gNB: cut OFDM symbol for PUSCH reception within 1/8th of CP to avoid ISI

openair1/PHY/MODULATION/slot_fep_nr.c

@@ -468,10 +468,12 @@ int nr_slot_fep_ul(NR_DL_FRAME_PARMS *frame_parms,
   
   slot_offset   = frame_parms->get_samples_slot_timestamp(Ns,frame_parms,0);
 
-  if(symbol == 0)
+  // offset of first OFDM symbol
   rxdata_offset  = slot_offset + nb_prefix_samples0 - SOFFSET;
-  else
-    rxdata_offset = slot_offset + nb_prefix_samples0 + (symbol * (frame_parms->ofdm_symbol_size + nb_prefix_samples)) - SOFFSET;
+  // offset of n-th OFDM symbol
+  rxdata_offset += symbol * (frame_parms->ofdm_symbol_size + nb_prefix_samples);
+  // use OFDM symbol from within 1/8th of the CP to avoid ISI
+  rxdata_offset -= nb_prefix_samples / 8;
 
   if(sample_offset>rxdata_offset) {
     memcpy1((void *)tmp_dft_in,

openair1/PHY/NR_ESTIMATION/nr_measurements_gNB.c

@@ -37,22 +37,20 @@
 
 int nr_est_timing_advance_pusch(PHY_VARS_gNB* gNB, int UE_id)
 {
-  int temp, i, aa, max_pos = 0, max_val = 0;
-  short Re, Im;
-  uint8_t cyclic_shift = 0;
+  int i, aa, max_pos = 0, max_val = 0;
   
   NR_DL_FRAME_PARMS *frame_parms = &gNB->frame_parms;
   NR_gNB_PUSCH *gNB_pusch_vars   = gNB->pusch_vars[UE_id];
   int32_t **ul_ch_estimates_time = gNB_pusch_vars->ul_ch_estimates_time;
   
-  int sync_pos = (frame_parms->ofdm_symbol_size - cyclic_shift*frame_parms->ofdm_symbol_size/12) % (frame_parms->ofdm_symbol_size);
+  int sync_pos = frame_parms->nb_prefix_samples / 8;
 
   for (i = 0; i < frame_parms->ofdm_symbol_size; i++) {
-    temp = 0;
+    int temp = 0;
 
     for (aa = 0; aa < frame_parms->nb_antennas_rx; aa++) {
-      Re = ((int16_t*)ul_ch_estimates_time[aa])[(i<<1)];
-      Im = ((int16_t*)ul_ch_estimates_time[aa])[1+(i<<1)];
+      short Re = ((int16_t*)ul_ch_estimates_time[aa])[(i<<1)];
+      short Im = ((int16_t*)ul_ch_estimates_time[aa])[1+(i<<1)];
       temp += (Re*Re/2) + (Im*Im/2);      
     }