Research on
Wireless Communications and
Signal Processing
In Two Laboratories at CISSIC:
WCRG: http://www.ece.mtu.edu/ee/faculty/rezaz/wireless_lab/
WLPS: http://www.ece.mtu.edu/pages/research_labs/wlps/index.html
Directed by Dr. Zekavat
1
Wireless Communication Research Group
(WCRG)
Research on:
• MIMO RFID/Cognitive Radio Development;
• Ad-hoc Network Capacity;
• Information Fusion;
• Blind Source Separation;
• Optimal Beam forming in Scattering Environment;
• Channel Modeling
• Time-of-Arrival (TOA) and Direction-of-Arrival (DOA)
Estimation Techniques;
• Dynamic Channel Allocation;
14 Graduate Students are involved in WCRG
2
Activities in
Wireless Local Positioning System
(WLPS)
Directed by
Seyed A. (Reza) Zekavat
Michigan Technological University
WLPS patent application was submitted on May 2003.
Supported by NSF ITR for National Priorities
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INTRODUCTION
4
An Introduction to Positioning Systems
 Global Positioning Systems
a. Satellites for Self Positioning,
c. Mainly for Navigation,
d. Command and Control via Communication,
Example: Battlefield Vehicle Control
e. Fails to perform in indoor and downtown areas,
f. Yet expensive.
 Local Positioning Systems
Base
1. Self Positioning
• Navigation (INS)
2. remote positioning
• Command, Control, Monitoring and Tracking
• Active and Passive
5
Motivation for WLPS
To develop an active remote positioning system:
Suitable:
• Urban and indoor areas;
• Any weather conditions;
• Variety of applications (defense, Security, Law enforcement,
Road Safety).
• High Pd and low Pfa (Possible via Active Target Systems)
It Means:
•
•
•
•
Not limited to the static base station.
Flexible coverage area.
Identify and Discriminate Mobiles;
Need limited Power
6
WLPS: An Active Remote Positioning System
• Has 2 main components: Dynamic Base Station (DBS), Transponder (TRX)
• DBS/TRX components can be installed in mobiles (vehicle, people, …)
• Based on application each mobile might be equipped with DBS, TRX or both.
• DBS discriminates mobiles (TRXes) via specific codes assigned to them.
• DBS locates and tracks all mobiles (TRXes).
TRX
TRX
7
Positioning via WLPS
TRX
DBS
ID Request (IDR) Signal
transmitted by DBS
DBS
R, TOA
, DOA
ID transmitted by the TRX
TRX
Time of Arrival
Duty Cycle =  / IRT
ID Request Repetition Time (IRT)
Time of Arrival  Distance of TRX (R)
Direction of arrival (Via antenna arrays at the DBS)  Direction of TRX ( )
8
WLPS Structure
• TRX: CDMA transceiver with omni-directional antenna.
• DBS:
Omni-directional
Antenna
Transmitter
CDMA
Spreading
Modulator
ID Request (IDR)
Signal Generator
Receiver
Antenna
Arrays
MA RCVR
and
DOA finder
Beamformer
& Diversity
Combiner
Processor
(Position
Finder)
• Hence, DBS transmits ID request signal whenever it is required (Not at all time).
• The whole system: FDD/TDD/CDMA communication system.
9
PROBABILITY-OF-DETECTION
PERFORMANCE
10
Performance Evaluation – TRX Receiver
DS-CDMA: Duty cycle = 0.001, 4 fold diversity
Standard RCVR: Duty cycle = 0.000015,
4 fold diversity
Standard RCVR: Duty cycle = 0.001,
1 fold diversity
● Further improvement is possible by selecting a larger IRT value, or a smaller  DBS value.
11
DBS Receiver: Beamforming Combined with DS-CDMA
r1 (t )
RAKE for TRX j
r2 (t )
RAKE for TRX j
Beamformer for the
1st path of TRX j
Beamformer for the
2nd path of TRX j
rM 1 (t )
RAKE for TRX j
rM (t )
RAKE for TRX j
Beamformer for the
Lth path of TRX j
z1j (i )
C
O
z 2j (i )
M z j (i )
B
Decision Rule
I
ID Detector
N
z Lj (i ) E
R
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Performance Evaluation – DBS RCVR
The best
Result with
Beamforming
DS-CDMA RCVR
Standard RCVR
(With the same BW as
DS-CDMA)
Standard RCVR
Beam Forming
● With the same bandwidth, standard RCVR outperforms DS-CDMA RCVR.
● SDMA (beamforming) techniques highly enhances the POD performance.
13
Linear Constrained Minimum Variance
(LCMV) Beam Forming
• Design criteria:
min w H (qj )R qj w(qj )
R  E[ y  y
j
q
j
q
jH
q
s.t. w H (qj ) v(qj )  1
]
• Solution:
w opt ( qj ) 
R
j 1
q
V( qj )
V ( )R
H
j
q
j 1
q
V( qj )
In general, LCMV leads to a better removal of interference
effects compared to the Conventional Beamforming.
