Efficient Routing Algorithm Based on Decisionmaking Sequence in Wireless Mesh Networks

Transcription

1 502 JOURNAL OF NETWORKS, VOL. 7, NO. 3, MARCH 2012 Effcent Routng Algorthm Based on Decsonmang Sequence n Wreless Mesh Networs Yngyng Qn, Rongbo Zhu * College of Computer Scence, South-Central Unversty for Natonaltes, Wuhan, Chna Abstract The ultmate goal of routng n wreless mesh networs (WMNs) s to fnd the good paths between the source and destnaton. Consderng of the characterstcs of ths new networng paradgm, such as low moblty and less restrcton from the energy effect, the focus s on the desgn and optmzaton of the technology to establsh the path that can reflect ths networ feature. In ths paper, an effcent routng algorthm s proposed based on decsonmang sequence n WMNs, and the routng process s mapped nto mult-stage decson process. We construct a mathematcal model for t and present a mult-decson sequental routng method tang use of the dea of dynamc programmng. In addton, a new metrc (EEDT) for routng based on the nformaton of MAC layer n WMNs s gven, whch optmzed the two objectves- end to end delay and throughput. In the end, the mult-decson sequental routng algorthm (MDSR) s proposed that syntheszed the suggestng method and new metrc. The path selected by MDSR would be better based on the mathematcal model, and t has lower delay of routng buldng. At the same tme, EEDT can accurately capture the qualty of the networ lns. Smulaton results show that the proposed routng algorthm sgnfcantly mproves the performance of the WMNs n terms of end-to-end delay and throughput. Index Terms wreless mesh networs, mult-stage decson, dynamc programmng, end to end delay, throughput I. INTRODUCTION Wth the development of wreless communcaton technology, wreless mesh networs (WMNs) [1, 2] have emerged as a promsng technology for next generaton wreless networng, whch ntegrates the advantages of wreless local area networ (WLAN) and ad hoc networ. WMNs have self-organzng self-confgurng, and selfhealng features wth smple mantenance at a low cost offerng hgh scalablty and relable servces as well as enhancng capacty, connectvty, and reslency of the exstng networ. Because of these advantages, WMNs have been wdely accepted n the tradtonal applcaton, whch wll have an mportant role n future generatons of wreless communcaton and receve consderable attenton recently. So t s very meanngful for WMNs to nvestgate all of crucal technques deeply. Despte the rapd progress mang n researchng for WMNs, many Manuscrpt receved Aprl 10, 2011; revsed July 1, 2011; accepted July 15, *Correspondng author, Rongbo Zhu, E-mal: rongbozhu@gmal.com. topcs have no satsfed solutons. Especally, routng s stll challengng. Because WMNs s smlar to a moble ad hoc networ, n that the node connecton s a wreless mult-hop connecton, many routng technologes appled to WMNs derved from some tradtonal routng protocols of ad hoc networ. However, the partcularty of routng schemes n WMNs may be specally taen nto account. WMNs consst of mesh routers (MRs) and mesh clents (MCs). Where mesh routers are manly statonary and provde wreless access to clents. Also, MRs forms a mult-hop envronment by forwardng and relayng data pacets from one mesh router to another. In such networs, most of nodes are ether statonary or mnmally moble and do not rely on batteres. Thus, routng protocols must deal wth relablty and mprovement of the overall networ performance rather than moblty or power savng. Up to now, most ad hoc routng protocols regard mnmum hop counts as the only routng metrc, whch has been proved not good for WMNs. Moreover, n ad hoc networ [3], n order to adapt to the dynamc topology of networ, the paths establshed by some routng protocols may not be the optmum. To solve these problems, we suggest a mult-decson sequental routng algorthm (MDSR), whch maes use of the dea of dynamc programmng to fnd the optmal path from source to destnaton, and ntroduce a new metrc for routng. The paper formulates the problem of routng as a mult-stage decson problem, and, constructs a mathematcal model for t, then we present a dynamc programmng algorthm to solve problem of the optmal path. At the same tme, the new metrc (EEDT) s gven n consderaton of the delay-senstve multmeda servces and networ throughput, and appled to the dynamc programmng algorthm. In the end of MDSR, the fnal decson-mang sequence s the optmal routng. It wll obtan the better performance path n terms of end to end and throughput. The remanders of ths paper are organzed as follows: In secton II, related wor s ntroduced. In secton III, descrbe detals of the routng problems and construct the mathematcal model. In secton IV, ntroduce a new routng metrc for the end to end delay and networ throughput. In secton V, present the proposed routng algorthm. Secton VI summarzes the smulaton results, and secton VII concludes the paper. II. RELATED WORK do: /jnw

