multipath_channel.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include "defs.h"
#include "SIMULATION/RF/defs.h"

//#define DEBUG_CH
uint8_t multipath_channel_nosigconv(channel_desc_t *desc)
{

  random_channel(desc,0);
  return(1);
}

//#define CHANNEL_SSE
#ifdef CHANNEL_SSE
void multipath_channel(channel_desc_t *desc,
                       double **tx_sig_re,
                       double **tx_sig_im,
                       double **rx_sig_re,
                       double **rx_sig_im,
                       uint32_t length,
                       uint8_t keep_channel)
{

  int i,ii,j,l;
  int length1, length2, tail;
  __m128d rx_tmp128_re_f,rx_tmp128_im_f,rx_tmp128_re,rx_tmp128_im, rx_tmp128_1,rx_tmp128_2,rx_tmp128_3,rx_tmp128_4,tx128_re,tx128_im,ch128_x,ch128_y,pathloss128;

  double path_loss = pow(10,desc->path_loss_dB/20);
  int dd = abs(desc->channel_offset);

  pathloss128 = _mm_set1_pd(path_loss);

#ifdef DEBUG_CH
  printf("[CHANNEL] keep = %d : path_loss = %g (%f), nb_rx %d, nb_tx %d, dd %d, len %d \n",keep_channel,path_loss,desc->path_loss_dB,desc->nb_rx,desc->nb_tx,dd,desc->channel_length);
#endif

  if (keep_channel) {
    // do nothing - keep channel
  } else {
    random_channel(desc,0);
  }

  start_meas(&desc->convolution);

#ifdef DEBUG_CH

  for (l = 0; l<(int)desc->channel_length; l++) {
    printf("%p (%f,%f) ",desc->ch[0],desc->ch[0][l].x,desc->ch[0][l].y);
  }

  printf("\n");
#endif

  tail = ((int)length-dd)%2;

  if(tail)
    length1 = ((int)length-dd)-1;
  else
    length1 = ((int)length-dd);

  length2 = length1/2;

  for (i=0; i<length2; i++) { //
    for (ii=0; ii<desc->nb_rx; ii++) {
      // rx_tmp.x = 0;
      // rx_tmp.y = 0;
      rx_tmp128_re_f = _mm_setzero_pd();
      rx_tmp128_im_f = _mm_setzero_pd();

      for (j=0; j<desc->nb_tx; j++) {
        for (l = 0; l<(int)desc->channel_length; l++) {
          if ((i>=0) && (i-l)>=0) { //SIMD correct only if length1 > 2*channel_length...which is almost always satisfied
            // tx.x = tx_sig_re[j][i-l];
            // tx.y = tx_sig_im[j][i-l];
            tx128_re = _mm_loadu_pd(&tx_sig_re[j][2*i-l]); // tx_sig_re[j][i-l+1], tx_sig_re[j][i-l]
            tx128_im = _mm_loadu_pd(&tx_sig_im[j][2*i-l]);
          } else {
            //tx.x =0;
            //tx.y =0;
            tx128_re = _mm_setzero_pd();
            tx128_im = _mm_setzero_pd();
          }

          ch128_x = _mm_set1_pd(desc->ch[ii+(j*desc->nb_rx)][l].x);
          ch128_y = _mm_set1_pd(desc->ch[ii+(j*desc->nb_rx)][l].y);
          //  rx_tmp.x += (tx.x * desc->ch[ii+(j*desc->nb_rx)][l].x) - (tx.y * desc->ch[ii+(j*desc->nb_rx)][l].y);
          //  rx_tmp.y += (tx.y * desc->ch[ii+(j*desc->nb_rx)][l].x) + (tx.x * desc->ch[ii+(j*desc->nb_rx)][l].y);
          rx_tmp128_1 = _mm_mul_pd(tx128_re,ch128_x);
          rx_tmp128_2 = _mm_mul_pd(tx128_re,ch128_y);
          rx_tmp128_3 = _mm_mul_pd(tx128_im,ch128_x);
          rx_tmp128_4 = _mm_mul_pd(tx128_im,ch128_y);
          rx_tmp128_re = _mm_sub_pd(rx_tmp128_1,rx_tmp128_4);
          rx_tmp128_im = _mm_add_pd(rx_tmp128_2,rx_tmp128_3);
          rx_tmp128_re_f = _mm_add_pd(rx_tmp128_re_f,rx_tmp128_re);
          rx_tmp128_im_f = _mm_add_pd(rx_tmp128_im_f,rx_tmp128_im);
        } //l
      }  // j

