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
[email protected]://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