Systems and methods for adjusting an access search window based on movement

• US 8,270,969 B1
• Filed: 03/24/2010
• Issued: 09/18/2012
• Est. Priority Date: 03/24/2010
• Status: Active Grant

• Current Assignee: Sprint Spectrum LLC (Deutsche Telekom AG)
• Original Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Inventors: Khanka, Bhagwan, Vargantwar, Sachin
• Primary Examiner(s): SHEDRICK, CHARLES TERRELL
• Application Number:
  US12/730,407
• Time in Patent Office: 909 Days
• Field of Search: 455/434, 455/440, 455/456.1, 370/335, 370/332, 370/350
• US Class Current: 455/434
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

Methods and systems for adjusting the access search window based on the movement of a mobile station (MS) are disclosed. The MS searches for pilot signals using a search window that has an initial size. At a first and second time, the MS determines its position. The MS then determines the distance between the position of the MS at the first time and the second time. When the distance is less than a threshold distance, the MS measures the strength of a pilot signal within the access search window and identifies one or more signal peaks within the access search window that are above a specified signal strength. Next, the MS modifies the access search window into one or more smaller access search windows. The one or more smaller access search windows collectively have a size that is smaller than the initial size.

Claims

1. A method for a mobile station having an access search window to adjust the access search window, the method comprising:

the mobile station determining its position at a first time;

the mobile station determining its position at a second time;

the mobile station determining whether a distance between the position of the mobile station at the first time and the position of the mobile station at the second time is less than a threshold distance; and

in response to determining that the distance is less than the threshold distance, the mobile station (i) measuring a strength of a signal within the access search window, wherein the access search window has an initial size, (ii) identifying one or more signal peaks within the access search window, wherein the one or more identified signal peaks are above a specified signal strength, and (iii) modifying the access search window into one or more smaller access search windows, wherein the one or more smaller access search windows collectively have a size that is smaller than the initial size, and wherein the one or more smaller access search windows encompass the one or more identified signal peaks.

2. The method of claim 1, further comprising:

at or about the first time, the mobile station (i) measuring the strength of the signal within the access search window, (ii) identifying one or more signal peaks within the access search window, wherein the one or more signal peaks are above the specified signal strength, and (iii) associating the position of the mobile station at the first time with the identified signal peaks.

3. The method of claim 2, further comprising:

at or about the second time, the mobile station (i) measuring the strength of the signal within the access search window, and (ii) identifying one or more signal peaks within the at least one smaller access search window, wherein the one or more signal peaks are above the specified signal strength, (iii) associating the position of the mobile station at the second time with the identified signal peaks, and (iv) correlating the one or more signal peaks identified at the second time with the one or more signal peaks identified at the first time.

4. The method of claim 3, wherein the mobile station determining whether the distance between the position of the mobile station at the first time and the position of the mobile station at the second time is less than the threshold distance comprises:

the mobile station determining a distance based on the correlated signal peaks.

5. The method of claim 4, wherein the mobile station determining the distance based on the correlated signal peaks comprises:

the mobile station determining a number of chips between the correlated signal peaks.

6. The method of claim 1, further comprising:

subsequent to modifying the access search window into one or more smaller access search windows, the mobile station determining its position at a third time;

the mobile station determining whether a distance between the position of the mobile station at the third time and the position of the mobile station at the second time is more than the threshold distance; and

in response to determining that the distance between the position of the mobile station at the third time and the position of the mobile station at the second time is more than the threshold distance, the mobile station resetting the access search window to the initial size.

7. The method of claim 1, further comprising:

subsequent to modifying the access search window into one or more smaller access search windows, the mobile station determining its position at a third time;

the mobile station determining whether a distance between the position of the mobile station at the third time and the position of the mobile station at the first time is more than the threshold distance; and

in response to determining that the distance between the position of the mobile station at the third time and the position of the mobile station at the first time is more than the threshold distance, the mobile station resetting the access search window to the initial size.

8. The method of claim 1, wherein the mobile station determining its position at the first time and the second time comprises the mobile station determining its position at the first time and the second time using GPS.

