裝置對裝置通訊 (Device-to-Device Communication) 提供了裝置不需要基地台 (Access Point) 的幫助而達到直接溝通的能力。隨著行動裝置的數量快速增加，裝置對裝置網路能夠進一步地增加頻譜效益以及有效地提供流量卸載 (Traffic Offloading)。裝置能夠利用Wi-Fi直連 (Wi-Fi Direct) 來達成裝置對裝置通訊。為了應付裝置的流動性以及應付突如其來的自然災害，網路拓樸應該要能自動並且動態地被建立。在本篇論文中，我們提出一個方法來自動地創建多個Wi-Fi直連群組並且利用這些群組來形成一個裝置對裝置網路。除此之外，群組之間的溝通能運作在沒有經過作業系統修改的Android行動裝置。整體方法由兩個部分組成，叢集初始化以及多叢集的連線。實驗結果顯示我們提出的方法能在一個開源的Android溝通應用平台來得到驗證，並且改善了網路組成時的延遲。

Device-to-Device (D2D) communication lets devices can directly communicate with each other without going through any access point. With the rapidly increasing number of mobile devices, the D2D network can further increase spectral efficiency and offers traffic offloading capabilities. Devices can achieve the D2D communication over Wi-Fi Direct mechanism. In order to handle the mobility of devices or natural disasters, the D2D network is required to be formed dynamically and automatically. In this thesis, we propose a method to automatically establish the D2D network over Wi-Fi Direct multiple groups formation and seamlessly enable cross-group communication. This method can apply to non-rooted Android devices. The whole proposed scheme consists of two procedures—cluster initialization and connection of multi-cluster. Our method is implemented and validated by an open-source Android communication application. Experiment results show that our method reduces network formation latency in comparison with other scheme.

Abstract iii
Table of Contents v
List of Figures vii
Chapter 1 Introduction 1
Chapter 2 Wi-Fi Direct Technology 4
2.1. Group Formation 5
2.1.1. Standard 5
2.1.2. Autonomous 8
2.1.3. Persistent 9
2.2. Service Discovery 9
2.3. Wi-Fi Direct in Android Device 10
2.3.1. Wi-Fi Direct Limitation in Android Device 10
2.3.2. IP Addresses Assignment 11
2.3.3. Multi-Group in Android Device 11
Chapter 3 Related Work 12
3.1. Single Group in Wi-Fi Direct 12
3.2. Multiple Groups in Wi-Fi Direct 13
Chapter 4 System Model 16
4.1. Problem Statement 16
4.2. Role in Network 17
4.3. Network Topology 19
4.2.1. IP Conflict Issue 20
Chapter 5 Automatic Cluster Formation 24
5.1. Cluster Initialization 24
5.2. Connection of multi-cluster 28
5.3. Role Transformation 35
Chapter 6 Experimental Evaluation 37
6.1. Experiment Environment 37
6.2. Serval Mesh Application 38
6.3. Yeh’s Scheme 39
6.4. Performance Evaluation 42
Chapter 7 Conclusion 48
Bibliography 49

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