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CHAPTER 1

INTRODUCTION TO MANET

1.1 INTRODUCTION

A Mobile Ad hoc Network is a collection of wireless mobile nodes

forming a temporary network without any infrastructure or centralized

administration (Chansu Yu et al 2003). Ad hoc wireless network is

comparatively a new paradigm of multi-hop wireless networking and has

become popular. It is an essential part of the computing environment,

consisting of infrastructure-less mobile networks (Carlo Kopp 1999). In

MANET, each node communicates with other nodes directly or indirectly

through intermediate nodes. The credit for the growth of ad-hoc network goes

for its self organizing and self configuring properties. All nodes in a MANET

basically function as mobile routers participating in some routing protocol

required for deciding and maintaining the routes.

Since MANETs are infrastructure-less, self-organizing, rapidly

deployable wireless networks, they are highly suitable for applications

involving special outdoor events, communications in regions with no wireless

infrastructure, emergencies and natural disasters, and military operations,

mine site operations, urgent business meetings and robot data acquisition

(Siva Ram Murthy and Manoj 2007).

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In general, routes between nodes in an ad hoc network may include

multiple hops and, hence, it is appropriate to call such networks as “multi-hop

wireless ad hoc networks”. The nodes in the MANET are battery operated.

Failure of some nodes operation can greatly impede performance of the

network and even affect the basic availability of the network, i.e., routing.

The movement pattern, location, direction of movement, pause distribution,

speeds and acceleration change over time of the mobile nodes can be

described by their mobility models (Mohd Izuan et al 2009). Figure 1.1 shows

an example mobile ad hoc network and its communication topology.

Figure 1.1 Mobile Ad Hoc Network

1.2 CHARACTERISTICS OF MANET

MANET is having the characteristics of wireless network in

general. Additional specific characteristics of the Ad Hoc Networking are:

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Wireless: Nodes communicate wirelessly and share the same

media (radio, infra-red, etc.).

Ad-hoc-based: A mobile ad hoc network is a temporary network

formed dynamically in an arbitrary manner by a collection of

nodes as and when need arises.

Autonomous and infrastructure-less: MANET does not depend

on any established infrastructure or centralized administration.

Each node operates in distributed peer-to-peer mode, acts as an

independent router, and generates independent data.

Multi-hop routing: No dedicated routers are necessary; every

node acts as a router and forwards each others’ packets to

enable information sharing between mobile hosts (Dow et al

2005).

Mobility: Each node is free to move about while communicating

with other nodes. The topology of such an ad hoc network is

dynamic in nature due to constant movement of the participating

nodes, causing the intercommunication patterns among nodes to

change continuously.

1.3 ADVANTAGES

Accessibility: MANET provides access to information and

services regardless of geographic position

Deployment: The networks can be set up at any place and time.

Infrastructure-less: The networks work without any pre-existing

infrastructure. This allows people and devices to interwork in

areas with no supporting infrastructure.

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Dynamic: Can freely and dynamically self-organize

into arbitrary and temporary network topologies (Bhavyesh

Divecha et al 2007).

1.4 MANET APPLICATIONS

Because ad hoc networks are flexible networks that can be set up

anywhere at any time, without any infrastructure, including pre-configuration

or administration, people have come to realize the commercial potential and

advantages that mobile ad hoc networking can bring.

This section describes some of the most prevalent applications for

ad hoc wireless networks. The self-configuring nature and lack of

infrastructure inherent to these networks make them highly appealing for

many applications, even if it results in a significant performance penalty. The

lack of infrastructure is highly desirable for low-cost commercial systems,

(Siva Ram Murthy and Manoj 2007) since it precludes a large investment to

get the network up and running, and deployment costs may then scale with

network success. Lack of infrastructure is also highly prevalent in military

systems, where communication networks need to be configured quickly as the

need arises, often in remote areas. Other advantages of ad hoc wireless

networks include ease of network reconfiguration and reduced maintenance

costs. However, these advantages must be balanced against any performance

penalty resulting from the multi-hop routing and distributed control inherent

to these networks.

1.4.1 Data Networks

Ad-hoc wireless data networks primarily support data exchange

between laptops, palmtops, personal digital assistants (PDAs), and other

information devices. These data networks generally fall into three categories

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based on their coverage area: LANs, MANs, and WANs. Infrastructure-based

wireless LANs are already quite prevalent, and deliver good performance at

low cost. However, ad hoc wireless data networks have some advantages over

these infrastructure-based networks. First, only one access point is needed to

connect to the backbone wired infrastructure: this reduces cost and installation

requirements. In addition, it can be inefficient for nodes to go through an

access point or base station. For example, PDAs that are next to each other

can exchange information directly rather than routing through an intermediate

node.

