itpp::Modulator_NCD Class Reference
[Digital Modulation]

#include <itpp/comm/modulator_nd.h>

Inheritance diagram for itpp::Modulator_NCD:

List of all members.

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 333 of file modulator_nd.h.


Public Types
enum	Soft_Demod_Method { FULL_ENUM_LOGMAP, ZF_LOGMAP }
	Soft demodulation method. More...
Public Member Functions
	Modulator_NCD ()
	Constructor.
	~Modulator_NCD ()
	Destructor.
Array< cvec >	get_symbols () const
	Get modulation symbols per dimension.
void	modulate_bits (const bvec &bits, cvec &symbols) const
	Modulate `bits` into `symbols`.
cvec	modulate_bits (const bvec &bits) const
	Modulation of bits.
void	demodulate_soft_bits (const cvec &y, const cmat &H, double sigma2, const QLLRvec &LLR_apriori, QLLRvec &LLR_aposteriori, Soft_Demod_Method method)
	Soft demodulation wrapper function for various methods.
QLLRvec	demodulate_soft_bits (const cvec &y, const cmat &H, double sigma2, const QLLRvec &LLR_apriori, Soft_Demod_Method method)
	Soft demodulation wrapper function for various methods.
void	demodulate_soft_bits (const cvec &y, const cmat &H, double sigma2, const QLLRvec &LLR_apriori, QLLRvec &LLR_aposteriori)
	Soft MAP demodulation for multidimensional channel, by "brute-force" enumeration of all constellation points.
void	demodulate_soft_bits (const cvec &y, const cvec &H, double sigma2, const QLLRvec &LLR_apriori, QLLRvec &LLR_aposteriori)
	Soft MAP demodulation for parallelchannels without crosstalk.
void	set_llrcalc (LLR_calc_unit llrcalc_in)
	Set LLR calculation unit.
LLR_calc_unit	get_llrcalc () const
	Get LLR calculation unit.
int	get_dim () const
	Get number of dimensions.
ivec	get_k () const
	Get number of bits per modulation symbol per dimension.
ivec	get_M () const
	Get number of modulation symbols per dimension.
Protected Member Functions
void	update_norm (double &norm, int k, int sold, int snew, const cvec &ytH, const cmat &HtH, const ivec &s)
	Update residual norm (for internal use).
QLLRvec	probabilities (QLLR l)
	Convert LLR to log-probabilities.
Array< QLLRvec >	probabilities (const QLLRvec &l)
	Convert LLR to log-probabilities, vector version.
void	update_LLR (const Array< QLLRvec > &logP_apriori, const ivec &s, QLLR scaled_norm, QLLRvec &num, QLLRvec &denom)
	Update LLR (for internal use).
void	update_LLR (const Array< QLLRvec > &logP_apriori, int s, QLLR scaled_norm, int j, QLLRvec &num, QLLRvec &denom)
	Update LLR, for scalar channel (for internal use).
Protected Attributes
Array< cvec >	symbols
	Vectors 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.
Array< bmat >	bitmap
	Bit mapping table (one table per dimension).
Array< 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 &m)
	Print some properties of the MIMO modulator (mainly to aid debugging).

Member Enumeration Documentation

enum itpp::Modulator_ND::Soft_Demod_Method [inherited]

Soft demodulation method.

Enumerator:

FULL_ENUM_LOGMAP	Log-MAP demodulation by "brute-force" enumeration of all points.
ZF_LOGMAP	Zero-Forcing Log-MAP approximated demodulation.

Definition at line 61 of file modulator_nd.h.

Member Function Documentation

void itpp::Modulator_NCD::demodulate_soft_bits	(	const cvec &	y,
		const cmat &	H,
		double	sigma2,
		const QLLRvec &	LLR_apriori,
		QLLRvec &	LLR_aposteriori,
		Soft_Demod_Method	method
	)

Soft demodulation wrapper function for various methods.

Soft demodulation wrapper function for various methods Currently the following two demodulation methods are supported:

FULL_ENUM_LOGMAP - exact demodulation, which use "brute-force" enumeration of all constellation points
ZF_LOGMAP - approximated methods with Zero-Forcing preprocessing, which sometimes tends to perform poorly, especially for poorly conditioned H

Parameters:

`[in]`	y	Received vector
`[in]`	H	Channel matrix
`[in]`	sigma2	Noise variance per complex dimension, i.e. the sum of real and imaginary parts (typically )
`[in]`	LLR_apriori	Vector of a priori LLR values per bit
`[out]`	LLR_aposteriori	Vector of a posteriori LLR values
`[in]`	method	Soft demodulation method

Definition at line 368 of file modulator_nd.cpp.

