ࡱ> +-*rbjbjUU >??r   0 'wyyyyyyby///y////w//w///I//c0////4////////yy///////////////// :Resumo: Nas Redes de Sensores Sem Fio, ns tipicamente operam por baterias no recarregveis ou substituveis. Logo, a otimizao do consumo energtico uma das principais preocupaes. Dentre as vrias solues j propostas, os mtodos de duty cycle assncrono baseados em escalonamento se mostram os mais simples por no demandarem mecanismos, protocolos ou hardwares especficos para sincronizao de relgio entre os ns. Esses mtodos, no entanto, resultam em alta latncia para comunicao de mltiplos saltos. Neste trabalho, demonstramos como os mecanismos assncronos j existentes podem se beneficiar de um baixo nvel de sincronismo, em resoluo de slots. Mostramos com simulaes numricas e modelos matemticos simplificados que o uso de offsets especficos entre os relgios de ns vizinhos, de acordo com suas distncias ao n sorvedouro, reduz drasticamente a latncia. Alm disso, implementamos sobre a plataforma TinyOS um prottipo de protocolo de roteamento com as funcionalidades propostas de sincronizao de baixa resoluo. Com base nesta implementao, realizamos simulaes de rede utilizando o simulador TOSSIM. Os resultados dessas simulaes corroboram os resultados das demais avaliaes, mostrando ganhos representativos em termos de latncia de comunicao. Palavras-chave: Rede de Sensores Sem Fio; Duty Cycle; Mecanismos Assncronos. Abstract In Wireless Sensor Networks, nodes typically employ batteries that cannot be recharged or replaced. Hence, optimizing energy consumption is a major concern. Among the several solutions already proposed, schedule-based asynchronous duty cycle methods are the simplest because they do not require mechanisms, protocols or specific hardware for clock synchronization between nodes. These solutions, however, result in high latency for multi-hop communication. In this work, we show how existing asynchronous mechanisms can benefit from a low level of synchronism, with resolution of slots. We show, using numerical simulations and simple mathematical models, that the use of specific offsets between clocks of neighboring nodes according to their distances to the sink node drastically reduces latency. Additionally, we implemented a routing protocol prototype with the proposed low resolution synchronization functionalities for the TinyOS plattaform. With this implementation, we were able to run network simulations using the well-known TOSSIM simulator. The results of these simulations agree with the results from the other evaluation methods, consistently showing representative gains in terms of communication delay. Keywords: Wireless Sensor Networks; Duty Cycle; Asynchronous Mechanisms.   6 @ [ d )2XrhLmH sH hhLmH sH hhL5\mH sH hhL6]hL hL5\hhL5\ Z [ d )rgd$a$gd<P1h:p B. A!"#$% Dpj  666666666666666666666666666666666666666666 6666666666 666666666666 6666666666666666666666666666666666666666666666666666666666666666662 0@P`p2( 0@P`p 0@P`p 0@P`p 0@P`p 0@P`p 0@P`p8XV~ OJPJQJ_HmHnHsHtHN`N  BNormal dCJ^J_HaJmHsHtH DA D 0Default Paragraph FontRiR 0 Table Normal4 l4a (k ( 0No List PK![Content_Types].xmlj0Eжr(΢Iw},-j4 wP-t#bΙ{UTU^hd}㨫)*1P' ^W0)T9<l#$yi};~@(Hu* Dנz/0ǰ $ X3aZ,D0j~3߶b~i>3\`?/[G\!-Rk.sԻ..a濭?PK!֧6 _rels/.relsj0 }Q%v/C/}(h"O = C?hv=Ʌ%[xp{۵_Pѣ<1H0ORBdJE4b$q_6LR7`0̞O,En7Lib/SeеPK!kytheme/theme/themeManager.xml M @}w7c(EbˮCAǠҟ7՛K Y, e.|,H,lxɴIsQ}#Ր ֵ+!,^$j=GW)E+& 8PK!Ptheme/theme/theme1.xmlYOo6w toc'vuر-MniP@I}úama[إ4:lЯGRX^6؊>$ !)O^rC$y@/yH*񄴽)޵߻UDb`}"qۋJחX^)I`nEp)liV[]1M<OP6r=zgbIguSebORD۫qu gZo~ٺlAplxpT0+[}`jzAV2Fi@qv֬5\|ʜ̭NleXdsjcs7f W+Ն7`g ȘJj|h(KD- dXiJ؇(x$( :;˹! I_TS 1?E??ZBΪmU/?~xY'y5g&΋/ɋ>GMGeD3Vq%'#q$8K)fw9:ĵ x}rxwr:\TZaG*y8IjbRc|XŻǿI u3KGnD1NIBs RuK>V.EL+M2#'fi ~V vl{u8zH *:(W☕ ~JTe\O*tHGHY}KNP*ݾ˦TѼ9/#A7qZ$*c?qUnwN%Oi4 =3ڗP 1Pm \\9Mؓ2aD];Yt\[x]}Wr|]g- eW )6-rCSj id DЇAΜIqbJ#x꺃 6k#ASh&ʌt(Q%p%m&]caSl=X\P1Mh9MVdDAaVB[݈fJíP|8 քAV^f Hn- "d>znNJ ة>b&2vKyϼD:,AGm\nziÙ.uχYC6OMf3or$5NHT[XF64T,ќM0E)`#5XY`פ;%1U٥m;R>QD DcpU'&LE/pm%]8firS4d 7y\`JnίI R3U~7+׸#m qBiDi*L69mY&iHE=(K&N!V.KeLDĕ{D vEꦚdeNƟe(MN9ߜR6&3(a/DUz<{ˊYȳV)9Z[4^n5!J?Q3eBoCM m<.vpIYfZY_p[=al-Y}Nc͙ŋ4vfavl'SA8|*u{-ߟ0%M07%<ҍPK! ѐ'theme/theme/_rels/themeManager.xml.relsM 0wooӺ&݈Э5 6?$Q ,.aic21h:qm@RN;d`o7gK(M&$R(.1r'JЊT8V"AȻHu}|$b{P8g/]QAsم(#L[PK-![Content_Types].xmlPK-!֧6 +_rels/.relsPK-!kytheme/theme/themeManager.xmlPK-!Ptheme/theme/theme1.xmlPK-! ѐ' theme/theme/_rels/themeManager.xml.relsPK] r r r _GoBack\t \t :`( BLur t @r @@UnknownG*Ax Times New Roman5Symbol3" Arial7.@CalibriACambria Math"SXSX!0$Pr !xxResumo:Andr R. SaraivaHelioOh+'0  @ L Xdlt|Resumo:Andr R. SaraivaNormal_WordconvHelio2Microsoft Office Outlook@Ik@j@j՜.+,0 hp   Particular Resumo: Title  !#$%&'(),Root Entry F$Q.1Table WordDocument>SummaryInformation(DocumentSummaryInformation8"CompObjy  F'Microsoft Office Word 97-2003 Document MSWordDocWord.Document.89q  F#Documento do Microsoft Office Word MSWordDocWord.Document.89q