A Novel Scheme to Reduce Control Overhead and Increase Link Duration in Highly Mobile Ad Hoc Networks

Transcription

1 Ths full text paper was peer revewed at the drecton of IEEE Communcatons Socety subect matter experts for publcaton n the WCNC 2007 proceedngs. A Novel Scheme to Reduce Control Overhead and Increase Lnk Duraton n Hghly Moble Ad Hoc Networks Ehssan Sakhaee, Tark Taleb, Abbas Jamalpour, Ne Kato, and Yoshak Nemoto School of Electrcal & Informaton Engneerng, Unversty of Sydney, Australa Graduate School of Informaton Scences, Tohoku Unversty, Japan Abstract Floodng-based approaches are ncorporated n reactve routng protocols as the fundamental strategy for route dscovery. They overtly affect traffc as the frequency of route dscovery ncreases along wth the moblty of users n a Moble Ad Hoc Network (MANET). Ths paper presents a scheme for reducng overall traffc and end-to-end delay n hghly MANET networks. Frstly a new routng algorthm s proposed to reduce the frequency of flood requests by elongatng the lnk duraton of the selected paths. In order to ncrease the path duraton, nondsont paths are also consdered. Ths concept s a novel approach n route dscovery as prevous reactve routng protocols seek only dsont paths. Secondly another novel approach s presented to estmate the Lnk Expraton Tme wthout the need for Global Postonng System (GPS) devces. To prevent broadcast storms that may be ntrgued durng the path dscovery operaton, another scheme s also ntroduced. The basc concept behnd the proposed scheme s to broadcast only specfc and well-defned packets, referred to as best packets n the paper. The new protocol s smulated wth regard to traffc overhead. Although our man am n ths paper s to reduce the net control traffc n a MANET network, there are other benefts arsng from the proposed schemes, namely the ncrease n lnk duraton, reducton n the end-to-end communcaton delay, less dsrupton n data flow, and fewer path setups. I. INTRODUCTION Floodng s the most essental mechansm for the route dscovery process n reactve (on-demand) Moble Ad Hoc Networks (MANETs). The number of flood request packets and the frequency of the floodng occurrence greatly affect network performance due to the ntroducton of addtonal network traffc nto the system and nterrupton n data transmsson. The frequency of route dscovery, and hence flood requests, can be lnked to another fundamental ssue n a MANET: path or lnk duraton, also known as path stablty. When a path breaks, not only are portons of data packets lost, but also n many cases there s a sgnfcant delay n establshng a new path. Ths delay depends on whether another vald path already exsts (n the case of mult-path routng protocols) or whether a new route dscovery process needs to take place. The latter scenaro ntroduces yet another problem. In addton to the delay n dscoverng new paths, floodng requred for path dscovery would greatly degrade the throughput of the network as t ntroduces large amount of network traffc, especally f the floodng s not locally drected, as n the case of Locaton Aded Routng (LAR) protocols [1]. However f the locatons of destnaton nodes are unknown, omn-drectonal floodng s nevtably the only opton. In a hghly moble system, where lnk breakage s frequent, floodng requests would largely degrade system performance. Two methods can be used to decrease overall control overhead n a MANET network. One s by reducng mass broadcastng, known as broadcast storms [2], and the other s by decreasng the frequency of broadcast floodng. The broadcast storms result n heavy traffc contenton and consequently collsons of packets due to the mass floodng broadcasts between neghborng nodes. Lmtng floodng has been wdely consdered n recent lterature [3]. Frequency of broadcastng s drectly dependent on the route dscovery process, and how often ths needs to be performed. Multpath routng [4-6] attempts to mnmze the need for frequent route dscovery processes by selectng an alternate path f one path fals. However f such alternate paths have also expred, a route dscovery s nevtablty carred out. A notable algorthm that tends to reduce the frequency of route dscovery s Assocatvty Based Routng (ABR) [7] whch tres to choose paths that are more stable and have long lnk duratons. However, ABR does not rebroadcast a request packet more than once, n order to retan the property of dsont paths. Although the property of dsont path dscovery has been prevously consdered