Add support for RRC redirect.

lib/include/srsran/interfaces/ue_nas_interfaces.h

@@ -64,7 +64,7 @@ public:
 class nas_5g_interface_procedures
 {
 public:
-  virtual int send_registration_request() = 0;
+  virtual int send_registration_request()                                                  = 0;
   virtual int send_pdu_session_establishment_request(uint32_t                 transaction_identity,
                                                      uint16_t                 pdu_session_id,
                                                      const pdu_session_cfg_t& pdu_session) = 0;

lib/include/srsran/interfaces/ue_phy_interfaces.h

@@ -96,7 +96,6 @@ struct phy_args_t {
 
   srsran::channel::args_t dl_channel_args;
   srsran::channel::args_t ul_channel_args;
-
 };
 
 /* RAT agnostic Interface MAC -> PHY */
@@ -158,7 +157,7 @@ public:
   virtual void meas_stop()                                                       = 0;
 
   /* Cell search and selection procedures */
-  virtual bool cell_search()                = 0;
+  virtual bool cell_search(int earfcn)      = 0;
   virtual bool cell_select(phy_cell_t cell) = 0;
   virtual bool cell_is_camping()            = 0;
 };

lib/include/srsran/test/ue_test_interfaces.h

@@ -76,7 +76,7 @@ class phy_dummy_interface : public phy_interface_rrc_lte
   void meas_stop() override {}
 
   /* Cell search and selection procedures */
-  bool cell_search() override { return true; }
+  bool cell_search(int earfcn) override { return true; }
   bool cell_select(phy_cell_t cell) override { return true; }
   bool cell_is_camping() override { return false; }
 };

srsue/hdr/phy/dummy_phy.h

@@ -53,7 +53,7 @@ public:
   void meas_stop() final {}
 
   /* Cell search and selection procedures */
-  bool cell_search() final { return false; }
+  bool cell_search(int earfcn) final { return false; }
   bool cell_select(phy_cell_t cell) final { return false; }
   bool cell_is_camping() final { return false; }
 

srsue/hdr/phy/phy.h

@@ -68,7 +68,7 @@ public:
 
   /********** RRC INTERFACE ********************/
 
-  bool cell_search() final;
+  bool cell_search(int earfcn) final;
   bool cell_select(phy_cell_t cell) final;
 
   // Sets the new PHY configuration for the given CC. The configuration is applied in the background. The notify()

srsue/hdr/phy/sync.h

@@ -68,7 +68,7 @@ public:
 
   // RRC interface for controling the SYNC state
   bool                                     cell_search_init();
-  rrc_interface_phy_lte::cell_search_ret_t cell_search_start(phy_cell_t* cell);
+  rrc_interface_phy_lte::cell_search_ret_t cell_search_start(phy_cell_t* cell, int earfcn);
   bool                                     cell_select_init(phy_cell_t cell);
   bool                                     cell_select_start(phy_cell_t cell);
   bool                                     cell_is_camping();

srsue/hdr/stack/rrc/phy_controller.h

@@ -40,7 +40,9 @@ public:
   struct cell_sel_cmd {
     phy_cell_t phy_cell;
   };
-  struct cell_search_cmd {};
+  struct cell_search_cmd {
+    int earfcn;
+  };
   struct in_sync_ev {
     static const bool log_verbose = false;
   };
@@ -52,7 +54,7 @@ public:
 
   // PHY procedures interfaces
   bool start_cell_select(const phy_cell_t& phy_cell, srsran::event_observer<bool> observer = {});
-  bool start_cell_search(srsran::event_observer<cell_srch_res> observer);
+  bool start_cell_search(srsran::event_observer<cell_srch_res> observer, int earfcn);
   void cell_search_completed(cell_search_ret_t cs_ret, phy_cell_t found_cell);
   void cell_selection_completed(bool outcome);
   void in_sync();
@@ -117,7 +119,7 @@ public:
     // clang-format on
   };
   struct searching_cell {
-    void enter(phy_controller* f);
+    void enter(phy_controller* f, const cell_search_cmd& ev);
   };
 
 private:

srsue/hdr/stack/rrc/rrc.h

@@ -211,6 +211,9 @@ private:
 
   meas_cell_list<meas_cell_nr> meas_cells_nr;
 
