臺灣博碩士論文加值系統

摘要
在本論文中，探討以一自主式等化器(blind equalizer)設計，應用於無線多用戶分碼多重接取(CDMA)線性通道(linear channel)系統上。利用適應性(Adaptive)演算法，並探討高階統計(Higher order statistics)接收端訊號之值，來分析與模擬等化器之特性。
分碼多重接取(CDMA)系統是第三代地面行動(land mobile)及衛星通訊(satellite communication)之主要系統之一，也是當前無線通訊中重要的研究課題之一。
一般CDMA 系統中，在設計及分析上，有二個主要的干擾因素；即 (1)經由多重路徑(multi-path)所造成的碼際間干擾(Intersymbol Interference, ISI)； (2)經由近遠效應(near-far effect)造成的多重接取干擾(Multiple Access Interference, MAI)。上述之干擾因素會使地面行動通訊及衛星通訊造成嚴重傳輸錯誤。
傳統克服 ISI之方法必須使用參考信號(reference signal)方可將訊號順利攫取(extraction)，但此種方法應用於多用戶(multiuser)通訊系統的限制頗大。因此我們發展一自主式等化器，只需利用接收端的訊號便可將ISI及MAI之干擾克服，並將傳輸訊號估測出來。
本論文乃直接由接收端訊號去分析，利用高階統計(Higher order statistics)訊號理論為準則(criterion)之演算法，來估測出原始訊號，並將此方法應用於多用戶多通道(multi-users multi-channels)之線性CDMA系統上。在此，比較兩個線性等化器模型，分析演算法收斂特性、穩定性，並改善其複雜度與運算量；在模擬結果中，証實了此篇文章提出的方法之正確性與其可行性。

ABSTRACT
In this thesis, the design of blind equalizer for linear multi-user communication system is discussed and applied to a DS-SS CDMA (Direct sequence-Spread spectrum Code Division Multiple Access) system. We design the blind equalizer, using adaptive algorithm and the value of Higher Order Statistics(HOS) of the receiver signals.
CDMA has become one of the systems of land mobile and satellite communications in the third generation. Then, the design of wireless CDMA is also one of the most important research topic of wireless communications.
In the design and analysis of the low-rate CDMA systems, the presence of intersymbol interference(ISI) is neglected. However, for the high-rate CDMA systems, there are two important interferences; i.e.：(1) Intersymbol interference(ISI) due to the multi-path nature of wireless channel. (2) Multiple access interference(MAI) due to near-far effect. These interferences are major impediment to the system performance in land mobile and satellite communication.
In general, we need an adaptive equalizer which uses a reference signal to overcome ISI(Intersymbol Interference) and MAI(Multiple Access Interference), but this kind of method has many constraints for the multi-user communication systems. In this thesis, the method of blind equalizer without reference signals is exploited to solve this problem.
We analyze the receiver signals directly, and estimate the original signal by algorithms which are based on the criterion of Higher Order Statistics signal theory. In order to improve the complexity and operating time, we analyze the stability and the property of convergent rate between two different models of linear equalizer by application for the linear multi-user and multi-channels CDMA systems. The outcome of simulation supports the correction and feasibility of the new idea.

目錄
中文摘要…………………………………………………………………I
英文摘要………………………………………………………………IV
目錄…………………………………………………………………VII
表目錄…………………………………………………………………IX
圖目錄………………………………………………………………X
前言………………………………………………………………………1
第一章 導論……………………………………………………………3
1.1 研究動機……………………………………………………3
1.2 論文結構……………………………………………………4
第二章 直接序列展頻DSS-SS系統…………………………………6
第三章 等化器模型…………………………………………………11
3.1 線性等化器模型 - 架構一……………………………11
3.2 線性等化器模型 - 架構二………………………17
第四章 高階統計訊號理論…………………………………………27
4.1 Cumulant之定義………………………………………27
4.2 Cumulant之特性………………………………………29
4.3 線性系統………………………………………………30
4.4 Kurtosis之特性…………………………………………32
第五章 等化器之設計………………………………………………37
5.1 自主式等化器………………………………………………38
5.2 適應性演算法應用於自主式等化器……………………39
5.2.1 適應性演算法應用於自主式等化器模型 — 架構一…39
5.2.2 適應性演算法應用於自主式等化器模型 — 架構二…41
第六章 電腦模擬………………………………………………43
6.1 M sequence編碼方式………………………………………43
6.2 Walsh code編碼方式………………………………………46
6.3 線性等化器模型 — 架構一………………………………48
6.4 線性等化器模型 — 架構二………………………………49
6.5 收斂特性之比較…………………………………………49
結論與展望…………………………………………………………61
參考文獻………………………………………………………………62

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