An Energy-Aware QoS Routing Protocol for Wireless Sensor Networks

Transcription

1 An Enegy-Awae QoS Routng Potocol fo Weless Senso Netwoks Kemal Akkaya and Mohamed Youns Depatment of Compute Scence and Electcal Engneeng Unvesty of Mayland, Baltmoe County Baltmoe, MD 225 kemal Abstact Recent advances n weless senso netwoks have led to many new outng potocols specfcally desgned fo senso netwoks. Almost all of these outng potocols consdeed enegy effcency as the ultmate obectve n ode to maxmze the whole netwok lfetme. Howeve, the ntoducton of vdeo and magng sensos has posed addtonal challenges. Tansmsson of vdeo and magng data eques both enegy and QoS awae outng n ode to ensue effcent usage of the sensos and effectve access to the gatheed measuements. In ths pape, we popose an enegy-awae QoS outng potocol fo senso netwoks whch can also un effcently wth best-effot taffc. The potocol fnds a least-cost, delay-constaned path fo eal-tme data n tems of lnk cost that captues nodes enegy eseve, tansmsson enegy, eo ate and othe communcaton paametes. Moeove, the thoughput fo non-eal-tme data s maxmzed by adustng the sevce ate fo both eal-tme and non-eal-tme data at the senso nodes. Smulaton esults have demonstated the effectveness of ou appoach fo dffeent metcs.. Intoducton Recent advances n mnatuzaton and low-powe desgn have led to actve eseach n lage-scale, hghly dstbuted systems of small-sze, weless unattended sensos. Each senso s capable of detectng ambent condtons such as tempeatue, sound, o the pesence of cetan obects. Ove the last few yeas, the desgn of senso netwoks has ganed nceasng mpotance due to the potental fo some cvl and mltay applcatons such as combat feld suvellance, secuty and dsaste management. These systems pocess data gatheed fom multple sensos to monto events n an aea of nteest. In a dsaste management setup a lage numbe of sensos can be dopped by a helcopte. Netwokng these sensos can assst escue opeatons by locatng suvvos, dentfyng sky aeas and makng the escue cew moe awae of the oveall stuaton. On the mltay sde, applcatons of senso netwoks ae numeous. Fo example, the use of netwoked set of sensos can lmt the need fo pesonnel nvolvement n the usually dangeous econnassance mssons and

2 can povde a moe cvc altenatve to landmnes. Secuty applcatons of senso netwoks nclude ntuson detecton and cmnal huntng. Routng of senso data has been one of the challengng aeas n weless senso netwok eseach. It usually nvolves mult-hop communcatons and has been studed as pat of the netwok laye poblems [,2,3,4]. Despte the smlaty between senso and moble ad-hoc netwoks, outng appoaches fo ad-hoc netwoks poved not to be sutable to sensos netwoks. Ths s due to dffeent outng equements fo ad-hoc and senso netwoks n seveal aspects. Fo nstance, communcaton n senso netwoks s fom multple souces to a sngle snk, whch s not the case n ad-hoc netwoks. Moeove, thee s a mao enegy esouce constant fo the senso nodes. As a consequence, many new algothms have been poposed fo the poblem of outng data n senso netwoks. These outng mechansms can be classfed as data-centc [], heachcal [2] o locaton-based [3]. Cuent eseach on outng of senso data mostly focused on potocols that ae enegy awae to maxmze the lfetme of the netwok, scalable fo lage numbe of senso nodes and toleant to senso damage and battey exhauston. Snce the data they deal wth s not n lage amounts and flow n low ates to the snk, the concepts of latency, thoughput, delay and tte wee not pmay concens n senso netwoks. Howeve, the development of vdeo and magng sensos eques the consdeaton of qualty of sevce (QoS) n senso netwoks, whch magnfes the dffcultes assocated wth the enegy effcency and awaeness. QoS potocols n senso netwoks have seveal applcatons ncludng eal tme taget tackng n battle envonments, emegent event tggeng n montong applcatons etc. Consde the followng scenao: In a battle envonment t s cucal to locate, detect and dentfy a taget. In ode to dentfy a taget, we should employ magng and/o vdeo sensos. Afte locatng and detectng the taget wthout the need of magng and vdeo sensos, we can tun on those sensos to get fo nstance an mage of the taget peodcally and send to the base staton o gateway. Snce, t s a battle envonment; ths eques a eal-tme data exchange between sensos and contolle n ode to take the pope actons. Howeve, we should deal wth eal-tme multmeda data, whch eques cetan bandwdth wth mnmum possble delay, and tte. In that case, a sevce dffeentaton mechansm s needed n ode to guaantee the elable delvey of the eal-tme data. Enegy-awae QoS outng n senso netwoks wll ensue guaanteed bandwdth (o delay) though the duaton of connecton as well as povdng the use of most enegy effcent path. To the best of ou knowledge, no pevous eseach has addessed QoS outng n senso netwoks. In ths pape, we pesent an enegy-awae QoS outng mechansm fo weless senso netwoks. Ou poposed potocol extends the outng appoach n [7] and consdes only end-to-end delay. The potocol looks fo a delay-constaned path wth the least possble cost based on a cost functon 2

