Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/8320
標題: 陣列天線通訊系統之移動通道模型與最佳化波束形成之研究
Antenna Array Based Mobile Channel Modeling and Beam-forming Optimization
作者: 胡元民
Hu, Yuan Ming
關鍵字: CDMA
分碼多工
Smart antenna
Power control
Equal gain combining
Maximum ratio combining
Mean square maximum ratio combining
Geometrically based circular model
智慧型天線
功率控制
相等增益合成器
最大比率合成器
均值平方最大比率合成器
幾何類通道模型
出版社: 電機工程學系
摘要: 本篇論文的內容主要分成二大部分,第一部份為分析無線移動通道模型的參數,並考慮在基地站使用陣列天線和在不同程度的環境變動條件下,其通道模型參數分佈變化的情形。第二部分為研究最佳化波束形成系統的效能。我們在分碼多工系統的架構下,在接收端使用不同訊號合成的RAKE接收機,觀察並分析其性能表現的優劣。 在本論文中,我們根據現實環境中的通道特性,介紹並提出了全圓通道模型、前半圓通道模型和後半圓通道模型。在此,我們假設有效反射物體皆均勻地分佈於有效反射範圍內。接著,我們考慮在不同的通道模型中,基地站採用全向性天線和指向性天線的條件下,分別從基地站和行動台不同的角度來分析三種主要通道參數(訊號之到達角分佈,延遲時間分佈和都普勒頻移分佈)的變化。其中,我們使用機率密度函數的方法來顯示接收訊號到達角的分佈,並提出橢圓圓周切割法與幾何相位累加法,分別用來計算接收訊號之能量在延遲時間上和都普勒頻移中的分佈變化情形。陣列天線通訊系統所擁有之空間濾波的性質,的確對於系統容量與使用者的表現有著明顯的幫助。因此,我們在有效地保障訊號傳輸品質、提高系統的整體容量和降低系統實現成本的多種考量下,介紹並分析了最佳化波束形成的算法,並比較相等增益合成、最大比率合成和均值平方合成等不同RAKE接收機之訊號合成的性能表現,以能夠有效地提昇系統之容量。 研究結果顯示:在三種通道模型的理論基礎下,使用橢圓圓周切割法與幾何相位累加法將可更快速和正確地反映因環境的變動所造成參數分佈變化的情形。另外,使用最佳化波束形成通訊系統將可大幅地降低多重使用者的干擾並增加整體系統的容量。
This thesis can be divided into two parts. In the first part, we consider an antenna array based mobile cellular system and its scattering channel models. In the second part, we will study the efficiency of beam-forming optimization algorithms and discuss system performance with various RAKE receivers in CDMA cellular mobile communication system. Taking into account channel characteristics of a mobile cellular environment, we introduce entire scattering circular channel model (using geometrically based circular model) and propose forward scattering semi-circular and backward scattering semi-circular channel model. In these channel models, we assume that scatterers are uniformly distributed within a certain range. Then, we analyze the variation of three principal parameter distributions (i.e., AOA, delay spread and Doppler spread) in diverse channel model when a base-station uses both omni-directional antenna and directional antenna. We derive the probability density function for the AOA distribution and use the circumference of ellipse approximation method to compute the delay spread and utilize geometrically accumulation method to calculate the Doppler spread. Because of the space filtering characteristics of antenna array communication systems, the results show that it is indeed helpful to improve the capacity and the performance of systems. Therefore, we propose a beam-forming optimization algorithm to increase the system capacity at a reasonable hardware cost. We also have compared the performance of equal gain combining, maximum ratio combining and mean square maximum ratio combining RAKE receivers. The obtained results show that the circumference of ellipse approximation method and geometrically accumulation method are very effective and accurate to compute parameter distributions of the channel model in varying environments, such as in entire scattering circular, forward scattering semi-circular and backward scattering semi-circular channel models. Also, the beam-forming optimization can greatly reduce multiple user interference and increase the system capacity in a mobile cellular communication system.
URI: http://hdl.handle.net/11455/8320
Appears in Collections:電機工程學系所

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