/*!
 * \file kf_vtl_tracking.cc
 * \brief Implementation of a Kalman filter based tracking with optional Vector
 * Tracking Loop message receiver block.
 * \author Javier Arribas, 2020. jarribas(at)cttc.es
 *
 * -----------------------------------------------------------------------------
 *
 * Copyright (C) 2010-2020  (see AUTHORS file for a list of contributors)
 *
 * GNSS-SDR is a software defined Global Navigation
 *          Satellite Systems receiver
 *
 * This file is part of GNSS-SDR.
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * -----------------------------------------------------------------------------
 */

#include "kf_vtl_tracking.h"
#include "Beidou_B1I.h"
#include "Beidou_B3I.h"
#include "GPS_L1_CA.h"
#include "GPS_L2C.h"
#include "GPS_L5.h"
#include "Galileo_E1.h"
#include "Galileo_E5a.h"
#include "Galileo_E5b.h"
#include "MATH_CONSTANTS.h"
#include "beidou_b1i_signal_replica.h"
#include "beidou_b3i_signal_replica.h"
#include "galileo_e1_signal_replica.h"
#include "galileo_e5_signal_replica.h"
#include "galileo_e6_signal_replica.h"
#include "gnss_satellite.h"
#include "gnss_sdr_create_directory.h"
#include "gnss_synchro.h"
#include "gps_l2c_signal_replica.h"
#include "gps_l5_signal_replica.h"
#include "gps_sdr_signal_replica.h"
#include "lock_detectors.h"
#include "tracking_discriminators.h"
#include "trackingcmd.h"
#include <glog/logging.h>
#include <gnuradio/io_signature.h>   // for io_signature
#include <gnuradio/thread/thread.h>  // for scoped_lock
#include <matio.h>                   // for Mat_VarCreate
#include <pmt/pmt_sugar.h>           // for mp
#include <volk_gnsssdr/volk_gnsssdr.h>
#include <algorithm>  // for fill_n
#include <array>
#include <cmath>      // for fmod, round, floor
#include <exception>  // for exception
#include <iostream>   // for cout, cerr
#include <map>
#include <numeric>
#include <vector>

#if HAS_GENERIC_LAMBDA
#else
#include <boost/bind/bind.hpp>
#endif

#if HAS_STD_FILESYSTEM
#if HAS_STD_FILESYSTEM_EXPERIMENTAL
#include <experimental/filesystem>
namespace fs = std::experimental::filesystem;
#else
#include <filesystem>
namespace fs = std::filesystem;
#endif
#else
#include <boost/filesystem/path.hpp>
namespace fs = boost::filesystem;
#endif


kf_vtl_tracking_sptr kf_vtl_make_tracking(const Kf_Conf &conf_)
{
    return kf_vtl_tracking_sptr(new kf_vtl_tracking(conf_));
}


kf_vtl_tracking::kf_vtl_tracking(const Kf_Conf &conf_)
    : gr::block("kf_vtl_tracking", gr::io_signature::make(1, 1, sizeof(gr_complex)),
          gr::io_signature::make(1, 1, sizeof(Gnss_Synchro)))
{
    // prevent telemetry symbols accumulation in output buffers
    this->set_max_noutput_items(1);
    d_trk_parameters = conf_;
    // Telemetry bit synchronization message port input
    this->message_port_register_out(pmt::mp("events"));
    this->set_relative_rate(1.0 / static_cast<double>(d_trk_parameters.vector_length));

    // Telemetry message port input
    this->message_port_register_in(pmt::mp("telemetry_to_trk"));
    this->set_msg_handler(
        pmt::mp("telemetry_to_trk"),
#if HAS_GENERIC_LAMBDA
        [this](auto &&PH1) { msg_handler_telemetry_to_trk(PH1); });
#else
#if USE_BOOST_BIND_PLACEHOLDERS
        boost::bind(&kf_vtl_tracking::msg_handler_telemetry_to_trk, this, boost::placeholders::_1));
#else
        boost::bind(&kf_vtl_tracking::msg_handler_telemetry_to_trk, this, _1));
#endif
#endif

    // PVT message port input
    this->message_port_register_in(pmt::mp("pvt_to_trk"));
    this->set_msg_handler(
        pmt::mp("pvt_to_trk"),
#if HAS_GENERIC_LAMBDA
        [this](auto &&PH1) { msg_handler_pvt_to_trk(PH1); });
#else
#if USE_BOOST_BIND_PLACEHOLDERS
        boost::bind(&kf_vtl_tracking::msg_handler_pvt_to_trk, this, boost::placeholders::_1));
#else
        boost::bind(&kf_vtl_tracking::msg_handler_pvt_to_trk, this, _1));
#endif
#endif

    // initialize internal vars
    d_veml = false;
    d_cloop = true;
    d_pull_in_transitory = true;
    d_code_chip_rate = 0.0;
    d_secondary_code_length = 0U;
    d_data_secondary_code_length = 0U;
    d_preamble_length_symbols = 0;
    d_interchange_iq = false;
    d_signal_type = std::string(d_trk_parameters.signal);

    std::map<std::string, std::string> map_signal_pretty_name;
    map_signal_pretty_name["1C"] = "L1 C/A";
    map_signal_pretty_name["1B"] = "E1";
    map_signal_pretty_name["1G"] = "L1 C/A";
    map_signal_pretty_name["2S"] = "L2C";
    map_signal_pretty_name["2G"] = "L2 C/A";
    map_signal_pretty_name["5X"] = "E5a";
    map_signal_pretty_name["7X"] = "E5b";
    map_signal_pretty_name["L5"] = "L5";
    map_signal_pretty_name["B1"] = "B1I";
    map_signal_pretty_name["B3"] = "B3I";

    d_signal_pretty_name = map_signal_pretty_name[d_signal_type];

