Method for the efficient reading of a population of radio frequency identification tags with unique identification numbers over a noisy air channel
First Claim
1. A method for communicating with a plurality of radio frequency identification (RFID) tags, comprising:
- (a) receiving a series of bits from the plurality of RFID tags and storing said series of bits in corresponding nodes in a binary tree, wherein each node in said binary tree is associated with a counter;
(b) incrementing a counter associated with a node in said binary tree when a bit received from said plurality of RFID tags matches a bit stored in said node;
(c) decrementing a counter associated with a node in said binary tree when a bit received from said plurality of RFID tags does not match a bit stored in said node; and
(d) assigning a value to a bit received from said plurality of RFID tags based on a value of a counter associated with a node in said binary tree.
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Abstract
A method for reading and tracking radio frequency identification (RFID) tags in the presence of a noisy air channel is provided. In accordance with the method, a binary tree data structure is used to characterize a plurality of RFID tags, each of which is associated with a unique identification (ID) number. During communication between a tag reader and one or more RFID tags, the tag reader traverses the binary tree, eliminating tags from communication until one tag with a unique ID number is isolated and verified. As the binary tree is traversed, counters associated with each node in the tree are incremented based on tag matches, such that, over time, counters associated with nodes in tag-populated branches will tend to have a high value and counters associated with nodes in unpopulated tree branches will tend to have low values. Where the read process is subject to noise and the tag reader is forced make a decision at a branching node, the tag reader makes a branch prediction based on the current value of the node counters associated with each of the possible alternative branches.
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Citations
27 Claims
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1. A method for communicating with a plurality of radio frequency identification (RFID) tags, comprising:
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(a) receiving a series of bits from the plurality of RFID tags and storing said series of bits in corresponding nodes in a binary tree, wherein each node in said binary tree is associated with a counter;
(b) incrementing a counter associated with a node in said binary tree when a bit received from said plurality of RFID tags matches a bit stored in said node;
(c) decrementing a counter associated with a node in said binary tree when a bit received from said plurality of RFID tags does not match a bit stored in said node; and
(d) assigning a value to a bit received from said plurality of RFID tags based on a value of a counter associated with a node in said binary tree.
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2. A method in a radio frequency identification (RFID) reader for interrogating a population of tags using binary tree traversal protocol, comprising the steps of:
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(a) entering a logical node in a binary tree;
(b) transmitting a symbol to the population of tags;
(c) determining if at least one symbol is received from the population of tags;
(d) if it is determined in step (c) that at least one symbol has been received, determining whether one symbol received from the population of tags corresponds to a first logical value;
(e) if it is determined in step (d) that one symbol received corresponds to a first logical value, incrementing a node counter value associated with the first logical value;
(f) if it is determined in step (d) that one symbol received does not correspond to a first logical value, decrementing the node counter value associated with the first logical value;
(g) if it is determined in step (c) that at least one symbol has been received, determining whether one symbol received from the population of tags corresponds to a second logical value;
(h) if it is determined in step (g) that one symbol received corresponds to a second logical value, incrementing a node counter value associated with the second logical value;
(i) if it is determined in step (g) that one symbol received does not correspond to a first logical value, decrementing the node counter value associated with the second logical value;
(j) selecting which logical value to store as a bit of a tag bit pattern;
(k) storing the selected logical value as the bit of the tag bit pattern;
(l) determining whether the bit pattern is complete; and
(m) if the bit pattern is not complete;
proceeding to step (a). - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 21)
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17. A method in a radio frequency identification (RFID) reader for interrogating a population of tags using binary tree traversal protocol, comprising the steps of:
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(a) entering a logical node in a binary tree;
(b) transmitting a symbol to the population of tags;
(c) determining if at least one symbol is received from the population of tags;
(d) if it is determined in step (c) that at least one symbol has been received, adjusting information stored for the logical node;
(e) selecting which logical value to store as a bit of a tag bit pattern;
(f) storing the selected logical value as the bit of the tag bit pattern;
(g) determining whether the bit pattern is complete; and
(h) if the bit pattern is not complete;
proceeding to step (a). - View Dependent Claims (18, 19)
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20. A method in a radio frequency identification (RFID) reader for interrogating a population of tags using a binary tree traversal protocol, comprising the steps of:
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reading a tag identification bit pattern as a result of a binary tree traversal interrogation of a tag in the population of tags;
receiving an error detection code from the tag;
identifying one or more bit positions in the read tag identification bit pattern potentially corrupted by noise;
identifying potential bit patterns having alternate bit values in one or more of the identified bit positions;
calculating an error detection code value for the accumulated tag identification bit pattern;
calculating an error detection code value for each identified potential bit pattern; and
determining whether any of the calculate error detection code values matches the received error detection code.
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22. A method in a radio frequency identification (RFID) reader for interrogating a population of tags using binary tree traversal protocol, comprising the steps of:
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storing data related to the tag population, wherein the tag population data includes information associated with each populated node in a binary tree;
during binary tree traversal, determining a traversal path based on the tag population data. - View Dependent Claims (23, 24, 25, 26, 27)
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Specification