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Routing Protocols for Sensor

Networks

Presented bySiva Desaraju

Computer Science

WMU

An Application Specific Protocol Architecture for WirelessMicrosensor Networks

by

Anantha Chandrakasan, Wendi Rabiner Heinzelman, and HariBalakrishnan


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LEACH


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Outline Introduction

Background

Architecture

Operation

Analysis and Simulation

Results

Comparisions

Conclusion


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Introduction

Sensor Network Challenges Limited communication bandwidth

Limited energy

Parameters (Design goals) Ease of deployment

System lifetime

Latency

Quality Neighboring nodes may have same data

End user cares about a higher-level description of events


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LEACH (Low-Energy Adaptive

Clustering Hierarchy) Techniques (to achieve the design goals)

Randomized, adaptive, self-configuring cluster formation.

Localized control of data transfers Low energy media access control (MAC)

Application specific data processing, such as data aggregationand compression.


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BackgroundSome application specific protocols developed for MSN

Minimum Transmission Energy (MTE)

For 3 nodes A, B and C, A would transmit to node C through Biff (ETX total transmit energy)

ETX(d=dAB) + ETX(d=dBC) < ETX(d=dAC) Only consider transmitter energy, neglects energy dissipationof the receivers

Clustering

Nodes send data to central cluster head

Cluster head forwards data

Cluster head has to be high energy node

Fixed Infrastructure


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LEACH Protocol Architecture

Assumptions

All nodes can transmit with enough power to reach the basestation if needed

Each node has computational power to support different

MAC protocols

Nodes always have data to send

Nodes located to each other have correlated data


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LEACH in brief All non-cluster head nodes transmit data to their cluster head

Cluster head receives this data and performs signal processingfunctions on the data and transmits data to the remote BS

Nodes organize themselves into local clusters, with one node ascluster head


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Operation

Divided into rounds

Set-up phase

Clusters are organized

Steady phase

Data transferred from nodes to cluster and on to BS


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LEACH Step by Step

Cluster Head Selection

Each sensor elects itself to be cluster head at the beginningof a round

Nodes that have not already been cluster heads recently,may become cluster heads

Probability of becoming a cluster head is set as a function ofnodes energy level relative to the aggregate energy

remaining in the network

Average energy of nodes in each cluster X Number ofnodes in the network


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LEACH Step by Step contd Cluster Formation

Each cluster head node broadcasts an advertisement message(ADV) using CSMA MAC Protocol

The message consists of the nodes ID and a header that distinguishes it

as an ADV message

Each non-cluster head node determines its cluster/cluster head thatrequires minimum communication energy

Largest signal strength, minimum transmit energy for communication

Each node transmits a join-request message (REQ) using CSMA

MAC Protocol The message consists of nodes ID and cluster head ID

Each cluster head node sets up a TDMA schedule and transmits it

This ensures that there is no collision in data messages, radiocomponents can be turned off at all times except during transmit time

Setup phase complete


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Flowchart


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LEACH step by step contd Steady State Phase

Nodes send data during their allocated time slot

Once the cluster head receives all data it performs dataaggregation

Resultant data is sent from cluster head to BS (a high

energy transmission) Uses transmitter based code assignment to reduce inter-

cluster interference

Cluster head senses the channel before transmission

Steady phase complete


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LEACH-C:BS Cluster Formation Uses a central control algorithm to form clusters

During setup phase each node sends its location andenergy level to BS

BS assigns cluster heads and clusters

BS broadcasts this information


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Analysis and Simulation Using ns

Experiment setup

100-node network Nodes randomly distributed between (0,0) and (100,100)

BS at location (50,175)

Bandwidth of the channel 1Mbps

Each data message 500 bytes long

Packet header 25 bytes

Simple radio model


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Results:Limited energy Simulations

LEACH distributes more data per unit energy than MTE

LEACH-C delivers 40% more data per unit energy than LEACH


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Results contd

LEACH can deliver 10 times the amount of effective data to BSas MTE for the same number of node deaths

Benefits of rotating cluster heads is seen


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Conclusions Advantages

Outperforms conventional routing protocols

LEACH is completely distributed, requiring no controlinformation from the base station

Nodes do not need global topology information

Disadvantages

Nodes must have data to send in the allotted time

Perfect correlation is assumed, which might not be true always


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Comparisions

SPIN LEACHDirectedDiffusion

Optimal

Route No No Yes

NetworkLifetime

Good Very Good Good

Resource

Awareness Yes Yes Yes

Use ofMeta-datadescriptors

Yes No Yes


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ReferencesAn Application Specific Protocol Architecture for

Wireless Microsensor Networks by AnanthaChandrakasan, Wendi Rabiner Heinzelman, andHari Balakrishnan

Energy-efficient Communication Protocol forWireless Sensor Networks by AnanthaChandrakasan, Wendi Rabiner Heinzelman, andHari Balakrishnan (IEEE Transactions on wireless

communications, vol. 1, no. 4, Oct 2002)


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Thanks

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