sched: fix pmi selection for the case of 1 layer and 2 ports

Author: frankist

lib/scheduler/ue_scheduling/ue_cell.cpp

@@ -29,7 +29,7 @@ ue_cell::ue_cell(du_ue_index_t                     ue_index_,
   ue_index(ue_index_),
   cell_index(ue_serv_cell.cell_index),
   harqs(crnti_val, (unsigned)ue_serv_cell.pdsch_serv_cell_cfg->nof_harq_proc, NOF_UL_HARQS, harq_timeout_notifier),
-  channel_state(expert_cfg_),
+  channel_state(ue_serv_cell, expert_cfg_),
   crnti_(crnti_val),
   expert_cfg(expert_cfg_),
   ue_cfg(cell_cfg_common_, ue_serv_cell),

lib/scheduler/ue_scheduling/ue_channel_state_manager.cpp

@@ -12,19 +12,36 @@
 
 using namespace srsran;
 
-static constexpr size_t TWO_LAYER_INDEX  = 0;
-static constexpr size_t FOUR_LAYER_INDEX = 1;
+/// Find the number of DL ports for a given UE serving cell configuration.
+static unsigned compute_nof_dl_ports(const serving_cell_config& serv_cell_cfg)
+{
+  if (not serv_cell_cfg.csi_meas_cfg.has_value()) {
+    return 1;
+  }
 
-ue_channel_state_manager::ue_channel_state_manager(const scheduler_ue_expert_config& expert_cfg) :
+  unsigned max_ports = 1;
+  for (const auto& nzp : serv_cell_cfg.csi_meas_cfg->nzp_csi_rs_res_list) {
+    if (max_ports < nzp.res_mapping.nof_ports) {
+      max_ports = nzp.res_mapping.nof_ports;
+    }
+  }
+  return max_ports;
+}
+
+ue_channel_state_manager::ue_channel_state_manager(const serving_cell_config&        ue_serv_cell,
+                                                   const scheduler_ue_expert_config& expert_cfg) :
+  nof_dl_ports(compute_nof_dl_ports(ue_serv_cell)),
+  pusch_snr_db(expert_cfg.initial_ul_sinr),
   wideband_cqi(expert_cfg.initial_cqi)
 {
-  // Set initial UL SINR.
-  update_pusch_snr(expert_cfg.initial_ul_sinr);
-
-  // Set initial precoding when no CSI has yet been received.
-  recommended_prg_info[TWO_LAYER_INDEX].type = pdsch_precoding_info::prg_info::two_antenna_port{0};
-  recommended_prg_info[FOUR_LAYER_INDEX].type =
-      pdsch_precoding_info::prg_info::typeI_single_panel_4ports_mode1{0, 0, nullopt, 0};
+  // Set initial precoding value when no CSI has yet been received.
+  if (nof_dl_ports == 2) {
+    recommended_prg_info.resize(2, pdsch_precoding_info::prg_info{pdsch_precoding_info::prg_info::two_antenna_port{0}});
+  } else if (nof_dl_ports == 4) {
+    recommended_prg_info.resize(3,
+                                pdsch_precoding_info::prg_info{
+                                    pdsch_precoding_info::prg_info::typeI_single_panel_4ports_mode1{0, 0, nullopt, 0}});
+  }
 }
 
 void ue_channel_state_manager::handle_csi_report(const csi_report_data& csi_report)
@@ -39,10 +56,11 @@ void ue_channel_state_manager::handle_csi_report(const csi_report_data& csi_repo
   // Update recommended number of layers based on RI.
   if (csi_report.ri.has_value()) {
     recommended_dl_layers = csi_report.ri.value().to_uint();
+    srsran_sanity_check(recommended_dl_layers < nof_dl_ports, "Invalid RI reported");
   }
 
   if (csi_report.pmi.has_value()) {
-    const unsigned table_idx        = recommended_dl_layers >> 2U;
+    const unsigned table_idx        = nof_layers_to_index(recommended_dl_layers);
     recommended_prg_info[table_idx] = csi_report.pmi.value();
   }
 }

lib/scheduler/ue_scheduling/ue_channel_state_manager.h

@@ -12,6 +12,7 @@
 
 #include "srsran/ran/csi_report/csi_report_wideband_cqi.h"
 #include "srsran/scheduler/config/scheduler_expert_config.h"
+#include "srsran/scheduler/config/serving_cell_config.h"
 #include "srsran/scheduler/scheduler_slot_handler.h"
 
 namespace srsran {
@@ -21,7 +22,7 @@ namespace srsran {
 class ue_channel_state_manager
 {
 public:
-  ue_channel_state_manager(const scheduler_ue_expert_config& expert_cfg_);
+  ue_channel_state_manager(const serving_cell_config& ue_serv_cell, const scheduler_ue_expert_config& expert_cfg_);
 
   const optional<csi_report_data>& get_latest_csi_report() const { return latest_csi_report; }
 
@@ -41,21 +42,30 @@ class ue_channel_state_manager
   /// \brief Fetches the precoding codebook to be used in DL based on reported PMI and the chosen nof layers.
   optional<pdsch_precoding_info> get_precoding(unsigned chosen_nof_layers, prb_interval pdsch_prbs) const
   {
+    srsran_assert(chosen_nof_layers <= nof_dl_ports, "Invalid number of layers chosen");
     optional<pdsch_precoding_info> precoding_info;
-    if (chosen_nof_layers <= 1) {
+    if (nof_dl_ports <= 1) {
+      // In case of 1 DL port, no precoding is used.
       return precoding_info;
     }
     precoding_info.emplace();
     precoding_info->nof_rbs_per_prg = pdsch_prbs.length();
-    precoding_info->prg_infos.emplace_back(recommended_prg_info[chosen_nof_layers >> 2U]);
+    precoding_info->prg_infos.emplace_back(recommended_prg_info[nof_layers_to_index(chosen_nof_layers)]);
     return precoding_info;
   }
 
   /// Update UE with the latest CSI report for a given cell.
   void handle_csi_report(const csi_report_data& csi_report);
 
 private:
-  static constexpr size_t NOF_LAYER_CHOICES = 2;
+  /// \brief Number of indexes -> nof_layers for precoding (Options: 1 layer, 2 layers, 4 layers).
+  static constexpr size_t NOF_LAYER_CHOICES = 3;
+
+  /// Mapping of number of layers to array index.
+  static size_t nof_layers_to_index(unsigned nof_layers) { return nof_layers >> 1U; }
+
+  /// \brief Number of DL ports.
+  unsigned nof_dl_ports;
 
   /// Estimated PUSCH SNR, in dB.
   float pusch_snr_db;
@@ -68,7 +78,7 @@ class ue_channel_state_manager
 
   /// \brief List of Recommended PMIs for different number of active layers. Position 0 is for 1 layer, position 1 is
   /// for 2 layers and position 3 for 4 layers.
-  std::array<pdsch_precoding_info::prg_info, NOF_LAYER_CHOICES> recommended_prg_info;
+  static_vector<pdsch_precoding_info::prg_info, NOF_LAYER_CHOICES> recommended_prg_info;
 
   /// Latest CSI report received from the UE.
   optional<csi_report_data> latest_csi_report;