reworking prach scheduler to use new rach occasion information

openair2/LAYER2/NR_MAC_UE/mac_defs.h

@@ -320,7 +320,7 @@ typedef struct {
   int Pc_max;
 } NR_PRACH_RESOURCES_t;
 
-typedef struct{
+typedef struct {
   float ssb_per_ro;
   int preambles_per_ssb;
 } ssb_ro_preambles_t;
@@ -362,8 +362,6 @@ typedef struct {
   bool RA_active;
   /// Random-access preamble index
   int ra_PreambleIndex;
-  // When multiple SSBs per RO is configured, this indicates which one is selected in this RO -> this is used to properly compute the PRACH preamble
-  uint8_t ssb_nb_in_ro;
   int zeroCorrelationZoneConfig;
   int restricted_set_config;
   // selected SSB for RACH (not the SSB-Index but the cumulative index, excluding not trasmitted SSBs)

openair2/LAYER2/NR_MAC_UE/main_ue_nr.c

@@ -302,4 +302,3 @@ void release_mac_configuration(NR_UE_MAC_INST_t *mac, NR_UE_MAC_reset_cause_t ca
   for (int i = mac->TAG_list.count; i > 0 ; i--)
     asn_sequence_del(&mac->TAG_list, i - 1, 1);
 }
-

openair2/LAYER2/NR_MAC_UE/nr_ra_procedures.c

@@ -403,7 +403,7 @@ static void ra_resource_selection(NR_UE_MAC_INST_t *mac)
           ssb = mac->mib_ssb;
           // set the PREAMBLE_INDEX to a ra-PreambleIndex corresponding to the selected SSB
           ra->ra_PreambleIndex = res->ra_PreambleIndex;
-          ra->ro_mask_index =  cfra->resourcesTwoStep_r16.ra_ssb_OccasionMaskIndex;
+          ra->ro_mask_index = cfra->resourcesTwoStep_r16.ra_ssb_OccasionMaskIndex;
           break;
         }
       }
@@ -454,7 +454,7 @@ static void select_prach_occasion(RA_config_t *ra,
   int idx_ssb = 0;
   int temp_idx = 0;
   if (ra->ssb_ro_config.ssb_per_ro < 1) {
-    num_ros_per_ssb = (int) (1 / ra->ssb_ro_config.ssb_per_ro);
+    num_ros_per_ssb = (int)(1 / ra->ssb_ro_config.ssb_per_ro);
     idx_ssb = (rand_r(&seed) % num_ros_per_ssb);
     temp_idx = ra->ra_ssb * num_ros_per_ssb + idx_ssb;
   } else {
@@ -508,13 +508,13 @@ static void configure_prach_occasions(NR_UE_MAC_INST_t *mac, int prach_config_in
           if (fs->frame_type == TDD && !check_mixed_slot_prach(fs, slot, start_symbol, end_symbol))
             continue;
           for (int f = 0; f < num_fd_occasions; f++) {  // fd occasions
-            ra_occasions_period[num_ra_occasions_period] = (prach_occasion_info_t) {
+            ra_occasions_period[num_ra_occasions_period] =
-              .slot = slot,
+                (prach_occasion_info_t){.slot = slot,
-              .frame_info[0] = prach_info.x,
+                                        .frame_info[0] = prach_info.x,
-              .frame_info[1] = n == 0 ? prach_info.y : prach_info.y2,
+                                        .frame_info[1] = n == 0 ? prach_info.y : prach_info.y2,
-              .start_symbol = start_symbol,
+                                        .start_symbol = start_symbol,
-              .fdm = f,
+                                        .fdm = f,
-              .format = prach_info.format};
+                                        .format = prach_info.format};
             LOG_D(NR_MAC,
                   "RA occasion %d: slot %d start symbol %d fd occasion %d\n",
                   num_ra_occasions_period,
@@ -533,10 +533,10 @@ static void configure_prach_occasions(NR_UE_MAC_INST_t *mac, int prach_config_in
   ra->association_periods = 1;
   int nb_eq_ssb = mac->ssb_list.nb_tx_ssb;
   if (ra->ssb_ro_config.ssb_per_ro < 1)
-    nb_eq_ssb *= (int) (1 / ra->ssb_ro_config.ssb_per_ro);
+    nb_eq_ssb *= (int)(1 / ra->ssb_ro_config.ssb_per_ro);
   int nb_eq_ro = num_ra_occasions_period;
   if (ra->ssb_ro_config.ssb_per_ro > 1)
-    nb_eq_ro *= (int) ra->ssb_ro_config.ssb_per_ro;
+    nb_eq_ro *= (int)ra->ssb_ro_config.ssb_per_ro;
   while (nb_eq_ssb > nb_eq_ro) {
     // not enough PRACH occasions -> need to increase association period
     ra->association_periods <<= 1;

