An Energy-Aware QoS Routing Protocol for Wireless Sensor Networks

Transcription

1 An Energy-Aware QoS Routng Protocol for Wreless Sensor Networks Abstract Recent advances n wreless sensor networks have led to any new routng rotocols secfcally desgned for sensor networks. Alost all of these routng rotocols consdered energy effcency as the ultate obectve n order to axze the whole network lfete. However, the ntroducton of vdeo and agng sensors has osed addtonal challenges. ranssson of vdeo and agng data requres both energy and QoS aware routng n order to ensure effcent usage of the sensors and effectve access to the gathered easureents. In ths aer, we roose an energy-aware QoS routng rotocol for sensor networks whch can also run effcently wth best-effort traffc. he rotocol fnds a least-cost, delay-constraned ath for realte data n ters of lnk cost that catures nodes energy reserve, transsson energy, error rate and other councaton araeters. Moreover, the throughut for non-real-te data s axzed by adustng the servce rate for both real-te and non-real-te data at the sensor nodes. Sulaton results have deonstrated the effectveness of our aroach for dfferent etrcs.. Introducton Recent advances n naturzaton and low-ower desgn have led to actve research n large-scale, hghly dstrbuted systes of sall-sze, wreless unattended sensors. Each sensor s caable of detectng abent condtons such as teerature, sound, or the resence of certan obects. Over the last few years, the desgn of sensor networks has ganed ncreasng ortance due to ther otental for soe cvl and ltary alcatons such as cobat feld survellance, securty and dsaster anageent. hese systes rocess data gathered fro ultle sensors to ontor events n an area of nterest. In a dsaster anageent setu a large nuber of sensors can be droed by a helcoter. Networkng these sensors can assst rescue oeratons by locatng survvors, dentfyng rsky areas and akng the rescue crew ore aware of the overall stuaton. On the ltary sde, alcatons of sensor networks are nuerous. For exale, the use of networked set of sensors can lt the need for ersonnel nvolveent n the usually dangerous reconnassance ssons and can rovde a ore cvc alternatve to landnes. Securty alcatons of sensor networks nclude ntruson detecton and crnal huntng. Keal Akkaya and Mohaed Youns Deartent of Couter Scence and Electrcal Engneerng Unversty of Maryland, Baltore County Baltore, MD 5 keal youns@cs.ubc.edu Routng of sensor data has been one of the challengng areas n wreless sensor network research [,,3,4]. Current research on routng of sensor data ostly focused on rotocols that are energy aware to axze the lfete of the network, scalable for large nuber of sensor nodes and tolerant to sensor daage and battery exhauston. However, the develoent of vdeo and agng sensors requres the consderaton of qualty of servce (QoS) n sensor networks, whch agnfes the dffcultes assocated wth the energy effcency and awareness. QoS rotocols n sensor networks have several alcatons ncludng real te target trackng n battle envronents, eergent event trggerng n ontorng alcatons etc. Consder the followng scenaro: In a battle envronent t s crucal to locate, detect and dentfy a target. In order to dentfy a target, we should eloy agng and/or vdeo sensors. After locatng and detectng the target wthout the need of agng and vdeo sensors, we can turn on those sensors to get for nstance an age of the target erodcally and send to the base staton or gateway. Snce, t s a battle envronent; ths requres a real-te data exchange between sensors and controller n order to take the roer actons. However, we should deal wth realte ulteda data, whch requres certan bandwdth wth nu ossble delay, and tter. In that case, a servce dfferentaton echans s needed n order to guarantee the relable delvery of the real-te data. Energy-aware QoS routng n sensor networks wll ensure guaranteed bandwdth (or delay) through the duraton of connecton as well as rovdng the use of ost energy effcent ath. o the best of our knowledge, no revous research has addressed QoS routng n sensor networks. In ths aer, we resent an energy-aware QoS routng echans for wreless sensor networks. Our roosed rotocol extends the routng aroach n [7] and consders only end-to-end delay. he rotocol looks for a delayconstraned ath wth the least ossble cost based on a cost functon defned for each lnk. Alternatve aths wth bgger costs are tred untl one, whch eets the end-to-end delay requreent and a xzes the throughut for best effort traffc s found. Our rotocol does not brng any extra overhead to the sensors. In the balance of ths secton we descrbe the sensor network archtecture that we consder and suarze the related work. In secton, we analyze the colexty of the QoS routng roble n sensor networks and descrbe our

