FFO estimation and compensation optional via command line

openair1/PHY/NR_REFSIG/pss_nr.h

@@ -137,6 +137,7 @@ int set_pss_nr(int ofdm_symbol_size);
 int pss_synchro_nr(PHY_VARS_NR_UE *PHY_vars_UE, int rate_change);
 int pss_search_time_nr(int **rxdata, ///rx data in time domain
                        NR_DL_FRAME_PARMS *frame_parms,
+		       int fo_flag,
                        int *eNB_id,
 		       int *f_off);
 

openair1/PHY/NR_UE_TRANSPORT/nr_initial_sync.c

@@ -203,18 +203,20 @@ int nr_initial_sync(PHY_VARS_NR_UE *ue, runmode_t mode)
 #endif
 
   // digital compensation of FFO for SSB symbols
-  double s_time = 1/(1.0e3*fp->samples_per_subframe);  // sampling time
+  if (ue->UE_fo_compensation){  
-  double off_angle = -2*M_PI*s_time*(ue->common_vars.freq_offset);  // offset rotation angle compensation per sample
+	double s_time = 1/(1.0e3*fp->samples_per_subframe);  // sampling time
+	double off_angle = -2*M_PI*s_time*(ue->common_vars.freq_offset);  // offset rotation angle compensation per sample
 
-  int start = ue->ssb_offset;  // start for offset correction is at ssb_offset (pss time position)
+	int start = ue->ssb_offset;  // start for offset correction is at ssb_offset (pss time position)
-  int end = start + 4*(fp->ofdm_symbol_size + fp->nb_prefix_samples);  // loop over samples in 4 symbols (ssb size), including prefix  
+  	int end = start + 4*(fp->ofdm_symbol_size + fp->nb_prefix_samples);  // loop over samples in 4 symbols (ssb size), including prefix  
 
-  for(int n=start; n<end; n++){  	
+	for(int n=start; n<end; n++){  	
-	for (int ar=0; ar<fp->nb_antennas_rx; ar++) {
+	  for (int ar=0; ar<fp->nb_antennas_rx; ar++) {
 		re = ((double)(((short *)ue->common_vars.rxdata[ar]))[2*n]);
 		im = ((double)(((short *)ue->common_vars.rxdata[ar]))[2*n+1]);
 		((short *)ue->common_vars.rxdata[ar])[2*n] = (short)(round(re*cos(n*off_angle) - im*sin(n*off_angle))); 
 		((short *)ue->common_vars.rxdata[ar])[2*n+1] = (short)(round(re*sin(n*off_angle) + im*cos(n*off_angle)));
+	  }
 	}
   }
 

openair1/PHY/NR_UE_TRANSPORT/pss_nr.c

@@ -663,6 +663,7 @@ int pss_synchro_nr(PHY_VARS_NR_UE *PHY_vars_UE, int rate_change)
   NR_DL_FRAME_PARMS *frame_parms = &(PHY_vars_UE->frame_parms);
   int synchro_position;
   int **rxdata = NULL;
+  int fo_flag = PHY_vars_UE->UE_fo_compensation;  // flag to enable freq offset estimation and compensation
 
 #ifdef DBG_PSS_NR
 
@@ -706,6 +707,7 @@ int pss_synchro_nr(PHY_VARS_NR_UE *PHY_vars_UE, int rate_change)
 
   synchro_position = pss_search_time_nr(rxdata,
                                         frame_parms,
+					fo_flag,
                                         (int *)&PHY_vars_UE->common_vars.eNb_id,
 					(int *)&PHY_vars_UE->common_vars.freq_offset);
 
@@ -817,14 +819,15 @@ static inline double angle64(int64_t x)
 
 int pss_search_time_nr(int **rxdata, ///rx data in time domain
                        NR_DL_FRAME_PARMS *frame_parms,
+		       int fo_flag,
                        int *eNB_id,
 		       int *f_off)
 {
   unsigned int n, ar, peak_position, pss_source;
   int64_t peak_value;
-  int64_t result,result1,result2;
+  int64_t result;
   int64_t avg[NUMBER_PSS_SEQUENCE];
-  double ffo_est;
+  double ffo_est=0;
 
 
   unsigned int length = (NR_NUMBER_OF_SUBFRAMES_PER_FRAME*frame_parms->samples_per_subframe);  /* 1 frame for now, it should be 2 TODO_NR */
@@ -894,34 +897,36 @@ int pss_search_time_nr(int **rxdata, ///rx data in time domain
     }
   }
 
+  if (fo_flag){
+	  // fractional frequency offser computation according to Cross-correlation Synchronization Algorithm Using PSS
+	  // Shoujun Huang, Yongtao Su, Ying He and Shan Tang, "Joint time and frequency offset estimation in LTE downlink," 7th International Conference on Communications and Networking in China, 2012.
 
-  // fractional frequency offser computation according to Cross-correlation Synchronization Algorithm Using PSS
+	  int64_t result1,result2;
-  // Shoujun Huang, Yongtao Su, Ying He and Shan Tang, "Joint time and frequency offset estimation in LTE downlink," 7th International Conference on Communications and Networking in China, 2012.
+	  // Computing cross-correlation at peak on half the symbol size for first half of data
-
+	  result1  = dot_product64((short*)primary_synchro_time_nr[pss_source], 
-  // Computing cross-correlation at peak on half the symbol size for first half of data
-  result1  = dot_product64((short*)primary_synchro_time_nr[pss_source], 
 				  (short*) &(rxdata[0][peak_position]), 
 				  frame_parms->ofdm_symbol_size>>1, 
 				  shift);
-  // Computing cross-correlation at peak on half the symbol size for data shifted by half symbol size 
+	  // Computing cross-correlation at peak on half the symbol size for data shifted by half symbol size 
-  // as it is real and complex it is necessary to shift by a value equal to symbol size to obtain such shift
+	  // as it is real and complex it is necessary to shift by a value equal to symbol size to obtain such shift
-  result2  = dot_product64((short*)primary_synchro_time_nr[pss_source]+(frame_parms->ofdm_symbol_size), 
+	  result2  = dot_product64((short*)primary_synchro_time_nr[pss_source]+(frame_parms->ofdm_symbol_size), 
 				  (short*) &(rxdata[0][peak_position])+(frame_parms->ofdm_symbol_size), 
 				  frame_parms->ofdm_symbol_size>>1, 
 				  shift);
 
