JP2014217049A - Wireless tag searching method and apparatus for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus for suppressing an increase in collision probability of simultaneous transmission between wireless tags due to shortening of a signal transmission interval from each wireless tag and capable of preventing reduction in wireless tag search performance due to extension of the signal transmission interval in a wireless tag searching system.SOLUTION: An increase in collision probability is suppressed by controlling each wireless tag so that a signal transmission interval is extended in accordance with an increase in the number of wireless tags existing in a wireless search area and a user is quickly and highly frequently notified of a position change of a wireless tag by controlling the wireless tag so that a signal transmission interval from the wireless tag is shortened before missing a wireless tag separated far from a tag search apparatus or a wireless tag moving away from the tag search apparatus at a high speed from the inside of the wireless search area.

Description

  The present invention relates to a search method and a search device using a wireless device, and more specifically to a method and device for searching for the position of a wireless tag using a wireless device.

  The wireless tag is attached to an identification target such as a product or a person, and is used for logistics management or entrance / exit management of a station or a company. For example, a wireless tag stores therein attribute information related to an identification target such as a product to which the tag is attached, and the attribute information and current position of the product to which the tag is attached are accessed from a user wireless terminal. Used for user identification.

  As means for searching for the current position of an active wireless tag, for example, the following wireless search device is known. First, the wireless search device requests the wireless tag to transmit an ID number. Subsequently, the wireless search device that has received the electromagnetic wave transmitted by the wireless tag estimates the distance and direction from the wireless device to the wireless tag based on the reception intensity of the electromagnetic wave and the arrival direction of the electromagnetic wave. Finally, the wireless search device displays the estimated position in association with the ID number of the wireless tag. At this time, in order to scan the direction in which the wireless tag is located in all directions, the direction of the wireless search device is manually changed over 360 degrees for each search operation, or the signal is obtained by application of beam forming technology. It is necessary to change the directivity of the antenna during reception over 360 degrees.

  In such a system for searching the current position of the wireless tag, if the signal transmission interval from the wireless tag is too long, the tag search performance (search accuracy and search success rate) deteriorates. Collision probability due to simultaneous transmission and battery consumption due to frequent transmission increase. Therefore, in the RFID tag searching system as described above, a technique for controlling the signal transmission interval to an optimum length according to the situation is required.

  Patent Document 1 discloses a terminal position search apparatus that measures the position of a mobile terminal based on a positioning signal from a mobile terminal as a mechanism for controlling the signal transmission interval according to the situation in a cellular radio communication system. . Specifically, the terminal location search apparatus transmits a control signal for controlling a time interval for periodically transmitting positioning signals to the mobile terminal according to the current moving speed of the mobile terminal, and receives the control signal. The mobile terminal transmits a positioning signal at a time interval instructed by the terminal position search device. That is, the terminal position search apparatus controls the positioning signal transmission interval to be shorter during high-speed movement than during low-speed movement so as to prevent a decrease in positioning accuracy.

  On the other hand, as a technical contrivance for overcoming the above-described problem of increased collision probability due to frequent simultaneous transmission from a large number of radio wave sources, Patent Document 2 prevents mutual signals from interfering between mobile terminals. Thus, a communication system and a base station that improve throughput are disclosed. Specifically, the base station apparatus monitors the number of mobile terminals (users) existing in the cell of the base station apparatus, and controls the RACH frame format in accordance with the number of mobile terminals. Frame format identification information) is transmitted to the mobile terminal in the cell by the RF transmitter. At this time, as the number of mobile terminals in the cell increases, the base station apparatus performs control so that the amount of overhead information included in a frame in a frame format corresponding to the number decreases. As a result, the amount of overhead information corresponding to the number of users can be reduced, and a shorter RACH frame can be transmitted. Even if the number of users increases, the probability of frame collision on the RACH can be reduced and throughput can be improved. can do.

  In addition, the invention disclosed in Patent Document 3 is such that the tag search device is in a search state in which the current operation state of its own device is searching for a desired wireless tag, or continues to communicate with a discovered wireless tag. The power control operation related to wireless transmission / reception is switched depending on whether the state is the state. Specifically, regarding the wireless transmission / reception of the own device, in the search state, the mode is switched to a power control mode corresponding to a high antenna output, and in the continuous state, the mode is switched to a power control mode corresponding to a lower antenna output.

JP 2011-049829 A Republished No. 2007/094202 International Publication WO2011 / 071307

  However, the terminal position search device described in Patent Document 1 is high-speed toward the outer edge of the search range even when the mobile terminal is moving at high speed so as to go around the short distance from the terminal position search device. Even when moving, the positioning signal transmission cycle is uniformly shortened. Therefore, when the mobile terminal is moving at high speed so as to go around the short distance from the terminal position search device, more power is consumed than necessary for transmitting the positioning signal. This is because when the mobile terminal orbits a short distance from the terminal location search device, the radio wave reception strength and radio propagation state are always good, and transmission of positioning signals is possible even during high-speed movement. This is because good positioning is possible to some extent without reducing the interval.

  As another problem in the invention described in Patent Document 1, the invention described in Patent Document 1 does not have a mechanism for solving the following problems. In the near future, mobile terminals that are far away from the terminal location search device and mobile terminals that are moving away from the terminal location search device will move out of the coverage area where wireless communication is possible centered on the terminal location search device. There is a possibility. Therefore, for mobile terminals located at the outer edge of a coverage area where radio communication is possible, or for mobile terminals trying to go out of the coverage area where radio communication is possible, the mobile terminal is affected by the moving speed of the mobile terminal. If the transmission cycle of the positioning signal is not set short, it is impossible to promptly present to the user a change in the position of the mobile terminal that the terminal position search device may miss.

  Also, as in Patent Document 2, in order to realize a mechanism for transmitting a RACH frame with a small amount of overhead information corresponding to the number of mobile terminals located in the cell, the mobile terminal, the base station apparatus, The following mechanism is required between That is, it is necessary to realize strict bit synchronization and frame synchronization between the mobile terminal and the base station apparatus so as to conform to the channel timing structure and frame format on the radio channel such as RACH.

  However, in an active RFID tag search system, if a synchronization mechanism equivalent to that of a mobile terminal is to be installed in the RFID tag in order to establish strict bit synchronization and frame synchronization on the wireless channel, the following problems occur. . First, by implementing such a synchronization mechanism in a wireless tag, signal processing in the wireless tag becomes very complicated, and the power consumed by the wireless tag for signal processing increases significantly. As a result, in the wireless tag, it is necessary to increase the wireless circuit mounting area or to increase the capacity of the battery, so beyond the original purpose such as attribute information identification and current position search of the tag mounted article, The wireless tag becomes larger and more complicated than necessary, and the manufacturing cost also increases.

  Further, as in Patent Document 3, depending on whether a search state in which a desired wireless tag is searched or a communication continuation state in communication with the found wireless tag, the wireless on the wireless search device In order to switch the power control operation related to transmission and reception, the same problem as the problem described above with respect to Patent Document 2 occurs. That is, implementing a complex power control mechanism that performs closed-loop power control and open-loop power control at the same level as a mobile terminal in the wireless tag results in attribute information identification of the tag-mounted article and current position search. In addition to exceeding the original purpose, the wireless tag becomes larger and more complex than necessary, and the manufacturing cost also increases.

  In view of the above problems, the present invention compensates for a decrease in search performance of a radio tag at a distance, and before losing sight of a radio tag that is likely to move out of service area, It aims at realizing the mechanism for notifying a user of the change rapidly and frequently.

