srsLTE/lte/phy/lib/common/src/fft.c

/**
 *
 * \section COPYRIGHT
 *
 * Copyright 2013-2014 The libLTE Developers. See the
 * COPYRIGHT file at the top-level directory of this distribution.
 *
 * \section LICENSE
 *
 * This file is part of the libLTE library.
 *
 * libLTE is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * libLTE 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 Lesser General Public License for more details.
 *
 * A copy of the GNU Lesser General Public License can be found in
 * the LICENSE file in the top-level directory of this distribution
 * and at http://www.gnu.org/licenses/.
 *
 */

#include <string.h>
#include <strings.h>
#include <stdlib.h>

#include "liblte/phy/common/base.h"
#include "liblte/phy/utils/dft.h"
#include "liblte/phy/common/fft.h"
#include "liblte/phy/utils/debug.h"
#include "liblte/phy/utils/vector.h"

int lte_fft_init_(lte_fft_t *q, lte_cp_t cp_type, int nof_prb, dft_dir_t dir) {
  int symbol_sz = lte_symbol_sz(nof_prb);

  if (symbol_sz == -1) {
    fprintf(stderr, "Error: Invalid nof_prb=%d\n", nof_prb);
    return -1;
  }
  if (dft_plan_c2c(&q->fft_plan, symbol_sz, dir)) {
    fprintf(stderr, "Error: Creating DFT plan\n");
    return -1;
  }
  q->tmp = malloc(symbol_sz * sizeof(cf_t));
  if (!q->tmp) {
    perror("malloc");
    return -1;
  }

  q->fft_plan.options = DFT_NORMALIZE;
  if (dir==FORWARD) {
    q->fft_plan.options |= DFT_DC_OFFSET | DFT_MIRROR_POS;
  } else {
    q->fft_plan.options |= DFT_DC_OFFSET | DFT_MIRROR_PRE;
  }
  q->symbol_sz = symbol_sz;
  q->nof_symbols = CP_NSYMB(cp_type);
  q->cp_type = cp_type;
  q->nof_re = nof_prb * RE_X_RB;
  q->nof_guards = ((symbol_sz - q->nof_re) / 2);
  DEBUG("Init %s symbol_sz=%d, nof_symbols=%d, cp_type=%s, nof_re=%d, nof_guards=%d\n",
      dir==FORWARD?"FFT":"iFFT", q->symbol_sz, q->nof_symbols,
          q->cp_type==CPNORM?"Normal":"Extended", q->nof_re, q->nof_guards);
  return 0;
}

void lte_fft_free_(lte_fft_t *q) {
  dft_plan_free(&q->fft_plan);
  if (q->tmp) {
    free(q->tmp);
  }
  bzero(q, sizeof(lte_fft_t));
}

int lte_fft_init(lte_fft_t *q, lte_cp_t cp_type, int nof_prb) {
  return lte_fft_init_(q, cp_type, nof_prb, FORWARD);
}

void lte_fft_free(lte_fft_t *q) {
  lte_fft_free_(q);
}

int lte_ifft_init(lte_fft_t *q, lte_cp_t cp_type, int nof_prb) {
  int i;
  if (lte_fft_init_(q, cp_type, nof_prb, BACKWARD)) {
    return -1;
  }
  /* set now zeros at CP */
  for (i=0;i<q->nof_symbols;i++) {
    bzero(q->tmp, q->nof_guards * sizeof(cf_t));
    bzero(&q->tmp[q->nof_re + q->nof_guards], q->nof_guards * sizeof(cf_t));
  }
  return 0;
}

void lte_ifft_free(lte_fft_t *q) {
  lte_fft_free_(q);
}

/* Transforms input samples into output OFDM symbols.
 * Performs FFT on a each symbol and removes CP.
 */
void lte_fft_run(lte_fft_t *q, cf_t *input, cf_t *output) {
  int i;
  for (i=0;i<q->nof_symbols;i++) {
    input += CP_ISNORM(q->cp_type)?CP_NORM(i, q->symbol_sz):CP_EXT(q->symbol_sz);
    dft_run_c2c(&q->fft_plan, input, q->tmp);
    memcpy(output, &q->tmp[q->nof_guards], q->nof_re * sizeof(cf_t));
    input += q->symbol_sz;
    output += q->nof_re;
  }
}

/* Transforms input OFDM symbols into output samples.
 * Performs FFT on a each symbol and adds CP.
 */
void lte_ifft_run(lte_fft_t *q, cf_t *input, cf_t *output) {
  int i, cp_len;
  for (i=0;i<q->nof_symbols;i++) {
    cp_len = CP_ISNORM(q->cp_type)?CP_NORM(i, q->symbol_sz):CP_EXT(q->symbol_sz);
    memcpy(&q->tmp[q->nof_guards], input, q->nof_re * sizeof(cf_t));
    dft_run_c2c(&q->fft_plan, q->tmp, &output[cp_len]);
    input += q->nof_re;
    /* add CP */
    memcpy(output, &output[q->symbol_sz], cp_len * sizeof(cf_t));
    output += q->symbol_sz + cp_len;
  }
}