Ranging Quality of QZSS L1-SAIF Signal - Electronic Navigation

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Ranging Quality of QZSS L1-SAIF Signal - Electronic Navigation Powered By Docstoc
					                                            ION ITM 2012
                                         Newport Beach, CA
                                         Jan.30 - Feb.1, 2012




           Ranging Quality of
          QZSS L1-SAIF Signal




        T. Sakai, H. Yamada, and K. Ito
Electronic Navigation Research Institute, Japan
                                                                ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                     SLIDE 1
   Introduction
• QZSS (Quasi-Zenith Satellite System) program:
    – Regional navigation service broadcast from high-elevation angle by a combination
      of three satellites on the inclined geosynchronous (quasi-zenith) orbit;
    – Broadcast GPS-like supplemental signals on three frequencies and two
      augmentation signals, L1-SAIF and LEX;
    – The first QZS satellite was successfully launched on Sept. 11, 2010.

• L1-SAIF (Submeter-class Augmentation with Integrity Function) signal offers:
    – Submeter accuracy wide-area differential correction service;
    – Integrity function for safety of mobile users; and
    – Ranging function for improving position availability; all on L1 single frequency.

• ENRI has been developing L1-SAIF signal and experimental facility:
    – Signal design: SBAS-like message stream on L1 C/A code (PRN 183);
    – Ranging function is now available: Ephemeris information has been broadcast
      during the experiments conducted by ENRI since Nov. 2011;
    – Investigated ranging quality of L1-SAIF signal.
         Expect comparable to GPS thanks to signal bandwidth of 24 MHz.
                                                                ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                     SLIDE 2
    QZSS Concept

                                            GPS/GEO                       QZS




                                           • Broadcast signal from high elevation angle;
                                           • Applicable to navigation services for
                                             mountain area and urban canyon;
• Footprint of QZSS orbit;                 • Augmentation signal from the zenith could
• Centered at 135E;                          help users to acquire other GPS satellites at
• Eccentricity 0.075, Inclination 43deg.     any time.
                                                              ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                   SLIDE 3
   Inclined Geosynchronous Orbit
                                           Apogee
                                          40000km


                                                                                8:40



                                                                             15:20
 Perigee
32000km


           Orbital Planes of QZSS (3 SVs)
                                                                Ground Track
    • Semi-major axis (42164km) is equal to GEO orbit: synchronous with rotation of
      the earth;
    • 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
      be provided from the zenith to regional users at any time.
                                                         ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                               SLIDE 4
   Space Segment: QZS-1
               4,020kg (wet) 1,802kg (dry)
   Mass
               (NAV Payload:320kg)

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

 Design Life   10 years


               Radiation Cooled TWT
                                                                  TWSTFT Antenna
Successfully launched on Sept.
11, 2010 and settled on Quasi-
Zenith Orbit (IGSO).                                          C-band TTC Antenna

Nickname: “Michibiki”

                                                                 Laser Reflector

                                      L1-SAIF Antenna   L-band Helical Array
                                                        Antenna
                                                         ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                              SLIDE 5
   QZSS Frequency Plan
 Signal   Channel    Frequency    Bandwidth Min. Rx Power         Interoperability

           L1CD                    24 MHz     –163.0 dBW
QZS-L1C
           L1CP     1575.42 MHz    24 MHz    – 158.25 dBW
                                                             GPS-like supplemental
  QZS-L1-C/A                       24 MHz    – 158.5 dBW
                                                             signals with minimum
                                                             modifications from GPS
   QZS-L2C          1227.6 MHz     24 MHz    – 160.0 dBW     signals
             L5I                   25 MHz    – 157.9 dBW
QZS-L5              1176.45 MHz
           L5Q                     25 MHz    – 157.9 dBW
                                                             SBAS-like augmentation
 QZS-L1-SAIF        1575.42 MHz    24 MHz    – 161.0 dBW     signal (250bps)
                                                             QZSS-specific augmenta-
   QZS-LEX          1278.75 MHz    42 MHz    – 155.7 dBW     tion signal (2kbps)

                                            Find detail in IS-QZSS document.
                                                                ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                      SLIDE 6
 QZSS L1-SAIF Signal
• QZSS broadcasts wide-area augmentation signal:
    – Called L1-SAIF (Submeter-class Augmentation with Integrity Function);
    – Designed and 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 improving position availability.

