High-sensitivity GPS receiver with infrequent use of GPS reference stations

摘要

A navigation-satellite receiver depends on a network server to occasionally provide key pieces of information needed during its initialization. The navigation-satellite receiver critically maintains its position uncertainty, sigmaPos, to under 150-km. Therefore, at least every five minutes, the navigation-satellite receiver uses a network connection to download all the ephemeris information for all the operational SV's. The power-off time uncertainty, sigmaTime, is kept under one millisecond by running a real-time clock with a software-compensated crystal oscillator reference. Such information is instantly available at power-up to reduce the time necessary to produce a first fix when receiver signal levels are under -150dbm even for the strongest SV.