ION ITM 2011
San Diego, CA
Jan. 24-26, 2011
QZSS L1-SAIF
Initial Experiment Results
T. Sakai, S. Fukushima, and K. Ito
Electronic Navigation Research Institute, Japan
ION ITM 24-26 Jan. 2011 - ENRI
Introduction
SLIDE 1
• QZSS (Quasi-Zenith Satellite System) program:
– Regional navigation service broadcast from high-elevation angle by three
satellites on the inclined geosynchronous (quasi-zenith) orbit;
– Broadcast GPS-compatible 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 been developing L1-SAIF signal and experimental facility:
– Signal design: SBAS-compatible on L1;
– Implemented L1-SAIF Master Station (L1SMS) which generates augmentation
message stream in realtime and transmits it to QZSS MCS;
– Now conducting experiments on L1-SAIF.
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 2
Part 1
Overview of QZSS Program
ION ITM 24-26 Jan. 2011 - ENRI
Launch of QZS-1 “Michibiki”
SLIDE 3
Sept. 11, ２０１０ 20:17JST
Launch of QZS-1 “Michibiki”
• Launched by H-IIA-18 from
Tanegashima Space Center of JAXA;
• “Michibiki” was separated successfully
28:27 after launch.
Michibiki
looked from the
second stage
(c) MHI
(c) JAXA/MHI
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 4
QZSS Concept
GPS/GEO
• Footprint of QZS orbit;
• Centered 137E;
• Eccentricity 0.1, Inclination 45deg.
QZS
• 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 all
the time.
ION ITM 24-26 Jan. 2011 - ENRI
QZSS Program
SLIDE 5
• QZSS (Quasi-Zenith Satellite System) program:
– Japan has been developing QZSS since FY 2003;
– Regional navigation service broadcast from high-elevation angle by combination
of three satellites on the inclined geosynchronous (quasi-zenith) orbit;
– Broadcast GPS-compatible supplemental signals on three frequencies (L1 C/A,
L1C, L2C, and L5) and two augmentation signals, L1-SAIF and LEX.
• Participating institutes:
– JAXA (Japan Aerospace Exploration Agency): Development and operation of the
space segment and Master Control Station;
– NICT (National Institute of Information and Communication Technology): Frequency
standard and time keeping system including Uplink Station;
– AIST (National Institute of Advanced Industrial Science and Technology): Time synchronization between space and ground;
– GSI (Geographical Survey Institute): Survey-grade carrier-based positioning service;
– ENRI (Electronic Navigation Research Institute): Navigation-grade WADGPS service
broadcast by L1-SAIF signal.
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 6
Overall Architecture
Navigation Signals
L1: 1575.42 MHz
L2: 1227.60 MHz
L5: 1176.45 MHz
LEX: 1278.75 MHz
QZS Satellite
GPS
Satellites
TWSTFT
Up:
4.43453GHz
Down: 12.30669GHz
Satellite
Laser Ranging
TT&C / NAV
Message Uplink
SLR Site
Monitor Station NW
Time Mgmt
Station
TT&C / NAV Msg
Uplink Station
User Receiver
Master Control
Station (MCS)
GEONET
(GSI)
Function distributed in each institute
Timing management by NICT,
WADGPS service by ENRI, etc.
TWSTFT: Two Way Satellite Time and Frequency Transfer
(Courtesy: JAXA QZSS PT)
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 7
Space Segment: QZS-1
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
Radiation Cooled TWT
TWSTFT Antenna
C-band TTC Antenna
Laser Reflector
L1-SAIF Antenna
L-band Helical Array
Antenna
ION ITM 24-26 Jan. 2011 - ENRI
QZSS Signals
SLIDE 8
• Supplemental signals:
– GPS-compatible L1C/A, L2C, L5, and L1C signals working with GPS;
improving availability of navigation;
– With minimum modifications from GPS signal specifications;
– Coordination with GPS Wing on broadcasting L1C signal;
– JAXA is responsible for all supplemental signals.
• Augmentation signals:
– Augmentation to GPS; Possibly plus Galileo;
– L1-SAIF: Compatible with SBAS; reasonable performance for mobile users;
– LEX: For carrier-based experimental purposes; member organizations may
use as 2kbps experimental data channel;
– ENRI is working for L1-SAIF while JAXA is developing LEX.
