Transcript QUO VADIS? Where are we going in Satellite Navigation?

TOWARDS
MULTI-FREQUENCY
MULTI-CONSTELLATION
GNSS AND SBAS
Guenter W. Hein
Head of Galileo Operations and Evolution Department
European Space Agency
2nd
2ndChina
ChinaSatellite
SatelliteNavigation
NavigationConference
Conference(CSNC),
(CSNC),2011
2011
Shanghai,
Shanghai,18-20
18-20May
May2011
2011
OVERVIEW
• The World of GNSS

International GNSS Trends

Compatibility and Interoperability

New Signals and Frequency Bands

The More Satellites The Better…?
• The Evolution of SBAS
• Conclusions
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 2
CURRENT AND PLANNED
SATELLITE NAVIGATION SYSTEMS
Global
Regional
GPS
QZSS
GLONASS
IRNSS
Augmentation
WAAS
EGNOS
MSAS
GAGAN
SDCM
MASS
Galileo
COMPASS
GINS (?)
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 3
International GNSS
Systems Trends
1
1. Flexibility, higher power, coverage, ...
a.
Signal flexibility and general increase of power level.
High increase of power level (>20 dBs) regionally
2. Alternative frequency bands
a.
S-Band Satellite Navigation allocated in ITU Region 2 and 3,
used and planned by IRNSS and perhaps others
3. Inter-Satellite Links (ISL) and better system autonomy
a.
GPS includes ISL for autonomy and NAVWAR purposes.
GPS III will use ISL to improve performance via faster
navigation message updates to whole constellation
b.
Glonass and Compass may include ISL in the future. Main
interest is up-linking all satellites from national territory
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 4
International GNSS
Systems Trends
2
4. System on-board integrity capabilities
a.
GPS III plans on-board integrity monitoring in few seconds
5. Worldwide positioning performance improvement
a.
GPS provides new signals L1C, L2C, L5 and faster refresh of
navigation message for world-wide meter-level point
positioning
b.
Similar plans apply with different time scales to all the other
systems: Glonass, Compass, IRNSS and QZSS
6. Alternative orbits
a.
QZSS introducing HEOs for better visibility over urban areas
b.
Compass and IRNSS are introducing GEOs and IGSOs to
establish their own regional service
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 5
COMPATIBILITY & INTEROPERABILITY
• Compatibility refers to the ability of space-based
positioning, navigation, and timing services to be used
separately or together without interfering with each
individual service or signal, and without adversely affecting
national security
• Interoperability refers to the ability of civil space-based
positioning, navigation, and timing services to be used
together to provide better capabilities at the user level than
would be achieved by relying solely on one service or signal
*NSPD-39: U.S. Space-Based Position, Navigation, and Timing Policy, December 15, 2004
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 6
NEW SIGNALS & FREQUENCY BANDS
MOTIVATION
•
Modernization of existing systems
•
Deployment of new systems
•
Intersystem interference is becoming an
issue
 Particularly for authorized services
 Spectral separation plays a
fundamental role
 But also for open services
 Galileo, GPS, Compass, QZSS,
GLONASS (potentially) will provide
interoperable signals increasing the
noise floor and the consequent
degradation of performance
•
L-Band may not serve all users in an
ideal way (indoor/single/frequency/
iono)
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 7
Spectral resources get
scarce
C-BAND DOWN-LINK FREQUENCY
• ITU Allocation C-Band (5010-5030) for RNSS since WRC 2000
• Technical difficulties and limitations in performance for that allocation
• Advantages
–
Higher resolution
–
Smaller ionospheric impact
–
Smaller antennas at satellite
• Drawbacks
–
Higher attenuation in atmosphere
–
Higher power at satellite or user array antennas needed
• Studies indicate that C-band for mass market is not (yet) mature
• C-band preferable for high-power signals and smaller antennas
• Search for more bandwidth on C-band necessary
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 8
S-BAND DOWN-LINK FREQUENCY
• S-Band (2483.5 – 2500 MHz) is RNSS regionally (Asia/America)
• S-Band already used today for telecommunication + WLAN + Bluetooth
• Advantage: Synergies between navigation & communication (front-end)
• Disadvantage: Harsh interference environment expected
Clarity needs to be gained on the added value of combining
navigation and communication in S-Band for mass market
•
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 9
ITU divides world into three regions for radio spectrum
management
• Region 1
• Europe, Africa, Middle East, west of the Persian
Gulf, Russia
• Region 2
• American continent, some eastern Pacific Islands
• Region 3
• China, Japan, East Asia and most of Oceania
INTEROPERABILITY TODAY
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 10
Interoperability achieved
Interoperability still to be achieved
THE MORE SATELLITES THE
BETTER?
Galileo
Galileo
GPS
Galileo
GPS
GLONASS
Galileo
GPS
GLONASS
COMPASS
Galileo
GPS
GLONASS
COMPASS
GINS
GDOP decreases as the inverse square root of the
number of satellites
?
1
GDOP 
N sat
Once GNSS interference is dominant, noise floor
increases linearly proportional to the number of satellites
I intra  N sat
ESA
UNCLASSIFIED
– Releasable
the Public
CSNC
2011 | Guenter
W. Hein | to
Shanghai,
China | 18/05/2011 | Slide 11
THE FUTURE
• Large number of GNSS satellites in
visibility in future
• The users will pick up the best
GNSS signals based on:
 Power level
 Easy acquisition
 Adherence to multi-constellation
standards
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 12
IS THE BATTLE REALLY LOST?
• Not really…fortunately!
• Conventional GPS receivers

