State of the Art Routing Protocols in VANETs: A Review

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Procedia Computer Science 130 (2018) 689–694

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The 9th International AmbientNetworks Systems,and Networks and Technologies 9th International ConferenceConference on Ambienton Systems, Technologies, ANT-2018 and The 9th International Conference on Ambient Systems, Networks and Technologies (ANT 2018) the 8th International Conference on Sustainable Energy Information Technology, (ANT 2018) SEIT 2018, 8-11 May, 2018, Porto, Portugal

State of the Art Routing Protocols in VANETs: A Review State of the Art Routing Protocols in VANETs: A Review

Ishtiaq Wahidaa*, Ataul Aziz Ikrambb, Masood Ahmadaa, Sajjad Aliaa, Arshad Aliaa Ishtiaq Wahid *, Ataul Aziz Ikram , Masood Ahmad , Sajjad Ali , Arshad Ali a Department of Computer Science, Abdul Wali Khan University Mardan, 23200, Pakistan a Department of Computer Science, Abdul Wali Khan University Mardan, 23200,Islamabad, Pakistan 44000, Pakistan Department of Electrical Engineering, National University of Computer and Emerging Sciences b Department of Electrical Engineering, National University of Computer and Emerging Sciences Islamabad, 44000, Pakistan b

Abstract Abstract Quality of service in Vehicular ad-hoc Network (VANET) is primarily dependent on routing protocols. Maximum throughput, Quality of packet service loss in Vehicular ad-hoc overhead Network (VANET) is primarily on of routing throughput, minimum and controlled are the major ultimatedependent objectives each protocols. proposed Maximum routing protocol. The minimum packet lossdesigning and controlled overhead for areVANET the major ultimate each proposed routing The challenging factor in routing protocols is the frequentobjectives change in of network topology. A numberprotocol. of protocols challenging factor in been designing routing protocols for VANET frequent change network topology. A number of protocols and algorithms have proposed for VANETs so for. Most is of the these algorithms areinbased on either simulation or theory. In this and algorithms been proposed for VANETs so for. theseand algorithms arediscussed. based on either or theory. In this article, recentlyhave proposed routing protocols along withMost theirof pros cons are In thesimulation review process, network article, recently proposed routing along with their pros and cons are discussed. In the review process, network parameters, distance, speed, no. ofprotocols nodes, no. of hops, communication overhead, relative mobility, simulation parameters, parameters, distance, speed, no. of nodes, no. of metrics hops, communication overhead,arerelative mobility, simulationThe parameters, simulation tool used, mobility model, performance and compared protocols taken under consideration. article i s simulation tool used, performance metrics and compared protocols are taken under consideration. The article i s concluded with overallmobility findingsmodel, and future recommendations. concluded with overall findings and future recommendations. © 2018 The Authors. Published by Elsevier B.V. © 2018 The Authors. Published by Elsevier B.V. © 2018 The Authors. Published by B.V. Program Chairs. Peer-review of Elsevier the Conference Conference Peer-review under under responsibility responsibility of the Program Chairs. Peer-review under responsibility of the Conference Program Chairs. Keywords:VANET; Routing ; Protocols ; Mobility; QoS ; Keywords:VANET; Routing ; Protocols ; Mobility; QoS ;

1. Introduction 1. Introduction VANET routing protocols are broadly categorized into vehicle-to-vehicle-based (V2V) and vehicle-toVANET routing (V2I) protocols broadly categorized into V2V vehicle-to-vehicle-based infrastructure-based on theare basis of VANET architecture. is further categorized(V2V) on the and basis vehicle-toof routing infrastructure-based (V2I) on thestrategies basis of VANET architecture. is further on multicast, the basis of routing information’s and transmission into topology based, V2V position basedcategorized and unicast, broadcast information’s and transmission strategies into topology based, position based and unicast, multicast, broadcast

* Corresponding author. Tel.: +92-345-936; fax: +0-000-000-0000 . * Corresponding Tel.: +92-345-936; fax: +0-000-000-0000 . E-mail address:author. [email protected] E-mail address: [email protected] 1877-0509 © 2018 The Authors. Published by Elsevier B.V. 1877-0509 ©under 2018responsibility The Authors. of Published by Elsevier B.V. Chairs. Peer-review the Conference Program Peer-review under responsibility of the Conference Program Chairs.