    if (d_trk_parameters.system == 'G')
        {
            d_systemName = "GPS";
            if (d_signal_type == "1C")
                {
                    d_signal_carrier_freq = GPS_L1_FREQ_HZ;
                    d_code_period = GPS_L1_CA_CODE_PERIOD_S;
                    d_code_chip_rate = GPS_L1_CA_CODE_RATE_CPS;
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_code_length_chips = static_cast<int32_t>(GPS_L1_CA_CODE_LENGTH_CHIPS);
                    // GPS L1 C/A does not have pilot component nor secondary code
                    d_secondary = false;
                    d_trk_parameters.track_pilot = false;
                    d_trk_parameters.slope = 1.0;
                    d_trk_parameters.spc = d_trk_parameters.early_late_space_chips;
                    d_trk_parameters.y_intercept = 1.0;
                    // symbol integration: 20 trk symbols (20 ms) = 1 tlm bit
                    // set the preamble in the secondary code acquisition to obtain tlm symbol synchronization
                    d_secondary_code_length = static_cast<uint32_t>(GPS_CA_PREAMBLE_LENGTH_SYMBOLS);
                    d_secondary_code_string = GPS_CA_PREAMBLE_SYMBOLS_STR;
                    d_symbols_per_bit = GPS_CA_TELEMETRY_SYMBOLS_PER_BIT;
                }
            else if (d_signal_type == "2S")
                {
                    d_signal_carrier_freq = GPS_L2_FREQ_HZ;
                    d_code_period = GPS_L2_M_PERIOD_S;
                    d_code_chip_rate = GPS_L2_M_CODE_RATE_CPS;
                    d_code_length_chips = static_cast<int32_t>(GPS_L2_M_CODE_LENGTH_CHIPS);
                    // GPS L2C has 1 trk symbol (20 ms) per tlm bit, no symbol integration required
                    d_symbols_per_bit = GPS_L2_SAMPLES_PER_SYMBOL;
                    d_correlation_length_ms = 20;
                    d_code_samples_per_chip = 1;
                    // GPS L2 does not have pilot component nor secondary code
                    d_secondary = false;
                    d_trk_parameters.track_pilot = false;
                    d_trk_parameters.slope = 1.0;
                    d_trk_parameters.spc = d_trk_parameters.early_late_space_chips;
                    d_trk_parameters.y_intercept = 1.0;
                }
            else if (d_signal_type == "L5")
                {
                    d_signal_carrier_freq = GPS_L5_FREQ_HZ;
                    d_code_period = GPS_L5I_PERIOD_S;
                    d_code_chip_rate = GPS_L5I_CODE_RATE_CPS;
                    // symbol integration: 10 trk symbols (10 ms) = 1 tlm bit
                    d_symbols_per_bit = GPS_L5_SAMPLES_PER_SYMBOL;
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_code_length_chips = static_cast<int32_t>(GPS_L5I_CODE_LENGTH_CHIPS);
                    d_secondary = true;
                    d_trk_parameters.slope = 1.0;
                    d_trk_parameters.spc = d_trk_parameters.early_late_space_chips;
                    d_trk_parameters.y_intercept = 1.0;
                    if (d_trk_parameters.track_pilot)
                        {
                            // synchronize pilot secondary code
                            d_secondary_code_length = static_cast<uint32_t>(GPS_L5Q_NH_CODE_LENGTH);
                            d_secondary_code_string = GPS_L5Q_NH_CODE_STR;
                            // remove data secondary code
                            // remove Neuman-Hofman Code (see IS-GPS-705D)
                            d_data_secondary_code_length = static_cast<uint32_t>(GPS_L5I_NH_CODE_LENGTH);
                            d_data_secondary_code_string = GPS_L5I_NH_CODE_STR;
                            d_signal_pretty_name = d_signal_pretty_name + "Q";
                        }
                    else
                        {
                            // synchronize and remove data secondary code
                            // remove Neuman-Hofman Code (see IS-GPS-705D)
                            d_secondary_code_length = static_cast<uint32_t>(GPS_L5I_NH_CODE_LENGTH);
                            d_secondary_code_string = GPS_L5I_NH_CODE_STR;
                            d_signal_pretty_name = d_signal_pretty_name + "I";
                            d_interchange_iq = true;
                        }
                }
            else
                {
                    LOG(WARNING) << "Invalid Signal argument when instantiating tracking blocks";
                    std::cerr << "Invalid Signal argument when instantiating tracking blocks\n";
                    d_correlation_length_ms = 1;
                    d_secondary = false;
                    d_signal_carrier_freq = 0.0;
                    d_code_period = 0.0;
                    d_code_length_chips = 0;
                    d_code_samples_per_chip = 0U;
                    d_symbols_per_bit = 0;
                }
        }
    else if (d_trk_parameters.system == 'E')
        {
            d_systemName = "Galileo";
            if (d_signal_type == "1B")
                {
                    d_signal_carrier_freq = GALILEO_E1_FREQ_HZ;
                    d_code_period = GALILEO_E1_CODE_PERIOD_S;
                    d_code_chip_rate = GALILEO_E1_CODE_CHIP_RATE_CPS;
                    d_code_length_chips = static_cast<int32_t>(GALILEO_E1_B_CODE_LENGTH_CHIPS);
                    // Galileo E1b has 1 trk symbol (4 ms) per tlm bit, no symbol integration required
                    d_symbols_per_bit = 1;
                    d_correlation_length_ms = 4;
                    d_code_samples_per_chip = 2;  // CBOC disabled: 2 samples per chip. CBOC enabled: 12 samples per chip
                    d_veml = true;
                    d_trk_parameters.spc = d_trk_parameters.early_late_space_chips;
                    d_trk_parameters.slope = static_cast<float>(-CalculateSlopeAbs(&SinBocCorrelationFunction<1, 1>, d_trk_parameters.spc));
                    d_trk_parameters.y_intercept = static_cast<float>(GetYInterceptAbs(&SinBocCorrelationFunction<1, 1>, d_trk_parameters.spc));
                    if (d_trk_parameters.track_pilot)
                        {
                            d_secondary = true;
                            d_secondary_code_length = static_cast<uint32_t>(GALILEO_E1_C_SECONDARY_CODE_LENGTH);
                            d_secondary_code_string = GALILEO_E1_C_SECONDARY_CODE;
                            d_signal_pretty_name = d_signal_pretty_name + "C";
                        }
                    else
                        {
                            d_secondary = false;
                            d_signal_pretty_name = d_signal_pretty_name + "B";
                        }
                    // Note that E1-B and E1-C are in anti-phase, NOT IN QUADRATURE. See Galileo ICD.
                }
            else if (d_signal_type == "5X")
                {
                    d_signal_carrier_freq = GALILEO_E5A_FREQ_HZ;
                    d_code_period = GALILEO_E5A_CODE_PERIOD_S;
                    d_code_chip_rate = GALILEO_E5A_CODE_CHIP_RATE_CPS;
                    d_symbols_per_bit = 20;
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_code_length_chips = static_cast<int32_t>(GALILEO_E5A_CODE_LENGTH_CHIPS);
                    d_secondary = true;
                    d_trk_parameters.slope = 1.0;
                    d_trk_parameters.spc = d_trk_parameters.early_late_space_chips;
                    d_trk_parameters.y_intercept = 1.0;
                    if (d_trk_parameters.track_pilot)
                        {
                            // synchronize pilot secondary code
                            d_secondary_code_length = static_cast<uint32_t>(GALILEO_E5A_Q_SECONDARY_CODE_LENGTH);
                            d_signal_pretty_name = d_signal_pretty_name + "Q";
                            // remove data secondary code
                            d_data_secondary_code_length = static_cast<uint32_t>(GALILEO_E5A_I_SECONDARY_CODE_LENGTH);
                            d_data_secondary_code_string = GALILEO_E5A_I_SECONDARY_CODE;
                        }
                    else
                        {
                            // synchronize and remove data secondary code
                            d_secondary_code_length = static_cast<uint32_t>(GALILEO_E5A_I_SECONDARY_CODE_LENGTH);
                            d_secondary_code_string = GALILEO_E5A_I_SECONDARY_CODE;
                            d_signal_pretty_name = d_signal_pretty_name + "I";
                            d_interchange_iq = true;
                        }
                }
            else if (d_signal_type == "7X")
                {
                    d_signal_carrier_freq = GALILEO_E5B_FREQ_HZ;
                    d_code_period = GALILEO_E5B_CODE_PERIOD_S;
                    d_code_chip_rate = GALILEO_E5B_CODE_CHIP_RATE_CPS;
                    d_symbols_per_bit = 4;
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_code_length_chips = static_cast<int32_t>(GALILEO_E5B_CODE_LENGTH_CHIPS);
                    d_secondary = true;
                    d_trk_parameters.slope = 1.0;
                    d_trk_parameters.spc = d_trk_parameters.early_late_space_chips;
                    d_trk_parameters.y_intercept = 1.0;
                    if (d_trk_parameters.track_pilot)
                        {
                            // synchronize pilot secondary code
                            d_secondary_code_length = static_cast<uint32_t>(GALILEO_E5B_Q_SECONDARY_CODE_LENGTH);
                            d_signal_pretty_name = d_signal_pretty_name + "Q";
                            // remove data secondary code
                            d_data_secondary_code_length = static_cast<uint32_t>(GALILEO_E5B_I_SECONDARY_CODE_LENGTH);
                            d_data_secondary_code_string = GALILEO_E5B_I_SECONDARY_CODE;
                        }
                    else
                        {
                            // synchronize and remove data secondary code
                            d_secondary_code_length = static_cast<uint32_t>(GALILEO_E5B_I_SECONDARY_CODE_LENGTH);
                            d_secondary_code_string = GALILEO_E5B_I_SECONDARY_CODE;
                            d_signal_pretty_name = d_signal_pretty_name + "I";
                            d_interchange_iq = true;
                        }
                }
            else
                {
                    LOG(WARNING) << "Invalid Signal argument when instantiating tracking blocks";
                    std::cout << "Invalid Signal argument when instantiating tracking blocks\n";
                    d_correlation_length_ms = 1;
                    d_secondary = false;
                    d_signal_carrier_freq = 0.0;
                    d_code_period = 0.0;
                    d_code_length_chips = 0;
                    d_code_samples_per_chip = 0U;
                    d_symbols_per_bit = 0;
                }
        }
    else if (d_trk_parameters.system == 'C')
        {
            d_systemName = "Beidou";
            if (d_signal_type == "B1")
                {
                    // GEO Satellites use different secondary code
                    d_signal_carrier_freq = BEIDOU_B1I_FREQ_HZ;
                    d_code_period = BEIDOU_B1I_CODE_PERIOD_S;
                    d_code_chip_rate = BEIDOU_B1I_CODE_RATE_CPS;
                    d_code_length_chips = static_cast<int32_t>(BEIDOU_B1I_CODE_LENGTH_CHIPS);
                    d_symbols_per_bit = BEIDOU_B1I_TELEMETRY_SYMBOLS_PER_BIT;  // todo: enable after fixing beidou symbol synchronization
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_secondary = true;
                    d_trk_parameters.track_pilot = false;
                    d_trk_parameters.slope = 1.0;
                    d_trk_parameters.spc = d_trk_parameters.early_late_space_chips;
                    d_trk_parameters.y_intercept = 1.0;
                    // synchronize and remove data secondary code
                    d_secondary_code_length = static_cast<uint32_t>(BEIDOU_B1I_SECONDARY_CODE_LENGTH);
                    d_secondary_code_string = BEIDOU_B1I_SECONDARY_CODE_STR;
                    d_data_secondary_code_length = static_cast<uint32_t>(BEIDOU_B1I_SECONDARY_CODE_LENGTH);
                    d_data_secondary_code_string = BEIDOU_B1I_SECONDARY_CODE_STR;
                }
            else if (d_signal_type == "B3")
                {
                    // GEO Satellites use different secondary code
                    d_signal_carrier_freq = BEIDOU_B3I_FREQ_HZ;
                    d_code_period = BEIDOU_B3I_CODE_PERIOD_S;
                    d_code_chip_rate = BEIDOU_B3I_CODE_RATE_CPS;
                    d_code_length_chips = static_cast<int32_t>(BEIDOU_B3I_CODE_LENGTH_CHIPS);
                    d_symbols_per_bit = BEIDOU_B3I_TELEMETRY_SYMBOLS_PER_BIT;  // todo: enable after fixing beidou symbol synchronization
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_secondary = false;
                    d_trk_parameters.track_pilot = false;
                    d_trk_parameters.slope = 1.0;
                    d_trk_parameters.spc = d_trk_parameters.early_late_space_chips;
                    d_trk_parameters.y_intercept = 1.0;
                    d_secondary_code_length = static_cast<uint32_t>(BEIDOU_B3I_SECONDARY_CODE_LENGTH);
                    d_secondary_code_string = BEIDOU_B3I_SECONDARY_CODE_STR;
                    d_data_secondary_code_length = static_cast<uint32_t>(BEIDOU_B3I_SECONDARY_CODE_LENGTH);
                    d_data_secondary_code_string = BEIDOU_B3I_SECONDARY_CODE_STR;
                }
            else
                {
                    LOG(WARNING) << "Invalid Signal argument when instantiating tracking blocks";
                    std::cout << "Invalid Signal argument when instantiating tracking blocks\n";
                    d_correlation_length_ms = 1;
                    d_secondary = false;
                    d_signal_carrier_freq = 0.0;
                    d_code_period = 0.0;
                    d_code_length_chips = 0;
                    d_code_samples_per_chip = 0;
                    d_symbols_per_bit = 0;
                }
        }
    else
        {
            LOG(WARNING) << "Invalid System argument when instantiating tracking blocks";
            std::cerr << "Invalid System argument when instantiating tracking blocks\n";
            d_correlation_length_ms = 1;
            d_secondary = false;
            d_signal_carrier_freq = 0.0;
            d_code_period = 0.0;
            d_code_length_chips = 0;
            d_code_samples_per_chip = 0U;
            d_symbols_per_bit = 0;
        }
    d_T_chip_seconds = 0.0;
    d_T_prn_seconds = 0.0;
    d_T_prn_samples = 0.0;
    d_K_blk_samples = 0.0;

    // Initialize tracking  ==========================================

    // Initialization of local code replica
    // Get space for a vector with the sinboc(1,1) replica sampled 2x/chip
    d_tracking_code.resize(2 * d_code_length_chips, 0.0);
    // correlator outputs (scalar)
    if (d_veml)
        {
            // Very-Early, Early, Prompt, Late, Very-Late
            d_n_correlator_taps = 5;
        }
    else
        {
            // Early, Prompt, Late
            d_n_correlator_taps = 3;
        }

    d_correlator_outs.reserve(d_n_correlator_taps);
    d_local_code_shift_chips.reserve(d_n_correlator_taps);
    // map memory pointers of correlator outputs
    if (d_veml)
        {
            d_Very_Early = &d_correlator_outs[0];
            d_Early = &d_correlator_outs[1];
            d_Prompt = &d_correlator_outs[2];
            d_Late = &d_correlator_outs[3];
            d_Very_Late = &d_correlator_outs[4];
            d_local_code_shift_chips[0] = -d_trk_parameters.very_early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_local_code_shift_chips[1] = -d_trk_parameters.early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_local_code_shift_chips[2] = 0.0;
            d_local_code_shift_chips[3] = d_trk_parameters.early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_local_code_shift_chips[4] = d_trk_parameters.very_early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_prompt_data_shift = &d_local_code_shift_chips[2];
        }
    else
        {
            d_Very_Early = nullptr;
            d_Early = &d_correlator_outs[0];
            d_Prompt = &d_correlator_outs[1];
            d_Late = &d_correlator_outs[2];
            d_Very_Late = nullptr;
            d_local_code_shift_chips[0] = -d_trk_parameters.early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_local_code_shift_chips[1] = 0.0;
            d_local_code_shift_chips[2] = d_trk_parameters.early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_prompt_data_shift = &d_local_code_shift_chips[1];
        }

    d_multicorrelator_cpu.init(static_cast<int>(2 * d_trk_parameters.vector_length), d_n_correlator_taps);

    if (d_trk_parameters.extend_correlation_symbols > 1)
        {
            d_enable_extended_integration = true;
        }
    else
        {
            d_enable_extended_integration = false;
            d_trk_parameters.extend_correlation_symbols = 1;
        }

    // Enable Data component prompt correlator (slave to Pilot prompt) if tracking uses Pilot signal
    if (d_trk_parameters.track_pilot)
        {
            // Extra correlator for the data component
            d_correlator_data_cpu.init(static_cast<int>(2 * d_trk_parameters.vector_length), 1);
            d_correlator_data_cpu.set_high_dynamics_resampler(d_trk_parameters.high_dyn);
            d_data_code.resize(2 * d_code_length_chips, 0.0);
        }

    // --- Initializations ---
    d_Prompt_circular_buffer.set_capacity(d_secondary_code_length);
    d_multicorrelator_cpu.set_high_dynamics_resampler(d_trk_parameters.high_dyn);
    // Initial code frequency basis of NCO
    d_code_freq_kf_chips_s = d_code_chip_rate;
    // Residual code phase (in chips)
    d_rem_code_phase_samples = 0.0;
    // Residual carrier phase
    d_rem_carr_phase_rad = 0.0;

    // sample synchronization
    d_sample_counter = 0ULL;
    d_acq_sample_stamp = 0ULL;

    d_current_prn_length_samples = static_cast<int32_t>(d_trk_parameters.vector_length);
    d_current_correlation_time_s = 0.0;

    d_carr_phase_error_disc_hz = 0.0;
    d_code_error_disc_chips = 0.0;
    d_code_error_kf_chips = 0.0;
    d_code_freq_kf_chips_s = 0.0;