3 defned fo each lnk. Altenatve paths wth bgge costs ae ted untl one, whch meets the end-toend delay equement and maxmzes the thoughput fo best effot taffc s found. Ou potocol does not bng any exta ovehead to the sensos. In the balance of ths secton we descbe the senso netwok achtectue that we consde and summaze the elated wok. In secton 2, we analyze the complexty of the QoS outng poblem n senso netwoks and descbe ou appoach. Secton 3 ncludes smulatons and evaluatons of the potocol. Fnally we conclude the pape n secton 4 and outlne ou futue eseach.. Senso Netwok Achtectue We consde the senso netwok achtectue depcted n Fg.. In the achtectue senso nodes ae gouped nto clustes contolled by a sngle command node. Sensos ae only capable of ado-based shot-haul communcaton and ae esponsble fo pobng the envonment to detect a taget/event. Evey cluste has a gateway node that manages sensos n the cluste. Clustes can be fomed based on many ctea such as communcaton ange, numbe and type of sensos and geogaphcal locaton [27][28]. In ths pape, we assume that senso and gateway nodes ae statonay and the gateway node s located wthn the communcaton ange of all the sensos of ts cluste. Clusteng the senso netwok s pefomed by the command node and s beyond the scope of ths pape. The command node wll nfom each gateway node of the ID and locaton of sensos allocated to the cluste. Command Node Fg. : Mult-gateway clusteed netwok sensos Senso nodes Gateway Node 3

4 Sensos eceve commands fom and send eadngs to ts gateway node, whch pocesses these eadngs. Gateways can tack events o tagets usng eadngs fom sensos n any clustes as deemed by the command node. Howeve, sensos that belong to a patcula cluste ae only accessble va the gateway of that cluste. Theefoe, a gateway should be able to oute senso data to othe gateways. Gateway nodes nteface the command node wth the senso netwok va longhaul communcaton lnks. The gateway node sends to the command node epots geneated though fuson of senso eadngs, e.g. tacks of detected tagets. The command node pesents these epots to the use and pefoms system-level fuson of the collected epots fo an oveall stuaton awaeness. Although the mult-gateway achtectue ases many ssues such as cluste fomaton, clustebased senso oganzaton and management, and nte-gateway communcaton potocol, ths pape only focuses on the QoS outng of data wthn one patcula cluste..2 Related Wok In tadtonal best-effot outng thoughput and aveage esponse tme ae the man concens. QoS outng s usually pefomed though esouce esevaton n a connecton-oented communcaton n ode to to meet the QoS equements fo each ndvdual connecton. Whle many mechansms have been poposed fo outng QoS constaned eal-tme multmeda data n we-based netwoks [5,6,7,8,9], they cannot be dectly appled to weless senso netwoks due to the lmted esouces, such as bandwdth and enegy, that a senso node has. On the othe hand, a numbe of potocols have been poposed fo QoS outng n weless adhoc netwoks takng the dynamc natue of the netwok nto account [,,2,3,4]. Howeve, none of these potocols consde enegy awaeness along wth the QoS paametes. Some of the poposed potocols consde the mpecse state nfomaton whle detemnng the outes [,]. In ou model, we do not have the poblem of mpecson snce the state of senso nodes ae mantaned by the gateway node. CEDAR s anothe QoS awae potocol, whch uses the dea of coe nodes (domnatng set) of the netwok whle detemnng the paths [2]. Usng outes found though the netwok coe, one can seach fo a QoS path easly. Snce, the data flow n ou senso netwok achtectue s manyto-one; thee s no need to fnd a coe of the netwok. Moeove, f any node n the coe s boken, t wll cost too much esouce to econstuct the coe. Ln [3] and Zhu et al. [4] have poposed QoS outng potocols specfcally desgned fo TDMA-based ad-hoc netwoks. Both potocols can 4