  Another object of the present invention is to reduce the collision probability due to simultaneous transmission from a large number of wireless tags without implementing a strict bit synchronization or frame synchronization mechanism between the tag search device and the wireless tag. And At the same time, the present invention realizes a mechanism that eliminates the trade-off between the battery consumption of the wireless tag due to the short transmission interval of the signal transmitted from the wireless tag and the decrease in tag search performance due to the long transmission interval. Objective.

  From the above, the first aspect of the present invention is to search for the position of one or more radio devices that are located in an area where radio communication with a user terminal is possible and each transmits a broadcast information signal periodically. A method executed by the user terminal comprising: detecting a number of the one or more radios located in the area based on the broadcast information; depending on a number of the radios, Determining a transmission cycle of the broadcast information signal; instructing the one or more radios located in the area to transmit the broadcast information signal according to the determined transmission cycle; Estimating a position of each of the one or more radios based on a signal; and listing a position estimated for each of the one or more radios to a user. Take.

  In the first aspect of the present invention, the step of determining the transmission period may include the step of simultaneously transmitting collisions between the radios due to a short transmission period when the number of radios are located in the area. The transmission period is determined in such a manner as to eliminate a trade-off between an increase in probability and a decrease in search performance of the user terminal due to a long transmission interval.

  According to a second aspect of the present invention, the user terminal is located in an area where wireless communication with the user terminal is possible, and the user terminal searches for the position of one or more wireless devices each transmitting a broadcast information signal periodically. And detecting the distance to each wireless device and the speed at which each wireless device moves away from the user terminal based on the radio field intensity of the signal received from each wireless device in the area and the amount of change. Determining a transmission cycle of the broadcast information signal according to the detected distance and speed; instructing each radio in the area to transmit the broadcast information signal according to the determined transmission cycle Determining the position of each radio in the area based on the broadcast information signal; and identifying the specified position for each radio in the area. A step of displaying on over The updates more frequently than the transmission period of the display is the determined step; employs a configuration comprising a.

  According to a second aspect of the present invention, in the step of determining the transmission period, the transmission period of the notification information signal is set to be shorter as the distance to each wireless apparatus becomes longer. The transmission period is set to be shorter as the speed of moving away from the terminal is higher.

  From the above, the present invention automatically sets the signal transmission interval from the wireless tag in consideration of the distance between each wireless tag to be searched by the tag searching device and the speed at which the wireless tag moves away from the tag searching device. Set to the optimal value. That is, the present invention sets the signal transmission interval to be shorter as the wireless tag is farther from the tag search device, and at this time, the signal transmission interval is set to be higher as the moving speed of the wireless tag along the direction away from the tag search device is higher. Set it shorter. As a result, the present invention can compensate for a decrease in search performance (search accuracy and search success rate) of a radio tag at a distance by increasing the signal transmission frequency. At the same time, the present invention can promptly and frequently notify the user of the distance to the wireless tag and its change before losing sight of the wireless tag that is likely to move out of the search range.

  Furthermore, the present invention automatically sets the signal transmission interval from the wireless tag to an optimum value in consideration of the list display on the search screen of the tag search device or the number of wireless tags to be searched. . As a result, the present invention reduces the collision probability due to simultaneous transmission from a large number of wireless tags, as well as battery consumption of the wireless tag due to a short signal transmission interval and a decrease in tag search performance due to a long signal transmission interval. Eliminate trade-offs between As a result, the present invention does not implement a radio channel synchronization mechanism or power control mechanism at the same level as that of a mobile terminal in the radio tag, and collisions due to frequent simultaneous transmissions from a large number of radio tags located in the search range. An increase in probability can be prevented.

Overall configuration diagram of radio communication system according to the present embodiment The figure which shows the hardware constitutions of the radio | wireless tag which concerns on embodiment of this invention, and a tag search device The figure explaining the function which a wireless tag search application provides to a user The figure which shows the functional block structure of the tag search apparatus which concerns on embodiment of this invention The figure which shows the relationship between the electric field strength of the signal received from the wireless tag, and the distance to a wireless tag The sequence diagram which shows the processing flow at the time of a tag search apparatus performing the method which concerns on 1st Example of this Embodiment The figure which shows the transmission interval setting value table which defines the correspondence of the tag number and Advertising signal transmission interval setting value The flowchart which shows the processing flow at the time of a tag search apparatus performing the method which concerns on 2nd Example of this Embodiment. Table listing thresholds referred to when determining signal transmission intervals based on the second embodiment Setting value table for determining signal transmission interval from radio wave reception intensity and the amount of decrease

<1> Outline The wireless tag is attached to an identification target such as a product or a person, and is used for logistics management or entrance / exit management of a station or company. Wireless tags are roughly classified into passive types and active types.

  The passive wireless tag does not have a built-in battery, generates electric power required inside by radio waves from an external reader / writer, and communicates with the reader / writer in response to a call from the reader / writer. Although the communication range cannot be made large and is about 1 m at the maximum, it can be downsized and the operation can be made permanent.

  On the other hand, an active type wireless tag has a battery inside and transmits radio waves to an external receiver. Since the battery is built in, the communication range is as wide as 10 to 20 m, but there is a difficulty in that the battery cannot be downsized because of the built-in battery and the battery has a lifetime. However, since information can be sent spontaneously, various applications can be considered by making good use of its functions. For example, when searching for an identification target existing in an unspecified location, an active wireless tag is more suitable than a passive wireless tag.

  As such an active wireless tag, a small wireless tag using a short-range wireless communication standard such as Bluetooth (registered trademark) is known. For example, small tags using Bluetooth Low Energy Wireless Technology are provided. As another example, there is a method in which a GPS module is mounted on a wireless tag in addition to the wireless module, and the tag location is estimated from the position of the GPS module.

  An active type wireless tag always needs to transmit an Advertising signal at a constant cycle. However, if the transmission interval is short, the battery to be mounted is consumed quickly, and the battery needs to be frequently replaced (or charged). In addition, when there are a large number of RFID tags in the searchable area of the RFID tag searching device, the RFID tag searching device side normally receives each RFID tag due to the collision of the advertising signal transmitted from each RFID tag. The signal from can not be received. On the other hand, if the transmission interval of the Advertising signal is increased, the interval at which the RFID tag searching device presents the distance to the RFID tag to the user based on the intensity level of the received signal also becomes longer. The search accuracy and search success rate are also reduced. In the prior art, the situation in which the above-described problem occurs is illustrated in more detail and specifically as follows.

In the prior art, the transmission interval of the Advertising signal from the active wireless tag is automatically switched according to the situation as follows. Specifically, the transmission interval of the Advertising signal is set to three different values according to three different states. The three different states include the following states (1) to (3).
(1) A standby state in which the wireless tag is not searched.
(2) A state in which the wireless tag searching device is displaying a list of all wireless tags located in the searchable area, and the wireless tags are listed simultaneously with other tags located in the area.
(3) A state in which the wireless tag is designated as a search target by the user by the tag ID information, and the current position of the wireless tag is searched by the wireless tag search device.

  In particular, in the standby state (1), battery consumption can be suppressed by setting the transmission interval of the Advertising signal to a relatively long interval such as 2 to 5 seconds.

  In the state of (2) above, by sending an instruction signal for instructing the wireless tag to change the setting of the transmission interval of the advertising signal from the wireless tag searching device to the wireless tag, for example, a comparison of about 1 second. An advertising signal from each wireless tag can be received at a short transmission interval.

