made cell select non-blocking using background threads

lib/include/srslte/interfaces/ue_interfaces.h

@@ -28,8 +28,8 @@
 #ifndef SRSLTE_UE_INTERFACES_H
 #define SRSLTE_UE_INTERFACES_H
 
-#include <string>
 #include <set>
+#include <string>
 
 #include "rrc_interface_types.h"
 #include "srslte/asn1/liblte_mme.h"
@@ -611,7 +611,7 @@ public:
 
   /* Cell search and selection procedures */
   virtual cell_search_ret_t cell_search(phy_cell_t* cell)              = 0;
-  virtual bool              cell_select(phy_cell_t* cell = NULL) = 0;
+  virtual bool              cell_select(const phy_cell_t* cell = NULL) = 0;
   virtual bool              cell_is_camping()                          = 0;
 
   virtual void reset() = 0;
@@ -644,6 +644,7 @@ class stack_interface_rrc
 {
 public:
   virtual void start_cell_search()                                              = 0;
+  virtual void start_cell_select(const phy_interface_rrc_lte::phy_cell_t* cell) = 0;
 };
 
 // Combined interface for PHY to access stack (MAC and RRC)

srsue/hdr/phy/phy.h

@@ -70,7 +70,7 @@ public:
   /********** RRC INTERFACE ********************/
   void              reset() final;
   cell_search_ret_t cell_search(phy_cell_t* cell) final;
-  bool              cell_select(phy_cell_t* cell) final;
+  bool              cell_select(const phy_cell_t* cell) final;
 
   void set_cells_to_meas(uint32_t earfcn, const std::set<uint32_t>& pci) final;
   void meas_stop() final;

srsue/hdr/phy/sync.h

@@ -66,7 +66,7 @@ public:
 
   // RRC interface for controling the SYNC state
   phy_interface_rrc_lte::cell_search_ret_t cell_search(phy_interface_rrc_lte::phy_cell_t* cell);
-  bool                                     cell_select(phy_interface_rrc_lte::phy_cell_t* cell);
+  bool                                     cell_select(const phy_interface_rrc_lte::phy_cell_t* cell);
   bool                                     cell_is_camping();
 
   // RRC interface for controlling the neighbour cell measurement

srsue/hdr/stack/rrc/rrc.h

@@ -356,6 +356,7 @@ public:
   // STACK interface
   void cell_search_completed(const phy_interface_rrc_lte::cell_search_ret_t& cs_ret,
                              const phy_interface_rrc_lte::phy_cell_t&        found_cell);
+  void cell_select_completed(bool cs_ret);
 
 protected:
   // Moved to protected to be accessible by unit tests

srsue/hdr/stack/rrc/rrc_procedures.h

@@ -29,6 +29,20 @@
 
 namespace srsue {
 
+/********************************
+ *           Events
+ *******************************/
+
+// background workers use this event to signal the result of a cell select phy procedure
+struct cell_select_event_t {
+  cell_select_event_t(bool c_) : cs_ret(c_) {}
+  bool cs_ret;
+};
+
+/********************************
+ *         Procedures
+ *******************************/
+
 class rrc::cell_search_proc
 {
 public:
@@ -36,13 +50,15 @@ public:
     phy_interface_rrc_lte::cell_search_ret_t cs_ret;
     phy_interface_rrc_lte::phy_cell_t        found_cell;
   };
-  enum class state_t { phy_cell_search, si_acquire, wait_measurement };
+  enum class state_t { phy_cell_search, si_acquire, wait_measurement, phy_cell_select };
 
   explicit cell_search_proc(rrc* parent_);
   srslte::proc_outcome_t init();
   srslte::proc_outcome_t step();
+  srslte::proc_outcome_t step_si_acquire();
   srslte::proc_outcome_t react(const cell_search_event_t& event);
-  srslte::proc_outcome_t check_sib();
+  srslte::proc_outcome_t react(const cell_select_event_t& event);
+  srslte::proc_outcome_t step_wait_measurement();
 
