Method and apparatus for signal searching

• US 8,565,690 B2
• Filed: 11/08/2007
• Issued: 10/22/2013
• Est. Priority Date: 11/08/2006
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Suwansantisuk, Watcharapan, Win, Moe Z.
• Primary Examiner(s): Maung, Nay A
• Assistant Examiner(s): FLEMING-HALL, ERICA L
• Application Number:
  US11/983,787
• Publication Number:
  US 20080139127A1
• Time in Patent Office: 2,175 Days
• Field of Search: 455/67.16
• US Class Current: 455/67.16
• CPC Class Codes: H04B 1/7183 Synchronisation

Abstract

A method and corresponding apparatus for searching for a signal is presented. The apparatus may be configured to select a first bin within a range of bins characterizing an uncertainty region. The bins may represent a phase within a bandwidth of interest. The apparatus may also be configured to compare a local signal, having a phase corresponding to the first bin, with a received signal, the received signal being received via a transmission medium. The apparatus may report whether the local signal matches the received signal. The apparatus may assign weightings to the bins if the local signal does not match the received signal. If a match is not found, the apparatus may select a next bin according to the weightings or according to characteristic of the transmission medium until a matching bin is obtained. One benefit of the search is reduced search time to allow, for example, a cell phone to synchronize the phase of a received signal more quickly than is currently done.

Claims

1. A method for searching for a signal comprising:

selecting a first bin within a range of bins, each bin corresponding to a phase of a transmitted signal;

comparing a local reference signal, having a phase corresponding to the first bin, with a received signal, the received signal being received via a transmission medium;

reporting whether the local reference signal matches the received signal;

assigning weightings to the bins if the local reference signal does not match the received signal, a weighting being a priority metric and being a function of a mismatch between the local reference signal and the received signal;

selecting a next bin according to the weightings; and

repeating the comparing, reporting, assigning, and selecting at least until the local reference signal, having a phase corresponding to the bin selected, matches the received signal.

2. The method of claim 1 wherein the weighting is further a function of the transmission medium.

3. The method of claim 1 wherein the weighting is further based on selecting randomly and uniformly from the range of bins excluding the previously selected bin.

4. The method of claim 1 wherein the weighting is further based on an a posteriori probability.

5. The method of claim 4 further comprising updating the weightings according to the a posteriori probability.

6. The method of claim 1 further comprising updating the weightings except when a previous bin is assigned a weighting of zero.

7. The method of claim 1 wherein the weighting is further based on a fixed serial search.

8. The method of claim 1 further comprising performing at least one preliminary comparison between the local reference signal and the received signal.

9. The method of claim 1 wherein the next bin is a set of bins and performing the comparing further includes comparing the received signal with local reference signals having phases corresponding to bins in the set, the reporting further includes reporting whether at least one local reference signal matches the received signal, the assigning further includes assigning weightings to sets of bins, and the selecting further includes selecting a next set of bins.

14. The method of claim 1 wherein the weighting is further based on the transmission medium by determining a characteristic of the received signal.

15. The method of claim 14 wherein the characteristic of the received signal is signal strength.

10. An apparatus for searching for a signal comprising:

a selecting unit configured to select a first bin within a range of bins, each bin corresponding to a phase of a transmitted signal;

a comparing unit configured to compare a local reference signal, having a phase corresponding to the first bin, with a received signal, the received signal being received via a transmission medium;

a reporting unit configured to report whether the local reference signal matches the received signal;

an assigning unit configured to assign weightings to the bins if the local reference signal does not match the received signal, a weighting being a priority metric and being a function of a mismatch between the local reference signal and the received signal;

the selecting unit further configured to select a next bin according to the weightings; and

the comparing unit, the reporting unit, the assigning unit, and the selecting unit further configured to compare, report, assign, and select, respectively, bins at least until the local reference signal, having a phase corresponding to the bin selected, matches the received signal.

11. The apparatus of claim 10 wherein the weighting is further a function of the transmission medium.

12. The apparatus of claim 10 wherein the weighting is further based on an a posteriori probability.

13. The apparatus of claim 12 wherein the assigning unit is further configured to update the weightings according to the a posteriori probability.

16. The apparatus of claim 10 wherein the weighting is further based on selecting randomly and uniformly from the range of bins excluding the previously selected bin.

17. The apparatus of claim 10 wherein the assigning unit is further configured to update the weightings except when a previous bin is assigned a weighting of zero.

18. The apparatus of claim 10 wherein the weighting is further based on a fixed serial search.

19. The apparatus of claim 10 wherein the comparing unit is further configured to perform at least one preliminary comparison between the local reference signal and the received signal.

20. The apparatus of claim 10 wherein the next bin is a set of bins and the comparing unit, the reporting unit, the assigning unit, and the selecting unit are further configured to compare the received signal with local reference signals having phases corresponding to bins in the set, to report whether at least one local reference signal matches the received signal, to assign weightings to sets of bins, and to select a next set of bins, respectively.

21. The apparatus of claim 10 wherein the weighting is further based on the transmission medium by determining a characteristic of the received signal.

22. The apparatus of claim 21 wherein the characteristic of the received signal is signal strength.