/*****************************************************************************//*   FIle Name : Equalizer.c                                                 *//*   Description : WiMax OFDM Subcarrier modulation DATA Equalizer           *//*   author : miffie                                                         *//*   Date   : Nov/04/05                                                      *//*   Copyright (c) 2005 miffie   All rights reserved.                        *//*****************************************************************************/struct complexset equalizer (struct complexset datain,  char index,                        struct complexset *sram , short *pilot_shifter,                        double *drift_phase, char *drift_cnt, char *sram_cnt ) {int 	ii , jj ;char 	shifter ;double 	realp, image ;char    pilot_polarity ;struct 	complexset cset ;struct  complex  *top ;struct	complex tmp1, tmp2 ;double  radius[8] ;double  angle , roffset, slope ;double  drift , difference;double  MAX_PILOTLENGTH  = 1.125 ;double  MIN_PILOTLENGTH  = 0.75 ;double  DRIFT_THRESHOLD  = 0.10 ;double  SRAM_THRESHOLD  = 0.0015 ;char    num_pilot = 8 ;char    sc_pilot[] = { -88, -63, -38, -13, 13, 38, 63, 88 } ;char    sc ;char    mask[256] ;  //Main     if ((top = (struct complex *)malloc(256*sizeof(struct complex)) ) == NULL) {        PRINTF( " malloc failed in equalizer.c\n") ;    } //fail    else { //allocated     //mask     mask_sc(&mask[0], index ) ;     //OFDM randomizer     pilot_polarity = *pilot_shifter & 0x1 ;     *pilot_shifter = pilot_randomizer( *pilot_shifter ) ;     PRINTF("equalizer size=%d pilot_polarity=%d\n", datain.size, pilot_polarity ) ;     jj=0;     for(ii=-100;ii<=100;ii++) { //each subcarrier       if ((mask[ii+128])&!(pilot_bool(ii))) { //enabled         top[ jj++ ] = multiply_complex(datain.data[ii+128],                                         sram->data[ii+100] ) ;        } //enabled     } //each subcarrier     cset.size = jj ;     cset.data = top ;       ////////////////////     //PILOT TRAINING     ////////////////////     angle=0;     drift=0;     for(ii=0;ii<num_pilot;ii++) { //each pilot subcarrier       sc = sc_pilot[ii] ;       tmp2  = multiply_complex(datain.data[sc+128], sram->data[sc+100] ) ;        //printf("pilot(%d) ( %6.3f  %6.3f )\n", sc, tmp2.realp, tmp2.image ) ;       //pilot sub        if ((sc==-63)|(sc==-13)|(sc==13)|(sc==38)) { //DL        //if ((sc==-63)|(sc==-13)) { //UL          tmp1.realp =  (pilot_polarity) ? 1 : -1 ;          tmp1.image =  0 ;        } else { //          tmp1.realp =  (pilot_polarity) ? -1 : 1 ;          tmp1.image =  0 ;        } //       tmp1 = multiply_complex(tmp1, tmp2 ) ;       printf("pilot(%d) ( %6.3f  %6.3f )\n", sc, tmp1.realp, tmp1.image ) ;       radius[ii] = tmp1.realp ;       angle += polarizer ( tmp1 )/((double)sc) ;       drift +=  polarizer ( tmp1 ) ;     } //each pilot subcarrier             //Take means of 4 pilot sub carriers     angle = angle/num_pilot ;     drift = drift/num_pilot ;     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)     //correct drift_phase      if ((fabs(drift)>DRIFT_THRESHOLD) & (*drift_cnt>=3)) {//correction         *drift_phase -= drift ;         PRINTF(" drift=%8.5f  drift_phase=%8.5f\n", drift, *drift_phase ) ;      } //correction     else if  (fabs(drift)>DRIFT_THRESHOLD) {         *drift_cnt = *drift_cnt +1 ;     }     //sram     //Nov/15/05 M.Inoue     //sram's change might not hapen in Wi-Max OFDM because, the clock      // is already locked and it's tolerance is less than 0.1ppm.     // Under the situation, the sample timing should not be drifted.     roffset =1.0 ;     slope =0 ;     if ((fabs(angle) > SRAM_THRESHOLD ) & (*sram_cnt>=3)) { //SRAM       PRINTF("...changing SRAM\n" ) ;       for(ii=-100;ii<=100;ii++) { //each subcarrier         tmp1.realp = cos(angle*1.5*ii) * (roffset+slope*abs(ii)) ;         tmp1.image = -sin(angle*1.5*ii) * (roffset+slope*abs(ii)) ;         PRINTF("sram(%d) %6.3f+j*%6.3f =>" , ii,                 sram->data[ii+100].realp, sram->data[ii+100].image ) ;         sram->data[ii+100] = multiply_complex(sram->data[ii+100], tmp1 ) ;         PRINTF(" %6.3f+j*%6.3f \n" , sram->data[ii+100].realp, sram->data[ii+100].image ) ;       } //each subcarrier       *sram_cnt=0 ;     } //SRAM     else if (fabs(angle) > SRAM_THRESHOLD ) {       *sram_cnt= *sram_cnt + 1 ;     }     else  *sram_cnt= 0 ;    }//allocated    free ( datain.data ) ;    return ( cset ) ;} //equalizer