• Augmentation to GPS L1C/A based on SBAS techniques:
    – Broadcast on L1 freq. with RHCP; Common antenna and RF front-end;
         Modulated by BPSK with C/A code (PRN 183);
         250 bps data rate with 1/2 FEC; message structure is identical with SBAS;
         Differences: Large Doppler and additional messages.
    – Specification of L1-SAIF: See IS-QZSS document (Available at JAXA HP).
                                                                 ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                      SLIDE 7
   L1-SAIF Signal
                         Ranging
   QZS satellites        Function
                                                                              GPS Constellation
                          Error
                        Correction

                                                                             Ranging Signal
                        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 with a single antenna and RF front-end;                           User GPS
• Message-oriented information transmission: flexible                       Receivers
  contents.
               SAIF: Submeter-class Augmentation with Integrity Function
                                                      ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                SLIDE 8
L1-SAIF Corrections
                                  • 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);
                                  • L1-SAIF provides corrections only;
                                    No L1-SAIF ranging.

                                                             Horizontal          Vertical
                                        System
                                                               Error              Error
           Standalone GPS         Standalone RMS               1.45 m            2.92 m
           Augmented by L1-SAIF      GPS     Max               6.02 m            8.45 m
                                                    RMS        0.29 m            0.39 m
                                   L1-SAIF
                                                    Max        1.56 m            2.57 m
  No L1-SAIF Ranging                Note: Results shown here were obtained with survey-
                                       grade antenna and receiver in open sky condition.
                                                        ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                             SLIDE 9
 Usage of L1-SAIF Ranging
• Ranging function of L1-SAIF signal:
    – RF signal design: Identical with GPS L1 C/A modulated by PRN 183 code;
    – Necessary to broadcast ephemeris information in order to make ranging
      function available to users.
         L1-SAIF extended message of Type 58 Ephemeris Information is designed
          for this purpose.
• Completed L1-SAIF Master Station (L1SMS) upgrade:
    – To be capable of broadcasting MT58 Ephemeris Information during the
      experiments conducted by ENRI;
    – Using JAXA monitor stations for generation of MT58.
• Investigation of ranging quality including effects of Ephemeris Information:
    – RF quality: Expect comparable to GPS thanks to signal bandwidth of 24MHz;
    – How about quality of ephemeris information on L1-SAIF ?
    – User receiver setup:
        JAVAD ALPHA-G3T with QZSS extension;
        Output pseudorange measurements are processed by ENRI;
        5 deg Elevation Mask, 100 seconds Carrier Smoothing.
                                                                  ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                      SLIDE 10
  L1-SAIF Message Structure
         Preamble        Message Type              Data Field               CRC parity
           8 bits           6 bits                  212 bits                 24 bits


