【正文】 green InternetI. INTRODUCTION Networked electronic devices consumed almost 4% (150 TWh) of all the electricity in the . in 2008, about 13% (20 TWh) of which was consumed by net work equipment such as network switches and routers [22]. Ethernet, as the dominant wireline technology for LANs, constitutes a significant portion of the energy use of puter networks. The most recent advance in reducing the energy consumption of Ethernet is Energy Efficient Ethernet (EEE) which was standardized as IEEE Std in September 2010 [12]. Products that use EEE are beginning to ship in mid to late 2011. EEE enables an Ethernet link that is idle to exit Active mode and enter a Low Power Idle (LPI) mode. The power used in LPI mode is significantly less than in Active mode since some ponents of the physical layer (PHY) can be powered off. The IEEE standard does not describe a policy for entering and exiting LPI. A simple policy would be to enter Active mode when packets are queued in the transmit queue in the interface and enter LPI mode when the queue is empty. Such a policy has been found to be ineffi cient (that is, wasteful of energy) due to excessive transitions between the Active and LPI modes [25]. Each transition incurs a delay and energy use. A policy to batch, or coalesce,packets was proposed and explored by Christensen et al. in 2010 [6]. Coalescing improves the energy efficiency of Ethernet interfaces in hosts as well as in Ethernet switches. The overall energy consumption of a switch is reduced by EEE as a result of the reduction in energy consumption of individual interfaces of the switch. However, we believe that energy savings by EEE can go beyond the savings in individual interfaces if all the switch ports enter LPI mode at the same time, or synchronously. Synchronized LPI periods provide the opportunity for additional ponents of the switch to power down since it would be certain that there are no packets in any port buffer, or within the switch fabric, that need to be forwarded. In synchronized coalescing the control of when to coalesce and for how long is moved to the switch (from the host interfaces) and the coalescing periods are synchronized on all the ports of the switch. The target switches for our synchronized coalescing method are the ones mostly used in households and small offices. This type of switch, which are referred to as SOHO (small or home office) switches hereafter, typically includes 4 to 10 ports and cost less than $100. Two factors motivated us to propose synchronized coalescing. The first is the typi cal low utilization of switches in general [9]. The second is that although SOHO Ethernet switches consume only a small amount of energy individually, the number of them deployed in the country is so high that it makes their consumption significant and even a small savings per switch would add up to a significant overall savings. Using a KillAWatt power meter, the power use of a Linksys EG005W Gigabit Ethernet switch with 4 connected active links was measured as 10 W. We estimate that the current consumption of SOHO Ethernet switches is approximately TWh/year based on the number of housing units in the . [26], assuming that about 70% have an Ethernet switch installed, and that each switch is powered on all the time. At the current average electricity cost ($) this is a total of about $790 million per year in electricity use. While current Ethernet links and switches are mostly 100 Mb/s and 1 Gb/s, we envision that they are likely to evolve to 10 Gb/s in the near future for several reasons including, 1) everdecreasing prices [20], 2) fast adoption by vendors [18], and 3) increasing bandwidth requirements of multimedia applications within households (for example audio/video transfer between storage device and player, and LANbased multiplayer video games). The contributions of this paper are the proposal and explanation of synchronized coalescing and evaluation of its performance tradeoffs and effects on typical Internet traffic and TCP through simulation. The remainder of this paper is organized as follows. Section II reviews EEE and previous work that has been done in policies to control EEE. Section III presents a microlevel study of the power use of SOHO Ethernet switches and the opportunity of powering down individual ponents. Section IV explains the new synchronized coalescing method. Section V is a simulation evaluation of the method. Section VI describes related work. Section VII summarizes, describes future work, and estimates the potential energy savings that could be gained by largescale deployment of the presented methods.II. OVERVIEW OF ENERGY EFFICIENT ETHERNET (EEE) EEE brings the energy consumption of Ethernet links closer to the ideal consumption, which is directly propor tional to the utilization of the link. Estimates show that using EEE in all current 1 Gb/s edge links in both residential and mercial buildings and network equipment links within residences could save about $180 million/year in the . alone [6]. Two modes are defined in EEE。 synchronized coalescing。page=1,2007119我順利的完成了大學(xué)的學(xué)業(yè)，即將成為一個就要步入社會的人，我會實現(xiàn)自我的價值，為自己、家庭，更為社會做出更大的貢獻！ 參考文獻[1] 黃智偉．單片無線數(shù)據(jù)通信 IC 原理與應(yīng)用[M]．北京：北京航空航天大學(xué)出版社，2004：1234. [2] 王宜懷．單片機原理及其嵌入式應(yīng)用教程[M]．北京：北京希望電子出版社，2002。為我的學(xué)習(xí)提供了良好的條件，成功的完成了畢設(shè)的軟硬件設(shè)計。跟隨老師學(xué)習(xí)以來，我獲得了一生中最寶貴的財富，就是豐富的知識和如何運用它的方法。在老師的指點和關(guān)注下，我的理論知識理解和動手經(jīng)驗都得到了很大的提高。老師嚴(yán)謹(jǐn)?shù)闹螌W(xué)態(tài)度、豐富的實踐經(jīng)驗、兢兢業(yè)業(yè)的工作精神都使我受益匪淺。我在這個過程中深刻的感受到了做畢業(yè)設(shè)計的意義所在，那就是堅持不放棄就會成功。在通信理論的學(xué)習(xí)和實際芯片的識別、電路的組建、分析以及后來的測試過程中，我不可避免地遇到各種問題，我在積極思考的前提下，請教了同學(xué)或指導(dǎo)老師，比較順利的一一解決了問題，圓滿完成了設(shè)計制作。這一切都使我的理論知識理解力和動手能力得到很大的加強。經(jīng)過四年學(xué)習(xí)的積累，在已經(jīng)掌握相關(guān)專業(yè)方面知識及其它各方面知識的情況下，我認(rèn)真且嚴(yán)肅的完成了我的畢業(yè)設(shè)計。 應(yīng)用單片機的定時中斷功能，該設(shè)計可以進行定時控制，并通過NRF24L01將信號送給接收部分，在定時時間到達(dá)時，接收端控制繼電器閉合，通過LED 燈可實現(xiàn)信號的反饋。結(jié)論在本次畢業(yè)設(shè)計課題的研究中,我大有收獲。 手動模式測試顯示時間交換機狀態(tài)（LED反饋）14：00：01燈亮15：00：01燈滅