Slotted mode acquisition

• US 7,848,272 B2
• Filed: 11/24/2008
• Issued: 12/07/2010
• Est. Priority Date: 03/18/2008
• Status: Active Grant

• Current Assignee: Ingenu Inc.
• Original Assignee: On-Ramp Wireless Incorporated
• Inventors: Hughes, Matthew, Myers, Theodore J., Boesel, Robert W., Werner, Daniel Thomas, Cohen, Lewis N.
• Primary Examiner(s): Phan; Tri H
• Application Number:
  US12/276,971
• Publication Number:
  US 20090238210A1
• Time in Patent Office: 743 Days
• Field of Search: 370436-437, 370442-462, 370464-465, 370/468, 370477-480, 370/311, 370/318, 370/321, 370/326, 370328-330, 370/337, 370345-348, 370/350
• US Class Current: 370/311
• 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 for conserving resources in a communication system includes entering an awake state from a sleep state at a first time, where the first time occurs a predetermined period prior to a communication event. The predetermined period is greater than or equal to a worst-case determination period for determining a timing offset relative to an access point. An initial timing offset relative to the access point is determined during the predetermined period. The sleep state is entered for a remainder of the predetermined period upon determination of the initial timing offset. The awake state is entered for the communication event. The timing offset relative to the access point is determined based at least in part on the initial timing offset.

Claims

1. A method for conserving resources at a tag, the method comprising:

entering an awake state at the tag from a sleep state at a first time, wherein the first time occurs within a predetermined period prior to a communication event, and further wherein the predetermined period is greater than or equal to a worst-case determination period for determining a timing offset relative to an access point;

determining an initial timing offset relative to the access point during the predetermined period;

entering the sleep state for a remainder of the predetermined period upon determination of the initial timing offset;

entering the awake state for the communication event; and

determining the timing offset relative to the access point based at least in part on the initial timing offset.

2. The method of claim 1, wherein the predetermined period is also greater than or equal to a second worst-case determination time for determining a frequency offset relative to the access point.

3. The method of claim 2, further comprising determining an initial frequency offset relative to the access point during the predetermined period, wherein the sleep state is entered for the remainder of the predetermined period upon determination of the initial frequency offset and the initial timing offset.

4. The method of claim 3, further comprising determining the frequency offset relative to the access point based at least in part on the initial frequency offset.

5. The method of claim 1, wherein the initial timing offset is determined based at least in part on a nominal timing value.

6. The method of claim 5, wherein the nominal timing value is based on a prior timing offset determined during a prior communication event.

7. The method of claim 1, wherein the initial timing offset is determined based on at least a portion of a received preamble.

8. A tag for communicating in a communication system, the tag comprising:

a receiver; and

a processor operatively coupled to the receiver and configured to

cause the tag to enter an awake state from a sleep state at a first time, wherein the first time occurs within a predetermined period prior to a communication event, and further wherein the predetermined period is greater than or equal to a worst-case determination period for determining a timing of an access point;

determine an initial timing of the access point during the predetermined period;

cause the tag to enter the sleep state for a remainder of the predetermined period upon determination of the initial timing;

cause the tag to enter the awake state for the communication event; and

determine the timing of the access point for use during the communication event, wherein the timing is determined based at least in part on the initial timing.

9. The tag of claim 8, wherein the receiver is configured to receive a preamble from the access point for use in determining the initial timing.

10. The tag of claim 8, wherein the communication event comprises a receive event.

11. The tag of claim 8, wherein the awake state is entered for the communication event at a beginning of a slot.

12. The tag of claim 8, wherein the processor is further configured to:

conduct an initial search to determine the initial timing; and

if the initial search does not identify the initial timing, conduct an expansive search to identify the initial timing.

13. The tag of claim 12, wherein the initial search is centered around a nominal timing value.

14. The tag of claim 13, wherein the nominal timing value is based at least in part on a timing information from a prior communication event.

15. A non-transitory computer-readable medium having computer-readable instructions stored thereon that, upon execution by a processor, cause a tag to:

enter an awake state from a sleep state at a first time, wherein the first time occurs within a predetermined period prior to a communication event, and further wherein the predetermined period is greater than or equal to a worst-case determination period for determining a timing offset relative to an access point;

determine an initial timing offset relative to the access point during the predetermined period;

enter the sleep state for a remainder of the predetermined period upon determination of the initial timing offset;

enter the awake state for the communication event; and

determine the timing offset relative to the access point for use during the communication event, wherein the timing offset is determined based at least in part on the initial timing offset.

16. The non-transitory computer-readable medium of claim 15, wherein the worst-case determination period is based at least in part on a worst-case drift of the tag.

17. The non-transitory computer-readable medium of claim 15, wherein the predetermined period is also greater than or equal to a second worst-case determination time for determining a frequency offset relative to the access point.

18. The non-transitory computer-readable medium of claim 17, wherein the computer-readable instructions further cause the tag to determine an initial frequency offset relative to the access point during the predetermined period, wherein the sleep state is entered for the remainder of the predetermined period upon determination of the initial frequency offset and the initial timing offset.

19. The non-transitory computer-readable medium of claim 18, wherein the computer-readable instructions further cause the tag to determine the frequency offset relative to the access point based at least in part on the initial frequency offset.

20. The non-transitory computer-readable medium of claim 15, wherein the computer-readable instructions further cause the tag to:

conduct an initial search to determine the initial timing offset; and

if the initial search does not identify the initial timing offset, conduct an expansive search to identify the initial timing offset.