on the issues and challenges of fiber-wireless

7/30/2019 On the Issues and Challenges of Fiber-Wireless

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Hndw Pshn CopotonJon o EnnnVom 2013, Atc ID 645745, 11 pshttp://dx.do.o/10.1155/2013/645745

Review ArticleOn the Issues and Challenges of Fiber-Wireless(Fi-Wi) Networks

Harry Tin Win and Al-Sakib Khan Pathan

Department o Computer Science, International Islamic University Malaysia (IIUM), Jalan Gombak, 53100 Kuala Lumpur, Malaysia

Cospondnc shod ddssd to A-Sk Khn Pthn; [email protected]

Rcvd 16 Dcm 2012; Rvsd 16 Mch 2013; Accptd 27 Mch 2013

Acdmc Edto: Qsh W

Copyht 2013 H. . Wn nd A.-S. K. Pthn. Ts s n opn ccss tc dsttd nd th Ctv CommonsAttton Lcns, whch pmts nstctd s, dstton, nd podcton n ny mdm, povdd th on wok spopy ctd.

T ojctv o ths tc s to psnt vos spcts o F-Wss (F-W) ntwoks, whch s tchnooy o cntntst o th schs. F-wss tchnooy, known n shot s F-W, s comnton o optc-f-sd ntwoknd wss ntwok. F-W hs cnty com owd s on o th mn t ntwok tchnoos yt th tm s onmxd p wth wss-fdty (W-F) tchnooy. In ct, W-F ntwok cod ncdd n F-W chtct. D toth nmty wth th tm, F-W nd sm sondn commony known W-F, mny stdnts, vn cdmcs ndpcttons somtms my not to dntt twn ths. In th cnt ys, ood nm o woks on vossss oF-W hv com ot, t n ov svy wth th tst dvncmnts n th s yt to ond. Hnc, n ths wok,

w nyz vos sss nd chns o mpmntn F-W ntwoks n pctc scnos to ow schs to fnd tdctons o sch nd n ds to ndstnd th sss tt.

1. Introduction

F-wss (F-W) o optc wss s th comnd so optical (optc f) nd wireless (do qncy)commncton to povd tcommncton svcs toth csts o nd ponts whch ophcy dstnt.It s th comnton o pssv optc ntwoks (PONs)nd wss msh ntwoks (WMNs). Optc ntwoks

dsnd to povd on-dstnc, hh-ndwdth com-mnctons wth th hp o wss ntwoks to povdqtos, x commnctons n commnty s.T hh-cpcty optc f s sd to spn th onst ds-tncs, nd ow cost wss nk cs th sn o thst m to ny ss. F-W ntwok cn sppot vostyps o commnctonssch s pstm, downstm, ndp-to-p (P2P) commncton.

A F-W ntwok conssts o wss sntwok sth ont nd nd n optc sntwok s th ck nd. AWMN conssts o mtp twys to th Intnt ccssnd op o wss msh ots wth mtpwss

msh cnts. PON sntwok n F-W ntwok cn povdp to 1.25 Gps EPON (Ethnt PON) nd GPON (GtPON) sppotn 2.488 Gps t n th downstm nd1.244 Gps t n th pstm whch vy hh nd-wdth cts, t th ntwok st cs th mpct ontncs n wss commnctons whch on dto svy mtn th ntwok thohpt n wss s-ntwoks. T ct o ntnc on ntwok thohpt

cn dcd y th nttd t o p-to-pcommncton om on wss cnt to noth wsscnt n F-W ntwok, whch hs com ocs pont nIEEE 802.11s stndd o WMNs [1]. Whn p-to-pcommncton s sd n F-W ntwok, ntwok thoh-pt cn ncsd y ncsn tc o ch ow thtch P2P commncton ow cod nt mo dmndo ntwok pckts to ncs th ov thohpt. Bysn ths mthod, th dy n P2P commncton cn dcd snc th tnsmsson n th PON sntwok cn mch st thn tht s n th mthop wss ntwokpt. W w dscss ths sss t n ths pp.


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1.1. Objectives o Tis Paper. A mjo ojctv o ths woks to nyz th chtct o F-W ntwok nd ts

vos spcts. T ntton o dnt tchnoos cn ddssd o ow cost o dpoymnt, hh ndwdthpovson, nd sc xtnson o commncton cov-. Sch wireless-optical-wireless commncton mod

ntodcd y F-W ntwok cn sstn th ntnc nwss sntwok cs pckts o ow snt thohmtp pths n wss ntwok ndthn, ths pckts snt to optc n tmn (OL) thoh dnt optcntwok nts (ONUs) n th optc sntwok. Anothojctv o th wok s to ndstnd th osvtons ontwok thohpt n o F-W ntwok n P2P comm-ncton nd th tc to th Intnt. O ppos s toxpo F-W ntwok om vos ns, tk ot thctc pomnc mtcs, nd mk t sy to sp yth sch commnty nd n ds. F-W cod th nxtwv o spdy wss commncton [2], yt,n ty, th vy w svy woks on ths topc[3, 4], nd wth vn th cnt dvncmnts nd tnds,w dm t ncssy to ddss vos sss wth tstchvmnts n ths .

1.2. Structure o TisPaper. Tspp s onzd s oows.A Scton 1, Scton 2 tks ot th stct spctso F-W ntwok. Scton 3 psnts th sss tht wnvsttd n vos v tts, Scton 4 tksot Qty o Svc (QoS) sss n F-W ntwokwh Scton 5 tks ot tnsmsson conto potoco(CP) pomnc sss. Scton 6 dscsss tc otnsss. Ts th mjo sss o whch F-W s thohtto pc th tvy sow todys ntwoks. Scton 7 s

o ov fndn o th s o potnt sch ndchn. Scton 8 concds th pp.

2. Structural Aspects of Fi-Wi Network

o ndstnd nd nyz th F-W ntwok chtct,th concpts o pssv optc ntwok, ndyn tch-noos, nd tdton wss ntwok ndd to ndstood. Bo pocdn th, n 1, w ptth mjo tmnoos sd n ths pp onsd thmnns o th s o dn.

