在頻率選擇性衰退通道下，為了消除因 頻率偏移所造成向下鏈結多載波分碼多重進階系統中子載波間正交性的破壞，我們探討頻率偏移的估測方法。在這裡我們利用向下鏈結多載波分碼多重進階系統的訊號模型去推導以ESPRIT為基礎的子空間頻率偏移估測方法來當作我們在這個架構下的估測器。本篇論文採用的這些高解析度的子空間演算法並不需要額外的訊號就提供較精準的估測，即是ESPRIT和它的變形。最後我們將會把fordward-backward averaging和smoothing的技巧與傳統的ESPRIT做結合來使得頻率偏移的估測更為精確。 In order to reduce the effect of the lost of orthogonality among the subcarriers due to the carrier frequency offset, we investigate the frequency offset estimations for the MC-CDMA downlink system over a frequency-selective fading channel. We used the structure of the MC-CDMA signal to derive the subspace-based estimation algorithms as the frequency offset estimators. These subspace-based algorithms offer the accuracy of a super resolution subspace method without using additional signals, viz. ESPRIT and its variants. We will combine the forward-backward averaging and smoothing techniques with these subspace-based algorithms for the accuracy of frequency offset estimation.