5 buld a QoS oute fom a souce to destnaton wth eseved bandwdth. The bandwdth calculaton s done hop-by-hop usng dstbuted algothms. The only potocol fo senso netwoks that ncludes the noton of QoS n ts outng decsons s Sequental Assgnment Routng (SAR) [5]. The SAR potocol ceates tees outed fom one-hop neghbo of the snk by takng QoS metc, enegy esouce on each path and poty level of each packet nto consdeaton. By usng ceated tees, multple paths fom snk to sensos ae fomed. Futhemoe, one of the paths can be selected accodng to the enegy esouces and QoS on each path. In ou appoach, we not only select a path fom a lst of canddate paths that meet the end-toend delay equement, but maxmze the thoughput fo best effot taffc as well. In addton, the SAR appoach suffes the ovehead of mantanng the node states at each senso node. Ou potocol does not eque senso s nvolvement n oute setup. 2. Enegy-awae QoS Routng Ou am s to fnd an optmal path to the gateway n tems of enegy consumpton and eo ate whle meetng the end-to-end delay equements. End-to-end delay equements ae assocated only wth the eal-tme data. Note that, n ths case we have both eal-tme and non-eal-tme taffc coexstng n the netwok, whch makes the poblem moe complex. We not only should fnd paths that meet the equements fo eal-tme taffc, but need to maxmze the thoughput fo non-eal tme taffc as well. Ths s because most of the ctcal applcatons such as battlefeld suvellance have to eceve fo nstance acoustc data egulaly n ode not to mss tagets. Theefoe t s mpotant to pevent the eal-tme taffc fom consumng the bulk of netwok bandwdth and leave non-eal-tme data stavng and thus ncung lage amount of delay. The descbed QoS outng poblem s vey smla to typcal path constaned path optmzaton (PCPO) poblems, whch ae poved to be NP-complete [8]. We ae tyng to fnd least-cost path, whch meets the end-to-end delay path constant. Howeve, n ou case thee s an exta goal, whch s bascally to maxmze the thoughput of non-eal-tme taffc. Ou appoach s based on assocatng a cost functon fo each lnk and used a K least cost path algothm to fnd a set of canddate outes. Such outes ae checked aganst the end-to-end constants and the one that povdes maxmum thoughput s pcked. Befoe explanng the detals of poposed algothm, we ntoduce the queung model. 5

6 2.2 Queung Model The queung model s specfcally desgned fo the case of coexstence of eal-tme and non-ealtme taffc n each senso node. The model we employ s nsped fom class-based queung model [6]. We use dffeent queues fo the two dffeent types of taffc. Bascally, we have eal-tme taffc and non-eal-tme (nomal) taffc whose packets ae labeled accodngly. On each node, thee s a classfe, whch checks the type of the ncomng packet and sends t to the appopate queue. Thee s also a schedule, whch detemnes the ode of packets to be tansmtted fom the queues accodng to the bandwdth ato of each type of taffc on that lnk. The model s depcted n Fg. 2. A cluste of sensos Queung model on a patcula node Classfe N Schedule Sensng only node Relayng only Gateway Non-eal tme packet Real tme packet One of the paths fo N data. Fg. 2: Queung model n cluste-based senso netwok The bandwdth ato, s actually an ntal value set by the gateway and epesents the amount of bandwdth to be dedcated both to the eal-tme and non-eal-tme taffc on a patcula outgong lnk n case of a congeston. Moeove, both classes can boow bandwdth fom each othe when one of the two types of the taffc s non-exstent o unde the lmts. As ndcated n Fg. 3, ths - value s also used to calculate the sevce ate of eal-tme and non-eal-tme taffc on that patcula 6

7 node, wth µ and ( ) µ beng espectvely the sevce ate fo eal-tme and non-eal-tme data on senso node. Snce the queung delay depends on ths -value, we cannot calculate the end-to-end delay fo a patcula path wthout knowng the -value. Theefoe we should fst fnd a lst of canddate leastcost paths and then select one that meets the end-to-end delay equement. = µ N = ) µ sevceate sevceate ( bw = bw bw = ( ) bw N Fg. 3: Bandwdth shang and sevce ates fo a senso node Ou appoach s based on a two-step stategy ncopoatng both lnk-based costs and end-toend constants. Fst we calculate the canddate paths wthout consdeng the end-to-end delay. What we do s smply calculate costs fo each patcula lnk and then use an extended veson of Dksta's algothm to fnd an ascendng set of least cost paths. Once we obtan these canddate paths then we mght futhe check them to see whch one meets ou end-to-end QoS equements by tyng to fnd an optmal -value that wll also maxmze the thoughput fo non-eal-tme taffc. 2.3 Calculaton of lnk costs We consde the factos fo the cost functon on each patcula lnk sepaately except the end-toend delay equement, whch should be fo the whole path (.e. all the lnks on that path). We defne the followng cost functon fo a lnk between nodes and : cost = 6 CF k = c ( dst ) l + c f ( enegy ) k = c /T c + c c + c f ( ) 6 e whee, dst s the dstance between the nodes and, f ( enegy ) s the functon fo fndng cuent esdual enegy of node, 7

