Revision c7dbfcc7 gnuradio-core/src/lib/general/gr_ofdm_correlator.h

b/gnuradio-core/src/lib/general/gr_ofdm_correlator.h
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/* -*- c++ -*- */
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/*
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 * Copyright 2006 Free Software Foundation, Inc.
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 * Copyright 2006, 2007 Free Software Foundation, Inc.
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 *
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 * This file is part of GNU Radio
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 *
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typedef boost::shared_ptr<gr_ofdm_correlator> gr_ofdm_correlator_sptr;
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gr_ofdm_correlator_sptr 







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gr_make_ofdm_correlator (unsigned int occupied_carriers, unsigned int vlen,








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gr_make_ofdm_correlator (unsigned int occupied_carriers, unsigned int fft_length,







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			 unsigned int cplen,







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			 std::vector<gr_complex> known_symbol1, 







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			 std::vector<gr_complex> known_symbol2);








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			 const std::vector<gr_complex> &known_symbol1, 








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			 const std::vector<gr_complex> &known_symbol2);







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/*!







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 * \brief take a vector of complex constellation points in from an FFT







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 * been corrected and that the samples fall in the middle of one FFT bin.







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 *







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 * It then uses one of those known







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 * symbosl to estimate the channel response overa all subcarriers and does a simple 








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 * symbols to estimate the channel response over all subcarriers and does a simple 







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 * 1-tap equalization on all subcarriers. This corrects for the phase and amplitude







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 * distortion caused by the channel.







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 */







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  /*! 







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   * \brief Build an OFDM correlator and equalizer.







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   * \param occupied_carriers   The number of subcarriers with data in the received symbol







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   * \param vlen                The size of the FFT vector (occupied_carriers + unused carriers)








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   * \param fft_length          The size of the FFT vector (occupied_carriers + unused carriers)







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   * \param known_symbol1       A vector of complex numbers representing a known symbol at the







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   *                            start of a frame (usually a BPSK PN sequence)







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   * \param known_symbol2       A vector of complex numbers representing a known symbol at the







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   *                            for phase changes between symbols. 







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   */







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  friend gr_ofdm_correlator_sptr







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  gr_make_ofdm_correlator (unsigned int occupied_carriers, unsigned int vlen,








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  gr_make_ofdm_correlator (unsigned int occupied_carriers, unsigned int fft_length,







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			   unsigned int cplen,







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			   std::vector<gr_complex> known_symbol1, 







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			   std::vector<gr_complex> known_symbol2);








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			   const std::vector<gr_complex> &known_symbol1, 








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			   const std::vector<gr_complex> &known_symbol2);







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 protected:







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  gr_ofdm_correlator (unsigned int occupied_carriers, unsigned int vlen,








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  gr_ofdm_correlator (unsigned int occupied_carriers, unsigned int fft_length,







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		      unsigned int cplen,







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		      std::vector<gr_complex> known_symbol1, 







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		      std::vector<gr_complex> known_symbol2);








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		      const std::vector<gr_complex> &known_symbol1, 








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		      const std::vector<gr_complex> &known_symbol2);







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 private:







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  unsigned char slicer(gr_complex x);







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  gr_complex coarse_freq_comp(int freq_delta, int count);







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  unsigned int d_occupied_carriers;  // !< \brief number of subcarriers with data







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  unsigned int d_vlen;               // !< \brief length of FFT vector








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  unsigned int d_fft_length;         // !< \brief length of FFT vector







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  unsigned int d_cplen;              // !< \brief length of cyclic prefix in samples







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  unsigned int d_freq_shift_len;     // !< \brief number of surrounding bins to look at for correlation







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  std::vector<gr_complex> d_known_symbol1, d_known_symbol2; // !< \brief known symbols at start of frame







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  std::vector<gr_complex> d_diff_corr_factor; // !< \brief factor used in correlation







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  std::vector<gr_complex> d_hestimate; // !< channel estimate







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  signed int d_coarse_freq; // !< \brief search distance in number of bins







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  unsigned int d_phase_count;        // !< \brief accumulator for coarse freq correction







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  float d_snr_est;  // !< an estimation of the signal to noise ratio








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  std::vector<gr_complex> d_hestimate;  // !< channel estimate








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  signed int d_coarse_freq;             // !< \brief search distance in number of bins








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  unsigned int d_phase_count;           // !< \brief accumulator for coarse freq correction








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  float d_snr_est;                      // !< an estimation of the signal to noise ratio







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  void forecast(int noutput_items, gr_vector_int &ninput_items_required);







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