openair2/LAYER2/NR_MAC_UE/nr_ue_scheduler.c

@@ -1939,91 +1939,6 @@ static void map_ssb_to_ro(NR_UE_MAC_INST_t *mac)
   }
 }
 
-// Returns a RACH occasion if any matches the SSB idx, the frame and the slot
-static int get_nr_prach_info_from_ssb_index(prach_association_pattern_t *prach_assoc_pattern,
-                                            int ssb_idx,
-                                            int frame,
-                                            int slot,
-                                            ssb_list_info_t *ssb_list,
-                                            prach_occasion_info_t **prach_occasion_info_pp)
-{
-  prach_occasion_slot_t *prach_occasion_slot_p = NULL;
-
-  *prach_occasion_info_pp = NULL;
-
-  // Search for a matching RO slot in the SSB_to_RO map
-  // A valid RO slot will match:
-  //      - ssb_idx mapped to one of the ROs in that RO slot
-  //      - exact slot number
-  //      - frame offset
-  int idx_list = ssb_list->nb_ssb_per_index[ssb_idx];
-  ssb_info_t *ssb_info_p = &ssb_list->tx_ssb[idx_list];
-  LOG_D(NR_MAC, "checking for prach : ssb_info_p->nb_mapped_ro %d\n", ssb_info_p->nb_mapped_ro);
-  for (int n_mapped_ro = 0; n_mapped_ro < ssb_info_p->nb_mapped_ro; n_mapped_ro++) {
-    LOG_D(NR_MAC,
-          "%d.%d: mapped_ro[%d]->frame.slot %d.%d, prach_assoc_pattern->nb_of_frame %d\n",
-          frame,
-          slot,
-          n_mapped_ro,
-          ssb_info_p->mapped_ro[n_mapped_ro]->frame,
-          ssb_info_p->mapped_ro[n_mapped_ro]->slot,
-          prach_assoc_pattern->nb_of_frame);
-    if ((slot == ssb_info_p->mapped_ro[n_mapped_ro]->slot) && prach_assoc_pattern->prach_conf_period_list[0].nb_of_frame != 0 &&
-        (ssb_info_p->mapped_ro[n_mapped_ro]->frame == (frame % prach_assoc_pattern->nb_of_frame))) {
-      uint8_t prach_config_period_nb = ssb_info_p->mapped_ro[n_mapped_ro]->frame / prach_assoc_pattern->prach_conf_period_list[0].nb_of_frame;
-      uint8_t frame_nb_in_prach_config_period = ssb_info_p->mapped_ro[n_mapped_ro]->frame % prach_assoc_pattern->prach_conf_period_list[0].nb_of_frame;
-      prach_occasion_slot_p = &prach_assoc_pattern->prach_conf_period_list[prach_config_period_nb].prach_occasion_slot_map[frame_nb_in_prach_config_period][slot];
-    }
-  }
-
-  // If there is a matching RO slot in the SSB_to_RO map
-  if (NULL != prach_occasion_slot_p) {
-    // A random RO mapped to the SSB index should be selected in the slot
-
-    // First count the number of times the SSB index is found in that RO
-    uint8_t nb_mapped_ssb = 0;
-
-    for (int ro_in_time = 0; ro_in_time < prach_occasion_slot_p->nb_of_prach_occasion_in_time; ro_in_time++) {
-      for (int ro_in_freq = 0; ro_in_freq < prach_occasion_slot_p->nb_of_prach_occasion_in_freq; ro_in_freq++) {
-        prach_occasion_info_t *ro_p =
-            prach_occasion_slot_p->prach_occasion + ro_in_time * prach_occasion_slot_p->nb_of_prach_occasion_in_freq + ro_in_freq;
-        for (uint8_t ssb_nb = 0; ssb_nb < ro_p->nb_mapped_ssb; ssb_nb++) {
-          if (ro_p->mapped_ssb_idx[ssb_nb] == ssb_idx) {
-            nb_mapped_ssb++;
-          }
-        }
-      }
-    }
-
-    // Choose a random SSB nb
-    uint8_t random_ssb_nb = 0;
-
-    random_ssb_nb = ((taus()) % nb_mapped_ssb);
-
-    // Select the RO according to the chosen random SSB nb
-    nb_mapped_ssb=0;
-    for (int ro_in_time=0; ro_in_time < prach_occasion_slot_p->nb_of_prach_occasion_in_time; ro_in_time++) {
-      for (int ro_in_freq=0; ro_in_freq < prach_occasion_slot_p->nb_of_prach_occasion_in_freq; ro_in_freq++) {
-        prach_occasion_info_t *ro_p =
-            prach_occasion_slot_p->prach_occasion + ro_in_time * prach_occasion_slot_p->nb_of_prach_occasion_in_freq + ro_in_freq;
-        for (uint8_t ssb_nb = 0; ssb_nb < ro_p->nb_mapped_ssb; ssb_nb++) {
-          if (ro_p->mapped_ssb_idx[ssb_nb] == ssb_idx) {
-            if (nb_mapped_ssb == random_ssb_nb) {
-              *prach_occasion_info_pp = ro_p;
-              return 1;
-            }
-            else {
-              nb_mapped_ssb++;
-            }
-          }
-        }
-      }
-    }
-  }
-
-  return 0;
-}
-
 // Build the SSB to RO mapping upon RRC configuration update
 void build_ssb_to_ro_map(NR_UE_MAC_INST_t *mac)
 {
@@ -2522,6 +2437,23 @@ void nr_schedule_csirs_reception(NR_UE_MAC_INST_t *mac, int frame, int slot)
   }
 }
 
