adding comments to clarify that DMRS samples generated for channel estimation...

adding comments to clarify that DMRS samples generated for channel estimation at reception already takes into account complex conjugate needed for said estimation

openair1/PHY/NR_ESTIMATION/nr_ul_channel_estimation.c

@@ -110,8 +110,16 @@ int nr_pusch_channel_estimation(PHY_VARS_gNB *gNB,
   }
 
   if (pusch_pdu->transform_precoding == transformPrecoder_disabled) {
-    nr_pusch_dmrs_rx(gNB, Ns, gNB->nr_gold_pusch_dmrs[pusch_pdu->scid][Ns][symbol], (int32_t *)pilot, (1000+p), 0, nb_rb_pusch,
-                     (pusch_pdu->bwp_start + pusch_pdu->rb_start)*NR_NB_SC_PER_RB, pusch_pdu->dmrs_config_type);
+    // Note: pilot returned by the following function is already the complex conjugate of the transmitted DMRS
+    nr_pusch_dmrs_rx(gNB,
+                     Ns,
+                     gNB->nr_gold_pusch_dmrs[pusch_pdu->scid][Ns][symbol],
+                     (int32_t *)pilot,
+                     (1000 + p),
+                     0,
+                     nb_rb_pusch,
+                     (pusch_pdu->bwp_start + pusch_pdu->rb_start) * NR_NB_SC_PER_RB,
+                     pusch_pdu->dmrs_config_type);
   } else { // if transform precoding or SC-FDMA is enabled in Uplink
     // NR_SC_FDMA supports type1 DMRS so only 6 DMRS REs per RB possible
     const uint16_t index = get_index_for_dmrs_lowpapr_seq(nb_rb_pusch * (NR_NB_SC_PER_RB/2));

openair1/PHY/NR_REFSIG/nr_dmrs_rx.c

@@ -195,9 +195,7 @@ int nr_pdcch_dmrs_rx(PHY_VARS_NR_UE *ue,
 }
 
 
-int nr_pbch_dmrs_rx(int symbol,
-                    unsigned int *nr_gold_pbch,
-                    int32_t *output)
+int nr_pbch_dmrs_rx(int symbol, unsigned int *nr_gold_pbch, int32_t *output)
 {
   int m,m0,m1;
   uint8_t idx=0;
@@ -257,14 +255,14 @@ void nr_gen_ref_conj_symbols(uint32_t *in, uint32_t length, int16_t *output, uin
 }
 
 int nr_pusch_lowpaprtype1_dmrs_rx(PHY_VARS_gNB *gNB,
-                     unsigned int Ns,
-                     int16_t *dmrs_seq,
-                     int32_t *output,
-                     unsigned short p,
-                     unsigned char lp,
-                     unsigned short nb_pusch_rb,
-                     uint32_t re_offset,
-                     uint8_t dmrs_type)
+                                  unsigned int Ns,
+                                  int16_t *dmrs_seq,
+                                  int32_t *output,
+                                  unsigned short p,
+                                  unsigned char lp,
+                                  unsigned short nb_pusch_rb,
+                                  uint32_t re_offset,
+                                  uint8_t dmrs_type)
 {
   int8_t w, nb_dmrs;
   int k;

openair1/PHY/NR_UE_ESTIMATION/nr_dl_channel_estimation.c

@@ -658,7 +658,8 @@ int nr_pbch_dmrs_correlation(PHY_VARS_NR_UE *ue,
 #endif
 
   // generate pilot
-  nr_pbch_dmrs_rx(dmrss,ue->nr_gold_pbch[n_hf][ssb_index], &pilot[0]);
+  // Note: pilot returned by the following function is already the complex conjugate of the transmitted DMRS
+  nr_pbch_dmrs_rx(dmrss, ue->nr_gold_pbch[n_hf][ssb_index], &pilot[0]);
 
   for (int aarx=0; aarx<ue->frame_parms.nb_antennas_rx; aarx++) {
 
@@ -898,7 +899,8 @@ int nr_pbch_channel_estimation(PHY_VARS_NR_UE *ue,
   }
   
   // generate pilot
-  nr_pbch_dmrs_rx(dmrss,ue->nr_gold_pbch[n_hf][ssb_index], &pilot[0]);
+  // Note: pilot returned by the following function is already the complex conjugate of the transmitted DMRS
+  nr_pbch_dmrs_rx(dmrss, ue->nr_gold_pbch[n_hf][ssb_index], &pilot[0]);
 
   for (int aarx=0; aarx<ue->frame_parms.nb_antennas_rx; aarx++) {
 
@@ -1111,7 +1113,8 @@ void nr_pdcch_channel_estimation(PHY_VARS_NR_UE *ue,
     dmrs_ref = BWPStart;
   // generate pilot
   int pilot[(nb_rb_coreset + dmrs_ref) * 3] __attribute__((aligned(16)));
-  nr_pdcch_dmrs_rx(ue,Ns,ue->nr_gold_pdcch[gNB_id][Ns][symbol], &pilot[0],2000,(nb_rb_coreset+dmrs_ref));
+  // Note: pilot returned by the following function is already the complex conjugate of the transmitted DMRS
+  nr_pdcch_dmrs_rx(ue, Ns, ue->nr_gold_pdcch[gNB_id][Ns][symbol], &pilot[0], 2000, (nb_rb_coreset + dmrs_ref));
 
   for (aarx=0; aarx<ue->frame_parms.nb_antennas_rx; aarx++) {
 
@@ -1648,7 +1651,15 @@ int nr_pdsch_channel_estimation(PHY_VARS_NR_UE *ue,
   }
 
   c16_t pilot[3280] __attribute__((aligned(16)));
-  nr_pdsch_dmrs_rx(ue, Ns, ue->nr_gold_pdsch[gNB_id][Ns][symbol][nscid], (int32_t *)pilot, 1000 + p, 0, nb_rb_pdsch + rb_offset, config_type);
+  // Note: pilot returned by the following function is already the complex conjugate of the transmitted DMRS
+  nr_pdsch_dmrs_rx(ue,
+                   Ns,
+                   ue->nr_gold_pdsch[gNB_id][Ns][symbol][nscid],
+                   (int32_t *)pilot,
+                   1000 + p,
+                   0,
+                   nb_rb_pdsch + rb_offset,
+                   config_type);
 
   uint8_t nushift = 0;
   if (config_type == NFAPI_NR_DMRS_TYPE1) {