  In the state of (3) above, an instruction signal for instructing the wireless tag to set and change the transmission interval of the Advertising signal is transmitted to the wireless tag from the wireless tag searching device, for example, several hundred milliseconds. The advertising signal from each wireless tag can be received at the shortest transmission interval.

  When the search for the wireless tag is completed and the state (3) returns to the state (1) or (2), the transmission interval of the Advertising signal is changed to a set value corresponding to each state. The wireless tag searching device instructs the wireless tag.

  In addition, the active wireless tag automatically sets the transmission interval of the Advertising signal in the standby state (1) when a certain time has elapsed after receiving the instruction signal instructing to set the transmission interval of the Advertising signal short. Change to the setting. As a result, even when the transmission interval of the Advertising signal is set to be short, even when the RFID tag searching apparatus moves outside the searchable area, it is possible to suppress wasteful battery consumption.

  The set value of the transmission interval is preferably set to be short in order to reduce the time required for estimating the current position of the wireless tag in the states (2) and (3). In particular, wireless tags located away from the wireless tag search device and wireless tags that are moving away from the wireless tag search device will move out of the coverage area where wireless communication is possible centering on the wireless tag search device in the near future. There is a possibility that. For this reason, it is desirable to set the transmission interval of the Advertising signal from the wireless tag short so that the change in the current position of the wireless tag that may be missed by the user can be quickly presented to the user.

  However, if the transmission interval of the Advertising signal is set to be short in this way, the following problem occurs when the number of wireless tags located in the coverage area where the wireless tag searching device can perform wireless communication increases. That is, since the collision probability of Advertising signals transmitted simultaneously from a large number of wireless tags increases, it becomes impossible to normally display a list of all wireless tags in the area on the display screen of the wireless tag searching device. In addition, in order to improve the display response performance in the above-mentioned list display of all the wireless tags in the area, it is necessary to shorten the update interval of the list display on the display screen, but the Advertising signal from the wireless tag If the transmission interval is not sufficiently shorter than that, the display becomes unstable.

  On the other hand, for wireless tags that are located at the outer edge of a coverage area where wireless communication is possible, or for wireless tags that are about to go out of the coverage area where wireless communication is possible, the signal transmission interval is set short. Otherwise, the position change of the wireless tag that may be lost by the user cannot be presented to the user quickly and frequently.

As described above, in the current position search system of the active type wireless tag, if the signal transmission interval from the wireless tag is too long, the tag search performance (search accuracy and search success rate) deteriorates. There is a problem that collision probability due to simultaneous transmission and battery consumption due to frequent transmission increase. On the other hand, for wireless tags that are located at the outer edge of a coverage area where wireless communication is possible, or for wireless tags that are about to go out of the coverage area where wireless communication is possible, the signal transmission interval is set short. Otherwise, the user is likely to lose sight of the wireless tag. Therefore, the present embodiment discloses a technique for controlling the signal transmission interval to an optimum length according to the situation in the search system for the active type radio tag as described above.
<2> Configuration of Radio Communication System According to the Present Embodiment (2-1) Overall Configuration of Radio Communication System An example of the overall configuration of the radio communication system will be described below with reference to FIG.

  One embodiment of the wireless communication system includes a tag searching device 100 used by a user as a portable user terminal device for searching for a wireless tag, and a tag 200n (n is an integer of n> 0) that is an active wireless tag. Have FIG. 1 shows a case where n = 4 as an example. The value of n may be 1-3 or 5 or more.

  The tag 200n may be called a slave unit. The tag 200n has a short-range wireless communication module. For example, the tag 200n may be a small wireless tag that performs short-range wireless communication according to Bluetooth Low Energy Wireless Technology. The tag 200n is affixed to various things. For example, the tag 200n may be affixed to what is not desired to be lost. In one embodiment of the wireless communication system, a tag 200n is attached to a key, a remote control, an umbrella, a wallet, or the like.

  Since the tag 200n is an active wireless tag, it is driven by a built-in battery and can spontaneously transmit a wireless signal to another wireless device. The tag 200n can intermittently transmit an Advertising signal at a constant cycle in order to inform its current position, and the transmission cycle of the Advertising signal is set by a setting command from the parent device described later. Is possible. The tag 200n can also notify the parent device of the current transmission cycle and transmission output of the Advertising signal.

Tag search device 100 may be referred to as a parent device. The near field communication module of the tag searching device 100 performs wireless communication with the near field communication module of the tag 200n. The tag search device 100 measures the electric field strength of the radio wave from the tag 200n. A sensor built in the tag search device 100 detects the dynamics of the tag search device 100. The tag search device 100 estimates the position of the tag 200n based on the electric field intensity of the radio wave from the tag 200n and the dynamics detected by the sensor. The tag search device 100 has a display screen having a user interface that can be intuitively operated by a user such as a GUI (Graphical User Interface), and the display screen displays the position of the tag 200n. The tag searching device 100 can simultaneously identify the plurality of wireless tags by simultaneously estimating the positions of the plurality of tags 200n, and display a list of all the identified wireless tags on the display screen. is there.
(2-2) 200n wireless tag
FIG. 2A shows an example of a tag 200n.

In one embodiment of a wireless communication system, the tag 200 ₁ is attached to the key, the tag 200 ₂ is attached to the remote control, the tag 200 ₃ is attached to the umbrella, the tag 200 ₄ is affixed to the wallet.

  The tag 200n includes a control unit 201, a notification information transmission unit 202, a wireless communication unit 203, a timing unit 204, a storage unit 205, a battery 206, a transmission / reception antenna 207, a transmission interval control signal reception unit 210, It comprises.

  The control unit 201 can be implemented by a general-purpose microprocessor, a digital signal processor, or the like, and controls the overall operation of the tag 200n.

  The broadcast information transmitting unit 202 is connected to the control unit 201 and the wireless communication unit 203 so as to be interposed between them, and transmits the advertising signal at the transmission cycle set by the tag search device 100 as the base unit. The wireless communication unit 203 is controlled. Specifically, the broadcast information transmission unit 202 counts down the internal counter value by the number of clock pulses set by the control unit 201, and performs wireless transmission of the Advertising signal when the counter value becomes zero. Instructs the transmission unit 203.

  The wireless communication unit 203 is connected to the broadcast information transmission unit 202 and the transmission / reception antenna 207, and performs wireless communication according to a short-range wireless communication standard such as Bluetooth, zigbee, Wi-Fi, or ANT +. It is not limited to Bluetooth, zigbee, Wi-Fi, and ANT +, and the short-range wireless communication module may perform wireless communication according to a short-range wireless communication standard other than these. In the embodiment of the tag 200n, a case will be described in which the wireless communication unit 203 performs short-range wireless communication according to Bluetooth Low Energy Wireless Technology.

  Whenever the advertising signal transmission cycle is newly set by the master unit, the timer unit 204 measures a time length equal to the newly set transmission cycle, and the number of clock pulses corresponding to the measured time length. Is set in the broadcast information transmitting unit 202. At this time, the number of clocks and pulses set by the time measuring unit 204 is output from the time measuring unit 204 to the notification information transmitting unit 202 via the control unit 201.

  The storage unit 205 stores various setting parameters related to the tag 200n. In such a setting parameter, the setting value of the Advertising signal transmission cycle in the standby state where the tag 200n is not a search target and the current Advertising signal transmission cycle are automatically returned to the setting value of the transmission cycle in the standby state. The waiting time is included.