+static bool is_prach_frame(frame_t frame, prach_occasion_info_t *prach_occasion_info, int association_periods)
+{
+  int config_period = prach_occasion_info->frame_info[0];
+  int frame_period = config_period * association_periods;
+  int frame_in_period = frame % frame_period;
+  if (association_periods > 1) {
+    int current_assoc_period = frame_in_period / config_period;
+    if (current_assoc_period != prach_occasion_info->association_period_idx)
+      return false;
+    frame_in_period %= config_period;
+  }
+  if (frame_in_period == prach_occasion_info->frame_info[1]) // SFN % x == y (see Tables in Table 6.3.3.2 of 38.211)
+    return true;
+  else
+    return false;
+}
+
 // This function schedules the PRACH according to prach_ConfigurationIndex and TS 38.211, tables 6.3.3.2.x
 // PRACH formats 9, 10, 11 are corresponding to dual PRACH format configurations A1/B1, A2/B2, A3/B3.
 // - todo:
@@ -2533,49 +2465,36 @@ static void nr_ue_prach_scheduler(NR_UE_MAC_INST_t *mac, frame_t frameP, slot_t
   if (ra->ra_state != nrRA_GENERATE_PREAMBLE)
     return;
 
-  fapi_nr_config_request_t *cfg = &mac->phy_config.config_req;
+  // Get any valid PRACH occasion in the current slot for the selected SSB index
-  fapi_nr_prach_config_t *prach_config = &cfg->prach_config;
+  prach_occasion_info_t *prach_occasion_info = &ra->sched_ro_info;
 
-  const int bwp_id = mac->current_UL_BWP->bwp_id;
+  if (!is_prach_frame(frameP, prach_occasion_info, ra->association_periods))
+    return;
 
