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feature: Estimate CFO from CSI-RS tracking signal

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TRS resources if configured by gnb, is present in two consequtive slots
and two symbols per slot. LS estimates from the first symbol is saved
and in second symbol frequency offset and time offset is estimated. The
estimated FO is saved in UE global structure which is used in the last
TRS slot. If the FO is above a threshold, the radio's center frequency
is adjusted.

Time offset is estimated but not used because time is already tracked
using PBCH DMRS.

Signed-off-by: Sakthivel Velumani <s.velumani@northeastern.edu>
This commit is contained in:
Sakthivel Velumani
2025-08-05 23:03:31 -04:00
parent 0dab3bb6a1
commit 7729bab5af
9 changed files with 202 additions and 49 deletions
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17
executables/nr-ue.c
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@@ -215,9 +215,8 @@ static void UE_synch(void *arg) {
((ret.rx_offset << 1) / fp->samples_per_subframe * fp->slots_per_subframe)
+ round((float)((ret.rx_offset << 1) % fp->samples_per_subframe) / fp->samples_per_slot0);
if (get_nrUE_params()->cont_fo_comp) {
UE->freq_offset = freq_offset - UE->dl_Doppler_shift;
} else {
UE->freq_offset = freq_offset - UE->dl_Doppler_shift;
if (!get_nrUE_params()->cont_fo_comp) {
// rerun with new cell parameters and frequency-offset
nrue_ru_set_freq(UE, ul_carrier, dl_carrier, freq_offset);
}
@@ -711,6 +710,18 @@ static inline int get_readBlockSize(uint16_t slot, const NR_DL_FRAME_PARMS *fp)
return rem_samples + next_slot_first_symbol;
}
void trs_freq_correction(PHY_VARS_NR_UE *ue, int cfo)
{
if (abs(cfo) > TRS_CFO_THRESH) {
LOG_A(PHY, "CFO estimated (%d) from TRS exceeded threshold (%d). Adjusting radio CF\n", cfo, TRS_CFO_THRESH);
ue->freq_offset += cfo;
uint64_t dl_carrier;
uint64_t ul_carrier;
nr_get_carrier_frequencies(ue, &dl_carrier, &ul_carrier);
nrue_ru_set_freq(ue, ul_carrier, dl_carrier, ue->freq_offset);
}
}
void *UE_thread(void *arg)
{
//this thread should be over the processing thread to keep in real time