COVERAGE BASED DENSITY ESTIMATION STRATEGY FOR VANET

Transcription

1 Intenatonal Jounal of Advanced Compute Technology (IJACT) ISSN: COVERAGE BASED DENSITY ESTIMATION STRATEGY FOR VANET Chun-Chh Lo, Depatment of Compute Scence and Infomaton Engneeng, Natonal Cheng Kung Unvesty, Tanan, Tawan; Yau-Hwang Kuo, Depatment of Compute Scence and Infomaton Engneeng, Natonal Cheng Kung Unvesty, Tanan, Tawan Abstact Vehcle densty s an mpotant metc n montong taffc condtons to mpove the safety and effcency of oads. Howeve, obtanng elable taffc densty esults that fathfully eflect actual oad condtons can be challengng. Ths pape pesents a fully-dstbuted appoach to obtanng estmatons of taffc densty n eal-tme wth a hgh degee of accuacy and mnmal eos. Ths s acheved by usng the coveage aea povded by each vehcle to detemne whch vehcle should be selected fo the collecton of taffc nfomaton capable of povdng accuate estmatons fo the taffc densty along the oad segment between two unctons. The poposed scheme does not eque any netwok nfastuctue, and t s well-suted to uban envonments. Smulaton esults demonstate that the poposed densty estmaton stategy s moe accuate and eques less tansmsson ovehead than estng methods. Intoducton Vehcula communcaton s an mpotant aea of eseach n the feld of ntellgent tanspotaton systems. Vehcles wth weless communcaton capablty ae able to echange taffc elated nfomaton and establsh mutual awaeness among one anothe to mpove oad safety and effcency. The coopeatve echange of nfomaton, such as taffc densty, can ncease the stuatonal awaeness of dves and the ablty to detect poblematc oad taffc condtons. It also mpoves the effcency of data delvey by avodng the congested netwoks. Howeve, the dynamc natue of vehcles n ths envonment makes the undelyng netwok ology changes fequently, whch can cause apd changes n the densty of taffc. Thus, the effcent collecton and povson of appopate oad taffc data s vtal to the estmaton of oad condtons wth the am of enhancng oad safety n the vehcula envonment. Taffc densty s among the most common metcs used to monto oad taffc condtons. A numbe of taffc nfomaton systems [1]-[3] have been desgned fo the collecton and dstbuton of oad taffc nfomaton n a centalzed manne. Howeve, most of these systems tend to leave out a mao facton of the oad by coveng only the specfc locatons n whch sensos ae deployed. Ths s due to the hgh cost of deployng and mantanng sensos acoss COVERAGE BASED DENSITY ESTIMATION STRATEGY FOR VANET an ente oad netwok. A numbe of studes have suggested one altenatve decentalzed appoach [4]-[7] n whch oad taffc nfomaton s obtaned wthout the need fo telecommuncaton nfastuctues. Vehcles n ths scheme act as moble sensos coopeatvely shang obsevatons concenng oad taffc condtons n ts vcnty, whch ae then made avalable to all patcpatng vehcles n the envonment. Ths povdes a moe detaled vew of oad condtons, such as taffc densty, whch s qualtatvely supeo to systems usng only statc taffc sensos. Ths pape poposes a dstbuted densty estmaton scheme efeed to as Coveage Based Densty Estmaton stategy fo VANET. The man obectve s to povde accuate estmatons elated to taffc densty wthn an uban oad envonment. Ths s acheved by employng the aea coveed by each vehcula node n the estmaton of taffc densty fo a patcula segment of the oad between two unctons. Based on the tansmsson ange of the node, t s possble to detemne the aea coveed by each node fo use n the selecton of the node that s the fathest fom the souce and povdes the most compehensve coveage aea n that neghbohood to act as the pont fom whch taffc nfomaton should be collected. By applyng ths technque thoughout the oad segments that ae beng tacked, ndependent