HDAR: Hole Detection and Adaptive Geographic Routing for Ad Hoc Networks

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1 : Hole Detection nd Adtive Geogrhic Routing for Ad Hoc Networks Jinjun Yng The Lortory for Advnced Networking Dertment of Comuter Science University of Kentucky Lexington, KY , USA Zongming Fei The Lortory for Advnced Networking Dertment of Comuter Science University of Kentucky Lexington, KY , USA Astrct Geogrhic routing for wireless d-hoc networks hs well known locl minimum rolem, which is cused y hole tht locks the greedy forwrding rocess. Existing geogrhic routing lgorithms use erimeter routing strtegies to find long detour th when such sitution occurs. In this er, we roose heuristic hole detecting lgorithm which cn identify the hole in dvnce nd dvertise the hole informtion to those nodes tht my e ffected. Our work differs from existing hole detection lgorithms in its simlicity nd efficiency. We study the trdeoff etween the re of hole nnoucement nd the routing th imrovement. In ddition, we roose simle reresenttion of hole informtion nd develo routing scheme sed on it. Simultion results illustrte tht our roch cn reduce the verge length nd numer of hos of routing ths, nd is comuttionlly more efficient thn other hole detection lgorithms. I. INTRODUCTION Geogrhic routing is simle, sclle nd efficient routing strtegy for wireless networks. It hs een considered s one of the most romising routing schemes in d-hoc networks. In such scheme, the loction informtion of nodes is ville either through GPS or using virtul coordintes [1]. It is ssumed tht ech node knows its own loction nd the loctions of its neighors. The source node knows the loction of the destintion node nd encsultes it in ech dt cket. In the sic greedy forwrding roch, node sends dt ckets to one of its neighors tht is closest to the destintion. Ech intermedite node reets the rocess until the ckets rech the destintion node. However, chllenge often fced in geogrhic greedy routing is the locl minimum rolem, when the greedy forwrding rocess is locked t node tht does not hve closer neighor to the destintion, even though there is th from the source to the destintion in the network. The occurrence of hole cn e cused y mny fctors in wireless d hoc networks, such s the jmming hole incurred y jm communiction, the srse deloyment, the hysicl ostcles nd ower exhustion [2]. To solve the locl minimum rolem, severl schemes sed on erimeter routing hve een roosed [3] [5]. When cket gets stuck t locl minimum node, erimeter routing hse will e strted nd the cket will e forwrded long the erimeter of the hole, until it reches node tht cn find one of its neighors tht is closer to the destintion. After tht, the forwrding mode returns to greedy. The fce routing fmily schemes cn gurntee delivery, ut often cuse long detour th. To del with the issue, recent work tries to detect the hole nd the nodes locted on the hole s oundry in dvnce. These nodes will then dvertise the hole informtion to other nodes [6] [7], which cn enefit for the future routing th. In this er, we roose Hole Detection nd Adtive geogrhicl Routing () lgorithm, which focuses on defining nd detecting holes in d hoc network, reresenting holes nd uilding routes round the holes. The contriutions of this er re threefold. First, we come u with heuristic lgorithm to detect hole quickly nd esily. And the hole cn e identified only y one time clcultion. Second, we rovide concise reresenttion of the hole. A hole is recorded s segment. Third, we develo n roch to let suset of the nodes locted on the hole s oundry nnounce the hole informtion to the nodes in the vicinity. We discuss the trdeoff etween the cost of hole informtion nnouncement nd the enefit for future routing. Simultions show tht comred with, reduces the length of routing th y 12.4% nd the numer of forwrding hos y 13.2% for ll the ths in tested res. And the length of long detour ths round the hole cn e reduced y 61.2%. The numer of hos cn e reduced y 64.6% comred with. The simultion lso indictes tht the overheds of re only 16.6% those of HAGR. The rest of the er is orgnized s follows. Section II discusses relted work. Section III rooses novel method for detecting holes nd resents new dtive routing lgorithm. We evlute the roosed schemes y simultions in Section IV. Section V concludes the er.

