Prioritizing Information for Achieving QoS Control in WSN

Transcription

1 th IEEE Internatonal Conference on Advanced Informaton Networkng and Applcatons Prortzng Informaton for Achevng os Control n WSN 1 Atf Sharf, 2 Vdyasagar Potdar Dgtal Ecosystems and Busness Intellgence Insttute, Curtn Unversty of echnology Perth, WA, Australa 1 atf.sharf@postgrad.curtn.edu.au 2 v.potdar@curtn.edu.au Abstract Achevng os objectve n Wreless Sensor Network (WSN that deals wth multmeda nformaton s of paramount mportance n the WSN research communty. From the applcaton pont of vew, meetng applcaton specfc os constrants s equally mportant as desgnng energy effcent embedded crcutry for WSN nodes. Among varous WSN communcaton protocol stack, the transport layer functonalty has gan fundamental fame lately n addressng the applcaton specfc os objectves by supportng Source prortzaton besdes the relablty and congeston control aspects of the desgn that helps n ganng hgh throughput wth mnmum end-to-end packet latency. hs paper present the desgn of a new transport layer protocol that prortzes sensed nformaton based on ts nature whle smultaneously supportng the data relablty and congeston control features. he proposed transport protocol s tested n three possble scenaros.e. wth prorty, wthout and dstrbuted prorty features. Smulaton results reveal that by prortzng the Source nformaton and prortzed ntermedate storage and forwardng reduces the End-to-End (E-2-E latency of Source packets havng <100 msec except for Source A where t s slghtly hgher than 400msec compared to non prortzed case where the E-2-E Source packet latency accounts to >400msec whch s qute sgnfcant. Smulaton test has been performed for dstrbuted prortzed ntermedate storage and forwardng among whch the network dstrbuton wth node K as prortzed ntermedate storage node (DIS-K outperformed all of the mentoned cases by havng 100% acheved Source prorty,0% packet drop rate and 0.28Mbps acheved bt rate. Keywords- WSN, prorty, os, transport protocol, congeston control, relablty. I. INRODUCION Wreless Sensor Network (WSN gathers the ntenton of the research communty from past few years n a varety of applcatons rangng from envronmental montorng to mltary by nvolvng multple dscplnes of control, sgnal processng and embedded computng [1-3, 9]. WSN comprsed of tny peces of hardware called mote, havng nbult features of sensng, processng and communcaton over wreless channel, dstrbuted randomly n space to form an ad-hoc network for communcatng the sensed nformaton from the regon of nterest to central control staton also called snk. Energy s a prmary concern whle desgnng the WSN and achevng the objectve of energy effcency researchers are consstently engaged n desgnng the power effcent hardware and communcaton protocol stack for WSN. Beng a network of A.J.D.Rathnayaka Department of Electronc and elecommuncaton Engneerng, Unversty of Moratuwa Sr Lanka ajdr03@ent.mrt.ac.lk energy hungry devces, energy effcent hardware and communcaton protocol stack desgn whle smultaneously enablng the feature of energy scavengng s of paramount mportance for longevty of the WSN. In WSN, among varous other layers of the communcaton protocol stack, transport layer s of fundamental mportance for ensurng the E-2-E relablty of the sensed nformaton as sgnfcant proporton of the overall mote s energy budget s spent for ths type of communcaton besdes mote s locally [1-3] sensng and processng the nformaton of nterest. he man causes of packet drop nclude: Congeston, Collsons due to hdden motes, Poor SNR due to bad channel qualty, Lnk breakage due to mote falure. Packet retransmsson caused by packet drop due to poor channel condtons or network congeston consderably consumes mote s power and therefore reduces the lfe of the WSN. Recently research communty s tryng to modfy the exstng WSN desgn (for fxed applcaton to target heterogeneous applcatons where the data s ether scalar or multmeda by nature. For such applcatons data prortzaton s also of sgnfcant mportance for achevng the longevty of the WSN as the multmeda packet drop retransmssons occurs at consderable dspense of the mote s power budget. ransport layer of the WSN s responsble for communcatng the sensed pece of nformaton from the Source mote to snk [3]. Data nformaton relablty ether Hop-by-Hop (H-b-H or E-2-E s of key mportance from the applcaton ualty of Servce (os pont of vew and transport layer s responsble for mantanng the applcaton specfc os [1]. he data packets fal to reach the snk can be retreved by snk whch sends the Negatve Acknowledgement (NACK to Source or some ntermedate node (desgnated for temporary storage. he number and the arrangement of these storage nodes are hghly depends upon the followng: Requred level of applcaton specfc os to be acheved, Network topology, X/10 $ IEEE DOI /AINA

