L-band Tracking and Data Output without GPS

Positioning Leadership
APN-043 Rev 1
December 11, 2007
L-band Tracking and Data Output without GPS
This application note describes the OmniSTAR demodulator features that allow the receiver to track Lband signals without the assistance of GPS. It is only available with OEMV 3.300 firmware or later.
GPS signals are normally used to steer the receiver's Voltage Controlled Temperature Compensated Crystal
Oscillator (VTCXO). With a more accurate VTCXO, the L-band signal can be acquired more readily.
However, with the GPS signals gone, the receiver must use a wider and more efficient search algorithm to
find the L-band signal.
This feature introduces the NL model which has 1 L-band OmniSTAR-enabled channel. Table 1, below, is
the VERSION log’s Model Designators table. Refer to the OEMV Family Firmware Reference Manual,
available from our website at www.novatel.com. There you can find details on the VERSION log and other
commands and logs mentioned in this application note.
Table 1 Model Designators
G
12 L1 or 12 L1/L2 GLONASS channels, frequencies to match GPS configuration
R
Receive RT2 and/or RT20 corrections
I
Synchronized Position Attitude Navigation (SPAN)
J
SPAN supporting 200 Hz IMUs and IGI higher rate IMU (256.144 Hz)
S
Reduces positions and measurement rates to 5 Hz, disables VARF and EVENT signals
A
Application Program Interface (API)
L
1 L-band channel with CDGPS and OmniSTAR HP/XP capability
NL
1 L-band channel with OmniSTAR enabled and no position, velocity, time (PVT)
or raw data output
B
1 L-band channel with CDGPS and OmniSTAR VBS capability
F
50 Hz output
When the receiver tracks an L-band signal, CDGPS or OmniSTAR, it saves the TCXO offset in NonVolatile Memory (NVM). The TCXO offset is the difference between the assigned frequency and the
actual tracking frequency. This allows the receiver to track L-band signals more quickly in future restarts
by centering the search for the signal around the known TCXO offset. The offset data is stored in NVM
with type LBAND_TCXO_OFFSET. The receiver updates the offset in NVM whenever the L-band signal
is tracking and the offset measures 50 Hz away from the currently stored value.
See also the ASSIGNLBAND command, starting on Page 2, for the new OMNISTARNARROW mode in
Table 2 L-band Mode on Page 3. Compared to the OMNISTAR mode, this mode uses a narrower search
window, and the L-band TCXO offset information, to look for the L-band signal. The L-band TCXO offset
information is only used in OMNISTARNARROW mode.
The tracking field, Field #6, of the LBANDSTAT log, now has the IDLE possible value, see Page 5. See
also the LBANDSTAT log starting on Page 4.
-1-
ASSIGNLBAND
Command to set L-band satellite
communication parameters
You must use this command to ensure that the receiver searches for a specified L-band satellite at a
specified frequency with a specified baud rate. The factory parameter default is ASSIGNLBAND IDLE.
Abbreviated ASCII Syntax:
Message ID: 729
ASSIGNLBAND mode freq baud
Factory Default:
assignlband idle
ASCII Example 1:
assignlband cdgps 1547547 4800
ASCII Example 2:
assignlband idle
ASCII Example 3:
assignlband omnistarnarrow 1535137500 1200
Field
Type
Field
ASCII
Value
1
ASSIGNLBAND
header
-
2
mode
See
Binary
Value
-
Binary
Format
Description
Binary
Bytes
Binary
Offset
This field contains the
command name or the
message header depending
on whether the command is
abbreviated ASCII, ASCII or
binary, respectively.
-
H
0
Set the mode and enter
specific frequency and baud
rate values
Enum
4
H
Table 2 L-band
Mode on Page 3
3
freq
1525000 to
1560000
or
1525000000 to
1560000000
L-band service beam
frequency of satellite (Hz or
kHz). See also Beam
Frequencies on Page 4
(default = 1536782 if the
mode is OMNISTAR)
Ulong
4
H+4
4
baud
300, 600, 1200,
2400 or 4800
Data rate for communication
with L-band satellite
(default = 1200)
Ulong
4
H+8
-2-
Table 2 L-band Mode
Binary
ASCII
Description
0
1
OMNISTAR
When you select OmniSTAR, enter a dedicated frequency and baud rate.
2
CDGPS
When you select CDGPS, enter a dedicated frequency and baud rate.
3
IDLE
When you select IDLE, the receiver is configured to stop tracking any L-band
satellites. The 'freq' and 'baud' fields are optional so that you may select IDLE
without specifying the other fields.
4
OMNISTARAUTO
When you select OMNISTARAUTO, the receiver automatically selects the best
OmniSTAR beam to track based on the receiver’s position. This requires the
receiver to have a downloaded satellite list from an OmniSTAR satellite.
Therefore, a manual assignment is necessary the first time an OmniSTAR
satellite is assigned on a new receiver. After collection, the satellite list is stored
in NVM for subsequent auto assignments. Lists are considered valid for 6
months and are constantly updated while an OmniSTAR signal is tracking. If the
receiver has a valid satellite list, it is reported in a status bit in the LBANDSTAT
log, see Page 4. 1
This OmniSTAR mode does not use the TCXO offset information (see also
OMNISTARNARROW in the row below).