Wireless MANs typically require multi-hop routing since they

cover a large area (Gopalsamy et al 2002). The challenge in these networks is

to deal with high data rates in a cost-effective manner, over multiple hops,

where the link quality of each hop is different and changes with time. The

lack of centralized network further complicates the control and potential

high-mobility users.

Military programs such as DARPA’s GLOMO (Global mobile

information systems) have invested much time and money in building high-

speed ad hoc wireless MANs that support multimedia, with limited success.

Wireless WANs are needed for applications where network infrastructure to

cover a wide area is too costly or impractical to deploy. For example, sensor

networks may be dropped into remote areas where network infrastructure

cannot be developed. In addition, networks that must be built up and torn

down quickly, (e.g. for military applications or disaster relief) are infeasible

without an ad hoc approach.

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1.4.2 Home Networks

Home networks are envisioned to support communication between

PCs, laptops, PDAs, cordless phones, smart appliances, security and

monitoring systems, consumer electronics, and entertainment systems

anywhere in and around the home. Such networks could enable smart rooms

that sense people and movement and adjust light and heating accordingly.

“Aware homes” with network sensors and computers, may assist living of

seniors and those with disabilities.

Home networks also encompass video or sensor monitoring

systems with intelligence to coordinate. It can interpret data and alert the

home owner and or police or fire department of unusual patterns. Intelligent

appliances can coordinate with each other and with the Internet for remote

control and software upgrades. It can schedule and maintenance,

entertainment systems that allow access to a VCR, set-top box, or PC from

any television or stereo system in the home.

1.4.3 Device Networks

Device networks support short-range wireless connections between

devices. Such networks are primarily intended to replace inconvenient cabled

connections with wireless connections (Tseng et al 2003). Thus, the need for

cables and the corresponding connectors between cell phones, modems,

headsets, PDAs, computers, printers, projectors, network access points, and

other such devices is eliminated. The main technology drivers for such

networks are low-cost and low-power radios with networking capabilities

such as Bluetooth. The radios are integrated into commercial electronic

devices to provide networking capabilities between devices. Some common

applications include a wireless headset for cell phones, a wireless USB or

RS232 connector, wireless cards, and wireless set-top boxes.

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1.4.4 Sensor Networks

Wireless sensor networks consist of small nodes with sensing,

computation, and wireless networking capabilities (Shio Kumar Singh et al

2010). These networks represent the convergence of three important

technologies. Sensor networks have enormous potential for both consumer

and military applications. Military missions require sensors and other

intelligence gathering mechanisms that can be placed closer to their intended

targets.

The potential threat to these mechanisms is therefore quite high. In

view of this, the technology adopted must be highly redundant that requires

only a little human intervention. An apparent solution to these constraints lies

in large arrays of passive electromagnetic, optical, chemical, and biological

sensors. These can be used to identify and track targets, and can also serve as

a first line detection mechanism for various types of attacks. Such networks

can also support the movement of unmanned, robotic vehicles. For example,

optical sensor networks (David Culler et al 2004) can provide networked

navigation, routing vehicles around obstacles while guiding them into position

for defensive or attacking operations.

The design considerations for some industrial applications are quite

similar to those of military applications. In particular, sensor arrays could be

deployed and used for remote sensing in nuclear power plants, mines, and

other industrial venues.

1.4.5 Military Applications

Ad hoc wireless networks can be very useful in establishing

communication among a group of soldiers for tactical operations. Setting up a

fixed infrastructure for communication among a group of soldiers in enemy

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territories or in inhospitable terrains may not be possible. In such

environments, ad hoc wireless networks can provide the required

communication mechanism quickly. Another application area could be the

coordination of military objects moving at high speeds like fleets of airplanes

or warships. Such application requires quick and reliable communication.

Secure communication is of prime importance to eavesdropping or

other security threats that can compromise the purpose of communication or

the safety of personnel in these tactical operations. They also require the

support of reliable and secure multimedia multicasting. For example the

leader of a group of soldiers might wants to order all the soldiers or set some

of selected personnel involved in the operation. Hence the routing protocol in

these applications should be able to provide quick, secure, and reliable

communication in real-time traffic.

