節點叢集化是一套古典的網路節點管理方式，藉由將節點叢集的方式可以幫助凌亂複雜的網路結構形成一套階層化的管理架構。在叢集架構中傳輸訊息時，可藉由位於階層頂端的叢集管理節點快速的將欲傳輸訊息散播出去，達到有效的網路訊息傳輸，本研究內容即是提出一套適合用於車載網路（VANET）交叉路口環境的叢集化方法。由於車載網路中的節點移動速率較一般無線網路存在的節點（例如：手持裝置、筆電）快速，且於真實道路環境通常具有交叉路口拓樸，並且存在利用紅綠燈去控制整體環境中車輛流動的特性，而以往在車載網路上的節點叢集方法其環境大部分位於高速公路長直道路之上，故本研究的主要考量在於需引入哪一些額外的環境已知訊息去代替原先固有的節點叢集方法，促使其符合交叉路口所具有的節點移動特性，並讓形成的叢集架構在經過移動之後不致於太快遠離其所屬叢集管理節點或是控管成員節點的傳輸範圍之外，加強叢集內節點之間的連線穩定性。研究最後將透過模擬驗證其穩定性指標，進一步證明此節點叢集方法之效能以及不同參數對於此方法之影響。 Using clustering technologies to manage nodes in a network is a classical and conventional approach. Node clustering is capable of arranging a network into a hierarchical structure that is tractable upon the requirements of management and maintenance of nodes in dynamic networks, where messages can be broadcast rapidly and efficiently by cluster-head nodes at the top of the hierarchy. The research in this thesis proposed an efficient clustering scheme at crossroads in vehicular ad-hoc network environments. Since nodes in vehicular networks have higher motion speed than those in traditional mobile ad-hoc networks. In addition, node movements in vehicular networks are affected by crossroads as well as traffic lights in real road environments. Thus, the main goal of this clustering scheme is to understand which well-known information of vehicular environments can help vehicular nodes to do clustering in a cost-effective manner corresponding to the surrounding of a crossroads. So that, vehicular nodes can form in a number of stable clusters that are not volatile and dismissed without frequently changes of cluster nodes. Finally, the simulation is employed to inspect the stability and robustness of the proposed scheme. Simulation results show that this scheme is able to avoid futile clustering around a crossroad with traffic lights, thereby reduce the cost of cluster organization in vehicular network environments.
