band_helper: add helper to derive DL/UL freq from abs_freq_point

calculate DL and UL freq in carrier struct based on given values

lib/include/srsran/common/band_helper.h

@@ -31,6 +31,9 @@ public:
   // Return frequency of given NR-ARFCN in Hz
   double nr_arfcn_to_freq(uint32_t nr_arfcn);
 
+  // Frequency in Hz to NR-ARFCN
+  uint32_t freq_to_nr_arfcn(double freq);
+
   // Possible values of delta f_raster in Table 5.4.2.3-1 and Table 5.4.2.3-2
   enum delta_f_raster_t {
     DEFAULT = 0, // for bands with 2 possible values for delta_f_raster (e.g. 15 and 30 kHz), the lower is chosen
@@ -70,6 +73,16 @@ public:
    */
   uint32_t get_ul_arfcn_from_dl_arfcn(uint32_t dl_arfcn) const;
 
+  /**
+   * @brief Compute the DL and UL center frequency for a NR carrier
+   *
+   * Results are stored inside the carrier struct.
+   *
+   * @param carrier  Reference to a carrier struct including PRB, abs. frequency point A and carrier offset.
+   * @return int SRSRAN_SUCESS The center frequency
+   */
+  int get_center_freq_from_abs_freq_point_a(srsran_carrier_nr_t& carrier);
+
   /**
    * @brief Selects the SSB pattern case according to the band number and subcarrier spacing
    * @remark Described by TS 38.101-1 Table 5.4.3.3-1: Applicable SS raster entries per operating band
@@ -165,25 +178,36 @@ private:
   }};
 
   struct nr_raster_params {
+    double   freq_range_start;
+    double   freq_range_end;
     double   delta_F_global_kHz;
     double   F_REF_Offs_MHz;
     uint32_t N_REF_Offs;
     uint32_t N_REF_min;
     uint32_t N_REF_max;
+
+    bool operator==(const nr_raster_params& rhs) const
+    {
+      return freq_range_start == rhs.freq_range_start && freq_range_end == rhs.freq_range_end &&
+             delta_F_global_kHz == rhs.delta_F_global_kHz && F_REF_Offs_MHz == rhs.F_REF_Offs_MHz &&
+             N_REF_Offs == rhs.N_REF_Offs && N_REF_min == rhs.N_REF_min && N_REF_max == rhs.N_REF_max;
+    }
   };
 
   // Helper to calculate F_REF according to Table 5.4.2.1-1
   nr_raster_params get_raster_params(uint32_t nr_arfcn);
+  nr_raster_params get_raster_params(double freq);
+  bool             is_valid_raster_param(const nr_raster_params& raster);
 
   static const uint32_t max_nr_arfcn                            = 3279165;
   static constexpr std::array<nr_raster_params, 3> nr_fr_params = {{
       // clang-format off
     // Frequency range 0 - 3000 MHz
-    {5, 0.0, 0, 0, 599999},
+    {0, 3000, 5, 0.0, 0, 0, 599999},
     // Frequency range 3000 - 24250 MHz
-    {15, 3000.0, 600000, 600000, 2016666},
+    {3000, 24250, 15, 3000.0, 600000, 600000, 2016666},
     // Frequency range 24250 - 100000 MHz
-    {60, 24250.08, 2016667, 2016667, max_nr_arfcn}
+    {24250, 100000, 60, 24250.08, 2016667, 2016667, max_nr_arfcn}
       // clang-format on
   }};
 

lib/src/common/band_helper.cc

@@ -29,9 +29,21 @@ constexpr std::array<srsran_band_helper::nr_band_ss_raster, srsran_band_helper::
 double srsran_band_helper::nr_arfcn_to_freq(uint32_t nr_arfcn)
 {
   nr_raster_params params = get_raster_params(nr_arfcn);
+  if (not is_valid_raster_param(params)) {
+    return 0.0;
+  }
   return (params.F_REF_Offs_MHz * 1e6 + params.delta_F_global_kHz * (nr_arfcn - params.N_REF_Offs) * 1e3);
 }
 
+uint32_t srsran_band_helper::freq_to_nr_arfcn(double freq)
+{
+  nr_raster_params params = get_raster_params(freq);
+  if (not is_valid_raster_param(params)) {
+    return 0;
+  }
+  return (((freq + params.F_REF_Offs_MHz * 1e6) / 1e3 / params.delta_F_global_kHz) + params.N_REF_Offs);
+}
+
 // Implements 5.4.2.1 in TS 38.104
 std::vector<uint32_t> srsran_band_helper::get_bands_nr(uint32_t                             nr_arfcn,
                                                        srsran_band_helper::delta_f_raster_t delta_f_raster)
@@ -94,7 +106,31 @@ uint32_t srsran_band_helper::get_ul_arfcn_from_dl_arfcn(uint32_t dl_arfcn) const
     }
   }
 
-  return UINT16_MAX;
+  return 0;
+}
+
+int srsran_band_helper::get_center_freq_from_abs_freq_point_a(srsran_carrier_nr_t& carrier)
+{
+  // for FR1 unit of resources blocks for freq calc is always 180kHz regardless for actual SCS of carrier
+  // TODO: add offset_to_carrier
+  double abs_freq_point_a_freq = nr_arfcn_to_freq(carrier.absolute_frequency_point_a);
+  carrier.dl_center_freq =
+      abs_freq_point_a_freq +
+      (carrier.nof_prb / 2 * SRSRAN_SUBC_SPACING_NR(srsran_subcarrier_spacing_t::srsran_subcarrier_spacing_15kHz) *
+       SRSRAN_NRE);
+
+  // UL depends on duplex
+  if (get_duplex_mode(get_band_from_dl_arfcn(carrier.absolute_frequency_point_a)) == SRSRAN_DUPLEX_MODE_TDD) {
+    // TDD case
+    carrier.ul_center_freq = carrier.dl_center_freq;
+  } else {
+    // FDD case
+    uint32_t dl_arfcn      = freq_to_nr_arfcn(carrier.dl_center_freq);
+    uint32_t ul_arfcn      = get_ul_arfcn_from_dl_arfcn(dl_arfcn);
+    carrier.ul_center_freq = nr_arfcn_to_freq(ul_arfcn);
+  }
+
+  return SRSRAN_SUCCESS;
 }
 
 srsran_ssb_patern_t srsran_band_helper::get_ssb_pattern(uint16_t band, srsran_subcarrier_spacing_t scs) const
@@ -198,4 +234,24 @@ srsran_band_helper::nr_raster_params srsran_band_helper::get_raster_params(uint3
   return {}; // return empty params
 }
 
+srsran_band_helper::nr_raster_params srsran_band_helper::get_raster_params(double freq)
+{
+  for (auto& fr : nr_fr_params) {
+    if (freq >= fr.freq_range_start * 1e6 && freq <= fr.freq_range_end * 1e6) {
+      return fr;
+    }
+  }
+  return {}; // return empty params
+}
+
+bool srsran_band_helper::is_valid_raster_param(const srsran_band_helper::nr_raster_params& raster)
+{
+  for (auto& fr : nr_fr_params) {
+    if (fr == raster) {
+      return true;
+    }
+  }
+  return false;
+}
+
 } // namespace srsran