Routing in Wireless Sensor Networks

ROUTING IN WIRELESS SENSOR

NETWORKS

By: Syed Ashar Zia

Elet-6316: Routing Algorithms & ProtocolsDr. Driss Benhaddou

BY: SYED ASHAR ZIA 2

About Presentation Phase I: Introduction to Wireless

sensor networks, its applications, architecture, and challenges.

Phase II: Routing Protocols introduction, DSDV, AODV, Cluster-based routing.

Phase III: Performance evaluation of AODV and DSDV through simulation.

PHASE - I:INTRODUCTION TO WIRELESS SENSOR

NETWORKS


WSN Introduction

WSN refers to a network of sensor nodes connected through wireless medium.

WSN is usually a large network connecting even more than a thousand nodes.

Sensor nodes are used to monitor, record and notify specific conditions at various locations.

Conditions could be temperature, humidity, wind, pressure, and many more.


WSN: Applications

WSN has a wide range of applications, such as:Military applications,Environmental monitoring,Industrial sensing,Security applications.

WSN is very useful for monitoring remote locations where human access is limited or not possible at all.


WSN Architecture


WSN Architecture

Fig: Sensor Network with Internet access


Components of WSN

Sensor nodes/End nodesResponsible for sensing the conditions.

Base Station/Sink nodeCollects information from end-nodes.

Gateways Processing Hub

Processes the collected data at BS. Storage Hub


Different Tiers in WSN


Protocol Stack in WSN Three layers are

added in TCP/IP model.

To increase the awareness at the nodes.

Task, Mobility & Power are crucial information in sensor networks.


Challenges in WSN

ArchitectureEnergy efficient architecture is priority.Compromises could be made on size,

capacity, cost & speed.

RoutingDifferent from the traditional IP

Networks.Talking to thousands of nodes makes it

complex and inefficient at the energy & storage level.


Challenges in WSN

Distributed Signal ProcessingImportant part at the low-level layer in

WSN.Provides BS with locations & signal

identification of nodes, etc.

Storage & Data retrievalCentral storage of data from several

nodes. Storage at nodes requires processing at

the nodes.


Challenges in WSN

ActuationRequired action for sensed quantity.Such as pointing cameras, alarming

sounds, opening valves, etc.

SecurityAttackers may change the behavior of

nodes leading to change in results. Confidentiality, integrity, robustness,

and authenticity matters in WSN.

PHASE - II:ROUTING PROTOCOLS IN

WIRELESS SENSOR NETWORKS


Routing in WSN

Routing in WSN

Network Structure

Flat Networks

Hierarchical Networks

Location based

Protocol Operation

Negotiation based

Multi-path based QoS based Query

based


Routing in WSN

WSNs are usually ad-hoc in nature. Nodes’ communication directly to

BS defines their MANET (Mobile Ad-hoc Network) nature.

Set of standards are defined for the protocols used in Ad-hoc networks

Mobility of nodes disturbs the standards, therefore routing is quiet challenging.


MANET Routing Standards

Routing Protocols for

MANET

Proactive/Table Driven

DSDV, FSR, STAR

Hybrid ZRP

Reactive/On-demand

Driven

DSR, AODV, TORA

Cluster-based

LANMAR, CEDAR


MANET Routing Standards Pro-Active Protocols

Routing table with all paths maintained at each node.

E.g. DSDV (Direct Sequenced Distance Vector)

Reactive ProtocolsDiscovers route when required. E.g. AODV (Ad-hoc On-demand

Distance Vector) Hybrid

Combination of Proactive & Reactive protocols.


Distance Vector Routing Each node maintains a routing table

containingList of all available destinationsNumber distance to each each destinationNext hop to reach a destination

The succession of next hops leads to a destination

Each node periodically broadcasts its current estimate of the shortest distance to each available destination to all of its neighbors

Typical representative: Distributed Bellman-Ford


Bellman-Ford Algorithm


Direct Sequenced DV Design Goals

Keeping the simplicity of Bellman-Ford.Avoid looping issues

Route information is transmitted by broadcast

Updates are transmitted periodically or immediately when any significant topology change is availableEven sequence no.s are assigned by destinationIf a broken link is detected: metric ∞ and

updated odd sequence no. are assigned by detecting host.


