fading.c

This a framework to test new ideas in transmission technology. Actual development is a LDPC-coder in

/***************************************************************************
    fading.c  -  Module for the net-server that makes a simple fading channel
                            -------------------
    begin                :  2002
    authors              :  Linus Gasser
    emails               :  [e-mail]
 ***************************************************************************/

/***************************************************************************
                                 Changes
                                 -------
 date - name - description
 02-12-16 - ineiti - begin
 
 **************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program 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 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/


#include <math.h>
#include "system.h"
#include "debugging.h"
#include "server.h"
#define DBG_LVL 0

/**
 * @short a simple fading channel with no reflexions
 */

double path_loss_fading[MAX_CLIENTS][MAX_CLIENTS];

/**
 * @short initialises the channel
 */
void fading_init() {
  path_loss_fading[0][0] = pow( 10.0, -4.0 );
  path_loss_fading[0][1] = pow( 10.0, -4.0 );
  path_loss_fading[0][2] = pow( 10.0, -4.0 );
  path_loss_fading[1][1] = pow( 10.0, -10.0 );
  path_loss_fading[1][0] = pow( 10.0, -4.0 );
  path_loss_fading[1][2] = pow( 10.0, -4.0 );
  path_loss_fading[2][2] = pow( 10.0, -10.0 );
  path_loss_fading[2][0] = pow( 10.0, -4.0 );
  path_loss_fading[2][1] = pow( 10.0, -4.0 );
}

/**
 * @short calculates the fading
 */
void fading_calc( int nb_clients ) {
  int n,i,j;
  short *rx, *tx;
  double gain;

  for ( i = 0; i < MAX_CLIENTS; i++ ) {
    if ( client[i].id == -1 ) {
      continue;
    }
    rx = (short*)rx_signal_buffer[i][BLOCK_ACT_RX(tx_block)];
    memset( rx, 0, DAQ_DMA_BLOCK_SIZE_BYTES );
    PR_DBG( 4, "rx_gain0 = %e,tx_gain0 = %e\n", rx_gain[0], tx_gain[0] );
    PR_DBG( 4, "rx_gain1 = %e,tx_gain1 = %e\n", rx_gain[1], tx_gain[1] );

    for ( j = 0; j < MAX_CLIENTS; j++ ) {
      if ( client[j].id == -1 ) {
        continue;
      }
      gain = rx_gain[i] * tx_gain[j] * path_loss_fading[i][j];
      tx = (short*)tx_signal_buffer[j][BLOCK_ACT_TX(tx_block)];

      for ( n = 0; n < DAQ_DMA_BLOCK_SIZE_SAMPLES; n++ ) {
        rx[n] += sqrt( gain * tx[n] );
      }
    }
  }
}