frameofdm.c

基于TMS320F2812的AMR+RS编解码+OFDM调制解调源程序。是stand alone运行版本

#include <stdio.h>
#include <math.h>
#include "Setting.H"
#include "RS.H"
#include "Function.H"
#include "asintable.h"
/*
 This script generates a COFDM waveform from an input data */ 
void OFDMModu(DType DataStr[], int BaseSignal[], DType RefPhase[])
/* DataStr:    RS coded data to transmit in the CodewordBit given,
 *             UsedCarrier * SymPerFrame in length;
 * BaseSignal: Final output modulated signal, SymbolSize * SymPerFrame in length;
 * RefPhase:   DPSK reference phase, UsedCarrier * 1 in length;
 */
{
	WordType i, j, k;
	DType DPSKdata[SymPerFrame * UsedCarrier];
	long int TxSpecR[FFTSize], TxSpecI[FFTSize];
	DType *pDPSK ,*pDataStr;
	long int *pTxSpecR, *pTxSpecI;
	int *pBase;
	
	pBase = BaseSignal;
	
	/* Convert to DQPSK */
	for (j = 0; j < UsedCarrier; j++)
	{
		DPSKdata[j] = (DType) (DataStr[j] + RefPhase[j]) &
			(DType) ((1 << CodewordBit) - 1);
	}
	pDPSK = DPSKdata + UsedCarrier;
	pDataStr = DataStr + UsedCarrier;
	for (i = 1; i < SymPerFrame; i++)
	{
		for (j = 0; j < UsedCarrier; j++)
		{
			*pDPSK = (DType) ((*pDataStr) + (*(pDPSK - UsedCarrier))) & (DType) ((1 << CodewordBit) - 1);
			pDataStr++;
			pDPSK++;
			//DPSKdata[j + i * UsedCarrier] = 
			//	(DType) (DataStr[j + i * UsedCarrier] + DPSKdata[j + (i - 1) * UsedCarrier]) &
			//	(DType) ((1 << CodewordBit) - 1);
		}
	}
	/* Store the last carrier data in RefPhase[] for next subframe */
	for (j = 0; j < UsedCarrier; j++)
	{
		RefPhase[j] = DPSKdata[j + (SymPerFrame - 1) * UsedCarrier];
	}

	/* Get the required spectrums */
	k = 0;
	for (j = 0; j < SymPerFrame; j++)
	{
		pTxSpecR = TxSpecR;
		pTxSpecI = TxSpecI;
		pDPSK = &DPSKdata[j * UsedCarrier + 1 - CarrierJumpPos];
		for (i = 0; i < FFTSize; i++)
		{
			if ((i > CarrierJumpPos - 2) && (i < CarrierJumpPos + UsedCarrier - 1))
			{
				switch (*pDPSK)
				{
				case 0: *pTxSpecR = 16384;   *pTxSpecI = 0;  break;
				case 1: *pTxSpecR = 0;   *pTxSpecI = 16384;  break;
				case 2: *pTxSpecR = -16384;  *pTxSpecI = 0;  break;
				case 3: *pTxSpecR = 0;   *pTxSpecI = -16384;
				}
			}
			else
			{
				*pTxSpecR = 0;
				*pTxSpecI = 0;
			}
			pTxSpecR++;
			pTxSpecI++;
			pDPSK++;
		}
	    
		/* Change to time waveform using IFFT */
		FFT(TxSpecR, TxSpecI, -1);
    
		/* Add cycle prefixion (guardtime) */
	   	pTxSpecR = TxSpecR + FFTSize - GuardTimeSize;
	   	for (i = GuardTimeSize; i > 0; i--)
		{
			*pBase =(int)(*pTxSpecR);
			k++;
			pBase++;
			pTxSpecR++;
		}
		pTxSpecR = TxSpecR;
		for (i = 0; i < FFTSize; i++)
		{
			*pBase =(int)(*pTxSpecR);
			k++;
			pBase++;
			pTxSpecR++;
		}

