phy: initial PRS generator

phy: review PRS generator related

include/srsran/phy/upper/signal_processors/prs/factories.h

@@ -0,0 +1,43 @@
+/*
+ *
+ * Copyright 2021-2025 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.
+ *
+ */
+
+#pragma once
+
+#include "srsran/phy/generic_functions/precoding/precoding_factories.h"
+#include "srsran/phy/upper/sequence_generators/sequence_generator_factories.h"
+#include "srsran/phy/upper/signal_processors/prs/prs_generator.h"
+#include "srsran/phy/upper/signal_processors/prs/prs_generator_validator.h"
+#include <memory>
+
+namespace srsran {
+
+/// PRS generator factory.
+class prs_generator_factory
+{
+public:
+  /// Default destructor.
+  virtual ~prs_generator_factory() = default;
+
+  /// Creates a PRS generator.
+  virtual std::unique_ptr<prs_generator> create() = 0;
+
+  /// Creates a PRS generator configuration validator.
+  virtual std::unique_ptr<prs_generator_validator> create_validator() = 0;
+};
+
+/// \brief Creates a generic PRS generator factory.
+/// \param[in] prg_factory      Pseudo-random sequence generator factory.
+/// \param[in] precoder_factory Channel precoder factory.
+/// \return A valid PRS generator factory if successful.
+std::shared_ptr<prs_generator_factory>
+create_prs_generator_generic_factory(std::shared_ptr<pseudo_random_generator_factory> prg_factory,
+                                     std::shared_ptr<channel_precoder_factory>        precoder_factory);
+
+} // namespace srsran

include/srsran/phy/upper/signal_processors/prs/formatters.h

@@ -0,0 +1,55 @@
+/*
+ *
+ * Copyright 2021-2025 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.
+ *
+ */
+
+#pragma once
+
+#include "srsran/phy/support/precoding_formatters.h"
+#include "srsran/phy/upper/signal_processors/prs/prs_generator_configuration.h"
+#include "srsran/ran/precoding/precoding_weight_matrix_formatters.h"
+
+namespace fmt {
+
+/// \brief Custom formatter for \c pdcch_processor::coreset_description.
+template <>
+struct formatter<srsran::prs_generator_configuration> {
+  /// Helper used to parse formatting options and format fields.
+  srsran::delimited_formatter helper;
+
+  /// Default constructor.
+  formatter() = default;
+
+  template <typename ParseContext>
+  auto parse(ParseContext& ctx)
+  {
+    return helper.parse(ctx);
+  }
+
+  template <typename FormatContext>
+  auto format(const srsran::prs_generator_configuration& config, FormatContext& ctx) const
+  {
+    helper.format_if_verbose(ctx, "slot={}", config.slot);
+    helper.format_if_verbose(ctx, "cp={}", config.cp);
+    helper.format_always(ctx, "n_id={}", config.n_id_prs);
+    helper.format_always(ctx, "comb_size={}", fmt::underlying(config.comb_size));
+    helper.format_always(ctx, "comb_offset={}", config.comb_offset);
+    helper.format_always(
+        ctx,
+        "t_alloc={}",
+        srsran::interval<unsigned>(config.start_symbol, config.start_symbol + static_cast<unsigned>(config.duration)));
+    helper.format_if_verbose(ctx, "rb_start={}", config.prb_start);
+    helper.format_always(ctx, "f_alloc={}", config.freq_alloc);
+    helper.format_if_verbose(ctx, "power_offset={}", config.power_offset_dB);
+    helper.format_if_verbose(ctx, "precoding={}", config.precoding);
+
+    return ctx.out();
+  }
+};
+
+} // namespace fmt