2.1. Network Architecture or Fi-Wi Based P2P Communica-

tion. In F-W ntwok, pssv optc ntwok consstso n optc n tmnton (OL) t th commnctoncompnys oc nd nm o optc ntwok nts(ONUs) n nd ss. ypcy, p to 32 ONUs cn connctd to n OL thoh Rmot Not (RN). An ONU sconnctd to th msh cnts thoh wss msh ots.A p-to-p (P2P) commncton n sch ntwok cn cd thoh th wireless-optical-wireless mod n whchth tc s snt om th soc wss cnt to ts nstONU, whch s thn snt to th cosst ONUo th dstntonwss cnt thoh th PON sntwok, nd thn tcs dvd to th dstnton wss cnt. Fo th tcot to th Intnt, th tc s snt om msh cnt to

able 1: Mjo tmnoos t nc.

Avtons F mnn

F-W F-wss

W-F Wss fdty

P2P P-to-p

PON Pssv optc ntwoksEPON Ethnt pssv optc ntwok

GPON Gt pssv optc ntwok

OL Optc n tmn

ONU Optc ntwok nts

LP Ln pommn

RN Rmot nod

WMN Wss msh ntwok

RoF Rdo-ov-f

R&F Rdo nd f

RAU Rmot ntnn nt

nst ONU thoh th cosst wss msh ot, thnsnt to OL, nd wds th tc s snt to Intnt omOL. Fo xmp, msh cnt wod k to commnctwth msh cnt , tc w otd om msh cnt to ts nst ONU thoh wss msh ot, thn toth OL om th nst ONU thoh RN, thn th OLodcsts th tc ck to ONUs, nd th ONU whchs th cosst to msh cnt cn snd th tc to cnt thoh th nst wss msh ot. F 1 shows typc F-W ntwok chtct tht ows sch P2Pcommnctons.

2.2. An Example Model o Fi-Wi. T chtct o F-Wntwok s dsnd s dctd ph = (,), wh s th comnton o th OL dnotd s 0, st o ONUs(twys) dnotd s , nd st o wss msh otsdnotd s .

T sn-chnn wss ots n th wss s-ntwok o F-W ntwoks sd wth sn chnn wthchnn cpcty. Awss nods wok on th sm fxdtnsmsson pow wth th tnsmsson n nd thntnc n . Gny, s tms o, wh > 1. T wss nks twn ny two wssnods thy wthn th tnsmsson n o ch oth.Fo ny two nods, nd , th wss nks V, V thy n th tnsmsson no ch oth.

In F-W ntwok, ONUs cn commnct wth choth y sndn th tc to th OL, nd thn OLsnds th tc ck to ONUs. In ny two ONU nods,, V , th dct commncton V (V ) wthnfnt cpcty (s F 2) cn pcd cs thndwdth cpcty povdd y th PON sntwok smch hh thn th cpcty povdd n th wsssntwok. I ths commncton hppns n th PONsntwok, th w no wss ntnc, nd thntnc st o sch nks s st to 0. I two twysn tdton WMNs wthn tnsmsson n o ch


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OLT

RN

Mesh client a Mesh client b

Wireless mesh router

PON

WMN

ONU no. 1 ONU no. 2 ONU no. 3 ONU no. 4

Figure 1: ypc chtct o F-W Ntwok.

1 2 3 4

0

Figure 2: Achtct o F-W Ntwok wth mtp ONUs,wh ONUs (.., ) connctd wth ch oth wth thwd nk o nfnt cpcty () nd so connctd to OL (0)wth th wd nk o nfnt cpcty (

).

oth, thy cn commnct wth ch oth thoh w-ss tnsmssons. I thy not covn ch oth wthth tnsmsson ns, th s no dct commnctontwn thm. T my oth typs o chtcts sw. Inth wok psntd n [5], nq nod psntnth wd ntwok s ntodcd onsd ndctonnk om ch twy to th nq nod wth nfntcpcty. A ndcton nk wth nfnt cpcty cn pcd o th commncton om ch ONU to th OL.Ts commncton hs no wss ntnc, nd thntnc st o sch typs o nks s st to 0.

Fo th ntnc mod, w cn ppy th sm mods s psntd n th woks k [1, 6] s V Int(V)cs th st o wss nks tht nt wth V sdnotd y Int(V) . Lt n ths pp, w ws ths nottons nd smp chtct to dsc th

ntwok tc nd otn sss.

2.3. RoF versus R&F Network echnologies. As sc nd-yn tchnoos o F-W ntwok, oth RoF (do-ov-f) nd R&F (do nd f) tchnoos cn ond.H, w w know n how ths tchnoos opt.

2.3.1. RoF (Radio-over-Fiber). In RoF W-F ntwoks, do-qncs (RFs) cd ov optc f nks twn cnt oc (CO) nd mtp ow-cost mot ntnnnts (RAUs) to sppot vty o wss ppctons.RoF ntwoks povd tnspncy nst modton tch-

nqs nd to sppot vos dt omts ndwss stndds n cost-ctv mnn. Ts nt-woks s optc f s n no tnsmsson mdmtwn cnt conto oc nd on o mo RAUs(do ntnn nts). T CO s n ch o contonccss to oth optc nd wss md. Howv, snn optc dstton systm n wss ntwoks my hv ntv mpct on th pomnc o mdm ccssconto (MAC) potocos. T ddton popton dymy xcd ctn tmots o wss MAC potocos,nd th ntwok pomnc wod com wos. F 3shows smp RoF W-F ccss ntwok chtct thtcn sd wthn F-W ntwok.


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OLT RN

RAU

ONU no.1

RAU: Remote antenna unit

SS: Subscriber station

ONU no.

SS no. 1

SS no. 2

Figure 3: RoF W-F ccss ntwok chtct: PON nd tswss xtnson RAU.

2.3.2. R&F (Radio and Fiber). R&F W-F ntwoks s twodnt MAC potocos spty o th optc nd w-ss md to ccss PON nd WMN. Potoco tnstonmst don t th ntc o optc nd wss smntsy n ppopt optc-wss dvc, sch s optcntwok nt-s stton (ONU-BS). In ths cs, wssMAC ms do not hv to tv on th optc fto pocssd t th cnt conto oc t smpy hvto tvs th ssoctd ccss pont nd mn n thwss msh ntwok. In WLAN-sd (wss oc ntwok-sd) R&F ntwoks, ccss conto s don ocynsd th wss sntwok wthot nvovn ny cntconto oc so tht t cn vod th ntv mpct o

f popton dy on th ntwok thohpt nd t cnso dc th ntncs n wss sntwok. R&Fntwoks th most std chtct to d WLAN-sd F-W ntwoks o xtndd cov. F 4 shows smp R&F W-F ccss ntwok mod tht cn ppdn F-W ntwok nstct.

