在我們生活當中有越來越多的藍芽相關應用，其中這些應用大多都是以連線的方式來傳送訊息，像我們日常生活中使用的藍芽喇叭，或是藍芽鍵盤滑鼠等等的物品，都會需要使用藍芽連線的方式才可以使用，而連線的缺點是在連線時我們需要手動的去操作他。我們提出的系統，因為是迫近警示系統，如果要用連線的方式傳遞訊息，時間會太長，而且我們也不可能去特別指定要去警示特定的用路人，所以我們會利用藍芽非連線的方式來一直廣播訊息。有關警示系統，有很多研究他們常會利用信標(beacon)來廣播訊號，然後再根據接收到的訊號強度來決定是否進行警示，不過這些研究都沒有考慮到時間延遲的問題。因為迫近警示系統，我們不會希望接收端收到訊號後反應時間太長，所以在之後的章節我們會去討論延遲敏感的問題和探討相關參數的設計及評估。最後我們也會將我們設計討論的參數，實際應用到安卓手機應用程式和藍芽裝置上。

There are more and more Bluetooth applications in our daily lives. In today’s market, most of Bluetooth applications are used to transmit data by connecting with other devices. For example, the Bluetooth speaker, Bluetooth keyboard, and Bluetooth mouse, and so on. These devices always need to use connecting method to transmit data. When we use the connecting method to transmit data, there is a disadvantage that we need manual operation when we need to connect with other devices. The system is designed to give proximity warning which can’t use the connecting method to transmit data. We can’t designate who needing to be warned since the road conditions are unpredictable. We use the Bluetooth non-connecting method to continuous advertising the data. There are many researches use beacon to advertise the signal in the alert system. According to the received signal strength, the system will determine the alert condition. However, these researches aren’t considering the time delay problem. In our proposed system, we will consider the delay sensitive service and the related parameters in the following chapters since the proximity warning system can’t tolerate the delay caused by scanner’s response time. Finally, we will build an application which based on the parameters and methods as we discuss in the previous. We will use the Android app and Bluetooth device to implementation the whole system.

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