include/srsran/phy/upper/signal_processors/prs/prs_generator.h

@@ -0,0 +1,31 @@
+/*
+ *
+ * Copyright 2021-2025 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.
+ *
+ */
+
+#pragma once
+
+namespace srsran {
+
+class resource_grid_writer;
+struct prs_generator_configuration;
+
+/// Positioning Reference Signals (PRS) generator interface.
+class prs_generator
+{
+public:
+  /// Default destructor.
+  virtual ~prs_generator() = default;
+
+  /// \brief Generates Positioning Reference Signals (PRS) according to TS38.211 Section 7.4.1.7.
+  /// \param[out] grid   Resource grid.
+  /// \param[in]  config PRS transmission configuration.
+  virtual void generate(resource_grid_writer& grid, const prs_generator_configuration& config) = 0;
+};
+
+} // namespace srsran

include/srsran/phy/upper/signal_processors/prs/prs_generator_configuration.h

@@ -0,0 +1,77 @@
+/*
+ *
+ * Copyright 2021-2025 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.
+ *
+ */
+
+#pragma once
+
+#include "srsran/phy/support/precoding_configuration.h"
+#include "srsran/ran/cyclic_prefix.h"
+#include "srsran/ran/prs/prs.h"
+#include "srsran/ran/slot_point.h"
+
+namespace srsran {
+
+/// \brief Positioning Reference Signals (PRS) transmission parameters.
+///
+/// \remark Not all combinations of comb size and time domain duration are valid, see \ref
+/// prs_valid_num_symbols_and_comb_size for more information.
+struct prs_generator_configuration {
+  /// Slot and subcarrier spacing.
+  slot_point slot;
+  /// Cyclic prefix.
+  cyclic_prefix cp;
+  /// \brief Sequence identifier.
+  ///
+  /// Parameter \f$n_{ID,seq}^{PRS}\f$ in TS38.211 Section 7.4.1.7.2. The range is {0, ..., 4095}. It is given by the
+  /// higher layer parameter \e dl-PRS-SequenceID.
+  ///
+  uint16_t n_id_prs;
+  /// \brief Transmission comb size.
+  ///
+  /// Parameter \f$K_{comb}^{PRS}\f$ in TS38.211 Section 7.4.1.7.3. It is given by the higher layer parameter \e
+  /// dl-PRS-CombSizeN.
+  prs_comb_size comb_size;
+  /// \brief Transmission comb offset.
+  ///
+  /// Parameter \f$k_{offset}^{PRS}\f$ in TS38.211 Section 7.4.1.7.3. It is given by the higher layer parameter \e
+  /// dl-PRS-CombSizeN-AndReOffset
+  uint8_t comb_offset;
+  /// \brief Transmission time domain duration.
+  ///
+  /// Parameter \f$L_{PRS}\f$ in TS38.211 Section 7.4.1.7.3. It is given by the higher layer parameter \e
+  /// dl-PRS-NumSymbols.
+  prs_num_symbols duration;
+  /// \brief First symbol index of the transmission.
+  ///
+  /// Parameter \f$l_{start}^{PRS}\f$ in TS38.211 Section 7.4.1.7.3. It is given by the higher layer parameter \e
+  /// dl-PRS-ResourceSymbolOffset.
+  uint8_t start_symbol;
+  /// \brief Physical resource block allocation start PRB.
+  ///
+  /// It is given by the higher layer parameter \e dl-PRS-StartPRB. The range is {0, ..., 2176}.
+  ///
+  /// It expresses the number of PRB between the PointA given by the higher layer parameter \e dl-PRS-PointA and the
+  /// lowest PRB of the PRS transmission.
+  uint16_t prb_start;
+  /// \brief Physical resource block allocation expressed as a start and number of physical resource blocks.
+  ///
+  /// The start position is relative to the lowest resource grid physical resource block. Set the start position equal
+  /// to \c prb_start, if the higher layer parameter \e dl-PRS-PointA matches with the lowest subcarrier of the resource
+  /// grid.
+  ///
+  /// The number of PRB is derived from the higher layer parameter \e dl-PRS-ResourceBandwidth. The range is
+  /// {24, ..., 276} in steps of 4.
+  interval<uint16_t> freq_alloc;
+  /// Ratio of PRS data EPRE to SSS EPRE in decibels.
+  float power_offset_dB;
+  /// Precoding configuration.
+  precoding_configuration precoding;
+};
+
+} // namespace srsran

