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Add ffo compensation based on SSS

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This commit is contained in:
luis_pereira87
2022-01-07 18:02:24 +00:00
parent 395c211e6d
commit ef298dc36c
3 changed files with 44 additions and 3 deletions
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openair1/PHY/NR_REFSIG/sss_nr.h
+1 -1
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@@ -96,7 +96,7 @@ int pss_ch_est_nr(PHY_VARS_NR_UE *ue,
int32_t pss_ext[NB_ANTENNAS_RX][LENGTH_PSS_NR],
int32_t sss_ext[NB_ANTENNAS_RX][LENGTH_SSS_NR]);
int rx_sss_nr(PHY_VARS_NR_UE *ue, UE_nr_rxtx_proc_t *proc, int32_t *tot_metric, uint8_t *phase_max);
int rx_sss_nr(PHY_VARS_NR_UE *ue, UE_nr_rxtx_proc_t *proc, int32_t *tot_metric, uint8_t *phase_max, int *freq_offset_sss);
#undef INIT_VARIABLES_SSS_NR_H
#undef EXTERN
openair1/PHY/NR_UE_TRANSPORT/nr_initial_sync.c
+28 -1
View File
@@ -295,7 +295,34 @@ int nr_initial_sync(UE_nr_rxtx_proc_t *proc,
LOG_I(PHY,"Calling sss detection (normal CP)\n");
#endif
rx_sss_nr(ue, proc, &metric_tdd_ncp, &phase_tdd_ncp);
int freq_offset_sss = 0;
rx_sss_nr(ue, proc, &metric_tdd_ncp, &phase_tdd_ncp, &freq_offset_sss);
accumulated_freq_offset += freq_offset_sss;
// digital compensation of FFO for SSB symbols
if (ue->UE_fo_compensation){
double s_time = 1/(1.0e3*fp->samples_per_subframe); // sampling time
double off_angle = -2*M_PI*s_time*freq_offset_sss; // offset rotation angle compensation per sample
// In SA we need to perform frequency offset correction until the end of buffer because we need to decode SIB1
// and we do not know yet in which slot it goes.
// start for offset correction
int start = sa ? is*fp->samples_per_frame : is*fp->samples_per_frame + ue->ssb_offset;
// loop over samples
int end = sa ? n_frames*fp->samples_per_frame-1 : start + NR_N_SYMBOLS_SSB*(fp->ofdm_symbol_size + fp->nb_prefix_samples);
for(int n=start; n<end; n++){
for (int ar=0; ar<fp->nb_antennas_rx; ar++) {
re = ((double)(((short *)ue->common_vars.rxdata[ar]))[2*n]);
im = ((double)(((short *)ue->common_vars.rxdata[ar]))[2*n+1]);
((short *)ue->common_vars.rxdata[ar])[2*n] = (short)(round(re*cos(n*off_angle) - im*sin(n*off_angle)));
((short *)ue->common_vars.rxdata[ar])[2*n+1] = (short)(round(re*sin(n*off_angle) + im*cos(n*off_angle)));
}
}
}
nr_gold_pbch(ue);
ret = nr_pbch_detection(proc, ue, 1); // start pbch detection at first symbol after pss
openair1/PHY/NR_UE_TRANSPORT/sss_nr.c
+15 -1
View File
@@ -420,7 +420,7 @@ int pss_sss_extract_nr(PHY_VARS_NR_UE *phy_vars_ue,
*
*********************************************************************/
int rx_sss_nr(PHY_VARS_NR_UE *ue, UE_nr_rxtx_proc_t *proc, int32_t *tot_metric, uint8_t *phase_max)
int rx_sss_nr(PHY_VARS_NR_UE *ue, UE_nr_rxtx_proc_t *proc, int32_t *tot_metric, uint8_t *phase_max, int *freq_offset_sss)
{
uint8_t i;
int32_t pss_ext[NB_ANTENNAS_RX][LENGTH_PSS_NR];
@@ -558,5 +558,19 @@ int rx_sss_nr(PHY_VARS_NR_UE *ue, UE_nr_rxtx_proc_t *proc, int32_t *tot_metric,
}
//#endif
int re = 0;
int im = 0;
d = (int16_t *)&d_sss[Nid2][Nid1];
for(i = 0; i<LENGTH_SSS_NR; i++) {
re += d[i]*sss[2*i];
im += d[i]*sss[2*i+1];
}
double ffo_sss = atan2(im,re)/M_PI/4.3;
*freq_offset_sss = (int)(ffo_sss*frame_parms->subcarrier_spacing);
double ffo_pss = ((double)ue->common_vars.freq_offset)/frame_parms->subcarrier_spacing;
LOG_I(NR_PHY, "ffo_pss %f (%i Hz), ffo_sss %f (%i Hz), ffo_pss+ffo_sss %f (%i Hz)\n",
ffo_pss, (int)(ffo_pss*frame_parms->subcarrier_spacing), ffo_sss, *freq_offset_sss, ffo_pss+ffo_sss, (int)((ffo_pss+ffo_sss)*frame_parms->subcarrier_spacing));
return(0);
}