References itpp::Modulator_ND::FULL_ENUM_LOGMAP, itpp::inv(), it_assert, it_error, itpp::Modulator_ND::k, itpp::ones_c(), itpp::real(), itpp::sqrt(), itpp::sum(), itpp::zeros_i(), and itpp::Modulator_ND::ZF_LOGMAP.

Referenced by demodulate_soft_bits().

QLLRvec itpp::Modulator_NCD::demodulate_soft_bits	(	const cvec &	y,
		const cmat &	H,
		double	sigma2,
		const QLLRvec &	LLR_apriori,
		Soft_Demod_Method	method
	)

Soft demodulation wrapper function for various methods.

Currently the following two demodulation methods are supported:

FULL_ENUM_LOGMAP - exact demodulation, which use "brute-force" enumeration of all constellation points
ZF_LOGMAP - approximated methods with Zero-Forcing preprocessing, which sometimes tends to perform poorly, especially for poorly conditioned H

Parameters:

`[in]`	y	Received vector
`[in]`	H	Channel matrix
`[in]`	sigma2	Noise variance per complex dimension, i.e. the sum of real and imaginary parts (typically )
`[in]`	LLR_apriori	Vector of a priori LLR values per bit
`[in]`	method	Soft demodulation method

Returns:: Vector of a posteriori LLR values

Definition at line 401 of file modulator_nd.cpp.

References demodulate_soft_bits().

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

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:

`[in]`	y	Received vector
`[in]`	H	Channel matrix
`[in]`	sigma2	Noise variance per complex dimension, i.e. the sum of real and imaginary parts (typically )
`[in]`	LLR_apriori	Vector of a priori LLR values per bit
`[out]`	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 443 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::demodulate_soft_bits	(	const cvec &	y,
		const cvec &	H,
		double	sigma2,
		const QLLRvec &	LLR_apriori,
		QLLRvec &	LLR_aposteriori
	)

Soft MAP demodulation for parallelchannels without crosstalk.

This function is a much faster equivalent to demodulate_soft_bits with $H = \mbox{diag}(h)$ . Its complexity is linear in the number of subchannels.

Definition at line 412 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().

void itpp::Modulator_NCD::update_norm	(	double &	norm,
		int	k,
		int	sold,
		int	snew,
		const cvec &	ytH,
		const cmat &	HtH,
		const ivec &	s
	)			`[protected]`

Update residual norm (for internal use).

Update the residual norm $|y-Hs|$ when moving from one constellation point to an adjacent point.

Parameters:

`[in,out]`	norm	Norm to be updated
`[in]`	k	Position where s changed
`[in]`	sold	Old value of s[k]
`[in]`	snew	New value of s[k]
`[in]`	ytH	y'H vector
`[in]`	HtH	Grammian matrix H'H
`[in]`	s	Symbol vector

Definition at line 528 of file modulator_nd.cpp.

References itpp::conj(), itpp::length(), itpp::real(), itpp::sqr(), and symbols.

Referenced by demodulate_soft_bits().

void itpp::Modulator_ND::update_LLR	(	const Array< QLLRvec > &	logP_apriori,
		const ivec &	s,
		QLLR	scaled_norm,
		QLLRvec &	num,
		QLLRvec &	denom
	)			`[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:

`[in]`	logP_apriori	Vector of a priori probabilities per bit
`[in]`	s	Symbol vector
`[in]`	scaled_norm	Argument of the exponents in the above equation
`[out]`	num	Logarithm of the numerator in the above expression
`[out]`	denom	Logarithm of the denominator in the above expression

Definition at line 91 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 demodulate_soft_bits(), and itpp::Modulator_NRD::demodulate_soft_bits().

void itpp::Modulator_ND::update_LLR	(	const Array< QLLRvec > &	logP_apriori,
		int	s,
		QLLR	scaled_norm,
		int	j,
		QLLRvec &	num,
		QLLRvec &	denom
	)			`[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:

`[in]`	logP_apriori	Vector of a priori probabilities per bit
`[in]`	s	Symbol
`[in]`	scaled_norm	Argument of the exponents in the above equation
`[in]`	j	Channel index (dimension)
`[out]`	num	Logarithm of the numerator in the above expression
`[out]`	denom	Logarithm of the denominator in the above expression

Definition at line 66 of file modulator_nd.cpp.

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

The documentation for this class was generated from the following files:

itpp/comm/modulator_nd.h
itpp/comm/modulator_nd.cpp

itpp::Modulator_NCD Class Reference [Digital Modulation]

Detailed Description

Public Types

Public Member Functions

Protected Member Functions

Protected Attributes

Friends

Member Enumeration Documentation

Member Function Documentation

itpp::Modulator_NCD Class Reference
[Digital Modulation]