ABSTRACT
Mobile ad hoc network (MANET) is an autonomous system of mobile nodes connected by wireless links. Each node operates not only as an end system, but also as a router to forward packets. The nodes are free to move about and organize themselves into a network. These nodes change position frequently. To accommodate the changing topology special routing algorithms are needed. For relatively small networks flat routing protocols may be sufficient. However, in larger networks either hierarchical or geographic routing protocols are needed. There is no single protocol that fits all networks perfectly. The protocols have to be chosen according to network characteristics, such as density, size and the mobility of the nodes. MANET does not require any fixed infrastructure, such as a base station, therefore, it is an attractive option for connecting devices quickly and spontaneous. MANETs can be used alone (for example in the military) or as a hybrid together with the Internet or other networks. Different MANET applications have different needs, and hence the various MANET routing protocols may be suitable in different areas. The size of the network and the frequency of the change in topology are factors that affect the choice of the protocols. There is no best protocol for all applications. There is still ongoing research on mobile ad hoc networks and the research may lead to even better protocols and will probably face new challenges. The current goal is to find an optimal balance between scalable routing and media access control, security, and service management.
1. INTRODUCTION
Information technology is rapidly changing from regular desktop computing, where isolated workstations communicate through shared servers in a fixed network, to an environment where a large number of different platforms communicate over multiple network platforms. In this environment the devices adapt and reconfigure themselves individually and collectively, to support the requirements of mobile workers and work teams. In the next generation of wireless communication systems, there will be a need for the rapid deployment of independent mobile users. Mobile Ad Hoc Networks (MANETs) provide communication between all nodes in the network topology without the presence of a centralized authority; instead all nodes can function as routers. This gives the MANETs two of its most desirable characteristics; adaptable and quick to deploy. MANET research is still in progress, and currently MANETs are not widely used. Suggested areas of use will include establishing efficient communication networks for mobile workers in desolate regions or in disaster areas where existing networks have been destroyed or do not exist. To communicate in an efficient way proper routing protocols are needed.
Mobile Ad Hoc Networks (MANETs) consist of nodes that change position frequently. To accommodate the changing topology special routing algorithms are needed. For relatively small networks flat routing protocols may be sufficient. However, in larger networks either hierarchical or geographic routing protocols are needed. There is no single protocol that fits all networks perfectly. The protocols have to be chosen according to network characteristics, such as density, size and the mobility of the nodes.Mobile ad hoc networking is one of the more innovative and challenging areas of wireless networking, one which promises to become increasingly present in our lives. Consisting of devices that are autonomously self- organizing in networks, ad hoc networks offer a large degree of freedom at a lower cost than other networking solutions. A MANET is an autonomous collection of mobile users that communicate over relatively “slow” wireless links. Since the nodes are mobile, the network topology may change rapidly and unpredictably over time. The network is decentralized, where all network activity, including discovering the topology and delivering messages must be executed by the nodes themselves. Hence routing functionality will have to be incorporated into the mobile nodes. since the nodes communicate over wireless links, they have to contend with the effects of radio communication, such as noise, fading, and interference. In addition, the links typically have less bandwidth than a wired network. Each node in a wireless ad hoc network functions as both a host and a router, and the control of the network is distributed among the nodes. The network topology is in general dynamic, because the connectivity among the nodes may vary with time due to node departures, new node arrivals, and the possibility of having mobile nodes.
An ad hoc wireless network should be able to handle the possibility of having mobile nodes, which will most likely increase the rate at which the network topology changes. Accordingly the network has to be able to adapt quickly to changes in the network topology. This implies the use of efficient handover protocols and auto configuration of arriving nodes.
III. MANET ROUTING PROTOCOLS
Generally routing protocols in MANETs are either based on the link-state (LS) routing algorithm or on the distance-vector (DV) routing-algorithm. Common for both of these algorithms is that they
Fig 1. Adhoc Network
try to find the shortest path from the source node to the destination node. The main difference is that in LS based routing a global network topology is maintained in every node of the network. In DV based routing the nodes only maintain information of and exchange information with their adjacency nodes. Keeping track of many other nodes in a MANET may produce overhead, especially when the network is large. Therefore one of the most important issues in MANET design is to come up with schemes that will contribute to reduce routing overheads.
MANET routing protocols fall into two general categories:
• Proactive routing protocols
• Reactive routing protocols
DIFFERENT ROUTING PROTOCOLS
3.1.1 FLAT ROUTING PROTOCOLS
• Pro-Active / Table Driven routing Protocols
• Reactive / On Demand Routing Protocols
3.1.2 HYBRID ROUTING PROTOCOLS
3.1.3 HIERARCHICAL ROUTING PROTOCOLS
3.1.4 GEOGRAPHICAL ROUTING PROTOCOLS
