Remove TX-GAIN multiplication with transmitted signal in ULSIM

- Removed tx_gain calculations and multiplication with tx signal
- Updated sigma value calculations and removed unused variables
- Re-indent the related code for better readability

openair1/SIMULATION/NR_PHY/ulsim.c

@@ -162,8 +162,6 @@ int main(int argc, char **argv)
   FILE *input_fd = NULL;
   SCM_t channel_model = AWGN;  //Rayleigh1_anticorr;
   uint16_t N_RB_DL = 106, N_RB_UL = 106, mu = 1;
-  double tx_gain=1.0;
-  double N0=30;
 
   //unsigned char frame_type = 0;
   NR_DL_FRAME_PARMS *frame_parms;
@@ -177,7 +175,6 @@ int main(int argc, char **argv)
   int gNB_id = 0;
   int ap;
   int tx_offset;
-  double txlev_float;
   int32_t txlev;
   int start_rb = 0;
   int UE_id =0; // [hna] only works for UE_id = 0 because NUMBER_OF_NR_UE_MAX is set to 1 (phy_init_nr_gNB causes segmentation fault)
@@ -953,8 +950,6 @@ int main(int argc, char **argv)
       nr_fill_ulsch(gNB,frame,slot,pusch_pdu);
 
       for (int i=0;i<(TBS/8);i++) ulsch_ue[0]->harq_processes[harq_pid]->a[i]=i&0xff;
-      double scale = 1;
-
       if (input_fd == NULL) {
 
 	  // set FAPI parameters for UE, put them in the scheduled response and call
@@ -977,21 +972,14 @@ int main(int argc, char **argv)
 	  
 	  txlev = signal_energy(&UE->common_vars.txdata[0][tx_offset + 5*frame_parms->ofdm_symbol_size + 4*frame_parms->nb_prefix_samples + frame_parms->nb_prefix_samples0],
 				frame_parms->ofdm_symbol_size + frame_parms->nb_prefix_samples);
-	  
-	  txlev_float = (double)txlev/scale; // output of signal_energy is fixed point representation
-	  
-	  
       }	
       else n_trials = 1;
 
-      if (input_fd == NULL ) {
-
-	sigma_dB = N0;
+      if (input_fd == NULL )
+      {
+        sigma_dB  = 10 * log10((double)txlev * ((double)frame_parms->ofdm_symbol_size/(12*nb_rb))) - SNR;
         sigma    = pow(10,sigma_dB/10);
-
-	tx_gain = sqrt(pow(10.0,.1*(N0+SNR))/txlev_float);
-	if(n_trials==1) printf("txlev_float %f, sigma_dB %f, tx_gain %f tx_offset %d, slot_offset %d\n",10*log10(txlev_float),sigma_dB,tx_gain,tx_offset,slot_offset);
-
+        if (n_trials==1) printf("sigma %f (%f dB), txlev %f (factor %f)\n",sigma,sigma_dB,10*log10((double)txlev),(double)(double)frame_parms->ofdm_symbol_size/(12*nb_rb));
         for (i=0; i<slot_length; i++) {
           for (int aa=0; aa<1; aa++) {
             s_re[aa][i] = ((double)(((short *)&UE->common_vars.txdata[aa][slot_offset]))[(i<<1)]);
@@ -999,7 +987,6 @@ int main(int argc, char **argv)
           }
         }
 
-
         if (UE2gNB->max_Doppler == 0) {
           multipath_channel(UE2gNB,s_re,s_im,r_re,r_im,
                             slot_length,0,(n_trials==1)?1:0);
@@ -1009,8 +996,8 @@ int main(int argc, char **argv)
         }
         for (i=0; i<slot_length; i++) {
           for (ap=0; ap<frame_parms->nb_antennas_rx; ap++) {
-      ((int16_t*) &gNB->common_vars.rxdata[ap][slot_offset])[(2*i) + (delay*2)]   = (int16_t)((tx_gain*r_re[ap][i])   + (sqrt(sigma/2)*gaussdouble(0.0,1.0))); // convert to fixed point
-      ((int16_t*) &gNB->common_vars.rxdata[ap][slot_offset])[(2*i)+1 + (delay*2)]   = (int16_t)((tx_gain*r_im[ap][i]) + (sqrt(sigma/2)*gaussdouble(0.0,1.0)));
+            ((int16_t*) &gNB->common_vars.rxdata[ap][slot_offset])[(2*i) + (delay*2)]    = (int16_t)(r_re[ap][i] + (sqrt(sigma/2)*gaussdouble(0.0,1.0))); // convert to fixed point
+            ((int16_t*) &gNB->common_vars.rxdata[ap][slot_offset])[(2*i)+1 + (delay*2)]  = (int16_t)(r_im[ap][i] + (sqrt(sigma/2)*gaussdouble(0.0,1.0)));
             /* Add phase noise if enabled */
             if (pdu_bit_map & PUSCH_PDU_BITMAP_PUSCH_PTRS) {
               phase_noise(ts, &((int16_t*)&gNB->common_vars.rxdata[ap][slot_offset])[(2*i)],
@@ -1018,7 +1005,6 @@ int main(int argc, char **argv)
             }
           }
         }
-
       }
 
       if(pusch_pdu->pdu_bit_map & PUSCH_PDU_BITMAP_PUSCH_PTRS)