maki/openairinterface5g
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Perform frequency offset correction in two consecutive frames for SA

Browse Source
This commit is contained in:
luis_pereira87
2021-12-22 18:27:26 +00:00
parent ad37d8ae5f
commit b830090a5a
2 changed files with 25 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files
openair1/PHY/NR_REFSIG/ss_pbch_nr.h
+1
View File
@@ -65,6 +65,7 @@
/* SS/PBCH parameters */
#define N_RB_SS_PBCH_BLOCK (20)
#define NB_SYMBOLS_PBCH (3)
#define NR_N_SYMBOLS_SSB (4)
#define IQ_SIZE (sizeof(int16_t) * 2) /* I and Q are alternatively stored into buffers */
#define N_SYMB_SLOT (14)
openair1/PHY/NR_UE_TRANSPORT/nr_initial_sync.c
+24 -13
View File
@@ -42,6 +42,7 @@
#include "common_lib.h"
#include <math.h>
#include <nr-uesoftmodem.h>
#include "PHY/NR_REFSIG/pss_nr.h"
#include "PHY/NR_REFSIG/sss_nr.h"
@@ -250,21 +251,31 @@ int nr_initial_sync(UE_nr_rxtx_proc_t *proc,
#endif
// 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*(ue->common_vars.freq_offset); // offset rotation angle compensation per sample
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*(ue->common_vars.freq_offset); // offset rotation angle compensation per sample
int start = is*fp->samples_per_frame+ue->ssb_offset; // start for offset correction is at ssb_offset (pss time position)
int end = start + 4*(fp->ofdm_symbol_size + fp->nb_prefix_samples); // loop over samples in 4 symbols (ssb size), including prefix
// In SA we need to perform frequency offset correction in two consecutive frames because we need to decode SIB1
// and we do not know yet in which slot it goes.
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)));
}
}
// start for offset correction
int start = get_softmodem_params()->sa ?
is*fp->samples_per_frame :
is*fp->samples_per_frame + ue->ssb_offset;
// loop over samples
int end = get_softmodem_params()->sa ?
start + (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)));
}
}
}
/* check that SSS/PBCH block is continuous inside the received buffer */