透過無線電波傳輸資訊所發展的無線傳輸技術已經行之有年。其中以IEEE 802.11所制定的DCF機制最具盛名。然而在水下聲納感測網路的環境中，聲波的傳輸將造成較低的傳輸速率與巨大的傳播延遲(Propagation Delay)。所以原本適用於無線電波的媒介存取控制(MAC)協定，在水下環境將變得不適用。本論文主要探討在水中高傳播延遲的特性下，使用IEEE 802.11 DCF四向交握機制時，無線傳輸設備如何設定持續抑制時間(NAV)，以避免傳輸碰撞。並提出一套Underwater Network Allocation Vector(UNAV)機制，本機制除了考量收送端之間的傳播延遲外，並且針對不同的干擾者和收送端之間傳播延遲的不同，進行彈性的設定NAV，來實現平行傳輸的概念，並進而減少網路中傳輸延遲的時間，來達到提升網路的效能。最後在實驗的部分，本篇論文與IEEE 802.11 DCF機制作比較。實驗結果發現本篇論文所提出的UNAV協定，在網路傳輸延遲與傳輸效能的表現上有顯著的改善。

Wireless technology has been developed and used for many years. Due to the nature of water, instead of radio wave, sound wave is used for underwater transmission. Recently, IEEE 802.11 DCF is the most famous MAC protocol but is not suitable for underwater scenarios. Therefore, this proposal mainly focuses on how to modify the Network Allocation Vector (NAV) setting for underwater acoustic network.

第1章	緒論	1
1.1	前言	1
1.2	研究動機與目的	3
1.3	研究方法	4
1.4	論文架構	5
第2章	相關文獻	6
2.1	水下聲波感測網路	6
第3章	預備知識	8
3.1	問題描述	8
3.1.1 NAV Duration Setting Problem	8
3.1.2 False Blocking problem	10
3.2	Spreading Loss Model	12
第4章 階梯式網路配置向量機制(Stair-like NAV mechanism )	14
4.1	基本理念	14
4.2	階梯式網路配置向量機制(Stair-like NAV mechanism )	17
4.2.1 NAVRTS設置	17
4.2.2 NAVCTS設置	19
4.2.3 NAVDATA設置	23
4.3	階梯式網路配置向量機制更新方法(Stair-like NAV mechanism update Scheme)	25
第5章	網路效能模擬	32
5.1 實驗場景及參數設定	32
5.2 實驗結果及分析	33
第6章	結論	38
參考文獻	39
附錄 英文論文	43

圖目錄
圖 1: 隱藏節點示意圖。	1
圖 2: 802.11DCF中RTS/CTS/DATA/ACK交換時序與NAV設定示意圖。	2
圖 3: A、B節點和S節點之間的不同傳播延遲。	4
圖 4: 無線電波和聲波所造成的傳播延遲差異。	8
圖 5: 不考慮傳播延遲設置NAV示意圖。	9
圖 6: 使用最大傳播延遲設置NAV示意圖。	10
圖 7: False Blocking Problem示意圖。	10
圖 8: False Blocking Problem時序圖。	12
圖 9: 無線電波和聲波發生控制封包碰撞之情形。	15
圖 10: Stair-like NAV Mechanism 核心理念。	16
圖 11: 利用階梯式網路配置向量舒緩False Blocking Problem。	16
圖 12: RTS/CTS/DATA的NAV持續抑制時間設定。	17
圖 13: RTS 封包格式。	18
圖 14: CTS 封包格式。	20
圖 15: NAVCTS設置未考量與鄰居節點傳播延遲時間示意圖。	21
圖 16: 干擾節點在收到封包後，動態調整NAV。	22
圖 17: NAVCTS設置考量與鄰居節點傳播延遲時間示意圖。	22
圖 18: NAVDATA設置未考量與鄰居節點傳播延遲時間示意圖。	23
圖 19: NAVDATA設置考量與鄰居節點傳播延遲時間示意圖。	24
圖 20: Stair-like NAV mechanism特色。	24
圖 21: NAVRTS持續抑制時間無法被NAVCTS和NAVDATA所更新。	26
圖 22: Stair-like NAV Update Scheme流程圖。	28
圖 23: 鄰居節點收到同一傳輸對封包並更新。	29
圖 24: 鄰居節點收到不同傳輸對封包並不更新。	30
圖 25: 網格狀拓樸。	32
圖 26: 節點距離與Average MAC Delay之關係。	34
圖 27: 節點距離與網路效能之關係。	35
圖 28: 封包錯誤率與Average MAC Delay之關係。	36
圖 29: 封包錯誤率與網路效能之關係。	37

