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/* File: Modulate.c
Description: Complex K-dimensional M-ary modulator
The calling syntax is:
[output] = Modulate( input, S_matrix )
Where:
output = K by N vector of modulated symbols
input = 1 by N*log2(M) vector of data bits
S_Matrix = K by M complex matrix containing the constellation signals
Each Column is one signal, each signal is K-dimensional
Note: For legacy purposes, S_matrix can be a M by 1 matrix when signal
set can be characterized by a one-dimensional complex value (QAM, etc).
Copyright (C) 2005-2006, Matthew C. Valenti
Last updated on May 6, 2006
Function Modulate 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
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <math.h>
#include <mex.h>
#include <Matrix.h>
#include <stdlib.h>
/* Input Arguments
prhs[0] is input
prhs[1] is S_matrix */
/* Output Arguments
plhs[0] is output */
/* main function that interfaces with MATLAB */
void mexFunction(
int nlhs,
mxArray *plhs[],
int nrhs,
const mxArray *prhs[] )
{
int M, K;
int number_symbols, number_bits, bits_per_symbol;
double *input, *Sr, *Si, *output_r, *output_i;
int i,j,temp_int,index;
int *data_int;
/* make sure there are enough inputs */
if (nrhs<2)
mexErrMsgTxt("Usage: [output] = Modulate( input, S_matrix )");
/* read in input bits */
number_bits = mxGetN(prhs[0]);
input = mxGetPr(prhs[0]);
/* read in the constellation matrix */
/* for legacy purposes, see if it is a single column */
if ( mxGetN( prhs[1] ) == 1 ) {
M = mxGetM( prhs[1] );
K = 1;
} else {
M = mxGetN( prhs[1] );
K = mxGetM( prhs[1] );
}
/* get the real part */
Sr = mxGetPr(prhs[1]);
/* if not complex, set imagainary part to zero */
if (!mxIsComplex(prhs[1]) )
Si = (double*)calloc( M*K, sizeof(double) );
else
Si = mxGetPi(prhs[1]);
/* determine the number of bits per symbol
for future development: check to make sure M is a power of 2 */
bits_per_symbol = 0;
temp_int = M;
while (temp_int>1) {
temp_int = temp_int/2;
bits_per_symbol++;
}
/* determine the number of output symbols */
number_symbols = number_bits/bits_per_symbol + (number_bits%bits_per_symbol>0);
/* read in the input data and cast to int */
data_int = (int*)calloc( number_symbols*bits_per_symbol, sizeof(int) );
for (i=0;i<number_bits;i++)
data_int[i] = input[i];
/* create the complex output matrix */
plhs[0]=mxCreateDoubleMatrix( K, number_symbols, mxCOMPLEX);
output_r = mxGetPr( plhs[0] );
output_i = mxGetPi( plhs[0] );
/* determine output */
for (i=0;i<number_symbols;i++) { /* create each modulated symbol */
index = 0;
for (j=0;j<bits_per_symbol;j++) { /* go through each associated bit */
index = index << 1; /* shift to the left (multiply by 2) */
index += data_int[i*bits_per_symbol+j];
}
/* assign the K-dimensional output symbol */
for (j=0;j<K;j++) {
output_r[K*i+j] = Sr[K*index+j];
output_i[K*i+j] = Si[K*index+j];
}
}
/* free memory */
free( data_int );
if(!mxIsComplex(prhs[1]) )
free(Si);
}
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