evaluation of ad hoc routing protocols in vehicular using opnet

7/26/2019 Evaluation of Ad Hoc Routing Protocols in Vehicular Using Opnet

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Evaluation of ad-hoc routing protocols in vehicular

ad-hoc network using OPNET

Xiaozhou FangInternational School

Beijing University of Posts and Telecommunications

Beijing, China

[email protected]

K K Chai, Y Alfadhl, Y SunSchool of Electronic Engineering and Computer Science

Queen Mary, University of London

London, UK

[email protected]

AbstractVehicular Ad-hoc NETwork (VANET) is becoming a

promising technology in which moving vehicles are able to

exchange information between them without the need of

infrastructure. The original idea of VANET is for the safety

purposes such as warning the drivers when there is an accident

happened in the front of the road. Nowadays, VANET is

extended to offer more services like downloading emails transfer,

assessing Internet and Global Positioning System (GPS) services.To make sure that information transmitted correctly, an efficient

routing protocol is crucial and indispensable for coping with the

rapid topology changes. In this paper, we developed an OPNET

model to evaluate the VANET performance of Ad-hoc On-

demand Distance Vector (AODV) and Dynamic Source Routing

(DSR) protocols in the city with different scenarios. We found out

that AODV outperforms DSR protocol in VANET with

increasing vehicles.

Keywords-Ad-hoc routing protocol; Vehicular Ad-hoc Network;

AODV; DSR; network simulation

I. INTRODUCTION

Vehicle-to-vehicle (V2V) communications have gained highinterest in recent years to provide a prospective that vehiclesare able to receive traffic information without fixedinfrastructure. In the VANET, the vehicles are equipped withon board unit (OBU) where serves as both router and terminalfunctions, that is able to communicate with the distant vehiclesvia intermediate vehicles through packet forwarding [1].

VANETs are proposed to offer wide range of applicationslike safety warning, traffic information broadcasting andInternet surfing. However, all these applications can only berealised if the packet routing protocol can meet the minimumQoS requirements. In most of previous work such as [2], theywere focusing on Mobile Ad-hoc Network (MANET) wherethe movements of nodes are random and totally different from

the realistic predefined vehicles' trajectories. In order to betterevaluate the routing protocols and get more realistic simulationresults, we developed VANET model and RSU model inOPNET Modeler 14.5.

The first contribution of this paper is the authors haveevaluated the two most commonly used ad hoc routingprotocols: Ad-hoc On Demand Vector (AODV) and DynamicSource Routing (DSR) protocols for VANET environments.The second contribution is, the authors have defined the vehicle

nodes which have to obey the traffic light signal and beendriven on the predefined roads, instead of random movingnodes that defined in most of the MANET projects.

The rest of this paper is organized as follow: In section II,

we briefly introduce the ad hoc routing protocols. Section III

discusses the design of the vehicular scenarios with traffic

signal mechanism and vehicles trajectories. The OPNETimplementation is presented in section VI. We present the

simulation results in section V and then we draw conclusion in

section VI.

II.

AD-HOC ROUTING PROTOCOLS

Packet routing is a process of discovering available pathsfor packets to go through and reach the destination in anefficient route. As for ad-hoc routing protocols, they can bemainly divided into two categories: Table-Driven protocols andDemand-Driven protocols. The main difference between table-driven and demand-driven routing protocols is the way ofstoring routing table information. Table-driven routingprotocols always attempt to update the routing table to maintainthe consistent overview of the whole network. On the otherhand, demand-Driven routing protocols only create routes thatare desired and hence the routing table information is only keptfor very short period of time in most cases [3].

In VANET, topology changes frequently because ofindividual driving behaviors. Thus, the latest routing tablewhich requires consistent update information in table-driven isconsidered to be efficient. Thus, in this paper, we only focus onthe performance of demand-driven routing protocols inVANET. AODV and DSR routing protocols will be introducedseparately in the following section.

AODV routing protocol

AODV routing protocol is an improvement on Destination-Sequenced Distance Vector (DSDV) protocol. AODVmaintains overall routing tables in the nodes and onlyestablishes routes when two nodes require a connection.AODV is classified as a pure on-demand route acquisitionsystem [4], because few routing information is stored in thenodes that are not on the selected route. A distinctive feature ofAODV is that it uses sequence number in routing discoveryprocess to avoid the counting to infinity problem [5].