2 II. RELATED WORK The first geogrhic routing rotocol is sed on simle greedy forwrding. In this roch, ech node forwrds ckets to one of its neighors tht is closest to the destintion node until the ckets rrive the destintion. This scheme is efficient, ut hs the locl minimum rolem. To mitigte locl minimum rolem, comss routing [8] ws roosed s the first fce routing scheme, in which the cket is forwrded long the fce until greedy forwrding is workle in node. However, comss routing cnnot gurntee cket delivery in ll geogrhic networks. Severl routing lgorithms in fce routing fmily hve een develoed. By comining greedy nd fce routing, Kr nd Kung roosed the Greedy Perimeter Stteless Routing () lgorithm [3]. It consists of the greedy forwrding mode nd the erimeter forwrding mode, which is lied in the regions where the greedy forwrding does not work. An enhnced lgorithm, clled Adtive Fce Routing (AFR), uses n eclise to restrict the serch re during routing so tht in the worst cse, the totl routing cost is no worse thn constnt fctor of the cost for the otiml route [9]. The ltest ddition to the fce routing fmily is Pth Vector Fce Routing(GPVFR) [10], which imroves routing efficiency y exloiting locl fce informtion. The rotocols in fce routing fmily cn void the hole. However, they often cuse long detour th. A new scheme ws roosed recently to detect the hole in dvnce. Then the nodes locted on the hole dvertise the hole informtion to other nodes, which will enefit for their future routing. Qing gve mthemticl definition of hole [6]. He defined hole to e simle region enclosed y olygon which contins ll the nodes where locl minimum cn er. He rought forth the get stuck concet nd roosed the hole detection mechnism. Once cket following greedy forwrding gets stuck t node, the node must e on the oundry of hole. The condition tht node cound get struck is tht the node hs n ngle etween two djcent edges tht is lrger thn 120 degrees. He then discussed tht hole roe messge could e circulted long olygon nd finlly come ck to the inititor. A hole detection mechnism in regrding to sensor network is roosed y Ji [11]. This method includes two stges: hole dvertisement nd routing. In the hole dvertisement stge, once node finds tht it is in hole ecuse none of its neighors is closer to the sink, the nodes dvertises the hole to its neighors. So ech of its neighors could select other nodes excet the hole node s next ho in the future. In the routing stge, if node s next ho to the sink is not null, it is first-clss node, otherwise it is second-clss node. A second-clss node will try to uild th to the sink vi one of its neighors which is first-clss node. Also relted is HAGR [7], which investigted the nodes incident to close loo in geogrhicl grh. For vertex u, if the ngle etween two djcent edges with resect to this vertex is lrger thn n ngle threshold, then vertex u considers tht it is locted on otentil hole. To further determine if it is locted on hole, u clcultes the dimeter of the loo. It loctes the isector tht eqully slits the ngle nd uses it s reference line. Then node u finds out the leftmost node nd the rightmost node furthest from the isector. The distnce etween them is the dimeter of the hole. If the dimeter is greter thn the dimeter threshold nd the ngle is igger thn the ngle threshold, u is regrded s sitting on hole. Once node is detected on hole, it dvertises the hole informtion to its neighors. Uon receiving the hole informtion, its neighor reclcultes the ngle nd dimeter sed on its loction. If oth of them re igger thn their thresholds, then the neighor considers tht it is on hole nd it continues to dvertise the hole informtion; otherwise it stos dvertisement. Bse on the hole detecting, HAGR divides the network lne into three regions, nd the nodes in different regions conduct different forwrding strtegies. The hole detecting method of HAGR is time-consuming since node hs to clculte the vlues of two metrics. And the hole dvertisement is exensive ecuse once node receives the hole informtion, it hs to reclculte the two vlues from its ersective nd comre them with their corresonding thresholds, so lots of nodes need to conduct the clcultions. In ddition, the dimeter threshold is n solute vlue nd is not djusted ccording to the trnsmission rnge of the nodes or the network deloyment in different scenrios. III. HOLE DETECTING AND ADAPTIVE ROUTING A. Hole Detection Algorithm The ide of the hole detection method of is sed on the following oservtion. The network th of two nodes sitting cross hole in the wireless network tyiclly is much longer thn their Eucliden distnce. The rtio of the network distnce over the Eucliden distnce is the metric we use to detect hole. Secificlly, in, node egins to detect whether it is locted on hole when the ngle etween its two djcent edges is greter thn 120 degrees. Node initites roe messge nd writes its loction to the messge. Then sends the messge to its leftmost node with resect to the ngle. The leftmost node is defined s follows. Node fces the re formed y the two rys of the ngle, then uses the ngle s isector line to conduct counterclockwise sweeing. The leftmost node is the first one met y the sweeing line. Uon receiving the roe messge, s leftmost neighor writes its loction into the messge nd sses it to its leftmost neighor. The roe messge will finlly come ck to node from s rightmost neighor with resect to the initil ngle. When the roe messge circultes, it collects the loctions of the nodes on its wy nd mkes them ville to node. Node then investigtes these nodes. For ech node on the wy, comutes the length of their roe th length ro() nd their Eucliden distnce dist euc(). For node x, length ro(, x)/dist euc(, x) is defined s the hole detection rtio. If there exists node v such tht its hole detection rtio is lrger thn redefined threshold δ, tht is,

3 length ro(, v)/dist euc(, v) > δ (1) then is considered to e sitting on hole. The vlue of δ ffects the hole detection results. If δ is too ig, it will introduce flse negtive. If δ is too smll, it will cuse flse ositive. We set δ = 2.25 in the simultion. Fig. 1 is n exmle for hole detection. Node initites the hole roe messge, which collects the loctions of nodes long the loo. Then finds tht there exists node v, stisfying length ro(, v)/dist euc(, v) > δ. Node is considered sitting on hole. d v e nnounced to the nodes in certin re nd these nodes will enefit from the hole nnouncement for future routing. It is lso ossile tht locl minimum node cnnot find hole. In Fig. 3, node is locl minimum node. initites hole roe messge ut it cnnot detect the hole. It is ecuse the length of the roe th from to ny node on the olygon over their Eucliden distnce is roximtely equl to 1. However, the hole cn e detected y nother node such s n nd the hole informtion will e nnounced to res (ekf nd e k f ) contining the nodes which will enefit from the hole informtion in future routing. This henomenon tht true locl minimum node cnnot detect hole occurs when the olygon is long nd nrrow. f f g h Fig. 1. P initites the roe messge nd it circultes the loo k n k The roe inititor must hve n ngle etween two djcent edges tht is lrger thn 120 degrees. Such n ngle is necessry ut not sufficient condition to determine tht the inititor is locl minimum node. The ojective of the hole roe messge is to find hole, ut not to determine if the roe inititor is locl minimum node. A secific destintion is needed to determine locl minimum node. e e Fig. 2. g k h P is not locl minimum ut finds the hole The roe inititor who finds hole finlly my e or my not e locl minimum node. In Fig. 1, node initites the hole roe messge nd finds tht it is locted on hole. It is locl minimum node if it sends cket to nodes in the vicinity of node d. In Fig. 2, node initites hole roe messge nd detects the hole, ut is not locl minimum node with regrd to destintion f. However, the hole informtion will k f f Fig. 3. B. Hole Announcement e P is locl minimum ut does not find the hole The th the roe messge goes through is olygon, which could e reresented y sequence of vertexes. However, in geogrhic routing, we do not hve to record ll the nodes on the olygon ecuse most of them hve minor effect on determining the routing ths. Wht we re concerned re the nodes tht will lock the greedy forwrding. With the loction informtion out ll the nodes on the olygon (Fig. 2), cn clculte the two nodes whose Eucliden distnce is the lrgest. The segment connecting these two nodes looks like ord tht locks the greedy forwrding. For instnce, segment in Fig. 2 is the ord tht locks the greedy forwrding. We cn thus reresent the hole y,. The greedy forwrding is locked y the ord, ecuse some otentil destintion nodes re hidden ehind the ord while the source nodes re locted on the oosite side. In the sic routing roch, source node just conducts the greedy forwrding until it fils due to the locl minimum node, where the greedy forwrding chnges to fce routing. Thus the detour th is generted. If the source figures out tht the ossile destintion nodes re hidden ehind the ord in dvnce, then the source nodes cn void locl minimum nodes nd significntly reduce the length the routing ths. After source node is mde wre of the hole reresetend y,, it cn determine shded re s follows. Drw lines e

4 r nd t erendiculr to segment where r nd t re on the oosite sides of from. Then the re rt is the shded re (Fig. 4). r j e Fig. 4. g d n m c k s h Hole Announcement The nodes in re rt re the ossile destintion nodes tht re locked y the hole, for some source nodes. We wnt to figure out n re contining these source nodes tht will e most signicntly ffected y the hole. If they re informed of the existence of the hole, they cn dtively djust the next forwrding hos to void detour routing ths. Oviously they re locted on the oosite side of rt with regrd to segment, s reresented y tringle efk in Fig. 4. In order to determine the hole nnouncement re, the nnouncement redth nd deth need to e figured out. We first find node e nd node f on the sme side s node with regrd to segment. They re the left nd right nodes frthest wy from ech other nd