qam_theory.cpp

《无线通信系统仿真——c++使用模型》这本书的源代码

//
//  File = qam_theory.cpp
//

#include <stdlib.h>
#include <math.h>
#include "qam_theory.h"
#include "sinc.h"
#include "q_func.h"
#include "log2.h"
#include <fstream>
#ifndef PI
  #define PI 3.1415926535897932
#endif
using namespace std;

void QamPsd( int big_m,
               double carrier_freq,
              double symb_energy,
              double bit_rate,
              double beg_freq,
              double end_freq,
              int num_pts,
              bool plot_in_db,
              char* out_filename)
{
  double freq, val;
  ofstream *out_file;
  out_file = new ofstream(out_filename, ios::out);

  double delta_freq = (end_freq - beg_freq)/double(num_pts-1);
  double m_factor = double(ilog2(big_m));
  double energy = symb_energy / 2.0;

  for(int n=0; n<num_pts; n++)
    {
    freq = beg_freq + n * delta_freq;
    val = energy * (  sinc_sqrd((freq-carrier_freq)*m_factor/bit_rate)
                        + sinc_sqrd((freq+carrier_freq)*m_factor/bit_rate) );
    if( plot_in_db )
      {
      if(val>0.0)
        {
        val = 10.0 * log10(val);
        }
      else
        {
        val = -200.0;
        }
      }
    (*out_file) << freq << ", " << val << endl;
    }
  delete out_file;
}

//==========================================================

void QamBer( int big_m,
               double beg_ebno,
               double end_ebno,
               int num_pts,
               char* out_filename)
{
  double ebno_numeric, ebno_db, bit_err, symb_err, q_arg;
  double m_factor, sin_arg;
  ofstream *out_file;
  out_file = new ofstream(out_filename, ios::out);

  double delta_ebno = (end_ebno - beg_ebno)/double(num_pts-1);
  m_factor = double(ilog2(big_m));
  sin_arg = PI/double(big_m);

  for(int n=0; n<num_pts; n++)
    {
    ebno_db = beg_ebno + n * delta_ebno;
    ebno_numeric = pow(10.0, ebno_db/10.0);
    q_arg = sqrt(2.0 * m_factor * ebno_numeric) * sin(sin_arg);
    symb_err = 2.0 * q_func(q_arg);
    bit_err = symb_err/m_factor;
    //bit_err = 0.5 * erfc(sqrt(ebno_numeric));
    //symb_err = bit_err * (2.0 - bit_err);
    (*out_file) << ebno_db << ", " << bit_err << ", " << symb_err << endl;
    }
  delete out_file;
}

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