+  // if this is set to a valid earfcn, this earfcn will be used for cell search
+  int cell_search_earfcn = -1;
+
   bool                     initiated                  = false;
   asn1::rrc::reest_cause_e m_reest_cause              = asn1::rrc::reest_cause_e::nulltype;
   uint16_t                 m_reest_rnti               = 0;
@@ -328,7 +331,8 @@ private:
   bool con_reconfig_ho(const asn1::rrc::rrc_conn_recfg_s& reconfig);
   void ho_failed();
   void start_go_idle();
-  void rrc_connection_release(const std::string& cause);
+  void handle_rrc_connection_release(const asn1::rrc::rrc_conn_release_s& release);
+  void start_rrc_redirect(uint32_t new_dl_earfcn);
   void radio_link_failure_push_cmd();
   void radio_link_failure_process();
   void leave_connected();

srsue/hdr/stack/upper/nas.h

@@ -80,9 +80,9 @@ public:
   void timer_expired(uint32_t timeout_id) override;
 
 private:
-  rrc_interface_nas*    rrc  = nullptr;
-  usim_interface_nas*   usim = nullptr;
-  gw_interface_nas*     gw   = nullptr;
+  rrc_interface_nas*  rrc  = nullptr;
+  usim_interface_nas* usim = nullptr;
+  gw_interface_nas*   gw   = nullptr;
 
   bool running = false;
 
@@ -108,10 +108,10 @@ private:
   typedef std::pair<uint8_t, eps_bearer_t> eps_bearer_map_pair_t;
   eps_bearer_map_t                         eps_bearer;
 
-  bool         have_guti       = false;
-  bool         have_ctxt       = false;
-  bool         auth_request    = false;
-  uint8_t      current_sec_hdr = LIBLTE_MME_SECURITY_HDR_TYPE_PLAIN_NAS;
+  bool    have_guti       = false;
+  bool    have_ctxt       = false;
+  bool    auth_request    = false;
+  uint8_t current_sec_hdr = LIBLTE_MME_SECURITY_HDR_TYPE_PLAIN_NAS;
 
   const uint32_t max_attach_attempts    = 5; // Sec. 5.5.1.2.6
   uint32_t       attach_attempt_counter = 0;
@@ -144,8 +144,8 @@ private:
   const uint8_t ue_svn_oct2 = 0x3;
 
   // Security
-  bool    eia_caps[8]   = {};
-  bool    eea_caps[8]   = {};
+  bool eia_caps[8] = {};
+  bool eea_caps[8] = {};
 
   // Airplane mode simulation
   typedef enum { DISABLED = 0, ENABLED } airplane_mode_state_t;

srsue/src/phy/phy.cc

@@ -342,12 +342,12 @@ bool phy::cell_select(phy_cell_t cell)
 
 // This function executes one part of the procedure immediatly and returns to continue in the background.
 // When it returns, the caller thread can expect the PHY to have switched to IDLE and have stopped all DL/UL/PRACH
-// processing.
-bool phy::cell_search()
+// processing. If a valid EARFCN (>0) is given, this is used for cell search.
+bool phy::cell_search(int earfcn)
 {
   sfsync.scell_sync_stop();
   if (sfsync.cell_search_init()) {
-    cmd_worker_cell.add_cmd([this]() {
+    cmd_worker_cell.add_cmd([this, earfcn]() {
       // Wait SYNC transitions to IDLE
       sfsync.wait_idle();
 
