JP2013115509A - Radio tag system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption of a radio tag which transmits identification information at predetermined time intervals without reducing radio tag monitoring accuracy at a receiver side in a system comprising the radio tag.SOLUTION: A radio tag determines, when tag information is transmitted (S110), whether or not a response signal from a receiver can be received (S130) and if the response signal cannot be received, a standard standby time ▵T2 is set as a transmission interval until next transmission of the tag information (S140). Furthermore, when the response signal is being received, a reception level L1 of tag information at a receiver side and a reception level L2 of the response signal at a radio tag side are acquired, and variations ▵L1 and ▵L2 from previous values of these levels are calculated (S160). In the case where both the variations ▵L1 and ▵L2 are equal to or more than a threshold value, a minimum standby time ▵T1 (<▵T2) is set as the transmission interval (S180) but if not, a maximum standby time ▵T3 (>▵T2) is set as the transmission interval (S190).

Description

  The present invention includes a receiving device that receives identification information wirelessly transmitted from a wireless tag attached to a monitoring target, and recognizes the monitoring target from the received identification information, and the position and movement of the monitoring target of the monitoring target. The present invention relates to a wireless tag system that is used to monitor the system.

  Conventionally, as a wireless tag, a passive type that operates by receiving power supply from a communication partner and transmits identification information stored in advance, a built-in battery, identification information without receiving power supply from the communication partner, etc. The active type that can transmit the is known.

  Among them, since the active type wireless tag can transmit the identification information periodically, a plurality of receiving devices that receive the transmission signal are distributed in the monitoring area, and the reception state of the identification information by each receiving device is set. By monitoring, it is possible to easily grasp the position and movement of the wireless tag (and hence the article or person to be monitored) (see, for example, Patent Documents 1 and 2).

JP 2005-268837 A JP 2010-130028 A

  However, in order to be able to monitor the position and movement of the wireless tag as described above, the identification information must be periodically transmitted from the wireless tag, and the battery power is frequently consumed by the periodic transmission. There was a problem that the battery life was shortened.

  In order to extend the battery life, the periodic transmission interval from the wireless tag may be increased. However, simply increasing the periodic transmission interval causes a delay in detection of movement of the monitoring target. It may be impossible to grasp the position and moving direction.

  The present invention has been made in view of such problems, and in a wireless tag system including a wireless tag that spontaneously transmits identification information, the transmission interval of the identification information from the wireless tag is adjusted to adjust the wireless tag. It aims at reducing the power consumption of the battery of a radio | wireless tag, without reducing monitoring precision.

The invention according to claim 1, which has been made to achieve the object,
A wireless device comprising a first wireless communication unit for performing wireless communication, transmission control means for repeatedly transmitting identification information from the first wireless communication unit at predetermined time intervals, and a battery for supplying power to these units. Tag,
A second wireless communication unit for performing wireless communication, and when the identification information transmitted from the wireless tag is received by the second wireless communication unit, the identification information is output to a monitoring unit that monitors the wireless tag Receiving control means, and a receiving device including power supply means for supplying power to each of these units;
A wireless tag system comprising:
The receiving device is:
First level detecting means for detecting a signal level of the received signal received by the second wireless communication unit;
The reception control means in the receiving means is
When the identification information transmitted from the wireless tag is received by the second wireless communication unit, a response signal including a reception level of the identification information detected by the first level detecting unit is sent to the second wireless communication unit. Transmit from the wireless communication unit to the wireless tag,
The wireless tag is
When the response signal transmitted from the receiving device is received by the first wireless communication unit, a change amount from the previous value of the reception level included in the response signal is calculated, and the calculated change amount is predetermined. Transmission for setting the transmission interval of the identification information by the transmission control means so that the transmission interval is shortened if the threshold is equal to or greater than the threshold, and the transmission interval is increased if the calculated change amount is less than the threshold. Interval setting means,
It is provided with.

