0. Recent Development of QZSS L1-SAIF Master Station
ION ITM 2010
San Diego, CA
Jan , 2010
Recent Development of
QZSS L1-SAIF Master Station
T. Sakai, S. Fukushima, and K. Ito
Electronic Navigation Research Institute, Japan

1. Introduction QZSS (Quasi-Zenith Satellite System) program:
ION ITM Jan ENRI
Introduction
QZSS (Quasi-Zenith Satellite System) program:
Regional navigation service broadcast from high-elevation angle by three satellites on the inclined geosynchronous (quasi-zenith) orbit;
Currently working for launch of the first satellite in 2010 Summer season;
Broadcast GPS-compatible supplemental signals on three frequencies and two augmentation signals, L1-SAIF and LEX.
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 facility:
Signal design: GPS/SBAS-compatible on L1;
Implemented L1-SAIF Master Station (L1SMS) which generates augmentation message stream in realtime and transmits it to QZSS MCS.

2. Overview of QZSS Program
ION ITM Jan ENRI
Part 1
Overview of QZSS Program

3. QZSS Concept Signal from high elevation angle
ION ITM Jan ENRI
QZSS Concept
QZS
GPS/GEO
Signal from high elevation angle
Applicable to navigation services for mountain area and urban canyon
Footprint of QZS orbit
Centered 137E
Eccentricity 0.1, Inclination 45deg

4. QZSS Program QZSS (Quasi-Zenith Satellite System) program:
ION ITM Jan ENRI
QZSS Program
QZSS (Quasi-Zenith Satellite System) program:
Japan has been developing QZSS since FY 2003;
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 (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 synch-ronization 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.

5. Overall Architecture GPS Satellites QZS Satellite User Receiver
ION ITM Jan ENRI
Overall Architecture
Function distributed in each institute
Timing management by NICT, WADGPS service by ENRI, etc.
SLR Site
Monitor Station NW
GPS Satellites
TT&C / NAV Msg Uplink Station
GEONET
(GSI)
Time Mgmt Station
TWSTFT: Two Way Satellite Time and Frequency Transfer
QZS Satellite
User Receiver
Satellite
Laser Ranging
Navigation Signals
L1: MHz
L2: MHz
L5: MHz
LEX: MHz
TT&C / NAV Message Uplink
TWSTFT
Up: GHz
Down: GHz
(Courtesy: JAXA QZSS PT)
Master Control Station (MCS)

6. Space Segment: QZS-1 25.3m L1-SAIF Antenna
ION ITM Jan ENRI
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
Mass
Approx. 1,800kg (dry)
(NAV Payload：Approx. 320kg)
Power
Approx. 5.3 kW (EOL)
(NAV Payload: Approx. 1.9kW)
Design Life
10 years

7. QZSS Signals Supplemental signals: Augmentation signals:
ION ITM Jan ENRI
QZSS Signals
Supplemental signals:
GPS-compatible L1C/A, L2C, L5, and L1C signals working with GPS; For 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:
Specifies RF signal interface between QZS satellite and user receiver;
First issue: Jan. 2007; Maintained by JAXA.

8. QZSS Frequency Plan Signal Channel Frequency Bandwidth Min. Rx Power
ION ITM Jan ENRI
QZSS Frequency Plan
Signal
Channel
Frequency
Bandwidth
Min. Rx Power
QZS-L1C
L1CD
MHz
24 MHz
–163.0 dBW
L1CP
– dBW
QZS-L1-C/A
– dBW
QZS-L1-SAIF
– dBW
QZS-L2C
MHz
– dBW
QZS-L5
L5I
MHz
25 MHz
– dBW
L5Q
QZS-LEX
MHz
42 MHz
– dBW
Find detail in IS-QZSS document.

9. ION ITM Jan ENRI
Part 2
L1-SAIF Signal Design

10. QZSS L1-SAIF Signal QZSS will broadcast wide-area augmentation signal:
ION ITM Jan ENRI
QZSS L1-SAIF Signal
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.

