A FFT-based space-differential cooperative algorithm for in-phase and orthogonal data/pilot signal acquisition

The modernization of GNSS has been promoting the adoption of innovative signal structure and modulation to provide better PVT services. The modern navigation signals in GPS and Galileo system all pick out the data/pilot composite signal structure, thus this paper mainly discusses the acquisition algorithm aiming at such signal type. Based on two prevailing hybrid modes, the in-phase and orthogonal signal models are first built. Then, under the analysis of the existing joint algorithms, NCC and CC methods, a universal algorithm operated in frequency domain, Space-Differential Cooperative (SDfC) method is proposed to solve "squaring loss" problem and other defects of existing joint algorithms. On the basic principles of SDfC illustrated in this paper, three concrete schemes are developed and explained in detail. After that, the uniform expressions of one-cell probabilities are deduced. To further study SDfC method, the performance of different schemes is test by Monte Carlo simulation on the basis of two signal models. According to the result, the proposed algorithm can successfully realize signal acquisition regardless of signal type. Moreover, SDfC with pre-estimation and optimized SDfC are investigated by intercomparsion as well as comparison with NCC and CC approaches in the aspect of probability characteristic, accuracy and average acquisition time.