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Actor Positioning Based on Molecular Geometryin Aerial Sensor Networks
Actor positioning strategy for aerial sensor networks
Mustafa Ilhan Akbas, Gürkan Solmaz and Damla Turgut
Department of Electrical Engineering and Computer ScienceUniversity of Central Florida - Orlando, FL
June 13, 2012
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 1 / 17
1 Application scenario
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 2 / 17
1 Application scenario
2 Problem definition
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 2 / 17
1 Application scenario
2 Problem definition
3 System model
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 2 / 17
1 Application scenario
2 Problem definition
3 System model
4 Positioning method
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 2 / 17
1 Application scenario
2 Problem definition
3 System model
4 Positioning method
5 Simulation study
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 2 / 17
1 Application scenario
2 Problem definition
3 System model
4 Positioning method
5 Simulation study
6 Conclusion
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 2 / 17
Application scenarioVolcanic eruption such as the volcano Eyjafjallajökull in 2010Close-up observation of the volcano was impossibleUAV system with built-in sensors to investigate volcanic plume
Sink UAV
Actor UAV
Actor UAV
Actor UAV
Actor UAV
Sensor UAV
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 3 / 17
Problem definition
Problem◮ For effective data collection, positioning of UAVs is important◮ Most dynamic node positioning strategies limited to 2-D space◮ Popular 2-D strategies become NP-Hard in 3-D space
Objective◮ Dynamic positioning of the actors in three dimensional space with
local communication
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 4 / 17
System model
Challenges◮ UAV system has autonomous flight operation mode◮ Autonomous flight may reduce situational awareness and error
correction◮ The communication must be simple yet effective◮ The actors must be able to reorganize in case of a loss
System◮ WSAN of small UAVs with built-in sensor nodes◮ Larger and more powerful UAVs with actor nodes◮ Central, most powerful UAV serving as the sink node
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 5 / 17
System dynamics
Affiliation of sensor to actor nodes is executed as in SOFROP†
◮ Actors assigned with weight k◮ Sensor nodes initially get random weight values◮ Sensor nodes update weight = k - (hop count of sensor node)◮ Only data available for a sensor node s, are the direct neighbors
Neigh(s) and their corresponding weights w(Neigh(si ))◮ Sensor nodes maintain and update only local information
Nodes have spherical transmission ranges
Network among actors and the sink form the communicationbackbone
†M. I. Akbas, M. R. Brust, and D. Turgut. “SOFROP: Self-Organizing and Fair Routing Protocol for Wireless Networks with Mobile
Sensors and Stationary Actors” Elsevier Journal of Computer Communications, in early access
DOI:10.1016/j.comcom.2011.01.006, 2011.
†M. I. Akbas, M. R. Brust, and D. Turgut. “SOFROP: Self-Organizing and Fair Routing Protocol for Wireless Networks with Mobile
Sensors and Stationary Actors” In the Proceedings of IEEE Local Computer Networks (LCN‘10), pp. 456–463, October 2010.
