Faster Acquisition Technique for Software-defined GPS Receivers

Abstract

Acquisition is a most important process and a challenge task for identifying visible satellites, coarse values of carrier frequency, and code phase of the satellite signals in designing software defined Global positioning system (GPS) receiver. This paper presents a new, simple, efficient and faster GPS acquisition via sub-sampled fast Fourier transform (ssFFT). The proposed algorithm exploits the recently developed sparse FFT (or sparse IFFT) that computes in sub-linear time. Further it uses the property of fourier transforms (FT): Aliasing a signal in the time domain corresponds to sub-sampling it in the frequency domain, and vice versa. The ssFFT is an FFT algorithm that computes sub-sampled version of the data by an integer factor 'd', and hence, the computational complexity is proportionately reduced by a factor of 'd log d' 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 is 8.5571 times faster than the conventional FFT-based acquisition computation time. The implementation of this method in an FPGA provides very fast processing of incoming GPS samples that satisfies real-time positioning requirements.

Multi-Peak Double-Dwell GPS Weak Signal Acquisition Method and VLSI Implementation for Energy-Constrained Applications

“…Step 3: The second dwell is carried only on the sets S (1) ij (τ i ,f j ), and double integration time 2T int is used to generate test variables ξ (2) ij (τ i ,f j ) with 2T int MC cell computation overhead.…”

“…Step 4: The largest ξ (2) ij (τ i ,f j ) is singled out, and its parameters are recognized as the final estimated τ and f d . The computation overhead of selecting the largest ξ (2) ij (τ i ,f j ) among M test variables is small.…”

“…The computation overhead of selecting the largest ξ (2) ij (τ i ,f j ) among M test variables is small.…”

“…These acquisition methods mainly focus on the reduction of acquisition time, thus reducing The Time to First Fix (TTFF), or increase the sensitivity while ignoring the energy consumption [2]. Research on GPS acquisition mainly addresses three aspects, which are correlation, integration, and searching strategy.…”

Energy Efficient GNSS Signal Acquisition Using Singular Value Decomposition (SVD)

“…Song proposed a faster acquisition algorithm via subsample FFT. The algorithm first downsamples by a factor ‘ d ’ and then multiplies the FFT of the received signal with the FFT of the locally-generated PRN code, and takes the IFFT of the resulting signal, which produces a single spike at the correct time shift [ 17 ]. The problem with this algorithm is that the downsampling factor ‘ d ’ increases the noise contamination linearly, even though the computation time decreases exponentially, .…”