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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 <gnuradio/io_signature.h>
#include "ofdm_ffe_all_in_one_impl.h"
#include <gnuradio/math.h>
namespace gr {
namespace dab {
/*
* Create a new instance of dab_ofdm_ffe_all_in_one and return
* a boost shared_ptr. This is effectively the public constructor.
*/
ofdm_ffe_all_in_one::sptr
ofdm_ffe_all_in_one::make(unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate)
{
return gnuradio::get_initial_sptr
(new ofdm_ffe_all_in_one_impl(symbol_length, fft_length, num_symbols, alpha, sample_rate));
}
ofdm_ffe_all_in_one_impl::ofdm_ffe_all_in_one_impl(unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate)
: gr::sync_block("ofdm_ffe_all_in_one",
gr::io_signature::make (1, 1, sizeof(gr_complex)),
gr::io_signature::make (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)
{
assert(symbol_length<=2*fft_length); /* cyclic prefix can not be longer than fft_length .. */
set_history(symbol_length+1);
set_tag_propagation_policy(TPP_DONT);
}
float
ofdm_ffe_all_in_one_impl::calc_ffe_estimate(const gr_complex *in) {
gr_complex sum = 0;
int cp_length = d_symbol_length - d_fft_length;
// for (int i=-cp_length;i<0;i++)
// sum += in[i-d_fft_length+d_symbol_length] * conj(in[i+d_symbol_length]);
for (int i=0;i<cp_length;i++)
sum += in[i] * conj(in[i+d_fft_length]);
return gr::fast_atan2f(sum);
}
int
ofdm_ffe_all_in_one_impl::work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const gr_complex *iptr = (const gr_complex *) input_items[0];
float *optr = (float *) output_items[0];
float new_estimate;
std::vector<int> tag_positions;
int next_tag_position = -1;
int next_tag_position_index = -1;
// Get all stream tags with key "dab_sync", and make a vector of the positions.
// "next_tag_position" contains the position within "iptr where the next "dab_sync" stream tag is found
std::vector<tag_t> tags;
get_tags_in_range(tags, 0, nitems_read(0), nitems_read(0) + noutput_items, pmt::mp("dab_sync"));
for(int i=0;i<tags.size();i++) {
int current;
current = tags[i].offset - nitems_read(0);
tag_positions.push_back(current);
next_tag_position_index = 0;
}
if(next_tag_position_index >= 0) {
next_tag_position = tag_positions[next_tag_position_index];
}
for (int i=0; i<noutput_items; i++) {
if (next_tag_position == i) { /* new frame starts */
// Action when stream tags is found:
d_cur_symbol = 0;
d_cur_sample = 0;
d_ffs_error_sum = 0;
//
next_tag_position_index++;
if (next_tag_position_index == tag_positions.size()) {
next_tag_position_index = -1;
next_tag_position = -1;
}
else {
next_tag_position = tag_positions[next_tag_position_index];
}
}
if (d_cur_sample==d_symbol_length) { /* new symbol starts */
d_cur_sample = 0;
if (d_cur_symbol<d_num_symbols) {
new_estimate = calc_ffe_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_ffe_all_in_one: 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_ffe_all_in_one: 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, because 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_ffe_all_in_one: 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++;
}
d_cur_sample++;
*optr++ = d_estimated_error_per_sample;
iptr++;
}
return noutput_items;
}
}
}
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