-  int64_t re1,re2,im1,im2;
+	  int64_t re1,re2,im1,im2;
-  re1=((int*) &result1)[0];
+	  re1=((int*) &result1)[0];
-  re2=((int*) &result2)[0];
+	  re2=((int*) &result2)[0];
-  im1=((int*) &result1)[1];
+	  im1=((int*) &result1)[1];
-  im2=((int*) &result2)[1];
+	  im2=((int*) &result2)[1];
 
-  // estimation of fractional frequency offset: angle[(result1)'*(result2)]/pi
+ 	  // estimation of fractional frequency offset: angle[(result1)'*(result2)]/pi
-  ffo_est=atan2(re1*im2-re2*im1,re1*re2+im1*im2)/M_PI;
+	  ffo_est=atan2(re1*im2-re2*im1,re1*re2+im1*im2)/M_PI;
   
 #ifdef DBG_PSS_NR
-  printf("ffo %lf\n",ffo_est);
+	  printf("ffo %lf\n",ffo_est);
 #endif
+  }
 
   // computing absolute value of frequency offset
   *f_off = ffo_est*frame_parms->subcarrier_spacing;  

openair1/PHY/defs_nr_UE.h

@@ -983,6 +983,8 @@ typedef struct {
   int UE_scan;
   /// \brief Indicator that UE should perform coarse scanning around carrier
   int UE_scan_carrier;
+  /// \brief Indicator that UE should enable estimation and compensation of frequency offset
+  int UE_fo_compensation;
   /// \brief Indicator that UE is synchronized to an eNB
   int is_synchronized;
   /// Data structure for UE process scheduling

openair1/SIMULATION/NR_PHY/pbchsim.c

@@ -462,6 +462,9 @@ int main(int argc, char **argv)
                       
   UE->perfect_ce = 0;
 
+  if(eps!=0.0)
+	UE->UE_fo_compensation = 1; // if a frequency offset is set then perform fo estimation and compensation
+
   if (init_nr_ue_signal(UE, 1, 0) != 0)
   {
     printf("Error at UE NR initialisation\n");

targets/RT/USER/nr-uesoftmodem.c

@@ -130,6 +130,7 @@ static char                    *itti_dump_file = NULL;
 
 int UE_scan = 0;
 int UE_scan_carrier = 0;
+int UE_fo_compensation = 0;
 runmode_t mode = normal_txrx;
 
 FILE *input_fd=NULL;
@@ -978,6 +979,7 @@ int main( int argc, char **argv ) {
     
     UE[CC_id]->UE_scan = UE_scan;
     UE[CC_id]->UE_scan_carrier = UE_scan_carrier;
+    UE[CC_id]->UE_fo_compensation = UE_fo_compensation;
     UE[CC_id]->mode    = mode;
     printf("UE[%d]->mode = %d\n",CC_id,mode);
     

targets/RT/USER/nr-uesoftmodem.h

@@ -55,6 +55,7 @@
 #define CONFIG_HLP_UENANTR       "set UE number of rx antennas\n"
 #define CONFIG_HLP_UENANTT       "set UE number of tx antennas\n"
 #define CONFIG_HLP_UESCAN        "set UE to scan around carrier\n"
+#define CONFIG_HLP_UEFO	         "set UE to enable estimation and compensation of frequency offset\n"
 #define CONFIG_HLP_DUMPFRAME     "dump UE received frame to rxsig_frame0.dat and exit\n"
 #define CONFIG_HLP_DLSHIFT       "dynamic shift for LLR compuation for TM3/4 (default 0)\n"
 #define CONFIG_HLP_UELOOP        "get softmodem (UE) to loop through memory instead of acquiring from HW\n"
@@ -135,6 +136,7 @@
 {"ue-nb-ant-rx",     	       CONFIG_HLP_UENANTR,    0,		u8ptr:&nb_antenna_rx,		    defuintval:1,   TYPE_UINT8,    0},     \
 {"ue-nb-ant-tx",     	       CONFIG_HLP_UENANTT,    0,		u8ptr:&nb_antenna_tx,		    defuintval:1,   TYPE_UINT8,    0},     \
 {"ue-scan-carrier",  	       CONFIG_HLP_UESCAN,     PARAMFLAG_BOOL,	iptr:&UE_scan_carrier,  	    defintval:0,    TYPE_INT,	   0},     \
+{"ue-fo-compensation", 	       CONFIG_HLP_UEFO,	      PARAMFLAG_BOOL,	iptr:&UE_fo_compensation,  	    defintval:0,    TYPE_INT,	   0},     \
 {"ue-max-power",     	       NULL,		      0,		iptr:&(tx_max_power[0]),	    defintval:90,   TYPE_INT,	   0},     \
 {"r"  ,                        CONFIG_HLP_PRB,        0,                iptr:&(frame_parms[0]->N_RB_DL),   defintval:25,   TYPE_UINT,    0},     \
 {"dlsch-demod-shift",     	 CONFIG_HLP_DLSHIFT,	0,		  iptr:(int32_t *)&dlsch_demod_shift,	defintval:0,			   TYPE_INT,	  0},			   \