SUMMERY, CONCLUSIONS AND FUTURE WORK

Chapter - 6 SUMMERY, CONCLUSIONS AND FUTURE WORK The entire Research Work on On-Demand Routing in Multi-Hop Wireless Mobile Ad hoc Networks has been presented in simplified and easy-to-read form in six chapters as follows- Chapter - 1 Introduction Chapter - 2 General concepts Chapter - 3 Overview of Mobile Ad hoc Networks Chapter - 4 Overview of Mobile Ad hoc routing protocols and their classification Chapter - 5 Simulation and implementation Chapter - 6 Summery, Conclusions and Future Work References 6.1 SUMMERY The chapter-1 covers the Scope of Research Work, Literature Survey, Aim and Objectives, Research Method used and thesis outline. The need to exchange digital information outside the typical wired office environment is growing. For example, business associates serendipitously meeting in an airport may wish to share files, or disaster recovery personnel may need to coordinate relief information after a hurricane or flood. Each of the devices used by these information producers and consumers can be considered a node in wireless Ad hoc network. Wireless Ad hoc networking is an emerging technology that allows users to access information and services electronically, regardless of their geographic position. In Ad hoc networks, communications are done over wireless media between stations directly in a peer-to-peer fashion without the help of wired base station or access points. Summery, Conclusions and Future Work 139

The aim of the research work is to provide a comprehensive analysis of various on-demand routing protocols and carry out the comparative study with table driven protocols. The idea is to implement and compare several on-demand routing protocols. The research work is aimed to study the performance of on-demand routing protocols like DSR, AODV and AOMDV under identical and mobility patterns of Ad hoc network with reference to table driven protocol DSDV. The chapter includes the literature survey and elaborates the formulation of the present research work based on the priori investigation reported by the earlier researchers. It was decided to carry out implementation of various protocols using simulation platform of NS-2 developed at UC Berkeley as a part of the VINT project that support Research and Education in networking. The chapter ends with thesis outline. The chapter-2 takes account of the general concepts of communication networks for both wired and wireless networks. It also gives the general routing concepts of conventional protocols like Link state, Distance vector, Source routing and flooding. A communication network is an interconnected collection of autonomous computing devices, which is used to transfer message from source to destination using wired or wireless transmission media. Wireless communications can support a high degree of mobility and deployment flexibility, so they are the main communication medium of choice for Ad hoc networks. Wireless networks may also be considered as infrastructure wireless networks (cellular) or infrastructureless wireless networks (Ad hoc networks). Routing, which is the process of finding optimal path between source and destination is the main challenging issue in networks. Conventional routing protocols like link state and distance vector are designed for static topology, which means that they have a problem to coverage to a steady state in an Ad hoc network with a very frequently changing topology. Many of the proposed Ad hoc protocols have a conventional routing protocol as underlying algorithm; it is necessary to understand the basic operation for Summery, Conclusions and Future Work 140

conventional protocols like distance vector, link state, source routing and flooding. This chapter briefly explains the conventional routing protocols. Chapter-3 overviews the historical development and operational feature of Ad hoc networks. Further it points out limitations, new challenges and application areas of Ad hoc networks. The whole life cycle of Ad hoc networks could be categorized into the first, second, and the third generation Ad hoc networks systems. In the 1990s, the concept of commercial Ad hoc networks (third generation) arrived with notebook computers and other viable communications equipments. At the same time, the idea of a collection of mobile nodes was proposed at several research gatherings. The IEEE 802.11 subcommittee adopted the term "Ad hoc networks" and the Research Community motivated towards the investigation of possibility of deploying Ad hoc networks in other areas of application. In Chapter-4 different routing protocols employed in Ad hoc network are introduced followed by their classification. The introduction of routing protocols consists of Ad hoc network routing challenges and need to analyze existing routing protocols. Features and design issues desired for a routing protocol in Ad hoc Networks are also considered. The main goal of a routing strategy is to efficiently deliver data all the way from the source to the destination. Although all routing protocols share this goal, each protocol adopts a different approach to achieve it. The routing strategy has a significant impact on the performance of Ad hoc networks, especially since the nodes act as routers. Ad hoc network routing challenges include resource-constrained devices with limited wireless transmission range, issues like hidden terminal problem which make routing more complex, higher packet losses due to transmission errors, high -mobility environments, varying etc. Summery, Conclusions and Future Work 141

