A Clustering-Based Fast and Stable Routing Protocol for Vehicular Ad Hoc Networks

Transcription

1 Journal of Physcs: Conference Seres PAPR OPN ACCSS A Clusterng-ased Fast and Stable Routng Protocol for Vehcular Ad Hoc Networks To cte ths artcle: P F Zhao et al 2018 J. Phys.: Conf. Ser Vew the artcle onlne for updates and enhancements. Related content - A survey on dfferent prvacy-preservng authentcaton schemes n VANT eepu Mathew and Hma Anns Roy - UMR: Mult-Path Routng Protocol for Underwater Ad Hoc Networks wth rectonal Antenna Janmn Yang, Songzuo Lu, Qpe Lu et al. - A HOC Networks for the Autonomous Car avdescu Ron and ugen Negrus Ths content was downloaded from IP address on 19/10/2018 at 19:20

2 A Clusterng-ased Fast and Stable Routng Protocol for Vehcular Ad Hoc Networks P F Zhao 1,2,3, K Lu 1,2,3, Y Zhang 1,2,3, T Zhang 1,2,3 and F Lu 1,2,3 1 School of lectroncs and Informaton ngneerng, ehang Unv., ejng, Chna 2 ejng Key Lab for Network-ased Cooperatve ATM, ejng, Chna 3 ejng Laboratory for General Avaton Technology, ejng, Chna zpf_wqt@163.com Abstract. For the sake of mprovng network performances,.e. end-to-end delay and packet drop rato (PR), n vehcular ad hoc networks (VANT), we propose a clusterng-based fast and stable routng (CFSR) protocol. The CFSR protocol ntroduces a lnk qualty assessment mechansm that evaluates the lnk qualty on road segments between ntersectons and adopts the end-to-end delay as an evaluaton metrcs to assgn a weght to the lnk correspondng to each road segment. The delay-senstve applcaton can drectly use ths weght as the lnk qualty ndcator to drectly establsh the routng path n the sub-zone by usng jkstra algorthm. At the same tme, the concept of local coordnator (LC) s ntroduced nto the routng protocol to help construct the routng path convenently and quckly. In addton, t can also avod the local optmum problem caused by sngle-step decson and reduce the network transmsson delay. In ths paper, the Smulaton of Urban Moblty (SUMO) and Network Smulaton 3 (NS3) are used to smulate ths protocol. Smulaton results reveal that CFSR protocol can obtan lower end-to-end delay and PR than those of the AOV and SV protocols. 1. Introducton Vehcular ad hoc network (VANT) bascally s a specfc form of moble ad hoc network (MANT) appled n modern transportaton system, servng as provdng communcaton among the adjacent vehcles and the nearby fxed road-sde equpment. VANT ncludes two communcaton approaches, Vehcles-to-Vehcles (V2V) and Vehcles-to-Infrastructure (V2I). Some applcatons of VANT focus on mprove the drvng safety va remndng drvers of avodng dangerous transportaton events, such as car crashes, extreme weather and so on, whle others pay attenton to makng trps more joyful and relaxng. For nstance, passengers can acqure real-tme nformaton about traffc statstcs so as to select a faster route to save tme. In addton, busness servces of malls and restaurants can be accessed through road sde unts (RSUs) [1]. There s a rsng demand for a lower end-to-end delay (2) for real-tme non-safety applcatons. That s to say, t s crucal to choose a routng protocol wth mnmum 2 to handle ths ssue. Most exstng routng protocols select the routng paths by usng greedy-based algorthms whch are lkely to account for local maxmum problem, leadng to hgher 2 [2][3]. For example, most postonbased routng protocols, such as GPSR and GSR, select the shortest dstance path between source and destnaton, whle GyTAR and A-STAR choose roads whch are well connected. As sad before, these protocols that use greedy algorthm and sngle-step decson are prone to the local maxmum problem Content from ths work may be used under the terms of the Creatve Commons Attrbuton 3.0 lcence. Any further dstrbuton of ths work must mantan attrbuton to the author(s) and the ttle of the work, journal ctaton and OI. Publshed under lcence by Ltd 1

