srsLTE/lib/src/common/band_helper.cc

/**
 *
 * \section COPYRIGHT
 *
 * Copyright 2013-2021 Software Radio Systems Limited
 *
 * By using this file, you agree to the terms and conditions set
 * forth in the LICENSE file which can be found at the top level of
 * the distribution.
 *
 */

#include "srsran/common/band_helper.h"
#include <algorithm>
#include <cmath>

namespace srsran {

// definition of static members
constexpr std::array<srsran_band_helper::nr_band, srsran_band_helper::nof_nr_bands_fr1>
          srsran_band_helper::nr_band_table_fr1;
constexpr std::array<srsran_band_helper::nr_raster_params, 3> srsran_band_helper::nr_fr_params;
constexpr std::array<srsran_band_helper::nr_operating_band, srsran_band_helper::nof_nr_operating_band_fr1>
          srsran_band_helper::nr_operating_bands_fr1;
constexpr std::array<srsran_band_helper::nr_band_ss_raster, srsran_band_helper::nof_nr_band_ss_raster>
          srsran_band_helper::nr_band_ss_raster_table;

// Formula in 5.4.2.1
double srsran_band_helper::nr_arfcn_to_freq(uint32_t nr_arfcn)
{
  nr_raster_params params = get_raster_params(nr_arfcn);
  return (params.F_REF_Offs_MHz * 1e6 + params.delta_F_global_kHz * (nr_arfcn - params.N_REF_Offs) * 1e3);
}

// Implements 5.4.2.1 in TS 38.401
std::vector<uint32_t> srsran_band_helper::get_bands_nr(uint32_t                             nr_arfcn,
                                                       srsran_band_helper::delta_f_raster_t delta_f_raster)
{
  std::vector<uint32_t> bands;
  for (const auto& nr_band : nr_band_table_fr1) {
    if (nr_arfcn >= nr_band.dl_nref_first && nr_arfcn <= nr_band.dl_nref_last && nr_arfcn % nr_band.dl_nref_step == 0) {
      // band must not already be present
      if (std::find(bands.begin(), bands.end(), nr_band.band) == bands.end()) {
        if (delta_f_raster == DEFAULT) {
          // add band if delta_f_raster has default value
          bands.push_back(nr_band.band);
        } else {
          // if delta_f_raster is set explicitly, only add if band matches
          if (nr_band.delta_f_raster == delta_f_raster) {
            bands.push_back(nr_band.band);
          }
        }
      }
    }
  }
  return bands;
}

uint16_t srsran_band_helper::get_band_from_dl_freq_Hz(double freq) const
{
  uint32_t freq_MHz = (uint32_t)round(freq / 1e6);
  for (const nr_operating_band& band : nr_operating_bands_fr1) {
    if (freq_MHz >= band.F_DL_low and freq_MHz <= band.F_DL_high) {
      return band.band;
    }
  }
  return UINT16_MAX;
}

uint16_t srsran_band_helper::get_band_from_dl_arfcn(uint32_t arfcn) const
{
  for (const nr_band& band : nr_band_table_fr1) {
    // Check given ARFCN is between the first and last possible ARFCN and matches step
    if (arfcn >= band.dl_nref_first and arfcn <= band.dl_nref_last and
        (arfcn - band.dl_nref_first) % band.dl_nref_step == 0) {
      return band.band;
    }
  }
  return UINT16_MAX;
}

srsran_ssb_patern_t srsran_band_helper::get_ssb_pattern(uint16_t band, srsran_subcarrier_spacing_t scs) const
{
  // Look for the given band and SCS
  for (const nr_band_ss_raster& ss_raster : nr_band_ss_raster_table) {
    // Check if band and SCS match!
    if (ss_raster.band == band && ss_raster.scs == scs) {
      return ss_raster.pattern;
    }

    // As bands are in ascending order, do not waste more time if the current band is bigger
    if (ss_raster.band > band) {
      return SRSRAN_SSB_PATTERN_INVALID;
    }
  }

  // Band is out of range, so consider invalid
  return SRSRAN_SSB_PATTERN_INVALID;
}

srsran_duplex_mode_t srsran_band_helper::get_duplex_mode(uint16_t band) const
{
  // Look for the given band
  for (const nr_operating_band& b : nr_operating_bands_fr1) {
    // Check if band and SCS match!
    if (b.band == band) {
      return b.duplex_mode;
    }

    // As bands are in ascending order, do not waste more time if the current band is bigger
    if (b.band > band) {
      return SRSRAN_DUPLEX_MODE_INVALID;
    }
  }

  // Band is out of range, so consider invalid
  return SRSRAN_DUPLEX_MODE_INVALID;
}

struct sync_raster_impl : public srsran_band_helper::sync_raster_t {
public:
  sync_raster_impl(uint32_t f, uint32_t s, uint32_t l) : sync_raster_t(f, s, l)
  {
    // Do nothing
  }
};

double srsran_band_helper::sync_raster_t::get_frequency() const
{
  // Row 1
  if (gscn >= 2 and gscn <= 7498) {
    double N = std::ceil((gscn - 1) / 3.0);
    double M = (gscn - 3 * N) / 2.0 + 3.0;
    return N * 1200e3 + M * 50e3;
  }

  // Row 2
  if (gscn >= 7499 and gscn <= 22255) {
    double N = gscn - 7499;
    return 3000e6 + N * 1.44e6;
  }

  // Row 3
  if (gscn >= 22256 and gscn <= 26639) {
    double N = gscn - 22256;
    return 2425.08e6 + N * 17.28e6;
  }

  // Unhandled case
  return NAN;
}

srsran_band_helper::sync_raster_t srsran_band_helper::get_sync_raster(uint16_t                    band,
                                                                      srsran_subcarrier_spacing_t scs) const
{
  // Look for the given band and SCS
  for (const nr_band_ss_raster& ss_raster : nr_band_ss_raster_table) {
    // Check if band and SCS match!
    if (ss_raster.band == band && ss_raster.scs == scs) {
      return sync_raster_impl(ss_raster.gscn_first, ss_raster.gscn_step, ss_raster.gscn_last);
    }

    // As bands are in ascending order, do not waste more time if the current band is bigger
    if (ss_raster.band > band) {
      return sync_raster_impl(0, 0, 0);
    }
  }

  // Band is out of range, so consider invalid
  return sync_raster_impl(0, 0, 0);
}

srsran_band_helper::nr_raster_params srsran_band_helper::get_raster_params(uint32_t nr_arfcn)
{
  for (auto& fr : nr_fr_params) {
    if (nr_arfcn >= fr.N_REF_min && nr_arfcn <= fr.N_REF_max) {
      return fr;
    }
  }
  return {}; // return empty params
}

} // namespace srsran