International Journal of Enhanced Research in Science Technology & Engineering, ISSN: 2319-7463 Vol. 3 Issue 11, November-2014, pp: (227-232), Impact Factor: 1.252, Available online at: www.erpublications.com Page | 227 End-to-End Delay Enhancment with AODV in VANET Rasha K. Aswed 1 , Mohammed A. Abdala 2 1,2 Network Engineering Department, College of Information Engineering, Al-Nahrain University, Baghdad, Iraq Abstract: The rise in the number of vehicles has led to a rapid increasing need for vehicle communication today, so the emerging Vehicular Ad Hoc Network (VANET) is becoming more and more important. Routing in VANET is a key issue which decides network performance. Ad Hoc On-Demand Distance Vector (AODV) is one of the widely used reactive routing algorithms that suffer from high delay. In this paper, a modified AODV (M-AODV) routing protocol is proposed to reduce the end-to-end delay. OMNeT++ simulator has been used to compare performances of AODV and M-AODV using IEEE 802.11p and IEEE 802.11g as MAC protocols with varying number of vehicles and vehicle speed in city and highway scenarios. The results show that the M-AODV has better performance than AODV in terms of end-to-end delay and average throughput. Keywords: VANET, AODV, Expanding Ring Search. Introduction Recent advances in wireless networks have led to the introduction of a new type of networks Called Vehicular Ad Hoc Network (VANET) which is a subclass of Mobile Ad Hoc Networks (MANET). VANETs help us to develop systems for enhancing drivers’ and passengers’ safety and comfort For example; warning messages sent by vehicles involved in an accident enhances traffic safety by helping the approaching drivers’ to take proper decisions before entering the crash dangerous zone. VANETs are developed as part of the Intelligent Transportation Systems (ITS). One of the main goals of the ITS is to improve safety on the roads, and reduce traffic congestion, waiting times, and fuel consumptions. Vehicular networks are composed of mobile nodes, vehicles equipped with On Board Units (OBU), and stationary nodes called Road Side Units (RSU) attached to infrastructure that will be deployed along the roads. Both OBU and RSU devices have wireless/wired communications capabilities. OBUs communicate with each other and with the RSUs in ad hoc manner. There are mainly two types of communications scenarios in vehicular networks: Vehicle-to-Vehicle (V2V) and Vehicle-to-RSU (V2R) [1]. VANET characteristics[2] are highly dynamic network topology, scalable network, frequent disconnected network, and unlimited power. Routing protocols are responsible for determining how to relay the packet to its destination, how to adjust the path in case of failure, and how to log connectivity data. Routing protocols [3] should be efficient and should adapt to vehicular network characteristics and applications, permitting different transmission priorities according to the application type (safety-related or not).Until now, most of vehicular network research has focused on analyzing routing algorithms to find a suitable one. Khan and Qayyum [4] and Haeeri et al [5] analyzed the performance of AODV and OLSR in VANET.They found OLSR has low delay compared with AODV. Singh and et al [6] compared the performance of AODV, OLSR and DSR, they found that AODV is better than other two protocols in terms of packet delivery ratio so it is suitable to carry sensitive information in VANET but it fails when transmission time should be very less as it has highest end to end delay. According to these studies, we have analyzed the performance of OLSR, AODV and DYMO in a previous study.We have found that AODV has the highest throughput and the lowest delay. Accordingly, we have decided to enhance the AODV delay performance. In this paper, we propose M-AODV routing protocol in order to reduce the end-to-end delay while keeping throughput high. AODV and M-AODV Routing Protocols A. AODV Ad-Hoc On-Demand Distance Vector (AODV) [7] routing protocol is one of the most popular reactive routing protocols. AODV uses an on demand approach for finding. It employs destination sequence number to identify the most recent path. AODV ensures loop-free routes even while repairing broken links. Because the protocol does not require global periodic routing advertisements, the overall bandwidth available that is needed for the mobile nodes is considerably less than in those protocols that do necessitate such advertisements. AODV consists of two operations: route discovery and route maintenance.Route discovery operation finds path between source and destination and route