METHODS AND APPARATUSES TO IDENTIFY DEVICES

• US 20100207739A1
• Filed: 05/03/2010
• Published: 08/19/2010
• Est. Priority Date: 11/07/2003
• Status: Active Grant

• Current Assignee: RUIZHANG TECHNOLOGY LIMITED COMPANY
• Original Assignee: Align Technology Incorporated
• Inventors: Smith, John Stephen, Carrender, Curtis L.
• Granted Patent: US 8,768,952 B2
• Time in Patent Office: Days
• US Class Current: 340/10.400
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99933 Query processing, i.e. searching
• CPC Class Codes: Y10S 707/99945 Object-oriented database structure processing

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.

Claims

1. A Tag responsive to queries from a Reader, the Tag comprising:

an antenna;

an Integrated Circuit (IC) coupled to the antenna to;

receive from the Reader a first query command with a first value of a probability parameter; and

decide randomly whether or not to reply to the first query command, wherein a probability of reply is determined by the first value of the probability parameter.

2. The Tag of claim 1, the IC coupled to the antenna further to send, responsive to a random decision to reply, a reply with first handshaking data.

3. The Tag of claim 2, wherein the first handshaking data is a random number generated in response to the first query command.

4. The Tag of claim 1, wherein the first value of the probability parameter is an integer Q, the first probability of reply for one of the plurality of Tags is substantially equal to p^Q, and p is less than 1.

5. The Tag of claim 4, wherein p is substantially equal to 0.5.

6. The Tag of claim 1, wherein the first query command further includes a state flag indicating a first state, 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.

7. The Tag of claim 6, the IC coupled to the antenna further to:

receive a second query command including a second value of the probability parameter and a state flag indicating the second state; and

decide randomly whether or not to reply to the second query command, wherein a probability of reply is according to 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 in the first state.

8. The Tag of claim 7, wherein the Tag processes the first and second query commands with symmetry with respect to the first and second states.

9. The Tag of claim 6, the IC coupled to the antenna further to:

send, responsive to a random decision to reply, a first reply with first handshaking data; and

send, responsive to receiving from the Reader a second command including the first handshake data, a second reply with Tag identification data.

10. The Tag of claim 9, the IC coupled to the antenna further to switch, responsive to receiving a query command after sending the second reply, from the first state to the second state, wherein after receiving a command indicating an error in receiving the Tag identification data at the Reader, the Tag remains in the first state if a query command is received after the command indicating the error.

11. The Tag of claim 1, the IC coupled to the antenna further to:

receive a second query command which does not include a value of the probability parameter; and

decide randomly whether or not to reply to the second query command, wherein a probability of reply is determined by the first value of the probability parameter.

12. The Tag of claim 11, wherein

the first query command includes first values of a plurality of parameters including the first value of the probability parameter;

the second query command does not include values of the plurality of parameters; and

the Tag processes the second query command according to the first values of the plurality of parameters.

13. The Tag of claim 12, wherein the second query command is substantially shorter than the first query command.

14. An apparatus to query a plurality of Tags, comprising:

an antenna; and

a Reader, comprising;

a receiver coupled to the antenna;

a transmitter coupled to the antenna;

a processor coupled to the receiver, the transmitter and a memory, the processor to control the transmitter and the receiver,

the Reader to broadcast one or more first query commands including a first value of a probability parameter, the first value of the probability parameter indicating a first probability of reply, wherein each of the plurality of Tags randomly determines whether or not to reply, and

the Reader further to detect a reply in response to the first query command.

15. The apparatus of claim 14, the Reader further to broadcast, responsive to a determination that there is no reply to the one or more first query commands, a second query command including a second value of the probability parameter, the second value of the probability parameter indicating a second probability of reply which is greater than the first probability of reply.

16. The apparatus of claim 14, the Reader further to broadcast, responsive to a determination that there is no legible reply to the one or more first query commands, a second query command including a second value of the probability parameter, the second value of the probability parameter indicating a second probability of reply which is less than the first probability of reply.

17. The apparatus of claim 14, wherein the first value of the probability parameter is an integer Q, the first probability of reply for one of the plurality of Tags is substantially equal to p^Q, and p is less than 1.

18. The apparatus of claim 14, wherein p is substantially equal to 0.5.

19. The apparatus of claim 14, wherein the first probability of reply for a first one of the plurality of Tags is different from the first probability of reply for a second one of the plurality of Tags.

20. The apparatus of claim 14, wherein the first query 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.

21. The apparatus of claim 20, the Reader further to broadcast 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, the Reader further to detect a reply in response to the second query command.

22. A machine readable medium containing instructions which when executed on a data processing system causes the system to perform a method to respond to queries from a Reader, the method comprising:

receiving from the Reader a first query command including a first value of a probability parameter; and

deciding randomly whether or not to reply to the first query command, wherein a probability of reply is determined by the first value of the probability parameter.

23. The method of claim 22, further comprising:

sending, responsive to a random decision to reply, a reply with first handshaking data.

24. The method of claim 23, wherein the first handshaking data is a random number generated in response to the first query command.

25. The method of claim 22, wherein the first value of the probability parameter is an integer Q, the first probability of reply is substantially equal to p^Q, and p is less than 1.