Design of FFT-Based TDCC for GNSS Acquisition

Due to the longer spreading code used for the next generation GNSS (Global Navigation Satellite System) signals, receivers have to spend longer time or require larger amount of hardware resources for signal acquisition. Since many recent GNSS receivers use DSP (Digital Signal Processor) to realize parallel signal acquisition scheme in the frequency domain, this paper proposes FFT-based TDCC (Two-Dimensional Compressed Correlator) with which coherently compressed hypotheses are tested using a reduced number of IFFT points in the 1st stage, and the individual hypotheses that construct the compressed hypothesis found in the 1st stage are tested using the conventional parallel search scheme in the 2nd stage. The performance of the proposed technique is demonstrated with numerous Monte Carlo simulations and a comparison to the conventional FFT-based search technique is provided. The results show that the proposed technique requires lower computation and has lower mean acquisition time than the conventional FFT-based search technique for moderate and high C/N₀ (Carrier-to-Noise Density Ratio) GNSS signals.