2 JOURNAL OF NETWORKS, VOL. 7, NO. 3, MARCH Networ routng plays a crtcal role n determnng the performance of a wreless mesh networ. A sgnfcant amount of research has been made n the past years regardng the best routng protocol that can maxmze the networ throughput whle satsfyng other constrans. Most of the exstng lteratures mproved the performance of routng by concernng wth the routng metrc and routng algorthm. A lot of popular routng protocols were desgned to smply get the shortest path from the mnmum hop metrc between the gven source and destnaton. In most cases, the optmal path can t be acqured. Recently, the most popular routng metrcs such as blocng metrc, expected transmsson count (ETX) [4], expected transmsson tme (ETT) [4], modfed ETX (metx), networ allocaton vector count (NAVC), and metrc of nterference and channel-swtchng (MIC) are used n WMNs. Also, [5] made overall comparson of these metrc, and analyss ther performances n WMNs. The authors of [6] consder the effects of underlyng layers and ntroduce a new cross-layer metrc for ad hoc on demand dstance vector (AODV) routng n WMNs. In [7], a multple-metrc approach was presented to mprove throughput and transmsson delay. And, other wors has been publshed regardng route metrcs that could dentfy hgh qualty paths n WMNs [4, 8, 9, 10], and sgnfcant performance mprovements have been demonstrated by usng sutable metrcs to estmate the ln qualty and other related factors. Beyond that problem, routng algorthm should also be carefully desgned tang nto account the specfc characterstcs of WMNs. To avod the bottlenec of access-pont (AP) communcatons, the authors of [11] formulated the routng tree problem for AP communcatons and proposed the greedy heurstc algorthm of sequentally selectng one ln that mnmzed the delay of the predcted tree. In order to effcently support dverse applcatons n WMNs, [12] suggested a smple soluton, namely, the servce-orented routng algorthm whch wored n a smlar manner as the doman name system (DNS), and could effcently provde dstrbuted servces n WMNs. In [13], a feasble method to solve wreless mesh networ routng problem wth QoS constrant was used by ntroduce the novel dynamc ant genetc algorthm. And another dynamc routng method based on genetc algorthm s used n [14] that amed to reduce networ overhead. There are many other consderatons, such as lower moblty and less restrcton from energy effect, n case of settng and mantan the path of networ. The routng algorthm should be desgned or optmzed that could reflect ths networ features. Then, the lnear programmng or dynamc programmng approach for routng n WMN wll be a good choce, that has been used several studes n recent years. In [15], the authors formulated the problem of routng as a networ optmzaton problem, and presented a general lnear programmng (LP) formulaton for modelng the problem, that could effectvely ncorporate the traffc demand uncertanty n routng optmzaton. In [16], the paper gave a QoS routng algorthm based on dynamc programmng soluton that solved mult-parameter routng problem wth the nature of NPC n WMNs. J. Crchgno et al. also proposed a mesh routng algorthm, a dynamc programmng approach to compute hgh capacty paths whle smultaneously boundng the end to end delay [17]. In [18], a dynamc programmng based ln schedulng algorthm was presented to provde an optmal resource allocaton n WMAX mesh networs. Talma Olvera et al suggest a stochastc approxmate dynamc programmng soluton that s capable of utlzng lmted networ nowledge and stochastc elements [19]. Based on mentoned above achevements n routng optmzaton, the paper vew the route settng process as a mult-stage decson process, and dynamc programmng soluton s ntroduced to obtan the optmal path n WMNs. In addton, A new routng metrc for end to end and networ throughput s used. Dfferent from prevous wors, we focus on the process of establshng routng by usng dynamc programmng algorthm, whch wll be beneft of fndng the optmal path and reduce the delay of path settng, and lead to the better performance of networ n WMNs. III. NETWORK MODEL A. Problem Descrpton WMNs communcate by the way of mult-hop mode n the whole wreless networs, where routng process between nodes wthn the networ accomplsh n a collaboratve manner. Parameters le ln bandwdth, end to end delay, and pacet loss rate between neghbor nodes are obtaned and mantaned by the approprate routng protocol, then gettng the optmal path based on ths crteron, whch consstent wth mult-stage decson problems. The selecton of decson at every stage, and affects the future development at the same tme. When all stages of decson-mang s determned to form a decson-mang sequence. Then, an effectve path for an entre process wll be presented. Such an nterrelated chan structure s also seen as sequental decson-mang process (Fg. 1). Fgure 1. Sequental decson-mang process Dynamc programmng algorthm s an effectve soluton to solve mult-stage decson problems that has 2 lnear tme complexty on ( * ), the worst s ο ( n ). Where n s the scale of the problem, and s the number of decomposed sub problems. Then, the dynamc programmng model based on WMNs wll be shown n the followng. B. System model We assume that the nodes are statonary, and the physcal layer supports bdrectonal lns n WMNs.

