Patent ID: 7239273
Filing Date: 2007-07-03
Classification: G01S

Abstract:
1. An apparatus for calculating satellite acquisition information for controlling a position determination entity (PDE) to determine a position of a mobile station (MS) in a network assisted GPS system, said PDE comprising: a satellite data collector for collecting satellite orbital information and pseudo range between a satellite and at least one of a mobile station (MS) and a base station (BS) of more than three consecutive times from a plurality of satellites; an interface for receiving a request message from an MS and requesting a calculation of satellite acquisition information; a satellite position calculator for receiving the request for the calculation of satellite acquisition information from the interface and calculating satellite position information using satellite orbital information from the satellite data collector; a pseudo range calculator for calculating a pseudo range using the calculated satellite position information from the satellite position calculator; a satellite velocity calculator for receiving the request for the calculation of satellite acquisition information from the interface and calculating velocity of satellites relative to the Earth-Centered, Earth-Fixed (ECEF) coordinate system using the satellite orbital information; a pseudo velocity calculator for calculating pseudo velocities between the MS and each satellite observed by the MS at a position measurement time of the MS using a velocity component directed to the MS from among a plurality of satellite velocity components; and a satellite acquisition information calculator for calculating a code phase using the pseudo range, and for calculating a Doppler shift using the pseudo velocity, and communicating the code phase and Doppler shift to the MS in response to the request message, wherein the PDE transmits reference time data and a time-dependent variation to the MS in order for correcting time difference, and wherein the PDE transmits a difference between the frequency variation generated at an estimated time and the time-dependent frequency variation to the MS when a frequency of the satellite is correctly fixed to a specific value, so that the MS calculates the final frequency using the difference between the frequency variation.