臺灣博碩士論文加值系統

在直接序列分碼多工擷取(DS-CDMA)中，大部份都是以Walsh碼來當作為展頻碼來使用。由於Walsh碼是從n×n的Hadmard矩陣得來的，而n是2的次方。因此，我們提出了正交延伸碼(OEWC)來做為在展頻碼。OEWC是個m×n的矩陣，而且OEWC有三種形式。第一個是m=n的矩陣，稱為Squared-type正交延伸碼(SOEWC)；第二個是m<n的矩陣，稱為Row-expanded正交延伸碼(ROEWC)；最後，第三個是m>n的矩陣，稱為Column-expanded部份類似正交延伸碼(CPEWC)。SOEWC和ROEWC是屬於正交的矩陣，而CPEWC是部份類似正交的矩陣。而這些OEWC可以用3、5、6、7的次方來延伸，並不限定為2的次方才能延伸。
在這篇論文中呈現出新的OEWC可以適用於DS-CDMA的展頻上。雖然OEWC的processing gain會增加，但是OEWC水平延伸的結果，使得容量增加，抗干擾的能力與傳輸的安全性也增加。而在調變方面中，OEWC可以透過二種方法來調變,第一種方法是二相相位鍵移(BPSK)，另一種是多相相位鍵移(MPSK)。使用BPSK的方法是將OEWC轉換成二進位的形式來傳送。而在MPSK的方法是將OEWC的每一碼片用MPSK其中的一個訊號單元來表示。因為OEWC有較高的安全性與抗干擾能力，使得OEWC能運用在下一代的CDMA。

In Direct-Sequence Code-Division Multiple-Access (DS-CDMA), the majority is use Walsh code to generate spread code. Due to Walsh code is n × n Hadamard matrix, where n is power of two. Therefore, we proposed Orthogonal Expanded Walsh Codes (OEWC), the OEWC is m by n of matrix, and have three kinds of situations. The first situation is m=n, that Squared-type Orthogonal Expanded Walsh Code (SOEWC); the second situation is m<n, that Row-expanded Orthogonal Expanded Walsh Code (ROEWC); the third situation is m>n, that Column-expanded Partial-quasi-orthogonal Expanded Walsh Code (CPEWC). The first and second situations are orthogonal matrix. The third situation is partial-quasi-orthogonal matrix. They can extend by power of 3, 5, 6, 7...etc.
A novel OEWC suited in DS-CDMA spreading is presented in this thesis. Although some processing gain increased, the OEWC can increase channel anti-interference and transmission security since of its elongated horizontal length. Moreover, Modulation has two ways. One is that the OEWC is transformed into binary form by BPSK to modulate. Another is that it can be applied with MPSK to modulate one of M signal units expressed with a chip of OEWC. This plus the higher security and anti-interference abilities make OEWC of interest to designers of next-generation CDMA systems.

誌謝...............................................................................................I
摘要..............................................................................................II
ABSTRACT.......................................................................................III
CONTENTS.........................................................................................V
List of Figures.........................................................................................VI
List of Tables.........................................................................................................................................VII
Chapter 1 Introduction.....................................................................................1
1.1 Background.......................................................................................1
1.2 Outline of the Thesis...........................................................................................8
Chapter 2 Related Technology for Wireless Communication System...........................................................................................9
2.1 Basic Principle of CDMA............................................................................................11
2.2 Property of Walsh Code............................................................................................13
Chapter 3 Orthogonal Expanded Walsh Code............................................................................................15
3.1 Gram-Schmidt Orthogonalization...............................................................................15
3.2 General Form of Orthogonal Expanded Walsh Code.............................................................................................................................................16
3.3 Squared-type Orthogonal Expanded Walsh Code.............................................................................................................................................17
3.4 Row-extended Orthogonal Expanded Walsh Code.............................................................................................................................................18
3.5 Column-extended Partial-quasi-orthogonal Expanded Walsh Code.............................................................................................................................................19
Chapter 4 Orthogonal Expanded Walsh Code’s Modulation.......................................................................................................................................23
4.1 BPSK Modulation Scheme...........................................................................................................................................23
4.2 MPSK Modulation Scheme...........................................................................................................................................26
Chapter 5 OEWC Performance Analyze on BPSK and MPSK.............................................................................................................................................29
Chapter 6 Conclusion.......................................................................................................................................39
References.......................................................................................................................................40

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