the intensity calculation step by a second period shorter than the first period and averaging the divided second averaging period, the second averaging period being configured by a number of values ​​exceeding a second threshold value and a number of values ​​equal to or less than the second threshold value; The communication method according to any one of claims 1 to 3.

6. In the carrier sensing step, a first carrier sensing step and a second carrier sensing step are alternately executed; In the first carrier sensing step, a strength calculation step of calculating a strength of a signal received during the carrier sensing; a first detection step of determining that a signal transmitted from a wireless tag other than the one wireless tag to the access point is being detected during a period in which a first averaged intensity obtained by dividing the intensity calculated in the intensity calculation step by a first period and averaging the divided intensity exceeds a first threshold value; In the second carrier sensing step, a strength calculation step of calculating a strength of a signal received during the carrier sensing; a second detection step of determining that a signal other than a signal transmitted to the access point by a wireless tag different from the first wireless tag is detected by determining a pattern of a second averaging period obtained by dividing the intensity calculated in the intensity calculation step by a second period shorter than the first period and averaging the divided second averaging period, the second averaging period being configured by a number of values ​​exceeding a second threshold value and a number of values ​​equal to or less than the second threshold value; The communication method according to any one of claims 1 to 3.

7. In the command interpretation step, interpreting a command included in the signal transmitted from the access point based on a combination of the number of second averaging periods that exceed a second threshold and the number that are equal to or less than the second threshold, the second averaging periods constituting the pattern determined in the second detection step; 7. The communication method according to claim 5 or 6.

8. A communication method performed by an access point of a communication system including an access point and a plurality of wireless tags, an ID information collection step of collecting ID information that is information for uniquely identifying each of the plurality of wireless tags; a signal transmitting step of broadcasting a signal including a command to the plurality of wireless tags to change the first frequency currently being used by the plurality of wireless tags to a second frequency at predetermined intervals; a signal stopping step of stopping broadcasting of a signal including the command when it is confirmed that information indicating that the command has been received has been received from all of the plurality of wireless tags; a recognition step of recognizing that the plurality of wireless tags are moving to an area where the second frequency different from the first frequency currently being used by the plurality of wireless tags is required, and recognizing that the plurality of wireless tags have started to move to the area; a confirmation step of confirming that the plurality of wireless tags have entered the area; In the signal transmission step, When it is recognized in the recognition step that the plurality of wireless tags have started to move to the area, a signal is broadcast at predetermined intervals to the plurality of wireless tags, the signal including a command to change the first frequency currently being used by the plurality of wireless tags to the second frequency and to instruct the plurality of wireless tags to stop transmission; Furthermore, when it is confirmed in the confirmation step that the plurality of wireless tags have entered the area, a signal including a command to instruct the plurality of wireless tags to resume transmission is broadcast at predetermined intervals. Communication method.

9. A communication method performed by an access point of a communication system including an access point and a plurality of wireless tags, an ID information collection step of collecting ID information that is information for uniquely identifying each of the plurality of wireless tags; a signal transmitting step of broadcasting a signal including a command to the plurality of wireless tags to change the first frequency currently being used by the plurality of wireless tags to a second frequency at predetermined intervals; a signal stopping step of stopping broadcasting of a signal including the command when it is confirmed that information indicating that the command has been received has been received from all of the plurality of wireless tags; a recognition step of recognizing that the plurality of wireless tags have started to move to an area where it is necessary to use the second frequency different from the first frequency currently being used by the plurality of wireless tags; a confirmation step of confirming that the plurality of wireless tags have entered the area; In the signal transmission step, Furthermore, when it is recognized in the recognition step that the plurality of wireless tags have started to move to the area, a signal including a command to instruct the plurality of wireless tags to stop transmission is broadcast to the plurality of wireless tags at predetermined intervals; When it is confirmed in the confirmation step that the plurality of wireless tags have entered the area, a signal including a command to instruct the plurality of wireless tags to change the first frequency currently being used by the plurality of wireless tags to the second frequency is broadcast at predetermined intervals to the plurality of wireless tags. Communication method.

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