mirror of https://github.com/gnss-sdr/gnss-sdr
163 lines
5.2 KiB
C++
163 lines
5.2 KiB
C++
/*!
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* \file sbas_l1_telemetry_decoder_gs.h
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* \brief Interface of a SBAS telemetry data decoder block
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* \author Daniel Fehr 2013. daniel.co(at)bluewin.ch
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*
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* -----------------------------------------------------------------------------
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*
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* GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
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* This file is part of GNSS-SDR.
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*
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* Copyright (C) 2010-2020 (see AUTHORS file for a list of contributors)
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* SPDX-License-Identifier: GPL-3.0-or-later
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*
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* -----------------------------------------------------------------------------
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*/
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#ifndef GNSS_SDR_SBAS_L1_TELEMETRY_DECODER_GS_H
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#define GNSS_SDR_SBAS_L1_TELEMETRY_DECODER_GS_H
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#include "gnss_block_interface.h"
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#include "gnss_satellite.h"
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#include <boost/crc.hpp> // for crc_optimal
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#include <gnuradio/block.h>
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#include <gnuradio/types.h> // for gr_vector_const_void_star
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#include <cstddef> // for size_t
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#include <cstdint>
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#include <deque>
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#include <fstream>
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#include <memory> // for std::shared_ptr
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#include <string>
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#include <utility> // for pair
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#include <vector>
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/** \addtogroup Telemetry_Decoder
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* \{ */
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/** \addtogroup Telemetry_Decoder_gnuradio_blocks
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* \{ */
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class Viterbi_Decoder_Sbas;
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class sbas_l1_telemetry_decoder_gs;
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using sbas_l1_telemetry_decoder_gs_sptr = gnss_shared_ptr<sbas_l1_telemetry_decoder_gs>;
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sbas_l1_telemetry_decoder_gs_sptr sbas_l1_make_telemetry_decoder_gs(
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const Gnss_Satellite &satellite,
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bool dump);
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/*!
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* \brief This class implements a block that decodes the SBAS integrity and
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* corrections data defined in RTCA MOPS DO-229
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*/
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class sbas_l1_telemetry_decoder_gs : public gr::block
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{
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public:
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~sbas_l1_telemetry_decoder_gs() override;
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void set_satellite(const Gnss_Satellite &satellite); //!< Set satellite PRN
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void set_channel(int32_t channel); //!< Set receiver's channel
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inline void reset(){};
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/*!
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* \brief This is where all signal processing takes place
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*/
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int general_work(int noutput_items, gr_vector_int &ninput_items,
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gr_vector_const_void_star &input_items, gr_vector_void_star &output_items) override;
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private:
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friend sbas_l1_telemetry_decoder_gs_sptr sbas_l1_make_telemetry_decoder_gs(
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const Gnss_Satellite &satellite,
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bool dump);
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sbas_l1_telemetry_decoder_gs(const Gnss_Satellite &satellite, bool dump);
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void viterbi_decoder(double *page_part_symbols, int32_t *page_part_bits);
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void align_samples();
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static const int32_t D_SAMPLES_PER_SYMBOL = 2;
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static const int32_t D_SYMBOLS_PER_BIT = 2;
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static const int32_t D_BLOCK_SIZE_IN_BITS = 30;
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bool d_dump;
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Gnss_Satellite d_satellite;
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int32_t d_channel;
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std::string d_dump_filename;
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std::ofstream d_dump_file;
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size_t d_block_size; //!< number of samples which are processed during one invocation of the algorithms
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std::vector<double> d_sample_buf; //!< input buffer holding the samples to be processed in one block
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typedef std::pair<int32_t, std::vector<int32_t>> msg_candiate_int_t;
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typedef std::pair<int32_t, std::vector<uint8_t>> msg_candiate_char_t;
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// helper class for sample alignment
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class Sample_Aligner
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{
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public:
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Sample_Aligner();
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void reset();
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/*
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* samples length must be a multiple of two
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* for block operation
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*/
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bool get_symbols(const std::vector<double> &samples, std::vector<double> &symbols);
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private:
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int32_t d_n_smpls_in_history{3};
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double d_iir_par{0.05};
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double d_corr_paired{};
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double d_corr_shifted{};
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bool d_aligned{};
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double d_past_sample{};
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} d_sample_aligner;
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// helper class for symbol alignment and Viterbi decoding
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class Symbol_Aligner_And_Decoder
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{
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public:
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Symbol_Aligner_And_Decoder();
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void reset();
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bool get_bits(const std::vector<double> &symbols, std::vector<int32_t> &bits);
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private:
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int32_t d_KK{7};
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std::shared_ptr<Viterbi_Decoder_Sbas> d_vd1;
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std::shared_ptr<Viterbi_Decoder_Sbas> d_vd2;
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double d_past_symbol{0};
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} d_symbol_aligner_and_decoder;
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// helper class for detecting the preamble and collect the corresponding message candidates
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class Frame_Detector
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{
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public:
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void reset();
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void get_frame_candidates(const std::vector<int32_t> &bits, std::vector<std::pair<int32_t, std::vector<int32_t>>> &msg_candidates);
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private:
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std::deque<int32_t> d_buffer;
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} d_frame_detector;
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// helper class for checking the CRC of the message candidates
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class Crc_Verifier
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{
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public:
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void reset();
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void get_valid_frames(const std::vector<msg_candiate_int_t> &msg_candidates, std::vector<msg_candiate_char_t> &valid_msgs);
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private:
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typedef boost::crc_optimal<24, 0x1864CFBU, 0x0, 0x0, false, false> crc_24_q_type;
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crc_24_q_type d_checksum_agent;
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void zerropad_front_and_convert_to_bytes(const std::vector<int32_t> &msg_candidate, std::vector<uint8_t> &bytes);
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void zerropad_back_and_convert_to_bytes(const std::vector<int32_t> &msg_candidate, std::vector<uint8_t> &bytes);
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} d_crc_verifier;
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};
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/** \} */
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/** \} */
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#endif // GNSS_SDR_SBAS_L1_TELEMETRY_DECODER_GS_H
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