Channel Equalizers for DS-CDMA Systems in Radio Fading Channel 王俊皓、李金椿
E-mail: 9315041@mail.dyu.edu.tw
ABSTRACT
The performance of DS-CDMA systems equipped with cyclic prefix and equalizers, transversal and decision feedback equalizers, equipped with the proposed RAKE equalizer is investigated based on simulations, and the results is compared with the simple RAKE receivers. Two type pf multipath channel, namely Rayleigh fading and non-fading channel are considered in this thesis.
According to the simulation results. We find that both inter-chip (ICI) and inter-symbol interference (ISI) can not be effectively removed without cyclic prefix. When the cyclic prefix is added, the inter-symbol interference is removed and the performance of equalizers is improved accordingly. In Rayleigh fading channels, the effect of the ISI and ICI is reduced, but the fading effect can not be mitigated without diversity schemes. Consequently the performance of equalization with cyclic prefix is worst than that of the pure RAKE receiver. However, the proposed RAKE equalizer is not only able to remove ISI and ICI, but also provide good diversity. As a result compared to the performance of RAKE receiver, the RAKE equalizer provides a performance gain of 2.3 and 1.7 dB for a performance gain of 16 and 8, respectively.
Keywords : CDMA ; RAKE receiver ; Equalizer ; Cyclic prefix ; RAKE Equalizer Table of Contents
封面內頁 簽名頁 授權書...iii 中文摘要...iv 英文摘要...v 誌
謝...vi 目錄...vii 圖目錄...ix 表目錄...xi 第一章 緒 論...1 第二章 展頻和CDMA基本理論...4 2.1 展頻技術...4 2.1.1假雜訊序列...5 2.1.2 處理增益...6 2.2 CDMA系統...7 第三章 無線衰變通道及通道均衡...9 3.1基本的傳輸現 象...9 3.2大尺度衰減...10 3.2.1大尺度衰減模型...11 3.3小尺度衰減...12 3.4多路 徑通道的數學模型...15 3.4.1雷利分佈...17 3.4.2萊斯分佈...17 3.5通道均衡...18 3.6均衡概念...18 3.7橫向均衡器...19 3.7.1強制為零規則...21 3.7.2最小均方誤差
法...23 3.8適應性均衡器...24 3.9決策-回授均衡器...25 3.10前置循環碼...27 3.11耙 式接收機...29 第四章 通道均衡器效能模擬...33 4.1多重路徑通道參數...33 4.2模擬的架
構...34 4.2.1使用傳統均衡器的模擬架構...34 4.2.2使用耙式均衡器的模擬架構...36 4.3模擬結
果...42 4.3.1使用傳統均衡器的效能...42 4.3.2耙式均衡器的效能...52 4.3.3均衡器中tap數對系統 的效能...55 第五章 結論...59 參考文獻...61
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