8 T s the expected tme unde the cuent consumpton ate untl the node enegy level eaches the mnmum acceptable theshold. f ( e ) s the functon fo fndng the eo ate on the lnk between and. The factoscf ae defned smla as n [7], howeve the cost functon s futhe extended k fo eo ate cost. The end-to-end delay s modeled as a constant on the whole path and ncludes the popagaton delay. Hence, t s not pat of the cost functon. Cost factos ae defned as follows: CF (Communcaton Cost)= ( ) l c dst, whee c s a weghtng constant and the paamete l depends on the envonment, and typcally equals to 2. Ths facto eflects the cost of the weless tansmsson powe, whch s dectly popotonal to the dstance ased to some powe l. The close a node to the destnaton, the less ts cost facto CF and moe attactve t s fo outng. CF (Enegy Stock)= c f ( ) enegy. Ths facto eflects the emanng battey lfetme, whch favos nodes wth moe enegy. The moe enegy the node contans, the bette t s fo outng. CF 2 (Enegy Consumpton Rate)= c 2 /T, whee c 2 s a weghtng constant and T s the expected tme unde the cuent consumpton ate untl the node enegy level hts the mnmum acceptable theshold. The factocf2 makes heavly used nodes less attactve, even f they have a lot of enegy. CF 3 (Relay enablng cost)= c 3, whee c 3 s a constant eflectng the ovehead equed to swtch an nactve node to become a elay. Ths facto favos elay-enabled nodes to be used fo outng athe than the nactve nodes. CF 4 (Sensng-state cost)= c 4, whee c 4 s a constant added when the node s n a sensngstate. Ths facto does not favo selectng sensng-enabled nodes to seve as elays. It s pefeed not to oveload these nodes n ode to keep functonng as long as possble. CF 5 (Maxmum connectons pe elay)= c 5. Once ths theshold s eached, we add an exta cost c5 to avod settng addtonal paths though that elay. Ths facto extends the lfe of oveloaded elay nodes by makng them less favoable. 8

9 CF (Eo ate)= c f ( ) 6 e 6 whee f s a functon of dstance between nodes and and buffe sze on node (.e. dst / buffe _ sze ). The lnks wth hgh eo ate wll ncease the cost functon, thus wll be avoded. 2.4 Calculaton of end-to-end delay fo a path In ode to fnd a QoS path fo sendng eal-tme data to the gateway, end-to-end delay equement should be met. Befoe explanng the computaton of the delay, whch conssts of queung delay and popagaton delay fo a patcula path P, we ntoduce the followng notaton: λ : Real-tme data geneaton ate fo magng sensos µ : Sevce ate fo eal-tme data on senso node ( )µ : Sevce ate fo non-eal-tme data on senso node p : The numbe of sensng-only neghbos of node on path P q : The numbe of elayng-only neghbos of node on path P () λ : Total eal-tme data ate on senso node () TQ : Total queung delay on a node fo eal-tme taffc T : End-to-end queung delay fo a patcula path P E T : End-to-end popagaton delay fo a patcula path P p T : Total end-to-end delay fo a patcula path P end end T : End-to-end delay equement fo all paths equed Total eal-tme data ate by p nodes wll be pλ and total eal-tme data ate by q nodes wll be q = µ (snce evey elayng-only node poduces eal-tme data by the ate µ ). Then total eal-tme data load on a senso node s: () λ = pλ q = + µ 9

10 Hence, total queung delay on a node s: () TQ = () λ / µ The end-to-end queung delay fo a patcula path s: E T = Path () TQ = Path + = µ µ λ q p = = + Path q Path p µ λ = = + Path q p µ λ The end-to-end popagaton delay fo the path s: p T = Path dst c, whee c s a constant, whch s obtaned by dvdng a weghtng constant by the speed of weless tansmsson. Hence, total end-to-end delay wll be:

11 T = T E + end end T p p λ = µ Path + = q + ( c dst ), Path 2.5 Algothm Whle we geneate a fomula fo calculatng the end-to-end delay fo a patcula path, fndng the optmal -values fo each lnk as fa as the queung delay s concened, wll be vey dffcult optmzaton poblem to solve. Moeove, the dstbuton of these -values to each node s not an easy task because the each value should be uncasted to the pope senso node athe than boadcastng t to all the sensos whch mght bng a lot of ovehead. Theefoe, we follow an appoach, whch wll elmnate the ovehead and complexty of the poblem. Bascally, we defne each -value to be same on each lnk so that the optmzaton poblem wll be smple and ths unque -value can be easly boadcasted to all the sensos by the gateway. If we let all -values be same fo evey lnk then the fomula wll be smplfed as: λ Tend end = µ p, Path + ( q + c dst ), Path Then the poblem s stated as an optmzaton poblem as follows: Max (( ) µ ) Path subect to; Tend end T and < equed By consdeng the above optmzaton poblem, we popose the algothm as shown n Fg. 4 to fnd a least-cost path, whch meets the constants and maxmzes the thoughput fo non-eal-tme data.