1877-0509 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the Conference Program Chairs. 10.1016/j.procs.2018.04.121

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respectively1. Literature further categorizes routing protocols as being either proactive, reactive or hybrid 2. Another classification is power aware routing protocols and predictive mobility protocols designed for efficient utilization of limited resources and quality of service improvement. For a centralized control there are cluster based routing protocols. Topology based or position based protocols are designed for efficient routing with low latency and no congestion. Why does the need for these protocols arise? The answer is, in ad hoc networks routing is responsible for initiating and maintaining routes with features of mobility support, bandwidth limitations and power constraints3. Secondly these protocols are designed for different scenarios, but the VANET has a dynamic topology and at run time the network may attain any kind of scenario. Dynamic topology conflict the routing algorithm in Ad-hoc Networks4. 2. Routing Protocols in VANETs The continuous research is in progress to improve routing, considering various aspects and challenging features of VANETs. This section of the article presents these designing considerations and the strategy adopted in each proposed scheme along with their limitations. This will help out new researchers of the area to analyze existing state of the art proposed schemes. Regardless of classification some randomly selected proposed routing schemes are described in the subsections below. Table in the end of each subsection shows simulation, routing and scenario parameters of the studied proposed routing scheme. 2.1. Grid based predictive geographical routing (GPGR) protocol V2V communication is multi-hop communication among wirelessly connected vehicles without any fixed infrastructure5. Data packets in VANET are passed through relay nodes from source to destination. The rapid change in topology and other features of VANET i.e. constrained movement of nodes due to obstacle, roads and traffic signals in urban areas causes frequent link breakage6. This shows that existing MANET routing protocols are not suitable for VANET. Geographical routing protocol Greedy Perimeter Statless Routing (GPSR) is more suitable to be used in such scenarios7. As compared to per-destination routing entries, geographical forwarding only keeps local information’s of the neighbours. The issue with these geographical routing protocols is the local maximum caused by the protocols relay node selection criteria that is select the nearest to destination node as relay. 8 Propose grid based predictive geographical routing (GPGR) protocol to cope these issues. It divides the road into two dimensional grid using map. GPGR use road grid during relay selection process and predict the moving position of the node considering all possible node movements. The next position of the node is predictable in this way and optimal relay node can be selected. Ns-2 is used as simulation tool and the performance is checked in terms of packet delivery rate and link breakage rate with probability of local maximum. The proposed protocol is based on single scenario and the VANET with dynamic topology and high speed characteristics can attain different operational scenario. The proposed protocol is simulated for two performance parameters, link breakage and packet delivery rate where the study of the protocol shows that it will increase the processing and must be checked for latency and delay. Real time applications may suffer in case of latency. 2.2. Proposes hybrid location based ad hoc routing (HLAR) protocol Variation in vehicle density, scalability and wireless channel fading are the issues that have made efficient routing in VANET challenging. The mentioned issues are the outcome of nodes high speed and natural obstacle in the urban scenarios. A sufficient amount research work is focused on realistic mobility and propagation models 9-14. These works draw attention to some of the important issues that new VANET routing protocols are facing. Topology based routing and geographic/position based routing are the two main categories in VANET routing protocols 15-18. Topology based routing protocols forward data packets using link state information. Ad hoc ondemand distance vector (AODV) topology based protocol outperforms other in low routing overhead 9, 19-21. Scalability is common problem among all topology based routing protocols 20. Geographic based routing protocols are not table driven and do not shares link state information’s. These overcome the problem of scalability.



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Proposes hybrid location based ad hoc routing (HLAR) protocol designed to cope the problem of scalability. It combines the worthy features of reactive topology based routing and geographic routing. The protocol switches to reactive when the geographic information is degraded. Through simulation the protocol is validated for scalability and low routing overhead. Most of the VANET applications required real time communication. Initial rout establishment causes delay in reactive routing. The protocol is only checked for routing overhead and scalability, packet loss and latency parameters are not checked in the simulation. The average speed of nodes is kept constant for different scenarios where it should vary because the speed of nodes in streets and multiline high way are not supposed to be same. This will lead nonrealistic results in simulation. 22

