近年來正交分頻多工系統受到相當大的重視，在未來將是無線廣域網路的主要技術。但是變化過大的時域訊號會增加傳送功率的消耗，因此，我們必須利用限制傳送訊號的振幅來降低峰值平均功率比。但是限制傳送端的訊號振幅後，卻造成系統增加了剪裁雜訊 (Clipping Noise)。本論文探討在傳送端只對資料部份作訊號峰值的剪裁，保留了導引訊號以維持通道估計與同步處理的準確性，在接收端使用已發表過的Decision-aided reconstruction (DAR)及Clipping Noise Estimation and Cancellation (CNEC) 方法來消除剪裁雜訊對於系統的影響。模擬結果顯示，新的訊號剪裁方法搭配雜訊消除法可以更為提升系統性能。 In the past decade, the orthogonal frequency division multiplexing technique has received a lot of attention, which will be the main technology used in the wireless metropolitan area network (MAN) application. But a high signal amplitude variation can increase the design requirement of the power amplifier at the transmitter. To solve this problem, we can clip the transmitted signal to reduce the peak to average power ratio (PAPR). However, this will also induce the clipping noise. In this paper, we study the method that only data signals are clipped and pilot signals are reserved at the transmitter in order to remain better channel estimation and synchronization performances. At the receiver, we apply the published methods, Decision-aided reconstruction (DAR) and Clipping Noise Estimation and Cancellation (CNEC), to reduce the effect of the clipping noise. Simulation results show that the new clipping method along with clipping noise cancellation algorithms can significantly improve the system performance.
