GPS satellite signal acquisition assistance system and method in a wireless communications network

Abstract

A system and method for assisting an integrated GPS/wireless terminal unit in acquiring one or more GPS satellite signals from the GPS satellite constellation. The invention includes a method for narrowing the PN-code phase search. That is, by accounting for the variables in geographic location and time delay relative to GPS time, the systems and methods of the present invention generate a narrow code-phase search range that enables the terminal unit to more quickly acquire and track the necessary GPS satellites, and thereby more quickly provide accurate position information to a requesting entity.

1. A system for transmitting a GPS receiver code-phase search range to a integrated GPS/wireless terminal unit operating in a wireless network, said system comprising:
 a receiver operable to generate a GPS time reference; 
 a controller operable to calculate a GPS code-phase search range with reference to a base station geographic location, the wireless coverage area, an angle between a vector extending from the base station to a GPS satellite and a vector extending from the base station to the GPS/wireless terminal unit, said GPS time reference and the estimated wireless signal propagation delay within said coverage area, and 
 a transmitter coupled to said controller and operable to transmit said calculated GPS code search range. 
 
     
     
       2. The invention of  claim 1  wherein said GPS code-phase search range is defined by a center value and a size value. 
     
     
       3. A system for transmitting a GPS receiver code-phase search range to a integrated GPS/wireless terminal unit operating in a wireless network, comprising:
 a GPS receiver operable to generate a GPS time reference; 
 means for obtaining a time offset for the GPS/wireless terminal unit relative to said GPS time reference; 
 a controller operable to calculate a GPS code-phase search range with reference to a base station geographic location, a radius of the wireless coverage area served by the base station, an elevation angle of a GPS satellite, the time offset, and said time reference; and 
 a transmitter coupled to said controller and operable to transmit said calculated GPS code search range. 
 
     
     
       4. The invention of  claim 3  wherein said GPS code-phase search range is defined by a center value and a size value. 
     
     
       5. The invention of  claim 3  wherein said means for obtaining a time offset utilizes the round-trip wireless signal propagation time between said base station and the terminal unit to establish said time offset. 
     
     
       6. A system for transmitting a GPS receiver code-phase search range to a integrated GPS/wireless terminal unit operating in a wireless network, comprising:
 a GPS receiver operable to generate a GPS time reference; 
 means for obtaining a time offset for the GPS/wireless terminal unit relative to said GPS time reference; 
 means for obtaining a location reference for the GPS/wireless terminal unit; 
 a controller operable to calculate a GPS code-phase search range with reference to a variance of a positioning error of said location reference, and said time reference; and 
 a transmitter coupled to said controller and operable to transmit said calculated GPS code search range. 
 
     
     
       7. The invention of  claim 6  wherein said GPS code-phase search range is defined by a center value and a size value. 
     
     
       8. The invention of  claim 6  wherein said means for obtaining a location reference utilizes means for providing terrestrial based trilateration to establish said location reference. 
     
     
       9. A method for defining a GPS receiver code-phase search range for an integrated GPS/wireless terminal unit operating in a wireless network having a base station comprising the steps of:
 calculating a GPS code-phase search range with reference to the base station geographic location plus the wireless coverage area, an angle between a vector extending from the base station to a GPS satellite and a vector extending from the base station to the GPS/wireless terminal unit, and with reference to a base station GPS time reference plus the estimated wireless signal propagation delay within said coverage area and 
 transmitting said calculated GPS code-phase search range. 
 
     
     
       10. The invention of  claim 9  wherein said GPS code-phase search range is defined by a center value and a size value. 
     
     
       11. A method for defining a GPS receiver code-phase search range for an integrated GPS/wireless terminal unit operating in a wireless network having a base station, comprising the steps of:
 obtaining a time reference for the GPS/wireless terminal unit establishing the time offset relative to the base station GPS time; 
 calculating a GPS code-phase search range with reference to the base station geographic location plus a radius of the wireless coverage area served by the base station, an elevation angle of a GPS satellite, and said time reference; and 
 transmitting said calculated GPS code-phase search range. 
 
