如何在短時間內於車載網路中廣播重要的安全信息是一項被廣為討論並試圖解決的議題。由於一般的廣播傳輸不具備回傳機制，常會發生碰撞問題，雖然可靠式廣播可以有效地降低碰撞率，但在行為處理等則要花費不少的時間成本，尤其是對於要廣播緊急的安全信息。這篇論文將會建立一套名為進階式廣播的新廣播傳輸機制，藉由整合分散式協調功能的概念和DSRC多頻道共用機制等方式，達到降低碰撞機率進而提升傳輸的效率、增加接收單位數量及縮短傳輸時間等。當車子收到安全信息時，會有一定的機率決定是否廣播來讓其他車子接收，決定廣播的同時會一併隨機選擇廣播的頻道和backoff來決定廣播的時間點。在控制頻道的車子廣播完安全信息後則回到原本狀態，而在服務頻道的車子則必須先傳通知信息提醒接收者切換到控制頻道，然後廣播的車子切換到控制頻道廣播安全信息，藉由這種方式可以通知其他不同頻道的車子並提升接收數量。backoff則是引用自分散式協調功能機制，在一個車子團體中根據每台車子各自的backoff來判斷傳輸的優先順序，使車子能夠降低在廣播中發生碰撞的機率，同時讓更多車子成功接收安全信息。

It is a widely discussed issue that how to broadcast important safety message in short time in VANET. Broadcast, generally speaking, has no feedback mechanism so that it usually causes collision problem. Reliable broadcast can effectively reduce the collision probability, but it wastes time on procedures, especially for broadcasting emergency safety message. In this paper, it will build AdvB, advanced broadcast which is a new type of broadcast mechanism, by combining the concept of DCF and multi-channel operation in DSRC to decrease collision probability so that it can increases transmission efficiency, plus number of receivers, reduce latency, etc. There is a probability to decide whether to rebroadcast to others for one vehicle after receiving safety message, and it also decides the channel and backoff to broadcast randomly. After finishing broadcasting in control channel the vehicles will return to the original state. The others in service channels have to announce receivers to switch to control channel to listen to safety message, and then those transmitters change to control channel to broadcast safety message. This method can inform other vehicles in different channels to increase receivers. Backoff comes from DCF mechanism. It can decide the transmission priorities by different value of backoff in a vehicle group so that it can reduce broadcast probability and let more vehicles receive safety message successfully.

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