Road to Seamless Positioning:
Hybrid Positioning System Combining GPS
and Television Signals
Ju-Yong Do
GPS Lab
Stanford University
April 18, 2007
Ju-Yong Do 2007/4/18
GPS: Time and Position Reference
Time & Position (4D)
Time (1D) Position (3D)
+ =
(GPS: Global Positioning System)
Hybrid Positioning System Combining GPS and TV Signals 1
Ju-Yong Do 2007/4/18
Challenges for GPS in Urban/Indoor
Blocked skyview limits GPS availability in urban/indoor areas.
Urban Suburban Residential Rural0
2
4
6
8
10
Site Category
Nu
mb
er
of
GP
S C
ha
nn
els
Outdoor
Indoor
Measured number of GPS satellites at 39 Bay Area sites. However, benign
urban/indoor areas usually allow better GPS reception.
Hybrid Positioning System Combining GPS and TV Signals 2
Ju-Yong Do 2007/4/18
GPS vs. Cell Phone
Positioning vs. Communication. Positioning (based on RF ranging)
differs from communication in a few aspects which make positioning
still challenging in urban/indoor areas where communication has been
very successful.
Positioning Communication
Goal Position Data or Voice
Measurement Time of arrival (TOA) Data bits
Required NTX 3 1
Redundancy NTX >3 Channel coding
Indirect Path TOA error Less sensitive
Hybrid Positioning System Combining GPS and TV Signals 3
Ju-Yong Do 2007/4/18
Contributions for Seamless Positioning
1. Hybrid Positioning System Combining GPS and TV Signals
• Implemented a hybrid position estimator based on GPS pseudorange and TVpseudorange measurements.
• Conducted extensive field tests at 39 Bay Area sites with a prototype.
2. Multi-Fault Tolerant RAIM (Receiver Autonomous Integrity Monitoring)
• Proposed and implemented Multi-Fault Tolerant Iterative RAIM for protectionagainst outlying terrestrial range measurements.
3. Interference Survey
• Conducted a spectrum survey on GPS L1, Unified-S, and ISM 2.4 GHz bands,an joint effort with NASA and Clemson Univ.
4. Multipath Mitigation
• Proposed Inverse Correlation Method optimized for multipath resolution.
Hybrid Positioning System Combining GPS and TV Signals 4
Ju-Yong Do 2007/4/18
Contribution I,II: Hybrid Positioning
Integration of GPS and TV opens door to seamless positioning.
Pseudo-Range
Estimator
TV RX
XGPS, prGPS
XTV,
tRX,TV
Monitor(TV RX) tTX,TV
GPS RX
Hybrid Position
Estimator
XTV,
prTV
RAIM
Clusterization
Regional
Optimization
Position FilterTest Stat
Interative Search
Position
Fixes
Final
Position
Fixes
Rosum
Fault Detection
(χ2, HPL,
MHSS)
Fault Exclusion
Contributions
Hybrid Positioning System Combining GPS and TV Signals 5
Ju-Yong Do 2007/4/18
Contents
1. Search for a Solution for Urban/Indoor Areas
2. Hybrid Positioning System Combining GPS and TV Signals
3. Multi-Fault Tolerant RAIM (Receiver Autonomous Integrity
Monitoring)
Hybrid Positioning System Combining GPS and TV Signals 6
Ju-Yong Do 2007/4/18
Search in Geographical Signal Space
Combining ranging sources for the end-to-end coverage!
Coverage
Num
ber
of T
ran
sm
itte
rs
Indoor/Urban Outdoor/Rural
101
103
GPS, Glonass, Galileo
TV, Cellular
WiFi
Dis
tance to
User
[Km
]
104
102
100
10-2
105
RFID
Hybrid Positioning System Combining GPS and TV Signals 7
Ju-Yong Do 2007/4/18
Search in Spectral Signal Space (RX)
Signal power and bandwidth are the key factors in positioning.
500 1000 1500 2000 2500−130
−120
−110
−100
−90
−80
−70
−60
−50
−40
Rec
eptio
n P
ower
[dB
m]
Frequency [MHz]
GPS L1
ISM
TV UHF
CellularPCS
Hybrid Positioning System Combining GPS and TV Signals 8
Ju-Yong Do 2007/4/18
Final Selection = GPS + TV
Pros and cons of candidate ranging sources (GPS and terrestrial
communication systems).