2 aroach. Secton 3 ncludes sulatons and evaluatons of the rotocol. Fnally we conclude the aer n secton 4 and outlne our future research... Sensor Ne twork Archtecture We consder the sensor network archtecture dected n Fgure. In the archtecture sensor nodes are groued nto clusters controlled by a sngle coand node. Sensors are only caable of rado-based short-haul councaton and are resonsble for robng the envronent to detect a target/event. Every cluster has a gateway node that anages sensors n the cluster. Clusters can be fored based on any crtera such as councaton range, nuber and tye of sensors and geograhcal locaton [4][5]. In ths aer, we assue that sensor and gateway nodes are statonary and the gateway node s located wthn the councaton range of all the sensors of ts cluster. Clusterng the sensor network s erfored by the coand node and s beyond the scoe of ths aer. he coand node wll nfor each gateway node of the ID and locaton of sensors allocated to the cluster. Sensors receve coands fro and send readngs to ts gateway node, whch rocesses these readngs. Gateways can track events or targets usng readngs fro sensors n any clusters as deeed by the coand node. However, sensors that belong to a artcular cluster are only accessble va the gateway of that cluster. herefore, a gateway should be able to route sensor data to other gateways. Gateway nodes nterface the coand node wth the sensor network va long-haul councaton lnks. he gateway node sends to the coand node reorts generated through fuson of sensor readngs, e.g. tracks of detected targets. he coand node resents these reorts to the user and Coand Node Sensor nodes Gateway Node Fgure. Mult-gateway clustered network sensors erfors syste-level fuson of the collected reorts for an overall stuaton awareness. Although the ult-gateway archtecture rases any ssues such as cluster foraton, cluster-based sensor organzaton and anageent, and nter-gateway councaton rotocol, ths aer only focuses on the QoS routng of data wthn one artcular cluster.. Related Work In tradtonal best-effort routng throughut and average resonse te are the an concerns. QoS routng s usually erfored through resource reservaton n a connectonorented councaton n order to eet the QoS requreents for each ndvdual connecton. Whle any echanss have been roosed for routng QoS constraned real-te ulteda data n wre-based networks [5,6,7,8,9], they cannot be drectly aled to wreless sensor networks due to the lted resources, such as bandwdth and energy, that a sensor node has. On the other hand, a nuber of rotocols have been roosed for QoS routng n wreless ad-hoc networks takng the dynac nature of the network nto account [,,,3,4]. However, none of these rotocols consder energy awareness along wth the QoS araeters. Soe of the roosed rotocols consder the recse state nforaton whle deternng the routes [,]. In our odel, we do not have the roble of recson snce the state of sensor nodes are antaned by the gateway node. CEDAR s another QoS aware rotocol, whch uses the dea of core nodes (donatng set) of the network whle deternng the aths []. Usng routes found through the network core, one can search for a QoS ath easly. Snce, the data flow n our sensor network archtecture s any-toone; there s no need to fnd a core of the network. Moreover, f any node n the core s broken, t wll cost too uch resource to reconstruct the core. Ln [3] and Zhu et al. [4] have roosed QoS routng rotocols secfcally desgned for DMA-based ad-hoc networks. Both rotocols can buld a QoS route fro a source to destnaton wth