btcdecode.c

wimax802.16e中的BTC编码仿真程序

/*
*********************************************************************************
* Copyright (c) National Mobile Communications Research Laboratory. 
* All rights reserved.
* 
* FILE NAME : BTCdecode.c
* ABSTRUCT:
*	This file is the C file for BTC decoding.
*	
* AUTHOR:	Zhang Tao	2007-02-13
*
*********************************************************************************
*/

/*
*********************************************************************************
*                               INCLUDE FILES
*********************************************************************************
*/

#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include "..\..\GlobalDef.h"
#include "..\..\GlobalVar.h"
#include "BTCstruct.h"
#include "BTCinit.h"
#include "chase.h"
/*
*********************************************************************************
*                              Function Definition
*********************************************************************************
*/
/*
*********************************************************************************
* NAME:		DBMatrixTrans
* PURPOSE:	perform the transposition of a double style matrix.
*
* Input:	data_in[]:  data input.
*			row : the row number of the matrix.
*			col : the column number of the matrix.
*				
* Output:	data_out[]: data output.
*					
* AUTHOR: 	Zhang Tao	2007-02-12	
* 
*********************************************************************************
*/
void DBMatrixTrans(double data_in[],int row,int col,double data_out[])
{
	int index1;
	int index2;
	int len1 = 0;
	int len2 = 0;

	for(index1=0;index1<row;index1++)
	{
		len2 = 0;
		for(index2=0;index2<col;index2++)
		{
			data_out[index1+len2] = data_in[len1+index2];
			len2 += row;
		}
		len1 += col;
	}
}
/*
*********************************************************************************
* NAME:		GenZeroSoft
* PURPOSE:	obtain the soft value of the zero bit.
*
* Input:	rowsoft[]:  soft value of the sequence in row order.
*			BTC :  the parameter for BTC.
*				
* Output:	
*					
* AUTHOR: 	Zhang Tao	2007-02-13	
* 
*********************************************************************************
*/
void GenZeroSoft(double rowsoft[],BTCstruct BTC)
{
	double softvalue = 2.0;
	int index;
	int i;
	int j;

	index = BTC.nx * BTC.Iy + BTC.Ix + BTC.B + BTC.Q;
	for(i=0;i<index;i++)
	{
		rowsoft[i] = softvalue;
	}
	index = BTC.nx * (BTC.Iy + 1);
	for(j=BTC.Iy+1;j<BTC.ny;j++)
	{
		for(i=0;i<BTC.Ix;i++)
		{
			rowsoft[index+i] = softvalue;
		}
		index += BTC.nx;
	}
}
/*
*********************************************************************************
* NAME:		oneBTCdecode
* PURPOSE:	one BTC block decoding without slot concatenation.
*
* Input:	code_in[]:  the code for decoding.
*			BTC :  the parameter for BTC.
*				
* Output:	data_out[]: one block data output.
*					
* AUTHOR: 	Zhang Tao	2007-02-13	
* 
*********************************************************************************
*/
void oneBTCdecode(double code_in[],int data_out[],BTCstruct BTC)
{
	int matrix_len = BTC.nx * BTC.ny; //the whole length of one BTC block.
	double *matrix_seq; //the whole sequence with received code and zero bits.
	double zero_soft = 1.0; //the soft value for the zero bits.
	int *mid_seq; //the middle decoded code vector.
	double *rowsoft; //extrinsic information from row decoding.
	double *colsoft; //extrinsic information from column decoding.
	double *reliable;//the sequence for the reliable value.
	double *matrix_seq_trans; //the transposition of the matrix_seq.
	double alfa1[4] = {0.0,0.3,0.7,1.0};
	double alfa2[4] = {0.2,0.5,0.9,1.0};
	double beta1[4] = {0.2,0.6,1.0,1.0};
	double beta2[4] = {0.4,0.8,1.0,1.0};
	int iterate = 0; //the counter for the iteration number.
	int index1,index2;
	int len;
	int i,j;

	//generate the matrix_seq
	matrix_seq = (double *)malloc(matrix_len * sizeof(double));
	index1 = BTC.nx * BTC.Iy + BTC.Ix + BTC.B + BTC.Q;
	index2 = BTC.Q;
	for(i=0;i<index1;i++)
	{
		matrix_seq[i] = zero_soft;
	}
	//first row
	len = BTC.nx - (BTC.Ix + BTC.B + BTC.Q);
	memcpy(matrix_seq+index1,code_in+index2,len*sizeof(double));
	//remaining rows
	index1 += len;
	index2 += len;
	len = BTC.nx - BTC.Ix;
	for(i=BTC.Iy+1;i<BTC.ny;i++)
	{
		for(j=0;j<BTC.Ix;j++)
		{
			matrix_seq[index1+j] = zero_soft;
		}
		index1 += BTC.Ix;
		memcpy((matrix_seq+index1),(code_in+index2),len*sizeof(double));
		index1 += len;
		index2 += len;
	}

	//initialization
	mid_seq = (int *)malloc(matrix_len * sizeof(int));
	rowsoft = (double *)malloc(matrix_len * sizeof(double));
	colsoft = (double *)malloc(matrix_len * sizeof(double));
	memset(colsoft, 0, matrix_len * sizeof(double));
	reliable = (double *)malloc(matrix_len * sizeof(double));
	matrix_seq_trans = (double *)malloc(matrix_len * sizeof(double));
	
	DBMatrixTrans(matrix_seq,BTC.ny,BTC.nx,matrix_seq_trans);

