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1 Scholars Journal of Engneerng and Technology (SJET) Sch. J. Eng. Tech., 05; 3(A):-3 Scholars Academc and Scentfc Publsher (An Internatonal Publsher for Academc and Scentfc Resources) ISSN 3-435X (Onlne) ISSN (Prnt) Research Artcle Optmal Cross-Layer Routng n 80.6 Mesh Networks Wth Dfferent Classes of Servce Yevsyeyeva Oksana*, Al-AawEssaMohammed Telecommuncaton systems department, Kharkv Natonal Unversty of Radoelectroncs, 4, Lenn ave., Kharkv, Ukrane, 666 Telecommuncaton systems department, Odessa Natonal Academy of Telecommuncatons named after O.S. Popov, Kovalska Str.,, Odessa,Ukrane,6509 *Correspondng author Yevsyeyeva Oksana Emal: Abstract: Permanent nterest n wreless mesh networks can be explaned by ther fast and easy deployment, selfconfgurng, self-healng, and large covered area. Substantally the advantages are related to possblty of every meshstaton to work as end- termnal and as transt node at same tme. In turn the capablty gves rse to set of problems one from whch s routng. In order to mprove network effcency and n complance wth next generaton network s concept routng must be optmal, adaptve, QoS-based and take nto account underlyng lnk layer. Whereas IEEE 80.6mesh networks are based on TDMA/OFDM the routng problem must be solved ontly wth slot allocaton. The artcle offers dynamc mathematcal model of IEEE 80.6 mesh network n space of state that allows to formulate cross-layer routng as constraned optmaton problem takng nto account requrements to bandwdth and delay of traffc delvery. Model s amed at slot reuse and multpath forwardng. As a result t allow to mprove network productvty up on 30-00% legacy sngle path delverng. Keywords: cross-layer optmaton, qualty of servce, routng, slot allocaton, WMax, wreless mesh network. INTRODUCTION Man gans of Wreless Mesh Networks (WMNs) n comparson wth conventonal pont-to-multpont cellularlke networks are related to capacty and relablty mprovng and wdenng of covered area. It s caused by hgher network connectvty so long as every mesh-staton can work as clent and as router for other clents at same tme, uplnk and downlnk aren t separated and traffc flow can be transmtted through any avalable nterface. Technologcally WMNs can be bult by usng IEEE 80., 80.5 or 80.6 standards. Last one descrbes WMax (Worldwde Interoperablty for Mcrowave Access) wreless networks whch were developed to provde hgh bandwdth access to large number of users []. In the artcle we ll focus on the WMax mesh networks. DEFINITION OF CROSS-LAYER ROUTING PROBLEM IN 80.6 MESHNETWORKS Lke as every next generaton telecommuncaton network IEEE 80.6 WMN must satsfy to set of requrements. On one hand t s provdng of wde range of applcatons wth dfferent levels of Qualty of Servce (QoS) and growng amount of user s traffc. On the other hand t s scalablty, robustness, easy n mantenance and low cost that gves rse to problem of network performance mprovng. In turn, t toughens up the requrements for traffc control problem whch ncludes two fundamental subproblems, QoS-routng and lnk resource allocaton. QoS-routng corresponds to fndng the best path (or paths) from source to destnaton along whch amount of avalable resources allows delverng of servced flow wth requred QoS parameters. Next step s related to assgnment requred amount of lnk resources to the flow. Solvng of the problems sgnfcantly depends on type (nature) of controlled resources. Workgroup IEEE 80.6 defnes Tme-Dvson Multple Access (TDMA) together wth Orthogonal Frequency Dvson Multplexng (OFDM) as man mode of WMax WMN []. Then as sngle unt of lnk resources s defned tme slot (so called mnslot) whch ons several OFDM-symbols and carres some porton of data. In turn, amount bytes carred by sngle OFDM-symbol and as a result by sngle slot depend on type of modulaton and codng scheme choce of whch s determned by current sgnal to nose rato on the lnk. Thus, problem of the lnk resources allocaton rses to the problem of tme slot assgnment.

