矩形脈波正交時頻間距調變系統之改進的初始時間同步

Abstract

本報告進行對初始時間同步(initial time synchronization; ITS)的研究，ITS對於在線性時變多路徑(linear time varying multipath; LTV)通道下運行的正交時頻間距調變(orthogonal time frequency space; OTFS)的相干解調至關重要。先前的研究已經開發了有效地基於前導訊框的ITS方法，並利用各種選擇最大值識別規則來估計LTV通道中具有強主導路徑的情況下的主導路徑延遲。然而，當LTV通道沒有強主導路徑時，這些ITS方法的估計準確性會明顯降低。本報告提出了一種基於梳狀前導訊框(comb-type preamble-frame; CPF)的ITS系統，該系統採用離散時間過取樣技術，並引入了兩種新的選擇主導峰值識別規則，以提升ITS的性能。無論LTV通道是否具有強主導路徑，改進的CPF型ITS系統在估計準確性和對都卜勒的穩健性方面均顯著優於現有的基於前導訊框的ITS系統。

Initial time synchronization (ITS) is essential for the coherent demodulation in orthogonal time frequency space systems operating over the linear time varying multipath (LTV) channels. Previous studies have developed efficacious preamble-frame-based ITS approaches using various select-the-largest identification rules to estimate the leading channel path delay over LTV channels exhibiting a strong leading path. However, such ITS approaches provide noticeable estimation inaccuracy under LTV channels without a strong leading path. In this paper, a comb-type preamble-frame (CPF)-based ITS system adopting discrete-time oversampling and two new select-the-leading-peak identification rules are proposed to provide improved ITS performance. Particularly, whether LTV channels exhibit a strong leading path or not, the improved CPF-based ITS system outperforms existing preamble-frame-based ITS systems significantly in estimation accuracy and robustness against Doppler spread.