Hybrid Search Single and Double-dwell Acquisition Architectures for Galileo Signal

GPS and Galileo receivers must perform two dimensional searches, in time and in frequency, in order to acquire the correct code phase and correct Doppler frequency. Accurate and fast acquisition plays an important role in achieving reliable satellite-based positioning. When the code length is high (e.g., Galileo and modernized GPS), the searching strategy is of utmost concern for fast signal acquisition. In this paper, we first introduce a double-dwell structure with hybrid search strategy for fast acquisition of CDMA signals with long spreading factors. We also derive its Mean Acquisition Time (MAT) and we compare its performance with that of single-dwell hybrid-search structures. Typically, doubledwell architectures have been preferred to single-dwell architectures. However, comparisons between the two structures are still hard to find in the existing literature, especially for hybrid-search approaches. We will show here that singledwell architectures may be still better than double-dwell architectures under certain conditions. We will also discuss the influence of various parameters, such as the penalty factors and the target detection and false alarm probabilities, on the proposed acquisition structure. The simulation results were carried out for Galileo signals.