timing offset algorithm updated during initial sync

    - command line options for timing offset rate and frequency offset at Point A

executables/nr-softmodem-common.h

@@ -140,6 +140,9 @@
 #define CONFIG_HLP_AMC           "flag to use adaptive modulation and coding: 1 = use AMC \n"
 #define CONFIG_HLP_SINR_OSET_DL  "Additional SINR offset in [dB] applied to the reported SINR from UE for DL AMC \n"
 #define CONFIG_HLP_SINR_OSET_UL  "Additional SINR offset in [dB] applied to the measured SINR at gNB for UL AMC \n"
+#define CONFIG_HLP_TO_Init_Rate     "change rate of the timing offset during the initialization phase, in samples/frame \n"
+#define CONFIG_HLP_FO_Sync_Offset   "frequency offset of point A \n"
+
 /*--------------------------------------------------------------------------------------------------------------------------------*/
 /*                                            command line parameters for LOG utility                                             */
 /*   optname         helpstr          paramflags          XXXptr                     defXXXval            type           numelt   */
@@ -206,5 +209,6 @@ extern double TO_PScaling;
 extern double TO_IScaling;
 
 extern int commonDoppler;
+extern int TO_init_rate; 
 
 #endif

executables/nr-softmodem.c

@@ -591,6 +591,7 @@ int tdriftComp = 1;
 int TO_IScalingInit = 0;
 int32_t fdopplerPrePost = 0; //pre/post compensation of the Doppler shift at the gNB side
 int commonDoppler = 0;  // common doppler to be compensated at UE, but set here to avoid linking error
+int TO_init_rate = 0;
 
 int main( int argc, char **argv ) {
   int ru_id, CC_id = 0;

executables/nr-ue.c

@@ -808,6 +808,8 @@ void *UE_thread(void *arg)
   NR_UE_MAC_INST_t *mac = get_mac_inst(0);
   int rx_offset_slot = 0; //samples to be shifted for the current slot
   int UL_TO_Tx_ofs = 0;
+  static int acc_UL_To_TX = 0;   // acculating samples compensated on UL through timing advance 
+  extern int tshift;
 
   bool syncRunning=false;
   const int nb_slot_frame = UE->frame_parms.slots_per_frame;
@@ -830,6 +832,17 @@ void *UE_thread(void *arg)
       if (res) {
         syncRunning=false;
         if (UE->is_synchronized) {
+          if (tshift)
+          {
+            int diff = TO_init_rate;   // shift in two frames       
+            UE->TO_I_Ctrl += diff;
+            UE->rx_offset_TO = (TO_PScaling*diff) + (UE->TO_I_Ctrl*TO_IScaling); //PI controller
+            UE->rx_offset_slot = 1;
+            UE->rx_offset_comp = 0;
+            int ta_shift = (UE->init_sync_frame + trashed_frames)*2*diff;
+            UE->timing_advance += ta_shift;
+            timing_advance = UE->timing_advance;
+          } 
           decoded_frame_rx = mac->mib_frame;
           LOG_I(PHY,"UE synchronized decoded_frame_rx=%d UE->init_sync_frame=%d trashed_frames=%d\n",
                 decoded_frame_rx,
@@ -922,7 +935,8 @@ void *UE_thread(void *arg)
       rx_offset_slot = UE->rx_offset_TO * UE->rx_offset_slot / nb_slot_frame - UE->rx_offset_comp;
       UE->rx_offset_comp += rx_offset_slot;
       UE->rx_offset_slot++;
-      UL_TO_Tx_ofs += 2*rx_offset_slot; //to adapt the UE's transmission time in order to get aligned at gNB
+      UL_TO_Tx_ofs = 2*rx_offset_slot; //to adapt the UE's transmission time in order to get aligned at gNB
+      acc_UL_To_TX += UL_TO_Tx_ofs;
     }
 
     readBlockSize=get_readBlockSize(slot_nr, &UE->frame_parms) + rx_offset_slot;
@@ -963,7 +977,7 @@ void *UE_thread(void *arg)
     //timing_advance += 2*rx_offset_slot;
 
