digital_ofdm_sync_sc_cfb.h

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/* -*- c++ -*- */
/* Copyright 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_SYNC_SC_CFB_H
#define INCLUDED_DIGITAL_OFDM_SYNC_SC_CFB_H

#include <digital_api.h>
#include <gr_hier_block2.h>

class digital_ofdm_sync_sc_cfb;
typedef boost::shared_ptr<digital_ofdm_sync_sc_cfb> digital_ofdm_sync_sc_cfb_sptr;

/*! \param fft_len FFT length
 *  \param cp_len Length of the guard interval (cyclic prefix) in samples
 *  \param use_even_carriers If true, the carriers in the sync preamble are occupied such
 *                     that the even carriers are used (0, 2, 4, ...). If you use all
 *                     carriers, that would include the DC carrier, so be careful.
 */
DIGITAL_API digital_ofdm_sync_sc_cfb_sptr
digital_make_ofdm_sync_sc_cfb (int fft_len, int cp_len, bool use_even_carriers=false);

/*!
 * \brief Schmidl & Cox synchronisation for OFDM
 * \ingroup ofdm_blk
 * \ingroup synchronizers_blk
 *
 * \details
 * Input: complex samples.
 * Output 0: Fine frequency offset, scaled by the OFDM symbol duration.
 *           This is \f$\hat{\varphi}\f$ in [1]. The normalized frequency
 *           offset is then 2.0*output0/fft_len.
 * Output 1: Beginning of the first OFDM symbol after the first (doubled) OFDM
 *           symbol. The beginning is marked with a 1 (it's 0 everywhere else).
 *
 * The evaluation of the coarse frequency offset is *not* done in this block.
 * Also, the initial equalizer taps are not calculated here.
 *
 * Note that we use a different normalization factor in the timing metric than
 * the authors do in their original work[1]. If the timing metric (8) is
 * \f[
 * M(d) = \frac{|P(d)|^2}{(R(d))^2},
 * \f]
 * we calculate the normalization as
 * \f[
 * R(d) = \frac{1}{2} \sum_{k=0}^{N-1} |r_{k+d}|^2,
 * \f]
 * i.e., we estimate the energy from *both* half-symbols. This avoids spurious detects
 * at the end of a burst, when the energy level suddenly drops.
 *
 * [1] Schmidl, T.M. and Cox, D.C., "Robust frequency and timing synchronization for OFDM",
 *     Communications, IEEE Transactions on, 1997.
 */
class DIGITAL_API digital_ofdm_sync_sc_cfb : public gr_hier_block2
{
 private:
  friend DIGITAL_API digital_ofdm_sync_sc_cfb_sptr digital_make_ofdm_sync_sc_cfb (int fft_len, int cp_len, bool use_even_carriers);
  digital_ofdm_sync_sc_cfb(int fft_len, int cp_len, bool use_even_carriers);

 public:
  ~digital_ofdm_sync_sc_cfb();

};

#endif /* INCLUDED_DIGITAL_OFDM_SYNC_SC_CFB_H */