• Interface Specification: IS-QZSS available on JAXA HP
– Specifies RF signal interface between QZS satellite and user receiver;
– First issue: Jan. 2007; Maintained by JAXA.
ION ITM 24-26 Jan. 2011 - ENRI
QZSS Frequency Plan
Signal
Channel
Frequency
SLIDE 9
Bandwidth
Min. Rx Power
L1CD
24 MHz
–163.0 dBW
L1CP
24 MHz
– 158.25 dBW
QZS-L1-C/A
24 MHz
– 158.5 dBW
QZS-L1-SAIF
24 MHz
– 161.0 dBW
24 MHz
– 160.0 dBW
25 MHz
– 157.9 dBW
25 MHz
– 157.9 dBW
42 MHz
– 155.7 dBW
QZS-L1C
1575.42 MHz
QZS-L2C
1227.6 MHz
L5I
QZS-L5
1176.45 MHz
L5Q
QZS-LEX
1278.75 MHz
Find detail in IS-QZSS document.
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 10
Part 2
L1-SAIF Signal Design
ION ITM 24-26 Jan. 2011 - ENRI
QZSS L1-SAIF Signal
SLIDE 11
• QZSS will broadcast wide-area augmentation signal:
– Called L1-SAIF (Submeter-class Augmentation with Integrity Function);
– Developed by ENRI.
• L1-SAIF signal offers:
– Wide-area differential correction service for improving position accuracy; Target
accuracy: 1 meter for horizontal;
– Integrity function for safety of mobile users; and
– Ranging function for position availability.
• Interoperable with GPS L1C/A and fully compatible with SBAS:
– Broadcast on L1 freq. with RHCP; Common antenna and RF front-end;
– Modulated by BPSK with C/A code;
– 250 bps data rate with 1/2 FEC; message structure is identical with SBAS;
– Differences: Large Doppler and additional messages;
– Specification of L1-SAIF: IS-QZSS document.
ION ITM 24-26 Jan. 2011 - ENRI
L1-SAIF Signal
QZS satellite
SLIDE 12
Ranging
Function
GPS Constellation
Error
Correction
Integrity
Function
• Three functions by a single signal: ranging, error
correction (Target accuracy: 1m), and integrity;
• User receivers can receive both GPS and L1-SAIF
signals by a single antenna;
• Message-oriented information transmission: flexible
contents.
SAIF： Submeter-class Augmentation with Integrity Function
Ranging Signal
User GPS
Receivers
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 13
WADGPS Concept
Clock Correction
Ionospheric Correction
• Function of user location;
• Up to 100 meters;
• Vertical structure may be
described as a thin shell.
Ionosphere
• Same contribution to any user
location;
• Not a function of location;
• Needs fast correction.
Orbit Correction
• Different contribution to different
user location;
• Not a function of user location; but
a function of line-of-sight direction;
• Long-term correction.
Tropospheric Correction
Troposphere
• Function of user location, especially height of user;
• Up to 20 meters;
• Can be corrected enough by a fixed model.
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 14
SBAS/L1-SAIF Message Structure
Preamble
8 bits
Message Type
6 bits
Data Field
212 bits
250 bits per second
Transmitted First
MT
CRC parity
24 bits
Contents
Interval
[s]
MT
Contents
Interval
[s]
0
Test mode
6
17
GEO almanac
300
1
PRN mask
120
18
IGP mask
300
Fast correction & UDRE
60
24
FC & LTC
6
6
UDRE
6
25
Long-term correction
7
Degradation factor for FC
120
26
Ionospheric delay & GIVE 300
9
GEO ephemeris
120
27
SBAS service message
300
10
Degradation parameter
120
28
Clock-ephemeris covariance
120
12
SBAS time information
300
63
Null message
2～5
120
—
Note: Some additional messages are also defined for L1-SAIF. See IS-QZSS.
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 15
GPS/L1-SAIF Simulator
• GPS/L1-SAIF Simulator:
– Simulates GPS L1 C/A and QZSS L1-SAIF signals;
– Generates RF signals based on pre-defined GPS and QZSS constellation
scenario and signal specifications
of IS-GPS and IS-QZSS;
– Manufactured by Spirent, modifying
GPS/SBAS simulator GSS7700.
• Special function for experiment:
– Added extra command to input
L1-SAIF message from Ethernet
port (TCP/IP);
– L1-SAIF message is either input
by the command externally or
generated by the simulator internally.