      //rx_sig_re[ii][i+dd] = rx_tmp.x*path_loss;
      //rx_sig_im[ii][i+dd] = rx_tmp.y*path_loss;
      rx_tmp128_re_f = _mm_mul_pd(rx_tmp128_re_f,pathloss128);
      rx_tmp128_im_f = _mm_mul_pd(rx_tmp128_im_f,pathloss128);
      _mm_storeu_pd(&rx_sig_re[ii][2*i+dd],rx_tmp128_re_f); // max index: length-dd -1 + dd = length -1
      _mm_storeu_pd(&rx_sig_im[ii][2*i+dd],rx_tmp128_im_f);
      /*
      if ((ii==0)&&((i%32)==0)) {
      printf("%p %p %f,%f => %e,%e\n",rx_sig_re[ii],rx_sig_im[ii],rx_tmp.x,rx_tmp.y,rx_sig_re[ii][i-dd],rx_sig_im[ii][i-dd]);
      }
      */
      //rx_sig_re[ii][i] = sqrt(.5)*(tx_sig_re[0][i] + tx_sig_re[1][i]);
      //rx_sig_im[ii][i] = sqrt(.5)*(tx_sig_im[0][i] + tx_sig_im[1][i]);

    } // ii
  } // i

  stop_meas(&desc->convolution);

}

#else
void multipath_channel(channel_desc_t *desc,
                       double **tx_sig_re,
                       double **tx_sig_im,
                       double **rx_sig_re,
                       double **rx_sig_im,
                       uint32_t length,
                       uint8_t keep_channel)
{

  int i,ii,j,l;
  struct complex rx_tmp,tx;

  double path_loss = pow(10,desc->path_loss_dB/20);
  int dd;
  dd = abs(desc->channel_offset);

#ifdef DEBUG_CH
  printf("[CHANNEL] keep = %d : path_loss = %g (%f), nb_rx %d, nb_tx %d, dd %d, len %d \n",keep_channel,path_loss,desc->path_loss_dB,desc->nb_rx,desc->nb_tx,dd,desc->channel_length);
#endif

  if (keep_channel) {
    // do nothing - keep channel
  } else {
    random_channel(desc,0);
  }

#ifdef DEBUG_CH

  for (l = 0; l<(int)desc->channel_length; l++) {
    printf("%p (%f,%f) ",desc->ch[0],desc->ch[0][l].x,desc->ch[0][l].y);
  }

  printf("\n");
#endif

  for (i=0; i<((int)length-dd); i++) {
    for (ii=0; ii<desc->nb_rx; ii++) {
      rx_tmp.x = 0;
      rx_tmp.y = 0;

      for (j=0; j<desc->nb_tx; j++) {
        for (l = 0; l<(int)desc->channel_length; l++) {
          if ((i>=0) && (i-l)>=0) {
            tx.x = tx_sig_re[j][i-l];
            tx.y = tx_sig_im[j][i-l];
          } else {
            tx.x =0;
            tx.y =0;
          }

          rx_tmp.x += (tx.x * desc->ch[ii+(j*desc->nb_rx)][l].x) - (tx.y * desc->ch[ii+(j*desc->nb_rx)][l].y);
          rx_tmp.y += (tx.y * desc->ch[ii+(j*desc->nb_rx)][l].x) + (tx.x * desc->ch[ii+(j*desc->nb_rx)][l].y);
        } //l
      }  // j

      rx_sig_re[ii][i+dd] = rx_tmp.x*path_loss;
      rx_sig_im[ii][i+dd] = rx_tmp.y*path_loss;
      /*
      if ((ii==0)&&((i%32)==0)) {
      printf("%p %p %f,%f => %e,%e\n",rx_sig_re[ii],rx_sig_im[ii],rx_tmp.x,rx_tmp.y,rx_sig_re[ii][i-dd],rx_sig_im[ii][i-dd]);
      }
      */
      //rx_sig_re[ii][i] = sqrt(.5)*(tx_sig_re[0][i] + tx_sig_re[1][i]);
      //rx_sig_im[ii][i] = sqrt(.5)*(tx_sig_im[0][i] + tx_sig_im[1][i]);

    } // ii
  } // i
}
#endif