Schedule PRACH (internally) one frame in advance

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler.c

@@ -397,8 +397,18 @@ void gNB_dlsch_ulsch_scheduler(module_id_t module_idP,
   schedule_nr_mib(module_idP, frame, slot, slots_per_frame[*scc->ssbSubcarrierSpacing]);
 
   // This schedule PRACH if we are not in phy_test mode
-  if (get_softmodem_params()->phy_test == 0)
-    schedule_nr_prach(module_idP, frame, slot);
+  if (get_softmodem_params()->phy_test == 0) {
+    /* we need to make sure that resources for PRACH are free. To avoid that
+       e.g. PUSCH has already been scheduled, make sure we schedule before
+       anything else: below, we simply assume an advance one frame (minus one
+       slot, because otherwise we would allocate the current slot in
+       UL_tti_req_ahead), but be aware that, e.g., K2 is allowed to be larger
+       (schedule_nr_prach will assert if resources are not free). */
+    const sub_frame_t n_slots_ahead = slots_per_frame[*scc->ssbSubcarrierSpacing] - 1;
+    const frame_t f = (frame + (slot + n_slots_ahead) / slots_per_frame[*scc->ssbSubcarrierSpacing]) % 1024;
+    const sub_frame_t s = (slot + n_slots_ahead) % slots_per_frame[*scc->ssbSubcarrierSpacing];
+    schedule_nr_prach(module_idP, f, s);
+  }
 
   // This schedule SR
   // TODO

openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_RA.c

@@ -200,7 +200,7 @@ void schedule_nr_prach(module_id_t module_idP, frame_t frameP, sub_frame_t slotP
   gNB_MAC_INST *gNB = RC.nrmac[module_idP];
   NR_COMMON_channels_t *cc = gNB->common_channels;
   NR_ServingCellConfigCommon_t *scc = cc->ServingCellConfigCommon;
-  nfapi_nr_ul_tti_request_t *UL_tti_req = RC.nrmac[module_idP]->UL_tti_req[0];
+  nfapi_nr_ul_tti_request_t *UL_tti_req = &RC.nrmac[module_idP]->UL_tti_req_ahead[0][slotP];
   nfapi_nr_config_request_scf_t *cfg = &RC.nrmac[module_idP]->config[0];
 
   if (is_nr_UL_slot(scc,slotP)) {