FFT processing of direct sequence spreading codes using modern DSP microprocessors

It is illustrated how a DSP (digital signal processing)-microprocessor-based module can be used for rapid identification and acquisition of the GPS (Global Positioning Satellite) system C/A codes. Specifically, the author describes the use of Inmos´ VecTram DSP module, which consists of an Inmos 32-b floating point transputer and Zoran´s 32-b floating point vector signal processor (VSP). The algorithm correlates a pseudorandom sequence in the frequency domain using the fast Fourier transform. The frequency-domain correlation algorithm is shown to be considerably more efficient than time-domain correlation, assuming that the time-domain correlation is performed with hardware of comparable performance The author explores the philosophy of the technique, and provides examples of the algorithm and results. A mathematically rigorous description is not provided