3. A Closer Look at the Works on Fi-Wi

In th st w ys, F-W ntwok stcts hv n sdxtnsvy n mny s, nd som schs hv nocsn on chtct sss k fndn th optmONUpcmnt to mxmz th ntwok thohpt, conf-

ton o th PON stcts, nd otn othms n thwss sntwok o ths ntwoks. T stts o thntwok thohpt nd th twy dpoymnt n wssmsh sntwok py snfcnt os. Amon vospshd woks on ths spcts, w w dscss som o thwoks n ths scton to hv tt ndstndn o thtopc.

Rnc [7] psnts n d on how to potct F-W ntwok stct om mtp smnt s. Tthos tm th schmn s RPMF (n-sd potctonconsdn mtp s). In ths schm, ckpONU s dsntd n ch smnt o th ntwok nd th smnts cstd n th ntwok. Tn, n ch

OLT RN

ONU-BS

ONU-BS: Optical wireless unit-base station

SS: Subscriber station

UserONU no.

SS no. 1

SS no. 2

ONU no. 1

Figure 4: R&F W-F ccss ntwok chtct: PON nd ts

wss xtnson ONU-BS.

cst, th thos dpoy ckp fs mon th ckpONUs n dnt smnts to d potcton n. Tsschm nts tht th smnts n ch cst hvnoh sd cpcty to cy th ntptd tc n thwost scno sch tht th ntwok cn tot thsmtnos s o mtp smnts. I smnt s,th schm ows th d smnt to tns ts tc ntony oth v smnts n th sm cst wth twotntv pths on th potcton n. Ts, ths schmcn tot th smtnos s o ny on smnt ndts ckp f.

An nttd ow ssnmnt nd st sqncnothm sstd n [6] to dc th ot-o-odpoty o pckts dptn om th OL wth vtyzo sqncn dy. Mxd nt pommn (MIP)Mod [8] nd smtd nnn (SA) othm [9] dsnd to mnmz th v dstnc o ny wssmsh ot to ts nho ONU. In od to mpov nd-wdth tzton, dynmc confton othm nWDM (wvnth-dvson mtpxn) PONs s poposdnthwok [10]. Dy-w otn othm (DARA) [11]nd cpcty nd dy w otn othm (CDAR)[12] hv n sstd to hhht th ss o ntwok

otn n th F-W ntwok. Moov, th stdy n [13]poposd cntzd nttd otn to ccompshth od ncn t ONUs nd to mxmz th ntwokthohpt.

Rnc [14] poposs nw schdn othmcd modfd dfct ond on schdn (MDRR) toncs th thohpt o CP nd to ns poss n-od pckt dvy t th dstnton. MDRR dpndson th DRR (Rond Ron Schdn) ndmnts. InMDRR, th qntm v vn to th qs s sd onth wht ssoctd wth thm. It povds tt qtyo svc nd vnty ds to chnn th thohpt,tncy, jtt, nd pckt ovow t th qs.


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T wok psntd n [15] shows tht n wss nt-wok wth nods, th p-nod thohpt s (1/ o )sn th ndom nod pcmnt nd commnctonmod. It coms (1/) sn th optm nod pcmntnd commncton pttn. T jont chnn ssnmntnd otn othms poposd [5, 16] n mtdo,

mtchnn WMNs to mxmz th ntwok thohptnd ctn nss constnts. T wok n [17] ts tottn th nss nt mon dnt tc ows ndto mxmz th ntwok thohpt. Som woks k [1823] ddss sn pocssn sss o tt pomnc oth nks n F-W stct.

T twy dpoymnt schm o wss ntwoks hsn stdd s w. T nyss n [24] ocss on thdownstm conton o F-W ntwoks nd poposs tc dstton schm whch tzs n spct o EPONto popy dstt tc od mon ONUs/GWs (t-wys). T thos dopt hop cont mtton mchnsmto vod thohpt ddton csd y ncsd wssntnc nd cts o coss tc n th WMN. Tsts show td-o tonshp twn od nc-n mon ONUs/GWs (twys) nd hh thohpt ond ss.

Moov, wy to dpoy th mnm nm otwys n WMNs s pontd ot n [25, 26] so tht th QoS(Qty o Svc) qmnts fd. Aothmso twy pcmnt nd dnt wss mods hvn poposd n [27], nd th othm s so ccontdo th tc od vnc om dnt ss. Rnc[28] stds WMNs optm mod to mnmz th costo ov ntwok nstton nd to povd covto wss cnts. Rnc [29] psnts how to ddnw twys nto xstd WMNs to chv mo ntwokcpcty. Howv, ths woks ony ocsd on th tcto th Intnt, not o p-to-p commnctons.

Rnc [30] ponts ot th mpct oht y thwireless-optical-wireless mod on th ntwok thohpt nF-W ntwoks nd ctn ONU pcmnt. In [30], thpomncmpovmnts o p-to-p commnctonstwn two msh ots n th sm F-W ntwok hvn nvsttd, nd th s o optc ns n PONs(nstd o nmos wss mthop connctons nWMN o th p-to-p commncton twn dstntypostond soc nd dstnton msh ots) hs npoposd. Accodn to [30], tzn PONs o commnc-ton twn soc nd dstnton msh ots mtts

th thohpt dcton nd nd-to-nd dy, csd ywss ntnc (whch s ncsd y mny hopsnvovd n WMN).

A on thoh ths woks mntond ov,w hv ond tht ony w woks tk ot F-Wntwok chtcts tht povd tntv otn op-to-p commnctons, whch cn tz th hhndwdth povdd y PON sntwok nd cod sntncs n wss sntwok to ncs th ntwokthohpt. In th nxt scton, w w ook nto th cso thohpt nhncmnt n sch ntwok s ths s thmn cty o whch F-W ntwoks consdd to ppn.