estmatons of the taffc densty n that segment of the oad can be obtaned ndependently by each selected node, based on the mutual awaeness establshed among one anothe. Smulaton esults demonstate the effectveness of the poposed stategy as well as hgh accuacy n the estmaton of taffc densty wth fa less tansmsson ovehead than that equed by estng methods. The emande of ths pape s oganzed as follows: Secton II outlnes pevous elated wok. The poblem statement s fomulated n Secton III. A detaled descpton of the poposed densty estmaton stategy s pesented n Secton IV. Secton V pesents smulaton esults and an evaluaton of pefomance. Fnally, conclusons ae dawn n Secton VI. Related Wok The vaous taffc densty estmaton schemes that have been poposed can be classfed as centalzed and decentalzed. 73

2 Intenatonal Jounal of Advanced Compute Technology (IJACT) The centalzed appoach eles on fed nfastuctue, such as nductve loop detectos, oadsde RADAR, nfaed sensos, and suvellance cameas to be nstalled fo the collecton of taffc nfomaton [8]-[11]. Ths eques the deployment of a lage numbe of sensos fo montong taffc condtons. Taffc densty can be estmated by compang camea mages o collectng nfomaton such as the numbe of vehcles passng a senso. Howeve, these appoaches tend not to be vey elable and povde lmted coveage despte hgh deployment and mantenance costs [15]. Thus, taffc nfomaton can only be obtaned fom steets on whch sensos ae mplemented. A numbe of decentalzed appoaches [], [16], [0] have also been poposed, wheen the vehcles utlzng the netwok coopeate wth each othe n gatheng taffc nfomaton and estmatng taffc densty on the uban oads. These appoaches have been wdely used wth outng potocols that eque nfomaton petanng to oad taffc densty [1]-[15]. In [], a decentalzed scheme was poposed wheen a table s compled usng data elated to the cuent poston and aveage velocty of vehcles. The table s peodcally updated and echanged wth neghbo vehcles. Consequently, evey vehcle becomes famla wth the poston and aveage velocty of neghbong vehcles. Howeve, ths method s ntended only fo hghway scenaos and depends on the decton of taffc fo the echange of tables among vehcles. In [16], data aggegaton was used to gathe and dssemnate taffc nfomaton n eal-tme; howeve, t peodcally dssemnates the poston and velocty of ndvdual vehcles nstead of aveage veloctes n a gven segment. Ths helps dves to fnd sutable outes and mpotant nfomaton concenng oad condtons; howeve, t s sutable only fo hghway scenaos and does not consde the decton of vehcles n the echange of taffc nfomaton among vehcles. ISSN: dvdng the oad nto cell poses vaous poblems elated to elablty. The followng secton dscusses these poblems n depth. Poblem Statement and Fomulaton Numeous eseaches [1]-[15] have used the dea of dvdng the oad segment nto multple fed sze cells and then sendng pobe packets fom a souce uncton to ts neghbong unctons fo the collecton of nfomaton. Howeve, the fact that the locaton of nodes on the oad s abtay and node densty vaes means that a node located close to the cental pont of each cell used to obtan netwok nfomaton does not necessaly est. In ths stuaton, the node selected n each cell may devate consdeably fom the cental pont of that patcula cell, such that t does not cove all the aea wthn that cell. Thus, nodes located n the uncoveed aea ae not ncluded n the nfomaton collecton pocess. Moe specfcally, a poton of the oad segment s not coveed by the selected node, such that only a poton of the taffc obsevatons ae used n the estmaton of taffc densty. Thus, nfomaton collected along that oad segment would not eflect the actual stuaton along that patcula oad, theeby compomsng the accuacy of