  The battery 206 supplies power to the notification information transmission unit 202, the wireless transmission / reception unit 203, the time measurement unit 204, the storage unit 205, and the transmission / reception antenna 207 via the control unit 201.

The transmission interval control signal receiving unit 210 is connected to these units so as to be interposed between the control unit 201 and the wireless communication unit 203, and receives a control signal from the tag search device 100 which is a master unit. The control signal received by the transmission interval control signal receiving unit 210 from the tag search device 100 is a signal for transmitting a command for controlling the length of the cycle in which the tag 200n transmits the Advertising signal from the tag search device 100, This is called a transmission interval control signal.
(2-3) Tag search device 100
FIG. 2B shows an embodiment of the tag search device 100.

  The tag search device 100 may be any appropriate terminal with which a user can communicate, and includes, but is not limited to, a user terminal such as a mobile phone, an information terminal, a personal digital assistant, a portable personal computer, and a smartphone. Not.

  The tag searching device 100 includes a control unit 101, a notification information receiving unit 202, a wireless communication unit 103, a display unit 104, a storage unit 105, a user input / output unit 106, a sensor 107, a transmission / reception antenna 108, A transmission interval control signal transmission unit 110.

  The control unit 101 can be implemented by a general-purpose microprocessor, a digital signal processor, or the like, and exchanges signals with the notification information receiving unit 102, the display unit 104, the storage unit 105, the user input / output unit 106, and the sensor 107. However, control of the entire tag search device 100 is executed. The control unit 101 functions according to a program stored in the storage unit 105 and performs predetermined processing. Specifically, the control unit 101 determines the tag 200n based on the electric field intensity of the radio wave from the tag 200n and information indicating the dynamics of the tag search device 100 (the direction and orientation of the tag search device 100 and their changes). Is estimated. The position of the tag 200n estimated by the control unit 101 may be a relative position with the tag search device 100. The control unit 101 outputs information representing the position of the tag 200n to the display unit 104.

  The broadcast information receiving unit 102 receives a wireless signal from the tag 200n, and when the received wireless signal is an Advertising signal, the broadcast information receiving unit 102 decodes the information content of the received signal to thereby detect the wireless tag identification information (tag ID information) and attribute information of the tag-fitted article are extracted and notified to the control unit 101. Thereby, the tag search device 100 can uniquely identify the wireless tag that is the transmission source of the received signal, and can identify the attribute information of the article on which the wireless tag is attached.

  The wireless communication unit 103 performs wireless communication according to a short-range wireless communication standard such as Bluetooth, zigbee, Wi-Fi, or ANT +. The wireless communication unit 103 is not limited to Bluetooth, zigbee, Wi-Fi, and ANT +, and may perform wireless communication in accordance with a short-range wireless communication standard other than these. In one embodiment of the tag search device 100, a case where the wireless communication unit 103 performs short-range wireless communication according to Bluetooth Low Energy Wireless Technology will be described. Further, the wireless communication unit 103 measures the electric field strength based on the radio wave from the tag 200n. For example, the wireless communication unit 103 may measure the received signal strength (RSSI: Received Signal Strength Indication, Received Signal Strength Indicator) based on the radio wave from the tag 200n.

  The display unit 104 is configured by a display, for example, and displays a processing state and a processing result by the tag search device 100. The processing state and the processing result include those according to the OS and applications. The display includes a liquid crystal display (LCD), a CRT (Cathode Ray Tube) display, a plasma display (PDP), an organic EL (Electro-Luminescence) display, and the like. When the tag search device 100 is executing the above-described RFID tag search application, the display unit 104 collectively displays the positions of all the wireless tags existing around the tag search device 100, or by the user A search screen is displayed while searching for a specific wireless tag to be searched.

  The storage unit 105 stores various setting parameters related to the tag 200n. In such a setting parameter, the set value of the Advertising signal transmission period in the standby state where the tag 200n is not a search target and the positions of all the wireless tags existing around the tag search device 100 are collectively displayed. The setting value of the advertising signal transmission period at the time, and the setting value of the advertising signal transmission period during the search for the specific wireless tag to be searched by the user are included.

  Further, the storage unit 105 stores an application and an operating system (OS: Operating System). The application is software that includes a program that is activated by an instruction command input by the user from the user input unit 106 and that is executed by the control unit 101, and that has a function of performing operations performed by the user on the tag search device 100. . The OS includes a system control program that is automatically started when the tag search device 100 is turned on and executed by the control unit 101. In the tag search device 100, an interface that abstracts hardware is provided to application software. Software. A specific example of such an OS includes Android OS (registered trademark). Note that the application in the present embodiment includes a wireless tag search application in which the user searches for the current position of the tag 200n and displays the current position of the tag 200n on the display unit 104 using the GUI.

  The user input / output unit 106 includes, for example, a keyboard and a mouse, and is a device for a user to give an instruction to the tag search device 100 and input data. The user input unit 106 may be configured with a touch panel. In addition, the user input / output unit 106 is configured by a microphone, for example, and inputs a voice uttered by the user. The voice may include a message to the called party and an instruction to the tag search device 100. The instruction includes an instruction for the OS and an application. Further, the user input / output unit 106 may be configured by a speaker, for example, and may output a sound to the user in accordance with a processing state and a processing result by the tag search device 100.

  The sensor 107 includes a dynamic sensor, and the dynamic sensor detects a movement of the apparatus including a change in the orientation and posture of the tag search apparatus 100 held by the user. One example of a dynamic sensor includes an acceleration sensor, a gyro sensor, a geomagnetic sensor, and the like. Not only an acceleration sensor, a gyro sensor, and a geomagnetic sensor, but sensors other than these may be included. The acceleration sensor is a sensor that measures angular acceleration (rotational acceleration) and acceleration (straight acceleration) when the direction and orientation of the tag search device 100 change. The gyro sensor is a sensor that detects the current orientation of the tag search device 100. The geomagnetic sensor is a sensor that detects an absolute direction such as east, west, south, and north as seen from the tag search device 100 based on geomagnetism.

The transmission interval control signal transmitting unit 110 is connected to the control unit 101 and the wireless communication unit 103 so as to be interposed between them, and receives a control signal toward the tag 200n in response to an instruction from the control unit 101. The control signal transmitted by the transmission interval control signal transmission unit 110 toward the tag 200n is a signal for transmitting a command for controlling the length of the cycle in which the tag 200n transmits the advertising signal from the tag search device 100, This is called a transmission interval control signal.
(2-4) Function provided by tag search device 100 to user and usage mode of tag search device 100 Hereinafter, using FIG. 3A and FIG. The functions to be provided will be described. The RFID tag search application executed on the tag search device 100 can also be implemented as an Android application executed by calling an API of Android OS (registered trademark). In this case, the RFID tag search application is activated when the user taps the corresponding icon on the touch panel screen displaying the Android OS (registered trademark) desktop with a finger. The RFID tag search application activated by the user executes either the in-area tag list display mode or the specific tag search mode, which will be specifically described below. Switching between the in-area tag list display mode and the specific tag search mode is executed when the user gives a switching instruction to the RFID tag searching application via the user input / output unit 106 or at the judgment of the application itself. Is done.
(2-4-A) In-area tag list display mode In the in-area tag list display mode, the tag search device 100 estimates the distances to all the wireless tags located in the searchable area, In this mode, a list is displayed on the display screen. The searchable area described above is the maximum range in which a signal transmitted from a wireless tag at a location where the tag search device 100 is remote can be received with a reception quality higher than a predetermined quality, and the tag search device 100 Corresponds to a coverage area where wireless communication is possible. The predetermined quality in this case may be a reception quality that allows the tag ID information to be extracted by correctly decoding the reception signal from the wireless tag with a certain probability.

