Introducing Ad Hoc Networks

8/7/2019 Introducing Ad Hoc Networks

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Introducing Ad Hoc NetworksIntroducing Ad Hoc Networks

Nishi Kanta Das

Roll:- IT200117168


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National Institute of Science & Technology

Presentation OutlinePresentation Outline

What is an Ad Hoc network?

Addressing schemes within Ad Hoc Networks

Ad Hoc network/Internet connectivity


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What is an Ad Hoc Network?

What is an Ad Hoc Network?

Dictionary definition of ad hoc:

Improvised and often impromptu

Therefore

MANETs (Mobile Ad hoc NETworks) are

networks which can come in and out of

existence without the need for any prior

planning


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BSC MSC

BTS

BTS

BTS

BSS

Other BSSs

Simplified example from GSM

BTS = Base Transceiver Station

BSC = Base Station Controller

BSS = Base Station SubsystemMSC = Mobile Switching Centre

Conventional Cellular SystemsConventional Cellular Systems


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communication is facilitatedcommunication is facilitated

by an infrastructureby an infrastructure

what if there is nowhat if there is no

infrastructure?infrastructure?


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How are MANETs different?How are MANETs different?


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Nodes discover and maintain routes automatically


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Applications and ScenariosApplications and ScenariosAnytime communication needs to occur but a

facilitating infrastructure is not available

Conference/Lecture

Sensor Networks

Military

Search & Rescue

Wireless Mesh Networks


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How doM

ANET

s route data?How doM

ANET

s route data?

using an ad hoc routingusing an ad hoc routing

protocolprotocol


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TheThe ad hocad hocFamily TreeFamily Tree

C

V W P

Pr -a ti e

V

TORA

L R

SSR

ABR

Re-a ti e

ad hocRouti Pr otocol

DSDV = Destination-Sequenced Distance-Vector Routing, CGSR = Clusterhead Gateway Switch Routing,WRP =

Wireless Routing Protocol, AODV = Ad Hoc On-Demand Distance Vector Routing, DSR = Dynamic Source

Routing, LMR = Lightweight Mobile Routing, TORA = Temporally Ordered Routing Algorithm, ABR =Associativity-Based Routing, SSR = Signal Stability Routing

Pro-active

actively seeks for routes

Re-active

seeks for routes only when required


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ProPro--Active ExampleActive ExampleDestination-Sequenced Distance- ector(DSD ) Routing

Main characteristics

Each node keeps a table of

routes to all otherdestinations in the network

Routing table updates are

periodically transmitted

throughout the network to

maintain consistency Number of nodes in network

limited as overhead due to

routing updates grows

rapidly with network size


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DSD RoutingDSD Routing

FE

D

C

B

A

Routing table for E: (simplified)Dest. Next Hop Metric Sequence Number

A D 3 S406_A

B D 2 S128_B

C D 2 S076_ C

D D 1 S050_D

F F 1 S392_F

Routes are kept fresh by periodically

sending UPDATE messages, which

contain part of the above information.

This can generate large amounts of

traffic as the number of nodes

increases


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ReRe--Active Routing ExampleActive Routing ExampleDynamic Source Routing (DSR)

FE

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A

Main characteristics

A route is established when

a node wants to transmit to

anoth

er node (e.g. A with

F) A doesnt know the route to

F, so it transmits a Route

Request (RREQ)

a

a-b

a-b-d

a-b-d

a-b-d

a-b-d-e

Each node forwards the

RREQ on all links except forthe one on which it was

received

The destination node picks

the shortest path, and sends

it in a Route Reply (RREP)


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FE

D

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Dynamic Source Routing (DSR)

a-b-d-fa-b-d-f

a-b-d-f

Node A receives the RREP

and caches the route

All intermediate nodes also

now know th

e route to nodeF, as well as the route to A

Differences with DSDV

Routes are kept fresh

through acknowledgements,not routing updates

Initial latency when sending

data as route needs to be

acquired first

ReRe--Active Routing ExampleActive Routing Example


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ProP

ro--active or Reactive or Re--activeactive --which method is best?which method is best?

depends upon the intendeddepends upon the intendedapplication/scenarioapplication/scenario


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SummarySummary

What is an Ad Hoc network?

An infrastructure less network that can beformed without any prior planning

Why?Infrastructure not available / has beendestroyed. E.g. battle-time scenario, remotesearch and rescue, sensor networks etc.

How is data routed?Using one of the many experimental protocolswhich can either pro-actively seek out routes,or can discover routes as and when they are

required

Introducing Ad Hoc Networks

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