隨著數位設備的普及，對於低成本與高速度的短距離無線通訊需求已是越來越強烈，而超寬頻 (Ultra-Wideband) 正是一種用於室內無線多重存取 (Multiple-Access) 通訊系統的熱門技術。受益於超寬頻訊號中豐富的頻率分集，超寬頻系統能以極低的功率頻譜密度進行高速傳輸。現今最被廣泛使用的超寬頻通道模型是由電機及電子工程師協會 (IEEE) 802.15.3a工作小組在2002年12月所發表的。由於高速資料傳輸的性質，超寬頻通道模型的統計特性和傳統的多重路徑通道模型有所不同，因此分析它並不容易。在這篇論文當中，考慮準確的超寬頻通道模型的特性，利用卜瓦松過程 (Poisson process) 的性質，我們提出了一種方法去推導出在實際直接序列展頻( Direct-Sequence) 超寬頻無線通訊系統之訊號干擾雜訊比 (Signal-to-Interference-Plus-Noise Ratio) 的理論分析表示式，其中包括了符號間干擾 (Intersymbol Interference) 和多重用戶間干擾 (Multiple-Access Interference)以及可加性白高斯雜訊 (additive white Gaussian noise)。在模擬的過程中，我們也證明了我們的訊號干擾雜訊比理論分析結果和模擬結果相當吻合。因此我們的分析結果提出了兩種應用，其中一種包括了在直接序列展頻超寬頻無線通訊系統下給定理想的訊號干擾雜訊比，我們該如何去決定耙式接收機 (Rake Receiver) 裡最少的耙指 (Finger) 個數，來達到理想的訊號干擾雜訊比值。另外一種應用是在給定的直接序列展頻超寬頻無線通訊系統下，我們要如何理論上的選擇能達到最大訊號干擾雜訊比的展頻碼 (Spreading Code)。

Ultra-wideband (UWB) is a popular technology to support
short-range high-data-rate transmissions for indoor wireless
multiple-access communication systems. Nowadays, the most widely used UWB channel model is the channel model released by IEEE 802.15 Task Group 3a. Due to its high-data-rate nature, the characteristics of the UWB channel model are different from those of other traditional multipath channel models so that it is not easy to conduct analysis. In this thesis, taking the precise multipath characteristics of the UWB channel model into consideration, we propose a method to derive exact analytical expressions of the output signal-to-interference-plus-noise ratio (SINR) in a realistic direct-sequence (DS) UWB system in presence of intersymbol interference (ISI) and multiple-access interference
(MAI). We also show that our analytical SINR results match the simulation results well. Applications of our results include determination of the least number of combining fingers in a partial Rake receiver with the corresponding desired SINR for DS-UWB systems, choice of spreading codes leading to the maximum output SINR in a given DS-UWB system theoretically, etc.

1 Introduction 1
2 Previous Works 3
2.1 Overview of IEEE 802.15.3a UWB Channel Model 3
2.2 Analysis of Average SINR for Indoor UWB Rake Receiver System
3 Direct-Sequence UWB Systems 7
3.1 System Models 7
3.2 Performance Analysis of Rake Receivers in Presence of Multipath and Multiple Access Interference 9
3.2.1 ISI Analysis 10
3.2.2 MAI Analysis 13
3.2.3 Noise Analysis 15
4 SINR Analysis for IEEE 802.15.3a UWB Channel Model 17
4.1 Useful Characteristics of Poisson Distribution 17
4.2 Evaluation of Exact SINR for DS-UWB Systems 18
4.2.1 Average Path Energy 18
4.2.2 Average Cross Path Energy 23
5 Numerical and Simulation Results 33
6 Conclusion 42

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