reserved bandwdth. he bandwdth calculaton s done hoby-ho usng dstrbuted algorths. he only rotocol for sensor networks that ncludes the noton of QoS n ts routng decsons s Sequental Assgnent Routng (SAR) [5]. he SAR rotocol creates trees routed fro one-ho neghbor of the snk by takng QoS etrc, energy resource on each ath and rorty level of each acket nto consderaton. By usng created trees, ultle aths fro snk to sensors are fored. Furtherore, one of the aths can be selected accordng to the energy resources and QoS on each ath. In our aroach, we not only select a ath fro a lst of canddate aths that eet the end-to-end delay requreent, but axze the throughut for best effort traffc as well. In addton, the SAR aroach suffers the overhead of antanng the node states at each sensor node. Our rotocol does not requre sensor s nvolveent n route setu.. Energy-aware QoS Routng

3 Our a s to fnd an otal ath to the gateway n ters of energy consuton and error rate whle eetng the end-toend delay requreents. End-to-end delay requreents are assocated only wth the real-te data. Note that, n ths A cluster of sensors case we have both real-te and non-real-te traffc coexstng n the network, whch akes the roble ore colex. We not only should fnd aths that eet the requreents for real-te traffc, but need to axze the throughut for non-real te traffc as well. hs s because ost of the crtcal alcatons such as battlefeld survellance have to receve for nstance acoustc data regularly n order not to ss targets. herefore t s ortant to revent the real-te traffc fro consung the bulk of network bandwdth and leave non-real-te data starvng and thus ncurrng large aount of delay. he descrbed QoS routng roble s very slar to tycal ath constraned ath otzaton (PCPO) robles, whch are roved to be NP-colete [8]. We are tryng to fnd least-cost ath, whch eets the end-to-end delay ath constrant. However, n our case there s an extra goal, whch s bascally to axze the throughut of non-real-te traffc. Our aroach s based on assocatng a cost functon for each lnk and used a K least cost ath algorth to fnd a set of canddate routes. Such routes are checked aganst the end-to-end constrants and the one that rovdes axu throughut s cked. Before exlanng the detals of roosed algorth, we ntroduce the queung odel.. Queung Model Queung odel on a artcular node Classfer N Scheduler Sensng Relayng only Gateway Real te Non-real acket te acket One of the aths for N data. Fgure. Queung odel n cluster-based sensor network he queung odel s secfcally desgned for the case of coexstence of real-te and non-real-te traffc n each sensor node. he odel we eloy s nsred fro classbased queung odel [6]. We use dfferent queues for the two dfferent tyes of traffc. Bascally, we have real-te traffc and non-real-te (noral) traffc whose ackets are labeled accordngly. On each node, there s a classfer, whch checks the tye of the ncong acket and sends t to the arorate queue. here s also a scheduler, whch deternes the order of ackets to be transtted fro the queues accordng to the bandwdth rato r of each tye of traffc on that lnk. he odel s dected n Fgure. he bandwdth rato r, s actually an ntal value set by the gateway and reresents the aount of bandwdth to be dedcated both to the real-te and non-real-te traffc on a artcular outgong lnk n case of a congeston. Moreover, both classes can borrow bandwdth fro each other when one of the two tyes of the traffc s non-exstent or under the lts. As ndcated n Fgure 3, ths r-value s also used to calculate the servce rate of real-te and non-real-te traffc on that artcular node, wth r µ and ( r ) µ r µ Nservcerat e ( r ) µ servcerate bw rbw beng resectvely the servce rate for real-te and nonreal-te data on sensor node. Snce the queung delay deends on ths r-value, we cannot calculate the end-to-end delay for a artcular ath wthout knowng the r-value. herefore we should frst fnd a lst of canddate least-cost aths and then select one that eets the end-to-end delay requreent. Our aroach s based on a two-ste strategy ncororatng both lnk-based costs and end-to-end constrants. Frst we calculate the canddate aths wthout consderng the end-to-end delay. What we do s