The invention according to claim 2
A wireless device comprising a first wireless communication unit for performing wireless communication, transmission control means for repeatedly transmitting identification information from the first wireless communication unit at predetermined time intervals, and a battery for supplying power to these units. Tag,
A second wireless communication unit for performing wireless communication, and when the identification information transmitted from the wireless tag is received by the second wireless communication unit, the identification information is output to a monitoring unit that monitors the wireless tag Receiving control means, and a receiving device including power supply means for supplying power to each of these units;
A wireless tag system comprising:
The reception control means in the receiving means is
When the identification information transmitted from the wireless tag is received by the second wireless communication unit, a response signal is transmitted from the second wireless communication unit to the wireless tag,
The wireless tag is
Second level detecting means for detecting a signal level of a received signal received by the first wireless communication unit;
When the response signal transmitted from the receiving device is received by the first wireless communication unit, the amount of change from the previous value of the reception level of the response signal detected by the second level detecting unit is calculated. When the calculated change amount is equal to or greater than a predetermined threshold, the transmission interval is shortened, and when the calculated change amount is less than the threshold, the transmission control unit increases the transmission interval. A transmission interval setting means for setting the transmission interval of the identification information;
A wireless tag system comprising:

The invention according to claim 3
A wireless device comprising a first wireless communication unit for performing wireless communication, transmission control means for repeatedly transmitting identification information from the first wireless communication unit at predetermined time intervals, and a battery for supplying power to these units. Tag,
A second wireless communication unit for performing wireless communication, and when the identification information transmitted from the wireless tag is received by the second wireless communication unit, the identification information is output to a monitoring unit that monitors the wireless tag Receiving control means, and a receiving device including power supply means for supplying power to each of these units;
A wireless tag system comprising:
The receiving device is:
First level detecting means for detecting a signal level of the received signal received by the second wireless communication unit;
The reception control means in the receiving device is:
When the identification information transmitted from the wireless tag is received by the second wireless communication unit, a response signal including a reception level of the identification information detected by the first level detecting unit is sent to the second wireless communication unit. Transmit from the wireless communication unit to the wireless tag,
The wireless tag is
Second level detecting means for detecting a signal level of a received signal received by the first wireless communication unit;
When the response signal transmitted from the reception device is received by the first wireless communication unit, the amount of change from the previous value of the reception level of the response signal detected by the second level detection unit, The amount of change from the previous value of the reception level included in the response signal is calculated, and if the two calculated amounts of change are both equal to or greater than a predetermined threshold, the transmission interval is shortened, and the two calculated A transmission interval setting means for setting a transmission interval of the identification information by the transmission control means so that the transmission interval becomes longer if at least one of the change amounts is less than the threshold;
It is provided with.

  As described above, the wireless tag system according to the present invention (Claims 1 to 3) includes the wireless tag and the receiving device. The wireless tag operates by receiving power supply from the battery, and the transmission control unit repeatedly transmits its identification information from the first wireless communication unit at a predetermined time interval.

  Further, the reception device operates by receiving power supply from the power supply means provided in the reception device, and when the identification information transmitted from the wireless tag is received by the second wireless communication unit, the reception control means, The identification information is output to monitoring means for monitoring the wireless tag.

  Although the wireless tag includes a battery, the power supply means of the receiving device is a power supply circuit that generates power supply voltage for driving an internal circuit by receiving power supply from an external commercial power supply, even if the battery is a battery. Also good.

  In the wireless tag system of the present invention (Claims 1 to 3), the wireless tag includes transmission interval setting means for setting a transmission interval when the transmission control means causes the first wireless communication unit to transmit the identification information. It has been.

  The transmission interval setting means in the wireless tag system according to claim 1, when the response signal transmitted from the receiving device is received by the first wireless communication unit, the previous value of the reception level included in the response signal The transmission control means calculates the amount of change from, and shortens the transmission interval if the calculated amount of change is equal to or greater than a predetermined threshold, and increases the transmission interval if the calculated amount of change is less than the threshold. Sets the transmission interval for identification information.

  In the wireless tag system according to claim 1, the receiving device is provided with first level detecting means for detecting the signal level of the received signal received by the second wireless communication unit, and the second wireless communication system is provided. When the identification information transmitted from the wireless tag is received by the communication unit, the reception control unit sends a response signal including the reception level of the identification information detected by the first level detection unit from the second wireless communication unit. This is because the wireless tag is transmitted.