GPS TV Cellular WiFi RFID
Distance (km) 20,000 < 100 < 10 < 0.5 < 0.01PRX (dBm) -125 -44 -55 -64BW (MHz) 24 336 25 83.5
Ch BW (MHz) 2 6 1.25 22Near-Far Mild None Severe High N/ACoverage Outdoor Out/In Out/In Indoor Proximity
Measurement Range Range Range PRX DetectionRequired None Clock None Periodic Installation
Investment monitoring surveying
TV channel allocations:
54–88 MHz (ch2–6), 174–216 MHz (ch7–13), and 470–806 MHz (ch14–69)
Hybrid Positioning System Combining GPS and TV Signals 9
Ju-Yong Do 2007/4/18
TV Positioning System
Pioneering works by Rabinowitz and Spilker (Rosum Corp. ’00)
Pseudo-
Range Estimator
TV RX
XGPS, prGPS
XTV,
tRX,TV
Monitor
(TV RX) tTX,TV
GPS RX
Hybrid
Position Estimator
XTV,
prTV
RAIM
Clusterization
Regional
Optimization
Position
FilterTest Stat
Interative Search
Position
Fixes
Final
Position
Fixes
Rosum
Fault Detection
(χ2, HPL,
MHSS)
Fault Exclusion
Contributions
Hybrid Positioning System Combining GPS and TV Signals 10
Ju-Yong Do 2007/4/18
TV Towers
Time synchronization = Range (distance) measurement.
ReceiverTransmitter 1
Transmitter 2 Transmitter 3
Time synchronization
= Time of arrival measurement
= Range measurement
Hybrid Positioning System Combining GPS and TV Signals 11
Ju-Yong Do 2007/4/18
Network Synchronization
• GPS, CDMA Cellular → synchronized networks
• TV, WiFi, GSM/TDMA cellular networks
→ Un-synchronized networks
Hybrid Positioning System Combining GPS and TV Signals 12
Ju-Yong Do 2007/4/18
Absolute/Relative Positioning
• Absolute positioning
ρli = rl
i + bl + Bi + ǫli
For GPS, Bi ≈ 0 for all i, but for others, Bi 6= 0.
• Relative positioning (no TX clock bias B)
∆ρl,mi = ∆r
l,mi + ∆bl,m + ∆ǫ
l,mi
• Pseudo-absolute (with an installed reference receiver)
ρi = ri + b + (Bi − B̂i) + ǫi
B̂i = ρrefi − (rref
i + b̂ref)
Hybrid Positioning System Combining GPS and TV Signals 13
Ju-Yong Do 2007/4/18
TV Positioning System
A monitor (reference) station calibrates out transmitter clock biases.
Monitor Station
Position Server
User Device
Hybrid Positioning System Combining GPS and TV Signals 14
Ju-Yong Do 2007/4/18
TV Positioning Equation
• Construction of Pseudoranges
ρi = t̃uRX,i − t̃refTX,i
= (tuRX,i − tuTX,i) + (bu − bref) + Niλi + (ǫui − ǫ
refi )
= ri + b + Niλi + ǫi
where t̃uRX,i = RX time at user = tuRX,i + bu + ǫui
t̃refTX,i = estimated TX time at reference
= trefTX,i + bref + ǫ
refi = (tuTX,i − Niλi) + bref + ǫ
refi
λ = 24.2 ms = 7254 Km
Hybrid Positioning System Combining GPS and TV Signals 15
Ju-Yong Do 2007/4/18
Frequency Instability Induced Range Error
Integer ambiguity + Frequency instability → Range error → Position error
Field Synch Data
N1=1 → N2=1 → N3=1
Field Synch Data ... Data Field Synch
Field Synch Data ... Data Field Synch
time
N1=2 → N2=2 → N3=2
TX 1
TX 2 TX 3
TX 1
TX 3
CH 1
CH 3
CH 2
Frequency instability
changes duty cycles
... Data Field Synch
TX 2
RX RX
Hybrid Positioning System Combining GPS and TV Signals 16
Ju-Yong Do 2007/4/18
Contents
1. Search for a Solution for Urban/Indoor Areas
2. Hybrid Positioning System Combining GPS and TVSignals
3. Multi-Fault Tolerant RAIM (Receiver Autonomous Integrity
Monitoring)
Hybrid Positioning System Combining GPS and TV Signals 17
Ju-Yong Do 2007/4/18
Contribution I: Hybrid Positioning System
Implemented Hybrid Positioning Estimator combining GPS/TV range
measurements on a MATLAB platform and conducted field tests with
its prototype.