densty estmaton. Ths phenomenon can be fomulated as follows: If P () epesents the cente pont of the cell, then we assume the pont n () O 0,0 of P s the ogn pont the Catesan coodnate system as llustated n Fgue 1. The wdth and the heght of the cell s W and H, the cone ponts of cell fom a set S. W H W H W H W H. S,,,,,,, Othe methods [19], [0] ae based on countng the numbe of vehcles n a patcula geogaphcal locaton va clusteng o goupng mechansms. The decentalzed taffc densty estmaton scheme n [19] dvdes each oad nto a numbe of fed sze cells based on the tansmsson ange of vehcles. The cell densty s calculated by havng the numbe of vehcles n the cell counted by the vehcle that s located closest to the cell cente. Ths vehcle s esponsble fo the estmaton of cell densty and the echange of ths nfomaton among othe cells along the oad untl t eaches the desgnated uncton. In ths manne, the taffc densty of each cell s combned wth that of othe cells to obtan the aveage densty on the oad. In [0], a neghbo-based scheme was poposed fo the estmaton of vehcle densty based on the numbe of vehcles n the vcnty of the pobe vehcle wthout the equement of fed sze cells. Howeve, Fgue 1. Eample of a cell used fo taffc densty estmaton When the dstance of any pont (, y) wthn the cell to any pont n set S s longe than the adus of the tansmsson ange, ths means that some of the aea INTERNATIONAL JOURNAL OF ADVANCED COMPUTER TECHNOLOGY VOLUME 4, NUMBER 6, 74

3 Intenatonal Jounal of Advanced Compute Technology (IJACT) wthn ths cell wll not be able to be coveed fom the tansmsson ange of that patcula pont. Fo eample, the tansmsson ange of node k located close to the -ght cone of the cell n Fgue does not cove all of the aea n ths cell. ISSN: data that must be sent to detemne the taffc condtons. Ths s due to the fact that the use of ntequatle ange deceases the pogess towad the destnaton. Thus, thee s a tadeoff between costs n estmaton eo and costs n data tansmsson. The accuacy of ths method eles heavly on the locaton and numbe of nodes located wthn a cell. Theefoe, ths pape poposes a soluton n whch coveage aea s used to educe eo n estmaton. Fgue. Eample of an uncoveed cell Based on the esult of above dscusson, when the condton n (1) cannot be satsfed by a gven pont wthn a cell, then the aea wthn the cell wll not be fully coveed by the tansmsson ange of that patcula pont and the accuacy of densty estmaton s compomsed. a bs s. t. a b y, (1) Geneally, the wdth of a oad s consdeably less than the ado tansmsson ange of a node. One smple way to mpove the accuacy of densty estmaton s to dvde the cell nto even smalle aeas. That s, nstead of selectng the node that s located closest to the cental pont of a cell, the ntequatle ange Q llustated n Fgue 3 can be 3 Q 1 used to dentfy the pont fom whch nfomaton should be collected when a node close to the cental pont of a cell cannot be located. 1 W W,0, Q3, Q () Thus, calculaton of the cental egon of a cell as the aveage value of the ntequatle ange poceeds as follows: Q 3 Q O 1 (3) The cental pont of a cell O s eplaced wth ntequatle ange Q 1 and Q 3 as the pont fom whch nfomaton should be collected when a node close to O cannot be found. Ths nceases the pobablty that the ente aea wthn a cell wll be coveed by the node that s selected. Ths appoach educes the nfluence of naccuacy nduced by the uncoveed aea; howeve, the degee to whch the aea s dvded s popotonal to the amount of Fgue 3. Eample of ntequatle ange The Poposed Soluton A. Assumptons In the followng, we consde an uban envonment compsng oads and unctons n whch a set of nodes s movng n the envonment. We assume that each node n the netwok has a unque ID and s awae of ts own