Optimized operation of a dense reader system

• US 7,969,282 B2
• Filed: 12/21/2005
• Issued: 06/28/2011
• Est. Priority Date: 12/21/2005
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Arneson, Michael R., Bandy, William R., Powell, Kevin J.
• Primary Examiner(s): Bugg; George A
• Assistant Examiner(s): Thompson; Bradley E
• Application Number:
  US11/312,606
• Publication Number:
  US 20070139163A1
• Time in Patent Office: 2,015 Days
• Field of Search: 340/10.2, 340/572.1, 340/10.5, 370/328
• US Class Current: 340/10.2
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: G06K 7/10475 arrangements to facilitate interaction with further interrogation devices, e.g. such that at least two interrogation devices may function and cooperate in a network of such devices
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks
• CPC Class Codes: H04W 88/02 Terminal devices

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. Each of the readers include a ID number which identifies that particular reader within a reader network during communications. Each reader includes a network interface module and an optimization module to receive and process statistical data obtained from other readers in the network. Aspects of the present invention include a ‘primary/secondary’ reader network configuration, as well as a ‘distributed elements’ reader network configuration. A set of operational rules for the environment is indicated, and tag interrogations are optimized according to the rules. Readers may communicate according to a “Listen Before Talk” (LBT) protocol to avoid undesirable interference. Individual readers are capable of dynamically establishing and joining a network, and leaving the network in a self-configured and semi-autonomous or autonomous manner.

Claims

1. A radio frequency identification (RFID) communications system, comprising:

a plurality of readers that form a network, wherein the plurality of readers comprise a primar reader and a plurality of secondary readers each communicatively coupled to the primary reader, and wherein each of the plurality of readers operates at least semi-autonomously in the network based on a set of local network rules, and wherein each reader of the plurality of readers comprises;

(a) at least one antenna;

(b) a tag communications module coupled to the at least one antenna and configured to interrogate tags within a communication range of the reader;

(c) an identification (ID) number that identifies the reader;

(d) a reader network interface module coupled to the at least one antenna and configured to communicate with readers of the network;

(e) a memory, wherein the memory stores at least one set of local reader network rules; and

(f) a timing module coupled to the tag communications module, the timing module providing a signal to the tag communications module that is related to a number of readers in the network and a number of available frequency channels, the signal indicating an amount of time the communications module is not to communicate to maintain a duty cycle of the reader.

2. The system of claim 1, wherein each reader of the plurality of readers further comprises:

an optimization module that uses logic to optimize interrogations of tags by the reader in the reader network.

3. The system of claim 1, further comprising:

a population of RFID tags, wherein each tag of the population is in communication range of at least one of the readers.

4. The system of claim 1, wherein a first reader of the plurality of readers is configured to transmit information regarding a tag within a communication range of the first reader to a second reader of the plurality of readers.

5. The system of claim 4, wherein the first reader and the second reader communicate with the at least one common tag according to one of the following communication protocols:

Gen2, Class0, or Class1.

6. The system of claim 1, wherein the primary reader is a first reader to enter the network.

7. The system of claim 1, wherein the plurality of readers other than the primary reader each receives the set of local network rules from the primary reader.

8. The system of claim 1, wherein the primary reader instructs each reader of the plurality of readers to use a particular set of local network rules stored in the memory.

9. The system of claim 1, wherein a reader of the plurality of readers listens for communications before transmitting a communication signal.

10. The system of claim 1, wherein each reader uses a selected rule set of the at least one set of local network rules to regulate communications with other readers of the network.

23. The RFID communications system of claim 1, wherein each of the plurality of readers comprises a time slot selector coupled to the tag communications module, the time slot selector configured to select a time slot for the tag communication module to interrogate at least one tag.

11. A radio frequency identification (RFID) reader, comprising:

(a) at least one antenna;

(b) a tag communications module coupled to the at least one antenna and configured to interrogate tags;

(c) an identification number (ID) that identifies the reader in a reader network as either a primary reader communicatively coupled to a plurality of secondary readers or a secondary reader communicatively coupled to another primary reader;

(d) a reader network interface module coupled to the at least one antenna configured to communicate with readers in the reader network;

(e) a memory, wherein the memory stores at least one set of local network rules, wherein the reader is configured to operate at least semi-autonomously in the reader network based on the at least one set of local network rules; and

(f) a timing module coupled to the tag communications module, the timing module providing a signal to the tag communications module that is related to a number of readers in the network and a number of available frequency channels, the signal indicating an amount of time the communications module is not to communicate to maintain a duty cycle of the reader.

12. The device of claim 11, wherein the reader further comprises:

an optimization module that uses logic to optimize interrogations of tags by the reader in the reader network.

13. The device of claim 11, wherein the device is configured to operate as primary reader in communication with a plurality of other readers operating as secondary readers.

24. The device of claim 11, wherein the reader comprises a time slot selector coupled to the tag communications module, the time slot selector configured to select a time slot for the tag communication module to interrogate at least one tag.

14. A method of communication for a reader in a reader network, comprising:

(a) transmitting a request to the reader network to interrogate a tag, the request including an identification number for the reader;

(b) receiving a response from the reader network; and

(c) interrogating the tag, wherein subsequent to interrogating the tag, the method comprising maintaining a duty cycle associated with the reader by prohibiting communication of the reader for a set amount of time approximately equal to the duty cycle, and wherein the duty cycle is related to a number of readers in the network and a number of available frequency channels;

wherein the reader network comprises a plurality of readers that each operate at least semi-autonomously in the reader network based on a set of rules, and wherein the plurality of readers comprises at least one primary reader communicatively coupled to a plurality of secondary readers.

15. The method of claim 14, further comprising:

(d) prior to step (c), listening to communications between at least one reader of the reader network and at least one tag; and

(e) determining whether the communications would interfere with a tag interrogation.

16. The method of claim 14, wherein step (c) comprises:

interrogating the tag if it is determined in step (e) of claim 16, that the communications would not interfere.

17. The method of claim 15, further comprising:

(d) entering the reader network.

18. The method of claim 17, wherein step (d) further comprises:

(1) determining whether a reader network exists;

(2) initiating the reader network if the reader network does not exist; and

(3) providing the identification number for the reader to the reader network.

19. The method of claim 14, further comprising:

(d) receiving the set of rules dictating interaction of the reader with the reader network.

20. The method of claim 14, further comprising:

(d) exiting the reader network.

21. The method of claim 20, wherein step (d) comprises:

(1) transmitting a request to exit the reader network;

(2) receiving an acknowledgement and approval of the exit request from the reader network; and

(3) exiting the reader network.

22. The method of claim 14, further comprising:

(d) receiving information in the response regarding requests to interrogate the tag by other readers of the reader network; and

(e) using the information to optimize an interrogation of the tag in step (c).

25. The method of claim 14, further comprising selecting a time slot for the tag communication module to interrogate at least one tag using a time slot selector of the reader.