- 學位論文
無線感測網路中具虛擬座標之低成本堅韌路由
Low-Cost Resilient Routing Using Virtual Coordinates in Wireless Sensor Networks
摘要
微型無線感測節點受限於供應電量、運算與儲存能力以及網路通信頻寬。感測網路中，感測節點將偵測資料併同位置資訊轉送至資料彙集端做相對處理。雖節點位置可透過人工佈署或是全球定位系統獲得，但節點若攜帶定位系統，其硬體成本提升與電量消耗，皆不符合感測器小體積與低成本的設計規範。 對於以上所述問題，許多學者提出使用虛擬座標系統的路由協定用以取代定位系統。本研究亦提出另一低成本堅韌路由協定（LCRR），且網路中各節點皆無GPS，根據感測節點與資料彙集端的跳躍數（似極座標系統半徑R），建置虛擬座標系統，此系統擁有多條“幹道”，作為虛擬座標的主軸（轉換後似極座標系統幅角θ）。事件發生時，感應節點註記自身的虛擬座標封包內，並記錄所經轉送節點的直線距離，藉此機制以達到事件定位之效果。訊息傳遞方式，由外圍節點向內圍節點遞送，藉由多個內圍節點來分散負載，來源節點至資料彙集端則有多條路徑提供轉傳，以避免資料彙集端周圍能量洞的形成，並增加路徑的強健性。最後由資料彙集端彙整各來源封包，估算出真實事件所在位置。由於LCRR的虛擬座標系統為一個邏輯拓撲，故路由維護易於一般路由，可降低網路維護的成本。 本研究的網路模擬效能以JAVA程式撰寫，比較真實事件發生的座標位置與LCRR所估算出的座標做比較分析。主要有以下效能評估的量測項目：1) 平均距離誤差在不同感測區域下，高節點密集的情況下距離誤差皆控制在一個跳躍數以內；2) 估算正確率在距離五個跳躍數以內的事件定位，可達到80%的高正確率；3) 定位誤差事件百分比可看出總體的定位正確率，在不同感測區域高節點密度的情況下，事件定位可達到80%以上的高正確率。最後模擬當網路運作長時間後的節點存活率，使用Power-aware轉傳機制可有效延緩能量洞形成，達到負載平衡。
並列摘要
Small wireless sensor node is limited to the storing ability, operation of computing, supply of power, and the network communication bandwidth. In Wireless Sensor Network, the data packet which has sensing datum with geographical information will be transferred to the Sink node by Source node. Although the position of sensor node is obtained through the Global Positioning System (GPS) or artificial deployment, it does not meet the requirement of small volume and low cost. If it equipped with the GPS, sensor node will increase more hardware cost and more power consumption. The questions we mention above, many researchers proposed that the routing protocol using virtual coordinate system in place of the positioning system. This research also proposes a novel routing protocol, called LCRR (Low-cost resilient routing using virtual coordinate in wireless sensor networks). We establish the virtual coordinate system, according the hop counts between the sensor nodes to the Sink node. Each node in the sensor networks has his virtual coordinate. It records the node's straight distance through virtual coordinate, when the sensing data are passed back. We take advantage of this mechanism to achieve effect of the event localization. The packet transfer mode is that the outer node has many inner nodes to choose to forward data packets in order to balance the load. By the way, the source node forward packet to the Sink node in using multi-path that would increase route robust and avoid the occurrence of Sink hole. The virtual coordinate system is a logical topology, therefore the route maintenance is easier than common route, and reduce the cost of maintenance. The network simulation of this research is performed by using JAVA program. We compare between the event position and the estimated position for distance error. The main measurement as follow: 1) Average Distance Error in different sensor field, densely sensor deployment, the Distance Error perform in the one hop. 2) Estimated Correctness Rate in five hop count event, it achieve 80% high accuracy. 3) Event Located Error Rate with densely sensor deployment show the high accuracy in different sensor field. and finally we compare, analysis with Survived Nodes Rate of the Tree-based topology, the power-aware forwarding mechanism efficiently delay the sink hole occurring and reach load balance.
參考文獻
延伸閱讀
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