Tag communications with access point

• US 7,526,013 B1
• Filed: 08/11/2008
• Issued: 04/28/2009
• Est. Priority Date: 03/18/2008
• Status: Active Grant

• Current Assignee: Ingenu Inc.
• Original Assignee: On-Ramp Wireless Incorporated
• Inventors: Myers, Theodore J.
• Primary Examiner(s): Bocure; Tesfaldet
• Application Number:
  US12/189,505
• Time in Patent Office: 260 Days
• Field of Search: 375/130, 375/140, 375/141, 375/144, 375/145, 375/147, 375148-150, 370/342, 370/441, 370/445, 370/335, 455/450
• US Class Current: 375/149
• CPC Class Codes: H03J 7/02 Automatic frequency control H03J7/18 takes precedence
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70752 Partial correlation
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/0074 Code shifting or hopping
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04J 3/0685 Clock or time synchronisation in a node; Intranode synchronisation
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04L 7/0004 Initialisation of the receiver H04L7/0075 and H04L7/10 take precedence

Abstract

A method of establishing communication at a tag includes calculating a metric for each of a plurality of automatic frequency control (AFC) hypotheses where the plurality of AFC hypotheses correspond to a timing used by an access point; based on the calculated metrics, identifying one or more relevant AFC hypotheses; performing a check on a demodulated data stream identified using the one or more relevant AFC hypotheses; identifying a valid AFC hypothesis based at least in part on the check; and determining where a frame starts based at least in part on the check.

Claims

1. A method of establishing communication at a tag, the method comprising:

calculating a metric at a processor for each of a plurality of automatic frequency control (AFC) hypotheses, wherein the plurality of AFC hypotheses correspond to a timing used by an access point;

based on the calculated metrics, identifying one or more relevant AFC hypotheses;

performing a check on a demodulated data stream identified using the one or more relevant AFC hypotheses;

identifying a valid AFC hypothesis based at least in part on the check; and

determining where a frame starts based at least in part on the check.

2. The method of claim 1, wherein the demodulated data stream is a single bit input from each of a plurality of analog-to-digital (ADC) modules.

3. The method of claim 1, further comprising:

identifying frame timing by iterating over a multi-slot timing hypothesis; and

using the frame timing to identify a time slot in which the access point is broadcasting.

4. The method of claim 1, wherein simultaneously evaluating the one or more relevant AFC hypotheses includes assigning the one or more relevant AFC hypotheses to a plurality of dedicated fingers.

5. The method of claim 1, further comprising simultaneously evaluating the one or more relevant AFC hypotheses to identify a fine AFC hypothesis, wherein the fine AFC hypothesis is used in the check on the data stream.

6. The method of claim 1, wherein the plurality of AFC hypotheses correspond to chip times four hypotheses for each of a plurality of coarse automatic frequency control values.

7. The method of claim 1, wherein the check comprises a cyclic redundancy check.

8. A tag for communicating with an access point, the tag comprising:

a receiver, wherein the receiver is configured to receive a data stream from the access point; and

a processor in communication with the receiver, wherein the processor is configured to

calculate, based on the received data stream, a metric for each of a plurality of automatic frequency control (AFC) hypotheses;

identify one or more relevant AFC hypotheses based on the calculated metrics;

perform a check on a demodulated data stream identified using the one or more relevant AFC hypotheses;

identify a valid AFC hypothesis based at least in part on the check; and

determine where a frame starts based at least in part on the check.

9. The tag of claim 8, wherein the calculated metrics are based at least in part on a pseudo-noise (PN) code which is unique to the tag.

10. The tag of claim 8, wherein the processor is further configured to assign the one or more relevant AFC hypotheses to a plurality of dedicated fingers based at least in part on the calculated metrics.

11. The tag of claim 8, wherein the processor is further configured to simultaneously evaluate the one or more relevant AFC hypotheses to identify a fine AFC hypothesis, wherein the fine AFC hypothesis is used in the check on the data stream.

12. The tag of claim 8, wherein the demodulated data stream is a single bit input from each of a plurality of analog-to-digital (ADC) modules.

13. The tag of claim 8, wherein the processor is further configured to provide a payload associated with the data stream to a medium access control layer of the tag.

14. The tag of claim 8, wherein the plurality of AFC hypotheses correspond to chip times four hypotheses for each of a plurality of coarse automatic frequency control values.

15. A computer-readable medium having computer-readable instructions stored thereon, where, upon execution by a processor, the computer-readable instructions cause the processor to:

calculate at the processor, based on a received data stream, a metric for each of a plurality of automatic frequency control (AFC) hypotheses, wherein the plurality of AFC hypotheses correspond to a timing used by an access point;

identify one or more relevant AFC hypotheses based on the calculated metrics;

perform a check on a data stream identified using the one or more relevant AFC hypotheses;

identify a valid AFC hypothesis based at least in part on the check; and

determine where a frame starts based at least in part on the check.

16. The computer-readable medium of claim 15, wherein the processor is further caused to assign the one or more relevant AFC hypotheses to a plurality of dedicated fingers based at least in part on the calculated metrics.

17. The computer-readable medium of claim 15, the demodulated data stream is a single bit input from each of a plurality of analog-to-digital (ADC) modules.

18. The computer-readable medium of claim 15, wherein the processor is further configured to simultaneously evaluate the one or more relevant AFC hypotheses to identify a fine AFC hypothesis, wherein the fine AFC hypothesis is used in the check on the data stream.

19. The computer-readable medium of claim 15, wherein the check comprises a cyclic redundancy check.

20. The computer-readable medium of claim 15, wherein the calculated metrics are based at least in part on a pseudo-noise (PN) code which is unique to the tag.