ION GNSS 2012 Nashville, TN Sept. 17-21, 2012

ION GNSS 2012ION GNSS 2012Nashville, TNNashville, TN

Sept. 17-21, 2012Sept. 17-21, 2012

The L1-SAIF SignalHow was it designed to be used?

The L1-SAIF SignalHow was it designed to be used?

Takeyasu SakaiElectronic Navigation Research Institute

Takeyasu SakaiElectronic Navigation Research Institute

ION GNSS Sept. 2012ION GNSS Sept. 2012 - Slide - Slide 22

IntroductionIntroduction• QZSS (Quasi-Zenith Satellite System) programQZSS (Quasi-Zenith Satellite System) program::

– Regional navigation service broadcast from high-elevation angle by a combination Regional navigation service broadcast from high-elevation angle by a combination of three or more satellites on the inclined geosynchronous (quasi-zenith) orbit;of three or more satellites on the inclined geosynchronous (quasi-zenith) orbit;

– Broadcast GPS-like supplemental signals on three frequencies and Broadcast GPS-like supplemental signals on three frequencies and Two AugmentaTwo Augmentation Signals, L1-SAIF and LEXtion Signals, L1-SAIF and LEX;;

– The first QZS satellite was successfully launched on Sept. 11, 2010.The first QZS satellite was successfully launched on Sept. 11, 2010.

• L1-SAIF L1-SAIF (Submeter-class Augmentation with Integrity Function) (Submeter-class Augmentation with Integrity Function) signal:signal:– Augmentation service on L1 single frequency designed for mobile users;Augmentation service on L1 single frequency designed for mobile users;

– Signal design: SBAS-like message stream on L1 C/A code (PRN 183).Signal design: SBAS-like message stream on L1 C/A code (PRN 183).

• ENRI has been developing L1-SAIF signal and conducting experimentsENRI has been developing L1-SAIF signal and conducting experiments::– L1-SAIF Master Station (L1SMS) experimental facility installed at ENRI;L1-SAIF Master Station (L1SMS) experimental facility installed at ENRI;

– IS-QZSS contains specification of L1-SAIF signal as well as other signals.IS-QZSS contains specification of L1-SAIF signal as well as other signals.


QZSS ConceptQZSS Concept

• Broadcast signal from high elevation angle;Broadcast signal from high elevation angle;

• Applicable to navigation services for Applicable to navigation services for mountain area and urban canyon;mountain area and urban canyon;

• Augmentation signal from the zenith could Augmentation signal from the zenith could help users to acquire other GPS satellites at help users to acquire other GPS satellites at any time.any time.

• Footprint of QZSS orbit;Footprint of QZSS orbit;• Centered at longitude of 135E;Centered at longitude of 135E;• Eccentricity 0.075, Inclination 43deg.Eccentricity 0.075, Inclination 43deg.

QZSQZSGPS/GEOGPS/GEO


Inclined Geosynchronous OrbitInclined Geosynchronous Orbit

Ground Track

• Semi-major axis (42,164km) is equal to GEO orbit: synchronous with rotation of Semi-major axis (42,164km) is equal to GEO orbit: synchronous with rotation of the earth;the earth;

• Inclined obit makes ground track ‘8’-figure; Called IGSO or Quasi-Zenith Orbit;Inclined obit makes ground track ‘8’-figure; Called IGSO or Quasi-Zenith Orbit;• With three or more satellites on the same ground track, navigation service can With three or more satellites on the same ground track, navigation service can

be provided from the zenith to regional users at any time.be provided from the zenith to regional users at any time.

Orbital Planes of QZSS (3 SVs)

8:408:40

15:2015:20Perigee Perigee

32,000km32,000km

ApogeeApogee40,000km40,000km


Broadcast from the ZenithBroadcast from the Zenith

• The constellation of 3 or more QZS satellites is capable of broadcasting signals The constellation of 3 or more QZS satellites is capable of broadcasting signals from near the zenith to regional users at any time;from near the zenith to regional users at any time;

• This property is attractive for augmentation channel; Users can expect to This property is attractive for augmentation channel; Users can expect to receive the augmentation signal anytime anywhere.receive the augmentation signal anytime anywhere.

3 satellites constellation @Tokyo3 satellites constellation @Tokyo

75.9 deg

4 satellites constellation @Tokyo4 satellites constellation @Tokyo

80.3 deg


Space Segment: QZS-1Space Segment: QZS-1

L-band Helical Array Antenna

L1-SAIF Antenna

Laser Reflector

C-band TTC Antenna

Radiation Cooled TWTTWSTFT Antenna

25.3m

Successfully launched on Sept. Successfully launched on Sept. 11, 2010 and settled on Quasi-Z11, 2010 and settled on Quasi-Zenith Orbit (IGSO).enith Orbit (IGSO).

