© 2008 IBM Corporation
IBM T. J. Watson Research Center
Slide 1
Enabling Accurate Node Control in Randomized Duty Cycling Networks
Kang-Won Lee*, Vasileios Pappas, Asser Tantawi
IBM T. J. Watson Research Center
Research was sponsored by the U.S. Army Research Laboratory and the U.K. Ministry of Defense and was accomplished under Agreement Number W911NF-06-3-0001. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the U.S. Army Research Laboratory, the U.S. Government, the U.K. Ministry of Defense or the U.K. Government.
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International Technology Alliance in International Technology Alliance in Network and Information SciencesNetwork and Information Sciences
Collaborative Alliance Managers/Consortium Managers Jay Gowens (ARL) Jack Lemon (MoD) Dinesh Verma (IBM) Dave Watson (IBM-UK)
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•4
International Technology Alliance in International Technology Alliance in Network and Information SciencesNetwork and Information Sciences
Collaborative Alliance Managers/Consortium Managers Jay Gowens (ARL) Jack Lemon (MoD) Dinesh Verma (IBM) Dave Watson (IBM-UK)
International Technology Alliance in International Technology Alliance in Network and Information SciencesNetwork and Information Sciences
Collaborative Alliance Managers/Consortium Managers Jay Gowens (ARL) Jack Lemon (MoD) Dinesh Verma (IBM) Dave Watson (IBM-UK)
Security Across a Security Across a System-of-SystemsSystem-of-Systems
Trevor Benjamin (Dstl)Trevor Benjamin (Dstl)Greg Cirincione (ARL)Greg Cirincione (ARL)
John McDermid (York U)John McDermid (York U)Dakshi Agrawal (IBM)Dakshi Agrawal (IBM)
Security Across a Security Across a System-of-SystemsSystem-of-Systems
Trevor Benjamin (Dstl)Trevor Benjamin (Dstl)Greg Cirincione (ARL)Greg Cirincione (ARL)
John McDermid (York U)John McDermid (York U)Dakshi Agrawal (IBM)Dakshi Agrawal (IBM)
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•IBM T. J. Watson Research Center
•© 2008 IBM Corporation•Slide 5 •Invited Seminar at Tsinghua University, June 20, 2008
Wireless Sensor Networks
Embed numerous distributed devices to monitor and interact with physical world
Exploit spatially and temporally dense, in situ, sensing and actuation
Network these devices so that they can coordinate to perform higher-level identification and tasks.
Requires robust distributed systems of hundreds or thousands of devices.
[Estrin, Introduction to wireless sensor networks]
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 6 KOCSEA 2008, October 25, 2008
Duty Cycling in Wireless Sensor Networks
Power saving Longevity of mission lifetime
Impacts the performance
Sensor coverage
Connectivity
Routing delay
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 7 KOCSEA 2008, October 25, 2008
Related Work
SPAN (Chen, 2001)
Local randomized decision to join a forwarding backbone based on the estimate how much it will benefit the neighbors
GAF (Xu, 2001)
Sets up a virtual grid based on location information, and only one node in a grid becomes active
STEM (Schurgers, 2002)
Nodes awaken sleeping neighbors when they need to forward data using beacons on a dedicated signaling channel
NAPS (Godfrey, 2004)
Local randomized algorithm based on number of neighbors with an aim to achieve global connectivity
…
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 8 KOCSEA 2008, October 25, 2008
STAR: spatial transition algorithm
Z Z Z …
Z Z Z …
Z Z Z …Z Z Z …
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 9 KOCSEA 2008, October 25, 2008
STAR: spatial transition algorithm
Hmm… 3 out of 7neighbors are awake.Therefore I should sleep for duration T…
Hmm… 3 out of 7neighbors are awake.Therefore I should sleep for duration T…
Sleep duration T is selected based on (1) intrinsic parameter, (2) extrinsic parameter and (3) state of its neighbors
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 10 KOCSEA 2008, October 25, 2008
STAR Duty Cycling Networks
Each node makes local decision
Sleep decision: where
Wake-up decision: where
We are interested in the steady state
What fraction of nodes will be active in a steady state?
Approach
Model the state of a duty cycling network as a spatial process
swtwetf )( )1('r
w wst
setf )()0('r
s
Intrinsic parameter
Externalfactor
No. of awake/sleepingneighbors
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 11 KOCSEA 2008, October 25, 2008
Modeling a duty cycling network – spatial process
State of the network
for a network with set of nodes V and E where |V| = n and |E| = e
),...,,( 21 nssss
Random field
steady state probability distribution )1,0(:)( Ss
Markov random field
probability only affected by neighbors
)|()|( neighborjjGj ssPssP
},{ activesleepsi
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 12 KOCSEA 2008, October 25, 2008
Steady state behavior
For a reversible Markov random field a simple general solution exists [F. Kelly]
Let
α(0) = 1, α(1) = μ / λ
λ : intrinsic rate of a node to transition to sleep state (0)
μ : intrinsic rate of a node to transition to wake-up state (1)
Equilibrium distribution)1()0()1()( RRMBs
Three main parameters: α (intrinsic), γ, δ (external)
How do they affect the duty cycling performance? Three main parameters: α (intrinsic), γ, δ (external)
How do they affect the duty cycling performance?
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 13 KOCSEA 2008, October 25, 2008
Impact of network size on the PDF
degree = 6, α = γ = δ = 1degree = 6, α = γ = δ = 1
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 14 KOCSEA 2008, October 25, 2008
Impact of the α parameter on the PDF
1000 nodes, degree = 6, γ = δ = 11000 nodes, degree = 6, γ = δ = 1
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 15 KOCSEA 2008, October 25, 2008
Impact of the γ and δ parameters
1000 nodes, degree = 6, α = 11000 nodes, degree = 6, α = 1
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 16 KOCSEA 2008, October 25, 2008
Impact of average node degree on the PDF
1000 nodes, α = 1, γ = δ = 1.051000 nodes, α = 1, γ = δ = 1.05
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 17 KOCSEA 2008, October 25, 2008
Convergence speed
IBM T. J. Watson Research Center
© 2008 IBM CorporationSlide 18 KOCSEA 2008, October 25, 2008
Summary
ITA is a new venture for collaborative research in network science
Presented an accurate node density control algorithm for a randomized WSN
Recommendations
Use α to control the peak of the PDF
Choose small γ and δ for small variance
Start with large λ and μ for quick convergence