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NR UE: calculate TA based on SIB19 information in NTN mode, if autonomous TA is not enabled

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This commit is contained in:
Thomas Schlichter
2025-11-19 10:05:45 +01:00
committed by francescomani
parent 654fadb116
commit b60a40ccbf
1 changed files with 39 additions and 30 deletions
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executables/nr-ue.c
+39 -30
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@@ -723,8 +723,37 @@ static inline int get_readBlockSize(uint16_t slot, NR_DL_FRAME_PARMS *fp) {
return rem_samples + next_slot_first_symbol;
}
static inline void apply_ntn_timing_advance(PHY_VARS_NR_UE *UE, const NR_DL_FRAME_PARMS *fp, int abs_subframe_tx)
{
const fapi_nr_dl_ntn_config_command_pdu *ntn_config_params = &UE->ntn_config_message->ntn_config_params;
const int abs_subframe_epoch = ntn_config_params->epoch_subframe
+ ntn_config_params->epoch_sfn * 10
+ ntn_config_params->epoch_hfn * 10240;
const int ms_since_epoch = abs_subframe_tx - abs_subframe_epoch;
const double total_ta_ms = ntn_config_params->ntn_total_time_advance_ms;
const double total_ta_drift = ntn_config_params->ntn_total_time_advance_drift; // µs/s
const double total_ta_drift_variant = ntn_config_params->ntn_total_time_advance_drift_variant; // µs/s²
UE->timing_advance = (total_ta_ms
+ (total_ta_drift / 1000.0) * (ms_since_epoch / 1000.0)
+ (total_ta_drift_variant / 1000.0) * (ms_since_epoch / 1000.0) * (ms_since_epoch / 1000.0))
* fp->samples_per_subframe;
LOG_D(PHY,
"total_ta_ms = %f ms, total_ta_drift = %f µs/s, total_ta_drift_variant = %f µs/s², ms_since_epoch = %d ms, "
"computed timing_advance = %d samples\n",
total_ta_ms,
total_ta_drift,
total_ta_drift_variant,
ms_since_epoch,
UE->timing_advance);
}
static inline void apply_ntn_config(PHY_VARS_NR_UE *UE,
NR_DL_FRAME_PARMS *fp,
int hfn_rx,
int frame_rx,
int slot_rx,
int *duration_rx_to_tx,
@@ -744,34 +773,8 @@ static inline void apply_ntn_config(PHY_VARS_NR_UE *UE,
*timing_advance -= fp->get_samples_slot_timestamp(slot_rx, fp, (*ntn_koffset - koffset) << mu);
*ntn_koffset = koffset;
const int abs_subframe_tx = 10 * frame_rx + ((slot_rx + *duration_rx_to_tx) >> mu);
const int abs_subframe_epoch =
10 * UE->ntn_config_message->ntn_config_params.epoch_sfn + UE->ntn_config_message->ntn_config_params.epoch_subframe;
int ms_since_epoch = abs_subframe_tx - abs_subframe_epoch;
// cope with sfn wrap-around
// this currently limits us to epoch times that are not more than 5.12 seconds in the future (allowed are up to 10.24 seconds)
// and ntn-UlSyncValidityDuration < 5.12 seconds (allowed are up to 900 seconds)
// TODO: fix this limitation by introducing the hyper frame number HFN
if (ms_since_epoch < -5120)
ms_since_epoch += 10240;
else if (ms_since_epoch > 5120)
ms_since_epoch -= 10240;
const double total_ta_ms = UE->ntn_config_message->ntn_config_params.ntn_total_time_advance_ms;
const double total_ta_drift = UE->ntn_config_message->ntn_config_params.ntn_total_time_advance_drift; // µs/s
const double total_ta_drift_variant = UE->ntn_config_message->ntn_config_params.ntn_total_time_advance_drift_variant; // µs/s²
UE->timing_advance = fp->samples_per_subframe * (total_ta_ms + (total_ta_drift / 1000.0) * (ms_since_epoch / 1000.0) + (total_ta_drift_variant / 1000.0) * (ms_since_epoch / 1000.0) * (ms_since_epoch / 1000.0));
LOG_I(PHY,
"k_offset = %d ms (%d slots), total_ta_ms = %f ms, total_ta_drift = %f µs/s, total_ta_drift_variant = %f µs/s², ms_since_epoch = %d ms, computed "
"timing_advance = %d samples\n",
*ntn_koffset,
*ntn_koffset << mu,
total_ta_ms,
total_ta_drift,
total_ta_drift_variant,
ms_since_epoch,
UE->timing_advance);
const int abs_subframe_tx = 10240 * hfn_rx + 10 * frame_rx + ((slot_rx + *duration_rx_to_tx) >> mu);
apply_ntn_timing_advance(UE, fp, abs_subframe_tx);
}
}
@@ -994,12 +997,18 @@ void *UE_thread(void *arg)
if (slot_nr == nb_slot_frame - 1) {
// we shift of half of measured drift, at each beginning of frame for both rx and tx
iq_shift_to_apply = shiftForNextFrame;
// TODO: remove this autonomous TA and use up-to-date values of ta-Common, ta-CommonDrift and ta-CommonDriftVariant from received SIB19 instead
// autonomous timing advance calculation, which does not use SIB19 information
if (get_nrUE_params()->autonomous_ta)
UE->timing_advance -= 2 * shiftForNextFrame;
shiftForNextFrame = -round(UE->max_pos_acc * get_nrUE_params()->time_sync_I);
}
// 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) {
const int abs_subframe_tx = (absolute_slot + duration_rx_to_tx) / fp->slots_per_subframe;
apply_ntn_timing_advance(UE, fp, abs_subframe_tx);
}
const int readBlockSize = get_readBlockSize(slot_nr, fp) - iq_shift_to_apply;
openair0_timestamp rx_timestamp;
int tmp = UE->rfdevice.trx_read_func(&UE->rfdevice, &rx_timestamp, rxp, readBlockSize, fp->nb_antennas_rx);
@@ -1068,7 +1077,7 @@ void *UE_thread(void *arg)
}
// apply new NTN timing information
apply_ntn_config(UE, fp, 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);
// 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