multiple ssb detection via pbch dmrs (selection of best ssb only, working in pbchsim for SNR>=0)

openair1/PHY/NR_UE_ESTIMATION/nr_dl_channel_estimation.c

@@ -32,6 +32,169 @@
 //#define DEBUG_PDCCH
 
 
+int nr_pbch_dmrs_correlation(PHY_VARS_NR_UE *ue,
+			       uint8_t eNB_offset,
+			       unsigned char Ns,
+			       unsigned char symbol,
+			       NR_UE_SSB *current_ssb)
+{
+  int pilot[200] __attribute__((aligned(16)));
+  unsigned char aarx;
+  unsigned short k;
+  unsigned int pilot_cnt;
+  int16_t ch[2],*pil,*rxF;
+  int symbol_offset;
+  int dmrss;
+
+  uint8_t nushift;
+  uint8_t ssb_index=current_ssb->i_ssb;
+  uint8_t n_hf=current_ssb->n_hf;
+  int **rxdataF=ue->common_vars.common_vars_rx_data_per_thread[ue->current_thread_id[Ns>>1]].rxdataF;
+
+  nushift =  ue->frame_parms.Nid_cell%4;
+  ue->frame_parms.nushift = nushift;
+  unsigned int  ssb_offset = ue->frame_parms.first_carrier_offset + ue->frame_parms.ssb_start_subcarrier;
+  if (ssb_offset>= ue->frame_parms.ofdm_symbol_size) ssb_offset-=ue->frame_parms.ofdm_symbol_size;
+
+  if (ue->is_synchronized ==0 ) dmrss = symbol-1;
+  else dmrss = symbol-5;
+
+  AssertFatal((symbol > 0 && symbol < 4 && ue->is_synchronized == 0) || 
+	      (symbol > 4 && symbol < 8 && ue->is_synchronized == 1),
+	      "symbol %d is illegal for PBCH DM-RS (is_synchronized %d)\n",
+	      symbol,ue->is_synchronized);
+
+  symbol_offset = ue->frame_parms.ofdm_symbol_size*symbol;
+
+
+  k = nushift;
+
+#ifdef DEBUG_CH
+  printf("PBCH DMRS Correlation : ThreadId %d, eNB_offset %d , OFDM size %d, Ncp=%d, Ns=%d, k=%d symbol %d\n",ue->current_thread_id[Ns>>1], eNB_offset,ue->frame_parms.ofdm_symbol_size,
+         ue->frame_parms.Ncp,Ns,k, symbol);
+#endif
+
+  // generate pilot
+  nr_pbch_dmrs_rx(dmrss,ue->nr_gold_pbch[n_hf][ssb_index], &pilot[0]);
+
+  int re_offset = ssb_offset;
+  for (aarx=0; aarx<ue->frame_parms.nb_antennas_rx; aarx++) {
+
+    pil   = (int16_t *)&pilot[0];
+    rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+k+re_offset)];
+
+#ifdef DEBUG_CH
+    printf("pbch ch est pilot addr %p RB_DL %d\n",&pilot[0], ue->frame_parms.N_RB_DL);
+    printf("k %d, first_carrier %d\n",k,ue->frame_parms.first_carrier_offset);
+    printf("rxF addr %p\n", rxF);
+#endif
+    //if ((ue->frame_parms.N_RB_DL&1)==0) {
+
+    // Treat first 2 pilots specially (left edge)
+    ch[0] = (int16_t)(((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1])>>15);
+    ch[1] = (int16_t)(((int32_t)pil[0]*rxF[1] + (int32_t)pil[1]*rxF[0])>>15);
+
+    current_ssb->c_re +=ch[0];
+    current_ssb->c_im +=ch[1];
+
+#ifdef DEBUG_CH
+    printf("ch 0 %d\n",((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1]));
+    printf("pilot 0 : rxF - > (%d,%d) addr %p  ch -> (%d,%d), pil -> (%d,%d) \n",rxF[0],rxF[1],&rxF[0],ch[0],ch[1],pil[0],pil[1]);
+#endif
+
+    pil+=2;
+    re_offset = (re_offset+4)&(ue->frame_parms.ofdm_symbol_size-1);
+    rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+k+re_offset)];
+
+
+    ch[0] = (int16_t)(((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1])>>15);
+    ch[1] = (int16_t)(((int32_t)pil[0]*rxF[1] + (int32_t)pil[1]*rxF[0])>>15);
+
+    current_ssb->c_re +=ch[0];
+    current_ssb->c_im +=ch[1];
+
+#ifdef DEBUG_CH
+    printf("pilot 1 : rxF - > (%d,%d) ch -> (%d,%d), pil -> (%d,%d) \n",rxF[0],rxF[1],ch[0],ch[1],pil[0],pil[1]);
+#endif
+
+    pil+=2;
+    re_offset = (re_offset+4)&(ue->frame_parms.ofdm_symbol_size-1);
+    rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+k+re_offset)];
+
+    current_ssb->c_re +=ch[0];
+    current_ssb->c_im +=ch[1];
+
+#ifdef DEBUG_CH
+    printf("pilot 2 : rxF - > (%d,%d) ch -> (%d,%d), pil -> (%d,%d) \n",rxF[0],rxF[1],ch[0],ch[1],pil[0],pil[1]);
+#endif
+
+    pil+=2;
+    re_offset = (re_offset+4)&(ue->frame_parms.ofdm_symbol_size-1);
+    rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+k+re_offset)];
+
+    for (pilot_cnt=3; pilot_cnt<(3*20); pilot_cnt+=3) {
+
+      //	if (pilot_cnt == 30)
+      //	  rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+k)];
+
+      // in 2nd symbol, skip middle  REs (48 with DMRS,  144 for SSS, and another 48 with DMRS) 
+      if (dmrss == 1 && pilot_cnt == 12) {
+	pilot_cnt=48;
+	re_offset = (re_offset+144)&(ue->frame_parms.ofdm_symbol_size-1);
+	rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+k+re_offset)];
+      }
+      ch[0] = (int16_t)(((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1])>>15);
+      ch[1] = (int16_t)(((int32_t)pil[0]*rxF[1] + (int32_t)pil[1]*rxF[0])>>15);
+      
+      current_ssb->c_re +=ch[0];
+      current_ssb->c_im +=ch[1];
+
+#ifdef DEBUG_CH
+      printf("pilot %d : rxF - > (%d,%d) ch -> (%d,%d), pil -> (%d,%d) \n",pilot_cnt,rxF[0],rxF[1],ch[0],ch[1],pil[0],pil[1]);
+#endif
+
+      pil+=2;
+      re_offset = (re_offset+4)&(ue->frame_parms.ofdm_symbol_size-1);
+      rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+k+re_offset)];
+        
+  
+      ch[0] = (int16_t)(((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1])>>15);
+      ch[1] = (int16_t)(((int32_t)pil[0]*rxF[1] + (int32_t)pil[1]*rxF[0])>>15);
+
+      current_ssb->c_re +=ch[0];
+      current_ssb->c_im +=ch[1];
+
+#ifdef DEBUG_CH
+      printf("pilot %d : rxF - > (%d,%d) ch -> (%d,%d), pil -> (%d,%d) \n",pilot_cnt+1,rxF[0],rxF[1],ch[0],ch[1],pil[0],pil[1]);
+#endif
+      pil+=2;
+      re_offset = (re_offset+4)&(ue->frame_parms.ofdm_symbol_size-1);
+      rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+k+re_offset)];
+        
+
+      ch[0] = (int16_t)(((int32_t)pil[0]*rxF[0] - (int32_t)pil[1]*rxF[1])>>15);
+      ch[1] = (int16_t)(((int32_t)pil[0]*rxF[1] + (int32_t)pil[1]*rxF[0])>>15);
+
+      current_ssb->c_re +=ch[0];
+      current_ssb->c_im +=ch[1];
+
+#ifdef DEBUG_CH
+      printf("pilot %d : rxF - > (%d,%d) ch -> (%d,%d), pil -> (%d,%d) \n",pilot_cnt+2,rxF[0],rxF[1],ch[0],ch[1],pil[0],pil[1]);
+#endif
+
+      pil+=2;
+      re_offset = (re_offset+4)&(ue->frame_parms.ofdm_symbol_size-1);
+      rxF   = (int16_t *)&rxdataF[aarx][(symbol_offset+k+re_offset)];
+
+    }
+
+
+    //}
+
+  }
+  return(0);
+}
+
 
