隨著物聯網技術的發展，無線感測器網路成為了物聯網重要的組成部分與研究重點。它是由大量且具有計算能力、通訊能力，但電力有限的感測器所構成。網際網路工程任務組(IETF)在2005年成立6LoWPAN的工作小組，定義出IPv6和IEEE 802.15.4之間的調配層，讓大量無線裝置可以透過IPv6直接連網，此稱為6LoWPAN標準協議，並在2012年制定了基於IPv6路由向量的IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL)協議。RPL協議是利用目標函數來進行面向目的地的有向無環圖的組網，對於路徑成本的計算則是使用最簡單的度量累加法來選擇最佳路徑的父親節點，但是這樣的累加值方式，有時候卻無法反映出節點路徑的真實成本。 本文以統計學的觀點來分析與篩選父節點的路徑成本，提出基於預期傳送次數的變異數來優化RPL協議鏈路路由的度量計算方法。同時考慮父親節點能耗方式，提出節點電池的使用率之能量路由度量方式。最後，再透過節點距離根節點的距離權重等級，來分配鏈路路由度量與能量路由度量，提供RPL協議一個父親節點選擇的機制，同時也考慮父親節點的能量的負載平衡。 ;With the development of Internet of Things (IoT) technology, wireless sensor networks (WSN) have become an important research of the Internet of Things. It is composed of a large number of sensors with computing and communication capabilities limited energy. The internet engineering task force (IETF) established the 6LoWPAN working group in 2005 to define the adaptation layer between IPv6 and IEEE 802.15.4, allowing a large number of wireless devices to connect directly to the Internet through IPv6. This is called the 6LoWPAN standard protocol. In 2012, the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) protocol formulated the routing vector based on IPv6.The RPL protocol uses an objective function to implement a destination-oriented directed acyclic graph(DODAG) networking. For the calculation of path costs, the simplest metric accumulation method is used to select the parent node of the best path. However, this accumulated value approach sometimes fails to reflect the real cost of the node path.This thesis analyzes and filters the path cost of the parent node from a statistical perspective and proposes a new variable calculation method based on ETX Variance to optimize the RPL link routing metrics.Considering the energy consumption method of the father node, this thesis also proposes an energy routing metric method in reference to the usage rate of node battery. Finally, according to the weighting level of distance between a node and its root node, the propose method can adjust the respective weights of link routing metrics and energy routing metric. Thus, the study in this thesis , provides a mechanism for RPL to choose a parent node, while considering the energy load balance of the parent node in a network.
