-/* -*- 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_CHANEST_VCVC_H

-#define INCLUDED_DIGITAL_OFDM_CHANEST_VCVC_H

-

-#include <digital/api.h>

-#include <gr_block.h>

-

-class digital_ofdm_chanest_vcvc;

-

-typedef boost::shared_ptr<digital_ofdm_chanest_vcvc> digital_ofdm_chanest_vcvc_sptr;

-

-/*

- * \param sync_symbol1 First synchronisation symbol in the frequency domain. Its length must be

- * the FFT length. For Schmidl & Cox synchronisation, every second sub-carrier

- * has to be zero.

- * \param sync_symbol2 Second synchronisation symbol in the frequency domain. Must be equal to

- * the FFT length, or zero length if only one synchronisation symbol is used.

- * Using this symbol is how synchronisation is described in [1]. Leaving this

- * empty forces us to interpolate the equalizer taps.

- * If you are using an unusual sub-carrier configuration (e.g. because of OFDMA),

- * this sync symbol is used to identify the active sub-carriers. If you only

- * have one synchronisation symbol, set the active sub-carriers to a non-zero

- * value in here, and also set \p force_one_sync_symbol parameter to true.

- * \param n_data_symbols The number of data symbols following each set of synchronisation symbols.

- * Must be at least 1.

- * \param eq_noise_red_len If non-zero, noise reduction for the equalizer taps is done according

- * to [2]. In this case, it is the channel influence time in number of

- * samples. A good value is usually the length of the cyclic prefix.

- * \param max_carr_offset Limit the number of sub-carriers the frequency offset can maximally be.

- * Leave this zero to try all possibilities.

- * \param force_one_sync_symbol See \p sync_symbol2.

- */

-DIGITAL_API digital_ofdm_chanest_vcvc_sptr

-digital_make_ofdm_chanest_vcvc (

- const std::vector<gr_complex> &sync_symbol1,

- const std::vector<gr_complex> &sync_symbol2,

- int n_data_symbols,

- int eq_noise_red_len=0,

- int max_carr_offset=-1,

- bool force_one_sync_symbol=false);

-

-/*!

- * \brief Estimate channel and coarse frequency offset for OFDM from preambles

- * \ingroup ofdm_blk

- * \ingroup sync_blk

- *

- * Input: OFDM symbols (in frequency domain). The first one (or two) symbols are expected

- * to be synchronisation symbols, which are used to estimate the coarse freq offset

- * and the initial equalizer taps (these symbols are removed from the stream).

- * The following \p n_data_symbols are passed through unmodified (the actual equalisation

- * must be done elsewhere).

- * Output: The data symbols, without the synchronisation symbols.

- * The first data symbol passed through has two tags:

- * 'ofdm_sync_carr_offset' (integer), the coarse frequency offset as number of carriers,

- * and 'ofdm_sync_eq_taps' (complex vector).

- * Any tags attached to the synchronisation symbols are attached to the first data

- * symbol. All other tags are propagated normally.

- *

- * This block assumes the frequency offset is even (i.e. an integer multiple of 2).

- *

- * [1] Schmidl, T.M. and Cox, D.C., "Robust frequency and timing synchronization for OFDM",

- * Communications, IEEE Transactions on, 1997.

- * [2] K.D. Kammeyer, "Nachrichtenuebertragung," Chapter. 16.3.2.

- */

-class DIGITAL_API digital_ofdm_chanest_vcvc : public gr_block

-{

- private:

- friend DIGITAL_API digital_ofdm_chanest_vcvc_sptr digital_make_ofdm_chanest_vcvc (const std::vector<gr_complex> &sync_symbol1, const std::vector<gr_complex> &sync_symbol2, int n_data_symbols, int eq_noise_red_len, int max_carr_offset, bool force_one_sync_symbol);

-

- int d_fft_len; //! FFT length

- int d_n_data_syms; //! Number of data symbols following the sync symbol(s)

- int d_n_sync_syms; //! Number of sync symbols (1 or 2)

- //! 0 if no noise reduction is done for the initial channel state estimation. Otherwise, the maximum length of the channel delay in samples.

- int d_eq_noise_red_len;

- //! Is sync_symbol1 if d_n_sync_syms == 1, otherwise sync_symbol2. Used as a reference symbol to estimate the channel.

- std::vector<gr_complex> d_ref_sym;

- //! If d_n_sync_syms == 2 this is used as a differential correlation vector (called 'v' in [1]).

- std::vector<gr_complex> d_corr_v;

- //! If d_n_sync_syms == 1 we use this instead of d_corr_v to estimate the coarse freq. offset

- std::vector<float> d_known_symbol_diffs;

- //! If d_n_sync_syms == 1 we use this instead of d_corr_v to estimate the coarse freq. offset (temp. variable)

- std::vector<float> d_new_symbol_diffs;

- //! The index of the first carrier with data (index 0 is not DC here, but the lowest frequency)

- int d_first_active_carrier;

- //! The index of the last carrier with data

- int d_last_active_carrier;

- //! If true, the channel estimation must be interpolated

- bool d_interpolate;

- //! Maximum carrier offset (negative value!)

- int d_max_neg_carr_offset;

- //! Maximum carrier offset (positive value!)

- int d_max_pos_carr_offset;

-

-

- digital_ofdm_chanest_vcvc(const std::vector<gr_complex> &sync_symbol1, const std::vector<gr_complex> &sync_symbol2, int n_data_symbols, int eq_noise_red_len, int max_carr_offset, bool force_one_sync_symbol);

-

- //! Calculate the coarse frequency offset in number of carriers

- int get_carr_offset(const gr_complex *sync_sym1, const gr_complex *sync_sym2);

- //! Estimate the channel (phase and amplitude offset per carrier)

- void get_chan_taps(const gr_complex *sync_sym1, const gr_complex *sync_sym2, int carr_offset, std::vector<gr_complex> &taps);

-

- public:

- ~digital_ofdm_chanest_vcvc();

-

- void forecast (int noutput_items, gr_vector_int &ninput_items_required);

- int general_work (int noutput_items,

- gr_vector_int &ninput_items,

- gr_vector_const_void_star &input_items,

- gr_vector_void_star &output_items);

-};

-

-#endif /* INCLUDED_DIGITAL_OFDM_CHANEST_VCVC_H */

-