include/srsran/phy/upper/signal_processors/prs/prs_generator_validator.h

@@ -0,0 +1,32 @@
+/*
+ *
+ * Copyright 2021-2025 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.
+ *
+ */
+
+#pragma once
+
+#include "srsran/adt/expected.h"
+#include <string>
+
+namespace srsran {
+
+struct prs_generator_configuration;
+
+/// \brief PRS generator validator.
+class prs_generator_validator
+{
+public:
+  /// Default destructor.
+  virtual ~prs_generator_validator() = default;
+
+  /// \brief Validates PRS generator configuration parameters.
+  /// \return A success if the parameters contained in \c config are supported, an error message otherwise.
+  virtual error_type<std::string> is_valid(const prs_generator_configuration& config) const = 0;
+};
+
+} // namespace srsran

include/srsran/ran/prs/prs.h

@@ -0,0 +1,34 @@
+/*
+ *
+ * Copyright 2021-2025 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.
+ *
+ */
+
+/// \file
+/// \brief Positioning Reference Signals (PRS) parameters.
+
+#pragma once
+
+namespace srsran {
+
+//// PRS transmission time domain duration.
+enum class prs_num_symbols : uint8_t { two = 2, four = 4, six = 6, twelve = 12 };
+
+/// PRS transmission comb size.
+enum class prs_comb_size : uint8_t { two = 2, four = 4, six = 6, twelve = 12 };
+
+/// \brief Determines whether the combination of time domain duration and comb size is valid.
+///
+/// The valid combinations are given in TS38.211 Section 7.4.1.7.3.
+inline bool prs_valid_num_symbols_and_comb_size(prs_num_symbols nsymb, prs_comb_size comb_sz)
+{
+  uint8_t nsymb_u8   = static_cast<uint8_t>(nsymb);
+  uint8_t comb_sz_u8 = static_cast<uint8_t>(comb_sz);
+  return (nsymb_u8 >= comb_sz_u8) && (nsymb_u8 % comb_sz_u8 == 0);
+}
+
+} // namespace srsran

lib/phy/upper/channel_processors/pdsch/pdsch_processor_concurrent_impl.cpp

@@ -18,7 +18,7 @@
 
 using namespace srsran;
 
-/// \brief Looks at the output of the validator and, if unsuccessful, fills msg with the error message.
+/// \brief Looks at the output of the validator and, if unsuccessful, fills \c msg with the error message.
 ///
 /// This is used to call the validator inside the process methods only if asserts are active.
 [[maybe_unused]] static bool handle_validation(std::string& msg, const error_type<std::string>& err)

lib/phy/upper/channel_processors/pdsch/pdsch_processor_impl.cpp

@@ -15,7 +15,7 @@
 
 using namespace srsran;
 
-/// \brief Looks at the output of the validator and, if unsuccessful, fills msg with the error message.
+/// \brief Looks at the output of the validator and, if unsuccessful, fills \c msg with the error message.
 ///
 /// This is used to call the validator inside the process methods only if asserts are active.
 [[maybe_unused]] static bool handle_validation(std::string& msg, const error_type<std::string>& err)

lib/phy/upper/channel_processors/pdsch/pdsch_processor_lite_impl.cpp

@@ -15,7 +15,7 @@
 
 using namespace srsran;
 
-/// \brief Looks at the output of the validator and, if unsuccessful, fills msg with the error message.
+/// \brief Looks at the output of the validator and, if unsuccessful, fills \c msg with the error message.
 ///
 /// This is used to call the validator inside the process methods only if asserts are active.
 [[maybe_unused]] static bool handle_validation(std::string& msg, const error_type<std::string>& err)

lib/phy/upper/channel_processors/pucch/pucch_processor_impl.cpp

@@ -15,7 +15,7 @@
 
 using namespace srsran;
 