   phy_interface_rrc_lte::cell_search_ret_t get_result() const { return search_result.cs_ret; }
   static const char*                       name() { return "Cell Search"; }
@@ -116,9 +132,12 @@ public:
   void                   then(const srslte::proc_result_t<cs_result_t>& proc_result) const;
   cs_result_t            get_result() const { return cs_result; }
   static const char*     name() { return "Cell Selection"; }
+  srslte::proc_outcome_t react(const cell_select_event_t& event);
 
 private:
-  srslte::proc_outcome_t step_cell_selection();
+  srslte::proc_outcome_t start_cell_selection();
+  srslte::proc_outcome_t step_cell_selection(const cell_select_event_t& event);
+  srslte::proc_outcome_t step_serv_cell_camp(const cell_select_event_t& event);
   srslte::proc_outcome_t step_wait_in_sync();
   srslte::proc_outcome_t step_cell_search();
   srslte::proc_outcome_t step_cell_config();
@@ -127,7 +146,7 @@ private:
   rrc* rrc_ptr;
 
   // state variables
-  enum class search_state_t { cell_selection, wait_in_sync, cell_config, cell_search };
+  enum class search_state_t { cell_selection, serv_cell_camp, wait_in_sync, cell_config, cell_search };
   cs_result_t                                                     cs_result;
   search_state_t                                                  state;
   uint32_t                                                        neigh_index;

srsue/hdr/stack/ue_stack_lte.h

@@ -120,6 +120,7 @@ public:
 
   // Interface for RRC
   void start_cell_search() final;
+  void start_cell_select(const phy_interface_rrc_lte::phy_cell_t* cell) final;
 
 private:
   void run_thread() final;

srsue/src/phy/phy.cc

@@ -325,7 +325,7 @@ void phy::meas_stop()
   sfsync.meas_stop();
 }
 
-bool phy::cell_select(phy_cell_t* cell)
+bool phy::cell_select(const phy_cell_t* cell)
 {
   return sfsync.cell_select(cell);
 }

srsue/src/phy/sync.cc

@@ -264,7 +264,7 @@ phy_interface_rrc_lte::cell_search_ret_t sync::cell_search(phy_interface_rrc_lte
 /* Cell select synchronizes to a new cell (e.g. during HO or during cell reselection on IDLE) or
  * re-synchronizes with the current cell if cell argument is NULL
  */
-bool sync::cell_select(phy_interface_rrc_lte::phy_cell_t* new_cell)
+bool sync::cell_select(const phy_interface_rrc_lte::phy_cell_t* new_cell)
 {
   std::unique_lock<std::mutex> ul(rrc_mutex);
 
@@ -272,7 +272,7 @@ bool sync::cell_select(phy_interface_rrc_lte::phy_cell_t* new_cell)
   int  cnt = 0;
 
   // Move state to IDLE
-  if (!new_cell) {
+  if (new_cell == nullptr) {
     Info("Cell Select: Starting cell resynchronization\n");
   } else {
     if (!srslte_cellid_isvalid(new_cell->pci)) {
@@ -298,7 +298,7 @@ bool sync::cell_select(phy_interface_rrc_lte::phy_cell_t* new_cell)
   srslte_ue_sync_reset(&ue_sync);
 
   /* Reconfigure cell if necessary */
-  if (new_cell) {
+  if (new_cell != nullptr) {
     cell.id = new_cell->pci;
     if (!set_cell()) {
       Error("Cell Select: Reconfiguring cell\n");

srsue/src/stack/rrc/rrc.cc

@@ -1385,6 +1385,13 @@ void rrc::cell_search_completed(const phy_interface_rrc_lte::cell_search_ret_t&
   cell_searcher.trigger(cell_search_proc::cell_search_event_t{cs_ret, found_cell});
 }
 
