prs resource mapping

openair1/PHY/NR_TRANSPORT/nr_prs.c

@@ -5,7 +5,8 @@
 #include "PHY/NR_REFSIG/nr_refsig.h"
 #include "PHY/sse_intrin.h"
 
-#define DEBUG_PRS
+//#define DEBUG_PRS
+#define DEBUG_PRS_MAP
 
 extern short nr_qpsk_mod_table[8];
 
@@ -15,14 +16,25 @@ int nr_generate_prs(uint32_t *nr_gold_prs,
                           uint8_t ssb_start_symbol,
                           nfapi_nr_config_request_scf_t *config,
                           NR_DL_FRAME_PARMS *frame_parms) {
-  //int k,l;
-  //int16_t a;
+  
+  
+  // Get K_Prime from the table for the length of PRS or LPRS
+  int k_prime_table[4][12] = {
+        {0,1,0,1,0,1,0,1,0,1,0,1},
+        {0,2,1,3,0,2,1,3,0,2,1,3},
+        {0,3,1,4,2,5,0,3,1,4,2,5},
+        {0,6,3,9,1,7,4,10,2,8,5,11}};
+    
+  int k_prime = 0;
+  int k=0;
   int16_t mod_prs[NR_MAX_PRS_LENGTH<<1];
   uint8_t idx=0;
-  uint8_t nushift = config->cell_config.phy_cell_id.value &3;
-  LOG_D(PHY, "PRS mapping started at symbol %d shift %d\n", ssb_start_symbol+1, nushift);
-
-  /// QPSK modulation
+  uint8_t combSize = 6;
+  uint8_t REOffset = 0;
+  uint8_t symbolStart = 5;
+  uint8_t NumPRSSymbols = 6;
+  
+  // QPSK modulation
   for (int m=0; m<NR_MAX_PRS_LENGTH; m++) {
     idx = (((nr_gold_prs[(m<<1)>>5])>>((m<<1)&0x1f))&3);
     mod_prs[m<<1] = nr_qpsk_mod_table[idx<<1];
@@ -33,8 +45,52 @@ int nr_generate_prs(uint32_t *nr_gold_prs,
            (((nr_gold_prs[((m<<1)+1)>>5])>>(((m<<1)+1)&0x1f))&1), mod_prs[(m<<1)], mod_prs[(m<<1)+1]);
 #endif
   }
+  
+   // PRS resource mapping with combsize=k which means PRS symbols exist in every k-th subcarrier in frequency domain
+   // According to ts138.211 sec.7.4.1.7.2
+
+  for (int l = symbolStart; l < symbolStart + NumPRSSymbols; l++) {
+
+  int symInd = l-5;
+        if (combSize==2) {
+            k_prime = k_prime_table[0][symInd];
+        }
+        else if (combSize==4){
+            k_prime = k_prime_table[1][symInd];
+        }
+        else if (combSize==6){
+            k_prime = k_prime_table[2][symInd];
+        }
+        else if (combSize==12){
+            k_prime = k_prime_table[3][symInd];
+        }
+
+  for (int m = 0; m < NR_MAX_PRS_LENGTH; m++) {
+#ifdef DEBUG_PRS_MAP
+    printf("m %d at k %d of l %d\n", m, k, l);
+#endif
+
+
+    ((int16_t *)txdataF)[(l*frame_parms->ofdm_symbol_size + k)<<1]       = (amp * mod_prs[m<<1]) >> 15;
+    ((int16_t *)txdataF)[((l*frame_parms->ofdm_symbol_size + k)<<1) + 1] = (amp * mod_prs[(m<<1) + 1]) >> 15;
+
+#ifdef DEBUG_PRS_MAP
+    printf("(%d,%d)\n",
+           ((int16_t *)txdataF)[(l*frame_parms->ofdm_symbol_size + k)<<1],
+           ((int16_t *)txdataF)[((l*frame_parms->ofdm_symbol_size + k)<<1)+1]);
+#endif
+    
+    k=m*combSize+(REOffset+k_prime)%combSize;
+
+    //if (k >= frame_parms->ofdm_symbol_size)
+      //k-=frame_parms->ofdm_symbol_size;
+      
+      }
+  }
+  
   return 0;
 }
  
 
 
+