2 There are some factors that must be taken nto account when solvng of routng and slot allocaton problems n WMax WMN. Most sgnfcant factor whch affects almost all processes n wreless networks s nterference from transmsson of neghborng statons. If some slot or set of slots s used by some wreless staton there s no neghbors that can use the slot or the set of slots. Takng nto account effect of hdden staton reuse of slot (slots) becomes to be possble f and only f dstance between the compettve statons s more than []. In whole the nterference condton lmts capacty of wreless network and affects slot allocaton process. The next mportant factor s related to QoS requrements whch must be ensured when delverng user s traffc. The requrements are preset boundary values for end-to-end delay, packet loss and data rate that defne amount of resources (number of slots) should be allocated n every lnk along used path. So far as current amount of avalable resources depends on set of slots used by -hops neghbors choosng of route must be based not only on QoS requrements and amount of unused slots but takes nto account the nterference effect. As a result the consderng nterference condton leads to hgher qualty and network productvty n whole. In addton n order to mprove network relablty and acheved qualty of servce routng n WMax WMN must be multpath. As we ll show below multpath routng n wreless envronment allows savng lnk resources by reusng of slots n dsont paths. Thus routng and resource allocaton problems are closely assocated and nterpenetratng. From the vewpont ther ont desgn becomes preferable. Though that all descrbed n lterature approaches can be dvded nto two groups, based on ont or separate soluton. The separaton can be explaned by smplfcaton where routng problem s related to fndng best route as sequence of lnks and nodes from source to destnaton but allocaton problem s assocated wth assgnment some set of slots n lnks along gven route. The process s teratve, shortage of slots n at least one lnk doesn t allow satsfyng QoS requrements and gves rse to route recalculaton. An advantage of the approach s related to possblty to use for path fndng any from developed for ad-hoc networks routng protocols, dstance vector (for example AODV, DSDV) or lnk state (for example OLSR), almost all of whch can be mplemented n WMax WMN [3, 4]. In order to mprove qualty of routng there are proposed to search path wth takng nto account state of wreless connectons at physcal and lnk layers by usng composte (cross-layer) metrcs. For example n [5] cost route metrc combnes end-to-end delay n the route, power and lnk qualty estmated va Exclusve Expected Transmsson Tme (EETT). Work [6] assumes mult-channel nterfaces of WMax mesh-statons and for the case proposes Multple Channel One Pass (MCOP) metrc that reflects physcal parameters such as modulaton and codng scheme and number of channels. Works [3, 7] gve suffcently complete classfcaton of dfferent cross-layer routng metrcs for WMNs. In whole although the metrcs attempt to take nto account dfferent parameter and even nterference effect the process of path fndng s based on shortest path algorthms. Wthn separate approach next after routng step s related to slot allocaton. Often for the purpose dstance- graph colorng s used [8, 9]. The algorthm ensures that all nodes wthn same collson group wll have dfferent colors (to elmnate nterference effect) and allows such slot allocaton that total number of slot (colors) should be optmed. Work [6] proposes other heurstc algorthm man dea of whch s replacement ntal multhop route by sngle hop by usng pre-calculated maxmal end-to-end rate (MEER) for every staton. The MEERs allow allocatng avalable set of slots among statons farly. Thus the parttonng of routng and slot allocaton problems where every from them s solved manly by heurstc algorthms doesn t allow maxmng slot utlty and network productvty n whole. On other hand as a rule proposed n lterature algorthm for ont routng and slot allocaton are based on heurstcs too. For example work [0] offers to send set of probe packets along all pre-establshed dsont paths from source to destnaton. Based on feedback report whch wll contan resdual energy, bandwdth, and delay for every path source selects best robust path sutable to QoS requrements. Idea of probes or path request messages les n the bass of works [, ]. Thus analyss of lterature allows formulatng set of requrements to whch perspectve methods of traffc control, ncludng routng and lnk resource allocaton, n WMax WMN must meet. In order to acheve maxmum productvty of wreless mesh network:. Routng and slot allocaton problems must be solved ontly.. The ntegrated problem of cross-layer routng must be formulated as optmaton problem that requres approprate mathematcal model of WMax WMN. 3. The mathematcal model must be flow-based and takng nto account QoS-requrements, be amed at multpath forwardng, be dynamc and takng nto account current state of WMN s lnks and nodes and nterference between them. In complance wth the requrements the artcle offers approprate mathematcal model of WMax WMN.