    // CN0 estimation and lock detector buffers
    d_cn0_estimation_counter = 0;
    d_Prompt_buffer.reserve(d_trk_parameters.cn0_samples);
    d_carrier_lock_test = 1.0;
    d_CN0_SNV_dB_Hz = 0.0;
    d_carrier_lock_fail_counter = 0;
    d_code_lock_fail_counter = 0;
    d_carrier_lock_threshold = d_trk_parameters.carrier_lock_th;
    d_Prompt_Data.reserve(1);
    d_cn0_smoother = Exponential_Smoother();
    d_cn0_smoother.set_alpha(d_trk_parameters.cn0_smoother_alpha);

    if (d_code_period > 0.0)
        {
            d_cn0_smoother.set_samples_for_initialization(d_trk_parameters.cn0_smoother_samples / static_cast<int>(d_code_period * 1000.0));
        }

    d_carrier_lock_test_smoother = Exponential_Smoother();
    d_carrier_lock_test_smoother.set_alpha(d_trk_parameters.carrier_lock_test_smoother_alpha);
    d_carrier_lock_test_smoother.set_min_value(-1.0);
    d_carrier_lock_test_smoother.set_offset(0.0);
    d_carrier_lock_test_smoother.set_samples_for_initialization(d_trk_parameters.carrier_lock_test_smoother_samples);

    d_acquisition_gnss_synchro = nullptr;
    d_channel = 0;
    d_acq_code_phase_samples = 0.0;
    d_acq_carrier_doppler_hz = 0.0;
    d_carrier_phase_kf_rad = 0;
    d_carrier_doppler_kf_hz = 0.0;
    d_carrier_doppler_rate_kf_hz_s = 0.0;
    d_acc_carrier_phase_rad = 0.0;

    d_extend_correlation_symbols_count = 0;
    d_code_phase_step_chips = 0.0;
    d_code_phase_rate_step_chips = 0.0;
    d_carrier_phase_step_rad = 0.0;
    d_carrier_phase_rate_step_rad = 0.0;
    d_rem_code_phase_chips = 0.0;
    d_state = 0;  // initial state: standby
    clear_tracking_vars();

    d_dump = d_trk_parameters.dump;
    d_dump_mat = d_trk_parameters.dump_mat and d_dump;
    if (d_dump)
        {
            d_dump_filename = d_trk_parameters.dump_filename;
            std::string dump_path;
            // Get path
            if (d_dump_filename.find_last_of('/') != std::string::npos)
                {
                    std::string dump_filename_ = d_dump_filename.substr(d_dump_filename.find_last_of('/') + 1);
                    dump_path = d_dump_filename.substr(0, d_dump_filename.find_last_of('/'));
                    d_dump_filename = dump_filename_;
                }
            else
                {
                    dump_path = std::string(".");
                }
            if (d_dump_filename.empty())
                {
                    d_dump_filename = "trk_channel_";
                }
            // remove extension if any
            if (d_dump_filename.substr(1).find_last_of('.') != std::string::npos)
                {
                    d_dump_filename = d_dump_filename.substr(0, d_dump_filename.find_last_of('.'));
                }

            d_dump_filename = dump_path + fs::path::preferred_separator + d_dump_filename;
            // create directory
            if (!gnss_sdr_create_directory(dump_path))
                {
                    std::cerr << "GNSS-SDR cannot create dump files for the tracking block. Wrong permissions?\n";
                    d_dump = false;
                }
        }
    d_corrected_doppler = false;
    d_acc_carrier_phase_initialized = false;
}


void kf_vtl_tracking::forecast(int noutput_items,
    gr_vector_int &ninput_items_required)
{
    if (noutput_items != 0)
        {
            ninput_items_required[0] = static_cast<int32_t>(d_trk_parameters.vector_length) * 2;
        }
}


void kf_vtl_tracking::msg_handler_telemetry_to_trk(const pmt::pmt_t &msg)
{
    try
        {
            if (pmt::any_ref(msg).type().hash_code() == d_int_type_hash_code)
                {
                    const int tlm_event = boost::any_cast<int>(pmt::any_ref(msg));
                    if (tlm_event == 1)
                        {
                            DLOG(INFO) << "Telemetry fault received in ch " << this->d_channel;
                            gr::thread::scoped_lock lock(d_setlock);
                            d_carrier_lock_fail_counter = 200000;  // force loss-of-lock condition
                        }
                }
        }
    catch (const boost::bad_any_cast &e)
        {
            LOG(WARNING) << "msg_handler_telemetry_to_trk Bad any_cast: " << e.what();
        }
}


void kf_vtl_tracking::msg_handler_pvt_to_trk(const pmt::pmt_t &msg)
{
    try
        {
            if (pmt::any_ref(msg).type().hash_code() == typeid(const std::shared_ptr<TrackingCmd>).hash_code())
                {
                    const auto cmd = boost::any_cast<const std::shared_ptr<TrackingCmd>>(pmt::any_ref(msg));
                    //                    std::cout << "RX pvt-to-trk cmd with delay: "
                    //                              << static_cast<double>(nitems_read(0) - cmd->sample_counter) / d_trk_parameters.fs_in << " [s]\n";
                }
            else
                {
                    std::cout << "hash code not match\n";
                }
        }
    catch (const boost::bad_any_cast &e)
        {
            LOG(WARNING) << "msg_handler_pvt_to_trk Bad any_cast: " << e.what();
        }
}


void kf_vtl_tracking::start_tracking()
{
    gr::thread::scoped_lock l(d_setlock);
    // correct the code phase according to the delay between acq and trk
    d_acq_code_phase_samples = d_acquisition_gnss_synchro->Acq_delay_samples;
    d_acq_carrier_doppler_hz = d_acquisition_gnss_synchro->Acq_doppler_hz;
    d_acq_sample_stamp = d_acquisition_gnss_synchro->Acq_samplestamp_samples;

    d_carrier_doppler_kf_hz = d_acq_carrier_doppler_hz;
    d_carrier_phase_step_rad = TWO_PI * d_carrier_doppler_kf_hz / d_trk_parameters.fs_in;
    d_carrier_phase_rate_step_rad = 0.0;
    std::array<char, 3> Signal_{};
    Signal_[0] = d_acquisition_gnss_synchro->Signal[0];
    Signal_[1] = d_acquisition_gnss_synchro->Signal[1];
    Signal_[2] = d_acquisition_gnss_synchro->Signal[2];

    if (d_systemName == "GPS" and d_signal_type == "1C")
        {
            gps_l1_ca_code_gen_float(d_tracking_code, d_acquisition_gnss_synchro->PRN, 0);
        }
    else if (d_systemName == "GPS" and d_signal_type == "2S")
        {
            gps_l2c_m_code_gen_float(d_tracking_code, d_acquisition_gnss_synchro->PRN);
        }
    else if (d_systemName == "GPS" and d_signal_type == "L5")
        {
            if (d_trk_parameters.track_pilot)
                {
                    gps_l5q_code_gen_float(d_tracking_code, d_acquisition_gnss_synchro->PRN);
                    gps_l5i_code_gen_float(d_data_code, d_acquisition_gnss_synchro->PRN);
                    d_Prompt_Data[0] = gr_complex(0.0, 0.0);
                    d_correlator_data_cpu.set_local_code_and_taps(d_code_length_chips, d_data_code.data(), d_prompt_data_shift);
                }
            else
                {
                    gps_l5i_code_gen_float(d_tracking_code, d_acquisition_gnss_synchro->PRN);
                }
        }
    else if (d_systemName == "Galileo" and d_signal_type == "1B")
        {
            if (d_trk_parameters.track_pilot)
                {
                    const std::array<char, 3> pilot_signal = {{'1', 'C', '\0'}};
                    galileo_e1_code_gen_sinboc11_float(d_tracking_code, pilot_signal, d_acquisition_gnss_synchro->PRN);
                    galileo_e1_code_gen_sinboc11_float(d_data_code, Signal_, d_acquisition_gnss_synchro->PRN);
                    d_Prompt_Data[0] = gr_complex(0.0, 0.0);
                    d_correlator_data_cpu.set_local_code_and_taps(d_code_samples_per_chip * d_code_length_chips, d_data_code.data(), d_prompt_data_shift);
                }
            else
                {
                    galileo_e1_code_gen_sinboc11_float(d_tracking_code, Signal_, d_acquisition_gnss_synchro->PRN);
                }
        }
    else if (d_systemName == "Galileo" and d_signal_type == "5X")
        {
            volk_gnsssdr::vector<gr_complex> aux_code(d_code_length_chips);
            const std::array<char, 3> signal_type_ = {{'5', 'X', '\0'}};
            galileo_e5_a_code_gen_complex_primary(aux_code, d_acquisition_gnss_synchro->PRN, signal_type_);
            if (d_trk_parameters.track_pilot)
                {
                    d_secondary_code_string = GALILEO_E5A_Q_SECONDARY_CODE[d_acquisition_gnss_synchro->PRN - 1];
                    for (int32_t i = 0; i < d_code_length_chips; i++)
                        {
                            d_tracking_code[i] = aux_code[i].imag();
                            d_data_code[i] = aux_code[i].real();  // the same because it is generated the full signal (E5aI + E5aQ)
                        }
                    d_Prompt_Data[0] = gr_complex(0.0, 0.0);
                    d_correlator_data_cpu.set_local_code_and_taps(d_code_length_chips, d_data_code.data(), d_prompt_data_shift);
                }
            else
                {
                    for (int32_t i = 0; i < d_code_length_chips; i++)
                        {
                            d_tracking_code[i] = aux_code[i].real();
                        }
                }
        }
    else if (d_systemName == "Galileo" and d_signal_type == "7X")
        {
            volk_gnsssdr::vector<gr_complex> aux_code(d_code_length_chips);
            const std::array<char, 3> signal_type_ = {{'7', 'X', '\0'}};
            galileo_e5_b_code_gen_complex_primary(aux_code, d_acquisition_gnss_synchro->PRN, signal_type_);
            if (d_trk_parameters.track_pilot)
                {
                    d_secondary_code_string = GALILEO_E5B_Q_SECONDARY_CODE[d_acquisition_gnss_synchro->PRN - 1];
                    for (int32_t i = 0; i < d_code_length_chips; i++)
                        {
                            d_tracking_code[i] = aux_code[i].imag();
                            d_data_code[i] = aux_code[i].real();  // the same because it is generated the full signal (E5bI + E5bsQ)
                        }
                    d_Prompt_Data[0] = gr_complex(0.0, 0.0);
                    d_correlator_data_cpu.set_local_code_and_taps(d_code_length_chips, d_data_code.data(), d_prompt_data_shift);
                }
            else
                {
                    for (int32_t i = 0; i < d_code_length_chips; i++)
                        {
                            d_tracking_code[i] = aux_code[i].real();
                        }
                }
        }
    else if (d_systemName == "Beidou" and d_signal_type == "B1")
        {
            beidou_b1i_code_gen_float(d_tracking_code, d_acquisition_gnss_synchro->PRN, 0);
            // GEO Satellites use different secondary code
            if (d_acquisition_gnss_synchro->PRN > 0 and d_acquisition_gnss_synchro->PRN < 6)
                {
                    d_symbols_per_bit = BEIDOU_B1I_GEO_TELEMETRY_SYMBOLS_PER_BIT;  // todo: enable after fixing beidou symbol synchronization
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_secondary = false;
                    d_trk_parameters.track_pilot = false;
                    // set the preamble in the secondary code acquisition
                    d_secondary_code_length = static_cast<uint32_t>(BEIDOU_B1I_GEO_PREAMBLE_LENGTH_SYMBOLS);
                    d_secondary_code_string = BEIDOU_B1I_GEO_PREAMBLE_SYMBOLS_STR;
                    d_data_secondary_code_length = 0;
                    d_Prompt_circular_buffer.set_capacity(d_secondary_code_length);
                }
            else
                {
                    d_symbols_per_bit = BEIDOU_B1I_TELEMETRY_SYMBOLS_PER_BIT;  // todo: enable after fixing beidou symbol synchronization
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_secondary = true;
                    d_trk_parameters.track_pilot = false;
                    // synchronize and remove data secondary code
                    d_secondary_code_length = static_cast<uint32_t>(BEIDOU_B1I_SECONDARY_CODE_LENGTH);
                    d_secondary_code_string = BEIDOU_B1I_SECONDARY_CODE_STR;
                    d_data_secondary_code_length = static_cast<uint32_t>(BEIDOU_B1I_SECONDARY_CODE_LENGTH);
                    d_data_secondary_code_string = BEIDOU_B1I_SECONDARY_CODE_STR;
                    d_Prompt_circular_buffer.set_capacity(d_secondary_code_length);
                }
        }

