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/* file: ConvEncode.c
Description: Convolutionally encode with either NSC or RSC code.
The calling syntax is:
[output] = ConvEncode(input, g_encoder, [code_type] )
output = code word
Required inputs:
input = data word
g_encoder = generator matrix for convolutional code
(If RSC, then feedback polynomial is first)
Optional inputs:
code_type = 0 for recursive systematic convolutional (RSC) code (default)
= 1 for non-systematic convolutional (NSC) code
= 2 for tail-biting NSC code
Copyright (C) 2005-2008, Matthew C. Valenti
Last updated on May 21, 2008
Function ConvEncode is part of the Iterative Solutions
Coded Modulation Library. The Iterative Solutions Coded Modulation
Library is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published
by the Free Software Foundation; either version 2.1 of the License,
or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <math.h>
#include <mex.h>
#include <Matrix.h>
#include <stdlib.h>
/* library of functions */
#include "./include/convolutional.h"
/* Input Arguments */
#define INPUT prhs[0]
#define GENENCODER prhs[1]
#define CODETYPE prhs[2]
/* Output Arguments */
#define OUTPUT plhs[0]
/* main function that interfaces with MATLAB */
void mexFunction(
int nlhs,
mxArray *plhs[],
int nrhs,
const mxArray *prhs[] )
{
double *input, *g_array;
double *output_p;
int DataLength, CodeLength, i, j, index;
mwIndex subs[] = {1,1};
int *g_encoder;
int nn, KK, mm, code_type, max_states;
double elm;
int *input_int, *output_int;
int *out0, *out1, *state0, *state1, *tail;
code_type = 0; /* Default:Code is RSC with terminated trellis */
/* Check for proper number of arguments */
if ((nrhs < 2 )||(nlhs > 1)) {
mexErrMsgTxt("Usage: [output] = ConvEncode(input, g_encoder, code_type )");
} else {
/* first input is the data word */
input = mxGetPr(INPUT);
DataLength = mxGetN(INPUT); /* number of data bits */
/* cast the input into a vector of integers */
input_int = (int*)calloc( DataLength, sizeof(int) );
for (i=0;i<DataLength;i++)
input_int[i] = (int) input[i];
/* second input specifies the code polynomial */
g_array = mxGetPr(GENENCODER);
nn = mxGetM(GENENCODER);
KK = mxGetN(GENENCODER);
mm = KK - 1;
max_states = 1 << mm;
if ( nrhs == 3 ) {
/* optional third input indicates if outer is RSC, NSC or tail-biting NSC */
code_type = (int) *mxGetPr(CODETYPE);
}
/* Determine the length of the output */
if (code_type < 2)
CodeLength = nn*(DataLength+mm);
else
CodeLength = nn*DataLength;
/* Convert code polynomial to binary */
g_encoder = (int*)calloc(nn, sizeof(int) );
for (i = 0;i<nn;i++) {
subs[0] = i;
for (j=0;j<KK;j++) {
subs[1] = j;
index = mxCalcSingleSubscript(GENENCODER, 2, subs);
elm = g_array[index];
if (elm != 0) {
g_encoder[i] = g_encoder[i] + (int) pow(2,(KK-j-1));
}
}
/* mexPrintf(" g_encoder[%d] = %o\n", i, g_encoder[i] ); */
}
}
/* create the output vector */
OUTPUT = mxCreateDoubleMatrix(1, CodeLength, mxREAL );
output_p = mxGetPr(OUTPUT);
output_int = (int*)calloc( CodeLength, sizeof( int ) );
/* create appropriate transition matrices */
out0 = (int*)calloc( max_states, sizeof(int) );
out1 = (int*)calloc( max_states, sizeof(int) );
state0 = (int*)calloc( max_states, sizeof(int) );
state1 = (int*)calloc( max_states, sizeof(int) );
tail = (int*)calloc( max_states, sizeof(int) );
if ( code_type ) {
nsc_transit( out0, state0, 0, g_encoder, KK, nn );
nsc_transit( out1, state1, 1, g_encoder, KK, nn );
if (code_type == 2)
tail[0] = -1;
} else {
rsc_transit( out0, state0, 0, g_encoder, KK, nn );
rsc_transit( out1, state1, 1, g_encoder, KK, nn );
rsc_tail( tail, g_encoder, max_states, mm );
}
/* Encode */
conv_encode( output_int, input_int, out0, state0, out1, state1, tail, KK, DataLength, nn );
/* cast to output */
for (i=0;i<CodeLength;i++)
output_p[i] = output_int[i];
/* Clean up memory */
free( output_int );
free( input_int );
free( g_encoder );
free( out0 );
free( out1 );
free( state0 );
free( state1 );
free( tail );
return;
}
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