3 MATHEMATICAL MODEL FOR OPTIMAL CROSS-LAYER ROUTING IN 80.6 MESHNETWORK Satsfacton to part of before defned requrements can be acheved by usng set of dfferental equaltes to develop mathematcal model of WMax WMN n space of states [3]: q, where 0,,,... NF,, ( k ) q, ( k) m, v ( k), v ( k) n mg, ( k) g, ( k) n, vs, r v (, ) E,,, Nv,, NF gs, r g,, N, QoS ( k) t, k ; t t k tk s the samplng nterval (perod of re-computaton and change of control,, v k varables); ( ) s bnary control varable, defned as, f r - th slot s used n the lnk (, ) l, for transmsson of the flow addressed to l - th staton,, n the frameworks of - th class of servce; 0, otherwse, q, ( k) s state varable representng the data volume wthn -th class of servce (CoS) that s kept at the nstant tk n buffer of the -th staton and ntended for transmsson to the -th staton; m, s number of bts of the user's data that can be carred by one slot n lnk (, ) E ; E s a set of lnks between statons of a mesh-network; () S s a set of dstance- neghborng statons to the -th staton;, ( k) s the ntensty of the data arrval to the -th staton at the nstant of tme t k n the frameworks of the -th class of servce addressed to the -th staton; n s the number of the frames transmtted durng tme t, n t TF ; T F s the frame duraton; N F s an number of slots per frame whch s used for transmsson of a user's traffc; N v s a total number of statons n mesh-network; NQoS s an number of QoS-classes supported by the network. In complance wth physcal meanng of defned varables and lmted amount of network resources followng nequaltes must be brngng nto mathematcal model. If to assume that the packets of dfferent QoS-classes are servced n dfferent queues, condton of lmted buffer se can be wrtten as q Nv max, ( k) 0, q, ( k) q, (), o n case of common (aggregated) queue t becomes max NQoS Nv, q max, ( k) q, (3) where q s the maxmal se of the queue assgned to the -thcos at the -th mesh staton; buffer at -th mesh staton.,, v k max q s total se of The control varables ( ) correspond to slot allocaton process where nterference plays key role. There are two approaches to elmnate nterference effect; frst one s one-tme utlaton of every slot that can be represented as N QoS Nv (, ) E, l, l l,, ( k) for every, Nv. (4) Howeve n order to mprove capacty of WMN reuse of the slots must be approved. Then condton (4) s complcated and becomes 3

4 NQoS Nv NQoS Nv l,, (, ),, (, ),, E l g E l l gs, l g where S s a set of statons nterfered to the -th staton. ( k) ( k) for every, Nv, (5) Wthn next generaton networks all tasks must be solve from vewpont of Qualty of Servce that means traffc delvery wth ensurng ts set of QoS requrements to end-to-end rate, delay, tter and packet loss. In wreless networks packet losses can be caused by two reasons, poor sgnal to nose rato n lnks and overflow of buffers n the nodes (statons). In frst case deteroraton of sgnal to nose rato leads to change type of modulaton type and codng scheme that n turn results n lower data rate n the lnk. The overflow of buffer wthn proposed model s ntercepted by condtons () and (3). Takng nto account that as a rule tter s decreasng together wth decreasng of delay QoS requrements on network layer can be reduced to where B and and QoS-constrants (6) (0). Choosng of approprate obectve functon s rsen from followng reasons. Frstly, obectve functon must be amed at savng of lnk and buffer resources, t does cost functon as most preferable form. Because reuse of slots furthers resource savng obectve functon must stmulate the reusng. Addtonally as t s shown n works [8, 3] order of slot assgned along delverng path from source to destnaton affects total end-to-end delay, then obectve functon must supervse the order. Then obectve functon for optmal ont routng and slot