  In other words, the reception level of the transmission signal from the wireless tag is given to the response signal transmitted by the receiving device, and if the position of the wireless tag does not change, the reception level is substantially constant. Moves relative to the receiving device, and the position of the wireless tag changes, the reception level changes.

  Therefore, in the wireless tag system according to claim 1, the wireless tag acquires the reception level of the identification information on the receiving device side, and the wireless tag depends on whether or not the amount of change in the reception level is equal to or greater than a threshold value. When the wireless tag itself is moving, the transmission interval of the identification information is shortened so that the monitoring means can grasp the change in position when the wireless tag itself is moving. When the tag is stopped or substantially stopped, the transmission interval of the identification information is lengthened to reduce the battery power consumption.

  Therefore, according to the wireless tag system of the first aspect, the transmission interval is required while transmitting the identification information from the first wireless communication unit so as not to decrease the monitoring accuracy of the wireless tag by the monitoring unit. The transmission interval can be set appropriately so as not to become shorter than that. Therefore, according to the present invention, the battery power consumption in the wireless tag can be reduced and the battery life can be extended.

  On the other hand, the transmission interval setting means in the wireless tag system according to claim 2 is configured such that when the response signal transmitted from the receiving device is received by the first wireless communication unit, the response detected by the second level detecting means. If the amount of change from the previous value of the signal reception level is calculated and the calculated amount of change is greater than or equal to a predetermined threshold, the transmission interval is shortened. If the calculated amount of change is less than the threshold, the transmission interval is The transmission interval of the identification information by the transmission control means is set so as to be longer.

  In the wireless tag system according to claim 2, the wireless tag includes a second level detecting means for detecting the signal level of the received signal received by the first wireless communication unit, and the first wireless This is because when the response signal transmitted from the receiving device is received by the communication unit, the reception level of the response signal is detected by the second level detecting means.

  That is, in the wireless tag, the signal level of the response signal detected by the second level detection means is substantially constant unless the position of the wireless tag with respect to the receiving device changes, and conversely, the wireless tag moves relative to the receiving device. If the position of the wireless tag changes, the signal level of the response signal changes.

  Therefore, in the wireless tag system according to claim 2, each time a response signal is received from the receiving device, the wireless tag side acquires the reception level of the response signal, and the amount of change in the acquired reception level is It is determined whether or not the wireless tag itself has moved depending on whether or not it is equal to or greater than the threshold value.

  Similarly to the wireless tag system according to claim 1, when the wireless tag itself is moving, the transmission interval of the identification information is shortened so that the monitoring means can grasp the position change accompanying the movement. In addition, when the wireless tag is stopped or substantially stopped, the transmission interval of the identification information is lengthened to reduce the power consumption of the battery.

Therefore, according to the wireless tag system of the second aspect, the same effect as that of the first aspect can be obtained.
Next, a wireless tag system according to a third aspect is a combination of the structure according to the first aspect and the structure according to the second aspect.

  When the response signal transmitted from the receiving device is received by the first wireless communication unit, the transmission interval setting unit changes the reception level of the response signal detected by the second level detection unit from the previous value. The amount of change and the amount of change from the previous value of the reception level included in the response signal are respectively calculated, and if the two calculated amounts of change are both equal to or greater than a predetermined threshold, the transmission interval is shortened and the calculated If at least one of the two changes is less than the threshold value, the transmission interval of the identification information by the transmission control means is set so that the transmission interval becomes longer.

For this reason, according to the wireless tag system described in claim 3, the same effects as those described in claim 1 and claim 2 can be obtained.
In particular, according to the wireless tag system of claim 3, in the wireless tag, both the reception level of the identification information on the receiving device side and the reception level of the response signal on the wireless tag side are equal to or greater than the threshold value. Because the wireless tag is judged to have moved and the transmission interval of the identification information is shortened, when any reception level fluctuates due to the glory of disturbance, the wireless tag is erroneously judged to move. Therefore, it is possible to prevent the transmission interval of the identification information from being shortened.

