T. Sakai, S. Fukushima, N. Takeichi, and K. Ito Electronic Navigation Research Institute, Japan T. Sakai, S. Fukushima, N. Takeichi, and K. Ito Electronic Navigation Research Institute, Japan Implementation of the QZSS L1-SAIF Message Generator Implementation of the QZSS L1-SAIF Message Generator ION NTM 2008 San Diego, CA Jan , 2008

ION NTM Jan ENRI S LIDE 1 QZSS will provide augmentation signals:QZSS will provide augmentation signals: –In addition to supplement signals; –L1-SAIF (Submeter-class Augmentation with Integrity Function) on GPS/SBAS L1 frequency and LEX on Galileo E6; –L1-SAIF augmentation signal offers: wide-area differential correction, integrity function, and ranging function. ENRI is responsible for developing L1-SAIF:ENRI is responsible for developing L1-SAIF: –Signal design: identical with SBAS; –Message design is in progress: upper compatible with SBAS. L1-SAIF Message Generator (L1SMG):L1-SAIF Message Generator (L1SMG): –Subsystem of L1-SAIF Master Station (L1SMS); –Generates message stream in realtime and transmit it to QZSS MCS. Introduction

ION NTM Jan ENRI S LIDE 2 Part 1 Overview of QZSS Program and L1-SAIF Signal

ION NTM Jan ENRI S LIDE 3 QZS GPS/GEO Signal from high elevation angleSignal from high elevation angle Applicable to navigation services for mountain area and urban canyonApplicable to navigation services for mountain area and urban canyon QZSS Concept Footprint of QZS orbitFootprint of QZS orbit Centered 137ECentered 137E Eccentricity 0.1, Inclination 45degEccentricity 0.1, Inclination 45deg

ION NTM Jan ENRI S LIDE 4 Supplement signals:Supplement 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 JPO on broadcasting L1C signal; –JAXA is responsible for all supplement signals. Augmentation signals:Augmentation signals: –Augmentation to GPS; Possibly plus Galileo; –L1-SAIF (Submeter-class Augmentation with Integrity Function): compatible with SBAS; reasonable performance for mobile users; –LEX: for experimental purposes; member organizations may use as 2kbps experimental data channel; –ENRI is working for L1-SAIF and JAXA is developing LEX. QZSS Signals

ION NTM Jan ENRI S LIDE 5 Frequency Plan SignalChannelFrequencyBandwidth Min. Rx Power QZS-L1CL1CD MHz 24 MHz –163.0 dBW L1CP 24 MHz – dBW QZS-L1-C/A 24 MHz – dBW QZS-L1-SAIF 24 MHz – dBW QZS-L2C MHz 24 MHz – dBW QZS-L5L5I MHz 25 MHz – dBW L5Q 25 MHz – dBW QZS-LEX MHz 42 MHz – dBW Find detail in IS-QZSS document.

ION NTM Jan ENRI S LIDE 6 QZSS will transmit wide-area augmentation signal:QZSS will transmit wide-area augmentation signal: –Called L1-SAIF (Submeter-class Augmentation with Integrity Function); –Developed by ENRI (Electronic Navigation Research Institute), Japan. L1-SAIF signal offers:L1-SAIF signal offers: –Wide-area differential corrections for improving position accuracy; Target accuracy: 1 meter for horizontal; –Integrity function for safety of mobile users; and –Ranging function to improve signal availability. Interoperable with GPS L1C/A and fully compatible with SBAS: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 same as SBAS. L1-SAIF Signal

ION NTM Jan ENRI S LIDE 7 L1-SAIF Augmentation Concept Troposphere Ionosphere Ranging QZS GPSSatellites …… Augmentation Error CorrectionsError Corrections IntegrityIntegrity User (Single Frequency) OrbitError Clock Error HighElevation

ION NTM Jan ENRI S LIDE 8 L1 PRN Assignment PRNSignalSatellite 183QZS-L1-SAIF QZS #1 184QZS-L1-SAIF QZS #2 185QZS-L1-SAIF QZS #3 186QZS-L1-SAIF QZS #4 187QZS-L1-SAIF QZS #5 188 to 192 QZS-L1-SAIF(Reserved) 193 to 197 QZS-L1-C/A QZS # to 202 QZS-L1-C/A(Reserved) Find detail in IS-QZSS document.

