nr_pbch.c

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/*! \file PHY/NR_TRANSPORT/nr_pbch.c
* \brief Top-level routines for generating the PBCH/BCH physical/transport channel V15.1 03/2018
* \author Guy De Souza
* \date 2018
* \version 0.1
* \company Eurecom
* \email: desouza@eurecom.fr
* \note
* \warning
*/

#include "PHY/defs_gNB.h"
#include "PHY/NR_TRANSPORT/nr_transport.h"
#include "PHY/LTE_REFSIG/lte_refsig.h"
#include "PHY/sse_intrin.h"

//#define DEBUG_PBCH
//#define DEBUG_PBCH_ENCODING
//#define DEBUG_PBCH_DMRS

extern short nr_mod_table[NR_MOD_TABLE_SIZE_SHORT];

int nr_generate_pbch_dmrs(uint32_t *gold_pbch_dmrs,
                          int32_t **txdataF,
                          int16_t amp,
                          uint8_t ssb_start_symbol,
                          nfapi_nr_config_request_t* config,
                          NR_DL_FRAME_PARMS *frame_parms)
{
  int k,l;
  int16_t a;
  int16_t mod_dmrs[NR_PBCH_DMRS_LENGTH<<1];
  uint8_t idx=0;
  uint8_t nushift = config->sch_config.physical_cell_id.value &3;

  LOG_I(PHY, "PBCH DMRS mapping started at symbol %d shift %d\n", ssb_start_symbol+1, nushift);

  /// QPSK modulation
  for (int m=0; m<NR_PBCH_DMRS_LENGTH; m++) {
    idx = ((((gold_pbch_dmrs[(m<<1)>>5])>>((m<<1)&0x1f))&1)<<1) ^ (((gold_pbch_dmrs[((m<<1)+1)>>5])>>(((m<<1)+1)&0x1f))&1);
    mod_dmrs[m<<1] = nr_mod_table[(NR_MOD_TABLE_QPSK_OFFSET + idx)<<1];
    mod_dmrs[(m<<1)+1] = nr_mod_table[((NR_MOD_TABLE_QPSK_OFFSET + idx)<<1) + 1];
#ifdef DEBUG_PBCH_DMRS
  printf("m %d idx %d gold seq %d b0-b1 %d-%d mod_dmrs %d %d\n", m, idx, gold_pbch_dmrs[(m<<1)>>5], (((gold_pbch_dmrs[(m<<1)>>5])>>((m<<1)&0x1f))&1),
  (((gold_pbch_dmrs[((m<<1)+1)>>5])>>(((m<<1)+1)&0x1f))&1), mod_dmrs[(m<<1)], mod_dmrs[(m<<1)+1]);
#endif
  }

  /// Resource mapping
  a = (config->rf_config.tx_antenna_ports.value == 1) ? amp : (amp*ONE_OVER_SQRT2_Q15)>>15;

  for (int aa = 0; aa < config->rf_config.tx_antenna_ports.value; aa++)
  {

    // PBCH DMRS are mapped  within the SSB block on every fourth subcarrier starting from nushift of symbols 1, 2, 3
      ///symbol 1  [0+nushift:4:236+nushift] -- 60 mod symbols
    k = frame_parms->first_carrier_offset + frame_parms->ssb_start_subcarrier + nushift;
    l = ssb_start_symbol + 1;

    for (int m = 0; m < 60; m++) {
#ifdef DEBUG_PBCH_DMRS
  printf("m %d at k %d of l %d\n", m, k, l);
#endif
      ((int16_t*)txdataF[aa])[(l*frame_parms->ofdm_symbol_size + k)<<1] = (a * mod_dmrs[m<<1]) >> 15;
      ((int16_t*)txdataF[aa])[((l*frame_parms->ofdm_symbol_size + k)<<1) + 1] = (a * mod_dmrs[(m<<1) + 1]) >> 15;
      k+=4;

      if (k >= frame_parms->ofdm_symbol_size)
        k-=frame_parms->ofdm_symbol_size;
    }