physcal locaton based on postonng devces, such as a GPS. Nodes ae equpped wth dgtal oad maps, whch nclude detals elated to the locaton of oads and unctons, to detemne whee nodes ae located. We also assume that each node s equpped wth a shot ange weless tansceve wth an dentcal tansmsson adus, allowng t to communcate wth neaby neghbos. The coveage aea of each node s detemned by ts tansmsson adus and the wdth of the oad s fa smalle than the tansmsson ange of a node. It s also assumed that two nodes can communcate wth each othe dectly only as long as they ae wthn each othe s tansmsson ange. Each node s equed to mantan a neghbo table and to nfom nodes n ts vcnty of ts cuent poston, decton, and velocty though the tansmsson of peodc beacon messages. The node that elays pobe packets s efeed to as the elay node. B. Coveage Based Densty Estmaton In ths wok, we popose a densty estmaton stategy based on coveage aea to addess the poblems descbed n the pevous secton. Ths stategy can adapt to changes n netwok ology caused by the moblty of nodes, whch 75 COVERAGE BASED DENSITY ESTIMATION STRATEGY FOR VANET

4 Intenatonal Jounal of Advanced Compute Technology (IJACT) makes t sutable fo any moble envonment. Instead of dvdng oad segment between two unctons nto multple fed sze cells, t uses the coveage aea of each node to dentfy the node that should be selected as the pont fom whch taffc nfomaton s collected. The mamum aea coveed by a elay node depends on the dstance between the souce and the elay node. Calculatng the dffeence n coveage aea makes t possble to decde whch node s the bette elay node canddate. Thus, estmatng the taffc densty of a oad segment nvolves sendng a peodcal pobe packet, efeed to as Infomaton Collecton (IC), fom the node at the souce uncton to the node at the destnaton uncton to obtan taffc nfomaton to estmate taffc densty fo that oad segment as llustated n Fgue 4., y y ISSN: d (4) cos The ado communcaton ange of each node s ; f d,, then s not consdeed n the elay node selecton pocess. The wdth of the oad s R w and the length fom to the bounday of the gven oad segment s B. To calculate the coveage aea of, we need to emove the ntesecton aea of and and the aea beyond the oad bounday. Fgue 4. Eample of a oad segment Let us consde a scenao n whch an applcaton seeks nfomaton elated to taffc densty along the segment of a oad between the souce and destnaton uncton. The node that s located at the souce uncton ntates a seach fo all nodes wthn ts tansmsson coveage aea. The node fathest fom the souce that povdes the most coveage among ts neghbos towad destnaton uncton s selected as the elay node fo the fowadng of IC packet. The peodc beacon sgnals sent by neghbong nodes help to establsh mutual awaeness among the nodes and mantans up-to-date nfomaton about neghbong nodes. Thus, the node selected as elay node s able to obseve the numbe of nodes n ts vcnty fo use n the ndependent estmaton of densty fo a gven oad egon. The IC packet s delveed to the node wth mamum coveage towad the destnaton uncton as the pont whee the nfomaton should be collected to acque taffc densty along the gven oad segment untl t eaches ts desgnated uncton. The IC packet s updated by each elay node and a node fom the desgnated uncton duplcates the IC packet and sendng t back towad the souce uncton n a geedy manne. In so dong, each elay node should cove most, f not all, of the aea along the gven oad segment between the souce and destnaton uncton. Let us consde two nodes, and, located n postons y, y n whch the mamum dstance d, as shown n Fgue 5,, and between and s denote as whee d, s defned as follows: Fgue 5. Eample of Coveage aea Knowledge of the ccumfeence of the