應用於VANET環境下以車輛密度為基礎之緊急訊息廣播

Abstract

車載隨意網路（Vehicular Ad Hoc NETwork, VANET）主要提供車輛意外緊急警告服務與一般性的資料傳送。為了讓駕駛者免於遭受緊急事故的波及，快速的緊急訊息傳遞為目前車載隨意網路上炙手可熱的研究議題。在緊急訊息多站廣播（Multi-hop broadcast）的方法中，下一轉送站點（Next hop forwarder）的選擇模式主要分為兩種：(1)傳送者導向轉送法藉由獲得鄰居資訊由傳送者選擇最佳的下一轉送站點；(2)接收者導向轉送法採用分散式的方法，由各轉送者自行決定何時將訊息送出，讓最早轉送出訊息者成為下一轉送站點。本論文提出一個植基於車輛密度的緊急訊息廣播法（Vehicle-Density-based Emergency Broadcast，簡稱VDEB）來解決傳輸者導向方法中的高額外負載（Overhead）問題，以及接收者導向方法中可能發生長延遲時間問題。實驗結果顯示，我們提出的VDEB只需非常低的額外負載便可達成相當不錯的延遲時間狀況。

The extension of wireless technology, vehicular ad hoc network (VANET), provides emergency warning services and general data transmission services. To rescue more drivers from being involved in an emergency event on the road, fast emergency message propagation is an important issue in VANET studies. There are two types of multi-hop broadcasting forwarder selection scheme for emergency broadcasting, known as sender-oriented schemes and receiver-oriented schemes. The sender-oriented schemes maintain the neighbor information to choose the best forwarder before broadcasting the message while the receiver-oriented schemes distributedly elect the forwarders. In this thesis, we proposed a vehicle-density-based emergency broadcast (VDEB) scheme to solve the problem of high overhead in sender-oriented schemes and long delay in receiver-oriented schemes. The simulation results show that our VDEB scheme can achieve a better performance with low delay and little overhead.