sss_nr.c

/*
 * Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The OpenAirInterface Software Alliance licenses this file to You under
 * the OAI Public License, Version 1.1  (the "License"); you may not use this file
 * except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.openairinterface.org/?page_id=698
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *-------------------------------------------------------------------------------
 * For more information about the OpenAirInterface (OAI) Software Alliance:
 *      contact@openairinterface.org
 */

/**********************************************************************
*
* FILENAME    :  sss_nr.c
*
* MODULE      :  Functions for secundary synchronisation signal
*
* DESCRIPTION :  generation of sss
*                3GPP TS 38.211 7.4.2.3 Secondary synchronisation signal
*
************************************************************************/

#include <stdio.h>
#include <assert.h>
#include <errno.h>

#include "PHY/defs_nr_UE.h"
#include "PHY/MODULATION/modulation_UE.h"

#include "PHY/NR_REFSIG/ss_pbch_nr.h"

#define DEFINE_VARIABLES_SSS_NR_H
#include "PHY/NR_REFSIG/sss_nr.h"
#undef DEFINE_VARIABLES_SSS_NR_H

/*******************************************************************
*
* NAME :         init_context_sss_nr
*
* PARAMETERS :   N_ID_2 : element 2 of physical layer cell identity
*                value : { 0, 1, 2 }
*
* RETURN :       generate binary sss sequence (this is a m-sequence)
*                d_sss is a third dimension array depending on
*                Cell identity elements:
*                - N_ID_1 : value from 0 to 335
*                - N_ID_2 : value from 0 to 2
*
* DESCRIPTION :  3GPP TS 38.211 7.4.2.3 Secundary synchronisation signal
*                Sequence generation
*
*********************************************************************/

#define INITIAL_SSS_NR    (7)

void init_context_sss_nr(int amp)
{
  int16_t x0[LENGTH_SSS_NR];
  int16_t x1[LENGTH_SSS_NR];
  int16_t dss_current;
  int m0, m1;

  const int x0_initial[INITIAL_SSS_NR] = { 1, 0, 0, 0, 0, 0, 0 };
  const int x1_initial[INITIAL_SSS_NR] = { 1, 0, 0, 0, 0, 0, 0 };

  for (int i=0; i < INITIAL_SSS_NR; i++) {
    x0[i] = x0_initial[i];
    x1[i] = x1_initial[i];
  }

  for (int i=0; i < (LENGTH_SSS_NR - INITIAL_SSS_NR); i++) {
    x0[i+7] = (x0[i + 4] + x0[i])%(2);
    x1[i+7] = (x1[i + 1] + x1[i])%(2);
  }

  for (int N_ID_2 = 0; N_ID_2 < N_ID_2_NUMBER; N_ID_2++) {

    for (int N_ID_1 = 0; N_ID_1 < N_ID_1_NUMBER; N_ID_1++) {

      m0 = 15*(N_ID_1/112) + (5*N_ID_2);
      m1 = N_ID_1%112;

      for (int n = 0; n < LENGTH_SSS_NR; n++) {

        dss_current = (1 - 2*x0[(n + m0)%(LENGTH_SSS_NR)])*(1 - 2*x1[(n + m1)%(LENGTH_SSS_NR)]);

      /* Modulation of SSS is a BPSK TS 36.211 chapter 5.1.2 BPSK */
#if 1
        d_sss[N_ID_2][N_ID_1][n]   = dss_current;// * amp;
	(void) amp;
#else
        (void) amp;
        d_sss[N_ID_2][N_ID_1][n]   = (dss_current * SHRT_MAX)>>SCALING_PSS_NR;
#endif
      }
    }
  }

#if 0
  for (int i = 0; i < LENGTH_SSS_NR; i++) {
    printf("sss ref[%i] : %d %d \n", i, d_sss[0][0][i], d_sss[0][0][i]);
  }
#endif
}

/*******************************************************************
*
* NAME :         insert_sss_nr
*
* PARAMETERS :   pointer to input buffer for which sss in inserted
*                amp amplitude applied to input
*                frame parameters for cell identity
*
* RETURN :       none
*
* DESCRIPTION :  Allow to generate a reference sss sequence according to cell identity
*
*********************************************************************/