4. Quality-of-Service (QoS) Issues

Qty-o-svc (QoS) pys ky o n nnn vosmtmd ppctons nd svcs ov F-W ntwokscs QoS tchnqs sd to ms ndwdth, todtct chnn ntwok condtons sch s conston ovty o ndwdth, nd to potz ntwok tc.In ct, tt QoS o F-W s th mn ttctv pontn choosn sch knd o ntwok o th mpmnttonov oth tntvs. QoS tchnoos cn ppd topotz tc o tncy-snstv ppctons sch s

voc o vdo nd to conto th mpct o tncy-nsnstvtc. Howv, th vty o wss chnn condtonsnd moty o wss nd ss mht chn th qtyo svc, whch qs qck spons tm.

Rcnty, vos QoS tchnqs w dvopd o F-W ntwoks. QoS sppot s chv y mnn thntwok y. Dnt tchnqs mht sd o thdsn o hyd F-W ntwoks to dv QoS-ndsvcs o nd-ss. In [31], cntzd nd dsttd

schdn ppochs w xmnd o th nttono EPON nd WMAX. T smton sts show nmpovd ntwok thohpt nd nd-to-nd dy odnt QoS dmnds. T nttd QoS-w dynmcndwdth octon (DBA) schm poposd n [32] sp-pots ndwdth nss t th ONU-BS (s stton)ntc whch snds optc ndwdth qsts to thoptc n tmn (OL) sd on th stts o ts qs.T potd sts show mpovd ntwok thohpt,dy, nd ndwdth tzton.

o n mxmm ntwok thohpt n oth wd ndwss ntwok tc, ky QoS mtcs, sch s pckt oss,ndwdth,dy, jtt, nd pckt-o to, mpotnt.

T dsn o st otn othms s noth mn tompov QoS sppot n F-W ntwoks.

5. TCP Performance in Fi-Wi Network

Btwn nod ps o F-W ntwok, tnsmsson contopotoco (CP) povds dt tns. In odto pvnt ntwok conston nd mpov thohpt,pckts o ow snt thoh mtp pths n wsssntwok nd thn snt to th OL thoh ONUs n thoptc sntwok. OL hs sponsty to tnsmt thpckts to th dstntons. As tc n sch ntwoks snt to OL, OL woks s convergence node, whch cn

sqnc th pckts o thos snt to th Intnto to noth wss cnt nsd wss sntwok.

Whn OL snds th pckts to th dstnton, pcktsmy v ot o od cs o th vnt dy onmtp pths n F-W ntwok. Whn ths hppns, dp-ct cknowdmnt (ACK) s snt y CP cvso chot-o-od (OOD) smnt. Whn CP snd cvsth dpct ACKs, snd wod ssm tht smnths n ost nd th ntwok s constd. T ost pcktcn covd y tnsmttn th ost pckt om CPsnds whn dpct ACK s cvd. T constonvodnc s pomd th st tnsmsson nd stcovy.


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Howv, th s pom whn mny pckts vdynmcy om dnt ows wth pckt odn tOL, wh th OL mntns q o ch ow ndth pocssn s dvdd nto mtp q tm sots. Echdvdd tm sot cn snd ot ony on pckt om thOL to th Intnt o noth wss cnt nsd wss

sntwok.T OL nds to dcd whch ows pckts shod

snt nd whch pckts om sctd ow shod snt toth dstntons. Ts w ctvt th st tnsmssonnd st covy cs o th dpct ACKs nd thnw cs ddtv ncs n CPs conston wndowsz () n th ntwok wh odd pckts wdspd. Ts cton cn ct th CP pomnc nF-W ntwok.

In od to ncs th thohpt o CP nd todc th ot-o-od pckts om OL, st pcktschdn othm s ndd. Schdn s don o odncn nd chvn QoS. In F-W ntwok, th schd-

n othm s sd t OL to sqnc th pckts och ow to povd n-od vs t th dstnton.T sqncn cn so don t th nd systm. Tsqncn t OL mst don st so tht too mchdy wod not ntodcd to th sqncd pckts.T most chnn pt o mkn schdn dcson sto mntn th nm o dpct ACKs o ch q.T som ndmnt schdn othms whchcn sd n pckt sqncn sch s FIFO (fst-n-fst-ot), DRR (dfct ond on), nd MDRR (modfddfct ond on schdn).

OL mntns poty q systm (PQ)wth two poty vs o ch ow. T ot-o-od

pckts to th OL pt to th hh poty v ndothws to th ow poty v; oth vs svdn th fst-n-fst-ot (FIFO) od. In FIFO, th odstpocss n th dy q s sctd o nnn whn thcnt nnn pocss s xctd.T v wtn tms qt on n FIFO schdn othm. Dfct ondon (DRR) cn hnd pckts o v sz wthotknown th mn sz. A mxmm pckt sz nms stctd om th pckt nth, nd pckts tht xcdtht nm hd ck nt th nxt vst o th schd.Modfd dfct ond on schdn (MDRR) othmdpnds on th DRR ndmnts. In MDRR, th qntm

v vn to th qs s sd on th wht ssoctd

wth thm.Accodn to th wok n [14], MDRR schdn o-

thm s mo ctv thn FIFO nd DRR to povd n-od vs t th dstnton. T sts show MDRR smo cnt n ssn nss mon th dnt owsnd dcn th ct o pckt odn nd th qd sz n th OL.

6. Traffic Routing Issues in Fi-Wi

T ntton o th optc ntwoks nd wss nt-woks os n ttctv nd s soton to msth tc ow nd cont th nm o hops n F-W

ntwok. Athoh th mny otn othms todv mxmm ntwok thohpt, n-pommn-(LP-) sd otn othm [5, 33] s mo st csth mtp ONUs nd f wd commnctonstwn ONUs. To, LP-sd otn othm sntodcd n ths scton o t stdy. It shod

notd tht LP-sd otn tchnq (whch s optmotn schm) s not ky to sd n th pctcscnos s thoy on dos not dcty tnst to thpctc mpmntton css. To, pctc otnschm cn ppd o tc twn wss p nF-W ntwok to chv mo ntwok thohpt nom th wireless-optical-wirelessmod. In ths scton, F-Wntwok tc chctstcs nd vos otn mods dscssd, whch doptd om [5, 30, 33].