12 Calculate cos,, V t 2 Fnd the least cost path fo each node by usng Dksta s shotest path algothm. 3 fo each magng senso node do 4 begn 5 compute fom Tend end ( p ) = T equed 6 f ( s n ange [,)) then 7 Add to a lst coespondng to node 8 else K P to the gateway by extended Dksta. 9 Fnd K least cost paths ( ) fo each k K do k Recompute fom Tend end ( p ) = T equed 2 f ( s n ange [,)) then 3 beak; 4 f no appopate s found 5 Reect the connecton 6 end 7 Fnd max fom the lst The algothm calculates the cost fo each lnk n lne of Fg. 4, based on the cost functon defned n secton 2.3. Then, fo each node the least cost path to the gateway s found by unnng Dksta s shotest path algothm n lne 2. Between lnes 5-5, appopate -values ae calculated fo paths fom magng sensos to the gateway. Fo each senso node that has magng capablty, an -value s calculated on the cuent path (lne 5). If that value s not between and, extended Dskta algothm fo K-shotest path s un n ode to fnd altenatve paths wth bgge costs (lne 9). K dffeent least-cost paths ae ted n ode to fnd a pope -value between and (lnes - 3). If thee s no such -value, the connecton equest of that node to the gateway s smply eected. The algothm mght geneate dffeent -values fo dffeent paths. Snce, the -values ae stoed n a lst; the maxmum of them s selected to be used fo the whole netwok (lne 7). That - value wll satsfy the end-to-end delay equement fo all the paths establshed fom magng sensos to the gateway. Fg. 4: Pseudo code fo the poposed algothm In ode to fnd the K least cost paths (.e. K shotest paths), we modfed an extended veson of Dksta s algothm. Fndng K shotest paths s a classcal netwok-pogammng poblem, whch has been studed extensvely n [9, 2, 2, 22]. In [22], a genealzaton of Dksta s algothm to solve K shotest path poblem s gven. The algothm uses Dksta s concepts but t does not use elaxaton at each node to fnd the shotest dstance fom the souce. Instead, the algothm ecods evey path fom the souce to a patcula node by addng new elements to the set 2

13 V. It s a labelng algothm, whch assgns labels to each node n the gaph and then fnds the paths. A labelng functon h s used to map numbes (labels) to the nodes. And the evese functon h etuns the labels fo a patcula node. The algothm ceates a tee lke stuctue fo evey path t has eached and keeps the cost of each path fom souce to any node n d []. Wheneve the numbe of paths fom souce to taget ( count ) eaches K, the algothm temnates and etuns the lst of K shotest paths fom souce to taget. t Snce, the algothm faces wth loops dung executon; we modfed the algothm n ode to avod loops and ensue smplcty and effcency. Each tme a new path s seached fo a patcula node, only node-dsont paths ae consdeed dung the pocess. Ths mght also help fndng a pope -value easly snce that node-dsont path wll not nhet the congeston n the fome path. Inteested eade s efeed to [22] fo futhe nfomaton. 3. Expemental Results The effectveness of the enegy-awae QoS outng appoach s valdated though smulaton. Ths secton descbes the pefomance metcs, smulaton envonment, and expemental esults. 3. Pefomance Metcs We used the followng metcs to captue the pefomance of ou QoS outng appoach: Aveage lfetme of a node: Ths gves a good measue of the netwok lfetme. A outng algothm, whch maxmzes the lfetme of netwok, s desable. Ths metc also shows how effcent s the algothm n enegy consumpton. Aveage delay pe packet: Defned as the aveage tme a packet takes fom a senso node to the gateway. Most enegy awae outng algothms ty to mnmze the consumed enegy. Howeve, the applcatons that deal wth eal-tme data s delay senstve, so ths metc s mpotant n ou case. Netwok Thoughput: Defned as the total numbe of data packets eceved at the gateway dvded by the smulaton tme. The thoughput fo both eal-tme and non-eal-tme taffc wll be consdeed ndependently. 3.2 Envonment Setup In the expements the cluste conssts of andomly placed nodes n a mete squae aea. The gateway poston s detemned andomly wthn the cluste boundaes. A fee space 3