    else if (d_systemName == "Beidou" and d_signal_type == "B3")
        {
            beidou_b3i_code_gen_float(d_tracking_code, d_acquisition_gnss_synchro->PRN, 0);
            // Update secondary code settings for geo satellites
            if (d_acquisition_gnss_synchro->PRN > 0 and d_acquisition_gnss_synchro->PRN < 6)
                {
                    d_symbols_per_bit = BEIDOU_B3I_GEO_TELEMETRY_SYMBOLS_PER_BIT;  // todo: enable after fixing beidou symbol synchronization
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_secondary = false;
                    d_trk_parameters.track_pilot = false;
                    // set the preamble in the secondary code acquisition
                    d_secondary_code_length = static_cast<uint32_t>(BEIDOU_B3I_GEO_PREAMBLE_LENGTH_SYMBOLS);
                    d_secondary_code_string = BEIDOU_B3I_GEO_PREAMBLE_SYMBOLS_STR;
                    d_data_secondary_code_length = 0;
                    d_Prompt_circular_buffer.set_capacity(d_secondary_code_length);
                }
            else
                {
                    d_symbols_per_bit = BEIDOU_B3I_TELEMETRY_SYMBOLS_PER_BIT;  // todo: enable after fixing beidou symbol synchronization
                    d_correlation_length_ms = 1;
                    d_code_samples_per_chip = 1;
                    d_secondary = true;
                    d_trk_parameters.track_pilot = false;
                    // synchronize and remove data secondary code
                    d_secondary_code_length = static_cast<uint32_t>(BEIDOU_B3I_SECONDARY_CODE_LENGTH);
                    d_secondary_code_string = BEIDOU_B3I_SECONDARY_CODE_STR;
                    d_data_secondary_code_length = static_cast<uint32_t>(BEIDOU_B3I_SECONDARY_CODE_LENGTH);
                    d_data_secondary_code_string = BEIDOU_B3I_SECONDARY_CODE_STR;
                    d_Prompt_circular_buffer.set_capacity(d_secondary_code_length);
                }
        }

    d_multicorrelator_cpu.set_local_code_and_taps(d_code_samples_per_chip * d_code_length_chips, d_tracking_code.data(), d_local_code_shift_chips.data());
    std::fill_n(d_correlator_outs.begin(), d_n_correlator_taps, gr_complex(0.0, 0.0));

    d_carrier_lock_fail_counter = 0;
    d_code_lock_fail_counter = 0;
    d_rem_code_phase_samples = 0.0;
    d_rem_carr_phase_rad = 0.0;
    d_rem_code_phase_chips = 0.0;
    d_acc_carrier_phase_rad = 0.0;
    d_cn0_estimation_counter = 0;
    d_carrier_lock_test = 1.0;
    d_CN0_SNV_dB_Hz = 0.0;

    if (d_veml)
        {
            d_local_code_shift_chips[0] = -d_trk_parameters.very_early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_local_code_shift_chips[1] = -d_trk_parameters.early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_local_code_shift_chips[3] = d_trk_parameters.early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_local_code_shift_chips[4] = d_trk_parameters.very_early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
        }
    else
        {
            d_local_code_shift_chips[0] = -d_trk_parameters.early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
            d_local_code_shift_chips[2] = d_trk_parameters.early_late_space_chips * static_cast<float>(d_code_samples_per_chip);
        }

    d_current_correlation_time_s = d_code_period;

    // Initialize tracking  ==========================================

    // DEBUG OUTPUT
    std::cout << "Tracking of " << d_systemName << " " << d_signal_pretty_name << " signal started on channel " << d_channel << " for satellite " << Gnss_Satellite(d_systemName, d_acquisition_gnss_synchro->PRN) << '\n';
    DLOG(INFO) << "Starting tracking of satellite " << Gnss_Satellite(d_systemName, d_acquisition_gnss_synchro->PRN) << " on channel " << d_channel;

    // enable tracking pull-in
    d_state = 1;
    d_cloop = true;
    d_pull_in_transitory = true;
    d_Prompt_circular_buffer.clear();
    d_corrected_doppler = false;
    d_acc_carrier_phase_initialized = false;
}


void kf_vtl_tracking::init_kf(double acq_code_phase_chips, double acq_doppler_hz)
{
    // Kalman Filter class variables
    const double Ti = d_correlation_length_ms * 0.001;
    // state vector: code_phase_chips, carrier_phase_rads, carrier_freq_hz,carrier_freq_rate_hz, code_freq_chips_s
    d_F = arma::mat(5, 5);
    d_F << 1 << 0 << 0 << 0 << Ti << arma::endr
        << 0 << 1 << 2.0 * GNSS_PI * Ti << GNSS_PI * (Ti * Ti) << 0 << arma::endr
        << 0 << 0 << 1 << Ti << 0 << arma::endr
        << 0 << 0 << 0 << 1 << 0 << arma::endr
        << 0 << 0 << 0 << 0 << 1 << arma::endr;

    const double B = d_code_chip_rate / d_signal_carrier_freq;  // carrier to code rate factor

    d_H = arma::mat(2, 5);
    d_H << 1 << 0 << -B * Ti / 2.0 << B * (Ti * Ti) / 6.0 << 0 << arma::endr
        << 0 << 1 << -GNSS_PI * Ti << GNSS_PI * (Ti * Ti) / 3.0 << 0 << arma::endr;

    // Phase noise variance
    // const double CN0_lin = pow(10.0, d_trk_parameters.expected_cn0_dbhz / 10.0);  // CN0 in Hz
    // const double N_periods = 1;  // Only 1 interval
    // const double Sigma2_Tau = 0.25 * (1.0 + 2.0 * CN0_lin * Ti) / (N_periods * pow(CN0_lin * Ti, 2.0)) * (1.0 + (1.0 + 2.0 * CN0_lin * Ti) / (pow(N_periods * (CN0_lin * Ti), 2.0)));
    // const double Sigma2_Phase = 1.0 / (2.0 * CN0_lin * Ti) * (1.0 + 1.0 / (2.0 * CN0_lin * Ti));

    // measurement covariance matrix (static)
    d_R = arma::mat(2, 2);
    //    d_R << Sigma2_Tau << 0 << arma::endr
    //      << 0 << Sigma2_Phase << arma::endr;

    d_R << pow(d_trk_parameters.code_disc_sd_chips, 2.0) << 0 << arma::endr
        << 0 << pow(d_trk_parameters.carrier_disc_sd_rads, 2.0) << arma::endr;

    // system covariance matrix (static)
    d_Q = arma::mat(5, 5);
    d_Q << pow(d_trk_parameters.code_phase_sd_chips, 2.0) << 0 << 0 << 0 << 0 << arma::endr
        << 0 << pow(d_trk_parameters.carrier_phase_sd_rad, 2.0) << 0 << 0 << 0 << arma::endr
        << 0 << 0 << pow(d_trk_parameters.carrier_freq_sd_hz, 2.0) << 0 << 0 << arma::endr
        << 0 << 0 << 0 << pow(d_trk_parameters.carrier_freq_rate_sd_hz_s, 2.0) << 0 << arma::endr
        << 0 << 0 << 0 << 0 << pow(d_trk_parameters.code_rate_sd_chips_s, 2.0) << arma::endr;

    // initial Kalman covariance matrix
    d_P_old_old = arma::mat(5, 5);

    d_P_old_old << pow(d_trk_parameters.init_code_phase_sd_chips, 2.0) << 0 << 0 << 0 << 0 << arma::endr
                << 0 << pow(d_trk_parameters.init_carrier_phase_sd_rad, 2.0) << 0 << 0 << 0 << arma::endr
                << 0 << 0 << pow(d_trk_parameters.init_carrier_freq_sd_hz, 2.0) << 0 << 0 << arma::endr
                << 0 << 0 << 0 << pow(d_trk_parameters.init_carrier_freq_rate_sd_hz_s, 2.0) << 0 << arma::endr
                << 0 << 0 << 0 << 0 << pow(d_trk_parameters.init_code_rate_sd_chips_s, 2.0) << arma::endr;

    // init state vector
    d_x_old_old = arma::vec(5);
    // states: code_phase_chips, carrier_phase_rads, carrier_freq_hz, carrier_freq_rate_hz_s, code_freq_rate_chips_s
    d_x_old_old << acq_code_phase_chips << 0 << acq_doppler_hz << 0 << 0 << arma::endr;

    //    std::cout << "F: " << d_F << "\n";
    //    std::cout << "H: " << d_H << "\n";
    //    std::cout << "R: " << d_R << "\n";
    //    std::cout << "Q: " << d_Q << "\n";
    //    std::cout << "P: " << d_P_old_old << "\n";
    //    std::cout << "x: " << d_x_old_old << "\n";
}


void kf_vtl_tracking::update_kf_narrow_integration_time()
{
    // Kalman Filter class variables
    const double Ti = d_current_correlation_time_s;

    // state vector: code_phase_chips, carrier_phase_rads, carrier_freq_hz,carrier_freq_rate_hz, code_freq_chips_s
    d_F << 1 << 0 << 0 << 0 << Ti << arma::endr
        << 0 << 1 << 2.0 * GNSS_PI * Ti << GNSS_PI * (Ti * Ti) << 0 << arma::endr
        << 0 << 0 << 1 << Ti << 0 << arma::endr
        << 0 << 0 << 0 << 1 << 0 << arma::endr
        << 0 << 0 << 0 << 0 << 1 << arma::endr;

    const double B = d_code_chip_rate / d_signal_carrier_freq;  // carrier to code rate factor

    d_H << 1 << 0 << -B * Ti / 2.0 << B * (Ti * Ti) / 6.0 << 0 << arma::endr
        << 0 << 1 << -GNSS_PI * Ti << GNSS_PI * (Ti * Ti) / 3.0 << 0 << arma::endr;

    // measurement covariance matrix (static)
    d_R << pow(d_trk_parameters.code_disc_sd_chips, 2.0) << 0 << arma::endr
        << 0 << pow(d_trk_parameters.carrier_disc_sd_rads, 2.0) << arma::endr;

