都卜勒效應所產生之正交分頻通訊系統相鄰載波間干擾(ICI)抑制方法研究

Abstract

在本篇論文中，我們將要討論都卜勒效應對正交分頻多工系統(orthogonal frequency division multiplexing)的影響。在許多行動通訊的應用上，都卜勒效應會造成通道時變性，使正交分頻多工系統產生載波間互相干擾(inter-carrier interference, ICI)。並且，隨著載波頻率，物體速度和符號長度增加，都卜勒效應所產生的載波間互相干擾會更嚴重。所以，我們必須去設法減緩載波間互相的干擾。 這本篇論文中，我們使用自我消除載波互相干擾(ICI self-cancellation)這個方法去解決都卜勒所產生的載波互相干擾，並且討論其特性。我們也提出一種方法來增進自我消除載波互相干擾的效能。最後，我們再對可適性的自我消除載波互相干擾加以探討。

In this thesis, we are going to discuss the Doppler effect in OFDM (orthogonal frequency division multiplexing) systems. In many mobile applications, Doppler effect makes the channel time-varying and causes inter-carrier interference (ICI) in OFDM systems. The ICI induced by Doppler will be severe as the carrier frequency, object velocity or symbol duration increases. Therefore, there is a need for ICI mitigation in OFDM systems. In this thesis, we use ICI self-cancellation scheme to improve the OFDM systems under mobile condition, and discuss its characteristics under mobile condition. We also propose a method to improve ICI self-cancellation and have a good performance. Finally, we are going to discuss an adaptive scheme using ICI self-cancellation.