sly calculate costs for each artcular lnk and then use an extended verson of Dkstra's algorth to fnd an ascendng set of least cost aths. Once we obtan these canddate aths then we ght further check the to see whch one eets our end-to-end QoS requreents by tryng to fnd an otal r-value that wll also axze the throughut for non-real-te traffc.. Calculaton of lnk costs bw ( r ) bw We consder the factors for the cost functon on each artcular lnk searately excet the end-to-end delay requreent, whch should be for the whole ath (.e. all the lnks on that ath). We defne the followng cost functon for a lnk between nodes and : N Fgure 3. Bandwdth sharng and servce rates for a sensor node

4 cos t 6 CF k c ( ) l dst + c f ( energy ) k c + c f ( ) c / + c 3 + c where, 6 e + dst s the dstance between the nodes and, f s the functon for fndng current energy ( ) resdual energy of node, s the exected te under the current consuton rate untl the node energy level reaches the nu accetable threshold. f s the functon for fndng the error rate on the e ( ) lnk between and. he factorscf are defned slar as n [7], however k the cost functon s further extended for error rate cost. he end-to-end delay s odeled as a constrant on the whole ath and ncludes the roagaton delay. Hence, t s not art of the cost functon. Cost factors are defned as follows: CF (Councaton Cost) c ( ) l dst, where s a weghtng constant and the araeter l deends on the envronent, and tycally equals to. hs factor reflects the cost of the wreless transsson ower, whch s drectly roortonal to the dstance rased to soe ower l. he closer a node to the destnaton, the CF and ore attractve t s for less ts cost factor routng. CF (Energy Stock) c f ( ) energy. hs factor reflects the reanng battery lfete, whch favors nodes wth ore energy. he ore energy the node contans, the better t s for routng. CF (Energy Consuton Rate) c c /, where c s a weghtng constant and s the exected te under the current consuton rate untl the node energy level hts the nu accetable threshold. he factorcf akes heavly used nodes less attractve, even f they have a lot of energy. CF (Relay enablng cost) c 3, where c 3 s a constant reflectng the overhead requred to swtch an nactve node to becoe a relay. hs factor favors relay-enabled nodes to be used for routng rather than the nactve nodes. CF (Sensng-state cost) c 4, where c 4 s a constant added when the node s n a sensng-state. hs factor does not favor selectng sensng-enabled nodes to serve 3 4 as relays. It s referred not to overload these nodes n order to kee functonng as long as ossble. CF (Maxu connectons er relay) c 5. Once ths 5 threshold s reached, we add an extra cost c5 to avod settng addtonal aths through that relay. hs factor extends the lfe of overloaded relay nodes by akng the less favorable. CF (Error rate) c 6 f ( e ) where f s a functon of dstance between nodes and and buffer sze on node (.e. dst / buffer _ sze ). he lnks wth hgh error 6 rate wll ncrease the cost functon, thus wll be avoded..3 Calculaton of end-to-end delay for a ath In order to fnd a QoS ath for sendng real-te data to the gateway, end-to-end delay requreent should be et. Before exlanng the coutaton of the delay, whch conssts of queung delay and roagaton delay for a artcular ath P, we ntroduce the notaton below: : Real-te data generaton rate for agng sensors r µ : Servce rate for real-te data on sensor node ( r )µ : Servce rate for non-real-te data on sensor node q : he nuber of sensng-only neghbors of node on ath P : he nuber of relayng-only neghbors of node on ath P () : otal real-te data rate on sensor node () Q : otal queung delay on a node for real-te traffc E end requred : End-to-end queung delay for a artcular ath P : End-to-end roagaton delay for a artcular ath P : otal end-to-end delay for a artcular ath P : End-to-end delay requreent for all aths : he nuber of nodes on ath P Nodes : he set of all the sensng only nodes usng ath P to send data to the gateway otal real-te data rate by nodes wll be and total real-te data rate by q nodes wll be added recursvely for each relayng only node (snce every relayng-only node roduces real-te data by the rate ).

