Vol. 6, No. 11, November 2015 ISSN 2079-8407 Journal of Emerging Trends in Computing and I nformation Sciences ©2009-2015 CIS Journal. All rights reserved. http://www.cisjournal.org 622 Ant Colony Optimization based Hybrid Routing Protocol for MANETs 1 Essam H. Houssein, 2 Alaa A. K. Ismaeel 1 Dept. of Computer Science, Faculty of Computers and Informatics Benha University, Benha, Egypt 2 Dept. of Computer Science, Faculty of Science, Minia University, El Minia, Egypt ABSTRACT An ad hoc mobile network is a collection of mobile nodes that are dynamically and arbitrarily located in such a manner that the interconnections between nodes are capable of changing on a continual basis. Routing in MANET is extremely challenging because of MANETs dynamic features, its limited bandwidth and power energy. The routing protocol is used to discover routes between nodes. Routing is a challenging task in ad hoc network due to mobility of nodes that frequently changes network topology. Nature-inspired algorithms (swarm intelligence) such as ant colony optimization (ACO) algorithms have shown to be a good technique for developing routing algorithms for MANETs. In this paper, we propose a new routing algorithm for MANETs called Ant-HRP which based on ACO, proactive and reactive routing protocol capability and is simulated on NS2. Results indicate that Ant-HRP effectively improve the connectivity, packet delivery ratio and reduce the end-to-end delay as compared with the Ant Net, AODV and DSDV routing protocols. Keywords: MANETs, AntNet, ACO, AODV and Ant-HRP 1. INTRODUCTION Mobile Ad hoc Networks (MANET) is a communication network of a set of mobile nodes, placed together in an ad hoc manner, without any fixed infrastructure that communicate with one another via wireless links. The devices used to form an Ad Hoc Network possess limited transmission range; therefore, the routes between a source and a destination are often multi hop. As there are no separate routers, nodes that are part of the network need to cooperate with each other for relaying packets of one another towards their ultimate destinations as they do not have central administration, it is easy to deploy and expand. This kind of network is very flexible and suitable for applications such as temporary information sharing in conferences, military actions and disaster rescues [1]. A fundamental problem in MANET is how to deliver packets among mobile nodes efficiently without predetermined topology or centralized control, which is the main objective of routing protocols. Since MANETs change their topology frequently, routing in such networks is a challenging task. So far, much work has been done on routing in MANETs and can be divided into: proactive protocols and reactive protocols [20]. Proactive routing protocol includes: Destination Sequenced Distance Vector (DSDV) etc. They attempt to maintain a correct view of the network topology add the time and build routes from each node to every other node before they are needed, hence they are also called table- driven protocols. Any changes in topology are propagated through the network, so that all nodes know of the changes in topology. Thereby, proactive protocols maintain routing information about the available paths in the network even if these paths are not currently used. The major drawback of these approaches is that the maintenance of unused paths may occupy an important part of the available bandwidth if the topology of the network changes frequently [5 and 21]. Reactive routing protocols includes: Ad hoc On- demand Distance Vector (AODV) Routing etc. Reactive maintain only the routes that are currently in use, thereby trying to maintain low control overhead, reducing the load on the network when only a small subset of all available routes is in use at any time. However, they still have some inherent limitations. First, since routes are only maintained while in use, it is usually required to perform a route discovery before packets can be exchanged between communication peers. This leads to a delay for the first packet to be transmitted. Second, even though route maintenance for reactive algorithms is restricted to the routes currently in use, it may still generate an important amount of network traffic when the topology of the network changes frequently. Finally, packets to the destination are likely to be lost if the route to the destination changes [19]. In general, reactive protocols are more efficient than proactive routing protocols in terms of control overhead and power consumption since routes are only established when required. By contrast, proactive protocols require periodic route updates to keep information current and consistent. In addition, many routes maintained might never be needed, which significantly adds to routing overhead in the bandwidth- constrained network. As routing overhead grows exponentially with network size, it prevents the application of these protocols in large-scaled networks. Proactive protocols generally provide better quality of service than reactive protocols. As in proactive protocols, routing information is constantly updated, routes to every destination are always available and up-to- date, and, hence, end-to-end delay can be minimized. For reactive protocols, the source node has to wait for the route to be discovered before communication can happen. This latency in route discovery might be intolerable for real-time communications. However, we will investigate this aspect in our work. 1 esam.halim@fci.bu.edu.eg , 2 alaa.ismaeel@mu.edu.eg