Article

Performance Metrics

Protocols in Comparison

Simulation metrics

Transmission Range

Operationa l Scenarios

Speed

No. of Nodes

Simulation Tool

Topolog y size

22

Routing overhead, pkt delivery , end to end delay

AODV-ETX, MTL

Bandwidth = 2 mbps, data rate = 8 kbps

150-250 m

Gaussian, Rayleigh, Uniform

40-100 km/h

40-240

NA

NA

8

Packet delivery rate, link breakage rate,

GPSR, GPUR, GPCR

Bandwidth = 2 mbps, packet size 1000 bytes

125 m

Urban city with traffic signals

0-80 km/h

100200

Ns-2

700*100 0 m2

23

Packet delivery rate, end to end delay, routing HO latency, overhead packet loss, HO jitter, msg overhead Packet delivery ratio, link failures, routing request ratio, Packet average end delivery to end routing delay ratio, overhead and end to end delay

GPSR, GyTAR

Transmissi on rate = 12 mbps, Packet size = 512 byte, Pkt Packet life size=320 time= 500b, Pkt ms rate = 100 pkt/s

250 m

City map

NA

6-12 per lane/k m

Matlab

7000 * 7000 m2

WiMAX = 1000 m, WLAN = 300 m

Highway with four lanes

5-100 km/h

0-100

Ns-2

1000 m * 1000 m

Packe size= 1500 bytes, data rate = 128 kb/s Packet size = 512 byets, simulation time = 2000 sec

NA

Highway with three lanes

40,60 and 80 km/h

30

OMNet++

5000 m highway

NA

Urban traffic scenario with streets

NA

25, 50, 75 and 100

NS2, VanetMobi Sim and AWK

500 m * 500 m

24

25

26

NEMO, fast NEMO

AODV, PBR

AODV, AMODV and GPSR

2.3. Intersection based traffic aware routing protocol (iCAR) Intelligent Transportation System (ITS) applications are categorized into one-hop that are usually used to pass information notifications to nearby vehicle and multi hop applications used in internet access, V2V communication and V2I communication. Multi hop applications reliability in VANET strongly concern with efficient routing. VANET highly dynamic topology is a challenge in the design of efficient multi hop routing. To cope these problems, CarTalk 200027, GEOGRAPHIC SOURCE ROUTING (GSR)21, GPSR28, A-STAR29, GyTAR30, EGyTAR31, STAR32 and NoW33 routing schemes are proposed by different research groups and communication projects. In routing protocols mostly priority is given to dense roads in road selection criterion. This leads to congestion as data routing converge to roads having high density. The vehicle itself is an obstacle and vehicular density may cause transmission failure. 23 Propose an intersection based traffic aware routing protocol (iCAR). iCAR is designed to improve overall performance in city scenarios utilizing offline map and real time traffic information’s. iCAR routing

