在無線隨意網路的環境下，由於每個節點都是由電池所提供電力，而電池的電力是有限而且不易補充的，所以省電一直是個非常重要的議題。在IEEE802.11 standard中，定義了一個簡單的省電方式，藉由讓網路中的每個節點，週期性的醒來接收資訊，而後再讓沒有需要傳送封包或是接收封包的節點進入省電模式關閉騎天線的電源來達到省電的目的，但這個方法對整體頻寬以及電量的消耗並沒有做到最佳化，反而減低了整體網路的吞吐量以及延長了封包的延遲。在本文之中，我們提出了一個提供無線隨意網路（Wireless Ad Hoc Network）使用的媒介擷取控制通訊協定（medium access control protocol）。在我們的方法中，可以依據當時的網路情況去動態的調整節點溝通以及傳輸資料的時間區隔（time interval）長度，使其能依據不同的網路情形，發揮出其最好的效能。此外我們也允許節點在傳輸完之後能立即進入省電模式，減少消耗不必要的電力。
實驗結果顯示，這個方法可以大幅度的提升整體網路的吞吐量（aggregate network throughput），以及在不增加傳送延遲的狀態下，更有效率的使用節點的電力，而我們所提出的動態調整的方式，也的確可以配合網路的狀態，更進一步的改善原有通訊協定的效能。

Power efficiency is one of the most important aspects in mobile networks, and is a critical issue for almost all kinds of portable devices. Much research has been done in saving power for mobile devices. IEEE802.11 features a power saving mechanism (PSM) in Distributed Coordination Function (DCF). In PSM for DCF, time is divided into so-called beacon intervals. At the start of each beacon interval, each node must stay awake for a fixed time, called an ATIM window (Ad-Hoc Traffic Indication Map window). The nodes are required to be synchronized to ensure that all nodes wake up at the same time. During the ATIM window, if the nodes do not have data to send or receive, they will enter the doze state in the data transmission interval. The size of the ATIM window has a significant impact on energy saving and throughput achieved by the nodes. However, ad hoc networks with PSM have larger end-to-end delays in delivering packets and suffer lower throughput than the standard IEEE802.11.
This thesis introduces a new MAC protocol, NMAC, to dynamically adjust the length of the beacon interval and the ATM window. We also allow the nodes to stay awake for only a fraction of the beacon interval following the ATIM window. On the other hand, IEEE 802.11 PSM only allows for the nodes to stay either awake or sleep for the entire beacon interval. Simulation results show that the proposed protocol reduces the delays and achieves high throughput and energy efficiency on various traffic loads.

[1]Yu-Chee Tseng, Chih-Shun Hsu, and Ten-Yueng Hsieh, “Power-Saving Protocols for IEEE 802.11-Based Multi-Hop Ad Hoc Networks” ,INFOCOM 2002
[2]J. Gomez, A. T. Campbell, M. Naghshineh, and C. Bisdikian, ”PARO: supporting dynamic power controlled routing in wireless ad-hoc networks”, WINET, 2003.
[3]Ming Liu, and M.T. Liu, ” A Power-saving Scheduling for IEEE 802.11 Mobile Ad Hoc Network”, ICCNMC 2003. 2003 International Conference on , 20-23 Oct. 2003 Pages:238 – 245
[4]Feeney L.M., and Nilsson M., “Investigating the Energy Consumption of a Wireless Network Interface in an Ad Hoc Networking Environment”, INFOCOM 2001.
[5]Wei Ye, John Heidemann, and Deborah Estrin, ” An energy-efficient MAC protocol for wireless sensor networks” , INFOCOM 2002.
[6]Takeuchi S., Yamazaki K., Sezaki K., and Yasuda Y., ”An improved power saving mechanism for MAC protocol in ad hoc networks” , GLOBECOM '04. IEEE
[7]Sameh Gobriel, Rami Melhem, and Daniel Mosse’, “BLAM : An Energy-Aware MAC Layer Enhancement for Wireless Adhoc Networks”, WCNC 2005
[8]J. Chen, K. Sivalingam, and P. Argawal, “Performance comparison of battery power consumption in wireless multiple access protocols” , ACM Wireless Networks
[9]M. J. Handy, M. Haase, and D. Timmermann, “Low energy adaptive clustering hierarchy with deterministic cluster-head selection”, IEEE MWCN, 2002.
[10]S. Singh, and C. S. Raghavendra, “Power efficient mac protocol for multihop radio networks”, IEEE PIMRC, 1998.
[11]Y. Xu, J. Heidemann, and D. Estrin, “Geography-informed energy conservation for ad hoc routing”, IEEE MobiCom, 2001.
[12]HagenWoesner, Jean-PierreEbert, MortenSchlager, andAdam Wolisz, ”Power-saving mechanisms in emerging standards for wireless lans : The mac level perspective”, IEEE Personal Communications 1998
[13]Eun-Sun Jung, and Nitin H. Vaidya., “An energy efficient mac protocol for wireless lans”, INFOCOM2002
[14]Mesquit Software, Development Toolkit for Simulation and Modeling, CSIM, http://mesquite.com/documentation/index.htm
[15]Wen-Tsuen Chen, and Ting-Kai Huang, “An Adaptive Multi-Channel MAC Protocol for Wireless Ad Hoc Networks”