nr,gnb: account for CORESET#0 RB offset (See 38.213, table 13-1) in computation of SSB center frequency

lib/include/srsran/common/band_helper.h

@@ -126,14 +126,29 @@ public:
 
   /**
    * @brief Compute the absolute frequency of the SSB for a DL ARFCN and a band. This selects an SSB center frequency
+   * following the band SS/PBCH frequency raster provided by TS38.104 table 5.4.3.1-1, which is the upper bound
+   * of the provided center frequency
+   *
+   * @param scs ssb subcarrier spacing.
+   * @param min_center_freq_hz center frequency above which the SSB absolute frequency must be.
+   * @return absolute frequency of the SSB in arfcn notation.
+   */
+  uint32_t find_lower_bound_abs_freq_ssb(uint16_t band, srsran_subcarrier_spacing_t scs, uint32_t min_center_freq_hz);
+
+  /**
+   * @brief Compute the absolute frequency of the SSB for a DL ARFCN and a band. This finds an SSB center frequency
    * following the band SS/PBCH frequency raster provided by TS38.104 table 5.4.3.1-1 as close as possible to PointA
-   * without letting any SS/PBCH subcarrier below PointA
+   * without letting any SS/PBCH subcarrier and CORESET#0 subcarrier (if RB offset is defined) below PointA
    *
    * @param scs ssb subcarrier spacing.
    * @param freq_point_a_arfcn frequency point a in arfcn notation.
+   * @param coreset0_offset_rb CORESET#0 RB offset. See TS 38.213, Table 13-1,2,3
    * @return absolute frequency of the SSB in arfcn notation.
    */
-  uint32_t get_abs_freq_ssb_arfcn(uint16_t band, srsran_subcarrier_spacing_t scs, uint32_t freq_point_a_arfcn);
+  uint32_t get_abs_freq_ssb_arfcn(uint16_t                    band,
+                                  srsran_subcarrier_spacing_t scs,
+                                  uint32_t                    freq_point_a_arfcn,
+                                  uint32_t                    coreset0_offset_rb = 0);
 
   /**
    * @brief Compute SSB center frequency for NR carrier

lib/src/common/band_helper.cc

@@ -133,23 +133,20 @@ double srsran_band_helper::get_abs_freq_point_a_from_center_freq(uint32_t nof_pr
           SRSRAN_NRE);
 }
 
-uint32_t
+uint32_t srsran_band_helper::find_lower_bound_abs_freq_ssb(uint16_t                    band,
-srsran_band_helper::get_abs_freq_ssb_arfcn(uint16_t band, srsran_subcarrier_spacing_t scs, uint32_t freq_point_a_arfcn)
+                                                           srsran_subcarrier_spacing_t scs,
+                                                           uint32_t                    min_center_freq_hz)
 {
   sync_raster_t sync_raster = get_sync_raster(band, scs);
   if (!sync_raster.valid()) {
     return 0;
   }
 
-  // double abs_freq_ssb_hz = sync_raster.get_frequency();
-  double freq_point_a_hz = nr_arfcn_to_freq(freq_point_a_arfcn);
-  double ssb_bw_hz       = SRSRAN_SSB_BW_SUBC * SRSRAN_SUBC_SPACING_NR(scs);
-
   while (!sync_raster.end()) {
     double abs_freq_ssb_hz = sync_raster.get_frequency();
 
-    if ((abs_freq_ssb_hz > (freq_point_a_hz + ssb_bw_hz / 2)) and
+    if ((abs_freq_ssb_hz > min_center_freq_hz) and
-        ((uint32_t)std::round(abs_freq_ssb_hz - freq_point_a_hz) % SRSRAN_SUBC_SPACING_NR(scs) == 0)) {
+        ((uint32_t)std::round(abs_freq_ssb_hz - min_center_freq_hz) % SRSRAN_SUBC_SPACING_NR(scs) == 0)) {
       return freq_to_nr_arfcn(abs_freq_ssb_hz);
     }
 
@@ -158,6 +155,17 @@ srsran_band_helper::get_abs_freq_ssb_arfcn(uint16_t band, srsran_subcarrier_spac
   return 0;
 }
 
+uint32_t srsran_band_helper::get_abs_freq_ssb_arfcn(uint16_t                    band,
+                                                    srsran_subcarrier_spacing_t scs,
+                                                    uint32_t                    freq_point_a_arfcn,
+                                                    uint32_t                    coreset0_offset_rb)
+{
+  double freq_point_a_hz    = nr_arfcn_to_freq(freq_point_a_arfcn);
+  double ssb_bw_hz          = SRSRAN_SSB_BW_SUBC * SRSRAN_SUBC_SPACING_NR(scs);
+  double coreset0_offset_hz = coreset0_offset_rb * SRSRAN_NRE * SRSRAN_SUBC_SPACING_NR(scs);
+  return find_lower_bound_abs_freq_ssb(band, scs, freq_point_a_hz + coreset0_offset_hz / 2 + ssb_bw_hz / 2);
+}
+
 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

