Dynamic data retrieval in a WLAN positioning system

1. In a wireless network having a plurality of access points, a method performed by a mobile device for selectively retrieving location information of the access points from an access point location server, the method comprising:

negotiating a number of configuration parameters with the location server, wherein one of the configuration parameters comprises a geographic area parameter indicating a preferred retrieval area for the mobile device;

determining whether the mobile device is in motion;

if the mobile device is not in motion, requesting the location server to provide, in a private fetching operation, location information of access points that are visible to the mobile device;

if the mobile device is in motion, requesting the location server to provide, in a public fetching operation, location information of access points that lie within the preferred retrieval area;

determining when a current public fetching operation was requested by the mobile device;

determining when a previous public fetching operation was requested by the mobile device;

comparing a difference in time between the current public fetching operation request and the previous public fetching operation request with a refresh rate of the location server; and

selectively reducing a size of the preferred retrieval area in response to the comparing.

2. The method of claim 1 , wherein requesting the location server to provide location information in the private fetching operation further comprises:

determining a media access control (MAC) address for each of the visible access points; and

transmitting the MAC addresses of the visible access points as look-up values to the location server.

3. The method of claim 1 , wherein requesting the location server to provide location information in the public fetching operation further comprises:

determining a current location of the mobile device; and

transmitting the current location to the location server.

4. The method of claim 3 , further comprising:

identifying, in the location server, the access points that lie within the preferred retrieval area of the mobile device's current location; and

transmitting location information of the identified access points to the mobile device.

5. The method of claim 1 , wherein determining whether the mobile device is in motion comprises:

determining first positional information of the mobile device at a first time;

determining second positional information of the mobile device at a second time; and

comparing the first and second positional information with each other.

6. The method of claim 1 , further comprising:

dynamically switching between the private fetching operation and the public fetching operation in response to the determining.

7. The method of claim 1 , further comprising:

determining a value indicating an uncertainty of the mobile device's current location; and

initiating the private fetching operation if the value is greater than a predetermined threshold.

8. The method of claim 1 , wherein another of the configuration parameters comprises a refresh time indicating how frequently the location server updates location data provided to the mobile device.

9. A system for selectively retrieving location information of a number of wireless access points from an access point location server to a mobile device, the system comprising:

means for negotiating a number of configuration parameters with the location server, wherein one of the configuration parameters comprises a geographic area parameter indicating a preferred retrieval area for the mobile device;

means for determining whether the mobile device is in motion;

means for requesting the location server to provide, in a private fetching operation, location information of access points that are visible to the mobile device if the mobile device is not in motion;

means for requesting the location server to provide, in a public fetching operation, location information of access points that lie within the preferred retrieval area if the mobile device is in motion;

means for determining when the current public fetching operation was requested by the mobile device;

means for determining when a previous public fetching operation was requested by the mobile device;

means for comparing a difference in time between the current public fetching operation request and the previous public fetching operation request with a refresh rate of the location server; and

means for selectively reducing the size of the preferred retrieval area in response to the comparing.

10. The system of claim 9 , wherein the means for requesting the location server to provide location information in the public fetching operation further comprises:

means for determining a current location of the mobile device; and

means for transmitting the current location to the location server.

11. The system of claim 10 , further comprising:

means for identifying, in the location server, a list of access points that lie within the preferred area of the mobile device's current location; and

means for transmitting location information of the identified access points to the mobile device.

12. The system of claim 9 , wherein determining whether the mobile device is in motion comprises:

means for determining first positional information of the mobile device at a first time;

means for determining second positional information of the mobile device at a second time; and

means for comparing the first and second positional information with each other.

13. The system of claim 9 , further comprising:

means for dynamically switching between the private fetching operation and the public fetching operation in response to the determining.

14. The system of claim 9 , further comprising:

means for determining a value indicating an uncertainty of the mobile device's current location; and

means for initiating the private fetching operation if the value is greater than a predetermined threshold.

15. The system of claim 9 , wherein another of the configuration parameters comprises a refresh time indicating how frequently the location server updates location data provided to the mobile device.

16. A system for selectively retrieving location information for a number of wireless access points from an access point location server to a mobile device, wherein the mobile device comprises:

a processor; and

a memory coupled to the processor and having stored therein computer-executable instructions that when executed cause the system to:

negotiate a number of configuration parameters with the location server, wherein one of the configuration parameters comprises a geographic area parameter indicating a preferred retrieval area for the mobile device;

determine whether the mobile device is in motion;

request the location server to provide, in a private fetching operation, location information of access points that are visible to the mobile device if the mobile device is not in motion;

request the location server to provide, in a public fetching operation, location information of access points that lie within the preferred retrieval area if the mobile device is in motion;

determine when the current public fetching operation was requested by the mobile device;

determine when a previous public fetching operation was requested by the mobile device;

compare a difference in time between the current public fetching operation request and the previous public fetching operation request with a refresh rate of the location server; and

selectively reduce the size of the preferred retrieval area in response to the comparing.

17. The system of claim 16 , wherein when requesting the location server to provide location information in the private fetching operation, the instructions further cause the system to:

determine a media access control (MAC) address for each of the visible access points; and

transmit the MAC addresses of the visible access points as look-up values to the location server.

18. The system of claim 16 , wherein when requesting the location server to provide location information in the public fetching operation, the instructions further cause the system to:

determine a current location of the mobile device; and

transmit the current location to the location server.

19. The system of claim 18 , wherein the instructions further cause the system to:

identify, in the location server, the access points that lie within the preferred retrieval area of the mobile device's current location; and

transmit location information of the identified access points to the mobile device.

20. The system of claim 16 , wherein to determine whether the mobile device is in motion, the instructions further cause the system to:

determine first positional information of the mobile device at a first time;

determine second positional information of the mobile device at a second time; and

compare the first and second positional information with each other.

21. The system of claim 16 , wherein the instructions further cause the system to:

dynamically switch between the private fetching operation and the public fetching operation in response to whether the mobile device is in motion.

22. The system of claim 16 , wherein the instructions further cause the system to:

determine a value indicating an uncertainty of the mobile device's current location; and

initiating the private fetching operation if the value is greater than a predetermined threshold.

23. The system of claim 16 , wherein another of the configuration parameters comprises a refresh time indicating how frequently the location server updates location data provided to the mobile device.