@@ -355,7 +355,7 @@ bool phy::cell_search()
       reset();
 
       phy_cell_t                               found_cell = {};
-      rrc_interface_phy_lte::cell_search_ret_t ret        = sfsync.cell_search_start(&found_cell);
+      rrc_interface_phy_lte::cell_search_ret_t ret        = sfsync.cell_search_start(&found_cell, earfcn);
       stack->cell_search_complete(ret, found_cell);
     });
   } else {

srsue/src/phy/sync.cc

@@ -179,10 +179,10 @@ void sync::reset()
  *
  */
 
-/* A call to cell_search() finds the strongest cell in the set of supported EARFCNs. When the first cell is found,
- * returns 1 and stores cell information and RSRP values in the pointers (if provided). If a cell is not found in the
- * current frequency it moves to the next one and the next call to cell_search() will look in the next EARFCN in the
- * set. If no cells are found in any frequency it returns 0. If error returns -1.
+/* A call to cell_search() finds the strongest cell at a given EARFCN or in the set of supported EARFCNs. When the first
+ * cell is found, returns 1 and stores cell information and RSRP values in the pointers (if provided). If a cell is not
+ * found in the current frequency it moves to the next one and the next call to cell_search() will look in the next
+ * EARFCN in the set. If no cells are found in any frequency it returns 0. If error returns -1.
  *
  * The first part of the procedure (call to _init()) moves the PHY To IDLE, ensuring that no UL/DL/PRACH will happen
  *
@@ -197,7 +197,6 @@ bool sync::cell_search_init()
   }
 
   // Move state to IDLE
-  Info("Cell Search: Start EARFCN index=%u/%zd", cellsearch_earfcn_index, worker_com->args->dl_earfcn_list.size());
   phy_state.go_idle();
 
   // Stop all intra-frequency measurement before changing frequency
@@ -208,10 +207,16 @@ bool sync::cell_search_init()
   return true;
 }
 
-rrc_interface_phy_lte::cell_search_ret_t sync::cell_search_start(phy_cell_t* found_cell)
+rrc_interface_phy_lte::cell_search_ret_t sync::cell_search_start(phy_cell_t* found_cell, int earfcn)
 {
   std::unique_lock<std::mutex> ul(rrc_mutex);
 
+  if (earfcn < 0) {
+    Info("Cell Search: Start EARFCN index=%u/%zd", cellsearch_earfcn_index, worker_com->args->dl_earfcn_list.size());
+  } else {
+    Info("Cell Search: Start EARFCN=%d", earfcn);
+  }
+
   rrc_interface_phy_lte::cell_search_ret_t ret = {};
   ret.found                                    = rrc_interface_phy_lte::cell_search_ret_t::ERROR;
   ret.last_freq                                = rrc_interface_phy_lte::cell_search_ret_t::NO_MORE_FREQS;
@@ -229,16 +234,20 @@ rrc_interface_phy_lte::cell_search_ret_t sync::cell_search_start(phy_cell_t* fou
     Info("SYNC:  Setting Cell Search sampling rate");
   }
 
-  try {
-    if (current_earfcn != (int)worker_com->args->dl_earfcn_list.at(cellsearch_earfcn_index)) {
-      current_earfcn = (int)worker_com->args->dl_earfcn_list[cellsearch_earfcn_index];
-      Info("Cell Search: changing frequency to EARFCN=%d", current_earfcn);
-      set_frequency();
+  if (earfcn < 0) {
+    try {
+      if (current_earfcn != (int)worker_com->args->dl_earfcn_list.at(cellsearch_earfcn_index)) {
+        current_earfcn = (int)worker_com->args->dl_earfcn_list[cellsearch_earfcn_index];
+      }
+    } catch (const std::out_of_range& oor) {
+      Error("Index %d is not a valid EARFCN element.", cellsearch_earfcn_index);
+      return ret;
     }
-  } catch (const std::out_of_range& oor) {
-    Error("Index %d is not a valid EARFCN element.", cellsearch_earfcn_index);
-    return ret;
+  } else {
+    current_earfcn = earfcn;
   }
+  Info("Cell Search: changing frequency to EARFCN=%d", current_earfcn);
+  set_frequency();
 
