reduce mcs for UL grants carrying UCI

lib/include/srslte/interfaces/sched_interface.h

@@ -60,6 +60,7 @@ public:
     uint32_t min_nof_ctrl_symbols = 1;
     uint32_t max_nof_ctrl_symbols = 3;
     int      max_aggr_level       = 3;
+    int      uci_mcs_dec          = 3;
   };
 
   struct cell_cfg_t {

srsenb/hdr/stack/mac/scheduler_ue.h

@@ -208,7 +208,8 @@ public:
                        ul_harq_proc::ul_alloc_t          alloc,
                        bool                              needs_pdcch,
                        srslte_dci_location_t             cce_range,
-                       int                               explicit_mcs = -1);
+                       int                               explicit_mcs = -1,
+                       bool                              carriers_uci = false);
 
   srslte_dci_format_t get_dci_format();
   sched_dci_cce_t*    get_locations(uint32_t enb_cc_idx, uint32_t current_cfi, uint32_t sf_idx);

srsenb/src/main.cc

@@ -136,6 +136,7 @@ void parse_args(all_args_t* args, int argc, char* argv[])
     ("scheduler.max_aggr_level", bpo::value<int>(&args->stack.mac.sched.max_aggr_level)->default_value(-1), "Optional maximum aggregation level index (l=log2(L)) ")
     ("scheduler.max_nof_ctrl_symbols", bpo::value<uint32_t>(&args->stack.mac.sched.max_nof_ctrl_symbols)->default_value(3), "Number of control symbols")
     ("scheduler.min_nof_ctrl_symbols", bpo::value<uint32_t>(&args->stack.mac.sched.min_nof_ctrl_symbols)->default_value(1), "Minimum number of control symbols")
+    ("scheduler.mcs_uci_dec", bpo::value<int>(&args->stack.mac.sched.uci_mcs_dec)->default_value(3), "Decrement of MCS in case UL grant carries UCI.")
 
     /* Downlink Channel emulator section */
     ("channel.dl.enable", bpo::value<bool>(&args->phy.dl_channel_args.enable)->default_value(false), "Enable/Disable internal Downlink channel emulator")

srsenb/src/stack/mac/scheduler_grid.cc

@@ -1045,6 +1045,27 @@ void sf_sched::set_dl_data_sched_result(const pdcch_grid_t::alloc_result_t& dci_
   }
 }
 
+//! Finds eNB CC Idex that currently holds UCI
+int get_enb_cc_idx_with_uci(const sf_sched_result& sf_result, const sched_ue* user)
+{
+  uint32_t ue_cc_idx      = sf_result.enb_cc_list.size();
+  int      sel_enb_cc_idx = -1;
+  for (uint32_t enbccidx = 0; enbccidx < sf_result.enb_cc_list.size(); ++enbccidx) {
+    for (uint32_t j = 0; j < sf_result.enb_cc_list[enbccidx].ul_sched_result.nof_dci_elems; ++j) {
+      // Checks all the UL grants already allocated for the given rnti
+      if (sf_result.enb_cc_list[enbccidx].ul_sched_result.pusch[j].dci.rnti == user->get_rnti()) {
+        auto p = user->get_cell_index(enbccidx);
+        // If the UE CC Idx is the lowest so far
+        if (p.first and p.second < ue_cc_idx) {
+          ue_cc_idx      = p.second;
+          sel_enb_cc_idx = enbccidx;
+        }
+      }
+    }
+  }
+  return sel_enb_cc_idx;
+}
+
 void sf_sched::set_ul_sched_result(const pdcch_grid_t::alloc_result_t& dci_result,
                                    sched_interface::ul_sched_res_t*    ul_result)
 {
@@ -1060,13 +1081,17 @@ void sf_sched::set_ul_sched_result(const pdcch_grid_t::alloc_result_t& dci_resul
       cce_range = dci_result[ul_alloc.dci_idx]->dci_pos;
     }
 
-    /* Set fixed mcs if specified */
+    // Set fixed mcs if specified
     int fixed_mcs = (ul_alloc.type == ul_alloc_t::MSG3) ? ul_alloc.mcs : -1;
 
+    // If UCI is encoded in the current carrier
+    uint32_t uci_enb_cc_idx = get_enb_cc_idx_with_uci(*cc_results, user);
+    bool     carries_uci    = uci_enb_cc_idx == cc_cfg->enb_cc_idx;
+
     /* Generate DCI Format1A */
     uint32_t pending_data_before = user->get_pending_ul_new_data(get_tti_tx_ul());
     int      tbs                 = user->generate_format0(
-        pusch, get_tti_tx_ul(), cell_index, ul_alloc.alloc, ul_alloc.needs_pdcch(), cce_range, fixed_mcs);
+        pusch, get_tti_tx_ul(), cell_index, ul_alloc.alloc, ul_alloc.needs_pdcch(), cce_range, fixed_mcs, carries_uci);
 
     ul_harq_proc* h = user->get_ul_harq(get_tti_tx_ul(), cell_index);
     if (tbs <= 0) {

srsenb/src/stack/mac/scheduler_ue.cc

@@ -669,7 +669,8 @@ int sched_ue::generate_format0(sched_interface::ul_sched_data_t* data,
                                ul_harq_proc::ul_alloc_t          alloc,
                                bool                              needs_pdcch,
                                srslte_dci_location_t             dci_pos,
-                               int                               explicit_mcs)
+                               int                               explicit_mcs,
+                               bool                              carries_uci)
 {
   ul_harq_proc*    h   = get_ul_harq(tti, cc_idx);
   srslte_dci_ul_t* dci = &data->dci;
@@ -698,6 +699,12 @@ int sched_ue::generate_format0(sched_interface::ul_sched_data_t* data,
       uint32_t N_srs     = 0;
       uint32_t nof_re    = (2 * (SRSLTE_CP_NSYMB(cell.cp) - 1) - N_srs) * alloc.L * SRSLTE_NRE;
       tbs                = carriers[cc_idx].alloc_tbs_ul(alloc.L, nof_re, req_bytes, &mcs);
+
+      if (carries_uci) {
+        // Reduce MCS to fit UCI
+        mcs -= std::min(main_cc_params->sched_cfg->uci_mcs_dec, mcs);
+        tbs = srslte_ra_tbs_from_idx(srslte_ra_tbs_idx_from_mcs(mcs, false, true), alloc.L) / 8;
+      }
     }
     h->new_tx(tti, mcs, tbs, alloc, nof_retx);