車聯網隨著自駕車的快速發展越趨受到重視。其中，車聯網和智慧運輸系統兩者間有著緊密相連的關係。各個國家都在積極地將通訊、感測甚至定位技術整合到系統當中。其中又以美國、日本和歐洲率先整合並發展成為世界上具有領先地位的國家。在1999年於加拿大所舉辦的智慧型運輸系統世界大會中，``Smarter, Smoother, Safer, Sooner"的會議主題。早已充分詮釋發展智慧運輸進程上的四大主軸。

本篇論文專注於探討如何設計出一套有效的演算法，配合現有針對車聯網的協議，讓未來智慧交通網路能夠更有效率的運作。為了能在提升車輛接收來自路側單元廣播訊息的成功率以及封包個數。透過路側單元之間相互合作和訊息共享實現。同個群組中通道狀況不佳的路側單元會選擇將訊息分享給狀況較好的路側單元進行廣播。讓車輛即使行駛在具有多重干擾和雜訊影響之中，依然能夠接收到來自路側單元廣播的安全性訊息。現今美國電機工程協會與歐洲電信標準協會針對安全性訊息各自制定了基本安全訊息和合作察覺訊息及分散式環境通知訊息。本篇透過軟體定義多路復用碼作為訊息共享的結構。將上述提到不同類型的安全性訊息進行合成。相較於傳統的封包形式，需要預先分配訊息長度和格式等訊息。多路復用碼是透過分隔符將訊息數據間隔開來，能夠更自由的融合訊息內容並且達到多工的資料傳輸。此外，透過網路模擬器當中的車聯網模組實現出具有合作式和訊息共享的路側單元，並將多路復用碼應用在合成廣播訊息。

With the vigorous development of autonomous cars, vehicle-to-everything (V2X) communications have received more and more attention. Among them, there is an inseparable relationship between V2X communications and the intelligent transportation system (ITS). Various advanced countries are actively integrating communication technology, sensing technology, and even positioning technology into ITS. The United States, Europe, and Japan took the lead in integrating and developing into the world's top three leading positions. In the Smarter Transportation System World Conference held in Canada in 1999, the theme of "Smarter, Smoother, Safer, Sooner" has already fully explained the four prospects of the development of intelligent transportation.

This paper focuses on how to enhance the safety of vehicles. To improve the success rate of vehicles receiving broadcast messages from RSUs, we achieve this through cooperation and a relaying-message scheme among RSUs. Roadside units with poor channel conditions in the same cluster will relay the information to RSU with better conditions for broadcasting. Allows vehicles to receive safety messages broadcast from roadside units even when driving in environments with multiple interferences and noise effects. Two standards organizations nowadays, the Institute of Electrical Engineering (IEEE) and the European Telecommunications Standards Institute (ETSI), have respectively formulated basic safety messages (BSM), cooperative awareness messages (CAM), and distributed environmental notification messages (DENM) for security messages. This article implements software-defined multiplexing codes (SDMC) as a code structure for aggregating different use cases of safety messages mentioned above. Compared with the conventional packet format, information message length and format needs to be pre-allocated. The multiplexing code separates the message data through the delimiter, which can more freely integrate the message content and multiplex the transmission. In addition, the roadside unit with cooperation and relaying messages is achieved through the DSRC/WAVE module in the network simulator 3 (NS-3) and the practical application of multiplexing codes in synthesizing broadcast messages.

[1] “Simulation of urban mobility,” Available: https://www.eclipse.org/sumo/.

[2] S. C.-H. Huang and H.-C. Wu, “Software-Defined Multiplexing Codes,” in 2015 IEEE Global Communications Conference (GLOBECOM), Dec. 2015, pp. 1–6.

[3] E. Y.-N. Sun, H.-C.Wu, and S. C.-H. Huang, “Theoretical Analysis of Various Software-Defined Multiplexing Codes,” IEEE/ACM Trans. Netw., vol. 27, no. 6, pp. 2444–2457, Nov. 2019.

[4] S. Elaine Y.-N., H.-C. Wu, H. Scott C.-H., Y. Wu, Y.-C. Kuan, and
J. Wu, “Novel Efficient Coding Scheme for Data-Rate Limited Journey-
Aware Graph-Data Transmission,” in 2019 IEEE International Symposium
on Broadband Multimedia Systems and Broadcasting (BMSB), Jun. 2019, pp.1–8.

[5] J. Benin, M. Nowatkowski, and H. Owen, “Vehicular Network simulation propagation loss model parameter standardization in ns-3 and beyond,” in 2012 Proceedings of IEEE Southeastcon, 2012, pp. 1–5.

[6] M. M. Abdellatif and O. Aly, “Studying Routing Issues in Vanets Using Ns-3 and SUMO,” Journal of Communications, vol. 17, no. 9, 2022.

[7] “Network simulator 3,” Available: https://www.nsnam.org.

[8] J. Barrachina, P. Garrido, M. Fogue, F. Martinez, J.-C. Cano, C. Calafate, and P. Manzoni, “Road Side Unit Deployment: A Density-Based Approach,” IEEE Intelligent Transportation Systems Magazine, vol. 5, pp. 30–39, 07 2013.

[9] C. Li, S. Wang, J. Yu, W. Chen, and K. Yang, “Distance-dependent V2I wireless channel characteristics and performance in 5G small cell based on measurements,” IET Communications, vol. 14, no. 20, pp. 3661–3668, 2020.

[10] R. Halili, M. Weyn, and R. Berkvens, “Comparing Localization Performance of IEEE 802.11p and LTE-V V2I Communications,” Sensors, vol. 21, no. 6, 2021.

