NR RRC - Choose the next available DRB from the 5QI

If it is a GBR flow, assign a dedicated DRB
If is is a NGBR flow, use an existing DRB, from the same PDU Session

Note: the case that we run out of DRBs is not handled yet, it is still a todo

openair2/RRC/NR/rrc_gNB.c

@@ -862,14 +862,18 @@ rrc_gNB_generate_dedicatedRRCReconfiguration(
             break;
         }
 
-        NR_DRB_ToAddMod_t *DRB_config = generateDRB(ue_p,
-                                                  drb_id,
-                                                  &ue_context_pP->ue_context.pduSession[i],
-                                                  rrc->configuration.enable_sdap,
-                                                  rrc->security.do_drb_integrity,
-                                                  rrc->security.do_drb_ciphering);
-        ASN_SEQUENCE_ADD(&(*DRB_configList)->list, DRB_config);
-        ASN_SEQUENCE_ADD(&(*DRB_configList2)->list, DRB_config);
+        if(drb_is_active(ue_p, drb_id)){ /* Non-GBR flow using the same DRB or a GBR flow with no available DRBs*/
+          nb_drb_to_setup--;
+        } else {
+          NR_DRB_ToAddMod_t *DRB_config = generateDRB(ue_p,
+                                                    drb_id,
+                                                    &ue_context_pP->ue_context.pduSession[i],
+                                                    rrc->configuration.enable_sdap,
+                                                    rrc->security.do_drb_integrity,
+                                                    rrc->security.do_drb_ciphering);
+          ASN_SEQUENCE_ADD(&(*DRB_configList)->list, DRB_config);
+          ASN_SEQUENCE_ADD(&(*DRB_configList2)->list, DRB_config);
+        }
       }
     }
 

openair2/RRC/NR/rrc_gNB_drbs.c

@@ -58,6 +58,11 @@ NR_DRB_ToAddMod_t *generateDRB(gNB_RRC_UE_t *ue,
     NR_QFI_t *qfi = calloc(1, sizeof(NR_QFI_t));
     *qfi = pduSession->param.qos[qos_flow_index].qfi;
     ASN_SEQUENCE_ADD(&SDAP_config->mappedQoS_FlowsToAdd->list, qfi);
+
+    if(pduSession->param.qos[qos_flow_index].fiveQI > 5)
+      ue->pduSession[pduSession->param.pdusession_id].param.used_drbs[drb_id-1] = DRB_ACTIVE_NONGBR;
+    else
+      ue->pduSession[pduSession->param.pdusession_id].param.used_drbs[drb_id-1] = DRB_ACTIVE;
   }
   
   SDAP_config->mappedQoS_FlowsToRelease = NULL;
@@ -100,18 +105,28 @@ NR_DRB_ToAddMod_t *generateDRB(gNB_RRC_UE_t *ue,
   }
 
   ue->DRB_active[drb_id-1] = DRB_ACTIVE;
-  ue->pduSession[pduSession->param.pdusession_id].param.used_drbs[drb_id] = DRB_ACTIVE;
 
   return DRB_config;
 }
 
 uint8_t next_available_drb(gNB_RRC_UE_t *ue, uint8_t pdusession_id, bool is_gbr) {
   uint8_t drb_id;
-  for (drb_id = 0; drb_id < NGAP_MAX_DRBS_PER_UE; drb_id++) {
-    if(ue->DRB_active[drb_id] == DRB_INACTIVE)
-      return drb_id+1;
+
+  if(is_gbr) { /* GBR Flow */
+    for (drb_id = 0; drb_id < NGAP_MAX_DRBS_PER_UE; drb_id++)
+      if(ue->DRB_active[drb_id] == DRB_INACTIVE)
+        return drb_id+1;
+  } else { /* Non-GBR Flow */
+    /* Find if Non-GBR DRB exists in the same PDU Session */
+    for (drb_id = 0; drb_id < NGAP_MAX_DRBS_PER_UE; drb_id++)
+      if(ue->pduSession[pdusession_id].param.used_drbs[drb_id-1] == DRB_ACTIVE_NONGBR)
+        return drb_id+1;
+    /* If a Non-GBR DRB does not exist in the same PDU Session, find an available DRB  */
+    for (drb_id = 0; drb_id < NGAP_MAX_DRBS_PER_UE; drb_id++)
+      if(ue->DRB_active[drb_id] == DRB_INACTIVE)
+        return drb_id+1;
   }
-  /* From this point, we handle the case that all DRBs are already used by the UE. */
+  /* From this point, we need to handle the case that all DRBs are already used by the UE. */
   LOG_E(RRC, "Error - All the DRBs are used - Handle this\n");
   return DRB_INACTIVE;
 }

openair2/RRC/NR/rrc_gNB_drbs.h

@@ -28,6 +28,7 @@
 
 #define MAX_DRBS_PER_UE         (32)  /* Maximum number of Data Radio Bearers per UE */
 #define MAX_PDUS_PER_UE         (8)   /* Maximum number of PDU Sessions per UE */
+#define DRB_ACTIVE_NONGBR       (2)   /* DRB is used for Non-GBR Flows */
 #define DRB_ACTIVE              (1)
 #define DRB_INACTIVE            (0)
 #define GBR_FLOW                (1)