2 Level of congeston n the dfferent parts of the network, Severty of nterference that causes massve data packet loss. We nvestgated the dependence of the WSN transport layer protocol on underlyng MAC/Wreless-Phy layer where we concluded that for the longevty of the WSN the transport layer has a drect relatonshp wth the underlyng MAC/Wreless- Phy layer [11]. Based on the observatons we had envsaged a transport protocol desgn based on stochastc control framework that manages congeston and E-2-E data relablty features of the WSN transport layer protocol [12]. In the followng paper we are ncorporatng the prorty feature n the exstng stochastc control frame work based transport layer protocol desgn that enables prortzaton of the Source nformaton and prortzed ntermedate storng and forwardng of the Source nformaton towards snk n-order to ensure the applcaton specfc os. he rest of the paper s organzed as followng. After ntroducng the related work s covered n Secton II followed by the problem defnton, system requrements and desgn consderatons n secton III. Secton IV descrbes the proposed transport layer protocol. Secton V descrbes the algorthm of the proposed transport layer protocol followed by secton VI where we have descrbe the smulaton setup used for observng ts behavor and the smulaton results we have taken. he dscusson followed by the conclusons wll be presented n the secton VII. II. RELAED WORK In ths secton we focus on the exstng transport protocols used for WSN. We begn the dscusson wth CP [13], UDP [14] and then extend t to varous other WSN transport protocols lke CODA [15], ESR [16], RMS [17], PSF [18], RBC [19], GARUDA [20], DC [21], SCP [22] and CPWW [23]. able 1 compares varous WSN transport protocols lke CODA, ESR, RMS, PSF, RBC, GARUDA, DC, SCP and CPWW. CP [13] (connecton orented by nature assumes congeston as the man cause of packet drop. It assures strct E-2-E relablty at very hgh energy cost, whch s not acceptable n WSN because of ts strct energy constrants. UDP [14] on the other hand, beng connectonless by nature, offers sgnfcant throughput n comparson to CP, but the packet drop rate s sgnfcantly hgher durng congeston [11]. herefore the basc nference s that UDP offers extremely hgh throughput but mnmum relablty, whereas CP offers extremely hgh relablty but low throughput. Our lterature study concludes that the exstng research n the feld of WSN transport protocol development exsts n between these two extremes, whch we now dscuss n detal. As show n able 1, CODA (.e. Congeston Detecton and Avodance protocol [15] lacks relablty but provdes excellent congeston control n the forward drecton. hs control s acheved by explct notfcaton of the congested scenaro to the chld motes. It utlzes wreless channel load and motes buffer occupancy for congeston detecton and uses open-loop H-b-H back pressure and closed loop E-2-E mult- Source regulaton for rate adjustment. Features Protocol CODA ESR ABLE I. Drecton Upstream Upstream RMS Upstream No PSF Downstream No GARUD A SCP Downstream Upstream WSN RANSPOR PROOCOLS Congeston Control Support Yes, Actve control, Explct Nototfcaton Passve Control, Implct Notfcaton No Passve Control, Implct Notfcaton Relablty Management Support CPWW [23] (CP Westwood s a sender based extenson of the exstng CP protocol. It refnes the wndow control and back-off process of the exstng CP desgn thereby achevng greater desgn effcency under sporadc or random data losses. Under congested network condtons CPWW uses the estmated value of the avalable channel bandwdth for properly settng the congeston wndow and slow start threshold lmts. It also ensures rapd data retreval, by avodng excessvely conservatve reductons of congeston wndow and the slow start threshold lmts. Other than CODA and CPWW, there are a number of other WSN transport protocols publshed n the lterature lke ESR, RMS, PSF, RBC, GARUDA and DC. hese protocols only am to provde relablty but completely lack congeston control feature. We now brefly explan ths set of protocols. Event-to-Snk Relable ransport (ESR [16] ams to provde Event Based (EB relablty support by employng mplct (Imp loss detecton and notfcaton and E-2-E loss recovery mechansm. It also provdes passve congeston control n the Forward (Fwd drecton by ncorporatng Imp congeston notfcaton feature. Relable Mult-Segment ransport protocol (RMS [17] offers Packet Based (PB relablty support, H-b-H Loss No CPWW Upstream Yes No Yes, Event Based, Implct loss detecton and notfcaton wt h E- 2-E recovery Yes, Packet Based, NACK based loss detecton and H-b-H recovery Yes, Packet Based, NACK based loss detecton and H-b-H recovery Yes, Packet Based, NACK based loss detecton and H-b-H recovery, wo-ter wo stage Yes, Packet Based and Event Based, NACK/ACK based loss detecton and E-2-E recovery 836