  Therefore, according to the wireless tag system of the third aspect, the battery power consumption in the wireless tag can be reduced better and the life of the battery can be reduced as compared with those of the first and second aspects. Can be extended.

It is a block diagram showing the structure of the radio | wireless tag system of embodiment. It is a flowchart showing the transmission process and reception process which are performed with a wireless tag and a receiver.

  As shown in FIG. 1, the wireless tag system according to the present embodiment is wirelessly transmitted from a plurality of wireless tags 10 attached to a person or article to be monitored and distributed in a monitoring area. It comprises a plurality of receiving devices 30 that receive identification information (so-called IDs, hereinafter referred to as tag information), and a monitoring device (not shown).

  Then, based on the tag information received by each receiving device 10, the monitoring device monitors the position and movement of the wireless tag 10 (and thus the person or article to which the wireless tag 10 is attached) in the monitoring area. To do.

  Here, the wireless tag 10 includes a wireless communication unit 12 for performing wireless communication with the receiving device 30 via an antenna, and a level detection unit that detects a signal level of a reception signal received by the wireless communication unit 12. 14, and a control unit 20 that is connected to these units 12 and 14 and controls wireless communication by the wireless communication unit 12.

  The control unit 20 is composed of a well-known microcomputer comprising a CPU, ROM, RAM, and the like, and performs a transmission process (see FIG. 2) for transmitting tag information from the wireless communication unit 12 at predetermined time intervals. Run.

  Further, the wireless tag 10 includes a storage unit 16 in which tag information of the wireless tag 10 itself is stored, and a battery 18 for supplying power to the above-described units constituting the wireless tag 10. The battery 18 is a lightweight and small (thin) battery such as a button battery.

  On the other hand, the receiving device 30 includes a wireless communication unit 32 for performing wireless communication with the wireless tag 10 via an antenna, and a level detection unit 34 for detecting the signal level of the received signal received by the wireless communication unit 32. And a wired communication unit 36 for communicating with an external monitoring device via a communication line, and a control unit connected to each of the units 32, 34, 36 to control communication by the communication units 32, 36. 40.

  Like the control unit 20, the control unit 40 is configured by a known microcomputer (microcomputer) including a CPU, a ROM, a RAM, and the like, and tag information transmitted from the wireless tag 10 is transferred to the wireless communication unit 12. And a communication process for performing data communication with the monitoring device via the wired communication unit 36, which will be described later (see FIG. 2), and transmitting a response signal to the wireless tag 10.

  The receiving device 30 includes a storage unit 38 in which identification information (receiving terminal information) necessary for wireless communication with the wireless tag 10 and the monitoring device is stored, and the receiving device 30. A power supply unit 42 is provided for supplying power to each of the above components. The power supply unit 42 receives power supply from a dry battery, a rechargeable secondary battery, or an external power supply (commercial power supply or the like), generates a power supply voltage, and supplies the power supply voltage to the respective units.

  Next, transmission processing and reception processing executed to transmit and receive tag information in the control units 20 and 40 of the wireless tag 10 and the receiving device 30 will be described with reference to the flowchart shown in FIG.

  As shown in FIG. 2, in the transmission processing on the wireless tag 10 side, first, in S110 (S represents a step), tag information which is its own identification information is read from the storage unit 16, and this wireless communication unit 12 reads this tag information. A transmission signal including tag information is transmitted.

  On the other hand, in the reception process on the receiving device 30 side, the wireless communication unit 32 determines whether or not the tag information transmitted from the wireless tag 10 is received by the wireless communication unit 32 in S210. When the tag information transmitted from the wireless tag 10 is received, the process proceeds to S220.

  In S220, the reception level L1 when the transmission signal including the tag information is received from the wireless tag 10 is read from the level detection unit 34, and the response signal including the reception level L1 and the tag information of the receiving device 30 is transmitted.

In subsequent S230, the received data representing the tag information of the wireless tag 10 received this time and the reception time thereof are stored in a memory (RAM or the like), and the process proceeds to S210 again.
Note that the received data stored in the memory in S230 is transmitted to the monitoring device in a communication process for performing data communication with the monitoring device.