//#define DEBUG_SSS_NR
//#define DEBUG_PLOT_SSS
void insert_sss_nr(int16_t *sss_time,
                   NR_DL_FRAME_PARMS *frame_parms)
{
  unsigned int ofdm_symbol_size = frame_parms->ofdm_symbol_size;
  unsigned int size = ofdm_symbol_size * IQ_SIZE; /* i & q */

  assert(size <= SYNCF_TMP_SIZE);
  assert(size <= SYNC_TMP_SIZE);

  bzero(synchroF_tmp, size);
  bzero(synchro_tmp, size);

  int Nid2 = GET_NID2(frame_parms->Nid_cell);
  int Nid1 = GET_NID1(frame_parms->Nid_cell);

  /* call of IDFT should be done with ordered input as below
    *
    *                n input samples
    *  <------------------------------------------------>
    *  0                                                n
    *  are written into input buffer for IFFT in this order
    *   -------------------------------------------------
    *  |xxxxxxx                       N/2       xxxxxxxx|
    *  --------------------------------------------------
    *  ^      ^                 ^               ^          ^
    *  |      |                 |               |          |
    * n/2    end of            n=0            start of    n/2-1
    *         sss                               sss
    *
    *                   Frequencies
    *      positives                   negatives
    * 0                 (+N/2)(-N/2)
    * |-----------------------><-------------------------|
    *
    * sample 0 is for continuous frequency which is not used here
    */

  unsigned int k = ofdm_symbol_size - ((LENGTH_SSS_NR/2)+1);

  /* SSS is directly mapped to subcarrier */
  for (int i=0; i<LENGTH_SSS_NR; i++) {
    synchroF_tmp[2*k] = d_sss[Nid2][Nid1][i];
    synchroF_tmp[2*k+1] = 0;

    k++;

    if (k >= ofdm_symbol_size) {
      k++;
      k-=ofdm_symbol_size;
    }
  }

  /* get sss in the frequency domain by applying an inverse FFT */
  idft(IDFT_2048,synchroF_tmp,          /* complex input */
           synchro_tmp,           /* complex output */
   	   1);                    /* scaling factor */

  /* then get final sss in time */
  for (unsigned int i=0; i<ofdm_symbol_size; i++) {
    ((int32_t *)sss_time)[i] = ((int32_t *)synchro_tmp)[i];
  }
}

/*******************************************************************
*
* NAME :         pss_ch_est
*
* PARAMETERS :   none
*
* RETURN :       none
*
* DESCRIPTION :  pss channel estimation
*
*********************************************************************/

int pss_ch_est_nr(PHY_VARS_NR_UE *ue,
                  int32_t pss_ext[NB_ANTENNAS_RX][LENGTH_PSS_NR],
                  int32_t sss_ext[NB_ANTENNAS_RX][LENGTH_SSS_NR])
{
  int16_t *pss;
  int16_t *pss_ext2,*sss_ext2,*sss_ext3,tmp_re,tmp_im,tmp_re2,tmp_im2;
  uint8_t aarx,i;
  NR_DL_FRAME_PARMS *frame_parms = &ue->frame_parms;

  pss = primary_synchro_nr2[ue->common_vars.eNb_id];

  sss_ext3 = (int16_t*)&sss_ext[0][0];

#if 0
  int16_t chest[2*LENGTH_PSS_NR];
#endif

  for (aarx=0; aarx<frame_parms->nb_antennas_rx; aarx++) {

    sss_ext2 = (int16_t*)&sss_ext[aarx][0];
    pss_ext2 = (int16_t*)&pss_ext[aarx][0];


#if 0

  int16_t *p = pss;

  for (int i = 0; i < LENGTH_PSS_NR; i++) {
    printf(" pss ref [%d]  %d  %d at address %p\n", i, p[2*i], p[2*i+1], &p[2*i]);
    printf(" pss ext [%d]  %d  %d at address %p\n", i, pss_ext2[2*i], pss_ext2[2*i+1], &pss_ext2[2*i]);
  }

#endif

#if 0

  for (int i = 0; i < LENGTH_PSS_NR; i++) {
    printf(" sss ext 2 [%d]  %d  %d at address %p\n", i, sss_ext2[2*i], sss_ext2[2*i+1], &sss_ext2[2*i]);
    printf(" sss ref   [%d]  %d  %d at address %p\n", i, d_sss[0][0][i], d_sss[0][0][i], &d_sss[0][0][i]);
  }