6.1. Multifow rac Demand. Mtpth otn s tzd

n od to ncs th tot ntwok tzton, hht ndwdth, ss dy, nd tt od nc-n whch mpov th ntwok thohpt nd sppotpstm, downstm, nd p-to-p commnctoncnty.

In th ntwok chtct shown n F 2 (sScton 2.2), th two tc ows tht hv to

consdd. T fst on s th tc om wss mshcnt to th Intnt, nd th scond on s p-to-p

commncton n F-W ntwoks. So, t th tcow vcto n th ntwok. To, th ow n th

vcto conssts o, , nd whch th soc nod,

th dstnton nod, nd th tc dmnd o th ow ,spctvy. In ptc, nd = 0 o .I = 0, th tc s o th ot to Intnt. T

tc ows n . So, t Int th st o ows otn toth Intnt, wh Int = { = 0}, nd t P2P thst o ows o p-to-p commncton n th ntwokwh P2P = { | }. Tn, = Int P2P. Echwss nod hs tc to th Intnt nd tc to vyoth wss nod.

6.2. LP-Based Routing Algorithm. As mnton n ov

chtct, ch wss nod hs ony on do woknon on chnn. To, th s no chnn ssnmntss. o n mxmm ntwok thohpt, ony w ndto consd otn nd nk schdn ppochs to nmxmm ntwok thohpt n p-to-p commnc-ton, th sm LP-sd otn othm cn sd tht spoposd n [30]. Lt s know ot th optn pncpso th othm.

Lt wh 1 th pcnt otc dmnd otd to th dstnton nod o ow n th vcto . To, s th tc otd to thdstnton nod o ow, nd V cn ssnd s thtc od o owon th nkV nd V s th tc od


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on nkV. Tn, w hv V = =1

V. o mxmz th

ntwok thohpt n th F-W ntwok:

mx

=1

, (1)

Sjct to V:V

V = , = 1 , = , (2)

V:V

V V:

V

V = ,

= 1 , = , ,(3)

V:

V

V = , = 1 , = ,

(4)

V :VInt(V)

=1

V

, V ,

(5)

V , = 1 , V , (6)

1, = 1 . (7)

T ow consvton t ch nod n th ntwok s nsdy (2), (3), nd (4). Eqton (5) shows th wss nkntnc constnt n th ntwok. Eqtons (6) nd (7)

mk s tht oth V nd wth nonntv vs.

6.3. Practical Routing Scheme. Lt s consd th scno

psntd n F 5. o pctcy s ny otn schmo th p-to-p commncton, th tc otn hstwo chocs twn cnt a nd cnt b.

Choice 1. T fstchoc s to pss tc thoh th vshotst pth twn cnts wthn th wss sntwok.

Choice 2. T scond choc s to snd tc thoh thwireless-optical-wirelessmod.

Fom ths two chocs, t s tt to choos th tcotn wth sm hop conts cs th wss ntwokthohpt w dcs th hop cont ncss. Idstnton cnts chd oth ONU, tc s dcty

otd to dstnton cnt om soc cnt. In ths cs,otn o th tc wod th sm s tdton wssmsh ntwok.

In th F-W ntwok nd tdton WMNs, th tcom wss cnts to th Intnt w wys otdto th nst ONU o th cnt thoh th wssshotst pth, nd th p-to-p commncton wthnth wss ntwok n WMN w thoh th shotstpth twn th p cnts. Ts s wht s cd thpctc otn schm o F-W ntwoks.

As th PON sntwok wod st noh consd-n th two pts nvovd n F-W stct, o mnconcn wod fndn shotst pth n th wss

smnt. o fnd ot th shotst pth n wss mshntwok, schm k tht s psntd n [34] cod sd. In ths wok, th thos s -shotst pth ppochwhch compts sv () cnddt pths n ch nodtowds soc nd thn chooss th st (shotst on)mon thm. Ech nod mntns st o-shotst pths

towd th soc. T otn phss ot dscovy,ot py, nd ot mntnnc. T dmsson contonts tht th ow on ch nk s no ss thn thqd ndwdth. Fth nvstton cn don onths ss, nd oth shotst pth otn mchnsms my dvsd.

7. Challenges and FutureProspects of Research

In ths scton, w w psnt th sss on whch monvsttons cod pomd n th comn dys.Toh mny sotons my v on dnt spcts

o th ntwok, som sss yt to fnd ny stnddzdo optm soton. In ct, on th chns mn wthth ppcton scno nd qmnts o ptcntwok sttn. Lt s fnd ot mo on ths.

7.1. Perormance. T pomnc o F-Wntwok s onth dsn o twy nods (ONUs) whch s vy mpotntn F-W ntton. T ndwdth octon, otn, ndnk schdn so mpotnt nctons n th ntwokdsn. Lnk schdn s sd n wss msh ntwoksto nt ntnc- tnsmsson on th shdwss mdm. Pomnc o sch ntwoks pnkcod so dd snfcnty cs o th mtpth

dspson ntodcd y th wss nk nd th nonndstoton csd y th do-ov-f (RoF) nk [35]. ostt t, n optc fs, mtpth dspson occsn wd co cs ht tvn on th xs o thco tvs shot dstnc p mt o f thn httht ptdy ndos tot ntn cton. A ps oht snt on wd co wod com on thn tht ths to . I t s too on, t wod m wth th nxt ps.Ts cts mtpth dstoton. On th oth hnd, non-n dstoton h mns th phnomnon o nonntonshp twn th input nd output sns o thctonc dvc (whch s sndn sns). Ts sss mynot msd om th cvs sd; hnc, chnn

qzton s chnn tsk n F-W ntwok. Chnnqzton mns th pocss o djstn th nctwn qncy componnts wthn n ctonc sno th ntwoks smooth opton nd tt pomnc.T som woks k [35, 36] to mpov pomncddssn ths ss; howv, dvsn n optm sotonppc n vos scnos s wys n opn chn.

