| 摘要: | 隨著近幾年物聯網技術的發展，無線感測網路已逐漸應用到各種領域中。物聯網裝置必須具備體積小、功耗低、存儲資源有限等特點，且大多運行在不可靠的通信媒介上。為了因應這些特性，IETF於RFC6550制訂了RPL路由演算法(IPv6 Routing Protocol for Low-Power and Lossy Networks)，這種路由演算法特別適用於低功耗與有損網路環境，用以建立點對點、單點對多點、多點對單點等資料流。同屬於鏈結層中針對低功耗及低傳輸成本有BLE及ZigBee兩種技術，ZigBee已支援利用6LoWPAN做為介於網路層與鏈結層中間的配適層，並且於網路層以RPL演算法建構路由。相對而言，直到2015年IETF RFC 7668才制訂出IPv6 over BLE的規範，而目前尚未見到RPL路由演算法應用於BLE環境。以此為由，本論文當中我們以模擬的方式將RPL路由演算法建構於BLE之上，利用RFC 6550所提出的存儲模式與選擇路徑，觀察不同組合之下的網路效能。最後，我們也於模擬環境中實作RPL節點的eather模式，這種模式可讓節點只協助鄰居轉送封包而不加入網狀網路拓樸。我們在模擬實驗中將部分節點啟用Feather模式，探討這種模式對於封包遺失率、拓樸變化、平均路由維護週期等網路效能之影響。
With the recent development of Internet of Things (IoT) technologies, wireless sensor networks have been used in various application domains. IoT devices have unique features and requirements such as small size, low power consumption, limited storage, and communication over unreliable wireless channels. To overcome these limitations, IETF RFC6550 defines the RPL routing protocol (IPv6 Routing Protocol for Low-Power and Lossy Networks), which supports traffic lows of point-to-point, point-to-multipoint, multipoint-to-point. At the link layer, BLE and ZigBee are two popular low-power and low-cost wireless transmission technologies. For ZigBee, it supports 6LoWPAN as the adaptation layer between the network layer and the link layer, and it establishes routing paths using the RPL protocol. However, the specification of IPv6 over BLE has not been specified until 2015, and currently the RPL routing protocol has not been used in the BLE environment. Therefore, in this thesis we simulate the operations of the RPL routing protocol over BLE, and study the network performance with different storing modes and path selections. Finally, we implement the feather mode of RPL nodes in the simulation environment. With feather mode enabled, a RPL node only forwards packets for its neighbors and will not join the mesh network. In our simulation, we enable the feather mode in some of the nodes and evaluate the network performance of packet loss rate, number of churns, and average beacon interval. |