as a correct approach to routng, ths paper wll show how dsont path dscovery can be qute lmtng n certan scenaros, partcularly n a pseudolnear moble envronment. Furthermore ths paper wll demonstrate how ABR and other path-dsont routng protocols are dsadvantageous n a hghly moble pseudo-lnear moble envronment wth no pause tme, such as an aeronautcal ad hoc network ntroduced n [8]. Other attempts at predctng and selectng stable lnks have been proposed n [9-11], however they all depend on statstcal analyss and probablstc models of lnk duraton. The schemes proposed n ths paper smultaneously deal wth the two concerns of MANETs: lnk duraton and control/broadcast overhead. Addtonally, unlke prevous algorthms, the proposed routng scheme, dubbed as Receve /07/$ IEEE

2 Ths full text paper was peer revewed at the drecton of IEEE Communcatons Socety subect matter experts for publcaton n the WCNC 2007 proceedngs. On Most Stable Path (ROMSP) updates cost parameters on the reverse (reply) path as the reply packet traverses back to the source node. Ths s to provde the source node wth the most updated nformaton for the selecton of the most stable path. There s also a setup tme when a route s not readly avalable, and packets are placed n a queue untl a new path s establshed for routng [4]. Ths obvously affects the end-toend delay and wastes the memory of nodes. Therefore, mantanng paths wth long duratons would ultmately reduce the frequency of occurrence of the above scenaro, as paths do not break as often. Mantanng a low level of control overhead s a prmary goal n reactve routng protocols. In ths paper, the proposed schemes wll effectvely reduce the control overhead n addton to other advantages, such as ncreased path duraton, decreasng end-to-end delays, and effectve reducton n overall network traffc. In general, control message overhead ncreases when nodes are hghly moble, due to the hgher rate of lnk breakage. These overhead messages consst of Route Request (RREQ) messages generated durng the route dscovery process and Route Error (RERR) packets caused by abrupt lnk falures. The total amount of control messages n a MANET network can be reduced by four fundamental strateges: 1. Increasng path duraton 2. Multpath routng 3. Rebroadcast mnmzaton 4. Route dscovery pror to path expraton The frst three scenaros have been dealt wth n recent lterature. In ths paper, we ntroduce more sutable schemes to delver more effcent results n hghly MANET scenaros. The paper consders also the fourth strategy to reduce route error packets. The novelty of the proposed routng protocol s that t explots non-dsont path dscovery n order to effectvely fnd more stable paths for routng. It s worth notng that although the use of non-dsont paths requres the use of addtonal control messages, however by usng the Forward Best Request (FOBREQ) technque, the added overhead s mnmal and the overall reducton n the entre network traffc s sgnfcant. Hence the acheved throughput of the network wll be more evdent than n the case of tradtonal algorthms that do not take nto account moblty, as demonstrated n the smulatons of secton IV. In the proposed protocol, due to the selecton of stable, more durable paths, there wll be fewer path breaks and handoffs. Ths consequently not only reduces the delay between new route establshments, but also causes fewer route dscoveres and hence effectvely reduces traffc floodng. In ths paper, we use a concept smlar n sprt to the multpath approach presented n [4-6]. However, the man dfference s that cached paths are not necessarly dsont. Indeed, when a path breaks, all paths that contan the broken lnk are smultaneously purged from the Path Cache, whch ncludes all sutable paths to a destnaton. Ths process s descrbed n more detals n Secton III. The remander of the paper s organzed n the followng fashon. Secton II surveys prevous attempts of reducng control overhead n MANETs and dscusses algorthms that ncrease lnk duraton. Secton III ntroduces the proposed schemes of ths paper and the routng protocol. Secton IV smulates the proposed scheme, followed by results and dscussons. Fnally the paper concludes wth a summary recappng the man advantages of the proposed system and future research work n Secton V. II. RELATED WORK Tradtonally, the Dynamc Source Routng (DSR) algorthm [12] s a wdely mplemented and well known routng algorthm for MANETs. However DSR, does not take nto account moblty parameters durng