11. WADGPS Concept Clock Correction Ionospheric Correction
ION ITM Jan ENRI
WADGPS Concept
Orbit Correction
Troposphere
Ionosphere
Ionospheric Correction
Tropospheric Correction
Clock Correction
Same contribution to any user location;
Not a function of location;
Needs fast correction.
Different contribution to different user location;
Not a function of user location; but a function of line-of-sight direction;
Long-term correction.
Function of user location;
Up to 100 meters;
Vertical structure may be described as a thin shell.
Function of user location, especially height of user;
Up to 20 meters;
Can be corrected enough by a fixed model.

12. SBAS/L1-SAIF Message Structure
ION ITM Jan ENRI
SBAS/L1-SAIF Message Structure
Preamble
8 bits
Message Type
6 bits
Data Field
212 bits
CRC parity
24 bits
250 bits per second MT 1
2～5 6 7 9 10 12 17 18
Contents
Test mode
PRN mask
Fast correction & UDRE
UDRE
Degradation factor for FC
GEO ephemeris
Degradation parameter
SBAS time information
GEO almanac
IGP mask
Interval
[s]
120 60
300 24 25 26 27 28 63
FC & LTC
Long-term correction
Ionospheric delay & GIVE
SBAS service message
Clock-ephemeris covariance
Null message —
Transmitted First

13. SBAS/L1-SAIF Message (1)
ION ITM Jan ENRI
SBAS/L1-SAIF Message (1)
Message Type
Contents
Compatibility
Status
Test mode
Both
Fixed 1
PRN mask
2 to 5
Fast correction & UDRE 6
UDRE 7
Degradation factor for FC 10
Degradation parameter 18
IGP mask 24
Mixed fast/long-term correction 25
Long-term correction 26
Ionospheric delay & GIVE 9
GEO ephemeris
SBAS 17
GEO almanac 12
SBAS network time 8
Reserved

14. SBAS/L1-SAIF Message (2)
ION ITM Jan ENRI
SBAS/L1-SAIF Message (2)
Message Type
Contents
Compatibility
Status 27
SBAS service message
SBAS
Fixed
29 to 51
(Undefined) — 28
Clock-ephemeris covariance
Both 62
Reserved 63
Null message 52
TGP mask
L1-SAIF
Tentative 56
Intersignal biases 57
(Ephemeris-related parameter)
TBD 58
QZS ephemeris 59
(QZS almanac) 60
(Regional information) 61 5３
Tropospheric delay
54 to 55
(Advanced Ionospheric delay)

15. GPS/L1-SAIF Simulator GPS/L1-SAIF Simulator:
ION ITM Jan ENRI
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
Receiver

16. GPS/L1-SAIF Receiver Prototype GPS/L1-SAIF Receiver:
ION ITM Jan ENRI
GPS/L1-SAIF Receiver
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

17. RF Compatibility Test GPS/L1-SAIF Simulator Receiver TCP/IP RF Cable
ION ITM Jan ENRI
RF Compatibility Test
GPS/L1-SAIF
Simulator
Receiver
TCP/IP
RF Cable
Spirent
Furuno Electric
File
L1-SAIF Message
Scenario
Decoded Message
Compare
L1-SAIF Signal
ENRI (Chofu, Tokyo)
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 2-second before the applicable time of transmission;
Successfully completed in Feb

18. RF Compatibility Test OK! 2008/9/10 00:05:00 to 06:00:00 (6 hours)
ION ITM Jan ENRI
RF Compatibility Test
2008/9/10 00:05:00 to 06:00:00 (6 hours)
Standalone GPS
L1-SAIF Augmentation
OK!