3 504 JOURNAL OF NETWORKS, VOL. 7, NO. 3, MARCH 2012 Then, let GV (, E ) be the weghted undrected graph representng the WMNs, where V s the set of nodes (MRs) and E s set of lns. n = V s the number of nodes (the scale of the problem). In ths paper, we formulate the routng problem n WMNs as a mult-stage decson problem. Mult-hop routng n WMNs wll be decomposed nto sngle-hop, n other words, a sngle-hop routng between the two adjacent nodes s defned as one stage for dynamc programmng soluton. And, we wll use the followng notaton n our mathematcal formulaton. : Stage varable. S : The set of effectve states n the stage of. apparently, S. L (, j) E from node to j. V, S s the number of nodes n stage : The value of weghted ln n the stage of x : The node n the stage of, the value of wll range from 1, S. And, S { x} =. u( x ) : A strategc decson-mang by the node x n the stage of. Qn, ( x ) : The sequence of decson functon arranged n order startng from the stage of. In ths networ model, there s u ( x) S 1.When the current stage s, and the decson s u ( x ), we say the cost of routng s L( u( x), x ).We frst defne the objectve functon of sub-process as follows: n φ n, x u xn+ 1 Lj uj xj xj j= (,,..., ) = ( ( ), ). (1) Then, select the one wth the smallest cost, whch results from fndng the mnmum n the followng equaton: F ( S ) = mn ( x, u,..., x ), φ, 1 ( u,..., un) n n + [ L S x F S ] = mn (, ) + ( ). (2) X S F( S ) s the optmzaton objectve of sub-process whch s shown n the optmalty theorem [20]. As shown n (2), routng decsons are raned based on the present cost and antcpated future sum at every stage. As =1, t s the optmum value of the entre of the proceedng. And the homologous optmal strategy s the optmal soluton of the routng protocol. We start by showng how the algorthm operates on the topology of Fg. 2, where the weght of ln has been gven. Suppose frst we want to fnd the path from u to w wth mnmum weghted sum. We adopt reverse dynamc programmng soluton on t. Then, S1 = { c, d}, F() c = 1, F( d ) = In the stage 2, we need to compute these two equatons: So, n the last stage, ln( a, c) + F1 ( c) F2 ( a) = mn, (3) ln( a, d) + F1 ( d) ln(,) b c + F1 () c F2 ( b) = mn, (4) ln(, b d) + F1 ( d) ln(, s a) + F2 () a F3 ( u) = mn. (5) ln(, s b) + F2 () b In the end of algorthm, we could fnd an optmal path: u b d w. Fgure 2. A networ wth weghted ln IV. A NEW ROUTING METRIC A good routng metrc can accurately capture the qualty of the networ lns and s capable of ranng all those parameters that consttute the best path [21]. As noted by references n [4, 22], the hop count metrc has been proved that s not effcent. In WMNs, paths wth the fewest number of hops mean the length of each hop ln s maxmzed. However, t has also been equated wth the maxmum of ln pacet loss rate. In a dense networ, the objectve such as data pacet loss rate, end to end delay, and throughput can not be guaranteed. Furthermore, effectve WMNs routng metrc needs to consder more about end-to-end delay and networ throughput to tae the delay-senstve multmeda servces nto account. To the best of our nowledge, the only technque proposed to smultaneously mnmze the end to end delay and maxmze the throughput s the weghted sum [4, 23], whereby an objectve functon f = β1 (end to end delay) + β 2 (throughput) s optmzed [4, 23, 24]. Therefore, we present a metrc adapted thought of weghted cumulatve. 1 EEDT = (1 β) + β PTT (6) TBT Where: TBT s the ln bandwdth transmsson tme. Ths reflects the total throughput of the routng. The parameter wll be obtaned by vrtual carrer sense (NAV method) n the MAC layer [25], perodcally sensng the busy state of node transmsson channel, and then estmatng by