route dscovery, resultng n paths whch break often n hghly moble scenaros, causng excessve broadcastng and floodng the entre network for new routes to be dscovered. Locaton Aded Routng (LAR) [1], lke other broadcast/flood reducng mechansms [13, 14], drects broadcastng towards the estmated destnaton node. However f there s no knowledge of the estmated destnaton, then ths knd of mechansm cannot work. In [15] broadcast flood s lmted by only forwardng consecutve RREQ packets whch have a path hop accumulaton smaller than the prevous dentcal or duplcate RREQ packet. Otherwse the newly arrved RREQ packet s dropped and hence not forwarded. In [2] several approaches are ntroduced to mnmze floodng n MANETs. One s the probablstc scheme, whch rebroadcasts a packet that has been receved for the frst tme wth a gven probablty P. In the counter-based approach a counter s ncremented each tme an dentcal packet s receved, and s used to prevent further re-broadcastng of the same packet comng from dfferent sources once the counter threshold value s reached. The dstance-based scheme consders relatve dstances between the nodes and decdes whether t s worth re-broadcastng a message dependng on the dstance from the source. If the dstance from the source s small, then there s no addtonal coverage beneft from rebroadcastng ths message. However, f the message s from a far away source, then re-broadcastng would provde a larger coverage. Consequently, f a message comes from a source whch s at a dstance greater than d mn, then the message s rebroadcasted. The Locaton-Based Scheme requres a Global Postonng System (GPS) to calculate the area of coverage f a message s re-broadcasted and decdes whether t s worth rebroadcastng such a message. Although the above-mentoned methods are qute satsfactory n provdng effcent re-broadcastng wth regard to coverage, ntegratng ths broadcast mnmzng schemes n routng does not ensure that the need for consecutve broadcastng s decreased, and nether does t consder path stablty durng the re-broadcastng procedure. Another dsadvantage s that n less populated and sparse networks the re-broadcastng of messages s not guaranteed as a result of the threshold values beng statc [16]. Hence we need a scheme that takes these ssues nto consderaton, whlst reducng broadcast overhead. A routng algorthm that consders stablty n the routng crteron s the Assocatvty Based Routng (ABR). ABR uses

3 Ths full text paper was peer revewed at the drecton of IEEE Communcatons Socety subect matter experts for publcaton n the WCNC 2007 proceedngs. assocatvty tcks messages (TICKs), whch are perodcally broadcasted n order to estmate lfetme of lnks. If a node has hgh assocatvty tcks wth ts neghbor node, then the degree of stablty (and hence lnk duraton) s hgh. The destnaton node chooses nodes on a path whch have a hgh degree of assocatvty. If we consder ABR n a pseudo-lnear moble ad hoc network wth no pause tme, all nodes wthn a tme range would receve equal assocatvty tcks regardless of ther speed and drecton. In ths case, hgh assocatvty means that the neghbor node has been wthn range for a consderable perod of tme. It does not ensure that the moble node wll contnue to reman wthn range, as the moble node may already be close to the edge of the communcaton boundary. A better node whch provdes a more stable lnk may have ust come nto the range of the target node, and would consequently have a lower assocatvty value. Thus ABR would not be sutable for the consdered moblty model. Fg. 1 llustrates ths dea. Let nodes A and B have hgher assocatvtes wth S than does C. Applyng ABR to such a scenaro wll lead to the selecton of ether node A or B for communcaton. Ths obvously yelds a poor performance of the entre network as nodes A and B wll soon dsappear from the range of node S. For ths reason we ntroduce a scheme whch takes nto account the relatve velocty and relatve dstances of nodes durng route dscovery n order to fnd most stable paths. Addtonally the rebroadcast reducton scheme s based on re-broadcastng best request packets whch would ultmately produce more stable lnks as the eventual path. A. The use of non-dsont path dscovery In order to descrbe the sgnfcance of non-dsont path dscovery, a scenaro shown n Fg. 2 s consdered. In ths scenaro, f a tradtonal DSR algorthm s used durng route dscovery, only ABD wll proceed to be forwarded n the RREQ packet at D. The duplcate RREQ that was receved from B wll arrve at D