Direct Sequenced DV

Types of Broadcast updatesFull Dump:All information from the

transmitting node.Incremental: All information that has

changed since the last full dump.

Full dump is transmitted if incremental dump exceeds the size of one NPDU.

Routing Table is maintained with latest sequence numbered route and least cost metric.


Advantages: DSDV

Excellent performance in small networks.

Energy efficient as route processing is minimal.

Routing overhead is approximately constant regardless of node movements and traffic load.

Simple implementation using Bellman-Ford algorithm.


Disadvantages: DSDV

Bandwidth and size of table increases with increasing number of nodes.

Overhead increases for maintaining large no. of nodes, hence degrades the performance of network.

Fails to converge if nodes are changing locations quickly.

Not very efficient in route updating. Limits no. of nodes that can join

network.


Ad-hoc On-demand DV Intended for the networks with

thousands of nodes. It’s a reactive or demand-driven protocol

which calculates the route when required and caches it for further use.

Routing table only maintains next hop for the destination rather than complete route.

Freshness of route is maintained by sequence numbers.


Ad-hoc On-demand DV

Routing Table maintains:Destination IP addressDestination sequence numberValid destination sequence number

flagOther state & routing flagsNetwork interfaceHop countNext hopLifetime (route expiration time)


Ad-hoc On-demand DV Basic message

set in AODV includes:Hello - For link

statusRREQ - Route

RequestRREP - Route ReplyRERR - Route Error

Only in case of Route is not in table and has to be discovered.

B?

B? B

?B

?

B?

B?

B?

B

ARREQ Message

B

A

A

A

A

A

A

A

RREP Message


Ad-hoc On-demand DV

Maintenance of Routes is handled very efficiently in AODVHello messages broadcast by active nodes

periodically called HELLO_INTERVAL.If no Hello reply from a neighbor within

DELETE_PERIOD link failure is identified.RERR message is broadcasted to other

neighbors.Entries based on that node invalidated.Route is rediscovered using RREQ when it is

required.

PHASE - III:PERFORMANCE ANALYSIS

DSDV & AODV

Simulation done by:Abdul Hadi Abd Rahman & Zuriati Ahmad ZukarnainEuropean Journal of Scientific Research


AODV vs DSDV

In AODV graph fluctuates between 0.3 and 2.4sec while in DSDV it is between 0.005 and 0.008 sec. This shows that route calculation or discovery method in AODV increases the End-to-End delay.

Scenario 1: End-to-End Delay with increasing number of nodes.


AODV vs DSDV

Here, three routing protocols are compared, AODV, DSDV and Improved DSDV. Here, we can see that with increasing no. of nodes routing overhead increases dramatically in DSDV which causes instability when it’s a large network.

Scenario 2: Routing Overhead with increasing number of nodes.


ANALYSIS RESULTS

Small WSN:DSDV is better than AODV.Less routing overheadDelay is negligible when compared to

the time it takes to calculate route in AODV.

Large WSN:AODV is better than DSDVEfficiently handles mobility and route

updates.Less overhead and appropriate delay.


REFERENCES Routing in Wireless sensor networks – Rachid

Ennaji & Muhammad Boulmalf – IEEE, 2009 Performance comparison of AODV, DSDV and I-

DSDV – Abdul Hadi & Zuriati Ahmed – European Journal of Sc. Research

Group-based clustering RP – Lei Zhang – IEEE, 2007

http://www.ece.ul.ie/homepage/tom_newe/RFP05.html

http://www.ece.gatech.edu/research/labs/bwn/WMSN/projectdescription.html

www.authorstream.com


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Routing in Wireless Sensor Networks