As a result, the monitoring device side can monitor the positions and movements of the plurality of wireless tags 10 to be monitored based on the reception data transmitted from the receiving device 30.
As described above, when the transmission signal including the tag information is transmitted from the wireless tag 10, the reception device 30 that has received the signal transmits a response signal including the reception level L <b> 1 of the signal to the wireless tag 10.

  For this reason, in the transmission processing on the wireless tag 10 side, after transmitting a transmission signal including tag information from the wireless communication unit 12 in S110, the process proceeds to S120, and the wireless communication unit 12 transmits from the receiving device 30. It waits for a certain time for the received response signal to be received.

In subsequent S130, it is determined whether or not a response signal is received within the predetermined time. If no response signal is received within the predetermined time, the process proceeds to S140.
In S140, a preset standard standby time ΔT2 is set as a standby time (in other words, transmission interval) from transmission of tag information in S110 to transmission of tag information next time. Wait for time ΔT2 to elapse. Then, when the standard standby time ΔT2 has elapsed, the process proceeds to S110 again.

  The standard standby time ΔT2 is set to a sufficiently long time (for example, 10 seconds) compared to the standby time (a predetermined time: at least 1 second or less) when receiving the response signal from the receiving device 30 in S120. Has been.

  On the other hand, if it is determined in S130 that the response signal has been received within a predetermined time, the process proceeds to S150, the received data included in the response signal is stored in a memory (such as a RAM), and the process proceeds to S160.

  In S160, the reception level L2 of the response signal is read from the level detection unit 14, and the reception level L2 of this response signal and the reception level L1 included in the response signal (specifically, the transmission signal that transmitted the tag information in S110). With respect to the reception level at the receiving device 30 side, the amount of change from the reception levels L2 and L1 (that is, the previous value) obtained when the processes of the previous S150 and S160 were executed is calculated.

  In the subsequent S170, it is determined whether or not the amounts of change ΔL1 and ΔL2 from the previous values of the reception levels L1 and L2 calculated in S160 are equal to or greater than a preset threshold value for movement determination, respectively. To do.

If it is determined in S170 that the amounts of change ΔL1 and ΔL2 are both greater than or equal to the threshold value, that is, if the wireless tag 10 has moved relative to the receiving device 30, the process proceeds to S180.
In S180, a preset shortest waiting time ΔT1 is set as a waiting time from the tag information transmission in S110 to the next tag information transmission, and the shortest waiting time ΔT1 elapses. stand by.

  Then, when the shortest standby time ΔT1 has elapsed, the process proceeds to S110 again. The shortest standby time ΔT1 is longer than the standby time (fixed time) when receiving the response signal from the receiving device 30 in S120, but shorter than the standard standby time ΔT2 (eg, 3 seconds). Is set.

  Next, if it is determined in S170 that the change amounts ΔL1 and ΔL2 are not equal to or greater than the threshold value (in other words, at least one of the change amounts ΔL1 and ΔL2 is less than the threshold value), The tag 10 is determined not to have moved relative to the receiving device 30, and the process proceeds to S190.

  In S190, the longest standby time ΔT3 (for example, set in advance to be longer than the standard standby time ΔT2) as the standby time from when tag information is transmitted in S110 until the next tag information is transmitted. 30 seconds) and wait for the longest waiting time ΔT3 to elapse. Then, when the longest standby time ΔT3 has elapsed, the process proceeds to S110 again.

  As described above, in this embodiment, the wireless tag 10 transmits tag information at a predetermined time interval. In the transmission interval, a response signal returned from the receiving device 30 in response to the transmission of tag information is transmitted. Different times are set depending on whether or not the response signal can be received.

  That is, when the wireless tag 10 cannot receive a response signal from the receiving device 30 (in other words, when the wireless tag 10 is far away from the receiving device 30 or between the wireless tag 10 and the receiving device 30). For example, when a defect occurs, a standard standby time ΔT2 (for example, 10 seconds) is set.