GPS/L1-SAIF
Simulator
GPS/L1-SAIF
Receiver
ION ITM 24-26 Jan. 2011 - ENRI
GPS/L1-SAIF Receiver
SLIDE 16
• Prototype GPS/L1-SAIF Receiver:
– Receives GPS L1 C/A and QZSS L1-SAIF signals;
– Decode and apply L1-SAIF message as defined by IS-QZSS;
– Manufactured by Furuno Electric.
• Special function for experiment:
– L1-SAIF message can be input from
Ethernet port (TCP/IP) as well as
L1-SAIF signal on RF;
– Enable to process L1-SAIF and SBAS,
totally three, augmentation signals
simultaneously;
– Portable equipage for experiment
at remote or on mobile.
GPS/L1-SAIF
Receiver
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 17
RF Compatibility Test
ENRI (Chofu, Tokyo)
Spirent
Scenario
File
GPS/L1-SAIF
Simulator
L1-SAIF Signal
RF Cable
Furuno Electric
GPS/L1-SAIF
Receiver
TCP/IP
L1-SAIF Message
Decoded Message
Compare
• Ranging function: The receiver output the proper position solution with pseudorange of
L1-SAIF signal generated by the simulator;
• Decoding message: The receiver decoded L1-SAIF message which matched with the
message input to the simulator via Ethernet port; The command needs to be given 2second before the applicable time of transmission;
• Successfully completed in Feb. 2009.
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 18
RF Compatibility Test
2008/9/10 00:05:00 to 06:00:00 (6 hours)
Standalone GPS
L1-SAIF Augmentation
OK!
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 19
Part 3
L1-SAIF Master Station (L1SMS)
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 20
ENRI L1SMS
• 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;
– Subsystems: GEONET Server, Primary Receiver, Interface Processor, Message
Generator, Ionosphere Processor, Troposphere Processor, and Batch Processor.
QZS
GPS
Closed
Loop
Measured
Data
L1-SAIF
Message
GEONET
L1SMS
QZSS MCS
GSI
ENRI
JAXA
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 21
L1SMS Installed at ENRI
I/F
Message
Generator
Ionosphere
Processor
Storage
Storage
Router to
GEONET
GEONET
Server
Storage
UPS
UPS
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 22
Configuration of L1SMS
GEONET
TCP/IP
Observation
File (RINEX)
via FTP
Batch Processor
(IFB Estimation)
Dual Freq. ANT
GEONET Server
Primary Receiver
Message
Output
via TCP/IP
Interface Processor
IFB
Estimates
L1SMS Batch Subsystem
Message Generator
(L1SMG)
Ionosphere Processor
Troposphere Processor
L1SMS Realtime Subsystems
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 23
Position Error Sample
Standalone GPS
L1-SAIF Augmentation
• Example of user position error at Site
940058 (Takayama; near center of
monitor station network);
• Realtime operation with MSAS-like 6
monitor stations;
• Period: 19-23 Jan. 2008 (5 days).
Horizontal
Error
Vertical
Error
Standalone RMS
GPS
Max
1.45 m
2.92 m
6.02 m
8.45 m
RMS
0.29 m
0.39 m
Max
1.56 m
2.57 m
System
L1-SAIF
Note: Results shown here were obtained with geodeticgrade antenna and receivers at open sky condition.
ION ITM 24-26 Jan. 2011 - ENRI
Realtime Operation using GEO
SLIDE 24
GPS
Satellites
ETS-VIII Satellite
L1-SAIF L1SMS
in Tokyo
350 km Separation
GPS/L1-SAIF Rx
in Sendai Airport
• ENRI joined communication experiment of ETS-VIII geostationary satellite;
• L1SMS transmitted L1-SAIF message to ETS-VIII; Received L1-SAIF message was
input to the GPS/L1-SAIF receiver and processed in realtime; No ranging function;
• Successfully completed in Feb. 2009.