ION NTM Jan ENRI S LIDE 9 Preamble 8 bits Message Type 6 bits Data Field 212 bits CRC parity 24 bits 250 bits MT 0 1 2～52～52～52～ 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] FC & LTC Long-term correction Ionospheric delay & GIVE SBAS service message Clock-ephemeris covariance Null message — MTContentsInterval[s] SBAS Message Structure

ION NTM Jan ENRI S LIDE 10 L1-SAIF Message (1) Message Type ContentsCompatibilityStatus 0 Test mode SBASFixed 1 PRN mask SBASFixed 2 to 5 Fast correction & UDRE SBASFixed 6UDRESBASFixed 7 Degradation factor for FC SBASFixed 9 GEO ephemeris UnusedFixed 10 Degradation parameter SBASFixed 17 GEO almanac UnusedFixed 18 IGP mask SBASFixed 24 Mixed fast/long-term correction SBASFixed 25 Long-term correction SBASFixed 26 Ionospheric delay & GIVE SBASFixed 12 SBAS network time UnusedFixed 8ReservedUnusedFixed

ION NTM Jan ENRI S LIDE 11 L1-SAIF Message (2) Message Type ContentsCompatibilityStatus 27 SBAS service message UnusedFixed 28 Clock-ephemeris covariance SBASFixed 29 to 51 (Undefined)—— 52 TGP mask NewTentative 56 Intersignal biases NewTentative 57 (Ephemeris-related parameter) NewTBD 58 QZS ephemeris NewTentative 59 (QZS almanac) NewTBD 60 (Regional information) NewTBD 61ReservedNewTentative 62ReservedSBASFixed 63 Null message SBASFixed 5３5３5３5３ Tropospheric delay NewTentative 54 to 55 (Advanced Ionospheric delay) NewTBD

ION NTM Jan ENRI S LIDE 12 Message Fast Correction Long-Term Correction Ionosphere Troposphere QZS Ephemeris FC Degradation Degradation Parameter PRN Mask IGP Mask C-E Covariance Total Type 2 to and Interval 10 s 60 s 30 s 60 s Messages Required for Constellation Messages per min Margin for Other Messages 16 Messaging Capacity

ION NTM Jan ENRI S LIDE 13 Part 2 L1-SAIF Message Generator

ION NTM Jan ENRI S LIDE 14 L1-SAIF Master Station (L1SMS):L1-SAIF Master Station (L1SMS): –Generates L1-SAIF message stream in realtime and transmits them to QZSS MCS developed by JAXA; –Installed at ENRI, Tokyo; –Subsystems: GEONET Server, Primary Receiver, Interface Processor, Message Generator, Ionosphere Processor, Troposphere Processor, and Batch Processor. ENRI L1SMS L1SMSGEONET QZS QZSS MCS GPS MeasuredDataL1-SAIFMessage GSIENRIJAXA L1-SAIF Signal L1C/A, L2P K-band ClosedLoop

ION NTM Jan ENRI S LIDE 15 GEONET Server:GEONET Server: –Receives dual frequency measurement from GEONET operated by Geographical Survey Institute (GSI), Japan; –Output rate: 1 sample per second (1 Hz); In native binary format of receivers; Latency is less than 2 seconds; –5 servers for 1,000 GEONET stations distributed all over Japan. Primary Receiver:Primary Receiver: –Installed inside L1SMS with connection via Ethernet LAN; –Provides measurements for immediate response to satellite failure to ensure integrity function; –Collects navigation message every subframe; –Provides the actual time to the message generator; –Currently NovAtel OEM-3 MiLLennium-STD. L1SMS Subsystems (1)

ION NTM Jan ENRI S LIDE 16 L1SMS Subsystems (2) Interface Processor:Interface Processor: –Distributes GPS measurement data stream to other processors; –Other subsystem processors access to this processor to obtain measurement to avoid generating lots of direct connections to GEONET Server and Primary Receiver; –Also relays L1-SAIF message packets from Message Generator to QZSS MCS at JAXA. Message Generator:Message Generator: –Generates L1-SAIF message and sends packets to Interface Processor; –Variable configuration of monitor stations; –Capable several types of receiver: RINEX, NovAtel, Trimble, JAVAD; –Standard planar fit algorithm for ionospheric correction; –Standard correction model for troposphere.

ION NTM Jan ENRI S LIDE 17 L1SMS Subsystems (3) Ionosphere Processor (under development):Ionosphere Processor (under development): –Generates ionospheric correction and integrity information based on vast number of monitor stations (tested up to 200 stations); –Implements ‘residual bounding’ algorithm (See ION GNSS 2007); –This processor is optional; If not exist, L1SMG employs its own standard algorithm. Troposphere Processor (under development):Troposphere Processor (under development): –Estimates atmospheric condition and generates tropospheric delay information; –Semi-realtime estimation: latency is less than 1 hour; –Formats delay information into vertical delay at TGP (tropospheric grid point) like IGP for ionosphere; –Also optional; If not exist, standard troposphere model is used.

