System and method for minimizing unwanted re-negotiation of a passive RFID tag
First Claim
1. A method in a radio frequency identification (RFID) tag device for minimizing unintended re-negotiation of the tag device wherein the tag includes a confirmed read flag indicating whether the tag has been previously read, comprising the steps of:
- (a) receiving a symbol from a reader when an operating state of the tag is a first state;
(b) if the received symbol has a first logical value, transitioning the operating state to a second state; and
(c) if the received symbol has a second logical value, performing the following steps;
(1) evaluating a confirmed read flag,(2) if the confirmed read flag indicates the tag has been previously read, transitioning the operating state to a dormant state, and(3) if the confirmed read flag indicates that the tag has not been previously read, transitioning the operating state, to the second statewherein the value of the confirmed read flag is retained upon removal from and re-entry into the field of interrogation.
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Accused Products
Abstract
A system and method is provided for minimizing the unwanted re-negotiation of passive RFID tags. Each tag stores a confirmed read flag to indicate whether the tag has been previously read. During subsequent interrogations of the tag population, the reader has the capability to address all tags in a tag population or to address only unread tags. When addressing all tags, the reader sends a symbol causing all tags to ignore their confirmed read flag value. Each tag may also clear its confirmed read flag when this symbol is received. When addressing only unread tags, the reader sends a symbol causing each tag to evaluate its confirmed read flag value. Those tags that have a confirmed read flag value indicating “read” will enter dormant state and will not be re-negotiated. Those tags that have a confirmed read flag value indicating “not read” will continue to communicate with the reader.
96 Citations
22 Claims
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1. A method in a radio frequency identification (RFID) tag device for minimizing unintended re-negotiation of the tag device wherein the tag includes a confirmed read flag indicating whether the tag has been previously read, comprising the steps of:
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(a) receiving a symbol from a reader when an operating state of the tag is a first state; (b) if the received symbol has a first logical value, transitioning the operating state to a second state; and (c) if the received symbol has a second logical value, performing the following steps; (1) evaluating a confirmed read flag, (2) if the confirmed read flag indicates the tag has been previously read, transitioning the operating state to a dormant state, and (3) if the confirmed read flag indicates that the tag has not been previously read, transitioning the operating state, to the second state wherein the value of the confirmed read flag is retained upon removal from and re-entry into the field of interrogation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method in a radio frequency identification (RFID) tag for minimizing unintended re-negotiation of the tag, wherein the tag includes a confirmed read flag indicating whether the tag has been previously read, comprising the steps of:
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(a) negotiating a complete tag identification number with a reader when an operating state is a tree traversal state; (b) receiving a symbol from the reader; (c) if the symbol has a the first logical value, setting the confirmed read flag to indicate that the tag has been read and transitioning the operating state to a dormant state; and (d) f the symbol has a second logical value, transitioning to a command state, wherein the value of the confirmed read flag is retained upon removal from and re-entry into the field of interrogation. - View Dependent Claims (13, 14)
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15. A radio frequency identification (RFID) tag, comprising:
- means for storing a confirmed read flag that indicates whether the tag has been recently read, wherein the value of the confirmed read flag is retained upon removal from and re-entry into the field of interrogation.
means for receiving a symbol from a reader and responding to the reader, including means for evaluating the value of the confirmed read flag when the received symbol has a first logical value and an operating state is a first state; and means for transmitting data to the reader. - View Dependent Claims (16, 17, 18, 19, 20)
- means for storing a confirmed read flag that indicates whether the tag has been recently read, wherein the value of the confirmed read flag is retained upon removal from and re-entry into the field of interrogation.
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21. A method in a radio frequency identification (RFID) reader for minimizing unintended re-negotiation of tags in a population of tags, comprising the steps of:
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(a) determining whether an interrogation of all tags in the population of tags is required or whether an interrogation of only unread tags is required; (b) if it is determined in step (a) that all tags in the population of tags are to be interrogated, transmitting a first symbol to the population of tags wherein the first symbol causes all tags in the population to transition to a first state; and (c) if it is determined in step (a) that only unread tags are to be interrogated, transmitting a second symbol to the population of tags wherein the second symbol causes the tags to evaluate their confirmed read flags, to transition to a dormant state if the confirmed read flag indicates the tag has been read, and to transition to the first state if the confirmed read flag indicates the tag has not been read, wherein the value of the confirmed read flag is retained upon removal from and re-entry into the field of interrogation. - View Dependent Claims (22)
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Specification