0. Quasi-Zenith Satellite System L1-SAIF Augmentation Signal
Munich SatNav Summit
Munich, Germany
March 25-27, 2014
Quasi-Zenith Satellite System
L1-SAIF Augmentation Signal
Takeyasu Sakai
Electronic Navigation Research Institute, Japan

1. Introduction QZSS (Quasi-Zenith Satellite System) program:
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Introduction
QZSS (Quasi-Zenith Satellite System) program:
Regional navigation service broadcast from high-elevation angle by three or more satellites on the inclined geosynchronous (quasi-zenith) orbit and GEO;
Broadcast GPS-like supplemental signals on three frequencies and two augmentation signals, L1-SAIF and LEX;
The first QZS satellite successfully launched on Sept. 11, 2010.
L1-SAIF (Submeter-class Augmentation with Integrity Function) signal offers:
Sub-meter accuracy wide-area differential correction service;
Integrity function for safety of mobile users; and
Ranging function for position availability; all on L1 single frequency.
ENRI has developed L1-SAIF signal and experimental facility:
Signal design: SBAS-like signal and message on L1 frequency;
Implemented L1-SAIF Master Station (L1SMS) which generates augmentation message stream in realtime and transmits it to the QZSS MCS;
Conducted experiments of L1-SAIF successfully.

2. QZSS Concept Broadcast signal from high elevation angle;
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QZSS Concept
QZS
GPS/GEO
Broadcast signal from high elevation angle;
Applicable to navigation services for mountain area and urban canyon;
Augmentation signal from the zenith could help users to acquire other GPS satellites at any time.
Footprint of QZSS orbit;
Centered at 135E;
Eccentricity 0.075, Inclination 43deg.

3. Space Segment: QZS-1 L1-SAIF Antenna 25.3m
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Space Segment: QZS-1
L-band Helical Array Antenna
L1-SAIF Antenna
Laser Reflector
C-band TTC Antenna
Radiation Cooled TWT
TWSTFT Antenna
25.3m
Successfully launched on Sept. 11, 2010 and settled on Quasi-Zenith Orbit (IGSO).
Nickname: “Michibiki”
Mass
4,020kg (wet) 1,802kg (dry)
(NAV Payload：320kg)
Power
Approx. 5.3 kW (EOL)
(NAV Payload: Approx. 1.9kW)
Design Life
10 years

4. Broadcast Ranging Signals
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Broadcast Ranging Signals
Supplemental
Signals
Supplemental Signals by JAXA
GPS-like L1C/A, L2C, L5, and L1C signals (PRN 193) working with GPS;
Improves availability of navigation;
Minimum modifications from GPS signals.
QZS satellites
L1-SAIF by ENRI
SBAS-like C/A code (PRN 183) signal on L1 freq.; Reasonable performance for mobile users;
Augmentation to GPS; Potentially plus GLONASS and Galileo.
LEX by JAXA
For carrier-based experimental purposes;
Original CPSK signal on E6 frequency;
Member organizations may use LEX as 2kbps experimental data channel.
Augmentation
Signals

5. SAIF： Submeter-class Augmentation with Integrity Function
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L1-SAIF Signal
Ranging
Function
Error
Correction
Integrity
QZS satellites
GPS Constellation
Ranging Signal
L1-SAIF Signal
SBAS-like augmentation signal; Differences are PRN code (183 for L1-SAIF) and Doppler only;
Three functions by a single signal: ranging, error correction (Target accuracy: 1m), and integrity;
User receivers can receive both GPS and L1-SAIF signals with a single antenna and RF front-end;
See IS-QZSS for detail (Available at JAXA HP).
User GPS
Receivers
SAIF： Submeter-class Augmentation with Integrity Function

6. ENRI L1-SAIF Master Station
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ENRI L1-SAIF Master Station
L1-SAIF Master Station (L1SMS):
Generates L1-SAIF message stream in realtime and transmits it to QZSS MCS developed by and installed at JAXA;
Installed at ENRI, Tokyo; 90km from JAXA Tsukuba Space Center;
Dual frequency GPS measurements at some locations in Japan necessary to generate L1-SAIF messages are sent from GEONET in realtime.
L1SMS
GEONET
QZS
QZSS MCS
GNSS
Satellites
Measure-
ments
L1-SAIF
Message
GSI Server
(Tokyo)
ENRI
JAXA TKSC
(Tsukuba)
L1-SAIF Signal
Ranging Signal
K-band Uplink

