使用錯誤更正碼以降低OFDM 的峰均比率及錯誤率的研究(2/3)

正交分頻多工調變已被廣泛的使用在諸多通 信系統中。但此調變有一個主要的缺點是調變後的 信號，先天具有高峰均比的特性。遞歸式剪除及過 濾是已知簡單而有效的峰均比降低方法，但隨著遞 歸次數的增加，固然峰均比與外溢頻譜都能夠有效 的降低，卻會引起嚴重的剪除失真以及錯誤地限的 現象。我們提出一種新式的峰均比降低方法，以適 當設計的失真限制，結合遞歸式剪除及過濾，在有 效地降低峰均比與外溢頻譜的同時，也能控制剪除 失真以達到較低的錯誤率。我們提出的方式不需額 外的附帶資訊，也就不用犧牲資料傳輸速率，接收 機毋須作任何變動，這對於數位廣播的應用特別有 利。OFDM has been popularly applied to many modern communication systems. However, one of the major disadvantages is the inherent high peak-to-average power ratio (PAPR). We propose a new PAPR reduction scheme for OFDM systems. The idea is to reduce PAPR and control clipping distortion simultaneously. The procedure includes setting a proper distortion bound and recursive operations of clipping, filtering and distortion control. The proposed scheme can achieve significant PAPR reduction while maintaining low error rate. For this scheme, PAPR reduction is obtained without any redundancy and no side information is needed. Hence, OFDM systems using this scheme do not pay the price of the reduction of transmission rate. The OFDM receiver can work as usual without any change. This is of extra benefits to DAB/DVB applications