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/* -*- c++ -*- */
/*
* Copyright 2004 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.
*/
/*
* config.h is generated by configure. It contains the results
* of probing for features, options etc. It should be the first
* file included in your .cc file.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdio.h>
#include <dab_ofdm_ffs_sample.h>
#include <gr_io_signature.h>
/*
* Create a new instance of dab_ofdm_ffs_sample and return
* a boost shared_ptr. This is effectively the public constructor.
*/
dab_ofdm_ffs_sample_sptr
dab_make_ofdm_ffs_sample (unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate)
{
return gnuradio::get_initial_sptr (new dab_ofdm_ffs_sample (symbol_length, fft_length, num_symbols, alpha, sample_rate));
}
dab_ofdm_ffs_sample::dab_ofdm_ffs_sample (unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate) :
gr_sync_block ("ofdm_ffs_sample",
gr_make_io_signature2 (2, 2, sizeof(float), sizeof(char)),
gr_make_io_signature (1, 1, sizeof(float))),
d_symbol_length(symbol_length), d_fft_length(fft_length), d_num_symbols(num_symbols), d_alpha(alpha), d_sample_rate(sample_rate), d_cur_symbol(num_symbols), d_cur_sample(0), d_ffs_error_sum(0), d_estimated_error(0), d_estimated_error_per_sample(0)
{
}
int
dab_ofdm_ffs_sample::work (int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const float *iptr = (const float *) input_items[0];
const char *trigger = (const char *) input_items[1];
float *optr = (float *) output_items[0];
float new_estimate;
for (int i=0; i<noutput_items; i++) {
if (*trigger++ == 1) { /* new frame starts */
d_cur_symbol = 0;
d_cur_sample = 0;
d_ffs_error_sum = 0;
}
d_cur_sample++;
if (d_cur_sample==d_symbol_length) { /* new symbol starts */
d_cur_sample = 0;
if (d_cur_symbol<d_num_symbols) {
new_estimate = *iptr;
if (d_cur_symbol>0) {
if (d_ffs_error_sum < 0 && new_estimate > 0 && new_estimate - d_ffs_error_sum/d_cur_symbol > M_PI)
new_estimate -= 2*M_PI;
else if (d_ffs_error_sum > 0 && new_estimate < 0 && d_ffs_error_sum/d_cur_symbol - new_estimate > M_PI)
new_estimate += 2*M_PI;
}
d_ffs_error_sum += new_estimate;
}
if (d_cur_symbol == d_num_symbols-1) { /* update estimated error */
d_ffs_error_sum /= d_num_symbols; /* average */
/* if the offset is close to half of the subcarrier bandwidth, it may
* jump from some large positive value to some large negative value.
* with averaging, this is a problem - we have to detect it (although
* it really only makes a difference when the offset is very close to
* half the subcarrier bandwidth)
* note: if there is an offset of one subcarrier bandwidth, the phase
* offset in fft_length samples is 2pi */
if (d_estimated_error < 0 && d_ffs_error_sum > 0 && d_ffs_error_sum - d_estimated_error > M_PI) {
fprintf(stderr, "ofdm_ffs_sample: switch detected: neg -> pos\n");
d_estimated_error += 2*M_PI;
} else if (d_estimated_error > 0 && d_ffs_error_sum < 0 && d_estimated_error - d_ffs_error_sum > M_PI) {
fprintf(stderr, "ofdm_ffs_sample: switch detected: pos -> neg\n");
d_estimated_error -= 2*M_PI;
}
/* the following distinction is not really needed; but without it,
* simulation would need to run much longer, becuase the
* synchronisation would need time to adjust to the offset */
if (d_estimated_error == 0)
d_estimated_error = d_ffs_error_sum; /* first time -> fast adjustment */
else
d_estimated_error = d_alpha*d_ffs_error_sum + (1-d_alpha)*d_estimated_error; /* slow adjustment */
d_estimated_error_per_sample = d_estimated_error / (float)d_fft_length;
// fprintf(stderr, "ofdm_ffs_sample: d_estimated_error: %f (%3.2f Hz)\n", d_estimated_error, d_estimated_error_per_sample*d_sample_rate/(2*M_PI));
}
d_cur_symbol++;
}
*optr++ = d_estimated_error_per_sample;
iptr++;
}
return noutput_items;
}
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