Nickname: “Michibiki”Nickname: “Michibiki”

Mass4,020kg (wet) 1,802kg (dry) (NAV Payload： 320kg)

PowerApprox. 5.3 kW (EOL) (NAV Payload: Approx. 1.9kW)

Design Life 10 years


Frequency PlanFrequency Plan

Find detail in IS-QZSS document.Find detail in IS-QZSS document.

SignalSignal ChannelChannel FrequencyFrequency BandwidthBandwidth Min. Rx PowerMin. Rx Power

QZS-L1CQZS-L1CL1CDL1CD

1575.42 MHz1575.42 MHz

24 MHz24 MHz ––163.0 dBW163.0 dBW

L1CPL1CP 24 MHz24 MHz – – 158.25 dBW158.25 dBW

QZS-L1-C/AQZS-L1-C/A 24 MHz24 MHz – – 158.5 dBW158.5 dBW

QZS-L1-SAIFQZS-L1-SAIF 24 MHz24 MHz – – 161.0 dBW161.0 dBW

QZS-L2CQZS-L2C 1227.6 MHz1227.6 MHz 24 MHz24 MHz – – 160.0 dBW160.0 dBW

QZS-L5QZS-L5L5IL5I

1176.45 MHz1176.45 MHz25 MHz25 MHz – – 157.9 dBW157.9 dBW

L5QL5Q 25 MHz25 MHz – – 157.9 dBW157.9 dBW

QZS-LEXQZS-LEX 1278.75 MHz1278.75 MHz 42 MHz42 MHz – – 155.7 dBW155.7 dBW

InteroperabilityInteroperability

GPS-like supplemental GPS-like supplemental signals with minimum signals with minimum modifications from GPS modifications from GPS signalssignals

SBAS-like augmentation SBAS-like augmentation signal (250bps)signal (250bps)

QZSS-specific augmenta-tiQZSS-specific augmenta-tion signal (2kbps)on signal (2kbps)

1575.42 MHz1575.42 MHz


QZSS L1-SAIF SignalQZSS L1-SAIF Signal• QZSS broadcasts wide-area augmentation signalQZSS broadcasts wide-area augmentation signal::

– Called L1-SAIF (Submeter-class Augmentation with Integrity Function);Called L1-SAIF (Submeter-class Augmentation with Integrity Function);– Augmentation signal for mobile users designed and developed by ENRI.Augmentation signal for mobile users designed and developed by ENRI.

• L1-SAIF signal offersL1-SAIF signal offers::– Wide-area differential correction service for improving position accuracy; TargeWide-area differential correction service for improving position accuracy; Targe

t accuracy: 1 meter for horizontal;t accuracy: 1 meter for horizontal;– Integrity function for safety of mobile users; andIntegrity function for safety of mobile users; and– Ranging function for improving position availability.Ranging function for improving position availability.

• Augmentation to GPS L1C/A based on the SBAS specificationsAugmentation to GPS L1C/A based on the SBAS specifications::– Broadcast on L1 freq. with RHCP; Common antenna and RF front-end;Broadcast on L1 freq. with RHCP; Common antenna and RF front-end;

Modulated by BPSK with C/A code (PRN 183);Modulated by BPSK with C/A code (PRN 183); 250 bps data rate with 1/2 FEC; Message structure is identical with SBAS;250 bps data rate with 1/2 FEC; Message structure is identical with SBAS; Differences from SBAS: PRN, large Doppler, and some additional messages.Differences from SBAS: PRN, large Doppler, and some additional messages.

– Developed easily if one has the experience to develop SBAS-capable receiver;Developed easily if one has the experience to develop SBAS-capable receiver;– Specification of L1-SAIF: See IS-QZSS document (Available at JAXA HP).Specification of L1-SAIF: See IS-QZSS document (Available at JAXA HP).


L1-SAIF Signal FunctionsL1-SAIF Signal Functions

User GPS/L1-SAIFUser GPS/L1-SAIFReceiversReceivers

• Three functions by a single signal: ranging, error Three functions by a single signal: ranging, error correction (Target accuracy: 1m), and integrity;correction (Target accuracy: 1m), and integrity;

• User receivers can receive both GPS and L1-SAIF User receivers can receive both GPS and L1-SAIF signals with a single antenna and RF front-end;signals with a single antenna and RF front-end;

• Message-oriented information transmission: Message-oriented information transmission: Flexible contents.Flexible contents.

