物聯網是由多個異質網路節點所組合的網路，所以會出現較為複雜的壅塞問題且出現的頻率較高。6LoWPAN以及RPL是網際網路工程任務組標準化的第六代網際網路通訊協定適應層，以及繞徑協定用於低功耗的無線個人網路，RPL使用目的導向的有向無環圖作為網路拓樸並以收集點作為目的地。透過實驗我們發現RPL在網路壅塞發生時並不能達到很好的分散流量的效果以致網路效能下降。本論文對壅塞問題發生在RPL的環境下進行研究，在此論文提出的方法中，我們設計一個使用賽局理論的父節點切換程序。當壅塞發生時，每個節點透過此程序來進行父節點選擇來使整個網路達到納許均衡。經過此程序後若仍無法消除壅塞則使用傳輸率縮減機制來降低來源節點之傳輸率。經由模擬實驗結果，相較於ContikiRPL我們的方法使得封包掉落率下降兩倍並提升兩倍的吞吐率但會些微提升節點的平均跳數至根節點。

In wireless sensor networks (WSNs), the presence of congestion can increase the ratio of packet loss, energy inefficiency and reduction of the network throughput. Especially, this situation will be more complex in Internet of Things (IoT) environ-ments, which is composed of thousands of heterogeneous nodes. RPL is an IPv6 rout-ing protocol in low power and lossy networks standardized by IETF. However, the RPL can induce problems like frequently change parent and throughput degrade under network congestion. In this paper, we address the congestion problem between child nodes and parent nodes in RPL-enabled networks, which typically consist of low power and resource constraint devices. We use game theory strategy to design a par-ent-change procedure which decides how nodes changing their next hop node toward sink to mitigate the effect of network congestion. Comparing to the ContikiRPL im-plementation, the simulation results show that our protocol can achieve more than two times improvement in loss rate and throughput with a few average hop count increas-ing.

