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srsLTE
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Changes in Cell Selection Procedure (#1557) 

* Fixes RRC cell reselection procedure
This commit is contained in:
Ismael Gomez 2020-07-17 17:05:19 +02:00 committed by GitHub
parent 1eaf7efab0
commit 443dee7035
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 28 additions and 29 deletions
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44
srsue/src/stack/rrc/rrc_procedures.cc
View File

@ -520,24 +520,32 @@ proc_outcome_t rrc::cell_selection_proc::start_serv_cell_selection()
return proc_outcome_t::yield;
}
/** Cell selection procedure defined in 36.304 5.2
* The procedure starts with Stored Information Cell Selection. In our implementation,
* we use known neighbour cells. If that fails, the procedure continues with Initial Cell Selection .
*
* The standard requires the UE to attach to any cell that meets the Cell Selection Criteria on any frequency.
* On each frequency, the UE shall select the strongest cell.
*
* In our implementation, we will try to select the strongest cell of all known frequencies, if they are still
* available, or the strongest of all available cells we've found on any frequency.
*/
proc_outcome_t rrc::cell_selection_proc::start_cell_selection()
{
// Neighbour cells are sorted in descending order of RSRP
// First of all, try to re-select the current serving cell if it meets the criteria
if (not serv_cell_select_attempted and
rrc_ptr->cell_selection_criteria(rrc_ptr->meas_cells.serving_cell().get_rsrp())) {
return start_serv_cell_selection();
}
// If serving is not available, use the stored information (known neighbours) to find the strongest
// cell that meets the selection criteria.
for (; neigh_index < rrc_ptr->meas_cells.nof_neighbours(); ++neigh_index) {
// If the serving cell is stronger, attempt to select it
if (not serv_cell_select_attempted and
rrc_ptr->cell_selection_criteria(rrc_ptr->meas_cells.serving_cell().get_rsrp()) and
rrc_ptr->meas_cells.serving_cell().greater(&rrc_ptr->meas_cells[neigh_index])) {
return start_serv_cell_selection();
}
/*TODO: CHECK that PLMN matches. Currently we don't receive SIB1 of neighbour cells
* meas_cells[i]->plmn_equals(selected_plmn_id) && */
// Matches S criteria
float rsrp = rrc_ptr->meas_cells.at(neigh_index).get_rsrp();
if (not rrc_ptr->phy_ctrl->is_in_sync() or
(rrc_ptr->cell_selection_criteria(rsrp) and rsrp > rrc_ptr->meas_cells.serving_cell().get_rsrp() + 5)) {
if (rrc_ptr->cell_selection_criteria(rrc_ptr->meas_cells.at(neigh_index).get_rsrp())) {
// currently connected and verifies cell selection criteria
// Try to select Cell
rrc_ptr->set_serving_cell(rrc_ptr->meas_cells.at(neigh_index).phy_cell, discard_serving);
@ -554,17 +562,9 @@ proc_outcome_t rrc::cell_selection_proc::start_cell_selection()
return proc_outcome_t::yield;
}
}
// Iteration over neighbor cells is over.
// If serving cell is weaker, but couldn't select neighbors
if (serv_cell_select_attempted) {
return proc_outcome_t::error;
} else if (rrc_ptr->cell_selection_criteria(rrc_ptr->meas_cells.serving_cell().get_rsrp())) {
return start_serv_cell_selection();
}
// If can not find any suitable cell, search again
Info("Cell selection and reselection in IDLE did not find any suitable cell. Searching again\n");
// If any of the known cells meets the selection criteria or could not be selected, search again.
Info("Could not select any kown cell. Searching new cells\n");
if (not rrc_ptr->cell_searcher.launch(&cell_search_fut)) {
return proc_outcome_t::error;
}
@ -607,7 +607,7 @@ srslte::proc_outcome_t rrc::cell_selection_proc::step_serv_cell_camp(const bool&
rrc_ptr->meas_cells.serving_cell().set_rsrp(-INFINITY);
Warning("Could not camp on serving cell.\n");
return neigh_index >= rrc_ptr->meas_cells.nof_neighbours() ? proc_outcome_t::error : proc_outcome_t::yield;
return start_cell_selection();
}
proc_outcome_t rrc::cell_selection_proc::step_cell_search()

13
srsue/test/upper/rrc_meas_test.cc
View File

@ -101,7 +101,6 @@ public:
}
phy_interface_rrc_lte::phy_cell_t last_selected_cell = {};
private:
bool meas_reset_called = false;
std::set<uint32_t> freqs_started;
@ -313,15 +312,15 @@ int cell_select_test()
// Start cell selection procedure. The RRC will start with strongest cell
TESTASSERT(rrctest.start_cell_select() == SRSLTE_SUCCESS);
stack.run_pending_tasks();
TESTASSERT(rrctest.phytest.last_selected_cell.earfcn == 1);
TESTASSERT(rrctest.phytest.last_selected_cell.pci == 1);
TESTASSERT(rrctest.has_neighbour_cell(2, 2));
TESTASSERT(!rrctest.has_neighbour_cell(1, 1));
TESTASSERT(rrctest.phytest.last_selected_cell.earfcn == 2);
TESTASSERT(rrctest.phytest.last_selected_cell.pci == 2);
TESTASSERT(!rrctest.has_neighbour_cell(2, 2));
TESTASSERT(rrctest.has_neighbour_cell(1, 1));
// PHY reports back the result
rrctest.cell_select_completed(true);
TESTASSERT(rrctest.has_neighbour_cell(2, 2));
TESTASSERT(!rrctest.has_neighbour_cell(1, 1));
TESTASSERT(!rrctest.has_neighbour_cell(2, 2));
TESTASSERT(rrctest.has_neighbour_cell(1, 1));
// Note: cell selection procedure is not done yet at this point.
}