band_helper: add helper class for RF bands

attempt to C++ify handling of radio bands and (E/NR)ARFCNs, etc.

lib/include/srslte/common/band_helper.h

@@ -0,0 +1,106 @@
+/**
+ *
+ * \section COPYRIGHT
+ *
+ * Copyright 2013-2020 Software Radio Systems Limited
+ *
+ * By using this file, you agree to the terms and conditions set
+ * forth in the LICENSE file which can be found at the top level of
+ * the distribution.
+ *
+ */
+
+#ifndef SRSLTE_BAND_HELPER_H
+#define SRSLTE_BAND_HELPER_H
+
+#include <array>
+#include <stdint.h>
+#include <vector>
+
+namespace srslte {
+
+// Helper class to handle frequency bands and ARFCNs
+// For NR: NR-ARFCN and channel raster as per TS 38.104
+class srslte_band_helper
+{
+public:
+  srslte_band_helper()  = default;
+  ~srslte_band_helper() = default;
+
+  // Return frequency of given NR-ARFCN in Hz
+  double nr_arfcn_to_freq(uint32_t nr_arfcn);
+
+  // Possible values of delta f_raster in Table 5.4.2.3-1 and Table 5.4.2.3-2
+  enum delta_f_raster_t {
+    DEFAULT = 0, // for bands with 2 possible values for delta_f_raster (e.g. 15 and 30 kHz), the lower is chosen
+    KHZ_15,
+    KHZ_30,
+    KHZ_60,
+    KHZ_100,
+    KHZ_120
+  };
+
+  // Return vector of bands that ARFCN is valid for
+  // For bands with 2 possible raster offsets, delta_f_raster needs to be specified
+  std::vector<uint32_t> get_bands_nr(uint32_t nr_arfcn, delta_f_raster_t delta_f_raster = DEFAULT);
+
+private:
+  // Table 5.4.2.1-1
+  struct nr_raster_params {
+    double   delta_F_global_kHz;
+    double   F_REF_Offs_MHz;
+    uint32_t N_REF_Offs;
+    uint32_t N_REF_min;
+    uint32_t N_REF_max;
+  };
+
+  // Helper to calculate F_REF according to Table 5.4.2.1-1
+  nr_raster_params get_raster_params(uint32_t nr_arfcn);
+
+  static const uint32_t max_nr_arfcn                            = 3279165;
+  static constexpr std::array<nr_raster_params, 3> nr_fr_params = {{
+      // clang-format off
+    // Frequency range 0 - 3000 MHz
+    {5, 0.0, 0, 0, 599999},
+    // Frequency range 3000 - 24250 MHz
+    {15, 3000.0, 600000, 600000, 2016666},
+    // Frequency range 24250 - 100000 MHz
+    {60, 24250.08, 2016667, 2016667, max_nr_arfcn}
+      // clang-format on
+  }};
+
+  // Elements of Table 5.4.2.3-1 in TS 38.104
+  struct nr_band {
+    uint8_t          band;
+    delta_f_raster_t delta_f_raster;
+    uint32_t         ul_nref_first;
+    uint32_t         ul_nref_step;
+    uint32_t         ul_nref_last;
+    uint32_t         dl_nref_first;
+    uint32_t         dl_nref_step;
+    uint32_t         dl_nref_last;
+  };
+
+  // List of NR bands for FR1 (Table 5.4.2.3-1)
+  // bands with more than one raster offset have multiple entries
+  // TODO: add remaining bands
+  static const uint32_t nof_nr_bands_fr1                                   = 7;
+  static constexpr std::array<nr_band, nof_nr_bands_fr1> nr_band_table_fr1 = {{
+      // clang-format off
+    {74, KHZ_100, 285400, 20, 294000, 295000, 20, 303600},
+    // n75+n76 missing
+    {77, KHZ_15, 620000, 1, 680000, 620000, 1, 680000},
+    {77, KHZ_30, 620000, 2, 680000, 620000, 2, 680000},
+
+    {78, KHZ_15, 620000, 1, 653333, 620000, 1, 653333},
+    {78, KHZ_30, 620000, 2, 653332, 620000, 2, 653332},
+
+    {79, KHZ_15, 693334, 2, 733333, 693334, 2, 733333},
+    {79, KHZ_30, 693334, 2, 733332, 693334, 2, 733332}
+    // clang-format on  
+  }};
+};
+
+} // namespace srslte
+
+#endif // SRSLTE_BAND_HELPER_H

lib/src/common/CMakeLists.txt

@@ -10,6 +10,7 @@
 set(SOURCES arch_select.cc
             enb_events.cc
             backtrace.c
+            band_helper.cc
             buffer_pool.cc
             crash_handler.c
             gen_mch_tables.c

