Recent Advancements In Wireless Networking Computer Science Essay

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In recent advancements wireless networking has a crucial role to play in situation where mobility and rapid deployment of a communication network is vital, when compared to the wired network. These advancements in wireless network has been lead to the development of a new system called mobile adhoc networks(MANET'S). A Mobile Adhoc Network is a multihop , self configuring network of wireless devices called nodes which are connected by wireless links.

These mobile nodes can communicate and share information without any central facilitated infrastructure. Because of its dynamic topology routing in mobile ad hoc networks has become a challenging and demanding aspect.

In mobile adhoc network there developed many routing protocols, as the traditional routing such as TCP/IP which are used in wired network has lack of mobility and resources, so this lead to development of many routing protocols, such as proactive, reactive and hybrid routing protocols.

This project is influenced by the observation that the scalability and performance of ad hoc routing protocols does vary, not only depending upon the type of routing approach (proactive and reactive) but also few other factors such as network size, network load, data rate etc influence them.

In this project, six ad hoc routing protocols namely AODV(Ad hoc on Demand Distance Vector routing ),DSR(Dynamic Source Routing),OLSR(Optimised Link State routin),IARP(INTRA zone routing protocol),ZRP(Zone Routing Protocol) and LANMAR(LAND MARK) have been compared in terms of its performance and scalability. The performance of these routing protocols is analysed using three metrics: packet delivery ratio, average end-to-end delay, jitter and throughput. On other hand, the scalability of the routing protocols is analysed primarily basing on the routing overhead produced and their respective average end-to-end delay.

The main purpose of the routing protocol is to establish most efficient, accurate and shortest route between a pair of nodes . However, not all routing protocols developed perform well in a given situation; hence factors affecting routing protocols require thorough investigation.

Mobile ad hoc networks (MANETs) are being extensively deployed currently since they provide features that traditional networks find impossible or difficult to emulate. Self organising and self configuring in between the nodes without depending on any fixed base station or neither requires any infrastructure ; some of the interesting facts that motivates the MANET are mobility ,inexpensive, rapid deployment, ability to connect to the internet or a sub-network etc[ietf, MANET]. The mobile nature of these networks usually tends the topology to be dynamic causing frequent route changes.

In this project there are some real scenarios which include disaster area, event coverage, military operation, farming and taxi service in each case all the six routing protocols performance has been investigated by varying the data rate, time interval and increasing the number of nodes, And to conclude which routing performs better in that particular situation.

In this study a comparison and performance evaluation of this routing protocols in different scenarios are done using QualNet Simulator to identify that which protocol is best suited for for which scenario in different MANET's.

1.2 Project Aim and Objectives:

The aim of this study is to investigating the performance of ad hoc routing protocols AODV(Ad Hoc on demand distance vector routing),DSR (Dynamic source routing),OLSR(Optimized link state routing),LANMAR(landmark ad hoc routing),IARP(intra zone routing protocols) and ZRP(zone routing protocol) for mobile ad-hoc networks.

Objectives:

· Undertaking a thorough review of ad hoc routing protocols.

· To create a simulation environment to assess the performance and routing of all six protocols.

· To carry out measurements and to assess the performance and understand the behaviour of all routing protocols in the presence of node movement and while varying various loads.

· To carry out measurements to assess the scalability routing protocols in terms of packet delivery ratio, throughput and end-to-end delay.

· To present the results obtained from Qualnet simulator.

1.3 Dissertation structure:

Dissertation structure is segregated into four chapters.Figure 1.1 shows the structure of this dissertation. Chapter 2 and Chapter 3 present background material,

Chapter 2 it presents a brief literature related to routing protocols in mobile ad hoc networks including the tools used to pursue the project.

Chapter 3 describes the research methodology adopted, with a comparison among simulation parameters used and the reasons behind making choices,it also gives an overview of real experiment and analytical methodologies.

Chapter 4 the experimental designs and investigation that the how the project is developed and implemented including the reasons behind making choices of tools adopted.

Chapter 5 details the testing and experimental results and proposed improvements.

Chapter 6 summarised the overall dissertation with further work and problems faced with tools adopted during the project.

Chapter 1

INTRODUCTION

Chapter 6

Conclusions

Chapter 5

Results and comparative analysis

Chapter 4

Experimental design and investigation

Chapter 2

MANET routing protocols

Chapter 3

Research methodology

Background material

------------------------------------------------------------------------------------------------------------------

Main contribution

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Concluding remarks

Figure 1.1

Chapter 2: Literature Review

2.1:Introduction:

In Chapter 1, the introduction and motivation for the impact of routing protocols on MANETs was outlined. This chapter 2 provides a literature review on MANET and its routing protocols. Mobile adhoc network consist of autonomous system of mobile nodes whereas each mobile node is a wireless communication device acts as a host and router ie. All the mobile nodes can communicate with each other using multi-hop wireless links.it does not require any stationary infrastructure or any base station it can be used any where indoor, oudoor or in any moving objects.the main concept in MANET's is the design of dynamic routing protocols and to find which routing protocols is the most efficient to find the routes in between two communicating mobile nodes.by definition MANET routing protocols is the mechanisms of transfering information in form of data packets from a source to a destination in a network. This routing protocol responsible is to keep the uptodate information of node mobility, which often changes the network topology drastically and unpredictably.

