Opportunistic Scanning: Interruption-Free Network Topology Discovery for Wireless Mesh Networks

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1 Oppruisi Sig: Irrupi-Fr Nwrk Tplgy isvry fr Wirlss sh Nwrks r Emmlm, Sv Wihlr, d Hyug-Tk Lim Thil Uivrsiy Brli Tlmmuii Nwrks Grup TN Brli, Grmy mmlm@i.rg, {wihl, lim}@k.u-rli.d sr This ppr prss h p d prlimiry prfrm vlui f shsi wrk disvry pprh md ppruisi sig. Thri, si ly puss is mmuii fr xrmly shr im irvl s fr hr hlgis / sysms. Th sld sig duri is shr ugh il y highr lyr ppliis. W pl his p i h 802. msh wrk x d vlu 802. pwr svig s pssil siglig prl usd pus h mmuii w h sig si d is irlur. W hri driv h hril prfrm limis f ppruisi sig i mii wih 802. pwr sv d prs firs rsuls lssifyig h im rquird fid ighrig hlgy / sysm giv priliy. Irdui Thusds f iis wrldwid hv dplyd lrgsl 802. wrks mplyig muli-lvl ir iludig msh khul xd h wrks vrg. s mprd rdiil wirlss wrk rhiurs, suh wrks ly fur limid umr f high piy iji pis ig h msh khul h (wird) ir. I suh rhiur, pprpri lik sli shms r rquird pimlly ssig dusrs (d hir rffi) ss pis i hir viiiy r v disriu rffi mg vrius liks w dj msh pis. ddiilly, if mmril prrs shuld Th uhrs wuld lik hk OPNET Thlgis I. fr prvidig h simuli virm udr h uivrsiy prgrm. This wrk ws prilly supprd y Eurp mmissi hrugh prj EU- ESH (Ehd, Uiquius, d pdl Brdd ss usig ESH Nwrks), FP7 IT irsigly fvr suh rhiurs, h lr hv gur QS v fr mil usrs i squ rquirig lw hdvr lis. I rdr rvlu h lik sli pridilly, dusrs s wll s msh pis frmig h wirlss k hv priiplly w si pis: ihr hy (iuusly) hk whhr lriv ss pis / liks r vill r hy rly ri siglig shms, whih upd hir ighrhd ifrmi rdigly. I his wrk, w pply h firs pi si w rg miimizig ddiil ld irdud h wirlss liks. Thus, his ppr prss ppruisi sig shm whih pridilly ss fr lriv ss liks whil uphldig QS sris i rms f gurig mximum ir-rrivl im w suiv usr dgrms. I ur pprh, his srg limii is hivd s h sig si lvs is mmuii hl ly fr xrmly shr im prid ffig h QS sris f highr ppliis. s rsul, h dwll im wihi sig s is shrr h h irvl f hr ds h mkig his wrk disvry pprh shsi prss. ddiilly, siglig prl pusig y mmuii w si d is ssid irlur is ssry vid lss f pks. s w hri pply h ppruisi sig shm IEEE 802.-sd msh wrk, h ms url hi fr suh siglig is h pwr svig fur f 802. s pwr svig sis r rquird ur ff hir irf u my isd us h dz s s fr lriv liks. This ppr prss h vl ppruisi sig p islf iludig prlimiry prfrm vlui f h ppruisi sig pprh i mii wih 802. pwr svig siglig. Th vl riuis r dild usiliy lysis f h 802. pwr svig mhd vluig if his fur ls ppruisi /09/$ IEEE

