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1、摘要摘要無線傳感器網(wǎng)絡(luò)由于具有廣闊的應(yīng)用前景而在近幾年受到學(xué)術(shù)界和工業(yè)界的廣泛關(guān)注，是21世紀(jì)最重要的技術(shù)之一。介質(zhì)訪問控制(MAC)是無線傳感器網(wǎng)絡(luò)協(xié)議棧的重要組成部分，負責(zé)在傳感器節(jié)點間分配有限的無線通信資源，協(xié)調(diào)網(wǎng)絡(luò)中各節(jié)點的傳輸，構(gòu)成傳感器網(wǎng)絡(luò)系統(tǒng)的底層基礎(chǔ)結(jié)構(gòu)。目前無線傳感器網(wǎng)絡(luò)中的MAC協(xié)議主要分為發(fā)送端啟動的MAC協(xié)議和接收端啟動的MAC協(xié)議兩類。發(fā)送端啟動的MAC協(xié)議主要利用時鐘同步或前導(dǎo)傳輸建立發(fā)送端和接收端的連接，前者同步代價過高，后者網(wǎng)絡(luò)利用率較低。接收端啟動的MAC協(xié)議（RI-MAC）通過接收端主動與發(fā)送端建立連接，克服了發(fā)
2、送端啟動算法的弊端，但又產(chǎn)生了發(fā)送端盲等的問題，導(dǎo)致數(shù)據(jù)傳輸延遲和發(fā)送端能耗增大。本文在仔細研究已有MAC協(xié)議的基礎(chǔ)上，結(jié)合發(fā)送端啟動的MAC協(xié)議和接收端啟動的MAC協(xié)議的優(yōu)點，提出了一種可自適應(yīng)變換數(shù)據(jù)傳輸模式的MAC協(xié)議（IL-MAC）。該協(xié)議通過局部同步算法減少了發(fā)送端與接收端在建立連接時的盲等；根據(jù)節(jié)點的消息隊列長度和數(shù)據(jù)的緊急程度決定當(dāng)前使用發(fā)送端啟動傳輸模式還是接收端啟動傳輸模式，有效地解決了以上兩類協(xié)議的問題。本文在網(wǎng)絡(luò)仿真平臺NS2上實現(xiàn)了IL-MAC協(xié)議，并在集中式拓撲、網(wǎng)狀拓撲和隨機拓撲三種網(wǎng)絡(luò)結(jié)構(gòu)下比較了IL-MAC和RI-M
3、AC的性能。仿真結(jié)果表明，IL-MAC在中低負載的條件下較有優(yōu)勢，而在高負載下明顯好于RI-MAC。關(guān)鍵詞：無線傳感器網(wǎng)絡(luò)，MAC協(xié)議，自適應(yīng)傳輸模式變換I摘要ABSTRACTWirelesssensornetworks(WSN)havebroadapplicationsandsignificantvalue,andhavearousedtheindustryandacademicattention,itisoneofthemostimportanttechnologiesin21century.MediumAccessControl(MAC)pr
4、otocol,whichisapartofdatalinklayerinwirelesssensornetworksystem.Itsprimaryresponsibilityistoallocatethelimitedresourcesinwirelessnetworks,establishreliablecommunicationlinksbetweennodes,anditisusedtobuildthesensornetworksystemsinfrastructure.MACprotocolincurrentresearchisdivid
5、edintotwocategories,thesender-initiatedandthereceiver-initiated.Thesender-initiatedprotocolusingsynchronizationorthepreambletoestablishtheirconnection,hasproblemsarethatthecostofusingthesynchronizationistoohigh,andthelargenumberoflongpreamblesgreatlyreducesthenetworkutilizatio
6、n.Thereceiver-initiatedprotocol(RI-MAC)usethemessageperiodicallysendbythereceivertoestablishaconnectionwiththesender,itcansolvetheproblemsofthesender-initiatedprotocol,butintheRI-MACprotocol,thewaitingtimeofthesenderisgreatlyincreased,andthenitdelaysthetransferandincreasesthee
7、nergy-consumingofthesender.ThisthesisbasedonthecurrentresearchoftheMACprotocol,madefulluseofthebenefitsofthesender-initiatedandthereceiver-initiatedprotocol,proposeanewdutycycleMACprotocol,calledInitiator-convertibleandLocallysynchronizedMACProtocol(IL-MAC).Thisprotocolreduced
8、thewaitingtimeofthesenderandreceivertoestablishaconnection;By