Pseudo-
Range Estimator
TV RX
XGPS, prGPS
XTV,
tRX,TV
Monitor
(TV RX) tTX,TV
GPS RX
Hybrid
Position Estimator
XTV,
prTV
RAIM
Clusterization
Regional
Optimization
Position
FilterTest Stat
Interative Search
Position
Fixes
Final
Position
Fixes
Rosum
Fault Detection
(χ2, HPL,
MHSS)
Fault Exclusion
Contributions
Hybrid Positioning System Combining GPS and TV Signals 18
Ju-Yong Do 2007/4/18
Hybrid Positioning System
Monitor Station
Position Server
User Device
Hybrid Positioning System Combining GPS and TV Signals 19
Ju-Yong Do 2007/4/18
Hybrid Positioning Equations
• TV and GPS Pseudoranges
TV: ρTV,i = ri + bTV + ǫTV,i
GPS: ρGPS,j = rj + bGPS + ǫGPS,j
• Combined Pseudoranges after Differentiation
Hybrid: δρ = Gδx + v
where
δρ = [δρTTV , δρT
GPS]T
δx = [δx, δy, δz, δbTV , δbGPS]T
Hybrid Positioning System Combining GPS and TV Signals 20
Ju-Yong Do 2007/4/18
Extensive Field Tests at 37 (+2) Bay Area Sites
Constructed a prototype with a SiRF GPS RX and a Rosum TV RX with the help
of Samra (Rosum) and conducted extensive field tests.
• Stationary tests of GPS and TV RXs
• 1 hour test per site
• 1 measurement per a minute
• Extreme urban indoor sites (2) removed
due to the lack of sufficient measurements
Category Location Outdoor Indoor
Urban San Francisco downtown 6 4 (+2)Suburban Palo Alto downtown 4 5Residential Stanford graduate housing 8 5
Rural Halfmoon Bay and Highway 280 5 N/A
Hybrid Positioning System Combining GPS and TV Signals 21
Ju-Yong Do 2007/4/18
Outdoor Test Sites
Hybrid Positioning System Combining GPS and TV Signals 22
Ju-Yong Do 2007/4/18
Indoor Test Sites
Hybrid Positioning System Combining GPS and TV Signals 23
Ju-Yong Do 2007/4/18
Number of Observed Channels
Many TV channels even in indoors but tend to be co-located: less
favorable for geometry but good for cross-check.
User Device
Urban Suburban Residential Rural0
2
4
6
8
10
12
14
16
18
20
Site Category
Nu
mb
er
of
Ch
an
ne
ls
GPS (outdoor)
GPS (indoor)
TV (outdoor)
TV (indoor)
Hybrid Positioning System Combining GPS and TV Signals 24
Ju-Yong Do 2007/4/18
Hybrid Position Fixes! (Urban Canyon)
• Epoch by epoch position estimation.
• GPS, TV, Hybrid (GPS+TV) fixes on an urban canyon at San
Francisco downtown.