2 sig i srily sdrd mpli wy; h drivi f h hril prfrm limis fr ppruisi sig sidrig h smlls hivl srvi irrupi usd y sig prss; ivsigis rgrdig h rquirms fr h hi f h sig frquy; d prlimiry prfrm vlui rvlig hw muh im ppruisi sig ds sud ( giv priliy) i dig hr sysm. Th rmidr f h ppr is sruurd s fllws: Th fllwig si irdus h sysm mdl fllwd y dsripi f h ppruisi sig pprh. pr frm prsig h grl p f ppruisi sig, h lr si lyzs h 802. pwr svig fur i dil. I idifis rly usd u irly sdrd mpli siglig flw lig pwr sv s pssil siglig prl did. Th fil si h prfrm vlui firsly summrizs h gls f h ssssm d hrf drivs h udrlyig usg sri. Fllwig h mri dsripi, w prs h hril prfrm limis f ur pprh. Th ppr luds y skhig rld wrk d summrizig h rsuls d fuur wrk. 2 Sysm mdl hr-ir rhiur dsris h sysm udr sidri (.f. Figur ). [6] Svrl msh pis (Ps) my mmui wih h hr vi wirlss liks frmd y ihr mi-diril r highly diriv s. Ths Ps frm h msh khul ig s piy pl fr d usrs. u hl hrrisis s wll s mplyig diriv sysms, Ps ig ggrphilly ld x h hr my ssrily hv dir mmuii. sus f Ps, dd s msh prls s h msh khul h Ir. sh prls my hv high piy wird i (.g. vi drk fir r high piy diriv wirlss liks) if dplyd y wrk prrs; u ls lw piy SL liks r pssil fr msh prls dplyd hms r smll d mdium rpriss. sh ss pis (sh Ps) frm h ls ir d prvid usrs ss h msh khul. sh Ps r hri ssumd suppr lgy IEEE 802. pri iludig pwr svig; h sh P frms ifrsruur si srvi s d h us h lr vi rsmissis. Ed usr sysms r ssumd quippd wih sigl IEEE 802. wrk irf rd. ls, i shuld d h w d imps y sris h hlgy usd wihi Figur. Exmplry Sysm rhiur h msh khul llwig hrgus virm frmd,.g., y IEEE 802. d WiX. 3 Oppruisi sig pprh Th dsig f h sig pprh is driv y hr mi sidris: Firsly, h sig prdur shuld pl suppr v rl im rffi wih smll pk irrrivl ims d hrd QS sris whih rquir lw pk lss d llw ly smll xr dly. VIP rffi is ypil rprsiv fr suh pr (.g., G.7-dd sph wih 0ms ir-pk gri im). Sdly, si h ppruisi sig hs sl wih h umr f sis pplyig his pprh, w rg irdu vrhd i rms f ddiil rffi h rg hl ig sd. Filly, fsil slui i rl hrdwr ly uil up mhisms h r sdrd mpli. 3. Grl p I rdr m hrd QS sris f rl-im rffi, h ppruisi sig pprh ly lvs h urr mmuii hl fr vry shr im s hr hls fr s uig ighrig sh Ps. N ff y gig mmuii, his rquirs siglig w h sh P d h ssid d sysm pus mmuii. Th fllwig sis disuss pssil siglig shm ig irly mpli h xisig IEEE 802. spifii mplyig h pwr sv prdur f h sdrd. Th ly diffr is h isd f slpig whil i pwr sv md, h mil ST disvrs h wrks plgy. 3.2 Siglig f IEEE 802. pwr svig IEEE 802. pwr svig dfis w mds f pri: h wk s (f h si) d h dz s.

