| 摘要 |
<P>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. <P>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). <P>COPYRIGHT: (C)2013,JPO&INPIT |
