OTFS系統中基於分離領航幀的改良型序列性通道估測

Abstract

對於在延遲–都卜勒(delay-Doppler)通道上運作的正交時頻空間調變(orthogonal time frequency space modulation)來說，為了實現數據決策(data decision)，延遲–都卜勒網格上的通道矩陣(delay-Doppler channel matrix, DD-CM)估測非常關鍵。然而，由於環境設定的不同，適用方法有很大的變化，且DD-CM的通道響應(channel responses)是由DD網格上的延遲位移(delay shifts)、都卜勒位移(Doppler shifts)和路徑響應(path responses)非線性組成，因此，DD-CM估測是非常有挑戰性的。本文論文看見前人的序列性通道估測(sequential channel estimation, SCE)在於高速度通訊環境下效能變差的問題，針對其進行改良，提出一種新型的改良型序列性通道估測(modified sequential channel estimation, MSCE)，通過分開傳送的均勻間隔的領航符元幀，依序執行延遲位移、路徑位移和都卜勒位移的估計，然後再補充上牛頓化正交匹配追蹤(Newtonized orthogonal matching pursuit, NOMP)方案，最後形成DD-CM的估測。MSCE方法在現有使用分離領航幀(separate pilot frames, SPF)的通道估測(channel estimation)方法中，擁有高精確度的DD-CM估計且低計算複雜度(computational complexity)的優勢，相較於前人的序列性通道估測，擁有著更低的誤碼率以及估測精準度，並適用於更高速度的通訊環境。

The estimation of delay-Doppler channel matrix (DD-CM) on the delay-Doppler grid is crucial for the data decision in orthogonal time frequency space (OTFS) systems which operate over delay-Doppler channel. However, because of the differences in the setting of the communication environment, there could be many applicable estimation methods. Moreover, DD-CM consists of delay shifts, Doppler shifts and path responses on the re-ceive DD grid nonlinearly. To solve the problem of sequential channel estimation (SCE) scheme that performances break down in high mobility environment. Modified sequential channel estimation (MSCE) scheme is proposed in this thesis. Through the separately transmitted uniformly spaced pilot frame, MSCE implement the estimation of delay shifts, path responses and Doppler shifts sequentially and carry out additional Newtonized or-thogonal matching pursuit (NOMP) method to enhance the accuracy. In the end, compose the DD-CM estimate indirectly. MSCE scheme provide accurate DD-CM estimation and employ the advantage of low computational complexity. Compared with SCE scheme, MSCE scheme shows lower bit-error rate and DD-CM NMSE and applicable for higher mobility environment.