Make PUCCH HARQ region a configurable parameter. Skip grants when ACK falls outside region

srsenb/enb.conf.example

@@ -171,6 +171,10 @@ enable = false
 # pusch_max_mcs:     Optional PUSCH MCS limit 
 # min_nof_ctrl_symbols: Minimum number of control symbols 
 # max_nof_ctrl_symbols: Maximum number of control symbols
+# pucch_multiplex_enable: Allow PUCCH HARQ to collide with PUSCH and other PUCCH
+# pucch_harq_max_rb: Maximum number of RB to be used for PUCCH on the edges of the grid.
+#                    If defined and greater than 0, the scheduler will avoid DL PDCCH allocations if
+#                    PUCCH HARQ falls outside this region
 # target_bler:       Target BLER (in decimal) to achieve via adaptive link
 # max_delta_dl_cqi:  Maximum shift in CQI for adaptive DL link
 # max_delta_ul_snr:  Maximum shift in UL SNR for adaptive UL link
@@ -196,6 +200,7 @@ enable = false
 #min_nof_ctrl_symbols = 1
 #max_nof_ctrl_symbols = 3
 #pucch_multiplex_enable = false
+#pucch_harq_max_rb = 1
 #target_bler = 0.05
 #max_delta_dl_cqi = 5
 #max_delta_ul_snr = 5

srsenb/hdr/stack/mac/sched_interface.h

@@ -58,6 +58,7 @@ public:
     int         max_aggr_level          = 3;
     bool        adaptive_aggr_level     = false;
     bool        pucch_mux_enabled       = false;
+    int         pucch_harq_max_rb       = 0;
     float       target_bler             = 0.05;
     float       max_delta_dl_cqi        = 5;
     float       max_delta_ul_snr        = 5;

srsenb/src/main.cc

@@ -152,6 +152,7 @@ void parse_args(all_args_t* args, int argc, char* argv[])
     ("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.pucch_multiplex_enable", bpo::value<bool>(&args->stack.mac.sched.pucch_mux_enabled)->default_value(false), "Enable PUCCH multiplexing")
+    ("scheduler.pucch_harq_max_rb", bpo::value<int>(&args->stack.mac.sched.pucch_harq_max_rb)->default_value(0), "Maximum number of RB to be used for PUCCH on the edges of the grid")
     ("scheduler.target_bler", bpo::value<float>(&args->stack.mac.sched.target_bler)->default_value(0.05), "Target BLER (in decimal) to achieve via adaptive link")
     ("scheduler.max_delta_dl_cqi", bpo::value<float>(&args->stack.mac.sched.max_delta_dl_cqi)->default_value(5.0), "Maximum shift in CQI for adaptive DL link")
     ("scheduler.max_delta_ul_snr", bpo::value<float>(&args->stack.mac.sched.max_delta_ul_snr)->default_value(5.0), "Maximum shift in UL SNR for adaptive UL link")

srsenb/src/stack/mac/sched_grid.cc

@@ -80,9 +80,15 @@ void sf_grid_t::init(const sched_cell_params_t& cell_params_)
   pucch_mask.resize(cc_cfg->nof_prb());
   pucch_nrb                    = (cc_cfg->cfg.nrb_pucch > 0) ? (uint32_t)cc_cfg->cfg.nrb_pucch : 0;
   srsran_pucch_cfg_t pucch_cfg = cell_params_.pucch_cfg_common;
-  pucch_cfg.n_pucch =
-      cc_cfg->nof_cce_table[cell_params_.sched_cfg->max_nof_ctrl_symbols - 1] - 1 + cc_cfg->cfg.n1pucch_an;
-  pucch_nrb                    = std::max(pucch_nrb, srsran_pucch_m(&pucch_cfg, cc_cfg->cfg.cell.cp) / 2 + 1);
+  uint32_t           harq_pucch = 0;
+  if (cc_cfg->sched_cfg->pucch_harq_max_rb > 0) {
+    harq_pucch = cc_cfg->sched_cfg->pucch_harq_max_rb;
+  } else {
+    pucch_cfg.n_pucch =
+        cc_cfg->nof_cce_table[cell_params_.sched_cfg->max_nof_ctrl_symbols - 1] - 1 + cc_cfg->cfg.n1pucch_an;
+    harq_pucch = srsran_pucch_m(&pucch_cfg, cc_cfg->cfg.cell.cp) / 2 + 1;
+  }
+  pucch_nrb = std::max(pucch_nrb, harq_pucch);
   if (pucch_nrb > 0) {
     pucch_mask.fill(0, pucch_nrb);
     pucch_mask.fill(cc_cfg->nof_prb() - pucch_nrb, cc_cfg->nof_prb());

srsenb/src/stack/mac/sched_phy_ch/sf_cch_allocator.cc

@@ -181,6 +181,15 @@ bool sf_cch_allocator::alloc_dfs_node(const alloc_record& record, uint32_t start
         // PUCCH allocation would collide with other PUCCH/PUSCH grants. Try another CCE position
         continue;
       }
+      int low_rb = node.pucch_n_prb < (int)cc_cfg->cfg.cell.nof_prb / 2
+                       ? node.pucch_n_prb
+                       : cc_cfg->cfg.cell.nof_prb - node.pucch_n_prb - 1;
+      if (cc_cfg->sched_cfg->pucch_harq_max_rb > 0 && low_rb >= cc_cfg->sched_cfg->pucch_harq_max_rb) {
+        // PUCCH allocation would fall outside the maximum allowed PUCCH HARQ region. Try another CCE position
+        logger.info("Skipping PDCCH allocation for CCE=%d due to PUCCH HARQ falling outside region\n",
+                    node.dci_pos.ncce);
+        continue;
+      }
     }
 
     node.current_mask.reset();