/* -*- c++ -*- */

/*

 * Copyright 2005 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 2, 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 <gr_lms_dfe_cc.h>

#include <gr_io_signature.h>

#include <gr_misc.h>

#include <iostream>

gr_complex

gr_lms_dfe_cc::slicer_0deg (gr_complex sample)

{

  gr_complex out;

  if(fabs(real(sample))>fabs(imag(sample))) {

    if(real(sample) > 0)

      out = gr_complex(1,0);

    else

      out = gr_complex(-1,0);

  }

  else {

    if(imag(sample) > 0)

      out = gr_complex(0,1);

    else

      out = gr_complex(0,-1);

  }

  return out;

}

gr_complex

gr_lms_dfe_cc::slicer_45deg (gr_complex sample)

{

  gr_complex out;

  if(real(sample) > 0)

    out = gr_complex(1,0);

  else

    out = gr_complex(-1,0);

  if(imag(sample) > 0)

    out += gr_complex(0,1);

  else

    out += gr_complex(0,-1);

  return out;

}

gr_lms_dfe_cc_sptr

gr_make_lms_dfe_cc (float lambda_ff, float lambda_fb, 

                    unsigned int num_fftaps, unsigned int num_fbtaps)

{

  return gr_lms_dfe_cc_sptr (new gr_lms_dfe_cc (lambda_ff, lambda_fb,

                                                num_fftaps, num_fbtaps));

}

gr_lms_dfe_cc::gr_lms_dfe_cc (float lambda_ff, float lambda_fb , 

                              unsigned int num_fftaps, unsigned int num_fbtaps)

  : gr_sync_block ("lms_dfe_cc",

                   gr_make_io_signature (1, 1, sizeof (gr_complex)),

                   gr_make_io_signature (1, 1, sizeof (gr_complex))),

    d_lambda_ff (lambda_ff), d_lambda_fb (lambda_fb), 

    d_ff_delayline(gr_rounduppow2(num_fftaps)),

    d_fb_delayline(gr_rounduppow2(num_fbtaps)),

    d_ff_taps(num_fftaps),d_fb_taps(num_fbtaps),

    d_ff_index(0), d_fb_index(0)

{

  gr_zero_vector(d_ff_taps);

  d_ff_taps [d_ff_taps.size()/2] = 1;

  gr_zero_vector(d_fb_taps);

  gr_zero_vector(d_ff_delayline);

  gr_zero_vector(d_fb_delayline);

}

int

gr_lms_dfe_cc::work (int noutput_items,

                   gr_vector_const_void_star &input_items,

                   gr_vector_void_star &output_items)

{

  const gr_complex *iptr = (const gr_complex *) input_items[0];

  gr_complex *optr = (gr_complex *) output_items[0];

  gr_complex acc, decision, error;

  unsigned int i;

  unsigned int ff_mask = d_ff_delayline.size() - 1;        // size is power of 2

  unsigned int fb_mask = d_fb_delayline.size() - 1;

  int        size = noutput_items;

  while (size-- > 0){

    acc = 0; 

    d_ff_delayline[d_ff_index] = *iptr++;

    // Compute output

    for (i=0; i < d_ff_taps.size(); i++) 

      acc += conj(d_ff_delayline[(i+d_ff_index) & ff_mask]) * d_ff_taps[i];

    for (i=0; i < d_fb_taps.size(); i++)

      acc -= conj(d_fb_delayline[(i+d_fb_index) & fb_mask]) * d_fb_taps[i];

    decision = slicer_45deg(acc);

    error = decision - acc;

    //  Update taps

    for (i=0; i < d_ff_taps.size(); i++)

      d_ff_taps[i] += d_lambda_ff * conj(error) * d_ff_delayline[(i+d_ff_index) & ff_mask];

    for (i=0; i < d_fb_taps.size(); i++)

      d_fb_taps[i] -= d_lambda_fb * conj(error) * d_fb_delayline[(i+d_fb_index) & fb_mask];

    d_fb_index = (d_fb_index - 1) & fb_mask;        // Decrement index

    d_ff_index = (d_ff_index - 1) & ff_mask;        // Decrement index

    d_fb_delayline[d_fb_index] = decision;        // Save decision in feedback

    *optr++ = acc;   // Output decision

  }

  if (0){

    std::cout << "FF Taps\t";

    for(i=0;i<d_ff_taps.size();i++)

      std::cout << d_ff_taps[i] << "\t";

    std::cout << std::endl << "FB Taps\t";

    for(i=0;i<d_fb_taps.size();i++)

      std::cout << d_fb_taps[i] << "\t";

    std::cout << std::endl;

  }

  return noutput_items;

}