多載波通訊系統已被使用於有線通訊系統中，且也被採用於未來的無線區域網路上。一般多載波調變技術的主要特性，是將任意寬頻通道分解成為一組多個窄頻通道。在這些多載波傳輸系統中，最常被使用的傳輸系統，其分別是正交分頻多工調變技術系統，與結合正交分頻多工調變與分碼多工擷取的整合技術系統。此兩項技術系統都是以離散傅利葉轉換為基石，來達成一個可實現、高性能的結構。經由編碼後的正交多工調變技術系統，已在多樣的高速無線資料傳輸系統中，成為時下相當流行的調變技術，其原因是在於此項技術能有效地抵抗多路徑衰減現象。OFDM與OFDM-CDMA系統都有著一個主要的缺點，那就是傳輸訊號擁有相當大的峰值功率對平均功率比值。在本論文中提出一種結合區塊編碼與格雷互補序列的技術，來改善OFDM系統中高峰值功率對平均功率比值。在OFDM-CDMA系統中，則提出一種快速找尋理想Walsh-Hadamard 字組，來保持最小峰值功率對平均功率比值的定則。

Multicarrier communication has been employed for wire-line communications and has been adapted for use in the future wireless local area network. The term multicarrier modulation includes a number of transmission schemes whose main characteristic is the decomposition of any wideband channel into a set of independent narrowband channels. With this family, the most commonly used schemes are Orthogonal Frequency Division Multiplexing (OFDM) and OFDM-CDMA (Code Division Multiple access), which are based on the Discrete Fourier Transform, resulting in an implementable, high performance structure. Due to its robustness against multipath fading with certain implementation advantage over single-carrier system, coded OFDM has become a popular technique in various high-speed wireless data transmission system. One of the main implementation disadvantages of OFDM and OFDM-CDMA is the high peak-to-average power ratio (PAPR) of the transmitted signals. In this paper, we proposed a technique that combines block code modulation (BCM) with Golay complementary sequence to reduce the peak to average power ratio (PAPR) in OFDM system. And we proposed a reduced algorithm to find optimum Walsh-Hadamard code sets which can maintain almost the minimum peak to average power ratio in OFDM-CDMA system.

致謝 i
中文摘要 ii
英文摘要 iii
目錄 iv
圖目錄 vii
表目錄 x
前言 xi
第一章 OFDM系統與OFDM-CDMA系統介紹 1
1.1 OFDM系統介紹 1
1.2 OFDM系統的起源 3
1.3 CDMA系統介紹 4
1.3.1 單一式CDMA 5
1.3.2 混合式CDMA 6
1.4 OFDM-CDMA系統介紹 6
第二章 OFDM系統和OFDM-CDMA下行傳輸系統架構 9
2.1 正交轉換 9
2.1.1 快速傅利葉轉換 11
2.2 OFDM訊號數學表示式 15
2.3 保護時間和循環擴張 18
2.3.1 保護區間 19
2.3.2 循環擴張 19
2.4 OFDM-CDMA下行傳輸系統 21
2.4.1 展頻碼 22
2.4.2 交錯器 25
第三章 峰值功率對平均功率比值 28
3.1 區塊碼 30
3.2 格雷互補對與格雷互補序列 32
3.3 布林函數 34
3.4 布林多項式 36
3.5 里得-米勒碼 37
3.6 里得-米勒碼建構格雷互補對集合 39
第四章 QPSK序列與16QAM序列 42
4.1 BPSK、QPSK、QAM調變方式介紹 42
4.2 QPSK群集興16QAM群集 45
4.3 QPSK序列與BPSK序列 46
第五章 區塊編碼調變 48
5.1 分配劃分 49
5.2 結合調變區塊碼 51
5.3 最小平方歐幾里得距離 53
第六章 OFDM-BCM與OFDM-CDMA改善高PAPR方法 54
6.1 運用區塊編碼調變方式來降低OFDM系統
高PAPR的特性 54
6.2 運用選取展頻碼來降低OFDM-CDMA系統高
PAPR特性 72
第七章 結論與總結 80
參考文獻 81

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