Wireless Sensor System Design
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Transcript of Wireless Sensor System Design
Wireless Sensor System Design
A Joint Course of the University of South Florida
and Tennessee Technological University
Spring 2002
Lecture 11 – Multipath / Course Wrap-up
Tennessee TechUNIVERSITY
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Course Introduction Analog and Digital Modulation Methods (1/11) Fundamentals of Antennas and Propagation (1/18) Signal Processing Techniques (1/25) Microwave Systems: Communications Hardware, Noise, Linearity (2/1) System Test, Evaluation and Documentation / Effective Presentation Styles (2/8) Preliminary Design Review (student presentations*) (2/15) Microwave Sensor Technology (2/22) @ TTU Modern Wireless Communication Systems (3/1) Microwave Proximity Sensors (3/8) Microelectromechanical Systems for Communications (RF - MEMS) (3/22) Internal CDR (4/5) Wireless Sensor System Research (Paul Flikkema from NAU) (4/12) Multipath / Course Wrap-up (4/19)
Weekly Lecture Topics
* On-site internal reviews/preparation will precede inter-university presentations.
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Motivation for Today’s Talk
Source: University of Kansas' Information & Telecommunications Technology Center and Kansas Applied Remote Sensing Program
Free space propagation is not reality!
Note: Path loss is directionally dependent
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Motivation for Today’s Lecture
Free space propagation is not (virtual) reality!
Dr. Sarabandi’s WAMI Forum presentation
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Propagation Loss – Two Categories
Large scale path loss – predicts mean signal strength from transmitter to receiver (T-R) Distance, Reflection, Diffraction and Scattering
Small scale path loss – rapid changes in signal strength over a small travel distance or time interval Multipath Doppler
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Multipath
The environment produces “echoes” The signal received gets spread out in time
From Fourier analysis: Spreading in time Reduction in Frequency Filtering of baseband signal (information)!
The environment changes due to Moving transmitter or receiver Dynamic environment
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
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USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
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USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
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USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
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Large scale effects
Small scale effects
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
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So what happens?
Fading Flat or Frequency-
Selective Fast or Slow
p. 211 of Rappaport
Speed: 75 mphWavelength: 0.33 m
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Why is this bad?
Signals corrupted by multipath are more susceptible to channel noise
Degradation in BER (digital) SNR (analog)
Bottom Line – Information quality is compromised
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Multipath Effects on Time Domain Data
W/O multipath W/ multipath
I
Q
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
So what can be done?
Equalization
Diversity
Channel Coding
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Equalization
Equalization “undoes” the multipath filtering effect Filtering will induce intersymbol interference (ISI) Equalization makes pulses look “rectangular” again
Two classes of algorithms Those requiring training sequence Those that don’t: Blind techniques
channel
Equalizer
time freq time time
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Equalization with a Training Sequence
A known sequence will be sent at regular intervals
The equalizer will adapt to minimize the error between the known signal and recovered signal (LMSE optimization)
Advantage: minimizes computation Disadvantage: utilizes bandwidth resources
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Equalization of Training Data
Known Desired Received
EqualizerLSMEAdaptive
Algorithm
New coefficients
Equalized outputequals known
I
Q
I
Q
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Blind Equalizations
Equalizer continuously adjusts based on the statistics of the received signal
Advantage: no training sequence
Disadvantage: more computationally intensive
e.g., 16-QAM
I
Q
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Blind Equalization Process
Equalizer
AdaptiveAlgorithm
Statistics of received data
Statistics of for 16-QAM
I
Q
I
Q
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
What is needed?
AGC
High-SpeedAdaptiveEqualizer
Flat Fading Frequency Selective
SlowFading
FastFading
Z-1
Z-1
Z-1
Z-1
1
2
0
3
4
Input
Output
Coefficients
Digital FIR Filter
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
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Antenna Diversity
Idea: if multipath is a small scale random effect that is spatially dependent, then the fading experienced by two antennas spaced a short distance from each other will be uncorrelated
Methods Selection diversity – use the antenna with the
strongest signal Maximal ratio combining – use the antennas as an
array to achieve max power out
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Maximal Ratio Combining
1
2
3
m
AdjustableWeightedSummer
Detector
AdaptiveControl
Output
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Frequency Diversity
Idea: if multipath is a small scale random effect that is wavelength dependent, then the fading experienced at two frequencies spaced a short distance from each other will be uncorrelated
Buzz words 1:N protection switching Frequency Hopping Spread Spectrum (use: WLAN) Direct Sequence Spread Spectrum (use: CDMA) OFDM (divide bits to modulate many different carriers)
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
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Time Diversity
Idea: if multipath is a small scale random effect that is time dependent, then the fading experienced by the signal at two different points in time will will be uncorrelated
Buzz words RAKE receiver
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
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RAKE Receiver
AdjustableWeightedSummer
Integrator/Detector
AdaptiveControl
Output
Correlator 1
Correlator 2
Correlator 3
Correlator m
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Channel Coding (Error Correction Codes)
Add redundancy (extra bits) in data so that information has better chance of being recovered (think parity on steroids)
Costs Complexity Bandwidth
Buzz word Turbo coding (aka Parallel Concatenated
Convolution Codes)
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Summary
Multipath effects band limit systems Will definitely be a driving factor in higher data
rate 3G systems
These effects can be counteracted through processing Requirements for DSP in 3G systems will thus be
more demanding
Wireless Sensor Systems Design Course Review
A Joint Course of the
University of South Florida
and
Tennessee Technological University
Spring 2002
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Course Objectives
As advertised: USF/TTU - This course satisfies the Senior Design Project
Requirement (3 Credit Hours) Objectives
Hands-on design experience Coverage of emerging wireless and sensor system technologies Interdisciplinary, collaborative project development (USF and
TTU) Putting the E into Experimental
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
What we hoped you learned
Problems/advantages of a distributed design process Ability to take an idea and make it happen
Design Analysis Implementation Scheduling
Ability to be objective in assessing performance Yours and others
How system level performance can be dependent on subsystem characteristics
Working on a team in an interdisciplinary environment in a relevant area
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Hands-On (BBD group)
Sensor Conditioner
Future USF grad student?