3 Recovery (LR n the forward drecton by ncorporatng Not Acknowledge (NACK based loss detecton and notfcaton control. It uses tmng nformaton for data loss detecton and once data loss s detected t sends a NACK to the Source mote or storage mote, whch then retransmts the correspondng data packet upon recevng the NACK. Pump Slowly Fetch uckly (PSF [18] ams to address the relablty support only n the reverse (Rev drecton from the snk motes to the Source motes. It uses NACK for data loss detecton and s facltated wth rapd H-b-H loss recovery mechansm. However t s unable to detect the loss of a sngle packet when packets are transmtted n bulk. It also requres more buffer storage (beng H-b-H nature at the ntermedate motes for data recovery. Relable Bursty Convergecast protocol (RBC [19] offers E-2-E packet based relablty support n the Fwd drecton. he level of relablty provded by RBC s comparatvely hgher than RMS and PSF because t ncorporates Imp H-b-H loss detecton, loss notfcaton and loss recovery mechansm at MAC level. It uses NACK/ACK (Acknowledge as a means for data loss notfcaton and Implct Acknowledgement (IACK for loss notfcaton at MAC level only. GARUDA [20] provdes relablty n the Rev drecton,.e., from the snk mote to the sensor motes. It uses core motes located at 3-hop dstance apart for temporary sensed data storage, whch could be retreved n the event of loss. It uses NACK for data loss detecton and two-ter two-stage loss recovery mechansm. Dstrbuted CP cashng protocol (DC [21] ams to provde total packet drven relablty n both drectons. It uses ACK and Selectve ACK (SACK for data loss detecton. In DC snk mote has the loss recovery control and uses H-b-H mechansm for possble loss recovery. Sensor CP (SCP [22] s the only protocol so far that offers both congeston control and data relablty. It uses open-loop H-b-H rate control mechansm wth Imp congeston notfcaton. It uses packet processng and nter-arrval tme for congeston detecton. It offers both packet and event drven relablty and uses ACK and NACK to facltate E-2-E relablty objectve. In ths secton we revewed the exstng transport protocol schemes for WSN. SCP s the closest work to what we are proposng, snce t addresses congeston control as well as relablty. In the next secton we gve an overvew of our proposed protocol. III. PROBLEM DEFINIION In WSN the factors lke packet collsons at the recevng node due to transmssons from other nodes havng the common destnaton (hdden node problem, congeston, route falure, crosstalk: resultng n hgh bt error rate (BER etc contrbutes towards hgh power cost for per data packet communcaton, lower system throughput and ncreased E-2-E data packet latency. So for enhancng the WSN energy effcency transport layer protocol plays a vtal role n ncreasng the network throughput and mnmal E-2-E packet latency whle mantanng the applcaton specfc os [11]. Also data nformaton routng based on the nature of the packet nformaton further elevates the energy effcency of WSN. In ths paper we present a lght weght transport protocol that takes E-2-E packet nformaton, ntermedate node storage memory occupancy for evaluatng the congeston ndex and packet nformaton type for packet prortzaton. he smulaton of the envsaged transport layer protocol enable us n better understandng of the above mentoned performance lmtng features and would open new dmensons n transport protocol desgnng for WSN. A. Requrements and Desgn Consderatons he key requrement of the proposed transport protocol s as follows: 1. Congeston Control 2. Data Relablty 3. Heterogeneous Applcaton Support 4. Snk Enabled Control he frst requrement for our proposed protocol s Congeston Control. o adhere to ths requrement the protocol should be able to detect, notfy and mtgate congeston n the network or at local hot-spots effectvely. hs s one of the man requrements because by adherng to ths requrement packet drops can be reduced and hence the energy assocated wth packet retransmssons can be saved. o address ths requrement the proposed protocol ncorporates the followng desgn consderaton. he congeston control functonalty n the proposed protocol employs end-to-end nformaton of each packet at the snk mote for measurng the congeston state of the network (or lnk. he new rate value for future