#endif

  int32_t amp;
  int shift;
    for (i = 0; i < LENGTH_PSS_NR; i++) {

      // This is H*(PSS) = R* \cdot PSS
      tmp_re = pss_ext2[i*2] * pss[i];
      tmp_im = -pss_ext2[i*2+1] * pss[i];
      
      amp = (((int32_t)tmp_re)*tmp_re) + ((int32_t)tmp_im)*tmp_im;
      shift = log2_approx(amp)/2;
#if 0
      printf("H*(%d,%d) : (%d,%d)\n",aarx,i,tmp_re,tmp_im);
      printf("pss(%d,%d) : (%d,%d)\n",aarx,i,pss[2*i],pss[2*i+1]);
      printf("pss_ext(%d,%d) : (%d,%d)\n",aarx,i,pss_ext2[2*i],pss_ext2[2*i+1]);
      if (aarx==0) {
       chest[i<<1]=tmp_re;
       chest[1+(i<<1)]=tmp_im;
      }
#endif      
      // This is R(SSS) \cdot H*(PSS)
      tmp_re2 = (int16_t)(((tmp_re * (int32_t)sss_ext2[i*2])>>shift)    - ((tmp_im * (int32_t)sss_ext2[i*2+1]>>shift)));
      tmp_im2 = (int16_t)(((tmp_re * (int32_t)sss_ext2[i*2+1])>>shift)  + ((tmp_im * (int32_t)sss_ext2[i*2]>>shift)));

      // printf("SSSi(%d,%d) : (%d,%d)\n",aarx,i,sss_ext2[i<<1],sss_ext2[1+(i<<1)]);
      // printf("SSSo(%d,%d) : (%d,%d)\n",aarx,i,tmp_re2,tmp_im2);
      // MRC on RX antennas
      if (aarx==0) {
        sss_ext3[i<<1]      = tmp_re2;
        sss_ext3[1+(i<<1)]  = tmp_im2;
      } else {
        sss_ext3[i<<1]      += tmp_re2;
        sss_ext3[1+(i<<1)]  += tmp_im2;
      }
    }
  }
#if 0
  LOG_M("pssrx.m","pssrx",pss,LENGTH_PSS_NR,1,1);
  LOG_M("pss_ext.m","pssext",pss_ext2,LENGTH_PSS_NR,1,1);
  LOG_M("psschest.m","pssch",chest,LENGTH_PSS_NR,1,1);
#endif
#if 0

  for (int i = 0; i < LENGTH_PSS_NR; i++) {
    printf(" sss ext 2 [%d]  %d  %d at address %p\n", i, sss_ext2[2*i], sss_ext2[2*i+1]);
    printf(" sss ref   [%d]  %d  %d at address %p\n", i, d_sss[0][0][i], d_sss[0][0][i]);
    printf(" sss ext 3 [%d]  %d  %d at address %p\n", i, sss_ext3[2*i], sss_ext3[2*i+1]);
  }

#endif

  // sss_ext now contains the compensated SSS
  return(0);
}

/*******************************************************************
*
* NAME :         do_pss_sss_extract
*
* PARAMETERS :   none
*
* RETURN :       none
*
* DESCRIPTION : it allows extracting sss from samples buffer
*
*********************************************************************/

int do_pss_sss_extract_nr(PHY_VARS_NR_UE *ue,
                          UE_nr_rxtx_proc_t *proc,
                          int32_t pss_ext[NB_ANTENNAS_RX][LENGTH_PSS_NR],
                          int32_t sss_ext[NB_ANTENNAS_RX][LENGTH_SSS_NR],
                          uint8_t doPss, uint8_t doSss,
                          uint8_t subframe) // add flag to indicate extracting only PSS, only SSS, or both
{
  uint8_t aarx;
  int32_t *pss_rxF,*pss_rxF_ext;
  int32_t *sss_rxF,*sss_rxF_ext;
  uint8_t pss_symbol, sss_symbol;
  int32_t **rxdataF;
  NR_DL_FRAME_PARMS *frame_parms = &ue->frame_parms;

  for (aarx=0; aarx<frame_parms->nb_antennas_rx; aarx++) {

    pss_symbol = 0;
    sss_symbol = SSS_SYMBOL_NB-PSS_SYMBOL_NB;

    rxdataF  =  ue->common_vars.common_vars_rx_data_per_thread[proc->thread_id].rxdataF;

    unsigned int ofdm_symbol_size = frame_parms->ofdm_symbol_size;

    pss_rxF  =  &rxdataF[aarx][pss_symbol*ofdm_symbol_size];
    sss_rxF  =  &rxdataF[aarx][sss_symbol*ofdm_symbol_size];

    pss_rxF_ext = &pss_ext[aarx][0];
    sss_rxF_ext = &sss_ext[aarx][0];

    unsigned int k = frame_parms->first_carrier_offset + frame_parms->ssb_start_subcarrier + 56;

