可適性正交多工調變系統於衰減通道之設計與分析

Abstract

傳統的可適性調變是根據不同的通道狀況，選擇適當的調變做傳輸，當通道雜訊比越高，表示通道情況越好，此時會使用資料傳輸率較高的方式作傳輸，以期能夠達到比傳統的單一調變方式還要高的平均頻譜效益；正交多工調變家族(Orthogonally Multiplexed Modulation, OMM) 的提出，除了囊括各式傳統的調變之外，更定義了許多新式的調變選擇，此家族包含了四個主要類別：正交多工正交振幅調變(Orthogonally Multiplexed Orthogonal Amplitude Modulation, OMOAM)、正交多工正交相位調變 (Orthogonally Multiplexed Orthogonal Phase Modulation, OMOPM) 、正交多工開關鍵振幅調變 (Orthogonally Multiplexed On-Off Keyed Amplitude Modulation, OMO2AM) 與正交多工開關鍵相位調變 (Orthogonally Multiplexed On-Off Keyed Phase Modulation, OMO2PM)。 因此在本篇論文裡，結合正交多工調變家族的多樣調變之選擇性，並且藉由子頻帶配置方式的改變，除了平坦衰減通道 (flat fading channel) 之外，進一步的延伸至不同的衰減通道，而針對此種情況，我們提出了功率平衡 (power balancing) 的觀念，將全部的載波面臨的衰減通道變成平坦的狀態，故仍可以採用原有的可適性調變選取準則。另外，我們分析了加入功率平衡後對頻譜的影響，也比較了不同子頻帶配置時，平均頻譜效益的結果。

The conventional adaptive modulation is the method selecting appropriate modulation according to situation of channel. When the signal to noise ratio (SNR) of channel is high, one can make use of the modulation with high data rate for transmission in order to achieve better average spectral efficiency than single modulation. The OMM (Orthogonally Multiplexed Modulation) families including OMOAM (Orthogonally Multiplexed Orthogonal Amplitude Modulation), OMOPM Orthogonally Multiplexed Orthogonal Phase Modulation), OMO2AM (Orthogonally Multiplexed On-Off Keyed Amplitude Modulation), and OMO2PM (Orthogonally Multiplexed On-Off Keyed Phase Modulation) not only contain many traditional multidimensional modulations but also provide several new modulations. In the thesis, we combine diversity of the OMM families with adaptive modulation and extend to different fading channels except for flat fading channel by changing the allocation of subband. Therefore, in order to make the fading channel as flat, we introduce the concept of power balancing, and the former criterion of adaptive OMM systems can still be continue using. Besides, we analyze the effect of adding power balancing and compare the average spectral efficiency with different allocation of subband.