Mobile station location determination in a radio communication system

A method for mobile station location determination in a radio communication system which includes a plurality of base stations configured for radio communication with at least one mobile station, the method comprising the steps of:

• (a) receiving at a base station of the radio communication system satellite ephemeris information and clock correction information for at least one earth orbiting satellite;
• (b) transmitting from the base station at predetermined intervals satellite position curve fit data and clock correction data;
• (c) at a mobile station, receiving the satellite position curve fit data and the clock correction data;
• and
• (d) at the mobile station, determining a position for the at least one satellite using the satellite position curve fit data and clock correction data.

A radiotelephone comprising:

• a transceiver configured for two-way communication with a remote base station and to receive satellite position curve fit data transmitted from the base station;
• a satellite receiver configured to receive satellite signals from one or more satellites and produce pseudo-range data in response to the satellite signals;
• and
• a processor coupled with the transceiver and the satellite receiver and configured to compute satellite positions of the one or more satellites in response to the satellite position curve fit data and the pseudo-range data.

A base station for a radio communication system, the base station comprising:

• means for receiving satellite ephemeris information and clock correction information;
• a processor configured to compute satellite position curve fit data in response to the satellite ephemeris data and clock correction information;
• and
• a transmitter coupled to the processor and configured to transmit the satellite position curve fit data at predetermined intervals.

A method of position location by a mobile station in a radio communication system, the method comprising the steps of:

• receiving raw satellite ephemeris and clock correction data for a plurality of satellites at a base station of the radio communication system;
• using the raw satellite ephemeris, computing the true satellite position and velocity data points for the plurality of satellites at at least three periods of time over a predetermined interval;
• using the clock correction data, computing clock corrections at the at least three periods of time over the predetermined interval;
• selecting a reference point that is near the mobile station;
• projecting the satellite position and velocity data points away from the reference point by an amount corresponding to the propagation delay associated with the clock correction data at each of the at least three periods of time;
• determining curve fit parameters for the projected satellite position and velocity data points;
• transmitting the curve fit parameters to the mobile station;
• and
• at the mobile station, using the curve fit parameters for the projected satellite position and velocity data points to compute position of the mobile station.