NR UE: provide velocity vector down to nr-ue.c, preparing for Doppler calculation

executables/nr-ue.c

@@ -732,15 +732,32 @@ static inline void apply_ntn_timing_advance(PHY_VARS_NR_UE *UE, const NR_DL_FRAM
                                + ntn_config_params->epoch_hfn * 10240;
   const int ms_since_epoch = abs_subframe_tx - abs_subframe_epoch;
 
-  const double omega = ntn_config_params->omega;
-  const double cos_wt = cos(omega * ms_since_epoch);
-  const double sin_wt = sin(omega * ms_since_epoch);
-
   const position_t pos_sat_0 = ntn_config_params->pos_sat_0;
-  const position_t pos_sat_90 = ntn_config_params->pos_sat_90;
-  const position_t pos_sat = {pos_sat_0.X * cos_wt + pos_sat_90.X * sin_wt,
-                              pos_sat_0.Y * cos_wt + pos_sat_90.Y * sin_wt,
-                              pos_sat_0.Z * cos_wt + pos_sat_90.Z * sin_wt};
+  const position_t vel_sat_0 = ntn_config_params->vel_sat_0;
+
+  position_t pos_sat;
+  position_t vel_sat;
+
+  const double omega = ntn_config_params->omega;
+  if (omega) {
+    const double cos_wt = cos(omega * ms_since_epoch);
+    const double sin_wt = sin(omega * ms_since_epoch);
+
+    const position_t pos_sat_90 = ntn_config_params->pos_sat_90;
+    pos_sat = (position_t){pos_sat_0.X * cos_wt + pos_sat_90.X * sin_wt,
+                           pos_sat_0.Y * cos_wt + pos_sat_90.Y * sin_wt,
+                           pos_sat_0.Z * cos_wt + pos_sat_90.Z * sin_wt};
+
+    const position_t vel_sat_90 = ntn_config_params->vel_sat_90;
+    vel_sat = (position_t){vel_sat_0.X * cos_wt + vel_sat_90.X * sin_wt,
+                           vel_sat_0.Y * cos_wt + vel_sat_90.Y * sin_wt,
+                           vel_sat_0.Z * cos_wt + vel_sat_90.Z * sin_wt};
+  } else {
+    pos_sat = (position_t){pos_sat_0.X + vel_sat_0.X * ms_since_epoch / 1000,
+                           pos_sat_0.Y + vel_sat_0.Y * ms_since_epoch / 1000,
+                           pos_sat_0.Z + vel_sat_0.Z * ms_since_epoch / 1000};
+    vel_sat = vel_sat_0;
+  }
 
   position_t pos_ue = {0};
   get_position_coordinates(UE->Mod_id, &pos_ue);
@@ -751,6 +768,9 @@ static inline void apply_ntn_timing_advance(PHY_VARS_NR_UE *UE, const NR_DL_FRAM
   // calculate distance between SAT and UE
   const double distance = sqrt(dir_sat_ue.X * dir_sat_ue.X + dir_sat_ue.Y * dir_sat_ue.Y + dir_sat_ue.Z * dir_sat_ue.Z);
 
+  // calculate projected velocity from SAT towards UE
+  const double vel_sat_ue = (vel_sat.X * dir_sat_ue.X + vel_sat.Y * dir_sat_ue.Y + vel_sat.Z * dir_sat_ue.Z) / distance;
+
   // calculate round-trip-time (factor 2) between SAT and UE in ms (factor 1000)
   const double N_UE_TA_adj = 2000 * distance / SPEED_OF_LIGHT;
 
@@ -764,14 +784,15 @@ static inline void apply_ntn_timing_advance(PHY_VARS_NR_UE *UE, const NR_DL_FRAM
                          * fp->samples_per_subframe;
 