9. The method of claim 8, wherein the mobile station determining whether the distance between the position of the mobile station at the first time and the position of the mobile station at the second time is less than a threshold distance comprises:

the mobile station determining a distance between a GPS position at the first time and a GPS position at the second time.

10. The method of claim 1, wherein modifying the access search window into one or more smaller access search windows comprises:

selecting two of the identified signal peaks, wherein the two selected signal peaks are above all other identified signal peaks within the access search window; and

modifying the access search window into one or more access search windows that encompass only the two selected peaks.

11. A mobile station comprising:

a communication interface;

a processing unit;

data storage; and

program logic stored in the data storage and executable by the processing unit to;

determine the position of the mobile station at a first time;

determine the position of the mobile station at a second time;

determine whether a distance between the position of the mobile station at the first time and the position of the mobile station at the second time is less than a threshold distance; and

in response to determining that the distance is less than the threshold distance, (i) measure a strength of a signal within the access search window, wherein the access search window has an initial size (ii) identify one or more signal peaks within the access search window, wherein the one or more identified signal peaks are above a specified signal strength, and (iii) modify the access search window into one or more smaller access search windows, wherein the one or more smaller access search windows collectively have a size that is smaller than the initial size, and wherein the one or more smaller access search windows encompass the one or more identified signal peaks.

12. The mobile station of claim 11, wherein the program logic is further executable by the processing unit to:

at or about the first time, (i) measure the strength of the signal within the access search window, (ii) identify one or more signal peaks within the access search window, wherein the one or more signal peaks are above a specified signal strength, and (iii) associate the position of the mobile station at the first time with the identified signal peaks.

13. The mobile station of claim 12, wherein the program logic is further executable by the processing unit to:

at or about the second time, (i) measure the strength of the signal within the access search window, and (ii) identify one or more signal peaks within the at least one smaller access search window, wherein the one or more signal peaks are above the specified signal strength, (iii) associate the position of the mobile station at the second time with the identified signal peaks, and (iv) correlate the one or more signal peaks identified at the second time with the one or more signal peaks identified at the first time.

14. The mobile station of claim 13, wherein the program logic is further executable by the processing unit to:

determine a distance based on the correlated signal peaks.

15. The mobile station of claim 13, wherein the program logic is further executable by the processing unit to:

determine a number of chips between the correlated signal peaks.

16. The mobile station of claim 11, wherein program logic is further executable by the processing unit to:

subsequent to the access search window being modified into one or more smaller access search windows, determine a position of the mobile station at a third time;

determine whether a distance between the position of the mobile station at the third time and the position of the mobile station at the second time is more than the threshold distance; and

in response to determining that the distance between the position of the mobile station at the third time and the position of the mobile station at the second time is more than the threshold distance, the mobile station resetting the access search window to the initial size.

17. The mobile station of claim 11, wherein program logic is further executable by the processing unit to:

subsequent to the access search window being modified into one or more smaller access search windows, determine a position of the mobile station at a third time;

determine whether a distance between the position of the mobile station at the third time and the position of the mobile station at the first time is more than the threshold distance; and

in response to determining that the distance between the position of the mobile station at the third time and the position of the mobile station at the first time is more than the threshold distance, the mobile station resetting the access search window to the initial size.

18. The mobile station of claim 11, wherein the program logic is executable by the processing unit to determine the position of the mobile station at the first time further comprises program logic executable by the processing unit to determine the position of the mobile station at the first time and the second time using GPS.

19. The mobile station of claim 18, wherein the program logic is executable by the processing unit to determine the distance between the position of the mobile station at the first time and the position of the mobile station at the second time further comprises program logic executable by the processing unit to determine a distance between a GPS position at the first time and a GPS position at the second time.

20. The mobile station of claim 11, wherein the program logic is executable by the processing unit to modify the access search window into one or more smaller access search windows comprises program logic executable by the processing unit to:

select two signal peaks, wherein the two selected signal peaks are above all other identified signal peaks within the access search window;

modify the access search window into one or more access search windows that encompass only the two selected peaks.