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Extend NTN LEO example in RUNMODEM.md to include continuous Doppler compensation

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Thomas Schlichter
2025-02-17 13:18:26 +00:00
parent 29ed144764
commit 4e3a7ad56e
1 changed files with 11 additions and 1 deletions
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12
doc/RUNMODEM.md
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@@ -141,6 +141,10 @@ Here are some useful command line options for the NR UE:
| `--initial-fo` | Sets the known initial frequency offset. Useful especially with large Doppler frequency, e.g. LEO satellite. |
| `--freq-sync-P` | Sets the coefficient for the Proportional part of the PI-controller for the continuous frequency offset compensation. Default value 0.01. |
| `--freq-sync-I` | Sets the coefficient for the Integrating part of the PI-controller for the continuous frequency offset compensation. Default value 0.001. |
| `--ntn-initial-time-drift` | Sets the initial NTN DL time drift (feeder link and service link), given in µs/s. |
| `--autonomous-ta` | Enables the autonomous TA update, based on DL drift (useful if main contribution to DL drift is movement, e.g. LEO satellite). |
| `--time-sync-P` | Sets the coefficient for the Proportional part of the PI-controller for the time synchronization. Default value 0.5. |
| `--time-sync-I` | Sets the coefficient for the Integrating part of the PI-controller for the time synchronization. Default value 0.0. |
| `--usrp-args` | Equivalent to the `sdr_addrs` field in the gNB config file. Used to identify the USRP and set some basic parameters (like the clock source). |
| `--clock-source` | Sets the clock source (internal or external). |
| `--time-source` | Sets the time source (internal or external). |
@@ -353,10 +357,16 @@ For LEO satellite scenarios, the parameter `--ntn-initial-time-drift` must be pr
This parameter provides the drift rate of the complete DL timing (incl. feeder link and service link) in µs/s.
Also, to perform an autonomous TA update based on the DL drift, the boolean parameter `--autonomous-ta` should be added in case of a LEO satellite scenario.
For LEO satellite scenario we assume the LO to be very accurate and the main FO contribution comes from Doppler shift.
Therefore, we use the command line parameter `--cont-fo-comp 2` to continuously compensate the DL Doppler and pre-compensate the UL Doppler.
The initial Doppler frequency offset must be provided via command line with the parameter `--initial-fo`.
For other information on optional NR UE command line options, please refer [here](#optional-nr-ue-command-line-options).
So an example NR UE command for FDD, 5MHz BW, 15 kHz SCS, transparent LEO satellite 5G NR NTN is this:
```
cd cmake_targets
sudo ./ran_build/build/nr-uesoftmodem -O ../targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf --band 254 -C 2488400000 --CO -873500000 -r 25 --numerology 0 --ssb 60 --rfsim --rfsimulator.prop_delay 20 --rfsimulator.options chanmod --time-sync-I 0.1 --ntn-initial-time-drift -46 --autonomous-ta
sudo ./ran_build/build/nr-uesoftmodem -O ../targets/PROJECTS/GENERIC-NR-5GC/CONF/ue.conf --band 254 -C 2488400000 --CO -873500000 -r 25 --numerology 0 --ssb 60 --rfsim --rfsimulator.prop_delay 20 --rfsimulator.options chanmod --time-sync-I 0.1 --ntn-initial-time-drift -46 --autonomous-ta --initial-fo 57340 --cont-fo-comp 2
```
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