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NR UE: set time sync PI controller integral weight to 0.0 by default

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Experiments did show that the time sync is less stable in terrestrial mode if the integral part of the PI controller is used.
So set it to 0.0 by default. For NTN LEO use case we can still use it by providing the command line parameter --time-sync-I 0.2 .
fixes #846
This commit is contained in:
Thomas Schlichter
2024-09-27 12:19:25 +02:00
parent 64380eaca2
commit 791cc4f648
3 changed files with 7 additions and 3 deletions
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2
doc/RUNMODEM.md
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@@ -298,7 +298,7 @@ Also, to perform an autonomous TA update based on the DL drift, the boolean para
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 --band 66 -C 2152680000 --CO -400000000 -r 25 --numerology 0 --ssb 48 --sa --rfsim --rfsimulator.prop_delay 20 --rfsimulator.options chanmod -O ../targets/PROJECTS/GENERIC-NR-5GC/CONF/channelmod_rfsimu_LEO_satellite.conf --ntn-koffset 40 --ntn-ta-common 37.74 --ntn-ta-commondrift -50 --autonomous-ta
sudo ./ran_build/build/nr-uesoftmodem --band 66 -C 2152680000 --CO -400000000 -r 25 --numerology 0 --ssb 48 --sa --rfsim --rfsimulator.prop_delay 20 --rfsimulator.options chanmod -O ../targets/PROJECTS/GENERIC-NR-5GC/CONF/channelmod_rfsimu_LEO_satellite.conf --time-sync-I 0.2 --ntn-koffset 40 --ntn-ta-common 37.74 --ntn-ta-commondrift -50 --autonomous-ta
```
# Specific OAI modes

6
executables/nr-ue.c
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@@ -883,7 +883,11 @@ void *UE_thread(void *arg)
stream_status = STREAM_STATUS_SYNCING;
syncInFrame(UE, &sync_timestamp, intialSyncOffset);
openair0_write_reorder_clear_context(&UE->rfdevice);
UE->max_pos_acc = get_nrUE_params()->ntn_ta_commondrift * 1e-6 * fp->samples_per_frame / get_nrUE_params()->time_sync_I; // ntn_ta_commondrift is in µs/s, max_pos_acc * time_sync_I is in samples/frame
if (get_nrUE_params()->time_sync_I)
// ntn_ta_commondrift is in µs/s, max_pos_acc * time_sync_I is in samples/frame
UE->max_pos_acc = get_nrUE_params()->ntn_ta_commondrift * 1e-6 * fp->samples_per_frame / get_nrUE_params()->time_sync_I;
else
UE->max_pos_acc = 0;
shiftForNextFrame = -(UE->init_sync_frame + trashed_frames + 2) * UE->max_pos_acc * get_nrUE_params()->time_sync_I; // compensate for the time drift that happened during initial sync
LOG_D(PHY, "max_pos_acc = %d, shiftForNextFrame = %d\n", UE->max_pos_acc, shiftForNextFrame);
// TODO: remove this autonomous TA and use up-to-date values of ta-Common, ta-CommonDrift and ta-CommonDriftVariant from received SIB19 instead

2
executables/nr-uesoftmodem.h
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@@ -65,7 +65,7 @@
{"SLC", CONFIG_HLP_SLF, 0, .u64ptr=&(sidelink_frequency[0][0]), .defuintval=2600000000,TYPE_UINT64,0}, \
{"num-ues", NULL, 0, .iptr=&(NB_UE_INST), .defuintval=1, TYPE_INT, 0}, \
{"time-sync-P", CONFIG_HLP_TIME_SYNC_P, 0, .dblptr=&(nrUE_params.time_sync_P), .defdblval=0.5, TYPE_DOUBLE, 0}, \
{"time-sync-I", CONFIG_HLP_TIME_SYNC_I, 0, .dblptr=&(nrUE_params.time_sync_I), .defdblval=0.2, TYPE_DOUBLE, 0}, \
{"time-sync-I", CONFIG_HLP_TIME_SYNC_I, 0, .dblptr=&(nrUE_params.time_sync_I), .defdblval=0.0, TYPE_DOUBLE, 0}, \
{"ntn-koffset", CONFIG_HLP_NTN_KOFFSET, 0, .uptr=&(nrUE_params.ntn_koffset), .defuintval=0, TYPE_UINT, 0}, \
{"ntn-ta-common", CONFIG_HLP_NTN_TA_COMMON, 0, .dblptr=&(nrUE_params.ntn_ta_common), .defdblval=0.0, TYPE_DOUBLE, 0}, \
{"ntn-ta-commondrift", CONFIG_HLP_NTN_TA_COMMONDRIFT, 0, .dblptr=&(nrUE_params.ntn_ta_commondrift), .defdblval=0.0, TYPE_DOUBLE, 0}, \