在車載網路中，當事故發生時，車輛藉由緊急訊息傳遞可以避免二次事故的
發生，以提升用路安全。但傳統廣播方式會導致廣播風暴的發生，使得整體網路
效能不佳，故本碩士論文致力於降低封包的轉傳數量。我們的設計提出了一個新
的方向，當緊急事件發生時，把緊急訊息傳給距離最近的路邊裝置，藉此連接到
後端網路來採取應對措施，同時也設計特定區域車輛通知的廣播設計，當車輛收
到緊急訊息時，該點先判斷是否位在合適的廣播區域，若位於合適的區域，車輛
再進一步透過鄰居列表資訊計算出一個等待廣播時間，節點條件越好等待廣播時
間越短，當等待廣播時間一到時，該節點可進行封包廣播；若其他還在等待廣播
的節點收到此封包時，則停止動作，藉此達到抑制的目的。最後，透過模擬結果
顯示，我們提出的機制相較於其他機制能有效降低封包轉傳次數，以避免廣播風
暴的發生，減少網路資源的消耗。

In a vehicular ad hoc network (VANET), the vehicle can avoid the occurrence of secondary
accidents through the emergency message forwarding when an accident occurs to
enhance the safety on roads. However, the traditional unlimited broadcast will cause the
so-called broadcast storm, making the overall network performance poor. Therefore, we
aim at lowering the number of packets to be transmitted by proposing a new direction in
our design. When an emergency occurs, the emergency message will be forwarded to the
nearest roadside unit (RSU) connected to the backhaul network to take countermeasures.
In addition, the emergency message forwarding mechanism can be extended to reach a
specific area. When the vehicle receives an emergency message and it is located in an
appropriate area, it starts to calculate the waiting time through the list of neighbors. The
better the condition is, the shorter the waiting time is. When the time is up, it broadcasts
the packet. If the other nodes still waiting for broadcasting receives the packet, it ceases
the transmission of the packet to mitigate the broadcast storm. Finally, we show the superiority
of our design over some related mechanisms in the literature in terms of amount
of packets transmitted via simulations. This definitely show the ability of broadcast storm
supression and saving of network resources exhibited by our proposed mechanisms.

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