In this thesis, a low-complexity OFDM channel estimation scheme is proposed based on a practical assumption that the propagation delays of multi-path components of the real channel are not necessarily integer multiples of the sampling period. By exploiting the algebraic structure of the autocorrelation matrix of pilot frequency responses, it is observed that certain sub-matrices already contain sufficient information for unique identification of the channel parameters; hence, the computations involved in the proposed method are only the inversion and eigen-decompositions of selective sub-matrices with reduced dimensions.
In comparison with existing solutions using the original autocorrelation matrix and developed under the same assumption, the proposed method is more suitable for a low-complexity algorithmic implementation.
Particularly and perhaps surprisingly, simulations show that less computations also improve the estimation mean square error due to less
accumulation of numerical errors.

在最近幾年來，正交分頻多工系統是一種非常受到注目的技術，因為將它應用在無線通訊系統上，此調變技本身具有一些特性，例如它可以提高傳輸的位元速率、使接收端的設計簡單化並透過這樣的技術可以對抗多重路徑衰退通道（multipathfadingchannel）處於frequencyselective的情形下大大降低對信號產生的影響。在這篇論文中，我們採用正交分頻多工系統去實現通道估測，一般而言，通道估測，主要可以被區分為二大部分，它們分別為通道參數（ChannelParametres）的估測及通道係數（ChannelCoeÿcients）的估測。在傳統研究通道估測問題時，通道的模型大致可分為非參數型（Non-Parameteric）及參數型（Parameteric）二種類別。很多的研究指出，在使用非參數型（Non-Parameteric）的通道模型時，由於沒有好好利用通道多路徑的特性，造成效能的表現不如參數型（Parameteric）的通道模型。當我們使用協調的正交多頻分工做通道估測並且假設通道模型為參數型（ParametericChannelModeling）時，一般大部份的估測方法都是基於假設其通道路徑的延遲（ChennelDelay）為接收端取樣週期的整數倍之情況下去做分析。然而，在實際傳輸通道，其通道路徑的延遲，往往非接收端取樣週期的整數倍，導致估測效能不如預期。針對這樣的情況，Yang首先提出了使用ESTRIT演算法來解決此問題。但由於ESTRIT演算法的複雜度太高，使得實現上非常的困難。故而本論文，提出另一演算法，主要目的是致力於降低估測複雜度並且改善其估測效能。

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