CHAPTER Motivation

Transcription

1 CHAPTER 2 PROBLEM STATEMENT AND OBJECTIVES 2.1 Motivation There is an ever-growing need for data transfer on move.this drives an urgent need to resolve heavy overhead consumption in routing issues. The efficiency and behavior of a MANET depends on how well information can be passed around and delivered. Routing becomes a central issue. Many protocols were developed to alleviate problems in routing; however, none of them could completely overcome the challenges faced in MANET. They were either application specific or sometimes the network will be overloaded with control packets, which would consume more bandwidth, leaving no space for data packets to travel. Swarm Intelligence based algorithms provide interesting solutions to the network routing problem. SI based routing in MANETs will enhance the reliability and efficiency of packet delivery. They help in reducing control overhead due to their inherent scalable nature. From the observation of real ant colonies, many Ant Colony Optimization (ACO) inspired algorithms were developed and applied to many optimization problems. The similarity between ants and nodes, colony and wireless network helps us to use ACO based routing in MANETs. The Termite algorithm is one such ACO based algorithm, which performs better than the Adhoc On demand Distance vector (AODV). The SI principle requires end to end communication for updating routing tables, however Termite requires pheromone value for every possible (neighbor, destination) pair in the network updated in the table with the help of Hello and seed packets. These packets are sent randomly around the network to gather information. If we compare these with other routing algorithms it will be a big boost to the mobile networks so that heavy overhead on routing updates can reduced [23].

2 However, when data is sent between nodes in MANETs by rerouting through intermediate nodes using Termite concepts, they follow the path with the link of neighboring node, which has more pheromone gradient as compared to other neighboring node links. This, after some time leads, to a problem called stagnation, where packets follow the same path (just because it has more pheromone concentration) and loses packets due to congestion. Therefore, there is a need for efficient stagnation avoidance technique for the Termite algorithm to handle continuous data flow in MANET. However, MANET faces several problems because of node mobility, network traffic, network size, and the possibility of node faults. The Termite algorithm needs efficient route maintenance strategy, which provides efficient local route repair strategy for best effort delivery services to the users in the form of QoS [23]. 2.2 Problem Statement ACO based routing algorithm were proven to provide an efficient heuristic methodology for MANETs. However, these algorithms converge fast to a single solution that causes network congestion. Current work focuses on development of an efficient routing algorithm for MANETs using Termites algorithm. The Termite algorithm contains several tunable parameters and methods to automate the selection of optimal routes for different network conditions. However, the Termite algorithm does not contain methods for efficient QoS, Route Maintenance, and Load Balancing etc. Some of the improvements to Termite algorithms could be - fine-tuning pheromone values with efficient evaporation technique (also avoids stagnation problem), reserving resources in the form of Time slots/ bandwidth and efficient local route repair strategy [25, 26]. The proposed research work address these areas The aim of this work is to find the optimal path for applications where it requires the best effort delivery services. Due to its dynamic topology, providing QoS is a challenging task. The network performance will degrade if the route maintenance is not taken care of. 21

3 2.3 Objectives Main objectives of this research work are to modify the Termite Algorithm using efficient pheromone evaporation methodology to overcome stagnation problem. The research also focuses on enhancement of performance of MANET with the help of bandwidth reservation and efficient local route repair strategy. Following are specific research objectives: 1. Determine the probability of choosing the optimal paths for data packet flow packet in MANETS using the pheromone concentration derived from different pheromone decay techniques namely- Discrete, Polynomial and Exponential decay models. 2. Develop an efficient technique for the exponential pheromone decay model to address the stagnation problem. 3. Develop a Modified Termite Algorithm (MTA) based on ACO and perform a detailed comparison of the performance of MTA with the Termite algorithm. 4. Study the developed Modified Termite Algorithm (MTA) for the distribution of data packet flow on different paths by varying the node stability factor Δ. 5. Determine the network performance in terms of throughput, time delay and routing overheads for different number of nodes. 6. Implementation of QoS requirements such as local repair strategy and bandwidth reservation by evaluating the performance of the network in terms of throughput, time delay and routing overheads for different number of nodes. 22

4 The Scope of the research work includes: Development of ACO based Modified Termite Algorithm (MTA) for MANETs. Implementation of algorithms for efficient packet delivery ratio, Low endto end delay, and efficient bandwidth utilization in the form of reduced control overhead. Investigation of traffic load balancing properties in more detail and reduced control overhead in a bandwidth-constrained environment will be investigated. 2.4 Organization of the Thesis This thesis is organized into seven chapters, chapter 1 through chapter 8 and a brief description of each of the chapters is as given below. CHAPTER 1 BACKGROUND This chapter covers introduction, discusses about the Introduction to the topic which tries to give a clear understanding about the Ad Hoc networks and the areas in which it can be utilized. The chapter also focusses on giving the reader, an overall bird view on the work that has been done currently in the particular topic after introducing the same. CHAPTER 2 PROBLEM STATEMENT AND OBJECTIVES This chapter covers motivation, objectives and problem formulation for the current thesis. The chapter introduces the related technologies along-with the relevant tasks carried out for the thesis work. CHAPTER 3 LITERATURE SURVEY This chapter presents the literature survey for the present investigation. The survey includes a comprehensive overview of related work in the area of routing protocols in MANETs, Swarm Intelligence routing algorithm, QoS in MANETs, and route 23

5 maintenance in Swarm Intelligence using predictive preemption based local route repair strategy. CHAPTER 4 ANALYSIS OF DIFFERENT PHEROMONE DECAY TECHNIQUES FOR ACO BASED ROUTING IN AD HOC WIRELESS NETWORKS This chapter focuses on the SI principle in detail. The major problem in balancing the pheromone trails by updating and at the same time evaporating to remove old solutions is discussed. An analysis is made using different decay techniques and its performance on MANETs. A new node stability based evaporation technique is proposed to deal with the stagnation avoidance problem. CHAPTER 5 MANET PERFORMANCE OF MODIFIED TERMITE ALGORITHM (MTA) BY FINE TUNING PHEROMONE CONCENTRATION In this chapter Modified Termite Algorithm (MTA) is developed inspired by an ACO based Termite Algorithm proven to be efficient as compared to AODV protocol. However, it has some tunable parameters, which helps MANETs to perform well when controlled evaporation is adopted for pheromone decay techniques. CHAPTER 6 MANET SPECIFIED QOS ASPECTS OF MTA USING EFFICIENT LOCAL ROUTE REPAIR STRATEGY In this chapter, Modified Termite Algorithm (MTA) is proposed with a prediction mechanism that anticipates link breaks and repairs, thereby avoiding unnecessary warning messages and reducing control overheads. The algorithm also provides QoS for providing best effort delivery and transmits its data only through those paths, which satisfy the required bandwidth. CHAPTER 7 - DEVELOPMENT OF MTA AND NETWORK IMPLEMENTATION This chapter details the design and implementation of tasks. The structured charts of four major modules used for the Termite algorithm is explained in detail. These modules help in understanding the neighbors, find a path with specified QoS service to reach its destination address, predict node failures and find alternative paths to send left over data. 24

6 CHAPTER 8 DISCUSSION, CONCLUSIONS AND FUTURE WORK This chapter presents a detailed discussion of the analysis carried out in earlier chapters and the results of the analysis. The advantages of fine-tuning of the pheromone concentration for exponential decay are highlighted. The benefits of implementation of the ACO based MTA on MANET with fine tuning of pheromone concentration on the performance of networks and the QOS for route repair strategy have been discussed in this chapter The conclusions are drawn based on the results and the future scope of the present work is also presented. 25