srsRAN_4G/lte/phy/lib/sync/src/sync.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 <strings.h>

#include "liblte/phy/utils/debug.h"
#include "liblte/phy/common/phy_common.h"
#include "liblte/phy/sync/sync.h"

int sync_init(sync_t *q, int frame_size) {

  bzero(q, sizeof(sync_t));
  q->threshold = 1.5;
  q->pss_mode = PEAK_MEAN;
  q->detect_cp = true;
  q->sss_en = true;

  if (pss_synch_init(&q->pss, frame_size)) {
    fprintf(stderr, "Error initializing PSS object\n");
    return -1;
  }
  if (pss_synch_init(&q->pss_track, TRACK_LEN)) {
    fprintf(stderr, "Error initializing PSS track object\n");
    return -1;
  }
  if (sss_synch_init(&q->sss)) {
    fprintf(stderr, "Error initializing SSS object\n");
    return -1;
  }
  DEBUG("PSS and SSS initiated\n",0);
  
  return 0;
}

void sync_free(sync_t *q) {
  pss_synch_free(&q->pss);
  pss_synch_free(&q->pss_track);
  sss_synch_free(&q->sss);
}

void sync_pss_det_absolute(sync_t *q) {
  q->pss_mode = ABSOLUTE;
}
void sync_pss_det_peak_to_avg(sync_t *q) {
  q->pss_mode = PEAK_MEAN;
}

void sync_set_threshold(sync_t *q, float threshold) {
  q->threshold = threshold;
}

void sync_sss_en(sync_t *q, bool enabled) {
  q->sss_en = enabled;
}

int sync_get_cell_id(sync_t *q) {
  if (q->N_id_1 >=0 && q->N_id_2 >= 0) {
    return q->N_id_1*3 + q->N_id_2;
  } else {
    return -1;
  }
}

int sync_get_N_id_1(sync_t *q) {
  return q->N_id_1;
}

int sync_get_N_id_2(sync_t *q) {
  return q->N_id_2;
}

int sync_get_slot_id(sync_t *q) {
  return q->slot_id;
}

float sync_get_cfo(sync_t *q) {
  return q->cfo;
}

float sync_get_peak_to_avg(sync_t *q) {
  return q->peak_to_avg;
}

void sync_cp_en(sync_t *q, bool enabled) {
  q->detect_cp = enabled;
}

lte_cp_t sync_get_cp(sync_t *q) {
  return q->cp;
}

int sync_sss(sync_t *q, cf_t *input, int N_id_2, int peak_pos, bool en_cp) {
  int m0, m1, sss_idx_n, sss_idx_e;
  float m0_value_e, m1_value_e,m0_value_n, m1_value_n;
  int slot_id_e, N_id_1_e, slot_id_n, N_id_1_n;

  sss_synch_set_N_id_2(&q->sss, N_id_2);
      
  /* Make sure we have enough room to find SSS sequence */
  sss_idx_n = peak_pos-2*(128+CP(128,CPNORM_LEN));
  sss_idx_e = peak_pos-2*(128+CP(128,CPEXT_LEN));

  if (en_cp) {
    if (sss_idx_n < 0 || sss_idx_e < 0) {
      INFO("Not enough room to decode SSS (%d, %d)\n", sss_idx_n, sss_idx_e);
      return -1;
    }
  } else {
    if (CP_ISNORM(q->cp)) {
      if (sss_idx_n < 0) {
        INFO("Not enough room to decode SSS (%d)\n", sss_idx_n);
        return -1;
      }
    } else {
      if (sss_idx_e < 0) {
        INFO("Not enough room to decode SSS (%d)\n", sss_idx_e);
        return -1;
      }
    }
  }
  
  N_id_1_e = -1;
  N_id_1_n = -1;
  slot_id_e = -1;
  slot_id_n = -1;
  
