使用循環前置碼於單載波系統之效能評估

Abstract

近幾年來，OFDM（正交分頻多工）已經被廣泛地應用於許多無線通訊系統。OFDM系統無須藉由複雜的接收器克服多俓效應的干擾，但是它有高PAPR（峰值對平均功率比）的問題。此篇論文中，我們考慮單載波系統。它擁有很低的PAPR，而且整體的複雜度和OFDM一樣。我們將考量具有頻譜空乏效應之通道、通道估測和FEC（錯誤更正機制）對於這兩個系統的影響。模擬結果可以歸納出幾點重要的結論：單載波系統較能抵抗頻譜空乏效應之通道，且頻譜空乏效應之通道會使OFDM的效能變差。此外，單載波系統之效能比OFDM系統更容易受估測誤差影響。最後在實際位元錯誤率的考量下，我們可發現單載波系統比OFDM系統有較佳的效能。

In recent years, OFDM (Orthogonal frequency division multiplexing) has been applied many wireless systems because of its capability to elegantly cope with multipath interference, without requiring complex receiver implementations. It is also known that the OFDM suffers from the problem of high PAPR (peak to average power ratio). In this thesis, we consider the Single Carrier system for the application of wireless transmission. It has very low PAPR and the overall complexity is the same as the OFDM system. We will perform simulation of these two systems by considering the impact of spectral null channels, channel estimation and FEC (forward error correction). The simulation results allow some relevant conclusions: Single Carrier system is more resistant to the channel spectral nulls, which lead to severe performance flooring in the OFDM system. And Single Carrier system is more sensitive to estimated errors than the OFDM system. For a practical range of bit error rate, the Single Carrier system performs better than the OFDM system.