Method and system for time to first fix (TTFF) reduction of GPS receivers using satellite based augmentation system (SBAS) signal

A GPS receiver, comprising:

• a receiver configured to receive a SBAS signal from a SBAS satellite;
• and
• a controller configured to calculate a satellite clock and a satellite position of a GPS satellite using the received SBAS signal,
• wherein the SBAS signal comprises a difference value between ephemeris data and almanac data of the GPS satellite,
• wherein the difference value between the ephemeris data and the almanac data comprises a satellite clock difference value and a satellite position difference value for the GPS satellite,
• wherein the satellite clock difference value between the ephemeris data and almanac data for the GPS satellite is calculated by:
• ΔTj(t0)=TEj(t0)−TAj(t0) [Equation 1]
• and the satellite position difference value between the ephemeris data and almanac data for the GPS satellite is calculated by:
• Δxj(t0)=xEj(t0)−xAj(t0) [Equation 2]
• where t0 is the time of calculating the satellite clock difference value at a ground station, ΔTj(t0) is the satellite clock difference value calculated at time t0 at the ground station for j-th GPS satellite among a plurality of GPS satellites, TEj(t0) is the satellite clock ephemeris data of the j-th GPS satellite, TAj(t0) is the satellite clock almanac data of the j-th GPS satellite, Δxj(t0) is the satellite position difference value calculated at time t0 at the ground station for the j-th GPS satellite among the plurality of GPS satellites, xEj(t0) is the satellite position ephemeris data of the j-th GPS satellite, and xAj(t0) is the satellite position almanac data of the j-th GPS satellite.

A ground station configured to calculate a difference value between ephemeris data and almanac data of a GPS satellite, and include the calculated difference value in a SBAS message and transmit the same to a SBAS satellite,

• wherein the difference value between the ephemeris data and the almanac data comprises a satellite clock difference value and a satellite position difference value for the GPS satellite,
• wherein the satellite clock difference value between the ephemeris data and almanac data for the GPS satellite is calculated by:
• ΔTj(t0)=TEj(t0)−TAj(t0) [Equation 1]
• and the satellite position difference value between the ephemeris data and almanac data for the GPS satellite is calculated by:
• Δxj(t0)=xEj(t0)−xAj(t0) [Equation 2]
• where t0 is the time of calculating the satellite clock difference value at a ground station, ΔTj(t0) is the satellite clock difference value calculated at time t0 at the ground station for j-th GPS satellite among a plurality of GPS satellites, TEj(t0) is the satellite clock ephemeris data of the j-th GPS satellite, TAj(t0) is the satellite clock almanac data of the j-th GPS satellite, Δxj(t0) is the satellite position difference value calculated at time t0 at the ground station for the j-th GPS satellite among the plurality of GPS satellites, xEj(t0) is the satellite position ephemeris data of the j-th GPS satellite, and xAj(t0) is the satellite position almanac data of the j-th GPS satellite.