dlrxdemod.cpp

在vc上做的802.16d ofdm phy的仿真

#include "typedef.h"
#include "global_var.h"
#include "globalMacro.h"
#include "dlRxDemod.h"
#include "math.h"
#include "fft.h"

//#define PI 3.1415926
//ȥcp, t, f
void freqDerotation(Int16 *pRxIn,
					Uint16 rxInLength,
					Int16 timeOffset,
					Int16 freqOffset,
					Int16 *pRxOut)
{
	int i;
	Int16 *pInTmp;
	Int16 *pOutTmp;
	double freq,tempi,tempq;
	Int16 cpLength;
	Int16 autoLag;  //autoCorrelation Lag ,NULL
	Int16 dataLength;

	autoLag = 2 * 64;
	cpLength = 2 * g_cpDataRatio;
	dataLength = rxInLength - autoLag;
	pOutTmp = pRxOut +  dataLength - cpLength  - 1;
	if (timeOffset >= 0)
    {// timeOffset greater than zero, delay the signal by timeOffset.
        pInTmp = pRxIn + dataLength - 2 * timeOffset - 1;
		for (i = 0; i < dataLength - cpLength  - 2 * timeOffset; i++)
        {
            *pOutTmp-- = *pInTmp--;
        }
        for (i = 0; i < 2 * timeOffset; i++)
        { 
            *pOutTmp-- = 0;
        }
	}
	else
	{//timeOffset less than zero. eliminate delay of signal by timeOffset.
        pInTmp = pRxIn + dataLength  - 1;
   
	    for (i = 0; i < 2 * (- timeOffset); i++)
        {
            *pOutTmp-- = 0;
        }

        for (i = 0; i < dataLength - cpLength + 2 * timeOffset; i++)
        {
            *pOutTmp-- = *pInTmp--;
        }
    }
	freq = freqOffset * 2 * PI / 32768 ;
	for (i = 0; i < (rxInLength - cpLength) /2; i++)
	{
		tempi = pRxOut[2 * i] * cos(freq * i) - pRxOut[2 * i + 1] * sin(freq * i);
		tempq = pRxOut[2 * i] * sin(freq * i) + pRxOut[2 * i + 1] * cos(freq * i);
		pRxOut[2 * i] = tempi;
		pRxOut[2 * i + 1] = tempq;
	}
}


void dlRxDemod()
{
	int i;
	Uint8	fftWeightBW;
	Uint16  fftSize;
	Uint16  rxDeInLength;
	Int16   *pFftOutBuff;
	fftWeightBW = FFT_WEIGHTS_BITWIDTH;
	fftSize = FFT_SIZE; 
	rxDeInLength = DL_RX_BUFF_SIZE;
	pFftOutBuff = g_dlRxFftOutBuff;

	freqDerotation (g_dlRxBuff, rxDeInLength, 0, 0, g_dlFreqDerotBuff);
	
	for (i = 1; i < fftSize; i+=2)
	{
		g_dlFreqDerotBuff[2*i] *= -1;;
		g_dlFreqDerotBuff[2*i+1] *= -1;
	}

	if (g_dlRxStcFlag == 1)	//not stc and stcflag=0
	{
		pFftOutBuff += 2 * fftSize;
	}

	fft (g_dlFreqDerotBuff, fftSize, fftWeights, fftWeightBW, pFftOutBuff);    
	
	for (i = 0; i < fftSize; i++)
	{
			pFftOutBuff[2*i] >>= 1;
			pFftOutBuff[2*i+1] >>= 1;
	}

}