The Comparative Analysis of Velocity and Density in VANET Using Prediction-Based Intelligent Routing Algorithms Mohammad Reza Jabbarpour 1 , Hossein Malakooti 2 , Masumeh Taheri 3 and Rafidah Md Noor 4 1, 2, 3, 4 Faculty of Computer Science and Information Technology, University of Malaya, Kuala Lumpur, 50603 Malaysia 1 reza.jabbarpour, 2 hossein.malakooti, 3 masumeh.taheri{@siswa.um.edu.my}, 4 fidah@um.edu.my Abstract— Recently, VANETs are getting more attraction in both academic and industry settings. One of the challenging issues in this domain is routing algorithms. They become even more challenging, when they get benefit from intelligent solutions to predict the most stable node in the network to communicate with. There are several contributing factors which have influence on this process; including density, velocity, location, and distance. To the best of our knowledge, density, and velocity have the most impact on the precision of an intelligent routing algorithm for VANET. In this paper, we investigate how density along with velocity can affect two major classes of intelligent prediction- based routing algorithms in vehicular networks. These types of algorithms are divided into velocity-based and density-based groups. Different scenarios have been performed through NS2 in order to realize how each category of algorithms can be affected by both velocity and density at the same time. The obtained results are then illustrated in graphs based on delay and packet delivery ratio as routing performance indicators. Keywords—vehicular network; velocity; density; routing; prediction; simulation I. INTRODUCTION Vehicular Ad hoc Network (VANET) is a subclass of Mobile Ad hoc Network (MANET) that enables vehicles to send/receive messages between each other (Vehicle-to-vehicle communication) and/or infrastructure (Vehicle-to- infrastructure communication). These kinds of networks attract car factories’ and researchers’ attention due to increasing number of vehicles on the roads. VANETs are designed to increase drivers and passengers’ safety and comfort. Dedicated Short Range Communications (DSRC) Service uses the frequency range of 5.850-5.925 GHz [1] for wireless communications in VANETs. VANETs are a challenging research area for scholars due to its unique characteristics such as: high mobility, fast topology changes, abundant energy source, unreliable communication media and time-sensitive data exchange. Packet or data routing is one of the major issues in VANETs because of aforementioned characteristics. Routing protocols in VANETs can be classified into six classes: 1) Topology based protocols: They find the routes between nodes and save them in neighboring table before sending data. This class can be further classified into reactive, proactive and hybrid protocols. Fisheye State Routing (FSR) [2], Optimized Link State Routing protocol (OLSR) [3] and Ad hoc On-Demand Distance Vector (AODV) Routing [4] protocols are some examples of this class. 2) Position based protocols: They utilize geographic positioning information in order to find the successive forwarding nodes, thus, there is no requirement to establish and save a rout between source and destination. This class can be further divided into greedy and delay tolerant protocols. Because of above mentioned advantage, many protocols have been proposed in this class like: Greedy Perimeter Stateless Routing (GPSR) [5], Geographic Source Routing (GSR) [6], Greedy Traffic Aware Routing (GyTAR) [7], Anchor-based Street and Traffic Aware Routing (A-STAR) [8] and Greedy Perimeter Coordinator Routing (GPCR) [9]. 3) Cluster based protocols: In these kinds of protocols, close vehicles try to make a cluster with each other. One of these vehicles is selected as cluster-head which responsible to manage and broadcast the intra/inter-cluster messages. Scalability is the advantage of cluster based protocols, while, high overhead and delay are their disadvantages in high mobility networks like VANETs. Cluster Based Location Routing (CBLR) [10] and Cluster Based Routing (BCR) [11] are two examples of this class. 4) Geo-cast based protocols: They try to send messages to a group of vehicles in a specific geographic area. They are similar to multicast routing. Suitable forwarding can be avoided by unfavorable neighbor nodes and partitioning which are two drawbacks in Geo-cast protocols. Robust Vehicular Routing (ROVER) [12] is a good example for this class. 5) Broadcast based protocols: These protocols are frequently used in VANETs for different purposes such as: data or traffic information sharing, advertisements and emergency news. Edge-Aware Epidemic Protocol (EAEP) [13] and Secure Ring Broadcasting (SRB) [14] are proposed based on this class idea. This research is supported by the Ministry of Higher Education (MOHE) and University of Malaya (project no. HIR-MOHEB00009).