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decision is based on vehicular density along with average communication delay. It distributes the data packet in the network evenly by avoiding selection of high density roads with high volume of data as forwarding path. The sparse traffic in VANET multi hop communication may leads to frequent disconnections. The simulation is supposed to check the performance for those parameters as well which have the possibility of degradation. In this particular scheme link breakage rate must be checked before the claim of overall performance improvement. The improvement of one parameter on degradation cost of another parameter is not desired. 2.4. Enhancement in network mobility (NEMO) protocol Seamless handoff in IP-based networks can be achieved only if the assignment and reassignment process of IP to mobile node (MN) is efficient. In V2I communication internet connectivity is provided to the vehicles. Vehicle speed is high on highways therefore seamless handoff and stable connection to the internet is a problem. MIPv4 34, MIPv635 and HMIPv636 are the gradually improved series of protocols that are developed in connection to seamlessly process handoff and provide stable internet to the vehicle. MIPv6 handle terminal mobility only. To accommodate network mobility (NEMO) in MIPv6 Internet Engineering Task Force (ITEF) request for comments is extended called NEMO basic support protocol. 24 Proposed an enhancement in NEMO to reduce vertical handoff latency. The V2V communication is utilized to initiate the handoff process. The vehicles play the role of relay for each other in the handoff process with the fixed infrastructure. In this pre handoff process the author claims that the overall latency will be reduced. Two networks WiMAX and Wi-Fi are used in the simulation process and the designed protocol is checked for the handoff latency, message overhead, packet loss, throughput, and handoff jitter performance metrics. MN binding update messaging to the home agent (HA) increases the traffic signaling. The V2V communication has its own application data traffic and the additional responsibility of being act as relay for the pre-handoff process will increase the communication overhead. Secondly, if the MN has two neighbors’ nodes ahead opposite in direction to each other, one is entering into the MN network and one is leaving the MN network, what will be the MN decision about handoff in this situation? 2.5. Evolving Graph Reliable Ad Hoc On-Demand Distance Vector Routing Protocol (EG-RAODV) The network topology is changed when the vehicles in the VANET change their lanes and/or velocity. Depending on the conditions of the road and drivers the changes take up and did not usually scheduled in advance. Graph theory is very efficient to analyze VANET dynamic topology. The evolving graph is a graph theoretical model able to capture the dynamic behavior of dynamic network whose mobility is predictable37, 38. Using the underlying road network and vehicle information the VANET dynamics can be esteemed. Hence, considering VANET as predicted pattern dynamic network evolving graph model can be used to design an efficient routing scheme. 25 Propose Evolving Graph Reliable Ad Hoc On-Demand Distance Vector Routing Protocol (EG-RAODV) based on own proposed model VANET oriented Evolving Graph (VoEG). An algorithm based on VoEG establishes the most reliable route from source to destination to maintain the overall QoS in VANET. The OMNet++ simulator is used to validate the proposed protocol for different QoS performance metrics. Evolving graph is applicable to those networks that topology dynamics are predictable at different time intervals. The author considers VANET topology as predictable, but the consideration that VANET can be categorized under fixed scheduled dynamic network (FSDNs) is not justified. The proposed protocol is not compared with the recent routing protocols for performance. 2.6. Mobility Aware Zone based Ant Colony Optimization Routing for VANET (MAZACORNET) VANET routing protocols can be identified as single path, carry and forward path or multi-path routing. Ad hoc On-Demand Multipath Distance Vector (AOMDV)39, S-AOMDV 40, AODVM 41 multi-path routing algorithms are the improved versions of AODV. These are non scalable reactive protocols. S-AOMDV uses additional packets for the improvement of route discovery and route failures, results in traffic congestion and under-use of the bandwidth.



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Various works in MANET 42, 43 have demonstrated that nature inspired algorithms such as ant colony based optimization (ACO), can be successfully used for designing efficient routing algorithms.44, 45 Find these algorithms more beneficial as compared to other routing algorithms. They share local information to cut down the routing overhead by for future routing decisions. In case of link failure on the previously chosen route, these algorithms offer multiple paths enabling selection of another path. 26 propose Mobility Aware Zone based Ant Colony Optimization Routing for VANET (MAZACORNET) is a hybrid routing algorithm 43 that divide the nodes into zones that makes efficient utilization of the bandwidth. MAZACORNET employ a proactive approach within a zone and reactive approach between zones to find routes. It utilizes local information stored in each zone, which reduce broadcast messaging and congestion. Vehicle’s movement pattern, density, velocity and fading conditions are used to build up multi-path algorithm; Mobility Aware Zone based Ant Colony Optimization Routing for VANET (MAZACORNET). The authors have mentioned in the paper that according to their knowledge Mobility-aware ant colony optimization routing algorithm for vehicular ad hoc networks (MAR-DYMO)46 is the only nature inspired routing algorithm for VANET and in simulation they have missed this algorithm for comparison. The proposed algorithm is close to cluster based routing and it is not compared with the existing cluster based algorithms. The speed of nodes and transmission range of the nodes is not mentioned. 3. Conclusion The literature shows that routing protocol performance in the ad-hoc network depends greatly on the operational scenario. Change in an operational environment cause effect on routing performance positively or negatively. This variation is higher in VANET due to its high speed feature. The operational scenario may either be constrained or statistical and city or highway. The city scenario is constrained due to obstacles and the vehicle passes through different streets or link roads where vehicle mobility in highway scenario is mostly random. The comparison among routing protocols has been drawn in many articles47, 48. Mostly routing algorithms optimize one parameter only3. The research articles 3, 4over the performance of routing protocols shows that one particular routing protocol outperforms the others in a particular mobility scenario and for a particular performance metric. Similarly another particular routing protocol may outperform others in another scenario. The mobility model plays an important role in the performance study of the vehicular ad-hoc Networks 49. It is concluded that the operational environment and desired performance matrices need to be properly analyzed for the designing of routing protocol. References 1.

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