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標題: 直接序列展頻分碼多工多使用者通訊系統中之適應性濾波器在多路徑衰減通道之應用
Adaptive Receivers for DS/CDMA Multiuser Communication in Multipath Fading Channels
作者: 楊佳諭
Yang, Jia-Yu
關鍵字: CDMA;分碼多工;ISI;MAI;LMS;RLS;Normalized-LMS;訊符間干擾;多重存取干擾;最小均方差;遞迴式最小均方差;正交化最小均方差
出版社: 電機工程學系
在分碼多工多使用者存取的通訊系統之中,訊符間干擾(Intersymbol interference)及多重存取干擾(Multiple-access interference)均是非常重要的議題。在多重使用者分碼多工的行動通訊系統中,因為時變性多重路徑的通道會造成嚴重的干擾。傳統的濾波器必須作出適當的改良來克服多路徑所造成的衰減,本篇論文提出六種適應性濾波器的架構來解決上述的問題,我們將最小均方差(Least Mean Square)、遞迴式最小均方差(Recursive least square)和正交化最小均方差(Normalized Least Mean Square )三種演算法,分別套用在有限脈衝響應(Finite Impulse Response)和無限脈衝響應(Infinite Impulse Response)的架構上,模擬的結果顯示,最小均方差、遞迴式最小均方差兩種演算法,相較於傳統的接收器而言可以得到較佳的效能,而正交化最小均方差演算法,則可以使我們所提出之濾波器其步階變數(step-size)擁有較好穩定度,此外均方差 (Mean Square Error)以及收斂值的分析,還有關於正交化最小均方差演算法其步階變數穩定之分析也包含在此篇論文中。

In direct-sequence code division multiple access (DS/CDMA) multiuser communication systems with multipath channels, both intersymbol interference (ISI) and multiple-access interference (MAI) must be considered. The multipath effect usually change the characteristics of the spreading codes. Modification of the conventional receiver structure is needed to account for the interference of the multipath fading. This paper proposes six adaptive receivers to solve the above-mentioned problems . We use Least Mean Square (LMS) , Recursive Least Squares (RLS) algorithms and Normalized- Least Mean Square (Normalized-LMS) on both finite impulse response (FIR) and infinite impulse response (IIR) receiver structures. Mean square error , convergence analysis , and analysis for the step-size of Normalized-LMS algorithm are also given in this paper.
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