 int nr_pbch_channel_estimation(PHY_VARS_NR_UE *ue,
 			       uint8_t eNB_offset,

openair1/PHY/NR_UE_ESTIMATION/nr_estimation.h

@@ -50,6 +50,12 @@ int nr_pdcch_channel_estimation(PHY_VARS_NR_UE *ue,
 				unsigned short coreset_start_subcarrier,
 				unsigned short nb_rb_coreset);
 
+int nr_pbch_dmrs_correlation(PHY_VARS_NR_UE *ue,
+                             uint8_t eNB_offset,
+                             unsigned char Ns,
+                             unsigned char symbol,
+			     NR_UE_SSB *current_ssb);
+
 int nr_pbch_channel_estimation(PHY_VARS_NR_UE *ue,
                                uint8_t eNB_offset,
                                unsigned char Ns,

openair1/PHY/NR_UE_TRANSPORT/nr_initial_sync.c

@@ -58,6 +58,11 @@ int nr_pbch_detection(PHY_VARS_NR_UE *ue, int pbch_initial_symbol, runmode_t mod
 {
   NR_DL_FRAME_PARMS *frame_parms=&ue->frame_parms;
   int ret =-1;
+  uint8_t best_ssb =0;
+  uint8_t n_hf =0;
+  uint32_t best_metric =0;
+
+  NR_UE_SSB *current_ssb = malloc(sizeof(NR_UE_SSB));
 
