WIRELESS mesh networks (WMNs) provide cheap, reliable,

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1 ynmic nwith ontrol in Wirlss Msh Ntworks: Qulity o xprinc bs pproch Rstin Pris, vi Hock, Nico yr, Mtthis Sibrt, irk Sthl, Vslin Rkocvic, ngnn Xu, Phuoc Trn-Gi bstrct Wirlss Msh Ntworks (WMNs) r gining n incrsingly importnt rol in nxt gnrtion wirlss ntworks. u to thir vntgs ovr othr wirlss n wir ntworks, WMNs r unrgoing rpi progrss n r suppos to livr wirlss srvics or lrg vrity o pplictions. spcilly rl-tim pplictions such s voic ovr IP mk high mns on wirlss msh ntworks. smll chng o th Qulity-o-Srvic (QoS) mtrics lik pckt loss, ly, n jittr hv signiicnt impct on th Qulity-o-xprinc (Qo), subjctiv msur rom th usr prspctiv o th ovrll vlu o th provi srvic or ppliction. In this ppr, w prsnt ynmic bnwith control mchnism which msurs th currnt sitution in th ntwork n pts th bnwith in orr to nsur high Qo lvl. Th mchnism is implmnt in Wirlss LN msh tstb n th rsults show tht rl-tim pplictions r succssully protct rom isturbing bst ort tric lows. Inx Trms Qo, Msh, WLN, 8.11, Tstb I. INTROUTION WIRLSS msh ntworks (WMNs) provi chp, rlibl, n lxibl brobn Intrnt ccss in locl n mtropolitn rs. Similr to wirlss -hoc ntworks, no cntrl unit is istributing tric n th t is snt irctly rom nighbor no to nighbor no. I t shll rch nos tht r not irctly rchbl nighbors, th pckts r snt on multi hop rout. ll nos provi rlying cpbilitis to orwr tric through th ntwork to rch th stintion. Howvr, in contrst to wirlss -hoc ntworks, WMNs r normlly sttic vics n ocus on rlibility, ntwork cpcity, n r minly us s n ltrntiv to wir ntwork inrstructur. u to th vntgs o WMNs lik sl-orgniztion n sl-hling, svrl stnriztion groups hv bn st up. Th irst stnriztion group or Wirlss Locl r Ntworks (WLNs) ws strt in 3 unr th xtnsion I 8.11s [1]. sis th I 8.11s stnr urthr stnriztion groups or WMNs lik I 8.1. [] n I 8.16j [3] unrlin th importnc o wirlss msh ntworks. R. Pris,. Hock,. Sthl, P. Trn-Gi r with th Univrsity o Würzburg, Institut o omputr Scinc, prtmnt o istribut Systms, Würzburg, Grmny, -mil:{pris,hock,sthl,trngi}@inormtik.uniwurzburg. N. yr, M. Sibrt,. Xu r with th utsch Tlkom/T-Systms, rmstt, Grmny, -mil:{nico.yr, M.Sibrt, ngnn.xu}@tsystms.com V. Rkocvic is with th School o nginring n Mthmticl Scincs, ity Univrsity, Lonon, UK, -mil:v.rkocvic@city.c.uk Mjor rsrch spcts in WMNs r intllignt routing strtgis n Qulity-o-Srvic (QoS) support. In this ppr, w prsnt istribut, msurmnt-bs pproch to support rl-tim tric in WLN-bs msh ntworks. Th im o th propos mchnism is to kp trck o th srvics currntly prsnt in th ntwork n to nsur stbl n high QoS. Th objctiv msurbl QoS prmtrs r thn mpp to th usr-prciv Qulity-o-xprinc (Qo), xprss through th Mn Opinion Scor (MOS) []. Th tools or th pproch r implmnt in WLN-bs msh tstb. Th rsults rvl tht th mchnism prvnts rl-tim lows rom isturbing bst ort lows by obsrving th QoS prmtrs n controlling th throughput o th bst ort lows on th ntwork lyr. s n xtnsion to our work in [], th prormnc o th mchnism is msur or two irnt scnrios, isturbing tric lows on th sm pth to th stintion s wll s on crossing pth in th wirlss msh ntwork. Th rminr o th ppr is orgniz s ollows. In Sction II th work rlt to QoS n Qo issus in wirlss msh ntworks is shown. This is ollow by Sction III, introucing wirlss msh ntworks n its known problms. Our pproch is prsnt in Sction IV n Sction V shows th rsults o prormnc msurmnts. inlly, short conclusion is givn in Sction VI. II. RLT WORK On stp towrs QoS support in I 8.11 ntworks is in in th I 8.11 stnr or srvic irntition, which slightly moiis th rrir Sns Multipl ccss/ollision voinc (SM/) mchnism. Howvr, th stnr os not gurnt goo QoS lvl, spcilly in highly lo ntworks. This hs bn tst n improv or singl hop nvironmnts in [6], [7], n [8]. M protocol or QoS support in WMNs is propos by rlson t l. [9]. It is cll istribut n-to-n lloction o tim slots or Rl-tim tric (R). In this protocol, tim slots r rsrv in ll msh nos long rltim tric s rout to nsur trnsmission with goo QoS prormnc. Th rsrvtions r thus on or ix routs but rpir mchnism r provi i link ils n th rout hs to b chng. Th R pproch is implmnt n tst in simultion with ns-. sis th simultion-bs pttion mchnisms, Guo t l. [1] implmnt mchnism cll Sotwr-bs Tim ivision Multipl ccss (STM) on top o th WLN

2 M lyr in tstb. Th pproch is sign to support WLN-bs VoIP ppplictions n it is clim tht signiicnt improvmnt o th mximum numbr o G.79- qulity voic convrstions in WLN is chiv. Typicl scnrios with both bst ort n rl-tim tric r though not in th scop. This ruction to singl us css is, bsis th M lyr chngs, th scon irnc to th pproch prsnt hr. Thr r lso propositions or Qo provisioning on highr lyrs. H t l. [11] introuc milwr-bs QoS control in 8.11 wirlss ntworks. Th i is to implmnt tric prioritiztion insi th msh nos bs on control thory. To rliz this prioritiztion milwr sign with cross-lyr rmwork is introuc n implmnt in Linux-bs tstb. bov th milwr, th pplictions hv th possibility to in rquirmnts or singl connctions. or srvic is strt, th ppliction inorms th milwr tht crtin QoS spciictions r n or th sir low btwn two n points. Th milwr s tsk is to choos n qut srvic clss on ynmicl bs pning on th currnt prormnc o th srvic n th mn rquirmnts. y control loop th currnt qulity is msur n compr to th sir on. pning on th currnt qulity rror ynmicl pckt schuling is prorm. To istinguish our pproch rom [11] two things r mntion. s th milwr pproch is bs on prioritiztion insi th msh nos, only problms cus by tric pssing through on o th nos prioritizing multimi strms cn b hnl. I th tric problms occur u to collisions on th ir intrc cus by nos tht r not mn to prioritiz ny rl-tim tric mong thmslvs, thy will not rcogniz ny problm n not control th isturbr to solv th problm. Thr is no signling mchnism btwn irnt nos using th milwr sotwr to loct problm outsi th rl-tim rout. pning on th ocus il o ppliction, thr might b scon rwbck o th pproch prsnt in [11]: ll srvics tht n crtin QoS prormnc hv to b nnounc irst. III. WLN MSH NTWORKS N TH MSH STUP Wirlss msh ntworks r n intrsting to provi brobn wirlss Intrnt ccss. ig. 1 shows WMN in hirrchicl structur. Strting t th bottom, norml nonmsh cpbl wirlss or wirlin clints r ttch to th msh ntwork by Msh ccss Points (s). Ths s orm togthr with othr Msh Points (s) th msh ntwork itsl. is rsponsibl or msh rlying, mning tht it is cpbl o orming n ssocition with its nighbors n orwring tric on bhl o othr s. Th top o th hirrchy in ig. 1 constituts Msh Point Portl (P). Th P brigs tric btwn irnt WMNs or conncts th WMN to th Intrnt. s toys tchnology n inrstructur vlopmnts hv vnc,.g. whn looking t WMNs, th srvics us by th customrs nowys hv s wll. s or instnc Voic Wirlss Msh Ntwork or-ntwork Msh Point Portls (P) Msh Points () Msh ccss Point () lints ig. 1. Intrnt link Msh rchitctur Msh GHz Msh GHz ovr IP (VoIP) hs bcom mor n mor populr. Ntworks n mchnisms r ncssry to nsur high qulity. Th prormnc o ths rl-tim pplictions in WMNs hs bn wily stui in trms o simultion, but only w tstbs xist. W hv invstigt th possibility o rltim ppliction support in WLN-bs msh ntwork tstb, cll Msh. Th Msh hs bn vlop n is ploy t T-Systms in rmstt, Grmny n hs bn st up to invstigt crrir-gr spcts rom ntwork oprtor s point o viw. Th Msh ors ll min spcts o WMNs to mk th tsting