Method and apparatus for an arbitration scheme for radio frequency identification devices
First Claim
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1. A method comprising:
- sending a first command from an interrogator to a plurality of wireless identification devices to select a first subset of the plurality of wireless identification devices in accordance with an arbitration scheme, the first subset associated with a first branch of a search tree corresponding to a tree search scheme, the first command requesting each of the plurality of wireless identification devices of the first subset to respond approximately simultaneously;
sending a second command from the interrogator to the plurality of wireless identification devices to select a second subset of the plurality of wireless identification devices in accordance with the arbitration scheme, the second subset associated with a second branch of the search tree, the second command requesting each of the plurality of wireless identification devices of the second subset to respond in an independently selected one of a plurality of time slots in accordance with an Aloha scheme;
detecting a collision between at least two wireless identification devices of the plurality of wireless identification devices; and
skipping at least one level of the search tree in response to detecting the collision.
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Abstract
RFID tags are identified. In one embodiment, RFID tags may be chosen to respond to an interrogator in accordance with an arbitration scheme. According to one arbitration scheme, each chosen tag may randomly pick a slot value. The interrogator may indicate that the number of slot values is to be adjusted. Each chosen tag may respond to the interrogator with a random number.
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Citations
87 Claims
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1. A method comprising:
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sending a first command from an interrogator to a plurality of wireless identification devices to select a first subset of the plurality of wireless identification devices in accordance with an arbitration scheme, the first subset associated with a first branch of a search tree corresponding to a tree search scheme, the first command requesting each of the plurality of wireless identification devices of the first subset to respond approximately simultaneously; sending a second command from the interrogator to the plurality of wireless identification devices to select a second subset of the plurality of wireless identification devices in accordance with the arbitration scheme, the second subset associated with a second branch of the search tree, the second command requesting each of the plurality of wireless identification devices of the second subset to respond in an independently selected one of a plurality of time slots in accordance with an Aloha scheme; detecting a collision between at least two wireless identification devices of the plurality of wireless identification devices; and skipping at least one level of the search tree in response to detecting the collision. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method comprising:
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sending a first command from an interrogator to a plurality of wireless identification devices to select a first subset of the plurality of wireless identification devices and to request each wireless identification device of the first subset to respond in an independently selected one of a first number of time slots in accordance with an adaptive arbitration scheme; and sending a second command from the interrogator to the plurality of wireless identification devices to select a second subset of wireless identification devices and to request each wireless identification device of the second subset to respond in an independently selected one of a second number of time slots in accordance with the adaptive arbitration scheme. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 84, 85)
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29. A wireless identification device comprising:
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a receiver to receive a first command comprising a first value, and a second command comprising a second value, the first and second values to select a plurality of wireless identification devices; a memory storing an identification number to be transmitted; a random number generator to generate a random number; and a backscatter transmitter to transmit a first response in an independently selected one of a first plurality of time slots in accordance with an arbitration scheme if it is determined, using the first value, that the wireless identification device is selected to respond to the first command, the backscatter transmitter further to transmit a second response in an independently selected one of a second plurality of time slots in accordance with the arbitration scheme if it is determined, using the second value, that the wireless identification device is selected to respond to the second command, the second plurality of time slots to be different in number than the first plurality of time slots. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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43. A system for tracking a plurality of objects, the system comprising:
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a plurality of wireless identification devices, each device attached to a respective one of the plurality of objects and storing a respective identification number to identify the respective object, and each device including a random number generator to generate a respective random number to be transmitted; and an interrogator to; send a first command to the plurality of wireless identification devices, the first command to include a first value to select a first set of the plurality of wireless identification devices in accordance with the first value, wherein in response to the first command at least a first wireless identification device of the first set is to respond with multiple bits of its respective identification number and random number in a randomly selected one of a first number of time slots in accordance with an arbitration scheme; and send a second command to the plurality of wireless identification devices, the second command to include a second value, different from the first value, to select a second set of the plurality of wireless identification devices in accordance with the second value, wherein in response to the second command at least a second wireless identification device of the second set is to respond with multiple bits of its respective identification number and random number in a randomly selected one of a second number of time slots in accordance with the arbitration scheme. - View Dependent Claims (44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 86)
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57. A system comprising:
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an interrogator to send a first command comprising a first value, and a second command comprising a second value; and at least one wireless identification device comprising a receiver, memory storing an identification number, a random number generator, and a transmitter, the wireless identification device to implement an arbitration scheme comprising; receiving the first and second commands; and transmitting a first signal in an independently selected one of a first plurality of time slots in accordance with the arbitration scheme if it is determined, using the first value, that the wireless identification device is selected for response to the first command, and transmitting a second signal in an independently selected one of a second plurality of time slots in accordance with the arbitration scheme if it is determined, using the second value, that the wireless identification device is selected for response to the second command, wherein in accordance with the arbitration scheme the second plurality of time slots may differ in number from the first plurality of time slots. - View Dependent Claims (58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70)
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71. A method for tracking a plurality of objects, the method comprising:
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attaching each of a plurality of wireless identification devices to a respective one of the plurality of objects, each device storing an identification number to identify the respective object, and each device including a random number generator to generate a random number; sending a first command to the plurality of wireless identification devices to select a first subset of the plurality of wireless identification devices and to request each wireless identification device of the first subset to respond in a randomly selected one of a first number of time slots in accordance with an arbitration scheme; sending a second command to the plurality of wireless identification devices to select a second subset of wireless identification devices and to request each wireless identification device of the second subset to respond in a randomly selected one of a second number of time slots in accordance with the arbitration scheme; and receiving a plurality of replies, each of the plurality of replies including the identification number and a random number for each respective wireless identification device. - View Dependent Claims (72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 87)
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Specification