−6000 −4000 −2000 0 2000 4000 6000−6000
−4000
−2000
0
2000
4000
6000
East (m)
No
rth
(m
)
−6000 −4000 −2000 0 2000 4000 6000−6000
−4000
−2000
0
2000
4000
6000
East (m)
No
rth
(m
)
−6000 −4000 −2000 0 2000 4000 6000−6000
−4000
−2000
0
2000
4000
6000
East (m)
No
rth
(m
)
GPS only
(62%, 206 m)
Hybrid = TV + GPS
(100%, 1173 m)TV only
(100%, 1473 m)
Hybrid Positioning System Combining GPS and TV Signals 25
Ju-Yong Do 2007/4/18
Frequency Instability Induced Range Error
12 14 16 18 20 22 24 26 28
−200
0
200
GPS Range Error
GPS Channel Number
0 10 20 30 40 50 60 70
−6000
−4000
−2000
0
TV Range Error
TV Channel Number
Field Synch Data
Field Synch Data ... Data Field Synch
Field Synch Data ... Data Field Synch
CH 1
CH 3
CH 2
Frequency instability
changes duty cycles
... Data Field Synch
time
Hybrid Positioning System Combining GPS and TV Signals 26
Ju-Yong Do 2007/4/18
Contents
1. Search for a Solution for Urban/Indoor Areas
2. Hybrid Positioning System Combining GPS and TV Signals
3. Multi-Fault Tolerant RAIM (Receiver AutonomousIntegrity Monitoring)
Hybrid Positioning System Combining GPS and TV Signals 27
Ju-Yong Do 2007/4/18
Contribution II: Multi-Fault Tolerant RAIM
Implemented Multi-fault tolerant iterative RAIM algorithms to detect
and exclude outlying range measurements from integrated signals, in
particular from TV pseudoranges.
Pseudo-
Range Estimator
TV RX
XGPS, prGPS
XTV,
tRX,TV
Monitor
(TV RX) tTX,TV
GPS RX
Hybrid
Position Estimator
XTV,
prTV
RAIM
Clusterization
Regional
Optimization
Position
FilterTest Stat
Interative Search
Position
Fixes
Final
Position
Fixes
Rosum
Fault Detection
(χ2, HPL,
MHSS)
Fault Exclusion
Contributions
Hybrid Positioning System Combining GPS and TV Signals 28
Ju-Yong Do 2007/4/18
Candidate RAIM Algorithms (Fault Detection)
• χ2 test
||w||2 < χ2th(PFA, k)
• HPL (Horizontal Protection Level) test (Brown ’94)
HPL = ∆max · pbiasB < HAL
• MHSS (Multi-Hypothesis Solution Separation) test (Pervan ’98)
(Hi : a bias in ρi) and X|Hi ∼ N(x̂i, σ2x,i)
PMD,i = Pr{||X − x̂0|| > HAL|Hi}
PMD =
n∑
i=0
PMD,i · P(Hi) < PMD,th
Hybrid Positioning System Combining GPS and TV Signals 29
Ju-Yong Do 2007/4/18
MHSS (Multi-Hypothesis Solution Separation) Test
Construct hypotheses (Hi : a bias in ρi and X|Hi ∼ N(x̂i, σ2x,i)). Then, validates
the initial position estimate (x̂0) based on PMD,i = Pr{||X − x̂0|| > HAL|Hi} and
PMD =∑n
i=0 PMD,i · P(Hi) < PMD,th.
χ2χth2
H0
PFAPFA
H1 H2H3
PMD < PMD, th
x0^ ^ ^x3 x2x̂1
PMD < PMD, th
x̂0 - HAL x̂0 + HAL
Hybrid Positioning System Combining GPS and TV Signals 30
Ju-Yong Do 2007/4/18
Candidate RAIM Algorithm (Fault Exclusion)
• Maximum likelihood test (Sturza ’88)
minimizing the distance, ||p−p̂i||, between the parity vector p = Pw
and its reconstruction p̂i based on Hi
i∗ = arg mini
||p − p̂i|| = arg maxi
(pTPi)2
(PTP )ii
where P is a parity transformation matrix, spanning the null space
of G. PG = 0 and PPT = I.
• Iteration of fault detection and exclusion steps until all outliers are
removed.
Hybrid Positioning System Combining GPS and TV Signals 31
Ju-Yong Do 2007/4/18
Iterative RAIM Implementation
k > 0No
Yes
||w||2< χth2
Yes
k > 1No
Yes
Fault Exclusion
PseudorangeMeasurements
Epoch Available
Unavailable
HPL < HAL PMD < PMD, th
Fault Detection
Yes
Yes Yes
No
No No
Hybrid Positioning System Combining GPS and TV Signals 32
Ju-Yong Do 2007/4/18
Position Fixes at the Urban Canyon
Availability and accuracy trade-off.