possibilitis s vrious s possibl. tils bout th Msh cn b oun in [1]. ig. shows th loor pln o th T-Systms builing in rmstt, whr th Msh hs bn st up. urrntly, th Msh consists o 1 msh points, which cn ll b conigur to srv s s. Th s consist o mb M Go S11 Systms with 66 MHz PUs n 6 M o RM. ll msh nos r quipp with two thros Wirlss Mini PI Wi-i rs s wll s n port n bin Linux is instll togthr with th mwii [13] rivr. urthrmor, two Ps r st up which r quipp with 3 GHz Intl Pntium procssors n 1 G o RM. Msh Point Msh ccss Point Msh Point Portl ig.. Msh inoor ploymnt

3 IV. ROUTING LYR S PPROH. I n Gnrl Structur 1) I o th pproch: Th gnrl i o th pproch is to prorm th QoS support t th routing lyr. M lyr chngs woul b possibl s wll but thy r not suit in this cs. WLN hs lry bcom wi spr tchnology. hnging somthing in th M lyr s currntly stnriz woul not just mn n upt to or rcrtion o ll rivrs or th WLN vics but lso implis possibl hrwr chngs in thos vics. This mks th ploymnt n usg o nw M mchnisms vry iicult. Routing lyr mchnisms to nhnc QoS r promising pproch or WLN-bs msh ntworks. Th routing lyr is sily xchngbl, s it is totlly bs on sotwr. Inpnnt o th oprting systm, th routing lyr is logiclly situt on top o th ntwork vic rivr n intrcting with it vi rivr inpnnt intrcs. In th prsnt pproch, mximl ptbility n lxibility is rch through istribut solution. vry rly no is quipp with cpcitis to monitor, jug, n rct on th currnt ntwork sitution. Th im o th propos mchnism is to kp trck o th srvics currntly prsnt in th ntwork. pproching or lry prsnt problms shll b rcogniz s st s possibl. Solutions to thos problms on irnt wys shll b provi to nsur stbl n high QoS lvl. This im bsiclly ns two min tools to b rliz, Tric Obsrvr tht nlyzs th currnt ntwork sitution n Tric ontrollr tht ors irnt possibilitis to inlunc th ctul sitution to provi high QoS. urthrmor, n ctiv wy to llow communiction btwn thos two componnts not only whn prsnt on on msh no but lso whn istribut throughout th ntwork is ncssry. Th ollowing sctions xplin th irnt prts o th mchnism in mor til. ) Gnrl Structur n Introprbility: ig. 3 shows th gnrl structur o th vlop mchnisms. Th cor o th implmnttion is orm by th OLSR implmnttion o nrs Tonnsn OLSR [1]. Running this sotwr on vry no nbls th msh routrs to connct to ch othr n to orm th Msh. Th Tric Obsrvr is implmnt s krnl moul. It is runnbl inpnntly o OLSR n cn b compil n us on ny linux mchin with th corrct krnl vrsion. Th Tric ontrollr is implmnt s plugin to th OLSR plugin intrc. It inclus signling unit mking us o th OLSR brocst mssgs n llows thus communiction btwn irnt Tric ontrollrs. Loct on on singl no, Tric Obsrvr n Tric ontrollr r contcting ch othr vi th Linux ntlink sockts.. Tric Obsrvr Th ky prt o th prsnt pproch is th componnt cll Tric Obsrvr. Its tsks r two ol. On th on hn this moul hs to monitor th currnt sitution in th Tric Obsrvr low Monitoring Thrshol Mngmnt Ntlink Sockt procs ig. 3. rocst olsr OLSR Signling Mssgs Plugin Intrc Gnrl structur Plugin Intrc Ntlink Sockt ilr Tric ontrollr Tric ontolling Mchnisms Signling msh ntwork by obsrving th tric lows, s wll s othr inormtion tht cn b obtin rom th ntwork. On th othr hn it hs to jug whthr th currnt ntwork sitution is ccptbl or, i this is not th cs, how to rct on th occurring problms. To rliz this, crtin thrshols r n. In th ollowing sctions ch o ths two tsks is prsnt in til. 1) low Monitoring: s mntion bor, th most importnt tsk o th Tric Obsrvr, s th nm sys, is obsrving th ntwork n th tric insi it. spcilly bcus Tric Obsrvr n Tric ontrollr r normlly situt in vry rly no, lot o inormtion is obtin n nlyz. In rw clssiiction on might sprt this inormtion into pckt