高車速下多輸入多輸出正交分頻多工系統中結合資料偵測及通道估計之遞迴式接收機架構

Abstract

對於應用於高移動通訊環境之正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM)系統，每一個OFDM符元期間的通道時變導致載波間干擾(Inter-carrier Interference, ICI)發生，使得系統效能降低。當載具速度、OFDM符元期間增加，影響將更為嚴重。在這篇論文中，針對高移動性無線通道下之多輸入多輸出(MIMO) OFDM系統，我們提出一個基於結合通道估計與資料偵測之遞迴式接收機架構，此架構主要由三級程序組成。在初始級，我們採用多重路徑干擾消除方法來粗略估計多重路徑延遲及多重路徑複數增益等通道參數；在追蹤級，我們先使用一個β-追蹤器，之後再使用基於V-BLAST資料偵測之決策迴授離散傅立葉轉換通道估測方式，以估計每條路徑的增益平均值；在最後一級中，我們採用一個線性模型來近似每條路徑的時域變化，然後再利用一個二維的V-BLAST方法做資料決策，來達到消除ICI效應的目的。最後，我們以電腦模擬結果驗證了此遞迴式接收機在高移動性通道的效能增進。

For orthogonal frequency division multiplexing (OFDM) systems in high-mobility environment, channel variations within one OFDM symbol will introduce intercarrier interference (ICI), thus lowering the system performance. This becomes more severe as vehicle speed or OFDM symbol duration increase. In this paper, an iterative receiver architecture based on joint channel estimation and data detection is proposed for MIMO OFDM systems in mobile wireless channels. The iterative receiver mainly consists of three-stage processing. In the initialization stage, we employ a multipath interference cancellation technique to roughly estimate multipath delays and multipath complex gains through the preamble. In the tracking stage, a -tracker is applied first, followed by decision-feedback (DF) DFT-based channel estimation which is based on V-BLAST data detection, so as to estimate the average channel variations of each path. In the final stage, we adopt a linear model to approximate time variations of each path, and a two-dimensional V-BLAST method is utilized to perform ICI cancellation and data detection. Finally, computer simulations are conducted to verify the performance of the iterative receiver in high-mobility channels.