Faster GPS/IRNSS acquisition via sub sampled fast Fourier transform (ssFFT) and thresholding

This paper presents a new, simple, efficient and faster GPS acquisition via sub-sampled fast Fourier transform (ssFFT) and thresholding. The proposed algorithm exploits the recently developed sparse FFT (or sparse IFFT) that computes in sublinear time. Further it uses the property of Fourier transforms (FT): Aliasing a signal in the time domain is equivalent to subsampling it in the frequency domain, and vice versa. The ssFFT is an FFT algorithm that computes with sub sampling factor `d', and hence the computational complexity is reduced by a factor of `d logd', compared to conventional FFT based algorithms for any length of the input GPS signal. The simulation results show that the proposed ssFFT based GPS acquisition computation time is 8.5571 times faster than that conventional FFT based acquisition computation. A clean spike is produced by thresholding the noisy signal.