Desired features for a Routing Protocol in Ad hoc Networks include adapting quickly to topology changes, loop free routing, multipath routing, minimal control message overhead, quick establishment of routes and security aspects. There are different criteria for designing and classifying routing protocols for wireless Ad hoc networks. The chapter elaborates the criteria based classifications of routing protocols followed by the designing aspects. Chapter-5 is devoted to the Research work carried out. The approach includes simulation based implementation of routing protocols to study the operational performance of different routing protocols. Chapter discusses the implementation of one table driven protocol (DSDV) and two on-demand routing protocols (DSR, AODV) in the first phase followed by implementation of multipath on-demand protocol AOMDV and compared with unipath protocol AODV in the next phase. Results obtained in the text based trace file which record the activities taking place in the network were analyzed using perl analysis program and Node movement were viewed through NAM animation tools. Simulation- All the protocols were implemented using NS2 (version 2.31) simulator. The chapter describes the simulation environment, which contains introduction, general structure, architecture of NS-2 simulator and sample simulation scripts. Simulation study also contains mobility generation models to provide node mobility and traffic generation models to provide. The CMU tools setdest was used to vary the mobility and cbrgen to vary offered. Tcl program was developed to simulate wireless mobile nodes with respect to the specific protocol, mobility and traffic models. Implementation Implementation [67,120] goes through two phase as follows- 1. In the first phase three protocols: DSDV, DSR and AODV were implemented. A comprehensive analysis and comparison has been made using six different evaluation metrics and AODV has been found to be best among all other protocols. Summery, Conclusions and Future Work 142

2. In the second phase stage two protocols were implemented namely AODV (unipath) and AOMDV (multipath). A comprehensive analysis and comparison of AODV and AOMDV has been made using various evaluation metrics. The procedure adopted in implementing the routing protocols is depicted in the flowchart shown in Fig. 6.1. Start Routing protocol is developed in C++ using built in library tools Required simulation parameters were specified Mobility generator models are developed using setdest tool by varying pause time 0,10,20,30,40 and 100 sec Traffic generator models are developed using cbrgen tool by varying Max. Number of connections as 10, 20, 30 and 40. Tcl program is developed to simulate wireless mobile nodes in which we referred routing protocol, mobility and traffic models. Tcl program is executed using NS-2 Yes Whether the result is to be viewed as text based trace file No Perl program is developed to evaluate performance metrics NAM command is used to obtain the output through NAM animation tool Stop Fig. 6.1: Flow chart of implementing the routing protocols Summery, Conclusions and Future Work 143

Comparison of Simulation Results Effect of Mobility To analyze the effect of mobility, pause time was varied from 0 seconds (high mobility) to 100 seconds (no mobility) as 0s, 10s, 20s, 30s, 40s and 100s. The numbers of nodes were taken as 50 and the maximum number of connection as 20. The simulation results were stored in text files and the results were analyzed using perl program and trace analyzer under various mobility condition. Results were plotted between pause time and six different performance evaluation metrics as follows- Pause time Vs Throughput Pause time Vs Packets dropped Pause time Vs Packet delivery ratio Pause time Vs Routing overhead Pause time Vs end to end delay Pause time Vs Optimal length Sample results for Pause time Vs Throughput are given in Fig 6.2(a-b) and Table 6.1(a-b) Fig 6.2(a): Pause Time Vs Throughput Table 6.1(a): Pause Time Vs Throughput Throughput(bits/s) 15000 14500 14000 13500 13000 12500 12000 11500 11000 10500 0 20 40 60 80 100 Pause time DSR DSDV AODV Pause time (sec) 0 10 20 30 40 100 Throughput (bits/sec) DSR DSDV AODV 12471 12768 14260 14840 14202 14640 10656 10748 12755 13031 12390 14253 12641 13081 14342 14451 14186 14179 Fig 6.2(b): Pause Time Vs Throughput Table 6.1(b): Pause Time Vs Throughput Throughput 1 0 3 9 0 1 0 3 8 0 1 0 3 7 0 1 0 3 6 0 1 0 3 5 0 1 0 3 4 0 1 0 3 3 0 1 0 3 2 0 0 2 0 4 0 6 0 8 0 1 0 0 P a u s e tim e A O D V A O M D V Pause time (sec) 0 10 20 30 40 100 Throughput AODV AOMDV 10365 10364 10327 10341 10334 10360 10337 10338 10370 10374 10381 10390 Summery, Conclusions and Future Work 144