  In the in-area tag list display mode, the RFID tag searching application executed by the tag searching device 100 stores the strength of the Advertising signal received from each wireless tag in the storage unit 105. Subsequently, the wireless tag search application displays a list of all the wireless tags in the area on the display screen of the tag search device 100 based on the estimated distances to the individual wireless tags. When displaying the distance to each wireless tag, a list of icon images corresponding to the tag ID information of each wireless tag is displayed at a position corresponding to the distance.

  FIG. 3A shows a state in which the tag search device 100 displays a list of all the wireless tags located in the searchable area on the display screen.

Subsequently, the user selects and taps one or more icon images corresponding to the plurality of wireless tags displayed in a list on the display screen in the manner illustrated in FIG. 3A with a finger. Thereby, the wireless tag corresponding to the tapped icon image is designated as the wireless tag selected as the search target by the user, and the tag search device 100 uses the tag ID information of the wireless tag selected as the search target. The data is stored in a search target storage area in the storage unit 105. Finally, in order to search for the position of the wireless tag selected as the search target, the wireless tag search application switches to a specific tag search mode to be described later.
(2-4-B) Specific Tag Search Mode The specific tag search mode is a radio in which tag ID information is stored as a search target in the storage unit 105 of the tag search device 100 as a result of being specified as a search target by the user. This mode is used to locate the tag. In the following description, a tag designated by the user as a search target is referred to as a search target tag.

In the specific tag search mode, the user first swings the tag search device 100 held in his hand left and right in an arbitrary direction, or makes one rotation on the spot. At this time, the RFID tag searching application executed by the tag searching device 100 stores in the storage unit 105 the strength of the Advertising signal received from each RFID tag and the direction at the time of receiving the signal. Subsequently, the RFID tag search application displays the direction and distance in which all searched RFID tags are located on the radar chart displayed on the display screen of the tag search device 100, centering on the current position of the user. Display a list. When displaying the direction and distance of each wireless tag on the radar chart, icon images corresponding to the tag ID information of each wireless tag are displayed in a list at positions in the radar chart corresponding to the direction and distance.
FIG. 3B shows a state in which the tag search device 100 displays a list of the positions of all the wireless tags located in the searchable area as a radar chart on the display screen. In FIG. 3B, an icon image 500 located at the center of the radar chart represents the current position of the user who has the tag search device 100 in his / her hand. Each of the plurality of concentric circles displayed in the radar chart represents a circular distance range that increases stepwise around the user position represented by the icon image 500, and the numbers appended to the concentric circles correspond to each other. Represents the radius of the distance range. In FIG. 3A, icon images 400 ₁ , 400 ₂ , 400 _3, and 400 ₄ in the radar chart represent the current positions of four wireless tags located in the searchable area. Icon image 400 ₁ displays the current position of the tag 200 ₁ affixed to the key, the icon image 400 ₂ displays the current location of tag 200 ₂ affixed to the remote control, icon image 400 _3, an umbrella display stuck current position of the tag 200 _3, the icon image 400 ₄ displays the current location of tag 200 ₄ affixed to purse.
(2-5) Functional Block Configuration Inside Tag Search Device 100 An embodiment of the functional block structure 300 of the tag search device 100 will be described.

  FIG. 4 is a diagram showing a functional block structure 300 of the tag search device 100. The functions represented by this functional block diagram are mainly executed by the control unit 101. That is, the function represented by the functional block diagram of FIG. 4 is executed by the control unit 101 in accordance with the RFID tag search application stored in the storage unit 105. The CPU that executes the function represented by the functional block diagram of FIG. 4 according to the application stored in the storage unit 105 may be referred to as an A-CPU (application-CPU) 300.

  Based on the measurement information from the dynamic sensor 107, the dynamic determination unit 302 changes the direction and posture of the tag search device 100 or the tag search that occurs when the user moves by itself. The physical movement of the device 100 is detected. Information indicating acceleration is input from the dynamic sensor 107 to the dynamic determination unit 302. The dynamic determination unit 308 determines whether or not the tag search device 100 has moved based on information representing the acceleration from the dynamic sensor 107. The dynamic determination unit 302 inputs information indicating whether or not the tag search device 100 has moved to the position estimation unit 304.

  Information indicating whether or not the tag search device 100 has moved from the dynamic determination unit 302 is input to the position estimation unit 304. For example, it is assumed that the user moves the tag searching device 100 to the left and right in order to search for the direction in which the wireless tag is located. At this time, the position estimation unit 304 detects the start timing of movement of the tag search device 100 and the end timing of the movement based on information from the dynamic determination unit 302. The position estimation unit 304 is detected by the wireless communication unit 103 between the timing of starting the movement and the timing of ending the movement after detecting the timing of starting the movement of the tag search device 100 and the timing of ending the movement. The position of the tag 200n is estimated based on the electric field strength, the information indicating the absolute azimuth detected by the dynamic sensor 107, and the information indicating the angular acceleration.

  The position estimation unit 304 estimates the position of the wireless tag based on the electric field strength of the signal received from the wireless tag and information from the dynamic sensor 107. The position estimation unit 304 estimates the distance between the tag search device 100 and the tag 200n based on information representing the electric field strength from the wireless communication unit 103. Specifically, the position estimation unit 304 may have a database including a relationship between the electric field strength and the distance.

  FIG. 5 shows an example of the relationship between electric field strength and distance. According to FIG. 5, it is shown that the distance between the tag search device 100 and the tag 200n is shorter (closer) as the electric field strength increases, and between the tag search device 100 and the tag 200n as the electric field strength decreases. It is shown that the distance of is long (far).

  The position estimation unit 304 estimates the distance between the tag search device 100 and the tag 200n based on the relationship between the electric field strength and the distance described by FIG.

  The position estimation unit 304 calculates the orientation of the tag search device 100 based on information representing the absolute orientation from the dynamic sensor 107. The position estimation unit 304 calculates the angle and rotation speed of the tag search device 100 based on information representing the angular velocity from the dynamic sensor 107.

The position estimation unit 304 estimates the position of the tag 200n based on the estimated distance value, the information indicating the azimuth, and the information indicating the angle and the rotation speed. Specifically, it is as follows. First, the position estimation unit 304 detects a change in the direction and orientation of the tag search device 100 caused by the user swinging the tag search device 100 left and right from the dynamic sensor 107, such as absolute azimuth information, angle, and rotation speed. Receive in form. Subsequently, the position estimation unit 304 estimates the position of the wireless tag based on the detected direction and the distance estimated based on the relationship between the electric field strength and the distance shown in FIG. The position estimation unit 304 outputs information indicating the estimated position of the tag 200n to the display unit 104, and the display unit 104 determines the position of the tag 200n based on the information indicating the position of the tag 200n from the position estimation unit 304. Is displayed on the screen.
<3> First Example According to this Embodiment Hereinafter, a first example according to this embodiment will be described with reference to FIGS. 6 and 7. First, the outline of the first embodiment will be described.