14 popagaton channel model s assumed [24] wth the capacty set to 2Mbps. Packet lengths ae Kbt fo data packets and 2 Kbt fo outng and efesh packets. Each node s assumed to have an ntal enegy of 5 oules. The buffes fo eal-me data and nomal data have default sze of 5 packets [25]. A node s consdeed non-functonal f ts enegy level eaches. Fo the tem CF n the cost functon, we used the lnea dschage cuve of the alkalne battey [23]. Fo a node n the sensng state, packets ae geneated at a constant ate of packet/sec. Ths value s consstent wth the specfcatons of the Acoustc Ballstc Module fom SenTech Inc. [26]. The eal-tme packet geneaton ate ( λ ) fo the nodes, whch have magng/vdeo capablty s geate than the nomal ate. The default value s 3 packets/sec. A sevce ate ( µ ) of 5 packets/sec s assumed. Each data packet s tme-stamped when t s geneated to allow the calculaton of aveage delay pe packet. In addton, each packet has an enegy feld that s updated dung the packet tansmsson to calculate the aveage enegy pe packet. A packet dop pobablty s taken to be.. Ths s used to make the smulato moe ealstc and to smulate the devaton of the gateway enegy model fom the actual enegy model of nodes. We assume that the cluste s tasked wth a taget-tackng msson n the expement. The ntal set of sensng nodes s chosen to be the nodes on the convex hull of sensos n the cluste. The set of sensng nodes changes as the taget moves. Snce tagets ae assumed to come fom outsde the cluste, the sensng ccuty of all bounday nodes s always tuned on. The sensng ccuty of othe nodes ae usually tuned off but can be tuned on accodng to the taget movement. We also assume that each senso node s capable of takng the mage of taget to dentfy t clealy and can tun on ts magng capablty on demand. Dung smulaton, a small subset of cuent actve nodes, whch ae the closest nodes to the taget, ae selected to tun on the magng capablty. Theefoe, the magng senso set may change wth the movement of the taget. The packet-sensng ate fo magng sensos s bgge than the nomal sensos; hence moe packets ae geneated when magng sensos ae employed. These packets ae labeled as eal-tme packets and teated dffeently n senso nodes. The -value s ntally assumed to be but t s ecalculated as magng sensos get actvated. The default end-to-end delay equement fo a QoS path s assumed to be seconds, whch s a easonable amount of tme to get mage data peodcally n a eal-tme taget tackng applcaton. Tagets ae assumed to stat at a andom poston outsde the convex hull. Tagets ae chaactezed by havng a constant speed chosen unfomly fom the ange 4 metes/s to 6 metes/s and a constant decton chosen unfomly dependng on the ntal taget poston n ode fo the taget to coss the convex hull egon. It s 4

15 assumed that only one taget s actve at a tme. Ths taget emans actve untl t leaves the deployment egon aea. In ths case, a new taget s geneated. 3.3 Pefomance Results In ths secton, we pesent some pefomance esults obtaned by the smulaton. Dffeent paametes ae consdeed fo end-to-end delay, buffe sze, packet dop pobablty and eal-tme data geneaton captue the effects on the pefomance metcs defned eale n ths secton. Effect of end-to-end delay and eal-tme date geneaton ate on netwok -values In ode to see how the algothm behaves unde stngent condtons, we vaed the end-to-end delay and montoed how ths change affects the netwok -value. The esults ae depcted n Fg. 5. The netwok -value goes down whle the end-to-end delay equement gets loose. Snce the delay s not too stct, most of the nodes wll be able to fnd a QoS path. On the othe hand, whle we congest the netwok wth moe eal-tme data packets by nceasng the eal-tme data geneaton ate, moe bandwdth wll be equed fo eal-tme packets. Ths wll cause the -value to ncease so that each node can seve moe eal-tme packets (See Fg. 6). Netwok -value End-To-End Delay(sec) Fg. 5: Netwok -value wth dffeent end-to-end delay values Netwok -value data Rate(packet/sec) Fg. 6: Netwok -value wth dffeent eal-tme data ates 5

16 Thoughput Avg. Thoughput Avg. N Thoughput data ate(packet/sec) Fg. 7: Effect of t-data ate on thoughput Tme data ate(packet/sec) Fg. 8: Effect of t-data ate on aveage delay fo a packet Tme data ate(packet/sec) Fg. 9: Effect of t-data ate on aveage lfetme of a node Thoughput Packet Dop Pobablty Fg. : Effect of packet dop pob. on thoughput Tme 2.5 Tme Packet Dop Pobablty Packet Dop Pobablty Fg. : Effect of packet dop pob. on aveage delay pe packet Fg. 2: Effect of packet dop pob. on aveage lfetme of a node Tme Buffe Sze Fg. 3: Effect of buffe sze on aveage delay pe packet Tme Buffe Sze Fg. 4: Effect of buffe sze on aveage lfetme of a node 6