      ///symbol 2  [0+u:4:44+nushift ; 192+nu:4:236+nushift] -- 24 mod symbols
    k = frame_parms->first_carrier_offset + frame_parms->ssb_start_subcarrier + nushift;
    l++;

    for (int m = 60; m < 84; m++) {
#ifdef DEBUG_PBCH_DMRS
  printf("m %d at k %d of l %d\n", m, k, l);
#endif
      ((int16_t*)txdataF[aa])[(l*frame_parms->ofdm_symbol_size + k)<<1] = (a * mod_dmrs[m<<1]) >> 15;
      ((int16_t*)txdataF[aa])[((l*frame_parms->ofdm_symbol_size + k)<<1) + 1] = (a * mod_dmrs[(m<<1) + 1]) >> 15;
      k+=(m==71)?148:4; // Jump from 44+nu to 192+nu

      if (k >= frame_parms->ofdm_symbol_size)
        k-=frame_parms->ofdm_symbol_size;
    }

      ///symbol 3  [0+nushift:4:236+nushift] -- 60 mod symbols
    k = frame_parms->first_carrier_offset + frame_parms->ssb_start_subcarrier + nushift;
    l++;

    for (int m = 84; m < NR_PBCH_DMRS_LENGTH; m++) {
#ifdef DEBUG_PBCH_DMRS
  printf("m %d at k %d of l %d\n", m, k, l);
#endif
      ((int16_t*)txdataF[aa])[(l*frame_parms->ofdm_symbol_size + k)<<1] = (a * mod_dmrs[m<<1]) >> 15;
      ((int16_t*)txdataF[aa])[((l*frame_parms->ofdm_symbol_size + k)<<1) + 1] = (a * mod_dmrs[(m<<1) + 1]) >> 15;
      k+=4;

      if (k >= frame_parms->ofdm_symbol_size)
        k-=frame_parms->ofdm_symbol_size;
    }

  }


#ifdef DEBUG_PBCH_DMRS
  write_output("txdataF_pbch_dmrs.m", "txdataF_pbch_dmrs", txdataF[0], frame_parms->samples_per_frame_wCP>>1, 1, 1);
#endif
  return 0;
}

void nr_pbch_scrambling(NR_gNB_PBCH *pbch,
                        uint32_t Nid,
                        uint8_t nushift,
                        uint16_t M,
                        uint16_t length,
                        uint8_t bitwise)
{
  uint8_t reset, offset;
  uint32_t x1, x2, s=0;
  uint8_t *pbch_e = pbch->pbch_e;
  uint32_t *pbch_a_prime = (uint32_t*)pbch->pbch_a_prime;
  uint32_t *pbch_a_interleaved = (uint32_t*)pbch->pbch_a_interleaved;
  uint32_t unscrambling_mask = 0x100006D;

  reset = 1;
  // x1 is set in lte_gold_generic
  x2 = Nid;

  // The Gold sequence is shifted by nushift* M, so we skip (nushift*M /32) double words
  for (int i=0; i<(uint16_t)ceil((nushift*M)/32); i++) {
    s = lte_gold_generic(&x1, &x2, reset);
    reset = 0;
  }
  // Scrambling is now done with offset (nushift*M)%32
  offset = (nushift*M)&0x1f;
#ifdef DEBUG_PBCH_ENCODING
  printf("Scrambling params: nushift %d M %d length %d bitwise %d offset %d\n", nushift, M, length, bitwise, offset);
#endif

  for (int i=0; i<length; i++) {
    if (((i+offset)&0x1f)==0) {
      s = lte_gold_generic(&x1, &x2, reset);
      reset = 0;
    }
#ifdef DEBUG_PBCH_ENCODING
  printf("s: %04x\t", s);
#endif
    if (bitwise) {
      (*pbch_a_prime) ^= ((unscrambling_mask>>i)&1)? (((*pbch_a_interleaved)>>i)&1)<<i : ((((*pbch_a_interleaved)>>i)&1) ^ ((s>>((i+offset)&0x1f))&1))<<i;      
    }