3 B P ST xhg IFS SIFS... slpig ST P: TI[I_s] LisIrvl ( * BIrvl) B P ST dz s P: TI[I_s] slpig ST LisIrvl ( * BIrvl) slp-ps wk s wi wk ST SIFS r siglwkupps wkup-prss-ps xhg P: TI[I_s]0 rd(0,w mi ) dz s Figur 3. ST iiid wk-up prdur sigl_slp-ps slp-ps slp-prss-ps Figur 2. Slp prdur f PS-ST I h frmr, rgulr mmuii w h P d h si (ST) urs whrs i h lr, h P uffrs y pdig d fr h ST mmuii is pusd Slp prdur Figur 2 illusrs h frm xhg usd y ll sdrd mpli sis hg i dz s. Th si hs g hrugh lr hl ssssm prdur () d my h sd uplik d frm i whih h pwr mgm i f h frm rl fild is s []. Th fllwig firmig h rpi, h ST my hg i dz s d h P uffrs d fr h si. ls, h P idis pdig rffi y sig rrspdig i i h rffi idii mp (TI) id i h Wk-up prdur Ev hugh ly rrly usd, 802. pwr svig sis my hg frm dz wk s y im d sigl his s hg immdily h P. s shw i Fig. 3, h ST hs wi fr giv im ( wi )fr hgig i wk s r hs sussfully i urr sig fr h wrk lli vr (NV). This gurs h h si ds irfr wih y gig rsmissi v physil idis idl hl (hidd prlm). frwrds, h ST mps fr hl ss d my rsmi uplik d frm idiig is s hg i h pwr mgm i f h frm hdr. Th P i ur idis if i hs y uffrd d fr h ST usig h mr d i i h frm hdr f h susqu. Bk i wk N h h ST my s ull-d frm if i hs pdig uplik d. s, h ST plls uffrd d frm h P usig h PS-Pll frm []. 3.3 Emplyd sig shm s h sdrd ds rquir pwr svig si swih ff is rsivr hi whil i dz s, h ST my frly us his im sp fr wrk plgy disvry. s ur gl is mply ly sdrd mpli prl pprhs, his r limid pssiv d iv sig. ls, w im hvig miimum ssumpis wrds h 802. ifrsruur suh s syhrizi f rsmissis mg sh Ps. H ST mplyig h ppruisi sig shm hivs is suprir sig hvir i y sdrd mpli 802. virm. Th hird dsig sidri rgs vid ddiil ld hr lls. Thugh rsulig i fsr wrk plgy disvry, iv sig wuld hv suh imp. This f hs ls kwldgd y h IEEE 802. wrkig grup. Th ms r mdm fr rdi rsur mgm (IEEE 802.k [2]) irdud pil frms : shr vrsi f h whih frquly rsmid fr hd pssiv sig prfrm hus supprig pssiv sig s h primry plgy disvry hi if h imp h sd wrk shll miimizd. rdigly, h fllwig prfrm vlui sidrs ly pssiv sig. I is hrfr srviv prfrm ssssm i rms f h im rquird disvr h msh wrk plgy. 4 Prfrm vlui 4. Gls d mhdlgy W hri im lssifyig h hril prfrm limis f h ppruisi sig pprh. I priulr, w i swr h fllwig qusis: Hw lrg is h miimum duri jus fr h whl pwr sv siglig?

4 Hw lg ds i k fid xisig si giv priliy? swrig h frmr quifis h smlls pssil urrud im frm d xhg sig d k d xhg if 802. pwr sv is usd s h udrlyig siglig prl. H i is msur fr h smlls supprl srvi irvl fr usr d. Th lri ur sssshim rquird i h vrlp f dj lls sussfully mpl h plgy disvry udr h pimisi ssumpi h h si ss ly hl whih lriv sh P is kw fud. ls, hs rsuls my ls usd quify uppr limi fr whih h ppruisi sig prss shuld sr is plgy disvry w hl if si hs fud. I h fllwig, w mply lysis ssss hs hril limis. 