無線感測網路已經被廣泛運用在不同的應用上，且其與標準的WLAN應用相比具有明顯的不同的特色與需求。在無線感測網路中的感測器通常是以電池來供電，且基本上電池是無法更換或充電，因此在無線感測網路中能量管理會是一項重要的挑戰。感測節點可切換至睡眠模式以達到節省能量的目的。然而，處於睡眠模式會導致處理功能的降低以及較長的延遲時間。換句話說，能量消耗、成功送達率與自來源節點至目標節點之封包延遲之間必須做明智的折衷。在本篇論文的第一部分中，我們提出一模擬模型去評估在不同的流量模型和緩衝器大小下T-MAC在單次跳躍無線感測網路中的效能。單次跳躍無線感測網路使用星狀拓撲。我們考慮了四種不同的流量模型: Poisson、Erlang、MMPP-Exponential 和MMPP-Weibull。感興趣之效能指標包含週期機率、能量消耗、平均進接延遲、成功送達率與佇列延遲。在論文的第二部分中，我們提出兩種MAC協定，分別稱為T-MAC-a和T-MAC-b，這些協定皆為T-MAC的延伸。我們提出的二協定運用了優先權機制、緩衝器臨界機制、壅塞避免的路由機制和宣佈機制的某些組合方式。我們提出另一模擬模型去評估在不同的流量下S-MAC, T-MAC, T-MAC-a 和T-MAC-b 在多次跳躍無線感測網路中的效能。此外，我們同時研究了T-MAC-b在不同的流量模型的效能。我們考慮兩種封包型態:高優先權的緊急封包和低優先權的非緊急封包。多次跳躍無線感測網路使用網格拓撲。感興趣之效能指標包含能量消耗、平均服務延遲、端對端延遲、成功送達率、傳遞比率和封包遺失率。藉由廣泛的模擬，結果顯示我們所提出的協定勝過S-MAC以及 T-MAC。其中電腦模擬程式是以C語言自行撰寫。

Wireless sensor networks have been used for a wide range of applications which are greatly different from standard WLAN applications in terms of characteristics and requirements. Since sensors in wireless sensor networks are usually battery-operated and basically batteries cannot be replaced or recharged, the energy management becomes a challenge in wireless sensor networks. The sensor nodes may transit to sleep mode to conserve energy. However, sleep mode leads to a reduced operation capacity and a larger latency. In other words, a wise trade-off must be made among energy consumption, throughput, and the packet delay form source node to the sink node. In the first part of this thesis, we present a simulation model to evaluate the performance of T-MAC in single-hop wireless sensor networks under different traffic models and buffer sizes. The single-hop wireless sensor network has a star topology. We consider four different traffic models: Poisson, Erlang, MMPP-Exponential and MMPP-Weibull. The performance measures of interest are cycle probability, energy consumption, average access delay, throughput, and queueing delay. In the second part of this thesis, we propose two MAC protocols called T-MAC-a and T-MAC-b, which are extensions of T-MAC. The proposed MAC protocols utilize some combination of the priority mechanism, the buffer threshold scheme, the congestion avoidance routing scheme, and the announce scheme. We present a simulation model to evaluate the performance of S-MAC, T-MAC, T-MAC-a and T-MAC-b in multi-hop wireless sensor networks under different traffic loads. Furthermore, we study the performance of T-MAC-b under different traffic models. We consider two classes of packets: high-priority emergency packets and low-priority non-emergency packets. The multi-hop wireless sensor network has a grid topology. The performance measures of interest are energy consumption, average service delay, end-to-end delay, throughput, delivery ratio, and drop probability. With extensive simulation experiments, it is shown that the proposed protocols outperform T-MAC and S-MAC. The simulation programs are written in C language.

References
[1] I.F. Akyildiz, W. Su, Y. Sanjarasubramaniam, and E. Cayirci. “A Survey on Sensor Networks,” IEEE Comm. Mag., pp.102-114, Aug. 2002.
[2] W. Ye, J. Heidemann, and D. Estrin, “An Energy Efficient MAC Protocol for Wireless Sensor Networks,” IEEE INFOCOM, New York. NY., June 2002.
[3] W. Ye, J. Heidemann, and D. Estrin, “Medium Access Control with Coordinated Adaptive Sleeping for Wireless Sensor Networks,” IEEE/ACM Transactions on Networking, vol. 12, pp. 493-506, Jun. 2004.
[4] H. Li and P. D. Mitchell, “Reservation Packet Medium Access Control for Wireless Sensor Networks,” PIMRC 2008, pp. 1-5, 2008.
[5] T. V. Dam and K. Langendoen, “An Adaptive Energy-Efficient MAC Protocol for Wireless Sensor Network,” The 1st international conference on Embedded networked sensor systems, pp. 171 – 180, Nov. 2003.
[6] G. P. Halkes, T. V. Dam, and K. G. Langendoen, “Comparing Energy-Saving MAC Protocols for Wireless Sensor Networks,” Mobile Networks & Applications, vol. 10, pp. 783-791, Oct 2005.
[7] K. T. Kim, W. J. Choi, and H. Y. Youn, “CA-MAC: Context Adaptive MAC Protocol for Wireless Sensor Networks,” CSE '09, pp. 344-349, 2009.
[8] O. Banimelhem and S. Khasawneh, “Grid-Based Multi-Path with Congestion Avoidance Routing (GMCAR) Protocol for Wireless Sensor Networks,” ICT '09, pp. 131-136, 2009.
[9] R. Akl and U. Sawant, “Grid-Based Coordinated Routing in Wireless Sensor Networks,” CCNC 2007, pp. 860-864, 2007.
[10] Z. Ye, H. Chen, and J. Lingge, “Modeling the S-MAC Protocol in Single-Hop Wireless Sensor Networks,” ICC '08, pp. 317-321, 2008.
[11] S. Sung, H. Kang, E. Kim, and K. Kim, “Energy Consumption Analysls of S-MAC Protocol in Single-Hop Wireless Sensor Networks,” APCC '06, pp. 1-5, 2006.
[12] B. P. Crow, I. Widjaja, L. G. Kim, and P. T. Sakai, “IEEE 802.11 Wireless Local Area Networks,” IEEE Comm. Mag., vol. 35, pp. 116-126, 1997.
[13] “IEEE Standard for Information Technology-Telecommunications and Information Exchange Between Systems-Local and Metropolitan Area Networks-Specific Requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” IEEE Std 802.11-2007 (Revision of IEEE Std 802.11-1999), pp. C1-1184, 2007.
[14] V. Bharghavan, A. Demers, S. Shenker, and L. Zhang, “MACAW: A Media Access Protocol for Wireless Lans,” Proc. ACM SIGCOMM, London, U.K., pp. 212-225, Sept. 1994.
[15] G. Bianchi, “Performance Analysis of the IEEE 802.11 Distributed Coordination Function,” IEEE Journal on Selected Areas in Communications, vol. 18, pp. 535-547, 2000.
[16] G. Anastasi and L. Lenzini, “QoS Provided by the IEEE 802.11 Wireless LAN to Advanced Data Applications: A Simulation Analysis,” Wireless Networks, vol. 6, pp. 99-108, 2000.