NR UE: introduce orbit propagation to improve N_UE_TA_adj accuracy

Instead of trying to estimate N_UE_TA_adj with a second degree polynomial,
we introduce orbit propagation to calculate N_UE_TA_adj with higher accuracy.

When we receive the satellite ephemeris data consisting of the satellite position vector
and the satellite velocity vector, we calculate parameters for orbit propagation, assuming
a circular orbit in the plane created by the satellite position vector and the satellite
velocity vector. This is done in the function prepare_ue_sat_ta().

Every millisecond, we use these parameters together with the time since epoch to calculate
the satellite position on that orbit and from this the reound-trip-time between UE and the
satellite, what corresponds to N_UE_TA_adj. This is done in the function apply_ntn_timing_advance().

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

@@ -24,6 +24,7 @@
 #include "PHY/impl_defs_top.h"
 #include "PHY/impl_defs_nr.h"
 #include "common/utils/nr/nr_common.h"
+#include "executables/position_interface.h"
 
 #define NFAPI_UE_MAX_NUM_CB 8
 #define NFAPI_MAX_NUM_UL_PDU 255
@@ -566,15 +567,22 @@ typedef struct {
   int epoch_sfn;
   int epoch_subframe;
 
+  // orbital angular velocity in rad/ms
+  double omega;
+  // satellite position at epoch time
+  position_t pos_sat_0;
+  // satellite position at 90° orbit
+  position_t pos_sat_90;
+
+  // N_common_ta_adj represents common round-trip-time between gNB and SAT received in SIB19 (ms)
+  double N_common_ta_adj;
+  // drift rate of common ta in µs/s
+  double N_common_ta_drift;
+  // change rate of common ta drift in µs/s²
+  double N_common_ta_drift_variant;
+
   // cell scheduling offset expressed in terms of 15kHz SCS
   long cell_specific_k_offset;
-
-  // ntn_total_time_advance_ms represents the complete round-trip-time between gNB and UE via SAT
-  double ntn_total_time_advance_ms;
-  // drift rate of ntn_total_time_advance_ms in µs/s
-  double ntn_total_time_advance_drift;
-  // change rate of ntn_total_time_advance_ms drift in µs/s²
-  double ntn_total_time_advance_drift_variant;
 } fapi_nr_dl_ntn_config_command_pdu;
 
 typedef struct {