    else
      pbch_e[i] = (pbch_e[i]&1) ^ ((s>>((i+offset)&0x1f))&1);
  }
}

// This portion of code is temporarily kept until the optimized version is validated
uint8_t nr_pbch_payload_interleaving_pattern[32] = {16, 23, 18, 17, 8, 30, 10, 6, 24, 7, 0, 5, 3, 2, 1, 4,
                                                9, 11, 12, 13, 14, 15, 19, 20, 21, 22, 25, 26, 27, 28, 29, 31};

uint8_t nr_pbch_payload_interleaver(uint8_t i) {
  uint8_t j_sfn=6, j_hrf=10, j_ssb=11, j_other=14;

  if (24<=i && i<=27) //Sfn bits
    return nr_pbch_payload_interleaving_pattern[j_sfn + i -24];
  else if (i==28) // Hrf bit
    return nr_pbch_payload_interleaving_pattern[j_hrf];
  else if (29<=i) // Ssb bits
    return nr_pbch_payload_interleaving_pattern[j_ssb + (i-29)];
  else
    return nr_pbch_payload_interleaving_pattern[(j_other + i)&0x1f];
}

/*This pattern takes into account the adjustments for the field specific counters j_sfn, j_hrf, j_ssb and j_other*/
//uint8_t nr_pbch_payload_interleaving_pattern[32] = {1,4,9,11,12,13,14,15,19,20,21,22,25,26,27,28,
//                                                    29,31,16,23,18,17,8,30,10,6,24,7,0,5,3,2};

int nr_generate_pbch(NR_gNB_PBCH *pbch,
                     uint8_t *pbch_pdu,
                     int32_t **txdataF,
                     int16_t amp,
                     uint8_t ssb_start_symbol,
                     uint8_t n_hf,
                     uint8_t Lmax,
                     uint8_t ssb_index,
                     int sfn,
                     nfapi_nr_config_request_t* config,
                     NR_DL_FRAME_PARMS *frame_parms)
{

  int k,l,m;
  int16_t a;
  int16_t mod_pbch_e[NR_POLAR_PBCH_E];
  uint8_t idx=0;
  uint16_t M;
  uint8_t nushift;
  uint8_t *xbyte = pbch->pbch_a;
  memset((void*) xbyte, 0, 1);

  LOG_I(PHY, "PBCH generation started\n");

  ///Payload generation
    // Fix byte endian
  if (!(sfn&7))
    for (int i=0; i<(NR_PBCH_PDU_BITS>>3); i++)
      pbch->pbch_a[(NR_POLAR_PBCH_PAYLOAD_BITS>>3)-i-1] = pbch_pdu[i];
#ifdef DEBUG_PBCH_ENCODING
  printf("Byte endian fix:\n");
  for (int i=0; i<4; i++)
    printf("pbch_a[%d]: 0x%02x\n", i, pbch->pbch_a[i]);
#endif

    // Extra byte generation
  for (int i=0; i<4; i++)
    (*xbyte) ^= ((sfn>>i)&1)<<i; // 4 lsb of sfn

  (*xbyte) ^= n_hf<<4; // half frame index bit

  if (Lmax == 64)
    for (int i=0; i<3; i++)
      (*xbyte) ^= ((ssb_index>>(3+i))&1)<<(5+i); // resp. 4th, 5th and 6th bits of ssb_index
  else
    (*xbyte) ^= ((config->sch_config.ssb_subcarrier_offset.value>>5)&1)<<5; //MSB of k_SSB
#ifdef DEBUG_PBCH_ENCODING
  printf("Extra byte:\n");
  for (int i=0; i<4; i++)
    printf("pbch_a[%d]: 0x%02x\n", i, pbch->pbch_a[i]);
#endif

    // Payload interleaving
  uint32_t in=0, out=0;
  for (int i=0; i<NR_POLAR_PBCH_PAYLOAD_BITS>>3; i++)
    in |= (uint32_t)(pbch->pbch_a[i]<<((3-i)<<3));

  for (int i=0; i<32; i++) {
    out |= ((in>>i)&1)<<(nr_pbch_payload_interleaver(i));//nr_pbch_payload_interleaving_pattern[i]
#ifdef DEBUG_PBCH_ENCODING
  printf("i %d in 0x%08x out 0x%08x ilv %d (in>>i)&1) %d\n", i, in, out, nr_pbch_payload_interleaver(i), (in>>i)&1);
#endif
  }

  for (int i=0; i<NR_POLAR_PBCH_PAYLOAD_BITS>>3; i++)
    pbch->pbch_a_interleaved[i] = (uint8_t)((out>>(i<<3))&0xff);