Generally, two activities take place in routing protocols which enables communication to occur between two nodes. First is to determine optimal routing paths and the transferring of packets through the network but still using low computing power. Second, to achieve these activities, each routing protocol uses different metrics to evaluate the best path that data packets should use when sending packets in a network. To accomplish effective performance the nature of routing algorithms, design and performance issues require careful consideration.

The mobile ad hoc network is mostly used because of its robustness, flexibility and moderate cost, due to its high flexibility it can automatically address dynamic changes while the mobile nodes joining, leaving or moving away from its network this lend to use this technology as not only in military application but also in rescue operations while after the natural disaster , in any event coverage, surveillance , intelligent transport systems (ITS) etc...

Overview of Research Themes. Keywords: Joining, Leaving, ITS system, surveillance system, wireless terminal, disaster area, delivery system for local information

Figure 1.2

[http://www.hitachi.com/rd/research/sdl/07/soc_02.html]

2.2 Mobile ad hoc network Routing protocol:

Mobile ad hoc network (MANET) influenced to develope many new routing protocols mainly through the efforts of the internet Engineering Task Force(IETF).{ S. Corson and J. Macker, BMobile ad hoc networking (MANET): Routing protocol performance issues and evaluation considerations,[ in RFC 2501, Jan. 1999.}there are various issues to be considered while designing this protocols , due to its distributed state of unreliable environments it has become a challenge to design manet routing protocols. It has got some different environments such as dynamic topology this results in mobility of nodes, limited network capacity interms of bandwidth. Some of the constraints are collision between internal nodes, energy consumption by the nodes and interference.{ S. Corson and J. Macker, "RFC2501: Mobile ad hoc networking (MANET): Routing protocol performance issues and evaluation considerations," Internet RFCs, no., 1999. }

Distributed state in unreliable environment

The distribution of mobile nodes or resources in any unreliable environment becomes a challenging aspect to enable communication since the performance of routing protocol depends on the significance of the environment. So to overcome this aspect routing protocol should utilise the best bandwidth, battery life and processing power.

Dynamic topology (Mobility)[ 26].

The network topology in manet is not constant it changes dynamically due to the mobility of nodes and the presence of transient network this leads to interference in packet transformation and frequent path breaks, when this path breaks routing protocol efficiently builds the new topology and reliable connections are established.this posses an hefty challenge for MANET to scale and perform efficiently in variable network conditions.

Limited network capacity (Bandwidth)

Wired network will have more bandwidth then wireless network ,due to this limited bandwidth data transferring rate is very less in manets.in addition the wireless communication throughput is much less then radio's maximum transmission rate by considering the effects of multiple access,noise,fading and interference condition. This limited bandwidth resulted in a less stored topology information. an efficient routing protocol requires a complete topology information. But for manet routing protocols this leads to an increase in node control message and overheads and this requires more bandwidth.this control messages are used for enabling nodes to setup connections before transferring packet message in network. to obtain a balanced usage of a limited bandwidth a well organised routing protocol is required.

Energy-constrained operation

mobile nodes in MANET are portable so they have only limited battery life and processing power ,this two are very essential resource constraints .during the overheads situation the system requires more processing and battery life. So the main optimisation of designing system is the energy conservation ie.. routing protocol design should allow transfer with limited battery life and less processing power.

{ http://paper.ijcsns.org/07_book/200908/20090834.pdf}

Routing protocol design issues:

The main objective of a routing protocols are maximise network life time, increase network throughput, minimise delay maximise the energy efficiency and minimise the overheads. this are determined in terms of routing protocol properties i.e. distributed in operation, free loop, routing computation and maintenance, multiple routes, demand based operation and power consumptions

Routing protocols are scalable network so any node does not dependent on a centralised node. The node mobility is very high as the nodes enter or leave the network, a distributed routing operation is more fault tolerant than a centralised routing operation.

Routing protocol updates the route and guarantees that supplied route is free loop that consumes less bandwidth and processing power. The another efficient property is route computation and maintenance which involved in finding route to destination node by using minimum number of nodes within a desired setup connection time.

Multiple routes are to avoid and reduce reactions to topological changes and congestion. In this every nodes tries to keep a valid record and an alternative route in case of route break. This helps in using less bandwidth and processing power.