17 Effect of eal-tme data ate on pefomance In ode to see the pefomance of the algothm fo dffeent eal-tme data ates, we an smulaton fo dffeent values of eal-tme packet data ates. The esults ae depcted n Fg. 7, 8 and 9. We looked at the eal-tme and non-eal-tme data thoughput. Whle the numbe of eal-tme packets ncease, t gets moe dffcult to satsfy nceasng numbe of QoS paths. Hence, ths can cause some eecton o packet dops fo eal-tme data causng thoughput fo eal-tme data to decease. Howeve, the thoughput fo non-eal-tme data does not change much snce thee s aleady a constant dedcated bandwdth fo such data, ensued by the -value. We estcted -value to be stctly less than causng the thoughput fo non-eal-tme data ( ( ) µ ) always geate than. The algothm does not sacfce the thoughput fo non-eal-tme data fo the sake of eal-tme data. Fgue 8 shows the effect of eal-tme data ate on aveage delay pe packet. The delay nceases wth the ate snce packets (especally eal-tme packets) ncu moe queung delay and shae the same amount of bandwdth. We also looked fo the lfetme of a node n ode to see the effect of eal-tme data ate on enegy metc. Fgue 9 shows that the aveage enegy fo a senso node nceases wth the eal-tme data ate. The eason fo ths ncease s that the thoughput deceases, causng the numbe of packets avng to the gateway to decease. Theefoe, fewe packets wll be elayed by the senso nodes, whch wll save enegy fom tansmsson and ecepton enegy costs. Effect of packet dop pobablty on pefomance To study the effect of packet dop pobablty on pefomance, we vaed the pobablty of packet dop fom. to.5. The esults ae depcted n Fgues, and 2. The aveage delay pe packet deceases wth the nceasng pobablty. Ths can be explaned by notng that as the numbe of hops the packet tavese nceases, the pobablty that t wll be dopped nceases. Ths means that the packets that ave to the gateway ae most pobable to take a small numbe of hops and thus ncung less delay. As expected, the thoughput deceases due to lost packets. The aveage node lfetme nceases snce not all packets each the destnaton and thus the node enegy s conseved. Effect of buffe sze on pefomance Snce, the queung model we employed uses buffes n each node and thee s a lmt on the sze of those buffes, we vaed the buffe sze to see f ths has any effect on the pefomance of the 7

18 algothm. The esults ae shown n Fg. 3 and 4. The aveage delay pe packet nceases wth the buffe sze snce the thoughput nceases. Packets ae not dopped when thee s enough space n the buffes. Ths wll ncease the numbe of packets avng to the gateway. The packets fom fa nodes wll be also able to each the gateway. Moe packets fom fa nodes mean moe delay, whch eventually nceases the aveage delay pe packet. The nceasng numbe of packets avng to the gateway wll also ncease the enegy consumpton by nceasng the numbe of tansmsson and ecepton costs, theefoe deceasng the aveage lfetme of a node. 4. Concluson and Futue Wok In ths pape, we pesented a new enegy-awae QoS outng potocol fo senso netwoks. The potocol fnds QoS paths fo eal-tme data wth cetan end-to-end delay equements. Moeove, the selected queung model fo the potocol allows the thoughput fo nomal data not to dmnsh by employng a netwok wde -value, whch guaantees cetan sevce ate fo eal-tme and noneal-tme data on each lnk. The effectveness of the potocol s valdated by smulaton. Smulaton esults show that ou potocol consstently pefoms well wth espect to QoS metcs, e.g. thoughput and aveage delay as well as enegy-based metc such as aveage lfetme of a node. The netwok -value s adusted accodngly n the case of bg eal-tme data ate on the nodes o stngent end-to-end delay equements. The esults have also shown that eal-tme data ate, buffe sze, and packet dop pobablty have sgnfcant effects on the pefomance of the potocol. We ae cuently extendng the model to allow dffeent -values can be assgned to senso nodes and plan to compae the pefomance of such extended model wth the enegy-awae QoS outng potocol pesented n ths pape. Refeences [] C. Intanagonwwat, R. Govndan and D. Estn, "Dected dffuson: A scalable and obust communcaton paadgm fo senso netwoks," In Poceedngs of the Sxth Annual Intenatonal Confeence on Moble Computng and Netwokng (MobCOM '), Boston, Massachussetts, August 2. [2] W. Henzelman, J. Kulk, and H. Balakshnan, Adaptve potocols fo nfomaton dssemnaton n weless senso netwoks, In Poc. Ffth Annual ACM/IEEE Intenatonal Confeence on Moble Computng and Netwokng (MobCom), 999. [3] W. Henzelman, A. Chandakasan, and H. Balakshnan, "Enegy-effcent communcaton potocol fo weless senso netwoks," n Poc. Hawa Intl. Conf. System Scences, Hawa, pp , 2. 8

