GNSS and Positioning for the Future - Kai Borre

DANISH GPS CENTER
GNSS
and
Positioning for the Future
Kai Borre
Danish GPS Center, Aalborg University, Denmark

DANISH GPS CENTER
GNSS Development Schedule
• GPS and
GLONASS
evolved slowly
in the first
decades
• In the last
decade the
development
of space and
ground control
segments is
intense
14/12/2011 Copyright © 2011 by Kai Borre 2
Test & deployment GPS III
GPS II
202020122010 2015
COMPASS
COMPASS 1 (end date unknown)
Test & deployment of L5
GPS III FOC
L1C FOC
L5 FOC
L2C Full Operational Capability (FOC)
GLONASS Full Operational Capability (FOC)
COMPASS 2 test & depl. COMPASS 2/3, regional service; global service depl. COMPASS 3 FOC
New
signals
FOC
SDCM design/tests
GLONASS-M
(launched until
2012)
GLONASS-K2 (KM after 2015)
New: L1OC, L3OC, L1SC, L2SC (CDMA), SAR
GLONASS-K1
New: L3OC (CDMA),
SAR
Galileo launch
Sys. testbed v1/v2 IOV Deployment
Galileo operational
SDCM fully deployed
18 SV OC
Test & deployment of L1C
Test & deploym. of L2C, staged roll-out of CNAV
Courtesy of Darius Plaušinaitis

DANISH GPS CENTERThe Menu of Future GNSS Signals
• Originally GPS and
GLONASS offered
one civilian signal on
one carrier
• Future GNSS offer
system diversity and
frequency diversity
System Signal
Carrier
frequency
[MHz]
Component Type
Data rate
[sps/bps]
Modulation
Chipping
rate
[Mcps]
Code length
[chips]
Full
length
[ms]
GLONASS L1
OF 1605.375-
1609.3125
standard Data -/50
BPSK
0.511 511 1
SF high accur. Military 5.11
COMPASS B1 1575.42
B1-CD
Open
100/50
MBOC(6,1,1/11) 1.023
B1-CP -/-
B1 Authorized
100/50
BOC(14,2) 2.046
-/-
Galileo E1 1575.42
A PRS cosBOC(15,2.5) 2.5575
B Data, SOL 250/125
CBOC(6,1,1/11) 1.023
4092 4
C Pilot, SOL -/- 4092 * 25 100
GLONASS L1 OC/SC 1575.42
GPS L1 1575.42
C/A Data -/50 BPSK 1.023 1023 1
P(Y)
Military
BPSK 10.23 7 days 7 days
M BOC(10,5) 5.115
Galileo E6 1278.75
A PRS cosBOC(10,5)
B Data 1000/500
BPSK(5) 5.115
5115 1
C Pilot -/- 5115 * 100 100
COMPASS B3 1268.52
B3
Authorized
-/500 QPSK(10) 10.23
B3-AD 100/50
BOC(15,2.5) 2.5575
B3-AP -/-
GLONASS L2
OF 1242.9375-
1248.1875
standard Data -/50
BPSK
0.511 511 1
SF high accur. Military 5.11
GPS L2 1227.6
L2 CM Data
50/25
or -/50 TM and BPSK 0.5115
10230 20
L2 CL Pilot -/- 767250 1500
P(Y)
Military
BPSK 10.23 7 days 7 days
M BOC(10,5) 5.115
GLONASS L3 OC 1207.14 QBSK(10)
GLONASS L3 OF/SF
1201.743-
1208.088
COMPASS B2 1191.795
B2aD
Open
50/25
AltBOC(15,10) 10.23
B2aP -/-
B2bD 100/50
B2bP -/-
Galileo
E5
(1191.795)
E5a 1176.45
a-I Data 50/25
AltBOC(15,10) 10.23
10230 * 20 20
a-Q Pilot -/- 10230 * 100 100
E5b 1207.14
b-I Data, SOL 250/150 10230 * 4 4
b-Q Pilot, SOL -/- 10230 * 100 100
GPS L5 1176.45
I Data 100/50
QPSK 10.23 10230
1
Q Pilot -/- 1
Courtesy of Darius Plaušinaitis

DANISH GPS CENTER
GNSS Signal Changes
• Increasing requirements to positioning, increasing
number of systems ask for redesign of GNSS signals
– New modulations are needed due to
• More heavy shearing of spectrum
• More signals per carrier
• Improved ranging performance
– New PRN code generators (Kazami,
Weil, Neuman-Hoffman) are
considered in addition to the
traditional Gold codes
• Several signals in a system and
several systems are using the same
carrier
• Better performance of week signals
• Better interference performance
• Better ranging performance
Figure source – “GPS World”
GNSS L1 (carrier) spectrum

DANISH GPS CENTERGlobal Navigation Satellite Systems
• GPS (II – 1980)
• GLONASS (1993)
• COMPASS
• Galileo
2006
~1981
• 80’s-90’s – the first professional
GPS + GLONASS receivers
• 2011 – “launch year” for the first
consumer, mobile phone GPS +
GLONASS receiver chips (from
Qualcomm, Broadcom, ST-
Ericsson, u-blox and others)

DANISH GPS CENTER
Relative Accuracy of Clocks
• Clock stability influences signal and
observation related parameters
Clock type Applications
Relative accuracy
[s/s]
Temperature compensated
crystal oscillator (TCXO)
Watches, clocks, consumer GNSS
receivers, mobile phones
10-6 – 5×10-7
Oven controlled crystal
oscillator (OCXO)
Geodetic GNSS receivers 10-7 – 10-8
GPS disciplined oscillator
(GPSDO) – GPS + above clock
Time and frequency synchronization 10-9 – 10-12
Chip scale atomic clock (CSAC)
Future high performance GNSS
receivers
5×10-12
Rubidium atomic clock Special space and terrestrial
applications that require extra high
stability and accuracy
10-11 – 10-12
Cesium atomic clock 10-12 – 10-13
Hydrogen maser
Space (new application) and
terrestrial applications
10-15 – 10-16