     //UE->timing_advance += 1*rx_offset_slot;
-    UE->timing_advance += 2*rx_offset_slot;
+    UE->timing_advance += UL_TO_Tx_ofs;
 
     extern uint64_t RFsim_PropDelay;
     LOG_D(PHY, "RFsim_PropDelay: %lu,         TA: %d,         diff: %d,          PI_Out: %d,       offset_slot: %d,     offset_UL: %d\n", 

executables/nr-uesoftmodem.c

@@ -449,6 +449,7 @@ double TO_IScaling = 0.1;
 int TO_IScalingInit = 0;
 
 int commonDoppler = 0; //421528;
+int TO_init_rate = 0;
 
 
 int main( int argc, char **argv ) {

executables/nr-uesoftmodem.h

@@ -80,7 +80,10 @@
   {"TOI" ,                         CONFIG_HLP_TI_Scaling,      0,               .dblptr=&TO_IScaling,                        .defdblval=0.1,    TYPE_DOUBLE,   0}, \
   {"TOII",                         CONFIG_HLP_TO_Iinit,        0,               .iptr=&TO_IScalingInit,                      .defintval=0,      TYPE_INT,      0},  \
   {"agc",                          CONFIG_HLP_AGC,         PARAMFLAG_BOOL,      .iptr=&(nrUE_params.enable_agc),             .defintval=0,      TYPE_INT,      0},\
-  {"ulpc",                         CONFIG_HLP_ULPC,        PARAMFLAG_BOOL,      .iptr=&(nrUE_params.enable_ulpc),            .defintval=0,      TYPE_INT,      0}}
+  {"ulpc",                         CONFIG_HLP_ULPC,        PARAMFLAG_BOOL,      .iptr=&(nrUE_params.enable_ulpc),            .defintval=0,      TYPE_INT,      0},\
+  {"TOIR",                         CONFIG_HLP_TO_Init_Rate,    0,               .iptr=&TO_init_rate,                         .defintval=0,      TYPE_INT,      0},  \
+  {"FOPA",                         CONFIG_HLP_FO_Sync_Offset,  0,               .iptr=&commonDoppler,                        .defintval=0,      TYPE_INT,      0},  \
+}
 // clang-format on
 
 typedef struct {

openair1/PHY/INIT/nr_init_ue.c

@@ -385,6 +385,8 @@ int init_nr_ue_signal(PHY_VARS_NR_UE *ue, int nb_connected_gNB)
   // set the initial frequency offset to 0
   ue->DopplerEst = 0;
   ue->DopplerEstTot = (float)commonDoppler;
+
+  ue->TO_I_Ctrl = 0;
   
   ue->f_pusch = 0;
   return 0;

openair1/PHY/NR_UE_ESTIMATION/nr_adjust_synch_ue.c

@@ -104,9 +104,9 @@ void nr_adjust_synch_ue(NR_DL_FRAME_PARMS *frame_parms,
 	  flagInitIScaling = 1;
   }
 
-  TO_I_Ctrl += diff; //integral of all offsets
+  ue->TO_I_Ctrl += diff; //integral of all offsets
   ue->rx_offset = diff;
-  ue->rx_offset_TO = (TO_PScaling*diff) + (TO_I_Ctrl*TO_IScaling); //PI controller
+  ue->rx_offset_TO = (TO_PScaling*diff) + (ue->TO_I_Ctrl*TO_IScaling); //PI controller
   ue->rx_offset_slot = 1;
   ue->rx_offset_comp = 0;
 

openair1/PHY/defs_nr_UE.h

@@ -566,6 +566,7 @@ typedef struct {
   int              rx_offset_TO; /// Timing offset used for compensating the time drift due to high speed
   int              rx_offset_slot; /// Indicating time (in slots) after rx_offset calculation
   int              rx_offset_comp; /// Already compensated rx_offset
+  int              TO_I_Ctrl;      /// accululative part for tracking timing offset 
 
   // Estimated Doppler frequency shift from the DMRS
   int32_t DopplerEst;

radio/rfsimulator/simulator.c

@@ -959,7 +959,7 @@ static int rfsimulator_read(openair0_device *device, openair0_timestamp *ptimest
           int nbAnt_tx = ptr->th.nbAnt;//number of Tx antennas
           
           double timeForDoppler = (double)pathStartingTime;
-          if (counter > 6000)
+          if ( ((t-> typeStamp != ENB_MAGICDL) && (TO_UE_flag == 1)) || ((TO_gNB_flag == 1) && (t->typeStamp == ENB_MAGICDL)) )
             timeForDoppler = (double)pathStartingTime + (double)SampIdxDoppler/fsamp;
           
           if (timeForDoppler > (double)pathEndingTime)
@@ -998,7 +998,7 @@ static int rfsimulator_read(openair0_device *device, openair0_timestamp *ptimest
               out[i].i += (short)(ptr->circularBuf[((t->nextRxTstamp-RFsim_PropDelay+i)*nbAnt_tx+a_tx)%CirSize].i*H_awgn_mimo[a][a_tx]);
             } // end for a_tx
 
-            if ((counter > 6000))
+            if ( ((t-> typeStamp != ENB_MAGICDL) && (TO_UE_flag == 1)) || ((TO_gNB_flag == 1) && (t->typeStamp == ENB_MAGICDL)) )
             {
               int16_t outRealTmp = out[i].r;
               int16_t outImagTmp = out[i].i;