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Covariance Matrix Estimation for LCMV BF
• Definition:
R  E[ y  y
j
q
j
q
jH
q
]
• Standard estimation method:
 1
1
j
j
jH
ˆ
R q   y q [ n]  y q [ n]
 n 0
• Valid if:
jH
q
jH
q
E[ y [n]  y [n]]  E[ y [n  1]  y [n  1]]
j
q
• However……
j
q
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Non-Stationarity in WLPS
• For WLPS:
jH
q
jH
q
E[ y [n]  y [n]]  E[ y [n  1]  y [n  1]]
j
q
j
q
Interfering User 1
Desired User
Interfering User 2
Different bits experience different interference
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Solution: Cyclostationarity
Received signal in IRT period T
Received signal in IRT period T+1
Interference Signal: TRX 3
Desired Signal: TRX 1
Interference Signal: TRX 2
Same Interference
Same Interference
Estimated covariance matrix
For nth chip of desired user
 1
1
j
jH
ˆ
R [n]   y q [ , n]  y q [ , n]
  0
Number of Static User Frames
j
q
Received signal at nth chip of ωth frame
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Probability of Miss-Detection Performance
Cyclostationarity remains for 8 frames (IRT)
25
50
-2
10
-4
Pmd
10
Conventional BF
Standard LCMV BF
Proposed LCMV BF
-6
10
10
20
30
40
Number of TRX
50
60
LCMV Beam-forming using cyclostationarity for observed signal
covariance matrix highly increases the performance and the capacity.
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DIRECTION-OF-ARRIVAL (DOA)
ESTIMATION PERFORMANCE
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DOA Estimation
DOA estimation techniques developed using:
1) The notion of Cyclostationarity; and
2) Application of MUSIC algorithm.
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Direction Combining: Approach 1
TRX2 ID signal:
TRX1 ID signal:
MUSIC
Alg.
MUSIC
Alg.
MUSIC
Alg.
ˆ1
ˆ2
ˆF
Direction Combining
ˆCom  App1
Estimated DOA
1

F
F
 ˆ
i
i 1
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Direction Combining: Approach 2
TRX2 ID signal:
TRX1 ID signal:
F
i 1
F

i 1
MUSIC Alg.
MUSIC Alg.
ˆ1
ˆ2
1
2
i
MUSIC Alg.
ˆF
Direction Combining
ˆCom  App2 

ˆi
 i2
Estimated
DOA
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DOA Mean Square Error Simulation Results
Mean Square Error (MSE)
10
10
10
10
10
0
Nocomb
Comb-App1
Comb-App2
-1
-2
-3
-4
10
15
20
SNR (dB)
MSE  E ( Real
25
 ˆ
Est )
2
23
Simulation Results (Cont.)
Mean Square Error (MSE)
10
10
10
10
10
0
-1
Nocomb
Comb-App1
Comb-App2
-2
-3
-4
1
2
3
4
# of TRX
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APPLICATIONS
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Application in Road Safety
• Injuries (or die) of Hundreds of thousands of people.
• Intelligent vehicle initiative was announced in 1998 by U.S. DOT.
• Eight areas where intelligent systems could “improve” or “impact” safety.
1. Four kinds of collision avoidance:
a. rear end,
b. lane change and merge,
c. road departure, and
d. intersection;
2. Two kinds of enhancements:
a. vision, and
b. vehicle stability,
3. Two kinds of monitoring:
c. driver condition and
d. driver distraction.
2008 is the Deadline
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Application in Road Safety
Implementation of WLPS for
Vehicle-to-Pedestrian Collision Avoidance
• About one Billion people are carrying wireless mobiles,
• Wireless systems offers new services everyday,
• It is anticipated the number of wireless customers increases,
• These people are mainly leaving in urban and highly populated
areas, with high probability of accident.
• WLPS protects wireless customers: Defines a new application
for wireless communications.
• A simple transponder in vehicles prevents Car-to-Car accident.
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Application in Airport Security
• Congress: Improvement of airport security is required [1].
• Security requires: Positioning, Monitoring, Communicating with
individuals, e.g., passengers, employees, guards.
• Desire: Security guards to find the position of everybody with respect to
themselves at all times and all positions, inside and outside of the
airport, and Whenever it is required.
• Hence, System Characterization: Infrastructure-less
High Probability of Detection
High Coverage (Indoor, Outdoor)
[1] Transportation Security Administration, “Aviation Security: Improvement still Needed in Federal Aviation Security
Efforts”, GAO-04-0592T, March 30, 2004.
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Application in Airport Security
Implementation of WLPS for Indoor Areas
(e.g., Airports): A Futuristic View
Plastic Card Boarding Pass
Name : ________
Flight No. : ______
Gate No. : ________
Date: _______
Boarding Pass No:
DBS antenna arrays
installed on the belt
__________________
TRX
Name : ___________
TRX
Gate No: ______ Flight No.
:
_______
Wristband Boarding Pass
● Communication: The wristband can receive the updated gate, flight, etc, information.
● Monitoring: The wristband can be equipped with a heart beat sensor which is required:
(a) for security guard safety, (b) to make sure the wristband is in its position.