or tric rlt inormtion n nonpckt or -tric rlt inormtion. vn though th lttr on, incluing things lik PU usg or mmory lo t th monitoring no, might lso b o big intrst, th min ocus lis on th ormr. Tric rlt inormtion r thos inormtion concrning th tric o th ntwork, i.. th pckts scribing this tric in th cs o IP s in WLN-bs msh ntworks. On o th min ims o th pproch prsnt in this work is istribut solution to th issu tht is highly ptbl to irnt scnrios n ntwork chngs. This hs lrg impct on th possibl choic o monitorbl inormtion. No inormtion o nighbor nos bout thir obsrvtions cn b inclu in th msurmnts or two rsons. irst, th stnr pckt structur o rl-tim srvics os not inclu ny plc to trnsport thos inormtion. Scon, sning this inormtion in sprt pckts with rgulr tim intrvls is impossibl u to n insolvbl tr o btwn too much signling ovrh n too imprcis inormtion. OLSRv might solv this problm bcus it provis mor lxibl signling rmwork but proucs mor ovrh u to prioic signling. ll inormtion th Tric Obsrvr cn nlyz bout th currntly ctiv srvics is obtin by th obsrvtion o th pckts pssing by in th own no. Thr irnt typs

4 o inormtion cn b obtin or crtin pckt strm. irst o ll thr is th xplicit tim inpnnt inormtion rbl out o th pckts contnt, s or instnc sourc or stintion rss or protocol typ. Nxt, thr is th implicit tim pnnt inormtion which is obtinbl t th momnt o th pckt monitoring,.g. th pckt bsolut rrivl tim or rltiv rrivl tim tr th lst pckt o th sm srvic. inlly, thr is sttisticl inormtion tht is bs on sris o pckts rthr thn on singl on. This inormtion provis long trm nlysis o th monitor srvics, or instnc pckt loss ovr th lst n pckts or th stnr vition o th pckt intr rrivl tim. Th msurmnt o th wily us on wy ly mtric is vintly not possibl in this pproch s inormtion o mor thn on tim stmp t othr nos in th ntwork woul b ncssry. Though obtining this inormtion is impossibl s xplin bor. ig. shows scrn shot o th grphicl inormtion pg isplying th inormtion provi by th Tric Obsrvr. In th ollowing sction ll isply vlus r shortly scrib n ssign to th bov clssiiction. urthrmor, th qutions to clcult th sttisticl inormtion n to comput th MOS r givn. ig.. scrnshot rom th browsrs monitoring pg Th inormtion collct or Prmium n RTP srvics r s ollows: sourc, stintion, n nxt hop IP rss o th pckt cn b obtin s xplicit inormtion, ithr out o th pckt hr, or in cs o th nxt hop rss out o th routing tbl by knowlg o th stintion rss. Th pylo typ o th RTP srvic n its uniqu SSR numbr r lso xplicitly rbl rom th pckt hr. Th combintion o SSR n nxt hop rss is us to ssign uniqu I to ch srvic. Pckts with th sm SSR n nxt hop obtin th sm I n r collct togthr. Th vlus mn IP, st IP, n loss r sttisticl inormtion. To xplin thir clcultion, th ollowing initions r givn: or vry pckt p i th ollowing implicit n xplicit inormtion cn b obtin: φ i : uniqu intiiction numbr o p i, t i : bsolut rrivl tim o p i, t i = ti ti 1 φ i φ i 1 : rltiv rrivl tim o p i, n l i : totl lngth o p i in yts. urthrmor, sts r hl contining th obtin vlus or th lst winow siz w pckts P = {p lst w+1,..., p lst } sort by tim o pckt rrivl: Φ = {φ lst w+1,..., φ lst }, T = {t lst w+1,..., t lst }, T = { t lst w+1,..., t lst }, n L = {l lst w+1,..., l lst }. Using ths initions, th sttisticl inormtion cn b obtin s ollows: Th mn intr pckt ly mn IP is in s x T mn IP = mn[ T ] = x. (1) w Th stnr vition o th intr pckt ly st IP is in s st IP = w w 1 ( ( x T x w n th pckt loss loss is in s x T x w ) ) Φ loss = 1 mx[φ] min[φ] + 1 = 1 w mx[φ] min[φ] + 1 (3) Th inormtion collct or othr tric, i.. non rl-tim tric r s ollows: Th protocol typ, sourc n stintion rsss, n ports r xplicit inormtion o th pckt hr. Th