3 whch occurs when no other connected roads are closer to the destnaton than the current one. Although ths ssue can be settled down by carry-and-forward mechansm, t ncurs longer delvery delay. Gvng preference to the global network topology s our motvaton to desgn a clusterng-based fast and stable routng (CFSR) protocol, whch can avod the local optmal problem. To acheve ths goal, the CFSR protocol ntroduces a lnk qualty assessment mechansm that evaluates the lnk qualty on road between ntersecton and uses the end-to-end delay as an evaluaton ndcator to assgn a weght to the lnk correspondng to each road, as desgned n [4]. The delay-senstve applcaton can drectly use ths weght as the lnk qualty ndcator to drectly establsh the routng path n the subzone by usng jkstra algorthm. In ths way, we can acheve the goal of reducng the Network Model Ths model ams at a typcal cty envronment and assumes that t merely conssts of road segments and ntersectons as shown n fgure 1. For ths network model, the artcle adopts a herarchcal structure to mplement network dvson and management. Specfcally, the road segment can be dvded nto several statonary clusters, meanng that the vehcles on the specfc road segment belong to relatve clusters [5]. Clusters can communcate wth each other through cluster heads; and communcaton between vehcles of dfferent road segments can be relayed through the gateways node selected at the ntersectons. Here are some assumptons and explanatons for the typcal scenaro. The herarchcal cluster structure s shown n fgure 2 and can be dvded nto three parts. The underlyng network conssts of cluster members (CMs) wthn each road segment. The mddlelevel network conssts of the cluster heads (CHs) of each lnk and the gateways of the crossroads. The hgh-level network conssts of local coordnators (LCs) selected by each subzone topology. Rj s defned as the road between ntersectons and j. At the same tme, the herarchcal network can be mapped nto a graph G(V, ), where V s a set of network nodes v and s a set of edges e between nodes. In addton, V' s a path set, and f ths set exsts a path e, ea, eb,, en, ej between the vehcle nodes and j, then Rj s called as connected state. Assume that nodes n the network are all assgned a state: cluster head (CH), cluster member (CM), gateway node (GW) or local coordnator (LC). ach node has a unque I, equpped wth GPS devces. LC CH GW CM Fgure 1. Network model. Fgure 2. Herarchcal clusterng structure. 3. Clusterng mechansm The road segment s desgned as a b-drecton road, and each s dvded nto multple cluster. Moreover, the dameter of clusters equals half of the transmsson range of a standard vehcle. As shown n fgure 3, due to the partcularty of the lateral extenson of the road, the length of a cluster s much larger than ts wdth, whch results n that the cluster shape on the road can be approxmated as a rectangle. 2

4 Fgure 3. Cluster structure for road segment Clusterng head selecton process After the statonary cluster dvson ends, the cluster head selecton process begns. Vehcles wthn a cluster nteracts nformaton <I, x, y, v, d, b> - where I s the dentfcaton of each vehcle, <x, y> s the uropean coordnates of the vehcle, v s the speed, d s the drecton, and b s the vehcle node flag to ndcate the status of the vehcle node (LC: 11, GW: 10, CH: 01, CM: 00). ased on these nteractons, ths paper selects two factors, velocty and locaton, as the cluster head selecton crtera to calculate stablty of nodes [6] Velocty factor. Ths performance of speed s crucal n VANT. It results n hgh dynamcs of the cluster structure and very fast change of the cluster topology. If the node wth strong moblty s selected as the cluster head, t wll cause the nstablty of the communcaton lnk and the cluster structure. The optmal result makes us choose a node as the vehcle node wth smallest speed dfferences between neghbor vehcles. Supposng that the CH selecton mechansm takes the nstantaneous speed v for each vehcle, where v u s the average of all vehcle nodes at tme t for calculatng the speed weghtng factor Pv () for each vehcle. v () vµ Pv() =, φn (1) vµ For a vehcle node wthn a cluster, ts velocty weghtng factor can be expressed as a vector n the followng formula: Pv( CI) = [ Pv(1), Pv(2), Pv(3),..., Pv( n)] (2) These values can be normalzed by scalng them between zero and one as: Pv( ) mn( Pv( CI)) Pv () =, φ norm n (3) max( Pv( CI)) mn( Pv( CI)) The vehcle wth the least P () value has the hghest speed prorty. v norm Locaton factor. When the poston of the cluster head s close to the start cluster boundary poston, the cluster head wll stay for a longer tme to prevent frequent replacement of cluster heads, whch can mprove the stablty of the cluster. Therefore, we also consder usng poston weght factor as one of metrcs. The locaton factor s defned as the dstance from current poston to statonary cluster boundary, the formula s as follows: L () P l() =, φn, 0 L () R (4) R 3