   LOG_D(PHY,
-        "N_UE_TA_adj = %f ms, N_common_ta_adj = %f ms, N_common_ta_drift = %f µs/s, N_common_ta_drift_variant = %f µs/s², ms_since_epoch = %d ms, "
-        "computed timing_advance_ntn = %d samples\n",
+        "N_UE_TA_adj = %f ms, N_common_ta_adj = %f ms, N_common_ta_drift = %f µs/s, N_common_ta_drift_variant = %f µs/s², "
+        "ms_since_epoch = %d ms, computed timing_advance_ntn = %d samples, satellite velocity towards UE = %f m/s\n",
         N_UE_TA_adj,
         N_common_ta_adj,
         N_common_ta_drift,
         N_common_ta_drift_variant,
         ms_since_epoch,
-        UE->timing_advance_ntn);
+        UE->timing_advance_ntn,
+        vel_sat_ue);
 }
 
 static inline void apply_ntn_config(PHY_VARS_NR_UE *UE,

nfapi/open-nFAPI/nfapi/public_inc/fapi_nr_ue_interface.h

@@ -569,10 +569,14 @@ typedef struct {
 
   // orbital angular velocity in rad/ms
   double omega;
-  // satellite position at epoch time
+  // satellite position vector at epoch time
   position_t pos_sat_0;
-  // satellite position at 90° orbit
+  // satellite position vector at 90° orbit
   position_t pos_sat_90;
+  // satellite velocity vector at epoch time
+  position_t vel_sat_0;
+  // satellite velocity vector at 90° orbit
+  position_t vel_sat_90;
 
   // N_common_ta_adj represents common round-trip-time between gNB and SAT received in SIB19 (ms)
   double N_common_ta_adj;

openair1/SCHED_NR_UE/fapi_nr_ue_l1.c

@@ -102,6 +102,8 @@ static void configure_ntn_params(PHY_VARS_NR_UE *ue, fapi_nr_dl_ntn_config_comma
   ue->ntn_config_message->ntn_config_params.omega = ntn_params_message->omega;
   ue->ntn_config_message->ntn_config_params.pos_sat_0 = ntn_params_message->pos_sat_0;
   ue->ntn_config_message->ntn_config_params.pos_sat_90 = ntn_params_message->pos_sat_90;
+  ue->ntn_config_message->ntn_config_params.vel_sat_0 = ntn_params_message->vel_sat_0;
+  ue->ntn_config_message->ntn_config_params.vel_sat_90 = ntn_params_message->vel_sat_90;
 
   ue->ntn_config_message->ntn_config_params.N_common_ta_adj = ntn_params_message->N_common_ta_adj;
   ue->ntn_config_message->ntn_config_params.N_common_ta_drift = ntn_params_message->N_common_ta_drift;

openair2/LAYER2/NR_MAC_UE/config_ue.c

@@ -279,29 +279,49 @@ static void prepare_ue_sat_ta(const NR_PositionVelocity_r17_t *sat_pos, ntn_timi
   const double vel_sat_2 = vel_sat.X * vel_sat.X + vel_sat.Y * vel_sat.Y + vel_sat.Z * vel_sat.Z;
   const double vel_mag = sqrt(vel_sat_2);
 
-  // calculate angular velocity in rad/ms
-  const double omega = vel_mag / (radius * 1000);
-
-  // calculate sat position in 90° orbit
-  position_t pos_sat_90 = pos_sat;
-  if (vel_mag) {
-    const double scaling = radius / vel_mag;
+  double omega; // angular velocity in rad/ms
+  position_t pos_sat_90; // sat position vector in 90° orbit
+  position_t vel_sat_90; // sat velocity vector in 90° orbit
+
+  // assuming circular orbit when satellite moves faster than 1000 m/s
+  // 1000 m/s are chosen because according to Wikipedia, this seems to be a reasonable minimal
+  // orbital velocity: https://en.wikipedia.org/wiki/Orbital_speed#Tangential_velocities_at_altitude
+  if (vel_mag > 1000) {
+    omega = vel_mag / (radius * 1000);
+    double scaling = radius / vel_mag;
     pos_sat_90 = (position_t){vel_sat.X * scaling, vel_sat.Y * scaling, vel_sat.Z * scaling};
+    scaling = -vel_mag / radius;
+    vel_sat_90 = (position_t){pos_sat.X * scaling, pos_sat.Y * scaling, pos_sat.Z * scaling};
+  } else {
+    omega = 0;
+    pos_sat_90 = pos_sat;
+    vel_sat_90 = vel_sat;
   }
 