ION ITM 24-26 Jan. 2011 - ENRI
L1-SAIF Receiver Output
SLIDE 25
2009/2/17 01:21:39 to 07:23:14 (6 hours)
Standalone GPS
L1-SAIF Augmentation
H Error RMS = 1.221m
V Error RMS = 4.043m
H Error RMS = 0.412m
V Error RMS = 0.464m
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 26
Part 4
Experiment with QZS-1 “Michibiki”
ION ITM 24-26 Jan. 2011 - ENRI
Reception of Test Signal
SLIDE 27
• Firstly received L1-SAIF test signal broadcast from QZS on orbit;
• By L1-SAIF prototype receiver on Oct. 23, 2010 09:46:48-10:48:07GPST at a
branch of ENRI in Sendai Airport, Located at the Northern part of Japan;
• Raw pseudorange: receiver clock variation is dominant and there are jumps due to
clock adjustment.
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 28
Experiment by Car
GPS+IMU
• 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: GPS+IMU sensor;
– Post-processing with GEONET stations (2030 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/L1-SAIF Rx
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 29
On the Freeway
GEONET
Ichinomiya
GEONET
Nakamichi
Plan View of the Route
2 km
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.
Position Error, m
Horizontal水平測位誤差（m）
0
15min
時刻（UTC）
UTC Time 1:22:08 to 1:37:08
1:36:08 AM
1:35:08 AM
1:34:08 AM
1:33:08 AM
1:32:08 AM
1:31:08 AM
1:30:08 AM
1:29:08 AM
1:28:08 AM
1:27:08 AM
1:26:08 AM
1:25:08 AM
1:24:08 AM
1:23:08 AM
1:22:08 AM
ION ITM 24-26 Jan. 2011 - ENRI
Freeway: L1-SAIF Augmented
SLIDE 30
Chuo Freeway:
L1-SAIF Augmentation
L1-SAIF測位精度（中央道）
5
4
3
2
1
0.5m
Position Error, m
Horizontal 水平測位誤差（m）
0
15min
時刻（UTC）
UTC Time 1:22:08 to 1:37:08
1:36:08 AM
1:35:08 AM
1:34:08 AM
1:33:08 AM
1:32:08 AM
1:31:08 AM
1:30:08 AM
1:29:08 AM
1:28:08 AM
1:27:08 AM
1:26:08 AM
1:25:08 AM
1:24:08 AM
1:23:08 AM
1:22:08 AM
ION ITM 24-26 Jan. 2011 - ENRI
Freeway: GPS No Augmentation
SLIDE 31
Chuo Freeway:
GPS without Augmentation
GPS測位精度（中央道）
5
4
3
2
1
1.2m
ION ITM 24-26 Jan. 2011 - ENRI
SLIDE 32
In Tsukuba City
GEONET
Tsukuba 1
1 km
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.
Error, m
Position
Horizontal水平測位誤差
（ｍ）
0
15min
時刻（UTC）
UTC Time 5:30:01
to 5:45:01
5:44:01 AM
5:43:01 AM
5:42:01 AM
5:41:01 AM
5:40:01 AM
5:39:01 AM
5:38:01 AM
5:37:01 AM
5:36:01 AM
5:35:01 AM
5:34:01 AM
5:33:01 AM
5:32:01 AM
5:31:01 AM
5:30:01 AM
ION ITM 24-26 Jan. 2011 - ENRI
Tsukuba: L1-SAIF Augmented
SLIDE 33
Tsukuba:
L1-SAIF Augmentation
L1-SAIF測位精度（つくば2）
5
4
3
2
1
0.6m
Error, m
Position
Horizontal水平測位誤差
（ｍ）
0
15min
時刻（UTC）
UTC Time 5:30:01
to 5:45:01
5:44:01 AM
5:43:01 AM
5:42:01 AM
5:41:01 AM
5:40:01 AM
5:39:01 AM
5:38:01 AM
5:37:01 AM
5:36:01 AM
5:35:01 AM
5:34:01 AM
5:33:01 AM
5:32:01 AM
5:31:01 AM
5:30:01 AM
ION ITM 24-26 Jan. 2011 - ENRI
Tsukuba: GPS No Augmentation
SLIDE 34
Tsukuba: GPS
without Augmentation
GPS測位精度（つくば2）
5
4
3
2
2.0m
1
ION ITM 24-26 Jan. 2011 - ENRI
Conclusion
SLIDE 35
• ENRI has been developing L1-SAIF signal:
– Signal design: GPS/SBAS-compatible;
– 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;
– Successfully passed initial function tests for Bus and Mission by end Nov.;
– Currently in the nominal operation status.
• Ongoing work:
– Now L1-SAIF experiment has been conducted by ENRI;
– Preliminary results show accuracy improvement by L1-SAIF augmentation.