stisfy the hole detection condition (1). Let c e the midoint of segment ef. Drw segment ck erendiculr to ef. Then the tringle efk is the re tht should e nnounced with the hole informtion. Note tht the lrger hole nnouncement re is, the more nodes will enefit nd hve shorter routing th. Of course, lrger re lso mens higher overhed of the nnouncement. There is clerly trdeoff etween the enefit to the future routing th nd the overhed of the nnouncement. The nnouncement redth is selected s segment ef since e nd f re most remote nodes on the oundry of the hole nd on the sme side s stisfying the hole detection condition. The nnouncement deth determines the size of the re. We derive tht the otiml length of the deth ck is The detils cn e found in our technicl reort. The nodes on the rc ef egin to dvertise the hole informtion, to their neighors. In order to void dulicte messges, once node in the re hs seen the received hole informtion efore, it simly discrds the dulicte. f t C. Adtive routing After the nnouncement, ech node in the tringle ekf knows tht there is hole, tht locks the greedy forwrding to ny destintion node in re rt. So the nodes in tringle ekf cn dtively djust the routing th. Once node s intends to send cket with destintion d, it first looks u its locl cche to see whether it hs hole informtion entry,. If there is no such entry, it just conducts. Otherwise if s nd d re locted on the sme side of segment or s nd d re locted on the oosite sides of ut d is not in the shded re rt, s just conducts ; if d is in the re rt, s will consider or s its tenttive trget y writing or into the cket s heder. Node s selects or s follows. Let m e the midoint of segment, mn e erendiculr to segment nd n e t the oosite side of with regrd to s. If d is locted in re rmn, s writes to the cket s hed s its tenttive trget; if d is locted in re nmt, s writes to the cket s hed s its tenttive trget. When the cket reches or, the tenttive trget will continue sending the cket to the destintion node d. In this scheme, only the nodes in the tringle ekf re need to sve the hole entry. Hence the storge of entry is indeendent of source nd destintion. Once the hole is figured out, the shded re nd the hole dvertisement re re fixed. The two res re only deendent on the she of the hole, no mtter where the source nd destintion re locted. The forwrding lgorithm is descried in detil in Fig. 5. forwrding() if this node is destintion d ends forwrding. Look t the forwrding cket whether this node hs tenttive trget T if true Comre whether this node is T ; if true Remove T nd forwrd the cket to next ho with its destintion d; Forwrd the cket to next ho with its destintion T ; Serch its locl cche if n entry, exists if this node nd d re on the sme side of Conduct ; if this node nd d re t oosite sides of if d is in rmn Write s tenttive trget T to the cket; Forwrd cket to next ho with destintion T ; if d is in nmt Write s tenttive trget T to the cket; Forwrd cket to next ho with destintion T ; Conduct ; Conduct. Fig. 5. Forwrding Algorithm

5 IV. PERFORMANCE EVALUATION We evlute the erformnce of y simultions sed on the esim3d wireless network simultor [12], which simultes IEEE rdios nd is tyiclly used for loction sed routing lgorithms. We use noiseless immoile rdio network environment. In the simultions, nodes hve trnsmission rdius of 20 meters nd re deloyed in n interested re of 400m*400m. We generte networks with the numer of nodes vried from 50 to 300. For ny given numer of nodes, 50 networks re generted. And the holes re generted utomticlly in ech network y the simultor. Averge ho of ll ths Averge length of ll ths Fig. 6. Numer of nodes The verge length of ths. We first comre the erformnce of with using two metrics, the length of routing ths nd the numer of routing hos. Fig. 6 shows the verge length of routing ths when the numer of nodes in network chnges from 50 to 300. consistently outerforms s exected. For exmle, when the numer of nodes in network is 150, the verge length of is 12.4% shorter thn tht of. Fig. 7 shows the verge numer of hos for oth schemes. Similr to Fig. 6, the numer of hos for scheme is lso consistenly smller thn. For exmle, when the numer of nodes in network is 150, the verge numer of hos for is 13.2% less thn tht of. In the revious results (Fig. 6 nd Fig. 7), we include oth the norml greedy th nd the th in the vicinity of holes nd ffected y the holes. So the effect of on the th ner the holes re not singled out. To demonstrte s effect, we mrk the ths tht enefit from the hole informtion s hole ths nd recorded the irs of source nd destintion nodes. We lso investigted the ths generted y with the sme irs of source nd destintion nodes. Then we comred the ths enefit from hole informtion in with the ths derived from. The erformnce of hole ths y nd re reorted in Fig. 8 nd Fig. 9. hs much shorter ths Averge length of hole ths Averge ho of hole ths Fig. 7. Numer of nodes The verge numer of hos Fig. 8. Numer of nodes The verge length of hole ths. 0 Fig. 9. Numer of nodes The verge numer of hos of hole ths.

