du: remove option to set UL ARFCN in config

Signed-off-by: Carlo Galiotto <[email protected]>

Author: carlo-gal

apps/units/flexible_du/du_high/du_high_config.h

@@ -547,10 +547,6 @@ struct du_high_unit_base_cell_config {
   std::optional<unsigned> sector_id;
   /// DL ARFCN of "F_REF", which is the RF reference frequency, as per TS 38.104, Section 5.4.2.1.
   unsigned dl_f_ref_arfcn = 536020;
-  /// UL ARFCN of "F_REF", which is the RF reference frequency, as per TS 38.104, Section 5.4.2.1.
-  /// \remark Only relevant for FDD bands. If set with TDD bands, it will be ignored.
-  /// For FDD bands, if not set, the UL ARFCN will be computed automatically.
-  std::optional<unsigned> ul_f_ref_arfcn = std::nullopt;
   /// Common subcarrier spacing for the entire resource grid. It must be supported by the band SS raster.
   subcarrier_spacing common_scs = subcarrier_spacing::kHz15;
   /// NR band.

apps/units/flexible_du/du_high/du_high_config_cli11_schema.cpp

@@ -1114,7 +1114,6 @@ static void configure_cli11_common_cell_args(CLI::App& app, du_high_unit_base_ce
       ->capture_default_str()
       ->check(CLI::Range(0U, (1U << 14) - 1U));
   add_option(app, "--dl_arfcn", cell_params.dl_f_ref_arfcn, "Downlink ARFCN")->capture_default_str();
-  add_option(app, "--ul_arfcn", cell_params.ul_f_ref_arfcn, "Uplink ARFCN")->capture_default_str();
   add_auto_enum_option(app, "--band", cell_params.band, "NR band");
   add_option_function<std::string>(
       app,

apps/units/flexible_du/du_high/du_high_config_translators.cpp

@@ -230,7 +230,6 @@ std::vector<srs_du::du_cell_config> srsran::generate_du_cell_config(const du_hig
     param.scs_common                               = base_cell.common_scs;
     param.channel_bw_mhz                           = base_cell.channel_bw_mhz;
     param.dl_f_ref_arfcn                           = base_cell.dl_f_ref_arfcn;
-    param.ul_f_ref_arfcn                           = base_cell.ul_f_ref_arfcn;
     param.band                                     = *base_cell.band;
     // Enable CSI-RS if the PDSCH mcs is dynamic (min_ue_mcs != max_ue_mcs).
     param.csi_rs_enabled      = base_cell.csi_cfg.csi_rs_enabled;

apps/units/flexible_du/du_high/du_high_config_validator.cpp

@@ -651,13 +651,12 @@ static bool validate_dl_ul_arfcn_and_band(const du_high_unit_base_cell_config& c
       fmt::print("Invalid DL ARFCN={} for band {}. Cause: {}.\n", config.dl_f_ref_arfcn, band, ret.error());
       return false;
     }
-    if (config.ul_f_ref_arfcn.has_value()) {
-      ret =
-          band_helper::is_ul_arfcn_valid_given_band(*config.band, config.ul_f_ref_arfcn.value(), config.channel_bw_mhz);
-      if (not ret.has_value()) {
-        fmt::print("Invalid UL ARFCN={} for band {}. Cause: {}.\n", config.dl_f_ref_arfcn, band, ret.error());
-        return false;
-      }
+    // Check if also the corresponding UL ARFCN is valid.
+    const uint32_t ul_arfcn = band_helper::get_ul_arfcn_from_dl_arfcn(config.dl_f_ref_arfcn, config.band.value());
+    ret                     = band_helper::is_ul_arfcn_valid_given_band(*config.band, ul_arfcn, config.channel_bw_mhz);
+    if (not ret.has_value()) {
+      fmt::print("Invalid DL ARFCN={} for band {}. Cause: {}.\n", config.dl_f_ref_arfcn, band, ret.error());
+      return false;
     }
   } else {
     if (band == nr_band::invalid) {
@@ -769,16 +768,16 @@ static bool validate_base_cell_unit_config(const du_high_unit_base_cell_config&
     return false;
   }
 
