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/* -*- c++ -*- */
/*
* Copyright 2011 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio 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, or (at your option)
* any later version.
*
* GNU Radio 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 GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <gr_io_signature.h>
#include <gr_prefs.h>
#include <digital_constellation_receiver_cb.h>
#include <stdexcept>
#include <gr_math.h>
#include <gr_expj.h>
#define M_TWOPI (2*M_PI)
#define VERBOSE_MM 0 // Used for debugging symbol timing loop
#define VERBOSE_COSTAS 0 // Used for debugging phase and frequency tracking
// Public constructor
digital_constellation_receiver_cb_sptr
digital_make_constellation_receiver_cb(digital_constellation_sptr constell,
float alpha, float beta,
float fmin, float fmax)
{
return gnuradio::get_initial_sptr(new digital_constellation_receiver_cb (constell,
alpha, beta,
fmin, fmax));
}
static int ios[] = {sizeof(char), sizeof(float), sizeof(float), sizeof(float)};
static std::vector<int> iosig(ios, ios+sizeof(ios)/sizeof(int));
digital_constellation_receiver_cb::digital_constellation_receiver_cb (digital_constellation_sptr constellation,
float alpha, float beta,
float fmin, float fmax)
: gr_block ("constellation_receiver_cb",
gr_make_io_signature (1, 1, sizeof (gr_complex)),
gr_make_io_signaturev (1, 4, iosig)),
d_constellation(constellation),
d_alpha(alpha), d_beta(beta), d_freq(0), d_max_freq(fmax), d_min_freq(fmin), d_phase(0),
d_current_const_point(0)
{
if (d_constellation->dimensionality() != 1)
throw std::runtime_error ("This receiver only works with constellations of dimension 1.");
}
void
digital_constellation_receiver_cb::phase_error_tracking(float phase_error)
{
d_freq += d_beta*phase_error; // adjust frequency based on error
d_phase += d_freq + d_alpha*phase_error; // adjust phase based on error
// Make sure we stay within +-2pi
while(d_phase > M_TWOPI)
d_phase -= M_TWOPI;
while(d_phase < -M_TWOPI)
d_phase += M_TWOPI;
// Limit the frequency range
d_freq = gr_branchless_clip(d_freq, d_max_freq);
#if VERBOSE_COSTAS
printf("cl: phase_error: %f phase: %f freq: %f sample: %f+j%f constellation: %f+j%f\n",
phase_error, d_phase, d_freq, sample.real(), sample.imag(),
d_constellation->points()[d_current_const_point].real(),
d_constellation->points()[d_current_const_point].imag());
#endif
}
int
digital_constellation_receiver_cb::general_work (int noutput_items,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const gr_complex *in = (const gr_complex *) input_items[0];
unsigned char *out = (unsigned char *) output_items[0];
int i=0;
float phase_error;
unsigned int sym_value;
gr_complex sample, nco;
float *out_err = 0, *out_phase = 0, *out_freq = 0;
if(output_items.size() == 4) {
out_err = (float *) output_items[1];
out_phase = (float *) output_items[2];
out_freq = (float *) output_items[3];
}
while((i < noutput_items) && (i < ninput_items[0])) {
sample = in[i];
nco = gr_expj(d_phase); // get the NCO value for derotating the current sample
sample = nco*sample; // get the downconverted symbol
sym_value = d_constellation->decision_maker_pe(&sample, &phase_error);
// phase_error = -arg(sample*conj(d_constellation->points()[sym_value]));
phase_error_tracking(phase_error); // corrects phase and frequency offsets
out[i] = sym_value;
if(output_items.size() == 4) {
out_err[i] = phase_error;
out_phase[i] = d_phase;
out_freq[i] = d_freq;
}
i++;
}
consume_each(i);
return i;
}
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