Optimized Search Window Alignment for A-GPS

The best performance of assisted-global positioning system (A-GPS) positioning is obtained when fine time assistance is provided to the terminal, i.e., when information on the GPS time of week is provided, and is accurate to within a few microseconds. This paper presents a new method for the minimization of the size of the coarse acquisition (C/A) code search windows, around their so-provided window centers. The method accounts for 1) the geometrical shape of the initial region where the terminal is known to be located; 2) the location of the radio base station; and 3) the azimuth and elevation angles of each space vehicle. Benefits include a reduced computational complexity of the GPS signal acquisition or a corresponding sensitivity enhancement.