#ifdef DEBUG_PBCH_ENCODING
  printf("Interleaving:\n");
  for (int i=0; i<4; i++)
    printf("pbch_a_interleaved[%d]: 0x%02x\n", i, pbch->pbch_a_interleaved[i]);
#endif

    // Scrambling
  M = (Lmax == 64)? (NR_POLAR_PBCH_PAYLOAD_BITS - 6) : (NR_POLAR_PBCH_PAYLOAD_BITS - 3);
  nushift = (((sfn>>2)&1)<<1) ^ ((sfn>>1)&1);
  nr_pbch_scrambling(pbch, (uint32_t)config->sch_config.physical_cell_id.value, nushift, M, NR_POLAR_PBCH_PAYLOAD_BITS, 1);
#ifdef DEBUG_PBCH_ENCODING
  printf("Payload scrambling:\n");
  for (int i=0; i<4; i++)
    printf("pbch_a_prime[%d]: 0x%02x\n", i, pbch->pbch_a_prime[i]);
#endif


  /// CRC, coding and rate matching
  polar_encoder (pbch->pbch_a_prime, pbch->pbch_e, &frame_parms->pbch_polar_params);
#ifdef DEBUG_PBCH_ENCODING
  printf("Channel coding:\n");
  for (int i=0; i<NR_POLAR_PBCH_E>>3; i++)
    printf("pbch_e[%d]: 0x%02x\t", i, pbch->pbch_e[i]);
  printf("\n");
#endif

  /// Scrambling
  M =  NR_POLAR_PBCH_E;
  nushift = (Lmax==4)? ssb_index&3 : ssb_index&7;
  nr_pbch_scrambling(pbch, (uint32_t)config->sch_config.physical_cell_id.value, nushift, M, NR_POLAR_PBCH_E, 0);
#ifdef DEBUG_PBCH_ENCODING
  printf("Scrambling:\n");
  for (int i=0; i<NR_POLAR_PBCH_E>>3; i++)
    printf("pbch_e[%d]: 0x%02x\t", i, pbch->pbch_e[i]);
  printf("\n");
#endif

  /// QPSK modulation
  for (int i=0; i<NR_POLAR_PBCH_E>>1; i++){
    idx = ((pbch->pbch_e[i<<1]&1)<<1) ^ (pbch->pbch_e[(i<<1)+1]&1);
    mod_pbch_e[i<<1] = nr_mod_table[(NR_MOD_TABLE_QPSK_OFFSET + idx)<<1];
    mod_pbch_e[(i<<1)+1] = nr_mod_table[((NR_MOD_TABLE_QPSK_OFFSET + idx)<<1)+1];

#ifdef DEBUG_PBCH
  printf("i %d idx %d  mod_pbch %d %d\n", i, idx, mod_pbch_e[2*i], mod_pbch_e[2*i+1]);
#endif
  }

  /// Resource mapping
  nushift = config->sch_config.physical_cell_id.value &3;
  a = (config->rf_config.tx_antenna_ports.value == 1) ? amp : (amp*ONE_OVER_SQRT2_Q15)>>15;

  for (int aa = 0; aa < config->rf_config.tx_antenna_ports.value; aa++)
  {

    // PBCH modulated symbols are mapped  within the SSB block on symbols 1, 2, 3 excluding the subcarriers used for the PBCH DMRS
      ///symbol 1  [0:239] -- 180 mod symbols
    k = frame_parms->first_carrier_offset + frame_parms->ssb_start_subcarrier;
    l = ssb_start_symbol + 1;
    m = 0;

