[develop] Added: common frequency offset compensation at gNB

    - post-compensation for UL and pre-compensation for DL
    - offset to be compensated is given through the  command-line option 'FDC'
    - compensation is default activated and it can be deactivated via the command-line option 'FC'

executables/nr-softmodem-common.h

@@ -121,6 +121,7 @@
 #define CONFIG_HLP_FDopplerRate  "Set the Doppler rate in Hz/s\n"
 #define CONFIG_HLP_FDopplerVar   "Set Doppler variance, [fdoppler +/- fdopplerVar]\n"
 #define CONFIG_HLP_TDriftComp    "Execute continous timing drift compensation\n"
+#define CONFIG_HLP_FDopplerPrePost      "Set the pre/post compensation value for the Doppler shift at the gNB side\n"
 /*--------------------------------------------------------------------------------------------------------------------------------*/
 /*                                            command line parameters for LOG utility                                             */
 /*   optname         helpstr          paramflags          XXXptr                     defXXXval            type           numelt   */
@@ -176,5 +177,6 @@ extern int RFsim_DriftPerFrame; //the timing offset/drift per frame in the RF si
 extern int32_t fdopplerRate; //Doppler rate in Hz/s
 extern uint32_t fdopplerVar; //Doppler variance, [fdoppler +/- fdopplerVar]
 extern int tdriftComp;         // flag to activate/deactivate continous timing drift compensation
+extern int32_t fdopplerPrePost; //pre/post compensation of the Doppler shift at the gNB side
 
 #endif

executables/nr-softmodem.c

@@ -577,6 +577,7 @@ int RFsim_DriftPerFrame = 0;
 int32_t fdopplerRate;
 uint32_t fdopplerVar;
 int tdriftComp = 1;
+int32_t fdopplerPrePost = 0; //pre/post compensation of the Doppler shift at the gNB side
 
 int main( int argc, char **argv ) {
   int ru_id, CC_id = 0;

executables/nr-softmodem.h

@@ -39,6 +39,8 @@
   {"TD" ,                   CONFIG_HLP_TDRIFT,         0,                .iptr=&RFsim_DriftPerFrame,          .defintval=0,                     TYPE_INT,    0},        \
   {"DSR" ,                  CONFIG_HLP_FDopplerRate,   0,                .iptr=&fdopplerRate,                 .defintval=0,                     TYPE_INT32,  0},        \
   {"DSV" ,                  CONFIG_HLP_FDopplerVar,    0,                .uptr=&fdopplerVar,                  .defintval=0,                     TYPE_UINT32, 0},        \
+  {"FDC" ,                  CONFIG_HLP_FDopplerPrePost,    0,            .iptr=&fdopplerPrePost,              .defintval=0,                     TYPE_INT32,  0},        \
+  {"FC" ,                   CONFIG_HLP_FDopplerComp,    0,               .iptr=&fdopplerComp,                 .defintval=0,                     TYPE_INT32,  0}        \
 }
 // clang-format on
 

executables/nr-uesoftmodem.c

@@ -433,6 +433,7 @@ int32_t fdopplerRate; //Doppler rate in Hz/s
 uint32_t fdopplerVar; //Doppler variance, [fdoppler +/- fdopplerVar]
 int fdopplerComp = 1; // flag to activate continous frequency offset compensation (=0 deacticated, =1 activated (default case))
 int tdriftComp = 1;
+int32_t fdopplerPrePost = 0; //pre/post compensation of the Doppler shift at the gNB side. Dummy definition at UE to avoid linking error.
 
 
 int main( int argc, char **argv ) {

openair1/PHY/MODULATION/slot_fep_nr.c

@@ -220,7 +220,8 @@ int nr_slot_fep_init_sync(PHY_VARS_NR_UE *ue,
   return 0;
 }
 
-
+extern int fdopplerPrePost; //Doppler frequency shift
+extern int fdopplerComp; 
 int nr_slot_fep_ul(NR_DL_FRAME_PARMS *frame_parms,
                    int32_t *rxdata,
                    int32_t *rxdataF,
@@ -242,6 +243,14 @@ int nr_slot_fep_ul(NR_DL_FRAME_PARMS *frame_parms,
     rxdata_offset += (idx_symb%(0x7<<frame_parms->numerology_index)) ? nb_prefix_samples : nb_prefix_samples0;
   rxdata_offset += frame_parms->ofdm_symbol_size * symbol;
 