     
     
       12. The invention of  claim 11  wherein said GPS code-phase search range is defined by a center value and a size value. 
     
     
       13. The invention of  claim 11  wherein said obtaining step utilizes the round-trip wireless signal propagation time between said base station and the terminal unit to establish the time offset. 
     
     
       14. A method for defining a GPS receiver code-phase search range for an integrated GPS/wireless terminal unit operating in a wireless network having a base station, comprising the steps of:
 obtaining a time reference for the GPS/wireless terminal unit establishing the time offset relative to the base station GPS time; 
 obtaining a location reference for the GPS/wireless terminal unit; 
 calculating a GPS code-phase search range with reference to a variance of a positioning error of said location reference, and said time reference; and 
 transmitting said calculated GPS code-phase search range by the base station. 
 
     
     
       15. The invention of  claim 14  wherein said GPS code-phase search range is defined by a center value and a size value. 
     
     
       16. The invention of  claim 14  wherein said obtaining a location reference step utilizes terrestrial based trilateration techniques to establish said location reference. 
     
     
       17. A system for transmitting a GPS receiver code-phase search range to an integrated GPS/wireless terminal unit operating in a wireless network, said system comprising:
 a receiver operable to generate a GPS time reference; 
 a controller operable to calculate the GPS code-phase search range with reference to a base station geographic location, a position estimate of the integrated GPS/wireless terminal unit having an uncertainty area with a center distinct from the base station geographic location, and said GPS time reference; and 
 a transmitter coupled to said controller and operable to transmit said calculated GPS code-phase search range. 
 
     
     
       18. The system of claim 17, wherein the controller is further operable to determining a propagation delay from the base station to the GPS/wireless terminal unit and correct the GPS time reference based on the propagation delay, and wherein the controller calculates the GPS code-phase search range based on the corrected GPS time reference. 
     
     
       19. The system of claim 18, wherein the controller is further operable to determine a signal delay at an antenna of the base station, and wherein the controller corrects the GPS time reference based on the signal delay at the antenna of the base station. 
     
     
       20. The system of claim 17, wherein the controller obtains the position estimate of the GPS/wireless terminal unit based on network measurements. 
     
     
       21. The system of claim 17, wherein the controller obtains the position estimate of the GPS/wireless terminal unit based on a terrestrial based trilateration system. 
     
     
       22. The system of claim 17, wherein the controller calculates the GPS code-phase search range by calculating a search window center and a search window size. 
     
     
       23. A method for defining a GPS receiver code-phase search range for an integrated GPS/wireless terminal unit operating in a wireless network having a base station, the method comprising:
 determining, with a GPS receiver, a GPS time reference;   determining a geographic location of a base station serving the GPS/wireless terminal unit;   obtaining a position estimate of the GPS/wireless terminal unit having a center distinct from the base station geographic location;   calculating a GPS code-phase search range based on the GPS time reference, the geographic location of the base station and the position estimate of the GPS/wireless terminal unit; and transmitting said calculated GPS code-phase search range.   
     
     
       24. The method of claim 23, further comprising:
 determining a propagation delay from the base station to the GPS/wireless terminal unit; and   correcting the GPS time reference based on the propagation delay,   wherein the calculating the GPS code-phase search range is based on the corrected GPS time reference.   
     
     
       25. The method of claim 24, further comprising:
 determining a signal delay at an antenna of the base station, and   wherein the correcting the GPS time reference is based on the signal delay at the antenna of the base station.   
     
     
       26. The method of claim 23, wherein the obtaining the position estimate of the GPS/wireless terminal unit comprises obtaining the position estimate based on network measurements. 
     
     
       27. The method of claim 23, wherein the obtaining the position estimate of the GPS/wireless terminal unit comprises obtaining the position estimate based on a terrestrial based trilateration system. 
     
     
       28. The method of claim 23, wherein the calculating the GPS code-phase search range comprises calculating a search window center and a search window size.