  When the response signal from the receiving device 30 is received on the wireless tag 10 side, the reception level L1 of the tag information on the receiving device 30 side and the reception level L2 of the response signal on the wireless tag 10 side are: If the amount of change ΔL1 or ΔL2 is greater than or equal to the threshold value according to the amount of change ΔL1 or ΔL2 from the previous value, it is assumed that the wireless tag 10 has moved relative to the receiving device 30, and tag information Is set to the minimum transmission time ΔT1 (for example, 3 seconds).

  When at least one of the change amounts ΔL1 and ΔL2 is less than the threshold value, it is assumed that the wireless tag 10 has not moved relative to the receiving device 30, and the maximum waiting time Δ is included in the next transmission interval of tag information. T3 (for example, 30 seconds) is set.

  Therefore, according to the wireless tag system of the present embodiment, when the wireless tag 10 (and thus the person or article to which the wireless tag 10 is attached) is moving, the position change associated with the movement is received by the receiving device 30 ( As a result, the transmission interval of the tag information can be shortened so that the monitoring device) can grasp.

  Further, when the wireless tag 10 is stopped or substantially stopped, the transmission interval of tag information from the wireless tag 10 is lengthened to reduce the power consumption of the battery 18 of the wireless tag 10 and extend the life of the battery 18. be able to.

  Further, if the transmission interval of the tag information from the wireless tag 10 is increased, the transmission interval of the response signal from the receiving device 30 can also be increased. Therefore, the power consumption caused by the transmission of the response signal on the receiving device 30 side can be reduced. It can also be reduced.

  Here, the wireless tag system of the present embodiment is an application of the invention described in claim 3, and the wireless communication unit 12 in the wireless tag 10 corresponds to the first wireless communication unit of the present invention, and the control unit 20 corresponds to the transmission control means and transmission interval setting means of the present invention, and the level detector 14 corresponds to the second level detection means of the present invention.

  And the function as a transmission control means of this invention is implement | achieved by S110 of the transmission process performed in the control part 20 of the wireless tag 10, and the function as a transmission interval setting means is similarly implement | achieved by S160-S190. Is done.

  The wireless communication unit 32 in the receiving device 30 corresponds to the second wireless communication unit of the present invention, the control unit 40 corresponds to the reception control unit of the present invention, and the level detection unit 34 corresponds to the first wireless communication unit of the present invention. The level detection means, and the power supply unit 42 corresponds to the power supply means of the present invention.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.
For example, in the above embodiment, the wireless tag 10 and the receiving device 30 are provided with level detection units 14 and 34, respectively, and on the wireless tag 10 side, tag information and response signals detected by the level detection units 14 and 34 are provided. The wireless tag 10 has been described as determining whether or not the wireless tag 10 has moved with respect to the receiving device 30 based on the received level.

  On the other hand, the level detection means for detecting the reception level is provided only in one of the wireless tag 10 and the receiving device 30, and on the wireless tag 10 side, the reception level detected by the one level detection unit 14 or 34 is set. Based on this, it may be determined whether or not the wireless tag 10 has moved relative to the receiving device 30.

  For this purpose, a change amount ΔL1 or ΔL2 of the reception level L1 or L2 is calculated in S160 of the transmission process executed on the wireless tag 10 side, and the calculated change amount ΔL1 is calculated in S170. Alternatively, it may be determined whether ΔL2 is equal to or greater than a threshold value.

  In the above embodiment, the receiving devices 30 that receive the transmission signals from the wireless tags 10 are distributed in the monitoring area, and the monitoring devices collect the reception data from the wireless tags 10 from the receiving devices 30. The wireless tag system configured to monitor the positions and movements of the plurality of wireless tags 10 has been described.

  However, the present invention is a wireless tag system that detects a wireless tag 10 (and thus a person or article to which the wireless tag 10 is attached) passing through the vicinity of the monitoring device with a single monitoring device having a function as a receiving device. However, the same effects can be obtained by applying the same as in the above embodiment.

  DESCRIPTION OF SYMBOLS 10 ... Wireless tag, 12 ... Wireless communication part, 14 ... Level detection part, 16 ... Memory | storage part, 18 ... Battery, 20 ... Control part, 30 ... Receiver, 32 ... Wireless communication part, 34 ... Level detection part, 36 ... Wired communication unit, 38 ... storage unit, 40 ... control unit, 42 ... power supply unit.