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There are three types of message are used in AODV

routing process: Route Request (RREQ), Route Reply (RREP)

and Route Error (RERR). The network keeps silent until the

source node needs to communicate with the destination node.

If no valid route existed, route discovery process will be

initiated. The source node then broadcasts RREQs to its

neighbours, which will also forward this RREQ to their

neighbours and so on, until the RREQ reaches the destination

or an intermediate node which contains valid route to thedestination. Each node will assign sequence number and

broadcast ID. The sequence number will be increased along

the path with every RREQ generated. Therefore, RREQ can be

identified based on broadcast ID and the IP address of source

node.

When RREQ reaches the destination or intermediate node

having an active route, it will reply back to the source. All

other RREQs arrive later from other nodes will be discarded.

When a link failure is detected by upstream node in the

network, RERR will be fed back to the source node and new

route discovery process will be initiated upon receives of

RERR.

DSR protocol

Dynamic Source Routing (DSR) protocol is a Demand-Driven routing protocol based on the concept of source routing[6]. It is a simple ad hoc routing protocol because it cachesrouting information in each node even though it is on-demandbasis. The cached routing information indicates existed route inthe network and it will be updated when any routes arediscovered. Because of the cached routing information, theoverhead is minimized for periodic information transmission.

DSR protocol composes two main processes: Route

discovery and Route maintenance. The same as AODV

protocol, the RREQ and RREP messages are used in DSRroute discovery process. Before sending RREQ, source node

will consult its routing cache to check whether there is any

unexpired routes can be used. If there is no available existing

route in the cache then the source node starts to broadcast

RREQ which contains a unique ID number and the addresses

of both source and destination node. Upon receive RREQ, the

node checks for any valid route to the destination. The process

continues to pass RREQ to the next nodes until it reaches final

destination or node that consists of the route to the destination.

The nodes on the route may receive several RREQs labelled

with same ID number but different route record due to the

broadcast mechanism from the source node. In this situation,

nodes only forward the first arrival of RREQ in which theiraddresses have not been recorded.

When the RREQ reach the destination or intermediate node

which holds an unexpired route to the destination, RREP

contains route message will be generated and forwarded back

to source. If it is an intermediate node then the route

information will be added in the RREP.

III. OVERALL DESIGN OF THE SIMULATION

We created two projects that include 14 scenarios. The firstproject is named VANET_1, which AODV and DSR protocolsare applied. The second project is called VANET_RSU, whichevaluates the VANET performance with RSU.

A. VANET_1

VANET_1 is the main project for analysing routing

protocols behaviour in VANET environment, in which detailslike traffic light signal and vehicular traces are beingconsidered.

Layout of the city scenario

In the design of scenarios, we assume that VANET_1 isapplied in the city centre. Thus, particular events, such as roadpattern and traffic light, should be taken into account. In orderto simplify the city centre scenarios, we designed a 3km*3kmarea which has 4 crossroads and 12 road segments--1km longof each. Also there are traffic lights equipped at the junction oftwo road segments; sum up to be 8 traffic lights in the entirearea. Fig.1 shows the virtual map of this city scenario.

Figure 1. Layout of city scenario with traffic signal

Traffic Control Mechanism

The most common element in traffic control mechanism is

traffic light. In the Fig.1, all the traffic lights are labeled withnumbers from T1 to T8. The time span of light switching is 1minute. The signals of two traffic lights located in the samecrossroad are complementary. The vehicles have four choiceswhen they approach crossroad: turning left, turning right,passing through and stop. A traffic turning mechanism is set infor vehicles to follow. When the traffic light is GREEN,vehicles can turn left or go through. When the traffic light isRED, vehicles can only turn right; otherwise they have to stopto wait until the light change. For example, in Fig.1, onevehicle on S3 is approaching T3 can directly turn right at 1minute and 45 seconds when light is red. Table 1shows thetraffic switching time interval.

TABLE I. SWITCH TIME IN TRAFFIC LIGHT IN MINUTE(S)

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Property Design of Vehicles in Network

The number of nodes has direct impacperformance in VANET. With a higher veconnectivity in the network will be better.with different number of vehicles have besimulated in OPNET.