+void rrc::cell_select_completed(bool cs_ret)
+{
+  cell_select_event_t ev{cs_ret};
+  cell_searcher.trigger(ev);
+  cell_selector.trigger(ev);
+}
+
 /*******************************************************************************
  *
  * Interface from RRC measurements class

srsue/src/stack/rrc/rrc_procedures.cc

@@ -49,10 +49,21 @@ proc_outcome_t rrc::cell_search_proc::init()
 /* Implements the SI acquisition procedure. Configures MAC/PHY scheduling to retrieve SI messages.*/
 proc_outcome_t rrc::cell_search_proc::step()
 {
-  if (state == state_t::phy_cell_search) {
-    // Waits for cell search to complete
+  switch (state) {
+    case state_t::phy_cell_search:
+    case state_t::phy_cell_select:
+      // Waits for cell select/search to complete
+      return proc_outcome_t::yield;
+    case state_t::si_acquire:
+      return step_si_acquire();
+    case state_t::wait_measurement:
+      return step_wait_measurement();
+  }
   return proc_outcome_t::yield;
-  } else if (state == state_t::si_acquire) {
+}
+
+proc_outcome_t rrc::cell_search_proc::step_si_acquire()
+{
   if (rrc_ptr->si_acquirer.run()) {
     return proc_outcome_t::yield;
   }
@@ -63,10 +74,6 @@ proc_outcome_t rrc::cell_search_proc::step()
   }
   Info("Completed successfully\n");
   return proc_outcome_t::success;
-  } else if (state == state_t::wait_measurement && std::isnormal(rrc_ptr->serving_cell->get_rsrp())) {
-    return check_sib();
-  }
-  return proc_outcome_t::yield;
 }
 
 proc_outcome_t rrc::cell_search_proc::handle_cell_found(const phy_interface_rrc_lte::phy_cell_t& new_cell)
@@ -82,27 +89,17 @@ proc_outcome_t rrc::cell_search_proc::handle_cell_found(const phy_interface_rrc_
   rrc_ptr->set_serving_cell(new_cell, false);
 
   // set new serving cell in PHY
-  if (not rrc_ptr->phy->cell_select(&rrc_ptr->serving_cell->phy_cell)) {
-    Error("Couldn't select new serving cell\n");
-    return proc_outcome_t::error;
-  }
-
-  if (not rrc_ptr->phy->cell_is_camping()) {
-    Warning("Could not camp on found cell.\n");
-    return proc_outcome_t::error;
+  state = state_t::phy_cell_select;
+  rrc_ptr->stack->start_cell_select(&rrc_ptr->serving_cell->phy_cell);
+  return proc_outcome_t::yield;
 }
 
+proc_outcome_t rrc::cell_search_proc::step_wait_measurement()
+{
   if (not std::isnormal(rrc_ptr->serving_cell->get_rsrp())) {
-    Info("No valid measurement found for the serving cell. Wait for valid measurement...\n");
-    state = state_t::wait_measurement;
     return proc_outcome_t::yield;
   }
 
-  return check_sib();
-}
-
-proc_outcome_t rrc::cell_search_proc::check_sib()
-{
   if (rrc_ptr->serving_cell->has_sib1()) {
     Info("Cell has SIB1\n");
     // What do we do????
@@ -119,6 +116,30 @@ proc_outcome_t rrc::cell_search_proc::check_sib()
   return step();
 }
 
+proc_outcome_t rrc::cell_search_proc::react(const cell_select_event_t& event)
+{
+  if (state != state_t::phy_cell_select) {
+    Warning("Received unexpected cell search result\n");
+    return proc_outcome_t::yield;
+  }
+
+  if (not event.cs_ret) {
+    Error("Couldn't select new serving cell\n");
+    return proc_outcome_t::error;
+  }
+
+  if (not rrc_ptr->phy->cell_is_camping()) {
+    Warning("Could not camp on found cell.\n");
+    return proc_outcome_t::error;
+  }
+
+  if (not std::isnormal(rrc_ptr->serving_cell->get_rsrp())) {
+    Info("No valid measurement found for the serving cell. Wait for valid measurement...\n");
+  }
+  state = state_t::wait_measurement;
+  return proc_outcome_t::yield;
+}
+
 proc_outcome_t rrc::cell_search_proc::react(const cell_search_event_t& event)
 {
   if (state != state_t::phy_cell_search) {
@@ -357,7 +378,25 @@ proc_outcome_t rrc::cell_selection_proc::init()
   return step();
 }
 