  /* try Normal CP length */
  if (en_cp || CP_ISNORM(q->cp)) {
    sss_synch_m0m1(&q->sss, &input[sss_idx_n],
        &m0, &m0_value_n, &m1, &m1_value_n);

    slot_id_n = 2 * sss_synch_subframe(m0, m1);
    N_id_1_n = sss_synch_N_id_1(&q->sss, m0, m1);
  }

  if (en_cp || CP_ISEXT(q->cp)) {
    /* Now try Extended CP length */
    sss_synch_m0m1(&q->sss, &input[sss_idx_e],
        &m0, &m0_value_e, &m1, &m1_value_e);

    slot_id_e = 2 * sss_synch_subframe(m0, m1);
    N_id_1_e = sss_synch_N_id_1(&q->sss, m0, m1);
  }
  
  /* Correlation with extended CP hypoteshis is greater than with normal? */
  if ((en_cp && m0_value_e * m1_value_e > m0_value_n * m1_value_n)
      || CP_ISEXT(q->cp)) {
    q->cp = CPEXT;
    q->slot_id = slot_id_e;
    q->N_id_1 = N_id_1_e;
  /* then is normal CP */
  } else {
    q->cp = CPNORM;
    q->slot_id = slot_id_n;
    q->N_id_1 = N_id_1_n;
  }
  
  INFO("SSS detected N_id_1=%d, slot_idx=%d, %s CP\n",
    q->N_id_1, q->slot_id, CP_ISNORM(q->cp)?"Normal":"Extended");

  return 0;
}

int sync_track(sync_t *q, cf_t *input) {
  float peak_value, mean_value;
  int peak_detected = 0;
  pss_synch_set_N_id_2(&q->pss_track, q->N_id_2);
  
  int peak_pos = pss_synch_find_pss(&q->pss, input, &peak_value, &mean_value);
  
  if (q->peak_to_avg > TRACK_THRESHOLD) {
    peak_detected = 1;    
  }
  if (peak_detected) {

    q->cfo = pss_synch_cfo_compute(&q->pss, &input[peak_pos-128]);

    if (q->sss_en) {
      if (sync_sss(q, input, q->N_id_2, peak_pos, false)) {
        return -1;
      }
    }
   
    return peak_pos;
  } else {
    return -1;
  }
}

int sync_find(sync_t *q, cf_t *input) {
  int N_id_2, peak_pos[3];
  float peak_value[3];
  float mean_value[3];
  float max=-999;
  int i;
  int peak_detected;

  for (N_id_2=0;N_id_2<3;N_id_2++) {
    pss_synch_set_N_id_2(&q->pss, N_id_2);
    peak_pos[N_id_2] = pss_synch_find_pss(&q->pss, input, &peak_value[N_id_2], &mean_value[N_id_2]);
  }
  for (i=0;i<3;i++) {
    if (peak_value[i] > max) {
      max = peak_value[i];
      N_id_2 = i;
    }
  }

  q->peak_to_avg = peak_value[N_id_2] / mean_value[N_id_2];

  DEBUG("PSS possible peak N_id_2=%d, pos=%d peak=%.2f par=%.2f threshold=%.2f\n",
      N_id_2, peak_pos[N_id_2], peak_value[N_id_2], q->peak_to_avg, q->threshold);

  /* If peak detected */
  peak_detected = 0;
  if (peak_pos[N_id_2] - 128 >= 0) {
    if (q->pss_mode == ABSOLUTE) {
      if (peak_value[N_id_2] > q->threshold) {
        peak_detected = 1;
      }
    } else {
      if (q->peak_to_avg  > q->threshold) {
        peak_detected = 1;
      }
    }
  }
  if (peak_detected) {
    q->N_id_2 = N_id_2;
    pss_synch_set_N_id_2(&q->pss, q->N_id_2);
    q->cfo = pss_synch_cfo_compute(&q->pss, &input[peak_pos[q->N_id_2]-128]);
    
    INFO("PSS peak detected N_id_2=%d, pos=%d peak=%.2f par=%.2f th=%.2f cfo=%.4f\n", N_id_2,
        peak_pos[N_id_2], peak_value[N_id_2], q->peak_to_avg, q->threshold, q->cfo);

    if (q->sss_en) {     
      if (sync_sss(q, input, q->N_id_2, peak_pos[q->N_id_2], q->detect_cp)) {
        return -1;
      }
    }

    return peak_pos[N_id_2];

  } else {
    return -1;
  }
}