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Hands On (TX and Power Group)
Sensmitter Power System FM transmitter
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
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Hands On – Literally! (RX group)
PLL
Bit detector
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Learned Something About Mixers
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Data Visualization (DSP Group)
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
USF EEL 4935/TTU ECE 499SPECIAL TOPICS: WIRELESS SENSOR SYSTEMS
2.45 GHz Antennas – Rob Harris
Circularly Polarized Antenna (Transmitter)
• T-junction with 90º phase shift
• λ / 4 transformers
• -16.67 dB @ 2.45 GHz
• ƒc~ 2 % design frequency
• Corporate-fed rectangular array.
• .65λ spacing
• -7.56 dB @ 2.45 GHz
• ƒc~ 1% design frequency
4 X 2 Linearly Polarized Antenna Array (Receiver)
55 X 55 mm
280 X 135 mmS11 (reflection coefficient) on VNA
S11 (reflection coefficient) on VNA
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Frequency Shift Key (FSK) Bit Detector by Leonard Guerra
LP FilterAmplifier
HP FilterF1 = 220 MHz
LP FilterF2 = 180 MHz
FSK Signal
EnvelopeDetector
EnvelopeDetector
Op-AmpComparator
+
T+Vcc
-Vcc
-
150 200 250 300 350
-40
-30
-20
-10
0
Frequency (MHz)
Atte
nuat
ion
(dB
)
RR1R=100 kOhm
CC1C=680 pF
LL1L=420 nH
DiodeDIODE1
Simulated vs. Actual
300 400 500
0
50
100
150
200
250
300
Time (nsec)
Vol
tage
(mV
)
150 200 250 300 350
-10
-8
-6
-4
-2
0
2
Frequency (MHz)
Atte
nuat
ion
(dB)
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Course Introduction Analog and Digital Modulation Methods (1/11) Fundamentals of Antennas and Propagation (1/18) Signal Processing Techniques (1/25) Microwave Systems: Communications Hardware, Noise, Linearity (2/1) System Test, Evaluation and Documentation / Effective Presentation Styles (2/8) Preliminary Design Review (student presentations*) (2/15) Microwave Sensor Technology (2/22) @ TTU Modern Wireless Communication Systems (3/1) Microwave Proximity Sensors (3/8) Microelectromechanical Systems for Communications (RF - MEMS) (3/22) Internal CDR (4/5) Wireless Sensor System Research (Paul Flikkema from NAU) (4/12) Multipath / Course Wrap-up (4/19)
Sensor/Microwave Topics
* On-site internal reviews/preparation will precede inter-university presentations.
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Course Introduction Analog and Digital Modulation Methods (1/11) Fundamentals of Antennas and Propagation (1/18) Signal Processing Techniques (1/25) Microwave Systems: Communications Hardware, Noise, Linearity (2/1) System Test, Evaluation and Documentation / Effective Presentation Styles (2/8) Preliminary Design Review (student presentations*) (2/15) Microwave Sensor Technology (2/22) @ TTU Modern Wireless Communication Systems (3/1) Microwave Proximity Sensors (3/8) Microelectromechanical Systems for Communications (RF - MEMS) (3/22) Internal CDR (4/5) Wireless Sensor System Research (Paul Flikkema from NAU) (4/12) Multipath / Course Wrap-up (4/19)
Communication Systems/Signal Processing Topics
* On-site internal reviews/preparation will precede inter-university presentations.
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Course Introduction Analog and Digital Modulation Methods (1/11) Fundamentals of Antennas and Propagation (1/18) Signal Processing Techniques (1/25) Microwave Systems: Communications Hardware, Noise, Linearity (2/1) System Test, Evaluation and Documentation / Effective Presentation Styles (2/8) Preliminary Design Review (student presentations*) (2/15) Microwave Sensor Technology (2/22) @ TTU Modern Wireless Communication Systems (3/1) Microwave Proximity Sensors (3/8) Microelectromechanical Systems for Communications (RF - MEMS) (3/22) Internal CDR (4/5) Wireless Sensor System Research (Paul Flikkema from NAU) (4/12) Multipath / Course Wrap-up (4/19)
Other Topics
* On-site internal reviews/preparation will precede inter-university presentations.
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Results: Our Impression
Unique educational experience – rewards depend on effort
Projects doable but require more time for successful integration
Collaboration Good with-in groups and within schools. Limited between schools. Should get students together early
Tutorials have a good range of topics Distance learning technology not perfect, but effective
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Results: Your Impression
Please fill out the course survey form and return them by Monday (TTU).
Your feedback will be compiled and disseminated
USF EEL 4935/TTU ECE 4720SPECIAL TOPIC: WIRELESS SENSOR SYSTEMS
Tennessee TechUNIVERSITY
Final Words
Wireless remote monitor is becoming ever more popular for industrial, environmental & military applications
Drones for military activities (monitoring/targeting/comm)
Global Hawk relays data @ 500 Mbit/sec Military arena predicted to require 20
Gbit/sec wireless data links (!) Program to use drones to drop low-data rate
ground sensors for in situ monitoring vs. using high-rate video
Requires systems level knowledge in comm/devices/processing/networks
http://www.msnbc.com/news/661255.asp#BODY