Three-Stage Based Rapid Long PN-codeAcquisition Method by EmployingTime-Frequency Folding Technique

Rapid long Pseudo-noise (PN) code acquisitionis challenging in Direct sequence spectrum system(DSSS) and Global navigation satellite system (GNSS).The difficulty is how to quickly detect numerous codephases and lots of frequency cells. In the study, a threestageacquisition method is proposed. In search stage one,a few code phases and several frequency cells are mergedinto a single cell, to directly reduce the cardinality of searchspace. The reduction is favorable to accelerate search process.Then, in search stage two and search stage three,fine acquisitions for frequency cells and code phases areperformed, respectively. Compared with the Extendedreplica folding acquisition search technique (XFAST), theproposed method tests more code phases and frequencycells simultaneously and consequently reduces mean acquisitiontime at the expense of degrading detection performance.Numerical results demonstrate the analysis.