   // Move to CELL SEARCH and wait to finish
   Info("Cell Search: Setting Cell search state");
@@ -266,7 +275,7 @@ rrc_interface_phy_lte::cell_search_ret_t sync::cell_search_start(phy_cell_t* fou
   }
 
   cellsearch_earfcn_index++;
-  if (cellsearch_earfcn_index >= worker_com->args->dl_earfcn_list.size()) {
+  if (cellsearch_earfcn_index >= worker_com->args->dl_earfcn_list.size() or earfcn < 0) {
     Info("Cell Search: No more frequencies in the current EARFCN set");
     cellsearch_earfcn_index = 0;
     ret.last_freq           = rrc_interface_phy_lte::cell_search_ret_t::NO_MORE_FREQS;

srsue/src/phy/test/ue_phy_test.cc

@@ -508,7 +508,7 @@ int main(int argc, char** argv)
   phy_test->start();
 
   // 1. Cell search
-  TESTASSERT(phy_test->get_phy_interface_rrc()->cell_search());
+  TESTASSERT(phy_test->get_phy_interface_rrc()->cell_search(-1));
   TESTASSERT(phy_test->get_stack()->wait_cell_search(default_timeout));
   TESTASSERT(phy_test->get_stack()->cell_search_ret.found ==
              srsue::rrc_interface_phy_lte::cell_search_ret_t::CELL_FOUND);

srsue/src/stack/rrc/phy_controller.cc

@@ -166,13 +166,13 @@ void phy_controller::selecting_cell::wait_in_sync::enter(selecting_cell* f)
  *************************************/
 
 //! Searches for a cell in the current frequency and retrieves SIB1 if not retrieved yet
-bool phy_controller::start_cell_search(srsran::event_observer<cell_srch_res> observer)
+bool phy_controller::start_cell_search(srsran::event_observer<cell_srch_res> observer, int earfcn)
 {
   if (is_in_state<searching_cell>()) {
     fsmInfo("Cell search already launched.");
     return true;
   }
-  trigger(cell_search_cmd{});
+  trigger(cell_search_cmd{earfcn});
   if (not is_in_state<searching_cell>()) {
     fsmWarning("Failed to launch cell search");
     return false;
@@ -186,10 +186,10 @@ void phy_controller::cell_search_completed(cell_search_ret_t cs_ret, phy_cell_t
   trigger(cell_srch_res{cs_ret, found_cell});
 }
 
-void phy_controller::searching_cell::enter(phy_controller* f)
+void phy_controller::searching_cell::enter(phy_controller* f, const cell_search_cmd& ev)
 {
   otherfsmInfo(f, "Initiating Cell search");
-  f->phy->cell_search();
+  f->phy->cell_search(ev.earfcn);
 }
 
 void phy_controller::handle_cell_search_res(searching_cell& s, const cell_srch_res& result)

srsue/src/stack/rrc/rrc.cc

@@ -1153,8 +1153,9 @@ void rrc::handle_rrc_con_reconfig(uint32_t lcid, const rrc_conn_recfg_s& reconfi
 }
 
 /* Actions upon reception of RRCConnectionRelease 5.3.8.3 */
-void rrc::rrc_connection_release(const std::string& cause)
+void rrc::handle_rrc_connection_release(const asn1::rrc::rrc_conn_release_s& release)
 {
+  std::string cause = release.crit_exts.c1().rrc_conn_release_r8().release_cause.to_string();
   // Save idleModeMobilityControlInfo, etc.
   srsran::console("Received RRC Connection Release (releaseCause: %s)\n", cause.c_str());
 
@@ -1164,6 +1165,36 @@ void rrc::rrc_connection_release(const std::string& cause)
 
