detect_drift.c

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

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/*   FIle Name : detect_drift.c                                              */
/*   Description : WLAN LONGsequence Phase drift detector                    */
/*   author : miffie                                                         */
/*   Date   : aug/17/05                                                      */
/*   Copyright (c) 2005 miffie   All rights reserved.                        */
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///////////////////////////////////////////////////////////////////////////////

double  detect_drift( struct complexset datain, short distance ) { // 
struct  complexset cset ;
struct  complexset ctop ;
struct  complex  *top  ;
struct  complex  tmp1  ;
int	ii , jj ;
double  p1, p2 ;
double  diff , accum ;
int     size ;

  //Main 
     PRINTF("detect_drift size=%d \n", datain.size ) ;
     accum =0 ;
     size = datain.size/2 ;
     for(ii=0;ii<size;ii++) { //each sample
        p1 = atan2(datain.data[ii].image, datain.data[ii].realp ) ;
        p2 = atan2(datain.data[ii+distance].image, datain.data[ii+distance].realp ) ;
        //-pi<=p1<pi, -pi<=p2<pi 
        diff = p1-p2 ;
        //-2*pi<diff<2*pi
        if (diff>=pi) diff=diff -2*pi ;
        else if (diff<-pi) diff=diff +2*pi ;
        PRINTF("detect_drift (%d) %6.3f radian\n", ii, diff ) ;
        accum += diff ; 
     } //each sample
    return( accum/(distance*size) ) ;
} //detect_drift