//CyclPref.c
//
// Project Red 2002: High Performance OFDM Modem 
// Against Channel Imperfections
// Auther: Linus Falk

#include "ofdm.h"

void addCyclPref(volatile float frame[FRAME_LENGTH]){
	int i;
	int j;
	short amp = 250;
	short * short_frame = (short*)frame;
	//convert float to short, and send all data on right channel, left channel = 0;
	for(i=PREFIX_LENGTH ,j=PREFIX_LENGTH*2; i<FRAME_LENGTH; i+=2, j+=2){
		short_frame[j] = (short)frame[i]*amp;
		short_frame[j+1] = 0;
	}
	
	//add guard bits
	#pragma MUST_ITERATE(GUARD_LENGTH,GUARD_LENGTH);
	for(i=0; i<GUARD_LENGTH; i++,j+=2){
		short_frame[j] = 0;
		short_frame[j+1] = 0;
	}
	
	//add prefix first
	for(i=0; i<PREFIX_LENGTH*2; i++){
		short_frame[i] = short_frame[i+FFT_SIZE*2];
	}

}