allocaton can 4 B D B D D are acheved total end-to-end rate and delay respectvely wthn -th class of servce; D req are requred end-to-end rate and delay wthn -th class of servce. or By usng before defned varables rate requrements can be wrtten as N req B F r NF req mn m, k) r where B s the transmsson rate of flow requred by the user; values of the transmsson rate of flow guaranteed by the network. l, g, req, req m, l,, ( B Breq max and (6) B req and l,, ( k), Breq (7) req max, (8) Breq mn are maxmum and mnmum Total end-to-end delay of delverng n WMax WMN s gven by [8, 3] (to smplfy notaton ndex of class of servce was omtted) D 0.5 T D D T F q sd s, (9) where D q s prmary (conventonal) queung delay; d s delay equal to tme nterval between the frst slot and the slot allocated to carry gven packet for staton-destnaton; T s s slot duraton. Assumng that outgong nterface of wreless mesh staton can be descrbed as queung system wth constant servcng tme T F,.e. M / D / system, prmary queung delay D q can be calculated as [8] where TF, s ntensty of packet arrvng, /s. D q T F ( ), (0) Proposed mathematcal model of WMAx WMN () (0) proects the user s requests onto slot allocaton va, control varables ( ) whch must be found wth meetng buffer constrants () (3), nterference constrants (5), v k

5 be formaled as where a s the number of ntervals t, for whch the control varables should be calculated; () s vector of state varables q, ( k) at the nstant of tme k weght matrces of buffer and lnk resources usage respectvely, of the slots reuse; W seq, t ; s vector of control varables ( ) ; W q,, v k W are the dagonal W reuse s the weght matrx presentng a gan at the cost s the weght matrx presentng a breach of the order of slots along the path. Its element s 0 f sequence number of slot n a lnk s hgher than sequence number of slot used n prevous lnk and more the 0 f sequence of slots s broken. Thus the mathematcal model of WMax WMN () () allows to fnd optmal soluton for cross-layer QoSroutng wth takng nto account dynamcs of flows and state of WMN s lnks and nodes, and nterference between them. PERFORMANCE ANALYSIS In order to evaluate the performance of proposed model () () a smulaton was conducted. In the smulaton for dfferent wreless mesh networks we solved cross-layer routng as optmaton problem () subect to () (), (5) (7), (9) (0). Smulated network structures are shown n fg.. We assumed all statons are mesh subscrber statons (MSS) every from whch can work as source, destnaton and transt router. All lnks are assumed to have same qualty and transmsson rate. Chosen lnk parameters are followng: frame duraton T F =0 ms, slot duraton T s =.5 s, type of modulaton s 6QAM, codng rate s ¾. It means one frame contans 600 OFDM-symbols whch must be allocated among 56 user s data slots and control slots. Assumed 5 control slots (MSH_CRTL_LEN=5) every from whch has 7 OFDM-symbols we have 6 OFDM-symbols per user s data slot. Chosen modulaton type and codng scheme defnes 7 bytes of data per OFDM-symbol. Then one frame wth length 0 ms can carry n every slot 43 bytes of data. It corresponds to data rate 7.8 kbps when one slot s usng n every frame. To smplfy the smulaton process we assumed two classes of servce: low-cost brone class and hgh-qualty gold class. Gold class ncludes all requests senstve to end-to-end delay such as voce and vdeo calls. It means that control decson for request wthn gold CoS must meet to both of QoS-constrants from (6). Traffc wthn brone class s tolerant to delay and t must be servced accordng to requred rate brone req network resources t s allowed to delver traffc of brone class wth lower than requred rate. B.Under hgh load and shortage of MSS MSS 7 MSS 3 MSS 8 MSS MSS MSS 4 MSS 9 MSS 5 MSS 0 MSS 6 a 5