4 JOURNAL OF NETWORKS, VOL. 7, NO. 3, MARCH movng weghted average method. MAC layer wll beleve the node transmsson channel s dle, When the followng three condtons are met: the value of NAV s less than the current tme value, that s the NAV tme been dstrbuted haven t reached yet; recevng state s dle; sendng state s dle. Correspondngly, MAC layer wll beleve the node transmsson channel s busy, When any one of the followng condtons are met: NAV s assgned a new value; recevng state convert from dle to any other state; send state convert from dle to any other state. PPT s the practcal transmsson tme. It measures the actual ln tme durng the route request pacet RREQ transferred from the source node to ts adjacent nodes n the process of rout dscovery. That reflects the correspondng channel transmsson rate and delay. β s adjustable system parameter. The greater the value of β s, the metrc wll be nclned to choose the path wth faster transmsson rate and less delay. The smaller the value of β, t wll be nclned more hgh throughput routng. Consderng the precse parameter requres the path wth maxmum value of TBT among all the canddate paths, Whereas, In terms of the PPT, It requres to choose the one of the mnmum of the practcal transmsson tme from all paths, Then, Ths artcle adopt the recprocal value of TBT, ensurng the monotoncty consstency of the two parameters. Both objectves tae dfferent orders of magntude. Ther weghs depend on the mportance of the relatve objectve to the problem at hand. And adjustable coeffcent β plays a balancng role n the weght dstrbuton, so that the system acheved an optmal tradeoff soluton wth the two objectves. V. PROPOSED ROUTING ALGORITHM In comparson wth a wreless ad hoc networ consstng of arbtrarly deployed nodes wth the power constrants, the low moblty of nodes and relatvely statc topology n WMNs s the pecularty. Classc routng protocol AODV n ad-hoc wreless networs can not satsfy the need of the systems any more. Addtonally, routng paths establshed after the process of routng dscovery may not be the optmum. due to the method fndng the good path of AODV, several problems wll occur now and then, (1) n the routng dscovery process, the path establshed by sendng the routng response pacet (RREP) through ntermedate nodes does not always mean the global optmum. (2) The processng method of the protocol may result n the data pacet loss, whle the ln falures occur. To solve these problems, dynamc programmng was adopted n the AODV protocol n ths paper, and the new metrc was seen as the weght of the ln. Then, we presented the mult-decson sequental routng algorthm (MDSR). A. Route metrc table formaton In ths paper, the hop count metrc wll be substtuted by a new metrc EEDT n the protocol AODV. The reserved feld of RREQ pacets should be utlzed to form a new rout table, whch recorded the value of the relevant ln parameters nvolved n the metrc EEDT, ncludng the ln bandwdth transmsson tme (TBT), the sendng tme of RREQ pacets (T), the value of stage varable (K), and the value of metrc EEDT, that occuped four feld poston n total. And, the reserved felds of RREP pacets need to mae the same correcton. The revsed format of RREQ request pacet s shown n Fg. 3. TYPE J R G D U TBT T K EEDT RREQ ID IP address of the destnaton node Seral number of destnaton node IP address of the source node Seral number of source node Fgure 3. Revsed format of RREQ pacet In the specfc operaton, the node send a RREQ pacet ncludng only the value of T and K, n the begnnng, the value of K wll be ntalzed to 0. As the RREQ pacet s sent to ts neghbors, K values wll ncrease by 1. Another two values of parameter are not ncluded n RREQ pacet n the begnnng of sendng. These felds wll be ntalzed to the value 0, the TBT value of the forward ln wll not be added nto the RREQ pacet untl the neghbors receve the RREQ pacet. At the same tme, neghbor nodes wll record the recevng tme of RREQ. The value of PPT wll be obtaned by the recevng tme of RREQ n neghbors mnus the sendng tme (T). Then, the value of metrc EEDT can be calculated to accumulate to the feld of EEDT n the RREQ pacet. When neghbor nodes contnue to forward RREQ pacets to there neghbors, The value of TBT wll be set to 0 agan, also, the value of T need to be updated to the current sendng tme. B. Routng process Contrary to AODV protocol, routng dscovery process s aroused by the destnaton node n the dssertaton. Correspondently, MDSR adopt reverse dynamc programmng soluton to establsh the rout path. Besdes, nodes forward the RREQ request pacets to ther neghbors n turn, updatng some parameters of the RREQ pacets constantly, so that the weghts of ln could be captured accurately (that s routng metrc). Routng dscovery occurred n case that a node needs a route path to destnaton and the current route s not avalable. The process started by the destnaton node. Pror to ths, the destnaton node wll receve the source node s notfcaton on ntatng a route dscovery process. Intermedate nodes wll do some calculatons and deal wth the request pacet. In the meantme, they choose the optmal route path based on the model of dynamc programmng algorthm and record the relatve prevous hop node. Then, a forward path s establshed from source to destnaton, whch s shown n Fg. 4.

5 506 JOURNAL OF NETWORKS, VOL. 7, NO. 3, MARCH 2012 transmsson, the route node can temporary transfer data to ts neghbor nodes, then transfer data through the optmal path from adjacent node to destnaton node. That reduced the pacet loss rate. Fgure 4. Buldng process of forward path In WMN, the value of EEDT for each ln s mapped the weght of the ln n model of dynamc programmng. That wll be used to evaluate the qualty of the path. Routng algorthm MDSR solves (1) durng the process of routng dscovery and then evaluates (2) to return a path. The procedure of MDSR s shown n Fg. 5. Routng Algorthm MDSR Input: source node S, destnaton node D Output: optmal decson u(s) 1. Source node notfy destnaton of start route dscovery by broadcastng message 2. Destnaton node receve notce, and start route dscovery process 3. /*destnaton node ntalzng RREQ pacet*/ 4. =0, T=current tme; TBT=0, EEDT=0 5. Send RREQ pacet to all t s neghbors 6. /*man loop*/ 7. for each neghbor node do 8. f <IP address, RREQ ID> exsts n the lst of node rout table then 9. Dscard RREQ pacet 10. end f 11. f stage varable value of RREQ the counterpart of node then 12. Dscard RREQ pacet 13. end f 14. f the value of EEDT n current receved RREQ the counterpart n former RREQ then 15. Receve RREQ, record the IP address of prevous-hop route node 16. else 17. Dscard RREQ pacet 18. end f 19. Node update parameters of RREQ pacet: =+1, T=current tme; TBT=0 20. Node forward RREQ pacet to ts neghbors 21. untl <node=source node> 22. f source node receved RREQ pacet then Choose the path wth mnmum accumulate value of EEDT, and record the prevous-hop route 23. end f 24. return optmal decson u(s) VI. SIMULATION RESULTS Extensve experment was performed to evaluate the performance of MDSR. As MDSR s modfed based on AODV, and s an essental outgrow of AODV n theory. We have compared results wth the AODV protocol, and the man goal of smulaton experment was to verfy our proposed decson-mang sequence approach have the expected mprovements over the ancestor protocol. In addton, the smulaton tool was OPNET Modeler (verson 14.5), that was selected because of ts growng reputaton and ts unversalty n performng the routng algorthm. It enabled testng dfferent telecommuncaton areas, ncludng routng protocols and modelng networ n great detal. Especally, t s convenent to smulaton some major routng protocols n wreless networ, because t comes wth the whole mplementaton of some classcal routng protocols, ncludng AODV, DSR, and OLSR. We recognzed that the efforts made about the problem of selectng the best path for routng n wreless mesh networ have led to the publcaton of many dfferent protocols. Whle more comparsons wth other routng protocols would be preferred, gven the selected