1.4.6 Emergency Operations

Ad hoc wireless networks are very useful in emergency operations

such as search and rescue, crowd control, and commando operations. The

major factors that favor ad hoc wireless networks for such tasks are self-

configuration of the system with minimal overhead, independent of fixed or

centralized infrastructure, the nature of the terrain of such applications, the

freedom and flexibility of mobility, and the unavailability of conventional

communication infrastructure.

In environments where the conventional infrastructure based

communication facilities are destroyed due to a war or due to natural

calamities such as earthquakes, immediate deployment of ad hoc wireless

networks require minimum initial network configuration for their functioning.

In that case, very little or no delay is involved in making the network fully

operational. The above-mentioned scenarios are unexpected; in most cases

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unavoidable, and can affect a large number of people. Ad hoc wireless

networks employed in such circumstances need to distributed and scalable to

a large number of nodes. They should also be able to provide fault-tolerant

communication paths. Real-time communication capability is also important

as voice communication predominates data communication in such situations

(Siva Ram Murthy and Manoj 2007).

1.5 MANET DESIGN ISSUES

Ad hoc wireless networks inherit the traditional problems of

wireless communications, such as bandwidth optimization, power control, and

transmission quality enhancement. In addition, their mobility, multi-hop

nature, and the lack of fixed infrastructure create a number of complexities

and design constraints that are new to mobile ad hoc networks.

In this section, the MANET research issues are presented and

classified (Haas and Tabrizi 1998). Hundreds of research aspects have already

been developed and discussed in this field. Various issues have to be

identified and solved so as to significantly increase MANET survivability.

They are discussed in the following.

(1) Routing: Routing is an essential protocol in this field, because

changes in network topology occur frequently (Rashmi

Rohankar et al 2012). An efficient routing protocol is required

to cope with highly fluid network conditions. The responsibility

of routing protocol includes exchanging of route information;

finding feasible path to a destination, based on criteria such as

hop length, minimum power requirement, and life of the

wireless link; gathering information about the path breaks;

mending the broken paths expending minimum processing

power (Singh and Raghavendra 1998) and bandwidth. The

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major requirements of a routing protocol (Cameron Lesiuk

1998) in ad hoc wireless networks are the followings:

Minimum route acquisition delay

Quick route reconfiguration

Loop-free routing

Distributed routing approach

Minimum control overhead

Scalability

Provisioning of QoS

Support of time-sensitive traffic

Security and privacy

(2) Multicasting/ Broadcasting: Multicast service supports users

communicating with other members in a multicast group.

Multicasting plays an important role in the typical applications

of ad hoc wireless networks, namely, emergency search-and-

rescue operations and military communication. In such an

environment, nodes form groups to carry out certain tasks that

require point-to-multipoint and multipoint-to-mutipoint (Imrich

Chlamtac et al 2003) voice and data communication. The

arbitrary movement of nodes changes the topology dynamically

in an unpredictable manner. The mobility of nodes, with the

constraints of power source and bandwidth, makes multicast

routing very challenging. Broadcast service supports users

communicating with all members on a network.

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(3) Location Service: Location information uses the Global

Positioning System (GPS) or the network-based geo-location

technique (Tseng et al 2001) to obtain the physical position

of a destination. Also the load on the wireless channel varies

with the number of nodes present in a given geographical

region (Dow et al 2005). This makes the contention for the

channel high when the number of nodes increases. The high

contention for the channel results in a high number of

collisions and a subsequent wastage of bandwidth. A good

routing protocol should be considered while designing built

in mechanisms for distributing the network load uniformly

across the network so that the formation of regions where

high channel contentions can be avoided.

(4) Clustering: Clustering is a method to partition the hosts into

several clusters (Dow et al 2002) and provide a convenient

framework for resource management, routing and virtual

circuit support.

(5) Mobility Management: One of the most important properties

of ad hoc wireless networks is the mobility associated with

the nodes. In the ad-hoc network environment, mobile hosts

can unrestrictly move from place to place. The mobility of

the nodes results in frequent path breaks, packet collisions,

transient loops, stale routing information, and difficulty in

resource reservation. Mobility management (Manoj Pandey

and Daniel Zappala 2003) handles the storage, maintenance

and retrieval of the mobile node position information.