6 MSS 0 MSS 0 MSS 6 MSS MSS 9 MSS 4 MSS MSS MSS 5 MSS MSS 9 MSS 3 MSS 7 MSS 3 MSS 4 MSS MSS 5 MSS 8 MSS 8 MSS 6 MSS 7 b Fg-: Smulated wreless mesh networks Examples of dfferent routng and slot allocaton solutons for network # (fg., a) are gven n fg. and 3. In both cases traffc was generated by staton MSS 7 and addressed to staton MSS 6. In frst scenaro (fg. ) all traffc gold belongs to gold class wth requrements B 500 kbps and D 40 ms. Under chosen lnk parameters gold req satsfacton of rate requrement s related to fndng path (or paths) wth total equvalent capacty 3 slots per frame. Resultng optmal cross-layer routng was obtaned as soluton of problem () and t s shown n fg.. The soluton defnes three paths for delverng traffc from MSS 7 to MSS 6: path MSS 7 MSS MSS MSS 5 MSS 6 along whch slots wth numbers, 3, 4 and 6 are assgned; path MSS 7 MSS MSS 9 MSS 6 along whch slots wth numbers, 4 and 5 are used; path MSS 7 MSS MSS 0 MSS 6 along whch slots 6, 7 and 8 are assgned. The slot allocaton defnes some delay n every path. Fgure shows delverng delays from source to destnaton whch takes nto account transmsson tme n both the source and destnaton MSSs,.e. d D D T s d sd s. In complance wth (9) end-to-end delvery delay along path s 0.57 ms, along path s 0.49 ms, along path 3 s 0.7 ms. So total multpath end-to-end delay s maxmum delay among all used paths and t equals to 0.7 ms. -th frame req Slot Slot Slot 3 Slot 4 Slot 5 Slot 6 Slot 7 Slot 8 Lnk (7,) Path Lnk (,) Lnk (,5) Lnk (5,6) d along path Lnk (7,) Path Lnk (,9) Lnk (9,6) d along path Lnk (7,) Path 3 Lnk (,0) Lnk (0,6) d along path3 Fg-: Example of cross-layer routng for gold class of servce 6

7 Thus servcng of gold traffc requred 8 slots and moreover mnmal delay was acheved. Now let us defne amount of traffc n brone class that can be delvered between same par of MSSs by usng same number of slots. Approprate soluton s shown n fg. 3. It defnes above mentoned three paths wth total equvalent capacty 4 slots per frame that rses to resultng rate kbps. In complance wth (9) end-to-end delvery delay along path s ms, along path s 30.4 ms, along path 3 s 30.7 ms. So total multpath end-to-end delay n comparson wth frst scenaro s growng from 0.7 to ms. Thus relaxaton of delay requrement and correspondng absence of component n obectve functon () lead to ncreasng of traffc rate or n other words to savng of lnk resources by changng of order of slot allocaton. -th frame (+)-th frame (+)-th frame Slot Slot Slot 3 Slot 4 Slot 5 Slot 6 Slot 7 Slot 8 Slot Slot Slot 3 Slot 4 Slot 5 Slot 6 Slot 7 Slot 8 Slot Slot Slot 3 Slot 4 Slot 5 Slot 6 Slot 7 Slot 8 Lnk (7,) Path Lnk (,) Lnk (,5) Lnk (5,6) d along path Lnk (7,) Path Lnk (,9) Lnk (9,6) d along path Lnk (7,) Path 3 Lnk (,0) Lnk (0,6) d along path3 Fg-3: Example of cross-layer routng for brone class of servce Dagrams n fg. 4 show maxmum data rates that are possble between par MSS 7 - MSS 6 n network # (fg., a) wthn dfferent classes of servce. Here gold class s dvded nto two subclasses: traffc that s delvered wthn frame, n the case all slots are assgned along paths sequentally and as a result D T, and traffc for whch endto-end delay ncludes at least whole frame,.e. D s d T F s d F. As far as for brone class delay requrement s relaxed n the case acheved maxmum data rate s 48.8% hgher than maxmum low wthn gold class. At same tme dfference n delays reaches up to 3 tmes. 7