   LOG_I(NR_MAC,
-        "Satellite angular velocity = %e rad/ms, sat_pos = {%f, %f, %f}, sat_pos_90 = {%f, %f, %f}\n",
-        omega,
+        "Satellite orbital radius %f m, pos_sat_0 = {%f, %f, %f}, pos_sat_90 = {%f, %f, %f}\n"
+        "Satellite velocity %f m/s, angular velocity = %e rad/ms, vel_sat_0 = {%f, %f, %f}, vel_sat_90 = {%f, %f, %f}\n",
+        radius,
         pos_sat.X,
         pos_sat.Y,
         pos_sat.Z,
         pos_sat_90.X,
         pos_sat_90.Y,
-        pos_sat_90.Z);
+        pos_sat_90.Z,
+        vel_mag,
+        omega,
+        vel_sat.X,
+        vel_sat.Y,
+        vel_sat.Z,
+        vel_sat_90.X,
+        vel_sat_90.Y,
+        vel_sat_90.Z);
 
   ntn_ta->omega = omega;
   ntn_ta->pos_sat_0 = pos_sat;
   ntn_ta->pos_sat_90 = pos_sat_90;
+  ntn_ta->vel_sat_0 = vel_sat;
+  ntn_ta->vel_sat_90 = vel_sat_90;
 }
 
 // populate ntn_ta structure from mac
@@ -332,11 +352,15 @@ static void configure_ntn_ta(ntn_timing_advance_componets_t *ntn_ta, const NR_NT
       ntn_ta->omega = 0;
       ntn_ta->pos_sat_0 = (position_t){0, 0, 0};
       ntn_ta->pos_sat_90 = (position_t){0, 0, 0};
+      ntn_ta->vel_sat_0 = (position_t){0, 0, 0};
+      ntn_ta->vel_sat_90 = (position_t){0, 0, 0};
     }
   } else { // Need R - Release if not present
     ntn_ta->omega = 0;
     ntn_ta->pos_sat_0 = (position_t){0, 0, 0};
     ntn_ta->pos_sat_90 = (position_t){0, 0, 0};
+    ntn_ta->vel_sat_0 = (position_t){0, 0, 0};
+    ntn_ta->vel_sat_90 = (position_t){0, 0, 0};
   }
 
   // handle cellSpecificKoffset_r17

openair2/LAYER2/NR_MAC_UE/mac_defs.h

@@ -552,10 +552,14 @@ typedef struct ntn_timing_advance_components {
 
   // orbital angular velocity in rad/ms
   double omega;
-  // satellite position at epoch time
+  // satellite position vector at epoch time
   position_t pos_sat_0;
-  // satellite position at 90° orbit
+  // satellite position vector at 90° orbit
   position_t pos_sat_90;
+  // satellite velocity vector at epoch time
+  position_t vel_sat_0;
+  // satellite velocity vector at 90° orbit
+  position_t vel_sat_90;
 
   // N_common_ta_adj represents common round-trip-time between gNB and SAT received in SIB19 (ms)
   double N_common_ta_adj;

openair2/LAYER2/NR_MAC_UE/nr_ue_scheduler.c

@@ -2855,6 +2855,8 @@ static void schedule_ntn_config_command(fapi_nr_dl_config_request_t *dl_config,
   ntn_config_command_pdu->omega = mac->ntn_ta.omega;
   ntn_config_command_pdu->pos_sat_0 = mac->ntn_ta.pos_sat_0;
   ntn_config_command_pdu->pos_sat_90 = mac->ntn_ta.pos_sat_90;
+  ntn_config_command_pdu->vel_sat_0 = mac->ntn_ta.vel_sat_0;
+  ntn_config_command_pdu->vel_sat_90 = mac->ntn_ta.vel_sat_90;
 
   ntn_config_command_pdu->N_common_ta_adj = mac->ntn_ta.N_common_ta_adj;
   ntn_config_command_pdu->N_common_ta_drift = mac->ntn_ta.N_common_ta_drift;