高頻寬效率OFDM系統之通道估計與等化

Abstract

在有限頻寛下，增加頻寛使用效率是重要的事情。為了消除IBI和ICI，傳統的正交分頻多工調變系統需要使用護衛間隔(GI)，這會使得頻寬使用效率降低。在本論文中，我們採用高頻寬效率的正交分頻多工調變系統。並且提出通道追蹤架構，它可以在時變通道中做通道估計。這個架構的表現是比適應性等化器來得好,但演算法的複雜度是比較高的。為了解決追踨速度不夠快的問題，我們提出了平衡收斂步伐控制方法。這方法將有助於通道追蹤架構獲得更好的均方誤差(MSE)。在電腦模擬中將會證實我們的推導以及提出的方法。

Conventional OFDM system needs a guard interval to cancel IBI and ICI. But, efficiency of bandwidth usage will be reduced. In this thesis, we adopt the bandwidth-efficient OFDM (BE-OFDM) system, which can adjust efficiency of bandwidth usage. A channel tracking structure is proposed for channel estimation in time variant channel. Its performance is better than the adaptive equalizer, but its all structure is more complex. To solve the slow tracking problem, we propose an balanced step-size control adaptive method with improved mean square error. Finally, our derivations and proposed methods will be validated in computer simulations.