8 End-to-end delay, s Granted rate, kbps.5 x 04 Maxmum traffc rate n gold class wthn frame "brone" class "gold" class (wthn frames) "gold" class (wthn frame) Maxmum traffc rate n gold class wthn frames Maxmum traffc rate n brone class 48.8 % Incomng traffc rate, kbps x 0 4 Traffc delvered wthn 3 frames Traffc delvered wthn frames Traffc delvered wthn frame % 34 % 8.9 % "brone" class "gold" class Incomng traffc rate, kbps x 0 4 Fg-4: Dependence of resultng granted rate and acheved end-to-end delay on rate of traffc arrvng Thus dependence of granted rate (n other words productvty of network) on ncomng traffc for brone class defnes upper bound for flow between gven par of statons but smlar dependence for gold class defnes upper bound for flow wth hghest qualty of servce. By averagng of the dependences for all pars across network average network productvty can be estmated. The characterstc plays mportant role for dynamc call admsson control to accept or deny new request. In whole maxmum flow between gven par of statons depends on dstance between them. It s related to dfferent number of slots requred to delver same traffc along dfferent number of lnks. For example for drectly connected statons ( hop dstance n fg. 5) all vacant slots can be used. If to assume all 56 slots are vacant then maxmum rate between the statons becomes 56 rs where r s s data rate acheved by usng one slot n every frame along chosen path. As t was noted above under 6QAM (3/4) r s 7. 8 kbps, so for drectly nteractng statons maxmum flow s bounded by =4437 kbps. If dstance between source and destnaton becomes hops the ntal number of slots must be allocated between two lnk (fg. 5). As a result maxmum flow s reduced to tmes. 8

9 tance Par sourcedestnaton Par sourcedestnaton For statons dstance between whch s 3 hops and more maxmum flow can be estmated as are vacant. 56 rs 3 f all 56 slots {,,,56} tance hop {,,,8} k {9,,56} tance hops {,,,85} k {86,,70} g {7,,56} tance 3 hops {,,,85} k {86,,70} g {7,,56} m {,,,85} Fg-5: Examples of slot allocaton between statons at dfferent dstances tance 4 hops Smulaton results for dfferent pars of MSSs wthn dfferent structures (fg. ) are gven n table and fg rs The results demonstrate that thanks to multpath traffc delverng maxmum flow s bounded by for gold 3 56 rs class and by for brone class of servce. brone CoS Table-:Smulaton results for dfferent pars of MSSs Structure # Structure # Maxmum rate of flow, kbps Maxmum rate of flow, kbps gold CoS gold CoS brone gold CoS wthn wthn CoS wthn frame frames frame gold CoS wthn frames

10 Granted rate, kbps Granted rate, kbps Granted rate, kbps Granted rate, kbps 5 x 04 4 par MSS - MSS3 par MSS - MSS5 par MSS - MSS9 5 x 04 4 par MSS - MSS3 par MSS - MSS5 par MSS - MSS Incomng traffc, kbps x 0 4 a b Fg-6: Dependence of resultng granted rate on rate of traffc arrvng for dfferent pars source-destnaton (a brone CoS, b gold CoS) However the boundares can be reached f and only f source and destnaton are connected by two or more nterference-ndependence paths where transt statons n dfferent paths don t nterfere to each other and slot reuse s possble. For example wthn structure # (fg., a) between MSS 7 and MSS 6 two such paths can be found: MSS 7 MSS MSS MSS 5 MSS 6 and MSS 7 MSS - MSS 0 - MSS 6. At same tme wthn structure # (fg., b) between MSS and MSS 7 all shortest paths (MSS MSS MSS 5 - MSS 7, MSS MSS 3 MSS 5 MSS 7, and MSS MSS 4 MSS 8 MSS 7) nterfere to each other. In order to avod the nterference effect longer path s used (MSS MSS MSS 6 - MSS 9 MSS MSS 7) and as a result delverng rate cannot reach upper boundary 56 rs (see table ). Gan n traffc rate due to multpath n comparson wth sngle path delverng s shown n fg. 7 and 8. The gan for -th class of servce was estmated as max s.p. where B and B max m.p. G Incomng traffc, kbps x 0 4 Bmax m.p. Bmax s.p. 00%, () B max s.p. are maxmum rates acheved under sngle and multpath routng respectvely..5 x 04 multpath delverng snglepath delverng 5 %.5 x 04 multpath delverng snglepath delverng 3 % Incomng traffc, kbps x Incomng traffc, kbps x 0 4 a b Fg-7: Dependence of resultng granted rate for par MSS 7 MSS 6 wthn strcture # (a) and par MSS MSS 7 wthn strcture # (b) under sngle and multpath 30