6 Averge overhed HARG Fig. 10. Numer of nodes The overhed nd fewer numer of hos comred with. When the numer of nodes in the network increses from 50 to 300, the difference in the length of routing th etween nd increse significntly. When the network hs 300 nodes, the length of routing th of is less thn 30% of tht of. Overll, the verge length of is only 38.8% tht of nd the numer of hos is only 35.4%. We lso comre the overhed of with n existing hole detection lgorithm HAGR. We used the sme simultion setting. In, only few nodes on the hole erimeter need to comute the hole detection rtios. However, in HAGR, in ddition to the nodes on the hole oundry, ech node in the vicinity hs to clculte the hole detecting rmeters including ngle nd dimeter individully. We define the numer of nodes tht need to conduct the hole detecting clcultions s the overhed. Fig. 10 illustrtes tht the overhed of is much less thn those of HAGR. V. CONCLUSION In this er, we resented simle nd efficient heuristic lgorithm tht cn detect the hole for wireless d hoc networks. The hole cn e reresented concisely nd nnounced to the nodes nery tht otentilly incur detour ths in fce routing. The nodes enefit from the hole informtion y dtively djusting the forwrding direction to void long detour th. The novelty of the roch is tht single node cn detect the hole efficiently nd then the nodes ner the hole cn enefit from it. The exeriments indicte tht our roch results in significnt shorter routing th nd fewer numer of hos for wireless d hoc network. Also it is comuttionlly more efficient thn n existing hole detection lgorithm. REFERENCES [1] Y.-B. Ko nd N. H. Vidy, Loction-ided routing (LAR) in moile d hoc networks. ACM/IEEE MoiCom, [2] N. Ahmed, S. Knhere, nd S. Jh, The holes rolem in wireless sensor networks: survey, SIGMOBILE Moile Comuting nd Communictions Review, vol. vol.9,. 4 18, Aril [3] B. Kr nd H. Kung, : Greedy erimeter stteless routing for wireless networks. ACM/IEEE Interntionl Conference on Moile Comuting nd Networking, [4] P. M. P. Bose nd I. Stojmenovic, Routing with gurnteed delivery in d hoc wireless networks. 3rd Interntionl Worksho on Discrete Algorithms nd Methods for Moile Comuting nd Communictions, [5] R. W. F. Kuhn nd A. Zollinger, Worst-cse otiml nd verge-cse efficient geometric d-hoc routing. 4th ACM Interntionl Symosium on Moile Ad Hoc Networking nd Comuting, [6] Q. Fng, J. Go, nd L. Guis, Locting nd yssing holes in sensor networks, Moile Networks nd Alictions, vol. 11, , Aril [7] F. Xing, Y. Xu, M. Zho, nd K. Hrfoush, HAGR: Hole Awre Greedy Routing for Geometric Ad Hoc Networks. Militry Communictions Conference, [8] E. Krnkis, H. Singh, nd J. Urruti, Comss routing on geometric networks. 11-th Cndin Conference on Comuttionl Geometry, [9] F. Kuhn, R. Wttenhofer, nd A. Zollinger, Asymtoticlly otiml geometirc moile d-hoc routing. 6th interntionl worksho on discrete lgorithms nd methods for moile comuting nd communictions, [10] B. Leong, S. Mitr, nd B. Liskov, Pth Vector Fce Routing:Geogrhic Routing with Locl Fce Informtion. Boston, MA: 13th IEEE Interntionl Conference on Network Protocols, [11] W. Ji, W. Tin, W. Guojun, nd G. Minyi, Hole Avoiding in Advnce Routing in Wireless Sensor Networks. Proc. IEEE WCNC, [12] C. Liu, Simultor in Dertment of Comuter Science nd Engineering t Florid Atlntic University, Htt : // roj/index.htm.