超高速移動環境下渦輪等化器結合正交分頻多工系統之研究

Abstract

渦輪等化器是一種結合通道等化與通道編碼的等化器，在高速移動環境使用單一載波下渦輪等化器的表現非常良好，因此我們嘗試在高速移動環境下渦輪等化器結合正交分頻多工系統，而在高速移動環境下正交分頻多工系統會受到嚴重的子載波間干擾，所以我們希望渦輪等化器能夠幫助正交分頻多工系統有效降低錯誤率。首先利用低點數快速傅立葉轉換的正交分頻多工系統結合渦輪等化器來確定可行性，之後嘗試使用更高點數快速傅立葉轉換的正交分頻多工系統並觀察系統錯誤率，再利用高速鐵路路徑固定等特性幫助系統估測通道，最後則是改變進入正交分頻多工系統前方的框架格式以位元錯誤率來換取系統有效傳輸率。

Turbo equalization is a new method which combines channel equalization and channel coding .It is different from traditional equalization. The performance of turbo equalizer (TE) with single carrier system in very high mobility environment is excellent. So we try to use TE combined with multicarrier system ,such as Orthogonal Frequency Division Multiplexing (OFDM), in very high mobility environment. OFDM system would suffer gravely from Intercarrier Interference effect (ICI) in very high mobility environment, so we hope that TE could help OFDM system lower its Bit Error Rate (BER). At first, we simulate TE combined with OFDM system with small FFT (Fast Fourier Transform) size in very high mobility environment to make sure about its feasibility. Then we substitute the low FFT size for higher FFT size. Secondly, we use the high speed rail’s characterization of the fixed path to demonstrate two kinds of channel information for channel estimation. In the end, we change the ratio of data symbols and training segments in frame format in order to improve our system useful data rate.