A Novel PN Weighted Timing Synchronization Algorithm in Ionospheric Scatter Channel

Ionospheric scatter channel (ISC) exhibits a wide range of signal-to-noise ratio (SNR), so transmission systems may work at a low SNR, and ISC also has a severe frequency-selective fading, causing low detection probability. A novel pseudonoise (PN) weighted timing synchronization algorithm is proposed. The constant amplitude zero autocorrelation (CAZAC) is weighted by PN to constitute a two-stage preamble, by employing hierarchical correlation detection at the receiver to decline the computational complexity; before executing the conventional adaptive threshold algorithm (CATA), the proposed non-coherent combining is performed to accumulate the sub-peaks power on main peak to obtain the new peak, which enhances the discrimination between the new peak and background noise under low SNRs and dense multi-path channels. Simulation results show that compared to CATAs based on constant false alarm rate (CFAR), the detection probability is improved by approximately 2 dB.