digital_mpsk_snr_est_cc.h

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/* -*- c++ -*- */
/*
 * Copyright 2011 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_MPSK_SNR_EST_CC_H
#define INCLUDED_DIGITAL_MPSK_SNR_EST_CC_H

#include <digital_api.h>
#include <gr_sync_block.h>
#include <digital_impl_mpsk_snr_est.h>

class digital_mpsk_snr_est_cc;
typedef boost::shared_ptr<digital_mpsk_snr_est_cc> digital_mpsk_snr_est_cc_sptr;

DIGITAL_API digital_mpsk_snr_est_cc_sptr
digital_make_mpsk_snr_est_cc(snr_est_type_t type,
                             int tag_nsamples=10000,
                             double alpha=0.001);

/*! \brief A block for computing SNR of a signal.
 *  \ingroup measurement_tools_blk
 *
 *  \details
 *  This block can be used to monitor and retrieve estimations of the
 *  signal SNR. It is designed to work in a flowgraph and passes all
 *  incoming data along to its output.
 *
 *  The block is designed for use with M-PSK signals especially. The
 *  type of estimator is specified as the \p type parameter in the
 *  constructor. The estimators tend to trade off performance for
 *  accuracy, although experimentation should be done to figure out
 *  the right approach for a given implementation. Further, the
 *  current set of estimators are designed and proven theoretically
 *  under AWGN conditions; some amount of error should be assumed
 *  and/or estimated for real channel conditions.
 */
class DIGITAL_API digital_mpsk_snr_est_cc : public gr_sync_block
{
 private:
  snr_est_type_t d_type;
  int d_nsamples, d_count;
  double d_alpha;
  digital_impl_mpsk_snr_est *d_snr_est;

  //d_key is the tag name, 'snr', d_me is the block name + unique ID
  pmt::pmt_t d_key, d_me; 

  /*! Factory function returning shared pointer of this class
   *
   *  Parameters:
   *
   *  \param type: the type of estimator to use \ref ref_snr_est_types
   *  "snr_est_type_t" for details about the available types.
   *  \param tag_nsamples: after this many samples, a tag containing
   *  the SNR (key='snr') will be sent
   *  \param alpha: the update rate of internal running average
   *  calculations.
   */
  friend DIGITAL_API digital_mpsk_snr_est_cc_sptr
    digital_make_mpsk_snr_est_cc(snr_est_type_t type,
                                 int tag_nsamples,
                                 double alpha);
  
  // Private constructor
  digital_mpsk_snr_est_cc(snr_est_type_t type,
                          int tag_nsamples,
                          double alpha);

public:

  ~digital_mpsk_snr_est_cc();

  int work (int noutput_items,
            gr_vector_const_void_star &input_items,
            gr_vector_void_star &output_items);

  //! Return the estimated signal-to-noise ratio in decibels
  double snr();

  //! Return the type of estimator in use
  snr_est_type_t type() const;

  //! Return how many samples between SNR tags
  int tag_nsample() const;

  //! Get the running-average coefficient
  double alpha() const;

  //! Set type of estimator to use
  void set_type(snr_est_type_t t);

  //! Set the number of samples between SNR tags
  void set_tag_nsample(int n);

  //! Set the running-average coefficient
  void set_alpha(double alpha);
};

#endif /* INCLUDED_DIGITAL_MPSK_SNR_EST_CC_H */