Quasi-Zenith Satellite System L1-SAIF Augmentation Signal

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

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QZSS Concept

• 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.

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Space Segment QZS-1
Mass 4,020kg (wet) 1,802kg (dry) (NAV Payload320kg)
Power Approx. 5.3 kW (EOL) (NAV Payload Approx. 1.9kW)
Design Life 10 years
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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
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L1-SAIF 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
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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.

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L1-SAIF Performance
GPS Only Result
6 reference stations
User location for this test
L1-SAIF expe- rimental area

• Example of user position error at Site 940058
  (Takayama)
• Realtime operation with MSAS-like 6 reference
  stations in Japan
• Period 19-23 Jan. 2008 (5 days).

Note Results shown here were obtained with
geodetic-grade antenna and receivers at open sky
condition.
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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. 2010 to March 2011.
• Experiment setup
• Reference GPSIMU sensor
• Post-processing with GEONET stations (20- 30 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.

GPSIMU
GPS/L1-SAIF Rx
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On the Freeway
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.

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Freeway GPS No Augmentation
Chuo Freeway GPS without Augmentation
Horizontal Position Error, m
1.2m
UTC Time 12208 to 13708
15min
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Freeway L1-SAIF Augmented
Chuo Freeway L1-SAIF Augmentation
Horizontal Position Error, m
0.5m
UTC Time 12208 to 13708
15min
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In Tsukuba City
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.

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Tsukuba GPS No Augmentation
Tsukuba GPS without Augmentation
Horizontal Position Error, m
2.0m
UTC Time 53001 to 54501
15min
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Tsukuba L1-SAIF Augmented
Tsukuba L1-SAIF Augmentation
Horizontal Position Error, m
0.6m
UTC Time 53001 to 54501
15min
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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 http//www.enri.go.jp
  /sat/qzss_e.htm