[11] B. Aslam, F. Amjad, and C. C. Zou, “Optimal roadside units placement in urban areas for vehicular networks,” in 2012 IEEE Symposium on Computers and Communications (ISCC), 2012, pp. 423–429.

[12] H. Yu, R. Liu, Z. Li, Y. Ren, and H. Jiang, “An RSU Deployment Strategy Based on Traffic Demand in Vehicular Ad Hoc Networks (VANETs),” IEEE Internet of Things Journal, vol. 9, no. 9, pp. 6496–6505, 2022.

[13] Z. Gao, D. Chen, S. Cai, and H.-C. Wu, “Optimal and Greedy Algorithms for the One-Dimensional RSU Deployment Problem With New Model,” IEEE Transactions on Vehicular Technology, vol. 67, no. 8, pp. 7643–7657, 2018.

[14] V. Nguyen, T. T. Khanh, T. Z. Oo, N. H. Tran, E.-N. Huh, and C. S. Hong, “A Cooperative and Reliable RSU-Assisted IEEE 802.11P-Based Multi-Channel MAC Protocol for VANETs,” IEEE Access, vol. 7, pp. 107 576–107 590, 2019.

[15] V. Maglogiannis, D. Naudts, S. Hadiwardoyo, D. van den Akker, J. Marquez-Barja, and I. Moerman, “Experimental V2X Evaluation for C-V2X and ITSG5 Technologies in a Real-Life Highway Environment,” IEEE Transactions on Network and Service Management, vol. 19, no. 2, pp. 1521–1538, 2022.

[16] H. Arbabi and M. C. Weigle, “Highway mobility and vehicular ad-hoc networks in ns-3,” in Proceedings of the 2010 Winter Simulation Conference, 2010, pp. 2991–3003.

[17] J. Vales-Alonso, F. Vicente-Carrasco, and J. Alcaraz, “Optimal configuration of roadside beacons in V2I communications,” Computer Networks, vol. 55, no. 14, pp. 3142–3153, 2011.

[18] D. Krajzewicz, J. Erdmann, M. Behrisch, and L. Bieker-Walz, “Recent Development and Applications of SUMO - Simulation of Urban MObility,” International Journal On Advances in Systems and Measurements, vol. 3,4,12 2012.

[19] C. Lochert, B. Scheuermann, C. Wewetzer, A. Luebke, and M. Mauve, “Data Aggregation and Roadside Unit Placement for a Vanet Traffic Information System,” 2008, p. 58–65.

[20] V. Kolici, T. Oda, E. Spaho, L. Barolli, M. Ikeda, and K. Uchida, “Performance Evaluation of a VANET Simulation System Using NS-3 and SUMO,” in 2015 IEEE 29th International Conference on Advanced Information Networking and Applications Workshops, 2015, pp. 348–353.

[21] A. Kchiche and F. Kamoun, “Centrality-based Access-Points deployment for vehicular networks,” in 2010 17th International Conference on Telecommunications, 2010, pp. 700–706.

[22] M. Fogue, P. Garrido, F. Martinez, J.-C. Cano, C. Calafate, and P. Manzoni, “A Realistic Simulation Framework for Vehicular Networks,” 03 2012.

[23] C. Tripp-Barba, M. Mateos, P. Soto, A. Mohamad-Mezher, and M. Aguilar-Igartua, “Smart city for VANETs using warning messages, traffic statistics and intelligent traffic lights,” 06 2012, pp. 902–907.

[24] S. Maaloul, H. Aniss, M. Kassab, and M. Berbineau, “Classification of c-its services in vehicular environments,” IEEE Access, vol. 9, pp. 117 868–117 879, 2021.

[25] Y. Liang, Z. Wu, H. Yang, and Y. Wang, “A Novel Framework for Road Side Unit Location Optimization for Origin-Destination Demand Estimation,” IEEE Transactions on Intelligent Transportation Systems, vol. 23, no. 11, pp.21 113–21 126, 2022.

[26] J. Gozalvez, M. Sepulcre, and R. Bauza, “IEEE 802.11p vehicle to infrastructure communications in urban environments,” IEEE Communications Magazine, vol. 50, no. 5, pp. 176–183, 2012.

[27] V. Milanes, J. Villagra, J. Godoy, J. Simo, J. Perez, and E. Onieva, “An Intelligent V2I-Based Traffic Management System,” IEEE Transactions on Intelligent Transportation Systems, vol. 13, no. 1, pp. 49–58, 2012.

[28] V. Shivaldova, A. Winkelbauer, and C. F. Mecklenbr¨auker, “Vehicular Link Performance: From Real-World Experiments to Reliability Models and Performance Analysis,” IEEE Vehicular Technology Magazine, vol. 8, no. 4, pp. 35–44, 2013.

[29] K. Abboud, H. A. Omar, and W. Zhuang, “Interworking of DSRC and Cellular Network Technologies for V2X Communications: A Survey,” IEEE Transactions on Vehicular Technology, vol. 65, no. 12, pp. 9457–9470, 2016.

[30] J.-K. Bae, M.-C. Park, E.-J. Yang, and D.-W. Seo, “Implementation and Performance Evaluation for DSRC-Based Vehicular Communication System,” IEEE Access, vol. 9, pp. 6878–6887, 2021.

[31] M. Noor-A-Rahim, G. G. M. N. Ali, H. Nguyen, and Y. L. Guan, “Performance Analysis of IEEE 802.11p Safety Message Broadcast With and Without Relaying at Road Intersection,” IEEE Access, vol. 6, pp. 23 786–23 799, 2018.