Ad Hoc Networks1

8/3/2019 Ad Hoc Networks1

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From:

Amritpal Singh

Master of Technology(ECE)

100016880471



Introduction

History

Mobile Ad-hoc Networks

±Infrastructure based Networks and Infrastructure-less Networks.

± Setting up a simple Mobile Ad-hoc Network

± Pros and Cons.

Wireless Ad-hoc Sensor Networks

±

Classification, types, network structure, basic requirements. Difference between Cellular and Ad-hoc Networks

Security Goals

Conclusions



An Ad-hoc network is a local area network or some other

small network, especially one with wireless (or temporary plug

in connections), in which some of the network devices are the

part of the network only for the duration of a communicationssession.

Allows new network devices to be quickly added.

Each user has a unique network address that is recognized as

the part of the network.



The first generationfirst generation goes back to 19721972. At the time, they werecalled PRNETPRNET

The second generationsecond generation of ad-hoc networks emerged in

1980s1980s,when the ad-hoc network systems were further enhanced and implemented as a part of the SURANSURAN(Survivable Adaptive Radio Networks) program

In the 1990s1990s the IEEE 802.11IEEE 802.11 subcommittee had adopted the

term "ad-hoc networks".

Mobile ad-hoc network was also be named as MANETMANET byIETFIETF.



Today the networks normally developed are of the type

having some fixed infrastructure. What would be

the solution if the network is required to be made for

some short period of time?



Nodes or devices can join together to make up a simple ad-hoc

network. Every device owes an equal status or designation in

the network.



One organization, for example arranges a conference, and the

attendees use their laptops or notebook computers to connect

to the nearby computers and the Internet through the wireless

router.



A better solution to this kind of network will be an ad-hoc

network in which the wireless router is replaced by a wireless

computer that can well act as a wireless router.

The computers communicate directly with each other.



Mobile Ad hoc Network (MANET) is a collection of

independent mobile nodes that can communicate to each other

via radio waves. The mobile nodes that are in radio range of

each other can directly communicate, whereas others needs the

aid of intermediate nodes to route their packets. These

networks are fully distributed, and can work at any place

without the help of any infrastructure. This property makes

these networks highly exible and robost.



On the basis of infrastructure we can classify the Ad-hoc

networks into two main categories. They are

1. Infrastructure-based networks.

± A network with pre-constructed infrastructure that is made of fixednetwork nodes and gateways, with typically network services delivered

via these preconfigured infrastructures.

± For example, cellular networks are infrastructure-based networks built

from PST N backbone switches, MSCs, base stations, and mobile hosts.

±Each node has its strict specific responsibility in the network. WLANstypically also fall into this category.



No expensive infrastructure must be installed

Use of unlicensed frequency spectrum

Quick distribution of information around sender

Use of ad-hoc networks can increase mobility and flexibility,as ad-hoc networks can be brought up and torn down in a very

short time.

Ad-hoc networks can be more economical in some cases, as

they eliminate fixed infrastructure costs and reduce power consumption at mobile nodes.

Because of multi-hop support in ad-hoc networks,

communication beyond the Line of Sight (LOS) is possible at

high frequencies.



Multi-hop ad-hoc networks can reduce the power consumption

of wireless devices. More transmission power is required for

sending a signal over any distance in one long hop than in

multiple shorter hops. It can easily be proved that the gain in

transmission power consumption is proportional to the number

of hops made.

Because of short communication links (multi-hop node-to-

node communication instead of long-distance node to central

base station communication), radio emission levels can be keptlow. This reduces interference levels, increases spectrum reuse

efficiency, and makes it possible to use unlicensed unregulated

frequency bands.



A wireless ad hoc sensor network consists of a number of

sensors spread across a geographical area.

Each sensor has wireless communication capability and some

level of intelligence for signal processing and networking of the data.



Military sensor networks to detect and gain as much

information as possible about enemy movements, and other

phenomena of interest. In a military sensor network, track an

enemy tank as it moves through the geographic area covered

by the network.

Also the military sensor networks designed to maintain a low

probability of intercept and/or a low probability of detection.

Hence the nodes prefer to radiate as little power as necessary

and transmit as infrequently as possible, thus decreasing the probability of detection and interception.

Sensor networks to detect and characterize Chemical,

Biological, Radiological, Nuclear, and Explosive material.



Individually addressable nodes.

Group or mixed addressable nodes.



Network self-organization: For large number of nodes and

their potential placement in hostile locations, it is essential that

the network be able to self-organized, manual configuration is

not feasible. Moreover, nodes may fail and new nodes may

join the network. Therefore, the network must be able to

periodically reconfigure itself so that it can continue to

function. Individual nodes may become disconnected from the

rest of the network, but a high degree of connectivity must be

maintained. Large number of sensors: Required for the collection of

information from different regions



Collaborative signal processing: Yet another factor that

distinguishes these networks from MANETs is that the end

goal is detection/estimation of some events of interest, and not

just communications.

Querying ability: A user may want to query an individual node

or a group of nodes for information collected in the region.

Various local nodes will collect the data from a given area and

create summary messages.

Low energy use: Since in many applications the sensor nodes

will be placed in a remote area, service of a node may not be

possible. In this case, the lifetime of a node may be

determined by the battery life, thereby requiring the

minimization of energy expenditure.



Acoustic used as the sound sensors.

Seismic for the prediction of earth quake.

Infrared for short range communication.

Still/Motion video camera.



Cellular Networks Ad-hoc Networks

Fixed, pre-located cell sites and base

stations.

No fixed base stations, very rapid

deployment.

Static backbone network topology Highly dynamic network topologies,

with multi-hop.

Relatively favorable environment and

stable connectivity.

Hostile environment (losses, noise)

and irregular connectivity.

Detailed planning before base stations

can be installed.

Ad-hoc network automatically forms

and conforms to change.



Lack of Infrastructure or centralized control

± Key management becomes difficult

Dynamic topology

± Challenging to design sophisticated & secure routingprotocols

Communication through Radio Waves

± Difficult to prevent eavesdropping

Vulnerabilities of routing mechanism ± Non-cooperation of nodes

SecurityChallenges in Ad HocSecurityChallenges in Ad Hoc

NetworksNetworks



Ad hoc networking will play an important role in this

evolution. Its intrinsic flexibility, ease of maintenance, lack of

needed infrastructure, auto configuration, self-administration

capabilities, and significant cost advantages make it a prime

candidate for becoming the stalwart technology for personal

pervasive communication

In moving forward and successfully fulfilling this opportunity,

developing and seamlessly integrating MANET with other

wireless networks and fixed internet infrastructures, thesuccessful addressing of many of the open research and

development issues will play a critical role

Ad Hoc Networks1

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