A fast acquisition algorithm based on FFT for BOC modulated signals

The Binary Offset Carrier (BOC) modulation is expected to be utilized in the modern Global Navigation Satellite Systems (GNSS) to increase utilization efficiency of the limited frequency spectrum resource. It splits the main energy component of pseudo random noise (PRN) signal spectrum symmetrically around the center, and thus helps to mitigate inter-satellite cross correlation and makes the signals more robust. However, the modulation of subcarrier leads to multiple secondary peaks, which will cause signal detection missing and false lock. On the other hand, the new signals will have much longer code length than traditional GPS C/A code. To shorten the time to first fix (TTFF), parallel acquisition algorithms are commonly adopted in practical receivers. In this paper, we propose an effective code acquisition technique for BOC signals exploiting Fast Fourier Transform (FFT). It modifies the standard full code-parallel FFT acquisition approach, in order to mitigate secondary peaks and expedite the calculation. Utilizing BOCsin(1,1) signal, numerical simulation results demonstrate that the proposed modified FFT-based code acquisition scheme works efficiently for sine BOC signal. At expense of little detection performance, it can reduce computation significantly compared with the traditional approach.