Doppler compensation and code acquisition techniques for LEO satellite mobile radio communications

LEO satellite channels can experience extremely large Doppler shifts which makes the PN code acquisition of spread spectrum signals difficult. The use of an FFT technique to estimate the Doppler offset on a pilot carrier signal is shown to allow Doppler shift compensation to within 250 Hz. This eliminates the need to search the Doppler ambiguity during code acquisition and considerable improves the mean code acquisition time performance. We consider the performance of a code acquisition architecture developed for satellite spread spectrum receivers.