多輸入多輸出正交分頻多工系統中使用不同通道估計方法的資料傳輸技術之研究

Abstract

在這篇論文中，我們針對不同的導引訊號放置方式之通道估計方法進行討論。一般而言，資料傳輸系統可分為以導引符元為基礎的傳輸系統及以導引載波為基礎的傳輸系統。對於以導引符元為基礎的傳輸系統，[1] 介紹了導引符元的設計，它能夠消除天線間干擾以及減少通道參數估計的複雜度。而在傳輸資料的時段，我們提出利用期望值最大化的演算法去得到更完善的通道估計以及資料偵測。即使在多重路徑衰減的環境下，我們所提出的演算法也能在重複幾次疊代後而達到在已知通道情況下的最佳表現。此外，[2] 針對以導引載波為基礎的傳輸系統提出了 IFFT, LS 和 MMSE 的通道估計算法。在相對等的導引訊號數量之下，我們針對以上兩種資料傳輸系統做了公平的比較。結果顯示以導引符元為基礎的傳輸系統比以導引載波為基礎的傳輸系統擁有較佳的效能。

In this thesis, channel estimation methods based on different pilot arrangements are discussed. In general, MIMO-OFDM data transmission systems can be divided into pilot-symbol based transmission systems and pilot-subcarrier based transmission systems. For polit-symbol based transmission systems, [1] introduced a pilot symbol design method that eliminated inter-antenna interference and reduced the complexity of channel parameter estimation. As for the data transmission phase, we propose an EM-based algorithm for joint channel refinement and data detection. The algorithm can achieve near-optimal performance after a few iterations in a multipath fading environment. Furthermore, IFFT, LS and MMSE estimators are introduced by [2] for pilot-subcarrier based transmission systems. Some comparisons for the two data transmission schemes are presented with similar amount of pilot signal overhead. Our simulation results show that a pilot-symbol based transmission system has better performance than a pilot-subcarrier based transmission system.