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

    for (int i=0; i < LENGTH_PSS_NR; i++) {
      if (doPss) {		  
        pss_rxF_ext[i] = pss_rxF[k];
      }

      if (doSss) {
        sss_rxF_ext[i] = sss_rxF[k];
      }

      k++;

      if (k == ofdm_symbol_size) k=0;
      
    }
  }

#if 0

  int16_t *p = (int16_t *)sss_rxF_ext;

  for (int i = 0; i < LENGTH_PSS_NR; i++) {
    printf(" sss ext 2 [%d]  %d  %d at address %p\n", i, p[2*i], p[2*i+1], &p[2*i]);
    printf(" sss ref   [%d]  %d  %d at address %p\n", i, d_sss[0][0][i], d_sss[0][0][i], &d_sss[0][0][i]);
  }

#endif

#if 0

  int16_t *p2 = (int16_t *)pss_rxF_ext;

  for (int i = 0; i < LENGTH_PSS_NR; i++) {
    printf(" pss_rxF_ext [%d]  %d  %d at address %p\n", i, p2[2*i], p2[2*i+1], &p2[2*i]);
  }

#endif

  return(0);
}

/*******************************************************************
*
* NAME :         pss_sss_extract_nr
*
* PARAMETERS :   none
*
* RETURN :       none
*
* DESCRIPTION :
*
*********************************************************************/

int pss_sss_extract_nr(PHY_VARS_NR_UE *phy_vars_ue,
                       UE_nr_rxtx_proc_t *proc,
                       int32_t pss_ext[NB_ANTENNAS_RX][LENGTH_PSS_NR],
                       int32_t sss_ext[NB_ANTENNAS_RX][LENGTH_SSS_NR],
                       uint8_t subframe)
{
  return do_pss_sss_extract_nr(phy_vars_ue, proc, pss_ext, sss_ext, 1 /* doPss */, 1 /* doSss */, subframe);
}

/*******************************************************************
*
* NAME :         rx_sss_nr
*
* PARAMETERS :   none
*
* RETURN :       Set Nid_cell in ue context
*
* DESCRIPTION :  Determine element Nid1 of cell identity
*                so Nid_cell in ue context is set according to Nid1 & Nid2
*
*********************************************************************/

int rx_sss_nr(PHY_VARS_NR_UE *ue, UE_nr_rxtx_proc_t *proc, int32_t *tot_metric, uint8_t *phase_max)
{
  uint8_t i;
  int32_t pss_ext[NB_ANTENNAS_RX][LENGTH_PSS_NR];
  int32_t sss_ext[NB_ANTENNAS_RX][LENGTH_SSS_NR];
  uint8_t Nid2 = GET_NID2(ue->common_vars.eNb_id);
  uint16_t Nid1;
  uint8_t phase;
  int16_t *sss;
  NR_DL_FRAME_PARMS *frame_parms=&ue->frame_parms;
  int32_t metric, metric_re;
  int16_t *d;


  // pss sss extraction
  pss_sss_extract_nr(ue,
                     proc,
                     pss_ext,
                     sss_ext,
                     0);          /* subframe */

#ifdef DEBUG_PLOT_SSS

  write_output("rxsig0.m","rxs0",&ue->common_vars.rxdata[0][0],ue->frame_parms.samples_per_subframe,1,1);
  write_output("rxdataF0_pss.m","rxF0_pss",&ue->common_vars.common_vars_rx_data_per_thread[proc->thread_id].rxdataF[0][0],frame_parms->ofdm_symbol_size,1,1);
  write_output("rxdataF0_sss.m","rxF0_sss",&ue->common_vars.common_vars_rx_data_per_thread[proc->thread_id].rxdataF[0][(SSS_SYMBOL_NB-PSS_SYMBOL_NB)*frame_parms->ofdm_symbol_size],frame_parms->ofdm_symbol_size,1,1);
  write_output("pss_ext.m","pss_ext",pss_ext,LENGTH_PSS_NR,1,1);