Claims (3)

A wireless device comprising a first wireless communication unit for performing wireless communication, transmission control means for repeatedly transmitting identification information from the first wireless communication unit at predetermined time intervals, and a battery for supplying power to these units. Tag,
A second wireless communication unit for performing wireless communication, and when the identification information transmitted from the wireless tag is received by the second wireless communication unit, the identification information is output to a monitoring unit that monitors the wireless tag Receiving control means, and a receiving device including power supply means for supplying power to each of these units;
A wireless tag system comprising:
The receiving device is:
First level detecting means for detecting a signal level of the received signal received by the second wireless communication unit;
The reception control means in the receiving means is
When the identification information transmitted from the wireless tag is received by the second wireless communication unit, a response signal including a reception level of the identification information detected by the first level detecting unit is sent to the second wireless communication unit. Transmit from the wireless communication unit to the wireless tag,
The wireless tag is
When the response signal transmitted from the receiving device is received by the first wireless communication unit, a change amount from the previous value of the reception level included in the response signal is calculated, and the calculated change amount is predetermined. Transmission for setting the transmission interval of the identification information by the transmission control means so that the transmission interval is shortened if the threshold is equal to or greater than the threshold, and the transmission interval is increased if the calculated change amount is less than the threshold. Interval setting means,
A wireless tag system comprising: A wireless device comprising a first wireless communication unit for performing wireless communication, transmission control means for repeatedly transmitting identification information from the first wireless communication unit at predetermined time intervals, and a battery for supplying power to these units. Tag,
A second wireless communication unit for performing wireless communication, and when the identification information transmitted from the wireless tag is received by the second wireless communication unit, the identification information is output to a monitoring unit that monitors the wireless tag Receiving control means, and a receiving device including power supply means for supplying power to each of these units;
A wireless tag system comprising:
The reception control means in the receiving means is
When the identification information transmitted from the wireless tag is received by the second wireless communication unit, a response signal is transmitted from the second wireless communication unit to the wireless tag,
The wireless tag is
Second level detecting means for detecting a signal level of a received signal received by the first wireless communication unit;
When the response signal transmitted from the receiving device is received by the first wireless communication unit, the amount of change from the previous value of the reception level of the response signal detected by the second level detecting unit is calculated. When the calculated change amount is equal to or greater than a predetermined threshold, the transmission interval is shortened, and when the calculated change amount is less than the threshold, the transmission control unit increases the transmission interval. A transmission interval setting means for setting the transmission interval of the identification information;
A wireless tag system comprising: A wireless device comprising a first wireless communication unit for performing wireless communication, transmission control means for repeatedly transmitting identification information from the first wireless communication unit at predetermined time intervals, and a battery for supplying power to these units. Tag,
A second wireless communication unit for performing wireless communication, and when the identification information transmitted from the wireless tag is received by the second wireless communication unit, the identification information is output to a monitoring unit that monitors the wireless tag Receiving control means, and a receiving device including power supply means for supplying power to each of these units;
A wireless tag system comprising:
The receiving device is:
First level detecting means for detecting a signal level of the received signal received by the second wireless communication unit;
The reception control means in the receiving device is:
When the identification information transmitted from the wireless tag is received by the second wireless communication unit, a response signal including a reception level of the identification information detected by the first level detecting unit is sent to the second wireless communication unit. Transmit from the wireless communication unit to the wireless tag,
The wireless tag is
Second level detecting means for detecting a signal level of a received signal received by the first wireless communication unit;
When the response signal transmitted from the reception device is received by the first wireless communication unit, the amount of change from the previous value of the reception level of the response signal detected by the second level detection unit, The amount of change from the previous value of the reception level included in the response signal is calculated, and if the two calculated amounts of change are both equal to or greater than a predetermined threshold, the transmission interval is shortened, and the two calculated A transmission interval setting means for setting a transmission interval of the identification information by the transmission control means so that the transmission interval becomes longer if at least one of the change amounts is less than the threshold;
A wireless tag system comprising:

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