combintion o sourc n stintion rsss n ports r us to ssign pckt to th corrct monitor srvic. its/sc n pkts/sc r sttisticl inormtion clcult s ollows using th bov initions: Th bnwith in bits/sc bps is in s l L bps = l () mx[t ] min[t ] Th pckt rt in pkts/sc is in s pktps = L mx[t ] min[t ] = w mx[t ] min[t ] ) Thrshol Mngmnt: Th prcing sction hs or look insi th Tric Obsrvr s monitoring cilitis. It isply which irnt typs o inormtion n prmtrs r msurbl n how thy r obtin. ll inormtion provi by th Tric Obsrvr is lwys vilbl up to th most rcnt pckt on mn vi th Linux proc ilsystm procs. Monitoring o th srvics lon is though not nough to o QoS/Qo monitoring n nhncmnt. Thr is lso th () ()

5 n or mchnism tht jugs th monitor inormtion n rcts in th cs o possibl qulity crs. To rliz this tsk, thrshol mngmnt in th Tric Obsrvr is ncssry. ollowing common wy o illustrtion, tric light chrts with colors grn, yllow, n r picting goo, vrg, n b qulity r us. Ky prmtrs hv to b compr to qut thrshols to ssign thm with th corrct color, i.. qulity lvl. Th ky prmtrs chosn in this work to jug QoS n possibl QoS grtion r th prviously introuc st IP n loss. In this work, th thrshols to o th QoS jugmnt on this prmtrs r conigur srvic pnnt. ch RTP pylo typ cn b conigur with our own vlus scribing th st IP grn yllow, st IP yllow r, loss grn yllow, n loss yllow r thrshols. On might imgin tht thrshols coul bcom lss mning in cs o lrgr numbr o srvics in th ntwork or mor climing in n mpty ntwork. Th thrshols in in this work r though intntionlly not pting to irnt ntwork situtions. Thy r st to ix vlus or vry typ o srvic. s si bor, th monitor vlus o th Tric Obsrvr r lwys vilbl on mn vi th procs. Mor prcisly, th xplicit n implicit inormtion or th w lst pckts r sv intrnlly. t th momnt o ccss to th procs, th sttisticl inormtion is clcult. Th jug ky prmtrs st IP n loss blong to th sttisticl inormtion s wll. Nvrthlss, thy hv to b compr to th thrshols rgulrly n not just on mn. st IP n loss r thus clcult whn w 1 nw pckts hv rriv. or instnc in cs o w = 1 with th rrivl o vry 1th pckt th st IP n loss vlus r upt. trwrs, th vlus r compr to th thrshols shown in Tbl I. I th thrshols r xc, n lrt is brocst vi th linux ntlink sockt. To voi n lrt looing uring th procss o th rction prio, lrts r snt with n intrvl o 1 scon. TL I QO THRSHOLS Qulity MOS loss thrshol st thrshol IP Lvl loss st IP goo 3.8- <.3 % < 1.7 ms vrg %.1 % ms 1. ms b 1-3 >1.7 % 1. % >7. ms 7. ms. Tric ontrollr Th scon importnt unit o th mchnism is th so cll Tric ontrollr. So r, th possibilitis o th Tric Obsrvr to tct problm n its wys to giv lrts hv bn prsnt. Th rmining logicl stps o th mchnism to solv qulity problms r signling th qulity problms to othr nos in th Msh n to rct on th isturbing inlunc to incrs th qulity. Ths tsks r rliz by th Tric ontrollr n r prsnt in this sction. 1) Tric controlling mchnisms: Qulity grtion cn occur or svrl rsons lik pckt loss, jittr, n long nto-n lys. common pproch to crs th pckt loss n th jittr is pckt prioritiztion using th typ o srvic bit in th IP hr. Howvr, u to problms on th ir intrc cus by subsqunt nos whn rlying tric ovr multipl hops, prioritiztion lon os not work in WMNs. onsiring th possibilitis o utomt n mnul WLN chnnl choic, it cn b stimt tht thr r no xtrnl inluncs to th WMN on th ir intrc. ll colliing pckts r originting rom on o th own msh routrs in th Msh. Unr ths circumstncs rction to ths collisions cn b on by ruction o th isturbing tric s pckt mount. y rucing th llow bnwith or non rl-tim tric to lowr but still ccptbl lvl, th rquncy o possibl isturbing pckts is utomticlly crs s wll. ) Stps o ontrolling: ig. shows th stps o Tric ontrollr rction