    for (int ssb_sc_idx = 0; ssb_sc_idx < 240; ssb_sc_idx++) {

      if ((ssb_sc_idx&3) == nushift) {  //skip DMRS
        k++;
        continue;
      }
      else {
#ifdef DEBUG_PBCH
  printf("m %d ssb_sc_idx %d at k %d of l %d\n", m, ssb_sc_idx, k, l);
#endif
        ((int16_t*)txdataF[aa])[(l*frame_parms->ofdm_symbol_size + k)<<1] = (a * mod_pbch_e[m<<1]) >> 15;
        ((int16_t*)txdataF[aa])[((l*frame_parms->ofdm_symbol_size + k)<<1) + 1] = (a * mod_pbch_e[(m<<1) + 1]) >> 15;
        k++;
        m++;
      }

      if (k >= frame_parms->ofdm_symbol_size)
        k-=frame_parms->ofdm_symbol_size;
    }

      ///symbol 2  [0:47 ; 192:239] -- 72 mod symbols
    k = frame_parms->first_carrier_offset + frame_parms->ssb_start_subcarrier;
    l++;
    m=180;

    for (int ssb_sc_idx = 0; ssb_sc_idx < 48; ssb_sc_idx++) {

      if ((ssb_sc_idx&3) == nushift) {
        k++;
        continue;
      }
      else {
#ifdef DEBUG_PBCH
  printf("m %d ssb_sc_idx %d at k %d of l %d\n", m, ssb_sc_idx, k, l);
#endif
        ((int16_t*)txdataF[aa])[(l*frame_parms->ofdm_symbol_size + k)<<1] = (a * mod_pbch_e[m<<1]) >> 15;
        ((int16_t*)txdataF[aa])[((l*frame_parms->ofdm_symbol_size + k)<<1) + 1] = (a * mod_pbch_e[(m<<1) + 1]) >> 15;
        k++;
        m++;
      }

      if (k >= frame_parms->ofdm_symbol_size)
        k-=frame_parms->ofdm_symbol_size;
    }

    k += 144;
    if (k >= frame_parms->ofdm_symbol_size)
      k-=frame_parms->ofdm_symbol_size;

    m=216;

    for (int ssb_sc_idx = 192; ssb_sc_idx < 240; ssb_sc_idx++) {

      if ((ssb_sc_idx&3) == nushift) {
        k++;
        continue;
      }
      else {
#ifdef DEBUG_PBCH
  printf("m %d ssb_sc_idx %d at k %d of l %d\n", m, ssb_sc_idx, k, l);
#endif
        ((int16_t*)txdataF[aa])[(l*frame_parms->ofdm_symbol_size + k)<<1] = (a * mod_pbch_e[m<<1]) >> 15;
        ((int16_t*)txdataF[aa])[((l*frame_parms->ofdm_symbol_size + k)<<1) + 1] = (a * mod_pbch_e[(m<<1) + 1]) >> 15;
        k++;
        m++;
      }

      if (k >= frame_parms->ofdm_symbol_size)
        k-=frame_parms->ofdm_symbol_size;
    }

      ///symbol 3  [0:239] -- 180 mod symbols
    k = frame_parms->first_carrier_offset + frame_parms->ssb_start_subcarrier;
    l++;
    m=252;

    for (int ssb_sc_idx = 0; ssb_sc_idx < 240; ssb_sc_idx++) {

      if ((ssb_sc_idx&3) == nushift) {
        k++;
        continue;
      }
      else {
#ifdef DEBUG_PBCH
  printf("m %d ssb_sc_idx %d at k %d of l %d\n", m, ssb_sc_idx, k, l);
#endif
        ((int16_t*)txdataF[aa])[(l*frame_parms->ofdm_symbol_size + k)<<1] = (a * mod_pbch_e[m<<1]) >> 15;
        ((int16_t*)txdataF[aa])[((l*frame_parms->ofdm_symbol_size + k)<<1) + 1] = (a * mod_pbch_e[(m<<1) + 1]) >> 15;
        k++;
        m++;
      }

      if (k >= frame_parms->ofdm_symbol_size)
        k-=frame_parms->ofdm_symbol_size;
    }

  }


#ifdef DEBUG_PBCH
  write_output("txdataF_pbch.m", "txdataF_pbch", txdataF[0], frame_parms->samples_per_frame_wCP>>1, 1, 1);
#endif


  return 0;
}