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Optimal Communication Coverage for Free-Space-Optical MANET
Building Blocks
Murat Yuksel, Jayasri Akella, Shivkumar Kalyanaraman, Partha Dutta
Electrical, Computer, and Systems Engineering DepartmentRensselaer Polytechnic Institute, Troy, NY
[email protected], [email protected], [email protected], [email protected]
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Outline Motivation FSO MANETs Node Designs Optimizing FSO Node Designs FSO Node Design Recommendations Summary
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MotivationFree-space-optical (FSO) communication requirements:
Line of sight (LOS) existence alignment between the communicating antennas
FSO against RF: Lower power per bit Significantly higher transmission rates due to optical
spectrum
FSO in MANETs: Inexpensive, mobility tolerant components needed
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FSO MANETs Node Designs
Traditional FSO node/component designs: sufficient for building sways or vibrations not sufficient for mobile ad hoc environments
To ensure uninterrupted data flow, auto-aligning transmitter and receiver modules are necessary.
FSO node designs that uses: spherical surfaces – angular diversity covered with multiple transmitter and receiver modules – spatial
reuse
LED
PhotoDetector
Micro Mirror
Spherical Antenna
Optical Transmitter/Receiver Unit
Spherical surface covered (tessellated) with
LED+PD pairs (transceivers)
Hybrid of spherical and array: honeycombed
arrays of transceivers
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FSO MANETs Node Prototypes
Electronic tracking of the other mobile node
allows maintenance of the logical optical link
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Optimizing FSO Node Designs
How good the node be in terms of coverage? range?
How many transceivers can/should be placed on the nodes?Various factors effect optimum coverage and the designs of FSO nodes:
Visibility – weather conditions Transmitter’s source power and detector’s sensitivity Divergence and reception angles of devices – higher cost for
smaller angles Number of transceivers per area – packaging optimality
We focus on a 2-d circular design
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Optimizing FSO Node Designs (cont’d)
Two cases are possible: overlapping or non-overlapping coverage.
)2/tan()(tan rRR )2/tan()(tan rRR
The interference area can be calculated if the
FSO propagation lobe is approximated by a
triangle and a half circle.
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Optimizing FSO Node Designs (cont’d)
For given source power and receiver sensitivity, we calculate the range Rmax based on the FSO propagation model (atmospheric and geometric attenuation):
Depending on transmitter source power P, divergence angle θ, and visibility V, optimal number of transceivers n that should be placed on the 2-d circular FSO node can differ. Since coverage of a single transceiver C is dependent on P, θ, V and n; for given node and transceiver sizes the optimization problem can be written as:
GL AAP )43(
),,,(max,,,
nVPnCnVP
mRad1.0 mWP 32 mV 200,20
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FSO Node Design Recommendations
The source power P and the visibility V have little or no effect on the optimality of n; rather, the geometric shape of the FSO node and the divergence angle plays the major role.FSO nodes allows adaptive tuning of the source power based on the actual visibility.
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FSO Node Design Recommendations
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Summary Modeled communication coverage and range for FSO MANET node designs.
two-dimensional modeling FSO node designs:
allow very dense packaging, and can scale to very long communication ranges as well
as large coverage.
Future work includes issues like: optimal transceiver packaging patterns for desired
coverage in three-dimensions, and application-specific designs of such node designs.
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Thank you !!
