srsRAN_4G/srslte/lib/fec/cbsegm.c

/**
 *
 * \section COPYRIGHT
 *
 * Copyright 2013-2015 Software Radio Systems Limited
 *
 * \section LICENSE
 *
 * This file is part of the srsLTE library.
 *
 * srsLTE is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * srsLTE 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 Affero General Public License for more details.
 *
 * A copy of the GNU Affero 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 <math.h>

#include "srslte/fec/turbodecoder_gen.h"
#include "srslte/fec/cbsegm.h"
#include "srslte/utils/debug.h"


const uint32_t tc_cb_sizes[SRSLTE_NOF_TC_CB_SIZES] = { 40, 48, 56, 64, 72, 80, 88, 96, 104, 112, 120,
    128, 136, 144, 152, 160, 168, 176, 184, 192, 200, 208, 216, 224, 232,
    240, 248, 256, 264, 272, 280, 288, 296, 304, 312, 320, 328, 336, 344,
    352, 360, 368, 376, 384, 392, 400, 408, 416, 424, 432, 440, 448, 456,
    464, 472, 480, 488, 496, 504, 512, 528, 544, 560, 576, 592, 608, 624,
    640, 656, 672, 688, 704, 720, 736, 752, 768, 784, 800, 816, 832, 848,
    864, 880, 896, 912, 928, 944, 960, 976, 992, 1008, 1024, 1056, 1088,
    1120, 1152, 1184, 1216, 1248, 1280, 1312, 1344, 1376, 1408, 1440, 1472,
    1504, 1536, 1568, 1600, 1632, 1664, 1696, 1728, 1760, 1792, 1824, 1856,
    1888, 1920, 1952, 1984, 2016, 2048, 2112, 2176, 2240, 2304, 2368, 2432,
    2496, 2560, 2624, 2688, 2752, 2816, 2880, 2944, 3008, 3072, 3136, 3200,
    3264, 3328, 3392, 3456, 3520, 3584, 3648, 3712, 3776, 3840, 3904, 3968,
    4032, 4096, 4160, 4224, 4288, 4352, 4416, 4480, 4544, 4608, 4672, 4736,
    4800, 4864, 4928, 4992, 5056, 5120, 5184, 5248, 5312, 5376, 5440, 5504,
    5568, 5632, 5696, 5760, 5824, 5888, 5952, 6016, 6080, 6144 };

/* Calculate Codeblock Segmentation as in Section 5.1.2 of 36.212 */
int srslte_cbsegm(srslte_cbsegm_t *s, uint32_t tbs) {
  uint32_t Bp, B, idx1;
  int ret; 

  if (tbs == 0) {
    bzero(s, sizeof(srslte_cbsegm_t));
    ret = SRSLTE_SUCCESS;
  } else {
    B = tbs + 24;
    s->tbs = tbs; 
    
    /* Calculate CB sizes */
    if (B <= SRSLTE_TCOD_MAX_LEN_CB) {
      s->C = 1;
      Bp = B;
    } else {
      s->C = (uint32_t) ceilf((float) B / (SRSLTE_TCOD_MAX_LEN_CB - 24));
      Bp = B + 24 * s->C;
    }
    ret = srslte_cbsegm_cbindex((Bp-1) / s->C + 1);
    if (ret != SRSLTE_ERROR) {
      idx1 = (uint32_t) ret;
      ret = srslte_cbsegm_cbsize(idx1);
      if (ret != SRSLTE_ERROR) {
        s->K1 = (uint32_t) ret;
        s->K1_idx = idx1;
        if (idx1 > 0) {
          ret = srslte_cbsegm_cbsize(idx1 - 1);        
        }
        if (ret != SRSLTE_ERROR) {
          if (s->C == 1) {
            s->K2 = 0;
            s->K2_idx = 0;
            s->C2 = 0;
            s->C1 = 1;
          } else {
            s->K2 = (uint32_t) ret;
            s->K2_idx = idx1-1;
            s->C2 = (s->C * s->K1 - Bp) / (s->K1 - s->K2);
            s->C1 = s->C - s->C2;
          }
          s->F = s->C1 * s->K1 + s->C2 * s->K2 - Bp;
          INFO("CB Segmentation: TBS: %d, C=%d, C+=%d K+=%d, C-=%d, K-=%d, F=%d, Bp=%d\n",
              tbs, s->C, s->C1, s->K1, s->C2, s->K2, s->F, Bp);         
          ret = SRSLTE_SUCCESS; 
        }
      }
    }  
    
  }
  return ret;
}

/*
 * Finds index of minimum K>=long_cb in Table 5.1.3-3 of 36.212
 */
int srslte_cbsegm_cbindex(uint32_t long_cb) {
  int j = 0;
  while (j < SRSLTE_NOF_TC_CB_SIZES && tc_cb_sizes[j] < long_cb) {
    j++;
  }

  if (j == SRSLTE_NOF_TC_CB_SIZES) {
    return SRSLTE_ERROR;
  } else {
    return j;
  }
}

/*
 * Returns Turbo coder interleaver size for Table 5.1.3-3 (36.212) index
 */
int srslte_cbsegm_cbsize(uint32_t index) {
  if (index < SRSLTE_NOF_TC_CB_SIZES) {
    return (int) tc_cb_sizes[index];
  } else {
    return SRSLTE_ERROR;
  }
}

bool srslte_cbsegm_cbsize_isvalid(uint32_t size) {
  for (int i=0;i<SRSLTE_NOF_TC_CB_SIZES;i++) {
    if (tc_cb_sizes[i] == size) {
      return true; 
    }
  }
  return false; 
}