−6000 −4000 −2000 0 2000 4000 6000−6000
−4000
−2000
0
2000
4000
6000
East (m)
No
rth
(m
)
−6000 −4000 −2000 0 2000 4000 6000−6000
−4000
−2000
0
2000
4000
6000
East (m)
No
rth
(m
)
−6000 −4000 −2000 0 2000 4000 6000−6000
−4000
−2000
0
2000
4000
6000
East (m)
No
rth
(m
)
GPS only
(62%, 206 m)
Hybrid = TV + GPS
(100%, 1173 m)TV only
(100%, 1473 m)
−6000 −4000 −2000 0 2000 4000 6000−6000
−4000
−2000
0
2000
4000
6000
East (m)
No
rth
(m
)
−6000 −4000 −2000 0 2000 4000 6000−6000
−4000
−2000
0
2000
4000
6000
East (m)
No
rth
(m
)
−6000 −4000 −2000 0 2000 4000 6000−6000
−4000
−2000
0
2000
4000
6000
East (m)
No
rth
(m
)
GPS w. RAIM
(53%, 64 m)
TV w. RAIM
(88%, 93 m)
Hybrid w. RAIM
(81%, 67 m)
Hybrid Positioning System Combining GPS and TV Signals 33
Ju-Yong Do 2007/4/18
Position Fixes at the Urban Canyon (zoomed)
Availability and accuracy trade-off.
−300 −200 −100 0 100 200 300−300
−200
−100
0
100
200
300
East (m)
No
rth
(m
)
−300 −200 −100 0 100 200 300−300
−200
−100
0
100
200
300
East (m)
No
rth
(m
)
−300 −200 −100 0 100 200 300−300
−200
−100
0
100
200
300
East (m)N
ort
h (
m)
−300 −200 −100 0 100 200 300−300
−200
−100
0
100
200
300
East (m)
No
rth
(m
)
−300 −200 −100 0 100 200 300−300
−200
−100
0
100
200
300
East (m)
No
rth
(m
)
−300 −200 −100 0 100 200 300−300
−200
−100
0
100
200
300
East (m)
No
rth
(m
)
GGGGPPPSSSSSSS oonly
(622%, 2066 m)
Hyybriddd == TTTTTVV +++ GPPS
((110000%%, 11117733 m)))TTTVV ooonnllyy
(1100%%, 114733 mm)
GPS ww. RAAIM
(5333%%, 66644 m)
TVV ww. RRAAIM
(8888%%%, 9933 mm)
HHyybrrid ww. RRAIMM
(811%%, 6677 mm)
Hybrid Positioning System Combining GPS and TV Signals 34
Ju-Yong Do 2007/4/18
Search for a Best RAIM in Two Goals
• Two Goals: Availability and Accuracy
Availability =number of available epochs
number of total epochs
Accuracy = DRMS (distance root mean squared) (m)
• Calculate average availability and accuracy from all sites for given
RAIM parameters.
– For χ2 test, adjust PFA = 0–0.999.
– For HPL and MHSS, adjust HAL= 101–105 (m) with fixed
PFA = 10−3 and PMD = 10−2.
Hybrid Positioning System Combining GPS and TV Signals 35
Ju-Yong Do 2007/4/18
Availability and Accuracy Trade-Off
Each point is an average from 37 sites for given RAIM parameters.
50 55 60 65 70 75 80 85 90 95 10010
2
103
Availability (%)
Acc
ura
cy (
DR
MS
) (m
)
No RAIM cases
χ2
HPL
MHSS
GPS only(53%, 181 m)
TV only(90%, 3341 m)
Hybrid = TV + GPS(98%, 3022 m)
Hybrid w. MHSS(90%, 339 m)
Hybrid Positioning System Combining GPS and TV Signals 36
Ju-Yong Do 2007/4/18
Trade-off Curve after Clusterization
Improves accuracy (339 m to 209 m) at the expense of availability (90% to 84%).
65 70 75 80 85 90 95 10010
2
103
Availability (%)
Acc
ura
cy (
DR
MS
) (m
)
MHSS
MHSS + Clusterization
MHSS(90%, 339 m)
MHSS + Clusterization(84%, 209 m)
User Device
Hybrid Positioning System Combining GPS and TV Signals 37
Ju-Yong Do 2007/4/18
Trade-off Curve after Regional Optimization
Optimize RAIM parameters for each categorical region or site.