in n xmpl scnrio insi th WMN nvironmnt isply in ig. 1. constnt bitrt rl-tim connction btwn n vi --- is isturb by crossovr high bnwith tric rom to vi -, s ig. (). () scnrio (b) problm tction s w hv sn rlly smll st IP uring th msurmnts or this ppr, th prmtr ws nglct in Sction V. Inst, w just us th QoS prmtr loss to clcult th Mn Opinion Scor (MOS). ccoring to Hossl t l. [1], [16] thr is clr xponntil rltionship btwn th pckt loss rtio n th MOS or th ITU-T G.711 voic coc [17]. s w r using this coc or th msurmnts, th MOS cn b clcult using th ollowing qution rom Hossl t l.: MOS = loss (6) (c) nighbor brocst ig.. () problm loction n rction Stps o controlling Th pckts rly rom to n rom to colli on th ir intrc with th pckts rly rom n which rsults in qulity crs o th rl-tim srvic, s illustrt in ig. (b). Th Tric Obsrvrs t,, n

6 tct th qulity problm n sn n lrt to thir Tric ontrollrs. t irst th nos try to in possibl isturbncs in thir own quus. To voi qulity crs cus by ovrlo quus, ll non rl-tim pplictions in th own no r chck irst, i crtin bnwith thrshol is xc. I this is th cs, th bnwith o th non rl-tim pplictions is ruc to prin thrshol. ynmicl stpwis pttion o th bnwith or non rl-tim tric is n intrsting topic to b rsrch n tst by simultion stuis in utur work. In th nxt stp s nighbor nos might cus crossovr problms, lik n in this scnrio, signling mssgs r snt to ll on-hop nighbors vi th OLSR Hllo Mssg systm. This is shown in ig. (c). ll nos rciving such brocst mssg o isturb no r s on-hop nighbors o th isturb no possibly rsponsibl or th isturbnc. Thror, thy chck n control th bnwith o possibl isturbing tric th sm wy s th isturb no i bor. In th isply scnrio, will ctivt th bnwith control. thn rcognizs tht th bnwith is lry ruc n no urthr rction is ncssry. ig. () shows th sitution tr th rction o th mchnism. is prorming bnwith control tht ls to slowr but still working high bnwith tric rom to. Th prormnc o th rl-tim lows incrss gin n th QoS/Qo mns cn b mt. V. PRORMN MSURMNTS To nlyz th prormnc o th prsnt pproch n to s i th usr prciv qulity cn b kpt on constnt n high lvl, two WMN scnrios r st up t T-Systms, s ig... In-n Tric isturbnc In th irst scnrio, shown in ig. 6, th isturbing bst ort low hs to us th sm wirlss link btwn msh point n msh point. W cll this scnrio th in-bn scnrio. Th cus o qulity grtion shoul thrby irctly b rcogniz by msh point. P ig. 6. Wirlss Msh GHz In-bn isturbing tric Msh GHz Th rl-tim connction btwn n is rliz by VoIP connction, similr to th ITU-T G.711 voic coc, with n intr rrivl tim o ms n pckt siz o yts. Th bnwith o th isturbing bst ort connction btwn n is stpwis incrs rom 1 to 6 Mbps. Whnvr th Tric ontrollr tcts QoS grtion o th VoIP connction, th bnwith o th isturbing bst ort low is crs to 1 Mbps. ig. 7 n ig. 8 succssivly prsnt th rsults o msurmnts with ctivt n ctivt controlling mchnism. Th x-xis shows th tim o th msurmnt in scons, th y-xs show th stimt MOS n th loss in prcnt o th rl-tim tric msur t s wll s th bnwith in Mbps o th isturbing srvic msur t. stimt MOS loss (%) W (Mbps) % pckt loss qulity thrshol msurmnt tim (s) ig. 7. In-bn scnrio without Tric ontrollr Th st IP hs lso bn msur t. Howvr, th msurmnts hv shown tht vn or th highst isturbing bnwith, this prmtr still stys t n ccptbl lvl blow ms. Thror, it is not isply in th msurmnt rsults. Howvr, th pckt loss hs lrg inlunc on th stimt MOS. Whnvr th sh lin t 1.7% pckt loss is cross, th MOS rops blow 3, rsulting in b voic qulity. This is lry th cs whn th bnwith o th isturbing bst ort is incrs to Mbps. urthr stimt MOS loss (%) W (Mbps) thrshol 1.% tction Rction msurmnt tim (s) ig. 8. In-bn scnrio with Tric ontrollr

