Doppler estimation for fast acquisition in spread spectrum communication systems

This paper describes a non-coherent technique which employs a fast Fourier transform (FFT) for the fast acquisition of direct sequence spread spectrum signals in the presence of large Doppler shifts. The application of an FFT to code acquisition results in decreased acquisition time and can improve the probability of detection. The technique discussed in this paper uses a set of partial correlators and a zero-padded FFT to reduce the search region for code acquisition whilst maintaining good frequency resolution for Doppler offset. This approach will prove most pertinent in future re-configurable terminals.