Movement of vehicles in VANET can be

most distinguish feature compared with Mtraffic simulation can generally be classifiedand microscopic approach [7]. Macroscopicon the overall network performance, wapproach concerns on the individual movesimulation, accurate vehicle position is reqprotocols and therefore we follow the microsc

In order to simulate the traffic condition iwe proposed an action rule based on thsituation. This action rule is used to determactions.

Fig. 2 (i) shows the percentage of vehiAccording to the rule, 60% of vehicles

through the 3km*3km area, slightly greater tAmong the 40% of vehicles which take turtake only 1 turning and 15% take 2 turnings inFig. 2 (ii) is the percentage of vehicle leavinginitial network contains 60% vehicles which athe network. Among these 60% of vehicles, 3leave the network via a long distance way awill take the shortest one. Meanwhile, 40% oare out of the network at the beginningnetwork after different interval from 10 secon

Figure 2. Action rules of vehicle movement i

Fig. 3 shows the samples of the VANETand 100 vehicles respectively. The red vehinode that sending traffic information during ithe initial locations of vehicles inside the netassigned. When the simulation begins, vehiclalong with their trajectories, which are alreaconsidering the traffic situation in urban abehavior, we set the range of velocity from 0 t

Through60% Twoturnings

15%

O

tur

25Turning40%

i) Ratio of vehicles taking turn

Getting

in

40%

Long

distance

35%Sh

dist

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ii) Ratio of vehicles leaving network

on the routingicle density, theultiple scenariosn designed and

considered as the

NET. Vehicularas macroscopicpproach focusesile microscopicent. In VANETired for routingpic approach.

n real city roads,general traffic

ine the vehicles

cle take turning.ill directly pass

an the 40% left.ing, about 25%their trajectories.

the network. There going to leave% of which willd 25% of whichf vehicles whichill get into thes to 4 minutes.

n VANET

opology with 40cle is the sources movement. Allork are random

es start to movey defined. After

rea and drivers50 km/hr.

Figure 3. Topology of VANETs

Design of data source and transmis

The data generation processsimulation. In this simulation,transmitted in VANET is assumedthis reason, raw packets areinformation forwarded in the VAsimulation result more concise, onlwill generate traffic information.

One of the factors that influperformance is the transmission ratransmission range increase, fewersource and destination. Thus it cannetwork connectivity and reducewider range of data transmission recould create higher interferencetransmission range in VANET is dmeters so we set the 200 meters as t

B.

VANET_RSU Project

The aim of this project is to eRSUs implemented in original Vthe work, only AODV protocol is

is a device which has great potensuch as traffic analyses, real-timeIn addition to that, RSUs can alsoVANET to forward data, especiaconnectivity within the network iserve as an intermediate node tdestination.

In the VANET_RSU project, 16in the simulation scenarios containRSUs are located at the middle ofintersections. All of these RSUs cocable link to form a ring network.equipped with RSU (tower icon) in

With RSUs, one vehicle moving iwill find an intermediate node, noin 250 meters.

e

ing

%

ort

ance

%

ith 40 and 100 vehicles

sion in VANET

is essential in VANETthe traffic information

to be relatively simply. Forsed to represent trafficET. In order to make theone vehicle in the network

nces the routing protocolge of the vehicles. As thehops are required betweenhelp to improve the overallthe bandwidth. However,

quires higher power, whichin the system. Since theefined between 100 to 300e range in the simulation.

aluate the performance ofNET. In order to simplifypplied in this project. RSU

ial for improving VANETonitoring and access point.act as a fixed node in thelly in the time when the

weak, RSUs are used toconnect the source and

RSU models are equippeding 20 and 40 vehicles. 12road segments and 4 at thenected with each other viaThe topology of VANET

OPNET is shown in Fig. 4.

the centre of the networkatter fixed or mobile one,

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Figure 4. Topology of VANETs equipped with RSUs

IV.

IMPLEMENTATION IN OPNET

In order to evaluate the performance of AODV and DSRprotocols in VANET, OPNET Modeler 14.5 is used [8].Sections below explain the implementation of two projects inOPNET Modeler 14.5 with details.

A.

