/* -*- 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.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <digital_impl_mpsk_snr_est.h>
#include <cstdio>

digital_impl_mpsk_snr_est::digital_impl_mpsk_snr_est(double alpha)
{
  set_alpha(alpha);
}

digital_impl_mpsk_snr_est::~digital_impl_mpsk_snr_est()
{}

void
digital_impl_mpsk_snr_est::set_alpha(double alpha)
{
  d_alpha = alpha;
  d_beta = 1.0-alpha;
}

double
digital_impl_mpsk_snr_est::alpha() const
{
  return d_alpha;
}

int
digital_impl_mpsk_snr_est::update(int noutput_items,
			  const gr_complex *in)
{
  throw std::runtime_error("digital_impl_mpsk_snr_est: Unimplemented");
}

double
digital_impl_mpsk_snr_est::snr()
{
  throw std::runtime_error("digital_impl_mpsk_snr_est: Unimplemented");
}


/********************************************************************/


digital_impl_mpsk_snr_est_simple::digital_impl_mpsk_snr_est_simple(
		   double alpha) :
  digital_impl_mpsk_snr_est(alpha)
{
  d_y1 = 0;
  d_y2 = 0;
}

int
digital_impl_mpsk_snr_est_simple::update(
		 int noutput_items,
		 const gr_complex *in)
{
  for (int i = 0; i < noutput_items; i++){
    double y1 = abs(in[i]);
    d_y1 = d_alpha*y1 + d_beta*d_y1;

    double y2 = real(in[i]*in[i]);
    d_y2 = d_alpha*y2 + d_beta*d_y2;
  }
  return noutput_items;
}

double
digital_impl_mpsk_snr_est_simple::snr()
{
  double y1_2 = d_y1*d_y1;
  double y3 = y1_2 - d_y2 + 1e-20;
  return 10.0*log10(y1_2/y3);
}


/********************************************************************/


digital_impl_mpsk_snr_est_skew::digital_impl_mpsk_snr_est_skew(
		   double alpha) :
  digital_impl_mpsk_snr_est(alpha)
{
  d_y1 = 0;
  d_y2 = 0;
  d_y3 = 0;
}


int
digital_impl_mpsk_snr_est_skew::update(
		 int noutput_items,
		 const gr_complex *in)
{
  for (int i = 0; i < noutput_items; i++){
    double y1 = abs(in[i]);
    d_y1 = d_alpha*y1 + d_beta*d_y1;

    double y2 = real(in[i]*in[i]);
    d_y2 = d_alpha*y2 + d_beta*d_y2;

    // online algorithm for calculating skewness
    // See:
    // http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Higher-order_statistics
    double d = abs(in[i]) - d_y1;
    double d_i = d / (i+1);
    double y3 = (d*d_i*i)*d_i*(i-1) - 3.0*d_i*d_y2;
    d_y3 = d_alpha*y3 + d_beta*d_y3;
  }
  return noutput_items;
}

double
digital_impl_mpsk_snr_est_skew::snr()
{
  double y3 = d_y3*d_y3 / (d_y2*d_y2*d_y2);
  double y1_2 = d_y1*d_y1;
  double x = y1_2 - d_y2;
  return 10.0*log10(y1_2 / (x + y3*y1_2));
}


/********************************************************************/


digital_impl_mpsk_snr_est_m2m4::digital_impl_mpsk_snr_est_m2m4(
		   double alpha) :
  digital_impl_mpsk_snr_est(alpha)
{
  d_y1 = 0;
  d_y2 = 0;
}

int
digital_impl_mpsk_snr_est_m2m4::update(
		 int noutput_items,
		 const gr_complex *in)
{
  for (int i = 0; i < noutput_items; i++){
    double y1 = abs(in[i])*abs(in[i]);
    d_y1 = d_alpha*y1 + d_beta*d_y1;

    double y2 = abs(in[i])*abs(in[i])*abs(in[i])*abs(in[i]);
    d_y2 = d_alpha*y2 + d_beta*d_y2;
  }
  return noutput_items;
}

double
digital_impl_mpsk_snr_est_m2m4::snr()
{
  double y1_2 = d_y1*d_y1;
  return 10.0*log10(2.0*sqrt(2*y1_2 - d_y2) / 
		    (d_y1 - sqrt(2*y1_2 - d_y2)));
}


/********************************************************************/


digital_impl_snr_est_m2m4::digital_impl_snr_est_m2m4(
		   double alpha, double ka, double kw) :
  digital_impl_mpsk_snr_est(alpha)
{
  d_y1 = 0;
  d_y2 = 0;
  d_ka = ka;
  d_kw = kw;
}

int
digital_impl_snr_est_m2m4::update(
		 int noutput_items,
		 const gr_complex *in)
{
  for (int i = 0; i < noutput_items; i++) {
    double y1 = abs(in[i])*abs(in[i]);
    d_y1 = d_alpha*y1 + d_beta*d_y1;

    double y2 = abs(in[i])*abs(in[i])*abs(in[i])*abs(in[i]);
    d_y2 = d_alpha*y2 + d_beta*d_y2;
  }
  return noutput_items;
}

double
digital_impl_snr_est_m2m4::snr()
{
  double M2 = d_y1;
  double M4 = d_y2;
  double s = M2*(d_kw - 2) + 
    sqrt((4.0-d_ka*d_kw)*M2*M2 + M4*(d_ka+d_kw-4.0)) /
    (d_ka + d_kw - 4.0);
  double n = M2 - s;
  
  return 10.0*log10(s / n);
}


/********************************************************************/


digital_impl_mpsk_snr_est_svr::digital_impl_mpsk_snr_est_svr(
		   double alpha) :
  digital_impl_mpsk_snr_est(alpha)
{
  d_y1 = 0;
  d_y2 = 0;
}

int
digital_impl_mpsk_snr_est_svr::update(
		 int noutput_items,
		 const gr_complex *in)
{
  for (int i = 0; i < noutput_items; i++){
    double x = abs(in[i]);
      double x1 = abs(in[i-1]);
    double y1 = (x*x)*(x1*x1);
    d_y1 = d_alpha*y1 + d_beta*d_y1;
    
    double y2 = x*x*x*x;
    d_y2 = d_alpha*y2 + d_beta*d_y2;
  }
  return noutput_items;
}

double
digital_impl_mpsk_snr_est_svr::snr()
{
  double x = d_y1 / (d_y2 - d_y1);
  return 10.0*log10(2.*((x-1) + sqrt(x*(x-1))));
}