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(6) Transport Layer Protocols (TCP/ UDP): The main objective

of the transport layer protocols include setting up and

maintaining end-to-end connections, reliable end-to-end

delivery of data packets, flow control, and congestion

control (Prasant Mohapatra and Srikanth Krishnamurthy

2009). There exist simple connectionless transport layer

protocols (UDP) which neither perform flow control and

congestion control nor provide reliable data transfer. Such

unreliable protocols (Fu et al 2003) do not take into account

the current network status such as congestion at the

intermediate links, the rate of collisions, or other similar

factors that affect network throughput. The major

performance degradation faced by a reliable connection-

oriented transport layer protocol such as transmission control

protocol (TCP) in an ad hoc wireless network arises due to

frequent path breaks, presence of stale routing information,

high channel error rate, and frequent network positions. TCP

and UDP are the standard protocols used in the Internet.

Data applications running over MANETs, such as http and

real audio need transport layer protocols like TCP and UDP

to send packets over the links.

(7) IP Addressing: One of the most important issues is the set of

IP addresses that are assigned to the ad-hoc network. IP

addressing and address auto-configuration have attracted

much attention in MANETs.

(8) Multiple Access: A major issue is to develop efficient

medium access protocols that optimize spectral reuse, and

hence, maximize aggregate channel utilization in MANETs

(Ya Xu et al 2000).

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(9) Radio Interface: Mobile nodes rely on the radio interface or

antenna to transmit packets. Investigations on packet

forwarding or receiving via radio interface or antenna

techniques in MANETs would be useful.

(10) Bandwidth Management: Bandwidth management (Chansu

YuBen et al 2003) in MANETs is a typical characterization.

Because the bandwidth is usually limited, effectively

managing and using it is a very important issue. Because

mobile nodes communicate each other via bandwidth-

constrained, variable capacity, error-prone, and insecure

wireless channels, wireless links will continue to have

significantly lower capacity than wired links and, hence,

more problematic in network congestion. Since the channel

is shared by all nodes in the broadcast region, the bandwidth

(Xu et al 2003) available per wireless link depends upon the

number of nodes and the traffic they handle.

(11) Power / Energy Management: Power constraints are another

big challenge in ad hoc wireless network design (Chansu

YuBen et al 2003). These constraints in wireless network

arise due to battery powered nodes which cannot be

recharged. This becomes a bigger issue in mobile ad hoc

networks because as each node is acting as both end system

and a router at the same time, additional energy is required

to forward packets. Energy management is defined as the

process of managing the sources and consumers of energy in

a node or in the network as a whole for enhancing the life

time of a network. Shaping the energy discharge pattern of a

node’s battery to enhance the battery life; finding routes that

result in minimum total energy consumption in the network;

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using distributed scheduling schemes to improve battery life;

and handling the processor and interface devices to

minimize power consumption are some of the functions of

energy management (Dehni et al 2005). A power

management approach would help reducing power

consumption and hence might prolong the battery life of

mobile nodes. Because most devices operate on batteries,

power management becomes an important issue. Energy

management can be classified into the following categories:

Transmission power management

Battery energy management

Processor power management

Devices power management

(12) Security: The mobile nodes in MANETs are highly

susceptible to malicious damage. Security issues are

important in MANETs to prevent potential attacks, threats

and system vulnerabilities. Mobile wireless networks are

more vulnerable to information and physical security threats

rather than fixed-wired networks. The use of open and

shared broadcast wireless channels means nodes with

inadequate physical protection are prone to security threats.

In addition, because a mobile ad hoc network is a distributed

infrastructure-less network, it mainly relies on individual

security solution from each mobile node, as centralized

security control is hard to implement. The major security

threats (Siva Ram Murthy and Manoj 2007) that exist in ad

hoc networks are as follows:

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Denial of services

Resource consumption

Energy depletion

Buffer overflow

Host impersonation

Information disclosure

Interference

(13) Fault Tolerance: This issue involves detecting and correcting

faults when network failures occur. Fault-tolerance

techniques (Ning and Sun 2003) are brought in for

maintenance when a failure occurs during node movement,

joining, or leaving the network.

(14) QoS/ Multimedia: Quality of Service (QoS) and Multimedia

require high bandwidth, low delay, and high reliability.

Quality of Service (QoS) guarantee is very much essential

for the successful communication of nodes in the network.

The different QoS metrics includes throughput, packet loss,

delay, and jitter and error rate. The dynamically changing

topology, limited bandwidth and quality makes difficulty in

achieving the desired QoS guarantee (Satyabrata Chakrabarti

and Amitabh Mishra 2001) for the network.

