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/* -*- c++ -*- */
/*
* Copyright 2006,2007,2011,2012 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_DIGITAL_OFDM_FRAME_ACQUISITION_H
#define INCLUDED_DIGITAL_OFDM_FRAME_ACQUISITION_H
#include <gnuradio/digital/api.h>
#include <gnuradio/block.h>
#include <vector>
namespace gr {
namespace digital {
/*!
* \brief take a vector of complex constellation points in from an
* FFT and performs a correlation and equalization.
* \ingroup ofdm_blk
* \ingroup deprecated_blk
*
* \details
* This block takes the output of an FFT of a received OFDM symbol
* and finds the start of a frame based on two known symbols. It
* also looks at the surrounding bins in the FFT output for the
* correlation in case there is a large frequency shift in the
* data. This block assumes that the fine frequency shift has
* already been corrected and that the samples fall in the middle
* of one FFT bin.
*
* It then uses one of those known symbols to estimate the channel
* response over all subcarriers and does a simple 1-tap
* equalization on all subcarriers. This corrects for the phase
* and amplitude distortion caused by the channel.
*/
class DIGITAL_API ofdm_frame_acquisition : virtual public block
{
public:
// gr::digital::ofdm_frame_acquisition::sptr
typedef boost::shared_ptr<ofdm_frame_acquisition> sptr;
/*!
* Make an OFDM correlator and equalizer.
*
* \param occupied_carriers The number of subcarriers with data in the received symbol
* \param fft_length The size of the FFT vector (occupied_carriers + unused carriers)
* \param cplen The length of the cycle prefix
* \param known_symbol A vector of complex numbers representing a known symbol at the
* start of a frame (usually a BPSK PN sequence)
* \param max_fft_shift_len Set's the maximum distance you can look between bins for correlation
*/
static sptr make(unsigned int occupied_carriers, unsigned int fft_length,
unsigned int cplen,
const std::vector<gr_complex> &known_symbol,
unsigned int max_fft_shift_len=4);
/*!
* \brief Return an estimate of the SNR of the channel
*/
virtual float snr() = 0;
};
} /* namespace digital */
} /* namespace gr */
#endif /* INCLUDED_DIGITAL_OFDM_FRAME_ACQUISITION_H */
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