Fixed Channel compensation for dlsim for multiple DMRS

- fixed channel compensation by choosing most recent DMRS symbol ina
  slot
- Removed code to find nearest DMRS symbol for channle compensation
- Updated TBS calculation in DLSIM
- Added debug prints in PTRS CPE estimation for DMRS symbol

openair1/PHY/NR_REFSIG/ptrs_nr.c

@@ -213,6 +213,11 @@ uint8_t get_next_estimate_in_slot(uint16_t  ptrsSymbPos,uint16_t  dmrsSymbPos, u
   {
     return nextPtrs;
   }
+  /* Special case when DMRS is next valid estimation */
+  if(nextPtrs == 0 && nextDmrs !=0)
+  {
+    return nextDmrs;
+  }
   return (nextPtrs > nextDmrs)?nextDmrs:nextPtrs;
 }
 
@@ -366,6 +371,9 @@ int8_t nr_ptrs_process_slot(uint16_t dmrsSymbPos,
           /* set DMRS estimation */
           estPerSymb[symb*2]=(int16_t)((1<<15)-1); // 32767
           estPerSymb[(symb*2)+1]= 0; // no angle
+#ifdef DEBUG_PTRS
+          printf("[PHY][PTRS]: DMRS Symbol %d :(%4d %4d)\n", symb, estPerSymb[symb*2],estPerSymb[(symb*2)+1]);
+#endif
         }
       /* Update left and right reference from an estimated symbol */
       if((is_ptrs_symbol(symb, ptrsSymbPos)) || (is_dmrs_symbol(symb,dmrsSymbPos)))
@@ -387,7 +395,11 @@ int8_t nr_ptrs_process_slot(uint16_t dmrsSymbPos,
               {
                 /* calculate slope from next valid estimates*/
                 tmp =  get_next_estimate_in_slot(ptrsSymbPos,dmrsSymbPos,rightRef+1,symbInSlot);
-                get_slope_from_estimates(rightRef, tmp, estPerSymb, slope_p);
+                /* Special case when DMRS is not followed by PTRS symbol then reuse old slope */
+                if(tmp!=0)
+                {
+                  get_slope_from_estimates(rightRef, tmp, estPerSymb, slope_p);
+                }
                 ptrs_estimate_from_slope(estPerSymb,slope_p,leftRef, rightRef);
                 symb = rightRef -1;
               }

openair1/PHY/NR_TRANSPORT/nr_dlsch.c

@@ -120,6 +120,7 @@ uint8_t nr_generate_pdsch(PHY_VARS_gNB *gNB,
   uint32_t ***pdsch_dmrs = gNB->nr_gold_pdsch_dmrs[slot];
   int32_t** txdataF = gNB->common_vars.txdataF;
   int16_t amp = AMP;
+  int xOverhead = 0;
   NR_DL_FRAME_PARMS *frame_parms = &gNB->frame_parms;
   time_stats_t *dlsch_encoding_stats=&gNB->dlsch_encoding_stats;
   time_stats_t *dlsch_scrambling_stats=&gNB->dlsch_scrambling_stats;
@@ -157,9 +158,7 @@ uint8_t nr_generate_pdsch(PHY_VARS_gNB *gNB,
     
     uint16_t dmrs_symbol_map = rel15->dlDmrsSymbPos;//single DMRS: 010000100 Double DMRS 110001100
     uint8_t dmrs_len = get_num_dmrs(rel15->dlDmrsSymbPos);
-    
-    uint16_t nb_re;
-    nb_re = ((12*rel15->NrOfSymbols)-nb_re_dmrs-dmrs_len)*rel15->rbSize*rel15->NrOfCodewords;
+    uint16_t nb_re = ((12*rel15->NrOfSymbols)-nb_re_dmrs*dmrs_len-xOverhead)*rel15->rbSize*rel15->NrOfCodewords;
     uint8_t Qm = rel15->qamModOrder[0];
     uint32_t encoded_length = nb_re*Qm;
     int16_t mod_dmrs[n_dmrs<<1] __attribute__ ((aligned(16)));

openair1/PHY/NR_UE_ESTIMATION/nr_dl_channel_estimation.c

@@ -1059,6 +1059,7 @@ void nr_pdsch_ptrs_processing(PHY_VARS_NR_UE *ue,
                                &phase_per_symbol[2* symbol],
                                &ptrs_re_symbol[symbol]);
         /* if very first symbol is PTRS then we need to undo conjugate done in estimation */
+        /* The PTRS estimation before DMRS symbol is pure error, shall be used as it is*/
         if(symbol == *startSymbIndex)
         {
           phase_per_symbol[(2* symbol)+1] = (-1) * phase_per_symbol[(2* symbol)+1]; 