(15) Standards/ Products: The standards and products issues that

allow the development of small scale is emerging for this

field. For instance, Bluetooth is a low-cost technology for

short-range communications techniques.

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(16) Infrastructure-less network: The most fundamental aspect of

an ad hoc wireless network is its lack of infrastructure, and

most design issues and challenges stem from this

characteristic. Also, lack of centralized mechanism brings

added difficulty in fault detection and correction.

(17) Dynamic Topology: The dynamically changing nature of

mobile nodes causes to the formation of an unpredicted

topology. This topology change causes frequent route

change, network partitioning and packet dropping.

(18) Robustness and Reliability: In MANET, network

connectivity is obtained by routing and forwarding among

multiple nodes. Although this replaces the constraints of

fixed infrastructure connectivity, it also brings design

challenges. Due to various conditions like overload, acting

selfishly, or failed links, a node may fail to forward the

packet. Misbehaving nodes and unreliable links can have a

severe impact on overall network performance. Due to the

lack of centralized monitoring and management mechanisms

these types of misbehaviors cannot be detected and isolated

quickly and easily. This increases the design complexity

significantly.

These MANET design issues are classified based on the layers and

the taxonomy is shown in the Figure 1.2.

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1.6 FACTORS FOR QUALITATIVE ANALYSIS

There are many qualitative factors (Dow et al 2005) related to

MANETs. In this section, eight important factors are as follows:

(1) Adaptability: It describes the reaction to change in a network.

Adaptability allows the network to operate despite changes in

the environment.

(2) Flexibility: It is the ease and speed with which changes can be

made to any part of the network platform and the range of

changes that can be made without having to replace,

redevelop, or discard existing network components.

(3) Heterogeneity: It describes a network consisting of dissimilar

devices that run dissimilar protocols and in many cases

support dissimilar functions or applications.

(4) Performance: Performance is responsible for analyzing and

controlling network efficiency, such as network throughput

and error rates.

(5) Reliability: It estimates continuous, error-free network

operations. Perfect reliability over a given period of time

means no failures and no errors (Lin and Liu 1999).

(6) Scalability: The network must be able to grow. The initial

design should grow or develop without any major changes to

the overall design.

(7) Security: The network’s physical facilities must be protected

from harm and sensitive information kept from unauthorized

(Griswold and Medidi 2003) users while providing simple

and inexpensive access on a wide-scale basis. Further research

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is needed to investigate how to stop intruders from invading

the network.

(8) Stability: In a network environment, the network topology is

affected greatly by mobility. When node mobility becomes

higher, the topology structure has a higher possibility for

disintegration and encounters stability problems.

An ad-hoc routing protocol must meet all these challenges to give

the average performance in every case. Energy is a limiting factor in case of

ad-hoc networks. Routing in ad-hoc networks has some unique

characteristics. First- Energy of nodes is crucial and depends upon battery

which has limited power supply. Second- Nodes can move in an uncontrolled

manner (Bor rong chen and Hwa Chang 2003) so frequent route failures are

possible. Third-Wireless channels have lower and more variable bandwidth

compared with wired network. Security is an another issue in ad-hoc

networks. Further research is needed to investigate how to stop intruders from

invading the network. The network’s physical facilities must be protected

from harm and sensitive information kept from unauthorized users while

providing simple and inexpensive access on a wide-scale basis. Here energy

efficiency does not mean only the less power consumption, but it means

increasing the time duration in which any network maintains certain levels of

performance level. The state of energy efficient routing can be achieved by

increasing the network lifetime (Eei Yu and jangwon Lee 2003) and

performance.

1.7 MANET MOBILITY MODELS

The mobility model plays a very important role in determining the

protocol performance in mobile ad hoc Network. The mobility model

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(Jeya Kumar and Rajesh 2009) is designed to describe the movement pattern

of MNs, and how their speeds and directions are changed over the time.

Currently there are two types of mobility models used in the

simulation study of MANET:

1. Traces base model

2. Synthetic base model

The traces base model obtains deterministic data from the real

system. This mobility model is still in its early stage of research, it is therefore

not recommended to be used. Choosing suitable movement pattern depends

on applications that use the model.

The synthetic base model is the imaginative model that uses

statistics. In the real world, nodes or objects have their target destination

before they decide to move. However, the movement of each MN to its

destination has a pattern that can be described by a statistical model that

expresses the movement behavior in the real environment. This type of

mobility model can be either Entity Mobility Model (EMM) or Group

Mobility Model (GMM).

