Initial Synchronization Assisted by Inherent Diversity over Time-Varying Frequency-Selective Fading Channels

An initial synchronization technique based on novel estimations of the time error and carrier frequency offset (CFO) is investigated in this paper to operate in frequency-selective fading environments. Based on motivation from statistical derivations, a novel estimator is proposed by embedding matched filters (MFs) into the RAKE fingers to approach the modified Cramer-Rao lower bounds (MCRLBs). Meanwhile, a dual chirp signal is proven to have the ability to decorrelate the performances between the time-error and the CFO estimators. By taking advantage of pseudo-noise (PN) MFs, the individual channel tap-weighting coefficients can be extracted from the interpath interference on a path-by-path basis. The proposed technique is then built to approach the MCRLBs by taking advantage of the maximum ratio combining (MRC) criterion. In practice, the proposed technique can significantly outperform a conventional initial synchronization technique that is not assisted by the diversity in terms of higher probabilities of burst acquisition and lower mean-square errors (MSEs) on the time-error and CFO estimations over multipath fading channels. Comprehensive computer simulations were conducted to verify the improvements achieved using the technique that is statistically derived in this paper.