SAIFSAIF ：： Submeter-class Augmentation with Integrity FunctionSubmeter-class Augmentation with Integrity Function

RangingRangingFunctionFunction

ErrorErrorCorrectionCorrection

IntegrityIntegrityFunctionFunction

QZS satellitesQZS satellites

GPS ConstellationGPS Constellation

Ranging SignalRanging Signal

3 Functions by L1-SAIF3 Functions by L1-SAIF


WADGPS ConceptWADGPS Concept

Orbit CorrectionOrbit Correction

TroposphereTroposphere

IonosphereIonosphere

Ionospheric CorrectionIonospheric Correction

Tropospheric CorrectionTropospheric Correction

Clock CorrectionClock Correction• Same contribution to any user Same contribution to any user

location;location;• Not a function of location;Not a function of location;• Needs fast correction. Needs fast correction.

• Different contribution to different Different contribution to different user location;user location;

• Not a function of user location; but Not a function of user location; but a function of line-of-sight direction;a function of line-of-sight direction;

• Long-term correction.Long-term correction.

• Function of user location;Function of user location;• Up to 100 meters;Up to 100 meters;• Vertical structure may be Vertical structure may be

described as a thin shell.described as a thin shell.

• Function of user location, especially height of user;Function of user location, especially height of user;• Up to 20 meters;Up to 20 meters;• Can be corrected enough by a fixed model.Can be corrected enough by a fixed model.

• Broadcast separate corrections to each error factor to enlarge the service area;Broadcast separate corrections to each error factor to enlarge the service area;• User receivers reconstruct pseudorange corrections with regard to its location.User receivers reconstruct pseudorange corrections with regard to its location.


L1-SAIF Message StructureL1-SAIF Message StructurePreamblePreamble

8 bits8 bitsMessage TypeMessage Type

6 bits6 bitsData FieldData Field212 bits212 bits

CRC parityCRC parity24 bits24 bits

250 bits per secondTransmitted firstTransmitted firstSync to GPS epochSync to GPS epoch

Message Type Contents

0 to 7, 10,

18 to 28, 62, 63

• Basic messages compatible with SBAS• Submeter accuracy correction could be achieved by these

messages only

9, 12, 17• These messages are for geostationary satellites• Not used for L1-SAIF

52 to 61• L1-SAIF original messages• Receiver implementation is optional

Note: Message Types 29 to 61 have no definitions in the current specification of SBAS.Note: Message Types 29 to 61 have no definitions in the current specification of SBAS.

• Message structure is identical with SBAS;Message structure is identical with SBAS;• Basic function is supported by only SBAS-compatible messages; Easy to develop!Basic function is supported by only SBAS-compatible messages; Easy to develop!


L1-SAIF Master StationL1-SAIF Master Station• L1-SAIF Master Station (L1SMS):L1-SAIF Master Station (L1SMS):

– Generates L1-SAIF message stream in realtime and transmits it to QZSS MCS deGenerates L1-SAIF message stream in realtime and transmits it to QZSS MCS developed by and installed at JAXA;veloped by and installed at JAXA;

– Installed at ENRI, Tokyo; 90km from JAXA Tsukuba Space Center;Installed at ENRI, Tokyo; 90km from JAXA Tsukuba Space Center;– Dual frequency GPS measurements at some locations in Japan necessary to geneDual frequency GPS measurements at some locations in Japan necessary to gene

rate L1-SAIF messages are sent from GEONET in realtime.rate L1-SAIF messages are sent from GEONET in realtime.

L1SMSL1SMSGEONETGEONET

QZSQZS

QZSS MCSQZSS MCS

GPSGPSSatellitesSatellites

Measure-Measure-mentsments

L1-SAIFL1-SAIFMessageMessage

GSI ServerGSI Server(Tokyo)(Tokyo)

ENRIENRI(Tokyo)(Tokyo)

JAXA TKSCJAXA TKSC(Tsukuba)(Tsukuba)

L1-S

AIF S

ignal

L1-S

AIF S

ignal

Ranging Signal

Ranging SignalRan

ging

Signal

Rangin

g Signa

l

K-band Uplink

K-band Uplink


L1SMS at ENRIL1SMS at ENRI

StorageStorage

Router toRouter toGEONET/JAXAGEONET/JAXA

I/FI/F

UPSUPSUPSUPS

MessageMessageGeneratorGenerator

GEONETGEONETServerServer

StorageStorage

Ionosphere Ionosphere ProcessorProcessor

StorageStorage


Preliminary ResultPreliminary Result

• Example of user position error at Site 94Example of user position error at Site 940058 (Takayama);0058 (Takayama);

• Realtime operation with MSAS-like 6 refeRealtime operation with MSAS-like 6 reference stations in Japan;rence stations in Japan;

• Period: 19-23 Jan. 2008 (5 days).Period: 19-23 Jan. 2008 (5 days).