Vehicle and RSU Models

In OPNET, manet_station_adv mobile node model is

selected to represent the vehicle in the network. This nodemodel has a raw packet generator which can transmit packetover IP and WLAN. As to the movement of nodes, trajectoriesof all the vehicles are defined manually instead of applying therandom waypoint in OPNET. By following the action rule,specifications of trajectory such as speed, waiting time are setindividually.

The red car labeled as S_0 is the source node that sendstraffic information. In addition, rx_config model is used todefine the transmission range of nodes.

Since the functionality of RSU is similar with a router,manet_gtwy_wlan_ethernet_slip4 fixed node model is used asthe prototype. Link ppp_28k, as a duplex point-to-point link

model, is used to connect these route models. The mostessential thing of RSU implementations is that the BSSidentifiers of all the nodes in one VANET must be the same,indicating they are in the same network. In addition, the AccessPoint Functionality in the RSUs must set to be Disable.Otherwise, errors will be detected during the simulation.

B.Raw Packet Generation and Protocols Assignment

As mentioned above, manet_station_adv model has aMANET Traffic Generation Parameter which can be used togenerate data packets. Multiple generation processes withdifferent destinations are set in this parameter. The destinationis identified by IP address. Thus, individual IP addresses, from192.1.1.1 to 192.1.1.X are assigned to vehicles in the network.

The packet transmit interval and packet size obey theexponential distribution with the mean outcome of 1 secondand 1024 bits.

OPNET Modeler 14.5 provides several ad-hoc routingprotocols in MANET models. In this simulation, AODV andDSR are selected for performance analyzing. In differentscenarios, either AODV or DSR protocols is selected in vehicleand RSU models. The settings of protocols remain default.

TABLE II. CONFIGURATION OF SCENARIOS IN TWO PROJECTS

C.

Simulation Statistics and Project Configurations

Before simulation running, statistics collection isindispensable. There are two types of results, Global Statisticsand Object Statistics in OPNET Modeler. Global Statistics usedfor entire network evaluation while Object Statistics used foranalyzing particular model. In VANET project, two globalstatistics are selected for routing protocols analysis: Delay andThroughput.

In order to evaluate the performance of AODV and DSRrouting protocols, a variety of scenarios with differentparameters are generated. Table 2 above shows the basicconfiguration of all 14 scenarios in three projects.

V. SIMULATION RESULTS

Fig. 5 demonstrates AODV performance in VANET_1project (throughput is shown in log distribution form).We can

observe that with more vehicles running in the VANETs,throughputs of network increased significantly, especially thethroughput variation from 40 to 60 vehicles. After the vehiclesnumber increased from 60 to 100, the results show the sametrend which decreased at the first, then increased to themaximum and finally decreased again. Also, we can easilyobserve that the results of VANET with 20 and 40 vehiclesappeared late at around 1 minute, which is because of the poorconnectivity in these two scenarios at the beginning.

We also can see average end-to-end delay in Fig. 5 againstnumber of vehicles. The trends in VANETs with 60, 80 and100 vehicles are quite similar. The overall delay slightlyincreases as the number of vehicles increased. The delay in

AODV_20 and AODV_40 begins to decreases around 1 minuteprobably due to poor connectivity during that time. After thesource node move into centre area of the network whereadjacent vehicles increased, more routes can be established,leading to delay decreased in the entire network.

Project

Scenario

name

Size

(km)

Num.

of

Vehicle

Num

of

RSU

Statistics

selection

Simulation

time

(minute)

VANET

_1

AODV_20

3*3

20

0

Delay,

Throug

h-put

5

AODV_40 40

AODV_60 60

AODV_80 80

AODV_100 100

DSR_20 20

DSR_40 40

DSR_60 60

DSR_80 80

DSR_100 100

VANET

_RSU

RSU_20

3*3

2016 Throug

h-put,

Delay

5RSU_40 40

No_20 200No_40 40

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Figure 5. Throughput and Delay of VANETs applying AODV

DSR performance is demonstrated in Fig. 6 in which boththroughput and delay are shown in log distribution form. Wecan see the diversity of trend appears after the number ofvehicles increased to 60 and above. We can see that thethroughput becomes higher when the number of vehiclesincreased. Meanwhile, we can find dips of throughput in thefirst minute of AODV_60, 80 and 100. The possible reason forthis is that V_0 were moving into an area in which the vehicledensity is low. And also that is the reason why AODV_20 andAODV _40, in which fewer vehicles can be served asintermediate nodes, had no result at around 1 minute.