The first example according to the present embodiment automatically sets the transmission interval of the Advertising signal to an optimum value according to the number of wireless tags searched simultaneously. Specifically, in the state (2) (the tag search device 100 is executing the in-area tag list display mode), the number of all wireless tags in the area to be listed on the display screen increases. The longer the transmission interval of the Advertising signal is set. In the state (3) (when the tag search device 100 is executing the specific tag search mode), the greater the number of wireless tags simultaneously selected as search targets by the user, the longer the transmission interval of the Advertising signal. Set.
(3-1) Process Flow of Signal Transmission Interval Control Method According to First Example In the first example of the present embodiment, the control unit 101 in the tag search device 100 is the following shown in the sequence diagram of FIG. This is realized by controlling the transmission interval of the Advertising signal according to the situation in accordance with the above procedure.
(I) First, in an initial state, each wireless tag transmits an Advertising signal at a transmission interval corresponding to the standby state of (1) above, and the tag search device 100 is turned on and stored in the storage unit 105. The OS stored in is started (S0 in FIG. 6). Subsequently, when the user instructs activation of the RFID tag search application via the GUI included in the user input / output unit 106, the control unit 101 activates the RFID tag search application (S1 in FIG. 6). The control unit 101 controls the entire tag search device 100 to execute detection (presence detection) of all wireless tags located in the searchable area in the in-area tag list display mode. Specifically, the control unit 101 executes detection (presence detection) of all the wireless tags located in the searchable area as follows. First, the control unit 101 temporarily stores in the storage unit 105 all of the tag ID information included in each Advertising signal received within a certain period of time from one or more wireless tags located in the searchable area. In addition, the control unit 101 stores tag ID information that does not overlap each other among all the temporarily stored tag ID information in the storage unit 105 as a visited tag list.

Subsequently, the control unit 101 calculates the number of wireless tags to be displayed in a list before displaying the current positions of all detected wireless tags on the display screen (S2 in FIG. 6). Specifically, the control unit 101 calculates the number of wireless tags by counting up the number of one or more pieces of tag ID information that are not overlapped with each other and are stored in the in-zone tag list in the storage unit 105. At this time, the wireless tags that are subject to calculation of the number of tags when the list is displayed are further designated by the user as a list display target among the wireless tags whose tag ID information is registered in advance in the tag ID database of the storage unit 105. It is possible to limit to the wireless tag which exists.
(Ii) Subsequently, the control unit 101 determines a setting value of the transmission interval of the Advertising signal corresponding to the number of tags calculated as the number of wireless tags listed on the display screen in (i) above ( S3 in FIG. Specifically, the control unit 101 refers to, for example, a transmission interval setting value table that defines the correspondence between the number of tags and the advertising signal transmission interval setting value, and the number of wireless tags listed on the display screen The transmission interval setting value of the Advertising signal corresponding to is determined. At this time, the signal transmission interval setting value in the transmission interval setting value table indicates that the simultaneous transmission of signals between the wireless tags becomes shorter as the signal transmission interval becomes shorter according to the number of wireless tags located in the searchable area. It is determined in such a manner as to eliminate a trade-off between an increase in the probability of collision and a decrease in RFID tag search performance (search accuracy and search success rate) as the signal transmission interval increases.

A specific example of a transmission interval setting value table that defines the correspondence between the number of tags and the Advertising signal transmission interval setting value is shown in FIG. In the table of FIG. 7, the number of tags to be listed on the display screen is “1 to 10”, “11 to 20”, “21 to 30”, and “31 or more”. For each of the cases where the wireless tag is present, the setting value of the Advertising signal transmission interval when the wireless tag is in the standby state (1) (state where the wireless tag is not searched), the state (2) (in the area search mode) Advertising signal transmission interval setting when the wireless tag is being searched) and Advertising signal transmission interval setting when the wireless tag is in the state of (3) above (the wireless tag is being searched in the specific tag search mode) The values are stored in the columns of “Standby”, “List display” and “Search”, respectively. For example, according to the table of FIG. 7, the number of tags to be displayed as a list on the display screen is 15, and each wireless tag is in the state (2) above (the wireless tag is searched in the in-area search mode). The transmission interval of the advertising signal by the wireless tag is set to 200 milliseconds.
(Iii) Subsequently, the control unit 101 instructs to change the transmission interval of the Advertising signal for all wireless tags located in the searchable area via the notification information receiving unit 102 and the wireless communication unit 103. To do. Specifically, the control unit 101 includes the transmission interval setting value of the Advertising signal determined in the above (ii) in the instruction signal and transmits it to all the wireless tags located in the searchable area. In response, all the wireless tags in the searchable area transmit the Advertising signal at the transmission interval indicated by the transmission interval setting value in the instruction signal (S4 in FIG. 6). After the control unit 101 confirms that the wireless tag that has received the instruction signal has started signal transmission at the specified transmission interval, the control unit 101 determines that all wireless tags located in the searchable area Are estimated, and the display unit 104 is instructed to display a list on the display screen based on the estimated distances.
(Iv) Subsequently, the user selects a wireless tag to be searched from among the plurality of wireless tags listed on the display screen (each of the wireless tags listed on the display screen is selected). When one or more of the corresponding icon images are tapped with a finger), the RFID tag search application switches to a specific tag search mode (S5 in FIG. 6).
(V) In the above (iv), when the wireless tag search application switches to the specific tag search mode, the control unit 101 calculates the number of wireless tags simultaneously designated as search targets by the user (S6 in FIG. 6).
(Vi) Subsequently, the setting value of the transmission interval of the Advertising signal corresponding to the number of tags calculated in (v) above is determined as the number of wireless tags simultaneously designated as search targets by the user (S7 in FIG. 6). . Specifically, the control unit 101 refers to, for example, a transmission interval setting value table that defines the correspondence between the number of tags and the Advertising signal transmission interval setting value, and the number of wireless tags simultaneously designated as search targets by the user The transmission interval setting value of the Advertising signal corresponding to is determined. At this time, the configuration of the transmission interval setting value table used for determining the transmission interval setting value of the Advertising signal can be the same as the configuration shown in FIG.
(Vii) Subsequently, the control unit 101 changes the transmission interval of the Advertising signal for one or more wireless tags simultaneously designated as search targets by the user via the notification information receiving unit 102 and the wireless communication unit 103. Instruct. Specifically, the control unit 101 includes, in the instruction signal, the transmission interval setting value of the Advertising signal determined in (vi) above, and the instruction signal is simultaneously specified by the user as a search target. Send to the wireless tag. In response, the one or more wireless tags simultaneously designated as search targets by the user transmit the Advertising signal at the transmission interval designated by the transmission interval setting value in the instruction signal (S8 in FIG. 6).
(Viii) The wireless tag search application executed by the control unit 101 after the control unit 101 confirms that the wireless tag that has received the instruction signal has started signal transmission at the specified transmission interval is a specific tag In accordance with the search mode, a process for estimating the direction and distance of the wireless tag designated as the search target by the user is executed.
(Ix) After the user specifies the position of the wireless tag specified as the search target by the user, the wireless tag search application ends execution of the specific tag search mode and returns to the state in which the in-area tag list display mode is being executed. (S9 in FIG. 6). Subsequently, according to the same procedure as in (i) and (ii) above, the wireless tag located in the communicable area of the tag search device 100 is advertising at the signal transmission interval corresponding to the in-area tag list display mode. The signal is set to be transmitted (S10 in FIG. 6).
(X) Subsequently, when the user determines that a new search for the RFID tag is unnecessary and terminates the RFID tag search application via the GUI of the user input / output unit 106 (S11 in FIG. 6), the RFID tag search is performed. As a process at the end of the application, the application sets the wireless tag located in the communicable area of the tag search device 100 to transmit the Advertising signal at the signal transmission interval corresponding to the standby state (S12 in FIG. 6). ). In another modified example of the present embodiment, the operation of returning the signal transmission interval of the wireless tag to the setting corresponding to the standby state is not performed by the application itself as a process at the end of execution, but is performed as follows. It is good also as composition to do. For example, it is possible to adopt a configuration in which the control unit 101 automatically executes regardless of the application after a predetermined time has elapsed after the execution of the RFID tag search application. Alternatively, the wireless tag notified from the tag searching device 100 of the end of the execution of the wireless tag searching application may be configured to automatically execute on the wireless tag side automatically after a lapse of a certain time after the notification.
(3-2) Effects of First Embodiment The signal transmission interval control method according to the first embodiment takes into account the number of wireless tags to be listed or displayed on the search screen of the tag search device 100. Then, the signal transmission interval from the wireless tag is automatically set to an optimum value. Accordingly, the method according to the first embodiment reduces the probability of collision due to simultaneous transmission from a large number of wireless tags, and also searches for a tag due to battery consumption of the wireless tag due to a short signal transmission interval and a long signal transmission interval. Eliminate the trade-off between performance degradation. As a result, the method according to the first embodiment does not frequently implement a radio channel synchronization mechanism and a power control mechanism at the same level as those of a mobile terminal, and frequently uses a large number of radio tags located in the search range. It is possible to prevent an increase in collision probability due to simultaneous transmission.
<4> Second Example According to this Embodiment Hereinafter, a second example according to this embodiment will be described with reference to FIGS. First, the outline of the second embodiment will be described.
(4-1) Overview of Second Example In the second example according to the present embodiment, a wireless tag at a distance away from the tag search device 100 is out of the communicable area of the tag search device 100. In addition, in order to notify the user of the position change of the wireless tag quickly and frequently, the transmission interval of the Advertising signal is automatically set to the optimum value based on the distance to the wireless tag and the speed at which the wireless tag moves away. Set to. Specifically, in the method according to the second example of the present embodiment, the tag searching device 100 sets the transmission interval of the advertising signal from the wireless tag so that the distance between the wireless tag and the tag searching device 100 decreases. The wireless tag is instructed, and at this time, the wireless tag is instructed to set a shorter signal transmission interval as the speed at which the wireless tag moves away from the tag search device 100 is faster. Thereby, the method according to the second embodiment can compensate for a decrease in search performance (search accuracy and search success rate) of the wireless tag located at a distance away from the tag search device 100 by increasing the signal transmission frequency. At the same time, the method according to the second embodiment quickly and frequently notifies the user of the distance to the wireless tag and its change before losing sight of the wireless tag that is likely to move out of the search range. .

