Communication Standards in Wireless Sensor Networks Bachelor Thesis - - PowerPoint PPT Presentation

Lehrstuhl für Netzarchitekturen und Netzdienste

Institut für Informatik Technische Universität München

Communication Standards in Wireless Sensor Networks

Bachelor Thesis Lukas Tillmann Advisors: Alexander Klein, Corinna Schmitt

2 Communication Standards in Wireless Sensor Networks

Outline

 Definition of WSN  Communication Standards  Goals of this thesis  Analysis technology and methods  Evaluation  Conclusion

3 Communication Standards in Wireless Sensor Networks

Outline

 Definition of WSN

 Communication Standards  Goals of this thesis  Analysis technology and methods  Evaluation  Conclusion

4 Communication Standards in Wireless Sensor Networks

Communication Standards - Overview

 There is no uniform protocol standard in Wireless Sensor Networks

(WSNs)



Independent development by different interest groups trying to meet similar challenges

 IEEE 802.15.4



Implementation of the Physical and Data Link Layers



Specifically designed for use in Wireless Low-Power Networks (WPANs)



Provides usage of different frequency ranges, CSMA and address ranges



Maximum Transmission Unit (MTU) of 128 bytes

 ZigBee and 6LoWPAN - two IEEE 802.15.4 based Standards

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Communication Standards - ZigBee

 ZigBee



Holistic standards solution in WSNs



Implements all Layers up to the

Application Layer



Provides mechanisms for network

creation, maintenance, adressing, application interfaces, etc.

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Communication Standards – 6LoWPAN

 6LoWPAN (IPv6 over Low-Power Wireless Personal Area Network)



Implementation of an Adaption Layer to enable the usage of IPv6 in WSNs



Provides several mechanisms to shorten IPv6 frames

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Goals of this thesis

 Presentation of ZigBee and 6LoWPAN regarding



Functional principles



Network creation



Data transmission / shortening mechanisms



Integrated security mechanisms



Behavior in simulations

 Questions handled in this thesis



What different approaches were taken?



How it data transmission handled?



How are the specific challenges in WSNs managed?



How do these protocol standards behave in simulations?

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Used Analysis Tool

 Simulating different scenarios using



OPNET – ZigBee simulator



6LoWPAN not supported by OPNET simulation

 Reasons for using just one simulator/protocol standard:



Very few noticeable differences between two similar standards.



Problems comparing the results of two different simulators because of



Different possiblities/limitations when it comes to data input



Different ways of computing the statistics

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Analysis Methods

 Used simulation topologies: Star,

Chain, Grid

 Used simulation variations:



Differing number of nodes active

within a network



Differing traffic intensity

 For each simulation run, one network model is used



Nodes are present and signed in to the PAN at all times



Differing start and stop times for application data transmission

10 Communication Standards in Wireless Sensor Networks

Gathering the data

 Gathering the data



Ten simulation runs with differing seed values are performed



Merging and sorting the data by using a small Java program

11 Communication Standards in Wireless Sensor Networks

Star topology



All traffic is directed towards the Coordinator



Nodes gradually join in on data transmission

12 Communication Standards in Wireless Sensor Networks

Star topology

Interarrival Time 5 seconds Packet size 64 bytes  Overall delay respective to the number of nodes active in the network

13 Communication Standards in Wireless Sensor Networks

Star topology

Interarrival Time 1 second Packet size 128 bytes  Overall delay respective to the number of nodes active in the network  Increase in delay as more retransmission become necessary  Decrease in variance as retransmission become the norm

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Star topology

Interarrival Time 1 second Packet size 128 bytes  Percentage of packets dropped (maximum number of backoff retransmissions reached (4)) in a star topology high traffic variant

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Chain topology



All traffic is directed towards the Coordinator



Increasing number of hops towards the destination



Only one node sends at a time

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Chain topology

Interarrival Time 5 seconds Packet size 128 bytes  Gradual and steady growth of End-to-End delay as number of hops increases (avg. 6.145 ms per additional hop)  Increase in variance due to escalation from previous values

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Grid topology

 All traffic is directed towards the Coordinator  Nodes drift away from the center with 0.25 meters/minute  Topology structure (parent-child associations) remains intact  Start: 10 meters spacing between adjacent nodes  End: 150 meters spacing between adjacent nodes

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Grid topology

Interarrival Time 2 seconds Packet size 64 bytes  Packet loss ratio after maximum number of backoffs (4) is reached  Decrease as node density is eased

19 Communication Standards in Wireless Sensor Networks

Grid topology

Interarrival Time 2 seconds Packet size 64 bytes  Load in bits/s respective to the distance between two adjacenting nodes  Load decreases as node density decreases due to fewer required retransmission attempts

20 Communication Standards in Wireless Sensor Networks

Conclusion

 ZigBee



All-in-One solution



Provides interfaces in the Application Layer



Best suited for secluded systems

 6LoWPAN



Built for adaption of IPv6 in WSNs



Handles the parsing between IPv6 and 6LoWPAN headers



No application support provided



Best suited for traffic that exceeds the WSN

 Used protocol standard can be chosen according to the needs of a specific WSN!

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Questions Thank you for your attention !

22 Communication Standards in Wireless Sensor Networks

OPNET Screenshot – Star Low Traffic „Time average“

23 Communication Standards in Wireless Sensor Networks

OPNET Screenshot – Star Low Traffic „As Is“