data packet s then estmated based on ths end-to-end nformaton or congeston state of the network. he Second requrement for our proposed protocol s Data Relablty and can be met by the ntroducton of the temporary dscrete data storage for possble data retreval n event of packet drop ether due to congeston or poor channel condtons. Any ntermedate mote, located at bottleneck locatons of the WSN (near snk or mote havng large number of chld motes, can serve the purpose of storage mote. In the proposed scheme the mmedate chld mote to snk and motes at locatons that relays large amount of data (ts own sensed data plus the data from large number of chld motes can serve the purpose of ntermedate storage. In the proposed scheme the ntermedate storage motes store data for predefned nterval of tme based on the apror estmated value of total probablty of data packet drop (P f. However n order to conserve the energy spectrum of the WSN network we possbly n future ncorporatng the dea of varable relablty that ensures the retreval of only hgh prorty data packet (e.g. event based nformaton f lost wll be retreved n comparson to less pror scalar nformaton. he data flow n the wreless network may be event drven, perodc or contnuous of ether multmeda or scalar by nature, so the proposed transport protocol should have the feature of Heterogeneous Applcaton Support and s not lmted to 837

4 certan applcaton scenaros. Such type of problem can be addressed by prortzng the data based on ts type. So the ntermedate motes processes the ncomng packets based on ts prorty/nature of data. Presently the proposed transport protocol scheme works based on Snk Enabled Control [12], as snk has hgh computatonal power n comparson to Source and ntermedate sensor motes. So majorty of the computatonally ntensve tasks related to congeston control and relablty are beng performed by the snk mote. In our case we have mplemented a state machne, as descrbed n the Secton V, whch predcts the congeston state of the network based on the (.e. packet E-2-E and usng ths ndex to defne a new Source rate plan. IV. PROPOSED PRIORIY BASEDRANSPOR PROOCOL SCHEME A. Proposed WSN ransport Protocol Scheme he block dagram of the proposed scheme s shown n Fgure 2. he proposed scheme comprsed of followng functonal modules Congeston Control Module Prortzaton and Relablty Module Congeston Detecton Fgure 1. he Proposed ransport Layer Protocol 1 Congeston Control Module Congeston control module [8] s used to detect, nform and mtgate the congeston n the network. Congeston n the network occurs when the data sendng rate from multple Sources exceeds the avalable channel bandwdth. Falure to prevent congeston n the network results n 1. Data packet drop and wll consderably deplete network energy budget. 2. Increased E-2-E data packet latency. Here the packet for sngle hop (1-hop propagaton s gven by (1 pr Prortzaton Rate Readjustment Congeston Control Module pp Data Retreval Prortzaton and Relablty Module Congeston Notfcaton For detaled mathematcal understandng please refer to [12]. We ncorporated Prortzed Source nformaton forwardng ncludng ntermedate storage feature n the exstng transport layer protocol [12] based on stochastc control framework. = average E-2-E packet n seconds, pr pp = average packet processng tme at node n seconds, = average node queue n seconds, = average 1-hop propagaton tme n seconds. o effectvely prevent congeston n the WSN we envsaged a prortzed transport layer protocol for WSN. he congeston ndex helps n dentfyng the level of congeston n the network and s gven by the followng equaton: C n * m ( E 2 E (2 m = congeston level whch s realzed by the ntermedate mote memory storage, n= number of ntermedate storage nodes, (E-2-E= E-2-E packet n seconds. locaton/word then m s gven by: otal free spaces n the storage m otal Memory space for storage * (3 m = * (4 Also for N number of hops between Source and snk wth per mote and per lnk propagaton of pr then ( E2E s gven by: ( E 2 E N * pr (5. (6 pr MAC = ueue at any ntermedate mote and s gven by = * (7 1 p = Current ueue ndex, 1-p = me to execute one packet. and MAC s gven by: MAC / (8 RS CS MAC = MAC access, RS/CS = Delay due to ongong transmsson as ndcated by RS/CS, ch = Channel access. So Eq.(2.e. congeston ndex, can now be gven as: C n * * N * ( * pp RS / CS ch (9 ch 838

