行動無線隨意網路之可適性拓撲控制

Abstract

在無線環境中，網路的效能會高度受到底層的拓撲所影響。而一個稀疏的拓撲具有減少多餘流量的特性，因此可提升網路擴增性。然而一個稀疏拓撲經常會犧牲許多重要的網路線段，這些線段有可能是型成要能源有效路由的必經路徑。因此，在拓撲的能源有效性和稀疏度之間存在了相互牽制的議題。 在這篇論文中，我們將提出以幾合圖型為基礎的拓撲控制方法，這個方法可透過參數的設定達到在能源有效性和稀疏度之間調整的彈性，理論結果證明此方法可保證拓撲的連通性、平行性，和對稱性。更重要的是，每一個節點利用區域內所收集的資訊即可建構出所需的拓撲。 為了解決節點的移動性，我們以前面的圖型方法為基礎，提出了一個可適性的拓撲控制協定，此協定具有在保有節點能源和改進整體耗能之間動態調整的能力。數據及摸擬結果提出，我們的方法可有效減少能源消耗，特別是對高度行動的網路有明顯的改進。

The wireless ad hoc network is convenient to many applications, such as conferences, hospitals, battlefields, and etc. In these environments, the network performance heavily relies on the underlying topology. Especially, keeping the topology sparser enhances network scalability. However, a sparse topology may sacrifice some routes that consume less power. Therefore, a tradeoff is between the sparseness and the energy efficiency of the topology. In this dissertation, we propose a geometric structure, named the r-neighborhood graph, to control the topology. The structure allows the flexibility to be adjusted between energy efficiency and node’s degree through a parameter r, 0 □ r □ 1. Theoretic results show that it can always result in a connected planar topology with symmetric edges. More importantly, the structure can be constructed in localized fashion using only 1-hop information. To cope with node’s mobility, we investigate an adaptive protocol, based on a generalized version of the r-neighborhood graph. In this protocol, the parameter r can be adjusted distributively by each node according to the overall energy efficiency. To reduce the construction power, we further incorporate the protocol with a shrinking power mechanism for the topology maintenance. Simulation and numeric results show that the proposed approaches can significantly improve the energy consumption, especially in high mobility environment.