5 hen total real-te data load on a sensor node s: () + q ( ) In [9], the average watng te ncludng the servce te n the queue s stated as: W µ Hence, total queung delay (ncludng the servce te), Q on a node s: () () Q r µ ( ) he end-to-end queung delay for a artcular ath s: () E Q Path Path Path r µ r µ ( ) q he end-to-end roagaton delay for the ath s: c, Path dst ( ) where c s a constant, whch s obtaned by dvdng a weghtng constant by the seed of wreless transsson. Hence, total end-to-end delay wll be: + end E end + c q Path ( ), Path r µ dst.4 Algorth Whle we generate a forula for calculatng the end-to-end delay for a artcular ath, fndng the otal r-values for each lnk as far as the queung delay s concerned, wll be very dffcult otzaton roble to solve. Moreover, the dstrbuton of these r-values to each node s not an easy task because the each value should be uncasted to the roer sensor node rather than broadcastng t to all the sensors whch ght brng a lot of overhead. herefore, we follow an aroach, whch wll elnate the overhead and colexty of the roble. Bascally, we defne each r- value to be sae on each lnk so that the otzaton roble wll be sle and ths unque r-value can be easly broadcasted to all the sensors by the gateway. If we let all r-values be sae for every lnk then the forula wll be stated as: end + c dst q Path ( ), Path rµ hen the roble s stated as an otzaton roble as follows: Max (( r) µ ) Path subect to; end requred and r < In order to fnd r fro the above nequalty of end, we dvde requred to equal te slots, where requred s the nuber of nodes on a artcular ath. Snce the last node wll be gettng the actual longest queung delay, we consder fndng an r-value whch wll satsfy the last node s delay. As a consequence, the other nodes before the last node wll already be satsfed wth that r-value. he calculaton of r s as follows: requred r µ Q requred rµ, Path ( + c dst k k Nodes + µ + ), ( + Path c dst ) k k Nodes By consderng the otzaton roble above, we roose the algorth as shown n Fgure 4 to fnd a leastcost ath, whch eets the constrants and axzes the throughut for non-real-te data. he algorth calculates the cost for each lnk n lne of Fgure 4, based on the cost functon defned n secton.3. hen, for each node the least cost ath to the gateway s found by runnng Dkstra s shortest ath algorth n lne. Between lnes 5-5, arorate r-values are calculated for aths fro agng sensors to the gateway. For each sensor node that has agng caablty, an r-value s calculated on the current ath (lne 5). If that value s not between and, extended Dsktra algorth for K-shortest ath s run n order to fnd alternatve aths wth bgger costs (lne 9). K dfferent leastcost aths are tred n order to fnd a roer r-value between and (lnes -3). If there s no such r-value, the connecton request of that node to the gateway s sly reected. he algorth ght generate dfferent r-values for dfferent aths. Snce, the r-values are stored n a lst; the axu of the s selected to be used for the whole

6 Calculate cos,, V t Fnd least cost ath for each node by usng Dkstra 3 for each agng sensor node do 4 begn 5 Coute r fro end ( ) requred (as above) 6 f (r s n range [,)) then 7 Add r to a lst corresondng to node 8 else K 9 Fnd K least cost aths ( P ) to the gateway for each k K do k Recoute r fro end ( ) requred f (r s n range [,)) then 3 break; 4 f no arorate r s found 5 Reect the connecton 6 end 7 Fnd ax r fro the lst Fgure 4. Pseudo code for the roosed algorth network (lne 7). hat r-value wll satsfy the end-to-end delay requreent for all the aths establshed fro agng sensors to the gateway. In order to fnd the K least cost aths (.e. K shortest aths), we odfed an extended verson of Dkstra s algorth gven n []. Snce, the algorth faces wth loos durng executon; we odfed the algorth n order to avod loos and ensure slcty and effcency. Each te a new ath s searched for a artcular node, only nodedsont aths are consdered durng the rocess. hs ght also hel fndng a roer r-value easly snce that nodedsont ath wll not nhert the congeston n the forer ath. Interested reader s referred to [] for further nforaton. 3. Exerental Results he effectveness of the energy-aware QoS routng aroach s valdated through sulaton. hs secton descrbes the erforance etrcs, sulaton envronent, and exerental results. 