表目錄
表 一.實驗的模擬參數設定	33

[1]	IEEE Std 802.11-1999, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, IEEE, Aug. 1999.
[2]	N. Chirdchoo, W.-S. Soh, and K. C. Chua, “MACA-MN: A MACA-based MAC protocol for underwater acoustic networks with packet train for multiple neighbors,” in Proceedings of the IEEE Vehicular Technology Conference (VTC), May 2008, pp. 46–50.
[3]	N. Chirdchoo, W.-S. Soh, and K. C. Chua, “RIPT: A receiver-initiated reservation-based protocol for underwater acoustic networks,” IEEE Journal on Selected Areas in Communications (JSAC), vol. 9, no. 9, pp. 1744–1753, Sep. 2008.
[4]	M. Molins, M. Stojanovic, “Slotted FAMA a MAC protocol for underwater acoustic networks,” in Proceedings of the IEEE OCEANS, September 2006, pp. 1–7.
[5]	N. Chirdchoo, W.-S. Soh, and K. C. Chua, “MACA-MN: A MACA-based MAC protocol for underwater acoustic networks with packet train for multiple neighbors,” in Proceedings of the IEEE Vehicular Technology Conference (VTC), May 2008, pp. 46–50.
[6]	H. H. Ng, W. S. Soh, and M. Motani, “MACA-U: A Media Access Protocol for Underwater Acoustic Networks” in Proceeding of the IEEE Global Telecommunication Conference (Globecom), Nov. 2008.
[7]	E. Cheng, B. Lin, F. Yuan and J. Deng, “A Modified Multiple Access Protocol for Underwater Acoustic Networks,” in Proceeding of the WNIS, May 2009, pp.46-49.
[8]	Y. Noh, P. Wang, U. Lee, D. Torres and M. Gerla, “DOTS: A Propagation Delay-aware Opportunistic MAC Protocol for Underwater Sensor Networks,” in Proceeding of the ICNP, May 2010, pp.183-192. 
[9]	Z. Azar and M. Taghi Manzuri, “A Latency-Tolerant MAC Protocol for Underwater Acoustic Sensor Networks,” in Proceeding of the ICCAS, Nov 2010, pp.849-854.
[10]	D. Fang, Y. Li, H. Huang and L. Yin, “A CSMA/CA-based MAC Protocol for Underwater Acoustic Networks,”  in Proceeding of the WICOM, May 2010, pp.1-4.
[11]	X. Guo, M. R. Frater, and M. Ryan, “An adaptive propagation-delay-tolerant MAC protocol for underwater acoustic sensor networks,” in OCEANS Europe, 2007, pp. 1–5.
[12]	X. Guo, M. R. Frater, and M. Ryan, “A propagation-delay-tolerant collision avoidance protocol for underwater acoustic sensor networks,” in Proceedings of the OCEANS, May 2007, pp. 1–6.
[13]	Y. Zhong, J. Huang, J. Han, “A Delay-tolerant MAC Protocol with Collision Avoidance for Underwater Acoustic Networks,” in Proceedings of the International Conference on Wireless Communications, Networking and Mobile Computing (WiCOM), 2009, pp. 1–4.
[14]	X. Guo, M. Frater, and M. Ryan, “Design of a propagation-delay-tolerant MAC protocol for underwater acoustic sensor networks,” IEEE Journal of Oceanic Engineering, vol. 34, pp. 170–180, 2009.
[15]	D. Shin and D. Kim, “A Dynamic NAV Determination Protocol in 802.11 based Underwater Networks” in proceeding of the IEEE International Symposium on Wireless Communication Systems, Oct. 2008.
[16]	Lawrence E. Kinsler (Author), Austin R. Frey, B. Coppens, V. Sanders;"Fundamentals of Acoustics," Wiley, 4 edition,1999.
[17]	S. Ray and D. Starobinski, “On False Blocking in RTS/CTS-Based Multi-hop Wireless Networks,” in Proceedings of the TVT, May 2007, pp. 849-862.
[18]	E. M. Sozer, M. Stojanovic, and J. G. Proakis. Design and Simulation of an Underwater Acoustic Local Area Network. Northeastern University, Communications and Digital Signal Processing Center, Boston, Massachusetts,, 1999.
[19]	G. Xie, J. Gibson, and L. Diaz-Gonzalez. Incorporating Realistic Acoustic Propagation Models in Simulation of Underwater Acoustic Networks: A Statistical Approach. In MTS/IEEE Oceans’06, Boston,MA, September 2006.