    // system covariance matrix (static)
    d_Q << pow(d_trk_parameters.narrow_code_phase_sd_chips, 2.0) << 0 << 0 << 0 << 0 << arma::endr
        << 0 << pow(d_trk_parameters.narrow_carrier_phase_sd_rad, 2.0) << 0 << 0 << 0 << arma::endr
        << 0 << 0 << pow(d_trk_parameters.narrow_carrier_freq_sd_hz, 2.0) << 0 << 0 << arma::endr
        << 0 << 0 << 0 << pow(d_trk_parameters.narrow_carrier_freq_rate_sd_hz_s, 2.0) << 0 << arma::endr
        << 0 << 0 << 0 << 0 << pow(d_trk_parameters.narrow_code_rate_sd_chips_s, 2.0) << arma::endr;
}


void kf_vtl_tracking::update_kf_cn0(double current_cn0_dbhz)
{
    // Kalman Filter class variables
    const double Ti = d_correlation_length_ms * 0.001;
    const double B = d_code_chip_rate / d_signal_carrier_freq;  // carrier to code rate factor

    d_H = arma::mat(2, 5);
    d_H << 1 << 0 << -B * Ti / 2.0 << B * (Ti * Ti) / 6.0 << 0 << arma::endr
        << 0 << 1 << -GNSS_PI * Ti << GNSS_PI * (Ti * Ti) / 3.0 << 0 << arma::endr;

    // Phase noise variance
    const double CN0_lin = pow(10.0, current_cn0_dbhz / 10.0);  // CN0 in Hz
    const double N_periods = 1;                                 // Only 1 interval
    const double Sigma2_Tau = 0.25 * (1.0 + 2.0 * CN0_lin * Ti) / (N_periods * pow(CN0_lin * Ti, 2.0)) * (1.0 + (1.0 + 2.0 * CN0_lin * Ti) / (pow(N_periods * (CN0_lin * Ti), 2.0)));
    const double Sigma2_Phase = 1.0 / (2.0 * CN0_lin * Ti) * (1.0 + 1.0 / (2.0 * CN0_lin * Ti));

    // measurement covariance matrix (static)
    d_R = arma::mat(2, 2);
    d_R << Sigma2_Tau << 0 << arma::endr
        << 0 << Sigma2_Phase << arma::endr;
}


kf_vtl_tracking::~kf_vtl_tracking()
{
    if (d_dump_file.is_open())
        {
            try
                {
                    d_dump_file.close();
                }
            catch (const std::exception &ex)
                {
                    LOG(WARNING) << "Exception in Tracking block destructor: " << ex.what();
                }
        }
    if (d_dump_mat)
        {
            try
                {
                    save_matfile();
                }
            catch (const std::exception &ex)
                {
                    LOG(WARNING) << "Error saving the .mat file: " << ex.what();
                }
        }
    try
        {
            if (d_trk_parameters.track_pilot)
                {
                    d_correlator_data_cpu.free();
                }
            d_multicorrelator_cpu.free();
        }
    catch (const std::exception &ex)
        {
            LOG(WARNING) << "Exception in Tracking block destructor: " << ex.what();
        }
}


bool kf_vtl_tracking::acquire_secondary()
{
    // ******* preamble correlation ********
    int32_t corr_value = 0;
    for (uint32_t i = 0; i < d_secondary_code_length; i++)
        {
            if (d_Prompt_circular_buffer[i].real() < 0.0)  // symbols clipping
                {
                    if (d_secondary_code_string[i] == '0')
                        {
                            corr_value++;
                        }
                    else
                        {
                            corr_value--;
                        }
                }
            else
                {
                    if (d_secondary_code_string[i] == '0')
                        {
                            corr_value--;
                        }
                    else
                        {
                            corr_value++;
                        }
                }
        }

    if (abs(corr_value) == static_cast<int32_t>(d_secondary_code_length))
        {
            return true;
        }

    return false;
}


bool kf_vtl_tracking::cn0_and_tracking_lock_status(double coh_integration_time_s)
{
    // ####### CN0 ESTIMATION AND LOCK DETECTORS ######
    if (d_cn0_estimation_counter < d_trk_parameters.cn0_samples)
        {
            // fill buffer with prompt correlator output values
            d_Prompt_buffer[d_cn0_estimation_counter] = d_P_accu;
            d_cn0_estimation_counter++;
            return true;
        }

    d_Prompt_buffer[d_cn0_estimation_counter % d_trk_parameters.cn0_samples] = d_P_accu;
    d_cn0_estimation_counter++;
    // Code lock indicator
    const float d_CN0_SNV_dB_Hz_raw = cn0_m2m4_estimator(d_Prompt_buffer.data(), d_trk_parameters.cn0_samples, static_cast<float>(coh_integration_time_s));
    d_CN0_SNV_dB_Hz = d_cn0_smoother.smooth(d_CN0_SNV_dB_Hz_raw);
    // Carrier lock indicator
    d_carrier_lock_test = d_carrier_lock_test_smoother.smooth(carrier_lock_detector(d_Prompt_buffer.data(), 1));
    // Loss of lock detection
    if (!d_pull_in_transitory)
        {
            if (d_carrier_lock_test < d_carrier_lock_threshold)
                {
                    d_carrier_lock_fail_counter++;
                }
            else
                {
                    if (d_carrier_lock_fail_counter > 0)
                        {
                            d_carrier_lock_fail_counter--;
                        }
                }

            if (d_CN0_SNV_dB_Hz < d_trk_parameters.cn0_min)
                {
                    d_code_lock_fail_counter++;
                }
            else
                {
                    if (d_code_lock_fail_counter > 0)
                        {
                            d_code_lock_fail_counter--;
                        }
                }
        }
    if (d_carrier_lock_fail_counter > d_trk_parameters.max_carrier_lock_fail or d_code_lock_fail_counter > d_trk_parameters.max_code_lock_fail)
        {
            std::cout << "Loss of lock in channel " << d_channel << "!\n";
            LOG(INFO) << "Loss of lock in channel " << d_channel
                      << " (carrier_lock_fail_counter:" << d_carrier_lock_fail_counter
                      << " code_lock_fail_counter : " << d_code_lock_fail_counter << ")";
            this->message_port_pub(pmt::mp("events"), pmt::from_long(3));  // 3 -> loss of lock
            d_carrier_lock_fail_counter = 0;
            d_code_lock_fail_counter = 0;
            return false;
        }
    return true;
}


// correlation requires:
// - updated remnant carrier phase in radians (rem_carr_phase_rad)
// - updated remnant code phase in samples (d_rem_code_phase_samples)
// - d_code_freq_chips
// - d_carrier_doppler_hz
void kf_vtl_tracking::do_correlation_step(const gr_complex *input_samples)
{
    // ################# CARRIER WIPEOFF AND CORRELATORS ##############################
    // perform carrier wipe-off and compute Early, Prompt and Late correlation
    d_multicorrelator_cpu.set_input_output_vectors(d_correlator_outs.data(), input_samples);
    d_multicorrelator_cpu.Carrier_wipeoff_multicorrelator_resampler(
        d_rem_carr_phase_rad,
        static_cast<float>(d_carrier_phase_step_rad), static_cast<float>(d_carrier_phase_rate_step_rad),
        static_cast<float>(d_rem_code_phase_chips) * static_cast<float>(d_code_samples_per_chip),
        static_cast<float>(d_code_phase_step_chips) * static_cast<float>(d_code_samples_per_chip),
        static_cast<float>(d_code_phase_rate_step_chips) * static_cast<float>(d_code_samples_per_chip),
        d_trk_parameters.vector_length);

    // DATA CORRELATOR (if tracking tracks the pilot signal)
    if (d_trk_parameters.track_pilot)
        {
            d_correlator_data_cpu.set_input_output_vectors(d_Prompt_Data.data(), input_samples);
            d_correlator_data_cpu.Carrier_wipeoff_multicorrelator_resampler(
                d_rem_carr_phase_rad,
                static_cast<float>(d_carrier_phase_step_rad), static_cast<float>(d_carrier_phase_rate_step_rad),
                static_cast<float>(d_rem_code_phase_chips) * static_cast<float>(d_code_samples_per_chip),
                static_cast<float>(d_code_phase_step_chips) * static_cast<float>(d_code_samples_per_chip),
                static_cast<float>(d_code_phase_rate_step_chips) * static_cast<float>(d_code_samples_per_chip),
                d_trk_parameters.vector_length);
        }
}


void kf_vtl_tracking::run_Kf()
{
    // Carrier discriminator
    if (d_cloop)
        {
            // Costas loop discriminator, insensitive to 180 deg phase transitions
            d_carr_phase_error_disc_hz = pll_cloop_two_quadrant_atan(d_P_accu) / TWO_PI;
        }
    else
        {
            // Secondary code acquired. No symbols transition should be present in the signal
            d_carr_phase_error_disc_hz = pll_four_quadrant_atan(d_P_accu) / TWO_PI;
        }

    // Code discriminator
    if (d_veml)
        {
            d_code_error_disc_chips = dll_nc_vemlp_normalized(d_VE_accu, d_E_accu, d_L_accu, d_VL_accu);  // [chips/Ti]
        }
    else
        {
            d_code_error_disc_chips = dll_nc_e_minus_l_normalized(d_E_accu, d_L_accu, d_trk_parameters.spc, d_trk_parameters.slope, d_trk_parameters.y_intercept);  // [chips/Ti]
        }

    // Kalman loop

    // Prediction
    d_x_new_old = d_F * d_x_old_old;
    d_P_new_old = d_F * d_P_old_old * d_F.t() + d_Q;

    // Innovation
    arma::vec z = {d_code_error_disc_chips, d_carr_phase_error_disc_hz * TWO_PI};

    // Measurement update
    arma::mat K = d_P_new_old * d_H.t() * arma::inv(d_H * d_P_new_old * d_H.t() + d_R);  // Kalman gain

    x_new_new = d_x_new_old + K * z;

    d_P_new_new = (arma::eye(5, 5) - K * d_H) * d_P_new_old;

    // new code phase estimation
    d_code_error_kf_chips = x_new_new(0);
    x_new_new(0) = 0;  // reset error estimation because the NCO corrects the code phase

    // new carrier phase estimation
    d_carrier_phase_kf_rad = x_new_new(1);

    // New carrier Doppler frequency estimation
    d_carrier_doppler_kf_hz = x_new_new(2);  // d_carrier_loop_filter.get_carrier_error(0, static_cast<float>(d_carr_phase_error_hz), static_cast<float>(d_current_correlation_time_s));

    d_carrier_doppler_rate_kf_hz_s = x_new_new(3);

    // std::cout << "d_carrier_doppler_hz: " << d_carrier_doppler_hz << '\n';
    // std::cout << "d_CN0_SNV_dB_Hz: " << this->d_CN0_SNV_dB_Hz << '\n';

    // New code Doppler frequency estimation
    if (d_trk_parameters.carrier_aiding)
        {
            // estimate the code rate exclusively based on the carrier Doppler
            d_code_freq_kf_chips_s = d_code_chip_rate + d_carrier_doppler_kf_hz * d_code_chip_rate / d_signal_carrier_freq;
        }
    else
        {
            // use its own KF code rate estimation
            d_code_freq_kf_chips_s -= x_new_new(4);
        }
    x_new_new(4) = 0;
    // Experimental: detect Carrier Doppler vs. Code Doppler incoherence and correct the Carrier Doppler
    //    if (d_trk_parameters.enable_doppler_correction == true)
    //        {
    //            if (d_pull_in_transitory == false and d_corrected_doppler == false)
    //                {
    // todo: alforithm here...
    //                }
    //        }

    // correct code and carrier phase
    d_rem_code_phase_samples += d_trk_parameters.fs_in * d_code_error_kf_chips / d_code_freq_kf_chips_s;
    d_rem_carr_phase_rad = d_carrier_phase_kf_rad;