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Application in Airport Security
Central Command and Control
• Specific clusters of ID codes can be assigned to each group of
people (employees, passengers, security guards)
Employee T. H.
Flight NW 1234
Security F. E.
Passenger A. W.
Static Base
Stations (SBS)
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Application in Battlefield Command and Control
Precise Location Information of All
Soldiers are Submitted to the Center
via Satellite
The Soldier with WLPS finds
the position of all soldiers in
its coverage area (equipped
just with a simple TRX)
TRX
Com Node
GPS/WLPS/Com
(e.g., Staelleite Com)
Node: WLPS: DBS/TRX
1. The position of the Soldier carrying WLPS (DBS
and TRX) is computed by the vehicle WLPS.
2. This position, along with the GPS positioning
leads to exact position of all soldiers.
Central Command and Control
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Applications in Law Enforcement:
Multi-Agent Operation
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Impact on Research and Education:
Development of a Laboratory for Positioning Studies
at Michigan Tech University
Anechoic Chamber
From Relay Antenna
Work
Station
Relay Antenna
Scaled Environment
WLPS set
(can be installed on a robot)
This Laboratory will serve many courses:
1. Wireless Communications
2. Advanced Wireless Communications
3. Communication Theory
4. Antennas
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5. Robotics
Conclusions
•
•
•
•
•
•
•
•
•
•
•
WLPS is an Active Target Remote Positioning System,
Consists of a Transceiver (TRX) and Dynamic Base Station (DBS),
With a variety of Civilian and Military Applications,
Much Cheaper/less complex than a GPS,
Can be used for Positioning AND Communication,
Can be a node in a MANET (Mobile Adhoc NETworks),
Can be merged with GPS (e.g., in one of the MANET nodes) to provide
Global Positioning for every MANET node,
WLPS, GPS, and Communication merger leads to Central Command
and Control,
An NSF award has been received (Sept. 2004) to initiate basic research
(non-application oriented),
Research is Required for WLPS application-based development,
A WLPS lab has been established at the Dept. of ECE at MTU.
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WLPS Laboratory
• The TRX Hardware and Software is complete;
• The DBS Transmitter Hardware and Software is Complete;
• Five Ph.D. Students, three master students and one undergraduate;
• Collaborating with Two Companies: Mercury Data Systems and GCI
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Selected Recent Publications
•
•
•
•
•
•
•
•
•
•
•
H. Tong and S. A. Zekavat, “A Novel Wireless Local Positioning System via Asynchronous DS-CDMA and
Beamforming: Implementation and Perturbation Analysis,” to appear in IEEE Transactions on Vehicular
Technology, May 2007.
S. A. Zekavat, and X. Li, “User Central Wireless Systems,” Journal of Communications, vol. 1, no 1, pp. 60 67, April 2006, Invited paper.
S. A. Zekavat, and P. T. Keong, “Beam-Pattern-Scanning Dynamic-Time Block Coding: Performance
Analysis,” IEEE Transactions on Wireless Communications, vol. 5, no. 9, pp. 2334 – 2337, Sept. 2006.
H. Tong and S. A. Zekavat, “Spatially Correlated Rayleigh Channel: Generation via Virtual Channel
Representation, ” IEEE Communication Letters, vol. 10, no. 05, pp. 332 – 334, May 2006.
S. A. Zekavat and C. R. Nassar, “Transmit diversity via oscillating beam pattern adaptive antennas: An
evaluation using geometric-based stochastic circular-scenario channel modeling,” IEEE Transactions on
Wireless Communication, Vol. 4, No. 3, pp. 1134-1141, July 2004.
S. A. Zekavat, C. R. Nassar and S. Shattil, “Merging multi-carrier CDMA and oscillating-beam smart antenna
arrays: Exploiting directionality, transmit diversity and frequency diversity, ” IEEE Transactions on
communications, Vol. 52, No. 1, pp. 110 – 119, Jan. 2004.
H. Tong and S. A. Zekavat, “A simple beamforming-SIMO merger in spatially correlated channel via virtual
channel representation,” Proceedings IEEE Globecom 2005, St. Louis, 28 Nov. – 02 Dec., 2005.
S. A. Zekavat and X. Li, “User-Central Wireless System: Ultimate Dynamic Channel Allocation, ” Proceedings
IEEE DySPAN’05, Baltimore, Nov. 8 – 11, 2005 (won graduate student travel award)
H. Tong and S. A. Zekavat, “Wireless local positioning system implementation via LCMV beamforming, ”
Proceedings SPIE’05 Conference on Defense and Security, Orlando, FL, April 2005.
R. Kulkarni and S. A. Zekavat, “Smart versus blind inter-vendor spectrum sharing for MC-CDMA systems, ”
Proceedings WNCG’04 Conference, Austin, TX, Oct. 2004.
S. A. Zekavat, H. Tong, and J. Tan, "A novel wireless local positioning system for airport (indoor) security, "
Proceedings SPIE Conference on Defense and Security 2004, Orlando, FL, pp. 522-533, April 2004.
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