ION NTM Jan ENRI S LIDE 18 L1SMS Subsystems (4) Batch Processor:Batch Processor: –Estimates satellite and receiver hardware biases so-called Inter- frequency bias or L1/L2 bias; –Runs on daily basis; Constructs model of ionosphere based on measurements for at least two days and performs estimation; –Provides stable and accurate estimation in comparison with a realtime sequential processing. Data Storage Server:Data Storage Server: –Very large capacity storage with RAID configuration; –Holds input measurements and resulted message stream for several months (depending on the number of monitor stations).

ION NTM Jan ENRI S LIDE 19 L1SMS Installed at ENRI Storage Router to GEONET I/F UPS UPSMessageGeneratorGEONETServer Storage Ionosphere Processor Storage

ION NTM Jan ENRI S LIDE 20 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 MessageOutput via TCP/IP Observation File (RINEX) via FTP IFBEstimates Primary Receiver Interface Processor Dual Freq. Ant.

ION NTM Jan ENRI S LIDE 21 Message Generator (L1SMG) Input Module L1-SAIF Message Generator (L1SMG) MessageOutput via TCP/IP Primary Receiver Messaging Module Ionosphere Module (Planar Fit) GEONET Server MessageLog Time and NAV Message Input from Iono Processor Monitor Stations Measurement Standard Ionospheric Correction Clock and Orbit Corrections Correction Module Dual Freq. Ant.

ION NTM Jan ENRI S LIDE 22 Transmission Latency QZS is not a Bent-Pipe transponder:QZS is not a Bent-Pipe transponder: –QZS synthesizes RF signals onboard; –Onboard computer has a message queue for synchronization to Z-count epoch; –MCS waits for available time slot of TTC channel to uplink L1-SAIF message; Again a queue; –Latency up to 10 seconds from departure at L1SMS to reception by user receivers. L1SMG generates message earlier:L1SMG generates message earlier: –10-15 seconds in advance; –Possible unless SA turned on; –Affects on integrity performance, TTA. QZSS MCS ENRI JAXA L1SMS ISDN Uplink Station Onboard Computer Modulator User Receiver K-band L-band QZS User Worst Case Latency [s] Total 10.00

ION NTM Jan ENRI S LIDE 23 Realtime Operation Test Tested L1SMG with 4 configurations of monitor stations;Tested L1SMG with 4 configurations of monitor stations; Analyzed user position error at 14 evaluation locations; Numbered from North to South;Analyzed user position error at 14 evaluation locations; Numbered from North to South; Used GEONET stations as all monitor stations and evaluation sites.Used GEONET stations as all monitor stations and evaluation sites. #1 JAXA Monitor Stations (4) #2 MSAS Domestic Stations (6) L1-SAIF Experimental Area #3 ENRI Realtime Sites (9) Evaluation Locations (14) #4(11)

ION NTM Jan ENRI S LIDE 24 Initial Results – Error Sample Example of user positioning error at Site (Takayama; near center of monitor station network);Example of user positioning error at Site (Takayama; near center of monitor station network); MSAS-like 6 monitor stations;MSAS-like 6 monitor stations; Period: Jan (5 days).Period: Jan (5 days). Standalone GPS L1-SAIF Augmentation HorizontalErrorVerticalError 1.45 m 2.92 m 6.02 m 8.45 m System StandaloneGPS 0.29 m 0.39 m 1.56 m 2.57 m L1-SAIF RMS Max RMS Max

ION NTM Jan ENRI S LIDE 25 Clock and Orbit Corrections Clock and orbit corrections for PRN 09 satellite;Clock and orbit corrections for PRN 09 satellite; IODE is changed by MT24 long-term correction message at 15:56:45;IODE is changed by MT24 long-term correction message at 15:56:45; Even discontinuities on corrections, pseudorange residual is continuous.Even discontinuities on corrections, pseudorange residual is continuous.

ION NTM Jan ENRI S LIDE 26 User Position Accuracy Needs at least 6 monitor stations;Needs at least 6 monitor stations; 11 stations configuration offers better accuracy in Southern region.11 stations configuration offers better accuracy in Southern region. HOR VER

ION NTM Jan ENRI S LIDE 27 Maximum User Position Error Unstable with 4 monitor stations configuration;Unstable with 4 monitor stations configuration; 11 stations configuration prevent large errors in Southern region.11 stations configuration prevent large errors in Southern region. HOR VER

ION NTM Jan ENRI S LIDE 28Conclusion ENRI has been developing QZSS L1-SAIF signal:ENRI has been developing QZSS L1-SAIF signal: –L1-SAIF augmentation signal on GPS/SBAS L1 frequency; –Signal design: compatible with SBAS; –Message design is in progress: upper compatible with SBAS. Development of L1SMS:Development of L1SMS: –Most subsystems including L1SMG successfully implemented; –Ionosphere and Troposphere Processors under development; –Realtime operation test successfully conducted. Future works will include:Future works will include: –Ionosphere and Troposphere Processors handling lots of monitor stations; –Implementation of integrity function and necessary monitors; –Contact: