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NR UE: correctly apply Doppler and TA for NTN target cell

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Make sure to apply Doppler and TA not directly when receiving the target cell ntn_config,
but apply Doppler just before the initial sync, and the TA after the initial sync when
we have tha actuel cell frame and slot numbers.
This commit is contained in:
Thomas Schlichter
2025-12-19 16:42:52 +01:00
parent 3dcaacb63b
commit 1f8fe224a0
3 changed files with 59 additions and 32 deletions
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executables/nr-ue.c
+50 -29
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@@ -523,7 +523,7 @@ static int handle_sync_req_from_mac(PHY_VARS_NR_UE *UE)
}
// Apply Doppler based on NTN-Config for target cell
if (UE->target_Nid_cell != fp->Nid_cell)
if (UE->nrUE_config.ntn_config.is_targetcell)
apply_ntn_timing_advance_and_doppler(UE, fp, -1);
// Apply NTN DL Doppler as initial FO
UE->initial_fo = UE->dl_Doppler_shift;
@@ -857,37 +857,46 @@ static void apply_ntn_config(PHY_VARS_NR_UE *UE,
int slot_rx,
int *duration_rx_to_tx,
int *timing_advance,
int *ntn_koffset)
int *ntn_koffset,
bool *ntn_targetcell)
{
if (UE->nrUE_config.ntn_config.params_changed) {
UE->nrUE_config.ntn_config.params_changed = false;
// return if there is no pending update
if (!UE->nrUE_config.ntn_config.params_changed)
return;
const fapi_nr_ntn_config_t *ntn_config_params = &UE->nrUE_config.ntn_config;
*ntn_targetcell = UE->nrUE_config.ntn_config.is_targetcell;
const int mu = fp->numerology_index;
const int koffset = ntn_config_params->cell_specific_k_offset;
// skip update if it is for the target cell
if (UE->nrUE_config.ntn_config.is_targetcell)
return;
*duration_rx_to_tx = NR_UE_CAPABILITY_SLOT_RX_TO_TX + (koffset << mu);
if (koffset > *ntn_koffset)
*timing_advance += get_samples_slot_duration(fp, slot_rx, (koffset - *ntn_koffset) << mu);
else if (koffset < *ntn_koffset)
*timing_advance -= get_samples_slot_duration(fp, slot_rx, (*ntn_koffset - koffset) << mu);
*ntn_koffset = koffset;
UE->nrUE_config.ntn_config.params_changed = false;
const int abs_subframe_tx = 10240 * hfn_rx + 10 * frame_rx + ((slot_rx + *duration_rx_to_tx) >> mu);
apply_ntn_timing_advance_and_doppler(UE, fp, abs_subframe_tx);
const fapi_nr_ntn_config_t *ntn_config_params = &UE->nrUE_config.ntn_config;
LOG_I(PHY,
"k_offset: %dms, N_Common_Ta: %fms, drift: %fµs/s, variant: %fµs/s², "
"timing_advance_ntn: %d samples, DL Doppler shift: %fkHz, UL Doppler shift: %fkHz\n",
koffset << mu,
ntn_config_params->N_common_ta_adj,
ntn_config_params->N_common_ta_drift,
ntn_config_params->N_common_ta_drift_variant,
UE->timing_advance_ntn,
UE->dl_Doppler_shift / 1000,
UE->ul_Doppler_shift / 1000);
}
const int mu = fp->numerology_index;
const int koffset = ntn_config_params->cell_specific_k_offset;
*duration_rx_to_tx = NR_UE_CAPABILITY_SLOT_RX_TO_TX + (koffset << mu);
if (koffset > *ntn_koffset)
*timing_advance += get_samples_slot_duration(fp, slot_rx, (koffset - *ntn_koffset) << mu);
else if (koffset < *ntn_koffset)
*timing_advance -= get_samples_slot_duration(fp, slot_rx, (*ntn_koffset - koffset) << mu);
*ntn_koffset = koffset;
const int abs_subframe_tx = 10240 * hfn_rx + 10 * frame_rx + ((slot_rx + *duration_rx_to_tx) >> mu);
apply_ntn_timing_advance_and_doppler(UE, fp, abs_subframe_tx);
LOG_I(PHY,
"k_offset: %dms, N_Common_Ta: %fms, drift: %fµs/s, variant: %fµs/s², "
"timing_advance_ntn: %d samples, DL Doppler shift: %fkHz, UL Doppler shift: %fkHz\n",
koffset << mu,
ntn_config_params->N_common_ta_adj,
ntn_config_params->N_common_ta_drift,
ntn_config_params->N_common_ta_drift_variant,
UE->timing_advance_ntn,
UE->dl_Doppler_shift / 1000,
UE->ul_Doppler_shift / 1000);
}
void *UE_thread(void *arg)
@@ -929,6 +938,7 @@ void *UE_thread(void *arg)
else
UE->max_pos_acc = 0;
bool ntn_targetcell = false;
int ntn_koffset = 0;
int duration_rx_to_tx = NR_UE_CAPABILITY_SLOT_RX_TO_TX;
int timing_advance = UE->timing_advance + UE->timing_advance_ntn;
@@ -1057,12 +1067,14 @@ void *UE_thread(void *arg)
const int frame_rx = (absolute_slot / nb_slot_frame) % 1024;
const int hfn_rx = (absolute_slot / nb_slot_frame) / 1024;
fix_ntn_epoch_hfn(UE, hfn_rx, frame_rx);
UE->nrUE_config.ntn_config.is_targetcell = false;
if (UE->nrUE_config.ntn_config.params_changed) {
apply_ntn_config(UE, fp, hfn_rx, frame_rx, 0, &duration_rx_to_tx, &timing_advance, &ntn_koffset);
apply_ntn_config(UE, fp, hfn_rx, frame_rx, 0, &duration_rx_to_tx, &timing_advance, &ntn_koffset, &ntn_targetcell);
} else {
const int mu = fp->numerology_index;
const int abs_subframe_tx = 10240 * hfn_rx + 10 * frame_rx + (duration_rx_to_tx >> mu);
apply_ntn_timing_advance_and_doppler(UE, fp, abs_subframe_tx);
ntn_targetcell = false;
}
UE->timing_advance = 0;
// We have resynchronized, maybe after RF loss so we need to purge any existing context
@@ -1124,7 +1136,8 @@ void *UE_thread(void *arg)
}
// Calculate new TA based on SIB19 information for each subframe in NTN mode, if "autonomous_ta" is not enabled
if (ntn_koffset && !get_nrUE_params()->autonomous_ta && (absolute_slot + duration_rx_to_tx) % fp->slots_per_subframe == 0) {
if (ntn_koffset && !ntn_targetcell && !get_nrUE_params()->autonomous_ta
&& (absolute_slot + duration_rx_to_tx) % fp->slots_per_subframe == 0) {
const int abs_subframe_tx = (absolute_slot + duration_rx_to_tx) / fp->slots_per_subframe;
apply_ntn_timing_advance_and_doppler(UE, fp, abs_subframe_tx);
}
@@ -1202,7 +1215,15 @@ void *UE_thread(void *arg)
}
// apply new NTN timing information
apply_ntn_config(UE, fp, curMsg.proc.hfn_rx, curMsg.proc.frame_rx, curMsg.proc.nr_slot_rx, &duration_rx_to_tx, &timing_advance, &ntn_koffset);
apply_ntn_config(UE,
fp,
curMsg.proc.hfn_rx,
curMsg.proc.frame_rx,
curMsg.proc.nr_slot_rx,
&duration_rx_to_tx,
&timing_advance,
&ntn_koffset,
&ntn_targetcell);
// Start TX slot processing here. It runs in parallel with RX slot processing
// in current code, DURATION_RX_TO_TX constant is the limit to get UL data to encode from a RX slot