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RACELOGIC Support Centre

09 - SatGen Wideband

SatGen v3 Wideband can create signals in the upper and lower L band and will take advantage of the LabSat 3 Wideband ability to read RF data at up to 80 MB/s. SatGen v3 is able to create the following signals in 1, 2 & 3 bit I & Q Format: GPS L1C/A, L1P, L1M1, L2C, L2P, L2M1, L5I, L5Q, GLONASS L1OF, L2OF, BeiDou B1I, B1-2I, B2I.

SatGen v3 Wideband Signals Description

 

Signal Description
GPS L1 C/A

Transmitted by all GPS satellites on the L1 (1575.42 MHz) frequency. The most important signal for civilian applications, accepted by a huge majority of GNSS receivers around the globe.

GPS L1 P & GPS L2 P

Transmitted by all GPS satellites on the L1 (1575.42 MHz) and the L2 (1227.6 MHz) frequencies. They are precision military signals, normally encrypted and referred as the P(Y) code. The encryption algorithm is classified, but receiver manufacturers managed to develop special codeless or semi-codeless techniques to acquire L1P(Y) and L2P(Y).

The position accuracy is improved, because dual-frequency receivers can now measure the difference between signal reception times between the two frequencies and calculate the exact value of the ionospheric delay (which is the main source of error). All receivers accepting the P(Y) code will also accept the unencrypted P code simulated by SatGen.

GPS L2 C

Transmitted by GPS IIR-M and newer satellites on the L2 (1227.6 MHz) frequency. It is the second civilian signal and the fact that it is transmitted on a different frequency than L1C/A makes it possible to measure the ionospheric delay and improve accuracy. Dual frequency civilian receivers can now provide the same level of accuracy as military receivers which use L1P(Y) and L2P(Y).

GPS L5 I & L5 Q

Transmitted by GPS IIF and newer satellites on the L5 (1176.45 MHz) frequency. It is a signal intended for life critical applications such as aircraft precision approach guidance. It consists of two signals L5 I and L5 Q transmitted on the same frequency. The L5 I signal is modulated by the navigation message. The L5 Q signal does not carry any data.

GPS L1 M & GPS L2 M

Transmitted by GPS IIR-M and newer satellites on the L1 (1575.42 MHz) and the L2 (1227.6 MHz) frequencies. They are modernised military signals intended to eventually replace L1P(Y) and L2P(Y). Very little has been published about them, but the modulation details are known and SatGen can transmit random data using the BOCsin (10,5) modulation and create signals matching the M-Code spectral characteristics.

GLONASS L1 OF

Transmitted by all GLONASS satellites on the GLONASS L1 frequency band (14 channels around the 1602 MHz nominal frequency). Standard precision civilian signal. Compared to GPS, thanks to more inclined orbits of GLONASS satellites, it is more suitable for navigation in the polar regions.

GLONASS L2 OF

Transmitted by GLONASS-M and newer satellites on the GLONASS L2 frequency band (14 channels around the 1246 MHz nominal frequency).

Standard precision civilian signal, identical to L1 OF (but with smaller channel spacing). The fact that it is transmitted on a different frequency band than L1 OF makes it possible to measure the ionospheric delay and improve accuracy when using a dual frequency receiver.

BEIDOU B1I, B1-2I

Transmitted by all BeiDou satellites on the B1 (1561.098 MHz) and the B1-2 (1589.742 MHz) frequency. Standard precision civilian signal, very similar to GPS L1C/A.

BEIDOU B2I

Transmitted by all BeiDou satellites on the B2 (1207.14 MHz) frequency. Standard precision civilian signal, identical to B1I. The fact that it is transmitted on a different frequency than B1I makes it possible to measure the ionospheric delay and improve accuracy when using a dual frequency receiver.

 

SatGen v3 Wideband Signal Description

Signals can be generally split into two categories; narrowband and wideband.

  • Narrowband: Signals have a modulation (chipping code) frequency of no more than a few megahertz, e.g. GPS L1C/A (1.023 MHz), GLONASS L1OF (0.511 MHz), BeiDou B1I (2.046 MHz).
  • Wideband: Signals use a modulation (chipping code) frequency of 10 or more megahertz, e.g. GPS L1P (10.23 MHz), GPS L5 (10.23 MHz).


When SatGen v3 Wideband simulates signals transmitted on no more than 3 frequencies, the following conditions will apply:

  • Each frequency band is transmitted on a different LabSat 3 Wideband output channel.
  • For narrowband signals the 10.5 MHz sampling rate and 10 MHz bandwidth is used.
  • For wideband signals, a 24, 30 or 32 MHz bandwidth is used depending on the actual signals used. If a single wideband signal is present, all output channels are forced to use a high sampling rate.
     
 

When SatGen v3 Wideband simulates signals transmitted on more than 3 frequencies:

  • The signals transmitted on frequencies which are close to each other are grouped together to form very wide output channels.
  • The following groups are examples of the grouping that can be used:
    • L1 with GPS L1C/A, GPS L1P, GPS L1M, GLONASS L1OF, BeiDou B1I and BeiDou B1-2I.
    • L2 with GPS L2C, GPS L2P, GPS L2M, GLONASS L2OF and BeiDou B2I.
    • L5 with GPS L5I and GPS L5Q.


To maximise performance, SatGen v3 software uses a sophisticated algorithm to create the correct centre frequency and bandwidth depending upon the signal required. The actual parameters used within the scenario can easily be checked by looking at the .ini file produced alongside the .LS3W scenario file on the PC.

Quantisation selection for SatGen v3 Wideband

LabSat 3 Wideband supports 1, 2 and 3-bit quantisation. The device has an internal data transfer limit, which is 70 MB/s for recording and 95 MB/s for replay. SatGen v3 simulations can't exceed the data transfer limit and 3-bit quantisation is disabled when 3 channels with wideband signals are used.


This means that the following combination of 3 narrowband signals can be simulated in 3-bit:

  • GPS L1C/A, GLONASS L1OF, BeiDou B1I.


However, the combination below which also has 3 signals, but includes a wideband signal, will be restricted to 2 bits:

  • GPS L1P, GLONASS L1OF, BeiDou B1I.
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