[1] C. Basaran, K. D. Kang, and M. H. Suzer, “Hop-by-Hop Congestion Control and Load Balancing in Wireless Sensor Networks”, Proceedings of the 35th Annual IEEE Conference on Local Computer Networks, pp. 448-455, Denver, Colorado, USA, Oct. 2010.
[2] M. M. Bhuiyan, I. Gondal, and J. Kamruzzaman, “LACAR: Location Aided Congestion Aware Routing in Wireless Sensor Networks”, Proceedings of Wireless Communications and Networking Conference, pp. 1-6, Sydney, Aus-tralia, Apr. 2010.
[3] D. S. J. D. Couto, D. Aguayo, J. Bicket, and R. Morris, “A High-Throughput Path Metric for Multi-hop Wireless Routing”, Proceedings of the 9th Annual International Conference on Mobile Computing and Networking, pp. 134-146, San Diego, CA, USA, Sep. 2003.
[4] S. Deering and R. Hinden, “Internet Protocol, Version 6 (IPv6) Specification”, RFC 2460 (Proposed Standard), Internet Engineering Task Force, Dec. 1998. http://www.ietf.org/rfc/rfc2460.txt
[5] V. S. Deshande, P. P. Chavan, V. M. Wadhai, and J. B. Helonde, “Congestion Control in Wireless Sensor Networks by using Differed Reporting Rate”, Pro-ceedings of the 2nd IEEE World Congress on Information and Communication Technologies, pp. 209-213, Trivandrum, India, Nov. 2012.
[6] D. F. J. Flora, V. Kavitha, and M. Muthuselvi, “A Survey on Congestion Con-trol Techniques in Wireless Sensor Networks”, Proceedings of the International Conference on Emerging Trends in Electrical and Computer Technology, pp. 1146-1149, Tamil Nadu, India, Mar. 2011.
[7] N. Gershenfeld, R. Krikorian, and D. Cohen, “The Internet of Things”, Scien-tific American, pp. 76-81, Oct. 2004.
[8] M. T. Lazarescu, “Design of a WSN Platform for Long-Term Environmental Monitoring for IoT Applications”, IEEE Journal on Emerging and Selected Topics in Circuits and Systems, Vol. 3, No. 1, pp. 45-54, Mar. 2013.
[9] G. Li and J. Li, “Global Weighted Fairness Guaranteed Congestion Avoidance Protocol for Wireless Sensor Networks”, Proceedings of IEEE INFOCOM, pp. 601-605, Shanghai, China, Apr. 2011.
[10] V. Michopoulos, L. Guan, G. Oikonomou, and I. Phillips, “A Comparative Study of Congestion Control Algorithms in IPv6 Wireless Sensor Networks”, Proceedings of International Conference on Distributed Computing in Sensor Systems and Workshops, pp. 1-6, Barcelona, Spain, Jun 2011.
[11] D. Monderer and L. S. Shapley, "Potential games", Games and Economics Behavior, Vol. 14, No. 1, pp. 124-143, Jan. 1996.
[12] G. Montenegro, N. Kushalnagar, J. Hui, and D. Culler, “Transmission of IPv6 Packets over IEEE 802.15.4 Networks”, RFC 4944 (Proposed Standard), In-ternet Engineering Task Force, Sep. 2007. http://tools.ietf.org/html/rfc4944/
[13] F. Osterlind, A. Dunkels, J. Eriksson, N. Finne, and T. Voigt, “Cross-Level Sensor Network Simulation with COOJA”, Proceedings of the 31st IEEE Conference on Local Computer Networks, pp. 641-648, Tampa, Florida, USA, Nov. 2006.
[14] D. Patil and S. N. Dhage, “Priority-based Congestion Control Protocol (PCCP) for Controlling Upstream Congestion in Wireless Sensor Network”, Proceed-ings of International Conference on Communication, Information & Computing Technology, pp. 1-6, Mumbai, India, Oct. 2012.
[15] H. M. Rathod and B. V. Buddhadev, “Comparative Study of Congestion Con-trol Techniques for Wireless Sensor Network”, Proceedings of Nirma Univer-sity International Conference on Engineering, pp. 1-5, Ahmedabad, Gujarat, India, Dec. 2011.
[16] F. Ren, T. He, S. K. Das, and C. Lin, “Traffic-Aware Dynamic Routing to Al-leviate Congestion in Wireless Sensor Networks”, IEEE Transactions on Par-allel and Distributed Systems, Vol. 22, No. 9, pp. 1585-1598, Sep. 2011.
[17] J. P. Sheu, L. J. Chang, and W. K. Hu, “Hybrid Congestion Control Protocol in Wireless Sensor Networks”, Journal of Information Science and Engineering, Vol. 25, No. 4, pp. 1103-1119, Aug. 2009.
[18] J. P. Sheu, C. C. Chang, and W. S. Yang, “A Distributed Wireless Sensor Net-work Testbed with Energy Consumption Estimation”, International Journal of Ad Hoc and Ubiquitous Computing, Vol. 6, No. 2, pp. 63-74, Jul. 2010.
[19] S. Sridevi, M. Usha, and G. P. A. Lithurin, “Priority Based Congestion Control for Heterogeneous Traffic in Multipath Wireless Sensor Networks”, Proceed-ings of IEEE International Conference on Computer Communication and In-formatics, pp. 1-5, Coimbatore, India, Jan. 2012.
[20] P. Thubert, “Objective Function Zero for the Routing Protocol for Low-Power and Lossy Networks”, RFC6552 (Proposed Standard), Internet Engineering Task Force, Mar. 2012. http://tools.ietf.org/html/rfc6552
[21] N. Tsiftes, J. Eriksson, and A. Dunkels, “Poster Abstract: Low-Power Wireless IPv6 Routing with ContikiRPL”, Proceedings of the 9th ACM/IEEE In-ternational Conference on Information Processing in Sensor Networks, pp. 406-407, Stockholm, Sweden, Apr. 2010.

[22] J. Vasseur, M. Kim, K. Pister, N. Dejean, and D. Barthel, “Routing Metrics Used for Path Calculation in Low-Power and Lossy Networks”, RFC 6551 (Proposed Standard), Internet Engineering Task Force, Mar. 2012. http://tools.ietf.org/html/rfc6551/
[23] J. Vasseur, N. Agarwal, J. Hui, Z. Shelby, P. Bertrand, and C. Chauvenet, “RPL : The IP Routing Protocol Designed for Low Power and Lossy Net-works”, Internet Protocol for Smart Objects Alliance, pp. 1-20, Apr. 2011.
[24] C. Y. Wan, S. B. Eisenman, and A. T. Campbell, “CODA: Congestion Detec-tion and Avoidance in Sensor Networks”, Proceedings of the 1st International Conference on Embedded Networked Sensor Systems, pp. 266-279, Los Ange-les, CA, USA, Nov. 2003.
[25] C. Y. Wan, S. B. Eisenman, A. T. Campbell, and J. Crowcroft, “Siphon: Over-load Traffic Management using MultiRadio Virtual Sinks in Sensor Networks”, Proceedings of the 3rd International Conference on Embedded Networked Sensor Systems, pp. 116-129, San Diego, CA, USA, Nov. 2005.
[26] T. Winter, P. Thubert, A. Brandt, J. Hui, R. Kelsey, P. Levis, K. Pister, R. Struik, J. Vasseur, and R. Alexander, “RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL)”, RFC 6550 (Proposed Standard), In-ternet Engineering Task Force, Mar. 2012. http://tools.ietf.org/html/rfc6550/