Two Directional Information Flow in Real Time Location Sensing RFID Networks
First Claim
Patent Images
1. A system comprising:
- a controllera plurality of base stations; and
a plurality of tags that most of the time are in a powered-down mode and are repetitively powered up to transmit a packet and to receive a packet, which tags consume significantly less power in the powered-down mode than in the powered-up mode,where a base station of said base stations transmits a packet that is addressed to a tag of said tags in response to a packet A from said tag when said base station has a directive from said controller to transmit to said tag, as well as in response to a message from the tag that is addressed to the base station.
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Abstract
An RFID system with a plurality of tags and base stations where transmission of information to a specific tag is carried out by one of the base stations, where said one of the base stations is selected based on received signal power of the tag relative to the plurality of the base stations.
18 Citations
9 Claims
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1. A system comprising:
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a controller a plurality of base stations; and a plurality of tags that most of the time are in a powered-down mode and are repetitively powered up to transmit a packet and to receive a packet, which tags consume significantly less power in the powered-down mode than in the powered-up mode, where a base station of said base stations transmits a packet that is addressed to a tag of said tags in response to a packet A from said tag when said base station has a directive from said controller to transmit to said tag, as well as in response to a message from the tag that is addressed to the base station. - View Dependent Claims (2, 3, 4, 5)
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6. In a system that includes a controller, base stations, and a plurality of tags, a method executed in a base station of said base stations, comprising:
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(a) receiving from a tag of said tags a broadcast packet that identifies the tag; (b) responsive to said receiving, developing a measure of received signal power of said packet, and sending a message that informs said controller of receipt of identity of said tag that is contained in the received packet, and received signal power of the received packet; (c) receiving from said controller a directive to respond to packets received from said tag; (d) transmitting a packet to said tag in response to a received broadcast packet from said tag when in possession of said directive; (e) transmitting a packet to said tag in response to a received packet that is addressed to said base station, without reference to said directive. - View Dependent Claims (7, 8)
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9. In a system that includes a controller, base stations, and a plurality of tags, a method executed in a tag of said tags, comprising:
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(a) responsive to a clock that cycles at a preselected rate, switching from a powered-down mode to a powered-up mode; (b) if a preselected location in a memory module of said tag contains a valid address of a base station, transmitting a packet having a destination address that is the address contained in said preselected location, and source address that is an identifier of said tag; (c) for a preselect duration following the packet transmitted by step (b), after which said tag switches to said powered-down mode, observing whether a packet is being transmitted that is addressed to said tag; (d) if step (e) observes that a packet is being transmitted that is addressed to said tag, extending said preselected duration to achieve complete reception of said packet; (e) said tag acting on information contained in the completely received packet; and (f) if step (e) fails to observe that a packet is being transmitted that is addressed to said tag, removing said valid address from said preselected location in said memory module pursuant to a preselected algorithm.
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Specification