4.2 Sri W sidr w dj msh ds hvig vrlppig vrg r. Bh msh ds u-syhrusly rsmi s u hir xis rgulr im irvls s dfid y h 802. sdrd. Th lysis sidrs h ppruisi sig si ig siry ld wihi h vrlp. I is ssid wih f h msh ds. pr frm h rsmissis d mmuii w h ppruisi s si wih is ssid msh d, h hl is ssumd idl. 4.3 ris Our lysis mks us f h fllwig w mris: pwr sv md duri d rpi priliy. Th pwr sv md duri dfis h im frm h giig f h siglig ivlvd rsii frm h wk i h dz d k i h wk s. I quifis h srvi irrupi impsd h pplii du h ppruisi sig pprh. Th rpi priliy quifis h umr f sig mps / im rquird sussfully riv giv priliy. 4.4 lyil rsuls fr idl hl 4.4. iimum pwr sv duri Figur 4 illusrs h siglig squ ivlvd i gig frm wk i dz d immdily k i wk s. s w d spd y im i h dz s, w r ully duig y ppruisi sig ll. This quifis h smlls pssil duri swih k d frh w hls. I rdr hld spifi P ST Nrml xhg rd(0,w mi ) IFS sigl-slp slp-prss wi dz/wk siglwkup s wkup-prss PS Nrml xhg Figur 4. Siglig squ fr miimum PS duri QS sri, h miimum pwr sv duri rprss h lwr ud fr h ir-rrivl im f pplii d lvl. Th miimum im sp i pwr sv md ( mip S ) is giv y whr mip S sigl slp + wi + + sigl wkup () sigl slp IFS + rd uifrm (0,w)+ + T + SIFS + pr, if hl is idl wi usy + IFS + + rd(0,w), if hl is usy sigl wkup T + SIFS + ssumig idl hl, Equi () dirly simplifid i mip S IFS +2 SIFS +2 T pr (2) pr frm PHY spifi prmrs ( IFS, SIFS, d pr ), mip S dpds h mplyd mduli d dig shm (S) fr h d kwldg frm []. Figur 5 shws h miiml hivl PS duri fr prmrizi d dfid S fr w siuis: firs ssumig h h siglig is rsmid i Null frm, d sd, if i is piggy kd i VIP d srm pk ssumig udrlyig G.7 d d 0 ms pkizi wihu sil supprssi. Oviusly, h smlls hivl irrupi f rughly.3 ms urs fr h lws pk siz (Null frm) h highs d r. Bu ls 2.6 ms-lg irrupi h ms rus S shms is pl v fr

5 5.5 6 x mips duri vryig diffr d rs[ pr.024μ s] 802. < piggyk> 802. <Null d> 802.g (OF) < piggyk> 802.g (OF) <Null d> Δ s B -h frm... BS BE mips [s] ffs (+)-sig s s2 s3 s4 s + Δ s SS SE s: fud Figur 6. luli f h umr f sig mps (siglig shw) R[i/s] f T Frm Figur 5. iimum PS duri hrd rl im srvis [9]. ls, h hril limis shw h ppruisi sig shuld fsil pprh ily ffig VIP ppliis s srvi irrupi fr piggy kd siglig my rdud lss h 6 ms fr h ms rus S Rquird s duri I rdr d ighrig msh P durig h h+ ppruisi sig mp, h giig f h sig SS hs fr h giig f h rpi / sr BS d h d f h s SE hs li fr h s d BE (.f. Fig. 6): Thri, SS BS BE SE (3) SS ffs + s Δ s BS Δ BE BS + SE SS + s whr ffs is rdm vril uifrmly disriud vr [0, Δ ), Δ h rg rsmissi im, Δ s h s irvl, d s h (ffiv) s duri rmiig fr h ivlvd siglig is ddud frm h im sp giv y Δ s. Equi 3 rdigly rwri i Δ ffs Δ s ( ) s Δ s s s Δ ffs Δ s (4) whih givs h dii if umr is sussfully rivd wihi s mp s. Slvig h lr qui umrilly d du h shsi ur f ffs, w i h priliy fuis f dig giv s mp / fr giv im (.f. Fig. 7). Oviusly, ffs d Δ my hv mm dividr gur di. s w ssum h prvidr will mply mm vlus wih mulipls f 0 ms fr h rg rsmissi im (.g., 00 ms) w hs prim umrs fr Δ s. s xpd, lgr s irvls yild r rsuls u irsigly, h ff is lss il if sidrs h im rquird fid s mprd h umr f sig mp. plgy disvry i w rg rsmissi ims (TBTT) is pssil. This is ly wi h im dd s mprd rdiil pssiv sig rsulig i lg srvi irrupis. Bu v usuil s irvls rsulig i high duri mplish sussful disvry wihi fiv TBTTs. 