11 G,% "brone" class "gold" class tance between source and destnaton, hops Fg-8: Gan n traffc rate due to multpath n comparson wth sngle path routng In whole multpath routng n comparson wth sngle path leads to ncreasng of traffc delvery rates together wth delay reducng. Gan due to multpath routng can reach 00% under same amount of avalable resources and user s QoS-requrements. In other words under same requred data rate offered model allows to use lower number of slots due to multpath delverng and slot reusng along the set of paths. CONCLUSIONS Offered mathematcal model s amed at optmal cross-layer routng n WMax (or other TDMA-based) wreless mesh network where dfferent classes of servce are supported. As far as the approach doesn t separate routng and slot allocaton problem the resultng routes contan enough number of slots that allow ensurng QoS-requrements of user s traffc. In turn the approach facltates task of call admsson control that s very mportant n general QoS network archtecture. The model formulates and solves WMN s routng problem as optmaton accordng to cost obectve functon whch leads to resource savng. Physcally t rses to slot reuse and multpath routng. As a smulaton results show gan n rate due to slot reuse and multpath routng can reach from 30 up to 00% under same amount of avalable resources and user s QoS-requrements (delay n the frst place). Maxmum rate that can be acheved n WMN under offered model approaches network capacty, the rate s affected by number of vacant slots, requested qualty level, dstance and structure of possble paths between source and destnaton MSSs. REFERENCES. IEEE Std , IEEE Standard for Local and metropoltan area networks Part 6: Ar Interface for Fxed Broadband Wreless Access System. IEEE, NY, Shou-Chh Lo, Lyu-Chen Ou; Effcent routng and centraled schedulng algorthms for IEEE 80.6 mesh networks. Internatonal Journal of Network Management, 0; (6): Ngad MA, Al S, Abdullah AH, Khokhar RH; A taxonomy of cross layer routng metrcs for wreless mesh networks. EURASIP J. Wreless Comm. and Networkng, 0, Carvalho T, Jalton JJ, Valente W, Natalno C, Francês R, Lopes Das K; A Moble WMAX Mesh Network wth Routng Technques and Qualty of Servce Mechansms. Selected Topcs n WMAX, Dr Gann Pasoln (Ed.), InTech, Maheswara Rao A, Varadaraan S, Gr Prasad MN; Cross-layer based QoS routng (CLBQR) protocol analyss based on data flow for 80.6 WMax. Internatonal Journal of Engneerng Scences & Emergng Technologes, 0; 3(): Nahle S, Malouch N; Fast-Convergng Schedulng and Routng Algorthms for WMAX Mesh Networks. Networkng, 0; : Pars S, Nta-Rotaru C, Martgnon F, Capone A; Cross-layer metrcs for relable routng n wreless mesh networks. IEEE/ACM Transactons on Networkng, 03; (3): Km JH, Cha JR, Park HJ; New delay-effcent TDMA-based dstrbuted schedule n wreless mesh networks. EURASIP Journal on Wreless Communcatons and Networkng. 0; Arumugam M, JhumkaA, AbuaradF, Kulkarn SS; Stablng Interference-Free Slot Assgnment for Wreless Mesh Networks. GudetoWreless Mesh Networks. Edtors Msra S, MsraSCa,Woungang I. Sprnger London, 009: Govndara E, Arunachalam VP, Karthk S; A QoS Aware Robust Multpath Routng Protocol for Wreless Mesh Networks. European Journal of Scentfc Research, 0; 78 (): -3. 3

12 . Mehroe M., Usman K., AhsanF, Asghar S; Farness Based Dynamc Routng Technque (FsBDRT) n Wreless Mesh Network. Research Journal of Informaton Technology,03; 5(4): Deva Prya M, Valarmath ML; A cross-layered path stablty based routng protocol for WMax networks. Amercan Journal of Appled Scences, 03; 0 (): Yevsyeyeva O, Al-Aaw EM; Mathematcal model for resource allocaton n TDMA-based wreless mesh networks. Eastern European Journal of Enterprse Technologes, 04; 3(69):