7 bnwith incrs ls to pckt loss o up to prcnt n MOS o 1. Howvr, i th Tric ontrollr is ctivt, th MOS is kpt on high lvl s shown in ig. 8. Th vrticl lins in th curvs show th tim o th problm tction n th tim o th controllr rction. Th irst xcing vlus lrt t th tim o th tction o nw problm r mrk with circl in th loss grph. Th Tric Obsrvr thrshol btwn vrg n b loss vlus is st to 1. % n isply in th grph by sh horizontl lin. Th unctionlity o our mchnism is most obvious tr s o msurmnts. t this point, th bnwith o th isturbing tric low is incrs to Mbps which rsults in 6 prcnt loss o th RTP pckts. Th problm is thn tct by th Tric Obsrvr n th bnwith or th bst ort low is ruc to 1 Mbps. trwrs, th loss crss n th mn opinion scor incrss to gin.. Out-n Tric isturbnc Th scon msurmnt scnrio is shown in ig. 9. This tim, th RTP srvic rom to is isturb by subsqunt crossovr high bnwith connctions rom to vi -. This scnrio is cll out-bn scnrio. rction to b Qo is prorm lik shown in ig.. Howvr, this tim th bnwith o th bst ort low is ruc to Mbps inst o 1 Mbps bcus th qulity crs os not origint rom ovrlo quus but rom intrrncs on th ir intrc which hv lss inlunc on th voic tric low. P ig. 9. Wirlss Msh GHz Out-bn isturbing tric Msh GHz In contrst to th irst msurmnt scnrio, th bnwith o th isturbing bst ort tric cn now b incrs rom to Mbps in stps o Mbps, u to th bov mntion rson. In th irst scnrio, both lows shr th sm quus t th WLN M lyr t n. In th scon scnrio, th qulity o th VoIP low is just gr by th intrrnc on th wirlss link. ig. 1 n ig. 11 show th msurmnt rsults with ctivt n ctivt controlling mchnism. Similr to th prvious rsults, th st IP is ngligibl n not plott. gin, th loss vlu is lot mor snsibl to collisions on th ir intrc. ig. 1 shows tht th thrshol is lry xc or isturbr bnwith o 1 Mbps. or isturbr bnwiths o Mbps n mor, th qulity rmins lwys stimt MOS 8 6 thrshol 1.7% msurmnt tim (s) loss (%) W (Mbps) stimt MOS loss (%) W (Mbps) ig qulity thrshol 1 3 ig. 1. tction Rction Inluncs o crossovr isturbrs thrshol 1.7% msurmnt tim (s) Improvmnts by th Tric ontrollr in th out-bn scnrio blow th thrshol. or th highst tst bnwith o Mbps, th srvic qulity t is totlly unccptbl s th loss vlu incrss rsticlly. ig. 11 shows th sm cs s ig. 1 but with ctivt mchnism t ll nos. Obviously, s irst prcption, th phss with high loss, invoking low MOS, r lot shortr thn without th inluncs o th mchnism. Th bnwith grph shows th ruction o th isturbrs bnwith to th conigur vlu o Mbps. This obviously ls to irct rturn to ccptbl qulity vlus in th loss n M OS curvs. To quntiy th prormnc o th mchnism, th ky prmtrs, rction tim n signling mssg lo, hv bn nlyz. pning on th numbr o nighbors msh routr in th pict scnrio rcivs on vrg btwn yt, bout 3 to pckts, n yt, 1 to pckts, o OLSR mssgs pr scon. s si bor, th Tric Obsrvr os not sn lrts mor rquntly thn with n intrvl o 1 scon to voi n lrt looing. n

8 lrt is urthrmor brocst by n OLSR mssg o siz itting in on singl OLSR pckt. This on itionl pckt pr scon os not show ny incrs o th vrg OL- SR signling bnwith. vn th highst msur OLSR signling bnwith o kbps is ignorbl vn in highly lo ntwork. Th signling lo issu is thus no problm o th prsnt mchnism. Th scon importnt mtric to quntiy th mchnism s prormnc is th rcting tim. s upcoming qulity loss is rcogniz ltst within th irst w isturb pckts, i.. in th ult cs with w = 1 n constnt bitrt ms in th irst two scons, th ly btwn th occurrnc o qulity crs n th rcognition cn b isrgr. Thn gin n ctivtion o th Tric ontrollr.g. rucing th isturbrs bnwith is suppos to solv th problm in mximlly w pckts s wll, wht cn b conirm by look t ig. 11. Th tim btwn th ctivtion o th Tric ontrollr n th rturn o n ccptbl