Letter Paper Int. J. of Recent Trends in Engineering and Technology, Vol. 4, No. 1, Nov 2010 © 2010 ACEEE DOI: 01.IJRTET.04.01.161 68 Applying Genetic Algorithm for Optimizing Broadcasting Process in Ad-hoc Network Said Elaiwat 1 , Ammar Alazab 1 , Sitalakshmi Venkatraman 2 , and Mamoun Alazab 2 1 School of Information Technology Deakin University, Australia {selaiwat, aalazab}@deakin.edu.au 2 Graduate School of ITMS University of Ballarat, Australia {s.venkatraman, m.alazab}@ballarat.edu.au Abstract— Optimizing broadcasting process in mobile ad hoc network (MANET) is considered as a main challenge due to many problems, such as Broadcast Storm problem and high complexity in finding the optimal tree resulting in an NP-hard problem. Straight forward techniques like simple flooding give rise to Broadcast Storm problem with a high probability. In this work, genetic algorithm (GA) that searches over a population that represents a distinguishable ‘structure’ is adopted innovatively to suit MANETs. The novelty of the GA technique adopted here to provide the means to tackle this MANET problem lies mainly on the proposed method of searching for a structure of a suitable spanning tree that can be optimized, in order to meet the performance indices related to the broadcasting problem. In other words, the proposed genetic model (GM) evolves with the structure of random trees (individuals) ‘genetically’ generated using rules that are devised specifically to capture MANET behaviour in order to arrive at a minimal spanning tree that satisfies certain fitness function. Also, the model has the ability to give different solutions depending on the main factors specified such as, ‘time’ (or speed) in certain situations and ‘reachability’ in certain others. Index Terms —MANET, Network, Genetic Algorithm, Optimisatoin, Spanning Tree. I. INTRODUCTION A mobile ad hoc network (MANET) is an independent system mobile host (any host can be a router) created on the fly, and connected by wireless links in the absence of a fixed wired infrastructure. The union of these models constitute a communication network formed as a model of an arbitrary communication graph. In MANET, all hosts can move freely without any limitations through the network, where each node can communicate directly with other neighbour nodes within the range of transmission, Generally, successful routing protocols provide devices to send packets to destination nodes with dynamic topologies [1][2][3][[4]. Broadcasting MANET is more complex than normal broadcasting in wired network because the nature of MANET is quite different from wired networks. When each host sends a particular message, this message will be received by all its neighbours within a radius range. This is due to the multi-hop structure, dynamic mobility, and decentralized network with no wired link that connects the hosts. The data broadcasting in MANET is important to study, as it is the main method of information distribution in many applications, such as sending an alarm signal to all hosts [5]. Many algorithms are proposed to find the best broadcast tree and to avoid the problems of redundancy, contention and collision or what is called Broadcast Storm problem. Starting from simplest technique like simple flooding to the most complex technique like minimum spanning tree (MST), it is observed from theory that the minimum spanning tree (MST) [13] could be considered as the best solution. But this solution is not practical due to the high complexity in computing MST and it could result in a NP- hard problem. Therefore, applying this solution is not feasible even with some research studies making some restrictions, such as redesigning central nodes to respond to rebroadcast messages. On the other hand, genetic algorithm (GA) is considered as an attractive solution to tackle a problem that has high complexity and requires optimization. Hence, in this work, a new model based on genetic algorithm to find minimal broadcast tree in MANET with reasonable time has been proposed. Also, this proposed model has the ability to give different solutions according to the main factor for optimization in the network, such as ‘time’ (or speed) in most situations and ‘reachability’ in some other situations. II. BACKGROUND Traditionally, simple flooding [6] is considered as a straightforward technique as there is no need for any complex computations. It is easy to implement and is characterized by high reliability. However, this technique harms the resources of the network, such as bandwidth and energy supplies because it suffers from serious problems such as redundancy, contention and collision (also termed as Broadcast Storm problem) due to huge number of retransmitted messages. Hence, this technique has not been used widely, though it could be considered appropriate for some type of mobile networks, especially when the network has high density and mobility, or in some situations where reachability is the main goal as is the case in battlefield survivability [8]. Many algorithms are proposed for optimizing broadcast process in MANET. Williams et al. [9] presented models to