openair1/PHY/NR_UE_TRANSPORT/nr_dlsch_decoding.c

@@ -275,8 +275,7 @@ uint32_t nr_dlsch_decoding(PHY_VARS_NR_UE *phy_vars_ue,
     nb_re_dmrs = 4*harq_process->n_dmrs_cdm_groups;
   }
   uint16_t dmrs_length = get_num_dmrs(harq_process->dlDmrsSymbPos);
-  AssertFatal(dmrs_length == 1 || dmrs_length == 2 || dmrs_length == 3 ,"Illegal dmrs_length %d\n",dmrs_length);
-
+  
   uint32_t i,j;
 
   __m128i *pv = (__m128i*)&z;

openair1/PHY/NR_UE_TRANSPORT/nr_dlsch_demodulation.c

@@ -39,6 +39,7 @@
 #include "T.h"
 #include "openair1/PHY/NR_UE_ESTIMATION/nr_estimation.h"
 #include "openair1/PHY/NR_TRANSPORT/nr_dlsch.h"
+#include "PHY/NR_REFSIG/nr_refsig.h"
 
 #ifndef USER_MODE
 #define NOCYGWIN_STATIC static
@@ -2098,9 +2099,8 @@ unsigned short nr_dlsch_extract_rbs_single(int **rxdataF,
   unsigned char i,aarx; //,nsymb,sss_symb,pss_symb=0,l;
   int *dl_ch0,*dl_ch0_ext,*rxF,*rxF_ext;
 
-  uint8_t ClosestDMRSIdx = 15; //closest DMRS index to the current OFDM symbol
-  uint8_t ClosestDMRSdist = 15; //temporarily save the distance to the closest DMRS symbol
   int8_t DMRSdist = 15; //temporarily save the distance to the DMRS symbol 
+  static uint8_t validDmrsEst = 0; //store last DMRS Symbol index
 
   unsigned char j=0;
 
@@ -2111,21 +2111,15 @@ unsigned short nr_dlsch_extract_rbs_single(int **rxdataF,
 
     k = frame_parms->first_carrier_offset + NR_NB_SC_PER_RB*start_rb;
 
-    if (high_speed_flag == 1) {
-      for (int i=0; i<16; i++) { //loop over all possible DMRS symbols
-        if ( (1<<i & dlDmrsSymbPos) > 0 ) {
-          DMRSdist = symbol-i;
-          DMRSdist = DMRSdist>=0 ? DMRSdist : -DMRSdist;
-          if ( DMRSdist < ClosestDMRSdist ) {
-            ClosestDMRSIdx = i;
-            ClosestDMRSdist = DMRSdist;
-          }
-        } 
-      }
-      dl_ch0     = &dl_ch_estimates[aarx][(ClosestDMRSIdx*(frame_parms->ofdm_symbol_size))]; //use closest DMRS
+    if(validDmrsEst == 0)
+    {
+      validDmrsEst = get_next_dmrs_symbol_in_slot(dlDmrsSymbPos, symbol, DMRSdist);
     }
-    else
-      dl_ch0     = &dl_ch_estimates[aarx][0];
+    if(is_dmrs_symbol(symbol,dlDmrsSymbPos ) == 1)
+    {
+      validDmrsEst = symbol;
+    }
+    dl_ch0     = &dl_ch_estimates[aarx][(validDmrsEst*(frame_parms->ofdm_symbol_size))]; //use closest DMRS
 
     dl_ch0_ext = &dl_ch_estimates_ext[aarx][symbol*(nb_rb_pdsch*12)];
 

openair1/SIMULATION/NR_PHY/dlsim.c

@@ -981,7 +981,7 @@ int main(int argc, char **argv)
       int16_t *UE_llr = pdsch_vars[0]->llr[0];
       
       TBS                  = UE_harq_process->TBS;//rel15->TBSize[0];
-      uint16_t length_dmrs = 1;
+      uint16_t length_dmrs = get_num_dmrs(rel15->dlDmrsSymbPos);
       uint16_t nb_rb       = rel15->rbSize;
       uint8_t  nb_re_dmrs  = rel15->dmrsConfigType == NFAPI_NR_DMRS_TYPE1 ? 6 : 4;
       uint8_t  mod_order   = rel15->qamModOrder[0];