routng metrc or proposed algorthm, we pay more attenton to the ntegral performance of the new metrc and proposed algorthm. In order to properly verfy the effectveness of the proposed method, our experment smulatons were performed under several scenaros wth dfferent confguratons ncludng the traffc load, moblty, and networ sze and networ densty. The objectve s to compare the performance of MDSR and AODV n these dfferent scenaros. To acheve ths objectve, end to end delay and networ throughput are used as the major evaluaton metrcs. In all smulatons, source node and the destnaton were specfed. At the MAC layer, 11Mbps IEEE wth drect sequence physcal layer technology s used, and the transmt power was set to w. A. Scenaro I The networ topology of 10 nodes was buldng n the frst scenaro, and each node s fxed, that s shown n Fg. 5. Fgure 5. MDSR algorthm descrpton Arbtrary sub-path ncluded the optmal path s also optmal. Addtonally, ntermedate nodes constantly update the prevous-hop node on optmal path durng the buldng process of the forward path n MDSR. Therefore, all ntermedate nodes establshed the optmal path to the destnaton node accompaned by the buldng process of the forward path, whch s shown n Fg. 3, that be beneft of decrease the number of route dscovery. It also has another advantage. If ln faled durng data Fgure 5. Networ topology

6 JOURNAL OF NETWORKS, VOL. 7, NO. 3, MARCH Frst, we collect the networ throughput n ths scenaro. The followng settngs were common to smulaton experments reported n ths scenaro. a) The smulaton duraton was seconds, and the seed was set to 128. b) Traffc load was 200. c) Communcaton range of each node was set to 50. In addton, the nterval tme of pacet sent by source node s set to exponental dstrbuton functon; ts parameter s 0.5, 0.3, 0.2, 0.1, 0.05, 0.01, and 11 runs n total. The result of smulaton s shown n Fg. 6. duraton s 300. We obtan the smulaton result of end to end delay that s shown n Fg. 7. (a) End to end delay of AODV (a) Throughput of AODV (b) End to end delay of MDSR Fgure 7. End to end delay of dfferent algorthms (b) Thoughput of MDSR Fgure 6. Throughput of dfferent algorthms In Fg. 6, X-drecton s channel traffc G, and Y- drecton s channel throughput S. The curve descrbes the developng trend of networ throughput varyng wth the traffc load. At low traffc levels, the throughput tae on ascend trend along wth the rsng traffc load, then, at hgh traffc levels, throughput fell off sharply after the maxmum throughput. Ths behavor s amply demonstrated by the smulaton results. In partcular, the maxmum throughput of AODV s acheved near G=17 and s close to the value of 6.5, and for MDSR, the maxmum throughput s about 7.5 acheved near G=18. Apparently, the maxmum networ throughput of MDSR n WMNs s greater than AODV protocol. The most lely reason for ths s that the smaller delay of routng buldng comparng AODV, and the better path selected by MDSR. It shows that the proposed approach s effcent algorthm. Then, we set the nterval tme of source to be dstrbuton constant (2); traffc load s 100; and the In demonstratons, the average delay of the two datagram s almost equal. But, from the delay curve t can be seen that the ampltude of fluctuaton of MDSR s small. It shows that MDSR s better than AODV n terms of delay jtter, an mportant parameter of QoS. In the delay-senstve multmeda servces, MDSR wll mae transfer performance more superor. B. Scenaro II In ths scenaro, the networ topology s the same as Fg. 4. Dfferent wth the former, we randomly selected 4 nodes from the 10 nodes, and set these 4 nodes to movement. We smulate n the moble envronment, and the result curve of throughput s shown as n Fg. 8, and the delay curve n Fg. 9. (a) Throughput of AODV

