由於正交分頻多工系統（ Orthogonal Frequency Division Multiple, OFDM ）已成為現今寬頻通訊系統之重要技術，因此改進OFDM之性能已成為重要的課題。在本篇論文中我們將針對當OFDM訊號在通過解決ICI問題、增加分集效應以及降低峰均值之預編碼後的頻譜效應來討論，並比較各個演算法外頻譜（out of band）及內頻譜平坦度(in-band flatness)的差異。 Orthogonal Frequency Division Multiple has become one of the key technologies in broadband communication systems nowadays. Improving the system performance of OFDM is therefore essential. The precoded-OFDM schemes for solving ICI problem, increasing diversity, and reducing PAPR are discussed in this thesis, inclusive of comparing the differences between out-of-band spectrum and in-band flatness.
