無線感測網路是一種專門用來收集資訊的網路，此種網路通常包含數千個節點，所有節點都是由電池供電，在這些節點被散佈到環境之後，要將這些節點重新回收充電是很困難的甚至是不可能的，因此節省能源是無線感測網路中一個很重要的訴求。
本篇論文提出新媒體存取控制協定去改善無線傳輸的效率，使其更省電更適合無線感測網路。在無線傳輸中會造成能源浪費的常見原因有偷聽(overhearing)、空轉(idle listening)、碰撞(collision)。
另外有些論文希望除了省電，還能改善傳輸效率，改善的目標有資料傳輸延遲時間(latency)、傳輸速率(throughput)、公平性(fairness)。
本篇論文提出新媒體存取控制協定希望能夠節省能源且改善傳輸效率，我們利用靜態無線感測網路中的傳輸特性達成這兩個目標，在許多無線感測網路的應用當中，感測器節點不會移動且收集到資料之後都是傳回基地台，所以新媒體存取控制協定在網路剛佈建完成時，由基地台發動初始程序，初始所有感測器節點的高度，所謂高度就是節點到基地台的節點計數(hop count)，之後讓高度差為1的節點工作時間連續，改善資料傳輸延遲時間，接著新媒體存取控制協定讓高度相同的節點採用錯開的工作排程表(alternative wakeup schedules)，讓高度相同的節點在不同的時間工作，降低碰撞發生機率，因此將新媒體存取控制協定取名為Alternative MAC，以下簡稱AMAC。
效能評估的結果顯示AMAC可以依據每個感測器節點的高度與編號為感測器節點安排適當的工作排程表，同時達到低資料傳輸延遲與降低碰撞機率的效果，達到更省電的效果。

A wireless sensor network consists of hundreds or thousands of sensor nodes and is usually deployed in an unprotected environment to collect the needed information. As sensor nodes are battery-powered and are difficult to get recharged after distribution, energy efficiency thus becomes a basic and critical issue. The limited energy resources of sensor nodes are usually wasted through overhearing, idle listening and collision.
Energy efficiency is important and so is transmission efficiency which can be attained through improvement on latency, throughput and load fairness.
Based on the above observation, this paper presents a new medium access control (MAC) protocol which utilizes the special features of the wireless sensor network to achieve power efficiency and low latency. The proposed protocol lets the base station start an initial process in which the height of all sensor nodes are set when the network is first deployed. The height of a node refers to its hop counts to the base station. The active time of nodes whose height difference = 1 is set to be continuous to reduce transmission latency, while the active time of nodes with the same height will stagger to avoid collision, i.e., to reduce the probability of simultaneous transmission. The proposed protocol allows neighbor nodes of the same height to have alternative wakeup schedules in order to avoid collision, so we name the proposed protocol Alternative MAC (AMAC). 
Experimental evaluation shows that with the specific design and function of different heights and numbers of the sensor nodes, AMAC is able to arrange favorable job schedules to facilitate data transmission with decreased transmission latency and packet collision probability.

目   錄

中文摘要	I
英文摘要	III
目   錄	V
圖 表 目 錄	VII
第一章 緒論	1
1.1 前言	1
1.2 章節架構	5
第二章 相關研究背景	6
2.1 背景知識	6
2.2-SMAC	10
2.3-DMAC	17
2.4-TMAC	19
第三章 新媒體存取控制協定(AMAC)之架構	21
3.1 研究動機	21
3.2 AMAC之構想	23
3.2.1 縮短空轉時間	23
3.2.2 減少資料傳輸延遲時間	24
3.2.3 避免碰撞	27
3.3 計算排程表之演算法	29
3.3.1 初始編號	31
3.3.2 初始高度	34
3.3.3 計算排程表	37
3.3.4 重新排程	43
第四章 效能評估	44
4.1 直線傳輸	46
4.2 隨機散佈拓撲	48
第五章 結論	51
第六章 未來工作	53
參考文獻	55