tansmsson coveage of node makes t possble to deve the spatal ntesecton of the coveed aeas denoted as nt, between two nodes located a dstance of d, apat, can be deved as follows: 4 INTERNATIONAL JOURNAL OF ADVANCED COMPUTER TECHNOLOGY VOLUME 4, NUMBER 6, nt d, d, d d d, d To calculate the aea of coveage that s ntesected wth node beyond the oad bounday denoted as assume _ nt _, y _ (5), we B s the -as, the cente of s y and the cente of s _, _. By usng the pont of ntesecton, J 1, J and J 3 at coodnate y, y, y and _ 1, _ 1 _, _ ths ntesecton aea can be deved as follows: _ 3, _ 3 76

5 _nt Intenatonal Jounal of Advanced Compute Technology (IJACT) _ 1 _ 3 _ 0 _ y y d d, y, y 0 0 (6) To calculate the aea of coveage that s ntesected wth node beyond the bottom oad bounday denoted as, we assume bot_ nt Bbot s the -as, the cente of s _ bot, y _ bot. By _ bot, y _ bot and the cente of s usng the pont of ntesecton, J bot1, J bot and J bot3 at coodnate _ bot1, y _ bot1, _ bot, y _ bot y _ bot3, _ bot3 follows: bot_nt 0 _ bot _ bot1 _ bot3 _ bot and, ths ntesecton aea can be deved as _ bot _ bot y y _ bot _ bot d d, y, y _ bot _ bot 0 0 (7) The aea of coveage beyond the oad bounday s denoted as, and gven by: 0, B d, The aea of coveage beyond the bottom oad bounday s denoted as bot, and gven by: bot COVERAGE BASED DENSITY ESTIMATION STRATEGY FOR VANET B B w R w B 0, R B d, The coveage of node s denoted as deved as follows: cov 0, nt _ nt bot_ nt R w bot B (8) (9) cov and can be, 0 d d,, (10) ISSN: The node that ntesects foms set I. Fom Equaton (10), we can calculate the aea of coveage fomed by all nodes n set I. We then select the node fom set I that s fathest fom wth the lagest cov to act as the elay node fo the collecton of taffc nfomaton. The node that s selected s esponsble fo estmatng taffc densty wthn ts coveage aea by consultng ts neghbo table and calculatng the numbe of nodes stuated wthn ts aea of coveage. Thus, the node that s selected nsets taffc densty data nto the IC packet fo popagaton along the oad segment to the net elay node ahead of the selected node. By dong so, the selected node povdes addtonal coveage ove what has aleady been coveed by node. By epeatng ths pocess untl the desgnated uncton s eached, the poposed densty estmaton stategy ensues that most of the aea s montoed and mamzes the lkelhood that all nodes located along the oad segment between the souce and the destnaton uncton ae ncluded n the estmaton of taffc densty. Once a node s selected as a node fo elayng IC packets fom set I, the selected node n set I s omtted fom the selecton pocess. Smulaton A. Smulaton Settng Smulatons wee conducted n an NS smulato and the moblty model of vehcles ae ceated by usng TaNS [1]. In the smulaton, a ology contanng 16 unctons and 4 b-dectonal oads was spead ove a smulaton aea of 1500m 000m obtaned fom the TIGER database []. The speed lmt of each oad s set at 80km/h. Each node was equpped wth an nteface wth ate of 0.5s. The total smulaton tme was 600s wth a node tansmsson ange of 50m. The souce oad segments used to estmate taffc densty wee andomly selected fom acoss the oad map. The numbe of nodes vaed between 75 and 300 and the nteval of Hello messages was 1s, theeby allowng the updatng of poston nfomaton evey second. Vaous numbes of vehcles wee used to obtan vaous taffc denstes. The pefomance of the poposed stategy was compaed wth that of Intequatle Range and IFTIS [19] usng vaous metcs, ncludng estmaton accuacy and ovehead. B. Smulaton Results A oad segment between two oad unctons was selected to demonstate the poposed densty estmaton stategy n an uban envonment. We began by compang the densty estmated ove tme wth vaous node denstes n an uban 77

