cu_cp: prepare rrc reconfig complete reception in target du before rrc reconfig is send to source du

Author: FabianEckermann

lib/cu_cp/routines/mobility/handover_reconfiguration_routine.cpp

@@ -35,6 +35,27 @@ handover_reconfiguration_routine::handover_reconfiguration_routine(
 {
   srsran_assert(
       source_ue.get_ue_index() != ue_index_t::invalid, "Invalid source UE index {}", source_ue.get_ue_index());
+
+  // Unpack MasterCellGroup to extract T304.
+  asn1::rrc_nr::cell_group_cfg_s cell_group_cfg;
+  asn1::cbit_ref                 bref(request.non_crit_ext->master_cell_group);
+  if (cell_group_cfg.unpack(bref) != asn1::SRSASN_SUCCESS) {
+    report_fatal_error("Failed to unpack MasterCellGroupCfg");
+  }
+  unsigned t304_ms = cell_group_cfg.sp_cell_cfg.recfg_with_sync.t304.to_number();
+  target_ue_release_timeout =
+      std::chrono::milliseconds{t304_ms + /*We add 1s of extra time for the UE to reestablish*/ 1000};
+
+  // Unpack SIB1 to extract T311.
+  asn1::rrc_nr::sib1_s sib1_msg;
+  asn1::cbit_ref       bref2(request.non_crit_ext->ded_sib1_delivery);
+  if (sib1_msg.unpack(bref2) != asn1::SRSASN_SUCCESS) {
+    report_fatal_error("Failed to unpack SIB1");
+  }
+  unsigned t301_ms = sib1_msg.ue_timers_and_consts.t301.to_number();
+  unsigned t311_ms = sib1_msg.ue_timers_and_consts.t311.to_number();
+
+  handover_ue_release_timeout = std::chrono::milliseconds{t301_ms + t304_ms + t311_ms};
 }
 
 void handover_reconfiguration_routine::operator()(coro_context<async_task<bool>>& ctx)
@@ -48,6 +69,13 @@ void handover_reconfiguration_routine::operator()(coro_context<async_task<bool>>
 
   generate_ue_context_modification_request();
 
+  // Notify CU-CP to prepare for RRC Reconfig Complete on target DU.
+  cu_cp_handler.handle_handover_reconfiguration_sent({target_ue_index,
+                                                      source_ue.get_ue_index(),
+                                                      (uint8_t)ho_reconf_ctxt.transaction_id,
+                                                      target_ue_release_timeout,
+                                                      target_bearer_context_modification_request});
+
   // Call F1AP procedure to send RRC reconfiguration to source UE via UE context modification request.
   CORO_AWAIT_VALUE(ue_context_mod_response,
                    source_f1ap_ue_ctxt_mng.handle_ue_context_modification_request(ue_context_mod_request));
@@ -62,13 +90,6 @@ void handover_reconfiguration_routine::operator()(coro_context<async_task<bool>>
   // Initialize UE release timer for source UE.
   initialize_handover_ue_release_timer(source_ue.get_ue_index());
 
-  // Notify CU-CP that RRC reconfiguration was sent.
-  cu_cp_handler.handle_handover_reconfiguration_sent({target_ue_index,
-                                                      source_ue.get_ue_index(),
-                                                      (uint8_t)ho_reconf_ctxt.transaction_id,
-                                                      target_ue_release_timeout,
-                                                      target_bearer_context_modification_request});
-
   // Store handover context in case of for possible re-establishment.
   logger.debug("ue={}: Storing handover context", source_ue.get_ue_index());
   cu_cp_ue_handover_context ue_ho_ctxt;
@@ -94,29 +115,10 @@ void handover_reconfiguration_routine::generate_ue_context_modification_request(
 
 void handover_reconfiguration_routine::initialize_handover_ue_release_timer(ue_index_t ue_index)
 {
-  // Unpack MasterCellGroup to extract T304.
-  asn1::rrc_nr::cell_group_cfg_s cell_group_cfg;
-  asn1::cbit_ref                 bref(request.non_crit_ext->master_cell_group);
-  if (cell_group_cfg.unpack(bref) != asn1::SRSASN_SUCCESS) {
-    report_fatal_error("Failed to unpack MasterCellGroupCfg");
-  }
-  unsigned t304_ms = cell_group_cfg.sp_cell_cfg.recfg_with_sync.t304.to_number();
-  target_ue_release_timeout =
-      std::chrono::milliseconds{t304_ms + /*We add 1s of extra time for the UE to reestablish*/ 1000};
-
-  // Unpack SIB1 to extract T311.
-  asn1::rrc_nr::sib1_s sib1_msg;
-  asn1::cbit_ref       bref2(request.non_crit_ext->ded_sib1_delivery);
-  if (sib1_msg.unpack(bref2) != asn1::SRSASN_SUCCESS) {
-    report_fatal_error("Failed to unpack SIB1");
-  }
-  unsigned t301_ms = sib1_msg.ue_timers_and_consts.t301.to_number();
-  unsigned t311_ms = sib1_msg.ue_timers_and_consts.t311.to_number();
-
   cu_cp_handler.initialize_handover_ue_release_timer(
       ue_index,
-      std::chrono::milliseconds{t301_ms + t304_ms + t311_ms +
-                                /*We add 1s of extra time for the UE to reestablish*/ 1000},
+      handover_ue_release_timeout +
+          std::chrono::milliseconds{1000} /*We add 1s of extra time for the UE to reestablish*/,
       cu_cp_ue_context_release_request{ue_index,
                                        source_ue.get_up_resource_manager().get_pdu_sessions(),
                                        ngap_cause_radio_network_t::ho_fail_in_target_5_gc_ngran_node_or_target_sys});

lib/cu_cp/routines/mobility/handover_reconfiguration_routine.h

@@ -53,6 +53,7 @@ class handover_reconfiguration_routine
 
   // (sub-)routine results
   std::chrono::milliseconds               target_ue_release_timeout;
+  std::chrono::milliseconds               handover_ue_release_timeout;
   rrc_ue_handover_reconfiguration_context ho_reconf_ctxt;
   f1ap_ue_context_modification_response   ue_context_mod_response;
 };

tests/unittests/cu_cp/mobility/handover_reconfiguration_routine_test.cpp

@@ -342,6 +342,4 @@ TEST_F(handover_reconfiguration_routine_test, when_ue_context_mod_unsuccessful_t
 
   // Reconfiguration complete was received.
   ASSERT_FALSE(get_result());
-
-  ASSERT_FALSE(check_transaction_id(test_transaction_id));
 }