ptrs: limit PTRS processing to one antenna port

    The current state of PTRS will not work for multiple antenna ports because the function assumes rxdataF_comp has signal for all antenna ports but it doesn't as we do MRC after DMRS compensation.
Signed-off-by: Rupanjali <rupanjali.srivastava@openairinterface.org>

openair1/PHY/NR_TRANSPORT/nr_ulsch_demodulation.c

@@ -272,15 +272,14 @@ static void inner_rx(PHY_VARS_gNB *gNB,
                            rel15_ul->qam_mod_order);
     nr_idft((int32_t *)&pusch_vars->rxdataF_comp[0][symbol * buffer_length], pusch_vars->ul_valid_re_per_slot[symbol]);
   }
+  /* PTRS processing for multiple antenna ports is broken because the following
+  function estimates phase offset from and applies compensation to rxdataF_comp
+  for each antenna port but rxdataF_comp has MRCed data. */
+  /* TODO: Move PTRS phase estimation before immediately after DMRS channels
+  estimation and apply PTRS phase compensation in nr_channel_compensationi() */
   if (rel15_ul->pdu_bit_map & PUSCH_PDU_BITMAP_PUSCH_PTRS) {
-    nr_pusch_ptrs_processing(gNB,
-                             frame_parms,
-                             rel15_ul,
-                             pusch_vars,
-                             slot,
-                             symbol,
-                             nb_rx_ant,
-                             buffer_length);
+    // rxdataF_comp is MRCed so no point in processing all antenna ports. Fixme.
+    nr_pusch_ptrs_processing(gNB, frame_parms, rel15_ul, pusch_vars, slot, symbol, 1, buffer_length);
     pusch_vars->ul_valid_re_per_slot[symbol] -= pusch_vars->ptrs_re_per_slot;
   }
   start_meas(ulsch_llr);

openair1/PHY/NR_UE_ESTIMATION/nr_dl_channel_estimation.c

@@ -1369,7 +1369,7 @@ void nr_pdsch_ptrs_processing(int nbRx,
   int nscid = dlsch_config->nscid;
 
   /* loop over antennas */
-  for (int aarx = 0; aarx < frame_parms->nb_antennas_rx; aarx++) {
+  for (int aarx = 0; aarx < nbRx; aarx++) {
     c16_t *phase_per_symbol = (c16_t*)ptrs_phase_per_slot[aarx];
     ptrs_re_symbol = (int32_t*)ptrs_re_per_slot[aarx];
     ptrs_re_symbol[symbol] = 0;
@@ -1440,5 +1440,5 @@ void nr_pdsch_ptrs_processing(int nbRx,
         }// if not DMRS Symbol
       }// symbol loop
     }// last symbol check
-  }//Antenna loop
+  } // Antenna loop
 }//main function

openair1/PHY/NR_UE_TRANSPORT/nr_dlsch_demodulation.c

@@ -1099,9 +1099,14 @@ int nr_rx_pdsch(PHY_VARS_NR_UE *ue,
     pduBitmap = dlsch_config->pduBitmap;
   }
 
+  /* PTRS processing for multiple antenna ports is broken because the following
+  function estimates phase offset from and applies compensation to rxdataF_comp
+  for each antenna port but rxdataF_comp has MRCed data. */
+  /* TODO: Move PTRS phase estimation before immediately after DMRS channels
+  estimation and apply PTRS phase compensation in nr_channel_compensationi() */
   /* Check for PTRS bitmap and process it respectively */
   if((pduBitmap & 0x1) && (dlsch->rnti_type == TYPE_C_RNTI_)) {
-    nr_pdsch_ptrs_processing(nbRx,
+    nr_pdsch_ptrs_processing(1, // rxdataF_comp is MRCed so no point in processing all antenna ports. Fixme.
                              ptrs_phase_per_slot,
                              ptrs_re_per_slot,
                              rx_size_symbol,