lib/src/common/band_helper.cc

@@ -0,0 +1,64 @@
+/**
+ *
+ * \section COPYRIGHT
+ *
+ * Copyright 2013-2020 Software Radio Systems Limited
+ *
+ * By using this file, you agree to the terms and conditions set
+ * forth in the LICENSE file which can be found at the top level of
+ * the distribution.
+ *
+ */
+
+#include "srslte/common/band_helper.h"
+#include <algorithm>
+
+namespace srslte {
+
+// definition of static members
+constexpr std::array<srslte_band_helper::nr_band, srslte_band_helper::nof_nr_bands_fr1>
+          srslte_band_helper::nr_band_table_fr1;
+constexpr std::array<srslte_band_helper::nr_raster_params, 3> srslte_band_helper::nr_fr_params;
+
+// Formula in 5.4.2.1
+double srslte_band_helper::nr_arfcn_to_freq(uint32_t nr_arfcn)
+{
+  nr_raster_params params = get_raster_params(nr_arfcn);
+  return (params.F_REF_Offs_MHz * 1e6 + params.delta_F_global_kHz * (nr_arfcn - params.N_REF_Offs) * 1e3);
+}
+
+// Implements 5.4.2.1 in TS 38.401
+std::vector<uint32_t> srslte_band_helper::get_bands_nr(uint32_t                             nr_arfcn,
+                                                       srslte_band_helper::delta_f_raster_t delta_f_raster)
+{
+  std::vector<uint32_t> bands;
+  for (const auto& nr_band : nr_band_table_fr1) {
+    if (nr_arfcn >= nr_band.dl_nref_first && nr_arfcn <= nr_band.dl_nref_last && nr_arfcn % nr_band.dl_nref_step == 0) {
+      // band must not already be present
+      if (std::find(bands.begin(), bands.end(), nr_band.band) == bands.end()) {
+        if (delta_f_raster == DEFAULT) {
+          // add band if delta_f_raster has default value
+          bands.push_back(nr_band.band);
+        } else {
+          // if delta_f_raster is set explicitly, only add if band matches
+          if (nr_band.delta_f_raster == delta_f_raster) {
+            bands.push_back(nr_band.band);
+          }
+        }
+      }
+    }
+  }
+  return bands;
+}
+
+srslte_band_helper::nr_raster_params srslte_band_helper::get_raster_params(uint32_t nr_arfcn)
+{
+  for (auto& fr : nr_fr_params) {
+    if (nr_arfcn >= fr.N_REF_min && nr_arfcn <= fr.N_REF_max) {
+      return fr;
+    }
+  }
+  return {}; // return empty params
+}
+
+} // namespace srslte

lib/src/common/test/CMakeLists.txt

@@ -16,3 +16,6 @@ target_link_libraries(thread_test
         srslte_common)
 add_test(thread_test thread_test)
 
+add_executable(band_helper_test band_helper_test.cc)
+target_link_libraries(band_helper_test srslte_common)
+add_test(band_helper_test band_helper_test)

lib/src/common/test/band_helper_test.cc

@@ -0,0 +1,48 @@
+/**
+ *
+ * \section COPYRIGHT
+ *
+ * Copyright 2013-2020 Software Radio Systems Limited
+ *
+ * By using this file, you agree to the terms and conditions set
+ * forth in the LICENSE file which can be found at the top level of
+ * the distribution.
+ *
+ */
+
+#include "srslte/common/band_helper.h"
+#include "srslte/common/test_common.h"
+
+int bands_test_nr()
+{
+  srslte::srslte_band_helper bands;
+
+  TESTASSERT(bands.nr_arfcn_to_freq(632628) == 3489.42e6);
+
+  const uint32_t max_valid_nr_arfcn = 3279165;
+
+  // Max ARFCN is 3279165 at almost 10 GHz
+  TESTASSERT(bands.nr_arfcn_to_freq(max_valid_nr_arfcn) == 99.99996e9);
+
+  // Invalid ARFCN
+  TESTASSERT(bands.nr_arfcn_to_freq(max_valid_nr_arfcn + 1) == 0.0);
+
+  std::vector<uint32_t> band_vector = bands.get_bands_nr(632628);
+  TESTASSERT(band_vector.size() == 2);
+  TESTASSERT(band_vector.at(0) == 77);
+  TESTASSERT(band_vector.at(1) == 78);
+
+  // Invalid configs
+  // For 30 kHz, 620001 is not a valid ARFCN, only every 2nd
+  band_vector = bands.get_bands_nr(620001, srslte::srslte_band_helper::KHZ_30);
+  TESTASSERT(band_vector.empty());
+
+  return SRSLTE_SUCCESS;
+}
+
+int main(int argc, char** argv)
+{
+  TESTASSERT(bands_test_nr() == SRSLTE_SUCCESS);
+
+  return SRSLTE_SUCCESS;
+}