7.2. Routing. Rotn, k ny oth ntwok, s vympotnt ss n F-W ntwok snc mthoppn hs t mpct on ntwok pomnc ddton nWMN. Rotn othms w ow wss tc to sth cpcty od y optc twys. Rotn othms


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8 Jon o Ennn

OLT

RN

Mesh client a Mesh client b

Wireless mesh router

ONU no. 1 ONU no. 2 ONU no. 3 ONU no. 4

Figure 5: Achtct o F-W ntwok wth pctc otn schm.

povd y-3 nctonty nd sv cnt othmswhch hp dc th nm o hops n WMN. Howv,ths othms cnnot sppot th nctonts tht tkpc t ow v. Intnsv sch woks on pstmschdn othms o PON o td systm hv nconttd n som pvos pps [3740]. In th F-W ntwok, tc ows v t th twy nod omcnts v wss pstm nks whch cn d to snttnton, dn, ntnc, nd nos. To, mosto th xstn othms cnnot dcty dptd wthottkn ts o wss nks nto consdton.

7.3. Architectural Issues. Mny schs hv poposdsv nttd ntwok chtcts whch comnoptc nd wss commncton to n mxmm nt-wok thohpt. Som o th sc chtcts [41] ndpndnt chtct nd do-ov-f (RoF). In thndpndnt chtct, th ONU s dcty connctdwth s stton (BS) v common stnddzd nt-c. T s no dct wss nk twn th ONUnd th cnts. T mn dvnt o ths chtct sth ndpndnt dpoymnt o th two ccss ntwoks.

Howv, th commncton twn ONU nd BS, whchxchns nomton, s nvod cs two domns spt. To, conto snn msss my s dy nd cs tc ovhd. Rdcn vos typs odys n oth pts o F-W s wys n opn ss whnsvcs k vdo-on-dmnd (VoD), v stmn, vdoconncn, nd oth mtmd dvy consdd[42, 43].

In do-ov-f (RoF), ts chtct conssts o cnt conto oc (CO) nd mot ntnn nt con-nctdy n optc f nkon whch thmcowv sns dsttd. T dvnts o RoF chtct s owttnton oss, mmnty to do qncy ntnc,

nd dcd powconsmpton.Howv, o nomod-ton nd nosn tnsmsson, th sn mpmntssch s nos nd dstoton com chnn sss tohnd.

7.4. Resource Utilization. Ech tchnooy n F-W ss tsown MAC potoco o svn cnt tc. I ths tch-noos wok ndpndnty, th mont o vsocs w not tzd n optc ntwoks. To,

th s o hyd nttd MAC potoco s vy mpotntn od to cnty tz th v socs ndchv hh ov ntwok thohpt. Ts potocosmst sppot nd-to-nd QoS so tht Svc Lv A-mnts (SLAs) cod stsfd nd cnts wod cvntd svc.

7.5. Supporting Dierent echnologies. An mpotnt ts th ntwoks cpty to sppot p-to-p commn-cton nd mtcstn tchnoos. F shn nd vdoconncn n p-to-p commncton xmpso wh ss xchn monts o dt. Ts knd otc cn svd mo cnty y sn dcntzd

soc octon mchnsms to vod poss ntwokottncks. T sm contnt mst dvd to mtpss n svcs k vdo on dmnd (VoD) nd Int-nt Potoco Vson (IPV). Mtcstn sppots onnq ow whch s smtnosy tnsmttd to mnyss vodn wst o socs. Ts vy mpotntts o cnt nd t ntwoks nd mst xpodn dt o F-W ntwoks.

7.6. Network Troughput. Concnd wth th tc to thIntnt, ch wss ot shod to ch tst on ONU o th Intnt ccss. Ech wss nodwod cct th shotst pth wth mnm hop cont


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Jon o Ennn 9

to ONUs nd sct on ONU s pmy twy oIntnt ccss. T ntwok thohpt wod hh whnth tc s ony dctd o th Intnt ccss. Howv,th ntwok thohpt wod dcs whn th tcdmnd ncss n p-to-p commncton, csth ntncs wod ncs n th wss ntwok.

Athoh th ntwok thohpt cn possy ss whnnod ds ncsd n th wss ntwok, w cnncs th ntwok thohpt n F-W ntwok nd n thtdton WMN y ppyn mo tc dmnd o chow o th ntwok.

7.7. Energy Consumption. A vy mpotnt ss o th F-W ntwok mpmntton s ts ny consmpton [44].Toh mny pts cod sppotd y constnt powsppy socs, psvn ny o ny cost s ctcss to mk t mo st nd ttctv ov othv tchnoos. As w movn towds th nnomton tchnooy (I) o n comptn , t s

vy mpotnt to know nd stdy th ny consmpton ovy dvc n th F-W ntwok. Wth th dvncmnts ossoctd ntwokn tchnoos, t s xpctd tht th F-W ntwok wod mo wdy sd o vos consmctoncs ppctons n th comn dys.

7.8. Green Computing. As th noton o n comptn [45,46] s thvn tody, k ny oth ntwokn tchnoos,F-W nds to ddss th nvonmnt sss s w.Invovmnt o nm o fs nd ssoctd dvcsto sppot th nstct wod podc ht nd nhos swhch nd to ddssd F-Wntwoks topc th tvy sow od o cnty stshd nt-

wok ckons. Hnc, dcn n hos s mssono ht (ths not conttn to o wmn) wod n nt pt o t sch n F-W s s w.

7.9. Integration with Smart Grid. A vy xctn oth nvstton cod comnn F-W ntwok wthsmt d [47]. Fo st opton o smt d, th F-Wcod wok s ckon.Anoth ntstn cod cod nstct wth F-W sppot. As dcton o tmn mny commc nd snss comptn ppctons s mjo ss, F-Ws st dt xchnn nstct my to ctt sch F-W Cod!

8. Conclusion

o smmz th ov contton o ths pp, thchtct o F-W ntwok s nvsttd sd on p-

vosy condctd sch woks. Vos spcts o thsntwok hv n nyzd to n som nshts o thtchnooy. W hv nvsttd th ntwok omtonsss, pomncsss, poss otn mchnsms, ndpst woks on spt ndyn sss. O conttons tht w hv dntfd th s o condctn thstds nd th possty o mn F-W tchnooy n thmnstm ntwokn sch. In n, F-W ntwoksom pow ptom o th sppot nd cton o

on dstnc, x, nd hh-ndwdth commnctonss w s o th t nosn ppctons nd svcs.To, thoh mny sss mntond n o wok,mny oth td sss to ths ntwok chtct ndd to xpod n t wth mo dts.