from C, but wll be dscarded. A DSR mechansm (and all tradtonal reactve routng algorthms such as AODV) wll drop ths duplcate packet. However, f we consder the Lnk Expraton Tme (LET) of these two nondsont paths, we see the advantage of also rebroadcastng the dentcal RREQ comng from C. For smplcty, let us frst assume all moble nodes have the same magntude of velocty wth only ther drectons beng dfferent. If we consder the LET on each lnk on the path, t becomes clear that the Path Expraton Tme (PET) would correspond to the mnmum LET on a path..e. PET(ABD) = mn{let AB, LET BD } and PET(ABCD) = mn{let AB, LET BC, LET CD }. Now lookng at each ndvdual lnk on the two paths and consderng the relatve velocty of the pars of nodes for each lnk, the relatve velocty v R of node wth respect to node -1 s shown n (1). α v R = v 2(1 cosα) = 2vsn (1) 2 where v s the speed of each node, α s the angle between the velocty vectors of the two nodes. The smplfed lnk expraton tme t c for each lnk s gven n (2), where d ntal s the ntal dstance between the two nodes. Also let s consder all nodes are at the same dstance from each other. Hence the factor affectng t c s the angle α between the nodes. d LOS dntal tc = (2) α 2vsn 2 where d LOS s the maxmum range, or lne-of-sght dstance to any node. We can clearly see that the smallest LET belongs to BD as t has the greatest angular dfference α. Hence although path ABD s the shortest path (least hop), ts stablty s lmted by lnk BD. It can be seen that mn{let BC, LET CD } s greater than LET BD. Hence PET(ABCD) > PET(ABD). Thus f we also rebroadcast the duplcate broadcast message comng from C, we can forward the knowledge of a more stable path. Ths llustrates the advantage of usng non-dsont path dscovery. However ths wll be at the prce of addtonal broadcast floodng, whch s mnmzed wth another proposed scheme called the Forward Best Request (FOBREQ), whch wll be explaned n part C. Fg. 1. An example scenaro where ABR does not work. C III. PROPOSED ROUTING PROTOCOL FOR DECREASING FLOOD REQUESTS IN MANETS A B D Fg. 2. An example of the use of non-dsont path dscovery. B. Defnton of Best Packets Before we defne the concept of best packets, t s mportant to descrbe the nature of Doppler shft. Doppler shft s the apparent change n the frequency of electromagnetc sgnals (such as rado waves) due to the relatve movement of the two communcatng enttes. When there s a small amount of Doppler shft subected to rado packets, there must be a

4 Ths full text paper was peer revewed at the drecton of IEEE Communcatons Socety subect matter experts for publcaton n the WCNC 2007 proceedngs. relatvely small moton or velocty between the two bodes. A new metrc termed the Doppler Value based on the Doppler shft alone was ntroduced n [8]. The best packets (and the best paths) are defned wth regard to stablty n our model. We develop four schemes to formulate best packets: 1) Packet subected to the least Doppler shft (based on relatve velocty alone) 2) Packets subected to the smallest Doppler Value 3) Packet wth the largest Lnk Expraton Tme as estmated usng the Doppler shft of packet and the power of sgnal 4) Packet wth longest LET as calculated usng GPS. The above schemes are smulated n secton IV. C. Forward Best Request (FOBREQ) The FOBREQ scheme forwards the best packet, by only forwardng better packets as defned by values calculated usng the schemes n part B. When a packet arrves at a node, the value of ths packet s stored at ths node, and compared wth consecutve duplcate/dentcal packets that arrve at the node. If a consecutve packet has a better value than the stored value, then ths packet s forwarded, else t s dropped. If each consecutve packet has a better value than the prevous packet, then t s also forwarded. However as wll be shown n the smulatons of secton IV, FOBREQ also effectvely manages the broadcast storm problem [2] mentoned earler by reducng rebroadcasts. FOBREQ also prevents the dscovery of multple paths that have the same bottleneck (lnk) values. Hence here the bottleneck value wll be the least stable lnk (e.g., one wth the smallest lnk duraton). As the packet contans the bottleneck value, redundant paths are elmnated. These are paths that have common bottleneck lnks, n addton to paths that have bottleneck values below the best path. D. Receve On Most Stable Path The Receve On Most Stable Path (ROMSP) works on the prncple of retrevng data from the most stable path based on