 
圖 表 目 錄

圖 1.1：無線感測網路基本架構	2
圖 2.1：無線傳輸非理想效應之偷聽示意圖	7
圖 2.2：無線傳輸非理想效應之碰撞示意圖	8
圖 2.3：RTS/CTS/DATA/ACK避免碰撞機制	11
圖 2.4：SMAC傳輸情形示意圖	12
圖 2.5：Adaptive listening 機制示意圖步驟一	14
圖 2.6：Adaptive listening 機制示意圖步驟二	14
圖 2.7：Adaptive listening 機制示意圖步驟三	15
圖 2.8：Adaptive listening 機制示意圖步驟四	15
圖 2.9：SMAC加入Adaptive listening.後傳輸情形示意圖	16
圖 2.10：DMAC錯開的排程表之示意圖	17
圖 2.11：DMAC傳輸情形示意圖	18
圖 2.12：TMAC動態週期排程表示意圖	20
圖 3.1：不同高度的感測器節點之工作排程表	25
圖 3.2：傳輸過程示意圖	25
圖 3.3：修改後的工作排程表	28
圖 3.4：感測器節點工作流程圖	30
圖 3.5：感測器節點初始編號流程圖	33
圖 3.6：感測器節點初始高度流程圖	36
圖 3.7：感測器節點週期時間劃分示意圖	37
圖 3.8：感測器節點運作狀況示意圖(工作週期為10%)	39
圖 3.9：感測器節點運作狀況示意圖(工作週期為40%)	41
圖 4.1：資料傳輸平均延遲時間(直線傳輸)	46
圖 4.2：隨機散佈拓樸	48
圖 4.3：資料傳輸平均延遲時間(隨機散佈拓樸)	49
圖 4.4：各種媒體存取控制協定傳輸時碰撞次數	50

[1]	D. P. Agrawal, and Q. A. Zeng, Introduction to Wireless and Mobile Systems, 2/e, Thomson, Mar. 2005, pp.303-357.
[2]	Y. Wei, J. Heidemann, and D. Estrin, “Medium Access Control with Coordinated Adaptive Sleeping for Wireless Sensor Networks,” IEEE/ACM Trans. on Networking, Vol. 12, No. 3, pp. 493-506, June 2004.
[3]	G. Lu, B. Krishnamachari, and C. S. Raghavendra, “An Adaptive Energy-Efficient and Low Latency MAC for Data Gathering in Wireless Sensor Networks,” Proc. 18th Parallel and Distributed Processing Symp., Apr. 2004, pp. 224-231.
[4]	T. van Dam and K. Langendoen, “An Adaptive Energy-Efficient MAC Protocol for Wireless Sensor Networks,” Proc. 1st Int’l Conf. on Embedded Networked Sensor Systems, Nov. 2003, pp. 171-180.
[5]	T. Aonishi, T. Matsuda, and S. Mikami, H. Kawaguchi, C. Ohta, and M. Yoshimoto, “Impact of Aggregation Efficiency on GIT Routing for Wireless Sensor Networks,” Proc. 2006 Int’l Conf. on Parallel Processing Workshops, Aug. 2006, pp. 151-158.
[6]	A. El-Hoiydi, J.-D. Decotignie and J. Hernandez, “Low Power MAC Protocol for Infrastructure Wireless Sensor Networks,” Proc. 5th European Wireless Conf., Feb. 2004, pp. 563-569.
[7]	S. Coleri, A. Puri, and P. Varaiya, “Power Efficient System for Sensor Networks,” Proc. IEEE 8th Int’l Symp. on Computers and Communication, June 2003, Vol. 2, pp. 837-842.
[8]	R. Kannan, R. Kalidindi, and S. S. Iyengar, “Energy and Rate based MAC protocol for Wireless Sensor Networks,” ACM Special Interest Group on Management of Data Record, Dec. 2003, Vol. 32, No. 4, pp. 60-65.
[9]	V. Rajendran, K. Obraczka, and J. J. Garcia-Luna-Aceves, “Energy-Efficient, Collision-Free Medium Access Control for Wireless Sensor Networks,” Proc. 1st Int’l Conf. on Embedded Networked Sensor Systems, Nov. 2003, pp. 181-192.

[10]	J. Elson, L. Girod, and D. Estrin, “Fine-Grained Network Time Synchronization Using Reference Broadcasts,” Proc. ACM 5th Symp. on Operation Systems Design and Implementation, Winter 2002, Vol. 36, pp. 147-163.
[11]	J. Arias, E. Santos, I. Marin, et al., “Node Synchronization in Wireless Sensor Networks,” Wireless and Mobile Communications, pp. 50-54, July 2006.
[12]	S. Raje, and Q. Liang, “Time Synchronization in Network-Centric Sensor Networks,” Proc. IEEE 2007 on Radio and Wireless Symp., Jan. 2007, pp. 333-336.