www.pudn.com > wimax_ofdm_implementation_code.rar > doubler.c

/*****************************************************************************/
/*   FIle Name : doubler.c                                                   */
/*   Description : Wi-Max Encoder's interpolation                            */
/*   author : miffie                                                         */
/*   Date   : aug/12/05                                                      */
/*   Copyright (c) 2005 miffie   All rights reserved.                        */
/*****************************************************************************/
double  cubic_spline (double y0, double y1, double y2, double y3, 
                double xx) { //cubic_spline
double yxx ;
double aa, bb, cc, dd ;
//Y(xx)= aa*xx^3 + bb*xx^2 + cc*xx +dd
//Y(0) = y1
//Y(1) = y2
//Y'(0) = (y2-y0)/2
//Y''(1) = (y3-y1)/2
       aa = ( y3 - 3*y2 + 3*y1 - y0 )/2 ;
       bb = (- y3 + 4*y2 - 5*y1 + 2*y0)/2 ;
       cc =           (y2       -   y0)/2 ;
       dd =                  y1 ;

       yxx = ( aa * xx * xx * xx ) +
             ( bb * xx * xx ) +
             ( cc * xx ) +
             ( dd ) ;

       return( yxx ) ;
} //cubic_spline

struct complexset doubler (struct complexset datain ) {
int 	ii ;
struct 	complex  *top ;
int     tx_floor , tx_ceil ;
struct  complexset  ctop ;
double  y0, y1, y2, y3 ;


   if ((top = (struct complex *)malloc(datain.size*2*sizeof(struct complex)) ) == NULL) {
        PRINTF( " malloc failed in doubler.c\n") ;
   } //fail
   else { //allocated
     PRINTF("doubler size=\n", datain.size ) ;
     for( ii=0;ii=datain.size) y2 = datain.data[ii].realp ;
        else y2 = datain.data[ii+1].realp ;

        if ((ii+2)>=datain.size) y3 = datain.data[ii].realp ;
        else y3 = datain.data[ii+2].realp ;

        top[2*ii].realp = y1 ;
        top[2*ii+1].realp = cubic_spline(y0, y1, y2, y3, 0.5) ;
 
        if(ii==0) y0 = datain.data[ 0 ].image  ;
        else y0 = datain.data[ii-1].image ;

        y1 = datain.data[ii].image ;

        if ((ii+1)>=datain.size) y2 = datain.data[ii].image ;
        else y2 = datain.data[ii+1].image ;

        if ((ii+2)>=datain.size) y3 = datain.data[ii].image ;
        else y3 = datain.data[ii+2].image ;

        top[2*ii].image = y1 ;
        top[2*ii+1].image = cubic_spline(y0, y1, y2, y3, 0.5) ;
     } //for
   } //allocated
   
   ctop.data = top ;
   ctop.size = datain.size * 2 ;
   free( datain.data ) ;
   return( ctop ) ;
}//doubler