隨著自動駕駛技術的發展，車載網路近來受到極大的關注。但車載網路的特性例如車子具有高移動性、兩車互相溝通的時間短、且缺乏短時間內end-to-end的路徑，因為這些特性，車載網路的封包抵達率 (PDR) 通常不高，要如何做到有效的傳輸封包是一極大挑戰。有一個能有效提升PDR的方法是透過複製多個相同的封包來幫助傳輸，這樣的方法主要是利用沒有在使用中的資源來幫助傳輸這些相同的封包。但這樣的方法在提升PDR的同時，也造成資源使用上的浪費，重複的封包在抵達目的地之前可能會一直被傳輸，直到該封包過期才會消失，且目的地端也可能會收到多個相同的封包。
為了更有效的提升PDR，我們提出了一個方法叫DREAMER，透過傳輸較小的控制封包取代較大的資料封包來減少資源上的浪費，除此之外我們還根據不同的情況更有效的分配複製封包的上限。模擬的結果顯示我們的方法可以更有效的使用頻寬資源並大幅提升PDR。

The vehicular networks have recently attracted significant attention with driverless car development. It is challenging to deliver the messages in a vehicular ad-hoc networks which are lack of instant end-to-end path, high vehicle mobility and short encounter time. With these features, VANET gets low packet delivery ratio (PDR) characteristic. The key idea we adopted to solve this problem is by trying to exploit the residual capacity for packet replication.
But it also makes another problem that wastes the capacity to transmit a lot of redundant packets if the replication scheme is not well designed. We proposed a scheme called DREAMER (Destination-based Replication by Efficient AssignMent and Early redundant packet Removal). Instead of transmitting the bigger size of data packets, we forward the smaller size of control packets. Moreover, we assign and reallocate replication number by different cases. The simulation results show that our scheme can efficiently enhance PDR and improve the network efficiency.

Acknowledgements iv
Abstract v
Table of Contents vi
List of Figures viii
Chapter 1 Introduction 1
1.1 Concept of limit number of replication packets 1
1.2 Replication-Based Schemes 2
Chapter 2 Related Work 5
2.1 Opportunistic protocols 5
2.2 Prediction-based protocol 7
Chapter 3 DREAMER Protocol 10
3.1 Replication number assignment 11
3.2 Remove redundant packet 12
A. Control packet generation 12
B. Control packet format 13
C. Update control information 14
D. Remove redundant packet 16
3.3 Packet forward or replicate 16
A. Predict the spending time 17
B. Replication number allocation 20
Chapter 4 Simulation 23
Chapter 5 Conclusion 30
Bibliography 31

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