data_enc.c

This model is just testing an idea of MIMO, which IEEE802.11n will have. But I havo not seen the s

/*****************************************************************************/
/*   FIle Name : data_enc.c                                                  */
/*   Description : WLAN DATA symbols Encoder                                 */
/*                 S(x) = x^7 + x^4 + 1 ;                                    */
/*   author : miffie                                                         */
/*   Date   : aug/09/05                                                      */
/*   Copyright (c) 2005 miffie   All rights reserved.                        */
/*****************************************************************************/

struct complexset data_enc(struct binaryset datain,
                          char RATE , short LENGTH, char pilot_shifter) { //main 
struct	binaryset bset0,bset1 ;
struct  complexset cset0, cset1 ;
struct  complexset ctop ;
struct  complex  ctmp1, ctmp2 ;
char 	*tmp1 , *tmp2 ;
char	Nbpsc, coding_rate ;
short	Ncbps, Ndbps, Nsym, Ndata, Npad ;
int	ii ;

// Rate(Mbps)   RATE(R1-R4) Coding_Rate Modulation Nbpsc Ncbps Ndbps
//     6          1101        0:1/2        BPSK     1     48    24 
//     9          1111        2:3/4        BPSK     1     48    36 
//    12          0101        0:1/2        QPSK     2     96    48 
//    18          0111        2:3/4        QPSK     2     96    72 
//    24          1001        0:1/2        QAM16    4    192    96 
//    36          1011        2:3/4        QAM16    4    192   144 
//    48          0001        1:2/3        QAM64    6    288   192 
//    54          0011        2:3/4        QAM64    6    288   216 
  //Main 
    switch ( RATE ) { //switch
      case 0xb: { //6Mbps
           Nbpsc  = 1 ;
           coding_rate = 0 ;
           Ncbps = 48 ;
           Ndbps = 24 ;
           break ;
      }
      case 0xf: { //9Mbps
           Nbpsc  = 1 ;
           coding_rate = 2 ;
           Ncbps = 48 ;
           Ndbps = 36 ;
           break ;
      }
      case 0xa: { //12Mbps
           Nbpsc  = 2 ;
           coding_rate = 0 ;
           Ncbps = 96 ;
           Ndbps = 48 ;
           break ;
      }
      case 0xe: { //18Mbps
           Nbpsc  = 2 ;
           coding_rate = 2 ;
           Ncbps = 96 ;
           Ndbps = 72 ;
           break ;
      }
      case 0x9: { //24Mbps
           Nbpsc  = 4 ;
           coding_rate = 0 ;
           Ncbps = 192 ;
           Ndbps = 96 ;
           break ;
      }
      case 0xd: { //36Mbps
           Nbpsc  = 4 ;
           coding_rate = 2 ;
           Ncbps = 192 ;
           Ndbps = 144 ;
           break ;
      }
      case 0x8: { //48Mbps
           Nbpsc  = 6 ;
           coding_rate = 1 ;
           Ncbps = 288 ;
           Ndbps = 192 ;
           break ;
      }
      case 0xc: { //54Mbps
           Nbpsc  = 6 ;
           coding_rate = 2 ;
           Ncbps = 288 ;
           Ndbps = 216 ;
           break ;
      }
    } //switch

    //Nsym , Ndata, Npad
    Nsym = (16 + 8* LENGTH +6+ Ndbps-1)/Ndbps ;
    Ndata = Nsym * Ndbps ;
    Npad = Ndata - ( 16 + 8*LENGTH + 6 ) ;

  //Make DATA bits
  //SERVICE field
    if ((tmp1 = (char *)malloc(2*sizeof(char)) ) == NULL) {
        PRINTF( " malloc failed in SERVICE\n") ;
    } //fail
    else { //allocated
       //bset1 for SERVICE field
       bset1.format = 1 ; //a byte octet
       bset1.size = 2 ; //a byte octet
       bset1.data = tmp1 ; //
       tmp2 = tmp1 ;
       *tmp2++ = 0 ; //first byte
       *tmp2++ = 0 ; //second byte
    } //allocated
    bset1 = byte2binary(bset1) ;
 
    //concatinate SERVICE & PSDU
    bset0 = cat_binaryset(bset1, datain) ;

  //Tail bit + pad bit
    bset1 = pad_binaryset(6+Npad) ;
    //concatinate (SERVICE & PSDU) & (tail&pad bit)
    bset0 = cat_binaryset(bset0, bset1) ;
    //COmpare with Table G.13 &G.14 for DATA bits
    //print_binaryset( bset0 ) ;

  //Scrambler
    bset0 = scrambler(bset0 , 0x5d ) ;
    //Tail bit locations are zeroed (please see p69 G.5.2)
    for (ii=0;ii<6;ii++) { //zeroed
      bset0.data[ 16 + 8*LENGTH + ii ] = 0 ; 
    } //zeroed

    //Compare with Table G.16 &G.17 for scrambling
    //print_binaryset( bset0 ) ;

  //Convolution encoder
    bset0 = convolution_encoder(bset0 , coding_rate ) ; //rate 2:3/4
    //Compare with Table G.18 for convolution encoder
    //print_binaryset( bset0 ) ;

    
    for(ii=0;ii<Nsym;ii++){ //every symbol 
      PRINTF(" the %dth Symbol out of %d\n" , ii, Nsym ) ;
      //interleaver
      bset1 = extract_binaryset(bset0 , ii*Ncbps, Ncbps ) ; //Ncbps=192
      bset1 = interleaver(bset1 , Nbpsc ) ; //Nbpsc=4
      //Compare with Table G.21 for interleaved bits
      //print_binaryset( bset1 ) ;

      //OFDM mapper
      cset0 = mapper (bset1, Nbpsc, &pilot_shifter) ; 
      //Compare with Table G.22 for Frequency Domain data
      print_complexset( cset0 ) ;
    
      //OFDM IFFT
      cset0 = idft64 ( cset0 ) ;
      //Compare with Table G.23 for Frequency Domain data
      //print_complexset( cset0 ) ;

      //save the first sample to ctmp1
      ctmp1.realp = cset0.data[0].realp ;
      ctmp1.image = cset0.data[0].image ;
      //build a DATA symbol
      cset1 = extract_complexset(cset0 , 48 , 16 ) ; //Guard Interval
      cset1 = cat_complexset(cset1 , cset0 ) ;
      if (ii == 0) { //first symbol
         ctop = cset1 ;
      } //first symbol
      else { //others
         cset1.data[0].realp = (cset1.data[0].realp + ctmp2.realp)/2 ;
         cset1.data[0].image = (cset1.data[0].image + ctmp2.image)/2 ;
         ctop = cat_complexset(ctop, cset1) ;
      } //others
      ctmp2.realp = ctmp1.realp ;
      ctmp2.image = ctmp1.image ;
    } //every symbol
    //add the last sample
    cset0.size = 1 ;
    cset0.data = &ctmp1 ;
    ctmp1.realp = ctop.data[ ctop.size-64 ].realp/2 ;
    ctmp1.image = ctop.data[ ctop.size-64 ].image/2 ;
    ctop = cat_complexset(ctop, cset0) ;
  
    return( ctop ) ;
} //data_enc