水下移動式感測器網路中具碰撞避免之媒體存取控制協定

由於全球化的氣候變遷，水下網路越來越受到重視。水下網路的傳輸方式是以聲波做為通訊載波，相較於陸地上的無線電波傳輸，水下網路的傳輸速度會慢上許多。此外洋流亦會影響水中的環境，水中溫度、密度的不同所形成推力便造成水下感測器的移動。因為洋流影響造成感測器的移動，傳輸延遲也會隨之產生變化。所以水下網路的傳輸延遲不會是固定不變的，如此一來水下網路的資料傳輸也更加困難。本文中，我們提出了一個考慮具移動特性的水下網路且基於分時多工的媒體存取控制協定，我們稱之為”移動排程協定”。本協定目標在於克服因感測器移動產生的傳輸延遲變化，而進一步產生不可預期的資料傳輸碰撞。再提出一個以分時多工為基礎的方法做為資料傳送的排程，來改善水下網路的整體網路產生量。藉由節點之間各種移動關係的討論，將發現各種不同的移動情境。不同的移動情境會產生不同節點間的相對速度，相對速度即是影響傳輸延遲變化的主因之一。各個節點可依照傳輸延遲的變化進行資料傳送的排程，並透過本文所提出的跳動式質數排程法來達到減低碰撞的機率。最後透過模擬來進行效能的比較，結果顯示出”移動排程協定”可比現有的媒體存取控制協定達到較好的整體網路產生量。

關鍵字

水下感測網路；傳輸延遲；媒體存取控制；碰撞避免；洋流

並列摘要

Underwater Sensor Networks (UWSNs) got a lot of attention recently because of Global Climate Change. Communication carrier of UWSNs is acoustic wave, so propagation speed of acoustic signals in underwater environments is much lower than Radio Frequency (RF) propagation in terrestrial environment. Underwater sensors are also affected by ocean current, sensors are moving by push generated from differences of temperature and density. Propagation delay is varying as a result of underwater sensors affected by ocean current. The propagation delay of UWSNs is not fixed so data transmission scheme in UWSNs is more difficult. In this paper, we propose a collision avoidance MAC called Mobi-MAC protocol for mobile UWSNs. The aim of this protocol is designed to overcome varying propagation delay which generates unpredictable data transmission collision. A data transmission scheduling based on TDMA-based MAC that improves network throughput of UWSNs proposed. All different moving patterns are found via researching the moving state between any two sensor nodes. Different moving state gets different relative velocity that is a main factor of propagation delay variation. Then nodes can schedule data transmission according to propagation delay variation, and then reduce the data collision probability by the prime-hopping (PH) data scheduling proposed in this paper. Finally, compare performance with existing MAC protocol for UWSNs via simulations and then results show Mobi-MAC protocol can achieve better than existing MAC protocol in terms of the network throughput.

並列關鍵字

Underwater sensor networks ； propagation delay ； MAC ； collision avoidance ； ocean current.

參考文獻

[1]J. Cui, J. Kong, M. Gerla and S. Zhou, “The Challenges of Building Scalable Mobile Underwater Wireless Sensor Networks for Aquatic Applications,” IEEE Journal on Network, vol. 20, no.3, pp. 12-19, 2006.

[3]J. A. Polton, D. M. Lewis and S. E. Belcher, “The Role of Wave-Induced Coriolis–Stokes Forcing on the Wind-Driven Mixed Layer,” Journal of physical oceanography, vol. 35, no.3, pp. 444-457, 2005.

[4]H. Sakai and T. Tanaka, “Study of the Underwater Observation System in Fast Water Current,” in Proc. Proceedings OCEANS (OCEANS 2003), Yokosuka, Japan, pp. 2189-2194, 22-26 Sept. 2003.

[7]P. Stoina, A. Quintero and L. Cobo “Transport protocol for real-time communication in Wireless Sensor Networks,” in Proc. In-ternational Journal of Ad Hoc and Ubiquitous Computing, vol. 5, no.2, pp. 86 – 102, 2010.

[8]I. Jawhar and J. Wu, “Resource allocation for real-time and multimedia communications in TDMA-based wireless networks,” In-ternational Journal of Ad Hoc and Ubiquitous Computing, vol. 4, no.5, pp. 304 – 319, 2009.

國際替代計量

水下移動式感測器網路中具碰撞避免之媒體存取控制協定

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