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Ali Abedi, Ph.D, Assistant ProfessorMauricio P. da Cunha, Ph.D, Associate Professor
Electrical and Computer Engineering DeptUniversity of Maine, Orono
2007 NASA Fly-by-Wireless Workshop, Grapevine, TX, March 27-28
Hybrid Wireless Communications with Hybrid Wireless Communications with High Reliability and Limited Power High Reliability and Limited Power Constraints in Noisy EnvironmentsConstraints in Noisy Environments
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Problem Visualization
SS
S
S
S
S
Mesh Network:
Noise/InterferenceLimited Spectrum
FusionCenter
Power limitedWireless sensor
Reliable Data ?
VariousSensortypes
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Outline
Reliability Based CommunicationError Correction in Wireless SensorsSensor Capabilities at UMaine Hybrid Architecture
Research TeamCurrent Opportunities
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Outline
Reliability Based Communication
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Reliability Based Communication
Reliable communication is NOT possible w/oError Correction Codes [Shannon, 1948]
Problem: How to Design Codes?– Power efficient (Shannon Limit)– Spectrum efficient (Source Entropy)– Reliable (Achieve Desired BER)
Performance Evaluation of high reliability codes takes a long time
BER: Bit Error Rate
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Likelihood MethodReceived vector
Transmitted BitReliability value
Probability density of LLR Parameter estimation
``A New Method for Performance Evaluation of Bit Decoding Algorithms Using Statistics of the Log Likelihood Ratio,'' 4th International Symposium on Turbo-codes, April 2006, Munich, Germany
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Turbo Principle
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Accuracy AnalysisVariance and sample reduction gain
Gain=43 @ BER=10-6
Probability (∆Pe < ε )– 106 samples
• proposed method=0.97• MC method=0.95
– 104 samples• proposed method=0.93• MC method=0.33
MC: Monte-Carlo Simulation is used to generate enough samples and count number of errors.
SampleReduction
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Summary of Contributions
Analytical performance evaluation:– Accurate (compared to bounds)
– Fast– Low cost
Enabling technology– Code optimization (min BER)
– Power minimizationNear theoretical limit operation
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Outline
Reliability Based CommunicationError Correction in Wireless Sensors
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Wireless Standards
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Implementation
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Proposed Approach
3.5 dB gain
1000 timesMore reliable
Invited paper: ``A Simple Error Correction Scheme for Performance Improvement of IEEE 802.15.4,''IEEE International Conference on Wireless Networks, June 2007, Las Vegas, NV
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Outline
Reliability Based CommunicationError Correction in Wireless SensorsSensor Capabilities at UMaine
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Sensor Capabilities at UMaineLASST/UMaine: Laboratory for Surface Science
and TechnologyR&D Areas of Expertise– Physical, Chemical and Biological Sensors– High Temperature Materials– Micro/Nano Systems and Devices
Interdisciplinary Research Center – Faculty, students, staff, and industrial collaborators– Physics, Chemistry, Microbiology, Electrical Eng., Chemical
Eng., Bio Eng, Food Science, Computer Science– Collaborative high-tech projects with industries and national
partners & business incubator – Clean room, state-of-the-art microlithography, micro and nano
fab., thin film synthesis and characterization, sensor testing and evaluation, wireless syst. and dev.
– Strong commitment to education NSF IGERT, GK-12, RET, REU
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Materials/Thin Film Preparation & CharacterizationMaterials/Thin Film Preparation & Characterization
Sensor Fab: metallization, photolithography, micromachining, patterning/etching, dicing/bonding/packaging Sensor Testing: gas chromatograph/
mass spec, microwave test facilities/equipHall effect, impedance spectrosc., gas delivery
Crystals aligning, X-Ray anal, auger, XPSCutting, polishing, n& dev. fabr. & test New Crystals
Cutting, grinding and polishingX-Ray & Crystal Analysis Device design, fabrication, and Test
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Types of Sensor
0 50 100 150 200 250 300 350 400 450 500
-15
-10
-5
0
5
10
Time [min]
∠S
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• Biosensors (& micro fluidics)Gas SensorsHarsh Environment (↑ 1000 °C)Physical Sensors (acceleration, stress, strain, vibr., pressure, temp.)Protective film layers for harsh environmentPackaging
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Wireless Passive Acoustic Wave Physical / Gas Sensors
Work beyond device →reliable communication →code identification, test & selection MultipathDevice design and optimizationHarsh environment packaging
SAW Passive Sensor
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Device Device fabfab. at UMaine for MSGC/NASA. at UMaine for MSGC/NASA
Safety: Fuel leak detection, Fire detection, Hostile Environment DetectionEnvironment: fuel efficiency in rocket propulsion & jet engines (NASA & commercial aviation)Detection of H2 and CxHY, NOx gases from temperatures ranging from 250 to 550 °C
162 164 166 168 170 172 174-55
-50
-45
-40
-35
-30
-25
-20
Freq [MHz]
S21
Res
pons
e (d
B)
750 °C 25 °C500 °C
0 50 100 150 200 250 300 350 400-5
-4
-3
-2
-1
0
1
2
3
4
Time [min]
FRE
QU
EN
CY
VA
RIA
TIO
N [
Δ K
Hz]
1 2 3 4
5 6
7 8
H2 off / N2 on
N2 off / H2 on
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Outline
Reliability Based CommunicationError Correction in Wireless SensorsSensor Capabilities at UMaineHybrid Architecture
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Tails are important
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Integrated Design
Sensor Channel
Sensor ChannelChannel Encoder
Conventional design
Integrated design
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Lower tier
Upper tier
nodes
Super nodes
sources
NS )ˆ( NSg)ˆ( NSf
NS1S
Gateway
Wireless/Optical
Wireless
Microwave
Hybrid Architecture
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Turbo Principle
RecursiveConvolutional
Encoder
RecursiveConvolutional
Encoder
π
NS
)ˆ( NSg
)ˆ( NSf
NS
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Outline
Research TeamCurrent Opportunities
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Research Team
University of Maine, Orono, ME– PI: Prof. Ali Abedi
Director, WiSe-Net Lab– Co-PI: Prof. Mauricio P. da Cunha
Director, Microwave Lab
NASA Johnson Space Center– Dr. Patrick Fink
Deputy Chief, Electromagnetic Systems Branch
MainelyWired, Swanville, ME– Tristan Petersen, Chief Engineer
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Future opportunities
Collaboration– Mechanical/Civil Engineers at UMaine– NASA centers– Industrial partners
[email protected]@eece.maine.edu