5 For a vehcle node wthn a cluster, ts locaton weght factor can be expressed as a vector n the followng formula: Pl( CI) = [ Pl(1), Pl(2), Pl(3),..., Pl( n)] (5) These values can be also normalzed by scalng them between zero and one as: P l( ) mn( PCI l( )) Pl () =, φ norm n (6) max( Pl( CI)) mn( Pl( CI)) The vehcle wth the least P value has the hghest locaton prorty. l norm Integrated stablty factor. For one cluster, the ntegrated stablty of vehcles can be obtaned by: S () = αpl () + (- 1 α) P (), (0,1) norm v α (7) norm The former part of the formula evaluates the mpact of dstance between vehcles on cluster stablty, because the greater the dstance from the boundary of the vehcle, the more frequently the cluster heads are replaced, whch s not conducve to cluster stablty. The latter part manly reflects the mpact of vehcle speed on vehcle stablty, because when the vehcle speed s small, the topology of the network changes slowly and the servce lfetme s relatvely long. On the other hand, f the vehcle speed s relatvely fast, the performance of the network lfe wll deterorate. In general, the smaller the value of the stablty S, the more stable the cluster Constructon of clusters Assumng that vehcle nodes on the road are equpped wth GPS, nformaton of the vehcle such as speed, poston, and drecton can be obtaned from the respectve on-board GPS. Therefore, at any tme, each vehcle node can confrm whch cluster t belongs to, based on the locaton nformaton. The I of the vehcle s generated randomly and s not repeated. And we set the ntal state of all nodes to the UNIFI state. Cluster constructon flow chart shown n fgure Intersecton gateway selecton The dvson of the segmented road clusters and the CH selecton are descrbed above. At ths tme, the communcaton on the segmented roads s bascally establshed. However, when the data transmsson crosses a road segment to an ntersecton, the communcaton should be transmtted wthout nterrupton. Therefore, ths paper selects gateway node at the ntersecton to perform relay transmsson of nformaton. Assumng that the vehcle nodes wll obtan the turn drecton (turn left, turn rght, go straght) tself through the turn sgnal when each vehcle crosses the ntersecton, and use the reactve locaton servce (RLS) to obtan ts current locaton. Then, the node located n the ntersecton area wll calculate ts own resdence tme accordng to formula (8). The crtera for selectng the gateway node at the ntersecton s to make the vehcle node as long as possble to ensure the relay of nformaton. For nstance, the gateway node s more nclned to select the vehcle node as a gateway node that spends the longest tme passng through the ntersecton. The selected gateway node wll announce ts own status and establsh a connecton wth the neghborng cluster head. As shown n fgure 5, for the calculaton of the dwell tme of ntersectons at the ntersecton, the followng are specfcally dvded nto three categores: straght, left, and rght. W d A,0 d A W, straght va 3W 2d A 3W t =,0 d A, left (8) 2va 2 W 2d A W,0 d A, rght 2va 2 Vehcle nodes determne whether they are located n the ntersecton area accordng to ther own poston nformaton, f located at the ntersecton, calculate and nteract wth ther respectve dwell 4

6 tme accordng to the current drecton of rotaton, the fnal selected gateway node requres the longest resdence tme. After the gateway node s selected successfully, t sends a HA frame to establsh a connecton wth the cluster head nodes n the neghborng area. Start Intalze nformaton of vehcles roadcast INQ message perodcally by vehcles Receve INQ message of neghbor nodes Wthn neghbor lst? N Complete nformaton nteracton Cluster head selecton Y Refresh nformaton Store nformaton CHs broadcast HA message Vehcles request jonng cluster wth INQ message v v v? a N Y Allow to be CMs end Fgure 4. Flow chart of cluster constructon. Fgure 5. Intersecton gateway selecton. 4. CFSR protocol ased on completon of the cluster structure, we start to establsh the routng path for the data transmsson. To acheve ths goal, the process of assessng lnk qualty and assgnng weght to each lnk s necessary. Then, the weght can be drectly used as the lnk qualty metrc to establsh an optmal routng path n every sub-zones Lnk qualty assessment The qualty of each road lnk wll be evaluated and the weght w R wll be assgned accordng to the end-to-end delay of each road segment. 5

