Modified Expanding Ring Search Algorithm for Ad-hoc Networks Shweta Mishra 1 , Jyoti Singh 2 , Arti Dixit 2 , Shiva Prakash 3 Department Of Computer Science and Engineering Madan Mohan Malvaiya Engineering College Gorakhpur, India Abstract-Ad-hoc on demand distance vector routing protocol is specially designed for mobile ad-hoc networks with reduced overhead using Expanding Ring Search technique (ERS). But energy consumption should also be considered in MANET due to battery constrain of nodes. In this paper, we propose an energy efficient route discovery process for AODV based on ERS .Our approach saves energy of nodes by avoiding the redundant rebroadcasting of the route request packets. It not only reduces the energy-consumption but also reduces the routing overhead occurs due to mobility between nodes. Keywords: Mobile Ad-hoc Networks, Ad-hoc On-Demand Distance Vector Routing Protocol, Energy Consumption, Expanding Ring Search. INTRODUCTION Network, a collection of interconnected nodes can be wired, wireless or wired cum wireless. A wireless Ad-hoc Network is decentralized type wireless network [5].It is known as Ad- hoc as it does not depend on pre-existing infrastructure. MANETS are self configuring wireless networks without any centralized control [6].They are highly dynamic and suffer from frequent unpredictable changes in the network topology [4]. The radio range of mobile node is usually very small so the node co-operate with each other to keep network alive. The communication between two nodes usually includes several intermediate nodes forwarding the data packets between the endpoints. The nodes can communicate without any established infrastructure. There are many applications of mobile ad-hoc network in various fields such as [4] such as military communication, automated battle fields, Emergency Services, Commercial and civilian environment, Home and enterprise networking, Education Entertainment Sensor networks, Context aware services and Coverage extension. The specific characteristics and complexities of Ad-Hoc network imposes many challenges such as [4] Autonomous and infrastructure less, Multi-hop routing , Dynamic network topology, Device Heterogeneity, Energy constrained operation, Bandwidth constrained variable capacity links, Limited physical security, Network scalability ,Self-creation, self-organization and self- administration. There are many protocols already have developed for MANETS environment [13]. All these protocols have been developed in many ways. Based on network structure the routing protocols can be classified as flat routing, hierarchical and geographical position assisted routing. In flat routing nodes communicate directly away with each other. The flat routing protocols can be further classified as proactive, reactive and hybrid. Proactive protocols follow the strategies which are mostly followed by conventional routing protocols. On-demand routing is a new emerging technology in ad-hoc networks. Hybrid protocols are includes the properties of both proactive and reactive types. MANET routing protocols do not follow the properties of conventional protocols. Hierarchical routing plays a major role in large size networks where flat routing protocols are struggling with constraints. Now-a-days geographical location information also provides better routing performance in ad-hoc networks. In proactive scheme, a very small delay is needed to determine the route but a significant amount of delay is needed for creating a route by routing protocols. Pure proactive scheme is not appropriate for the ad-hoc networking environment, because it has to keep the current information in a large network. Reactive protocols require significant control traffic due to the long delay and excessive control traffic. As a result pure reactive routing protocols can not be implemented in large networks. Geographical Position Assisted Routing needs to know their geo-coordinates routes to move packet closer to end point for example DREAM, GPSR, and LAR [11][12]. LITERATURE SURVEY There has been significant work on routing in MANETs [7][8][9][10]. AODV is a reactive protocol which finds route between source destination pair only when it is required. Traditional AODV uses the concepts of blind flooding for forwarding the RREQ packets from source to all other nodes in the network to find route. The RREQ is broadcasted to entire network so every neighbor nodes will receive and process it. All nodes which receive RREQ for the first time check the routing table for route. If there is route, it unicasts the RREP to source, otherwise it rebroadcasts the RREQ to its neighbors. If RREQ is received, it will silently drop RREQ. If the node is destination, it unicasts the RREP to the source. Once the route is established it is maintained as long as it is required. However, when intermediates nodes loses connectivity, the RERR will be sent to the source and source sends packets either through alternate paths or it will restart route discovery process. Thus, route discovery process leads to consumption of energy. Shweta Mishra et al, / (IJCSIT) International Journal of Computer Science and Information Technologies, Vol. 3 (3) , 2012,4067-4070 4067