  Transmitted First                            1 message = 250 bits broadcast every second
                                        Interval                                           Interval
 MT                   Contents             [s]      MT              Contents                  [s]
  0       Test mode                        6         17     GEO almanac                     300
  1       PRN mask                       120         18     IGP mask                        300
2 to 5    Fast correction & UDRE          60         24     FC & LTC                          6
  6       UDRE                             6         25     Long-term correction            120
  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                     —
                                                        ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                            SLIDE 11
  L1-SAIF Message (1)
Message Type               Contents                  Used by              Status
     0         Test mode                         SBAS and L1-SAIF          Fixed
     1         PRN mask                          SBAS and L1-SAIF          Fixed
   2 to 5      Fast correction & UDRE            SBAS and L1-SAIF          Fixed
     6         UDRE                              SBAS and L1-SAIF          Fixed
     7         Degradation factor for FC         SBAS and L1-SAIF          Fixed
     8         Reserved                               SBAS                 Fixed
     9         GEO ephemeris                          SBAS                 Fixed
    10         Degradation parameter             SBAS and L1-SAIF          Fixed
    12         SBAS network time                      SBAS                 Fixed
    17         GEO almanac                            SBAS                 Fixed
    18         IGP mask                          SBAS and L1-SAIF          Fixed
    24         Mixed fast/long-term correction   SBAS and L1-SAIF          Fixed
    25         Long-term correction              SBAS and L1-SAIF          Fixed
    26         Ionospheric delay & GIVE          SBAS and L1-SAIF          Fixed
                                                    ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                        SLIDE 12
  L1-SAIF Message (2)
Message Type                Contents             Used by              Status
    27         SBAS service message               SBAS                 Fixed
    28         Clock-ephemeris covariance    SBAS and L1-SAIF          Fixed
  29 to 51     Undefined                            —                    —
    52         TGP mask                          L1-SAIF             Tentative
    53         Tropospheric delay                L1-SAIF             Tentative
  54 to 55     Advanced Ionospheric delay        L1-SAIF               TBD
    56         Intersignal biases                L1-SAIF             Tentative
    57         Ephemeris-related parameter       L1-SAIF               TBD
    58         QZS ephemeris                     L1-SAIF             Tentative
    59         QZS almanac                       L1-SAIF               TBD
    60         Regional information              L1-SAIF               TBD
    61         Reserved                          L1-SAIF             Tentative
    62         Reserved                      SBAS and L1-SAIF          Fixed
    63         Null message                  SBAS and L1-SAIF          Fixed
                                                     ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                         SLIDE 13
  L1-SAIF Ephemeris (MT58)
Item    Bits     Range       Resolution                   Contents
 t0,Q    8      0-10740 s       60 s      Epoch time/IODN
URA      4        0-15           1        Accuracy indicator
  x     26     42950 km      1.28 m      Position X in ECEF
  y     26     42950 km      1.28 m      Position Y in ECEF
  z     26     42950 km      1.28 m      Position Z in ECEF
 vx     24     4.194 km/s   0.5 mm/s     Velocity X in ECEF
 vy     24     4.194 km/s   0.5 mm/s     Velocity Y in ECEF
 vz     24     4.194 km/s   0.5 mm/s     Velocity Z in ECEF
 ..
 x       5     32 mm/s2      2 mm/s2     Acceleration X in ECEF (only perturbation)
 ..
 y       5     32 mm/s2      2 mm/s2     Acceleration Y in ECEF (only perturbation)
  ..
 z       5     32 mm/s2      2 mm/s2     Acceleration Z in ECEF (only perturbation)
aGf0    22     1.953 ms       2-30 s     Clock correction, offset
aGf1    13     3.725 ns/s    2-40 s/s    Clock correction, drift
Total   212                               Stored in 1 message (1sec)
                                                              ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                  SLIDE 14
 Generation of Ephemeris
                       QZS-1




                                        JAXA MCS


                             Decode                 Format
                            ephemeris             into MT58        L1-SAIF Users
                                        Compute
                                          PVA
                                                                  No need to receive
                                                                 QZS-L1-C/A (PRN 193)
    L1-C/A Users               Ephemeris Reconstruction
                      L1-SAIF Master Station (L1SMS) at ENRI
• Ephemeris information is generated based on reconstruction from MCS products
  broadcast on QZS-L1-C/A (PRN 193):
     L1SMS receives L1 C/A Nav message and extract QZS-1 PVA for generation of MT58.
• Users do not need to receive any signals other than L1-SAIF (PRN 183).
                                                          ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                              SLIDE 15
SV Position Error of MT58
                                                              QZS-1
                                                              Reconstructed from
                                                              broadcast Nav Msg
                                                              on L1C/A PRN 193
                                                              2011-08-18
                                                              00:00 to 24:00 GPST

