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研究生:劉大勇
研究生(外文):Ta-Yung Liu
論文名稱:寬展頻通訊系統的空域及時域信號處理
論文名稱(外文):Spatial- and Time-Domain Signal Processing for W-CDMA Communication System
指導教授:李學智李學智引用關係
指導教授(外文):Hsueh-Jyh Li
學位類別:博士
校院名稱:國立臺灣大學
系所名稱:電機工程學研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2001
畢業學年度:89
語文別:英文
論文頁數:122
中文關鍵詞:寬展頻通訊系統多重接收干擾信號領導位元二維梳型波束來向方法直接矩陣逆轉方法單一波束複合波束
外文關鍵詞:W-CDMA Communication SystemMultiple-Access InterferencePilot bits2D-RAKEDirection of Arrival MethodDirect Matrix Inversion MethodSingle-beamMultiple-beam
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在本篇論文中,我們首先簡單描述時變射頻通道衰落的特性和寬展頻通訊系統的實體層規格,然後,針對基地台使用陣列天線的第三代寬展頻通訊系統,我們提出通道參數估測方法及無線電波束形成方法。
以便在多重接收干擾信號(MAI)中,能夠準確估測欲接收信號者的通道參數,這些參數含有訊號到達時間,訊號波的來向和訊號的強度,我們首先提出增加接收信號與干擾雜訊比的方法,這個方法是藉由連續同條相加不同領導位元(pilot bits)的匹配濾波器輸出和非同條相加所有天線陣列位元的匹配濾波器輸出結果,經由這兩種訊號處理過程,欲接收者的信號強度可以大幅的提升。然後,將得到的通道估測數據應用到資料接收通道,運用二維梳型(2D-RAKE)信號組合技巧,我們可以發現欲接收資料的信號干擾雜訊比值極接近理論計算值。
我們也比較不同無線電波束集成方法的信號上傳及下傳資料的信號干擾雜訊比值。在資料上傳部分,我們發現波束來向(DOA)方法和共軛複數(complex conjugate)方法有非常相近的信號干擾雜訊比值,然而共軛複數方法只需要較少的運算處理時間;直接矩陣逆轉(DMI)方法與波束來向方法比較,我們發現當只有少數人同時在上傳資料時,直接矩陣逆轉方法有較佳的信號干擾雜訊比值,但是這種優勢隨著人數的增加而降低,最後會接近波束來向方法的結果。直接矩陣逆轉方法的缺點是需要較長的運算處理時間。
在資料上傳部分,針對直接矩陣逆轉方法,我們得到一個信號干擾雜訊比值的解析解表示式,由電腦模擬的數據結果發現與解析解值非常相近。除此之外,我們也比較單一波束(single-beam)集成方法與複合波束(multiple-beam)集成方法,在資料上傳及下傳時遭遇到不同的通道衰落時,其接收到的信號干擾雜訊比值結果,當信號干擾雜訊比值在很低的範圍時,我們發現複合波束會有較佳的信號干擾雜訊比值結果,這是因為單一波束受到信號極度衰落的結果,反之,當信號干擾雜訊比值較大時,單一波束會有較佳的接收信號干擾雜訊比值結果,這是因為單一波束集成方法在波的傳遞方向有較大的天線增益,較小的波束涵蓋範疇,以及可以維持調變碼的正交特性。
最後,我們使用最新採購的向量通道探測儀模擬寬展頻通訊系統,以實際量測到的通道參數數據,評估及比較不同波束集成方法的上傳及下傳資料傳輸品質,在資料下傳時,信號干擾雜訊比值結果與行動器(mobile)所在的位置有很高的聯動性,同時,實驗的模擬結果也顯示波束來向方法所得到的信號干擾雜訊比值結果會比直接矩陣逆轉方法好,其理由及結果均會在內文中一一詳細說明。

