1

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

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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

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Activities inWireless 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

4

INTRODUCTION

5

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

6

Motivation for WLPSTo 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

7

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

8

Positioning via WLPS

Time of Arrival

Time of Arrival Distance of TRX (R)

Direction of arrival (Via antenna arrays at the DBS) Direction of TRX ( )

R, TOA, DOA

ID Request (IDR) Signal transmitted by DBS ID transmitted by the TRX

DBS TRX

ID Request Repetition Time (IRT)

TRX

DBS

Duty Cycle = / IRT

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WLPS Structure

• TRX: CDMA transceiver with omni-directional antenna.

• DBS:

Receiver

Transmitter

ModulatorID Request (IDR) Signal Generator

Antenna Arrays

Omni-directional Antenna

MA RCVR and

DOA finder

Processor(Position Finder)

CDMASpreading

Beamformer& Diversity Combiner

• Hence, DBS transmits ID request signal whenever it is required (Not at all time).• The whole system: FDD/TDD/CDMA communication system.

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PROBABILITY-OF-DETECTION

PERFORMANCE

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Performance Evaluation – TRX ReceiverDS-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 value. DBS

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RAKE for TRX j

RAKE for TRX j

Beamformer for the1st path of TRX j

COMBINERBeamformer for the

Lth path of TRX j

Decision Rule

ID Detector

)(1 tr

)(2 tr

)(1 trM

)(trM

)(1 iz j

)(iz j

L

)(iz j

RAKE for TRX j

RAKE for TRX j

Beamformer for the2nd path of TRX j

)(2 iz j

DBS Receiver: Beamforming Combined with DS-CDMA

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Performance Evaluation – DBS RCVR

● With the same bandwidth, standard RCVR outperforms DS-CDMA RCVR.● SDMA (beamforming) techniques highly enhances the POD performance.

The best Result with

Beamforming

Standard RCVR

(With the same BW as DS-CDMA)

DS-CDMA RCVR

Standard RCVR

Beam Forming

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Linear Constrained Minimum Variance (LCMV) Beam Forming

• Design criteria:

• Solution:

1)()(..)()(min jq

jq

Hjq

jq

jq

H ts vwwRw

)()(

)()( 1

1

jq

jq

jq

H

jq

jqj

qopt

VRV

VRw

]E[Hj

qjq

jq yyR

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:

• Standard estimation method:

• Valid if:

• However……

]E[Hj

qjq

jq yyR

1

0

][][1ˆ

n

Hjq

jq

jq nn yyR

]]1[]1[E[]][][E[ nnnnHj

qjq

Hjq

jq yyyy

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Non-Stationarity in WLPS

• For WLPS:

]]1[]1[E[]][][E[ nnnnHj

qjq

Hjq

jq yyyy

Interfering User 1

Desired User

Interfering User 2

Different bits experience different interference

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Solution: Cyclostationarity

Interference Signal: TRX 3

Desired Signal: TRX 1

Interference Signal: TRX 2

Same Interference Same Interference

Received signal in IRT period TReceived signal in IRT period T+1

],[],[1

][ˆ1

0

nnnHj

qjq

jq

yyR

Estimated covariance matrix For nth chip of desired user

Number of Static User Frames Received signal at nth chip of ωth frame

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Probability of Miss-Detection Performance Cyclostationarity remains for 8 frames (IRT)

10 20 30 40 50 60

10-6

10-4

10-2

Number of TRX

Pm

d

Conventional BFStandard LCMV BFProposed LCMV BF

LCMV Beam-forming using cyclostationarity for observed signal covariance matrix highly increases the performance and the capacity.

25 50

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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

MUSIC Alg.

MUSIC Alg.

MUSIC Alg.

1̂ 2̂ F̂

Direction Combining

Estimated DOA

TRX1 ID signal:

TRX2 ID signal:

F

iiAppCom F

11

ˆ1ˆ

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Direction Combining: Approach 2

TRX1 ID signal:

TRX2 ID signal:

MUSIC Alg.

MUSIC Alg.

MUSIC Alg.

1̂

2̂

F̂

Dire

ction

Co

mb

inin

g

Estimated DOA

F

i i

F

i i

i

AppCom

12

12

21

ˆ

ˆ

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DOA Mean Square Error Simulation Results

2Real )ˆ( EstEMSE

10 15 20 2510

-4

10-3

10-2

10-1

100

SNR (dB)

Me

an

Sq

ua

re E

rro

r (M

SE

)NocombComb-App1Comb-App2

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Simulation Results (Cont.)

1 2 3 410

-4

10-3

10-2

10-1

100

# of TRX

Me

an

Sq

ua

re E

rro

r (M

SE

)NocombComb-App1Comb-App2

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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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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.

Application in Road Safety

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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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Implementation of WLPS for Indoor Areas (e.g., Airports): A Futuristic View

Name : ________Flight No. : ______Gate No. : ________Date: _______Boarding Pass No:__________________

TRX

Plastic Card Boarding Pass

Gate No: ______ Flight No. : _______

Name : ___________

TRX

Wristband Boarding Pass

DBS antenna arrays installed on the belt

● 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.

Application in Airport Security

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Central Command and Control

• Specific clusters of ID codes can be assigned to each group of people (employees, passengers, security guards)

Passenger A. W.Security F. E.

Static Base Stations (SBS)

Employee T. H. Flight NW 1234

Application in Airport Security

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Node: WLPS: DBS/TRX

TRX

Com NodeGPS/WLPS/Com

(e.g., Staelleite Com)

Precise Location Information of All Soldiers are Submitted to the Center

via Satellite

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.

The Soldier with WLPS finds the position of all soldiers in its coverage area (equipped

just with a simple TRX)

Central Command and Control

Application in Battlefield 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 Studiesat Michigan Tech University

Anechoic Chamber

Scaled Environment

WLPS set (can be installed on a robot)

Relay Antenna

From Relay Antenna

Work Station

This Laboratory will serve many courses:

1. Wireless Communications

2. Advanced Wireless Communications

3. Communication Theory

4. Antennas

5. Robotics

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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.