65 70 75 80 85 90 95 10010
2
103
Availability (%)
Acc
ura
cy (
DR
MS
) (m
)
MHSS
MHSS + Clusterization
MHSS + Cat−Optimization
MHSS + Site−Optimization
MHSS(90%, 339 m)
MHSS + Clusterization(84%, 209 m)
MHSS + Site-Optimization(89%, 208 m)
Hybrid Positioning System Combining GPS and TV Signals 38
Ju-Yong Do 2007/4/18
Position Domain Filtering
A solution for the last 10% availability.
Pseudo-
Range Estimator
TV RX
XGPS, prGPS
XTV,
tRX,TV
Monitor
(TV RX) tTX,TV
GPS RX
Hybrid
Position Estimator
XTV,
prTV
RAIM
Clusterization
Regional
Optimization
Position
FilterTest Stat
Interative Search
Position
Fixes
Final
Position
Fixes
Rosum
Fault Detection
(χ2, HPL,
MHSS)
Fault Exclusion
Contributions
Hybrid Positioning System Combining GPS and TV Signals 39
Ju-Yong Do 2007/4/18
Trade-off Curve after Averaging Position Fixes
Averaging (sliding window of 5 epochs) can fill the gap between fixes.
65 70 75 80 85 90 95 10010
2
103
Availability (%)
Acc
ura
cy (
DR
MS
) (m
)
MHSS
MHSS + Clusterization
MHSS + Cat−Optimization
MHSS + Site−Optimization
MHSS + Averaging
MHSS + Site-Optimization(89%, 208 m)
MHSS + Averaging(98%, 190 m)
Hybrid Positioning System Combining GPS and TV Signals 40
Ju-Yong Do 2007/4/18
Availability & Accuracy Summary
Processing Method Availability (%) CEP (m) DRMS (m)
GPS only 53 17 181No RAIM 98 215 3022
Hybrid MHSS 90 83 339MHSS+Site-Optimization 89 73 208
MHSS+Averaging 98 63 190
Processing Method Outdoor Indoor% CEP DRMS % CEP DRMS
GPS only 87 18 247 18 15 69No RAIM 99 31 1269 96 400 4082
Hybrid MHSS 96 17 38 83 149 478MHSS+Site-Optimization 96 17 36 82 129 292
MHSS+Averaging 99.6 14 26 95 111 268
Hybrid Positioning System Combining GPS and TV Signals 41
Ju-Yong Do 2007/4/18
Road to Seamless Positioning
High Accuracy
Glonass
GalileoCellular
High Availability
Seamless
Positioning
RFID
TV
WiFi
WAASGPS
(WAAS: Wide Area Augmentation System)
Hybrid Positioning System Combining GPS and TV Signals 42
Ju-Yong Do 2007/4/18
Summary
• Hybrid positioning (combining space and land-based signals) is the road toseamless positioning.
• Implemented Matlab-based Hybrid Positioning System using GPS/TVmeasurements.
• Extensive field tests of a prototype demonstrated the enhanced availability bythe integration of TV and GPS.
• Iterative RAIM (MHSS) for Multi-Fault Tolerance required for signalintegration. (+ Clusterization, Regional Optimization)
• Performance on continuous fixes (averaging):for outdoor sites, 99.6%, 14 m (CEP) and 26 m (DRMS);for indoor sites, 95.4%, 111 m (CEP) and 268 m (DRMS).
Hybrid Positioning System Combining GPS and TV Signals 43
Ju-Yong Do 2007/4/18
Recommendations for Infrastructural Investments
Still need a solution for extreme sites (2 zero-availability urban indoor sites)—highmultipath and low observability.
• Receiver: Utilization of data segmentonly 0.3% of TV signals are used for range measurement. The rest 99.7% ofTV signals can provide a higher SNR for survival in extreme sites.
• Monitor: Better clock monitoringparallel RF tuners at a monitor station, dedicated to each channel, can providebetter transmitter clock monitoring.
• Network: TV towers synchronized to GPS or Lorana frequency/time/position reference to urban/indoor users.In particular, TV+Loran can be a backup system in case of GPS outage.