   // delay actions by 60ms as per 5.3.8.3
   task_sched.defer_callback(60, [this]() { start_go_idle(); });
+
+  uint32_t earfcn = 0;
+  if (release.crit_exts.c1().rrc_conn_release_r8().redirected_carrier_info_present) {
+    switch (release.crit_exts.c1().rrc_conn_release_r8().redirected_carrier_info.type()) {
+      case asn1::rrc::redirected_carrier_info_c::types_opts::options::eutra:
+        earfcn = release.crit_exts.c1().rrc_conn_release_r8().redirected_carrier_info.eutra();
+        break;
+      default:
+        srsran::console("Ignoring RedirectedCarrierInfo with unsupported type (%s)\n",
+                        release.crit_exts.c1().rrc_conn_release_r8().redirected_carrier_info.type().to_string());
+        break;
+    }
+    if (earfcn != 0) {
+      srsran::console("RedirectedCarrierInfo present (type %s, earfcn: %d) - Redirecting\n",
+                      release.crit_exts.c1().rrc_conn_release_r8().redirected_carrier_info.type().to_string(),
+                      earfcn);
+      logger.info("RedirectedCarrierInfo present (type %s, earfcn: %d) - Redirecting",
+                  release.crit_exts.c1().rrc_conn_release_r8().redirected_carrier_info.type().to_string(),
+                  earfcn);
+
+      // delay actions by 60ms as per 5.3.8.3
+      task_sched.defer_callback(60, [this, earfcn]() { start_rrc_redirect(earfcn); });
+    }
+  }
+}
+
+void rrc::start_rrc_redirect(uint32_t new_dl_earfcn)
+{
+  cell_search_earfcn = (int)new_dl_earfcn;
+  plmn_search();
 }
 
 /// TS 36.331, 5.3.12 - UE actions upon leaving RRC_CONNECTED
@@ -1818,7 +1849,7 @@ void rrc::parse_dl_dcch(uint32_t lcid, unique_byte_buffer_t pdu)
       handle_ue_capability_enquiry(c1->ue_cap_enquiry());
       break;
     case dl_dcch_msg_type_c::c1_c_::types::rrc_conn_release:
-      rrc_connection_release(c1->rrc_conn_release().crit_exts.c1().rrc_conn_release_r8().release_cause.to_string());
+      handle_rrc_connection_release(c1->rrc_conn_release());
       break;
     case dl_dcch_msg_type_c::c1_c_::types::ue_info_request_r9:
       transaction_id = c1->ue_info_request_r9().rrc_transaction_id;

srsue/src/stack/rrc/rrc_procedures.cc

@@ -41,7 +41,7 @@ proc_outcome_t rrc::cell_search_proc::init()
 {
   Info("Starting...");
   state = state_t::phy_cell_search;
-  if (not rrc_ptr->phy_ctrl->start_cell_search(rrc_ptr->cell_searcher)) {
+  if (not rrc_ptr->phy_ctrl->start_cell_search(rrc_ptr->cell_searcher, rrc_ptr->cell_search_earfcn)) {
     Warning("Failed to initiate Cell Search.");
     return proc_outcome_t::error;
   }
@@ -1256,11 +1256,14 @@ proc_outcome_t rrc::go_idle_proc::step()
 
 void rrc::go_idle_proc::then(const srsran::proc_state_t& result)
 {
-  if (rrc_ptr->nas->is_registered() and not rrc_ptr->cell_reselector.launch()) {
-    rrc_ptr->logger.error("Failed to initiate a Cell Reselection procedure...");
-    return;
+  // only start cell reselection if no RRC redirect is present (redirect will trigger a cell search)
+  if (rrc_ptr->cell_search_earfcn < 0) {
+    if (rrc_ptr->nas->is_registered() and not rrc_ptr->cell_reselector.launch()) {
+      rrc_ptr->logger.error("Failed to initiate a Cell Reselection procedure...");
+      return;
+    }
+    rrc_ptr->callback_list.add_proc(rrc_ptr->cell_reselector);
   }
-  rrc_ptr->callback_list.add_proc(rrc_ptr->cell_reselector);
 }
 
