gnss-sdr/src/algorithms/libs/gnss_signal_processing.cc

/*!
 * \file gnss_signal_processing.cc
 * \brief This library gathers a few functions used by the algorithms of gnss-sdr,
 *  regardless of system used
 * \author Luis Esteve, 2012. luis(at)epsilon-formacion.com
 *
 * Detailed description of the file here if needed.
 *
 * -------------------------------------------------------------------------
 *
 * Copyright (C) 2010-2015  (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 "gnss_signal_processing.h"
#include <gnuradio/fxpt_nco.h>
#include "GPS_L1_CA.h"


auto auxCeil2 = [](float x){ return static_cast<int>(static_cast<long>((x)+1)); };

void complex_exp_gen(std::complex<float>* _dest, double _f, double _fs, unsigned int _samps)
{
    gr::fxpt_nco d_nco;
    d_nco.set_freq((GPS_TWO_PI * _f) / _fs);
    d_nco.sincos(_dest, _samps, 1); 
}


void complex_exp_gen_conj(std::complex<float>* _dest, double _f, double _fs, unsigned int _samps)
{
    gr::fxpt_nco d_nco;
    d_nco.set_freq(-(GPS_TWO_PI * _f) / _fs);
    d_nco.sincos(_dest, _samps, 1); 
}

void hex_to_binary_converter(int * _dest, char _from)
{
    switch(_from)
    {
    case '0':
        *(_dest) = 1;
        *(_dest+1) = 1;
        *(_dest+2) = 1;
        *(_dest+3) = 1;
        break;
    case '1':
        *(_dest) = 1;
        *(_dest+1) = 1;
        *(_dest+2) = 1;
        *(_dest+3) = -1;
        break;
    case '2':
        *(_dest) = 1;
        *(_dest+1) = 1;
        *(_dest+2) = -1;
        *(_dest+3) = 1;
        break;
    case '3':
        *(_dest) = 1;
        *(_dest+1) = 1;
        *(_dest+2) = -1;
        *(_dest+3) = -1;
        break;
    case '4':
        *(_dest) = 1;
        *(_dest+1) = -1;
        *(_dest+2) = 1;
        *(_dest+3) = 1;
        break;
    case '5':
        *(_dest) = 1;
        *(_dest+1) = -1;
        *(_dest+2) = 1;
        *(_dest+3) = -1;
        break;
    case '6':
        *(_dest) = 1;
        *(_dest+1) = -1;
        *(_dest+2) = -1;
        *(_dest+3) = 1;
        break;
    case '7':
        *(_dest) = 1;
        *(_dest+1) = -1;
        *(_dest+2) = -1;
        *(_dest+3) = -1;
        break;
    case '8':
        *(_dest) = -1;
        *(_dest+1) = 1;
        *(_dest+2) = 1;
        *(_dest+3) = 1;
        break;
    case '9':
        *(_dest) = -1;
        *(_dest+1) = 1;
        *(_dest+2) = 1;
        *(_dest+3) = -1;
        break;
    case 'A':
        *(_dest) = -1;
        *(_dest+1) = 1;
        *(_dest+2) = -1;
        *(_dest+3) = 1;
        break;
    case 'B':
        *(_dest) = -1;
        *(_dest+1) = 1;
        *(_dest+2) = -1;
        *(_dest+3) = -1;
        break;
    case 'C':
        *(_dest) = -1;
        *(_dest+1) = -1;
        *(_dest+2) = 1;
        *(_dest+3) = 1;
        break;
    case 'D':
        *(_dest) = -1;
        *(_dest+1) = -1;
        *(_dest+2) = 1;
        *(_dest+3) = -1;
        break;
    case 'E':
        *(_dest) = -1;
        *(_dest+1) = -1;
        *(_dest+2) = -1;
        *(_dest+3) = 1;
        break;
    case 'F':
        *(_dest) = -1;
        *(_dest+1) = -1;
        *(_dest+2) = -1;
        *(_dest+3) = -1;
        break;
    }
}


void resampler(std::complex<float>* _from, std::complex<float>* _dest, float _fs_in,
        float _fs_out, unsigned int _length_in, unsigned int _length_out)
{
    unsigned int _codeValueIndex;
    float aux;
    //--- Find time constants --------------------------------------------------
    const float _t_in = 1 / _fs_in;  // Incoming sampling  period in sec
    const float _t_out = 1 / _fs_out;   // Out sampling period in sec
    for (unsigned int i = 0; i < _length_out - 1; i++)
        {
            //=== Digitizing =======================================================
            //--- compute index array to read sampled values -------------------------
            //_codeValueIndex = ceil((_t_out * ((float)i + 1)) / _t_in) - 1;
            aux = (_t_out * (i + 1)) / _t_in;
            _codeValueIndex = auxCeil2(aux) - 1;

            //if repeat the chip -> upsample by nearest neighborhood interpolation
            _dest[i] = _from[_codeValueIndex];
        }
    //--- Correct the last index (due to number rounding issues) -----------
    _dest[_length_out - 1] = _from[_length_in - 1];
}