 #ifdef DEBUG_INITIAL_SYNCH
   LOG_I(PHY,"[UE%d] Initial sync: starting PBCH detection (rx_offset %d)\n",ue->Mod_id,
@@ -70,30 +75,53 @@ int nr_pbch_detection(PHY_VARS_NR_UE *ue, int pbch_initial_symbol, runmode_t mod
   // loops over possible pbch dmrs cases to retrive best estimated i_ssb (and n_hf for Lmax=4) for multiple ssb detection
   for (int hf = 0; hf < N_hf; hf++) {
     for (int l = 0; l < N_L ; l++) {
-      if (ret !=0) {
+
+      // initialization of structure parameters
+      current_ssb->n_hf = hf;
+      current_ssb->i_ssb = l;
+      current_ssb->c_re = 0;
+      current_ssb->c_im = 0;
 
 #if UE_TIMING_TRACE
-        start_meas(&ue->dlsch_channel_estimation_stats);
+      start_meas(&ue->dlsch_channel_estimation_stats);
 #endif
-        for(int i=pbch_initial_symbol; i<pbch_initial_symbol+3;i++)
-          nr_pbch_channel_estimation(ue,0,0,i,i-pbch_initial_symbol,l,hf);
+      // computing correlation between received DMRS symbols and transmitted sequence for current i_ssb and n_hf
+      for(int i=pbch_initial_symbol; i<pbch_initial_symbol+3;i++)
+          nr_pbch_dmrs_correlation(ue,0,0,i,current_ssb);
 #if UE_TIMING_TRACE
-        stop_meas(&ue->dlsch_channel_estimation_stats);
+      stop_meas(&ue->dlsch_channel_estimation_stats);
 #endif
-
-        ret = nr_rx_pbch(ue,
-	                 &ue->proc.proc_rxtx[0],
-		         ue->pbch_vars[0],
-		         frame_parms,
-		         0,
-			 l,
-                         SISO,
-		         ue->high_speed_flag);
-
+      
+      current_ssb->metric = current_ssb->c_re*current_ssb->c_re + current_ssb->c_im+current_ssb->c_re;
+      
+      if(current_ssb->metric > best_metric) { // if metric of current structure is higher than the best one
+        best_metric = current_ssb->metric;
+        best_ssb = l;
+        n_hf = hf;
       }
+
     }
   }
 
+#if UE_TIMING_TRACE
+  start_meas(&ue->dlsch_channel_estimation_stats);
+#endif
+  // computing channel estimation for selected best ssb
+  for(int i=pbch_initial_symbol; i<pbch_initial_symbol+3;i++)
+    nr_pbch_channel_estimation(ue,0,0,i,i-pbch_initial_symbol,best_ssb,n_hf);
+#if UE_TIMING_TRACE
+  stop_meas(&ue->dlsch_channel_estimation_stats);
+#endif
+
+  ret = nr_rx_pbch(ue,
+	           &ue->proc.proc_rxtx[0],
+		   ue->pbch_vars[0],
+		   frame_parms,
+		   0,
+		   best_ssb,
+                   SISO,
+		   ue->high_speed_flag);
+
   if (ret==0) {
     
     frame_parms->nb_antenna_ports_eNB = 1; //pbch_tx_ant;
@@ -116,6 +144,7 @@ int nr_pbch_detection(PHY_VARS_NR_UE *ue, int pbch_initial_symbol, runmode_t mod
 #ifdef DEBUG_INITIAL_SYNCH
     LOG_I(PHY,"[UE%d] Initial sync: pbch decoded sucessfully\n",ue->Mod_id);
 #endif
+
     return(0);
   } else {
     return(-1);

openair1/PHY/defs_nr_UE.h

@@ -950,6 +950,15 @@ typedef struct {
   int16_t *prach;
 } NR_UE_PRACH;
 
+// structure used for multiple SSB detection
+typedef struct NR_UE_SSB {
+  uint8_t i_ssb;   // i_ssb between 0 and 7 (it corresponds to ssb_index only for Lmax=4,8)
+  uint8_t n_hf;    // n_hf = 0,1 for Lmax =4 or n_hf = 0 for Lmax =8,64
+  uint32_t metric; // metric to order SSB hypothesis
+  uint32_t c_re;
+  uint32_t c_im;
+} NR_UE_SSB;
+
 /*typedef enum {
   /// do not detect any DCIs in the current subframe
   NO_DCI = 0x0,