DANISH GPS CENTER
Satellite Based Augmentation
System (SBAS)
• The primary driver for SBAS is aviation applications
that require high safety
• SBAS provides services that are not available in GPS
or other existing systems
– DGPS type corrections for
improved standard receiver
precision
– Massive signal integrity
monitoring and user alert in
less than 6 seconds from
the start of an integrity
failure
– Other system safety and
service quality data that are
vital for reliable positioning

DANISH GPS CENTERSpace Based Augmentation Systems
• Wide Area Augmentation System (WAAS), USA
• European Geostationary Navigation Overlay Service
(EGNOS)
• System for Differential Correction and Monitoring
(SDCM), Russia
• GPS And Geo-Augmented Navigation (GAGAN)
system, India
• Quasi-Zenith Satellite System (QZSS), Japan
• Multi-functional Satellite Augmentation System
(MSAS), Japan

DANISH GPS CENTER
Alternative Systems
• Research and development continuously
adapt to or modify existing systems to provide
positioning services
– Legacy ground based systems (no perspectives)
– WiFi (very limited capabilities)
– Mobile Networks (does not meet today’s GNSS
precision level, new versions under development)
– TV (DVB) signals based
– Proprietary, local (for example LOCATA)
– New methods based on GPS+LEO satellites (for
example Boeing Timing & Location)

DANISH GPS CENTERBoeing Timing & Location (BTL) I
• BTL Geo-location builds on Transit heritage. It
complements GPS with an enhanced version
of the existing Iridium system
• BTL Geo-location provides key technical
advantages in 2 parts – (GPS-based systems
can not do this)
– Iridium signal power (BTL) >> GPS – Iridium
penetrates buildings better
– Spot beams form unique local contours. Extremely
difficult to spoof (today spoofing is of big concern
for civil applications in the GNSS world)

DANISH GPS CENTERBoeing Timing & Location (BTL) II

DANISH GPS CENTERBoeing Timing & Location (BTL) III
Figure source – Wikipedia

DANISH GPS CENTER
Receiver Development

DANISH GPS CENTERCurrent Receiver Development
Copyright © 2011 by Kai Borre 14
2007 Future
Research and
development
2008-2010
•Snapshot techniques
•High sensitivity
•Multi-system & multi-
frequency receiver
•Multipath mitigation
•Antenna arrays
•Further SDR
development
•GNSS integrity
•Integration of other
positioning methods
14/12/2011

DANISH GPS CENTER
Matlab SDR Plots
4 4.005 4.01 4.015 4.02 4.025 4.03 4.035
x 10
4
-2000
0
2000
4000
6000
Samples (time)
Correlation
Real correlation result from GNSS SDR
-1 0 1 2
0
0.5
1
1.5
Code Offset [chips]
Correlation
Theoretical
correlation
0 5 10 15 20 25 30
0
5
10
15
Acquisition results
PRN number (no bar - SV is not in the acquisition list)
AcquisitionMetric
Not acquired signals
Acquired signals
14/12/2011

DANISH GPS CENTER
Matlab SDR Conclusions
• An extremely convenient educational tool
• Quick prototyping
– A demo acquisition for Galileo in less than an hour
– Students have converted the GPS SDR to EGNOS
and Galileo SDRs in ~6 months
• Very convenient exploration of particular
signal cases (anomalies) or algorithms
because the GNSS signal record can be
replayed again and again …
• Acceleration of some key signal processing
steps is much recommended
Copyright © 2011 by Kai Borre 1614/12/2011

DANISH GPS CENTER
The Old Setup (Virtex IIP)
• Virtex IIP 50
FPGA
• GPS
front-end
from Simrad
• 1 bit samples
• 16 HW
channels
• Adjustable
correlator
spacing (on
the fly)
• About 50%
FPGA in use
• PPC cores
not used
Old
front-end
New
front-
end
14/12/2011

DANISH GPS CENTER
DGC SDR Simulink Model
• Simulink receiver version allows modularity
and out of the box good visual representation
• The modularity gives benefits similar to the
Software Communications Architecture (SCA)
The adaptor block inside
calls nearly unmodified C
code of the FPGA receiver
14/12/2011

DANISH GPS CENTER
Simulink Model Plots

DANISH GPS CENTER
The ML507 Setup
Battery
adapter
New
front-end
14/12/2011

DANISH GPS CENTER
DGC Receiver Results

DANISH GPS CENTER
DGC Receiver Results
4 m 8 m
14/12/2011

DANISH GPS CENTER
Future DGC Receiver Version
• Universal channels for GPS, Galileo, and other GNSS
signals (BOC, BPSK, and other types)
• Real-time operation with optional GNSS signal
recording or processing of such signal records
• Possible options
– Flexible support for multiple front-ends to process multiple
carriers or antennas
– Plotting on a PC of receiver tracking in real-time (non real-
time version already exists)
– Processing of other, non-GNSS signals (under consideration)
• Modular design (friendly for student project)
• Inspiration: AGGA-4, GNU Radio, Artus (IFEN) and
others…

DANISH GPS CENTER
Thank You For Your Attention
Also visit http://gps.aau.dk
DGC is organizing an international
workshop with the same title as the present
talk on August 27-September 2, 2012 at the
North Sea, Denmark. Interested participants
should contact borre@gps.aau.dk

GNSS and Positioning for the Future - Kai Borre

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