any of the metrcs descrbed n part B. It s mportant to emphasze here that there may also be more than one node from whch data can be retreved from n ROMSP. The algorthm s as follows. The requestng node broadcasts a route request (RREQ) to all nodes wthn range. The recevng node frst checks whether the current request packet s better (accordng to Secton C) than the prevous dentcal request. If t s, t wll then check whether t can provde the requested data, or whether t has knowledge of a path that can provde ths requested data. If t does, t wll produce a route reply (RREP), else t wll add ts own address to the request packet, add ts value as the best value so far, and rebroadcast the packet. A new route dscovery s always ntated pror to the lnk beng expred. Ths happens at a tme t before the estmated lnk expraton tme. In addton to FOBREQ, settng a maxmum lfetme for packets mnmzes broadcastng. The lfetme of packet ensures that rebroadcastng of packets ceases after ether certan number of rebroadcasts by dfferent nodes (hopcount), or when the lfetme of a packet s reached (packet expraton). We also lke to pont out that when data transfer s complete, the resources are released; however the path remans n the Path Cache of the node untl t expres, and s then purged from the Path Cache. The reason behnd ths s that f there are further attempts of the same data retreval or f another request s receved wshng to obtan the same data, ths path can be reused. Intutvely, nodes whch forward the RREQ, wll also learn about the new path and store ths nformaton n ther Path Cache. E. Packet Format The route request (RREQ) packet format s as follows: <CNA><#scheme><CSF><lfetme> The Cached Node Addresses (CNA) feld s where the addresses of the forwardng nodes are stored. Before a node forwards the packet, t adds ts own address to the CNA. The scheme feld dentfes the cost scheme whch s to be used as outlned n part B. The Cost So Far (CSF) feld s used by FOBREQ n order to determne best packets to forward and gnore the rest. Ths feld s also updated on the reverse (reply) path and s hence used to determne cost of paths n order to determne the best path for routng at the requestng node. The lfetme feld wll determne the expraton parameters for the RREQ packet so that the packet s not ndefntely rebroadcasted over the entre network. When the lfetme of a packet s up, t s dropped. F. Calculaton of Lnk Expraton Tme Although the use of GPS should become commonplace n moble nodes, we ntroduce a scheme to estmate the LET wthout the need of GPS (n case the GPS s not able to effectvely estmate the velocty of nodes or s smply not avalable). We use the Doppler shft subected to packets to calculate the relatve velocty of nodes. The dstance between nodes s calculated usng the scheme used n [3], whch uses the power of sgnals to calculate the dstance between the nodes by usng the smplfed free space propagaton model gven n [17]. For the moblty model t s assumed that moble nodes are pseudo-lnear, and hghly moble n nature. A good example of ths knd of system s an aeronautcal ad hoc network [8]. The estmated ntal LET usng the Doppler shft of packets and power of sgnal (of packets) s gven by 2 2 ( 2d 4( d R ) d 2 ) 1 2 LET + 2v f ( f < 1) for approachng nodes f o LET 2v 2 2 ( 2d 4( d R ) d 2 ) 1 2 f ( f > 1) for recedng nodes f o where f s the actual frequency of the sgnal, f o s the observed frequency, R s the maxmum communcaton range between

5 Ths full text paper was peer revewed at the drecton of IEEE Communcatons Socety subect matter experts for publcaton n the WCNC 2007 proceedngs. two moble nodes and d s the ntal dstance between two nodes gven by d λ = 4π pt p r where p r s the ntal receved sgnal power, p t s the known transmsson sgnal power and λ s the carrer s wavelength. LET s used for determnng the best path for routng (durng the routng decson). Each node possesses a Path Cache whch automatcally expres and purges paths, once they expre or become nvald. Ths occurs when a node receves a RERR packet correspondng to a lnk n a path or when the estmated Lnk expry s reached. Control packets must be propagated usng a much lower frequency than the actual data transmsson, n order to mnmze the effect of atmospherc attenuaton and hence be able to effectvely estmate the LET. Note that f f/f 0 s one, the LET s nfnte and hence nodes wll ndefntely reman wthn each other s range. Addtonally, GPS can be used to determne the dstance