	//iterative decoding
	while(iterate<4)
	{
		DBMatrixTrans(colsoft,BTC.nx,BTC.ny,rowsoft);
		
		GenZeroSoft(rowsoft,BTC);
		
		//generate reliable value sequence.
		for(i=0;i<matrix_len;i++)
		{
			reliable[i] = matrix_seq[i] + alfa1[iterate] * rowsoft[i];
		}
		
		//row decoding
		index1 = BTC.nx * BTC.Iy;
		for(i=BTC.Iy;i<BTC.ny;i++)
		{
			Chase((reliable+index1),0,beta1[iterate],BTC,(mid_seq+index1),(rowsoft+index1));
			index1 += BTC.nx;
		}

		GenZeroSoft(rowsoft,BTC);

		DBMatrixTrans(rowsoft,BTC.ny,BTC.nx,colsoft);

		//generate reliable value sequence.
		for(i=0;i<matrix_len;i++)
		{
			reliable[i] = matrix_seq_trans[i] + alfa2[iterate] * colsoft[i];
		}

		//column decoding
		index1 = BTC.ny * BTC.Ix;
		for(i=BTC.Ix;i<BTC.nx;i++)
		{
			Chase((reliable+index1),1,beta2[iterate],BTC,(mid_seq+index1),(colsoft+index1));
			index1 += BTC.ny;
		}

		iterate++;
	}

	//output
	index1 = BTC.ny * (BTC.Ix + BTC.B + BTC.Q) + BTC.Iy;
	len = BTC.kx - (BTC.Ix + BTC.B + BTC.Q);
	for(i=0;i<len;i++)
	{
		data_out[i] = mid_seq[index1];
		index1 += BTC.ny;
	}
	
	index2 = len;
	len = BTC.kx - BTC.Ix;
	for(j=BTC.Iy+1;j<BTC.ky;j++)
	{
		index1 = BTC.ny * BTC.Ix + j;
		for(i=0;i<len;i++)
		{
			data_out[index2+i] = mid_seq[index1];
			index1 += BTC.ny;
		}
		index2 += len;
	}


	free(matrix_seq);
	free(mid_seq);
	free(rowsoft);
	free(colsoft);
	free(reliable);
	free(matrix_seq_trans);
}

/*
*********************************************************************************
* NAME:		BTCdecode
* PURPOSE:	decoding BTC with concatenation of slots.
*
* Input:	data_in[]:  the received data for decoding.
*			nslot: the slot number for the encoded and modulated data.
*			rep: the repetition factor.
*			fec: the struct for the FEC type.
*				
* Output:	data_out[]: the data output.
*					
* AUTHOR: 	Zhang Tao	2007-02-13	
* 
*********************************************************************************
*/
void BTCdecode(double data_in[],int nslot,int rep,FEC_TYPE fec,int data_out[])
{
	int n_slot = 0;//n_slot=nslot/rep;
	int cnt_block = 0;
	int para_j = 0;//parameter dependent on the modulation and FEC rate
	int para_k = 0;//floor(n_slot/para_j).
	int para_m = 0;//n_slot modulo para_j.
	double *pdata_in = data_in;
	int *pdata_out = data_out;
	BTCstruct BTC; //BTC parameter.
	int slot_num = 0;
	int encoded_len;
	
	switch(fec.modID)
	{
	case 2:
		if(fec.rateID==1)
			para_j = 6;
		else
			para_j = 4;
		break;
	case 4:
		if(fec.rateID==1)
			para_j = 3;
		else
			para_j = 2;
		break;
	case 6:
		if(fec.rateID==1)
			para_j = 2;
		else if(fec.rateID==2)
			para_j = 1;
		else
			para_j = 1;
		break;
	}


	n_slot = nslot / rep;
	para_k = n_slot / para_j;
	para_m = n_slot % para_j;
	
	if(n_slot<=para_j)
	{
		encoded_len = n_slot * fec.modID * 48;
		BTCInit(encoded_len,fec.rateID,&BTC);
		oneBTCdecode(pdata_in,pdata_out,BTC);	
	}
	else if(n_slot>para_j && para_m==0)
	{
		encoded_len = para_j * fec.modID * 48;
		BTCInit(encoded_len,fec.rateID,&BTC);
		for(cnt_block=0;cnt_block<para_k;cnt_block++)
		{
			pdata_in = data_in + cnt_block * encoded_len;
			oneBTCdecode(pdata_in,pdata_out,BTC);
			pdata_out += BTC.msg_len;
		}
	}
	else
	{
		encoded_len = para_j * fec.modID * 48;
		BTCInit(encoded_len,fec.rateID,&BTC);
		for(cnt_block=0;cnt_block<para_k-1;cnt_block++)
		{
			pdata_in = data_in + cnt_block * encoded_len;
			oneBTCdecode(pdata_in,pdata_out,BTC);
			pdata_out += BTC.msg_len;
		}

		pdata_in += encoded_len;
		slot_num = (para_m+para_j) / 2;
		encoded_len = slot_num * 48 * fec.modID;
		BTCInit(encoded_len,fec.rateID,&BTC);
		oneBTCdecode(pdata_in,pdata_out,BTC);
		pdata_out += BTC.msg_len;

		pdata_in += encoded_len;
		slot_num = n_slot - para_j*(para_k-1) - (para_m+para_j) / 2;
		encoded_len = slot_num * 48 * fec.modID;
		BTCInit(encoded_len,fec.rateID,&BTC);
		oneBTCdecode(pdata_in,pdata_out,BTC);
		
	}

}