qulity lvl is thus lso ngligibl. Th scop lis on th ly btwn th tction n th rction. ig. 11 shows tht this ly pns on th bnwith o th isturbr. or th bnwiths o, 1, 1 Mbps th ly rmins btwn 1 n 3 scons. Such ly rsults only in short QoS loss which is still ccptbl or usr. or th tst css with highr bnwiths o Mbps n Mbps, which r though not xpct to occur in rl msh ntworks, th lys incrs signiicntly up to 7 scons. n nlysis o th singl controlling stps hs shown tht th high lys in th msurmnt stup r minly cus insi th Tric ontrollr whil ctivting th tric ruction. Th lys r u to high PU us o th us msh points. In this cs th prrquisit o Sction IV tht th nos cn b chosn st nough to not b th bottlnck o trnsmission is not mt nymor with th us quipmnt. Th cts r though xpct to isppr whn mor powrul mchins or hrwr bs rliztion r us. Invstigting such rliztion might b promising topic or utur work. VI. ONLUSION In this ppr, w prsnt n pproch to mt high Qulity o xprinc lvl or rl-tim pplictions in wirlss msh ntworks. Th pproch is bs on two min ntitis, Tric Obsrvr n Tric ontrollr. Th Tric Obsrvr concurrntly msurs th ntwork sitution. Whnvr problm is tct in th wirlss msh ntwork, or xmpl high rt bst ort low blocks rl-tim ppliction, th Tric ontrollr orcs this low priority low to ruc th bnwith. In contrst to othr publictions in this r, th vlop pproch ws not just tst in simultion nvironmnt, but implmnt in rl WLN-bs msh ntwork. Two irnt scnrios hv bn invstigt, on with isturbing bst ort tric on th sm pth n on scnrio with isturbing tric within th covrg r o th msh points. Th rsults hv shown tht without th Tric ontrollr, th subjctiv qulity, xprss in th mn opinion scor, crss rsticlly whn only smll isturbing bnwith is st up. Howvr, whn th Tric ontrollr is ctivt, th MOS only rops or on to thr scons blow. ompring th two scnrios, it cn b si tht th rltim ppliction is by r mor inlunc by bst ort low on th sm pth thn on crossing pth. This is u to quuing cts on th M lyr. Th nxt stp is to ruc th bst ort bnwith not to ix vlu, but to utomticlly pt it to th mximum possibl bnwith without isturbing th rl-tim tric lows. RRNS [1] I 8.11s/1., rt mnmnt to Stnr or Inormtion Tchnology - Tlcommunictions n inormtion xchng btwn systms - Locl n mtropolitn r ntworks - Spciic rquirmnts - SS Msh Ntworking, Mrch 7, I 8.11s/1. [] I 8.1 Stnr Group Wb Sit. vilbl rom: [3] I 8.16j Mobil Multihop Rly Projct uthoriztion Rqust (PR), Oicil I 8.16j Wbsit: org/bor/ns/projcts/8-16j.p, Mrch 6. [] ITU-T, Sris P: Tlphon Trnsmission Qulity, Mthos or objctiv n subjctiv ssssmnt o qulity; Mn Opinion Scor (MOS) trminology, July 6, itu-t Rcommntion P.8.1. []. Hock, R. Pris,. Sthl, V. Rkocvic, N. yr, M. Sibrt, n. Xu, QoS Provisioning in WLN Msh Ntworks Using ynmic nwith ontrol, uropn Wirlss 8, Jun 8. [6] R. Pris, S. Mnth,. Sthl, M. Mnth, n P. Trn-Gi, ynmic ontntion Winow pttion (W) in I 8.11 Wirlss Locl r Ntworks, in Th Scon Intrntionl onrnc on ommunictions n lctronics, HUT-I, Hoi n, Vitnm, Jun 8. [7] H. Zhu, G. o,. Ynr, n.. Mthis, -M: Novl nhnc istribut oorintion unction or Wirlss Hoc Ntworks, in I I, Pris, rnc, Jun, pp [8] L. 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Trn-Gi, n M. ilr, Quntiiction o Qulity o xprinc or g-s pplictions, in th Intrntionl Tltric ongrss (IT), Ottw, n, Jun 7. [16] T. Hoßl,. Hock, K. Tutschku, P. Trn-Gi, n M. ilr, Tsting th IQX Hypothsis or xponntil Intrpnncy btwn QoS n Qo o Voic ocs il n G.711, 18th IT Spcilist Sminr on Qulity o xprinc, Krlskron, Swn, My 8. [17] ITU-T Rcommntion G.711, Puls co moultion (pcm) o voic rquncis, Intrntionl Tlcommuniction Union, Rcommntion G.711, Tlcommuniction Stnriztion Sctor o ITU, Gnv, Switzrln, Novmbr 1998.