References

[1] G. R. Htz, D. Dntn, S. Mx t ., IEEE 802.11s: thWLAN msh stndd, IEEE Wireless Communications, vo. 17,no. 1, pp. 104111, 2010.

[2] N. Ghzsd, M. Schtzow, nd M. M, Svvtynyss o nxt-nton pssv optc ntwoks nd f-wss ccss ntwoks, IEEE ransactions on Reliability, vo.60, no. 2, pp. 479492, 2011.

[3] N. Ghzsd nd M. M, F-wss (FW) ccssntwoks: chns nd oppotnts, IEEE Network, vo. 25,no. 1, pp. 3642, 2011.

[4] A. Nom, H. Yn, nd J. Go, Inttd f-wss

ntwoks: wht, why nd how, n Proceedings o the IEEEAricon, pp. 13201325, Lvnston, Zm, Sptm 2011.

[5] M. Achy, R. Bht, nd L. E. L, Jont chnn ssnmntnd otn o thohpt optmzton n mtdo wssmsh ntwoks, IEEE Journal on Selected Areas in Communica-tions, vo. 24, no. 11, pp. 19601971, 2006.

[6] J. Wn, K. W, S. L, nd C. Qo, Pomnc modnnd nyss o mt-pth otn n nttd f-wssntwoks, n Proceedingso the IEEEINFOCOM, pp. 15,Mch2010.

[7] Y. L, L. Go, nd B. Gon, Rn-sd potcton schmo svv f-wss (FW) ccss ntwok consdnmtp s, n Proceedings o the 1st IEEE InternationalConerence on Communications in China (ICCC 12), pp. 285

290, Ast 2012.

[8] S. Sk, H.-H. Yn, S. Dxt, nd B. Mkhj, A mxdnt pommn mod o optmm pcmnt o ssttons nd optc ntwok nts n hyd wss-optcodnd ccss ntwok (WOBAN), n Proceedings o theIEEE Wireless Communications and Networking Conerence(WCNC 07), pp. 39073911, Mch 2007.

[9] S. Sk, B. Mkhj, nd S. Dxt, owds o opt-mzton o mtp ONU pcmnt n hyd optc-wssodnd ccss ntwoks, n Proceedings o the Joint Inter-national Conerence on Optical Internet and Next GenerationNetwork (COIN-NGNCON 06), pp. 6567, Jy 2006.

[10] S. Bhnd nd E. K. Pk, Hyd optc wss ntwoks,

n Proceedings o the International Conerence on Networking,International Conerence on Systems and International Con-erence on Mobile Communications and Learning echnologies(ICNICONSMCL 06), p. 113, 2006.

[11] S. Sk, H.-H. Yn, S. Dxt, nd B. Mkhj, DARA:dy-w otn othm n hyd Wss-OptcBodnd Accss Ntwok (WOBAN), n Proceedings o theIEEE InternationalConerenceon Communications (ICC07),pp.24802484, Jn 2007.

[12] A. Rz, V. Rmmth, S. Sk, D. Ghos, S. Dxt, ndB. Mkhj, CDAR: n cnt otn othm o wssoptc odnd ccss ntwok (WOBAN), Journalo Optical Communications and Networking, vo. 1, no. 5, pp.392403, 2009.


10/12

10 Jon o Ennn

[13] W.-. Shw, S.-W. Won, N. Chn t ., Hyd chtctnd nttd otn n sc optc-wss ccssntwok, Journal o Lightwave echnology, vo. 25, no. 11, pp.34433451, 2007.

[14] G. Svkm nd A. V. Rmpsd, Anyss o FW nt-woks to mpov CP pomnc, n Proceedings o the

International Conerence on Computing, Communication andApplications (ICCCA 12), pp. 16, Fy 2012.

[15] P. Gpt nd P. R. Km, T cpcty o wss ntwoks,IEEEransactionson Inormation Teory,vo.46,no.2,pp.388404, 2000.

[16] M. Achy, R. Bht, nd L. L, Jont chnn ssnmntnd otno thohpt optmztonn mt-do wssmsh ntwoks, n Proceedings o the 11th Annual InternationalConerence on Mobile Computing and Networking (MobiCom05), pp. 5872, Sptm 2005.

[17] R. Dvs, J.Pdhy, ndB. Z, Rotn n mt-do, mt-hop wss msh ntwoks, n Proceedings o the 10th AnnualInternational Conerence on Mobile Computing and Networking(MobiCom 04), pp. 114128, Octo 2004.

[18] Y. Zho, X. Pn, L. Dn t ., Expmnt dmonst-ton o 5-G/s pozton-mtpxd f-wss MIMOsystms, n Proceedings o the International opical Meetingon Microwave Photonics & Microwave Photonics Conerence(MWP/APMP 11), pp. 1316, As-Pcfc, Octo 2011.

[19] X. Pn, X. Y, Y. Zho, L. Dn, D. Z, nd I. .Monoy, Chnn msmnts o optc f-wsstnsmsson systm n th 75-110 GHz nd, n Proceedingso the International opical Meeting on Microwave Photonics &Microwave Photonics Conerence (MWP/APMP 11), pp. 2124,As-Pcfc, Octo 2011.

[20] L. Dn, M. Btn, X. Pn t ., F wss tnsmssono 8. 3-G/s/ch QPSK-OFDM sns n 75-110-GHz nd,

IEEE Photonics echnology Letters, vo. 24, no. 5, pp. 383385,2012.

[21] X. Pn, A. Co, A. Dodv t ., 25 Gt/s QPSKhyd f-wss tnsmsson n th W-Bnd (75-110 GHz)wth mot ntnn nt o n-dn wss ntwoks,IEEE Photonics Journal, vo. 4, no. 3, pp. 691698, 2012.

[22] C. Lm, C. Pkks, nd K.-L. L, A stdy on LCoS-sd mot nods Fo 60 GHz f-wss nks, Journalo Lightwave echnology, vo. 30, no. 19, pp. 31103117, 2012.

[23] X. Y, . B. Gon, R. Rods, .-. Phm, nd I. . Mon-oy, Systm wd mpmntton o photoncy ntdmps do t-wdnd o t f-wss ccss,Jounral o Lightwave echnology, vo. 31,no. 2, pp. 264275, 2013.

