Faster Acquisition Technique for Software-defined GPS Receivers

M. Venu Gopala Rao; D. Venkata Ratnam

doi:10.14429/dsj.65.5579

M. Venu Gopala Rao K.L. University, Guntur
D. Venkata Ratnam K.L. University, Guntur

DOI: https://doi.org/10.14429/dsj.65.5579

Keywords: GPS, sub-sampling, aliasing, acquisition, sub-sampled fast Fourier transform

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.

Defence Science Journal, Vol. 65, No. 1, January 2015, pp.5-11, DOI:http://dx.doi.org/10.14429/dsj.65.5579

Author Biographies

M. Venu Gopala Rao, K.L. University, Guntur

Dr M. Venu Gopala Rao obtained his MTech from Regional Engineering College, Warangal, in 1999, and PhD from Osmania University, Hyderabad, in 2011. Presently, he is Professor in the Department of ECE, KL University, Guntur, A.P., India. He received a ‘Credit Award’ in Radio Servicing Theory from City and Guild’s London Institute, London, in 1978. He is a Fellow of IETE and Life Member in IAE, ISTE, SSI, and ISOI. His research interests include signal, image processing, GPS and compressive sensing. He has published more than 38 papers in various international and national journals, conferences and workshops.

D. Venkata Ratnam, K.L. University, Guntur

Dr D. Venkata Ratnam obtained his MSc (Electronics) and MTech (Radar and Microwave Eng) from Andhra University. PhD from JNTUH, Hyderabad. Presently, Associate Professor, Dept. of Electronics and Communication Engineering, KL University, Guntur, A.P., India. Research interests: navigation electronics, global positioning system, space science, radio wave propagation, satellite communications. Publications: author of 12 international and 4 national journal papers and 23 national and international conference papers.