由於低地球軌道衛星環境具有長傳播延遲和高移動性等特點，對於 前導設計需要考慮時序提前和載波頻率偏移。為了處理頻率偏移對時 序估計造成的影響，前導訊號廣泛採用具有多個根的 Zadoff-Chu (ZC) 序列。然而，這樣的前導訊號會受到非正交干擾的影響。我們採用空 間多樣性來設計區域特定的前導訊號的樣式以有效緩解 NOI，並且能 夠在大的頻率偏移環境下進行時序估計。我們提出的前導訊號設計可 以達到更高的接入率，並且在頻率偏移較大或多個用戶同時訪問的情 況下也能保持良好效果。;Due to the features of low earth orbit (LEO) satellite environment, such as long propagation delays and high mobility, the preamble design needs to consider the large timing advance and carrier frequency offset (CFO). To handle the adverse impact of CFO on the timing detection, preambles constructed using Zadoff-Chu (ZC) sequence with multiple roots are widely considered. However, such preambles suffer from the non-orthogonal interference (NOI). We adopt spatial diversity to develop region specific preamble patterns to effectively mitigate NOI and estimate timing advance under the large CFO environment. Our proposed preamble design achieves high access rate, even in scenarios with large CFO or when multiple users access simultaneously.