Hybrid Positioning System Combining GPS and TV Signals 44
Ju-Yong Do 2007/4/18
Publications
1. J. Do, M. Rabinowitz, and P. Enge, ”Multi-Fault Tolerant RAIM Algorithm for Hybrid GPS/TV Positioning,” to be appeared on IONNational Technical Meeting Proceeding, San Diego, January 2007
2. J. Do, M. Rabinowitz, and P. Enge, ”Robustness of TOA and TDOA Positioning,” submitted to IEEE AESS, January 2007
3. J. Do, M. Rabinowitz, and P. Enge, ”Performance of Hybrid Positioning System Combining GPS and Television Signals,” IEEE/ION
Position Location and Navigation Symposium 2006, pp 556 - 564, San Diego, April 2006
4. J. Do, M. Rabinowitz, and P. Enge, ”Performance of TOA and TDOA in a Non-homogeneous Transmitter Network Combining GPS andTerrestrial Signals,” ION National Technical Meeting Proceeding, pp 642 - 649, Monterey, January 2006
5. J. Do, M. Rabinowitz, and P. Enge, ”Linear Time-of-Arrival Estimation in a Multipath Environment by Inverse Correlation Method,” IONAnnual Meeting Proceeding, pp 720 - 725, Cambridge, June 2005
6. J. Do, D. Akos, and P. Enge, ”L and S Bands Spectrum Survey in the San Francisco Bay Area,” IEEE Position Location and Navigation
Symposium 2004, pp 566 - 572, Monterey, April 2004
7. P. Enge, D. Akos, J. Do, J. Simoneau, L. P. Wilson, and V. Seetharam, ”Measurements of Man-Made Spectrum Noise Floor,” NationalAeronautics and Space Administration, CR-2004-213551, November 2004
Hybrid Positioning System Combining GPS and TV Signals 45
Ju-Yong Do 2007/4/18
Acknowledgment
• Committee members: Per Enge (Advisor), Teresa Meng, Matthew
Rabinowitz, Dennis Akos, and Paul Segall (Chair)
• Rosum people (TV experts): Harvind, Guttorm, Kam,...
• Staffs: Diane (EE), Sherann, Dana, Doug, and Aldo (AA)
• Former and current GPS labmates, friends...
• My family: My mother. My wife, Younju. Two sons, Wonho (for
master) and Wonyoung (for Ph.D.)
Hybrid Positioning System Combining GPS and TV Signals 46
Ju-Yong Do 2007/4/18
Thank You
I thank Federal Aviation Administration (FAA), Rosum Corporation,
and National Aeronautics and Space Administration (NASA) for their
supports for this research.
Thank you all for your attention!
Hybrid Positioning System Combining GPS and TV Signals 47
Ju-Yong Do 2007/4/18
χ2 Test
A widely used test for verification of Gaussian distribution of a given
data set.
||w||2 < χ2th(PFA, k)
P(χ2)
χ2
χth2
H1H0
PFA
PMD = Miss Detection
= False Negative
χth2
P(χ2)
χ2
χth2
H1H0
PFA = False Alarm
= False Positive
||w||2
χth2 ||w||
2
Hybrid Positioning System Combining GPS and TV Signals 48
Ju-Yong Do 2007/4/18
HPL (Horizontal Protection Level) Test
Projects the worst case horizontal position error based on the worst case geometry
(∆max = maxi
√P2j=1(G
†ji
)
(P T P )ii) and the worst case measurement error (pbiasB =
{β|PMD = F non-centralχ2 (χ2
th; k, β2)}).
Position Error
χ2
χth2
H0
χth ||w||
∆max
H1
∆min
pBiasB
HPL HPL < HAL
Position Error
χ2
χth2
H0
PFA = PFA, th
χth ||w||
H1
PMD = PMD, th
pBiasB
Hybrid Positioning System Combining GPS and TV Signals 49
Ju-Yong Do 2007/4/18
MHSS (Multi-Hypothesis Solution Separation) Test
Construct hypotheses (Hi : a bias in ρi and X|Hi ∼ N(x̂i, σ2x,i)). Then, validates
the initial position estimate (x̂0) based on PMD,i = Pr{||X − x̂0|| > HAL|Hi} and
PMD =∑n
i=0 PMD,i · P(Hi) < PMD,th.
