ofdm_mod.c

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/*
* @defgroup _PHY_MODULATION_
* @ingroup _physical_layer_ref_implementation_
* @{
\section _phy_modulation_ OFDM Modulation Blocks
This section deals with basic functions for OFDM Modulation.


*/

#include "PHY/defs.h"
#include "UTIL/LOG/log.h"

//static short temp2[2048*4] __attribute__((aligned(16)));

//#define DEBUG_OFDM_MOD


void normal_prefix_mod(int32_t *txdataF,int32_t *txdata,uint8_t nsymb,LTE_DL_FRAME_PARMS *frame_parms)
{

  uint8_t i;
  int short_offset=0;

  if ((2*nsymb) < frame_parms->symbols_per_tti)
    short_offset = 1;

  //  printf("nsymb %d\n",nsymb);
  for (i=0; i<((short_offset)+2*nsymb/frame_parms->symbols_per_tti); i++) {

#ifdef DEBUG_OFDM_MOD
    printf("slot i %d (txdata offset %d, txoutput %p)\n",i,(i*(frame_parms->samples_per_tti>>1)),
           txdata+(i*(frame_parms->samples_per_tti>>1)));
#endif

    PHY_ofdm_mod(txdataF+(i*NUMBER_OF_OFDM_CARRIERS*frame_parms->symbols_per_tti>>1),        // input
                 txdata+(i*frame_parms->samples_per_tti>>1),         // output
                 frame_parms->log2_symbol_size,                // log2_fft_size
                 1,                 // number of symbols
                 frame_parms->nb_prefix_samples0,               // number of prefix samples
                 CYCLIC_PREFIX);
#ifdef DEBUG_OFDM_MOD
    printf("slot i %d (txdata offset %d)\n",i,OFDM_SYMBOL_SIZE_COMPLEX_SAMPLES0+(i*frame_parms->samples_per_tti>>1));
#endif

    PHY_ofdm_mod(txdataF+NUMBER_OF_OFDM_CARRIERS+(i*NUMBER_OF_OFDM_CARRIERS*(frame_parms->symbols_per_tti>>1)),        // input
                 txdata+OFDM_SYMBOL_SIZE_COMPLEX_SAMPLES0+(i*(frame_parms->samples_per_tti>>1)),         // output
                 frame_parms->log2_symbol_size,                // log2_fft_size
                 (short_offset==1) ? 1 :(frame_parms->symbols_per_tti>>1)-1,//6,                 // number of symbols
                 frame_parms->nb_prefix_samples,               // number of prefix samples
                 CYCLIC_PREFIX);


  }
}

void PHY_ofdm_mod(int *input,                       /// pointer to complex input
                  int *output,                      /// pointer to complex output
                  unsigned char log2fftsize,        /// log2(FFT_SIZE)
                  unsigned char nb_symbols,         /// number of OFDM symbols
                  unsigned short nb_prefix_samples,  /// cyclic prefix length
                  Extension_t etype                /// type of extension
                 )
{

  static short temp[2048*4] __attribute__((aligned(16)));
  unsigned short i,j;
  short k;

  volatile int *output_ptr=(int*)0;

  int *temp_ptr=(int*)0;
  void (*idft)(int16_t *,int16_t *, int);

  switch (log2fftsize) {
  case 7:
    idft = idft128;
    break;

  case 8:
    idft = idft256;
    break;

  case 9:
    idft = idft512;
    break;

  case 10:
    idft = idft1024;
    break;

  case 11:
    idft = idft2048;
    break;

  default:
    idft = idft512;
    break;
  }

#ifdef DEBUG_OFDM_MOD
  msg("[PHY] OFDM mod (size %d,prefix %d) Symbols %d, input %p, output %p\n",
      1<<log2fftsize,nb_prefix_samples,nb_symbols,input,output);
#endif



  for (i=0; i<nb_symbols; i++) {

#ifdef DEBUG_OFDM_MOD
    msg("[PHY] symbol %d/%d (%p,%p -> %p)\n",i,nb_symbols,input,&input[i<<log2fftsize],&output[(i<<log2fftsize) + ((i)*nb_prefix_samples)]);
#endif

    idft((int16_t *)&input[i<<log2fftsize],
         (log2fftsize==7) ? (int16_t *)temp : (int16_t *)&output[(i<<log2fftsize) + ((1+i)*nb_prefix_samples)],
         1);
    //    write_output("fft_out.m","fftout",temp,(1<<log2fftsize)*2,1,1);

    //memset(temp,0,1<<log2fftsize);


