viterbi23.h

自己写的Viterbi Decoder 可以解码 213 417 码率

/*
	Viterbi decorder for convolution code [2 1 3] HEADER
	Code rate				1/2
	constrained len(K)		3
	Use hard decision

	jinle@2008.2.29
*/

#ifndef _VITERBI_213_H_
#define _VITERBI_213_H_

//#define VITERBI_DEBUG


#define KL				3				//constrained len
#define STATE_NUM		4				//(2^(KL-1)) number of states
#define	PATH_DEPTH		5				//Path depth
#define MAX_COLUMN		PATH_DEPTH+1	//5 path need 6 grid

#ifndef TRUE
	#define TRUE	0
#endif

#ifndef FALSE
	#define FALSE	1
#endif

#define UPPER	0	//upper path
#define LOWER	1	//lower path
#define NOT_VALID	-1

//As we know when K=3, all state for decoding is 2^(K-1) = 4
//So we define below structures stand for each grid, and total states
typedef struct Grid
{
	unsigned char acc_metric;		//accumulated metric
	unsigned char lastgrid;			//last_grid
}Grid;

//Viterbi decorder handler
typedef struct ViterbiDec
{
	Grid			grids[MAX_COLUMN][STATE_NUM];
	unsigned char	column_pointer;
	_Bool			beInited;
}ViterbiDec;

//Stand for 4 grid in same row's output data in encoder
//both upper and lower path

unsigned char Viterbi23_output_table[4][2] =
{
	{0, 3},
	{2, 1},
	{3, 0},
	{1, 2},
};

//Stand for 4 grid in same row's last state number
//both upper and lower path
unsigned char Viterbi23_last_state_table[4][2] =
{
	{0, 1},
	{2, 3},
	{0, 1},
	{2, 3},
};

//[From][to][value] -1 stand for invalid
char Viterbi23_path2value[4][4] = 
{
	{0, -1, 1, -1},	//Form 0 to 0,1,2,3
	{0, -1, 1, -1},	//Form 1 to 0,1,2,3
	{-1, 0, -1, 1},	//Form 2 to 0,1,2,3
	{-1, 0, -1, 1},	//Form 3 to 0,1,2,3
};
#endif