#endif

#if 0
  int16_t *p = (int16_t *)sss_ext[0];
  int16_t *p2 = (int16_t *)pss_ext[0];

  for (int i = 0; i < LENGTH_SSS_NR; i++) {
    printf("sss ref  [%i] : %d %d \n", i, d_sss[0][0][i], d_sss[0][0][i]);
    printf("sss ext  [%i] : %d %d \n", i, p[2*i], p[2*i+1]);

    printf("pss ref [%i] : %d %d \n", i, primary_synchro_nr2[0][2*i], primary_synchro_nr2[0][2*i+1]);
    printf("pss ext [%i] : %d %d \n", i, p2[2*i], p2[2*i+1]);
  }
#endif

  // get conjugated channel estimate from PSS, H* = R* \cdot PSS
  // and do channel estimation and compensation based on PSS

  pss_ch_est_nr(ue,
                pss_ext,
                sss_ext);

  // now do the SSS detection based on the precomputed sequences in PHY/LTE_TRANSPORT/sss.h
  *tot_metric = INT_MIN;

  sss = (int16_t*)&sss_ext[0][0];

#ifdef DEBUG_PLOT_SSS

  write_output("sss_ext.m","sss_ext",sss_ext[0],LENGTH_SSS_NR,1,1);
  write_output("sss_ref.m","sss_ref", d_sss,LENGTH_SSS_NR,1,1);

#endif


#if 0

  /* simulate of a phase shift on the signal */

  int phase_shift_index = 0;

  phase_shift_samples(sss, LENGTH_SSS_NR, phase_re_nr[phase_shift_index], phase_im_nr[phase_shift_index]);

#endif

#if 0
        int16_t *ps = (int16_t *)pss_ext;

        for (int i = 0; i < LENGTH_SSS_NR; i++) {
          printf("sss ref  [%i] : %d \n", i, d_sss[0][0][i]);
          printf("sss ext  [%i] : %d %d \n", i, sss[2*i], sss[2*i+1]);

          printf("pss ref [%i] : %d %d \n", i, primary_synchro_nr2[0][2*i], primary_synchro_nr2[0][2*i+1]);
          printf("pss ext [%i] : %d %d \n", i, ps[2*i], ps[2*i+1]);
        }
#endif

  /* for phase evaluation, one uses an array of possible phase shifts */
  /* then a correlation is done between received signal with a shift pĥase and the reference signal */
  /* Computation of signal with shift phase is based on below formula */
  /* cosinus cos(x + y) = cos(x)cos(y) - sin(x)sin(y) */
  /* sinus   sin(x + y) = sin(x)cos(y) + cos(x)sin(y) */

   for (Nid1 = 0 ; Nid1 < N_ID_1_NUMBER; Nid1++) {          // all possible Nid1 values
      for (phase=0; phase < PHASE_HYPOTHESIS_NUMBER; phase++) {  // phase offset between PSS and SSS


      metric = 0;
      metric_re = 0;

      d = (int16_t *)&d_sss[Nid2][Nid1];

      // This is the inner product using one particular value of each unknown parameter
      for (i=0; i < LENGTH_SSS_NR; i++) {

	
        metric_re += d[i]*(((phase_re_nr[phase]*sss[2*i])>>SCALING_METRIC_SSS_NR) - ((phase_im_nr[phase]*sss[2*i+1])>>SCALING_METRIC_SSS_NR));
                   
#if 0
	  printf("i %d, phase %d/%d: metric %d, phase (%d,%d) sss (%d,%d) d %d\n",i,phase,PHASE_HYPOTHESIS_NUMBER,metric_re,phase_re_nr[phase],phase_im_nr[phase],sss[2*i],sss[1+(2*i)],d[i]);
#endif
      }

      metric = metric_re;

      // if the current metric is better than the last save it
      if (metric > *tot_metric) {
        *tot_metric = metric;
        ue->frame_parms.Nid_cell = Nid2+(3*Nid1);
        *phase_max = phase;

#ifdef DEBUG_SSS_NR

        printf("(phase,Nid1) (%d,%d), metric_phase %d tot_metric %d, phase_max %d \n",phase, Nid1, metric, *tot_metric, *phase_max);

#endif
      }
    }
  }

//#ifdef DEBUG_SSS_NR
  
#define SSS_METRIC_FLOOR_NR   (30000)
  if (*tot_metric > SSS_METRIC_FLOOR_NR) {	
    Nid2 = GET_NID2(frame_parms->Nid_cell);
    Nid1 = GET_NID1(frame_parms->Nid_cell);
    printf("Nid2 %d Nid1 %d tot_metric %d, phase_max %d \n", Nid2, Nid1, *tot_metric, *phase_max);
  }
  //#endif

  return(0);
}