    // Copy to frame buffer with Cyclic Extension
    // Note:  will have to adjust for synchronization offset!

    switch (etype) {
    case CYCLIC_PREFIX:
      output_ptr = &output[(i<<log2fftsize) + ((1+i)*nb_prefix_samples)];
      temp_ptr = (int *)temp;


      //      msg("Doing cyclic prefix method\n");

      if (log2fftsize==7) {
        for (j=0; j<((1<<log2fftsize)) ; j++) {
          output_ptr[j] = temp_ptr[j];
        }
      }

      j=(1<<log2fftsize);

      for (k=-1; k>=-nb_prefix_samples; k--) {
        output_ptr[k] = output_ptr[--j];
      }

      break;

    case CYCLIC_SUFFIX:


      output_ptr = &output[(i<<log2fftsize)+ (i*nb_prefix_samples)];

      temp_ptr = (int *)temp;

      //      msg("Doing cyclic suffix method\n");

      for (j=0; j<(1<<log2fftsize) ; j++) {
        output_ptr[j] = temp_ptr[2*j];
      }


      for (j=0; j<nb_prefix_samples; j++)
        output_ptr[(1<<log2fftsize)+j] = output_ptr[j];

      break;

    case ZEROS:

      break;

    case NONE:

      //      msg("NO EXTENSION!\n");
      output_ptr = &output[(i<<log2fftsize)];

      temp_ptr = (int *)temp;

      for (j=0; j<(1<<log2fftsize) ; j++) {
        output_ptr[j] = temp_ptr[2*j];


      }

      break;

    default:
      break;

    }



  }

  /*
  printf("input %p, output %p, log2fftsize %d, nsymb %d\n",input,output,log2fftsize,nb_symbols);
  for (i=0;i<16;i++)
    printf("%d %d\n",((short *)input)[i<<1],((short *)input)[1+(i<<1)]);
  printf("------\n");
  for (i=0;i<16;i++)
    printf("%d %d\n",((short *)output)[i<<1],((short *)output)[1+(i<<1)]);
  */
}


void do_OFDM_mod(mod_sym_t **txdataF, int32_t **txdata, uint32_t frame,uint16_t next_slot, LTE_DL_FRAME_PARMS *frame_parms)
{

  int aa, slot_offset, slot_offset_F;

  slot_offset_F = (next_slot)*(frame_parms->ofdm_symbol_size)*((frame_parms->Ncp==1) ? 6 : 7);
  slot_offset = (next_slot)*(frame_parms->samples_per_tti>>1);

  for (aa=0; aa<frame_parms->nb_antennas_tx; aa++) {
    if (is_pmch_subframe(frame,next_slot>>1,frame_parms)) {
      if ((next_slot%2)==0) {
        LOG_D(PHY,"Frame %d, subframe %d: Doing MBSFN modulation (slot_offset %d)\n",frame,next_slot>>1,slot_offset);
        PHY_ofdm_mod(&txdataF[aa][slot_offset_F],        // input
                     &txdata[aa][slot_offset],         // output
                     frame_parms->log2_symbol_size,                // log2_fft_size
                     12,                 // number of symbols
                     frame_parms->ofdm_symbol_size>>2,               // number of prefix samples
                     CYCLIC_PREFIX);

        if (frame_parms->Ncp == EXTENDED)
          PHY_ofdm_mod(&txdataF[aa][slot_offset_F],        // input
                       &txdata[aa][slot_offset],         // output
                       frame_parms->log2_symbol_size,                // log2_fft_size
                       2,                 // number of symbols
                       frame_parms->nb_prefix_samples,               // number of prefix samples
                       CYCLIC_PREFIX);
        else {
          LOG_D(PHY,"Frame %d, subframe %d: Doing PDCCH modulation\n",frame,next_slot>>1);
          normal_prefix_mod(&txdataF[aa][slot_offset_F],
                            &txdata[aa][slot_offset],
                            2,
                            frame_parms);
        }
      }
    } else {
      if (frame_parms->Ncp == EXTENDED)
        PHY_ofdm_mod(&txdataF[aa][slot_offset_F],        // input
                     &txdata[aa][slot_offset],         // output
                     frame_parms->log2_symbol_size,                // log2_fft_size
                     6,                 // number of symbols
                     frame_parms->nb_prefix_samples,               // number of prefix samples
                     CYCLIC_PREFIX);
      else {
        normal_prefix_mod(&txdataF[aa][slot_offset_F],
                          &txdata[aa][slot_offset],
                          7,
                          frame_parms);
      }
    }
  }

}

/** @} */