3. Perforance Metrcs We used the followng etrcs to cature the erforance of our QoS routng aroach: e to network artton: When the frst node runs out of energy, the network wthn the cluster s sad to be arttoned. he nae network arttonng reflects the fact that soe routes becoe nvald and cluster-wde reroutng ay be anent. Average lfete of a node: hs gves a good easure of the network lfete. A routng algorth, whch axzes the lfete of network, s desrable. hs etrc also shows how effcent s the algorth n energy consuton. Average delay er acket: Defned as the average te a acket takes fro a sensor node to the gateway. Most energy aware routng algorths try to nze the consued energy. However, the alcatons that deal wth real-te data s delay senstve, so ths etrc s ortant n our case. Network hroughut: Defned as the total nuber of data ackets receved at the gateway dvded by the sulaton te. he throughut for both real-te and non-real-te traffc wll be consdered ndeendently. 3. Envronent Setu In the exerents the cluster conssts of randoly laced nodes n a eter square area. he gateway oston s deterned randoly wthn the cluster boundares. A free sace roagaton channel odel s assued [] wth the caacty set to Mbs. Packet lengths are Kbt for data ackets and Kbt for routng and refresh ackets. Each node s assued to have an ntal energy of 5 oules. he buffers for real-re data and noral data have default sze of 5 ackets []. A node s consdered non-functonal f ts energy level reaches. For the ter CF n the cost functon, we used the lnear dscharge curve of the alkalne battery []. For a node n the sensng state, ackets are generated at a constant rate of acket/sec. hs value s consstent wth the secfcatons of the Acoustc Ballstc Module fro Senech Inc. [6]. he real-te acket generaton rate ( ) for the nodes, whch have agng/vdeo caablty s greater than the noral rate. he default value s 3 ackets/sec. A servce rate ( µ ) of 5 ackets/sec s assued. Each data acket s te -staed when t s generated to allow the calculaton of average delay er acket. In addton, each acket has an energy feld that s udated durng the acket transsson to calculate the average energy er acket. A acket dro robablty s taken to be.. hs s used to ake the sulator ore realstc and to sulate the devaton of the gateway energy odel fro the actual energy odel of nodes. We assue that the cluster s tasked wth a target-trackng sson n the exerent. he ntal set of sensng nodes s chosen to be the nodes on the convex hull of sensors n the cluster. he set of sensng nodes changes as the target oves. Snce targets are assued to coe fro outsde the cluster, the sensng crcutry of all boundary nodes s always turned on. he sensng crcutry of other nodes are usually turned off but can be turned on accordng to the target oveent. We also assue that each sensor node s caable of takng the age

7 of target to dentfy t clearly and can turn on ts agng caablty on deand. Durng sulaton, a sall subset of current actve nodes, whch are the closest nodes to the target, are selected to turn on ther agng caablty. herefore, the agng sensor set ay change wth the oveent of the target. he acket-sensng rate for agng sensors s bgger than the noral sensors; hence ore ackets are generated when agng sensors are eloyed. hese ackets are labeled as real-te ackets and treated dfferently n sensor nodes. he r-value s ntally assued to be but t s recalculated as agng sensors get actvated. he default end-to-end delay requreent for a QoS ath s assued to be seconds, whch s a reasonable aount of te to get age data erodcally n a real-te target trackng alcaton. argets are assued to start at a rando oston outsde the convex hull. argets are characterzed by havng a constant seed chosen unforly fro the range 4 eters/s to 6 eters/s and a constant drecton chosen unforly deendng on the ntal target oston n order for the target to cross the convex hull regon. It s assued that only one target s actve at a te. hs target reans actve untl t leaves the deloyent regon area. In ths case, a new target s generated. 3.3 Perforance Results In ths secton, we resent soe erforance results obtaned by the sulaton. Dfferent araeters are consdered for end-to-end delay, buffer sze, acket dro robablty and real-te data generaton cature the effects on the erforance etrcs defned earler n ths secton. In order to see how the algorth behaves under strngent condtons, we vared the end-to-end delay and ontored how ths change affects the network r-value. he results are dected n Fgure 5. Effect of end-to-end delay and real-te date generaton rate on network r-values he network r-value goes down whle the end-to-end delay requreent gets looser. Snce the delay s not too strct, ost of the nodes wll be able to fnd a QoS ath. On the other hand, whle we congest the network wth ore real-te data ackets by ncreasng the real-te data generaton rate, ore bandwdth wll be requred for realte ackets. hs wll cause the r-value to ncrease so that each node can serve ore real-te ackets (See