19. L1-SAIF Master Station (L1SMS)
ION ITM Jan ENRI
Part 3
L1-SAIF Master Station (L1SMS)

20. ENRI L1SMS L1-SAIF Master Station (L1SMS): GSI ENRI JAXA
ION ITM Jan ENRI
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.
L1SMS
GEONET
QZS
QZSS MCS
GPS
Measured
Data
L1-SAIF
Message
GSI
ENRI
JAXA
L1-SAIF Signal
L1C/A, L2P
K-band
Closed
Loop

21. L1SMS Installed at ENRI Storage Router to GEONET I/F UPS Message
ION ITM Jan ENRI
L1SMS Installed at ENRI
Storage
Router to
GEONET
I/F
UPS
Message
Generator
Server
Ionosphere Processor

22. Configuration of L1SMS GEONET Server Ionosphere Processor
ION ITM Jan ENRI
Configuration of L1SMS
GEONET Server
Ionosphere Processor
Troposphere Processor
Message Generator
(L1SMG)
GEONET
Batch Processor
(IFB Estimation)
L1SMS Batch Subsystem
L1SMS Realtime Subsystems
TCP/IP
Message
Output
via TCP/IP
Observation
File (RINEX)
via FTP
IFB
Estimates
Primary Receiver
Interface Processor
Dual Freq. ANT

23. JAXA-ENRI Interface (G-ICD)
ION ITM Jan ENRI
JAXA-ENRI Interface (G-ICD)
Ground System ICD (Interface Control Document):
Defines interface between JAXA QZSS MCS and ENRI L1SMS;
First issue: Jan. 2008;
Specifies data stream on TCP/IP connection bit-by-bit.
Dual communication lines for redundancy:
ISDN (64kbps) and optical (1.5Mbps) links;
Low-rate ISDN: Reliable transmission for uploading L1-SAIF message;
High-rate optical link: Exchange station status and monitor station observation;
Only for the experiment; no definition of service levels.
L1SMS
MCS A
MCS B
Router
ISDN
Optical
Upload Message
Other Data
JAXA
ENRI

24. JAXA-ENRI Interface (G-ICD)
ION ITM Jan ENRI
JAXA-ENRI Interface (G-ICD)
Packet ID
Contents
Direction
Link
Interval
0xC0
Upload Message
L1SMS -> MCS
ISDN
1 s
0xC1
Upload Message Echo
L1SMS <- MCS
0x02
SMS Status
Optical
5 s
0xE2
GPS/QZS Observation
0xE4
GPS Observation
0xE1
Monitor Station Status
0x11
Telemetry Command
L1SMS <-> MCS
N/A
0x12
Telemetry Data
min 1 s
0x01
Experiment Status
10 s
0x21
Orbit and Clock
30 s

25. Closed-Loop Interface Test
ION ITM Jan ENRI
Closed-Loop Interface Test
HUB
LAN
Upload Message
JAXA
ENRI
Log
MCS B
Navigation
Payload EM
RF Cable
L1-SAIF Signal
L1SMS
Simulator
NEC (Fuchu, Tokyo)
GPS/L1-SAIF
Receiver
L1SMS Sim
Nav payload
Receiver
Interface test between JAXA MCS and ENRI L1SMS and between Nav payload and receiver;
Checked the format of transmitted and received data packets, then compared log files bit-by-bit;
Successfully completed in Dec

26. JAXA-ENRI Interface Test
ION ITM Jan ENRI
JAXA-ENRI Interface Test
L1SMS
Simulator
Router
ISDN
Optical
Upload Message
Other Data
JAXA
ENRI
Log
MCS A
MCS B
ENRI (Chofu, Tokyo)
JAXA (Tsukuba)
Interface test between two facilities, JAXA MCS and ENRI L1SMS, with the complete configuration of communication lines;
Confirmed the format of transmitted and received data packets, then compared log files taken at both facilities bit-by-bit;
Successfully completed in Jan

27. Realtime Operation Test
ION ITM Jan ENRI
Part 4
Realtime Operation Test

28. Realtime Operation Test
ION ITM Jan ENRI
Realtime Operation Test
GMS Stations (6) for L1SMG
L1-SAIF Experimental Area
IMS Station (200) for ICP
Evaluation Locations (14)
Tested performance of the ICP Implemented as a subsystem of L1SMS; running with L1SMG;
Analyzed user position error at 14 evaluation locations; Numbered from North to South;
Used GEONET stations as all monitor stations and evaluation sites.