5
OMNISTARNARROW
When you select OMNISTARNARROW, enter a dedicated frequency and baud
rate.
For re-acquisitions of the L-band signal, the receiver uses a 1500 Hz search
window and the stored TCXO offset information.
To remove the TCXO offset information from NVM, use the FRESET
LBAND_TCXO_OFFSET command. A standard FRESET command does not do
this, see Page 10.
1
The receiver always tracks an available local beam over a global beam. The receiver constantly
monitors the satellite list to ensure it is tracking the best one and automatically switches beams if it
is not. You can view the satellite list by logging the OMNIVIS log. Refer to the OEMV Family
Firmware Reference Manual.
-3-
Beam Frequencies
You can switch between OmniSTAR VBS and CDGPS by using the following commands:
Use CDGPS
assignlband cdgps <freq> 4800
psrdiffsource cdgps
Use OmniSTAR VBS
assignlband omnistar <freq> 1200
psrdiffsource omnistar
Where <freq> is determined for CDGPS or OmniSTAR as follows:
1. CDGPS beam frequency chart:
• East
• East-Central
• West-Central
• West
1547646 or 1547646000
1557897 or 1557897000
1557571 or 1557571000
1547547 or 1547547000
2. The OmniSTAR beam frequency chart can be found at http://www.omnistar.com/chart.html.
For example:
Eastern US (Coverage is Northern Canada to southern Mexico) 1530359 or 1530359000
LBANDSTAT
Log to output L-band status information
This log outputs status information for a standard L-band, OmniSTAR XP (Extra Precision) or OmniSTAR
HP (High Performance) service.
Message ID:
Log Type:
731
Asynch
Recommended Input:
log lbandstata ontime 1
ASCII Example:
#LBANDSTATA,COM1,0,73.5,FINESTEERING,1314,494510.000,00000000,c797,1846;
1551488896,43.19,62.3,0.00,0082,0000,7235,11,0,0000,0001,7762,04000000,0
*93f7d2af
-4-
Field
#
Field Type
Data Description
1
LBANDSTAT
header
Log header
2
freq
Measured frequency of L-band signal (Hz)
3
C/No
4
locktime
5
Reserved
6
tracking
7
Format
Binary
Bytes
Binary
Offset
H
0
Ulong
4
H
Carrier to noise density ratio (dB-Hz)
Float
4
H+4
Number of seconds of continuous tracking (no
cycle slipping)
Float
4
H+8
Float
4
H+12
Tracking status of L-band signal (see Table 3 Lband Signal Tracking Status on Page 6)
Hex
2
H+16
VBS status
Status word for OmniSTAR VBS (see Table 4
OmniSTAR VBS Status Word on Page 7)
Hex
2
H+18
8
#bytes
Number of bytes fed to the standard process
Ulong
4
H+20
9
#good dgps
Number of standard updates
Ulong
4
H+24
10
#bad data
Number of missing standard updates
Ulong
4
H+28
11
Hex
Reserved (the hp status 1 field is obsolete and has been replaced
by the longer OmniSTAR HP Status field. The shorter legacy status
here is maintained for backward compatibility)
2
H+32
12
hp status 2
Additional status pertaining to the HP or XP
process (see Table 5 OmniSTAR HP/XP
Additional Status Word on Page 8)
Hex
2
H+34
13
#bytes hp
Number of bytes fed to the HP or XP process
Ulong
4
H+36
14
hp status
Status from the HP or XP process (see Table 6
HP/XP Status Word on Page 9)
Hex
4
H+40
15
Reserved
Hex
4
H+44
16
xxxx
32-bit CRC (ASCII and Binary only)
Hex
4
H+48
17
[CR][LF]
Sentence terminator (ASCII only)
-
-
-
-5-
Table 3 L-band Signal Tracking Status
Nibble #
N0
N1
N2
N3
Bit #
Mask
Description
Range Value
0
0x0001
1
0x0002
2
0x0004
3
0x0008
4
0x0010
5
0x0020
6
0x0040
Bit Timing Lock
0 = Not Locked, 1 = Locked
7
0x0080
Phase Locked
0 = Not Locked, 1 = Locked
8
0x0100
DC Offset Unlocked
0 = Good, 1 = Warning
9
0x0200
AGC Unlocked
0 = Good, 1 = Warning
10
0x0400
11
0x0800
12
0x1000
13
0x2000
14
0x4000
15
0x8000
Tracking State
0 = Searching, 1 = Pull-in,
2 = Tracking, 3 = Idle
Reserved
Reserved
Error
0 = Good, 1 = Error
-6-
Table 4 OmniSTAR VBS Status Word
Nibble #
N0
N1
N2
N3
2
Bit #
Mask
Description
0
0x0001
Subscription Expired
1
0x0002
2
Bit = 0
2
Bit = 1
False
True
Out of Region
False
True
0x0004
Wet Error
False
True
3
0x0008
Link Error
False
True
4
0x0010
No Remote Sites
False
True
5
0x0020
No Almanac
False
True
6
0x0040
No Position
False
True
7
0x0080
No Time
False
True
8
0x0100
Reserved
9
0x0200
10
0x0400
11
0x0800
12
0x1000
13
0x2000
14
0x4000
15
0x8000
False
True
Updating Data
Contact OmniSTAR for subscription support. All other status values are updated by collecting
OmniSTAR data for 20-35 minutes.
