- Added support for random RO selection for a given SSB index in a slot (as per 38.321)

- Fixed random preamble selection in contention-based RA
- Cleaned-up comments and commented code

openair2/LAYER2/NR_MAC_UE/nr_ra_procedures.c

@@ -144,27 +144,27 @@ void nr_get_prach_resources(module_id_t mod_id,
       case NR_RACH_ConfigCommon__ssb_perRACH_OccasionAndCB_PreamblesPerSSB_PR_oneEighth:
         multiple_ssb_per_ro = false;
         ssb_rach_ratio = 8;
-        cb_preambles_per_ssb = nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.oneEighth;
+        cb_preambles_per_ssb = 4 * (nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.oneEighth + 1);
         break;
       case NR_RACH_ConfigCommon__ssb_perRACH_OccasionAndCB_PreamblesPerSSB_PR_oneFourth:
         multiple_ssb_per_ro = false;
         ssb_rach_ratio = 4;
-        cb_preambles_per_ssb = nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.oneFourth;
+        cb_preambles_per_ssb = 4 * (nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.oneFourth + 1);
         break;
       case NR_RACH_ConfigCommon__ssb_perRACH_OccasionAndCB_PreamblesPerSSB_PR_oneHalf:
         multiple_ssb_per_ro = false;
         ssb_rach_ratio = 2;
-        cb_preambles_per_ssb = nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.oneHalf;
+        cb_preambles_per_ssb = 4 * (nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.oneHalf + 1);
         break;
       case NR_RACH_ConfigCommon__ssb_perRACH_OccasionAndCB_PreamblesPerSSB_PR_one:
         multiple_ssb_per_ro = true;
         ssb_rach_ratio = 1;
-        cb_preambles_per_ssb = nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.one;
+        cb_preambles_per_ssb = 4 * (nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.one + 1);
         break;
       case NR_RACH_ConfigCommon__ssb_perRACH_OccasionAndCB_PreamblesPerSSB_PR_two:
         multiple_ssb_per_ro = true;
         ssb_rach_ratio = 2;
-        cb_preambles_per_ssb = nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.two;
+        cb_preambles_per_ssb = 4 * (nr_rach_ConfigCommon->ssb_perRACH_OccasionAndCB_PreamblesPerSSB->choice.two + 1);
         break;
       case NR_RACH_ConfigCommon__ssb_perRACH_OccasionAndCB_PreamblesPerSSB_PR_four:
         multiple_ssb_per_ro = true;
@@ -313,6 +313,7 @@ void nr_get_prach_resources(module_id_t mod_id,
         prach_resources->ra_PreambleIndex = starting_preamble_nb + sizeOfRA_PreamblesGroupA + ((taus()) % (cb_preambles_per_ssb - sizeOfRA_PreamblesGroupA));
       }
     }
+
     LOG_D(MAC, "[RAPROC] - Selected RA preamble index %d for contention-based random access procedure... \n", prach_resources->ra_PreambleIndex);
   }