臺灣博碩士論文加值系統

近年來隨著移動計算技術和無線通訊技術的發展，一個很受歡迎的網路通訊模式稱之為機會網路的也因此受到關注。雖然在目前的機會網路下的資料散佈有了很多的解決方法，但是還是有許多特點是值得去研究的。在我們的論文中我們提出了一個在機會網路下新穎的資料散佈的情境: 人們在同一個地點會隨著時間的不同而會有不同的資料需求。此情境就代表在機會網路下我們不只是要減少點到點中的延遲和提高傳輸的效率，我們也應該要考慮當資料有時效性的問題應該如何解決。
基於上述的資料散佈的情境，在我們論文中我們提出了一個方法叫做
時效性之傳輸方法(Time-Sensitive Data dissemination Scheme,簡稱 TSDD )。在我們方法中，我們去會去介紹有關於時效性的問題並使得有時效問題的資料能夠有效率的散布。為了解決時效性的問題，我們使用節點的歷史資訊去預測他的移動模式。之後我們利用馬可夫鏈(Markov Chains)和人的移動模式去預測未來能散佈的最大機率，進而預測我們目前所需傳遞的最小機率。從這些預測的結果我們去尋找適合的節點去增加我們的傳輸效率。最後，我們可以從移動路徑去推測節點能到目的地的可能性，當我們發現節點是完全不可能送達到目的地時，我們就去尋找繼任者(Successor)，幫助那些不可能送達到的節點去完成他們未完成的任務。
從本篇的實驗結果中我們可以看出時效性之傳輸方法不只可以增加傳輸效率和減少傳輸造成的封包浪費，還可以增加網路的數據傳遞的效率。

With recent development in mobile computing technology and wireless communications, a popular communication paradigm called Opportunistic Networks have received considerable attention in recent times. Although data dissemination has been extensively addressed, many unique characteristics of opportunistic networks offer newer research challenges. This thesis introduces a novel data dissemination scenario in opportunistic networks, where data required by a user in this environment may be required to deliver the different data to the same community at different times. That means data dissemination in opportunistic networks should not only consider reducing end-to-end delay and increasing delivery ratio in the network, but need to consider the time-sensitivity of a data.
Based on the aforementioned data dissemination scenario, this thesis proposes a data dissemination scheme called Time-Sensitive Data Dissemination (TSDD). The propose scheme that investigates the problems that may be arise from such scenario and enable propose scheme to disseminate data to the destination in a timely and efficient manner. To achieve this, we used user’s movement historical information to predict user mobility pattern. By utilizing Markov Chain with the predicted pattern, maximum delivery rate and minimum delivery rate within a time slot can be predicted. With these predictions, primary and secondary relay user can be located and is used to improve delivery rate and reduce transmission overhead. To further improve the performance of the propose scheme, a successor is selected the primary or the secondary user is unable to deliver the data to its destination within in the limited time frame. Experiment results demonstrate that TSDD not only improves the delivery rate and decreases the transmission overhead, but it also increases the efficiency of data dissemination in the network.

LIST OF CONTENTS VIII
LIST OF TABLES X
LIST OF FIGURE XI
CHAPTER 1. INTRODUCTION 1
1.1 MOTIVATION 3
1.2 CONTRIBUTION 4
1.3 ORGANIZATION 5
CHAPTER 2. . RELATED WORK 6
2.1 BACKGROUND OF OPPORTUNISTIC NETWORKS 6
2.2 EXISTING ROUTING/FORWARDING TECHNIQUES IN OPPORTUNISTIC NETWORKS 7
2.2.1 Non context-aware (zero-knowledge) routing 8
2.2.2 Context-aware (knowledge) routing 10
CHAPTER 3. TIME-SENSITIVE DATA DISSEMINATION SCHEME 13
3.1 PROBLEM DESCRIPTION NETWORK MODEL 13
3.1.1 Problem Description 14
3.1.2 Network Roles 14
3.1.3 Community-based Environment 14
3.1.4 Message Description 15
3.2 MOBILITY PATTERN PREDICTION 16
3.3 RELAY NODE SELECTION 17
3.3.1 Deriving the Lower Bound Value (LBV) of delivery rate 17
3.3.2 Delivery Capability Check 23
3.3.3 Primary Relay Node Selection 23
3.3.4 Secondary Relay Node Selection 24
3.4 SUCCESSOR DETERMINATION 27
3.4.1 Successor_sender 27
3.4.2 Successor_relay 28
3.5 CACHE MANAGEMENT 28
CHAPTER 4. EXPERIMENT 32
4.1 COMPARED SCHEMES 32
4.2 EXPERIMENT ENVIRONMENT AND SETUP 32
4.3 SIMULATION RESULTS AND ANALYSIS 35
4.3.1 Buffer Size Influence 35
4.3.2 Number of Messages Influence 39
4.3.3 Number of Nodes Influence 43
4.3.4 Trend of Different Time Slots 45
CHAPTER 5. CONCLUSION AND FUTURE WORKS 47
5.1 CONCLUSION 47
5.2 FUTURE WORK 48
REFERENCES 49

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