-proc_outcome_t rrc::cell_selection_proc::step_cell_selection()
+proc_outcome_t rrc::cell_selection_proc::react(const cell_select_event_t& event)
+{
+  switch (state) {
+    case search_state_t::cell_selection: {
+      return step_cell_selection(event);
+    }
+    case search_state_t::serv_cell_camp: {
+      return step_serv_cell_camp(event);
+    }
+    case search_state_t::cell_search:
+      // cell search may call cell_select
+      break;
+    default:
+      Warning("Unexpected cell selection event received\n");
+  }
+  return proc_outcome_t::yield;
+}
+
+proc_outcome_t rrc::cell_selection_proc::start_cell_selection()
 {
   Info("Current serving cell: %s\n", rrc_ptr->serving_cell->to_string().c_str());
 
@@ -377,32 +416,20 @@ proc_outcome_t rrc::cell_selection_proc::step_cell_selection()
       Info("Selected cell: %s\n", rrc_ptr->serving_cell->to_string().c_str());
 
       /* BLOCKING CALL */
-      if (rrc_ptr->phy->cell_select(&rrc_ptr->serving_cell->phy_cell)) {
-        Info("Wait PHY to be in-synch\n");
-        state                   = search_state_t::wait_in_sync;
-        rrc_ptr->phy_sync_state = phy_unknown_sync;
-        return step();
-      } else {
-        rrc_ptr->phy_sync_state = phy_unknown_sync;
-        Error("Could not camp on serving cell.\n");
-        discard_serving = true;
-        // Continue to next neighbour cell
-      }
+      state = search_state_t::cell_selection;
+      rrc_ptr->stack->start_cell_select(&rrc_ptr->serving_cell->phy_cell);
+      return proc_outcome_t::yield;
     }
   }
+  // Iteration over neighbor cells is over.
+
   if (rrc_ptr->phy_sync_state == phy_in_sync && rrc_ptr->cell_selection_criteria(rrc_ptr->serving_cell->get_rsrp())) {
     if (not rrc_ptr->phy->cell_is_camping()) {
       Info("Serving cell %s is in-sync but not camping. Selecting it...\n", rrc_ptr->serving_cell->to_string().c_str());
 
-      /* BLOCKING CALL */
-      if (rrc_ptr->phy->cell_select(&rrc_ptr->serving_cell->phy_cell)) {
-        Info("Selected serving cell OK.\n");
-      } else {
-        rrc_ptr->phy_sync_state = phy_unknown_sync;
-        rrc_ptr->serving_cell->set_rsrp(-INFINITY);
-        Error("Could not camp on serving cell.\n");
-        return proc_outcome_t::error;
-      }
+      state = search_state_t::serv_cell_camp;
+      rrc_ptr->stack->start_cell_select(&rrc_ptr->serving_cell->phy_cell);
+      return proc_outcome_t::yield;
     }
     cs_result = cs_result_t::same_cell;
     return proc_outcome_t::success;
@@ -417,22 +444,54 @@ proc_outcome_t rrc::cell_selection_proc::step_cell_selection()
   return step();
 }
 
