/*****************************************************************************//*   FIle Name : viterbi_turbo2.c                                            *//*   Description : WiMax FEC Viterbi Decoder for BTC                         *//*   author : miffie                                                         *//*   Date   : Nov/19/05                                                      *//*   Copyright (c) 2005 miffie   All rights reserved.                        *//*****************************************************************************///One line correction in turbo decoder will be done through 3 pipeline stages//#1  check metrics calculation in normal order//    write into Soft memory (in first row iteration )//#2  Error estimation in reverse order//    read from Soft memory//    write into path memory//#3  trace back with SoftOutput//    read from both Soft memory & pathmemory//    write back to Soft memory//In this viterbi_turbo2, #2 &#3 are exercised.struct binaryset viterbi_turbo2 (char type, struct binaryset datain ,                                 struct binaryset metric, char *parity ) {int 	ii , jj , kk ;char    nn , pp ;short 	tmp0, tmp1, tmp2 ;struct 	binaryset bset ;short	brmetric[4] ;short 	metric0[128], metric1[128] ;short	minimum_metric ;short	won_metric ;char    state[128][4] ;char	branch[128] ;char    pathmem[64][128] ; short	MAX_METRIC = 0x7f ;char    SISO_SHIFT = 4 ;char    BRANCH_OFFSET = 1 ;  //Main   PRINTF( "viterbi_turbo2.c size=%x parity=%d\n", datain.size,*parity) ;  if (type<4) { //Hamming code    //initialize     nn =  (type==1) ? 0x1f :          (type==2) ? 0x3f : 0x7f ;    pp =  (type==1) ? 0x5 :   //lfsr+parity length          (type==2) ? 0x6 : 0x7 ;    for(ii=0;ii<=nn;ii++) { //init      state[ii][0] = ((lfsr( type, 0 , (ii>>1) ) & nn)<<1)                      + ((ii&0x1) ? 1 : 0) ; //parity      state[ii][1] = ((lfsr( type, 1 , (ii>>1) ) & nn)<<1)                      + ((ii&0x1) ? 0 : 1) ; //parity    } //init    //for(ii=0;ii<=nn;ii++) printf("state(%x %x) %x\n", ii, 0, state[ii][0] ) ;    //for(ii=0;ii<=nn;ii++) printf("state(%x %x) %x\n", ii, 1, state[ii][1] ) ;////////////////////////////////////////////////////////////////////#2  Error estimation in reverse order//////////////////////////////////////////////////////////////////    //initialize metrics    for(ii=0;ii<=nn;ii++)  { //each state      metric0[ii] = metric.data[ii>>1]  ;      if(( *parity<0 ) & (ii%2)) metric0[ii] -=  *parity ;      if(( *parity>0 ) & ((ii%2)==0)) metric0[ii] +=  *parity ;    } //each state    for(ii=datain.size-1;ii>=0;ii--) { //each cycle in normal order      //branch metric      //state0-31      brmetric[0] = (datain.data[ii]>=8)  ? 0xf-datain.data[ii] : datain.data[ii]  ;      brmetric[0] += BRANCH_OFFSET;      brmetric[1] = 0xf - brmetric[0] ;      minimum_metric = MAX_METRIC ;      //metric      for(jj=0;jj<=nn;jj++) { //each state         if ( ii == datain.size-1) {//parity           tmp0 = jj  ;            tmp1 = jj ^0x01 ;         } else {           tmp0 = state[jj][0] ;           tmp1 = state[jj][1] ;         } //parity         //printf("%d %x metric[%x]=%x+br%x metric[%x]=%x+br%x\n",          //  ii, jj, tmp0, metric0[tmp0], brmetric[0], tmp1, metric0[tmp1], brmetric[1] ) ;         tmp0 = metric0[tmp0] + brmetric[0]  ;         tmp0 = (tmp0>MAX_METRIC) ? MAX_METRIC : tmp0 ;         tmp1 = metric0[tmp1] + brmetric[1]  ;         tmp1 = (tmp1>MAX_METRIC) ? MAX_METRIC : tmp1 ;         pathmem[ii][jj] = tmp0 - tmp1 ;         //printf("pathmem( %d, %x %d ) =%d\n",ii, (jj>>1), (jj&0x1), pathmem[ii][jj] )  ;         metric1[jj] = (tmp0>=tmp1) ? tmp1 : tmp0 ; //min(tmp0,tmp1) ;         //limitter         if (metric1[jj] > MAX_METRIC ) metric1[jj] = MAX_METRIC ;         //printf("%d metric[%d]=%d\n", ii, jj,  metric1[jj] ) ;                  if (metric1[jj] < minimum_metric) {             minimum_metric = metric1[jj] ;             won_metric = jj ;         }      } //each state      //printf("%d won_metric = %x %x\n", ii, won_metric>>1 , won_metric&0x1 ) ;      //printf("%d pathmem1(%x) = %x\n", ii, won_metric, pathmem1[won_metric]) ;      for(jj=0;jj<=nn;jj++) { //each metric1        //Normalization        metric1[jj] -= minimum_metric ; //force the won_metric to zero        //copy metric1 to metric0 for the next cycle operation        metric0[jj] = metric1[jj] ;        //copy metric1 to metric0 for the next cycle operation      } //each metric1    } //each cycle    ////////////////////////////////////////////////////////////////////#3  trace back with SoftOutput//////////////////////////////////////////////////////////////////      //output       *parity = 0 ;      won_metric=0 ; //because check should be zero at the end of calcuration      for(jj=0;jj<datain.size;jj++)  { //output        tmp1 = pathmem[jj][won_metric] ;        printf("datain.data(%d)=%x path(%x)=%x ", jj,  datain.data[jj], won_metric, tmp1&0xff) ;        //SISO Softin Softout        datain.data[jj] = ((tmp1>=0)&(datain.data[jj]<8))  ? datain.data[jj]+2 :                          ((tmp1>=0)&(datain.data[jj]>=8)) ? datain.data[jj]-2 :                                                              datain.data[jj] ;        /*****        //Following complicated solution did not work well.        //Because some corrections will  not be right,  it's dangerous to change        //Soft data, which is not assumed to be corrected.  Miffie Nov/19/05        datain.data[jj] = ((tmp1<0)&(datain.data[jj]==0))  ? 0 :                          ((tmp1<0)&(datain.data[jj]<8))  ? datain.data[jj]+(tmp1>>SISO_SHIFT) :                          ((tmp1<0)&(datain.data[jj]==0xf))  ? 0xf :                           (tmp1<0) ? datain.data[jj]-(tmp1>>SISO_SHIFT) :                           ((tmp1>=0)&(datain.data[jj]<8))  ? 8+(tmp1>>SISO_SHIFT) :                         7-(tmp1>>SISO_SHIFT) ;        datain.data[jj] = (datain.data[jj]<0 ) ? 0 :                          (datain.data[jj]>0xf) ? 0xf : datain.data[jj] ;        *******/        printf("=>%x\n", datain.data[jj]) ;        *parity ^= (datain.data[jj]>=8) ? 1 : 0 ;        if ( tmp1 >= 0  ) won_metric = state[won_metric][1]  ;         else  won_metric = state[won_metric][0] ;      } //output  } //Hamming code   else { //parity only    *parity = 0 ;    for(jj=0;jj<datain.size;jj++)  { //parity       *parity ^= (datain.data[jj]>=8) ? 1 : 0 ;    } //parity    if (parity==0) {// no parity error        for(jj=0;jj<datain.size;jj++)  { //each sample        datain.data[jj] = (datain.data[jj]==0 ) ? 0 :                          (datain.data[jj]==0xf) ? 0xf :                          (datain.data[jj]>=8) ? datain.data[jj] +1  : datain.data[jj] -1 ;      } //each sample    } //no parity errors    else { //error      for(jj=0;jj<datain.size;jj++)  { //each sample          datain.data[jj] = (datain.data[jj]>=8)  ? datain.data[jj] -1  :                             datain.data[jj] +1 ;      } //each sample    } //error  } //parity only  free( metric.data ) ;  return ( datain ) ;} //viterbi_turbo2