Positioning with wireless local area networks and WLAN-aided global positioning systems
Accurate position capability can be quickly provided using a Wireless Local Area Network (WLAN). When associated with a WLAN, a wireless device can quickly determine its relative and/or coordinate position based on information provided by an access point in the WLAN. Before a wireless device disassociates with the access point, the WLAN can periodically provide time, location, and decoded GPS data to the wireless device. In this manner, the wireless device can significantly reduce the time to acquire the necessary GPS satellite data (i.e. on the order if seconds instead of minutes) to determine its coordinate position.
1. A wireless device comprising:
a wireless baseband configured to:
receive decoded global positioning system (GPS) data from one or more access points in a communication system;
a GPS baseband configured to:
identify a first GPS satellite based at least in part on the decoded GPS data;
acquire a first GPS signal from the first GPS satellite;
determine a first frequency offset of the first GPS signal based at least in part on a frequency difference between an oscillator frequency of the first GPS satellite and a receiver frequency of the wireless device; and
determine a frequency offset for one or more other GPS satellites based at least in part on the first frequency offset of the first GPS signal.
2. The wireless device of claim 1 , wherein the GPS baseband is further configured to:
acquire a second GPS signal from a second GPS satellite based at least in part on the determined frequency offset of the first GPS signal and ephemeris data included in the decoded GPS data; and
determine a location of the wireless device based at least in part on the second GPS signal.
3. The wireless device of claim 1 , wherein the GPS baseband is further configured to identify the first GPS satellite based on an elevation angle between the wireless device and the first GPS satellite.
4. The wireless device of claim 3 , wherein the elevation angle is determined based at least in part on the decoded GPS data.
5. The wireless device of claim 3 , wherein the elevation angle is determined based at least in part on GPS almanac data provided by the wireless baseband.
6. The wireless device of claim 3 , wherein the GPS baseband is further configured to determine a Doppler effect on a second GPS signal based at least in part on the decoded GPS data.
7. The wireless device of claim 1 , wherein the decoded GPS data includes GPS almanac data.
8. The wireless device of claim 7 , wherein the GPS baseband is configured to identify the first GPS satellite based at least in part on the GPS almanac data.
9. The wireless device of claim 1 , wherein the decoded GPS data is received periodically from the one or more access points.
10. A method comprising:
receiving, by a wireless baseband of a wireless device, decoded global positioning system (GPS) data from one or more access points in a communication system;
identifying, by a GPS baseband of the wireless device, a first GPS satellite based at least in part on the decoded GPS data;
acquiring a first GPS signal from the first GPS satellite;
determining a first frequency offset of the first GPS signal based at least in part on a frequency difference between an oscillator frequency of the first GPS satellite and a receiver frequency of the wireless device; and
determining a frequency offset for one or more other GPS satellites based at least in part on the determined frequency offset of the first GPS signal.
11. The method of claim 10 , further comprising:
acquiring a second GPS signal from a second GPS satellite based at least in part on the determined frequency offset of the first GPS signal and ephemeris data included in the decoded GPS data; and
determining a location of the wireless device based at least in part on the second GPS signal.
12. The method of claim 10 , further comprising:
identifying the first GPS satellite based on an elevation angle between the wireless device and the first GPS satellite.
13. The method of claim 12 , wherein the elevation angle is determined based at least in part on the decoded GPS data.
14. The method of claim 12 , wherein the elevation angle is determined based at least in part on GPS almanac data provided by the wireless baseband.
15. The method of claim 12 , further comprising:
determining a Doppler effect on a second GPS signal based at least in part on the decoded GPS data.
16. The method of claim 10 , wherein the decoded GPS data includes GPS almanac data.
17. The method of claim 16 , further comprising:
identifying the first GPS satellite based at least in part on the GPS almanac data.
18. The method of claim 10 , wherein the decoded GPS data is received periodically from the one or more access points.