   if (is_ul_slot(slotP, &mac->frame_structure)) {
-    // WIP Need to get the proper selected ssb_idx
+    if (slotP == prach_occasion_info->slot) {
-    //     Initial beam selection functionality is not available yet
-    uint8_t selected_gnb_ssb_idx = mac->mib_ssb;
-
-    // Get any valid PRACH occasion in the current slot for the selected SSB index
-    prach_occasion_info_t *prach_occasion_info_p;
-    int is_nr_prach_slot = get_nr_prach_info_from_ssb_index(&mac->prach_assoc_pattern[bwp_id],
-                                                            selected_gnb_ssb_idx,
-                                                            (int)frameP,
-                                                            (int)slotP,
-                                                            &mac->ssb_list,
-                                                            &prach_occasion_info_p);
-
-    if (is_nr_prach_slot) {
-      AssertFatal(NULL != prach_occasion_info_p,"PRACH Occasion Info not returned in a valid NR Prach Slot\n");
-
       nr_get_RA_window(mac);
-
-      uint16_t format = prach_occasion_info_p->format;
-      uint16_t format0 = format & 0xff;        // single PRACH format
-      uint16_t format1 = (format >> 8) & 0xff; // dual PRACH format
-
       fapi_nr_ul_config_request_pdu_t *pdu = lockGet_ul_config(mac, frameP, slotP, FAPI_NR_UL_CONFIG_TYPE_PRACH);
       if (!pdu) {
         LOG_E(NR_MAC, "Error in PRACH allocation\n");
         return;
       }
+
+      uint16_t format = prach_occasion_info->format;
+      uint16_t format0 = format & 0xff;        // single PRACH format
+      uint16_t format1 = (format >> 8) & 0xff; // dual PRACH format
+
+      fapi_nr_prach_config_t *prach_config = &mac->phy_config.config_req.prach_config;
       pdu->prach_config_pdu = (fapi_nr_ul_config_prach_pdu){
           .phys_cell_id = mac->physCellId,
           .num_prach_ocas = 1,
-          .prach_slot = prach_occasion_info_p->slot,
+          .prach_slot = prach_occasion_info->slot,
-          .prach_start_symbol = prach_occasion_info_p->start_symbol,
+          .prach_start_symbol = prach_occasion_info->start_symbol,
-          .num_ra = prach_occasion_info_p->fdm,
+          .num_ra = prach_occasion_info->fdm,
           .num_cs = get_NCS(ra->zeroCorrelationZoneConfig, format0, ra->restricted_set_config),
-          .root_seq_id = prach_config->num_prach_fd_occasions_list[prach_occasion_info_p->fdm].prach_root_sequence_index,
+          .root_seq_id = prach_config->num_prach_fd_occasions_list[prach_occasion_info->fdm].prach_root_sequence_index,
           .restricted_set = prach_config->restricted_set_config,
-          .freq_msg1 = prach_config->num_prach_fd_occasions_list[prach_occasion_info_p->fdm].k1};
+          .freq_msg1 = prach_config->num_prach_fd_occasions_list[prach_occasion_info->fdm].k1};
 
       LOG_I(NR_MAC,
             "PRACH scheduler: Selected RO Frame %u, Slot %u, Symbol %u, Fdm %u\n",
@@ -2584,15 +2503,6 @@ static void nr_ue_prach_scheduler(NR_UE_MAC_INST_t *mac, frame_t frameP, slot_t
             pdu->prach_config_pdu.prach_start_symbol,
             pdu->prach_config_pdu.num_ra);
 
-      // Search which SSB is mapped in the RO (among all the SSBs mapped to this RO)
-      for (int ssb_nb_in_ro=0; ssb_nb_in_ro<prach_occasion_info_p->nb_mapped_ssb; ssb_nb_in_ro++) {
-        if (prach_occasion_info_p->mapped_ssb_idx[ssb_nb_in_ro] == selected_gnb_ssb_idx) {
-          ra->ssb_nb_in_ro = ssb_nb_in_ro;
-          break;
-        }
-      }
-      AssertFatal(ra->ssb_nb_in_ro<prach_occasion_info_p->nb_mapped_ssb, "%u not found in the mapped SSBs to the PRACH occasion", selected_gnb_ssb_idx);
-
       if (format1 != 0xff) {
         switch (format0) { // dual PRACH format
           case 0xa1:
@@ -2706,7 +2616,7 @@ static void nr_ue_prach_scheduler(NR_UE_MAC_INST_t *mac, frame_t frameP, slot_t
 
         // Compute MsgB RNTI
         ra->MsgB_rnti =
-            nr_get_MsgB_rnti(prach_occasion_info_p->start_symbol, slot_RA, prach_occasion_info_p->fdm, 0);
+            nr_get_MsgB_rnti(prach_occasion_info->start_symbol, slot_RA, prach_occasion_info->fdm, 0);
         LOG_D(NR_MAC, "ra->ra_state %s\n", nrra_ue_text[ra->ra_state]);
         ra->ra_state = nrRA_WAIT_MSGB;
         ra->t_crnti = 0;
@@ -2715,8 +2625,6 @@ static void nr_ue_prach_scheduler(NR_UE_MAC_INST_t *mac, frame_t frameP, slot_t
       } else {
         AssertFatal(false, "RA type %d not implemented!\n", ra->ra_type);
       }
-
-      // rnti = ra->t_crnti;
     } // is_nr_prach_slot
   } // if is_nr_UL_slot
 }