between nodes. From [18], f we consder two moble nodes and wth a transmsson or lne-of-sght (LOS) range of r, speeds v and v, coordnates (x, y ) and (x, y ), and velocty angles θ and θ respectvely, the LET s predcted by ( ab + cd) + ( a + c ) r ( ad bc) LET = (3) 2 2 a + c a = v cosθ v cosθ b = x x d = y y c = v snθ v snθ G. Lnk Breakage When a prmary path breaks, the node that notces ths change sends a RERR packet back to the source node. For an example, let us assume lnk AB breaks n Fg. 2. In ths scenaro, node B notces that there are no acknowledgement of data packets beng receved from node A, and assumes the lnk s broken. Hence t wll send a RERR packet specfyng the suspected lnk that s broken. Here t s RERR(B, A). The RERR packet s forwarded to the source node S. Frst the source node wll select the next best path that does not contan the lnk BA. The Path Cache s then updated by removng (purgng) all paths that contan the lnk BA. If yet another unexpected lnk breakage occurs, a new path s selected from the (updated) Path Cache. When a lnk breaks, a local repar procedure takes place, smlar to ABR. However as soon as the lnk s repared, the node whch s responsble for the repar wll send a RERR. If there s a sudden broken lnk one of two thngs wll happen: 1. If there s an alternatve path at the node whch realzes the lnk break, the alternatve path s chosen, and a RERR packet contanng the broken lnk nformaton s sent back to the source node. The data packets already on ther way (havng the node caches contanng the broken lnk) are sent va the new lnk..e. packets are salvaged, adapted from DSR packet salvagng [12], where the orgnal route cache n packet s replaced by the new alternatve route cache, and then forwarded. 2. If there s no alternatve path, a local recovery smlar to ABR s performed. If the broken lnk s less than h hops (where h s usually 1 to 3 hops) from the source, an RERR message wth the detal of broken lnk s sent to the source node and the source node ntates a route dscovery. Otherwse a local route recovery procedure takes place where the node detectng the broken lnk wll broadcast a 2-hop recovery request smlar to that of [19]. Once the node n charge dscovers a new route to the destnaton, t wll send a Route Recovery RREC(A-B, A-C) showng the broken lnk and the new lnk back to the source. The source wll then update ts Path Cache, purgng and updatng the paths n the Cache. However unlke [19], snce the process resembles source routng, the source needs to know the local repar, so that f the node responsble for the local repar fals, the source node or the nodes on the upstream of the faled node can handle the broken lnk. The proposed scheme also reduces RERR packets by selectng/choosng new paths before the path (lnk) expres. Thus t prevents the path to be broken and RREPs beng sent. RREP packets are hence only produced due to unexpected lnk falures. Ths effectvely reduces the total number of control messages. At a tme t before the prmary lnk s estmated expry, a new route dscovery takes place, and the Path Cache at source s updated. At the tme of lnk s estmate expry, the new found route s selected. Ths s done so that the delay between actual lnk breakage, notfcaton and path re-establshment s avoded. The alternate paths are only there to supplement unexpected lnk breakage. We note that n most cases the prmary path usually has the longest lnk duraton. Hence close to the expry of ths prmary path the alternate paths have already been exhausted and most lkely purged from the Path Cache. Effectvely they are not sutable, and hence a new route dscovery must take place. IV. SIMULATION OF THE PROPOSED SCHEME In the followng smulaton we can see the performance of ROMSP wth regard to usng dfferent stablty metrcs. In these smulatons 5000 nodes are smulated and ther speeds vared to nvestgate the effect of the schemes wth regards to control overhead. Nodes move n a lnear fashon, n a predefned drecton wth no pause tmes. Fg. 3 shows the results of the effect of ncreasng speed on number of control messages propagated (overhead). From the fgure, t can be seen that LET outperforms the other schemes, followed by Power-Doppler (PD) combnaton estmaton of LET, and the Doppler Value (DV), and lastly the relatve velocty (VREL) scheme whch only looks at the Doppler shft subected to a receved packet. Fg. 4. shows the performance compared to that of DSR usng shortest dstance as the metrc for path

