International Journal of Computer Applications (0975 – 8887) Volume 51– No.14, August 2012 9 Unicaste Routing Protocols in Mobile Ad Hoc Networks: A Survey Vivek Sharma Amity School of Engg. & Tech. Bijwasan, New Delhi ,India Bashir Alam Phd, Jamia Milia Islamia University New Delhi, India ABSTRACT Mobile Ad hoc-networks (MANETs) are becoming increasingly important in today’s world. An important and essential issue for mobile ad hoc networks is routing protocol design. A major technical challenge in routing is due to the mobility of nodes in the network. During the last decade, active research work resulted in a variety of proposals. Routing protocols can be classified via the type of caste property, whether they are unicaste, multicast and broadcast. Further, ad-hoc unicaste routing protocols are classified into three categories: table driven, on-demand and hybrid. We filtered the total studies and reviewed various research papers published between 1998 and 2012. This paper presents a review and discusses 19 unicaste routing protocols designed for mobile ad hoc networks belonging to each category. Further advantages and disadvantages of each protocol are discussed. General Terms Mobile Ad-hoc networks, Routing Protocol, Keywords Unicast routing protocol, On-demand, active, reactive and hybrid protocols. 1. INTRODUCTION The Recent Research and survey shows that demand of wireless portable devices such as mobile phones, laptops and PDAs is increasing in everyday life. It leads to the possibility of spontaneous or ad hoc wireless communication. Two variations of mobile wireless network are: infrastructure network and infrastructure less network .Infrastructure network has bridges, known as base stations [1].These networks communicate with the nearest base station which lies within the range. Other variation is infrastructures less, which are also called as Mobile ad hoc network (MANET)[2].A MANET is a self-organizing collection of wireless mobile nodes that form a temporary network without the aid of a fixed networking infrastructure or centralized administration. In it each node can move freely and topology keeps on changing. Mobile nodes that are within each other’s radio range communicate directly via wireless links, while those that are far apart, rely on the other nodes to relay messages i.e. act as a router[1]. Two main features of MANET are low cost since no base stations or fixed infrastructure is required and convenience which makes it an excellent tool to handle the situations like disaster recovery, crowd control, search and rescue operation, and automated battlefields, etc. The behaviour of nodes in MANET is not unique, due to arbitrarily mobility, changes in topology, limited bandwidth, traffic density, hidden and exposed terminal node problem etc. Thus, routing in MANET [3], [4], [5] becomes extremely challenging. A lot of innovative protocols have been introduced to get the best performance and the performance of each routing protocol differs in different environment. Thus, no single protocol is suitable for all the conditions. This paper reviews the key studies of nineteen unicaste Mobile ad hoc routing protocols introduced by various authors. First we introduce classification of unicaste routing protocols based on the route discovery and routing information update mechanisms. Then we discuss the mobile ad hoc routing protocols routing mechanism. Further on, we discuss their advantages and disadvantages so that their behavior and performance can be captured under different circumstances. 2. CLASSIFICATION OF ROUTING PROTOCOLS In wireless networks various parameters such as dynamism of the network, the impacts from transmission power, receiver sensitivity, noise, fading and interference, high error rate, power restrictions and bandwidth limitations[6] lead to active research work for mobile ad hoc networks. A lot of mobile ad hoc network routing protocols have been proposed in the last four decade. These protocols can be can be classified into three main categories [7]: proactive (or table driven), reactive (or on-demand driven) and hybrid on the basis of route discovery and routing information update mechanisms. 2.1 Proactive protocols In proactive routing protocols [8], [9], [10], [11], the routes to all the destinations (or parts of the network) are determined at the start up, and maintained by using a periodic route update process. In proactive routing protocol each node maintains the information about the other nodes in the form of a table. The various proactive routing protocols differ in the way in which they update the routing information in the tables. 2.2 Reactive Protocols Reactive routing protocols establish routes only when they are needed. When a source node requires a route to a destination, it initiates a route discovery process by flooding the entire network with a route request (RREQ) packet. Once a route has been established by receiving a route reply (RREP) packet at the source node, some form of route maintenance procedure is used to maintain it, until either the destination becomes inaccessible or the route is no longer desired. These protocols use less bandwidth for maintaining the routing tables at every node compared to proactive routing protocols by avoiding unnecessary periodic updates of routing information. However, route discovery latency can be greatly increased, leading to long packet delays before a communication can start.