Impact of Radio Irregularity on Wireless Sensor Networks

1
Impact of Radio Irregularity on Wireless
Sensor Networks

• Gang Zhou, Tian He, Sudha Krishnamurthy, John A.
  Stankovic
• Computer Science Department,University of
  Virginia
• June 2004

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Outline

• Motivation, State of Art and Contributions
• Analyze Radio Irregularity
• Radio Irregularity Model (RIM)
• Impact on Routing and MAC Layer
• Solutions for Radio Irregularity
• Conclusion and Future Work

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Motivation

• Evidence of radio irregularity of low power
  wireless devices in physical environment
• Need for models to regenerate radio irregularity
  in simulations
• Need for better protocols to address irregularity
  in running systems

4
State of Art

• Spherical radio range assumption in current
  research
• Localization, Sensing Coverage, Topology Control
• Experiments Related to Radio Irregularity
• Deepak Ganesan, etc., Complex Behavior at Scale
  An Experimental Study of Low-Power Wireless
  Sensor Networks , UCLA/CSD-TR 02-0013, 2002
• Alberto Cerpa, etc., SCALE A Tool for Simple
  Connectivity Assessment in Lossy Environments,
  CENS-TR 03-0021, 2003
• Jerry Y. Zhao, etc., Understanding Packet
  Delivery Performance in Dense Wireless Sensor
  Network, ACM SenSys, 2003
• Alec Woo, etc., Taming the Underlying Challenges
  of Reliable Multihop Routing in Sensor Networks,
  ACM SenSys, 2003
• DOI Concept (our previous work)
• Tian He, etc., Range-Free Localization Schemes
  in Large Scale Sensor Networks, MobiCom, 2003

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Contributions

• RIM a new radio energy model that considers
  irregularity
• Implemented in GlomoSim
• Review the impact of radio irregularity on
• MAC layer
• Routing layer
• Solutions to deal with radio irregularity
• Symmetric Geographic Forwarding
• Bounded Distance Forwarding
• Bidirectional Flooding
• Learning Function
• RTS Broadcast
• High Energy Asymmetry Detection

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• Motivation, State of Art and Contributions
• Analyze Radio Irregularity
• Radio Irregularity Model (RIM)
• Impact on Routing Layer
• Impact on Routing and MAC Layer
• Solutions for Radio Irregularity
• Conclusion and Future Work

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Radio signal properties - 1

• Non-isotropic Path Loss The radio signal from a
  transmitter has different path losses in
  different directions.

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Non-isotropic Path Loss

• Reasons
• Reflection, diffraction and scattering in
  environment
• Hardware calibration differences (non-isotropic
  antenna gain)

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Radio signal properties - 2

• Continuous variation The signal path loss varies
  continuously with incremental changes of the
  propagation direction from a transmitter.

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Radio signal property - 3

• Heterogeneity Different nodes have different
  signal sending powers

• Reasons
• Different battery status
• Different hardware calibration

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• Motivation, State of Art and Contributions
• Contributions
• Analyze Radio Irregularity
• Radio Irregularity Model (RIM)
• Impact on Routing Layer
• Impact on Routing and MAC Layer
• Solutions for Radio Irregularity
• Conclusion and Future Work

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RIM - DOI

• Degree of Irregularity (DOI)
• Definition the maximum received signal strength
  percentage variation per unit degree change in
  the direction of radio propagation.
• Account for non-isotropic path loss

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RIM - VSP

• Variance of Sending Power (VSP)
• Definition the maximum percentage variance of
  the signal sending power among different devices.
• Account for heterogeneous sending power

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RIM propagation formula
Signal receiving power signal sending power -
path loss fading
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• Motivation, State of Art and Contributions
• Analyze Radio Irregularity
• Radio Irregularity Model (RIM)
• Impact on Routing and MAC Layer
• Solutions for Radio Irregularity
• Conclusion and Future Work

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Analyze the Impact

• Impact on
• Path-Reversal technique
• Multi-Round technique
• Used in AODV, DSR, LAR

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Analyze the Impact

• Impact on
• Neighbor-Discovery technique
• Used in GF, GPSR, SPEED

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Simulation Configuration
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E2E Loss Ratio

• GF has rapidly increasing E2E loss ratio
• AODV and DSR have low E2E loss ratio

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Average E2E Delay

• GF has constant E2E delay
• AODV and DSR have increasing E2E delay

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of Control Packets

• GF has constant of control packets
• AODV and DSR have increasing of control packets

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Energy Consumption

• GF has decreasing energy consumption
• AODV and DSR increasing energy consumption

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• Motivation, State of Art and Contributions
• Analyze Radio Irregularity
• Radio Irregularity Model (RIM)
• Impact on Routing and MAC Layer
• Solutions for Radio Irregularity
• Conclusion and Future Work

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Solutions

• Symmetric Geographic Forwarding
• Bounded Distance Forwarding
• Bidirectional Flooding
• Learning Function
• RTS Broadcast
• High Energy Asymmetry Detection

• Symmetric Geographic Forwarding
• Detect and block asymmetric channels
• Only use symmetric channels for geographic
  forwarding
• Implementation Add all neighbors IDs in beacon
  messages
• Optimization estimate the channel quality
  statistically
• Currently implemented in a tracking system
  MobiSys 2004

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SGF --- E2E Loss Ratio

• SGF has constantly low E2E loss ratio

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SGF --- Average E2E Delay

• SGF has almost constant E2E delay

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SGF --- of Control Packets

• SGF has the same of control packets as that of
  GF

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SGF --- Energy Consumption

• SGF has a little increasing energy consumption

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Bounded Distance Forwarding

• Bounded Distance Forwarding restricts the
  distance over which a node can forward a message
  in a single hop.
• An add-on rule
• Tested in a running system with 60 MICA2 motes

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• Motivation, State of Art and Contributions
• Analyze Radio Irregularity
• Radio Irregularity Model (RIM)
• Impact on Routing and MAC Layer
• Solutions for Radio Irregularity
• Conclusion and Future Work

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Conclusion - 1

• The first effort to bridge the gap
• between isotropic radio energy models assumed by
  most simulators in WSN and the real non-isotropic
  radio properties

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Conclusion - 2

• Review the impact of radio irregularity on
  Routing and MAC layers
• Radio irregularity has a greater impact on the
  routing layer than on the MAC layer.
• Routing protocols, such as AODV and DSR, that use
  multi-round discovery technique, can deal with
  radio irregularity, but with high overhead.
• Routing protocols, such as geographic forwarding,
  which are based on neighbor discovery technique,
  are severely affected by radio irregularity.
• Solutions for radio irregularity
• SGF has as low loss ratio as that of AODV and
  DSR, but much lower control overhead and energy
  consumption.

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Future work

• To evaluate and further refine the RIM model
• Experiments in more types of environments
• Experiments with different types of devices and
  different types of antennas
• Radio pattern variation with system aging and
  environment changes
• Analyze the impact of radio irregularity on other
  protocols
• Localization, Sensing Coverage, Topology Control
• Analyze and evaluate the remaining four solutions
• Bidirectional Flooding
• Learning Function
• RTS Broadcast
• High Energy Asymmetry Detection

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Thanks to the MobiSys Shepherd and anonymous
reviewers for their valuable criticisms!
The End!