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A mobile ad-hoc network is an assortment of wireless mobile hosts, which establishes a momentary network without any assist of centralized administrator. The characteristics of an ad-hoc network can be explored on the base of routing protocols. The dynamic topology is the vital characteristic in which nodes frequently change their position. In the ad-hoc networks, there are mobile nodes such as personal digital assistance (PDA), smart phone and laptops; they have limited operational resources like battery power and bandwidth. Thus the control traffic is to be minimized, which is the main responsibility of routing protocols by selecting the shortest path and controlling the traffic. In this study work we focus on performance issues of routing protocols Optimized Link State Routing (OLSR), Ad Hoc On-Demand Distance Vector (AODV), Dynamic Source Routing (DSR), and Temporally Ordered Routing Algorithm (TORA) in mobility and standalone ad-hoc networks. For this purpose we first study and explain these protocols and then we use the Optimized Network Engineering Tool (OPNET) modeler tool and analyze the performance metrics delay, throughput and network load.
Keywords: MANET, Performance Evaluation, Routing Protocols, Ad-hoc Network, Routing Challenges, Performance Metrics and Mobility
A form of wireless network where each node communicates with other node using multi-hop links without stationary infrastructure is called Ad-hoc network. According to , an Ad hoc network is crew of wireless mobile nodes that creates a network without any assist of centralized administrator. It uses multi-hope point-to-point (P2P) routing as an alternative of stationary network communication to offer network connectivity . In such circumstances, due to partial range of mobile host in wireless transmission, each node needs to join up other node in order to communicate with each other and to reach to the destination if located far away. This communication involves the mechanism of finding paths from one end node to other through which data can be transferred.
Routing in ad-hoc networks has been a challenging task ever since the wireless networks came into existence. The major reason for this is the nature of ad-hoc networks where network topologies cannot be static . The non-static nature of Ad-hoc networks raises various performance challenges for routing protocols.
The conceptual framework of routing involves decision as to what appropriate optimal routing paths should be taken for transferring the data (packets) through an internetwork. The first concept, i.e. determining an optimal path, is a very complex activity while the later one, i.e. forwarding data through selected path, is a straight forward activity . In order to exchange information between different nodes, routing needs to be done by using different routing protocols. Therefore efficient routing protocols are key components of successful, reliable and proficient communications. Efficient routing protocol means that an optimal route selection is done by the protocol in different scenarios to improve the overall network performance .
In order to evaluate the performance of protocols in terms of effectiveness, different performance metrics can be used. In this study, our focus is on delay, network load and throughput for the selected protocols.
Though extensive research , , ,  has been done on the performance assessment of ad-hoc routing protocols, there is still need for more results regarding comparison of different protocols. In this study, we first identify different performance challenges for routing protocols then we will evaluate the selected routing protocols with respect to selected performance metrics in different network scenarios.
1.1 Aims and Objectives
The aim of this thesis is to assess the relative performance of routing protocols for the considered mobile ad-hoc network and to identify their performance challenges. The outcome for this study is in the form of quantitative results of efficiency of the routing protocols with reference to performance metrics. These results can be used as baseline for selecting routing protocols in a variety of situations.
The objectives are:
To conduct a detailed literature survey to review the current state of art of routing protocols used in Ad-hoc networks.
To explore different classifications of routing protocols in Ad-hoc networks and their mobility features. Furthermore, to identify the performance challenges for routing protocols in such networks.
To study the mobility features in Ad-hoc networks. For this purpose, network scenarios having mobile nodes are designed. The performance of routing protocols in mobile nodes network is evaluated to identify the impact on node mobility.
To evaluate the routing protocols with reference to their performances in fixed nodes network. In this evaluation, static network nodes are selected while designing network scenario. The performance statistics of each routing protocols for set of performance metrics are collected.
Comparison regarding performance of different routing protocols for a set of performance metrics in fixed nodes networks. A table is maintained showing the results of this comparison. This helps to identify which routing protocol performs best in static nodes network.
To design different network scenarios using OPNET simulator for implementation of different routing protocols. These scenarios will mainly be different based on network nodes i.e., mobile and static nodes. Secondly, the number of communicating nodes, application classes and selection of routing protocol differentiate these scenarios from each other.
Comparison regarding performance of different routing protocols for the same set of performance metrics in mobile nodes network. For this purpose tabulated results are shown. This comparison helps to see which routing protocol performs best in mobile nodes network.
Comparison of overall results of different routing protocols in both mobile and fixed nodes network for the same set of performance metrics.
In order to assess the performance of routing protocols, a cross comparison is performed based on collected statistic, which will be shown in a table. The collected statistics present the protocol performance with respect to nodes type, i.e., static or mobile. This helps to assess the best routing protocols for different network scenarios.
1.2 Research Question
The focus is on the following:
What are the performance challenges for routing protocols in MANET, which will address the performance challenges of routing protocols?
How to assess the performance of routing protocols in MANET, which further shows how the performance of routing protocols can be evaluated?
How to select the most appropriate routing protocols in MANET with respect to performances, which addresses the overall performance of routing protocols?
What are the most appropriate routing protocols in the presence of mobility?
1.3 Thesis Scope
Routing protocols have two classes, one is reactive (DSR, AODV and TORA) and the other is proactive (OLSR). The combination of reactive and proactive protocols is referred to as hybrid class. As in the ad-hoc networks both classes of routing protocols are used thatâ€™s why it is called hybrid. In this project we evaluate the performance of routing protocols when these are implemented in a network. In order to understand the effect on network we briefly mention and explain the design of these protocols.
1.4 Thesis Outline
The thesis document is divided into seven chapters. Chapter 1 is introduction of the topic. It describes the MANET, research question and the problem statement. Chapter 2 describes the background of mobile ad-hoc network and the related works. In chapter 3 there is theoretical concepts of ad-hoc routing protocols that are considered in this the thesis. Chapter 4 describes the performance metrics, network load, throughput and end-to-end delay of considered protocols. Chapter 5 describes the analysis and results of routing protocols. Chapter 6 is about conclusions and future work.