[24] M. Hond, H. Nshym, H. Nom, . Yd, H. Ymd,nd N. Kto, On th pomnc o downstm tc ds-tton schm n f-wss ntwoks, n Proceedings othe IEEE Wireless Communications and Networking Conerence(WCNC 11), pp. 434439, Mch 2011.

[25] B. Aon, R. Bot, Y. Iq, nd G. Knwd, Gtwypcmnt optmzton n wss msh ntwoks wth QoSconstnts, IEEE Journal on Selected Areas in Communications,vo. 24, no. 11, pp. 21272136, 2006.

[26] Y. D nd H. Pyv, Gtwy pcmnt wth QoSconstnts n wss msh ntwoks, n Proceedings o the 7thInternational Conerence on Networking (ICN 08), pp. 4651,Ap 2008.

[27] R. Chnd, L. Q, K. Jn, nd M. Mhdn, Optmznth pcmnt o Intnt APs n wss nhohood nt-woks, n Proceedings o the 12th IEEE International Conerenceon Network Protocols (ICNP 04), pp. 271282, Octo 2004.

[28] E. Amd, A. Cpon, M. Csn, I. Fppn, nd F. Mc,Optmzton mods nd mthods o pnnn wss mshntwoks, Computer Networks, vo. 52, no. 11, pp. 21592171,2008.

[29] J. Ronson, M. Uys, R. Swmnthn, nd E. Knhty,Addn cpcty ponts to wss msh ntwok sn ocsch, n Proceedings o the 27th IEEE Communications SocietyConerence on Computer Communications (INFOCOM 08), pp.12471255, Ap 2008.

[30] Z. Zy, W. Jnpn, nd W. Jn, A stdy o ntwok thoh-pt n n optc-wss (FW) ntwoks sjct to p-to-p commnctons, n Proceedings o the IEEE InternationalConerence on Communications (ICC 09), pp. 16, Jn 2009.

[31] Y. Lo, S. Yn, . Wn t ., QoS-w schdn ovhyd optc wss ntwoks, n Proceedings o the OpticalFiber Communication and the National Fiber Optic Engineers

Conerence (OFC/NFOEC 07), pp. 17, Mch 2007.[32] K. Yn, S. O, K. Gd, nd H.-H. Chn, Convnc o

thnt PON nd IEEE 802.16 odnd ccss ntwoks ndts QoS-w dynmc ndwdth octon schm, IEEEJournal on Selected Areas in Communications, vo. 27, no. 2, pp.101116, 2009.

[33] M. Kodm nd . Nndop, Chctzn th cpctyon n mt-do mt-chnn wss msh ntwoks,n Proceedings o the 11th Annual International Conerence onMobile Computing and Networking (MobiCom 05), pp. 7387,Sptm 2005.

[34] Y.-Y. Zn, B. X, Z.-M. Zn, nd H. Wn, Bndwdthntd shotst pth otn n wss msh ntwoks, n

Proceedings o the 1st International Conerence on Communica-tions and Networking in China (ChinaCom 06), pp. 13,Octo2006.

[35] Y. H. N, A. H. n, nd. C. Chh, Chnn dntfcton oconctntd f-wss pnk sn tny sns, IEEEransactions on Vehicular echnology, vo. 60, no. 7, pp. 32073217, 2011.

[36] C. Lm, A. Nmths, nd Y. Yn, Dtzd wsstnspot o f-wss systms, n Proceedings o the13th International Conerence on ransparent Optical Networks(ICON 11), pp. 14, Jn 2011.

[37] K. S. Km, D. Gtz, F. . An, nd L. G. Kzovsky,Btch schdn othm o SUCCESS WDM-PON, nProceedings o the IEEE Global elecommunications Conerence

(GLOBECOM 04), vo. 3, pp. 18351839, Dcm 2004.

[38] W. Yo, L. Y, nd W. H, Upstm ndwdth oc-ton sppotn dnttd svcs n OFDMA PONs, nProceedings o the 17th Opto-Electronics and CommunicationsConerence (OECC 12), pp. 132133, Jy 2012.

[39] L. Chn nd L. Zhn, A concnttd-nt-sd ndwdthocton othm o thnt pssv optc ntwoks, nProceedings o the Symposium on Photonics and Optoelectronics(SOPO 12), pp. 14, My 2012,.

[40] K. S. Km, D. Gtz, F.-. An, nd L. G. Kzovsky, Dsnnd pomnc nyss o schdn othms o WDM-PON nd SUCCESS-HPON chtct, Journal o Light-wave echnology, vo. 23, no. 11, pp. 37163731, 2005.


11/12

Jon o Ennn 11

[41] Y. Yn, H. Y, nd L. Dttmnn, Wss chnn condtonw schdn othm o hyd optc/wss nt-woks, n AccessNets, C. Wn, Ed., vo. 6 o Lecture Noteso the Institute or Computer Sciences, Social Inormatics andelecommunications Engineering, pp. 397409, 2009.

[42] S. J.H. Zd, H. B. Kh, ndA. Bsh, Rdcndys n F-W ntwoks, n High Capacity Optical Networks and Enablingechnologies (HONE 11), pp. 133137, Dcm 2011.

[43] Y. X nd Y. L, ONU ptchn o cnt VoD svc ovnttd f-wss (FW) ccss ntwoks, n Proceedingso the 6th International ICS Conerence on Communicationsand Networking in China (CHINACOM 11), pp. 10021007,Ast 2011.

[44] A. A, . q, nd S. M. H. Zd, Eny w otnothmo FW ntwoks (EARF), n Proceedingso the HighCapacity Optical Networks and Enabling echnologies (HONE11), pp. 8994, Dcm 2011.

[45] S. Msn, Hnssn n I: pncps nd pctcs,I Proessional, vo. 10, no. 1, pp. 2433, 2008.

[46] B. Kntc nd H. . Moh, Ethnt pssv optc

ntwok-on-tm voton dpoymnt o n ccssntwok, IE Optoelectronics, vo. 6, no. 4, pp. 183191, 2012.

[47] S. Zdy, Pthn, A. S. K. Pthn, C. Acz, nd M. Bd,owds pvcy potcton n smt d, Wireless PersonalCommunications, 2012.


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