+  if ((fdopplerComp == 1) && (fdopplerPrePost != 0)){
+    unsigned int curr_nb_prefix = (abs_symbol%(0x7<<frame_parms->numerology_index)) ? nb_prefix_samples : nb_prefix_samples0;
+    unsigned int nsamps = frame_parms->ofdm_symbol_size + curr_nb_prefix;
+    int16_t *rxdataDopp_ptr = (int16_t *)&rxdata[rxdata_offset - sample_offset - curr_nb_prefix];
+    uint32_t IdxDopp_Rx = rxdata_offset - curr_nb_prefix; //sample index in the calculation of the Doppler shift compensation for a slot
+    nr_apply_Doppler( rxdataDopp_ptr, nsamps, fdopplerPrePost, &IdxDopp_Rx, frame_parms);
+  }
+
   // use OFDM symbol from within 1/8th of the CP to avoid ISI
   rxdata_offset -= (nb_prefix_samples / frame_parms->ofdm_offset_divisor);
 

openair1/SCHED_NR/nr_ru_procedures.c

@@ -50,7 +50,8 @@
 
 
 extern int oai_exit;
-
+extern int fdopplerPrePost; //Doppler frequency shift
+extern int fdopplerComp; 
 // OFDM modulation core routine, generates a first_symbol to first_symbol+num_symbols on a particular slot and TX antenna port
 void nr_feptx0(RU_t *ru,int tti_tx,int first_symbol, int num_symbols, int aa) {
 
@@ -58,6 +59,7 @@ void nr_feptx0(RU_t *ru,int tti_tx,int first_symbol, int num_symbols, int aa) {
 
   unsigned int slot_offset,slot_offsetF;
   int slot = tti_tx;
+  uint32_t IdxDopp_Tx; //sample index in the calculation of the Doppler shift compensation for a slot on gNB side
 
 
   //VCD_SIGNAL_DUMPER_DUMP_FUNCTION_BY_NAME(VCD_SIGNAL_DUMPER_FUNCTIONS_PHY_PROCEDURES_RU_FEPTX_OFDM+(first_symbol!=0?1:0) , 1 );
@@ -75,6 +77,7 @@ void nr_feptx0(RU_t *ru,int tti_tx,int first_symbol, int num_symbols, int aa) {
 
   LOG_D(PHY,"SFN/SF:RU:TX:%d/%d aa %d Generating slot %d (first_symbol %d num_symbols %d) slot_offset %d, slot_offsetF %d\n",ru->proc.frame_tx, ru->proc.tti_tx,aa,slot,first_symbol,num_symbols,slot_offset,slot_offsetF);
   
+  IdxDopp_Tx = slot_offset;
   if (fp->Ncp == 1) {
     PHY_ofdm_mod(&ru->common.txdataF_BF[aa][slot_offsetF],
                  (int*)&ru->common.txdata[aa][slot_offset],
@@ -99,6 +102,11 @@ void nr_feptx0(RU_t *ru,int tti_tx,int first_symbol, int num_symbols, int aa) {
                      num_symbols-1,
                      fp->nb_prefix_samples,
                      CYCLIC_PREFIX);
+       
+        if ((fdopplerComp == 1) && (fdopplerPrePost != 0)){
+          nr_apply_Doppler( &ru->common.txdata[aa][slot_offset], (num_symbols-1)*(fp->nb_prefix_samples+fp->ofdm_symbol_size)
+              +fp->ofdm_symbol_size+fp->nb_prefix_samples0, fdopplerPrePost, &(IdxDopp_Tx), fp); //Doppler pre-compensation at gNB Tx
+        }
       }
       else { // all symbols in slot have shorter prefix
         PHY_ofdm_mod(&ru->common.txdataF_BF[aa][slot_offsetF],
@@ -107,6 +115,10 @@ void nr_feptx0(RU_t *ru,int tti_tx,int first_symbol, int num_symbols, int aa) {
                      num_symbols,
                      fp->nb_prefix_samples,
                      CYCLIC_PREFIX);
+        if ((fdopplerComp == 1) && (fdopplerPrePost != 0)){
+          nr_apply_Doppler( &ru->common.txdata[aa][slot_offset], num_symbols*(fp->nb_prefix_samples+fp->ofdm_symbol_size),
+            fdopplerPrePost, &(IdxDopp_Tx), fp); //Doppler pre-compensation at gNB Tx
+        }
       }
     } // numerology_index!=0
     else { //numerology_index == 0