χ2χth2
H0
PFAPFA
H1 H2H3
PMD < PMD, th
x0^ ^ ^x3 x2x̂1
PMD < PMD, th
x̂0 - HAL x̂0 + HAL
Hybrid Positioning System Combining GPS and TV Signals 50
Ju-Yong Do 2007/4/18
TV Stations (364 in US = 229(A)+ 135(D))
100 200 300 400 500 600 700 80060
65
70
75
80
85
90
95
100T
X E
IRP
[dB
m]
Frequency [MHz]
Avg PATV
= 90.4283
Avg PDTV
= 84.1207
Hybrid Positioning System Combining GPS and TV Signals 51
Ju-Yong Do 2007/4/18
Digital TV (ATSC) Signal Structure
Field Synch Data 1 ... Data 312
1 Field = 313 Segments = 24.2 ms
4 PN (511)PN (63)
128
1 Segment = 832 Symbols = 77.3 us
PN (63)
PN (63)
1 Symbol = 92.9 ns
(PN: pseudo random sequence)
Hybrid Positioning System Combining GPS and TV Signals 52
Ju-Yong Do 2007/4/18
Autocorrelation of Field Synch Segment
Quite similar to GPS signal processing.
100 200 300 400 500 600 700−10
−5
0
5
10fie
ld s
ynch
−600 −400 −200 0 200 400 600
0
0.2
0.4
0.6
0.8
1
Aut
ocor
rela
tion
1st to 2nd peak ratio = 0.14429
−10 −8 −6 −4 −2 0 2 4 6 8 10
0
0.2
0.4
0.6
0.8
1
Aut
ocor
rela
tion
delay [Tchip
]
Hybrid Positioning System Combining GPS and TV Signals 53
Ju-Yong Do 2007/4/18
Candidate Positioning Sources
Signal specification for candidate ranging sources (GNSS andterrestrial communication systems)
GPS TV Cellular WiFi RFID INS
Distance (km) 20,000 < 100 < 10 < 0.5 < 0.01 N/APTX (dBm) 55 84 50 30 TBD N/A
PRX (dBm) -125 -44 -55 -64 TBD N/AFrequency (MHz) 1563–1587 470–806 869-894 2400–2484 TBD N/A
Bandwidth (MHz) 24 336 25 83.5 TBD N/AChannel Bandwidth (MHz) 2 6 1.25 22 TBD N/A
Multiple Access CDMA FDMA CDMA FDMA TBD N/A
Near-Far Problem Mild None Severe Severe TBD N/ANetwork Synchronization Synch Asynch Synch Asynch TBD N/A
Positioning 3D 2D 2D 2D 2D 3D
Coverage Global National National Indoors Proximity N/AMeasurement Range Range Range Signal strength Signal strength Acceleration
Continuous Operation Yes Yes Yes Yes Yes No
Clock Stability Good Medium Good Bad N/A N/AMultipath Mild Severe Severe Severe N/A N/A
Requirement None Clock Monitoring None Periodic surveying Installation None
Hybrid Positioning System Combining GPS and TV Signals 54
Ju-Yong Do 2007/4/18
Absolute/Relative and TOA/TDOA (cont’d)
∆TX
∆2TX, RX∆RX
Range
Absolute /TOAfor GPS
Absolute/TDOAfor Loran
Relative /TOAfor TV, WiFi, Cellular
Relative /TDOAfor TV, WiFi, Cellular
AbsoluteSingle
DifferencingDouble
Differencing
Hybrid Positioning System Combining GPS and TV Signals 55
Ju-Yong Do 2007/4/18
Television Standards
• Analog Television
– NTSC (National Television Systems Committee)
– PAL (Phase Alternating Line)
– SECAM (Color Sequential with Memory)
• Digital Television (supporting MPEG-2 standard)
– ATSC (Advanced Television Systems Committee) in US, using
VSB + 8/16 ASK
– DVB (Digital Video Broadcasting) in Europe, using COFDM +
16/64 QAM
– ISDB (Integrated Services Digital Broadcasting) in Japan, using
COFDM + 16/64 QAM
Hybrid Positioning System Combining GPS and TV Signals 56