5 Eq. (9 represents the congeston ndex or the congeston state of the network and s helpful n decdng the future rate plans for the Source motes. Based on ths C the envsaged ransport Layer Protocol wll then measure or estmate the new rate plan (based on the E-2-E data packet nformaton (E-2-E for the Sources and notfy them n order to mtgate congeston. he newly estmated (E-2-E nvolvng C s gven by [6] c C ˆ / (10 Hence the new estmated rate value Rˆ c comes to be: ˆ ( c Rˆ c (11 N N = total number of hops between Source and snk. 2 Prortzaton and Relablty Module he purpose of the Prortzaton and Relablty module of the envsaged WSN transport layer protocol s to Retan the sensed nformaton at selected ntermedate motes [10] for some defned tme nterval. Resend the sensed nformaton upon recevng the Negatve Acknowledgement (NACK from the snk. Receve the ncomng packets from all possble Sources (Scalar and Multmeda sensor equpped and rearrange the packets based on ther nformaton content prorty. If the ntermedate node receves data packets from multple Sources havng smlar nformaton prorty then the packet wth mnmum E-2-E tme to lve value (L wll be served frst. V. PROPOSED PROOCOL -ALGORIHM In the prevous secton we dscussed the man modules of our proposed transport protocol and also outlned how we calculate the key parameters used for congeston control and relablty. In ths secton we outlne each step nvolved n computng the new rate nformaton and the network congeston level as beng proposed by our lght weght transport protocol scheme meant for congeston detecton and relablty assurance. he key steps are as follows: Step1: Generaton and transmsson of the new packets at Source node hs s the frst step n whch the Source node sense the envronment and start generatng the data packets of sze 1 KB and start sendng ths nformaton at a rate R c 0 specfed by the snk control. Step2: Storage of the packets at the ntermedate buffer node also beng used for routng too When the Source starts sendng the data packets at some defned rate they are then stored at the ntermedate storage node s buffer. At any partcular storage node the packet s storage tme s beng dctated by the packet s probablty of success.e. P success. Step3: Data packets beng receved by the Snk node he ntermedate storage nodes pror for beng used for storage can also be used for routng purposes, the routed Source nformaton reaches the snk for post processng of the packet.e. ˆ ( (E-2-E. c Step4: Congeston Detecton After started recevng the data packets the snk controller starts computng the new rate value based on the exstng congeston state of the network by lookng at the E-2-E of each packet. Followng steps are nvolved for the computaton of the new estmated rate value 1. f t c Jont densty functon that relates ( C, the E-2-E packet and congeston ndex C. 2. Posteror estmate for receved packets ˆ ( c 3. Compare ths posteror estmate of ˆ ( c wth threshold hres, f exceeds then congeston has been detected else no congeston. Step5: Estmated error J computaton In ths step the snk controller compares the estmated ˆ ( c of the receved packet wth the actual ( c and based on ths the snk controller computes the estmaton error J. Step6: Condtonal mean-square error computaton Condtonal mean-square error fndng usng helps n fndng the means-square estmate of the new [6, 12] Step7: Computaton of new estmated rate value ˆ ( c Usng equaton Rˆ c, the snk controller N starts computng the new rate value computed based on the estmated ˆ (. c Step8: New rate notfcaton to Source nodes Fnally the new estmated rate value s beng communcated to the Source nodes by the snk ncludng the level of congestonc. VI. SIMULAION SEUP AND RESULS hs secton descrbes the smulaton setup used for an extensve testng of the proposed transport layer protocol. he smulaton setup s shown n the Fgure 2 where Sources A, B and J are vdeo sensor motes whle Source C and H are generc scalar sensor motes. he prorty of the vdeo data packet s hgher than the scalar data packet and follows the followng prorty rule: Pr(A=Pr(B=Pr(J>Pr(C>Pr(H (12 For detaled understandng of the proposed ransport Layer Algorthm refer [12] 839

6 Pr(A = Prorty of data packet from Source A, Pr(B = Prorty of data packet from Source B, Pr(C = Prorty of data packet from Source C, Pr(H = Prorty of data packet from Source H, Pr(J = Prorty of data packet from Source J. Fgure 2. he Network opology Used For Evaluaton In ths smulaton we have used Network Smulator NS-2 [16] and we consder that the entre mult-hop network s comprsed of 10 nodes as an ad-hoc network for the case of IEEE [4]. For ths wreless setup we performed the extensve analyss of E-2-E throughput, E-2-E packet latency and the average percentage prorty acheved. he network parameters are lsted n able II. In order to ensure the relablty n the results the smulatons have been performed fve tmes for the three possble cases of the proposed transport layer