在本篇論文中,吾人考慮在第三代行動通訊寬頻分碼多重進接(WCDMA)的系統架構上,首先討論WCDMA技術相關規範、天線陣列的基本原理及天線參數相互之間的關係,以為空域信號處理的基礎。其次討論在多路徑時空通道下之WCDMA信號模型,並結合空域之波束成型器及時域之RAKE combiner架構,以做為一WCDMA Space-time RAKE(S-T RAKE)接收機的基礎,然後以電腦模擬此一空-時耙式接收機之天線場型及收斂特性。由實驗得知,當天線陣列自由度不足時,將致接收機性能衰退,為求進一步改善多重接取干擾(MAI),我們再以S-T RAKE receiver與平行干擾消除(Parallel Interference Cancellation,PIC)技術為基礎發展出一種多用戶時空干擾消除系統(Multiuser Space-Time Interference Cancellation System),首先我們檢測所有用戶的多路徑信號,然後利用反波束成型處理器(Inverse Beamforming)在每根天線上來重新產生每一用戶信號的展頻信號複本,最後在波束成型處器之前進行干擾消除。電腦模擬結果顯示,此種時空干擾消除系統能更進一步改善S-T RAKE receiver之性能。
In this thesis, the problem of smart antenna design is considered in the context of 3G WCDMA (Wideband Code Division Multiple Access) System. First, we consider the related specifications of WCDMA system, basic principle of antenna array, and design of antenna excitation parameters for synthesizing a desired beam pattern. Such a beamformer structure can serve as the first-stage signal processing in spatial domain to suppress the multiple access interference (MAI). Second, under the multipath fading channel environment, a subsequent Rake combiner is employed that serves as the second-stage signal processing in temporal domain to combat signal fading. In this way, an overall smart antenna structure, termed the WCDMA space-time (S-T) Rake receiver, is obtained. It antenna pattern and convergence properties are investigated via computer simulation. It is found that if the antenna array has not enough degree of freedom, it will result in performance degradation. To further enhance the performance and capacity under MAI-dominant environment, we extend the former S-T RAKE sturcture into a parallel- interference-cancellation (PIC) based multiuser detector (MUD). At each stage of the PIC-MUD, we detect the symbol sequences of all users, and then use inverse beamformers to regenerate each users’ wibeband signal on every antenna elements for the next-stage IC operation. Through computer simulation, it is shown that after about three PIC stages, the PIC-MUD can significantly improve the performance of original S-T RAKE receiver which is simply the first stage of the PIC-MUD.