以使用率為基準之省電型感測器連結層協定設計

Abstract

在這篇論文中，我們提出一個專屬於無線感測器網路的連結層協定，稱為U-MAC(Utilization based energy efficient medium access control protocol)。現今的感測器網路是由許多數量的感測器所組成，而這些感測器通常是使用電池當能量來源，而且不能很容易地去將它們充電，因為它們可能被散佈在一些人類所不能輕易到達的地方。因此如何延長這些感測器的壽命即變成了設計連結層協定的一項重要課題。基於以上的理由，Ye et al.為了減少感測器能源的消耗而提出了S(Sensor)-MAC，S-MAC週期性地讓感測器進入休眠模式和工作模式，進而使感測器能在休眠模式中省下不少無謂能源的消耗。經由導出S-MAC之數學模型，我們可以發現過度減低能源消耗會導致較長的延遲時間。針對這樣的情形，U-MAC提出了改變責任週期，根據使用率來調整責任週期，以及在傳送結束後選擇性地進入休眠模式去找到能源消耗和延遲時間的平衡點。我們選擇了ns-2(network simulator 2)作為我們的網路模擬器平台來模擬U-MAC在網路中的行為，而且我們把U-MAC和S-MAC以及DSMAC做比較，其實驗結果顯示出U-MAC省下了比S-MAC還多43%的能源，以及65%的延遲時間。

In this work, we propose U-MAC, a medium access control protocol designed for wireless sensor networks. Nowadays, wireless sensor network are formed by a great quantity of sensor nodes, which are generally battery-powered and may not recharge easily. Consequently, how to prolong the lifetime of the nodes is an important issue while designing a MAC protocol. Ye et al. proposed S(Sensor)- MAC that uses a periodically listen and sleep schedule scheme in order to lower the energy consumption of sensor nodes. By evaluating the analytical model of S-MAC in Section 3, we can know that lowering the energy consumption may result in higher latency. Addressing on such tradeoff, U-MAC balances the tradeoff by varying duty cycle, utilization based tuning of duty cycle and selective sleeping after transmission. We choose ns-2 as our network simulator to evaluate the effectiveness of U-MAC, and we compare U-MAC with S-MAC and DSMAC in a chain and a cross topology. The experiment results show that our proposed schemes save energy about 43% and reduce latency by 65% from S-MAC.