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Authors:Mrs.C.Chandralekha R.Balachandar

Associate Professor II MCA

SNS College of TechnologyCoimbatore

Kelpi: The Dynamic VirtualBackbone

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Agenda

Introduction to Mobile Ad hocnetworks (MANETs)

Routing in MANETsVirtual Backbone Routing

Kelpi: Algorithm and implementation

Conclusion

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MANET

MobileRandom and perhaps constantly

changing

Ad-hoc

Not engineered

NetworksElastic data applications which usenetworks to communicate

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Sensor networks Networks deployed in

random distribution

Low power

Delivering sensor datato a central site forsome purpose

Area monitoring,

Air pollutionmonitoring, Forestfires detection

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Traffic networks

Smart cars and smart

roads

Onboard systems talk tothe road:

Map obstacles and delays

Obtain maps

Inform the road of its actions

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Military applications

Combat regiment in the field

Intercommunication of forces

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Characteristics of MANETs Dynamic topology

links formed and broken with mobility

Possibly unidirectional links Constrained resources

battery power

wireless transmitter range

Network partitions

A B AB

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Problem of Routing in MANETs

To find and maintainroutes between nodes in a

dynamic topology withpossibly

unidirectional links, usingminimum resources.

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Dynamic Source Routing(DSR)

Routing is through source routing complete path with each packet

Route discovery

flooding RREQ till a node replies Route maintainance

explicit link breakage notification

Mobility of a node can break routes passing throughit.

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Destination Sequenced DistanceVector (DSDV)

Modified Distance Vector protocol periodic DV updates

High frequency of DV updates

topology is dynamic

Does not scale well

size of DV updates increase

high routing overheads

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Observations

Most ad hoc routing protocols are

combinations/variations of DSR/DSDV

Mobility in DSR causes short-lived routes

DSDV is not scalable

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The Dynamic Virtual Backbone

The dynamic virtual backbone is a conceptwherein a set of relatively stable routes areformed despite nodes being mobile.

a possible way is to abstract mobilitythrough aggregation a dynamic group of nodes by preventing some

information from moving out of the group, keepsmobility transparent to the rest of the network.

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Node

Router

SD

(x0, y0)

(xl, yl)

Cell

OperationalArea

Virtual Backbone in Kelpi

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Kelpi

Kelpi: a MANET routing algorithm based onthe concept of Virtual Backbone Routing(VBR).

Assumptions:

nodes equipped with positioning system, say aGPS receiver

nodes capable of multi-level transmission

mobility scenario

upto vehicular speeds of mobility

area of a few kilometres

fairly dense network

typical battlefield/disaster relief scenario

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Routing in Kelpi

Area of operation divided into squaregeographical cells

In each cell one node is a router

Inter-cell communication is throughroutersRouters transmit at a higher transmission

powerNodes communicate through their cellrouters

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Node

Router

SD

(x0, y0)

(xl, yl)

Cell

OperationalArea

Routing in Kelpi

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1.Area of operation is known

2..Initialization parameters: boundingco-ordinates and maxTxPower.

(x0, y0)

(xl, yl)

Initialization: Node comes on:1.Node calculates grid

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2.Node sends HI

3. Does not receive reply and

declares itself router of cell 21

Another node comes on:1.Node sends HI

2 Receives reply from router

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Kelpi: Router

Data structures at router: node_list, routing_table, forwarding_pointers

The new router sends a RH (Router Here) message

prevents multiple routers in a cell

starts listening on the CRA starts sending/receiving DV updates to/from

neighbouring routers

receives HI messages and enters sending node intonode_list

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Kelpi: Route Discovery

node S wants to send to node DS must know Ds cell

S discovers Ds cell by sending a

FIND_CELL packet to its routerRouters flood FIND_CELL amongthemselves

A router with the node in its node_listreplies directly to S

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Node

Router

SD

(x0, y0)

(xl, yl)

Cell

OperationalArea

Routing in Kelpi

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Kelpi: Handling node mobility

Node detects it is in a new cell

sends BYEto previous cells router

sends HIto new cells router

sends MOVED_CELL to nodes communicating with itRouter detects it is approaching a new cell initiates router handoff

appoints new router

messages: RTR_MOVE, RTR_MOVE_ACK,RTR_HANDOFF

sends routing_table, sequence numbers, node_list tonew router

becomes a node

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Implementation

ns-2 network simulator used forimplementing Kelpi

open source, used widely in MANETresearch

critical modifications to ns-2

packet headersphysical layer code for multi-poweredtransmitter

introduction of new routing agent: Kelpi

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Kelpi: Implementation

following functionality has been successfullyimplemented

topology related functions

cell discovery destination cell caching

packet buffering

packet forwarding

router hand-offs

these have been validated for small testcases

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Kelpi vs. other algorithms

Advantages designed to provide stable routes

increased throughput due to two levels of

transmission reduced flooding overhead

Disadvantages

positioning system required

muliple levels of transmission preferred routers may be overloaded in a dense network

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Future Directions

Remove requirement of GPS from Kelpi

Generalize concept of Virtual BackboneRouting to other existing routing

algorithms

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Questions

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THANK YOU