在車載網路的研究中，緊急訊息的傳遞一直是一個重要的議題。然而，由於車載網路是由高速移動的車輛所組成，網路拓樸的變動非常快速，所以大多數的相關研究都是藉由廣播來傳遞緊急訊息，而非傳統的路由策略。然而，網路廣播可能導致廣播風暴，進而影響緊急訊息的傳遞。
　　本論文提出了一個以分群為基礎的緊急訊息傳遞機制，簡稱CBED。在這個方法中，我們先藉由車輛的位置、速度等資訊來計算出各車輛的移動模式，建立數個車輛移動模式相像的穩定車輛叢集。藉由車輛叢集的結構，可以有效率的傳遞緊急訊息，並避免廣播風暴的產生，快速地將緊急訊息傳播到鄰近的車輛上。
　　我們使用NS2及IMPORTANT MOBILITY GENERATOR等工具作模擬實驗，將CBED跟先前研究所提出的EDB、VDEB這兩個方法做比較。實驗結果顯示，無論是在高密度車輛還是低密度車輛的道路環境下，CBED均可以用較少的傳輸時間，傳播緊急訊息給一定範圍內的車輛知道，且在傳遞的過程中所產生的封包數量，也較其他兩個方法要來得少，避免廣播風暴的發生。

　　Emergency data dissemination is an important issue in a VANET. The topology of a VANET changes rapidly due to fast moving of the vehicles in the VANET. Therefore, most researchers proposed to use data broadcasting, instead of routing, to disseminate emergency data in a VANET. However, data broadcasting is prone to induce a broadcasting storm in the network so as to hinder efficient dissemination of the emergency data.
　　In this thesis, we present a cluster-based emergency data dissemination method, termed CBED. In CBED, we first form several stable clusters of vehicles according to their locations and speeds. With the stable vehicle clusters, emergency data can be efficiently disseminated.
　　To compare the performance of CBED and those of two existing methods-- EDB and VDEB, we perform several experiments using NS2 and IMPORTANT MOBILITY GENERATOR. The simulation results show that CBED outperforms EDB and VDEB in offering the shortest delay time in disseminating emergency data.

[1] 葉彥憑(2012)•車載隨意網路中以移動模式為基礎的權重叢集演算法•未發表的碩士論文，台北市：國立台灣科技大學。
[2] A. Wegener, H. Hellbr‥uck, S. Fischer, C. Schmidt, and S. Fekete, “AutoCast: An adaptive data dissemination protocol for traffic information systems,” in Proc. IEEE Vehicular Technology Conf. (VTC), Baltimore, MD, Sep. 2007.
[3] D. Li, H. Huang, X. Li, M. Li, and F. Tang, “A distance-based directional broadcast protocol for urban vehicular ad hoc network,” in Proc. IEEE Int’l Conf. on Wireless Comm., Networking and Mobile Computing(WiCom), Shanghai, China, Sep. 2007.
[4] E. Fasolo, A. Zanella, and M. Zorzi, “An effective broadcast scheme for alert message propagation in vehicular ad hoc networks,” in Proc. IEEE Int’l Conf. on Comm. (ICC), Istanbul, Turkey, Jun. 2006.
[5] F. Bai, N. Sadagopan, and A. Helmy, User Manual for IMPORTANT Mobility Tool Generators in ns-2 Simulator, University of Southern California, 2004.
[6] G. Korkmaz, E. Ekici, F. ‥Ozg‥uner, and ‥U. ‥Ozg‥uner, “Urban multi-hop broadcast protocol for inter-vehicle communication systems,” in Proc. ACM Int’l Workshop on Vehicular Ad Hoc Networks. (VANET), Philadelphia, PA, Sep. 2004.
[7] N. Wisitpongphan, O. K. Tonguz, J. S. Parikh, P. Mudalige, F. Bai, and V. Sadekar, “Broadcast storm mitigation techniques in vehicular ad hoc networks,” IEEE Wireless Commun., vol. 14, no. 6, Dec.2007.
[8] Sin, H.G., “Field Evaluation Methodology for quantifying Network-Wide Efficiency,Energy, Emission, and Safety Impacts of Operational-Level Transportation Projects,”Ph.D. Dissertation. School of Civil and Environmental Engineering, VirginiaPolytechnic Institute and State University, Virginia, 2001.
[9] S. Panichpapiboon and G. Ferrari, “Irresponsible forwarding,” inProc. IEEE Int’l Conf. on ITS Telecomm. (ITST), Phuket, Thailand, Oct. 2008.
[10] S. Panichpapiboon and W. Pattara-atikom, ” A Review of Information
Dissemination Protocols for Vehicular Ad Hoc Networks,” IEEE
COMMUNICATIONS SURVEYS & TUTORIALS, Nov. 2011.
[11] The Network Simulator ns2. http://www.isi.edu/nsnam/ns
[12] W. Su, S.J. Lee, and M. Gerla, “Mobility Prediction and Routing in Ad Hoc
Wireless Networks, International Journal of Network Management, vol. 11, no. 1, 2001.
[13] X. Yang, J. Liu, F. Zhao, and Nitin H. Vaidya, “A vehicle-to-vehicle communication protocol for cooperative collision warning,” in Proc. MOBIQUITOUS 2004, Boston, USA, Aug. 2004.
[14] Y. Tseng, R. Jan, C. Chen, C. Wang, and H. Li, “A vehicle-density-based forwarding scheme for emergency message broadcasts in VANETs,” in Proc. IEEE Int’l Conf. on Mobile Ad Hoc and Sensor Sys. (MASS), San Francisco, CA, Nov. 2010.