At this time, the distance between the tag searching device 100 and each wireless tag is estimated based on the received radio wave intensity from each wireless tag. Further, the moving speed of the wireless tag along the direction away from the tag search device 100 is estimated based on the amount of decrease in the reception intensity of the signal from the wireless tag.
An individual transmission interval is set for each tag according to the distance between the search terminal and the wireless tag and the change (speed) of the distance.

That is, according to the second example of the present embodiment, the transmission interval of the Advertising signal from the wireless tag can be determined according to the following two methods.
(A) When the transmission interval is controlled only in accordance with the distance between the tag search device 100 and the wireless tag, the tag search device 100 is wireless as the reception intensity of the signal from the wireless tag is smaller (the distance is longer). Instructs the tag to set a shorter transmission interval.
(B) When the transmission interval is controlled according to the speed at which the wireless tag moves away from the tag search device 100 (the rate of increase in the distance from the wireless tag), the reception intensity of the signal from the wireless tag measured over a certain period of time The tag search device 100 instructs the wireless tag to set the transmission interval to be shorter as the amount of decrease is larger (as the moving speed is higher).

  Even when the tag search device 100 controls the transmission interval of the Advertising signal according to either the method (A) or the method (B), the receiving strength (or change) of the Advertising signal is a certain value or more. The transmission interval may be set short only for the wireless tag, and the default transmission interval may be set for the wireless tag that is equal to or less than a certain value. The reason why the transmission interval control method according to the second embodiment is configured as described above is as follows. As shown in FIG. 5, the rate of change per unit distance of the reception strength (electric field strength) of the Advertising signal decreases as the distance between the tag search device 100 and the wireless tag increases. Therefore, if the value of the receiving strength (or change) of the Advertising signal is below a certain value, the value of such receiving strength (electric field strength) is used as a reference for strictly estimating the distance to the wireless tag and the amount of change. Insufficient accuracy and significance.

  In addition, the control unit 101 stores a relationship between the received radio wave intensity from the wireless tag (or its change) and the setting value of the Advertising signal transmission interval to be set in advance in the database, and corresponds from the database. You may acquire by reading a setting value. As another embodiment, the control unit 101 may calculate an Advertising signal transmission interval setting value to be set based on a specific calculation formula using the received radio wave intensity (or change thereof) from the wireless tag as an input parameter. good.

  Further, as an embodiment in which the method (A) and the method (B) described above are combined, a tag in which the radio wave intensity of the Advertising signal received from the radio tag is small and the decrease in radio wave intensity within a certain time is large. Alternatively, the signal transmission interval may be set to be short only, or conversely, the signal transmission interval may be set to be long only for a tag having a high radio wave intensity and a small amount of decrease in radio wave intensity within a certain time.

The flowchart in FIG. 8 instructs the control unit 101 to set the signal transmission interval to be short only for tags whose radio signal strength of the Advertising signal received from the radio tag is small and whose radio field strength decrease amount within a certain time is large. An example of a transmission interval control method is shown. In FIG. 8, the threshold value regarding the radio wave intensity of the Advertising signal received from the wireless tag is expressed as a, the threshold value of the decrease amount of the radio wave intensity within a predetermined time is expressed as b, and the default signal transmission interval is expressed as c. A list of specific set values of “threshold a”, “threshold b”, and “threshold c” is shown in FIG. The list of FIG. 9 is stored in the storage unit 105, and is referred to by the control unit 101 when the control unit 101 executes the transmission interval control method according to the second embodiment according to the flowchart of FIG.
(4-2) Process Flow of Signal Transmission Interval Control Method According to Second Example In the second example of the present embodiment, the control unit 101 in the tag search device 100 performs the following processing shown in the flowchart of FIG. This is realized by repeatedly executing the procedure at regular time intervals, and as a result, the transmission interval of the Advertising signal for each wireless tag is controlled according to the situation.

  First, in step S <b> 1, the control unit 101 determines whether or not the radio field intensity of the Advertising signal received from each wireless tag is greater than “threshold a”. At this time, the control unit 101 acquires the measured value of the radio field intensity by receiving the intensity of the received radio wave from the wireless tag measured by the wireless communication unit 103 via the notification information receiving unit 102. If the radio wave intensity is greater than “threshold a”, the process proceeds to step S2, and if not, the process proceeds to step S5.

  Subsequently, in step S <b> 2, the control unit 101 determines whether or not the amount of decrease in radio wave intensity of the Advertising signal received from each wireless tag is greater than “threshold b”. The amount of decrease in radio wave intensity is obtained by calculating the difference between the radio wave intensity measured at the current loop execution and the radio wave intensity measured at the previous loop execution in the flowchart of FIG. Is possible. Alternatively, as another embodiment, the amount of decrease in radio wave intensity may be calculated by a least square method or the like using three or more radio wave intensities measured by three or more repeated executions of the flowchart of FIG. 7 as sample values. . If the control unit 101 determines whether or not the calculated decrease amount of the radio field intensity is greater than the “threshold value b”, the process proceeds to step S3 if the decrease amount of the radio field intensity is greater than the “threshold value b”. Otherwise, the process proceeds to step S5.