In EMM, each node moves independently. Examples of this type of

mobility model are Random Waypoint, Random Walk and Random Direction.

For GMM, the movement of each MN depends on some other MNs in the

group. Examples of GMM are Column Mobility Model and Reference Point

Group Mobility Model. For EMM, the Random Waypoint mobility model is

widely used for the simulation study of MANET. The major problems of

using this model are shape turn and sudden stop.

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The following section discusses the random mobility models like

Random Waypoint, Random Walk and Random Direction. These models with

various parameters reflect the realistic traveling pattern of the mobile nodes.

The following are the three models with the traveling pattern of the mobile

nodes during the simulation time.

1.7.1 Random Waypoint

The Random Way Point Mobility Model includes pauses between

changes in direction and/or speed. A Mobile node begins by staying in one

location for a certain period of time (i.e. pause). Once this time expires, the

mobile node chooses a random destination in the simulation area and a speed

that is uniformly distributed between them [min-speed, max-speed]. The

mobile node then travels toward the newly chosen destination at the selected

speed. Upon arrival, the mobile node pauses for a specified period of time

re-starting the process again.

The random waypoint model (Rashmi Rohankar et al 2012) is a

commonly used mobility model in the simulation of ad hoc networks. It is

known that the spatial distribution of network nodes moving according to this

model is non uniform. However, a closed-form expression of this distribution

and an in-depth investigation on it is not to be found. This fact impairs the

accuracy of the current simulation methodology of ad hoc networks and

makes it impossible to relate simulation based performance results to

corresponding analytical results. To overcome these problems, it is presented

a detailed analytical study of the spatial node distribution generated by

random waypoint mobility.

The movement trace of a mobile node using the Random Waypoint

model is shown in Figure 1.3. It is considered that a generalization of the

model in which the pause time of the mobile nodes is chosen arbitrarily in

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each waypoint and a fraction of nodes may remain static during the entire

simulation time.

Figure 1.3 Node Movement in Random Way Point

1.7.2 Random Walk

In this mobility model, a mobile node moves from its current

location to a new location by randomly choosing a direction and speed in

which to travel. The new speed and direction are both chosen from pre-

defined ranges, [min-speed, max-speed] and [0, 2*pi] respectively. Each

movement in the Random Walk Mobility Model occurs in either a constant

time interval ‘t’ or a constant travelled ‘d’ distance, at the end of which a new

direction and speed are calculated.

Since many entities in nature move in extremely unpredictable

ways, the Random Walk Mobility Model was developed to mimic this erratic

movement. If an MN which moves according to this model reaches a

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simulation boundary, then it bounces off the simulation border with an angle

that is determined by the incoming direction. The MN then continues along

this new path.

Random walk on a one or two dimensional surface returns to the

origin with complete certainty, i.e., a probability of 1.0. This characteristic

ensures that the random walk represents a mobility model that tests the

movements of entities around their starting points, without worry of the

entities wandering away never to return. Random Walk is a memory-less

mobility pattern. This characteristic can generate unrealistic movements such

as sudden stops and sharp turns.

1.7.3 Random Direction

A mobile node chooses a random direction (Mohd Izuan et al 2009)

in which to travel similar to the Random Walk Mobility Model. The node

then travels to the border of the simulation area in that direction. Once the

simulation boundary is reached, the node pauses for a specified time, then

chooses another angular direction (between 0 and 180 degrees) and continues

the process.

The Random Direction Mobility Model (Camp et al 2002) was

created to overcome clustering of nodes in one part of the simulation area

produced by the Random Waypoint Mobility Model. In the case of the

Random Waypoint Mobility Model, this clustering occurs near the center of

the simulation area. In the Random Waypoint Mobility Model, the probability

of an MN choosing a new destination, that is located in the center of the

simulation area, or a destination which requires travel through the middle of

the simulation area, is high.

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In this model, MNs choose a random direction in which to travel

similar to the Random Walk Mobility Model. An MN then travels to the

border of the simulation area in that direction. Once the simulation boundary

is reached, the MN then pauses for a specified time, chooses another angular

direction [0, 180] and continues with the process. In a slightly modified

version, MNs continue to choose random directions but they are no longer

forced to travel to the simulation boundary before stopping to change the

direction. Instead, an MN chooses a random direction and selects a

destination any where along that direction of travel.

