gnss-sdr/src/algorithms/input_filter/gnuradio_blocks/notch_lite_cc.cc

/*!
 * \file notch_lite_cc.cc
 * \brief Implements a multi state notch filter algorithm
 * \author Antonio Ramos (antonio.ramosdet(at)gmail.com)
 *
 * -------------------------------------------------------------------------
 *
 * Copyright (C) 2010-2017 (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.
 *
 * GNSS-SDR is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * GNSS-SDR is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
 *
 * -------------------------------------------------------------------------
 */

#include "notch_lite_cc.h"
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <gnuradio/io_signature.h>
#include <volk/volk.h>
#include <iostream>
#include <glog/logging.h>
#include <boost/math/distributions/chi_squared.hpp>
#include <armadillo>

using google::LogMessage;

notch_lite_sptr make_notch_filter_lite(float p_c_factor, float pfa, int length_, int n_segments_est, int n_segments_reset, int n_segments_coeff)
{
    return notch_lite_sptr(new NotchLite(p_c_factor, pfa, length_, n_segments_est, n_segments_reset, n_segments_coeff));
}

NotchLite::NotchLite(float p_c_factor, float pfa, int length_, int n_segments_est, int n_segments_reset, int n_segments_coeff) : gr::block("NotchLite",
                                                   gr::io_signature::make (1, 1, sizeof(gr_complex)),
                                                   gr::io_signature::make (1, 1, sizeof(gr_complex)))
{
    const int alignment_multiple = volk_get_alignment() / sizeof(gr_complex);
    set_alignment(std::max(1, alignment_multiple));
    set_history(2);
    this->p_c_factor = gr_complex(p_c_factor , 0);
    this->n_segments_est = n_segments_est;
    this->n_segments_reset = n_segments_reset;
    this->n_segments_coeff_reset = n_segments_coeff;
    this->n_segments_coeff = 0;
    this->length_ = length_;
    set_output_multiple(length_);
    this->pfa = pfa;
    n_segments = 0;
    n_deg_fred = 2 * length_;
    noise_pow_est = 0.0;
    filter_state_ = false;
    z_0 = gr_complex(0 , 0);
    last_out = gr_complex(0, 0);
    boost::math::chi_squared_distribution<float> my_dist_(n_deg_fred);
    thres_ = boost::math::quantile(boost::math::complement(my_dist_, pfa));
    c_samples1 = gr_complex(0, 0);
    c_samples2 = gr_complex(0, 0);
    angle1 = 0.0;
    angle2 = 0.0;
    power_spect = static_cast<float *>(volk_malloc(length_ * sizeof(float), volk_get_alignment()));
    
}

NotchLite::~NotchLite()
{
    volk_free(power_spect);
}


int NotchLite::general_work(int noutput_items __attribute__((unused)), gr_vector_int &ninput_items __attribute__((unused)),
        gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
{
    int index_out = 0;
    float sig2dB = 0.0;
    float sig2lin = 0.0;
    lv_32fc_t dot_prod_;
    gr_complex* in = (gr_complex *) input_items[0];
    gr_complex* out = (gr_complex *) output_items[0];
    in++;
    arma::cx_fvec signal_segment;
    arma::cx_fvec signal_segment_fft;
    while((index_out + length_) < noutput_items)
    {
        if((n_segments < n_segments_est) && (filter_state_ == false))
        {
            signal_segment = arma::cx_fvec(in, length_, false, false);
            signal_segment_fft = arma::fft(signal_segment);
            volk_32fc_s32f_power_spectrum_32f(power_spect, signal_segment_fft.memptr(), 1.0, length_);
            volk_32f_s32f_calc_spectral_noise_floor_32f(&sig2dB, power_spect, 15.0, length_);
            sig2lin = std::pow(10.0, (sig2dB / 10.0)) / ((float) n_deg_fred);
            noise_pow_est = (((float) n_segments) * noise_pow_est + sig2lin) / ((float)(n_segments + 1));
            memcpy(out, in, sizeof(gr_complex) * length_);
        }
        else
        {
            volk_32fc_x2_conjugate_dot_prod_32fc(&dot_prod_, in, in, length_);
            if( (lv_creal(dot_prod_) / noise_pow_est) > thres_)
            {
                if(filter_state_ == false)
                {
                    filter_state_ = true;
                    last_out = gr_complex(0,0);
                    n_segments_coeff = 0;
                }
                if(n_segments_coeff == 0)
                {
                    volk_32fc_x2_multiply_conjugate_32fc(&c_samples1, (in + 1), in, 1);
                    volk_32fc_s32f_atan2_32f(&angle1, &c_samples1, ((float)1.0), 1);
                    volk_32fc_x2_multiply_conjugate_32fc(&c_samples2, (in + length_ - 1), (in + length_ - 2), 1);
                    volk_32fc_s32f_atan2_32f(&angle2, &c_samples2, ((float)1.0), 1);
                    float angle_ = (angle1 + angle2) / 2.0;
                    z_0 = std::exp(gr_complex(0,1) * angle_);
                }
                for(int aux = 0; aux < length_; aux++)
                {
                    *(out + aux) = *(in + aux) - z_0 * (*(in + aux - 1)) + p_c_factor * z_0 * last_out;
                    last_out = *(out + aux);
                }
                n_segments_coeff++;
                n_segments_coeff = n_segments_coeff % n_segments_coeff_reset;
            }
            else
            {
                if (n_segments > n_segments_reset)
                {
                    n_segments = 0;
                }
                filter_state_ = false;
                memcpy(out, in, sizeof(gr_complex) * length_);
            }
        }
        index_out += length_;
        n_segments++;
        in += length_;
        out += length_;
    }
    consume_each(index_out);
    return index_out;
}