HorizontalHorizontalErrorError

VerticalVerticalErrorError

1.45 m1.45 m 2.92 m2.92 m

6.02 m6.02 m 8.45 m8.45 m

SystemSystem

StandaloneStandaloneGPSGPS

0.29 m0.29 m 0.39 m0.39 m

1.56 m1.56 m 2.57 m2.57 mL1-SAIFL1-SAIF

RMSRMS

MaxMax

RMSRMS

MaxMax

Note: Results shown here were obtained with geodetic-Note: Results shown here were obtained with geodetic-grade antenna and receivers at open sky condition.grade antenna and receivers at open sky condition.

User location User location for this testfor this test

6 reference6 referencestationsstations

L1-SAIF expe- L1-SAIF experimental arearimental area

Standalone GPSL1-SAIF Augmentation


Realtime Operation using GEORealtime Operation using GEO

ETS-VIII SatelliteETS-VIII Satellite

L1-SAIF L1SMSL1-SAIF L1SMSin Tokyoin Tokyo

GPS/L1-SAIF RxGPS/L1-SAIF Rxin Sendai Airportin Sendai Airport

GPSGPSSatellitesSatellites

• ENRI joined communication experiment of ETS-VIII geostationary satellite;ENRI joined communication experiment of ETS-VIII geostationary satellite;

• L1SMS transmitted L1-SAIF message to ETS-VIII; Received L1-SAIF message was inpuL1SMS 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;t to the GPS/L1-SAIF receiver and processed in realtime; No ranging function;

• Successfully completed in Feb. 2009.Successfully completed in Feb. 2009.

350 km Separation350 km Separation


Resulted Position via GEOResulted Position via GEO2009/2/17 01:21:39 to 07:23:14 (6 hours)2009/2/17 01:21:39 to 07:23:14 (6 hours)

Standalone GPSStandalone GPS L1-SAIF AugmentationL1-SAIF Augmentation

H Error RMS = 0.412mH Error RMS = 0.412mV Error RMS = 0.464mV Error RMS = 0.464m

H Error RMS = 1.221mH Error RMS = 1.221mV Error RMS = 4.043mV Error RMS = 4.043m


Experiment by CarExperiment by Car• L1-SAIF technical verification experimentL1-SAIF technical verification experiment::

– L1-SAIF is originally planned as an augmentatiL1-SAIF is originally planned as an augmentation for mobile users;on for mobile users;

– Conducted experiment with a car;Conducted experiment with a car;– Location: urban/suburban environment, freewaLocation: urban/suburban environment, freewa

y;y;– Experiment period: Dec. 2010 to March 2011.Experiment period: Dec. 2010 to March 2011.

• Experiment setup:Experiment setup:– Reference: GPS+IMU sensor;Reference: GPS+IMU sensor;– Post-processing with GEONET stations (20- 3Post-processing with GEONET stations (20- 3

0 km separation) for accurate reference;0 km separation) for accurate reference;– GPS/L1-SAIF receiver and PC in cabin;GPS/L1-SAIF receiver and PC in cabin;– Receives L1-SAIF signal on PRN 183;Receives L1-SAIF signal on PRN 183;– Applies L1-SAIF corrections in realtime and ouApplies L1-SAIF corrections in realtime and ou

tputs position fix.tputs position fix.

GPS+IMUGPS+IMU

GPS/L1-SAIFGPS/L1-SAIFReceiverReceiver


On the FreewayOn the Freeway

• On Dec. 14, 2010; QZS near the Zenith;On Dec. 14, 2010; QZS near the Zenith;• About 10 km drive at the Kofu Basin on Chuo Freeway going About 10 km drive at the Kofu Basin on Chuo Freeway going

westward from Tokyo;westward from Tokyo;• Plain ground with less bridges across the Freeway.Plain ground with less bridges across the Freeway.

