dlsch_scrambling.c

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/*! \file PHY/LTE_TRANSPORT/dlsch_scrambling.c
* \brief Routines for the scrambling procedure of the PDSCH physical channel from 36-211, V8.6 2009-03
* \author R. Knopp
* \date 2011
* \version 0.1
* \company Eurecom
* \email: knopp@eurecom.fr,florian.kaltenberger@eurecom.fr
* \note
* \warning
*/

//#define DEBUG_SCRAMBLING 1

#include "PHY/defs.h"
#include "PHY/CODING/extern.h"
#include "PHY/CODING/lte_interleaver_inline.h"
#include "defs.h"
#include "extern.h"
#include "PHY/extern.h"
#include "UTIL/LOG/vcd_signal_dumper.h"

void dlsch_scrambling(LTE_DL_FRAME_PARMS *frame_parms,
		      int mbsfn_flag,
		      LTE_eNB_DLSCH_t *dlsch,
		      int G,
		      uint8_t q,
		      uint8_t Ns) {

  int i,j,k=0;
  //  uint8_t reset;
  uint32_t x1, x2, s=0;
  uint8_t *e=dlsch->e;

  vcd_signal_dumper_dump_function_by_name(VCD_SIGNAL_DUMPER_FUNCTIONS_ENB_DLSCH_SCRAMBLING, VCD_FUNCTION_IN);

  //  reset = 1;
  // x1 is set in lte_gold_generic
  if (mbsfn_flag == 0) {
    x2 = (dlsch->rnti<<14) + (q<<13) + ((Ns>>1)<<9) + frame_parms->Nid_cell; //this is c_init in 36.211 Sec 6.3.1
  }
  else {
    x2 = ((Ns>>1)<<9) + frame_parms->Nid_cell_mbsfn; //this is c_init in 36.211 Sec 6.3.1
  }
#ifdef DEBUG_SCRAMBLING
  printf("scrambling: rnti %x, q %d, Ns %d, Nid_cell %d, length %d\n",dlsch->rnti,q,Ns,frame_parms->Nid_cell, G);  
#endif
  s = lte_gold_generic(&x1, &x2, 1);
  for (i=0; i<(1+(G>>5)); i++) {
 
    for (j=0;j<32;j++,k++) {
#ifdef DEBUG_SCRAMBLING
      printf("scrambling %d : %d => ",k,e[k]);
#endif
      e[k] = (e[k]&1) ^ ((s>>j)&1);
#ifdef DEBUG_SCRAMBLING
      printf("%d\n",e[k]);
#endif
    }
   s = lte_gold_generic(&x1, &x2, 0);
  }

  vcd_signal_dumper_dump_function_by_name(VCD_SIGNAL_DUMPER_FUNCTIONS_ENB_DLSCH_SCRAMBLING, VCD_FUNCTION_OUT);

}


void dlsch_unscrambling(LTE_DL_FRAME_PARMS *frame_parms,
			int mbsfn_flag,
			LTE_UE_DLSCH_t *dlsch,
			int G,
			int16_t* llr,
			uint8_t q,
			uint8_t Ns) {

  int i,j,k=0;
  //  uint8_t reset;
  uint32_t x1, x2, s=0;
  
  //  reset = 1;
  // x1 is set in first call to lte_gold_generic

  if (mbsfn_flag == 0)
    x2 = (dlsch->rnti<<14) + (q<<13) + ((Ns>>1)<<9) + frame_parms->Nid_cell; //this is c_init in 36.211 Sec 6.3.1
  else
    x2 = ((Ns>>1)<<9) + frame_parms->Nid_cell_mbsfn; //this is c_init in 36.211 Sec 6.3.1
#ifdef DEBUG_SCRAMBLING
  printf("unscrambling: rnti %x, q %d, Ns %d, Nid_cell %d length %d\n",dlsch->rnti,q,Ns,frame_parms->Nid_cell,G);
#endif
  s = lte_gold_generic(&x1, &x2, 1);
  for (i=0; i<(1+(G>>5)); i++) {
    for (j=0;j<32;j++,k++) {
#ifdef DEBUG_SCRAMBLING
      printf("unscrambling %d : %d => ",k,llr[k]);
#endif
      llr[k] = ((2*((s>>j)&1))-1)*llr[k];
#ifdef DEBUG_SCRAMBLING
      printf("%d\n",llr[k]);
#endif
    }
    s = lte_gold_generic(&x1, &x2, 0);
  }
}