+proc_outcome_t rrc::cell_selection_proc::step_cell_selection(const cell_select_event_t& event)
+{
+  rrc_ptr->phy_sync_state = phy_unknown_sync;
+
+  if (event.cs_ret) {
+    // successful selection
+    Info("Wait PHY to be in-synch\n");
+    state = search_state_t::wait_in_sync;
+    return step();
+  }
+
+  Error("Could not camp on serving cell.\n");
+  discard_serving = true;
+  // Continue to next neighbour cell
+  ++neigh_index;
+  return start_cell_selection();
+}
+
+srslte::proc_outcome_t rrc::cell_selection_proc::step_serv_cell_camp(const cell_select_event_t& event)
+{
+  // if we are now camping, the proc was successful
+  if (event.cs_ret) {
+    Info("Selected serving cell OK.\n");
+    cs_result = cs_result_t::same_cell;
+  } else {
+    rrc_ptr->phy_sync_state = phy_unknown_sync;
+    rrc_ptr->serving_cell->set_rsrp(-INFINITY);
+    Error("Could not camp on serving cell.\n");
+  }
+
+  return event.cs_ret ? proc_outcome_t::success : proc_outcome_t::error;
+}
+
 proc_outcome_t rrc::cell_selection_proc::step_wait_in_sync()
 {
   if (rrc_ptr->phy_sync_state == phy_in_sync) {
     if (rrc_ptr->cell_selection_criteria(rrc_ptr->serving_cell->get_rsrp())) {
       Info("PHY is in SYNC and cell selection passed\n");
-      serv_cell_cfg_fut = rrc_ptr->serv_cell_cfg.get_future();
       if (not rrc_ptr->serv_cell_cfg.launch(&serv_cell_cfg_fut, rrc_ptr->ue_required_sibs)) {
         return proc_outcome_t::error;
       }
       state = search_state_t::cell_config;
     } else {
       Info("PHY is in SYNC but cell selection did not pass. Go back to select step.\n");
-      neigh_index     = 0;
       cs_result       = cs_result_t::no_cell;
-      state           = search_state_t::cell_selection;
+      neigh_index     = 0;    // TODO: go back to the start?
       discard_serving = true; // Discard this cell
+      return start_cell_selection();
     }
   }
   return proc_outcome_t::yield;
@@ -467,16 +526,19 @@ proc_outcome_t rrc::cell_selection_proc::step_cell_config()
   }
   Error("While configuring serving cell\n");
   // resume cell selection
-  state = search_state_t::cell_selection;
   ++neigh_index;
-  return step();
+  return start_cell_selection();
 }
 
 proc_outcome_t rrc::cell_selection_proc::step()
 {
   switch (state) {
     case search_state_t::cell_selection:
-      return step_cell_selection();
+      // this state waits for phy event
+      return proc_outcome_t::yield;
+    case search_state_t::serv_cell_camp:
+      // this state waits for phy event
+      return proc_outcome_t::yield;
     case search_state_t::wait_in_sync:
       return step_wait_in_sync();
     case search_state_t::cell_config:

srsue/src/stack/ue_stack_lte.cc

@@ -319,7 +319,6 @@ void ue_stack_lte::start_prach_configuration()
   });
 }
 
-
 /********************
  *  RRC Interface
  *******************/
@@ -334,4 +333,13 @@ void ue_stack_lte::start_cell_search()
   });
 }
 
+void ue_stack_lte::start_cell_select(const phy_interface_rrc_lte::phy_cell_t* phy_cell)
+{
+  background_tasks.push_task([this, phy_cell](uint32_t worker_id) {
+    bool ret = phy->cell_select(phy_cell);
+    // notify back RRC
+    pending_tasks.push(background_queue_id, [this, ret]() { rrc.cell_select_completed(ret); });
+  });
+}
+
 } // namespace srsue

srsue/test/ttcn3/hdr/lte_ttcn3_phy.h

@@ -87,7 +87,7 @@ public:
 
   // Cell search and selection procedures
   cell_search_ret_t cell_search(phy_cell_t* found_cell);
-  bool              cell_select(phy_cell_t* cell);
+  bool              cell_select(const phy_cell_t* cell) override;
   bool              cell_is_camping();
   void              reset();
 

srsue/test/ttcn3/src/lte_ttcn3_phy.cc

@@ -153,7 +153,7 @@ phy_interface_rrc_lte::cell_search_ret_t lte_ttcn3_phy::cell_search(phy_cell_t*
   return ret;
 };
 
-bool lte_ttcn3_phy::cell_select(phy_cell_t* rrc_cell)
+bool lte_ttcn3_phy::cell_select(const phy_cell_t* rrc_cell)
 {
   // try to find RRC cell in current cell map
   for (auto& cell : cells) {

srsue/test/upper/rrc_meas_test.cc

@@ -54,7 +54,7 @@ public:
   void              set_config_mbsfn_mcch(const srslte::mcch_msg_t& mcch) override {}
   cell_search_ret_t cell_search(phy_cell_t* cell) override { return {}; }
   bool              cell_is_camping() override { return false; }
-  bool              cell_select(phy_cell_t* cell = nullptr) override { return false; }
+  bool              cell_select(const phy_cell_t* cell = nullptr) override { return false; }
   void              reset() override {}
   void              enable_pregen_signals(bool enable) override {}