Implementation of a RA timer to remove UE in the case of Msg4 not be decoded by the UE

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c

@@ -1829,6 +1829,7 @@ void nr_generate_Msg4(module_id_t module_idP, int CC_id, frame_t frameP, sub_fra
       nr_clear_ra_proc(module_idP, CC_id, frameP, ra);
       UE->Msg3_dcch_dtch = true;
       UE->Msg4_ACKed = true;
+      UE->ra_timer = 0;
 
       remove_front_nr_list(&sched_ctrl->feedback_dl_harq);
       harq->feedback_slot = -1;
@@ -1867,6 +1868,7 @@ void nr_check_Msg4_Ack(module_id_t module_id, int CC_id, frame_t frame, sub_fram
       if (stats->dl.errors == 0) {
         LOG_A(NR_MAC, "(UE RNTI 0x%04x) Received Ack of RA-Msg4. CBRA procedure succeeded!\n", ra->rnti);
         UE->Msg4_ACKed = true;
+        UE->ra_timer = 0;
 
         // Pause scheduling according to:
         // 3GPP TS 38.331 Section 12 Table 12.1-1: UE performance requirements for RRC procedures for UEs

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c

@@ -2508,6 +2508,8 @@ NR_UE_info_t *add_new_nr_ue(gNB_MAC_INST *nr_mac, rnti_t rntiP, NR_CellGroupConf
               "uplinkBWP_ToAddModList has %d BWP!\n",
               ul_bwp->n_ul_bwp);
 
+  UE->ra_timer = 12000 << UE->current_DL_BWP.scs; // TODO: temporary value, 12000 ms from experimental results
+
   /* get Number of HARQ processes for this UE */
   // pdsch_servingcellconfig == NULL in SA -> will create default (8) number of HARQ processes
   create_dl_harq_list(sched_ctrl, dl_bwp->pdsch_servingcellconfig);
@@ -2974,6 +2976,15 @@ void nr_mac_update_timers(module_id_t module_id,
                                  ups);
       }
     }
+
+    // RA timer
+    if (UE->ra_timer > 0) {
+      UE->ra_timer--;
+      if (UE->ra_timer == 0) {
+        LOG_W(NR_MAC, "Removing UE %04x because RA timer expired\n", UE->rnti);
+        mac_remove_nr_ue(RC.nrmac[module_id], UE->rnti);
+      }
+    }
   }
 }
 

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_ulsch.c

@@ -668,6 +668,7 @@ void nr_rx_sdu(const module_id_t gnb_mod_idP,
         if(ra->cfra) {
 
           LOG_A(NR_MAC, "(rnti 0x%04x) CFRA procedure succeeded!\n", ra->rnti);
+          UE->ra_timer = 0;
           nr_mac_remove_ra_rnti(gnb_mod_idP, ra->rnti);
           nr_clear_ra_proc(gnb_mod_idP, CC_idP, frameP, ra);
           process_CellGroup(ra->CellGroup, UE_scheduling_control);

openair2/LAYER2/NR_MAC_gNB/nr_mac_gNB.h

@@ -709,6 +709,7 @@ typedef struct {
   uint8_t UE_beam_index;
   bool Msg3_dcch_dtch;
   bool Msg4_ACKed;
+  uint32_t ra_timer;
   /// Sched CSI-RS: scheduling decisions
   NR_gNB_UCI_STATS_t uci_statS;
   float ul_thr_ue;