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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.
*/
#ifndef INCLUDED_DAB_OFDM_FFS_SAMPLE_H
#define INCLUDED_DAB_OFDM_FFS_SAMPLE_H
#include <gr_sync_block.h>
class dab_ofdm_ffs_sample;
typedef std::shared_ptr<dab_ofdm_ffs_sample> dab_ofdm_ffs_sample_sptr;
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);
/*!
* \brief samples FFS error estimation at the correct time and averages it
* \ingroup DAB
* \param symbol_length number of samples in an OFDM symbol
* \param fft_length number of samples in an OFDM symbol without the cyclic prefix
* \param num_symbols number of symbols to use for averaging (more symbols is better, but symbols towards the end of the frame tend to have larger time offsets and worse values)
* \param alpha how fast should we adapt to new FFS error values (1=immediately)
* \param sample_rate sampling rate - needed to calculate the offset estimation in Hz
*
* input: port 0: float - actual data; port 1: byte - trigger signal indicating the start of a frame
* output: float fine frequency offset estimation (in radian per sample)
*/
class dab_ofdm_ffs_sample : public gr_sync_block
{
private:
// The friend declaration allows dab_make_ofdm_ffs_sample to
// access the private constructor.
friend 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);
dab_ofdm_ffs_sample (unsigned int symbol_length, unsigned int fft_length, unsigned int num_symbols, float alpha, unsigned int sample_rate); // private constructor
unsigned int d_symbol_length; // length of a symbol in samples
unsigned int d_fft_length; // length of a symbol without cyclic prefix in samples
unsigned int d_num_symbols; // number of symbols per frame to average over
float d_alpha; // adjustment speed factor
unsigned int d_sample_rate; // sample rate -- only needed to print the ffs error in Hz
unsigned int d_cur_symbol; // which symbol in the frame is currently under observation?
unsigned int d_cur_sample; // which sample in the symbol is currently under observation?
float d_ffs_error_sum; // sum of error samples in current frame
float d_estimated_error; // total estimated error
float d_estimated_error_per_sample; // total estimated error / fft_length
public:
/*! \return fine frequency error estimate in Hz */
float ffe_estimate() { return d_estimated_error_per_sample*d_sample_rate/(2*M_PI); }
int work (int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items);
};
#endif /* INCLUDED_DAB_OFDM_FFS_SAMPLE_H */
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