7 508 JOURNAL OF NETWORKS, VOL. 7, NO. 3, MARCH 2012 Then, we collected the throughput statstc, and the result curve was shown n Fg. 10. (b) Thoughput of MDSR Fgure 8. Throughput of dfferent algorthms (a) Throughput of AODV (a) End to end delay of AODV (b) Thoughput of MDSR Fgure 10. Throughput of dfferent algorthms The above smulaton result ndcates that our proposed reaches the prospectve effect. Comparng AODV routng protocol, t could ncrease the networ throughput and obtan the smaller delay jtter whether n a small and bg networ or n a statc and dynamc envronment. MDSR s a stable and effcent algorthm n WMNs, especally n an WMNs wth QoS constraned. (b) End to end delay of MDSR Fgure 9. End to end delay dfferent algorthms In the moble envronment of WMNs, MDSR stll have the same effect on the networ throughput and end to end delay. In Fg. 7, the maxmum throughput of MDSR can acheve 7.5 near G=18 and AODV s only close to the value of 7. And, In Fg. 8, the curve fluctuates of MDSR tends to stablze n terms of end to end delay. The result of tests ndcates that MDSR algorthm s not only outperforms the AODV protocol n general but also be stable to changes n movements. C. Scenaro III In the thrd scenaro, we ncrease the number of nodes to 50. The smulaton feld was 220*140 (m) wde, the nodes randomly deployed n hs rectangle grd. The traffc load s set to 800, and other smulaton confguratons adopt the parameters n the scenaro I. VII. CONCLUSION In ths paper, we have developed dynamc programmng solvng the routng problem depend on the characterstcs of WMNs. The nodes of networ are dvded nto mult-stage durng the process of buldng route path, and the new routng metrc s adoped to dentfy hgh qualty paths. We have compared MDSR wth AODV protocol and found that our proposed algorthm provdes superor performance, especally n the delay-senstve multmeda servces. At the same tme, t s smple and easy to be mplement. As for future wors, we wll extend our proposed model to support mult-rado mult-channel WMNs envronment. ACKNOWLEDGMENT Ths wor was supported by the Natonal Natural Scence Foundaton of Chna (No ), the Natural Scence Foundaton Hube Provnce of Chna (No. 2008CDB339), and the Scence and Technology Research Plannng of Educatonal Commsson of Hube Provnce of Chna (No. B ). The authors

8 JOURNAL OF NETWORKS, VOL. 7, NO. 3, MARCH gratefully acnowledge the helpful comments and suggestons of the revewers. REFERENCES [1] Mcrosoft Mesh Networs, [2] I. F. Ayldz, X. Wang, and W. Wang, Wreless mesh networs: a Survey, Comput. Networ, vol. 47, no. 4, pp , Mar [3] C. S. Ram, B. S. Murthy, and Manoj, Ad hoc wreless networs: archtectures and protocols, New Jersey: Prentce Hall PTR, [4] R. Draves, J. Padhye, and B. Zll, Routng n mult-rado mult-hop wreless mesh networs, ACM Annual Internatonal Conference on Moble Computng and Networng (MOBICOM), pp , [5] S. Waharte, B. Ishbash, R. Boutaba, and D. Meddour, Performance study of wreless mesh networs routng metrcs, Computer Systems and Applcatons, pp , [6] D. Guo, J. L, M. Song, and J. Song, A novel cross-layer routng algorthm n wreless mesh networ, Pervasve Computng and Applcatons, pp , [7] W. A. Morera, R. Lopes Gomes, and A. J. Gomes Abelem, A multple-metrc approach for routng n wreless mesh networs, WoWMoM, IEEE Internatonal Symposum, pp. 1-6, [8] A. N. Le, D. W. Kum, and Y. Z. Cho, LARM: A loadaware routng metrc for mult-rado wreless mesh networs, IEEE Worshop on Internatonal Conference Advanced Technologes for Communcatons, [9] A. A. Przada, M. Portmann, and J. Indulsa, Hybrd mesh ad-hoc on-demand dstance vector routng protocol, Thrteth Australasan Computer Scence Conference (ACSC 07), vol. 29, pp , [10] H. L, Y. Cheng, and C. Zhou, Mnmzng end-to-end delay: a novel routng metrc for mult-rado wreless mesh networs, IEEE INFOCOM, [11] N. Funab, K. Uemura, T. Naansh, and W. Hassan, A mnmum-delay routng tree algorthm for access-pont communcatons n wreless mesh networs, IEEE Internatonal Conference, pp , [12] H. M. Lugo-Cordero, L. Keje, D. Rodrguez, and S. Kota, A