    // prepare data for next KF epoch
    d_x_old_old = x_new_new;
    d_P_old_old = d_P_new_new;
}


void kf_vtl_tracking::check_carrier_phase_coherent_initialization()
{
    if (d_acc_carrier_phase_initialized == false)
        {
            d_acc_carrier_phase_rad = -d_rem_carr_phase_rad;
            d_acc_carrier_phase_initialized = true;
        }
}


void kf_vtl_tracking::clear_tracking_vars()
{
    std::fill_n(d_correlator_outs.begin(), d_n_correlator_taps, gr_complex(0.0, 0.0));
    if (d_trk_parameters.track_pilot)
        {
            d_Prompt_Data[0] = gr_complex(0.0, 0.0);
            d_P_data_accu = gr_complex(0.0, 0.0);
        }
    d_P_accu_old = gr_complex(0.0, 0.0);
    d_current_symbol = 0;
    d_current_data_symbol = 0;
    d_Prompt_circular_buffer.clear();
    d_carrier_phase_rate_step_rad = 0.0;
    d_code_phase_rate_step_chips = 0.0;
}


// todo: IT DOES NOT WORK WHEN NO KF IS RUNNING (extended correlation epochs!!)
void kf_vtl_tracking::update_tracking_vars()
{
    d_T_chip_seconds = 1.0 / d_code_freq_kf_chips_s;
    d_T_prn_seconds = d_T_chip_seconds * static_cast<double>(d_code_length_chips);

    // ################## CARRIER AND CODE NCO BUFFER ALIGNMENT #######################
    // keep alignment parameters for the next input buffer
    // Compute the next buffer length based in the new period of the PRN sequence and the code phase error estimation
    d_T_prn_samples = d_T_prn_seconds * d_trk_parameters.fs_in;
    // d_K_blk_samples = d_T_prn_samples + d_rem_code_phase_samples + d_trk_parameters.fs_in * d_code_error_kf_chips / d_code_freq_kf_chips_s;
    // KF will update d_rem_code_phase_samples
    d_K_blk_samples = d_T_prn_samples + d_rem_code_phase_samples;
    d_current_prn_length_samples = static_cast<int32_t>(std::floor(d_K_blk_samples));  // round to a discrete number of samples

    // ################### PLL COMMANDS #################################################
    // carrier phase step (NCO phase increment per sample) [rads/sample]
    d_carrier_phase_step_rad = TWO_PI * d_carrier_doppler_kf_hz / d_trk_parameters.fs_in;
    // d_rem_carr_phase_rad = d_carrier_phase_kf_rad;

    // remnant carrier phase to prevent overflow in the code NCO
    d_rem_carr_phase_rad += static_cast<float>(d_carrier_phase_step_rad * static_cast<double>(d_current_prn_length_samples) + 0.5 * d_carrier_phase_rate_step_rad * static_cast<double>(d_current_prn_length_samples) * static_cast<double>(d_current_prn_length_samples));
    d_rem_carr_phase_rad = fmod(d_rem_carr_phase_rad, TWO_PI);

    // carrier phase rate step (NCO phase increment rate per sample) [rads/sample^2]
    if (d_trk_parameters.high_dyn)
        {
            d_carrier_phase_rate_step_rad = TWO_PI * d_carrier_doppler_rate_kf_hz_s / d_trk_parameters.fs_in;
        }
    // std::cout << d_carrier_phase_rate_step_rad * d_trk_parameters.fs_in * d_trk_parameters.fs_in / TWO_PI << '\n';
    // remnant carrier phase to prevent overflow in the code NCO
    //    d_rem_carr_phase_rad += static_cast<float>(d_carrier_phase_step_rad * static_cast<double>(d_current_prn_length_samples) + 0.5 * d_carrier_phase_rate_step_rad * static_cast<double>(d_current_prn_length_samples) * static_cast<double>(d_current_prn_length_samples));
    //    d_rem_carr_phase_rad = fmod(d_rem_carr_phase_rad, TWO_PI);

    // carrier phase accumulator
    // double a = d_carrier_phase_step_rad * static_cast<double>(d_current_prn_length_samples);
    // double b = 0.5 * d_carrier_phase_rate_step_rad * static_cast<double>(d_current_prn_length_samples) * static_cast<double>(d_current_prn_length_samples);
    // std::cout << fmod(b, TWO_PI) / fmod(a, TWO_PI) << '\n';
    d_acc_carrier_phase_rad -= (d_carrier_phase_step_rad * static_cast<double>(d_current_prn_length_samples) + 0.5 * d_carrier_phase_rate_step_rad * static_cast<double>(d_current_prn_length_samples) * static_cast<double>(d_current_prn_length_samples));

    // ################### DLL COMMANDS #################################################
    // code phase step (Code resampler phase increment per sample) [chips/sample]
    d_code_phase_step_chips = d_code_freq_kf_chips_s / d_trk_parameters.fs_in;
    // todo: extend kf to estimate code rate
    //    if (d_trk_parameters.high_dyn)
    //        {
    //            d_code_phase_rate_step_chips = d_code_freq_kf_rate_chips_s / d_trk_parameters.fs_in;
    //        }

    // remnant code phase [chips]
    d_rem_code_phase_samples = d_K_blk_samples - static_cast<double>(d_current_prn_length_samples);  // rounding error < 1 sample
    d_rem_code_phase_chips = d_code_freq_kf_chips_s * d_rem_code_phase_samples / d_trk_parameters.fs_in;
}


void kf_vtl_tracking::save_correlation_results()
{
    if (d_secondary)
        {
            if (d_secondary_code_string[d_current_symbol] == '0')
                {
                    if (d_veml)
                        {
                            d_VE_accu += *d_Very_Early;
                            d_VL_accu += *d_Very_Late;
                        }
                    d_E_accu += *d_Early;
                    d_P_accu += *d_Prompt;
                    d_L_accu += *d_Late;
                }
            else
                {
                    if (d_veml)
                        {
                            d_VE_accu -= *d_Very_Early;
                            d_VL_accu -= *d_Very_Late;
                        }
                    d_E_accu -= *d_Early;
                    d_P_accu -= *d_Prompt;
                    d_L_accu -= *d_Late;
                }
            d_current_symbol++;
            // secondary code roll-up
            d_current_symbol %= d_secondary_code_length;
        }
    else
        {
            if (d_veml)
                {
                    d_VE_accu += *d_Very_Early;
                    d_VL_accu += *d_Very_Late;
                }
            d_E_accu += *d_Early;
            d_P_accu += *d_Prompt;
            d_L_accu += *d_Late;
        }

    // data secondary code roll-up
    if (d_symbols_per_bit > 1)
        {
            if (d_data_secondary_code_length > 0)
                {
                    if (d_trk_parameters.track_pilot)
                        {
                            if (d_data_secondary_code_string[d_current_data_symbol] == '0')
                                {
                                    d_P_data_accu += d_Prompt_Data[0];
                                }
                            else
                                {
                                    d_P_data_accu -= d_Prompt_Data[0];
                                }
                        }
                    else
                        {
                            if (d_data_secondary_code_string[d_current_data_symbol] == '0')
                                {
                                    d_P_data_accu += *d_Prompt;
                                }
                            else
                                {
                                    d_P_data_accu -= *d_Prompt;
                                }
                        }

                    d_current_data_symbol++;
                    // data secondary code roll-up
                    d_current_data_symbol %= d_data_secondary_code_length;
                }
            else
                {
                    if (d_trk_parameters.track_pilot)
                        {
                            d_P_data_accu += d_Prompt_Data[0];
                        }
                    else
                        {
                            d_P_data_accu += *d_Prompt;
                            // std::cout << "s[" << d_current_data_symbol << "]=" << (int)((*d_Prompt).real() > 0) << '\n';
                        }
                    d_current_data_symbol++;
                    d_current_data_symbol %= d_symbols_per_bit;
                }
        }
    else
        {
            if (d_trk_parameters.track_pilot)
                {
                    d_P_data_accu = d_Prompt_Data[0];
                }
            else
                {
                    d_P_data_accu = *d_Prompt;
                }
        }

    if (d_trk_parameters.track_pilot)
        {
            // If tracking pilot, disable Costas loop
            d_cloop = false;
        }
    else
        {
            d_cloop = true;
        }
}


void kf_vtl_tracking::log_data()
{
    if (d_dump)
        {
            // Dump results to file
            float prompt_I;
            float prompt_Q;
            float tmp_VE;
            float tmp_E;
            float tmp_P;
            float tmp_L;
            float tmp_VL;
            float tmp_float;
            double tmp_double;
            uint64_t tmp_long_int;
            if (d_trk_parameters.track_pilot)
                {
                    prompt_I = d_Prompt_Data.data()->real();
                    prompt_Q = d_Prompt_Data.data()->imag();
                }
            else
                {
                    prompt_I = d_Prompt->real();
                    prompt_Q = d_Prompt->imag();
                }
            if (d_veml)
                {
                    tmp_VE = std::abs<float>(d_VE_accu);
                    tmp_VL = std::abs<float>(d_VL_accu);
                }
            else
                {
                    tmp_VE = 0.0;
                    tmp_VL = 0.0;
                }
            tmp_E = std::abs<float>(d_E_accu);
            tmp_P = std::abs<float>(d_P_accu);
            tmp_L = std::abs<float>(d_L_accu);

            try
                {
                    // Dump correlators output
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_VE), sizeof(float));
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_E), sizeof(float));
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_P), sizeof(float));
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_L), sizeof(float));
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_VL), sizeof(float));
                    // PROMPT I and Q (to analyze navigation symbols)
                    d_dump_file.write(reinterpret_cast<char *>(&prompt_I), sizeof(float));
                    d_dump_file.write(reinterpret_cast<char *>(&prompt_Q), sizeof(float));
                    // PRN start sample stamp
                    tmp_long_int = d_sample_counter + static_cast<uint64_t>(d_current_prn_length_samples);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_long_int), sizeof(uint64_t));
                    // accumulated carrier phase
                    tmp_float = static_cast<float>(d_acc_carrier_phase_rad);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    // carrier and code frequency
                    tmp_float = static_cast<float>(d_carrier_doppler_kf_hz);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    // carrier phase rate [Hz/s]
                    tmp_float = static_cast<float>(d_carrier_doppler_rate_kf_hz_s);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    tmp_float = static_cast<float>(d_code_freq_kf_chips_s);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    // code phase rate [chips/s^2]
                    tmp_float = static_cast<float>(d_code_phase_rate_step_chips * d_trk_parameters.fs_in * d_trk_parameters.fs_in);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    // Carrier estimation
                    tmp_float = static_cast<float>(d_carr_phase_error_disc_hz);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    tmp_float = static_cast<float>(x_new_new(2));
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    // code estimation
                    tmp_float = static_cast<float>(d_code_error_disc_chips);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    tmp_float = static_cast<float>(d_code_error_kf_chips);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    // CN0 and carrier lock test
                    tmp_float = static_cast<float>(d_CN0_SNV_dB_Hz);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    tmp_float = static_cast<float>(d_carrier_lock_test);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    // AUX vars (for debug purposes)
                    tmp_float = static_cast<float>(d_rem_code_phase_samples);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_float), sizeof(float));
                    tmp_double = static_cast<double>(d_sample_counter + d_current_prn_length_samples);
                    d_dump_file.write(reinterpret_cast<char *>(&tmp_double), sizeof(double));
                    // PRN
                    uint32_t prn_ = d_acquisition_gnss_synchro->PRN;
                    d_dump_file.write(reinterpret_cast<char *>(&prn_), sizeof(uint32_t));
                }
            catch (const std::ifstream::failure &e)
                {
                    LOG(WARNING) << "Exception writing trk dump file " << e.what();
                }
        }
}