The average end-to-end delay of DSR in Fig. 6 shows thatin DSR_20, 40 and 60 keep falling as the time goes on.However, with the number of vehicle increased, delay in DSRascended sharply and suddenly after first minute. One possiblereason is that DSR protocol requires more update informationfor route cache maintenance. With more vehicles in thenetwork, the topology change is more frequent and thereforethe time used to refresh the route cache increased.

Figure 6. Throughput and Delayof VANETs applying DSR

In the result of throughput, we find out that AODV andDSR perform more or less in the same curve. All thethroughputs of AODV are about 10% higher than that of DSRin the same VANET except for the one contains 100 vehicles.The throughput of DSR in VANET with 100 vehicles gothigher and reaches 1Mbps while the AODV one slightly fallsdown. These results clearly demonstrate the effect of vehicledensity to DSR performance. As to delay evaluation, all delaysof VANETs containing 20, 40 and 60 vehicles are high at thebeginning. After the routing table is updated, the time for routediscovery descent rapidly and therefore the end-to-end delayfall to a stable level. However, most significant differencecomes to the VANETs contain 80 and 100 vehicles. In these

two VANETs, we can see that the delay of DSR increases afterthe middle of the simulation. On the contrary, delay of AODVin both VANETs decline to less than 5ms.

All in all, we can summarize that AODV suffers nearly thesame delay as DSR while provides higher throughput in lowand medium vehicle density. In high vehicle density situation,high throughput obtained in DSR requires cost of high delay.

The results of VANET applying RSUs are represented inFig. 7 and Fig. 8, in which delay and throughput are included.The delay performances in both VANET projects using RSUdecline consistently and hold in a stable level at 0.5ms, whichis lower than VANET without RSU. The results also indicatethat RSUs improve the connectivity of entire network sincedelay value appears at the start of simulation. The significantperformance difference is throughput between VANETs withand without RSUs. Compared with original VANET, thethroughputs in VANETs using RSUs keep in a relative highlevel. However, the values in original VANET are less than5Kbps. Also, we can find out that RSUs solved the non-throughput problem appeared in original network at the verybeginning of simulation. A dig of result in VANETs with RSU

indicates that RSU, to some extent, can improve theconnectivity in VANET.

Figure 7. Comparative analysis of VANET_RSU with 20 vehicles

Figure 8. Comparative analysis of VANET_RSU with 40 vehicles

VI. CONCLUSION

In this paper, performances of AODV and DSR protocols inthe city scenario of VANET are evaluated in OPNET Modeler14.5. Entire VANET, containing traffic signal mechanism,vehicle model and RSU model, was developed in OPNET.Based on the results and analysis, we can find out that AODVoutperforms DSR protocol in VANET by providing sufficientthroughput with lower delay. In addition, simulation results

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show that RSUs applied in VANET to some extent canimprove the overall network efficiency in data delivery. Andwe believe that VANET or InVANET will play an importantrole in future city for improving the overall traffic situation.

REFERENCES

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Rajput, M. Khatri, P. Shastri, A. Solanki, K.,"Comparison of Ad-hocReactive Routing Protocols using OPNET Modeler"ComputerInformation Systems and Industrial Management Applications (CISIM),Krackow, pp.530 - 534, 2010

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J. Broch, D. A. Maltz, D. B. Johnson, Y.-C. Hu, J. Jetcheva, "Aperformance comparison of multi-hop wireless ad hoc networks routingprotocols", In Proc. of MOBICOM 98, Dallas, Tx, pp. 85-97, 1998.

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C. E. Perkins & E. M. Royer, Ad-hoc On-Demand Distance VectorRouting, Proc. 2nd IEEE Wksp. Mobile Comp. Sys. And Apps., Feb.1999, pp. 90100.

[5] Das S. Perkins C.E., Belding-Royer E.M. Ad-hoc on-demand

distance vector (AODV) routing.RFC 3561, IETF NetworkWorking Group, 2003.

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D. B. Johnson and D. A. Maltz, Dynamic Source Routing in Ad HocWireless Networks, Mobile Computing , Chapter 5, pp. 153-181,Kluwer Academic Publishers, 1996.

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evaluation of ad hoc routing protocols in vehicular using opnet

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