mirror of https://github.com/gnss-sdr/gnss-sdr
163 lines
5.4 KiB
C++
163 lines
5.4 KiB
C++
/*!
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* \file sbas_l1_telemetry_decoder_cc.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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* Copyright (C) 2010-2018 (see AUTHORS file for a list of contributors)
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*
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* GNSS-SDR is a software defined Global Navigation
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* Satellite Systems receiver
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*
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* This file is part of GNSS-SDR.
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*
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* GNSS-SDR is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* GNSS-SDR is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNSS-SDR. If not, see <https://www.gnu.org/licenses/>.
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*
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* -------------------------------------------------------------------------
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*/
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#ifndef GNSS_SDR_SBAS_L1_TELEMETRY_DECODER_CC_H
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#define GNSS_SDR_SBAS_L1_TELEMETRY_DECODER_CC_H
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#include "gnss_satellite.h"
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#include "viterbi_decoder.h"
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#include <boost/crc.hpp>
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#include <gnuradio/block.h>
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#include <algorithm> // for copy
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#include <cstdint>
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#include <deque>
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#include <fstream>
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#include <string>
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#include <utility> // for pair
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#include <vector>
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class sbas_l1_telemetry_decoder_cc;
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using sbas_l1_telemetry_decoder_cc_sptr = boost::shared_ptr<sbas_l1_telemetry_decoder_cc>;
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sbas_l1_telemetry_decoder_cc_sptr
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sbas_l1_make_telemetry_decoder_cc(const Gnss_Satellite &satellite, bool dump);
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/*!
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* \brief This class implements a block that decodes the SBAS integrity and corrections data defined in RTCA MOPS DO-229
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*
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*/
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class sbas_l1_telemetry_decoder_cc : public gr::block
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{
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public:
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~sbas_l1_telemetry_decoder_cc();
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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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/*!
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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);
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private:
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friend sbas_l1_telemetry_decoder_cc_sptr
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sbas_l1_make_telemetry_decoder_cc(const Gnss_Satellite &satellite, bool dump);
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sbas_l1_telemetry_decoder_cc(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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~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;
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double d_iir_par;
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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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~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;
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Viterbi_Decoder *d_vd1;
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Viterbi_Decoder *d_vd2;
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double d_past_symbol;
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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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#endif
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