	}
}

/* This script demodulates a COFDM waveform from an input data:
 * DataStr:    Received real signal, SymbolSize * SymPerFrame in length;
 * SpecSignal: Demodulated RS data in CodewordBit size per symbol,
 *             UsedCarrier * SymPerFrame in length;
 * RefPhase:   DPSK reference phase, UsedCarrier * 1 in length;
 */
void OFDMDemo(int BaseSignal[], DType SpecSignal[], long int RefPhase[])
{
	WordType i, j;
	long int RxSpecR[FFTSize], RxSpecI[FFTSize];
	long int CarrPh[SymPerFrame * UsedCarrier];
	//int index;
	int * pBase;
	long int *pRxSpecR, *pRxSpecI,*pCarrPh,xR,xI;
	DType *pSpec;

	
	/* Reshape the linear time waveform into FFT segments & remove guard time */

	for (i = 0; i < SymPerFrame; i++)
	{
		pRxSpecR = RxSpecR;
		pRxSpecI = RxSpecI;
		pBase = &BaseSignal[i * SymbolSize + GuardTimeSize];
		for (j = 0; j < FFTSize; j++)
		{
			*pRxSpecR = (long int)(*pBase);
            *pRxSpecI = 0;
			pRxSpecR++;
			pRxSpecI++;
			pBase++;
		}

    	/* Apply FFT on the rest of received data */
    	FFT(RxSpecR, RxSpecI, 1);

	    /* Convert to QPSK phase */
	    pCarrPh = &CarrPh[i * UsedCarrier];
		pRxSpecR = RxSpecR + CarrierJumpPos - 1;
		pRxSpecI = RxSpecI + CarrierJumpPos - 1;
	  	for (j = 0; j < UsedCarrier; j++)
		{
		/*	xR = *pRxSpecR;
			xI = *pRxSpecI;
			index = (float)90 * xI*xI/(xI*xI+xR*xR);
			*pCarrPh = asin_tab[index];                     //Q15
			if(xR>=0 && xI<0)
			 {
				*pCarrPh = -(*pCarrPh) + PI2Q15;
			 }
			 else if(xR<0 && xI<=0)
			 {
				 *pCarrPh = *pCarrPh + PIQ15;
			 }
			 else if(xR<0 && xI>0)
			 {
				*pCarrPh = -(*pCarrPh) + PIQ15;
			 }*/
			*pCarrPh = arctan2(*pRxSpecI, *pRxSpecR);
			pRxSpecR++;
			pRxSpecI++;
			pCarrPh++;	
		}
	   
	}

	/* Apply DQPSK on the received data */
    for (j = 0; j < UsedCarrier; j++)
	{
		SpecSignal[j] = (DType) ((CarrPh[j] - RefPhase[j] + PI2Q15 + PIQ15 / (1 << CodewordBit)) / 
			(PIQ15 / (1 << CodewordBit) * 2)) & (DType) ((1 << CodewordBit) - 1);
	}
	pSpec = SpecSignal + UsedCarrier;
	pCarrPh = CarrPh + UsedCarrier;
	for (i = 1; i < SymPerFrame; i++)
	{		 
		for (j = 0; j < UsedCarrier; j++)
		{
			xR = *pCarrPh;
			xI = *(pCarrPh - UsedCarrier);
			*pSpec = (DType) ((xR - xI + PI2Q15 + PIQ15 / (1 << CodewordBit)) / (PIQ15 / (1 << CodewordBit) * 2)) & 
					 (DType) ((1 << CodewordBit) - 1);
			pSpec++;
			pCarrPh++;
		}
	}

	/* Save the RefPhase for next subframe */
	pCarrPh = CarrPh + (SymPerFrame - 1) * UsedCarrier;
	for (j = 0; j < UsedCarrier; j++)
	{
		RefPhase[j] = *pCarrPh;
		pCarrPh++;
	}
}