7 dr, d rap Ts wr = d, j R + d e Ts < drap < Tmax (9), drap Tmax where d R s the transmsson delay of a Lnk Assessment Packet (LAP), d e s the extra delay when a LAP encounters a dsconnected path and caused by the carry-and-forward strategy, and d rap d = t Tmestamp ) s the propagaton delay whch s related wth the receved tme and tmestamp ( rap r of LAP. T s ( T T ( max vav s hmax = t ) s the sum of transmsson delays of road segments along the path, and T max ts = 1 L = ) s maxmum tolerable transmsson delay. d R represents the average delay for transmttng a new data packet over a road segment. It s defned as below. d R n = d (10) = 1 C d C conssts of two parts: T q : representng the queung delay and T ts : denotng the transmsson delay. d = t [ + t ] (11) C q ts Actually, T q and T ts are correlated. The queung delay of a packet corresponds to the servce tme of those packets queued ahead of t, whch ndcates that when a new packet arrves to a queue contanng k packets, d C can be defned as below. dc = ( k+ 1) t [ ] ts (12) In addton, the extra delay d e can be nterpreted as the product of addtonal delay and the dsconnected probablty. de = dds ρds (13) d ds- s the addtonal delay to ncur when choosng carry-and-forward. To compute t, we dvde L nto n sub-segments of length R, meanng n clusters as shown n fgure 6. We assume that the cluster s connected f t contans at least one vehcle. Thus, the total addtonal delay of m dsconnected subsegments s expressed as below. m* R d = ds, m n v (14) Fgure 6. xtra delay caused by carry-and-forward. ρ ds- represents the probablty of carry-and-forward. We use Posson process as the model of the vehcle arrvals to road segments. Hence, we obtan: m m n m ρ = C ρ (1 ρ ) (15) ds n null null λ ( ) exp n ρnull = (16) ased on all above, we can assgn weghts to road segments as below. 6

8 dr, d rap Ts wr = d, j R + d ds ρds Ts drap T, drap Tmax max (17) 4.2. Local coordnator selecton The method to solve the path local optmum problem s to understand the global topology structure and weght nformaton of the entre network, but t s extremely dffcult gven the consderable sze of modern cty. Therefore, we dvde the urban network topology nto sub-zones and establsh a local coordnator n every one of them through nformaton exchange. Consderng ths, we set the sze of sub-zone to 3*3 blocks for the sake of lmtng LAPs floodng and complexty of algorthm. The local coordnator s defned as the specfc gateway node that connects the most ntersecton gateway nodes n ther respectve scopes. In dong so, on the one hand, the effcency of route dscovery s hgh. On the other hand, t also avods the problems of excessve nformaton storms and mantenance overhead of the LAPs. W 1 W A C W 3 WA WC W W 1 W A C W 2 G W WG 0 3 F W W WF W 2 I W WI F W 1 W I I WI 1 WI I F 0 2 H WF WH G H I (a) C W 3 W W+WC W+W C F WC W W+W W+WF A W 3 W W+WA W+W A C W 5 W I WI W+W W+W H WI+WH F F WI+WF 2 I WI F WI+WF WF+W 3 F WF H WH WF+W G H I (b) 7

9 A C C F G I WC W W+W W+WF W+W+WG W+WF+WI F W 8 W I WI W+W W+W H WI+WH A W+WA C W+WC G W+WG G H I (c) Fgure 7. Local coordnators selecton process. As shown n fgure 7, n the ntalzaton phase, each gateway node n the local-area topology sets tself as LC, and sets the number n of other gateway nodes connected to tself to zero. After the frst round of LAP nformaton nteracton, each gateway node updates ts neghborng lnk nformaton and n value accordng to ts own receved LAP condton and compares t wth other gateway nodes, manly comparng the number of ts connectng gateway nodes, n determnes the coordnator after the frst round of comparson. For example, n fgure 7(a), the gateway nodes A, G, and H specfy,, and I as ther coordnators, and, and F desgnate as ther own coordnator. For A,, they have the same value of n, then select the node wth the lower total weght as the coordnator. In the second round of nteractons, each gateway node embeds ts own routng table n the LAP (optons feld) before broadcastng. Such nteracton process contnues untl the local area network generates a common coordnator. As shown n fgure 7(c), the gateway node can reach any gateway node wthn three hops, and therefore the gateway node s selected as the local coordnator. 5. Performance evaluaton 5.1. Smulaton envronment Ths paper uses the SUMO [7] and NS3 [8] smulaton platform to buld a typcal 3*3 urban road smulaton scenaro as shown n fgure 8 and 9 to verfy the performance of the CFSR protocol whch compares wth SV [9] and AOV [10]. It assumes that there s an ntersecton, two-drecton carrageway, four lanes n each drecton, ncludng left-turn lanes, straght lanes, and rght-turn lanes. The length of each road segment s 1000m, and a total of 9 crossroads are set. Table 1. Parameter settngs. Parameters Value Numbers of vehcles 500 Average speed of vehcles (km/h) 40 Communcaton range (m) 50 ~ 350 Smulaton tme (s) 300 The smulaton parameters are set out n Table 1 above. In the table, the total number of vehcles n the 3*3 sub-zone network s 500, whch s generated by dfferent nodes. The average speed of the 8

