近年來，正交分頻多工(Orthogonal Frequency Division Multiplexing；OFDM) 技術已經被廣泛的應用在許多不同類型的數位通訊系統，例如：Wi-Fi、WiMAX和長期演進技術(Long Term Evolution；LTE)。
其中全球互通微波存取(WiMAX)是一結合了定點無線寬頻與行動無線寬頻兩種應用的技術，而
IEEE 802.16e即是針對WiMAX系統應用於移動性環境而設計的標準。無線通訊系統要維持良好的性能表現，一個很重要的步驟就是運用有限的領航訊號(Pilot)進行通道估測。由於使用者的移動速度所造成的通道時變特性，加上802.16e的領航訊號在頻域上不完全規則的排列方式，這些因素都增加了通道估測的困難度。本論文中，我們提出適用於WiMAX系統以離散傅立葉轉換(Discrete Fourier Transform; DFT)為基礎之通道估測(DFT-based Channel Estimation)方法。透過不同的通道模型模擬，本論文所提出的方法，可提供良好的系統效能。

Recent years, Orthogonal Frequency Division Multiplexing (OFDM) has been widely applied to various digital communication systems，such as：Wi-Fi、WiMAX and LTE. WiMAX (Worldwide Interoperability for Microwave Access) is a technique that can provide fixed or mobile broadband wireless access. The IEEE 802.16e is a standard specially developed for the WiMAX system in a mobile environment. Basically, in order to achieve robust performance, a high performance channel estimation procedure with limited number of pilot signals is required. However, the time variant characteristics of a channel, which is highly dependent on the user’s mobility and irregular arrangement of pilot signals, will make it more difficulty on exact channel estimation for IEEE 802.16e system. In this paper, considering of the effects of mobility and AWGN, we will propose a DFT-Based OFDM channel estimation scheme for the WiMAX systems. Simulation results show that the performance of our proposed channel estimation scheme is robust and closed to the real situation.