Plan View of the RoutePlan View of the Route Typical SituationTypical Situation

2 kmGEONETGEONETNakamichiNakamichi

GEONETGEONETIchinomiyaIchinomiya


Freeway: No AugmentationFreeway: No Augmentation

1.2m1.2m

15min15min

Hor

izon

tal P

ositi

on E

rror

, m

Chuo Freeway: GPS without Augmentation

UTC Time 1:22:08 to 1:37:08


Freeway: L1-SAIF AugmentedFreeway: L1-SAIF Augmented

0.5m0.5m

15min15min

Hor

izon

tal P

ositi

on E

rror

, m

Chuo Freeway: L1-SAIF Augmentation

UTC Time 1:22:08 to 1:37:08


In the CityIn the City

• On Dec. 16, 2010; QZS near the Zenith;On Dec. 16, 2010; QZS near the Zenith;• About 6 km drive in West part of Tsukuba City in Ibaraki Pref.;About 6 km drive in West part of Tsukuba City in Ibaraki Pref.;• Road on the ground level with less tall buildings around.Road on the ground level with less tall buildings around.

Plan View of the RoutePlan View of the Route Typical SituationTypical Situation

1 km

GEONETGEONETTsukuba 1Tsukuba 1


City: No AugmentationCity: No Augmentation

2.0m2.0m

15min15min

Hor

izon

tal P

ositi

on E

rror

, m

Tsukuba: GPS without Augmentation

UTC Time 5:30:01 to 5:45:01


City: L1-SAIF AugmentedCity: L1-SAIF Augmented

0.6m0.6m

15min15min

Hor

izon

tal P

ositi

on E

rror

, m

Tsukuba: L1-SAIF Augmentation

UTC Time 5:30:01 to 5:45:01


Ranging by L1-SAIFRanging by L1-SAIF2011-08-182011-08-1802:18:45 to 21:16:2002:18:45 to 21:16:20

L1-SAIF (PRN183) Ranging ONL1-SAIF (PRN183) Ranging ON

L1SMS Configuration:L1SMS Configuration: 6 DF GPS GMS (GEONET)6 DF GPS GMS (GEONET) 4 SF GPS/QZS GMS (JAXA)4 SF GPS/QZS GMS (JAXA)

User location:User location: @ENRI, Tokyo@ENRI, Tokyo

Receiver:Receiver: JAVAD ALPHA-G3TJAVAD ALPHA-G3T

Processing by ENRIProcessing by ENRI Mask 5deg, Smoothing 100sMask 5deg, Smoothing 100s

L1-SAIF CorrectionL1-SAIF Correction L1-SAIF RangingL1-SAIF Ranging Hor RMSHor RMS Hor MaxHor Max Ver RMSVer RMS Ver MaxVer Max

ONONOFFOFF 0.680 m0.680 m 8.686 m8.686 m 0.988 m0.988 m 13.308 m13.308 m

ONON 0.658 m0.658 m 2.494 m2.494 m 0.937 m0.937 m 4.682 m4.682 m


ConclusionConclusion• ENRI has developed L1-SAIF augmentation signalENRI has developed L1-SAIF augmentation signal::

– Planned as an augmentation for mobile users;Planned as an augmentation for mobile users;– Signal design: SBAS-like message stream on L1 C/A code (PRN 183);Signal design: SBAS-like message stream on L1 C/A code (PRN 183);– The first QZSS satellite “Michibiki” has been broadcasting L1-SAIF signal.The first QZSS satellite “Michibiki” has been broadcasting L1-SAIF signal.

• Experiments for L1-SAIFExperiments for L1-SAIF::– ENRI has implemented L1-SAIF Master Station (L1SMS) which generates augmentaENRI has implemented L1-SAIF Master Station (L1SMS) which generates augmenta

tion message stream in realtime and transmit it to QZSS MCS;tion message stream in realtime and transmit it to QZSS MCS;– Preliminary tests have shown promising performance;Preliminary tests have shown promising performance;– Technical verification experiments confirmed the performance for mobile users.Technical verification experiments confirmed the performance for mobile users.

• Ongoing workOngoing work::– Continue experiments regularly (two weeks per month);Continue experiments regularly (two weeks per month);– Define messages to be used to broadcast regional information; Define messages to be used to broadcast regional information; – Support augmentation to GLONASS satellites for further improvement of availability;Support augmentation to GLONASS satellites for further improvement of availability;– Support dual frequency operations.Support dual frequency operations.

Information available atInformation available at: : http://www.enri.go.jp/sat/qzss_e.htmhttp://www.enri.go.jp/sat/qzss_e.htm

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