-/// \brief Looks at the output of the validator and, if unsuccessful, fills msg with the error message.
+/// \brief Looks at the output of the validator and, if unsuccessful, fills \c msg with the error message.
 ///
 /// This is used to call the validator inside the process methods only if asserts are active.
 [[maybe_unused]] static bool handle_validation(std::string& msg, const error_type<std::string>& err)

lib/phy/upper/channel_processors/pusch/pusch_demodulator_impl.cpp

@@ -123,7 +123,7 @@ void pusch_demodulator_impl::demodulate(pusch_codeword_buffer&      codeword_buf
   // Number of receive antenna ports.
   unsigned nof_rx_ports = static_cast<unsigned>(config.rx_ports.size());
 
-  // Initialise sequence.
+  // Initialize sequence.
   unsigned c_init = config.rnti * pow2(15) + config.n_id;
   descrambler->init(c_init);
 

lib/phy/upper/channel_processors/pusch/pusch_processor_impl.cpp

@@ -24,7 +24,7 @@
 
 using namespace srsran;
 
-/// \brief Looks at the output of the validator and, if unsuccessful, fills msg with the error message.
+/// \brief Looks at the output of the validator and, if unsuccessful, fills \c msg with the error message.
 ///
 /// This is used to call the validator inside the process methods only if asserts are active.
 [[maybe_unused]] static bool handle_validation(std::string& msg, const error_type<std::string>& err)

lib/phy/upper/signal_processors/CMakeLists.txt

@@ -7,6 +7,8 @@
 #
 
 set(SOURCES
+        prs/factories.cpp
+        prs/prs_generator_impl.cpp
         ptrs/ptrs_pdsch_generator_impl.cpp
         ptrs/ptrs_pdsch_generator_factory.cpp
         pucch/dmrs_pucch_estimator_format1.cpp

lib/phy/upper/signal_processors/prs/factories.cpp

@@ -0,0 +1,55 @@
+/*
+ *
+ * Copyright 2021-2025 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 "srsran/phy/upper/signal_processors/prs/factories.h"
+#include "prs_generator_impl.h"
+#include "prs_generator_validator_impl.h"
+
+using namespace srsran;
+
+namespace {
+
+/// Implements a generic PRS generator factory.
+class prs_generator_factory_generic_impl : public prs_generator_factory
+{
+public:
+  prs_generator_factory_generic_impl(std::shared_ptr<pseudo_random_generator_factory> prg_factory_,
+                                     std::shared_ptr<channel_precoder_factory>        precoder_factory_) :
+    prg_factory(std::move(prg_factory_)), precoder_factory(std::move(precoder_factory_))
+  {
+    srsran_assert(prg_factory, "Invalid pseudo-random sequence generator factory.");
+    srsran_assert(precoder_factory, "Invalid channel precoder factory.");
+  }
+
+  // See interface for documentation.
+  std::unique_ptr<prs_generator> create() override
+  {
+    return std::make_unique<prs_generator_impl>(prg_factory->create(), precoder_factory->create());
+  }
+
+  // See interface for documentation.
+  std::unique_ptr<prs_generator_validator> create_validator() override
+  {
+    return std::make_unique<prs_generator_validator_impl>();
+  }
+
+private:
+  std::shared_ptr<pseudo_random_generator_factory> prg_factory;
+  std::shared_ptr<channel_precoder_factory>        precoder_factory;
+};
+
+} // namespace
+
+std::shared_ptr<prs_generator_factory>
+srsran::create_prs_generator_generic_factory(std::shared_ptr<pseudo_random_generator_factory> prg_factory,
+                                             std::shared_ptr<channel_precoder_factory>        precoder_factory)
+{
+  return std::make_shared<prs_generator_factory_generic_impl>(std::move(prg_factory), std::move(precoder_factory));
+}