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Multi-Carrier Technology for Precision

Personnel Location

Electrical and Computer Engineering DepartmentWorcester Polytechnic Institute

Worcester, Massachusetts

funded by

US Department of Justice

National Institute of Justice

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The PPL Team

Research Assistants

� Jack Coyne

� Hauke Daempfling

� Jason Farmer

� Jason Huang

� Shashank Kulkarni

� Hemish Parikh

� Ben Woodacre

� Vincent Amendolare

� David Holl

Faculty

� David Cyganski

� R. James Duckworth

� Sergey Makarov

� William Michalson

� John Orr

Technician

� Bob Boisse

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System Overview

Personnel

Unit

Reference units

Commander

Display

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Locator Concept Drawing

PIFA Wide

BW

Antenna

Distress

Button

Data Channel

Antenna

Electronics and

Battery

Compartment

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Basic Concept

�Sharply defined energy pulses are unnecessary

for precise location

� Avoids problems of wide and flat bandwidth

antenna, receiver, and transmitter design

�Multiple continuous carriers that sample frequency

space can be utilized

� Spectrally friendly, near 0 bandwidth

components

�Superresolution techniques can trade SNR for

increased precision at fixed bandwidth

� Also provides means for multipath resolution

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Multi-Carrier Wideband

�Super-resolution SAR/ISAR Radar

� Enhances Radar resolution to centimeters

�Orthogonal Frequency Division Multiplexing

� A data communications innovation which allows high speed data to be transmitted over low-quality telephone wires (DSL service) or via wireless

Approach based upon two recent innovations:

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Spectrally Friendly System

�The spectral footprint of the MC-WB signal

can be tailored to avoid existing services

MC-WB

Existing Services

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System Analysis and Design

�To move from concept to implementation:

� Complete analysis of performance

• Mathematical performance modeling

• System Engineering criteria

• Simulation of end-to-end system

�Prototype Construction/Evaluation

� Troubleshooting/Feedback/Re-analysis

�Development of encompassing technology

� Auto-calibration, data exchange, …

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Embedded System Design

� Transmitter requirements

� Continuously transmits the OFDM signal

� Must be small, lightweight, and have low power

consumption (battery powered)

� Receiver requirements

� Self configuring

� Continuously receives transmitter signals to

determine position in 3-dimension

� Complex signal processing

� Approach: FPGA based Software Radio Architecture

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First Generation Receiver RF Chain

A/D

FPGA (PC

interface)

Antenna

Mixer

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Second Generation RF and digital Receiver Boards

Digital Controller

board

Analog to Digital

board

RF Front End

board

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Antenna Design

PIFA (Planar Inverted

Foam Antenna)

reduced size, wide

bandwidth patch

antenna and control

board

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Antenna Testing

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Rapid Concept Evaluation

•We often used off-the-shelf components and tested low

bandwidth scale model systems first.

•Outdoor shake-downs were very common.

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Super-res Multi-path TOA observations

The laboratory tests

shown here demonstrate

separability of multipath

signals inside a room

Here each “bounce” is

resolved from the others

What is the practical

resolvability of multi-path

signals?

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0

5

10

15

20

25

30

-10 0 10 20 30 40 50 60 70

SNR, dB

Path Length Difference, m

1 Mhz

2 Mhz

4 MHz

8 MHz

Minimum Resolvable PathLength Difference

We proved mathematically and observed experimentally that

there is a tradeoff between SNR, bandwidth and path

difference resolution

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Forensic Test Analysis

Laboratory tests reveal new

and important phenomena

that must be understood for

further improvement of PPL

performance.

Electromagnetic simulations

are applied to gain this

understanding through

forensic analysis of test

results.

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Effects of resonant metallic reflectors

Experiments revealed positive and

negative distance errors. By

simulation and analysis we showed

narrow band reflectors push or pull

distances as a function of center

frequency and position.

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Outdoor 2D TDOA results (free roving transmitter -30dBm tx power)

Geometry Effects

Receivers

Multipath Errors

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Indoor Testing

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Indoor Environment

Metal ceiling and floor decks

Steel building structure

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Antenna Effects (Indoor LOS)

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Bandwidth Effects (Indoor LOS)

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Receiver and Transmitter Positions

Positions 8-15 are NLOS

4 our of 8 NLOS result in direct path solutions

TOA Range Solution Arcs

Target Location

26 by 16

meter area of

Atwater Kent

3rd Floor

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Using NLOS information only

Target Location

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MCWB/Superres/TDOA: The Problem

� Solving TDOA problem requires pre-selection and

grouping of “good” direct path solutions without

“first arrival information”

� Once this selection is made, multi-lateralization

must be performed

� Unfortunately, errors are already captured in

each single TDOA sub-result

� There are too many permutations of sensors

and multiple solutions to consider….

� There was much gnashing of teeth…. A new

approach was needed

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� Center of red

region denotes

highest

certainty

solution

� 26 by 16 meter

area of Atwater

Kent 3rd Floor

New WPI Algorithm: All NLOS data

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Low Sensitivity to input errors

Simulation: variation in

solution location

approximately equal to

random variation of the

sensor positions from

registered values.

Likewise indicates

sensitivity to insertion of

random high index

materials (concrete, etc.) in

sensor paths

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Kaven Hall Demo

Antennas on

3 sides of

area

Antennas

facing

directly into

masonary

No training

information

or pre-sited

devices

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Kaven Hall Geo-lab test site

Demo site is

the Civil Eng.

Dept.

Geology Lab

Steel Frame

and concrete

block

construction

with heavy

equipment

and metal

furnishings

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The command post

Real-Time-

update

display of

location

solution

and signal

integrity

on

command

console

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Command Console

� 2D position

and signal

integrity

display from

Kaven Hall

demo

� White

square

indicates

true position

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Conclusions

�Real-time computation and display of 2-D location from through-wall signals has been demonstrated with a only a 30 MHz multi-carrier signal

� 3-D location will soon be tested

�We await granting of experimental access of additional bandwidth by the FCC to pursue evaluation in increasingly difficult environments

�Approaching commercialization stage