最近的無線感測網路技術發展使感測器與質致動器能積極地跟彼此互相通訊溝通與一起執行來完成特定的目標，這就是所謂的物聯網(IoT)。現在的物聯網中有非常多種低耗能無線鏈結層協定，如：ZigBee、低功耗藍牙。為了輕鬆部署物聯網裝置，ZigBee的IP規範已經支援了基於RPL路由協議的網狀拓墣。然而藍牙是基於Master-Slave架構形成星狀拓墣，它的Piconet由一個Master與最多7個Slave所組成。雖然在藍牙4.1之後一個裝置可以同時扮演Master與Slave的角色，理論上可以藉此形成網狀網路，但裝置們需要在互相交換數據之前先建立連線。 因此在本研究中我們使用藍牙廣播性質的優勢來實現基於廣播訊息的低功耗藍牙網狀網路，並建立一個互動式定位以及追蹤系統來證明我們低功耗藍牙網狀網路的可用性。特別的是在我們的低功耗藍牙網狀網路裡，每個低功耗藍牙裝置廣播beacon訊息都符合Apple公司的iBeacon協議規範，因此一個支援低功耗藍牙的智慧型手機就能夠根據收到的beacon訊息來執行定位的動作。在定位完成後，智慧型手機能傳送它的定位結果，並經由在網狀網路裡的低功耗藍牙裝置中繼到我們的後端伺服器中。當定位結果被後端伺服器收到後，後端伺服器亦可以利用低功耗藍牙裝置所組成的網狀網路將確認訊息回傳到使用者端。利用特定使用者的定位結果歷史紀錄，我們能追蹤使用者的移動模式，並為他們提供個人化的適地性服務。實驗結果顯示在我們的低功耗藍牙網狀網路中，雙向傳輸延遲時間是在適當的範圍內，做為一個定位與追蹤系統是可行的。 Recent development of wireless sensor network technologies has enabled sensors and actuators to actively communicate with each other and work together to achieve specific goals. This scenario is the so-called Internet of Things (IoT). There are a variety of low-power wireless link-layer protocols for IoT such as ZigBee and Bluetooth Low Energy (BLE). To ease the deployment of IoT devices, the ZigBee IP Specification has already supported the mesh topology based on the RPL routing protocol. However, Bluetooth is based on a master-slave architecture to form a star topology, where a piconet consists of a master and up to 7 active slaves. Although later in Bluetooth 4.1 a device can act as a master and a slave simultaneously, and theoretically a mesh network can be formed, it would require devices to establish a connection before they can exchange data. Therefore, in this research we take advantage of the broadcasting nature of Bluetooth devices to implement a BLE mesh network based on advertisement messages, and build an interactive positioning and tracking system to demonstrate the usefulness of our BLE mesh network. Specifically, in our mesh network every BLE device broadcasts beacon messages compliant with the Apple iBeacon protocol, so a BLE-enabled smartphone can perform locationing based on the received beacon messages. After the locationing process completes, the smartphone can send its locationing result back to our backend server, via the relay of BLE devices in the mesh network. Once the locationing result is received at the backend server, a confirmation message will be sent to the smartphone user, again via the relay of BLE devices. With the history records of the locationing results from specific users, we can track the moving patterns of the users and provide them with personalized location-based services. Our experimental results show that our system is practicable with moderate transmission latencies in the BLE mesh network.