6 Intenatonal Jounal of Advanced Compute Technology (IJACT) envonment. Fgue 6 pesents the estmatons obtaned n a low-densty envonment. Densty estmaton usng the poposed Coveage Based stategy was vey close to the actual densty value, theeby demonstatng the accuacy of the estmates n whch the focus was on fndng the fathest node wth the best coveage n ts neghbohood as the pont fom whch taffc data should be collected. The Intequatle Range s vey close to the actual taffc values; howeve, both Intequatle Range and IFTIS uses cell fomaton technques fo the estmaton of taffc densty, and s theefoe pone to a dop n accuacy n cases whee the cell densty s low o when a node located closest to the cell cente cannot be found. Consequently, some of the nodes ae not ncluded n densty estmaton. Futhemoe, when taffc densty s low, connectons between nodes ae not always avalable, whch deceases the lkelhood of fndng a node located close to the cente of the cell. ISSN: hghe accuacy n ths stuaton than n a low-densty envonment because an ncease n taffc densty povdes moe nodes to select fom, whch nceases the pobablty that a node close to the cell cente can be obtaned. It also nceases the chances of fndng a efeence pont when the nodes n a cell devate fa fom the cente. The taffc densty estmatons of IFTIS vay consdeably fom the actual taffc values due to the fact that a poton of the cells s left uncoveed when a node cannot be located nea the cente of the cell. Consequently, the node located at the uncoveed aea ae left out n the densty estmaton pocess, whch ultmately deceases the accuacy of the estmaton esults. Table 1 shows the ovehead of dffeent methods unde dffeent taffc scenaos. Ovehead hee s defned as the numbe of beacons sent fom the souce to the destnaton uncton. The poposed Coveage Based stategy has the least ovehead on the netwok followed by Intequatle Range and IFTIS. Table 1. Ovehead Method Low Densty Hgh Densty IFTIS Intequatle Range Coveage Based Conclusons Fgue 6. Densty Estmaton - Low Densty In ths pape, we popose a fully dstbuted densty estmaton stategy capable of povdng taffc densty estmatons n eal-tme usng the coveage aea povded by each node to estmate taffc densty fo a oad segment between two unctons. Ths appoach makes t possble to select the appecate elay node fo the collecton of taffc nfomaton and deceases the lkelhood of nodes beng ecluded fom the pocess of taffc densty estmaton. Smulaton esults demonstate that the poposed densty estmaton stategy s moe accuate than estng schemes unde a vaety of scenaos. These fndngs demonstate the effectveness of usng coveage aea to detemne the pont fom whch taffc nfomaton should be collected n educng estmaton eo. Acknowledgments Fgue 7. Densty Estmaton - Hgh Densty As shown n Fgue 7, densty estmaton usng the poposed Coveage Based stategy s vey close to the actual densty values. Usng the Intequatle Range povdes The authos would lke to thank the Mnsty of Scence and Technology fo suppotng ths eseach, whch s pat of the poect numbeed E MY3 and E INTERNATIONAL JOURNAL OF ADVANCED COMPUTER TECHNOLOGY VOLUME 4, NUMBER 6, 78

7 Intenatonal Jounal of Advanced Compute Technology (IJACT) ISSN: Confeence on Communcatons, pp , Refeences 007. [15] J.W. Lee, C.C. Lo, S.P. Tang, M.F. Hong and Y.H. [1] Taffc Infomaton fo US Ctes. Kuo, A Hybd Taffc Geogaphc Routng wth [] L. Wschhof, A. Ebne and H. Rohlng, SOTIS - A Coopeatve Taffc Infomaton Collecton Scheme Self Oganzng Taffc Infomaton System based on n VANET, 13th Intenatonal Confeence on Ca-to-Ca Communcaton: Pototype Advanced Communcaton Technology, pp Implementaton, 1st Intenatonal Wokshop on 1501, 011. Intellgent Tanspotaton, pp , 