29. Results – Position Error Sample
ION ITM Jan ENRI
Results – Position Error Sample
MSAS Augmentation
Standalone GPS
L1-SAIF Augmentation
Example of user positioning error at Site # Choshi (East of Tokyo);
ICP: 200 IMS, 5-deg IGP, 0th Order Fit;
Period: Jan (5 days).
System
HorizontalError
Vertical Error
L1-SAIF
RMS
0.23 m
0.36 m
MAX
1.67 m
3.35 m
MSAS
0.46 m
0.59 m
1.73 m
2.43 m
Standalone GPS
1.25 m
2.99 m
4.30 m
8.11 m

30. Location vs. Horizontal Accuracy
ION ITM Jan ENRI
Location vs. Horizontal Accuracy
ICP improves position accuracy in the Southern Region;
First order estimation is better to ensure accuracy.

31. Location vs. Vertical Accuracy
ION ITM Jan ENRI
Location vs. Vertical Accuracy
1 meter accuracy is achievable even for vertical direction;
Note that these results associate with solar minimum phase.

32. Realtime Operation Using GEO
ION ITM Jan ENRI
Realtime Operation Using GEO
ETS-VIII satellite:
Engineering Test Satellite for mobile communication and onboard clock of navigation-grade;
Geostationary satellite with very large
(19m) folding antenna;
Launched in Dec by JAXA.
ENRI joined the experiment:
Communication experiment between
two fixed points;
L1SMG transmitted L1-SAIF message
to ETS-VIII;
Received L1-SAIF message was input
to the GPS/L1-SAIF receiver and
processed properly;
Successfully completed in Feb
ETS-VIII Satellite

33. Uplink from Tokyo ETS-VIII Satellite Ethernet L1-SAIF message
ION ITM Jan ENRI
Uplink from Tokyo
ETS-VIII Satellite
Ethernet
L1-SAIF message
L1-SAIF Master Station
RF signal
ETS-VIII Terminal Equipment
SATCOM Antenna

34. Downlink to Sendai GPS signal L1-SAIF message ETS-VIII Satellite
ION ITM Jan ENRI
Downlink to Sendai
GPS signal
L1-SAIF message
ETS-VIII Satellite
RF signal
Ethernet
GPS/L1-SAIF
Receiver
SATCOM Antenna
(400km away from Tokyo)
ETS-VIII Terminal Equipment

35. L1-SAIF Receiver Output
ION ITM Jan ENRI
L1-SAIF Receiver Output
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

36. Resulted User Position Accuracy at Some Locations [unit: m]
ION ITM Jan ENRI
Stability Test
Runs L1SMG for several months:
To investigate stability of the software implemented in L1SMG;
Period I: 2008/3/11 to 2008/5/24 (74 days);
Period II: 2008/6/10 to 2008/8/28 (79 days).
Result: No major trouble:
The software runs for the periods without human interaction;
User position accuracy was reasonable.
Resulted User Position Accuracy at Some Locations [unit: m]
Site
940030
Oga
93101
Omaezaki
940058
Takayama
940085
Tosashimizu
950491
Sata
Period I
Hor
0.362
0.363
0.423
0.502
Ver
0.517
0.536
0.548
0.608
0.739
Period II
0.460
0.440
0.347
0.416
0.552
0.657
1.236
0.678
0.699
1.371

37. Conclusion ENRI has been developing L1-SAIF signal: Completed, so far:
ION ITM Jan ENRI
Conclusion
ENRI has been developing L1-SAIF signal:
Signal design: GPS/SBAS-compatible;
Implemented L1-SAIF Master Station (L1SMS) which generates augmentation message stream in realtime and transmit it to QZSS MCS.
Completed, so far:
Design of L1-SAIF signal and publishing as a part of IS-QZSS;
Development of GPS/L1-SAIF simulator and receiver;
Development of G-ICD between L1SMS and QZSS MCS, and interface test of them;
Interface test at the closed-loop configuration including L1SMS, MCS, QZSS navigation payload, and GPS/L1-SAIF receiver;
Realtime operation test with/without geostationary satellite (ETS-VIII); and
Stability test of L1SMS.
Currently working for:
Final interface test at the full-configuration of ground/space systems;
Preparation of performance experiment with the first QZS space vehicle.