allocate only necessary amount of RBs

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_dlsch.c

@@ -552,27 +552,26 @@ void nr_simple_dlsch_preprocessor(module_id_t module_id,
     // Time-domain allocation
     sched_ctrl->time_domain_allocation = 2;
 
-    // Freq-demain allocation
-    while (rbStart < bwpSize && vrb_map[rbStart]) rbStart++;
-    int rbSize = 1;
-    while (rbStart + rbSize < bwpSize && !vrb_map[rbStart + rbSize]) rbSize++;
-    DevAssert(rbSize >= 3); /* just ensure we have at least 3 RBs */
-    sched_ctrl->rbSize = rbSize;
-    sched_ctrl->rbStart = rbStart;
-
     // modulation scheme
     sched_ctrl->mcsTableIdx = 0;
     sched_ctrl->mcs = 9;
     sched_ctrl->numDmrsCdmGrpsNoData = 1;
 
+    // Freq-demain allocation
+    while (rbStart < bwpSize && vrb_map[rbStart]) rbStart++;
+
     uint8_t N_PRB_DMRS =
         getN_PRB_DMRS(sched_ctrl->active_bwp, sched_ctrl->numDmrsCdmGrpsNoData);
     int nrOfSymbols = getNrOfSymbols(sched_ctrl->active_bwp,
                                      sched_ctrl->time_domain_allocation);
-    const uint32_t TBS =
-        nr_compute_tbs(nr_get_Qm_dl(sched_ctrl->mcs, sched_ctrl->mcsTableIdx),
+
+    int rbSize = 0;
+    uint32_t TBS = 0;
+    do {
+      rbSize++;
+      TBS = nr_compute_tbs(nr_get_Qm_dl(sched_ctrl->mcs, sched_ctrl->mcsTableIdx),
                            nr_get_code_rate_dl(sched_ctrl->mcs, sched_ctrl->mcsTableIdx),
-                       sched_ctrl->rbSize,
+                           rbSize,
                            nrOfSymbols,
                            N_PRB_DMRS, // FIXME // This should be multiplied by the
                                        // number of dmrs symbols
@@ -580,7 +579,9 @@ void nr_simple_dlsch_preprocessor(module_id_t module_id,
                            0 /* tb_scaling */,
                            1 /* nrOfLayers */)
             >> 3;
-    AssertFatal(TBS != 0, "TBS is zero but requested %d RBs!\n", sched_ctrl->rbSize);
+    } while (rbStart + rbSize < bwpSize && !vrb_map[rbStart + rbSize] && TBS < sched_ctrl->num_total_bytes);
+    sched_ctrl->rbSize = rbSize;
+    sched_ctrl->rbStart = rbStart;
   }
 
   /* mark the corresponding RBs as used */