6 Ths full text paper was peer revewed at the drecton of IEEE Communcatons Socety subect matter experts for publcaton n the WCNC 2007 proceedngs. selecton. In ths case moblty parameters are not taken nto account for path selecton. Other tradtonal algorthms that do not consder moblty would yeld smlar results to DSR. In Fg. 4, the large overhead seen n DSR s a result of the excessve lnk-breakages due to the selecton of random unstable paths, and hence the re-broadcastng of control (RREQ) messages for dscovery of new paths. As the speed of nodes ncrease, the number of lnks and hence path breaks ncrease, consequently resultng n hgher control overhead. The other schemes use moblty nformaton to choose more stable paths, causng much fewer lnk breakages durng the smulaton, and hence dramatcally decreasng the overhead caused by route dscovery. control overhead (no. of control packets/smulaton control overhead (no. of control packets/smulaton DSR LET PD DV VREL LET PD DV VREL speed (km/h) Fg. 3. Control overhead vs. speed speed(km/h) Fg. 4. Control overhead wth respect to DSR. V. CONCLUSIONS AND FUTURE WORKS In ths paper we ntroduced new schemes to reduce control overhead and ncrease lnk duraton and stablty n hghly moble ad hoc networks. Smulaton results show the effectveness of these schemes n hghly moble scenaros wth respect to reducng control overhead. Future work should focus on further optmzaton of the proposed metrcs and comparson wth regard to other exstng routng protocols used for MANETs. It s also beleved that a better estmaton of Doppler-Power equaton can be derved to further enhance the performance of the routng protocol. REFERENCES [1] Y. Ko and N. H. Vadya, Locaton-aded routng (LAR) n moble ad hoc networks, n Proc. IEEE/ACM MobCom, pp ,. Dallas, Texas, USA, Oct [2] S. Y. N, Y. C. Tseng, Y-S. Chen, and J. P. Sheu, The broadcast storm problem n a moble ad hoc network, n Proc. Int. Conf. on Moble Computerng and Networkng (MobCom 99) pp , [3] D. Km, C. K. Toh, J. C. Cano, and P. Manzon, A boundng algorthm for the broadcast strom problem n moble ad hoc networks, n Proc. IEEE Wreless Communcaton and Networkng Conference, WCNC 03, vol. 2, pp , New Orleans, LA, USA, Mar [4] P. McCarthy and D. Grgoras, Multpath assocatvty based routng, n Proc. 2 nd IEEE Annual Conference on Wreless On-demand Network Systems and Servces (WONS 05), [5] S. -J. Lee and M. Gerla, Splt multpath routng wth maxmally dsont paths n ad hoc networks, n Proc. IEEE ICC 01, vol. 10, pp , Jun [6] A. Naspur and S. R. Das, On-demand multpath routng for moble ad hoc networks, n Proc. IEEE ICCCN 99, pp , Oct [7] C.-K. Toh. Assocatvty based routng for ad hoc moble networks, Wreless Personal Communcatons Journal, Specal Issue on Moble Networkng and Computng Systems, pp , Mar [8] E. Sakhaee, A. Jamalpour, and N. Kato, Aeronautcal ad hoc networks, n Proc. IEEE WCNC 06, vol. 1, pp , Apr [9] S. Jang, An enhanced predcton-based lnk avalablty estmaton for MANETs, IEEE Transactons on Communcatons, vol. 52, Issue 2, pp , Feb [10] M. Gerharz, C. de Waal, M. Frank, and P. Martn, Lnk stablty n moble wreless ad hoc networks, n Proc. 27 th Annual IEEE Conference on Local Computer Networks, (LCN 02) pp , Nov [11] A.B. McDonald, and T. Znat, A path avalablty model for wreless ad-hoc networks, n Proc. IEEE WCNC 99, vol. 1, pp 35-40, Sep [12] D. B. Johnson, D. A. Maltz, and Y. C. Hu, The dynamc source routng protocol for moble ad hoc networks (DSR), [13] S. Basagn, I. Chlamtac, V. R. Syrotuk, and B. A. Woodward, A dstance routng effect algorthm for moblty (DREAM), n Proc. IEEE/ACM MobCom, pp ,. Dallas, Texas, USA, Oct [14] B. Karp and H. T. Kung, GPSR: Greedy permeter stateless routng for wreless networks, n Proc. IEEE/ACM MobCom, pp , Boston, Massachusetts, USA, Aug [15] X. L and L. Cuthbert, On-demand node dsont multpath routng n wreless ad hoc networks n Proc. 29 th Annual IEEE Internatonal Conference on Local Computer Networks, pp , Nov [16] G. Aggelou, Moble ad hoc networks : from wreless LANs to 4G networks, p 91. McGraw-Hll Professonal Engneerng, [17] T. S. Rappaport, Wreless Communcatons: Prncples and Practce, Prentce Hall, [18] W. Su, S. J. Lee, and M. Gerla, Moblty predcton and routng n ad hoc wreless networks, Int. J. of Network Mgmt, 2001, vol. 11, pp [19] G. Lu et al., PATCH: a novel local recovery mechansm for moble adhoc networks, n Proc. IEEE Vehcular Technology Conference (VTC 2003), vol. 5, pp , Oct. 2003, Florda, USA.