004. [16] T. Nadeem, S. Dashtnezhad, C. Lao and L. Iftode, [3] GCM Tavel. Taffcvew: Taffc Data Dssemnaton Usng Cato-Ca Communcaton, Moble Computng and [4] X. Zhang, H. Su and H. H. Chen, Cluste-Based Multchannel Communcatons Potocols n Vehcle Communcatons Revew, vol. 8, no. 3, pp. 6-19, Ad-Hoc Netwoks, IEEE Weless Communcaton, 004. vol. 13, no. 5, pp , 006. [17] J. Yoon, B. Noble and M. Lu, Suface Steet Taffc [5] Q. Xu, T. Mak, J. Ko and R. Sengupta, Vehcle-to- Estmaton, 5th Intenatonal Confeence on Moble Vehcle Safety Messagng n DSRC, 1st ACM Systems, Applcatons and Sevces, pp. 0-3, Wokshop on Vehcula Ad-hoc Netwoks, pp. 19-8, [18] R. Anand, L. Vanaaksh and S. Subamanan, [6] T. Elbatt, S. Goel, G. Holland, H. Kshnan and J. Taffc Densty Estmaton Unde Heteogeneous Pakh, Coopeatve Collson Wanng usng Taffc Condtons usng Data Fuson, IEEE Dedcated Shot Range Weless Communcatons, Intellgent Vehcles Symposum, pp , d ACM Wokshop on Vehcula Ad-Hoc Netwoks, [19] M Jeb, S.M. Senouc, T Rasheed and Y Ghampp. 1-9, 006. Doudane, An nfastuctue-fee taffc nfomaton [7] S.M. Blal, A. R. Khan, S. U. Khan, S. A. Madan, B. system fo vehcula netwoks, IEEE 66th Naz and M. Othman, Road Oented Taffc Vehcula Technology Confeence, pp , Infomaton System fo Vehcula Ad hoc Netwoks, 007. Weless Pesonal Communcatons, vol. 77, no. 4, [0] J Kponyo, Y Kuang, E Zhang and K Domenc, pp , 014. VANET Cluste-on-Demand Mnmum Spannng [8] R. L. Andeson, Electomagnetc Loop Vehcle Tee (MST) Pm Clusteng Algothm, 013 Detectos, IEEE Tansacton n Vehcula Intenatonal Confeence on Computatonal Poblemsolvng, pp , 013. Technology, vol. 19, no. 1, pp. 3-30, [9] P. G. Mchalopoulos, Vehcle detecton vdeo [1] TaNS, though mage pocessng: The autoscope system, [] TIGER Map, IEEE Tansacton n Vehcula Technology, vol. 40, no. 1, pp. 1-9, [10] C. Sun and S. G. Rtche, Indvdual Vehcle Speed Bogaphes Estmaton usng Sngle Loop Inductve Wavefoms, Calfona PATH Wokng Pape UCB-ITS-PWP-99-14, CHUN-CHIH LO eceved hs M.S. degee n Compute Scence fom Tungha Unvesty, Tachung, Tawan n [11] W. Leow, D. N, and H. Psho-Nk, A Samplng Theoem Appoach to Taffc Senso Optmzaton, IEEE Tansactons on Intellgent Tanspotaton Systems, vol. 9 no., pp , He s cuently wokng towad the Ph.D. degee n Compute Scence and Infomaton Engneeng at Natonal Cheng Kung Unvesty. Hs eseach nteests evolve aound weless communcaton, wth patcula attenton to [1] Z. Mo, H. Zhu, K. Makk and N. Pssnou, MURU: A mult-hop outng potocol fo uban vehcula ad hoc netwoks, 3d Annual Intenatonal Confeence on Moble and Ubqutous Systems: Netwokng & Sevces, pp. 1-8, 006. weless netwokng poblems pesented by vehcula netwokng. YAU-HWANG KUO eceved the Ph.D. degee n compute engneeng fom Natonal Cheng Kung Unvesty [13] K.W. Lm and Y.B. Ko, Mult-hop data havestng n vehcula senso netwoks, IET Communcatons, vol.4, no. 7, pp , 010. (NCKU), Tanan, Tawan n He s a Dstngushed Pofesso wth the Depatment of Compute Scence and Infomaton Engneeng, NCKU. In hs caee, he has been [14] M. Jeb, S. Senouc, R. Meah and Y. Gham- Doudane, An Impoved Vehcula Ad Hoc Routng Potocol fo Cty Envonments, IEEE Intenatonal consstently actve n the felds of academa, educaton accedtaton, and govenment polcy plannng. He was a Deputy Eecutve Secetay of the Scence and Technology Advsoy Goup n the Eecutve Yuan (Cabnet), the 79 COVERAGE BASED DENSITY ESTIMATION STRATEGY FOR VANET

8 Intenatonal Jounal of Advanced Compute Technology (IJACT) Decto of the Compute Cente n the Mnsty of Educaton. Hs eseach nteests nclude weless boadband communcaton, cloud computng, computatonal ntellgence, ntellgent nfomaton analytcs, and contetawae computng. ISSN: INTERNATIONAL JOURNAL OF ADVANCED COMPUTER TECHNOLOGY VOLUME 4, NUMBER 6, 80