In this thesis we briefly review the time-varying radio fading channel characteristics and the specification of the physical layer of the W-CDMA communication system. We propose channel parameters estimation algorithms and beamforming algorithms for the 3G W-CDMA basestation transceiver employing antenna array.
To accurately estimate the channel parameters, including the Time of arrival (TOA), Direction of arrival (DOA), and complex amplitude of the desired user's signal in the presence of multiple-access interference (MAI), we propose a method to increase the SINR of the resultant delay profile, which is obtained by coherently integrating the matched filter output over different pilot bits and incoherently integrating all matched filter outputs of antenna array elements. With these two stages of integration, the desired signals are greatly enhanced. We exploit the estimated channel parameters to the data-branch for 2D-RAKE combining and find that the SINR performance after RAKE receiver can approach the theoretical values.
We compare the uplink and downlink SINR performance obtained by different beamforming methods. In the uplink, we found that the DOA method and the complex conjugate method almost have the same SINR performance. However, the complex conjugate method doesn't need any computational loading. The DMI (Direct Matrix inversion) method can have much better performance than the DOA method when few users are present in the channel. When the number of users is much greater than the number of antenna element, however, we found that these two methods almost have the same performance. Nevertheless, the DMI method requires much higher computation loading. We have derived an analytical form of the SINR after 2D-RAKE receiver for the DMI method and the simulation results are very close to the analytic value.
In the downlink, we compare the single-beam and multiple-beam beamforming techniques considering the independent fading of the uplink and downlink. We found that the multiple-beam method has a better SINR performance in the low SINR region because the single-beam method is more likely to suffer from deep fading. While in the moderate or high SINR region, the single-beam method has a much better SINR performance because it has a higher antenna gain in the main path direction, a smaller angular coverage of the mainlobe and the orthogonality between different code sequences.
We employ the channel data measured by a newly purchased vector channel sounder to simulate the W-CDMA system and compare the uplink and downlink SINR performance using different beamforming techniques. In the uplink we found that the SINR performance obtained by measurement data has the same trend as that obtained by the simulation data. However, the SINR performance is very location dependent in the downlink. The SINR performance obtained by the DMI method is worse than the obtained by the DOA method. Explanations of the reasons are given in the content.

Cover
Abstract
Contents
List of Tables
List of Figures
Chapter 1 Introduction 1
1.1 Concepts of Spatial and Time Diversity
1.2 Motivation
1.3 Thesis Overview
1.4 Thesis Contributions
Chapter 2 Channel Characteristics and Modeling for Wireless Communications
2.1 Fundaments of Radio Propagation
2.2 Fast fading
2.3 Vector Mobile Radio Channel
2.4 Summary
Chapter 3 Overview of the Wideband CDMA Wireless Communication System
3.1 Uplink Physical Channel
3.2 Downlink Physical Channel
3.3 Summary
Chapter 4 Channel Estimation Algorithm of 2D-RAKE Receiver for the W-CDMA System
4.1 Spatial-Time Signal Model
4.2 New Algorithm for Channel Estimation
4.3 Simulation Results
4.4 Summary
Chapter 5 Performance of 2D-RAKE Receiver for W-CDMA System
5.1 Reception of 2D-RAKE Receiver
5.2 Simulation Results
5.3 Summary
Chapter 6 Comparison of Beamforming Techniques for W-CDMA Communication System
6.1 Description of the Complex-Conjugate Method and the DOA Method
6.2 Downlink Beamforming and Signal Processing
6.3 Simulation Results
6.4 Summary
Chapter 7 Comparison of Different Adaptive Array Techniques for W-CDMA Communication System
7.1 Adaptive Algorithm and Weight Equation
7.2 Simulation Results
7.3 Summary
Chapter 8 Beamforming Performance Comparison Using Channel Measurement Data
8.1 Principle and Functions of the Vector Channel Sounder System
8.2 measurement Setup and measurement Results
Chapter 9 Discussion and Conclusion
9.1 Suggestion for Further Studies
Bibliography

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