int32_t kf_vtl_tracking::save_matfile() const
{
    // READ DUMP FILE
    std::ifstream::pos_type size;
    const int32_t number_of_double_vars = 1;
    const int32_t number_of_float_vars = 19;
    const int32_t epoch_size_bytes = sizeof(uint64_t) + sizeof(double) * number_of_double_vars +
                                     sizeof(float) * number_of_float_vars + sizeof(uint32_t);
    std::ifstream dump_file;
    std::string dump_filename_ = d_dump_filename;
    // add channel number to the filename
    dump_filename_.append(std::to_string(d_channel));
    // add extension
    dump_filename_.append(".dat");
    std::cout << "Generating .mat file for " << dump_filename_ << '\n';
    dump_file.exceptions(std::ifstream::failbit | std::ifstream::badbit);
    try
        {
            dump_file.open(dump_filename_.c_str(), std::ios::binary | std::ios::ate);
        }
    catch (const std::ifstream::failure &e)
        {
            std::cerr << "Problem opening dump file:" << e.what() << '\n';
            return 1;
        }
    // count number of epochs and rewind
    int64_t num_epoch = 0;
    if (dump_file.is_open())
        {
            size = dump_file.tellg();
            num_epoch = static_cast<int64_t>(size) / static_cast<int64_t>(epoch_size_bytes);
            dump_file.seekg(0, std::ios::beg);
        }
    else
        {
            return 1;
        }
    auto abs_VE = std::vector<float>(num_epoch);
    auto abs_E = std::vector<float>(num_epoch);
    auto abs_P = std::vector<float>(num_epoch);
    auto abs_L = std::vector<float>(num_epoch);
    auto abs_VL = std::vector<float>(num_epoch);
    auto Prompt_I = std::vector<float>(num_epoch);
    auto Prompt_Q = std::vector<float>(num_epoch);
    auto PRN_start_sample_count = std::vector<uint64_t>(num_epoch);
    auto acc_carrier_phase_rad = std::vector<float>(num_epoch);
    auto carrier_doppler_hz = std::vector<float>(num_epoch);
    auto carrier_doppler_rate_hz = std::vector<float>(num_epoch);
    auto code_freq_chips = std::vector<float>(num_epoch);
    auto code_freq_rate_chips = std::vector<float>(num_epoch);
    auto carr_error_hz = std::vector<float>(num_epoch);
    auto carr_error_filt_hz = std::vector<float>(num_epoch);
    auto code_error_chips = std::vector<float>(num_epoch);
    auto code_error_filt_chips = std::vector<float>(num_epoch);
    auto CN0_SNV_dB_Hz = std::vector<float>(num_epoch);
    auto carrier_lock_test = std::vector<float>(num_epoch);
    auto aux1 = std::vector<float>(num_epoch);
    auto aux2 = std::vector<double>(num_epoch);
    auto PRN = std::vector<uint32_t>(num_epoch);
    try
        {
            if (dump_file.is_open())
                {
                    for (int64_t i = 0; i < num_epoch; i++)
                        {
                            dump_file.read(reinterpret_cast<char *>(&abs_VE[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&abs_E[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&abs_P[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&abs_L[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&abs_VL[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&Prompt_I[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&Prompt_Q[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&PRN_start_sample_count[i]), sizeof(uint64_t));
                            dump_file.read(reinterpret_cast<char *>(&acc_carrier_phase_rad[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&carrier_doppler_hz[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&carrier_doppler_rate_hz[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&code_freq_chips[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&code_freq_rate_chips[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&carr_error_hz[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&carr_error_filt_hz[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&code_error_chips[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&code_error_filt_chips[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&CN0_SNV_dB_Hz[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&carrier_lock_test[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&aux1[i]), sizeof(float));
                            dump_file.read(reinterpret_cast<char *>(&aux2[i]), sizeof(double));
                            dump_file.read(reinterpret_cast<char *>(&PRN[i]), sizeof(uint32_t));
                        }
                }
            dump_file.close();
        }
    catch (const std::ifstream::failure &e)
        {
            std::cerr << "Problem reading dump file:" << e.what() << '\n';
            return 1;
        }

    // WRITE MAT FILE
    mat_t *matfp;
    matvar_t *matvar;
    std::string filename = dump_filename_;
    filename.erase(filename.length() - 4, 4);
    filename.append(".mat");
    matfp = Mat_CreateVer(filename.c_str(), nullptr, MAT_FT_MAT73);
    if (reinterpret_cast<int64_t *>(matfp) != nullptr)
        {
            std::array<size_t, 2> dims{1, static_cast<size_t>(num_epoch)};
            matvar = Mat_VarCreate("abs_VE", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), abs_VE.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("abs_E", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), abs_E.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("abs_P", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), abs_P.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("abs_L", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), abs_L.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("abs_VL", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), abs_VL.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("Prompt_I", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), Prompt_I.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("Prompt_Q", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), Prompt_Q.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("PRN_start_sample_count", MAT_C_UINT64, MAT_T_UINT64, 2, dims.data(), PRN_start_sample_count.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("acc_carrier_phase_rad", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), acc_carrier_phase_rad.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("carrier_doppler_hz", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), carrier_doppler_hz.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("carrier_doppler_rate_hz", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), carrier_doppler_rate_hz.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("code_freq_chips", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), code_freq_chips.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("code_freq_rate_chips", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), code_freq_rate_chips.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("carr_error_hz", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), carr_error_hz.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("carr_error_filt_hz", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), carr_error_filt_hz.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("code_error_chips", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), code_error_chips.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("code_error_filt_chips", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), code_error_filt_chips.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("CN0_SNV_dB_Hz", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), CN0_SNV_dB_Hz.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("carrier_lock_test", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), carrier_lock_test.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("aux1", MAT_C_SINGLE, MAT_T_SINGLE, 2, dims.data(), aux1.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("aux2", MAT_C_DOUBLE, MAT_T_DOUBLE, 2, dims.data(), aux2.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);

            matvar = Mat_VarCreate("PRN", MAT_C_UINT32, MAT_T_UINT32, 2, dims.data(), PRN.data(), 0);
            Mat_VarWrite(matfp, matvar, MAT_COMPRESSION_ZLIB);  // or MAT_COMPRESSION_NONE
            Mat_VarFree(matvar);
        }
    Mat_Close(matfp);
    return 0;
}


void kf_vtl_tracking::set_channel(uint32_t channel)
{
    gr::thread::scoped_lock l(d_setlock);
    d_channel = channel;
    LOG(INFO) << "Tracking Channel set to " << d_channel;
    // ############# ENABLE DATA FILE LOG #################
    if (d_dump)
        {
            std::string dump_filename_ = d_dump_filename;
            // add channel number to the filename
            dump_filename_.append(std::to_string(d_channel));
            // add extension
            dump_filename_.append(".dat");

            if (!d_dump_file.is_open())
                {
                    try
                        {
                            d_dump_file.exceptions(std::ifstream::failbit | std::ifstream::badbit);
                            d_dump_file.open(dump_filename_.c_str(), std::ios::out | std::ios::binary);
                            LOG(INFO) << "Tracking dump enabled on channel " << d_channel << " Log file: " << dump_filename_.c_str();
                        }
                    catch (const std::ifstream::failure &e)
                        {
                            LOG(WARNING) << "channel " << d_channel << " Exception opening trk dump file " << e.what();
                        }
                }
        }
}


void kf_vtl_tracking::set_gnss_synchro(Gnss_Synchro *p_gnss_synchro)
{
    gr::thread::scoped_lock l(d_setlock);
    d_acquisition_gnss_synchro = p_gnss_synchro;
}


void kf_vtl_tracking::stop_tracking()
{
    gr::thread::scoped_lock l(d_setlock);
    d_state = 0;
}


int kf_vtl_tracking::general_work(int noutput_items __attribute__((unused)), gr_vector_int &ninput_items,
    gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
{
    gr::thread::scoped_lock l(d_setlock);
    const auto *in = reinterpret_cast<const gr_complex *>(input_items[0]);
    auto **out = reinterpret_cast<Gnss_Synchro **>(&output_items[0]);
    Gnss_Synchro current_synchro_data = Gnss_Synchro();
    current_synchro_data.Flag_valid_symbol_output = false;

    if (d_pull_in_transitory == true)
        {
            if (d_trk_parameters.pull_in_time_s < (d_sample_counter - d_acq_sample_stamp) / static_cast<int>(d_trk_parameters.fs_in))
                {
                    d_pull_in_transitory = false;
                    d_carrier_lock_fail_counter = 0;
                    d_code_lock_fail_counter = 0;
                }
        }
    switch (d_state)
        {
        case 0:  // Standby - Consume samples at full throttle, do nothing
            {
                d_sample_counter += static_cast<uint64_t>(ninput_items[0]);
                consume_each(ninput_items[0]);
                return 0;
                break;
            }
        case 1:  // Pull-in
            {
                // Signal alignment (skip samples until the incoming signal is aligned with local replica)
                const int64_t acq_trk_diff_samples = static_cast<int64_t>(d_sample_counter) - static_cast<int64_t>(d_acq_sample_stamp);
                const double acq_trk_diff_seconds = static_cast<double>(acq_trk_diff_samples) / d_trk_parameters.fs_in;
                const double delta_trk_to_acq_prn_start_samples = static_cast<double>(acq_trk_diff_samples) - d_acq_code_phase_samples;

                d_code_freq_kf_chips_s = d_code_chip_rate;
                d_code_phase_step_chips = d_code_freq_kf_chips_s / d_trk_parameters.fs_in;
                d_code_phase_rate_step_chips = 0.0;
                const double T_chip_mod_seconds = 1.0 / d_code_freq_kf_chips_s;
                const double T_prn_mod_seconds = T_chip_mod_seconds * static_cast<double>(d_code_length_chips);
                const double T_prn_mod_samples = T_prn_mod_seconds * d_trk_parameters.fs_in;

                d_acq_code_phase_samples = T_prn_mod_samples - std::fmod(delta_trk_to_acq_prn_start_samples, T_prn_mod_samples);
                d_current_prn_length_samples = round(T_prn_mod_samples);

                const int32_t samples_offset = round(d_acq_code_phase_samples);
                d_acc_carrier_phase_rad -= d_carrier_phase_step_rad * static_cast<double>(samples_offset);
                d_state = 2;
                d_sample_counter += samples_offset;  // count for the processed samples
                d_cn0_smoother.reset();
                d_carrier_lock_test_smoother.reset();

                // init KF
                //                d_T_chip_seconds = 1.0 / d_code_freq_chips;
                //                d_T_prn_seconds = d_T_chip_seconds * static_cast<double>(samples_offset);
                //                // keep alignment parameters for the next input buffer
                //                // Compute the next buffer length based in the new period of the PRN sequence and the code phase error estimation
                //                d_T_prn_samples = d_T_prn_seconds * d_trk_parameters.fs_in;
                //                d_K_blk_samples = d_T_prn_samples + d_rem_code_phase_samples;
                //                // remnant code phase [chips]
                //                d_rem_code_phase_samples = d_K_blk_samples - static_cast<double>(d_current_prn_length_samples);  // rounding error < 1 sample
                //                d_rem_code_phase_chips = d_code_freq_chips * d_rem_code_phase_samples / d_trk_parameters.fs_in;

                init_kf(0, d_carrier_doppler_kf_hz);

                LOG(INFO) << "Number of samples between Acquisition and Tracking = " << acq_trk_diff_samples << " ( " << acq_trk_diff_seconds << " s)";
                DLOG(INFO) << "PULL-IN Doppler [Hz] = " << d_carrier_doppler_kf_hz
                           << ". PULL-IN Code Phase [samples] = " << d_acq_code_phase_samples;

                consume_each(samples_offset);  // shift input to perform alignment with local replica
                return 0;
            }
        case 2:  // Wide tracking and symbol synchronization
            {
                do_correlation_step(in);
                // Save single correlation step variables
                if (d_veml)
                    {
                        d_VE_accu = *d_Very_Early;
                        d_VL_accu = *d_Very_Late;
                    }
                d_E_accu = *d_Early;
                d_P_accu = *d_Prompt;
                d_L_accu = *d_Late;
                d_trk_parameters.spc = d_trk_parameters.early_late_space_chips;
                // if (std::string(d_trk_parameters.signal) == "E1")
                //    {
                //        d_trk_parameters.slope = -CalculateSlopeAbs(&SinBocCorrelationFunction<1, 1>, d_trk_parameters.spc);
                //        d_trk_parameters.y_intercept = GetYInterceptAbs(&SinBocCorrelationFunction<1, 1>, d_trk_parameters.spc);
                //    }

