行動無線感測網路下基於能源節約的叢集式路由方法

Abstract

散佈在無線感測網路下的各個節點對於周圍環境有感測、計算與傳送的能力。由於GPS的價格昂貴，我們使用少部分不會移動的錨節點(已知位置)來幫助我們計算其他的感測節點的位置。為了有效率地傳送感測資料到目的地(伺服器)，確認每個感測節點的位置對於建置路由有很大的幫助。我們使用一個基於色彩理論的行動定位演算法，CDL [1]，來幫助感測節點的定位。因為感測節點的能源是有限的，我們提出一個基於能源節約的叢集式路由方法(CEER)來延長感測節點的使用壽命。CEER把整個目標區域分割成許多個子區域(網格)，使得每個在網格內的感測節點彼此都能在無線電範圍內，然後每個網格都會選出一個叢集頭。每個錨節點會廣播自己的RGB值及位置資訊到各個感測節點，包括叢集頭。每個感測節點會週期性的把感測資料(如果有的話)及其RGB值資訊傳送到對應的叢集頭。接下來叢集頭會把聚集的資料利用兩個步驟經由錨節點傳送到伺服器。步驟一是它會比較叢集成員中的RGB值以選擇一些更接近所屬錨節點的感測節點當作下一個可能的跳躍點。步驟二是叢集頭會在那些被選中的叢集成員中找尋具最大能源的感測節點當作下一個跳躍點。本方法的獨特性在於藉由比較鄰近節點對應的RGB值資訊，可以找到一條考量到能源的路由。模擬的結果顯示，與另一個在行動無線感測網路下的路由方法ESDSR[2]相比，CEER的平均能源節約比ESDSR好約50-60%。另外，CEER的平均封包傳送時間比ESDSR少約50%。

Wireless sensor networks (WSNs) with nodes spreading in a target area have abilities of sensing, computing, and communication. Since the GPS device is expensive, we use a small number of fixed anchor nodes that are aware of their locations to help estimate the locations of other sensor nodes in WSNs. To efficiently route sensed data to the destination (the server), identifying the location of each sensor node can be of great help. We adopted a range-free Color-theory based Dynamic Localization, CDL [1], to help identify each sensor node’s location. Since sensor nodes are battery-powered, we propose a Cluster-based Energy Efficient Routing algorithm (CEER) to prolong the life time of each sensor node. CEER divides a target area into sub-areas called grids such that all sensor nodes in a grid are within the radio range, and a cluster head is selected in each grid. Each anchor will broadcast its RGB values to each sensor node, including cluster heads. A sensor node will periodically forward its RGB values along with sensed data (if available) to its associated cluster head. The cluster head will then forward the aggregated data to a nearby anchor in two steps. In step 1, it selects those cluster members that are closer to the anchor than itself as next possible hops by comparing their RGB values. In step 2, among those selected cluster members, the sensor node with the highest energy level is selected as the next hop. The uniqueness of our approach is that by comparing the associated RGB values among neighboring nodes, we can efficiently choose a better routing path with energy awareness. Simulation results have shown that our routing algorithm can save 50% - 60% energy than ESDSR [2] in mobile wireless sensor networks. In addition, the latency per packet of CEER is 50% less than that of ESDSR.