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/* -*- c++ -*- */
/*
* Copyright 2004,2010,2011 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 <digital_clock_recovery_mm_ff.h>
#include <gri_mmse_fir_interpolator.h>
#include <stdexcept>
#define DEBUG_CR_MM_FF 0 // must be defined as 0 or 1
// Public constructor
digital_clock_recovery_mm_ff_sptr
digital_make_clock_recovery_mm_ff(float omega, float gain_omega,
float mu, float gain_mu,
float omega_relative_limit)
{
return gnuradio::get_initial_sptr(new digital_clock_recovery_mm_ff (omega,
gain_omega,
mu,
gain_mu,
omega_relative_limit));
}
digital_clock_recovery_mm_ff::digital_clock_recovery_mm_ff (float omega, float gain_omega,
float mu, float gain_mu,
float omega_relative_limit)
: gr_block ("clock_recovery_mm_ff",
gr_make_io_signature (1, 1, sizeof (float)),
gr_make_io_signature (1, 1, sizeof (float))),
d_mu (mu), d_gain_omega(gain_omega), d_gain_mu(gain_mu),
d_last_sample(0), d_interp(new gri_mmse_fir_interpolator()),
d_logfile(0), d_omega_relative_limit(omega_relative_limit)
{
if (omega < 1)
throw std::out_of_range ("clock rate must be > 0");
if (gain_mu < 0 || gain_omega < 0)
throw std::out_of_range ("Gains must be non-negative");
set_omega(omega); // also sets min and max omega
set_relative_rate (1.0 / omega);
if (DEBUG_CR_MM_FF)
d_logfile = fopen("cr_mm_ff.dat", "wb");
}
digital_clock_recovery_mm_ff::~digital_clock_recovery_mm_ff ()
{
delete d_interp;
if (DEBUG_CR_MM_FF && d_logfile){
fclose(d_logfile);
d_logfile = 0;
}
}
void
digital_clock_recovery_mm_ff::forecast(int noutput_items, gr_vector_int &ninput_items_required)
{
unsigned ninputs = ninput_items_required.size();
for (unsigned i=0; i < ninputs; i++)
ninput_items_required[i] =
(int) ceil((noutput_items * d_omega) + d_interp->ntaps());
}
static inline float
slice(float x)
{
return x < 0 ? -1.0F : 1.0F;
}
/*
* This implements the Mueller and Müller (M&M) discrete-time error-tracking synchronizer.
*
* See "Digital Communication Receivers: Synchronization, Channel
* Estimation and Signal Processing" by Heinrich Meyr, Marc Moeneclaey, & Stefan Fechtel.
* ISBN 0-471-50275-8.
*/
int
digital_clock_recovery_mm_ff::general_work (int noutput_items,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const float *in = (const float *) input_items[0];
float *out = (float *) output_items[0];
int ii = 0; // input index
int oo = 0; // output index
int ni = ninput_items[0] - d_interp->ntaps(); // don't use more input than this
float mm_val;
while (oo < noutput_items && ii < ni ){
// produce output sample
out[oo] = d_interp->interpolate (&in[ii], d_mu);
mm_val = slice(d_last_sample) * out[oo] - slice(out[oo]) * d_last_sample;
d_last_sample = out[oo];
d_omega = d_omega + d_gain_omega * mm_val;
d_omega = d_omega_mid + gr_branchless_clip(d_omega-d_omega_mid, d_omega_relative_limit); // make sure we don't walk away
d_mu = d_mu + d_omega + d_gain_mu * mm_val;
ii += (int) floor(d_mu);
d_mu = d_mu - floor(d_mu);
oo++;
if (DEBUG_CR_MM_FF && d_logfile){
fwrite(&d_omega, sizeof(d_omega), 1, d_logfile);
}
}
consume_each (ii);
return oo;
}
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