consist of several parallel scalar DLLs, which individually
estimate the individual pseudoranges

These measured pseudoranged are further fed to the
Kalman Filter Estimator

Conventional receivers assume thus truly
independence of measurements
• As more satellites add to the noise floor, the lower will be the C/N0
of each individual acquisition/tracking channel

At a certain number of satellites, the acquisition/tracking
channel C/N0 will be below the required threshold

Conventional GPS receivers could stop functioning

Selection algorithms and Interference Cancellation
help in mitigating higher interference
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 13
SOME SOLUTIONS FOR
CONVENTIONAL RECEIVERS
• At ageometry
certain number
of satellites,
Convex
selection
is based some channels will have a too low
individual
C/N0 to perform
acquisition
or not
tracking.
This to
requires:
• Since
conventional
receivers
might
be able
process
on the approximate
equivalence
all satellites
in view,
the assumption
thatthe
the
GDOP
 Selection
of individual
channels to compute
navigation
between minimizing the geometric
decreases
as the inverse square root of the number
solution:
dilution
of precision
and more valid
of satellites
is(GDOP)
notofany
 Selection
channels
with best C/N0
maximizing the size of the polytope

Selection of channels with best geometry
•(polyhedron
On the other
hand
thein aggregate
GNSS interference
in 3D or
polygon
2D)
 Selection of channels with best error budget
will still
grow
linearly
contained
in the
convex
hull of allas the number of satellites
 Additional constraints result from the fact that
increases
regardless
of ofhow many are actually used for
vector’s endpoints
for
the
set
conventional receivers have a limited number of
computing
the navigation solution
satellites
in view
*
channels
to process,
resulting in
 Reduction
of satellites
to process
using convex
• As a result,
at a certain
number
of satellites
the number
* the acquisition or tracking
of channels geometry
with C/Ntheory
above
0
Maximization
polytope:
Chan’s
algorithm, Graham’s
threshold will
be lower of
than
4, and
conventional
Scan algorithm,
etc…
receivers
that
estimate
individually the
*
Blanco Delgado, N. and Nunes, F. (2010), A Satellite Selection Method for Multi-Constellation GNSS Using
Convex
Geometry, IEEE Transactions
on Vehicular
Technology
pseudoranges
could
unavoidably
fail
ESA
UNCLASSIFIED
– Releasable
the Public
CSNC
2011 | Guenter
W. Hein | to
Shanghai,
China | 18/05/2011 | Slide 14
VECTOR PROCESSING IS THE
ANSWER
•
Vector tracking (VDLL) estimates the signal delays of all satellites in
view in a single processing loop
 Generalization of Extended Kalman Filter (EKF)
 Total noise is reduced by considering all channels together
 VDLL accounts for the actual correlation amongst channels
 Shannon-Theorem on GNSS channel capacity
 It is the total power received from all GNSS satellites
what defines the capacity of a GNSS channel (!!)
 VDLL explodes the capacity increase from additional
satellites
“The use of signals from different satellites may provide enough
total signal power to track successfully and to obtain position
estimates under the same conditions where the signal
strength from each individual satellite is so low that none
of the individual scalar DLL can remain in lock” *
* James J. Spilker Jr. Global Positioning System: Theory and Applications Vol. I, chapter 7
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 15
SHANNON-THEOREM ON GNSS
CHANNEL CAPACITY
•
•
• High-speed and low-cost computer chips make
this task
more
feasible now for tracking,
C  B log
2 (1  SNR)  B log2 (1   Pi N 0 B)
where
1
in the
past
it would i have
been too
whereas
B is the bandwidth
of the
GNSS channel
complex
Pi is the power of each received signal
Total multiple access channel capacity C increases with number of signals N
N