protocol and are: Proposed protocol wthout prortzed Source nformaton storage and forwardng, Proposed protocol wth complete prortzed Source nformaton storage and forwardng, Proposed protocol wth dstrbuted prortzed Source nformaton storage and forwardng. A. Performance metrcs he extensve performance of the envsaged transport layer protocol s evaluated aganst the followng performance metrcs 1. Average E-2-E Packet Latency: It s defned as the total tme a packet would take ncludng all the s resultng from queung, retransmssons at the MAC layer, propagaton s and transfer tme from the Source to snk (E-2-E. 2. Average E-2-E hroughput: It s defned as the number of data packets send by all the potental Sources to the data receved by the snk correspondng to each Source. 3. Percentage Average Data Loss: It s defned as the percentage rato of the data loss, dfference of sent and receved data, to the send data. he man contrbutors of data loss are collsons at the recevng end n the presence of blnd nodes, congeston and lnk falure due to node energy depleton. 4. Average Percentage Prorty Acheved: It s defned as the average number of specfc Source data packets receved at the snk to the number of data packets send by the same Source. ABLE II. Parameter NEWORK PARAMEERS Values Frequency 2.472e+9 ransport Protocols 1. Proposed protocol wthout prortzed Source nformaton storage and forwardng 2. Proposed protocol wth complete prortzed Source nformaton storage and forwardng 3. Proposed protocol wth dstrbuted prortzed Source nformaton storage and forwardng MAC IEEE [4] RX and CS e-10W hreshold e-10 W Routng agent Ad hoc On-Demand Dstance Vector (AODV [7] Ifqlen (ueue 200 packets length at MAC level Energy Model Yes: NS-2 based Energy computaton [5] CP hreshold 10 Mote Intal power Mote Idle power Mote Rx power 100 W 712e-6 W 35.28e-3 W Mote x power 31.32e-3W Mote Sleep power 0.001W B. Smulaton Results In the followng secton we wll dscuss the smulaton results obtaned. he smulaton has been performed 5 tmes and the results mentoned here show the average values taken to ensure the relablty n the results. 1 Average E-2-E packet comparson of the proposed prorty based transport protocol Fgure 3 shows the average E-2-E packet comparson of the proposed transport layer protocol for three possble cases. he results shown here represent the average E-2-E that a data packet suffers orgnated from varous Sources. It would be obvous that for the frst case where there has been no ntermedate data packet storage and prortzed delvery of Source packets the average E-2-E latency of the Source data packet s qute sgnfcant and s above than 400 msec on average. Also except for the Source J whose prorty s hghest (same as Source A and B as compared to Source C and H has suffered comparably less average E-2-E (beng close to snk whch s approxmately 368 msec. However, an mproved response (less than 60 msec average E-2-E Source packet latency for Sources C, H and J except for the Source A and B whose average E-2-E packet latency accounts to 431 and 116 msec has been observed n second case where the strct relablty and prorty has been lad down n WSN. Lastly for thrd (dstrbuted prortzed ntermedate storage and forwardng case we observed least E-2-E Source data packet for the followng dstrbuted network topology: DIS-K havng average E-2-E Source packet latency s <40 msec, where the mote K s used for storage and prortzed data forwardng, 840

7 DIS-I havng average E-2-E Source packet latency s <52 msec, where the mote I s used for storage and prortzed data forwardng, DIS-F-K havng average E-2-E Source packet latency s <40 msec, where the motes F and K s used for storage and prortzed data forwardng. he worst performance s observed n case of network topology where the motes G and F are used for storage and prortzed data forwardng. For DIS G case the average E-2- E latency for Source A packets s around 1.22 sec, 0.97 sec for Source B and C packets whle 131 and 390 msec for Source H and J packets. For DIS-F case the average E-2-E latency for Source A, B, C, H and J packets s around sec, 1.97 sec, 2.42 sec, sec and sec respectvely. However, an acceptable result s observed (below 120 msec n case of network topology where the motes combnaton F-I and F-G-I are used for storage and prorty. G, F and Source J so lkely prevents the chances of packet drop to best possble. Fgure 4. Average throughput comparson 3 Average Packet Drop comparson of the proposed prorty based transport protocol he average Source data packet drop comparson for varous network confguratons s shown n the Fgure 5. Fgure 3. Average E-2-E packet Delay comparson 