From 4e3a7ad56e500e4a5a62f91cf1b59ccafd1afcda Mon Sep 17 00:00:00 2001 From: Thomas Schlichter Date: Mon, 17 Feb 2025 13:18:26 +0000 Subject: [PATCH] Extend NTN LEO example in RUNMODEM.md to include continuous Doppler compensation --- doc/RUNMODEM.md | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/doc/RUNMODEM.md b/doc/RUNMODEM.md index eb47a8f753..f2e71390c7 100644 --- a/doc/RUNMODEM.md +++ b/doc/RUNMODEM.md @@ -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 ``` # Specific OAI modes