5 Rld wrk Rgrdig wrk disvry (prig) ig h ms isivly sudid hdvr phs, w ly summriz ms vl rsrh rsulig i h s kw, pulishd rdui f is duri. Th SyS lgrihm prsd y Rmi d Svg [7] iuusly rks ry ss pis y syhrizig shr lisig prids h li wih h pridi rsmissi f s f ighrig Ps. Hry, kwldg wh ighrig P shuld rsmis is is rquird fr shdulig h syhrizd s mps. T vid pk lss durig hs s mps, h P d ST uffr usr d i h mim; h xpriig vry frquly urrig dly whih h uhrs quify i h rdr f 5 ms. Sigh, wl d Shi [8] s wll s hui d Yu [5] xd h SyS pprh d prs ss pi rdii d siglig shms prvidig (disriud) pprh syhriz rsmissis wihi giv im prid fr ll Ps i h disriui sysm prig h sm hl. Thir wrk, hwvr, ds ff h dly ssid wih h hdvr prss. Whil h rigil SyS lgrihm ly kws wh

6 P [ X ] P [ X fud ] SI 7ms <S4.288ms> 0. SI ms <S8.288ms> SI 3ms <S0.288ms> SI 7ms <S4.288ms> : s mps () F vr umr f sig mps 0.2 SI 7ms <S4.288ms> 0. SI ms <S8.288ms> SI 3ms <S0.288ms> SI 7ms <S4.288ms> Tim fid frm fud [s] () F vr im Figur 7. Priliy f rivig f y P shuld rsmid, STs sill mp s fr s f Ps v if hy r wihi h lr s vrg. us prsd y h l. [3,4] mis ighrhd grphs wih SyS h rduig h s mps hls whr h priliy riv is high. ddiilly, hy us (ggrphi) psii ifrmi f Ps sim mil s mvm sd h rdi sigl srgh idir (RSSI) rivd frm Ps. Bsd simuli rsuls, us rdu h ssid srvi irrupi dw 3.5mswhih rrspds h rsmissi im f IEEE 802. pr rqus prsumly sidrig h hl swihig im ddig ddiil dly f 0 ms s srvd y [7]. Ev hugh hs s kw pris my rlizd uphldig lgy mpiiliy, hy rquird mr kwldg f h ifrsruur i rms f prisly gussig rsmissis r v rquirig srily syhrizd rsmissis mg ighrig ss pis. 6 lusi This ppr prsd prlimiry prfrm vlui f h vl ppruisi sig pprh mplyig 802. pwr svig s udrlyig siglig prl. W shwd h dpdig h mplyd S shm, srvi irrupi my rdud vlus i w.5 d 5.8 ms. This mks ppruisi sig riv fr rl-im mmuii wih igh QS sris whil ig irly mpli wih h 802. sdrd. Our prlimiry prfrm vlui shwd fr idl hl h rpi gurd i lss h 200 ms whih is ly wi s lg s rdiil pssiv sig ssumig mm TBTT f 00ms. Our fuur wrk will furhr vlu h prfrm f h ppruisi sig pprh rvlig h ffs f hl ld usd y hr sis s wll s dild vlui f pprh s s i rms f quifyig h vrhd f h siglig prl. Rfrs [] I wirlss l mdium ss rl (m) d physil lyr (phy) spifiis, [2] I 802.k/d7.0 rdi rsur msurm, drf mdm. (802.k), Jury [3] Y.-S. h,.-. h, d.-. hug. us: u-sd fs hdff shm i i 802. wirlss wrks. VT-2006 Fll IEEE 64h, : 5, Sp [4] Y.-S. h,.-. hug, d.-. h. us: u-sd fs hdff shm i i 802. wirlss wrks. Vhiulr Thlgy, IEEE Trs., 57(2):26 4, rh [5] S.. hui d O.-. Yu. ss pi rdii sysm fr imprvd vip/wl hdvr prfrm. VT 2006-Sprig. IEEE 63rd, :50 505, y [6] E.-. srium. Eu-msh sysm rhiur. Thil Rpr 2.2, July [7] I. Rmi d S. Svg. Sys: pril fs hdff fr 802. ifrsruur wrks. INFOO h ul Ji fr f h IEEE mpur d mmuiis Siis. Prdigs IEEE, : vl., rh [8] G. Sigh,. P. S. wl, d B. S. Shi. ffii ighr ifrmi siglig mhd fr hdff ssis i 802. wirlss. I iliy 06: Prdigs f h 3rd iril fr il hlgy, ppliis & sysms, pg 4, Nw Yrk, NY, US, [9] Virul umi Nwrks srium. Rl im fr mddd umi sysms iludig sus d lysis d lsd lp rl im rl. livrl 04.-, E Ifrmi Siy Thlgy, July 2006.