Mobile nodes such as laptops and personal digital assistants (PDA) have only limited battery life therefore an optimal use of power consumption is crucial.

Adhoc network routing protocols have been classified into three broad categories as shown in figure.

Flat routing schemes: This routing approaches adopt flat addressing scheme, all the nodes which are participating in routin plays an equal role. This scheme is further classified into two classes: proactive and reactive, according to their design philosophy

Hierarchical routing : it assigns a different roles to a network.whereas some protocols requires a hierarchical addressing systems.

Geographic position assisted routing: in this each mobile node is equipped with the global positioning system(GPS).as routing is based on geographical location information. Nowadays this requirement is quite realistic as advancement in communications made the devices to provide reasonable precision and at very low cost.

This research focuses on flat and hierarchical routing scheme.at first the flat routing scheme this are further classified into table-driven (proactive), on-demand (reactive) and hybrid protocols

In reactive or on-demand approach, protocols are source initiated, the source node is which sends the packet in this routes are identified and established only when it is required by a source node for transmitting data packets. If the route to the destination is not known then route discovery process is initiated(i.e only when a data packet has to be sent)and maintains route by a route maintenance procedure . The reactive algorithms are designed to reduce the

bandwidth consumed by control packets by eliminating the periodic table update messages. This routing is further classified into source routing and hop by hop routing. In source routing the source contains the entire information of the destination node including the next hop information of intervening node,whereas in hop by hop the source node will have destination and the next hope address i.e. the destination address given by the source node to the intermediate nodes routes the packet to the destination node using routing table

Ad hoc networks deployed with nodes using proactive routing protocols will have an idea of entire network topology with each node maintaining routing information to every other node in the network. It maintains consistent and up to date information of all possible routes ,to all destination at all times, regardless of whether the routes are needed. To support this consistency, the protocol sends messages by propagates (broadcast) to gather update information and all possible connectivity through the network and thereby making fresh use of fresh available routes with the help of sequence numbers and in this each node is expected to have atleast one or more routing tables . [A. K. Pandey and H. Fujinoki, "Study of MANET routing protocols by GloMoSim simulator," International Journal of Network Management,

Hybrid protocols are a combination of both proactive and reactive protocols. Unlike proactive protocol, routes in a network using reactive protocol are discovered on demand (Abolhasan et al, 2003).

The classification of ad hoc routing protocols is shown in the figure

[http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1020231]

2.3 Examples of Ad hoc routing protocols :

Some of the ad hoc routing protocols specifications developed by IETF MANET working group are

DSR (Dynamic Source Routing)

OLSR (Optimized Link State Routing)

AODV (Ad hoc On-demand Distance Vector)

TORA (Temporally-ordered routing algorithm)

ZRP (Zone Routing Protocol)

LANMAR (Landmark Routing Protocol)

FSR (Fisheye State Routing)

TBRPF (Topology Broadcast based on Reverse-Path Forwarding)

2.3.1 LANMAR:

Lanmar(landmark ad-hoc routing) protocol, it is an efficient pro active routing protocol in a "flat" ad-hoc network. It was developed by the wireless adaptive Mobility (WAM) laboratory [1]at computer science department, university of California, Los Angeles.

Lanmar it uses the notion of landmark, which was first introduced in a wired area networks [2].the main original scheme required is predefined multi-level hierarchical addressing. This hierarchical address reflects the position of each node within the hierarchy and helps to find the route to it.each node not only know the route to the node in its hierarchy partition but also know the routes to various landmarks at different hierarchical levels.packet forwarding is compatible with the landmark hierarchy and when the packet is approaching to its destination the path is gradually refined from the top level hierarchy to the lower level hierarchy.

LANMAR scheme uses the notion of landmark to keep track of logical subnets it does not require any predefined hierarchical address .and Thus the concept of landmark was extended to the wireless ad hoc environment. It assumes a group of large scale ad-hoc network into a logical subnets and this subnets moves in a group . The track of such logical subnets implies the notion of landmark. This logical subnets consist of nodes that have common interests and are likely to move as a "group"(example: team of co workers at a convention and brigade in the battlefield). and in each subnet group a representative landmark node which is dynamically elected. This elected landmark node is used to recover any failures.this election of landmark provides flexible way for the LANMAR protocol to cope with a dynamic and mobile network.this protocol even provides a solution for the nodes that are outside the scope of the landmark of their logical groups(drifters).for example a tank in batalion may become stranded or lost,that time this protocol is usefull.

The nodes within the scope in each group will get the accurate routing information from the underlying scoped routing algorithm. The routes in between the nodes are updated by routing update packets and this are restricted only within the scope. And if the nodes want to communicate to the remotee nodes (nodes outside the node's scope) this can be summarised by the corresponding landmarks. Thus the routing update traffic overhead and routing table are reduced by LANMAR scheme, it also improves the scalability.

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