  Subsequently, in step S3, the control unit 101 determines the optimum transmission interval of the Advertising signal based on the radio signal strength of the Advertising signal and the amount of decrease thereof, and the optimum transmission according to the radio signal strength and the amount of reduction thereof. The interval setting value is selected from the setting value table shown in FIG. Specifically, it is as follows. Each column of the two-dimensional table in the matrix format shown in FIG. 10 corresponds to various values of the radio field intensity of the Advertising signal, and each row corresponds to various values of the decrease amount of the radio field intensity. The first column of the table of FIG. 10 shows the setting of the advertising signal transmission interval as the amount of decrease in radio field intensity changes to 11 dB, 12 dB, 13 dB,... When the radio field intensity of the signal received from the wireless tag is −51 dBm. It shows how the value changes as 900 milliseconds, 850 milliseconds, 800 milliseconds,. Similarly, the second column of the table of FIG. 10 shows the Advertising signal as the amount of decrease in radio field intensity changes to 11 dB, 12 dB, 13 dB,... When the radio field intensity of the signal received from the wireless tag is −52 dBm. The transmission interval setting value changes from 850 milliseconds, 800 milliseconds, 750 milliseconds,... Similarly, the third column of the table of FIG. 10 shows the Advertising signal as the amount of decrease in radio field intensity changes to 11 dB, 12 dB, 13 dB,... When the radio field intensity of the signal received from the wireless tag is −53 dBm. This shows how the transmission interval setting value changes as 800 milliseconds, 750 milliseconds, 700 milliseconds,. This is because the transmission interval of the Advertising signal is set shorter as the distance to the wireless tag becomes longer as viewed from the tag search device 100. At this time, the signal transmission interval is increased as the speed at which the wireless tag moves away from the tag search device 100 is faster. This corresponds to a shorter setting.

  Therefore, the control unit 101 selects a column corresponding to the radio wave intensity of the signal received from the wireless tag in the table of FIG. 10, and further sets a row corresponding to the amount of decrease in the radio wave intensity from the selected column. By selecting a value, an optimum signal transmission interval setting value is selected. For example, when the radio wave intensity of the signal received from the wireless tag is −52 dBm and the decrease amount of the radio wave intensity is 12 dB, the control unit 101 starts the signal transmission interval from the second row of the second column of the table of FIG. A value of 800 milliseconds is selected as the setting value.

  Subsequently, in step S <b> 4, the control unit 101 instructs each wireless tag to set and change the transmission interval of the Advertising signal via the notification information receiving unit 102 and the wireless communication unit 103. Specifically, the control unit 101 includes the transmission interval setting value of the Advertising signal determined in step S3 in the instruction signal, and transmits the instruction signal to each wireless tag. In response, each wireless tag transmits an Advertising signal at a transmission interval indicated by the transmission interval setting value in the instruction signal.

  On the other hand, when it is determined in step S1 or step S2 that the radio wave intensity or the amount of decrease is equal to or less than the threshold value and the process proceeds to step S5, the control unit 101 uses the wireless tag as the transmission interval setting value of the advertising signal. The default transmission interval c shown in the table of FIG. 9 is selected, and each wireless tag is instructed to change the setting of the transmission interval of the Advertising signal to the default transmission interval c.

In the second embodiment, when the signal transmission interval of each wireless tag is selected in step S3, the tag searching device 100 displays the current position of each wireless tag on the display screen. Update at a cycle shorter than the transmission interval. This is because, in step S3, a short signal transmission interval may be selected for a radio tag that is likely to go out of the searchable area of the tag search device 100, so that the user can search for the radio tag. This is to notify the user of a change in the position of the wireless tag quickly and frequently before losing sight of the area.
(4-3) Operational Effects of Second Embodiment From the above, in the second embodiment, the distance between each wireless tag to be searched by the tag search device 100 and the speed at which the wireless tag moves away from the tag search device 100. In consideration of the above, the signal transmission interval from the wireless tag is automatically set to an optimum value. That is, in the second embodiment, the signal transmission interval is set shorter as the radio tag is further away from the tag search device 100. At this time, the signal transmission interval is further increased as the speed at which the wireless tag is moved away from the tag search device 100 is higher. Set it short. As a result, the signal transmission interval control method according to the second embodiment can compensate for a decrease in search performance (search accuracy and search success rate) of wireless tags at a distant distance by increasing the signal transmission frequency. At the same time, the signal transmission interval control method according to the second embodiment allows the user to quickly and highly determine the distance to the wireless tag and its change before losing sight of the wireless tag that is likely to move out of the search range. The frequency can be notified.

  INDUSTRIAL APPLICABILITY The present invention can be used as a portable user device for searching for a wireless transmitter that assists a user in searching for the current position of a wireless transmitter such as an active wireless tag.

DESCRIPTION OF SYMBOLS 100 Tag search apparatus 101 Control part 102 Notification information receiving part 103 Wireless communication part 104 Display part 105 Storage part 106 User input / output part 107 Sensor 108 Transmission / reception antenna 200 Radio tag 201 Control part 202 Notification information transmission part 203 Wireless communication part 204 Timekeeping part 205 Storage Unit 206 Battery 207 Transmission / Reception Antenna 300 Functional Block Structure of Tag Searching Device 302 Dynamic Determination Unit 304 Position Estimation Unit 400 Icon image for displaying the position of the wireless tag

Claims (7)

A method performed by the user terminal to locate one or more radios that are located within an area that can wirelessly communicate with the user terminal and each periodically transmits a broadcast information signal:
Detecting at least a radio field intensity of a signal received from each radio in the area;
Setting the transmission cycle of the notification information signal to be shorter as the detected radio wave intensity is smaller; and
Instructing each radio in the area to transmit the broadcast information signal according to the determined transmission period;
A method comprising: Identifying the location of each radio in the area based on the broadcast information signal; and
Further displaying to the user the identified location for each radio in the area;
The method according to claim 1, wherein: The step of determining the transmission cycle includes a step of setting the transmission cycle to a predetermined value regardless of the radio wave intensity when the radio wave intensity of the received signal is equal to or less than a predetermined threshold value.
The method according to claim 1, wherein: A program executed by a control circuit in the user terminal in order to search for the position of one or more radios that are located in an area where radio communication with the user terminal is possible and each transmits a broadcast information signal periodically There:
Causing the control circuit to detect a radio field intensity of a signal received from each radio in at least the area;
A step of causing the control circuit to set a transmission cycle of the notification information signal shorter as the detected radio field intensity decreases; and
Causing the control circuit to perform an operation of instructing each radio in the area to transmit the broadcast information signal according to the determined transmission cycle;
A program comprising Causing the control circuit to identify the position of each radio in the area based on the notification information signal; and
Causing the control circuit to perform an operation of displaying the specified position for each radio in the area to a user;
The program according to claim 4, further comprising: The user terminal used to search for the location of one or more radios that are located in an area where radio communication with the user terminal is possible and each periodically transmits a broadcast information signal:
Means for detecting a radio field intensity of a signal received from each radio in the area;
Means for setting the transmission period of the notification information signal to be shorter as the detected radio wave intensity is smaller; and
Means for instructing each radio in the area to transmit the broadcast information signal according to the determined transmission cycle;
A user terminal comprising: Means for identifying the position of each radio in the area based on the broadcast information signal; and
Means for displaying to the user the identified location for each radio in the area;
The user terminal according to claim 6, further comprising:

Images