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 6 / 17
“VSEPR theory” based approach
VSEPR (Valence Shell Electron Pair Repulsion) model is the mostsuccessful model for the molecular geometry prediction
Arrangement of electron pairs in valence shell of the central atomare due to the repulsion between them
VSEPR theory is adopted to build a self-configuring dynamicnetwork architecture
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 7 / 17
“VSEPR theory” geometriesPeripheral atoms mapped to actors and central atom to the sink
Linear
Trigonal planar
Tetrahedral
Trigonal bipyramid Pentagonal bipyramid
Octahedral Square Antiprismatic
Sink
Sink Sink
Sink Sink
Sink
Sink
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 8 / 17
Formulation of VSEPR geometries
Examples:
Positions of actors in Linear geometry:
pa1(x , y , z) = (r , 0, 0) pa2(x , y , z) = (−r , 0, 0)
Positions of actors in Trigonal planargeometry:
pa1(x , y , z) = (r , 0, 0)pa2(x , y , z) = (−r .sin(30◦), r .sin(60◦), 0)pa3(x , y , z) = (−r .sin(30◦),−r .sin(60◦), 0)
Positions of actors in Tetrahedral geometry:
pa1(x , y , z) = (0, 0, r)pa2(x , y , z) = (−r .a,−r .b, r .cos(109.5◦))pa3(x , y , z) = (−r .sin(109.5◦), 0, r .cos(109.5◦)pa4(x , y , z) = (−r .a, r .b, r .cos(109.5◦))
Sink
x
y
z
a 1 a 2
Sink
120
120
120 o
o
o x
y
z
a 1
a 2
a 3
Sink
a 1
a 4
x
y
z
a 2
a 3
109.5 o
109.5 o
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 9 / 17
Formulation of VSEPR geometries
Actor locations must be identified according to a reference point
Sink taken as the reference origin in XYZ coordinate system inflight
Transition between geometries must not be complex◮ Geometries formulated s.t. transition from one to another requires
least number of position changes⋆ When number of actors is between 1-3, actors located on a single
plane⋆ When number of actors is between 4-7, 2 actors located on z-axis,
others located on single plane with equal connection angles⋆ When number of actors is 8, actors located on 2 planes
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 10 / 17
Dynamic positioning
Transitions betweengeometries done with alightweight (depending onbasic rules) algorithm
There is no operation center orremote control
Changes and maintenancethrough local communicationonly
Affiliation of sensor nodes tothe actors are handled bySOFROP networkorganization
Transitions between geometriesif n < 4 then
Position on z = 0 planePositions with Θ = 360
nelse if 8 > n > 4 then
Positions:Θ = 360
n−2 on z = 0 plane
Θ = 90◦ for y -axis and z = 0 neighborselse if 13 > n > 7 then
Positions:Θ = 360
a and (z = h2 )&(x = 0 or y = 0)
Θ = 360a and (z = −h
2 )&(x = y or x = −y)
Θ = 90◦ for y -axis and z = 0 neighborsif n = 9 then
Θ = 360n/3 on z = 0 plane
end ifelse if ids = Minimum among neighbors then
Position on z-axiselse
Position at z = −r .cos(109.5◦) equally spacedend if
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 11 / 17
1-hop Coverage for Different GeometriesScalability improvement by
◮ Inreasing number of actors and sinks◮ Specifying VSEPR geometries for multiple sinks
The performance difference becomes apparent as the number ofactors exceeds 7
2 4 6 8 10 12 140
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2x 10
6
Number of data collectors
1−ho
p co
vera
ge o
f net
wor
k ba
ckbo
ne (
m3 )
1−sink geometries2−sink geometries
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 12 / 17
1-hop Coverage of Actors
Our protocol vs. Random positioning with a central node
Our protocol performs better with an increasing difference as thenumber of actors increases
0 2 4 6 8 10 120
2
4
6
8
10
12
14
16
x 105
Number of actors
1−ho
p co
vera
ge o
f net
wor
k ba
ckbo
ne (
m3 )
VTBP
PRP
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 13 / 17
1-hop Coverage of Actors with 2 sinks
Our protocol vs. Random positioning with 2 sinks
Performance improves as the number of actors increases
0 2 4 6 8 10 120
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2x 10
6
Number of actors
1−ho
p co
vera
ge o
f net
wor
k ba
ckbo
ne (
m3 )
VTBP
PRP
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 14 / 17
Average maximum and minimum weight values
Higher average weight values mean small hop-counts, so bettersharing of the sensor nodes
2 3 4 5 6 7 80
1
2
3
4
5
6
7
8
Number of actors
Wei
ght v
alue
Max. weight
Min. weight
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 15 / 17
Cardinality of actors
Fluctuation in cardinality reduces as number of actors increases
2 4 6 8 10 12 140
5
10
15
Simulation run
Ave
rage
car
dina
lity
LinearTrigonal planarTetrahedralTrigonal bipyramidOctahedralPentagonal bipyramidSquare Antiprismatic
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 16 / 17
Conclusion
Scalable heuristic algorithm for positioning of actors in aerialWSANs
Simulation results show our protocol provides high connectivityand coverage
Future steps:◮ Increasing scalability and extending our protocol to large networks◮ Exploring other concepts of VSEPR theory and molecular geometry◮ Real-life experiments with UAVs
M. I. Akbas, G. Solmaz, D. Turgut (UCF) ICC 2012 June 13, 2012 17 / 17