/usr/include/itpp/comm/exit.h is in libitpp-dev 4.3.1-8.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 | /*!
* \file
* \brief Definitions for EXtrinsic Information Transfer (EXIT) chart class
* \author Bogdan Cristea
*
* -------------------------------------------------------------------------
*
* Copyright (C) 1995-2010 (see AUTHORS file for a list of contributors)
*
* This file is part of IT++ - a C++ library of mathematical, signal
* processing, speech processing, and communications classes and functions.
*
* IT++ is free software: you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any
* later version.
*
* IT++ 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 General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along
* with IT++. If not, see <http://www.gnu.org/licenses/>.
*
* -------------------------------------------------------------------------
*/
#ifndef EXIT_H
#define EXIT_H
#include <itpp/itbase.h>
#include <itpp/comm/modulator.h> //BPSK class for a priori information generation
#include <itpp/itexports.h>
namespace itpp
{
/*!
\ingroup misccommfunc
\brief EXtrinsic Information Transfer (%EXIT) chart
Computes the A priori Mutual Information assuming a Gaussian distribution of the a priori information and
the Extrinsic Mutual Information between the emitted bits and their extrinsic information
Description:
- the a priori mutual information is computed using relation (14)
- the extrinsic mutual information is computed by estimating first the conditional Probability Density Functions (PDF),
given the emitted bits, and then numerically integrating according to relation (19)
Reference:
Stephan ten Brink, ''Convergence behavior of iteratively decoded parallel concatenated codes,``
IEEE Transactions on Communications, oct. 2001
*/
class ITPP_EXPORT EXIT
{
public:
//! Computes the a priori mutual information
/*! It is assumed that the a priori information has a Gaussian distribution
*/
double apriori_mutual_info(const double &in_sigma2A, //!< variance of the a priori information
const double &lim=100 //!< [-lim,+lim] is the integration interval (theoretically it should be [-inf,+inf])
)
{
_gaussian_fct = Gaussian_Fct(in_sigma2A);
return 1.0-itpp::quad(_gaussian_fct, -lim, lim);
};
//! Generates a priori information assuming a Gaussian distribution of the a priori information
/*! The variance of the a priori information must be already initialized through EXIT::apriori_mutual_info function.
* The information generated in this way is used sometimes as intrinsic information at the SISO module input.
*/
itpp::vec generate_apriori_info(const itpp::bvec &bits)
{
itpp::BPSK bpsk;
double sigma2A = _gaussian_fct.sigma();
return (-sigma2A/2)*bpsk.modulate_bits(bits)+std::sqrt(sigma2A)*itpp::randn(bits.length());
};
//! Computes the extrinsic mutual information
/*! The conditional Probability Density Function (PDF) of the extrinsic information is estimated using the histogram of the
* extrinsic information and the knowledge of the emitted bits corresponding to the extrinsic information.
*/
double extrinsic_mutual_info(const itpp::vec &obs, //!< extrinsic information obtained from the SISO module output
const itpp::bvec &cond, //!< emitted bits corresponding to the extrinsic information
const int &N=100 //!< number of subintervals used to compute the histogram
);
private:
class ITPP_EXPORT Gaussian_Fct
{
double _sigma;
public:
Gaussian_Fct(): _sigma(0.0){}
Gaussian_Fct(double sigma): _sigma(sigma){}
double sigma() const {return _sigma;}
double operator()(double x) const;
};
Gaussian_Fct _gaussian_fct;
};
}
#endif /* EXIT_H_ */
|