-7-
Table 5 OmniSTAR HP/XP Additional Status Word
Nibble #
N0
N1
N2
N3
3
Bit #
Mask
Description
Bit = 0
Bit = 1
0
0x0001
Solution not fully converged
False
True
1
0x0002
OmniSTAR satellite list
available
False
True
2
0x0004
Reserved
3
0x0008
4
0x0010
HP not authorized 3
Authorized
Unauthorized
5
0x0020
XP not authorized 3
Authorized
Unauthorized
6
0x0040
Reserved
7
0x0080
8
0x0100
9
0x0200
10
0x0400
11
0x0800
12
0x1000
13
0x2000
14
0x4000
15
0x8000
This authorization is related to the receiver model and not the OmniSTAR subscription. To view
OmniSTAR subscription information use the LBANDINFO log, refer to the OEMV Family
Firmware Reference Manual.
-8-
Table 6 HP/XP Status Word
Nibble #
N0
N1
N2
N3-N5
Bit #
Mask
Description
0
0x00000001
Subscription Expired
1
0x00000002
2
Bit = 0
4
Bit = 1
False
True
Out of Region
False
True
0x00000004
Wet Error
False
True
3
0x00000008
Link Error
False
True
4
0x00000010
No Measurements
False
True
5
0x00000020
No Ephemeris
False
True
6
0x00000040
No Initial Position
False
True
7
0x00000080
No Time Set
False
True
8
0x00000100
Velocity Error
False
True
9
0x00000200
No base stations
False
True
10
0x00000400
No Mapping Message
False
True
11
Reserved
Static Initialization Mode
False
True
Updating Data
False
True
12-23
24-25
N6
N7
26
0x04000000
27
Reserved
28-30
31
4
0x80000000
Contact OmniSTAR for subscription support. All other status values are updated by collecting
OmniSTAR data for 20-35 minutes.
-9-
FRESET
Command to clear selected data from NVM and reset
This command clears data stored in NVM. Such data includes the almanac, ephemeris, and any userspecific configurations. The commands, ephemeris, almanac, and L-band related data, excluding the
subscription information, can be cleared by using the STANDARD target. The model can only be cleared
by using the MODEL target. The receiver is forced to hardware reset. In addition, values entered using the
CLOCKCALIBRATE, or the ASSIGNLBAND OMNISTARNARROW, command can only be cleared by
using their respective targets. See also Table 7 FRESET Target on Page 11.
FRESET STANDARD (which is also the default) causes any commands, ephemeris, GPS almanac
and SBAS almanac data (COMMAND, GPSALMANAC, GPSEPHEM and SBASALMANAC in
Table 7 on Page 11) previously saved to NVM to be erased.
Abbreviated ASCII Syntax:
Message ID: 20
FRESET [target]
Input Example:
freset command
Field
Field
Type
ASCII
Value
Binary
Value
1
FRESET
header
-
-
2
target
See Table 7
FRESET Target
on Page 11
Binary
Format
Description
Binary
Bytes
Binary
Offset
This field contains the command
name or the message header
depending on whether the
command is abbreviated ASCII,
ASCII or binary, respectively.
-
H
0
Data to be reset by the receiver
Enum
4
H
- 10 -
Table 7 FRESET Target
Binary
ASCII
Description
0
STANDARD
Resets commands, ephemeris, and
almanac (default). Also resets L-band
related data except for subscription
information.
1
COMMAND
Resets the stored commands (saved
configuration)
2
GPSALMANAC
Resets the stored GPS almanac
3
GPSEPHEM
Resets the stored GPS ephemeris
4
GLOEPHEM
Resets the stored GLONASS ephemeris
5
MODEL
Resets the currently selected model
11
CLKCALIBRATION
Resets the parameters entered using the
CLOCKCALIBRATE command
20
SBASALMANAC
Resets the stored SBAS almanac
21
LAST_POSITION
Resets the position using the last stored
position
31
GLOALMANAC
Resets the stored GLONASS almanac
38
LBAND_TCXO_OFFSET
Removes the TCXO offset information
from NVM (entered using the
ASSIGNLBAND command)
Final Points
If you require any further information regarding the topics covered within this
application, please contact:
NovAtel Customer Service
1120 – 68 Ave. N.E.
Calgary, Alberta, Canada, T2E 8S5
Phone:
+1-800-NOVATEL (in Canada or the U.S.) or +1-403-295-4500
Fax:
+1-403-295-4501
E-mail:
support@novatel.com
Website:
www.novatel.com
- 11 -
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