為了要滿足所有無線通訊服務在聲音、資料及視訊上對頻寬的強大需求，正交分頻多工(OFDM)技術被廣為使用。OFDM系統將大量的資料分散成許多個較小的容量，並由許多個子載波同時間的傳送，這些子載波在頻率上一樣交疊著，只是藉由FFT運算有效地分散彼此，使彼此間不會和傳統FDM系統一樣會有干擾問題。 為了更進一步地改善通訊系統的效能，遂衍生出了可調適性正交分頻多工(AOFDM)技術，而為了有效地調適通道負載，通道狀態(CSI)必須被傳回至傳送端；且為了解決高速移動所帶來的通道問題，我們使用長時間通道預估法於AOFDM系統中，而本論文針對AOFDM系統來探討幾項長時間通道預估法，藉著模擬結果來了解其預估法的特性，並探討如何使系統的性能更有效地被利用。 To accomplish the increasing demand for all types of wireless services such as voice, data, and multimedia, orthogonal frequency division multiplexing (OFDM) technology is promoted. OFDM splits a high-rate data stream into a number of lower rate streams that are transmitted simultaneously over a number of sub-carrier. These sub-carriers typically overlap in frequency, but are designed not to interfere with each other as would be the case with traditional FDM, and may be efficiently separated by using a fast Fourier transform (FFT) algorithm. Adaptive orthogonal frequency division multiplexing (AOFDM) technology improves the ability of OFDM. To accomplish efficient adaptive channel loading, the channel state information (CSI) needs to be fed back to the transmitter. Since the fading channel varies rapidly for fast vehicle speeds, long range fading prediction is required for mobile AOFDM to insure reliable adaptation. In this thesis, we investigate several long range predictions in AOFDM system. We’d also know the characteristics of prediction algorithms by simulation results.