novel servce-orented routng algorthm for wreless mesh networ, Mltary Communcatons Conference, pp. 1-6, [13] X. Sun, and X. Lv, Novel dynamc ant genetc algorthm for QoS routng n wreless mesh networs, WCom th Internatonal Conference, pp. 1-4, [14] C. Yoon, and R. Hwang-Bn, A genetc algorthm for the routng protocol desgn of wreless mesh networs, Informaton Scence and Applcatons (ICISA), pp. 1-6, [15] B. K. Gupta, B. M. Acharya, and M. K. Mshra, Optmzaton of routng algorthm n wreless mesh networs, Nature & Bologcally Inspred Computng (NaBIC), pp , [16] W. Song, and X. Fang, QoS routng algorthm and performance evaluaton based on dynamc programmng method n wreless mesh networ, Journal of Electroncs and Informaton Technology, vol. 29. no. 12, [17] J. Crchno, J. Khoury, and M. Y. Wu, A dynamc programmng approach for routng n wreless mesh networs, In Proceedng of CLOBECOM, pp , [18] L. Peng, and S. Sun, Dynamc programmng based ln schedulng n WMAX mesh networ, Internatonal Symposum on Computer Networ and Multmeda Technology, [19] T. Olvera, and D. P. Agrawal, Stochastc approxmate dynamc programmng wth ln estmaton for hgh qualty path selecton n wreless mesh networs, IEEE Globecom Worshop on Complex and Communcaton Networs, [20] C. H. Papadmtrou, and Stegltz, Combnatoral optmzaton: algorthms and complexty, New Jersey: Prentce Hall PTR, [21] B. K. Addagada, V. Ksara, and K. Desa, A survey: routng metrcs for wreless mesh networs, URL: [22] A. Hassen, Mogabel, and O. Mohamed, Revew of routng protocols and t s metrc for wreless mesh networs, IEEE Worshop on Internatonal Assocaton of Computer Scence and Informaton Technology, [23] Y. Yang, J. Wang, and R. Kravets, Desgnng routng metrcs for mesh networs, Santa Clara, CA-USA: IEEE Worshop on Wreless Mesh Networs (WMesh), [24] W. Zhong, D. Zhang, and D. Qao, Comparatve study of routng metrcs for mult-rado mult-channel wreless networs, Las Vegas: WCNC, [25] L. Chen, W. B. Henzelman, Qos-aware routng based on bandwdth estmaton for moble ad hoc networs, IEEE Journal on Selected Areas n Communcatons, vol 23, no. 3, pp , Yngyng Qn receved the B.S. degree n Computer Scence from South-Central Unversty for Natonaltes, Chna, n She s currently a graduate n College of Computer Scence of South-Central Unversty for Natonaltes. Her man research nterest s n protocol desgn n WMNs. Rongbo Zhu receved the B.S. and M.S. degrees n Electronc and Informaton Engneerng from Wuhan Unversty of Technology, Chna, n 2000 and 2003, respectvely; and Ph. D degree n communcaton and nformaton systems from Shangha Jao Tong Unversty, Chna, n He s currently an Assocate Professor n College of Computer Scence of South-Central Unversty for Natonaltes. He has publshed over 50 papers n nternatonal journals and conferences n the areas of wreless communcatons, coverng 3G moble systems and beyond, MAC and routng protocols, and wreless ad hoc, sensor, and mesh networs. He receved the Outstandng B. S. Thess and M. S. Thess awards from Wuhan Unversty of Technology n 2000 and 2003, respectvely. Hs current research nterests are n the areas of wreless communcatons, protocol desgn and optmzaton. The research actvtes have been supported by the Natural Scence Foundaton of Chna, the Natural Scence Foundaton of Hube provnce and the Natural Scence Foundaton of South-Central Unversty for Natonaltes. He s the Edtor-In-Chef of Internatonal Journal of Satellte Communcatons Polcy and Management, Assocate Edtor of Internatonal Journal of Rado Frequency Identfcaton Technology and Applcatons. He serves as a guest edtor for several journals, such as, Future Generaton Computer Systems, Telecommuncaton Systems, and as a revewer for numerous referred journals such as IEEE System Journal etc. He has been actvely nvolved n around 10 nternatonal conferences, servng as TPC Char of GCN 11, General Co-char of ICICA 10 and so on. Dr. Zhu s a member of the ACM and IEEE.