lib/src/common/test/band_helper_test.cc

@@ -47,9 +47,11 @@ int bands_test_nr()
   TESTASSERT(bands.nr_arfcn_to_freq(342000) == 1710.0e6);
   TESTASSERT(bands.nr_arfcn_to_freq(348000) == 1740.0e6);
   TESTASSERT(bands.nr_arfcn_to_freq(361000) == 1805.0e6);
+  TESTASSERT_EQ(1842.5e6, bands.nr_arfcn_to_freq(368500));
   TESTASSERT(bands.nr_arfcn_to_freq(376000) == 1880.0e6);
   TESTASSERT(bands.get_abs_freq_point_a_arfcn(52, 368500) == 367564);
   TESTASSERT(bands.get_abs_freq_ssb_arfcn(3, srsran_subcarrier_spacing_15kHz, 367564) > 367924);
+  TESTASSERT_EQ(368410, bands.get_abs_freq_ssb_arfcn(3, srsran_subcarrier_spacing_15kHz, 367564, 16));
   // n5
   TESTASSERT(bands.get_duplex_mode(5) == SRSRAN_DUPLEX_MODE_FDD);
   TESTASSERT(bands.nr_arfcn_to_freq(176300) == 881.5e6);

srsenb/src/enb_cfg_parser.cc

@@ -1161,6 +1161,21 @@ int parse_cfg_files(all_args_t* args_, rrc_cfg_t* rrc_cfg_, rrc_nr_cfg_t* rrc_nr
     return SRSRAN_ERROR;
   }
 
+  // update number of NR cells
+  rrc_cfg_->num_nr_cells = rrc_nr_cfg_->cell_list.size();
+  args_->rf.nof_carriers = rrc_cfg_->cell_list.size() + rrc_nr_cfg_->cell_list.size();
+  ASSERT_VALID_CFG(args_->rf.nof_carriers > 0, "There must be at least one NR or LTE cell");
+  if (rrc_nr_cfg_->cell_list.size() > 0) {
+    // NR cells available.
+    if (rrc_cfg_->cell_list.size() == 0) {
+      // SA mode.
+      rrc_nr_cfg_->is_standalone = true;
+    } else {
+      // NSA mode.
+      rrc_nr_cfg_->is_standalone = false;
+    }
+  }
+
   // Set fields derived from others, and check for correctness of the parsed configuration
   if (enb_conf_sections::set_derived_args(args_, rrc_cfg_, phy_cfg_, cell_common_cfg) != SRSRAN_SUCCESS) {
     fprintf(stderr, "Error deriving EUTRA cell parameters\n");
@@ -1174,20 +1189,15 @@ int parse_cfg_files(all_args_t* args_, rrc_cfg_t* rrc_cfg_, rrc_nr_cfg_t* rrc_nr
   }
 
   // update number of NR cells
-  rrc_cfg_->num_nr_cells = rrc_nr_cfg_->cell_list.size();
-  args_->rf.nof_carriers = rrc_cfg_->cell_list.size() + rrc_nr_cfg_->cell_list.size();
-  ASSERT_VALID_CFG(args_->rf.nof_carriers > 0, "There must be at least one NR or LTE cell");
   if (rrc_nr_cfg_->cell_list.size() > 0) {
     // NR cells available.
-    if (rrc_cfg_->cell_list.size() == 0) {
+    if (rrc_nr_cfg_->is_standalone) {
       // SA mode. Update NGAP args
-      rrc_nr_cfg_->is_standalone   = true;
       args_->nr_stack.ngap.gnb_id  = args_->enb.enb_id;
       args_->nr_stack.ngap.cell_id = rrc_nr_cfg_->cell_list[0].phy_cell.cell_id;
       args_->nr_stack.ngap.tac     = rrc_nr_cfg_->cell_list[0].tac;
     } else {
       // NSA mode.
-      rrc_nr_cfg_->is_standalone = false;
       // update EUTRA RRC params for ENDC
       rrc_cfg_->endc_cfg.abs_frequency_ssb = rrc_nr_cfg_->cell_list.at(0).ssb_absolute_freq_point;
       rrc_cfg_->endc_cfg.nr_band           = rrc_nr_cfg_->cell_list.at(0).band;
@@ -1633,8 +1643,19 @@ int set_derived_args_nr(all_args_t* args_, rrc_nr_cfg_t* rrc_nr_cfg_, phy_cfg_t*
     }
 
     // fill remaining SSB fields
+    uint32_t coreset0_rb_offset = 0;
+    if (rrc_nr_cfg_->is_standalone) {
+      // Taken from TS 38.213, Table 13-1
+      if (cfg.phy_cell.carrier.nof_prb > 96) {
+        coreset0_rb_offset = 96;
+      } else if (cfg.phy_cell.carrier.nof_prb > 48) {
+        coreset0_rb_offset = 16;
+      } else {
+        coreset0_rb_offset = 4;
+      }
+    }
     cfg.ssb_absolute_freq_point =
-        band_helper.get_abs_freq_ssb_arfcn(cfg.band, cfg.ssb_cfg.scs, cfg.dl_absolute_freq_point_a);
+        band_helper.get_abs_freq_ssb_arfcn(cfg.band, cfg.ssb_cfg.scs, cfg.dl_absolute_freq_point_a, coreset0_rb_offset);
     if (cfg.ssb_absolute_freq_point == 0) {
       ERROR("Can't derive SSB freq point for dl_arfcn %d and band %d", cfg.dl_arfcn, cfg.band);
       return SRSRAN_ERROR;

srsgnb/src/stack/rrc/rrc_nr.cc

@@ -51,7 +51,7 @@ int rrc_nr::init(const rrc_nr_cfg_t&         cfg_,
   cfg = cfg_;
   if (cfg.is_standalone) {
     // Generate parameters of Coreset#0 and SS#0
-    const uint32_t coreset0_idx                        = 7;
+    const uint32_t coreset0_idx                        = 6;
     cfg.cell_list[0].phy_cell.pdcch.coreset_present[0] = true;
     // Get pointA and SSB absolute frequencies
     double pointA_abs_freq_Hz = cfg.cell_list[0].phy_cell.carrier.dl_center_frequency_hz -