VIRTUAL SURROUNDING FACE GEOCASTING IN WIRELESS AND ADHOC SENSOR NETWORKS

AN IMPROVED FACE TRAVERSAL FOR GEOCASTING IN WIRESS

ADHOC AND SENSOR NETWORKS

ByN.A.P.Sivasubramaniyan,

ME-CSE, IInd Year

Guided ByDr. E.Baburaj

Problem Definition

• GEOCASTING– a task to deliver a message from a source node to all

nodes within a given geographic region.

• It requires ensured message delivery with low transmission cost.

• Limited energy of sensors requires geocasting to consume a little energy

as possible.

• Location Based Routing

• Face Routing

• Greedy Face Greedy Routing

• Geocasting Algorithms

• Broadcasting Algorithms

Existing Approaches for Routing

Vitrual Surrounding Face Geocasting 3


• Face Routing






Location Based Routing

• Every node in network knows its location and its neighbors.

• Routing made based on destination location and location of neighbors.

• Nodes don’t maintain routing tables.

Greedy LBR• Each node choses the neighbor closest to the destination as next forwarding node.

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Greedy LBR• Fails when a message gets stuck in a

dead end.

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• Face Routing







• Face Routing






Face RoutingDerive a planar graph from the network topology

Face RoutingPartition into set of faces……..

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Face Routing

s t

Face Routing

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Face Routing


s t

Face Routing


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Face Routing


s t

Face Routing


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Face Routing


Disadvantage:

High transmission cost

Face Routing



• Face Routing







• Face Routing






Greedy Face Routing

• Combines greedy LBR and Face Routing.

• Generally uses greedy routing.

• When a void is reached, uses Face Routing.

Drawback in existing Face Routing

Though x is a direct neighbor of v, message is sent from v to w and then to x, introducing an extra transmission.

In dense networks, this may be significant compared with the total number of transmissions for face traversal.

Solution: We propose a SKIP method to allow skipping of such nodes.



• Face Routing







• Face Routing






Geocasting

• can be easily achieved by flooding the network.

• Problem: Not energy efficient.

Requires atleast ‘N’ transmissions.

• Three classes of geocasting algorithms exist.

GeocastingClass I: limits the scope of flooding by creating a restricted forwarding zone.

minimum rectangle containing source and geocasting region is chosen as forwarding zone.

restricted flooding is performed.

Drawback:forwarding zone larger than geocasting region.

Flooding cost don’t go down.

message delivery not guaranteed.Vitrual Surrounding Face Geocasting 28

Geocasting

Class II: reduces flooding costs.

restricted forwarding zone is intelligently flooded.

Drawback:message delivery not guaranteed.


GeocastingClass III:

phase 1: message sent from source node to a node in geocasting region.

phase 2: performs restricted flooding.

Reduces transmission cost.

Drawback:message delivery not guaranteed.


Some algorithms combine location based unicasting and restricted flooding with face traversal to guarantee message delivery.

• Depth First Face Tree Traversal

• Restricted Flooding with Intersected Face Traversal

• Entrance Zone Multicasting based Geocasting

Drawbacks :

Complex, longer delivery time, high message cost, potentially series contention.

RFIFT: Restricted Flooding with Intersected Face Traversal

Phase 1: Uses GFG to deliver a geocasting message to a node in geocasting region R.

Phase 2: Performs restricted flooding within R and traverses all the faces intersecting R. Each face traversal determined by two nodes:

an internal border node

an external border node


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Some concerns:• Cost• Potential collision• Delivery speed

RFIFT Basic


Another Problem in RFIFT

• In some cases, RFIFT needs to be modified to guarantee message delivery

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Region

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z



• Face Routing







• Face Routing






Broadcasting

• It is a process to send a message to all nodes in a network.

• Efficient broadcasting can be modified to reduce the cost of restricted flooding in geocasting.

• Drawbacks:

high cost, contention, message collision.


Broadcasting

• based on domain set based algorithms.

• a connected domain set(CDS) is defined, such that for every node in the network, the node either belongs to CDS or has a direct neighbor in CDS.

• flooding performed only by the nodes belonging to the CDS.



Dominating Set - Example

Our Goals

• Guaranteed message delivery

• Short delivery time

• Low transmission cost

• Avoid potential message collisions

• Reducing message complexity of RFIFT


Proposed Scheme……

Virtual Surrounding Face Geocasting (VSFG)



Basic Idea of VSF: Virtual Surrounding Face

For any two faces that share an edge, if the shared edge is ignored, the two faces can be merged into one face with a larger area.


Virtual Surround Face (VSF)

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v

Overview of VSFG

• VSFG algorithm based on VSF acheives geocasting with guaranteed message delivery.

• SKIP algorithm let nodes skip some intermediate nodes during face traversal.

• DS based restricted flooding reduces the number of transmissions.

• RFIFT reduces the transmission cost.

• We assume that all nodes donot change their locations during the geocasting task.


VSFG• composed of three tasks.

VSF Forwarding

VSF Traversal

VSF Restricted Flooding



VSF Forwarding

VSF Traversal



VSF Forwarding:

A source node transmits a geocasting message containing the specification of the region to a node on the boundary of the VSF by LBR or GFG.



VSF Forwarding

VSF Traversal




VSF Forwarding

VSF Traversal



VSF Traversal:

Node which received the message starts double directional face traversal.

Thus messages will never collide.

Traversal is also aided by SKIP algorithm to reduce the number of transmissions.



VSF Forwarding

VSF Traversal




VSF Forwarding

VSF Traversal



VSF Restricted Flooding:

Every node on the boundary of VSF performs DS based Restricted flooding.



Example of VSF Geocasting

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QUERIES…???

Vitrual Surrounding Face Geocasting

Documents

VIRTUAL SURROUNDING FACE GEOCASTING IN WIRELESS AND ADHOC SENSOR NETWORKS