/*****************************************************************************//*   FIle Name : pseudo_channel.c                                            *//*   Description : Wi-Max SC Pseudo Channel Estimatitor                      *//*                 mode : [3]  1:step 0:bilinear interpolation               *//*                      : [1:0]  0:drift both in freq & time domain          *//*                      : [1:0]  1:drift only in freq_domain                 *//*                 multi : number of multiple paths                          *//*                 level : White Noise level 0:-120dB@peak 6:-114dB...120:0dB*//*                 tx_freqerr : Transmitter's Frequency error                *//*                            : 0:0ppm 1:0.01ppm -10:-0.1ppm(-0.1<=f<=0.1ppm)*//*                 rx_freqerr : Receiver's Frequency error                   *//*                            : 0:0ppm 1:0.01ppm -10:-0.1ppm(-0.1<=f<=0.1ppm)*//*   author : miffie                                                         *//*   Date   : oct/20/05                                                      *//*   Copyright (c) 2005 miffie   All rights reserved.                        *//*****************************************************************************///In Wi-MAX SC the SS's clock is locked to BS. //And only allowed 1ppm of clock frequecny error.struct complexset pseudo_channel(struct complexset datain,                                 char mode, char multi, char level,                                char tx_freqerr, char rx_freqerr ) { int 	ii,kk ;int 	size ;int     tmp0 ;int     startpoint ;double  tx_clock, rx_clock ;double  tx_carrierclock, rx_carrierclock ;double  tx_phase, rx_phase ;double  rx_time ;struct 	complex  *top ;struct 	complex  *cdata ;struct 	complex  tmp1, tmp2 , tmp3;int     tx_floor , tx_ceil ;struct  complexset  ctop ;double  white ;char    NO_NOISE = 0 ;static  double   sample_period = 125 ; //ns //8MHzstatic  double   carrier_period = 0.1 ; //ns //10GHzstatic  int      delay = 60 ; //ns   PRINTF("pseudo_channel size=%d multi=%d level=%d tx_freqerr=%d rx_freqerr=%d\n",           datain.size , multi, level, tx_freqerr, rx_freqerr) ;   if (mode<4) { //doubler     tx_clock = (sample_period/2.0)*(1.0+(tx_freqerr/100000000.0)) ; //ns     rx_clock = (sample_period)*(1.0+(rx_freqerr/100000000.0)) ; //ns     size = (datain.size/2) +32 ; //+32 for extention   } //doubler   else { //single     tx_clock = (sample_period)*(1.0+(tx_freqerr/100000000.0)) ; //ns     rx_clock = (sample_period)*(1.0+(rx_freqerr/100000000.0)) ; //ns     size = datain.size +32 ; //+32 for extention   } //single   tx_carrierclock = carrier_period*(1.0+(tx_freqerr/100000000.0)) ; //ns    rx_carrierclock = carrier_period*(1.0+(rx_freqerr/100000000.0)) ; //ns    //noises   NO_NOISE = (multi==0) && (level==0) ; //if 1  NO Noise   white = pow(2, ((double)level-120.0)/6.0) ; //WhiteNoiseGain      //sampling clock width    if (((top = (struct complex *)malloc(size*sizeof(struct complex)) ) == NULL) |       ((cdata = (struct complex *)malloc((datain.size+200)*sizeof(struct complex)) ) == NULL)){        PRINTF( " malloc failed in pseudo_channel.c\n") ;   } //fail   else { //allocated     //initialize     for( ii=0;ii<size;ii++) {//for       top[ ii ].realp = 0 ;       top[ ii ].image = 0 ;     } //for     for( ii=0;ii<(datain.size+200);ii++) {//for       cdata[ ii ].realp = 0 ;       cdata[ ii ].image = 0 ;     } //for     //add blank period     startpoint = (NO_NOISE) ? 16 : int_random( 16 )+16 ;     for( ii=0;ii<(datain.size);ii++) { //datain         cdata[ii+startpoint].realp += datain.data[ ii ].realp ;        cdata[ii+startpoint].image += datain.data[ ii ].image ;     } //datain     //Multi paths generation     for( kk=0;kk<=multi;kk++) {//for        //receiver's phase is randomized         rx_time = (NO_NOISE) ? 0 : ((double )int_random(1024)/1024.0)*1 ; //ns 2pi=0.1ns        if (NO_NOISE==0) { //NO_NOISE          if(kk==0) rx_time += delay ;          else if (kk>=1) rx_time += delay - gamma_random(delay)  ;        } //NO_NOISE        //rotation        if(kk==0) { //first path's gain is fixed           tmp3.realp = 1.0 ;           tmp3.image = 0 ;        } else { //second path and beyond          tmp3.realp = ((double)int_random(8)+8)/32.0 ;          tmp3.image = ((double)int_random(8)+8)/32.0 ;          tmp3.realp = (int_random(2)) ? -tmp3.realp : tmp3.realp ;          tmp3.image = (int_random(2)) ? -tmp3.image : tmp3.image ;        }        printf("rx_time %8.5f r=%8.5f i=%8.5f\n" , rx_time , tmp3.realp , tmp3.image) ;           for( ii=0;ii<size;ii++) {//for          //Bi-Linear Interpolation @rx_time          tx_floor = floor(rx_time/tx_clock) ;          tx_ceil = tx_floor +1 ;          //printf("%d cdata=%6.3f %6.3f ", tx_floor, cdata[tx_floor].realp, cdata[tx_floor].image ) ;          tmp1 = multiply_complex(cdata[tx_floor], tmp3 ) ;           //printf("tmp1=%6.3f %6.3f\n", tmp1.realp, tmp1.image ) ;          tmp2 = multiply_complex(cdata[tx_ceil], tmp3 ) ;              if (mode&0x8)  { //step            //step             top[ii].realp += tmp1.realp ;            top[ii].image += tmp1.image ;          } //step          else { //else            //Bi-Linear interpolation            top[ii].realp +=             (((rx_time - (tx_clock*tx_floor))* tmp2.realp) +             (((tx_clock*tx_ceil) - rx_time)* tmp1.realp)) /             tx_clock  ;               top[ii].image +=             (((rx_time - (tx_clock*tx_floor))* tmp2.image) +             (((tx_clock*tx_ceil) - rx_time)* tmp1.image)) /             tx_clock  ;          } //else          if (((mode&0x1)==0)&&(kk==multi)) { //time domain drift & freq            //noise generation            tmp0 = int_random( 2 ) ;            if (tmp0==0) tmp0= -1 ;            top[ii].realp += (tmp0 * white * gamma_random( 4096 )/4096.0)  ;            tmp0 = int_random( 2 ) ;            if (tmp0==0) tmp0= -1 ;            top[ii].image += (tmp0 * white * gamma_random( 4096 )/4096.0) ;            //calculate phase drift in Tx            tx_phase = (rx_time*2.0*pi)/tx_carrierclock ;            tmp1.realp = cos ( tx_phase ) ;            tmp1.image = sin ( tx_phase ) ;            tmp2 = multiply_complex(top[ ii ] , tmp1 ) ;            //calculate phase drift in Rx            rx_phase = (rx_time*2.0*pi)/rx_carrierclock ;            tmp1.realp = cos ( rx_phase ) ;            tmp1.image = sin ( rx_phase ) ;            top[ ii ] = multiply_complex(tmp2  ,tmp1 )  ;          } //time domain drift & freq          rx_time += rx_clock ;        } //for     } //multi    } //allocated      ctop.data = top ;   ctop.size = size ;   free( datain.data ) ;   free( cdata ) ;   return( ctop ) ;}//pseudo_channel