此篇論文提出一種以符元層網路編碼和多對多廣播為基礎的競爭協定用於增加網路編碼與傳輸的效能。利用車載網路的廣播特性結合網路編碼技術來增加網路傳輸效能，降低傳輸時間的延遲。目前為止已經有一些研究針對車載環境的網路編碼與傳輸效能進行分析和討論，但只有極少數的論文能夠提出有效的辦法來增加車載環境的網路編碼與傳輸效能。由於車載網路對於資訊傳遞有即時性的需求，此篇論文提出一個網路協定方式增加網路編碼與傳輸的效能。此協定包括了三個主要機制，包括車輛內的資料編碼(Intra-Vehicle Symbol Coding)、合適傳輸車輛選擇(Proper Forwarder Selector)和車輛節點間的競爭(Inter-Vehicle Contention)，這三個方法可提高具有高傳輸效能的車輛在轉傳過程中的傳輸機會。此篇論文也考慮到車輛節點對訊息接收的完整性與系統中所有行駛車輛的多對多廣播特性，以適應在車載環境的訊息傳遞。而實驗結果顯示此篇論文所提出的以符元編碼為基礎的競爭傳送協定可以有效的降低資訊散佈至全體網路的時間，進而提升整個車載網路的傳輸效能。

This thesis proposes a contention-based protocol on symbol level network coding and many-to-many broadcast in order to improve the performance of network coding and transmission efficiency. Utilizing VANET broadcast characteristic and network coding technique to enhance network traffic and reduce transmission time. So far, there have been some studies of network coding and transmission in VANET for analysis and discussion. However, only a handful of works come up with effective ways to improve it. There is immediate demand for VANET information, but environmental factors usually cause data loss and error in the transmission duration. In this work, a novel network protocol with three mechanisms can promote the efficiency of network coding and transmission. By applying Intra-Vehicle Symbol Coding, Proper Forwarder Selector and Inter-Vehicle Contention, a vehicle with high Information Availability can obtain more transmission opportunities. We also consider the integrity of the information received and the characteristic of many-to-many broadcast to adapt VANET. The experimental results show that the symbol level coding-based contention forwarding protocol can effectively reduce the information propagation time and enhance the transmission efficiency of VANET.

[1] J. Luo and J. P. Hubaux, “A Survey of Inter-Vehicle Communications,” Technical Report IC/2004/04, EPFL, Mar. 2004.

[2] T. L. Willke and P. Tientrakool and N. F. Maxemchuk, “A Survey of inter- Vehicle Communication Protocols and Their Applications,” IEEE Commun. Surveys Tutorials, vol. 11, no. Issue 2, pp. 3–20, 2nd Quarter 2009.

[3] M. Li, K. Zeng, and W. Lou, “Oppcast: Opportunistic broadcast of warning messages in vanets with unreliable links,” in IEEE MASS ’09,Oct. 2009.

[4] T. ElBatt, S. K. Goel, G. Holland, H. Krishnan, and J. Parikh, “Cooperative Collision Warning Using Dedicated Short Range Wireless Communications”, Proceedings of the 3rd ACM International Workshop on Vehicular Ad Hoc Network VANET’06.

[5] Y. Bi, K.-H. Liu, X. Shen, and H. Zhao, “A multi-channel token ring protocol for inter-vehicle communications,” in Proc. IEEE Global Telecommun. Conf., 2008, pp. 1–5.

[6] J.-S. Park, U. Lee, S. Y. Oh, M. Gerla, and D. S. Lun, “Emergency related video streaming in vanet using network coding,” in ACM VANET ’06, 2006, pp. 102–103.

[7] S. Ahmed and S. S. Kanhere, “Vanetcode: network coding to enhance cooperative downloading in vehicular ad-hoc networks,” in IWCMC ’06, 2006, pp. 527–532.

[8] S.-H. Lee, U. Lee, K.-W. Lee, and M. Gerla, “Content distribution in vanets using network coding: The effect of disk i/o and processing o/h,” in IEEE SECON ’08, June 2008, pp. 117–125.

[9] M. Johnson, L. D. Nardis, and K. Ramchandran, “Collaborative content distribution for vehicular ad hoc networks,” in Proc. 44th Allerton Conference on Communication, Control, and Computing, 2006.

