本篇論文中，所討論的是，在一個使用UWB (ultrawide bandwidth)訊號做通訊的分散式偵測感測網路(Distributed Detection in UWB-IR Sensor Networks)中，為了使感測器的生命週期增加，且資訊融合中心(Fusion center)的偵測機率(probability of detection)與失敗警告率(false alarm rate)亦達到限定的目標，我們找出一演算法。此演算法可計算出感測器在限定的目標下所需傳送的最小脈波數，值得注意的是，此最佳的脈波數可能是一非整數的數值，故一般傳統的作法為傳送比此值大的最小整數，但這樣的作法會使得感測器多耗損不必要的傳送能量。所以我們又提出隨機脈波數的ultrawide bandwidth (UWB)訊號來傳送感測器的訊息，此方法在長期的統計量下，平均的傳送脈波數與演算法所計算出的最小脈波數幾乎相同，可以說是一個near-optimal design。

In this thesis, we consider a distributed detection problem in wireless sensor networks (WSNs)
using ultrawide bandwidth (UWB) communications. Due to the severe restrictions on power
consumption, energy efficiency becomes a critical design issue in WSNs. UWB technology
has low-power transceivers, low-complexity and low-cost circuitry which are well suited to the
physical layer requirements for WSNs. In a typical parallel fusion network, local decisions are
made by local sensors and transmitted through a wireless channel to a fusion center, where
the final decision is made. In this thesis, we control the number of UWB pulses to achieve
the energy efficient distributed detection. We first theoretically characterize the performance
of distributed detection using UWB communications. Both AWGN and fading channels are
considered. Based on the analysis, we then obtain the minimum number of the pulses per
detection to meet the required performance. To achieve a near-optimal design, we further
propose a multiple access technique based on the random number of UWB pulses. Finally, the
performance evaluation is provided to demonstrate the advantage of our design.

1 Introduction 1
2 System Model and Signal Model 3
2.1 System Model and Problem
Formulation . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Signal model . . . . . . . . . . . . . . . . . . . . . 4
2.2.1 Case I. AWGN channel for synchronization
communication . . . . . . . . . . . . . .. . .5
2.2.2 Case II. AWGN channel for asynchronous
communication .. . . . . . . . . . . . . . . 6
2.3 Case III. Multipath
channel . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3 Performance Analysis 10
3.1 Case I. AWGN channel for synchronization
communication . . . . . . . . . . . . . . . . . . . .10
3.2 Case II. AWGN channel for asynchronous
communication . . . . . . . . . . . . . . . . .. .. 13
3.3 Case III. Multipath
channel . . . . . . . . . . . . . . . . . . . . . . . . . .. 21
4 Performance Evaluation 33
4.1 Case I. AWGN channel for synchronous
communication . . . . . . . . . . . . .. . . . . . . 33
4.2 Case II. AWGN channel for asynchronous
communication . . . . . . . . . . . . . . . . . . 36
4.3 Case III. Multipath
channel . . . . . . . . . . . . . . .. . . . . . . . . . . . 39
5 Conclusion 50

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