MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-1

Advances in Ultra WidebandIndoor Geolocation Systems

Robert J. Fontana, Ph.D.

Multispectral Solutions, Inc.Germantown, Maryland USA

rfontana@multispectral.comhttp://www.multispectral.com

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-2

UWB Geolocation Systems

• System Architectures– Untethered Transponders + Tag Transceiver

– Tethered Receivers + Tag Transmit Only

• System Issues– Parameters

• Power, bandwidth, frequency

– Propagation anomalies

– Leading edge detection

• Deployments– Indoors vs. Indoors/outdoors

• Resolution/accuracy– Experimental data

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-3

UWB Precision Geolocation Hardware - I

Design Characteristics– 3-D position from precise time-of-flight

measurements• UWB Rover with multiple untethered UWB

Beacons

– Implementation• 2.5W ERP, 400 MHz instantaneous BW

– Spectrally shaped waveform design

– L-band center frequency

– 27% fractional BW

– Packet burst, 100 updates/second

• Leading edge detector for sub-foot resolution

• Range– Up to 2 km outdoors

– Up to 350 feet indoors (5-25 dB/wall measuredattenuation)

– US Patent No. 6,054,950DSP/ControllerDual Tunnel Detector

CFAR (FPGA) Controller/Timing

UWB Single Pulse Receiver

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-4

Principle of Operation - Untethered

( ) ( ) ( ) ( )[ ]( ) N,1,i ,2d

25.0 222

L=≡

−+−+−=∆−∆

i

iiiii

rr

zzyyxxtc

UWBBeacon

#1

UWBBeacon

#2

UWBBeacon

#3

UWBBeacon

#N

UWBRover

(x1,y1,z1)

(x2,y2,z2)

(x,y,z)

(x3,y3,z3)

(xN,yN,zN)d(r,r1)

d(r,rN)

d(r,r2)

d(r,r3)

– UWB Rover sends out sequence of packetbursts

– UWB Beacons transpond after knowndelay Di

– UWB Rover determines N round tripdelays/distances

– Minimize error functional via Fletcher-Powell algorithm

( ) ( )∑ =

∆−∆−−=

N

i iii tcrrdE1

2

2

1

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-5

UWB Precision Geolocation Hardware - II

Design Characteristics– 3-D position from precise differential time-of-

flight measurements• UWB Rover with multiple tethered UWB

Receivers

• Daisy-chained CAT-5 cables relay processedtime-of-arrival data

– Implementation• 0.25W peak, 400 MHz instantaneous BW

– Spectrally shaped waveform design

– L-band center frequency

– 27% fractional BW

– Packet burst, 12 updates/minute

• Leading edge detector for sub-foot resolution

• Range– 100+ feet indoors (low power units)

– US patent applied for

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-6

Principle of Operation - Tethered

– UWB Tag sends out sequence of packetbursts

– Frequency-locked UWB Receiversmeasure times-of-arrival

– Processor determines set of differentialtimes-of-arrival

– Minimize error functional (utilizing timedifferences of arrival) via Fletcher-Powellalgorithm

UWBReceiver

#N

UWBReceiver

#3

UWBReceiver

#2

UWBReceiver

#1

(x1,y1,z1)

(x2,y2,z2)

(x,y,z)

(x3,y3,z3)

(xN,yN,zN)d(r,r1)

d(r,rN)

d(r,r2)

d(r,r3)

UWBTag

To Processor

CAT-5CAT-5

CAT-5

CAT-5

Transmit Only

Receive Only

Low FrequencyClock

Distribution

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-7

UWB Receiver Characteristics

∫ ≥=t

thresholdqduuiQ0

)(

• Receiver utilizes integrating (charge sensitive) tunneldiode detector– Leading edge detection

– Constant false alarm rate (CFAR) bias loop for devicestability

– Detection statistics related to level-crossing problem forBrownian motion process (e.g., Gikhman-Skorokhod 1969)

• Single pulse detection capability– Analogous to optical “photon” detection

– Charge sensitive detection of single UWB pulse

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-8

Why Leading Edge Detection is EssentialTypical Pulse Responses

0 5 10 15 20-4

-2

0

2

4x 10

-5

Sign

al le

vel (

Vol

ts)

Free space measurement ofUWB transmit pulse

12.8 meter“Hallway” pulse

reverberation

0 2 4 6 8 10-3

-2

-1

0

1

2

3x 10

-3

Sign

al L

evel

(V

olts

)

0Time (ns)

2 4 6 8 10-3

-2

-1

0

1

2

3A

mpl

itude

0 20 40 60 80 100-4

-2

0

2

4x 10

-5

Sign

al L

evel

(V

olts

)

0Time (ns)

20 40 60 80 100

0 5 10 15 20Time (ns)

0 5 10 15 20-3

-2

-1

0

1

2

3x 10

-4

Sig

nal L

evel

(V

olts

)

0 5 10 15 20Time (ns)

Another“Hallway” responseexhibiting close-in

multipath

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-9

Time Increment (seconds)0 50 100 150

0

25

50

75

100

125

150

175

200

225

250Beacon #5 with Rover #6

Dis

tanc

e (f

eet)

MultipathEffects

2

3

1

4

5 6

1

0

2

34

5 6

1

2

3 4

5

6

Distance Measurement (Single Beacon)

σ = 0.44 ft

σ = 0.52 ft

σ = 0.42 ft

σ = 0.56 ft

σ = 2.55 ft

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-10

Distance Measurement (Single Beacon)

0 500 1000 1500 200060

65

70

75

80

85

90

95

100

Time Increment (100'ths of seconds)

Dis

tanc

e (f

eet)

Direct (LOS) path return

Multipath return

Antenna rotated to reduce reflections

Hallway “reverberation”

6

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-11

UWB Beacon Locations

Indoor UWB Geolocation Experiment

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-12

UWB Beacon Location

Indoor UWB Geolocation Experiment

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-13

UWB Beacon Location

“Autometric”

Indoor/Outdoor UWB Geolocation Experiment

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-14

0

10

20

30

40

50

60

70

80

90

0

10

20

30

40

50

60

70

80

90

90 80 70 60 50 40 30 20 10 0 -10

Outdoor UWB Geolocation Experiment

“Period” in “2000.”

2.4 inches

“2000.”

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-15

UWB Geolocation

Asset TrackingUWB Tagging System

Raw Data

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-16

An Unique Propagation Environment

• Container ship with floor-to-ceilingmetal walls

• Exaggerated distances due to “billiardball” reflections

True pathUWB Beacon Location

44’ 10”

MULTISPECTRAL SOLUTIONS, INC.Advances in Ultra Wideband Indoor Geolocation Systems-17

Conclusions & Recommendations• Demonstrated feasibility of UWB technology for precision tracking within and outside of

a building

• Performance– Maximum range

• typically 300+ feet (in commercial buildings)

• > 2 km demonstrated (line-of-sight outdoors/indoors - omnidirectional antennas)

– RMS error (400 MHz BW system)• 0.5 to 3 feet (indoors) – geometric dilution of precision

• < 0.5 feet (outdoors)

• Areas for further system improvement– Increase transmitter power for extended range

• Currently 2.5W/0.25W ERP

• FCC issues for Part 15 operation

– Decrease pulsewidth for better resolution• Currently 2.5 ns (400 MHz instantaneous BW)

– Optimize frequency selection for better building penetration• Currently L-band (1.5 GHz)

• FCC issues for Part 15 operation

– Optimize antenna design for coverage• Vertical polarization

• Circular polarization with squinted vertical beam pattern