Navigation system and method
Patent 4445118 Issued on April 24, 1984. Estimated Expiration Date: 
May 22, 2001. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
May 22, 2001. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3384891 3430234 3471856 3544995 3641433 3763492 3789409 3852750 3906204 InventorsAssigneeApplicationNo. 06/266253 filed on 05/22/1981US Classes:342/357.09, With transmission of location-indicative information to or from a remote station342/356Synchronous satelliteExaminersPrimary: Blum, Theodore M.Attorney, Agent or FirmInternational ClassesG01S 5/00 (20060101)G01S 1/00 (20060101) AbstractIn a global positioning system (GPS), such as the NAVSTAR/GPS system, wherein the position coordinates of user terminals (14) are obtained by processing multiple signals transmitted by a constellation of orbiting satellites (16), an acquisition-aiding signal generated by an earth-based control station (12) is relayed to user terminals via a geostationary satellite (10) to simplify user equipment. The aiding signal is FSK modulated on a reference channel slightly offset from the standard GPS channel. The aiding signal identifies satellites in view having best geometry and includes Doppler prediction data as well as GPS satellite coordinates and identification data associated with user terminals within an area being served by the control station (12) and relay satellite (10). The aiding signal significantly reduces user equipment by simplifying spread spectrum signal demodulation and reducing data processing functions previously carried out at the user terminals (14).Other References
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