-  const auto ssb_scs = band_helper::get_most_suitable_ssb_scs(
-      band_helper::get_band_from_dl_arfcn(config.dl_f_ref_arfcn), config.common_scs);
+  const nr_band band =
+      config.band.has_value() ? config.band.value() : band_helper::get_band_from_dl_arfcn(config.dl_f_ref_arfcn);
+  const auto ssb_scs = band_helper::get_most_suitable_ssb_scs(band, config.common_scs);
   if (ssb_scs != config.common_scs) {
     fmt::print("Common SCS {}kHz is not equal to SSB SCS {}kHz. Different SCS for common and SSB is not supported.\n",
                scs_to_khz(config.common_scs),
                scs_to_khz(ssb_scs));
     return false;
   }
-  const nr_band band =
-      config.band.has_value() ? config.band.value() : band_helper::get_band_from_dl_arfcn(config.dl_f_ref_arfcn);
+
   const unsigned nof_crbs =
       band_helper::get_n_rbs_from_bw(config.channel_bw_mhz, config.common_scs, band_helper::get_freq_range(band));
 

include/srsran/scheduler/config/cell_config_builder_params.h

@@ -31,11 +31,6 @@ struct cell_config_builder_params {
   /// This ARFCN represents "f_ref" for DL, as per TS 38.104, Section 5.4.2.1. As per TS 38.104, Section 5.4.2.2,
   /// "f_ref" maps to the central frequency of the band.
   unsigned dl_f_ref_arfcn = 365000;
-  /// This ARFCN represents "f_ref" for UL, as per TS 38.104, Section 5.4.2.1. As per TS 38.104, Section 5.4.2.2,
-  /// "f_ref" maps to the central frequency of the band.
-  /// \remark Only relevant for FDD bands.
-  /// If set, this value has been set by the application user.
-  std::optional<unsigned> ul_f_ref_arfcn = std::nullopt;
   /// <em>NR operating band<\em>, as per Table 5.2-1 and 5.2-2, TS 38.104. If not specified, a valid band for the
   /// provided DL ARFCN is automatically derived.
   std::optional<nr_band> band;

lib/ran/band_helper.cpp

@@ -809,6 +809,16 @@ srsran::band_helper::is_ul_arfcn_valid_given_band(nr_band band, uint32_t arfcn_f
 
   for (const nr_band_raster& raster_band : nr_band_table) {
     if (raster_band.band == band and raster_band.delta_f_rast == band_delta_freq_raster) {
+      // Check if the ARFCN doesn't exceed the band upper-bound for bands that support asymmetrical UL and DL channel
+      // BWs.
+      if ((band == nr_band::n66 or band == nr_band::n70 or band == nr_band::n92 or band == nr_band::n94) and
+          (arfcn_f_ref < raster_band.ul_nref_first or arfcn_f_ref > raster_band.ul_nref_last)) {
+        return make_unexpected(
+            fmt::format("Asymmetrical UL and DL channel BWs are not supported. The UL ARFCN resulting from the DL "
+                        "ARFCN for band n{} must not exceed the band upper-bound={}",
+                        band,
+                        raster_band.ul_nref_last));
+      }
       if (arfcn_f_ref >= raster_band.ul_nref_first and arfcn_f_ref <= raster_band.ul_nref_last and
           ((arfcn_f_ref - raster_band.ul_nref_first) % raster_band.ul_nref_step) == 0) {
         return {};
@@ -845,9 +855,11 @@ uint32_t srsran::band_helper::get_ul_arfcn_from_dl_arfcn(uint32_t dl_arfcn, std:
     if (b_it.band == operating_band) {
       const uint32_t offset             = (dl_arfcn - b_it.dl_nref_first) / b_it.dl_nref_step;
       const uint32_t candidate_ul_arfcn = b_it.ul_nref_first + offset * b_it.ul_nref_step;
-      // For band n65, n66, n70, n92, n94, the UL spectrum is smaller than the corresponding DL spectrum, therefore we
-      // need to cap the UL ARFCN to its upper-bound.
-      return std::min(candidate_ul_arfcn, b_it.ul_nref_last);
+      // For band n66, n70, n92, n94, the UL spectrum is smaller than the corresponding DL spectrum, as these bands
+      // supports asymmetrical UL anc DL channel operations. However, the current GNB doesn't support this feature.
+      // If the resulting UL ARFCN is outside the valid range, return 0.
+      return (candidate_ul_arfcn >= b_it.ul_nref_first and candidate_ul_arfcn <= b_it.ul_nref_last) ? candidate_ul_arfcn
+                                                                                                    : 0U;
     }
   }
 

