Transcript
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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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Questions/Comments?
Thanks
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