1.7.4 Limitations of the Random Waypoint Model and other

Random Models

The Random Waypoint model and its variants (Babak Pazand and

Chris McDonald 2007) are designed to mimic the movement of mobile nodes

in a simplified way. Because of its simplicity of implementation and analysis,

they are widely accepted. However, they may not adequately capture certain

mobility characteristics (detailed below) of some realistic scenarios, including

temporal dependency, spatial dependency and geographic restriction:

Temporal Dependency of Velocity: In Random Waypoint and

other random models, the velocity of mobile node is a memory-

less random process, i.e., the velocity at current epoch is

independent of the previous epoch. Thus, some extreme

mobility behaviour, such as sudden stop, sudden acceleration

and sharp turn, may frequently occur in the trace generated by

the Random Waypoint model. However, in many real life

scenarios, the speed of vehicles and pedestrians will accelerate

incrementally. In addition, the direction change is also smooth.

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Spatial Dependency of Velocity: In Random Waypoint and

other random models, the mobile node is considered to be an

entity that moves independently of other nodes. This kind of

mobility model is classified as entity mobility model. However,

in some scenarios including battlefield communication and

museum touring, the movement pattern of a mobile node may

be influenced by certain specific 'leader' node in its

neighbourhood. Hence, the mobility of various nodes is indeed

correlated.

Geographic Restrictions of Movement: In Random Waypoint

and other random models, the mobile nodes can move freely

within simulation field without any restrictions. However, in

many realistic cases, especially for the applications used in

urban areas, the movement of a mobile node may be bounded

by obstacles, buildings, streets or freeways.

1.8 SELF-ORGANIZATION IN AD HOC NETWORKS

One very important property that an ad hoc wireless network

should exhibit is organising and maintaining the network by itself. The major

activities that an ad hoc wireless network required to perform for self-

organisation (Osianoh Glenn Aliu and et al 2012) are neighbour discovery,

topology organisation (Mills, 2007) and topology reorganisation. The

categories of self organisation are as follows:

Self-healing - mechanisms that allow to detect, localize, and

repair failures automatically; primarily distinguished by the

cause of the failure, e.g. breakdown, overload, malfunction.

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Self-configuration - methods for (re-)generating adequate

configurations depending on the current situation in terms of

environmental circumstances, e.g. connectivity, QoS parameters

(MacKenzie and Wicker 2001).

Self-management - capability to maintain devices or networks

depending on the current parameters of the system.

Self-optimization - similar to self-management but focuses on

the optimal choice of methods and their parameters based on the

system behaviour.

Adaptation - adaptation to changing environmental conditions,

e.g. the changing number of neighbouring nodes.

The definitions of Self organisation are as follows:

Definition 1 (Self-Organization): Self-organization (Dressler 2008)

is a process in which pattern at the global level of a system emerges solely

from numerous interactions among the lower-level components of a system.

Moreover, the rules specifying interactions among the systems’ components

are executed using only local information, without reference to the global

pattern. This definition of self-organization focuses on the emergence of

patterns. Similar definitions can be found in the literature concerning well-

studied methodologies in biological systems. The interaction of single

components finally defines the behaviour of the global system. Applied to ad

hoc networks, self-organization can be seen as the interactions between nodes

in the network leading to globally visible effects, e.g. the transport of

messages from a source node to a sink node. Since we speak of the emergence

of a pattern or a system behaviour, the term emergence needs to be defined as

well.

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Definition 2 (Emergence): Emergent behaviour of a system is

provided by the apparently meaningful collaboration of components

(individuals) in order to show capabilities of the overall system (far) beyond

the capabilities of the single components. Self-organization is often referred

to as the multitude of algorithms and methods that organize the global

behaviour of a system based on inter-system communication. Most

networking algorithms work like that. Therefore, self-organization in this

context is not a new solution in this research area. Nevertheless, most of these

algorithms are based on global state information, e.g. routing tables. In the

networking community, it is commonly agreed that such global state is the

primary source of scalability problem of the particular algorithm. Especially

in the area of ad hoc networks, new solutions were discovered that show the

properties of the new definition of self-organization.

1.8.1 Classification of Self-Organization Methods

Methodologies for self-organization in ad hoc networks can be

categorized in multiple dimensions. Categorization of self-organization

(Schmelz and Van den Berg 2009) methods and some well-known

mechanisms and ongoing developments are discussed in the following.

