應用於地面數位影像廣播系統的聯合時域與頻域通道估測法以及載波間干擾消除法

Abstract

對於數位影像廣播系統來說，系統的效能非常仰賴通道估測的結果。最近有研究者提出的聯合時域與頻域通道估測法，比舊有頻域通道估測法明顯有更好的效能。然而，所使用的領航訊號數目多寡將會影響聯合時域與頻域通道估測法的效能，所以這篇論文的第一部份就是提出改善的聯合時域與頻域通道估測法，可在領航訊號數目很少情況下得到很高的效能。在高速移動的環境下，OFDM系統會有載波間干擾的問題，這會嚴重使系統效能下降。現有的載波間干擾消除法往往需要很高的運算複雜度，所以在論文的第二部份，我們提出了幾個低運算複雜度的載波間干擾消除法。我們所提出演算法不但有較低運算複雜度，而且從模擬結果可以驗證提出的方法和現有的方法有近似的效能，

In DVB-T systems, the system performance heavily relies on that of the channel estimation. Recently, a join time-and-frequency-domain channel estimator has been proposed. It has been shown that its performance is significantly better than the conventional frequency domain estimator. However, the performance of the join time-and-frequency-domain channel estimator depends on the number of pilot subcarrier it uses. In the first part of this thesis, we propose an improved time-and-frequency-domain channel estimation method that can have high performance even when the number of pilot subcarriers is low. It has been well-known that the intercarrier-interference (ICI), induced when OFDM systems operated in high-mobility environments, can degrade the system performance seriously. Existing ICI cancellation methods often require high computational complexity. In the second part of the thesis, we propose a number of low-complexity ICI cancellation methods. Simulations show that the proposed algorithms can have the performance similar to existing method, while the computational complexity is significantly lower.