在這篇論文中，我們將探討正交分頻多工系統在Nakagami衰減下，使用適應性調變及在接收端使用最大比例結合法時的效能。文中除了介紹系統原理及架構外，還利用數學分析出系統在Nakagami衰減下的平均頻寬使用效率下限值。首先，推導出在Nakagami衰減下使用理想最大比例結合多樣性時，平均通道容量的下限值；然後，在固定位元錯誤率的情況下，再推導出使用正交振幅調變時，正交分頻多工系統在Nakagami衰減下，最高傳輸速率的頻寬使用效率下限值，最後再經由電腦模擬做驗證。

In this thesis, we investigate the performance of adaptive loading orthogonal frequency division multiplexing (OFDM) under Nakagami fading with maximal ratio combining (MRC) diversity at receiver. We not only expound the principles and structures of the system, but also analyze its performance of the lower bound on the average capacity under Nakagami fading. First, we defined the lower bound on the average capacity under Nakagami fading with ideal MRC diversity. Then, we fixed the values of bit error rate. A maximum rate adaptive loading strategy is derived for uncoded quadrature-amplitude-modulation modulated OFDM. Simple lower bound expressions are provided for average spectral efficiency of the maximum rate adaptive loading OFDM under Nakagami fading channel. Finally, the numerical results will be also shown.

中文摘要 I
Abstract II
目錄 III
圖目錄 V
表目錄 VII
第一章 導論 1
1.1 前言 1
1.2 研究動機 1
1.3 論文章節介紹 2
第二章 正交分頻多工系統的基本原理與介紹 4
2.1 正交分頻多工的特性與系統架構 4
2.1.1 傳統的正交分頻多工架構 5
2.1.2 基於離散傅立葉轉換的正交分頻多工系統架構 8
2.1.3正交性 11
2.2保護區間與循環字首(Guard Interval and Cyclic Prefix) 13
2.3正交分頻多工系統的優缺點 16
2.3.1 正交分頻多工系統的優點 16
2.3.2 正交分頻多工系統的缺點 17
2.4 單載波與正交分頻多工系統之比較 18

第三章 適應性調變技術及多樣性簡介 19
3.1 適應性調變技術之架構 19
3.2 適應性調變技術之發展 21
3.3 適應性調變技術之步驟 22
3.4 多樣性技術的簡介 25
3.5 結合技術的簡介 27
3.5.1 選擇多樣性(Selection Diversity, SD) 27
3.5.2 等增益結合(Equal Gain Combining, EGC) 28
3.5.3 最大比例結合(Maximal Ratio Combining, MRC) 29
第四章 應用最大比例結合之頻寬使用效率 33
4.1 系統模型 33
4.2 通道容量 36
4.3 正交分頻多工系統在Nakagami衰減之通道容量 37
4.4 正交振幅調變在固定位元錯誤率之通道容量 40
第五章 模擬結果之比較與分析 44
5.1 正交分頻多工系統在Nakagami衰減之通道容量模擬圖 44
5.2 正交振幅調變在固定位元錯誤率之通道容量模擬圖 49
第六章 結論與未來展望 57
附錄 平均頻寬使用效率下限值之推導 58
參考文獻 61

[1] H. Suzuki, “A statistical model for urban multipath propagation,” IEEE Trans. on Communications, vol. COM-25, pp. 673-680, July 1977.
[2] R. van Nee and R. Prasad, OFDM for Wireless Multimedia Communications, Artech House Publishers, Boston, 2000.
[3] John G. Proakis, Dimitris G. Manolakis, Digital Signal Processing: Principles, algorithms, and applications, 3rd ed.
[4] Hayes, J., “Adaptive Feedback Communications,”IEEE Trans. Comm. , Vol. 16 , pp. 29-34, Feb 1968.
[5] Cavers, J., “Variable-Rate Transmission for Rayleigh Fading Channels,” IEEE Trans. Commu., Vol. 20, pp. 15-22 Feb 1972.
[6] “part 16：Air Interface for fixed broadband wireless access system---Amendment 2： medium access control modifications and additional physical layer specifications for 2-11 GHz,”IEEE Std 802.16a-2003（Amendment to IEEE Std 802.16-2001）, Pages：0_1-292, 2003
[7] Keller, T., Hanzo, L., “Adaptive modulation techniques for duplex OFDM transmission,” IEEE Trans. on Vehicular Technology, Vol. 49, pp. 1893- 1906, Sept. 2000.
[8] Terry, J., Heiskala, J., “OFDM Wireless LANs: A Theoretical and Practical Guide,” SAMS Publishing, 2001.
[9] Jakes, William C., “Microwave mobile communications,” New York/IEEE Communications Society, 1994.
[10] John G. Proakis, Dimitris G. Manolakis, Digital Signal Processing: Principles, algorithms, and applications, 4th ed.
[11] Canpolat, B.; Tanik, Y.,” Performance analysis of adaptive loading OFDM under Rayleigh fading ,” IEEE Trans. on Veh. Tech., vol. 53, pp. 1105–1115, July 2004 .
[12] M. Nakagami, “The m-distribution- A general formula of intensity distribution of rapid fading,” in Statistical Methods in Radio Wave Propagation, pp 3-36, Pergamon Press, Oxford, England, 1960.
[13] T. Aulin, “Characteristics of a digital mobile radio channel,” IEEE Trans. on Veh. Tech., Vol. VT-30, pp. 45-53, May 1981.
[14] A. U. Sheikh, M. Handforth, and M. Abdi, “Indoor mobile radio channels under different adaptive transmission and diversity technique,” To appear in the IEEE Trans. on Veh. Tech..
[15] U. Charash, “Reception through Nakagami fading multipath channels with random delays,” IEEE Trans. On Commun., vol. COM-27, No. 4, April 1979.
[16] S. Haykin, Communication Systems, New York: Wiley, 4th ed.
[17] R.G. Gallager, Information Theory and Reliable Communication, New York: Wiley, 1968.
[18] J. Wolfowitz, Coding Theorems of Information Theory, New York: McGraw-Hill, 2en ed. 1995.
[19] A. J. Goldsmith and P. P. Varaiya, “Capacity of fading channels with channel side information,” IEEE Trans. Inform. Throry, vol. 43, pp. 1982-1992, Nov. 1997.
[20]潘積桂, “多調分碼多重接取系統結合碼域傳送多樣性之通道估測效能分析,” 國立中山大學通訊工程研究所碩士論文,2004.
[21] 林佳漢, “無線正交分頻分工系統中適應性調變技術之研究,” 國立暨南國際大學電機工程學系碩士論文,2004.