OFDM 系統中通道估測方法一直被廣泛討論與研究。在本論文 中，我們採用半盲目的方法來研究 SFBC OFDM 系統通道的追蹤， 半盲目方法的好處在於不會使用太多的頻寬。所研究的方法在接收端追蹤通道時，依據當時通道的特性來選擇使用決策迴授機制或是改良式固定模數演算法(Modified Constant Modulus Algorithm)來進行估測，其中我們使用了一個自動切換方式。並且，修正的通道估測法使用線性內插或外插方式來進行補償。由模擬結果得知，如此切換的方式加上改良式的通道補償，比傳統僅使用決策迴授法或改良式固定模數演算法的效能更佳。Channel estimation has been a widely studied research topic in OFDM systems. In this thesis, we consider the semi-blind approach for channel tracking used in space frequency block code (SFBC) MIMO-OFDM. The advantage of the semi-blind method is little occupancy of bandwidth. The proposed algorithm can estimate the channel response by using the conventional decision feedback scheme or a modified constant modulus algorithm (CMA) based on an automatic switching mechanism in terms of the channel status. Besides, a modified channel estimation method is performed by applying the interpolation or the extrapolation scheme for channel compensation. Simulation results show that the proposed switching method in combination with the modified channel compensation scheme outperforms the method using only decision feedback or the modified CMA.
