improvements in selecting DL MCS table

openair2/LAYER2/NR_MAC_COMMON/nr_mac_common.c

@@ -3727,12 +3727,36 @@ int16_t fill_dmrs_mask(const NR_PDSCH_Config_t *pdsch_Config,int dmrs_TypeA_Posi
   return l_prime;
 }
 
+uint8_t get_pdsch_mcs_table(long *mcs_Table, int dci_format, int rnti_type, int ss_type)
+{
+
+  // Set downlink MCS table (Semi-persistend scheduling ignored for now)
+  uint8_t mcsTableIdx = 0; // default value
+  if (mcs_Table &&
+      *mcs_Table == NR_PDSCH_Config__mcs_Table_qam256 &&
+      dci_format == NR_DL_DCI_FORMAT_1_1 &&
+      rnti_type == NR_RNTI_C)
+    mcsTableIdx = 1;
+  else if (rnti_type != NR_RNTI_MCS_C &&
+           mcs_Table &&
+           *mcs_Table == NR_PDSCH_Config__mcs_Table_qam64LowSE &&
+           ss_type == NR_SearchSpace__searchSpaceType_PR_ue_Specific)
+    mcsTableIdx = 2;
+  else if (rnti_type == NR_RNTI_MCS_C)
+    mcsTableIdx = 2;
+
+  LOG_D(NR_MAC,"DL MCS Table Index: %d\n", mcsTableIdx);
+  return mcsTableIdx;
+
+}
+
 uint8_t get_pusch_mcs_table(long *mcs_Table,
                             int is_tp,
                             int dci_format,
                             int rnti_type,
                             int target_ss,
-                            bool config_grant) {
+                            bool config_grant)
+{
 
   // implementing 6.1.4.1 in 38.214
   if (mcs_Table != NULL) {

openair2/LAYER2/NR_MAC_COMMON/nr_mac_common.h

@@ -151,6 +151,8 @@ uint8_t compute_nr_root_seq(NR_RACH_ConfigCommon_t *rach_config,
 
 int ul_ant_bits(NR_DMRS_UplinkConfig_t *NR_DMRS_UplinkConfig,long transformPrecoder);
 
+uint8_t get_pdsch_mcs_table(long *mcs_Table, int dci_format, int rnti_type, int ss_type);
+
 int get_format0(uint8_t index, uint8_t unpaired,frequency_range_t);
 
 int64_t *get_prach_config_info(frequency_range_t freq_range,

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c

@@ -2445,17 +2445,6 @@ void configure_UE_BWP(gNB_MAC_INST *nr_mac,
   UL_BWP->initial_BWPSize = NRRIV2BW(scc->uplinkConfigCommon->initialUplinkBWP->genericParameters.locationAndBandwidth, MAX_BWP_SIZE);
   UL_BWP->initial_BWPStart = NRRIV2PRBOFFSET(scc->uplinkConfigCommon->initialUplinkBWP->genericParameters.locationAndBandwidth, MAX_BWP_SIZE);
 
-  // Set downlink MCS table
-  if (DL_BWP->pdsch_Config &&
-      DL_BWP->pdsch_Config->mcs_Table) {
-    if (*DL_BWP->pdsch_Config->mcs_Table == 0)
-      DL_BWP->mcsTableIdx = 1;
-    else
-      DL_BWP->mcsTableIdx = 2;
-  } else
-    DL_BWP->mcsTableIdx = 0;
-  LOG_D(NR_MAC,"DL MCS Table Index: %d\n",DL_BWP->mcsTableIdx);
-
   if (UL_BWP->pusch_Config == NULL || !UL_BWP->pusch_Config->transformPrecoder)
     UL_BWP->transform_precoding = !scc->uplinkConfigCommon->initialUplinkBWP->rach_ConfigCommon->choice.setup->msg3_transformPrecoder;
   else
@@ -2539,14 +2528,17 @@ void configure_UE_BWP(gNB_MAC_INST *nr_mac,
     DL_BWP->dci_format = NR_DL_DCI_FORMAT_1_0;
   }
 
-  // Set uplink MCS table
-  long *mcs_Table = NULL;
+  // Set MCS tables
+  long *dl_mcs_Table = DL_BWP->pdsch_Config ? DL_BWP->pdsch_Config->mcs_Table : NULL;
+  DL_BWP->mcsTableIdx = get_pdsch_mcs_table(dl_mcs_Table, DL_BWP->dci_format, NR_RNTI_C, target_ss);
+
+  long *ul_mcs_Table = NULL;
   if (UL_BWP->pusch_Config)
-    mcs_Table = UL_BWP->transform_precoding ?
-                UL_BWP->pusch_Config->mcs_Table :
-                UL_BWP->pusch_Config->mcs_TableTransformPrecoder;
+    ul_mcs_Table = UL_BWP->transform_precoding ?
+                   UL_BWP->pusch_Config->mcs_Table :
+                   UL_BWP->pusch_Config->mcs_TableTransformPrecoder;
 
-  UL_BWP->mcs_table = get_pusch_mcs_table(mcs_Table,
+  UL_BWP->mcs_table = get_pusch_mcs_table(ul_mcs_Table,
                                           UL_BWP->transform_precoding ? 0 : 1,
                                           UL_BWP->dci_format,
                                           NR_RNTI_C,