                                                              Processing by ENRI
                                                              Assumed user location:
                                                                @ENRI, Tokyo




• Integration error in user receiver with regard to time after broadcast of
  MT58 with LTC (long-term correction) in MT24/25 messages;
• Range error is within 0.3m for 300 seconds integration.
     Note that ephemeris message of SBAS has timeout interval of 240-360s.
                                     ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                         SLIDE 16
User Receiver Setup




      JAVAD ALPHA-G3T with QZSS extension
                                                           ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                               SLIDE 17
HPE w/L1-SAIF Ranging
                                                  2011-08-18
                                                  02:18:45 to 21:16:20
                                                  L1-SAIF (PRN183) Ranging ON
                                                  L1SMS Configuration:
                                                    6 DF GPS GMS (GEONET)
                                                    4 SF GPS/QZS GMS (JAXA)
                                                  User location:
                                                    @ENRI, Tokyo
                                                  Receiver:
                                                    JAVAD ALPHA-G3T
                                                  Processing by ENRI
                                                    Mask 5deg, Smoothing 100s

L1-SAIF Correction   L1-SAIF Ranging   Hor RMS   Hor Max     Ver RMS       Ver Max
                          OFF          1.809 m   6.241 m     2.673 m       7.187 m
      OFF
                           ON          1.403 m   8.982 m     3.714 m       15.196 m
                          OFF          0.680 m   8.686 m     0.988 m       13.308 m
       ON
                           ON          0.658 m   2.494 m     0.937 m       4.682 m
                                                           ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                               SLIDE 18
HPE w/o L1-SAIF Ranging
                                                  2011-08-18
                                                  02:18:45 to 21:16:20
                                                  L1-SAIF (PRN183) Ranging OFF
                                                  L1SMS Configuration:
                                                    6 DF GPS GMS (GEONET)
                                                    4 SF GPS/QZS GMS (JAXA)
                                                  User location:
                                                    @ENRI, Tokyo
                                                  Receiver:
                                                    JAVAD ALPHA-G3T
                                                  Processing by ENRI
                                                    Mask 5deg, Smoothing 100s

L1-SAIF Correction   L1-SAIF Ranging   Hor RMS   Hor Max     Ver RMS       Ver Max
                          OFF          1.809 m   6.241 m     2.673 m       7.187 m
      OFF
                           ON          1.403 m   8.982 m     3.714 m       15.196 m
                          OFF          0.680 m   8.686 m     0.988 m       13.308 m
       ON
                           ON          0.658 m   2.494 m     0.937 m       4.682 m
                                                       ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                           SLIDE 19
Observed Residuals
                                                    2011-08-18
                                                    02:18:45 to 21:16:20
                                                    L1-SAIF Correction ON
                                                    L1SMS Configuration:
                                                      6 DF GPS GMS (GEONET)
                                                      4 SF GPS/QZS GMS (JAXA)
                                                    User location:
                                                      @ENRI, Tokyo
                                                    Receiver:
                                                      JAVAD ALPHA-G3T
                                                    Processing by ENRI
                                                      Mask 5deg, Smoothing 100s




• Residual error dependents upon elevation angle for GPS satellites;
• L1-SAIF: Looks small dependency.
                                                        ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                            SLIDE 20
Observed Residuals
                                                     2011-08-18
                                                     02:18:45 to 21:16:20
                                                     L1-SAIF Correction ON
                                                     L1SMS Configuration:
                                                       6 DF GPS GMS (GEONET)
                                                       4 SF GPS/QZS GMS (JAXA)
                                                     User location:
                                                       @ENRI, Tokyo
                                                     Receiver:
                                                       JAVAD ALPHA-G3T
                                                     Processing by ENRI
                                                       Mask 5deg, Smoothing 100s