•
•
N0 is the one-sided noise density
N is far
the number
of GNSS signals
receivedsatellites the better *
•  As
as C>R(D),
the more
BUT
For PiB/N0>>1 the channel capacity increases in proportion to log2N
•
With N satellites in sight with good geometry, it
The total information rate sought from the channel (x,y,z – navigation position)
should
be possible
to operate
with
a signal
is •
a constant
independent
of relatively
N (!!!)
VDLL
requires
high
speed
since the
 power/satellite
where the desired information
rate (rate
distortion
function)
ratiomust
that
can
decrease
as N for three
computation
delay
be
small
coordinates is
2
increases *D
x , y , z  E x, y, z  xˆ, yˆ , zˆ


 
 
being the rate at which measurements are sought 2W
3
• In particular for acquisition,
processing
  x2, y ,vector

z




R
D

W
log

2
is still an issue today
D

x , y , z 

x, y, z

* James J. Spilker Jr. Global Positioning System: Theory and Applications Vol. I, chapter 7
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 16
OVERVIEW
• The World of GNSS

International GNSS Trends

Compatibility and Interoperability

New Signals and Frequency Bands

The More Satellites The Better…?
• The Evolution of SBAS
• Conclusions
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 17
OVERVIEW
• The World of GNSS
• The Evolution of SBAS

International SBAS Developments

EGNOS and SBAS Evolution

Arctic and Antarctic Coverage

Integrity
• Conclusions
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 18
Overview existing SBAS
–
EGNOS v2.3 being certified for
APV-I, 2 GEO*, 38 RIMS, 4 MCC, 4
NLES.
–
WAAS operational LPV (250 ft),
2 GEO**, 38 RIMS, 2 MCC, 4 NLES.
–
MSAS operational RNAV,
2 GEO, 4 RIMS, 2 MCC, 4 NLES.
–
Combined GEO footprints cover
most of world land areas.
–
SBAS looking ahead to LPV-200.
SBAS Systems LPV-200 coverage analysis
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 19
* One GEO used for test purpose.
** Recent GEO failure CRW, planned to be replaced
soon.
International SBAS developments
–
WAAS delivers full LPV-200 service in 2013 by enhancing the
current system.
–
WAAS will deliver a dual frequency L1/L5 service by 2018;
first upgrades ongoing.
–
FAA studies ARAIM dual frequency & constellation for the
2025-2030 timeframe.
–
MSAS faces obsolesce issues now, but plans to deliver LPV200 in 2014.
–
GAGAN to be operational in 2012. Failed GEO launch in 2010
delayed the introduction.
–
Russia develops SDCM with 3 Luch GEO satellites (2011-13).
High precision services will be included.
–
China develops MASS system; transmission by GEO and/or
Compass. Augments GPS, Compass and Galileo. High precision
services will be included.
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 20
Upgrade Ground Segment to GPS/Galileo
improves current EGNOS L1 service
APV-I Coverage Performance for EGNOS GPS L1 users
Current Performance
Future Performance: GPS+Galileo G/S
70
60
60
50
50
> 99.9%
> 99.5%
> 99.5%
> 99%
Latitude (deg)
Latitude (deg)
> 95%
40
> 90%
40
> 85%
30
30
20
20
> 75%
> 50%
Availability for HAL:40 VAL:50
MinDOC:3 MinIPP:2 PullInRadIPP:400km
70
> 99.9%
> 99%
> 95%
> 90%
> 85%
> 75%
> 50%
< 50%
-40
-30
-20
-10
0
10
Longitude (deg)
20
30
40
50
10
-40
ESA
UNCLASSIFIED
– For
CSNC
2011 | Guenter
W.Official
Hein | Use
Shanghai, China | 18/05/2011 | Slide 21
-30
< 50%
-20
-10
0
10
Longitude (deg)
20
30
40
50
Availability for HAL:40 VAL:50
MinDOC:3 MinIPP:2 PullInRadIPP:400km
80
80
LPV-200 L1/L5 GPS Only
L1/L5 Service / 24GPS Satellites / GEOs set to monitored / RIMS Elevation Mask 15deg / MT28 Implemented
Timestep 300s / Duration 1 day / Gridsize 2.5x2.5deg
90
> 99.9%
> 99.5%
> 99%
30
Latitude (deg)
> 95%
0
> 90%
> 85%
-30
> 75%
-60
> 50%
< 50%
-90
-180
-120
-60
0
Longitude (deg)
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 22
60
120
180
Availability for HAL:40m VAL:35m
MinDOC:5 MinIPP:3 PullInRadIPP:500km
60
LPV-200 L1/L5 GPS+ Galileo Complete Coverage of Africa
L1/L5 Service / 24GPS+27GAL Satellites / GEOs set to monitored / RIMS Elevation Mask 15deg / MT28 Implemented
Timestep 300s / Duration 1 day / Gridsize 2.5x2.5deg
90
> 99.9%
> 99.5%
> 99%
30
Latitude (deg)
> 95%
0
> 90%
> 85%
-30
> 75%
-60
> 50%
< 50%
-90
-180
-120
-60
0
Longitude (deg)
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 23
60
120
180
Availability for HAL:40m VAL:35m
MinDOC:5 MinIPP:5 PullInRadIPP:500km
60
LPV-200 L1/L5 GPS+Galileo Multi-Regional
L1/L5 Service / 24 GPS + 27 GAL Satellites / GEOs set to monitored / RIMS Elevation Mask 15deg / MT28 Implemented
Timestep 300s / Duration 1 Day / Grid 2.5 x 2.5 deg
90
> 99.9%
> 99.5%
> 99%
30
Latitude (deg)
> 95%
0
> 90%
> 85%
-30
> 75%
-60
> 50%
< 50%
-90
-180
-120
-60
0
Longitude (deg)
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 24
60
120
180
Availability for HAL:40m VAL:35m
MinDOC:5
60
CAT-I L1/L5 GPS + GAL
L1/L5 Service / 24GPS+27GAL Satellites / GEOs set to monitored / RIMS Elevation Mask 15deg / MT28 Implemented
Timestep 300s / Duration 1 day / Gridsize 2.5x2.5deg
90
> 99.9%
> 99.5%
> 99%
30
Latitude (deg)
> 95%
0
> 90%
> 85%
-30
> 75%
-60
> 50%
< 50%
-90
-180
-120
-60
0
Longitude (deg)
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 25
60
120
180
Availability for HAL:40m VAL:10m
MinDOC:5 MinIPP:5 PullInRadIPP:500km
60
ARCTIC COVERAGE STUDIED BY ESA
With only a few more RIMS in polar
region LPV-200 service could be
provided, but region outside of GEO
coverage. Alternative orbits needed:
EGNOS /PCW LPV-200 L1/L5 Availability
–
Polar Communication & Weather
(PCW) HEO Molniya type satellite(s)
–
Alternative orbits like IGSO are also
an option. Artemis could be test
candidate.
with +10 RIMS in Arctic
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 26
INTEGRITY – From where? For whom?
GNSS ?
SBAS ?
RAIM ?
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 27
OVERVIEW
• The World of GNSS
• The Evolution of SBAS
• Conclusions
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 28
CONCLUSIONS
1
• After 2020: More than 40 MEO navigation
satellites in view
 Higher accuracy and availability (urban areas),
redundancy allows more sophisticated methods
 If signals RF compatible and interoperable
 The more the better … right or wrong, questionable ?
 Increase of noise floor
 Conventional receivers and vector processing
• Integrity: Global versus SBAS versus User Level
 Multi-frequency/system regional SBAS can cover almost
whole world and ARAIM may be a new concept
 Just sophisticated RAIM for non-aviation integrity?
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 29
CONCLUSIONS
2
• Radio Frequency spectrum is full
 Intentional versus unintentional interference
 Degradation of navigation performance
 Security aspects for protected signals

No spectral overlap
• New frequency bands, S-band, C-band ?
• RF Interference might be the biggest GNSS
problem in future
CSNC 2011 | Guenter W. Hein | Shanghai, China | 18/05/2011 | Slide 30