data_track.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_track.c                                                     */
/*   Description : WLAN OFDM Subcarrier modulation DATA(&SIGNAL) tracking    */
/*   author : miffie                                                         */
/*   Date   : aug/11/05                                                      */
/*   Copyright (c) 2005 miffie   All rights reserved.                          */
/*****************************************************************************/
struct complexset data_track (struct complexset datain, 
                        struct complexset *sram ,char *pilot_shifter,
                        double *previous_drift , double *drift_amount, char *drift_change) {
int 	ii ;
char 	shifter ;
double 	realp, image ;
char    pilot_polarity ;
struct 	complexset cset ;
struct  complex  *top ;
struct	complex tmp1, tmp2 ;
double  angle , radius7, radius21, radius, slope ;
double  drift , difference;
char    pilot_length ;
double  MAX_PILOTLENGTH  = 1.125 ;
double  MIN_PILOTLENGTH  = 0.75 ;
double  DRIFT_THRESHOLD  = 0.3 ;

  //Main 
    if ((top = (struct complex *)malloc(64*sizeof(struct complex)) ) == NULL) {
        PRINTF( " malloc failed in data_track.c\n") ;
    } //fail
    else { //allocated
     //OFDM randomizer
     *pilot_shifter = pilot_randomizer( *pilot_shifter ) ;
     pilot_polarity = *pilot_shifter & 0x1 ;
     if ( pilot_polarity ==1) pilot_polarity = -1 ;
     else pilot_polarity =1 ;
     PRINTF("data_track size=%d pilot_polarity=%d\n", datain.size, pilot_polarity ) ;

     for(ii=-26;ii<=26;ii++) { //each subcarrier
         top[ ii+32 ] = multiply_complex(datain.data[ii+32],
                                         sram->data[ii+26] ) ; 
     } //each subcarrier
  

     ////////////////////
     //PILOT TRAINING
     ////////////////////
     pilot_length =1 ; //assume pilot_length is within the range
     //-21
     tmp1.realp = 1 * pilot_polarity ;
     tmp1.image = 0 ;
     tmp1 = multiply_complex(tmp1, top[-21+32]) ;
     PRINTF ("pos -21 :" ) ;
     //detect violation
     if ((tmp1.realp>MAX_PILOTLENGTH)|(tmp1.realp<MIN_PILOTLENGTH)) pilot_length=0 ;

     radius21 = tmp1.realp ;
     angle = -polarizer ( tmp1 )/21.0 ;
     drift =  polarizer ( tmp1 ) ;
        
     //-7
     tmp1.realp = 1 * pilot_polarity ;
     tmp1.image = 0 ;
     tmp1 = multiply_complex(tmp1, top[-7+32]) ;
     PRINTF ("pos -7 :" ) ;
     //detect violation
     if ((tmp1.realp>MAX_PILOTLENGTH)|(tmp1.realp<MIN_PILOTLENGTH)) pilot_length=0 ;
     radius7 = tmp1.realp ;
     angle -= polarizer ( tmp1 )/7.0 ;
     drift +=  polarizer ( tmp1 ) ;
 
     //+7
     PRINTF ("pos +7 :" ) ;
     tmp1.realp = 1 * pilot_polarity ;
     tmp1.image = 0 ;
     tmp1 = multiply_complex(tmp1, top[7+32]) ;
     //detect violation
     if ((tmp1.realp>MAX_PILOTLENGTH)|(tmp1.realp<MIN_PILOTLENGTH)) pilot_length=0 ;
     radius7 += tmp1.realp ;
     angle += polarizer ( tmp1 )/7.0 ;
     drift +=  polarizer ( tmp1 ) ;
     

     //+21
     PRINTF ("pos +21 :" ) ;
     tmp1.realp = -1 * pilot_polarity ;
     tmp1.image = 0 ;
     tmp1 = multiply_complex(tmp1, top[21+32]) ;
     //detect violation
     if ((tmp1.realp>MAX_PILOTLENGTH)|(tmp1.realp<MIN_PILOTLENGTH)) pilot_length=0 ;
     radius21 += tmp1.realp ;
     angle += polarizer ( tmp1 )/21.0 ;
     drift +=  polarizer ( tmp1 ) ;
     //Take means of 4 pilot sub carriers
     angle = angle/4 ;
     PRINTF("angle =%6.3f\n" , angle ) ;
     PRINTF("drift =%8.5f\n" , drift ) ;
    
     //calculate radius & slope
     radius21 = 2/radius21 ;
     radius7 = 2/radius7 ;
     //assume radius will be linear against freq
     slope = (radius21-radius7)/14 ;
     radius = radius7-slope*7 ;  //radius(0)

     if (*previous_drift <10) { //DATA symbol
       difference = (drift - *previous_drift )/(160*4) ;
       //drift_change shall prevent from  back2back change on drift_amount 
       if ((fabs(drift)>DRIFT_THRESHOLD)&(*drift_change==0)) {//correction
         *drift_amount -= difference ;
         PRINTF(" drift=%8.5f  drift_amount=%8.5f\n", drift, *drift_amount ) ; 
         *drift_change=1 ;
       } //correction
       else *drift_change = 0 ;
     }  //DATA symbol
     *previous_drift = drift ;
     

     //sram
     if ((fabs(angle) > 0.002 ) & pilot_length) { //SRAM
       PRINTF("...changing SRAM\n" ) ;
       for(ii=-26;ii<=26;ii++) { //each subcarrier
         tmp1.realp = cos(angle*ii) * (radius+slope*abs(ii)) ;
         tmp1.image = -sin(angle*ii) * (radius+slope*abs(ii)) ;
         PRINTF("sram(%d) %6.3f+j*%6.3f =>" , ii, 
                sram->data[ii+26].realp, sram->data[ii+26].image ) ;
         sram->data[ii+26] = multiply_complex(sram->data[ii+26], tmp1 ) ;
         PRINTF(" %6.3f+j*%6.3f \n" , sram->data[ii+26].realp, sram->data[ii+26].image ) ;
       } //each subcarrier
     } //SRAM

     cset.size = 64 ;
     cset.data = top ;
    }//allocated
    free ( datain.data ) ;
    return ( cset ) ;
} //data_track