digital_probe_mpsk_snr_est_c.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_PROBE_MPSK_SNR_EST_C_H
#define INCLUDED_DIGITAL_PROBE_MPSK_SNR_EST_C_H

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

class digital_probe_mpsk_snr_est_c;
typedef boost::shared_ptr<digital_probe_mpsk_snr_est_c> digital_probe_mpsk_snr_est_c_sptr;

DIGITAL_API digital_probe_mpsk_snr_est_c_sptr
digital_make_probe_mpsk_snr_est_c(snr_est_type_t type,
                                  int msg_nsamples=10000,
                                  double alpha=0.001);

/*! \brief A probe for computing SNR of a signal.
 *  \ingroup measurement_tools_blk
 *
 * \details
 *  This is a probe block (a sink) that can be used to monitor and
 *  retrieve estimations of the signal SNR. This probe 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_probe_mpsk_snr_est_c : 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 message name, 'snr'
  pmt::pmt_t d_key;

  /*! Factory function returning shared pointer of this class
   *
   *  \param type: the type of estimator to use \ref ref_snr_est_types
   *  "snr_est_type_t" for details about the available types.
   *  \param msg_nsamples: [not implemented yet] after this many
   *  samples, a message containing the SNR (key='snr') will be sent
   *  \param alpha: the update rate of internal running average
   *  calculations.
   */
  friend DIGITAL_API digital_probe_mpsk_snr_est_c_sptr
    digital_make_probe_mpsk_snr_est_c(snr_est_type_t type, 
                                      int msg_nsamples,
                                      double alpha);
  
  //! Private constructor
  digital_probe_mpsk_snr_est_c(snr_est_type_t type,
                               int msg_nsamples,
                               double alpha);

public:

  ~digital_probe_mpsk_snr_est_c();

  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 messages
  int msg_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 messages
  void set_msg_nsample(int n);

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

#endif /* INCLUDED_DIGITAL_PROBE_MPSK_SNR_EST_C_H */