正交轉換用於OFDM傳輸系統之研究

Abstract

正交分頻多工(OFDM)系統的研究和發展已有30年以上的歷史，其利用DFT 完成多重載波調變(MCM)亦已被提出。在此論文中，我們討論以多種正交 轉換為基底的OFDM傳輸系統。對OFDM系統以DFT、DHT、WPT以及CMFB為基 底的架構在某些數位通訊通道中做一比較。由這些比較中，以DFT為基底 的OFDM系統具有等化器容易實現及對頻率漂移有較好的免疫力的特性。在 這些正交轉換中，DFT是實現OFDM系統的最佳選擇。 The research and development of orthogonal frequency division multiplexing (OFDM) system has already been more than 30 years. Also, using discrete Fourier transform (DFT) to implement multicarrier modulation (MCM) has been proposed.In this thesis, OFDM systems based on several orthogonal transforms are studied. DFT-, discrete Hartley transform (DHT)-, wavelet packet transform (WPT)-, and cosine-modulated filter bank (CMFB)-based OFDM systems are compared in some digital communication channels. From these comparisons, DFT-based OFDM system has the advantages in easy implementation of equalizers and better immunity of frequency offset effect. It is the best choice among these orthogonal transforms for implementation of an OFDM system.