10 urban vehcles s set to 40 km/h, assumng that the communcaton range of each vehcle s m. The smulaton tme s set to 300s. Fgure 8. Urban road smulaton scenaro. Fgure 9. Urban road smulaton scenaro (SUMO) Performance metrcs We propose two performance metrcs to evaluate the CFSR protocol, ncludng end-to-end delay ( c ) and packet drop rato (p d ). c s defned as the average duraton of a packet from source to destnaton. p d s the rato of dscarded packets to total exstng packets. The relevant formulas are as follows. c = N success = 1, N success where N success s the number of packets that are sent successfully, N falure s the number of dropped packets, and s the delay of the th packet Smulaton results In the secton, we compare CFSR protocol wth AOV and SV, and smulaton results are as follows. p d = N N falure falure + N success. (18) Fgure 10. nd-to-end delay. Fgure 11. Packet droppng rate. The change of 2 relatve to the communcaton range s shown n fgure 10. We have observed that the average 2 of all protocols ncreases as the communcaton range becomes larger. Snce both AOV and SV use hop-by-hop forwardng, they can all lead to data congeston and thus ncrease 2. Snce the CFSR uses a clusterng structure, the data forwardng only passes through the cluster head and the gateway node, so the effcency s hgher and a lower 2 s provded. The relatonshp between the packet delvery rate and the maxmum communcaton range of the node s shown n fgure 11. We observe that the PR for all protocols decreases as the range of communcaton. The PR of AOV and SV s poor because the cost of route mantenance becomes large for large-scale networks and the hgh dynamcs of the vehcle, the effcency becomes very low, the lnk detecton s not tmely, and thus many packets are lost. The CFSR does not need to 9

11 mantan every node. It only needs to mantan the relevant nformaton of the cluster head and gateway nodes. In the route dscovery phase, the CFSR can quckly query the local coordnator related routes to establsh the routng path. The effcency s hgh, and the lnk s relable, so PR s hgher. 6. Concluson In ths paper, we propose the CFSR protocol based on the clusterng structure, ntroduce the lnk qualty assessment, the selecton process of the local coordnator, and establshes and updates the routng based on the weght dstrbuton. In the sub-zone, we use jkstra algorthm to buld the routng path. On the one hand, the optmal path of the routng s selected n the case of ensurng acceptable mantenance overhead, and on the other hand, sub-zone dvson s used to solve the local optmum problem and mantenance overhead of LAPs prolferaton. Fnally, performance comparson of the AOV, SV and CFSR protocols s made by usng SUMO and NS3. Smulaton results show that CFSR has lower 2 and hgher PR than the other protocols. Acknowledgments Ths work was supported n part by the Natonal Key R& Program of Chna under Grant No. 2016YF , NSFC under Grant Nos , and , Natonal Scence Foundaton for Innovatve Research Groups of Chna under Grant No References [1] Zeadally S, Hunt R, Chen Y S, et al. Vehcular ad hoc networks (VANTS): status, results, and challenges[j]. Telecommuncaton Systems, 2012, 50(4): [2] Cheng J J, Cheng J L, Zhou M C, et al. Routng n Internet of Vehcles: A Revew[J]. I Transactons on Intellgent Transportaton Systems, 2015, 16(5): [3] Sharef T, Alsaqour R A, Ismal M. Vehcular communcaton ad hoc routng protocols: A survey[j]. Journal of Network & Computer Applcatons, 2014, 40(1): [4] Togou M A, Hafd A, Khoukh L. SCRP: Stable CS-ased Routng Protocol for Urban Vehcular Ad Hoc Networks[J]. I Transactons on Intellgent Transportaton Systems, 2016, 17(5): [5] Abuashour A, Kadoch M. Performance Improvement of Cluster-ased Routng Protocol n VANT[J]. I Access, 2017: [6] Nasr M M M, Wang Z G, Shen L F. VANT Clusterng ased Routng Protocol Sutable for eserts[j]. Sensors, 2016, 16(4): 1-23 [7] SUMO: Smulaton of Urban Moblty, [Onlne]. Avalable: [8] The Network Smulator: ns3. [Onlne]. Avalable: [9] Perkns C, hagwat P. Hghly dynamc estnaton-sequenced stance-vector routng (SV) for moble computers[c]// Conference on Communcatons Archtectures, Protocols and Applcatons. ACM, 1994: [10] Perkns, eldngroyer. Ad hoc On-emand stance Vector (AOV) Routng[J]. Internet- raft, draft-etf-manet-aodv-13.txt, 2003, 6(7):90 10