DLSCH scheduler allocation for multiple UEs

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_dlsch.c

@@ -247,29 +247,27 @@ void nr_dlsch_pre_processor(module_id_t Mod_id, frame_t f, sub_frame_t s) {
 }
 
 void nr_schedule_ue_spec(module_id_t module_idP, frame_t frameP, sub_frame_t slotP){
-  NR_UE_list_t *UE_list = &RC.nrmac[module_idP]->UE_list;
+  const int bwp_id = 1;
+  const int CC_id = 0;
+
+  gNB_MAC_INST *gNB_mac = RC.nrmac[module_idP];
+  NR_UE_list_t *UE_list = &gNB_mac->UE_list;
   if (UE_list->num_UEs == 0)
     return;
 
   nr_dlsch_buffer_update(module_idP, frameP, slotP);
 
-  // for every user, defines frequency allocation, MCS, etc
+  /* the preprocessor determines resource block allocation, MCS, etc. for all
+   * UEs.  Currently, these values are kept in the (LTE) UE_sched_ctrl_t
+   * structure */
   nr_dlsch_pre_processor(module_idP, frameP, slotP);
 
-  const int bwp_id = 1;
-  const int CC_id = 0;
-
-  gNB_MAC_INST *gNB_mac = RC.nrmac[module_idP];
-  nfapi_nr_dl_tti_request_body_t *dl_req = &gNB_mac->DL_req[CC_id].dl_tti_request_body;
-  nfapi_nr_pdu_t *tx_req = &gNB_mac->TX_req[CC_id].pdu_list[gNB_mac->TX_req[CC_id].Number_of_PDUs];
-
   LOG_D(MAC, "Scheduling UE specific search space DCI type 1\n");
-
   int rbStart = 0;
-  int UE_id = 0;
+  for (int UE_id = UE_list->head; UE_id >= 0; UE_id = UE_list->next[UE_id]) {
     UE_sched_ctrl_t *sched_ctrl = &UE_list->UE_sched_ctrl[UE_id];
     if (sched_ctrl->pre_nb_available_rbs[CC_id] == 0)
-    return;
+      continue;
 
     int CCEIndex = allocate_nr_CCEs(gNB_mac,
                                     bwp_id, // bwp_id
@@ -280,9 +278,15 @@ void nr_schedule_ue_spec(module_id_t module_idP, frame_t frameP, sub_frame_t slo
                                     0); // m
     if (CCEIndex < 0) {
       LOG_E(MAC, "%d.%d can not allocate CCE for UE %d\n", frameP, slotP, UE_id);
-    return;
+      continue;
     }
 
+    /* this pre-fills the PDCCH and PDSCH PDUs of FAPI. At the same time, it
+     * calculates the TBS. We could do the latter in a separate step first, but
+     * this involves multiple variables (like code rate, etc) that we'd need to
+     * carry along the TBS so we avoid this for the moment since at this point
+     * we can be sure that (a) resource blocks have been allocated and (b) this
+     * UE's CCEs can be allocated, hence this will run until the end */
     int TBS_bytes = configure_fapi_dl_pdu(gNB_mac,
                                           CC_id,
                                           UE_id,
@@ -295,12 +299,11 @@ void nr_schedule_ue_spec(module_id_t module_idP, frame_t frameP, sub_frame_t slo
     unsigned char sdu_lcids[NB_RB_MAX] = {0};
     uint16_t sdu_lengths[NB_RB_MAX] = {0};
     uint8_t mac_sdus[MAX_NR_DLSCH_PAYLOAD_BYTES];
-  uint16_t rnti = UE_list->rnti[UE_id];
-  int ta_len = gNB_mac->ta_len;
+    const uint16_t rnti = UE_list->rnti[UE_id];
+    int ta_len = gNB_mac->ta_len; /* TODO needs to be UE specific? */
     int header_length_total = 0;
     int sdu_length_total = 0;
     int num_sdus = 0;
-  int header_length_last;
     for (int i = 0; i < sched_ctrl->dl_lc_num; i++) {
       int lcid = sched_ctrl->dl_lc_ids[i];
       // if nothing is allocated for this RB, continue
@@ -340,8 +343,7 @@ void nr_schedule_ue_spec(module_id_t module_idP, frame_t frameP, sub_frame_t slo
 
       sdu_lcids[num_sdus] = lcid;
       sdu_length_total += sdu_lengths[num_sdus];
-    header_length_last = 1 + 1 + (sdu_lengths[num_sdus] >= 128);
-    header_length_total += header_length_last;
+      header_length_total += 1 + 1 + (sdu_lengths[num_sdus] >= 128);
 
       num_sdus++;
 
@@ -351,17 +353,20 @@ void nr_schedule_ue_spec(module_id_t module_idP, frame_t frameP, sub_frame_t slo
         break;
     }
 
-  // check if there is at least one SDU or TA command
+    /* check if there is at least one SDU or TA command. Actually this should
+     * never be true (a UE is only allocated resource blocks if it has data to
+     * transmit), but leave it as a final check */
     if (ta_len + sdu_length_total + header_length_total <= 0)
-    return;
+      continue;
 
     // Check if we have to consider padding
     int post_padding = TBS_bytes >= 2 + header_length_total + sdu_length_total + ta_len;
 
-  int offset = nr_generate_dlsch_pdu(module_idP,
-                                 (unsigned char *) mac_sdus,
-                                 (unsigned char *) gNB_mac->UE_list.DLSCH_pdu[0][0].payload[0], //(unsigned char *) mac_pdu,
-                                 num_sdus, //num_sdus
+    int offset = nr_generate_dlsch_pdu(
+        module_idP,
+        (unsigned char *)mac_sdus,
+        (unsigned char *)UE_list->DLSCH_pdu[0][UE_id].payload[0],
+        num_sdus, // num_sdus
         sdu_lengths,
         sdu_lcids,
         255, // no drx
@@ -371,15 +376,20 @@ void nr_schedule_ue_spec(module_id_t module_idP, frame_t frameP, sub_frame_t slo
     // Padding: fill remainder of DLSCH with 0
     if (post_padding > 0)
       for (int j = 0; j < (TBS_bytes - offset); j++)
-      gNB_mac->UE_list.DLSCH_pdu[0][UE_id].payload[0][offset + j] = 0;
+        UE_list->DLSCH_pdu[0][UE_id].payload[0][offset + j] = 0;
 
-  configure_fapi_dl_Tx(
-      gNB_mac, CC_id, frameP, slotP, TBS_bytes, UE_list->DLSCH_pdu[0][0].payload[0]);
+    configure_fapi_dl_Tx(gNB_mac,
+                         CC_id,
+                         frameP,
+                         slotP,
+                         TBS_bytes,
+                         UE_list->DLSCH_pdu[0][UE_id].payload[0]);
 
 #if defined(ENABLE_MAC_PAYLOAD_DEBUG)
     LOG_I(MAC, "%d.%d first 10 payload bytes UE %d TBSsize %d:", frameP, slotP, UE_id, TBS_bytes);
     for(int i = 0; i < 10; i++)
-    printf(" %02x.", gNB_mac->UE_list.DLSCH_pdu[0][UE_id].payload[0][i]);
+      printf(" %02x.", UE_list->DLSCH_pdu[0][UE_id].payload[0][i]);
     prinf("..\n");
 #endif
+  }
 }