Token passing protocol for RFID systems
First Claim
1. A method in a first reader for time multiplexing access to a communication medium in a first radio frequency identification (RFID) communications system that includes a plurality of RFID readers, wherein the method comprises the steps of:
- (a) entering into a token passing mode;
(b) waiting for a predetermined time interval before accessing the communication medium;
(c) possessing a token, possession of which permits the reader to access the communication medium for tag interrogation;
(d) determining whether to access the communication medium for tag interrogation;
(e) retaining the token for a period of time; and
(f) passing the token to a second reader.
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Accused Products
Abstract
Methods, systems and apparatuses for RFID readers forming a reader network are described. In an aspect of the present invention, a plurality of RFID readers are configured to interrogate tags. Furthermore, the readers are configured to communicate with one another by transferring a token, represented by a signal. Possession of the token enables the reader to access a RF communications medium. Readers can be arranged in a ring configuration, and interconnected via wired links. A secondary token may circulate in the ring in addition to the primary token, to ensure redundancy in the system. A reader waits for a predetermined time interval before accessing the RF communications medium.
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Citations
22 Claims
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1. A method in a first reader for time multiplexing access to a communication medium in a first radio frequency identification (RFID) communications system that includes a plurality of RFID readers, wherein the method comprises the steps of:
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(a) entering into a token passing mode;
(b) waiting for a predetermined time interval before accessing the communication medium;
(c) possessing a token, possession of which permits the reader to access the communication medium for tag interrogation;
(d) determining whether to access the communication medium for tag interrogation;
(e) retaining the token for a period of time; and
(f) passing the token to a second reader. - View Dependent Claims (2, 3, 4, 5)
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6. A radio frequency identification (RFID) communications system, comprising:
a plurality of RFID readers that form a token passing network, wherein at least two of the readers are configured to receive and transfer a token for time multiplexing access to a communication medium to perform at least one RF tag interrogation. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A radio frequency identification (RFID) reader, comprising:
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at least one antenna;
a tag communications module coupled to the at least one antenna and configured to interrogate tags;
a token interface module configured to generate and transfer a token to another reader within a token passing reader network; and
a timing module coupled to the tag communications module and the token interface module, wherein the timing module calculates a desired variable time interval for interrogating tags. - View Dependent Claims (22)
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Specification