CECCO::LLRCalculator< T > Class Template Reference

Compute symbol-level log-likelihood ratios. More...

#include <blocks.hpp>

Inheritance diagram for CECCO::LLRCalculator< T >:

Public Member Functions
	LLRCalculator (const NRZMapper &nrz, const AWGN &transmission) noexcept
	Construct a BI-AWGN calculator from a matching mapper and channel.
	LLRCalculator (const BI_AWGN &bi_awgn) noexcept
	Construct a BI-AWGN calculator from a BI-AWGN channel (convenience).
	LLRCalculator (const SDMEC< T > &channel) noexcept
	Construct an SDMEC calculator from a discrete channel.
double	operator() (const std::complex< double > &in)
	Compute the LLR of a received complex symbol (BI-AWGN model).
Vector< double >	operator() (const Vector< std::complex< double > > &in)
	Compute LLRs for a received complex word (BI-AWGN model).
Matrix< double >	operator() (const Matrix< std::complex< double > > &in)
	Compute the symbol-level LLR matrix of a received binary image (BI-AWGN model).
Vector< double >	operator() (const T &r)
	Compute symbol LLRs for one received field symbol (SDMEC model).
Matrix< double >	operator() (const Vector< T > &r)
	Compute the symbol-LLR matrix of a received word (SDMEC model).

Detailed Description

template<FiniteFieldType T = Fp<2>>
class CECCO::LLRCalculator< T >

Compute symbol-level log-likelihood ratios.

Template Parameters

T	Code-symbol field

Produces a (q − 1) × n matrix whose entry (a − 1, j) is ln(P(r_j | 0) / P(r_j | a)). Positive values favor zero; magnitude is reliability.

Supports prime-field SDMEC observations and binary-image BI-AWGN observations. BI-AWGN requires characteristic two and combines the independent bit LLRs of each extension-field symbol.

Definition at line 811 of file blocks.hpp.

Constructor & Destructor Documentation

LLRCalculator() [1/3]

template<FiniteFieldType T = Fp<2>>

CECCO::LLRCalculator< T >::LLRCalculator ( const NRZMapper & nrz, const AWGN & transmission )

inlinenoexcept

Construct a BI-AWGN calculator from a matching mapper and channel.

Parameters

nrz	Source mapper providing (a, b)
transmission	Channel providing variance

Definition at line 818 of file blocks.hpp.

LLRCalculator() [2/3]

template<FiniteFieldType T = Fp<2>>

CECCO::LLRCalculator< T >::LLRCalculator ( const BI_AWGN & bi_awgn )

inlinenoexcept

Construct a BI-AWGN calculator from a BI-AWGN channel (convenience).

Parameters

bi_awgn

Channel providing (a, b) and variance

Definition at line 831 of file blocks.hpp.

LLRCalculator() [3/3]

template<FiniteFieldType T = Fp<2>>

CECCO::LLRCalculator< T >::LLRCalculator ( const SDMEC< T > & channel )

inlinenoexcept

Construct an SDMEC calculator from a discrete channel.

Parameters

channel

Symmetric discrete memoryless erasure channel providing pe and px

Definition at line 844 of file blocks.hpp.

Member Function Documentation

operator()() [1/5]

template<FiniteFieldType T = Fp<2>>

Matrix< double > CECCO::LLRCalculator< T >::operator() ( const Matrix< std::complex< double > > & in )

inline

Compute the symbol-level LLR matrix of a received binary image (BI-AWGN model).

Parameters

in	Received complex matrix; the [T:𝔽_2]-row binary image of the code word, column j holding the bits of symbol j in as_vector()/CECCO::DEMUX order

Returns

(q−1) × n matrix; entry (a−1, j) = ln(P(r_j|0)/P(r_j|a)) for symbol a = 1, …, q−1

Exceptions

std::logic_error	if this calculator was constructed from an SDMEC
std::invalid_argument	if the input does not have [T:𝔽_2] rows

The bits of a symbol are transmitted over independent channel uses, so a symbol LLR is the sum of the bit LLRs selected by its nonzero coordinates. For a binary code (T = 𝔽_2) this is one LLR per symbol.

Definition at line 885 of file blocks.hpp.

operator()() [2/5]

template<FiniteFieldType T = Fp<2>>

double CECCO::LLRCalculator< T >::operator() ( const std::complex< double > & in )

inline

Compute the LLR of a received complex symbol (BI-AWGN model).

Parameters

in	Received complex symbol

Returns

LLR = b·(a − Re(in)) / σ² in nats; positive ⇒ bit 0, negative ⇒ bit 1

Exceptions

std::logic_error

if this calculator was constructed from an SDMEC

Definition at line 854 of file blocks.hpp.

operator()() [3/5]

template<FiniteFieldType T = Fp<2>>

Vector< double > CECCO::LLRCalculator< T >::operator() ( const T & r )

inline

Compute symbol LLRs for one received field symbol (SDMEC model).

Parameters

r	Received 𝔽_p symbol, possibly erased

Returns

Vector with entry a−1 equal to ln(P(r|0)/P(r|a))

Exceptions

std::logic_error

if this calculator was constructed from a BI-AWGN channel

Definition at line 918 of file blocks.hpp.

operator()() [4/5]

template<FiniteFieldType T = Fp<2>>

Vector< double > CECCO::LLRCalculator< T >::operator() ( const Vector< std::complex< double > > & in )

inline

Compute LLRs for a received complex word (BI-AWGN model).

Parameters

in	Received complex word

Returns

Vector of binary LLRs

Exceptions

std::logic_error

if this calculator was constructed from an SDMEC

Definition at line 867 of file blocks.hpp.

operator()() [5/5]

template<FiniteFieldType T = Fp<2>>

Matrix< double > CECCO::LLRCalculator< T >::operator() ( const Vector< T > & r )

inline

Compute the symbol-LLR matrix of a received word (SDMEC model).

Parameters

r	Received word of 𝔽_p symbols, possibly erased

Returns

(p−1) × n matrix; entry (a−1, j) = ln(P(r_j|0)/P(r_j|a))

Exceptions

std::logic_error

if this calculator was constructed from a BI-AWGN channel

Definition at line 947 of file blocks.hpp.

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

• blocks.hpp