Effect of Traffic Load To study the effect of on the network, number of connections here varied as 10, 20, 30 and 40 connections. The network was simulated for high mobility scenario keeping the pause time 0 seconds. The simulation results were stored in text files and the results were analyzed using perl program and trace analyzer under various. Results were plotted between number connection and six different performance evaluation metrics as follows- Max. number of connections Vs Throughput Max. number of connections Vs Packets dropped Max. number of connections Vs Packet delivery ratio Max. number of connections Vs Routing overhead Max. number of connections Vs end to end delay Max. number of connections Vs Optimal path Sample results for Max number of connection Vs Throughput are given in Fig 6.3 (a-b) and Table 6.2 (a-b). Fig 6.3(a): Max. Number of connections Vs Throughput Table 6.2(a): Max. Number of connections Vs Throughput Throughput(bits/s) 14 0 00 13 0 00 12 0 00 11 0 00 10 0 00 9 0 00 8 0 00 7 0 00 6 0 00 5 0 00 D S R D S D V A O D V Max. Number of Connections 10 20 30 40 Throughput DSR DSDV AODV 6031 10299 12471 13070 5033 7937 10656 12067 6015 10223 12641 13354 4 0 00 1 0 15 2 0 2 5 3 0 35 40 M ax.num ber of connections Fig 6.3(b): Max. Number of connections Vs Throughput Table 6.2(b): Max. Number of connections Vs Throughput Throughput(bits) 1 1 0 0 0 1 0 0 0 0 9 0 0 0 8 0 0 0 7 0 0 0 6 0 0 0 A O D V A O M D V 1 0 1 5 2 0 2 5 3 0 3 5 4 0 M a x. n u m b e r o f c o n n e c t i o n s Max. Number of Connections 10 20 30 40 Throughput (bits/sec) AODV AOMDV 10065 10364 9065 9365 7065 7364 6006 6317 Summery, Conclusions and Future Work 145

6.2 CONCLUSION A large number of different kinds of routing protocols are practiced in mobile Ad hoc networks. The use of a specific routing protocol in mobile Ad hoc network depends upon number factors including size of the network, load, mobility requirements, routing overhead and end-to-end delay. In recent years on-demand routing protocols have attained more attention in mobile Ad hoc networks as compared to other routing schemes due to their potential flexibility in deployment and efficiency in terms throughput. They are able to organize themselves dynamically with lower memory overhead and lower bandwidth requirement than table driven protocols. There exist many on-demand routing protocols for mobile Ad hoc networks (MANETS). Most of the protocols, however, discover a single route and fail to utilize multiple alternate paths. Multipath routing allows the establishment of multiple paths between a single source and single destination node and in the event the path breaks, an alternate path is used instead of initiating a new route discovery. Hence multipath routing stands a promising routing method for wireless mobile Ad hoc networks. Multipath routing protocols achieve lower routing overhead, lower end-to-end delay, more resilient to route failures and alleviate congestion in comparison with single path routing protocols. In the present research we have implemented and carried out comprehensive analysis and comparison of unipath on-demand routing protocols (DSR, AODV) and multipath on-demand routing protocol (AOMDV) using NS-2 simulator. Comparison of on-demand routing protocols with one of the efficient table driven routing protocol DSDV has also been made to illustrate that on-demand protocols work better than table driven protocols. Performance of all protocols was carried out under identical and mobility patterns condition. The overall analysis of routing protocols has been summarized in the tables 6.3, 6.4 and 6.5. Summery, Conclusions and Future Work 146

