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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_KURTOTIC_EQUALIZER_CC_H
#define INCLUDED_DIGITAL_KURTOTIC_EQUALIZER_CC_H
#include <digital_api.h>
#include <gr_adaptive_fir_ccc.h>
#include <gr_math.h>
#include <iostream>
class digital_kurtotic_equalizer_cc;
typedef boost::shared_ptr<digital_kurtotic_equalizer_cc> digital_kurtotic_equalizer_cc_sptr;
DIGITAL_API digital_kurtotic_equalizer_cc_sptr
digital_make_kurtotic_equalizer_cc(int num_taps, float mu);
/*!
* \brief Implements a kurtosis-based adaptive equalizer on complex stream
* \ingroup eq_blk
* \ingroup digital
*
* "Y. Guo, J. Zhao, Y. Sun, "Sign kurtosis maximization based blind
* equalization algorithm," IEEE Conf. on Control, Automation,
* Robotics and Vision, Vol. 3, Dec. 2004, pp. 2052 - 2057."
*/
class DIGITAL_API digital_kurtotic_equalizer_cc : public gr_adaptive_fir_ccc
{
private:
float d_mu;
float d_p, d_m;
gr_complex d_q, d_u;
float d_alpha_p, d_alpha_q, d_alpha_m;
friend DIGITAL_API digital_kurtotic_equalizer_cc_sptr digital_make_kurtotic_equalizer_cc(int num_taps,
float mu);
digital_kurtotic_equalizer_cc(int num_taps, float mu);
gr_complex sign(gr_complex x)
{
float re = (float)(x.real() >= 0.0f);
float im = (float)(x.imag() >= 0.0f);
return gr_complex(re, im);
}
protected:
virtual gr_complex error(const gr_complex &out)
{
// p = E[|z|^2]
// q = E[z^2]
// m = E[|z|^4]
// u = E[kurtosis(z)]
float nrm = norm(out);
gr_complex cnj = conj(out);
float epsilon_f = 1e-12;
gr_complex epsilon_c = gr_complex(1e-12, 1e-12);
d_p = (1-d_alpha_p)*d_p + (d_alpha_p)*nrm + epsilon_f;
d_q = (1-d_alpha_q)*d_q + (d_alpha_q)*out*out + epsilon_c;
d_m = (1-d_alpha_m)*d_m + (d_alpha_m)*nrm*nrm + epsilon_f;
d_u = d_m - 2.0f*(d_p*d_p) - d_q*d_q;
gr_complex F = (1.0f / (d_p*d_p*d_p)) *
(sign(d_u) * (nrm*cnj - 2.0f*d_p*cnj - conj(d_q)*out) -
abs(d_u)*cnj);
//std::cout << "out: " << out << " p: " << d_p << " q: " << d_q;
//std::cout << " m: " << d_m << " u: " << d_u << std::endl;
//std::cout << "error: " << F << std::endl;
float re = gr_clip(F.real(), 1.0);
float im = gr_clip(F.imag(), 1.0);
return gr_complex(re, im);
}
virtual void update_tap(gr_complex &tap, const gr_complex &in)
{
tap += d_mu*in*d_error;
}
public:
void set_gain(float mu)
{
if(mu < 0)
throw std::out_of_range("digital_kurtotic_equalizer::set_gain: Gain value must be >= 0");
d_mu = mu;
}
};
#endif
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