du: functions to compute srs resource cell list

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

Author: carlo-gal

lib/du_manager/ran_resource_management/srs_resource_generator.cpp

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+/*
+ *
+ * Copyright 2021-2024 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 "srs_resource_generator.h"
+
+using namespace srsran;
+using namespace srs_du;
+
+std::vector<du_srs_resource> srsran::srs_du::generate_cell_srs_list(const du_cell_config& du_cell_cfg)
+{
+  std::vector<du_srs_resource> srs_res_list;
+  // Compute the available TX comb offsets. \ref tx_comb_cyclic_shift, in \c srs_config::srs_resource::tx_comb_params.
+  std::vector<unsigned> tx_comb_offsets = du_cell_cfg.srs_cfg.tx_comb == srsran::tx_comb_size::n2
+                                              ? std::vector<unsigned>{0U, 1U}
+                                              : std::vector<unsigned>{0U, 1U, 2U, 3U};
+
+  // Compute the available Cyclic Shifts.
+  const unsigned        max_cs  = du_cell_cfg.srs_cfg.tx_comb == srsran::tx_comb_size::n2 ? 8U : 12U;
+  const unsigned        cs_step = max_cs / static_cast<unsigned>(du_cell_cfg.srs_cfg.cyclic_shift_reuse_factor);
+  std::vector<unsigned> cs_values;
+  for (unsigned cs = 0; cs < max_cs; cs += cs_step) {
+    cs_values.push_back(cs);
+  }
+
+  // Compute the available Sequence IDs.
+  // NOTE: we only consider the number of orthogonal sequences that can be generated, as per TS 38.211,
+  // Section 6.4.1.4.2, which is 30.
+  constexpr unsigned max_seq_id_values = 30U;
+  const unsigned seq_id_step = max_seq_id_values / static_cast<unsigned>(du_cell_cfg.srs_cfg.sequence_id_reuse_factor);
+  std::vector<unsigned> seq_id_values;
+  for (unsigned seq_id = 0; seq_id < max_seq_id_values; seq_id += seq_id_step) {
+    seq_id_values.push_back(static_cast<unsigned>(du_cell_cfg.pci) + seq_id);
+  }
+
+  // Find the first symbol within the UL slot (considering all options FDD, TDD pattern 1 and TDD pattern 2) where the
+  // SRS resource can be placed.
+  unsigned starting_sym = NOF_OFDM_SYM_PER_SLOT_NORMAL_CP - du_cell_cfg.srs_cfg.max_nof_symbols.to_uint();
+  if (du_cell_cfg.tdd_ul_dl_cfg_common.has_value()) {
+    const auto& tdd_cfg = du_cell_cfg.tdd_ul_dl_cfg_common.value();
+    starting_sym        = std::min(starting_sym, NOF_OFDM_SYM_PER_SLOT_NORMAL_CP - tdd_cfg.pattern1.nof_ul_symbols);
+    if (tdd_cfg.pattern2.has_value()) {
+      starting_sym = std::min(starting_sym, NOF_OFDM_SYM_PER_SLOT_NORMAL_CP - tdd_cfg.pattern2.value().nof_ul_symbols);
+    }
+  }
+  // The number of SRS symbols cannot be larger than 6.
+  starting_sym = std::max(starting_sym, NOF_OFDM_SYM_PER_SLOT_NORMAL_CP - du_cell_cfg.srs_cfg.max_nof_symbols.max());
+
+  // We use the counter to define the cell resource ID.
+  unsigned srs_res_cnt = 0;
+  for (unsigned sym_start = NOF_OFDM_SYM_PER_SLOT_NORMAL_CP - static_cast<unsigned>(du_cell_cfg.srs_cfg.nof_symbols);
+       sym_start >= starting_sym;
+       sym_start -= static_cast<unsigned>(du_cell_cfg.srs_cfg.nof_symbols)) {
+    const ofdm_symbol_range srs_res_symbols{sym_start,
+                                            sym_start + static_cast<unsigned>(du_cell_cfg.srs_cfg.nof_symbols)};
+    for (auto tx_comb_offset : tx_comb_offsets) {
+      for (auto cs : cs_values) {
+        for (auto seq_id : seq_id_values) {
+          du_srs_resource srs_res;
+          srs_res.cell_res_id    = srs_res_cnt;
+          srs_res.tx_comb_offset = tx_comb_offset;
+          srs_res.symbols        = srs_res_symbols;
+          srs_res.sequence_id    = seq_id;
+          srs_res.cs             = cs;
+          srs_res_list.push_back(srs_res);
+          ++srs_res_cnt;
+        }
+      }
+    }
+  }
+  return srs_res_list;
+}

lib/du_manager/ran_resource_management/srs_resource_generator.h

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+/*
+ *
+ * Copyright 2021-2024 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.
+ *
+ */
+
+#pragma once
+
+#include "du_ue_resource_config.h"
+
+namespace srsran::srs_du {
+
+/// Contains the parameters for the SRS resources of a cell.
+struct du_srs_resource {
+  /// Id of the cell SRS resource.
+  unsigned cell_res_id;
+  /// Comb offset, as per \c transmissionComb, \c SRS-Resource, \c SRS-Config, TS 38.331.
+  bounded_integer<uint8_t, 0, 4> tx_comb_offset;
+  /// OFDM symbol range where the SRS resource is placed.
+  ofdm_symbol_range              symbols;
+  /// \c freqDomainPosition, as per \c SRS-Resource, \c SRS-Config, TS 38.331.
+  unsigned                       freq_dom_position = 0;
+  /// \c sequenceId, as per \c SRS-Resource, \c SRS-Config, TS 38.331.
+  unsigned                       sequence_id       = 0;
+  /// Cyclic shift, as per \c transmissionComb, \c SRS-Resource, \c SRS-Config, TS 38.331.
+  unsigned                       cs                = 0;
+};
+
+/// \brief Generates the list of orthogonal SRS resources available in a cell.
+/// The resources of this cells are meant to be used by the UEs; the same resources can be reused by different UEs over
+/// different slots. Note that this function does not allocate the resources to the UEs, it only creates the cell
+/// resource list.
+/// \param[in] du_cell_cfg Cell configuration parameters.
+/// \return List of orthogonal SRS resources.
+std::vector<du_srs_resource> generate_cell_srs_list(const du_cell_config& du_cell_cfg);
+
+} // namespace srsran::srs_du