[10] R. Ahlswede, N. Cai, S.-Y. Li, and R. Yeung, “Network information flow,” IEEE Trans. Inf. Theory, vol. 46, no. 4, pp. 1204–1216, Jul 2000.

[11] U. Lee, J.-S. Park, J. Yeh, G. Pau, and M. Gerla, “Code torrent: content distribution using network coding in vanet,” in MobiShare ’06, 2006, pp. 1–5.
[12] Standard Specification for Telecommunications and Information Exchange between Roadside and Vehicle Systems—5 GHz Band Dedicated Short Range Communications (DSRC) Medium Access Control (MAC) and Physical Layer (PHY) Specifications, ASTM E2213, Nov. 2007. [Online]. Available: http://www.astm.org

[13] ITS project, Nov. 2007. [Online]. Available: http://www.its.dot.gov/index.htm

[14] K. Nakanishi, T. Umedu, T. Higashino, H. Kitaoka, H. Mori, “Synthesizing Realistic Vehicular Mobility for More Precise Simulation of Inter-vehicle Communication,” IEEE Globecom Workshops ’07, 2007.

[15] N. Oyamada, K. Mizui, “A study on an Inter-Vehicle Communication Experiments using Wireless LAN,” IEEE Conference on Advanced Communication technology, 2007.

[16] C.-X. Wang, X. Cheng, and D. Laurenson, “Vehicle-to-vehicle channel modeling and measurements: Recent advances and future challenges,” IEEE Commun. Mag., vol. 47, no. 11, pp. 96–103, Nov. 2009.

[17] S. Katti, D. Katabi, H. Balakrishnan, and M. Medard, “Symbol-level network coding for wireless mesh networks,” ACM SIGCOMM Comput.Commun. Rev., vol. 38, no. 4, pp. 401–412, 2008.

[18] Z. Yang, M. Li, and W. Lou, “Codeplay: Live multimedia streaming in vanets using symbol-level network coding,” in Network Protocols, 2010. (ICNP ’2010) Proceedings. Eighteenth International Conference on, November 2010.

[19] M. Li, Z. Yang, and W. Lou, “Codeon: Cooperative popular content distribution for vehicular networks using symbol level network coding,” IEEE Journal on Selected Areas in Communicaiton, vol. 29, no. 1, pp. 223 –235, January 2011.

[20] Holger Füßler, Jörg Widmer†, Martin Mauve‡, and Hannes Hartenstein, “A Novel Forwarding Paradigm for Position-Based Routing (with Implicit Addressing)”, IEEE Conferences on Computer Communications, 2003.

[21] H. F¨ußler, H. Hartenstein, J. Widmer, M. Mauve and W. Effelsberg, “Contention-Based Forwarding for Street Scenarios,” Proceedings of the 1st International Workshop on Intelligent Transportation (WIT) , March 2004, pp. 155-160, Hamburg, Germany

[22] H. F¨ußler, J. Widmer, M. K¨asemann, M. Mauve, and H. Hartenstein., “Contention- Based Forwarding for Mobile Ad-Hoc Networks,” Elsevier Ad Hoc Networks, vol.1, no.4, pp.351--369, Nov. 2003.

[23] Sunghyun Choi, Javier del Prado, Sai Shankar N and Stefan Mangold, “IEEE 802.11e Contention-Based Channel Access (EDCF) Performance Evaluation”, IEEE International Conference on Communications, 2003.

[24] Zhen-ning Kong, Student Member, IEEE, Danny H. K. Tsang, Senior Member, IEEE, Brahim Bensaou, Member, IEEE,and eyun Gao, “Performance analysis of IEEE 802.11e Contention-Based Channel Access”, IEEE Journal on Selected Area in Communications, vol. 22, no. 10, Dec. 2004.

[25] Pablo Serrano, Albert Banchs, Paul Patras and Arturo Azcorra, “Optimal Configuration of 802.11e EDCA for Real-Time and Data Traffic”, IEEE Transactions on Vehicular Technology, vol. 59, no. 5, Jun. 2010.

[26] Q. Yan, M. Li, Z. Yang, and W. Lou, H. Zhai, “Throughput Analysis of Cooperative Mobile Content Distribution in Vehicular Network using Symbol Level Network Coding,” IEEE Journal on Selected Areas in Communicaiton., vol. 30, no. 2, pp. 484 –492, January 2012.

[27] J. G. Proakis, “Digital communication,” August 2000.