                // fail-safe: check if the secondary code or bit synchronization has not succeeded in a limited time period
                if (d_trk_parameters.bit_synchronization_time_limit_s < (d_sample_counter - d_acq_sample_stamp) / static_cast<int>(d_trk_parameters.fs_in))
                    {
                        d_carrier_lock_fail_counter = 300000;  // force loss-of-lock condition
                        LOG(INFO) << d_systemName << " " << d_signal_pretty_name << " tracking synchronization time limit reached in channel " << d_channel
                                  << " for satellite " << Gnss_Satellite(d_systemName, d_acquisition_gnss_synchro->PRN) << '\n';
                    }
                // Check lock status
                if (!cn0_and_tracking_lock_status(d_code_period))
                    {
                        clear_tracking_vars();
                        d_state = 0;  // loss-of-lock detected
                    }
                else
                    {
                        bool next_state = false;
                        // Perform DLL/PLL tracking loop computations. Costas Loop enabled
                        run_Kf();
                        update_tracking_vars();

                        // enable write dump file this cycle (valid DLL/PLL cycle)
                        log_data();

                        if (!d_pull_in_transitory)
                            {
                                if (d_secondary)
                                    {
                                        // ####### SECONDARY CODE LOCK #####
                                        d_Prompt_circular_buffer.push_back(*d_Prompt);
                                        if (d_Prompt_circular_buffer.size() == d_secondary_code_length)
                                            {
                                                next_state = acquire_secondary();
                                                if (next_state)
                                                    {
                                                        LOG(INFO) << d_systemName << " " << d_signal_pretty_name << " secondary code locked in channel " << d_channel
                                                                  << " for satellite " << Gnss_Satellite(d_systemName, d_acquisition_gnss_synchro->PRN) << '\n';
                                                        std::cout << d_systemName << " " << d_signal_pretty_name << " secondary code locked in channel " << d_channel
                                                                  << " for satellite " << Gnss_Satellite(d_systemName, d_acquisition_gnss_synchro->PRN) << '\n';
                                                    }
                                            }
                                    }
                                else if (d_symbols_per_bit > 1)  // Signal does not have secondary code. Search a bit transition by sign change
                                    {
                                        // ******* preamble correlation ********
                                        d_Prompt_circular_buffer.push_back(*d_Prompt);
                                        if (d_Prompt_circular_buffer.size() == d_secondary_code_length)
                                            {
                                                next_state = acquire_secondary();
                                                if (next_state)
                                                    {
                                                        LOG(INFO) << d_systemName << " " << d_signal_pretty_name << " tracking bit synchronization locked in channel " << d_channel
                                                                  << " for satellite " << Gnss_Satellite(d_systemName, d_acquisition_gnss_synchro->PRN) << '\n';
                                                        std::cout << d_systemName << " " << d_signal_pretty_name << " tracking bit synchronization locked in channel " << d_channel
                                                                  << " for satellite " << Gnss_Satellite(d_systemName, d_acquisition_gnss_synchro->PRN) << '\n';
                                                    }
                                            }
                                    }
                                else
                                    {
                                        next_state = true;
                                    }
                            }
                        else
                            {
                                next_state = false;  // keep in state 2 during pull-in transitory
                            }
                        if (next_state)
                            {  // reset extended correlator
                                d_VE_accu = gr_complex(0.0, 0.0);
                                d_E_accu = gr_complex(0.0, 0.0);
                                d_P_accu = gr_complex(0.0, 0.0);
                                d_P_data_accu = gr_complex(0.0, 0.0);
                                d_L_accu = gr_complex(0.0, 0.0);
                                d_VL_accu = gr_complex(0.0, 0.0);
                                d_Prompt_circular_buffer.clear();
                                d_current_symbol = 0;
                                d_current_data_symbol = 0;

                                if (d_enable_extended_integration)
                                    {
                                        // UPDATE INTEGRATION TIME
                                        d_extend_correlation_symbols_count = 0;
                                        d_current_correlation_time_s = static_cast<float>(d_trk_parameters.extend_correlation_symbols) * static_cast<float>(d_code_period);
                                        d_state = 3;  // next state is the extended correlator integrator
                                        LOG(INFO) << "Enabled " << d_trk_parameters.extend_correlation_symbols * static_cast<int32_t>(d_code_period * 1000.0) << " ms extended correlator in channel "
                                                  << d_channel
                                                  << " for satellite " << Gnss_Satellite(d_systemName, d_acquisition_gnss_synchro->PRN);
                                        std::cout << "Enabled " << d_trk_parameters.extend_correlation_symbols * static_cast<int32_t>(d_code_period * 1000.0) << " ms extended correlator in channel "
                                                  << d_channel
                                                  << " for satellite " << Gnss_Satellite(d_systemName, d_acquisition_gnss_synchro->PRN) << '\n';
                                        // Set narrow taps delay values [chips]
                                        update_kf_narrow_integration_time();
                                        if (d_veml)
                                            {
                                                d_local_code_shift_chips[0] = -d_trk_parameters.very_early_late_space_narrow_chips * static_cast<float>(d_code_samples_per_chip);
                                                d_local_code_shift_chips[1] = -d_trk_parameters.early_late_space_narrow_chips * static_cast<float>(d_code_samples_per_chip);
                                                d_local_code_shift_chips[3] = d_trk_parameters.early_late_space_narrow_chips * static_cast<float>(d_code_samples_per_chip);
                                                d_local_code_shift_chips[4] = d_trk_parameters.very_early_late_space_narrow_chips * static_cast<float>(d_code_samples_per_chip);
                                                d_trk_parameters.spc = d_trk_parameters.early_late_space_narrow_chips;
                                                // if (std::string(d_trk_parameters.signal) == "E1")
                                                //    {
                                                //        d_trk_parameters.slope = -CalculateSlopeAbs(&SinBocCorrelationFunction<1, 1>, d_trk_parameters.spc);
                                                //        d_trk_parameters.y_intercept = GetYInterceptAbs(&SinBocCorrelationFunction<1, 1>, d_trk_parameters.spc);
                                                //    }
                                            }
                                        else
                                            {
                                                d_local_code_shift_chips[0] = -d_trk_parameters.early_late_space_narrow_chips * static_cast<float>(d_code_samples_per_chip);
                                                d_local_code_shift_chips[2] = d_trk_parameters.early_late_space_narrow_chips * static_cast<float>(d_code_samples_per_chip);
                                                d_trk_parameters.spc = d_trk_parameters.early_late_space_narrow_chips;
                                            }
                                    }
                                else
                                    {
                                        d_state = 4;
                                    }
                            }
                    }
                break;
            }
        case 3:  // coherent integration (correlation time extension)
            {
                // perform a correlation step
                do_correlation_step(in);
                save_correlation_results();
                update_tracking_vars();
                if (d_current_data_symbol == 0)
                    {
                        log_data();
                        // ########### Output the tracking results to Telemetry block ##########
                        // Fill the acquisition data
                        current_synchro_data = *d_acquisition_gnss_synchro;
                        if (d_interchange_iq)
                            {
                                current_synchro_data.Prompt_I = static_cast<double>(d_P_data_accu.imag());
                                current_synchro_data.Prompt_Q = static_cast<double>(d_P_data_accu.real());
                            }
                        else
                            {
                                current_synchro_data.Prompt_I = static_cast<double>(d_P_data_accu.real());
                                current_synchro_data.Prompt_Q = static_cast<double>(d_P_data_accu.imag());
                            }
                        current_synchro_data.Code_phase_samples = d_rem_code_phase_samples;
                        current_synchro_data.Carrier_phase_rads = d_acc_carrier_phase_rad;
                        current_synchro_data.Carrier_Doppler_hz = d_carrier_doppler_kf_hz;
                        current_synchro_data.CN0_dB_hz = d_CN0_SNV_dB_Hz;
                        current_synchro_data.correlation_length_ms = d_correlation_length_ms;
                        current_synchro_data.Flag_valid_symbol_output = true;
                        d_P_data_accu = gr_complex(0.0, 0.0);
                    }
                d_extend_correlation_symbols_count++;
                if (d_extend_correlation_symbols_count == (d_trk_parameters.extend_correlation_symbols - 1))
                    {
                        d_extend_correlation_symbols_count = 0;
                        d_state = 4;
                    }
                break;
            }
        case 4:  // narrow tracking
            {
                // perform a correlation step
                do_correlation_step(in);
                save_correlation_results();

                // check lock status
                if (!cn0_and_tracking_lock_status(d_code_period * static_cast<double>(d_trk_parameters.extend_correlation_symbols)))
                    {
                        clear_tracking_vars();
                        d_state = 0;  // loss-of-lock detected
                    }
                else
                    {
                        if (d_trk_parameters.use_estimated_cn0 == true)
                            {
                                if (d_CN0_SNV_dB_Hz > 0)
                                    {
                                        update_kf_cn0(d_CN0_SNV_dB_Hz);
                                    }
                            }
                        run_Kf();
                        update_tracking_vars();
                        check_carrier_phase_coherent_initialization();
                        if (d_current_data_symbol == 0)
                            {
                                // enable write dump file this cycle (valid DLL/PLL cycle)
                                log_data();
                                // ########### Output the tracking results to Telemetry block ##########
                                // Fill the acquisition data
                                current_synchro_data = *d_acquisition_gnss_synchro;
                                if (d_interchange_iq)
                                    {
                                        current_synchro_data.Prompt_I = static_cast<double>(d_P_data_accu.imag());
                                        current_synchro_data.Prompt_Q = static_cast<double>(d_P_data_accu.real());
                                    }
                                else
                                    {
                                        current_synchro_data.Prompt_I = static_cast<double>(d_P_data_accu.real());
                                        current_synchro_data.Prompt_Q = static_cast<double>(d_P_data_accu.imag());
                                    }
                                current_synchro_data.Code_phase_samples = d_rem_code_phase_samples;
                                current_synchro_data.Carrier_phase_rads = d_acc_carrier_phase_rad;
                                current_synchro_data.Carrier_Doppler_hz = d_carrier_doppler_kf_hz;
                                current_synchro_data.CN0_dB_hz = d_CN0_SNV_dB_Hz;
                                current_synchro_data.correlation_length_ms = d_correlation_length_ms;
                                current_synchro_data.Flag_valid_symbol_output = true;
                                d_P_data_accu = gr_complex(0.0, 0.0);
                            }

                        // reset extended correlator
                        d_VE_accu = gr_complex(0.0, 0.0);
                        d_E_accu = gr_complex(0.0, 0.0);
                        d_P_accu = gr_complex(0.0, 0.0);
                        d_L_accu = gr_complex(0.0, 0.0);
                        d_VL_accu = gr_complex(0.0, 0.0);
                        if (d_enable_extended_integration)
                            {
                                d_state = 3;  // new coherent integration (correlation time extension) cycle
                            }
                    }
            }
        }
    consume_each(d_current_prn_length_samples);
    d_sample_counter += static_cast<uint64_t>(d_current_prn_length_samples);
    if (current_synchro_data.Flag_valid_symbol_output)
        {
            current_synchro_data.fs = static_cast<int64_t>(d_trk_parameters.fs_in);
            current_synchro_data.Tracking_sample_counter = d_sample_counter;
            *out[0] = current_synchro_data;
            return 1;
        }
    return 0;
}