Optimized signal acquisition algorithm for UAV emergency communication in mountainous signal-occluded environments

The coupling effects of multipath fading, shadowing, and Doppler shift make signal acquisition extremely challenging for unmanned aerial vehicle (UAV) emergency communication in mountainous environments. To address this issue, an optimized acquisition algorithm is proposed. The algorithm first buffers discrete-time digital intermediate frequency signals and enhances signal segments using adaptive spectral kurtosis filtering. The generalized likelihood ratio test (GLRT) is then employed to detect the presence of emergency communication signals. By integrating prior information, a dynamic guided search space is constructed, and the correlation power spectrum is obtained through guided parallel cycling. An ordered statistic-based adaptive threshold, which offers stronger robustness, is established to acquire initial estimates of code phase and Doppler frequency. Subsequently, a small continuous observation region is determined to calculate test statistics, confirm successful acquisition, and refine the final code phase and Doppler frequency for handover to the tracking loop. Experimental results demonstrate that the code phase and Doppler frequency acquired by the proposed algorithm closely match the actual values, achieving a minimum false acquisition rate of 2%.