7. L1-SAIF Performance GPS Only Result Horizontal Error Vertical 1.45 m
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L1-SAIF Performance
Standalone GPS
L1-SAIF Augmentation
GPS Only Result
6 reference
stations
User location for this test
L1-SAIF expe- rimental area
Horizontal
Error
Vertical
1.45 m
2.92 m
6.02 m
8.45 m
System
Standalone
GPS
0.29 m
0.39 m
1.56 m
2.57 m
w/ L1-SAIF
RMS
Max
Example of user position error at Site (Takayama);
Realtime operation with MSAS-like 6 reference stations in Japan;
Period: Jan (5 days).
Note: Results shown here were obtained with geodetic-grade antenna and receivers at open sky condition.

8. Experiment by Car L1-SAIF experiment: Experiment setup: GPS+IMU
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Experiment by Car
L1-SAIF experiment:
L1-SAIF is originally planned as an augmentation to mobile users with a certain velocity;
Experiment with a car;
Location: urban/suburban environment, freeway;
Experiment period: Dec to March 2011.
Experiment setup:
Reference: GPS+IMU sensor;
Post-processing with GEONET stations ( km separation) for accurate reference;
GPS/L1-SAIF receiver and PC in cabin;
Receives L1-SAIF signal on PRN 183;
Applies L1-SAIF corrections in realtime and outputs position fix.
GPS+IMU
GPS/L1-SAIF Rx

9. On the Freeway Plan View of the Route Typical Situation
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On the Freeway
2 km
GEONET
Nakamichi
Ichinomiya
Plan View of the Route
Typical Situation
On Dec. 14, 2010; QZS near the Zenith;
About 10 km drive at the Kofu Basin on Chuo Freeway going westward from Tokyo;
Plain ground with less bridges across the Freeway.

10. Freeway: GPS No Augmentation
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Freeway: GPS No Augmentation
Chuo Freeway: GPS without Augmentation
Horizontal Position Error, m
1.2m
UTC Time 1:22:08 to 1:37:08
15min

11. Freeway: L1-SAIF Augmented
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Freeway: L1-SAIF Augmented
Chuo Freeway: L1-SAIF Augmentation
Horizontal Position Error, m
0.5m
UTC Time 1:22:08 to 1:37:08
15min

12. In Tsukuba City Plan View of the Route Typical Situation
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In Tsukuba City
1 km
GEONET
Tsukuba 1
Plan View of the Route
Typical Situation
On Dec. 16, 2010; QZS near the Zenith;
About 6 km drive in West part of Tsukuba City in Ibaraki Pref.;
Road on the ground level with less tall buildings around.

13. Tsukuba: GPS No Augmentation
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Tsukuba: GPS No Augmentation
Tsukuba: GPS without Augmentation
Horizontal Position Error, m
2.0m
UTC Time 5:30:01 to 5:45:01
15min

14. Tsukuba: L1-SAIF Augmented
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Tsukuba: L1-SAIF Augmented
Tsukuba: L1-SAIF Augmentation
Horizontal Position Error, m
0.6m
UTC Time 5:30:01 to 5:45:01
15min

15. Conclusion ENRI has developed QZSS L1-SAIF signal:
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Conclusion
ENRI has developed QZSS L1-SAIF signal:
Signal design: SBAS-like C/A code signal (PRN 183) on L1 frequency;
Planned as an augmentation to mobile users;
Implemented L1-SAIF Master Station (L1SMS) which generates augmentation message stream in realtime and transmit it to QZSS MCS.
QZSS satellite “Michibiki”:
The first satellite for QZSS, “Michibiki”, was successfully launched in 2010;
Continuously broadcasting navigation signals just as planned.
L1-SAIF Experiments:
ENRI has conducted L1-SAIF experiments successfully and confirmed submeter-class accuracy as originally planned;
Currently investigations are in progress on usage of Multi-GNSS with GLONASS, dual frequency augmentation, and application in short message service;
Information is available at: