itpp::Modulator_NCD Class Reference
[Digital Modulation]

Base class for vector ("MIMO") channel modulator/demodulators with complex valued components. More...

#include <itpp/comm/modulator_nd.h>

Inheritance diagram for itpp::Modulator_NCD:


Public Member Functions
	Modulator_NCD ()
	Constructor.
	~Modulator_NCD ()
	Destructor.
Vec< cvec >	get_symbols ()
	Get modulation symbols per dimension.
cvec	modulate_bits (const bvec &bits) const
	Modulation of bits.
void	map_demod (QLLRvec &LLR_apriori, QLLRvec &LLR_aposteriori, double sigma2, cmat &H, cvec &y)
	Soft MAP demodulation for multidimensional channel, by "brute-force" enumeration of all constellation points.
void	map_demod (QLLRvec &LLR_apriori, QLLRvec &LLR_aposteriori, double sigma2, cvec &H, cvec &y)
	Soft MAP demodulation for diagonal channels (without crosstalk).
int	get_dim ()
	Get number of dimensions.
LLR_calc_unit	get_llrcalc () const
	Get LLR calculation unit.
ivec	get_k ()
	Get number of bits per modulation symbol.
ivec	get_M ()
	Get number of modulation symbols per dimension.
Protected Member Functions
void	update_norm (double &norm, int k, int sold, int snew, cvec &ytH, cmat &HtH, ivec &s)
QLLRvec	probabilities (QLLR l)
	Convert LLR to log-probabilities.
Vec< QLLRvec >	probabilities (QLLRvec &l)
	Convert LLR to log-probabilities, vector version.
void	update_LLR (Vec< QLLRvec > &logP_apriori, QLLRvec &numerator, QLLRvec &denominator, ivec &s, QLLR x)
	Update LLR (for internal use).
void	update_LLR (Vec< QLLRvec > &logP_apriori, QLLRvec &numerator, QLLRvec &denominator, int s, QLLR scaled_norm, int j)
	Update LLR, for scalar channel (for internal use).
Protected Attributes
Vec< cvec >	symbols
	Vector of modulation symbols (along each dimension).
int	nt
	Number of dimensions.
LLR_calc_unit	llrcalc
	LLR calculation unit.
ivec	k
	Number of bits per modulation symbol.
ivec	M
	Number of modulation symbols along each dimension.
Vec< bmat >	bitmap
	Bit mapping table (one table per dimension).
Vec< ivec >	bits2symbols
	Bit pattern in decimal form ordered and the corresponding symbols (one pattern per dimension).
Friends
std::ostream &	operator<< (std::ostream &os, const Modulator_NCD &mod)
	Print some properties of the MIMO modulator in plain text (mainly to aid debugging).

Detailed Description

Base class for vector ("MIMO") channel modulator/demodulators with complex valued components.

This class is equivalent to Modulator_NRD except for that all quantities are complex-valued. See ND_UPAM for examples.

Definition at line 236 of file modulator_nd.h.

Constructor & Destructor Documentation

itpp::Modulator_NCD::Modulator_NCD ( ) [inline]

Constructor.

Definition at line 239 of file modulator_nd.h.

itpp::Modulator_NCD::~Modulator_NCD ( ) [inline]

Destructor.

Definition at line 241 of file modulator_nd.h.

Member Function Documentation

Vec<cvec> itpp::Modulator_NCD::get_symbols ( ) [inline]

Get modulation symbols per dimension.

Definition at line 244 of file modulator_nd.h.

References symbols.

cvec itpp::Modulator_NCD::modulate_bits ( const bvec & bits ) const

Modulation of bits.

Definition at line 355 of file modulator_nd.cpp.

References itpp::bin2dec(), itpp::Modulator_ND::bits2symbols, it_assert, itpp::Modulator_ND::k, itpp::length(), itpp::Modulator_ND::nt, itpp::sum(), and symbols.

void itpp::Modulator_NCD::map_demod	(	QLLRvec &	LLR_apriori,
		QLLRvec &	LLR_aposteriori,
		double	sigma2,
		cmat &	H,
		cvec &	y
	)

Soft MAP demodulation for multidimensional channel, by "brute-force" enumeration of all constellation points.

This function computes the LLR values

$LLR(k) = \log \left( \frac{ \sum_{s: b_k=0} \exp \left( -\frac{ |y - Hs|^2 }{\sigma^2} \right) P(s)}{ \sum_{s: b_k=1} \exp \left( -\frac{ |y - Hs|^2 }{\sigma^2} \right) P(s)} \right)$

without approximations. It is assumed that H, y and s are complex-valued.

Parameters:

	H	channel matrix (m*n)
	y	received vector (m*1)
	sigma2	noise variance, per complex dimension
	LLR_apriori	vector of a priori LLR values per bit
	LLR_aposteriori	vector of a posteriori LLR values

The function performs an exhaustive search over all possible points s in the n-dimensional constellation. This is only feasible for relatively small constellations. The Jacobian logarithm is used to compute the sum-exp expression.

Definition at line 264 of file modulator_nd.cpp.

References itpp::conj(), it_assert, itpp::Modulator_ND::k, itpp::length(), itpp::Modulator_ND::llrcalc, itpp::Modulator_ND::M, itpp::norm(), itpp::Modulator_ND::nt, itpp::ones_i(), itpp::Modulator_ND::probabilities(), itpp::sqr(), itpp::sum(), symbols, itpp::LLR_calc_unit::to_qllr(), itpp::Modulator_ND::update_LLR(), and update_norm().

void itpp::Modulator_NCD::map_demod	(	QLLRvec &	LLR_apriori,
		QLLRvec &	LLR_aposteriori,
		double	sigma2,
		cvec &	H,
		cvec &	y
	)

Soft MAP demodulation for diagonal channels (without crosstalk).

This function is equivalent to map_demod with a diagonal H, but much faster.

Definition at line 165 of file modulator_nd.cpp.

References it_assert, itpp::Modulator_ND::k, itpp::length(), itpp::Modulator_ND::llrcalc, itpp::Modulator_ND::M, itpp::Modulator_ND::nt, itpp::ones_i(), itpp::Modulator_ND::probabilities(), itpp::sqr(), itpp::sum(), symbols, itpp::LLR_calc_unit::to_qllr(), and itpp::Modulator_ND::update_LLR().

int itpp::Modulator_ND::get_dim ( ) [inline, inherited]

Get number of dimensions.

Definition at line 57 of file modulator_nd.h.

References itpp::Modulator_ND::nt.

LLR_calc_unit itpp::Modulator_ND::get_llrcalc ( ) const [inline, inherited]

Get LLR calculation unit.

Definition at line 60 of file modulator_nd.h.

References itpp::Modulator_ND::llrcalc.

ivec itpp::Modulator_ND::get_k ( ) [inline, inherited]

Get number of bits per modulation symbol.

Definition at line 63 of file modulator_nd.h.

References itpp::Modulator_ND::k.

ivec itpp::Modulator_ND::get_M ( ) [inline, inherited]

Get number of modulation symbols per dimension.

Definition at line 66 of file modulator_nd.h.

References itpp::Modulator_ND::M.

QLLRvec itpp::Modulator_ND::probabilities ( QLLR l ) [protected, inherited]

Convert LLR to log-probabilities.

Definition at line 44 of file modulator_nd.cpp.

References itpp::LLR_calc_unit::jaclog(), and itpp::Modulator_ND::llrcalc.

Referenced by map_demod(), itpp::Modulator_NRD::map_demod(), and itpp::Modulator_ND::probabilities().

Vec< QLLRvec > itpp::Modulator_ND::probabilities ( QLLRvec & l ) [protected, inherited]

Convert LLR to log-probabilities, vector version.

Definition at line 58 of file modulator_nd.cpp.

References itpp::length(), and itpp::Modulator_ND::probabilities().

void itpp::Modulator_ND::update_LLR	(	Vec< QLLRvec > &	logP_apriori,
		QLLRvec &	numerator,
		QLLRvec &	denominator,
		ivec &	s,
		QLLR	x
	)			`[protected, inherited]`

Update LLR (for internal use).

This function updates the numerator and denominator in the expression

$\log \left( \frac{ \sum_{s: b_k=0} \exp (-x^2) P(s) }{ \sum_{s: b_k=1} \exp (-x^2) P(s) } \right)$

Parameters:

	logP_apriori	vector of a priori probabilities per bit
	numerator	the logarithm of the numerator in the above expression
	denominator	the logarithm of the denominator in the above expression
	s	the symbol vector

Definition at line 87 of file modulator_nd.cpp.

References itpp::Modulator_ND::bitmap, itpp::LLR_calc_unit::jaclog(), itpp::Modulator_ND::k, itpp::Modulator_ND::llrcalc, and itpp::Modulator_ND::nt.

Referenced by map_demod(), and itpp::Modulator_NRD::map_demod().

void itpp::Modulator_ND::update_LLR	(	Vec< QLLRvec > &	logP_apriori,
		QLLRvec &	numerator,
		QLLRvec &	denominator,
		int	s,
		QLLR	scaled_norm,
		int	j
	)			`[protected, inherited]`

Update LLR, for scalar channel (for internal use).

This function updates the numerator and denominator in the expression

$\log \left( \frac{ \sum_{s: b_k=0} \exp (-x^2) P(s) }{ \sum_{s: b_k=1} \exp (-x^2) P(s) } \right)$

Parameters:

	logP_apriori	vector of a priori probabilities per bit
	numerator	the logarithm of the numerator in the above expression
	denominator	the logarithm of the denominator in the above expression
	s	the symbol vector