fix potential bug with grouping of RARs with same RA-RNTI but different prach_tti. The scheduler might not clear the old tti on time before the grouping.

srsenb/hdr/stack/mac/scheduler_grid.h

@@ -221,6 +221,7 @@ public:
   };
   struct pending_rar_t {
     uint16_t                             ra_rnti    = 0;
+    uint32_t                             prach_tti  = 0;
     uint32_t                             nof_grants = 0;
     sched_interface::dl_sched_rar_info_t msg3_grant[sched_interface::MAX_RAR_LIST];
   };

srsenb/src/stack/mac/scheduler_carrier.cc

@@ -151,7 +151,7 @@ void ra_sched::dl_sched(srsenb::sf_sched* tti_sched)
 
   while (not pending_rars.empty()) {
     sf_sched::pending_rar_t& rar       = pending_rars.front();
-    uint32_t                 prach_tti = rar.msg3_grant[0].prach_tti;
+    uint32_t                 prach_tti = rar.prach_tti;
 
     // Discard all RARs out of the window. The first one inside the window is scheduled, if we can't we exit
     if (not sched_utils::is_in_tti_interval(tti_tx_dl, prach_tti + 3, prach_tti + 3 + cfg->prach_rar_window)) {
@@ -226,7 +226,6 @@ int ra_sched::dl_rach_info(dl_sched_rar_info_t rar_info)
               rar_info.temp_crnti,
               rar_info.ta_cmd,
               rar_info.msg3_size);
-
   // RA-RNTI = 1 + t_id + f_id
   // t_id = index of first subframe specified by PRACH (0<=t_id<10)
   // f_id = index of the PRACH within subframe, in ascending order of freq domain (0<=f_id<6) (for FDD, f_id=0)
@@ -234,7 +233,7 @@ int ra_sched::dl_rach_info(dl_sched_rar_info_t rar_info)
 
   // find pending rar with same RA-RNTI
   for (sf_sched::pending_rar_t& r : pending_rars) {
-    if (r.ra_rnti == ra_rnti) {
+    if (r.prach_tti == rar_info.prach_tti and ra_rnti == r.ra_rnti) {
       r.msg3_grant[r.nof_grants] = rar_info;
       r.nof_grants++;
       return SRSLTE_SUCCESS;
@@ -244,6 +243,7 @@ int ra_sched::dl_rach_info(dl_sched_rar_info_t rar_info)
   // create new RAR
   sf_sched::pending_rar_t p;
   p.ra_rnti       = ra_rnti;
+  p.prach_tti     = rar_info.prach_tti;
   p.nof_grants    = 1;
   p.msg3_grant[0] = rar_info;
   pending_rars.push_back(p);

srsenb/src/stack/mac/scheduler_grid.cc

@@ -510,10 +510,9 @@ std::pair<alloc_outcome_t, uint32_t> sf_sched::alloc_rar(uint32_t aggr_lvl, cons
   for (uint32_t nof_grants = rar.nof_grants; nof_grants > 0; nof_grants--) {
     uint32_t buf_rar         = 7 * nof_grants + 1; // 1+6 bytes per RAR subheader+body and 1 byte for Backoff
     uint32_t total_msg3_size = msg3_grant_size * nof_grants;
-    uint32_t msg3_prb_attempt = last_msg3_prb;
 
     // check if there is enough space for Msg3, try again with a lower number of grants
-    if (msg3_prb_attempt + total_msg3_size > sched_params->cfg->cell.nof_prb - sched_params->cfg->nrb_pucch) {
+    if (last_msg3_prb + total_msg3_size > sched_params->cfg->cell.nof_prb - sched_params->cfg->nrb_pucch) {
       ret.first = alloc_outcome_t::RB_COLLISION;
       continue;
     }
@@ -540,10 +539,10 @@ std::pair<alloc_outcome_t, uint32_t> sf_sched::alloc_rar(uint32_t aggr_lvl, cons
       rar_grant.msg3_grant[i].data            = rar.msg3_grant[i];
       rar_grant.msg3_grant[i].grant.tpc_pusch = 3;
       rar_grant.msg3_grant[i].grant.trunc_mcs = 0;
-      uint32_t rba = srslte_ra_type2_to_riv(msg3_grant_size, msg3_prb_attempt, sched_params->cfg->cell.nof_prb);
+      uint32_t rba = srslte_ra_type2_to_riv(msg3_grant_size, last_msg3_prb, sched_params->cfg->cell.nof_prb);
       rar_grant.msg3_grant[i].grant.rba = rba;
 
-      msg3_prb_attempt += msg3_grant_size;
+      last_msg3_prb += msg3_grant_size;
     }
 
     rar_allocs.emplace_back(ret2.second, rar_grant);