• PRN 3 operates with Cs AFS; PRN 6 with Rb AFS;
• L1-SAIF is comparable to GPS signal; A bit noisy at high elevation.
                                                      ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                           SLIDE 21
Residuals on L1-SAIF
                                                    2011-08-18
                                                    02:18:45 to 21:16:20
                                                    L1-SAIF Correction ON
                                                    L1SMS Configuration:
                                                      6 DF GPS GMS (GEONET)
                                                      4 SF GPS/QZS GMS (JAXA)
                                                    User location:
                                                      @ENRI, Tokyo
                                                    Receiver:
                                                      JAVAD ALPHA-G3T
                                                    Processing by ENRI
                                                      Mask 5deg, Smoothing 100s


• Residual error within 1.8m from low to high elevation angle; 0.44m RMS;
• Observed a small uncorrected bias.
                                                     ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                         SLIDE 22
Residuals on GPS




  PRN 3 with Cs AFS                               PRN 6 with Rb AFS
       • RMS of residual error: 0.4 to 0.5m for GPS satellites;
       • Largely biased.
                                                                          ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                              SLIDE 23
   Continuous Observation
 • ENRI has been conducting continuous observation of L1-SAIF signal for technical
   verification since October 2011; Also observes other supplement signals;
 • Observation is available on the web: URL http://www.enri.go.jp/sat/qzss_e.htm
 • Range measurements are converted into RINEX format and navigation message is
   formatted in EMS file; Both are slightly extended for QZSS;
      Identifier: ‘J01’ for L1C/A and ‘S83’ for L1-SAIF.
 • Data files are stored on daily basis.

  Receiver       JAVAD ALPHA-G3T
                 ENRI, Tokyo - Top of the tower of No. 6 Building
  Antenna
                 35.679518936N 139.560964491E 109.1971m from ellipsoid
  Location
                 X=-3947737.9910 Y=3364428.7640 Z=3699428.9764
  Antenna        Trimble Zephyr Geodetic 2 (L1/L2/L5)
  Target SV      GPS, GLONASS, SBAS, QZSS (incl. L1-SAIF)
Measurements     Code Range, Carrier Range, Doppler, C/N0 (L1, L2, L5)
   Note - Sometimes there is missing data due to some reason such as power outage.
                                                           ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                               SLIDE 24
  QZSS L1-SAIF Data Source




QZSS L1-SAIF General Information                        List of RINEX Files
  http://www.enri.go.jp/sat/qzss_e.htm       http://www.enri.go.jp/cnspub/sat/data/rinex/

• URL http://www.enri.go.jp/sat/qzss_e.htm
• General Information, RINEX observation, EMS message archive, and schedule of
  L1-SAIF experiments by ENRI
                                                                ION ITM 30 Jan.-1 Feb. 2012 - ENRI
                                                                                    SLIDE 25
    Conclusion
• ENRI has been developing L1-SAIF signal:
    – Signal design: GPS/SBAS-like L1 C/A code (PRN 183);
    – Planned as an augmentation to mobile users.

• Ranging Function of L1-SAIF:
    – Available as an additional ranging source with self-contained Ephemeris Information;
    – L1-SAIF Master Station (L1SMS) has been upgraded to broadcast Ephemeris
      Information and Corrections for L1-SAIF signal itself;
    – Tested successfully; Confirmed that residual error was comparable to GPS;
    – Ranging function reduces the maximum position error for both horizontal and vertical.

• Ongoing work:
    – Experiments on mobile conditions;
    – Broadcasting corrections for MSAS and GLONASS satellites.

• L1-SAIF observation is available at http://www.enri.go.jp/sat/qzss_e.htm
        RINEX    http://www.enri.go.jp/cnspub/sat/data/rinex/
        EMS      http://www.enri.go.jp/cnspub/sat/data/ems/

				
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