 /**************************************
@@ -1362,7 +1365,7 @@ proc_outcome_t rrc::connection_reest_proc::init(asn1::rrc::reest_cause_e cause)
 {
   // Save Current RNTI before MAC Reset
   uint16_t crnti             = rrc_ptr->mac->get_crnti();
-  size_t nof_scells_active = rrc_ptr->phy_ctrl->current_config_scells().count();
+  size_t   nof_scells_active = rrc_ptr->phy_ctrl->current_config_scells().count();
 
   // 5.3.7.1 - Conditions for Reestablishment procedure
   if (not rrc_ptr->security_is_activated or rrc_ptr->state != RRC_STATE_CONNECTED or crnti == SRSRAN_INVALID_RNTI) {
@@ -1384,9 +1387,9 @@ proc_outcome_t rrc::connection_reest_proc::init(asn1::rrc::reest_cause_e cause)
   reest_cellid = rrc_ptr->meas_cells.find_cell(reest_source_freq, reest_source_pci)->get_cell_id();
 
   Info("Starting... cause: \"%s\", UE context: {C-RNTI=0x%x, PCI=%d, CELL ID=%d}",
-       reest_cause == asn1::rrc::reest_cause_opts::recfg_fail
-           ? "Reconfiguration failure"
-           : cause == asn1::rrc::reest_cause_opts::ho_fail ? "Handover failure" : "Other failure",
+       reest_cause == asn1::rrc::reest_cause_opts::recfg_fail ? "Reconfiguration failure"
+       : cause == asn1::rrc::reest_cause_opts::ho_fail        ? "Handover failure"
+                                                              : "Other failure",
        reest_rnti,
        reest_source_pci,
        reest_cellid);

srsue/src/stack/rrc/test/rrc_meas_test.cc

@@ -40,7 +40,7 @@ public:
   void set_config_mbsfn_sib2(srsran::mbsfn_sf_cfg_t* cfg_list, uint32_t nof_cfgs) override {}
   void set_config_mbsfn_sib13(const srsran::sib13_t& sib13) override {}
   void set_config_mbsfn_mcch(const srsran::mcch_msg_t& mcch) override {}
-  bool cell_search() override { return true; }
+  bool cell_search(int earfcn) override { return true; }
   bool cell_is_camping() override { return true; }
   void deactivate_scells() override {}
   bool cell_select(phy_cell_t cell) override

srsue/src/stack/rrc/test/rrc_phy_ctrl_test.cc

@@ -81,7 +81,7 @@ int test_phy_ctrl_fsm()
   TESTASSERT(phy_ctrl.is_in_sync());
 
   // TEST: Correct initiation of Cell Search state
-  TESTASSERT(phy_ctrl.start_cell_search(csearch_tester));
+  TESTASSERT(phy_ctrl.start_cell_search(csearch_tester, -1));
   TESTASSERT(not phy_ctrl.is_in_sync());
 
   // TEST: Cell Search only listens to a cell search result event

srsue/src/test/ttcn3/hdr/lte_ttcn3_phy.h

@@ -69,7 +69,7 @@ public:
   void set_mch_period_stop(uint32_t stop) override{};
 
   // Cell search and selection procedures
-  bool cell_search() override;
+  bool cell_search(int earfcn) override;
   bool cell_select(phy_cell_t cell) override;
   bool cell_is_camping() override;
 

srsue/src/test/ttcn3/src/lte_ttcn3_phy.cc

@@ -87,7 +87,7 @@ void lte_ttcn3_phy::meas_stop() {}
 // configured by the SS, including the ones that we should not even detect because
 // their power is too weak. The cell search should only report the cells that
 // are actually visible though.
-bool lte_ttcn3_phy::cell_search()
+bool lte_ttcn3_phy::cell_search(int earfcn)
 {
   std::lock_guard<std::mutex> lock(phy_mutex);