lib/scheduler/config/serving_cell_config_factory.cpp

@@ -89,9 +89,7 @@ static carrier_configuration make_default_carrier_configuration(const cell_confi
     cfg.arfcn_f_ref = params.dl_f_ref_arfcn;
     cfg.nof_ant     = params.nof_dl_ports;
   } else {
-    cfg.arfcn_f_ref = params.ul_f_ref_arfcn.has_value()
-                          ? params.ul_f_ref_arfcn.value()
-                          : band_helper::get_ul_arfcn_from_dl_arfcn(params.dl_f_ref_arfcn, cfg.band);
+    cfg.arfcn_f_ref = band_helper::get_ul_arfcn_from_dl_arfcn(params.dl_f_ref_arfcn, cfg.band);
     cfg.nof_ant     = 1;
   }
   const min_channel_bandwidth min_channel_bw = band_helper::get_min_channel_bw(cfg.band, params.scs_common);
@@ -336,9 +334,7 @@ srsran::config_helpers::make_default_ul_config_common(const cell_config_builder_
 {
   ul_config_common cfg{};
   // This is the ARFCN of the UL f_ref, as per TS 38.104, Section 5.4.2.1.
-  const uint32_t ul_arfcn                 = params.ul_f_ref_arfcn.has_value()
-                                                ? params.ul_f_ref_arfcn.value()
-                                                : band_helper::get_ul_arfcn_from_dl_arfcn(params.dl_f_ref_arfcn, params.band);
+  const uint32_t ul_arfcn                 = band_helper::get_ul_arfcn_from_dl_arfcn(params.dl_f_ref_arfcn, params.band);
   const double   ul_absolute_freq_point_a = band_helper::get_abs_freq_point_a_from_f_ref(
       band_helper::nr_arfcn_to_freq(ul_arfcn), params.cell_nof_crbs, params.scs_common);
   // \c absolute_freq_point_a needs to be expressed as in ARFCN, as per \c absoluteFrequencyPointA definition in 38.211,

tests/unittests/ran/band_helper_test.cpp

@@ -112,13 +112,16 @@ TEST(get_ul_arfcn_from_dl_arfcn, mixed_frequencies)
   ASSERT_EQ(142600, get_ul_arfcn_from_dl_arfcn(153600, nr_band::n28));
   ASSERT_EQ(144608, get_ul_arfcn_from_dl_arfcn(155608, nr_band::n28));
 
-  // For n65, m66, n70, n92, n94, the UL spectrum is smaller than the DL spectrum. When we convert the DL ARFCN
-  // upper-bound to the corresponding UL ARFCN, we need to cap the value to the UL spectrum upper-bound.
-  ASSERT_EQ(402000, get_ul_arfcn_from_dl_arfcn(440000, nr_band::n65));
-  ASSERT_EQ(356000, get_ul_arfcn_from_dl_arfcn(440000, nr_band::n66));
-  ASSERT_EQ(342000, get_ul_arfcn_from_dl_arfcn(404000, nr_band::n70));
-  ASSERT_EQ(172400, get_ul_arfcn_from_dl_arfcn(303400, nr_band::n92));
-  ASSERT_EQ(183000, get_ul_arfcn_from_dl_arfcn(303400, nr_band::n94));
+  // For n66, n70, n92, n94, the UL spectrum is smaller than the DL spectrum. When we convert the DL ARFCN
+  // to the corresponding UL ARFCN, if the UL ARFCN exceeds the band upper-bound, we return 0.
+  ASSERT_EQ(356000, get_ul_arfcn_from_dl_arfcn(436000, nr_band::n66));
+  ASSERT_EQ(0, get_ul_arfcn_from_dl_arfcn(440000, nr_band::n66));
+  ASSERT_EQ(342000, get_ul_arfcn_from_dl_arfcn(402000, nr_band::n70));
+  ASSERT_EQ(0, get_ul_arfcn_from_dl_arfcn(404000, nr_band::n70));
+  ASSERT_EQ(172400, get_ul_arfcn_from_dl_arfcn(292400, nr_band::n92));
+  ASSERT_EQ(0, get_ul_arfcn_from_dl_arfcn(303400, nr_band::n92));
+  ASSERT_EQ(183000, get_ul_arfcn_from_dl_arfcn(293400, nr_band::n94));
+  ASSERT_EQ(0, get_ul_arfcn_from_dl_arfcn(303400, nr_band::n94));
 }
 
 TEST(test_get_abs_freq_point_a_arfcn, mixed_frequencies)