19 [4] R. Shah and J. Rabaey, "Enegy Awae Routng fo Low Enegy Ad Hoc Senso Netwoks", n the Poceedngs of the IEEE Weless Communcatons and Netwokng Confeence (WCNC 2), Olando, FL, Mach 22. [5] W. C. Lee, M. G. Hluchy and P. A. Humblet, "Routng Subect to Qualty of Sevce Constants Integated Communcaton Netwoks," IEEE Netwok, July/Aug [6] Z. Wang and J. Cowcaft, "QoS-based Routng fo Suppotng Resouce Resevaton," IEEE Jounal on Selected Aea of Communcatons, Sept 996. [7] Q. Ma and P. Steenkste, "Qualty-of-Sevce outng wth Pefomance Guaantees," n the Poceedngs of the 4 th Intenatonal IFIP Wokshop on Qualty of Sevce, May 997. [8] L. Zhang et al., "RSVP: A New Resouce ReSevaton Potocol," IEEE Netwok, Sept 993. [9] E. Cowley, R. Na, B. Raagopalan and H. Sandck, A famewok fo QoS based outng n the Intenet, Intenet-daft, daft-etf-qos-famewok-6.txt, Aug [] R. Quen and A. Oda, QoS-based outng n netwoks wth naccuate nfomaton: Theoy and algothms, n Poc. IEEE INFOCOM 97, Japan, pp , 997. [] S. Chen and K. Nahstedt, Dstbuted Qualty-of-Sevce Routng n ad-hoc Netwoks, IEEE Jounal on Selected aeas n Communcatons, Vol. 7, No. 8, August 999. [2] R. Svakuma, P. Snha and V. Bhaghavan, Coe extacton dstbuted ad hoc outng (CEDAR) specfcaton, IETF Intenet daft daft-etf-manet-ceda-spec-.txt, 998. [3] C. R. Ln, On Demand QoS outng n Multhop Moble Netwoks, IEICE Tansactons on Communcatons, July 2. [4] C. Zhu and M. S. Coson, QoS outng fo moble ad hoc netwoks, In the Poceedngs of IEEE INFOCOM, 22. [5] K. Sohab, J. Gao, V. Alawadh, G. J. Pote, "Potocols fo self-oganzaton of a weless senso netwok, IEEE Pesonal Communcatons, pp. 6-27, Octobe 2. [6] S. Floyd and V. Jacobson, Lnk Shang and Resouce Management Models fo Packet Netwoks, IEEE/ACM Tansactons on Netwokng, Vol. 3 No. 4 pp , August 995. [7] M. Youns, M. Youssef and K. Asha, Enegy-awae Routng n Cluste-Based Senso Netwoks, n the Poceedngs of the th IEEE/ACM Intenatonal Symposum on Modelng, Analyss and Smulaton of Compute and Telecommuncaton Systems(MASCOTS22), Foth Woth, Texas, Octobe 22. [8] G. Feng, C. Doulges, K. Makk and N. Pssnou, Pefomance Evaluaton of Delay- Constaned Least-Cost Routng Algothms Based on Lnea and Nonlnea Lagange Relaxaton, In the Poceedngs of the IEEE Intenatonal Confeence on Communcatons (ICC'22), New Yok, Apl 22. [9] D. She, On algothms fo fndng the k shotest paths n a netwok, Netwoks, 9:95-24,

20 [2] J. Y. Yen, Fndng the k shotest loopless paths n a netwok, Management Scence, 7:72-76, 97 [2] D. Epsten, Fndng the k shotest paths, SIAM J. Computng, 28(2): , 998. [22] Q.V.M. Enesto, M.M. Mata and L.E.S Jose, The K shotest paths poblem, Reseach Repot, CISUC, June 998. [23] S. Sngh, M. Woo and C. S. Raghavenda, "Powe-Awae Routng n Moble Ad-Hoc Netwoks", n the Poceedngs of ACM MOBICOM'98, Dallas, Texas, Octobe 998. [24] J.B. Andesen, T.S. Rappapot, and S. Yoshda, Popagaton Measuements and Models fo Weless Communcatons Channels, IEEE Communcatons Magazne, Vol. 33, No., Januay 995. [25] M. Gela, G. Pe, and S.-J. Lee, Weless, Moble Ad-Hoc Netwok Routng, n the Poceedngs of IEEE/ACM FOCUS'99, New Bunswck, NJ, May 999. [26] "Data sheet fo the Acoustc Ballstc Module", SenTech Inc., [27] A. Buczak and V. Jamalabad, "Self-oganzaton of a Heteogeneous Senso Netwok by Genetc Algothms," Intellgent Engneeng Systems Though Atfcal Neual Netwoks, C.H. Dagl, et. a.. (eds.), Vol. 8, pp , ASME Pess, New Yok, 998. [28] C.R. Ln and M. Gela, "Adaptve Clusteng fo Moble Weless Netwoks," IEEE Jounal on Selected Aeas of Communcatons, Vol. 5, No. 7, Septembe