Fgure 6). Effect of real-te data rate on erforance In order to see the erforance of the algorth for dfferent real-te data rates, we ran sulaton for dfferent values of real-te acket data rates. he results are dected n Fgure 7, 8 and 9. We looked at the real-te and non-real-te data throughut. Whle the nuber of real-te ackets ncrease, t gets ore dffcult to satsfy ncreasng nuber of QoS aths. Hence, ths can cause reecton of aths or acket dros for real-te data causng throughut for such data to decrease. However, the throughut for non-real-te data does not change uch snce there s already a constant dedcated bandwdth for such data, ensured by the r-value. We restrcted r-value to be strctly less than, causng the throughut for non-real-te data (( r ) µ ) always greater than. he algorth does not sacrfce the throughut for non-real-te data for the sake of real-te data. Fgure 8 shows the effect of real-te data rate on average delay er acket. he delay ncreases wth the rate snce ackets (esecally real-te ackets) ncur ore queung delay and share the sae aount of bandwdth. We also looked for the lfete of a node n order to see the effect of real-te data rate on energy etrc. Fgure 9 shows that the average lfete for a sensor node ncreases wth the real-te data rate. he reason for ths ncrease s that the throughut decreases, causng the nuber of ackets arrvng to the gateway to decrease. herefore, fewer ackets wll be relayed by the sensor nodes, whch wll save energy fro transsson and receton energy costs. he te for frst node to de wll also ncrease due to sae reason (Fg. ). Network r-value Network r-value End-o-End Delay(sec) Fgure 5. Network r-value wth dfferent end-toend delay values data Rate(acket/sec) Fgure 6. Network r-value wth dfferent realte data rates

8 e hroughut e e 95 9 Avg. hroughut Avg. N hroughut data rate(acket/sec) Fgure 7. Effect of rt-data rate on throughut data rate(acket/sec) Fgure 8. Effect of rt-data rate on average delay for a acket Fgure 9. Effect of rt-data rate on average lfete of a node data rate(acket/sec) Rt-data rate(acket/sec) Fgure. Effect of rt-data rate on te for frst node to de 4. Conclusons and Future Work In ths aer, we resented a new energy-aware QoS routng rotocol for sensor networks. he rotocol fnds QoS aths for real-te data wth certan end-to-end delay requreents. Moreover, the selected queung odel for the rotocol allows the throughut for noral data not to dnsh by eloyng a network wde r-value, whch guarantees certan servce rate for real-te and non-realte data on each lnk. he effectveness of the rotocol s valdated by sulaton. Sulaton results show that our rotocol consstently erfors well wth resect to QoS etrcs, e.g. throughut and average delay as well as energybased etrc such as average lfete of a node. he network r-value s adusted accordngly n the case of bg real-te data rate on the nodes or strngent end-to-end delay requreents. he results have also shown that real-te data rate, buffer sze, and acket dro robablty have sgnfcant effects on the erforance of the rotocol. We are currently extendng the odel to allow dfferent r-values can be assgned to sensor nodes and lan to coare the erforance of such extended odel wth the energy-aware QoS routng rotocol resented n ths aer. References [] C. Intanagonwwat, R. Govndan and D. Estrn, "Drected dffuson: A scalable and robust councaton aradg for sensor networks," n the Proceedngs of the 6 th ACM/IEEE Annual Internatonal Conference on Moble Coutng and Networkng (MobCOM '), Boston, Massachussetts, August. [] W. Henzelan, J. Kulk, and H. Balakrshnan, Adatve rotocols for nforaton dssenaton n wreless sensor networks, n the Proceedngs of 5 th Annual ACM/IEEE Internatonal Conference on Moble Coutng and Networkng (MobCo 99), Seattle, WA, August 999. [3] W. Henzelan, A. Chandrakasan, and H. Balakrshnan, "Energy -effcent councaton rotocol for wreless sensor networks," n the Proceedngs of Hawa Intl. Conf. Syste Scences, Hawa,. [4] R. Shah and J. Rabaey, "Energy Aware Routng for Low Energy Ad Hoc Sensor Networks", n the Proceedngs of the IEEE Wreless Councatons and Networkng Conference (WCNC ), Orlando, FL, March. [5] W. C. Lee, M. G. Hluchy and P. A. Hublet, "Routng Subect to Qualty of Servce Constrants Integrated Councaton Networks," IEEE Network, July/Aug [6] Z. Wang and J. Crowcraft, "QoS-based Routng for Suortng Resource Reservaton," IEEE Journal on Selected Area of Councatons, Set 996. [7] Q. Ma and P. Steenkste, "Qualty-of-Servce routng wth Perforance Guarantees," n the Proceedngs of the 4 th Internatonal IFIP Worksho on Qualty of Servce, May 997.

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