Location-based mechanisms - Geographical positions or

affiliation to a group of surrounding nodes, i.e. clustering

mechanisms, are used to reduce necessary state information to

perform routing decisions or synchronizations. Usually, similar

methods that are known for global state operations can be

employed in this context. Depending on the size of active

clusters or the complexity to perform localization methods, such

location-based mechanisms vary in communication and

processing overhead.

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Neighbourhood information - Further state reduction can be

achieved by decreasing the size of previously mentioned

clusters to a one-hop diameter. In this case, only

neighbourhood information is available to perform necessary

decisions. Usually, hello messages are exchanged in regular

periods of time. This keeps the neighbourhood information up-

to-date and allows the exchange of performance estimates such

as the current load of a system.

Probabilistic algorithms - In some cases, it is useful to store no

state information at all. For example, if messages are very

infrequently exchanged or in case of high mobility, pure

probabilistic methods can lead to optimal results. Statistical

estimates can be used to describe the behaviour of the overall

system in terms of predicted load and performed operations.

Obviously, no guarantee can be given that a desired goal will be

reached or not.

Bio-inspired methods - Biologically inspired methods build a

category that is composed of neighbourhood-depending and

probabilistic operations. All objectives are addressed by using

positive and negative feedback loops. Positive feedback acts as

an amplifier intensifying a reaction. Overload situations or over-

reactions are counteracted using negative feedback. Many

applications in ad hoc networks have been evaluated and

published.

While the required state is reduced towards the probabilistic

methods, the determinism or predictability of the algorithms is reduced as

well. Therefore, the best solution for a particular application scenario must be

chosen carefully by comparing all application requirements at once.

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In view of the above issues, the proposed research specifies itsresearch objectives.

1.9 OBJECTIVES

The main objectives of this thesis work are as follows:

To evolve a method to increase the network life time.

To determine how to reduce the control overheads and end toend delay.

To try out increasing the packet delivery ratio.

1.9.1 Methodology

Strategy 1 : To improve the network life,

1) Evolve mechanisms of optimal allocation of nodes dynamicallyfor routing, based on residual energy level of nodes.

2) Reduce the number of control packets during route discoveryand maintenance process, and thereby reduce energyconsumption of nodes.

Strategy 2 : To improve the control overhead and end to end delay,

1) Reduce the number of retransmissions by reducing the packetdrop rates in the established path.

2) Reduce the route discovery time by minimizing the number ofcontrol packets.

3) Reduce the packetisation time by using smaller packet size.

4) Stable route formation by using high energy level nodes.

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Strategy 3 : To improve Packet Delivery Ratio,

1) Reduce the number of retransmission by reducing the frequent

link failure.

2) Minimise the network congestion by reducing the number of

control packets.

1.10 CONTRIBUTIONS

The major contributions of this research work are listed below.

1) The proposed protocol EEDSR-RUC increases the network

lifetime by 35.32% over the existing DSR protocol by varying

the speed of the nodes. It increases by 42.74% by varying the

density of the nodes in the network.

2) The proposed protocol CBEER minimizes the control overhead

by 45.43% over the existing DSR protocol by varying the

density of the network. It reduces by 54.98% by varying the

mobility speed of the nodes.

3) The proposed protocol EEDSR-RUC increases the packet

delivery ratio by 37.03 % over the existing DSR protocol by

varying the density of the network.

4) The proposed protocol CBEER reduces the end to end delay by

35.98 % over the DSR protocol by varying the number of

source destination pairs. It reduces 38.36% by varying the

density of the mobile network.

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1.11 ORGANISATION OF THE THESIS

The organization of the thesis is as follows:

Chapter 1 presents the introduction to MANET and its

characteristics, the need for improving the life time of the MANET, the issues

and challenges in the MANET, and also the objective of the research work.

Chapter 2 discusses the various existing research works that are

relevant to the work presented in this thesis.

Chapter 3 deals with detailed study of the existing on-demand DSR

and AODV protocols with their route discovery and route maintenance

procedures.

Chapter 4 describes three modified energy efficient routing

protocols called EEDTR, MEER and EEDSR-RUC protocols proposed to

increase the life time of the mobile ad hoc network and to improve the QoS

parameters.

Chapter 5 discusses on energy efficient clustering protocols called

CBEER and CBEER-NN suggested to increase the lifetime of the network by

selecting energy efficient cluster head as well as the energy efficient virtual

backbone.

Chapter 6 compares the various proposed energy efficient routing

protocols for evaluating their performances.

Chapter 7 concludes the contributions and findings in addition to

suggestions for future enhancement.