Methods and apparatuses to identify devices
First Claim
1. A method to query a plurality of Tags, the method comprising:
- broadcasting through an antenna, one or more first query commands, a first query command of the one or more first query commands including a first value of a probability parameter, the first value of the probability parameter indicating a first level of probability of reply according to which each of the plurality of Tags randomly determines whether or not to reply with handshaking data which comprises a random number, wherein the first value of the probability parameter includes a first number Q, and the probability of reply for one of the plurality of tags includes a second number p based on the first number Q; and
detecting a reply in response to the first query command, the reply including the handshaking data comprising the random number generated in response to the first query command, wherein the first query command further includes a state fin indicating a first state, wherein Tags in a second state do not reply to the first query command and Tags in the first state reply to the first query command randomly according to the first value of the probability parameter;
broadcasting a second query command including a second value of the probability parameter and a state flag indicating the second state, wherein Tags in the first state do not reply to the second query command and Tags in the second state reply to the second query command randomly according to the second value of the probability parameter; and
detecting a reply in response to the second query command, wherein the first and second query commands arc symmetric with respect to the first and second states.
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Abstract
Embodiments of the present invention include systems with Readers and Tags in which a Reader queries the Tags with a parameter that includes a level of probability of reply according to which the Tags individually and randomly decide whether or not to reply. In one embodiment, the Tags can switch between two states: A and B. The query command also specifies a state (A or B) so that only the Tags in the specified state can reply. After successfully sending the Tag identification data from a Tag to the Reader, the Tag switches to the other state from the specified state. In one embodiment, the operations about the two states are symmetric. In one embodiment, the Tags can remember the parameters used in a query so that a short form of query command can be used to repeat the query with the same query parameters.
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Citations
66 Claims
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1. A method to query a plurality of Tags, the method comprising:
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broadcasting through an antenna, one or more first query commands, a first query command of the one or more first query commands including a first value of a probability parameter, the first value of the probability parameter indicating a first level of probability of reply according to which each of the plurality of Tags randomly determines whether or not to reply with handshaking data which comprises a random number, wherein the first value of the probability parameter includes a first number Q, and the probability of reply for one of the plurality of tags includes a second number p based on the first number Q; and detecting a reply in response to the first query command, the reply including the handshaking data comprising the random number generated in response to the first query command, wherein the first query command further includes a state fin indicating a first state, wherein Tags in a second state do not reply to the first query command and Tags in the first state reply to the first query command randomly according to the first value of the probability parameter; broadcasting a second query command including a second value of the probability parameter and a state flag indicating the second state, wherein Tags in the first state do not reply to the second query command and Tags in the second state reply to the second query command randomly according to the second value of the probability parameter; and detecting a reply in response to the second query command, wherein the first and second query commands arc symmetric with respect to the first and second states. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for a Tag to respond to queries from a Reader, the method comprising:
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receiving, through an antenna from the Reader a first query command including a first value of a probability parameter that indicates a first level of probability of reply; deciding randomly whether or not to reply to the first query command according to the first value of the probability parameter, wherein the first value of the probability parameter includes a first number Q, and the probability of reply includes a second number p based on the first number Q; and sending, responsive to a random decision to reply, a reply with handshaking data which comprises a random number generated in response to the first query command, wherein the first query command further includes a state flag indicating a first slate, and wherein the Tag does not reply to the first query command if the Tag is in a second state, and the Tag replies to the first query command randomly according to the first value of the probability parameter if the Tag is in the first state; receiving a second query command including a second value of the probability parameter and a state flag indicating the second state; and deciding randomly whether or not to reply to the second query command, wherein the level of probability of reply is determined by the second value of the probability parameter if the Tag is in the second state, and wherein the Tag does not reply to the second query command if the Tag is in the first state, wherein the Tag processes the first and second query commands with symmetry with respect to the first and second states. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A Reader to query a plurality of Tags, the Reader comprising:
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means for broadcasting one or more first query commands, a first query command of the one or more first query commands including a first value of a probability parameter, the first value of the probability parameter indicating a first level of probability of reply according to which each of the plurality of Tags randomly determines whether or not to reply with handshaking data which comprises a random number, wherein the first value of the probability parameter includes a first number Q, and the probability of reply for one of the plurality of tags includes a second number p based on the first number Q; and means for detecting a reply in response to the first query command, the reply including the handshaking data comprising the random number generated in response to the first query command, wherein the first tier command further includes a state flag indicating a first state, wherein Tags in a second state do not reply to the first query command and Tags in the first state reply to the first query command randomly according to the first value of the probability parameter; means for broadcasting a second query command including a second value of the probability parameter and a state flag indicating the second state, wherein Tags in the first state do not reply to the second query command and Tags in the second state reply to the second query command randomly according to the second value of the probability parameter; and means for detecting a reply in response to the second tier command, wherein the first and second query commands are symmetric with respect to the first and second states. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A Tag responsive to queries from a Reader, the Tag comprising:
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means for receiving from the Reader a first query command including a first value of a probability parameter that indicates a level of probability of reply; means for deciding randomly whether or not to reply to the first query command according to the first value of the probability parameter, wherein the first value of the probability parameter includes a first number Q, and the probability of reply includes a second number p based on the first number Q; and means for sending, responsive to a random decision to reply, a reply with handshaking data which comprises a random number generated in response to the first query command, wherein the first query command further includes a state flag indicating a first state, and wherein the Tag does not reply to the first query command if the Tag is in a second state, and the Tag replies to the first query command randomly according to the first value of the probability parameter if the Tag is in the first state;
means for receiving a second query command including a second value of the probability parameter and a state ha r indicating the second state; andmeans for deciding randomly whether or not to reply to the second query command, wherein a level of probability of reply is determined by the second value of the probability parameter if the Tag is in the second state, and wherein the Tag does not reply to the second query command if the Tag is in the first state, wherein the Tag processes the first and second query commands with symmetry with respect to the first and second states. - View Dependent Claims (45, 46, 47, 48, 49, 50, 51, 52, 53)
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54. A machine readable storage medium storing instructions which when executed on a data processing system causes the system to perform a method to query a plurality of Tags, the method comprising:
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broadcasting one or more first query commands, a first query command of the one or more first query commands including a first value of a probability parameter, the first value of the probability parameter indicating a first level of probability of reply according to which each of the plurality of Tags randomly determines whether or not to reply with handshaking data which comprises a random number, wherein the first value of the probability parameter includes a first number Q, and the probability of reply for one of the plurality of tags includes a second number p based on the first number Q; and detecting a reply in response to the first query command, the reply including the handshaking data comprising the random number generated in response to the first query command, wherein the first query command further includes a slate flag indicating a first state, wherein Tags in a second state do not reply to the first query command and Tags in the first state reply to the first query command randomly according to the first value of the probability parameter, wherein the method further comprises; broadcasting a second query command including a second value of the probability parameter and a state flag indicating the second state, wherein Tags in the first state do not reply to the second query command and Tags in the second state reply to the second query command randomly according to the second value of the probability parameter; and detecting a reply in response to the second query command, wherein the first and second query commands arc symmetric with respect to the first and second states. - View Dependent Claims (55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66)
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Specification