viterbi_ctc.c

这个文件包括wimax中所有的编解码源代码

/*****************************************************************************/
/*   FIle Name : viterbi_ctc.c                                               */
/*   Description : WiMax OFDM FEC Viterbi decoder for CTC                    */
/*                 8x32 search                                               */
/*   author : miffie                                                         */
/*   Date   : Nov/21/05                                                      */
/*   Copyright (c) 2005 miffie   All rights reserved.                        */
/*****************************************************************************/
struct binaryset viterbi_ctc (struct binaryset datain ) {
int 	ii , jj ;
short 	tmp0, tmp1, tmp2, tmp3 ;
short 	exp0, exp1, exp2, exp3 ;
struct 	binaryset bset ;
char    *top ;
short	brmetric[4] ;
short	expmetric[2] ;
short 	metric0[8], metric1[8] ;
short	minimum_metric ;
short	won_metric ;
char	exp[8][4] ;
char	rev[8][4] ;
char	won[8] ;
char    state ;
int     NN ;
long long   sdata0[8],sdata1[8] ;
short	MAX_METRIC = 0x7f ;
char    soft[1296] ;
char    DELAY=16 ;

  //Main 
    PRINTF("viterbi_ctc size=%d\n", datain.size ) ;
    //initialize
    NN = datain.size/3 ;
    for(ii=0;ii<8;ii++) { //init
      metric0[ii] = 0 ;
      state =ii ;
      exp[ii][0]  = constituent_encoder ( 0, 0, &state ) ;
      rev[state][0]=ii;
      state =ii ;
      exp[ii][1]  = constituent_encoder ( 0, 1, &state ) ;
      rev[state][1]=ii;
      state =ii ;
      exp[ii][2]  = constituent_encoder ( 1, 0, &state ) ;
      rev[state][2]=ii;
      state =ii ;
      exp[ii][3]  = constituent_encoder ( 1, 1, &state ) ;
      rev[state][3]=ii;
    } //init
   
    
    //metric0[0] = 0 ; //assumed the shiftregister reset to 0
    for(ii=0;ii<(2*NN+DELAY);ii=ii+2) { //each cycle
        //branch metric
        tmp1 = (ii>=2*NN) ? 0 : datain.data[ii] ;
        tmp2 = (ii>=2*NN) ? 0 : datain.data[ii+1] ;
        tmp3 = (ii>=2*NN) ? 0 : datain.data[2*NN+(ii/2)] ;
        brmetric[0] = tmp1 + tmp2 ;
        brmetric[1] = tmp1 + (0xf-tmp2) ;
        brmetric[2] = (0xf-tmp1) + tmp2 ;
        brmetric[3] = (0xf-tmp1) + (0xf-tmp2) ;
        expmetric[0] = tmp3 ;
        expmetric[1] = 0xf - tmp3 ;
       
        //metric
        minimum_metric = MAX_METRIC ;
        for(jj=0;jj<8;jj++) { //each metric1
           tmp0 = rev[jj][0] ;
           tmp1 = rev[jj][1] ;
           tmp2 = rev[jj][2] ;
           tmp3 = rev[jj][3] ;
           exp0 = exp[tmp0][0] ;
           exp1 = exp[tmp1][1] ;
           exp2 = exp[tmp2][2] ;
           exp3 = exp[tmp3][3] ;
           //printf("%d %d 0: %2x + %2x + %2x = ", ii, jj, metric0[tmp0], brmetric[0], expmetric[ exp[tmp0][0] ] ) ;
           tmp0 = metric0[tmp0] + brmetric[0] + expmetric[ exp[tmp0][0] ] ;
           //printf("%3x exp=%x\n", tmp0 , exp0) ;
           //printf("%d %d 0: %2x + %2x + %2x = ", ii, jj, metric0[tmp1], brmetric[1], expmetric[ exp[tmp1][1] ] ) ;
           tmp1 = metric0[tmp1] + brmetric[1] + expmetric[ exp[tmp1][1] ];
           //printf("%3x exp=%x\n", tmp1 , exp1) ;
           //printf("%d %d 0: %2x + %2x + %2x = ", ii, jj, metric0[tmp2], brmetric[2], expmetric[ exp[tmp2][2] ] ) ;
           tmp2 = metric0[tmp2] + brmetric[2] + expmetric[ exp[tmp2][2] ];
           //printf("%3x exp=%x\n", tmp2 , exp2) ;
           //printf("%d %d 0: %2x + %2x + %2x = ", ii, jj, metric0[tmp3], brmetric[3], expmetric[ exp[tmp3][3] ] ) ;
           tmp3 = metric0[tmp3] + brmetric[3] + expmetric[ exp[tmp3][3] ];
           //printf("%3x exp=%x\n", tmp3 , exp3) ;
           
           //tmp0=min(tmp0,tmp1,tmp2,tmp3) ;
           if (tmp0>tmp1) {
              tmp0 = tmp1 ; //tmp0 =min(tmp0,tmp1) ;
              tmp1 =1 ;
              exp0 =exp1 ;
           } else tmp1=0 ;
           if (tmp2>tmp3) {
              tmp2 = tmp3 ; //tmp2 =min(tmp2,tmp3) ;
              tmp3 =3 ;
              exp2 =exp3 ;
           } else tmp3=2 ;
           if (tmp0>tmp2) {
              tmp0 = tmp2 ; //tmp0 =min(tmp0,tmp2) ;
              tmp1 = tmp3 ; //tmp1 is a position of won metric
              exp0 = exp2 ;
           } else tmp1=tmp1 ;
           metric1[jj] = tmp0 ;
           //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 ;
           }
           //serial data process
           sdata1[ jj ] = (sdata0[rev[jj][tmp1]]<<3 ) + (tmp1&0x3) + (exp0<<2) ;
           //printf( "sdata1(%d) = 0x%x\n", jj , sdata1[ jj] ) ;
           
      } //each metric1

      for(jj=0;jj<8;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
          sdata0[jj] = sdata1[jj] ;
      } //each metric1
      
      if (ii>=DELAY)  {//output
           //printf("sdata1(%d)=0x%x\n", (ii-DELAY), sdata1[won_metric] ) ;
           tmp0 = datain.data[ii-DELAY+0] ;
           tmp1 = (sdata1[won_metric]>>((DELAY/2)*3+1))&0x1 ;
           datain.data[ii-DELAY+0] = ((tmp0>=8) & (tmp1==0))  ? tmp0-2:
                                     ((tmp0<8) & (tmp1==1))   ? tmp0+2: tmp0 ;
           tmp0 = datain.data[ii-DELAY+1] ;
           tmp1 = (sdata1[won_metric]>>((DELAY/2)*3+0))&0x1 ;
           datain.data[ii-DELAY+1] = ((tmp0>=8) & (tmp1==0))  ? tmp0-2:
                                     ((tmp0<8) & (tmp1==1))   ? tmp0+2: tmp0 ;
           tmp0 = datain.data[(ii-DELAY)/2 + 2*NN ] ;
           tmp1 = (sdata1[won_metric]>>((DELAY/2)*3+2))&0x1 ;
           //printf("(%d %d) tmp0=%x tmp1=%x\n", ii-DELAY, won_metric, tmp0, tmp1 ) ;
           datain.data[(ii-DELAY)/2+2*NN] = ((tmp0>=8) & (tmp1==0))  ? tmp0-2:
                                     ((tmp0<8) & (tmp1==1))   ? tmp0+2: tmp0 ;
      } //output
        
    } //each cycle
    return ( datain ) ;
} //viterbi_ctc