# Impact of Direction Parameter in Performance of Modified AODV in VANET
## 1 Introduction  
Intelligent traffic systems (ITS) and vehicular ad hoc networks (VANETs) are established to permit communication among vehicles to decrease traffic congestion and increase safety. A VANET uses moving cars as wireless routers (nodes) to establish a mobile network for communication [1]. The network is created by applying the principles of mobile ad hoc networks (MANET) to build a wireless network for exchanging data spontaneously. In this technology, only the vehicles equipped with wireless transceivers can exchange data with neighboring vehicles to transfer data packets to destinations that are not within direct communication range. Compared to a MANET, a VANET has higher, structured mobility and a broad coverage area. It requires little or no power and has no service fee. However, it needs continuous data exchange to update the road structure, such as the number of lanes, the number of cars on the road, the number of roadside units (RSUs), etc. In addition, a VANET requires fast, reliable environmental data for proper and safe vehicle navigation and speed control. Because of the continuously changing number of nodes and their mobility, the throughput is low in a VANET; and packet loss is high due to connection failure. The topology created in a VANET is dynamic and not uniformly distributed. Therefore, maintaining the quality of service (QoS) is crucial; and routing of the packets is a major challenge, especially when bandwidth is limited [2]. Among the routing protocols suggested for VANETs, the Ad hoc On-Demand Vector (AODV) [3] offers rapid adaptation to changes in dynamic link, has low overhead for processing and memory usage, and provides low network utilization to determine unicast routes to a destination within the network. The AODV is an on-demand or reactive routing protocol for a wireless ad hoc network. It initiates a route discovery when it needs to transmit data packets to a destination node, and it does not have any path towards the destination node prior to transmitting the data packets. This network consists of three procedures: (1) route discovery process, (2) route message generation, and (3) route maintenance. Since the route is only created when needed, it requires less overhead as compared to proactive routing protocols. Therefore, one of the main advantages of an AODV is the low overhead required for the data packets. In an AODV, the routing information is not updated after a specific period, which is also bandwidth efficient. This approach decreases the effects of inactive routes along with the need for route maintenance for unused routes. To improve the performance of an AODV in a VANET, [PERSON] et al. [4] proposed the use of direction information for each node as a parameter for selecting the next hop during a route discovery phase. However, their study did not include end-to-end (E2E) delay, throughput (TH), and packet delivery ratio (PDR). The broadcasting effect to mitigate flooding problems was also not addressed. [PERSON] et al. [5] used fuzzy logic and fuzzy control to make a routing decision. They developed fuzzy control-based AODV (FCAR) routing protocols. By comparing AODV and FCAR, they concluded that FCAR outperforms AODV in E2E delay and packet drop percentage. One of the main caveats of this study is that the packet drop rate of FCAR increases significantly when the network size is more than 70 nodes or the speed of the nodes (cars) is more than 10 m per second. Therefore, further study is required to reduce the packet drop rate for performance improvement. [PERSON] et al. [6] suggested improved AODV routing protocols to enhance stability and decrease the control overhead of the route. In this study, they used two-step optimization in the route discovery and route selection. One of the main contributions of this method is that it reduces the number of broken links. However, this method does not provide satisfactory performance in terms of packet delivery ratio.