Table 6.3: Analysis of DSDV, DSR and AODV with Varying Mobility Performance metrics Throughput Table driven On demand (unipath) DSDV DSR AODV Better at low mobility, decreases as mobility increases Good at moderate mobility. Good at high mobility Packets dropped High Low Low Packet delivery ratio Better at low mobility, decreases as mobility increases High. Increases as mobility increases Good at moderate mobility. Good at high mobility. Routing overhead Less at moderate Less mobility End to End delay Low High High Optimal path length Low Low at moderate mobility high Table 6.4: Analysis of DSDV, DSR and AODV with varying Performance metrics Throughput Table driven On demand (unipath) DSDV DSR AODV Better at low traffic load, decreases as increases Good at moderate Good at high Packets dropped High low low Packet delivery ratio Routing overhead End to End delay Optimal path length low High High High. Increases as increases Low at less traffic load Less at moderate Low at high High Low at high Low High High Summery, Conclusions and Future Work 147

Table 6.5: Analysis of AODV and AOMDV with Varying Traffic Load and Mobility Performance metrics On demand AODV (unipath) AOMDV (multipath) Throughput Good Better than AODV Packets dropped Higher than AOMDV Low Packet delivery ratio Good Better than AODV Routing overhead Higher than AOMDV Low End to End delay Higher than AOMDV Low Optimal path length High Low The entire research study on On-Demand Routing in Multi-Hop Wireless Mobile Ad Hoc networks concludes with the following remarks summarized as follows- For a network with low mobility and less number of nodes, results reveal that DSDV is preferable. The performance of DSR which uses source routing is preferable for the normal situations where a network is of general nature with moderate traffic and moderate mobility as it delivers more packets at the destination with lowest routing overheads. For robust scenario where mobility is high, nodes are dense, area is large, the amount of traffic is more and network pattern sustains for longer period the results reveals that AODV performs better. To achieve lower routing overhead, lower end-to-end delay, to be more resilient to route failures and alleviate traffic congestion for robust scenario where mobility is high, nodes are dense and traffic is more, simulation results reveals AOMDV is the best choice. The overall conclusion is that a multipath routing protocol, AOMDV is best choice to move towards a network with better Quality of Service (QoS). Summery, Conclusions and Future Work 148

6.3 FUTURE WORK Ad hoc networking is a boiling concept in personal communications World wide research is going on in this area and many issues still have to be addressed. We focused on concepts like unipath and multipath routing protocols with respect to their performance in the mobile Ad hoc network. Multipath routing is a step towards achieving a network with better Quality of Service. However there are many more issues related to routing that could be subjected to further research studies. The present research work can be extended to design and develop new routing protocols to meet the following additional desirable features. Robust Scenario- A routing protocol must work with robust scenarios where mobility is high, nodes are dense, area is large and the amount of traffic is more. Probabilistic Route Maintenance- A more research in the field like probabilistic route maintenance is required to identify the probability of route failure before the occurrences of route failures. Quality of service (QoS) - Ad hoc routing protocols must meet the desired requirements of QoS to achieve lower end-to-end delay, high throughput improved delivery ratio, reduced routing overhead and more energy efficiency. Security- A vital issue that has to be addressed is the security in Ad hoc networks. Applications like Military and Confidential Meetings require high degree of security against enemies and active /passive eavesdropping attackers. A new protocol must have authentication headers and necessary key management to distribute keys to the members of Ad hoc networks. Summery, Conclusions and Future Work 149

Routing Overhead Routing messages will utilize most of the precious bandwidth of Ad hoc networks; a new protocol has to be devised to reduce the routing overhead still further compared to AOMDV. Energy Aware Routing Since mobile nodes are working on small portable batteries in most of the applications, developing an energy aware routing protocol, which maximizes the life of batteries, is of paramount importance. Newer operational demands on Ad hoc networks are going to bring in new trends and directions in the research field towards designing robust protocols, and Mobile Wireless Communication keeps on evolving forever making the research an endless paradigm. Summery, Conclusions and Future Work 150