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Diffstat (limited to 'gr-digital/include/digital_ofdm_sync_sc_cfb.h')
| -rw-r--r-- | gr-digital/include/digital_ofdm_sync_sc_cfb.h | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/gr-digital/include/digital_ofdm_sync_sc_cfb.h b/gr-digital/include/digital_ofdm_sync_sc_cfb.h new file mode 100644 index 0000000000..26cf5b3de5 --- /dev/null +++ b/gr-digital/include/digital_ofdm_sync_sc_cfb.h @@ -0,0 +1,83 @@ +/* -*- 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 */ + |