2 Average hroughput comparson of the proposed prorty based transport protocol he average throughput comparson of the proposed transport protocol for varous possble network confguratons s shown n Fgure 4. From the result the confguraton DIS- F-G-I has the hghest possble throughput havng a peak value of Mbps and s because of havng three stage dstrbuted prortzed storage and forwardng (so chances of packet drop reduces. Where as DIS-F shows the poorest response among all havng average throughput of 0.15 Mbps ths degradaton s because of congeston and ncreased packet queue latency. Although F s recevng all the nformaton packets from ts chld Sources A, B and C but stll counters must be made to prevent congeston related packet drop due to nformaton packets from Source H, J and possble relay nformaton of G, I and K that wll ncrease the queung and thus results n poor E-2-E packet latency. Also the confguratons lke DIS- K and DIS-I acheve a far average throughput level of 0.28 and 0.3 Mbps and the reason for ths farness s that these nodes are close to snk so they gather maxmum packet nformaton form the chld Source and relay nodes and then based on prortzed storage and forwardng rule pass the nformaton to snk. After DIS-F-G-I, DIS-F-I (whch has an acceptable Source data packet E-2-E latency shows better average throughput response of 0.34Mbps (here n addton to node F whch gathers packet nformaton from ts chld Source nodes A, B and C the node I also gathers the relay nformaton from Fgure 5. Average Percentage Packet Drop From the results t would be obvous that hghest possble data loss has been observed for the wthout case (percentage data loss for Source B s 4%, percentage data loss for Source A s 7%, percentage data loss for Source C s 9% whle for Source J and H s 0% and s obvous because of havng no prortzed ntermedate storage and forwardng of the Source nformaton whch s qute vtal for strct os orented applcatons lke Wreless Multmeda Sensor Networks (WMSNs. Sgnfcantly hgh loss has also been observed n case of DIS-F network confguraton and the reason for ths hgh data loss s that the node F s gatherng nformaton from Sources A, B and C at hgh rate but relayng the entre nformaton on ts output lnk whch s shared by node G (that relay nformaton of Source H s qute dffcult and also snce ths dstrbuted storage node (node F s at dstant from the snk so the lkely probablty of packet drop due to large queung at node F and at ntermedate nodes and congeston at the later end (node K whch s close to snk s hgh. Among others he DIS-F-K (nodes F and K are storage nodes and DIS-K (mmedate to snk shows better result where n DIS-K the percentage average data loss s 0% for all possble Sources whle for DIS-F-K the percentage average data loss for all Sources s 0% whle 1.5% for Source A. 841

8 4 Average Percentage prorty acheved comparson of the proposed prorty based transport protocol Fgure 6 shows the average percentage Source prorty acheved for varous possble network confguratons the major reasonng nvolved for varous cases under ths secton s already covered n the Average Packet Drop comparson secton above (Secton VI subsecton B-3. Agan for ths case only DIS-K and DIS-F-K acheves the 100% Source prortes. Also for the wthout prorty network confguraton case only the Sources H and J acheve the level of 100% whle for Sources A, B and C the acheved prorty level s 93.02%, 97.5% and 90.9% respectvely. However for wth complete prorty network confguraton case only Sources B, H and J acheves the 100% level whle for Source A and C the acheved prorty level s 96.5% and 94.24%. Smlarly for the dstrbuted prortzed storage and forwardng network confguratons lke DIS-F-G, DIS-F-G-I and DIS-I, where the Sources whch faled to acheve 100% level are Source C and A (for DIS-F-G-I, DIS-F-G and DIS-I respectvely. he acheved prorty level for Source A and C are 95.45% and 94.2% for DIS-F-G-I, 94.12% and 98.25% for DIS-F-G and 98.98% and 94.12% for DIS-I. Agan the DIS-G network confguraton whch performed poorly for the cases of Average E-2-E data packet latency, Average data packet drop and throughput shows degraded results for Acheved average Source prorty (acheved Source prorty level of 89.19%, 92.16%, 91.18%, 100% &100% for Sources A, B, C, H and J. Fgure 6. Average Percentage prorty acheved VII. DISCUSSIONS AND CONCLUSIONS In the followng paper we have presented a scheme for WSN transport layer whch guarantees congeston control, relablty and Source prorty. he congeston control has been acheved by takng nto account the E-2-E of Source data packet at the snk. 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